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REVIEWED BLD2023-1599+Storm_Drainage_Report+12.13.2023_2.39.54_PM+3951179RECEIVED Dec 28 2023 CITY OF EDMONDS DEVELOPMENT SERVICES DEPARTMENT BLD2023-1599 Drainage Report Addendum Meadowdale Short Plat City of Edmonds, Washington Tax Parcel: 00513600000100 Group Four Job No. 17-0523 Prepared For: Duncan Spence 701 Daley St, Edmonds WA 98020 206-565-9832 Dec 08, 2021 Prepared By: Curt Iffrig, P.E. Group Four, Inc. 1901 Vernon Road, Suite #A Lake Stevens, WA 98258 425-408-1152 COMPLIES WITH APPLICABLE CITY STORMWATER CODE 03/11 /2022 Executive Summary This drainage report was prepared as an addendum to the approved drainage report prepared by Group Four Inc. dated April 26, 2019. The applicant proposes a change to how this project meets the retrofit requirement for the existing impervious surface. Approved Report The approved report proposed the following. For the 25% retrofit requirement 1,300 sf of gravel in Lot 1 will be removed and replaced with lawn to satisfy this requirement. 1,000 sf in Lot 2 will be also removed and replaced with permeable lawn. The total amount of impervious removed is approximately 46% of the existing impervious surface. Proposed Amendment The 1,300 sf of gravel in Lot 1 will remain. To meet the retrofit requirement the applicant proposes to instead reroute four downspouts on the existing house to splash blocks. The splash blocks will be constructed per BMP T5.11. They will have a minimum 50 ft vegetated now path to disperse roof runoff. A single splash blocks provides mitigation for up to 700 sf thus providing an effective alternative to removing the existing gravel. The 1,000 sf of gravel in Lot 2 will still be removed. The total amount of existing impervious surface being removed or mitigated is still approximately 46%. Drainage Report RECEIVED HAY 06 2019 DEVELOPMENT SERVICES COUNTER Meadowdale Short Plat JFC.,WC,t' City of Edmonds, Washington 'QLsl zo11 UD 5ri Tax Parcel: 00513600000100 Group Four Job No. 17-0523 April 26, 2019 Prepared For: Duncan Spence 701 Daley St, Edmonds WA 98020 206-565-9832 MPUES WITH TPPLI ODE E ITY ST R Prepared By: Curt Iffrig, E.I.T Group Four, Inc. 1901 Vernon Road, Suite #A Lake Stevens, WA 98258 425-408-1152 Meadowdale Short Plat Drainage Report Table of Contents Apr. 26, 2019 SectionI......................................................................................................................Pages 4-7 Project Overview and Executive Summary Existing Conditions Summary Off -Site Analysis and Mitigation Upstream Analysis Downstream Analysis SectionII...................................................................................................................Pages 8-11 MR 1-Preparation of Stormwater Site Plans MR 2- Construction Stormwater Pollution Prevention Plan (SWPPP) MR 3-Source Control of Pollution MR 4-Preservation of Natural Drainage Systems and Outfalls MR 5-On-site Stormwater Management MR 6-Runoff Treatment MR 7-Flow Control MR 8-Wetlands Protection MR 9-Operations and Maintenance SectionIII..................................................................................................................Pages 12-14 Element #1 — Preserve Vegetation/Mark Clearing Limits Element #2 — Establish Construction Access Element #3 — Control Flow Rates Element #4 — Install Sediment Controls Element #5 — Stabilize Soils Element #6 — Protect Slopes Element #7 — Protect Drain Inlets Element #8 — Stabilize Channels and Outlets Element #9 — Control Pollutants Element #10 — Control De -watering Element #11 — Maintain BMPs Element #12 — Manage the Project Element #13 — Protect on -site storm water management BMPs from runoff from roofs and other hard surfaces. SectionIV........................................................................................................................Page 15 King County Site Improvement Bond Quantity Worksheet Group Four, Inc. 2 17-0523 Meadowdale Short Plat Drainage Report Figures Apr. 26, 2019 Figure1-Proposed Site Plan................................................................................................Page 5 Figure2-Vicinity Map.......................................................................................................Page 7 Figure 3-Existing Site Plan...................................................................................................Page 7 Figure 4-Downstream Flowpath.............................................................................................Page 7 Appendix A- Soils Map................................................................................................................Page 17 B - Infiltration Evaluation...................................................................................................Page 18 C - Post Construction Amended Soils...............................................................:..................Page 19 D- W WHM Output.......................................................................................................Page 20 E - Maintenance Standards...............................................................................................Page 21 Group Four, Inc. 3 17-0523 Meadowdale Short Plat Drainage Report Section I Project Overview and Executive Summary Name: Meadowdale Short Plat PFN: PLN20170057 Tax Parcel: 00513600000100 Owner/Applicant: Engineer: Site Address: Duncan Spence 701 Daley St, Edmonds, WA 98020 Group Four, Inc. P.O. Box 1059 Lake Stevens, WA 98258 425-408-1152 17606 72"d Ave Edmonds, WA 98258 Apr. 26, 2019 This drainage report was prepared per the request of the City of Edmonds to supplement civil short plat plans produced by Group Four. This report is prepared according to the standards found in The City of Edmonds Stormwater Manual 2016, The City of Edmonds Stormwater Addendum 2017, and The Department of Ecology Stormwater Management Manual for Western Washington 2014. (SWMMWW 2014) The applicant proposes to divide his 36,287 square feet (0.83 ac) parcel into two lots. Lot 1 totaling 22,659 sf (0.52ac), Lot 2 totaling 12,527 sf (0.29 ac) and a Right of Way dedication totaling 1,101 sf (0.03ac). The applicant also proposes to build a new single-family residence on Lot 2. This single-family residence will be approximately 1,200 sf in area. The house will also have a driveway that is approximately 440 sf and a patio that is approximately 200 sf. These improvements to Lot 2 are subject to a separate building permit. A new driveway will also be constructed on Lot 1 off of 176d' St SW. This new driveway area will be approximately 216 sf in area. The city also requested for 25% of the existing impervious surface on Lot 1 and Lot 2 to be mitigated using MR #5 per Edmonds Community Development Code (ECDC) 18.30.060.D.b.i. To meet this requirement, 2,300 sf of the existing gravel surface will be removed and replaced with permeable lawn. The City of Edmonds has also requested widening the pavement on both 176d' St SW and 72"d Ave W adjacent to the property. This Group Four, Inc. 4 17-0523 Meadowdale Short Plat Drainage Report Apr. 26, 2019 widening will bring both streets to the standard width of 22 ft by adding 2.5 ft of width to 1761, St SW and 1.5 ft to 72°a St W. All these improvements are subject to this permit which is number PLN20170057. The runoff from the proposed roof in Lot 2, driveway in Lot 1, and the proposed road widening will be mitigated by full infiltration through infiltration trenches See Figure 1 for proposed site plan. Existing Conditions Summary The existing site is 0.83 acres in an area zoned RS-12 in the City of Edmonds. See the Vicinity Map (Figure 2). The project site is generally flat, with an average approximate slope of 2%. The existing site improvement includes an existing house and a detached garage that are approximately 1,100 sf and 800 sf. The existing driveway is approximately 3,100 sf. See figure 3 for existing site plan. Mitigation Presented here is a summary of new and replaced impervious areas treated solely by on -site storm water management: TDA Area, SF BMP Note Proposed Impervious 4,384 Infiltration and Subject to Separate Permit, Includes Roof, Lot 2 Permeable Pavement Deck and Parking Surfaces. Proposed Asphalt 216 Infiltration Lot 1: Subject to PLN20170057 Parking Surface, Lot 1 Included in Equivalent Area * Replaced Parking 2,300 Remove Impervious 25% Retrofit Requirement Surface, Lots 1 & 2 Approximately 46% Removed Subject to PLN20170057 Proposed Road 1,500 Infiltration Subject to PLN20170057 Widening and Replaced Included in Equivalent Road Surface Area* *It is infeasible to collect the entire area of new and replaced pavement (An area including 1,500 sf of pavement in right of way and the 216 sf parking in Lot 1, totaling 1,716 sf) for infiltration on -site so runoff from an equivalent existing pavement area totaling 1,770 sf will be collected and routed into infiltration on -site. See Figure 3. Group Four, Inc. 5 17-0523 Meadowdale Short Plat Drainage Report Upstream Analysis Apr. 26, 2019 Approximately 1,000 SF of road area in NE 72°a Ave is tributary to the project site. See Figure 3 the existing site plan. Runoff from this area will be collected by a thickened edge curb and a catch basin to be routed to the on -site infiltration system. Downstream Analysis The site and downstream was walked by Curt Iffrig on 2/15/2018. No drainage problems were observed on site. Runoff from the proposed project site sheet flows over lawn to low point on the site's north boundary where it flows into the Right of Way for 176`h St. SW. Per city as -built information there are no existing storm lines in 176h St SW near this property. Runoff from the property flows onto 176`h and flows to the west for approximately 600 ft where it enters the city storm system by a catch basin. The City of Edmonds has confirmed there are no known issues with stormwater conveyance downstream of the site. See Figure 4. Group Four, Inc. 6 17-0523 t t R: -176TH STSW e • . F r ____ =M—_ 04 v,.om Ly 6 RUM GRRTR a 1�1 ,S ^�'yY-f'.. ERR 1.... o•y R ��: }i• ..� I IZ021 a m 1 C O ma's '; •.: "iFt":: <�:;:;:.;... Vr r �ml \ \ Ra.t a I RO R1 G IOUARD"�" ji--------------------1� Figure 1:Proposed Site Plan N SCALE: 1"=20' ®aa 0 J IL w s LLI p U N a 2 W W 2 J CL Q O. w D_ O 0 Q W m s e IRRITV CONFLICT NOTE: CAS N: PFN'r20t 70057 wave o,u �mAo maw APPROVED FOR CONSTRUCTION ec s'�eaer Imas nsn CffY OF EDMONDS 4'Q � � iMawOr rt SNEET Of IGOYo�6 O a � m0®L�1 A �nfo4r �p� �Omi M1C C, I(wlial'S Ello":. m "0, tOmLO� IaM1OR O ma NNO ! fM 4 % 9 Call — Muhiess � R ears pElwe ra, aq. cnx sm .�m� A . m'®Oemm. 17-0523 Meadowdale Short Plat Drainage Report Apr. 26, 2019 ............. ....................... ....................... ...................... ...................... .. WE- 1681 H ST SW .................. .................... ............. ............. ............ ........... .......... SITE <01 173TH -L SW 176TH ST SW SOUTHWEST ,COUNTY PARK --LBOTH ST SW 18 186TH ST SW 4 188TH ST SW LYNND LE PARK - PICNIC SHELTER 192T SYJ VICINITY MAP SCALE I" = 2,000' Figure 2: Vicinity Map Group Four, Inc. 7 17-0523 DATUM: r..o a - x.aw BENCH: rr.n m m u av ama SITE BENCH:,+. n BASIS O� F BEARINGS' SURVEY NOTES: �- m s.sc ,w. aaacn n LEGAL DESCRIPTION: —' 76TH ST rLo%/S v jrp.*N' S7I E f * f RO �pS E O . Ste!17E N SCALE: i APax YC N d! 7OO SF.�---car cLEGTEd r^rnGlfT2oN LD B Y T P-ATzv N •1- f s �-1--_-,aL ... a_�. m� i p '176 i•I S75�V 7I� �/j ..;'``.w^ur-.__—.__x.y— ir.._ _: .+-.,�_ � �_._�_ • I � _S. T�.1 �' _' - is � _ _r � l - _ �s?.�=r—.._.*,�� .s .- -:•�4-a.2'a �.,r. - -L -•-� >. _ _ � r � I �Pr _ a A f_. sr Rs i0-""'�,Oy"� 1 = I i .+r . :• .. _ PROJECT MPORMATION: MPLIC/M�s Ft .m v - / � �,' ..•[ !'--•*vd�` .. I.Ip _ r. I ••.., r �' !tl .: Z +....`.. r •.. • nm�w'�io ,4 1 �.•��.., •�-.5�i,94,,.v... x''4 �-•` r„ /I� t SURYEVOR'1:NGUEER: ^�_'� Id °•rrg'.. �4 i z� _ 72NO ' PSTRtAcM - 'w� X. 070 SF . >AW - PPRD ` ---- �+c .'�w l•., F•' .. r. 1 of ---- =--- m Q A-.AIS :a 52rE : *awe lmr. _ �:wx�x.,..._.„I''— -=�-� r�.---�. _ - x ,o r.TL6ATVW 8 i .NcyLTRAhON \� w.o :..,.. �� (. -I °•'.-ter— _ 72ivD VP If / APP" +�. 78f 5F DRATI$t ra Nr.Ierleoa'S Pr+oPraTY • i \ I. Figure 3: Predeveloped Site Plan. r I I Qa a a� Figure 4: Downstream Flow NTS Meadowdale Short Plat Drainage Report Section II: Minimum Requirements Apr. 26, 2019 Per the City of Edmonds Stormwater Manual 2016, this project is Category 2 because it proposes more than 5,000 sf of impervious surface area including new and replaced impervious pavement in the right of way but not including the retrofit requirement. Category 2 projects must comply with Minimum Requirements 1 through 9. The 25% retrofit requirement and the road way expansion must comply with only Minimum Requirement 5. MR 1-Preparation of Stormwater Site Plans A set of civil plans have been prepared per City of Edmonds standards. The additional work in Lot 2 will be covered by another permit. MR 2-Construction Stormwater Pollution Prevention Plan (SWPPP) This site disturbs less than one acre so a full SWPPP is not required. A Temporary Erosion and Sediment Control Plan (TESC) is included in the plan set. The SWPPP elements are addressed in Section III. MR 3-Source Control of Pollution This residential site is required to comply with BMP S411, BMPs for Landscaping and Lawn/Vegetation Managements. These BMPs include the good house -keeping measures for the property owner to maintain concerning landscaping, pesticides and vegetation management. MR 4-Preservation of Natural Drainage Systems and Outfalls The proposed runoff mitigation system preserves the site's natural drainage outfall. MR 5-On-site Stormwater Management BMPs for this project have been selected from List No. 1 of the City of Edmonds Stormwater Manual 2016. The first BMP from List No. 1 for lawn and landscaped surfaces is post -construction amended soils. All proposed lawn and landscaped surfaces will be treated with post -construction amended soils per BMP T5.13 of the SWMMWW 2014, including the impervious gravel being removed to satisfy the retrofit requirement. See Appendix C. The first BMP from List No. 1 for roofs is downspout full infiltration. A geotechnical study performed by Robinson Noble determined the infiltration rate of the soils on site is 5.4 in/hr which is within the threshold for full infiltration. Full infiltration will be done by a series of Group Four, Inc. 8 17-0523 Meadowdale Short Plat Drainage Report Apr. 26, 2019 infiltration trenches constructed per BMP T5.10A of the SWMMWW 2014. See the infiltration evaluation letter included in Appendix B. 300 linear feet of infiltration trenches will be constructed to mitigate for the maximum impervious area allowed on Lot 2 and the equivalent area (1,770 sf). The maximum impervious area allowed on Lot 2 is 4,384 sf which is 35% of the total lot area. Approximately 440 sf of that will be permeable pavement so the 3,944 SF remainder will be mitigated by infiltration. The sizing of this infiltration facility was determined using the Western Washington Hydrology Model 2012 (See MR 7) The first BMP from List No.I for other hard surfaces including the parking areas is full dispersion. This BMP is infeasible because there is not enough native growth area on site. The second BMP from List No. 1 is permeable pavement. Permeable pavement is feasible because the infiltration rate of 5.4 in/hr falls within the acceptable threshold. Permeable concrete will be used in the new parking areas for Lot 2 but cannot be used in Lot 1. The pavement will be constructed per Figure V-5.3.4 of the SWMMWW 2014. For the 216 SF driveway in Lot 1 permeable pavement or another infiltration BMP is infeasible because the geotechnical information provided cannot support infiltration at that depth and location. This surface area will not be mitigated but runoff of an equivalent area upstream will be mitigated instead (as described below). Per the City of Edmonds, Minimum Requirement 5 shall be applied to the proposed widening. Due to site topography it is infeasible to collect runoff from the whole road widening. Instead, runoff from 1,770 sf of road area, an area equivalent to the amount of new pavement added to the right of way and Lot 1 will be collected and mitigated by the on -site infiltration system. The area collected for mitigation includes approximately 1,070 sf in area from W 72nd Ave and approximately 700 sf in 176'h St SW. See Figure 3. For the 25% retrofit requirement 1,300 sf of gravel in Lot 1 will be removed and replaced with lawn to satisfy this requirement. 