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Ex09_Preliminary_Technical_Information_Report
Western Washington Division Eastern Washington Division 165 NE Juniper St., Ste 201, Issaquah, WA 98027 108 East 2nd Street, Cle Elum, WA 98922 Phone: (425) 392-0250 Fax: (425) 391-3055 Phone: (509) 674-7433 Fax: (509) 674-7419 www.EncompassES.net CITY OF RENTON PRELIMINARY TECHNICAL INFORMATION REPORT For Jefferson Highlands Unit Lot Subdivision 1526 Jefferson Ave NE, 1513 Kirkland Ave NE and 1518 Jefferson Ave NE Renton, WA 98056 September 24, 2021 09/24/2021 Prepared By: Briana Bennington Encompass Engineering Job No. 21561 Prepared For: Anita Woo 12906 NE 25th Place Bellevue, WA 98005 Exhibit 9 RECEIVED Clark Close 10/27/2021 PLANNING DIVISION DocuSign Envelope ID: E4190986-0960-4AF4-9156-D3C7AC5C2491 Jefferson Highlands Unit Lot Subdivision Technical Information Report 09/24/2021 Page i TABLE OF CONTENTS I. PROJECT OVERVIEW ................................................................................................................ 1 II. CONDITIONS AND REQUIREMENTS SUMMARY ...................................................................... 6 III. OFFSITE ANALYSIS .................................................................................................................. 12 IV. FLOW CONTROL AND WATER QUALITY FACILITY ANALYSIS AND DESIGN ........................... 19 V. CONVEYANCE SYSTEM ANALYSIS AND DESIGN ..................................................................... 22 VI. SPECIAL REPORTS AND STUDIES ............................................................................................ 22 VII. OTHER PERMITS ..................................................................................................................... 22 VIII. CSWPPP ANALYSIS AND DESIGN............................................................................................ 23 IX. BOND QUANTITIES AND DECLARATION OF COVENANT ....................................................... 23 X. OPERATION AND MAINTENANCE MANUAL .......................................................................... 23 LIST OF FIGURES 1. TIR Worksheet 2. Vicinity Map 3. Soils Map and Legend 4. Existing Conditions Map 5. Developed Conditions Map 6. Drainage Review Flow Chart 7. Flow Control Applications Map 8. Aquifer Protection Zone Map 9. Downstream Map 10. Flow Frequency Return Periods 11. Water Quality Treatment Rate 12. Conveyance Calculations LIST OF APPENDICES A. Geotechnical Engineering Reports by The Riley Group, Inc. dated April 6, 2018 and September 1, 2021. B. WWHM2012 Output C. Bond Quantities Worksheet (TO BE PROVIDED WITH FINAL ENGINEERING) D. Declaration of Covenant (TO BE PROVIDED WITH FINAL ENGINEERING) E. Operation & Maintenance Manual F. BioClean Modular Wetland Design Information DocuSign Envelope ID: E4190986-0960-4AF4-9156-D3C7AC5C2491 1513 Kirkland Ave NE, 1526 Jefferson Ave NE, 1518 Jefferson Ave NE Jefferson Highlands Unit Lot Subdivision SW 4 Anita Woo (425) 985-2040 12906 NE 25th Place Renton, WA 98005 Costa Philippides Encompass Engineering and Surveying (425)392-0250 TBD 23 5 4 4 9/24/2021 4 9/24/2021 4 4 4 DocuSign Envelope ID: E4190986-0960-4AF4-9156-D3C7AC5C2491 - Exemption NONE East Lake Washington N/A Newcastle None No Flow Control Duration 4 DocuSign Envelope ID: E4190986-0960-4AF4-9156-D3C7AC5C2491 Low5-15%Indianola Loamy Sand NONE Alderwood 6-15%Low East Lake Washington 1 1 3/12/18 Peak Rate Flow Control Standard Infiltration Trenches T.B.D. T.B.D. 4 DocuSign Envelope ID: E4190986-0960-4AF4-9156-D3C7AC5C2491 Private No Yes Enhanced Basic None None None N/A No DocuSign Envelope ID: E4190986-0960-4AF4-9156-D3C7AC5C2491 x Infiltration trench 4 4 4 4 4 4 4 4 4 4 4 4 4 4 4 4 modular wetland 4 4 DocuSign Envelope ID: E4190986-0960-4AF4-9156-D3C7AC5C2491 9/24/2021 DocuSign Envelope ID: E4190986-0960-4AF4-9156-D3C7AC5C2491 Jefferson Highlands Unit Lot Subdivision Technical Information Report 09/24/2021 Page 1 I. PROJECT OVERVIEW Project: Jefferson Highlands Unit Lot Subdivision Tax Parcel #: 722780-1560, 722780-1485, and 722780-1555 Site Address: 1526 Jefferson Avenue NE, 1513 Kirkland Avenue NE, and 1518 Jefferson Ave NE, Renton WA 98056 Site Area: The combined tax parcel area is 43,332 SF (0.99 AC) Zoning: R-14 Legal Descriptions: Renton Highlands # 2 Correct Plat, Plat Block: 45, Plat Lot: 3 Renton Highlands # 2 Correct Plat, Plat Block: 45, Plat Lot: 17 Renton Highlands # 2 Correct Plat, Plat Block: 45, Plat Lot: 18 Figure 2: Vicinity Map Existing Site Conditions: The site consists of three (3) separate parcels which are currently developed with two duplexes, a single- family home, several out buildings, and paved driveways for each property. The remainder of the project site is vegetated with grass, trees, and shrubs. The site is divided into two subbasins; the eastern and western. The eastern parcel is divided by a high point that runs north to south through the center of the property. Runoff from the eastern quarter of the site (the eastern subbasin) sheet flows directly to Kirkland Ave NE. Runoff from the remaining portion of the site (the western subbasin) sheet flows toward the center of the site to a localized low point. It then flows to the southeast approximately 300 FT before reaching Kirkland Ave NE. See Section III of this report for a full Offsite Analysis. See Figure 4 for a map of the existing site conditions. DocuSign Envelope ID: E4190986-0960-4AF4-9156-D3C7AC5C2491 Jefferson Highlands Unit Lot Subdivision Technical Information Report 09/24/2021 Page 2 Critical Areas: The parcels contain no critical areas or critical area buffers. Soils: Per the US Department of Agriculture (USDA), Natural Resources Conservation Service (NCRS) Web Soil Survey information, the project site is generally underlain with Arents, Alderwood material (AmC), and Indianola loamy sand (InC). Per the Geotechnical Engineering Reports prepared by Riley Group dated April 6, 2018 and September 1, 2021, the site is underlain with some fill over native silty sand and sand with varying amounts of gravel, sand and silt. Dense glacial till was encountered at one area of site exploration. A field infiltration test was performed on the northern half of the site with a calculated long term, design infiltration rate of 2.6 inches/hour. The field infiltration test on the southern half of the site yielded a calculated long term, design infiltration rate of 1.6 inches/hour. The full Geotechnical Engineering Reports are included in Appendix A of this report. Figure 3: Soils Map and Legend DocuSign Envelope ID: E4190986-0960-4AF4-9156-D3C7AC5C2491 KIRKLAND AVE NE JEFFERSON AVE NE NE 15TH STREETPREPARED FOR ANITA WOO JEFFERSON HIGHLANDS Encompass Eastern Washington Division 407 Swiftwater Blvd. ▪ Cle Elum, WA 98922 ▪ Phone: (509) 674-7433 Western Washington Division 165 NE Juniper Street, Suite 201 ▪ Issaquah, WA 98027 ▪ Phone: (425) 392-0250 ENGINEERING & SURVEYING REVISIONS JOB NO. DATE SCALE SHEET 1 of 1EXISTING CONDITIONS NORTHEXISTING IMPERVIOUS AREANOTE:DocuSign Envelope ID: E4190986-0960-4AF4-9156-D3C7AC5C2491 Jefferson Highlands Unit Lot Subdivision Technical Information Report 09/24/2021 Page 4 Developed Site Conditions: This proposal incorporates the demolition, clearing, and grading of the entire project site to accommodate the construction of 18 single-family unit lots. The 18 residences will be constructed in townhouse configurations, consisting of three (3) separate residential buildings with six (6) units each. A public alley will be used to access the residences from Kirkland Avenue NE. The two fronting streets, Kirkland Ave NE, and Jefferson Ave NE, will be improved with new curb/gutters, sidewalks and bioretention/landscape strips per RMC 4-4-070. The project will include the clearing and grading of the entire site as well as construction of the three (3) townhouse buildings, two (2) detached garage buildings, access roads, all public utilities (i.e., water, sewer, storm), and the Kirkland Ave NE frontage improvements. The frontage improvements on Jefferson Avenue NE are being constructed separately under the future City of Renton NE 16th Street/Jefferson Avenue SE Stormwater Green Connection Capital Improvement Project (CIP). A combination of full infiltration beds and a BioClean Linear Modular Wetland filtration device will provide the required water quality and flow controls for the final developed surface areas. The proposed stormwater system will be constructed with emergency overflow connections to the existing storm systems in Kirkland Avenue NE and Jefferson Ave NE. Target surfaces located within the public right of ways (Kirkland Avenue NE, Jefferson Avenue NE) will be mitigated using two road-side bioretention ditches as required per the City of Renton. See Section IV of this report for a full discussion of the proposed stormwater controls and Figure 5 for a map of the developed site conditions. DocuSign Envelope ID: E4190986-0960-4AF4-9156-D3C7AC5C2491 KIRKLAND AVE NE JEFFERSON AVE NE NE 15TH STREETLOT 18LOT 14LOT 15LOT 13LOT 7LOT 9LOT 8LOT 10TRACT CLOT 11LOT 6TRACT BTRACT ALOT 12LOT 4LOT 3LOT 5LOT 2LOT 1LOT 16LOT 17PREPARED FOR ANITA WOO JEFFERSON HIGHLANDS Encompass Eastern Washington Division 407 Swiftwater Blvd. ▪ Cle Elum, WA 98922 ▪ Phone: (509) 674-7433 Western Washington Division 165 NE Juniper Street, Suite 201 ▪ Issaquah, WA 98027 ▪ Phone: (425) 392-0250 ENGINEERING & SURVEYING REVISIONS JOB NO. DATE SCALE SHEET 1 of 1EXISTING CONDITIONS NORTHNOTE:TOTAL IMPERVIOUS AREADocuSign Envelope ID: E4190986-0960-4AF4-9156-D3C7AC5C2491 Jefferson Highlands Unit Lot Subdivision Technical Information Report 09/24/2021 Page 6 II. CONDITIONS AND REQUIREMENTS SUMMARY The 2017 City of Renton Surface Water Design Manual (RSWDM) has been utilized for stormwater design per the City of Renton requirements. The development will result in over 2,000 SF of new plus replaced impervious surface but does not result in over 50 acres of new impervious surface within a subbasin or multiple subbasins that are hydraulically connected. Therefore, per Figure 1.1.2.A of the RSWDM, this project must meet the Full Drainage Review requirements as detailed in Section 1.1.2.4. See Figure 6 below for more information on how the type of drainage review was determined. Figure 6: Drainage Review Flow Chart DocuSign Envelope ID: E4190986-0960-4AF4-9156-D3C7AC5C2491 Jefferson Highlands Unit Lot Subdivision Technical Information Report 09/24/2021 Page 7 Core Requirements: Core Requirement #1: Discharge at the Natural Location Currently, the site drains to the existing, public storm system within Kirkland Avenue NE (in addition to infiltrating into the underlying soil). This project proposes to preserve the existing site drainage patterns via the use of infiltration BMPs with emergency overflow connections to the existing storm systems in the public right-of-way (ROW). Core Requirement #2: Offsite Analysis A Level 1 Downstream analysis has been prepared and is included in Section III of this TIR. Core Requirement #3: Flow Control Facilities Per the City of Renton Flow Control Application Map (Figure 7), this project site is located within the “Peak Rate Flow Control Standard (Existing Site Conditions)” area. In this area, flow control facilities are required to be designed to match the existing conditions 2-, 10- and 100-year peak- rate runoff from the site. The flow control BMPs for this project have been designed for the final developed impervious surface areas. After applying the modeling credits per Table 1.2.9.A of the RSWDM for the Flow Control BMPs listed in Core Requirement #9, the WWHM output displayed a decrease in the 100- year peak flow runoff of 0.4006 CFS using 15-minute timesteps. Therefore, the project meets the exemption for Peak Rate Flow Control Standard Areas per Section 1.2.3.1 of the RSWDM. See Section IV for further discussion and Appendix B for the full WWHM2012 Output. Figure 7: Flow Control Application Map DocuSign Envelope ID: E4190986-0960-4AF4-9156-D3C7AC5C2491 Jefferson Highlands Unit Lot Subdivision Technical Information Report 09/24/2021 Page 8 Core Requirement #4: Conveyance System The development proposes the creation of a new conveyance system and is therefore subject to the Conveyance Requirements for New Systems per Section 1.2.4.1 of the RSWDM. See Section V of this report for the full design and analysis of the proposed conveyance system. Core Requirement #5: Construction Stormwater Pollution Prevention A temporary erosion and sediment control (TESC) plan and a Construction Stormwater Pollution Prevention Plan (CSWPPP) will be provided with final engineering. Core Requirement #6: Maintenance and Operations See Section X of this report for a full discussion of the maintenance and operations. Core Requirement #7: Financial Guarantees and Liability The owner will arrange for any financial guarantees and liabilities required by the permit. Core Requirement #8: Water Quality Facilities This project proposes the creation of more than 5,000 SF of new pollution-generating impervious surfaces (PGIS). Therefore, Enhanced Basic water quality treatment per Section 6.1.2 of the RSWDM is required for the project. The water quality requirements are proposed to be met using a BioClean Linear Modular Wetland filtration device. This method has received DOE GULD approval for basic, enhanced, and phosphorous water quality treatment. See Section IV for additional discussion and Appendix F for the Modular Wetland design information and DOE GULD approval. Core Requirement #9: Flow Control BMPs This project is considered to be a “subdivision development”, and has been designed to comply with the Small Subdivision Project BMP Requirements detailed in Section 1.2.9.3.1 of the RSWDM. Flow Control BMPs detailed below have been evaluated in order of preference as prescribed by the Small Subdivision Project BMP Requirements. The flow control BMPs for this project have been designed per the final developed impervious surface areas. See Section IV of this report for further discussion. Impervious Surface BMPs Full Dispersion: Infeasible. The site design does not allow for the minimum 100-foot native vegetated flowpath lengths required per Appendix C.2.1 of the RSWDM. Full Infiltration: Feasible; per the Geotechnical Engineering Reports by Riley Group that are provided in Appendix A. Full Infiltration of rooftop runoff is proposed in the form of Gravel Filled Full Infiltration Beds per Appendix C.2.2.3 of the RSWDM. Per the Geotechnical Engineering Reports, the site is underlain with silty sand. Silty sands require a 30-foot-long trench section per 1,000 SF of impervious surface area infiltrated. The Kirkland building’s rooftop area is approximately 4,630 SF, and the runoff will be conveyed to a full infiltration bed located within Open Space Tract B along Kirkland Ave NE. In addition, runoff from the proposed 5,900 SF of road and 3,000 SF of uncovered driveway will be conveyed to this infiltration bed. The total tributary impervious surface area is 13,530 SF. Therefore, 13,530 SF/1,000 SF * 30 LF = 406 LF of trenching is required to fully infiltrate this tributary area (assumes DocuSign Envelope ID: E4190986-0960-4AF4-9156-D3C7AC5C2491 Jefferson Highlands Unit Lot Subdivision Technical Information Report 09/24/2021 Page 9 minimum 2-FT wide trench). This results in a total infiltration area of 406 FT *2 FT = 812 SF. The maximum allowable trench length is 100-FT; therefore, the project proposes a 9-FT wide and 100- FT long full infiltration bed to provide 900 SF of infiltration area. The infiltration bed has been designed with a 12” emergency overflow to the Kirkland Ave NE storm system. Each of the Jefferson Residential buildings have a rooftop area of approximately 4,630 SF, and each of the Jefferson Detached Garage buildings have a rooftop area of 2,450 SF. Therefore, the total rooftop area for the lots adjacent to Jefferson Ave NE is 14,160 SF. Runoff from these rooftop areas will be conveyed to two (2) equally sized full infiltration beds located in Open Space Tract C along Jefferson Ave NE. To mitigate the rooftop runoff for these buildings, a 14,160 SF/1,000 SF * 30 LF = 425 LF of trenching is required to fully infiltrate this tributary area (assumes minimum 2 - FT wide trench). This results in a total infiltration area of 425 FT *2 FT = 850 SF, or 425 SF per trench. The maximum allowable trench length is 100-FT; therefore, the project proposes two (2) 5-FT wide and 90-FT long full infiltration beds to provide 450 SF of infiltration area each. Each infiltration bed has been designed with a 12” emergency overflow. The northern trench overflows to the Jefferson Ave NE storm system, and the southern trench overflows to the proposed on-site storm system and subsequently to the Kirkland Ave NE storm system. Please refer to Section IV of this report for additional discussion on flow control and BMP credits. Bioretention: Feasible; per the Geotechnical report provided in Appendix A. Two road-side bioretention ditches, designed per Appendix C.2.6.2 of the RSWDM, will be constructed along the Kirkland Avenue NE improvements within the 11.5’-wide bioretention/filter strip area. Approximately 4,000 SF of upstream off-site impervious surfaces (sidewalks and streets) are tributary to the proposed northern bioretention cell; however, there is not enough on-site area available to provide bioretention for this upstream tributary area. The project assumes that when the parcel to the north develops, they will be responsible to provide bioretention for their frontage along Kirkland Ave NE. Therefore, the bioretention swale has been sized only to accommodate the tributary half-street improvements (from center of ROW) along the project’s eastern extents. The total tributary area for which the bioretention swale is designed for is 2,527 SF. The swale is designed with a minimum footprint as measured at the overflow elevation equal to 5% of the tributary impervious surface (2,527 SF * 0.05 = 126 SF). A combined surface area of 131 SF is provided by the proposed bioretention swale to mitigate the Kirkland Ave NE improvements. This exceeds the minimum requirement of 126 SF. Please refer to Section IV of this report for additional discussion on flow control and BMP credits. Permeable Pavement: All on-site walkways will be constructed of materials meeting the requirements for permeable pavement per Section C.2.7 of the 2016 KCSWDM. The project will utilize a combination of porous pavement and permeable pavers for the approximately 4,150 SF of on-site walkways. Please refer to Section IV of this report for additional discussion on flow control and BMP credits. DocuSign Envelope ID: E4190986-0960-4AF4-9156-D3C7AC5C2491 Jefferson Highlands Unit Lot Subdivision Technical Information Report 09/24/2021 Page 10 Basic Dispersion: No other BMPs were evaluated for the site. All proposed target surfaces are being mitigated by a preferred BMP. Pervious Surface BMPs Soil Amendment: Feasible for new pervious surfaces Retention of the existing soils and restoration of all disturbed soils shall be applied to all of the landscaped areas both on- and off-site per Appendix C.2.13 of the RSWDM. Special Requirements: Special Requirement #1: Other Adopted Area-Specific Requirements Master Drainage Plan – N/A Basin Plan – N/A Salmon Conservation Plan – N/A Lake Management Plan – Lake Washington Management Plan Hazard Mitigation Plan – N/A Shared Facility Drainage Plan – N/A Special Requirement #2: Flood Hazard Area Delineation The limits of this project do not lie in the FEMA 100-year floodplain. Special Requirement #3: Flood Protection Facilities This special requirement is applicable for Class 1 or 2 streams with an existing flood protection facility. The site does not contain any streams. Therefore, Special Requirement #3 is not applicable to this project. Special Requirement #4: Source controls Source control is not required for this project. Special Requirement #5: Oil Control This project is not considered high-use in need of oil control. Special Requirement #6: Aquifer Protection Area As shown in Figure 8 on the following page, the site is not located within an Aquifer Protection Area per the City of Renton GIS mapping system. DocuSign Envelope ID: E4190986-0960-4AF4-9156-D3C7AC5C2491 Jefferson Highlands Unit Lot Subdivision Technical Information Report 09/24/2021 Page 11 Figure 8: Aquifer Protection Zone Map SITE DocuSign Envelope ID: E4190986-0960-4AF4-9156-D3C7AC5C2491 Jefferson Highlands Unit Lot Subdivision Technical Information Report 09/24/2021 Page 12 III. OFFSITE ANALYSIS Task 1: Study Area Definition and Maps A Level 1 Offsite Analysis has been performed for the project site per Section 2.3.1.1 of the RSWDM. The project site is comprised of three adjacent tax parcels. The site is currently developed with two existing duplex residences, a single-family residence, several out buildings, and asphalt driveways for each of the properties. The remainder of the project site is vegetated with grass, trees, and shrubs. The site is contained within a single drainage basin , the East Lake Washington – Renton basin. Slopes range from 2-5% across the site. The study area for this analysis extends downstream of the project site for approximately one mile and includes no upstream offsite drainage area tributary to the project site. All neighboring properti es, while located at higher elevations, have been previously developed and do not direct stormwater runoff to the subject properties. A map showing the study area is included in Figure 8. Task 2: Resource Review Encompass has reviewed the site and the applicable resources for both listed and potential problems. The project site contains no critical areas or critical area buffers per the City of Renton maps, FEMA maps, King County Sensitive Areas Folio, CED Wetlands Inventory, or the Washington State DOE Section 303d list. Task 3: Field Inspection A Level 1 Downstream Analysis was performed by Encompass Engineering and Surveying on Monday, March 12, 2018. The analysis was performed at approximately 8:00 AM with a temperature of about 55°. The tributary basins detailed in Task 1 were confirmed during the site visit. Information collected during this study is included in the Task 4 system description. Task 4: Drainage System Description and Problem Descriptions The site is divided into two subbasins; the eastern and western. The eastern parcel is divided by a high point that runs north to south through the center of the property. Runoff from the remaining portion of the site (the western subbasin) sheet flows to the center of the site to a localized low point. It then flows to the southeast approximately 300’ before reaching Kirkland Ave NE. Runoff from the Eastern quarter of the project site sheet flows (A) towards Kirkland Ave NE. It then runs South along the existing curb (B) to either a Type 2 Catch Basin (C) at the intersection of NE 15th Street and Kirkland Ave NE, or a Type 1 Catch Basin (G) approximately 310’ downstream of the project’s eastern area discharge location. Element C collects stormwater runoff from Kirkland Ave NE and drains to the south via a section of 12” Concrete Pipe (D) which enters a Type 2 Catch Basin (E). Element G connects to Element E via a section of 8” Concrete Pipe (H). Runoff from the remaining western portion of the site sheet flows towards a low area, extending north to south in the center of the site. It then flows (F) to the Southeast approximately 300’ before reaching Kirkland Ave NE and entering Element G. This is where the runoff from the two drainage paths converge and continue to the south via sections of 12” Concrete Pipe (I) before entering a Type 2 Catch Basin (J) at the intersection of Kirkland Ave NE and N E 12th St. This CB DocuSign Envelope ID: E4190986-0960-4AF4-9156-D3C7AC5C2491 Jefferson Highlands Unit Lot Subdivision Technical Information Report 09/24/2021 Page 13 outlets to the west via a 36” Corrugated Metal Pipe (K) located under NE 12th Street. This Analysis was concluded at Element K, which continues to the west for over ¼ mile downstream of the site discharge location and ultimately drains into Lake Washington. See Figure 9: Downstream Map and the photos on the following pages for more information. Figure 9: Downstream Map DocuSign Envelope ID: E4190986-0960-4AF4-9156-D3C7AC5C2491 Jefferson Highlands Unit Lot Subdivision Technical Information Report 09/24/2021 Page 14 OFFSITE ANALYSIS DRAINAGE SYSTEM TABLE BASIN: East Lake Washington SUBBASIN NAME: SUBBASIN NUMBER: SYMBOL DRAINAGE COMPONENT TYPE, NAME, AND SIZE DRAINAGE COMPONENT DESCRIPTION SLOPE DISTANCE FROM SITE DISCHARGE EXISTING PROBLEMS POTENTIAL PROBLEMS OBSERVATIONS OF FIELD INSPECTOR, RESOURCE REVIEWER, OR RESIDENT (See map) Type: sheet flow, swale, stream, channel, pipe, pond; Size: diameter, surface area Drainage basin, vegetation, cover, depth, type of sensitive area, volume % 1/4 Mile = 1,320 ft Constrictions, under capacity, ponding, overtopping, flooding, habitat or organism destruction, scouring, bank sloughing, sedimentation, incision, other erosion Tributary area, likelihood of problem, overflow pathways, potential impacts A SHEET FLOW RUNOFF FROM EASTERN QUARTER OF SITE 1-5% ONSITE - 5' NONE EROSION, PONDING IN FLAT AREAS PERMANENT DRAINAGE PATH TO BE ESTABLISHED BY RE- DEVELOPMENT. B KIRKLAND AVE NE CURB AND GUTTER CONCRETE CURB AND GUTTER 1-5% 5 - 200' NONE EROSION, SEDIMENTATION PERMANENT DRAINAGE PATH TO BE ESTABLISHED BY RE- DEVELOPMENT. C CATCH BASIN #1, 54" TYPE 2 DEPTH = 6.5, FACILITY ID NO. 113357 N/A 20' NONE NONE LOCATED AT INTERSECTION OF NE 15TH ST AND