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APPROVED Stormwater Report 12-08-2020MFE) INSIGHT ENGINEERING CO. STORMWATER SITE PLAN For KISAN ENTERPRISES Prepared for The City of Edmonds 121 5th Ave N Edmonds, WA 98020 425-771-0220 Project Site Location: 22810 Edmonds Way, Edmonds, WA 98020 Applicant: Contact: Kisan Enterprise, LLC IECO 20607 State Route 9 S.E, P.O. Box 1478 Snohomish, WA 98296 Everett, WA98206 Ph: 425-402-9900 425-303-9363 Fax: 425-489-0222 Tax Id:27033600102300 IECO Project:20-1062 Certified Erosion and Sedimentation Control Lead: To be named by contractor Stormwater Site Plan Prepared By: Shilpa Xavier, E. I. T. Stormwater Site Plan Preparation Date: July 29, 2020 Date Revised: December 8, 2020 Approximate Construction Date: May 1, 2021 P.O Box 1478 *Everett, WA98206• P: 425.303.9363 info@insightengineering.net 12/08/2020 TABLE OF CONTENTS 1.0 Executive Summary................................................................................................................3 1.1 Drainage Information Summary...................................................................................................6 1.2 Minimum Requirements Summary..............................................................................................8 2.0 Existing Conditions...............................................................................................................10 3.0 Offsite Analysis.....................................................................................................................15 3.1 Upstream Analysis.....................................................................................................................15 3.2 Downstream Analysis................................................................................................................15 4.0 Developed Conditions..........................................................................................................17 5.0 Site Hydraulic Analysis.........................................................................................................18 5.1 Existing Basin Summary............................................................................................................19 5.2 Developed Basin Summary........................................................................................................19 5.3 Water Quality.............................................................................................................................21 5.4 Conveyance Analysis.................................................................................................................25 6.0 Appendix...............................................................................................................................26 Figures Figure 1 - Minimum Requirements Flow Chart.........................................................................5 Figure2 - Vicinity Map.................................................................................................................7 Figure3 - Soil Map......................................................................................................................I t Figure 4 - Downstream Analysis Map-1...................................................................................16 Figure 5 - Downstream Analysis Map-2...................................................................................17 Insight Engineering Co. - Stormwater Site Plan -1- Acronyms and Abbreviations BLA Boundary Line Adjustment BMP Best Management Practices DOE Department of Ecology ECDC Edmonds Community Development Code EDDS Engineering Design and Development Standards ESC Erosion and Sediment Control IECO Insight Engineering Company MR Minimum Requirement SWPPP Stormwater Pollution Prevention Plan SWMMWW Stormwater Management Manual for Western Washington TESC Temporary Erosion and Sediment Control WWHM Western Washington Hydrology Model Insight Engineering Co. - Stormwater Site Plan 12/08/2020 -2- 1.0 Executive Summary The proposed project Kisan Enterprises located at 22810 Edmonds Way, Edmonds, Washington. More generally, the site is located in Section 36, Township 27 North, and Range 3 East of the Willamette Meridian in Snohomish County, Washington. Please refer to the Vicinity Map attached later in the section. This report follows the City of Edmond's requirements and the requirements defined in DOE's 2012 SWMMWW as amended in Dec 2014. The site was developed with a home and an asphalt driveway from Edmonds Way. The home has been demolished already. The site contains one drainage basin that drains to the northern portion of the lot. Please refer to the downstream analysis map for more details. Per NRCS survey of Snohomish County, the majority of the project site contains Everett soils that have a hydrologic classification of Type "A", The rest of the site contains Pits soil and Alderwood soil which has a hydrologic classification of Type "C". Please refer to the soils map and descriptions attached later in this report for more details. A Geotechnical Engineering Study was performed by Earth Solutions NW, LLC. Please refer to the report attached under the Section 6 Appendix E for more details. The site area contains 0.71 Acres. The proposal is to construct 4 residential buildings with a driveway and associated utilities. The total proposed impervious area is 23,658 SF (0.54 AC) which is greater than 5,000 SF, and therefore, per Figure 2.2, (flow chart for new development requirements) Volume I SWMMWW, Minimum requirements #1 through 9 shall apply for this project. Flow control requirements will be met using a detention vault located under the access drive. The detention vault will have a capacity of 17,504 CF. The developed site drainage will be discharged to the existing drainage system on Edmonds Way to continue its natural drainage flow path. Water quality will be met by 1-27" single cartridge steel catch basin stormfilter manufactured by Contech Engineered Solutions LLC located upstream of detention. Per ECDC 18.30.060.D.5.d Minimum Requirement #5: On -site Stormwater Management, the following roof BMPs must be considered in the following order: Full Dispersion or Full Insight Engineering Co. - Stormwater Site Plan 12/08/2020 -3- Infiltration, Bioretention, Downspout Dispersion Systems, Perforated Stub -out Connections, and Detention Vaults or Pipes. The roof drains will be directed to the detention vault. Please refer to Appendix A for tables detailing BMP feasibility. Per ECDC 18.30.060.D.5.d Minimum Requirement #5: On -site Stormwater Management, the BMP's for other hard surfaces must be considered in the following order: Full Dispersion, Permeable Pavement, Bioretention Sheet Flow Dispersion, Detention Vault or Pipe. The runoff from the access drive and driveways will be directed to the detention vault through a Contech stormfilter. Please refer to Section 6 Appendix A for tables detailing BMP feasibility. Post -Construction Soil Quality and Depth BMP T.5.13 is proposed to provide onsite stormwater management for the pervious areas of the site. Insight Engineering Co. - Stormwater Site Plan 12/08/2020 -4- Figure 1 - Minimum Requirements (MR's) for New Development Projects Start Here Does the site have !et See Redevelopment 35% or more of Minimum existing impervious Requirements and coverage? Flaw Chart Does the project conveii (Figure 2.3) No a acres or more of native vegetation to lawn or Does the project add Na landscaped) areas, or 3,000 square feet or convert 2.1 acres or more more of new of native vegetation to impervious surfaoes'r pasture? yde All Minimum Requirements apply to the new impervious surfaces and converted pervious surfaces_ 7 F#o Does the project have 2,000 square feet or more of new, replaced, or new plus replaced impervious surfaces? yet N-a Minimum Requirements # through 45 apply to the new and replaced impervious surfaces and the land disturbed Does the project have larhd-disturbing activities of 7,040 Y,= square feet or more`? P" See Minimum Requirement ##2, Construction Stormwater pollution Prevention Figure 2.2 — Flow Chart for Determining Requirements for New Devalapmant Insight Engineering Co. - Stormwater Site Plan 12/08/2020 -5- 1.1 Drainage Information Summary Project Name: Visan Enterprises Project Engineer: INSIGHT ENGINEERING COMPANY Project Applicant: Kisan Enterprise, LLC Total Site Area: 0.71 Ac Project Development Area Including Frontage Improvements: 0.77 Ac I Number of Buildings:4 Summary Table Drainage Basin Information Individual Basin Desi nation A B C D Basin Area (Acres) 0.77 Type of Storage Proposed Detention Vault Approximate Storage Volume (CF) NA Soil types (Type A) Pre -developed Runoff Rate Q (cfs) 2-year 0.01 10-year 0.02 50-year 0.04 Post -developed Runoff Rate without quantity controls Q (cfs) 2-year 0.13 10-year 0.21 50-year 0.29 Post -Developed Runoff Rate with quantity controls Q (cfs) 2-year 0.01 10-year 0.02 50-year 0.04 Insight Engineering Co. - Stormwater Site Plan 12/08/2020 IM IEC INSIGHT ENGINEERING Ci P.O. Box 1478Everett, WA98206 425-303-9363, 425-303-9362 f. Info@insightengineering.net FIGURE Z VICINITYMAP TAKEN FROM PDS MAP PORTAL Figure 2 -Vicinity May Kisan Enterprises Edmonds, Washington I SCALE: I DATE: 12/8/20 I JOB #: 20-1062 I NTS FILE NAME: BY: NAM 20-1062/doc/Stormwater Site Plan Insight Engineering Co. - Stormwater Site Plan 12/08/2020 -7- 1.2 Minimum Requirements Summary MR : Minimum Requirement SWPPP : Stormwater Pollution Prevention Plan MR #1 Stormwater Site Plan Narrative: The Stormwater Site Plan preparation follows the City of Edmonds requirements and in accordance with DOE's 2012 SWMMWW as amended in Dec 2014. Refer to the executive summary within Section 1.0. MR #2 SWPPP Narrative: A SWPPP has been included in the Appendix C under Section 6. MR #3 Water Pollution Source Control for New Development: Source control of garbage and waste, typical of residential development will be satisfied by the use of dumpstrers with operable covers, and grading that does not allow runoff from adjacent areas to flow into the dumsters. MR #4 Preservation of Natural Drainage Systems and Outfalls: The developed site runoff will be discharged to the existing drainage system on Edmonds Way to continue on its natural drainage flow path. MR #5 Onsite Stormwater Management: Per ECDC 18.30.060.D.5.d Minimum Requirement #5: On -site Stormwater Management, the following roof BMPs must be considered in the following order: Full Dispersion or Full Infiltration, Bioretention, Downspout Dispersion Systems, Perforated Stub -out Connections, and Detention Vaults or Pipes. The roof drains will be directed to the detention vault. Please refer to Appendix A for tables detailing BMP feasibility. Per ECDC 18.30.060.D.5.d Minimum Requirement #5: On -site Stormwater Management, the BMP's for other hard surfaces must be considered in the following order: Full Dispersion, Permeable Pavement, Bioretention Sheet Flow Dispersion, Detention Vault or Pipe. The runoff from the access drive and driveways will be directed to the detention vault through a Contech stormfilter. Please refer to Section 6 Appendix A for tables detailing BMP feasibility. Post -Construction Soil Quality and Depth BMP T.5.13 is proposed to provide onsite stormwater management for the pervious areas of the site. Insight Engineering Co. - Stormwater Site Plan 12/08/2020 -8- MR #6 Runoff Treatment: The developed site drainage will be discharged to the existing drainage system on Edmonds Way to continue its natural drainage flow path. Water quality will be met by 1-27" single cartridge steel catch basin stormfllter manufactured by Contech Engineered Solutions LLC located upstream of detention. MR #7 Flow Control: Flow control requirements will be met using a detention vault located under the access drive. The detention vault will have a capacity of 17,504 CF. The developed site drainage will be discharged to the existing drainage system on Edmonds Way to continue its natural drainage flow path. MR #8 Wetlands Protection: There are no wetlands on the site and the site will not discharge to any wetlands. MR #9 Operations and Maintenance: Refer to Appendix D for a complete Operation and Maintenance Manual. Insight Engineering Co. - Stormwater Site Plan 12/08/2020 -9- 2.0 Existing Conditions The proposed project Kisan Enterprises located at 22810 Edmonds Way, Edmonds, Washington. More generally, the site is located in Section 36, Township 27 North, and Range 3 East of the Willamette Meridian in Snohomish County, Washington. Please refer to the Vicinity Map attached later in the section. The site was developed with a home and an asphalt driveway from Edmonds Way. The home has been demolished already. The site contains one drainage basin that drains to the northern portion of the lot. Please refer to the downstream analysis map for more details. Per NRCS survey of Snohomish County, the majority of the project site contains Everett soils that have a hydrologic classification of Type "A", The rest of the site contains Pits soil and Alderwood soil which has a hydrologic classification of Type "C". Please refer to the soils map and descriptions attached later in this report for more details. A Geotechnical Engineering Study was performed by Earth Solutions NW, LLC. Please refer to the report attached under the Section 6 Appendix E for more details. Insight Engineering Co. - Stormwater Site Plan 12/08/2020 -10- FIGURE 3. SOIL MAP SOILS LEGEND 17- Everett very gravelly sandy loam 0-8% slopes 51- Pits 6- Alderwood-Urban land complex 8-15% slopes a9f5 INSIGHT ENGINEERING CO. P.O. Box 1478 Everett, WA 98206 425-303-9363, 425-303-9362 f Info@insightengineering.net -f t, Figure 3 - Soil Map Kisan Enterprises Edmonds, Washington SCALE: DATE: 12/8/20 JOB #: 20-1062 NONE FILE NAME: BY: NAM I 20-1062\docs\drainage report Insight Engineering Co. - Stormwater Site Plan 12/08/2020 -11- Snohomish County Area, Washington 17—Everett very gravelly sandy loam, 0 to 8 percent slopes Map Unit Setting • National map unit symbol: 2t629 • Elevation: 30 to 900 feet • Mean annual precipitation: 35 to 91 inches • Mean annual air temperature: 48 to 52 degrees F • Frost -free period: 180 to 240 days • Farmland classification: Farmland of statewide importance Map Unit Composition • Everett and similar soils: 80 percent • Minor components: 20 percent • Estimates are based on observations, descriptions, and transects of the mapunit. Description of Everett Settinci • Landform: Eskers, moraines, kames • Landform position (two-dimensional): Summit, shoulder • Landform position (three-dimensional): Crest, interfluve • Down -slope shape: Convex • Across -slope shape: Convex • Parent material: Sandy and gravelly glacial outwash Typical profile • Oi - 0 to 1 inches: slightly decomposed plant material • A - 1 to 3 inches: very gravelly sandy loam • Bw - 3 to 24 inches: very gravelly sandy loam • CI - 24 to 35 inches: very gravelly loamy sand • C2 - 35 to 60 inches: extremely cobbly coarse sand Properties and aualities • Slope: 0 to 8 percent • Depth to restrictive feature: More than 80 inches • Natural drainage class: Somewhat excessively drained • Capacity of the most limiting layer to transmit water (Ksat): High (1.98 to 5.95 in/hr) • Depth to water table: More than 80 inches • Frequency of flooding: None • Frequency of ponding: None • Available water storage in profile: Low (about 3.2 inches) Interpretive groups • Land capability classification (irrigated): None specified • Land capability classification (nonirrigated): 4s • Hydrologic Soil Group: A • Forage suitability group: Droughty Soils (G002XN402WA), Droughty Soils (G002XF403WA), Droughty Soils (G002XS401WA) • Hydric soil rating: No Insight Engineering Co. - Stormwater Site Plan -12- Minor Components Alderwood • Percent of map unit: 10 percent • Landform: Ridges, hills • Landform position (two-dimensional): Summit • Landform position (three-dimensional): Crest, talf • Down -slope shape: Linear, convex • Across -slope shape: Convex • Hydric soil rating: No Indianola • Percent of map unit: 10 percent • Landform: Eskers, kames, terraces • Landform position (three-dimensional): Tread • Down -slope shape: Linear • Across -slope shape: Linear • Hydric soil rating: No Snohomish County Area, Washington 6—Alderwood-Urban land complex, 8 to 15 percent slopes Map Unit Setting • National map unit symbol: 2hzn • 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 • Alderwood and similar soils: 60 percent • Urban land: 25 percent • Minor components: 5 percent • Estimates are based on observations, descriptions, and transects of the mapunit. Description of Alderwood Setting • Landform: Till plains • Parent material: Basal till Tvpical profile • HI - 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 Insight Engineering Co. - Stormwater Site Plan 12/08/2020 -13- Properties and aualities • Slope: 8 to 15 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 • Forage suitability group: Limited Depth Soils (G002XN302WA) • Hydric soil rating: No Minor Components Norma, undrained • Percent of map unit: 5 percent • Landform: Drainageways • Hydric soil rating: Yes Snohomish County Area, Washington 51—Pits Map Unit Composition • Pits: 100 percent • Estimates are based on observations, descriptions, and transects of the mapunit. Description of Pits Interpretive groups • Land capability classification (irrigated): None specified • Land capability classification (nonirrigated): 8 • Hydric soil rating: No Insight Engineering Co. - Stormwater Site Plan 12/08/2020 -14- 3.0 Offsite Analysis A site reconnaissance was performed by Brian Kalab of Insight engineering on June 22, 2020 to verify the downstream flow paths and observe any drainage problems downstream of the site. The sky was sunny with a temperature of 72 degrees. The site was developed with a home and an asphalt driveway from Edmonds Way. The home has been demolished already. The site contains one drainage basin that drains to the northern portion of the lot. Please refer to the downstream analysis map for more details. No visible on -site drainage problems were observed at the time of field investigations. 3.1 Upstream Analysis Based on the site reconnaissance and the topographic survey of the site, upstream flows appear to be minimal. Refer to the Downstream Analysis Maps attached in the next page for more details. 