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HomeMy WebLinkAboutStormwater Calcs & SWPPPDEPARTMENT OF COMMUNITY DEVELO . 621 Sheridan Street, Port Townsend, WA 98368 lt%n Tel: 360.379.4450 1 Pas: 360.379.4451 Web: �t ��n =.cu.j c:rson, ►� a.u�Igctl2iliL4Ui�j dc� e1u�u:rnt r E-mail: JePF Ul9 4f.: SON CO STORMWATER CALCULATION WORKSHEET IJNrvoc, MLA # PROJECT/APPLICANT NAME: DETERMINING STORMWATER MANAGEMENT REQUIREMENTS: This stormwater calculation worksheet should be completed first to classify the proposal as "small," "medium," or "large." The size determines whether a Stormwater Site Plan is required in conjunction with a stand-alone stormwater management permit application, building permit application, or other land use approval application that involves stormwater review. The basic information will also be helpful for completing a stormwater Site Plan, if required. PARCEL SIZE I.E. SITE I' Size of parcel acres An acre contains 43,560 square feet. Multiply the acreage by this figure. Size of parcel in square feet 3 7 2, 9 7L sq/ft Land -disturbing activity is any activity that results in movement of earth, or a change in the existing soil cover (both vegetative and non -vegetative) and/or the existing soil topography. Land disturbing activities include, but are not limited to clearing, grading, filling, excavation, and compaction associated with stabilization of structures and road construction. Native vegetation is vegetation comprised on plant species, other than noxious weeds, that are indigenous to the coastal region of the Pacific Northwest and which reasonably could have been expected to naturally occur on the site. Examples include species such as Douglas fir, western hemlock, western red cedar, alder, big -leaf maple, and vine maple; shrubs such as willow, elderberry, salmonberry, and salal; herbaceous plants such as sword fern, foam flower, and fireweed. LAND DISTURBING ACTIVITY, CONVERSION OF NATIVE VEGETATION, AND VOLUME OF CUT/FILL Calculate the total area to be cleared, graded, filled, Answer the following two questions related to excavated• and/or compacted for proposed development conversion of native vegetation: project. Include in this calculation the area to be cleared for: Construction site for structures 7 (4 sq/ft Does the project convert % acres or more of native vegetation to lawn or landscaped areas? Drainfield, septic tank, etc. 2) 0 so sq/ft Circle: Yes No Well, utilities, etc. �._ sq/ft Does the project convert 2 1/2 acres or more of Driveway, parking, roads, etc. sq/ft native vegetation to pasture? Circle: Yes oNo Lawn, landscaping, etc. sq/ft Other compacted surface, etc. sq/ft Indicate Total Volumes of Proposed: Total Land Disturbance }. �1) 27 if sq/ft Cut) D Fill 2g 71. (cutyd) impervious surface is a hard surface that either prevents or retards the entry of water into the soil mantle as under natural conditions prior to development. A hard surface area which causes water to run off the surface in greater quantities or at an increased rate of flow from the flow present under natural conditions prior to development. Common impervious surfaces include, but are not limited to roof tops, walkways, patios, driveways, parking lots or storage areas, concrete or asphalt paving, gravel roads, packed earthen materials, and oiled, macadam or other surfaces which similarly impede the natural infiltration of stormwater. stormwater ealc worksheet —REV. 10/20/2014 STORMWATER CALULATiONS — IMPERVIOUS SURFACE NEW Structures (all roof area) C' q) 170 sq/ft Sidewalks Patios Solid Decks (without infiltration below) Driveway, parking, roads, etc. i 5 Lf) coo Other sq/tt sq/ft sq/ft sglft Total New _ 212-270 sq/ft TOTAL NEW + TOTAL EXISTING* `Z i i sq/ft EXISTING Q Structures (all roof area) 3,]_�2 v sq/ft Sidewalks sq/ft Patios sq/ft Solid Decks sq/ft (without infiltration below) Driveway, parking, roads, etc 3, 6 sq/ft Other sq/ft Total Existing sglft *This amount will be used to check total lot coverage. The following questions will help determine whether the proposed project is considered development or redevelopment. DEVELOPMENT v. REDEVELOPMENT Divide the total existing impervious surface above by the size of the parcel and convert to a percentage: +' 7 Does the site have 35% or more of existing impervious surface? Circle. Yes No FURTHER INSTRUCTIONS: If the answer is yes, the proposal is considered redevelopment and the attached Figure 2 should be used to determine the applicable Minimum Requirements. If the answer is no, the proposal is considered new development and the attached Figure 1 should be used. At this juncture, the applicant should refer to the applicable Flow Chart to determine the Minimum Requirements for stormwater management. DCD staff will help verify the classification of the project and the application requirements. For proponents of "small" projects who must comply only with Minimum Requirement #2—Construction Stormwater Pollution Prevention —an additional submittal is not required. The proponent is responsible for employing the 12 Elements to control erosion and prevent sediment and other pollutants from leaving the site during the construction phase of the project. Pick up the Construction Stormwater Pollution Prevention (SWPP) Best Management Practices (BMPs) Packet. Proponents of "medium" projects —those that must meet only Minimum Requirements #1 through #5—and for "large" projects —those that must meet all 10 Minimum Requirements —are required to submit a Stormwater Site Plan. DCD has prepared a submittal template of a Stormwater Site Plan, principally for rural residential projects. Complete the template in the Stormwater Site Plan Instructions and Submittal Template or prepare a Stormwater Site Plan using the step-by-step guidance in the Stormwater Management Manual, APPLICANT SIGNATURE By signing the Stormwater Calculation Worksheet, I as the applicant/owner attest that the information provided herein is true and correct to the best of my knowledge. I also certify that this application is being made with the full knowledge and consent of all owners of the affected property, V-0-0, / ec—' (LANDOWNER Oft AUTH EDREPRESENTATIVESIGNATURE) (DATE) FOR OFFICE USE ONLY SMALL MEDIUM LARGE REDEVELOPMENT Stormwater Site Plan: Yes No dorm Ier talc worksheel — REV. 10/20/2014 NTI January 8, 2019 NORTHWESTERN TERRITORIES, INC 717 SOUTH PEABODY STREET, PORT ANGELES, WA Engineers Land Surveyors Geologists Construction Inspection Materials Testing 360-452-8491 info@nti4u.com Stormwater. Erosion, and Sediment Control 006d_M #001213015 8012 Highway 20 Port Townsend, Washington 98368 1.0 BACKGROUND AND SCOPE OF WORK NTI Engineering and Land Surveying (NTI) was requested by Brad Hoover to prepare a Preliminary Stormwater, Erosion, and Sediment Control Plan for a self -storage facility on Jefferson County tax parcel #001213015 near the intersection of highways 19 and 20 in Port Townsend. This 8.7-acre parcel is located approximately 2 miles south of Port Townsend within the Southwest quarter of Section 21, Township 30 North, Range 1 West, WM, on the east side of Highway 20. The proposed construction includes a new mini storage facility with parking and sidewalks. 2.0 SITE CONDITIONS Topography The site has an average overall slope of roughly 5-6% downward from the northeast to the southwest, with some areas of the slope as steep as 17% before grading. Existing Development The 8.7-acre site of the proposed mini storage is currently vacant with electrical power and water lines available nearby. The adjacent parcels are mostly undeveloped and forested with the exception of a U-Haul garage and parking area to the south. Vegetation The site is forested with scattered clearings and trails with medium -length grass. Soil Conditions Per the United States Department of Agriculture Natural Resources Conservation Services (NRCS) Web Soil Survey, site soils are hydrologic soil group A, gravelly loamy sand with an expected infiltration rate of 5.95 to 19.98 inches per hour. The expected depth to the water table is more than 80". Based on the NRCS soils information for the site, infiltration for stormwater management for the proposed facility is almost certainly feasible. Nine test pits were excavated in the late summer of 2018. All test pits had gravelly loamy sand/sandy loam to varying depths below the surface, ranging from 18 inches deep at the northeast corner to more than 84 inches deep at the southwest corner. Test pits in the north and east of the property contained fine sand and silt loam below the gravelly sand/loam layer. Test pits in the southwest quarter of the property showed coarse soils that extended to the bottom of the test pits. Stormwater Report — 2019 On October 19, 2018, a Pilot infiltration test was performed in the southwest quarter of the site and measured an infiltration rate of 7.0 in/h. With appropriate adjustment factors specified by the 2014 Stormwater Management Manual for Western Washington (SMMWW), the design infiltration rate is 2.5 in/hr. 3.0 DRAINAGE DESIGN New Development The proposed development is a new mini -storage facility with multiple storage buildings and an office/residence. The development will occupy the southern half of the property, with pavement in the area not used for storage buildings, and bioretention (BMP T5.14B and T7.30) around the perimeter of the new development area. Roof runoff from the proposed 58,710 sf (1.3478 ac) of storage buildings will be collected via roof gutters and downspouts and conveyed to bioretention swales. (9 storage buildings at 6250 square feet each and an office/residence at 2460 for a total of 58,710 square feet of roofs.) Runoff from the proposed 157,600 sf (3.6180 ac) of pavement will drain to bioretention swales surrounding the parking area. The infiltration facilities will serve as the treatment component as well as the flow control component. (Total developed area of approximately 216,274 square feet minus 58,710 square feet of roofs and 2,080 square feet of septic drainfield and 884 square feet of landscaping leaves 154,600 square feet of pavement.) Bioretention swales will total 541 linear feet and have a width of 5 ft at the bottom, spreading to 20 ft wide at the top. A smaller area would be sufficient for infiltration, so the SWMMWW minimum of 5% the area of contributing surfaces controls. An existing drainage swale along Highway 20 will remain undisturbed to the extent possible to continue to serve as the collection facility for Highway 20. The project results in more than 5,000 square feet of new hard surfaces, so all Minimum Requirements, as outlined in the Department of Ecology's 2014 Stormwater Management Manual for Western Washington, apply. The Erosion and Sediment Control mitigation used for this project will be modeled after MR #1-#9 of the SMMWW as outlined below: Minimum Requirement #1— Stormwater Site Plans The elements described below are detailed in a set of engineering drawings attached as an appendix to this document. Minimum Requirement #2 — Construction Stormwater Pollution Prevention Plan For description of Best Management Practices (BMPs) listed below for Elements #1 through #13, and except where specifically noted otherwise, refer to the 2014 SMMWW. Element #1— Preserve Vegetation/Mark Clearing Limits Before land disturbing activity begins, the clearing limits must be marked with silt fence (BMP C233), where potential for sediment leaving the site is present, or high visibility fence elsewhere. The native top soil and existing vegetation must be retained in an undisturbed state to the maximum degree practical (BMP C101). 2 �F .. ... ... ...... ... ... ... ... ... ... ... ... ... ... ... ... ... ... ... ... ...... ... ... ........ ... ... ,..... i ... Stormwater Report — 2019 Element #2 — Establish Construction Access Unless a written variance is granted in advance, a stabilized construction entrance (BMP C105) for this project shall be provided via an easement from the neighboring property to the south. This construction entrance must be maintained throughout the course of construction. Any sediment tracked off the site must be cleaned thoroughly at the end of each day, or more frequently if determined necessary, by shoveling, sweeping, transporting to a controlled sediment disposal area, street washing, and/or other necessary and appropriate measures. Element #3 — Control Flow Rates Because of the mostly mild topography of the site and high in -situ soil infiltration rates, stormwater flows are not expected to concentrate in any significant volume or flow rate. Infiltration systems, by their nature, must be constructed in advance to serve roofs, pavements, sidewalks, and other impervious areas. Activities such as roof gutter and downspout installation, paving, and similar construction activities, must be promptly completed in the proper sequence to control flows and minimize the potential for erosion and sedimentation. Silt fence (BMP C233), wattles (BMP C235), and/or other appropriate BMPs must be used as necessary for control of flow rates. Element #4 — Install Sediment Controls Silt fence must be installed and maintained throughout the duration of the project. The location of the silt fence is shown on the Temporary Erosion and Sediment Control Plan and must be in place in all areas where sediment could potentially leave the site. Acceptable oil -absorbent -rated fabric sediment protection inserts shall also be placed in all existing and new catch basins and inlets that could potentially receive stormwater flows directly from the site. In addition to site perimeter and inlet sediment controls, sediment controls must also be provided to protect new infiltration trenches from sedimentation and clogging. Silt fence (BMP C233), wattles (BMP C235), oil -absorbent -rated fabric catch basin insert bags (BMP C220), and/or other appropriate BMPs must be used as necessary for control of sediment. Element #5 — Stabilize Soils Soils must not remain exposed and unworked for more than the time periods set forth below: • May 1 - September 30: 7 days. • October 1 - April 30: 2 days. Bare soils - particularly bare slopes - and soil stockpiles must be protected from erosion with sediment trapping measures. To the maximum extent possible, stockpiles must be located away from storm drain inlets, waterways, and drainage channels. Temporary and permanent seeding (BMP C120), mulching (BMP C121), nets and blanketing (BMP C122), plastic covering (BMP C123), top -soiling and/or composting (BMP C125), and/or other appropriate BMPs must be used as necessary for stabilizing of soils. Additionally, post -construction soil quality and depth enhancement (BMP-T5.13; refer to Building Soil; Guidelines and Resources for Implementing Soil quality„and Depth BMPTS.13, 2016 Edition) must be implemented to improve infiltration capacity of the newly created and restored lawn areas. 3 A ... ... ... ... ... ... ... ... ... ... ... ... ... ... ... ... ... ... ...... .............. ... ... ... ... ... ... ... ... ... ...... ... ... ... ... ... ... ... ... ........ ... ... ...... ... ... ... ... ... ...... ... ........ ...... ......... .. ... ...... ...... ... ...... ... ...... ... ... ..... ... ...... ... ... ... ... ...... ...... ...... ... ... ... ... ... ... ... ... ... ...... ... ... Stormwater Report — 2019 Element #6 — Protect Slopes Site slopes are shallow, but if temporary slopes are required during construction, blanketing or other effective temporary measures shall be taken to prevent erosion. Slope construction and slope stabilization should be scheduled during dry weather (usually May 1 to September 30) to minimize potential for erosion. Temporary and permanent seeding (BMP C120), mulching (BMP C121), nets and blanketing (BMP C122), plastic covering (BMP C123), and/or other appropriate BMPs must be used as necessary for protection of slopes. Element #7 — Protect Drain Inlets Inlet protection shall also be placed in all existing and new catch basins and inlets that could potentially receive stormwater flows directly from the site. Storm drain inlet protection (BMP C220), use of oil -absorbent -rated catch basin inlet fabric insert bags, and/or other appropriate BMPs must be used as necessary for inlet protection. Inlet protection must not obstruct vehicle traffic on the site. Element #8 — Stabilize Channels and Outlets This project does not have any channels or outlets where concentrated flows could leave the site and enter natural or man-made bodies of water or wetlands. Element #9 —Control Pollutants All chemicals, liquid products, petroleum products, and other materials that have the potential to pose a threat to human health or the environment must be provided with secondary containment and protection from weather, vandalism, and/or other adverse circumstances. Secondary containment means placing tanks and/or containers within an impervious structure capable of containing 110% of the volume contained in the largest tank or container within the containment structure. Fueling, maintenance, and repair of heavy equipment and vehicles must include use of spill prevention and control measures. Washout of concrete trucks, dumping of excess concrete, and similar activities shall not be performed on -site. Washout of concrete trucks, dumping of excess concrete, and similar activities shall only be performed in off -site locations specifically approved for such activities. Proper concrete handling (BMP C151), saw cutting and surfacing pollution prevention (BMP C152), proper material delivery, storage, and containment (BMP C153), and/or other appropriate BMPs must be used as necessary for control of pollutants. Any and all spills associated with this project, either on site or off site, must be reported to the proper authorities and thoroughly cleaned up to meet applicable City, County, State, and/or Federal standards. Element #10 — Control Dewatering Dewatering is not expected to be required. However, in the event that dewatering is required, water from dewatering operations shall be discharged in such a manner that it does not result in erosion and sedimentation. Special care shall be taken to avoid sedimentation of existing and 4 ..k ...... ...... ..... ... ... ...... ... ... ... ... ...... ... ... ... ...... ... ...... ... ... ... ... ... ... ... ... ... ... ...... : " ... : "... ... ... ... ... ... ..... ... ......... ... ... ...... ...... .......... ... ... ... ...... ...... ...... ... ... ... ...... ... ... ...... ... ... ... ...... ... ...... ... ... ... ... ...... ...... ... ... ...... ... ... ...... ... ...... ... k E tt« S tormw ater Report — 2019 new infiltration facilities. Element #11— Maintain BMPs All temporary and permanent erosion and sediment control BMPs must be maintained and repaired as needed to assure continued performance of their intended function in accordance with BMP specifications. All temporary erosion and sediment control BMPs shall be removed within 30 days after achieving final site stabilization or after the temporary BMPs are no longer needed. An adequate supply of appropriate spare materials shall be kept on site for maintenance of BMPs (BMP C150). Element #12 — Manage the Project Accurate and timely BMP installation, monitoring, and maintenance, SWPPP preparation and up- dating as necessary, and record -keeping of construction SWPPP activities for the project, shall be underthe supervision of a Certified Erosion and Sediment Control Lead (BMP C150 and BMP C160). To the extent possible, work.shall be scheduled to take advantage of normal seasonal dry weather conditions (BMP C162). Element #13 — Protect Low Impact Development BMPs Bioretention/Infiltration swales and associated facilities shall be protected from sedimentation and other harmful processes. Silt fence (BMP C233), wattles (BMP C235), oil absorbent fabric catch basin inlet bags, and/or other appropriate BMPs must be used as necessary to protect infiltration trenches and associated facilities. Prevent foot or vehicle traffic from passing through stormwater facilities during construction. Minimum Requirement #3 — Source Control of Pollution Construction -related pollution control is addressed above under Minimum Requirement #2, Element #9 above. Long term pollution control is the responsibility of the owner and/or operator of the site. Minimum Requirement #4 — Preservation of Natural Drainage Systems and Outfalls All of the stormwater runoff generated from the impervious surfaces will be infiltrated onsite. Infiltration trench bottoms will be set into undisturbed native material. No natural channels will receive runoff from the site. See the WWHM report for flow duration analysis. Minimum Requirement #5 — On -site Stormwater Management All stormwater will be infiltrated on site as described in New Development, above. Minimum Requirement #6 — Runoff Treatment All of the collected runoff will be infiltrated onsite through infiltration trenches or soil -enhanced vegetated areas. Minimum Requirement #7 — Flow Control As all stormwater will be infiltrated on -site, and sedimentation control BMPs will be kept in place throughout construction, impact to off -site water quality will be mitigated. Stormwater will discharge to the groundwater after complete treatment of the stormwater occurs in the required separation from the bottom of the infiltration facility to the groundwater table. 5 Stormwater Report — 2019 Minimum Requirement #8 — Wetlands Protection No known wetlands exist on or near the site. Minimum Requirement #9 — Operation and Maintenance An operations and maintenance manual will be prepared for on -site stormwater facilities. 4.0 THE LIMITATIONS OF OUR INVESTIGATION AND FINDINGS The observations and conclusions of this report apply only to the subject property and they are not transferable to nearby or adjoining property. This report was prepared for Brad Hoover and may be used by others only with his permission. Northwestern Territories Inc. warrants this report was conscientiously prepared in accordance with the practice of professional civil engineering. No other warranty, either express nor implied, is provided. For Northwestern Territories, Inc., Sincerely yours, �i � � I •. Stephen Hanes, EIT, MEngr. Staff Engineer Zachary N. Slota, P.E. Principal Engineer ... Yi q .... ... .......... q: Stormwater Report — 2019 Appendix I — Drainage, Erosion, and Sediment Control Plan m m Stormwater Report — 2019 Appendix II — Stormwater Pollution Prevention BMPs JEFFERWN COUNTY DW ,,, w BMP C101: Preserving Natural Vegetation Purpose The purpose of preserving natural vegetation is to reduce erosion wherever practicable. Limiting site disturbance is the single most effective method for reducing erosion. For example, conifers can hold up to about 50 percent of all rain that falls during a storm. Up to 20-30 percent of this rain may never reach the ground but is taken up by the tree or evaporates. Another benefit is that the rain held in the tree can be released slowly to the ground after the storm. Conditions of Use Natural vegetation should be preserved on steep slopes, near perennial and intermittent watercourses or swales, and on building sites in wooded areas. . As required by local governments. Phase construction to preserve natural vegetation on the project site for as long as possible during the construction period. Design and Installation Specifications Natural vegetation can be preserved in natural clumps or as individual trees, shrubs and vines. The preservation of individual plants is more difficult because heavy equipment is gen- erally used to remove unwanted vegetation. The points to remember when attempting to save individual plants are: Is the plant worth saving? Consider the location, species, size, age, vigor, and the work involved. Local governments may also have ordinances to save natural veget- ation and trees. Fence or clearly mark areas around trees that are to be saved. It is preferable to keep ground disturbance away from the trees at least as far out as the dripline. Plants need protection from three kinds of injuries: Construction Equipment- This injury can be above or below the ground level. Damage results from scarring, cutting of roots, and compaction of the soil. Placing a fenced buffer zone around plants to be saved prior to construction can prevent construction equipment injuries. Grade Changes - Changing the natural ground level will alter grades, which affects the plant's ability to obtain the necessary air, water, and minerals. Minor fills usu- ally do not cause problems although sensitivity between species does vary and should be checked. Trees can typically tolerate fill of 6 inches or less. For shrubs 2014 Stormwater Management Manual for Western Washington Volume 11 - Chapter 4 - Page 266 and other plants, the fill should be less. When there are major changes in grade, it may become necessary to supply air to the roots of plants. This can be done by placing a layer of gravel and a tile system over the roots before the fill is made. A tile system protects a tree from a raised grade. The tile system should be laid out on the original grade leading from a dry well around the tree trunk. The system should then be covered with small stones to allow air to circulate over the root area. Lowering the natural ground level can seriously damage trees and shrubs. The highest percentage of the plant roots are in the upper 12 inches of the soil and cuts of only 2-3 inches can cause serious injury. To protect the roots it may be neces- sary to terrace the immediate area around the plants to be saved. If roots are exposed, construction of retaining walls may be needed to keep the soil in place. Plants can also be preserved by leaving them on an undisturbed, gently sloping mound. To increase the chances for survival, it is best to limit grade changes and other soil disturbances to areas outside the dripline of the plant. . Excavations - Protect trees and other plants when excavating for drainfields, power, water, and sewer lines. Where possible, the trenches should be routed around trees and large shrubs. When this is not possible, it is best to tunnel under them. This can be done with hand tools or with power augers. If it is not possible to route the trench around plants to be saved, then the following should be observed: • Cut as few roots as possible. When you have to cut, cut clean. Paint cut root ends with a wood dressing like asphalt base paint if roots will be exposed for more than 24-hours. • Backfill the trench as soon as possible. • Tunnel beneath root systems as close to the center of the main trunk to pre- serve most of the important feeder roots. Some problems that can be encountered with a few specific trees are: . Maple, Dogwood, Red alder, Western hemlock, Western red cedar, and Douglas fir do not readily adjust to changes in environment and special care should be taken to protect these trees. . The windthrow hazard of Pacific silver fir and madrona is high, while that of Western hemlock is moderate. The danger of windthrow increases where dense stands have been thinned. Other species (unless they are on shallow, wet soils less than 20 inches deep) have a low windthrow hazard. • Cottonwoods, maples, and willows have water -seeking roots. These can cause trouble in sewer lines and infiltration fields. On the other hand, they thrive in high moisture conditions that other trees would not. . Thinning operations in pure or mixed stands of Grand fir, Pacific silver fir, Noble fir, 2014 Stormwater Management Manual for Westem Washington Volume 11- Chapter - Page 267 Sitka spruce, Western red cedar, Western hemlock, Pacific dogwood, and Red alder can cause serious disease problems. Disease can become established through damaged limbs, trunks, roots, and freshly cut stumps. Diseased and weakened trees are also susceptible to insect attack. Maintenance Standards Inspect flagged and/or fenced areas regularly to make sure flagging or fencing has not been removed or damaged. If the flagging or fencing has been damaged or visibility reduced, it shall be repaired or replaced immediately and visibility restored. If tree roots have been exposed or injured, "prune" cleanly with an appropriate prun- ing saw, or loppers directly above the damaged roots and recover with native soils. Treatment of sap flowing trees (fir, hemlock, pine, soft maples) is not advised as sap forms a natural healing barrier. BMP C102: Buffer Zones Purpose Creation of an undisturbed area or strip of natural vegetation or an established suitable planting that will provide a living filter to reduce soil erosion and runoff velocities. Conditions of Use Natural buffer zones are used along streams, wetlands and other bodies of water that need protection from erosion and sedimentation. Vegetative buffer zones can be used to protect natural swales and can be incorporated into the natural landscaping of an area. Critical -areas buffer zones should not be used as sediment treatment areas. These areas shall remain completely undisturbed. The local permitting authority may expand the buffer widths temporarily to allow the use of the expanded area for removal of sed- iment. Design and Installation Specifications • Preserving natural vegetation or plantings in clumps, blocks, or strips is generally the easiest and most successful method. • Leave all unstable steep slopes in natural vegetation. . Mark clearing limits and keep all equipment and construction debris out of the nat- ural areas and buffer zones. Steel construction fencing is the most effective method in protecting sensitive areas and buffers. Alternatively, wire -backed silt fence on steel posts is marginally effective. Flagging alone is typically not effective. . Keep all excavations outside the dripline of trees and shrubs. • Do not push debris or extra soil into the buffer zone area because it will cause 2014 Stormwater Management Manual for Westem Washington Volume 11 - Chapter 4 - Page 268 Metal fences shall be designed and installed according to the manufacturer's spe- cifications. Metal fences shall be at least 3 feet high and must be highly visible. Fences shall not be wired or stapled to trees. Maintenance Standards If the fence has been damaged or visibility reduced, it shall be repaired or replaced immediately and visibility restored. BMP C105: Stabilized Construction Entrance / Exit Purpose Stabilized Construction entrances are established to reduce the amount of sediment transported onto paved roads by vehicles or equipment. This is done by constructing a stabilized pad of quarry spalls at entrances and exits for construction sites. Conditions of Use Construction entrances shall be stabilized wherever traffic will be entering or leaving a construction site if paved roads or other paved areas are within 1,000 feet of the site. For residential construction provide stabilized construction entrances for each residence, rather than only at the main subdivision entrance. Stabilized surfaces shall be of suf- ficient length/width to provide vehicle access/parking, based on lot size/configuration. On large commercial, highway, and road projects, the designer should include enough extra materials in the contract to allow for additional stabilized entrances not shown in the initial Construction SWPPP. It is difficult to determine exactly where access to these projects will take place; additional materials will enable the contractor to install them where needed. Design and Installation Specifications See Figure II-4.1.1 Stabilized Construction Entrance(p.273) for details. Note: the 100' minimum length of the entrance shall be reduced to the maximum practicable size when the size or configuration of the site does not allow the full length (100'). Construct stabilized construction entrances with a 12-inch thick pad of 4-inch to 8-inch quarry spalls, a 4-inch course of asphalt treated base (ATB), or use existing pavement. Do not use crushed concrete, cement, or calcium chloride for construction entrance sta- bilization because these products raise pH levels in stormwater and concrete discharge to surface waters of the State is prohibited. 2014 Stormwater Management Manual for Western Washington Volume 11 - Chapter - Page 270 A separation geotextile shall be placed under the spalls to prevent fine sediment from pumping up into the rock pad. The geotextile shall meet the following standards: Grab Tensile Strength (ASTM D4751) 200 psi -min. Grab Tensile Elongation (ASTM D4632) 30% max. Mullen Burst Strength (ASTM D3786-80a) 400 psi min. AOS (ASTM D4751) 20-45 (U.S. standard sieve size) Consider early installation of the first lift of asphalt in areas that will paved; this can be used as a stabilized entrance. Also consider the installation of excess concrete as a stabilized entrance. During large concrete pours, excess concrete is often available for this purpose. Fencing (see BMP C103: High Visibility Fence (p.269)) shall be installed as neces- sary to restrict traffic to the construction entrance. . Whenever possible, the entrance shall be constructed on a firm, compacted sub - grade. This can substantially increase the effectiveness of the pad and reduce the need for maintenance. Construction entrances should avoid crossing existing sidewalks and back of walk drains if at all possible. If a construction entrance must cross a sidewalk or back of walk drain, the full length of the sidewalk and back of walk drain must be covered and protected from sediment leaving the site. Maintenance Standards Quarry spalls shall be added if the pad is no longer in accordance with the spe- cifications. If the entrance is not preventing sediment from being tracked onto pavement, then alternative measures to keep the streets free of sediment shall be used. This may include replacement/cleaning of the existing quarry spalls, street sweeping, an increase in the dimensions of the entrance, or the installation of a wheel wash. Any sediment that is tracked onto pavement shall be removed by shoveling or street sweeping. The sediment collected by sweeping shall be removed or sta- bilized on site. The pavement shall not be cleaned by washing down the street, except when high efficiency sweeping is ineffective and there is a threat to public safety. If it is necessary to wash the streets, the construction of a small sump to con- tain the wash water shall be considered. The sediment would then be washed into the sump where it can be controlled. Perform street sweeping by hand or with a high efficiency sweeper. Do not use a non -high efficiency mechanical sweeper because this creates dust and throws soils into storm systems or conveyance ditches. 2014 Stormwater Management Manual for Western Washington Volume 11 - Chapter 4 - Page 271 Any quarry spalls that are loosened from the pad, which end up on the roadway shall be removed immediately. If vehicles are entering or exiting the site at points other than the construction entrance(s), fencing (see BMP C103) shall be installed to control traffic. Upon project completion and site stabilization, all construction accesses intended as permanent access for maintenance shall be permanently stabilized. 2014 Stormwater Management Manual for Westem Washington Volume 11 - Chapter 4 - Page 272 Figure 11-4.1.1 Stabilized Construction Entrance cu roadsi Notes: 1. Driveway shall meet the requirements of the permitting agency. 2. It is recommended that the entrance be crowned so that runoff drains off the pad. wiiiim� DEPARTMENT OF ECOLOGY State of Washington NOT TO SCALE n. 15' min. 12" minimum thickness Provide full width ofingress/egress area Figure II-4.1.1 Stabilized Construction Entrance Revised June 2015 Please see http://www.ecy.wa gov/copyright.html for copyright notice including permissions, limitation of liability, and disclaimer. 2014 Stormwater Management Manual for Westem Washington Volume 11 - Chapter 4 - Page 273 Approved as Equivalent Ecology has approved products as able to meet the requirements of BMP C105: Stab- ilized Construction Entrance / Exit. The products did not pass through the Technology Assessment Protocol — Ecology (TAPE) process. Local jurisdictions may choose not to accept this product approved as equivalent, or may require additional testing prior to con- sideration for local use. The products are available for review on Ecology's website at http://www.ecy.\Aa.go"/ uivalent.html BMP C106: Wheel Wash Purpose Wheel washes reduce the amount of sediment transported onto paved roads by motor vehicles. Conditions of Use When a stabilized construction entrance (see BMP C105: Stabilized Construction Entrance / Exit (p.270) is not preventing sediment from being tracked onto pavement. . Wheel washing is generally an effective BMP when installed with careful attention to topography. For example, a wheel wash can be detrimental if installed at the top of a slope abutting a right-of-way where the water from the dripping truck can run unimpeded into the street. . Pressure washing combined with an adequately sized and surfaced pad with dir- ect drainage to a large 10-foot x 10-foot sump can be very effective. • Discharge wheel wash or tire bath wastewater to a separate on -site treatment sys- tem that prevents discharge to surface water, such as closed -loop recirculation or upland land application, or to the sanitary sewer with local sewer district approval. . Wheel wash or tire bath wastewater should not include wastewater from concrete washout areas. Design and Installation Specifications Suggested details are shown in Figure 11-4.1.2 Wheel Wash (p.276). The Local Per- mitting Authority may allow other designs. A minimum of 6 inches of asphalt treated base (ATB) over crushed base material or 8 inches over a good subgrade is recommended to pave the wheel wash. Use a low clearance truck to test the wheel wash before paving. Either a belly dump or lowboy will work well to test clearance. Keep the water level from 12 to 14 inches deep to avoid damage to truck hubs and filling the truck tongues with water. 2014 Stormwater Management Manual for Western Washington Volume 11 - Chapter - Page 274 Storm drain inlets shall be protected to prevent sediment -laden water entering the storm drain system (see BMP C220: Storm Drain Inlet Protection (p.357)). Maintenance Standards Inspect stabilized areas regularly, especially after large storm events. Crushed rock, gravel base, etc., shall be added as required to maintain a stable driving surface and to stabilize any areas that have eroded. Following construction, these areas shall be restored to pre -construction condition or bet- ter to prevent future erosion. Perform street cleaning at the end of each day or more often if necessary. SIP C120: Temporary and Permanent Seeding Purpose Seeding reduces erosion by stabilizing exposed soils. A well -established vegetative cover is one of the most effective methods of reducing erosion. Conditions of Use Use seeding throughout the project on disturbed areas that have reached final grade or that will remain unworked for more than 30 days. The optimum seeding windows for western Washington are April 1 through June 30 and September 1 through October 1. Between July 1 and August 30 seeding requires irrigation until 75 percent grass cover is established. Between October 1 and March 30 seeding requires a cover of mulch with straw or an erosion control blanket until 75 percent grass cover is established. Review all disturbed areas in late August to early September and complete all seeding by the end of September. Otherwise, vegetation will not establish itself enough to provide more than average protection. . Mulch is required at all times for seeding because it protects seeds from heat, mois- ture loss, and transport due to runoff. Mulch can be applied on top of the seed or simultaneously by hydroseeding. See (3MP C 121: Mulching .284 for spe- cifications. . Seed and mulch, all disturbed areas not otherwise vegetated at final site sta- bilization. Final stabilization means the completion of all soil disturbing activities at the site and the establishment of a permanent vegetative cover, or equivalent per- 2014 Stormwater Management Manual for Western Washington Volume 11 - Chapter 4 - Page 278 manent stabilization measures (such as pavement, riprap, gabions, or geotextiles) which will prevent erosion. Design and Installation Specifications Seed retention/detention ponds as required. Install channels intended for vegetation before starting major earthwork and hydroseed with a Bonded Fiber Matrix. For vegetated channels that will have high flows, install erosion control blankets over hydroseed. Before allowing water to flow in vegetated channels, establish 75 percent vegetation cover. If vegetated channels cannot be estab- lished by seed before water flow; install sod in the channel bottom —over hydromulch and erosion control blankets. O Confirm the installation of all required surface water control measures to prevent seed from washing away. . Hydroseed applications shall include a minimum of 1,500 pounds per acre of mulch with 3 percent tackifier. See BMP C121: Mul&iing ��.284 j for specifications. o Areas that will have seeding only and not landscaping may need compost or meal - based mulch included in the hydroseed in order to establish vegetation. Re -install native topsoil on the disturbed soil surface before application. . When installing seed via hydroseeding operations, only about 1/3 of the seed actu- ally ends up in contact with the soil surface. This reduces the ability to establish a good stand of grass quickly. To overcome this, consider increasing seed quantities by up to 50 percent. . Enhance vegetation establishment by dividing the hydromulch operation into two phases: 1. Phase 1- Install all seed and fertilizer with 25-30 percent mulch and tackifier onto soil in the first lift. 2. Phase 2- Install the rest of the mulch and tackifier over the first lift. Or, enhance vegetation by: 1. Installing the mulch, seed, fertilizer, and tackifier in one lift. 2. Spread or blow straw over the top of the hydromulch at a rate of 800-1000 pounds per acre. 3. Hold straw in place with a standard tackifier. Both of these approaches will increase cost moderately but will greatly improve and enhance vegetative establishment. The increased cost may be offset by the reduced need for: 2014 Stormwater Management Manual for Westem Washington Volume 11 - Chapter - Page 279 . Irrigation. u Reapplication of mulch. Repair of failed slope surfaces. This technique works with standard hydromulch (1,500 pounds per acre minimum) and BFM/MBFMs (3,000 pounds per acre minimum). . Seed may be installed by hand if: . Temporary and covered by straw, mulch, or topsoil. Permanent in small areas (usually less than 1 acre) and covered with mulch, topsoil, or erosion blankets. . The seed mixes listed in the tables below include recommended mixes for both temporary and permanent seeding. . Apply these mixes, with the exception of the wetland mix, at a rate of 120 pounds per acre. This rate can be reduced if soil amendments or slow - release fertilizers are used. . Consult the local suppliers or the local conservation district for their recom- mendations because the appropriate mix depends on a variety of factors, including location, exposure, soil type, slope, and expected foot traffic. Altern- ative seed mixes approved by the local authority may be used. . Other mixes may be appropriate, depending on the soil type and hydrology of the area. . Table II-4.1.2 Temporary Erosion Control Seed Mix (p 280) lists the standard mix for areas requiring a temporary vegetative cover. Table 11-4.1.2 Temporary Erosion Control Seed Mix % Weight % Purity % Germination Chewings or annual blue grass 40 98 90 Festuca rubra var. commutata or Poa anna Perennial rye 50 98 90 Lolium perenne Redtop or colonial bentgrass 5 92 85 Agrostis alba or Agrostis tenuis White dutch clover 5 98 90 Trifolium repens . Table II-4.1.3 Landscaping Seed Mix (p.281) lists a recommended mix for land- scaping seed. 2014 Stormwater Management Manual for Western Washington Volume 11- Chapter 4 - Page 280 Tabie H-4.1.3 Landscapinq Seed Mix % Weight % Purity'% Germination Perennial rye blend 70 98 90 Lolium perenne Chewings and red fescue blend 30 98 90 Festuca rubra var. commutata or Festuca rubra . Table II-4.1.4 Low -Growing Turf Seed Mix .281) lists a turf seed mix for dry situ- ations where there is no need for watering. This mix requires very little main- tenance. Table 11-4.1.4 Low -Growing Turf Seed Mix % Weigh % Purity % Germination Dwarf tall fescue (several varieties) 45 98 90 Festuca arundinacea var. Dwarf perennial rye (Barclay) 30 98 90 Lolium perenne var. barclay Red fescue 20 98 90 Festuca rubra Colonial bentgrass 5 98 90 Agrostis tenuis . Table II-4.1.5 Bioswale Seed Mix* .281 lists a mix for bioswales and other inter- mittently wet areas. Table 11-4.1.5 Bioswale Seed Mix* % Weight % Purity % Germination Tall or meadow fescue Festuca arundinacea or Festuca ela- 75-80 98 90 tior Seaside/Creeping bentgrass 10-15 92 85 Agrostis palustris Redtop bentgrass 5-10 90 80 Agrostis alba or Agrostis gigantea * Modified Briargreen, Inc. Hydroseeding Guide Wetlands Seed Mix . Table 11-4.1.6 Wet Area Seed Mix* .282) lists a low -growing, relatively non-invas- ive seed mix appropriate for very wet areas that are not regulated wetlands. Apply 2014 Stormwater Management Manual for Western Washington Volume 11- Chapter 4 - Page 281 this mixture at a rate of 60 pounds per acre. Consult Hydraulic Permit Authority (HPA) for seed mixes if applicable. Table 11-4.1.6 Wet Area Seed Mix* % Weight % Purity % Germination Tall or meadow fescue Festuca arundinacea or Festuca ela- 60-70 98 90 tior Seaside/Creeping bentgrass 10-15 98 85 Agrostis palustris Meadow foxtail 10-15 90 80 Alepocurus pratensis Alsike clover 1-6 98 90 Trifolium hybridum Redtop bentgrass 1-6 92 85 Agrostis alba * Modified Briargreen, Inc. Hydroseeding Guide Wetlands Seed Mix . Table II-4.1.7 Meadow Seed Mix (p.282) lists a recommended meadow seed mix for infrequently maintained areas or non -maintained areas where colonization by native plants is desirable. Likely applications include rural road and utility right-of- way. Seeding should take place in September or very early October in order to obtain adequate establishment prior to the winter months. Consider the appro- priateness of clover, a fairly invasive species, in the mix. Amending the soil can reduce the need for clover. Table 11-4.1.7 Meadow Seed Mix '% Weight % Purity % Germination Redtop or Oregon bentgrass 20 92 85 Agrostis alba or Agrostis oregonensis Red fescue '70 98 90 Festuca rubra White dutch clover 10 98 90 Trifolium repens • Roughening and Rototilling: The seedbed should be firm and rough. Roughen all soil no matter what the slope. Track walk slopes before seeding if engineering purposes require 2014 Stormwater Management Manual for Westem Washington Volume 11 - Chapter 4 - Page 282 compaction. Backblading or smoothing of slopes greater than 4H:1V is not allowed if they are to be seeded. Restoration -based landscape practices require deeper incorporation than that provided by a simple single -pass rototilling treatment. Wherever prac- tical, initially rip the subgrade to improve long-term permeability, infiltration, and water inflow qualities. At a minimum, permanent areas shall use soil amendments to achieve organic matter and permeability performance defined in engineered soil/landscape systems. For systems that are deeper than 8 inches complete the rototilling process in multiple lifts, or prepare the engineered soil system per specifications and place to achieve the specified depth. Fertilizers: . Conducting soil tests to determine the exact type and quantity of fertilizer is recommended. This will prevent the over -application of fertilizer. Organic matter is the most appropriate form of fertilizer because it provides nutrients (including nitrogen, phosphorus, and potassium) in the least water- soluble form. In general, use 10-4-6 N-P-K (nitrogen -phosphorus -potassium) fertilizer at a rate of 90 pounds per acre. Always use slow -release fertilizers because they are more efficient and have fewer environmental impacts. Do not add fer- tilizer to the hydromulch machine, or agitate, more than 20 minutes before use. Too much agitation destroys the slow -release coating. . There are numerous products available that take the place of chemical fer- tilizers. These include several with seaweed extracts that are beneficial to soil microbes and organisms. If 100 percent cottonseed meal is used as the mulch in hydroseed, chemical fertilizer may not be necessary. Cottonseed meal provides a good source of long-term, slow -release, available nitrogen. . Bonded Fiber Matrix and Mechanically Bonded Fiber Matrix: On steep slopes use Bonded Fiber Matrix (BFM) or Mechanically Bonded Fiber Matrix (MBFM) products. Apply BFM/MBFM products at a minimum rate of 3,000 pounds per acre of mulch with approximately 10 percent tackifier. Achieve a minimum of 95 percent soil coverage during application. Numer- ous products are available commercially. Installed products per man- ufacturer's instructions. Most products require 24-36 hours to cure before rainfall and cannot be installed on wet or saturated soils. Generally, products come in 40-50 pound bags and include all necessary ingredients except for seed and fertilizer. 