KIRKLAND AVE NE. D 12" CONCRETE PIPE UNDER KIRKLAND AVE NE 3% 20 - 320' NONE NONE EXISTING KIKRLAND AVE NE SYSTEM. E CATCH BASIN #2, 54" TYPE 2 DEPTH = 4.95, FACILITY ID NO. 113354 N/A 320' NONE NONE LOCATED AT INTERSECTION OF NE 15TH PL AND KIRKLAND AVE NE. DocuSign Envelope ID: E4190986-0960-4AF4-9156-D3C7AC5C2491 Jefferson Highlands Unit Lot Subdivision Technical Information Report 09/24/2021 Page 15 F SHEET FLOW RUNOFF FROM WESTERN PORTION OF SITE 1-5% ONSITE - 300' NO ESTABLISHED DRAINAGE PATH OR CHANNEL NONE PERMANENT DRAINAGE PATH TO BE ESTABLISHED BY RE- DEVELOPMENT. G CATCH BASIN #3, TYPE 1 DEPTH = 1.8, FACILITY ID NO. 113355 N/A 300' NONE SEDIMENTATION PERMANENT DRAINAGE PATH TO BE ESTABLISHED BY RE- DEVELOPMENT. H 8" CONCRETE PIPE UNDER KIRKLAND AVE NE 2% 300 - 320' NONE NONE PERMANENT DRAINAGE PATH TO BE ESTABLISHED BY RE- DEVELOPMENT. I 12" CONCRETE PIPE UNDER KIRKLAND AVE NE 2-5% 320 - 1235' NONE NONE CONVEYANCE OF STORMWATER SOUTH UNDER KIRKLAND AVE NE. J CATCH BASIN #4, 54" TYPE 2 DEPTH = 10.37, FACILITY ID NO. 114081 N/A 1235' NONE NONE COLLECTS FLOWS FROM KIRKLAND AVE NE, NE 12TH ST, AND LYNNWOOD AVE NE SYSTEMS. K 36" CORRUGATED METAL PIPE UNDER NE 12TH ST 2-5% 1235 - 1320' NONE NONE CONVEYANCE OF STORMWATER WEST UNDER NE 12TH ST. END OF LEVEL 1 ANALYSIS. Table 1: Downstream Table DocuSign Envelope ID: E4190986-0960-4AF4-9156-D3C7AC5C2491 Jefferson Highlands Unit Lot Subdivision Technical Information Report 09/24/2021 Page 16 Existing Residence on Eastern Parcel Kirkland Ave NE and Existing Access (Taken Facing South) DocuSign Envelope ID: E4190986-0960-4AF4-9156-D3C7AC5C2491 Jefferson Highlands Unit Lot Subdivision Technical Information Report 09/24/2021 Page 17 Existing Residence and Backyard on Northern most West Parcel Jefferson Ave NE (Taken Facing South) DocuSign Envelope ID: E4190986-0960-4AF4-9156-D3C7AC5C2491 Jefferson Highlands Unit Lot Subdivision Technical Information Report 09/24/2021 Page 18 Intersection of Kirkland Ave NE and NE 12th Std Task 5: Mitigation of Existing or Potential Problems Both King County iMap and the City of Renton GIS Maps show no drainage complaints relevant to the project or the downstream drainage paths within the study limits. No existing or potential problems were observed within the site or downstream area during the field reconnaissance. DocuSign Envelope ID: E4190986-0960-4AF4-9156-D3C7AC5C2491 Jefferson Highlands Unit Lot Subdivision Technical Information Report 09/24/2021 Page 19 IV. FLOW CONTROL, LOW IMPACT DEVELOPMENT (LID) AND WATER QUALITY FACILITY ANALYSIS AND DESIGN Part A: Existing Site Hydrology The site is currently developed with two existing duplex residences, a single-family residence, several out buildings, and asphalt driveways for each property. The remainder of the project site is vegetated with grass, trees, and shrubs. Although the project site is made up of two subdrainage basins, they converge within a ¼ mile of leaving the site within the East Lake Washington – Renton drainage basin. Per the USDA NCRS Web Soil Survey information, the project site is generally underlain with Arents, Alderwood material (AmC), and Indianola loamy sand (InC). Per the Geotechnical Engineering Reports prepared by Riley Group, and dated April 6, 2018 and September 1, 2021, the site is underlain with some fill over native silty sand and sand with varying amounts of gravel, sand and silt. Dense glacial till was encountered at one area of site exploration. A field infiltration test was performed on the northern half of the site with a calculated long term, design infiltration rate of 2.6 inches/hour. The field infiltration test on the southern half of the site yielded a calculated long term, design infiltration rate of 1.6 inches/hour. The full Geotechnical Engineering Reports are included in Appendix A of this report. Per Core Requirement #3, the pre-developed site has been modeled as “Existing Conditions” for the purposes of stormwater calculations. Table 2 below shows a breakdown of the measured and modeled acreages for the existing conditions. See Figure 4 for a map of the existing site conditions and Appendix B for the full stormwater modeling calculations. Existing Conditions Areas Measured Modeled Condition Area (AC) Area (AC) Pasture: 0.000 0.000 Lawn: 0.714 0.714 Roof: 0.156 0.156 Street: 0.000 0.000 Sidewalk: 0.044 0.044 Driveway: 0.081 0.081 Offsite Pasture: 0.000 0.000 Offsite Lawn: 0.054 0.054 Offsite Street: 0.043 0.043 Offsite Sidewalk: 0.050 0.050 Total Area: 1.142 1.142 Table 2: Existing Conditions Model Part B: Developed Site Hydrology The developed site will consist of three new residential buildings, two detached garage buildings, a public alley, and frontage improvements along Kirkland Avenue NE and Jefferson Avenue NE. The flow control and water quality facilities proposed for this project have been designed per the final developed surface areas. All stormwater runoff from the developed site will be discharged to the natural locations or fully infiltrated on-site. Three (3) full infiltration beds and a BioClean Linear Modular Wetland filtration system will provide flow DocuSign Envelope ID: E4190986-0960-4AF4-9156-D3C7AC5C2491 Jefferson Highlands Unit Lot Subdivision Technical Information Report 09/24/2021 Page 20 control and water quality for the on-site target surfaces. Emergency overflows will be provided to the existing storm systems in Kirkland Avenue NE and Jefferson Ave NE. The 18,790 SF (0.431 AC) of rooftop, 5,900 SF (0.135 AC) of roadway, and 3,000 SF (0.069 AC) of uncovered driveway that are proposed to be fully infiltrated have been subtracted from the developed WWHM model per Table 1.2.9.A of the RSWDM. The 4,150 SF (0.095 AC) of on-site sidewalks and walkways that are proposed to meet permeable pavement requirements have been modeled as 50% sidewalk and 50% lawn per Table 1.2.9.A of the RSWDM. Target surfaces located within the public right of ways will be mitigated using two road-side bioretention ditches. These off-site target surfaces have been modeled as 90% impervious and 10% lawn per Table 1.2.9.A of the RSWDM. In addition, the Soil Amendment BMP shall be implemented for all on- and off-site vegetated areas per Appendix C.2.13 of the RSWDM. Areas meeting this criterion have been modeled as “pasture” rather than “lawn” in WWHM. Table 3 shows a breakdown of the measured and modeled acreages for the developed conditions. See Figure 5 for a map of the developed site conditions and Appendix B for the full stormwater modeling calculations. Developed Conditions Areas Measured Modeled Condition Area (AC) Area (AC) Pasture: 0.265 0.265 Lawn: 0.000 0.0475 Roof: 0.431 0.000 Street: 0.135 0.000 Sidewalk: 0.095 0.0475 Driveway: 0.069 0.000 Offsite Pasture: 0.069 0.069 Offsite Lawn: 0.000 0.007 Offsite Street: 0.044 0.040 Offsite Sidewalk: 0.034 0.031 Total Area: 1.142 0.507 Table 3: Developed Conditions Model Part C: Performance Standards This project site is located within the “Peak Rate Flow Control Standard (Existing Site Conditions)” area. In this area, flow control facilities are required to be designed to match the existing conditions 2-, 10- and 100-year peak-rate runoff from the site. In addition, this site is considered to be a subdivision, and has been designed to comply with the Small Subdivision Project Flow Control BMP Requirements detailed in Section 1.2.9.3.1 of the RSWDM. Flow Control BMPs have been considered in order of preference as prescribed by the Small Subdivision Project BMP Requirements and are detailed in Core Requirement #9 in Section II of this report. This project proposes the creation of more than 5,000 SF of new PGIS; therefore, Enhanced Basic water quality treatment per Section 1.2.8.1 of the RSWDM is required for the project. Part D: Flow Control System After applying the modeling credits per Table 1.2.9.A of the RSWDM for the Flow Control BMPs listed in Core Requirement #9, the WWHM output displayed a decrease in the 100-year peak flow runoff of 0.4006 DocuSign Envelope ID: E4190986-0960-4AF4-9156-D3C7AC5C2491 Jefferson Highlands Unit Lot Subdivision Technical Information Report 09/24/2021 Page 21 CFS using 15-minute timesteps. Therefore, the project meets the exemption for Peak Rate Flow Control Standards per Section 1.2.3.1 of the RSWDM, which states that the flow control requirement is waived for a project that results in less than a 0.15 CFS increase in the 100-year peak flow. The summary output table from WWHM is provided as Figure 10 below, and the full WWHM output is provided in Appendix B. No additional flow control facilities are required at this time. Figure 10: Flow Frequency Return Periods Part E: Water Quality System Stormwater runoff from the 8,900 SF of on-site PGIS (driveways and streets) will be treated for Enhanced Basic Water quality. The water quality treatment rate was determined using WWHM 2012. A summary output table is provided below, and the full WWHM results are provided in Appendix B. Figure 11: Water Quality Treatment Rate A BioClean Linear Modular Wetland filtration device will provide the required treatment level for these target surfaces. This method has received DOE GULD approval for basic, enhanced, and phosphorous water quality treatment. The device has been sized using the WWHM water quality flow rate of 0.0331 CFS and the BioClean sizing guidelines. An MWS-L-4-4 Stormwater Biofiltration System with a treatment flow capacity of 0.052 CFS will be utilized for the on-line facility. See Appendix F for the BioClean Modular Wetland design information and GULD approval documentation. See the engineering plan set for further structure and sizing details. DocuSign Envelope ID: E4190986-0960-4AF4-9156-D3C7AC5C2491 Jefferson Highlands Unit Lot Subdivision Technical Information Report 09/24/2021 Page 22 V. CONVEYANCE SYSTEM ANALYSIS AND DESIGN The project is considered to be a new system and must comply with the Conveyance Requirements for New Systems detailed in Section 1.2.4.1 of the RSWDM. New pipe, culvert, and ditch/channel systems shall be designed with sufficient capacity to convey and contain (at minimum) the 25-year peak flow, assuming developed conditions for the onsite tributary areas and existing conditions for any offsite tributary areas. Per the WWHM output, the 25-year peak flow for the developed site is equal to 0.0874 CFS. Using Manning’s Equation (Figure 10), a 12” PVC pipe at a slope of 0.5% has a maximum volumetric flow rate (Q) of 2.98 CFS. This is significantly greater than the calculated 25-year peak flow; therefore, the proposed system is sufficient. Figure 12: Conveyance Calculations VI. SPECIAL REPORTS AND STUDIES Geotechnical Engineering Reports prepared by Riley Group, dated April 6, 2018 and September 1, 2021 (Appendix A). VII. OTHER PERMITS A Building Permit, R.O.W. Permit, and a Clearing and Grading Permit will be required. DocuSign Envelope ID: E4190986-0960-4AF4-9156-D3C7AC5C2491 Jefferson Highlands Unit Lot Subdivision Technical Information Report 09/24/2021 Page 23 VIII. CSWPPP ANALYSIS AND DESIGN A temporary erosion and sediment control (ESC) plan and a Construction Stormwater Pollution Prevention Plan (CSWPPP) will be provided with final engineering. IX. BOND QUANTITIES AND DECLARATION OF COVENANT A Bond Quantities Worksheet and Declaration of Covenant will be provided with final engineering. X. OPERATION AND MAINTENANCE MANUAL An Operation and Maintenance Manual has been prepared for the site and is included in Appendix E of this Report. DocuSign Envelope ID: E4190986-0960-4AF4-9156-D3C7AC5C2491 Appendix A Geotechnical Engineering Reports prepared by The Riley Group dated April 6, 2018 and September 1, 2021 DocuSign Envelope ID: E4190986-0960-4AF4-9156-D3C7AC5C2491 Corporate Office 17522 Bothell Way Northeast Bothell, Washington 98011 Phone 425.415.0551 ♦ Fax 425.415.0311 www.riley-group.com GEOTECHNICAL ENGINEERING REPORT PREPARED BY: THE RILEY GROUP, INC. 17522 BOTHELL WAY NORTHEAST BOTHELL, WASHINGTON 98011 PREPARED FOR: ANITA WOO 12906 NORTHEAST 25TH PLACE BELLEVUE, WASHINGTON 98004 RGI PROJECT NO. 2018-070 JEFFERSON AND KIRKLAND TOWNHOMES 1513 KIRKLAND AVENUE NORTHEAST AND 1526 JEFFERSON AVENUE NORTHEAST RENTON, WASHINGTON APRIL 6, 2018 DocuSign Envelope ID: E4190986-0960-4AF4-9156-D3C7AC5C2491 DocuSign Envelope ID: E4190986-0960-4AF4-9156-D3C7AC5C2491 Geotechnical Engineering Report i April 6, 2018 Jefferson and Kirkland Townhomes, Renton, Washington RGI Project No. 2018-070 TABLE OF CONTENTS 1.0 INTRODUCTION ............................................................................................................................... 1 2.0 PROJECT DESCRIPTION ............................................................................................................... 1 3.0 FIELD EXPLORATION AND LABORATORY TESTING .......................................................... 2 3.1 FIELD EXPLORATION ................................................................................................................................... 2 3.2 LABORATORY TESTING ................................................................................................................................ 2 4.0 SITE CONDITIONS ........................................................................................................................... 2 4.1 SURFACE .................................................................................................................................................. 2 4.2 GEOLOGY ................................................................................................................................................. 3 4.3 SOILS ....................................................................................................................................................... 3 4.4 GROUNDWATER ........................................................................................................................................ 3 4.5 SEISMIC CONSIDERATIONS ........................................................................................................................... 4 4.6 GEOLOGIC HAZARD AREAS .......................................................................................................................... 4 5.0 DISCUSSION AND RECOMMENDATIONS ................................................................................. 5 5.1 GEOTECHNICAL CONSIDERATIONS ................................................................................................................. 5 5.2 EARTHWORK ............................................................................................................................................. 5 5.2.1 Erosion and Sediment Control ..................................................................................................... 5 5.2.2 Stripping and Subgrade Preparation ............................................................................................ 6 5.2.3 Excavations................................................................................................................................... 6 5.2.4 Structural Fill ................................................................................................................................ 7 5.2.5 Wet Weather Construction Considerations ................................................................................. 8 5.3 FOUNDATIONS .......................................................................................................................................... 9 5.4 RETAINING WALLS ................................................................................................................................... 10 5.5 SLAB-ON-GRADE CONSTRUCTION ............................................................................................................... 10 5.6 DRAINAGE .............................................................................................................................................. 11 5.6.1 Surface ....................................................................................................................................... 11 5.6.2 Subsurface .................................................................................................................................. 11 5.6.3 Infiltration .................................................................................................................................. 11 5.7 UTILITIES ................................................................................................................................................ 12 6.0 ADDITIONAL SERVICES .............................................................................................................. 12 7.0 LIMITATIONS ................................................................................................................................. 12 LIST OF FIGURES AND APPENDICES Figure 1 ..................................................................................................................... Site Vicinity Map Figure 2 ............................................................................................... Geotechnical Exploration Plan Figure 3 ............................................................................................... Retaining Wall Drainage Detail Figure 4 ....................................................................................................Typical Footing Drain Detail Appendix A .......................................................................... Field Exploration and Laboratory Testing DocuSign Envelope ID: E4190986-0960-4AF4-9156-D3C7AC5C2491 Geotechnical Engineering Report ii April 6, 2018 Jefferson and Kirkland Townhomes, Renton, Washington RGI Project No. 2018-070 Executive Summary This Executive Summary should be used in conjunction with the entire Geotechnical Engineering Report (GER) for design and/or construction purposes. It should be recognized that specific details were not included or fully developed in this section, and the GER must be read in its entirety for a comprehensive understanding of the items contained herein. Section 7.0 should be read for an understanding of limitations. RGI’s geotechnical scope of work included the advancement of five test pits to approximate depths of 5 to 9.5 feet below existing site grades. Based on the information obtained from our subsurface exploration, the site is suitable for development of the proposed project. The following geotechnical considerations were identified: Soil Conditions: The soils encountered during field exploration include loose to medium dense fill comprised of silty sand with trace gravel and sand with some silt and trace gravel over native deposits of loose to dense silty sand with varying amounts of gravel, sand with varying amounts of silt and gravel and gravel with varying amounts of sand and silt. Very dense glacial till comprised of silty sand with some gravel was encountered at one location. Groundwater: No groundwater seepage was encountered during our subsurface exploration. Foundations: Foundations for the proposed building may be supported on conventional spread footings bearing on medium dense to dense native soil or structural fill. Slab-on-grade: Slab-on-grade floors and slabs for the proposed building can be supported on medium dense to dense native soil or structural fill. DocuSign Envelope ID: E4190986-0960-4AF4-9156-D3C7AC5C2491 Geotechnical Engineering Report 1 April 6, 2018 Jefferson and Kirkland Townhomes, Renton, Washington RGI Project No. 2018-070 1.0 Introduction This Geotechnical Engineering Report (GER) presents the results of the geotechnical engineering services provided for the Jefferson and Kirkland Townhomes in Renton, Washington. The purpose of this evaluation is to assess subsurface conditions and provide geotechnical recommendations for the construction of 11 townhomes. Our scope of services included field explorations, laboratory testing, engineering analyses, and preparation of this GER. The recommendations in the following sections of this GER are based upon our current understanding of the proposed site development as outlined below. If actual features vary or changes are made, RGI should review them in order to modify our recommendations as required. In addition, RGI requests to review the site grading plan, final design drawings and specifications when available to verify that our project understanding is correct and that our recommendations have been properly interpreted and incorporated into the project design and construction. 2.0 Project description The project site is located at 1513 Kirkland Avenue Northeast and 1526 Jefferson Avenue Northeast in Renton, Washington. The approximate location of the site is shown on Figure 1. The site is currently occupied by two multi-family homes, one adjacent to Jefferson Avenue Northeast and one adjacent to Kirkland Avenue Northeast. Several outbuildings also occupy the site. RGI understands that 11 townhomes will be constructed at the site. Based on review of a proposed site layout prepared by Daniel Umbach Architect, 6 units will be located along Jefferson Avenue Northeast, and 5 units along Kirkland Avenue Northeast. Vehicle access will be via a paved driveway extending west from Kirkland Avenue Northeast in the southeast site corner, with garages in the lower level of each unit. RGI understands the central portion of the site is being considered for infiltration of stormwater. At the time of preparing this GER, building plans were not available for our review. Based on our experience with similar construction, RGI anticipates that the proposed building will be supported on perimeter walls with bearing loads of two to six kips per linear foot, and a series of columns with a maximum load up to 30 kips. Slab-on-grade floor loading of 250 pounds per square foot (psf) are expected. DocuSign Envelope ID: E4190986-0960-4AF4-9156-D3C7AC5C2491 Geotechnical Engineering Report 2 April 6, 2018 Jefferson and Kirkland Townhomes, Renton, Washington RGI Project No. 2018-070 3.0 Field Exploration and Laboratory Testing 3.1 FIELD EXPLORATION On March 30, 2018, RGI observed the excavation of five test pits and completed one infiltration test. The approximate exploration locations are shown on Figure 2. Field logs of each exploration were prepared by the geologist that continuously observed the excavation. These logs included visual classifications of the materials encountered during excavation as well as our interpretation of the subsurface conditions between samples. The test pits logs included in Appendix A represent an interpretation of the field logs and include modifications based on laboratory observation and analysis of the samples. 3.2 LABORATORY TESTING During the field exploration, a representative portion of each recovered sample was sealed in containers and transported to our laboratory for further visual and laboratory examination. Selected samples retrieved from the test pits were tested for moisture content and grain size analysis to aid in soil classification and provide input for the recommendations provided in this GER. The results and descriptions of the laboratory tests are enclosed in Appendix A. 4.0 Site Conditions 4.1 SURFACE The subject site is comprised of two rectangular-shaped parcels of land totaling approximately 0.77 acres in size. The site is bound to the north and south by residential properties, to the east by Kirkland Avenue Northeast, and to the west by Jefferson Avenue Northeast. The existing site is occupied by two multi-family homes and several outbuildings. A concrete slab that appears to be from a garage is located in the northeast site corner. Several small brick walls and numerous fences divide the property into four yard areas. The site is relatively flat with about five feet of elevation change across the site. The site slopes down from the streets along the east and west perimeter to a topographic low extending in a north-south direction through the central portion of the property, which has a slight slope toward the south. The site is vegetated primarily with grass, with numerous decorative plants, shrubs, and fruit trees scattered about the property. A large- diameter cedar tree is located in the south-central portion of the property. DocuSign Envelope ID: E4190986-0960-4AF4-9156-D3C7AC5C2491 Geotechnical Engineering Report 3 April 6, 2018 Jefferson and Kirkland Townhomes, Renton, Washington RGI Project No. 2018-070 4.2 GEOLOGY Review of the Preliminary Geologic Map of Seattle and Vicinity, Washington, by Howard H. Waldron, etc. (1962) indicates that the soil in the project vicinity is mapped as Vashon till (Qt), which is light to dark gray, nonsorted, nonstratified mixture of clay, silt, sand, and gravel. Till was encountered at a depth of 9 feet in TP-1, and likely underlies the entire property. The sand and gravel soils encountered above the till throughout the site match the descriptions for Younger Sand (Qys) and Younger Gravel (Qyg) mapped to the west and northwest of the site. 4.3 SOILS The soils encountered during field exploration include loose to medium dense fill comprised of silty sand with trace gravel and sand with some silt and trace gravel over native deposits of loose to dense silty sand with varying amounts of gravel, sand with varying amounts of silt and gravel and gravel with varying amounts of sand and silt. Very dense glacial till comprised of silty sand with some gravel was encountered at one location. More detailed descriptions of the subsurface conditions encountered are presented in the test pits included in Appendix A. Sieve analysis was performed on seven selected soil samples. Grain size distribution curves are included in Appendix A. 4.4 GROUNDWATER No groundwater seepage was encountered during our subsurface exploration. Iron oxide staining was observed that may be indicative of seasonal groundwater travelling through subsurface soils. It should be recognized that fluctuations of the groundwater table will occur due to seasonal variations in the amount of rainfall, runoff, and other factors not evident at the time the explorations were performed. In addition, perched water can develop within seams and layers contained in fill soils or higher permeability soils overlying less permeable soils following periods of heavy or prolonged precipitation. Therefore, groundwater levels during construction or at other times in the future may be higher or lower than the levels indicated on the logs. Groundwater level fluctuations should be considered when developing the design and construction plans for the project. DocuSign Envelope ID: E4190986-0960-4AF4-9156-D3C7AC5C2491 Geotechnical Engineering Report 4 April 6, 2018 Jefferson and Kirkland Townhomes, Renton, Washington RGI Project No. 2018-070 4.5 SEISMIC CONSIDERATIONS Based on the 2012/2015 International Building Code (IBC), RGI recommends the follow seismic parameters for design. Table 1 2012/2015 IBC Parameter Value Site Soil Class1 D2 Site Latitude 47.50635oN Site Longitude 122.17967oW Short Period Spectral Response Acceleration, SS (g) 1.426 1-Second Period Spectral Response Acceleration, S1 (g) 0.537 Adjusted Short Period Spectral Response Acceleration, SMS (g) 1.426 Adjusted 1-Second Period Spectral Response Acceleration, SM1 (g) 0.806 1. Note: In general accordance with Chapter 20 of ASCE 7-10. The Site Class is based on the average characteristics of the upper 100 feet of the subsurface profile. 