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Home My WebLink AboutBLD2021-00253 - 05 Approved Stormwater02-\-'h\ DEPARTMENT OF COMMUNITY DEI'ELOPMENT 621 Sheridan Strcct, Pon Townseod, WA 98368 Tel -160.379.4450 | Fax: 360.379.4451 Web: \r,ww.co.ie fferson.wa. us / communiwdevdoPment F--mlL dcd@co.icfferson.wa.us Scan the QR code to access the digital form STORMWATER CALCULATION WORKSHEET ,o"..,0 Q!8-I eaotecr/aerltc.lr,,tt tavt;a DETERMTNTNG 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 req uired. Lond-disturbing octivw 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 soiltopography. Land disturbing activities include, but are not limited to clearing, grading, filling, excavation, and compaction associated with stabilization of structures and road construction. Notive vegetation is vegetation comprised of plant species, other than noxious weeds, which reasonably could have been expected to naturally occur on th€ site. Examples include species such as Douglas fir, western hemlock, western red cedar, alder, big-leaf maple, and vlne maple; shrubs such as willow, elderberry, salmonberry, and salal; herbaceous plants such as sword fern, foam flower, and fireweed, ES,t#l:E;ri,Ffuffi An acre contains 43,560 square feet. Multiply the acreage bythisfigure PARCEL Size of parcel in sq ,rr"t .t 11,lbh sq/ft fl.E.. StTE) size of parcel 0'{Li u"r". lo15 l8D 0 qDD r/-Fi| 5A)% @utydl15 2 t?.Cut Y 7 G + Constructio n site tor structures 3 Abq sq/ft sq/ft sq/ft f, rr) Other compacted surface, etc- Does the project convert 2 % acres or more of native vegetation to paslure Drainfield, septic tank, etc. Well, utilities, etc. Temporary construction area Total Land Disturbance Driveway, parking, roads, etc Lawn, landscaping, etc. \360 35 Calculate the total area to be cleared, graded, fllled, excavated, and/or compacted for proposed development project. lnclude in this calculation the area to be cleared for: sq/ft sq/ft sqift sq/ft lndicate Total Volumes of Proposed: (lncludes BMP T5.13 Fill Volume) Answer the following two questions related to conversion of native vegetation: Does the project convert % acres or more of native vegetation to lawn or landscaped areas? Circle: Yes Circle: Yes lJ tv L$ 15, 2021 iiAPR 22 stormwater calc worksheel QR code REV.5/31/2019 _t LAND DISTURBING ACTIVITY. CONVERSION OF NATIVE VEGETATION. AND VOLUME OF CUT/FILL @ lmperviout suiace 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' )bt qblp Total ExistingTotal New {-) ) sq/ft I STORMWATE M tft tft tfi /ft tft sqfft LATIONS - I JS SIIRFACFCALCU sq/n .sq/ft D;iveway, parking, roads, etc Other EXISTING Structures (all roof area) Sidewalks Patios Solid Decks (without infl ltration below) Driveway, parking, roads, etc Other NEW Structures (all roof area) Sidewalks Patios Solid Decks (without infiltration below) Divide the total existinq impervious surface above by the size of the parcel and convert to a percentage Does the site have > 35% or more existinq imDervious surface? ++no + yesF The proposal is considered redevelopment Answer questions in Figure 2.4,2. Flow chart for Redevelopment to determine project size (next page), The proposal is considered new development. Answer questions in Figure 2.4.1 Flow Chart for New Development to determine project size lnext page). NT SIGNATURE By signing the stormwater Calculation Worksheet. I as the applicant/owner attest that the information Provided herein knowledge. I also certify that this application is being made with the fult knowledge and consent of all owners aDaA (oArE)PESENT d correct to the best of m of affected proPertY is tru slotuter €lc wo.ksh6€l QR @de - REV. 5/31/2019 b o TOTAL NEW + TOTAL EXISTING' sq/ft 'This amount will be used lo check total lot coverage. DEvELOPMENT v. REOEVELOPMENT - Applicants for "small" projects must comply only with Minimum Requirement #2-Construction Stormwater Pollution Prevention. please submit the Small Project Cenification (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 proiect. Pick up the Construction Stormwater Pollution Prevention (SWPPP) Best Management Practices (BMPs) Fact Sheet. - Applicants for "medium" projects-those that must meet only Minimum Requirements #1 through #5 must submit Worksheet A1 and 81, a stormwater site plan and a construction stormwater pollution prevention site plan (See Reference A1A and B1A for guidance).). - "Large" projects-those that must meet all 9 Minimum Requirements- must submit Worksheet A1 and 81, 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. WorkheetAl Medium & Large Proiect Report Minimum Requirement # 1 : Preparation of Stormwater Site Plan Com the following: Submit a site plan demonstrating the project. Refer to REFERENCE A1A for examples of Best Management Practices (BMP's) thatyoucanuse. Rememberthatall site plans submitted forthe project must be consistent and accurate. Describe both existing and proposed site conditions for the following items as applicable in the space below each bullet point. Attach additional pages if needed. we 5 Minimum Requirement # 2 : Constru on Stormwater Po ution Prevention Plan SWPPP A SWPPP is designed to be a stand-alone document that addresses !9!SUUEE!! stormwater management concerns. This document is required to be kept by the contractor performinB the work at the jobsite for reference and update during the life of the project. Construction BMP'S must be indicated on the stormwater site plan. REFERENCE B1A includes diasra d ms of common BMP's that may be used on the site plan. My completed SWPPP (WORKSHEET 81 or equivalent) is included in this application packet! Minimum Requirement # 3 : Source Control of Pollution (not construction related) The intent of source control is to prevent stormwater from coming in contact with pollutants. Source control BMPs can be operational or structural in nature. A roof over a material storage area is an example of a structural source control BMP Washing your vehicle on the lawn rather than in the street is an operational BMP This requirement is Benerally not applicable to Slngle Family Residences (SFRs); however, ways to minimize pollution from moving downstream should be considered during the design phase of every project. Specifications on standard source control BM ps that are applicable to various commercial and industrial-type facilities can be found ln Volume lV of the 2014 Stormwater Management Manual for Western Washington (SWMMWw) (continued on page 2). {n ero .ELEM , vr- Colncr 74 page 1 of 6 { May 21 2021 May 24 2021 BLD2021-00253 d Minimum Requirement # 3 :source Control of Pollution (continued from page 1) Check one of the following boxes that best represents your project with regards to fMR #3. My project is not a StR and after reviewing Vol. lV of the SWMMWW I have determined that this MR is not applicable because of the following reason: My project is not a SFR and after reviewing Vol. lV of the SWMMWW I have determined that the following source control BMPs are applicable to my project and shall be incorporated into the project design and operation. My project is a Single Family Residence (SFR) and after considering operational and structural measures to prevent stormwater from coming in contact with pollutants, I have, tr determined this MR to not be applicable. ff made appropriate adjustments to my project. page 2 of6 WorlsheetAl Medium & Iarge Project Report i l_ \, 1I N L-; WorkheetAl Medium & Large Project Report Minimum Requirement # 4 : Preservation of Natural Drainage Systems Creating new drainage patterns results in more site disturbance and more potential for erosion and sedimentation during and after construction, to the maximum extent possible, proponents must 1) maintain the natural on-site drainage pattern and concentrated discharge location at the downstream property boundary and 2) prevent erosion at and downstream of the discharge location. NOTE: All outfalls require energy dissipation. See Table 4.5,1. in Vol. V of the SWMMWW for minimum design standards for rock protection at outfalls, Choose the option below that best describes your project: The project site does not currently have any intermittent, seasonal, or continuous concentrated water moving across any part of the property and the proposed improvements to the site will not create new concentrated flow paths or not discharging to existing drainage systems. The project site has existng concentrated flow drainage systems and outfalls. (NOTE: These items must be graphically shown on the Site Plan or equivalent, to includei type, slope, dimensions, channel lining, direction of flow, buffer, etc.) select below how it will be addressed. This pro.iect will not alter the existinB drainage system in any way. lf the existing outfall(s) show signs of erosion and scour, energy dissipation measures will be installed or improved upon. Construction activity of any kind will not occur within at least 10 ft. of the edge of the channelized flow. BMp C1O2: BUFFER ZONES will be implemented durinB the life of the project to include visible flagging or other demarcation technique. The existing concentrated drainage system traversing the property will be impacted as part of this project, as described in