2014 Stormwater Management Manual for Western Washington Volume 11 - Chapter 4 - Page 283 . BFMs and MBFMs provide good alternatives to blankets inmost areas requir- ing vegetation establishment. Advantages over blankets include: BFM and MBFMs do not require surface preparation. . Helicopters can assist in installing BFM and MBFMs in remote areas. On slopes steeper than 2.5H:1V, blanket installers may require ropes and harnesses for safety. Installing BFM and MBFMs can save at least $1,000 per acre com- pared to blankets. Maintenance Standards Reseed any seeded areas that fail to establish at least 80 percent cover (100 percent cover for areas that receive sheet or concentrated flows). If reseeding is ineffective, use an alternate method such as sodding, mulching, or nets/blankets. If winter weather pre- vents adequate grass growth, this time limit may be relaxed at the discretion of the local authority when sensitive areas would otherwise be protected. . Reseed and protect by mulch any areas that experience erosion after achieving adequate cover. Reseed and protect by mulch any eroded area. • Supply seeded areas with adequate moisture, but do not water to the extent that it causes runoff. Approved as Equivalent Ecology has approved products as able to meet the requirements of BMP C120: Tem- porary and Permanent Seeding. The products did not pass through the Technology Assessment Protocol — Ecology (TAPE) process. Local jurisdictions may choose notto accept this product approved as equivalent, or may require additional testing prior to con- sideration for local use. The products are available for review on Ecology's website at httr)://www.ecv.wa.aov/Droarams/wa/stormwater/newtech/eauivalent.html. BMP C121: Mulching Purpose Mulching soils provides immediate temporary protection from erosion. Mulch also enhances plant establishment by conserving moisture, holding fertilizer, seed, and top- soil in place, and moderating soil temperatures. There is an enormous variety of mulches that can be used. This section discusses only the most common types of mulch. Conditions of Use As a temporary cover measure, mulch should be used 2014 Stormwater Management Manual for Western Washington Volume 11- Chapter 4 - Page 284 • For less than 30 days on disturbed areas that require cover. • At all times for seeded areas, especially during the wet season and during the hot summer months. During the wet season on slopes steeper than 3H:1V with more than 10 feet of ver- tical relief. Mulch may be applied at any time of the year and must be refreshed periodically. . For seeded areas mulch may be made up of 100 percent: cottonseed meal; fibers made of wood, recycled cellulose, hemp, kenaf; compost; or blends of these. Tack- ifier shall be plant -based, such as guar or alpha plantago, or chemical -based such as polyacrylamide or polymers. Any mulch or tackifier product used shall be installed per manufacturer's instructions. Generally, mulches come in 40-50 pound bags. Seed and fertilizer are added at time of application. Design and Installation Specifications For mulch materials, application rates, and specifications, see Table II-4.1.8 Mulch Standards and Guidelines (p.286). Always use a 2-inch minimum mulch thickness; increase the thickness until the ground is 95% covered (i.e. not visible under the mulch layer). Note: Thickness may be increased for disturbed areas in or near sensitive areas or other areas highly susceptible to erosion. Where the option of "Compost" is selected, it should be a coarse compost that meets the following size gradations when tested in accordance with the U.S. Composting Council "Test Methods for the Examination of Compost and Composting" (TMECC) Test Method 02.02-B. Coarse Compost Minimum Percent passing 3" sieve openings 100% Minimum Percent passing 1"sieve openings 90% Minimum Percent passing 3%" sieve openings 70% Minimum Percent passing'/4" sieve openings 40% Mulch used within the ordinary high-water mark of surface waters should be selected to minimize potential flotation of organic matter. Composted organic materials have higher specific gravities (densities) than straw, wood, or chipped material. Consult Hydraulic Permit Authority (HPA) for mulch mixes if applicable. Maintenance Standards . The thickness of the cover must be maintained. . Any areas that experience erosion shall be remulched and/or protected with a net 2014 Stormwater Management Manual for Western Washington Volume 11 - Chapter 4 - Page 285 or blanket. If the erosion problem is drainage related, then the problem shall be fixed and the eroded area remulched. Table II-4.1.8 Mulch Standards and Guidelines Mulch Quality Application Remarks Material Standards Rates Cost-effective protection when applied with adequate thickness. Hand -application generally requires greater thickness than blown straw. The thickness of straw may be reduced by half when used in conjunction with seeding. In windy areas Air-dried; 2"-3" thick; straw must be held in place by crimping, using a free from 5 bales per tackifier, or covering with netting. Blown straw Straw undesirable 1 000 sf or always has to be held in place with a tackifier as seed and ,3 tons per 'even light winds will blow it away. Straw, how - coarse ever, has several deficiencies that should be con - material. acre ;sidered when selecting mulch materials. It often introduces and/or encourages the propagation of weed species and it has no significant long-term benefits It should also not be used within the ordinary high-water elevation of surface waters (due to flotation). Approx. 25- 30 Ibs per Shall be applied with h dromulcher. Shall n pp y of be No growth 1 000 sf or used without seed and tackifier unless the applic- Hydromulch inhibiting 1,500 - ation rate is at least doubled. Fibers longer than factors. 2,000 Ibs about 3/4 - 1 inch clog hydromulch equipment. Fibers should be kept to less than 3/4 inch. per acre No visible water or More effective control can be obtained by increas- dust during ing thickness to 3". Excellent mulch for protecting handling. 2" thick final grades until landscaping because it can be Must be pro in.; directly seeded or tilled into soil as an amend- duced per approx. 100 ment. Compost used for mulch has a coarser size Compost WAC 173- tons per gradation than compost used for BMP C125: Top- 350, Solid acre soiling / Composting (p.297} or BMP T5.13: Post - Waste (approx. Construction Soil Quality and Depth (p.911). It is Handling 800 Ibs per more stable and practical to use in wet areas and Standards, yard) during rainy weather conditions. Do not use near but may wetlands or near phosphorous impaired water have up to bodies. 35% 2014 Stormwater Management Manual for Western Washington Volume 11 - Chapter 4 - Page 286 Table 11-4.1.8 Mulch Standards and Guidefines (continued) Mulch Quality Application I Remarks Material I Standards Rates biosolids. Average size shall This is a cost-effective way to dispose of debris be several from clearing and grubbing, and it eliminates the inches. problems associated with burning. Generally, it Gradations should not be used on slopes above approx. 10% Chipped from fines 2 thick because of its tendency to be transported by run- Site Veget- to 6 inches min.; off. It is not recommended within 200 feet of sur- ation in length for face waters. If seeding is expected shortly after 'texture, vari mulch, the decomposition of the chipped veget- ation, and ation may tie up nutrients important to grass estab interlocking lishment. properties. No visible water or dust during handling. This material is often called "hog or hogged fuel". Must be pur 2" thick The use of mulch ultimately improves the organic Wood- chased min.; 100 matter in the soil. Special caution is advised based from a sup- approx. regarding the source and composition of wood- Mulch or plierwith a tons per based mulches. Its preparation typically does not Wood Solid acre provide any weed seed control, so evidence of Straw Waste (approx. residual vegetation in its composition or known Handling lbs. per inclusion of weed plants or seeds should be mon- Permit or cubic yard) itored and prevented (or minimized). one exempt from solid waste reg- ulations. Wood Strand Mulch A blend of loose, long, thin wood pieces derived from native conifer or deciduous trees with Cost-effective protection when applied with adequate thickness. A minimum of 95-percent of the wood strand shall have lengths between 2 and 10-inches, with a width and thickness " thick min. between 1/16 and 3/8-inches. The mulch shall no contain resin, tannin, or other compounds in quantities that would be detrimental to plant life. Sawdust or wood shavings shall not be used as mulch. (WSDOT specification (9-14.4(4)) 2014 Stormwater Management Manual for Western Washington Volume 11 - Chapter 4 - Page 287 Table 11-4.1.8 Mulch Standards and Guidelines (continued) Mulch Quality Application Material Standards Rates Remarks high length - to -width ratio. BMP C122: Nets and Blankets Purpose Erosion control nets and blankets are intended to prevent erosion and hold seed and mulch in place on steep slopes and in channels so that vegetation can become well established. In addition, some nets and blankets can be used to permanently reinforce turf to protect drainage ways during high flows. Nets (commonly called matting) are strands of material woven into an open, but high -tensile strength net (for example, coconut fiber matting). Blankets are strands of material that are not tightly woven, but instead form a layer of interlocking fibers, typically held together by a biodegradable or photodegradable netting (for example, excelsior or straw blankets). They generally have lower tensile strength than nets, but cover the ground more completely. Coir (coconut fiber) fabric comes as both nets and blankets. Conditions of Use Erosion control nets and blankets should be used: . To aid permanent vegetated stabilization of slopes 2H:1 V or greater and with more than 10 feet of vertical relief. For drainage ditches and swales (highly recommended). The application of appro- priate netting or blanket to drainage ditches and swales can protect bare soil from channelized runoff while vegetation is established. Nets and blankets also can cap- ture a great deal of sediment due to their open, porous structure. Nets and blankets can be used to permanently stabilize channels and may provide a cost-effective, environmentally preferable alternative to riprap. 100 percent synthetic blankets manufactured for use in ditches may be easily reused as temporary ditch liners. Disadvantages of blankets include: . Surface preparation required. On slopes steeper than 2.5H:1V, blanket installers may need to be roped and har- nessed for safety. . They cost at least $4,000-6,000 per acre installed. Advantages of blankets include: 2014 Stormwater Management Manual for Westem Washington Volume 11- Chapter 4 - Page 288 . Installation without mobilizing special equipment. . Installation by anyone with minimal training . Installation in stages or phases as the project progresses. . Installers can hand place seed and fertilizer as they progress down the slope. . Installation in any weather. . There are numerous types of blankets that can be designed with various para- meters in mind. Those parameters include: fiber blend, mesh strength, longevity, biodegradability, cost, and availability. Design and Installation Specifications . See Figure II-4.1.3 Channel Installation (p.292) and Figure 11-4.1.4 Slope Install- ation (p.293) for typical orientation and installation of blankets used in channels and as slope protection. Note: these are typical only; all blankets must be installed per manufacturer's installation instructions. Installation is critical to the effectiveness of these products. If good ground contact is not achieved, runoff can concentrate under the product, resulting in significant erosion. . Installation of Blankets on Slopes: 1. Complete final grade and track walk up and down the slope. 2. Install hydromulch with seed and fertilizer. 3. Dig a small trench, approximately 12 inches wide by 6 inches deep along the top of the slope. 4. Install the leading edge of the blanket into the small trench and staple approx- imately every 18 inches. NOTE: Staples are metal, "U"-shaped, and a min- imum of 6 inches long. Longer staples are used in sandy soils. Biodegradable stakes are also available. 5. Roll the blanket slowly down the slope as installer walks backwards. NOTE: The blanket rests against the installer's legs. Staples are installed as the blanket is unrolled. It is critical that the proper staple pattern is used for the blanket being installed. The blanket is not to be allowed to roll down the slope on its own as this stretches the blanket making it impossible to main- tain soil contact. In addition, no one is allowed to walk on the blanket after it is in place. 6. If the blanket is not long enough to cover the entire slope length, the trailing edge of the upper blanket should overlap the leading edge of the lower 2014 Stormwater Management Manual for Western Washington Volume 11 - Chapter - Page 289 blanket and be stapled. On steeper slopes, this overlap should be installed in a small trench, stapled, and covered with soil. With the variety of products available, it is impossible to cover all the details of appropriate use and installation. Therefore, it is critical that the design engineer consult the manufacturer's information and that a site visit takes place in order to ensure that the product specified is appropriate. Information is also available at the following web sites: 1. WSDOT (Section 3.2.4): //www.wsdot.wa.gov/NR/rdonlvres/3B41 E087-FA86-4717-932D- D7A8556CC D57/0/ErosionTrai ni ng Man ual.pdf 2. Texas Transportation Institute: http://www.txdot.gov/business/doing_business/product_evaluation/erosion_ control.htm • Use jute matting in conjunction with mulch (BMP C121: Mulching (p.284}). Excel- sior, woven straw blankets and coir (coconut fiber) blankets maybe installed without mulch. There are many other types of erosion control nets and blankets on the market that may be appropriate in certain circumstances. . In general, most nets (e.g., jute matting) require mulch in order to prevent erosion because they have a fairly open structure. Blankets typically do not require mulch because they usually provide complete protection of the surface. • Extremely steep, unstable, wet, or rocky slopes are often appropriate candidates for use of synthetic blankets, as are riverbanks, beaches and other high-energy environments. If synthetic blankets are used, the soil should be hydromulched first. . 100-percent biodegradable blankets are available for use in sensitive areas. These organic blankets are usually held together with a paper or fiber mesh and stitching which may last up to a year. . Most netting used with blankets is photodegradable, meaning they break down under sunlight (not UV stabilized). However, this process can take months or years even under bright sun. Once vegetation is established, sunlight does not reach the mesh. It is not uncommon to find non -degraded netting still in place several years after installation. This can be a problem if maintenance requires the use of mowers or ditch cleaning equipment. In addition, birds and small animals can become trapped in the netting. Maintenance Standards Maintain good contact with the ground. Erosion must not occur beneath the net or blanket. 2014 Stormwater Management Manual for Westem Washington Volume 11 - Chapter 4 - Page 290 Repair and staple any areas of the net or blanket that are damaged or not in close contact with the ground. Fix and protect eroded areas if erosion occurs due to poorly controlled drainage. 2014 Stormwater Management Manual for Western Washington Volume 11 - Chapter - Page 291 Figure 1I-4.1.3 Channel Installation LONGITUDINAL ANCHOR TRENCH NnT Tn RCAI F TERMINAL SLOPE AND CHANNEL ANCHOR TRENCH F STAKE AT 3'-5' P INTERVALS. 1 INITIAL CHANNEL ANCHOR TRENCH CHECK SLOT AT 25' INTERVALS INTERMITTENT CHECK SLOT Source: Clackamas County 2009 Notes: Erosion Prevention Planning and 1. Check slots to be constructed per manufacturers specifications. Design Manual 2. Staking or stapling layout per manufacturers specifications. Figure II-4.1.3 Channel Installation DEPARTMENT OF Revised June 2015 ECOLOGY Please see http://www.ecy.wa.govlcopyright.html for copyright notice including permissions, State of Washington limitation of liability, and disclaimer. J 2014 Stormwater Management Manual for Westem Washington Volume 11 - Chapter - Page 292 Figure 11-4.1.4 Slope Installation Min. 2" overlap Notes: 1. Slope surface shall be smooth before placement for proper soil contact. 2. Stapling pattern as per manufacturer's recommendations. 3. Do not stretch blankets/mattings tight - allow the rolls to mold to any irregularities. 4. For slopes less than 3HAV, rolls may be placed in horizontal strips. 5. If there is a berm at the top of the slope, anchor upslope of the berm. 6. Lime, fertilize, and seed before installation. Planting of shrubs, trees, etc. should occur after installation. Anchor in 6" x 6" min. trench and staple at 12" intervals 1 J = 1 ~ Min. 6" overlap Staple overlaps max. 5" spacing Bring material down to a level area, turn the end under 4" and staple at 12" intervals NOT TO SCALE Figure II-4.1.4 Slope Installation DEPARTMENT OF Revised June 2015 ECOLOGY Please see http://www.ecy. wa.govlcopyright.html for copyright notice including permissions, State of Washington limitation of liability, and disclaimer. 2014 Stormwater Management Manual for Westem Washington Volume 11 - Chapter - Page 293 BIVIP C123: Plastic Covering Purpose Plastic covering provides immediate, short-term erosion protection to slopes and dis- turbed areas. Conditions of Use Plastic covering may be used on disturbed areas that require cover measures for less than 30 days, except as stated below. . Plastic is particularly useful for protecting cut and fill slopes and stockpiles. Note: The relatively rapid breakdown of most polyethylene sheeting makes it unsuitable for long-term (greater than six months) applications. • Due to rapid runoff caused by plastic covering, do not use this method upslope of areas that might be adversely impacted by concentrated runoff. Such areas include steep and/or unstable slopes. • Plastic sheeting may result in increased runoff volumes and velocities, requiring additional on -site measures to counteract the increases. Creating a trough with wattles or other material can convey clean water away from these areas. • To prevent undercutting, trench and backfill rolled plastic covering products. . While plastic is inexpensive to purchase, the added cost of installation, main- tenance, removal, and disposal make this an expensive material, up to $1.50-2.00 per square yard. • Whenever plastic is used to protect slopes install water collection measures at the base of the slope. These measures include plastic -covered berms, channels, and pipes used to covey clean rainwater away from bare soil and disturbed areas. Do not mix clean runoff from a plastic covered slope with dirty runoff from a project. • Other uses for, plastic include: 1. Temporary ditch liner. 2. Pond liner in temporary sediment pond. 3. Liner for bermed temporary fuel storage area if plastic is not reactive to the type of fuel being stored. 4. Emergency slope protection during heavy rains. 5. Temporary drainpipe ("elephant trunk") used to direct water. 2014 Stormwater Management Manual for Western Washington Volume 11 - Chapter 4 - Page 294 Design and Installation Specifications . Plastic slope cover must be installed as follows: 1. Run plastic up and down slope, not across slope. 2. Plastic may be installed perpendicular to a slope if the slope length is less than 10 feet. 3. Minimum of 8-inch overlap at seams. 4. On long or wide slopes, or slopes subject to wind, tape all seams. 5. Place plastic into a small (12-inch wide by 6-inch deep) slot trench at the top of the slope and backfill with soil to keep water from flowing underneath. 6. Place sand filled burlap or geotextile bags every 3 to 6 feet along seams and tie them together with twine to hold them in place. 7. Inspect plastic for rips, tears, and open seams regularly and repair imme- diately. This prevents high velocity runoff from contacting bare soil which causes extreme erosion. 8. Sandbags may be lowered into place tied to ropes. However, all sandbags must be staked in place. . Plastic sheeting shall have a minimum thickness of 0.06 millimeters. . If erosion at the toe of a slope is likely, a gravel berm, riprap, or other suitable pro- tection shall be installed at the toe of the slope in order to reduce the velocity of run- off. Maintenance Standards . Torn sheets must be replaced and open seams repaired. Completely remove and replace the plastic if it begins to deteriorate due to ultra- violet radiation. . Completely remove plastic when no longer needed. . Dispose of old tires used to weight down plastic sheeting appropriately. Approved as Equivalent Ecology has approved products as able to meet the requirements of BMP C 123: Plastic Covering. The products did not pass through the Technology Assessment Protocol — Ecology (TAPE) process. Local jurisdictions may choose not to accept this product approved as equivalent, or may require additional testing prior to consideration for local use. The products are available for review on Ecology's website at http://www.ecy.wa.gov/programs/wq/stormwater/newtech/equivalent.html 2014 Stormwater Management Manual for Westem Washington Volume // - Chapter 4 - Page 295 BMP C124: Sodding Purpose The purpose of sodding is to establish permanent turf for immediate erosion protection and to stabilize drainage ways where concentrated overland flow will occur. Conditions of Use Sodding may be used in the following areas: . Disturbed areas that require short-term or long-term cover. Disturbed areas that require immediate vegetative cover. . All waterways that require vegetative lining. Waterways may also be seeded rather than sodded, and protected with a net or blanket. Design and Installation Specifications Sod shall be free of weeds, of uniform thickness (approximately 1-inch thick), and shall have a dense root mat for mechanical strength. The following steps are recommended for sod installation: . Shape and smooth the surface to final grade in accordance with the approved grad- ing plan. The swale needs to be overexcavated 4 to 6 inches below design elev- ation to allow room for placing soil amendment and sod. . Amend 4 inches (minimum) of compost into the top 8 inches of the soil if the organic content of the soil is less than ten percent or the permeability is less than 0.6 inches per hour. See http_//www.ecv.wa.gov/prams/swfa/organics/soil.html for further information. . Fertilize according to the supplier's recommendations. . Work lime and fertilizer 1 to 2 inches into the soil, and smooth the surface. . Lay strips of sod beginning at the lowest area to be sodded and perpendicular to the direction of water flow. Wedge strips securely into place. Square the ends of each strip to provide for a close, tight fit. Stagger joints at least 12 inches. Staple on slopes steeper than 3H:1V. Staple the upstream edge of each sod strip. . Roll the sodded area and irrigate. . When sodding is carried out in alternating strips or other patterns, seed the areas between the sod immediately after sodding. 2014 Stormwater Management Manual for Western Washington Volume 11 - Chapter 4 - Page 296 Maintenance Standards If the grass is unhealthy, the cause shall be determined and appropriate action taken to reestablish a healthy groundcover. If it is impossible to establish a healthy groundcover due to frequent saturation, instability, or some other cause, the sod shall be removed, the area seeded with an appropriate mix, and protected with a net or blanket. BMP C125: Topsoiiing / Composting Purpose Topsoiling and composting provide a suitable growth medium for final site stabilization with vegetation. While not a permanent cover practice in itself, topsoiling and com- posting are an integral component of providing permanent cover in those areas where there is an unsuitable soil surface for plant growth. Use this BMP in conjunction with other BMPs such as seeding, mulching, or sodding. Note that this BMP is functionally the same as BMP T5.13: Post -Construction Soil Quality and Depth (p.911) which is required for all disturbed areas that will be developed as lawn or landscaped areas at the completed project site. Native soils and disturbed soils that have been organically amended not only retain much more stormwater, but they also serve as effective biofilters for urban pollutants and, by supporting more vigorous plant growth, reduce the water, fertilizer and pesticides needed to support installed landscapes. Topsoil does not include any subsoils but only the material from the top several inches including organic debris. Conditions of Use . Permanent landscaped areas shall contain healthy topsoil that reduces the need for fertilizers, improves overall topsoil quality, provides for better vegetal health and vitality, improves hydrologic characteristics, and reduces the need for irrigation. . Leave native soils and the duff layer undisturbed to the maximum extent prac- ticable. Stripping of existing, properly functioning soil system and vegetation for the purpose of topsoiling during construction is not acceptable. Preserve existing soil systems in undisturbed and uncompacted conditions if functioning properly. . Areas that already have good topsoil, such as undisturbed areas, do not require soil amendments. . Restore, to the maximum extent practical, native soils disturbed during clearing and grading to a condition equal to or better than the original site condition's mois- ture -holding capacity. Use on -site native topsoil, incorporate amendments into on - site soil, or import blended topsoil to meet this requirement. . Topsoiling is a required procedure when establishing vegetation on shallow soils, and soils of critically low pH (high acid) levels. 2014 Stormwater Management Manual for Western Washington Volume II - Chapter 4 - Page 297 Beware of where the topsoil comes from, and what vegetation was on site before disturbance, invasive plant seeds may be included and could cause problems for establishing native plants, landscaped areas, or grasses. Topsoil from the site will contain mycorrhizal bacteria that are necessary for healthy root growth and nutrient transfer. These native mycorrhiza are acclimated to the site and will provide optimum conditions for establishing grasses. Use com- mercially available mycorrhiza products when using off -site topsoil. Design and Installation Specifications Meet the following requirements for disturbed areas that will be developed as lawn or landscaped areas at the completed project site: Maximize the depth of the topsoil wherever possible to provide the maximum pos- sible infiltration capacity and beneficial growth medium. Topsoil shall have: • A minimum depth of 8-inches. Scarify subsoils below the topsoil layer at least 4-inches with some incorporation of the upper material to avoid stratified lay- ers, where feasible. Ripping or re -structuring the subgrade may also provide additional benefits regarding the overall infiltration and interllow dynamics of the soil system. • A minimum organic content of 10% dry weight in planting beds, and 5% organic matter content in turf areas. Incorporate organic amendments to a minimum 8-inch depth except where tree roots or other natural features limit the depth of incorporation. • A pH between 6.0 and 8.0 or matching the pH of the undisturbed soil. • If blended topsoil is imported, then fines should be limited to 25 percent passing through a 200 sieve. • Mulch planting beds with 2 inches of organic material Accomplish the required organic content, depth, and pH by returning native topsoil to the site, importing topsoil of sufficient organic content, and/or incorporating organic amendments. When using the option of incorporating amendments to meet the organic content requirement, use compost that meets the compost specification for Bioretention (See BMP T7.30: Bioretention Cells, Swales, and Planter Boxes 959 ), with the exception that the compost may have up to 35% biosolids or manure. Sections three through seven of the document entitled, Guidelines and Resources for Implementing Soil Quality and Depth BMP T5.13 in WDOE Stormwater Man- agement Manual for Western Washington, provides useful guidance for imple- menting whichever option is chosen. It includes guidance for pre -approved default strategies and guidance for custom strategies. Check with your local jurisdiction 2014 Stormwater Management Manual for Western Washington Volume 11- Chapter 4 - Page 298 concerning its acceptance of this guidance. It is available through the organization, Soils for Salmon. As of this printing the document may be found at: http://www.soils- forsalmon.orq/pdf/Soil BMP Manual.pdf. . The final composition and construction of the soil system will result in a natural selection or favoring of certain plant species over time. For example, incorporation of topsoil may favor grasses, while layering with mildly acidic, high -carbon amend- ments may favor more woody vegetation. . Allow sufficient time in scheduling for topsoil spreading prior to seeding, sodding, or planting. . Take care when applying top soil to subsoils with contrasting textures. Sandy top- soil over clayey subsoil is a particularly poor combination, as water creeps along the junction between the soil layers and causes the topsoil to slough. If topsoil and subsoil are not properly bonded, water will not infiltrate the soil profile evenly and it will be difficult to establish vegetation. The best method to prevent a lack of bond- ing is to actually work the topsoil into the layer below for a depth of at least 6 inches. • Field exploration of the site shall be made to determine if there is surface soil of suf- ficient quantity and quality to justify stripping. Topsoil shall be friable and loamy (loam, sandy loam, silt loam, sandy clay loam, and clay loam). Avoid areas of nat- ural ground water recharge. • Stripping shall be confined to the immediate construction area. A 4-inch to 6-inch stripping depth is common, but depth may vary depending on the particular soil. All surface runoff control structures shall be in place prior to stripping. • Do not place topsoil while in a frozen or muddy condition, when the subgrade is excessively wet, or when conditions exist that may otherwise be detrimental to proper grading or proposed sodding or seeding. • In any areas requiring grading remove and stockpile the duff layer and topsoil on site in a designated, controlled area, not adjacent to public resources and critical areas. Stockpiled topsoil is to be reapplied to other portions of the site where feas- ible. . Locate the topsoil stockpile so that it meets specifications and does not interfere with work on the site. It may be possible to locate more than one pile in proximity to areas where topsoil will be used. Stockpiling of topsoil shall occur in the following manner: • Side slopes of the stockpile shall not exceed 2H:1V. . Between October 1 and April 30: 2014 Stormwater Management Manual for Western Washington Volume // - Chapter 4 - Page 299 . An interceptor dike with gravel outlet and silt fence shall surround all topsoil. . Within 2 days complete erosion control seeding, or covering stockpiles with clear plastic, or other mulching materials. Between May 1 and September 30: . An interceptor dike with gravel outlet and silt fence shall surround all topsoil if the stockpile will remain in place for a longer period of time than active construction grading. Within 7 days complete erosion control seeding, or covering stockpiles with clear plastic, or other mulching materials. When native topsoil is to be stockpiled and reused the following should apply to ensure that the mycorrhizal bacterial, earthworms, and other beneficial organisms will not be destroyed: 1. Re -install topsoil within 4 to 6 weeks. 2. Do not allow the saturation of topsoil with water. 3. Do not use plastic covering. Maintenance Standards . Inspect stockpiles regularly, especially after large storm events. Stabilize any areas that have eroded. . Establish soil quality and depth toward the end of construction and once estab- lished, protect from compaction, such as from large machinery use, and from erosion. . Plant and mulch soil after installation. • Leave plant debris or its equivalent on the soil surface to replenish organic matter. . Reduce and adjust, where possible, the use of irrigation, fertilizers, herbicides and pesticides, rather than continuing to implement formerly established practices. BMP C126: Polyacrylamide (PAM) for Soil Erosion Protection Purpose Polyacrylamide (PAM) is used on construction sites to prevent soil erosion. Applying PAM to bare soil in advance of a rain event significantly reduces erosion and controls sediment in two ways. First, PAM increases the soil's available pore volume, 2014 Stormwater Management Manual for Westem Washington Volume 11 - Chapter 4 - Page 300 . Lower speed limits. High vehicle speed increases the amount of dust stirred up from unpaved roads and lots. • Upgrade the road surface strength by improving particle size, shape, and mineral types that make up the surface and base materials. . Add surface gravel to reduce the source of dust emission. Limit the amount of fine particles (those smaller than .075 mm) to 10 to 20 percent. • Use geotextile fabrics to increase the strength of new roads or roads undergoing reconstruction. • Encourage the use of alternate, paved routes, if available. • Restrict use of paved roadways by tracked vehicles and heavy trucks to prevent damage to road surface and base. . Apply chemical dust suppressants using the admix method, blending the product with the top few inches of surface material. Suppressants may also be applied as surface treatments. . Pave unpaved permanent roads and other trafficked areas. . Use vacuum street sweepers. . Remove mud and other dirt promptly so it does not dry and then turn into dust. . Limit dust -causing work on windy days. • Contact your local Air Pollution Control Authority for guidance and training on other dust control measures. Compliance with the local Air Pollution Control Authority constitutes compliance with this BMP. Maintenance Standards Respray area as necessary to keep dust to a minimum. BMP C150: Materials on Band Purpose Keep quantities of erosion prevention and sediment control materials on the project site at all times to be used for regular maintenance and emergency situations such as unex- pected heavy summer rains. Having these materials on -site reduces the time needed to implement BMPs when inspections indicate that existing BMPs are not meeting the Con- struction SWPPP requirements. In addition, contractors can save money by buying some materials in bulk and storing them at their office or yard. 2014 Stormwater Management Manual for Western Washington Volume 11 - Chapter - Page 311 Conditions of Use Construction projects of any size or type can benefit from having materials on hand. A small commercial development project could have a roll of plastic and some gravel available for immediate protection of bare soil and temporary berm construction. A large earthwork project, such as highway construction, might have several tons of straw, several rolls of plastic, flexible pipe, sandbags, geotextile fab- ric and steel "T" posts. Materials are stockpiled and readily available before any site clearing, grubbing, or earthwork begins. A large contractor or developer could keep a stockpile of mater- ials that are available for use on several projects. If storage space at the project site is at a premium, the contractor could maintain the materials at their office or yard. The office or yard must be less than an hour from the project site. Design and Installation Specifications Depending on project type, size, complexity, and length, materials and quantities will vary. A good minimum list of items that will cover numerous situations includes: Material Clear Plastic, 6 mil Drainpipe, 6 or 8 inch diameter Sandbags, filled Straw Bales for mulching, Quarry Spalls Washed Gravel Geotextile Fabric Catch Basin Inserts Steel "T" Posts Silt fence material Straw Wattles Maintenance Standards All materials with the exception of the quarry spalls, steel "T" posts, and gravel should be kept covered and out of both sun and rain. Re -stock materials used as needed. 