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Home My WebLink AboutBLD2016-00351 - 05 STORMWATER • , ��soN Com DEPARTMENT OF COMMUNITY DEVELOPMENT W621 Sheridan Street,Port Townsend,WA 98368 ti Tel:360.379.4450 I Fax:360.379.4451 Web:www.co.jefferson.wa.us/communitydevelopment E-mail:dcd@co.jefferson.wa.us r_________________—"' STORMWATER CALCULATION ` AUG - i WORKSH , � � 2 206 Til MLA# -- PROJECT/APPLICANT NAME: /E`FERSON COUNTY L_____`75 OFCi'M'IllvlyDI'r.IOPI"P! 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) Size of parcel acres An acre contains 43,560 square feet. Multiply the acrea e bythis f 9 gure. Size of parcel in square feet 2, 446,46. sq/ft Land-disturbing activity is any activity that results in movement of earth, or a change in the existing soil cover(both vegetati ie 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: Does the project convert%acres or more of Construction site for structures ., sq/ft native vegetation to lawn or landscaped areas? Drainfield, septic tank,etc. "/�'"' / sq/ft Circle: Yes Well, utilities,etc. A/ Ail sq/ft Does the project convert 2 1/2 acres or more of /� native vegetation to pasture? Driveway, parking, roads, etc. / sq/ft Lawn, sq/ft landscaping,etc. I Circle: Yes No Other compacted surface, etc. sq/ft Indicate Total Volumes of Proposed: Total Land Disturbance 3 5d sq/ft Cut Fill (cu/yd) 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 calc worksheet—REV.10/20/2014 1 STORMWATER CALULATIONS—IMPERVIOUS SURFACE NEW � EXISTING Structures(all roof area) Jo(2f)-) �J sq/ft Structures(all roof area) 1 73 5 sq/ft Sidewalks �� sq/ft Sidewalks �� sq/ft Patios sq/ft Patios sq/ft �--.0 Solid Decks sq/ft50 Solid Decks "11 sq/ft (without infiltration below) (without infiltration below) Driveway, parking, roads,etc Imo]f 00 sq/ft Driveway, parking, roads,etc - 0 sq/ft Other 3_ sq/ft Other C sq/ft Total New S sq/ft Total Existing 5 9 33 sggt 1 TOTAL NEW+TOTAL EXISTING* q II sq/ft `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 % Does the site have 35%or more of existing impervious surface? Circle: Yes ii 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 Storm water 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 prop 7J2o/ J G DOWNER OR A THOR ZED REPR SENTATIVE SIGNATURE) (DATE) S` 3a ""n �v wx ` q-�t,.`. lis �„ � �. . ��,__ :.,,�.�.� :a. .. =..tea.xe. ,si::nai._v,. .v�.:.�. . I2 stormwater talc worksheet—REV.10/20/2014 • ,cz._SoN cow DEPARTMENT OF COMMUNITY DEVELOPMENT Y-1.. 621 Sheridan Street,Port Townsend,WA 98368 W Tel:360.379.4450 Fax:360.379.4451 Web:www.co.jefferson.wa.us/communitydevelopment *11 E-mail:dcdaco.jefferson.wa.us 1's41 t, NO�o STORMWATER CALCULATION WORKSHEET 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) Size of parcel 5 acres An acre contains 43,560 square feet. Multiply the acreage by this figure. Size of parcel in square feet =�{r WAle 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: ,�*�, Does the project convert%acres or more of Construction site for structures sq/ft native vegetation to lawn or landscaped areas? Drainfield, septic tank, etc. "" // ^Lf sq/ft Circle: Yes No Well, utilities, etc. sq/ft Does the project convert 2%acres or more of native vegetation to pasture? Driveway, parking, roads, etc. /1 sq/ft Lawn, landscaping,etc. iX/y sq/ft Circle: Yes No Other compacted surface, etc. sq/ft Indicate Total Volumes of Proposed: Total Land Disturbance 3 560 sq/ft Cut Fill (cu/yd) 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 calc worksheet—REV.10/20/2014 1 0 • STORMWATER CALULATIONS—IMPERVIOUS SURFACE NEW EXISTING Structures(all roof area) J9` 0; sq/ft Structures(all roof area) 1 T S 5 sq/ft Sidewalks sq/ft Sidewalks sq/ft Patios sq/ft Patios sq/ft Solid Decks sq/ft Solid Decks 174 1CO sq/ft (without infiltration below) (without infiltration below) ( Driveway, parking, roads, etc l7 100 sq/ft Driveway, parking, roads,etc - 0 sq/ft Other sq/ft Other —f V sq/ft Total New 3 S C sq/ft Total Existing 5 14 33 sq/ft TOTAL NEW+TOTAL EXISTING* 1' -3 sq/ft *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 % Does the site have 35%or more of existing impervious surface? Circle: Yes n No X 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 Storm water 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 prop ,,-'''''' lir/ 20 I g DOWNER OR A THORIZED REPR SENTATIVE SIGNATURE) (DATE) stormwater talc worksheet—REV.10/20/2014 2 o I .,,.„0 N --"-c- \\ DEPARTMENT OF COMMUNITY DEVELOPMENT 621 Sheridan Street, Port Townsend,WA 98368 Tel: 360.379A450 I Fax: 360.379.4451 lG Web: www.co.iefferson.wa.us/communitydevelopment -is sh'I NICO E-mail: dcdco.jefferson.wa.us STORMWATER SITE PLAN INSTRUCTIONS AND SUBMITTAL TEMPLATE "Medium" and "Large" Projects [Includes Construction Stormwater Pollution Prevention Plan (SWPPP) and Permanent Stormwater Control Plan] The submittal template for a Stormwater Site Plan has been developed from information presented in the Department of Ecology 2012 Stormwater Management Manual for Western Washington (Manual), which is the set of stormwater management standards for new development and redevelopment in Jefferson County. The Stormwater Site Plan, Minimum Requirement #1 in the Manual, is the comprehensive report containing all of the technical information and analysis necessary to evaluate a proposed new development or redevelopment for compliance with stormwater requirements. A Stormwater Site Plan is required for all "medium" and "large" projects. (For background information, refer to the Stormwater Management Information Sheet.) The Stormwater Site Plan includes a Construction Stormwater Pollution Prevention Plan (SWPPP - Minimum Requirement #2) that addresses sediment and erosion control during construction and a Permanent Stormwater Control Plan that addresses stormwater on the project site in its developed condition through dispersion, infiltration, or, if necessary, flow control and/or treatment facilities. The steps for preparing and the content of a Stormwater Site Plan are summarized below and more fully described in Chapter 3 of Volume I of the Manual. The attached submittal template is intended to be a format applicable to typical rural residential construction. For these cases, completion and submittal of the template results in a complete land use application. THE TWO MAIN COMPONENTS OF A STORMWATER SITE PLAN I. Construction Stormwater Pollution Prevention Plan A Construction Stormwater Pollution Prevention Plan (SWPPP) is a document that describes the potential for pollution problems on a construction project and which explains and illustrates the measures to be taken to control these problems. The basis for requiring a SWPPP, the twelve elements required to be in a SWPPP, the suggested step-by step procedure to follow, and the suggested Best Management Practices (BMPs) to follow, are all described in Volume II of the Manual. A SWPPP consists of two sections, a narrative and the drawings. A description of the contents of the narrative and the drawings sections, and checklists for each of these sections, are in Section 3.3 of Volume II. For typical rural residential projects, DCD provides a Construction Stormwater Pollution Prevention (SWPP) Best Management Practices (BMPs) Packet to assist with the preparation of the Construction SWPPP. II. Permanent Stormwater Control Plan A Permanent Stormwater Control Plan is a document that describes the basis for, and the means of implementing, permanent Best Management Practices (BMPs)for flow control and treatment facilities after the project is completed. The content of a Permanent Stormwater Control Plan is described in Section 3.1.5 of Volume I of the Manual. The permanent BMPs and facilities for flow control and treatment are described in Volumes III, IV, and V of the Manual. The submittal template is intended for rural residential projects that can fully disperse or infiltrate stormwater. The template may not be appropriate or sufficient for applications involving larger or more complex projects. stormwater site plan template—rev.4/7/2016 1 • INSTRUCTIONS To prepare a Stormwater Site Plan, follow the steps outlined below, complete the Stormwater Site Plan template, sign and submit together with the Master Land Use Application (MLA). This information may also be provided on other diagrams, plans, studies, or attachments submitted with the project application. If so, please indicate such on this supplemental permit application. As the template is designed mostly for rural residential development, it may not be as useful for a larger project as an independently prepared Stormwater Site Plan. For any particular project, the Administrator may waive specific submittal requirements determined to be unnecessary for review of the application. Note: Prior to filling out the submittal template, read through these steps for preparing a Stormwater Site Plan. Preliminary or draft versions of the individual components may be helpful in the case that redesigning an original layout would result in a proposal that has less environmental impacts and is significantly simpler in terms of meeting stormwater requirements. For example, if the proposal can utilize the "full dispersion"BMP (T5.30 in the Manual), there is no need to provide for flow control or flow treatment on the site. For more information on the easiest way to meet storm water requirements, refer to the "Low Impact Development" Information Sheet. BMPs used during the construction phase and that are included in the Construction SWPPP may also be useful as elements of the Permanent Stormwater Control Plan. STEP 1: COLLECT AND ANALYZE INFORMATION ON EXISTING CONDITIONS Collect and review information on existing site conditions, including topography, drainage patterns, soils, ground cover, critical areas, adjacent areas, existing development, existing stormwater facilities. The Jefferson County website provides an Internet Map Server (IMS)function(http://www.co.jefferson.wa.us). If available,a Development Review Division(DRD)planner may be able to assist you in collecting this information. Analyze the information to determine site limitations,including: • Areas with high potential for erosion and sediment deposition(based on soil properties,slope, etc.); • Locations of sensitive and critical areas (e.g., vegetative buffers, wetlands, steep slopes, floodplains, geologically hazardous areas, streams,susceptible aquifer recharge areas, etc.);and • The natural receiving waters to which the stormwater runoff either directly or eventually discharges. This information will be useful in site design and in the completion of the Permanent Stormwater Control Plan and Construction SWPPP. STEP 2: PREPARE PRELIMINARY DEVELOPMENT LAYOUT Based upon the analysis of existing site conditions, locate the buildings,driveways, roads, parking lots,and landscaping features for the proposed development. Consider the following points when laying out the site: • Fit development to the terrain to minimize land disturbance; confine construction activities to the least area necessary and away from critical areas; • Preserve areas with natural vegetation(especially forested areas)as much as possible; • On sites with a mix of soil types, locate impervious areas over less permeable soil (e.g., till) and try to restrict development over more porous soils(e.g., outwash); • Cluster buildings together; • Minimize impervious areas;and • Maintain and utilize the natural drainage patterns. The preliminary development layout will assist in determining threshold discharge areas for calculating whether size thresholds under Minimum Requirements #6, #7, and #8 (for"large" projects) are exceeded and as a basis for the drawings and maps required for the Stormwater Site Plan. stormwater site plan template—rev.4/7/2016 2 • • STEP 3: PERFORM AN OFF-SITE ANALYSIS This step is for "large" projects (i.e., adding 5,000 square feet or more of new impervious surface, converting 3/ acres of pervious surfaces to lawn or landscaped areas, or converting 2 1/2 acres of forested area to pasture)at