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Civil Engineers ● Structural Engineers ● Landscape Architects ● Community Planners ● Land Surveyors Technical Information Report PREPARED FOR: ADF Properties, LLC 15007 Woodinville-Redmond Rd, Suite A Woodinville, WA 98072 PROJECT: Walker Subaru Service Center Renton, WA 2240819.10 PREPARED BY: Nathan Kaser Project Engineer REVIEWED BY: Scott T. Kaul, PE, LEED AP Principal DATE: January 2026 Revised April 2026 DEVELOPMENT ENGINEERING msippo 06/12/2026 Technical Information Report PREPARED FOR: ADF Properties, LLC 15007 Woodinville-Redmond Rd, Suite A Woodinville, WA 98072 PROJECT: Walker Subaru Service Center Renton, WA 2240819.10 PREPARED BY: Nathan Kaser Project Engineer REVIEWED BY: Scott T. Kaul, PE, LEED AP Principal DATE: January 2026 Revised April 2026 I hereby state that this Technical Information Report for Walker Subaru Service Center has been prepared by me or under my supervision and meets the standard of care and expertise that is usual and customary in this community for professional engineers. I understand that City of Renton does not and will not assume liability for the sufficiency, suitability, or performance of drainage facilities prepared by me. 04/08/202606/11/2026 Technical Information Report Walker Subaru Service Center 2240819.10 Table of Contents Section Page 1.0 Project Overview ............................................................................................................................ 1 1.1 Purpose and Scope............................................................................................................. 1 1.2 Predeveloped Conditions .................................................................................................... 1 1.3 Development Conditions ..................................................................................................... 1 2.0 Conditions and Requirements Summary .................................................................................... 2 2.1 Core Requirements ............................................................................................................. 2 2.1.1 CR 1 – Discharge at the Natural Location ............................................................. 2 2.1.2 CR 2 – Offsite Analysis .......................................................................................... 2 2.1.3 CR 3 – Flow Control Facilities ................................................................................ 2 2.1.4 CR 4 – Conveyance System .................................................................................. 2 2.1.5 CR 5 – Construction Stormwater Pollution Prevention .......................................... 2 2.1.6 CR 6 – Maintenance and Operations .................................................................... 2 2.1.7 CR 7 – Financial Guarantees and Liability ............................................................ 2 2.1.8 CR 8 – Water Quality Facilities .............................................................................. 3 2.1.9 CR 9 – Onsite Best Management Practices (BMPs) ............................................. 3 2.2 Special Requirements ......................................................................................................... 4 2.2.1 SR 1 – Critical Drainage Areas .............................................................................. 4 2.2.2 SR 2 – Flood Hazard Area Delineation .................................................................. 4 2.2.3 SR 3 – Flood Protection Facilities .......................................................................... 4 2.2.4 SR 4 – Source Controls ......................................................................................... 4 2.2.5 SR 5 – Oil Control .................................................................................................. 4 2.2.6 SR 6 – Aquifer Protection Area .............................................................................. 4 3.0 Offsite Analysis .............................................................................................................................. 5 3.1 Downstream Analysis.......................................................................................................... 5 3.2 Upstream Analysis .............................................................................................................. 5 4.0 Flow Control, Low Impact Development (LID), and Water Quality Facility Analysis and Design ............................................................................................................................................. 5 4.1 Existing Site Hydrology ....................................................................................................... 5 4.2 Developed Site Hydrology .................................................................................................. 5 4.3 Performance Standards ...................................................................................................... 5 4.4 Flow Control System ........................................................................................................... 6 4.5 Water Quality System ......................................................................................................... 6 Technical Information Report Walker Subaru Service Center 2240819.10 5.0 Conveyance System Analysis and Design .................................................................................. 6 6.0 Special Reports and Studies ........................................................................................................ 6 7.0 Other Permits ................................................................................................................................. 7 8.0 Construction Stormwater Pollution Prevention Analysis and Design ..................................... 7 8.1 ESC Plan Analysis and Design ........................................................................................... 7 8.2 SWPPS Plan Design ........................................................................................................... 7 9.0 Bond Quantities, Facility Summaries, and Declaration of Covenant ....................................... 7 10.0 Operation and Maintenance Manual ............................................................................................ 7 11.0 Conclusion ...................................................................................................................................... 7 Technical Information Report Walker Subaru Service Center 2240819.10 Appendices Appendix A Figures A-1 ............Vicinity Map A-2 ............Soils Map A-3 ............Existing Conditions Map A-4 ............Developed Conditions Map A-5 ............FEMA Flood Map A-6 ............Aquifer Protection Map A-7 ............Downstream Analysis Appendix B TIR Worksheet Appendix C Hydrologic Analysis C-1 ............Existing Basin Map C-2 ............Developed Basin Map C-3 ............WWHM Printout C-4 ............Backwater Analysis C-5 ............Water Quality Calculations Appendix D Geotechnical Engineering Report Appendix E Non-Structural BMPs A-1 ............Required Best Management Practices (BMPs) for all Properties with Commercial Activities A-8 ............Storage or Solid and Food Wastes (Including Cooking Grease) A-45 ..........Maintenance of Public and Private Utility Corridors and Facilities Appendix F Construction Stormwater Pollution Prevention Plan Appendix G Stormwater Maintenance Plan Appendix H OWS Design Memo Technical Information Report Walker Subaru Service Center 1 2240819.10 1.0 Project Overview 1.1 Purpose and Scope This report accompanies the State Environmental Policy Act (SEPA) application for the Walker Subaru Service Center. The project site is located in the Northwest Quarter of the Northwest Quarter of Section 19, Township 23 North, Range 5 East, Willamette Meridian, in the city of Renton, King County, Washington. This site is located at 519 SW 12th Street (see Appendix A-1 for the Vicinity Map). The Walker Subaru Service Center project is located on Parcel 3340404265 totaling approximately 2.13 acres, with approximately 0.99 acres of ground disturbing activities. The proposed project is for a building addition of approximately 14,450 square feet onto the existing Subaru Facility. The project also includes relocating stormwater, water, sanitary sewer, and dry utilities. The design for this project meets or exceeds the requirements of the 2022 City of Renton Surface Water Design Manual (Storm Manual), which establishes the methodology and design criteria used for this project. 1.2 Predeveloped Conditions The existing condition is a developed site consisting of the Subaru Service Building and parking. Existing Vegetation/Cover: Most of the existing site is impervious. The existing building and paved parking make up a majority of the site. The existing stormwater swale and pond, along with a few landscape islands, are the only vegetated cover. There are four driveways accessing the site, two from the north end and two from the west end. An existing 8-inch sanitary sewer main runs along the south side of the existing building with an existing manhole located near the southeast corner of the building. There is an existing 6-inch water main running along the south side of the existing building. Power and other utilities are also running south of the existing building. There are several existing driveways at the north and west end of the site. The site is relatively flat and collects all stormwater via catch basins at low points. The site directs stormwater to the existing bioswale/pond at the south end of the site. Refer to Appendix A-3 for the Existing Conditions Map. To our knowledge, no critical areas are located on or near the site. 1.3 Development Conditions Approximately 0.99 acres of ground disturbing activities will occur on the 2.13-acre plot. Existing landscape trees within the building addition footprint will be removed. The proposed improvements are a building addition and new parking. The project also includes the relocation of multiple utilities, including storm, water, sanitary sewer, and dry utilities. The existing stormwater pond will continue to mitigate the stormwater onsite because there will be no net increase in impervious surfaces. The bioswale will be replaced with an underground BioPod for water quality. Refer to Section 4.5 for water quality sizing details. Refer to Appendix A-4 for the Developed Conditions Map. Technical Information Report Walker Subaru Service Center 2 2240819.10 2.0 Conditions and Requirements Summary 2.1 Core Requirements 2.1.1 CR 1 – Discharge at the Natural Location Currently, runoff from the project site flows to an existing bioswale and stormwater pond. The proposed addition will retain the pond, leaving the discharge point unchanged. The bioswale filtration will be switched out for an underground BioPod. 2.1.2 CR 2 – Offsite Analysis Downstream analysis is included in Section 3.0 below. 2.1.3 CR 3 – Flow Control Facilities Per the Storm Manual, the project requires Flow Control Duration Standard – Match Existing Condition. The existing system is proposed to remain to meet flow control requirements. Refer to Appendix C-3. The site’s runoff will be directed toward the existing detention pond. The portion of the site conveyed to the existing pond in the developed condition is unchanged from the existing condition. Therefore, the existing pond will continue to meet flow control requirements. Refer to Appendices C-1 and C-2 for Existing and Developed Basin Maps. 2.1.4 CR 4 – Conveyance System The project includes the construction of a new conveyance system to redirect stormwater around the building addition and back into the existing system. A portion of roof drains connect into the conveyance system while others are conveyed directly to the stormwater pond. A sump pump is proposed as part of the conveyance system. A complete backwater analysis was performed for the proposed conveyance network. The analysis does not account for the sump pump to simulate if the pump were to fail. Analysis resulted in zero flooding. Refer to Section 5 for further analysis. Refer to Appendix C-4 for the results of Backwater Analysis. 2.1.5 CR 5 – Construction Stormwater Pollution Prevention Construction Stormwater Pollution Prevention (CSWPP) and Temporary Erosion and Sediment Control (TESC) plans have been prepared for the site development submittal package. 2.1.6 CR 6 – Maintenance and Operations A maintenance plan for the stormwater management system has been provided with the site development permit. 2.1.7 CR 7 – Financial Guarantees and Liability A bond, assignment of funds, or certified check will be provided, as required, prior to construction. Technical Information Report Walker Subaru Service Center 3 2240819.10 2.1.8 CR 8 – Water Quality Facilities In the existing conditions, a bioswale provides water quality treatment for areas subject to pollution generating surfaces. In the proposed system, Basin 1 will have a new underground BioPod vault installed to treat stormwater directed into the existing storm pond. A detailed discussion of the water quality system is provided in Section 4.5. 2.1.9 CR 9 – Onsite Best Management Practices (BMPs) The project falls under the Large Lot BMP requirements, based on the size of the property. Core Requirement 9 BMPs have been evaluated in the order described per the Storm Manual, with infeasibility justification provided. 1. Full Dispersion Infeasibility Justification: Full dispersion requires that a 100-foot minimum vegetated flow path be provided. The small area and site plan do not allow for the required flow path. Full dispersion also requires a maximum 15 percent of the site be impervious surfaces. The project will convert approximately 76 percent of the site to impervious surfaces. 2. Full Infiltration of Roof Runoff Infeasibility Justification: Full infiltration of Roof Runoff has been determined infeasible by the geotechnical analysis performed by Migizi Group, Inc. The geotechnical analysis recommends not using infiltration. 3. Option 1 - Full Infiltration Infeasibility Justification: Full infiltration has been determined infeasible by the geotechnical analysis performed by Migizi Group, Inc. The groundwater level is shallow, and soils are not suited for infiltration; therefore, infiltration was determined infeasible. 3. Option 2 - Limited Infiltration Infeasibility Justification: Limited infiltration BMPs, per the Storm Manual, are the same as full infiltration systems but located in poor infiltrative soils that are likely to clog and work less effectively over time. Infiltration has been determined infeasible by the geotechnical analysis performed by Migizi Group, Inc. Limited infiltration facilities would not adequately provide infiltration. 3. Option 3 - Bioretention The existing bioswale was determined not to meet the enhanced basic water quality treatment requirement. An alternative form of treatment will be necessary, making Bioretention infeasible. 3. Option 4 - Permeable Pavement Permeable paving is considered infeasible. The geotechnical analysis has determined soils in the area do not meet requirements and that all stormwaters should be managed onsite through detention or diverted to the existing systems offsite. 4. Soil Amendment All disturbed areas will be amended per the Soil Amendment BMP. The pollution generating impervious surfaces will be provided with treatment and flow control. Technical Information Report Walker Subaru Service Center 4 2240819.10 2.2 Special Requirements 2.2.1 SR 1 – Critical Drainage Areas The project does not lie within a critical drainage area. 1. Master Drainage Plans (MDPs) The project does not lie within an area covered by an approved Master Drainage Plan. 2. Basin Plans (BPs) The project does not lie within an area with an adopted Basin Plan. 3. Salmon Conservation Plans (SCPs) The project does not lie within an area with an adopted Salmon Conservation Plan. 4. Lake Management Plans The project does not lie within an area with an adopted Lake Management Plan. 5. Hazard Mitigation Plan The project does not lie within a flood hazard area and is not tributary to any identified flooding per the City of Renton Hazard Mitigation Plan, April 2010. 6. Shared Facility Drainage Plans (SFDPs) The project does not propose a Shared Facility Drainage Plan. 2.2.2 SR 2 – Flood Hazard Area Delineation The proposed project is not within or adjacent to a flood hazard area, as identified by City of Renton in the Hazard Plan per FEMA study. Refer to Appendix A-5 for FEMA Flood Map. 2.2.3 SR 3 – Flood Protection Facilities The project does not meet the conditions requiring flood protection facilities. 2.2.4 SR 4 – Source Controls Source control BMPs, as identified in the King County Stormwater Pollution Prevention Manual and Renton Municipal Code, Title IV, have been incorporated into the layout and design of the proposed stormwater management system. The site use will require non-structural BMPs to maintain source control. BMPs A-01, A-08, and A-45 from the King County Stormwater Pollution Prevention Manual shall be adhered to. Refer to Appendix E for Source Control BMPs. 2.2.5 SR 5 – Oil Control The proposed site is expected to meet the high-use site criteria. An oil-water separator (OWS) is proposed to meet the oil control requirement. The existing OWS is proposed to be relocated and upsized, as required for the additional service bays. A second OWS has been sized for the proposed covered drive through waiting area. Refer to Appendix H for Full OWS sizing memos. 