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APPROVED DRAINAGE REPORTDonna Breske . & Associates RESUB 3/1 /2021 CITY OF EDMONDS Civil Engineering & Land Use Planning DEVELOPMENT SERVICES DEPARTMENT Drainage Report For Mirel & Magdalena Rogoj an BLD2019-1496 REVISION DATE: 3-1-2021, REVISE DOWNSTREAM ANALYSIS VERBIAGE TO INCLUDE DESCRIPTION OF OVERFLOW FROM THE BIORETENTION SYSTEM IS VIA A WEIR AND AND THEN CAPTURED BY A SPREADER TRENCH WITH FLOW PATH. Revision Date: 3-2-20 per Stormwater Review Comments issued 12-27-2019 & Plan Review Comments issued 1-29-20 Original Date Prepared: October 02, 2019 Site Address: 21705 96th Ave W Edmonds,WA 98020 Parcel Number: 00373600700802 Donna Breske & Associates 21 Ave A, Suite 4 Snohomish, WA 98290 Phone: 206-715-9582 Email: donnab@donnabreske.com APPLIES WITH APPLICABLE CITY STROMWATER CODE Table of Contents Narrative: Executive Summary.................................................................................................................Page 1 VicinityMap............................................................................................................................Page 2 Figure 3.2 Flow Chart for Det. Req. New Dev.........................................................................Page 3 Minimum Requirements #1- 5...............................................................................................Page 4 SWPPPNarrative.....................................................................................................................Page 9 Appendix: A: WWHM12 Bioretention Sizing Calcs B: Geotech Report from Nelson Geotech Associates C: Survey from BT Surveys D: Operations and Maintenance E: Bio-retention location email F: Resident letter G: Approval Memo Rogojan March 02, 2020 Executive Summary This is a new development project in the City of Edmonds. The site address and parcel number are as follows; 21705 96thAve W Edmonds, Wa 98020, #00373600700802. The site is .2 Acres in size and zoned R-8. This project demonstrates compliance with the 2014 Department of Ecology Drainage Manual and the 2017 City of Edmonds Stormwater Addendum. The existing condition of the site is developed with a single-family home and driveway. All existing impervious surface will be removed before the construction of the new development. However, the existing driveway will act as temporary construction access during work on the proposed house. The topography on site slopes from the street level on 96thAve W down towards the southern property line. Vegetation on site consists of grass and light shrubbery. A Geotech Analysis was performed for the site by Nelson Geotechnical Associates. Said Analysis categorizes soils on site as Glacial Till comprised of medium sands and gravel. Per the professional opinion of the geotech engineer, infiltration is feasible with the .76" per hour infiltration rate. The proposed development includes a new single-family house and driveway. The proposed impervious area is less than 5,000 sf and thus will satisfy Minimum Requirements #1-5. Per the City of Edmonds Stormwater Addendum this is a Category 1 project and will evaluate BMP's in the hierarchal order of List #1 for Minimum Requirement #5 Stormwater Management. Per List #1 On -Site Stormwater Management BMP's the first feasible BMP for Rooftop as well as pollutuin-generating hard surface mitigation is Bioretention. Thus, a bioretention facility has been sized using WWHM12 to handle stormwater flows from all proposed impervious surface on site. In addition, the bioretention facility is equipped with an overflow riser that provide a safe overflow pathway to the City of Edmonds stormwater utility system. See Appendix A for Bioretention sizing calculations. A Stormwater Pollution Prevention plan has been provided in this report. In addition, BMP T5.13 will be ensured throughout the life of the project. WALNUT ST YOST PARK 212TH ST SW L �0/N lygY j (PINE S FIR ST SITE L 'Q w 20TH ST SW ~ `O 10 cn co w Q ESPERANCE 99 W c Q 224TH ST SW 224TH ST SW PARK 3 ~ � o 226TH ST W Q � W Q x SW 00 00 228TH ST SW 10 PREPARED BY. - DONNA BRESKE & ASSOCIATES, LLC 21 AVE A, SUITE 4 SNOHOMISH, WA 98290 PHONE: (425) 334-9980 DONNABRESKE©COMCAST. NET VICINITY MAP N. T. S. TAX NO. 00373600700802 PROJECT PROPONENT• ROGOJAN VICINITY MAP SITE ADDRESS ZONING: RS-8 21705 96TH AVE. W, EDMONDS, WA 98020 EDMONDS STORMWATER ADDENDUM JUNE 2017 Does the project result in 2,000 square feet, or greater, of new plus replaced hard surface area? OR Does the land disturbing activity total 7,000 square feet or greater? es No Minimum Requirements No. 1 through 5 apply Minimum Requirement No. 2 applies Next Question Does the project add 5,000 square feet or more of new plus replaced hard surfaces? OR Convert 0.75 acres or more of vegetation to lawn or landscaped areas? OR Convert 2.5 acres or more of native vegetation to pasture? Yes No No Yes Is this a road related project? Does the project add 5,000 square feet or No more of new hard surfaces? Yes All Minimum Requirements Yes apply to the new and replaced Do new hard surfaces add 50% or hard surfaces and converted more to the existing hard surfaces vegetation areas. within the project limits? All Minimum Requirements No additional apply to the new hard surfaces e r requirements. and converted vegetation areas. Figure 3.1. Flow Chart for Determining Requirements for Development. 8 3. APPLICABILITY OF THE MINIMUM REQUIREMENTS Table 1-2.5.1 On -Site Stormwater Management Requirements for Projects Triggering Minimum Requirements #1 - #9 Project Type and Location Requirement New deveopment on any parcel inside Low Impact Development Performance Standard BMP T5.13: Post the UGA, or Rew development outside the and -Construction UGA on a parcel less than 5 acres Soil Quality and Depth (p.911); or List #2 (applicant option). New development ou ide the UGA on a Low Impact Development Performance parcel of 5 acres or larg Standard and BMP T5.13: Post -Construction Soil Quality and Depth (p.911). Redevelopment on any parcel ' side the Low Impact Development Performance UGA, or redevelopment outside t UGA Standard and BMP T5.13: Post -Construction on a parcel less than 5 acres Soil Quality and Depth (p.911); or List #2 (applicant option). Redevelopment outside the UGA on a par -Low Impact Development Performance cel of 5 acres or larger ndard and BMP T5.13: Post -Construction Soil ualit and Depth .911 . as designated under the Note: This table refers to the Urban Growth Area (NRC Growth Management Act (GMA) (Chapter 36.70A of the State of Washington. If the Permittee is located in a county that is not subject to nning under the GMA, the city limits shall be used. Low Impact Development Performance Standard Stormwater discharges shall match developed discharge duration to pre - developed durations for the range of pre -developed discharge rates om 8% of the 2-year peak flow to 50% of the 2-year peak flow. Refer to the Standa%also( Control Requirement section in Minimum Requirement #7 for informati the assignment of the pre -developed condition. Project sites that must minimum requirement #7 — flow control - must match flow durations between 81 the 2-year flow through the full 50-year flow. List #1: On -site Stormwater Management BMPs for Projects Triggering Minimum Requirements #1 through #5 For each surface, consider the BMP's in the order listed for that type of surface. Use the first BMP that is considered feasible. No other On -site Stormwater Man- agement BMP is necessary for that surface. Feasibility shall be determined by eval- uation against: 1. Design criteria, limitations, and infeasibility criteria identified for each BMP in this manual; and 2014 Stormwater Management Manual for Western Washington Volume 1- Chapter 2 - Page 56 2. Competing Needs Criteria listed in Chapter V-5 - On -Site Stormwater Man- agement (p.903). Lawn and landscaped areas: . Post -Construction Soil Quality and Depth in accordance with BMP T5.13: Post -Construction Soil Quality and Depth (p.911). Roofs: Infeasible due to space constraints and impervious coverage 1. Full Dispersion in accordance with BMP T5.30: Full Dispersion (p.939), or Downspout Full Infiltration Systems in accordance with BMP T5.10A: Down- spout Full Infiltration (p.905)<--Infeasible-site is in till soils not outwash or loam 2. Rain Gardens in accordance with BMP T5.14A: Rain Gardens (P.915), or Bioretention in accordance with BMP T7.30: Bioretention Cells, Swales, and Planter Boxes (p.959). The rain garden or bioretention facility must have a minimum horizontal projected surface area below the overflow which is at least 5% of the area draining to it. Yes, Bioretention has been sized using WWHM12 3. Downspout Dispersion Systems in accordance with BMP T5.1013: Down- spout Dispersion Systems (p.905) 4. Perforated Stub -out Connections in accordance with BMP T5.10C: Per- forated Stub -out Connections .905 Other Hard Surfaces: Infeasible- not enough space or preserved vegetation 1. Full Dispersion in accordance with BMP T5.30: Full Dispersion (p.939) 2. Permeable pavementl in accordance with BMP T5.15: Permeable Pavements .917 , or Rain Gardens in accordance with BMP T5.14A: Rain Gardens (p 915), or Bioretention in accordance with BMP T7.30: Bioretention Cells, Swales, and Planter Boxes (p.959).Thn rnmn nnrclan t%r hor%ratantion fa ity must have a minimum horizontal pr YES, Bioretention has been v rflow which is at least 5% of the area drah sized to accomodate driveway and rooftop runoff 3. Sheet Flow Dispersion in accordance with Sheet ow Dispersion (p 908), or Concentrated Flow Dispersion in accordance with BMP T5.11: Con- centrated Flow Dispersion (p.905). List #2: On -site Stormwater Management BMPs for Projects Triggering Minimum Requirements #1 through #9 For each surface, consider the BMPs in the order listed for that type of surface. Use the first BMP that is considered feasible. No other On -site Stormwater 1This is not a requirement to pave these surfaces. Where pavement is proposed, it must be permeable to the extent feasible unless full dispersion is employed. 2014 Stormwater Management Manual for Western Washington Volume 1- Chapter 2 - Page 57 Edmonds Chapter 18.30 and 2014 DOE Stormwater Management Manual for Western Washington 2.5.1 Minimum Requirement #1: Preparation of Stormwater Site Plans 3.1.1 Site Analysis: Volume 1, Section 3.1 Boundary Survey & Topography Map A survey has been conducted by BT Surveying. Vegetation and Utility Infrastructure The site has a few existing shrubs and a grassy lawn. There are existing utilities on site in use by the existing house on the property, including; water, gas, sewer, and electricity. Soils Report A Geotech report has been prepared for the site by Nelson Geotechnical Associates. Soils on site are classified as Glacial Till comprised of Medium sands and gravel. Site Analysis and Summary of Existing Conditions The site contains a single-family house, and a paved driveway. There are no wetlands or critical areas on or near the site. 3.1.2 Preliminary Development Layout: Vol 1, Section 3.1.2 A development layout showing proposed and existing houses and driveway, is included with this submittal. 3.1.3 Off -Site Upstream and Downstream Analysis: Vol 1, Section3.1.3 • Upstream Analysis: Per the city of Edmonds drainage inventory map and the survey there are several catch basins directly in front of the site on 96th Ave W. The frontage of the property has a high point and drainage piping system in the right-of-way slope northward or southward. The development of this site is not expected to have any adverse effects on any upstream properties, nor is it anticipated that flows will reach the site from upstream as there are ample stormwater conveyance systems in the area. REVISED 3-1-2021 D'owdstreanT Adal3rsis:' Storniwafer r'hnoff febm'the'§ub]ect7sitdis fiot 8xpdcted to haVb ally ative?se ` effect on downstream properties. The proposed Bioretention Facility for stormwater management has been designed to infiltrate contributing stormwater at 100% and demonstrates. compliance with the the Low Impact Performance Standard for flow control of storm durations. Low Impact Development Performance Standard Stormwater discharges shall match developed discharge durations to pre - developed durations for the range of pre -developed discharge rates from 8% of the 2-year peak flow to 50% of the 2-year peak flow. Refer to the Standard Flow Control Requirement section in Minimum Requirement #7 for information about the assignment of the pre -developed condition. Project sites that must also meet minimum requirement #7 — flow control - must match flow durations between 8% of the 2-year flow through the full50-year flow. The bioretention system is sized to accept stormwater runoff for flow durations through the full 100- year flow, which is greater than the required 50-year LID Performance standard. It is unlikely there will be any overflow. However, in the unlikely event that there is, this engineer has also designed a spreader trench and 25-foot flow path for distribution of flows on -site if there should be overflow from the bioretention weir. The dual LID BMP features provide a system that ensures storm water runoff is managed on -site to the extent feasible. 1-2.5.5 Minimum Requirement #5: On -site Stormwater Management Projects shall employ On -site Stormwater Management BMPs in accordance with the following projects thresholds, standards, and lists to infiltrate, disperse, and retain stormwater runoff on -site to the extent feasible without causing flooding or erosion impacts. Also, keep in mind, the Downstream Analysis objective is intertwined with MR#5 to retain stormwater on site to the maximum extent feasible without causing flooding or erosion impact.. This engineer has taken into consideration the overflow path and has concluded, it is unlikely any overflow will occur and that furthermore, it there is any overflow, stormwater it is not anticipated to leave the site, nor cause flooding or erosion impacts. 