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HomeMy WebLinkAboutBLD2021-00238 - 05 Stormwater or Approved StormwaterWorksheet A1 Medium & Large Project Report structures roads Complete the following: X X New Garage/Shop withStudioBuild - 720 sq.ft of driveway is existing- Power, water to be installed with this permit- N/A SEP2021-00029 N/A N/A Project does include a retaining wall to be built 8ft x 29 ft long X Apr 13 2021 BLD2021-00238 May 18 2021 Worksheet A1 Medium & Large Project Report X X DRYWELL to be installed for new garage, shop with studio on 2nd floor Apr 13 2021 BLD2021-00238 Worksheet A1 Medium & Large Project Report Engineering X Apr 13 2021 BLD2021-00238 Worksheet A1 Medium & Large Project Report LIST #1 LIST #1 LIST #3 X Apr 13 2021 x BLD2021-00238 Worksheet Al Medium & Large Project Report JEFFERSON COUNTY OCD Minimum Requirement# 5 : On-site Stormwater Management (continued) LIST# 1 : Applicable to projects that directly or indirectly drain to freshwater. For each category below, proceed through the LIST from top down. Use WORKSHEET C to determine if the BMP can be used. If number 1 on the list is not possible, document why on WORKSHEET C and move down to number 2, and so on. INSTRUCTIONS: Check the first option that will work for Each Category Below: Category A: Lawn and Landscape Areas 1 D My project does not have disturbed soils not covered by impervious surfaces. D 1. Post-Construction Soil Quality and Depth Disturbed soils shall be amended (BMP TS.13: ). Category B: Roofs □ □ □ Q My project does not have Roof areas. 1.Full Dispersion (BMP TS.30) OR Downspout Full Infiltration (BMP TS.lOA) 2. Rain Garden (LARGE PROJECTS CANNOT USE) (BMP TS.14A) 3. Downspout Dispersion System (BMP TS.lOB) D 4. Perforated Stub-Out Connection (BMP TS.10) □5. Each BMP above is infeasible, see WORKSHEET C. STOP. COMPLETE AND SUBMIT WORKSHEET Bl. NO OTHER INFORMATION REQUIRED AT THIS TIME. Category C: Other Hard Surfaces, e.g. gravel and paved driveways, solid decks and patios without infiltration below D My project does not have Other Hard Surface areas □1. Full dispersion (BMP TS.30) □2. Permeable Pavement (BMP TS.15) OR Rain Garden (LARGE PROJECTS CANNOT USE) (BMP TS.14A) � 3. Sheet Flow Dispersion (BMP TS.12) OR Concentrated Flow Dispersion (BMP TS.11) □4. Each item above is infeasible, see WORKSHEET C. STOP. COMPLETE AND SUBMIT WORKSHEET Bl. NO OTHER INFORMATION REQUIRED AT THIS TIME. x BLD2021-00238 stormwater calc worksheet QR code REV. 5/31/2019 page 1 of 2 DEPARTMENT OF COMMUNITY DEVELOPMENT 621 Sheridan Street, Port Townsend, WA 98368 Tel: 360.379.4450 | Fax: 360.379.4451 Web: www.co.jefferson.wa.us/communitydevelopment E-mail: dcd@co.jefferson.wa.us STORMWATER CALCULATION WORKSHEET PARCEL # PROJECT/APPLICANT NAME: DETERMINING STORMWATER MANAGEMENT REQUIREMENTS: This stormwater calculation worksheet should be completed first to quired 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. 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 of plant species, other than noxious weeds, 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 ¾ 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 No Well, utilities, etc. ___________________________ sq/ft Does the project convert 2 ½ acres or more of native vegetation to pasture? Driveway, parking, roads, etc. ___________________sq/ft Circle: Yes No Lawn, landscaping, etc. ______________________ sq/ft Other compacted surface, etc. _________________ sq/ft Indicate Total Volumes of Proposed: Includes BMP T5.13 Fill Volume) Temporary construction area ______________ sq/ft Total Land Disturbance ____________________ sq/ft Cut __________ Fill __________ (cu/yd) PARCEL SIZE (I.E., SITE) Size of parcel _________ acres An acre contains 43,560 square feet. Multiply the acreage by this figure. Size of parcel in square feet _________________ sq/ft Scan the QR code to access the digital form Irick 34 14917 2021 2520 232 4773 255 80 Apr 13 2021 BLD2021-00238 stormwater calc worksheet QR code REV. 5/31/2019 page 2 of 2 Applicants for small Construction Stormwater Pollution Prevention. Please submit the Small Project Certification (Worksheet s). 