1,000 sf in Lot 2 will be also removed and replaced with permeable lawn. The total amount of impervious removed is approximately 46% of the existing impervious surface. MR 6-Runoff Treatment Runoff treatment is not applicable for this project because this project proposes less than 5,000 SF. MR 7-Flow Control The Flow Control requirement is met by demonstrating with the Western Washington Hydrology Model 2012 (WWHM 2012) that the 100-year peak runoff from the developed condition is not more than 0.15 cfs greater than the 100-year peak runoff from the predeveloped condition. This Group Four, Inc. 9 17-0523 Meadowdale Short Plat Drainage Report Apr. 26, 2019 model demonstrates that an infiltration trench that is 300 ft long will provide sufficient flow control to meet this standard. The targeted area includes 4,384 sf of impervious area in lot 2 and 1,770 sf impervious road area collected as an equivalent area in place of the 1,500 sf new and replaced pavement in the frontage improvements and the 216 new paved parking area in lot 1. The predeveloped condition was modeled using the historic condition which is fully forested. Both the predeveloped and developed targeted areas were entered into WWHM 2012 as parallel flow basins with the developed basins all flowing into an infiltration trench. The basin input parameters are described in the table below. SURFACE SLOPE COVER AREA (ac) PRE -DEVELOPED Historic Lot 2 Impervious 0-2% Forest 0.09 Historic Lot 2 Parking Permeable 0-2% Forest 0.01 Historic Equivalent Area Collected for Frontage 0-2% Forest 0.041 Historic Infiltration Trench Area 0-2% Forest 0.02 Historic Lot 1 Parking 0-2% Forest 0.007 DEVELOPED Lot 2 Impervious 0-2% Roof 0.09 Lot 2 Parking Permeable 0-2% Permeable Pvmt 0.01 Equivalent Area Collected for Frontage 0-2% Road 0.041 Infiltration Trench 0-2% Trench 0.02 Lot 1 Parking 0-2% Driveway 0.007 The permeable pavement and infiltration trench input parameters are shown in the tables below respectively. Model Input Value Note Permeable Pavement Width 20 ft Design Width Depth 1 ft Design Depth Length 22 ft Design Length Top Course Thickness 4 in Top Course Porosity 25% Approximate Porosity Base Course Thickness 8 in Base Course Porosity 40% Approximate Porosity Infiltration Rate 5.4 in/hr From Geotech Group Four, Inc. 10 17-0523 Meadowdale Short Plat Drainage Report Apr. 26, 2019 Model Input Value Note Trench Width 2 ft Design Width Depth 2 ft Design Depth Length 300 ft Design Length Porosity 40% Design Porosity Infiltration Rate 5.4 in/hr From Geotech Riser Height 2 ft Flat/ Top of Trench The peak flows for the predeveloped and the developed condition are shown in the table below. This shows that the 300 LF of infiltration trenching will fully infiltrate the design impervious area for both Lot 2 and the equivalent mitigation area. The total 100-year peak runoff from the developed site is 0.007 cfs which is within the flow control threshold. See the full WWHM 2012 output in Appendix D. Flow Frequency Flowlcfsy Predeveloped Mitigated 2 Year = 0.0011 0.0028 5 Year = 0.0017 0.0037 10 Year = 0.0021 0.0044 25 Year = 0.0024 0.0054 50 Year = 0.0026 0.0062 100 Year = 0.0028 0.0070 MR 8-Wetlands Protection Wetland protection is not applicable for this project because there are no wetlands on the site and there are no flow control facilities discharging into wetlands. MR 9-Operation and Maintenance Stormwater facilities shall be operated and maintained per the standards found in the SWMMWW 2014. The maintenance standards are found in Appendix E. Group Four, Inc. 11 17-0523 Meadowdale Short Plat Drainage Report Section III Apr. 26, 2019 A SWPPP is not required because less than one acre is being disturbed. All areas of construction shall adhere to Erosion and Sediment Control measures as necessary. Element #1— Preserve Vegetation/Mark Clearing Limits The limits of construction will be clearly marked before land disturbing activities begin. The trees which are to be preserved shall be clearly delineated, both in the field and on the plans. BMPs: C101, Preserving Natural Vegetation, C102 Buffer Zones, C103 High Visibility Plastic or Metal Fence. Element #2 - Establish Construction Access Construction access and activities occurring on unpaved areas shall be minimized. Access points shall be stabilized to minimize the tracking of sediment outside of construction areas. BMPs: C105 Stabilized Construction Entrance Element #3 - Control Flow Rate Stormwater discharges shall be controlled to protect the downstream waterways. BMPs: C200 Interceptor Dike and Swale, C207 Check Dams Element #4 - Install Sediment Controls All storm water runoff from disturbed areas shall pass through an appropriate sediment removal BMP before leaving the construction site. BMPs: C233 Silt Fence, C235 Straw Wattles Element #5 - Stabilize Soils Exposed and unworked soils shall be stabilized with effective erosion control BMPs. BMPs: C120 Temporary and Permanent Seeding, C121 Mulching, C122 Nets and Blankets, C123 Plastic Covering Group Four, Inc. 12 17-0523 Meadowdale Short Plat Drainage Report Apr. 26, 2019 Element #6 - Protect Slopes All cut and fill slopes will be designed, constructed and protected in a manner that minimizes erosion. BMPs: C120 Temporary and Permanent Seeding, C130 Surface Roughening, C131 Gradient Terraces, C200 Interceptor Dike and Swale Element #7 - Protect Drain Inlets Any storm drain inlets shall be protected by applying storm drain protection BMP C220. Element #8 — Stabilize Channels and Outlets Stabilize channels and outlets. Temporary and permanent conveyance systems and their outlets shall be protected and stabilized to prevent erosion during and after construction. BMPs: C202 Channel Lining and C290 Outlet Protection 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 storm water. BMPs: C151 Concrete Handling Element #10 - Control De -watering De -watering is not expected to be a concern during this project. However, if it is found to be necessary, foundation, vault, and trench dewatering water shall be discharged into a controlled conveyance system before discharge to a sediment trap or sediment pond. 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 specification. Visual monitoring of the BMPs will be conducted at least once every calendar week and within 24 hours of any storm water 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. Group Four, Inc. 13 17-0523 Meadowdale Short Plat Drainage Report Apr. 26, 2019 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 - Protect on -site storm water management BMPs from runoff from roofs and other hard surfaces. Runoff from impervious surfaces will not be allowed to sheet -flow over lawn or cleared areas. The infiltration trenches should be in -place and on-line prior to roof construction completion. Group Four, Inc. 14 17-0523 Meadowdale Short Plat Drainage Report Section IV Apr. 26, 2019 Per the City of Edmonds, an itemized cost estimate per the King County Site Improvement Bond Quantity Worksheet is required for erosion control measures and right of way improvements. This document is attached below. Group Four, Inc. 15 17-0523 Site Improvement Bond Quantity Worksheet S15 web date: 04/03/2015 ISM LN King County Department of Permitting & Environmental Review 35030 SE Douglas Street, Suite 210 Snoqualmie, Washington 98065-9266 For alternate formats, Call 206-296-6600. 206-296-6600 7 Y Relay 711 Project Name: Meadowdale Short Plat Date: 1/9/2019 Location: of Edmonds Clearing greater than or equal to 5,000 board feet of timber? yes If yes, Forest Practice Permit Number. (RCW 76.09) Page 1 of 9 King County Bond Quantity Meadowdale.xls x no Project No.: PLN20170057 Activity No.: Note: All prices include labor, equipment, materials, overhead and profit. Prices are from RS Means data adjusted for the Seattle area or from local sources if not included in the RS Means database. Unit prices updated. 3/2/2015 Version: 31212015 Report Date_ 412612019 Site Improvement Bond Quantity Worksheet S 15 Web date: 04/03/2015 Reference # Unit Price Unit Quantity # of Applications Cost EROSION/SEDIMENT CONTROL Number Backfrll & compaction -embankment ESCA _ $ 6.00 CY Check dams, 4" minus rock ESC-2 SWDM 5.4.6.3 $ 80.00 Each Crushed surfacing 1 114" minus ESC-3 WSDOT 9-03.9 3 $ 95.00 CY Ditching ESC-4 $ 9.00 CY Excavation -bulk ESC-5 $ 2.00 CY Fence, silt ESC-6 SWDM 5.4.3.1 $ 1.50 LF 341 1 512 Fence, Temporary NGPE ESC-7 $ 1.50 LF Hydroseeding ESC-8 SWDM 5.4.2.4 $ 0.80 SY Jute Mesh ESC-9 SWDM 5.4.2.2 $ 3.50 SY Mulch, by hand, straw, 3" deep ESC-10 SWDM 5.4.2.1 $ 2.50 SY Mulch, by machine, straw, 2" deep ESC-11 SWDM 5.4.2.1 $ 2.00 SY Piping, temporary, CPP, 6" ESC-12 $ 12.00 LF Piping, temporary, CPP, 8" ESC-13 $ 14.00 LF Piping, temporary, CPP, 12" ESC-14 $ 18.00 LF Plastic covering, 6mm thick, sandbagged ESC-15 SWDM 5.4.2.3 $ 4.00 SY Rip Rap, machine placed; slopes ESC-16 WSDOT 9-13.1(2) $ 45.00 CY Rock Construction Entrance, 50 x15x1' ESC-17 SWDM 5.4.4.1 $ 1,800.00 Each 1 1 1800 Rock Construction Entrance, 100'x15x1' ESC-18 SWDM5.4.4.1 $ 3,200.00 Each Sediment pond riser assembly ESC-19 SWDM 5.4.5.2 $ 2,200.00 Each Sediment trap, 5' high berm ESC-20 SWDM 5.4.5.1 $ 19.00 LF Sed. trap, 5' high, riprapped spillway berm section ESC-21 SWDM 5.4.5.1 $ 70.00 LF Seeding, by hand ESC-22 SWDM 5.4.2.4 $ 1.00 SY Sodding, 1 " deep, level ground ESC-23 SWDM 5.4.2.5 $ 8.00 SY Sodding, I" deep, sloped ground ESC-24 SWDM 5.4.2.5 $ 10.00 SY TESC Supervisor ESC-25 $ 110.00 FIR 100 1 11000 Water truck, dust control ESC-26 SWDM 5.4.7 $ 140.00 HR WRITE -IN -ITEMS **** (see aacle 9) _ Catch Basin Socks $ 100.00 Each 4 1 400 Page 2 of 9 King County Bond Quantity Meadowdale.x/s ESC SUBTOTAL: $ 13,711.50 30% CONTINGENCY & MOBILIZATION: $ 4,113.45 ESC TOTAL: $ 17, 824.95 COLUMN: A Unit prices updated: 3/2/2015 Version: 31212015 Report Date: 412612019 Site Improvement Bond Quantity Worksheet Web date. 0M3r2015 Existing Right -of -Way Future Public Right of Way & Drainage Facilities Private Improvements Unit Price Unit Quant. Cost Quant. Cost Quant. I Cost GENERAL ITEMS No. Backfrll & Compaction- embankment GI - 1 $ 6.00 CY Backfill & Compaction- trench GI-2 $ 9.00 CY Clear/Remove Brush, by hand Gl - 3 $ 1.00 SY Clearing/Grubbing/Tree Removal GI-4 $ 10,000,00 Acre 0.06 600.00 Excavation - bulk GI-5 $ 2.00 CY Excavation - Trench GI-6 $ 5.00 CY 300 1,500.00 Fencing, cedar, 6' high Gl - 7 $ 20.00 LF Fencing, chain link, vinyl coated, 6' high Gi - 8 $ 20.00 LF Fencing, chain link, gate, vinyl coated, 20' Gi - 9 $ Fencing, split rail, 3'high Gl - 10j!$j Fill & compact - common barrow GI - 11 qOO Fill & compact - gravel base G1- 12 Fill & compact - screened topsoil G1- 13 Gabion, 12" deep, stone filled mesh GI - 14 $ 65.00 SY Gabion, 18" deep, stone filled mesh Gl - 15 $ 90.00 SY Gabion, 36' deep, stone filled mesh GI -16 $ 150.00 SY Grading, fine, by hand Gi - 17 $ 2.50 SY Grading, fine, with grader Gi - 16 $ 2.00 SY 110 220.00 Monuments, Y long GI - 19 $ 250.00 Each Sensitive Areas Sign GI - 20 $ 7.00 Each Sodding, 1' dee , sloped ground Gi - 21 $ 8.00 SY Surveying, line & grade Gl - 22 $ 8W, 00 Day Surveying, lot location/lines Gl - 23 $ 1,800.00 Acre Traffic control crew (2 fia ers) Gl - 24 $ 120.00 HR 80 9,600.00 Trail, 4' chipped wood GI - 25 $ 8.00 SY Trail, 4' crushed cinder Gl - 26 $ 9.00 SY Trail, 4" top course Gl - 27 $ 12.00 SY Wall, retaining, concrete Gl - 28 $ 55.00 SF Wall, rockery G1- 29 $ 15.00 SF Page 3 of 9 SUBTOTAL 10, 200.00 1,720.00 Unit prices updated: 0310212015 'KCC 27A authorizes only one bond reduction. Version: 0310212015 King County Bond Quantity Meadowdale.xls Report Date: 4/2&2019 Site Improvement Bond Quantity Worksheet Web date: 0410312015 Existing Right-of-way Future Public Right of Way & Drainage Facilities Private Improvements Unit Price Unit Quant. Cost Quant. Cost Quant. Cost ROADIMPROVEMENT No. AC Grinding, 4' wide machine < 1000s R1- 1 $ 30.00 SY 10 300,00 AC Grinding, 4' wide machine 1000-2000sy Rl - 2 $ 16.00 SY AC Grinding, 4' wide machine > 2000sy RI - 3, $ 10.00 SY AC RemovaMsposal Ri - 4 $ 35.00 SY 48 1,680.00 Barricade, type Nl (Permanent) R1- 6 $ 56.00 LF Curb & Gutter, rolled R1- 7 $ 17.00 LF Curb & Gutter, vertical RI - 8 $ 12.50 LF Curb and Gutter, demolition and disposal R1- 9 $ 18.00 LF Curb, extruded asphalt RI - 10 $ 5.50 LF Curb, extruded concrete R1- 11 $ 7.00 LF Sawcut, asphalt, 3" depth R1- 121 $ 1.85 LF 430 795.50 Sawcut, concrete, per 1" depth R1- 13 $ 3.00 LF Sealant, asphalt Rl - 14 $ 2.00 LF Shoulder, AC, ( see AC road unit price) Rl - 15 $ - SY Shoulder, gravel, 4" thick Rt - 16 $ 15.00 SY Sidewalk, 4" thick R1- 17 $ 38.00 SY Sidewalk, 4* thick demolition and disposal R1- 18 $ 32.00 SY Sidewalk, 5'thick R1- 19 $ 41.00 SY Sidewalk, 5'thick, demolition and disposal Rl - 20 $ 40.00 SY Sign, handicap RI - 21 $ 85.00 Each Striping, per stall RI - 22 $ 7.00 Each Striping, thermoplastic, for crosswalk) RI - 23 $ 3.00 SF Striping, 4" reflectorized line JR1 - 24 $ 0.50 1 LF Page 4 of 9 SUBTOTAL 2,775.50 Unit prices updated. 0310212015 'KCC 27A authorizes only one bond reduction. Version: 0310212015 King County Bond Quantity Meadowdale.xls Report Date: 4/26/2019 Site Improvement Bond Quantity Worksheet Web date: 04M3/2015 Existing Right-of-way Future Public Right of Way if Drainage Facilities Private Improvements Unit Price Unit Quant. Cost Quant. Cost Quant. Cost ROAD SURFACING No. 4" Rock = 2.5 base & 1.5" top course 9112" Rock= 8" base & 1.5"top course Additional 2.5" Crushed Surfacing RS- 1 $ 3.60 SY HMA 112" Overlay, 1.5" RS-2 $ 14.00 SY HMA 112" Overlay 2" RS-3 $ 18.00 SY 18 324.00 HMA Road, 2- 4" rock, First 2500 SY RS-4 $ 28.00 SY 65 1,820.00 HMA Road, 2", 4" rock, W over 2500 SY RS - 5 1 $ 21.00 SY HMA Road, 3", 9 112" Rock, First 2500 SY RS - 6 $ 42.00 SY 155 6,510.00 HMA Road, 3", 9 112" Rock, Qty Over 2500 SY RS- 7 $ 35.00 SY Not Used RS - 8 Not Used RS - 9 HMA Road, 6" Depth, First 2500 SY RS -10 $ 33.10 SY HMA Road, 6" Depth, Ot . Over 2500 SY RS - 11 $ 30.00 SY HMA 314" or I", 4" Depth RS - 12 $ 20.00 SY Gravel Road, 4" rock, First 2500 SY RS -13 $ 15.00 SY Gravel Road, 4" rock, Qty. over 2500 SY RS - 14 $ 10.00 SY PCC Road Add Under Write-ins w/Design RS- 15 Thickened Edge RS- 1 $ 8.60 LF Page 5 of 9 SUBTOTAL 8,854.00 Unit prices updated. 0310212015 'KCC 27A authorizes only one bond reduction. Version: 0310212015 King County Bond Quantity Meadowdate.xis Report Date: 4/26/2019 Site Improvement Bond Quantity Worksheet Web date. 04103r2015 Existing Right-of-way Future Public Right of Way & Drainage Facilities Private Improvements Unit Price Unit Quant. T Cost Quant. I Cost Quant.T Cost DRAINAGE (CPP = Corrugated Plastic Pipe, N12 or Equivalent) For Culvertprices, Average of 4' cover was assumed. Assumeperforated PVC is same price as solid pipe. Access Road, RID D - 1 $ 21.00 SY Bollards - fixed D - 2 $ 240.74 Each Bollards - removable D - 3 $ 452.34 Each * (CBs include frame and lid CB Type 1 D - 4 $ 1,500.00 Each 2 3,000.00 2 3,000.00 CB Type IL D - 5 $ 1,750.00 Each CB Type 11, 48" diameter D - 6 $ 2, 300.00 Each for additional depth over 4' D - 7 $ 480.00 FT CB Type 11, 54" diameter D - 8 $ 2,500.00 Each for additional depth over 4' D - 9 1 $ 495.00 FT CB Type 11, 60" diameter D - 10 $ 2, 800.00 Each for additional depth over 4' D - 11 $ 600.00 FT CB Type 1l, 72" diameter D- 12 $ 3,600.00 Each for additional depth over 4' D - 13 $ 850.00 FT Through -curb Inlet Framework (Add) D - 14 $ 400.00 Each Cleanout, PVC, 4" D - 15 $ 150.00 Each Cleanout, PVC, 6" D - 16 $ 170.00 Each i 170.00 Cleanout, PVC, 8" D - 17 $ 200.00 Each Culvert, PVC, 4" D - 18 $ 10.00 LF 76 760.00 Culvert, PVC, 6" D - 19 $ 13.00 LF 300 3,900.00 Culvert, PVC, 8" D- 20 $ 15.00 LF 40 520.00 Culvert, PVC, 12" D - 21 $ 23.00 LF Culvert, CMP, 8" D - 22 $ 19.00 LF Culvert, CMP, 12" D - 23 $ 29.00 LF Culvert, CMP, 15" D - 24 $ 35.00 LF Culvert, CMP, 18" D - 25 $ 41.00 LF Culvert, CMP, 24" D - 26 $ 56.00 LF Culvert, CMP, 30" D - 27 $ 78.00 LF Culvert, CMP, 36" D - 28 $ 130.00 LF Culvert, CMP, 48" D - 29 $ 190.00 LF Culvert, CMP, 60" 1 D - 30 $ 270.001 LF Culvert, CMP, 72" 1 D - 31 $ 350.001 LF Page 6 of 9 SUBTOTAL 3,170.00 8,180.00 Unit prices updated: 03(02/2015 *KCC 27A authorizes only one bond reduction. Version: 0310212015 King County Bond Quantity Meadowdale.xis Report Date: 412612019 Site Improvement Bond Quantity Worksheet Web date: 0410312015 DRAINAGE CONTINUED Existing Future Public Right-of-way Right of Way & Drainage Facilities Private Improvements No. Unit Price Unit Quant. Cost Quant. Cost Quant. Cost Culvert, Concrete, 8" D - 32 $ 25.00 LF Culvert, Concrete, 12" D - 33 $ 36.00 LF Culvert, Concrete, 15" D - 34 $ 42.00 LF Culvert, Concrete, 18" D - 35 $ 48.00 LF Culvert, Concrete, 24" D - 36 $ 78.00 LF Culvert, Concrete, 30" D - 37 $ 125.00 LF Culvert, Concrete, 36" D - 38 $ 150.00 LF Culvert, Concrete, 42" D - 39 S 175.00 LF Culvert, Concrete, 48" D- 40 $ 205.00 LF Culvert, CPP, 6" 0 - 41 $ 14.00 LF Cotvert, CPP, 8" 0 - 42 $ 16.00 LF Culvert, CPP, 12" 0 - 43 $ 24.00 LF Culvert, CPP, 15" 0 - 44 $ 35.00 LF Culvert, CPP, 18" D - 45 $ 41.00 LF Culvert, CPP, 24" D - 46 $ 56.00 LF Culvert, CPP, 30" D - 47 $ 78.00 LF Culvert CPP, 36" D - 48 $ 130.00 LF Ditching D - 49 $ 9.50 CY Flow Dispersal Trench (1,436 base+) D - 50 S 28.00 LF 300 9836 French Drain (3' depth) D - 51 $ 26.00 LF 20 520 Geotextile, laid in trench, polypropylene D - 52 $ 3.00 SY Mid -tank Access Riser, 48" dia, 6' deep D - 54 S 2,000.00 Each Pond Overflow Spillway D - 55 $ 16.00 SY Restrictor/Oil Separator, 12" D-561 $ 1,150.00 Each Restrictor/Oil Separator, 15" D - 57 $ 1,350.00 Each Reslrictor/Oil Separator, 18" D - 58 $ 1,700.00 Each Ripra , placed D - 59 S 42.00 CY 66 2772 Tank End Reducer 36" diameter D - 60 $ 1,200.00 Each Trash Rack, 12" D - 61 $ 350.001 Each Trash Rack, 15" D - 621 $ 410.00 Each Trash Rack, 18" D - 63 $ 480.00 Each Trash Rack, 21 " D - 64 $ 550.00 Each Page 7 of 9 SUBTOTAL 13128 Unit prices updated: 0310212015 'KCC 27A authorizes only one bond reduction. Version: 03/02/2015 King