2014 Stormwater Management Manual for Westem Washington Volume 11 - Chapter 4 - Page 312 BMP C151: Concrete Handling Purpose Concrete work can generate process water and slurry that contain fine particles and high pH, both of which can violate water quality standards in the receiving water. Concrete spillage or concrete discharge to surface waters of the State is prohibited. Use this BMP to minimize and eliminate concrete, concrete process water, and concrete slurry from entering waters of the state. Conditions of Use Any time concrete is used, utilize these management practices. Concrete construction projects include, but are not limited to, the following: . Curbs . Sidewalks . Roads Bridges . Foundations Floors . Runways Design and Installation Specifications . Assure that washout of concrete trucks, chutes, pumps, and internals is performed at an approved off -site location or in designated concrete washout areas. Do not wash out concrete trucks onto the ground, or into storm drains, open ditches, streets, or streams. Refer to BMP C 154: Concrete Washout Area p 317) for inform- ation on concrete washout areas. . Return unused concrete remaining in the truck and pump to the originating batch plant for recycling. Do not dump excess concrete on site, except in designated con- crete washout areas. . Wash off hand tools including, but not limited to, screeds, shovels, rakes, floats, and trowels into formed areas only. . Wash equipment difficult to move, such as concrete pavers in areas that do not dir- ectly drain to natural or constructed stormwater conveyances. • Do not allow washdown from areas, such as concrete aggregate driveways, to drain directly to natural or constructed stormwater conveyances. . Contain washwater and leftover product in a lined container when no formed areas 2014 Stormwater Management Manual for Westem Washington Volume 11 - Chapter - Page 313 are available. Dispose of contained concrete in a manner that does not violate ground water or surface water quality standards. . Always use forms or solid barriers for concrete pours, such as pilings, within 15- feet of surface waters. Referto BMP C252: High 12H Neutralization Using CO2 (p.409) and BMP C253: pH Control for High pH Water (p_412) for pH adjustment requirements. Refer to the Construction Stormwater General Permit for pH monitoring require- ments if the project involves one of the following activities: • Significant concrete work (greater than 1,000 cubic yards poured concrete or recycled concrete used over the life of a project). . The use of engineered soils amended with (but not limited to) Portland cement -treated base, cement kiln dust or fly ash. • Discharging stormwater to segments of water bodies on the 303(d) list (Cat- egory 5) for high pH. Maintenance Standards Check containers for holes in the liner daily during concrete pours and repair the same day. BIVIP C152: Sawcutting and Surfacing Pollution (Prevention Purpose Sawcutting and surfacing operations generate slurry and process water that contains fine particles and high pH (concrete cutting), both of which can violate the water quality standards in the receiving water. Concrete spillage or concrete discharge to surface waters of the State is prohibited. Use this BMP to minimize and eliminate process water and slurry created through sawcutting or surfacing from entering waters of the State. Conditions of Use Utilize these management practices anytime sawcutting or surfacing operations take place. Sawcutting and surfacing operations include, but are not limited to, the following: Sawing . Coring Grinding . Roughening 2014 Stormwater Management Manual for Western Washington Volume 11 - Chapter 4 - Page 314 . Hydro -demolition . Bridge and road surfacing Design and Installation Specifications . Vacuum slurry and cuttings during cutting and surfacing operations. . Slurry and cuttings shall not remain on permanent concrete or asphalt pavement overnight. • Slurry and cuttings shall not drain to any natural or constructed drainage con- veyance including stormwater systems. This may require temporarily blocking catch basins. • Dispose of collected slurry and cuttings in a manner that does not violate ground water or surface water quality standards. . Do not allow process water generated during hydro -demolition, surface rough- ening or similar operations to drain to any natural or constructed drainage con- veyance including stormwater systems. Dispose process water in a manner that does not violate ground water or surface water quality standards. . Handle and dispose cleaning waste material and demolition debris in a manner that does not cause contamination of water. Dispose of sweeping material from a pick-up sweeper at an appropriate disposal site. Maintenance Standards Continually monitor operations to determine whether slurry, cuttings, or process water could enter waters of the state. If inspections show that a violation of water quality stand- ards could occur, stop operations and immediately implement preventive measures such as berms, barriers, secondary containment, and vacuum trucks. DMP C153: Material Delivery, Storage and Containment Purpose Prevent, reduce, or eliminate the discharge of pollutants to the stormwater system or watercourses from material delivery and storage. Minimize the storage of hazardous materials on -site, store materials in a designated area, and install secondary con- tainment. Conditions of Use These procedures are suitable for use at all construction sites with delivery and storage of the following materials: 2014 Stormwater Management Manual for Westem Washington Volume 11 - Chapter 4 - Page 315 • Petroleum products such as fuel, oil and grease . Soil stabilizers and binders (e.g., Polyacrylamide) . Fertilizers, pesticides and herbicides • Detergents . Asphalt and concrete compounds • Hazardous chemicals such as acids, lime, adhesives, paints, solvents, and curing compounds . Any other material that may be detrimental if released to the environment Design and Installation Specifications The following steps should be taken to minimize risk: • Temporary storage area should be located away from vehicular traffic, near the con- struction entrance(s), and away from waterways or storm drains. • Material Safety Data Sheets (MSDS) should be supplied for all materials stored. Chemicals should be kept in their original labeled containers. . Hazardous material storage on -site should be minimized. . Hazardous materials should be handled as infrequently as possible. . During the wet weather season (Oct 1 — April 30), consider storing materials in a covered area. . Materials should be stored in secondary containments, such as earthen dike, horse trough, or even a children's wading pool for non -reactive materials'such as deter- gents, oil, grease, and paints. Small amounts of material may be secondarily con- tained in "bus boy" trays or concrete mixing trays. • Do not store chemicals, drums, or bagged materials directly on the ground. Place these items on a pallet and, when possible, and within secondary containment. • If drums must be kept uncovered, store them at a slight angle to reduce ponding of rainwater on the lids to reduce corrosion. Domed plastic covers are inexpensive and snap to the top of drums, preventing water from collecting. Material Storage Areas and Secondary Containment Practices: • Liquids, petroleum products, and substances listed in 40 CFR Parts 110, 117, or 302 shall be stored in approved containers and drums and shall not be overfilled. Containers and drums shall be stored in temporary secondary containment facil- ities. • Temporary secondary containment facilities shall provide for a spill containment 2014 Stormwater Management Manual for Westem Washington Volume 11 - Chapter 4 - Page 316 volume able to contain 10% of the total enclosed container volume of all con- tainers, or 110% of the capacity of the largest container within its boundary, whichever is greater. . Secondary containment facilities shall be impervious to the materials stored therein for a minimum contact time of 72 hours. . Secondary containment facilities shall be maintained free of accumulated rain- water and spills. In the event of spills or leaks, accumulated rainwater and spills shall be collected and placed into drums. These liquids shall be handled as haz- ardous waste unless testing determines them to be non -hazardous. . Sufficient separation should be provided between stored containers to allow for spill cleanup and emergency response access. . During the wet weather season (Oct 1 —April 30), each secondary containment facility shall be covered during non -working days, prior to and during rain events. . Keep material storage areas clean, organized and equipped with an ample supply of appropriate spill clean-up material (spill kit). . The spill kit should include, at a minimum: 1-Water Resistant Nylon Bag 3-Oil Absorbent Socks 3"x 4' 2-Oil Absorbent Socks 3"x 10' 12-Oil Absorbent Pads 17"x19" 1-Pair Splash Resistant Goggles 3-Pair Nitrile Gloves 10-Disposable Bags with Ties Instructions BMP C154: Concrete Washout Area Purpose Prevent or reduce the discharge of pollutants to stormwater from concrete waste by con- ducting washout off -site, or performing on -site washout in a designated area to prevent pollutants from entering surface waters or ground water. Conditions of Use Concrete washout area best management practices are implemented on construction projects where: 2014 Stormwater Management Manual for Western Washington Volume 11 - Chapter 4 - Page 317 . Concrete is used as a construction material • It is not possible to dispose of all concrete wastewater and washout off -site (ready mix plant, etc.). . Concrete trucks, pumpers, or other concrete coated equipment are washed on -site. • Note: If less than 10 concrete trucks or pumpers need to be washed out on -site, the washwater may be disposed of in a formed area awaiting concrete or an upland disposal site where it will not contaminate surface or ground water. The upland dis- posal site shall be at least 50 feet from sensitive areas such as storm drains, open ditches, or water bodies, including wetlands. Design and Installation Specifications Implementation The following steps will help reduce stormwater pollution from concrete wastes: • Perform washout of concrete trucks at an approved off -site location or in des- ignated concrete washout areas only. . Do not wash out concrete trucks onto the ground, or into storm drains, open ditches, streets, or streams. . Do not allow excess concrete to be dumped on -site, except in designated concrete washout areas. Concrete washout areas may be prefabricated concrete washout containers, or self -installed structures (above -grade or below -grade). . Prefabricated containers are most resistant to damage and protect against spills and leaks. Companies may offer delivery service and provide regular maintenance and disposal of solid and liquid waste. • If self -installed concrete washout areas are used, below -grade structures are pre- ferred over above -grade structures because they are less prone to spills and leaks. • Self -installed above -grade structures should only be used if excavation is not prac- tical. Education Discuss the concrete management techniques described in this BMP with the ready -mix concrete supplier before any deliveries are made. . Educate employees and subcontractors on the concrete waste management tech- niques described in this BMP. . Arrange for contractor's superintendent or Certified Erosion and Sediment Control 2014 Stormwater Management Manual for Western Washington Volume 11 - Chapter 4 - Page 318 Lead (CESCL) to oversee and enforce concrete waste management procedures. A sign should be installed adjacent to each temporary concrete washout facility to inform concrete equipment operators to utilize the proper facilities. Contracts Incorporate requirements for concrete waste management into concrete supplier and sub- contractor agreements. Location and Placement Locate washout area at least 50 feet from sensitive areas such as storm drains, open ditches, or water bodies, including wetlands. . Allow convenient access for concrete trucks, preferably near the area where the concrete is being poured. . If trucks need to leave a paved area to access washout, prevent track -out with a pad of rock or quarry spalls (see BMP C105: Stabilized Construction Entrance / Exit (p.270)). These areas should be far enough away from other construction traffic to reduce the likelihood of accidental damage and spills. . The number of facilities you install should depend on the expected demand for stor- age capacity. . On large sites with extensive concrete work, washouts should be placed in mul- tiple locations for ease of use by concrete truck drivers. On -site Temporary Concrete Washout Facility, Transit Truck Washout Procedures: . Temporary concrete washout facilities shall be located a minimum of 50 ft from sensitive areas including storm drain inlets, open drainage facilities, and water- courses. See Figure II-4.1.7a Concrete Washout Area (p.322), Figure II-4.1.7b Con- crete Washout Area (1?.323), and Figure 11-4.1.8 Prefabricated Concrete Washout Container wlRamp (p.324). Concrete washout facilities shall be constructed and maintained in sufficient quant- ity and size to contain all liquid and concrete waste generated by washout oper- ations. - Washout of concrete trucks shall be performed in designated areas only. • Concrete washout from concrete pumper bins can be washed into concrete pumper trucks and discharged into designated washout area or properly disposed of off -site. • Once concrete wastes are washed into the designated area and allowed to 2014 Stormwater Management Manual for Westem Washington Volume 11- Chapter - Page 319 harden, the concrete should be broken up, removed, and disposed of per applic- able solid waste regulations. Dispose of hardened concrete on a regular basis. Temporary Above -Grade Concrete Washout Facility . Temporary concrete washout facility (type above grade) should be con- structed as shown on the details below, with a recommended minimum length and minimum width of 10 ft, but with sufficient quantity and volume to contain all liquid and concrete waste generated by washout operations. • Plastic lining material should be a minimum of 10 mil polyethylene sheeting and should be free of holes, tears, or other defects that compromise the imper- meability of the material. . Temporarti Below -Grade Concrete Washout Facilitv Temporary concrete washout facilities (type below grade) should be con- structed as shown on the details below, with a recommended minimum length and minimum width of 10 ft. The quantity and volume should be suf- ficient to contain all liquid and concrete waste generated by washout oper- ations. . Lath and flagging should be commercial type. Plastic lining material shall be a minimum of 10 mil polyethylene sheeting and should be free of holes, tears, or other defects that compromise the imper- meability of the material. Liner seams shall be installed in accordance with manufacturers' recom- mendations. . Soil base shall be prepared free of rocks or other debris that may cause tears or holes in the plastic lining material. Maintenance Standards Inspection and Maintenance Inspect and verifv that concrete washout BMPs are in place prior to the com- mencement of concrete work. . Durin eriods of concrete work inspect dailV to verify continued performance. Check overall condition and performance. . Check remaining capacity (% full). . If using self -installed washout facilities, verify plastic liners are intact and side - walls are not damaged. If using prefabricated containers, check for leaks. 2014 Stormwater Management Manual for Western Washington Volume 11 - Chapter 4 - Page 320 . Washout facilities shall be maintained to provide adequate holding capacity with a minimum freeboard of 12 inches. . Washout facilities must be cleaned, or new facilities must be constructed and readv for use once the washout is 75% full. If the washout is nearing capacity, vacuum and dispose of the waste material in an approved manner. • Do not discharge liquid or slurry to waterways, storm drains or directly onto ground. . Do not use sanitary sewer without local approval. • Place a secure, non -collapsing, non -water collecting cover over the concrete washout facility prior to predicted wet weather to prevent accumulation and overflow of precipitation. • Remove and dispose of hardened concrete and return the structure to a func- tional condition. Concrete may be reused on -site or hauled away for disposal or recycling. When you remove materials from the self -installed concrete washout, build a new structure; or, if the previous structure is still intact, inspect for signs of weakening or damage, and make any necessary repairs. Re -line the structure with new plastic after each cleaning. Removal of Temporary Concrete Washout Facilities When temporary concrete washout facilities are no longer required for the work, the hardened concrete, slurries and liquids shall be removed and properly dis- posed of. Materials used to construct temporary concrete washout facilities shall be removed from the site of the work and disposed of or recycled. Holes, depressions or other ground disturbance caused by the removal of the tem- porary concrete washout facilities shall be backfilled, repaired, and stabilized to prevent erosion. 2014 Stormwater Management Manual for Westem Washington Volume 11 - Chapter 4 - Page 321 0 Varies I I Figure 11-4.1.7a Concrete Washout Area 3m Minimum � a Plan Lath and flagging on 3 sides 6 - Sandbag — Berm 10 mil plastic lining At A } 1m x Section A -A - 10 mil plastic lining Type "Below Grade" Stake (typ.) iil plastic lining Sandbag Berm 1. Actual layout determined in the field. 2. A concrete washout sign shall be installed within 10 m of the temporary concrete washout facility. Wood frame securely fastened around entire perimeter with two stakes 10 mil plastic lining Section B-B 2x12 rough Plan wood frame Tvpe "Above Grade" with Wood Planks NOT TO SCALE 1 Figure II-4.1.7a Concrete Washout Area DEPARTMENT OF Revised June2015 ECOLOGY Please see http://www.ecy.wa.govlcopyright.html for copyright notice including permissions, State of Washington limitation of liability, and disclaimer. 2014 Stormwater Management Manual for Westem Washington Volume 11 - Chapter 4 - Page 322 Straw bale Staples (2 per bale) Wood or metal stakes (2 per bale) Figure II-4.1.7b Concrete Washout Area 10 mil plastic lining Native material (optional) !� - 3m Minimum T Stake (typ) -� 131 Varies L Straw bale (typ•) la s ■ is ■ ■ ■ ■ a ■ wamm� DEPARTMENT OF ECOLOGY State of Washington Plan Binding wire Plywood 1200 mm x 610 mm Wood post painted white (89 mm x 89 mm Lag screws x 2.4 m) (12.5 mm) CONCRETE' ' WASHOUT ` Black letters 150 mm height 915 mm 915 mm T Concrete Washout Sign Detail (or equivalent} 1B \ - 10 mil plastic lining ��— 50 mm 200 mm � steel mm dia. steel wire Staple Detail Notes: 1. Actual layout determined in the field. 2. The concrete washout sign shall be installed within 10 m of the temporary concrete washout facility. Type "Above Grade" with Straw Bales Figure II-4.1.7b Concrete Washout Area NOT TO SCALE Revised June 2015 Please see http://www.ecy. wa. gov/copyright html for copyright notice including permissions, limitation of liability, and disclaimer. 2014 Stormwater Management Manual for Western Washington Volume 11 - Chapter - Page 323 Figure II-4.1.8 Prefabricated Concrete Washout Container w/Ramp NOT TO SCALE 0110� Figure II-4.1.8 Prefabricated Concrete Washout Container w/Ramp DEPARTMENT OF Revised June 2015 ECOLOGY Please see http://www.ecy. wa.gov/copyright.html for copyright notice including permissions, State of Washingtoni limitation of liability, and disclaimer. 2014 Stormwater Management Manual for Western Washington Volume 11- Chapter 4 - Page 324 BMP C160: Certified Erosion and Sediment Control Lead Purpose The project proponent designates at least one person as the responsible representative in charge of erosion and sediment control (ESC), and water quality protection. The des- ignated person shall be the Certified Erosion and Sediment Control Lead (CESCL) who is responsible for ensuring compliance with all local, state, and federal erosion and sed- iment control and water quality requirements. Conditions of Use A CESCL shall be made available on projects one acre or larger that discharge storm - water to surface waters of the state. Sites less than one acre may have a person without CESCL certification conduct inspections; sampling is not required on sites that disturb less than an acre. . The CESCL shall: . Have a current certificate proving attendance in an erosion and sediment con- trol training course that meets the minimum ESC training and certification requirements established by Ecology (see details below). Ecology will maintain a list of ESC training and certification providers at: hftp:/AAtww.ecy.wa.gov/programs/wq/Stormwater/cesci.html OR Be a Certified Professional in Erosion and Sediment Control (CPESC); for additional information go to: http:/twww.envirocertintl.org/cpesc/ Specifications • Certification shall remain valid for three years. . The CESCL shall have authority to act on behalf of the contractor or developer and shall be available, or on -call, 24 hours per day throughout the period of con- struction. . The Construction SWPPP shall include the name, telephone number, fax number, and address of the designated CESCL. e A CESCL may provide inspection and compliance services for multiple con- struction projects in the same geographic region. Duties and responsibilities of the CESCL shall include, but are not limited to the fol- lowing: 2014 Stormwater Management Manual for Westem Washington Volume 11 - Chapter - Page 325 . Maintaining permit file on site at all times which includes the Construction SWPPP and any associated permits and plans. . Directing BMP installation, inspection, maintenance, modification, and removal. • Updating all project drawings and the Construction SWPPP with changes made. . Completing any sampling requirements including reporting results using WebDMR. • Keeping daily logs, and inspection reports. Inspection reports should include: . Inspection date/time. . Weather information; general conditions during inspection and approximate amount of precipitation since the last inspection. . A summary or list of all BMPs implemented, including observations of all erosion/sediment control structures or practices. The following shall be noted: 1. Locations of BMPs inspected. 2. Locations of BMPs that need maintenance. 3. Locations of BMPs that failed to operate as designed or intended. 4. Locations of where additional or different BMPs are required. . Visual monitoring results, including a description of discharged stormwater. The presence of suspended sediment, turbid water, discoloration, and oil sheen shall be noted, as applicable. . Any water quality monitoring performed during inspection. • General comments and notes, including a brief description of any BMP repairs, maintenance or installations made as a result of the inspection. Facilitate, participate in, and take corrective actions resulting from inspections per- formed by outside agencies or the owner. BMP C162: Scheduling Purpose Sequencing a construction project reduces the amount and duration of soil exposed to erosion by wind, rain, runoff, and vehicle tracking. Conditions of Use The construction sequence schedule is an orderly listing of all major land -disturbing activities together with the necessary erosion and sedimentation control measures 2014 Stormwater Management Manual for Westem Washington Volume 11 - Chapter 4 - Page 326 planned for the project. This type of schedule guides the contractor on work to be done before other work is started so that serious erosion and sedimentation problems can be avoided. Following a specified work schedule that coordinates the timing of land -disturbing activ- ities and the installation of control measures is perhaps the most cost-effective way of controlling erosion during construction. The removal of surface ground cover leaves a site vulnerable to accelerated erosion. Construction procedures that limit land clearing provide timely installation of erosion and sedimentation controls, and restore protective cover quickly can significantly reduce the erosion potential of a site. Design Considerations Minimize construction during rainy periods. Schedule projects to disturb only small portions of the site at any one time. Com- plete grading as soon as possible. Immediately stabilize the disturbed portion before grading the next portion. Practice staged seeding in order to revegetate cut and fill slopes as the work progresses. 11-4.2 Runoff Conveyance and Treatment BMPs This section contains the standards and specifications for Runoff Conveyance and Treat- ment BMPs. Table II-4.2.1 Runoff Conveyance and Treatment BMPs by SWPPP Ele- ment (p.327), below, shows the relationship of the BMPs in II-4.2 Runoff Conveyance and Treatment BMPs to the Construction Stormwater Pollution Prevention Plan (SWPPP) Elements described in II-3.3.3 Ste 3 - Construction SWPPP Development and Implementation .236 . Table 11-4.2.1 Runoff Conveyance and Treatment BMPs by SWPPP Element Ele- (Element (Element Ele- ment #4 Ele- Ele- #8 Stab- ment Element #3 Install ment ment ilize Element #10 #13 Protect BMP or Ele- Con- , Sed- #6 Pro- #? Pro- Chan- #9 Con- , Pol- Control Low Impact ment Name trot iment tect tect nels trol De- Devel- Flow Con- Slopes bets and Out lutants Water- opment i Rates trols lets ing BMP C200: ✓ ✓ Interceptor Dike and Swale .331 2014 Stormwater Management Manual for Western Washington Volume 11 - Chapter 4 - Page 327 1. If the discharge velocity at the outlet is less than 5 fps (pipe slope less than 1 percent), use 2-inch to 8-inch riprap. Minimum thickness is 1-foot. 2. For 5 to 10 fps discharge velocity at the outlet (pipe slope less than 3 per- cent), use 24-inch to 48-inch riprap. Minimum thickness is 2 feet. 3. For outlets at the base of steep slope pipes (pipe slope greater than 10 per- cent), an engineered energy dissipater shall be used. . Filter fabric or erosion control blankets should always be used under riprap to pre- vent scour and channel erosion. . New pipe outfalls can provide an opportunity for low-cost fish habitat improve- ments. For example, an alcove of low -velocity water can be created by con- structing the pipe outfall and associated energy dissipater back from the stream edge and digging a channel, over -widened to the upstream side, from the outfall. Overwintering juvenile and migrating adult salmonids may use the alcove as shel- ter during high flows. Bank stabilization, bioengineering, and habitat features may be required for disturbed areas. This work may require a HPA. See Volume V 765 for more information on outfall system design. Maintenance Standards • Inspect and repair as needed. . Add rock as needed to maintain the intended function. . Clean energy dissipater if sediment builds up. DMP C220: Storm Drain inlet Protection Purpose Storm drain inlet protection prevents coarse sediment from entering drainage systems prior to permanent stabilization of the disturbed area. Conditions of Use Use storm drain inlet protection at inlets that are operational before permanent sta- bilization of the disturbed drainage area. Provide protection for all storm drain inlets downslope and within 500 feet of a disturbed or construction area, unless conveying run- off entering catch basins to a sediment pond or trap. Also consider inlet protection for lawn and yard drains on new home construction. These small and numerous drains coupled with lack of gutters in new home construction can add significant amounts of sediment into the roof drain system. If possible delay installing lawn and yard drains until just before landscaping or cap these drains to pre- 2014 Stormwater Management Manual for Western Washington Volume 11 - Chapter - Page 357 vent sediment from entering the system until completion of landscaping. Provide 18- inches of sod around each finished lawn and yard drain. Table II-4.2.2 Storm Drain Inlet Protection .358) lists several options for inlet protection. All of the methods for storm drain inlet protection tend to plug and require a high fre- quency of maintenance. Limit drainage areas to one acre or less. Possibly provide emer- gency overflows with additional end -of -pipe treatment where stormwater ponding would cause a hazard. Table H-4.2o2 Storm Drain inlet Protection Type of Inlet Emergency Applicable for Paved/ Earthen Conditions of Use Protection j Overflow Surfaces Drop Inlet Protection Yes, tem- Applicable for heavy flows. Easy Excavated drop porary flood- Earthen to maintain. Large area Require- inletprotection ing will occur ment: 30'x30'/acre _ Block and Applicable for heavy concentrated gravel drop inlet Yes Paved or Earthen flows. Will not pond. protection Gravel and wire Applicable for heavy concentrated drop inlet pro- No flows. Will pond. Can withstand tection traffic. Catch basin fil- Yes Paved or Earthen Frequent Maintenance required. ters Curb Inlet Protection Curb inlet pro- Small capacity Used for sturdy, more compact tection with overflow Paved installation. wooden weir Block and gravel curb inlet Yes Paved Sturdy, but limited filtration. p rote cti on Culvert Inlet Protection Culvert inlet Sed 18 month expected life. iment trap Design and Installation Specifications Excavated Drop Inlet Protection - An excavated impoundment around the storm drain. Sediment settles out of the stormwater prior to entering the storm drain. 2014 Stormwater Management Manual for Western Washington Volume 11 - Chapter - Page 358 . Provide a depth of 1-2 ft as measured from the crest of the inlet structure. • Slope sides of excavation no steeper than 2H:1 V. . Minimum volume of excavation 35 cubic yards. . Shape basin to fit site with longest dimension oriented toward the longest inflow area. . Install provisions for draining to prevent standing water problems. . Clear the area of all debris. . Grade the approach to the inlet uniformly. . Drill weep holes into the side of the inlet. . Protect weep holes with screen wire and washed aggregate. . Seal weep holes when removing structure and stabilizing area. • Build a temporary dike, if necessary, to the down slope side of the structure to pre- vent bypass flow. Block and Gravel Filter- A barrier formed around the storm drain inlet with standard con- crete blocks and gravel. See Figure II-4.2.8 Block and Gravel Filter (p.360). . Provide a height of 1 to 2 feet above inlet. . Recess the first row 2-inches into the ground for stability. . Support subsequent courses by placing a 2x4 through the block opening. Do not use mortar. Lay some blocks in the bottom row on their side for dewatering the pool. . Place hardware cloth or comparable wire mesh with '/z-inch openings over all block openings. Place gravel just below the top of blocks on slopes of 2H:1 V or flatter. e An alternative design is a gravel donut. Provide an inlet slope of 3H:1V. Provide an outlet slope of 2H:1 V. Provide al -foot wide level stone area between the structure and the inlet. Use inlet slope stones 3 inches in diameter or larger. Use gravel Y2- to 3/-inch at a minimum thickness of 1-foot for the outlet slope. 2014 Stormwater Management Manual for Westem Washington Volume 11 - Chapter 4 - Page 359 Figure 11-4.2.8 Block and Gravel Filter Drain grate X Plan View crete block Gravel backfill Concrete block Wire screen or filter fabric Gravel backfill n Overflow water I./nding height Drop inlet Section A -A Notes: 1. Drop inlet sediment barriers are to be used for small, nearly level drainage areas. (less than 5%) 2. Excavate a basin of sufficient size adjacent to the drop inlet. 3. The top of the structure (ponding height) must be well below the ground elevation downslope to prevent runoff from bypassing the inlet. A temporary dike may be necessary on the downslope side of the structure. NOT TO SCALE i Figure II-4.2.8 Block and Gravel Filter DEPARTMENT OF Revised August 2015 ECOLOGY Please see http://www.ecy. wa gov/copyright html for copyright notice including permissions, State of Washington limitation of liability, and disclaimer. 2014 Stormwater Management Manual for Westem Washington Volume 11- Chapter 4 - Page 360 Gravel and Wire Mesh Filter- A gravel barrier placed over the top of the inlet. This struc- ture does not provide an overflow. . Use a hardware cloth or comparable wire mesh with Y2-inch openings. Use coarse aggregate. Provide a height 1-foot or more, 18-inches wider than inlet on all sides. . Place wire mesh over the drop inlet so that the wire extends a minimum of 1-foot beyond each side of the inlet structure. Overlap the strips if more than one strip of mesh is necessary. Place coarse aggregate over the wire mesh. . Provide at least a 12-inch depth of gravel over the entire inlet opening and extend at least 18-inches on all sides. Catchbasin Filters — Use inserts designed by manufacturers for construction sites. The limited sediment storage capacity increases the amount of inspection and maintenance required, which may be daily for heavy sediment loads. To reduce maintenance require- ments combine a catchbasin filter with another type of inlet protection. This type of inlet protection provides flow bypass without overflow and therefore may be a better method for inlets located along active rights -of -way. • Provides 5 cubic feet of storage. • Requires dewatering provisions. . Provides a high -flow bypass that will not clog under normal use at a construction site. . Insert the catchbasin filter in the catchbasin just below the grating. Curb Inlet Protection with Wooden Weir— Barrier formed around a curb inlet with a wooden frame and gravel. • Use wire mesh with Y2-inch openings. • Use extra strength filter cloth. • Construct a frame. . Attach the wire and filter fabric to the frame. . Pile coarse washed aggregate against wire/fabric. . Place weight on frame anchors. Block and Gravel Curb Inlet Protection — Barrier formed around a curb inlet with concrete blocks and gravel. See Figure II-4.2.9 Block and Gravel Curb Inlet Protection (p.363). 2014 Stormwater Management Manual for Western Washington Volume 11 - Chapter - Page 361 Use wire mesh with Yz-inch openings. Place two concrete blocks on their sides abutting the curb at either side of the inlet opening. These are spacer blocks. . Place a 2x4 stud through the outer holes of each spacer block to align the front blocks. . Place blocks on their sides across the front of the inlet and abutting the spacer blocks. Place wire mesh over the outside vertical face. . Pile coarse aggregate against the wire to the top of the barrier. Curb and Gutter Sediment Barrier— Sandbag or rock berm (riprap and aggregate) 3 feet high and 3 feet wide in a horseshoe shape. See Figure II-4.2.10 Curb and Gutter Barrier 364 . Construct a horseshoe shaped berm, faced with coarse aggregate if using riprap, 3 feet high and 3 feet wide, at least 2 feet from the inlet. . Construct a horseshoe shaped sedimentation trap on the outside of the berm sized to sediment trap standards for protecting a culvert inlet. Maintenance Standards Inspect catch basin filters frequently, especially after storm events. Clean and replace clogged inserts. For systems with clogged stone filters: pull away the stones from the inlet and clean or replace. An alternative approach would be to use the clogged stone as fill and put fresh stone around the inlet. Do not wash sediment into storm drains while cleaning. Spread all excavated material evenly over the surrounding land area or stockpile and stabilize as appro- priate. Approved as Equivalent Ecology has approved products as able to meet the requirements of BMP C220: Storm Drain Inlet Protection. The products did not pass through the Technology Assessment Protocol — Ecology (TAPE) process. Local jurisdictions may choose not to accept this product approved as equivalent, or may require additional testing prior to consideration for local use. The products are available for review on Ecology's website at htt://www.ec .wa. ov/ ro rams/w /stormwater/newtech/e uivalent.html 2014 Stormwater Management Manual for Western Washington Volume // - Chapter 4 - Page 362 Figure 1I-4.2.9 Block and Gravel Curb Inlet Protection Back of sidewalk Back of curb Wire screen or filter fabric inch (2„ ..„„. Drain gravel %a inch (20 mm Drain grave Wire screen or filter fabric 1 M, Plan View Ponding height Section A -A )d stud crete block Notes: 1. Use block and gravel type sediment barrier when curb inlet is located in gently sloping street segment, where water can pond and allow sediment to separate from runoff. 2. Barrier shall allow for overflow from severe storm event. 3. Inspect barriers and remove sediment after each storm event. Sediment and gravel must be removed from the traveled way immediately. NOT TO SCALE Figure II-4.2.9 Block and Gravel Curb Inlet Protection DEPARTMENT OF Revised August 2015 ECOLOGY Please see http://www.ecy.wa gov/copynght.html for copyright notice including permissions, State of Washington limitation of liability, and disclaimer. 2014 Stormwater Management Manual for Westem Washington Volume 11 - Chapter 4 - Page 363 Figure 11-4.2.10 Curb and Gutter Barrier Back of sidewalk Burlap sacks to overlap onto curb Back of curb Runoff Runoff f Spillway Plan View Gravel filled sandbags stacked tightly Curb inlet Catch basin Notes: 1. Place curb type sediment barriers on gently sloping street segments, where water can pond and allow sediment to separate from runoff. 2. Sandbags of either burlap or woven 'geotextile' fabric, are filled with gravel, layered and packed tightly. 3. Leave a one sandbag gap in the top row to provide a spillway for overflow. 4. Inspect barriers and remove sediment after each storm event. Sediment and gravel must be removed from the traveled way immediately. NOT TO SCALE 81"� Figure 11-4.2.10 Curb and Gutter Barrier DEPARTMENT OF Revised September 2015 ECOLOGY Please see http://www.ecy.wa gov/copyright.html for copyright notice including permissions, State of Washington I limitation of liability, and disclaimer. 2014 Stormwater Management Manual for Western Washington Volume 11 - Chapter 4 - Page 364 BMP C232: Gravel Filter Berm Purpose A gravel filter berm is constructed on rights -of -way or traffic areas within a construction site to retain sediment by using a filter berm of gravel or crushed rock. Conditions of Use Where a temporary measure is needed to retain sediment from rights -of -way or in traffic areas on construction sites. Design and Installation Specifications . Berm material shall be 3/ to 3 inches in size, washed well -grade gravel or crushed rock with less than 5 percent fines. . Spacing of berms: Every 300 feet on slopes less than 5 percent o Every 200 feet on slopes between 5 percent and 10 percent o Every 100 feet on slopes greater than 10 percent . Berm dimensions: 1 foot high with 3HAV side slopes 8 linear feet per 1 cfs runoff based on the 10-year, 24-hour design storm Maintenance Standards Regular inspection is required. Sediment shall be removed and filter material replaced as needed. BMP C233: Silt Fence Purpose Use of a silt fence reduces the transport of coarse sediment from a construction site by providing a temporary physical barrier to sediment and reducing the runoff velocities of overland flow. See Figure II-4.2.12 Silt Fence .369 for details on silt fence con- struction. Conditions of Use Silt fence may be used downslope of all disturbed areas. 2014 Stormwater Management Manual for Western Washington Volume 11- Chapter - Page 367 . Silt fence shall prevent soil carried by runoff water from going beneath, through, or over the top of the silt fence, but shall allow the water to pass through the fence. Silt fence is not intended to treat concentrated flows, nor is it intended to treat sub- stantial amounts of overland flow. Convey any concentrated flows through the drainage system to a sediment pond. Do not construct silt fences in streams or use in V-shaped ditches. Silt fences do not provide an adequate method of silt control for anything deeper than sheet or overland flow. 2014 Stormwater Management Manual for Westem Washington Volume 11 - Chapter 4 - Page 368 Figure 11-4.2.12 Silt Fence Joints in filter fabric shall be spliced at posts. Use staples, wire rings or equivalent to attach fabric to posts 2"x2" by 14 Ga. wire or equivalent, if standard strength fabric used r r------------------------ r.l Minimum I I 6' max I I 4"x4"trench I_ � I Post spacing may be increased to 8' if wire backing is used 2"x2" wood posts, steel fence posts, or equivalent DEPARTMENT OF ECOLOGY State of Washington 2'W" by 14 Ga. wire or equivalent, if standard strength fabric used Backfill trench with native soil or %" - 1.5" washed gravel Filter fabric 2' min Minimum 4"x4" trench 2"x2" wood posts, steel fence posts, or equivalent Figure II-4.2.12 Silt Fence NOT TO SCALE Revised October 2014 Please see http://www.ecy.wa.govlcopyright.html for copyright notice including permissions, limitation of liability, and disclaimer. 2014 Stormwater Management Manual for Western Washington Volume 11 - Chapter 4 - Page 369 Design and Installation Specifications . Use in combination with sediment basins or other BMPs. . Maximum slope steepness (normal (perpendicular) to fence line) 1 H:1 V. C Maximum sheet or overland flow path length to the fence of 100 feet. . Do not allow flows greater than 0.5 cfs. . The geotextile used shall meet the following standards. All geotextile properties lis- ted below are minimum average roll values (i.e., the test result for any sampled roll in a lot shall meet or exceed the values shown in Table II-4.2.3 Geotextile Stand - ands (p.3 Table 11-4.2.3 Geotextile Standards 0.60 mm maximum for slit film woven (#30 sieve). Polymeric Mesh AOS 0.30 mm maximum for all other geotextile types (#50 sieve). (ASTM D4751) 0.15 mm minimum for all fabric types (#100 sieve). Water Permittivity 0.02 sec-1 minimum (ASTM D4491) Grab Tensile Strength 180 lbs. Minimum for extra strength fabric. (ASTM D4632) 100 lbs minimum for standard strength fabric. Grab Tensile Strength 30% maximum (ASTM D4632) Ultraviolet Resistance 70% minimum (ASTM D4355) . Support standard strength fabrics with wire mesh, chicken wire, 2-inch x 2-inch wire, safety fence, or jute mesh to increase the strength of the fabric. Silt fence materials are available that have synthetic mesh backing attached. Filter fabric material shall contain ultraviolet ray inhibitors and stabilizers to provide a minimum of six months of expected usable construction life at a temperature range of 0°F. to 120°F. . One -hundred percent biodegradable silt fence is available that is strong, long last- ing, and can be left in place after the project is completed, if permitted by local reg- ulations. . Refer to Figure II-4.2.12 Silt Fence .369 for standard silt fence details. Include the following standard Notes for silt fence on construction plans and specifications: 2014 Stormwater Management Manual for Western Washington Volume 11 - Chapter - Page 370 1. The contractor shall install and maintain temporary silt fences at the locations shown in the Plans. 2. Construct silt fences in areas of clearing, grading, or drainage prior to starting those activities. 3. The silt fence shall have a 2-feet min. and a 2Y2-feet max. height above the original ground surface. 4. The filter fabric shall be sewn together at the point of manufacture to form fil- ter fabric lengths as required. Locate all sewn seams at support posts. Altern- atively, two sections of silt fence can be overlapped, provided the Contractor can demonstrate, to the satisfaction of the Engineer, that the overlap is long enough and that the adjacent fence sections are close enough together to prevent silt laden water from escaping through the fence at the overlap. 5. Attach the filter fabric on the up -slope side of the posts and secure with staples, wire, or in accordance with the manufacturer's recommendations. Attach the filter fabric to the posts in a manner that reduces the potential for tearing. 6. Support the filter fabric with wire or plastic mesh, dependent on the properties of the geotextile selected for use. If wire or plastic mesh is used, fasten the mesh securely to the up -slope side of the posts with the filter fabric up -slope of the mesh. 7. Mesh support, if used, shall consist of steel wire with a maximum mesh spa- cing of 2-inches, or a prefabricated polymeric mesh. The strength of the wire or polymeric mesh shall be equivalent to or greater than 180 lbs. grab tensile strength. The polymeric mesh must be as resistant to the same level of ultra- violet radiation as the filter fabric it supports. 8. Bury the bottom of the filter fabric 4-inches min. below the ground surface. Backfill and tamp soil in place over the buried portion of the filter fabric, so that no flow can pass beneath the fence and scouring cannot occur. When wire or polymeric back-up support mesh is used, the wire or polymeric mesh shall extend into the ground 3-inches min. 9. Drive or place the fence posts into the ground 18-inches min. A 12—inch min. depth is allowed if topsoil or other soft subgrade soil is not present and 18- inches cannot be reached. Increase fence post min. depths by 6 inches if the fence is located on slopes of 3H:1 V or steeper and the slope is perpendicular to the fence. If required post depths cannot be obtained, the posts shall be adequately secured by bracing or guying to prevent overturning of the fence due to sediment loading. 10. Use wood, steel or equivalent posts. The spacing of the support posts shall 2014 Stormwater Management Manual for Westem Washington Volume 11 - Chapter - Page 371 be a maximum of 6-feet. Posts shall consist of either: Wood with dimensions of 2-inches by 2-inches wide min. and a 3-feet min. length. Wood posts shall be free of defects such as knots, splits, or gouges. No. 6 steel rebar or larger. . ASTM A 120 steel pipe with a minimum diameter of 1-inch. U, T, L, or C shape steel posts with a minimum weight of 1.35 lbs./ft. Other steel posts having equivalent strength and bending resistance to the post sizes listed above. 11. Locate silt fences on contour as much as possible, except at the ends of the fence, where the fence shall be turned uphill such that the silt fence captures the runoff water and prevents water from flowing around the end of the fence. 12. If the fence must cross contours, with the exception of the ends of the fence, place gravel check dams perpendicular to the back of the fence to minimize concentrated flow and erosion. The slope of the fence line where contours must be crossed shall not be steeper than 3H:1 V. Gravel check dams shall be approximately 1-foot deep at the back of the fence. Gravel check dams shall be continued perpendicular to the fence at the same elevation until the top of the check dam intercepts the ground surface behind the fence. Gravel check dams shall consist of crushed surfacing base course, I ravel backfill for walls, or shoulder ballast. Gravel check dams shall be located every 10 feet along the fence where the fence must cross con- tours. Refer to Fic]LHo II-4.2.13 Silt Fence Installation by Slicing Method (p.374} for slicing method details. Silt fence installation using the slicing method specifications: The base of both end posts must be at least 2- to 4-inches above the top of the filter fabric on the middle posts for ditch checks to drain properly. Use a hand level or string level, if necessary, to mark base points before install- ation. 2. Install posts 3- to 4-feet apart in critical retention areas and 6- to 7-feet apart in standard applications. 3. Install posts 24-inches deep on the downstream side of the silt fence, and as close as possible to the filter fabric, enabling posts to support the filter fabric from upstream water pressure. 4. Install posts with the nipples facing away from the filter fabric. 2014 Stormwater Management Manual for Westem Washington Volume 11 - Chapter 4 - Page 372 5. Attach the filter fabric to each post with three ties, all spaced within the top 8- inches of the filter fabric. Attach each tie diagonally 45 degrees through the fil- ter fabric, with each puncture at least 1-inch vertically apart. Each tie should be positioned to hang on a post nipple when tightening to prevent sagging. 6. Wrap approximately 6-inches of fabric around the end posts and secure with 3 ties. 7. No more than 24-inches of a 36-inch filter fabric is allowed above ground level. Compact the soil immediately next to the filter fabric with the front wheel of the tractor, skid steer, or roller exerting at least 60 pounds per square inch. Compact the upstream side first and then each side twice for a total of four trips. Check and correct the silt fence installation for any deviation before compaction. Use a flat -bladed shovel to tuck fabric deeper into the ground if necessary. 2014 Stormwater Management Manual for Westem Washington Volume 11 - Chapter 4 - Page 373 Figure I1-4.2.13 Silt Fence Installation by Slicing Method Ponding height max. 24" Attach fabric to upstream side of post FLOW — Drive over each side of silt fence 2 to 4 times with device exerting 60 p.s.i. or greater 100% compaction POST SPACING: 7' max. on open runs 4' max. on pooling areas POST DEPTH: As much below ground as fabric above ground 100% No more than 24" of a 36" fabric is allowed above ground f Operation Horizontal chisel point (76 mm width) Top of Fabric Belt topy 8" 1 Diagonal attachment doubles strength Attachment Details: • Gather fabric at posts, if needed. • Utilize three ties per post, all within top 8" of fabric. • Position each tie diagonally, puncturing holes vertically a minimum of 1" apart. • Hang each tie on a post nipple and tighten securely. Use cable ties (50 Ibs) or soft wire. Roll of silt fence Slicing blade (18 mm width) Vibratory plow is not acceptable because of horizontal compaction DEPARTMENT OF ECOLOGY State of Washington Fabric above ground 200 - 300mm r Post installed after compaction Silt Fence Completed Installation NOT TO SCALE Figure II-4.2.13 Silt Fence Installation by Slicing Method Revised November 2015 Please see http://www ecy wa gov/copyright html for copyright notice including permissions, limitation of liability, and disclaimer. 2014 Stonnwater Management Manual for Westem Washington Volume 11 - Chapter 4 - Page 374 Maintenance Standards . Repair any damage immediately. Intercept and convey all evident concentrated flows uphill of the silt fence to a sed- iment pond. . Check the uphill side of the fence for signs of the fence clogging and acting as a barrier to flow and then causing channelization of flows parallel to the fence. If this occurs, replace the fence or remove the trapped sediment. . Remove sediment deposits when the deposit reaches approximately one-third the height of the silt fence, or install a second silt fence. . Replace filter fabric that has deteriorated due to ultraviolet breakdown. B M P C234: Vegetated Strip Purpose Vegetated strips reduce the transport of coarse sediment from a construction site by providing a temporary physical barrier to sediment and reducing the runoff velocities of overland flow. Conditions of Use . Vegetated strips may be used downslope of all disturbed areas. Vegetated strips are not intended to treat concentrated flows, nor are they intended to treat substantial amounts of overland flow. Any concentrated flows must be con- veyed through the drainage system to a sediment pond. The only circumstance in which overland flow can be treated solely by a strip, rather than by a sediment pond, is when the following criteria are met (see Table II-4.2.4 Contributing Drain- age Area for Vegetated Strips (p.375)): Table II-4.2.4 Contributing Drainage Area for Vegetated Strips Average Contributing Area Slope Average Contributing Area Percent Slope Max Contributing area Flowpath Length 1.5H : IV or flatter 67% or flatter 100 feet 2H : 1 V or flatter 50% or flatter 115 feet 4H : IV or flatter 25% or flatter 1150 feet 6H : 1 V or flatter 16.7% or flatter 200 feet 1 OH : 1 V or flatter 10% or flatter 250 feet 2014 Stormwater Management Manual for Western Washington Volume 11 - Chapter 4 - Page 375 Design and Installation Specifications The vegetated strip shall consist of a minimum of a 25-foot flowpath length con- tinuous strip of dense vegetation with topsoil. Grass -covered, landscaped areas are generally not adequate because the volume of sediment overwhelms the grass. Ideally, vegetated strips shall consist of undisturbed native growth with a well -developed soil that allows for infiltration of runoff. . The slope within the strip shall not exceed 4H:1V. . The uphill boundary of the vegetated strip shall be delineated with clearing limits. Maintenance Standards . Any areas damaged by erosion or construction activity shall be seeded imme- diately and protected by mulch. . If more than 5 feet of the original vegetated strip width has had vegetation removed or is being eroded, sod must be installed. If there are indications that concentrated flows are traveling across the buffer, sur- face water controls must be installed to reduce the flows entering the buffer, or addi- tional perimeter protection must be installed. BMP C235: Wattles Purpose Wattles are temporary erosion and sediment control barriers consisting of straw, com- post, or other material that is wrapped in biodegradable tubular plastic or similar encas- ing material. They reduce the velocity and can spread the flow of rill and sheet runoff, and can capture and retain sediment. Wattles are typically 8 to 10 inches in diameter and 25 to 30 feet in length. Wattles are placed in shallow trenches and staked along the contour of disturbed or newly constructed slopes. See Figure 11-4.2.14 Wattles (p.378j for typical construction details. WSDOT Standard Plan 1-30.30-00 also provides information on Wattles (http://www.wsdot.wa.gov/Design/Standards/Plans.htm#Sectioni) Conditions of Use . Use wattles: . In disturbed areas that require immediate erosion protection. On exposed soils during the period of short construction delays, or over winter months. On slopes requiring stabilization until permanent vegetation can be estab- lished. 