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 (SWPPP) Best Management Practices (BMPs) Fact Sheet . Applicants for medium those that must meet only Minimum Requirements #1 through #5 must submit Worksheet A1 and B1, a stormwater site plan and a construction stormwater pollution prevention site plan (See Reference A1A and B1A for guidance).). Large those that must meet all 9 Minimum Requirements must submit Worksheet A1 and B1, a stormwater site plan and a construction stormwater pollution prevention site plan (See Reference A1A and B1A for guidance). Large projects also may require engineering. See Worksheet L to determine additional large project requirements. APPLICANT SIGNATURE By signing the Stormwater Calculation Worksheet, I as the applicant/owner attest that the information provided herein is true and correct to the best of my knowledge. I also certify that this application is being made with the full knowledge and consent of all owners of the affected property. LANDOWNER OR AUTHORIZED REPRESENTATIVE SIGNATURE) (DATE) STORMWATER CALCULATIONS IMPERVIOUS SURFACE Impervious surface is a hard surface that either prevents or slows the entry of water into the soil 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. NEW EXISTING Structures (all roof area) _________________sq/ft Structures (all roof area) _________________sq/ft Sidewalks _________________sq/ft Sidewalks _________________sq/ft Patios _________________sq/ft Patios _________________sq/ft Solid Decks _________________sq/ft Solid Decks _________________sq/ft without infiltration below) (without infiltration below) Driveway, parking, roads, etc _______________sq/ft Driveway, parking, roads, etc _______________sq/ft Other _________________sq/ft Other _________________sq/ft Total New _________________sq/ft Total Existing _________________sq/ft TOTAL NEW + TOTAL EXISTING* _________________sq/ft *This amount will be used to check total lot coverage. 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 existing impervious surface? The proposal is considered new development. Answer questions in Figure 2.4.1 Flow Chart for New Development to determine project size (next page). The proposal is considered redevelopment Answer questions in Figure 2.4.2. Flow Chart for Redevelopment to determine project size (next page). yes no 1924 140 2520 232 4816 720 720 5 5536 Apr 13 2021 BLD2021-00238 Worksheet B1 Choose any of the following that apply: Choose one of the following: X Apr 13 2021 BLD2021-00238 Worksheet B1 This element does not apply to my project because (check any that apply): Select one of the two statements applicable to the project. Select one of the three statements applicable to the project. This element does not apply to my project because: X X X X Apr 13 2021 BLD2021-00238 Worksheet B1 Select one of the two statements applicable to the project. Select one of the three statements applicable to the project. x X Apr 13 2021 BLD2021-00238 Worksheet B1 Select one of the three statements applicable to the project. This element does not apply to my project because (circle any that apply - X X X X x X Apr 13 2021 Worksheet B1 Select one of the two statements applicable to the project. Describe the steps you will take: X X Apr 13 2021 BLD2021-00238 Worksheet B1 X Apr 13 2021 1 Worksheet C What’s the best option for your site? Roofs BMP and Applicable Lists Reason why the BMP will not work on site. Additional Comments If needed Lawn and Landscaped Areas BMP and Applicable Lists Reason why the BMP will not work on site. Additional Comments If needed Minimum Requirement #5 (On-Site Stormwater Management) The following tables summarize the criteria that can be used to justify why you cannot use various stormwater management best management practices (BMPs) for consideration for Minimum Requirement #5. This information is also included under the detailed descriptions of each BMP in the Department of Ecology’s Stormwater Management Manual for Western Washington (SWMMWW [2014]). Where any inconsistencies or lack of clarity exists, the requirements in the main text of the SWMMWW shall be applied. HOW TO USE: Evaluate the feasibility of the BMPs in priority order based on Worksheet A1 page 5 (List #1) or 6 (List #3) or Worksheet L for Large Projects (List #2). Only one criterion needs to be selected for a BMP before evaluating the next BMP on the list. Full Dispersion BMP T5.30, SWMMWW Volume V, Section 5.3 A 65 to 10 ratio of forested or native vegetation area to impervious area cannot be achieved. surface) and protected by easement cannot be achieved. Siting and design criteria cannot be achieved on site. There is an alternatie septic system on this lot or an adjacent treatment unit). Therefore, there is not at least 3 feet or seasonal high groundwater table or other impermeable layer. There is not at least 1 foot or more of permeable soil from high groundwater table or other impermeable layer. Downspout Full BMP T5.10A, SWMMWW Volume III, Section 3.1.1 Post-construction Soil Quality and Depth BMP T5.13 SWMMWW Volume V, Section 5.3) Lawn and landscape area is on till slopes greater than 33 percent. Siting and design criteria cannot be achieved on site. List #1, #2 and #3 List #1 and #2 List #1, #2 and #3 None of the above boxes are checked. This is the BMP that must be used for lawn and landscaped areas. On Worksheet A1, indicate that