County Bond Quantity Meadowdale. xrs Report Date: 4/26/2019 Site Improvement Bond Quantity Worksheet Web date: 041032015 Existing Right-of-way Future Public Right of Way & Drainage Facilities Private Improvements Unit Price Unit I Quant. Price Quant. Cost Quant. Cost PARKING LOT SURFACING Not To Be Used For Roads Or Shoulders No. 2" AC, 2" top course rock & 4" borrow PL -1 $ 21.00 SY NA NA 2" AC, 1.5' top course & 2.5" base course PL - 2 $ 28.00 SY NA NA 4" select borrow PL - 3 $ 5.00 SY NA j NA 1.5' top course rock & 2.5' base course PL - 4 $ 14.00 SY NA I NA UTILITY POLES & STREET LIGHTING Utility le relocation costs must be accompanied by Franchise Utility's Cost Estimate Utility Pole(s) Relocation UP-1 Lump Sum Street Light Poles w/Luminaires UP-2 $ T 500.00 Each WRITE -IN -ITEMS (Such as detention/water quality vaults.) No. Stormwater Vault W1- 1 $ 380, 000.00 Each Stock Wall W1- 2 $ 16.00 SY Trench Cleanout W1- 3 $ 225.00 Each 23 5,175.00 Wl - 4 LF W1- 5 FT W1-6 W1- 7 W1-8 WI-9 Hn - to SUBTOTAL SUBTOTAL (SUM ALL PAGES): 30% CONTINGENCY & MOBILIZATION: GRANDTOTAL: COLUMN: Page 8 of 9 24, 799.50 28, 203.00 7,439.85 8,460.90 32,239.35 36,663.90 C D Unit prices updated: 03/02/2015 •KCC 27A authorizes only one bond reduction. Version: 03/02/2015 King County Bond Quantity Meadowdale.xis Report Date: 4/26/2019 Site Improvement Bond Quantity Worksheet Web date: 0410312015 Original bond computations prepared by: Name: Curt Iffrig, EIT Date: 11912019 PE Registration Number: Tel. #: 425-408-1152 Firm Name: Group Four, inc Address: PO Box 1059 Lake Stevens, WA 98258 Project No: PLN20170057 Stab lization/Erosion Sediment Control (ESC) Existing Right -of -Way Improvements Future Public Right of Way & Drainage Facilities Private Improvements Calculated Quantity Completed Total Right -of Way and/or Site Restoration Bond`/" (First $7, 500 of bond' shall be cash.) Performance Bond' Amount (A+B+C+D) = TOTAL Maintenance/Defect Bond" Total NAME OF PERSON PREPARING BOND' REDUCTION: FINANCIAL GUARANTEE REQUIREMENTS PERFORMANCE BOND' MINIMUM BOND' AMOUNT PUBLIC ROAD & DRAINAGE AMOUNT REQUIRED FOR RECORDING OR MAINTENANCE/DEFECT BOND' TEMPORARY OCCUPANCY AT (A) $ 17,825.0 SUBSTANTIAL COMPLETION — (B) $ - (C) $ 32, 239.4 (D) $ 36, 663.9 (A+B) $ 17, 825.0 (T), $ 86, 728.2 Minimum is $2000. T x 0.30 $ 26, 016.5 Minimum is $2000. (B+C) x 0.25 = $ 8,059.8 Minimum is $2000. Date: ' NOTE: The word "bond" as used in this document means a financial guarantee acceptable to Kng County. `* NOTE: KCC 27A authorizes right of way and site restoration bonds to be combined when both are required_ The restoration requirement shall include the total cost for all TESC as a minimum, not a maximum. In addition, corrective work, both on- and off -site needs to be included. Quantities shall reflect worse case scenarios not just minimum requirements. For example, if a salmonid stream may be damaged, some estimated costs for restoration needs to be reflected in this amount. The 30% contingency and mobilization costs are computed in this quantity. NOTE: Per KCC 27A, total bond amounts remaining after reduction shall not be less than 30% of the original amount (T) or as revised by major design changes. REQUIRED BOND' AMOUNTS ARE SU13JECT TO REVIEW AND MODIFICATION BY KiNG COUNTY Page 9 of 9 Unit prices updated. 0310212015 Check out the DDES Web site at www.kingcounty.goylpermits Version: 0310212015 King County Bond Quantity Meadowdale.xls Report Date: 412612019 Meadowdale Short Plat Drainage Report Appendices A - Soils Map B - Infiltration Evaluation Letter C - Post Construction Soils D- WWHM Output E - Maintenance Standards Apr. 26, 2019 Group Four, Inc. 16 17-0523 Meadowdale Short Plat Drainage Report Appendix A NRCS Soils Report Apr. 26, 2019 Group Four, Inc. 17 17-0523 USDA United States Department of Agriculture MRCS Natural Resources Conservation Service A product of the National Cooperative Soil Survey, a joint effort of the United States Department of Agriculture and other Federal agencies, State agencies including the Agricultural Experiment Stations, and local participants Custom Soil Resource Report for Snohomish County Area, Washington September 27, 2017 Preface Soil surveys contain information that affects land use planning in survey areas. They highlight soil limitations that affect various land uses and provide information about the properties of the soils in the survey areas. Soil surveys are designed for many different users, including farmers, ranchers, foresters, agronomists, urban planners, community officials, engineers, developers, builders, and home buyers. Also, conservationists, teachers, students, and specialists in recreation, waste disposal, and pollution control can use the surveys to help them understand, protect, or enhance the environment. Various land use regulations of Federal, State, and local governments may impose special restrictions on land use or land treatment. Soil surveys identify soil properties that are used in making various land use or land treatment decisions. The information is intended to help the land users identify and reduce the effects of soil limitations on various land uses. The landowner or user is responsible for identifying and complying with existing laws and regulations. Although soil survey information can be used for general farm, local, and wider area planning, onsite investigation is needed to supplement this information in some cases. Examples include soil quality assessments (http://www.nres.usda.gov/wps/ portal/nres/main/soils/health/) and certain conservation and engineering applications. For more detailed information, contact your local USDA Service Center (https:Hoffices.sc.egov.usda.gov/locator/app?agency=nres) or your NRCS State Soil Scientist (http://www.nres.usda.gov/wps/portal/nres/detail/soils/contactus/? cid=nres 142p2_053951). Great differences in soil properties can occur within short distances. Some soils are seasonally wet or subject to flooding. Some are too unstable to be used as a foundation for buildings or roads. Clayey or wet soils are poorly suited to use as septic tank absorption fields. A high water table makes a soil poorly suited to basements or underground installations. The National Cooperative Soil Survey is a joint effort of the United States Department of Agriculture and other Federal agencies, State agencies including the Agricultural Experiment Stations, and local agencies. The Natural Resources Conservation Service (NRCS) has leadership for the Federal part of the National Cooperative Soil Survey. Information about soils is updated periodically. Updated information is available through the NRCS Web Soil Survey, the site for official soil survey information. The U.S. Department of Agriculture (USDA) prohibits discrimination in all its programs and activities on the basis of race, color, national origin, age, disability, and where applicable, sex, marital status, familial status, parental status, religion, sexual orientation, genetic information, political beliefs, reprisal, or because all or a part of an individual's income is derived from any public assistance program. (Not all prohibited bases apply to all programs.) Persons with disabilities who require 2 alternative means for communication of program information (Braille, large print, audiotape, etc.) should contact USDA's TARGET Center at (202) 720-2600 (voice and TDD). To file a complaint of discrimination, write to USDA, Director, Office of Civil Rights, 1400 Independence Avenue, S.W., Washington, D.C. 20250-9410 or call (800) 795-3272 (voice) or (202) 720-6382 (TDD). USDA is an equal opportunity provider and employer. Contents Preface............................................................................................ How Soil Surveys Are Made ......................................................... SoilMap.......................................................................................... SoilMap....................................................................................... Legend......................................................................................... MapUnit Legend......................................................................... Map Unit Descriptions.................................................................. Snohomish County Area, Washington ..................................... 5—Alderwood-Urban land complex, 2 to 8 percent slopes... References ....................... 2 ....................... 5 ....................... 8 .......................9 .....................10 ..................... 11 ......................11 .....................13 ..................... 13 .....................15 How Soil Surveys Are Made Soil surreys are made to provide information about the soils and miscellaneous areas in a specific area. They include a description of the soils and miscellaneous areas and their location on the landscape and tables that show soil properties and limitations affecting various uses. Soil scientists observed the steepness, length, and shape of the slopes; the general pattern of drainage; the kinds of crops and native plants; and the kinds of bedrock. They observed and described many soil profiles. A soil profile is the sequence of natural layers, or horizons, in a soil. The profile extends from the surface down into the unconsolidated material in which the soil formed or from the surface down to bedrock. The unconsolidated material is devoid of roots and other living organisms and has not been changed by other biological activity. Currently, soils are mapped according to the boundaries of major land resource areas (MLRAs). MLRAs are geographically associated land resource units that share common characteristics related to physiography, geology, climate, water resources, soils, biological resources, and land uses (USDA, 2006). Soil survey areas typically consist of parts of one or more MLRA. The soils and miscellaneous areas in a survey area occur in an orderly pattern that is related to the geology, landforms, relief, climate, and natural vegetation of the area. Each kind of soil and miscellaneous area is associated with a particular kind of landform or with a segment of the landform. By observing the soils and miscellaneous areas in the survey area and relating their position to specific segments of the landform, a soil scientist develops a concept, or model, of how they were formed. Thus, during mapping, this model enables the soil scientist to predict with a considerable degree of accuracy the kind of soil or miscellaneous area at a specific location on the landscape. Commonly, individual soils on the landscape merge into one another as their characteristics gradually change. To construct an accurate soil map, however, soil scientists must determine the boundaries between the soils. They can observe only a limited number of soil profiles. Nevertheless, these observations, supplemented by an understanding of the soil -vegetation -landscape relationship, are sufficient to verify predictions of the kinds of soil in an area and to determine the boundaries. Soil scientists recorded the characteristics of the soil profiles that they studied. They noted soil color, texture, size and shape of soil aggregates, kind and amount of rock fragments, distribution of plant roots, reaction, and other features that enable them to identify soils. After describing the soils in the survey area and determining their properties, the soil scientists assigned the soils to taxonomic classes (units). Taxonomic classes are concepts. Each taxonomic class has a set of soil characteristics with precisely defined limits. The classes are used as a basis for comparison to classify soils systematically. Soil taxonomy, the system of taxonomic classification used in the United States, is based mainly on the kind and character of soil properties and the arrangement of horizons within the profile. After the soil 5 Custom Soil Resource Report scientists classified and named the soils in the survey area, they compared the individual soils with similar soils in the same taxonomic class in other areas so that they could confirm data and assemble additional data based on experience and research. The objective of soil mapping is not to delineate pure map unit components; the objective is to separate the landscape into landforms or landform segments that have similar use and management requirements. Each map unit is defined by a unique combination of soil components and/or miscellaneous areas in predictable proportions. Some components may be highly contrasting to the other components of the map unit. The presence of minor components in a map unit in no way diminishes the usefulness or accuracy of the data. The delineation of such landforms and landform segments on the map provides sufficient information for the development of resource plans. If intensive use of small areas is planned, onsite investigation is needed to define and locate the soils and miscellaneous areas. Soil scientists make many field observations in the process of producing a soil map. The frequency of observation is dependent upon several factors, including scale of mapping, intensity of mapping, design of map units, complexity of the landscape, and experience of the soil scientist. Observations are made to test and refine the soil -landscape model and predictions and to verify the classification of the soils at specific locations. Once the soil -landscape model is refined, a significantly smaller number of measurements of individual soil properties are made and recorded. These measurements may include field measurements, such as those for color, depth to bedrock, and texture, and laboratory measurements, such as those for content of sand, silt, clay, salt, and other components. Properties of each soil typically vary from one point to another across the landscape. Observations for map unit components are aggregated to develop ranges of characteristics for the components. The aggregated values are presented. Direct measurements do not exist for every property presented for every map unit component. Values for some properties are estimated from combinations of other properties. While a soil survey is in progress, samples of some of the soils in the area generally are collected for laboratory analyses and for engineering tests. Soil scientists interpret the data from these analyses and tests as well as the field -observed characteristics and the soil properties to determine the expected behavior of the soils under different uses. Interpretations for all of the soils are field tested through observation of the soils in different uses and under different levels of management. Some interpretations are modified to fit local conditions, and some new interpretations are developed to meet local needs. Data are assembled from other sources, such as research information, production records, and field experience of specialists. For example, data on crop yields under defined levels of management are assembled from farm records and from field or plot experiments on the same kinds of soil. Predictions about soil behavior are based not only on soil properties but also on such variables as climate and biological activity. Soil conditions are predictable over long periods of time, but they are not predictable from year to year. For example, soil scientists can predict with a fairly high degree of accuracy that a given soil will have a high water table within certain depths in most years, but they cannot predict that a high water table will always be at a specific level in the soil on a specific date. After soil scientists located and identified the significant natural bodies of soil in the survey area, they drew the boundaries of these bodies on aerial photographs and A Custom Soil Resource Report identified each as a specific map unit. Aerial photographs show trees, buildings, fields, roads, and rivers, all of which help in locating boundaries accurately. 7 Soil Map The soil map section includes the soil map for the defined area of interest, a list of soil map units on the map and extent of each map unit, and cartographic symbols displayed on the map. Also presented are various metadata about data used to produce the map, and a description of each soil map unit. 3 Custom Soil Resource Report 3 Soil Map w 47° 50' 22" N 47" 50' 19" N 550MO 550010 550020 550000 55OD40 55005D 3 Map Scale: 1:560 i printed on A landscape (11" x 8.5') sheet N Meters 0 5 10 20 30 /V 0 25 50 100 150 Map projection: Web Mercator Comer coordinates: WGS84 Edge bcs: UTM Zane 1ON WGS84 9 55008D 550070 55= 550090 550100 550110 3 47- 50' 22" N I o_ 47° 50' 19" N MAP LEGEND Area of Interest (AOI) Area of Interest (AOI) Soils Soil Map Unit Polygons __0 Soil Map Unit Lines 13 Soil Map Unit Points Special Point Features v Blowout ® Borrow Pit Clay Spot 0 Closed Depression Gravel Pit Gravelly Spot O Landfill A. Lava Flow Marsh or swamp s�► Mine or Quarry O Miscellaneous Water ® Perennial Water V Rock Outcrop + Saline Spot Sandy Spot Severely Eroded Spot Sinkhole Slide or Slip o, Sodic Spot Custom Soil Resource Report MAP INFORMATION Spoil Area The soil surveys that comprise your AOI were mapped at 1:24,000. jo Stony Spot ® Very Stony Spot Warning: Soil Map may not be valid at this scale. + Wet Spot Enlargement of maps beyond the scale of mapping can cause Other misunderstanding of the detail of mapping and accuracy of soil .