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APPROVED STM BLD2021-0259+Storm_Drainage_Report+2.16.2021_5.22.43_PM+2050249Donna Breske & Associates Civil Engineering & Land Use Planning Drainage Report For Ryker Young Original Date Prepared: June-27-2018 Current Revision: January 31, 2019 Site Address: 20114 83rd W Edmonds, WA 98026 Parcel Number: 00431200000402 Prepared By: Alex White, EIT RECEIVED Apr 12 2021 CITY OF EDMONDS DEVELOPMENT SERVICES DEPARTMENT APPLIES WITH APPLICABLE CITY STORMWATER CODE BLD2021-0259 Reviewed By: Donna L. Breske, P.E. �q r Donna Breske & Associates, LLC 21 Ave A, Suite 4 Snohomish, WA 98290 Phone: (360) 294-8941 Email: donnab@donnabreske.com RECEIVED FEB 0 8 2019 DEVELO MENT SERVICES Table of Contents Narrative: ExecutiveSummary................................................................................................................. Page 3 VicinityMap............................................................................................................................ Page 4 Impervious Area Exhibit.......................................................................................................... Page 5 DisturbedArea Exhibit.....................................................................................................................Page 6 TreeRemoval Exhibit........................................................................................................................Page 7 TreeRetention Exhibit......................................................................................................................Page 8 Flow Chart for Edmonds Stormwater Management............................................................. Page 9 Minimum Requirements #1-#9...........................................................................................Page 10 SWPPPNarrative...................................................................................................................Page 15 Appendix: A: Drainage Inventory Map B: WWHM20102 Bioretention Calcs C: Soils Info D: Operations and Maintenance 2 Executive Summar The site consists of a single tax parcel that has a gross area of 19,835 square feet (0.45 Acres). The site address is 20114 83rd Ave W Edmonds, WA 98026, with tax parcel number 00431200000402. The proposal of this project includes a subdivision that will divide the site into a two -lot short plat. The first lot will be 0.21 Acres and the second will be 0.24 Acres. There will be a hammerhead driveway that connects the road to the two lots. There is an existing house on the site as well as an old house foundation located on the back perimeter of the property. These structures will be torn down before construction of the new project. A two -hole test has been performed by Conrad Elledge resulting in long term infiltration rates of 5.64 "per hour- 6.36" per hour. Additionally, the short-term infiltration rates were 8.06" per hour — 9.09" per hour. Correction factors have been applied to the lowest measured rate of 6.6 in/hr per Table B.1. This resulted in a design infiltration rate of 2.97 in/hr, and this was the rate used in the current bioretention calculations. The naturally occurring slopes on site are approximately 25% The existing vegetation on site is grassy with some bamboo and scattered trees. The pertaining Elements of Stormwater Pollution Prevention Plan (SWPPP) are addressed on the drawing sheet titled Storm Water Prevention Plan and as well as in this report. Per the City of Edmonds' Chapter 18.30 this project must comply with the drainage requirements listed in the DOE 2014 Stormwater Management Manual for Western Washington. Since this project proposes greater than 5,000 square feet of impervious surface, minimum requirements 1-9 must be evaluated. Since this project proposes less than 10,000 square feet of impervious surface, flow control will not be required. This project proposes to route impervious surface runoff into a bioretention facility designed to infiltrate 100% of all impervious surface runoff routed to it. Post construction soil in the disturbed areas, not covered by impervious surface, are to be installed in accordance to BMP T5.13. �o 196TH ST SW 1967H ST SW a cv oo a 987H STrswZ ov oo ^� ap ,, 1997H ST SW 200TH ST SW 2007H ST SW o a 201ST ST SW 202ND ST SW 202ND PL SW 203RD ST SW PREPARED BY.• DONNA BRESKE & ASSOCIATES, LLC 21 AVE A, SUITE 4 SNOHOMISH, WA 98290 PHONE: (425) 334-9980 DONNABRESKE®COMCAST. NET VICINITY MAP N. T. S. VICINITY MAP TAX NO. 004JI200000402 SIZE ADDRESS• PROJECT PROPONENT RYKER YOUNG ISSUE DATE.- 2-5-2019 20114 83RD AVE W, EDMONDS, WA 98026-6727 TO BIOREIEN71ON \ j TO BIORETENRON AREA = 745 SF \ I AREA = 927 SF BYPASS TO CB J2 AREA = 927 SF AREA = 2,673 SF GRAVEL AREA = 172 SF GRAVEL AREA = 172 SF IMPERVIOUS AREA EXHIBIT SCALE. 1 "=30' et PARED Br.• IMPERVIOUS AREA EXHIBIT DONNA BRESKE & ASSOCIATES, LLC 21 AVE A, SUITE 4 TAX NO. 00431200000402 S17E ADDRESS: 20114 83RD AVE. W, SNOHOMISH, WA 98290 PROJECT PROPONENT RYKER YOUNG EDMONDS, WA 98026-6727 PHONE: (425) 334-9980 DONNABRESKE®COMCAST.NET ISSUE DA7E.- 2-5-2019 D ------------ Ai Ai I D D I D Ai D Ai Ai D I I D D Ai Ai -D i I D D = DISTURBED AREA (9,442 SF) - INSTALL 8" MINIMUM DEPTH STOCKPILED SOIL Ai = PROPOSED I11iPERVIOUS AREA (7,657 SF) POST CONSTRUCTION SOILS PLACEMENT EXHIBIT SCALE: 1 "=30' p�PARED 8K POST CONSTRUCTION SOIL PLACEMENT EXHIBIT DONNA BRESKE & ASSOCIATES, LLC 21 AVE A, SUITE 4 TAX NO. 00431200000402 S17E ADDRESS: 20114 83RD Aff W, SNOHOMISH, WA 98290 PROJECT PROPONENT RWER YOUNG EDMONDS, WA 98026-6727 PHONE: (425) 334-9980 DONNABRE'SKE®COMCAST.NET ISSUE DA7E 2-5-2019 TREE REM 0 VA L EXHI BI T SCALE. 1 "=30' PREPARED BY- TREE REMOVAL EXHIBIT DONNA BRESKE & ASSOCIATES, LLC 21 AVE A, SUITE 4 TAX NO. 00431200000402 S17E ADDRESS: 20114 83RD AVE. W, SNOHOMISH, WA 98290 PROJECT PROPONENT RYKER YOUNG EDMONDS, WA 98026-6727 PHONE: (425) 334-9980 DONNABRESKEPCOMCAST. NET ISSUE WE 2-5-2019 nrn TREE RETENTION EXHIBIT SCALE: 1 "=30' PREPARED_ BK TREE RETENTION EXHIBIT DONNA BRESKE & ASSOCIATES, LLC 21 AVE A, SUITE 4 TAX NO. 00431200000402 SIZE ADDRESS• 20114 83RD AW. W, SNOHOMISH, WA 98290 PROJECT PROPONENT RWER YOUNG EOMONDS, WA 98026-6727 PHONE: (425) 334-9980 DONNABRESKEOCOMCAST.NET ISSUE WE 2-5-2019 Figure 1-2.4.1 Flow Chart for Determining Requirements for New Development Start Here Does the site have 35% I Yes I See Redevelopment Minimum or more of existing Requirements and Flow Chart impervious coverage? (Figure 1-2.4.2). No Does the project convert %4 acres or more of vegetation to Does the project result in lawn or landscaped areas, or 5,000 square feet, or No convert 2.5 acres or more of greater, of new plus native vegetation to pasture? replaced hard surface �, area? No Yes es Does the project result in 2,000 square feet, or greater, of new plus All Minimum Requirements replaced hard surface area? apply to the new and replaced hard surfaces and converted YeS No vegetation areas. Does the project have land Minimum Requirements #1 disturbing activities of 7,000 through #5 apply to the new Yes square feet or greater? and replaced hard surfaces and the land disturbed. No IF Minimum Requirement #2 applies. Figure 1-2.4.1 Flow Chart for Determining Requirements for New Development DEPARTMENT OF Revised June 2015 ECOLOGY Please see http://www.ecy. wa.gov/copyright.html for copyright notice including permissions, State of Washington limitation of liability, and disclaimer. 2014 Stormwater Management Manual for Westem Washington Volume 1- Chapter 2 - Page 37 9 Edmonds Chapter 18.30 and 2014 Stormwater Management Manual for Western Washington 2.5.1 Minimum Requirement #1. Preparation of Stormwater Site Plans 3.1.1 Site Analysis: Volume 1, Section 3.1 Boundary Survey & Topography Map A survey conducted by Axis Mapping & Surveying was used to determine the site boundary and topography. Vegetation and Utility Infrastructure The site is grassy and has several existing trees with locations determined by the survey conducted by Axis Mapping & Surveying. Utility locations including existing stormwater, sewer, and overhead power were also provided by the survey and are shown on the plans. Soils Report An infiltration test was conducted by Conrad Elledge, a licensed on -site sewage disposal designer. Two holes were dug and used for the infiltration testing. The lowest long-term infiltration rate determined by Conrad was 5.64 in/hr. However, the city has requested calculations of design infiltration rates that apply the correction factors shown in Table B.1. Per the soils report, 6.6 in/hr was the lowest measured infiltration rate observed during the Small- scale PIT. The following values from Table B.1 were used in the calculation of the design infiltration rate: CF, = 1.0 (Two soil logs were taken that indicate consistent soil types found at the exploration depths) CFT =0.5 (Small-scale PIT) CFM =0.9 Ksataesign =6.6 in/hr * 1.0 * 0.5 * 0.9 Ksataesig„ =2.97 in/hr (Value used in WWHM2012) Site Analysis and Summary of Existing Conditions The site contains a single-family house, garage, an undeveloped concrete foundation and paved driving surface. A number of trees exist on site. The topography shows the site sloping naturally 25% +/-. The permeable ground surface appears to primarily consist of grass. No wetlands, or other critical areas exist on site or appear to be within the site's immediate vicinity. 