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bld20110546_Woldesenbet_ENG1.pdf City of EdmondsBLD20110546 TH 121 5AVENUE NORTHEDMONDS, WA 98020 • (425) 771-0220 FAX(425) 771-0221 Website: www.ci.edmonds.wa.us PUBLIC WORK DEPARTMENT Planning • Building • Engineering Engineering Plan Review Comments PermitApplication:Date: #BLD20110546July 28, 2011 th Project Name/Address: Woldensenbet –8606-196St SW Contact Person/Address, Fax or E-mail: Nebiyou Woldesenbet - Reviewer: JENNIFERLAMBERTDivision: ENGINEERING During review of the subject submittal, it was found that the following information, corrections, or clarifications would need to be addressed. All Handouts referred to in these comments can be accessed at our website: www.ci.edmonds.wa.usunder City Government / Development Services Department / Engineering Division then scroll down to Handouts: th 1)The city does not approve for vehicles to back onto 196St SW. a.Please install an on-site turnaround to allow for vehicles to leave the property front first. I’ve attachedtheCity Standard DetailE2.6for an example of the on-site turnaround requirements. b.It appears that vehicles leaving the subject parcel may be existing onto the private drive. i.If this is intended, please provide a copy of the access easement allowing for the subject parcel to use the private drive. A city approved driveway approach may be required. ii.If this is not intended or permitted a clear delineation must be in place. Such as installing a landscape buffer between the sidewalk on the private drive and the on-site turnaround. 2)Please revise the Site Plan to show the streets as they exist. thth a.86Ave W does not continuing south of 196St SW. th b.86Ave W shown adjacent to the subject parcel is actually a private road. Please show as such on the plans. th c.Please also note that 86and the private drive are not in line with each other. 3)Please show all impervious surface areas on the plans (i.e. walkways, gravel areas, shed, patios, etc)and revise the impervious surface calculations accordingly. 4)Clearly show on site plan areas of existing pavement and landscaping and areas of new pavement. DATE E-MAILED7/29/2011PAGE(1) City of EdmondsBLD20110546 TH 121 5AVENUE NORTHEDMONDS, WA 98020 • (425) 771-0220 FAX(425) 771-0221 Website: www.ci.edmonds.wa.us PUBLIC WORK DEPARTMENT Planning • Building • Engineering Engineering Plan Review Comments 5)Please add the impervious surface chart(provided in the E72 Handout),asshown below, to the Site Plan. LineTypeArea (square feet) 1.Non-Regulated ExemptRegulated 2.Replaced 3.New (Post 1977)+ Total Regulated Impervious Area = 4. Mitigation required if in excess of 2000sf - 5.Total Area Mitigatedby Existing Stormwater Management System(s) = 6.Regulated Area Not Yet Mitigated = 7.Area Proposed to be Mitigated by Low Impact Development Techniques = 8.Area Proposed to be Mitigated through Conventional SWM Techniques 6)Please show all fences, retaining walls, and rockeries that exist on the property. Please resubmit 3 copies of the revised plansand associated documents with a written response to each item to a Permit Coordinator. Please contact me at 425-771-0220ext 1321or by e-mail at jennifer.lambert@ci.edmonds.wa.usif you have specific questions regarding these plan corrections. DATE E-MAILED7/29/2011PAGE(1) #E72 STORMWATER MANAGEMENT (SWM) DRAINAGE SYSTEM DESIGN, AND EROSION & SEDIMENT CONTROL REQUIREMENTS Overall Stormwater Management Approach This handout contains an overall summary of the requirements and options available to assist an applicant in designing, constructing, and maintaining stormwater Best Management Practices (BMPs) in the City of Edmonds to meet the intent of ECDC 18.30. The Stormwater Code Supplement is available for use in our Development Services Department as well as on the Citys Website (www.ci.edmonds.wa.us). Please refer to the Supplement for a more detailed explanation of each requirement. Applicants are encouraged to use the Classification Worksheet on page 5 of this handout to help determine the requirements for their project. found on page 2 of this handout. For specific site Step 1 Determine Applicability requirements for each classification refer to The first step is to determine if the Stormwater Stormwater Code Supplement. Management code applies to your project. Use Figure-A, page 3, in this handout to establish Step 4 Plan Your Site and Select BMPs whether your project or site meets any of the Plan your site and select BMPs as described in the criteria for applicability. Supplement to meet or exceed the minimum requirements for your project. Step 2 Determine Your Project Sites Classification and Watershed Step 5 Submit