� Special Line Features line placement. The maps do not show the small areas of contrasting soils that could have been shown at a more detailed Water Features scale. Streams and Canals Transportation Please rely on the bar scale on each map sheet for map +44 Rails measurements. ti Interstate Highways Source of Map: Natural Resources Conservation Service US Routes Web Soil Survey URL: Coordinate System: Web Mercator (EPSG:3857) Major Roads Local Roads Maps from the Web Soil Survey are based on the Web Mercator projection, which preserves direction and shape but distorts Background distance and area. A projection that preserves area, such as the . Aerial Photography Albers equal-area conic projection, should be used if more accurate calculations of distance or area are required. This product is generated from the USDA-NRCS certified data as of the version date(s) listed below. Soil Survey Area: Snohomish County Area, Washington Survey Area Data: Version 14, Sep 8, 2016 Soil map units are labeled (as space allows) for map scales 1:50,000 or larger. Date(s) aerial images were photographed: Jul 7, 2014—Jul 8, 2014 The orthophoto or other base map on which the soil lines were compiled and digitized probably differs from the background imagery displayed on these maps. As a result, some minor shifting of map unit boundaries may be evident. Custom Soil Resource Report Map Unit Legend Snohomish County Area, Washington (WA661) Map Unit Symbol Map Unit Name Acres in AOI Percent of AOI 5 Alderwood-Urban land complex, 2 to 8 percent slopes 0.9 100.0% Totals for Area of Interest 0.9 100.0% Map Unit Descriptions The map units delineated on the detailed soil maps in a soil survey represent the soils or miscellaneous areas in the survey area. The map unit descriptions, along with the maps, can be used to determine the composition and properties of a unit. A map unit delineation on a soil map represents an area dominated by one or more major kinds of soil or miscellaneous areas. A map unit is identified and named according to the taxonomic classification of the dominant soils. Within a taxonomic class there are precisely defined limits for the properties of the soils. On the landscape, however, the soils are natural phenomena, and they have the characteristic variability of all natural phenomena. Thus, the range of some observed properties may extend beyond the limits defined for a taxonomic class. Areas of soils of a single taxonomic class rarely, if ever, can be mapped without including areas of other taxonomic classes. Consequently, every map unit is made up of the soils or miscellaneous areas for which it is named and some minor components that belong to taxonomic classes other than those of the major soils. Most minor soils have properties similar to those of the dominant soil or soils in the map unit, and thus they do not affect use and management. These are called noncontrasting, or similar, components. They may or may not be mentioned in a particular map unit description. Other minor components, however, have properties and behavioral characteristics divergent enough to affect use or to require different management. These are called contrasting, or dissimilar, components. They generally are in small areas and could not be mapped separately because of the scale used. Some small areas of strongly contrasting soils or miscellaneous areas are identified by a special symbol on the maps. If included in the database for a given area, the contrasting minor components are identified in the map unit descriptions along with some characteristics of each. A few areas of minor components may not have been observed, and consequently they are not mentioned in the descriptions, especially where the pattern was so complex that it was impractical to make enough observations to identify all the soils and miscellaneous areas on the landscape. The presence of minor components in a map unit in no way diminishes the usefulness or accuracy of the data. The objective of mapping is not to delineate pure taxonomic classes but rather to separate the landscape into landforms or landform segments that have similar use and management requirements. The delineation of such segments on the map provides sufficient information for the development of resource plans. If intensive use of small areas is planned, however, 11 Custom Soil Resource Report onsite investigation is needed to define and locate the soils and miscellaneous areas. An identifying symbol precedes the map unit name in the map unit descriptions. Each description includes general facts about the unit and gives important soil properties and qualities. Soils that have profiles that are almost alike make up a soil series. Except for differences in texture of the surface layer, all the soils of a series have major horizons that are similar in composition, thickness, and arrangement. Soils of one series can differ in texture of the surface layer, slope, stoniness, salinity, degree of erosion, and other characteristics that affect their use. On the basis of such differences, a soil series is divided into soil phases. Most of the areas shown on the detailed soil maps are phases of soil series. The name of a soil phase commonly indicates a feature that affects use or management. For example, Alpha silt loam, 0 to 2 percent slopes, is a phase of the Alpha series. Some map units are made up of two or more major soils or miscellaneous areas. These map units are complexes, associations, or undifferentiated groups. A complex consists of two or more soils or miscellaneous areas in such an intricate pattern or in such small areas that they cannot be shown separately on the maps. The pattern and proportion of the soils or miscellaneous areas are somewhat similar in all areas. Alpha -Beta complex, 0 to 6 percent slopes, is an example. An association is made up of two or more geographically associated soils or miscellaneous areas that are shown as one unit on the maps. Because of present or anticipated uses of the map units in the survey area, it was not considered practical or necessary to map the soils or miscellaneous areas separately. The pattern and relative proportion of the soils or miscellaneous areas are somewhat similar. Alpha -Beta association, 0 to 2 percent slopes, is an example. An undifferentiated group is made up of two or more soils or miscellaneous areas that could be mapped individually but are mapped as one unit because similar interpretations can be made for use and management. The pattern and proportion of the soils or miscellaneous areas in a mapped area are not uniform. An area can be made up of only one of the major soils or miscellaneous areas, or it can be made up of all of them. Alpha and Beta soils, 0 to 2 percent slopes, is an example. Some surveys include miscellaneous areas. Such areas have little or no soil material and support little or no vegetation. Rock outcrop is an example. 12 Custom Soil Resource Report Snohomish County Area, Washington 5—Alderwood-Urban land complex, 2 to 8 percent slopes Map Unit Setting National map unit symbol: 2hz9 Elevation: 50 to 800 feet Mean annual precipitation: 25 to 60 inches Mean annual air temperature: 48 to 52 degrees F Frost -free period: 180 to 220 days Farmland classification: Not prime farmland Map Unit Composition A/derwood and similar soils: 60 percent Urban land: 25 percent Minor components: 6 percent Estimates are based on observations, descriptions, and transects of the mapunit. Description of Alderwood Setting Landform: Till plains Parent material: Basal till Typical profile H1 - 0 to 7 inches: gravelly ashy sandy loam H2 - 7 to 35 inches: very gravelly ashy sandy loam H3 - 35 to 60 inches: gravelly sandy loam Properties and qualities Slope: 2 to 8 percent Depth to restrictive feature: 20 to 40 inches to densic material Natural drainage class: Moderately well drained Capacity of the most limiting layer to transmit water (Ksat): Very low to moderately low (0.00 to 0.06 in/hr) Depth to water table: About 18 to 36 inches Frequency of flooding: None Frequency of ponding: None Available water storage in profile: Low (about 3.0 inches) Interpretive groups Land capability classification (irrigated): None specified Land capability classification (nonirrigated): 4s Hydrologic Soil Group: B Other vegetative classification: Limited Depth Soils (G002XN302WA) Hydric soil rating: No Minor Components Mckenna Percent of map unit: 2 percent Landform: Depressions Hydric soil rating: Yes Norma Percent of map unit: 2 percent 13 Custom Soil Resource Report Landform: Depressions Hydric soil rating: Yes Terric medisaprists Percent of map unit: 2 percent Landform: Depressions Hydric soil rating: Yes 14 References American Association of State Highway and Transportation Officials (AASHTO). 2004. Standard specifications for transportation materials and methods of sampling and testing. 24th edition. American Society for Testing and Materials (ASTM). 2005. Standard classification of soils for engineering purposes. ASTM Standard D2487-00. Cowardin, L.M., V. Carter, F.C. Golet, and E.T. LaRoe. 1979. Classification of wetlands and deep -water habitats of the United States. U.S. Fish and Wildlife Service FWS/OBS-79/31. Federal Register. July 13, 1994. Changes in hydric soils of the United States. Federal Register. September 18, 2002. Hydric soils of the United States. Hurt, G.W., and L.M. Vasilas, editors. Version 6.0, 2006. Field indicators of hydric soils in the United States. National Research Council. 1995. Wetlands: Characteristics and boundaries. Soil Survey Division Staff. 1993. Soil survey manual. Soil Conservation Service. U.S. Department of Agriculture Handbook 18. http://www.nres.usda.gov/wps/portal/ nres/detail/national/soils/?cid=nres142p2_054262 Soil Survey Staff. 1999. Soil taxonomy: A basic system of soil classification for making and interpreting soil surveys. 2nd edition. Natural Resources Conservation Service, U.S. Department of Agriculture Handbook 436. http:// www. nres.usda.gov/wps/portal/nres/detail/national/soils/?cid=nres142p2_053577 Soil Survey Staff. 2010. Keys to soil taxonomy. 11th edition. U.S. Department of Agriculture, Natural Resources Conservation Service. http:// www. nres. usda.gov/wps/portal/nres/detail/national/soils/?cid=nresl42p2_053580 Tiner, R.W., Jr. 1985. Wetlands of Delaware. U.S. Fish and Wildlife Service and Delaware Department of Natural Resources and Environmental Control, Wetlands Section. United States Army Corps of Engineers, Environmental Laboratory. 1987. Corps of Engineers wetlands delineation manual. Waterways Experiment Station Technical Report Y-87-1. United States Department of Agriculture, Natural Resources Conservation Service. National forestry manual. http://www.nres.usda.gov/wps/portal/nres/detail/soils/ home/?cid=nres 142p2_053374 United States Department of Agriculture, Natural Resources Conservation Service. National range and pasture handbook. http://www.nres.usda.gov/wps/portal/nres/ detail/national/landuse/rangepasture/?cid=stelprdb1043084 15 Custom Soil Resource Report United States Department of Agriculture, Natural Resources Conservation Service. National soil survey handbook, title 43041. http://www.nres.usda.gov/wps/portal/ n res/deta il/soils/scientists/?cid=n res 142p2_054242 United States Department of Agriculture, Natural Resources Conservation Service. 2006. Land resource regions and major land resource areas of the United States, the Caribbean, and the Pacific Basin. U.S. Department of Agriculture Handbook 296. http://www.nres.usda.gov/wps/portal/nres/detail/national/soils/? cid=nres142p2_053624 United States Department of Agriculture, Soil Conservation Service. 1961. Land capability classification. U.S. Department of Agriculture Handbook 210. http:// www.nrcs.usda.gov/lnternet/FSE—DOCUMENTS/nrcsl42p2_052290.pdf 16 Meadowdale Short Plat Drainage Report Appendix B Infiltration Evaluation Letter Robinson Noble February 23, 2018 Revised April 17, 2018 Apr. 26, 2019 Group Four, Inc. 18 17-0523 r ROBINSON NOBLE April 17, 2018 Duncan and Stephanie Spence 701 Daley Street Edmonds, Washington 98020 Revised Infiltration Evaluation 17606 72"d Avenue West Edmonds, Washington RN File No. 3273-001 A Dear Mr. and Mrs. Spence: This letter presents the results of our infiltration evaluation at your single family residential project located at 17606 72,11 Avenue in Edmonds, Washington. The site is currently developed with a single family residence and outbuilding. We understand project plans are to subdivide the site into two lots, and construct a new single family residence on the eastern lot. We have been provided with a Memorandum from the City of Edmonds dated December 27, 2017 requesting additional information, and a development plan showing the site layout prepared by Group Four dated November 10, 2017. We have also been provided with the City of Edmonds review comments dated April 2, 2018. Development plans potentially include a rain garden or an infiltration trench in the northwest region of Lot 2. We understand per the City of Edmonds Municipal Code (EMC) Section 18.30.060 that the sources of stormwater management for the City include the following documents: 2014 Department of Ecology Stormwater Management Manual for Western Washington (DOE) and The Edmonds Stormwater Addendum (ESA). The Memorandum provided by the City of Edmonds requires that a stormwater report consistent with the previously listed documents be prepared that includes full infiltration calculations. Appendix B of ESA and Section 3.4 of the DOE state that infiltration testing for rain gardens be conducted using the Small Scale Pilot Infiltration Test (PIT) method. We performed one PIT at the location of the proposed rain garden. The test was performed at a depth of 3.0 feet. The testing depth was determined by assuming a ponding depth of 12 inches and a rain garden soil mix depth of 24 inches. This was based on Plan 1 of the Rain Garden Handbook for Western Washington. Prior to performing the PIT, Test Pit 1 was excavated in the general area of the test to confirm that no confining soil layer existed within 1 foot of the proposed testing depth. In general the soils in Test Pit 1 and the PIT excavation consisted of a surficial layer of topsoil that ranged in thickness from 0.6 to 1.0 feet. Underlying the topsoil we 2105 South C Street 17625 130" Avenue NE, Suite 102 Tacoma, Washington 98402 www.robinson-noble.com Woodinville, Washington 98072 P: 253.475.77111 F: 253.472.5846 P: 425.488.0599 1 F: 425.488.2330 Revised Infiltration Evaluation 17606 7211 Avenue West April 17, 2018 RN File No. 3273-001A Page 2 encountered loose fine to medium sand with silt and gravel to the depth explored in Test Pit 1 and at the testing depth in the PIT. This description was confirmed with a grain size analysis laboratory test. The test results are presented as Figure 4. The conditions observed in Test Pit 1 indicated that no confining soil layer or groundwater table was observed within 1 foot of the testing depth. We therefore proceeded with the PIT excavations and subsequent testing. The PIT was performed using the following method per the DOE and Appendix B of the ESA. The tests were begun by pre-soaking for a period of 6 hours until a constant steady rate was achieved. Following the pre-soak period the water level in each hole was maintained at a constant depth for a period of at least 1 hour. Readings of the flow rate and cumulative volume required to maintain the water level were taken every 15 minutes. Following the completion of the steady state period the water was shut off and a falling head test was performed during which the rate of the water level drop was measured. The design infiltration rate is determined by applying correction factors, as prescribed in Checklist 4 and Table 13,1 of the ESA, to the measured infiltration rate. This is shown in Equation 1 below. The measured infiltration rate is calculated as the lowest hourly rate determined during the falling head portion of the PIT. Ksat,design = Ksat.measuredX CFv x CFtxCFm (Equation 1) The correction factor CF, accounts for site variability and the number of locations tested as compared to the proposed infiltration area. CFt accounts for uncertainty in the testing method. CF., must be within the range of 0.33 to 1.0 per Table 3.4.1 of the DOE and Table B.1 of the ESA. CF, is prescribed as 0.5 for the small-scale PIT per Appendix B of the ESA. The correction factor for influent control is prescribed in the ESA as 0.9. The table below presents the measured infiltration rate from the test. This table also presents our recommended correction factors and design rate. Design Infiltration Rate Ksat,measured (In/hr) CF CF, CFM Ksat, design (in/hr) 18.0 0.7 0.5 0.9 5.4 We recommend we review the project plans as they develop. This will enable us to evaluate the effects, if any, of potential overflow onto adjacent properties. Use of This Letter We have prepared this letter for Duncan and Stephanie Spence and their agents, for use in design of this project. This letter is not a complete geotechnical report. The data and letter should be provided to prospective contractors for their bidding and estimating purposes, but our letter, conclusions, and interpretations should not be construed as a warranty of subsurface conditions. Within the limitations of scope, schedule and budget for our services, we have strived to take care that our services have been completed in accordance with generally Robinson Noble, Inc. Revised Infiltration Evaluation 17606 72" d Avenue West April 17, 2018 RN File No. 3273-001 A Page 3 accepted practices followed in this area at the time this letter was prepared. No other conditions, expressed or implied, should be understood. We appreciate the opportunity to be of service to you. If there are any questions concerning this letter or if we can provide additional services, please call. Sincerely, Robinson Noble, Inc. Barbara A. Gallagher, PE Senior Engineer JHA:BAG:RBP:am Four Figures Robinson Noble, Inc. --'�`io SILAS .5y4- /-CONC. 1MALL - -Sr- !ASPHALT --us 3--^� 199.63 44rc � tt' ;rIDE I�CIFANOUT 8 F,L IR\ j1��j�lF'j -o' Y�, _ _ �u:r—• o;�-_ 1203� C�;,IDJGI�� • j,\.