10 B.2 Correction Factors The Ksat obtained from the field tests or soil grain analyses is a measured (initial) rate. This measured rate must be reduced through correction factors that are appropriate for the design situation to produce an acceptable design infiltration rate. This adjustment is made in Step 5 of the Design of Infiltration Facilities (SWMMWW Volume III, Section 3.3.4 Steps for the Design of Infiltration Facilities — Simplified Approach [also summarized in Addendum Checklist 6]). Note that the correction factors below may not apply to the infiltration testing conducted for bioretention, permeable pavement, and/or rain gardens (see Volume III, Section 3.4 and Addendum Checklist 5 for additional information). The following equation estimates the maximum design infiltration rate (Ksataesip) using correction factors to account for site variability, number of tests conducted, uncertainty of test method, and the potential for long-term clogging due to siltation and bio-build up. The specific correction factors used shall be determined based on the professional judgment of the site designer, considering all issues that may affect the infiltration rate over the long term, subject to the approval of the City. Ksatdesig„ = Ksat;n,t;al x CFv x CFT x CFM Table B.1. Correction Factors to be Used With In -Situ Saturated Hydraulic Conductivity Measurements to Estimate Design Rates. Issue Partial Correction Factor Site variability and number of locations tested (CF,) CF, = 0.33 to 1.0 Test Method (CFT) CFT: • Large-scale PIT ■ CFT = 0.75 for Large-scale PIT • Small-scale PIT ■ CFT = 0.5 for Small-scale PIT • Other small-scale (e.g., Double ring, falling head) • CFT = 0.4 for other small-scale test • Grain Size Method • CFT = 0.4 for Grain Size Method Degree of influent control to prevent siltation and bio-buildup CF. = 0.9 Site Variability and Number of Locations Tested (CFv): The number of locations tested must be capable of producing a picture of the subsurface conditions that fully represents the conditions throughout the facility site. The partial correction factor used for this issue depends on the level of uncertainty that adverse subsurface conditions may occur. If the range of uncertainty is low — — for example, conditions are known to be uniform through previous exploration and site geological factors — — one field test (or grain size analysis location) may be adequate to justify a partial correction factor at the high end of the range. If the level of uncertainty is high, a partial correction factor near the low end of the range may be appropriate. This might be the case where the site conditions are highly variable due to conditions such as a deposit of ancient landslide debris, or buried stream channels. In these cases, even with many explorations and several field tests (or several grain size test locations), the level of uncertainty may still be high. A partial correction factor near the low end of the range could be assigned where conditions have a more typical variability, but few explorations and only one field test (or one grain size analysis location) is conducted. That is, the number of explorations and tests conducted do not match the degree of site variability anticipated. 3.1.2 Preliminary Development Layout: Vol 1, Section 3.1.2 A development layout has been prepared that shows the proposed locations of residential structures, driving surfaces, drainage facilities, and BMPs. LID techniques are used to the maximum extent feasible given the proposed layout. 3.1.3 Off -Site Upstream and Downstream Analysis: Vol 1, Section 3.1.3 Upstream Analysis: Properties along 83rd Ave West seem to flow upstream through the city's stormwater conveyance system and then discharge into a creek crossing Pine Ridge Park down to where it intersects Main St and flows through continual storm lines down Pioneer Way to the corner of Shell Valley Road where it flows upwards through Yost Park into Shell creek. This flow continues, and discharges directly into the Puget Sound. The development of this project is not anticipated to have an effect on the upstream properties due to the implementation of on -site stormwater management and appropriate overflow direction into a proposed catch basin on 83rd Ave W. Runoff from this site is not anticipated to contribute significant runoff to any of the conveyance systems collecting runoff from the upstream areas because the on -site stormwater management BMPs have been design per the requirements of the 2014 DOE. Downstream Analysis: This project proposes to rout runoff into proposed bioretention facilities sized with WWHM2012. The calculations indicate that this project will infiltrate 100% of the runoff volume routed to the bioretention, and is not anticipated to contribute significant increases in runoff, or create drainage problems for downstream conveyance systems or properties. This project may improve the existing drainage conditions within the area by removing currently unmitigated surfaces, and replacing them with surfaces that will route runoff to an infiltration facility. 3.1.4 Determination of Applicable Minimum Requirements: Vol 1, Section 3.1.4 This project proposes greater than 5,000 square feet of hard surface and triggers the evaluation of minimum requirements 1-9. 3.1.5 Preparation of Permanent Stormwater Control Plan: Vol 1, Section 3.1.5 A permanent Stormwater Control Plan has been prepared with relevant elements shown on the drainage plan. Elements of the stormwater control plan include bioretention. 3.1.6 Preparation of Construction Stormwater Pollution Prevention Plan (SWPPP), Vol 1, Section 3.1.6 A construction stormwater pollution prevention plan has been included in this report with elements shown on the TESC plan. 3.1.7 Completion of Stormwater Site Plan, Vol. 1, Section 3.1.7 A stormwater site plan has been prepared showing the locations of all proposed drainage elements. 12 2.5.2 Minimum Requirement 42: Construction Stormwater Pollution Prevention SWPPP The construction stormwater pollution prevention plan has been included in this report. Relevant elements include temporary construction entrance, tree protection, silt fences, and straw wattles. 2.5.3 Minimum Requirement #3: Source Control of Pollution Source control of pollutants will be satisfied with the implementation of appropriate stormwater pollution prevention BMPs. Elements of source control are indicated on the site plans and in the S w"PPP narrative. 2.5.4 Minimum Requirement #4: Preservation of Natural Drainage Systems and Outfalls The site's topography indicates that natural drainage occurs as surface runoff flowing west to east, dispersing, infiltrating, and being collected by the conveyance system in 83rd Ave W. This project proposes that the site's runoff will be routed to a proposed bioretention facility and is not anticipated to have a significant or negative impact on the downstream drainage systems. 2.5.5 Minimum Requirement #5: On Site Stormwater Management This project proposes greater than 5,000 sf of impervious surface and therefore must either demonstrate compliance with the low impact development performance standard, or select BMPs from List #2. This project will propose to select BMPs from List #2 to meet this requirement. Rooftops Full Dispersion is infeasible due to the lack of preserved native vegetation and lack of available flow path space. Infiltration per BMP T5.10A: Full Downspout Infiltration is infeasible due to lack of available space required for an infiltration trench system. The proposed house rooftop area will be routed to a proposed bioretention facility that is anticipated to infiltrate 100% of all rooftop runoff. This has been sized with WWHM2012. Other Hard Surfaces Full dispersion is infeasible due to the lack of flow path space, and preserved vegetation. Permeable pavement is infeasible due the proposed driveway slopes, and their close proximity to steep slopes. The proposed driving surface will be routed to the proposed bioretention facility to the maximum extent feasible. The bioretention has been sized to infiltrate 100% of the proposed driving surface runoff however, a portion of the runoff must bypass the facility due to a combination of grading constraints, and the existing IE of the stormwater system within 83rd Ave W. 13 Bypass Area The proposed bioretention facility has been conservatively sized to infiltrate 100% of the driving surface runoff, however a 295 sf portion will bypass the facility. The WWHM2012 calculations indicate that the 100 year flow rate from the bypass area contributes 0.005 cfs, and is therefore not anticipated to have an adverse effect on the downstream conveyance system. W WHM2012 Calculation Discussion The bioretention has been conservatively sized to infiltrate 100% of the runoff volumes from all proposed impervious surfaces, and converted vegetated areas on -site. The landscaped areas have been modeled as pasture with A/B soil type, as BMP T5.13 will be applied to all disturbed areas of the site not to be covered by impervious surfaces. The bypass area has been modeled as -well to demonstrate that the low runoff rates from a 100 year storm event are not anticpated to create a problem for downstream conveyance systems or properties. 