2.2.6 SR 6 – Aquifer Protection Area The project site is not within an aquifer protection zone. Technical Information Report Walker Subaru Service Center 5 2240819.10 3.0 Offsite Analysis 3.1 Downstream Analysis The site will continue to direct all runoff to the stormwater facilities in the southeast corner of the site. The project improvements will not affect the discharge point, and the downstream will remain unchanged. Within a quarter mile of discharging offsite, stormwater is conveyed across I-405 before being discharged into a surface water channel. Refer to Appendix A-7 for the Downstream Analysis. 3.2 Upstream Analysis The project site does not receive any substantive runoff from offsite properties. 4.0 Flow Control, Low Impact Development (LID), and Water Quality Facility Analysis and Design An existing stormwater pond will remain to meet flow control requirements for Basin 1. The existing bioswale will be replaced with an underground BioPod to provide water quality treatment for Basin 1. Design is based on the Appendix C-2 Developed Basin Map and the basin characteristics below. Refer to Appendix C-3 for a WWHM printout of the existing and proposed flow control. Basin 1 is characterized as follows: Total Area: 1.89 acres Building Area: 0.80 acre Asphalt Pavement Area: 1.09 acres 4.1 Existing Site Hydrology The existing site is fully developed. The existing conveyance system directs runoff to a bioswale, which treats stormwater before flowing into a detention pond. The existing detention pond will remain to mitigate runoff. Refer to Appendix C-1 for the Existing Basin Map. 4.2 Developed Site Hydrology All onsite improvements will redirect stormwater into new and existing facilities to mimic the existing conditions. The entire site (Basin 1) will be discharged to the existing detention pond. Refer to Appendix C-2 the for Developed Basin Map. 4.3 Performance Standards The Area-Specific Flow Control Facility requirement for this project will be the Peak Rate Flow Control Standard – Match Existing Conditions. The City has identified the required flow control standards per the City of Renton Flow Control Application Map. This project falls under the Large Lot BMP requirements. The existing detention pond will remain to meet onsite BMP requirements. The Bioswale will be replaced with a BioPod, which can meet the enhanced basic treatment standard. Because of site constraints and the elevation of the existing stormwater facilities. The new pipe systems will match minimum slopes of the existing system to mimic existing conditions. Technical Information Report Walker Subaru Service Center 6 2240819.10 Enhanced Basic Water Quality Treatment is required for pollution generating target surfaces. The pollution generating surfaces from Basin 1 will be conveyed to an underground BioPod for treatment before entering the existing detention system. A commercial site development permit is required; therefore, source control BMPs are required. Structural source controls will be provided based on the use of the site as commercial. Nonstructural source control measures will be provided per SR 4. Refer to Appendix E for Non- Structural BMPs. The site will need an oil control facility due to vehicle maintenance bays. 4.4 Flow Control System The flow control system schematic layout can be found on the civil plan sheets. Basin 1 meets the LID - match existing condition requirements; the entire site is sent to the existing detention facility. Refer to Appendix C-3. 4.5 Water Quality System Due to the need for enhanced basic water quality treatment, the existing bioswale will be replaced with an underground BioPod to treat runoff from Basin 1. Sizing details are provided below. Refer to Appendix C-5 for Water Quality Calculations. Site 6x12 BioPod Impervious Area 0.75 ac Roof Area 0.20 ac Online Flow 0.155 cfs Enhanced Basic Treatment Capacity 0.213 cfs 100 Year Flow 0.739 cfs Bypass Capacity 5.0 cfs 5.0 Conveyance System Analysis and Design Closed-pipe conveyance is provided to redirect runoff around the building improvements. The project includes the construction of a new conveyance system to redirect stormwater around the building addition and back into the existing system. Some roof drains discharge into the conveyance system while others are conveyed directly to the stormwater pond. A sump pump is proposed to direct stormwater into the existing pond. A complete backwater analysis was performed for the proposed conveyance network. As outlined in the Stormwater Manual, the system was tested for a 25-year storm event. Pipes at the end of Storm Run 1 were submerged but not close to flooding. A 100-year storm event was also tested for the possibility of flooding. Storm Run 1 was almost entirely submerged, however water level stayed relatively low within the catch basins. No flooding occurred in the 100-year storm event. The analysis was completed without the sump pump to simulate conditions if the pump were to fail. The conveyance system as proposed has been determined not to be at risk of flooding. Refer to Appendix C-4 for the results of the Backwater Analysis. 6.0 Special Reports and Studies A geotechnical engineering report has been prepared by Migizi Group, Inc. (see Appendix D). Technical Information Report Walker Subaru Service Center 7 2240819.10 7.0 Other Permits This project will require a Building Permit and Civil Construction Permit. 8.0 Construction Stormwater Pollution Prevention Analysis and Design 8.1 ESC Plan Analysis and Design A Construction Stormwater Pollution Prevention Plan has been prepared for final site development plans. 8.2 SWPPS Plan Design A Temporary Erosion and Sediment Control Plan (TESC Plan) has been prepared for the final site development plans. A Construction Stormwater Pollution Prevention (CSWPP) supervisor will be appointed by the Contractor at the time of construction to implement and update TESC plans, as required. The CSWPP supervisor shall be a Certified Professional in Erosion and Sediment Control or a Certified Erosion and Sediment Control Lead. The CSWPP supervisor will be responsible for compliance with all City of Renton construction stormwater requirements. 9.0 Bond Quantities, Facility Summaries, and Declaration of Covenant A bond quantities worksheet will be provided for the final site development permit. All easement requests will be submitted to the City of Renton Community and Economic Development (CED) Department. 10.0 Operation and Maintenance Manual An Operation and Maintenance Manual has been prepared and submitted along with final site development. 11.0 Conclusion This project is designed to meet the 2022 City of Renton Surface Water Design Manual guidelines for stormwater management. This analysis is based on data and records either supplied to or obtained by AHBL, Inc. These documents are referenced within the text of the analysis. The analysis has been prepared using procedures and practices within the standard accepted practices of the industry. We conclude that this project, as proposed, will not create any new problems within the existing downstream drainage system. AHBL, Inc. Nathan Kaser Project Engineer NK/lsk January 2026 Revised April 2026 Q:\2024\2240819\WORDPROC\Reports\20260408 Rpt (TIR) 2240819.10.docx Technical Information Report Walker Subaru Service Center 2240819.10 Appendix A Figures A-1 .................... Vicinity Map A-2 .................... Soils Map A-3 .................... Existing Conditions Map A-4 .................... Developed Conditions Map A-5 .................... FEMA Flood Map A-6 .................... Aquifer Protection Map A-7 .................... Downstream Analysis 2215 North 30th Street Suite 300 Tacoma, WA 98403 253.383.2422 TEL 253.383.2572 FAX SUNSET HIGHLANDS MIXED USE 2190210.10 VICINITY MAP A-1 NOT TO SCALE VICINITY MAP SUNSET HIGHLANDS - 2230621.10WALKER SUBARU SERVICE CENTER - 2240819.10 United States Department of Agriculture A product of the National Cooperative Soil Survey, a joint effort of the United States Department of Agriculture and other Federal agencies, State agencies including the Agricultural Experiment Stations, and local participants Custom Soil Resource Report for King County Area, Washington Natural Resources Conservation Service February 5, 2025 Preface Soil surveys contain information that affects land use planning in survey areas. They highlight soil limitations that affect various land uses and provide information about the properties of the soils in the survey areas. Soil surveys are designed for many different users, including farmers, ranchers, foresters, agronomists, urban planners, community officials, engineers, developers, builders, and home buyers. Also, conservationists, teachers, students, and specialists in recreation, waste disposal, and pollution control can use the surveys to help them understand, protect, or enhance the environment. Various land use regulations of Federal, State, and local governments may impose special restrictions on land use or land treatment. Soil surveys identify soil properties that are used in making various land use or land treatment decisions. The information is intended to help the land users identify and reduce the effects of soil limitations on various land uses. The landowner or user is responsible for identifying and complying with existing laws and regulations. Although soil survey information can be used for general farm, local, and wider area planning, onsite investigation is needed to supplement this information in some cases. Examples include soil quality assessments (http://www.nrcs.usda.gov/wps/ portal/nrcs/main/soils/health/) and certain conservation and engineering applications. For more detailed information, contact your local USDA Service Center (https://offices.sc.egov.usda.gov/locator/app?agency=nrcs) or your NRCS State Soil Scientist (http://www.nrcs.usda.gov/wps/portal/nrcs/detail/soils/contactus/? cid=nrcs142p2_053951). Great differences in soil properties can occur within short distances. Some soils are seasonally wet or subject to flooding. Some are too unstable to be used as a foundation for buildings or roads. Clayey or wet soils are poorly suited to use as septic tank absorption fields. A high water table makes a soil poorly suited to basements or underground installations. The National Cooperative Soil Survey is a joint effort of the United States Department of Agriculture and other Federal agencies, State agencies including the Agricultural Experiment Stations, and local agencies. The Natural Resources Conservation Service (NRCS) has leadership for the Federal part of the National Cooperative Soil Survey. Information about soils is updated periodically. Updated information is available through the NRCS Web Soil Survey, the site for official soil survey information. The U.S. Department of Agriculture (USDA) prohibits discrimination in all its programs and activities on the basis of race, color, national origin, age, disability, and where applicable, sex, marital status, familial status, parental status, religion, sexual orientation, genetic information, political beliefs, reprisal, or because all or a part of an individual's income is derived from any public assistance program. (Not all prohibited bases apply to all programs.) Persons with disabilities who require 2 alternative means for communication of program information (Braille, large print, audiotape, etc.) should contact USDA's TARGET Center at (202) 720-2600 (voice and TDD). To file a complaint of discrimination, write to USDA, Director, Office of Civil Rights, 1400 Independence Avenue, S.W., Washington, D.C. 20250-9410 or call (800) 795-3272 (voice) or (202) 720-6382 (TDD). USDA is an equal opportunity provider and employer. 3 Contents Preface....................................................................................................................2 Soil Map..................................................................................................................5 Soil Map................................................................................................................6 Legend..................................................................................................................7 Map Unit Legend..................................................................................................8 Map Unit Descriptions..........................................................................................8 King County Area, Washington.......................................................................10 Ur—Urban land...........................................................................................10 4 Soil Map The soil map section includes the soil map for the defined area of interest, a list of soil map units on the map and extent of each map unit, and cartographic symbols displayed on the map. Also presented are various metadata about data used to produce the map, and a description of each soil map unit. 5 6 Custom Soil Resource Report Soil Map 52 5 7 4 1 0 52 5 7 4 3 0 52 5 7 4 5 0 52 5 7 4 7 0 52 5 7 4 9 0 52 5 7 5 1 0 52 5 7 5 3 0 52 5 7 5 5 0 52 5 7 5 7 0 52 5 7 5 9 0 52 5 7 4 1 0 52 5 7 4 3 0 52 5 7 4 5 0 52 5 7 4 7 0 52 5 7 4 9 0 52 5 7 5 1 0 52 5 7 5 3 0 52 5 7 5 5 0 52 5 7 5 7 0 52 5 7 5 9 0 558370 558390 558410 558430 558450 558470 558490 558510 558370 558390 558410 558430 558450 558470 558490 558510 47° 28' 8'' N 12 2 ° 1 3 ' 3 1 ' ' W 47° 28' 8'' N 12 2 ° 1 3 ' 2 4 ' ' W 47° 28' 2'' N 12 2 ° 1 3 ' 3 1 ' ' W 47° 28' 2'' N 12 2 ° 1 3 ' 2 4 ' ' W N Map projection: Web Mercator Corner coordinates: WGS84 Edge tics: UTM Zone 10N WGS84 0 45 90 180 270 Feet 0 10 20 40 60 Meters Map Scale: 1:937 if printed on A portrait (8.5" x 11") sheet. Soil Map may not be valid at this scale. MAP LEGEND MAP INFORMATION Area of Interest (AOI) Area of Interest (AOI) Soils Soil Map Unit Polygons Soil Map Unit Lines Soil Map Unit Points Special Point Features Blowout Borrow Pit Clay Spot Closed Depression Gravel Pit Gravelly Spot Landfill Lava Flow Marsh or swamp Mine or Quarry Miscellaneous Water Perennial Water Rock Outcrop Saline Spot Sandy Spot Severely Eroded Spot Sinkhole Slide or Slip Sodic Spot Spoil Area Stony Spot Very Stony Spot Wet Spot Other Special Line Features Water Features Streams and Canals Transportation Rails Interstate Highways US Routes Major Roads Local Roads Background Aerial Photography The soil surveys that comprise your AOI were mapped at 1:24,000. Warning: Soil Map may not be valid at this scale. Enlargement of maps beyond the scale of mapping can cause misunderstanding of the detail of mapping and accuracy of soil line placement. The maps do not show the small areas of contrasting soils that could have been shown at a more detailed scale. Please rely on the bar scale on each map sheet for map measurements. Source of Map: Natural Resources Conservation Service Web Soil Survey URL: Coordinate System: Web Mercator (EPSG:3857) Maps from the Web Soil Survey are based on the Web Mercator projection, which preserves direction and shape but distorts distance and area. A projection that preserves area, such as the Albers equal-area conic projection, should be used if more accurate calculations of distance or area are required. This product is generated from the USDA-NRCS certified data as of the version date(s) listed below. Soil Survey Area: King County Area, Washington Survey Area Data: Version 20, Aug 27, 2024 Soil map units are labeled (as space allows) for map scales 1:50,000 or larger. Date(s) aerial images were photographed: Jul 31, 2022—Aug 8, 2022 The orthophoto or other base map on which the soil lines were compiled and digitized probably differs from the background imagery displayed on these maps. As a result, some minor shifting of map unit boundaries may be evident. Custom Soil Resource Report 7 Map Unit Legend Map Unit Symbol Map Unit Name Acres in AOI Percent of AOI Ur Urban land 2.6 100.0% Totals for Area of Interest 2.6 100.0% Map Unit Descriptions The map units delineated on the detailed soil maps in a soil survey represent the soils or miscellaneous areas in the survey area. The map unit descriptions, along with the maps, can be used to determine the composition and properties of a unit. A map unit delineation on a soil map represents an area dominated by one or more major kinds of soil or miscellaneous areas. A map unit is identified and named according to the taxonomic classification of the dominant soils. Within a taxonomic class there are precisely defined limits for the properties of the soils. On the landscape, however, the soils are natural phenomena, and they have the characteristic variability of all natural phenomena. Thus, the range of some observed properties may extend beyond the limits defined for a taxonomic class. Areas of soils of a single taxonomic class rarely, if ever, can be mapped without including areas of other taxonomic classes. Consequently, every map unit is made up of the soils or miscellaneous areas for which it is named and some minor components that belong to taxonomic classes other than those of the major soils. Most minor soils have properties similar to those of the dominant soil or soils in the map unit, and thus they do not affect use and management. These