the discretion of the UDC Administrator. See Volume I, Section 2.6.2 for more information. STEP 4: REVIEW THE APPLICABLE MINIMUM REQUIREMENTS The Stormwater Calculation Worksheet is a required submittal for all development and redevelopment land use applications. Completing the Worksheet helps determine the broad category of the proposal—"small," "medium," or "large" project—and the applicable Minimum Requirements. "Small" projects need to meet Minimum Requirement #2 only. "Medium" projects need to meet Minimum Requirements #1 through #5. "Large" projects need to meet all the Minimum Requirements, #1 through #9. The Minimum Requirements are as follows: 1. Preparation of Stormwater Site Plans(Chapter 3 of Manual) 6. Runoff Treatment 2. Construction Stormwater Pollution Prevention 7. Flow Control 3. Source Control of Pollution 8. Wetlands Protection 4. Preservation of Natural Drainage Systems and Outfalls 9. Operations and Maintenance 5. On-site Stormwater Management The Manual provides descriptions and instructions in Volume I, Chapter 2. Information sheets,application materials,and DRD planners can help describe the Minimum Requirements to applicants. Note: "Large" projects, as part of meeting Minimum Requirements #6 – Runoff Treatment – and #7 – Flow Control, are compared to Volume I, Chapter 2 in the Manual to determine whether on-site stormwater management BMPs are sufficient or treatment facilities or flow control facilities are required. The flow control determination may necessitate use of the Western Washington Hydrology Model managed by the Department of Ecology. Consult Sections 2.5.6 and 2.5.7 of Volume I, Chapter 2 of the Manual for more information. Again, the easiest way to meet stormwater requirements is to design the project so that natural drainage is preserved, impervious surface is limited, and full dispersion (BMP T5.30) is implemented. By using "low impact development" techniques in the site design, the need for treatment and flow control facilities is eliminated, simplifying preparation of the Stormwater Site Plan and often the site construction process itself. For more information on these techniques,consult the"Low Impact Development" Information Sheet. STEP 5: PREPARE A PERMANENT STORMWATER CONTROL PLAN Select stormwater control BMPs and facilities that will serve the project site in its developed condition. The selection process is presented in Volume I, Chapter 4. After consideration is given to how selected BMPs and facilities fit within and serve the entire preliminary development layout, the designer may want to reconsider the site layout to reduce the need for construction of facilities or the size of the facilities by reducing the amount of impervious surfaces created and increasing the areas to be left undisturbed. The Permanent Stormwater Control Plan should contain the following sections(Section 3.1.5 of Volume I, Chapter 3): • Existing Site Hydrology(i.e.,the behavior of water on the site—above, below, and on the ground) • Developed Site Hydrology (special requirements for projects and threshold discharge areas within projects that requirement treatment and flow facilities) • Performance Standards and Goals • Flow Control System • Water Quality System • Conveyance System Analysis and Design Essentially, in terms of site hydrology, the developed condition of the site should match the pre-developed condition, with is forested land cover (unless reasonable, historic information is provided that indicates the site was prairie prior to settlement). For "large" projects, totals of impervious surfaces, pollution-generating impervious surfaces, and pollution generating pervious surfaces must be tabulated for each threshold discharge area for which on-site BMPs are the sole stormwater management approach. stormwater site plan template—rev.4/7/2016 3 • • • STEP 6: PREPARE A CONSTRUCTION STORMWATER POLLUTION PREVENTION PLAN (SWPPP) The Construction SWPPP for projects adding or replacing 2,000 square feet of impervious surface or more or clearing 7,000 square feet or more (i.e., "medium" or"large" projects), must contain sufficient information to demonstrate to the UDC Administrator that the potential pollution problems have been adequately addressed for the proposed project. An adequate Construction SWPPP includes a narrative and drawings. The narrative is a written statement to explain and justify the pollution prevention decisions made for a particular project. The narrative contains concise information concerning existing site conditions, construction schedules, and other pertinent items that are not contained on the drawings. The drawings and notes describe where and when the various BMPs should be installed, the performance the BMPs are expected to achieve, and actions to be taken if the performance goals are not achieved. There are 13 Elements that must be considered in the development of a Construction SWPPP, unless site conditions render that element unnecessary and the exemption from that element is clearly justified in the narrative. The 13 Elements cover the general water quality protection strategies for limiting site impacts during construction and are described in detail in Section 2.5.2, Volume I of the Manual. The 13 Elements of Minimum Requirement#2, Construction Stormwater Pollution Prevention, are: 1. Mark Clearing Limits 6. Protect Slopes 11. Maintain BMPs 2. Establish Construction Access 7. Protect Drain Inlets 12. Manage the Project 3. Control Flow Rates 8. Stabilize Channels and Outlets 13. Protect Low Impact Development 4. Install Sediment Controls 9. Control Pollutants BMP's 5. Stabilize Soils 10.Control De-watering For ease of use, the Stormwater Site Plan submittal template below includes a section that lists the 13 Elements and provides the opportunity to include sufficient information for rural residential and other relatively simple Construction SWPPPs. For more complex projects, a separate narrative and set of plans may be preferred or required. Volume II of the Manual is dedicated to Construction Stormwater Pollution Prevention. A step-by-step BMP selection process and a complete description of the BMPs applicable to each element is provided in Chapters 3 and 4. Additionally, DCD provides a Construction Stormwater Pollution Prevention (SWPP) Best Management Practices (BMPs) Packet that summarizes the 12 Elements and excerpts from the Manual sample sediment and erosion control measures for typical rural residential development. The Packet should prove useful for completing the Construction SWPPP component of the submittal template. On construction sites that infiltrate all stormwater runoff,the primary consideration in the preparation of the Construction SWPPP is the protection of the infiltration facilities from fine sediments during the construction phase and protection of ground water from other pollutants. On construction sites that discharge to surface water, the primary consideration in the preparation of the Construction SWPPP is compliance with the State Water Quality Standards. The step-by-step procedure outlined in Volume II, Section 3.2 is recommended for the development of these Construction SWPPPs. STEP 7: COMPLETE THE STORMWATER SITE PLAN The Stormwater Site Plan encompasses the entire submittal to Jefferson County in conjunction with a land use or building permit application. The following documents or sections should be included: • Project Overview • Existing Conditions Summary • Off-site Analysis Report(if required; usually for"large" projects) • Permanent Stormwater Control Plan • Special Reports and Studies(such as soil testing,wetland delineation, etc.,if applicable) • Other Permits(approvals required by other regulatory agencies that include stormwater management conditions) • Operation and Maintenance Manual(for each flow control and treatment facility, if applicable) • Bond Quantities Worksheet (for performance bond or other financial guarantee for proper construction and operation of construction site BMPs and permanent drainage facilities, if required) The submittal template below is designed for rural residential and other relatively small or simple projects. For larger and more complex projects—particularly those that involve stormwater treatment and/or flow control—more information may be required and an independent Stormwater Site Plan may be the preferable submittal format. STEP 8: CHECK COMPLIANCE WITH ALL APPLICABLE MINIMUM REQUIREMENTS A Stormwater Site Plan as designed and implemented should specifically fulfill all Minimum Requirements applicable to the project. The applicant should review to check that these requirements are satisfied and that all information provided is true and correct prior to signing and submitting the Stormwater Site Plan. (The signature box appears at the end of the submittal template.) 4 stormwater site plan template—rev.4/7/2016 • >13ON DEPARTMENT OF COMMUNITY DEVELOPMENT 621 Sheridan Street, Port Townsend, WA 98368 Tel: 360.379.4450 I Fax: 360.379.4451 Web: www.co.jefferson.wa.us/communitydevelopment "II NO E-mail: dcdr7a co.jefferson.wa.us STORMWATER SITE PLAN SUBMITTAL TEMPLATE MLA# PROJECT/APPLICANT NAME: Please answer all of the following questions to the best of your ability. Where the question calls for depiction on a site map, the applicant may choose to either incorporate the elements into the general plot plan for the Master Land Use Application or to submit a separate stormwater site plan map. Project Overview 1. Describe the proposed developed conditions of the site. Indicate position and relative size of proposed improvements on the site map. j94 as 5-4" naw p ,b‘.. )1 639 Existing Conditions Summary 2. Describe the existing topography. Indicate contours on the site map. F 3. Describe the existing vegetation. Indicate native vegetation areas on the site map. S vvt a ti '-v s cyr35'5 V SPZC 4. Describe the existing soils. Indicate soil type on the site map. 5. Describe the existing site hydrology(i.e., drainage; behavior of water on the site—above, below, and on the ground). Indicate existing stormwater drainage to and from the site on the site map. Depict separate drainage basins on the site map, if applicable,and indicate acreage of each. 1L-6 ‘04- 1.-- 6. . Describe any excess levels of noise generated by the proposed use or activity: � ° cow y �� r �? e–k" < 7. Describe significant geographic features and critical areas (i.e., environmentally sensitive areas such as wetlands, streams, steep slopes, etc.)on the site. Indicate location on the site map. stormwater site plan template—rev.4/7/2016 5 • • 8. Describe the general vicinity of the site, including adjacent land uses and structures, utilities, roads, and sensitive/critical areas (streams,wetlands, lakes,steep slopes,etc.). Permanent Stormwater Control Plan This portion of the Stormwater Site Plan consists of the selection and installation of the appropriate stormwater control BMPs and facilities to remain in place after construction of the project is completed. "Medium" size projects are required to have the totals calculated of all impervious surfaces, pollution-generating impervious surfaces, and pollution-generating pervious surfaces to verify that the thresholds for treatment facilities and flow control facilities are not exceeded. g. Describe the developed site hydrology, as proposed. Indicate whether stormwater will be fully dispersed (i.e., per BMP T5.30 in the Manual) or, if not, what types of stormwater flow control will be utilized for the site or specific threshold discharge areas within the site. Locate these facilities on the site plan and differentiate proposed facilities from existing facilities. -OW-Iev 5690Jrs _ ) /.2_ cis _ c4 ) 10. If the project requires the use of stormwater treatment facilities, describe the types of stormwater treatment facilities proposed for use on the site. Locate these facilities on the site plan and differentiate proposed facilities from existing facilities. [This is normally for"large"projects or projects that involve the potential for dispersion of contaminants.] ()Tj711. Describe the performance goals and standards applicable to the project. 