2.5.6 Minimum Requirement #6: Runoff Treatment This project proposes less than 5,000 square feet of pollution generating hard surface and does not trigger this requirement. 2.5.7 Minimum Requirement #7. Flow Control This project proposes less than 10,000 square feet of hard surfaces and does not trigger the requirement for flow control. Runoff from the site is proposed to be infiltrated through a bioretention facility. 2.5.8 Minimum Requirement #8: Wetlands Protection N/A- This project does not contain wetlands, and does not appear to be within the vicinity of a wetland. 2.5.9 Minimum Requirement #9: Operation and Maintenance An operations and maintenance section has been included in appendix D of this report. 14 Stormwater Pollution Prevention Plan Narrative A Stormwater Pollution Prevention Plan (SWPPP) has been prepared as part of the construction Stormwater permit requirements. The site is 0.45 acres in size and is located at 20114 83rd Ave. W, Edmonds, WA 98020-6727, with tax parcel number 0043200000402. A new asphalt driving surface and two single family homes are proposed to be constructed. The limits of disturbance will be 16,877 SF with more than 5,000 sf of impervious surface triggering minimum requirements #1-9. The purpose of the SWPPP is to describe all temporary and permanent erosion and sediment control (TESC) measures, pollution prevention measures, inspection/monitoring activities, and recordkeeping that will be implemented during the proposed project. This narrative is to be considered a "living document." This project's Certified Erosion and Sediment Control Specialist is to amend this document as needed during construction. Applications of these elements are shown on the TESC Plan Sheet. The specific elements included in the SWPPP are: Element #1: Mark Clearing Limits Prior to the beginning of land disturbing activities, the clearing limits are defined on the TESC plan. Applicable BMP's for this project are: ■ BMP C233 - Silt Fence ■ BMP C103 - High Visibility Fence Element #2 — Establish Construction Access The existing gravel driveway will be used as a temporary construction entrance. Element #3 — Control Flow Rates Applicable BMP's are shown on the TESC Plan and include: • BMP C120-Temporary or Permanent Seeding • BMP C233 - Silt Fence Element #4 — Install Sediment Controls Specific controls include: ■ Temporary or Permanent Seeding (BMP C120) • BMP C233 - Silt Fence 15 Element #5 — Stabilize Soils Areas that are to remain uncovered for more than 7 days, are to be stabilized with BMPs. Specific BMP's to be implemented include Temporary and Permanent Seeding (BMP C120), Mulching (BMP C121), and Plastic Covering (BMP C123). Element #6 — Protect Slopes Cut and fill slopes shall be protected as necessary through use of Temporary and Permanent Seeding (BMP C120), Mulching (BMP C121), and Plastic Covering (BMP C123). Element #7 — Protect Drain Inlets Inlet protection will be utilized on catch basins down gradient and in the vicinity of the disturbed areas. i BMP C220: Storm Drain Inlet Protection Element #8 — Stabilize Channels and Outlets Silt fence will be installed at the lower end of the site and will be used to control runoff flows, it is not anticipated that any flows of significant velocity will leave the site or cause any negative impact to the downstream residential and commercial areas. Element #9 — Control Pollutants All pollutants, including waste materials and demolition debris, that occur onsite shall be handled and disposed of in a manner that does not cause contamination of stormwater. Good housekeeping and preventative measures will be taken to ensure that the site will be kept clean, well -organized, and free of debris. ■ BMP C 153-Material Storage, Delivery, and Containment Element #10 — Control Dewatering No de -watering is anticipated for this project. N Element #11— Maintain BMPs All temporary and permanent erosion and sediment control BMPs shall be maintained and repaired as needed to assure continued performance of their intended function. Maintenance and repair shall be conducted in accordance with each particular BMP's specifications. Visual monitoring of the BMPs will be conducted at least once every calendar week and within 24 hours of any rainfall event that causes a discharge from the site. If the site becomes inactive, and is temporarily stabilized, the inspection frequency will be reduced to once every month. All temporary erosion and sediment control BMPs shall be removed within 30 days after the final site stabilization is achieved or after the temporary BMPs are no longer needed. Trapped sediment shall be removed or stabilized on site. Disturbed soil resulting from removal of BMPs or vegetation shall be permanently stabilized. Element #12 — Manage the Project Erosion and sediment control BMPs for this project have been designed based on the following principles: • Design the project to fit the existing topography, soils, and drainage patterns. • Emphasize erosion control rather than sediment control. ■ Minimize the extent and duration of the area exposed. ■ Keep runoff velocities low. ■ Retain sediment on site. ■ Thoroughly monitor site and maintain all ESC measures. • Schedule major earthwork during the dry season. Element #13 — Protection of Lid BMP's During the life of the Ryker project all proposed BMP's on -site shall fully comply with the DOE's and City of Edmonds regulations for Element #13. Stormwater runoff from construction activities is not to enter the proposed bioretention shown on the plans. Heavy equipment should not travel over and compact the native soils within the location of the bioretention. 17 Appendix A Drainage Inventory Map 18 a 812 •r•w [11 w+ I1 • arlw S eur u4 a�ro '+.r zuU's6 [ _ 8i ^"' -G3:' 851 CAS! is, B11 B10 817 Ol _i_gi �00 ,3D7p{ -J o 747 750 92/1 9111 20105 j 20101 2011d 20121 8711 - 20110t\ 20110 m o BO1 B00 B01 m 20111 S1f 93ao1i 1j1 g �l.W0 4�10}3i1 737 7+611i5 6�7114fiB 202-tz0 ozo2 f 9123020 17zo2103�2o 1� 20125 i2t01 e'�6P2ZD69f3 20112 —30 c� a7BU�4 711 7806 114 20208 202ae 86 20223 20214 9021 04 20213 960 0 B21 fi22 ry 1130 701 — ; �f 20216 ZD0f7?Q36� I mfS� 20307 qT � 0 1140 fi02 j� .. � 20226 � �i I '$ 20223 a iDI�7 ty ^ +•��'+�f� 9 �ry'�%N' ! e0s 580 '—{� 2031t '9022�; aRi7a 3 615 12 20227 aali 20302 20231 iGlel see 'P A ` I (Y .. j 1 203 j � a' .� ' 612 11 ray 561 so 5I h �y ! 20301 ,0,77..�� ,m 20302 �9 0` --r��T'� 1 7117p{ �iWGi 2DiTa 3y7 ,1p2�'k A 'y1g n OC.E1d 57 520 �R1 ' 1476 540 I 22f 31i yQ11 1' 1 1 xOtiT &tRD P♦_ r n 511 v w � � Se• } � � a15 7 gg If12f a2/T STQ9 b 20312 pp ^ y �9120 ea15 1 iS�� 0 520 9210 912E L P--� 1516 f116 1 510 ' 20322 20317 20320 �1A�m 20412 `8 20417 30i06 De20W41Ai $1� to �22 431 42e � :A 27 20414 _ pPi3, 2a+7i � d• ■ 1g o o� o I a j 412 s t > > /f�� �8 20425 ^ 2WSi 30ii6 i1 20420 ■ 1Nal�+ 2'1 o 10f7 7faf4. ice, P Icy 1 7E - _ 613 404 "t _ 20505 I ram+ 20427 20429 m 3 i� i ' "�"� OM21 402 7� ,� 20429 3T w 20501 20500 20501 T 346 1 I �2a5Aa - �i� SOf1 iee,1 ycp4 LX 341 f 1s I [ 20505 20508 o ±- — 70503 20512 7feS1x .�jr p !T2 tail,74l1 206f]r 47 i�T N fC' g �1 336 i 17fj -•7 . 321 fiQ6 _ _ k. e 0 311 320 312 310 .���,� a m m y5a7 J 20584 20520 !.t x f� �k1 4ia 6tYDygp a 13 0 311 m !4N! 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Olin T Designate as Bypass for POD Surface Interflow firoundwater Facility Name B,~-�:1 Outlet 1 Outlet 2 Outlet 3 Downstream Connection 9 0 Facility Type Biecowkinswde iG Use simple Bioretention _ QuickSwele __ Size Water Quality SizeFacilitd I Ir Underdrain Used Bioretention Bottom Elevatior 0-`.-�--„ aioretenlion Dimensions Flow Through Underdrain [ec-ft) 0 BiaeteLengthTotal Outflow [acft) Bifnaer4ed" nfiniteeryidhlft] S.t►ii Freeboard (ft) 0.'S06 WQ Percent Filtered 100 OveraoadFlooding (fil .BOQ Facility Dimension Diagram Effective Total Depth(ft) IF;pj w f I RDD � - _-H 8ouam slope of bivelention 01 Riser Outlet Structure Sidewall Invert Location Outlet Structure Data FxOri and Back side slope (HN] Riser Height Above bioretention suilace (It) S (;t'fVAF11O$ � Raderalaped �Mt19+fad Flows To: SaxEace reSerdidri:l aee tdlRltien 1 Area in Basin r- ShowOnlySeleded Available Pervious Acres Available Impervious Acres CAM- FerwLFiat I r ROADS/FLAT r; FGfEN._M7tf r ROADS/MOD � A/B. e 0 P ROADS/STEEP pu j-►l1B-Pathae, Flel r ROOFTOFS/FIAT tt3 A18.Pa*&a.Mod DRIVEWAYS/FLAT O a r �Y+lB.Paatue.5tae.