�� ✓•` �O�'�P — IG -...% 1' OR 3/4" iL oHF i ?` : �,'•- t l STOP I'vL � 14" R PIT-1 EiER ..--- SIGN f L.S Ib' r1R �..�- pQ6- EX. E' UTJL3"'rTP-1 CLEARING UMIT8 \\ / "!•, .•!,• WOOD FENCE n ra51�hF,� 7- vI LOT 12 PUWER POLc 2F' FIR ', \ \\ 1 �,�F IL C"CF COLIC. o r- 62 SF (DECOVINSS109ED) COWC •, ------ `!��6" Fr.. _l{ i.Iv' -� G IVCPtlT' SILT FENCE 2s 8S9L � — — — — � _ — _ F I a, APPF,UaIVtTc --- ---_. ! IOCA11r;N or GA 7."✓ %�rR CARACI' I s 6- PVC YD5 BSBL� COrMEC110N FEF IN 4S-OUII T$ ;a RIM=393.03 I DECK o •� ( tO Imo' 'k. r•:.v:E� -rr• -' �� _ _._-Y:='r. ia....'.1G'T =� . .N m IE=392.02 Ito Im LOT 1 22,659 SF >< u ! t a• Pvc i PROPOSED t N F CGN(.. STAIRS �• I ! p1 J HOUSE ro -} J I o a, I_ __ FFE-394r9O w 'N CONC.— 9 �I'"� im 41 LF }9 E" rRUi 8" FRUIT n IDr! Imo' FrtJ:' 1 { Q' I ! a 4 A JIT i 0 6" PVC I ' '1 .- �... 71 'f.. • F� r�., z4: , z I 4...y `;� i `r r. i� o 40' IE=392.23 CCL!" SLOTTED DRAM5 LF PARKING Fi/` ' L^N3?_RIM=394.06 m � :_-- ---- -�' 7•R�- J LEGEND TP-1 Number and Approximate Location of Test Pit PIT-1 Number and Approximate Location of PIT 0 20 40 Scale 1" = 20' / 26" F'R ^ 4RTICAL CUP.n a _ .... j - ` oI� % O 0 _ RET)WOOC �S z j/ ��. , 15` COGWOGJ NIA BIRCH c� _—'^ . 0 38' CC0 Figure 1 • _ ^r, Note: Basemaptaken from Preli ninary PM: BAG Site Plan Development Plan April 2018 ROBINSON* d,epaedbyGro Group 3273-001A Edmonds 2-Lot Infiltration: 17606 72nd Avenue West NOBLE 2017 Unified Soil Classification System MAJOR DIVISIONS GROUP SYMBOL GROUP NAME GRAVEL CLEAN GRAVEL GW WELL -GRADED GRAVEL, FINE TO COARSE GRAVEL COARSE - GP POORLY -GRADED GRAVEL GRAINED MORE THAN 50% OF COARSE FRACTION GRAVEL WITH FINES GM SILTY GRAVEL SOILS RETAINED ON NO.4 SIEVE GC CLAYEY GRAVEL MORE THAN 50% RETAINED ON number 200 SIEVE SAND CLEAN SAND SW WELL -GRADED SAND, FINE TO COARSE SAND SP POORLY -GRADED SAND MORE THAN 50% OF SAND COARSE FRACTION PASSES NO.4 SIEVE WITH FINES SM SILTY SAND SC CLAYEY SAND FINE - SILT AND CLAY INORGANIC ML SILT CL CLAY GRAINED LIQUID LIMIT LESS THAN 50% SOILS ORGANIC OL ORGANIC SILT, ORGANIC CLAY MORE THAN 50% PASSES NO.200 SIEVEMH SILT AND CLAY INORGANIC SILT OF HIGH PLASTICITY, ELASTIC SILT CH CLAY OF HIGH PLASTICITY, FAT CLAY LIQUID LIMIT 50°% OR MORE ORGANIC OH ORGANIC CLAY, ORGANIC SILT HIGHLY ORGANIC SOILS PT PEAT NOTES: SOIL MOISTURE MODIFIERS 1) Field classification is based on visual examination of soil in general Dry -Absence of moisture, dusty, dry to the touch accordance with ASTM D 2488-83. 2) Soil classification using laboratory Moist- Damp, but no visible water tests is based on ASTM D 2487-83. Wet- Visible free water or saturated, 3) Descriptions of soil density or consistency are based on usually soil is obtained from below water table interpretation of blowcount data, visual appearance of soils, and/or test data. Figure 2 PM: BAG ROBINSON April 2018 3273-001A Unified Soil Classification System Edmonds 2-Lot Infiltration: 17606 72nd Avenue West NOBLE U.S. Standard Sieve Opening in Inches U.S. Standard Sieve Numbers Hydrometer Results 100% 20 6 4 3 1'/, V. 'rS % #4 10 16 20 30 40 50 100 200 I 0% - - 90% - 10% - - - - - 80% �- -- - -� --- 20% 70% r 1T 30% 3 60% - 40% al 50% - - _...__ 50% c 40% - •v co - - 60% c 0 30% - - - 70% 20% - 80% - - 10% - 90% 0% 100% 1000 100 10 1 0.1 0.01 0.001 Grain Size in Millimeters Gravels Sands Cobbles Silts CIE Coarse Fine Coarse MediumFine RN File No. 3273-001A Figure 3 LOG OF EXPLORATION DEPTH USC SOIL DESCRIPTION TEST PIT ONE 0.0 - 0.5 SM Dark brown silty fine sand with organics (loose, moist) (Topsoil) 0.5 - 4.0 SP-SM Gray brown fine to medium sand with silt and gravel (loose, moist) Samples were not collected Groundwater seepage was not encountered Test pit caving was not encountered Test pit was completed at 4.0 feet on 2/21/2018 PIT-1 0.0 - 1.0 SM Dark brown silty fine sand with organics (roots) (loose, moist) (Topsoil) 1.0 - 3.0 SP-SM Gray brown fine to medium sand with silt and gravel (loose, moist) Sample was collected at 3.0 feet Groundwater seepage was not encountered Test pit caving was not encountered Test pit was completed at 3.0 feet on 2/21/2018 ROBINSON NOBLE, INC. FILE NO 3273-001A FIGURE 4 Meadowdale Short Plat Drainage Report Appendix C Post Construction Amended Soils Snohomish County Apr. 26, 2019 Group Four, Inc. 19 17-0523 4*4� Post -construction Snohomish County Planning ai1d DevQlopmenf Services Visit us at : 2nd Floor Robert J• Drewel Bldg. 3000 Rockefeller Avenue Everett, WA 98201 42S-388-3311 1-8D0-562-4367, ext. 3311 Soil Standard WWW .SNOCO.ORG Assistance Bulletin #94 Revised February 2016 Keyword: Assistance Bulletins Initial effective date September 30, 2010 Revised effective date January 22, 2016 SCC 30.63A.525 Minimum Requirement (MR) 5 On -Site ,Soils Management and BMP T5.13 Preserving and Restoring Healthy Soils on Site Developments in Snohomish County Pursuant to the County's Phase I Municipal Stormwater Management Permit require- ments, land disturbing activity project applications vested on or after September 30, 2010, must control stormwater on -site. SCC 30.63A.525 ensures that projects will be designed to infiltrate, disperse, and retain stormwater runoff on -site to the maximum extent feasible without causing flooding or erosion impacts, and to reduce the hydrologic disruption of developed sites. Engineering analysis will generally be required to comply with this requirement and other stormwater control requirements in MRs 1 through 5. Compliance with MR 5 — On -site Soils Management in the Snohomish County Drainage Manual Volume 5, Chapter 5 is achieved by implementing best management practice ONLINE INFORMATION (BMP) T 5.13. The purpose of BMP T5.13 Post -Construction Soil Quality and Depth is vtww.snohom1shcounWw_a.Pov11190 to establish soil quality and depth to improve stormwater functions in the post develop- ment landscape. Implementation of this BMP provides increased treatment of pollutants and sediments that result from development and habitation. It will minimize the need for some landscaping chemicals, thus reducing pollution through prevention. Naturally occurring (undisturbed) soil and vegetation provide important stormwater func- tions including: water infiltration; nutrient, sediment, and pollutant adsorption; sediment and pollutant biofiltration; water interflow storage and transmission; and pollutant decom- position. These functions are largely lost when development strips away native soil and vegetation and replaces it with minimal topsoil and sod. Not only are these important stormwater functions lost, but also such landscapes themselves become pollution - generating pervious surfaces due to increased use of pesticides, fertilizers and other land- scaping chemicals, and the concentration of pet wastes. Note: MR S is triggered on sites with more than 2,000 sq. ft of new, replaced, or new plus replaced impervious surface, or 7, 000 sq. ft. or greater of land disturbing activity. This bulletin is intended only as an information guide. The information may not be complete and is subject to change. - •' <`' For complete legal information refer to Snohomish County Code. Soil Treatment Options There are four Soil Treatment Options that can be used to meet the post - construction soil standard. These options can be used individually, or in combination (more than one may be used in different areas of a single site), so that they work best for the situation. The most convenient and economical methods for achieving the standards depend on site soil conditions, grading and subgrade compaction, practicality of stockpiling site topsoil during grading, and site access issues. Choose Options 1, 2, 3 and/or 4 in areas where grading and soil disturbance are unavoidable, and follow the attached design guidelines : Option 1: Leave native soil undisturbed, and protect from compaction during con- struction. NOTE: Option 1 is only applicable to sites that have the original, undisturbed soil native to the site. This will most often be forested land that is being left un- disturbed in the current project. This option is the most economical and best for the environment, but is not always feasible. • Plan site development to leave areas where native vegetation does not need to be dis- turbed. • Pence off areas of native vegetation on the site that will not be stripped, logged, or graded to protect them fiom disturbance during con- struction. - Undisturbed areas do not require soil amend- tnent. Option 2: Amend disturbed soil according to the following procedures: a. Scarify subsoil to a depth of one foot. b. In planting beds, place three inches of com- post and till in to an eight -inch depth. c. In turf areas, place two inches of compost and till in to an eight -inch depth. d. Apply two to four inches of arborist wood chip, coarse bark mulch, or compost mulch to planting beds after final planting. Alternatively, disturbed soil can be amended on a site -customized manner so that it meets the soil quality criteria set forth above, as deter- mined by a licensed engineer, geologist, land- scape architect, or other person as approved by Snohomish County, Note: MR 5 is triggered on sites with more than 2, 000 sq. ft. of new, replaced, or new plus replaced impervious surface, or 7, 000 sq. ft. or greater of land disturbing activity. Option 3: Disturbed Soil. Stockpile existing topsoil during grading and replace it prior to planting. Stockpiled topsoil must be amended if needed to meet the organic matter and depth requirements by following the procedures in option (2). Remove forest duff layer and topsoil and stockpile separately, in an approved lo- cation prior to grading. Cover soil and duff piles with woven weed barrier (available from nursery supply stores) that sheds moisture yet allows airflow. Option 4: Import topsoil mix with 8-13% soil organic mat- ter content. Import topsoil mix of sufficient organic content and depth to meet the organic matter and depth requirements. What is the human impact on soils? 55-70% surface water runoff (carries pesticides, silt and animal waste) 15% surface water detained/ infiltrated 15-30% evapo- ranspiration 0% rainfall detained n Subsoil Groundwater Bedrock Note: MR 5 is triggered on sites with more than 2,000 sq. ft. of new, replaced, or new plus replaced impervious surFace, or 7, 000 sq. ft. or greater of land disturbing activity. Figuring Compost, Stockpiling and/or Imported Topsoil Needs Step 1. Review site conditions, landscape and grading plans. • Examine site plans and soils. Use a shovel to dig in several areas that have been or will be graded to deter- mine if the newly exposed grades can be easily amended, or if compaction will require plowing/tilling of the subsoil or topsoil import. Determine if there are areas where soil could be stockpiled on -site. • Identify areas where soil can be: left undisturbed (Optionl), amended in place with compost (Option 2), re- moved and replaced with imported purchased topsoil (Option 4), or stockpiled and later reapplied (Option 3). Step 2. Select soil treatment option and suitable pH for each planting area. Amending with compost is often the most economical way to bring poor soils up to the required soil organic mat- ter content. On sites with the original, undisturbed, native soil, and where space permits, stockpiling and reapply- ing topsoil may be less costly. Importing topsoil usually costs more than amending existing soil, though it may be easier where subsoil conditions make cultivation difficult. • To determine a custom compost amendment rate for Options 2 and/or 3, use an accredited soil -testing labora- tory (website provided) to sample and test the site soil to determine the soil bulk density (lbs/cubic yard dry weight) and soil organic matter percentage. These values will be used to calculate the custom compost amendment rate in inches (see BMP T 5.13(3)). • Identify the areas where the selected Soil Treatment. Option(s) will be applied. Outline those areas on the site plan with a dark, thick -line pen. • Assign each area an identifying letter (A, B, C... ) on the site drawing. • Determine desired pH for each lettered area, based on suitability for proposed plants. • Include required information on the Soil Management Plan Summary Fonn. Step 3. Calculate compost and/or topsoil volumes for each area. • Calculate the square footage of each lettered area on the Soil Management Site plan. • If using the pre -approved amendment rate, complete the attached Compost and Topsoil Calculation Work - sheet to calculate the quantities of compost and/or topsoil needed. Step 4. Identify compost and/or topsoils to be applied and retain records. • Contact a compost or topsoil facility permitted by Washington state and select products that meet the require- ments. • If preparing to use a custom compost amendment rate for Options 2 and/or 3: ■ Determine the target percentage of soil organic matter you wish to achieve. Note: 8% is better for grassy areas and lawns and 10-13% is better for planting beds. ■ Request copies of compost test result reports that include the compost (lbs/cubic yard dry weight) and the percentage compost organic matter. These values will be used to calculate the custom amendment rate in inches. • Complete the Soil Management Plan Summary form in this bulletin, with required attachments. These will become part of your stormwater site plan documenting how you intend to comply with SCC 30.63A.525 Min- imum Requirement 5, On Site Stormwater Management. Retain original delivery tickets for compost and/or topsoil products for verification purposes. Step 5. Obtain professional certification. • A licensed engineer, geologist, landscape architect, or permitted compost facility must verify that soil amend- ments meet the content, depth and installation standards consistent with BMP T5.13 requirements. • Provide a certification letter, signed by the appropriate professional, to the county inspector prior to obtaining final occupancy 0 Questions? For questions related to Snohomish County's post -construction soil standards, please contact: Planning and Development Services Phone: (425) 388-3311 Soil pH Use an accredited soil -testing laboratory to test the pH of the soil and ask the laboratory to provide information on how to adjust the soil pH, should that be necessary. To find accredited soil testing laboratories, see attachments. A nursery can provide specific information about suitable pH for landscape plants. Here are optimal soil pI-I ranges for various plant types: Lawns — 5.5 to 7.5 pH Shrubs (except acid -tolerant plants) — 5.5 to 7.0 pH Acid -Tolerant Shrubs (Rhododendrons, Azaleas, Mountain Laurels, Camellias, Blueberries, native plants) — 4.5 to 5.5 pH Annual Flower and Vegetable Gardens — 6.0 to 7.0 pH Compost and Topsoil Calculation Worksheet for the Pre -approved Amend- ment Rate Compost sold in Washington must comply with state standards for compost quality found in the state solid waste rule (WAC 173-350-220). Compost sources include both permitted compost facilities and facilities that do not require permits because they are exempt under the state rule. Some compost facilities produce compost and topsoil mixes, and topsoil supply companies may use compost produced elsewhere to create topsoil mix products. To achieve the post -construction soil standard, topsoil mixes must contain organic matter content of ten percent dry weight in planting beds, and 5% organic matter content (based on a losson-ignition test) in turf areas, and a pH from 6.0 to 8.0 or matching the pH of the original undisturbed soil. The topsoil layer shall have a minimum depth of eight inches except where tree roots limit the depth of incorporation of amendments needed to meet the criteria. Subsoils below the topsoil layer should be scarified at least 4 inches with some incorporation of the upper material to avoid stratified layers, where feasible. Permit applicants that compost their own material at a maximum of 250 cubic yards of compost on site at any one time, may use that material for a project, pro- vided the appropriate tests are conducted and documented. In addition to the annu- al testing required by WAC 173-350-220, tests must include: 1) organic matter con- tent (range: 35-65%); and, if using a cus- tom compost amendment rate, compost bulk density (lbs./cubic yard dry weight). Resources Permitted Compost Facilities Jim in Snohomish County For a list of permitted compost facilities in Snohomish County, see the Washington State Department of Ecology Web site @ www.ec}.wa.gov/ programs/air/outdoor woodsmoke/recyclinai Snohomish Count) .htm Soil Testing Laboratories For a list of accredited soil testing laboratories and guidance on obtaining soil tests: www.SoilsforSalmon.org Compost and Topsoil Calculation Worksheet for the Pre -approved Amend- ment Rate NOTE: For Options 2 and 3, use this worksheet if you plan to use the pre -approved compost amendment rate of 2 inches. This worksheet should not be used if a custom compost amendment rate is selected for Options 2 and/ or 3. OnV - I r Leave native soil undisturbed, and protect from compaction during construc- tion. • Enter lettered areas from site plan where this option will be used: No calculations for compost or topsoil are necessary for this option. Amend existing soil in -place (2-inch layer of compost). • Enter lettered areas from site plan where this option will be used: • Enter combined square footage of lettered areas in thousands (example: for 4,525 sq ft, enter 4.525; for 500 sq ft, enter 0.5) Multiply combined square footage by 6.2 and enter product in box A A=Cubic Yards AMOUNT OF COMPOST NEEDED FOR THESE ARE- AS Note; MR S is triggered on sites with more than 2,000 sq. ft. of new, replaced, or new plus replaced impervious surface, or 7, 000 sq. ft. or greater of land disturbing activity. Option 3 Pon 4 Native Soil — stockpile site duff and topsoil and reapply after grading and con- struction. • Enter lettered areas from site plan where this option will be used: I� L P R.a fees FO L/kc,.,/v ,4.R5A 11.9 • Enter combined square footage of lettered areas in thousands (example: for 4,525 sq ft, enter 4.525; for 500 sq ft, enter 0.5) Multiply combined square footage by 25 and enter product in box B: B 297.5 =Cubic Yards AMOUNT OF TOPSOIL TO BE STOCKPILED AND REAPPLIED IN THESE AREAS Import topsoil. • Enter lettered areas from site plan where this option will be used: • Enter combined square footage of lettered areas in thousands (example: for 4,525 sq ft, enter 4.525; for 500 sq ft, enter 0.5) • Multiply combined square footage by 25 and enter product in box C: C=Cubic Yards AMOUNT OF IMPORTED TOPSOIL NEEDED FOR THESE AREAS Order These Amounts: Enter amount in Box A: Enter amount in Box C : Cubic Yards of Compost Cubic Yards of Topsoil Note: MR 5 is triggered on sites with more than 2,000 sq. ft. of new, replaced, or new plus replaced impervious surface, or 7, 000 sq. ft. or greater of land disturbing activity. Design Guidelines (see BMP T5.13) Soil retention. The duff layer and native topsoil should be retained in an undisturbed state to the maximum extent practicable. In any areas requiring grading remove and stockpile the duff layer and topsoil on site in a designated, controlled area, not adjacent to public resources and critical areas, to be reapplied to other por- tions of the site where feasible. Soil quality. All areas subject to clearing and grading that have not been covered by impervious surface, incorporated into a drainage facility or engineered as structural fill or slope shall, at project completion, demonstrate the following: 1. A topsoil layer with a minimum organic matter content of ten percent dry weight in planting beds, and 5% organic matter content (based on a loss on- ignition test) in turf areas, and a pH from 6.0 to 8.0 or matching the pH of the original undisturbed soil. The topsoil layer shall have a minimum depth of eight inches except where tree roots limit the depth of incorporation of amendments needed to meet the criteria. Subsoils below the topsoil layer should be scarified at least 4 inches with some incorporation of the upper material to avoid stratified layers, where feasible. 2. Planting beds must be mulched with 2 inches of organic material. �f 3. Quality of compost and other materials used to meet the organic content requirements: a. The organic content for "pre -approved" amendment rates can be met only using compost that meets the defmition of "composted materials" in WAC 173-350-220. This code is available online at: www.ec).wa..L,,ov/i)roLrams/swfa/ors!anics/law.html. Compost used in bioretention areas should be stable, mature and derived from yard debris, wood waste, or other organic ma- terials that meet the intent of the organic soil amendment specification. Biosolids and manure composts can be higher in bio-available phosphorus than compost derived from yard or plant waste and therefore are not allowed in bioretention areas due to the possibility of exporting bio- available phosphorus in effluent. The compost must also have an organic matter content of 35% to 65%, and a carbon to nitrogen ratio below 25:1. The carbon to nitrogen ratio may be as high as 35:1 for plantings composed entirely of plants native to the Puget Sound Lowlands re- gion. b. Calculated amendment rates may be met through use of composted materials as defined above; or other organic materials amended to meet the carbon to nitrogen ratio requirements, and meet- ing the contaminant standards of Grade A Compost. Note: MR 5 is triggered on sites with more than 2, 000 sq. ft. of new, replaced, or new plus replaced impervious surface, or 7, 000 sq. ft. or greater of land disturbing activity. Meadowdale Short Plat Drainage Report Appendix D WWHM Output Apr. 26, 2019 Group Four, Inc. 20 17-0523 WWHM2012 PROJECT REPORT Project Name: Spence Full infiltration Model Site Name: Site Address: City Report Date: 4/25/2019 Gage : Everett Data Start : 1948/10/01 Data End : 2009/09/30 Precip Scale: 0.80 Version Date: 2017/04/14 Version : 4.2.13 Low Flow Threshold for POC 1 : 50 Percent of the 2 Year High Flow Threshold for POC 1: 50 year PREDEVELOPED LAND USE Name : Historic Lot 2 Impervious Bypass: No Groundwater: No Pervious Land Use acre C, Forest, Mod .09 Element Flows To: Surface Interflow Groundwater Historic Infiltration Historic Infiltration Name : Historic Lot 2 Parking Permeable Bypass: No GroundWater: No Pervious Land Use C, Forest, Mod acre O1 Element Flows To: Surface Interflow Groundwater Historic Infiltration Historic Infiltration Name : Historic Equivalent Area Collected for Frontage Bypass: No Groundwater: No Pervious Land Use acre C, Forest, Mod .041 Element Flows To: Surface Interflow Groundwater Historic Infiltration Historic Infiltration Name : Historic Infiltration Trench Area Bypass: No GroundWater: No Pervious Land Use acre C, Forest, Mod .02 Element Flows To: Surface Interflow Name : Historic Lot 1 Parking Bypass: No Groundwater: No Pervious Land Use acre C, Forest, Mod .007 Pervious Total 0.007 Impervious Land Use acre Impervious Total 0 Basin Total 0.007 Groundwater Element Flows To: Surface Interflow Groundwater MITIGATED LAND USE Name : Lot 2 Impervious Bypass: No Impervious Land Use acre ROOF TOPS FLAT LAT 0.09 Element Flows To: Outlet 1 Outlet 2 Infiltration Trench Name : Lot 2 Parking Permeable Pavement Area: 0.0101 ft. Pavement Length: 22.00 ft. Pavement Width: 20.00 ft. Pavement slope 1: 0.02 To 1 Pavement thickness: 0.33 Pour Space of Pavement: 0.25 Material thickness of second layer: 0.66 Pour Space of material for second layer: 0.4 Material thickness of third layer: 0 Pour Space of material for third layer: 0 Infiltration On Infiltration rate: 5.4 Infiltration safety factor: 1 Total Volume Infiltrated (ac-ft.): 0.712 Total Volume Through Riser (ac-ft.): 0 Total Volume Through Facility (ac-ft.): 0.712 Percent Infiltrated: 100 Total Precip Applied to Facility: 0 Total Evap From Facility: 0.093 Element Flows To: Outlet 1 Outlet 2 Infiltration Trench Permeable Pavement Hydraulic Table Stage(feet) Area(ac.) volume(ac-ft.) Discharge(cfs) Infilt(cfs) 0.0000 0.010 0.000 0.000 0.000 0.0111 0.010 0.000 0.000 0.055 0.0222 0.010 0.000 0.000 0.055 0.0333 0.010 0.000 0.000 0.055 0.0444 0.010 0.000 0.000 0.055 0.0556 0.010 0.000 0.000 0.055 0.0667 0.010 0.000 0.000 0.055 0.0778 0.010 0.000 0.000 0.055 0.0889 0.010 0.000 0.000 0.055 0.1000 0.010 0.000 0.000 0.055 0.1111 0.010 0.000 0.000 0.055 0.1222 0.010 0.000 0.000 0.055 0.1333 0.010 0.000 0.000 0.055 0.1444 0.010 0.000 0.000 0.055 0.1556 0.010 0.000 0.000 0.055 0.1667 0.010 0.000 0.000 0.055 0.1778 0.010 0.000 0.000 0.055 0.1889 0.010 0.000 0.000 0.055 0.2000 0.010 0.000 0.000 0.055 0.2111 0.010 0.000 0.000 0.055 0.2222 0.010 0.000 0.000 0.055 0.2333 0.010 0.000 0.000 0.055 0.2444 0.010 0.001 0.000 0.055 0.2556 0.010 0.001 0.000 0.055 0.2667 0.010 0.001 0.000 0.055 0.2778 0.010 0.001 0.000 0.055 0.2889 0.010 0.001 0.000 0.055 0.3000 0.010 0.001 0.000 0.055 0.3111 0.010 0.001 0.000 0.055 0.3222 0.010 0.001 0.000 0.055 0.3333 0.010 0.001 0.000 0.055 0.3444 0.010 0.001 0.000 0.055 0.3556 0.010 0.001 0.000 0.055 0.3667 0.010 0.001 0.000 0.055 0.3778 0.010 0.001 0.000 0.055 0.3889 0.010 0.001 0.000 0.055 0.4000 0.010 0.001 0.000 0.055 0.4111 0.010 0.001 0.000 0.055 0.4222 0.010 0.001 0.000 0.055 0.4333 0.010 0.001 0.000 0.055 0.4444 0.010 0.001 0.000 0.055 0.4556 0.010 0.001 0.000 0.055 0.4667 0.010 0.001 0.000 0.055 0.4778 0.010 0.001 0.000 0.055 0.4889 0.010 0.002 0.000 0.055 0.5000 0.010 0.002 0.000 0.055 0.5111 0.010 0.002 0.000 0.055 0.5222 0.010 0.002 0.000 0.055 0.5333 0.010 0.002 0.000 0.055 0.5444 0.010 0.002 0.000 0.055 0.5556 0.010 0.002 0.000 0.055 0.5667 0.010 0.002 0.000 0.055 0.5778 0.010 0.002 0.000 0.055 0.5889 0.010 0.002 0.000 0.055 0.6000 0.010 0.002 0.000 0.055 0.6111 0.010 0.002 0.000 0.055 0.6222 0.010 0.002 0.000 0.055 0.6333 0.010 0.002 0.000 0.055 0.6444 0.010 0.002 0.000 0.055 0.6556 0.010 0.002 0.000 0.055 0.6667 0.010 0.002 0.000 0.055 0.6778 0.010 0.002 0.000 0.055 0.6889 0.010 0.002 0.000 0.055 0.7000 0.010 0.002 0.000 0.055 0.7111 0.010 0.002 0.000 0.055 0.7222 0.010 0.002 0.000 0.055 0.7333 0.010 0.002 0.000 0.055 0.7444 0.010 0.002 0.000 0.055 0.7556 0.010 0.002 0.000 0.055 0.7667 0.010 0.002 0.000 0.055 0.7778 0.010 0.003 0.000 0.055 0.7889 0.010 0.003 0.000 0.055 0.8000 0.010 0.003 0.000 0.055 0.8111 0.010 0.003 0.000 0.055 0.8222 0.010 0.003 0.000 0.055 0.8333 0.010 0.003 0.000 0.055 0.8444 0.010 0.003 0.000 0.055 0.8556 0.010 0.003 0.000 0.055 0.8667 0.010 0.003 0.000 0.055 0.8778 0.010 0.003 0.000 0.055 0.8889 0.010 0.003 0.000 0.055 0.9000 0.010 0.003 0.000 0.055 0.9111 0.010 0.003 0.000 0.055 0.9222 0.010 0.003 0.000 0.055 0.9333 0.010 0.003 0.000 0.055 0.9444 0.010 0.003 0.000 0.055 0.9556 0.010 0.003 0.000 0.055 0.9667 0.010 0.003 0.000 0.055 0.9778 0.010 0.003 0.000 0.055 0.9889 0.010 0.003 0.000 0.055 1.0000 0.010 0.003 0.016 0.055 Name : Equivalent Area Collected for Frontage Bypass: No Impervious Land Use acre ROADS MOD LAT 0.041 Element Flows To: Outlet 1 Outlet 2 Infiltration Trench Name : Infiltration Trench Bottom Length: 300.00 ft. Bottom Width: 2.00 ft. Trench bottom slope 1: 0 To 1 Trench Left side slope 0: 0 To 1 Trench right side slope 2: 0 To 1 Material thickness of first layer: 2 Pour Space of material for first layer: Material thickness of second layer: 0 Pour Space of material for second layer: Material thickness of third layer: 0 Pour Space of material for third layer: Infiltration On Infiltration rate: 5.4 Infiltration safety factor: 1 Wetted surface area On Total Volume Infiltrated (ac-ft.): 15.276 Total Volume Through Riser (ac-ft.): 0 0.4 1 1 Total Volume Through Facility (ac-ft.): 15.276 Percent Infiltrated: 100 Total Precip Applied to Facility: 0 Total Evap From Facility: 0 Discharge Structure Riser Height: 2 ft. Riser Diameter: 0 in. Element Flows To: Outlet 1 Outlet 2 Gravel Trench Bed Hydraulic Table Stage(feet) Area(ac.) Volume(ac-ft.) Discharge(cfs) Infilt(cfs) 0.0000 0.013 0.000 0.000 0.000 0.0222 0.013 0.000 0.000 0.075 0.0444 0.013 0.000 0.000 0.075 0.0667 0.013 0.000 0.000 0.075 0.0889 0.013 0.000 0.000 0.075 0.1111 0.013 0.000 0.000 0.075 0.1333 0.013 0.000 0.000 0.075 0.1556 0.013 0.000 0.000 0.075 0.1778 0.013 0.001 0.000 0.075 0.2000 0.013 0.001 0.000 0.075 0.2222 0.013 0.001 0.000 0.075 0.2444 0.013 0.001 0.000 0.075 0.2667 0.013 0.001 0.000 0.075 0.2889 0.013 0.001 0.000 0.075 0.3111 0.013 0.001 0.000 0.075 0.3333 0.013 0.001 0.000 0.075 0.3556 0.013 0.002 0.000 0.075 0.3778 0.013 0.002 0.000 0.075 0.4000 0.013 0.002 0.000 0.075 0.4222 0.013 0.002 0.000 0.075 0.4444 0.013 0.002 0.000 0.075 0.4667 0.013 0.002 0.000 0.075 0.4889 0.013 0.002 0.000 0.075 0.5111 0.013 0.002 0.000 0.075 0.5333 0.013 0.002 0.000 0.075 0.5556 0.013 0.003 0.000 0.075 0.5778 0.013 0.003 0.000 0.075 0.6000 0.013 0.003 0.000 0.075 0.6222 0.013 0.003 0.000 0.075 0.6444 0.013 0.003 0.000 0.075 0.6667 0.013 0.003 0.000 0.075 0.6889 0.013 0.003 0.000 0.075 0.7111 0.013 0.003 0.000 0.075 0.7333 0.013 0.004 0.000 0.075 0.7556 0.013 0.004 0.000 0.075 0.7778 0.013 0.004 0.000 0.075 0.8000 0.013 0.004 0.000 0.075 0.8222 0.013 0.004 0.000 0.075 0.8444 0.013 0.004 0.000 0.075 0.8667 0.013 0.004 0.000 0.075 0.8889 0.013 0.004 0.000 0.075 0.9111 0.013 0.005 0.000 0.075 0.9333 0.013 0.005 0.000 0.075 0.9556 0.013 0.005 0.000 0.075 0.9778 0.013 0.005 0.000 0.075 1.0000 0.013 0.005 0.000 0.075 1.0222 0.013 0.005 0.000 0.075 1.0444 0.013 0.005 0.000 0.075 1.0667 0.013 0.005 0.000 0.075 1.0889 0.013 0.006 0.000 0.075 1.1111 0.013 0.006 0.000 0.075 1.1333 0.013 0.006 0.000 0.075 1.1556 0.013 0.006 0.000 0.075 1.1778 0.013 0.006 0.000 0.075 1.2000 0.013 0.006 0.000 0.075 1.2222 0.013 0.006 0.000 0.075 1.2444 0.013 0.006 0.000 0.075 1.2667 0.013 0.007 0.000 0.075 1.2889 0.013 0.007 0.000 0.075 1.3111 0.013 0.007 0.000 0.075 1.3333 0.013 0.007 0.000 0.075 1.3556 0.013 0.007 0.000 0.075 1.3778 0.013 0.007 0.000 0.075 1.4000 0.013 0.007 0.000 0.075 1.4222 0.013 0.007 0.000 0.075 1.4444 0.013 0.008 0.000 0.075 1.4667 0.013 0.008 0.000 0.075 1.4889 0.013 0.008 0.000 0.075 1.5111 0.013 0.008 0.000 0.075 1.5333 0.013 0.008 0.000 0.075 1.5556 0.013 0.008 0.000 0.075 1.5778 0.013 0.008 0.000 0.075 1.6000 0.013 0.008 0.000 0.075 1.6222 0.013 0.008 0.000 0.075 1.6444 0.013 0.009 0.000 0.075 1.6667 0.013 0.009 0.000 0.075 1.6889 0.013 0.009 0.000 0.075 1.7111 0.013 0.009 0.000 0.075 1.7333 0.013 0.009 0.000 0.075 1.7556 0.013 0.009 0.000 0.075 1.7778 0.013 0.009 0.000 0.075 1.8000 0.013 0.009 0.000 0.075 1.8222 0.013 0.010 0.000 0.075 1.8444 0.013 0.010 0.000 0.075 1.8667 0.013 0.010 0.000 0.075 1.8889 0.013 0.010 0.000 0.075 1.9111 0.013 0.010 0.000 0.075 1.9333 0.013 0.010 0.000 0.075 1.9556 0.013 0.010 0.000 0.075 1.9778 0.013 0.010 0.000 0.075 2.0000 0.013 0.011 0.000 0.075 Name : Lot 1 Parking Bypass: Yes GroundWater: No Pervious Land Use acre Pervious Total 0 Impervious Land Use acre DRIVEWAYS MOD 0.007 Impervious Total 0.007 Basin Total 0.007 Element Flows To: Surface Interflow Groundwater ANALYSIS RESULTS Stream Protection Duration Predeveloped Landuse Totals for POC #1 Total Pervious Area:0.168 Total Impervious Area:O Mitigated Landuse Totals for POC #1 Total Pervious Area:O Total Impervious Area:0.148101 Flow Frequency Return Periods for Predeveloped. POC #1 Return Period Flow(cfs) 2 year 0.001079 5 year 0.001706 10 year 0.00205 25 year 0.002402 50 year 0.002613 100 year 0.002786 Flow Frequency Return Periods for Mitigated. POC #1 Return Period Flow(cfs) 2 year 0.002782 5 year 0.003745 10 year 0.004446 25 year 0.005408 50 year 0.006181 100 year 0.007005 Stream Protection Duration Annual Peaks for Predeveloped and Mitigated. POC #1 Year Predeveloped Mitigated 1949 0.000 0.003 1950 0.001 0.003 1951 0.001 0.004 1952 0.001 0.003 1953 0.001 0.003 1954 0.001 0.004 1955 0.002 0.003 1956 0.002 0.002 1957 0.002 0.002 1958 0.001 0.006 1959 0.001 0.003 1960 0.001 0.003 1961 0.001 0.008 1962 0.001 0.003 1963 0.001 0.003 1964 0.001 0.002 1965 0.001 0.002 1966 0.001 0.002 1967 0.001 0.005 1968 0.001 0.003 1969 0.001 0.005 1970 0.001 0.002 1971 0.001 0.003 1972 0.001 0.004 1973 0.001 0.003 1974 0.001 0.004 1975 0.001 0.003 1976 0.001 0.002 1977 0.000 0.002 1978 0.001 0.002 1979 0.001 0.003 1980 0.001 0.003 1981 0.001 0.002 1982 0.001 0.002 1983 0.001 0.003 1984 0.001 0.003 1985 0.002 0.004 1986 0.004 0.004 1987 0.001 0.003 1988 0.001 0.003 1989 0.001 0.002 1990 0.001 0.002 1991 0.001 0.003 1992 0.001 0.003 1993 0.000 0.002 1994 0.000 0.002 1995 0.001 0.002 1996 0.002 0.004 1997 0.005 0.003 1998 0.001 0.004 1999 0.001 0.001 2000 0.001 0.006 2001 0.000 0.002 2002 0.001 0.002 2003 0.001 0.003 2004 0.001 0.005 2005 0.001 0.002 2006 0.002 0.003 2007 0.002 0.003 2008 0.002 0.003 2009 0.001 0.002 Stream Protection Duration Ranked Annual Peaks for Predeveloped and Mitigated. POC #1 Rank Predeveloped Mitigated 1 0.0051 0.0080 2 0.0039 0.0063 3 0.0024 0.0062 4 0.0023 0.0054 5 0.0022 0.0051 6 0.0018 0.0049 7 0.0018 0.0043 8 0.0017 0.0037 9 0.0016 0.0037 10 0.0015 0.0037 11 0.0015 0.0036 12 0.0014 0.0036 13 0.0014 0.0036 14 0.0014 0.0035 15 0.0014 0.0035 16 0.0014 0.0034 17 0.0013 0.0032 18 0.0013 0.0032 19 0.0013 0.0032 20 0.0013 0.0031 21 0.0013 0.0031 22 0.0012 0.0030 23 0.0012 0.0030 24 0.0012 0.0030 25 0.0012 0.0029 26 0.0012 0.0029 27 0.0011 0.0029 28 0.0011 0.0029 29 0.0011 0.0029 30 0.0011 0.0028 31 0.0010 0.0028 32 0.0010 0.0028 33 0.0010 0.0027 34 0.0010 0.0027 35 0.0009 0.0027 36 0.0009 0.0026 37 0.0009 0.0026 38 0.0009 0.0026 39 0.0009 0.0026 40 0.0008 0.0025 41 0.0008 0.0025 42 0.0008 0.0025 43 0.0008 0.0024 44 0.0008 0.0024 45 0.0008 0.0023 46 0.0007 0.0023 