3.1.4 Determination of Applicable Minimum Requirements: Vol 1, Section3.1.4 This report addresses the development of a new single-family house and driveway. The total hard surface area results in less than 5,000 sf, therefore.' herefo e, �a. vat'on f ini u e it e is -1 1 1 Preparation of Permanent Stormwater Control Plan: Vol 1, Section 3.1.5 A permanent Stormwater Control Plan has been prepared with relevant elements shown on the drainage plan. 3.1.5 Preparation of Construction Stormwater Pollution PreventionPlan (SWPPP), Vol 1, Section 3.1.6 A construction stormwater pollution prevention plan has been included in this report with elements shown on the TESC plan. 3.1.6 Completion of Stormwater Site Plan, Vol. 1, Section 3.1.7 A stormwater site plan has been prepared showing the locations of all proposed drainage elements. 5.2 Minimum Requirement #2: Construction Stormwater Pollution Prevention (SWPPP) The construction stormwater pollution prevention plan has been included in this report. 2.5.3 Minimum Requirement #3: Source Control of Pollution: Source control of pollutants is addressed with the implementation of appropriate stormwater pollution prevention BMPs including BMP T5.13 Post Construction Soil Quality and Depth. Elements of source control are indicated on the site plans and in the SWPPP narrative. 2.5.4 Minimum Requirement #4: Preservation of Natural Drainage Systems and Outfalls The natural drainage path will stay relatively the same as the existing path since stormwater flows will be routed to a bioretention facility located at the low point of the site. In the case of overflow, stormwater will be dispersed in accordance with the existing topography sloping away from the house. Minimum Requirement #5: On Site Stormwater Management This project proposes less than 5,000 sf of impervious surface and therefore must select BMPs from List #1. Full Dispersion is infeasible as the ratio of impervious area to preserved vegetation does not meet the 10% to 65%ratio. Full Infiltration is infeasible since the soils on site are considered Glacial Till and the City of Edmonds Stormwater Addendum Appendix A Infeasibility criteria prohibits Infiltration in soils that are not considered Outwash or Loam. Bioretention is feasible. Per the professional opinion of the geotech engineer infiltration is feasible utilizing the measured .76" per hour infiltration rate. Bioretention is not required to be placed in outwash or loam soils, thus, the site's Till soils will be suitable. The facility's overflow riser will have a safe overflow path offsite between the neighboring parcels; 00373600700805 and 00373600700806. The projected overflow is clear of all neighboring structures and will not propose any threats to downstream properties. The flows will reach a catch basin that leads to the stormwater utility under 217th st, to the north of the site. The proposed driveway cannot utilize Full Dispersion as there is not enough space. Permeable Pavement is infeasible due to the high cost of permeable pavement and the client does not wish to encumber the financial burden. • Bioretention will be utilized to handle flows from the proposed driveway and Type IV driveway approach leading to the site. The proposed Bioretention facility will accommodate flows from all proposed impervious area on site. The Bioretention facility has been sized using WWHM12. See Appendix A for calcs. Rogojan March 2, 2020 Stormwater Pollution Prevention Plan Narrative A Stormwater Pollution Prevention Plan (SWPPP) has been prepared as part of the construction Stormwater permit requirements. The site is 0.2 acres in size and is located at 21705 961' Ave. W, Edmonds, WA 98020-4526, with tax parcel number 00373600700802. A new asphalt driving surface is proposed to be constructed. The limits of disturbance will be +/-7,420 SF with less than 5,000 sf of proposed impervious surface triggering minimum requirements #1-5. The purpose of the SWPPP is to describe all temporary and permanent erosion and sediment control (TESC) measures, pollution prevention measures, inspection/monitoring activities, and recordkeeping that will be implemented during the proposed project. This narrative is to be considered a "living document." This project's Certified Erosion and Sediment Control Specialist is to amend this document as needed during construction. Applications of these elements are shown on the TESC Plan Sheet. The specific elements included in the SWPPP are: Element #1: Mark Clearing Limits Prior to the beginning of land disturbing activities, the clearing limits are defined on the TESC plan. Applicable BMP's for this project are: • BMP C233 - Silt Fence • BMP C 103 -High Visibility Fence Element #2 — Establish Construction Access The existing concrete driveway will be used as a temporary construction entrance. Element #3 — Control Flow Rates Applicable BMP's are shown on the TESC Plan and include: • BMP C 120-Temporary or Permanent Seeding • BMP C233 - Silt Fence Element #4 — Install Sediment Controls Specific controls include: • Temporary or Permanent Seeding (BMP C 120) • BMP C233 - Silt Fence Element #5 — Stabilize Soils Areas that are to remain uncovered for more than 7 days, are to be stabilized with BMPs. Specific BMP's to be implemented include Temporary and Permanent Seeding (BMP C 120), Mulching (BMP C 121), and Plastic Covering (BMP C 123). Element #6 — Protect Slopes Rogojan March 2, 2020 Cut and fill slopes shall be protected as necessary through use of Temporary and Permanent Seeding (BMP C 120), Mulching (BMP C 121), and Plastic Covering (BMP C 123). Element #7 — Protect Drain Inlets Inlet protection will be utilized on catch basins down gradient and in the vicinity of the disturbed areas. • BMP C220: Storm Drain Inlet Protection Element #8 — Stabilize Channels and Outlets Due to the flat nature of the site, it is not anticipated that any flows of significant velocity will leave the site or cause any negative impact to the downstream residential and commercial areas. Element #9 — Control Pollutants All pollutants, including waste materials and demolition debris, that occur onsite shall be handled and disposed of in a manner that does not cause contamination of stormwater. Good housekeeping and preventative measures will be taken to ensure that the site will be kept clean, well -organized, and free of debris. • BMP C 153-Material Storage, Delivery, and Containment Element #10 — Control Dewatering No de -watering is anticipated for this project. 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: Rogojan March 2, 2020 • Design the project to fit the existing topography, soils, and drainage patterns. • Emphasize erosion control rather than sediment control. • Minimize the extent and duration of the area exposed. • Keep runoff velocities low. • Retain sediment on site. • Thoroughly monitor site and maintain all ESC measures. • Schedule major earthwork during the dry season. Element #13 — Protection of Lid BMP's During the life of the Rogojan project all proposed BMP's on -site shall fully comply with the DOE's regulations for Element #13. Stormwater runoff from construction activities is not to enter the bioretention facility shown on the plans. Subgrade soils beneath the bioretention must be protected from compaction. High visibility fence will be used to delineate the bioretention area to be protected. If sediments enter the facility, they must be removed, and bioretention materials, and subgrade soils must be replaced as needed to ensure proper functioning. Appendix A WWHM 12 Bioretention Sizing Calcs Q Western Washington Hydrology Model DOE Version File Edit View Help Summary Report ❑a® A%Ift inni mim i na im SCENARIOS 0 Predeveloped ❑ Mitigated Run S cenario Basic Elements ®®IN® Pro Clements -1 W M ®0 Commercial T oolbox Move Elements iF Save x,y Load x y Y I� ,� Mon 8:11 a - default[-0I Finish Mitigated 2J &61M I•1i;0moil I(D(DoI Basin Help N Basin 1 Predeveloped Subbasin Neme: Basin 1 - Surface Interflow Groundwater Flows To Area in Basin Available Pervious Acres (^ A/B, Forest, Flat 0 r A/B, Forest. Mod r A/B, Forest. Steep r A/B, Pasture, Flat i" A/B, Pasture, Mod L� r A/9, Pasture, Steep 0� r- A/B, Lawn, Flat L � i- AM, Lawn, M od 0 r A/B, Lawn, S tw p r C, Forest, Rat 0 i✓ C, Forest, Mod r- C, Forest, Steep 0 r C, Pasture, Flat r C, Pasture. Mod 0 r- C, Pasture, Steep 0 j- C, Lawn, Flat j- C, Lawn, Mod 0 j- C, Lawn, Steep r- SAT, Forest, Flat 0 --''r' SAT, Forest, Mod �J r SAT, Forest, Steep 0 0 Pervious Total O.OB94 Acres Impervious Total 0 Acres Basin Tolal 0.0694 Acres r Show Only Selected Available Impervious Acres (- ROADS/FLAT r ROADS/MOD r ROADS/STEEP I- ROOFTOPS r DRVEWAYS/FLAT r DRIVEWAYS/MDD r- DRIVEWAYS/STEEP �{ r SIDEWALKS/FLAT r SIDEWALKS/MOD r SIDEWALKS/STEEP f PARKING/FLAT r- PARKING/MOD r PARKING/STEEP r POND r Porous Pavement DeselectZero ! Select By:F- GO Q Western Washington Hydrology Model DOE Version File Edit View Help Summary Report ❑ a61 A %Ift ® Fvwl Ir. � q Ib b ®I0Illil;000IiilI(D(Z)01 eosin Help F--I0® 4 Basin 1 Mitigated SCENARIOS ❑ Predeveloped ❑ Mitigated R un S cenario Basic Elements Ud- A ® U Pro Elements Commercial T oolbox Move Elements 1 Save x,y Load x y Y L= I LWJ A Mon 811 a - default[41 Finish Mitigated Subbasin Name: Basin 1 r Designate as Bypass forPOC: Surface Interflow Groundwater Flows To- Surface Swale I SurfaceSwale 1 Area in Basin Available Pervious Acres r A/B, Forest, Flat =0 r A/B, Forest. Mod r A/B, Forest. Steep r A/B, Pasture, Flat r A/B, Pasture, M od r A/B, Pashxe, Steep 0� r A/B, Lawn, Flat L� r A/B, Lawn, M od 0 r A/B, Lawn, Steep r C, Forest, Flat r%—o C, Forest, Mod L J r C, Forest, Steep 0 r C, Pasture, Flat 0 r C, Pasture. Mod 0 r C, Pasture, Steep 0 f C, Lawn, Flat r C, Lawn, Mod 0 r C, Lawn, Steep t SAT, Forest, Flat 0 Jr SAT, Forest, Mad r SAT, Forest, Steep 0 0 Pervious Total 0 Acres Impervious Total p.0894 Acres Basin Total D.OBBd Acres r Show Only Selected Available Impervious Acres r ROADS/FLAT r ROADS/MOD r ROADS/STEEP FM- p9 r ROOFTOPS f- DRIVEWAYS/FLAT r DRIVEWAYSJMOD f DRIVEWAYS/STEEP r SIDEWALKS/FIAT r SIDEWALKS/MOD r SIDEWALKS/STEEP IL� [ PARKING/FLAT PARKING/MOD r PARKING/STEEP r POND r Porous Pavement _-' I Deselect Zero ! Select By-F— GO 2 Western Washington Hydrology Model DOE Version File Edit View Zoom Help inni nimi nu im Is Schematic OC® =t rl F93� Facility Name Bioretention 1 SCENARIOS Outlet 1 Outlet 2 Outlet 3 Downstream Connection D 10 D ❑ Predeveloped ❑� Mitigated We Use simple Bioretention Quick Swale Size Water Quality Size Facility r Underdrain Used Bioretention Bottom Elevatior 0 Bioretention Dimensions Flow Through Underdrain(ac-ft) 0 Biaretention Length (It) 8,0gq Total Outflow (ac-ft) Basic Elements ®� ® ®® Bioretention Bottom Width Iftl 8.000 ®®� Freeboard (ftJ q.5gq WO Percent Filtered 100 Over -road Flooding (ftl 0.000 EflectiveTotal Depth (ft) 375 Facility Dimension Diagram ®� Pro Elements Bottom slope of bioretention.I0.1 J 0.000 c 0 Riser Dutlet structure r SidewalllnvertLocation-Outlet Structure Data Front and Back side slope JHN) 3.g00 Riser Height Above bioretention surface (It) 0 5 (" n ® 00 6_61 21 Left Side Slope (HNJ 3.000 Riser Diameter (in) 72 Right Side Slope [HIV) 3.000 Riser Type Flat i Material Layers for Layer 1 Layer 2 Layer 3 Depth IfI) P071.500 1.000 Sail Layer 1 ASTM 100 Commercial Tvvlbvx Soil Layer 2 SMMWw 12 infhr Orifice Diameter Height Soil Layer 3 GRAVEL Number (in) (1t) __1 Edit Soi[ Types 1 2 F� F� -i None r-' 2 3 �� -'i r �" None 2 4 BioretentionVolume at Riser Head (ac-ft) .025 Move Elements Show Bioretention Open Table Native Infiltration Yes Total Volume Infiltrated [acltJ 10,942 Save 8 JLoad x,y ; Measured Infiltration Rate (in/hi) 0.7g J Total Volume Through Riser Jac -It) 0 Reduction Factor (infilt'lactor) Fj_ =-I Total Volume Through Facility(ac-ft) 10142 Use Wetted Surface Area (sidewalls] yes ;-j Percent Infiltrated 100 Total Inflow ac•ft 11.465 Precipitation on Facility (acre-fl) 0.842 E vaporation from Facility (acre-ft) 0.523 Y{ f Mon 8:11 a - default(4J Finish Mitigated WWHM2012 PROJECT REPORT Project Name: default[4] Site Name: rogojan Site Address: 21705 96th Ave W City : Edmonds Report Date: 3/2/2020 Gage : Everett Data Start : 1948/10/01 Data End : 2009/09/30 Precip Scale: 0.80 Version Date: 2018/07/12 Version : 4.2.15 Low Flow Threshold for POC 1 : 50 Percent of the 2 Year High Flow Threshold for POC 1: 50 year PREDEVELOPED LAND USE Name : Basin 1 Bypass: No Groundwater: No Pervious Land Use C, Forest, Mod acre .0894 Pervious Total 0.0894 Impervious Land Use acre Impervious Total 0 Basin Total 0.0894 Element Flows To: Surface Interflow Groundwater MITIGATED LAND USE Name : Basin 1 Bypass: No Groundwater: No Pervious Land Use acre Pervious Total 0 Impervious Land Use acre ROOF TOPS FLAT 0.0625 DRIVEWAYS MOD 0.0269 Impervious Total 0.0894 Basin Total 0.0894 Element Flows To: Surface Interflow Groundwater Surface retention 1 Surface retention 1 Name : Bioretention 1 Bottom Length: 8.00 ft. Bottom Width: 8.00 ft. Material thickness of first layer: 0.25 Material type for first layer: ASTM 100 Material thickness of second layer: 1.5 Material type for second layer: SMMWW 12 in/hr Material thickness of third layer: 1 Material type for third layer: GRAVEL Infiltration On Infiltration rate: 0.76 Infiltration safety factor: 1 Wetted surface area On Total Volume Infiltrated (ac-ft.): 