� r DRIVEWAYS/MOD 0 � DRIVEWAYS%STEEP �r J' PJB_Lawn. Mod T SIDEWALKS/FLAT Al �"' p�$,t,yrin $tegp� r SIDEWALKS/MOD f crwadL Flat r SIDEWALKS/STEEP fl Run Scenario Beeie Elmrnrts ®®®® I®�a® f ®� Pro Elements ®® r C. FceosL Mod r PARKIf1G/FL.4T i Foma. $feep - r PARKING/MOD L� Left Side Slope(HN) Riser Diameter [in) 12 Riyk Side Slope IHN) Riser Type Fyt -_] P311E� I. Pa=bra,mt r PARKING/STEEP B _ f C PashFe- Ti� F_ PUN - _ R Material Layers for Layer 1 Layer 2 Layer 3 r C,Pasttae,Steep r PbtowPavement 0 Deph(ftl FLQKJED t.500 r C, Lawn, Flat D Sd Layer 1 f.15TM 1ltB I L. La 1m cd Sd Layer 2 rs_W_WT2in(hr Orifice Diameter Height Commercial Toolbox — -I Ir lr CLsv Steen _ l ]A=. Fppyr_ Tat _ If_ EAT. Foram -� -:JrU Faast.5 SW Layer Number (in) (tt) BPA9L Etkt Sud Types 1 lu lu J _._ ._,._- 2 � -r YSaSSflfelyFador - 3 r None r 2 A' 4 Show Bioretention oven Table - Move Elements �. I _ Bioretention Volume al Riser Head (acft) 039 - Native Infiltration 1'es -J Tda[Volume Infiltrated lac-ftl 70.349 Save x,y l Load x.y I----� Pervious Total 0.273 Acres Impervious Total l77 Acres Basin Total ®Acres Measured Infiltration Rate (in/hr1 J Total Volume Through Riser (ac-kl 0.002 2.97 - r Reduclion Factor linfil'actorl F—J TotalVolume Though Facldy(acft) 71,111 1J: Wetted Surface Area lsidewalls) Yes Percent lnfilhated 100 P ecip lation on Facility (acre -It) 3403 Y ��f Wed11:10. Rykerl2-13-18-FawhMiiigeted,• _ DeselectZeroo SelectBY=f•_.7 GO � Evaporation from Facility (acre -It) 1.323 N • Basin 2 Wiifigated RP SCENARIOS Subbasin Name: jBasinn2 r Designate as Bypass for POC: Surface Interflow Groundwater Flows To = _ I ram•*� � Bmin 2 ❑ Predevefaped ®� Alitigaldd Area in Basin r Show Only Selected Available Pervious Acres Available Im prvia Acres r'418-raesLFld I7 r IMS)FiAT 0� r WB:FtreU r ROADSRt00 j r ;Forad tt,Gan I7 ro RQADS67EEP 005 006 r61,PeliWaMo r ADOFWASIFLRT �l r pJB, Peuute, Mod I) r Ai4EWAYSIFIAT � r;] r VS. Pasture, S" p r DRIVEwAysmoD D Run Scenario Basic Elements 1 ®®®®_ 1` YI it No. LervLFfei 1 r AR EWAYS)SiE P o r AM. LWOL Mod o r roNARsiFLAr 7 o I Pro Elements r 7W Laren, Steep D r StOEWALKS MDD t1 r C.FoieaLFW � r SIDEWALx5rSTEEP i] Fn ® RE- r Forod. Modd r PARMNGr7T,AT (1 j r-C. FnreaL Sleep r PARYJNGRACID 0 ' r C,Qdl1. Flat D j' PpA NGISTEEP D ----- r C. Pasture, Mod I7 r PDND i7 j C. Yauue, Steep r Porous P0v_emera_ — f) i r C.Lawn.Flet D r C. LaW Mod O Commercial T oobox rCLewn.5l6ev D r SAT, ForeN. Fiat r SAT. FOlea. Med D -n r SAT, Irmo. Sim Mara Eleffa is IM Save x,y Load x,y Pervious Total Acres Impervious Total® Acres Basin Total Acres Deselect Zero Select ByF- GO WarTl):10e•Rykeel2.13•ig•Frnsh#1Ripeted _ Flow Frequency Flow ( cfs ) Predeve locked 2 Year = 0.0001 5 Year = 0.0001 10 Year = 0.0001 ,25 Year = 0.0001 50 Year = 0.0001 100 Year = 0.0002 M.1 t1•gated 0.0017 0.0023 0.0028 0.0036 0.0043 0.0050 4 24 WWHM2012 PROJECT REPORT Project Name: Ryker 1-30-19 Site Name: Site Address: City Report Date: 1/30/2019 MGS Regoin : Puget East Data Start : 1901/10/1 Data End : 2058/09/30 DOT Data Number: 03 Version Date: 2016/02/25 Version : 4.2.12 Low Flow Threshold for POC 1 : 50 Percent of the 2 Year High Flow Threshold for POC 1: 50 year PREDEVELOPED LAND USE MITIGATED LAND USE Name : Basin 1 Bypass: No Groundwater: No Pervious Land Use acre A B, Pasture, Mod .273 Pervious Total 0.273 Impervious Land Use acre ROADS STEEP 0.044 ROOF TOPS FLAT 0.123 SIDEWALKS FLAT 0.01 Impervious Total 0.177 Basin Total 0.45 Element Flows To: Surface Interflow Surface retention 1 Surface retention 1 Name : Bioretention 1 Bottom Length: 7.00 ft. Groundwater 25 Bottom Width: 5.00 ft. Material thickness of first layer: 0.25 Material type for first layer: ASTM 100 Material thickness of second layer: 1.5 Material type for second layer: SMMWW 12 in/hr Material thickness of third layer: 1.5 Material type for third layer: GRAVEL Infiltration On Infiltration rate: 2.97 Infiltration safety factor: 1 Wetted surface area On Total Volume Infiltrated (ac-ft.): 70.349 Total Volume Through Riser (ac-ft.): 0.002 Total Volume Through Facility (ac-ft.): 70.351 Percent Infiltrated: 100 Total Precip Applied to Facility: 3.483 Total Evap From Facility: 1.323 Underdrain not used Discharge Structure Riser Height: 1 ft. Riser Diameter: 12 in. Element Flows To: Outlet 1 Outlet 2 Bioretention 1 Hydraulic Table Sta e(feet Area ac. Volume(ac-ft.) Dischar e(cfs) lnfilt(.nfs) 0.0000 0.0149 0.0000 0.0000 0.0000 0.0522 0.0148 0.0000 0.0000 0.0000 0.1044 0.0144 0.0000 0.0000 0.0000 0.1566 0.0141 0.0001 0.0000 0.0000 0.2088 0.0137 0.0001 0.0000 0.0000 0.2610 0.0134 0.0001 0.0000 0.0000 0.3132 0.0130 0.0002 0.0000 0.0000 0.3654 0.0127 0.0002 0.0000 0.0000 0.4176 0.0124 0.0002 0.0000 0.0001 0.4698 0.0120 0.0003 0.0000 0.0001 0.5220 0.0117 0.0003 0.0000 0.0002 0.5742 0.0114 0.0004 0.0000 0.0003 0.6264 0.0111 0.0004 0.0000 0.0004 0.6786 0.0107 0.0005 0.0000 0.0005 0.7308 0.0104 0.0005 0.0000 0.0006 0.7830 0.0101 0.0006 0.0000 0.0007 0.8352 0.0098 0.0007 0.0000 0.0010 0.8874 0.0095 0.0007 0.0000 0.0012 0.9396 0.0092 0.0008 0.0000 0.0016 0.9918 0.0090 0.0009 0.0000 0.0019 1.0440 0.0087 0.0009 0.0000 0.0021 1.0962 0.0084 0.0010 0.0000 0.0022 1.1484 0.0081 0.0011 0.0000 0.0027 1.2005 0.0079 0.0012 0.0000 0.0033 1.2527 0.0076 0.0013 0.0000 0.0039 1.3049 0.0073 0.0014 0.0000 0.0047 26 1.3571 0.0071 0.0015 0.0000 0.0051 1.4093 0.0068 0.0016 0.0000 0.0059 1.4615 0.0066 0.0017 0.0000 0.0069 1.5137 0.0063 0.0019 0.0000 0.0081 1.5659 0.0061 0.0020 0.0000 0.0094 1.6181 0.0059 0.0021 0.0000 0.0106 1.6703 0.0056 0.0023 0.0000 0.0114 1.7225 0.0054 0.0024 0.0000 0.0131 1.7747 0.0052 0.0025 0.0000 0.0150 1.8269 0.0050 0.0027 0.0000 0.0171 1.8791 0.0048 0.vv^28 C.CCOC C.0194 1.9313 0.0046 0.0030 0.0000 0.0212 1.9835 0.0044 0.0031 0.0000 0.0220 2.0357 0.0042 0.0033 0.0000 0.0227 2.0879 0.0040 0.0035 0.0000 0.0235 2.1401 0.0038 0.0036 0.0000 0.0243 2.1923 0.0036 0.0038 0.0000 0.0252 2.2445 0.0034 0.0040 0.0000 0.0260 2.2967 0.0033 0.0042 0.0000 0.0268 2.3489 0.0031 0.0044 0.0000 0.0277 2.4011 0.0029 0.0046 0.0000 0.0286 2.4533 0.0028 0.0048 0.0000 0.0294 2.5055 0.0026 0.0050 0.0000 0.0303 2.5577 0.0025 0.0052 0.0000 0.0313 2.6099 0.0023 0.0055 0.0000 0.0322 2.6621 0.0022 0.0057 0.0000 0.0331 2.7143 0.0020 0.0060 0.0000 0.0341 2.7665 0.0019 0.0062 0.0000 0.0350 2.8187 0.0018 0.0065 0.0000 0.0360 2.8709 0.0016 0.0067 0.0000 0.0370 2.9231 0.0015 0.0070 0.0000 0.0380 2.9753 0.0014 0.0073 0.0000 0.0390 3.0275 0.0013 0.0076 0.0000 0.0401 3.0797 0.0012 0.0079 0.0000 0.0411 3.1319 0.0011 0.0082 0.0000 0.0422 3.1841 0.0010 0.0085 0.0000 0.0433 3.2363 0.0009 0.0088 0.0000 0.0443 3.2500 0.0008 0.0089 0.0000 0.0446 Surface retention 1 Hydraulic Table Stage(feet) Area(ac.) Volume(ac-£t.) Discharge(cfs) To Amended.(c£s) Wetted Surface . 3.2500 0.0149 0.0089 0.0000 0.0100 0.0011 3.3022 0.0153 0.0097 0.0000 0.0100 0.0022 3.3544 0.0156 0.0105 0.0000 0.0103 0.0034 3.4066 0.0160 0.0113 0.0000 0.0106 0.0045 3.4588 0.0164 0.0121 0.0000 0.0109 0.0057 3.5110 0.0168 0.0130 0.0000 0.0112 0.0068 3.5632 0.0172 0.0139 0.0000 0.0115 0.0080 3.6154 0.0176 0.0148 0.0000 0.0118 0.0092 3.6676 0.0180 0.0157 0.0000 0.0120 0.0104 3.7198 0.0184 0.0167 0.0000 0.0123 0.0117 3.7720 0.0188 0.0176 0.0000 0.0126 0.0129 3.8242 0.0192 0.0186 0.0000 0.0129 0.0141 3.8764 0.0196 0.0196 0.0000 0.0132 0.0154 3.9286 0.0201 0.0207 0.0000 0.0135 0.0167 3.9808 0.0205 0.0217 0.0000 0.0138 0.0180 4.0330 0.0209 0.0228 0.0000 0.0141 0.0193 27 4.0852 0.0213 0.0239 0.0000 0.0144 0.0206 4.1374 0.0218 0.0250 0.0000 0.0147 0.0220 4.1896 0.0222 0.0262 0.0000 0.0149 0.0233 4.2418 0.0227 0.0274 0.0000 0.0152 0.0247 4.2940 0.0231 0.0286 0.0977 0.0155 0.0260 4.3462 a.0236 0.0298 0.3147 0.0158 0.0274 4.3984 0.0241 0.0310 0.5952 0.0161 0.0288 4.4505 0.0245 0.0323 0.9111 0.0164 0.0302 4.5027 0.0250 0.0336 1.2343 0.0167 0.0317 4.5549 0.0255 0.0349 1.5367 0.0170 0.0331 4.6071 0.0260 0.0362 1.7939 0.0173 0.0346 4.6593 0.0264 0.0376 1.9905 0.0176 0.0360 4.7115 0.0269 0.0390 2.1274 0.0178 0.0371 4.7500 0.0273 0.0401 2.2575 0.0181 0.0198 Name : Surface retention 1 Element Flows To: Outlet 1 Outlet 2 Bioretention 1 Name . Basin 2 Bypass: Yes Groundwater: No Pervious Land Use acre Pervious Total 0 Impervious Land Use acre ROADS STEEP 0.006 Impervious Total 0.006 Basin Total 0.006 Element Flows To: Surface Interflow Groundwater ANALYSIS RESULTS POC #1 was not reported because POC must exist in both scenarios and both scenarios must have been run.Perind and Impind Changes No changes have been made. 28 This program and accompanying documentation are provided 'as -is' without warranty of any kind. The entire risk regarding the performance and results of this program is assumed by End User. Clear Creek Solutions Inc. and the governmental licensee or sublicensees disclaim all warranties, either expressed or implied, including but not limited to implied warranties of program and accompanying documentation. In no event shall Clear Creek Solutions Inc. be liable for any damages whatsoever (including without limitation to damages for loss of business profits, loss of business information, business interruption, and the like) arising out of the use of, or inability to use this program even if Clear Creek Solutions Inc. or their authorized representatives have been advised of the possibility of such damages. Software Copyright © by : Clear Creek Solutions, Inc. 2005-2019; All Rights Reserved. 