Reports and Plans for Review Determine if your site is classified as a Large Site Submit all required reports and plans for review. Project by using Figure-B, page 4. If you have a The handout for the appropriate classification of Large Site Project, you do not have to fill out the your project (Large, Small or Minor Site) will Classification Worksheet, page 5 of this handout. provide information regarding the submittal If you do not have a Large Site Project, use the requirements. The stormwater submittals will be Classification Worksheet, page 5 and Figure-B, reviewed concurrently with all other permit page 4, to determine whether your project is submittals. Revisions to reports and plans may be considered a Small or Minor Site Project. For required per City of Edmonds review. Small Site Projects, you will further need to Step 6 Construction determine whether it is a Category 1 or a Category Erosion & Sediment Control Measures must be 2 project. Next, identify the watershed for your inspected and approved by the Citys Engineering Small or Minor Site project using the City of Division prior to the start of construction. The Edmonds Watershed Map, Figure-C, page 7. This project shall be constructed per approved plans. will clarify some of the site-specific requirements Any changes proposed to the approved plans must in Step 3. be submitted to the Engineering Division for review and approval prior to construction. Step 3 Determine the Minimum Requirements Needed and Where on the Site They Apply Step 7 Operate and Maintain BMPs The minimum requirements are based on the Operate and maintain BMPs as required by the project classification determined in Step 2. A approved submittals. summary of the Minimum Requirements can be 1 of 13 Revised on 4/21/11 E72-SWM_Erosion_Control--04.21.11-FINAL Page Overview of Stormwater Management Minimum Requirements Depending on the type, location, and size of the proposed project, different combinations of these minimum requirements apply. The following is a brief list of the overall Minimum Requirements for Large, Small, and Minor sites. Please refer to the Stormwater Code Supplement for additional information. LARGE SITES Stormwater Supplement Chapter 4 land disturbing activity A project or overall development involving 1 acre or more of would potentially require the following Minimum Requirements: 1. Preparation of Stormwater Site Plan 7. Flow Control 2. Construction Stormwater Pollution Prevention Plan 8. Wetland Protection 3. Source Control of Pollution 9. Operation and Maintenance 4. Preservation of Natural Drainage Systems and Outfalls 10. Offsite Analysis and Mitigation 5. Onsite Stormwater Management/Low Impact 11. Financial Liability Development Techniques 6. Runoff Treatment SMALL SITES Category 1 and 2 - Stormwater Supplement Chapter 5 Small Site Minimum Requirements, #s 1-11 listed below, may be required for projects that involve: newreplaced impervious surface; or A) 2,000 square feet (sf) or more of regulated plus land-disturbing activity; or B) 7,000 sf or more of or C) 50 cubic yards (cy) or more of grading, fill or excavation; or D) Conversion of ¾ acre or more of native vegetation to lawn or landscaped area; E) Causes an increase of 0.1 cubic feet per second (cf/s) or more in the 100 year flow frequency from a threshold discharge area. 1. Preparation of Stormwater Site Plan including: 7. Flow Control 2. Erosion and Sediment Control Plan 8. Wetland Protection 3. Source Control of Pollution 9. Operation and Maintenance 4. Preservation of Natural Drainage Systems and Outfalls 10. Offsite Analysis and Mitigation 5. Onsite Stormwater Management/Low Impact 11. Financial Liability Development Techniques 6. Runoff Treatment MINOR SITES Stormwater Supplement Chapter 6 A project that involves 500 sf or more of new development or redevelopment including land- disturbing activity or a utility project that causes land disturbance, and is not considered a Large or Small Site Project, must employ Minor Site Construction Stormwater Pollution Prevention Practices. Additional Requirements may be imposed to meet the intent of the Stormwater Code based on site specific factors. Note: Terms in bold italics are described in the Glossary on pages 10-11. Definitions are found in ECDC Chapter 18.30.010 and the Stormwater Code Supplement. The information presented in this handout (E72) should not be used as a substitute for City codes and regulations. The Edmonds Community Development Code (ECDC) may be viewed at www.ci.edmonds.wa.us/codes.stm. The applicant is responsible for ensuring compliance with the fees and regulations that are applicable at the time of submittal. If you have a specific question about a certain aspect of your project, please contact the Engineering Division at 121 Fifth Avenue North, (425) 771-0220. Please note that other local, state, and/or federal permits or approvals may be required. 