3.2 Downstream Analysis Refer to the Downstream Analysis Maps attached to the next page for a visual description of the downstream flow. The site slopes to the north where runoff flows west along the existing drainage system along Edmonds Way. The runoff flows through this system for about one mile north-west, where is drains into Willow Creek, which drains into the Puget Sound about one mile downstream. There did not appear to be any restrictions or erosional problems within 1 mile of the site. Refer to the downstream analysis map for more information. Insight Engineering Co. - Stormwater Site Plan 12/08/2020 -15- FIGURE 4. DOWNSTREAM ANALYSIS MAP-1 Page Break I EC INSIGHT ENGINEERING CO. P.O. Box 1478 Everett, WA 98206 425-303-9363, 425-303-9362 f. Info@insightengineering.net PD1 : Figure 4 - Downstream Analysis Map-1 Kisan Enterprises Edmonds, Washington ISCALE: I DATE: 12/8/20 I JOB #: 20-1062 I NONE I FILE NAME: BY: NAM 20-1062/doc/Stormwater Site Plan Insight Engineering Co. - Stormwater Site Plan 12/08/2020 -16- FIGURE 5. DOWNSTREAM ANALYSIS MAP-2 Mrf INSIGHT ENGINEERING CO, P.O. Box 1478 Everett, WA 98206 425-303-9363, 425-303-9362 f. Info@insightengineering.net Page Break Figure 5 - Downstream Analysis Map-2 Kisan Enterprises Edmonds, Washington SCALE: DATE: 12/8/20 JOB #: 20- NONE FILE NAME: BY: NAM 20-1062/doc/Stormwater Site Plan Insight Engineering Co. - Stormwater Site Plan 12/08/2020 -17- 4.0 Developed Conditions The proposed project Kisan Enterprises located at 22810 Edmonds Way, Edmonds, Washington. More generally, the site is located in Section 36, Township 27 North, and Range 3 East of the Willamette Meridian in Snohomish County, Washington. Please refer to the Vicinity Map attached at the beginning of this report. This report follows the City of Edmond's requirements and the requirements defined in DOE's 2014 SWMMWW. The site area contains 0.71 Acres. The proposal is to construct 4 residential buildings with a driveway and associated utilities. The total proposed impervious area is 23,658 SF (0.54 AC) which is greater than 5,000 SF, and therefore, per Figure 2.2, (flow chart for new development requirements) Volume I SWMMWW, Minimum requirements #1 through 9 shall apply for this project. Flow control requirements will be met using a detention vault located under the access drive. The detention vault will have a capacity of 17,504 CF. The developed site drainage will be discharged to the existing drainage system on Edmonds Way to continue its natural drainage flow path. Water quality will be met by 1-27" single cartridge steel catch basin stormfilter manufactured by Contech Engineered Solutions LLC located upstream of detention. Per ECDC 18.30.060.D.5.d Minimum Requirement #5: On -site Stormwater Management, the following roof BMPs must be considered in the following order: Full Dispersion or Full Infiltration, Bioretention, Downspout Dispersion Systems, Perforated Stub -out Connections, and Detention Vaults or Pipes. The roof drains will be directed to the detention vault. Please refer to Appendix A for tables detailing BMP feasibility. Per ECDC 18.30.060.D.5.d Minimum Requirement #5: On -site Stormwater Management, the BMP's for other hard surfaces must be considered in the following order: Full Dispersion, Permeable Pavement, Bioretention Sheet Flow Dispersion, Detention Vault or Pipe. The runoff from the access drive and driveways will be directed to the detention vault through a Contech stormfilter. Please refer to Section 6 Appendix A for tables detailing BMP feasibility. Post -Construction Soil Quality and Depth BMP T.5.13 is proposed to provide onsite stormwater management for the pervious areas of the site. Insight Engineering Co. - Stormwater Site Plan 12/08/2020 -18- 5.0 Site Hydraulic Conditions to Determine Flow Control Constraints Total Site Area = 0.71 Acres Total Frontaize Area = 0.06 Acres Total Area Included in the Analysis = 0.77 Acres The area included in the analysis will be the area where the new impervious is proposed. From the Soil Conservation Service Map of Snohomish County, the majority of the site contains Everett soils that have a hydrologic classification of Type "A" 5.1 Existing Basin Summary Existing Basin = 0.77 Acres Total area included in the analysis = 0.77 Acres Entire existing basin was modeled as forested areas. Refer to the Existing Basin Map and WWHM report attached under Appendix B for more details. 5.2 Developed Basin Summary Developed Basin = 0.71 Acres Total area included in the analysis = 0.71 Acres Refer to the Developed Basin Map for representation. Impervious: Roof Area = 0.29 Acres (12,845 SF) Walkway = 0.01 Acres ( 310 SF) Road = 0.20 Acres ( 8,553 SF) Total Developed Impervious = 0.50 Acres (21,708 SF) Pervious Area = 0.21 Acres Insight Engineering Co. - Stormwater Site Plan 12/08/2020 -19- Detention Volume Required: 17,504 CF Detention Volume Provided: 17,504 CF Bypass Area = 0.06 Acres Total area included in the analysis = 0.06 Acres Refer to the Developed Basin Map and WWHM report attached under Appendix B for more details. Impervious: Asphalt/Sidewalk = 0.04 Acres (1,950 SF) Total Impervious = 0.04 Acres (1,950 SF) Pervious Area = 0.02 Acres Total New Impervious Area: 23,658 SF (0.54 Acres) Insight Engineering Co. - Stormwater Site Plan 12/08/2020 -20- _ R=410.23' \ PAID MON IN CASE L1=61'2942" EX. 6"" WM \ 0.5" BELOW RIM C. BEARINGS 68'46"01" E 2" ROUND GONG W/ CORD 4I9.46' INVERTED NAIL EX. 6" WM — SS —39.22 \� wq y l 55 X. STOP BAR _ \ 6 RSi �.•�\'\`' IS \ O \\ 0 \ \ 11 2" /CAP 348 SLOPE �•' TOP 348± INV=341.74 1 59620 SEM 50 EN A.F. N0. 9 0150390 ` O H 15-769 TOP +/ 34 20 7 \ ` SETBACK LINE /CA L EX. CURB ♦ Eg, A sP�`� EX. ROCKERY . I 2 l �5 (mv \ I EX, C.B FT SETBACK LINE TOP=351.44 TOP=349.58 N�8.99�bW' 35004 EX TOP I SIGN TBR) 'ss \ ) INV=345.14-36" INV=344.74-12"NW 0.F.=349.54 I� \ / �,q$— METER / EX. S.S.M.H. I I 16 ^ EX. INGRESS, EG SS ^ ti EASEMENT A.F. N 7801230217 o m I z I I 1 / l 15.01�' / \/ 12B�Ofk(SpN \ \ TOP=350.23 INV=343.99 1 65,00' N 8 0'49" W EX. 6" 70 FH TEE 5bb 7- EXISTING BASIN a j I 9- i (0. 77 AC) L \ IX n 9" 1 — \ CB RIM 351.1, T 1 7\\\ 27033600100100 \ EDMONDSWAY LLC \ 9504 EDMONL�S WAY CB RIM 349.81 EDMOND`S WAI 9 5 FT Ih SE7BAC \i LINE- I( 2, 3&4 L 0 T 1 6 27OJ3600102200 TRIMARK-WESTGATE APARTMENTS LLC 22816 EDMONDS WAY EDMONDS, WA. 98020 EXISTING RETIREMENT HOUSING BUILDING SCALE: 1 " = 40' 0 20 40 EXISTING BASIN MAP R=4f023' \ FND BON IN CASE C HE = EX 6" WM \ BE 0.5' BELOW RIM ARINGRING S 68'46'01" E 2" ROUND GONG W/ CORD 479.46' D INVERTED NAIL _ o BASIN 104 __------_ o (0.06 AC) OVWSD EX. 6" WM — � L-1,'f9.72' O \ SS X STOP 13AR M �j 8 EX. S.S.M.H. CAP TOP=348t 12' 1 96 INV=341.14 50 9010150390 O MH 75-769 0P +/ 34 H RIM 37 8 1 � =341.9 ET CK B T) A �VIT.7 D 1 2 0\ /CA L \ EX. RB RS pL1 l�oY — C.B. M. H. EX. C.B NE a - - TOP=351.44 TOP=349.58 - - N .b9 �b"W 350.04 I l,p INV=345.14-6" 3 EX 70P INV=344.74-12'NW \ SIGN TBR) O S .F.=349.54 S.S 1 16 se TOP 350.23 EX INGRESS, E SS ✓ INV=343.99 N EASEMENT A.F. N 78012JO217 I c' I �18 A II ZB7pF riNc \ 1 65.00' ' I F MGA'OS H• 12 T N 86 0 49' W LD II EX. 6" TO FH TEE I I UNfT 1 CK ( II 6 F MI I DD 32 t4 A3S o DEVELOPED BASIN �I I UNTT16 6 " 31 (0.71 AC) \ II J 1s I lo' urM�.B I I I I. MT 15 30 ��P / I zs• EX b 9" 17 asI 99 27 EX. C.1 1 RIM- 35124 C TOP0I-6'W,6'5 \ UNIT 14 ' INV=349.0\ 1Y UM7'!0 1 ss q F - v CB RIM 351,;4 21 DETENTION VAULT T I 1 7`\ 1 (2,052 AND 10.25) 27033600100POO \ _ EDMONDSWAY LLC 9504 EDMONIiS WAY CB RIM 349.81 EDMONDS, WAI 9 5 FT IL�fNG \ SETBAC N 1 ILO \\\ \ � LINE-2, 3 & 4 .25 13 L 0 T 1 6 27033600102200 26 TRIMARK-WESTGA7E APARTMENTS LLC 7" I 10' 22816 EDMONDS WAY 15 BSB( EDMONDS, WA 98020 fol \ I S g59V 1 9" SCALE: 1" = 40' EXISTING \ RETIREMENT HOUSING BUILDING nT� \ 0 20 40 \ I \ n 8 \ DEVELOPED BASIN MAP 5.3 Water Quality The developed site drainage will be discharged to the existing drainage system on Edmonds Way to continue its natural drainage flow path. Water quality will be met by 1-27" single cartridge steel catch basin stormfllter manufactured by Contech Engineered Solutions LLC located upstream of detention. No metal roof or roof equipment proposed for this project and therefore pollution generating roof surfaces are not proposed. Please refer to Appendix F for Ecology Approval for Filter. Also refer to Appendix G for Water Quality Ccalculations from Contech. Water Quality Basin = 0.49 Acres Impervious Areas: Roof = 0.06 Acres ( 2,627 SF) Walkway = 0.01 Acres ( 310 SF) Road = 0.20 Acres ( 8,553 SF) Total Impervious = 0.27 Acres (I 1,490SF) Pervious Areas = 0.49 Acres- 0.27 Acres=0.22 Acres Please refer to the Water Quality Basin map and WWHM report provided in the following pages for more details. Insight Engineering Co. - Stormwater Site Plan 12/08/2020 -21- 0 ♦ _� M`_ In i e � � t �l� MAI I iT ;l e N i ® ,F Z'B Rl� 351.58 i WATER QUALITY BASIN = 0.49 AC a SCALE: V = 40' EXISTING RETIREMENT HOUSING BUILDING / 0 20 40 \ 8 9„ WATER QUALITY BASIN MAP WWHM2012 PROJECT REPORT Project Name: Kisan Enterprises Site Name: Kisan Enterprises Site Address: 22810 Edmonds Way,Edmonds, WA City : Edmonds Report Date: 7/17/2020 MGS Regoin Puget East Data Start 1901/10/1 Data End : 2058/09/30 DOT Data Number: 03 Version Date: 2019/09/13 Version : 4.2.17 Low Flow Threshold for POC 1 : 50 Percent of the 2 Year High Flow Threshold for POC 1: 50 year PREDEVELOPED LAND USE Name : Existing Basin Bypass: No Groundwater: No Pervious Land Use acre C, Forest, Mod .49 Pervious Total 0.49 Impervious Land Use acre Impervious Total 0 Basin Total 0.49 Element Flows To: Surface Interflow Groundwater MITIGATED LAND USE Name : Developed Basin Bypass: No Insight Engineering Co. - Stormwater Site Plan 12/08/2(, -22- Groundwater: No Pervious Land Use acre C, Lawn, Mod .22 Pervious Total 0.22 Impervious Land Use acre ROADS FLAT 0.2 ROOF TOPS FLAT 0.06 SIDEWALKS FLAT 0.01 Impervious Total 0.27 Basin Total 0.49 Element Flows To: Surface Interflow ANALYSIS RESULTS Stream Protection Duration Predeveloped Landuse Totals for POC #1 Total Pervious Area:0.49 Total Impervious Area:O Mitigated Landuse Totals for POC #1 Total Pervious Area:0.22 Total Impervious Area:0.27 Groundwater Flow Frequency Return Periods for Predeveloped. POC #1 Return Period Flow(cfs) 2 year 0.008359 5 year 0.013879 10 year 0.017011 25 year 0.020278 50 year 0.022253 100 year 0.023894 Flow Frequency Return Periods for Mitigated. POC #1 Return Period Flow(cfs) 2 year 0.075337 Insight Engineering Co. - Stormwater Site Plan - 23 - 5 year 10 year 25 year 50 year 100 year 0.103353 0.124488 0.154302 0.178887 0.205609 The development has an increase in flow durations from 1/2 Predeveloped 2 year flow to the 2 year flow or more than a 10% increase from the 2 year to the 50 year flow. The development has an increase in flow durations for more than 50% of the flows for the range of the duration analysis. Water Quality BMP Flow and volume for POC #1 On-line facility volume: 0.0292 acre-feet On-line facility target flow: 0.0342 cfs. Adjusted for 15 min: 0.0367 cfs. Off-line facility target flow: 0.0191 cfs. Adjusted for 15 min: 0.0204 cfs. LID Report LID Technique Used for Total Volume Percent Water Quality Percent Comment Treatment? Needs Volume Water Quality Treatment Infiltrated Treated (ac-ft) Total Volume Infiltrated 0.00 0.00 0.00 0% No Treat. Credit Compliance with LID Standard 8 Duration Analysis Result = Failed Perind and Impind Changes No changes have been made. Volume Infiltration Cumulative Through Volume Volume Facility (ac-ft.) Infiltration (ac-ft 0.00 0.00 Credit 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. 2005-2020; All Rights Reserved. Insight Engineering Co. - Stormwater Site Plan 12/08/2020 -24- 5.4 Conveyance Analysis The 100yr peak flow for the project is only 0.33 cfs. A 12-inch pipe can convey 3 cfs at a minimum slope of 0.5-percent. The minimum size of the proposed system is 12-inch for the project that can easily convey 0.33 cfs and therefore a detailed conveyance analysis was not performed. The roof drains for Buildings B, C and D will be directly connected to the detention system via 6-inch pipe at 2% minimum. Insight Engineering Co. - Stormwater Site Plan 12/08/2020 -25- 6. Appendix A. Minimum Requirement #5 BMP Feasibility B. WWHM Report C. Stormwater Pollution Prevention Plan D. Operations and Maintenance Manual E. Geotechnical Report F. Ecology Approval for Filter G. Water Quality Ccalculations from Contech Insight Engineering Co. - Stormwater Site Plan 12/08/2020 -26- A. MINIMUM REQUIREMENT #5 BMP FEASIBILITY Roof BMPs (List #2) Per ECDC 18.30.060.D.5.d Minimum Requirement #5 BMP Feasibility BMP Feasibility Conditions T5.30 Full Dispersion Infeasible Full Dispersion is infeasible because of the required flow path and preserved vegetation area could not be achieved. Bioretention Infeasible As per Geotech Report attached under Appendix E shallow groundwater was encountered at depths of l' to 2'. T5.1 OB Downspout Infeasible Downspout Dispersion is infeasible because the site Dispersion cannot provide the required vegetated flow paths for each unit. T5.1 OC Perforated Stub- Infeasible As per Geotech Report attached under Appendix E out Connections shallow groundwater was encountered at depths of l' to 2'. Detention Pipe or Vault Feasible A detention vault sized with WWHM2012 has been provided Other Hard Surface BMPs (List #2) Per ECDC 18.30.060.D.5.d Minimum Requirement #5 BMP Feasibility BMP Feasibility Conditions T5.30 Full Dispersion Infeasible Full Dispersion is infeasible because of the lack of preserved vegetated could not be achieved for this MR zoned project. Permeable Pavement or Infeasible As per Geotech Report attached under Appendix E Bioretention shallow groundwater was encountered at depths of 1' to 2'. T5.12 Sheet Flow Infeasible Sheet Flow Dispersion is infeasible because the site Dispersion cannot provide the required vegetated flow paths for each unit. Detention Pipe or Vault Feasible A detention vault sized with WWHM2012 has been Insight Engineering Co. - Stormwater Site Plan 12/08/2020 -27- provided Lawn and landscaped areas (List #2) Per ECDC 18.30.060.D.5.d Minimum Requirement #5 BMP Feasibility BMP Feasibility Conditions T513. Post -Construction Soil Quality and Depth Feasible BMP T5.13 is proposed for all lawn and landscape areas. Insight Engineering Co. - Stormwater Site Plan 12/08/2020 -28- Insight Engineering Co. - Stormwater Site Plan 12/08/2020 -29- WWH? PROJECT General Model Information Project Name: Kisan Enterprises Site Name: KISAN ENTERPRISES Site Address: 22810 EDMONDS WAY City: EDMONDS Report Date: 7/29/2020 MGS Region: Puget East Data Start: 1901 /10/1 Data End: 2058/09/30 Timestep: Hourly DOT Data Number03 Version Date: 2019/09/13 Version: 4.2.17 POC Thresholds Low Flow Threshold for POC1: 50 Percent of the 2 Year High Flow Threshold for POC1: 50 Year Kisan Enterprises 7/29/2020 10:58:54 AM Page 2 Landuse Basin Data Predeveloped Land Use EXISTING Bypass: No GroundWater: No Pervious Land Use acre C, Forest, Mod 0.77 Pervious Total 0.77 Impervious Land Use acre Impervious Total 0 Basin Total 0.77 Element Flows To: Surface I nterflow Groundwater Kisan Enterprises 7/29/2020 10:58:54 AM Page 3 Mitigated Land Use DEVELOPED BASIN Bypass: No GroundWater: No Pervious Land Use acre C, Lawn, Mod 0.21 Pervious Total 0.21 Impervious Land Use acre ROADS FLAT 0.2 ROOF TOPS FLAT 0.29 SIDEWALKS FLAT 0.01 Impervious Total 0.5 Basin Total 0.71 Element Flows To: Surface Vault 1 Interflow Vault 1 Groundwater Kisan Enterprises 7/29/2020 10:58:54 AM Page 4 BYPASS BASIN Bypass: Yes GroundWater: No Pervious Land Use acre C, Lawn, Flat 0.02 Pervious Total 0.02 Impervious Land Use acre ROADS FLAT 0.04 Impervious Total 0.04 Basin Total 0.06 Element Flows To: Surface Interflow Groundwater Kisan Enterprises 7/29/2020 10:58:54 AM Page 5 Routing Elements Predeveloped Routing Kisan Enterprises 7/29/2020 10:58:54 AM Page 6 Mitigated Routing Vault 1 Width: Length: Depth: Discharge Structure Riser Height: Riser Diameter: Notch Type: Notch Width: Notch Height: Orifice 1 Diameter: Element Flows To: Outlet 1 19 ft. 108 ft. 9.53 ft. 8.53 ft. 12 in. Rectangular 1.000 ft. 0.071 ft. 0.285 in. Elevation:0 ft. Outlet 2 Vault Hydraulic Table Stage(feet) Area(ac.) Volume(ac-ft.) Discharge(cfs) Infilt(cfs) 0.0000 0.047 0.000 0.000 0.000 0.1059 0.047 0.005 0.000 0.000 0.2118 0.047 0.010 0.001 0.000 0.3177 0.047 0.015 0.001 0.000 0.4236 0.047 0.020 0.001 0.000 0.5294 0.047 0.024 0.001 0.000 0.6353 0.047 0.029 0.001 0.000 0.7412 0.047 0.034 0.001 0.000 0.8471 0.047 0.039 0.002 0.000 0.9530 0.047 0.044 0.002 0.000 1.0589 0.047 0.049 0.002 0.000 1.1648 0.047 0.054 0.002 0.000 1.2707 0.047 0.059 0.002 0.000 1.3766 0.047 0.064 0.002 0.000 1.4824 0.047 0.069 0.002 0.000 1.5883 0.047 0.074 0.002 0.000 1.6942 0.047 0.079 0.002 0.000 1.8001 0.047 0.084 0.003 0.000 1.9060 0.047 0.089 0.003 0.000 2.0119 0.047 0.094 0.003 0.000 2.1178 0.047 0.099 0.003 0.000 2.2237 0.047 0.104 0.003 0.000 2.3296 0.047 0.109 0.003 0.000 2.4354 0.047 0.114 0.003 0.000 2.5413 0.047 0.119 0.003 0.000 2.6472 0.047 0.124 0.003 0.000 2.7531 0.047 0.129 0.003 0.000 2.8590 0.047 0.134 0.003 0.000 2.9649 0.047 0.139 0.003 0.000 3.0708 0.047 0.144 0.003 0.000 3.1767 0.047 0.149 0.003 0.000 3.2826 0.047 0.154 0.004 0.000 3.3884 0.047 0.159 0.004 0.000 3.4943 0.047 0.164 0.004 0.000 3.6002 0.047 0.169 0.004 0.000 3.7061 0.047 0.174 0.004 0.000 3.8120 0.047 0.179 0.004 0.000 Kisan Enterprises 7/29/2020 10:58:54 AM Page 7 3.9179 0.047 0.184 0.004 0.000 4.0238 0.047 0.189 0.004 0.000 4.1297 0.047 0.194 0.004 0.000 4.2356 0.047 0.199 0.004 0.000 4.3414 0.047 0.204 0.004 0.000 4.4473 0.047 0.209 0.004 0.000 4.5532 0.047 0.214 0.004 0.000 4.6591 0.047 0.219 0.004 0.000 4.7650 0.047 0.224 0.004 0.000 4.8709 0.047 0.229 0.004 0.000 4.9768 0.047 0.234 0.004 0.000 5.0827 0.047 0.239 0.005 0.000 5.1886 0.047 0.244 0.005 0.000 5.2944 0.047 0.249 0.005 0.000 5.4003 0.047 0.254 0.005 0.000 5.5062 0.047 0.259 0.005 0.000 5.6121 0.047 0.264 0.005 0.000 5.7180 0.047 0.269 0.005 0.000 5.8239 0.047 0.274 0.005 0.000 5.9298 0.047 0.279 0.005 0.000 6.0357 0.047 0.284 0.005 0.000 6.1416 0.047 0.289 0.005 0.000 6.2474 0.047 0.294 0.005 0.000 6.3533 0.047 0.299 0.005 0.000 6.4592 0.047 0.304 0.005 0.000 6.5651 0.047 0.309 0.005 0.000 6.6710 0.047 0.314 0.005 0.000 6.7769 0.047 0.319 0.005 0.000 6.8828 0.047 0.324 0.005 0.000 6.9887 0.047 0.329 0.005 0.000 7.0946 0.047 0.334 0.005 0.000 7.2004 0.047 0.339 0.005 0.000 7.3063 0.047 0.344 0.006 0.000 7.4122 0.047 0.349 0.006 0.000 7.5181 0.047 0.354 0.006 0.000 7.6240 0.047 0.359 0.006 0.000 7.7299 0.047 0.364 0.006 0.000 7.8358 0.047 0.369 0.006 0.000 7.9417 0.047 0.374 0.006 0.000 8.0476 0.047 0.379 0.006 0.000 8.1534 0.047 0.384 0.006 0.000 8.2593 0.047 0.389 0.006 0.000 8.3652 0.047 0.394 0.006 0.000 8.4711 0.047 0.399 0.010 0.000 8.5770 0.047 0.404 0.177 0.000 8.6829 0.047 0.409 0.691 0.000 8.7888 0.047 0.414 1.340 0.000 8.8947 0.047 0.419 1.895 0.000 9.0006 0.047 0.424 2.216 0.000 9.1064 0.047 0.429 2.461 0.000 9.2123 0.047 0.434 2.671 0.000 9.3182 0.047 0.439 2.866 0.000 9.4241 0.047 0.443 3.048 0.000 9.5300 0.047 0.448 3.219 0.000 9.6359 0.047 0.453 3.382 0.000 9.7418 0.000 0.000 3.537 0.000 Kisan Enterprises 7/29/2020 10:58:54 AM Page 8 Analysis Results POC 1 Ni 10 100 Percent Time Exce edirig + Predeveloped Predeveloped Landuse Totals for POC #1 Total Pervious Area: 0.77 Total Impervious Area: 0 Mitigated Landuse Totals for POC #1 Total Pervious Area: 0.23 Total Impervious Area: 0.54 Cumulative Pro6a6ility 0 000, o 000, D.6 1 2 6 10 20 30 b0 ]0 90 90 �6 13 6 1 D x Mitigated Flow Frequency Method: Log Pearson Type III 17B Flow Frequency Return Periods for Predeveloped. POC #1 Return Period Flow(cfs) 2 year 0.013136 5 year 0.02181 10 year 0.026732 25 year 0.031865 50 year 0.034968 100 year 0.037547 Flow Frequency Return Periods for Mitigated. POC #1 Return Period Flow(cfs) 2 year 0.013521 5 year 0.01892 10 year 0.023489 25 year 0.030562 50 year 0.036903 100 year 0.04428 Annual Peaks Annual Peaks for Predeveloped and Mitigated. POC #1 Year Predeveloped Mitigated 1902 0.018 0.012 1903 0.006 0.015 1904 0.016 0.019 1905 0.007 0.011 1906 0.003 0.010 1907 0.020 0.015 1908 0.013 0.012 1909 0.014 0.013 1910 0.024 0.015 1911 0.011 0.012 Kisan Enterprises 7/29/2020 10:58:54 AM Page 9 1912 0.049 0.026 1913 0.019 0.012 1914 0.004 0.030 1915 0.006 0.010 1916 0.010 0.013 1917 0.005 0.009 1918 0.013 0.012 1919 0.009 0.010 1920 0.012 0.013 1921 0.012 0.012 1922 0.014 0.014 1923 0.012 0.014 1924 0.006 0.013 1925 0.006 0.009 1926 0.011 0.014 1927 0.014 0.011 1928 0.009 0.013 1929 0.023 0.017 1930 0.012 0.018 1931 0.012 0.011 1932 0.009 0.012 1933 0.010 0.012 1934 0.031 0.100 1935 0.010 0.011 1936 0.017 0.012 1937 0.015 0.016 1938 0.014 0.012 1939 0.001 0.013 1940 0.011 0.017 1941 0.011 0.014 1942 0.017 0.016 1943 0.005 0.016 1944 0.017 0.024 1945 0.012 0.015 1946 0.011 0.012 1947 0.008 0.010 1948 0.026 0.014 1949 0.022 0.019 1950 0.011 0.010 1951 0.014 0.011 1952 0.045 0.025 1953 0.036 0.025 1954 0.010 0.012 1955 0.008 0.011 1956 0.006 0.009 1957 0.015 0.013 1958 0.036 0.018 1959 0.022 0.018 1960 0.008 0.011 1961 0.022 0.030 1962 0.011 0.012 1963 0.005 0.009 1964 0.010 0.022 1965 0.026 0.089 1966 0.005 0.011 1967 0.010 0.012 1968 0.013 0.012 1969 0.009 0.013 Kisan Enterprises 7/29/2020 10:59:14 AM Page 10 1970 0.017 0.015 1971 0.028 0.016 