2. Note: The 2012/2015 IBC and ASCE 7-10 require a site soil profile determination extending to a depth of 100 feet for seismic site classification. The current scope of our services does not include the required 100 foot soil profile determination. Test pits extended to a maximum depth of 9.5 feet, and this seismic site class definition considers that similar soil continues below the maximum depth of the subsurface exploration. Additional exploration to deeper depths would be required to confirm the conditions below the current depth of exploration. Liquefaction is a phenomenon where there is a reduction or complete loss of soil strength due to an increase in water pressure induced by vibrations from a seismic event. Liquefaction mainly affects geologically recent deposits of fine-grained sands that are below the groundwater table. Soils of this nature derive their strength from intergranular friction. The generated water pressure or pore pressure essentially separates the soil grains and eliminates this intergranular friction, thus reducing or eliminating the soil’s strength. RGI reviewed the results of the field and laboratory testing and assessed the potential for liquefaction of the site’s soil during an earthquake. Since the site is underlain by glacial till and depth and lacks a shallow groundwater table, RGI considers that the possibility of liquefaction during an earthquake is minimal. 4.6 GEOLOGIC HAZARD AREAS Regulated geologically hazardous areas include erosion, landslide, earthquake, or other geological hazards. Based on the definition in the Renton Municipal Code, the site does not contain geologically hazardous areas. DocuSign Envelope ID: E4190986-0960-4AF4-9156-D3C7AC5C2491 Geotechnical Engineering Report 5 April 6, 2018 Jefferson and Kirkland Townhomes, Renton, Washington RGI Project No. 2018-070 5.0 Discussion and Recommendations 5.1 GEOTECHNICAL CONSIDERATIONS Based on our study, the site is suitable for the proposed construction from a geotechnical standpoint. Foundations for the proposed building can be supported on conventional spread footings bearing on medium dense to dense native soil or structural fill. Slab-on- grade floors can be similarly supported. Detailed recommendations regarding the above issues and other geotechnical design considerations are provided in the following sections. These recommendations should be incorporated into the final design drawings and construction specifications. 5.2 EARTHWORK The earthwork is expected to include excavating and backfilling the building foundations and preparing slab subgrades. 5.2.1 EROSION AND SEDIMENT CONTROL Potential sources or causes of erosion and sedimentation depend on construction methods, slope length and gradient, amount of soil exposed and/or disturbed, soil type, construction sequencing and weather. The impacts on erosion-prone areas can be reduced by implementing an erosion and sedimentation control plan. The plan should be designed in accordance with applicable city and/or county standards. RGI recommends the following erosion control Best Management Practices (BMPs): Scheduling site preparation and grading for the drier summer and early fall months and undertaking activities that expose soil during periods of little or no rainfall Retaining existing vegetation whenever feasible Establishing a quarry spall construction entrance Installing siltation control fencing or anchored straw or coir wattles on the downhill side of work areas Covering soil stockpiles with anchored plastic sheeting Revegetating or mulching exposed soils with a minimum 3-inch thickness of straw if surfaces will be left undisturbed for more than one day during wet weather or one week in dry weather Directing runoff away from exposed soils and slopes Minimizing the length and steepness of slopes with exposed soils and cover excavation surfaces with anchored plastic sheeting Decreasing runoff velocities with check dams, straw bales or coir wattles Confining sediment to the project site DocuSign Envelope ID: E4190986-0960-4AF4-9156-D3C7AC5C2491 Geotechnical Engineering Report 6 April 6, 2018 Jefferson and Kirkland Townhomes, Renton, Washington RGI Project No. 2018-070 Inspecting and maintaining erosion and sediment control measures frequently (The contractor should be aware that inspection and maintenance of erosion control BMPs is critical toward their satisfactory performance. Repair and/or replacement of dysfunctional erosion control elements should be anticipated.) Permanent erosion protection should be provided by reestablishing vegetation using hydroseeding and/or landscape planting. Until the permanent erosion protection is established, site monitoring should be performed by qualified personnel to evaluate the effectiveness of the erosion control measures. Provisions for modifications to the erosion control system based on monitoring observations should be included in the erosion and sedimentation control plan. 5.2.2 STRIPPING AND SUBGRADE PREPARATION Stripping efforts should include removal of pavements, vegetation, organic materials, and deleterious debris from areas slated for building, pavement, and utility construction. The test pits encountered 6 to 16 inches of topsoil and rootmass. Deeper areas of stripping may be required in forested or heavily vegetated areas of the site. Subgrade soils that become disturbed due to elevated moisture conditions should be overexcavated to reveal firm, non-yielding, non-organic soils and backfilled with compacted structural fill. In order to maximize utilization of site soils as structural fill, RGI recommends that the earthwork portion of this project be completed during extended periods of warm and dry weather if possible. If earthwork is completed during the wet season (typically November through May) it will be necessary to take extra precautionary measures to protect subgrade soils. Wet season earthwork will require additional mitigative measures beyond that which would be expected during the drier summer and fall months. 5.2.3 EXCAVATIONS All temporary cut slopes associated with the site and utility excavations should be adequately inclined to prevent sloughing and collapse. The site soils consist of medium dense to dense silty sand with trace gravel and sand with some silt and trace gravel, with localized gravel beds. Accordingly, for excavations more than 4 feet but less than 20 feet in depth, the temporary side slopes should be laid back with a minimum slope inclination of 1H:1V (Horizontal:Vertical). If there is insufficient room to complete the excavations in this manner, or excavations greater than 20 feet in depth are planned, using temporary shoring to support the excavations should be considered. For open cuts at the site, RGI recommends: No traffic, construction equipment, stockpiles or building supplies are allowed at the top of cut slopes within a distance of at least five feet from the top of the cut DocuSign Envelope ID: E4190986-0960-4AF4-9156-D3C7AC5C2491 Geotechnical Engineering Report 7 April 6, 2018 Jefferson and Kirkland Townhomes, Renton, Washington RGI Project No. 2018-070 Exposed soil along the slope is protected from surface erosion using waterproof tarps and/or plastic sheeting Construction activities are scheduled so that the length of time the temporary cut is left open is minimized Surface water is diverted away from the excavation The general condition of slopes should be observed periodically by a geotechnical engineer to confirm adequate stability and erosion control measures In all cases, however, appropriate inclinations will depend on the actual soil and groundwater conditions encountered during earthwork. Ultimately, the site contractor must be responsible for maintaining safe excavation slopes that comply with applicable OSHA or WISHA guidelines. 5.2.4 STRUCTURAL FILL RGI recommends fill below the foundation and floor slab, behind retaining walls, and below pavement and hardscape surfaces be placed in accordance with the following recommendations for structural fill. The structural fill should be placed after completion of site preparation procedures as described above. The suitability of excavated site soils and import soils for compacted structural fill use will depend on the gradation and moisture content of the soil when it is placed. As the amount of fines (that portion passing the U.S. No. 200 sieve) increases, soil becomes increasingly sensitive to small changes in moisture content and adequate compaction becomes more difficult or impossible to achieve. Soils containing more than about 5 percent fines cannot be consistently compacted to a dense, non-yielding condition when the moisture content is more than 2 percent above or below optimum. Optimum moisture content is that moisture that results in the greatest compacted dry density with a specified compactive effort. Non-organic site soils are only considered suitable for structural fill provided that their moisture content is within about two percent of the optimum moisture level as determined by ASTM D1557. Excavated site soils may not be suitable for re-use as structural fill depending on the moisture content and weather conditions at the time of construction. If soils are stockpiled for future reuse and wet weather is anticipated, the stockpile should be protected with plastic sheeting that is securely anchored. Even during dry weather, moisture conditioning (such as, windrowing and drying) of site soils to be reused as structural fill may be required. Some of the site soils are moisture sensitive and may require moisture conditioning prior to use as structural fill. If on-site soils are or become unusable, it may become necessary to import clean, granular soils to complete site work that meet the grading requirements listed in Table 2 to be used as structural fill. DocuSign Envelope ID: E4190986-0960-4AF4-9156-D3C7AC5C2491 Geotechnical Engineering Report 8 April 6, 2018 Jefferson and Kirkland Townhomes, Renton, Washington RGI Project No. 2018-070 Table 2 Structural Fill Gradation U.S. Sieve Size Percent Passing 4 inches 100 No. 4 sieve 22 to 100 No. 200 sieve 0 to 5* *Based on minus 3/4 inch fraction. Prior to use, an RGI representative should observe and test all materials imported to the site for use as structural fill. Structural fill materials should be placed in uniform loose layers not exceeding 12 inches and compacted as specified in Table 3. The soil’s maximum density and optimum moisture should be determined by ASTM D1557. Table 3 Structural Fill Compaction ASTM D1557 Location Material Type Minimum Compaction Percentage Moisture Content Range Foundations On-site granular or approved imported fill soils: 95 +2 -2 Retaining Wall Backfill On-site granular or approved imported fill soils: 92 +2 -2 Slab-on-grade On-site granular or approved imported fill soils: 95 +2 -2 General Fill (non- structural areas) On-site soils or approved imported fill soils: 90 +3 -2 Placement and compaction of structural fill should be observed by RGI. A representative number of in-place density tests should be performed as the fill is being placed to confirm that the recommended level of compaction is achieved. 5.2.5 WET WEATHER CONSTRUCTION CONSIDERATIONS RGI recommends that preparation for site grading and construction include procedures intended to drain ponded water, control surface water runoff, and to collect shallow subsurface seepage zones in excavations where encountered. It will not be possible to successfully compact the subgrade or utilize on-site soils as structural fill if accumulated water is not drained prior to grading or if drainage is not controlled during construction. Attempting to grade the site without adequate drainage control measures will reduce the amount of on-site soil effectively available for use, increase the amount of select import fill materials required, and ultimately increase the cost of the earthwork phases of the DocuSign Envelope ID: E4190986-0960-4AF4-9156-D3C7AC5C2491 Geotechnical Engineering Report 9 April 6, 2018 Jefferson and Kirkland Townhomes, Renton, Washington RGI Project No. 2018-070 project. Free water should not be allowed to pond on the subgrade soils. RGI anticipates that the use of berms and shallow drainage ditches, with sumps and pumps in utility trenches, will be required for surface water control during wet weather and/or wet site conditions. 5.3 FOUNDATIONS Following site preparation and grading, the proposed building foundation can be supported on conventional spread footings bearing on medium dense to dense native soil or structural fill. Loose, organic, or other unsuitable soils may be encountered in the proposed building footprint. If unsuitable soils are encountered, they should be overexcavated and backfilled with structural fill. If existing fill soils are encountered at subgrade elevations, the suitability of the soils for foundation support should be evaluated by a RGI representative. Perimeter foundations exposed to weather should be at a minimum depth of 18 inches below final exterior grades. Interior foundations can be constructed at any convenient depth below the floor slab. Finished grade is defined as the lowest adjacent grade within 5 feet of the foundation for perimeter (or exterior) footings and finished floor level for interior footings. Table 4 Foundation Design Design Parameter Value Allowable Bearing Capacity 2,000 psf1 Friction Coefficient 0.30 Passive pressure (equivalent fluid pressure) 250 pcf2 Minimum foundation dimensions Columns: 24 inches Walls: 16 inches 1. psf = pounds per square foot 2. pcf = pounds per cubic foot The allowable foundation bearing pressures apply to dead loads plus design live load conditions. For short-term loads, such as wind and seismic, a 1/3 increase in this allowable capacity may be used. At perimeter locations, RGI recommends not including the upper 12 inches of soil in the computation of passive pressures because they can be affected by weather or disturbed by future grading activity. The passive pressure value assumes the foundation will be constructed neat against competent soil or backfilled with structural fill as described in Section 5.2.4. The recommended base friction and passive resistance value includes a safety factor of about 1.5. DocuSign Envelope ID: E4190986-0960-4AF4-9156-D3C7AC5C2491 Geotechnical Engineering Report 10 April 6, 2018 Jefferson and Kirkland Townhomes, Renton, Washington RGI Project No. 2018-070 With spread footing foundations designed in accordance with the recommendations in this section, maximum total and differential post-construction settlements of 1 inch and 1/2 inch, respectively, should be expected. 5.4 RETAINING WALLS If retaining walls are needed in the building area or for a below grade vault, RGI recommends cast-in-place concrete walls be used. The magnitude of earth pressure development on retaining walls will partly depend on the quality of the wall backfill. RGI recommends placing and compacting wall backfill as structural fill. Wall drainage will be needed behind the wall face. A typical retaining wall drainage detail is shown in Figure 3. With wall backfill placed and compacted as recommended, and drainage properly installed, RGI recommends using the values in the following table for design. Table 5 Retaining Wall Design Design Parameter Value Allowable Bearing Capacity 2,000 psf Active Earth Pressure (unrestrained walls) 35 pcf At-rest Earth Pressure (restrained walls) 50 pcf For seismic design, an additional uniform load of 7 times the wall height (H) for unrestrained walls and 14H in psf for restrained walls should be applied to the wall surface. Friction at the base of foundations and passive earth pressure will provide resistance to these lateral loads. Values for these parameters are provided in Section 5.3. 5.5 SLAB-ON-GRADE CONSTRUCTION Once site preparation has been completed as described in Section 5.2, suitable support for slab-on-grade construction should be provided. RGI recommends that the concrete slab be placed on top of medium dense native soil or structural fill. Immediately below the floor slab, RGI recommends placing a four-inch thick capillary break layer of clean, free-draining sand or gravel that has less than five percent passing the U.S. No. 200 sieve. This material will reduce the potential for upward capillary movement of water through the underlying soil and subsequent wetting of the floor slab. Where moisture by vapor transmission is undesirable, an 8- to 10-millimeter thick plastic membrane should be placed on a 4-inch thick layer of clean gravel. For the anticipated floor slab loading, we estimate post-construction floor settlements of 1/4- to 1/2-inch. DocuSign Envelope ID: E4190986-0960-4AF4-9156-D3C7AC5C2491 Geotechnical Engineering Report 11 April 6, 2018 Jefferson and Kirkland Townhomes, Renton, Washington RGI Project No. 2018-070 5.6 DRAINAGE 5.6.1 SURFACE Final exterior grades should promote free and positive drainage away from the building area. Water must not be allowed to pond or collect adjacent to foundations or within the immediate building area. For non-pavement locations, RGI recommends providing a minimum drainage gradient of 3 percent for a minimum distance of 10 feet from the building perimeter. In paved locations, a minimum gradient of 1 percent should be provided unless provisions are included for collection and disposal of surface water adjacent to the structure. 5.6.2 SUBSURFACE RGI recommends installing perimeter foundation drains. A typical footing drain detail is shown on Figure 4. The foundation drains and roof downspouts should be tightlined separately to an approved discharge facility. Subsurface drains must be laid with a gradient sufficient to promote positive flow to a controlled point of approved discharge. 5.6.3 INFILTRATION RGI understands that an infiltration system is being considered for the on-site disposal of stormwater run-off in the central portion of the property. A field infiltration test at test pit TP-2 was performed in general accordance with a Small-Scale Pilot Infiltration Test described in Reference 6A – Infiltration Rate Test Methods in the King County, Washington, Surface Water Design Manual. Table 6 Measured Infiltration Rates Test Location Test Depth Measured Rate (Inches per hour) Design Rate (Inches per hour) TP-2 4’ 6.5 2.6 King County Surface Water Design Manual correction factors were applied to the field measured rate of 6.5 inches per hour. No groundwater was encountered in the test pits. Very dense glacial till was encountered at 9 feet below grade in test pit, TP-1 and is a restrictive layer. Idesign = Imeasured x Ftesting x Fplugging x Fgeometry Correction factors of 0.5 (Ftesting) for the PIT test method and 0.8 (Fplugging) for fine sands were applied to the field measured rate to estimate the long-term design infiltration rate. We assumed Fgeometry = 1. The application of the correction factors yield a long-term design rate (Idesign) of 2.6 inches per hour. DocuSign Envelope ID: E4190986-0960-4AF4-9156-D3C7AC5C2491 Geotechnical Engineering Report 12 April 6, 2018 Jefferson and Kirkland Townhomes, Renton, Washington RGI Project No. 2018-070 5.7 UTILITIES Utility pipes should be bedded and backfilled in accordance with American Public Works Association (APWA) specifications. For site utilities located within the right-of-ways, bedding and backfill should be completed in accordance with City of Renton specifications. At a minimum, trench backfill should be placed and compacted as structural fill, as described in Section 5.2.4. Where utilities occur below unimproved areas, the degree of compaction can be reduced to a minimum of 90 percent of the soil’s maximum density as determined by the referenced ASTM D1557. 6.0 Additional Services RGI is available to provide further geotechnical consultation throughout the design phase of the project. RGI should review the final design and specifications in order to verify that earthwork and foundation recommendations have been properly interpreted and incorporated into project design and construction. RGI is also available to provide geotechnical engineering and construction monitoring services during construction. The integrity of the earthwork and construction depends on proper site preparation and procedures. In addition, engineering decisions may arise in the field in the event that variations in subsurface conditions become apparent. Construction monitoring services are not part of this scope of work. If these services are desired, please let us know and we will prepare a cost proposal. 