47 0.0007 0.0022 48 0.0007 0.0022 49 0.0007 0.0022 50 0.0007 0.0022 51 0.0007 0.0022 52 0.0006 0.0022 53 0.0006 0.0021 54 0.0005 0.0021 55 0.0005 0.0021 56 0.0005 0.0019 57 0.0005 0.0018 58 0.0004 0.0018 59 0.0003 0.0017 60 0.0001 0.0015 61 0.0001 0.0014 Stream Protection Duration POC #1 The Facility PASSED The Facility PASSED. Flow(cfs) Predev Mit Percentage Pass/Fail 0.0005 60402 13922 23 Pass 0.0006 56381 12769 22 Pass 0.0006 52616 11668 22 Pass 0.0006 48702 10692 21 Pass 0.0006 45237 9820 21 Pass 0.0006 42179 8998 21 Pass 0.0007 39142 8239 21 Pass 0.0007 36340 7617 20 Pass 0.0007 33687 7022 20 Pass 0.0007 31249 6487 20 Pass 0.0007 29110 6019 20 Pass 0.0008 27035 5542 20 Pass 0.0008 25175 5138 20 Pass 0.0008 23570 4761 20 Pass 0.0008 22009 4408 20 Pass 0.0009 20711 4115 19 Pass 0.0009 19321 3869 20 Pass 0.0009 17935 3628 20 Pass 0.0009 16942 3358 19 Pass 0.0009 15926 3136 19 Pass 0.0010 14964 2937 19 Pass 0.0010 13973 2753 19 Pass 0.0010 13118 2590 19 Pass 0.0010 12455 2440 19 Pass 0.0010 11871 2289 19 Pass 0.0011 11188 2154 19 Pass 0.0011 10705 2033 18 Pass 0.0011 10224 1902 18 Pass 0.0011 9700 1798 18 Pass 0.0011 9216 1703 18 Pass 0.0012 8699 1605 18 Pass 0.0012 8188 1511 18 Pass 0.0012 7704 1425 18 Pass 0.0012 7249 1342 18 Pass 0.0013 6761 1269 18 Pass 0.0013 6436 1190 18 Pass 0.0013 6066 1136 18 Pass 0.0013 5698 1074 18 Pass 0.0013 5360 1020 19 Pass 0.0014 5052 974 19 Pass 0.0014 4723 921 19 Pass 0.0014 4496 868 19 Pass 0.0014 4280 826 19 Pass 0.0014 4062 783 19 Pass 0.0015 3856 749 19 Pass 0.0015 3623 709 19 Pass 0.0015 3461 686 19 Pass 0.0015 3296 647 19 Pass 0.0015 3144 607 19 Pass 0.0016 3022 579 19 Pass 0.0016 2892 556 19 Pass 0.0016 2774 530 19 Pass 0.0016 2616 509 19 Pass 0.0016 2509 484 19 Pass 0.0017 2402 452 18 Pass 0.0017 2295 430 18 Pass 0.0017 2216 411 18 Pass 0.0017 2129 395 18 Pass 0.0018 2051 384 18 Pass 0.0018 1981 371 18 Pass 0.0018 1888 359 19 Pass 0.0018 1808 343 18 Pass 0.0018 1764 321 18 Pass 0.0019 1713 304 17 Pass 0.0019 1670 294 17 Pass 0.0019 1636 290 17 Pass 0.0019 1600 280 17 Pass 0.0019 1570 268 17 Pass 0.0020 1533 258 16 Pass 0.0020 1500 250 16 Pass 0.0020 1463 246 16 Pass 0.0020 1427 238 16 Pass 0.0020 1378 230 16 Pass 0.0021 1327 221 16 Pass 0.0021 1276 216 16 Pass 0.0021 1219 207 16 Pass 0.0021 1179 201 17 Pass 0.0022 1140 190 16 Pass 0.0022 1094 184 16 Pass 0.0022 1034 180 17 Pass 0.0022 1007 167 16 Pass 0.0022 974 156 16 Pass 0.0023 947 152 16 Pass 0.0023 904 147 16 Pass 0.0023 852 144 16 Pass 0.0023 790 141 17 Pass 0.0023 749 135 18 Pass 0.0024 706 131 18 Pass 0.0024 678 128 18 Pass 0.0024 673 123 18 Pass 0.0024 667 118 17 Pass 0.0024 662 115 17 Pass 0.0025 657 112 17 Pass 0.0025 652 109 16 Pass 0.0025 646 107 16 Pass 0.0025 640 102 15 Pass 0.0026 635 101 15 Pass 0.0026 630 100 15 Pass 0.0026 625 98 15 Pass 0.0026 621 92 19 Pass Water Quality BMP Flow and Volume for POC #1 On-line facility volume: 0 acre-feet On-line facility target flow: 0 cfs. Adjusted for 15 min: 0 cfs. Off-line facility target flow: 0 cfs. Adjusted for 15 min: 0 cfs. LID Report LID Technique Used for Total Volumn Volumn Infiltration Cumulative Percent Water Quality Percent Comment Treatment? Needs Through Volumn Volumn Volumn Water Quality Treatment Facility (ac-ft.) Infiltration Infiltrated Treated (ac-ft) (ac-ft) Credit Infiltration Trench POC N 14.17 N 98.10 Lot 2 Parking Permeable N 1.00 N 64.82 Total Volume Infiltrated 15.17 0.00 0.00 95.91 0.00 0% No Treat. Credit Compliance with LID Standard 8 Duration Analysis Result = Passed Perind and Impind Changes No changes have been made. 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. Meadowdale Short Plat Drainage Report Appendix E Maintenance Standards SWMMWW 2014 Apr. 26, 2019 Group Four, Inc. 21 17-0523 Table V-4.5.2(1) Maintenance Standards - Detention Ponds (continued) Maintenance Conditions When Results Expected When Component Defect Maintenance Is Maintenance Is Per - Needed formed potential for erosion to continue. (Recommend a Goeth- echnical engineer be called in to inspect and evaluate condition and recommend repair of condition. Only one layer of rock exists above native soil in area five square feet or larger, or any expos - Emergency Over- Emergency Over- ure of native soil at the Rocks and pad depth are flow/Spillway flow/Spillway top of outflow path of restored to design stand - spillway. ards. (Rip -rap on inside slopes need not be replaced.) Erosion See "Side Slopes of pond" Table V-4.5.2(2) Maintenance Standards - Infiltration Results Expec Maintenance Defect Conditions When Maintenance Is ted When Component Needed Maintenance Is Performed Trash & Debris See "Detention Ponds" (No. 1). See "Detention Ponds" (No. 1). Poisonous/Noxious "Detention See "Detention Vegetation See Ponds" (No. 1). Ponds" (No. 1). General Contaminants and See "Detention Ponds" (No. 1). See "Detention Pollution Ponds" (No. 1). Rodent Holes See "Detention Ponds" (No. 1). See "Detention Ponds" (No. 1) Water ponding in infiltration pond Sediment is Storage Area Sediment after rainfall ceases and appropriate removed 2014 Stormwater Management Manual for Westem Washington Volume V - Chapter 4 - Page 833 Table V-4.5.2(2) Maintenance Standards - Infiltration (continued) Results Expec Maintenance Defect Conditions When Maintenance Is ted When Component Needed Maintenance Is Performed time allowed for infiltration. Treat- ment basins should infiltrate Water Quality Design Storm Volume within and/or facility is 48 hours, and empty within 24 hours cleaned so that after cessation of most rain events. infiltration sys- (A percolation test pit or test of facility tem works indicates facility is only working at according to 90% of its designed capabilities. Tes design. every 2 to 5 years. If two inches or more sediment is present, remove). Filter bag is Filter Bags (if Filled with Sed- Sediment and debris fill bag more replaced or sys applicable) iment and Debris than 1/2 full. tem is redesigned. Sediment and By visual inspection, little or no water Gravel in rock Rock Filters Debris flows through filter during heavy rain filter is storms. replaced. Side Slopes Erosion See "Detention Ponds" (No. 1). See "Detention of Pond Ponds" (No. 1). Emergency See "Detention Overflow Tree Growth See Detention Ponds(No. 1). "" Ponds" (No. 1). Spillway and Berms over piping See "Detention Ponds" (No. 1). See "Detention feet in height. Ponds" (No. 1). Emergency Rock Missing See "Detention Ponds" (No. 1). See "Detention Ponds" (No. 1). Overflow Spillway Erosion See "Detention Ponds" (No. 1). See "Detention Ponds" (No. 1). Pre-settling Facility or sump 6" or designed sediment trap depth Sediment is Ponds and filled with Sediment of sediment. removed. Vaults and/or debris 2014 Stormwater Management Manual for Westem Washington Volume V - Chapter 4 - Page 834 Table V-4.5.2(5) Maintenance Standards - Catch Basins Results Maintenance Defect Conditions When Maintenance is Expected When Main- Component Needed tenance is performed No Trash or debris loc- Trash or debris which is located imme- ated imme- diately in front of the catch basin opening or diately in is blocking inletting capacity of the basin by front of catch more than 10%. basin or on Trash or debris (in the basin) that exceeds grate open- 60 percent of the sump depth as measured ing. from the bottom of basin to invert of the low- No trash or est pipe into or out of the basin, but in no debris in the Trash & case less than a minimum of six inches catch basin. Debris clearance from the debris surface to the invert of the lowest pipe. Inlet and out- let pipes free Trash or debris in any inlet or outlet pipe of trash or blocking more than 1/3 of its height. debris. General Dead animals or vegetation that could gen- No dead erate odors that could cause complaints or animals or dangerous gases (e.g., methane). vegetation present within the catch basin. Sediment (in the basin) that exceeds 60 per- cent of the sump depth as measured from the bottom of basin to invert of the lowest pipe into or out of the basin, but in no case No sediment Sediment less than a minimum of 6 inches clearance in the catch from the sediment surface to the invert of the basin lowest pipe. Structure Top slab has holes larger than 2 square Top slab is Damage to inches or cracks wider than 1/4 inch. (Intent free of holes Frame and/or is to make sure no material is running into and cracks. Top Slab basin). Frame is sit- 2014 Stormwater Management Manual for Westem Washington Volume V - Chapter 4 - Page 838 Table V-4.5.2(5) Maintenance Standards - Catch Basins (continued) Results Maintenance Defect Conditions When Maintenance is Expected When Main- Component Needed tenance is performed Frame not sitting flush on top slab, i.e., sep- ting flush on the riser rings aration of more than 3/4 inch of the frame from the top slab. Frame not securely or top slab and firmly attached attached. Basin Maintenance person judges that structure is replaced or unsound. repaired to Fractures or design stand - Cracks in Grout fillet has separated or cracked wider ards. Basin Walls/ than 112 inch and longer than 1 foot at the Bottom joint of any inlet/outlet pipe or any evidence Pipe is of soil particles entering catch basin through regrouted cracks. and secure at basin wall. Basin Settlement/ If failure of basin has created a safety, func- replaced or Misalignment tion, or design problem. repaired to design stand- ards. No veget- Vegetation growing across and blocking ation block - more than 10% of the basin opening. ing opening to basin. Vegetation Vegetation growing in inlet/outlet pipe joints that is more than six inches tall and less No veget- than six inches apart. ation or root growth present. Contamination See Detention Ponds (No. 1). No pollution and Pollution present. Cover is missing or only partially in place. Catch basin Cover Not in Any open catch basin requires main- cover is Catch Basin Place tenance. closed Cover Locking Mech- Mechanism cannot be opened by one main- Mechanism anism Not tenance person with proper tools. Bolts into opens with 2014 Stormwater Management Manual for Western Washington Volume V - Chapter 4 - Page 839 Table V-4.5.2(5) Maintenance Standards - Catch Basins (continued) Results Maintenance Conditions When Maintenance is Expected Component Defect Needed When Main- tenance is performed Working frame have less than 1/2 inch of thread. proper tools. One maintenance person cannot remove lid Cover can be Cover Difficult after applying normal lifting pressure. removed by to Remove (Intent is keep cover from sealing off access one main - tenance per - to maintenance.) son. Ladder meets design stand Ladder Rungs Ladder is unsafe due to missing rungs, not ards and Ladder Unsafe securely attached to basin wall, mis- allows main - alignment, rust, cracks, or sharp edges. tenance per- son safe access. Grate open - Grate opening Grate with opening wider than 7/8 inch. ing meets Unsafe design stand- ards. Metal Grates Trash and Trash and debris that is blocking more than Grate free of (IfApplic- Debris o 20 /o of grate surface inletting capacity. trash and able) debris. Grate is in Damaged or Grate missing or broken member(s) of the place and Missing. grate. meets design standards. Table V-4.5.2(6) Maintenance Standards - Debris Barriers (e.g., Trash Racks) Maintenance Condition When Maintenance is Results Expected Com- Defect Needed When Maintenance is ponents Performed Trash and Trash or debris that is plugging Barrier cleared to design General Debris more than 20% of the openings in flow capacity. the barrier. Damaged/ Bars are bent out of shape more Bars in place with no Metal Missing than 3 inches. bends more than 3/4 2014 Stormwater Management Manual for Western Washington Volume V - Chapter 4 - Page 840 Table V-4.5.2(6) Maintenance Standards - Debris Barriers (e.g., Trash Racks) (continued) Maintenancel Com- ponents Defect Condition When Maintenance is Needed Results Expected When Maintenance is Performed inch. Bars are missing or entire barrier missing. Bars in place according to design. Bars. Bars are loose and rust is causing 50% deterioration to any part of bar- Barrier replaced or rier. repaired to design stand- ards. Inlet/Outlet Debris barrier missing or not Barrier firmly attached to Pipe attached to pipe 1pipe Table V-4.5.2(7) Maintenance Standards - Energy Dissipaters Results Expec Maintenance Conditions When Maintenance is led When Main Components Defect Needed tenance is Performed External: Missing or Only one layer of rock exists above nat Rock pad Moved ive soil in area five square feet or lar- replaced to Rock ger, or any exposure of native soil. design stand - ards. Rock Pad Rock pad Erosion Soil erosion in or adjacent to rock pad. replaced to design stand- ards. Pipe Pipe cleaned/ - Plugged Accumulated sediment that exceeds flushed so that with Sed- 20% of the design depth. it matches iment design. Not Dis- Visual evidence of water discharging Trench Dispersion Trench charging at concentrated points along trench redesigned or Water Prop- (normal condition is a sheet flow of rebuilt to stand- erl water along trench). Intent is to prevent ards. y erosion damage. perforations Over 1/2 of perforations in pipe are Perforated pipe Plugged. plugged with debris and sediment. cleaned or replaced. 2014 Stormwater Management Manual for Western Washington Volume V - Chapter - Page 841 Table V-4.5.2(17) Maintenance Standards - Coalescing Plate Oil/Water Separators (continued) Maintenance Defect Component Sediment mulation Trash and Debris Accu- mulation Oil Accu- mulation Damaged Coalescing Plates Damaged Pipes Condition When Main- tenance is Needed ,ediment depth in bottom of ault exceeds 6-inches in epth and/or visible signs of ediment on plates. Trash and debris accumulated in vault, or pipe inlet/outlet, floatables and non-floatables. Oil accumulation that exceeds 1-inch at the water surface. Plate media broken, deformed, cracked and/or showing signs of failure. Inlet or outlet piping damaged or broken and in need of repair. Results Expected When Maintenance is Per- formed No sediment deposits on vault bottom and plate media, which would impede flow through the vault and reduce sep- aration efficiency. Trash and debris removed from vault, and inlet/outlet piping. Oil is extracted from vault using vactoring methods. Coalescing plates are cleaned by thoroughly rinsing and flushing. Should be no visible oil depth on water. A portion of the media pack or the entire plate pack is replaced depend- ing on seventy of failure. Pipe repaired and or replaced. Baffles corroding, cracking, warping and/or showing signs Baffles repaired or Baffles of failure as determined by replaced to specifications. maintenance/inspection per - Vault Structure Cracks wider than 1/2-inch or Damage- evidence of soil particles ente Includes Cracks in ing the structure through the Walls, Bottom, cracks, or main - Damage to tenance/inspection personnel Frame and/or determine that the vault is not Top Slab structurally sound. Vault replaced or repairs made so that vault meets design specifications and is structurally sound. Vault repaired so that no cracks exist wider than 1/4-inch at the joint of the 2014 Stormwater Management Manual for Westem Washington Volume V - Chapter 4 - Page 858 Table V-4.5.2(17) Maintenance Standards - Coalescing Plate Oil/Water Separators (continued) Maintenance Component Defect Condition When Main- tenance is Needed Results Expected When Maintenance is Per- formed Cracks wider than 1/2-inch at the joint of any inlet/outlet pipe inlet/outlet pipe. or evidence of soil particles entering through the cracks. Ladder is corroded or deteri- Ladder replaced or Access Ladder orated, not functioning prop- repaired and meets spe- Damaged erly, not securely attached to cifications, and is safe to structure wall, missing rungs, use as determined by cracks, and misaligned. linspection personnel. Table V-4.5.2(18) Maintenance Standards - Catch Basin Inserts Maintenance Conditions When Main- Results Expected When Component Defect tenance is Needed Maintenance is Performed Sediment When sediment forms a cap No sediment cap on the Accumulation over the insert media of the insert media and its unit. insert and/or unit. Trash and Trash and debris accumulates Trash and debris removed Debris Accu- on insert unit creating a block- from insert unit. Runoff mulation age/restriction. freely flows into catch basin. Media Insert Effluent water from media Effluent water from media Not Remov- insert has a visible sheen. insert is free of oils and has ing Oil no visible sheen. General Media Insert Catch basin insert is saturated Remove and replace media Water Sat- with water and no longer has insert urated the capacity to absorb. Media Insert- Media oil saturated due to pet- Remove and replace media Oil Saturated roleum spill that drains into insert. catch basin. Media Insert Media has been used beyond Remove and replace media Use Beyond the typical average life of at regular intervals, depend - Product Life Imedia insert product. ling on insert product. 