10.942 Total Volume Through Riser (ac-ft.): 0 Total Volume Through Facility (ac-ft.): 10.942 Percent Infiltrated: 100 Total Precip Applied to Facility: 0.842 Total Evap From Facility: 0.523 Underdrain not used Discharge Structure Riser Height: 0.5 ft. Riser Diameter: 12 in. Element Flows To: Outlet 1 Outlet 2 Bioretention 1 Hydraulic Table Stage(feet) Area(ac.) Volume(ac-ft.) Discharge(cfs) Infilt(cfs) 0.0000 0.013780 0.000000 0.0000 0.0000 0.0412 0.013577 0.000032 0.0000 0.0000 0.0824 0.013302 0.000065 0.0000 0.0000 0.1236 0.013030 0.000101 0.0000 0.0000 0.1648 0.012761 0.000138 0.0000 0.0000 0.2060 0.012495 0.000178 0.0000 0.0000 0.2473 0.012231 0.000220 0.0000 0.0000 0.2885 0.011971 0.000260 0.0000 0.0001 0.3297 0.011713 0.000302 0.0000 0.0001 0.3709 0.011458 0.000346 0.0000 0.0002 0.4121 0.011206 0.000392 0.0000 0.0003 0.4533 0.010956 0.000441 0.0000 0.0004 0.4945 0.010710 0.000492 0.0000 0.0005 0.5357 0.010466 0.000545 0.0000 0.0007 0.5769 0.010225 0.000600 0.0000 0.0009 0.6181 0.009987 0.000658 0.0000 0.0012 0.6593 0.009751 0.000719 0.0000 0.0015 0.7005 0.009519 0.000782 0.0000 0.0019 0.7418 0.009289 0.000848 0.0000 0.0024 0.7830 0.009062 0.000916 0.0000 0.0027 0.8242 0.008838 0.000987 0.0000 0.0029 0.8654 0.008617 0.001061 0.0000 0.0031 0.9066 0.008398 0.001138 0.0000 0.0032 0.9478 0.008182 0.001218 0.0000 0.0033 0.9890 0.007969 0.001300 0.0000 0.0034 1.0302 0.007759 0.001386 0.0000 0.0035 1.0714 0.007552 0.001474 0.0000 0.0037 1.1126 0.007347 0.001566 0.0000 0.0038 1.1538 0.007146 0.001661 0.0000 0.0039 1.1951 0.006947 0.001758 0.0000 0.0040 1.2363 0.006751 0.001860 0.0000 0.0042 1.2775 0.006558 0.001964 0.0000 0.0043 1.3187 0.006367 0.002072 0.0000 0.0045 1.3599 0.006179 0.002183 0.0000 0.0046 1.4011 0.005995 0.002298 0.0000 0.0047 1.4423 0.005813 0.002416 0.0000 0.0049 1.4835 0.005633 0.002538 0.0000 0.0050 1.5247 0.005457 0.002663 0.0000 0.0052 1.5659 0.005283 0.002792 0.0000 0.0053 1.6071 0.005112 0.002925 0.0000 0.0055 1.6484 0.004944 0.003062 0.0000 0.0056 1.6896 0.004779 0.003202 0.0000 0.0058 1.7308 0.004617 0.003346 0.0000 0.0059 1.7720 0.004457 0.003481 0.0000 0.0061 1.8132 0.004300 0.003619 0.0000 0.0063 1.8544 0.004147 0.003761 0.0000 0.0064 1.8956 0.003995 0.003906 0.0000 0.0066 1.9368 0.003847 0.004056 0.0000 0.0068 1.9780 0.003701 0.004209 0.0000 0.0069 2.0192 0.003559 0.004366 0.0000 0.0071 2.0604 0.003419 0.004526 0.0000 0.0073 2.1016 0.003282 0.004691 0.0000 0.0075 2.1429 0.003147 0.004860 0.0000 0.0077 2.1841 0.003016 0.005033 0.0000 0.0078 2.2253 0.002887 0.005210 0.0000 0.0080 2.2665 0.002761 0.005391 0.0000 0.0082 2.3077 0.002638 0.005576 0.0000 0.0084 2.3489 0.002518 0.005765 0.0000 0.0086 2.3901 0.002400 0.005959 0.0000 0.0088 2.4313 0.002286 0.006157 0.0000 0.0090 2.4725 0.002174 0.006360 0.0000 0.0092 2.5137 0.002065 0.006567 0.0000 0.0094 2.5549 0.001958 0.006778 0.0000 0.0096 2.5962 0.001855 0.006994 0.0000 0.0098 2.6374 0.001754 0.007215 0.0000 0.0100 2.6786 0.001656 0.007440 0.0000 0.0102 2.7198 0.001561 0.007670 0.0000 0.0104 2.7500 0.001469 0.007841 0.0000 0.0106 Surface retention 1 Hydraulic Table Stage(feet) Area(ac.) Volume(ac-ft.) Discharge(cfs) To Amended(cfs) Wetted Surface 2.7500 0.013780 0.007841 0.0000 0.0104 0.0002 2.7912 0.014059 0.008415 0.0000 0.0104 0.0004 2.8324 0.014342 0.009000 0.0000 0.0104 0.0006 2.8736 0.014627 0.009597 0.0000 0.0104 0.0009 2.9148 0.014915 0.010206 0.0000 0.0104 0.0011 2.9560 0.015206 0.010826 0.0000 0.0104 0.0013 2.9973 0.015499 0.011459 0.0000 0.0104 0.0015 3.0385 0.015796 0.012104 0.0000 0.0104 0.0018 3.0797 0.016095 0.012761 0.0000 0.0104 0.0020 3.1209 0.016397 0.013430 0.0000 0.0104 0.0022 3.1621 0.016701 0.014112 0.0000 0.0104 0.0025 3.2033 0.017009 0.014807 0.0000 0.0104 0.0027 3.2445 0.017320 0.015514 0.0000 0.0104 0.0030 3.2857 0.017633 0.016234 0.0716 0.0104 0.0032 3.3269 0.017949 0.016968 0.2257 0.0104 0.0034 3.3681 0.018268 0.017714 0.4267 0.0104 0.0037 3.4093 0.018589 0.018473 0.6597 0.0104 0.0039 3.4505 0.018914 0.019246 0.9111 0.0104 0.0042 3.4918 0.019241 0.020032 1.1671 0.0104 0.0044 3.5330 0.019571 0.020832 1.4136 0.0104 0.0047 3.5742 0.019904 0.021645 1.6378 0.0104 0.0050 3.6154 0.020240 0.022472 1.8292 0.0104 0.0052 3.6566 0.020578 0.023313 1.9818 0.0104 0.0055 3.6978 0.020919 0.024168 2.0963 0.0104 0.0057 3.7390 0.021263 0.025037 2.1826 0.0104 0.0058 3.7500 0.021356 0.025272 2.2934 0.0104 0.0019 Name : Surface retention 1 Element Flows To: Outlet 1 Outlet 2 Bioretention 1 ANALYSIS RESULTS Stream Protection Duration Predeveloped Landuse Totals for POC #1 Total Pervious Area:0.0894 Total Impervious Area:O Mitigated Landuse Totals for POC #1 Total Pervious Area:O Total Impervious Area:0.0894 Flow Frequency Return Periods for Predeveloped. POC #1 Return Period Flow(cfs) 2 year 0.001101 5 year 0.001722 10 year 0.002108 25 year 0.002558 50 year 0.002865 100 year 0.003149 Flow Frequency Return Periods for Mitigated. POC #1 Return Period Flow(cfs) 2 year 0.030344 5 year 0.041125 10 year 0.049019 25 year 0.059888 50 year 0.068657 100 year 0.078022 Stream Protection Duration Annual Peaks for Predeveloped and Mitigated. POC #1 Year Predeveloped Mitigated 1949 0.000 0.029 1950 0.001 0.036 1951 0.001 0.035 1952 0.001 0.029 1953 0.001 0.037 1954 0.002 0.047 1955 0.002 0.035 1956 0.002 0.016 1957 0.002 0.027 1958 0.001 0.069 1959 0.001 0.028 1960 0.001 0.027 1961 0.001 0.089 1962 0.001 0.035 1963 0.001 0.039 1964 0.001 0.021 1965 0.001 0.024 1966 0.001 0.024 1967 0.002 0.061 1968 0.002 0.032 1969 0.001 0.060 1970 0.001 0.024 1971 0.001 0.034 1972 0.001 0.043 1973 0.001 0.035 1974 0.001 0.044 1975 0.001 0.034 1976 0.001 0.024 1977 0.000 0.024 1978 0.001 0.018 1979 0.002 0.040 1980 0.001 0.024 1981 0.001 0.024 1982 0.001 0.025 1983 0.001 0.032 1984 0.001 0.029 1985 0.002 0.043 1986 0.004 0.040 1987 0.001 0.036 1988 0.001 0.029 1989 0.001 0.029 1990 0.001 0.022 1991 0.001 0.028 1992 0.001 0.029 1993 0.001 0.022 1994 0.000 0.023 1995 0.001 0.022 1996 0.002 0.032 1997 0.005 0.034 1998 0.001 0.039 1999 0.001 0.018 2000 0.001 0.062 2001 0.000 0.022 2002 0.001 0.021 2003 0.001 0.028 2004 0.001 0.055 2005 0.001 0.025 2006 0.003 0.031 2007 0.002 0.031 2008 0.002 0.024 2009 0.001 0.026 Stream Protection Duration Ranked Annual Peaks for Predeveloped and Mitigated. POC #1 Rank Predeveloped Mitigated 1 0.0045 0.0889 2 0.0042 0.0690 3 0.0025 0.0616 4 0.0025 0.0612 5 0.0024 0.0604 6 0.0019 0.0549 7 0.0019 0.0472 8 0.0019 0.0438 9 0.0017 0.0432 10 0.0016 0.0428 11 0.0016 0.0400 12 0.0016 0.0398 13 0.0015 0.0390 14 0.0015 0.0388 15 0.0014 0.0372 16 0.0014 0.0362 17 0.0013 0.0360 18 0.0013 0.0354 19 0.0013 0.0349 20 0.0012 0.0349 21 0.0012 0.0348 22 0.0012 0.0344 23 0.0012 0.0342 24 0.0012 0.0339 25 0.0012 0.0324 26 0.0012 0.0323 27 0.0012 0.0321 28 0.0011 0.0310 29 0.0011 0.0307 30 0.0011 0.0294 31 0.0011 0.0293 32 0.0011 0.0292 33 0.0011 0.0290 34 0.0010 0.0287 35 0.0010 0.0285 36 0.0009 0.0283 37 0.0009 0.0281 38 0.0009 0.0276 39 0.0009 0.0273 40 0.0009 0.0267 41 0.0009 0.0255 42 0.0009 0.0252 43 0.0009 0.0251 44 0.0009 0.0245 45 0.0008 0.0244 46 0.0008 0.0243 47 0.0008 0.0243 48 0.0008 0.0242 49 0.0007 0.0241 50 0.0007 0.0238 51 0.0007 0.0237 52 0.0007 0.0228 53 0.0007 0.0224 54 0.0006 0.0221 55 0.0006 0.0221 56 0.0006 0.0218 57 0.0006 0.0212 58 0.0004 0.0206 59 0.0004 0.0182 60 0.0002 0.0179 61 0.0001 0.0160 Stream Protection Duration POC #1 The Facility PASSED The Facility PASSED. Flow(cfs) Predev Mit Percentage Pass/Fail 0.0006 0 0 0 Pass 0.0006 0 0 0 Pass 0.0006 0 0 0 Pass 0.0006 0 0 0 Pass 0.0006 0 0 0 Pass 0.0007 0 0 0 Pass 0.0007 0 0 0 Pass 0.0007 0 0 0 Pass 0.0007 0 0 0 Pass 0.0008 0 0 0 Pass 0.0008 0 0 0 Pass 0.0008 0 0 0 Pass 0.0008 0 0 0 Pass 0.0009 0 0 0 Pass 0.0009 0 0 0 Pass 0.0009 0 0 0 Pass 0.0009 0 0 0 Pass 0.0009 0 0 0 Pass 0.0010 0 0 0 Pass 0.0010 0 0 0 Pass 0.0010 0 0 0 Pass 0.0010 0 0 0 Pass 0.0011 0 0 0 Pass 0.0011 0 0 0 Pass 0.0011 0 0 0 Pass 0.0011 0 0 0 Pass 0.0012 0 0 0 Pass 0.0012 0 0 0 Pass 0.0012 0 0 0 Pass 0.0012 0 0 0 Pass 0.0013 0 0 0 Pass 0.0013 0 0 0 Pass 0.0013 0 0 0 Pass 0.0013 0 0 0 Pass 0.0013 0 0 0 Pass 0.0014 0 0 0 Pass 0.0014 0 0 0 Pass 0.0014 0 0 0 Pass 0.0014 0 0 0 Pass 0.0015 0 0 0 Pass 0.0015 0 0 0 Pass 0.0015 0 0 0 Pass 0.0015 0 0 0 Pass 0.0016 0 0 0 Pass 0.0016 0 0 0 Pass 0.0016 0 0 0 Pass 0.0016 0 0 0 Pass 0.0016 0 0 0 Pass 0.0017 0 0 0 Pass 0.0017 0 0 0 Pass 0.0017 0 0 0 Pass 0.0017 0 0 0 Pass 0.0018 0 0 0 Pass 0.0018 0 0 0 Pass 0.0018 0 0 0 Pass 0.0018 0 0 0 Pass 0.0019 0 0 0 Pass 0.0019 0 0 0 Pass 0.0019 0 0 0 Pass 0.0019 0 0 0 Pass 0.0020 0 0 0 Pass 0.0020 0 0 0 Pass 0.0020 0 0 0 Pass 0.0020 0 0 0 Pass 0.0020 0 0 0 Pass 0.0021 0 0 0 Pass 0.0021 0 0 0 Pass 0.0021 0 0 0 Pass 0.0021 0 0 0 Pass 0.0022 0 0 0 Pass 0.0022 0 0 0 Pass 0.0022 0 0 0 Pass 0.0022 0 0 0 Pass 0.0023 0 0 0 Pass 0.0023 0 0 0 Pass 0.0023 0 0 0 Pass 0.0023 0 0 0 Pass 0.0024 0 0 0 Pass 0.0024 0 0 0 Pass 0.0024 0 0 0 Pass 0.0024 0 0 0 Pass 0.0024 0 0 0 Pass 0.0025 0 0 0 Pass 0.0025 0 0 0 Pass 0.0025 0 0 0 Pass 0.0025 0 0 0 Pass 0.0026 0 0 0 Pass 0.0026 0 0 0 Pass 0.0026 0 0 0 Pass 0.0026 0 0 0 Pass 0.0027 0 0 0 Pass 0.0027 0 0 0 Pass 0.0027 0 0 0 Pass 0.0027 0 0 0 Pass 0.0027 0 0 0 Pass 0.0028 0 0 0 Pass 0.0028 0 0 0 Pass 0.0028 0 0 0 Pass 0.0028 0 0 0 Pass 0.0029 0 0 0 Pass Water Quality BMP Flow and Volume for POC #1 On-line facility volume: 0 acre-feet On-line facility target flow: 0 cfs. Adjusted for 15 min: 0 cfs. Off-line facility target flow: 0 cfs. Adjusted for 15 min: 0 cfs. LID Report LID Technique Used for Total Volume Percent Water Quality Percent Comment Treatment? Needs Volume Water Quality Treatment Infiltrated Treated Volume Infiltration Cumulative Through Volume Volume Facility (ac-ft.) Infiltration (ac-ft) (ac-ft) Credit Total volume Infiltrated 0.00 0.00 0.00 0.00 0.00 0% No Treat. Credit Compliance with LID Standard 8 Duration Analysis Result = Passed Perind and Impind Changes No changes have been made. This program and accompanying documentation is provided 'as -is' without warranty of any kind. The entire risk regarding the performance and results of this program is assumed by the user. Clear Creek Solutions, Inc. disclaims 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. has been advised of the possibility of such damages. Appendix B Geotech Report from Nelson Geotechnical Associates NC7A Main Office 17311 — 135i, Ave NE, A-500 Woodinville, WA 98072 (425) 486-1669 - FAX (425) 481-2510 September 25, 2019 Mr. Al Rogojan VIA Email: bii alrogokgmail.com NELSON GEOTECHNICAL ASSCGIATES, INC. GEOTECHNICAL ENGINEERS & GEOLOGISTS Geotechnical Engineering Evaluation Rogojan 96" Avenue West Infiltration 21705 — 96" Avenue West Edmonds, Washington NGA Project No. 1130119 Dear Mr. Rogojan: Engineering -Geology Branch 5526 Industry Lane, #2 East Wenatchee, WA 98802 (509) 665-7696 • FAX (509) 665-7692 We are pleased to submit the attached report titled "Geotechnical Engineering Evaluation — Rogojan 96t°` Avenue West Infiltration — 21705 — 96'4 Avenue West — Edmonds, Washington. " This report summarizes our observations of the existing surface and subsurface conditions within the site, and provides general recommendations for the proposed site development. Our services were completed in general accordance with the proposal signed by you on August 22nd, 2019. The site consists of a rectangular -shaped parcel covering approximately 0.21 acres with an existing single- family residence structure situated within the central portion of the property. Grass covered yard areas, landscaping plants, and shrubs surround the existing structures. The property is bordered by neighboring residential lots to the north, south, and east, with driveway access extending from 96' Avenue West within the southwestern portion of the property. The ground surface within the property is relatively level to gently sloping from the southeast down to the northwest. We understand that the proposed site development will include demolishing the existing house and constructing a new single-family residence within the west - central portion of the property. In aid of preparing this report, we were provided with a preliminary site plan by BT Surveys, Inc. dated July 2019. Specific grading and stormwater handling plans were not available at the time this report was prepared. However, we do understand that stormwater generated within the property may be directed to onsite infiltrations systems, if feasible. We performed three test pit explorations within the site on September loth, 2019. Our explorations indicated that the site was underlain by competent, native glacial soils at relatively shallow depths, below a surficial layer of topsoil and/or undocumented fill. We have concluded that the site planned development is feasible. We have recommended that the new structure be founded on the native glacial soil for bearing capacity and settlement considerations. These soils should generally be encountered approximately two to four feet below the existing ground surface, based on our explorations. We also performed on -site infiltration testing in accordance with the 2012 Department of Ecology (DOE) Stormwater Management Manual for Western Washington, amended in 2014. Our on -site testing consisted of performing a small pilot infiltration test (PIT) within the eastern portion of the property. The subsurface soils generally consisted of loose -medium dense topsoil, underlain by medium dense to dense sand and Geotechnical Engineering Evaluation Rogojan 961 Ave West Infiltration Edmonds, Washington NGA File No. 1130119 September 25, 2019 Summary - Page 2 varying amounts of gravel that we interpreted as native glacial soils. Based on our field testing results, we have concluded that the site soils are marginally suitable for stormwater infiltration. In the attached report we have provided design infiltration rates. In the attached report, we also include recommendations for erosion control, site preparation and grading, structural fill, foundations, and site drainage. It has been a pleasure to provide service to you on this project. Please contact us if you have any questions regarding this report or require further information. Sincerely, NELSON GEOTECHNICAL ASSOCIATES, INC. M Khaled M. Shawish, PE Principal TABLE OF CONTENTS INTRODUCTION............................................................................................................. I SCOPE............................................................................................................................... I SITECONDITIONS......................................................................................................... 