2014 Stormwater Management Manual for Westem Washington Volume 11- Chapter - Page 376 . The material used dictates the effectiveness period of the wattle. Generally, Wattles are typically effective for one to two seasons. • Prevent rilling beneath wattles by properly entrenching and abutting wattles together to prevent water from passing between them. Design Criteria Install wattles perpendicular to the flow direction and parallel to the slope contour. Narrow trenches should be dug across the slope on contour to a depth of 3- to 5- inches on clay soils and soils with gradual slopes. On loose soils, steep slopes, and areas with high rainfall, the trenches should be dug to a depth of 5- to 7- inches, or 1/2 to 2/3 of the thickness of the wattle. Start building trenches and installing wattles from the base of the slope and work up. Spread excavated material evenly along the uphill slope and compacted using hand tamping or other methods. • Construct trenches at intervals of 10- to 25-feet depending on the steepness of the slope, soil type, and rainfall. The steeper the slope the closer together the trenches. • Install the wattles snugly into the trenches and abut tightly end to end. Do not over- lap the ends. • Install stakes at each end of the wattle, and at 4-foot centers along entire length of wattle. • If required, install pilot holes for the stakes using a straight bar to drive holes through the wattle and into the soil. • Wooden stakes should be approximately 3/4 x 3/4 x 24 inches min. Willow cuttings or 3/8-inch rebar can also be used for stakes. . Stakes should be driven through the middle of the wattle, leaving 2 to 3 inches of the stake protruding above the wattle. Maintenance Standards . Wattles may require maintenance to ensure they are in contact with soil and thor- oughly entrenched, especially after significant rainfall on steep sandy soils. 2014 Stormwater Management Manual for Western Washington Volume 11 - Chapter 4 - Page 377 Figure 11-4.2.1411Yattles Straw rolls must be placed along slope contours /1111-� 10' - 25' (3-8m) Spacing depends on soil type and slope steepness Live Stake DEPARTMENT OF ECOLOGY State of Washington 1�y T - 4' 71 ' (1.2m) Sediment, organic matter, and native seeds are captured behind the rolls. 3" - 5" (75-125mm) 8" -10" Dia. (200-250mm) 1" x 1" Stake (25 x 25mm) NOTE: 1. Straw roll installation requires the placement and secure staking of the roll in a trench, 3" - 5" (75-125mm) deep, dug on contour. Runoff must not be allowed to run under or around roll. NOT TO SCALE Figure II-4.2.14 Wattles Revised November 2015 Please see http://www.ecy.wa.gov/copyright.html for copyright notice including permissions, limitation of liability, and disclaimer. 2014 Stormwater Management Manual for Western Washington Volume 11 - Chapter - Page 378 Inspect the slope after significant storms and repair any areas where wattles are not tightly abutted or water has scoured beneath the wattles. Approved as Equivalent Ecology has approved products as able to meet the requirements of BMP C235: Wattles. The products did not pass through the Technology Assessment Protocol — Ecology (TAPE) process. Local, jurisdictions may choose not to accept this product approved as equivalent, or may require additional testing prior to consideration for local use. The products are available for review on Ecology's website at http://www,ecy.wa.gov- /prog ra m s/wq/sto rmwate r/newtech /eq u i va le nt. h tml BMP C236: Vegetative Filtration Purpose Vegetative Filtration may be used in conjunction with BMP C241: Temporary Sediment Pond (p.388), BMP C206: Level Spreader (p.348) and a pumping system with surface intake to improve turbidity levels of stormwater discharges by filtering through existing vegetation where undisturbed forest floor duff layer or established lawn with thatch layer are present. Vegetative Filtration can also be used to infiltrate dewatering waste from foundations, vaults, and trenches as long as runoff does not occur. Conditions of Use . For every five acre of disturbed soil use one acre of grass field, farm pasture, or wooded area. Reduce or increase this area depending on project size, ground water table height, and other site conditions. . Wetlands shall not be used for filtration. . Do not use this BMP in areas with a high ground water table, or in areas thatwill have a high seasonal ground water table during the use of this BMP. . This BMP may be less effective on soils that prevent the infiltration of the water, such as hard till. . Using other effective source control measures throughout a construction site will prevent the generation of additional highly turbid water and may reduce the time period or area need for this BMP. . Stop distributing water into the vegetated area if standing water or erosion results. Design Criteria . Find land adjacent to the project that has a vegetated field, preferably a farm field, or wooded area. • If the project site does not contain enough vegetated field area consider obtaining 2014 Stormwater Management Manual for Western Washington Volume // - Chapter - Page 379 BMP T5.13: Post -Construction Soil Quality and Depth Purpose and Definition Naturally occurring (undisturbed) soil and vegetation provide important stormwater func- tions including: water infiltration; nutrient, sediment, and pollutant adsorption; sediment and pollutant biofiltration; water interflow storage and transmission; and pollutant decom- position. These functions are largely lost when development strips away native soil and vegetation and replaces it with minimal topsoil and sod. Not only are these important stormwater functions lost, but such landscapes themselves become pollution generating pervious surfaces due to increased use of pesticides, fertilizers and other landscaping and household/industrial chemicals, the concentration of pet wastes, and pollutants that accompany roadside litter. Establishing soil quality and depth regains greater stormwater functions in the post devel- opment landscape, provides increased treatment of pollutants and sediments that result from development and habitation, and minimizes the need for some landscaping chem- icals, thus reducing pollution through prevention. Applications and Limitations Establishing a minimum soil quality and depth is not the same as preservation of nat- urally occurring soil and vegetation. However, establishing a minimum soil quality and depth will provide improved on -site management of stormwater flow and water quality. Soil organic matter can be attained through numerous materials such as compost, com- posted woody material, biosolids, and forest product residuals. It is important that the materials used to meet the soil quality and depth BMP be appropriate and beneficial to the plant cover to be established. Likewise, it is important that imported topsoils improve soil conditions and do not have an excessive percent of clay fines. This BMP can be considered infeasible on till soil slopes greater than 33 percent. Design Guidelines Soil retention. Retain, in an undisturbed state, the duff layer and native topsoil to the maximum extent practicable. In any areas requiring grading remove and stock- pile the duff layer and topsoil on site in a designated, controlled area, not adjacent to public resources and critical areas, to be reapplied to other portions of the site where feasible. . Soil quality. All areas subject to clearing and grading that have not been covered by impervious surface, incorporated into a drainage facility or engineered as struc- tural fill or slope shall, at project completion, demonstrate the following: 1. A topsoil layer with a minimum organic matter content of 10% dry weight in planting beds, and 5% organic matter content in turf areas, and a pH from 6.0 2014 Stormwater Management Manual for Westem Washington Volume V - Chapter 5 - Page 911 to 8.0 or matching the pH of the undisturbed soil. The topsoil layer shall have a minimum depth of eight inches except where tree roots limit the depth of incorporation of amendments needed to meet the criteria. Subsoils below the topsoil layer should be scarified at least 4 inches with some incorporation of the upper material to avoid stratified layers, where feasible. 2. Mulch planting beds with 2 inches of organic material 3. Use compost and other materials that meet these organic content require- ments: a. The organic content for "pre -approved" amendment rates can be met only using compost meeting the compost specification for BMP T7.30: Bioretention Cells, Swaless and Planter Boxes (p.959), with the excep- tion that the compost may have up to 35% biosol ids or manure. The compost must also have an organic matter content of 40% to 65%, and a carbon to nitrogen ratio below 25:1. The carbon to nitrogen ratio may be as high as 35:1 for plantings com- posed entirely of plants native to the Puget Sound Lowlands region. b. Calculated amendment rates may be met through use of composted material meeting (a.) above; or other organic materials amended to meet the carbon to nitrogen ratio requirements, and not exceeding the contaminant limits identified in Table 220-B, Testing Parameters, in WAC 173-350-220. The resulting soil should be conducive to the type of vegetation to be established. Implementation Options: The soil quality design guidelines listed above can be met by using one of the methods listed below: 1. Leave undisturbed native vegetation and soil, and protect from compaction during construction. 2. Amend existing site topsoil or subsoil either at default "pre -approved" rates, or at custom calculated rates based on tests of the soil and amendment. 3. Stockpile existing topsoil during grading, and replace it prior to planting. Stockpiled topsoil must also be amended if needed to meet the organic mat- ter or depth requirements, either at a default "pre -approved" rate or at a cus- tom calculated rate. 4. Import topsoil mix of sufficient organic content and depth to meet the require- ments. 2014 Stormwater Management Manual for Westem Washington Volume V - Chapter 5 - Page 912 More than one method may be used on different portions of the same site. Soil that already meets the depth and organic matter quality standards, and is not com- pacted, does not need to be amended. Planning/Permittinglinspection/Verification Guidelines & Procedures Local governments are encouraged to adopt guidelines and procedures similar to those recommended in Guidelines and Resources For Implementing Soil Quality and Depth BMP T5.13 in WDOE Stormwater Management Manual for Western Washington. This document is available at: http://www.soilsforsalmon.or(i/r)df/Soil BMP Manual.pdf Maintenance Establish soil quality and depth toward the end of construction and once estab- lished, protect from compaction, such as from large machinery use, and from erosion. Plant vegetation and mulch the amended soil area after installation. Leave plant debris or its equivalent on the soil surface to replenish organic matter. . Reduce and adjust, where possible, the use of irrigation, fertilizers, herbicides and pesticides, rather than continuing to implement formerly established practices. Runoff Model Representation Areas meeting the design guidelines may be entered into approved runoff models as "Pasture" rather than "Lawn." Flow reduction credits can be taken in runoff modeling when BMP T5.13: Post -Con- struction Soil Quality Depth is used as part of a dispersion design under the con- ditions described in: • BMP T5.10B: Downspout Dispersion Systems (p.905) . BMP T5.11: Concentrated Flow Dispersion (p.905) • BMP T5.12: Sheet Flow Dispersion .908 . BMP T5.18: Reverse Slope Sidewalks .937 • BMP T5.30: Full Dispersion .939 (for public road projects) 2014 Stormwater Management Manual for Westem Washington Volume V - Chapter 5 - Page 913 Figure V-5.3.3 Planting bed Cross -Section Mulch Loose soil with visible dark organic matter Loose or fractured subsoil Reprinted from Guidelines and Resources For Implementing Soil Quality and Depth BMP T5.13 in WDOE Stormwater Management Manual for Western Washington, 2010, Washington Organic Recycling Council NOT TO SCALE `ma= Figure V-5.3.3 Planting Bed Cross -Section DEPARTMENT OF Revised January 2016 ECOLOGY Please see http://www.ecy.wa.gov/copyright.html for copyright notice including permissions, State of Washington limitation of liability, and disclaimer. 2014 Stormwater Management Manual for Westem Washington Volume V - Chapter 5 - Page 914 For amending the native soil within the rain garden, Ecology recommends use of com- post that meets the compost specification for bioretrention (see BMP T7.30: Bioretention Cells, Swales, and Planter Boxes tx=959)). Compost that includes biosolids or manures shall not be used. For design on projects subject to 1-2.5.5 Minimum Requirement#5: On -site Stormwater Management (12.55), and choosing to use List #1 of that requirement, rain gardens shall have a horizontally projected surface area below the overflow which is at least 5% of the total impervious surface area draining to it. If lawn/landscape area will also be draining to the rain garden, Ecology recommends that the rain garden's horizontally projected sur- face area below the overflow be increased by 2% of the lawn/landscape area. Underdrains Ecology does not recommend the use of underdrains for rain gardens. Design and con- struction of an underdrain system likely requires professional expertise. Where a muni- cipality intends to require or allow underdrained rain gardens in areas with initial infiltration rates between 0.3 and 0.6 inches per hour, the invert of the underdrain shall be 6 inches above the bottom of the aggregate bedding for the underdrain. A larger dis- tance between the underdrain and the bottom of the aggregate bedding is desirable, but cannot be used to trigger infeasibility due to inadequate vertical separation to the sea- sonal high water table, bedrock, or other impermeable layer. Ecology recommends that the municipality establish standard design specifications and drawings. Maintenance Please refer to the Rain Garden Handbook for Westem Washington (2013) for tips on mulching, watering, weeding, pruning, and soil management. The "Western Washington Low Impact Development (LID) Operation and Maintenance (O&M) Guidance Docu- ment" may be consulted for more detailed guidance. BAP T5.14113: Bioretention Purpose and Definition Bioretention areas are shallow landscaped depressions, with a designed soil mix and plants adapted to the local climate and soil moisture conditions, that receive stormwater from a contributing area. Bioretention provides effective removal of many stormwater pollutants by passing storm - water through a soil profile that meets specified characteristics. Bioretention can also reduce stormwater runoff quantity and surface runoff flow rates significantly where the exfiltrate from the design soil is allowed to infiltrate into the surrounding native soils. 2014 Stormwater Management Manual for Westem Washington Volume V - Chapter 5 - Page 916 Bioretention can be used as a primary or supplemental detention/retention system. Where the native soils have low infiltration rates, underdrain systems can be installed and the facility used to filter pollutants and detain flows. However, designs utilizing underdrains provide less flow control benefits. Applications and Limitations Bioretention facilities are an On -site BMP option for projects that only have to comply with Minimum Requirements #1 - #5. For projects electing to use Mandatory List #2 of I- 2.5.5 Minimum Requirement #5: On -site Stormwater Management (p.55), bioretention facilities are to be used to the extent feasible for runoff from roofs and other hard surfaces unless a higher priority BMP is feasible. Use of bioretention can be restricted by site limitations. Please see Bioretention infeas- ibility criteria in BMP T7.30: Bioretention Cells, Swales, and Planter Boxes (p.959). Design Guidelines Refer to BMP T7.30: Bioretention Cells, Swales, and Planter „Boxes (p.959) for detailed design guidelines. For design on projects subject to 1-2.5.5 Minimum Requirement #5: On_ -site Stormwater Management (p.55), and choosing to use List #1 or List #2 of that requirement, a biore- tention facility shall have a horizontally projected surface area below the overflow which is at least 5% of the total impervious surface area draining to it. If lawn/landscape area will also be draining to the bioretention facility, Ecology recommends that the biore- tention facility's horizontally projected surface area below the overflow be increased by 2% of the lawn/landscape area. Maintenance Refer to BMP T7.30: Bioretention Cells, Swales, and Planter Boxes (p.959) and V-4.6 Maintenance Standards for Drainage Facilities (p.829) for maintenance guidelines. BMP T5.15: Permeable Pavements Purpose and Definition Pavement for vehicular and pedestrian travel occupies roughly twice the space of build- ings. Stormwater from vehicular pavement can contain significant levels of solids, heavy metals, and hydrocarbon pollutants. Both pedestrian and vehicular pavements also con- tribute to increased peak flow durations and associated physical habitat degradation of streams and wetlands. Optimum management of stormwater quality and quantity from paved surfaces is, therefore, critical for improving fresh and marine water conditions in Puget Sound. 2014 Stormwater Management Manual for Westem Washington Volume V - Chapter 5 - Page 917 BMP T7.20: infiltration Trenches The design criteria and design procedures for infiltration trenches for treatment are in III- 3.3 Infiltration Facilities for Flow Control and for Treatment .512 . III-3.3.1 Purpose (p 512) through 111-3.3.9 General Design, Maintenance, and Construction Criteria for Infiltration Facilities (p.538) provide information pertinent to all infiltration facilities. III- 3.3.11 Infiltration Trenches (p.543) provides information specific to infiltration trenches. BMP T7.30: Bioretention Cells, Swages, and Planter Boxes Purpose To provide effective removal of many stormwater pollutants, and provide reductions in stormwater runoff quantity and surface runoff flow rates. Where the surrounding native soils have adequate infiltration rates, bioretention can help comply with flow control and treatment requirements. Where the native soils have low infiltration rates, underdrain sys- tems can be installed and the facility used to filter pollutants and detain flows that exceed infiltration capacity of the surrounding soil. However, designs utilizing under - drains provide less flow control benefits. Description Bioretention areas are shallow landscaped depressions, with a designed soil mix and plants adapted to the local climate and soil moisture conditions, that receive stormwater from a contributing area. The term, bioretention, is used to describe various designs using soil and plant com- plexes to manage stormwater. The following terminology is used in this manual: Bioretention cells: Shallow depressions with a designed planting soil mix and a variety of plant material, including trees, shrubs, grasses, and/or other herbaceous plants. Bioretention cells may or may not have an underdrain and are not designed as a conveyance system. (See Figure V-7.4.1a Typical Bioretention (p.961), Figure V-7.4.1 b Typical Bioretention w/Underdrain (p.962), and Figure V-7.4.1 c Typical Bioretention w/Liner (Not LID) (p.963)) Bioretention swales: Incorporate the same design features as bioretention cells, however, bioretention swales are designed as part of a system that can convey stormwater when maximum ponding depth is exceeded. Bioretention swales have relatively gentle side slopes and ponding depths that are typically 6 to 12 inches. (See Figure V-7.4.1a Typical Bioretention (p.961), Figure V-7.4.1b Typic_a_! Biore- tention w/Underdrain (p.962), and Figure V-7.4.1c Typical Bioretention w/Liner (Not LID) (p.963)} 2014 Stormwater Management Manual for Westem Washington Volume V - Chapter 7 - Page 959 Bioretention planters and planterboxes: Designed soil mix and a variety of plant material including trees, shrubs, grasses, and/or other herbaceous plants within a vertical walled container usually constructed from formed concrete, but could include other materials. Planter boxes are completely impervious and include a bot- tom (must include an underdrain). Planters have an open bottom and allow infilt- ration to the subgrade. These designs are often used in ultra -urban settings. (See Figure V-7.4.2 Example of a Bioretention Planter (p.964)) Note: Ecology has approved use of certain patented treatment systems that use specific, high rate media for treatment. Such systems are not considered LID BMPs and are not options for meeting the requirements of 1-2.5.5 Minimum Requirement #5: On -site Storm - water Management (p.55). The Ecology approval is meant to be used for 1-2.5.6 Min- imum Requirement #6_Runoff Treatment (p.61), where appropriate. 2014 Stormwater Management Manual for Western Washington Volume V - Chapter 7 - Page 960 Figure V-7.4.1 a Typical Bioretention Provide a 1" drop Provide a 1" drop from the edge of r from the edge of sidewalk pavement BSM bottom width Edge of varies, 1' minimum pavement Overflow,stand pipe Sidewalk )r curb -cut 6" min. freeboard Ponding depth vri • arieS ! 3" woodchip mulch, — 3" woodchip mule aggregate, or sod aggregate, or sod 3" coarse compost Minimum separation varies, in ponding area see design guidance 18" Bioretention Soil Media (BSM) Seasonal high water table, bedrock, or other impervious layer Notes: 1. Scarify subgrade 3" min. before bioretention soil installation 2. Compact BSM to 85% per ASTM 1577 DEPARTMENT OF ECOLOGY State of Washington Figure V-7.4.1 a Typical Bioretention NOT TO SCALE Revised February 2016 Please see http:1Avww ecy. wa. gov/copynght html for copyright notice including permissions, limitation of liability, and disclaimer. 2014 Stormwater Management Manual for Westem Washington Volume V - Chapter 7 - Page 961 Figure V-7.4.1 b Typical Bioretention w/Underdrain Provide a 1" drop Provide a 1" drop from the edge of sidewalk from the edge of pavement Jam; BSM bottom width y i varies, 1' minimum Edge of pavement Overflow sEaruipipe Sidewalk or curb -cut 6" min. freeboard Panding depth Varies VI , 3" woodchip mulch, 3" woodchip mulc aggregate, or sod aggregate, or sod 6" to 12" 3" coarse compost in ponding area — --- --- — 18" Bioretention Soil 6 Media (BSM) Mineral aggregate Mineral aggregate 1 Underdrain pipe - bottom width to match 1� BSM bottom width Notes: 1. Scarify subgrade 3" min. before bioretention soil installation 2. Compact BSM to 85% per ASTM 1577 DEPARTMENT OF ECOLOGY State of Washington NOT TO SCALE Figure V-7.4.1 b Typical Bioretention w/Underdrain Revised February 2016 2014 Stormwater Management Manual for Western Washington Volume V - Chapter 7 - Page 962 Figure V-7.4.1 c Typical Bioretention wlLiner (Not LID) Provide a 1" drop Provide a 1" drop from the edge of sidewalk from the edge of pavement J� BSM bottom width Edge of varies, 1' minimum pavement Sidewalk p�/ Overflow standpipe it curb -cut '\ i 11 3" woodchip mulch, aggregate, or sod 6" min, freeboard Ponadepth varies �l 3" woodchip mulch 6" to 12" Low permeability liner Notes: 1. Scarify subgrade 3" min. before bioretention soil installation 2. Compact BSM to 85% per ASTM 1577 DEPARTMENT OF ECOLOGY State of Washington aggregate, or sod 3" coarse compost in ponding area 18" Bioretention Soil Media (BSM) Width Mineral aggregate varies Underdrain pipe NOT TO SCALE Figure V-7.4.1 c Typical Bioretention w/Liner (Not LID) Revised February 2016 Please see http://www.ecy.wa gov/copyright html for copyright notice including permissions, limitation of liability, and disclaimer. 2014 Stormwater Management Manual for Westem Washington Volume V - Chapter 7 - Page 963 Figure V-7.4.2 Example of a Bioretention Planter 'E DESIGNER INFORMATION: U 0+ � Channel & grate 1. Adapt plan view example to your (see note 2) engineered design. 4" notch for sidewalk 2. Include beginning and ending stations for 1 f drianage, as necessary each facility. Provide stations and dimensions and elevations at every inlet, outlet, check dam, planter corner and Check dam sidewalk notch. tr (see note 2) 3. Longitudinal slope of planter matches road. =�!: °_'..'._: !� 4. Sidewalk elevation must be set above inlet -= T and outlet elevations to allow overflow to !' i : I:- : • T � � ;/q drain to street before sidewalk. 5. Minimum interior planter width is 3 feet. A m minimum of 4 feet interior planter width is required for street trees in planter. 6. Existing utility lines must be sleeved or utility Proposed relocated. Pro lines to be P Y located out of the facility. •'r';;: rr 7. Area and depth of facility are based upon a-x•, =-=- + 4" thick concrete engineering calculations and right-of-way splash pad at inlet constraints. B. May use concrete or pavers. ! = `' _ Concrete or avers �iV TJI Metal inlet r _ Sidewalk drainage notch to be 1" lower Top of wall at _... �!—r:�� F.. :. _ ......, .{.. ....... Finished — than sidewalk, end of planter Curb 1 grade of sloped to facility g, 2'-6" 3'-0' min. Sidewalk planter / 4" min. gutter 6" 6" I r,(/ exposed Concrete or I� 2'-6"i 1 12" max wall Plan View pavers (to be specified by Existing i ; designer) suisting 18bgrade" min Planter Curb and gutter wall (by others) Bioretention soil mixture — 6" bench for curb Open graded aggregate - construction (when required) Section A -A NOT TO SCALE Figure V-7.4.2 Example of a Bioretention Planter DEPARTMENT OF Revised February 2016 ECOLOGY Please see http://www.ecy.wa.gov/copyright htm1 for copyright notice including permissions, State of Washington limitation of liability, and disclaimer. 2014 Stormwater Management Manual for Westem Washington Volume V - Chapter 7 - Page 964 Applications and Limitations Because bioretention facilities use an imported soil mix that has a moderate design infilt- ration rate, they are best applied for small drainages, and near the source of the storm - water. Cells may be scattered throughout a subdivision; a swale may run alongside the access road; or a series of planter boxes may serve the road. In these situations, they can but are not required to fully meet the requirement to treat 91 % of the stormwater run- off file from pollution -generating surfaces. But the amount of stormwater that is predicted to pass through the soil profile may be estimated and subtracted from the 91 % volume that must be treated. Downstream treatment facilities may be significantly smaller as a result. Bioretention facilities that infiltrate into the ground can also serve a significant flow reduc- tion function. They can, but are not required to fully meet the flow control duration stand- ard of 1-2.5.7 Minimum Requirement #7: Flow Control .64 . Because they typically do not have an orifice restricting overflow or underflow discharge rates, they typically don't fully meet 1-2.5.7 Minimum Requirement #7: Flow Control (p.64). However, their per- formance contributes to meeting the standard, and that can result in much smaller flow control facilities at the bottom of the project site. When used in combination with other low impact development techniques, they can also help achieve compliance with the Performance Standard option of 1-2.5.5 Minimum Requirement#5: On -site Stormwater Management (p.55). Bioretention constructed with imported composted material should not be used within one -quarter mile of phosphorus -sensitive waterbodies if the underlying native soil does not meet the soil suitability criteria for treatment in Chapter III-3 - Flow Control Design_ (p 449). Preliminary monitoring indicates that new bioretention facilities can add phos- phorus to stormwater. Therefore, they should also not be used with an underdrain when the underdrain water would be routed to a phosphorus -sensitive receiving water. Applications with or without underdrains vary extensively and can be applied in new development, redevelopment and retrofits. Typical applications include: • Individual lots for rooftop, driveway, and other on -lot impervious surface. . Shared facilities located in common areas for individual lots. . Areas within loop roads or cul-de-sacs. . Landscaped parking lot islands. . Within right-of-ways along roads (often linear bioretention swales and cells). . Common landscaped areas in apartment complexes or other multifamily housing designs. Planters on building roofs, patios, and as part of streetscapes. 2014 Stormwater Management Manual for Westem Washington Volume V - Chapter 7 - Page 965 Infeasibility Criteria: The following criteria describe conditions that make bioretention or rain gardens not required. If a project proponent wishes to use a bioretention or rain garden BMP though not required to because of these feasibility criteria, they may propose a functional design to the local government. Note: Criteria with setback distances are as measured from the bottom edge of the biore- tention soil mix. Citation of any of the following infeasibility criteria must be based on an evaluation of site -specific conditions and a written recommendation from an appropriate licensed pro- fessional (e.g., engineer, geologist, hydrogeologist): . Where professional geotechnical evaluation recommends infiltration not be used due to reasonable concerns about erosion, slope failure, or down gradient flood- ing. . Within an area whose ground water drains into an erosion hazard, or landslide haz- ard area. Where the only area available for siting would threaten the safety or reliability of pre-existing underground utilities, pre-existing underground storage tanks, pre- existing structures, or pre-existing road or parking lot surfaces. . Where the only area available for siting does not allow for a safe overflow pathway to the municipal separate storm sewer system or private storm sewer system. . Where there is a lack of usable space for rain garden/bioretention facilities at re- development sites, or where there is insufficient space within the existing public right-of-way on public road projects. . Where infiltrating water would threaten existing below grade basements. . Where infiltrating water would threaten shoreline structures such as bulkheads. The following criteria can be cited as reasons for a finding of infeasibility without further justification (though some require professional services): . Within setbacks from structures as established by the local government with jur- isdiction. • Where they are not compatible with surrounding drainage system as determined by the local government with jurisdiction (e.g., project drains to an existing storm - water collection system whose elevation or location precludes connection to a properly functioning bioretention facility). • Where land for bioretention is within area designated as an erosion hazard, or land- slide hazard. 2014 Stormwater Management Manual for Western Washington Volume V - Chapter 7 - Page 966 . Where the site cannot be reasonably designed to locate bioretention facilities on slopes less than 8%. . Within 50 feet from the top of slopes that are greater than 20% and over 10 feet of vertical relief. . For properties with known soil or ground water contamination (typically federal Superfund sites or state cleanup sites under the Model Toxics Control Act (MTCA)): • Within 100 feet of an area known to have deep soil contamination; • Where ground water modeling indicates infiltration will likely increase or change the direction of the migration of pollutants in the ground water; • Wherever surface soils have been found to be contaminated unless those soils are removed within 10 horizontal feet from the infiltration area; • Any area where these facilities are prohibited by an approved cleanup plan under the state Model Toxics Control Act or Federal Superfund Law, or an environmental covenant under Chapter 64.70 RCW. . Within 100 feet of a closed or active landfill. . Within 100 feet of a drinking water well, or a spring used for drinking water supply. . Within 10 feet of small on -site sewage disposal drainfield, including reserve areas, and grey water reuse systems. For setbacks from a "large on -site sewage disposal system", see Chapter 246-272B WAC. . Within 10 feet of an underground storage tank and connecting underground pipes when the capacity of the tank and pipe system is 1100 gallons or less. (As used in these criteria, an underground storage tank means any tank used to store pet- roleum products, chemicals, or liquid hazardous wastes of which.10% or more of the storage volume (including volume in the connecting piping system) is beneath the ground surface. . Within 100 feet of an underground storage tank and connecting underground pipes when the capacity of the tank and pipe system is greater than 1100 gallons. . Where the minimum vertical separation of 1 foot to the seasonal high water table, bedrock, or other impervious layer would not be achieved below bioretention or rain gardens that would serve a drainage area that is: 1) less than 5,000 sq. ft. of pollution -generating impervious surface, and 2) less than 10,000 sq. ft. of imper- vious surface; and, 3) less than 3/4 acres of pervious surface. . Where the a minimum vertical separation of 3 feet to the seasonal high water table, bedrock or other impervious layer would not be achieved below bioretention that: 1) would serve a drainage area that meets or exceeds: a) 5,000 square feet of 2014 Stormwater Management Manual for Western Washington Volume V - Chapter 7 - Page 967 pollution -generating impervious surface, or b) 10,000 square feet of impervious sur- face, or c) three-quarter (3/4) acres of pervious surfaces; and 2) cannot reasonably be broken down into amounts smaller than indicated in (1). Where the field testing indicates potential bioretention/rain garden sites have a measured (a.k.a., initial) native soil saturated hydraulic conductivity less than 0.30 inches per hour. If the measured native soil infiltration rate is less than 0.30 in/hour, this option should not be used to meet the requirements of 1-2.5.5 Minimum Requirement #5: On -site Stormwater Management (p.55). In these slow draining soils, a bioretention facility with an underdrain may be used to treat pollution- gen- erating surfaces to help meet 1-2.5.6 Minimum_ Requirement #6: Runoff Treatment (p.61). If the underdrain is elevated within a base course of gravel, the bioretention facility will also provide some modest flow reduction benefit that will help achieve I- 2.5.7 Minimum Requirement #7: Flow Control (r).64). A local government may designate geographic boundaries within which bioretention cells, swales, or planters may be designated as infeasible due to year-round, seasonal or periodic high groundwater conditions, or due to inadequate infiltration rates. Desig- nations must be based upon a pre-ponderance of field data, collected within the area of concern, that indicate a high likelihood of failure to achieve the minimum groundwater clearance or infiltration rates identified in the above infeasibility criteria. The local gov- ernment must develop a technical report and make it available upon request to the Dept. of Ecology. The report must be authored by (a) professional(s) with appropriate expertise (e.g., registered engineer, geologist, hydrogeologist, or certified soil scientist), and doc- ument the location and the pertinent values/observations of data that were used to recom- mend the designation and boundaries for the geographic area. The types of pertinent data include, but are not limited to: . Standing water heights or evidence of recent saturated conditions in observation wells, test pits, test holes, and well logs. Observations of areal extent and time of surface ponding, including local gov- ernment or professional observations of high water tables, frequent or long dur- ations of standing water, springs, wetlands, and/or frequent flooding. . Results of infiltration tests In addition, a local government can map areas that meet a specific infeasibility criterion listed above provided they have an adequate data basis. Criteria that are most amen- able to mapping are: Where land for bioretention is within an area designated by the local government as an erosion hazard, or landslide hazard . Within 50 feet from the top of slopes that are greater than 20% and over 10 feet ver- 2014 Stormwater Management Manual for Westem Washington Volume V - Chapter 7 - Page 968 tical relief . Within 100 feet of a closed or active landfill Other Site Suitability Factors: • Utility conflicts: Consult local jurisdiction requirements for horizontal and vertical separation required for publicly -owned utilities, such as water and sewer. Consult the appropriate franchise utility owners for separation requirements from their util- ities, which may include communications and gas. When separation requirements cannot be met, designs should include appropriate mitigation measures, such as impermeable liners over the utility, sleeving utilities, fixing known leaky joints or cracked conduits, and/or adding an underdrain to the bioretention. . Transportation safety: The design configuration and selected plant types should provide adequate sight distances, clear zones, and appropriate setbacks for road- way applications in accordance with local jurisdiction requirements. • Ponding depth and surface water draw -down: Flow control needs, as well as loc- ation in the development, and mosquito breeding cycles will determine draw -down timing. For example, front yards and entrances to residential or commercial devel- opments may require rapid surface dewatering for aesthetics. • Impacts of surrounding activities: Human activity influences the location of the facil- ity in the development. For example, locate bioretention areas away from traveled areas on individual lots to prevent soil compaction and damage to vegetation or provide elevated or bermed pathways in areas where foot traffic is inevitable. and provide barriers, such as wheel stops, to restrict vehicle access in roadside applic- ations. . Visual buffering: Bioretention facilities can be used to buffer structures from roads, enhance privacy among residences, and for an aesthetic site feature. . Site growing characteristics and plant selection: Appropriate plants should be selected for sun exposure, soil moisture, and adjacent plant communities. Native species or hardy cultivars are recommended and can flourish in the properly designed and placed Bioretention Soil Mix with no nutrient or pesticide inputs and 2-3 years irrigation for establishment. Invasive species control may be necessary. Field and Design Procedures Geotechnical analysis is an important first step to develop an initial assessment of the variability of site soils, infiltration characteristics and the necessary frequency and depth of infiltration tests. See the Site Planning guidance in Chapter 1-3 - Preparation of Storm - water Site Plans ().77). See III-3.4 Stormwater-related Site Procedures and Design Guidance for Bioretention and Permeable Pavement 554) for more specific guidance regarding required field 2014 Stormwater Management Manual for Westem Washington Volume V - Chapter 7 - Page 969 testing, assignment of infiltration rate correction factors, project submission require- ments, and modeling. Determining subgrade infiltration rates Determining infiltration rates of the site soils is necessary to determine feasibility of designs that intend to infiltrate stormwater on -site. It is also necessary to estimate flow reduction benefits of such designs when using the Western Washington Hydrologic Model (WWHM) or MISS Flood. The following provides recommended tests for the soils underlying bioretention areas. The test should be run at the anticipated elevation of the top of the native soil beneath the bioretention facility. Method 1: Small bioretention cells (bioretention facilities receiving water from 1 or 2 indi- vidual lots or < 1/4 acre of pavement or other impervious surface): Small -Scale Pilot Infiltration Test (PIT). See III-3.3.6 Design Saturated Hydraulic Conductivity — Guidelines and Criteria (p.523) for small-scale PIT method description. See III-3.4 Stormwater-related Site Procedures and Design Guidance for Bioretention and Per- meable Pavement (p.554) for a discussion of the assignment of an appropriate infilt= ration correction factor. Large bioretention cells (bioretention facilities receiving water from several lots or 1/4 acre or more of pavement or other impervious surface): Multiple small or one large-scale PIT. If using the small-scale test, measurements should be taken at sev- eral locations within the area of interest. After completing the infiltration test, excav- ate the test site at least 3 feet if variable soil conditions or seasonal high water tables are suspected. Observe whether water is infiltrating vertically or only spread- ing horizontally because of ground water or a restrictive soil layer. See III-3.4 Storm - water -related Site Procedures and Design Guidance for Bioretention and Permeable Pavement (p.554) for a discussion of the assignment of an appropriate infiltration correction factor. . Bioretention swales: approximately 1 small --scale PIT per 200 feet of swale, and within each length of road with significant differences in subsurface characteristics. However, if the site subsurface characterization, including soil borings across the development site, indicate consistent soil characteristics and depths to seasonal high ground water conditions, the number of test locations may be reduced to a fre- quency recommended by a geotechnical professional. See III-3.4 Stormwater- related Site Procedures and Design Guidance for Bioretention and Permeable Pavement (p.554) for a discussion of the assignment of an appropriate infiltration correction factor. 2014 Stormwater Management Manual for Westem Washington Volume V - Chapter 7 - Page 970 Method 2: Soil Grain Size Analysis Method: This method is restricted to sites underlain with soils not consolidated by glacial advance (e.g., recessional outwash soils). Small bioretention cells: Use the grain size analysis method described in III-3.3.6 Design Saturated Hydraulic Conductivity — Guidelines and Criteria ( .523) based on the layer(s) identified in results of one soil test pit or boring. . Large bioretention cells: Use the grain size analysis method based on more than one soil test pit or boring. The more test pits/borings used, and the more evidence of consistency in the soils, the less of a correction factor may be used. Bioretention swales: Approximately 1 soil test pit/boring per 200 feet of swale and within each length of road with significant differences in subsurface characteristics. However, if the site subsurface characterization, including soil borings across the development site, indicate consistent soil characteristics and depths to seasonal high ground water conditions, the number of test locations may be reduced to the minimum frequency indicated above. Determining Bioretention soil mix infiltration rate: Option 1: If using the Bioretention Soil Mix recommended herein, the VWWHM assumes a default infiltration rate of 12 inches per hour (15.24 cm/hr)Option 2: If creating a custom bioretention soil mix, Use ASTM D 2434 Standard Test Method for Permeability of gran- ular Soils (Constant Head) with a compaction rate of 85 percent using ASTM D 1557 Test Method for Laboratory Compaction Characteristics of Soil Using Modified Effort. See Appendix V-B for specific procedures for conducting ASTM D 2434. The VWWHM user must enter the derived value into VWWHM using "View/Edit Soil Types" pull down menu and adjusting the Ksat value. After selecting option 1 or 2 above, determine the appropriate safety factor for the sat- urated hydraulic conductivity (Ksat). If the contributing area of the bioretention cell or swale is equal to or exceeds any of the following limitations: 5,000 square feet of pollution -generating impervious surface; 10,000 square feet of impervious surface; % acre of lawn and landscape, use 4 as the infiltration rate (Ksat) safety factor. If the contributing area is less than all of the above areas, or if the design includes a pretreatment device for solids removal, use 2 as the Ksat safety factor. The VWWHM has a field for entering the appropriate safety factor. 