6D. 6)0,Itj 0 0 S 12. Describe the flow control system. 13. Describe the water quality system. N s stormwater site plan template—rev.4/7/2016 • • 14. Describe the conveyance system analysis and design. 14,1 15. Describe the source of fill material, physical characteristics of fill material, and deposition of excess material. /7 1 V'c.• ? cs 1.) 16. Proposed methods of placement and compaction consistent with the applicable standards on Appendix Chapter 33 of the Uniform Building Code. 17. Des ribe the proposed surfacing material. 18. Describe methods for restoration of the site. W /41 19. An Operation and Maintenance Manual is required for each flow control and treatment facility. [This is normally required for "large"projects only and only those for which facilities are required to control flow or treat runoff.] If included,list the Manuals here. / A 20. List here and include any special reports or studies conducted to prepare the Stormwater Site Plan. 21. List other necessary permits and approvals as required by other regulatory agencies. If those permits or approvals include conditions that affect the drainage plan or contain more restrictive drainage-related requirements,describe those conditions or restrictions here. AI /A stormwater site plan template—rev.4/7/2016 7 s • CONSTRUCTION STORMWATER POLLUTION PREVENTION PLAN(SWPPP) The Construction SWPPP addresses sediment and erosion control during construction. The BMPs indicated by the applicant in the template that follows must be installed on the ground during all construction phases of the project. The proponent is responsible for preventing sediment and erosion impacts to environmentally sensitive areas and off-site areas. Consult the Construction Stormwater Pollution Prevention (SWPP) Best Management Practices (BMPs) Packet for guidance, particularly with rural residential development. SECTION I—CONSTRUCTION SWPPP NARRATIVE 1. Construction Stormwater Pollution Plan Elements. Describe how each of the Construction SWPPP elements has been or will be addressed. Identify the type and location of BMPs used to satisfy the required element. If an element is not applicable to the proposal,justify in writing. Detailed descriptions of the 13 Elements are found at Volume II Section 3.3.3 of the Manual (beginning on page 3-11). 13 Required Elements—Construction SWPPP 1. Mark Clearing Limits. J /lel 2 r ) C I I v►1 2. Establish Construction Access. 5 4nya. V 6 Jrvz 3. Control Flow Rates. Ai 4. Install Sediment Controls. /11 5. Stabilize Soils. //1 6. n Protect Slopes. 7. Protect Drain Inlets. stormwater site plan template—rev.4/7/2016 8 r • 13 Required Elements—Construction SWPPP(continued) 8. Stabilize Channels and Outlets. 9. Control Pollutants. N /A 10. Control De-Watering(the act of pumping groundwater or stormwater away from an active construction site). 11. Maintain Best Management Practices(BMPs). t / —cal( 1 ,D1.,4" S" a i/e t\ 12. Manage the Project. 13. Protect Low Impact Development BMP's /1 //13 2. Adjacent Areas. a. Description of the adjacent areas that may be affected by site disturbance (e.g., streams, lakes, wetlands, residential areas, roads). i z( sty, L4A- b. Description of the downstream drainage path leading from the site to the receiving body of water(minimum distance of 400 yards). 4 3. Environmentally Sensitive Areas. a. Description of environmentally sensitive areas that are on or adjacent to the site. 240 Z G S lt^�1 9 stormwater site plan template—rev.4/7/2016 4110 b. A Description of special requirements for working in or near environmentally sensitive areas. 1 V 1 4. Erosion Problem Areas. Description of potential erosion problems on site in the context of the characteristics of the on-site soils(e.g., erodibility, settleability, permeability, depth,texture, soil structure). 5. Construction Phasing. a. Construction sequenc 4-7 (0 (t, . £' h e, c 'z A (C." Ghee. -o-) -r4 ��, atm&-± &IA v A 44 b. Construction phasing(if proposed) v`2I"'t + vel` 6. Construction Schedule. Wet season is October 1 through April 30(page 2-20 of the Manual). Provide a proposed construction schedule. t 01 CD II. Wet Season Construction Activities. a. Proposed wet season construction activities. / b. Proposed wet season construction activities for environmentally sensitive areas. N 7. Financial/Ownership Responsibilities. a. Identify the property owner responsible f the initiation of bonds and/or other financial securities. — 1 Con y j SIA. b. Describe bonds and/or other evidence of financial responsibility for liability associated with erosion and sedimentation impacts. 8. Engineering Calculations. Provide Design Calculations on a separate sheet for the following, if applicable. a. Sediment Ponds/Traps. b. Diversions. c. Waterways. d. Runoff/Stormwater Detention Calculations stormwater site plan template—rev.4/7/2016 10 411/ SECTION II—EROSION AND SEDIMENT CONTROL PLAN Sediment and erosion control measures may be depicted on the master land use application plot plan,a stormwater site plan,and/or a separate Construction SWPPP site plan. This is a checklist to ensure that the following are depicted on a site plan: 1. General. a. Vicinity Map b. Jefferson County Approval Block c. Erosion and Sediment Control Notes 2. Site Plan. a. Legal description of subject property. b. North arrow. c. Indicate boundaries of existing vegetation(e.g.,tree lines,pasture areas, etc.). d. Identify and label areas of potential erosion problems. e. Identify FEMA base flood boundaries and Shoreline Management boundaries(if applicable). f. Show existing and proposed contours. g. Indicate drainage basins and direction of flow for individual drainage areas. h. Label final grade contours and identify developed condition drainage basins. i. Delineate areas that are to be cleared and graded. j. Show all cut and fill slopes indicating top and bottom of slope catch lines. 3. Conveyance Systems. a. Designate locations for swales, interceptor trenches,or ditches. b. Show all temporary and permanent drainage pipes,ditches,or cut-off trenches required for erosion&sediment control. c. Provide minimum slope and cover for all temporary pipes or call out pipe inverts. d. Shows grades, dimensions,and direction of flow in all ditches, swales,culverts and pipes. e. Provide details for bypassing off-site runoff around disturbed areas. f. Indicate locations and outlets of any dewatering systems. 4. Location of Detention Best Management Practices(BMPs). Identify location of detention BMPs. 5. Erosion and Sediment Control Facilities. a. Show the locations of sediment trap(s), pond(s), pipes and structures. b. Dimension pond berm widths and inside and outside pond slopes. c. Indicate the trap/pond storage required and the depth,length,and width dimensions. d. Provide typical section views through pond and outlet structure. e. Provide typical details of gravel cone and standpipe, and/or other filtering devices. f. Detail stabilization techniques for outlet/inlet. g. Detail control/restrictor device location and details. h. Specify mulch and/or recommended cover of berms and slopes. i. Provide rock specifications and detail for rock check dam(s), if applicable. j. Specify spacing for rock check dams as required. k. Provide front and side sections of typical rock check dams. I. Indicate the locations and provide details and specifications for silt fabric. m. Locate the construction entrance and provide a detail. 6. Detailed Drawings. Any structural practices used that are not referenced in the Ecology Manual should be explained and illustrated with detailed drawings. 7. Other Pollutant BMPs. Indicate on the site plan the locations of BMPs to be used for the control of pollutants other than sediment(e.g.,concrete wash water). 8. Monitoring Locations. Indicate on the site plan the water quality sampling locations to be used for monitoring water quality on the construction site. Sampling stations should be located upstream and downstream of the project site. stormwater site plan template—rev.4/7/2016 11 • Stormwater Site Plan Changes If the designer wishes to make changes or revisions to the originally approved Stormwater Site Plan, the proposed revisions shall be submitted to DCD prior to construction. The submittal shall include substitute pages that include all proposed changes, revised drawings showing any structural changes,and any other supporting information that explains and supports the reason for the change. Final Corrected Plan Submittal If the project included construction of conveyance systems, treatment facilities, flow control facilities, or structural source control BMPs (not standard on-site stormwater management BMPs), the applicant shall submit a final corrected plan ("as-builts")when the project is completed. These should be engineering drawings (stamped by a licensed civil engineer) that accurately represent the project as constructed. APPLICANT SIGNATURE By sit • he Construction SWPPP worksheet, I as the applicant/owner attest that the information provided herein is true and corP-ct to th.• best o owledge. I also certify that this application is being made with the full knowledge and consent of all o ners of t•- ---cted p sperty. (LANDOWNER OR AUTHORIZED REPRESENTATIVE SIGNATURE) (DATE) THIS SPACE MAY BE USED FOR ADDITIONAL NOTES, IF NEEDED: 12 stormwater site plan template—rev.4/7/2016 • 3.1.3 Perforated Stub-Out Connections (BMP T5.10C) A perforated stub-out connection is a length of perforated pipe within a gravel-filled trench that is placed between roof downspouts and a stub-out to the local drainage system. Figure 3.1.8 illustrates a perforated stub-out connection. These systems are intended to provide some infiltration during drier months. During the wet winter months, they may provide little or no flow control. Applications& Perforated stub-outs are not appropriate when seasonal water table is less Limitations than one foot below trench bottom. In projects subject to Minimum Requirement f15 (see Volume 1), perforated stub-out connections may be used only when,611 other higher priority on-site stormwater management BMPs are noffeasible, per the criteria for each of those BMPs. Select the location of the connection to allow ainaximum amount of runoff to infiltrate into the ground (ideally a dry,relatively well drained, location). To facilitate maintenance, do not locate the perforated pipe portion of the system under impervious or heavily compacted(e.g., driveways and parking areas)surfaces. Use the same setbacks as for infiltration trenches in Section 3.1.1. Have a licensed geologist, hydrogeologist,or engineering geologist evaluate potential runoff discharges towards landslide hazard areas. Do not place the perforated portion of the pipe on or above slopes greater than 20%or above erosion hazard areas without evaluation by a professional engineer with geotechnical expertise or qualified geologist and jurisdiction approval. For sites with septic systems, the perforated portion of the pipe must be downgradient of the drainfield primary and reserve areas. This requirement can be waived if site topograp will clearly prohibit flows from intersecting the drainfield or where site onditions(soil permeability, distance between systems,etc.)indicate that th is unnecessary. Design Criteria Perforated stub-out connections consist of at leas 10 feet of perforated pipe per 5,000 square feet of roof area laid in a ley- 2-foot wide trench backfilled with washed drain rock. Extend the drain 'ck to a depth of at least 8 inches below the bottom of the pipe and cover e pipe. Lay the pipe level and cover the rock trench with filter fabric an. 6 inches of fill (see Figure 3.1.8). Runoff Model Any flow reduction is variable and unpredictable.No cornpu•-r modeling Representation techniques are allowed that would predict any reduction in flip, rates and volumes from the connected area. Volume III Hydrologic Analysis and Flow Control BMPs—December 2014 3-17 house I I t1 I Roof downspout serves up to 700 sf.Of roof 11111111Piii 1111 50'min. Vegetated flow path Splash 1011166. Downspout extension NTS Splash block vokliwkim"- Figure 3.t7-Typical Downspout Splashblock Dispersion Voli ie III—Hydrologic Analysis and Flow Control BNIPs—December 2014 3-16 • • pipe O.D. r-o ro mut min erd cap or plug Ilow to second dispersal trench 1113 pi(74: clean outwe from pipe if recPa.iy .iiia 0 le 0 0 70 0 4"o r 6"perbralad pipe lad Retriever note hed . ... glade board 1 2"x 2notches a 1 Aa 4 . 