29 Appendix C Infiltration Test Pit Rates 30 DRAINFIELD DESIGNS P. O. Box 164 Lk. Stevens, WA 98258-0164 (425)246.0734 Ryker Young Real Property Funding Group LLC 7500 Roosevelt Way NE Seattle, WA 98115 Dated 9/153/18 Soils Infiltration Report Site Location: "20114-83`d Ave W." Edmonds Tax Acct. #0043200000402 Lots 1 & 2 Dear Ryker, This letter is to provide results of the investigation requested by you for the above referenced property. The purpose of this study was to estimate the infiltrative capacity of soils in the area of the proposed Rain Garden intended to handle storm waters generated on the subject property. SUMMARY Lot 1 Infiltration Rate =8.06 inches per hour --short term rate; 5.64 inches per hour—long, term rate Depth to Estimated Seasonal High Ground water=94" Soils classified as Gray and Brown Medium and Coarse Gravelly Sands based United States Dept. of Agriculture(USDA) Page 1 of 4 31 Lot 2 Infiltration Rate =9.09 inches per hour --short term rate; 6.36 inches per hour --long term rate Depth to Estimated Seasonal High Ground water=96" Soils classified as Gray and Brown Medium and Coarse Gravelly Sands based United States Dept. of Agriculture(USDA) METHOD AND DETAIL The method used for this analysis is provided in the Department of Ecology Stormwater Management Manual for Western Washington(June, 2016) for "Small Scale Pilot Infiltration Test". This testing was conducted throughout the day on the 5th of July, 2018. In accordance with this method, two types of infiltration testing were applied to a single test pit for each lot with a bottom dimension of 22" by 6.7 feet giving a total bottom area of 12.28 square feet for Lot 1 a bottom dimension of 22" by 7 feet giving a total bottom area of 12.83 square feet for Lot 2. Test depth of each pit was 42" below ground level as determined in conversations with your engineer and which comprises the bottom of the proposed facility. The morning following the infiltration testing, the test pit was over excavated to a depth of 103" (inches) for Lot 1 and 101"(inches) for Lot 2 and further observation made regarding soils and the impact of the infiltration testing. The infiltration testing was preceeded by a 6 hour soaking period during which a V level was maintained in the test pit by adding waters as necessary. After stabilization, water was applied at rate of 1.76 GPM for Lot 1 and 3.0 GPM for Lot 2 to maintain the static test level. The first infiltration test taken at the end of the pre-soak period involved applying waters so as to establish and maintain a 1 foot static level in the test pit and then measuring waters applied to achieve a gallons per minute rate of waters infiltrating into the soils in the test pit over a I hour time period. That rate was 1.76 gal./min. for Lot 1 and 3.0 GPM for Lot 2. The second infiltration test measured the falling static level of the water in the test pit at the conclusion of the first infiltration test until the test pit was empty. Measurements were taken on a measuring rod in the test pit to establish the rate Page 2 of 4 32 of fall in inches per hour. The rate of 7.44 inches/hour for Lot 1 and 6.6 inches /'hour for Lot 2. The lower extent of the test profile was slightly slower due to the formation of finer soils accumulating in the bottom of the pit in the course of the procedure. After both infiltration measurements were taken the test pit was left covered overnight and overexcavated the next morning to obtain a log of deeper soils in the area of the proposed facility and to assess the impact of the hydraulic loading from the soaking period and the application of infiltration waters. The soil log is attached. There was no static level of groundwater in either soil log. This report was prepared in accordance with generally accepted standards and practices. No other warranty is expressed or implied. Unanticipated soil conditions are commonly encountered and cannot be full determined by soil sampling and text explorations. Such unexpected conditions frequently require that additional expenditures be made to attain a properly constructed project. Therefore, a contingency fund is recommended to accommodate such potential extra costs. Thank you for your business and let me know if anything further is required. Very truly yours, Conrad C. Elledge Washington State Certified Designer #5100169 Snohomish County Installer #I2200 King County Installer #M-123 CCE:bto cc:file; Donna Breske, P.E. Page 3 of 4 -a• y wAt f,J*rj{[ gtie0ti�� 4r 33 SOIL DATA: 7/5/18 and 7/6/18 Soil Log 1(Test Pit) Lot 1 0-12" Gravels and subbase material existing drive 12-24" Gray Loamy Sand 24-52" Red/Brown Medium Loamy Sand; some gravel 52-103"+ Gray coarse sand some gravel; small rock Roots to 96" Located infiltration area shown on site plan NE corner Soil Log 2 0-30" Light Brown Loamy Sand 30-36" Brown Loamy Coarse Sand; dense roots 36- 101" Red/Brown/Gray Medium/Coarse Sand; Roots 91" Located infiltration area shown on site plan SE corner Page 4 of 4 34 Appendix D Operations and Maintenance 35 Table V-4.5.2(20) Maintenance Standards - Compost Amended Vegetated Filter Strip (CAVFS) (continued) Maintenance Component Defect Conditions When Main- tenance is Needed Results Expected When Maintenance I is Performed For ruts or bare areas less than 12 inches wide, repair the damaged area by ,Areas have filling with a 50/50 mixture of crushed eroded or gravel and compost. The grass will Erosion/scouring scoured due creep in over the rock in time. If bare to flow chan- areas are large, generally greater than nelization or 12 inches wide, the vegetated filter strip high flows. should be regraded and reseeded. For smaller bare areas, overseed when bare spots are evident. Flow spreader is uneven or clogged so Level the spreader and clean so that Flow spreader that flows are flows are spread evenly over entire filter not uniformly width distributed over entire fil- ter width. Table V-4.5.2(21) Maintenance Standards - Bioretentiion Facilities Recommended Fre- Condition quency, when Main - Maintenance a Action Needed (Pro - Component tenance is cedures) p Routine Main -Needed (Stand - Inspection tenance ards) Facility Footprint Earthen side slopes and B, S berms . Eliminate cause of Erosion (gullies/ erosion and stabilize rills) greater damaged area than 2 inches (regrade, rock, veget deep around ation, erosion control inlets, outlet, matting) and alongside . For deep channels slopes or cuts (over 3 inches in ponding 2014 Stormwater Management Manual for Western Washington Volume V - Chapter 4 - Page 862 36 Table V-4.5.2(21) Maintenance Standards - Bioretention Facilities (continued) Recommended Fre- Condition Maintenance quency a when Main - tenance is Action Needed (Pro - Routine Main- Component p Needed (Stand- cedures) Inspection tenance ards) depth), temporary erosion control meas ures should be put in place until per- manent repairs can be made. . Properly designed, constructed and established facilities with appropriate flow velocities should not have erosion prob- lems except perhaps in extreme events. If erosion problems persist, the following should be reas- sessed: (1) flow volumes from con- tributing areas and bioretention facility sizing; (2) flow velo- cities and gradients within the facility; and (3) flow dis- sipation and erosion protection strategies at the facility inlet. Erosion of sides Take actions to eliminate A causes slope to the hazard and stabilize become a haz- slopes a rd A, S Settlement greater than 3 Restore to design height 2014 Stormwater Management Manual for Western Washington Volume V - Chapter 4 - Page 863 37 Table V-4.5.2(21) Maintenance Standards - Bioretention Facilities (continued) Recommended Fre- Condition Maintenance uenc q Y a when Main - Action Needed (Pro - Component p tenance is (Stand- cedures) Routine Main -Needed Inspection tenance ards) inches (relative to undisturbed sections of berm) Downstream Plug any holes and com- face of berm pact berm (may require A, S consultation with engin- wet, seeps or eer, particularly for larger leaks evident berms) . Eradicate rodents (see "Pest control") .Any evidence of Fill holes and com- A rodent holes or pact (may require water