2014 Stormwater Management Manual for Western Washington Volume V - Chapter 7 - Page 971 Design Criteria for Bioretention These design criteria are from the LID Technical Guidance Manual for Puget Sound (2012). Refer to that document for additional explanations and background. Note that the LID Technical Guidance Manual for Puget Sound (2012) is for additional information purposes only. You must follow the guidance within this manual if there are any discrepancies between this manual and the LID Technical Guidance Manual for Puget Sound (2012). Flow entrance and presettling Flow entrance design will depend on topography, flow velocities and volume entering the pretreatment and bioretention area, adjacent land use and site constraints. Flow velo- cities entering bioretention should be less than 1.0 ft/second to minimize erosion poten- tial. Five primary types of flow entrances can be used for bioretention: Dispersed, low velocity flow across a landscape area: Landscape areas and veget- ated buffer strips slow incoming flows and provide an initial settling of particulates and are the preferred method of delivering flows to the bioretention cell., Dispersed flow may not be possible given space limitations or if the facility is controlling road- way or parking lot flows where curbs are mandatory. Dispersed or sheet flow across pavement or gravel and past wheel stops for park- ing areas. Curb cuts for roadside, driveway or parking lot areas: Curb cuts should include a rock pad, concrete or other erosion protection material in the channel entrance to dissipate energy. Minimum curb cut width should be 12 inches; however, 18 inches is recommended. Avoid the use of angular rock or quarry spalls and instead use round (river) rock if needed. Removing sediment from angular rock is difficult. Flow entrance should drop 2 to 3 inches from curb line and provide an area for set- tling and periodic removal of sediment and coarse material before flow dissipates to the remainder of the cell. Curb cuts used for bioretention areas in high use parking lots or roadways require increased level of maintenance due to high coarse particulates and trash accu- mulation in the flow entrance and associated bypass of flows. The following are methods recommended for areas where heavy trash and coarse particulates are anticipated: • Curb cut width: 18 inches. • At a minimum the flow entrance should drop 2 to 3 inches from gutter line into the bioretention area and provide an area for settling and periodic removal of debris. Anticipate relatively more frequent inspection and maintenance for areas with 2014 Stormwater Management Manual for Western Washington Volume V - Chapter 7 - Page 972 large impervious areas, high traffic loads and larger debris loads. Catch basins or forebays may be necessary at the flow entrance to adequately capture debris and sediment load from large contributing areas and high use areas. Piped flow entrance in this setting can easily clog and catch basins with regular maintenance are necessary to capture coarse and fine debris and sediment. . Pipe flow entrance: Piped entrances should include rock or other erosion pro- tection material in the channel entrance to dissipate energy and disperse flow. Catch basin: In some locations where road sanding or higher than usual sediment inputs are anticipated, catch basins can be used to settle sediment and release water to the bioretention area through a grate for filtering coarse material. Trench drains: can be used to cross sidewalks or driveways where a deeper pipe conveyance creates elevation problems. Trench drains tend to clog and may require additional maintenance. Woody plants can restrict or concentrate flows and can be damaged by erosion around the root ball and should not be placed directly in the entrance flow path. Bottom area and side slopes Bioretention areas are highly adaptable and can fit various settings such as rural and urban roadsides, ultra urban streetscapes and parking lots by adjusting bottom area and side slope configuration. Recommended maximum and minimum dimensions include: Maximum planted side slope if total cell depth is greater than 3 feet: 3HAV. If steeper side slopes are necessary rockeries, concrete walls or soil wraps may be effective design options. Local jurisdictions may require bike and/or pedestrian safety features, such as railings or curbs with curb cuts, when steep side slopes are adjacent to sidewalks, walkways, or bike lanes. Minimum bottom width for bioretention swales: 2 feet recommended and 1 foot min- imum. Carefully consider flow depths and velocities, flow velocity control (check dams) and appropriate vegetation or rock mulch to prevent erosion and chan- nelization at bottom widths less than 2 feet. Bioretention areas should have a minimum shoulder of 12 inches (30.5 cm) between the road edge and beginning of the bioretention side slope where flush curbs are used. Com- paction effort for the shoulder should 90 percent proctor. Ponding area Ponding depth recommendations: 2014 Stormwater Management Manual for Westem Washington Volume V - Chapter 7 - Page 973 Maximum ponding depth: 12 inches (30.5 cm). . Surface pool drawdown time: 24 hours For design on projects subject to 1-2.5.5 Minimum Requirement #5: On -site Stormwater Manaqement (p.55), and choosing to use List #1 or List #2 of that requirement, a biore- tention facility shall have a horizontally projected surface area below the overflow which is at least 5% of the total impervious surface area draining to it. If lawn/landscape area will also be draining to the bioretention facility, Ecology recommends that the biore- tention facility's horizontally projected surface area below the overflow be increased by 2% of the lawn/landscape area. The ponding area provides surface storage for storm flows, particulate settling, and the first stages of pollutant treatment within the cell. Pool depth and draw -down rate are recommended to provide surface storage, adequate infiltration capability, and soil mois- ture conditions that allow for a range of appropriate plant species. Soils must be allowed to dry out periodically in order to: restore hydraulic capacity to receive flows from sub- sequent storms; maintain infiltration rates; maintain adequate soil oxygen levels for healthy soil biota and vegetation; provide proper soil conditions for biodegradation and retention of pollutants. Maximum designed depth of ponding (before surface overflow to a pipe or ditch) must be considered in light of drawdown time. For bioretention areas with underdrains, elevating the drain to create a temporary sat- urated zone beneath the drain is advised to promote denitrification (conversion of nitrate to nitrogen gas) and prolong moist soil conditions for plant survival during dry periods (see Underdrain section below for details). Surface overflow Surface overflow can be provided by vertical stand pipes that are connected to under - drain systems, by horizontal drainage pipes or armored overflow channels installed at the designed maximum ponding elevations. Overflow can also be provided by a curb cut at the down -gradient end of the bioretention area to direct overflows back to the street. Overflow conveyance structures are necessary for all bioretention facilities to safely con- vey flows that exceed the capacity of the facility and to protect downstream natural resources and property. The minimum freeboard from the invert of the overflow stand pipe, horizontal drainage pipe or earthen channel should be 6 inches unless otherwise specified by the local jur- isdiction's design standards. Default Bioretention Soil Media (BSM) Projects which use the following requirements for the bioretention soil media do not have to test the media for it saturated hydraulic conductivity (aka. Infiltration rate). They 2014 Stormwater Management Manual for Western Washington Volume V - Chapter 7 - Page 974 may assume the rates specified in the subsection titled "Determining Bioretention Soil Mix Infiltration Rate." Mineral Aggregate Percent Fines: A range of 2 to 4 percent passing the #200 sieve is ideal and fines should not be above 5 percent for a proper functioning specification according to ASTM D422. Aggregate Gradation The aggregate portion of the BSM should be well -graded. According to ASTM D 2487- 98 (Classification of Soils for Engineering Purposes (Unified Soil Classification Sys- tem)), well -graded sand should have the following gradation coefficients: . Coefficient of Uniformity (CU = D60/D10) equal to or greater than 4, and Coefficient of Curve (Cc = (D30)2/D60 x D10) greater than or equal to land less than or equal to 3. Table V-7.4.1 General Guideline for MineralAqgregate Gradation (p.975) provides a gradation guideline for the aggregate component of a Bioretention Soil Mix specification in western Washington (Hinman, Robertson, 2007). The sand gradation below is often supplied as a well -graded utility or screened. With compost this blend provides enough fines for adequate water retention, hydraulic conductivity within recommended range (see below), pollutant removal capability, and plant growth characteristics for meeting design guidelines and objectives. Table V-7.4.1 General Guideline for Mineral Aggregate Gradation Sieve Size (Percent Passing 3/8" 100 #4 95-100 :#10 75-90 #40 25-40 :#100 4-10 #200 2-5 Where existing soils meet the above aggregate gradation, those soils may be amended rather than importing mineral aggregate. Compost to Aggregate Ratio, Organic Matter Content, Cation Exchange Capacity . Compost to aggregate ratio: 60-65 percent mineral aggregate, 35 — 40 percent com- post by volume. . Organic matter content: 5 — 8 percent by weight. 2014 Stormwater Management Manual for Western Washington Volume V - Chapter 7 - Page 975 . Cation Exchange Capacity (CEC) must be > 5 milliequivalents/100 g dry soil Note: Soil mixes meeting the above specifications do not have to be tested for CEC. They will readily meet the minimum CEC. Compost To ensure that the BSM will support healthy plant growth and root development, con- tribute to biofiltration of pollutants, and not restrict infiltration when used in the pro- portions cited herein, the following compost standards are required. . Meets the definition of "composted material" in WAC 173-350-100 and complies with testing parameters and other standards in WAC 173-350-220. Produced at a composting facility that is permitted by the jurisdictional health authority. Permitted compost facilities in Washington are included on a list avail- able at http://www.ecy.wa.gov/programs/swfa/organics/soil.html The compost product must originate a minimum of 65 percent by volume from recycled plant waste comprised of "yard debris," "crop residues," and "bulking agents" as those terms are defined in WAC 173-350-100. A maximum of 35 per- cent by volume of "post -consumer food waste" as defined in WAC 173-350-100, but not including biosolids, may be substituted for recycled plant waste. Stable (low oxygen use and CO2 generation) and mature (capable of supporting plant growth) by tests shown below. This is critical to plant success in a biore- tention soil mixes. Moisture content range: no visible free water or dust produced when handling the material. . Tested in accordance with the U.S. Composting Council "Test Method for the Examination of Compost and Composting" (TMECC), as established in the Com- posting Council's "Seal of Testing Assurance" (STA) program. Most Washington compost facilities now use these tests. . Screened to the following size gradations for Fine Compost when tested in accord- ance with TMECC test method 02.02-13, Sample Sieving for Aggregate Size Clas- sification." Fine Compost shall meet the following gradation by dry weight Minimum percent passing 2": 100% Minimum percent passing 1 ". 99% Minimum percent passing 5/8": 90% Minimum percent passing'/4": 75% . pH between 6.0 and 8.5 (TMECC 04.11-A). "Physical contaminants" (as defined in WIC 173-350-100) content less that 1 % by weight (TMECC 03.08-A) total, not to 2014 Stormwater Management Manual for Westem Washington Volume V - Chapter 7 - Page 976 exceed 0.25 percent film plastic by dry weight. . Minimum organic matter content of 40% (TMECC 05.07-A "Loss on Ignition) . Soluble salt content less than 4.0 dS/m (mmhos/cm) (TMECC 04.10-A "Electrical Conductivity, 1:5 Slurry Method, Mass Basis") . Maturity indicators from a cucumber bioassay (TMECC 05.05-A "Seedling Emer- gence and Relative Growth ) must be greater than 80%for both emergence and vigor") . Stability of 7 mg CO2-C/g OM/day or below (TMECC 05.08-B "Carbon Dioxide Evolution Rate") . Carbon to nitrogen ratio (TMECC 05.02A " Carbon to Nitrogen Ratio" which uses 04.01 "Organic Carbon" and 04.02D "Total Nitrogen by Oxidation") of less than 25:1. The C:N ratio may be up to 35:1 for plantings composed entirely of Puget Sound Lowland native species and up to 40:1 for coarse compost to be used as a surface mulch (not in a soil mix). Design Criteria for Custom Bioretention Soil Mixes. Projects which prefer to create a custom Bioretention Soil Mix rather than using the default requirements above must demonstrate compliance with the following criteria using the specified test method: . CEC >_ 5 meq/100 grams of dry soil; USEPA 9081 . pH between 5.5 and 7.0 . 5 - 8 percent organic matter content before and after the saturated hydraulic con- ductivity test; ASTM D2974(Standard Test Method for Moisture, Ash, and Organic Matter of Peat and Other Organic Soils) e 2-5 percent fines passing the 200 sieve; TMECC 04.11-A . Measured (Initial) saturated hydraulic conductivity of less than 12 inches per hour; ASTM D 2434 (Standard Test Method for Permeability of Granular Soils (Constant Head)) at 85% compaction per ASTM D 1557 (Standard Test Method s for Lab- oratory Compaction Characteristics of Soil Using Modified Effort). Also, use Appendix V-B: Recommended Modifications to ASTM D 2434 When Measuring_ Hydraulic Conductivity for Bioretention Soil Mixes (p.1133). . Design (long-term) saturated hydraulic conductivity of more than 1 inch per hour. Note: Design saturated hydraulic conductivity is determined by applying the appro- priate infiltration correction factors as explained above under "Determining Biore- tention soil mix infiltration rate." . If compost is used in creating the custom mix, it must meet all of the specifications 2014 Stormwater Management Manual for Westem Washington Volume V - Chapter 7 - Page 977 listed above for compost except for the gradation specification. An alternative grad- ation specification must indicate the minimum percent passing for a range of sim- ilar particle sizes. Soil Depth: Soil depth must be a minimum of 18 inches to provide water quality treatment and good growing conditions for selected plants Filter Fabrics: Do not use filter fabrics between the subgrade and the Bioretention Soil Mix. The grad- ation between existing soils and Bioretention Soil Mix is not great enough to allow sig- nificant migration of fines into the Bioretention Soil Mix. Additionally, filter fabrics may clog with downward migration of fines from the Bioretention Soil Mix. Underdrain (optional): Where the underlying native soils have an estimated initial infiltration rate between 0.3 and 0.6 inches per hour, bioretention facilities without an underdrain, or with an elevated underdrain directed to a surface outlet, may be used to satisfy List#2 of 1-2.5.5 Minimum Requirement #5: On -site Stormwater Management (p.55). Underdrained bioretention facilities that drain to a retention/detention facility must meet the following criteria if they are used to satisfy list #2 of 1-2.5.5 Minimum_ Requirement #5: On -site Stormwater Man- agement (p.55). . the invert of the underdrain must be elevated 6 inches above the bottom of the aggregate bedding layer. A larger distance between the underdrain and bottom of the bedding layer is desirable, but cannot be used to trigger infeasibility due to inadequate vertical separation to the seasonal high water table, bedrock, or other impermeable layer. . the distance between the bottom of the bioretention soil mix and the crown of the underdrain pipe must be not less than 6 but not more than 12 inches; . the aggregate bedding layer must run the full length and the full width of the bottom of the bioretention facility; . the facility must not be underlain by a low permeability liner that prevents infilt- ration into the native soil. Figure V-7.4.1b Typical Bioretention w/Underdrain (p.962) depicts a bioretention facility with an elevated underdrain. Fiqure V-7.4.1 c Typical Bioretention w/Liner (Not LID) 963 depicts a bioretention facility with an underdrain and a low permeability liner. The latter is not considered a low impact development BMP. It cannot be used to imple- ment List #2 of 1-2.5.5 Minimum Requirement #5: On -site Stormwater Management (p.55) 2014 Stormwater Management Manual for Western Washington Volume V - Chapter 7 - Page 978 The volume above an underdrain pipe in a bioretention facility provides pollutant filtering and minor detention. However, only the void volume of the aggregate below the under - drain invert and above the bottom of the bioretention facility (subgrade) can be used in the WWHM or MGSFlood for dead storage volume that provides flow control benefit. Assume a 40% void volume for the Type 26 mineral aggregate specified below. Underdrain systems should only be installed when the bioretention facility is: . Located near sensitive infrastructure (e.g., unsealed basements) and potential for flooding is likely. . Used for filtering storm flows from gas stations or other pollutant hotspots (requires impermeable liner). . Located above native soils with infiltration rates that are not adequate to meet max- imum pool and system dewater rates, or are below a minimum rate allowed by the local government. . In an area that does not provide the minimum depth to a hydraulic restriction layer, e.g., high seasonal ground water. The underdrain can be connected to a downstream open conveyance (bioretention swale), to another bioretention cell as part of a connected treatment system, daylight to a dispersion area using an effective flow dispersion practice, or to a storm drain. Underdrain pipe: Underdrains shall be slotted, thick-walled plastic pipe. The slot opening should be smal- ler than the smallest aggregate gradation for the gravel filter bed (see underdrain filter bed below) to prevent migration of material into the drain. This configuration allows for pressurized water cleaning and root cutting if necessary. Underdrain pipe recommendations: . Minimum pipe diameter: 4 inches (pipe diameter will depend on hydraulic capacity required, 4 to 8 inches is common). • Slotted subsurface drain PVC perASTM D1785 SCH 40. . Slots should be cut perpendicular to the long axis of the pipe and be 0.04 to 0.069 inches by 1 inch long and be spaced 0.25 inches apart (spaced longitudinally). Slots should be arranged in four rows spaced on 45-degree centers and cover'/2 of the circumference of the pipe. See Filter Materials section for aggregate gradation appropriate for this slot size. . Underdrains should be sloped at a minimum of 0.5 percent unless otherwise spe- cified by an engineer. Perforated PVC or flexible slotted HDPE pipe cannot be cleaned with pressurized water or root cutting equipment, are less durable and are not recommended. Wrapping the 2014 Stormwater Management Manual for Westem Washington Volume V - Chapter 7 - Page 979 underdrain pipe in filter fabric increases chances of clogging and is not recommended. A 6-inch rigid non -perforated observation pipe or other maintenance access should be con- nected to the underdrain every 250 to 300 feet to provide a clean -out port, as well as an observation well to monitor dewatering rates. Underdrain aggregate filter and bedding layer. Aggregate filter and bedding layers buffer the underdrain system from sediment input and clogging. When properly selected for the soil gradation, geosynthetic filter fabrics can provide adequate protection from the migration of fines. However, aggregate filter and bedding layers, with proper gradations, provide a larger surface area for protecting underdrains and are preferred. . Guideline for underdrain aggregate filter and bedding layers with heavy walled slot- ted pipe (see underdrain pipe guideline above): Sieve size Percent Passing inch 100 % inch 30-60 US No. 8 20-50 US No. 50 3-12 US No. 200 0-1 The above gradation is a Type 26 mineral aggregate (gravel backfill for drains, City of Seattle). Place underdrain on a bed of the Type 26 aggregate with a minimum thickness of 6 inches and cover with Type 26 aggregate to provide a 1-foot minimum depth around the top and sides of the slotted pipe. See the LID Technical Guidance Manual for Puget Sound (2012) for a related figure. Note that the LID Technical Guidance Manual for Puget Sound (2012) is for addi- tional informational purposes only. You must follow the guidance within this manual if there are any discrepancies between this manual and the LID Technical Guidance Manual for Puget Sound (2012). Orifice and other flow control structures: The minimum orifice diameter should be 0.5 inches to minimize clogging and main- tenance requirements. Check dams and weirs Check dams are necessary for reducing flow velocity and potential erosion, as well as increasing detention time and infiltration capability on sloped sites. Typical materials include concrete, wood, rock, compacted dense soil covered with vegetation, and veget- ated hedge rows. Design depends on flow control goals, local regulations for structures 2014 Stormwater Management Manual for Westem Washington Volume V - Chapter 7 - Page 980 within road right-of-ways and aesthetics. Optimum spacing is determined by flow control benefit (modeling) in relation to cost consideration. See the LID Technical Guidance Manual for Puget Sound (2012) for displays of typical designs. Note that the LID Technical Guidance Manual for Puget Sound (2012) is for additional informational purposes only. You must follow the guidance within this manual if there are any discrepancies between this manual and the LID Technical Guidance Manual for Puget Sound (2012). UIC discharge Stormwater that has passed through the bioretention soil mix may also discharge to a gravel -filled dug or drilled drain. Underground Injection Control (UIC) regulations are applicable and must be followed (ChaG)ter 173-218 WAC). Hydraulic restriction layers: Adjacent roads, foundations or other infrastructure may require that infiltration pathways are restricted to prevent excessive hydrologic loading. Two types of restricting layers can be incorporated into bioretention designs: . Clay (bentonite) liners are low permeability liners. Where clay liners are used underdrain systems are necessary. See V-4.4.3 Design Criteria for Low Per- meability Liner Options (p.804) for guidelines. Geomembrane liners completely block infiltration to subgrade soils and are used for ground water protection when bioretention facilities are installed to filter storm flows from pollutant hotspots or on sidewalls of bioretention areas to restrict lateral flows to roadbeds or other sensitive infrastructure. Where geomembrane liners are used to line the entire facility underdrain systems are necessary. The liner should have a minimum thickness of 30 mils and be ultraviolet (UV) resistant. Plant materials In general, the predominant plant material utilized in bioretention areas are facultative species adapted to stresses associated with wet and dry conditions. Soil moisture con- ditions will vary within the facility from saturated (bottom of cell) to relatively dry (rim of cell). Accordingly, wetland plants may be used in the lower areas, if saturated soil con- ditions exist for appropriate periods, and drought -tolerant species planted on the peri- meter of the facility or on mounded areas. See the LID Technical Guidance Manual for Puget Sound (2012) for additional guidance and recommended plant species. Note that the LID Technical Guidance Manual for Puget Sound (2012) is for additional informational purposes only. You must follow the guidance within this manual if there are any discrepancies between this manual and the LID Technical Guidance Manual for Puget Sound (2012). 2014 Stormwater Management Manual for Westem Washington Volume V - Chapter 7 - Page 981 Mulch layer You can design Bioretention areas with or without a mulch layer. When used, mulch shall be: - Coarse compost in the bottom of the facilities (compost is less likely to float during cell inundation). Compost shall not include biosolids or manures. - Shredded or chipped hardwood or softwood on side slopes above ponding elev- ation and rim area. Arborist mulch is mostly woody trimmings from trees and shrubs and is a good source of mulch material. Wood chip operations are a good source for mulch material that has more control of size distribution and con- sistency. Do not use shredded construction wood debris or any shredded wood to which preservatives have been added. - Free of weed seeds, soil, roots and other material that is not bole or branch wood and bark. - A maximum of 2 to 3 inches thick. Mulch shall not be: . Grass clippings (decomposing grass clippings are a source of nitrogen and are not recommended for mulch in bioretention areas). - Pure bark (bark is essentially sterile and inhibits plant establishment). In bioretention areas where higher flow velocities are anticipated an aggregate mulch may be used to dissipate flow energy and protect underlying Bioretention Soil Mix. Aggregate mulch varies in size and type, but 1 to 1 1/2 inch gravel (rounded) decorative rock is typical. Installation Excavation Soil compaction can lead to facility failure; accordingly, minimizing compaction of the base and sidewalls of the bioretention area is critical. Excavation should never be allowed during wet or saturated conditions (compaction can reach depths of 2-3 feet dur- ing wet conditions and mitigation is likely not be possible). Excavation should be per- formed by machinery operating adjacent to the bioretention facility and no heavy equipment with narrow tracks, narrow tires, or large lugged, high pressure tires should be allowed on the bottom of the bioretention facility. If machinery must operate in the bioretention cell for excavation, use lightweight, low ground -contact pressure equipment and rip the base at completion to refracture soil to a minimum of 12 inches. If machinery operates in the facility, subgrade infiltration rates must be field tested and compared to design rates. Failure to meet or exceed the design infiltration rate will require revised 2014 Stormwater Management Manual for Western Washington Volume V - Chapter 7 - Page 982 engineering designs to verify achievement of treatment and flow control benefits that were estimated in the Stormwater Site Plan. Prior to placement of the BSM, the finished subgrade shall: . Be scarified to a minimum depth of 3 inches. Have any sediment deposited from construction runoff removed. To remove all introduced sediment, subgrade soil should be removed to a depth of 3-6 inches and replaced with BSM. . Be inspected by the responsible engineer to verify required subgrade condition. Sidewalls of the facility, beneath the surface of the BSM, can be vertical if soil stability is adequate. Exposed sidewalls of the completed bioretention area with BSM in place should be no steeper than 3H:1 V. The bottom of the facility should be flat. Soil Placement On -site soil mixing or placement shall not be performed if Bioretention Soil Mix or sub - grade soil is saturated. The bioretention soil mixture should be placed and graded by machinery operating adjacent to the bioretention facility. If machinery must operate in the bioretention cell for soil placement, use light weight equipment with low ground -contact pressure. If machinery operates in the facility, subgrade infiltration rates must be field tested and compared to design rates. Failure to meet or exceed the design infiltration rate will require revised engineering designs to verify achievement of treatment and flow control benefits that were estimated in the Stormwater Site Plan. The soil mixture shall be placed in horizontal layers not to exceed 6 inches per lift for the entire area of the bioretention facility. Compact the Bioretention Soil Mix to a relative compaction of 85 percent of modified maximum dry density (ASTM D 1557). Compaction can be achieved by boot packing (simply walking over all areas of each lift), and then apply 0.2 inches (0.5 cm) of water per 1 inch (2.5 cm) of Bioretention Soil Mix depth. Water for settling should be applied by spraying or sprinkling. Temporary Erosion and Sediment Control (TESC) Controlling erosion and sediment are most difficult during clearing, grading, and con- struction; accordingly, minimizing site disturbance to the greatest extent practicable is the most effective sediment management. During construction: Bioretention facilities should not be used as sediment control facilities and all drain- age should be directed away from bioretention facilities after initial rough grading. Flow can be directed away from the facility with temporary diversion swales or other approved protection. If introduction of construction runoff cannot be avoided see below for guidelines. 2014 Stormwater Management Manual for Western Washington Volume V - Chapter 7 - Page 983 Construction on Bioretention facilities should not begin until all contributing drain- age areas are stabilized according to erosion and sediment control BMPs and to the satisfaction of the engineer. If the design includes curb and gutter, the curb cuts and inlets should be blocked until Bioretention Soil Mix and mulch have been placed and planting completed (when possible), and dispersion pads are in place. Every effort during design, construction sequencing and construction should be made to prevent sediment from entering bioretention facilities. However, bioretention areas are often distributed throughout the project area and can present unique challenges during construction. See the LID Technical Guidance Manual for Puget Sound (2012) for guidelines if no other options exist and runoff during construction must be directed through the bioretention facilities. Note that the LID Technical Guidance Manual for Puget Sound (2012) is for additional informational purposes only. You must follow the guidance within this manual if there are any discrepancies between this manual and the LID Technical Guidance Manual for Puget Sound (2012). Erosion and sediment control practices must be inspected and maintained on a regular basis. Verification If using the default bioretention soil media, pre -placement laboratory analysis for sat- urated hydraulic conductivity of the bioretention soil media is not required. Verification of the mineral aggregate gradation, compliance with the compost specifications, and the mix ratio must be provided. If using a custom bioretention soil media, verification of compliance with the minimum design criteria cited above for such custom mixes must be provided. This will require laboratory testing of the material that will be used in the installation. Testing shall be per- formed by a Seal of Testing Assurance, AASHTO, ASTM or other standards organ- ization accredited laboratory with current and maintained certification. Samples for testing must be supplied from the BSM that will be placed in the bioretention areas. If testing infiltration rates is necessary for post -construction verification use the Pilot Infiltration Test (PIT) method or a double ring infiltrometer test (or other small-scale test- ing allowed by the local government with jurisdiction). If using the PIT method, do not excavate Bioretention Soil Mix (conduct test at level of finished Bioretention Soil Mix elevation), use a maximum of 6 inch ponding depth and conduct test before plants are installed. 2014 Stormwater Management Manual for Western Washington Volume V - Chapter 7 - Page 984 Maintenance Bioretention areas require annual plant, soil, and mulch layer maintenance to ensure optimum infiltration, storage, and pollutant removal capabilities. In general, bioretention maintenance requirements are typical landscape care procedures and include: . Watering: Plants should be selected to be drought tolerant and not require water- ing after establishment (2 to 3 years). Watering may be required during prolonged dry periods after plants are established. . Erosion control: Inspect flow entrances, ponding area, and surface overflow areas periodically, and replace soil, plant material, and/or mulch layer in areas if erosion has occurred. Properly designed facilities with appropriate flow velocities should not have erosion problems except perhaps in extreme events. If erosion problems occur the following should be reassessed: (1) flow volumes from contributing areas and bioretention cell sizing; (2) flow velocities and gradients within the cell; and (3) flow dissipation and erosion protection strategies in the pretreatment area and flow entrance. If sediment is deposited in the bioretention area, immediately determine the source within the contributing area, stabilize, and remove excess surface deposits. Sediment removal: Follow the maintenance plan schedule for visual inspection and remove sediment if the volume of the ponding area has been compromised. . Plant material: Depending on aesthetic requirements, occasional pruning and removing dead plant material may be necessary. Replace all dead plants and if specific plants have a high mortality rate, assess the cause and replace with appro- priate species. Periodic weeding is necessary until plants are established. . Weeding: Invasive or nuisance plants should be removed regularly and not allowed to accumulate and exclude planted species. At a minimum, schedule weeding with inspections to coincide with important horticultural cycles (e.g., prior to major weed varieties dispersing seeds). Weeding should be done manually and without herbicide applications. The weeding schedule should become less fre- quent if the appropriate plant species and planting density are used and the selec- ted plants grow to capture the site and exclude undesirable weeds. Nutrient and pesticides: The soil mix and plants are selected for optimum fertility, plant establishment, and growth. Nutrient and pesticide inputs should not be required and may degrade the pollutant processing capability of the bioretention area, as well as contribute pollutant loads to receiving waters. By design, biore- tention facilities are located in areas where phosphorous and nitrogen levels may be elevated and these should not be limiting nutrients. If in question, have soil ana- lyzed for fertility. Mulch: Replace mulch annually in bioretention facilities where heavy metal 2014 Stormwater Management Manual for Western Washington Volume V - Chapter 7 - Page 985 deposition is high (e.g., contributing areas that include gas stations, ports and roads with high traffic loads). In residential settings or other areas where metals or other pollutant loads are not anticipated to be high, replace or add mulch as needed (likely 3 to 5 years) to maintain a 2 to 3 inch depth. . Soil: Soil mixes for bioretention facilities are designed to maintain long-term fertility and pollutant processing capability. Estimates from metal attenuation research sug- gest that metal accumulation should not present an environmental concern for at least 20 years in bioretention systems, but this will vary according to pollutant load. Replacing mulch media in bioretention facilities where heavy metal deposition is likely provides an additional level of protection for prolonged performance. If in question, have soil analyzed for fertility and pollutant levels. BMP T7.40: Compost -amended Vegetated Filter Strips (CAVFS) Description The CAVFS is a variation of the basic vegetated filter strip that adds soil amendments to the roadside embankment (See Figure V-7.4.3 Example of a Com ostAmended Veget- ated Filter Strip (CAVFS) (p.987)). The soil amendments improve infiltration char- acteristics, increase surface roughness, and improve plant sustainability. Once permanent vegetation is established, the advantages of the CAVFS are higher surface roughness; greater retention and infiltration capacity; improved removal of soluble cationic contaminants through sorption; improved overall vegetative health; and a reduc- tion of invasive weeds. Compost -amended systems have somewhat higher construction costs due to more expensive materials, but require less land area for runoff treatment, which can reduce overall costs. 2014 Stormwater Management Manual for Western Washington Volume V - Chapter 7 - Page 986 ...... ... ...... ... ... ... ... ...... .......... ... ... ........ ... ...... ...... .. .. ... ... ... .. ...... ... ......... ..... ... . . ...... . ...... ... ... ... ... ... ... . ... . . ...... ... ... .. ... ... ... ...... ..... ........... .. .............. ... ...... ...... .... .. ...... .... .. ......... ... .. ...... ... ... .......... ... ... . ......... ...... ... ... ... ... ... ... ...... ... . ..... ...... ... ......... ... ...... ... ... ... ... ... ... ...... ... ... ... ... ... ... ...... ... ... ... .......... ... ... ........... ... .. ... ... ... ... ... ........... ... ........ ...... .. ... ........ ... ... ........ ... ... ... ... ..... .. ... ....... ... ... ... ...... ...... ...... ... ... ... ... .. ...... ... ......... ...... ......... ... ......... ........... ...... ... ... ... ... ... ... ... ...... .. ............ ... ... ...... ... ... ........ ... ..... ..... ... ... ...... ...... ... ... . ...... ... ... .... ................. ...... ... ... ... ................. ... ... ...... ... ... .. ........ ...... ... ... ... ... ... .......... .... ... ... ...... ... ... ... ... ... ......... ......... ......... ... ..... ........... ...... ...... ... ... ... ......... ... ........... ... ... ... ...... ... ....... .. ...... ........ ... ..... ...... ........ ... ...... .......... ..... ........ ........ ..... .............. ...... ...... ........ ... ...... ... ... ... ......... ... ...... ... ... . ..... .............. ... ...... ... ...... ... ...... ......... ......... . . . . . . . . . . ... ...... ............. ........ ... ... . ...... ... . ........ .. . ... ... ....... .... . ... .. ... ... ... ........ ...... ... ...... ... ........ ... ... ...... ...... .......... .. ... ... ... ........ ...... ... ........ ... ........... . ...... ...... .. ...... .......... ....... ...... ............... . ... .. ... ..... ... ... ...... .. ... ...... ... ......... ....... ...... ... .. ......................... ...... . . . . . .... .............. .............. ......... ..... ... ... ......... .... ................. ... ... ... ... ... ... ...... ...... ........ ...... .. ...... ...... . ........ ... ... ... ... ... ..... ... ... ... .. ... ... ........ ... ... ........ ... ......... ... ... .. ... ... ..... ... ... ...... ...... ... ........ ... ........... 12 Stormwater Report — 2019 Appendix III — Soils Information E HuC—Hoypus gravelly loamy sand, 0 to 15 percent slopes Map Unit Setting ■ National map unit symbol: 2grm ■ Elevation: 50 to 490 feet • Mean annual precipitation: 24 inches • Mean annual air temperature: 48 degrees F • Frost -free period: 200 to 240 days • Farmland classification: Not prime farmland Map Unit Composition • Hoypus and similar soils: 100 percent • Estimates are based on observations, descriptions, and transects of the mapunit. Description of Hoypus Setting • Landform: Terraces • Parent material: Glacial outwash Typical profile ■ H1 - 0 to 2 inches: gravelly loamy sand • H2 - 2 to 10 inches: gravelly loamy sand ■ H3 - 10 to 26 inches: gravelly loamy sand ■ H4 - 26 to 60 inches: gravelly loamy sand Properties and qualities • Slope: 0 to 15 percent • Depth to restrictive feature: More than 80 inches ■ Natural drainage class: Somewhat excessively drained • Capacity of the most limiting layer to transmit water (Ksat): High to very high (5.95 to 19.98 in/hr) • Depth to water table: More than 80 inches • Frequency of flooding: None • Frequency of ponding: None • Available water storage in profile: Very low (about 1.6 inches) Interpretive groups • Land capability classification (irrigated): None specified • Land capability classification (nonirrigated): 4s ■ Hydrologic Soil Group: A • Forage suitability group: Droughty Soils (G002XN402WA) • Hydric soil rating: No CmC—Clallam gravelly sandy loam, 0 to 15 percent slopes Map Unit Setting • National map unit symbol: 2ggp ■ Elevation: 50 to 820 feet • Mean annual precipitation: 23 inches • Mean annual air temperature: 48 degrees F • Frost -free period: 160 to 200 days • Farmland classification: Farmland of statewide importance Map Unit Composition • Clallam and similar soils: 100 percent • Estimates are based on observations, descriptions, and transects of the mapunit. Description of Clallam Setting • Parent material: Basal till Typical profile • H1 - 0 to 3 inches: gravelly sandy loam • H2 - 3 to 23 inches: very gravelly sandy loam • H3 - 23 to 60 inches: gravelly sandy loam Properties and qualities ■ Slope: 0 to 15 percent • Depth to restrictive feature: 20 to 40 inches to densic material • Natural drainage class: Well drained • Capacity of the most limiting layer to transmit water (Ksat): Very low to moderately low (0.00 to 0.06 in/hr) • Depth to water table: About 19 to 39 inches • Frequency of flooding: None • Frequency of ponding: None ■ Available water storage in profile: Very low (about 1.9 inches) Interpretive groups • Land capability classification (irrigated): 6s • Land capability classification (nonirrigated): 4s • Hydrologic Soil Group: D • Forage suitability group: Limited Depth Soils (G002XN302WA) ■ Hydric soil rating: No Stormwater Report — 2019 Appendix IV — WWHM Analysis U m WWHM20 OJECT General Model Information Project Name: HOBR1801-2 Site Name: Site Address: City: Report Date: Gage: Data Start: Data End: 12/19/2018 Port Angeles 1948/10/01 2009/09/30 Timestep: 15 Minute Precip Scale: 0.800 Version Date: 2018/10/10 Version: 4.2.16 POC Thresholds Low Flow Threshold for POC1: 50 Percent of the 2 Year High Flow Threshold for POC1: 50 Year HOBR1801-2 12/19/2018 2:41:39 PM Page 2 Landuse Basin Data Predeveloped Land Use Basin 1 Bypass: No GroundWater: No Pervious Land Use acre A B, Forest, Flat 4.9658 Pervious Total 4.9658 Impervious Land Use acre Impervious Total 0 Basin Total 4.9658 Element Flows To: Surface Interflow Groundwater HOBR1801-2 12/19/2018 2:41:39 PM Page 3 Mitigated Land Use Roofs Bypass: No GroundWater: No Pervious Land Use acre Pervious Total 0 Impervious Land Use acre ROOF TOPS FLAT 1.3478 Impervious Total 1.3478 Basin Total 1.3478 Element Flows To: Surface Interflow Groundwater Surface retention 1 Surface retention 1 HOBR1801-2 12/19/2018 2:41:39 PM Page 4 Pavements Bypass: GroundWater: Pervious Land Use Pervious Total Impervious Land Use PARKING FLAT Impervious Total Basin Total Element Flows To: Surface Surface retention 1 No No acre 0 acre 3.618 3.618 3.618 Interflow Groundwater Surface retention 1 HOBR1801-2 12/19/2018 2:41:39 PM Page 5 Routing Elements Predeveloped Routing HOBR1801-2 12/19/2018 2:41:39 PM Page 6 Mitigated Routing Bioretention 1 Bottom Length: Bottom Width: Material thickness of first layer: Material type for first layer: Material thickness of second layer: Material type for second layer: Material thickness of third layer: Material type for third layer: Infiltration On Infiltration rate: Infiltration safety factor: Wetted surface area On Total Volume Infiltrated (ac-ft.): Total Volume Through Riser (ac-ft.): Total Volume Through Facility (ac-ft.): Percent Infiltrated: Total Precip Applied to Facility: Total Evap From Facility: Underdrain not used Discharge Structure Riser Height: 2 ft. Riser Diameter: 12 in. Element Flows To: Outlet 1 Outlet 2 541.00 ft. 5.00 ft. 0.25 SMMWW 12 in/hr 1.5 Sand 0 G RAVE L 7 0.36 360.839 0 360.839 100 7.818 5.798 Bioretention Hydraulic Table Stage(feet) Area(ac.) Volume(ac-ft.) Discharge(cfs) Infilt(cfs) 0.0000 0.1962 0.0000 0.0000 0.0000 0.0522 0.1941 0.0015 0.0000 0.0000 0.1044 0.1900 0.0032 0.0000 0.0002 0.1566 0.1860 0.0049 0.0000 0.0011 0.2088 0.1819 0.0067 0.0000 0.0028 0.2610 0.1778 0.0083 0.0000 0.0059 0.3132 0.1738 0.0101 0.0000 0.0106 0.3654 0.1697 0.0119 0.0000 0.0173 0.4176 0.1657 0.0138 0.0000 0.0264 0.4698 0.1616 0.0158 0.0000 0.0290 0.5220 0.1576 0.0179 0.0000 0.0397 0.5742 0.1536 0.0201 0.0000 0.0552 0.6264 0.1496 0.0223 0.0000 0.0743 0.6786 0.1455 0.0247 0.0000 0.0975 0.7308 0.1415 0.0271 0.0000 0.1253 0.7830 0.1375 0.0296 0.0000 0.1580 0.8352 0.1335 0.0321 0.0000 0.1836 0.8874 0.1295 0.0348 0.0000 0.2024 0.9396 0.1255 0.0375 0.0000 0.2477 0.9918 0.1215 0.0404 0.0000 0.2996 1.0440 0.1175 0.0433 0.0000 0.3585 1.0962 0.1135 0.0463 0.0000 0.3698 1.1484 0.1095 0.0494 0.0000 0.3800 1.2005 0.1056 0.0525 0.0000 0.3902 1.2527 0.1016 0.0558 0.0000 0.4005 HOBR1801-2 12/19/2018 2:41�39 PM Page 7 1.3049 0.0976 0.0591 0.0000 0.4107 1.3571 0.0936 0.0625 0.0000 0.4210 1.4093 0.0897 0.0660 0.0000 0.4313 1.4615 0.0857 0.0696 0.0000 0.4416 1.5137 0.0818 0.0733 0.0000 0.4519 1.5659 0.0778 0.0770 0.0000 0.4622 1.6181 0.0739 0.0809 0.0000 0.4725 1.6703 0.0700 0.0848 0.0000 0.4829 1.7225 0.0660 0.0888 0.0000 0.4932 1.7500 0.0621 0.0910 0.0000 0.4986 Bioretention Hydraulic Table Stage(feet)Area(ac.)VoIume(ac-ft.)Disc harge(cfs)To Amended (cfs)Infilt(cfs) 1.7500 0.1962 0.0910 0.0000 0.6978 0.0104 1.8022 0.2003 0.1013 0.0000 0.6978 0.0207 1.8544 0.2044 0.1119 0.0000 0.7180 0.0311 1.9066 0.2085 0.1226 0.0000 0.7382 0.0415 1.9588 0.2126 0.1336 0.0000 0.7584 0.0519 2.0110 0.2167 0.1448 0.0000 0.7787 0.0624 2.0632 0.2208 0.1563 0.0000 0.7989 0.0728 2.1154 0.2249 0.1679 0.0000 0.8191 0.0832 2.1676 0.2290 0.1797 0.0000 0.8393 0.0937 2.2198 0.2331 0.1918 0.0000 0.8595 0.1042 2.2720 0.2372 0.2041 0.0000 0.8797 0.1146 2.3242 0.2414 0.2166 0.0000 0.8999 0.1251 2.3764 0.2455 0.2293 0.0000 0.9201 0.1356 2.4286 0.2496 0.2422 0.0000 0.9403 0.1461 2.4808 0.2538 0.2553 0.0000 0.9606 0.1567 2.5330 0.2579 0.2687 0.0000 0.9808 0.1672 2.5852 0.2620 0.2823 0.0000 1.0010 0.1778 2.6374 0.2662 0.2960 0.0000 1.0212 0.1883 2.6896 0.2703 0.3100 0.0000 1.0414 0.1989 2.7418 0.2745 0.3243 0.0000 1.0616 0.2095 2.7940 0.2787 0.3387 0.0000 