2 of 13 Revised on 4/21/11 E72-SWM_Erosion_Control--04.21.11-FINAL Page Figure-A Determining Applicability of Stormwater Management Code ECDC Chapter 18.30 If any of the descriptions in the Blue Boxes apply to your project or project site, the Stormwater Management Code applies. Does your Project Site require the issuance of a City Yes permit under any of the following: ECDC Title 18 - Engineering Division ECDC Title 19 - Building Division 2 A Stormwater Permit No Yes Are you submitting a Subdivision application per ECDC Chapter 20.75? No Does your Project site involve any of the following: Stormwater Management 500 square feet or more of land-disturbing Yes requirements of ECDC activity, new impervious surface, or replaced Chapter 18.30 are impervious surface? applicable to your A utility or other construction project Project or Site. consisting of 500 lineal feet or more of trench excavation? Is located in, adjacent to, or drains into (currently or as a result of the project) a Critical Area or a Critical Area Buffer? No Stormwater Management requirements of ECDC Chapter 18.30 are not applicable to your 1 Project or Site Note: The definitions of the terms in italics are found in ECDC Chapter 18.30.010 and the Stormwater Code Supplement. ______________________________ 1 This chart provides an initial screening for determining the applicability of ECDC Chapter 18.30. The results from using this chart do not substitute for a determination of applicability by the Public Works Director or Designee per ECDC Chapter 18.30.030 and the relevant portions of the Supplement. 2 If ECDC Chapter 18.30 is applicable to the proposed project and it does not require any other City-issued permit, a Stormwater Permit and associated fees will be required. 3 of 13 Revised on 4/21/11 E72-SWM_Erosion_Control--04.21.11-FINAL Page Figure-B Project Classification If you have determined that the Stormwater Management Code applies to your project (Figure-A), follow the Blue boxes in the chart below to determine the Classification of your project. Yes Does the project involve 1- acre or more of land- Large Site Project: 1 disturbing activity ? See Stormwater Supplement No Chapter 4 for specific Yes Is the project part of a larger requirements . common plan of development or sale where the total disturbed area for the entire plan will total 1-acre Does the project create or add 5,000 square feet or or more of land-disturbing activity? more of new impervious surface, regulated replaced impervious surface or new plus No regulated replaced impervious surface? OR Does the Project involve one or more of the Convert ¾ acre or more of native vegetation to following: lawn or landscaped area Yes new 2,000 square feet (sf) or more of OR impervious surfaceregulated replaced , Through a combination of creating effective impervious surface or new plus regulated impervious surface and converted pervious replaced impervious surface? surfaces, causes an increase of 0.1 cubic feet per OR second in the 100-year flow frequency from a land-disturbing activity 7,000 sf or more of ? threshold discharge area as estimated using an OR approved model? 50 cubic yards or more of either grading, fill, or excavation as defined in Chapter 18.40.000 ECDC? No Yes No Minor Site Project: Category 1 Small Site Project: Category 2 Small Site Project: See Stormwater Supplement See Stormwater Supplement See Stormwater Supplement Chapter 6 for specific Chapter 5 or specific Chapter 5 for specific requirements requirements requirements Notes: Terms in bold italics are described in the Glossary on pages 10-11. The definitions of the all terms in italics are found in ECDC Chapter 18.30.010 and the Stormwater Code Supplement The Classification flowchart assumes the project in question meets the applicability requirements of ECDC18.30.030. ________________________________ 1 Land-disturbing Activity: Any activity that results in the movement of earth, or a change in the existing soil cover (both vegetative and non-vegetative) or the existing soil topography. Land disturbing activities include, but are not limited to grading, filling, excavation, and compaction associated with stabilization of structures and/or road construction. 