1972 0.018 0.038 1973 0.021 0.020 1974 0.014 0.018 1975 0.033 0.023 1976 0.013 0.018 1977 0.008 0.010 1978 0.025 0.018 1979 0.007 0.013 1980 0.012 0.014 1981 0.013 0.014 1982 0.008 0.011 1983 0.021 0.017 1984 0.005 0.015 1985 0.012 0.014 1986 0.010 0.011 1987 0.021 0.015 1988 0.015 0.011 1989 0.012 0.010 1990 0.015 0.011 1991 0.012 0.015 1992 0.018 0.017 1993 0.015 0.016 1994 0.026 0.014 1995 0.006 0.010 1996 0.031 0.043 1997 0.013 0.012 1998 0.013 0.014 1999 0.000 0.012 2000 0.009 0.016 2001 0.007 0.011 2002 0.025 0.021 2003 0.014 0.012 2004 0.016 0.015 2005 0.023 0.022 2006 0.009 0.012 2007 0.010 0.015 2008 0.013 0.013 2009 0.008 0.012 2010 0.006 0.014 2011 0.008 0.010 2012 0.011 0.015 2013 0.010 0.011 2014 0.006 0.011 2015 0.029 0.021 2016 0.004 0.010 2017 0.023 0.020 2018 0.041 0.024 2019 0.044 0.021 2020 0.015 0.017 2021 0.017 0.017 2022 0.006 0.017 2023 0.014 0.018 2024 0.055 0.029 2025 0.011 0.010 2026 0.020 0.014 2027 0.008 0.014 Kisan Enterprises 7/29/2020 10:59:14 AM Page 11 2028 0.004 0.007 2029 0.014 0.014 2030 0.030 0.016 2031 0.007 0.008 2032 0.006 0.010 2033 0.007 0.009 2034 0.008 0.010 2035 0.032 0.017 2036 0.017 0.013 2037 0.003 0.013 2038 0.019 0.014 2039 0.001 0.019 2040 0.006 0.011 2041 0.009 0.013 2042 0.034 0.018 2043 0.014 0.015 2044 0.020 0.015 2045 0.012 0.013 2046 0.014 0.014 2047 0.009 0.013 2048 0.012 0.012 2049 0.012 0.016 2050 0.008 0.012 2051 0.013 0.020 2052 0.007 0.011 2053 0.013 0.012 2054 0.024 0.019 2055 0.005 0.012 2056 0.005 0.014 2057 0.008 0.011 2058 0.010 0.014 Ranked Annual Peaks Ranked Annual Peaks for Predeveloped and Rank Predeveloped Mitigated 1 0.0554 0.0998 2 0.0495 0.0886 3 0.0451 0.0433 4 0.0439 0.0383 5 0.0411 0.0301 6 0.0365 0.0298 7 0.0362 0.0289 8 0.0342 0.0261 9 0.0328 0.0252 10 0.0316 0.0248 11 0.0311 0.0240 12 0.0306 0.0236 13 0.0298 0.0232 14 0.0289 0.0222 15 0.0276 0.0221 16 0.0265 0.0215 17 0.0262 0.0213 18 0.0261 0.0209 19 0.0250 0.0201 20 0.0250 0.0201 21 0.0244 0.0196 22 0.0239 0.0192 23 0.0229 0.0189 Mitigated. POC #1 Kisan Enterprises 7/29/2020 10:59:14 AM Page 12 24 0.0227 0.0187 25 0.0227 0.0185 26 0.0223 0.0184 27 0.0217 0.0183 28 0.0217 0.0182 29 0.0212 0.0182 30 0.0209 0.0177 31 0.0207 0.0176 32 0.0205 0.0176 33 0.0200 0.0176 34 0.0198 0.0172 35 0.0193 0.0171 36 0.0192 0.0171 37 0.0180 0.0171 38 0.0180 0.0170 39 0.0179 0.0169 40 0.0173 0.0166 41 0.0172 0.0166 42 0.0170 0.0163 43 0.0168 0.0163 44 0.0168 0.0162 45 0.0166 0.0161 46 0.0159 0.0160 47 0.0157 0.0159 48 0.0155 0.0158 49 0.0154 0.0155 50 0.0152 0.0154 51 0.0150 0.0153 52 0.0149 0.0153 53 0.0148 0.0153 54 0.0144 0.0152 55 0.0144 0.0152 56 0.0142 0.0150 57 0.0141 0.0149 58 0.0140 0.0149 59 0.0140 0.0149 60 0.0138 0.0147 61 0.0138 0.0147 62 0.0138 0.0147 63 0.0137 0.0145 64 0.0136 0.0145 65 0.0135 0.0145 66 0.0133 0.0145 67 0.0131 0.0144 68 0.0130 0.0144 69 0.0128 0.0143 70 0.0127 0.0143 71 0.0127 0.0142 72 0.0126 0.0141 73 0.0126 0.0141 74 0.0125 0.0140 75 0.0125 0.0139 76 0.0124 0.0138 77 0.0122 0.0138 78 0.0121 0.0137 79 0.0121 0.0137 80 0.0121 0.0136 81 0.0120 0.0134 Kisan Enterprises 7/29/2020 10:59:14 AM Page 13 82 0.0120 0.0133 83 0.0119 0.0133 84 0.0119 0.0132 85 0.0119 0.0131 86 0.0118 0.0131 87 0.0117 0.0129 88 0.0115 0.0129 89 0.0114 0.0128 90 0.0114 0.0128 91 0.0113 0.0128 92 0.0112 0.0127 93 0.0111 0.0127 94 0.0110 0.0127 95 0.0108 0.0126 96 0.0108 0.0125 97 0.0105 0.0125 98 0.0103 0.0125 99 0.0103 0.0124 100 0.0101 0.0124 101 0.0101 0.0123 102 0.0100 0.0123 103 0.0100 0.0123 104 0.0098 0.0123 105 0.0097 0.0122 106 0.0097 0.0122 107 0.0094 0.0121 108 0.0093 0.0121 109 0.0092 0.0120 110 0.0092 0.0120 111 0.0090 0.0120 112 0.0089 0.0118 113 0.0088 0.0118 114 0.0087 0.0117 115 0.0085 0.0117 116 0.0085 0.0116 117 0.0084 0.0116 118 0.0082 0.0116 119 0.0081 0.0116 120 0.0080 0.0115 121 0.0078 0.0115 122 0.0077 0.0114 123 0.0076 0.0114 124 0.0076 0.0114 125 0.0075 0.0114 126 0.0074 0.0113 127 0.0074 0.0112 128 0.0070 0.0112 129 0.0066 0.0111 130 0.0066 0.0111 131 0.0065 0.0110 132 0.0063 0.0109 133 0.0063 0.0108 134 0.0063 0.0107 135 0.0062 0.0107 136 0.0061 0.0107 137 0.0060 0.0105 138 0.0058 0.0104 139 0.0058 0.0104 Kisan Enterprises 7/29/2020 10:59:14 AM Page 14 140 0.0057 0.0102 141 0.0057 0.0100 142 0.0056 0.0100 143 0.0053 0.0100 144 0.0053 0.0099 145 0.0050 0.0099 146 0.0050 0.0098 147 0.0049 0.0098 148 0.0049 0.0097 149 0.0046 0.0096 150 0.0045 0.0095 151 0.0041 0.0093 152 0.0035 0.0091 153 0.0027 0.0091 154 0.0026 0.0085 155 0.0011 0.0085 156 0.0006 0.0084 157 0.0002 0.0070 Kisan Enterprises 7/29/2020 10:59:14 AM Page 15 Duration Flows The Facility PASSED Flow(cfs) Predev Mit Percentage Pass/Fail 0.0066 12736 12607 98 Pass 0.0069 11576 9848 85 Pass 0.0071 10526 7905 75 Pass 0.0074 9594 6394 66 Pass 0.0077 8782 5255 59 Pass 0.0080 8066 4290 53 Pass 0.0083 7428 3571 48 Pass 0.0086 6845 3006 43 Pass 0.0089 6296 2510 39 Pass 0.0091 5809 2133 36 Pass 0.0094 5327 1852 34 Pass 0.0097 4899 1587 32 Pass 0.0100 4509 1350 29 Pass 0.0103 4181 1152 27 Pass 0.0106 3848 1012 26 Pass 0.0109 3544 902 25 Pass 0.0112 3275 786 24 Pass 0.0114 3031 680 22 Pass 0.0117 2803 608 21 Pass 0.0120 2615 545 20 Pass 0.0123 2443 484 19 Pass 0.0126 2290 432 18 Pass 0.0129 2121 387 18 Pass 0.0132 1985 354 17 Pass 0.0135 1868 331 17 Pass 0.0137 1763 307 17 Pass 0.0140 1654 271 16 Pass 0.0143 1562 245 15 Pass 0.0146 1478 230 15 Pass 0.0149 1393 208 14 Pass 0.0152 1324 192 14 Pass 0.0155 1242 175 14 Pass 0.0157 1173 160 13 Pass 0.0160 1120 152 13 Pass 0.0163 1053 139 13 Pass 0.0166 1001 132 13 Pass 0.0169 953 124 13 Pass 0.0172 901 114 12 Pass 0.0175 868 112 12 Pass 0.0178 833 103 12 Pass 0.0180 800 101 12 Pass 0.0183 774 93 12 Pass 0.0186 740 89 12 Pass 0.0189 717 82 11 Pass 0.0192 688 81 11 Pass 0.0195 659 79 11 Pass 0.0198 630 78 12 Pass 0.0201 598 77 12 Pass 0.0203 564 71 12 Pass 0.0206 538 71 13 Pass 0.0209 511 69 13 Pass 0.0212 488 65 13 Pass 0.0215 465 64 13 Pass Kisan Enterprises 7/29/2020 10:59:14 AM Page 16 0.0218 447 62 13 Pass 0.0221 435 62 14 Pass 0.0223 412 60 14 Pass 0.0226 399 59 14 Pass 0.0229 375 57 15 Pass 0.0232 360 56 15 Pass 0.0235 343 55 16 Pass 0.0238 326 54 16 Pass 0.0241 309 53 17 Pass 0.0244 292 50 17 Pass 0.0246 279 47 16 Pass 0.0249 264 46 17 Pass 0.0252 254 43 16 Pass 0.0255 237 40 16 Pass 0.0258 225 37 16 Pass 0.0261 214 36 16 Pass 0.0264 203 36 17 Pass 0.0266 186 36 19 Pass 0.0269 176 34 19 Pass 0.0272 166 34 20 Pass 0.0275 156 34 21 Pass 0.0278 139 34 24 Pass 0.0281 128 34 26 Pass 0.0284 120 33 27 Pass 0.0287 112 32 28 Pass 0.0289 99 31 31 Pass 0.0292 93 31 33 Pass 0.0295 84 31 36 Pass 0.0298 79 29 36 Pass 0.0301 77 28 36 Pass 0.0304 73 27 36 Pass 0.0307 66 27 40 Pass 0.0310 61 27 44 Pass 0.0312 54 26 48 Pass 0.0315 47 26 55 Pass 0.0318 43 26 60 Pass 0.0321 39 25 64 Pass 0.0324 36 24 66 Pass 0.0327 34 24 70 Pass 0.0330 31 24 77 Pass 0.0332 29 24 82 Pass 0.0335 27 23 85 Pass 0.0338 27 23 85 Pass 0.0341 25 22 88 Pass 0.0344 21 21 100 Pass 0.0347 21 20 95 Pass 0.0350 19 20 105 Pass Kisan Enterprises 7/29/2020 10:59:14 AM Page 17 Water Quality 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. Kisan Enterprises 7/29/2020 10:59:14 AM Page 18 LID Report LID Technique Used for Total Volume Volume Infiltration Cumulative Percent Waterfluality Percent Comment Treatment? Needs Through Volume Volume Volume Water Quality Treatment Facility (ac-ft) Infiltration Infiltrated Treated (ac-ft) (ac-ft) Credit Vault 1 PDC ❑ 202.48 ❑ 0.00 Total Volume Infiltrated 202.48 0.00 0.00 0.00 0.00 0% No Treat. Credit Duration Compliance with LID Analysis Standard B% of2-yrto 50% of Result = 2 yr Failed Kisan Enterprises 7/29/2020 10:59:14 AM Page 19 Model Default Modifications Total of 0 changes have been made. PERLND Changes No PERLND changes have been made. IMPLND Changes No IMPLND changes have been made. Kisan Enterprises 7/29/2020 10:59:28 AM Page 20 Appendix Predeveloped Schematic EEXISTING 0.77ac Kisan Enterprises 7/29/2020 10:59:28 AM Page 21 Kisan Enterprises 7/29/2020 10:59:28 AM Page 21 Mitigated Schematic Kisan Enterprises 7/29/2020 10:59:37 AM Page 22 C. STORMWATER POLLUTION PREVENTION PLAN This Stormwater Pollution Prevention Plan (SWPPP) has been prepared as part of the Construction stormwater permit requirements for the Kisan Enterprises located at 22810 Edmonds Way, Edmonds, Washington. More generally, the site is located in Section 36, Township 27 North, and Range 3 East of the Willamette Meridian in Snohomish County, Washington. The site was developed with a home and an asphalt driveway from Edmonds Way. The home has been demolished already. The site contains one drainage basin that drains to the northern portion of the lot. Please refer to the downstream analysis map for more details. Per NRCS survey of Snohomish County, the majority of the project site contains Everett soils that have a hydrologic classification of Type "A", The rest of the site contains Pits soil and Alderwood soil which has a hydrologic classification of Type "C". Please refer to the soils map and descriptions attached later in this report for more details. A Geotechnical Engineering Study was performed by Earth Solutions NW, LLC. Please refer to the report attached under the Section 6 Appendix E for more details. The site area contains 0.71 Acres. The proposal is to construct 4 residential buildings with a driveway and associated utilities. The total proposed impervious area is 23,658 SF (0.54 AC) which is greater than 5,000 SF, and therefore, per Figure 2.2, (flow chart for new development requirements) Volume I SWMMWW, Minimum requirements #1 through 9 shall apply for this project. Flow control requirements will be met using a detention vault located under the access drive. The detention vault will have a capacity of 17,504 CF. The developed site drainage will be discharged to the existing drainage system on Edmonds Way to continue its natural drainage flow path. Water quality will be met by 1-27" single cartridge steel catch basin stormfilter manufactured by Contech Engineered Solutions LLC located upstream of detention. Per ECDC 18.30.060.D.5.d Minimum Requirement #5: On -site Stormwater Management, the following roof BMPs must be considered in the following order: Full Dispersion or Full Infiltration, Bioretention, Downspout Dispersion Systems, Perforated Stub -out Connections, and Detention Vaults or Pipes. The roof drains will be directed to the detention vault. Please refer to Insight Engineering Co. - Stormwater Site Plan 12/08/2020 -30- Appendix A for tables detailing BMP feasibility. Per ECDC 18.30.060.D.5.d Minimum Requirement #5: On -site Stormwater Management, the BMP's for other hard surfaces must be considered in the following order: Full Dispersion, Permeable Pavement, Bioretention Sheet Flow Dispersion, Detention Vault or Pipe. The runoff from the access drive and driveways will be directed to the detention vault through a Contech stormfilter. Please refer to Section 6 Appendix A for tables detailing BMP feasibility. Post -Construction Soil Quality and Depth BMP T.5.13 is proposed to provide onsite stormwater management for the pervious areas of the site. The purpose of this SWPPP is to describe the proposed construction activities and all temporary and permanent erosion and sediment control (TESC) measures, pollution prevention measures, inspection/monitoring activities, and recordkeeping that will be implemented during the proposed construction project. The objectives of the SWPPP are to: 1. Implement Best Management Practices (BMPs) to prevent erosion and sedimentation, and to identify, reduce, eliminate or prevent stormwater contamination and water pollution from construction activity. 2. Prevent violations of surface water quality, ground water quality, or sediment management standards. 3. Prevent, during the construction phase, adverse water quality impacts including impacts on beneficial uses of the receiving water by controlling peak flow rates and volumes of stormwater runoff at the Permittee's outfalls and downstream of the outfalls. This SWPPP was prepared using the Ecology SWPPP Template. This SWPPP was prepared based on the requirements set forth in the Construction Stormwater General Permit and in the Stormwater Management Manual for Western Washington (SWMMWW 2005). Insight Engineering Co. - Stormwater Site Plan 12/08/2020 -31- The 13 BMP Elements Element #1— Mark Clearing Limits To protect adjacent properties and to reduce the area of soil exposed to construction, the limits of construction will be clearly marked before land -disturbing activities begin. Element #2 — Establish Construction Access Construction access or activities occurring on unpaved areas shall be minimized, yet where necessary, access points shall be stabilized to minimize the tracking of sediment onto public roads, and wheel washing, street sweeping, and street cleaning shall be employed to prevent sediment from entering state waters. Install the temporary construction entrance, according to the approved construction plans, prior to any clearing or grading activities. Maintain until the access road is paved. Element #3 — Control Flow Rates In order to protect the properties and waterways downstream of the project site, stormwater discharges from the site will be controlled. In general, discharge rates of stormwater from the site will be controlled where increases in impervious area or soil compaction during construction could lead to downstream erosion, or where necessary to meet local agency stormwater discharge requirements. Element #4 — Install Sediment Controls Install silt fencing, according to the approved plans, prior to any clearing or grading activities. Maintain until all construction activities are completed. Install storm drain inlet protection, according to the approved construction plans, as catch basins become operable. Maintain until all construction activities are completed. Element #5 — Stabilize Soils Exposed and un-worked soils shall be stabilized with the application of effective BMPs to prevent erosion throughout the life of the project. Apply temporary hydro -seed to exposed and un-worked soils, according to the approved construction plans, as needed to prevent erosion during site grading. Apply permanent hydro - seed to areas at final grade as site grading is completed. Apply mulching to exposed and un-worked soils, according to the approved construction plans, as needed to prevent erosion during site grading. Maintain until site grading is completed and permanent hydro -seed is applied. Cover stockpiles with plastic sheeting, according to the approved construction plans, as needed to prevent erosion during site grading. Maintain until stockpiles are removed from site. Element #6 — Protect Slopes All cut and fill slopes will be designed, constructed, and protected in a manner than minimizes erosion. The following specific BMPs will be used to protect slopes for this project. Element #7 — Protect Drain Inlets All storm drain inlets and culverts made operable during construction shall be protected to prevent unfiltered or untreated water from entering the drainage conveyance system. However, Insight Engineering Co. - Stormwater Site Plan 12/08/2020 -32- the priority is to keep all access roads clean of sediment and keep street wash water separate from entering storm drains until treatment can be provided. Element #8 — Stabilize Channels and Outlets Where site runoff is to be conveyed in channels or discharged to a stream or some other natural drainage point, efforts will be taken to prevent downstream erosion. Element #9 — Control Pollutants All pollutants, including waste materials and demolition debris, that occur onsite shall be handled and disposed of in a manner that does not cause contamination of stormwater. Good housekeeping and preventative measures will be taken to ensure that the site will be kept clean, well organized, and free of debris. Element #10 — Control Dewatering There will be no dewatering expected as part of this proposal. If it occurs, Baker tanks will be used for dewatering. Element #11— Maintain BMPs All temporary and permanent erosion and sediment control BMPs shall be maintained and repaired as needed to assure continued performance of their intended function. Maintenance and repair shall be conducted in accordance with each particular BMP's specifications. Visual monitoring of the BMPs will be conducted at least once every calendar week and within 24 hours of any rainfall event that causes a discharge from the site. If the site becomes inactive, and is temporarily stabilized, the inspection frequency will be reduced to once every month. All temporary erosion and sediment control BMPs shall be removed within 30 days after the final site stabilization is achieved or after the temporary BMPs are no longer needed. Trapped sediment shall be removed or stabilized on site. Disturbed soil resulting from removal of BMPs or vegetation shall be permanently stabilized. Element #12 — Manage the Project Erosion and sediment control BMPs for this project have been designed based on the following principles: Design the project to fit the existing topography, soils, and drainage patterns; Emphasize erosion control rather than sediment control; Minimize the extent and duration of the area exposed; Keep runoff velocities low; Retain sediment on site; Thoroughly monitor site and maintain all ESC measures and Schedule major earthwork during the dry season. The SWPPP shall be modified as necessary to include additional or modified BMPs designed to correct problems identified. Revisions to the SWPPP shall be completed within seven (7) days following the inspection. Element #13 - Protect Onsite Stormwater Management BMPS for Runoff from Roofs and other Hard surfaces NA Insight Engineering Co. - Stormwater Site Plan 12/08/2020 -33- D. OPERATIONS AND MAINTENANCE MANUAL Refer to the following pages for the O&M manual. Insight Engineering Co. - Stormwater Site Plan 12/08/2020 -34- No. 3 — Closed Detention Systems (Tanks/Vaults) Maintenance Defect Conditions When Maintenance is Needed Results Expected Component When Maintenance is Performed Storage Area Plugged Air Vents One-half of the cross section of a vent is Vents open and blocked at any point or the vent is damaged. functioning. Debris and Sediment Accumulated sediment depth exceeds 10% of the diameter of the storage area for 1/2 All sediment and debris removed from length of storage vault or any point depth storage area. exceeds 15% of diameter. (Example: 72-inch storage tank would require cleaning when sediment reaches depth of 7 inches for more than 1/2 length of tank.) Joints Between Any openings or voids allowing material to All joint between Tank/Pipe Section be transported into facility. tank/pipe sections (Will require engineering analysis to are sealed. determine structural stability). Tank Pipe Bent Out Any part of tank/pipe is bent out of shape Tank/pipe repaired or of Shape more than 10% of its design shape. (Review replaced to design. required by engineer to determine structural stability). Vault Structure Cracks wider than 1/2-inch and any Vault replaced or Includes Cracks in evidence of soil particles entering the repaired to design Wall, Bottom, structure through the cracks, or specifications and is Damage to Frame maintenance/inspection personnel structurally sound. and/or Top Slab determines that the vault is not structurally sound. Cracks wider than 1/2-inch at the joint of any No cracks more than inlet/outlet pipe or any evidence of soil 1/4-inch wide at the particles entering the vault through the walls. joint of the inlet/outlet pipe. Manhole Cover Not in Place Cover is missing or only partially in place. Manhole is closed. Any open manhole requires maintenance. Locking Mechanism Mechanism cannot be opened by one Mechanism opens Not Working maintenance person with proper tools. Bolts with proper tools. into frame have less than 1/2 inch of thread (may not apply to self-locking lids). Cover