2 SurfaceConditions....................................................................................................... 2 Subsurface Conditions.................................................................................................. 2 HydrogeologicConditions........................................................................................... 3 SENSITIVE AREA EVALUATION............................................................................... 3 SeismicHazard............................................................................................................. 3 ErosionHazard............................................................................................................. 4 CONCLUSIONS AND RECOMMENDATIONS.......................................................... 4 General......................................................................................................................... 4 ErosionControl............................................................................................................ 5 Site Preparation and Grading....................................................................................... 5 Foundations.................................................................................................................. 6 StructuralFill................................................................................................................ 7 Slab-on-Grade.............................................................................................................. 8 Pavements..................................................................................................................... 8 Utilities......................................................................................................................... 9 Stormwater Infiltration................................................................................................. 9 SiteDrainage.............................................................................................................. 10 CONSTRUCTION MONITORING.............................................................................11 USE OF THIS REPORT................................................................................................ 11 LIST OF FIGURES Figure 1 — Vicinity Map Figure 2 — Site Plan Figure 3 — Soil Classification Chart Figure 4 — Log of Explorations NELSON GEOTECHNICAL ASSOCIATES, INC. Geotechnical Engineering Evaluation Rogojan 96' Avenue West Infiltration 21705 — 96' Avenue West Edmonds, Washington INTRODUCTION This report presents the results of our geotechnical engineering investigation and evaluation of the planned Residential Redevelopment project in Edmonds, Washington. The project site is located at 21705 — 961h Avenue West in Edmonds, Washington, as shown on the Vicinity Map in Figure 1. The purpose of this study is to explore and characterize the site's surface and subsurface conditions and to provide geotechnical recommendations for the planned site development. The proposed development consists of a rectangular -shaped parcel covering approximately 0.21 acres. The property is currently occupied by a single-family residence structure within the east -central portion of the property surrounded by grass -covered yard areas and scattered landscaping plants. The site is bordered by neighboring residential lots to the north, south, and east, with driveway access through the western property boundary off 961}i Avenue West. The ground surface within the property is relatively level to gently sloping from the southeast down to the northwest. We understand that the proposed site development will include demolishing the existing house and constructing a new single-family residence within the western portion of the property. In aid of preparing this proposal, we were provided with a preliminary site plan by BT Surveys, Inc. dated July 2019. Specific grading and stormwater plans were not available at the time this report was prepared. However, we do understand that stormwater generated within the property may be directed to onsite infiltrations systems, if feasible. The existing site layout is shown on the Site Plan in Figure 2. SCOPE The purpose of this study is to explore and characterize the site surface and subsurface conditions, and provide general recommendations for site development. Specifically, our scope of services includes the following: 1. Review available soil and geologic maps of the area. 2. Explore the subsurface soil and conditions within the site with trackhoe excavated test pits. 3. Provide long-term design infiltration rates based on on -site Small Pilot Infiltration Testing (PIT) per the 2014 Department of Ecology SWMMWW. 4. Provide recommendations for infiltration system installation. 5. Perform laboratory analysis on selected soil samples, as needed. NELSON GEOTECHNICAL ASSOCIATES, INC. Geotechnical Engineering Evaluation NGA File No. 1130119 Rogojan 961 Ave West Infiltration September 25, 2019 Edmonds, Washington Page 2 6. Provide recommendations for grading and site preparation 7. Provide recommendations for new foundation support 8. Provide general recommendations for site drainage and erosion control. 9. Document the results of our findings, conclusions, and recommendations in a written geotechnical report. SITE CONDITIONS Surface Conditions The site consists of a rectangular -shaped parcel covering approximately 0.21 acres. There is an existing single-family residence structure within the east -central portion of the property. The ground surface within the property is generally flat. Vegetation on the property consists of grass and landscaping shrubs throughout the property. The site is bound by residential properties to the north, east, and south, and 96' Ave West to the west. We did not observe surface water during our site visit on September 10, 2019. Subsurface Conditions Geology: The geologic units for this area are shown in the Geologic map of the Edmonds East and part of the Edmonds West quadrangles, Washington, by James P. Minard (1983). The site is mapped as glacial till (Qvt). The till is described as a poorly sorted mixture of clay, silt, sand, and pebbles. Our explorations generally encountered a surficial layer of topsoil and/or undocumented fill underlain by silty sand with gravel, in a medium dense to dense condition. It is our opinion that these soils match the description of glacial till. Explorations: The subsurface conditions within the site were explored on September 10'h, 2019 by excavating two test pits and a small-scale infiltration pit to depths ranging from 3.5 to 6.0 feet below the existing ground surface using a miniature, track -mounted backhoe. We conducted on -site infiltration testing within Infiltration Pit 1 on the same day. The approximate locations of our explorations are shown on the Site Plan in Figure 2. A geologist from NGA was present during the explorations, examined the soils and geologic conditions encountered, obtained samples of the different soil types, and maintained logs of the explorations. The soils were visually classified in general accordance with the Unified Soil Classification System, presented in Figure 3. The logs of our test pits are attached to this report and are presented as Figure 4. We present a brief summary of the subsurface conditions in the following paragraph. For a detailed description of the subsurface conditions, the test pit logs should be reviewed. NELSON GEOTECHNICAL ASSOCIATES, INC. Geotechnical Engineering Evaluation NGA File No. 1130119 Rogojan 961 Ave West Infiltration September 25, 2019 Edmonds, Washington Page 3 At the surface of Infiltration Pit 1 and Test Pits 1 and 2 we generally encountered 1.7 to 3.8 feet of dark brown to orange -brown, silty fine to medium sand with varying amounts of gravel, roots, organics, and concrete debris, which we interpreted as undocumented fill soils and/or topsoil. Underlying the fill and topsoil we encountered gray, silty fine to medium sand with gravel in a medium dense to dense condition, which we interpreted as competent native glacial material. Infiltration Pit 1 and Test Pits 1 and 2 terminated at respective depths of 3.5, 6.0, and 5.5 feet below the existing ground surface. Hydrogeologic Conditions Groundwater seepage was not observed to the depths explored. If groundwater is encountered within the site during construction, we would interpret it to be perched water and not a regional groundwater table. Perched water occurs when surface water infiltrates through less dense, more permeable soils and accumulates on top of a relatively low permeability material. Perched water does not represent a regional groundwater "table" within the upper soil horizons. Perched water tends to vary spatially and is dependent upon the amount of rainfall. We would expect the amount of perched groundwater to decrease during drier times of the year and increase during wetter periods. SENSITIVE AREA EVALUATION Seismic Hazard We reviewed the 2018 International Building Code (IBC) for seismic site classification for this project. Since dense soils are interpreted to underlie the site at depth, the site best fits the IBC description for Site Class D. Table 1 below provides seismic design parameters for the site that are in conformance with the 2018 IBC, which specifies a design earthquake having a 2% probability of occurrence in 50 years (return interval of 2,475 years), and the 2008 USGS seismic hazard maps. Table 1— 2018 IBC Seismic Design Parameters Site Class Spectral Spectral Acceleration Site Coefficients Design Spectral Acceleration at 0.2 at 1.0 sec. (g) Response sec. (g) S 1 Parameters IS, Fa Fv SDS SDI D 1.266 0.495 1.000 1.505 0.844 0.497 The spectral response accelerations were obtained from the USGS Earthquake Hazards Program Interpolated Probabilistic Ground Motion website (2008 data) for the project latitude and longitude. NELSON GEOTECHNICAL ASSOCIATES, INC. Geotechnical Engineering Evaluation NGA File No. 1130119 Rogojan 961 Ave West Infiltration September 25, 2019 Edmonds, Washington Page 4 The site is likely located within the South Whidbey Island Fault Zone (SWIFZ): an active, shallow region of seismicity within central Puget Sound stretching from the Strait of Juan de Fuca to North Bend. Information published in 2013 by the Washington State Department of Natural Resources suggests the SWIFZ last ruptured less than 2,700 years ago, and that the fault zone can produce a M7.5 earthquake. Based on available data, the risk of a surface rupture is low within the site. Hazards associated with seismic activity include liquefaction potential and amplification of ground motion. Liquefaction is caused by a rise in pore pressures in a loose, fine sand deposit beneath the groundwater table. It is our opinion that the glacial deposits interpreted to underlie the site have a low potential for liquefaction or amplification of ground motion. Erosion Hazard The criteria used for determination of the erosion hazard for affected areas include soil type, slope gradient, vegetation cover, and groundwater conditions. The erosion sensitivity is related to vegetative cover and the specific surface soil types, which are related to the underlying geologic soil units. The Soil Surveyof Snohomish County Area, Washington by the Natural Resources Conservation Service (MRCS) classifies the soil as Alderwood-Urban land complex, 2 to 8 percent slopes. Based on our experience in the area and our observations in the field, it is our opinion that the site would have a slight erosion hazard for areas where the soils are exposed. It is our opinion that the erosion hazard for site soils should be low in areas where vegetation is not disturbed. CONCLUSIONS AND RECOMMENDATIONS General It is our opinion from a geotechnical standpoint that the proposed site development is feasible. Our explorations generally encountered a surficial layer of topsoil and/or undocumented fill underlain by deposits of silty sand with gravel, in a medium dense to dense condition, consistent with the description of glacial till at depth. The native glacial soils should provide adequate support for foundation, slab, and pavement loads. We recommend that the new structure be designed utilizing shallow foundations. Footings should extend through any loose soil, and be founded on the medium dense or better native bearing soil, or structural fill extending to these soils. The competent soil should typically be encountered approximately two to four feet below the existing surface throughout the site, based on our explorations. However, if loose soils or undocumented fill are encountered during construction, this condition would require deeper excavations in foundation, slab, and pavement areas to remove the unsuitable soils. NELSON GEOTECHNICAL