4 of 13 Revised on 4/21/11 E72-SWM_Erosion_Control--04.21.11-FINAL Page The projects Site Classification will dictate the specific stormwater management requirements applicable to your site. Completing this worksheet will help determine the amount of Small Site regulated impervious surface and whether your project falls into the classification of a Minor Site (Category 1 or Category 2), or a . Please reference the Glossary (pp. 10-11), Figures D and E, (pp. 8-9), and Examples (pp. 12-13), to assist with completion of this worksheet. 1 1)Is Permeable Pavement Proposed For Use on this Site? Yes No Refer to Stormwater Supplement Chapter 5.1 YES If , the subject area is to be considered impervious for initial site classification purposes. Include total permeable pavement area in the calculation of Non-Regulated, Replaced and/or New impervious surface areas in the table below. 2)Determine the Amount and Type of Existing & Proposed Impervious Surface for the Site Refer to Stormwater Supplement Chapter 2 and Fig. C Line 1Non-Regulated Impervious Surface Area. : Identify the Line 2Replaced Impervious Surface Area : Identify the , dividing the total between Exempt and Regulated; either or both Replaced Impervious may be zero. Note: For project classification purposes, may only be considered exempt under certain conditions. Refer to the Glossary and Figure D. Line 3New Impervious Surface Area : Identify the for your project. All impervious areas created post-July 7, 1977 or after the date of annexation into the City are regulated & should be included in this total unless they can be categorized separately as a Replaced-Regulated area. Line 4plus : Enter the sum of the total Replaced-Regulated the total New impervious areas. Line 5 : Identify the total area currently mitigated by an existing city-approved stormwater management system. Line 6 : Enter the sum of the value in Line 4 less the value in Line 5 to identify the total Regulated area in which stormwater controls have not yet been applied. Line 7 : Identify the total area proposed to be mitigated through the use of Low Impact Development Techniques. Line 8 : Identify the total area proposed to be mitigated through conventional Stormwater Management Techniques. ** Provide a copy of the following table on the drainage plan sheet for the proposed project ** Line Type Area (square feet) 1. Non-Regulated Exempt Regulated 2. Replaced 3. New (Post 1977) + Total Regulated Impervious Area = 4. Mitigation required if in excess of 2000sf 5. Total Area Mitigated by Existing Stormwater Management System(s) - 6. Regulated Area Not Yet Mitigated = 7. Area Proposed to be Mitigated by Low Impact Development Techniques = 8. Area Proposed to be Mitigated through Conventional SWM Techniques = 1 (e.g. porous asphalt, porous concrete, paver blocks, concrete open celled paving grids, or plastic lattices filled with turf or stone) 5 of 13 Revised on 4/21/11 E72-SWM_Erosion_Control--04.21.11-FINAL Page 3)Determine the Total Area of Land Disturbing Activity ________ sf Refer to Stormwater Supplement Chapter 8 4) Determine the Quantity of Grading, Fill and/or Excavation ________cy 5) Will the project convert ¾ Acre or More of Native Vegetation to Lawn or Yes No Landscaped Area? 6) Identify the Watershed the Existing Site Runoff Discharges to Refer to Stormwater Supplement Chapter 2.3 Based on Site Location and Watershed Map Figure-C. Check all that apply. A. Direct Discharge B. Creek or Lake Basin Edmonds Way Basin Puget Sound Basin Puget Sound Piped Basin DETERMINE PROJECT CLASSIFICATION USING THE INFORMATION ABOVE PROJECT CLASSIFICATION CHART AND THE (Figure B, pg 4) Small Site - Category 1 Small Site - Category 2 Minor Site Stormwater Supplement Stormwater Supplement Stormwater Supplement Chapter 5 Chapter 5Chapter 6 6 of 13 Revised on 4/21/11 E72-SWM_Erosion_Control--04.21.11-FINAL Page Figure-C 2 City of Edmonds Watersheds No warranty of any sort, including accuracy, fitness, or merchantability accompany this product. 1 A larger version of the Edmonds Watershed Map is available in the Development Services Office and on the City of Edmonds . website at ci.edmonds.wa.us 7 of 13 Revised on 4/21/11 E72-SWM_Erosion_Control--04.21.11-FINAL Page Figure-D What Qualifies as Replaced Impervious Surface? 8 of 13 Revised on 4/21/11 E72-SWM_Erosion_Control--04.21.11-FINAL Page Figure-E Regulation of NEW Impervious Surface Areas for Determining Site Classification Note: For the purpose of this flowchart, it is assumed that all existing impervious surface will remain after the proposed project is complete. If any existing impervious surface will be demolished for this project, the project may contain a combination of new and replaced impervious surface. See Glossary, p. 10-11. ______________________________ 1 Mitigation requirements are based on the total cumulative impervious area created on a project site since July 6, 1977, the effective date of the Citys first drainage control ordinance. 