the space below and shown on the site plans. Engineering calculations are required that show the altered drainage design can accommodate the existing flows and the added runoff contributed by the project. page 3 of6 tr tr Minimum Requirement # 5 : On-site Stormwater Management On-site stormwater management techniques shall be implemented where possible to accommodate the permanently added stormwater runoff being generated by development. Some on-site stormwater management techniques provide better stormwater detention and treatment than others; however, they are not always appropriate for use due to varying individual site characteristics. Therefore, techniques are presented to applicants on the next pages in a hierarchical order and shall be considered for use in the order listed. The first technique on the list that is determined to be possible shall be implemented. See WoRKSHEET C to determine which techniques are feasible. Runoff from developments occurring in drainage basins that drain directly or indirectly to a creek require a higher level of stormwater management, thus, the techniques are presented in three lists below: All properties will be in one of these three categories:d My project is located in a drainage subbasan that drains to directly or indirectly to freshwater. PROCEED to Page 5 to use LIST #1, My Project will discharBe to a subasin draining to salt water, Dosewallips River, or Hoh River. PROCEED to Page 6 to use LIST #3. My project is a large pro.iect. Refer to Worksheet [. lf full dispersion isn't feasible, use LtsT #1 (List g2 and List #1 are the same except raingardens are not permitted in List #2). page 4 of 6 WorksheetAl Medium & Large Proiect Report tr May 21 2021 N |!1r)lIN .,.Workheet 81 Construction Protection: Medium and Large Projects (Slll/PPP: Stormwater Pollution P'revention Planl Submit a site plan demonstrating the construction protective measures or best management practices that will be used for the project during the construction phase. Refer to REFERENCE B1A for exa m ples of Constructio n Best Management Practices (BMP's) that you can use. The activities that take place during construction are the highest risk for stormwater problems such as erosion and sediment control (you may need to provide an additional site plan with greater detail for stormwater features. lf so, make sure it is consistent with the primary site plan. Remember that all site plans submitted for the project must be consistent and accurate). Element 1: Preserve Vegetation / Mark Clearing Limits The goal of this element is to preserve native vegetation and to clearly show the limits of disturbance Cho ony of the following that opply: The perimeter of the area to be cleared shall be marked prior to clearing operation with visible flagging, orange plastic barrier fencing and/or orange silt fencing as shown on the SWPPP site plan. Vehicles will only be allowed in the a reas to be graded, so no compaction of the undeveloped areas will occur. lf this option is selected check the BMPS you will use below: C10I Preservine Natural Vegetation Cl02 Buffer Zones CI03 Hieh Visibilitv Fence existing site conditions, property not covered by hard surface at the end of Post-Construction Soil Quality and Depth. Cl07 Construction Road / Parkins Area Stabilization It is necessary to disturb the entire property during this project due to constraints, and proposed design, I understand that all disturbed land the project is subject to soil amendment requirements per BMP T5.13 The site was cleared as part of clearing activity that is subject to an enforcement action and will be re-vegetated Restoration may be necessary to comply with Critical Area Regulations or stormwater requirements. Buffer Zones- BMP C1O2 may apply if Critical Areas exist on-site and buffer zones shall be protected. Element 2 : Construction Access The goal of this element is to provide a stabilized construction entrance/exit to prevent or reduce or sediment track out. Choose one ol the following: The driveway to the construction area already exists and will be used for construction access, All equipment and vehicles will be restricted to staying on that existing impervious surface. lf sediment is tracked off site, the road- way will be cleaned thoroughly at the end of each day. A stabilized construction entrance will be installed prior to any vehicles entering the site, at the location shown on the SWppP site plan. lf sediment is tracked off site, the roadway will be cleaned thoroughly at the end of each d7y, lf this option is selected check the BIYIPS you will use below: A Clo5Stabilized [[ ctoawh""l Construction Entrance / Wash Exit page 1 of 6 r d )i !'