9 type IC B wiso lid coyer(locking) " I CB A - type - . i -18.0.G. wisold coye r 0 IIMMI=1 110:a 11111111111111111 'It-. influent pipe(max r.ksign 0 1. 4,e, fbw.-..,0.6 0 FS per trench) a ,o, clean out wye from pipe I a kwroi a • 9 a Nom to otter branching C113's PLAN as recessary NTS ODI ii1?'0.C. 1 1,.pipe . •_ galvanized bolts co / r-o 11.41W4-1 fie--2" 1,Orils .--f- 10' d- -,',.1,i'N':' Press— A ,:'1.-:'-•:.'t' 0 :":„Z , treated grade -N. 0 ",".t,t'&AI'..."‘ b a %"... . .. 4"ore perforated .*-!" 5.!".: pipe lad flaz • •-• 01 'oV j. 439 *.f.i"'$., NOTES' 4"x I support post 7 1,0, qt, clean(S.5%,lines) 1.Th is trenc h shall be construed so i 4/2"-Pft"washed nook as lo prevent point discharge and.lor io 1 4 4144...N' erosion. 2.Trenches may be placed no closer filter fabric than 50 feet b one ahothe r.(100 feet aiong flowline) 6.15% rmx for tom cerci 3.Trench and grade board must be treatrrert in rural areas. a).0.11.Align'to foncio contoursof siv,. SECTION AA 4.Su ppo rt post spacing as required by NTS soil conditions to ensure grade board remains level. Figure 3.1.6-Standard Dispersion Trench with Notched Grade Board Volume III-Hydrologic Analysis and Flow Control BMPs-December 2014 3-14 Design Criteria for Splashblocks A typical downspout splashblock is shown in Figure 3.1.7. In general, if the ground is sloped away from the foundation and there is adequate vegetation and area for effective dispersion, splashblocks will adequately disperse storm runoff. If the ground is fairly level, if the structure includes a basement,or if foundation drains are proposed,splashblocks with downspout extensions may be a better choice because the discharge point is moved away from the foundation. Downspout extensions can include piping to a splashblock/discharge point a considerable distance from the downspout,as long as the runoff can travel through a well-vegetated area as described below. The following apply to the use of splashblocks: 1. Maintain a vegetated flowpath of at least 50 feet between the discharge point and any property line,structure, slope steeper than 15%,stream, wetland, lake,or other impervious surface. Sensitive area buffers may count toward flowpath lengths. 2. A maximum of 700 square feet of roof area may drain to each splashblock. 3. For purposes of maintaining adequate separation of flows discharged from adjacent dispersion devices,the vegetated flowpath segment for the splashblock must not overlap with other flowpath segments,except those associated with sheet flow from a non-native pervious surface. 4. Place a splashblock or a pad of crushed rock(2 feet wide by 3 feet long by 6 inches deep)at each downspout discharge point. 5. No erosion or flooding of downstream properties may result. 6. Have a geotechnical engineer or a licensed geologist, hydrogeologist, or engineering geologist evaluate runoff discharged towards landslide hazard areas. Do not place Splashblocks on or above slopes greater than 15%or above erosion hazard areas without evaluation by a professional engineer with geotechnical expertise or a licensed geologist,hydrogeologist,or engineering geologist,and approval by the Local Plan Approval Authority. 7. For sites with septic systems,the discharge point must be downslope of the primary and reserve drainfield areas. This requirement may be waived if site topography clearly prohibits flows from intersecting the drainfield or where site conditions (soil permeability,distance between systems,etc.)indicate that this is unnecessary. Volume HI-Hydrologic Analysis and Flow Control BMPs-December 2014 3-15 • Design Criteria for Splashblocks A typical downspout splashblock is shown in Figure 3.L7. In general, if the ground is sloped away from the foundation and there is adequate vegetation and area for effective dispersion,splashblocks will adequately disperse storm runoff. If the ground is fairly level, if the structure includes a basement,or if foundation drains are proposed, splashblocks with downspout extensions may be a better choice because the discharge point is moved away from the foundation. Downspout extensions can include piping to a splashblock/discharge point a considerable distance from the downspout,as long as the runoff can travel through a well-vegetated area as described below. The following apply to the use of splashblocks: 1. Maintain a vegetated flowpath of at least 50 feet between the discharge point and any property line,structure, slope steeper than 15%,stream, wetland, lake,or other impervious surface. Sensitive area buffers may count toward flowpath lengths. 2. A maximum of 700 square'feet of roof area may drain to each splashblock. 3. For purposes of maintaining adequate separation of flows discharged from adjacent dispersi r devices,the vegetated flowpath segment for the splashblock must not verlap with other flowpath segments, except those associated with sheet low from a non-native pervious surface. 4. Place a splashblock or a pad o rushed rock(2 feet wide by 3 feet long by 6 inches deep)at each de spout discharge point. 5. No erosion or flooding of downstre.,1 properties may result. 6. Have a geotechnical engineer or a lice ed geologist, hydrogeologist, or engineering geologist evaluate runoff..scharged towards landslide hazard areas. Do not place Splashblocks o 'r above slopes greater than 15%or above erosion hazard areas with. t evaluation by a professional engineer with geotechnical expert e or a licensed geologist,hydrogeologist,or engineering geolog t,and approval by the Local Plan Approval Authority. 7. For sites with septic systems,the discharge point mus be downslope of the primary and reserve drainfield areas. This requir• ent may be waived if site topography clearly prohibits flows from inti secting the drainfield or where site conditions (soil permeability, distan e between systems,etc.)indicate that this is unnecessary. Volume III—Hydrologic Analysis and Flow Control BMPs—December 2014 3-15 0 111110 pipe O.D. 1%0 rol. 114T' erd cap or plug flow to second dispersal tr.=_nc h 0" i lei.7 0 c ari out wye from pipe if necPs".-Api :A 4 1.0 111 7 0 A 4"or 5"perforaed pipe lad flavlevel a 0 notched a c, =.1 4 grade board 174 AA i tYPe I CB 2"x 2'notches 7 4 9 type 1013w/solid coke':(locking) = le.c.c. .,141 , 7._ 1 a A aim= wisol id coxer b a Influent pipe rna‘x cies' n to I - A f'bro e,0.5 C FS per tren9ch) = 4.9- 11 Al 74* ;.)::‘ clean out we from pipe :-. LE4 oa„r, kr...i e Il fbiv to other branching CB's PLAN as necerary NTS /.pipe 0.D. I -18"O.C. I galvanized bolts r-a / I Kt....„,,,,.• 1.- (1.41••• I W .1.-7,,,,, 'tiV,-' 2 x1,2"--/ --..--4C1,VilaZg.,• a• :,..,f. .;.&,;0.7 grade .r.,,A.4...,..:zs._.,..<1 mim b tr ,Vt.Z."..,'.. 2„ pressure .44laZVIA,..e49,,rtt ow a at. 'i'''',,- board notches treated grade 1 g Itifia7 % ,;,.1' 4"ore'perforated 09 49 ,.f.: pi pe laid flat 07 t'J '''''. NOTES: -'," - 4”x 4'support past vii • ..,140 clean(.‘59,...fires) i.This tie rch shall be constructed so tolg ,./."_."washed rcc.k as ti prevent point discharge arid.br erosion. , 2.Trenches may be pl-wed no c 09er fitter fabric."" " than 50 1t 0 one aoother.(I00 feet alorg tiovoline) '15% rrox for tow co-to:IV/tater quality 3.Trench and grade board must be treatment in rural areas. i.,e I.Align to fol kw conto urs of sl'e. SECTIONAA 4.Support post spacing required by NTS soil co rd itions to ensure grade board remains level. — — — — Figure 3.1.6-Standard Dispersion Trench with Notched Grade Board Volume III-Hydrologic Analysis and Flow Control BMPs-December 2014 3-14 • v0 . ./ level outlet • d z 0o VA d d a 0 V 0 ci oa• °vac' • v v ° a . 0, 00 o0 0 • 0 0 6"min ' • ° - •'59 dr,° 00 rf • , ,e _ D Pe PIPe •04,40 act-1 d 0d O0..3 18-min 0 7D .Do°0 yo a° ° a ° ° " 1 V2 -3/4 washed rock "a oNo k 00 v vo 0 0 0 7 0 0 0 a q 0000 C' 0.04 Da OP Co V aeda Do , 0o .*, 24'min--,1 TRENCH X-SECTION NTS slope small catch basin or yard drain e I 2'x level trenches <300 sq.ft. Type I CB >700 sq.ft. standard dispersion trench wf notched grade board length 10'per 700 sq.ft. of roof area. PLAN VIEW OF ROOF AITC Figure 3.1.5-Typical Downspout Dispersion Trench Source: King County Volume III—Hydrologic Analysis and Flow Control BMPs—December 2014 3-13 Note-For all other types of projects, the use of a perforated stub-out in lieu of downspout dispersion shall be as determined by the Local Plan Approval Authority. 5. For sites with septic systems,the discharge point of all dispersion systems must be downgradient of the drainfield. This requirement may be waived if site topography clearly prohibits flows from intersecting the drainfield. Design Criteria for Dispersion Trenches 1. A vegetated flowpath of at least 25 feet in length must be maintained between the outlet of the trench and any property line,structure, stream, wetland,or impervious surface.A vegetated flowpath of at least 50 feet in length must be maintained between the outlet of the trench and any slope steeper than 15%. Sensitive area buffers may count towards flowpath lengths. 2. Trenches serving up to 700 square feet of roof area may be simple 10- foot-long by 2-foot wide gravel filled trenches as shown in Figure 3.1.5. For roof areas larger than 700 square feet,a dispersion trench with notched grade board as shown in Figure 3.1.6 or alternative material approved by the Local Plan Approval Authority may be used.The total length of this design must not exceed 50 feet and must provide at least 10 feet of trench per 700 square feet of roof area. 3. Maintain a setback of at least 5 feet between any edge of the trench and any structure or property line. 4. No erosion or flooding of downstream properties may result. 5. Have a geotechnical engineer or a licensed geologist,hydrogeologist, or engineering geologist evaluate runoff discharged towards landslide hazard areas. Don not place the discharge point on or above slopes greater than 15%or above erosion hazard areas without evaluation by a geotechnical engineer or qualified geologist and jurisdiction approval. 6. For purposes of maintaining adequate separation of flows discharged from adjacent dispersion devices,the outer edge of the vegetated flowpath segment for the dispersion trench must not overlap with other flowpath segments,except those associated with sheet flow from a non- native pervious surface. Volume III—Hydrologic Analysis and Flow Control BMPs—December 2014 3-12 • Setbacks Local governments may require specific setbacks in sites with slopes over 40%, land slide areas,open water features, springs,wells,and septic tank drain fields.Adequate room for maintenance cess and equipment should also be considered.Examples of setbacks c monly used include the following: 1. All infiltration systems should be/at least 10 feet from any structure, property line,or sensitive area(except slopes over 40%). 2. All infiltration systems must be at least 50 feet from the top of any slope over 40%.This setback may be reduced to 15 feet based on a geotechnical evaluation,but in no instances may it be less than the buffer width. 