7.0 Limitations This GER is the property of RGI, Anita Woo, and her designated agents. Within the limits of the scope and budget, this GER was prepared in accordance with generally accepted geotechnical engineering practices in the area at the time this GER was issued. This GER is intended for specific application to the Jefferson and Kirkland Townhomes project in Renton, Washington, and for the exclusive use of Anita Woo and her authorized representatives. No other warranty, expressed or implied, is made. Site safety, excavation support, and dewatering requirements are the responsibility of others. The scope of services for this project does not include either specifically or by implication any environmental or biological (for example, mold, fungi, bacteria) assessment of the site or identification or prevention of pollutants, hazardous materials or conditions. If the owner is concerned about the potential for such contamination or pollution, we can provide a proposal for these services. The analyses and recommendations presented in this GER are based upon data obtained from the explorations performed on site. Variations in soil conditions can occur, the nature and extent of which may not become evident until construction. If variations DocuSign Envelope ID: E4190986-0960-4AF4-9156-D3C7AC5C2491 Geotechnical Engineering Report 13 April 6, 2018 Jefferson and Kirkland Townhomes, Renton, Washington RGI Project No. 2018-070 appear evident, RGI should be requested to reevaluate the recommendations in this GER prior to proceeding with construction. It is the client’s responsibility to see that all parties to the project, including the designers, contractors, subcontractors, are made aware of this GER in its entirety. The use of information contained in this GER for bidding purposes should be done at the contractor’s option and risk. DocuSign Envelope ID: E4190986-0960-4AF4-9156-D3C7AC5C2491 USGS, 2014, Mercer Island, Washington USGS, 2014, Renton, Washington 7.5-Minute Quadrangle Approximate Scale: 1"=1000' 0 500 1000 2000 N Site Vicinity Map Figure 1 04/2018 Corporate Office 17522 Bothell Way Northeast Bothell, Washington 98011 Phone: 425.415.0551 Fax: 425.415.0311 Jefferson and Kirkland Townhomes RGI Project Number 2018-070 Date Drawn: Address: 1513 Kirkland Avenue Northeast & 1526 Jefferson Avenue Northeast Renton, Washington 98056 SITE DocuSign Envelope ID: E4190986-0960-4AF4-9156-D3C7AC5C2491 TP-1TP-2TP-3TP-4TP-504/2018Corporate Office17522 Bothell Way NortheastBothell, Washington 98011Phone: 425.415.0551Fax: 425.415.0311Jefferson and Kirkland TownhomesRGI Project Number2018-070Date Drawn:Address: 1513 Kirkland Avenue Northeast & 1526 Jefferson Avenue Northeast Renton, Washington 98056Geotechnical Exploration PlanFigure 2Approximate Scale: 1"=30'0153060N= Test pit by RGI, 3/30/18= Site boundaryDocuSign Envelope ID: E4190986-0960-4AF4-9156-D3C7AC5C2491 Incliniations) 12" Over the Pipe 3" Below the Pipe Perforated Pipe 4" Diameter PVC Compacted Structural Backfill (Native or Import) 12" min. Filter Fabric Material 12" Minimum Wide Free-Draining Gravel Slope to Drain (See Report for Appropriate Excavated Slope 04/2018 Corporate Office 17522 Bothell Way Northeast Bothell, Washington 98011 Phone: 425.415.0551 Fax: 425.415.0311 Jefferson and Kirkland Townhomes RGI Project Number 2018-070 Date Drawn: Address: 1513 Kirkland Avenue Northeast & 1526 Jefferson Avenue Northeast Renton, Washington 98056 Retaining Wall Drainage Detail Figure 3 Not to Scale DocuSign Envelope ID: E4190986-0960-4AF4-9156-D3C7AC5C2491 3/4" Washed Rock or Pea Gravel 4" Perforated Pipe Building Slab Structural Backfill Compacted Filter Fabric 04/2018 Corporate Office 17522 Bothell Way Northeast Bothell, Washington 98011 Phone: 425.415.0551 Fax: 425.415.0311 Jefferson and Kirkland Townhomes RGI Project Number 2018-070 Date Drawn: Address: 1513 Kirkland Avenue Northeast & 1526 Jefferson Avenue Northeast Renton, Washington 98056 Typical Footing Drain Detail Figure 4 Not to Scale DocuSign Envelope ID: E4190986-0960-4AF4-9156-D3C7AC5C2491 Geotechnical Engineering Report April 6, 2018 Jefferson and Kirkland Townhomes, Renton, Washington RGI Project No. 2018-070 APPENDIX A FIELD EXPLORATION AND LABORATORY TESTING On March 30, RGI performed field explorations using a rubber tracked excavator. We explored subsurface soil conditions at the site by observing the excavation of five test pits to a maximum depth of 9.5 feet below existing grade. The test pit locations are shown on Figure 2. The test pit locations were approximately determined by measurements from existing property lines and paved roads. A geologist from our office conducted the field exploration and classified the soil conditions encountered, maintained a log of each test exploration, obtained representative soil samples, and observed pertinent site features. All soil samples were visually classified in accordance with the Unified Soil Classification System (USCS). Representative soil samples obtained from the explorations were placed in closed containers and taken to our laboratory for further examination and testing. As a part of the laboratory testing program, the soil samples were classified in our in house laboratory based on visual observation, texture, plasticity, and the limited laboratory testing described below. Moisture Content Determinations Moisture content determinations were performed in accordance with ASTM D2216-10 Standard Test Methods for Laboratory Determination of Water (Moisture) Content of Soil and Rock by Mass (ASTM D2216) on representative samples obtained from the exploration in order to aid in identification and correlation of soil types. The moisture content of typical sample was measured and is reported on the test pit logs. Grain Size Analysis A grain size analysis indicates the range in diameter of soil particles included in a particular sample. Grain size analyses was determined using D6913-04(2009) Standard Test Methods for Particle-Size Distribution (Gradation) of Soils Using Sieve Analysis (ASTM D6913) on seven of the samples. DocuSign Envelope ID: E4190986-0960-4AF4-9156-D3C7AC5C2491 Project Name:Jefferson Highlands Townhomes Project Number:2018-070 Client:Anita Woo Test Pit No.: TP-1 Date(s) Excavated:3/30/2018 Excavation Method:Trackhoe Excavator Type:Rubber Tracked Excavator Groundwater Level:Not Encountered Test Pit Backfill:Cuttings Logged By ELW Bucket Size:N/A Excavating Contractor:Ryatt Construction Sampling Method(s)Grab Location 1513 Kirkland Avenue NE & 1526 Jefferson Avenue NE, Renton, Washington Surface Conditions:Grass Total Depth of Excavation:9.5 feet bgs Approximate Surface Elevation N/A Compaction Method Bucket USCS SymbolTPSL SM GP SP-SM SM SM REMARKS AND OTHER TESTS 12% moisture 4% moisture, 1% fines 7% moisture, 10% fines 8% moisture, 15% fines 13% moistureGraphic LogMATERIAL DESCRIPTION 16" topsoil Reddish brown silty SAND with trace gravel, loose to medium dense, moist Gray GRAVEL with some sand and trace silt, medium dense, moist Gray SAND with some silt and trace gravel, medium dense, moist Contains roots Localized iron oxide staining Gray silty SAND with trace gravel, dense, moist Gray silty SAND with some gravel, very dense, moist (Glacial Till) Test Pit terminated at 9.5'Depth (feet)0 5 10 Sample NumberSample TypeElevation (feet)Sheet 1 of 1 The Riley Group, Inc. 17522 Bothell Way NE, Bothell, WA 98011 DocuSign Envelope ID: E4190986-0960-4AF4-9156-D3C7AC5C2491 Project Name:Jefferson Highlands Townhomes Project Number:2018-070 Client:Anita Woo Test Pit No.: TP-2 Date(s) Excavated:3/30/2018 Excavation Method:Trackhoe Excavator Type:Rubber Tracked Excavator Groundwater Level:Not Encountered Test Pit Backfill:Cuttings Logged By ELW Bucket Size:N/A Excavating Contractor:Ryatt Construction Sampling Method(s)Grab Location 1513 Kirkland Avenue NE & 1526 Jefferson Avenue NE, Renton, Washington Surface Conditions:Grass Total Depth of Excavation:6.5 feet bgs Approximate Surface Elevation N/A Compaction Method Bucket USCS SymbolTPSL SM GP SP-SM SM REMARKS AND OTHER TESTS 3% moisture, 1% fines 9% moisture, 11% fines 15% moisture, 14% fines 12% moisture, 14% finesGraphic LogMATERIAL DESCRIPTION 12" topsoil Reddish brown silty SAND with trace gravel, loose to medium dense, moist Gray GRAVEL with some sand and trace silt, medium dense, moist Gray SAND with some silt and trace gravel, medium dense, moist Infiltration test at 4' Gray silty SAND with trace gravel, dense, wet Iron oxide staining Becomes moist to wet Test Pit terminated at 6.5'Depth (feet)0 5 10 Sample NumberSample TypeElevation (feet)Sheet 1 of 1 The Riley Group, Inc. 17522 Bothell Way NE, Bothell, WA 98011 DocuSign Envelope ID: E4190986-0960-4AF4-9156-D3C7AC5C2491 Project Name:Jefferson Highlands Townhomes Project Number:2018-070 Client:Anita Woo Test Pit No.: TP-3 Date(s) Excavated:3/30/2018 Excavation Method:Trackhoe Excavator Type:Rubber Tracked Excavator Groundwater Level:Not Encountered Test Pit Backfill:Cuttings Logged By ELW Bucket Size:N/A Excavating Contractor:Ryatt Construction Sampling Method(s)Grab Location 1513 Kirkland Avenue NE & 1526 Jefferson Avenue NE, Renton, Washington Surface Conditions:Grass Total Depth of Excavation:5 feet bgs Approximate Surface Elevation N/A Compaction Method Bucket USCS SymbolTPSL SM SP-SM REMARKS AND OTHER TESTS 14% moisture 7% moisture 7% moistureGraphic LogMATERIAL DESCRIPTION 12" topsoil Reddish brown silty SAND with trace gravel, loose to medium dense, moist Gray SAND with some silt and trace gravel, medium dense, moist Test Pit terminated at 5'Depth (feet)0 5 10 Sample NumberSample TypeElevation (feet)Sheet 1 of 1 The Riley Group, Inc. 17522 Bothell Way NE, Bothell, WA 98011 DocuSign Envelope ID: E4190986-0960-4AF4-9156-D3C7AC5C2491 Project Name:Jefferson Highlands Townhomes Project Number:2018-070 Client:Anita Woo Test Pit No.: TP-4 Date(s) Excavated:3/30/2018 Excavation Method:Trackhoe Excavator Type:Rubber Tracked Excavator Groundwater Level:Not Encountered Test Pit Backfill:Cuttings Logged By ELW Bucket Size:N/A Excavating Contractor:Ryatt Construction Sampling Method(s)Grab Location 1513 Kirkland Avenue NE & 1526 Jefferson Avenue NE, Renton, Washington Surface Conditions:Grass Total Depth of Excavation:5.5 feet bgs Approximate Surface Elevation N/A Compaction Method Bucket USCS SymbolTPSL Fill SM SP-SM SM REMARKS AND OTHER TESTS 17% moisture 9% moisture 12% moistureGraphic LogMATERIAL DESCRIPTION 6" topsoil Brown silty SAND with trace gravel, loose, moist (Fill) Contains brick debris Reddish brown silty SAND with trace gravel, loose to medium dense, moist Gray SAND with some silt and trace gravel, medium dense, moist Gray silty SAND with trace gravel, medium dense, moist Trace iron oxide stasining Test Pit terminated at 5.5'Depth (feet)0 5 10 Sample NumberSample TypeElevation (feet)Sheet 1 of 1 The Riley Group, Inc. 17522 Bothell Way NE, Bothell, WA 98011 DocuSign Envelope ID: E4190986-0960-4AF4-9156-D3C7AC5C2491 Project Name:Jefferson Highlands Townhomes Project Number:2018-070 Client:Anita Woo Test Pit No.: TP-5 Date(s) Excavated:3/30/2018 Excavation Method:Trackhoe Excavator Type:Rubber Tracked Excavator Groundwater Level:Not Encountered Test Pit Backfill:Cuttings Logged By ELW Bucket Size:N/A Excavating Contractor:Ryatt Construction Sampling Method(s)Grab Location 1513 Kirkland Avenue NE & 1526 Jefferson Avenue NE, Renton, Washington Surface Conditions:Grass Total Depth of Excavation:6.5 feet bgs Approximate Surface Elevation N/A Compaction Method Bucket USCS SymbolTPSL Fill Fill TPSL SM SP-SM REMARKS AND OTHER TESTS 10% moisture 13% moisture 8% moistureGraphic LogMATERIAL DESCRIPTION 6" topsoil Brown silty SAND with trace gravel, medium dense, moist (Fill) Contains brick and metal debris Gray SAND with some silt and trace gravel, medium dense, moist (Fill) 6" topsoil Reddish brown silty SAND with trace gravel, medium dense, moist Gray SAND with some silt and trace gravel, medium dense, moist Test Pit terminated at 6.5'Depth (feet)0 5 10 Sample NumberSample TypeElevation (feet)Sheet 1 of 1 The Riley Group, Inc. 17522 Bothell Way NE, Bothell, WA 98011 DocuSign Envelope ID: E4190986-0960-4AF4-9156-D3C7AC5C2491 Project Name:Jefferson Highlands Townhomes Project Number:2018-070 Client:Anita Woo Key to Logs USCS SymbolREMARKS AND OTHER TESTSGraphic LogMATERIAL DESCRIPTIONDepth (feet)Sample NumberSample TypeElevation (feet)1 2 3 4 5 6 7 8 COLUMN DESCRIPTIONS 1 Elevation (feet): Elevation (MSL, feet). 2 Depth (feet): Depth in feet below the ground surface. 3 Sample Type: Type of soil sample collected at the depth interval shown. 4 Sample Number: Sample identification number. 5 USCS Symbol: USCS symbol of the subsurface material. 6 Graphic Log: Graphic depiction of the subsurface material encountered. 7 MATERIAL DESCRIPTION: Description of material encountered. May include consistency, moisture, color, and other descriptive text. 8 REMARKS AND OTHER TESTS: Comments and observations regarding drilling or sampling made by driller or field personnel. FIELD AND LABORATORY TEST ABBREVIATIONS CHEM: Chemical tests to assess corrosivity COMP: Compaction test CONS: One-dimensional consolidation test LL: Liquid Limit, percent PI: Plasticity Index, percent SA: Sieve analysis (percent passing No. 200 Sieve) UC: Unconfined compressive strength test, Qu, in ksf WA: Wash sieve (percent passing No. 200 Sieve) MATERIAL GRAPHIC SYMBOLS AF Poorly graded GRAVEL (GP) Silty SAND (SM) Poorly graded SAND with Silt (SP-SM) Topsoil TYPICAL SAMPLER GRAPHIC SYMBOLS Auger sampler Bulk Sample 3-inch-OD California w/ brass rings CME Sampler Grab Sample 2.5-inch-OD Modified California w/ brass liners Pitcher Sample 2-inch-OD unlined split spoon (SPT) Shelby Tube (Thin-walled, fixed head) OTHER GRAPHIC SYMBOLS Water level (at time of drilling, ATD) Water level (after waiting) Minor change in material properties within a stratum Inferred/gradational contact between strata ?Queried contact between strata GENERAL NOTES 1: Soil classifications are based on the Unified Soil Classification System. Descriptions and stratum lines are interpretive, and actual lithologic changes may be gradual. Field descriptions may have been modified to reflect results of lab tests. 2: Descriptions on these logs apply only at the specific boring locations and at the time the borings were advanced. They are not warranted to be representative of subsurface conditions at other locations or times. Sheet 1 of 1 The Riley Group, Inc. 17522 Bothell Way NE, Bothell, WA 98011 DocuSign Envelope ID: E4190986-0960-4AF4-9156-D3C7AC5C2491 THE RILEY GROUP, INC. 17522 Bothell Way NE Bothell, WA 98011 PHONE: (425) 415-0551 FAX: (425) 415-0311 GRAIN SIZE ANALYSIS ASTM D421, D422, D1140, D2487, D6913 PROJECT TITLE Jefferson Highlands Townhomes SAMPLE ID/TYPE TP-1 PROJECT NO.2018-070 SAMPLE DEPTH 2.5' TECH/TEST DATE ELW 3/31/2018 DATE RECEIVED 3/30/2018 WATER CONTENT (Delivered Moisture) Total Weight Of Sample Used For Sieve Corrected For Hygroscopic Moisture Wt Wet Soil & Tare (gm) (w1)666.3 Weight Of Sample (gm)641.7 Wt Dry Soil & Tare (gm)(w2)641.7 Tare Weight (gm) 15.4 Weight of Tare (gm)(w3)15.4 (W6) Total Dry Weight (gm)626.3 Weight of Water (gm)(w4=w1-w2)24.6 SIEVE ANALYSIS Weight of Dry Soil (gm) (w5=w2-w3)626.3 Cumulative Moisture Content (%) (w4/w5)*100 4 Wt Ret (Wt-Tare) (%Retained)% PASS +Tare {(wt ret/w6)*100}(100-%ret) % COBBLES 0.0 12.0"15.4 0.00 0.00 100.00 cobbles % C GRAVEL 58.2 3.0"15.4 0.00 0.00 100.00 coarse gravel % F GRAVEL 14.8 2.5" coarse gravel % C SAND 2.6 2.0" coarse gravel % M SAND 14.5 1.5"15.4 0.00 0.00 100.00 coarse gravel % F SAND 9.0 1.0" coarse gravel % FINES 1.0 0.75"379.8 364.40 58.18 41.82 fine gravel % TOTAL 100.0 0.50" fine gravel 0.375"457.7 442.30 70.62 29.38 fine gravel D10 (mm)0.41 #4 472.6 457.20 73.00 27.00 coarse sand D30 (mm)9.5 #10 488.6 473.20 75.55 24.45 medium sand D60 (mm)23 #20 medium sand Cu 56.1 #40 579.4 564.00 90.05 9.95 fine sand Cc 9.6 #60 fine sand #100 630.3 614.90 98.18 1.82 fine sand #200 635.6 620.20 99.03 0.97 fines PAN 641.7 626.30 100.00 0.00 silt/clay 322 DESCRIPTION GRAVEL with some sand and trace silt USCS GP Prepared For:Reviewed By: Anita Woo KMW 0 10 20 30 40 50 60 70 80 90 100 0.0010.010.11101001000 % P A S S I N G Grain size in millimeters 12"3"2"1".75".375"#4 #10 #20 #40 #60 #100 #200 DocuSign Envelope ID: E4190986-0960-4AF4-9156-D3C7AC5C2491 THE RILEY GROUP, INC. 17522 Bothell Way NE Bothell, WA 98011 PHONE: (425) 415-0551 FAX: (425) 415-0311 GRAIN SIZE ANALYSIS ASTM D421, D422, D1140, D2487, D6913 PROJECT TITLE Jefferson Highlands Townhomes SAMPLE ID/TYPE TP-1 PROJECT NO.2018-070 SAMPLE DEPTH 4' TECH/TEST DATE ELW 3/31/2018 DATE RECEIVED 3/30/2018 WATER CONTENT (Delivered Moisture) Total Weight Of Sample Used For Sieve Corrected For Hygroscopic Moisture Wt Wet Soil & Tare (gm) (w1)371.4 Weight Of Sample (gm)347.4 Wt Dry Soil & Tare (gm)(w2)347.4 Tare Weight (gm) 15.6 Weight of Tare (gm)(w3)15.6 (W6) Total Dry Weight (gm)331.8 Weight of Water (gm)(w4=w1-w2)24.0 SIEVE ANALYSIS Weight of Dry Soil (gm) (w5=w2-w3)331.8 Cumulative Moisture Content (%) (w4/w5)*100 7 Wt Ret (Wt-Tare) (%Retained)% PASS +Tare {(wt ret/w6)*100}(100-%ret) % COBBLES 0.0 12.0"15.6 0.00 0.00 100.00 cobbles % C GRAVEL 0.0 3.0"15.6 0.00 0.00 100.00 coarse gravel % F GRAVEL 6.7 2.5" coarse gravel % C SAND 4.2 2.0" coarse gravel % M SAND 26.8 1.5"15.6 0.00 0.00 100.00 coarse gravel % F SAND 52.0 1.0" coarse gravel % FINES 10.2 0.75"15.6 0.00 0.00 100.00 fine gravel % TOTAL 100.0 0.50" fine gravel 0.375"26.3 10.70 3.22 96.78 fine gravel D10 (mm)0.075 #4 37.9 22.30 6.72 93.28 coarse sand D30 (mm)0.2 #10 51.9 36.30 10.94 89.06 medium sand D60 (mm)0.4 #20 medium sand Cu 5.3 #40 140.9 125.30 37.76 62.24 fine sand Cc 1.3 #60 fine sand #100 288.0 272.40 82.10 17.90 fine sand #200 313.5 297.90 89.78 10.22 fines PAN 347.4 331.80 100.00 0.00 silt/clay 322 DESCRIPTION SAND with some silt and trace gravel USCS SP-SM Prepared For:Reviewed By: Anita Woo KMW 0 10 20 30 40 50 60 70 80 90 100 0.0010.010.11101001000 % P A S S I N G Grain size in millimeters 12"3"2"1".75".375"#4 #10 #20 #40 #60 #100 #200 DocuSign Envelope ID: E4190986-0960-4AF4-9156-D3C7AC5C2491 THE RILEY GROUP, INC. 17522 Bothell Way NE Bothell, WA 98011 PHONE: (425) 415-0551 FAX: (425) 415-0311 GRAIN SIZE ANALYSIS ASTM D421, D422, D1140, D2487, D6913 PROJECT TITLE Jefferson Highlands Townhomes SAMPLE ID/TYPE TP-1 PROJECT NO.2018-070 SAMPLE DEPTH 6.5' TECH/TEST DATE ELW 3/31/2018 DATE RECEIVED 3/30/2018 WATER CONTENT (Delivered Moisture) Total Weight Of Sample Used For Sieve Corrected For Hygroscopic Moisture Wt Wet Soil & Tare (gm) (w1)490.6 Weight Of Sample (gm)454.9 Wt Dry Soil & Tare (gm)(w2)454.9 Tare Weight (gm) 15.4 Weight of Tare (gm)(w3)15.4 (W6) Total Dry Weight (gm)439.5 Weight of Water (gm)(w4=w1-w2)35.7 SIEVE ANALYSIS Weight of Dry Soil (gm) (w5=w2-w3)439.5 Cumulative Moisture Content (%) (w4/w5)*100 8 Wt Ret (Wt-Tare) (%Retained)% PASS +Tare {(wt ret/w6)*100}(100-%ret) % COBBLES 0.0 12.0"15.4 0.00 0.00 100.00 cobbles % C GRAVEL 5.1 3.0"15.4 0.00 0.00 100.00 coarse gravel % F GRAVEL 7.6 2.5" coarse gravel % C SAND 2.4 2.0" coarse gravel % M SAND 19.2 1.5"15.4 0.00 0.00 100.00 coarse gravel % F SAND 50.9 1.0" coarse gravel % FINES 14.9 0.75"37.9 22.50 5.12 94.88 fine gravel % TOTAL 100.0 0.50" fine gravel 0.375"65.9 50.50 11.49 88.51 fine gravel D10 (mm)#4 71.1 55.70 12.67 87.33 coarse sand D30 (mm)#10 81.6 66.20 15.06 84.94 medium sand D60 (mm)#20 medium sand Cu #40 165.8 150.40 34.22 65.78 fine sand Cc #60 fine sand #100 349.2 333.80 75.95 24.05 fine sand #200 389.3 373.90 85.07 14.93 fines PAN 454.9 439.50 100.00 0.00 silt/clay 322 DESCRIPTION Silty SAND with trace gravel USCS SM Prepared For:Reviewed By: Anita Woo KMW 0 10 20 30 40 50 60 70 80 90 100 0.0010.010.11101001000 % P A S S I N G Grain size in millimeters 12"3"2"1".75".375"#4 #10 #20 #40 #60 #100 #200 DocuSign Envelope ID: E4190986-0960-4AF4-9156-D3C7AC5C2491 THE RILEY GROUP, INC. 17522 Bothell Way NE Bothell, WA 98011 PHONE: (425) 415-0551 FAX: (425) 415-0311 GRAIN SIZE ANALYSIS ASTM D421, D422, D1140, D2487, D6913 PROJECT TITLE Jefferson Highlands Townhomes SAMPLE ID/TYPE TP-2 PROJECT NO.2018-070 SAMPLE DEPTH 3' TECH/TEST DATE ELW 3/31/2018 DATE RECEIVED 3/30/2018 WATER CONTENT (Delivered Moisture) Total Weight Of Sample Used For Sieve Corrected For Hygroscopic Moisture Wt Wet Soil & Tare (gm) (w1)884.5 Weight Of Sample (gm)860.6 Wt Dry Soil & Tare (gm)(w2)860.6 Tare Weight (gm) 15.4 Weight of Tare (gm)(w3)15.4 (W6) Total Dry Weight (gm)845.2 Weight of Water (gm)(w4=w1-w2)23.9 SIEVE ANALYSIS Weight of Dry Soil (gm) (w5=w2-w3)845.2 Cumulative Moisture Content (%) (w4/w5)*100 3 Wt Ret (Wt-Tare) (%Retained)% PASS +Tare {(wt ret/w6)*100}(100-%ret) % COBBLES 0.0 12.0"15.4 0.00 0.00 100.00 cobbles % C GRAVEL 61.0 3.0"15.4 0.00 0.00 100.00 coarse gravel % F GRAVEL 17.8 2.5" coarse gravel % C SAND 3.5 2.0" coarse gravel % M SAND 12.1 1.5"15.4 0.00 0.00 100.00 coarse gravel % F SAND 4.9 1.0" coarse gravel % FINES 0.7 0.75"531.0 515.60 61.00 39.00 fine gravel % TOTAL 100.0 0.50" fine gravel 0.375"641.6 626.20 74.09 25.91 fine gravel D10 (mm)0.7 #4 681.7 666.30 78.83 21.17 coarse sand D30 (mm)12 #10 711.0 695.60 82.30 17.70 medium sand D60 (mm)24 #20 medium sand Cu 34.3 #40 813.2 797.80 94.39 5.61 fine sand Cc 8.6 #60 fine sand #100 850.4 835.00 98.79 1.21 fine sand #200 854.7 839.30 99.30 0.70 fines PAN 860.6 845.20 100.00 0.00 silt/clay 322 DESCRIPTION GRAVEL with some sand and trace silt USCS GP Prepared For:Reviewed By: Anita Woo KMW 0 10 20 30 40 50 60 70 80 90 100 0.0010.010.11101001000 % P A S S I N G Grain size in millimeters 12"3"2"1".75".375"#4 #10 #20 #40 #60 #100 #200 DocuSign Envelope ID: E4190986-0960-4AF4-9156-D3C7AC5C2491 THE RILEY GROUP, INC. 17522 Bothell Way NE Bothell, WA 98011 PHONE: (425) 415-0551 FAX: (425) 415-0311 GRAIN SIZE ANALYSIS ASTM D421, D422, D1140, D2487, D6913 PROJECT TITLE Jefferson Highlands Townhomes SAMPLE ID/TYPE TP-2 PROJECT NO.2018-070 SAMPLE DEPTH 4' TECH/TEST DATE ELW 3/31/2018 DATE RECEIVED 3/30/2018 WATER CONTENT (Delivered Moisture) Total Weight Of Sample Used For Sieve Corrected For Hygroscopic Moisture Wt Wet Soil & Tare (gm) (w1)335.3 Weight Of Sample (gm)308.8 Wt Dry Soil & Tare (gm)(w2)308.8 Tare Weight (gm) 15.4 Weight of Tare (gm)(w3)15.4 (W6) Total Dry Weight (gm)293.4 Weight of Water (gm)(w4=w1-w2)26.5 SIEVE ANALYSIS Weight of Dry Soil (gm) (w5=w2-w3)293.4 Cumulative Moisture Content (%) (w4/w5)*100 9 Wt Ret (Wt-Tare) (%Retained)% PASS +Tare {(wt ret/w6)*100}(100-%ret) % COBBLES 0.0 12.0"15.4 0.00 0.00 100.00 cobbles % C GRAVEL 0.0 3.0"15.4 0.00 0.00 100.00 coarse gravel % F GRAVEL 9.6 2.5" coarse gravel % C SAND 5.2 2.0" coarse gravel % M SAND 21.0 1.5"15.4 0.00 0.00 100.00 coarse gravel % F SAND 53.1 1.0" coarse gravel % FINES 11.1 0.75"15.4 0.00 0.00 100.00 fine gravel % TOTAL 100.0 0.50" fine gravel 0.375"27.9 12.50 4.26 95.74 fine gravel D10 (mm)0.07 #4 43.7 28.30 9.65 90.35 coarse sand D30 (mm)0.19 #10 58.9 43.50 14.83 85.17 medium sand D60 (mm)0.39 #20 medium sand Cu 5.6 #40 120.6 105.20 35.86 64.14 fine sand Cc 1.3 #60 fine sand #100 249.7 234.30 79.86 20.14 fine sand #200 276.3 260.90 88.92 11.08 fines PAN 308.8 293.40 100.00 0.00 silt/clay 322 DESCRIPTION SAND with some silt and trace gravel USCS SP-SM Prepared For:Reviewed By: Anita Woo KMW 0 10 20 30 40 50 60 70 80 90 100 0.0010.010.11101001000 % P A S S I N G Grain size in millimeters 12"3"2"1".75".375"#4 #10 #20 #40 #60 #100 #200 DocuSign Envelope ID: E4190986-0960-4AF4-9156-D3C7AC5C2491 THE RILEY GROUP, INC. 17522 Bothell Way NE Bothell, WA 98011 PHONE: (425) 415-0551 FAX: (425) 415-0311 GRAIN SIZE ANALYSIS ASTM D421, D422, D1140, D2487, D6913 PROJECT TITLE Jefferson Highlands Townhomes SAMPLE ID/TYPE TP-2 PROJECT NO.2018-070 SAMPLE DEPTH 5' TECH/TEST DATE ELW 3/31/2018 DATE RECEIVED 3/30/2018 WATER CONTENT (Delivered Moisture) Total Weight Of Sample Used For Sieve Corrected For Hygroscopic Moisture Wt Wet Soil & Tare (gm) (w1)499.0 Weight Of Sample (gm)435.6 Wt Dry Soil & Tare (gm)(w2)435.6 Tare Weight (gm) 15.4 Weight of Tare (gm)(w3)15.4 (W6) Total Dry Weight (gm)420.2 Weight of Water (gm)(w4=w1-w2)63.4 SIEVE ANALYSIS Weight of Dry Soil (gm) (w5=w2-w3)420.2 Cumulative Moisture Content (%) (w4/w5)*100 15 Wt Ret (Wt-Tare) (%Retained)% PASS +Tare {(wt ret/w6)*100}(100-%ret) % COBBLES 0.0 12.0"15.4 0.00 0.00 100.00 cobbles % C GRAVEL 0.0 3.0"15.4 0.00 0.00 100.00 coarse gravel % F GRAVEL 10.6 2.5" coarse gravel % C SAND 4.9 2.0" coarse gravel % M SAND 21.8 1.5"15.4 0.00 0.00 100.00 coarse gravel % F SAND 48.6 1.0" coarse gravel % FINES 14.1 0.75"15.4 0.00 0.00 100.00 fine gravel % TOTAL 100.0 0.50" fine gravel 0.375"33.4 18.00 4.28 95.72 fine gravel D10 (mm)#4 60.1 44.70 10.64 89.36 coarse sand D30 (mm)#10 80.7 65.30 15.54 84.46 medium sand D60 (mm)#20 medium sand Cu #40 172.3 156.90 37.34 62.66 fine sand Cc #60 fine sand #100 340.7 325.30 77.42 22.58 fine sand #200 376.4 361.00 85.91 14.09 fines PAN 435.6 420.20 100.00 0.00 silt/clay 322 DESCRIPTION Silty SAND with trace gravel USCS SM Prepared For:Reviewed By: Anita Woo KMW 0 10 20 30 40 50 60 70 80 90 100 0.0010.010.11101001000 % P A S S I N G Grain size in millimeters 12"3"2"1".75".375"#4 #10 #20 #40 #60 #100 #200 DocuSign Envelope ID: E4190986-0960-4AF4-9156-D3C7AC5C2491 THE RILEY GROUP, INC. 17522 Bothell Way NE Bothell, WA 98011 PHONE: (425) 415-0551 FAX: (425) 415-0311 GRAIN SIZE ANALYSIS ASTM D421, D422, D1140, D2487, D6913 PROJECT TITLE Jefferson Highlands Townhomes SAMPLE ID/TYPE TP-2 PROJECT NO.2018-070 SAMPLE DEPTH 6' TECH/TEST DATE ELW 3/31/2018 DATE RECEIVED 3/30/2018 WATER CONTENT (Delivered Moisture) Total Weight Of Sample Used For Sieve Corrected For Hygroscopic Moisture Wt Wet Soil & Tare (gm) (w1)384.0 Weight Of Sample (gm)343.2 Wt Dry Soil & Tare (gm)(w2)343.2 Tare Weight (gm) 15.5 Weight of Tare (gm)(w3)15.5 (W6) Total Dry Weight (gm)327.7 Weight of Water (gm)(w4=w1-w2)40.8 SIEVE ANALYSIS Weight of Dry Soil (gm) (w5=w2-w3)327.7 Cumulative Moisture Content (%) (w4/w5)*100 12 Wt Ret (Wt-Tare) (%Retained)% PASS +Tare {(wt ret/w6)*100}(100-%ret) % COBBLES 0.0 12.0"15.5 0.00 0.00 100.00 cobbles % C GRAVEL 0.0 3.0"15.5 0.00 0.00 100.00 coarse gravel % F GRAVEL 10.5 2.5" coarse gravel % C SAND 5.5 2.0" coarse gravel % M SAND 24.4 1.5"15.5 0.00 0.00 100.00 coarse gravel % F SAND 45.7 1.0" coarse gravel % FINES 13.9 0.75"15.5 0.00 0.00 100.00 fine gravel % TOTAL 100.0 0.50" fine gravel 0.375"34.5 19.00 5.80 94.20 fine gravel D10 (mm)#4 49.9 34.40 10.50 89.50 coarse sand D30 (mm)#10 68.0 52.50 16.02 83.98 medium sand D60 (mm)#20 medium sand Cu #40 148.1 132.60 40.46 59.54 fine sand Cc #60 fine sand #100 272.1 256.60 78.30 21.70 fine sand #200 297.8 282.30 86.15 13.85 fines PAN 343.2 327.70 100.00 0.00 silt/clay 322 DESCRIPTION Silty SAND with trace gravel USCS SM Prepared For:Reviewed By: Anita Woo KMW 0 10 20 30 40 50 60 70 80 90 100 0.0010.010.11101001000 % P A S S I N G Grain size in millimeters 12"3"2"1".75".375"#4 #10 #20 #40 #60 #100 #200 DocuSign Envelope ID: E4190986-0960-4AF4-9156-D3C7AC5C2491 Corporate Office 17522 Bothell Way Northeast Bothell, Washington 98011 Phone 425.415.0551 ♦ Fax 425.415.0311 www.riley-group.com GEOTECHNICAL ENGINEERING REPORT PREPARED BY: THE RILEY GROUP, INC. 17522 BOTHELL WAY NORTHEAST BOTHELL, WASHINGTON 98011 PREPARED FOR: ANITA WOO 12906 NORTHEAST 25TH PLACE BELLEVUE, WASHINGTON 98004 RGI PROJECT NO. 2021-123 JEFFERSON TOWNHOMES 1518 JEFFERSON AVENUE NORTHEAST RENTON, WASHINGTON SEPTEMBER 1, 2021 DocuSign Envelope ID: E4190986-0960-4AF4-9156-D3C7AC5C2491 Corporate Office 17522 Bothell Way Northeast Bothell, Washington 98011 Phone 425.415.0551 ♦ Fax 425.415.0311 www.riley-group.com September 1, 2021 Anita Woo 12906 Northeast 25th Place Bellevue, Washington 98004 Subject: Geotechnical Engineering Report Jefferson Townhomes 1518 Jefferson Avenue Northeast Renton, Washington RGI Project No. 2021-123 Dear Ms. Woo: As requested, The Riley Group, Inc. (RGI) has performed a Geotechnical Engineering Report (GER) for the Jefferson Townhomes located at 1518 Jefferson Avenue Northeast, Renton, Washington. Our services were completed in accordance with our proposal dated February 23rd, 2021 and authorized by you on July 9, 2021. The information in this GER is based on our understanding of the proposed construction, and the soil and groundwater conditions encountered in the test pits completed by RGI at the site on August 2nd, 2021. RGI recommends that you submit the project plans and specifications to RGI for a general review so that we may confirm that the recommendations in this GER are interpreted and implemented properly in the construction documents. RGI also recommends that a representative of our firm be present on site during portions of the project construction to confirm that the soil and groundwater conditions are consistent with those that form the basis for the engineering recommendations in this GER. If you have any questions or require additional information, please contact us. Respectfully submitted, THE RILEY GROUP, INC. Eric L. Woods, LG Kristina M. Weller, PE Project Geologist Principal Geotechnical Engineer DocuSign Envelope ID: E4190986-0960-4AF4-9156-D3C7AC5C2491 Geotechnical Engineering Report i September 1, 2021 Jefferson Townhomes, Renton, Washington RGI Project No. 2021-123 TABLE OF CONTENTS 1.0 INTRODUCTION ............................................................................................................................... 