\ 1I N This ment does not opp ty to my proiect becouse (check ony thot apply): Site is mildly sloped (<5%), There are no individually sloped sections greater than 10%, The bulk of the project is scheduled to occur during dry season (May 1-Sept 30) Element 4: Sediment Control The goal of this element is to construct sediment control BMPs that minimize sediment discharges from the site. Select one of the two statements dpplicable to the proiect. The site has already been stabilized and re-vegetated, Sediment control BMPs shall be placed at the locations shown on the SWPPP Site Plan. lf thls option is selected check the BMPS you will use below: Worksheet 81 Construction Protection: Medium and Large Projects (SWPPP: Stormwater Pollution Prevention Plan) d C233 Silt Fence I-l t1235 Watttes C232 Gravel Filter trBerm SIEP Element 5: Stabilize Soils The goal of this element is to stabilize exposed and unworked soils by implementing erosion control BMPs. Selegtd one of the three statements applicoble to the proiect. My proiect will ensure the following:. Soiistockpiles will be located within the disturbed area shown on the SWPPP Site Plan. . Soil excavated for the foundation will be backfilled against the foundation and graded to drain away from the build ing. . No soils shalt remain exposed and unworked for more than 7 days from May 1to September 30 or more than 2 days from October 1to April 30. . Once the disturbed landscape areas are graded, the grass areas will be amended. . All stockpiles will be covered with plastic or burlap if left unworked. This element &qll-! opply to my proiect because: My proiect must implement specific BMP's to ensure compliance. (Check BMP'S you will use on the next page), Element 3: Control Flow Rates The goal of this element is to construct retention or detention facilities when necessary to protect properties and waterways downstream of development sites from erosion and turbid discharges. C23l Brush Barrier trd tr tr C234 Vegetated tr page 2 of 6 iC'lIN Worksheet Bt Construction Protection: Medium and large Projects (SWPPP: Stormwater Pollution Prevention Planl n crz2 Nets & Blankets f] crz+ soaaing ! tr Cl23 Plastic Coverins C125 Topsoil / E C140 Dust Control Composting Element 6: Protect Slopes The goal of this element is to design and construct cut-and-fill slopes in a manner to minimize erosion. Select one of the two statements opplicoble to the proiect. No cut slopes over 4 feet high or slopes steeper than 2 feet horizontal to 1 foot vertical, and no fill slopes over 4 feet high will exceed 3 feet horizontal to l foot vertical. Therefore, there is no requirement for additional engineered slope protection. The above checkbox is not checked. My submittal is designed by a licensed geologist to protect slopes. Based on the licensed professionals recommendation (please attach their evaluation), the following BMP's will be used: Tc c C205 Subsurface f- c2o7 Check Damst__J Cl20 Temoorarv & Permanent Seeding Seeding C204 Pioe SIooe Drains C13l Gradient Terraces Drains C206 Level Spreader tr C208 Triangular Silt Dike (Geotextile-Encased Check Dam) Element 7: Protect Permanent Drain lnlets The goal of this element is to protect storm drain inlets during construction to prevent stormwater runoff from entering the conveyance system without being filtered or treated. Select one of the three stotements opplicable to the proiect tr The site has open ditches in the right-of-way or private road right-of-way. There are no catch basins on or near the site pa8e 3 of6 d l-l ctzt Mulchine I_l czrs wuttles Catch basins on the site or immediately off site in the right-of-way are shown on the SWPPP Site Plan. Storm drain inlet protection shall be installed. lf this option is selected check the BMPS you will use below: [-l t::zo Srorm Drain Inlet Protection tr Element 8: Stabilize Channels and Outlets The goal of this element is to design, construct, and stabilize on-site conveyance channels to prevent erosion from entering existing stormwater outfalls and conveyance systems. one oI the three stotements opplicoble to the proiect. Construction will occur during the dry weather. No storm drainage channels or ditches shall be constructed either temporary or permanent. There are no existing or proposed stormwater conveyance channels on the project site. A wattle shall be placed at the end of the swale to prevent erosion at the outlet of the swale. lf this option is selected check the BMPS you will use below: Select d l-l e :o: Chrnnel Linirrg l-l Element 9: Control Pollutants