are called noncontrasting, or similar, components. They may or may not be mentioned in a particular map unit description. Other minor components, however, have properties and behavioral characteristics divergent enough to affect use or to require different management. These are called contrasting, or dissimilar, components. They generally are in small areas and could not be mapped separately because of the scale used. Some small areas of strongly contrasting soils or miscellaneous areas are identified by a special symbol on the maps. If included in the database for a given area, the contrasting minor components are identified in the map unit descriptions along with some characteristics of each. A few areas of minor components may not have been observed, and consequently they are not mentioned in the descriptions, especially where the pattern was so complex that it was impractical to make enough observations to identify all the soils and miscellaneous areas on the landscape. The presence of minor components in a map unit in no way diminishes the usefulness or accuracy of the data. The objective of mapping is not to delineate pure taxonomic classes but rather to separate the landscape into landforms or landform segments that have similar use and management requirements. The delineation of such segments on the map provides sufficient information for the development of resource plans. If intensive use of small areas is planned, however, onsite investigation is needed to define and locate the soils and miscellaneous areas. Custom Soil Resource Report 8 An identifying symbol precedes the map unit name in the map unit descriptions. Each description includes general facts about the unit and gives important soil properties and qualities. Soils that have profiles that are almost alike make up a soil series. Except for differences in texture of the surface layer, all the soils of a series have major horizons that are similar in composition, thickness, and arrangement. Soils of one series can differ in texture of the surface layer, slope, stoniness, salinity, degree of erosion, and other characteristics that affect their use. On the basis of such differences, a soil series is divided into soil phases. Most of the areas shown on the detailed soil maps are phases of soil series. The name of a soil phase commonly indicates a feature that affects use or management. For example, Alpha silt loam, 0 to 2 percent slopes, is a phase of the Alpha series. Some map units are made up of two or more major soils or miscellaneous areas. These map units are complexes, associations, or undifferentiated groups. A complex consists of two or more soils or miscellaneous areas in such an intricate pattern or in such small areas that they cannot be shown separately on the maps. The pattern and proportion of the soils or miscellaneous areas are somewhat similar in all areas. Alpha-Beta complex, 0 to 6 percent slopes, is an example. An association is made up of two or more geographically associated soils or miscellaneous areas that are shown as one unit on the maps. Because of present or anticipated uses of the map units in the survey area, it was not considered practical or necessary to map the soils or miscellaneous areas separately. The pattern and relative proportion of the soils or miscellaneous areas are somewhat similar. Alpha-Beta association, 0 to 2 percent slopes, is an example. An undifferentiated group is made up of two or more soils or miscellaneous areas that could be mapped individually but are mapped as one unit because similar interpretations can be made for use and management. The pattern and proportion of the soils or miscellaneous areas in a mapped area are not uniform. An area can be made up of only one of the major soils or miscellaneous areas, or it can be made up of all of them. Alpha and Beta soils, 0 to 2 percent slopes, is an example. Some surveys include miscellaneous areas. Such areas have little or no soil material and support little or no vegetation. Rock outcrop is an example. Custom Soil Resource Report 9 King County Area, Washington Ur—Urban land Map Unit Composition Urban land:100 percent Estimates are based on observations, descriptions, and transects of the mapunit. Description of Urban Land Interpretive groups Land capability classification (irrigated): None specified Land capability classification (nonirrigated): 8 Hydric soil rating: No Custom Soil Resource Report 10 2215 North 30th Street, Suite 300, Tacoma, WA 98403 253.383.2422 TEL 253.383.2572 FAX JOB NO. DATE: WALKER SUBARU SERVICE CENTER EXISTING CONDITIONS A-3 2240819.10 1/15/2026 N GRAPHIC SCALE 0 30 60 1" = 30 FEET 15 GPGP GP GP GP GP GP GP GP GP GP GP GP GP GP GP GP GP GP P P GP GP S0 1 ° 2 3 ' 1 0 " W 2 7 8 . 3 5 ' ( M ) RAMP C/C C/C C/C C/C RAMP 12" MAPLE 12" MAPLE 14" MAPLE 8" UNKNOWN DECIDUOUS DRIVEWAY C/G C/G C/G E/C E/C E/CE/C E/C E/C 6' CLF 6' CLF 6' CLF 0.6' 0.5' NOT PART OF SURVEY (TAX PARCEL NO. 3340404150) NOT PART OF SURVEY (TAX PARCEL NO. 3340404150) GATE 0.3' 0.1' 4.9' 8.0' 6' CLF 7' CLF 6' CLF 6' CLF 6' CLF ANGLE POINT BEARS S84°11'E, 0.6' FROM CALCULATED LOT CORNER 6' CLF 6' CLF 6' CLF 6' CLF 8' CLF E/C E/C E/C E/C 5.1' 9.0' 8.2' 17.5' 3.1' 0.3' 10' CLF GATE 0.3' 0.1' 3X8" UNKNOWN DECIDUOUS GATE E/C E/C 6' CLF 6' CLF 6' CLF STOP BAR C/G C/G C/G C/G 30.0' DRIVEWAY E/C RA/W RA/W RA/W RA/W RA/W RA/W BUILDING FINISH FLOOR AT CENTER OF PED. DOOR LABELED "SPRINKLER ROOM" ELEV=21.95' NAVD 88 BUILDING FINISH FLOOR AT CENTER OF DOUBLE PED. DOOR ELEV=22.03' NAVD 88 E/C E/C E/C E/C E/C CONC. CANOPY COLUMN CONC. CANOPY COLUMN CONC. CANOPY COLUMN CONC. CANOPY COLUMN GATE GATE GATE 4' CLF4' CLF 4' CLF 4' CLF 4' CLF 4' CLF EDGE CANOPY (TYPICAL) EDGE CANOPY (TYPICAL) 12"MAPLE 13" MAPLE 17" MAPLE 11" MAPLE 14" MAPLE GATE 6' CLF "STOP" STEEL POST FOR AERIAL WALKER'S RENTON SUBARU PARTS AND SERVICE CENTER SIGN SERVICE CENTER DIRECTIONS SIGN C/C C/C RAMP E/C C/C C/C RAMP STEEL POST FOR AERIAL SUBARU SIGN 26.9'DRIVEWAY C/G RA/W 6' CLF 6' CLF 6' CLF 6' CLF 6' CLF 6' CLF 6' CLF GATE 6' CLF FENCE TRANSITION 6' CLF/6' STEEL 6' STEEL STORMWATER DETENTION POND 6' CLF 6' CLF 6' CLF 6' CLF 6' CLF 8' CLF 8' CLF 8' CLF 8' CLF 8' CLF 6' CLF 4' CLF 0.7' 1.2' 4.4' 2.8' 1.5' 0.8' 0.8' 1.5' 1.4' 1.0' 2.1' 0.4' 0.9' 1.0' 0.9' UNKNOWN USE CLEANOUT RIM=22.06' UNKNOWN USE CLEANOUT RIM=21.96' 525.46'(C) 117.44' S0 1 ° 2 2 ' 4 2 " W 11 6 . 4 3 ' N77°26'10" E 119.92' N0 1 ° 2 2 ' 4 3 " E 11 6 . 3 8 ' L1 8 L17 S0 9 ° 3 9 ' 1 5 " E 1 0 5 . 0 4 ' L2 0 L2 1 N77°24'38" E 123.29' 11 4 . 3 4 ' S86°20'10"W 391.52' 25 4 . 8 8 ' L1 0 L1 9 FND 1/2" REBAR AND CAP STAMPED "LS 19635" REBAR BEARS S88°24'33"E, 0.23' FROM THE CALCULATED LOT CORNER VISITED 11/18/2024 A/W A/W 0.7' 0.9' 1.0' 0.8' 3-WAY 6' CLF INTERSECTION BEARS S15°13'E, 6.2' GATE 8'/6' CLF INTERSECTION BEARS S79°15'W, 2.9' FROM THE CALCULATED LOT CORNER 75 . 2 0 ' PRIVATE INGRESS/EGRESS EASEMENT PER EASEMENT AGREEMENT WITH RIGHTS AND RESPONSIBILITIES AFN 20020612000622 QWEST TELECOMMUNICATIONS EASEMENT PER AFN 20030327000925 PRIVATE INGRESS/EGRESS EASEMENT PER EASEMENT AGREEMENT WITH RIGHTS AND RESPONSIBILITIES AFN 20020612000622 UTILITIES EASEMENT TO THE CITY OF RENTON PER AFN 20010906002177, CITY OF RENTON ORDINANCE 4914 (ENCOMPASSES WHOLE VACATED ALLEY) BUILDING FINISH FLOOR AT CENTER OF BAY DOOR ELEV=21.94' NAVD 88 6' CLF ANGLE POINT BEARS N53°23'W, 1.3' FROM CALCULATED LOT CORNER 8' CLF END BEARS N25°48'W, 1.0' FROM CALCULATED LOT CORNER PSE ELECTRICAL EASEMENT PER AFN 20030128002591 UTILITIES EASEMENT TO THE CITY OF RENTON PER AFN 20010906002177, CITY OF RENTON ORDINANCE 4914 (ENCOMPASSES WHOLE VACATED ALLEY) PSE ELECTRICAL EASEMENT PER AFN 20030128002591 PSE ELECTRICAL EASEMENT PER AFN 20030128002591 UTILITIES EASEMENT TO THE CITY OF RENTON PER AFN 20020207002539, CITY OF RENTON ORDINANCE 4942 (ENCOMPASSES WHOLE VACATED STREET) SE N E C A A V E S W SW 12TH S T SW 13TH S T INTERSTATE 405 CB #6 CB #5 CB #4 CB #3 CB #2 CB #1 BLDG ADDITION FF: 21.95 CB #7 EXIST. CB1 EXIST. CB3 EXISTING BUILDING FF: 21.95BLDG ADDITION EXIST. CB4 61 LF 8" DI CL52 @ 0.25% 89 LF 8" CPEP @ 0.25% 57 LF 8" CPEP @ 0.25% 86 LF 8" CPEP @ 0.46% 57 LF 8" DI CL52 @ 0.25% 28 LF 8" DI CL52 @ 0.25% 130 LF 6" PVC SDR-35 @ 0.25% 16 LF 6" PVC SDR-35 @ 0.25% 16+10 10+00 11 + 0 0 12 + 0 0 13 + 0 0 14+00 15+00 16+00 STORM RUN 1 SHEET C3.4 20+ 0 0 20+ 4 7 30 + 0 0 31 + 0 0 3 1 + 5 0 STORM RUN 3 SHEET C3.4 STORM RUN 2 SHEET C3.4 CO #3 91 LF 6" PVC SDR-35 @ 0.50% CO #4 128 LF 6" PVC SDR-35 @ 1.13% CO #5 9 LF 6" PVC SDR-35 @ 0.50% CO #6 103 LF 6" PVC SDR-35 @ 0.25% 108 LF 6" PVC SDR-35 @ 1.51% CO #7 13 LF 6" PVC SDR-35 @ 0.50% CO #2 CO #1 69 LF 8" CPEP @ 0.26% 18 LF 8" CPEP @ 1.48% IE: 17.55 8" (W) IE: 17.00 6" (W) EXISTING STORM PIPE TO REMAIN EXISTING STORM PIPE TO REMAIN CB #8 APPROX. POND BOTTOM EG: 16.50 EXISTING DETENTION POND TO REMAIN 21 LF 6" PVC SDR-35 @ 0.25% 22.00 22.00 22.00 22 . 0 0 23.0 0 23 . 0 0 23 . 0 0 23 . 0 0 21.00 2 1 . 0 0 22.00 22 . 0 0 22.00 22.0022.00 CONNECT EXISTING BUILDING ROOF DRAINS, CONTRACTOR TO POTHOLE AND VERIFY DEPTH PRIOR TO CONSTRUCTION. CONNECT EXISTING BUILDING ROOF DRAINS, CONTRACTOR TO POTHOLE AND VERIFY DEPTH PRIOR TO CONSTRUCTION. OUTLET PROTECTION 2 C3.5 EXISTING POND TO BE REFRESHED. REMOVE ALL DEBRIS AND SEDIMENT BUILD-UP. REMOVE ALL NOXIOUS WEEDS. POND OUTLET TO BE CLEARED AND CLEANED. EXISTING STORM PIPE TO REMAIN STA:12+50.33, 0.00' EXIST. CB2 STORM STRUCTURE TABLE STRUCTURE NAME CB #1 TYPE 1 N 173874.77 E 1296386.65 CB #2 TYPE 1 N 173790.74 E 1296405.48 CB #3 TYPE 1 N 173778.29 E 1296350.24 CB #4 TYPE 1 N 173758.79 E 1296263.78 CB #5 TYPE 1 N 173795.86 E 1296220.61 CB #6 TYPE 1 N 173815.39 E 1296240.61 CB #7 48" TYPE 2 W/ SUMP PUMP 0.4CFS @ 5' TDH N 173835.29 E 1296174.69 CB #8 6x12 BIOPOD UNDERGROUND VAULT N 173792.17 E 1296477.46 CO #1 CO N 173976.94 E 1296166.26 STRUCTURE DETAILS RIM = 21.59 IE = 18.90 (8" S) IE = 18.90 (8" NE) RIM = 21.60 IE = 18.50 (8" W) IE = 18.50 (8" N) IE = 18.50 (8" E) RIM = 21.60 IE = 18.64 (8" W) IE = 18.64 (8" E) RIM = 21.60 IE = 18.86 (8" NW) IE = 18.86 (8" E) RIM = 21.66 IE = 19.00 (8" NW) IE = 19.00 (8" SE) IE = 19.00 (8" NE) RIM = 21.40 IE = 19.07 (8" SW) RIM = 21.17 IE = 19.15 (8" SE) IE = 19.32 (6" NE) IE = 19.32 (6" NW) IE = 18.50 (8" N) RIM = 22.93 IE = 18.32 (8" W) IE = 17.82 (8" E) RIM = 21.37 IE = 19.68 (6" S) STORM STRUCTURE TABLE STRUCTURE NAME CO #2 CO N 173847.01 E 1296163.19 CO #3 CO N 173855.79 E 1296253.46 CO #4 CO N 173766.96 E 1296273.50 CO #5 CO N 173795.13 E 1296398.36 CO #6 CO N 173804.01 E 1296396.36 CO #7 CO N 173909.80 E 1296372.49 EXIST. CB1 EXISTING TYPE 1 N 173898.95 E 1296401.89 EXIST. CB2 EXISTING TYPE 1 N 174067.99 E 1296401.66 EXIST. CB3 EXISTING TYPE 1 N 173985.44 E 1296176.98 STRUCTURE DETAILS RIM = 21.38 IE = 19.36 (6" N) IE = 19.36 (6" SE) RIM = 21.95 IE = 19.22 (6" S) RIM = 21.85 IE = 18.76 (6" E) IE = 18.76 (6" N) RIM = 21.85 IE = 17.31 (6" N) IE = 17.31 (6" W) RIM = 21.90 IE = 17.26 (6" E) IE = 17.26 (6" S) IE = 17.26 (6" N) RIM = 21.89 IE = 18.90 (6" S) IE = 18.90 (6" E) RIM = 21.31 IE = 19.00 (8" SW) IE = 19.00 (8" N) RIM = 21.46 IE = 19.69 (8" S) RIM = 21.20 IE = 18.75 (8" S) IE = 18.88 (12" NE) IE = 18.77 (6" E) STRUCTURE NAME CITY OF RENTON IN COMPLIANCE WITH CITY OF RENTON STANDARDS T A C O M A 2215 North 30th Street, Suite 300 Tacoma, WA 98403 253.383.2422TEL 253.383.2572FAX www.ahbl.comWEB S E A T T L E S P O K A N E T R I - C I T I E S WALKER SUBARU SERVICE CENTER PERMIT SET AHBL JOB #2240819.10 54 Know what's below. before you dig.Call R C2 6 0 0 0 6 3 8 LU A 2 5 - 0 0 0 1 7 1 PR 2 5 - 0 0 0 0 3 1 TE D - 4 0 - 4 3 8 8 N GRAPHIC SCALE 0 20 40 1" = 20 FEET 10 HELD COMPUTED NAD 83/91, WASHINGTON STATE PLANE, NORTH ZONE, GRID BEARING OF NORTH 89°43'16" WEST BETWEEN A MONUMENT FOUND AT THE INTERSECTION OF LIND AVE. SW AND SW 16TH ST., BEING CITY OF RENTON CONTROL ID. 1895, TO A MONUMENT FOUND ON ALONG THE NORTHERLY MARGIN OF SW 16TH ST. AT A BRIDGE CROSSING OF SPRINGBROOK CREEK, BEING CITY OF RENTON CONTROL ID. 1891, RESPECTIVELY. NAD 83/91, WASHINGTON STATE PLANE, NORTH ZONE, AS DEFINED BY THE CITY OF RENTON PUBLISHED HORIZONTAL CONTROL NETWORK UNIT OF MEASUREMENT IS U.S. SURVEY FEET ALL DISTANCES SHOWN ARE GROUND A COMBINED GRID SCALE FACTOR OF 0.999987504615 (GRID TO GROUND) WAS HELD AT CITY OF RENTON CONTROL ID. 1895 NAVD 88 (AS DEFINED BY THE PUBLISHED CITY OF RENTON VERTICAL BENCHMARK NETWORK) (NGS2018 GEOID - USED) PROJECT PRIMARY BENCHMARK: CITY OF RENTON CONTROL ID. 1895 PUBLISHED ELEVATION: 25.702' NAVD 88 DESCRIPTION: ENCASED 3" BRASS DISK W/PUNCH LOCATED AT THE INTERSECTION OF LIND AVE. SW AND SW 16TH ST. PROJECT SECONDARY BENCHMARK: CITY OF RENTON CONTROL ID. 1891 PUBLISHED ELEVATION: 24.1568' NAVD 88 OBSERVED ELEVATION: 24.06' NAVD 88 DESCRIPTION: MONUMENT FOUND ALONG THE NORTHERLY MARGIN OF SW 16TH ST. AT A BRIDGE CROSSING OF SPRINGBROOK CREEK. SITE BENCHMARK OBSERVED ELEVATION: 27.41' NAVD 88 DESCRIPTION: ENCASED 1 7/8" BRASS DISK W/PUNCH AT THE INTERSECTION OF SW GRADY WAY AND SENECA AVE. SW BASIS OF BEARING HORIZONTAL DATUM VERTICAL DATUM 23 STORM PLAN C3.3Q: \ 2 0 2 4 \ 2 2 4 0 8 1 9 \ 1 0 _ C I V \ C A D \ _ F i n a l D e s i g n \ 2 2 4 0 8 1 9 - S H - S T R M . d w g 1.PROVIDE 4" PERFORATED FOUNDATION DRAINS AROUND BUILDING FOUNDATION. CONNECT TO STORM SYSTEM. 2.PROVIDE 6" PVC SDR-35 ROOF DRAIN LINES AT 0.5% MINIMUM SLOPE UNLESS OTHERWISE NOTED. 3.PROVIDE HERRINGBONE GRATE INLETS FOR ALL CATCH BASINS PER WSDOT STANDARD PLAN B30.50.03 UNLESS OTHERWISE NOTED. 4.CONTRACTOR SHALL COORDINATE AND CONFIRM DOWNSPOUT ROOF DRAIN LOCATIONS WITH BUILDING PLANS PRIOR TO CONSTRUCTION. DOWNSPOUTS SHALL BE COORDINATED WITH FOOTING CONSTRUCTION TO ENSURE ADEQUATE COVER. STORM NOTES 1 C3.6 R-438823 National Flood Hazard Layer FIRMette 0 500 1,000 1,500 2,000250 Feet Ü SEE FIS REPORT FOR DETAILED LEGEND AND INDEX MAP FOR FIRM PANEL LAYOUT SPECIAL FLOODHAZARD AREAS Without Base Flood Elevation (BFE)Zone A, V, A99With BFE or Depth Zone AE, AO, AH, VE, AR Regulatory Floodway 0.2% Annual Chance Flood Hazard, Areasof 1% annual chance flood with averagedepth less than one foot or with drainageareas of less than one square mile Zone X Future Conditions 1% Annual Chance Flood Hazard Zone X Area with Reduced Flood Risk due to Levee. See Notes.Zone X Area with Flood Risk due to LeveeZone D NO SCREEN Area of Minimal Flood Hazard Zone X Area of Undetermined Flood Hazard Zone D Channel, Culvert, or Storm Sewer Levee, Dike, or Floodwall Cross Sections with 1% Annual Chance 17.5 Water Surface Elevation Coastal Transect Coastal Transect Baseline Profile Baseline Hydrographic Feature Base Flood Elevation Line (BFE) Effective LOMRs Limit of Study Jurisdiction Boundary Digital Data Available No Digital Data Available Unmapped This map complies with FEMA's standards for the use of digital flood maps if it is not void as described below.The basemap shown complies with FEMA's basemapaccuracy standards The flood hazard information is derived directly from theauthoritative NFHL web services provided by FEMA. This mapwas exported on 2/5/2025 at 5:44 PM and does notreflect changes or amendments subsequent to this date andtime. The NFHL and effective information may change orbecome superseded by new data over time. This map image is void if the one or more of the following map elements do not appear: basemap imagery, flood zone labels, legend, scale bar, map creation date, community identifiers, FIRM panel number, and FIRM effective date. Map images for unmapped and unmodernized areas cannot be used for regulatory purposes. Legend OTHER AREAS OF FLOOD HAZARD OTHER AREAS GENERAL STRUCTURES OTHER FEATURES MAP PANELS 8 B 20.2 The pin displayed on the map is an approximatepoint selected by the user and does not representan authoritative property location. 