2014 Stormwater Management Manual for Western Washington Volume V - Chapter 4 - Page 859 Table V-4.5.2(21) Maintenance Standards - Bioretention Facilities (continued) Recommended Fre- Condition Maintenance quency a when Main - Action Needed (Pro - Component tenance is Needed (Stand cedures) Inspection Routine Main tenance ards) up pet waste. . Reduce hiding places for pests by removing diseased Every site Signs pests, and dead plants visit asso- such as wilting s leaves, chewed For infestations, fol- Insect pests ciated with leaves and bark, low IPM protocols vegetation spotting (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 quencya when Main - Component tenance is Action Needed (Procedures) Inspection Routine Needed Maintenance (Standards) SurfaceMearing Course Permeable �A, S Runofffrom Clean deposited soil or 2014 Stormwater Management Manual for Western Washington Volume V - Chapter 4 - Page 887 Table V-4.5.2(22) Maintenance Standards - Permeable Pavement (continued) Recommended Fre- Condition quency a when Main - Component tenance is Action Needed (Procedures) Inspection Routine Needed Maintenance (Standards) other materials from per- meable pavement or other adjacent surfacing . Check if surface elevation adjacent per- of planted area is too high, or slopes towards pave - vious areas merit, and can be regraded Pavements, deposits soil, (prior to regrading, protect all mulch or sed- permeable pavement by iment on pav- covering with temporary ing plastic and secure covering in place) . Mulch and/or plant all exposed soils that may erode to pavement surface Clean surface debris from pave- ment surface using one or a com- bination of the following methods: . Remove sediment, debris, trash, vegetation, and other debris deposited onto pave Porous ment (rakes and leaf asphalt or A or B None (routine blowers can be used for pervious maintenance) removing leaves) concrete Vacuum/sweep permeable paving installation using: • Walk -behind vacuum (sidewalks) • High efficiency regen- erative air or vacuum sweeper (roadways, parking lots) 2014 Stormwater Management Manual for Westem Washington Volume V - Chapter 4 - Page 888 Table V-4.5.2(22) Maintenance Standards - Permeable Pavement (continued) Recommended Fre- Condition quencya when Main - Component tenance is Action Needed (Procedures) Inspection Routine Needed Maintenance (Standards) ShopVac or brush brooms (small areas) . Hand held pressure washer or power washer with rotat- ing brushes Follow equip- ment manufacturer guidelines for when equip- ment is most effective for cleaning permeable pave- ment. Dry weather is more effective for some equip- ment. . Review the overall per- formance of the facility (note that small clogged areas may not reduce over- all performance of facility) . Test the surface infiltration Surface is rate using ASTM C1701 as clogged: Pond a corrective maintenance ing on surface indicator. Perform one test or water flows per installation, up to 2,500 Ab off the per- square feet. Perform an meable pave- additional test for each addi ment surface tional 2,500 square feet up during a rain to 15,000 square feet total. event (does Above 15,000 square feet, not infiltrate) add one test for every 10,000 square feet. . If the results indicate an infiltration rate of 10 inches per hour or less, then per- form corrective main- 2014 Stormwater Management Manual for Western Washington Volume V - Chapter 4 - Page 889 Table V-4.5.2(22) Maintenance Standards - Permeable Pavement (continued) Recommended Fre- Condition quency a when Main - Component tenance is Action Needed (Procedures) Inspection Routine Needed Maintenance (Standards) tenance to restore per- meability. To clean clogged pavement surfaces, use one or combination of the following methods: • Combined pressure wash and vacuum system calibrated to not dislodge wearing course aggregate. • Hand held pressure washer or power washer with rotating brushes • Pure vacuum sweep- ers Note: If the annual/biannual routine maintenance stand- ard to clean the pavement surface is conducted using equipment from the list above, corrective main- tenance may not be needed. . Assess the overall per- formance of the pavement system during a rain event. Sediment If water runs off the pave - A present at the ment and/or there is pond - surface of the ing then see above. pavement Determine source of sed- iment loading and evaluate whether or not the source 2014 Stormwater Management Manual for Westem Washington Volume V - Chapter 4 - Page 890 Table V-4.5.2(22) Maintenance Standards - Permeable Pavement (continued) Recommended Fre- Condition quency a when Main - Component tenance is Action Needed (Procedures) Inspection Routine Needed Maintenance (Standards) can be reduced/eliminated. If the source cannot be addressed, consider increasing frequency of routine cleaning (e.g., twice per year instead of once per year). . Sidewalks: Use a stiff broom to remove moss in the summer when it is dry Moss growth . Parking lots and roadways: inhibits infilt- Pressure wash, vacuum Summer ration or sweep, or use a com- poses slip bination of the two for clean safety hazard ing moss from pavement surface. May require stiff broom or power brush in areas of heavy moss. . Fill potholes or small cracks with patching mixes . Large cracks and set- tlement may require cutting and replacing the pave - Major cracks ment section. Replace in - or trip hazards kind where feasible. Repla- A and concrete cing porous asphalt with spalling and conventional asphalt is raveling acceptable if it is a small percentage of the total facil- ity area and does not impact the overall facility function. . Take appropriate pre- 2014 Stormwater Management Manual for Western Washington Volume V - Chapter 4 - Page 891 Table V-4.5.2(22) Maintenance Standards - Permeable Pavement (continued) Recommended Fre- Condition quency a when Main - Component tenance is Action Needed (Procedures) Inspection Routine Needed Maintenance (Standards) cautions during pavement repair and replacement efforts to prevent clogging of adjacent porous mater- ials Clean pavement surface using one or a combination of the fol- lowing methods: . Remove sediment, debris, trash, vegetation, and other debris deposited onto pave- ment (rakes and leaf blowers can be used for removing leaves) . Vacuum/sweep permeable paving installation using: * Walk -behind vacuum Interlocking (sidewalks) concrete A or B None (routine maintenance) , High efficiency regen- paver blocks erative air or vacuum and aggreg- sweeper (roadways, ate pavers parking lots) * ShopVac or brush brooms (small areas) Note: Vacuum settings may have to be adjusted to pre- vent excess uptake of aggregate from paver open- ings orjoints. Vacuum sur- face openings in dry weather to remove dry, encrusted sediment. Ab Surface is . Review the overall per- 2014 Stormwater Management Manual for Westem Washington Volume V - Chapter 4 - Page 892 Table V-4.5.2(22) Maintenance Standards - Permeable Pavement (continued) Component Recommended Fre- quency a Condition when Main - tenance is Needed Action Needed (Procedures) Inspection Routine Maintenance (Standards) formance of the facility (note that small clogged areas may not reduce over- all performance of facility) . Test the surface infiltration rate using ASTM C1701 as a corrective maintenance indicator. Perform one test per installation, up to 2,500 square feet. Perform an additional test for each addi tional 2,500 square feet up clogged: Pond to 15,000 square feet total. ing on surface Above 15,000 square feet, or water flows add one test for every off the per- 10,000 square feet. meable pave- . If the results indicate an ment surface infiltration rate of 10 inches during a rain per hour or less, then per - event (does form corrective main - not infiltrate) tenance to restore permeability. . Clogging is usually an issue in the upper 2 to 3 centimeters of aggregate. Remove the upper layer of encrusted sediment, and fines, and/or vegetation from openings and joints between the pavers by mechanical means and/or suction equipment (e.g., pure vacuum sweeper). 2014 Stormwater Management Manual for Western Washington Volume V - Chapter 4 - Page 893 Table V-4.5.2(22) Maintenance Standards - Permeable Pavement (continued) Recommended Fre- Condition quency a when Main - Component tenance is Action Needed (Procedures) Inspection Routine Needed Maintenance (Standards) . Assess the over- all per- formance of the pave- ment sys- tem during a rain event. If water runs off the pave- ment Sediment and/or present at the there is A surface of the ponding, pavement then see above. . Determi- ne source of sed- iment loading and eval- uate whether or not the source can be 2014 Stormwater Management Manual for Western Washington Volume V - Chapter 4 - Page 894 Table V-4.5.2(22) Maintenance Standards - Permeable Pavement (continued) Recommended Fre- Condition quency a when Main - Component tenance is Action Needed (Procedures) Inspection Routine Needed Maintenance (Standards) reduced/- elim- inated. If the source cannot be address- ed, con- sider increas- ing fre- quency of routine cleaning (e.9., twice per year instead of once per year). . Side- walks: Use a vloss growth stiff nhibits infilt- broom to Summer ration or remove poses slip moss in safety hazard the sum- mer when it is dry 2014 Stormwater Management Manual for Western Washington Volume V - Chapter 4 - Page 895 Table V-4.5.2(22) Maintenance Standards - Permeable Pavement (continued) Recommended Fre- Condition quency a when Main - Component tenance is Action Needed (Procedures) Inspection Routine Needed Maintenance (Standards) . Parking lots and road- ways: Vacuum sweep or stiff broom/ - power brush for cleaning moss from pave- ment sur- face Remove indi- vidual dam- aged paver blocks by Paver block hand and A missing or replace or damaged repair per man- ufacturer's recom- mendations Refill per man - Loss of ufacturer's aggregate recom- A material mendations between for interlocking paver blocks paver sec- tions May require A Settlement of 2014 Stormwater Management Manual for Western Washington Volume V - Chapter 4 - Page 896 Table V-4.5.2(22) Maintenance Standards - Permeable Pavement (continued) Recommended Fre- Condition quency a when Main - Component tenance is Action Needed (Procedures) Inspection Routine Needed Maintenance (Standards) surface resetting . Remove sediment, debris, trash, vegetation, and other debris deposited onto pave - (rakes and leaf A or B None (routine None blowers can be used for maintenance) removing leaves) . Follow equipment man- ufacturer guidelines for cleaning surface. Aggregate is clogged: Pond ing on surface . Use vacuum truck to or water flows remove and replace top A b off the per- course aggregate meable pave- . Replace aggregate in pav- Open-celled ment surface ing grid per manufacturer's paving grid during a rain recommendations with gravel event (does not infiltrate) . Remove pins, pry up grid segments, and replace gravel Paving grid • Replace grid segments A where three or more adja- missing or damaged cent rings are broken or damaged . Follow manufacturer guidelines for repairing sur- face. A Settlement of May require resetting surface A Loss of Replenish aggregate material by 2014 Stormwater Management Manual for Western Washington Volume V - Chapter 4 - Page 897 Table V-4.5.2(22) Maintenance Standards - Permeable Pavement (continued) Recommended Fre- Condition quency a when Main - Component tenance is Action Needed (Procedures) Inspection Routine Needed Maintenance (Standards) spreading gravel with a rake (gravel level should be main - aggregate tained at the same level as the material in plastic rings or no more than 1/4 paving grid inch above the top of rings). See manufacturer's recom- mendations. . Manually remove weeds . Presence of weeds may Weeds indicate that too many fines A present are present (refer to Actions Needed under "Aggregate is clogged" to address this issue) . Remove sediment, debris, trash, vegetation, and other debris deposited onto pave - (rakes and leaf A or B None (routine None blowers can be used for maintenance) removing leaves) Follow equipment man- ufacturer guidelines for Open -celled cleaning surface. paving grid Aggregate is with grass clogged: Pond ing on surface or water flows off the per- Rehabilitate per manufacturer's A b meable pave- recommendations. ment surface during a rain event (does not infiltrate) 2014 Stormwater Management Manual for Western Washington Volume V - Chapter 4 - Page 898 Table V-4.5.2(22) Maintenance Standards - Permeable Pavement (continued) Recommended Fre- Condition quency a when Main - Component tenance is Action Needed (Procedures) Inspection Routine Needed Maintenance (Standards) . Remove pins, pry up grid segments, and replace grass Paving grid • Replace grid segments A where three or more adja- missing or damaged cent rings are broken or damaged . Follow manufacturer guidelines for repairing sur- face. A Settlement of May require resetting surface . Restore growing medium, reseed or plant, aerate, and/or amend vegetated Poor grass area as needed A coverage in paving grid • Traffic loading may be inhibiting grass growth; reconsider traffic loading if feasible As needed None (routine Use a mulch mower to mow maintenance) grass . Sprinkle a thin layer of com post on top of grass surface A None (routine (1/2" top dressing) and maintenance) sweep it in . Do not use fertilizer . Manually remove weeds A Weeds . Mow, torch, or inoculate present and replace with preferred vegetation Inlets/Oudets/Pipes Inlet/outlet JA JPipe is dam- Repair/replace 2014 Stormwater Management Manual for Westem Washington Volume V - Chapter - Page 899 Table V-4.5.2(22) Maintenance Standards - Permeable Pavement (continued) Recommended Fre- Condition quency a when Main - Component tenance is Action Needed (Procedures) Inspection Routine Needed Maintenance (Standards) aged pipe A cogged Remove roots or debris Clean orifice Plant roots, . Jet clean or rotary cut at least bian- sediment or debris/roots from under- nually (may debris redu- drain(s) Underdrain Clean pipe pip need more cing capacity of underdrain If underdrains are equipped pipe as needed frequent (may causeprolonged with a flow restrictor (e.g., cleaning dur- orifice) to attenuate flows, ing wet sea- drawdown the orifice must be cleaned son) period) regularly Clean orifice . Jet clean or rotary cut at least bian- Plant roots, debris/roots from under - Raised sub- nually (may sediment or drain(s) surface over Clean pipe need more debris redu- - If underdrains are equipped flow pipe as needed frequent cing capacity with a flow restrictor (e.g., cleaning dur- of underdrain orifice) to attenuate flows, ing wet sea- the orifice must be cleaned son) regularly Sediment, vegetation, or . Clear the blockage Outlet struc- AS debris redu- . Identify the source of the ture ' cing capacity blockage and take actions of outlet struc- to prevent future blockages to re Native soil is exposed or other signs of Repair erosion and stabilize sur- OverFlow B erosion dam- face age are present at dis- charge point 2014 Stormwater Management Manual for Westem Washington Volume V - Chapter 4 - Page 900 Table V-4.5.2(22) Maintenance Standards - Permeable Pavement (continued) Recommended Fre- Condition quency a when Main - Component tenance is Action Needed (Procedures) Inspection Routine Needed Maintenance (Standards) Aggregate Storage Reservoir Water remains in the storage If immediate cause of extended Observation aggregate longer than ponding is not identified, sched- port A, S anticipated by ule investigation of subsurface design after materials or other potential the end of a causes of system failure. storm Vegetation . Sweep leaf litter and sed- iment to prevent surface related fallout clogging and ponding As needed clogs or will potentially • Prevent large root systems clog voids from damaging subsurface Adjacent structural components large shrubs Vegetation Edging and trimming of planted or trees growing bey- areas to control groundcovers Once in May and facility and shrubs from overreaching and Once in edge onto the sidewalks, paths and street September sidewalks, edge improves appearance and paths, and reduces clogging of permeable street edge pavements by leaf litter, mulch and soil. In fall (Octo- ber to Decem Use leaf blower or vacuum to Leaves, ber) after leaf Accumulation blow or remove leaves, ever - needles, drop (1-3 of organic green needles, and debris (i.e., and organic times, debris and flowers, blossoms) off of and debris depending leaf litter away from permeable pavement on canopy cover) Note that the inspection and routine maintenance frequencies listed above are recom- 2014 Stormwater Management Manual for Westem Washington Volume V - Chapter 4 - Page 901 Table V-4.5.2(22) Maintenance Standards - Permeable Pavement (continued) Recommended Fre- Condition quency a when Main - Component tenance is Action Needed (Procedures) Inspection Routine Needed Maintenance (Standards) mended by Ecology. They do not supersede or replace the municipal stormwater permit requirements for inspection frequency required of municipal stormwater permittees for "stormwatertreatment and flow control BMPs/facilities". a Frequency: A= Annually; B= Biannually (twice per year); S = Perform inspections after major storm events (24-hour storm event with a 10-year or greater recurrence interval). b Inspection should occur during storm event. 2014 Stormwater Management Manual for Western Washington Volume V - Chapter - Page 902