1.0818 0.2201 2.8462 0.2828 0.3534 0.0000 1.1020 0.2307 2.8984 0.2870 0.3682 0.0000 1.1222 0.2413 2.9505 0.2912 0.3,833 0.0000 1.1424 0.2519 3.0027 0.2954 0.3986 0.0000 1.1627 0.2625 3.0549 0.2996 0.4142 0.0000 1.1829 0.2732 3.1071 0.3038 0.4299 0.0000 1.2031 0.2839 3.1593 0.3080 0.4459 0..0000 1.2233 0.2945 3.2115 0.3122 0.4620 0.0000 1.2435 0.3052 3.2637 0.3164 0.4785 0.0000 1.2637 0.3159 3.3159 0.3206 0.4951 0.0000 1.2839 0.3266 3.3681 0.3248 0.5119 0.0000 1.3041 0.3373 3.4203 0.3290 0.5290 0.0000 1.3243 0.3481 3.4725 0.3332 0.5463 0.0000 1.3446 0.3588 3.5247 0.3374 0.5638 0.0000 1.3648 0.3696 3.5769 0.3417 0.5815 0.0000 1.3850 0.3803 3.6291 0.3459 0.5994 0.0000 1.4052 0.3911 3.6813 0.3502 0.6176 0.0000 1.4254 0.4019 3.7335 0.3544 0.6360 0.0000 1.4456 0.4127 3.7857 0.3587 0.6546 0.0716 1.4658 0.4235 3.8379 0.3629 0.6734 0.2754 1.4860 0.4343 3.8901 0.3672 0.6925 0.5479 1.5062 0.4452 3.9423 0.3714 0.7118 0.8600 1.5265 0.4560 3.9945 0.3757 0.7313 1.1839 1.5467 0.4669 4.0467 0.3800 0.7510 1.4914 1.5669 0.4777 HOBR1801-2 12/19/2018 2:41:39 PM Page 8 4.0989 0.3842 0.7709 1.7571 1.5871 0.4886 4.1511 0.3885 0.7911 1.9637 1.6073 0.4995 4.2033 0.3928 0.8115 2.1091 1.6275 0.5104 4.2555 0.3971 0.8321 2.2393 1.6477 0.5213 4.3077 0.4014 0.8529 2.3521 1.6679 0.5322 4.3599 0.4057 0.8740 2.4597 1.6881 0.5432 4.4121 0.4100 0.8953 2.5628 1.7084 0.5541 4.4643 0.4143 0.9168 2.6619 1.7286 0.5651 4.5165 0.4186 0.9386 2.7575 1.7488 0.5761 4.5687 0.4229 0.9605 2.8498 1.7690 0.5870 4.6209 0.4273 0.9827 2.9393 1.7892 0.5980 4.6731 0.4316 1.0051 3.0261 1.8094 0.6090 4.7253 0.4359 1.0278 3.1104 1.8296 0.6143 4.7500 0.4380 1.0386 3.1926 1.8392 0.0000 HOBR1801-2 12/19/2018 2:41:39 PM Page 9 Surface retention 1 Element Flows To: Outlet 1 Outlet 2 Bioretention 1 HOBR1801-2 12/19/2018 2:41:39 PM Page 10 Analysis Results POC 1 W U 0 10 100 Parcarit Tima E_ aaadirig + Predeveloped Predeveloped Landuse Totals for POC #1 Total Pervious Area: 4.9658 Total Impervious Area: 0 Mitigated Landuse Totals for POC #1 Total Pervious Area: 0 Total Impervious Area: 4.9658 coy 1 Cumul�ve Probebifly ... . + r F —. + a 0 000i a mop s.s i 2 0 u PI p a re u m vs m w ses � x Mitigated Flow Frequency Method: Log Pearson Type III 17B Flow Frequency Return Periods for Predeveloped. POC #1 Return Period Flow(cfs) 2 year 0.002779 5 year 0.00387 10 year 0.00442 25 year 0.004957 50 year 0.005268 100 year 0.005518 Flow Frequency Return Periods for Mitigated. POC #1 Return Period Flow(cfs) 2 year 0 5 year 0 10 year 0 25 year 0 50 year 0 100 year 0 Annual Peaks Annual Peaks for Predeveloped and Mitigated. POC #1 Year Predeveloped Mitigated 1949 0.004 0.000 1950 0.003 0.000 1951 0.003 0.000 1952 0.003 0.000 1953 0.004 0.000 1954 0.004 0.000 1955 0.004 0.000 1956 0.002 0.000 1957 0.003 0.000 1958 0.001 0.000 HOBR1801-2 12/19/2018 2:41:39 PM Page 11 1959 0.003 0.000 1960 0.004 0.000 1961 0.004 0.000 1962 0.002 0.000 1963 0.003 0.000 1964 0.004 0.000 1965 0.004 0.000 1966 0.002 0.000 1967 0.002 0.000 1968 0.003 0.000 1969 0.003 0.000 1970 0.003 0.000 1971 0.003 0.000 1972 0.003 0.000 1973 0.002 0.000 1974 0.001 0.000 1975 0.003 0.000 1976 0.002 0.000 1977 0.001 0.000 1978 0.001 0.000 1979 0.002 0.000 1980 0.004 0.000 1981 0.004 0.000 1982 0.004 0.000 1983 0.003 0.000 1984 0.002 0.000 1985 0.004 0.000 1986 0.003 0.000 1987 0.003 0.000 1988 0.003 0.000 1989 0.003 0.000 1990 0.002 0.000 1991 0.003 0.000 1992 0.003 0.000 1993 0.002 0.000 1994 0.000 0.000 1995 0.002 0.000 1996 0.004 0.000 1997 0.003 0.000 1998 0.000 0.000 1999 0.004 0.000 2000 0.004 0.000 2001 0.001 0.000 2002 0.004 0.000 2003 0.003 0.000 2004 0.004 0.000 2005 0.004 0.000 2006 0.004 0.000 2007 0.004 0.000 2008 0.002 0.000 2009 0.002 0.000 Ranked Annual Peaks Ranked Annual Peaks for Predeveloped and Mitigated. POC #1 Rank Predeveloped Mitigated 1 0.0040 0.0000 2 0.0040 0.0000 3 0.0040 0.0000 HOBR1801-2 12/19/2018 2AZ05 PM Page 12 4 0.0039 0.0000 5 0.0038 0.0000 6 0.0038 0.0000 7 0.0038 0.0000 8 0.0038 0.0000 9 0.0037 0.0000 10 0.0037 0.0000 11 0.0037 0.0000 12 0.0037 0.0000 13 0.0037 0.0000 14 0.0037 0.0000 15 0.0036 0.0000 16 0.0036 0.0000 17 0.0036 0.0000 18 0.0035 0.0000 19 0.0035 0.0000 20 0.0035 0.0000 21 0.0034 0.0000 22 0.0034 0.0000 23 0.0034 0.0000 24 0.0033 0.0000 25 0.0032 0.0000 26 0.0032 0.0000 27 0.0032 0.0000 28 0.0031 0.0000 29 0.0031 0.0000 30 0.0030 0.0000 31 0.0029 0.0000 32 0.0029 0.0000 33 0.0029 0.0000 34 0.0029 0.0000 35 0.0028 0.0000 36 0.0028 0.0000 37 0.0028 0.0000 38 0.0028 0.0000 39 0.0026 0.0000 40 0.0026 0.0000 41 0.0025 0.0000 42 0.0025 0.0000 43 0.0024 0.0000 44 0.0021 0.0000 45 0.0021 0.0000 46 0.0021 0.0000 47 0.0021 0.0000 48 0.0020 0.0000 49 0.0020 0.0000 50 0.0020 0.0000 51 0.0019 0.0000 52 0.0019 0.0000 53 0.0017 0.0000 54 0.0017 0.0000 55 0.0015 0.0000 56 0.0015 0.0000 57 0.0012 0.0000 58 0.0010 0.0000 59 0.0009 0.0000 60 0.0005 0.0000 61 0.0004 0.0000 HOBR1801-2 12/19/2018 2:42:05 PM Page 13 HOBR1801-2 12/19/2018 2:42:05 PM Page 14 Duration Flows The Facility PASSED Flow(cfs) Predev Mit Percentage Pass/Fail 0.0014 530 0 0 Pass 0.0014 507 0 0 Pass 0.0015 480 0 0 Pass 0.0015 458 0 0 Pass 0.0015 434 0 0 Pass 0.0016 410 0 0 Pass 0.0016 383 0 0 Pass 0.0017 369 0 0 Pass 0.0017 348 0 0 Pass 0.0017 330 0 0 Pass 0.0018 322 0 0 Pass 0.0018 308 0 0 Pass 0.0019 296 0 0 Pass 0.0019 288 0 0 Pass 0.0019 272 0 0 Pass 0.0020 257 0 0 Pass 0.0020 246 0 0 Pass 0.0021 236 0 0 Pass 0.0021 222 0 0 Pass 0.0021 211 0 0 Pass 0.0022 199 0 0 Pass 0.0022 188 0 0 Pass 0.0023 184 0 0 Pass 0.0023 168 0 0 Pass 0.0023 157 0 0 Pass 0.0024 153 0 0 Pass 0.0024 149 0 0 Pass 0.0024 146 0 0 Pass 0.0025 139 0 0 Pass 0.0025 135 0 0 Pass 0.0026 133 0 0 Pass 0.0026 123 0 0 Pass 0.0026 115 0 0 Pass 0.0027 108 0 0 Pass 0.0027 106 0 0 Pass 0.0028 103 0 0 Pass 0.0028 99 0 0 Pass 0.0028 97 0 0 Pass 0.0029 94 0 0 Pass 0.0029 85 0 0 Pass 0.0030 79 0 0 Pass 0.0030 75 0 0 Pass 0.0030 73 0 0 Pass 0.0031 70 0 0 Pass 0.0031 68 0 0 Pass 0.0032 60 0 0 Pass 0.0032 54 0 0 Pass 0.0032 51 0 0 Pass 0.0033 49 0 0 Pass 0.0033 48 0 0 Pass 0.0033 45 0 0 Pass 0.0034 39 0 0 Pass 0.0034 33 0 0 Pass HOBR1801-2 12/19/2018 2:42:05 PM Page 15 0.0035 30 0 0 Pass 0.0035 28 0 0 Pass 0.0035 23 0 0 Pass 0.0036 22 0 0 Pass 0.0036 19 0 0 Pass 0.0037 16 0 0 Pass 0.0037 14 0 0 Pass 0.0037 10 0 0 Pass 0.0038 6 0 0 Pass 0.0038 4 0 0 Pass 0.0039 4 0 0 Pass 0.0039 3 0 0 Pass 0.0039 3 0 0 Pass 0.0040 1 0 0 Pass 0.0040 0 0 0 Pass 0.0041 0 0 0 Pass 0.0041 0 0 0 Pass 0.0041 0 0 0 Pass 0.0042 0 0 0 Pass 0.0042 0 0 0 Pass 0.0042 0 0 0 Pass 0.0043 0 0 0 Pass 0.0043 0 0 0 Pass 0.0044 0 0 0 Pass 0.0044 0 0 0 Pass 0.0044 0 0 0 Pass 0.0045 0 0 0 Pass 0.0045 0 0 0 Pass 0.0046 0 0 0 Pass 0.0046 0 0 0 Pass 0.0046 0 0 0 Pass 0.0047 0 0 0 Pass 0.0047 0 0 0 Pass 0.0048 0 0 0 Pass 0.0048 0 0 0 Pass 0.0048 0 0 0 Pass 0.0049 0 0 0 Pass 0.0049 0 0 0 Pass 0.0050 0 0 0 Pass 0.0050 0 0 0 Pass 0.0050 0 0 0 Pass 0.0051 0 0 0 Pass 0.0051 0 0 0 Pass 0.0052 0 0 0 Pass 0.0052 0 0 0 Pass 0.0052 0 0 0 Pass 0.0053 0 0 0 Pass HOBR1801-2 12/19/2018 2:42:05 PM Page 16 Water Quality Water Quality BMP Flow and Volume for POC #1 On-line facility volume: Q acre-feet On-line facility target flow: 0 cfs. Adjusted for 15 min: D cfs. Off-line facility target flow: Q cfs. Adjusted for 15 min: D cfs. HOBR1801-2 12/19/2018 2:42:05 PM Page 17 LID Report LID Technique Used for Total Volume Volume Infiltration Cumulative Percent Water Quality Percent Comment Treatment 7 Needs Through Volume Volume Volume Wale Quality Treatment Facility (ac-ft) IrAltratlon Infiltrated Treated (ac-ft) (ac 11) Credit retention 1 POC ❑ 328.36 ❑ 100.00 Total Volume Infiltrated 328.36 0.00 0.00 100.00 0.00 0% No Treal Credit Duration Compliance with LID Analysis Standard 8% of 2-yr to 50% of Result = 2•yr Passed HOBR1801-2 12/19/2018 2:42:05 PM Page 18 Model- Default Modifications Total of 0 changes have been made. PERLND Changes No PERLND changes have been made. IMPLND Changes No IMPLND changes have been made. HOBR1801-2 12/19/2018 2:42:11 PM Page 19 Appendix Predeveloped Schematic ff asin 1 Pr,.97ac HOBR1801-2 12/19/2018 2:42:11 PM Page 20 Mitigated Schematic Pavements B ioretention HOBR1801-2 12/19/2018 2:42:11 PM Page 21 Predeveloped UCI File RUN GLOBAL WWHM4 model simulation START 1948 10 01 END RUN INTERP OUTPUT LEVEL 3 0 RESUME 0 RUN 1 END GLOBAL FILES <File> <Un#> END FILES OPN SEQUENCE 2009 09 30 UNIT SYSTEM 1 <-----------File Name ------------------------------>*** *** INGRP INDELT 00:15 PERLND 1 COPY 501 DISPLY 1 END INGRP END OPN SEQUENCE DISPLY DISPLY-INFO1 # - #<---------- Title ----------- >***TRAN PIVL DIG1 FIL1 1 Basin 1 MAX END DISPLY-INFO1 END DISPLY COPY TIMESERIES # - # NPT NMN *** 1 1 1 501 1 1 END TIMESERIES END COPY GENER OPCODE # # OPCD *** END OPCODE PARM # # K *** END PARM END GENER PERLND GEN-INFO PYR DIG2 FIL2 YRND 1 2 30 9 <PLS ><------- Name ------- >NBLKS Unit -systems Printer *** # - # User t-series Engl Metr *** in out *** 1 A/B, Forest, Flat 1 1 1 1 27 0 END GEN-INFO *** Section PWATER*** ACTIVITY <PLS > ************* Active Sections ***************************** # - # ATMP SNOW PWAT SED PST PWG PQAL MSTL PEST NITR PHOS TRAC *** 1 0 0 1 0 0 0 0 0 0 0 0 0 END ACTIVITY PRINT -INFO <PLS > ***************** Print -flags ***************************** PIVL PYR # - # ATMP SNOW PWAT SED PST PWG PQAL MSTL PEST NITR PHOS TRAC ********* 1 0 0 4 0 0 0 0 0 0 0 0 0 1 9 END PRINT -INFO HOBR1801-2 12/19/2018 2:42:12 PM Page 22 PWAT-PARM1 <PLS > PWATER variable monthly parameter value flags *** # - # CSNO RTOP UZFG VCS VUZ VNN VIFW VIRC VLE INFC HWT *** 1 0 0 0 0 0 0 0 0 0 0 0 END PWAT-PARM1 PWAT-PARM2 <PLS > PWATER input info: Part 2 *** # - # ***FOREST LZSN INFILT LSUR SLSUR KVARY 1 0 5 2 400 0.05 0.3 END PWAT-PARM2 PWAT-PARM3 <PLS > PWATER input info: Part 3 # - # ***PETMAX PETMIN INFEXP 1 0 0 2 END PWAT-PARM3 PWAT-PARM4 <PLS > PWATER input info: Part 4 # - # CEPSC UZSN NSUR 1 0.2 0.5 0.35 END PWAT-PARM4 AGWRC 0.996 *** INFILD DEEPFR BASETP AGWETP 2 0 0 0 *** INTFW IRC LZETP *** 0 0.7 0.7 PWAT-STATEI <PLS > *** Initial conditions at start of simulation ran from 1990 to end of 1992 (pat 1-11-95) RUN 21 *** # - # *** CEPS SURS UZS IFWS LZS AGWS 1 0 0 0 0 3 1 END PWAT-STATEI END PERLND IMPLND GEN-INFO <PLS ><------- Name ------- > Unit -systems Printer *** # - # User t-series Engl Metr *** in out *** END GEN-INFO *** Section IWATER*** ACTIVITY <PLS > ************* Active Sections ***************************** # - # ATMP SNOW IWAT SLD IWG IQAL *** END ACTIVITY PRINT -INFO <ILS > ******** Print -flags ******** PIVL PYR # - # ATMP SNOW IWAT SLD IWG IQAL ********* END PRINT -INFO IWAT-PARM1 <PLS > IWATER variable monthly parameter value flags *** # - # CSNO RTOP VRS VNN RTLI *** END IWAT-PARM1 IWAT-PARM2 <PLS > IWATER input info: Part 2 *** # - # *** LSUR SLSUR NSUR RETSC END IWAT-PARM2 IWAT-PARM3 <PLS > IWATER input info: Part 3 *** # - # ***PETMAX PETMIN END IWAT-PARM3 IWAT-STATEI <PLS > *** Initial conditions at start of simulation # - # *** RETS SURS END IWAT-STATEI GWVS 0 HOBR1801-2 12/19/2018 2:42:12 PM Page 23 END IMPLND SCHEMATIC <-Source-> <Name> # Basin 1*** PERLND 1 PERLND 1 ******Routing****** END SCHEMATIC <--Area--> <-Target-> MBLK <-factor-> <Name> # Tbl# 4.9658 COPY 501 12 4.9658 COPY 501 13 NETWORK <-Volume-> <-Grp> <-Member-><--Mult-->Tran <-Target vols> <-Grp> <-Member-> *** <Name> # <Name> # #<-factor->strg <Name> # # <Name> # # *** COPY 501 OUTPUT MEAN 1 1 48.4 DISPLY 1 INPUT TIMSER 1 <-Volume-> <-Grp> <-Member-><--Mult-->Tran <-Target vols> <-Grp> <-Member-> *** <Name> # <Name> # #<-factor->strg <Name> # # <Name> # # *** END NETWORK RCHRES GEN-INFO RCHRES Name Nexits Unit Systems Printer *** # - #<------------------ >< --- > User T-series Engl Metr LKFG *** in out *** END GEN-INFO *** Section RCHRES*** ACTIVITY <PLS > ************* Active Sections ***************************** # - # HYFG ADFG CNFG HTFG SDFG GQFG OXFG NUFG PKFG PHFG *** END ACTIVITY PRINT -INFO <PLS > ***************** Print -flags ******************* PIVL PYR # - # HYDR ADCA CONS HEAT SED GQL OXRX NUTR PLNK PHCB PIVL PYR ********* END PRINT -INFO HYDR-PARM1 RCHRES Flags for each HYDR Section *** # - # VC Al A2 A3 ODFVFG for each *** ODGTFG for each FUNCT for each FG FG FG FG possible exit *** possible exit possible exit * * * * * * * * * * * * * * *** END HYDR-PARM1 HYDR-PARM2 # - # FTABNO LEN DELTH STCOR KS DB50 *** <------ ><-------- ><--------><--------><--------><--------><--------> *** END HYDR-PARM2 HYDR-INIT RCHRES Initial conditions for each HYDR section *** # - # *** VOL Initial value of COLIND Initial value of OUTDGT *** ac-ft for each possible exit for each possible exit <------><-------- > <--- ><--- ><---><---><---> *** <---><---><---><---><---> END HYDR-INIT END RCHRES SPEC -ACTIONS END SPEC -ACTIONS FTABLES END FTABLES EXT SOURCES <-Volume-> <Member> SsysSgap<--Mult-->Tran <-Target vols> <-Grp> <-Member-> *** <Name> # <Name> # tem strg<-factor->strg <Name> # # <Name> # # *** WDM 2 PREC ENGL 0.8 PERLND 1 999 EXTNL PREC WDM 2 PREC ENGL 0.8 IMPLND 1 999 EXTNL PREC HOBR1801-2 12/19/2018 2:42:12 PM Page 24 WDM 1 EVAP ENGL 0.76 PERLND 1 999 EXTNL PETINP WDM 1 EVAP ENGL 0.76 IMPLND 1 999 EXTNL PETINP END EXT SOURCES EXT TARGETS <-Volume-> <-Grp> <-Member-><--Mult-->Tran <-Volume-> <Member> Tsys Tgap Amd *** <Name> # <Name> # #<-factor->strg <Name> # <Name> tem strg strg*** COPY 501 OUTPUT MEAN 1 1 48.4 WDM 501 FLOW ENGL REPL END EXT TARGETS MASS -LINK <Volume> <-Grp> <-Member-><--Mult--> <Target> <-Grp> <-Member->*** <Name> <Name> # #<-factor-> <Name> <Name> # #*** MASS -LINK 12 PERLND PWATER SURO 0.083333 COPY INPUT MEAN END MASS -LINK 12 MASS -LINK 13 PERLND PWATER IFWO 0.083333 COPY INPUT MEAN END MASS -LINK 13 END MASS -LINK END RUN HOBR1801-2 12/19/2018 2:42:12 PM Page 25 Mitigated UCI File RUN GLOBAL WWHM4 model simulation START 1948 10 01 END 2009 09 30 RUN INTERP OUTPUT LEVEL 3 0 RESUME 0 RUN 1 UNIT SYSTEM 1 END GLOBAL FILES <File> <Un#> < ----------- File Name ------------------------------ >*** <-ID-> *** WDM 26 HOBR1801-2.wdm MESSU 25 MitHOBR1801-2.MES 27 MitHOBR1801-2.L61 28 MitHOBR1801-2.L62 30 POCHOBR1801-21.dat END FILES OPN SEQUENCE INGRP INDELT 00:15 IMPLND 4 IMPLND 11 GENER 2 RCHRES 1 RCHRES 2 COPY 1 COPY 501 DISPLY 1 END INGRP END OPN SEQUENCE DISPLY DISPLY-INFO1 # - #<---------- Title ----------- >***TRAN PIVL DIG1 FIL1 PYR DIG2 FIL2 YRND 1 Surface retention 1 MAX 1 2 30 9 END DISPLY-INFO1 END DISPLY COPY TIMESERIES # - # NPT NMN *** 1 1 1 501 1 1 END TIMESERIES END COPY GENER OPCODE # # OPCD *** 2 24 END OPCODE PARM # # K *** 2 0. END PARM END GENER PERLND GEN-INFO <PLS ><------- Name ------- >NBLKS Unit -systems Printer *** # - # User t-series Engl Metr *** in out *** END GEN-INFO *** Section PWATER*** ACTIVITY <PLS > ************* Active Sections ***************************** # - # ATMP SNOW PWAT SED PST PWG PQAL MSTL PEST NITR PHOS TRAC *** END ACTIVITY PRINT -INFO HOBR1801-2 12/19/2018 2:42:12 PM Page 26 <PLS > ***************** Print -flags ***************************** PIVL PYR # - # ATMP SNOW PWAT SED PST PWG PQAL MSTL PEST NITR PHOS TRAC ********* END PRINT -INFO PWAT-PARM1 <PLS > PWATER variable monthly parameter value flags *** # - # CSNO RTOP UZFG VCS VUZ VNN VIFW VIRC VLE INFC HWT *** END PWAT-PARM1 PWAT-PARM2 <PLS > PWATER input info: Part 2 *** # - # ***FOREST LZSN INFILT LSUR SLSUR KVARY AGWRC END PWAT-PARM2 PWAT-PARM3 <PLS > PWATER input info: Part 3 # - # ***PETMAX PETMIN INFEXP END PWAT-PARM3 PWAT-PARM4 <PLS > PWATER input info: Part 4 # - # CEPSC UZSN NSUR END PWAT-PARM4 *** INFILD DEEPFR BASETP AGWETP *** INTFW IRC LZETP *** PWAT-STATEI <PLS > *** Initial conditions at start of simulation ran from 1990 to end of 1992 (pat 1-11-95) RUN 21 *** # - # *** CEPS SURS UZS IFWS LZS AGWS END PWAT-STATEI END PERLND IMPLND GEN-INFO <PLS ><- ------ Name ------- > Unit -systems Printer *** # - # User t-series Engl Metr *** in out *** 4 ROOF TOPS/FLAT 1 1 1 27 0 11 PARKING/FLAT 1 1 1 27 0 END GEN-INFO *** Section IWATER*** ACTIVITY <PLS > ************* Active Sections ***************************** # - # ATMP SNOW IWAT SLD IWG IQAL *** 4 0 0 1 0 0 0 11 0 0 1 0 0 0 END ACTIVITY PRINT -INFO <ILS > ******** Print -flags ******** PIVL PYR # - # ATMP SNOW IWAT SLD IWG IQAL ********* 4 0 0 4 0 0 0 1 9 11 0 0 4 0 0 0 1 9 END PRINT -INFO IWAT-PARM1 <PLS > IWATER variable monthly parameter value flags *** # - # CSNO RTOP VRS VNN RTLI *** 4 0 0 0 0 0 11 0 0 0 0 0 END IWAT-PARM1 IWAT-PARM2 <PLS > 4 11 END IWAT-PARM2 IWAT-PARM3 IWATER input info: Part 2 LSUR SLSUR NSUR 400 0.01 0.1 400 0.01 0.1 *** RETSC 0.1 0.1 GWVS HOBR1801-2 12/19/2018 2:42:12 PM Page 27 <PLS > IWATER input info: Part 3 *** # - # ***PETMAX PETMIN 4 0 0 11 0 0 END IWAT-PARM3 IWAT-STATEI <PLS > *** Initial conditions at start of simulation # - # *** RETS SURS 4 0 0 11 0 0 END IWAT-STATEI END IMPLND SCHEMATIC <-Source-> <--Area--> <-Target-> MBLK *** <Name> # <-factor-> <Name> # Tbl# *** Roofs*** IMPLND 4 1.3478 RCHRES 1 5 Pavements*** IMPLND 11 3.618 RCHRES 1 5 ******Routing****** IMPLND 4 1.3478 COPY 1 15 IMPLND 11 3.618 COPY 1 15 RCHRES 1 1 RCHRES 2 8 RCHRES 2 1 COPY 501 17 RCHRES 1 1 COPY 501 17 END SCHEMATIC NETWORK <-Volume-> <-Grp> <-Member-><--Mult-->Tran <-Target vols> <-Grp> <-Member-> *** <Name> # <Name> # #<-factor->strg <Name> # # <Name> # # *** COPY 501 OUTPUT MEAN 1 1 48.4 DISPLY 1 INPUT TIMSER 1 GENER 2 OUTPUT TIMSER .0011111 RCHRES 1 EXTNL OUTDGT 1 <-Volume-> <-Grp> <-Member-><--Mult-->Tran <-Target vols> <-Grp> <-Member-> *** <Name> # <Name> # #<-factor->strg <Name> # # <Name> # # *** END NETWORK RCHRES GEN-INFO RCHRES Name Nexits Unit Systems Printer *** # - #<------------------ ><---> User T-series Engl Metr LKFG *** in out *** 1 Surface retentio-007 3 1 1 1 28 0 1 2 Bioretention 1 2 1 1 1 28 0 1 END GEN-INFO *** Section RCHRES*** ACTIVITY <PLS > ************* Active Sections ***************************** # - # HYFG ADFG CNFG HTFG SDFG GQFG OXFG NUFG PKFG PHFG *** 1 1 0 0 0 0 0 0 0 0 0 2 1 0 0 0 0 0 0 0 0 0 END ACTIVITY PRINT -INFO <PLS > ***************** Print -flags ******************* PIVL PYR # - # HYDR ADCA CONS HEAT SED GQL OXRX NUTR PLNK PHCB PIVL PYR ********* 1 4 0 0 0 0 0 0 0 0 0 1 9 2 4 0 0 0 0 0 0 0 0 0 1 9 END PRINT -INFO HYDR-PARM1 RCHRES Flags for each HYDR Section *** # - # VC Al A2 A3 ODFVFG for each *** ODGTFG for each FUNCT for each HOBR1801-2 12/19/2018 2:42:12 PM Page 28 FG FG FG FG possible exit *** possible exit possible exit * * * * * * * * * * * * * * *** 1 0 1 0 0 4 5 6 0 0 0 1 0 0 0 2 1 2 2 2 2 0 1 0 0 4 5 0 0 0 0 0 0 0 0 2 2 2 2 2 END HYDR-PARM1 HYDR-PARM2 # - # FTABNO LEN DELTH STCOR KS DB50 *** <------ ><--------><-------- ><-------- ><-------- ><-------- ><-------- > *** 1 1 0.01 0.0 0.0 0.0 0.0 2 2 0.1 0.0 0.0 0.5 0.0 END HYDR-PARM2 HYDR-INIT RCHRES Initial conditions for each HYDR section *** # - # *** VOL Initial value of COLIND Initial value of OUTDGT *** ac-ft for each possible exit for each possible exit <------><-------- > <--- ><--- ><--- ><--- ><---> *** <--- ><--- ><---><--- ><---> 1 0 4.0 5.0 6.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 2 0 4.0 5.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 END HYDR-INIT END RCHRES SPEC -ACTIONS *** User -Defined Variable Quantity Lines *** addr *** <------> *** kwd varnam optyp opn vari sl s2 s3 tp multiply lc is ac as agfn *** <****> < ----> < ----> <-> <---- ><-><-><-><-><--------> <><-> <><-> UVQUAN vo12 RCHRES 2 VOL 4 UVQUAN v2m2 GLOBAL WORKSP 1 3 UVQUAN vpo2 GLOBAL WORKSP 2 3 UVQUAN v2d2 GENER 2 K 1 3 *** User -Defined Target Variable Names *** addr or addr or *** <------> <------> *** kwd varnam ct vari sl s2 s3 frac oper vari sl s2 s3 frac oper <****> <---- ><-> <---- ><-><-><-> < ---> <--> <----><-><-><-> <---> <--> UVNAME v2m2 1 WORKSP 1 1.0 QUAN UVNAME vpo2 1 WORKSP 2 1.0 QUAN UVNAME v2d2 1 K 1 1.0 QUAN *** opt foplop dcdts yr mo dy hr mn d t vnam sl s2 s3 ac quantity tc is rp <****><-><--><><-><--> <> <> <> <><><> <---- ><-><-><-><-><-------- > <> <-><-> GENER 2 v2m2 = 4411.03 *** Compute remaining available pore space GENER 2 vpo2 = v2m2 GENER 2 vpo2 -= vo12 *** Check to see if VPORA goes negative; if so set VPORA = 0.0 IF (vpo2 < 0.0) THEN GENER 2 vpo2 = 0.0 END IF *** Infiltration volume GENER 2 v2d2 = vpo2 END SPEC -ACTIONS FTABLES FTABLE 2 35 5 Depth Area Volume Outflowl Outflow2 Velocity Travel Time*** (ft) (acres) (acre-ft) (cfs) (cfs) (ft/sec) (Minutes)*** 0.000000 0.196241 0.000000 0.000000 0.000000 0.052198 0.194096 0.001529 0.000000 0.000000 0.104396 0.190024' 0.003152 0.000000 0.000227 0.156593 0.185956 0.004869 0.000000 0.001050 0.208791 0.181893 0.006680 0.000000 0.002826 0.260989 0.177835 0.008346 0.000000 0.005895 0.313187 0.173781 0.010095 0.000000 0.010601 0.365385 0.169732 0.011926 0.000000 0.017301 0.417582 0.165687 0.013840 0.000000 0.026364 0.469780 0.161646 0.015837 0.000000 0.029045 0.521978 0.157610 0.017916 0.000000 0.039725 0.574176 0.153579 0.020079 0.000000 0.055204 HOBR1801-2 12/19/2018 2:42:12 PM Page 29 0.626374 0.678571 0.730769 0.782967 0.835165 0.887363 0.939560 0.991758 1.043956 1.096154 1.148352 1.200549 1.252747 1.304945 1.357143 1.409341 1.461538 1.513736 1.565934 1.618132 1.670330 1.722527 1.750000 END FTABL FTABLE 59 6 Depth Time*** (ft) (Minutes)*** 0.000000 0.052198 0.104396 0.156593 0.208791 0.260989 0.313187 0.365385 0.417582 0.469780 0.521978 0.574176 0.626374 0.678571 0.730769 0.782967 0.835165 0.887363 0.939560 0.991758 1.043956 1.096154 1.148352 1.200549 1.252747 1.304945 1.357143 1.409341 1.461538 1.513736 1.565934 1.618132 1.670330 1.722527 1.774725 1.826923 1.879121 1.931319 1.983516 2.035714 0.149552 0.022324 0.000000 0.074332 0.145529 0.024653 0.000000 0.097541 0.141511 0.027064 0.000000 0.125276 0.137498 0.029559 0.000000 0.157994 0.133489 0.032138 0.000000 0.183633 0.129485 0.034799 0.000000 0.202420 0.125485 0.037545 0.000000 0.247711 0.121489 0.040374 0.000000 0.299562 0.117498 0.043286 0.000000- 0.358490 0.113512 0.046283 0.000000 0.369790 0.109530 0.049363 0.000000 0.380011 0.105553 0.052528 0.000000 0.390243 0.101580 0.055777 0.000000 0.400487 0.097611 0.059110 0.000000 0.410743 0.093647 0.062527 0.000000 0.421010 0.089688 0.066028 0.000000 0.431288 0.085733 0.069615 0.000000 0.441577 0.081783 0.073285 0.000000 0.451879 0.077837 0.077041 0.000000 0.462191 0.073895 0.080881 0.000000 0.472515 0.069959 0.084806 0.000000 0.482851 0.066026 0.088816 0.000000 0.493198 0.062098 0.101263 0.000000 0.498648 E 2 1 Area Volume Outflowl Outflow2 outflow 3 Velocity Travel (acres) (acre-ft) (cfs) (cfs) (cfs) (ft/sec) 0.062098 0.000000 0.000000 0.000000 0.010364 0.200320 0.010350 0.000000 0.697809 0.010364 0.204403 0.020913 0.000000 0.718020 0.020740 0.208491 0.031689 0.000000 0.738231 0.031127 0.212583 0.042678 0.000000 0.758442 0.041526 0.216680 0.053882 0.000000 0.778653 0.051936 0.220782 0.065299 0.000000 0.798864 0.062358 0.224887 0.076930 0.000000 0.819075 0.072791 0.228998 0.088776 0.000000 0.839286 0.083235 0.233113 0.100837 0.000000 0.859497 0.093691 0.237232 0.113112 0.000000 0.879708 0.104159 0.241356 0.125603 0.000000 0.899918 0.114638 0.245484 0.138309 0.000000 0.920129 0.125128 0.249617 0.151230 0.000000 0.940340 0.135629 0.253755 0.164368 0.000000 0.960551 0.146143 0.257897 0.177721 0.000000 0.980762 0.156667 0.262043 0.191291 0.000000 1.000973 0.167203 0.266194 0.205078 0.000000 1.021184 0.177751 0.270349 0.219081 0.000000 1.041395 0.188310 0.274509 0.233301 0.000000 1.061606 0.198880 0.278674 0.247739 0.000000 1.081817 0.209462 0.282843 0.262394 0.000000 1.102028 0.220055 0.267016 0.277266 0.000000 1.122239 0.230660 0.291194 0.292357 0.000000 1.142450 0.241276 0.295376 0.307666 0.000000 1.162661 0.251903 0.299563 0.323193 0.000000 1.182872 0.262542 0.303755 0.338939 0.000000 1.203082 0.273193 0.307951 0.354904 0.000000 1.223293 0.283855 0.312151 0.371088 0.000000 1.243504 0.294528 0.316356 0.387491 0.000000 1.263715 0.305213 0.320566 0.404114 0.000000 1.283926 0.315909 0.324780 0.420957 0.000000 1.304137 0.326617 0.328998 0.438020 0.000000 1.324348 0.337336 0.333221 0.455303 0.000000 1.344559 0.348066 0.337448 0.472807 0.000000 1.364770 0.358808 0.341680 0.490531 0.000000 1.384981 0.369562 0.345917 0.508477 0.000000 1.405192 0.380327 0.350158 0.526643 0.000000 1.425403 0.391103 0.354403 0.545032 0.000000 1.445614 0.401891 0.358653 0.563642 0.071570 1.465825 0.412690 HOBR1801-2 12/19/2018 2:42:12 PM Page 30 2.087912 0.362908 0.582474 0.275387 1.486036 0.423501 2.140110 0.367167 0.601528 0.547857 1.506246 0.434323 2.192308 0.371430 0.620804 0.859995 1.526457 0.445157 2.244505 0.375698 0.640304 1.183934 1.546668 0.456002 2.296703 0.379971 0.660026 1.491422 1.566879 0.466858 2.348901 0.384248 0.679971 1.757079 1.587090 0.477726 2.401099 0.388529 0.700140 1.963728 1.607301 0.488605 2.453297 0.392815 0.720532 2.109107 1.627512 0.499496 2.505495 0.397106 0.741148 2.239328 1.647723 0.510398 2.557692 0.401401 0.761988 2.352106 1.667934 0.521312 2.609890 0.405700 0.7830S3 2.459718 1.688145 0.532237 2.662088 0.410004 0.804342 2.562816 1.708356 0.543173 2.714286 0.414313 0.825855 2.661923 1.728567 0.554121 2.766484 0.418626 0.847594 2.757471 1.748778 0.565081 2.818681 0.422944 0.869558 2.849817 1.768989 0.576052 2.870879 0.427266 0.891748 2.939263 1.789200 0.587034 2.923077 0.431592 0.914163 3.026067 1.809411 0.598028 2.975275 0.435923 0.936804 3.110449 1.829621 0.609033 3.000000 0.437976 0.947608 3.192601 1.839195 0.614250 END FTABLE 1 END FTABLES EXT SOURCES <-Volume-> <Member> SsysSgap<--Mult-->Tran <-Target vols> <-Grp> <-Member-> *** <Name> # <Name> # tem strg<-factor->strg <Name> # ## <Name> # # *** WDM 2 PREC ENGL 0.8 PERLND 1 999 EXTNL PREC WDM 2 PREC ENGL 0.8 IMPLND 1 999 EXTNL PREC WDM 1 EVAP ENGL 0.76 PERLND 1 999 EXTNL PETINP WDM 1 EVAP ENGL 0.76 IMPLND 1 999 EXTNL PETINP WDM 2 PREC ENGL 0.8 RCHRES 1 EXTNL PREC WDM 1 EVAP ENGL 0.5 RCHRES 1 EXTNL POTEV WDM 1 EVAP ENGL 0.76 RCHRES 2 EXTNL POTEV END EXT SOURCES EXT TARGETS <-Volume-> <-Grp> <-Member-><--Mult-->Tran <-Volume-> <Member> Tsys Tgap Amd *** <Name> # <Name> # #<-factor->strg <Name> # <Name> tem strg strg*** RCHRES 2 HYDR RO 1 1 1 WDM 1000 FLOW ENGL REPL RCHRES 2 HYDR 0 1 1 1 WDM 1001 FLOW ENGL REPL RCHRES 2 HYDR 0 2 1 1 WDM 1002 FLOW ENGL REPL RCHRES 2 HYDR STAGE 1 1 1 WDM 1003 STAG ENGL REPL RCHRES 1 HYDR STAGE 1 1 1 WDM 1004 STAG ENGL REPL RCHRES 1 HYDR 0 1 1 1 WDM 1005 FLOW ENGL REPL COPY 1 OUTPUT MEAN 1 1 48.4 WDM 701 FLOW ENGL REPL COPY 501 OUTPUT MEAN 1 1 48.4 WDM 801 FLOW ENGL REPL END EXT TARGETS MASS -LINK <Volume> <-Grp> <-Member-><--Mult--> <Target> <-Grp> <-Member->*** <Name> <Name> # #<-factor-> <Name> <Name> # #*** MASS -LINK 5 IMPLND IWATER SURO 0.083333 RCHRES INFLOW IVOL END MASS -LINK 5 MASS -LINK 8 RCHRES OFLOW OVOL 2 RCHRES INFLOW IVOL END MASS -LINK 8 MASS -LINK 15 IMPLND IWATER SURO 0.083333 COPY INPUT MEAN END MASS -LINK 15 MASS -LINK 17 RCHRES OFLOW OVOL 1 COPY INPUT MEAN END MASS -LINK 17 END MASS -LINK HOBR1801-2 12/19/2018 2:42:12 PM Page 31 END RUN HOBR1801-2 12/19/2018 2:42:12 PM Page 32 Predeveloped HSPF Message File HOBR1801-2 12/19/2018 2:42:12 PM Page 33 Mitigated HSPF Message File HOBR1801-2 12/19/2018 2:42:12 PM Page 34 Disclaimer Legal Notice This program and accompanying documentation are provided 'as -is' without warranty of any kind. The entire risk regarding the performance and results of this program is assumed by End User. Clear Creek Solutions Inc. and the governmental licensee or sublicensees disclaim all warranties, either expressed or implied, including but not limited to implied warranties of program and accompanying documentation. In no event shall Clear Creek Solutions Inc. be liable for any damages whatsoever (including without limitation to damages for loss of business profits, loss of business information, business interruption, and the like) arising out of the use of, or inability to use this program even if Clear Creek Solutions Inc. or their authorized representatives have been advised of the possibility of such damages. Software Copyright © by: Clear Creek Solutions, Inc. 2005-2018; All Rights Reserved. Clear Creek Solutions, Inc. 6200 Capitol Blvd. Ste F Olympia, WA. 98501 Toll Free 1(866)943-0304 Local (360)943-0304 www.clearcreeksolutions.com HOBR1801-2 12/19/2018 2:42:12 PM Page 35 ... ...... ...... ... ... ...... ... ... ... .............. ... ... ... . ............ ........... ... ...... ...... . ... ... ... ... ...... ..... ... ... ... ... ... ... ... ...... ... ... ... .. ... ...... ... .... ... ... ... ... ... ... ... ... ...... ...... ....... ...... ... ... ... ... ... ...... ...... ... ... ... ... ... ... .. ............ ... ... ......... ...... ...... ......... ... ... ...... ... ... ... .... ... ... .... .... ... ... ...... ... ...... .......... ...... ... ........... ...... .. : ... ... ... ... ... ... ......... ...... ... ... ... ... ... . ...... ... ..... ... ... ... ...... ...... ...... ......... ...... ... ...... ... ...... ... ...... ... ... ... .. .. ..... ........... ...... ... ... ...... ......... ... ... ... ... ............... ...... ........ ........ ... ... ...... ..... ... ... ... ... ... ... : ... ... .... ... ... ...... ... ........... ...... ... ... ... ... ... ........... ... ...... ...... ...... ... .. ...... ... ... ..... ... ... ...... ... ... ... ... ... ... ... ... ...... ... ........ ... ........... ...... ........... ... .%:.:: ............ ... ......... ... ... ... ... ........... ... ...... ... ... ... . ... ... ... ... .. .. .. ... ... ... ... ...... ...... ... ... ...... ... ...... ........ ... ..... ....... ... ... ... ... .. ... .. ... ... ...... ... ... .............. ... ...... ...... ... ... ......... ...... ...... ......... .......... .. ... ...... ... ... ... .. ..... ...... ... ... ... ...... ... ... ... ... ... ...... ...... ... ........ ...... ...... ... ... . .. ............. ... ... ... ... ... ... ... ... ... ... ... ........... ... ....... ... ............... ... ... ... ... .......... ... ...... ... ...... . . ... ... ........ ... ... ... .. ... ... ...... ... .. ... ....... .. ... ... . ..... . .. ... ...... ... ... ...... ... ... ... ... ... ... ... ... ... ........ ... ... ... ... ........ ...... ... ..... ...... m ... ... ...... Stormwater Report — 2019 Appendix V — Operation and Maintenance m m KING COUNTY, WASHINGTON, SURFACE WATER DESIGN MANUAL; APPENDIX A FAI _13 4N MAINTENANCE REQUIREMENTS FOR FLOW CONTROL, CONVEYANCE, AND WATER QUALITY FACILITIES This appendix contains the maintenance requirements for the following typical stormwater control and water quality facilities and components (ctrl/click ► to follow the link): ► No. 1 — Detention Ponds (p. A-2) ► No. 2 — Infiltration Facilities (p. A-3) ► No. 3 — Detention Tanks and Vaults (p. A-5) ► No. 4 — Control Structure/Flow Restrictor (p. A-7) ► No. 5 — Catch Basins and Manholes (p. A-9) ► No. 6 — Conveyance Pipes and Ditches (p. A-11) ► No. 7 — Debris Barriers (e.g., Trash Racks) (p. A-12) ► No. 8 — Energy Dissipaters (p. A- 13) ► No. 9 — Fencing (p. A-14) ► No. 10 — Gates/Bollards/Access Barriers (p. A-15) ► No. 11 — Grounds (Landscaping) (p. A-16) ► No. 12 — Access Roads (p. A-17) ► No. 13 — Basic Bioswale (grass) (p. A-1 8) ► No. 14 — Wet Bioswale (p. A-19) ► No. 15 — Filter Strip (p. A-20) ► No. 16 — Wetpond (p. A-21) ► No. 17 — Wetvault (p. A-23) ► No. 18 — Stormwater Wetland (p. A-24) ► No. 19 — Sand Filter Pond (p. A-26) ► No. 20 — Sand Filter Vault (p. A-28) ► No. 21 — Stormfilter (Cartridge Type) (p. A-30) ► No. 22 — Baffle Oil/Water Separator (p. A-32) ► No. 23 — Coalescing Plate Oil/Water Separator (p. A-33) ► No. 24 — Catch Basin Insert (p. A-34) ► No. 25 — Drywell BMP (p. A-35) ► No. 26 — Gravel Filled Infiltration Trench BMP (p. A-35) ► No. 27 — Gravel Filled Dispersion Trench BMP (p. A-36) ► No. 28 —Native Vegetated Surface / Native Vmetated Landscape BMP (p. A-37) No. No. 29 — Perforated Pipe Connections BMP (p. A-37) ► No. 30 — Permeable Pavement BMP (p. A-38) ► No. 31—Bioretention BMP (p. A-39) ► No. 32 — RainWater Harvesting BMP (p. A- 40) ► No. 33 — Rock Pad BMP (p. A-40) ► No. 34 — Sheet Flow BMP (p. A-40) ► No. 35 — Splash Block BMP (p. A-41) ► No. 36 — Vegetated Roof BMP (p. A-42) 2016 Surface Water Design Manual — Appendix A 4/24/2016 A-1 APPENDIX A MAINTENANCE REQUIREMENTS FLOW CONTROL, CONVEYANCE, AND WQ FACILITIES 1: NO. 1- DETENTION PONDS Maintenance Defect or Problem Conditions When Maintenance Is Needed Results Expected When Component Maintenance Is Performed Trash and debris cleared from site. Site Trash and debris Any trash and debris which exceed 1 cubic foot per 1,000 square feet (this is about equal to the amount of trash it would take to fill up one standard size office garbage can). In general, there should be no visual evidence of dumping. Any noxious or nuisance vegetation which may Noxious and nuisance vegetation Noxious weeds constitute a hazard to County personnel or the removed according to applicable public regulations. No danger of noxious vegetation where County personnel or the public might normally be. Contaminants and Any evidence of contaminants or pollution such Materials removed and disposed of pollution as oil, gasoline, concrete slurries or paint according to applicable regulations Source control BMPs implemented if appropriate. No contaminants present other than a surface oil film. Grass/groundcover Grass or groundcover exceeds 18 inches in Grass or groundcover mowed to a height. height no greater than 6 inches. Top or Side Slopes Rodent holes Any evidence of rodent holes if facility is acting Rodents removed or destroyed and of Dam, Berm or as a dam or berm, or any evidence of water dam or berm repaired. Embankment piping through dam or berm via rodent holes. Tree growth Tree growth threatens integrity of slopes, does Trees do not hinder facility not allow maintenance access, or interferes with performance or maintenance maintenance activity If trees are not a threat or activities. not interfering with access or maintenance, they do not need to be removed. ....................................... Erosion Eroded damage over 2 inches deep where cause Slopes stabilized using appropriate of damage is still present or where there is erosion control measures. If erosion potential for continued erosion Any erosion is occurring on compacted slope, a observed on a compacted slope licensed civil engineer should be consulted to resolve source of erosion. Settlement l Any part of a dam, berm or embankment that Top or side slope restored to design has settled 4 inches lower than the design dimensions. If settlement is elevation. significant, a licensed civil engineer should be consulted to determine the cause of the settlement. Storage Area ....................... Sediment Accumulated sediment that exceeds 10% of the Sediment cleaned out to designed accumulation designed pond depth. pond shape and depth; pond reseeded if necessary to control erosion. Liner repaired or replaced. Liner damaged Liner is visible or pond does not hold water as (If Applicable) designed. Inlet/Outlet Pipe Sediment Sediment filling 20% or more of the pipe. Inlet/outlet pipes clear of sediment. accumulation Trash and debris Trash and debris accumulated in inlet/outlet No trash or debris in pipes. pipes (includes floatables and non-floatables). ................. .... Damaged Cracks wider than %-inch at the joint of the No cracks more than 'Y inch wide at inlet/outlet pipes or any evidence of soil entering the joint of the inlet/outlet pipe. at the joints of the inlet/outlet pipes. ................... Emergency Tree growth Tree growth impedes flow or threatens stability of Trees removed. Overflow/Spillway spillway. Rock missing Only one layer of rock exists above native soil in Spillway restored to design area five square feet or larger or any exposure of standards. native soil on the spillway. 4/24/2016 2016 Surface Water Design Manual — Appendix A A-2 APPENDIX A MAINTENANCE REQUIREMENTS FOR FLOW CONTROL, CONVEYANCE, AND WQ FACILITIES NO.2 - INFILTRATION FACILITIES Maintenance Defect or Problem Conditions When Maintenance Is Needed Results Expected When Component Maintenance Is Performed Site Trash and debris Any trash and debris which exceed 1 cubic foot Trash and debris cleared from site. per 1,000 square feet (this is about equal to the amount of trash it would take to fill up one standard size office garbage can). In general, there should be no visual evidence of dumping. Noxious weeds Any noxious or nuisance vegetation which may Noxious and nuisance vegetation constitute a hazard to County personnel or the removed according to applicable public. regulations. No danger of noxious vegetation where County personnel or the public might normally be. Contaminants and Any evidence of contaminants or pollution such Materials removed and disposed of pollution as oil, gasoline, concrete slurries or paint. according to applicable regulations. Source control BMPs implemented if appropriate. No contaminants present other than a surface oil film. Grass/groundcover Grass or groundcover exceeds 18 inches in Grass or groundcover mowed to a height. height no greater than 6 inches. Infiltration Pond, Rodent holes Any evidence of rodent holes if facility is acting Rodents removed or destroyed and Top or Side Slopes as a dam or berm, or any evidence of water dam or berm repaired. of Dam, Berm or piping through dam or berm via rodent holes. Embankment, Tree growth Tree growth threatens integrity of dams, berms Trees do not hinder facility or slopes, does not allow maintenance access, performance or maintenance or interferes with maintenance activity. If trees activities. are not a threat to dam, berm, or embankment integrity or not interfering with access or maintenance, they do not need to be removed. Erosion Eroded damage over 2 inches deep where cause Slopes stabilized using appropriate of damage is still present or where there is erosion control measures. If erosion potential for continued erosion. Any erosion is occurring on compacted slope, a observed on a compacted slope. licensed civil engineer should be consulted to resolve source of erosion. Settlement Any part of a dam, berm or embankment that Top or side slope restored to design has settled 4 inches lower than the design dimensions. If settlement is elevation. significant, a licensed civil engineer should be consulted to determine the cause of the settlement. ........................... Infiltration Pond, Sediment If two inches or more sediment is present or a Facility infiltrates as designed. Tank, Vault, Trench, accumulation percolation test indicates facility is working at or or Small Basin less than 90% of design. Storage Area Liner damaged Liner is visible or pond does not hold water as Liner repaired or replaced (If Applicable) designed. Infiltration Tank Plugged air vent Any blockage of the vent. Tank or vault freely vents. Structure Tank bent out of Any part of tank/pipe is bent out of shape more Tank repaired or replaced to design. shape than 10% of its design shape. Gaps between A gap wider than %-inch at the joint of any tank No water or soil entering tank sections, damaged sections or any evidence of soil particles entering through joints or walls. joints or cracks or the tank at a joint or through a wall. tears in wall Infiltration Vault Damage to wall, Cracks wider than'/2-inch, any evidence of soil Vault is sealed and structurally Structure frame, bottom, and/or entering the structure through cracks or qualified sound. top slab inspection personnel determines that the vault is not structurally sound. 2016 Surface Water Design Manual — Appendix A 4/24/2016 A-3 APPENDIX A MAINTENANCE REQUIREMENTS FLOW CONTROL, CONVEYANCE, AND WQ FACILITIES NO.2 - INFILTRATION FACILITIES Maintenance Defect or Problem Conditions When Maintenance Is Needed Results Expected When Component Maintenance Is Performed Inlet/Outlet Pipes Sediment Sediment filling 20% or more of the pipe Inlet/outlet pipes clear of sediment. accumulation Trash and debris Trash and debris accumulated in inlet/outlet No trash or debris in pipes. pipes (includes floatables and non-floatables). Damaged Cracks wider than 1/2-inch at the joint of the No cracks more than %,inch wide at inlet/outlet pipes or any evidence of soil entering the joint of the inlet/outlet pipe. Cover/lid not in place at the joints of the inlet/outlet pipes. Cover/lid is missing or only partially in place Access Manhole Manhole access covered Any open manhole requires immediate maintenance. Locking mechanism ......... Mechanism cannot be opened by one Mechanism opens with proper tools. not working maintenance person with proper tools. Bolts cannot be seated. Self-locking cover/lid does not work Cover/lid difficult to One maintenance person cannot remove Cover/lid can be removed and remove cover/lid after applying 80 Ibs of lift reinstalled by one maintenance person. Ladder rungs unsafe Missing rungs, misalignment, rust, or cracks Ladder meets design standards. Allows maintenance person safe access. Large access Damaged or difficult Large access doors or plates cannot be Replace or repair access door so it doors/plate to open opened/removed using normal equipment. can opened as designed. Gaps, doesn't cover Large access doors not flat and/or access Doors close flat; covers access completely opening not completely covered. opening completely. Lifting Rings missing, Lifting rings not capable of lifting weight of door Lifting rings sufficient to lift or rusted or plate. remove door or plate. Infiltration Pond, Plugged _..-.............. _ - Filter bag more than 1/2 full. Replace filter bag or redesign Tank, Vault, Trench, system. or Small Basin Filter Bags Infiltration Pond, _............ Sediment ...... ......... 6" or more of sediment has accumulated. Pre -settling occurs as designed Tank, Vault, Trench, accumulation or Small Basin Pre - settling Ponds and Vaults _......................... Infiltration Pond, Plugged High water level on upstream side of filter Rock filter replaced evaluate need Rock Filter remains for extended period of time or little or no for filter and remove if not water flows through filter during heavy rain necessary. storms. Infiltration Pond Rock missing ............... Only one layer of rock exists above native soil in Spillway restored to design Emergency area five square feet or larger, or any exposure standards. Overflow Spillway of native soil at the top of out flow path of spillway. Rip -rap on inside slopes need not be replaced. Tree growth .... . Tree growth impedes flow or threatens stability of Trees removed. spillway. 4/24/2016 2016 Surface Water Design Manual — Appendix A A-4 APPENDIX A MAINTENANCE REQUIREMENTS FOR FLOW CONTROL. CONVEYANCE, AND WQ FACILITIES �.. _. NO.3 - DETENTION TANKS AND VAULTS Maintenance Defect or Problem Conditions When Maintenance is Needed Results Expected When Component Maintenance is Performed Site Trash and debris Any trash and debris which exceed 1 cubic foot Trash and debris cleared from site per 1,000 square feet (this is about equal to the amount of trash it would take to fill up one standard size office garbage can). In general, there should be no visual evidence of dumping. Noxious weeds Any noxious or nuisance vegetation which may Noxious and nuisance vegetation constitute a hazard to County personnel or the removed according to applicable public. regulations. No danger of noxious vegetation where County personnel or the public might normally be. Contaminants and Any evidence of contaminants or pollution such Materials removed and disposed of pollution as oil, gasoline, concrete slurries or paint. according to applicable regulations. Source control BMPs implemented if appropriate. No contaminants present other than a surface oil film. Grass/groundcover Grass or groundcover exceeds 18 inches in Grass or groundcover mowed to a height. Any trash and debris accumulated in vault or height no greater than 6 inches. Tank or Vault Trash and debris No trash or debris in vault. Storage Area tank (includes floatables and non-floatables). Sediment Accumulated sediment depth exceeds 10% of All sediment removed from storage accumulation the diameter of the storage area for length of storage vault or any point depth exceeds 15% of area. diameter. Example: 72-inch storage tank would require cleaning when sediment reaches depth of 7 inches for more than % length of tank. Tank Structure Plugged air vent Any blockage of the vent. Tank or vault freely vents. Tank bent out of Any part of tank/pipe is bent out of shape more Tank repaired or replaced to design. shape than 10% of its design shape. Gaps between A gap wider than '/z-inch at the joint of any tank No water or soil entering tank sections, damaged sections or any evidence of soil particles entering through joints or walls. joints or cracks or the tank at a joint or through a wall. tears in wall Vault Structure Damage to wall, Cracks wider than %-inch, any evidence of soil Vault is sealed and structurally frame, bottom, and/or entering the structure through cracks or qualified sound. top slab inspection personnel determines that the vault is not structurally sound. Inlet/Outlet Pipes Sediment Sediment filling 20% or more of the pipe. Inlet/outlet pipes clear of sediment accumulation Trash and debris Trash and debris accumulated in inlet/outlet No trash or debris in pipes. pipes (includes floatables and non-floatables) Damaged Cracks wider than '/z-inch at the joint of the No cracks more than wide at inlet/outlet pipes or any evidence of soil entering the joint of the inlet/outlet pipe. at the joints of the inlet/outlet pipes. 2016 Surface Water Design Manual — Appendix A 4/24/2016 A-5 APPENDIX A MAINTENANCE REQUIREMENTS FLOW CONTROL, CONVEYANCE, AND WQ FACILITIES NO.3 - DETENTION TANKS AND �VAULTS Maintenance Defect or Problem 1 Conditions When Maintenance is Needed Component Access Manhole Cover/lid not in place Locking mechanism not working Cover/lid difficult to remove Ladder rungs unsafe Cover/lid is missing or only partially in place. Any open manhole requires immediate maintenance. - Mechanism cannot be opened by one maintenance person with proper tools. Bolts cannot be seated. Self-locking cover/lid does not work. One maintenance person cannot remove cover/lid after applying 80 Ibs of lift. Missing rungs, misalignment, rust, or cracks. Large access Damaged or difficult Large access doors or plates cannot be doors/plate to open opened/removed using normal equipment. Gaps, doesn't cover Large access doors not flat and/or access completely opening not completely covered. Lifting Rings missing, Lifting rings not capable of lifting weight of door rusted or plate. Results Expected When Maintenance is Performed Manhole access covered. Mechanism opens with proper tools. Cover/lid can be removed and reinstalled by one maintenance person. Ladder meets design standards. Allows maintenance person safe access. Replace or repair access door so it can opened as designed. Doors close flat; covers access opening completely. Lifting rings sufficient to lift or remove door or plate. 