1:6,000 122°13'49"W 47°28'18"N 122°13'11"W 47°27'54"N Basemap Imagery Source: USGS National Map 2023 PROJECT SITE 2215 North 30th Street, Suite 300, Tacoma, WA 98403 253.383.2422 TEL 253.383.2572 FAX JOB NO. DATE: WALKER SUBARU SERVICE CENTER DOWNSTREAM ANALYSIS A-7 2240819.10 1/5/2026 PROJECT SITE AND POND OUTLET STRUCTURE QUARTER MILE DOWNSTREAM - DISCHARGE TO SURFACE WATER CHANNEL Technical Information Report Walker Subaru Service Center 2240819.10 Appendix B TIR Worksheet CITY OF RENTON SURFACE WATER DESIGN MANUAL 2017 City of Renton Surface Water Design Manual 12/12/2016 8-A-1 REFERENCE 8-A TECHNICAL INFORMATION REPORT (TIR) WORKSHEET Part 1 PROJECT OWNER AND PROJECT ENGINEER Part 2 PROJECT LOCATION AND DESCRIPTION Project Owner _____________________________ Phone ___________________________________ Address __________________________________ _________________________________________ Project Engineer ___________________________ Company _________________________________ Phone ___________________________________ Project Name __________________________ CED Permit # ________________________ Location Township ________________ Range __________________ Section _________________ Site Address __________________________ _____________________________________ Part 3 TYPE OF PERMIT APPLICATION Part 4 OTHER REVIEWS AND PERMITS Land Use (e.g., Subdivision / Short Subd.) Building (e.g., M/F / Commercial / SFR) Grading Right-of-Way Use Other _______________________ DFW HPA COE 404 DOE Dam Safety FEMA Floodplain COE Wetlands Other ________ Shoreline Management Structural Rockery/Vault/_____ ESA Section 7 Part 5 PLAN AND REPORT INFORMATION Technical Information Report Site Improvement Plan (Engr. Plans) Type of Drainage Review (check one): Date (include revision dates): Date of Final: Full Targeted Simplified Large Project Directed ____________________________________ __________________ Plan Type (check one): Date (include revision dates): Date of Final: Full Modified Simplified ____________________________________ __________________ HHJ Inc. 601 St Helens Ave Tacoma, Wa 98402 SCOTT KAUL, PE AHBL 253-383-2422 Walker Subaru Service Center 23 NORTH 5 EAST 19 519 SW 12TH ST, Renton, Wa 98057 X X X X 01/15/2026 01/15/2026 REFERENCE 8: PLAN REVIEW FORMS AND WORKSHEET TECHNICAL INFORMATION REPORT (TIR) WORKSHEET 12/12/2016 2017 City of Renton Surface Water Design Manual 8-A-2 Part 6 SWDM ADJUSTMENT APPROVALS Type (circle one): Standard / Blanket Description: (include conditions in TIR Section 2) ____________________________________________________________________________________ ____________________________________________________________________________________ ____________________________________________________________________________________ Approved Adjustment No. ______________________ Date of Approval: _______________________ Part 7 MONITORING REQUIREMENTS Monitoring Required: Yes / No Start Date: _______________________ Completion Date: _______________________ Describe: _________________________________ _________________________________________ _________________________________________ Re: SWDM Adjustment No. ________________ Part 8 SITE COMMUNITY AND DRAINAGE BASIN Community Plan: ____________________________________________________________________ Special District Overlays: ______________________________________________________________ Drainage Basin: _____________________________________________________________________ Stormwater Requirements: _____________________________________________________________ Part 9 ONSITE AND ADJACENT SENSITIVE AREAS River/Stream ________________________ Lake ______________________________ Wetlands ____________________________ Closed Depression ____________________ Floodplain ___________________________ Other _______________________________ _______________________________ Steep Slope __________________________ Erosion Hazard _______________________ Landslide Hazard ______________________ Coal Mine Hazard ______________________ Seismic Hazard _______________________ Habitat Protection ______________________ _____________________________________ SpringBrook Creek / Black River/ Duwamish - Green River Valley REFERENCE 8-A: TECHNICAL INFORMATION REPORT (TIR) WORKSHEET TECHNICAL INFORMATION REPORT (TIR) WORKSHEET 2017 City of Renton Surface Water Design Manual 12/12/2016 Ref 8-A-3 Part 10 SOILS Soil Type ______________________ ______________________ ______________________ ______________________ Slopes ________________________ ________________________ ________________________ ________________________ Erosion Potential _________________________ _________________________ _________________________ _________________________ High Groundwater Table (within 5 feet) Other ________________________________ Sole Source Aquifer Seeps/Springs Additional Sheets Attached Part 11 DRAINAGE DESIGN LIMITATIONS REFERENCE Core 2 – Offsite Analysis_________________ Sensitive/Critical Areas__________________ SEPA________________________________ LID Infeasibility________________________ Other________________________________ _____________________________________ LIMITATION / SITE CONSTRAINT _______________________________________ _______________________________________ _______________________________________ _______________________________________ _______________________________________ _______________________________________ Additional Sheets Attached Part 12 TIR SUMMARY SHEET (provide one TIR Summary Sheet per Threshold Discharge Area) Threshold Discharge Area: (name or description) Core Requirements (all 8 apply): Discharge at Natural Location Number of Natural Discharge Locations: Offsite Analysis Level: 1 / 2 / 3 dated:__________________ Flow Control (include facility summary sheet) Standard: _______________________________ or Exemption Number: ____________ On-site BMPs: _______________________________ Conveyance System Spill containment located at: _____________________________ Erosion and Sediment Control / Construction Stormwater Pollution Prevention CSWPP/CESCL/ESC Site Supervisor: _____________________ Contact Phone: _________________________ After Hours Phone: _________________________ 1 January 2026 DETENTION SYSTEM WITH CONTROL STRUCTURE DETERMINED BY CONTRACTOR DETERMINED BY CONTRACTOR DETERMINED BY CONTRACTOR Ur 0-5%Low REFERENCE 8: PLAN REVIEW FORMS AND WORKSHEET TECHNICAL INFORMATION REPORT (TIR) WORKSHEET 12/12/2016 2017 City of Renton Surface Water Design Manual 8-A-4 Part 12 TIR SUMMARY SHEET (provide one TIR Summary Sheet per Threshold Discharge Area) Maintenance and Operation Responsibility (circle one): Private / Public If Private, Maintenance Log Required: Yes / No Financial Guarantees and Liability Provided: Yes / No Water Quality (include facility summary sheet) Type (circle one): Basic / Sens. Lake / Enhanced Basic / Bog or Exemption No. _______________________ Special Requirements (as applicable): Area Specific Drainage Requirements Type: SDO / MDP / BP / Shared Fac. / None Name: ________________________ Floodplain/Floodway Delineation Type (circle one): Major / Minor / Exemption / None 100-year Base Flood Elevation (or range): _______________ Datum: Flood Protection Facilities Describe: Source Control (commercial / industrial land use) Describe land use: Describe any structural controls: Oil Control High-Use Site: Yes / No Treatment BMP: _________________________________ Maintenance Agreement: Yes / No with whom? _____________________________________ Other Drainage Structures Describe: COMMERCIAL AND RESIDENTIAL REFERENCE 8-A: TECHNICAL INFORMATION REPORT (TIR) WORKSHEET TECHNICAL INFORMATION REPORT (TIR) WORKSHEET 2017 City of Renton Surface Water Design Manual 12/12/2016 Ref 8-A-5 Part 13 EROSION AND SEDIMENT CONTROL REQUIREMENTS MINIMUM ESC REQUIREMENTS DURING CONSTRUCTION Clearing Limits Cover Measures Perimeter Protection Traffic Area Stabilization Sediment Retention Surface Water Collection Dewatering Control Dust Control Flow Control Control Pollutants Protect Existing and Proposed BMPs/Facilities Maintain Protective BMPs / Manage Project MINIMUM ESC REQUIREMENTS AFTER CONSTRUCTION Stabilize exposed surfaces Remove and restore Temporary ESC Facilities Clean and remove all silt and debris, ensure operation of Permanent BMPs/Facilities, restore operation of BMPs/Facilities as necessary Flag limits of sensitive areas and open space preservation areas Other _______________________ Part 14 STORMWATER FACILITY DESCRIPTIONS (Note: Include Facility Summary and Sketch) Flow Control Type/Description Water Quality Type/Description Detention Infiltration Regional Facility Shared Facility On-site BMPs Other ________________ ________________ ________________ ________________ ________________ ________________ Vegetated Flowpath Wetpool Filtration Oil Control Spill Control On-site BMPs Other ________________ ________________ ________________ ________________ ________________ ________________ ________________ Part 15 EASEMENTS/TRACTS Part 16 STRUCTURAL ANALYSIS Drainage Easement Covenant Native Growth Protection Covenant Tract Other ____________________________ Cast in Place Vault Retaining Wall Rockery > 4′ High Structural on Steep Slope Other _______________________________ X X X X X X X X X X X X X X X EXISTING STORM POND X BIOPOD REFERENCE 8: PLAN REVIEW FORMS AND WORKSHEET TECHNICAL INFORMATION REPORT (TIR) WORKSHEET 12/12/2016 2017 City of Renton Surface Water Design Manual 8-A-6 Part 17 SIGNATURE OF PROFESSIONAL ENGINEER I, or a civil engineer under my supervision, have visited the site. Actual site conditions as observed were incorporated into this worksheet and the attached Technical Information Report. To the best of my knowledge the information provided here is accurate. __________________________________________________________________________________ Signed/Date 5/17/201801/15/2026 Technical Information Report Walker Subaru Service Center 2240819.10 Appendix C Hydrologic Analysis C-1.................... Existing Basin Map C-2.................... Developed Basin Map C-3.................... WWHM Printout C-4.................... Backwater Analysis C-5.................... Water Quality Calculations SD SD SD SD SD SD L15 OHU OHU OHU OHU OHU OHU OHU OHU OHU OHU OHU OHU OHU OHU OHU OHU OHU OHU OHU OH U OH U OH U OH U OHU OHU OHU OHU OHU OHU OHU OHU OHU OHU OHU OHU OHU OHU OHU OHU OHU OHU OHU OHU OHU OHU OHU O H U O H U P C SS GP GPGP GP GP GP GP RD IRR SS RD RD IRR IRR GP GP SS SS GP GP P IRR GP GP BOL BOL IRR HVACHVAC RD RD BOL IRR IRR GP GP GP GP GPG P GP GP GP RD RD BOLBOL RD RD RD RD RD BOL FDC SSSS COCOBOLBOLBOL SS BOLBOL BOL GP SD SD RDBOLBOL BOL BOL BOLBOL GP GP CORD GP BOL BOL CO RDGP GP GP GP P BOLCOBOL GP GP BOLBOLGP GP HVACHVAC P GP GP GP GP GP SS \ \\\\\\\\\\\\\\\\\\\\\\\\\ \\ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \\\\\\\\\\\ \ \ \\\\ \\\ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\ \ \ \ \ \ TOPTOPTOP TO P TOP TOP TOP TO P TOETOETOE TOE TOE TOE TO E TOP TOP TO P TO P T O P TOP TO P TO P TO P TOE TO E TO E T O E TO E TO E TO E \ \\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\ \ \ \ \ \ \ \ \\\\\\\ \ \ \ \ \ \ \ \\\\ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \\\\\\\\ \ \ \ \ \ \ \\\\\\\\\\\\\\\\\\\ \ \\\\ \ \\\\\\ \\ \ \ \ \ \ \\\\\\\\\\ \ \ \ \ \ \ \ \ \\\\ G G G G T T T T T T T T T P P P P P P P P P P P P P P P P P P P P P P W FO FO FO FO FO P P G G G G G G G G G G G W W W T T T PW W W W W W W W W W W W P P P P P P P PP P P P P P P P P P P P P P P P P P P W W T T T T T T T T T T P P P P P P P P P P P P P P P P P P P P P P P P P P P P P P P P P P P P P P P P P P P P P P P P P P P P P P P P P P P P P P P P P P P P P P P P P P P P P P P P P P P P P P P P P W W W W W W W W W W W WW P P P P P P T T T T T T T T T T T T T T T T T T T T T T T W W W W W W W W W W W W W W W W W T T T P T T PPP P P P P P P P P P P P P P P W N77°27'44"E 9 8 8 . 6 6 ' ( C ) S0 1 ° 2 3 ' 1 0 " W 2 7 8 . 3 5 ' ( M ) S0 1 ° 2 1 ' 0 3 " W 1 0 7 6 . 5 8 ' ( M ) SD SS SS SS SS SS SS SS SS SS SS SS SS SS SS SS S D S D C/GC/G C/G C/G E/C E/C E/C C/C C/C RAMP RAMP C/C C/C C/C C/C RAMP 12"MAPLE 12"MAPLE 14" MAPLE 8"UNKNOWN DECIDUOUS C/C C/C 31.3' DRIVEWAY C/G C/G C/G C/G E/C E/C E/C E/C E/C E/C C/G C/C 6' CLF 6' CLF 6' CLF 0.6' 0.5' NOT PART OF SURVEY(TAX PARCEL NO. 3340404150) 23.9' DRIVEWAY G G G G G G G G G G G 20.6' DRIVEWAY 24.2' DRIVEWAY C/C ASPHALTRAMP C/G C/G C/G E/CE/C A/W A/W NOT PART OF SURVEY(TAX PARCEL NO. 3340404150) NOT PARTOF SURVEY(TAXPARCEL NO. 3340404150) GATE GATE GATE C/C C/C GATE 0.5' 0.4' 0.3' 0.1' 4.9' 8.0' 6' CLF 7' CLF 7' CLF 0.2' 0.3' 0.2' 7' CLF 6' CLF 6' CLF 6' CLF 6' CLF LI N D A V E N U E S W (V A L E N T I N E A V E N U E ) SE N E C A A V E N U E S W (R I C E A V E N U E ) LIN D A V E N U E S W (SECOND AV E N U E ) SW 12TH STR E E T (SECOND AVE N U E ) SW 12TH ST R E E T (V A L E N T I N E A V E N U E ) SE N E C A A V E N U E S W (THIRD AVEN U E ) SW 13TH STR E E T ( V A C A T E D - C . O . R . O R D I N A N C E 4 9 4 2 ) (THIRD AVEN U E ) SW 13TH STR E E T (THIRD AVEN U E ) SW 13TH STR E E T ( V A C A T E D ) ALLEY (VACA T E D - C . O . R . ORDINANCE 4 9 1 4 ) ALLEY (VACAT E D - C . O . R . ORDINANCE 4 9 1 4 ) OHU 6' CLF ANGLE POINTBEARS S84°11'E, 0.6'FROM CALCULATEDLOT CORNER 6'/7' CLF ANGLE POINT BEARS N89°50'E, 0.6'FROM CALCULATEDLOT CORNER 14.4' 6' CLF 6' CLF 6' CLF 6' CLF 8' CLF7.9' TALL CMU WALLW/CANOPY ASPHALTCONTAINMENTHUMP E/C E/C E/C E/C 5.1' 9.0' 8.2' 17.5' 3.1' 0.3' 10' CLF GATE 0.3' 0.1' 3X8"UNKNOWNDECIDUOUS GATE GATE 6' CLF 7.9' TALL CMU WALLW/CANOPY E/C E/C E/C E/C 6' CLF 6' CLF 6' CLF "STOP" STOP BAR STOP BAR C/G C/G C/G C/G C/G C/C C/C 30.0'DRIVEWAY E/C RA/W RA/W RA/W RA/W RA/W RA/W DUMPSTERCONC. PAD AREA ECOBLOCKS BUILDING FINISH FLOOR ATCENTER OF PED. DOORLABELED "SPRINKLER ROOM"ELEV=21.95' NAVD 88 BUILDING FINISH FLOOR ATCENTER OF DOUBLE PED. DOORELEV=22.03' NAVD 88 E/C E/C E/C E/C E/C CONC.CANOPYCOLUMN CONC.CANOPYCOLUMN CONC.CANOPY COLUMN CONC.CANOPYCOLUMN GATE GATE GATE 4' CLF4' CLF 4' CLF 4' CLF 4' CLF 4' CLF EDGECANOPY(TYPICAL) EDGECANOPY(TYPICAL) 12" MAPLE 13"MAPLE 12"MAPLE 13"MAPLE 17"MAPLE 11"MAPLE 14" MAPLE GATE 6' CLF (V A L E N T I N E A V E N U E ) SE N E C A A V E N U E S W O H U O H U O H U O H U OH U OH U OH U OH U OH U OHU "STOP" STEEL POST FORAERIALWALKER'S RENTONSUBARU PARTS ANDSERVICE CENTER SIGN SERVICE CENTERDIRECTIONS SIGN C/C C/C RAMP E/C C/C C/C RAMP STEEL POST FOR AERIALSUBARU SIGN E/C E/C E/C E/C E/C E/C E/C E/C E/C C/C 26.9'DRIVEWAY C/G C/G GATE RA/W 6' CLF 6' CLF 6' CLF 6' CLF 6' CLF 6' CLF 6' CLF 6' CLF GATE 6' CLF FENCE TRANSITION 6' CLF/6' STEEL 6' STEEL 8"UNKNOWNDECIDUOUS 6"UNKNOWNDECIDUOUS 1X7" 1X6"UNKNOWNDECIDUOUS 1X6" 1X5"UNKNOWNDECIDUOUS STORMWATER DETENTION POND ECOBLOCK WALL STORMWATER DETENTIONPOND ECOBLOCK WALL STORMWATERDETENTION POND STORMWATERDETENTIONPOND 4' CLF 4' CLF 6' CLF 6' CLF 6' CLF 6' CLF 6' CLF 8' CLF 8' CLF 8' CLF 8' CLF 8' CLF 6' CLF 6' CLF GATE 4' CLF E/C E/C 0.7' 1.2' 4.4' 2.8' 1.5' 0.8' 0.8' 1.5' 1.4' 1.0' 2.1' 0.4' STORMDRAIN CULVERT ENDIE=18.16' 12" PVC NW STORMDRAIN CULVERT ENDIE=17.82' 12" PVC NE STORMDRAIN CULVERT ENDIE=17.46' 12" PVC SW STORMDRAINCULVERT ENDIE=17.13' 12" PVC SW SANITARY SEWERMANHOLEW/ CONC. CHANNELRIM=21.61'IE=14.61' 6" PVC NIE=14.33' 8" PVC EIE=14.06' 8" CONC. WLADDER=NW SD SD SD SS ( R E C ) STORMDRAIN CATCHBASINTYPE IRIM=21.16'IE=18.47' 8" PVC NIE=18.37' 8" PVC NEIE=18.18' 12" PVC SEIE=18.25' 8" PVC NW SD SD SD SD SD S D S D SD SD SD SD STORMDRAIN CATCHBASINTYPE IRIM=20.93' IE=18.91' 6" PVC NWIE=18.68' 8" PVC SE STORMDRAIN CATCHBASINTYPE IRIM=21.17'IE=18.50' 8" PVC NIE=18.90' 6" PVC NEIE=18.44' 8" PVC SEIE=18.98' 6" PVC W SD SD SD SD SD STORMDRAIN CATCHBASINTYPE IRIM=21.31'IE=19.00' 8" PVC NIE=18.79' 8" PVC SWIE=19.15' 6" PVC W SD SD SD SD SD STORMDRAIN MANHOLETYPE IIRIM=20.35'IE=14.80' 8" PVC E8" STANDPIPE STRUCTURE ON WEST SIDEIE=14.80' 8" PVC WTOP STANDPIPE=17.55'BOTTOM STANDPIPE=13.85' LADDER=N STORMDRAIN MANHOLETYPE IIRIM=20.36' IE=14.86' 8" S (FULL OF DIRT)8" STANDPIPE STRUCTUREON WEST SIDEIE=15.27' 8" PVC WTOP STANDPIPE=17.81'BOTTOM STANDPIPE=14.81'LADDER=N STORMDRAIN CATCHBASINTYPE I RIM=21.46'IE=19.69 8" PVC S SANITARY SEWER MANHOLEOIL WATER SEPARATOR VAULT NORTH ACCESS LID W/CONC. BAFFLE WALL UNDERNEATHRIM=21.54'BOTTOM VAULT NORTH OF BAFFLE WALL=13.7'TOP OF CONC. BAFFLE WALL=17.84'BOTTOM VAULT SOUTH OF BAFFLE WALL=13.4'WATER LEVEL BOTH SIDES OF BAFFLE WALL=17.0'NOTE: BOTTOM OF VAULT HAS HEAVY SLUDGE DEBRISAND NO PIPE SEEN HEADING TO THE NORTH TOWARDSOBSERVED CLEANOUTS SANITARY SEWER MANHOLEOIL WATER SEPARATOR VAULT SOUTH ACCESS LIDW/CONC. BAFFLE WALL UNDERNEATHRIM=21.41'IE=17.18' 6" PVC W/OIL WATER SEPARATOR ELBOW SEBOTTOM VAULT NORTH OF BAFFLE WALL=13.1'TOP OF CONC. BAFFLE WALL=17.86'BOTTOM VAULT SOUTH OF BAFFLE WALL=13.1' WATER LEVEL BOTH SIDES OF BAFFLE WALL=17.0'NOTE: BOTTOM OF VAULT HAS HEAVY SLUDGE DEBRIS 0.9' 1.0' 0.9' UNKNOWN USE CLEANOUTRIM=21.61' UNKNOWN USECLEANOUTRIM=21.65' UNKNOWN USECLEANOUTRIM=22.06' UNKNOWN USE CLEANOUTRIM=21.96' STORMDRAIN CATCHBASINTYPE IRIM=20.04' IE=18.32' 12" PVC N SANITARY SEWERMANHOLE W/ CONC. CHANNELRIM=20.83'IE=12.93' 8" CONC. NIE=13.03' 8" CONC. NELADDER=W SANITARY SEWERMANHOLE W/ CONC. CHANNELRIM=20.52'IE=12.41' 8" CONC. NEIE=12.52' 8" CONC. S IE=12.22 8" CONC. SWLADDER=S SANITARY SEWER MANHOLENO CHANNELIZATION - PIPE PASSESTHROUGH IN AIR WITHCLEANOUT/REDUCER IN MIDDLE - NO ACCESS TO IE'S - STRUCTURE FILLED WITHWATERRIM=21.34'TOP PIPE=16.94' 6" PVC NETOP PIPE=17.01' 8" PVC SW TOP WATER=16.75'LADDER=NW SS(REC) SS(REC) SS(REC) SS(REC) SS(REC) SS(REC) SS(REC) SS(REC) SS(REC) SS(REC) SS(REC) SS(REC) SD SD STORMDRAIN CATCHBASINTYPE IRIM=21.20'IE=19.10' 12" PVC SW STORMDRAIN CATCHBASINTYPE IRIM=20.70'IE=17.92' 12" PVC NEIE=18.01' 12" PVC S SD SD SD STORMDRAIN CATCHBASINTYPE IRIM=20.39' IE=17.67' 12" PVC EIE=17.68' 12" PVC SWIE=17.65' 12" PVC NW S D STORMDRAIN CATCHBASINTYPE IRIM=20.61'IE=17.45' 12" PVC NIE=17.48' 12" PVC S SD STORMDRAIN CATCHBASINDID NOT OPENRIM=22.04' 12"MAPLE 17"MAPLE SD SD SD SD SD STORMDRAIN CATCHBASIN TYPE IRIM=21.20'IE=18.13' 12" PVC NEIE=18.41' 12" PVC SEIE=18.17' 12" PVC SW STORMDRAIN CATCHBASINTYPE IRIM=21.80'IE=19.04' 8" SWIE=18.97' 12" PVC NW SD STORMDRAIN CATCHBASINTYPE IRIM=21.15'IE=18.22' 12" PVC NEIE=18.27' 12" PVC SW SD STORMDRAIN CATCHBASINTYPE I RIM=21.07'IE=18.55' 8" PVC NEIE=18.42' 12" PVC SW SD SD S D STORMDRAIN CATCHBASINTYPE IRIM=20.76'FULL OF DIRT SANITARY SEWERMANHOLE - FULLOF WATER - NOINVERTS FELTRIM=21.35'TOP WATER=20.01' STORMDRAIN CATCHBASINTYPE I RIM=20.70'IE=17.88' 12" PVC NEIE=17.81' 12" PVC NW 79 8 . 8 4 ' ( C ) 525.46'(C) 3 0 ' 3 0 ' 30'30' 1 6 ' 1 6 ' 80' 80' 80'80' 90'90' (R I C E A V E N U E ) LIN D A V E N U E S W 237.36' 117.44' S0 1 ° 2 2 ' 4 2 " W 11 6 . 4 3 ' N77°26'10" E 119.92' N0 1 ° 2 2 ' 4 3 " E 11 6 . 3 8 ' L1 8 L17 S0 9 ° 3 9 ' 1 5 " E 10 5 . 0 4 ' L16 L2 0 L2 1 N77°24'38" E 123.29' 11 4 . 3 4 ' S86°20'10"W 391.52' 25 4 . 