3. For sites with septic systems, infiltration systems must be downgradient of the drainfield unless the site topography clearly prohibits subsurface flows from intersecting the drainfield. N Volume III—Hydrologic Analysis and Flow Control BMPs—December 2014 3-10 • • 3.1.2 Downspout Dispersion Systems (BMP T5.10B) Downspout dispersion systems are splash blocks or gravel-filled trenches, which serve to spread roof runoff over vegetated pervious areas. Dispersion attenuates peak flows by slowing the runoff entering into the conveyance system, allowing some infiltration,and providing some water quality benefits. Applications & Downspout dispersion may be used in all subdivision lots where Limitations downspout full infiltration, full dispersion, and bioretention/rain gardens are not feasible. Runoff Modeling In WWHM,roof areas may be modeled as grassed surfaces(landscape) if for Roof roof runoff is dispersed according to the requirements of this section on Downspout lots greater than 22,000 square feet,and the vegetated flowpath is 50 feet Dispersion or larger through undisturbed native landscape or lawn/landscape area that meets BMP T5.13. If the available vegetated flowpath is 25 to 50 feet, use of a dispersion trench allows modeling the roof as 50% impervious/50% landscape. This is done in WWHM on the Mitigated Scenario screen by entering the roof area into one of the entry options for dispersal of impervious area runoff For WWHM2012,see Appendix 111-C in this Volume. Design Criteria 1. Use downspout trenches designed as shown in Figures 3.1.5 and 3.1.6 for all downspout dispersion applications except where splash blocks are allowed below. 2. Splash blocks shown in Figure 3.1.7 may be used for downspouts discharging to a vegetated flowpath at least 50 feet in length as measured from the downspout to the downstream property line, structure,slope over 15%,stream,wetland,or other impervious surface. Sensitive area buffers may count toward flowpath lengths. 3. Cover the vegetated flowpath with well-established lawn or pasture, landscaping with well-established groundcover,or native vegetation with natural groundcover. The groundcover shall be dense enough to help disperse and infiltrate flows and to prevent erosion. 4. If the vegetated flowpath(measured as defined above)is less than 25 feet,a perforated stub-out connection per Section 3.1.3 may be used in lieu of downspout dispersion. A perforated stub-out may also be used where implementation of downspout dispersion might cause erosion or flooding problems,either on site or on adjacent lots. For example,this provision might be appropriate for lots constructed on steep hills where downspout discharge could culminate and might pose a potential hazard for lower lying lots,or where dispersed flows could create problems for adjacent off-site lots. This provision does not apply to situations where lots are flat and on-site downspout dispersal would result in saturated yards. Perforated stub-outs are not appropriate when seasonal water table is<1 foot below trench bottom. Volume III—Hydrologic Analysis and Flow Control BMPs—December 2014 3-11 • • 2. Permeable pavements in accordance with BMP T5.15 in chapter 5 of Volume V 3. Bioretention BMP's (See Chapter 7,Volume V of the SIVIMWW) that have a minimum horizontally projected surface area below the overflow which is at least 5% of the total surface area draining to it. 4. Sheet Flow Dispersion in accordance with BMP T5.12,or Concentrated Flow Dispersion in accordance with BMP T5.11 in Chapter 5 of Volume V. Objective To use practices distributed across a development that reduce the amount of disruption of the natural hydrologic characteristics of the site. Supplemental Guidelines "Flooding or erosion impacts"include flooding of septic systems,crawl spaces,living areas,outbuildings,etc.; increased ice or algal growth on sidewalks/roadways;earth movement/settlement ;erosion and other potential damage. Recent research indicates that traditional development techniques in residential,commercial,and industrial land development cause gross disruption of the natural hydrologic cycle with severe impacts to water and water-related natural resources. Based upon gross level applications of continuous runoff modeling and assumptions concerning minimum flows needed to maintain beneficial uses,watersheds must retain the majority of their natural vegetation cover and soils,and developments must minimize their disruption of the natural hydrologic cycle in order to avoid significant natural resource degradation in lowland streams. The BMPs described in Section 3.1 of Volume 111,and Section 5.3.1 of Volume V are likely insufficient by themselves to prevent significant hydrologic disruptions and impacts to streams and their natural resources. Therefore, local governments should look for opportunities to change their local development codes to minimize impervious surfaces and retain native vegetation in all development situations. Most importantly,to maintain the beneficial uses of our lowland freshwater systems will require land use planning that targets retention of a majority of a creek's watershed in its natural condition,and retains most of the benefits of headwater areas,connected wetlands,riparian,and floodplain areas. Volume 1—Minimum Technical Requirements—August 2012 2-32 • • 2. Permeable pavement' in accordance with BMP T5.15 in Chapter 5 of Volume V,or Rain Gardens in accordance with BMP T5.14 in Chapter 5 of Volume V,or Bioretention in accordance with Chapter 7 of of Volume V. The rain garden or bioretention facility must have a minimum horizontal projected surface area below the overflow which is at least 5% of the area draining to it. 3. Sheet Flow Dispersion in accordance with BMP T5.12,or Concentrated Flow Dispersion in accordance with BMP T5.11 in Chapter 5 of Volume V. List#2:On-site Stormwater Management BMPs for Projects Triggering Minimum Requirements#1 through #9 For each surface,consider the BMPs in the order listed for that type of surface.Use the first BMP that is considered feasible.No other On- site Stormwater Management BMP is necessary for that surface. Feasibility shall be determined by evaluation against: 1. Design criteria,limitations,and infeasibility criteria identified for each BMP in this manual; and 2. Competing Needs Criteria listed in Chapter 5 of Volume V of this manual. Lawn and landscaped areas: • Post-Construction Soil Quality and Depth in accordance with BMP T5.13 in Chapter 5 of Volume V. Roofs: 1. Full Dispersion in accordance with BMP T5.30 in Chapter 5 of Volume V,or Downspout Full Infiltration Systems in accordance with BMP T5.10A in Section 3.1.1 in Chapter 3 of Volume III 2. Bioretention (See Chapter 7 of Volume V)facilities that have a minimum horizontally projected surface area below the overflow which is at least 5% of the total surface area draining to it. 3. Downspout Dispersion Systems in accordance with BMP T5.10B in Section 3.1.2 in Chapter 3 of Volume III 4. Perforated Stub-out Connections in accordance with BMP T5.10C in Section 3.1.3 in Chapter 3 of Volume III Other Hard Surfaces: 1. Full Dispersion in accordance with BMP T5.30 in Chapter 5 of Volume V 1 This is not a requirement to pave these surfaces. Where pavement is proposed,it must be permeable to the extent feasible unless full dispersion is employed. Volume 1—Minimum Technical Requirements—August 2012 2-31 • Low Impact Development Performance Standard Stormwater discharges shall match developed discharge durations to pre-developed durations for the range of pre-developed discharge rates from 8% of the 2-year peak flow to 50% of the 2-year peak flow. Refer to the Standard Flow Control Requirement section in Minimum Requirement#7 for information about the assignment of the pre- developed condition. Project sites that must also meet minimum requirement#7-flow control - must match flow durations between 8% of the 2-year flow through the full 50-year flow. List#1: On-site Stormwater Management BMPs for Projects Triggering Minimum Requirements#1 through #5 For each surface,consider the BMP's in the order listed for that type of surface. Use the first BMP that is considered feasible. No other On- site Stormwater Management BMP is necessary for that surface. Feasibility shall be determined by evaluation against: 1. Design criteria, limitations, and infeasibility criteria identified for each BMP in this manual; and 2. Competing Needs Criteria listed in Chapter 5 of Volume V of this manual. Lawn and landscaped areas: • Post-Construction Soil Quality and Depth in accordance with BMP T5.13 in Chapter 5 of Volume V Roofs: 1. Full Dispersion in accordance with BMP T5.30 in Chapter 5 of Volume V,or Downspout Full Infiltration Systems in accordance with BMP T5.10A in Section 3.1.1 in Chapter 3 of Volume III 2. Rain Gardens in accordance with BMP T5.14 in Chapter 5 of Volume V,or Bioretention in accordance with Chapter 7 of Volume V. The rain garden or bioretention facility must have a minimum horizontal projected surface area below the overflow which is at least 5% of the area draining to it. 3. Downspout Dispersion Systems in accordance with BMP T5.10B in Section 3.1.2 in Chapter 3 of Volume HI 4. Perforated Stub-out Connections in accordance with BMP T5.10C in Section 3.1.3 in Chapter 3 of Volume III Other Hard Surfaces: I. Full Dispersion in accordance with BMP T5.30 in Chapter 5 of Volume V Volume I—Minimum Technical Requirements—August 2012 2-30 • Projects qualifying as flow control exempt in accordance with Section 2.5.7 of this chapter do not have to achieve the LID performance standard, nor consider bioretention,rain gardens,permeable pavement,and full dispersion if using List#1 or List#2.However, those projects must implement BMP T5.13; BMPs T5.10A,B,or C; and BMP T5.11or T5.12,if feasible. Project Thresholds Projects triggering only Minimum Requirements#1 through#5 shall either: a. Use On-site Stormwater Management BMPs from List#1 for all surfaces within each type of surface in List#1; or b. Demonstrate compliance with the LID Performance Standard. Projects selecting this option cannot use Rain Gardens.They may choose to use Bioretention BMPs as described in Chapter 7 of Volume V to achieve the LID Performance Standard. Projects triggering Minimum Requirements#1 through#9,must meet the requirements in Table 2.5.1. Table 2.5.1 On-site Stormwater Management Requirements for Projects Triggering Minimum Requirements#1 -#9 Project Type and Location Requirement New development on any parcel inside the Low Impact Development Performance UGA,or new development outside the Standard and BMP T5.13;or List#2 UGA on a parcel less than 5 acres (applicant option). New development outside the UGA on a Low Impact Development Performance parcel of 5 acres or larger Standard and BMP T5.13. Redevelopment on any parcel inside the Low Impact Development Performance UGA,or redevelopment outside the UGA Standard and BMP T5.13;or List#2 on a parcel less than 5 acres (applicant option). Redevelopment outside the UGA on a Low Impact tandard and BMP T5.13.Development Performance parcel of 5 acres or larger NOTE: This table refers to the Urban Growth Area(UGA)as designated under the Growth Management Act (GMA) (Chapter 36.70A RCW)of the State of Washington.If the Permittee is located in a county that is not subject to planning under the GMA,the city limits shall be used instead. Volume 1—Minimum Technical Requirements—August 2012 2-29 IP Where no conveyance system exists at the adjacent downgradient property line and the discharge was previously unconcentrated flow or significantly lower concentrated flow,then measures must be taken to prevent downgradient impacts. Drainage easements from downstream property owners may be needed and should be obtained prior to approval of engineering plans. The following discharge requirement is recommended: Where no conveyance system exists at the abutting downstream property line and the natural (existing)discharge is unconcentrated, any runoff concentrated by the proposed project must be discharged as follows: a) If the 100-year peak discharge is less than or equal to 0.2 cfs(0.3 cfs using 15 minute time steps) under existing conditions and will remain less than or equal to 0.2 cfs under developed conditions, then the concentrated runoff may be discharged onto a rock pad or to any other system that serves to disperse flows. b) If the 100-year peak discharge is less than or equal to 0.5 cfs(0.75 cfs using 15 minute time steps)under existing conditions and will remain less than or equal to 0.5 cfs under developed conditions,then the concentrated runoff may be discharged through a dispersal trench or other dispersal system,provided the applicant can demonstrate that there will be no significant adverse impact to downhill properties or drainage systems. c) If the 100-year peak discharge is greater than 0.5 cfs for either existing or developed conditions,or if a significant adverse impact to downgradient properties or drainage systems is likely,then a conveyance system must be provided to convey the concentrated runoff across the downstream properties to an acceptable discharge point(i.e.,an enclosed drainage system or open drainage feature where concentrated runoff can be discharged without significant adverse impact). Stormwater control or treatment structures should not be located within the expected 25-year water level elevations for salmonid-bearing waters. Such areas may provide off-channel habitat for juvenile salmonids and salmonid fry. Designs for outfall systems to protect against adverse impacts from concentrated runoff are included in Volume V, Chapter 4. 