4/24/2016 2016 Surface Water Design Manual — Appendix A A-6 APPENDIX A MAINTENANCE REQUIREMENTS FOR FLOW CONTROL, CONVEYANCE, AND WQ FACILITIES NO.4 - CONTROL STRUCTUREIFLOW RESTRICTOR Maintenance Defect or Problem Condition When Maintenance is Needed Results Expected When Component Maintenance is Performed No Trash or debris blocking or Structure Trash and debris Trash or debris of more than % cubic foot which is located immediately in front of the structure potentially blocking entrance to opening or is blocking capacity of the structure structure. by more than 10%. Trash or debris in the structure that exceeds 1/3 the depth from the bottom of basin to invert the No trash or debris in the structure, lowest pipe into or out of the basin. Deposits of garbage exceeding 1 cubic foot in No condition present which would volume. attract or support the breeding of insects or rodents. Sediment Sediment exceeds 60% of the depth from the Sump of structure contains no bottom of the structure to the invert of the lowest sediment. pipe into or out of the structure or the bottom of the FROP-T section or is within 6 inches of the invert of the lowest pipe into or out of the structure or the bottom of the FROP-T section. Damage to frame Frame is even with curb Corner of frame extends more than'/< inch past and/or top slab curb face into the street (If applicable). Top slab has holes larger than 2 square inches Top slab is free of holes and cracks. or cracks wider than % inch. Frame not sitting flush on top slab, i.e., Frame is sitting flush on top slab. separation of more than 3/< inch of the frame from the top slab. Cracks in walls or Cracks wider than inch and longer than 3 feet, Structure is sealed and structurally bottom any evidence of soil particles entering structure sound. through cracks, or maintenance person judges that structure is unsound. Cracks wider than inch and longer than 1 foot No cracks more than ,/a inch wide at at the joint of any inlet/outlet pipe or any the joint of inlet/outlet pipe. evidence of soil particles entering structure through cracks. Settlement/ Structure has settled more than 1 inch or has Basin replaced or repaired to design misalignment rotated more than 2 inches out of alignment. standards. Damaged pipe joints Cracks wider than 1/2-inch at the joint of the No cracks more than %-inch wide at inlet/outlet pipes or any evidence of soil entering the joint of inlet/outlet pipes. the structure at the joint of the inlet/outlet pipes. Contaminants and Any evidence of contaminants or pollution such Materials removed and disposed of pollution as oil, gasoline, concrete slurries or paint. according to applicable regulations Source control BMPs implemented if appropriate. No contaminants present other than a surface oil film. Ladder rungs missing Ladder is unsafe due to missing rungs, Ladder meets design standards and or unsafe misalignment, rust, cracks, or sharp edges allows maintenance person safe access. FROP-T Section Damage T section is not securely attached to structure T section securely attached to wall wall and outlet pipe structure should support at and outlet pipe. least 1,000 Ibs of up or down pressure. Structure is not in upright position (allow up to Structure in correct position. 10% from plumb). . _ . Connections to outlet pipe are not watertight or ...... Connections to outlet pipe are water show signs of deteriorated grout. tight; structure repaired or replaced and works as designed. Any holes —other than designed holes —in the Structure has no holes other than structure. designed holes. 2016 Surface Water Design Manual — Appendix A 4/24/2016 A-7 APPENDIX A MAINTENANCE REQUIREMENTS FLOW CONTROL, CONVEYANCE, AND WQ FACILITIES NO.4 - CONTROL STRUCTURE/FLOW RESTRICTOR Maintenance Defect or Problem Condition When Maintenance is Needed Results Expected When Component Damaged or missing Maintenance is Performed Cleanout Gate Cleanout gate is missing. Replace cleanout gate. Cleanout gate is not watertight Gate is watertight and works as designed- ......... ...... Gate cannot be moved up and down by one Gate moves up and down easily and maintenance person. is watertight. Chain/rod leading to gate is missing or damaged. Chain is in place and works as designed. Orifice Plate Damaged or missing Control device is not working properly due to Plate is in place and works as missing, out of place, or bent orifice plate. designed. Obstructions Any trash, debris, sediment, or vegetation Plate is free of all obstructions and blocking the plate. works as designed. Overflow Pipe Obstructions Any trash or debris blocking (or having the Pipe is free of all obstructions and potential of blocking) the overflow pipe. works as designed. Deformed or Lip of overflow pipe is bent or deformed. Overflow pipe does not allow damaged lip overflow at an elevation lower than design Inlet/Outlet Pipe Sediment Sediment filling 20% or more of the pipe. Inlet/outlet pipes clear of sediment. accumulation Trash and debris Trash and debris accumulated in inlet/outlet No trash or debris in pipes. pipes (includes floatables and non-floatables). Damaged Cracks wider than '%-inch at the joint of the No cracks more than '/,-inch wide at inlet/outlet pipes or any evidence of soil entering the joint of the inlet/outlet pipe. ...... at the joints of the inlet/outlet pipes- ........... Grate opening meets design Metal Grates ............................. Unsafe grate opening Grate with opening wider than 7/8 inch. (If Applicable) standards. Trash and debris Trash and debris that is blocking more than 20% Grate free of trash and debris, of grate surface- footnote to guidelines for disposal Damaged or missing Grate missing or broken member(s) of the grate. Grate is in place and meets design standards. Manhole Cover/Lid Cover/lid not in place Cover/lid is missing or only partially in place Cover/lid protects opening to Any open structure requires urgent structure. maintenance. Locking mechanism Mechanism cannot be opened by one Mechanism opens with proper tools. Not Working maintenance person with proper tools. Bolts cannot be seated. Self-locking cover/lid does not work. Cover/lid difficult to One maintenance person cannot remove Cover/lid can be removed and Remove cover/lid after applying 80 lbs. of lift. reinstalled by one maintenance person. 4/24/2016 2016 Surface Water Design Manual — Appendix A A-8 APPENDIX A MAINTENANCE REQUIREMENTS FOR FLOW CONTROL, CONVEYANCE, AND WQ FACILITIES NO.5 - CATCH BASINS AND MANHOLES Maintenance Defect or Problem Condition When Maintenance is Needed I Results Expected When Component Maintenance is Performed Structure Sediment Sediment exceeds 60% of the depth from the Sump of catch basin contains no bottom of the catch basin to the invert of the sediment. lowest pipe into or out of the catch basin or is within 6 inches of the invert of the lowest pipe into or out of the catch basin. Trash and debris Trash or debris of more than % cubic foot which No Trash or debris blocking or is located immediately in front of the catch basin potentially blocking entrance to opening or is blocking capacity of the catch basin catch basin. by more than 10%. ..................... Trash or debris in the catch basin that exceeds No trash or debris in the catch 1/3 the depth from the bottom of basin to invert basin. the lowest pipe into or out of the basin. Dead animals or vegetation that could generate No dead animals or vegetation odors that could cause complaints or dangerous present within catch basin. gases (e.g., methane). Deposits of garbage exceeding 1 cubic foot in No condition present which would volume. attract or support the breeding of insects or rodents. Damage to frame Corner of frame extends more than % inch past Frame is even with curb and/or top slab curb face into the street (If applicable). Top slab has holes larger than 2 square inches Top slab is free of holes and cracks. or cracks wider than '% inch. Frame not sitting flush on top slab, i.e., Frame is sitting flush on top slab. separation of more than % inch of the frame from the top slab. Cracks in walls or Cracks wider than % inch and longer than 3 feet, Catch basin is sealed and is bottom any evidence of soil particles entering catch structurally sound. basin through cracks, or maintenance person judges that catch basin is unsound. Cracks wider than'/z inch and longer than 1 foot No cracks more than 1/4 inch wide at at the joint of any inlet/outlet pipe or any the joint of inlet/outlet pipe. evidence of soil particles entering catch basin through cracks. Settlement/ Catch basin has settled more than 1 inch or has Basin replaced or repaired to design misalignment rotated more than 2 inches out of alignment. standards. Damaged pipe joints Cracks wider than %-inch at the joint of the No cracks more than 1/4-inch wide at inlet/outlet pipes or any evidence of soil entering the joint of inlet/outlet pipes. the catch basin at the joint of the inlet/outlet pipes. Contaminants and Any evidence of contaminants or pollution such Materials removed and disposed of pollution as oil, gasoline, concrete slurries or paint. according to applicable regulations. Source control BMPs implemented if appropriate. No contaminants present other than a surface oil film. Inlet/Outlet Pipe Sediment Sediment filling 20% or more of the pipe. Inlet/outlet pipes clear of sediment. accumulation Trash and debris Trash and debris accumulated in inlet/outlet No trash or debris in pipes. pipes (includes floatables and non-floatables). Damaged Cracks wider than at the joint of the No cracks more than %< inch wide at inlet/outlet pipes or any evidence of soil entering the joint of the inlet/outlet pipe. at the joints of the inlet/outlet pipes. 2016 Surface Water Design Manual — Appendix A 4/24/2016 A-9 APPENDIX A MAINTENANCE REQUIREMENTS FLOW CONTROL, CONVEYANCE, AND WQ FACILITIES NO.5 -- CATCH BASINS AND MANHOLES Maintenance Defect or Problem Component Metal Grates Unsafe grate opening (Catch Basins) Trash and debris Damaged or missing Manhole Cover/Lid I Cover/lid not in place Locking mechanism Not Working Cover/lid difficult to Remove Condition When Maintenance is Needed Results Expected When Maintenance is Performed Grate with opening wider than 7/8 inch. Grate opening meets design standards. Trash and debris that is blocking more than 20% Grate free of trash and debris. of grate surface. footnote to guidelines for disposal Grate missing or broken member(s) of the grate. Grate is in place and meets design Any open structure requires urgent standards. maintenance. Cover/lid is missing or only partially in place. Cover/lid protects opening to Any open structure requires urgent structure. maintenance Mechanism cannot be opened by one Mechanism opens with proper tools. maintenance person with proper tools. Bolts cannot be seated. Self-locking cover/lid does not work. One maintenance person cannot remove Cover/lid can be removed and cover/lid after applying 80 lbs. of lift. reinstalled by one maintenance person. 4/24/2016 2016 Surface Water Design Manual — Appendix A A-10 APPENDIX A MAINTENANCE REQUIREMENTS FOR FLOW CONTROL: CONVEYANCE. AND WQ FACILITIES NO.6 - CONVEYANCE PIPES AND DITCHES4, Maintenance Defect or Problem Conditions When Maintenance is Needed Results Expected When Component Maintenance is Performed Water flows freely through pipes. Pipes Sediment & debris ...�.......� ._...W.....—. Accumulated sediment or debris that exceeds accumulation 20% of the diameter of the pipe. Vegetation/roots Water flows freely through pipes, Vegetation/roots that reduce free movement of water through pipes. Contaminants and Any evidence of contaminants or pollution such Materials removed and disposed of pollution as oil, gasoline, concrete slurries or paint according to applicable regulations. Source control BMPs implemented if appropriate. No contaminants present other than a surface oil film. Protective coating is damaged; rust or corrosion Pipe repaired or replaced. Damage to protective coating or corrosion is weakening the structural integrity of any part of pipe. Damaged Any dent that decreases the cross section area Pipe repaired or replaced. of pipe by more than 20% or is determined to have weakened structural integrity of the pipe. Ditches Trash and debris Trash and debris exceeds 1 cubic foot per 1,000 Trash and debris cleared from square feet of ditch and slopes. ditches. Sediment Accumulated sediment that exceeds 20% of the Ditch cleaned/flushed of all accumulation design depth. sediment and debris so that it matches design. Noxious weeds Noxious and nuisance vegetation Any noxious or nuisance vegetation which may constitute a hazard to County personnel or the removed according to applicable public regulations, No danger of noxious vegetation where County personnel or the public might normally be. Contaminants and Any evidence of contaminants or pollution such Materials removed and disposed of pollution as oil, gasoline, concrete slurries or paint according to applicable regulations. Source control BMPs implemented if appropriate. No contaminants present other than a surface oil film. Vegetation Vegetation that reduces free movement of water Water flows freely through ditches. through ditches. Erosion damage to Any erosion observed on a ditch slope. Slopes are not eroding. slopes Rock lining out of One layer or less of rock exists above native soil Replace rocks to design standards. place or missing (If area 5 square feet or more, any exposed native Applicable) soil. 2016 Surface Water Design Manual — Appendix A 4/24/2016 A-11 APPENDIX A MAINTENANCE REQUIREMENTS FLOW CONTROL, CONVEYANCE, AND WQ FACILITIES NO.7 - DEBRIS BARRIERS (E.G., TRASH RACKS) Maintenance Defect or Problem Condition When Maintenance is Needed Component Site Trash and debris Trash or debris plugging more than 20% of the area of the barrier. Sediment Sediment accumulation of greater than 20% of accumulation the area of the barrier Structure Cracked broken or Structure which bars attached to is damaged - loose pipe is loose or cracked or concrete structure is cracked, broken of loose. Bars Bar spacing Bar spacing exceeds 6 inches. Damaged or missing Bars are bent out of shape more than 3 inches. bars Bars are missing or entire barrier missing. Bars are loose and rust is causing 50% deterioration to any part of barrier. Results Expected When Maintenance is Performed. Barrier clear to receive capacity flow. Barrier clear to receive capacity flow. Structure barrier attached to is sound. Bars have at most 6 inches spacing. Bars in place with no bends more than % inch. Bars in place according to design. Repair or replace barrier to design standards. 4/24/2016 2016 Surface Water Design Manual —Appendix A A-12 APPENDIX A MAINTENANCE REQUIREMENTS FOR FLOW CONTROL. CONVEYANCE, AND WQ FACILITIES NO.8 - ENERGY DISSIPATERS Maintenance Defect or Problem Conditions When Maintenance is Needed Results Expected When Component Trash and/or debris accumulation. Maintenance is Performed. Site Trash and debris Dissipater clear of trash and/or debris. Contaminants and Any evidence of contaminants or pollution such Materials removed and disposed of pollution as oil, gasoline, concrete slurries or paint. according to applicable regulations. Source control BMPs implemented if appropriate. No contaminants present other than a surface oil film. Rock pad prevents erosion. Rock Pad Missing or moved Only one layer of rock exists above native soil in Rock area five square feet or larger or any exposure of native soil. Dispersion Trench Pipe plugged with Accumulated sediment that exceeds 20% of the Pipe cleaned/flushed so that it sediment design depth. matches design. Not discharging water ...— Visual evidence of water discharging at ...... ............. ................. Water discharges from feature by properly concentrated points along trench (normal sheet flow. condition is a "sheet flow" of water along trench). Perforations plugged. Over 1/4 of perforations in pipe are plugged with Perforations freely discharge flow, debris or sediment. ................ Water flows out top of Water flows out of distributor catch basin during No flow discharges from distributor "distributor" catch any storm less than the design storm. catch basin. basin Receiving area over- ........ ...� Water in receiving area is causing or has No danger of landslides saturated potential of causing landslide problems. Mesh is intact, no rock missing. Gabions Damaged mesh Mesh of gabion broken, twisted or deformed so structure is weakened or rock may fall out, Corrosion Gabion mesh shows corrosion through more All gabion mesh capable of than % of its gage. containing rock and retaining designed form. Gabion basket shape deformed due to any All gabion baskets intact, structure Collapsed or deformed baskets cause, stands as designed. Missing rock Any rock missing that could cause gabion to No rock missing. loose structural integrity Manhole/Chamber Worn or damaged Structure dissipating flow deteriorates to % or Structure is in no danger of failing. post, baffles or side of original size or any concentrated worn spot chamber exceeding one square foot which would make structure unsound. Damage to wall, Cracks wider than or any evidence of soil Manhole/chamber is sealed and frame, bottom, and/or entering the structure through cracks, or structurally sound. top slab maintenance inspection personnel determines that the structure is not structurally sound. Damaged pipe joints Cracks wider than %-inch at the joint of the No soil or water enters and no water inlet/outlet pipes or any evidence of soil entering discharges at the joint of inlet/outlet the structure at the joint of the inlet/outlet pipes. pipes. 2016 Surface Water Design Manual — Appendix A 4/24/2016 A-13 APPENDIX A MAINTENANCE REQUIREMENTS FLOW CONTROL, CONVEYANCE, AND WQ FACILITIES NO. 9 - FENCING Maintenance Defect or Problem Conditions When Maintenance is Needed Results Expected When Component Maintenance is Performed Site Erosion or holes Erosion or holes more than 4 inches high and 12- No access under the fence. under fence 18 inches wide permitting access through an opening under a fence. Wood Posts, Boards Missing or damaged Missing or broken boards, post out of plumb by No gaps on fence due to missing or and Cross Members parts more than 6 inches or cross members broken broken boards, post plumb to within 1% inches, cross members sound. —. Weakened by rotting ............. Any part showing structural deterioration due to All parts of fence are structurally or insects rotting or insect damage sound. Damaged or failed Concrete or metal attachments deteriorated or Post foundation capable of post foundation unable to support posts. supporting posts even in strong Damaged parts Post out of plumb more than 6 inches. wind. Post plumb to within 1 % inches. Metal Posts, Rails and Fabric Top rails bent more than 6 inches. Top rail free of bends greater than 1 inch. Fence is aligned and meets design Any part of fence (including post, top rails, and fabric) more than 1 foot out of design alignment. standards. Missing or loose tension wire- Tension wire in place and holding fabric. Deteriorated paint or Part or parts that have a rusting or scaling Structurally adequate posts or parts protective coating condition that has affected structural adequacy. with a uniform protective coating. Openings in fabric Openings in fabric are such that an 8-inch Fabric mesh openings within 50% of diameter ball could fit through. grid size. 4/24/2016 2016 Surface Water Design Manual — Appendix A A-14 APPENDIX A MAINTENANCE REQUIREMENTS FOR FLOW CONTROL, CONVEYANCE, AND WQ FACILITIES NO. 10 - GATES/BOLLARDS/ACCESS BARRIERS Maintenance Defect or Problem Conditions When Maintenance is Needed Results Expected When Component Maintenance is Performed Chain Link Fencing Damaged or missing Missing gate. Gates in place. Gate members Broken or missing hinges such that gate cannot Hinges intact and tubed. Gate is be easily opened and closed by a maintenance working freely. person Gate is out of plumb more than 6 inches and Gate is aligned and vertical. more than 1 foot out of design alignment. Missing stretcher bar, stretcher bands, and ties. Stretcher bar, bands, and ties in place. Locking mechanism Locking device missing, no -functioning or does Locking mechanism prevents does not lock gate not link to all parts. opening of gate. Openings in fabric Openings in fabric are such that an 8-inch Fabric mesh openings within 50% of diameter ball could fit through. grid size. Bar Gate Damaged or missing Cross bar does not swing open or closed, is Cross bar swings fully open and cross bar missing or is bent to where it does not prevent closed and prevents vehicle access. vehicle access. Locking mechanism Locking device missing, no -functioning or does Locking mechanism prevents does not lock gate not link to all parts opening of gate Support post Support post does not hold cross bar up. Cross bar held up preventing vehicle . ....... damaged ........ .................. ... -............ ....- access into facility. Bollard broken, missing, does not fit into support No access for motorized vehicles to Bollards Damaged or missing hole or hinge broken or missing. get into facility. Does not lock Locking assembly or lock missing or cannot be No access for motorized vehicles to attached to lock bollard in place. get into facility. Boulders Dislodged Boulders not located to prevent motorized No access for motorized vehicles to vehicle access. get into facility. Circumvented Motorized vehicles going around or between No access for motorized vehicles to boulders. get into facility. 2016 Surface Water Design Manual — Appendix A 4/24/2016 A-15 APPENDIX A MAINTENANCE REQUIREMENTS FLOW CONTROL, CONVEYANCE, AND WQ FACILITIES NO.11 -GROUNDS (LANDSCAPING) Maintenance Defect or Problem Conditions When Maintenance is Needed Results Expected When Component Maintenance is Performed Trash or litter Any trash and debris which exceed 1 cubic foot Trash and debris cleared from site. Site per 1,000 square feet (this is about equal to the amount of trash it would take to fill up one standard size office garbage can). In general, there should be no visual evidence of dumping. Noxious weeds Any noxious or nuisance vegetation which may Noxious and nuisance vegetation constitute a hazard to County personnel or the removed according to applicable public regulations. No danger of noxious vegetation where County personnel or the public might normally be. Contaminants and Any evidence of contaminants or pollution such Materials removed and disposed of pollution as oil, gasoline, concrete slurries or paint. according to applicable regulations. Source control BMPs implemented if appropriate. No contaminants present other than a surface oil film. Grass/groundcover Grass or groundcover mowed to a Grass or groundcover exceeds 18 inches in height. Any tree or limb of a tree identified as having a height no greater than 6 inches. No hazard trees in facility. Trees and Shrubs Hazard potential to fall and cause property damage or threaten human life. A hazard tree identified by a qualified arborist must be removed as soon as possible. Damaged Trees and shrubs with less than 5% Limbs or parts of trees or shrubs that are split or broken which affect more than 25% of the total of total foliage with split or broken foliage of the tree or shrub. limbs. Trees or shrubs that have been blown down or No blown down vegetation or knocked over knocked over vegetation Trees or shrubs free of injury. Trees or shrubs which are not adequately Tree or shrub in place and supported or are leaning over, causing exposure adequately supported; dead or of the roots. diseased trees removed. 4/24/2016 2016 Surface Water Design Manual — Appendix A A-16 APPENDIX A MAINTENANCE REQUIREMENTS FOR FLOW CONTROL, CONVEYANCE, AND WQ FACILITIES NO. 12 - ACCESS ROADS Maintenance Defect or Problem Condition When Maintenance is Needed Results Expected When Component Maintenance is Performed Site Trash and debris Trash and debris exceeds 1 cubic foot per 1,000 Roadway drivable by maintenance square feet (i.e., trash and debris would fill up vehicles. one standards size garbage can). Debris which could damage vehicle tires or Roadway drivable by maintenance prohibit use of road. vehicles. Contaminants and Any evidence of contaminants or pollution such Materials removed and disposed of pollution as oil, gasoline, concrete slurries or paint. according to applicable regulations. Source control BMPs implemented if appropriate. No contaminants present other than a surface oil film. Blocked roadway Any obstruction which reduces clearance above Roadway overhead clear to 14 feet road surface to less than 14 feet. high Any obstruction restricting the access to a 10- to At least 12-foot of width on access 12 foot width for a distance of more than 12 feet road. or any point restricting access to less than a 10 foot width Road Surface Erosion, settlement, Any surface defect which hinders or prevents Road drivable by maintenance potholes, soft spots, maintenance access. vehicles. ruts Vegetation on road Trees or other vegetation prevent access to Maintenance vehicles can access surface facility by maintenance vehicles. facility, Shoulders and Erosion Erosion within 1 foot of the roadway more than 8 Shoulder free of erosion and Ditches inches wide and 6 inches deep. matching the surrounding road. Weeds and brush Weeds and brush exceed 18 inches in height or Weeds and brush cut to 2 inches in hinder maintenance access. height or cleared in such a way as to allow maintenance access. Modular Grid Contaminants and Any evidence of contaminants or pollution such Materials removed and disposed of Pavement pollution as oil, gasoline, concrete slurries or paint. according to applicable regulations. Source control BMPs implemented if appropriate. No contaminants present other than a surface oil film. Damaged or missing Access surface compacted because of broken Access road surface restored so on missing modular block. road infiltrates. 2016 Surface Water Design Manual — Appendix A 4/24/2016 A-1 7 APPENDIX A MAINTENANCE REQUIREMENTS FLOW CONTROL, CONVEYANCE. AND WQ FACILITIES NO. 13 - BASIC BIOSWALE (GRASS) Maintenance Defect or Problem Condition When Maintenance is Needed Results Expected When Component Maintenance is Performed ..... Site Trash and debris Any trash and/or debris accumulated on the No trash or debris on the bioswale bioswale site. site. Contaminants and Any evidence of contaminants or pollution such Materials removed and disposed of pollution as oil, gasoline, concrete slurries or paint. according to applicable regulations - Source control BMPs implemented if appropriate. No contaminants present other than a surface oil film. Swale Section Sediment Sediment depth exceeds 2 inches in 10% of the No sediment deposits in grass accumulation swale treatment area. treatment area of the bioswale. Sediment inhibits grass growth over 10% of • Grass growth not inhibited by swale length. sediment. Sediment inhibits even spreading of flow. Flow spreads evenly through swale Erosion/scouring Eroded or scoured swale bottom due to No eroded or scoured areas in channelization or high flows. bioswale. Cause of erosion or scour addressed. Poor vegetation Grass is sparse or bare or eroded patches occur Swale has no bare spots and grass coverage in more than 10% of the swale bottom. is thick and healthy. Grass too tall Grass excessively tall (greater than 10 inches), Grass is between 3 and 4 inches grass is thin or nuisance weeds and other tall, thick and healthy. No clippings vegetation have taken over. left in swale. No nuisance vegetation present. Excessive shade Grass growth is poor because sunlight does not Health grass growth or swale reach Swale. converted to a wet bioswale. Constant baseflow Continuous flow through the swale, even when it Baseflow removed from swale by a has been dry for weeks or an eroded, muddy low -flow pea -gravel drain or channel has formed in the swale bottom. bypassed around the swale. Standing water Water pools in the swale between storms or Swale freely drains and there is no does not drain freely, standing water in swale between storms- Channelization Flow concentrates and erodes channel through No flow channels in swale- swale. Flow Spreader Concentrated flow Flow from spreader not uniformly distributed Flows are spread evenly over entire across entire swale width. swale width. Inlet/Outlet Pipe Sediment Sediment filling 20% or more of the pipe. Inlet/outlet pipes clear of sediment. accumulation Trash and debris Trash and debris accumulated in inlet/outlet No trash or debris in pipes pipes (includes floatables and non-floatables). Damaged ............... Cracks wider than 1/2-inch at the joint of the No cracks more than wide at inlet/outlet pipes or any evidence of soil entering the joint of the inlet/outlet pipe. at the joints of the inlet/outlet pipes. 4/24/2016 2016 Surface Water Design Manual — Appendix A A-18 APPENDIX A MAINTENANCE REQUIREMENTS FOR FLOW CONTROL, CONVEYANCE, AND WQ FACILITIES t.14 - WET BIOSWALE tenance Defect or Problem Condition When Maintenance is Needed Results Expected When ponent Maintenance Is Performed Site Trash and debris Any trash and/or debris accumulated at the site. No trash or debris at the site. Contaminants and Any evidence of contaminants or pollution such Materials removed and disposed of pollution as oil, gasoline, concrete slurries or paint. according to applicable regulations. Source control BMPs implemented if appropriate. No contaminants present other than a surface oil film. Swale Section Sediment Sediment depth exceeds 2 inches in 10% of the No sediment deposits in treatment accumulation swale treatment area. area. Erosion/scouring Eroded or scoured swale bottom due to No eroded or scoured areas in channelization or high flows- bioswale. Cause of erosion or scour addressed. Water depth Water not retained to a depth of about 4 inches Water depth of 4 inches through out during the wet season. swale for most of wet season. Vegetation ineffective Vegetation sparse, does not provide adequate Wetland vegetation fully covers filtration or crowded out by very dense clumps of bottom of swale and no cattails or cattail or nuisance vegetation. nuisance vegetation present Insufficient water Wetland vegetation dies due to lack of water. Wetland vegetation remains healthy (may require converting to grass lined bioswale Flow Spreader Concentrated flow Flow from spreader not uniformly distributed Flows are spread evenly over entire across entire swale width. swale width. Inlet/Outlet Pipe ..... ...... I. ... . Sediment _.....w........ ...__................. -.................... Sediment filling 20% or more of the pipe. Inlet/outlet pipes clear of sediment. accumulation Trash and debris Trash and debris accumulated in inlet/outlet No trash or debris in pipes. pipes (includes floatables and non-floatables). Damaged Cracks wider than %-inch at the joint of the No cracks more than Y inch wide at inlet/outlet pipes or any evidence of soil entering the joint of the inlet/outlet pipe, at the joints of the inlet/outlet pipes. 2016 Surface Water Design Manual — Appendix A 4/24/2016 A-19 APPENDIX A MAINTENANCE REQUIREMENTS FLOW CONTROL, CONVEYANCE, AND WQ FACILITIES NO. 15 - FILTER STRIP Maintenance Defect or Problem Condition When Maintenance is Needed Results Expected When Component Maintenance Is Performed Site Trash and debris Any trash and debris accumulated on the filter Filter strip site free of any trash or strip site. debris Contaminants and Any evidence of contaminants or pollution such Materials removed and disposed of pollution as oil, gasoline, concrete slurries or paint. according to applicable regulations. Source control BMPs implemented if appropriate. No contaminants present other than a surface oil film. Grass Strip Sediment Sediment accumulation on grass exceeds 2 No sediment deposits in treatment accumulation inches depth. area Erosion/scouring Eroded or scoured swale bottom due to No eroded or scoured areas in channelization or high flows. bioswale. Cause of erosion or scour addressed. Grass too tall Grass excessively tall (greater than 10 inches), Grass is between 3 and 4 inches grass is thin or nuisance weeds and other tall, thick and healthy. No clippings vegetation have taken over. left in swale. No nuisance vegetation present. Vegetation ineffective Grass has died out, become excessively tall Grass is healthy, less than 9 inches (greater than 10 inches) or nuisance vegetation high and no nuisance vegetation is taking over. present. Flow Spreader ................................—... Concentrated flow Flow from spreader not uniformly distributed .... .......--- Flows are spread evenly over entire across entire swale width. swale width. Inlet/Outlet Pipe Sediment _ accumulation Sediment filling 20% or more of the pipe. Inlet/outlet pipes clear of sediment Trash and debris Trash and debris accumulated in inlet/outlet No trash or debris in pipes. pipes (includes floatables and non-floatables). Damaged Cracks wider than'/2-inch at the joint of the No cracks more than wide at inlet/outlet pipes or any evidence of soil entering the joint of the inlet/outlet pipe. at the joints of the inlet/outlet pipes. 4/24/2016 2016 Surface Water Design Manual —Appendix A A-20 APPENDIX A MAINTENANCE REQUIREMENTS FOR FLOW CONTROL. CONVEYANCE, AND WQ FACILITIES NO.16 - WETPOND Maintenance Defect or Problem Condition When Maintenance is Needed Results Expected When Component Maintenance Is Performed Site Trash and debris Any trash and debris accumulated on the Wetpond site free of any trash or wetpond site. debris. .-.. .......................................... Noxious weeds Any noxious or nuisance vegetation which may Noxious and nuisance vegetation constitute a hazard to County personnel or the removed according to applicable public regulations. No danger of noxious vegetation where County personnel or the public might normally be, Contaminants and Any evidence of contaminants or pollution such Materials removed and disposed of pollution as oil, gasoline, concrete slurries or paint. according to applicable regulations. Source control BMPs implemented if appropriate. No contaminants present other than a surface oil film. Grass/groundcover Grass or groundcover exceeds 18 inches in Grass or groundcover mowed to a height. height no greater than 6 inches. Side Slopes of Dam, Rodent holes Any evidence of rodent holes if facility is acting Rodents removed or destroyed and Berm, internal berm as a dam or berm, or any evidence of water dam or berm repaired. or Embankment piping through dam or berm via rodent holes Tree growth Tree growth threatens integrity of dams, berms Trees do not hinder facility or slopes, does not allow maintenance access, performance or maintenance or interferes with maintenance activity. If trees activities. are not a threat to dam, berm or embankment integrity, are not interfering with access or maintenance or leaves do not cause a plugging problem they do not need to be removed. Erosion Eroded damage over 2 inches deep where cause Slopes stabilized using appropriate of damage is still present or where there is erosion control measures. If erosion potential for continued erosion Any erosion is occurring on compacted slope, a observed on a compacted slope. licensed civil engineer should be consulted to resolve source of erosion. Top or Side Slopes Settlement Any part of a dam, berm or embankment that Top or side slope restored to design of Dam, Berm, has settled 4 inches lower than the design dimensions. If settlement is internal berm or elevation significant, a licensed civil engineer Embankment should be consulted to determine the cause of the settlement. Irregular surface on Top of berm not uniform and level. Top of berm graded to design internal berm elevation. Pond Areas Sediment Accumulated sediment that exceeds 10% of the Sediment cleaned out to designed accumulation (except designed pond depth. pond shape and depth. first wetpool cell) Sediment Sediment accumulations in pond bottom that Sediment storage contains no accumulation (first exceeds the depth of sediment storage (1 foot) sediment. wetpool cell) plus 6 inches. Liner damaged (If Liner is visible or pond does not hold water as Liner repaired or replaced. Applicable) designed - Water level (all Cell level(s) drops more than 12 inches in any 7- Cell level(s) drops less than 12 wetpool cells) day period. inches in any 7-day period. Algae mats develop over more than 10% of the Algae mats removed (usually in the Algae mats (first wetpool cell) water surface should be removed- late summer before Fall rains, especially in Sensitive Lake Protection Areas.) 2016 Surface Water Design Manual — Appendix A 4/24/2016 A-21 APPENDIX A MAINTENANCE REQUIREMENTS FLOW CONTROL, CONVEYANCE, AND WQ FACILITIES NO.16 - WETPON❑ Maintenance Defect or Problem Condition When Maintenance is Needed Results Expected When Component Maintenance Is Performed Design planting and Sparse or dying design planting, or when design Design plantings and vegetation are vegetation survival plantings are not thriving across 80% or more of thriving and appropriately spaced and maintenance the design vegetated areas within the pond; across 80% or more of the design invasive vegetation e.g., cattails vegetated areas within the pond; invasives removed including root clumps Gravity Drain Inoperable valve Valve will not open and close. Valve opens and closes normally - Valve won't seal Valve does not seal completely. Valve completely seals closed. Emergency Tree growth Tree growth impedes flow or threatens stability of Trees removed. Overflow Spillway spillway. Rock missing Only one layer of rock exists above native soil in Spillway restored to design area five square feet or larger, or any exposure standards. of native soil at the top of out flow path of spillway. Rip -rap on inside slopes need not be replaced. Sediment filling 20% or more of the pipe. Inlet/Outlet Pipe Sediment Inlet/outlet pipes clear of sediment. accumulation Trash and debris Trash and debris accumulated in inlet/outlet No trash or debris in pipes. pipes (includes floatables and non-floatables)- Damaged Cracks wider than '/,inch at the joint of the No cracks more than %-inch wide at inlet/outlet pipes or any evidence of soil entering the joint of the inlet/outlet pipe. at the joints of the inlet/outlet pipes. 4/24/2016 2016 Surface Water Design Manual — Appendix A A-22 APPENDIX A MAINTENANCE REQUIREMENTS FOR FLOW CONTROL. CONVEYANCE, AND WQ FACILITIES NO.17 - WET% Maintenance Component Site Treatment Area Vault Structure Inlet/Outlet Pipe Gravity Drain Access Manhole MULT Defect or Problem Condition When Maintenance is Needed Results Expected When Maintenance is Performed Trash and debris Trash and debris accumulated on facility site Trash and debris removed from facility site. Trash and debris Any trash and debris accumulated in vault No trash or debris in vault. (includes floatables and non-floatables). Sediment Sediment accumulation in vault bottom exceeds No sediment in vault. accumulation the depth of the sediment zone plus 6 inches. Contaminants and Any evidence of contaminants or pollution such Materials removed and disposed of pollution as oil, gasoline, concrete slurries or paint. according to applicable regulations. Source control BMPs implemented if appropriate. No contaminants present other than a surface oil film. Vault is sealed and structurally Damage to wall, Cracks wider than any evidence of soil frame, bottom, and/or entering the structure through cracks, vault does sound. top slab not retain water or qualified inspection personnel determines that the vault is not structurally sound —................. Baffles damaged — _... Baffles corroding, cracking, warping and/or Repair or replace baffles or walls to showing signs of failure or baffle cannot be specifications. removed. ..._..._..._ _... No reduction of ventilation area Ventilation Ventilation area blocked or plugged. exists. Sediment Sediment filling 20% or more of the pipe. Inlet/outlet pipes clear of sediment. accumulation Trash and debris Trash and debris accumulated in inlet/outlet No trash or debris in pipes. pipes (includes floatables and non-floatables)- Damaged Cracks wider than''/z-inch at the joint of the No cracks more than %-inch wide at inlet/outlet pipes or any evidence of soil entering the joint of the inlet/outlet pipe. at the joints of the inlet/outlet pipes. Inoperable valve Valve will not open and close. Valve opens and closes normally. Valve won't seal Valve does not seal completely Valve completely seals closed. Access cover/lid .......... Access cover/lid cannot be easily opened by one Access cover/lid can be opened by damaged or difficult to person. Corrosion/deformation of cover/lid. one person. open Locking mechanism Mechanism cannot be opened by one Mechanism opens with proper tools. not working maintenance person with proper tools. Bolts cannot be seated. Self-locking cover/lid does not work. Cover/lid difficult to One maintenance person cannot remove Cover/lid can be removed and remove cover/lid after applying 80 Ibs of lift. reinstalled by one maintenance person. Access doors/plate Large access doors not flat and/or access Doors close flat; covers access has gaps, doesn't opening not completely covered. opening completely - cover completely Lifting Rings missing, Lifting rings not capable of lifting weight of door Lifting rings sufficient to lift or rusted or plate. remove door or plate. Ladder rungs unsafe Missing rungs, misalignment, rust, or cracks. Ladder meets design standards. Allows maintenance person safe access 2016 Surface Water Design Manual — Appendix A 4/24/2016 A-23 APPENDIX A MAINTENANCE REQUIREMENTS FLOW CONTROL, CONVEYANCE, AND WQ FACILITIES lNO. 18 -- STORMWATER WETLAND Maintenance Defect or Problem Condition When Maintenance is Needed Results Expected When Component Maintenance Is Performed Site Trash and debris Trash and debris accumulated on facility site. Trash and debris removed from facility site. Noxious weeds Any noxious or nuisance vegetation which may Noxious and nuisance vegetation constitute a hazard to County personnel or the removed according to applicable public. regulations. No danger of noxious vegetation where County personnel or the public might normally be. Contaminants and Any evidence of contaminants or pollution such Materials removed and disposed of pollution as oil, gasoline, concrete slurries or paint. according to applicable regulations. Source control BMPs implemented if appropriate. No contaminants present other than a surface oil film Grass/groundcover Grass or groundcover exceeds 18 inches in Grass or groundcover mowed to a height. height no greater than 6 inches. Side Slopes of Dam, Rodent holes Any evidence of rodent holes if facility is acting Rodents removed or destroyed and Berm, internal berm as a dam or berm, or any evidence of water dam or berm repaired or Embankment piping through dam or berm via rodent holes. Tree growth Tree growth threatens integrity of dams, berms Trees do not hinder facility or slopes, does not allow maintenance access, performance or maintenance or interferes with maintenance activity. If trees activities. are not a threat to dam, berm, or embankment integrity or not interfering with access or maintenance, they do not need to be removed. Erosion Eroded damage over 2 inches deep where cause Slopes stabilized using appropriate of damage is still present or where there is erosion control measures If erosion potential for continued erosion. Any erosion is occurring on compacted slope, a observed on a compacted slope. licensed civil engineer should be consulted to resolve source of erosion. Top or Side Slopes Settlement Any part of a dam, berm or embankment that Top or side slope restored to design of Dam, Berm, has settled 4 inches lower than the design dimensions. If settlement is internal berm or elevation. significant, a licensed civil engineer Embankment should be consulted to determine the cause of the settlement. Irregular surface on Top of berm not uniform and level. ............. ............. Top of berm graded flat to design internal berm elevation. Pond Areas Sediment Sediment accumulations in pond bottom that Sediment storage contains no accumulation (first exceeds the depth of sediment storage (1 foot) sediment. cell/forebay) plus 6 inches. Sediment Accumulated sediment that exceeds 10% of the Sediment cleaned out to designed accumulation (wetland designed pond depth. pond shape and depth. cell) ....................................._.. Liner damaged (If Liner is visible or pond does not hold water as .......... Liner repaired or replaced. Applicable) designed. Water level (first Cell level drops more than 12 inches in any 7- Cell level drops no more than 12 cell/forebay) day period. inches in any 7-day period. Water level (wetland Cell does not retain water for at least 10 months Water retained at least 10 months of cell) of the year or wetland plants are not surviving. the year or wetland plants are surviving. Algae mats (first Algae mats develop over more than 10% of the Algae mats removed (usually in the cell/forebay) water surface should be removed. late summer before Fall rains, especially in Sensitive Lake Protection Areas.) 