1 2.0 PROJECT DESCRIPTION ............................................................................................................... 1 3.0 FIELD EXPLORATION AND LABORATORY TESTING .......................................................... 1 3.1 FIELD EXPLORATION ................................................................................................................................... 1 3.2 LABORATORY TESTING ................................................................................................................................ 2 4.0 SITE CONDITIONS ........................................................................................................................... 2 4.1 SURFACE .................................................................................................................................................. 2 4.2 GEOLOGY ................................................................................................................................................. 2 4.3 SOILS ....................................................................................................................................................... 2 4.4 GROUNDWATER ........................................................................................................................................ 3 4.5 SEISMIC CONSIDERATIONS ........................................................................................................................... 3 4.6 GEOLOGIC HAZARD AREAS .......................................................................................................................... 4 5.0 DISCUSSION AND RECOMMENDATIONS ................................................................................. 4 5.1 GEOTECHNICAL CONSIDERATIONS ................................................................................................................. 4 5.2 EARTHWORK ............................................................................................................................................. 4 5.2.1 Erosion and Sediment Control ..................................................................................................... 4 5.2.2 Stripping and Subgrade Preparation ............................................................................................ 5 5.2.3 Excavations................................................................................................................................... 6 5.2.4 Structural Fill ................................................................................................................................ 6 5.2.5 Cut and Fill Slopes ........................................................................................................................ 7 5.2.6 Wet Weather Construction Considerations ................................................................................. 8 5.3 FOUNDATIONS .......................................................................................................................................... 8 5.4 RETAINING WALLS ..................................................................................................................................... 9 5.5 SLAB-ON-GRADE CONSTRUCTION ............................................................................................................... 10 5.6 DRAINAGE .............................................................................................................................................. 10 5.6.1 Surface ....................................................................................................................................... 10 5.6.2 Subsurface .................................................................................................................................. 11 5.6.3 Infiltration .................................................................................................................................. 11 6.0 ADDITIONAL SERVICES .............................................................................................................. 11 7.0 LIMITATIONS ................................................................................................................................. 12 LIST OF FIGURES AND APPENDICES Figure 1 ..................................................................................................................... Site Vicinity Map Figure 2 ............................................................................................... Geotechnical Exploration Plan Figure 3 ............................................................................................... Retaining Wall Drainage Detail Figure 4 ....................................................................................................Typical Footing Drain Detail Appendix A .......................................................................... Field Exploration and Laboratory Testing DocuSign Envelope ID: E4190986-0960-4AF4-9156-D3C7AC5C2491 Geotechnical Engineering Report ii September 1, 2021 Jefferson Townhomes, Renton, Washington RGI Project No. 2021-123 Executive Summary This Executive Summary should be used in conjunction with the entire Geotechnical Engineering Report (GER) for design and/or construction purposes. It should be recognized that specific details were not included or fully developed in this section, and the GER must be read in its entirety for a comprehensive understanding of the items contained herein. Section 7.0 should be read for an understanding of limitations. RGI’s geotechnical scope of work included the advancement of five test pits to approximate depths of 7 feet below existing site grades. Based on the information obtained from our subsurface exploration, the site is suitable for development of the proposed project. The following geotechnical considerations were identified: Soil Conditions: The soils encountered during field exploration include up to 6.5 feet of loose fill comprised of silty sand with some gravel and sand with some gravel and silt over loose to medium dense silty sand with some gravel, gravelly sand with some silt, and sand with some silt and gravel. Groundwater: No groundwater seepage was encountered during our subsurface exploration. Foundations: Foundations for the proposed building may be supported on conventional spread footings bearing on medium dense native soil or structural fill. Slab-on-grade: Slab-on-grade floors and slabs for the proposed building can be supported on medium dense native soil or structural fill. DocuSign Envelope ID: E4190986-0960-4AF4-9156-D3C7AC5C2491 Geotechnical Engineering Report 1 September 1, 2021 Jefferson Townhomes, Renton, Washington RGI Project No. 2021-123 1.0 Introduction This Geotechnical Engineering Report (GER) presents the results of the geotechnical engineering services provided for the Jefferson Townhomes in Renton, Washington. The purpose of this evaluation is to assess subsurface conditions and provide geotechnical recommendations for the construction of a townhome development. Our scope of services included field explorations, laboratory testing, engineering analyses, and preparation of this GER. The recommendations in the following sections of this GER are based upon our current understanding of the proposed site development as outlined below. If actual features vary or changes are made, RGI should review them in order to modify our recommendations as required. In addition, RGI requests to review the site grading plan, final design drawings and specifications when available to verify that our project understanding is correct and that our recommendations have been properly interpreted and incorporated into the project design and construction. 2.0 Project description The project site is located at 1518 Jefferson Avenue Northeast in Renton, Washington. The approximate location of the site is shown on Figure 1. The site is currently occupied by a single-family residence. RGI understands that the existing structure will be demolished and townhomes will be constructed on the site. At the time of preparing this GER, building plans were not available for our review. Based on our experience with similar construction, RGI anticipates that the proposed building will be supported on perimeter walls with bearing loads of two to six kips per linear foot, and a series of columns with a maximum load up to 30 kips. Slab-on-grade floor loading of 250 pounds per square foot (psf) are expected. 3.0 Field Exploration and Laboratory Testing 3.1 FIELD EXPLORATION On August 2nd, 2021, RGI observed the excavation of five test pits. The approximate exploration locations are shown on Figure 2. Field logs of each exploration were prepared by the geotechnical technician that continuously observed the excavation. These logs included visual classifications of the materials encountered during excavation as well as our interpretation of the subsurface conditions between samples. The test pit logs included in Appendix A represent an interpretation of the field logs and include modifications based on laboratory observation and analysis of the samples. DocuSign Envelope ID: E4190986-0960-4AF4-9156-D3C7AC5C2491 Geotechnical Engineering Report 2 September 1, 2021 Jefferson Townhomes, Renton, Washington RGI Project No. 2021-123 3.2 LABORATORY TESTING During the field exploration, a representative portion of each recovered sample was sealed in containers and transported to our laboratory for further visual and laboratory examination. Selected samples retrieved from the test pits were tested for moisture content and grain size analysis to aid in soil classification and provide input for the recommendations provided in this GER. The results and descriptions of the laboratory tests are enclosed in Appendix A. 4.0 Site Conditions 4.1 SURFACE The subject site is a rectangular-shaped parcel of land approximately 0.22 acres in size. The site is bound to the north, east and south by single-family residences, and to the west by Jefferson Avenue NE. The existing site is occupied by a single-family residence. The site slopes generally to the east with an overall elevation difference of approximately 8 feet. The site is vegetated with grass, decorative plants and shrubs, and several medium- to large-diameter trees. 4.2 GEOLOGY Review of the Geologic Map of Surficial Deposits in the Seattle 30’ by 60’ Quadrangle, Washington, by James C. Yount, etc. (1993) indicates that the soil in the project vicinity is mapped as Vashon till (Qt), which is light to dark gray, nonsorted, nonstratified mixture of clay, silt, sand, and gravel. However soil encountered at the site matches the description for Vashon recessional outwash deposit (Qvr) found mapped to the west of the site, which is poorly to moderately sorted stratified gravel and sand with some silt and clay. 4.3 SOILS The soils encountered during field exploration include up to 6.5 feet of loose fill comprised of silty sand with some gravel and sand with some gravel and silt over loose to medium dense silty sand with some gravel, gravelly sand with some silt, and sand with some silt and gravel. More detailed descriptions of the subsurface conditions encountered are presented in the Test pits included in Appendix A. Sieve analysis was performed on four selected soil samples. Grain size distribution curves are included in Appendix A. DocuSign Envelope ID: E4190986-0960-4AF4-9156-D3C7AC5C2491 Geotechnical Engineering Report 3 September 1, 2021 Jefferson Townhomes, Renton, Washington RGI Project No. 2021-123 4.4 GROUNDWATER No groundwater seepage was encountered during our subsurface exploration It should be recognized that fluctuations of the groundwater table will occur due to seasonal variations in the amount of rainfall, runoff, and other factors not evident at the time the explorations were performed. In addition, perched water can develop within seams and layers contained in fill soils or higher permeability soils overlying less permeable soils following periods of heavy or prolonged precipitation. Therefore, groundwater levels during construction or at other times in the future may be higher or lower than the levels indicated on the logs. Groundwater level fluctuations should be considered when developing the design and construction plans for the project. 4.5 SEISMIC CONSIDERATIONS Based on the International Building Code (IBC), RGI recommends the follow seismic parameters for design. Table 1 IBC Parameter 2018 Value Site Soil Class1 D2 Site Latitude 47.506039 N Site Longitude -122.179538 W Short Period Spectral Response Acceleration, SS (g) 1.426 1-Second Period Spectral Response Acceleration, S1 (g) 0.489 Adjusted Short Period Spectral Response Acceleration, SMS (g) 1.426 Adjusted 1-Sec Period Spectral Response Acceleration, SM1 (g) 0.8853 Numeric seismic design value at 0.2 second; SDS(g) 0.951 Numeric seismic design value at 1.0 second; SD1(g) 0.593 1. Note: In general accordance with Chapter 20 of ASCE 7-16. The Site Class is based on the average characteristics of the upper 100 feet of the subsurface profile. 2. Note: ASCE 7-16 require a site soil profile determination extending to a depth of 100 feet for seismic site classification. The current scope of our services does not include the required 100 foot soil profile determination. Test pits extended to a maximum depth of 7 feet, and this seismic site class definition considers that similar soil continues below the maximum depth of the subsurface exploration. Additional exploration to deeper depths would be required to confirm the conditions below the current depth of exploration. 3. Note: In accordance with ASCE 11.4.8, a ground motion hazard analysis is not required for the following cases: • Structures on Site Class E sites with SS greater than or equal to 1.0, provided the site coefficient Fa is taken as equal to that of Site Class C. • Structures on Site Class D sites with S1 greater than or equal to 0.2, provided that the value of the seismic response coefficient Cs is determined by Eq. 12.8-2 for values of T ≤ 1.5Ts and taken as equal to 1.5 times the value computed in accordance with either Eq. 12.8-3 for TL ≥ T > 1.5Ts or Eq. 12.8-4 for T > TL. • Structures on Site Class E sites with S1 greater than or equal to 0.2, provided that T is less than or equal to Ts and the equivalent static force procedure is used for design. The above exceptions do not apply to seismically isolated structures, structures with damping systems or structures designed using the response history procedures of Chapter 16. DocuSign Envelope ID: E4190986-0960-4AF4-9156-D3C7AC5C2491 Geotechnical Engineering Report 4 September 1, 2021 Jefferson Townhomes, Renton, Washington RGI Project No. 2021-123 Liquefaction is a phenomenon where there is a reduction or complete loss of soil strength due to an increase in water pressure induced by vibrations from a seismic event. Liquefaction mainly affects geologically recent deposits of fine-grained sands that are below the groundwater table. Soils of this nature derive their strength from intergranular friction. The generated water pressure or pore pressure essentially separates the soil grains and eliminates this intergranular friction, thus reducing or eliminating the soil’s strength. RGI reviewed the results of the field and laboratory testing and assessed the potential for liquefaction of the site’s soil during an earthquake. Since the site is underlain by medium dense soils and lacks an established shallow groundwater table, RGI considers that the possibility of liquefaction during an earthquake is low. 4.6 GEOLOGIC HAZARD AREAS Regulated geologically hazardous areas include erosion, landslide, earthquake, or other geological hazards. Based on the definition in the Renton Municipal Code, the site does not contain geologically hazardous areas. 5.0 Discussion and Recommendations 5.1 GEOTECHNICAL CONSIDERATIONS Based on our study, the site is suitable for the proposed construction from a geotechnical standpoint. Foundations for the proposed building can be supported on conventional spread footings bearing on competent native soil or structural fill. Slab-on-grade floors can be similarly supported. Detailed recommendations regarding the above issues and other geotechnical design considerations are provided in the following sections. These recommendations should be incorporated into the final design drawings and construction specifications. 5.2 EARTHWORK The earthwork is expected to include excavating and backfilling the building foundations and preparing slab subgrades. 5.2.1 EROSION AND SEDIMENT CONTROL Potential sources or causes of erosion and sedimentation depend on construction methods, slope length and gradient, amount of soil exposed and/or disturbed, soil type, construction sequencing and weather. The impacts on erosion-prone areas can be reduced by implementing an erosion and sedimentation control plan. The plan should be designed in accordance with applicable city and/or county standards. DocuSign Envelope ID: E4190986-0960-4AF4-9156-D3C7AC5C2491 Geotechnical Engineering Report 5 September 1, 2021 Jefferson Townhomes, Renton, Washington RGI Project No. 2021-123 RGI recommends the following erosion control Best Management Practices (BMPs): Scheduling site preparation and grading for the drier summer and early fall months and undertaking activities that expose soil during periods of little or no rainfall Retaining existing vegetation whenever feasible Establishing a quarry spall construction entrance Installing siltation control fencing or anchored straw or coir wattles on the downhill side of work areas Covering soil stockpiles with anchored plastic sheeting Revegetating or mulching exposed soils with a minimum 3-inch thickness of straw if surfaces will be left undisturbed for more than one day during wet weather or one week in dry weather Directing runoff away from exposed soils and slopes Minimizing the length and steepness of slopes with exposed soils and cover excavation surfaces with anchored plastic sheeting Decreasing runoff velocities with check dams, straw bales or coir wattles Confining sediment to the project site Inspecting and maintaining erosion and sediment control measures frequently (The contractor should be aware that inspection and maintenance of erosion control BMPs is critical toward their satisfactory performance. Repair and/or replacement of dysfunctional erosion control elements should be anticipated.) Permanent erosion protection should be provided by reestablishing vegetation using hydroseeding and/or landscape planting. Until the permanent erosion protection is established, site monitoring should be performed by qualified personnel to evaluate the effectiveness of the erosion control measures. Provisions for modifications to the erosion control system based on monitoring observations should be included in the erosion and sedimentation control plan. 5.2.2 STRIPPING AND SUBGRADE PREPARATION Stripping efforts should include removal of pavements, vegetation, organic materials, and deleterious debris from areas slated for building, pavement, and utility construction. The Test pits encountered 6 to 8 inches of topsoil and rootmass. Deeper areas of stripping may be required in heavily vegetated areas of the site. Subgrade soils that become disturbed due to elevated moisture conditions should be overexcavated to reveal firm, non-yielding, non-organic soils and backfilled with compacted structural fill. In order to maximize utilization of site soils as structural fill, RGI recommends that the earthwork portion of this project be completed during extended DocuSign Envelope ID: E4190986-0960-4AF4-9156-D3C7AC5C2491 Geotechnical Engineering Report 6 September 1, 2021 Jefferson Townhomes, Renton, Washington RGI Project No. 2021-123 periods of warm and dry weather if possible. If earthwork is completed during the wet season (typically November through May) it will be necessary to take extra precautionary measures to protect subgrade soils. Wet season earthwork will require additional mitigative measures beyond that which would be expected during the drier summer and fall months. 5.2.3 EXCAVATIONS All temporary cut slopes associated with the site and utility excavations should be adequately inclined to prevent sloughing and collapse. The site soils consist of medium dense silty sand with some gravel, gravelly sand with some silt, and sand with some gravel and silt. Accordingly, for excavations more than 4 feet but less than 20 feet in depth, the temporary side slopes should be laid back with a minimum slope inclination of 1.5H:1V (Horizontal:Vertical). If there is insufficient room to complete the excavations in this manner, or excavations greater than 20 feet in depth are planned, using temporary shoring to support the excavations should be considered. For open cuts at the site, RGI recommends: No traffic, construction equipment, stockpiles or building supplies are allowed at the top of cut slopes within a distance of at least five feet from the top of the cut Exposed soil along the slope is protected from surface erosion using waterproof tarps and/or plastic sheeting Construction activities are scheduled so that the length of time the temporary cut is left open is minimized Surface water is diverted away from the excavation The general condition of slopes should be observed periodically by a geotechnical engineer to confirm adequate stability and erosion control measures In all cases, however, appropriate inclinations will depend on the actual soil and groundwater conditions encountered during earthwork. Ultimately, the site contractor must be responsible for maintaining safe excavation slopes that comply with applicable OSHA or WISHA guidelines. 5.2.4 STRUCTURAL FILL RGI recommends fill below the foundation and floor slab, behind retaining walls, and below pavement and hardscape surfaces be placed in accordance with the following recommendations for structural fill. The structural fill should be placed after completion of site preparation procedures as described above. The suitability of excavated site soils and import soils for compacted structural fill use will depend on the gradation and moisture content of the soil when it is placed. As the amount of fines (that portion passing the U.S. No. 200 sieve) increases, soil becomes increasingly DocuSign Envelope ID: E4190986-0960-4AF4-9156-D3C7AC5C2491 Geotechnical Engineering Report 7 September 1, 2021 Jefferson Townhomes, Renton, Washington RGI Project No. 2021-123 sensitive to small changes in moisture content and adequate compaction becomes more difficult or impossible to achieve. Soils containing more than about 5 percent fines cannot be consistently compacted to a dense, non-yielding condition when the moisture content is more than 2 percent above or below optimum. Optimum moisture content is that moisture that results in the greatest compacted dry density with a specified compactive effort. Non-organic site soils are only considered suitable for structural fill provided that their moisture content is within about two percent of the optimum moisture level as determined by American Society of Testing and Materials D1557-09 Standard Test Methods for Laboratory Compaction Characteristics of Soil Using Modified Effort (ASTM D1557). Excavated site soils may not be suitable for re-use as structural fill depending on the moisture content and weather conditions at the time of construction. If soils are stockpiled for future reuse and wet weather is anticipated, the stockpile should be protected with plastic sheeting that is securely anchored. Even during dry weather, moisture conditioning (such as, windrowing and drying) of site soils to be reused as structural fill may be required. The site soils are moisture sensitive and may require moisture conditioning prior to use as structural fill. If on-site soils are or become unusable, it may become necessary to import clean, granular soils to complete site work that meet the grading requirements listed in Table 2 to be used as structural fill. Table 2 Structural Fill Gradation U.S. Sieve Size Percent Passing 4 inches 100 No. 4 sieve 22 to 100 No. 200 sieve 0 to 5* *Based on minus 3/4 inch fraction. Prior to use, an RGI representative should observe and test all materials imported to the site for use as structural fill. Structural fill materials should be placed in uniform loose layers not exceeding 12 inches and compacted to 95 percent of the maximum dry density. The soil’s maximum density and optimum moisture should be determined by ASTM D1557. Placement and compaction of structural fill should be observed by RGI. 5.2.5 CUT AND FILL SLOPES All permanent cut and fill slopes should be graded with a finished inclination no greater than 2H:1V. Upon completion of construction, the slope face should be trackwalked, compacted and vegetated, or provided with other physical means to guard against erosion. DocuSign Envelope ID: E4190986-0960-4AF4-9156-D3C7AC5C2491 Geotechnical Engineering Report 8 September 1, 2021 Jefferson Townhomes, Renton, Washington RGI Project No. 2021-123 All fill placed for slope construction should meet the structural fill requirements as described this section. Final grades at the top of the slopes must promote surface drainage away from the slope crest. Water must not be allowed to flow in an uncontrolled fashion over the slope face. If it is necessary to direct surface runoff towards the slope, it should be controlled at the top of the slope, piped in a closed conduit installed on the slope face, and taken to an appropriate point of discharge beyond the toe of the slope. 