2.5.5 Minimum Requirement#5: On-site Stormwater Management Projects shall employ On-site Stormwater Management BMP s in accordance with the following projects thresholds,standards,and lists to infiltrate,disperse,and retain stormwater runoff on-site to the extent feasible without causing flooding or erosion impacts. Volume 1—Minimum Technical Requirements—August 2012 2-28 I 2.5.3 Minimum Requirement#3: Source Control of Pollution All known,available and reasonable source control BMPs must be applied to all projects.Source control BMPs must be selected, designed,and maintained according to this manual. Objective The intent of source control BMPs is to prevent stormwater from coming in contact with pollutants.They are a cost-effective means of reducing pollutants in stormwater,and,therefore,should be a first consideration in all projects. Supplemental Guidelines An adopted and implemented basin plan or a Total Maximum Daily Load (TMDL,also known as a Water Clean-up Plan)may be used to develop more stringent source control requirements that are tailored to a specific basin. Source Control BMPs include Operational BMPs and Structural Source Control BMPs. See Volume IV for design details of these BMPs. For construction sites,see Volume II, Chapter 4. Structural source control BMPs should be identified in the stormwater site plan and should be shown on all applicable plans submitted for local government review and approval. 2.5.4 Minimum Requirement#4: Preservation of Natural Drainage Systems and Outfalls Natural drainage patterns shall be maintained,and discharges from the project site shall occur at the natural location,to the maximum extent practicable.The manner by which runoff is discharged from the project site must not cause a significant adverse impact to downstream receiving waters and downgradient properties.All outfalls require energy dissipation. Objective To preserve and utilize natural drainage systems to the fullest extent because of the multiple stormwater benefits these systems provide; and to prevent erosion at and downstream of the discharge location. Supplemental Guidelines Creating new drainage patterns results in more site disturbance and more potential for erosion and sedimentation during and after construction. Creating new discharge points can create significant stream channel erosion problems as the receiving water body typically must adjust to the new flows. Diversions can cause greater impacts than would otherwise occur by discharging runoff at the natural location. Volume I—Minimum Technical Requirements—August 2012 2-27 Objective To control erosion and prevent sediment and other pollutants from leaving the site during the construction phase of a project. To have fully functional stormwater facilities and BMP's for the developed site upon completion of construction. Supplemental Guidelines If a Construction SWPPP is found to be inadequate(with respect to erosion and sediment control requirements),then the Plan Approval Authority within the Local Government should require that other BMPs be implemented, as appropriate. The Plan Approval Authority may allow development of generic Construction SWPPP's that apply to commonly conducted public road activities,such as road surface replacement,that trigger this minimum requirement. They may also develop an abbreviated SWPPP format for project sites that will disturb less than 1 acre. Based on the information provided and/or local weather conditions,the local permitting authority may expand or restrict the seasonal limitation on site disturbance. The local permitting authority shall take enforcement action-such as a notice of violation,administrative order,penalty,or stop-work order under the following circumstances: • lf,during the course of any construction activity or soil disturbance during the seasonal limitation period,sediment leaves the construction site causing a violation of the surface water quality standard;or • If clearing and grading limits or erosion and sediment control measures shown in the approved plan are not maintained. Coordination with Utilities and Other Contractors-The primary project proponent shall evaluate, with input from utilities and other contractors, the stormwater management requirements for the entire project,including the utilities,when preparing the Construction SWPPP. Element#13,Protect Low Impact Development BMPs, is not yet included as a permit condition in the NPDES Construction Stormwater General Permit. That permit is not scheduled for reissuance until December,2015. Until that permit is reissued with element#13 added as a permit condition, the element may be enforceable only through the requirements of local stormwater codes that may have been updated to include it. Municipal Stormwater Permittees must incorporate this element into local requirements per the timelines in their Municipal Stormwater Permit. The Plan Approval Authority is defined as that department within a local government that has been delegated authority to approve stormwater site plans. Volume I—Minimum Technical Requirements—August 2012 2-26 • • Documenting BMP implementation and maintenance in the site log book(sites larger than I acre). . The CESCL or inspector must inspect all areas disturbed by construction activities,all BMPs,and all stormwater discharge points at least once every calendar week and within 24 hours of any discharge from the site. (For purposes of this condition,individual discharge events that last more than one day do not require daily inspections. For example,if a stormwater pond discharges continuously over the course of a week,only one inspection is required that week.)The CESCL or inspector may reduce the inspection frequency for temporary stabilized, inactive sites to once every calendar month. Element 13: Protect Low Impact Development BMPs . Protect all Bioretention and Rain Garden BMPs from sedimentation through installation and maintenance of erosion and sediment control BMPs on portions of the site that drain into the Bioretention and/or Rain Garden BMPs.Restore the BMPs to their fully functioning condition if they accumulate sediment during construction.Restoring the BMP must include removal of sediment and any sediment-laden Bioretention/rain garden soils, and replacing the removed soils with soils meeting the design specification. • Prevent compacting Bioretention and rain garden BMPs by excluding construction equipment and foot traffic.Protect completed lawn and landscaped areas from compaction due to construction equipment. . Control erosion and avoid introducing sediment from surrounding land uses onto permeable pavements.Do not allow muddy construction equipment on the base material or pavement.Do not allow sediment-laden runoff onto permeable pavements or base materials. . Pavement fouled with sediments or no longer passing an initial infiltration test must be cleaned using procedures in accordance with this manual or the manufacturer's procedures. • Keep all heavy equipment off existing soils under LID facilities that have been excavated to final grade to retain the infiltration rate of the soils. Volume 1—Minimum Technical Requirements—August 2012 2-25 Element 12: Manage The Project • Phase development projects to the maximum degree practicable and take into account seasonal work limitations. • Inspection and monitoring-Inspect,maintain and repair all BMPs as needed to assure continued performance of their intended function.Projects regulated under the Construction Stormwater General Permit must conduct site inspections and monitoring in accordance with Special Condition S4 of the Construction Stormwater General Permit. • Maintaining an updated construction SWPPP-Maintain,update, and implement the SWPPP. • Projects that disturb one or more acres must have site inspections conducted by a Certified Erosion and Sediment Control Lead (CESCL).Project sites disturbing less than one acre may have a CESCL or a person without CESCL certification conduct inspections.By the initiation of construction,the SWPPP must identify the CESCL or inspector,who must be present on-site or on-call at all times. • The CESCL or inspector(project sites less than one acre)must have the skills to assess the: • Site conditions and construction activities that could impact the quality of stormwater. • Effectiveness of erosion and sediment control measures used to control the quality of stormwater discharges. • The CESCL or inspector must examine stormwater visually for the presence of suspended sediment,turbidity,discoloration,and oil sheen.They must evaluate the effectiveness of BMPs and determine if it is necessary to install,maintain,or repair BMPs to improve the quality of stormwater discharges. Based on the results of the inspection,construction site operators must correct the problems identified by: • Reviewing the SWPPP for compliance with the 13 construction SWPPP elements and making appropriate revisions within 7 days of the inspection. • Immediately beginning the process of fully implementing and maintaining appropriate source control and/or treatment BMPs as soon as possible,addressing the problems not later than within 10 days of the inspection.If installation of necessary treatment BMPs is not feasible within 10 days, the construction site operator may request an extension within the initial 10-day response period. Volume 1-Minimum Technical Requirements-August 2012 2-24 • Obtain written approval from Ecology before using chemical treatment other than CO2 or dry ice to adjust pH. Element 10: Control De-Watering • Discharge foundation,vault,and trench de-watering water,which has similar characteristics to stormwater runoff at the site,into a controlled conveyance system before discharge to a sediment trap or sediment pond. • Discharge clean, non-turbid de-watering water,such as well-point ground water,to systems tributary to,or directly into surface waters of the State,as specified in Element#8,provided the de- watering flow does not cause erosion or flooding of receiving waters.Do not route clean dewatering water through stormwater sediment ponds.Note that"surface waters of the State" may exist on a construction site as well as off site; for example,a creek running through a site. • Handle highly turbid or otherwise contaminated dewatering water separately from stormwater. • Other treatment or disposal options may include: 1. Infiltration. 2. Transport off-site in a vehicle,such as a vacuum flush truck, for legal disposal in a manner that does not pollute state waters. 3. Ecology-approved on-site chemical treatment or other suitable treatment technologies. 4. Sanitary or combined sewer discharge with local sewer district approval,if there is no other option. 