8 8 ' L1 2 L9 L1 0 L11 L4 L3 L5 L1 9 FND 1/2" REBAR AND CAP STAMPED"LS 19635"REBAR BEARS S88°24'33"E, 0.23'FROM THE CALCULATED LOT CORNERVISITED 11/18/2024 INTERSTATE 405 INTERSTATE 405 A/W A/W 0.7' 0.9' 1.0' 0.8' 4' CLF 3-WAY 6' CLFINTERSECTIONBEARS S15°13'E,0.6' FROM THECALCULATED LOT CORNER 6.2' 8'/6' CLF INTERSECTIONBEARS S26°55'W, 0.8' FROM THECALCULATED LOT CORNER GATE 8'/6' CLF INTERSECTIONBEARS S79°15'W, 2.9' FROM THECALCULATED LOT CORNER GP GP C C C T O E TO P TO P PP TT T T T T T G P P T T T T T T T T T T T T T T T T P P P P T G S D SD C/G C/G C/C C/C14.9' DRIVEWAY GATE E/C E/C 15"UNKNOWNDECIDUOUS 13"UNKNOWNDECIDUOUS 15"UNKNOWNDECIDUOUS CONC. STEPSW/HANDRAIL AT CENTER C/C C/C RAMP 6' CLF 6' CLF 1X7", 5X4", 4X3"UNKNOWNDECIDUOUS 6' CLF 6' WDF 6' WDF OHU OHU OHU OHU 6' CLF 6' CLF 6' CLF STORMDRAIN CULVERT END IE=19.03' 16" CMP S D UTILITYLOCATEPAINTEDSTUB MARK C/G C/G C/G 1X9",2X7",1X4"UNKNOWNDECIDUOUS STORMDRAIN CATCHBASINTYPE IRIM=21.08' IE=19.65' 6" PVC NEIE=19.58' 8" CMP SEIE=19.74' 6" DI NW STORMDRAIN CATCHBASINTYPE II W/GRATED LIDRIM=21.88'IE=19.46' 12" DI NEIE=19.39' 16" CMP SEIE=19.74' 8" SWIE=19.07' 8" DI NWFULL OF WATERTOP WATER=20.25' "STOP" STORMDRAIN CATCHBASIN TYPE IRIM=20.87'IE=19.58' 12" DI NE C/G C/G C/G 10 9 . 2 0 ' 75 . 2 0 ' QWEST TELECOMMUNICATIONS EASEMENT PER AFN 20030327000925 PRIVATE INGRESS/EGRESS EASEMENTPER EASEMENT AGREEMENT WITH RIGHTS AND RESPONSIBILITIESAFN 20020612000622 QWEST TELECOMMUNICATIONS EASEMENTPER AFN 20030327000925 PRIVATE INGRESS/EGRESS EASEMENTPER EASEMENT AGREEMENT WITH RIGHTS AND RESPONSIBILITIESAFN 20020612000622 UTILITIES EASEMENT TO THE CITY OF RENTON PER AFN 20010906002177, CITY OF RENTON ORDINANCE 4914(ENCOMPASSES WHOLE VACATED ALLEY) BUILDING FINISH FLOOR AT CENTER OFBAY DOORELEV=21.94' NAVD 88 6' CLF ANGLE POINTBEARS N53°23'W, 1.3' FROM CALCULATED LOT CORNER8' CLF END BEARS N25°48'W, 1.0' FROM CALCULATED LOTCORNER UTILITIES EASEMENT TO THE CITY OF RENTONPER AFN 20020207002539, CITY OF RENTON ORDINANCE 4942(ENCOMPASSES WHOLE VACATED STREET) PSE ELECTRICALEASEMENT PER AFN20030128002591 UTILITIES EASEMENT TO THE CITY OF RENTONPER AFN 20010906002177, CITY OF RENTON ORDINANCE 4914(ENCOMPASSES WHOLE VACATED ALLEY) PSE ELECTRICALEASEMENT PER AFN20030128002591 STORMDRAIN CATCHBASINTYPE IRIM=21.20'IE=18.88' 12" PVC NEIE=18.77' 6" PVC SEIE=18.75' 12" PVC S PSE ELECTRICALEASEMENT PER AFN20030128002591 UTILITIES EASEMENT TO THE CITY OF RENTONPER AFN 20020207002539, CITY OF RENTON ORDINANCE 4942(ENCOMPASSES WHOLE VACATED STREET) UTILITIES EASEMENT TO THE CITY OF RENTONPER AFN 20020207002539, CITY OF RENTON ORDINANCE 4942(ENCOMPASSES WHOLE VACATED STREET) UTILITIES EASEMENT TO THE CITY OF RENTONPER AFN 20020207002539, CITY OF RENTON ORDINANCE 4942 (ENCOMPASSES WHOLE VACATED STREET) (THIRD AVEN U E ) SW 13TH STR E E T ( V A C A T E D - C . O . R . O R D I N A N C E 4 9 4 2 ) SE N E C A A V E S W SW 12TH S T SW 13TH S T INTERSTATE 405 N GRAPHIC SCALE 0 30 60 1" = 30 FEET 15 Q: \ 2 0 2 4 \ 2 2 4 0 8 1 9 \ 1 0 _ C I V \ C A D \ E X H I B I T S \ 2 0 2 5 0 5 0 2 E x i s t i n g B a s i n M a p . d w g 2215 North 30th Street, Suite 300, Tacoma, WA 98403 253.383.2422 TEL 253.383.2572 FAX JOB NO. DATE: WALKER SUBARU SERVICE CENTER EXISTING BASIN MAP C-1 2240819.10 1/15/2026 BASIN 1 STORMWATER POND BASIN 1 AREA (ACRES) ROOF 0.45 ROAD / PARKING 1.44 TOTAL 1.89 BIOSWALE L15 GP GPGP GP GP GP GP GP GP GP GP GP GPGP GP GP GP GP GP GP GP GP P GP GP GP GP P GP GP GP GP GP N77°27'44"E 9 8 8 . 6 6 ' ( C ) S0 1 ° 2 3 ' 1 0 " W 2 7 8 . 3 5 ' ( M ) S0 1 ° 2 1 ' 0 3 " W 1 0 7 6 . 5 8 ' ( M ) 12" MAPLE 12" MAPLE 14" MAPLE 8" UNKNOWN DECIDUOUS 3X8" UNKNOWN DECIDUOUS 12" MAPLE 13" MAPLE 17" MAPLE 11" MAPLE 14" MAPLE UNKNOWN USE CLEANOUT RIM=22.06' UNKNOWN USE CLEANOUT RIM=21.96' 12" MAPLE 17" MAPLE 79 8 . 8 4 ' ( C ) 525.46'(C) 3 0 ' 30 ' 30'30' 1 6 ' 1 6 ' 80' 80'80' 90' 237.36' 117.44' S0 1 ° 2 2 ' 4 2 " W 11 6 . 4 3 ' N77°26'10" E 119.92' N0 1 ° 2 2 ' 4 3 " E 11 6 . 3 8 ' L1 8 L17 S0 9 ° 3 9 ' 1 5 " E 10 5 . 0 4 ' L16 L2 0 L2 1 N77°24'38" E 123.29' 11 4 . 3 4 ' S86°20'10"W 391.52' 25 4 . 8 8 ' L1 2 L9 L1 0 L11 L4 L3 L5 L1 9 FND 1/2" REBAR AND CAP STAMPED "LS 19635" REBAR BEARS S88°24'33"E, 0.23' FROM THE CALCULATED LOT CORNER VISITED 11/18/2024 GP GP 15" UNKNOWN DECIDUOUS13" UNKNOWN DECIDUOUS 15" UNKNOWN DECIDUOUS CONC. STEPS W/HANDRAIL AT CENTER 1X7", 5X4", 4X3" UNKNOWN DECIDUOUS 1X9",2X7",1X4" UNKNOWN DECIDUOUS 10 9 . 2 0 ' 75 . 2 0 ' QWEST TELECOMMUNICATIONS EASEMENT PER AFN 20030327000925 PRIVATE INGRESS/EGRESS EASEMENT PER EASEMENT AGREEMENT WITH RIGHTS AND RESPONSIBILITIES AFN 20020612000622 QWEST TELECOMMUNICATIONS EASEMENT PER AFN 20030327000925 PRIVATE INGRESS/EGRESS EASEMENT PER EASEMENT AGREEMENT WITH RIGHTS AND RESPONSIBILITIES AFN 20020612000622 UTILITIES EASEMENT TO THE CITY OF RENTON PER AFN 20010906002177, CITY OF RENTON ORDINANCE 4914 (ENCOMPASSES WHOLE VACATED ALLEY) PSE ELECTRICAL EASEMENT PER AFN 20030128002591 UTILITIES EASEMENT TO THE CITY OF RENTON PER AFN 20010906002177, CITY OF RENTON ORDINANCE 4914 (ENCOMPASSES WHOLE VACATED ALLEY) PSE ELECTRICAL EASEMENT PER AFN 20030128002591 PSE ELECTRICAL EASEMENT PER AFN 20030128002591 UTILITIES EASEMENT TO THE CITY OF RENTON PER AFN 20020207002539, CITY OF RENTON ORDINANCE 4942 (ENCOMPASSES WHOLE VACATED STREET) SE N E C A A V E S W SW 12TH S T SW 13TH S T INTERSTATE 405 N GRAPHIC SCALE 0 30 60 1" = 30 FEET 15 Q: \ 2 0 2 4 \ 2 2 4 0 8 1 9 \ 1 0 _ C I V \ C A D \ E X H I B I T S \ 2 0 2 5 0 5 0 2 D e v e l o p e d B a s i n M a p . d w g 2215 North 30th Street, Suite 300, Tacoma, WA 98403 253.383.2422 TEL 253.383.2572 FAX JOB NO. DATE: WALKER SUBARU SERVICE CENTER DEVELOPED BASIN MAP C-2 2240819.10 2/5/2025 BASIN 1 STORMWATER POND BASIN 1 AREA (ACRES) ROOF 0.80 ROAD / PARKING 1.09 TOTAL 1.89 BIOPOD BASIN 1 TREATMENT AREA (ACRES) ROOF 0.20 ROAD / PARKING 1.09 TOTAL 1.29 WWHM2012 PROJECT REPORT Detention 4/2/2026 9:31:06 AM Page 2 General Model Information WWHM2012 Project Name:Detention Site Name:Walker Subaru Site Address: City: Report Date:4/2/2026 Gage:Seatac Data Start:1948/10/01 Data End:2009/09/30 Timestep:15 Minute Precip Scale:1.000 Version Date:2024/06/28 Version:4.3.1 POC Thresholds Low Flow Threshold for POC1:50 Percent of the 2 Year High Flow Threshold for POC1:50 Year Detention 4/2/2026 9:31:06 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 1.44 ROOF TOPS FLAT 0.45 Impervious Total 1.89 Basin Total 1.89 Element Flow Componants: Surface Interflow Groundwater Componant Flows To: Trapezoidal Pond 1 Trapezoidal Pond 1 Detention 4/2/2026 9:31:06 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 1.09 ROOF TOPS FLAT 0.8 Impervious Total 1.89 Basin Total 1.89 Element Flow Componants: Surface Interflow Groundwater Componant Flows To: Trapezoidal Pond 1 Trapezoidal Pond 1 Detention 4/2/2026 9:31:06 AM Page 5 Routing Elements Predeveloped Routing Trapezoidal Pond 1 Bottom Length:75.00 ft. Bottom Width:25.00 ft. Depth:4.5 ft. Volume at riser head:0.2468 acre-feet. Side slope 1:3 To 1 Side slope 2:3 To 1 Side slope 3:3 To 1 Side slope 4:3 To 1 Discharge Structure Riser Height:3.5 ft. Riser Diameter:12 in. Orifice 1 Diameter:3.125 in.Elevation:0 ft. Orifice 2 Diameter:2.500 in.Elevation:1.4 ft. Orifice 3 Diameter:2.500 in.Elevation:2.1 ft. Element Outlets: Outlet 1 Outlet 2 Outlet Flows To: Pond Hydraulic Table Stage(feet)Area(ac.)Volume(ac-ft.)Discharge(cfs)Infilt(cfs) 0.0000 0.043 0.000 0.000 0.000 0.0500 0.043 0.002 0.059 0.000 0.1000 0.044 0.004 0.083 0.000 0.1500 0.045 0.006 0.102 0.000 0.2000 0.045 0.008 0.118 0.000 0.2500 0.046 0.011 0.132 0.000 0.3000 0.047 0.013 0.145 0.000 0.3500 0.048 0.015 0.156 0.000 0.4000 0.048 0.018 0.167 0.000 0.4500 0.049 0.020 0.177 0.000 0.5000 0.050 0.023 0.187 0.000 0.5500 0.050 0.025 0.196 0.000 0.6000 0.051 0.028 0.205 0.000 0.6500 0.052 0.031 0.213 0.000 0.7000 0.053 0.033 0.221 0.000 0.7500 0.053 0.036 0.229 0.000 0.8000 0.054 0.039 0.237 0.000 0.8500 0.055 0.041 0.244 0.000 0.9000 0.056 0.044 0.251 0.000 0.9500 0.056 0.047 0.258 0.000 1.0000 0.057 0.050 0.265 0.000 1.0500 0.058 0.053 0.271 0.000 1.1000 0.059 0.056 0.277 0.000 1.1500 0.060 0.059 0.284 0.000 1.2000 0.060 0.062 0.290 0.000 1.2500 0.061 0.065 0.296 0.000 1.3000 0.062 0.068 0.302 0.000 1.3500 0.063 0.071 0.307 0.000 1.4000 0.063 0.074 0.313 0.000 1.4500 0.064 0.077 0.357 0.000 Detention 4/2/2026 9:31:06 AM Page 6 1.5000 0.065 0.081 0.378 0.000 1.5500 0.066 0.084 0.395 0.000 1.6000 0.067 0.087 0.411 0.000 1.6500 0.068 0.091 0.425 0.000 1.7000 0.068 0.094 0.438 0.000 1.7500 0.069 0.097 0.450 0.000 1.8000 0.070 0.101 0.462 0.000 1.8500 0.071 0.104 0.474 0.000 1.9000 0.072 0.108 0.485 0.000 1.9500 0.073 0.112 0.495 0.000 2.0000 0.073 0.115 0.506 0.000 2.0500 0.074 0.119 0.516 0.000 2.1000 0.075 0.123 0.525 0.000 2.1500 0.076 0.127 0.573 0.000 2.2000 0.077 0.131 0.598 0.000 2.2500 0.078 0.134 0.619 0.000 2.3000 0.079 0.138 0.638 0.000 2.3500 0.080 0.142 0.656 0.000 2.4000 0.080 0.146 0.673 0.000 2.4500 0.081 0.150 0.688 0.000 2.5000 0.082 0.155 0.704 0.000 2.5500 0.083 0.159 0.718 0.000 2.6000 0.084 0.163 0.733 0.000 2.6500 0.085 0.167 0.746 0.000 2.7000 0.086 0.171 0.760 0.000 2.7500 0.087 0.176 0.773 0.000 2.8000 0.088 0.180 0.786 0.000 2.8500 0.089 0.185 0.798 0.000 2.9000 0.089 0.189 0.810 0.000 2.9500 0.090 0.194 0.822 0.000 3.0000 0.091 0.198 0.834 0.000 3.0500 0.092 0.203 0.846 0.000 3.1000 0.093 0.207 0.857 0.000 3.1500 0.094 0.212 0.868 0.000 3.2000 0.095 0.217 0.879 0.000 3.2500 0.096 0.222 0.890 0.000 3.3000 0.097 0.226 0.901 0.000 3.3500 0.098 0.231 0.911 0.000 3.4000 0.099 0.236 0.921 0.000 3.4500 0.100 0.241 0.932 0.000 3.5000 0.101 0.246 0.942 0.000 3.5500 0.102 0.251 1.070 0.000 3.6000 0.103 0.257 1.295 0.000 3.6500 0.104 0.262 1.576 0.000 3.7000 0.105 0.267 1.889 0.000 3.7500 0.106 0.272 2.208 0.000 3.8000 0.107 0.278 2.510 0.000 3.8500 0.108 0.283 2.771 0.000 3.9000 0.109 0.289 2.979 0.000 3.9500 0.110 0.294 3.129 0.000 4.0000 0.111 0.300 3.240 0.000 4.0500 0.112 0.305 3.382 0.000 4.1000 0.113 0.311 3.494 0.000 4.1500 0.114 0.316 3.603 0.000 4.2000 0.115 0.322 3.707 0.000 4.2500 0.116 0.328 3.809 0.000 4.3000 0.117 0.334 3.907 0.000 4.3500 0.118 0.340 4.002 0.000 Detention 4/2/2026 9:31:06 AM Page 7 4.4000 0.119 0.346 4.094 0.000 4.4500 0.120 0.352 4.185 0.000 4.5000 0.121 0.358 4.273 0.000 4.5500 0.122 0.364 4.359 0.000 Discharge Structure Riser Height:3.5 ft. Riser Diameter:12 in. Orifice 1 Diameter:3.125 in.Elevation:0 ft. Orifice 2 Diameter:2.500 in.Elevation:1.4 ft. Orifice 3 Diameter:2.500 in.Elevation:2.1 ft. Element Flow Outlets: Outlet 1 Outlet 2 Outlets Flow To: Pond Hydraulic Table Stage(feet)Area(ac.)Volume(ac-ft.)Discharge(cfs)Infilt(cfs) 0.0000 0.043 0.000 0.000 0.000 0.0500 0.043 0.002 0.059 0.000 0.1000 0.044 0.004 0.083 0.000 0.1500 0.045 0.006 0.102 0.000 0.2000 0.045 0.008 0.118 0.000 0.2500 0.046 0.011 0.132 0.000 0.3000 0.047 0.013 0.145 0.000 0.3500 0.048 0.015 0.156 0.000 0.4000 0.048 0.018 0.167 0.000 0.4500 0.049 0.020 0.177 0.000 0.5000 0.050 0.023 0.187 0.000 0.5500 0.050 0.025 0.196 0.000 0.6000 0.051 0.028 0.205 0.000 0.6500 0.052 0.031 0.213 0.000 0.7000 0.053 0.033 0.221 0.000 0.7500 0.053 0.036 0.229 0.000 0.8000 0.054 0.039 0.237 0.000 0.8500 0.055 0.041 0.244 0.000 0.9000 0.056 0.044 0.251 0.000 0.9500 0.056 0.047 0.258 0.000 1.0000 0.057 0.050 0.265 0.000 1.0500 0.058 0.053 0.271 0.000 1.1000 0.059 0.056 0.277 0.000 1.1500 0.060 0.059 0.284 0.000 1.2000 0.060 0.062 0.290 0.000 1.2500 0.061 0.065 0.296 0.000 1.3000 0.062 0.068 0.302 0.000 1.3500 0.063 0.071 0.307 0.000 1.4000 0.063 0.074 0.313 0.000 1.4500 0.064 0.077 0.357 0.000 1.5000 0.065 0.081 0.378 0.000 1.5500 0.066 0.084 0.395 0.000 1.6000 0.067 0.087 0.411 0.000 1.6500 0.068 0.091 0.425 0.000 1.7000 0.068 0.094 0.438 0.000 1.7500 0.069 0.097 0.450 0.000 1.8000 0.070 0.101 0.462 0.000 1.8500 0.071 0.104 0.474 0.000 Detention 4/2/2026 9:31:06 AM Page 8 1.9000 0.072 0.108 0.485 0.000 1.9500 0.073 0.112 0.495 0.000 2.0000 0.073 0.115 0.506 0.000 2.0500 0.074 0.119 0.516 0.000 2.1000 0.075 0.123 0.525 0.000 2.1500 0.076 0.127 0.573 0.000 2.2000 0.077 0.131 0.598 0.000 2.2500 0.078 0.134 0.619 0.000 2.3000 0.079 0.138 0.638 0.000 2.3500 0.080 0.142 0.656 0.000 2.4000 0.080 0.146 0.673 0.000 2.4500 0.081 0.150 0.688 0.000 2.5000 0.082 0.155 0.704 0.000 2.5500 0.083 0.159 0.718 0.000 2.6000 0.084 0.163 0.733 0.000 2.6500 0.085 0.167 0.746 0.000 2.7000 0.086 0.171 0.760 0.000 2.7500 0.087 0.176 0.773 0.000 2.8000 0.088 0.180 0.786 0.000 2.8500 0.089 0.185 0.798 0.000 2.9000 0.089 0.189 0.810 0.000 2.9500 0.090 0.194 0.822 0.000 3.0000 0.091 0.198 0.834 0.000 3.0500 0.092 0.203 0.846 0.000 3.1000 0.093 0.207 0.857 0.000 3.1500 0.094 0.212 0.868 0.000 3.2000 0.095 0.217 0.879 0.000 3.2500 0.096 0.222 0.890 0.000 3.3000 0.097 0.226 0.901 0.000 3.3500 0.098 0.231 0.911 0.000 3.4000 0.099 0.236 0.921 0.000 3.4500 0.100 0.241 0.932 0.000 3.5000 0.101 0.246 0.942 0.000 3.5500 0.102 0.251 1.070 0.000 3.6000 0.103 0.257 1.295 0.000 3.6500 0.104 0.262 1.576 0.000 3.7000 0.105 0.267 1.889 0.000 3.7500 0.106 0.272 2.208 0.000 3.8000 0.107 0.278 2.510 0.000 3.8500 0.108 0.283 2.771 0.000 3.9000 0.109 0.289 2.979 0.000 3.9500 0.110 0.294 3.129 0.000 4.0000 0.111 0.300 3.240 0.000 4.0500 0.112 0.305 3.382 0.000 4.1000 0.113 0.311 3.494 0.000 4.1500 0.114 0.316 3.603 0.000 4.2000 0.115 0.322 3.707 0.000 4.2500 0.116 0.328 3.809 0.000 4.3000 0.117 0.334 3.907 0.000 4.3500 0.118 0.340 4.002 0.000 4.4000 0.119 0.346 4.094 0.000 4.4500 0.120 0.352 4.185 0.000 4.5000 0.121 0.358 4.273 0.000 4.5500 0.122 0.364 4.359 0.000 Detention 4/2/2026 9:31:06 AM Page 9 Mitigated Routing Trapezoidal Pond 1 Bottom Length:75.00 ft. Bottom Width:25.00 ft. Depth:4.5 ft. Volume at riser head:0.2468 acre-feet. Side slope 1:3 To 1 Side slope 2:3 To 1 Side slope 3:3 To 1 Side slope 4:3 To 1 Discharge Structure Riser Height:3.5 ft. Riser Diameter:12 in. Orifice 1 Diameter:3.125 in.Elevation:0 ft. Orifice 2 Diameter:2.500 in.Elevation:1.4 ft. Orifice 3 Diameter:2.500 in.Elevation:2.1 ft. Element Outlets: Outlet 1 Outlet 2 Outlet Flows To: Pond Hydraulic Table Stage(feet)Area(ac.)Volume(ac-ft.)Discharge(cfs)Infilt(cfs) 0.0000 0.043 0.000 0.000 0.000 0.0500 0.043 0.002 0.059 0.000 0.1000 0.044 0.004 0.083 0.000 0.1500 0.045 0.006 0.102 0.000 0.2000 0.045 0.008 0.118 0.000 0.2500 0.046 0.011 0.132 0.000 0.3000 0.047 0.013 0.145 0.000 0.3500 0.048 0.015 0.156 0.000 0.4000 0.048 0.018 0.167 0.000 0.4500 0.049 0.020 0.177 0.000 0.5000 0.050 0.023 0.187 0.000 0.5500 0.050 0.025 0.196 0.000 0.6000 0.051 0.028 0.205 0.000 0.6500 0.052 0.031 0.213 0.000 0.7000 0.053 0.033 0.221 0.000 0.7500 0.053 0.036 0.229 0.000 0.8000 0.054 0.039 0.237 0.000 0.8500 0.055 0.041 0.244 0.000 0.9000 0.056 0.044 0.251 0.000 0.9500 0.056 0.047 0.258 0.000 1.0000 0.057 0.050 0.265 0.000 1.0500 0.058 0.053 0.271 0.000 1.1000 0.059 0.056 0.277 0.000 1.1500 0.060 0.059 0.284 0.000 1.2000 0.060 0.062 0.290 0.000 1.2500 0.061 0.065 0.296 0.000 1.3000 0.062 0.068 0.302 0.000 1.3500 0.063 0.071 0.307 0.000 1.4000 0.063 0.074 0.313 0.000 1.4500 0.064 0.077 0.357 0.000 1.5000 0.065 0.081 0.378 0.000 1.5500 0.066 0.084 0.395 0.000 Detention 4/2/2026 9:31:06 AM Page 10 1.6000 0.067 0.087 0.411 0.000 1.6500 0.068 0.091 0.425 0.000 1.7000 0.068 0.094 0.438 0.000 1.7500 0.069 0.097 0.450 0.000 1.8000 0.070 0.101 0.462 0.000 1.8500 0.071 0.104 0.474 0.000 1.9000 0.072 0.108 0.485 0.000 1.9500 0.073 0.112 0.495 0.000 2.0000 0.073 0.115 0.506 0.000 2.0500 0.074 0.119 0.516 0.000 2.1000 0.075 0.123 0.525 0.000 2.1500 0.076 0.127 0.573 0.000 2.2000 0.077 0.131 0.598 0.000 2.2500 0.078 0.134 0.619 0.000 2.3000 0.079 0.138 0.638 0.000 2.3500 0.080 0.142 0.656 0.000 2.4000 0.080 0.146 0.673 0.000 2.4500 0.081 0.150 0.688 0.000 2.5000 0.082 0.155 0.704 0.000 2.5500 0.083 0.159 0.718 0.000 2.6000 0.084 0.163 0.733 0.000 2.6500 0.085 0.167 0.746 0.000 2.7000 0.086 0.171 0.760 0.000 2.7500 0.087 0.176 0.773 0.000 2.8000 0.088 0.180 0.786 0.000 2.8500 0.089 0.185 0.798 0.000 2.9000 0.089 0.189 0.810 0.000 2.9500 0.090 0.194 0.822 0.000 3.0000 0.091 0.198 0.834 0.000 3.0500 0.092 0.203 0.846 0.000 3.1000 0.093 0.207 0.857 0.000 3.1500 0.094 0.212 0.868 0.000 3.2000 0.095 0.217 0.879 0.000 3.2500 0.096 0.222 0.890 0.000 3.3000 0.097 0.226 0.901 0.000 3.3500 0.098 0.231 0.911 0.000 3.4000 0.099 0.236 0.921 0.000 3.4500 0.100 0.241 0.932 0.000 3.5000 0.101 0.246 0.942 0.000 3.5500 0.102 0.251 1.070 0.000 3.6000 0.103 0.257 1.295 0.000 3.6500 0.104 0.262 1.576 0.000 3.7000 0.105 0.267 1.889 0.000 3.7500 0.106 0.272 2.208 0.000 3.8000 0.107 0.278 2.510 0.000 3.8500 0.108 0.283 2.771 0.000 3.9000 0.109 0.289 2.979 0.000 3.9500 0.110 0.294 3.129 0.000 4.0000 0.111 0.300 3.240 0.000 4.0500 0.112 0.305 3.382 0.000 4.1000 0.113 0.311 3.494 0.000 4.1500 0.114 0.316 3.603 0.000 4.2000 0.115 0.322 3.707 0.000 4.2500 0.116 0.328 3.809 0.000 4.3000 0.117 0.334 3.907 0.000 4.3500 0.118 0.340 4.002 0.000 4.4000 0.119 0.346 4.094 0.000 4.4500 0.120 0.352 4.185 0.000 Detention 4/2/2026 9:31:06 AM Page 11 4.5000 0.121 0.358 4.273 0.000 4.5500 0.122 0.364 4.359 0.000 Detention 4/2/2026 9:31:06 AM Page 12 Analysis Results POC 1 + Predeveloped x Mitigated Predeveloped Landuse Totals for POC #1 Total Pervious Area:0 Total Impervious Area:1.89 Mitigated Landuse Totals for POC #1 Total Pervious Area:0 Total Impervious Area:1.89 Flow Frequency Method:Log Pearson Type III 17B Flow Frequency Return Periods for Predeveloped. POC #1 Return Period Flow(cfs) 2 year 0.30041 5 year 0.385785 10 year 0.448184 25 year 0.533888 50 year 0.602879 100 year 0.676436 Flow Frequency Return Periods for Mitigated. POC #1 Return Period Flow(cfs) 2 year 0.30041 5 year 0.385785 10 year 0.448184 25 year 0.533888 50 year 0.602879 100 year 0.676436 Annual Peaks Annual Peaks for Predeveloped and Mitigated. POC #1 Year Predeveloped Mitigated 1949 0.345 0.345 1950 0.298 0.298 1951 0.312 0.312 1952 0.260 0.260 1953 0.259 0.259 