this will be the BMP used. CONTINUE to complete the form for other surface types applicable to the project. If none, STOP. None of the above boxes are checked. This is the BMP that must be used for roofs. On Worksheet A1, indicate that this will be the BMP used. CONTINUE to complete the form for other surface types applicable to the project. If none, STOP. X X Apr 13 2021 2 Worksheet C What’s the best option for your site? Roofs (cont.) BMP and Applicable Lists Reason why the BMP will not work on site.Additional Comments If needed Where professional geotechnical evaluation recommends Within an area whose ground water drains into an erosion hazard, or landslide hazard area. Where the only area available for siting would threaten the Where the only area available for siting does not allow for private storm sewer system. Where there is a lack of usable space for bioretention areas Note: Criteria with setback distances are as measured from the bottom edge of the bioretention soil mix. Citation of any of the following infeasibility criteria must be recommendation from an appropriate licensed professional (e.g., engineer, geologist, hydrogeologist): such as bulkheads. basements. Bioretention or Rain Gardens BMP T7.30 or T5.14A SWMMWW Volume V, Section 7.4 List #1 (both) and List #2 bioretention only) Downspout Full cont.) BMP T5.10A, SWMMWW Volume Slopes steeper than 25% or less than 200’ from slope steeper than 40%. Siting and design criteria cannot be achieved on site. None of the above boxes are checked. This is the BMP that must be used for roofs. On Worksheet A1, indicate that this will be the BMP used. CONTINUE to complete the form for other surface types applicable to the project. If none, STOP. X Apr 13 2021 3 Worksheet C What’s the best option for your site? Roofs (cont.) BMP and Applicable Lists Reason why the BMP will not work on site.Additional Comments If needed Bioretention or Rain Gardens cont.) BMP T7.30 or T5.14A SWMMWW Volume V, Section 7.4 Where land for bioretention is within an erosion hazard, or Where the site cannot be reasonably designed to locate bioretention areas on slopes less than 8 percent. Within 50 feet from the top of slopes that are greater than 20 percent and over 10 feet of vertical relief. For properties with known soil or groundwater contamination typically federal Superfund sites or state cleanup sites under the Model Toxics Control Act [MTCA]): Within 100 feet of an area known to have deep soil contamination. will likely increase or change the direction of the migration of pollutants in the groundwater. Wherever surface soils have been found to be contaminated unless those soils are removed within Within 10 feet of an underground storage tank and connecting underground pipes when the capacity of the tank and pipe system is 1,100 gallons or less. As used in these criteria, an underground storage tank means any tank used to store petroleum products, chemicals, or liquid hazardous wastes of which 10 percent or more of the storage volume including volume in the connecting piping system) is beneath the ground surface. Within 100 feet of an underground storage tank and connecting underground pipes when the capacity of the tank and pipe system is greater than 1,100 gallons. The following criteria can be cited as reasons for infeasibility services to make the observation): Within setback provided for BMP T7.30 (SWMMWW Volume V, Section 7.4) Where they are not compatible with surrounding drainage system as determined by the county (e.g., project drains to an existing stormwater collection system whose elevation or location precludes connection to a properly functioning bioretention area). Apr 13 2021 BLD2021-00238 4 Worksheet C What’s the best option for your site? Roofs (cont.) BMP and Applicable Lists Reason why the BMP will not work on site.Additional Comments If needed garden sites have a measured (a.k.a., initial) native soil saturated hydraulic conductivity less than 0.30 inches per SWMMWW Volume III, Section 3.3.6 (or an alternative be used to demonstrate infeasibility of bioretention areas. to be evaluated as an option in List #1 or List #2. In these slow draining soils, a bioretention area with an underdrain underdrain is elevated within a base course of gravel, it will achieve Minimum Requirement #7. Where the minimum vertical separation of 3 feet to the seasonal high groundwater elevation or other impermeable layer would not be achieved below bioretention that would serve a drainage area that exceeds the following thresholds and cannot reasonably be broken down into amounts smaller than indicated): o 10,000 square feet of impervious area o 0.75 acres of lawn and landscape. Any area where these facilities are prohibited by an approved cleanup plan under the