5.2.6 WET WEATHER CONSTRUCTION CONSIDERATIONS RGI recommends that preparation for site grading and construction include procedures intended to drain ponded water, control surface water runoff, and to collect shallow subsurface seepage zones in excavations where encountered. It will not be possible to successfully compact the subgrade or utilize on-site soils as structural fill if accumulated water is not drained prior to grading or if drainage is not controlled during construction. Attempting to grade the site without adequate drainage control measures will reduce the amount of on-site soil effectively available for use, increase the amount of select import fill materials required, and ultimately increase the cost of the earthwork phases of the project. Free water should not be allowed to pond on the subgrade soils. RGI anticipates that the use of berms and shallow drainage ditches, with sumps and pumps in utility trenches, will be required for surface water control during wet weather and/or wet site conditions. 5.3 FOUNDATIONS Following site preparation and grading, the proposed building foundation can be supported on conventional spread footings bearing on competent native soil or structural fill. Loose, organic, or other unsuitable soils may be encountered in the proposed building footprint. If unsuitable soils are encountered, they should be overexcavated and backfilled with structural fill. If loose soils are encountered, the soils should be moisture conditioned and compacted to a firm and unyielding condition. The foundation design value assumes the foundation is supported on at least two feet of medium dense native soil or structural fill. DocuSign Envelope ID: E4190986-0960-4AF4-9156-D3C7AC5C2491 Geotechnical Engineering Report 9 September 1, 2021 Jefferson Townhomes, Renton, Washington RGI Project No. 2021-123 Table 3 Foundation Design Design Parameter Value Allowable Bearing Capacity 2,000 psf1 Friction Coefficient 0.30 Passive pressure (equivalent fluid pressure) 250 pcf2 Minimum foundation dimensions Columns: 24 inches Walls: 16 inches 1. psf = pounds per square foot 2. pcf = pounds per cubic foot The allowable foundation bearing pressures apply to dead loads plus design live load conditions. For short-term loads, such as wind and seismic, a 1/3 increase in this allowable capacity may be used. At perimeter locations, RGI recommends not including the upper 12 inches of soil in the computation of passive pressures because they can be affected by weather or disturbed by future grading activity. The passive pressure value assumes the foundation will be constructed neat against competent soil or backfilled with structural fill as described in Section 5.2.4. The recommended base friction and passive resistance value includes a safety factor of about 1.5. Perimeter foundations exposed to weather should be at a minimum depth of 18 inches below final exterior grades. Interior foundations can be constructed at any convenient depth below the floor slab. Finished grade is defined as the lowest adjacent grade within 5 feet of the foundation for perimeter (or exterior) footings and finished floor level for interior footings. With spread footing foundations designed in accordance with the recommendations in this section, maximum total and differential post-construction settlements of 1 inch and 1/2 inch, respectively, should be expected. 5.4 RETAINING WALLS If retaining walls are needed in the building area, RGI recommends cast-in-place concrete walls be used. The magnitude of earth pressure development on retaining walls will partly depend on the quality of the wall backfill. RGI recommends placing and compacting wall backfill as structural fill. Wall drainage will be needed behind the wall face. A typical retaining wall drainage detail is shown in Figure 3. With wall backfill placed and compacted as recommended, and drainage properly installed, RGI recommends using the values in the following table for design. DocuSign Envelope ID: E4190986-0960-4AF4-9156-D3C7AC5C2491 Geotechnical Engineering Report 10 September 1, 2021 Jefferson Townhomes, Renton, Washington RGI Project No. 2021-123 Table 4 Retaining Wall Design Design Parameter Value Allowable Bearing Capacity 2,000 psf Active Earth Pressure (unrestrained walls) 35 pcf At-rest Earth Pressure (restrained walls) 50 pcf For seismic design, an additional uniform load of 7 times the wall height (H) for unrestrained walls and 14H in psf for restrained walls should be applied to the wall surface. Friction at the base of foundations and passive earth pressure will provide resistance to these lateral loads. Values for these parameters are provided in Section 5.3. 5.5 SLAB-ON-GRADE CONSTRUCTION Once site preparation has been completed as described in Section 5.2, suitable support for slab-on-grade construction should be provided. RGI recommends that the concrete slab be placed on top of medium dense native soil or structural fill. Immediately below the floor slab, RGI recommends placing a four-inch thick capillary break layer of clean, free-draining sand or gravel that has less than five percent passing the U.S. No. 200 sieve. This material will reduce the potential for upward capillary movement of water through the underlying soil and subsequent wetting of the floor slab. Where moisture by vapor transmission is undesirable, an 8- to 10-millimeter thick plastic membrane should be placed on a 4-inch thick layer of clean gravel. For the anticipated floor slab loading, we estimate post-construction floor settlements of 1/4- to 1/2-inch. 5.6 DRAINAGE 5.6.1 SURFACE Final exterior grades should promote free and positive drainage away from the building area. Water must not be allowed to pond or collect adjacent to foundations or within the immediate building area. For non-pavement locations, RGI recommends providing a minimum drainage gradient of 3 percent for a minimum distance of 10 feet from the building perimeter. In paved locations, a minimum gradient of 1 percent should be provided unless provisions are included for collection and disposal of surface water adjacent to the structure. DocuSign Envelope ID: E4190986-0960-4AF4-9156-D3C7AC5C2491 Geotechnical Engineering Report 11 September 1, 2021 Jefferson Townhomes, Renton, Washington RGI Project No. 2021-123 5.6.2 SUBSURFACE RGI recommends installing perimeter foundation drains. A typical footing drain detail is shown on Figure 4. The foundation drains and roof downspouts should be tightlined separately to an approved discharge facility. Subsurface drains must be laid with a gradient sufficient to promote positive flow to a controlled point of approved discharge. 5.6.3 INFILTRATION RGI evaluated the potential to infiltrate stormwater runoff at the site. An infiltration test was completed in test pit TP-5 at a depth of approximately 5 feet below existing grade in general accordance with a Small-Scale Pilot Infiltration Test described in the 2017 City of Renton Surface Water Design Manual (CRSWDM). Table 5 Infiltration Rates Test Location Test Depth Field Measured Rate (Inches per hour) Design Rate (Inches per hour) TP-5 5 4.08 1.6 CRSWDM correction factors were applied to the field measured rate of 4.08 inches per hour. Idesign = Imeasured x Ftesting x Fplugging x Fgeometry Correction factors of 0.5 (Ftesting) for the PIT test method and 0.8 (Fplugging) for loamy sand loams were applied to the field measured rate to estimate the long-term design infiltration rate. We assumed Fgeometry = 1. The application of the correction factors yield a long-term design rate (Idesign) of 1.6 inches per hour. This rate can be used to design a site specific infiltration element. 6.0 Additional Services RGI is available to provide further geotechnical consultation throughout the design phase of the project. RGI should review the final design and specifications in order to verify that earthwork and foundation recommendations have been properly interpreted and incorporated into project design and construction. RGI is also available to provide geotechnical engineering and construction monitoring services during construction. The integrity of the earthwork and construction depends on proper site preparation and procedures. In addition, engineering decisions may arise in the field in the event that variations in subsurface conditions become apparent. Construction monitoring services are not part of this scope of work. If these services are desired, please let us know and we will prepare a cost proposal. DocuSign Envelope ID: E4190986-0960-4AF4-9156-D3C7AC5C2491 Geotechnical Engineering Report 12 September 1, 2021 Jefferson Townhomes, Renton, Washington RGI Project No. 2021-123 7.0 Limitations This GER is the property of RGI, Anita Woo, and its designated agents. Within the limits of the scope and budget, this GER was prepared in accordance with generally accepted geotechnical engineering practices in the area at the time this GER was issued. This GER is intended for specific application to the Jefferson Townhomes project in Renton, Washington, and for the exclusive use of Anita Woo and its authorized representatives. No other warranty, expressed or implied, is made. Site safety, excavation support, and dewatering requirements are the responsibility of others. The scope of services for this project does not include either specifically or by implication any environmental or biological (for example, mold, fungi, bacteria) assessment of the site or identification or prevention of pollutants, hazardous materials or conditions. If the owner is concerned about the potential for such contamination or pollution, we can provide a proposal for these services. The analyses and recommendations presented in this GER are based upon data obtained from the explorations performed on site. Variations in soil conditions can occur, the nature and extent of which may not become evident until construction. If variations appear evident, RGI should be requested to reevaluate the recommendations in this GER prior to proceeding with construction. It is the client’s responsibility to see that all parties to the project, including the designers, contractors, subcontractors, are made aware of this GER in its entirety. The use of information contained in this GER for bidding purposes should be done at the contractor’s option and risk. DocuSign Envelope ID: E4190986-0960-4AF4-9156-D3C7AC5C2491 USGS, 2020, Mercer Island, Washington USGS, 2020, Renton, Washington 7.5-Minute Quadrangle Approximate Scale: 1"=1000' 0 500 1000 2000 N Site Vicinity Map Figure 1 08/2021 Corporate Office 17522 Bothell Way Northeast Bothell, Washington 98011 Phone: 425.415.0551 Fax: 425.415.0311 Jefferson Townhomes RGI Project Number: 2021-123-1 Date Drawn: Address: 1518 Jefferson Avenue Northeast, Renton, Washington 98056 SITE DocuSign Envelope ID: E4190986-0960-4AF4-9156-D3C7AC5C2491 TP-1TP-2TP-3TP-4TP-508/2021Corporate Office17522 Bothell Way NortheastBothell, Washington 98011Phone: 425.415.0551Fax: 425.415.0311Jefferson TownhomesRGI Project Number:2021-123-1Date Drawn:Address: 1518 Jefferson Avenue Northeast, Renton, Washington 98056Figure 2Approximate Scale: 1"=30'0153060N= Test pit by RGI, 08/02/21= Site boundaryGeotechnical Exploration PlanDocuSign Envelope ID: E4190986-0960-4AF4-9156-D3C7AC5C2491 Incliniations) 12" Over the Pipe 3" Below the Pipe Perforated Pipe 4" Diameter PVC Compacted Structural Backfill (Native or Import) 12" min. Filter Fabric Material 12" Minimum Wide Free-Draining Gravel Slope to Drain (See Report for Appropriate Excavated Slope 08/2021 Corporate Office 17522 Bothell Way Northeast Bothell, Washington 98011 Phone: 425.415.0551 Fax: 425.415.0311 Jefferson Townhomes RGI Project Number: 2021-123-1 Date Drawn: Address: 1518 Jefferson Avenue Northeast, Renton, Washington 98056 Retaining Wall Drainage Detail Figure 3 Not to Scale DocuSign Envelope ID: E4190986-0960-4AF4-9156-D3C7AC5C2491 3/4" Washed Rock or Pea Gravel 4" Perforated Pipe Building Slab Structural Backfill Compacted Filter Fabric 08/2021 Corporate Office 17522 Bothell Way Northeast Bothell, Washington 98011 Phone: 425.415.0551 Fax: 425.415.0311 Jefferson Townhomes RGI Project Number: 2021-123-1 Date Drawn: Address: 1518 Jefferson Avenue Northeast, Renton, Washington 98056 Typical Footing Drain Detail Figure 4 Not to Scale DocuSign Envelope ID: E4190986-0960-4AF4-9156-D3C7AC5C2491 Geotechnical Engineering Report September 1, 2021 Jefferson Townhomes, Renton, Washington RGI Project No. 2021-123 APPENDIX A FIELD EXPLORATION AND LABORATORY TESTING On August 2nd, 2021, RGI performed field explorations using a backhoe. We explored subsurface soil conditions at the site by observing the excavation of five test pits to a maximum depth of 7 feet below existing grade. The test pit locations are shown on Figure 2. The test pit locations were approximately determined by measurements from existing property lines and paved roads. A geologist from our office conducted the field exploration and classified the soil conditions encountered, maintained a log of each test exploration, obtained representative soil samples, and observed pertinent site features. All soil samples were visually classified in accordance with the Unified Soil Classification System (USCS). Representative soil samples obtained from the explorations were placed in closed containers and taken to our laboratory for further examination and testing. As a part of the laboratory testing program, the soil samples were classified in our in house laboratory based on visual observation, texture, plasticity, and the limited laboratory testing described below. Moisture Content Determinations Moisture content determinations were performed in accordance with ASTM D2216-10 Standard Test Methods for Laboratory Determination of Water (Moisture) Content of Soil and Rock by Mass (ASTM D2216) on representative samples obtained from the exploration in order to aid in identification and correlation of soil types. The moisture content of typical sample was measured and is reported on the test pit logs. Grain Size Analysis A grain size analysis indicates the range in diameter of soil particles included in a particular sample. Grain size analyses was determined using D6913-04(2009) Standard Test Methods for Particle-Size Distribution (Gradation) of Soils Using Sieve Analysis (ASTM D6913) on four of the samples. DocuSign Envelope ID: E4190986-0960-4AF4-9156-D3C7AC5C2491 DocuSign Envelope ID: E4190986-0960-4AF4-9156-D3C7AC5C2491 DocuSign Envelope ID: E4190986-0960-4AF4-9156-D3C7AC5C2491 DocuSign Envelope ID: E4190986-0960-4AF4-9156-D3C7AC5C2491 DocuSign Envelope ID: E4190986-0960-4AF4-9156-D3C7AC5C2491 DocuSign Envelope ID: E4190986-0960-4AF4-9156-D3C7AC5C2491 DocuSign Envelope ID: E4190986-0960-4AF4-9156-D3C7AC5C2491 THE RILEY GROUP, INC. 17522 Bothell Way NE Bothell, WA 98011 PHONE: (425) 415-0551 FAX: (425) 415-0311 GRAIN SIZE ANALYSIS ASTM D421, D422, D1140, D2487, D6913 PROJECT TITLE Jefferson Townhomes SAMPLE ID/TYPE TP-1 PROJECT NO.2021-123-1 SAMPLE DEPTH 1.5 feet TECH/TEST DATE LB 8/3/2021 DATE RECEIVED 8/3/2021 WATER CONTENT (Delivered Moisture) Total Weight Of Sample Used For Sieve Corrected For Hygroscopic Moisture Wt Wet Soil & Tare (gm) (w1)735.6 Weight Of Sample (gm)704.2 Wt Dry Soil & Tare (gm) (w2)704.2 Tare Weight (gm) 15.7 Weight of Tare (gm) (w3)15.7 (W6) Total Dry Weight (gm) 688.5 Weight of Water (gm) (w4=w1-w2) 31.4 SIEVE ANALYSIS Weight of Dry Soil (gm) (w5=w2-w3) 688.5 Cumulative Moisture Content (%) (w4/w5)*100 5 Wt Ret (Wt-Tare) (%Retained)% PASS +Tare {(wt ret/w6)*100}(100-%ret) % COBBLES 0.0 12.0"15.7 0.00 0.00 100.00 cobbles % C GRAVEL 26.6 3.0"15.7 0.00 0.00 100.00 coarse gravel % F GRAVEL 17.7 2.5" coarse gravel % C SAND 6.8 2.0" coarse gravel % M SAND 16.9 1.5"15.7 0.00 0.00 100.00 coarse gravel % F SAND 21.6 1.0" coarse gravel % FINES 10.3 0.75"198.8 183.10 26.59 73.41 fine gravel % TOTAL 100.0 0.50" fine gravel 0.375"273.4 257.70 37.43 62.57 fine gravel D10 (mm)0.075 #4 321.0 305.30 44.34 55.66 coarse sand D30 (mm)0.38 #10 368.1 352.40 51.18 48.82 medium sand D60 (mm)7.5 #20 medium sand Cu 100.0 #40 484.8 469.10 68.13 31.87 fine sand Cc 0.3 #60 fine sand #100 607.0 591.30 85.88 14.12 fine sand #200 633.2 617.50 89.69 10.31 fines PAN 704.2 688.50 100.00 0.00 silt/clay DESCRIPTION Gravelly SAND with some silt USCS SP-SM Prepared For:Reviewed By: Anita Woo ELW 0 10 20 30 40 50 60 70 80 90 100 0.0010.010.11101001000 % P A S S I N G Grain size in millimeters 12"3" 2" 1".75" .375" #4 #10 #20 #40 #60 #100 #200 DocuSign Envelope ID: E4190986-0960-4AF4-9156-D3C7AC5C2491 THE RILEY GROUP, INC. 17522 Bothell Way NE Bothell, WA 98011 PHONE: (425) 415-0551 FAX: (425) 415-0311 GRAIN SIZE ANALYSIS ASTM D421, D422, D1140, D2487, D6913 PROJECT TITLE Jefferson Townhomes SAMPLE ID/TYPE TP-1 PROJECT NO.2021-123-1 SAMPLE DEPTH 5.5 feet TECH/TEST DATE LB 8/3/2021 DATE RECEIVED 8/3/2021 WATER CONTENT (Delivered Moisture) Total Weight Of Sample Used For Sieve Corrected For Hygroscopic Moisture Wt Wet Soil & Tare (gm) (w1)791.0 Weight Of Sample (gm)759.3 Wt Dry Soil & Tare (gm) (w2)759.3 Tare Weight (gm) 15.7 Weight of Tare (gm) (w3)15.7 (W6) Total Dry Weight (gm) 743.6 Weight of Water (gm) (w4=w1-w2) 31.7 SIEVE ANALYSIS Weight of Dry Soil (gm) (w5=w2-w3) 743.6 Cumulative Moisture Content (%) (w4/w5)*100 4 Wt Ret (Wt-Tare) (%Retained)% PASS +Tare {(wt ret/w6)*100}(100-%ret) % COBBLES 0.0 12.0"15.7 0.00 0.00 100.00 cobbles % C GRAVEL 7.7 3.0"15.7 0.00 0.00 100.00 coarse gravel % F GRAVEL 21.7 2.5" coarse gravel % C SAND 9.4 2.0" coarse gravel % M SAND 20.8 1.5"15.7 0.00 0.00 100.00 coarse gravel % F SAND 30.6 1.0" coarse gravel % FINES 9.9 0.75"72.6 56.90 7.65 92.35 fine gravel % TOTAL 100.0 0.50" fine gravel 0.375"150.4 134.70 18.11 81.89 fine gravel D10 (mm)0.075 #4 233.9 218.20 29.34 70.66 coarse sand D30 (mm)0.29 #10 303.7 288.00 38.73 61.27 medium sand D60 (mm)2 #20 medium sand Cu 26.7 #40 458.1 442.40 59.49 40.51 fine sand Cc 0.6 #60 fine sand #100 660.2 644.50 86.67 13.33 fine sand #200 686.0 670.30 90.14 9.86 fines PAN 759.3 743.60 100.00 0.00 silt/clay DESCRIPTION SAND with some gravel and silt USCS SP-SM Prepared For:Reviewed By: Anita Woo ELW 0 10 20 30 40 50 60 70 80 90 100 0.0010.010.11101001000 % P A S S I N G Grain size in millimeters 12"3" 2" 1".75" .375" #4 #10 #20 #40 #60 #100 #200 DocuSign Envelope ID: E4190986-0960-4AF4-9156-D3C7AC5C2491 THE RILEY GROUP, INC. 17522 Bothell Way NE Bothell, WA 98011 PHONE: (425) 415-0551 FAX: (425) 415-0311 GRAIN SIZE ANALYSIS ASTM D421, D422, D1140, D2487, D6913 PROJECT TITLE Jefferson Townhomes SAMPLE ID/TYPE TP-1 PROJECT NO.2021-123-1 SAMPLE DEPTH 6.5 feet TECH/TEST DATE LB 8/3/2021 DATE RECEIVED 8/3/2021 WATER CONTENT (Delivered Moisture) Total Weight Of Sample Used For Sieve Corrected For Hygroscopic Moisture Wt Wet Soil & Tare (gm) (w1)845.0 Weight Of Sample (gm)807.9 Wt Dry Soil & Tare (gm) (w2)807.9 Tare Weight (gm) 15.6 Weight of Tare (gm) (w3)15.6 (W6) Total Dry Weight (gm) 792.3 Weight of Water (gm) (w4=w1-w2) 37.1 SIEVE ANALYSIS Weight of Dry Soil (gm) (w5=w2-w3) 792.3 Cumulative Moisture Content (%) (w4/w5)*100 5 Wt Ret (Wt-Tare) (%Retained)% PASS +Tare {(wt ret/w6)*100}(100-%ret) % COBBLES 0.0 12.0"15.6 0.00 0.00 100.00 cobbles % C GRAVEL 16.2 3.0"15.6 0.00 0.00 100.00 coarse gravel % F GRAVEL 8.4 2.5" coarse gravel % C SAND 7.4 2.0" coarse gravel % M SAND 18.1 1.5"15.6 0.00 0.00 100.00 coarse gravel % F SAND 40.7 1.0" coarse gravel % FINES 9.1 0.75"144.3 128.70 16.24 83.76 fine gravel % TOTAL 100.0 0.50" fine gravel 0.375"185.4 169.80 21.43 78.57 fine gravel D10 (mm)0.09 #4 210.7 195.10 24.62 75.38 coarse sand D30 (mm)0.25 #10 269.6 254.00 32.06 67.94 medium sand D60 (mm)1.1 #20 medium sand Cu 12.2 #40 413.4 397.80 50.21 49.79 fine sand Cc 0.6 #60 fine sand #100 712.9 697.30 88.01 11.99 fine sand #200 735.8 720.20 90.90 9.10 fines PAN 807.9 792.30 100.00 0.00 silt/clay DESCRIPTION SAND with some gravel and silt USCS SP-SM Prepared For:Reviewed By: Anita Woo ELW 0 10 20 30 40 50 60 70 80 90 100 0.0010.010.11101001000 % P A S S I N G Grain size in millimeters 12"3" 2" 1".75" .375" #4 #10 #20 #40 #60 #100 #200 DocuSign Envelope ID: E4190986-0960-4AF4-9156-D3C7AC5C2491 THE RILEY GROUP, INC. 17522 Bothell Way NE Bothell, WA 98011 PHONE: (425) 415-0551 FAX: (425) 415-0311 GRAIN SIZE ANALYSIS ASTM D421, D422, D1140, D2487, D6913 PROJECT TITLE Jefferson Townhomes SAMPLE ID/TYPE TP-5 PROJECT NO.2021-123-1 SAMPLE DEPTH 4.5 feet TECH/TEST DATE LB 8/3/2021 DATE RECEIVED 8/3/2021 WATER CONTENT (Delivered Moisture) Total Weight Of Sample Used For Sieve Corrected For Hygroscopic Moisture Wt Wet Soil & Tare (gm) (w1)787.4 Weight Of Sample (gm)731.8 Wt Dry Soil & Tare (gm) (w2)731.8 Tare Weight (gm) 15.7 Weight of Tare (gm) (w3)15.7 (W6) Total Dry Weight (gm) 716.1 Weight of Water (gm) (w4=w1-w2) 55.6 SIEVE ANALYSIS Weight of Dry Soil (gm) (w5=w2-w3) 716.1 Cumulative Moisture Content (%) (w4/w5)*100 8 Wt Ret (Wt-Tare) (%Retained)% PASS +Tare {(wt ret/w6)*100}(100-%ret) % COBBLES 0.0 12.0"15.7 0.00 0.00 100.00 cobbles % C GRAVEL 4.1 3.0"15.7 0.00 0.00 100.00 coarse gravel % F GRAVEL 13.4 2.5" coarse gravel % C SAND 4.9 2.0" coarse gravel % M SAND 14.4 1.5"15.7 0.00 0.00 100.00 coarse gravel % F SAND 43.3 1.0" coarse gravel % FINES 20.0 0.75"44.8 29.10 4.06 95.94 fine gravel % TOTAL 100.0 0.50" fine gravel 0.375"96.9 81.20 11.34 88.66 fine gravel D10 (mm)#4 140.7 125.00 17.46 82.54 coarse sand D30 (mm)#10 175.5 159.80 22.32 77.68 medium sand D60 (mm)#20 medium sand Cu #40 278.5 262.80 36.70 63.30 fine sand Cc #60 fine sand #100 555.2 539.50 75.34 24.66 fine sand #200 588.4 572.70 79.97 20.03 fines PAN 731.8 716.10 100.00 0.00 silt/clay DESCRIPTION Silty SAND with some gravel USCS SM Prepared For:Reviewed By: Anita Woo ELW 0 10 20 30 40 50 60 70 80 90 100 0.0010.010.11101001000 % P A S S I N G Grain size in millimeters 12"3" 2" 1".75" .375" #4 #10 #20 #40 #60 #100 #200 DocuSign Envelope ID: E4190986-0960-4AF4-9156-D3C7AC5C2491 Appendix B WWHM2012 Output DocuSign Envelope ID: E4190986-0960-4AF4-9156-D3C7AC5C2491 WWHM2012 PROJECT REPORT DocuSign Envelope ID: E4190986-0960-4AF4-9156-D3C7AC5C2491 Jefferson Highlands Final 9/16/2021 1:26:22 PM Page 2 General Model Information Project Name:Jefferson Highlands Final Site Name: Site Address: City: Report Date:9/16/2021 Gage:Seatac Data Start:1948/10/01 Data End:2009/09/30 Timestep:15 Minute Precip Scale:1.000 Version Date:2019/09/13 Version:4.2.17 POC Thresholds Low Flow Threshold for POC1:50 Percent of the 2 Year High Flow Threshold for POC1:50 Year DocuSign Envelope ID: E4190986-0960-4AF4-9156-D3C7AC5C2491 Jefferson Highlands Final 9/16/2021 1:26:22 PM Page 3 Landuse Basin Data Predeveloped Land Use Basin 1 Bypass:No GroundWater:No Pervious Land Use acre C, Lawn, Flat 0.768 Pervious Total 0.768 Impervious Land Use acre ROADS FLAT 0.043 ROOF TOPS FLAT 0.156 DRIVEWAYS FLAT 0.081 SIDEWALKS FLAT 0.094 Impervious Total 0.374 Basin Total 1.142 Element Flows To: Surface Interflow Groundwater DocuSign Envelope ID: E4190986-0960-4AF4-9156-D3C7AC5C2491 Jefferson Highlands Final 9/16/2021 1:26:22 PM Page 4 Mitigated Land Use Basin 1 Bypass:No GroundWater:No Pervious Land Use acre C, Pasture, Flat 0.334 C, Lawn, Flat 0.0545 Pervious Total 0.3885 Impervious Land Use acre ROADS FLAT 0.04 SIDEWALKS FLAT 0.0785 Impervious Total 0.1185 Basin Total 0.507 Element Flows To: Surface Interflow Groundwater DocuSign Envelope ID: E4190986-0960-4AF4-9156-D3C7AC5C2491 Jefferson Highlands Final 9/16/2021 1:26:22 PM Page 7 Analysis Results POC 1 + Predeveloped x Mitigated Predeveloped Landuse Totals for POC #1 Total Pervious Area:0.768 Total Impervious Area:0.374 Mitigated Landuse Totals for POC #1 Total Pervious Area:0.3885 Total Impervious Area:0.1185 Flow Frequency Method:Log Pearson Type III 17B Flow Frequency Return Periods for Predeveloped. POC #1 Return Period Flow(cfs) 2 year 0.19597 5 year 0.274604 10 year 0.332458 25 year 0.412363 50 year 0.476977 100 year 0.546077 Flow Frequency Return Periods for Mitigated. POC #1 Return Period Flow(cfs) 2 year 0.056248 5 year 0.076377 10 year 0.091138 25 year 0.111485 50 year 0.127919 100 year 0.145484 Annual Peaks Annual Peaks for Predeveloped and Mitigated. POC #1 Year Predeveloped Mitigated 1949 0.296 0.082 1950 0.295 0.074 1951 0.183 0.056 1952 0.118 0.038 1953 0.120 0.036 1954 0.157 0.047 1955 0.167 0.049 1956 0.167 0.048 1957 0.220 0.063 1958 0.146 0.044 DocuSign Envelope ID: E4190986-0960-4AF4-9156-D3C7AC5C2491 Jefferson Highlands Final 9/16/2021 1:26:54 PM Page 8 1959 0.121 0.038 1960 0.193 0.062 1961 0.179 0.052 1962 0.126 0.037 1963 0.173 0.050 1964 0.154 0.044 1965 0.235 0.062 1966 0.128 0.040 1967 0.298 0.076 1968 0.265 0.068 1969 0.212 0.054 1970 0.181 0.054 1971 0.216 0.061 1972 0.286 0.074 1973 0.112 0.037 1974 0.213 0.057 1975 0.227 0.066 1976 0.164 0.049 1977 0.153 0.040 1978 0.186 0.051 1979 0.217 0.065 1980 0.336 0.095 1981 0.193 0.057 1982 0.336 0.093 1983 0.199 0.056 1984 0.144 0.041 1985 0.197 0.051 1986 0.182 0.059 1987 0.223 0.065 1988 0.121 0.038 1989 0.151 0.048 1990 0.543 0.160 1991 0.383 0.101 1992 0.143 0.043 1993 0.109 0.032 