piping in consultation with berm engineer, par- ticularly for larger berms) Cracks or failure - Repair/ seal cracks Concrete side- A of concrete side- - Replace if repair is walls walls insufficient Stabilize rockery side - Rockery side walls (may require con - Rockery side- A walls are insec- sultation with engineer, ,walls ure particularly for walls 4 feet or greater in height) All main - Facility area tenance visits Trash and Clean out trash and debris (at least bian- debris present nually) Accumulated Remove excess sed- Facility bottom S sediment to iment area A extent that infiIt- Replace any veget- ration rate is ation damaged or 2014 Stormwater Management Manual for Westem Washington Volume V - Chapter 4 - Page 864 38 Table V-4.5o2(21) Maintenance Standards - Bioretention Facilities (continued) Recommended Fre- Condition Maintenance uenc q Y a when Main - tenance is Action Needed (Pro - Routine Main- Component p Needed (Stand- cedures ) Inspection tenance ards) destroyed by sed- iment accumulation and removal . Mulch newly planted vegetation reduced (see "Ponded water") • Identify and control or surface stor- the sediment source age capacity sig (if feasible) nificantly • If accumulated sed- impacted iment is recurrent, consider adding pre - settlement or installing berms to create a forebay at the inlet Remove leaves if there is During/after Accumulated a risk to clogging outlet fall leaf drop leaves in facility structure or water flow is impeded Sediment, veget ation, or debris accumulated at or blocking (or ,A, S having the Clear the blockage Low per- potential to meability block) check check dams 'dam, flow con - and weirs 'trot weir or ori- fice Erosion and/or Repair and take pre - A, S undercutting ventative measures to pre - present vent future erosion and/or undercutting 2014 Stormwater Management Manual for Western Washington Volume V - Chapter - Page 865 39 Table V-4.5.2(21) Maintenance Standards - Bioretention Facilities (continued) Recommended Fre- uenc Maintenance; q Y a Component p Routine Main -Needed Inspection � tenance Condition when Main - (Stand- ards) Action Needed (Pro - ) _ f Grade board or A top of weir dam- Restore to level position aged or not level Determine cause and resolve in the following order: 1. Confirm leaf or debris buildup in the bottom of the facility is not impeding infilt- ration. If necessary, remove leaf lit - Excessive pond ter/debris. ing water: Water 2. Ensure that under - overflows during drain (if present) is storms smaller not clogged. If neces than the design sary, clear under- Ponded water B, S event or ponded drain. water remains in 3. Check for other the basin 48 water inputs (e.g., hours or longer groundwater, illicit after the end of connections). a storm. 4. Verify that the facility is sized appro- priately for the con- tributing area. Confirm that the con- tributing area has not increased. If steps #14 do not solve the problem, 2014 Stormwater Management Manual for Western Washington Volume V - Chapter 4 - Page 866 40 Table V-4.5.2(21) Maintenance Standards - Bioretention Facilities (continued) Recommended Fre- Condition Maintenance uenc q y a � � c when Main - Action Needed (Pro - Component p tenance is (Stand- cedures ) Routine Main -Needed Inspection tenance ards) the bioretention soil is likely clogged by sediment accu- mulation at the sur- face or has become overly compacted. Dig a small hole to observe soil profile and identify com- paction depth or clog ging front to help determine the soil depth to be removed or otherwise rehab- ilitated (e.g., tilled). Consultation with an engineer is recom- mended. Minimize all loading in the facility foot- print (foot traffic and other loads) to the Bioretention soil degree feasible in media pro- order to prevent com- tection is paction of biore- Bioretention needed when tention soils. soil media As needed performing main . Never drive equip- tenance requir- ment or apply heavy ing entrance loads in facility foot - into the facility print. footprint . Because the risk of compaction is higher during saturated soil 2014 Stormwater Management Manual for Western Washington Volume V - Chapter 4 - Page 867 41 Table V-4.5.2(21) Maintenance Standards - Bioretention Facilities (continued) Recommended Fre- Condition uenc when Main - Maintenance ' q y a � Action Needed (Pro- Com Component � tenance is cedures p Routine Main- Needed (Stand- ) Inspection tenance ards) conditions, any type of loading in the cell (including foot traffic) should be minimized during wet con- ditions. a€¢ Con- sider measures to distribute loading if heavy foot traffic is required or equip- ment must be placed in facility. As an example, boards may be placed across soil to dis- tribute loads and min imize compaction. a€¢ If compaction occurs, soil must be loosened or oth- erwise rehabilitated to original design state. Inlets/Outlets/Pipes Water is not being directed Reconfigure/ repair blocks Splash block A properly to the to direct water to facility inlet facility and and away from structure .away from the inlet structure M during the Accumulated Clear leaves (particularly Curb cut wet season Weekly during leaves at curb important for key inlets inlet/outlet and before fall leaf drop cuts and low points along long, severe storm linear facilities) 2014 Stormwater Management Manual for Western Washington Volume V - Chapter - Page 868 42 Table V-4.5.2(21) Maintenance Standards - Bioretention Facilities (continued) Recommended Fre- Condition Maintenance uenc q Y a when Main - Action Needed (Pro - Component tenance is (Stand. cedures) --I- Routine Main -Needed Inspection tenance ards) its forecasted A dam- Repair/ replace aPipedis W Pipe is clogged Remove roots or debris . Clear the blockage Sediment, debris, trash, or .Identify the source of A, S mulch reducing the blockage and capacity of take actions to pre- inlet/outlet vent future block- ages Accumulated Clear leaves (particularly Weekly during leaves at important for key inlets Pipe inlet/out- fall leaf drop inlets/outlets and low points along long, let linear facilities) o Clear vegetation (transplant veget- ation when possible) within 1 foot of inlets and outlets, maintain Maintain access access pathways A -for inspections Consultation with a landscape architect is recommended for removal, transplant, or substitution of plants Maintain a cover of rock or cobbles or other erosion Erosion con- Concentrated protection measure (e.g., trol at inlet A flows are caus- matting) to protect the ing erosion ground where con- centrated water enters the facility (e.g., a pipe, curb 2014 Stormwater Management Manual for Western Washington Volume V - Chapter - Page 869 43 Table V-4.5.2(21) Maintenance Standards - Bioretention Facilities (continued) Recommended Fre- Condition Maintenance quency a when Main - Action Needed (Pro- Com Component tenance is Needed (Stand- cedures ) Routine Main- Inspection tenance ards) cut or swaie) Trash or other S debris present Remove/dispose Trash rack on trash rack A Bar screen dam- Repair/replace aged or missing Capacity Remove sediment or Overflow ,A, S reduced by sed- debris/dispose iment or debris Plant roots, sed- • Jet clean or rotary iment or cut debris/roots from Clean orifice debris underdrain(s) at least bian- reducing nually (may capacity of If underdrains are Underdrain Clean pipe need more fre- underdrain equipped with a flow pipe as needed quent clean- . Prolonged g restrictor (e.g., ori- ing during wet surface fice) to attenuate season ponding flows, the orifice (see "Pon- must be cleaned reg- ded water" ularly. Vegetation Vegetation sur- • Determine cause of vival rate falls poor vegetation below 75% growth and correct Facility bottom within first two condition area and Fall and years of estab- . Replant as neces- upland slope Spring Iishment (unless sary to obtain 75% vegetation project O&M survival rate or manual or greater. Refer to ori- record drawing ginal planting plan, stipulates more or approved jur- 2014 Stormwater Management Manual for Western Washington Volume V - Chapter - Page 870 44 Table V-4,5.2(21) Maintenance Standards - Bioretention Facilities (continued) Recommended Fre- Condition , Maintenance quenc Y a when Main- Action Needed (Pro - tenance is Routine Main- Component p cedures) Needed (Stand- Inspection tenance ards) isdictional species list for appropriate plant replacements (See Appendix 3 - Bioretention Plant List, in the LID Tech- nical Guidance Manual for Puget ,or less than Sound). '75% survival . Confirm that plant rate). selection is appro- priate for site grow- ing conditions - Consultation with a landscape architect is recommended for removal, transplant, or substitution of plants - Remove any dis- eased plants or plant parts and dispose of in an approved loc- ation (e.g., com- Presence of dis- mercial landfill) to Vegetation eased plants avoid risk of spread - (general) As needed and plant mater- ing the