5. Use of a sedimentation bag with outfall to a ditch or swale for small volumes of localized dewatering. Element 11: Maintain BMPs . Maintain and repair all temporary and permanent erosion and sediment control BMPs as needed to assure continued performance of their intended function in accordance with BMP specifications. ▪ Remove all temporary erosion and sediment control BMPs within 30 days after achieving final site stabilization or after the temporary BMPs are no longer needed. Volume I—Minimum Technical Requirements—August 2012 2-23 4110 S Element 9: Control Pollutants • Design, install,implement and maintain effective pollution prevention measures to minimize the discharge of pollutants. • Handle and dispose of all pollutants,including waste materials and demolition debris that occur on-site in a manner that does not cause contamination of stormwater. • Provide cover,containment,and protection from vandalism for all chemicals, liquid products, petroleum products,and other materials that have the potential to pose a threat to human health or the environment. On-site fueling tanks must include secondary containment. Secondary containment means placing tanks or containers within an impervious structure capable of containing 110% of the volume contained in the largest take within the containment structure. Double-walled tanks do not require additional secondary containment. • Conduct maintenance,fueling, and repair of heavy equipment and vehicles using spill prevention and control measures. Clean contaminated surfaces immediately following any spill incident. • Discharge wheel wash or tire bath wastewater to a separate on-site treatment system that prevents discharge to surface water,such as closed-loop recirculation or upland application,or to the sanitary sewer,with local sewer district approval. • Apply fertilizers and pesticides in a manner and at application rates that will not result in loss of chemical to stormwater runoff. Follow manufacturers' label requirements for application rates and procedures. • Use BMPs to prevent contamination of stormwater runoff by pH modifying sources.The sources for this contamination include,but are not limited to: bulk cement,cement kiln dust,fly ash,new concrete washing and curing waters,waste streams generated from concrete grinding and sawing,exposed aggregate processes, dewatering concrete vaults,concrete pumping and mixer washout waters. • Adjust the pH of stormwater if necessary to prevent violations of water quality standards. • Assure that washout of concrete trucks is performed off-site or in designated concrete washout areas only. Do not wash out concrete trucks onto the ground,or into storm drains,open ditches,streets, or streams. Do not dump excess concrete on-site,except in designated concrete washout areas. Concrete spillage or concrete discharge to surface waters of the State is prohibited. Volume 1—Minimum Technical Requirements—August 2012 2-22 I 41, storm for the developed condition.Alternatively,the 10-year and 1-hour flow rate predicted by an approved continuous runoff model, increased by a factor of 1.6,may be used.The hydrologic analysis must use the existing land cover condition for predicting flow rates from tributary areas outside the project limits.For tributary areas on the project site,the analysis must use the temporary or permanent project land cover condition,whichever will produce the highest flow rates. If using the Western Washington Hydrology Model(WWHM) to predict flows,bare soil areas should be modeled as "landscaped" area. . Place excavated material on the uphill side of trenches,consistent with safety and space considerations. • Place check dams at regular intervals within constructed channels that are cut down a slope. Element 7: Protect Drain Inlets • Protect all storm drain inlets made operable during construction so that stormwater runoff shall not enter the conveyance system without first being filtered or treated to remove sediment. . Clean or remove and replace inlet protection devices when sediment has filled one-third of the available storage(unless a different standard is specified by the product manufacturer). Element 8: Stabilize Channels and Outlets • Design,construct,and stabilize all on-site conveyance channels to prevent erosion from the following expected peak flows: • Channels must handle the peak 10-minute velocity of flow from a Type 1A, 10-year,24-hour frequency storm for the developed condition.Alternatively,the 10-year, 1-hour flow rate indicated by an approved continuous runoff model, increased by a factor of 1.6,may be used.The hydrologic analysis must use the existing land cover condition for predicting flow rates from tributary areas outside the project limits.For tributary areas on the project site,the analysis must use the temporary or permanent project land cover condition, whichever will produce the highest flow rates.If using the Western Washington Hydrology Model (WWHM)to predict flows,bare soil areas should be modeled as "landscaped area. • Provide stabilization,including armoring material,adequate to prevent erosion of outlets, adjacent stream banks,slopes and downstream reaches at the outlets of all conveyance systems. Volume 1—Minimum Technical Requirements—August 2012 2-21 • S Element 5: Stabilize Soils • Stabilize exposed and unworked soils by application of effective BMPs that prevent erosion. Applicable BMPs include, but are not limited to: temporary and permanent seeding,sodding, mulching, plastic covering,erosion control fabrics and matting,soil application of polyacrylamide (PAM),the early application of gravel base early on areas to be paved,and dust control. • Control stormwater volume and velocity within the site to minimize soil erosion. • Control stormwater discharges, including both peak flow rates and total stormwater volume,to minimize erosion at outlets and to minimize downstream channel and stream bank erosion. • Soils must not remain exposed and unworked for more than the time periods set forth below to prevent erosion: • During the dry season (May 1 -Sept.30): 7 days • During the wet season (October 1 -April 30): 2 days • Stabilize soils at the end of the shift before a holiday or weekend if needed based on the weather forecast. • Stabilize soil stockpiles from erosion,protected with sediment trapping measures,and where possible, be located away from storm drain inlets,waterways and drainage channels. • Minimize the amount of soil exposed during construction activity. • Minimize the disturbance of steep slopes. • Minimize soil compaction and, unless infeasible, preserve topsoil. Element 6: Protect Slopes • Design and construct cut-and-fill slopes in a manner to minimize erosion.Applicable practices include, but are not limited to, reducing continuous length of slope with terracing and diversions, reducing slope steepness, and roughening slope surfaces(for example,track walking). • Divert off-site stormwater(run-on) or ground water away from slopes and disturbed areas with interceptor dikes,pipes and/or males. Off-site stormwater should be managed separately from stormwater generated on the site. • At the top of slopes,collect drainage in pipe slope drains or protected channels to prevent erosion. • Temporary pipe slope drains must handle the peak 10-minute velocity of flow from a Type 1A, 10-year,24-hour frequency Volume I—Minimum Technical Requirements—August 2012 2-20 • . Control street wash wastewater by pumping back on-site, or otherwise prevent it from discharging into systems tributary to waters of the State. Element 3: Control Flow Rates Protect properties and waterways downstream of development sites from erosion and the associated discharge of turbid waters due to increases in the velocity and peak volumetric flow rate of stormwater runoff from the project site. . Where necessary to comply with the bullet above,construct stormwater retention or detention facilities as one of the first steps in grading.Assure that detention facilities function properly before constructing site improvements(e.g. impervious surfaces). • If permanent infiltration ponds are used for flow control during construction,protect these facilities from siltation during the construction phase. Element 4: Install Sediment Controls • Design,install,and maintain effective erosion controls and sediment controls to minimize the discharge of pollutants. . Construct sediment control BMPs(sediment ponds,traps,filters, etc.)as one of the first steps in grading.These BMPs shall be functional before other land disturbing activities take place. • Minimize sediment discharges from the site.The design, installation and maintenance of erosion and sediment controls must address factors such as the amount,frequency, intensity and duration of precipitation,the nature of resulting stormwater runoff,and soil characteristics,including the range of soil particle sizes expected to be present on the site. • Direct stormwater runoff from disturbed areas through a sediment pond or other appropriate sediment removal BMP, before the runoff leaves a construction site or before discharge to an infiltration facility.Runoff from fully stabilized areas may be discharged without a sediment removal BMP,but must meet the flow control performance standard in Element#3,bullet#1. • Locate BMPs intended to trap sediment on-site in a manner to avoid interference with the movement of juvenile salmonids attempting to enter off-channel areas or drainages. ▪ Where feasible,design outlet structures that withdraw impounded stormwater from the surface to avoid discharging sediment that is still suspended lower in the water column. Volume 1-Minimum Technical Requirements-August 2012 2-19 • 2. Limitations on activities and the extent of disturbed areas. 3. Proposed erosion and sediment control measures. The following activities are exempt from the seasonal clearing and grading limitations: 1. Routine maintenance and necessary repair of erosion and sediment control BMPs. 2. Routine maintenance of public facilities or existing utility structures that do not expose the soil or result in the removal of the vegetative cover to soil. 3. Activities where there is one hundred percent infiltration of surface water runoff within the site in approved and installed erosion and sediment control facilities. Project Requirements -Construction SWPPP Elements Element 1: Preserve Vegetation/Mark Clearing Limits • Before beginning land disturbing activities, including clearing and grading,clearly mark all clearing limits,sensitive areas and their buffers,and trees that are to be preserved within the construction area. • Retain the duff layer, native top soil, and natural vegetation in an undisturbed state to the maximum degree practicable. Element 2: Establish Construction Access • Limit construction vehicle access and exit to one route, if possible. • Stabilize access points with a pad of quarry spalls, crushed rock, or other equivalent BMPs,to minimize tracking of sediment onto public roads. • Locate wheel wash or tire baths on site, if the stabilized construction entrance is not effective in preventing tracking sediment onto roads. • If sediment is tracked off site,clean the affected roadway thoroughly at the end of each day,or more frequently as necessary (for example,during wet weather).Remove sediment from roads by shoveling,sweeping,or pick up and transport the sediment to a controlled sediment disposal area. • Conduct street washing only after sediment is removed in accordance with the above bullet. Volume I—Minimum Technical Requirements—August 2012 2-18 • 2.5.2 Minimum Requirement#2: Construction Stormwater Pollution Prevention (SVVPP) Thresholds All new development and redevelopment projects are responsible for preventing erosion and discharge of sediment and other pollutants into receiving waters. Projects which result in 2,000 square feet or more of new plus replaced hard surface area,or which disturb 7,000 square feet or more of land must prepare a Construction SWPP Plan(SWPPP) as part of the Stormwater Site Plan (see Section 2.5.1). Projects that result in less than 2,000 square feet of new plus replaced hard surface area,or disturb less than 7,000 square feet of land are not required to prepare a Construction SWPPP,but must consider all of the 13 