1954 0.252 0.252 1955 0.358 0.358 1956 0.282 0.282 1957 0.368 0.368 1958 0.271 0.271 Detention 4/2/2026 9:31:29 AM Page 13 1959 0.248 0.248 1960 0.331 0.331 1961 0.259 0.259 1962 0.232 0.232 1963 0.231 0.231 1964 0.275 0.275 1965 0.250 0.250 1966 0.251 0.251 1967 0.307 0.307 1968 0.288 0.288 1969 0.275 0.275 1970 0.268 0.268 1971 0.263 0.263 1972 0.402 0.402 1973 0.256 0.256 1974 0.240 0.240 1975 0.336 0.336 1976 0.246 0.246 1977 0.247 0.247 1978 0.368 0.368 1979 0.269 0.269 1980 0.299 0.299 1981 0.293 0.293 1982 0.432 0.432 1983 0.354 0.354 1984 0.232 0.232 1985 0.287 0.287 1986 0.410 0.410 1987 0.398 0.398 1988 0.247 0.247 1989 0.228 0.228 1990 0.623 0.623 1991 0.499 0.499 1992 0.278 0.278 1993 0.212 0.212 1994 0.220 0.220 1995 0.267 0.267 1996 0.401 0.401 1997 0.373 0.373 1998 0.251 0.251 1999 0.428 0.428 2000 0.309 0.309 2001 0.252 0.252 2002 0.394 0.394 2003 0.251 0.251 2004 0.720 0.720 2005 0.387 0.387 2006 0.253 0.253 2007 0.580 0.580 2008 0.613 0.613 2009 0.387 0.387 Ranked Annual Peaks Ranked Annual Peaks for Predeveloped and Mitigated. POC #1 Rank Predeveloped Mitigated 1 0.7202 0.7202 2 0.6227 0.6227 3 0.6127 0.6127 Detention 4/2/2026 9:31:29 AM Page 14 4 0.5795 0.5795 5 0.4986 0.4986 6 0.4325 0.4325 7 0.4280 0.4280 8 0.4099 0.4099 9 0.4024 0.4024 10 0.4013 0.4013 11 0.3976 0.3976 12 0.3937 0.3937 13 0.3871 0.3871 14 0.3867 0.3867 15 0.3727 0.3727 16 0.3683 0.3683 17 0.3682 0.3682 18 0.3575 0.3575 19 0.3536 0.3536 20 0.3454 0.3454 21 0.3363 0.3363 22 0.3308 0.3308 23 0.3118 0.3118 24 0.3092 0.3092 25 0.3071 0.3071 26 0.2991 0.2991 27 0.2978 0.2978 28 0.2929 0.2929 29 0.2877 0.2877 30 0.2865 0.2865 31 0.2825 0.2825 32 0.2776 0.2776 33 0.2755 0.2755 34 0.2754 0.2754 35 0.2706 0.2706 36 0.2685 0.2685 37 0.2681 0.2681 38 0.2667 0.2667 39 0.2634 0.2634 40 0.2596 0.2596 41 0.2592 0.2592 42 0.2591 0.2591 43 0.2557 0.2557 44 0.2535 0.2535 45 0.2523 0.2523 46 0.2520 0.2520 47 0.2507 0.2507 48 0.2507 0.2507 49 0.2506 0.2506 50 0.2503 0.2503 51 0.2477 0.2477 52 0.2473 0.2473 53 0.2469 0.2469 54 0.2460 0.2460 55 0.2397 0.2397 56 0.2324 0.2324 57 0.2324 0.2324 58 0.2310 0.2310 59 0.2280 0.2280 60 0.2201 0.2201 61 0.2117 0.2117 Detention 4/2/2026 9:31:29 AM Page 15 Detention 4/2/2026 9:31:29 AM Page 16 Duration Flows The Facility PASSED Flow(cfs)Predev Mit Percentage Pass/Fail 0.1502 15620 15620 100 Pass 0.1548 14326 14326 100 Pass 0.1593 12942 12942 100 Pass 0.1639 11973 11973 100 Pass 0.1685 10859 10859 100 Pass 0.1731 9794 9794 100 Pass 0.1776 9062 9062 100 Pass 0.1822 8239 8239 100 Pass 0.1868 7623 7623 100 Pass 0.1914 6939 6939 100 Pass 0.1959 6423 6423 100 Pass 0.2005 5781 5781 100 Pass 0.2051 5221 5221 100 Pass 0.2096 4787 4787 100 Pass 0.2142 4308 4308 100 Pass 0.2188 3980 3980 100 Pass 0.2234 3578 3578 100 Pass 0.2279 3277 3277 100 Pass 0.2325 2922 2922 100 Pass 0.2371 2635 2635 100 Pass 0.2417 2417 2417 100 Pass 0.2462 2184 2184 100 Pass 0.2508 2016 2016 100 Pass 0.2554 1805 1805 100 Pass 0.2599 1655 1655 100 Pass 0.2645 1455 1455 100 Pass 0.2691 1297 1297 100 Pass 0.2737 1194 1194 100 Pass 0.2782 1078 1078 100 Pass 0.2828 994 994 100 Pass 0.2874 886 886 100 Pass 0.2920 798 798 100 Pass 0.2965 678 678 100 Pass 0.3011 599 599 100 Pass 0.3057 536 536 100 Pass 0.3102 462 462 100 Pass 0.3148 433 433 100 Pass 0.3194 411 411 100 Pass 0.3240 401 401 100 Pass 0.3285 375 375 100 Pass 0.3331 359 359 100 Pass 0.3377 350 350 100 Pass 0.3422 338 338 100 Pass 0.3468 329 329 100 Pass 0.3514 315 315 100 Pass 0.3560 305 305 100 Pass 0.3605 295 295 100 Pass 0.3651 279 279 100 Pass 0.3697 265 265 100 Pass 0.3743 249 249 100 Pass 0.3788 232 232 100 Pass 0.3834 223 223 100 Pass 0.3880 211 211 100 Pass Detention 4/2/2026 9:31:29 AM Page 17 0.3925 199 199 100 Pass 0.3971 190 190 100 Pass 0.4017 182 182 100 Pass 0.4063 175 175 100 Pass 0.4108 169 169 100 Pass 0.4154 168 168 100 Pass 0.4200 164 164 100 Pass 0.4246 160 160 100 Pass 0.4291 151 151 100 Pass 0.4337 148 148 100 Pass 0.4383 144 144 100 Pass 0.4428 140 140 100 Pass 0.4474 136 136 100 Pass 0.4520 134 134 100 Pass 0.4566 132 132 100 Pass 0.4611 125 125 100 Pass 0.4657 122 122 100 Pass 0.4703 121 121 100 Pass 0.4748 118 118 100 Pass 0.4794 112 112 100 Pass 0.4840 109 109 100 Pass 0.4886 103 103 100 Pass 0.4931 97 97 100 Pass 0.4977 90 90 100 Pass 0.5023 84 84 100 Pass 0.5069 82 82 100 Pass 0.5114 78 78 100 Pass 0.5160 68 68 100 Pass 0.5206 62 62 100 Pass 0.5251 55 55 100 Pass 0.5297 55 55 100 Pass 0.5343 53 53 100 Pass 0.5389 52 52 100 Pass 0.5434 51 51 100 Pass 0.5480 49 49 100 Pass 0.5526 45 45 100 Pass 0.5572 45 45 100 Pass 0.5617 44 44 100 Pass 0.5663 43 43 100 Pass 0.5709 43 43 100 Pass 0.5754 38 38 100 Pass 0.5800 36 36 100 Pass 0.5846 35 35 100 Pass 0.5892 32 32 100 Pass 0.5937 31 31 100 Pass 0.5983 26 26 100 Pass 0.6029 24 24 100 Pass Detention 4/2/2026 9:31:29 AM Page 18 Water Quality Water Quality BMP Flow and Volume for POC #1 On-line facility volume:0.0577 acre-feet On-line facility target flow:0.0763 cfs. Adjusted for 15 min:0.0763 cfs. Off-line facility target flow:0.0431 cfs. Adjusted for 15 min:0.0431 cfs. Detention 4/2/2026 9:31:29 AM Page 19 POC 2 POC #2 was not reported because POC must exist in both scenarios and both scenarios must have been run. Detention 4/2/2026 9:31:29 AM Page 20 Model Default Modifications Total of 0 changes have been made. PERLND Changes No PERLND changes have been made. IMPLND Changes No IMPLND changes have been made. Detention 4/2/2026 9:31:29 AM Page 21 Appendix Predeveloped Schematic Detention 4/2/2026 9:31:31 AM Page 22 Mitigated Schematic Detention 4/2/2026 9:31:33 AM Page 23 Predeveloped UCI File RUN GLOBAL WWHM4 model simulation START 1948 10 01 END 2009 09 30 RUN INTERP OUTPUT LEVEL 3 0 RESUME 0 RUN 1 UNIT SYSTEM 1 END GLOBAL FILES <File> <Un#> <-----------File Name------------------------------>*** <-ID-> *** WDM 26 Detention.wdm MESSU 25 PreDetention.MES 27 PreDetention.L61 28 PreDetention.L62 30 POCDetention1.dat END FILES OPN SEQUENCE INGRP INDELT 00:15 IMPLND 1 IMPLND 4 RCHRES 1 COPY 501 DISPLY 1 END INGRP END OPN SEQUENCE DISPLY DISPLY-INFO1 # - #<----------Title----------->***TRAN PIVL DIG1 FIL1 PYR DIG2 FIL2 YRND 1 Trapezoidal Pond 1 MAX 1 2 30 9 END DISPLY-INFO1 END DISPLY COPY TIMESERIES # - # NPT NMN *** 1 1 1 501 1 1 END TIMESERIES END COPY GENER OPCODE # # OPCD *** END OPCODE PARM # # K *** END PARM END GENER PERLND GEN-INFO <PLS ><-------Name------->NBLKS Unit-systems Printer *** # - # User t-series Engl Metr *** in out *** END GEN-INFO *** Section PWATER*** ACTIVITY <PLS > ************* Active Sections ***************************** # - # ATMP SNOW PWAT SED PST PWG PQAL MSTL PEST NITR PHOS TRAC *** END ACTIVITY PRINT-INFO <PLS > ***************** Print-flags ***************************** PIVL PYR # - # ATMP SNOW PWAT SED PST PWG PQAL MSTL PEST NITR PHOS TRAC ********* END PRINT-INFO PWAT-PARM1 Detention 4/2/2026 9:31:33 AM Page 24 <PLS > PWATER variable monthly parameter value flags *** # - # CSNO RTOP UZFG VCS VUZ VNN VIFW VIRC VLE INFC HWT *** END PWAT-PARM1 PWAT-PARM2 <PLS > PWATER input info: Part 2 *** # - # ***FOREST LZSN INFILT LSUR SLSUR KVARY AGWRC END PWAT-PARM2 PWAT-PARM3 <PLS > PWATER input info: Part 3 *** # - # ***PETMAX PETMIN INFEXP INFILD DEEPFR BASETP AGWETP END PWAT-PARM3 PWAT-PARM4 <PLS > PWATER input info: Part 4 *** # - # CEPSC UZSN NSUR INTFW IRC LZETP *** END PWAT-PARM4 PWAT-STATE1 <PLS > *** Initial conditions at start of simulation ran from 1990 to end of 1992 (pat 1-11-95) RUN 21 *** # - # *** CEPS SURS UZS IFWS LZS AGWS GWVS END PWAT-STATE1 END PERLND IMPLND GEN-INFO <PLS ><-------Name-------> Unit-systems Printer *** # - # User t-series Engl Metr *** in out *** 1 ROADS/FLAT 1 1 1 27 0 4 ROOF TOPS/FLAT 1 1 1 27 0 END GEN-INFO *** Section IWATER*** ACTIVITY <PLS > ************* Active Sections ***************************** # - # ATMP SNOW IWAT SLD IWG IQAL *** 1 0 0 1 0 0 0 4 0 0 1 0 0 0 END ACTIVITY PRINT-INFO <ILS > ******** Print-flags ******** PIVL PYR # - # ATMP SNOW IWAT SLD IWG IQAL ********* 1 0 0 4 0 0 4 1 9 4 0 0 4 0 0 0 1 9 END PRINT-INFO IWAT-PARM1 <PLS > IWATER variable monthly parameter value flags *** # - # CSNO RTOP VRS VNN RTLI *** 1 0 0 0 0 0 4 0 0 0 0 0 END IWAT-PARM1 IWAT-PARM2 <PLS > IWATER input info: Part 2 *** # - # *** LSUR SLSUR NSUR RETSC 1 400 0.01 0.1 0.1 4 400 0.01 0.1 0.1 END IWAT-PARM2 IWAT-PARM3 <PLS > IWATER input info: Part 3 *** # - # ***PETMAX PETMIN 1 0 0 4 0 0 END IWAT-PARM3 Detention 4/2/2026 9:31:33 AM Page 25 IWAT-STATE1 <PLS > *** Initial conditions at start of simulation # - # *** RETS SURS 1 0 0 4 0 0 END IWAT-STATE1 END IMPLND SCHEMATIC <-Source-> <--Area--> <-Target-> MBLK *** <Name> # <-factor-> <Name> # Tbl# *** Basin 1*** IMPLND 1 1.44 RCHRES 1 5 IMPLND 4 0.45 RCHRES 1 5 ******Routing****** RCHRES 1 1 COPY 501 16 END SCHEMATIC NETWORK <-Volume-> <-Grp> <-Member-><--Mult-->Tran <-Target vols> <-Grp> <-Member-> *** <Name> # <Name> # #<-factor->strg <Name> # # <Name> # # *** COPY 501 OUTPUT MEAN 1 1 48.4 DISPLY 1 INPUT TIMSER 1 <-Volume-> <-Grp> <-Member-><--Mult-->Tran <-Target vols> <-Grp> <-Member-> *** <Name> # <Name> # #<-factor->strg <Name> # # <Name> # # *** END NETWORK RCHRES GEN-INFO RCHRES Name Nexits Unit Systems Printer *** # - #<------------------><---> User T-series Engl Metr LKFG *** in out *** 1 Trapezoidal Pond-012 1 1 1 1 28 0 1 END GEN-INFO *** Section RCHRES*** ACTIVITY <PLS > ************* Active Sections ***************************** # - # HYFG ADFG CNFG HTFG SDFG GQFG OXFG NUFG PKFG PHFG *** 1 1 0 0 0 0 0 0 0 0 0 END ACTIVITY PRINT-INFO <PLS > ***************** Print-flags ******************* PIVL PYR # - # HYDR ADCA CONS HEAT SED GQL OXRX NUTR PLNK PHCB PIVL PYR ********* 1 4 0 0 0 0 0 0 0 0 0 1 9 END PRINT-INFO HYDR-PARM1 RCHRES Flags for each HYDR Section *** # - # VC A1 A2 A3 ODFVFG for each *** ODGTFG for each FUNCT for each FG FG FG FG possible exit *** possible exit possible exit * * * * * * * * * * * * * * *** 1 0 1 0 0 4 0 0 0 0 0 0 0 0 0 2 2 2 2 2 END HYDR-PARM1 HYDR-PARM2 # - # FTABNO LEN DELTH STCOR KS DB50 *** <------><--------><--------><--------><--------><--------><--------> *** 1 1 0.01 0.0 0.0 0.5 0.0 END HYDR-PARM2 HYDR-INIT RCHRES Initial conditions for each HYDR section *** # - # *** VOL Initial value of COLIND Initial value of OUTDGT *** ac-ft for each possible exit for each possible exit Detention 4/2/2026 9:31:33 AM Page 26 <------><--------> <---><---><---><---><---> *** <---><---><---><---><---> 1 0 4.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 END HYDR-INIT END RCHRES SPEC-ACTIONS END SPEC-ACTIONS FTABLES FTABLE 1 91 4 Depth Area Volume Outflow1 Velocity Travel Time*** (ft) (acres) (acre-ft) (cfs) (ft/sec) (Minutes)*** 0.000000 0.043044 0.000000 0.000000 0.050000 0.043735 0.002169 0.059258 0.100000 0.044430 0.004374 0.083803 0.150000 0.045129 0.006613 0.102637 0.200000 0.045832 0.008887 0.118515 0.250000 0.046539 0.011196 0.132504 0.300000 0.047251 0.013541 0.145151 0.350000 0.047966 0.015921 0.156781 0.400000 0.048686 0.018337 0.167606 0.450000 0.049410 0.020790 0.177773 0.500000 0.050138 0.023278 0.187389 0.550000 0.050870 0.025804 0.196535 0.600000 0.051606 0.028365 0.205274 0.650000 0.052346 0.030964 0.213656 0.700000 0.053091 0.033600 0.221721 0.750000 0.053840 0.036274 0.229504 0.800000 0.054592 0.038984 0.237030 0.850000 0.055349 0.041733 0.244325 0.900000 0.056110 0.044519 0.251409 0.950000 0.056875 0.047344 0.258298 1.000000 0.057645 0.050207 0.265008 1.050000 0.058418 0.053109 0.271552 1.100000 0.059196 0.056049 0.277943 1.150000 0.059977 0.059028 0.284189 1.200000 0.060763 0.062047 0.290302 1.250000 0.061553 0.065105 0.296288 1.300000 0.062347 0.068202 0.302155 1.350000 0.063145 0.071339 0.307911 1.400000 0.063948 0.074517 0.313562 1.450000 0.064754 0.077734 0.357037 1.500000 0.065565 0.080992 0.378201 1.550000 0.066379 0.084291 0.395620 1.600000 0.067198 0.087630 0.411061 1.650000 0.068021 0.091011 0.425211 1.700000 0.068848 0.094433 0.438424 1.750000 0.069680 0.097896 0.450912 1.800000 0.070515 0.101401 0.462813 1.850000 0.071355 0.104947 0.474224 1.900000 0.072198 0.108536 0.485217 1.950000 0.073046 0.112167 0.495846 2.000000 0.073898 0.115841 0.506153 2.050000 0.074754 0.119557 0.516173 2.100000 0.075614 0.123316 0.525935 2.150000 0.076479 0.127119 0.573385 2.200000 0.077347 0.130964 0.598403 2.250000 0.078220 0.134854 0.619568 2.300000 0.079096 0.138786 0.638655 2.350000 0.079977 0.142763 0.656362 2.400000 0.080862 0.146784 0.673050 2.450000 0.081751 0.150850 0.688936 2.500000 0.082645 0.154960 0.704165 2.550000 0.083542 0.159114 0.718839 2.600000 0.084444 0.163314 0.733034 2.650000 0.085349 0.167559 0.746808 2.700000 0.086259 0.171849 0.760207 2.750000 0.087173 0.176185 0.773269 2.800000 0.088091 0.180566 0.786024 2.850000 0.089013 0.184994 0.798499 Detention 4/2/2026 9:31:33 AM Page 27 2.900000 0.089939 0.189468 0.810714 2.950000 0.090870 0.193988 0.822691 3.000000 0.091804 0.198555 0.834444 3.050000 0.092743 0.203168 0.845988 3.100000 0.093686 0.207829 0.857337 3.150000 0.094633 0.212537 0.868502 3.200000 0.095584 0.217293 0.879493 3.250000 0.096539 0.222096 0.890319 3.300000 0.097499 0.226947 0.900988 3.350000 0.098462 0.231846 0.911509 3.400000 0.099430 0.236793 0.921888 3.450000 0.100402 0.241789 0.932131 3.500000 0.101377 0.246833 0.942245 3.550000 0.102357 0.251927 1.070717 3.600000 0.103342 0.257069 1.295625 3.650000 0.104330 0.262261 1.576647 3.700000 0.105322 0.267502 1.889183 3.750000 0.106319 0.272793 2.208602 3.800000 0.107320 0.278134 2.510156 3.850000 0.108324 0.283525 2.771899 3.900000 0.109333 0.288967 2.979101 3.950000 0.110346 0.294459 3.129706 4.000000 0.111364 0.300001 3.240615 4.050000 0.112385 0.305595 3.382084 4.100000 0.113410 0.311240 3.494840 4.150000 0.114440 0.316936 3.603271 4.200000 0.115474 0.322684 3.707859 4.250000 0.116512 0.328484 3.809003 4.300000 0.117554 0.334335 3.907039 4.350000 0.118600 0.340239 4.002247 4.400000 0.119650 0.346195 4.094870 4.450000 0.120705 0.352204 4.185116 4.500000 0.121763 0.358266 4.273168 END FTABLE 1 END FTABLES EXT SOURCES <-Volume-> <Member> SsysSgap<--Mult-->Tran <-Target vols> <-Grp> <-Member-> *** <Name> # <Name> # tem strg<-factor->strg <Name> # # <Name> # # *** WDM 2 PREC ENGL 1 PERLND 1 999 EXTNL PREC WDM 2 PREC ENGL 1 IMPLND 1 999 EXTNL PREC WDM 1 EVAP ENGL 0.76 PERLND 1 999 EXTNL PETINP WDM 1 EVAP ENGL 0.76 IMPLND 1 999 EXTNL PETINP END EXT SOURCES EXT TARGETS <-Volume-> <-Grp> <-Member-><--Mult-->Tran <-Volume-> <Member> Tsys Tgap Amd *** <Name> # <Name> # #<-factor->strg <Name> # <Name> tem strg strg*** RCHRES 1 HYDR RO 1 1 1 WDM 1002 FLOW ENGL REPL RCHRES 1 HYDR STAGE 1 1 1 WDM 1003 STAG ENGL REPL COPY 501 OUTPUT MEAN 1 1 48.4 WDM 501 FLOW ENGL REPL END EXT TARGETS MASS-LINK <Volume> <-Grp> <-Member-><--Mult--> <Target> <-Grp> <-Member->*** <Name> <Name> # #<-factor-> <Name> <Name> # #*** MASS-LINK 5 IMPLND IWATER SURO 0.083333 RCHRES INFLOW IVOL END MASS-LINK 5 MASS-LINK 16 RCHRES ROFLOW COPY INPUT MEAN END MASS-LINK 16 END MASS-LINK END RUN Detention 4/2/2026 9:31:33 AM Page 28 Mitigated UCI File RUN GLOBAL WWHM4 model simulation START 1948 10 01 END 2009 09 30 RUN INTERP OUTPUT LEVEL 3 0 RESUME 0 RUN 1 UNIT SYSTEM 1 END GLOBAL FILES <File> <Un#> <-----------File Name------------------------------>*** <-ID-> *** WDM 26 Detention.wdm MESSU 25 MitDetention.MES 27 MitDetention.L61 28 MitDetention.L62 30 POCDetention1.dat END FILES OPN SEQUENCE INGRP INDELT 00:15 IMPLND 1 IMPLND 4 RCHRES 1 COPY 1 COPY 501 DISPLY 1 END INGRP END OPN SEQUENCE DISPLY DISPLY-INFO1 # - #<----------Title----------->***TRAN PIVL DIG1 FIL1 PYR DIG2 FIL2 YRND 1 Trapezoidal Pond 1 MAX 1 2 30 9 END DISPLY-INFO1 END DISPLY COPY TIMESERIES # - # NPT NMN *** 1 1 1 501 1 1 END TIMESERIES END COPY GENER OPCODE # # OPCD *** END OPCODE PARM # # K *** END PARM END GENER PERLND GEN-INFO <PLS ><-------Name------->NBLKS Unit-systems Printer *** # - # User t-series Engl Metr *** in out *** END GEN-INFO *** Section PWATER*** ACTIVITY <PLS > ************* Active Sections ***************************** # - # ATMP SNOW PWAT SED PST PWG PQAL MSTL PEST NITR PHOS TRAC *** END ACTIVITY PRINT-INFO <PLS > ***************** Print-flags ***************************** PIVL PYR # - # ATMP SNOW PWAT SED PST PWG PQAL MSTL PEST NITR PHOS TRAC ********* END PRINT-INFO Detention 4/2/2026 9:31:33 AM Page 29 PWAT-PARM1 <PLS > PWATER variable monthly parameter value flags *** # - # CSNO RTOP UZFG VCS VUZ VNN VIFW VIRC VLE INFC HWT *** END PWAT-PARM1 PWAT-PARM2 <PLS > PWATER input info: Part 2 *** # - # ***FOREST LZSN INFILT LSUR SLSUR KVARY AGWRC END PWAT-PARM2 PWAT-PARM3 <PLS > PWATER input info: Part 3 *** # - # ***PETMAX PETMIN INFEXP INFILD DEEPFR BASETP AGWETP END PWAT-PARM3 PWAT-PARM4 <PLS > PWATER input info: Part 4 *** # - # CEPSC UZSN NSUR INTFW IRC LZETP *** END PWAT-PARM4 PWAT-STATE1 <PLS > *** Initial conditions at start of simulation ran from 1990 to end of 1992 (pat 1-11-95) RUN 21 *** # - # *** CEPS SURS UZS IFWS LZS AGWS GWVS END PWAT-STATE1 END PERLND IMPLND GEN-INFO <PLS ><-------Name-------> Unit-systems Printer *** # - # User t-series Engl Metr *** in out *** 1 ROADS/FLAT 1 1 1 27 0 4 ROOF TOPS/FLAT 1 1 1 27 0 END GEN-INFO *** Section IWATER*** ACTIVITY <PLS > ************* Active Sections ***************************** # - # ATMP SNOW IWAT SLD IWG IQAL *** 1 0 0 1 0 0 0 4 0 0 1 0 0 0 END ACTIVITY PRINT-INFO <ILS > ******** Print-flags ******** PIVL PYR # - # ATMP SNOW IWAT SLD IWG IQAL ********* 1 0 0 4 0 0 4 1 9 4 0 0 4 0 0 0 1 9 END PRINT-INFO IWAT-PARM1 <PLS > IWATER variable monthly parameter value flags *** # - # CSNO RTOP VRS VNN RTLI *** 1 0 0 0 0 0 4 0 0 0 0 0 END IWAT-PARM1 IWAT-PARM2 <PLS > IWATER input info: Part 2 *** # - # *** LSUR SLSUR NSUR RETSC 1 400 0.01 0.1 0.1 4 400 0.01 0.1 0.1 END IWAT-PARM2 IWAT-PARM3 <PLS > IWATER input info: Part 3 *** # - # ***PETMAX PETMIN 1 0 0 4 0 0 Detention 4/2/2026 9:31:33 AM Page 30 END IWAT-PARM3 IWAT-STATE1 <PLS > *** Initial conditions at start of simulation # - # *** RETS SURS 1 0 0 4 0 0 END IWAT-STATE1 END IMPLND SCHEMATIC <-Source-> <--Area--> <-Target-> MBLK *** <Name> # <-factor-> <Name> # Tbl# *** Basin 1*** IMPLND 1 1.09 RCHRES 1 5 IMPLND 4 0.8 RCHRES 1 5 ******Routing****** IMPLND 1 1.09 COPY 1 15 IMPLND 4 0.8 COPY 1 15 RCHRES 1 1 COPY 501 16 END SCHEMATIC NETWORK <-Volume-> <-Grp> <-Member-><--Mult-->Tran <-Target vols> <-Grp> <-Member-> *** <Name> # <Name> # #<-factor->strg <Name> # # <Name> # # *** COPY 501 OUTPUT MEAN 1 1 48.4 DISPLY 1 INPUT TIMSER 1 <-Volume-> <-Grp> <-Member-><--Mult-->Tran <-Target vols> <-Grp> <-Member-> *** <Name> # <Name> # #<-factor->strg <Name> # # <Name> # # *** END NETWORK RCHRES GEN-INFO RCHRES Name Nexits Unit Systems Printer *** # - #<------------------><---> User T-series Engl Metr LKFG *** in out *** 1 Trapezoidal Pond-013 1 1 1 1 28 0 1 END GEN-INFO *** Section RCHRES*** ACTIVITY <PLS > ************* Active Sections ***************************** # - # HYFG ADFG CNFG HTFG SDFG GQFG OXFG NUFG PKFG PHFG *** 1 1 0 0 0 0 0 0 0 0 0 END ACTIVITY PRINT-INFO <PLS > ***************** Print-flags ******************* PIVL PYR # - # HYDR ADCA CONS HEAT SED GQL OXRX NUTR PLNK PHCB PIVL PYR ********* 1 4 0 0 0 0 0 0 0 0 0 1 9 END PRINT-INFO HYDR-PARM1 RCHRES Flags for each HYDR Section *** # - # VC A1 A2 A3 ODFVFG for each *** ODGTFG for each FUNCT for each FG FG FG FG possible exit *** possible exit possible exit * * * * * * * * * * * * * * *** 1 0 1 0 0 4 0 0 0 0 0 0 0 0 0 2 2 2 2 2 END HYDR-PARM1 HYDR-PARM2 # - # FTABNO LEN DELTH STCOR KS DB50 *** <------><--------><--------><--------><--------><--------><--------> *** 1 1 0.01 0.0 0.0 0.5 0.0 END HYDR-PARM2 HYDR-INIT Detention 4/2/2026 9:31:33 AM Page 31 RCHRES Initial conditions for each HYDR section *** # - # *** VOL Initial value of COLIND Initial value of OUTDGT *** ac-ft for each possible exit for each possible exit <------><--------> <---><---><---><---><---> *** <---><---><---><---><---> 1 0 4.