2 For parcels that were annexed into the City after this date, the date of annexation shall substitute for the effective date of the Citys first drainage control ordinance. 3 For annexed parcels, a functioning Snohomish County-approved stormwater management facility can substitute for a City-approved facility. 9 of 13 Revised on 4/21/11 E72-SWM_Erosion_Control--04.21.11-FINAL Page Glossary This glossary provides explanations of the terminology used in this handout. The actual definitions can be found in ECDC Chapter 18.30.010 or the Supplement. Impervious Surface: Hard surface area that either prevents or retards the entry of water into the ground as it would occur in natural, undeveloped conditions. Impervious surfaces include, but are not limited to, rooftops, driveways, walkways, concrete, asphalt, and packed earthen materials. Decks will be considered impervious if one or more of the following apply: Deck is made of solid material that does not allow rain water to run through it · Deck has slots where rainwater can run through but the ground under the deck does not allow the · rainwater to infiltrate into the ground. Open, uncovered retention/detention facilities shall not be considered impervious surfaces for purpose of determining whether the thresholds for application of minimum requirements are exceeded. However, open, uncovered retention/detention facilities shall be considered impervious surfaces for purposes of runoff modeling. Outdoor swimming pools shall be considered impervious surfaces in all situations. For the purpose of determining stormwater control requirements, impervious surfaces are divided into four categories: Non-Regulated, Exempt Replaced, Regulated Replaced , and New. See explanations below: Non-Regulated Impervious Surface: All impervious surface area installed prior to July 7, 1977 or prior to the date the parcel was annexed into the City from Snohomish County that will remain unchanged during the site redevelopment. Replaced Impervious Surface: All impervious surface area on the project site existing at the time of application that is proposed to 3 be removed and re-established in the same footprint. This does not include impervious surface removed for the sole purpose of installing utilities or performing maintenance. Exempt Replaced - Some of the replaced impervious surface may be Exempt if it meets the following condition: On single-family residential parcels only: the replacement of a driveway, walkway, or similar surface in the same footprint in which it was originally installed prior to July 7, 1977 or prior to the date the parcel was annexed into the City from Snohomish County. Regulated Replaced - All other replaced impervious surfaces on any parcel that do not qualify as Exempt are considered Regulated. New Impervious Surface: All areas converted from pervious surfaces (native vegetation, etc.) to impervious surfaces and permeable pavements on a project site on or after July 7, 1977 or the date the parcel was annexed 3 Removed refers to the removal of building down to bare soil or subgrade. Roof replacement such as re-shingling, is considered to be a maintenance activity and not considered replacing an impervious surface. For others surfaces, such as pavement, removed means the removal of concrete (PCC) or asphalt (AC) slabs, driveways, sidewalks or similar surfaces down to bare soil or base course. The pulverization in-place and replacement with a similar wearing course is considered replaced impervious surface. The partial grinding of surfaces for overlay (not down to base soil or base course) is considered to be a maintenance activity. 10 of 13 Revised on 4/21/11 E72-SWM_Erosion_Control--04.21.11-FINAL Page into the City from Snohomish County. See Figure-E for exemptions for sites located outside of Creek or Lake drainage basins. Land-disturbing Activity: Any activity that results in movement of earth, a change in the existing soil cover (both vegetative and non-vegetative), or in the existing soil topography. Land-disturbing activities include but are not limited to clearing, grading, filling, excavation, and compaction of soils associated with structure stabilization and road construction. Pervious Surface: Any surface that allows the entry of water into the ground as it would occur in nature. 