1994 0.101 0.032 1995 0.167 0.049 1996 0.248 0.078 1997 0.211 0.062 1998 0.166 0.048 1999 0.436 0.107 2000 0.197 0.056 2001 0.170 0.050 2002 0.296 0.077 2003 0.230 0.069 2004 0.396 0.102 2005 0.184 0.055 2006 0.173 0.051 2007 0.493 0.138 2008 0.376 0.104 2009 0.228 0.068 Ranked Annual Peaks Ranked Annual Peaks for Predeveloped and Mitigated. POC #1 Rank Predeveloped Mitigated 1 0.5428 0.1595 2 0.4932 0.1378 3 0.4360 0.1065 DocuSign Envelope ID: E4190986-0960-4AF4-9156-D3C7AC5C2491 Jefferson Highlands Final 9/16/2021 1:26:54 PM Page 9 4 0.3963 0.1035 5 0.3834 0.1018 6 0.3757 0.1007 7 0.3359 0.0951 8 0.3358 0.0929 9 0.2980 0.0824 10 0.2962 0.0782 11 0.2961 0.0771 12 0.2948 0.0764 13 0.2864 0.0742 14 0.2647 0.0741 15 0.2478 0.0690 16 0.2347 0.0683 17 0.2304 0.0680 18 0.2277 0.0662 19 0.2265 0.0654 20 0.2234 0.0648 21 0.2201 0.0630 22 0.2172 0.0625 23 0.2162 0.0623 24 0.2130 0.0617 25 0.2121 0.0605 26 0.2111 0.0587 27 0.1987 0.0572 28 0.1971 0.0568 29 0.1965 0.0564 30 0.1933 0.0558 31 0.1930 0.0556 32 0.1856 0.0550 33 0.1841 0.0541 34 0.1826 0.0535 35 0.1822 0.0520 36 0.1807 0.0515 37 0.1790 0.0514 38 0.1735 0.0506 39 0.1731 0.0502 40 0.1696 0.0498 41 0.1672 0.0493 42 0.1672 0.0492 43 0.1666 0.0488 44 0.1657 0.0481 45 0.1640 0.0480 46 0.1573 0.0478 47 0.1543 0.0467 48 0.1529 0.0441 49 0.1510 0.0436 50 0.1456 0.0428 51 0.1440 0.0411 52 0.1428 0.0404 53 0.1283 0.0399 54 0.1255 0.0385 55 0.1213 0.0383 56 0.1208 0.0379 57 0.1205 0.0372 58 0.1177 0.0366 59 0.1119 0.0358 60 0.1092 0.0322 61 0.1007 0.0319 DocuSign Envelope ID: E4190986-0960-4AF4-9156-D3C7AC5C2491 Jefferson Highlands Final 9/16/2021 1:27:27 PM Page 28 Disclaimer Legal Notice This program and accompanying documentation are provided 'as-is' without warranty of any kind. The entire risk regarding the performance and results of this program is assumed by End User. Clear Creek Solutions Inc. and the governmental licensee or sublicensees disclaim all warranties, either expressed or implied, including but not limited to implied warranties of program and accompanying documentation. In no event shall Clear Creek Solutions Inc. be liable for any damages whatsoever (including without limitation to damages for loss of business profits, loss of business information, business interruption, and the like) arising out of the use of, or inability to use this program even if Clear Creek Solutions Inc. or their authorized representatives have been advised of the possibility of such damages. Software Copyright © by : Clear Creek Solutions, Inc. 2005-2021; All Rights Reserved. Clear Creek Solutions, Inc. 6200 Capitol Blvd. Ste F Olympia, WA. 98501 Toll Free 1(866)943-0304 Local (360)943-0304 www.clearcreeksolutions.com DocuSign Envelope ID: E4190986-0960-4AF4-9156-D3C7AC5C2491 WWHM2012 PROJECT REPORT DocuSign Envelope ID: E4190986-0960-4AF4-9156-D3C7AC5C2491 Jefferson Highlands Final_Water Quality 8/6/2021 9:39:25 AM Page 2 General Model Information Project Name:Jefferson Highlands Final_Water Quality Site Name: Site Address: City: Report Date:8/6/2021 Gage:Seatac Data Start:1948/10/01 Data End:2009/09/30 Timestep:15 Minute Precip Scale:1.000 Version Date:2019/09/13 Version:4.2.17 POC Thresholds Low Flow Threshold for POC1:50 Percent of the 2 Year High Flow Threshold for POC1:50 Year DocuSign Envelope ID: E4190986-0960-4AF4-9156-D3C7AC5C2491 Jefferson Highlands Final_Water Quality 8/6/2021 9:39:25 AM Page 3 Landuse Basin Data Predeveloped Land Use Basin 1 Bypass:No GroundWater:No Pervious Land Use acre Pervious Total 0 Impervious Land Use acre ROADS FLAT 0.135 DRIVEWAYS FLAT 0.069 Impervious Total 0.204 Basin Total 0.204 Element Flows To: Surface Interflow Groundwater DocuSign Envelope ID: E4190986-0960-4AF4-9156-D3C7AC5C2491 Jefferson Highlands Final_Water Quality 8/6/2021 9:39:25 AM Page 4 Mitigated Land Use Basin 1 Bypass:No GroundWater:No Pervious Land Use acre Pervious Total 0 Impervious Land Use acre ROADS FLAT 0.135 DRIVEWAYS FLAT 0.069 Impervious Total 0.204 Basin Total 0.204 Element Flows To: Surface Interflow Groundwater DocuSign Envelope ID: E4190986-0960-4AF4-9156-D3C7AC5C2491 Jefferson Highlands Final_Water Quality 8/6/2021 9:39:25 AM Page 7 Analysis Results POC 1 + Predeveloped x Mitigated Predeveloped Landuse Totals for POC #1 Total Pervious Area:0 Total Impervious Area:0.204 Mitigated Landuse Totals for POC #1 Total Pervious Area:0 Total Impervious Area:0.204 Flow Frequency Method:Log Pearson Type III 17B Flow Frequency Return Periods for Predeveloped. POC #1 Return Period Flow(cfs) 2 year 0.077778 5 year 0.098243 10 year 0.112147 25 year 0.130183 50 year 0.143987 100 year 0.158127 Flow Frequency Return Periods for Mitigated. POC #1 Return Period Flow(cfs) 2 year 0.077778 5 year 0.098243 10 year 0.112147 25 year 0.130183 50 year 0.143987 100 year 0.158127 Annual Peaks Annual Peaks for Predeveloped and Mitigated. POC #1 Year Predeveloped Mitigated 1949 0.101 0.101 1950 0.109 0.109 1951 0.063 0.063 1952 0.056 0.056 1953 0.060 0.060 1954 0.063 0.063 1955 0.072 0.072 1956 0.071 0.071 1957 0.080 0.080 1958 0.065 0.065 DocuSign Envelope ID: E4190986-0960-4AF4-9156-D3C7AC5C2491 Jefferson Highlands Final_Water Quality 8/6/2021 9:39:54 AM Page 8 1959 0.066 0.066 1960 0.065 0.065 1961 0.068 0.068 1962 0.060 0.060 1963 0.066 0.066 1964 0.065 0.065 1965 0.082 0.082 1966 0.055 0.055 1967 0.095 0.095 1968 0.108 0.108 1969 0.075 0.075 1970 0.072 0.072 1971 0.086 0.086 1972 0.089 0.089 1973 0.054 0.054 1974 0.079 0.079 1975 0.091 0.091 1976 0.061 0.061 1977 0.066 0.066 1978 0.081 0.081 1979 0.111 0.111 1980 0.099 0.099 1981 0.081 0.081 1982 0.115 0.115 1983 0.093 0.093 1984 0.059 0.059 1985 0.081 0.081 1986 0.070 0.070 1987 0.108 0.108 1988 0.066 0.066 1989 0.082 0.082 1990 0.139 0.139 1991 0.111 0.111 1992 0.058 0.058 1993 0.050 0.050 1994 0.055 0.055 1995 0.072 0.072 1996 0.077 0.077 1997 0.074 0.074 1998 0.075 0.075 1999 0.154 0.154 2000 0.077 0.077 2001 0.084 0.084 2002 0.099 0.099 2003 0.077 0.077 2004 0.145 0.145 2005 0.066 0.066 2006 0.058 0.058 2007 0.135 0.135 2008 0.109 0.109 2009 0.101 0.101 Ranked Annual Peaks Ranked Annual Peaks for Predeveloped and Mitigated. POC #1 Rank Predeveloped Mitigated 1 0.1544 0.1544 2 0.1445 0.1445 3 0.1386 0.1386 DocuSign Envelope ID: E4190986-0960-4AF4-9156-D3C7AC5C2491 Jefferson Highlands Final_Water Quality 8/6/2021 9:39:55 AM Page 9 4 0.1351 0.1351 5 0.1146 0.1146 6 0.1108 0.1108 7 0.1107 0.1107 8 0.1089 0.1089 9 0.1088 0.1088 10 0.1084 0.1084 11 0.1080 0.1080 12 0.1007 0.1007 13 0.1005 0.1005 14 0.0994 0.0994 15 0.0985 0.0985 16 0.0950 0.0950 17 0.0933 0.0933 18 0.0908 0.0908 19 0.0892 0.0892 20 0.0864 0.0864 21 0.0845 0.0845 22 0.0825 0.0825 23 0.0823 0.0823 24 0.0813 0.0813 25 0.0811 0.0811 26 0.0809 0.0809 27 0.0800 0.0800 28 0.0788 0.0788 29 0.0769 0.0769 30 0.0767 0.0767 31 0.0766 0.0766 32 0.0755 0.0755 33 0.0751 0.0751 34 0.0745 0.0745 35 0.0725 0.0725 36 0.0721 0.0721 37 0.0717 0.0717 38 0.0706 0.0706 39 0.0703 0.0703 40 0.0684 0.0684 41 0.0662 0.0662 42 0.0661 0.0661 43 0.0660 0.0660 44 0.0659 0.0659 45 0.0658 0.0658 46 0.0649 0.0649 47 0.0647 0.0647 48 0.0646 0.0646 49 0.0632 0.0632 50 0.0629 0.0629 51 0.0611 0.0611 52 0.0604 0.0604 53 0.0596 0.0596 54 0.0588 0.0588 55 0.0583 0.0583 56 0.0583 0.0583 57 0.0560 0.0560 58 0.0551 0.0551 59 0.0549 0.0549 60 0.0540 0.0540 61 0.0505 0.0505 DocuSign Envelope ID: E4190986-0960-4AF4-9156-D3C7AC5C2491 Jefferson Highlands Final_Water Quality 8/6/2021 9:39:55 AM Page 13 Water Quality Water Quality BMP Flow and Volume for POC #1 On-line facility volume:0.025 acre-feet On-line facility target flow:0.0331 cfs. Adjusted for 15 min:0.0331 cfs. Off-line facility target flow:0.0187 cfs. Adjusted for 15 min:0.0187 cfs. DocuSign Envelope ID: E4190986-0960-4AF4-9156-D3C7AC5C2491 Jefferson Highlands Final_Water Quality 8/6/2021 9:40:31 AM Page 28 Disclaimer Legal Notice This program and accompanying documentation are provided 'as-is' without warranty of any kind. The entire risk regarding the performance and results of this program is assumed by End User. Clear Creek Solutions Inc. and the governmental licensee or sublicensees disclaim all warranties, either expressed or implied, including but not limited to implied warranties of program and accompanying documentation. In no event shall Clear Creek Solutions Inc. be liable for any damages whatsoever (including without limitation to damages for loss of business profits, loss of business information, business interruption, and the like) arising out of the use of, or inability to use this program even if Clear Creek Solutions Inc. or their authorized representatives have been advised of the possibility of such damages. Software Copyright © by : Clear Creek Solutions, Inc. 2005-2021; All Rights Reserved. Clear Creek Solutions, Inc. 6200 Capitol Blvd. Ste F Olympia, WA. 98501 Toll Free 1(866)943-0304 Local (360)943-0304 www.clearcreeksolutions.com DocuSign Envelope ID: E4190986-0960-4AF4-9156-D3C7AC5C2491 Appendix C Bond Quantities Worksheet (TO BE PROVIDED WITH FINAL ENGINEERING) DocuSign Envelope ID: E4190986-0960-4AF4-9156-D3C7AC5C2491 Appendix D Declaration of Covenant (TO BE PROVIDED WITH FINAL ENGINEERING) DocuSign Envelope ID: E4190986-0960-4AF4-9156-D3C7AC5C2491 Appendix E Operation & Maintenance Manual DocuSign Envelope ID: E4190986-0960-4AF4-9156-D3C7AC5C2491 MAINTENANCE INSTRUCTIONS FOR FULL INFILTRATION Your property contains an on-site BMP (best management practice) called “full infiltration,” which was installed to mitigate the stormwater quantity and quality impacts of some or all of the impervious surfaces on your property. Full infiltration is a method of soaking runoff from impervious area (such as paved areas and roofs) into the ground. If properly installed and maintained per Appendix A of the City of Renton’s Surface Water Design Manual, full infiltration can manage runoff so that a majority of precipitation events are absorbed. Infiltration devices, such as gravel filled trenches, drywells, and ground surface depressions, facilitate this process by putting runoff in direct contact with the soil and holding the runoff long enough to soak most of it into the ground. To be successful, the soil condition around the infiltration device must be reliably able to soak water into the ground for a reasonable number of years. Infiltration Devices The infiltration devices used on your property include the following as indicated on the site plan (CHECK THE BOX(ES) THAT APPLY): gravel filled trenches, drywells, ground surface depressions. MAINTENANCE RESTRICTIONS The size, placement, and composition of these devices as depicted by the site plan and design details must be maintained and may not be changed without written approval from the City of Renton or through a future development permit from the City of Renton. INSPECTION FREQUENCY AND MAINTENANCE GUIDELINES Infiltration devices must be inspected annually and after major storm events to identify and repair any physical defects. Maintenance and operation of the system should focus on ensuring the system’s viability by preventing sediment-laden flows from entering the device. Excessive sedimentation will result in a plugged or non-functioning facility. If the infiltration device has a catch basin, sediment accumulation must be removed on a yearly basis or more frequently if necessary. Prolonged ponding around or atop a device may indicate a plugged facility. If the device becomes plugged, it must be replaced. Keeping the areas that drain to infiltration devices well swept and clean will enhance the longevity of these devices. For roofs, frequent cleaning of gutters will reduce sediment loads to these devices. x DocuSign Envelope ID: E4190986-0960-4AF4-9156-D3C7AC5C2491 RECORDING REQUIREMENT These full infiltration on-site BMP maintenance and operation instructions must be recorded as an attachment to the required declaration of covenant and grant of easement per Requirement 3 of Section C.1.3.4 of the City of Renton Surface Water Design Manual. The intent of these instructions is to explain to future property owners, the purpose of the BMP and how it must be maintained and operated. These instructions are intended to be a minimum; the City of Renton may require additional instructions based on site-specific conditions. See the City of Renton’s Surface Water Design Manual website for additional information and updates. DocuSign Envelope ID: E4190986-0960-4AF4-9156-D3C7AC5C2491 TYPICAL FULL INFILTRATION APPLICATIONS 6" 24" 12" 24" WASHED ROCK 1 1 2"- 3 4" LEVEL INFILTRATION TRENCH SECTION A NTS PLAN VIEW NTS SECTION VIEW NTS VARIES A A 6" 6" 4" RIGID OR 6" FLEXIBLE PERFORATED PIPE CB SUMP w/SOLID LID ROOF DRAIN 4" RIGID OR 6" FLEXIBLE PERFORATED PIPE OVERFLOW SPLASH BLOCK ROOF DRAIN CB SUMP w/SOLID LID 12" FINE MESH SCREEN SETBACK FROM BUILDING 5' MIN. 1' MIN. 1' MIN. FILTER FABRIC COMPACTED BACKFILL 4" RIGID OR 6" FLEXIBLE PERFORATED PIPE 11 2" - 3 4" WASHED ROCK MIN. 1' ABOVE SEASONAL HIGH GROUNDWATER TABLE, SEE SECTION C.2.2.2 TRENCH SETBACK FROM BUILDING AS REQUIRED, 15' MIN. D R I V E W A Y X-SECTION NTS 2' MIN. FILTER STRIP SEE SECTIONS 6.3.4 & 6.3.5 18" MIN. 6" MIN. 3/4" TO 1-1/2" WASHED DRAIN ROCK GRASS OVERFLOW NOTE: SEE C.2.2.3 FOR TRENCH LENGTHS, TRENCH SPACING AND SITE LIMITATIONS MIN. 1' ABOVE SEASONAL HIGH GROUNDWATER TABLE, SEE SECTION C.2.2.2 X-SECTION NTS GRASS 2' MIN. 18" MIN. 6" MIN. 3/4" TO 1-1/2" WASHED DRAIN ROCK OVERFLOW 15' MIN. AS REQUIRED, SEE C.2.2.3 FROM ROOF N S T T SMIN. 1' ABOVE SEASONAL HIGH GROUNDWATER TABLE, SEE SECTION C.2.2.2 HOUSE FLOW 48 INCH DIAMETER HOLE FILLED WITH 1 1 2" - 3" WASHED DRAIN ROCK SECTION NTS MARK CENTER OF HOLE WITH 1" CAPPED PVC OR OTHER MEANS FLUSH WITH SURFACE ROOF DOWNSPOUT OVERFLOW SPLASH BLOCK TOPSOIL FINE MESH SCREEN MIN. 4" DIA. PVC PIPE SIDES OF HOLE LINED WITH FILTER FABRIC CATCH BASIN (YARD DRAIN) 15' MIN. AS REQUIRED, SEE SECTION C.2.2.3 VARIES 1' MIN. MIN. 1' ABOVE SEASONAL HIGH GROUNDWATER TABLE, SEE SECTION C.2.2.2 5' MIN. SETBACK FROM BUILDING FLOW PLAN VIEW NTS HOUSE ROOF DOWNSPOUT ROOF DOWNSPOUT CATCH BASIN (YARD DRAIN) 48 INCH DIAMETER HOLE FILLED WITH 1 1 2" - 3" WASHED DRAIN ROCK DocuSign Envelope ID: E4190986-0960-4AF4-9156-D3C7AC5C2491 MAINTENANCE INSTRUCTIONS FOR A BIORETENTION CELL Your property contains an on-site BMP (best management practice) called “bioretention,” which was installed to mitigate the stormwater quantity and quality impacts on both the impervious (paved or roof) and pervious surfaces (lawn or landscape) on your property. Bioretention cells, like rain gardens, are vegetated closed depressions or ponds that retain and filter stormwater from an area of impervious surface or nonnative pervious surface. Bioretention cells rely on effective infiltration performance more so than rain gardens. The soil in the bioretention cell has been enhanced to encourage and support vigorous plant growth that serves to filter the water and sustain a minimum infiltration capacity. Depending on soil conditions, bioretention cells may have water in them throughout the wet season and may overflow during major storm events. However, standing water can also be an indicator that periodic maintenance is required to sustain infiltrative performance. This on-site BMP shall be maintained per Appendix A of the City of Renton’s Surface Water Design Manual. MAINTENANCE RESTRICTIONS The size, placement, and design of the rain garden as depicted by the site plan and design details must be maintained and may not be changed without written approval from the City of Renton or through a future development permit from the City of Renton. Chemical fertilizers and pesticides must not be used. INSPECTION FREQUENCY AND MAINTENANCE GUIDELINES Bioretention cells must be inspected annually for physical defects and sediment accumulation. Bioretention cells have inflow and overflow inlets and outlets. These need to be maintained to ensure that water is moving into and out of the bioretention area. Check inlets/outlets for debris/sediment blockage, bare spots (exposed soil), or other signs of erosion damage (soil movement). Remove debris and obstructions as necessary. After major storm events, the bioretention cell should be checked to see that the overflow system is working properly and sedimentation is not occurring at the inlet. If erosion damage or bare spots are evident, they should be stabilized with soil, plant material, mulch, or landscape rock. Sediment deposits should be carefully removed and the sediment source eliminated. Plants must be adapted to wet winter conditions and dry summer conditions. Vegetation is to be watered and pruned as needed. Frequent watering is required to keep the plants healthy: o Year 1: weekly, o Year 2: bimonthly, o Year 3: bimonthly, o Year 4 and beyond: as needed for established plantings and dry periods. Chemical fertilizers and pesticides must not be used. Bioretention soil must be replaced in areas where sediment accumulation is preventing adequate infiltration of water through the soil. DocuSign Envelope ID: E4190986-0960-4AF4-9156-D3C7AC5C2491 Compacted soil should be decompacted. Trash and debris must be removed often from the bioretention depression. Mulch must be applied to bare soil at a minimum of 2 inches to maintain healthy growth. Compost may be added if soil nutrients are no longer adequate to support plant growth. Plant materials may be changed to suit tastes. Vegetation should be maintained as follows: 1) Replace all dead vegetation as soon as possible; 2) Remove fallen leaves and debris as needed; 3) Remove all noxious vegetation when discovered; 4) Manually weed without herbicides or pesticides; 5) To protect infiltration performance, do not compact soils in the bioretention cell with heavy maintenance equipment and/or excessive foot traffic; 6) During drought conditions, use mulch to prevent excess solar damage and water loss. RECORDING REQUIREMENT These bioretention on-site BMP maintenance and operation instructions must be recorded as an attachment to the required declaration of covenant and grant of easement per Requirement 3 of Section C.1.3.4 of the City of Renton Surface Water Design Manual. The intent of these instructions is to explain to future property owners, the purpose of the BMP and how it must be maintained and operated. These instructions are intended to be a minimum; the City of Renton may require additional instructions based on site-specific conditions. See the City of Renton’s Surface Water Design Manual website for additional information and updates. DocuSign Envelope ID: E4190986-0960-4AF4-9156-D3C7AC5C2491 TYPICAL BIORETENTION CELL (SPILLWAY OR CATCH BASIN OUTLET) TREES, SHRUBS GROUND COVER BIORETENTION AREA PLAN VIEW NTS VEGETATED COMPACTED EARTH BERM ROCKED SPILLWAY, 2'Wx4'L (OR BEYOND BERM IF LONGER), OVERFLOW TO SUITABLE DISCHARGE AREA TREES, SHRUBS GROUND COVER BIORETENTION AREA PLAN VIEW NTS VEGETATED COMPACTED EARTH BERM, TOP WIDTH 2' MIN 4" RIGID PIPE OUTLET TO STORM SYSTEM CATCH BASIN w/GRATE SECTION A-A NTS BIORETENTION AREA GROUND COVER TREES TREES SHRUBS 6" MIN TO 12" MAX WATER DEPTH OVERFLOW TO SUITABLE SURFACE DISCHARGE AREA 2' MIN TOP WIDTH COMPACTED EARTH BERM (AS NEEDED) 6" MIN FREEBOARD ABOVE OVERFLOW WS TO TOP OF BERM OR ADJACENT ROADWAY BIORETENTION SOIL MIX PER REFERENCE 11-C, MIN.18" DEPTH MAX SLOPE 3H:1V BELOW OVERFLOW WATER SURFACE ELEVATION (TYP.) DocuSign Envelope ID: E4190986-0960-4AF4-9156-D3C7AC5C2491 x DocuSign Envelope ID: E4190986-0960-4AF4-9156-D3C7AC5C2491 MAINTENANCE INSTRUCTIONS FOR SOIL AMENDMENT Your property contains an on-site BMP (best management practice) called “soil amendment,” which was installed to mitigate the stormwater quantity and quality impacts of some or all of the pervious surfaces on your property. Soil amendment is a method of regaining greater stormwater functions in the post development landscape by increasing treatment of pollutants and sediments, and minimizing the need for some landscaping chemicals. To be successful, the soil condition must be able to soak water into the ground for a reasonable number of years. This on-site BMP shall be maintained per Appendix A of the City of Renton’s Surface Water Design Manual. MAINTENANCE RESTRICTIONS The size, placement, and composition of these devices as depicted by the site plan and design details must be maintained and may not be changed without written approval from the City of Renton or through a future development permit from the City of Renton. INSPECTION FREQUENCY AND MAINTENANCE GUIDELINES To be successful, the soil must be able to soak water into the ground for a reasonable number of years. Return leaf fall and shredded woody materials from the landscape to the site when possible in order to replenish soil nutrients and structure. On turf areas, “grasscycle” (mulch-mow or leave the clippings) to build turf health. Maintain 2 to 3 inches of mulch over bare areas in landscape beds. Re-seed bare turf areas until the vegetation fully covers the ground surface. Avoid using pesticides (bug and weed killers) which damage the soil. Where fertilization is needed (mainly turf and annual flower beds), a moderate fertilization program should be used which relies on compost, natural fertilizers, or slow-release synthetic balanced fertilizers. RECORDING REQUIREMENT These on-site BMP maintenance and operation instructions must be recorded as an attachment to the required declaration of covenant and grant of easement per Requirement 3 of Section C.1.3.4 of the City of Renton Surface Water Design Manual. The intent of these instructions is to explain to future property owners, the purpose of the BMP and how it must be maintained and operated. These instructions are intended to be a minimum; the City of Renton may require additional instructions based on site-specific conditions. See the City of Renton’s Surface Water Design Manual website for additional information and updates. DocuSign Envelope ID: E4190986-0960-4AF4-9156-D3C7AC5C2491 Appendix F BioClean Modular Wetland Design Information DocuSign Envelope ID: E4190986-0960-4AF4-9156-D3C7AC5C2491 MWS Linear Advanced Stormwater Biofiltration DocuSign Envelope ID: E4190986-0960-4AF4-9156-D3C7AC5C2491 Contents 1 Introduction 2 Applications 3 Configurations 4 Advantages 5 Operation 6 Orientations | Bypass 7 Performance | Approvals 8 Sizing 9 Installation | Maintenance | Plants DocuSign Envelope ID: E4190986-0960-4AF4-9156-D3C7AC5C2491 www.ModularWetlands.com The Urban Impact For hundreds of years natural wetlands surrounding our shores have played an integral role as nature’s stormwater treatment system. But as our cities grow and develop, these natural wet- lands have perished under countless roads, rooftops, and parking lots. Plant A Wetland Without natural wetlands our cities are deprived of water purification, flood control, and land stability. Modular Wetlands and the MWS Linear re-establish nature’s presence and rejuvenate water ways in urban areas. MWS Linear The Modular Wetland System Linear represents a pioneering breakthrough in stormwater tech- nology as the only biofiltration system to utilize patented horizontal flow, allowing for a smaller footprint and higher treatment capacity. While most biofilters use little or no pre-treatment, the MWS Linear incorporates an advanced pre-treatment chamber that includes separation and pre- filter cartridges. In this chamber sediment and hydrocarbons are removed from runoff before it enters the biofiltration chamber, in turn reducing maintenance costs and improving performance. DocuSign Envelope ID: E4190986-0960-4AF4-9156-D3C7AC5C2491 Parking Lots Parking lots are designed to maximize space and the MWS Linear’s 4 ft. standard planter width al- lows for easy integration into parking lot islands and other landscape medians. Mixed Use The MWS Linear can be installed as a raised plant- er to treat runoff from rooftops or patios, making it perfect for sustainable “live-work” spaces. Industrial Many states enforce strict regulations for dis- charges from industrial sites. The MWS Linear has helped various sites meet difficult EPA mandated effluent limits for dissolved metals and other pol- lutants. Residential Low to high density developments can benefit from the versatile design of the MWS Linear. The system can be used in both decentralized LID de- sign and cost-effective end-of-the-line configura- tions. Streets Street applications can be challenging due to limited space. The MWS Linear is very adaptable, and offers the smallest footprint to work around the constraints of existing utilities on retrofit pro- jects. Commercial Compared to bioretention systems, the MWS Lin- ear can treat far more area in less space - meeting treatment and volume control requirements. Applications The MWS Linear has been successfully used on numerous new construction and retrofit projects. The system’s superior versatility makes it beneficial for a wide range of stormwater and waste water applications - treating rooftops, streetscapes, parking lots, and industrial sites. More applications are available on our website: www.ModularWetlands.com/Applications • Agriculture • Reuse • Low Impact Development • Waste Water DocuSign Envelope ID: E4190986-0960-4AF4-9156-D3C7AC5C2491 www.ModularWetlands.com Configurations The MWS Linear is the preferred biofiltration system of Civil Engineers across the country due to its versatile design. This highly versatile system has available “pipe-in” options on most models, along with built-in curb or grated inlets for simple integration into your stormdrain design. Curb Type The Curb Type configuration accepts sheet flow through a curb opening and is commonly used along road ways and parking lots. It can be used in sump or flow by