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 END HYDR-INIT END RCHRES SPEC-ACTIONS END SPEC-ACTIONS FTABLES FTABLE 1 91 4 Depth Area Volume Outflow1 Velocity Travel Time*** (ft) (acres) (acre-ft) (cfs) (ft/sec) (Minutes)*** 0.000000 0.043044 0.000000 0.000000 0.050000 0.043735 0.002169 0.059258 0.100000 0.044430 0.004374 0.083803 0.150000 0.045129 0.006613 0.102637 0.200000 0.045832 0.008887 0.118515 0.250000 0.046539 0.011196 0.132504 0.300000 0.047251 0.013541 0.145151 0.350000 0.047966 0.015921 0.156781 0.400000 0.048686 0.018337 0.167606 0.450000 0.049410 0.020790 0.177773 0.500000 0.050138 0.023278 0.187389 0.550000 0.050870 0.025804 0.196535 0.600000 0.051606 0.028365 0.205274 0.650000 0.052346 0.030964 0.213656 0.700000 0.053091 0.033600 0.221721 0.750000 0.053840 0.036274 0.229504 0.800000 0.054592 0.038984 0.237030 0.850000 0.055349 0.041733 0.244325 0.900000 0.056110 0.044519 0.251409 0.950000 0.056875 0.047344 0.258298 1.000000 0.057645 0.050207 0.265008 1.050000 0.058418 0.053109 0.271552 1.100000 0.059196 0.056049 0.277943 1.150000 0.059977 0.059028 0.284189 1.200000 0.060763 0.062047 0.290302 1.250000 0.061553 0.065105 0.296288 1.300000 0.062347 0.068202 0.302155 1.350000 0.063145 0.071339 0.307911 1.400000 0.063948 0.074517 0.313562 1.450000 0.064754 0.077734 0.357037 1.500000 0.065565 0.080992 0.378201 1.550000 0.066379 0.084291 0.395620 1.600000 0.067198 0.087630 0.411061 1.650000 0.068021 0.091011 0.425211 1.700000 0.068848 0.094433 0.438424 1.750000 0.069680 0.097896 0.450912 1.800000 0.070515 0.101401 0.462813 1.850000 0.071355 0.104947 0.474224 1.900000 0.072198 0.108536 0.485217 1.950000 0.073046 0.112167 0.495846 2.000000 0.073898 0.115841 0.506153 2.050000 0.074754 0.119557 0.516173 2.100000 0.075614 0.123316 0.525935 2.150000 0.076479 0.127119 0.573385 2.200000 0.077347 0.130964 0.598403 2.250000 0.078220 0.134854 0.619568 2.300000 0.079096 0.138786 0.638655 2.350000 0.079977 0.142763 0.656362 2.400000 0.080862 0.146784 0.673050 2.450000 0.081751 0.150850 0.688936 2.500000 0.082645 0.154960 0.704165 2.550000 0.083542 0.159114 0.718839 2.600000 0.084444 0.163314 0.733034 2.650000 0.085349 0.167559 0.746808 2.700000 0.086259 0.171849 0.760207 Detention 4/2/2026 9:31:33 AM Page 32 2.750000 0.087173 0.176185 0.773269 2.800000 0.088091 0.180566 0.786024 2.850000 0.089013 0.184994 0.798499 2.900000 0.089939 0.189468 0.810714 2.950000 0.090870 0.193988 0.822691 3.000000 0.091804 0.198555 0.834444 3.050000 0.092743 0.203168 0.845988 3.100000 0.093686 0.207829 0.857337 3.150000 0.094633 0.212537 0.868502 3.200000 0.095584 0.217293 0.879493 3.250000 0.096539 0.222096 0.890319 3.300000 0.097499 0.226947 0.900988 3.350000 0.098462 0.231846 0.911509 3.400000 0.099430 0.236793 0.921888 3.450000 0.100402 0.241789 0.932131 3.500000 0.101377 0.246833 0.942245 3.550000 0.102357 0.251927 1.070717 3.600000 0.103342 0.257069 1.295625 3.650000 0.104330 0.262261 1.576647 3.700000 0.105322 0.267502 1.889183 3.750000 0.106319 0.272793 2.208602 3.800000 0.107320 0.278134 2.510156 3.850000 0.108324 0.283525 2.771899 3.900000 0.109333 0.288967 2.979101 3.950000 0.110346 0.294459 3.129706 4.000000 0.111364 0.300001 3.240615 4.050000 0.112385 0.305595 3.382084 4.100000 0.113410 0.311240 3.494840 4.150000 0.114440 0.316936 3.603271 4.200000 0.115474 0.322684 3.707859 4.250000 0.116512 0.328484 3.809003 4.300000 0.117554 0.334335 3.907039 4.350000 0.118600 0.340239 4.002247 4.400000 0.119650 0.346195 4.094870 4.450000 0.120705 0.352204 4.185116 4.500000 0.121763 0.358266 4.273168 END FTABLE 1 END FTABLES EXT SOURCES <-Volume-> <Member> SsysSgap<--Mult-->Tran <-Target vols> <-Grp> <-Member-> *** <Name> # <Name> # tem strg<-factor->strg <Name> # # <Name> # # *** WDM 2 PREC ENGL 1 PERLND 1 999 EXTNL PREC WDM 2 PREC ENGL 1 IMPLND 1 999 EXTNL PREC WDM 1 EVAP ENGL 0.76 PERLND 1 999 EXTNL PETINP WDM 1 EVAP ENGL 0.76 IMPLND 1 999 EXTNL PETINP END EXT SOURCES EXT TARGETS <-Volume-> <-Grp> <-Member-><--Mult-->Tran <-Volume-> <Member> Tsys Tgap Amd *** <Name> # <Name> # #<-factor->strg <Name> # <Name> tem strg strg*** RCHRES 1 HYDR RO 1 1 1 WDM 1000 FLOW ENGL REPL RCHRES 1 HYDR STAGE 1 1 1 WDM 1001 STAG ENGL REPL COPY 1 OUTPUT MEAN 1 1 48.4 WDM 701 FLOW ENGL REPL COPY 501 OUTPUT MEAN 1 1 48.4 WDM 801 FLOW ENGL REPL END EXT TARGETS MASS-LINK <Volume> <-Grp> <-Member-><--Mult--> <Target> <-Grp> <-Member->*** <Name> <Name> # #<-factor-> <Name> <Name> # #*** MASS-LINK 5 IMPLND IWATER SURO 0.083333 RCHRES INFLOW IVOL END MASS-LINK 5 MASS-LINK 15 IMPLND IWATER SURO 0.083333 COPY INPUT MEAN END MASS-LINK 15 MASS-LINK 16 Detention 4/2/2026 9:31:33 AM Page 33 RCHRES ROFLOW COPY INPUT MEAN END MASS-LINK 16 END MASS-LINK END RUN Detention 4/2/2026 9:31:33 AM Page 34 Predeveloped HSPF Message File Detention 4/2/2026 9:31:33 AM Page 35 Mitigated HSPF Message File Detention 4/2/2026 9:31:33 AM Page 36 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. 2005-2026; 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 Civil Engineers ● Structural Engineers ● Landscape Architects ● Community Planners ● Land Surveyors Backwater Analysis PREPARED FOR: ADF Properties, LLC 15007 Woodinville-Redmond Road Suite A Woodinville, WA 98072 PROJECT: Walker Subaru Service Center Renton, WA 2240819.10 PREPARED BY: Nate Kaser Project Engineer REVIEWED BY: Scott T. Kaul, PE, LEED AP Associate Principal DATE: January 2026 Pg. 1 25 Year Storm Run 1 25 Year Storm Run 1 Pg. 2 25 Year Storm Run 2 Pg. 3 25 Year Storm Run 2 Pg. 4 25 Year Storm Run 3 Pg. 5 25 Year Storm Run 3 Pg. 6 100 Year Worst Pipe Run Pg. 7 100 Year Worst Pipe Run Pg. 8 2215 North 30th Street Suite 300 Tacoma, WA 98403 253.383.2422 TEL 253.383.2572 FAX WALKER SUBARU SERVICE CENTER WQ CALCS EXHIBIT C-5 1 OF 1 WATER QUALITY PRE-DETENTION: Basin 1 Areas and flows: 6x12 Underground BioPod: Treatment Capacity: 0.213 > 0.2095 Bypass: 5.0 > 0.9999 Therefore, a 6x12 BioPod Vault is sufficiently sized. Technical Information Report Walker Subaru Service Center 2240819.10 Appendix D Geotechnical Engineering Report Geotechnical Engineering Report Walker’s Renton Subaru 519 SW 12th Street Renton, WA 980057 P/N. 3340404265, 3340404148 December 11, 2024 prepared for: HHJ Construction Attention: John Manuel 601 St Helens Avenue Tacoma, WA 98402 prepared by: Migizi Group, Inc. PO Box 44840 Tacoma, WA 98448 (253) 537-9400 MGI Project Z0816 i TABLE OF CONTENTS Page No. 1.0 SITE AND PROJECT DESCRIPTION .............................................................................................. 1 2.0 EXPLORATORY METHODS ............................................................................................................ 2 2.1 Auger Boring Procedures...................................................................................................... 3 3.0 SITE CONDITIONS ............................................................................................................................ 3 3.1 Surface Conditions ................................................................................................................. 3 3.2 Soil Conditions ....................................................................................................................... 4 3.3 Groundwater Conditions ...................................................................................................... 6 3.4 Infiltration Conditions ........................................................................................................... 6 3.5 Seismic Conditions ................................................................................................................. 6 3.6 Liquefaction Potential ........................................................................................................... 7 4.0 CONCLUSIONS AND RECOMMENDATIONS............................................................................ 8 4.1 Site Preparation ...................................................................................................................... 9 4.2 Spread Footings and Bearing Pads .................................................................................... 12 4.3 Slab-On-Grade-Floors .......................................................................................................... 13 4.4 Drainage Systems ................................................................................................................. 14 4.5 Asphalt Pavement ................................................................................................................. 14 4.6 Structural Fill ........................................................................................................................ 16 5.0 RECOMMENDED ADDITIONAL SERVICES ............................................................................. 17 6.0 CLOSURE ........................................................................................................................................... 18 List of Tables Table 1. Approximate Locations and Depths of Explorations ............................................................................. 2 Table 2. Seismic Design Parameters ........................................................................................................................ 7 List of Figures Figure 1. Topographic and Location Map Figure 2. Site and Exploration Plan Figure 3. Geologic Map of Immediate Project Area Figure 2. Regional Liquefaction Susceptibility Map APPENDIX A Soil Classification Chart and Key to Test Data .................................................................................................. A-1 Logs of Auger Borings B-1 through B-5 .................................................................................................... A-2…A-6 Page 1 of 16 MIGIZI GROUP, INC. PO Box 44840 PHONE (253) 537-9400 Tacoma, Washington 98448 FAX (253) 537-9401 December 11, 2024 HHJ Construction 601 St Helens Ave Tacoma, WA 98402 Attention: John Manuel Subject: Geotechnical Engineering Report Walker’s Renton Subaru 519 SW 12th Street Renton, WA 98057 Parcel Nos. 3340404265, -4148 MGI Project Z0816 Dear Mr. Manuel: Migizi Group, Inc. (MGI) is pleased to submit this report describing the results of our geotechnical engineering evaluation of the improvements proposed for the existing Walker’s Renton Subaru facility located in Renton, Washington. This report has been prepared for the exclusive use of HHJ Construction and their consultants for specific application to this project, in accordance with generally accepted geotechnical engineering practices. 1.0 SITE AND PROJECT DESCRIPTION The project site consists of two contiguous tax parcels along the south side of SW 12th Street, between Seneca Ave SW and Lind Ave SW, towards the western city limits of Renton, Washington, as shown on the enclosed Topographic and Location Map (Figure 1). The larger parcel incorporate the existing Subaru parts, service, and repair facility, while the smaller parcel contains an outbuilding for additional parts and vehicle storage. The existing Subaru facility consists of a 19,292-sf building, with a customer waiting area, parts and services department and offices, and a large repair facility with multiple vehicle lifts for servicing. The work area is irregularly shaped, encompassing a total area of approximately 2.30 acres. Asphalt pavement surrounds the primary building for vehicle storage and drive lanes, with only asphalt parking in front of the ancillary parts building. HHJ Const. – Walker’s Renton Subaru, 519 SW 12th Street, Renton, WA December 11, 2024 Geotechnical Engineering Report Z0816 Migizi Group, Inc. Page 2 of 18 Improvement plans involve the partial demolition of the existing Subaru facility, and expansion of the existing service shop to provide additional vehicle bays. The western end of the building addition will be a 2,380-sf, two story facility, constructed to expand the parts department. The building will be a pre-engineering, metal-frame structure, with slab-on-grade at the existing elevation of the current facility. Plans also call for onsite stormwater to be retained and treated onsite in a new precast concrete vault at the southeast corner of the parcel. This stormwater facility will be buried, with asphalt pavement over top for additional vehicle parking. 2.0 EXPLORATORY METHODS We explored surface and subsurface conditions at the project site on November 4-5, 2024. Our exploration and evaluation program comprised the following elements: • Surface reconnaissance of the site, • Five auger boring explorations (designated B-1 through B-5), advanced on November 4-5, 2024, and • A review of published geologic and seismologic maps and literature. Table 1 summarizes the approximate functional locations and termination depths of our subsurface explorations, and Figure 2 depicts their approximate relative locations. The following sections describe the procedures used for excavation of borings. TABLE 1 APPROXIMATE LOCATIONS AND DEPTHS OF EXPLORATIONS Exploration Functional Location Termination Depth (feet) B-1 B-2 B-3 B-4 B-5 Parking Lot, Outbuilding; 47.468761, -122.224168 SE Property corner; 47.467968, -122.223976 SW Building corner; 47.468043, -122.225023 Southern parking lot; 47.468083, -122.224413 NW customer parking; 47.468596, -122.225141 21.5 31.5 31.5 31.5 31.5 The specific number and locations of our explorations were selected by your office, in relation to the existing site features and underground utility conflicts. It should be realized that the explorations performed and utilized for this evaluation reveal subsurface conditions only at discrete locations across the project site and that actual conditions in other areas could vary. Furthermore, the nature and extent of any such variations would not become evident until additional explorations are performed or until construction activities have begun. If significant variations are observed at that time, we may need to modify our conclusions and recommendations contained in this report to reflect the actual site conditions. HHJ Const. – Walker’s Renton Subaru, 519 SW 12th Street, Renton, WA December 11, 2024 Geotechnical Engineering Report Z0816 Migizi Group, Inc. Page 3 of 18 2.1 Auger Boring Procedures Our exploratory borings were advanced through the soil with a hollow stem auger, using a track- mounted drill rig operated by an independent drilling firm working under subcontract to MGI. An engineering geologist from our firm continuously observed the borings, logged the subsurface conditions, and collected representative soil samples. All samples were stored in watertight containers and later transported to a laboratory for further visual examination. After the borings were completed, they were backfilled with bentonite chips and topped with mixed concrete and black dye to better match existing asphalt. Throughout the drilling operation, soil samples were obtained at 2½ or 5-foot depth intervals by means of the Standard Penetration Test (SPT) per ASTM:D-1586. This testing and sampling procedure consists of driving a standard 2-inch-diameter steel split-spoon sampler 18 inches into the soil with a 140-pound hammer free-falling 30 inches. The number of blows required to drive the sampler through each 6-inch interval is counted, and the total number of blows struck during the final 12 inches is recorded as the Standard Penetration Resistance, or "SPT blow count." If a total of 50 blows are struck within any 6-inch interval, the driving is stopped, and the blow count is recorded as 50 blows for the actual penetration distance. The resulting Standard Penetration Resistance values indicate the relative density of granular soils and the relative consistency of cohesive soils. The enclosed boring logs (Appendix A) describe the vertical sequence of soils and materials encountered in the borings, based primarily on our field classifications and supported by our subsequent laboratory examination and testing. Where soil contact was observed to be gradational, our logs indicate the average contact depth. Where a soil type changed between sample intervals, we inferred the contact depth. Our logs also graphically indicate the blow count, sample type, sample number, and approximate depth of each soil sample obtained from the boring, as well as any laboratory tests performed on these soil samples. If any groundwater was encountered in the borehole, the approximate groundwater depth is depicted on the boring log. Groundwater depth estimates are typically based on the moisture content of soil samples, the wet height on the drilling rods, and the water level measured in the borehole after the auger has been extracted. The soils were classified visually in general accordance with the system described in Figure A-1, which includes a key to the exploration logs. Summary logs of our explorations are included as Figures A-2 through A-6. 