Difficult to One maintenance person cannot remove lid Cover can be Remove after applying normal lifting pressure. Intent removed and is to keep cover from sealing off access to reinstalled by one maintenance. maintenance person. Ladder Rungs Unsafe Ladder is unsafe due to missing rungs, Ladder meets design misalignment, not securely attached to standards. Allows structure wall, rust, or cracks. maintenance person safe access. Catch Basins See "Catch Basins" See "Catch Basins" (No. 5). See "Catch Basins" (No. 5) (No. 5). Volume V — Runoff Treatment BMPs — December 2014 4-36 No. 4 - Control Structure/Flow Restrictor Maintenance Defect Condition When Maintenance is Needed Results Expected Component When Maintenance is Performed General Trash and Debris Material exceeds 25% of sump depth or 1 Control structure (Includes Sediment) foot below orifice plate. orifice is not blocked. All trash and debris removed. Structural Damage Structure is not securely attached to Structure securely manhole wall. attached to wall and outlet pipe. Structure is not in upright position (allow up Structure in correct to 10% from plumb). position. Connections to outlet pipe are not watertight Connections to outlet and show signs of rust. pipe are water tight; structure repaired or replaced and works as designed. Any holes --other than designed holes --in the Structure has no structure. holes other than designed holes. Cleanout Gate Damaged or Missing Cleanout gate is not watertight or is missing. Gate is watertight and works as designed. Gate cannot be moved up and down by one Gate moves up and maintenance person. down easily and is watertight. Chain/rod leading to gate is missing or Chain is in place and damaged. works as designed. Gate is rusted over 50% of its surface area. Gate is repaired or replaced to meet design standards. Orifice Plate Damaged or Missing Control device is not working properly due to Plate is in place and missing, out of place, or bent orifice plate. works as designed. Obstructions Any trash, debris, sediment, or vegetation Plate is free of all blocking the plate. obstructions and works as designed. Overflow Pipe Obstructions Any trash or debris blocking (or having the Pipe is free of all potential of blocking) the overflow pipe. obstructions and works as designed. Manhole See "Closed See "Closed Detention Systems" (No. 3). See "Closed Detention Systems" Detention Systems" (No. 3). (No. 3). Catch Basin See "Catch Basins" See "Catch Basins" (No. 5). See "Catch Basins" (No. 5). (No. 5). Volume V — Runoff Treatment BMPs — December 2014 4-37 No. 5 — Catch Basins Maintenance Defect Conditions When Maintenance is Needed Results Expected When Component Maintenance is performed General Trash & Trash or debris which is located immediately No Trash or debris located Debris in front of the catch basin opening or is immediately in front of blocking inletting capacity of the basin by catch basin or on grate more than 10%. opening. Trash or debris (in the basin) that exceeds 60 No trash or debris in the percent of the sump depth as measured from catch basin. the bottom of basin to invert of the lowest pipe into or out of the basin, but in no case less than a minimum of six inches clearance from the debris surface to the invert of the lowest pipe. Trash or debris in any inlet or outlet pipe Inlet and outlet pipes free blocking more than 1 /3 of its height. of trash or debris. Dead animals or vegetation that could No dead animals or generate odors that could cause complaints vegetation present within or dangerous gases (e.g., methane). the catch basin. Sediment Sediment (in the basin) that exceeds 60 No sediment in the catch percent of the sump depth as measured from basin the bottom of basin to invert of the lowest pipe into or out of the basin, but in no case less than a minimum of 6 inches clearance from the sediment surface to the invert of the lowest pipe. Structure Top slab has holes larger than 2 square Top slab is free of holes Damage to inches or cracks wider than 1/4 inch and cracks. Frame and/or Top Slab (Intent is to make sure no material is running into basin). Frame not sitting flush on top slab, i.e., Frame is sitting flush on separation of more than 3/4 inch of the frame the riser rings or top slab from the top slab. Frame not securely and firmly attached. attached Fractures or Maintenance person judges that structure is Basin replaced or repaired Cracks in unsound. to design standards. Basin Walls/ Bottom Grout fillet has separated or cracked wider Pipe is regrouted and than 1/2 inch and longer than 1 foot at the secure at basin wall. joint of any inlet/outlet pipe or any evidence of soil particles entering catch basin through cracks. Settlement/ If failure of basin has created a safety, Basin replaced or repaired Misalignment function, or design problem. to design standards. Vegetation Vegetation growing across and blocking more No vegetation blocking than 10% of the basin opening. opening to basin. Vegetation growing in inlet/outlet pipe joints No vegetation or root that is more than six inches tall and less than growth present. six inches apart. Contamination See "Detention Ponds" (No. 1). No pollution present. and Pollution Volume V — Runoff Treatment BMPs — December 2014 4-38 No. 5 — Catch Basins Maintenance Defect Conditions When Maintenance is Needed Results Expected When Component Maintenance is performed Catch Basin Cover Not in Cover is missing or only partially in place. Catch basin cover is Cover Place Any open catch basin requires maintenance. closed Locking Mechanism cannot be opened by one Mechanism opens with Mechanism maintenance person with proper tools. Bolts proper tools. Not Working into frame have less than 1/2 inch of thread. Cover Difficult One maintenance person cannot remove lid Cover can be removed by to Remove after applying normal lifting pressure. one maintenance person. (Intent is keep cover from sealing off access to maintenance.) Ladder Ladder Rungs Ladder is unsafe due to missing rungs, not Ladder meets design Unsafe securely attached to basin wall, standards and allows misalignment, rust, cracks, or sharp edges. maintenance person safe access. Metal Grates Grate opening Grate with opening wider than 7/8 inch. Grate opening meets (If Applicable) Unsafe design standards. Trash and Trash and debris that is blocking more than Grate free of trash and Debris 20% of grate surface inletting capacity. debris. Damaged or Grate missing or broken member(s) of the Grate is in place and Missing. I grate. meets design standards. No. 6 — Debris Barriers (e.g., Trash Racks) Maintenance Defect Condition When Maintenance is Results Expected When Components Needed Maintenance is Performed General Trash and Trash or debris that is plugging more Barrier cleared to design flow Debris than 20% of the openings in the barrier. capacity. Metal Damaged/ Bars are bent out of shape more than 3 Bars in place with no bends more Missing inches. than 3/4 inch. Bars. Bars are missing or entire barrier Bars in place according to design. missing. Bars are loose and rust is causing 50% Barrier replaced or repaired to deterioration to any part of barrier. design standards. Inlet/Outlet Debris barrier missing or not attached to Barrier firmly attached to pipe Pipe pipe Volume V Runoff Treatment BMPs December 2014 4-39 No. 18 — Catchbasin Inserts Maintenance Defect Conditions When Maintenance is Results Expected When Component Needed Maintenance is Performed General Sediment When sediment forms a cap over the No sediment cap on the insert Accumulation insert media of the insert and/or unit. media and its unit. Trash and Trash and debris accumulates on insert Trash and debris removed Debris unit creating a blockage/restriction. from insert unit. Runoff freely Accumulation flows into catch basin. Media Insert Not Effluent water from media insert has a Effluent water from media Removing Oil visible sheen. insert is free of oils and has no visible sheen. Media Insert Catch basin insert is saturated with water Remove and replace media Water Saturated and no longer has the capacity to insert absorb. Media Insert -Oil Media oil saturated due to petroleum spill Remove and replace media Saturated that drains into catch basin. insert. Media Insert Use Media has been used beyond the typical Remove and replace media at Beyond Normal average life of media insert product. regular intervals, depending on Product Life insert product. Volume V — Runoff Treatment BMPs — December 2014 4-51 e y� �r ,L �,� - sr�: - ``J r =- r'S - n y Y r �� <� Maintenance Guidelines The primary purpose of the Stormwater Management StormFilter® is to filter and prevent pollutants from entering our waterways. Like any effective filtration system, periodically these pollutants must be removed to restore the StormFilter to its full efficiency and effectiveness. Maintenance requirements and frequency are dependent on the pollutant load characteristics of each site. Maintenance activities may be required in the event of a chemical spill or due to excessive sediment loading from site erosion or extreme storms. It is a good practice to inspect the system after major storm events. Maintenance Procedures Although there are many effective maintenance options, we believe the following procedure to be efficient, using common equipment and existing maintenance protocols. The following two-step procedure is recommended:: 1. Inspection Inspection of the vault interior to determine the need for maintenance. 2. Maintenance • Cartridge replacement • Sediment removal Inspection and Maintenance Timing At least one scheduled inspection should take place per year with maintenance following as warranted. First, an inspection should be done before the winter season. During the inspection the need for maintenance should be determined and, if disposal during maintenance will be required, samples of the accumulated sediments and media should be obtained. Second, if warranted, a maintenance (replacement of the filter cartridges and removal of accumulated sediments) should be performed during periods of dry weather. In addition to these two activities, it is important to check the condition of the StormFilter unit after major storms for potential damage caused by high flows and for high sediment accumulation that may be caused by localized erosion in the drainage area. It may be necessary to adjust the inspection/ maintenance schedule depending on the actual operating conditions encountered by the system. In general, inspection activities can be conducted at any time, and maintenance should occur, if warranted, during dryer months in late summer to early fall. Maintenance Frequency The primary factor for determining frequency of maintenance for the StormFilter is sediment loading. A properly functioning system will remove solids from water by trapping particulates in the porous structure of the filter media inside the cartridges. The flow through the system will naturally decrease as more and more particulates are trapped. Eventually the flow through the cartridges will be low enough to require replacement. It may be possible to extend the usable span of the cartridges by removing sediment from upstream trapping devices on a routine as -needed basis, in order to prevent material from being re -suspended and discharged to the StormFilter treatment system. The average maintenance lifecycle is approximately 1-5 years. Site conditions greatly influence maintenance requirements. StormFilter units located in areas with erosion or active construction may need to be inspected and maintained more often than those with fully stabilized surface conditions. Regulatory requirements or a chemical spill can shift maintenance timing as well. The maintenance frequency may be adjusted as additional monitoring information becomes available during the inspection program. Areas that develop known problems should be inspected more frequently than areas that demonstrate no problems, particularly after major storms. Ultimately, inspection and maintenance activities should be scheduled based on the historic records and characteristics of an individual StormFilter system or site. It is recommended that the site owner develop a database to properly manage StormFilter inspection and maintenance programs.. Inspection Procedures The primary goal of an inspection is to assess the condition of the cartridges relative to the level of visual sediment loading as it relates to decreased treatment capacity. It may be desirable to conduct this inspection during a storm to observe the relative flow through the filter cartridges. If the submerged cartridges are severely plugged, then typically large amounts of sediments will be present and very little flow will be discharged from the drainage pipes. If this is the case, then maintenance is warranted and the cartridges need to be replaced. Warning: In the case of a spill, the worker should abort inspection activities until the proper guidance is obtained. Notify the local hazard control agency and Contech Engineered Solutions immediately. To conduct an inspection: Maintenance Decision Tree The need for maintenance is typically based on results of the inspection. The following Maintenance Decision Tree should be used as a general guide. (Other factors, such as Regulatory Requirements, may need to be considered). Please note Stormwater Management StormFilter devices installed downstream of, or integrated within, a stormwater storage facility typically have different operational parameters (i.e. draindown time). In these cases, the inspector must understand the relationship between the retention/detention facility and the treatment system by evaluating site specific civil engineering plans, or contacting the engineer of record, and make adjustments to the below guidance as necessary. Sediment deposition depths and patterns within the StormFilter are likely to be quite different compared to systems without upstream storage and therefore shouldn't be used exclusively to evaluate a need for maintenance. Sediment loading on the vault floor. a. If >4" of accumulated sediment, maintenance is required. 2. Sediment loading on top of the cartridge. a. If >1/4" of accumulation, maintenance is required. 3. Submerged cartridges. a. If >4" of static water above cartridge bottom for more than 24 hours after end of rain event, maintenance is required. (Catch basins have standing water in the cartridge bay.) 4. Plugged media. a. While not required in all cases, inspection of the media within the cartridge may provide valuable additional information. Important: Inspection should be performed by a person who is b. If pore space between media granules is absent, familiar with the operation and configuration of the StormFilter maintenance is required. treatment unit and the unit's role, relative to detention or 5. Bypass condition. retention facilities onsite. a. If inspection is conducted during an average rain fall 1. If applicable, set up safety equipment to protect and notify event and StormFilter remains in bypass condition surrounding vehicle and pedestrian traffic. (water over the internal outlet baffle wall or submerged 2. Visually inspect the external condition of the unit and take notes cartridges), maintenance is required. concerning defects/problems. 6. Hazardous material release. 3. Open the access portals to the vault and allow the system vent. 4. Without entering the vault, visually inspect the inside of the unit, and note accumulations of liquids and solids. 5. Be sure to record the level of sediment build-up on the floor of the vault, in the forebay, and on top of the cartridges. If flow is occurring, note the flow of water per drainage pipe. Record all observations. Digital pictures are valuable for historical documentation. 6. Close and fasten the access portals. 7. Remove safety equipment. 8. If appropriate, make notes about the local drainage area relative to ongoing construction, erosion problems, or high loading of other materials to the system. 9. Discuss conditions that suggest maintenance and make decision as to whether or not maintenance is needed. a. If hazardous material release (automotive fluids or other) is reported, maintenance is required. 7. Pronounced scum line. a. If pronounced scum line (say >_ 1/4" thick) is present above top cap, maintenance is required. 3 Maintenance Depending on the configuration of the particular system, maintenance personnel will be required to enter the vault to perform the maintenance. Important: If vault entry is required, OSHA rules for confined space entry must be followed. Filter cartridge replacement should occur during dry weather. It may be necessary to plug the filter inlet pipe if base flows is occurring. Replacement cartridges can be delivered to the site or customers facility. Information concerning how to obtain the replacement cartridges is available from Contech Engineered Solutions. Warning: In the case of a spill, the maintenance personnel should abort maintenance activities until the proper guidance is obtained. Notify the local hazard control agency and Contech Engineered Solutions immediately. To conduct cartridge replacement and sediment removal maintenance: 1. If applicable, set up safety equipment to protect maintenance personnel and pedestrians from site hazards. 2. Visually inspect the external condition of the unit and take notes concerning defects/problems. 3. Open the doors (access portals) to the vault and allow the system to vent. 4. Without entering the vault, give the inside of the unit, including components, a general condition inspection. 5. Make notes about the external and internal condition of the vault. Give particular attention to recording the level of sediment build-up on the floor of the vault, in the forebay, and on top of the internal components. 6. Using appropriate equipment offload the replacement cartridges (up to 150 lbs. each) and set aside. 7. Remove used cartridges from the vault using one of the following methods: Method 1: A. This activity will require that maintenance personnel enter the vault to remove the cartridges from the under drain manifold and place them under the vault opening for lifting (removal). Disconnect each filter cartridge from the underdrain connector by rotating counterclockwise 1/4 of a turn. Roll the loose cartridge, on edge, to a convenient spot beneath the vault access. Using appropriate hoisting equipment, attach a cable from the boom, crane, or tripod to the loose cartridge. Contact Contech Engineered Solutions for suggested attachment devices. B. Remove the used cartridges (up to 250 lbs. each) from the vault. Important: Care must be used to avoid damaging the cartridges during removal and installation. The cost of repairing components damaged during maintenance will be the responsibility of the owner. C. Set the used cartridge aside or load onto the hauling truck. D. Continue steps a through c until all cartridges have been removed. Method 2: A. This activity will require that maintenance personnel enter the vault to remove the cartridges from the under drain manifold and place them under the vault opening for lifting (removal). Disconnect each filter cartridge from the underdrain connector by rotating counterclockwise 1/4 of a turn. Roll the loose cartridge, on edge, to a convenient spot beneath the vault access. B. Unscrew the cartridge cap. C. Remove the cartridge hood and float. D. At location under structure access, tip the cartridge on its side. E. Empty the cartridge onto the vault floor. Reassemble the empty cartridge. F. Set the empty, used cartridge aside or load onto the hauling truck. G. Continue steps a through e until all cartridges have been removed. 4 8. Remove accumulated sediment from the floor of the vault and from the forebay. This can most effectively be accomplished by use of a vacuum truck. 