Workheet 81 Construction Protection: Medium and Large Projects (SWPPP: Stormwater Pollution Prevention Planl I-l czos outlet Protection [-l C235 WattlesC207 Check Dams The goal of this element is to design, install, implement and maintain BMPS to minimize the discharge of pollutants from material storage areas, fuel handling, equipment cleanrng, management of waste materials, etc. fhis eiement dgg!!q! opply to my Woject becouse (circle ony thot dpply - lf any box is unchecked this element applies. There will be no concrete work, There will be no sawcutting work, M d l-l lhere witt be no heavy equipment associated with this project, El rn"r" will be no pressure washing, equipment maintenance or dewatering lf one or more of the checkboxes above are unchecked. Any and all pollutants, chemicals, liquid products and other materials that have the potentialto pose a threat to human health or the environment will be covered, contained, and protected from vandalism. All such products shall be kept under cover in a secure location on-site. Concrete handling shall follow BM P C151 C154. lf this option is selected check the BMPS you will use below: C15 i Concrete Handling C 152 Sawcutting and Surfacing nP There will be no hazardous materials on-site, There will be no fertilizer or pesticide application, C153 Materi al Deliverv. Storase, and Containment C 154 Concrete Washout Area page 4 of 6 tr tr Wor{sheet 81 Construction Protection: Medium and Large Projects (SWPPP: Stormwater Pollution Prevemion Plan) Element 10: Control De-watering The goal of this element is to handle turbid or contaminated water from dewatering (removal of water) separately f rom stormwater. 5e ne of the two stotements opplicoble to the proiect No dewatering ofthe site is anticipated, Dewatering ofthe site is anticipated. If this option is selected check the BMPS you will use below: C203 Watq ia$E C236 Vegetated Filtration ! Czoe Level Spreader Element 11: Maintain Best Management Practices The goal of this element is to maintain and repair all temporary and permanent erosion and sediment control BMPs to assure continued performance. Describe the steps you will take: Best Management Practices or BMPs shall be inspected and maintained during construction and removed within 30 days after the County lnspector or determines that the site is stabilized, provided that they may be removed when they are no longer needed. Element 12: Manage the Project The goal of this element is to ensure that the owner and those performing the site work comply with the SWPPP and properly coordinate to ensure that all BMPs are deployed at the proper time to achieve full compliance with county regulations throughout the project. The SWppP will be implemented at all times, lf applicable to the project, erosion control BMP5 will be implemented in the following sequence: L. Mark clearing limits 2. lnstall stabilized construction entrance 3. lnstall protection for existing drainage systems and permanent drain inlets 4. Establish staging areas for storaBe and handling polluted material and BMPs 5. lnstall sediment control BMPS 6. Grade and install stabilization measures for disturbed areas 7. Maintain BMPs until site stabilization, at which time they may be removed page 5 of 6 t Element 13: Protect Low lmpact Development BMPs The goal of this element is to protect permanent stormwater mana8ement BMPs from siltation and compaction during construction. The permanent stormwater management BMPs used for runoff from roofs and other hard surfaces include: full dispersion, roof downspout full infiltration or dispersion systems, perforated stubout connections, rain gardens, bioreten6on systems, permeable pavement, sheetflow dispersion, and concentrated flow d ispersion. Metlods that will be used to protect permanent stormwater management BMPs include: f?r Sequencing the construction in a fashion to install these permanent BM Ps at the latter part of theU construction gradingoperations, n Excluding equipment from the BMPs and the associated areas, 5 Using the erosion and sedimentation control BMPs listed below to protect facilities such as drywells, lJ raingardens, permeable pavement, or bioretention from accumulating sediment during construction and before site restoration. lf this option is selected check the BMPS you will use below: l-l c toz Buffer Zone l-l cz3: silt r"n." n czgt Brush Barrier [-l ctor Hish visibilitv Fence C234 Vegetated Strip Othertr Applicant or Representative Signature fuz*' page 6 o[6 Worksheet 81 Consffuction Protection: Medium and Large Prcjects (SWPPP: Stormwater Pollution Prwention Plan)