disease to ial other plants . Disinfect gardening tools after pruning to prevent the spread of disease . See Pacific North- 2014 Stormwater Management Manual for Western Washington Volume V - Chapter 4 - Page 871 45 Table V-4.5.2(21) Maintenance Standards - Bioretention Facilities (continued) Recommended Fre- Condition Maintenance quenc y a when Main - Action Needed (Pro- Componenttenance is ( Stand- cedures ) Routine Main -Needed Inspection tenance ards) west Plant Disease Management Hand- book for information on disease recog- nition and for addi- tional resources . Replant as neces- sary according to recommendations provided for "facility bottom area and upland slope veget- ation". . Prune trees and shrubs in a manner appropriate for each species. Pruning should be performed by landscape pro- fessionals familiar seasons (tim- Pruning as with proper pruning ing varies by needed techniques species) . All pruning of mature Trees and trees should be per- shrubs formed by or under the direct guidance of an ISA certified arborist Large trees and . Prune trees and shrubs interfere shrubs using most with operation of current ANSI A300 A the facility or standards and ISA access for main- BMPs. tenance . Remove trees and 2014 Stonnwater Management Manual for Western Washington Volume V - Chapter 4 - Page 872 46 Table V-4.5.2(21) Maintenance Standards - Bioretention Facilities (continued) Recommended Fre- Condition when Main - Maintenance quenc Y a Action Needed (Pro- Componenttenance is cedures Routine Main -Needed Stand- ) Inspection tenance ( ards) shrubs, if necessary. 2014 Stormwater Management Manual for Westem Washington Volume V - Chapter 4 - Page 873 47 Table V-4.5.2(21) Maintenance Standards - Bioretention Facilities (continued) Recommended Fre- Condition Maintenance uenc q Y a when Main - tenance is Action Needed (Pro - Routine Main -Needed Component p (Stand- cedures Inspection tenance ards) . Remove standing dead vegetation . Replace dead veget- ation within 30 days of reported dead and dying plants (as prat tical depending on weather/planting sea son) . If vegetation replace- ment is not feasible within 30 days, and absence of veget- ation may result in Standing dead erosion problems, Fall and vegetation is temporary erosion Spring present control measures should be put in place immediately. . Determine cause of dead vegetation and address issue, if pos- sible . If specific plants have a high mortality rate, assess the cause and replace with appropriate spe- cies. Consultation with a landscape architect is recom- mended. Fall and Planting • When working 2014 Stormwater Management Manual for Western Washington Volume V - Chapter 4 - Page 874 48 Table V-4.5.2(21) Maintenance Standards - Bioretention Facilities (continued) Maintenance Component Recommended Fre- 1 Condition quenc Y a when Main- tenance is Routine Main -(Needed ( Stand- Inspection tenance ards) Action Needed (Pro- cedures) around and below mature trees, follow the most current ANSI A300 stand- ards and ISA BMPs to the extent prac- ticable (e.g., take care to minimize any damage to tree roots and avoid com- paction of soil). Spring beneath mature Planting of small trees shrubs or ground - covers beneath mature trees may be desirable in some cases; such plant- ings should use mainly plants that come as bulbs, bare root or in 4-inch pots; plants should be in no larger than 1-gal- lon containers. . Verify location of facility liners and Presence of or underdrain (if any) need for stakes prior to stake install - Fall and and guys (tree ation in order to pre - Spring growth, mat- vent liner puncture uration, and sup or pipe damage port needs) . Monitor tree support systems: Repair and adjust as needed to 2014 Stormwater Management Manual for Western Washington Volume V - Chapter 4 - Page 875 49 Table V-4.5,2(21) Maintenance Standards - Bioretention Facilities (continued) Recommended Fre- Condition Maintenance quency a � ' when Main - Action Needed (Pro - Component (Stand- cedures) Routine Main -Needed Inspection tenance I ards) provide support and prevent damage to tree. . Remove tree sup- ports (stakes, guys, etc.) after one grow- ing season or max- imum of 1 year. • Backfill stake holes after removal. . Maintain appropriate height for sight clear- ance . When continued, reg ular pruning (more than one time/ grow- ing season) is Trees and required to maintain shrubs adja- visual sight lines for cent to vehicle Vegetation safety or clearance travel areas causes some along a walk or (or areas A visibility (line of drive, consider relo- where vis- sight) or driver cating the plant to a ibility needs to safety issues more appropriate loc be main- ation. tained) . Remove or trans- plant if continual safety hazard e Consultation with a landscape architect is recommended for removal, transplant, or substitution of 2014 Stormwater Management Manual for Western Washington Volume V - Chapter 4 - Page 876 50 Table V-4.5.2(21) Maintenance Standards - Bioretention Facilities (continued) Recommended Fre- Condition Maintenance uenc q Y a when Main - Action Needed (Pro - Routine Main -Needed Component (Stand- cedures) � Inspection tenance ards) plants Flowering A Dead or spent Remove spent flowers plants Flowers present (deadhead) Cut back dying or dead Perennials Fall Spent plants and fallen foliage and stems Hand rake sedges and rushes with a small rake -or fingers to remove dead Emergent 'Vegetation com- foliage before new growth vegetation Spring promises con- emerges in spring or veyance earlier only if the foliage is blocking water flow (sedges and rushes do not respond well to pruning) . Leave dry foliage for winter interest . Hand rake with a Dead material small rake or fingers from previous to remove dead Ornamental Winter and year's growing foliage back to grasses (per- Spring cycle or dead within several ,ennial) collapsed inches from the soil foliage before new growth emerges in spring or earlier if the foliage collapses and is blocking water flow . Hand rake with a Ornamental Dead growth small rake or fingers grasses (ever- Fall and present in to remove dead green) Spring spring growth before new growth emerges in spring 2014 Stormwater Management Manual for Western Washington Volume V - Chapter 4 - Page 877 51 Table V-4.5.2(21) Maintenance Standards - Bioretention Facilities (continued) Recommended Fre- Condition Maintenance quenc Y a when Main - Action Needed (Pro- Componenttenance is Needed (Stand- cedures ) Routine Main- Inspection tenance ards) Clean, rake, and comb grasses when they become too tall . Cut back to ground or thin every 2-3 years as needed . By law, class A & B noxious weeds must be removed, bagged and dis- posed as garbage immediately . Reasonable attempts must be made to remove and Listed noxious dispose of class C M (March - vegetation is noxious weeds Noxious October, pre- present (refer to weeds ceding seed current county - It is strongly encour- dispersal) noxious weed aged that herbicides list) and pesticides not be used in order to protect water quality; use of herbicides and pesticides may be prohibited in some jurisdictions Apply mulch after weed removal (see "Mulch" ) M (March - • Remove weeds with Weeds October, pre- Weeds are their roots manually ceding seed present with pincer -type dispersal) weeding tools, flame 2014 Stormwater Management Manual for Western Washington Volume V - Chapter 4 - Page 878 52 Table V-4.5.2(21) Maintenance Standards - Bioretention Facilities (continued) Recommended Fre- Condition ' Maintenance Quenc y a when Main- Action Needed (Pro- Component tenance is ( Stand-1 cedures) Routine Main -Needed Inspection tenance ards) weeders, or hot water weeders as appropriate . Follow IPM pro- tocols for weed man- agement (see "Additional Main- tenance Resources" section for more information on IPM protocols) . Edge or trim ground - Low -lying veget- covers and shrubs at ation growing facility edge beyond facility ■ Avoid mechanical edge onto side- blade -type edger walks, paths, or and do not use Once in early street edge edger or trimmer to mid- May poses ped- within 2 feet of tree and once in estrian safety trunks early- to mid- hazard or may September clog adjacent While some clip - Excessive permeable pave pings can be left in vegetation ment surfaces the facility to replen- �due to asso- ish organic material ciated leaf litter, in the soil, excessive mulch, and soil leaf litter can cause surface soil clogging Excessive veget Determine whether ation density pruning or other inhibits storm- routine maintenance As needed water flow bey- is adequate to main- ond design tain proper plant ponding or density and aes- thetics 2014 Stormwater Management Manual for Western Washington Volume V - Chapter 4 - Page 879 53 Table V-4.5.2(21) Maintenance Standards - Bioretention Facilities (continued) Recommended Fre- Maintenance ; quency a Component E Routine Main -Needed Inspection tenance Condition