9. Once the sediments are removed, assess the condition of the vault and the condition of the connectors. 10. Using the vacuum truck boom, crane, or tripod, lower and install the new cartridges. Once again, take care not to damage connections. 11.Close and fasten the door. 12. Remove safety equipment. 13. Finally, dispose of the accumulated materials in accordance with applicable regulations. Make arrangements to return the used empty cartridges to Contech Engineered Solutions. Related Maintenance Activities - Performed on an as -needed basis StormFilter units are often just one of many structures in a more comprehensive stormwater drainage and treatment system. In order for maintenance of the StormFilter to be successful, it is imperative that all other components be properly maintained. The maintenance/repair of upstream facilities should be carried out prior to StormFilter maintenance activities. In addition to considering upstream facilities, it is also important to correct any problems identified in the drainage area. Drainage area concerns may include: erosion problems, heavy oil loading, and discharges of inappropriate materials. Material Disposal The accumulated sediment found in stormwater treatment and conveyance systems must be handled and disposed of in accordance with regulatory protocols. It is possible for sediments to contain measurable concentrations of heavy metals and organic chemicals (such as pesticides and petroleum products). Areas with the greatest potential for high pollutant loading include industrial areas and heavily traveled roads. Sediments and water must be disposed of in accordance with all applicable waste disposal regulations. When scheduling maintenance, consideration must be made for the disposal of solid and liquid wastes. This typically requires coordination with a local landfill for solid waste disposal. For liquid waste disposal a number of options are available including a municipal vacuum truck decant facility, local waste water treatment plant or on -site treatment and discharge. Date: Personnel: Location: System Size: Months in Service: System Type: Vault ❑ Cast -In -Place ❑ Linear Catch Basin ❑ Manhole ❑ Other: Sediment Thickness in Forebay: Date: Sediment Depth on Vault Floor: Sediment Depth on Cartridge Top(s): Structural Damaae: Estimated Flow from Drainage Pipes (if available): Cartridges Submerged: Yes ❑ No ❑ Depth of Standing Water: StormFilter Maintenance Activities (check off if done and give description) ❑ Trash and Debris Removal: n Minor Structural ReDairs: n Drainage Area Report Excessive Oil Loading: Yes ❑ No ❑ Source: Sediment Accumulation on Pavement: Yes ❑ No ❑ Source: Erosion of Landscaped Areas: Yes ❑ No ❑ Source: Items Needina Further Work: Owners should contact the local public works department and inquire about how the department disposes of their street waste residuals. Other Comments: Review the condition reports from the previous inspection visits. Date: Location: —Personnel: _System Size: _ System Type: Vault ❑ Cast -In -Place ❑ List Safety Procedures and Equipment Used: System Observations Months in Service: Oil in Forebay (if present): Sediment Depth in Forebay (if present): Sediment Depth on Vault Floor: Sediment Depth on Cartridge Top(s): — Structural Damage: Linear Catch Basin ❑ Manhole ❑ Other: Yes ❑ No ❑ Drainage Area Report Excessive Oil Loading: Yes ❑ No ❑ Source: Sediment Accumulation on Pavement: Yes ❑ No ❑ Source: Erosion of Landscaped Areas: Yes ❑ No ❑ Source: StormFilter Cartridge Replacement Maintenance Activities Remove Trash and Debris: Yes ❑ No ❑ Details: Replace Cartridges: Yes ❑ No ❑ Details: Sediment Removed: Yes ❑ No ❑ Details: Quantity of Sediment Removed (estimate?): Minor Structural Repairs: Yes ❑ No ❑ Details: Residuals (debris, sediment) Disposal Methods N otes: C O NTECH® ENGINEERED SOLUTIONS © 2020 CONTECH ENGINEERED SOLUTIONS LLC, A QUIKRETE COMPANY 800-338-1122 www.ContechES.com All Rights Reserved. Printed in the USA. Contech Engineered Solutions LLC provides site solutions for the civil engineering industry. Contech's portfolio includes bridges, drainage, sanitary sewer, stormwater and earth stabilization products. For information on other Contech division offerings, visit www.ContechES.com or call 800.338.1122. Support • Drawings and specifications are available at www.conteches.com. • Site -specific design support is available from our engineers. NOTHING IN THIS CATALOG SHOULD BE CONSTRUED AS A WARRANTY APPLICATIONS SUGGESTED HEREIN ARE DESCRIBED ONLY TO HELP READERS MAKE THEIR OWN EVALUATIONS AND DECISIONS, AND ARE NEITHER GUARANTEES NOR WARRANTIES OF SUITABILITY FOR ANY APPLICATION. CONTECH MAKES NO WARRANTY WHATSOEVER, EXPRESS OR IMPLIED, RELATED TO THE APPLICATIONS, MATERIALS, COATINGS, OR PRODUCTS DISCUSSED HEREIN. ALL IMPLIED WARRANTIES OF MERCHANTABILITY AND ALL IMPLIED WARRANTIES OF FITNESS FOR ANY PARTICULAR PURPOSE ARE DISCLAIMED BY CONTECH. SEE CONTECH'S CONDITIONS OF SALE (AVAILABLE AT WWW.CONTECHES.COM/COS) FOR MORE INFORMATION. StormFilter Inspection and Maintenance Procedures 4/20 800.338.1122 www.conteches.com E. GEOTECHNICAL REPORT Insight Engineering Co. - Stormwater Site Plan 12/08/2020 -35- Earth Solution NV LLC Geotechnical Engineerii Geolol Environmental Servic Construction Observation/Testis UCU 1 r_Wl l%.#lAL r-NUINCEMINU J 1 UU T PROPOSED SINGLE-FAMILY RESIDENCES 22810 EDMONDS WAY EDMONDS, WASHINGTON ES-5932 PREPARED FOR KISAN ENTERPRISES, LLC May 29, 2018 Samuel E. Suruda, G.I.T. Staff Geologist PZ,R.CA4 �V oV'IIK00�4 Is rz� �' (� Kyle R. Campbell, P.E. Principal Engineer GEOTECHNICAL ENGINEERING STUDY PROPOSED SINGLE-FAMILY RESIDENCES 22810 EDMONDS WAY EDMONDS, WASHINGTON ES-5932 Earth Solutions NW, LLC 1805 —136t" Place Northeast, Suite 201 Bellevue, Washington 98005 Phone: 425-449-4704 1 Fax: 425-449-4711 www.earthsolutionsnw.com 59 r Geotechnical Engineering Report � Geotechnical Services Are Performed for Specific Purposes. Persons, and Projects Geotechnical engineers structure their services to meet the specific needs of their clients. A geotechnical engineering study conducted for a civil engi- neer may not fulfill the needs of a construction contractor or even another civil engineer. Because each geotechnical engineering study is unique, each geotechnical engineering report is unique, prepared solelyfor the client. No one except you should rely on your geotechnical engineering report without first conferring with the geotechnical engineer who prepared it. And no one — not even you —should apply the report for any purpose or project except the one originally contemplated. Read the Full Report Serious problems have occurred because those relying on a geotechnical engineering report did not read it all. Do not rely on an executive summary Do not read selected elements only. A Geotechnical Engineering Report Is Based on A Unique Set of Project Specific Factors Geotechnical engineers consider a number of unique, project -specific fac- tors when establishing the scope of a study. Typical factors include: the client's goals, objectives, and risk management preferences; the general nature of the structure involved, its size, and configuration; the location of the structure on the site; and other planned or existing site improvements, such as access roads, parking lots, and underground utilities. Unless the geotechnical engineer who conducted the study specifically indicates oth- erwise, do not rely on a geotechnical engineering report that was: • not prepared for you, • not prepared for your project, ■ not prepared for the specific site explored, or • completed before important project changes were made. Typical changes that can erode the reliability of an existing geotechnical engineering report include those that affect: • the function of the proposed structure, as when it's changed from a parking garage to an office building, or from a light industrial plant to a refrigerated warehouse, • elevation, configuration, location, orientation, or weight of the proposed structure, • composition of the design team, or • project ownership. As a general rule, always inform your geotechnical engineer of project changes ---even minor ones —and request an assessment of their impact. Geotechnical engineers cannot accept responsibility or liability for problems that occur because their reports do not consider developments of which they were not informed. Subsurface Conditions Can Change A geotechnical engineering report is based on conditions that existed at the time the study was performed. Do not rely on a geotechnical engineer- ing report whose adequacy may have been affected by: the passage of time; by man-made events, such as construction on or adjacent to the site; or by natural events, such as floods, earthquakes, or groundwater fluctua- tions. Always contact the geotechnical engineer before applying the report to determine if it is still reliable. A minor amount of additional testing or analysis could prevent major problems. Most Geotechnical Findings Are Professional opinlons Site exploration identifies subsurface conditions only at those points where subsurface tests are conducted or samples are taken. Geotechnical engi- neers review field and laboratory data and then apply their professional judgment to render an opinion about subsurface conditions throughout the site. Actual subsurface conditions may differ —sometimes significantly — from those indicated in your report. Retaining the geotechnical engineer who developed your report to provide construction observation is the most effective method of managing the risks associated with unanticipated conditions. A Report's Recommendations Are WHO Do not overrely on the construction recommendations included in your report. Those recommendations are not final, because geotechnical engi- neers develop them principally from judgment and opinion. Geotechnical engineers can finalize their recommendations only by observing actual 60 subsurface conditions revealed during construction. The geotechnical engineer who developed your report cannot assume responsibility or liability for the report's recommendations if that engineer does not perform construction observation. A Geotechnical Engineering Report Is Subject to Misinterpretation Other design team members' misinterpretation of geotechnical engineering reports has resulted in costly problems. Lower that risk by having your geo- technical engineer confer with appropriate members of the design team after submitting the report. Also retain your geotechnical engineer to review perti- nent elements of the design team's plans and specifications. Contractors can also misinterpret a geotechnical engineering report. Reduce that risk by having your geotechnical engineer participate in prebid and preconstruction conferences, and by providing construction observation. Do Not Redraw the Engineer's Logs Geotechnical engineers prepare final boring and testing logs based upon their interpretation of field logs and laboratory data. To prevent errors or omissions, the logs included in a geotechnical engineering report should neverbe redrawn for inclusion in architectural or other design drawings. Only photographic or electronic reproduction is acceptable, but recognize that separating logs from the report can elevate risk. Give Contractors a Complete Report and Guidance Some owners and design professionals mistakenly believe they can make contractors liable for unanticipated subsurface conditions by limiting what they provide for bid preparation. To help prevent costly problems, give con- tractors the complete geotechnical engineering report, butpreface it with a clearly written letter of transmittal. In that letter, advise contractors that the report was not prepared for purposes of bid development and that the report's accuracy is limited; encourage them to confer with the geotechnical engineer who prepared the report (a modest fee may be required) and/or to conduct additional study to obtain the specific types of information they need or prefer. A prebid conference can also be valuable. Be sure contrac- tors have sufficient time to perform additional study. Only then might you be in a position to give contractors the best information available to you, while requiring them to at least share some of the financial responsibilities stemming from unanticipated conditions. Read Responsibility Provisions Closely Some clients, design professionals, and contractors do not recognize that geotechnical engineering is far less exact than other engineering disci- plines, This lack of understanding has created unrealistic expectations that have led to disappointments, claims, and disputes; To help reduce the risk of such outcomes, geotechnical engineers commonly include a variety of explanatory provisions in their reports. Sometimes labeled "limitations" many of these provisions indicate where geotechnical engineers' responsi- bilities begin and end, to help others recognize their own responsibilities and risks. Read these provisions closely. Ask questions. Your geotechnical engineer should respond fully and frankly. Geoenvironmental Concerns Are Not Covered The equipment, techniques, and personnel used to perform a geoenviron- mental study differ significantly from those used to perform a geotechnical study. For that reason, a geotechnical engineering report does not usually relate any geoenvironmental findings, conclusions, or recommendations; e.g., about the likelihood of encountering underground storage tanks or regulated contaminants. Unanticipated environmental problems have led to numerous project failures. If you have not yet obtained your own geoen- vironmental information, ask your geotechnical consultant for risk man- agement guidance. Do not rely on an environmental report prepared for someone else. Obtain Professional Assistance To Deal with Mold Diverse strategies can be applied during building design, construction, operation, and maintenance to prevent significant amounts of mold from growing on indoor surfaces. To be effective, all such strategies should be devised for the express purpose of mold prevention, integrated into a com- prehensive plan, and executed with diligent oversight by a professional mold prevention consultant. Because just a small amount of water or moisture can lead to the development of severe mold infestations, a num- ber of mold prevention strategies focus on keeping building surfaces dry. While groundwater, water infiltration, and similar issues may have been addressed as part of the geotechnical engineering study whose findings are conveyed in -this report, the geotechnical engineer in charge of this project is not a mold prevention consultant; none of the services per- formed in connection with the geotechnical engineer's study were designed or conducted for the purpose of mold preven- tion. Proper implementation of the recommendations conveyed in this report will not of itself he sufficient to prevent mold from growing in or on the structure involved. Rely, on Your ASFE-Member Geotechncial Engineer for Additional Assistance Membership in ASFE/The Best People on Earth exposes geotechnical engineers to a wide array of risk management techniques that can be of genuine benefit for everyone involved with a construction project. Confer with you ASFE-member geotechnical engineer for more information. ASFE The Best People an Earth 8811 ColesviIle Road/Suite G106, Silver Spring, MD 20910 Telephone:301/565-2733 Facsimile:301/589-2017 e-mail: info@asfe.org www.asfe.org Copyright 2004 by ASFE, Inc. Duplication, reproduction, or copying of this document, in whole or in part, by any means whatsoever, is strictly prohibited, except with ASFE's specific written permission. Excerpting, quoting, or otherwise extracting wording from this document is permitted only with the express written permission of ASFE, and only for purposes of scholarly research or book review. Only members of ASFE may use this document as a complement to or as an element of a geotechnical engineering report. Any other firm, individual, or other entity that so uses this document without being an ASFE member could be committing negligent or intentional (fraudulent) misrepresentation. IGER06045.01M 61 May 29, 2018 ES-5932 Kisan Enterprises, LLC 20607 State Route 9 Snohomish, Washington 98296 Attention: Ms. Yvette Johnson Dear Ms. Johnson: Earth I Solutions NW«< Earth Solutions NW I_I_c Geotechnical Engineering, Construction Observation/Testing and Environmental Services Earth Solutions NW, LLC (ESNW) is pleased to present this report titled "Geotechnical Engineering Study, Proposed Single -Family Residences, 22810 Edmonds Way, Edmonds, Washington". Based on the results of our study, construction of the proposed single-family residences at the subject site is feasible from a geotechnical standpoint. The proposed residential structures can be supported on a conventional foundation system bearing on competent native soil, recompacted native soil, or structural fill. Competent native soils, suitable for support of foundations, should be encountered beginning at a depth of roughly two feet below existing grades across the majority of the site. Slab -on -grade floors should be supported on dense native soil, re -compacted native soil, or structural fill. Where loose, organic or other unsuitable materials are encountered at or below the footing subgrade elevation, the material should be removed and replaced with structural fill, as necessary. This report includes recommendations for foundation subgrade preparation, foundation and retaining wall design parameters, drainage, the suitability of on -site soils for use as structural fill, and other pertinent geotechnical recommendations. The opportunity to be of service to you is appreciated. If you have any questions regarding the content of this geotechnical engineering study, please call. Sincerely, EARTH SOLUTIONS NW, LLC ia ;m;uZe �I E. Suruda, G.I.T. Staff Geologist 1805 - 136th Place N.E., Suite 201 • Bellevue, WA 98005 • (425) 449-4704 • FAX (425) 449-4711 62 Table of Contents ES-5932 PAGE INTRODUCTION...........................................................:......I.... General......................................................................... . Proiect Description. .... __ ................. mm ........................... m. SITE CONDITIONS............................................................... _... 2 Surface.............................................. _...................... ....... 2 Subsurface....................................................................... 2 Geologic Setting ............... ............. .......................... 2 Groundwater.......................................................... 3 Geol❑ ical Hazards Assessment ....................................... 3 DISCUSSION AND RECOMMENDATIONS ..................................... 3 General.......................................................................... 3 Site Preparation and Earthwork ......................................... 3 Temporary Erosion Control ............................................. 4 In -Situ Soils....................................................................... 4 StructuralFill...................................................................... 4 Excavations and Slopes............ ................................ 4 Foundations.................................................................... 5 Seismic Considerations........................................................ 5 Slab -on -Grade Floors ...................................................... 5 RetainingWails............................................................... 6 Drainage.................................................................. 6 Infiltration Evaluation.........,,.,...,,,.., . ........................ 7 Low Impact Development...... ................................... 