11 of 13 Revised on 4/21/11 E72-SWM_Erosion_Control--04.21.11-FINAL Page EXAMPLES Non-RegulatedExempt Replaced Regulated Replaced The following are examples of how to determine the , , New and impervious surface totals for a specific project. If you have any questions, please contact an Engineering Technician. Example 1: 1972 House 1,200 square feet (sf) roofline Driveway (paved) 60 sf 1999 House Addition 400 sf 2004 Detached Garage 600 sf with no stormwater system installed Proposal: Garage Addition 140 sf roofline before The 1972 House and Driveway were constructed to July 7,1977 so are considered Non-Regulated impervious area. The 1999 House Addition and 2004 Detached Garage and proposed Garage Addition are after ) considered New impervious surface since built July 7, 1977(zero replacedimpervious. 1,140 sf Total Regulated New Impervious Surface: 400sf + 600sf + 140sf = Example 2 : 1968 Single-Family House 1,500 sf roofline Gravel Driveway 400 sf Sidewalks/Patios 55 sf Proposal: Pave driveway with asphalt, same footprint as gravel driveway (400 sf). The existing gravel driveway is a combination of gravel and packed earthen material, this meets the definition of impervious surface. Paving the gravel driveway counts as Exempt Replaced impervious surface (the before proposed paving in same footprint of the original driveway installed July 7, 1977). 0 sf Total regulated New + replaced Impervious Surface: Example 3a : 1976 House 2,000 sf roofline Concrete Driveway 200 sf 1999 Garage w/concrete slab (no stormwater system) 300 sf Proposal: New garage (300 sf) demolish existing garage and slab; new garage will be same size and in same location of the concrete slab and original garage to be replaced. Proposed garage will be considered Regulated Replaced because the replaced impervious surface (garage & after slab) was first constructed July 7, 1977. 300 sf Total Regulated New + Replaced: 0 + 300 sf = Example 3b : 1976 House 2,000 sf roofline Concrete Driveway 200 sf Garage w/concrete slab 300 sf Proposal: New garage (300 sf) demolish existing garage (leave slab); new garage will be same size and in same location as original garage that will be replaced. Proposed garage will be considered Exempt Replaced because the slab remains (not taken down to bare prior to ground or sub base), the new garage is in the same footprint as the old one that was first constructed July 7, 1977. 0 sf Total Regulated New + Replaced Impervious Surface: 12 of 13 Revised on 4/21/11 E72-SWM_Erosion_Control--04.21.11-FINAL Page Example 4: 1979 House 1,200 sf Gravel driveway 300 sf Patio/Walkways 100 sf 1989 Garage 250 sf (No stormwater system on the site) Proposal: Garage addition 200 sf and replacing gravel driveway with asphalt (300 sf) after House, patio/walkways, original garage and garage addition built July 7, 1977 with no storm system and therefore are considered New impervious surface: 1,200+100+250 +200 sf = 1,750 sf. Driveway was after installed July 7, 1977. It is now changing from gravel to asphalt (both impervious) in same footprint it is considered Regulated Replaced impervious surface: 300 sf 2,050 sf Total Regulated New + Replaced Impervious: 1,750 sf + 300 sf = Example 5: 1989 House 2,800 sf Driveway/patio/walkways 700 sf The 1989 construction was approved with a detention system sized for 3,500 sf of impervious surface that was adequate under the provisions of the stormwater code effective at that time. Proposal: 300 sf addition to house Revised New impervious total 3,800 sf (zero replaced impervious). after The house, patio and walkways were installed July 7, 1977 with a storm system. The existing system does not meet the sizing requirements of todays stormwater code for 3,500 sf of impervious surface. In this case, there are two options available to meet the stormwater flow control requirements. Option 1 Install a separate stormwater system (such as an infiltration trench or rain garden, if feasible) that is sized only for the 300 sf new addition using current standards. Since the existing system was approved at the time of construction for requirements of the code in effect at that time, resizing is not required. Option 2 Upgrade the existing system to meet to handle both the existing impervious surface of (3,500 sf) and the proposed impervious surface (300 sf). The existing system would need to be sized for 3,800 sf under the sizing requirements of the current code. If, for example, a detention system is chosen as the flow control BMP: Code requirements in effect in 1989 for 3,500sf of impervious surface (existing system) is 49 lineal ft of 18 diameter pipe with ¾ orifice. Current Code requirements for 3,800sf of impervious surface is 81 lineal ft of 18 diameter pipe with ¾ orifice. Therefore applicant would need to add 32 lineal feet of 18 diameter pipe to existing detention system. Other options include the Low Impact Development techniques such as pervious pavement or rain gardens. 13 of 13 Revised on 4/21/11 E72-SWM_Erosion_Control--04.21.11-FINAL Page