ASSOCIATES, INC. Geotechnical Engineering Evaluation NGA File No. 1130119 Rogojan 961 Ave West Infiltration September 25, 2019 Edmonds, Washington Page 5 We also performed on -site infiltration testing based on the 2014 WSDOE Stormwater Management Manual for Western Washington. Our explorations generally encountered silty fine to medium sand and gravel which we interpreted as native glacial soils. One small pilot infiltration test (small PIT) was conducted on the central western portion of the property. Based on our on -site testing, it is our opinion that stormwater infiltration is marginally feasible within this site. This is further discussed in the Stormwater Infiltration subsection of this report. The surficial soils encountered on this site are considered moisture -sensitive and may disturb easily when wet. We recommend that construction take place during the drier summer months, if possible. If construction is to take place during wet weather, the soils may disturb and additional expenses and delays may be expected due to the wet conditions. Additional expenses could include the need for placing a blanket of rock spalls to protect exposed subgrades and construction traffic areas. Some of the native on - site soils may be suitable for use as structural fill depending on the moisture content of the soil during construction. NGA should be retained to determine if the on -site soils can be used as structural fill material during construction. Erosion Control The erosion hazard for the on -site soils is interpreted to be slight to moderate for exposed soils, but actual erosion potential will be dependent on how the site is graded and how water is allowed to concentrate. Best Management Practices (BMPs) should be used to control erosion. Areas disturbed during construction should be protected from erosion. Erosion control measures may include diverting surface water away from the stripped or disturbed areas. Silt fences and/or straw bales should be erected to prevent muddy water from leaving the site. Disturbed areas should be planted as soon as practical and the vegetation should be maintained until it is established. The erosion potential of areas not stripped of vegetation should be low. Site Preparation and Grading After erosion control measures are implemented, site preparation should consist of removing loose soils, topsoil, and any undocumented fill from foundations, slab, and pavement areas, to expose medium dense or better native bearing soils at depth. The stripped soil should be removed from the site or stockpiled for later use as a landscaping fill. Based on our observations, we anticipate native, medium dense or better soil to be encountered at approximately two to four feet throughout the site. We should note that additional deeper areas of unsuitable soils and/or undocumented fill could be encountered in unexplored areas of the site. This condition, if encountered, would require deeper excavations in foundation, slab, and pavement areas to remove the unsuitable soils. NELSON GEOTECHNICAL ASSOCIATES, INC. Geotechnical Engineering Evaluation NGA File No. 1130119 Rogojan 961 Ave West Infiltration September 25, 2019 Edmonds, Washington Page 6 After site preparation, if the exposed subgrade is deemed loose, it should be compacted to a non -yielding condition and then proof -rolled with a heavy rubber -tired piece of equipment. Areas observed to pump or weave during the proof -roll test should be reworked to structural fill specifications or over -excavated and replaced with properly compacted structural fill or rock spalls. If loose soils are encountered in the foundation areas, the loose soils should be removed and replaced with rock spalls. If significant surface water flow is encountered during construction, this flow should be diverted around areas to be developed, and the exposed subgrades should be maintained in a semi -dry condition. If wet conditions are encountered, alternative site grading techniques might be necessary. These could include using large excavators equipped with wide tracks and a smooth bucket to complete site grading, and covering exposed subgrade with a layer of crushed rock for protection. If wet conditions are encountered or construction is attempted in wet weather, the subgrade should not be compacted, as this could cause further subgrade disturbance. In wet conditions, it may be necessary to cover the exposed subgrade with a layer of crushed rock as soon as it is exposed to protect the moisture sensitive soils from disturbance by machine or foot traffic during construction. The prepared subgrade should be protected from construction traffic and surface water should be diverted around areas of prepared subgrade. Foundations Conventional shallow spread foundations should be placed on medium dense or better native bearing soils, or be supported on structural fill or rock spalls extending to those soils. Medium dense soils should be encountered approximately two to four feet below ground surface within the site, based on our explorations. We should note that deeper areas of unsuitable soils and/or undocumented fill could be encountered in the unexplored areas of the site. Where undocumented fill or less dense soils are encountered at footing bearing elevation, the subgrade should be over -excavated to expose suitable bearing soil. The over -excavation may be filled with structural fill, or the footing may be extended down to the competent native bearing soils. If footings are supported on structural fill, the fill zone should extend outside the edges of the footing a distance equal to one half of the depth of the over -excavation below the bottom of the footing. Footings should extend at least 18 inches below the lowest adjacent finished ground surface for frost protection and bearing capacity considerations. Foundations should be designed in accordance with the 2018 IBC. Footing widths should be based on the anticipated loads and allowable soil bearing pressure. Water should not be allowed to accumulate in footing trenches. All loose or disturbed soil should be removed from the foundation excavation prior to placing concrete. NELSON GEOTECHNICAL ASSOCIATES, INC. Geotechnical Engineering Evaluation NGA File No. 1130119 Rogojan 961 Ave West Infiltration September 25, 2019 Edmonds, Washington Page 7 For foundations constructed as outlined above, we recommend an allowable bearing pressure of not more than 2,000 pounds per square foot (psf) be used for the design of footings founded on the medium dense or better native soils or rock spalls extending to the competent native material. The foundation bearing soil should be evaluated by a representative of NGA. We should be consulted if higher bearing pressures are needed. Current IBC guidelines should be used when considering increased allowable bearing pressure for short-term transitory wind or seismic loads. Potential foundation settlement using the recommended allowable bearing pressure is estimated to be less than 1-inch total and'/2-inch differential between adjacent footings or across a distance of about 20 feet, based on our experience with similar projects. Lateral loads may be resisted by friction on the base of the footing and passive resistance against the subsurface portions of the foundation. A coefficient of friction of 0.35 may be used to calculate the base friction and should be applied to the vertical dead load only. Passive resistance may be calculated as a triangular equivalent fluid pressure distribution. An equivalent fluid density of 200 pounds per cubic foot (pcf) should be used for passive resistance design for a level ground surface adjacent to the footing. This level surface should extend a distance equal to at least three times the footing depth. These recommended values incorporate safety factors of 1.5 and 2.0 applied to the estimated ultimate values for frictional and passive resistance, respectively. To achieve this value of passive resistance, the foundations should be poured "neat" against the native medium dense soils or compacted fill should be used as backfill against the front of the footing. We recommend that the upper one foot of soil be neglected when calculating the passive resistance. Structural Fill General: Fill placed beneath foundations, pavement, or other settlement -sensitive structures should be placed as structural fill. Structural fill, by definition, is placed in accordance with prescribed methods and standards, and is monitored by an experienced geotechnical professional or soils technician. Field monitoring procedures would include the performance of a representative number of in -place density tests to document the attainment of the desired degree of relative compaction. The area to receive the fill should be suitably prepared as described in the Site Preparation and Grading subsection prior to beginning fill placement. Sloping areas to receive fill should be benched using a minimum 8-foot wide horizontal benches keyed into competent soils. Materials: Structural fill should consist of a good quality, granular soil, free of organics and other deleterious material, and be well graded to a maximum size of about three inches. All-weather fill should contain no more than five -percent fines (soil finer than U.S. No. 200 sieve, based on that fraction passing the U.S. 3/4-inch sieve). Some of the more granular on -site soils may be suitable for use as structural fill; however, this will be highly dependent on the moisture content of the soil during construction. The use of NELSON GEOTECHNICAL ASSOCIATES, INC. Geotechnical Engineering Evaluation NGA File No. 1130119 Rogojan 961 Ave West Infiltration September 25, 2019 Edmonds, Washington Page 8 the on -site soils as structural fill during wet weather will be very difficult, if not impossible. We should be retained to evaluate all proposed structural fill material prior to placement. Fill Placement: Following subgrade preparation, placement of structural fill may proceed. All filling should be accomplished in uniform lifts up to eight inches thick. Each lift should be spread evenly and be thoroughly compacted prior to placement of subsequent lifts. All structural fill underlying building areas and pavement subgrade should be compacted to a minimum of 95 percent of its maximum dry density. Maximum dry density, in this report, refers to that density as determined by the ASTM D-1557 Compaction Test procedure. The moisture content of the soils to be compacted should be within about two percent of optimum so that a readily compactable condition exists. It may be necessary to over -excavate and remove wet soils in cases where drying to a compactable condition is not feasible. All compaction should be accomplished by equipment of a type and size sufficient to attain the desired degree of compaction and should be tested. Slab -on -Grade Slabs -on -grade should be supported on subgrade soils prepared as described in the Site Preparation and Grading subsection of this report. We recommend that all floor slabs be underlain by at least six inches of free -draining gravel with less than three percent by weight of the material passing Sieve #200 for use as a capillary break. We recommend that the capillary break be hydraulically connected to the footing drain system to allow free drainage from under the slab. A suitable vapor barrier, such as heavy plastic sheeting (6-mil, minimum), should be placed over the capillary break material. An additional 2-inch-thick moist sand layer may be used to cover the vapor barrier. This sand layer is optional, and is intended to be used to protect the vapor barrier membrane and to aid in curing the concrete. Pavements Pavement subgrade preparation and structural filling where required, should be completed as recommended in the Site Preparation and Grading and Structural Fill subsections of this report. The pavement subgrade should be proof -rolled with a heavy, rubber -tired piece of equipment, to identify soft or yielding areas that require repair. Any pavement section should be underlain by a minimum of six inches of clean granular pit run or crushed rock. We should be retained to observe the proof -rolling and recommend subgrade repairs prior to placement of any asphalt or hard surfaces. NELSON GEOTECHNICAL ASSOCIATES, INC. Geotechnical Engineering Evaluation Rogojan 961 Ave West Infiltration Edmonds, Washington NGA File No. 1130119 September 25, 2019 Page 9 Utilities We recommend that underground utilities be bedded with a minimum six inches of pea gravel prior to backfilling the trench with on -site or imported material. Trenches within settlement sensitive areas should be compacted to 95% of the modified proctor as described in the Structural Fill subsection of this report. Trenches located in non-structural areas should be compacted to a minimum 90% of the maximum dry density. Trench backfill compaction should be tested. Stormwater Infiltration General: The 2014 WSDOE Stormwater Management Manual for Western Washington was utilized to determine the long-term design infiltration rate of the site soils. According to this manual, on -site infiltration testing consisting of the Small -Scale Pilot Infiltration Test (PIT) and Soil Grain Size Analysis were used to determine the long-term design infiltration rates. We conducted a Small PIT within Infiltration Pit 1, as shown on the attached Site Plan in Figure 2. The subsurface soils generally consisted of silty fine to medium sand and gravel that we interpreted as native glacial soils. Small Scale PIT: The PIT test was conducted within a pit that measured 4.0-feet long by 3.0-feet wide by 3.5-feet deep. As soon as the infiltration pit was excavated, the pit was filled