7 Stormwater Vault Design ......................................... 8 Utilitv Trench Support and Backfill..................................... 9 Pavement Sections.......................................................... 9 LIMITATIONS........................................................................... . 10 Additional Services.......................................................... 10 Earth Solutions NW, LLC 63 GRAPHICS Plate 1 Plate 2 Plate 3 Plate 4 APPENDICES Appendix A Appendix B Table of Contents Cont'd ES-5932 Vicinity Map Test Pit Location Plan Retaining Wall Drainage Detail Footing Drain Detail Subsurface Exploration Test Pit Logs Laboratory Test Results Earth Solutions NW, LLC 64 GEOTECHNICAL ENGINEERING STUDY PROPOSED SINGLE-FAMILY RESIDENCES 22810 EDMONDS WAY EDMONDS, WASHINGTON ES-5932 INTRODUCTION General This geotechnical engineering study was prepared for the proposed single-family residential structures to be constructed at 22810 Edmonds Way, in Edmonds, Washington. To complete the scope of services detailed in our proposal, we performed the following: • Subsurface exploration and characterization of soil and groundwater conditions by way of test pits excavated at accessible areas of the site; • Laboratory testing of soil samples obtained during subsurface exploration; • An infiltration evaluation based on observed soil conditions and two small-scale Pilot Infiltration Tests (PITs); • Geotechnical engineering analyses, and; • Preparation of this report. The following documents and resources were reviewed as part of our report preparation: • Geologic Map of the Edmonds East and Part of the Edmonds West Quadrangles, Washington, prepared by James P. Minard, dated 1983; • Department of Ecology 2012 Stormwater Management Manual for Western Washington, Volume III Hydrologic Analysis and Flow Control BMPs, dated August 2014; • Edmonds City Code, Chapter 23.80 (Geologically Hazardous Areas), and; ■ Online Web Soil Survey (WSS) resource provided by United States Department of Agriculture (USDA), Natural Resources Conservation Services. Project Description Based on our review of the preliminary site plan, the existing single-family residence will be demolished, and 20 new single-family residential structures will be constructed. We anticipate grade cuts of up to four feet will be necessary to establish the planned building alignments and roadway improvements. Site improvements will also include underground utility installations. Earth Solutions NW, LLC 65 Kisan Enterprises, LLC ES-5932 May 29, 2018 Page 2 At the time this report was prepared, specific building load values were not available. However, we anticipate the proposed residential structures will consist of relatively lightly loaded wood framing supported on conventional foundations. Based on our experience with similar developments, we estimate wall loads of approximately one to two kips per linear foot and slab - on -grade loading of roughly 150 pounds per square foot (psf) will be incorporated into the construction. If the above design assumptions are incorrect or change, ESNW should be contacted to review the recommendations provided in this report. ESNW should review the final design to verify the geotechnical recommendations provided in this report have been incorporated into the plans. SITE CONDITIONS Surface The subject site is located at 22810 Edmonds Way, in Edmonds, Washington, as illustrated on the Vicinity Map (Plate 1). The site consists of one residential tax parcel (Snohomish County Parcel Number 270336-001-023-00) totaling approximately 0.71 acres of land area. The property is currently developed with a single-family residence and associated improvements. The majority of the site is relatively level, with a gently descending slope on the north side of the property adjacent to Edmonds Way. The subject site is bordered to the west, south, and east by residential developments, and to the north by Edmonds Way. The Test Pit Location Plan (Plate 2) illustrates the approximate limits of the property. Subsurface Five test pits were excavated in accessible portions of the site for purposes of assessing soil and groundwater conditions. The test pits were advanced to a maximum depth of approximately 10 feet below existing grade. Please refer to the test pit logs provided in Appendix A for a more detailed description of the subsurface conditions. Fill was encountered at TP-3 and TP-4 to depths of approximately two and one-half to three feet. The fill was characterized as loose, well -graded sand with silt (Unified Soil Classification System: SW). Seepage was observed within the fill layers and was present until the contact with the native soil. Underlying the fill, soil conditions observed at test pit locations consisted of medium dense well - graded sand (USCS: SW), medium dense poorly graded sand (USCS: SP), and silty sand with gravel (USCS: SM). Overall soil relative density increased with depth. Geologic Setting According to the referenced geologic map resource, the subject site is underlain by advance outwash (Qva) and glacial till (Qvt) deposits. According to the referenced NRCS soil survey, the subject site consists of Everett series soils (Map Unit: 17). Everett series soils were formed in glacial moraines and are classified as outwash deposits. Outwash soils are consistent with observations made in the field. Earth Solutions NW. LLC 66 Kisan Enterprises, LLC May 29, 2018 Groundwater ES-5932 Page 3 Groundwater seepage was observed at TP-3 and TP-4 beginning at depths of one to two feet during our fieldwork on March 30, 2018. Groundwater seepage rates and elevations fluctuate depending on many factors, including precipitation duration and intensity, the time of year, and soil conditions. In general, groundwater elevations and flow rates are higher during the winter, spring and early summer months. Geological Hazards Assessment. As part of this geotechnical engineering study, the referenced chapter of the Edmonds City Code (ECC) was reviewed. Per the ECC requirements, the site was reviewed for erosion, landslide, and seismic hazards. No such hazards were observed to be present on the site or within 200 feet of the site. DISCUSSION AND RECOMMENDATIONS General Based on the results of our study, construction of the proposed residential structures at the subject site is feasible from a geotechnical standpoint. The primary geotechnical considerations associated with the proposed development include foundation support, temporary excavations, retaining walls, infiltration and drainage, and the suitability of on -site soils for use as structural fill. The proposed residential structures can be supported on a conventional foundation system bearing on competent native soil, recompacted native soil, or structural fill. Competent soils suitable for support of foundations should be encountered beginning at a depth of roughly two feet below existing grades across the majority of the site. Slab -on -grade floors should be supported on dense native soil, re -compacted native soil, or structural fill. Where loose, organic or other unsuitable materials are encountered at or below the footing subgrade elevation, the material should be removed and replaced with structural fill, as necessary. This study has been prepared for the exclusive use of Kisan Enterprises, LLC and their representatives. No warranty, expressed or implied, is made. This study has been prepared in a manner consistent with the level of care and skill ordinarily exercised by other members of the profession currently practicing under similar conditions in this area. Site Preparation and Earthwork Based on the referenced site plans and given the existing topography, we anticipate grading for the project will involve cuts of up to about four feet to establish building pad and foundation subgrade alignments. Silt fencing and temporary erosion control measures should be placed along the perimeter of the site prior to beginning grading activities. Earth Solutions NW, LLC 67 Kisan Enterprises, LLC May 29, 2018 Temporary Erosion Control ES-5932 Page 4 Temporary construction entrances, consisting of at least six inches of quarry spalls, can be considered to minimize off -site soil tracking and to provide a temporary road surface. Silt fences should be placed along the margins of the property. Interceptor swales and a temporary sediment pond may be necessary for control of surface water during construction. Erosion control measures should conform to the Washington State Department of Ecology (DOE) and City of Edmonds standards. In -Situ Soils From a geotechnical standpoint, the soils encountered at the test pit locations are generally suitable for use as structural fill provided the moisture content of the soils is at or slightly above the optimum level at the time of placement and compaction. The site soils were generally in a moist condition at the time of the exploration on March 30, 2018. Based on the conditions encountered during our fieldwork, the sandy soils generally have a low sensitivity to moisture. Silty sands observed at TP-5 and underlying the sands at TP-3 and TP- 4 have a higher sensitivity to moisture. If the on -site soils cannot be successfully compacted, the use of an imported soil may be necessary. Imported soil intended for use as structural fill should consist of a well -graded granular soil with a moisture content that is at or near the optimum level. During wet weather conditions, imported soil intended for use as structural fill should consist of a well -graded, granular soil with a fines content of 5 percent or less (where the fines content is defined as the percent passing the Number 200 sieve, based on the minus three-quarter inch fraction). Structural Fill Structural fill is defined as compacted soil placed in foundation, slab -on -grade, and roadway areas. Fills placed to construct permanent slopes and throughout retaining wall and utility trench backfill areas are also considered structural fill. Soils placed in structural areas should be placed in loose lifts of 12 inches or less and compacted to a relative compaction of 95 percent, based on the laboratory maximum dry density as determined by the Modified Proctor Method (ASTM D- 1557). For soil placed in utility trenches underlying structural areas, compaction requirements are dictated by the local city, county, or utility district, and in general are specified as 95 percent relative compaction. Excavations and Slopes The native soils encountered at the test pit locations primarily consisted of outwash sands in a medium dense condition. Temporary slopes should maintain a gradient of no steeper than 1 Horizontal :1 Vertical (1 H:1 V). If groundwater is present within a cut, the temporary slope gradient should be no steeper than 1.5H:1V. The presence of perched groundwater may cause caving of the temporary slopes due to hydrostatic pressure. ESNW should observe site excavations to confirm the soil type and allowable slope inclination are appropriate for the soil exposed by the excavation. If the recommended temporary slope inclination cannot be achieved, temporary shoring may be necessary to support excavations. Earth Solutions NW, LLC 68 Kisan Enterprises, LLC ES-5932 May 29, 2018 Page 5 Permanent slopes should maintain a gradient of 2H:1V, or flatter, and should be planted with vegetation to enhance stability and to minimize erosion. A representative of ESNW should observe temporary and permanent slopes to confirm the slope inclinations are suitable for the exposed soil conditions and to provide additional excavation and slope recommendations, as necessary. Foundations The proposed residential structures can be supported on a conventional foundation system bearing on competent native soil, recompacted native soil, or structural fill. Competent soils suitable for support of foundations should be encountered beginning at a depth of roughly two feet bgs across the majority of the site. Where loose, organic or other unsuitable materials are encountered at or below the footing subgrade elevation, the material should be removed and replaced with structural fill, as necessary. Provided the structures will be supported as described above, the following parameters can be used for design of the new foundations: • Allowable soil bearing capacity 2,500 psf • Passive earth pressure Coefficient of friction 300 pcf (equivalent fluid) AM A one-third increase in the allowable soil bearing capacity can be assumed for short-term wind and seismic loading conditions. With structural loading as expected, total settlement in the range of one inch is anticipated, with differential settlement of about one-half inch. The majority of the settlements should occur during construction, as dead loads are applied. Seismic Considerations The 2015 International Building Code recognizes the American Society of Civil Engineers (ASCE) for seismic site class definitions. In accordance with Table 20.3-1 of the ASCE Minimum Design Loads for Buildings and Other Structures manual Site Class D should be used for design. In our opinion, site susceptibility to liquefaction is low. The soil relative density and the absence of a uniformly established, shallow groundwater table are the primary bases for this opinion. Slab -on -Grade Floors Slab -on -grade floors should be supported on firm and unyielding subgrades consisting of competent native soil or at least 12 inches of structural fill. Unstable or yielding areas of the subgrades should be recompacted or overexcavated and replaced with suitable structural fill prior to slab construction. A capillary break consisting of a minimum of four inches of free -draining crushed rock or gravel should be placed below the slab. The free -draining material should have a fines content of 5 percent or less defined as the percent passing the Number 200 sieve, based on the minus three-quarters inch fraction. In areas where slab moisture is undesirable, installation of a vapor barrier below the slab should be considered. If used, the vapor barrier should consist of a material specifically designed to function as a vapor barrier and should be installed in accordance with the specifications of the manufacturer. Earth Solutions NW, LLC 69 Kisan Enterprises, LLC May 29, 2018 Retaining Walls ES-5932 Page 6 Retaining walls must be designed to resist earth pressures and applicable surcharge loads. The following parameters may be used for retaining wall design: Active earth pressure (yielding condition) . At -rest earth pressure (restrained condition) e Traffic surcharge (passenger vehicles) . Passive earth pressure Coefficient of friction • Seismic surcharge Where applicable ** Where H equals the retained height (in feet) 35 pcf 55 pcf 70 psf (rectangular distribution) * 300 pcf 0.40 6H psf ** Where sloping or other surcharge conditions will be present, supplemental recommendations and design earth pressure values should be provided by ESNW. Drainage should be provided behind retaining walls such that hydrostatic pressures do not develop. If drainage is not provided, hydrostatic pressures should be included in the wall design. Retaining walls should be backfilled with free -draining material that extends along the height of the wall and a distance of at least 18 inches behind the wall. The upper one foot of the wall backfill may consist of a less permeable soil, if desired. A perforated drain pipe should be placed along the base of the wall and should be connected to an approved discharge location. A typical retaining wall drainage detail is provided on Plate 3. Drainage Groundwater seepage was observed at TP-3 and TP-4 at depths of one to two feet during our fieldwork on March 30, 2018. Groundwater seepage should be anticipated in site excavations, particularly in the winter, spring, and early summer months. Temporary measures to control groundwater seepage and surface water runoff during construction will likely involve passive elements such as interceptor trenches and sumps, as necessary. Surface water should not be allowed to flow over sloped areas and should not be allowed to pond near the top of sloped areas or retaining structures. Surface grades must be designed to direct water away from buildings. The grade adjacent to buildings should be sloped away from the buildings at a gradient of at least 2 percent for a horizontal distance of four feet or more (as setbacks allow). In our opinion, perimeter footing drains should be installed at or below the invert of the building footings. A typical footing drain detail is provided on Plate 4. Earth Solutions NW, LLC 70 Kisan Enterprises, LLC May 29, 2018 Infiltration Evaluation ES-5932 Page 7 We understand drywells, trenches, or other small-scale methods are proposed for on -site infiltration. For design, the long-term infiltration rate was evaluated using the results of two small- scale Pilot Infiltration Tests (PITs) completed at a depth of three feet in TP-1 and five feet in TP- 2. No infiltration occurred after the initial soaking period. It should be noted that these are not typical results for infiltration into more granular soils types as those found on site. Infiltration testing was attempted at varying depths at both testing locations. On this basis, we do not recommend infiltration be incorporated into this project. ESNW should be notified of any changes to stormwater management designs. Low Impact Development The following table provides our evaluation and recommendations regarding low impact development (LID) BMPs for the proposed project: Limitations of BIIAP Viable? Infeasiblilty Criteria I Lawns and Landscaped Areas T5.13: Post -construction soil quality and Yes Considered infeasible on slopes of 33 percent or depth (Volume V, Chapter 5) greater. Roofs T5.30: Full dispersion (Volume V, Chapter No _ T5.30: Dispersion is not recommended due to a lack 5) of adequate vegetated flow paths. T5.10A: Infiltration is infeasible with a design rate of 0 T5.10A: Downspout full infiltration systems No inches per hour. (Volume III, Chapter 3) Infiltration is infeasible with a design rate of 0 inches Bioretention (Volume V, Chapter 7) No per hour. T5.1013: Dispersion is not recommended due to a lack T5.10B: Downspout dispersion systems No (Volume III, Chapter 3) of adequate vegetated flow paths. T5.10C: Perforated stub -out connections Yes No limitations_ (Volume III, Chapter 3 Other Hard Surfaces T5.30: Full dispersion (Volume V, Chapter NO T5.30: Dispersion is not recommended due to a lack 5) of adequate vegetated flow paths. T5.15: Permeable pavement (Volume V, NO T5.15: Infiltration is infeasible with a design rate of 0 Chapter 5) inches per hour. Bioretention (Volume V, Chapter 7) No Infiltration is infeasible with a design rate of 0 inches per hour. T5.12: Sheet flow dispersion T5.12: Dispersion is not recommended due to a lack T5.11: Concentrated flow dispersion No of adequate vegetated flow paths. (Volume V, Chapter 5) Earth Solutions NW, LLC 71 Kisan Enterprises, LLC May 29, 2018 Stormwater Vault Design ES-5932 Page 8 We understand a stormwater vault is proposed for this property. Vault foundations should be supported on competent native soil or crushed rock placed on competent native soil. Final storm vault designs must incorporate adequate buffer space from property boundaries such that temporary excavations to construct the vault structure can be successfully completed. Perimeter drains should be installed around the vault and conveyed to an approved discharge point. The presence of perched groundwater seepage should be anticipated during excavation activities for the vault. The following parameters may be used for stormwater vault design: • Allowable soil bearing capacity (dense native soil) 5,000 psf Active earth pressure (unrestrained) 35 pcf Active earth pressure (unrestrained, hydrostatic) 80 pcf At -rest earth pressure (restrained) 55 pcf At -rest