state MTCA or Federal Superfund Law, or an environmental covenant under Chapter 64.70 RCW. Within 100 feet of a drinking water well, or a spring used for drinking water supply. Bioretention or Rain Gardens cont.) Where the minimum vertical separation of 1 foot to the seasonal high groundwater or other impermeable layer would not be achieved below bioretention that would serve a drainage area less than the above thresholds Apr132021 Apr 13 2021 BLD2021-00238 5 Worksheet C What’s the best option for your site? Roofs (cont.) BMP and Applicable Lists Reason why the BMP will not work on site.Additional Comments If needed Perforated Stub-Out Connections BMP T5.10C SWMMWW Volume III, Section 3.1.3 For sites with septic systems, the only location available for permeability, distance between systems, etc.) indicate that this is unnecessary. device on this or an adjacent lot. Therefore, there is not at highest estimated groundwater table or other impermeable layer. connection is under impervious or heavily compacted soils. The only location available is on or above slopes greater than 20% Siting and design criteria cannot be achieved on site. length from the downspout to the downstream property line, structure, stream, wetland, slope over 15 percent, or other impervious surface is not feasible. between the outlet of the trench and any property line, structure, stream, wetland, or impervious surface is not outlet of the trench and any slope steeper than 15 percent is not feasible. Siting and design criteria cannot be achieved on site. Downspout Dispersion Systems BMP T5.10B SWMMWW Volume III, Section 3.1.2 List #1, #2 and #3 List #1, #2 and #3 including reserve areas, and grey water reuse systems. For None of the above boxes are checked. This is the BMP that must be used for roofs. On Worksheet A1, indicate that this will be the BMP used. CONTINUE to complete the form for other surface types applicable to the project. If none, STOP. None of the above boxes are checked. This is the BMP that must be used for roofs. On Worksheet A1, indicate that this will be the BMP used. CONTINUE to complete the form for other surface types applicable to the project. If none, STOP. None of the above boxes are checked. This is the BMP that must be used for roofs. On Worksheet A1, indicate that this will be the BMP used. CONTINUE to complete the form for other surface types applicable to the project. If none, STOP. X X Apr 13 2021 6 Worksheet C What’s the best option for your site? Other Hard Surfaces BMP and Applicable Lists Reason why the BMP will not work on site.Additional Comments If needed Where professional geotechnical evaluation recommends Within an area whose ground water drains into an erosion hazard, or landslide hazard area. pavement area would compromise adjacent impervious pavements. area would threaten existing below grade basements. such as bulkheads. Down slope of steep, erosion prone areas that are likely to deliver sediment to the area of pervious pavement. saturated. Excessively steep slopes where water within the aggregate base layer or at the subgrade surface cannot be controlled by detention structures and may cause erosion and structural Citation of any of the following infeasibility criteria must be recommendation from an appropriate licensed professional (e.g., engineer, geologist, hydrogeologist): Permeable Pavement BMP T5.15, SWMMWW Volume V, Section 5.3 List #1 and #2 Full Dispersion BMP T5.30 SWMMWW Volume V, Section 5.3 A 65 to 10 ratio of forested or native vegetation area to impervious area cannot be achieved. surface) cannot be achieved. Siting and design criteria cannot be achieved on site. List #1 and #2 None of the above boxes are checked. This is the BMP that must be used for hard surfaces. On Worksheet A1, indicate that this will be the BMP used. CONTINUE to complete the form for other surface types applicable to the project. If none, STOP. Note that Raingardens may be used in lieu of permeable pavement if subject to List #1. X Apr 13 2021 BLD2021-00238 7 Worksheet C What’s the best option for your site? Other Hard Surfaces (cont.) BMP and Applicable Lists Reason why the BMP will not work on site.Additional Comments If needed Permeable Pavement cont.) BMP T5.15, SWMMWW Vol ume V, Section 5.3 Within an area designated as an erosion hazard, or landslide hazard. Within 50 feet from the top of slopes that are greater than 20 percent. For properties with known soil or groundwater contamination (typically federal Superfund sites or state cleanup sites under MTCA): Within 100 feet of an area known to have deep soil contamination. will likely increase or change the direction of the migration of pollutants in the groundwater. Wherever surface soils have been found to be contaminated unless those