with 12 inches of water and we began the soaking period of the PIT for approximately 6 hours. At this time, the water flow rate into the hole was monitored with a Great Plains Industries (GPI) TM 075 water flow meter for the pre-soak period. After the 6-hour soaking period was completed, the water level was maintained at approximately 12-inches for one hour for the steady-state period. The flow rate for Infiltration Pit 1 stabilized at 0.218 gallons per minute (13.1 gallons per hour). This equated to an approximate infiltration rate of 1.75 inches per hour. The water was shut off after the steady-state period and monitored at least every 15 minutes for one hour. After 60 minutes, the water level in the pit had dropped to 10.125 inches, resulting in an infiltration rate of 1.875 inches per hour. In accordance with the Table 3.5 of the 2014 WSDOE Stormwater Management Manual for Western Washington, correction factors of 0.9, 0.5, and 0.9 for CF,,, CFt, and the long-term conductivity loss factor, respectively were applied to the field measured infiltration rate. A total correction factor of 0.405 was applied to the measured field infiltration rate obtained from the falling head portion of the test to determine the long-term design infiltration rate. The 1.875 inches per hour rate obtained from the falling head period was utilized as the overall measured field infiltration rate. NELSON GEOTECHNICAL ASSOCIATES, INC. Geotechnical Engineering Evaluation NGA File No. 1130119 Rogojan 961 Ave West Infiltration September 25, 2019 Edmonds, Washington Page 10 Using the above correction factor, we calculated a long-term design infiltration rate of approximately 0.76 inches per hour. In our opinion, a long-term design infiltration rate of 0.76 inches per hour could be utilized to design the on -site infiltration systems within the silty fine to medium sand and gravel found on this site. We recommend that the base of any on -site infiltration systems be terminated within the native glacial soils. We anticipate that the infiltration systems will encounter these soils within approximately 2.0 to 4.0 feet below existing grade. We should be retained during construction to evaluate the soils exposed in the infiltration locations to confirm that the soils are appropriate for infiltration. The stormwater manual recommends a minimum three-foot separation between the base of an infiltration system and any underlying bedrock, impermeable horizon, or groundwater. We did not encounter groundwater or any impermeable layers to the extent of our subsurface soil explorations. Material observed between 2.0 and 6.0 feet within explorations did not appear to be impermeable based on our infiltration testing. In our opinion, the maximum seasonal high groundwater level appears to be greater than three feet below the bottom of the expected infiltration trenches within this site, and as such, we do not anticipate that groundwater would impact the performance of the infiltration systems. Site Drainage Surface Drainage: The finished ground surface should be graded such that stormwater is directed to an approved stormwater collection system. Water should not be allowed to stand in any areas where footings, slabs, or pavements are to be constructed. Final site grades should allow for drainage away from the residences. We suggest that the finished ground be sloped at a minimum gradient of three percent, for a distance of at least 10 feet away from the structures. Surface water should be collected by permanent catch basins and drain lines, and be discharged into an approved discharge system. The overflow water should be directed to discharge into an approved location. Subsurface Drainage: If groundwater is encountered during construction, we recommend that the contractor slope the bottom of the excavation and collect the water into ditches and small sump pits where the water can be pumped out and routed into a permanent storm drain. We recommend the use of footing drains around the structures. Footing drains should be installed at least one foot below planned finished floor elevation. The drains should consist of a minimum 4-inch-diameter, rigid, slotted or perforated, PVC pipe surrounded by free -draining material wrapped in a filter fabric. We recommend that the free -draining material consist of an 18-inch-wide zone of clean (less than three -percent fines), granular material. Pea gravel is an acceptable drain material. The free -draining material should extend to one foot below the finished surface. The top foot of backfill should consist of impermeable soil placed over plastic sheeting or building paper to minimize surface water or fines migration into the footing drain. Footing drains should discharge into tightlines leading to an approved collection and discharge point NELSON GEOTECHNICAL ASSOCIATES, INC. Geotechnical Engineering Evaluation NGA File No. 1130119 Rogojan 961 Ave West Infiltration September 25, 2019 Edmonds, Washington Page 11 with convenient cleanouts to prolong the useful life of the drains. Roof drains should not be connected to footing drains. CONSTRUCTION MONITORING We should be retained to provide construction monitoring services during the earthwork phase of the project to evaluate subgrade conditions, temporary cut conditions, fill compaction, and drainage system installation. USE OF THIS REPORT NGA has prepared this report for Mr. Al Rogojan and his agents, for use in the planning and design of the development on this site only. The scope of our work does not include services related to construction safety precautions and our recommendations are not intended to direct the contractors' methods, techniques, sequences, or procedures, except as specifically described in our report for consideration in design. There are possible variations in subsurface conditions between the explorations and also with time. Our report, conclusions, and interpretations should not be construed as a warranty of subsurface conditions. A contingency for unanticipated conditions should be included in the budget and schedule. We recommend that NGA be retained to provide monitoring and consultation services during construction to confirm that the conditions encountered are consistent with those indicated by the explorations, to provide recommendations for design changes should the conditions revealed during the work differ from those anticipated, and to evaluate whether or not earthwork and foundation installation activities comply with contract plans and specifications. We should be contacted a minimum of one week prior to construction activities and could attend pre -construction meetings if requested. Within the limitations of scope, schedule, and budget, our services have been performed in accordance with generally accepted geotechnical engineering practices in effect in this area at the time this report was prepared. No other warranty, expressed or implied, is made. Our observations, findings, and opinions are a means to identify and reduce the inherent risks to the owner. NELSON GEOTECHNICAL ASSOCIATES, INC. Geotechnical Engineering Evaluation Rogojan 961 Ave West Infiltration Edmonds, Washington NGA File No. 1130119 September 25, 2019 Page 12 It has been a pleasure to provide service to you on this project. If you have any questions or require further information, please call. Sincerely, NELSON GEOTECHNICAL ASSOCIATES, INC. Austin J. Slabaugh Staff Geologist Khaled M. Shawish. PE Principal AJS:KMS:dy Four Figures Attached NELSON GEOTECHNICAL ASSOCIATES, INC. VICINITY MAP Not to Scale __D9�m1---wurnta 1dS0 y Z Ed nonds Main St Main St )rids Kin ton rry Toll Bdoth 11 -��' y yy Maple Wey � E ids Maple SI S y n Maple St y Yost Pool Q Caffe Ladro Edmonds e Alder St 0 Alder St Glrardl's Osteria © m 9acktn " Yost Park 3� walnut St Inds Shelleberger Ilclly Dr cedar S1 ©�, ` Bar Dojo 2112th sh Creek o• Spruce St Spruce St - pion s f Edmonds n m N Project City Park y p m < Hemlock Way N Hemlock St m B a OW�Q1n wv'' ry N n y N 214thPISWSite Laurel St Q Puget Sound D Christian Church Q N Pine St Pine Sr Pacific Salmon 0216th PI SW�'Forsyth 216th St SW In > J1 SVI D 217m St sv' < (D m y — 5 D n Y N D m N I It St 2181h w > a St SW a z PINE PARK a Iglesia Cristiana NEIGHBORHOOD = 'CristoVive'® n creek rim St Westgate a 220th St SW Q 220th St SW !' 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N A 1130119 Development Infiltration p 1 9/17/19 Original DPN ABR GEOTECHNICAL ENGINEERS & GEOLOGISTS E Figure 1 Vicinity Map Woodinville ve nrticA East Wenatchee Office s J (i •`� Ave. 98A-500 55261ndustry Lane, 88 17 Woodi-ill., Woodinville, WA 98072 East Wenatchee, WA 98602 J (425) 486-1669 / Fax: 481-2510 w.nelsonyeotech.com (509) 665-7696 / Fax: 665-7692 = o , 1D 0 < REBAR h CAP — CD _ 0 ` 7 CD CD 1y N 7 IN3 � Q .- CD N 0 . m � s rn D =sF m $gw8 Z N b 0 /1 l7 Y� � Z m z DN N m O Z "s m n G1 3 y D m >P i O SET REBAR R CAP N m aEP= m _n Raim�'. Z 0 Z �ndi o o Rm" N n R»Y 4 D r LEGEND Property line d 8 ro INF-1 Number and approximate 0. S._�_ o location of infiltration test pit ' TP-1 Number and approximate location of test pit 0 A Reference: Site plan based on a plan dated Jul \HILL\company\2019 NGA Project Folders\11301-19 Rogojan 96th Ave W Edmonds Infltration0n Site Plan RNER OF CHAINLINK FENCE 1.2 N. OF PROPERTY LINE TP-2 I I LOT 8 PARCE ,# 00735MMIM N 69'44'46' W 126.01 N • • • • • • SET REBAR h CAP TP-1 ., ......1—V- 20.E Existing N Residence A,4j6, CORNER OF WOOD FENCE IS 1.0 N. OF PROPERTY LINE 0 20 40 Scale: 1 inch = 20 feet UNIFIED SOIL CLASSIFICATION SYSTEM GROUP MAJOR DIVISIONS GROUP NAME SYMBOL CLEAN GW WELL -GRADED, FINE TO COARSE GRAVEL COARSE- GRAVEL GRAVEL GP POORLY -GRADED GRAVEL GRAINED MORE THAN 50 GM OF COARSE FRACTION OF SILTY GRAVEL RETAINED ON SOILS NO.4 SIEVE WITH FINES GC CLAYEY GRAVEL SAND CLEAN SW WELL -GRADED SAND, FINE TO COARSE SAND SAND SP POORLY GRADED SAND MORE THAN 50 % RETAINED ON MORE THAN 50 % NO. 200 SIEVE OF COARSE FRACTION SAND SM SILTY SAND PASSES NO. 4 SIEVE WITH FINES SC CLAYEY SAND FINE - SILT AND CLAY ML SILT INORGANIC GRAINED LIQUID LIMIT CL CLAY LESS THAN 50 % SOILS ORGANIC OL ORGANIC SILT, ORGANIC CLAY SILT AND CLAY MH SILT OF HIGH PLASTICITY, ELASTIC SILT INORGANIC MORE THAN 50 % PASSES LIQUID LIMIT CH CLAY OF HIGH PLASTICITY, FAT CLAY NO. 200 SIEVE 50 % OR MORE ORGANIC OH ORGANIC CLAY, ORGANIC SILT HIGHLY ORGANIC SOILS PT PEAT NOTES: 1) Field classification is based on visual SOIL MOISTURE MODIFIERS: examination of soil in general accordance with ASTM D 2488-93. Dry - Absence of moisture, dusty, dry to the touch 2) Soil classification using laboratory tests is based on ASTM D 2488-93. Moist - Damp, but no visible water. 3) Descriptions of soil density or Wet - Visible free water or saturated, consistency are based on usually soil is obtained from interpretation of blowcount data, below water table visual appearance of soils, and/or test data. Project Number NELSON GEOTECHNICAL No. Date Revision By CK 1130119 Rogojan Residence NGA ASSOCIATES, INC. Development Infiltration GEOTECHNICAL ENGINEERS & GEOLOGISTS 1 9/17/19 Original DPN ABR Figure 3 Soil Classification Chart Woodinville Office East Wenatchee Office 17311-135th Ave. NE, A-500 5526Industry Lane, #2 Woodinville, WA 98072 East Wenatchee, WA 98802 (425)486-16691 Fax: 481-2510 w.nelsongeotech.com (509) 665-7696 1 Fax: 665-7692 LOG OF EXPLORATION DEPTH (FEET) USC SOIL DESCRIPTION INFILTRATION PIT ONE 0.0 - 1.7 GRASS UNDERLAIN BY DARK BROWN TO LIGHT BROWN, SILTY FINE TO MEDIUM SAND WITH GRAVEL, ROOTS, AND ORGANICS (LOOSE TO MEDIUM DENSE, MOIST) (FILL) 1.7 - 3.5 SM GRAY, SILTY FINE TO MEDIUM SAND WITH GRAVEL (MEDIUM DENSE TO DENSE, MOIST) SAMPLE WAS NOT COLLECTED GROUNDWATER SEEPAGE WAS NOT ENCOUNTERED TEST PIT CAVING WAS NOT ENCOUNTERED TEST PIT WAS COMPLETED AT 3.5 FEET ON 9/10/2019 TEST PIT ONE 0.0 - 3.8 GRASS UNDERLAIN BY LIGHT BROWN TO BROWN, SILTY FINE TO MEDIUM SAND WITH ROOTS, GRAVEL, ORGANICS, AND TRACE CONCRETE DEBRIS (LOOSE TO MEDIUM DENSE, DRY TO MOIST) (FILL) 3.8 - 6.0 SM GRAY, SILTY FINE TO MEDIUM SAND WITH GRAVEL (MEDIUM DENSE TO DENSE, MOIST) SAMPLE WAS NOT COLLECTED GROUNDWATER SEEPAGE WAS NOT ENCOUNTERED TEST PIT CAVING WAS NOT ENCOUNTERED TEST PIT WAS COMPLETED AT 6.0 FEET ON 9/10/2019 TEST PIT TWO 0.0 - 2.4 GRASS UNDERLAIN BY ORANGE -BROWN TO LIGHT BROWN, SILTY FINE TO MEDIUM SAND WITH ROOTS, GRAVEL, AND ORGANICS (LOOSE TO MEDIUM DENSE, DRY TO MOIST) (FILL) 2.4 - 5.5 SM GRAY, SILTY FINE TO MEDIUM SAND WITH GRAVEL (MEDIUM DENSE TO DENSE, MOIST) SAMPLES WERE COLLECTED AT 3.5 AND 5.0 FEET GROUNDWATER SEEPAGE WAS NOT ENCOUNTERED TEST PIT CAVING WAS NOT ENCOUNTERED TEST PIT WAS COMPLETED AT 5.5 FEET ON 9/10/2019 ABR:KMS NELSON GEOTECHNICAL ASSOCIATES, INC. FILE NO 1130119 FIGURE 4 Appendix C Record of Survey from BT Surveying P�137W PLACE SW (MONUMENT) PUNCHED BRASS DISK IN CONIC. IN CASE n0^ GRAPFIIC SCALE 56 Sb CONCRETE WALL END OF CHAMUNK FENCE (O PO2) 1 MY Fv,+ IS 1.5 N. OF PROPERTY LINE / _ _ _ _._•_._•-•_._._•-•_._._. _._._ _._._ _ _ _ _ _ _ _ _ _ _ _ _ •128.01 _ _ _ _._ i SET REBAR A CAP{_ S BB'4448 E �T&EBAR k CAP GPI COWER OF FENCE IS 1.2 N. OF PROPERTY Y L9RE �O 13.8 f .0 cl ALL DIMENSIONS SHOWN Y.0 ARE TO THE FACADE OF 20.7 R. S THE HOUSES F007 PRINT, / FINISH FLOOR EL_ 3BCK bl 1A C EST ROOF DOE Y ' /ELL-/3/7¢A 2 30.1 b LOT8 iPARCCEL# OW73SM703M 3 30• 0 9 I` CORNER OF W000 FENCE b 4y,' i IS 1.D N. OF PROPERTY LINE I 3— SET REBAR Q CAP N 8R44'46' W 126.01 0-0 o-ob-o-o-- i LEGAL DESCRIPTION THE VEST 126 FEET OF THE SOUTH 70 FEET OF LOT B, BLOCX SET REBAR ee CAP G.,. 