earth pressure (restrained, hydrostatic) 100 pcf Coefficient of friction 0.40 • Passive earth pressure 300 pcf Seismic surcharge 6H* * Where H equals the retained height (in feet) The vault walls should be backfilled with free -draining material or suitable sheet drainage that extends along the height of the walls. The upper one foot of the wall backfill can consist of a less permeable soil, if desired. A perforated drain pipe should be placed along the base of the wall and connected to an approved discharge location. If the elevation of the vault bottom is such that gravity flow to an outlet is not possible, the portion of the vault below the drain should be designed to include hydrostatic pressure. Design values accounting for hydrostatic pressure are included above. ESNW should observe grading operations for the vault and the subgrade conditions prior to concrete forming and pouring to confirm conditions are as anticipated, and to provide supplemental recommendations as necessary. Additionally, ESNW should be contacted to review final vault designs to confirm that appropriate geotechnical parameters have been incorporated. Earth Solutions NW, LLC 72 Kisan Enterprises, LLC May 29, 2018 Utility Trench Support and Backfill ES-5932 Page 9 In our opinion, the soils observed at the test pit locations are generally suitable for support of utilities. The on -site soils may not be suitable for use as structural backfill in the utility trench excavations unless the soil is at or near the optimum moisture content at the time of placement and compaction. Moisture conditioning of the soils may be necessary at some locations prior to use as structural fill. Utility trench backfill should be placed and compacted to the specifications of structural fill provided in this report, or to the applicable requirements of the City of Edmonds of other responsible agency. Pavement Sections The performance of site pavements is largely related to the condition of the underlying subgrade. To ensure adequate pavement performance, the subgrade should be in a firm and unyielding condition when subjected to proofrolling with a loaded dump truck. Structural fill in pavement areas should be compacted to the specifications detailed in the Site Preparation and Earthwork section of this report. It is possible that soft, wet, or otherwise unsuitable subgrade areas may still exist after base grading activities. Areas of unsuitable or yielding subgrade conditions may require remedial measures, such as overexcavation and replacement with structural fill or thicker crushed rock sections, prior to pavement. For relatively lightly loaded pavements subjected to passenger vehicles and occasional truck traffic, the following sections may be considered for preliminary design: • Two inches of hot mix asphalt (HMA) placed over four inches of crushed rock base (CRIB), or; Two inches of HMA placed over three inches of asphalt treated base (ATB). The HMA, CRIB and ATB materials should conform to WSDOT specifications. All soil base material should be compacted to a relative compaction of 95 percent, based on the laboratory maximum dry density as determined by ASTM D1557. Additionally, city or county Road Standards may supersede the recommendations provided in this report. Road standards utilized by the City of Edmonds may supersede the recommendations provided in this report. Earth Solutions NW, LLC 73 Kisan Enterprises, LLC May 29, 2018 LIMITATIONS ES-5932 Page 10 The recommendations and conclusions provided in this geotechnical engineering study are professional opinions consistent with the level of care and skill that is typical of other members in the profession currently practicing under similar conditions in this area. A warranty is not expressed or implied. Variations in the soil and groundwater conditions observed at the test locations may exist and may not become evident until construction. ESNW should reevaluate the conclusions provided in this geotechnical engineering study if variations are encountered. Additional Services ESNW should have an opportunity to review the final design with respect to the geotechnical recommendations provided in this report. ESNW should also be retained to provide testing and consultation services during construction. 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S+ =v'f•-K . a � ., is#� � Reference: NORTH ' Solutions Snohomish County, Washington NWLLC echnical Engineering, Construction Map 474 '' ' and Environmental Services By The Thomas Guide Rand McNally Vicinity Map 32nd Edition Kisan Townhomes Edmonds, Washington NOTE: This plate may contain areas of color. ESNW cannot be Drwn. MRS Date 05/21 /2018 Proj. No. 5932 responsible for any subsequent misinterpretation of the information resulting from black & white reproductions of this plate. Checked SES Date May 2018 Plate 1 75 ,DMONDS WAY I I I I � I TP-5 I P-2 / ' TP 1 ! I / TP-4■ / 1 � I I TP-3 LEGEND NORTH TP-1 Approximate Location of — ■ — ESNW Test Pit, Proj. No. ES-5932, Mar. 2018 Subject Site Proposed Building NOT - TO - SCALE Existing Building NOTE: The graphics shown on this plate are not intended for design ' ' ' purposes or precise scale measurements, but only to illustrate theEngineering, approximate test locations relative to the approximate locations of ion/Testing and Enviro existing and / or proposed site features. The information illustrated is largely based on data provided by the client at the time of our Test Pit Location Plan study. ESNW cannot be responsible for subsequent design changes Kisan Townhomes or interpretation of the data by others. Edmonds, Washington NOTE: This plate may contain areas of color. ESNW cannot be Drwn. MRS Date 05/21 /2018 Proj. No. 5932 responsible for any subsequent misinterpretation of the information resulting from black & white reproductions of this plate. Checked SES Date May 2018 Plate 2 76 18" Min. -0.0 0 0 o 0 0 �O o �O 00 0 0 opo 0 0 0 0 00 0 �o p 0o p o o 0 0o O000 �0 00 o 0 o 0 0 0 oo o0 0 oO ogo o'?0 o o 0 0 0 0 _ o o D o p 0o o O o 0 op -0 oo 0 0 0o of 0 o 0 o op o 0o o.00 00 0 o. 0 0.0 0 o opo o (? o 0 O o 0 0 op Oo 0 o p o 0 0 0 0g0000oo oo o 8 o o o 00 o 0 0 00O o o o 00 Oo'p o �o o o oO o p o o po o o 000s B o o 000 o 0 8 0 o p 00 o 0 o a o o o0 o 0 * NOTES: • Free -draining Backfill should consist of soil having less than 5 percent fines. Percent passing No. 4 sieve should be 25 to 75 percent. • Sheet Drain may be feasible in lieu of Free -draining Backfill, per ESNW recommendations. • Drain Pipe should consist of perforated, rigid PVC Pipe surrounded with 1-inch Drain Rock. LEGEND: 0opo 0 p o0 op Free -draining Structural Backfill .r.r.rr. ti•ti•ti•ti 1-inch Drain Rock .r.r.rr. Structural Fill Perforated Rigid Drain Pipe (Surround in Drain Rock) SCHEMATIC ONLY - NOT TO SCALE NOTA CONSTRUCTION DRAWING Earth Solutions NW ��c RETAINING WALL DRAINAGE DETAIL Kisan Townhomes Edmonds, Washington Drwn. MRS Date 05/21/2018 Proj. No. 5932 Checked SES Date May 2018 Plate 3 77 Perforated Rigid Drain Pipe (Surround in Drain Rock) NOTES: • Do NOT tie roof downspouts to Footing Drain. • Surface Seal to consist of 12" of less permeable, suitable soil. Slope away from building. LEGEND: Surface Seal: native soil or other low -permeability material. �•r•rr•r ti•ti•ti•ti• 1-inch Drain Rock ti•ti•L•ti• SCHEMATIC ONLY - NOT TO SCALE NOT A CONSTRUCTION DRAWING FOOTING DRAIN DETAIL Kisan Townhomes Edmonds, Washington Drwn. MRS Date05/21/2018 Proj. No. 5932 Checked SES Date May 2018 Plate 4 78 Appendix A Subsurface Exploration ES-5932 The subsurface conditions at the site were explored by excavating two test pits at the approximate locations illustrated on Plate 2 of this report. The test pit logs are provided in this Appendix. The subsurface exploration was completed on March 30, 2018. The test pits were excavated to a maximum depth of approximately 10 feet bgs. Logs of the test pits advanced by ESNW are presented in Appendix A. The final logs represent the interpretations of the field logs and the results of laboratory analyses. The stratification lines on the logs represent the approximate boundaries between soil types. In actuality, the transitions may be more gradual. Earth Solutions NW, LLC 79 Earth Solutions NWLLC SOIL CLASSIFICATION CHART MAJOR DIVISIONS SYMBOLS TYPICAL DESCRIPTIONS GRAPH LETTER GRAVEL AND CLEAN GRAVELS �� 6 * 15,� Gw WELL -GRADED GRAVELS, GRAVEL - SAND MIXTURES, LITTLE OR NO FINES 0 0 OQ�+D Q 0s❑ GP POORLY -GRADED GRAVELS, GRAVEL- SAND MIXTURES, LITTLE OR NO FINES GRAVELLY SOILS (LITTLE OR NO FINES) COARSE GRAINED SOILS MORE THAN 50% OF COARSE GRAVELS WITH FINES °� Q ° D a GM SILTY GRAVELS, GRAVEL -SAND - SILT MIXTURES FRACTION GC CLAYEY GRAVELS, GRAVEL - SAND - CLAY MIXTURES RETAINED ON NO. 4 SIEVE (APPRECIABLE AMOUNT OF FINES) MORE THAN 50% OF MATERIAL IS SAND AND CLEAN SANDS Sw WELL -GRADED SANDS, GRAVELLY SANDS, LITTLE OR NO FINES SP POORLY -GRADED SANDS, GRAVELLY SAND, LITTLE OR NO FINES LARGER THAN NO, 200 SIEVE SIZE SANDY SOILS (LITTLE OR NO FINES)><I SANDS WITH FINES SM SILTY SANDS, SAND - SILT MIXTURES MORE THAN 50% OF COARSE FRACTION S`+ CLAYEY SANDS, SAND - CLAY MIXTURES PASSING ON NO, 4 SIEVE (APPRECIABLE AMOUNT OF FINES) INORGANIC SILTS AND VERY FINE ML SANDS, ROCK FLOUR, SILTY OR CLAYEY FINE SANDS OR CLAYEY SILTS WITH SLIGHT PLASTICITY FINE GRAINED SOILS SILTS LIQUID LIMIT AND LESS THAN 50 CLAYS CL INORGANIC CLAYS OF LOW TO MEDIUM PLASTICITY, GRAVELLY CLAYS, SANDY CLAYS, SILTY CLAYS, LEAN CLAYS _+ OL ORGANIC SILTS AND ORGANIC SILTY CLAYS OF LOW PLASTICITY MORE THAN 50% OF MATERIAL IS MH INORGANIC SILTS, MICACEOUS OR DIATOMACEOUS FINE SAND OR SMALLER THAN NO. 200 SIEVE SILTY SOILS SIZE SILTS LIQUID LIMIT AND CLAYS GREATER THAN 50 CH INORGANIC CLAYS OF HIGH PLASTICITY OH ORGANIC CLAYS OF MEDIUM TO HIGH PLASTICITY. ORGANIC SILTS HIGHLY ORGANIC SOILS PT PEAT, HUMUS, SWAMP SOILS WITH HIGH ORGANIC CONTENTS DUAL SYMBOLS are used to indicate borderline soil classifications. The discussion in the text of this report is necessary for a proper understanding of the nature of the material presented in the attached logs. IE Earth Solutions NW TEST PIT NUMBER TP-1 1805 - 136th Place N.E., Suite 201 Bellevue, Washington 98005 PAGE 1 OF 1 VAX Telephone: 425-449-4704 Fax: 425-449-4711 PROJECT NUMBER ES-5932 PROJECT NAME Kisan Townhomes DATE STARTED 3/30/18 COMPLETED 3/30/18 GROUND ELEVATION TEST PIT SIZE EXCAVATION CONTRACTOR NW Excavating GROUND WATER LEVELS: EXCAVATION METHOD AT TIME OF EXCAVATION -- LOGGED BY SES CHECKED BY HTW AT END OF EXCAVATION -- NOTES Depth of Topsoil & Sod 6": grass AFTER EXCAVATION w U a iC wow- �w TESTS U vi a 0 qQ� MATERIAL DESCRIPTION n az 0 Tf 5L ' ' ' n y Dark brown highly organic TOPSOIL, root intrusions to 1' Gray well -graded SAND with silt, medium dense, moist to wet MC = 17.50% SW- SM -becomes wet CS 5 Gray poorly graded SAND with gravel, medium dense to dense, moist — - MC = 8.50% [USDA Classification: very gravelly coarse SAND] SP 8.0 -becomes wet MC = 16.90% Test pit terminated at 8.0 feet below existing grade. No groundwater encountered during excavation. No caving observed. Bottom of test pit at 8.0 feet. a Earth Solutions NW TEST PIT NUMBER TP-2 1805 - 136th Place N.E., Suite 201 Bellevue, Washington 98005 PAGE 1 OF 1 Telephone: 425-449-4704 Fax: 425-449-4711 PROJECT NUMBER ES-5932 PROJECT NAME Kisan Townhomes DATE STARTED 3/30/18 COMPLETED 3/30/18 GROUND ELEVATION TEST PIT SIZE EXCAVATION CONTRACTOR NW Excavating GROUND WATER LEVELS: EXCAVATION METHOD AT TIME OF EXCAVATION --- LOGGED BY SES CHECKED BY HTW AT END OF EXCAVATION — NOTES Depth of Topsoil & Sod 3": grass AFTER EXCAVATION -- w � w U _ a~ w COTESTS rn U a p MATERIAL DESCRIPTION Q.. a7 v� �_j Qz O U) 0 Gray poorly graded SAND, medium dense, damp MC = 5.50% MC = 10.30% -becomes dense, wet 5 SP MC = 8.50% MC = 15.60% 10 MC = 13.30% Fines = 3.70% 10.0 [USDA Ciassifcation: slightly gravelly SAND] Test pit terminated at 10.0 feet below existing grade. No groundwater encountered during excavation. No caving observed. Bottom of test pit at 10.0 feet. 82 Earth Solutions NW TEST PIT NUMBER TP-3 1805 - 136th Place N.E., Suite 201 Bellevue, Washington 98005 PAGE 1 OF 1 Telephone: 425-449-4704 Fax: 425-449-4711 PROJECT NUMBER ES-5932 PROJECT NAME Kisan Townhnmes DATE STARTED 3/30/18 COMPLETED 3/30/18 GROUND ELEVATION TEST PIT SIZE EXCAVATION CONTRACTOR NW Excavating GROUND WATER LEVELS: EXCAVATION METHOD AT TIME OF EXCAVATION LOGGED BY SES CHECKED BY HTW AT END OF EXCAVATION -- NOTES Depth of Topsoil & Sod 6": grass AFTER EXCAVATION --- w _ �of W U a " g TESTS U vi a 0 MATERIAL DESCRIPTION o Q. Mz 0 Gray well -graded SAND with silt, loose, wet (Fill) SW 12.5 -groundwater seepage - MC = 9.50% Gray silty SAND with gravel, dense to very dense, damp MC = 6.90% SM -weakly cemented Gray poorly graded SAND with silt, medium dense to dense, moist SP- SM :.:. MC = 10.00% 5.5 Test pit terminated at 6.5 feet below existing grade. Groundwater seepage encountered at 1.0 foot during excavation. No caving observed. Bottom of test pit at 6.5 feet. 83 Earth Solutions NW TEST PIT NUMBER TP-4 1805 - 136th Place N.E., Suite 201 Bellevue, Washington 98005 PAGE 1 OF 1 WAX Telephone: 425-449-4704 Fax: 425-449-4711 PROJECT NUMBER ES-5932 PROJECT NAME Kisan Townhomes DATE STARTED 3/30/18 COMPLETED 3/30/18 GROUND ELEVATION TEST PIT SIZE EXCAVATION CONTRACTOR NW Excavating GROUNDWATER LEVELS: EXCAVATION METHOD AT TIME OF EXCAVATION LOGGED BY SES CHECKED BY HTW AT END OF EXCAVATION NOTES Surface Conditions: fill AFTER EXCAVATION --- w �WU ow to TESTS 0_O MATERIAL DESCRIPTION a_ Qz 0 Gray well -graded SAND with silt and gravel, medium dense, moist (Fill) SW - MC = 8.70% -groundwater seepage _ 3.0 Gray silty SAND with gravel, dense damp to moist 5 MC = 7.70% Fines = 15.90% [USDA Classification: gravelly loamy SAND] SM e.0 -becomes moist MC = 11.30% Test pit terminated at 8.0 feet below existing grade. Groundwater seepage encountered at 2.0 feet during excavation. No caving observed. Bottom of test pit at 8.0 feet. 84 Earth Solutions NW TEST PIT NUMBER TP-5 1805 - 136th Place N.E., Suite 201 Bellevue, Washington 98005 PAGE 1 OF 1 Telephone: 425-449-4704 Fax: 425-449-4711 PROJECT NUMBER ES-5932 PROJECT NAME Kisan Townhomes DATE STARTED 3/30/18 COMPLETED 3/30/18 GROUND ELEVATION TEST PIT SIZE EXCAVATION CONTRACTOR NW Excavating GROUND WATER LEVELS: EXCAVATION METHOD AT TIME OF EXCAVATION LOGGED BY SES CHECKED BY HTW AT END OF EXCAVATION --- NOTES Depth of Topsoil & Sad 3": duff AFTER EXCAVATION -- w a. U _ wCOLU �w TESTS (L O MATERIAL DESCRIPTION M Z C9 0 P L Dark brown highly organic TOPSOIL Brown silty SAND with gravel, medium dense, damp to moist MC = 11.60% SM -becomes moist 4.5 5 MC = 10.30% Brown poorly graded SAND with silt and gravel, medium dense, moist Fines = 9.00% [USDA Classification: very gravelly coarse SAND] SP- _ SM 7.5 -becomes wet MC = 13.70% - Test pit terminated at 7.5 feet below existing grade. No groundwater encountered during excavation. No caving observed. Bottom of test pit at 7.5 feet. 85 Appendix B Laboratory Test Results ES-5932 Earth Solutions NW, LLC 86 INS HE liiiiiinmiiiiii llmmiiiiiilmmi milamismillillismilliillom limmillillismil linsillillismillill mmiiiiiiimm INN Ilion USE llmmiiiiiiimmiiiiiiimwil IHNNEIIIII IEEIIIIII limmillillismillillinoll 11111,111111 MENOMINEE INS HUM IMMEM Em= gnu I'll ''I'll III COBBLES GRAVEL coarse fine SAND SILT OR CLAY coarse medium fine Report Distribution ES-5932 EMAIL ONLY Kisan Enterprises, LLC 20607 State Route 9 Snohomish, Washington 98296 Attention: Ms. Yvette Johnson Earth Solutions INK LLC 88 F. ECOLOGY APPROVAL FOR FILTER Insight Engineering Co. - Stormwater Site Plan 12/08/2020 -36- lwww� WASHIN GT0N STATE EECAOTLEOTG GY April 2017 GENERAL USE LEVEL DESIGNATION FOR BASIC (TSS) TREATMENT For CONTECH Engineered Solutions Stormwater Management StormFilter' With ZPG Media at 1 gpm/sq ft media surface area Ecology's Decision: Based on the CONTECH Engineered Solutions' (CONTECH) application submissions, Ecology hereby issues a General Use Level Designation (GULD) for the Stormwater Management StormFilter® (StormFilter): 1. As a basic stormwater treatment practice for total suspended solids (TSS) removal, Using ZPGTM media (zeolite/perlite/granular activated carbon), with the size distribution described below, Sized at a hydraulic loading rate of 1 gpm/ft' of media surface area, per Table 1, and Internal bypassing needs to be consistent with the design guidelines in CONTECH's current product design manual. Table 1. StormFilter Design Flow Rates per Cartridge Effective Cartridge Height (inches) 12 18 27 Cartridge Flow Rate m/cartrid e 5 7.5 11.3 2. Ecology approves StormFilter systems containing ZPGTM media for treatment at the hydraulic loading rates shown in Table 1, and sized based on the water quality design flow rate for an off-line system. Contech designs their StormFilter systems to maintain treatment of the water quality design flow while routing excess flows around the treatment chamber during periods of peak bypass. The water quality design flow rates are calculated using the following procedures: • Western Washington: For treatment installed upstream of detention or retention, the water quality design flow rate is the peak 15-minute flow rate as calculated using the latest version of the Western Washington Hydrology Model or other Ecology -approved continuous runoff model. CONTECH - StormFilter'l GULD Maintenance Update (November 2012) Page 11 Eastern Washington: For treatment installed upstream of detention or retention, the water quality design flow rate is the peak 15-minute flow rate as calculated using one of the three methods described in Chapter 2.2.5 of the Stormwater Management Manual for Eastern Washington (SWMMEW) or local manual. • Entire State: For treatment installed downstream of detention, the water quality design flow rate is the full 2-year release rate of the detention facility. 3. This designation has no expiration date, but Ecology may amend or revoke it. Ecology's Conditions of Use: The StormFilter with ZPG media shall comply with the following conditions: 1. Design, install, operate, and maintain the StormFilter with ZPG media in accordance with applicable Contech Engineered Solutions manuals, documents, and the Ecology Decision. 2. Install StormFilter systems to bypass flows exceeding the water quality treatment rate. Additionally, high flows will not re -suspend captured sediments. Design StormFilter systems in accordance with the performance goals in Ecology's most recent Stormwater Manual and CONTECH's Product Design Manual Version 4.1 (April 2006), or most current version, unless otherwise specified. 3. Owners must follow the design, pretreatment, land use application, and maintenance criteria in CONTECH's Design Manual. 4. Pretreatment of TSS and oil and grease may be necessary, and designers shall provide pre-treatment in accordance with the most current versions of the CONTECH's Product Design Manual (April 2006) or the applicable Ecology Stormwater Manual. Design pre-treatment using the performance criteria and pretreatment practices provided on Ecology's "Evaluation of Emerging Stormwater Treatment Technologies" website. 