soils are removed Any area where these facilities are prohibited by an approved cleanup plan under the state MTCA or Federal Superfund Law, or an environmental covenant under Chapter 64.70 RCW. Within 100 feet of a drinking water well, or a spring used generating surface. The following criteria can be cited as reasons for infeasibility without make the observation): strength to support heavy loads at industrial facilities such as ports. Where installation of permeable pavement would threaten subgrades. Note that Raingardens may be used in lieu of permeable pavement if subject to List #1. Apr 13 2021 BLD2021-00238 8 Worksheet C What’s the best option for your site? including reserve areas, and grey water reuse systems. For Within 10 feet of any underground storage tank and connecting underground pipes, regardless of tank size. As used in these criteria, an underground storage tank means any tank used to store petroleum products, chemicals, or liquid hazardous wastes of which 10 percent or more of the storage volume (including volume in the connecting piping system) is beneath the ground surface. bridges. Where the site design cannot avoid putting pavement deposition after construction (e.g., construction and landscaping material yards). Where the site cannot reasonably be designed to have a porous asphalt surface at less than 5 percent slope, or a pervious concrete surface at less than 10 percent slope, or a permeable interlocking concrete pavement surface (where upper slope limit can range from 6 to 12 percent; check with manufacturer and local supplier. permeable pavement (e.g., road or parking lot) do not meet the soil suitability criteria for providing treatment. See soil suitability criteria for treatment in the SWMMWW Volume III, Section 3.3.7. Note: In these instances, the construction. loads when saturated. Soils meeting a California Bearing Ratio of 5 percent are considered suitable for residential access roads. Where replacing existing impervious surfaces unless the an outwash soil with a saturated hydraulic conductivity of 4 inches per hour or greater. Other Hard Surfaces (cont.) BMP and Applicable Lists Reason why the BMP will not work on site.Additional Comments If needed Permeable Pavement cont.) BMP T5.15, SWMMWW Volume V, Section 5.3 Note that Raingardens may be used in lieu of permeable pavement if subject to List #1. Apr132021 BLD2021-00238 9 Worksheet C What’s the best option for your site? measured (a.k.a., initial) subgrade soil saturated hydraulic SWMMWW Volume III, Section 3.3.6 (or an alternative small evaluate infeasibility of permeable pavement areas. (Note: In these instances, unless other infeasibility restrictions apply, roads and parking lots may be built with an underdrain, or less are very low volume roads (AASHTO 2001) (U.S. Department of Transportation, 2013). Areas with very low utility trucks (e.g., garbage, recycling), daily school bus use, trucks, and maintenance vehicles. Note: This infeasibility bearing surfaces associated with the collector or arterial. the SWMMWW Volume I). 122.26(b)(14). Where the risk of concentrated pollutant spills is more likely such as gas stations, truck stops, and industrial chemical storage sites. Where routine, heavy applications of sand occur in frequent snow zones to maintain traction during weeks of snow and ice accumulation. Where the seasonal high groundwater or an underlying conditions within 1 foot of the bottom of the lowest gravel base course. Other Hard Surfaces (cont.) BMP and Applicable Lists Reason why the BMP will not work on site.Additional Comments If needed Permeable Pavement cont.) BMP T5.15, SWMMWW Volume V, Section 5.3 None of the above boxes are checked. This is the BMP that must be used for hard surfaces. On Worksheet A1, indicate that this will be the BMP used. (List #1 may use Raingardens in lieu of Permeable Pavement). CONTINUE to complete the form for other surface types applicable to the project. If none, STOP. Note that Raingardens may be used in lieu of permeable pavement if subject to List #1. Apr 13 2021 BLD2021-00238 10 Worksheet C What’s the best option for your site? Other Hard Surfaces (cont.) BMP and Applicable Lists Reason why the BMP will not work on site.Additional Comments If needed Where professional geotechnical evaluation recommends Within an area whose ground water drains into an erosion hazard, or landslide hazard area. Where the only area available for siting would threaten the Where the only area available for siting does not allow for private storm sewer system. Where there is a lack of usable space for bioretention areas Note: Criteria with setback distances are as measured from the bottom edge of the bioretention soil mix. Citation of any of the following infeasibility criteria