when Main - tenance is (Stand- ards) Action Needed (Pro- cedures ) Detenrine if plaiting type should be replaced to avoid ongoing main- tenance issues (an aggressive grower under perfect grow- ing conditions should be trans- planted to a location where it will not becomes a haz- impact flow) and for ped- . Remove plants that estrian and are weak, broken or vehicular cir- not true to form; culation and replace in -kind safety . Thin grass or plants impacting facility function without leav- ing visual holes or bare soil areas . Consultation with a landscape architect is recommended for removal, transplant, or substitution of plants Vegetation blocking curb As needed cuts, causing Remove vegetation and excessive sed- sediment buildup iment buildup and flow bypass 2014 Stormwater Management Manual for Western Washington Volume V - Chapter 4 - Page 880 54 Table V-4.5.2(21) Maintenance Standards - Bioretention Facilities (continued) Recommended Fre- Condition Maintenance quenc y a when Main- Action Needed (Pro- Component tenance is cedures) 'Needed Stand-! ( Routine Main - Inspection tenance ards) Mulch . Supplement mulch with hand tools to a depth of 2 to 3 inches Bare spots Replenish mulch per (without mulch O&M manual. Often Following cover) are coarse compost is Mulch weeding present or used in the bottom of mulch depth the facility and arbor - less than 2 ist wood chips are inches used on side slopes and rim (above typ- ical water levels) . Keep all mulch away from woody stems Watering Based on man Irrigation system Follow manufacturer's ufacturer's instructions present instructions for O&M Irrigation sys- Sprinklers or tem (if any) drip irrigation Redirect sprinklers or A not dir- move drip irrigation to ected/located to desired areas properly water plants . 10 to 15 gallons per Once every 1- Trees, shrubs tree Summer water 2 weeks or as and ground- . 3 to 5 gallons per ing (first year) needed during covers in first shrub prolonged dry year of estab- 2 gallons water per periods lishment period square foot for groundcover areas 2014 Stormwater Management Manual for Western Washington Volume V - Chapter 4 - Page 881 55 Table V-4.5.2(21) Maintenance Standards - Bioretention Facilities (continued) Maintenance Component Recommended Fre- quenc Y a Condition when Main - (Stand- Action Needed (Pro - cedures) Inspection Routine Main -Needed tenance ards) . Water deeply, but infrequently, so that the top 6 to 12 inches of the root zone is moist . Use soaker hoses or spot water with a shower type wand when irrigation sys- tem is not present • Pulse water to enhance soil absorption, when feasible • Pre -moisten soil to break surface tension of dry or hydro- phobic soils/mulch, fol- lowed by sev- eral more passes. With this method , each pass increases soil absorption and allows more water to infilt- rate prior to run off . Add a tree bag or slow -release water- ing device (e.g., 2014 Stormwater Management Manual for Westem Washington Volume V - Chapter 4 - Page 882 56 Table V-4.5.2(21) Maintenance Standards - Bioretention Facilities (continued) Recommended Fre- Condition Maintenance uenc q Y a when Main - Action Needed (Pro - Component p tenance is Needed (Stand- cedures ) Routine Main- Inspection tenance ards) bucket with a per- forated bottom) for watering newly installed trees when irrigation system is not present . 10 to 15 gallons per tree . 3 to 5 gallons per shrub . 2 gallons water per square foot for groundcover areas . Water deeply, but infrequently, so that the top 6 to 12 inches of the root once every 2- Trees, shrubs zone is moist Summer water 4 weeks or as and ground- • Use soaker hoses or ing (second needed during covers in spot water with a and third prolonged dry second or third shower type wand years) periods year of estab- when irrigation sys- lishment period tem is not present • Pulse water to enhance soil absorption, when feasible • Pre -moisten soil to break surface tension of dry or hydro- phobic soils/mulch, fol 2014 Stormwater Management Manual for Western Washington Volume V - Chapter 4 - Page 883 57 Table V-4.5.2(21) Maintenance Standards - Bioretention Facilities (continued) Recommended Fre- Condition Maintenance quenc Y a when Main - is Action Needed (Pro- Routine Main -Needed Componenttenance (Stand- cedures ) Inspection tenance ards) lowed by sev- eral more passes. With this method , each pass increases soil absorption and allows more water to infilt- rate prior to run off . Plants are typically selected to be drought tolerant and not require regular watering after estab- lishment; however, trees may take up to 5 years of watering to become fully established Summer water Established . Identify trigger mecli- ing (after As needed vegetation (after anisms for drought - establishment) 3 years) stress (e.g., leaf wilt, leaf senescence, etc.) of different spe- cies and water imme diately after initial signs of stress appear . Water during drought conditions or more often if necessary to main- 2014 Stormwater Management Manual for Western Washington Volume V - Chapter 4 - Page 884 58 Table V-4.5.2(21) Maintenance Standards - Bioretention Facilities (continued) Recommended Fre- Condition uenc when Main - Maintenance q Y a Action Needed (Pro - Component tenance is cedures p (Routine Main -Needed Stand- ) Inspection II ( tenance ards) .Pest Control Mosquitoes Standing water remains for more than 3 days after the end of a storm tam plant cover . Identify the cause of the standing water and take appropriate actions to address the problem (see "Ponded water") . To facilitate main- tenance, manually remove standing water and direct to the storm drainage system (if runoff is from non pollution - generating surfaces) or sanitary sewer system (if runoff is from pollution -gen- erating surfaces) after getting approval from san- itary sewer authority. Use of pesticides or Bacillus thuring- iensis israelensis (Bti) may be con- sidered only as a temporary measure while addressing the standing water cause. If overflow to 2014 Stormwater Management Manual for Western Washington Volume V - Chapter - Page 885 59 Table V-4.5.2(21) Maintenance Standards - Bioretention Facilities (continued) Recommended Fre- Condition Maintenance uenc q y a when Main - Action Needed (Pro - Component tenance is (Stand- cedures ) Routine Main -Needed Inspection I� tenance ards) f j a surface water will occur within 2 weeks after pesticide use, apply for coverage under the Aquatic Mosquito Control NPDES General Per mit. . Reduce site con- ditions that attract nuisance species where possible (e.g., plant shrubs and tall grasses to reduce open areas for geese, etc.) . Place predator Nuisance anim- decoys als causing . Follow IPM pro - Nuisance erosion, dam- tocols for specific animals As needed aging plants, or nuisance animal depositing large issues (see "Addi- valumes of tional Maintenance feces Resources" section for more information on IPM protocols) . Remove pet waste regularly . For public and right- of-way sites con- sider adding garbage cans with dog bags for picking 2014 Stormwater Management Manual for Western Washington Volume V - Chapter 4 - Page 886 60 Table V-4.5.2(21) Maintenance Standards - Bioretention Facilities (continued) Recommended Fre- Condition Maintenance quenc y a when Main - Action Needed (Pro- [__ IRoutine Main- Componenttenance is Needed (Stand- � cedures ) Inspection tenance ards) up pet waste. . Reduce hiding places for pests by removing diseased Every site Signs of pests, and dead plants visit asso- such as wilting leaves, chewed e For infestations, fol- Insect pests ciated with leaves and bark, low IPM protocols vegetation spotting or (see "Additional management other indicators Maintenance Resources" section for more information on IPM protocols) Note that the inspection and routine maintenance frequencies listed above are recom- mended by Ecology. They do not supersede or replace the municipal stormwater permit requirements for inspection frequency required of municipal stormwater permittees for "stormwater treatment and flow control BMPs/facilities". a Frequency: A = Annually; B = Biannually (twice per year); M = Monthly; W = At least one visit should occur during the wet season (for debris/clog related maintenance, this inspection/maintenance visit should occur in the early fall, after deciduous trees have lost their leaves); S = Perform inspections after major storm events (24-hour storm event with a 10-year or greater recurrence interval). IPM - Integrated Pest Management ISA - International Society of Arboriculture Table V-4.5.2(22) Maintenance Standards - Permeable Pavement Recommended Fre- Condition quency a when Main - Component tenance is Action Needed (Procedures) Inspection Routine Needed Maintenance (Standards) Surface/Wearing Course Permeable IA, S Runoff from . Clean deposited soil or 2014 Stormwater Management Manual for Western Washington Volume V - Chapter 4 - Page 887 61