Elements of Construction Stormwater Pollution Prevention and develop controls for all elements that pertain to the project site. General Requirements The SWPPP shall include a narrative and drawings.All BMPs shall be clearly referenced in the narrative and marked on the drawings. The SWPPP narrative shall include documentation to explain and justify the pollution prevention decisions made for the project.Each of the 13 elements must be considered and included in the Construction SWPPP unless site conditions render the element unnecessary and the exemption from that element is clearly justified in the narrative of the SWPPP. Clearing and grading activities for developments shall be permitted only if conducted pursuant to an approved site development plan (e.g., subdivision approval)that establishes permitted areas of clearing, grading,cutting,and filling.These permitted clearing and grading areas and any other areas required to preserve critical or sensitive areas,buffers,native growth protection easements,or tree retention areas shall be delineated on the site plans and the development site. The SWPPP shall be implemented beginning with initial land disturbance and until final stabilization.Sediment and Erosion control BMPs shall be consistent with the BMPs contained in chapters 3 and 4 of Volume II. Seasonal Work Limitations-From October 1 through April 30, clearing,grading,and other soil disturbing activities shall only be permitted if shown to the satisfaction of the local permitting authority that silt-laden runoff will be prevented from leaving the site through a combination of the following: 1. Site conditions including existing vegetative coverage,slope, soil type and proximity to receiving waters. Volume I—Minimum Technical Requirements—August 2012 2-17 S • thresholds. Local governments should be prepared to demonstrate that by comparing the number and types of historical projects that would have been regulated using the Ecology thresholds versus the local government's thresholds. Local governments are allowed to institute a stop-loss provision on the application of stormwater requirements to replaced hard surfaces.A stop- loss provision is an upper limit on the extent to which a requirement is applied. For instance,there could be a maximum percentage of the estimated total project costs that are dedicated to meeting stormwater requirements. A project would not have to incur additional stormwater costs above that maximum though the standard redevelopment requirements will not be fully achieved. The allowance for a stop-loss provision pertains to the extent that treatment,flow control and wetlands protection requirements are imposed on replaced hard surfaces.It does not 'apply to meeting stormwater requirements for new hard surfaces. Local governments can also establish criteria for allowing redevelopment projects to pay a fee in lieu of constructing water quality or flow control facilities on a redeveloped site. At a minimum,the fee should be the equivalent\of an engineering estimate of the cost of meeting all applicable stormwater\requirements for the project. The local government should use such funds for the implementation of stormwater control projects that would have similar benefits to the same receiving water as if the project had constructed its required improvements. Expenditure of such funds is subject to other state statutory requirements. Ecology cautions local governments about the potential long-term consequences of allowing a fee-in-lieu of stormwater facilities.Sites that are allowed to pay a fee continue without stormwater controls. If it is determined,through future basin planning for instance,that controls on such sites are necessary to achieve water quality goals or legal requirements,the public may bear the costs for providing those controls. Underground utility projects that replac \the ground surface with in-kind material or materials with similar runoff characteristics should not be subject to redevelopment requirements except construction site erosion control. \, Local governments are also encouraged to review all road projects for changes in elevations or drainage flowpath that could cause flooding, upland or stream erosion, or changes to discharges to wetlands. For example,adding curbs will result in redirecting flows and possibly causing new downstream impacts. The local government should set project- specific requirements to avoid or mitigate those impacts. Volume I—Minimum Technical Requirements—August 2012 2-15 • • 2.5 Minimum Requirements This section describes the minimum requirements for stormwater management at development and redevelopment sites. Section 2.4 should be consulted to determine which requirements apply to any given project. Figures 2.4.1 and 2.4.2 should be consulted to determine whether the minimum requirements apply to new surfaces,replaced surfaces,or new and replaced surfaces. Volumes II through V of this manual present Best Management Practices(BMPs)for use in meeting the Minimum Requirements. Throughout this chapter,requirements are written in bold and supplemental guidelines that serve as advice and other materials are not in bold. 2.5.1 Minimum Requirement#1: Preparation of Stormwater Site Plans All projects meeting the thresholds in Section 2.4 shall prepare a Stormwater Site Plan for local government review. Stormwater Site Plans shall use site-appropriate development principles,as required and encouraged by local development codes,to retain native vegetation and minimize impervious surfaces to the extent feasible. Stormwater Site Plans shall be prepared in accordance with pter 3 of this volume. Objective The 2,000 square feet threshold for hard surfaces and 7,000 square foot threshold for land disturbance are chosen to capture most single family home construction and their equivalent.Note that the scope of the stormwater site plan only covers compliance with Minimum Requirements #2 through#5 if the thresholds of 5,000 square feet of hard surface or conversion of/,acre of vegetation to lawn or landscape,or conversion of 2.5 acres of vegetation to pasture are not exceeded. Supplemental guidelines Projects proposed by departments and agencies within the local government with jurisdiction must comply with this requirement. The local government shall determine the process for ensuring proper project review,inspection,and compliance by its own depaitinents and agencies. Volume I—Minimum Technical Requirements—August 2012 2-16 • • as causing harm, harassing, or damaging habitat for the listed species). In addition, the National Marine Fisheries Service can levy penalties. Portions of Jefferson County, including marine waters, are included as "critical habitat"for a listed species. Development of property along any marine shoreline, freshwater shoreline, or floodplains could harm habitat if protective measures are not taken. To minimize the potential to damage habitat, all property owners developing adjacent to marine shoreline, freshwater shoreline, or floodplains are advised to do the following: All development activities should avoid unstable slopes, wetlands, and forested areas near surface waters Remove minimal vegetation for site development, especially large trees Allow trees that have fallen into surface waters to remain there Infiltrate stormwater from buildings and driveways onsite through drywells rather than discharging directly into surface waters or roadside ditches The Federal Bald and Golden Eagle Protection Act requires landowners within 660 feet (1/8th of a mile) of an eagle nest to consult with the US Fish and Wildlife Service. This Eagle Act prohibits anyone from "taking" bald eagles. This federal law defines the term "take" and describes the possible legal consequences when a "take" occurs. Among other actions, "take" includes a disturbance of bald eagles or their habitat. Under federal law a permit may still be required for activities that impact bald eagles or their habitat. Contact the US Fish and Wildlife Service (http://www.fws.gov/pacific/eagle/)to learn more about how this law affects your project. Any individual, group, or agency can bring suit for a listed species "taking", even if you are in compliance with Jefferson County development codes. The risk of a lawsuit against you can be reduced by consulting with a professional fisheries habitat biologist, and following the recommendations for site development provided by the biologist. For more information, contact the National Marine Fisheries Service in Seattle, or the U.S. Fish and Wildlife Service. 2013-09-06_SFR_StdConditions 9/6/2013 2 • Standard Conditions for Residential Development in Jefferson County 1. LIGHTING: Lighting fixtures shall be designed and hooded to prevent the light source from being directly visible from outside the boundaries of the property. The intensity or brightness of all lighting, during construction and after project completion shall not adversely affect the use of surrounding properties or adjoining rights-of-way. Exterior lighting for residential uses shall not exceed twenty feet(20') in height from the finished grade, excepting when such lighting is an integral part of a building or structure. Ground level lighting is encouraged. 2. BUILDING HEIGHT: The building height is not to exceed 35 feet. 3. OUTDOOR STORAGE: Outdoor residential storage shall be maintained in an orderly manner and shall create no fire, safety, health or sanitary hazard. 4. UNLICENSED VEHICLES: Not more than 2 unlicensed vehicles shall be stored on any lot unless totally screened from view of neighboring dwellings and rights-of-way. Such screening shall meet all applicable performance and development standards specific to the district in which the storage is kept, and shall be in keeping with the character of the area. Screening shall meet the requirements of Chapter 18.30 JCC. Outdoor storage of 3 or more junk motor vehicles is prohibited except in those districts where specified as an automobile wrecking yard or junk (or salvage) yard and allowed as a permitted use in Table 3-1 or Chapter 18.18 JCC, and such storage shall meet the requirements of JCC 18.20.100, Automobile wrecking yards and junk (or salvage) yards. In no case, shall any such junk motor vehicles be stored in a critical area. 5. PARKING: A minimum of two (2) on-site parking spaces shall be provided for the single family residence. 6. This permit has been reviewed consistent with JCC 18.40.130 & 140. Notice: this permit does not excuse the applicant from complying with other local, state and federal ordinances, regulations or statues, applicable to the proposed development, but consistent with RCW 90.58. Future development beyond that specified in this permit shall require further review. 7. BMPs: The project shall adhere to the Best Management Practices (BMPs)to control stormwater, erosion and sediment during construction. BMPs shall address permanent measures to stabilize soil exposed during construction, and in the design and operation of stormwater and drainage control systems. 8. NOTICE: This permit does not excuse the proponent from complying with other local, state, and federal ordinances, regulations, or statutes applicable to the proposed development, but consistent with RCW 90.58. Development pursuant to this permit shall be undertaken subject to the applicable policies and performance standards of the Jefferson County Shoreline Management Master Program and the Jefferson County Unified Development Code. If during excavation or development of the site an area of potential archaeological significance is uncovered, all activity in the immediate area shall be halted, and the Administrator shall be notified at once. The Federal Endangered Species Act rules to protect threatened Chinook and Summer-run Chum salmon became effective on January 8, 2001. Bull trout have been listed as threatened since early 2000. Under the ESA, any person may bring lawsuit against any individual or agency that "takes" listed species (defined 1 2013-03-07 SFR StdConditions 3/7/2013