conditions. Length of curb opening varies based on model and size. Grate Type The Grate Type configuration offers the same features and benefits as the Curb Type but with a grated/drop inlet above the systems pre-treatment chamber. It has the added benefit of allowing for pedestrian access over the inlet. ADA compliant grates are available to assure easy and safe access. The Grate Type can also be used in scenarios where runoff needs to be intercepted on both sides of landscape islands. Downspout Type The Downspout Type is a variation of the Vault Type and is designed to accept a vertical downspout pipe from roof top and podium areas. Some models have the option of utilizing an internal bypass, simplifying the overall design. The system can be installed as a raised planter and the exterior can be stuccoed or covered with other finishes to match the look of adjacent buildings. Vault Type The system’s patented horizontal flow biofilter is able to accept inflow pipes directly into the pre-treatment chamber, meaning the MWS Linear can be used in end-of-the-line installations. This greatly improves feasibility over typical decentralized designs that are required with other biofiltration/bioretention systems. Another benefit of the “pipe in” design is the ability to install the system downstream of underground detention systems to meet water quality volume requirements. Page 3 DocuSign Envelope ID: E4190986-0960-4AF4-9156-D3C7AC5C2491 Cartridge Housing Pre-filter Cartridge Curb Inlet Individual Media Filters Advantages & Operation The MWS Linear is the most efficient and versatile biofiltration system on the market, and the only system with horizontal flow which improves performance, reduces footprint, and minimizes maintenance. Figure-1 and Figure-2 illustrate the invaluable benefits of horizontal flow and the multiple treatment stages. • Horizontal Flow Biofiltration • Greater Filter Surface Area • Pre-Treatment Chamber • Patented Perimeter Void Area • Flow Control • No Depressed Planter Area Separation • Trash, sediment, and debris are separated before entering the pre-filter cartridges • Designed for easy maintenance access Pre-Filter Cartridges • Over 25 ft2 of surface area per cartridge • Utilizes BioMediaGREEN filter material • Removes over 80% of TSS & 90% of hydrocarbons • Prevents pollutants that cause clogging from migrating to the biofiltration chamber Pre-Treatment1 1 2 Drain- 1 2Vertical Underdrain Manifold Featured Advantages DocuSign Envelope ID: E4190986-0960-4AF4-9156-D3C7AC5C2491 www.ModularWetlands.com Fig. 1 Horizontal Flow • Less clogging than downward flow biofilters • Water flow is subsurface • Improves biological filtration Patented Perimeter Void Area • Vertically extends void area between the walls and the WetlandMEDIA on all four sides. • Maximizes surface area of the media for higher treatment capacity WetlandMEDIA • Contains no organics and removes phosphorus • Greater surface area and 48% void space • Maximum evapotranspiration • High ion exchange capacity and light weight Flow Control • Orifice plate controls flow of water through WetlandMEDIA to a level lower than the media’s capacity. • Extends the life of the media and improves performance Drain-Down Filter • The Drain-Down is an optional feature that completely drains the pre-treatment chamber • Water that drains from the pre-treatment chamber between storm events will be treated 2x to 3x More Surface Area Than Traditional Downward Flow Bioretention Systems.Fig. 2 - Top View Biofiltration2 Discharge3 Perimeter Voi d A r e a 3 4 3Flow Control Riser -Down Line Outlet Pipe Page 5 DocuSign Envelope ID: E4190986-0960-4AF4-9156-D3C7AC5C2491 Orientations Bypass Internal Bypass Weir (Side-by-Side Only) The Side-By-Side orientation places the pre-treat- ment and discharge chambers adjacent to one an- other allowing for integration of internal bypass. The wall between these chambers can act as a by- pass weir when flows exceed the system’s treatment capacity, thus allowing bypass from the pre-treat- ment chamber directly to the discharge chamber. External Diversion Weir Structure This traditional offline diversion method can be used with the MWS Linear in scenarios where run- off is being piped to the system. These simple and effective structures are generally configured with two outflow pipes. The first is a smaller pipe on the upstream side of the diversion weir - to divert low flows over to the MWS Linear for treatment. The second is the main pipe that receives water once the system has exceeded treatment capacity and water flows over the weir. Flow By Design This method is one in which the system is placed just upstream of a standard curb or grate inlet to intercept the first flush. Higher flows simply pass by the MWS Linear and into the standard inlet down- stream. End-To-End The End-To-End orientation places the pre-treat- ment and discharge chambers on opposite ends of the biofiltration chamber therefore minimizing the width of the system to 5 ft (outside dimension). This orientation is perfect for linear projects and street retrofits where existing utilities and sidewalks limit the amount of space available for installation. One limitation of this orientation is bypass must be ex- ternal. Side-By-Side The Side-By-Side orientation places the pre-treat- ment and discharge chamber adjacent to one an- other with the biofiltration chamber running paral- lel on either side. This minimizes the system length, providing a highly compact footprint. It has been proven useful in situations such as streets with di- rectly adjacent sidewalks, as half of the system can be placed under that sidewalk. This orientation also offers internal bypass options as discussed below. This simple yet innovative diversion trough can be installed in existing or new curb and grate inlets to divert the first flush to the MWS Linear via pipe. It works similar to a rain gutter and is installed just below the opening into the inlet. It captures the low flows and channels them over to a connecting pipe exiting out the wall of the inlet and leading to the MWS Linear. The DVERT is perfect for retrofit and green street applications that allows the MWS Lin- ear to be installed anywhere space is available. DVERT Low Flow Diversion DVERT Trough DocuSign Envelope ID: E4190986-0960-4AF4-9156-D3C7AC5C2491 www.ModularWetlands.com Rhode Island DEM Approved Approved as an authorized BMP and noted to achieve the following minimum removal efficiencies: 85% TSS, 60% Pathogens, 30% Total Phosphorus for discharges to freshwater systems, and 30% Total Nitrogen for discharges to saltwater or tidal systems. MASTEP Evaluation The University of Massachusetts at Amherst – Water Resources Research Center, issued a technical evaluation report noting removal rates up to 84% TSS, 70% Total Phosphorus, 68.5% Total Zinc, and more. Washington State DOE Approved The MWS Linear is approved for General Use Level Designation (GULD) for Basic, En- hanced, and Phosphorus treatment at 1 gpm/ft2 loading rate. The highest performing BMP on the market for all main pollutant categories. Approvals The MWS Linear has successfully met years of challenging technical reviews and testing from some of the most prestigious and demanding agencies in the nation, and perhaps the world. DEQ Assignment The Virginia Department of Environmental Quality assigned the MWS Linear, the highest phosphorus removal rating for manufactured treatment devices to meet the new Virginia Stormwater Management Program (VSMP) Technical Criteria. VA TSS Total Phosphorus Ortho Phosphorus Nitrogen Dissolved Zinc Dissolved Copper Total Zinc Total Copper Motor Oil 85%64%67%45%66%38%69%50%95% Performance The MWS Linear continues to outperform other treatment methods with superior pollutant removal for TSS, heavy metals, nutrients, hydrocarbons and bacteria. Since 2007 the MWS Linear has been field tested on nu- merous sites across the country. With it’s advanced pre-treatment chamber and innovative horizontal flow biofilter, the system is able to effectively remove pollutants through a combination of physical, chemical, and biological filtration processes. With the same biological processes found in natural wetlands, the MWS Linear harnesses natures ability to process, transform, and remove even the most harmful pollutants. Page 7 DocuSign Envelope ID: E4190986-0960-4AF4-9156-D3C7AC5C2491 Treatment Flow Sizing Table Model #Dimensions WetlandMedia Surface Area Treatment Flow Rate (cfs) MWS-L-4-4 4’ x 4’23 ft2 0.052 MWS-L-4-6 4’ x 6’32 ft2 0.073 MWS-L-4-8 4’ x 8’50 ft2 0.115 MWS-L-4-13 4’ x 13’63 ft2 0.144 MWS-L-4-15 4’ x 15’76 ft2 0.175 MWS-L-4-17 4’ x 17’90 ft2 0.206 MWS-L-4-19 4’ x 19’103 ft2 0.237 MWS-L-4-21 4’ x 21’117 ft2 0.268 MWS-L-8-8 8’ x 8’100 ft2 0.230 MWS-L-8-12 8’ x 12’151 ft2 0.346 MWS-L-8-16 8’ x 16’201 ft2 0.462 Flow Based Sizing The MWS Linear can be used in stand alone applica- tions to meet treatment flow requirements. Since the MWS Linear is the only biofiltration system that can ac- cept inflow pipes several feet below the surface it can be used not only in decentralized design applications but also as a large central end-of-the-line application for maximum feasibility. Volume Based Sizing Many states require treatment of a water quality volume and do not offer the option of flow based design. The MWS Linear and its unique horizontal flow makes it the only biofilter that can be used in volume based design installed downstream of ponds, detention basins, and underground storage systems. Treatment Volume Sizing Table Model #Treatment Capacity (cu. ft.) @ 24-Hour Drain Down Treatment Capacity (cu. ft.) @ 48-Hour Drain Down MWS-L-4-4 1140 2280 MWS-L-4-6 1600 3200 MWS-L-4-8 2518 5036 MWS-L-4-13 3131 6261 MWS-L-4-15 3811 7623 MWS-L-4-17 4492 8984 MWS-L-4-19 5172 10345 MWS-L-4-21 5853 11706 MWS-L-8-8 5036 10072 MWS-L-8-12 7554 15109 MWS-L-8-16 10073 20145 DocuSign Envelope ID: E4190986-0960-4AF4-9156-D3C7AC5C2491 www.ModularWetlands.com Installation The MWS Linear is simple, easy to install, and has a space efficient design that offers lower excavation and in- stallation costs compared to traditional tree-box type systems. The structure of the system resembles pre-cast catch basin or utility vaults and is installed in a similar fashion. The system is delivered fully assembled for quick in- stallation. Generally, the structure can be unloaded and set in place in 15 minutes. Our experienced team of field technicians are available to supervise installations and provide technical support. Plant Selection Abundant plants, trees, and grasses bring value and an aesthetic benefit to any urban setting, but those in the MWS Linear do even more - they increase pollutant removal. What’s not seen, but very important, is that below grade the stormwater runoff/flow is being subjected to nature’s secret weapon: a dynamic physical, chemi- cal, and biological process working to break down and remove non-point source pollutants. The flow rate is controlled in the MWS Linear, giving the plants more “contact time” so that pollutants are more successfully decomposed, volatilized and incorporated into the biomass of The MWS Linear’s micro/macro flora and fauna. A wide range of plants are suitable for use in the MWS Linear, but selec- tions vary by location and climate. View suitable plants by selecting the list relative to your project location’s hardy zone. Please visit www.ModularWetlands.com/Plants for more information and various plant lists. Maintenance Reduce your maintenance costs, man hours, and materials with the MWS Linear. Unlike other biofiltration systems that provide no pre-treatment, the MWS Linear is a self-contained treatment train which incorporates simple and effective pre-treatment. Maintenance requirements for the biofilter itself are almost completely eliminated, as the pre-treatment chamber removes and isolates trash, sediments, and hydrocarbons. What’s left is the simple maintenance of an easily accessible pre-treatment chamber that can be cleaned by hand or with a standard vac truck. Only periodic replacement of low- cost media in the pre-filter cartridges is required for long term opera- tion and there is absolutely no need to replace expensive biofiltration media. Page 9 DocuSign Envelope ID: E4190986-0960-4AF4-9156-D3C7AC5C2491 www.ModularWetlands.com | (855) 5MOD-WET | info@ModularWetlands.com DocuSign Envelope ID: E4190986-0960-4AF4-9156-D3C7AC5C2491 July 2017 GENERAL USE LEVEL DESIGNATION FOR BASIC, ENHANCED, AND PHOSPHORUS TREATMENT For the MWS-Linear Modular Wetland Ecology’s Decision: Based on Modular Wetland Systems, Inc. application submissions, including the Technical Evaluation Report, dated April 1, 2014, Ecology hereby issues the following use level designation: 1. General use level designation (GULD) for the MWS-Linear Modular Wetland Stormwater Treatment System for Basic treatment Sized at a hydraulic loading rate of 1 gallon per minute (gpm) per square foot (sq ft) of wetland cell surface area. For moderate pollutant loading rates (low to medium density residential basins), size the Prefilters at 3.0 gpm/sq ft of cartridge surface area. For high loading rates (commercial and industrial basins), size the Prefilters at 2.1 gpm/sq ft of cartridge surface area. 2. General use level designation (GULD) for the MWS-Linear Modular Wetland Stormwater Treatment System for Phosphorus treatment Sized at a hydraulic loading rate of 1 gallon per minute (gpm) per square foot (sq ft) of wetland cell surface area. For moderate pollutant loading rates (low to medium density residential basins), size the Prefilters at 3.0 gpm/sq ft of cartridge surface area. For high loading rates (commercial and industrial basins), size the Prefilters at 2.1 gpm/sq ft of cartridge surface area. 3. General use level designation (GULD) for the MWS-Linear Modular Wetland Stormwater Treatment System for Enhanced treatment Sized at a hydraulic loading rate of 1 gallon per minute (gpm) per square foot (sq ft) of wetland cell surface area. For moderate pollutant loading rates (low to medium density residential basins), size the Prefilters at 3.0 gpm/sq ft of cartridge surface area. For high loading rates (commercial and industrial basins), size the Prefilters at 2.1 gpm/sq ft of cartridge surface area. DocuSign Envelope ID: E4190986-0960-4AF4-9156-D3C7AC5C2491 4. Ecology approves the MWS - Linear Modular Wetland Stormwater Treatment System units for Basic, Phosphorus, and Enhanced treatment at the hydraulic loading rate listed above. Designers shall calculate the water quality design flow rates using the following procedures: Western Washington: For treatment installed upstream of detention or retention, the water quality design flow rate is the peak 15-minute flow rate as calculated using the latest version of the Western Washington Hydrology Model or other Ecology-approved continuous runoff model. Eastern Washington: For treatment installed upstream of detention or retention, the water quality design flow rate is the peak 15-minute flow rate as calculated using one of the three methods described in Chapter 2.2.5 of the Stormwater Management Manual for Eastern Washington (SWMMEW) or local manual. Entire State: For treatment installed downstream of detention, the water quality design flow rate is the full 2-year release rate of the detention facility. 5. These use level designations have no expiration date but may be revoked or amended by Ecology, and are subject to the conditions specified below. Ecology’s Conditions of Use: Applicants shall comply with the following conditions: 1. Design, assemble, install, operate, and maintain the MWS – Linear Modular Wetland Stormwater Treatment System units, in accordance with Modular Wetland Systems, Inc. applicable manuals and documents and the Ecology Decision. 2. Each site plan must undergo Modular Wetland Systems, Inc. review and approval before site installation. This ensures that site grading and slope are appropriate for use of a MWS – Linear Modular Wetland Stormwater Treatment System unit. 3. MWS – Linear Modular Wetland Stormwater Treatment System media shall conform to the specifications submitted to, and approved by, Ecology. 4. The applicant tested the MWS – Linear Modular Wetland Stormwater Treatment System with an external bypass weir. This weir limited the depth of water flowing through the media, and therefore the active treatment area, to below the root zone of the plants. This GULD applies to MWS – Linear Modular Wetland Stormwater Treatment Systems whether plants are included in the final product or not. 5. Maintenance: The required maintenance interval for stormwater treatment devices is often dependent upon the degree of pollutant loading from a particular drainage basin. Therefore, Ecology does not endorse or recommend a “one size fits all” maintenance cycle for a particular model/size of manufactured filter treatment device. Typically, Modular Wetland Systems, Inc. designs MWS - Linear Modular Wetland systems for a target prefilter media life of 6 to 12 months. Indications of the need for maintenance include effluent flow decreasing to below the design flow rate or decrease in treatment below required levels. Owners/operators must inspect MWS - Linear Modular Wetland systems for a minimum of twelve months from the start of post-construction operation to determine site-specific DocuSign Envelope ID: E4190986-0960-4AF4-9156-D3C7AC5C2491 maintenance schedules and requirements. You must conduct inspections monthly during the wet season, and every other month during the dry season. (According to the SWMMWW, the wet season in western Washington is October 1 to April 30. According to SWMMEW, the wet season in eastern Washington is October 1 to June 30). After the first year of operation, owners/operators must conduct inspections based on the findings during the first year of inspections. Conduct inspections by qualified personnel, follow manufacturer’s guidelines, and use methods capable of determining either a decrease in treated effluent flowrate and/or a decrease in pollutant removal ability. When inspections are performed, the following findings typically serve as maintenance triggers: Standing water remains in the vault between rain events, or Bypass occurs during storms smaller than the design storm. If excessive floatables (trash and debris) are present (but no standing water or excessive sedimentation), perform a minor maintenance consisting of gross solids removal, not prefilter media replacement. Additional data collection will be used to create a correlation between pretreatment chamber sediment depth and pre-filter clogging (see Issues to be Addressed by the Company section below) 6. Discharges from the MWS - Linear Modular Wetland Stormwater Treatment System units shall not cause or contribute to water quality standards violations in receiving waters. Applicant: Modular Wetland Systems, Inc. Applicant's Address: PO. Box 869 Oceanside, CA 92054 Application Documents: Original Application for Conditional Use Level Designation, Modular Wetland System, Linear Stormwater Filtration System Modular Wetland Systems, Inc., January 2011 Quality Assurance Project Plan: Modular Wetland system – Linear Treatment System performance Monitoring Project, draft, January 2011. Revised Application for Conditional Use Level Designation, Modular Wetland System, Linear Stormwater Filtration System Modular Wetland Systems, Inc., May 2011 Memorandum: Modular Wetland System-Linear GULD Application Supplementary Data, April 2014 Technical Evaluation Report: Modular Wetland System Stormwater Treatment System Performance Monitoring, April 2014. DocuSign Envelope ID: E4190986-0960-4AF4-9156-D3C7AC5C2491 Applicant's Use Level Request: General use level designation as a Basic, Enhanced, and Phosphorus treatment device in accordance with Ecology’s Guidance for Evaluating Emerging Stormwater Treatment Technologies Technology Assessment Protocol – Ecology (TAPE) January 2011 Revision. Applicant's Performance Claims: The MWS – Linear Modular wetland is capable of removing a minimum of 80-percent of TSS from stormwater with influent concentrations between 100 and 200 mg/l. The MWS – Linear Modular wetland is capable of removing a minimum of 50-percent of Total Phosphorus from stormwater with influent concentrations between 0.1 and 0.5 mg/l. The MWS – Linear Modular wetland is capable of removing a minimum of 30-percent of dissolved Copper from stormwater with influent concentrations between 0.005 and 0.020 mg/l. The MWS – Linear Modular wetland is capable of removing a minimum of 60-percent of dissolved Zinc from stormwater with influent concentrations between 0.02 and 0.30 mg/l. Ecology Recommendations: Modular Wetland Systems, Inc. has shown Ecology, through laboratory and field- testing, that the MWS - Linear Modular Wetland Stormwater Treatment System filter system is capable of attaining Ecology's Basic, Total phosphorus, and Enhanced treatment goals. Findings of Fact: Laboratory Testing The MWS-Linear Modular wetland has the: Capability to remove 99 percent of total suspended solids (using Sil-Co-Sil 106) in a quarter-scale model with influent concentrations of 270 mg/L. Capability to remove 91 percent of total suspended solids (using Sil-Co-Sil 106) in laboratory conditions with influent concentrations of 84.6 mg/L at a flow rate of 3.0 gpm per square foot of media. Capability to remove 93 percent of dissolved Copper in a quarter-scale model with influent concentrations of 0.757 mg/L. Capability to remove 79 percent of dissolved Copper in laboratory conditions with influent concentrations of 0.567 mg/L at a flow rate of 3.0 gpm per square foot of media. Capability to remove 80.5-percent of dissolved Zinc in a quarter-scale model with influent concentrations of 0.95 mg/L at a flow rate of 3.0 gpm per square foot of media. Capability to remove 78-percent of dissolved Zinc in laboratory conditions with influent concentrations of 0.75 mg/L at a flow rate of 3.0 gpm per square foot of media. DocuSign Envelope ID: E4190986-0960-4AF4-9156-D3C7AC5C2491 Field Testing Modular Wetland Systems, Inc. conducted monitoring of an MWS-Linear (Model # MWS-L-4-13) from April 2012 through May 2013, at a transportation maintenance facility in Portland, Oregon. The manufacturer collected flow-weighted composite samples of the system’s influent and effluent during 28 separate storm events. The system treated approximately 75 percent of the runoff from 53.5 inches of rainfall during the monitoring period. The applicant sized the system at 1 gpm/sq ft. (wetland media) and 3gpm/sq ft. (prefilter). Influent TSS concentrations for qualifying sampled storm events ranged from 20 to 339 mg/L. Average TSS removal for influent concentrations greater than 100 mg/L (n=7) averaged 85 percent. For influent concentrations in the range of 20-100 mg/L (n=18), the upper 95 percent confidence interval about the mean effluent concentration was 12.8 mg/L. Total phosphorus removal for 17 events with influent TP concentrations in the range of 0.1 to 0.5 mg/L averaged 65 percent. A bootstrap estimate of the lower 95 percent confidence limit (LCL95) of the mean total phosphorus reduction was 58 percent. The lower 95 percent confidence limit of the mean percent removal was 60.5 percent for dissolved zinc for influent concentrations in the range of 0.02 to 0.3 mg/L (n=11). The lower 95 percent confidence limit of the mean percent removal was 32.5 percent for dissolved copper for influent concentrations in the range of 0.005 to 0.02 mg/L (n=14) at flow rates up to 28 gpm (design flow rate 41 gpm). Laboratory test data augmented the data set, showing dissolved copper removal at the design flow rate of 41 gpm (93 percent reduction in influent dissolved copper of 0.757 mg/L). Issues to be addressed by the Company: 1. Modular Wetland Systems, Inc. should collect maintenance and inspection data for the first year on all installations in the Northwest in order to assess standard maintenance requirements for various land uses in the region. Modular Wetland Systems, Inc. should use these data to establish required maintenance cycles. 2. Modular Wetland Systems, Inc. should collect pre-treatment chamber sediment depth data for the first year of operation for all installations in the Northwest. Modular Wetland Systems, Inc. will use these data to create a correlation between sediment depth and pre-filter clogging. Technology Description: Download at http://www.modularwetlands.com/ Contact Information: Applicant: Zach Kent BioClean A Forterra Company. 398 Vi9a El Centro Oceanside, CA 92058 zach.kent@forterrabp.com DocuSign Envelope ID: E4190986-0960-4AF4-9156-D3C7AC5C2491 Applicant website: http://www.modularwetlands.com/ Ecology web link: http://www.ecy.wa.gov/programs/wg/stormwater/newtech/index.html Ecology: Douglas C. Howie, P.E. Department of Ecology Water Quality Program (360) 407-6444 douglas.howie@ecy.wa.gov Revision History Date Revision June 2011 Original use-level-designation document September 2012 Revised dates for TER and expiration January 2013 Modified Design Storm Description, added Revision Table, added maintenance discussion, modified format in accordance with Ecology standard December 2013 Updated name of Applicant April 2014 Approved GULD designation for Basic, Phosphorus, and Enhanced treatment December 2015 Updated GULD to document the acceptance of MWS-Linear Modular Wetland installations with or without the inclusion of plants July 2017 Revised Manufacturer Contact Information (name, address, and email) DocuSign Envelope ID: E4190986-0960-4AF4-9156-D3C7AC5C2491 DocuSign Envelope ID: E4190986-0960-4AF4-9156-D3C7AC5C2491