must be recommendation from an appropriate licensed professional (e.g., engineer, geologist, hydrogeologist): such as bulkheads. basements. The following criteria can be cited as reasons for infeasibility services to make the observation): Within setback provided for BMP T7.30 (SWMMWW Volume V, Section 7.4) Where they are not compatible with surrounding drainage system as determined by the county (e.g., project drains to an existing stormwater collection system whose elevation or location precludes connection to a properly functioning bioretention area). Bioretention or Rain Gardens BMP T7.30, SWMMWW Volume V, Section 7.4 List #1 (both) and List #2 bioretention only) Apr 13 2021 11 Worksheet C What’s the best option for your site? Other Hard Surfaces (cont.) BMP and Applicable Lists Reason why the BMP will not work on site.Additional Comments If needed Bioretention or Rain Gardens cont.) BMP T7.30, SWMMWW Volume V, Section 7.4 Where land for bioretention is within an erosion hazard, or Where the site cannot be reasonably designed to locate bioretention areas on slopes less than 8 percent. Within 50 feet from the top of slopes that are greater than 20 percent and over 10 feet of vertical relief. For properties with known soil or groundwater contamination typically federal Superfund sites or state cleanup sites under the Model Toxics Control Act [MTCA]): Within 100 feet of an area known to have deep soil contamination. will likely increase or change the direction of the migration of pollutants in the groundwater. Wherever surface soils have been found to be contaminated unless those soils are removed within Within 10 feet of an underground storage tank and connecting underground pipes when the capacity of the tank and pipe system is 1,100 gallons or less. As used in these criteria, an underground storage tank means any tank used to store petroleum products, chemicals, or liquid hazardous wastes of which 10 percent or more of the storage volume including volume in the connecting piping system) is beneath the ground surface. Within 100 feet of an underground storage tank and connecting underground pipes when the capacity of the tank and pipe system is greater than 1,100 gallons. Where the minimum vertical separation of 1 foot to the seasonal high groundwater or other impermeable layer would not be achieved below bioretention that would serve a drainage area less than the above thresholds Apr 13 2021 BLD2021-00238 12 Worksheet C What’s the best option for your site? Other Hard Surfaces (cont.) BMP and Applicable Lists Reason why the BMP will not work on site.Additional Comments If needed garden sites have a measured (a.k.a., initial) native soil saturated hydraulic conductivity less than 0.30 inches per SWMMWW Volume III, Section 3.3.6 (or an alternative be used to demonstrate infeasibility of bioretention areas. to be evaluated as an option in List #1 or List #2. In these slow draining soils, a bioretention area with an underdrain underdrain is elevated within a base course of gravel, it will achieve Minimum Requirement #7. Where the minimum vertical separation of 3 feet to the seasonal high groundwater elevation or other impermeable layer would not be achieved below bioretention that would serve a drainage area that exceeds the following thresholds and cannot reasonably be broken down into amounts smaller than indicated): o 10,000 square feet of impervious area o 0.75 acres of lawn and landscape. Any area where these facilities are prohibited by an approved cleanup plan under the state MTCA or Federal Superfund Law, or an environmental covenant under Chapter 64.70 RCW. Within 100 feet of a drinking water well, or a spring used for drinking water supply. including reserve areas, and grey water reuse systems. For Bioretention or Rain Gardens cont.) BMP T7.30, SWMMWW Volume V, Section 7.4 None of the above boxes are checked. This is the BMP that must be used for hard surfaces. On Worksheet A1, indicate that this will be the BMP used. CONTINUE to complete the form for other surface types applicable to the project. If none, STOP. Apr 13 2021 BLD2021-00238 13 Worksheet C What’s the best option for your site? Other Hard Surfaces (cont.) BMP and Applicable Lists Reason why the BMP will not work on site.Additional Comments If needed Sheet Flow Dispersion BMP T5.12, SWMMWW Volume V, Section 5.3 Area to be dispersed (e.g., driveway, patio) cannot be graded to have less than a 15 percent slope. contributing surface cannot be achieved. For variably sloped cannot be achieved. Siting and design criteria cannot be achieved on site. Concentrated Flow Dispersion BMP T5.11, SWMMWW Volume V, Section 5.3 sq. ft. of drainage area followed with applicable setbacks cannot be achieved. More than 700 sq. ft. drainage