5. Maintenance: The required maintenance interval for stormwater treatment devices is often dependent upon the degree of pollutant loading from a particular drainage basin. Therefore, Ecology does not endorse or recommend a "one size fits all" maintenance cycle for a particular model/size of manufactured filter treatment device. Typically, CONTECH designs StormFilter systems for a target filter media replacement interval of 12 months. Maintenance includes removing accumulated sediment from the vault, and replacing spent cartridges with recharged cartridges. CONTECH - StormFilterl GULD Maintenance Update (November 2012) Page 12 Indications of the need for maintenance include effluent flow decreasing to below the design flow rate, as indicated by the scumline above the shoulder of the cartridge. Owners/operators must inspect StormFilter with ZPG media for a minimum of twelve months from the start of post -construction operation to determine site -specific maintenance schedules and requirements. You must conduct inspections monthly during the wet season, and every other month during the dry season. (According to the SWMMWW, the wet season in western Washington is October 1 to April 30. According to SWMMEW, the wet season in eastern Washington is October 1 to June 30). After the first year of operation, owners/operators must conduct inspections based on the findings during the first year of inspections. • Conduct inspections by qualified personnel, follow manufacturer's guidelines, and use methods capable of determining either a decrease in treated effluent flowrate and/or a decrease in pollutant removal ability. When inspections are performed, the following findings typically serve as maintenance triggers: • Accumulated vault sediment depths exceed an average of 2 inches, or • Accumulated sediment depths on the tops of the cartridges exceed an average of 0.5 inches, or • Standing water remains in the vault between rain events, or • Bypass occurs during storms smaller than the design storm. Note: If excessive floatables (trash and debris) are present, perform a minor maintenance consisting of gross solids removal, not cartridge replacement. 6. CONTECH shall maintain readily available reports listed under "Application Documents" (above) as public, as well as the documentation submitted with its previous conditional use designation application. CONTECH shall provide links to this information from its corporate website, and make this information available upon request, at no cost and in a timely manner. 7. ZPGTM media used shall conform with the following specifications: Each cartridge contains a total of approximately 2.6 cubic feet of media. The ZPGTM cartridge consists of an outer layer of perlite that is approximately 1.3 cubic feet in volume and an inner layer, consisting of a mixture of 90% zeolite and 10% granular activated carbon, which is approximately 1.3 cubic feet in volume. • Perlite Media: Perlite media shall be made of natural siliceous volcanic rock free of any debris or foreign matter. The expanded perlite shall CONTECH - StormFilterl GULD Maintenance Update (November 2012) Page 13 have a bulk density ranging from 6.5 to 8.5 lbs per cubic foot and particle sizes ranging from 0.09" (#8 mesh) to 0.38" (3/8" mesh). • Zeolite Media: Zeolite media shall be made of naturally occurring clinoptilolite. The zeolite media shall have a bulk density ranging from 44 to 50 lbs per cubic foot and particle sizes ranging from 0.13" (#6 mesh) to 0.19" (#4 mesh). Additionally, the cation exchange capacity (CEC) of zeolite shall range from approximately 1.0 to 2.2 meq/g. • Granular Activated Carbon: Granular activated carbon (GAC) shall be made of lignite coal that has been steam -activated. The GAC media shall have a bulk density ranging from 28 to 31 lbs per cubic foot and particle sizes ranging from a 0.09" (#8 mesh) to 0.19" (#4 mesh). Approved Alternate Configurations Peak Diversion StormFilter The Peak Diversion StormFilter allows for off-line bypass within the StormFilter structure. Design capture flows and peak flows enter the inlet bay which contains an internal weir. The internal weir allows design flows to enter the cartridge bay through a transfer hole located at the bottom of the inlet bay while the unit routs higher flows around the cartridge bay. 2. To select the size of the Peak Diversion StormFilter unit, the designer must determine the number of cartridges required and size of the standard StormFilter using the site - specific water quality design flow and the StormFilter Design Flow Rates per Cartridge as described above. 3. New owners may not install the Peak Diversion StormFilter at an elevation or in a location where backwatering may occur. Applicant: Contech Engineered Solutions Applicant's Address: 11835 NE Glenn Widing Dr. Portland, OR 97220 Application Documents: The applicant's master report, titled, "The Stormwater Management StormFilter Basic Treatment Application for General Use Level Designation in Washington", Stormwater Management, Inc., November 1, 2004, includes the following reports: • (Public) Evaluation of the Stormwater Management StormFilter Treatment System: Data Validation Report and Summary of the Technical Evaluation Engineering Report (TEER) by Stormwater Management Inc., October 29, 2004 Ecology's technology assessment protocol requires the applicant to hire an independent consultant to complete the following work: CONTECH - StormFilter'l GULD Maintenance Update (November 2012) Page 14 1. Complete the data validation report. 2. Prepare a TEER summary, including a testing summary and conclusions compared with the supplier's performance claims. 3. Provide a recommendation of the appropriate technology use level. 4. Work with Ecology to post recommend relevant information on Ecology's website. 5. Provide additional testing recommendations, if needed." 6. This report, authored by Dr. Gary Minton, Ph. D., P.E., Resource Planning Associates, satisfies the Ecology requirement. • (Public) "Performance of the Stormwater Management StormFilter Relative to the Washington State Department of Ecology Performance Goals for Basic Treatment," is a summary of StormFilter performance that strictly adheres to the criteria listed in the Guidance for Evaluating Emerging Stormwater Treatment Technologies, Technology Assessment Protocol — Ecology (TAPE). • "Heritage Marketplace Field Evaluation: Stormwater Management StormFilter with ZPGTM Media," is a report showing all of the information collected at Site A as stated in the SMI Quality Assurance Project Plan (QAPP). This document contains detailed information regarding each storm event collected at this site, and it provided a detailed overview of the data and project. • "Lake Stevens Field Evaluation: Stormwater Management StormFilter with ZPGTM Media," is a report that corresponds to Site E as stated in the SMI QAPP. This document contains detailed information regarding each storm collected at this site, and includes a detailed overview of the data and project. • (Public) "Evaluation of the Stormwater Management StormFilter for the removal of SIL-CO-SIL 106, a standardized silica product: ZPGTM at 7.5 GPM" is a report that describes laboratory testing at full design flow. • "Factors Other Than Treatment Performance." • "State of Washington Installations." • "Peak Diversion StormFilter" is a technical document demonstrating the Peak Diversion StormFilter system complies with the Stormwater Management Manual for Western Washington Volume V Section 4.5.1. Above -listed documents noted as "public" are available by contacting CONTECH. Applicant's Use Level Request: That Ecology grant a General Use Level Designation for Basic Treatment for the StormFilter using ZPGTM media (zeolite/perlite/granular activated carbon) at a hydraulic loading rate of 1 gpm/ft2 of media surface area in accordance with Ecology's 2011 Technical Guidance Manual for Evaluating Emerging Stormwater Treatment Technologies Technology Assessment Protocol — Ecology (TAPE). CONTECH - StormFiltefl GULD Maintenance Update (November 2012) Page 15 Applicant's Performance Claim: The combined data from the two field sites reported in the TER (Heritage Marketplace and Lake Stevens) indicate that the performance of a StormFilter system configured for inline bypass with ZPGTM media and a hydraulic loading rate of 1 gpm/ft2 of media surface area meets Ecology performance goals for Basic Treatment. Ecology's Recommendations: Based on the weight of the evidence and using its best professional judgment, Ecology finds that: • StormFilter, using ZPGTM media and operating at a hydraulic loading rate of no more than 1 gpm/ft2 of media surface area, is expected to provide effective stormwater treatment achieving Ecology's Basic Treatment (TSS removal) performance goals. Contech demonstrated this is through field and laboratory testing performed in accordance with the approved protocol. StormFilter is deemed satisfactory with respect to factors other than treatment performance (e.g., maintenance; see the protocol's Appendix B for complete list). Findings of Fact: • Influent TSS concentrations and particle size distributions were generally within the range of what Ecology considers "typical" for western Washington (silt -to -silt loam). • Contech sampled thirty-two (32) storm events at two sites for storms from April 2003 to March 2004, of which Contech deemed twenty-two (22) as "qualified" and were therefore included in the data analysis set. • Statistical analysis of these 22 storm events verifies the data set's adequacy. • Analyzing all 22 qualifying events, the average influent and effluent concentrations and aggregate pollutant load reduction are 114 mg/L, 25 mg/L, and 82%, respectively. • Analyzing all 22 qualifying events based on the estimated average flow rate during the event (versus the measured peak flow rate), and more heavily weighting those events near the design rate (versus events either far above or well below the design rate) does not significantly affect the reported results. • For the 7 qualifying events with influent TSS concentrations greater than 100 mg/L, the average influent and effluent concentrations and aggregate pollutant load reduction are 241 mg/L, 34 mg/L, and 89%, respectively. If we exclude the 2 of 7 events that exceed the maximum 300 mg/L specified in Ecology's guidelines, the average influent and effluent concentrations and aggregate pollutant load reduction are 158 mg/L, 35 mg/L, and 78%, respectively. • For the 15 qualifying events with influent TSS concentrations less than 100 mg/L, the average influent and effluent concentrations and aggregate pollutant load reduction are 55 mg/L, 20 mg/L, and 61 %, respectively. If the 6 of 15 events that fall below the minimum 33 mg/L TSS specified in Ecology's guidelines are excluded, the average CONTECH - StormFilter'l GULD Maintenance Update (November 2012) Page 16 influent and effluent concentrations and aggregate pollutant load reduction are 78 mg/L, 26 mg/L, and 67%, respectively. • For the 8 qualifying events with peak discharge exceeding design flow (ranging from 120 to 257% of the design rate), results ranged from 52% to 96% TSS removal, with an average of 72%. • Due to the characteristics of the hydrographs, the field results generally reflect flows below (ranging between 20 and 60 percent of) the tested facilities' design rate. During these sub -design flow rate periods, some of the cartridges operate at or near their individual full design flow rate (generally between 4 and 7.5 GPM for an 18" cartridge effective height) because their float valves have opened. Float valves remain closed on the remaining cartridges, which operate at their base "trickle" rate of 1 to 1.5 GPM. • Laboratory testing using U.S. Silica's Sil-Co-Sil 106 fine silica product showed an average 87% TSS removal for testing at 7.5 GPM per cartridge (100% design flow rate). • Other relevant testing at I-5 Lake Union, Greenville Yards (New Jersey), and Ski Run Marina (Lake Tahoe) facilities shows consistent TSS removals in the 75 to 85% range. Note that the evaluators operated the 1-5 Lake Union at SO%, 100% and 125% of design flow. • SMI's application included a satisfactory "Factors other than treatment performance" discussion. Note: Ecology's 80% TSS removal goal applies to 100 mg1l and greater influent TSS. Below 100 mg/L influent TSS, the goal is 20 mg1L effluent TSS. Technology Description: The Stormwater Management StormFilter® (StormFilter), a flow -through stormwater filtration system, improves the quality of stormwater runoff from the urban environment by removing pollutants. The StormFilter can treat runoff from a wide variety of sites including, but not limited to: retail and commercial development, residential streets, urban roadways, freeways, and industrial sites such as shipyards, foundries, etc. Operation: The StormFilter is typically comprised of a vault that houses rechargeable, media -filled, filter cartridges. Various media may be used, but this designation covers only the zeolite- perlite-granulated activated carbon (ZPGTM) medium. Stormwater from storm drains percolates through these media -filled cartridges, which trap particulates and may remove pollutants such as dissolved metals, nutrients, and hydrocarbons. During the filtering process, the StormFilter system also removes surface scum and floating oil and grease. Once filtered through the media, the treated stormwater is directed to a collection pipe or discharged to an open channel drainage way. This document includes a bypass schematic for flow rates exceeding the water quality design flow rate on page 8. CONTECH - StormFiltefl GULD Maintenance Update (November 2012) Page 17 StormFilter Configurations: Contech offers the StormFilter in multiple configurations: precast, high flow, catch basin, curb inlet, linear, volume, corrugated metal pipe, drywell, and CON/Span form. Most configurations use pre -manufactured units to ease the design and installation process. Systems may be either uncovered or covered underground units. The typical precast StormFilter unit is composed of three sections: the energy dissipater, the filtration bay, and the outlet sump. As Stormwater enters the inlet of the StormFilter vault through the inlet pipe, piping directs stormwater through the energy dissipater into the filtration bay where treatment will take place. Once in the filtration bay, the stormwater ponds and percolates horizontally through the media contained in the StormFilter cartridges. After passing through the media, the treated water in each cartridge collects in the cartridge's center tube from where piping directs it into the outlet sump by a High Flow Conduit under -drain manifold. The treated water in the outlet sump discharges through the single outlet pipe to a collection pipe or to an open channel drainage way. In some applications where you anticipate heavy grit loads, pretreatment by settling may be necessary. CONTECH - StormFiltefl GULD Maintenance Update (November 2012) Page 18 5TORMGATE ANMOLE, IIGM FLOW BYPA55 EFFECTIVE CARTRIDGE Ht Gh" 1 2" 1 S" 27 CARTRIDGE FLOW RATE (gprrdcart) 5 7.5 1 1.3 DGF D W) 02MOCCHFECHSh m mWaokr&m Jl%QAAjVWOhU6 STORMFILTER WITH STORMGATE OR4WIU i FAM SCHEMATIC DETAIL STOR MWAiER 50L1lTIOIAIS_ PLAN VIEW m�1mlr .mrn OATS:11MIM6 SCALE:NONE FILE NAME: SV"H-SF6l"TIS-5GH DRAWN: MM I rNECKED.W Figure 1. Stormwater Management StormFilter Configuration with Bypass CONTECH - StormFilterl GULD Maintenance Update (November 2012) Page 19 AIR LOCK CAP WITH CHECK VALVE _ / LIFTING TAB FLOAT VALVE FILTER MEDIA \J OUTER „FOOD CENTERTUBE SCRUBBING REGULATOR WATER UNFILTERED AKK�� ED WATER UNDER -DRAIN MANIFOLD .L FILTERED WATER UNDER -DRAIN MANIFOLD CAST INTO VAULT FLOOR Figure 2. The StormFilter Cartridge Cartridge Operation: FLOOR As the water level in the filtration bay begins to rise, stormwater enters the StormFilter cartridge. Stormwater in the cartridge percolates horizontally through the filter media and passes into the cartridge's center tube, where the float in the cartridge is in a closed (downward) position. As the water level in the filtration bay continues to rise, more water passes through the filter media and into the cartridge's center tube. Water displaces the air in the cartridge and it purges from beneath the filter hood through the one-way check valve located in the cap. Once water fills the center tube there is enough buoyant force on the float to open the float valve and allow the treated water to flow into the under -drain manifold. As the treated water drains, it tries to pull in air behind it. This causes the check valve to close, initiating a siphon that draws polluted water throughout the full surface area and volume of the filter. Thus, water filters through the entire filter cartridge throughout the duration of the storm, regardless of the water surface elevation in the filtration bay. This continues until the water surface elevation drops to the elevation of the scrubbing regulators. At this point, the siphon begins to break and air quickly flows beneath the hood through the scrubbing regulators, causing energetic bubbling between the inner surface of the hood and the outer surface of the filter. This bubbling agitates and cleans the surface of the filter, releasing accumulated sediments on the surface, flushing them from beneath the hood, and allowing them to settle to the vault floor. Adjustable cartridge flow rate: Inherent to the design of the StormFilter is the ability to control the individual cartridge flow rate with an orifice -control disc placed at the base of the cartridge. Depending on the treatment requirements and on the pollutant characteristics of the influent stream as CONTECH - StormFiltefl GULD Maintenance Update (November 2012) Page 110 specified in the CONTECH Product Design Manual, operators may adjust the flow rate through the filter cartridges. By decreasing the flow rate through the filter cartridges, the influent contact time with the media is increased and the water velocity through the system is decreased, thus increasing both the level of treatment and the solids removal efficiencies of the filters, respectively (de Ridder, 2002). Recommended research and development: Ecology encourages CONTECH to pursue continuous improvements to the StormFilter. To that end, CONTECH recommends the following actions: • Determine, through laboratory testing, the relationship between accumulated solids and flow rate through the cartridge containing the ZPGTM media. Completed 11105. • Determine the system's capabilities to meet Ecology's enhanced, phosphorus, and oil treatment goals. • Develop easy -to -implement methods of determining that a StormFilter facility requires maintenance (cleaning and filter replacement). Contact Information: Applicant Contact: Jeremiah Lehman Contech Engineered Solutions 11835 NE Glenn Widing Drive Portland, OR, 97220 503-258-3136 j lehman(c,conteche s. com Applicant Web link http://www.conteches.com/ CONTECH - StormFiltefl GULD Maintenance Update (November 2012) Page 111 Ecology web link: http://www.ecy.wa.gov/programs/wq/stormwater/newtech/index.html Ecology Contact: Douglas C. Howie, P.E. Department of Ecology Water Quality Program (360) 407-6444 douglas.howienecy.wa. og_v Revision History Date Revision Jan 2005 Original Use Level Designation Dec 2007 Revision May 2012 Maintenance requirements updated November 2012 Design Storm and Maintenance requirements updated January 2013 Updated format to match Ecology standard format September 2014 Added Peak Diversion StormFilter Alternate Configuration November 2016 Revised Contech contact information April 2017 Revised sizing language to note sizing based on Off-line calculations CONTECH - StormFilter' GULD Maintenance Update (November 2012) Page 112 G.WATER QUALITY CALCULATIONS FROM CONTECH Insight Engineering Co. - Stormwater Site Plan 12/08/2020 -37- 05w,*-NTECH' ENGINEERED SOLUTIONS Project Name: Kisan Enterprises Site Designation: CB #4 Date: 12/1/20 County or Independent City: Edmonds Designer: SKJ State: WA Flow Based Data: Peak Design Flow (cfs) Water Quality Flow (cfs) Annual Rainfall (inches) Total Drainage Area, A (ac) Post Development Impervious Area, A, (ac) Pervious Area, Ap (ac) % Impervious Runoff Coefficient, Rc Flow Based Filter Sizing: Filter Type Structure Type Cartridge Height Media Type Cartridge Flow Rate, gpm/sf Cartridges Required Recommended Model Maximum Water Quality Flow 0.21 0.02 36 0.21 0.21 0.00 100 % 0.95 StormFilter Catchbasin (Steel) 27" ZPG 1.00 gpm/sf 1 SFCB1 0.03 cfs