7, ALDER VNOD MANOR NO. 9 ACCORDING TO THE PLAT THEREOF. RECORDED IN VOLUME 10 OF PLATS. PACE 0, oRECORDS OF SNOHOMISH COUNTY. WASHINGTON. �SH p�AY -{y�ty� (MONUMENT) P JE S ROD BASIS OF BEARING /^/ o N CONOBRN I q WASHING70N STATE PLANE GRID SYSTEM (NORTH ZONE). p_ W1 INSTRUMENT k PRECISION LEICA TCR 40S TOTAL STATION WITH A OIC CPS RECEIVER �I g w TRAVERSE EXCEEDS 1:20,000. CLOSURE o I A6EA �I (MONUMENT) bll21. SOUAf1E FEET OR 0.2 ACRES PUNCHED BRASS ROD NQg: `I N BB'JB'S3' W 1 853.06' N BB'38'S3' W �_`J IN CONIC. IN CASE, DISTANCES ARE IN FEET, TEN7NB AND HUNDREDTHS OF A POOL 0.21 SOUTH OF MON LINE CONVERSION TO INCH'= DIVIDE DECIMAL FEET BY 0.0833333 (MONUMENT) EAST 1/4 CORNER, PUN CNm BRASS DISK_____: 4J9.BB' -By�r y IN CONC. IN CASE (MONUMEN Z__________________N _ N BB39'33' IF 887.18' IASIBLE USED I—WTH PLACE WEST IN CAN THE SE 1 /4 OF THE NE 1 /4 OF SECTION 25. TOWNSHIP 27 NORTH. RANGE 03 EAST. W.M.. SNOHOMISH WASHINGTON RECORDERS CERTIFICATE SURVEYOR'S CERTIFICATE RECORD OF Filed for record this — day of ,20__pt _ M. Thl. map camatby represents a survey made by me or LAl�SIDRI�Yl1G AL ROGOJAN In Book —of Surreyo at page _ t the request of BY SURVEYS INC under my direction In aonformanae With tna requirements of the Survey Retarding Act at the request of �BT SURVEYS INC 21705 98TM AVE WEST EDMONDS, WASHINGTON 98020 JOB 19035 SHEET 1 OF 1 DRA BY EIR COUNTY AUDITOR, RECORDS DIVISION AL ROGOJAN in JULY . 2019 12415 Mx DANE SF NERETT, WA91Ma1rX1 02M w6-eol-lmo Count Auditor Deputy Recorder Surw d b Brian Raaum Certificate Number J7534 -ATE: 7-19I SCALE: 1- = 10' 1CRECKED BY OR Appendix D Maintenance and Operations Table V-4.5.2(5) Maintenance Standards - Catch Basins Results Maintenance Conditions When Maintenance is Expected Component Defect Needed When Main- tenance is performed No Trash or debris loc- Trash or debris which is located imme- ated imme- diately in front of the catch basin opening or diately in is blocking inletting capacity of the basin by front of catch more than 10%. basin or on Trash or debris (in the basin) that exceeds grate open- 60 percent of the sump depth as measured ing. from the bottom of basin to invert of the low- No trash or est pipe into or out of the basin, but in no debris in the Trash & case less than a minimum of six inches catch basin. Debris clearance from the debris surface to the invert of the lowest pipe. Inlet and out- let pipes free Trash or debris in any inlet or outlet pipe of trash or blocking more than 1/3 of its height. debris. General Dead animals or vegetation that could gen- No dead erate odors that could cause complaints or animals or dangerous gases (e.g., methane). vegetation present within the catch basin. Sediment (in the basin) that exceeds 60 per- cent of the sump depth as measured from the bottom of basin to invert of the lowest pipe into or out of the basin, but in no case No sediment Sediment less than a minimum of 6 inches clearance in the catch from the sediment surface to the invert of the basin lowest pipe. Structure Top slab has holes larger than 2 square Top slab is Damage to inches or cracks wider than 1/4 inch. (Intent free of holes Frame and/or is to make sure no material is running into and cracks. Top Slab basin). Frame is sit- 2014 Stormwater Management Manual for Western Washington Volume V - Chapter 4 - Page 838 Table V-4.5.2(5) Maintenance Standards - Catch Basins (continued) Results Maintenance Conditions When Maintenance is Expected Component Defect Needed When Main- tenance is performed Frame not sitting flush on top slab, i.e., sep- ting flush on aration of more than 3/4 inch of the frame the riser rings from the top slab. Frame not securely or top slab attached and firmly attached. Basin Maintenance person judges that structure is replaced or unsound. repaired to Fractures or design stand - Cracks in Grout fillet has separated or cracked wider ards. Basin Walls/ than 1/2 inch and longer than 1 foot at the g Bottom joint of any inlet/outlet pipe or any evidence Pipe is of soil particles entering catch basin through regrouted cracks. and secure at basin wall. Basin Settlement/ If failure of basin has created a safety, func- replaced or Misalignment tion, or design problem. repaired to design stand- ards. No veget- Vegetation growing across and blocking ation block - more than 10% of the basin opening. ing opening to basin. Vegetation Vegetation growing in inlet/outlet pipe joints No that is more than six inches tall and less veget- than six inches apart. ation or root growth present. Contamination See "Detention Ponds" (No. 1). No pollution and Pollution present. Cover Not in Cover is missing or only partially in place. Catch basin Catch Basin Place Any open catch basin requires main- cover is tenance. closed Cover Locking Mech- Mechanism cannot be opened by one main- Mechanism anism Not tenance person with proper tools. Bolts into opens with 2014 Stormwater Management Manual for Western Washington Volume V - Chapter 4 - Page 839 Table V-4.5.2(5) Maintenance Standards - Catch Basins (continued) Results Maintenance Conditions When Maintenance is Expected Component Defect Needed When Main- tenance is performed Working frame have less than 1/2 inch of thread. proper tools. One maintenance person cannot remove lid Cover can be Cover Difficult after applying normal lifting pressure. removed by to Remove (Intent is keep cover from sealing off access one main - tenance per - to maintenance.) son. Ladder meets design stand Ladder Rungs Ladder is unsafe due to missing rungs, not ards and Ladder Unsafe securely attached to basin wall, mis- allows main - alignment, rust, cracks, or sharp edges. tenance per- son safe access. Grate open - Grate opening Grate with opening wider than 7/8 inch. ing meets Unsafe design stand- ards. Metal Grates Trash and Trash and debris that is blocking more than Grate free of (If Applic- Debris 20% of grate surface inletting capacity. trash and able) debris. Grate is in Damaged or Grate missing or broken member(s) of the place and Missing. grate. meets design standards. Table V-4.5.2(6) Maintenance Standards - Debris Barriers (e.g., Trash Racks) Maintenance Condition When Maintenance is Results Expected Com- Defect When Maintenance is ponents Needed Performed Trash and Trash or debris that is plugging Barrier cleared to design General Debris more than 20% of the openings in flow capacity. the barrier. Damaged/ Bars are bent out of shape more Bars in place with no Metal Missing than 3 inches. bends more than 3/4 2014 Stormwater Management Manual for Western Washington Volume V - Chapter 4 - Page 840 Table V-4.5.2(6) Maintenance Standards - Debris Barriers (e.g., Trash Racks) (continued) Maintenance Com- ponents Defect Condition When Maintenance is Needed Results Expected When Maintenance is Performed inch. Bars are missing or entire barrier missing. Bars in place according Bars. Bars are loose and rust is causing to design. 50%deterioration to any part of bar- Barrier replaced or rier. repaired to design stand- ards. Inlet/Outlet Debris barrier missing or not Barrier firmly attached to Pipe attached to pipe pipe Table V-4.5.2(7) Maintenance Standards - Energy Dissipaters Results Expec- Maintenance Conditions When Maintenance is led When Main Components Defect Needed tenance is Performed External: Missing or Only one layer of rock exists above nat- Rock pad Moved ive soil in area five square feet or lar- replaced to Rock ger, or any exposure of native soil. design stand - ards. Rock Pad Rock pad Erosion Soil erosion in or adjacent to rock pad. replaced to design stand- ards. Pipe Pipe cleaned/ - Plugged Accumulated sediment that exceeds flushed so that with Sed- 20% of the design depth. it matches iment design. Not Dis- Visual evidence of water discharging Trench at concentrated points along trench Dispersion Trench charging normal condition is a "sheet flow" of redesigned or Water Prop- rebuilt to stand - water along trench). Intent is to prevent erly ards. erosion damage. Perforations Over 1/2 of perforations in pipe are Perforated pipe Plugged. plugged with debris and sediment. cleaned or replaced. 2014 Stormwater Management Manual for Western Washington Volume V - Chapter 4 - Page 841 Table V-4.5.2(7) Maintenance Standards - Energy Dissipaters (continued) Results Expec- Maintenance Defect Conditions When Maintenance is ed When Main Components Needed tenance is Performed Water Maintenance person observes or Flows Out receives credible report of water flow- Facility rebuilt Top of "Dis- ing out during any storm less than the or redesigned tributor" design storm or its causing or appears to standards. Catch likely to cause damage. Basin. Receiving Water in receiving area is causing or No danger of Area Over- has potential of causing landslide prob-landslides. Saturated lems. Internal: Worn or Structure dissipating flow deteriorates Damaged to 1/2 of original size or any con- Structure Manhole/Chamber , Post Post,Baffles, centrated worn spot exceeding one replaced to design stand - Side of square foot which would make struc- ards. Chamber ture unsound. Other See "Catch Basins" (No. 5). See "Catch Bas Defects ins" (No. 5). Table V-4.5.2(8) Maintenance Standards - Typical Biofiltration Swale Maintenance Component Defect or Prob- lem Condition When Maintenance is Needed Recommended Maintenance to Correct Problem Remove sediment deposits on grass treatment area of the bio-swale. SedimentAccu- Sediment depth When finished, swale should be level mulation on exceeds 2 from side to side and drain freely Grass inches. toward outlet. There should be no areas of standing water once inflow General has ceased. When water Any of the following may apply: stands in the remove sediment or trash blockages, Standing Water swale between improve grade from head to foot of storms and does swale, remove clogged check dams, not drain freely. add underdrains or convert to a wet 2014 Stormwater Management Manual for Western Washington Volume V - Chapter 4 - Page 842 Appendix E Bio-Retention Location Email Richardson, Zachary From: Donna Breske <donnab@donnabreske.com> Sent: Monday, June 1, 2020 12:04 PM To: Richardson, Zachary Cc: Lambert, Jennifer Subject: Re: BLD20191496 Hi Zach, The previous design location was too far uphill in the back yard. I changed all the pipe to 6 inch pvc at 1 percent slope, ( as opposed to 4 inch at 2 percent minimum slope) in order to get all the grades to work. This design places the bioretention as far away from the downhill property line, while at the same time harmonizing all the pipe slopes for the conveyance path of stormwater to travel to bioretention. Also, LID BMPs are to be designed to the maximum extent feasible, ( not to life and safety standards, say like the engineering design for a Boeing Airplane.) The design I present meets the maximum extent feasible standard in my professional opinion. Sincerely, Donna L. Breske, PE 21 Ave A, Suite 4, Snohomish, WA 98290 Mobile: 206-715-9582 Phone: 360-294-8941 Donna Breske As sod ates From: Richardson, Zachary <Zachary.Richardson @edmondswa.gov> Sent: Monday, June 1, 2020 6:25 AM To: Donna Breske <donnab@donnabreske.com> Cc: Lambert, Jennifer <Jennifer.Lambert@edmondswa.gov> Subject: RE: BLD20191496 I see you shifted the rain garden location again, but the previous location was far preferred. The last location you had shown lengthen the overflow path significantly before impacting other property and kept it as far from the slope as possible. Is there a the BMP had to shift again? Unless its infeasible, we would prefer the previous design location (further south). Zachary Richardson, PE Stormwater Engineer I City of Edmonds 121-5th Ave N Edmonds, WA 98020 425.771.0220 Ext. 1323 Zachary. Richardson(aDedmondswa.gov CITY HALL IS CURRENTLY CLOSED TO THE PUBLIC Services will continue to be provided by email and phone. Please visit www.edmondswa.gov for up-to-date information Appendix F Resident Letter Mirel Al and Magdalena Rogojan 23828 Brier Rd Brier, WA 98036 Date: January 21, 2021 RE: BLD2019-1496 / 21705 96th Ave W To: Zachary Richardson, PE CC: Rob English, City of Edmonds, City Engineer RESUB Jan 21 2021 CITY OFEDMONDS BLD219-1496 DEVELOPMENT SERVICES DEPARTMENT Jeannie McConnell, City of Edmonds, Engineering Program Jennifer Lambert, City of Edmonds, Engineering Technician III After receiving the documents from the city of Edmonds asking us to sign the OVERFLOW/FLOODING INDEMNITY COVENANT (second covenant) we reached out for legal advice from the offices of Brian D Amsbary, PLLC. Following consultations with our attorney and after studying the documents presented to us including the draft letter intended for the downstream neighbors, we would like to give a response to the City of Edmonds and firmly state our reasons for not accepting to sign the OVERFLOW/FLOODING INDEMNITY COVENANT (second covenant). In addition, our attorney has contacted Jeff Taraday with LightHouse Law Group, PLLC, who represents the City of Edmonds. After months of no resolution, we intend to present our position on the matter. In this letter we would like to point out what we believe to be several of the (second covenant) document's flaws and examples of the city's abuse of authority. There also appears to be double standard and lack of transparency on behalf of the city when we're presented with one set of requirements, while our neighbors are given a different set of facts. The document (second covenant) contradicts on many levels the information (that would be) provided to downstream neighboring properties as demonstrated in the city's proposed letter to them. As a result, we question the city's motives as to why we're singled out to sign such a document. Again, the assertions of second covenant are simply false and we cannot sign such document. 