area drains to any dispersion device. Siting and design criteria cannot be achieved on site. List #1, #2 and #3 List #1, #2 and #3 None of the above boxes are checked. This is the BMP that must be used for hard surfaces. On Worksheet A1, indicate that this will be the BMP used. CONTINUE to complete the form for other surface types applicable to the project. If none, STOP. None of the above boxes are checked. This is the BMP that must be used for hard surfaces. On Worksheet A1, indicate that this will be the BMP used. CONTINUE to complete the form for other surface types applicable to the project. If none, STOP. Apr 13 2021 Apr132021 BLD2021-00238 stormwater calc worksheet QR code REV. 5/31/2019 page 1 of 2 DEPARTMENT OF COMMUNITY DEVELOPMENT 621 Sheridan Street, Port Townsend, WA 98368 Tel: 360.379.4450 | Fax: 360.379.4451 Web: www.co.jefferson.wa.us/communitydevelopment E-mail: dcd@co.jefferson.wa.us STORMWATER CALCULATION WORKSHEET PARCEL # PROJECT/APPLICANT NAME: DETERMINING STORMWATER MANAGEMENT REQUIREMENTS: This stormwater calculation worksheet should be completed first to quired 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. 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 of plant species, other than noxious weeds, 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 ¾ 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 No Well, utilities, etc. ___________________________ sq/ft Does the project convert 2 ½ acres or more of native vegetation to pasture? Driveway, parking, roads, etc. ___________________sq/ft Circle: Yes No Lawn, landscaping, etc. ______________________ sq/ft Other compacted surface, etc. _________________ sq/ft Indicate Total Volumes of Proposed: Includes BMP T5.13 Fill Volume) Temporary construction area ______________ sq/ft Total Land Disturbance ____________________ sq/ft Cut __________ Fill __________ (cu/yd) PARCEL SIZE (I.E., SITE) Size of parcel _________ acres An acre contains 43,560 square feet. Multiply the acreage by this figure. Size of parcel in square feet _________________ sq/ft Scan the QR code to access the digital form 962115902 Irick 34 14917 2021 3240 5261 255 80 Apr 13 2021 BLD2021-00238 stormwater calc worksheet QR code REV. 5/31/2019 page 2 of 2 Applicants for small Construction Stormwater Pollution Prevention. Please submit the Small Project Certification (Worksheet s). 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 (SWPPP) Best Management Practices (BMPs) Fact Sheet . Applicants for medium those that must meet only Minimum Requirements #1 through #5 must submit Worksheet A1 and B1, a stormwater site plan and a construction stormwater pollution prevention site plan (See Reference A1A and B1A for guidance).). Large those that must meet all 9 Minimum Requirements must submit Worksheet A1 and B1, a stormwater site plan and a construction stormwater pollution prevention site plan (See Reference A1A and B1A for guidance). Large projects also may require engineering. See Worksheet L to determine additional large project requirements. APPLICANT SIGNATURE By signing the Stormwater Calculation Worksheet, I as the applicant/owner attest that the information provided herein is true and correct to the best of my knowledge. I also certify that this application is being made with the full knowledge and consent of all owners of the affected property. LANDOWNER OR AUTHORIZED REPRESENTATIVE SIGNATURE) (DATE) STORMWATER CALCULATIONS IMPERVIOUS SURFACE Impervious surface is a hard surface that either prevents or slows the entry of water into the soil 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. NEW EXISTING Structures (all roof area) _________________sq/ft Structures (all roof area) _________________sq/ft Sidewalks _________________sq/ft Sidewalks _________________sq/ft Patios _________________sq/ft Patios _________________sq/ft Solid Decks _________________sq/ft Solid Decks _________________sq/ft without infiltration below) (without infiltration below) Driveway, parking, roads, etc _______________sq/ft Driveway, parking, roads, etc _______________sq/ft Other _________________sq/ft Other _________________sq/ft Total New _________________sq/ft Total Existing _________________sq/ft TOTAL NEW + TOTAL EXISTING* _________________sq/ft *This amount will be used to check total lot coverage. 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 existing impervious surface? The proposal is considered new development. Answer questions in Figure 2.4.1 Flow Chart for New Development to determine project size (next page). The proposal is considered redevelopment Answer questions in Figure 2.4.2. Flow Chart for Redevelopment to determine project size (next page). yes no 1924 3240 05164 5164 0 7202520 140 232 4816 5536 720 Apr 13 2021 BLD2021-00238