4/24/2016 2016 Surface Water Design Manual — Appendix A A-24 APPENDIX A MAINTENANCE REQUIREMENTS FOR FLOW CONTROL, CONVEYANCE, AND WQ FACILITIES NO. 1 S - STORMWATER WETLAND Maintenance Defect or Problem Condition When Maintenance is Needed Results Expected When Component Maintenance Is Performed Vegetation Vegetation dead, dying, or overgrown (cattails) or Plants in wetland cell surviving not meeting original planting specifications across 80% or more of the entire across more than 20% of the entire design design vegetated area within the vegetated area within the pond. pond and not interfering with wetland function. Gravity Drain Inoperable valve Valve will not open and close. Valve opens and closes normally. Valve won't seal Valve does not seal completely. Tree growth impedes flow or threatens stability of Valve completely seals closed. Emergency Tree growth Trees removed. Overflow Spillway spillway. Rock missing Only one layer of rock exists above native soil in Spillway restored to design area five square feet or larger, or any exposure standards. of native soil at the top of out flow path of spillway. Rip -rap on inside slopes need not be replaced. Inlet/Outlet Pipe Sediment Sediment filling 20% or more of the pipe. Inlet/outlet pipes clear of sediment. accumulation Trash and debris Trash and debris accumulated in inlet/outlet No trash or debris in pipes. pipes (includes floatables and non-floatables). Cracks wider than 1/2-inch at the joint of the No cracks more than %-inch wide at Damaged inlet/outlet pipes or any evidence of soil entering the joint of the inlet/outlet pipe. at the joints of the inlet/outlet pipes. 2016 Surface Water Design Manual — Appendix A 4/24/2016 A-25 APPENDIX A MAINTENANCE REQUIREMENTS FLOW CONTROL, CONVEYANCE, AND WQ FACILITIES NO 19 - SAND FILTER POND Maintenance Defect or Problem Condition When Maintenance is Needed Results Expected When Component Maintenance Is Performed Site Trash and debris Trash and debris accumulated on facility site. Trash and debris removed from facility site. Noxious weeds Any noxious or nuisance vegetation which may Noxious and nuisance vegetation constitute a hazard to County personnel or the removed according to applicable public. regulations. No danger of noxious vegetation where County personnel or the public might normally be. Contaminants and Any evidence of contaminants or pollution such Materials removed and disposed of pollution as oil, gasoline, concrete slurries or paint. according to applicable regulations. Source control BMPs implemented if appropriate. No contaminants present other than a surface oil film. Grass/groundcover Grass or groundcover exceeds 18 inches in Grass or groundcover mowed to a (not in the treatment height- height no greater than 6 inches. area) Pre -Treatment (if Sediment Sediment accumulations in pond bottom that Sediment storage contains no applicable) accumulation exceeds the depth of sediment storage (1 foot) sediment. plus 6 inches. Liner damaged (If Liner is visible or pond does not hold water as Liner repaired or replaced - Applicable) designed. Water level Cell empty, doesn't hold water. Water retained in first cell for most of the year. Algae mats Algae mats develop over more than 10% of the Algae mats removed (usually in the water surface should be removed. late summer before Fall rains, especially in Sensitive Lake Protection Areas.) Pond Area Sediment Sediment or crust depth exceeds'/2-inch over 10 No sediment or crust deposit on accumulation % of surface area of sand filter. sand filter that would impede permeability of the filter section. Grass (if applicable) Grass becomes excessively tall (greater than 6 Mow vegetation and/or remove inches) or when nuisance weeds and other nuisance vegetation. vegetation start to take over or thatch build up occurs. Side Slopes of Pond Rodent holes Any evidence of rodent holes if facility is acting Rodents removed or destroyed and as a dam or berm, or any evidence of water dam or berm repaired. piping through dam or berm via rodent holes. Tree growth Tree growth threatens integrity of dams, berms Trees do not hinder facility or slopes, does not allow maintenance access, performance or maintenance or interferes with maintenance activity If trees activities are not a threat to dam, berm, or embankment integrity or not interfering with access or maintenance, they do not need to be removed. Erosion Eroded damage over 2 inches deep where cause Slopes stabilized using appropriate of damage is still present or where there is erosion control measures. If erosion potential for continued erosion. Any erosion is occurring on compacted slope, a observed on a compacted slope. licensed civil engineer should be consulted to resolve source of erosion. 4/24/2016 2016 Surface Water Design Manual — Appendix A A-26 APPENDIX A MAINTENANCE REQUIREMENTS FOR FLOW CONTROL. CONVEYANCE, AND WQ FACILITIES NO. 19 - SAND FILTER POND Maintenance Defect or Problem Condition When Maintenance is Needed Results Expected When Component Maintenance Is Performed Sand Filter Media Plugging Drawdown of water through the sand filter media, Sand filter media surface is aerated takes longer than 24 hours, and/or flow through or the surface is scraped and the overflow pipes occurs frequently. A sieve replaced, and drawdown rate is analysis of >4% -100 or >2% -200 requires normal. replacing sand filter media. Prolonged flows Sand is saturated for prolonged periods of time Excess flows bypassed or confined (several weeks) and does not dry out between to small portion of filter media storms due to continuous base flow or prolonged surface. flows from detention facilities. Short circuiting Flows become concentrated over one section of Flow and percolation of water the sand filter rather than dispersed or drawdown through the sand filter is uniform and rate of pool exceeds 12 inches per hour. dispersed across the entire filter area and drawdown rate is normal. Media thickness Sand thickness is less than 18 inches. Rebuild sand thickness to a minimum of 18 inches. Underdrains and Sediment/debris Underdrains or clean -outs partially plugged or Underdrains and clean -outs free of Clean -Outs filled with sediment and/or debris. Junction sediment and debris and are box/cleanout wyes not watertight. watertight. Inlet/Outlet Pipe Sediment Sediment filling 20% or more of the pipe Inlet/outlet pipes clear of sediment. accumulation Trash and debris Trash and debris accumulated in inlet/outlet No trash or debris in pipes. pipes (includes floatables and non-floatables). Damaged Cracks wider than '/,inch at the joint of the No cracks more than %-inch wide at inlet/outlet pipes or any evidence of soil entering the joint of the inlet/outlet pipe. at the joints of the inlet/outlet pipes. Rock Pad Missing or out of Only one layer of rock exists above native soil in Rock pad restored to design place area five square feet or larger, or any exposure standards. of native soil. Flow spreader Concentrated flow Flow from spreader not uniformly distributed Flows spread evenly over sand filter. across sand filter. 2016 Surface Water Design Manual — Appendix A 4/24/2016 A-27 APPENDIX A MAINTENANCE REQUIREMENTS FLOW CONTROL, CONVEYANCE, AND WQ FACILITIES NO.20 - SAND FILTER VAULT Maintenance Defect or Problem Condition When Maintenance is Needed Results Expected When Component Maintenance is Performed Site Trash and debris Trash and debris accumulated on facility site. Trash and debris removed from facility site. Noxious weeds Any noxious or nuisance vegetation which may Noxious and nuisance vegetation constitute a hazard to County personnel or the removed according to applicable public- regulations. No danger of noxious vegetation where County personnel or the public might normally be. Contaminants and Any evidence of contaminants or pollution such Materials removed and disposed of pollution as oil, gasoline, concrete slurries or paint. according to applicable regulations. Source control BMPs implemented if appropriate. No contaminants present other than a surface oil film. Grass/groundcover Grass or groundcover exceeds 18 inches in Grass or groundcover mowed to a height. height no greater than 6 inches. Pre -Treatment Sediment Sediment accumulation exceeds the depth of the Sediment storage contains no Chamber accumulation sediment zone plus 6 inches. sediment. Sand Filter Media Sediment Sediment depth exceeds'/2-inch on sand filter Sand filter freely drains at normal accumulation media. ... rate. _... Trash and debris ...... ... I -..--.... ... ... ...I", .................. .. .... .......__.�. Trash and debris accumulated in vault (floatables _... ... ... No trash or debris in vault - and non-floatables). Plugging Drawdown of water through the sand filter media, Sand filter media drawdown rate is takes longer than 24 hours, and/or flow through normal. the overflow pipes occurs frequently. A sieve analysis of >4% -100 or >2% -200 requires replacing sand filter media. Short circuiting Seepage or flow occurs along the vault walls and Sand filter media section re-laid and corners. Sand eroding near inflow area. compacted along perimeter of vault Cleanoutwyes are not watertight to form a semi -seal. Erosion protection added to dissipate force of incoming flow and curtail erosion. Vault Structure Damaged to walls, Cracks wider than 1/2-inch, any evidence of soil Vault replaced or repaired to provide frame, bottom and/or entering the structure through cracks or qualified complete sealing of the structure. top slab. inspection personnel determines that the vault is not structurally sound. Ventilation Ventilation area blocked or plugged. No reduction of ventilation area exists. Underdrains and clean -outs free of Underdrains and Sediment/debris Underdrains or clean -outs partially plugged, filled Cleanouts with sediment and/or debris or not watertight. sediment and debris and sealed. Sediment Sediment filling 20% or more of the pipe. Inlet/outlet pipes clear of sediment. Inlet/Outlet Pipe accumulation Trash and debris Trash and debris accumulated in inlet/outlet No trash or debris in pipes. pipes (includes floatables and non-floatables). Damaged Cracks wider than '/,inch at the joint of the No cracks more than %-inch wide at inlet/outlet pipes or any evidence of soil entering the joint of the inlet/outlet pipe. at the joints of the inlet/outlet pipes. 4/24/2016 2016 Surface Water Design Manual — Appendix A A-28 APPENDIX A MAINTENANCE REQUIREMENTS FOR FLOW CONTROL, CONVEYANCE, AND WQ FACILITIES NO. 20 - SAND FILTER VAULT Maintenance Defect or Problem Component ................................. _I ............ .._ Access Manhole Cover/lid not in place Locking mechanism not working Cover/lid difficult to remove Condition When Maintenance is Needed Cover/lid is missing or only partially in place. Any open manhole requires immediate maintenance. Mechanism cannot be opened by one maintenance person with proper tools. Bolts cannot be seated. Self-locking cover/lid does not work. One maintenance person cannot remove cover/lid after applying 80 Ibs of lift. Ladder rungs unsafe I Missing rungs, misalignment, rust, or cracks Large access Damaged or difficult Large access doors or plates cannot be doors/plate to open opened/removed using normal equipment. Gaps, doesn't cover Large access doors not flat and/or access completely opening not completely covered. Lifting Rings missing, Lifting rings not capable of lifting weight of door rusted or plate. Results Expected When Maintenance is Performed Manhole access covered. Mechanism opens with proper tools. Cover/lid can be removed and reinstalled by one maintenance person. Ladder meets design standards. Allows maintenance person safe access. Replace or repair access door so it can opened as designed. Doors close flat; covers access opening completely. Lifting rings sufficient to lift or remove door or plate. 2016 Surface Water Design Manual — Appendix A 4/24/2016 A-29 APPENDIX A MAINTENANCE REQUIREMENTS FLOW CONTROL, CONVEYANCE, AND WQ FACILITIES NO. 21 -- STORMFILTER (CARTRIDGE TYPE) - — ........ -- Maintenance Defect or Problem Condition When Maintenance is Needed Results Expected When Component Maintenance is Performed Facility Documentation Update facility inspection record after each Maintenance records are up to date. inspection. Filter media is certified to meet Provide certification of replaced filter media. Stormfilter® specifications. Site Trash and debris Any trash or debris which impairs the function of Trash and debris removed from the facility. facility. Contaminants and Any evidence of contaminants or pollution such Materials removed and disposed of pollution as oils, gasoline, concrete slurries or paint. according to applicable regulations. Source control BMPs implemented if appropriate. No contaminants present other than a surface oil film Life cycle System has not been inspected for three years. Facility is re -inspected and any needed maintenance performed. Vault Treatment Sediment on vault Greater than 2 inches of sediment. Vault is free of sediment. Area floor Sediment on top of Greater than % inch of sediment. Vault is free of sediment. cartridges Multiple scum lines Thick or multiple scum lines above top of Cause of plugging corrected, above top of cartridges. Probably due to plugged canisters or canisters replaced if necessary. cartridges underdrain manifold. Cracks wider than %-inch and any evidence of Vault replaced or repaired to design Vault Structure Damage to wall, Frame, Bottom, soil particles entering the structure through the specifications. and/or Top Slab cracks, or qualified inspection personnel determines the vault is not structurally sound. Baffles damaged Baffles corroding, cracking warping, and/or Repair or replace baffles to showing signs of failure as determined by specification. maintenance/inspection person. Filter Media Standing water in 9 inches or greater of static water in the vault for No standing water in vault 24 hours vault more than 24 hours following a rain event and/or after a rain event. overflow occurs frequently. Probably due to plugged filter media, underdrain or outlet pipe. Short circuiting Sediment/debris Flows do not properly enter filter cartridges. Flows go through filter media- Underdrains and Underdrains or clean -outs partially plugged or Underdrains and clean -outs free of Clean -Outs filled with sediment and/or debris. sediment and debris. Inlet/Outlet Pipe Sediment Sediment filling 20% or more of the pipe. Inlet/outlet pipes clear of sediment accumulation Trash and debris Trash and debris accumulated in inlet/outlet No trash or debris in pipes. pipes (includes floatables and non-floatables). Damaged Cracks wider than'/2-inch at the joint of the No cracks more than %-inch wide at inlet/outlet pipes or any evidence of soil entering the joint of the inlet/outlet pipe. at the joints of the inlet/outlet pipes. Access Manhole Cover/lid not in place Cover/lid is missing or only partially in place. Manhole access covered Any open manhole requires immediate maintenance. Locking mechanism Mechanism cannot be opened by one Mechanism opens with proper tools. not working maintenance person with proper tools. Bolts cannot be seated. Self-locking cover/lid does not work. Cover/lid difficult to One maintenance person cannot remove Cover/lid can be removed and remove cover/lid after applying 80 Ibs of lift. reinstalled by one maintenance person. 4/24/2016 2016 Surface Water Design Manual — Appendix A A-30 APPENDIX A MAINTENANCE REQUIREMENTS FOR FLOW CONTROL, CONVEYANCE, AND WQ FACILITIES NO. 21 -- STORMFILTER [CARTRIDGE TYPE] Maintenance Defect or Problem Condition When Maintenance is Needed Results Expected When Component Maintenance is Performed Ladder rungs unsafe Missing rungs, misalignment, rust, or cracks. Ladder meets design standards. Allows maintenance person safe access. Large access Damaged or difficult Large access doors or plates cannot be Replace or repair access door so it doors/plate to open opened/removed using normal equipment. can opened as designed Gaps, doesn't cover Large access doors not flat and/or access Doors close flat and cover access completely opening not completely covered. opening completely. Lifting Rings missing, Lifting rings not capable of lifting weight of door Lifting rings sufficient to lift or rusted or plate. remove door or plate. Inspection Frequency Maintenance conditions are site -specific, Inspect Stormfilter facility for any depending on pollutant loading. maintenance deficiencies; maintain or replace as required per FIRST YEAR POST CONSTRUCTION: Monthly established site -specific schedule during wet season, every other month during dry and manufacturer's requirements. season FOLLOWING FIRST YEAR: Continue monthly until site -specific frequency is established, then follow that schedule AT A MINIMUM, FOLLOWING FIRST YEAR: Annually (or quarterly if used as primary treatment) and following significant storms. 2016 Surface Water Design Manual —Appendix A 4/24/2016 A-31 APPENDIX A MAINTENANCE REQUIREMENTS FLOW CONTROL, CONVEYANCE, AND WQ FACILITIES NO. 22 -- BAFFLE OILfWATER SEPARATOR Maintenance Defect Condition When Maintenance is Needed Results Expected When Component Maintenance is Performed Site Trash and debris Any trash or debris which impairs the function of Trash and debris removed from the facility. facility. ........... Contaminants and Floating oil in excess of 1 inch in first chamber, ............ No contaminants present other than pollution any oil in other chambers or other contaminants a surface oil film. of any type in any chamber. Vault Treatment Sediment Sediment accumulates exceeds 6 inches in the No sediment in the vault. Area accumulation vault. Discharge water not Effluent discharge is clear Inspection of discharge water shows obvious clear signs of poor water quality- effluent discharge from vault shows thick visible sheen. Trash or debris Any trash and debris accumulation in vault Vault is clear of trash and debris. accumulation (floatables and non-floatables). Oil accumulation Oil accumulations that exceed 1 inch, at the No visible oil depth on water surface of the water in the oil/water separator Damage to Wall, chamber. Vault Structure Cracks wider than'% -inch or evidence of soil Vault replaced or repaired to design Frame, Bottom, particles entering the structure through the specifications. and/or Top Slab cracks, or maintenance/inspection personnel determines that the vault is not structurally sound. Baffles damaged Baffles corroding, cracking, warping and/or Repair or replace baffles to showing signs of failure as determined by specifications. maintenance inspection personnel. Gravity Drain Inoperable valve Valve will not open and close. Valve opens and closes normally. Valve won't seal Valve does not seal completely. Valve completely seals closed. Inlet/Outlet Pipe Sediment Sediment filling 20% or more of the pipe Inlet/outlet pipes clear of sediment. accumulation Trash and debris Trash and debris accumulated in inlet/outlet No trash or debris in pipes. pipes (includes floatables and non-floatables). Damaged Cracks wider than '/2-inch at the joint of the No cracks more than '%-inch wide at inlet/outlet pipes or any evidence of soil entering the joint of the inlet/outlet pipe. at the joints of the inlet/outlet pipes. Access Manhole Cover/lid not in place Cover/lid is missing or only partially in place. Manhole access covered Any open manhole requires immediate maintenance. Locking mechanism Mechanism cannot be opened by one Mechanism opens with proper tools. not working maintenance person with proper tools. Bolts cannot be seated. Self-locking cover/lid does not work. Cover/lid difficult to One maintenance person cannot remove Cover/lid can be removed and remove cover/lid after applying 80 Ibs of lift. reinstalled by one maintenance person. Ladder rungs unsafe Missing rungs, misalignment, rust, or cracks- Ladder meets design standards. Allows maintenance person safe access. Large access Damaged or difficult Large access doors or plates cannot be Replace or repair access door so it doors/plate to open opened/removed using normal equipment. can opened as designed. ............... Gaps, doesn't cover Large access doors not flat and/or access Doors close flat and cover access completely opening not completely covered. opening completely. Lifting Rings missing, Lifting rings not capable of lifting weight of door Lifting rings sufficient to lift or rusted or cover/lid. remove cover/lid. 4/24/2016 2016 Surface Water Design Manual — Appendix A A-32 APPENDIX A MAINTENANCE REQUIREMENTS FOR FLOW CONTROL. CONVEYANCE, AND WQ FACILITIES NO.23 - COALESCING PLATE OILNVATER SEPARATOR Maintenance Defect Condition When Maintenance is Needed Results Expected When Component Maintenance is Performed Site Trash and debris Any trash or debris which impairs the function of Trash and debris removed from the facility. facility. Contaminants and Floating oil in excess of 1 inch in first chamber, No contaminants present other than pollution any oil in other chambers or other contaminants a surface oil film. of any type in any chamber. Vault Treatment Sediment Sediment accumulation of 6 inches or greater in No sediment in the forebay. Area accumulation in the the forebay. forebay Discharge water not Inspection of discharge water shows obvious Repair function of plates so effluent clear signs of poor water quality - effluent discharge is clear. from vault shows thick visible sheen. Trash and debris accumulation in vault Trash or debris Trash and debris removed from accumulation (floatables and non-floatables). vault. Oil accumulation Oil accumulation that exceeds 1 inch at the water No visible oil depth on water and surface in the in the coalescing plate chamber. coalescing plates clear of oil. Coalescing Plates Damaged Plate media broken, deformed, cracked and/or Replace that portion of media pack showing signs of failure. or entire plate pack depending on severity of failure. Sediment Any sediment accumulation which interferes with No sediment accumulation accumulation the operation of the coalescing plates. interfering with the coalescing ................... plates _ Vault Structure Damage to Wall, Cracks wider than '/,inch and any evidence of Vault replaced or repaired to design Frame, Bottom, soil particles entering the structure through the specifications. and/or Top Slab cracks, or maintenance inspection personnel determines that the vault is not structurally sound. Baffles damaged Baffles corroding, cracking, warping and/or Repair or replace baffles to showing signs of failure as determined by specifications. maintenance/inspection person. Ventilation Pipes Plugged Any obstruction to the ventilation pipes. Ventilation pipes are clear. Shutoff Valve Damaged or Shutoff valve cannot be opened or closed. Shutoff valve operates normally. inoperable Inlet/Outlet Pipe Sediment Sediment filling 20% or more of the pipe. Inlet/outlet pipes clear of sediment. accumulation Trash and debris Trash and debris accumulated in inlet/outlet No trash or debris in pipes. pipes (includes floatables and non-floatables). Damaged Cracks wider than %-inch at the joint of the No cracks more than '%-inch wide at inlet/outlet pipes or any evidence of soil entering the joint of the inlet/outlet pipe. at the joints of the inlet/outlet pipes - Access Manhole Cover/lid not in place Cover/lid is missing or only partially in place. Manhole access covered. Any open manhole requires immediate maintenance. Locking mechanism Mechanism cannot be opened by one Mechanism opens with proper tools. not working maintenance person with proper tools. Bolts cannot be seated. Self-locking cover/lid does not work. Cover/lid difficult to One maintenance person cannot remove Cover/lid can be removed and remove cover/lid after applying 80 Ibs of lift. reinstalled by one maintenance person Ladder rungs unsafe Missing rungs, misalignment, rust, or cracks. Ladder meets design standards. Allows maintenance person safe access. 2016 Surface Water Design Manual — Appendix A 4/24/2016 A-33 APPENDIX A MAINTENANCE REQUIREMENTS FLOW CONTROL, CONVEYANCE, AND WQ FACILITIES N0.23 - COALESCING PLATE OILIWATER SEPARATOR -- ---- _ - Maintenance _- Defect Condition When Maintenance is Needed _ Results Expected When I Component Maintenance is Performed Large access Damaged or difficult Large access doors or plates cannot be Replace or repair access door so it doors/plate to open opened/removed using normal equipment can opened as designed. Gaps, doesn't cover Large access doors not flat and/or access Doors close flat and cover access completely opening not completely covered. opening completely Lifting Rings missing, Lifting rings not capable of lifting weight of door Lifting rings sufficient to lift or rusted or plate. remove door or plate NO.24 - CATCH BASIN INSERT Maintenance Defect or Problem Conditions When Maintenance is Needed Results Expected When Component Maintenance is Performed Media Insert Visible Oil Visible oil sheen passing through media Media inset replaced Insert does not fit Flow gets into catch basin without going through All flow goes through media. catch basin properly media. Filter media plugged Filter media plugged. Flow through filter media is normal. Oil absorbent media Media oil saturated Oil absorbent media replaced. saturated Water saturated Catch basin insert is saturated with water, which Insert replaced. no longer has the capacity to absorb. Service life exceeded Regular interval replacement due to typical Media replaced at manufacturer's average life of media insert product, typically one recommended interval. month. Seasonal When storms occur and during the wet season. Remove, clean and replace or install maintenance new insert after major storms, monthly during the wet season or at manufacturer's recommended interval. 4/24/2016 2016 Surface Water Design Manual — Appendix A A-34 APPENDIX A MAINTENANCE REQUIREMENTS FOR FLOW CONTROL. CONVEYANCE, AND WQ FACILITIES NO.25 - DRYWELL BMP,' Maintenance Defect or Problem Conditions When Maintenance is Needed Results Expected When Component Maintenance is Performed Preventative Plugging, obstructions Any cause limiting flow into drywell. Drywell able to receive full flow prior to and during wet season. Site Trash and debris Trash or debris that could end up in the drywell No trash or debris that could get into is evident. the drywell can be found. Pipes Inlet is plugged The entrance to the pipe is restricted due to The entrance to the pipe is not sediment, trash, or debris. restricted. Vegetation/roots Vegetation/roots that reduce free movement of Water flows freely through pipes, water through pipes Plugged Sediment or other material prevents free flow of Water flows freely through pipes. water through the pipe. Broken or joint leaks. Damage to the pipe or pipe joints allowing water Pipe does not allow water to exit to seep out other than at the outlet. Structure Basin leaks Holes or breaks in the basin allow water to leave Basin is sealed and allows water to the basin at locations other than per design. exit only where designed. Filter Media Filter media plugged Filter media plugged. Flow through filter media is normal. Inspection Frequency Annually and prior to and following significant Inspect drywell system for any storms. defects of deficiencies. NO.26 - GRAVEL FILLED INFILTRATION TRENCH BMP Maintenance Defect or Problem Conditions When Maintenance is Needed Results Expected When Component Maintenance is Performed Preventative Blocking, obstructions Debris or trash limiting flow to infiltration trench. Infiltration trench able to receive full flow prior to and during wet season. Site Trash and debris _...................... ................. Trash or debris that could end up in the No trash or debris that could get into infiltration trench is evident. the infiltration trench can be found. Pipes Inlet is plugged The entrance to the pipe is restricted due to The entrance to the pipe is not sediment, trash, or debris. restricted. Vegetation/roots Vegetation/roots that reduce free movement of Water flows freely through pipes. water through pipes. Plugged Sediment or other material prevents free flow of Water flows freely through pipes water through the pipe. Broken or joint leaks Damage to the pipe or pipe joints allowing water Pipe does not allow water to exit to seep out. other than at the outlet to the trench. Structure Flow not reaching Flows are not getting into the trench as Water enters and exits trench as trench designed. designed. Cleanout/inspection . ....- The cleanout/inspection access is not available. Cleanout/inspection access is access does not allow available. cleaning or inspection of trench Filter Media Filter media plugged Filter media plugged. Flow through filter media is normal. Inspection Frequency Annually and prior to and following significant In infiltration trench system for storms. any defects of deficiencies. 2016 Surface Water Design Manual —Appendix A 4/24/2016 A-35 APPENDIX A MAINTENANCE REQUIREMENTS FLOW CONTROL, CONVEYANCE, AND WQ FACILITIES N0.27 - GRAVEL FILLED DISPERSION TRENCH BMP Maintenance Defect or Problem Conditions When Maintenance is Needed Results Expected When Component Maintenance is Performed - .............. Preventative Blocking, obstructions Debris or trash limiting flow to dispersion trench Dispersion trench able to receive full or preventing spreader function. flow prior to and during wet season. Site Trash and debris Trash or debris that could end up in the No trash or debris that could get into dispersion trench is evident. the dispersion trench can be found. Pipes Inlet is plugged The entrance to the pipe is restricted due to The entrance to the pipe is not sediment, trash, or debris. restricted- Vegetation/roots Vegetation/roots that reduce free movement of Water flows freely through pipes. water through pipes. Plugged Sediment or other material prevents free flow of Water flows freely through pipes. water through the pipe. Broken joint or joint Damage to the pipe or pipe joints allowing water Pipe does not allow water to exit leaks to seep out. other than at the outlet to the trench. Cleanout caps Cleanout caps are broken, missing, or buried. Cleanout caps are accessible and intact. Water enters and exits trench as Structure Flow not reaching Flows are not getting into the trench as designed. trench designed - Perforated pipe Flow not able to enter or properly exit from Water freely enters and exits plugged perforated pipe. perforated pipe. Flow not spreading Outlet flows channelizing or not spreading evenly Sheet flow occurs at the outlet of the evenly at outlet of from trench trench - trench _ Cleanout/inspection The cleanout/inspection access is not available. Cleanout/inspection access is access does not allow available. cleaning or inspection of perforated pipe Filter Media Filter media plugged Filter media plugged. Flow through filter media is normal. Inspection Frequency ........... --------- _............... Annually and prior to and following significant Inspect dispersion trench system for storms. any defects of deficiencies. 4/24/2016 2016 Surface Water Design Manual — Appendix A A-36 APPENDIX A MAINTENANCE REQUIREMENTS FOR FLOW CONTROL: CONVEYANCE, AND WQ FACILITIES NO.28 - NATIVE VEGETATED SURFACE / NATIVE VEGETATED LANDSCAPE BMP Maintenance Defect or Problem Condition When Maintenance is Needed Results Expected When Component Maintenance Is Performed Site Trash and debris Trash and debris accumulated on the native Native vegetated surface site free vegetated surface/native vegetated landscape of any trash or debris. site Vegetation Native vegetation Less than two species each of native trees, A minimum of two species each of type shrubs, and groundcover occur in the design native trees, shrubs, and area. groundcover is established and healthy. Native vegetated area Less than 90% if the required vegetated area has A minimum of 90% of the required healthy growth. vegetated area has healthy growth. Undesirable Weeds, blackberry, and other undesirable plants Less than 10% undesirable vegetation are invading more than 10% of vegetated area. vegetation occurs in the required native vegetated surface area. Vegetated Area Soil compaction Soil in the native vegetation area compacted. Less than 8% of native vegetation area is compacted. Insufficient area Less than 3.5 square feet of native vegetation A minimum of 3.5 square feet of area for every 1 square foot of impervious native vegetation area for every 1 surface square foot of impervious surface. Excess slope Slope of native vegetation area greater than 15%. Slope of native growth area does not exceed 15%. Inspection Frequency Annually Inspect native vegetation area for any defects of deficiencies NO.29 - PERFORATED PIPE CONNECTIONS BMP Maintenance Defect or Problem Conditions When Maintenance is Needed Results Expected When Component Maintenance is Performed Preventative Blocking, obstructions Debris or trash limiting flow into perforated pipe Outfall of BMP is receiving system or outfall of BMP is plugged or otherwise designed flows from perforated pipe nonfunctioning. connection. Inflow Inflow impeded Inflow into the perforated pipe is partially or fully Inflow to the perforated pipe is blocked or altered to prevent flow from getting unimpeded. into the pipe Pipe Trench Area Surface compacted Ground surface over the perforated pipe trench is Ground surface over the perforated compacted or covered with impermeable material. pipe is not compacted and free of any impervious cover. Outflow Outflow impeded Outflow from the perforated pipe into the public Outflow to the public drainage drainage system is blocked system is unimpeded. Outfall Area Erosion or landslides Existence of the perforated pipe is causing or Perforated pipe system is sealed off exasperating erosion or landslides. and an alternative BMP is implemented. Inspection Frequency Annually and prior to and following significant ;Perforated pipe system is operating storms. j as designed. 2016 Surface Water Design Manual — Appendix A 4/24/2016 A-37 APPENDIX A MAINTENANCE REQUIREMENTS FLOW CONTROL, CONVEYANCE, AND WQ FACILITIES NO.30 - PERMEABLE PAVEMENT BMP - - _.... ..... ......... _ _- Maintenance Defect or Problem Conditions When Maintenance is Needed Results Expected When Component Maintenance is Performed Preventative Surface cleaning/ Media surface vacuumed or pressure washed No dirt, sediment, or debris clogging vegetation control annually, vegetation controlled to design porous media, or vegetation limiting maximum Weed growth suggesting sediment infiltration. accumulation. Porous Concrete, Trash and debris Trash and debris on the pavement interfering No trash or debris interfering with Porous Asphaltic with infiltration; leaf drop in fall season. infiltration. Concrete, and Permeable Pavers Sediment accumulation Sediment accumulation on the pavement interfering with infiltration; runoff from adjacent Pavement infiltrates as designed; adjacent areas stabilized. areas depositing sediment/debris on pavement. Infiltration rate Pavement does not infiltrate at a rate of 10 Pavement infiltrates at a rate greater inches per hour than 10 inches per hour, Ponding Standing water infiltrates at the Standing water for a long period of time on the surface of the pavement. desired rate. Broken or cracked Pavement is broken or cracked- No broken pavement or cracks on pavement the surface of the pavement. Settlement Uneven pavement surface indicating settlement Pavement surface is uniformly level. of the subsurface layer. Moss growth Moss growing on pavement interfering with No moss interferes with infiltration. infiltration. Inflow Inflow to the pavement is diverted, restricted, or Inflow to pavement is unobstructed depositing sediment and debris on the and not bringing sediment or debris pavement. to the pavement. Underdrain Underdrain is not flowing when pavement has Underdrain flows freely when water been infiltrating water is present. Overflow Overflow not controlling excess water to desired Overflow permits excess water to location; native soil is exposed or other signs of leave the site at the desired location; erosion damage are present. Overflow is stabilized and appropriately armored. Permeable Pavers Broken or missing Broken or missing paving blocks on surface of No missing or broken paving blocks pavers pavement. interfering with infiltration. Level surface Uneven surface due to settlement or scour of fill Pavement surface is uniformly level. in the interstices of the paving blocks. Compaction Poor infiltration due to soil compaction between No soil compaction in the interstices paving blocks. of the paver blocks limiting infiltration. Dead grass Grass in the interstices of the paving blocks is Healthy grass is growing in the dead interstices of the paver blocks. Inspection Frequency Annually and after large storms, and as needed Permeable pavement is functioning seasonally to control leaf drop, evergreen normally. needles etc 4/24/2016 2016 Surface Water Design Manual — Appendix A A-38 APPENDIX A MAINTENANCE REQUIREMENTS FOR FLOW CONTROL, CONVEYANCE, AND WQ FACILITIES NO.37 -- BIORETENTiON BMP Maintenance Defect or Problem Conditions When Maintenance h Needed Results Expected When Component Vegetation to be watered and pruned as Maintenance is Performed Preventative Vegetation Healthy vegetation growth with full needed and mulch applied to a minimum of 2 coverage as designed. inches to maintain healthy growth. Bioretention Area Trash and debris Trash and debris in the bioretention area; leaf No trash or debris In the bioretention drop in the fall season. area. Sediment Sediment accumulation in the bioretention area Water in the bioretention infiltrates as accumulation interfering with infiltration. designed. Ponding Standing water in the bioretention area for Standing water infiltrates at the more than two days. desired rate. Inflow Inflow not getting into bioretention; Unobstructed and properly routed debris/sediment blockage at inlet features; inflow into bioretention area; inlet is native soil is exposed or other signs of erosion stabilized and appropriately armored damage is present. Overflow outlet Overflow water not controlled by outlet Outlet features control overflow; features; native soil is exposed or other signs overflow is stabilized and appropriately of erosion damage is present. armored Underdrain Underdrain is not flowing when bioretention Underdrain flows freely when water is area has been infiltrating water. present. Vegetation Plant health Plants not thriving across at least 80% of the Healthy water tolerant plants in entire design vegetated area within the BMP; bioretention area, plants thriving overly dense vegetation requiring pruning. across at least 60% of the entire design vegetated area within the facility. Plant species Plants not water tolerant species. Plants are water tolerant. Weeds Weeds growing in bioretention area. No weeds in bioretention area. Watering Planting schedule requires frequent watering Plants are established and thriving (approx. weekly Year 1, bimonthly Years 2 and 3) for new facilities, and as needed for established plantings or dry periods Pest Control Signs of pests, such as wilting or chewed Plant community is pest -free when leaves or bark, spotting or other indicators; following an approved Integrated Pest extended ponding period encouraging Management plan; bioretention mosquitoes functioning normally and ponding controlled as needed for pest control Containment Berm Erosion; Erosion occurring at earthen slopes or Erosion on the containment berm and and Earthen Slopes containment berm side slope. side slopes has been repaired and the i cause of the erosion corrected. ...... .............. Voids created by Voids affecting berm integrity or creating leaky Voids have been repaired; facility is nuisance animals pond condition free of nuisance animals following an (e.g., rodents) or tree approved Integrated Pest roots Management plan. Settlement Any part of they containment berm top has less A minimum of 6 inches freeboard from than 6 inches of freeboard from the maximum the maximum pond level to the top of pond level to the top of the berm. the berm. Amended Soil Soil nutrients Soil not providing plant nutrients. Soil providing plant nutrients. Bare spots Bare spots on soil in bioretention area No bare spots, bioretention area covered with vegetation or mulch mixed into the underlying soil. Compaction Poor infiltration due to soil compaction in the No soil compaction in the bioretention bioretention area. area. Inspection ............. Frequency Annually and after large storms, and as Bioretention facility is functioning needed seasonally for pruning, plant normally; plant community is thriving maintenance, pest control and to control leaf and pest -free. drop, evergreen needles etc. 2016 Surface Water Design Manual — Appendix A 4/24/2016 A-39 APPENDIX A MAINTENANCE REQUIREMENTS FLOW CONTROL, CONVEYANCE, AND WQ FACILITIES NO.32 - RAINWATER HARVESTING BMP .............. _. _..---..... _ ..... .. Maintenance Defect or Problem Conditions When Maintenance is Needed Results Expected When Component Maintenance is Performed Preventative Storage volume No rain water in storage unit at the beginning of Maximum storage available at the 1 the rain season. beginning of the rain season (Oct. 15`). Collection Area Trash and debris Trash of debris on collection area may plug filter Collection area clear of trash and system debris. Filter Restricted or plugged Filter is partially or fully plugged preventing water Filter is allowing collection water from getting in to the storage unit. into storage unit Rain harvesting equipment is Inspection Frequency Annually and after large storms functioning normally. Maintenance log A Maintenance log must be kept and available for Maintenance log is kept and is I review by KC staff. available to KC staff. NO.33 - ROCK PAD BMP 1 Maintenance Defect or Problem Conditions When Maintenance is Needed Results Expected When Component Maintenance is Performed Site Trash and debris Trash and debris accumulated on rock pad site. Rock pad site free of any trash or debris. Rock Pad Area Rock pad size Rock pad is not 2 feet by 3 feet by 6 inches thick Rock pad is 2 feet by 3 feet by 6 or as designed. inches thick or as designed. Vegetation Vegetation is seen growing in or through rock No vegetation within rock pad area. pad. Rock Exposed soil Soil can be seen through the rock pad. Full thickness of the rock pad is in place, no soil visible through rock i pad. Inspection Frequency Annually and after large storms Rock pad is functioning normally. NO.34 - SHEET FLOW BMP Maintenance Defect or Problem Component Site Trash and debris Sheet flow area Inspection Erosion i Concentrated flow Frequency Conditions When Maintenance is Needed Results Expected When Maintenance is Performed Trash and debris accumulated on the sheet flow Sheet flow site free of any trash or site debris. Soil erosion occurring in sheet flow zone. Soil erosion is not occurring and rills and channels have been repaired. Sheet flow is not occurring in the sheet flow zone. Sheet flow area is regraded to provide sheet flow. Annually and after large storms Rain harvesting equipment is functioning normally. 4/24/2016 2016 Surface Water Design Manual — Appendix A A-40 APPENDIX A MAINTENANCE REQUIREMENTS FOR FLOW CONTROL. CONVEYANCE, AND WQ FACILITIES r fI NO. 35 - SPLASH BLOCK BMP l_ .... ....... Maintenance Defect or Problem Conditions When Maintenance is Needed I Results Expected When Component Maintenance is Performed Site Trash and debris Trash and debris accumulated on the splash Splash block site free of any trash or block. debris. Splash Block Dislodged Splash block moved from outlet of downspout. Splash block correctly positioned to catch discharge from downspout. Channeling Water coming off the splash block causing No erosion occurs from the splash erosion. block. Downspout water Water coming from the downspout is not Water is discharging normally to the misdirected discharging to the dispersal area. dispersal area. Inspection Frequency Annually and after large storms. Rain harvesting equipment is functioning normally. 2016 Surface Water Design Manual — Appendix A 4/24/2016 A-41 APPENDIX A MAINTENANCE REQUIREMENTS FLOW CONTROL, CONVEYANCE, AND WQ FACILITIES NO. 36 - VEGETATED ROOF BMP (Retained from the 2009 SWDM for reference) Maintenance Defect or Problem Conditions When Maintenance is Needed Results Expected When Component Maintenance is Performed Preventative Vegetation Vegetation to be watered and pruned as needed Healthy vegetation growth with full to maintain healthy growth. coverage as designed. Site Trash and debris Trash and debris has accumulated on the Vegetated roof free of any trash or j vegetated roof. debris. Waterproof Leaking Waterproof membrane breached. Waterproof membrane has no tears Membrane or holes allowing water through it. Drainage Layer Drainage pathway Drainage layer flow plugged or obstructed. Drainage layer passing water with no obstruction. Drainage Overflow Drainage of overflow is obstructed. Overflow has no obstruction. Growth Media Compaction Soil in the growth media area compacted. No part of the growth media is compacted. Erosion Growth media washed out. Growth media is not being washed away. Nutrients Plants are not thriving Growth media has proper nutrients to support plant growth. Vegetation Vegetation Type Vegetation species not succulents, grass, herbs, Correct species of vegetation is and/or wildflowers adapted to harsh conditions. used. Vegetation Area Healthy vegetation covers less than 90% of Healthy vegetation covers more vegetation area. than 90% of vegetation area. Undesirable Weeds and other undesirable plants are invading No undesirable vegetation occurs in Vegetation more than 10% of vegetated area. the vegetated area. No herbicides or pesticides used to control undesirable vegetation. Special Vegetation Special vegetation not thriving. Special vegetation is kept healthy and inspected on frequent schedule. Border zone is kept open so Border Zone Access Border zone limited by vegetation overgrowth or other means. vegetated area is accessible. Gravel Stop Containment ......... _ Gravel stop does not contain overflow or divert it ...... Overflow water is only exits from to a designed outlet. the designed outlet. Inspection Frequency Annually and after large storms. Rain harvesting equipment is functioning normally. Vegetation inspected monthly Vegetation is kept healthy and thriving. 4/24/2016 2016 Surface Water Design Manual — Appendix A A-42