1. The title of the document OVERFLOW/FLOODING INDEMNITY COVENANT contradicts the very purpose of requiring the installation of the bioretention system meant to manage the runoff from the rooftop of proposed house and proposed driveway. (a) The Superior Court decision in Current v. Sleek, 138 Wn.2d 858— September 9, 1999 underscores: Waters - Surface Water- Common Enemy Rule - Scope. Under the common enemy rule, a landowner may alter the flow of surface water without incurring liability for surface water flooding damage to neighboring properties so long as the landowner does not inhibit the flow of a watercourse or natural drainway or collect and discharge water onto the neighboring property in quantities greater than, or in a manner different from its natural flow. Since we're not dumping any water on adjoining properties by fulfilling required mitigation for managing stormwater, the question of liability should not even be presented. (b) Furthermore, the draft letter addressed to downstream neighboring properties RECOGNIZES and STATES the following: The City has reviewed the project engineers work and notes that the design does successfully demonstrate infiltration of the full 100 year storm, leaves additional storage/freeboard in the bioretention facility above that shown in the design calculation, and includes a dispersion trench (an additional BMP) to mimic natural sheet flow. It is also noted that any overflow from a drainage system on this site, even if pumping uphill was permitted, likely would follow the natural topography toward your and your neighbor's properties. Because drainage ALREADY flows in that direction today, WE DO NOT BELIEVE WE HAVE A BASIS TO DENY the proposed development permit... Accordingly, the project is likely to be approved as meeting the City's stormwater code as submitted. If our project meets stormwater code as submitted, why are we presented with the additional hurdle/demand to sign a second covenant? 2. In your second covenant you state "WHEREAS, the project engineer has designed a storm water mitigation system that demonstrates runoff up to the 100year storm will be infiltrated within the property boundaries." The second covenant fails to recognize the conclusion communicated on August 13, 2020 email (at 2:30 pm) between Donna Breske, PE and Doug Beyerlein, PE, PH, D. WRE with Clear Creek Solution, Inc. In the referenced email, where it is clearly stated that the sizing of bioretention proposed system for our project will get 100% infiltration including 100-year storm. The chart and graph in the email dated August 17, 2020 at 10:39 am between Donna Breske, PE and Doug Beyerlein, PE, PH, D. WRE with Clear Creek Solution, Inc demonstrate zero flow to be anticipated from the bioretention including 100-year storm. Any overflow from the bioretention (related to a storm bigger than 100-years storm) would be managed by the dispersion trench (an additional BMP) before mimicking the natural drainage course. One additional flaw of your statement is the fact that while the second covenant denies the above conclusion it contradicts the very statement expressly spelled out in the letter to the downstream neighbors where the city DOES recognize the following: the design does successfully demonstrate infiltration of the full 100 year storm, leaves additional storage/freeboard in the bioretention facility above that shown in the design calculation, and includes a dispersion trench (an additional BMP) to mimic natural sheet flow. 3. Per your document (second covenant) our project satisfied all elements of the drainage code with the exception of "the absence of safe and certain overflow route." Again, this is a contradiction since the natural drainage path that surface waters have always followed will not change. Again, allow us to state that the letter to downstream neighboring properties recognizes that "drainage already flows in that direction today." In addition, the proposed project "will collect no more water than it does now and it will discharge less thanks to the new stormwater system. If a bigger storm than 100-years does hit, any overflow will mimic the natural sheet flow along the natural drainage path thanks to the dispersion trench." (text from letter of Brian D. Amsbary, PLLC to Jeff Taraday of Lighthouse Law Group). Thus, your concern for overflow and flooding is unfounded and the contradictions between the two documents is unacceptable. 4. You also further state, "under certain exceptions to the Common Enemy Doctrine, the Owner would likely have liability for any damage..." The City's statement unfairly singles out our project by bankrupting our legal protection summarized by the Common Enemy Doctrine as decided in Current v. Sleek, 138 Wn. 2d 858 (1999). The Common Enemy Doctrine provides that storm and other surface waters are a common enemy to all, and a property owner is entitled to dispose of such waters off of his or her property so long as the waters are not artificially collected and discharged in quantities greater or in a manner different than the natural flow. As stated previously, Donna Breske, PE has shown that our redeveloped site, by having bioretention and a dispersion trench, will improve management of stormwater and surface water while preserving watercourse and natural drainways. Thus, we should benefit from the Superior Court's decision since, in good faith, our project complies with DOE Manual. The above -named decision (Current v. Sleek) also states that "Courts should not change or alter a rule of law for light or transient reasons." Thus, the City is overstepping its authority above and beyond the decision of the Superior Court. 5. Another firm reason for our unyielding refusal to sign this illegal document is because "this covenant expressly includes, without limitation, any and all claims, injuries, liabilities, losses, damages, demands, or suits brought by owners of adjacent property for flooding damage." The City's statement here gives full protection to city officials whether intentional or unintentional, while at the same time stripping us of all legal protections. The City's OVERFLOW/FLOODING INDEMNITY COVENANT, the instrument itself, proves intentional misconduct on behalf of the city by using the terms "without limitation, any and all claims" and by demanding signature of such illegal document in exchange for getting the permit. In good faith, we have already signed a DECLARATION of COVENANT -PRIVATE STORMWATER FACILITY (dated May 11,2020) protecting the City of Edmonds, but these new terms outlined in the OVERFLOW/FLOODING INDEMNITY COVENANT are unacceptable. 6. One final point to underscore our inability to concede to the terms of the proposed covenant is the City's interpretation that "the Owner would benefit from the permit being issued." Does this specific language imply that we should be compelled to sign an (un)lawf it covenant? We can only conclude this to be an overreach of power on behalf of city officials whose legitimate responsibilities are to determine if applicable development regulations have been satisfied. Instead, city officials are blackmailing and punishing us for not accepting their (il)legal terms. We have never been provided —even though it was requested by our civil engineer the documentation that this legal interpretation comes from the Edmonds City attorney. Per e-mail dated August 10, 2020 from Zachary Richardson to Donna Breske, "the City attorney was consulted and the email below was the conclusion." If such is the case, we are entitled to written documentation expressly spelling out the legal opinion of the City's legal adviser, Mr Jeff Taraday before being demanded by the city to concur to such unacceptable terms. Since you have refused to provide this written conclusion from the City legal adviser, we can rightfully find that such document does not exist and this interpretation is strictly that of City Officials. The OVERFLOW/FLOODING INDEMNITY COVENANT expressly spells out that this is a concern of the city — indicating that the law and municipal codes have been met. The attempt on behalf of the city to over -ride applicable development regulations is, as stated numerous times in this letter, an overreach and abuse of power on behalf of the City of Edmonds. The second option offered by the City Officials was that of procuring an easement from the downstream neighbors. This is also an overreach on the part of the city to require such document from our neighbors and it is unacceptable to them since such easement will de -value their respective properties. The second reason this is unacceptable refers to the fact that there already exists a natural drainage path which would not be disturbed by our project. In addition, as shown above, the proposed project would actually will improve management of stormwater and surface water while preserving watercourse and natural drainways. Again, it is noteworthy to point out that the letter to downstream neighbors expressly recognizes that "any overflow from a drainage system on this site ... likely would follow the natural topography toward your and your neighbor's properties." If such assertion is true, there is no need for easement from those neighboring properties since stormwater already follows natural topography today. We feel that the additional request for a second covenant is an overreach and abuse of power on behalf of the city causing undue, unreasonable, and unfair hardship on a permitting process that has continuously hurdled numerous demands from the Stormwater Engineering Department. The various e-mails and the many requests our Civil Engineer had to overcome stand testament to this. We have already offered the City of Edmonds the Covenant dated May 11, 2020 which protects the City by making us responsible for the construction, maintenance and operation of the proposed Stormwater system on the owner's property. The additional (il)legal terms demanded by the second covenant are contingencies we cannot accept or surrender to. In conclusion, we request that the City of Edmonds remove its conditional approval of our building permit requiring an OVERFLOW/FLOODING INDEMNITY COVENANT, since we have fulfilled all elements of the drainage code. Sincerely, Mirel Al and Magdalena Rogojan Appendix G Approval memo MEMORANDUM City of Edmonds Engineering Division Date: March 15, 2021 To: BLD2019-1496 File From: Zachary Richardson, City of Edmoi Subject: Storm Approval for BLD2019-1496 This memo is intended document the decision process prior to approval of permit BLD2019-1496 after reviewing the applicant submittal letter dated 1/21/2021. Without implying any warranty or approval of specifical claims or statements made in said letter, the City has re -reviewed its role on the referenced permit and believes the permit has adequately met City code and should be approved. We find that all drainage requirements per ECDC 18.30 have been satisfied and provided mitigation exceeds the minimum requirements. The project has demonstrated, with industry standard hydraulic modelling, that the site will infiltrate flows up to and including the 100-year flow. The project plans also show 6" of additional ponding depth provided in the proposed infiltration facility which would be anticipated to manage some flow in excess of the 100-year storm. An addition dispersion mechanism is also provided after the infiltration facility overflow spillway to attempt to spread overflow runoff out to sheet flow and mimic the natural condition as much as feasible. The mitigation provided here exceeds the minimum required per City code. The City's role in excess of the 100-year flow is limited to ensuring there is a safe and certain overflow route as described in ECDC 18.30.060.D.4. It is not the role of the City to remove any and all potential liability for the developer and/or design engineer. The project engineer and property owner have both stated in written statements that the overflow from the infiltration facility will flow in the same manner as the site did prior to development and will be adequate as a safe and certain overflow path. With a dully licensed professional making such a statement (see approved drainage report & appendices in file BLD2019-1496), the City must except this as the safe and certain overflow route. As noted in the applicant submitted letter, the City does require owners and operators of storm water best management practices (BMPs) or facilities to sign and record a covenant on title to ensure the facility's protection, maintenance, and continued operation. Said covenant does include a hold harmless clause, which the City believes would be sufficient to protect itself from future claims which may extend beyond the City's role of ensuring projects meet City code. The hold harmless appears to adequately protect the City against future poor construction, maintenance, or operation of the facility, all of which could potentially result in impacts downstream neighbors. Accordingly, I recommend that BLD2019-1496 be approved for construction with a condition of approval to require completion of the LID covenant typically required for implementation of stormwater BMPs. This approval is only a statement that the proposed drainage plan appears to meet City drainage code per ECDC 18.30. The City has based its decision for approval on the limits of the City code, signed statements from the property owner, and the signed plans and report produced by a civil engineer appropriately licensed in the State of Washington. This approval shall not be interpreted to waive or relieve the applicant or the engineer of record of any liability as a result of the approved drainage plan; such liabilities may still exist and/or may be beyond the City role in applying the municipal code. Page 2 of 2