3.0 SITE CONDITIONS The following sections present our observations, measurements, findings, and interpretations regarding surface, soil, groundwater, infiltration and seismic conditions, and liquefaction potential. 3.1 Surface Conditions As noted above, the project site consists of two contiguous tax parcels along the south side of SW 12th Street, between Seneca Ave SW and Lind Ave SW, towards the western city limits of Renton, Washington. The larger parcel incorporates the existing Walker’s Renton Subaru facility, a 19,292- sf building used for vehicle servicing, office space, and a customer waiting area. The smaller HHJ Const. – Walker’s Renton Subaru, 519 SW 12th Street, Renton, WA December 11, 2024 Geotechnical Engineering Report Z0816 Migizi Group, Inc. Page 4 of 18 outbuilding is used for additional parts storage. The two parcels total 2.30 acres in size and create an irregular-shaped project area. The service building is surrounded by asphalt pavement used for customer parking, vehicle storage, and drive lanes, while the outbuilding has asphalt pavement along the north side of the structure. The site is situated south of the Bryn Mawr - Skyway highlands, in the valley between the Black River 2,000 feet to the west and the Cedar River 1.4 miles to the east. Topographically, the project area is flat, with minimal grade changes being observed across the paved areas. The topographic low point of the site, sitting roughly 5 to 8 feet below adjacent asphalt, occurs at the southeast corner of the property. Site vegetation is limited to immature deciduous trees and some small flower planting areas around the existing building and in small landscaping planters across the parking areas. In addition, the open stormwater facility is moderately overgrown with thick grass, blackberries, and small deciduous trees. No natural hydrologic features were observed on site, such as seeps, springs, ponds, and streams, nor were there indications of surface hydrology, such ripple marks or scouring present. The property’s existing open stormwater retention facility is located at the southeast corner. 3.2 Soil Conditions Subsurface conditions were observed through the advancement of five auger boring explorations, with three located adjacent to the existing facility, and two located towards the perimeter of the property. All five explorations revealed relatively consistent subgrade conditions, consisting of a typical asphalt section, with loose to medium dense non-native asphalt subbase. The underlying native soil consists of very soft silts and sands, grading to coarser, medium dense sands and gravels at approximately 23 feet. The alluvial deposits encountered onsite are generally associated with flood plain deposits and the historic Black River channel, which drained Lake Washington until 1916, when the opening of the Lake Washington Ship Canal lowered the lake level, causing this portion of the Black River to dry up. All explorations encountered loose to medium dense imported gravely sand between 2 to 4 thick beneath the asphalt base course. This layer of structural fill was observed to be somewhat thicker in B-4, where the exploration was drilled adjacent to a located trench line, with the bottom of the non-native soil being deeper than the surrounding gravel borrow section. Native soils that underlie the project area consist of thick beds of silt and fine to medium sand in varying amounts. This very soft and loose soil was relatively consistent across the project area and were generally found to be on the order of 5 to 11 feet thick. Some organic content (i.e. vegetation roots, small-diameter woody fibers) was also observed within thicker zones of silt-rich soil. Soils were generally observed to increase in density with both depth and increased grain size. Beginning approximately 20 feet below surrounding grade in all four of the deeper explorations (B-2 through B-5), soils graded to more dense and coarse-grained sands with varying amounts of HHJ Const. – Walker’s Renton Subaru, 519 SW 12th Street, Renton, WA December 11, 2024 Geotechnical Engineering Report Z0816 Migizi Group, Inc. Page 5 of 18 gravel. These soils were observed throughout the termination of the four noted auger bore holes down to a maximum depth of 31.5 feet below grade. In the Geologic Map of the Tacoma 1:100,000-scale Quadrangle, Washington, as prepared by the Washington State Department of Natural Resources Division of Geology and Earth Resources (WSDNR) (2015), the entire project area is mapped as containing Qa, or Holocene alluvium, which is described as loose, stratified to massively bedded fluvial silt, sand, and gravel; typically, well rounded and moderately to well sorted; locally includes sandy to silty estuarine deposits. An excerpt of this map is shown below as Figure 3. Fig. 3: Excerpt from the Geologic Map of the Tacoma 1:100,000-scale Quadrangle, Washington (WSDNR) (2015) The National Resources Conservation Services (NRCS) for King County classifies soils onsite as Ur - Urban Land, indicating that the project site and surrounding areas have been significantly modified through manmade activities. Our field observations generally correspond with the site classifications performed by both the WSDNR and the NRCS. The enclosed exploration logs (Appendix A) provide a detailed description of the soil strata encountered in our subsurface explorations. Project Site HHJ Const. – Walker’s Renton Subaru, 519 SW 12th Street, Renton, WA December 11, 2024 Geotechnical Engineering Report Z0816 Migizi Group, Inc. Page 6 of 18 3.3 Groundwater Conditions We encountered groundwater in four of the five subsurface explorations at a depth of approximately 8 to 14 feet below existing grade. Given the fact that our explorations were conducted within what is generally considered the rainy season in Western Washington (November 1 to March 31), we anticipate that groundwater levels will rise somewhat higher than that which we observed. Seasonally perched groundwater should be anticipated atop fine- grained soil lenses in close proximity to existing grade. Groundwater levels will fluctuate with localized geology and levels of precipitation. 3.4 Infiltration Conditions As indicated in the Soil Conditions section of the report, the site is underlain by alluvial soils, which can be readily subdivided into three soil horizons: upper fine-grained, intermediate fine- grained sands, and deeper coarse sands and gravels. Given the fact that groundwater levels were observed at between 8 to 14 feet below surrounding grades, the upper soil horizon is the only horizon which could potentially support infiltration. However, these soils range in composition from silty fine sand to silt, the latter of which should be considered relatively impermeable. Given the hydrogeologic setting of the project area, we do not interpret infiltration as being feasible for this project, and site produced stormwater should be managed through detention, and/or diverted to an appropriate discharge location along SW 12th St. 3.5 Seismic Conditions The site is in the Puget Sound basin which has experienced several earthquakes. A detailed description of the regional seismicity is beyond the scope of this report; however, previous regional earthquakes can be split into two general categories: 1.) large earthquakes with a moment magnitude greater than 8.0 (MW > 8.0), and 2.) modest size earthquakes with a moment magnitude generally less than 7.25 (MW < 7.25). In all cases, the thickness of the soil between the bedrock and the ground surface can change (usually amplify) the seismically induced ground motions and therefore the inertial loads acting on surface structures. “Site Class” is a classification system used by the IBC and ASCE 7 to provide some insight to the potential for ground motion amplification. The site class is based on the properties of the upper 100 feet of the soil and rock materials at the site. MGI used a combination of onsite explorations, and our review of the geologic mapping of the site to derive a site class for the site. Based on evaluation and the definitions of Site Class as provided in Table 20.3-1 of ASCE 7-16 (as required by the 2018 International Building Code), the soil conditions on this site satisfy the definition of Site Class D - Default. Our evaluation assumes the soil conditions encountered in the bottom of our explorations, and those from nearby properties, is similar to or increasing in density/consistency down to 100 feet below ground surface. The 2018 IBC considers earthquake shaking to have a 2 percent probability of exceedance in 50 years (i.e. a 2475-year return period), as the code-based design requirement. Using the third- party graphical user interface tools made available by the USGS at https://seismicmaps.org, MGI derived the design ground motions to be used for design of the structures. Our evaluation used HHJ Const. – Walker’s Renton Subaru, 519 SW 12th Street, Renton, WA December 11, 2024 Geotechnical Engineering Report Z0816 Migizi Group, Inc. Page 7 of 18 IBC 2018 as the code reference, Risk Category I/II/III, and Site Class D - Default. The results of our evaluation are provided in Table 2 (below). TABLE 2 SEISMIC DESIGN PARAMETERS Parameter Value Basis Site Class D - Default Table 20.3-1 of ASCE 7-16 SS 1.444 seismicmaps.org Fa 1.2A seismicmaps.org SMS 1.733 = Fa · SS, 2018 IBC Eqn. 16-36 SDS 1.155 = 2/3 SMS, 2018 IBC Eqn. 16-38 S1 0.492 seismicmaps.org FV 1.808B, C 2018 IBC SM1 0.889B, C = FV · S1, 2018 IBC Eqn. 16-37 SD1 0.593B, C = 2/3 SM1, 2018 IBC Eqn. 16-39 PGA 0.615g seismicmaps.org PGAM 0.737g seismicmaps.org T0 -- C Not applicable TS -- C Not applicable TL 6 sec. seismicmaps.org Notes: A. Use the value provided unless the simplified design procedure of ASCE 7 Section 12.14 is used. If this occurs, please contact our office for more information. B. Based on Table 1613.2.3(2) of the 2018 IBC – An ASCE 7-16 Chapter 21 analysis has not been performed. C. More detailed seismic design criteria are available upon request. Please contact MGI’s office for more information. 3.6 Liquefaction Potential Liquefaction is a sudden increase in pore water pressure and a sudden loss of soil shear strength caused by shear strains, as could result from an earthquake. Research has shown that saturated, loose, fine to medium sands with a fine (silt and clay) content of less than about 20 percent are most susceptible to liquefaction. Subsurface explorations performed within the confines of the project area revealed that native soils are comprised of soft silts and fine sands between 4 to 20 feet beneath the project area. Based on observed groundwater at 8 to 14 feet, these native soils will generally stay in a saturated condition. Given the geologic/hydrogeologic conditions of the project area, we interpret this site as having a moderate to high susceptibility to liquefaction. This interpretation corresponds to the findings by the King County Flood Control map of Liquefaction Susceptibility. The liquefaction susceptibility map of the immediate project area is shown in Figure 4. HHJ Const. – Walker’s Renton Subaru, 519 SW 12th Street, Renton, WA December 11, 2024 Geotechnical Engineering Report Z0816 Migizi Group, Inc. Page 8 of 18 Figure 4: Excerpt of the Liquefaction Susceptibility map of King Co. (2010). During large-scale seismic events, some degree of liquefaction and related post-construction settlement should be anticipated. To potentially mitigate these risks, we recommend constructing engineered structural fill bearing pads beneath the foundation elements, as discussed in Section 4.2 of this report. Section 4.2 provides detailed recommendations on the design and implementation of these bearing pads, including material specifications, compaction requirements, and thickness to improve load distribution and reduce settlement potential. The use of structural fill bearing pads could help improve the performance of the foundations in these challenging soil conditions, particularly regarding liquefaction-related risks. These measures may provide a practical approach to mitigating the identified challenges, depending on the specific site conditions and design requirements. 4.0 CONCLUSIONS AND RECOMMENDATIONS Improvement plans involve the partial demolition of the existing Walker’s Renton Subaru facility, expansion of the existing vehicle service area, and construction of a new 2-story addition on the Project Site HHJ Const. – Walker’s Renton Subaru, 519 SW 12th Street, Renton, WA December 11, 2024 Geotechnical Engineering Report Z0816 Migizi Group, Inc. Page 9 of 18 western end of the building. The building addition plans to be metal-framed, with a slab-on- grade at existing elevation. This addition will serve as a customer waiting area and include office space for employees. Construction plans also call for the existing asphalt around the building to be removed and replaced with a new asphalt surface. Plans call for stripping and grading the existing stormwater facility, and installation of a new concrete, pre-cast stormwater vault in the southeast corner of the property. After installation of the new facility, the vault will be filled around and over, with new asphalt pavement placed over top for expanded parking. We offer these recommendations: • Feasibility: Based on our field explorations, research and analyses, the proposed structures and pavements appear feasible from a geotechnical standpoint. • Foundation Options: Over-excavation of spread footing subgrades, to a depth of 3 to 5 feet, and the construction of structural fill bearing pads will be necessary for foundation support of the new structure. If foundation construction occurs during wet conditions, it is likely that a geotextile fabric, placed between bearing pads and native soils, will also be necessary. Recommendations for spread footings are provided in Section 4.2. • Floor Options: We recommend over-excavation of slab-on-grade floor subgrades to a minimum depth of 2 feet, then placement of properly compacted structural fill as a floor subbase. If floor construction occurs during wet conditions, it is likely that a geotextile fabric, placed between the structural fill floor subbase and native soils, will be necessary. Recommendations for slab-on-grade floors are included in Section 4.3. Fill underlying floor slabs should be compacted to 95 percent (ASTM:D-1557). • Pavement Sections: We recommend over-excavation of pavement subgrades to a minimum depth of 12 inches, then placement of properly compacted structural fill as pavement subbase. We recommend a conventional pavement section comprised of an asphalt concrete pavement over a crushed rock base course over a properly prepared (compacted) subgrade or a granular subbase, depending on subgrade conditions during pavement subgrade preparation. All soil subgrades should be thoroughly compacted, then proof-rolled with a loaded dump truck or heavy compactor. Any localized zones of yielding subgrade disclosed during this proof-rolling operation should be over-excavated to a depth of 2 feet and replaced with a suitable structural fill material. • Infiltration Conditions: As indicated in the Soil Conditions section of the report, the site is underlain by shallow, fine-grained alluvial soils. Given the fact that groundwater levels are likely to rise higher than 8 feet below existing grade, which was the shallowest groundwater encountered during explorations, the upper fine-grained soil horizon would be the only horizon which could potentially support infiltration. However, this material ranges in compositions from silty fine sand to silt, the latter of which should be considered relatively impermeable. Given the hydrogeologic setting of the project area, we do not interpret infiltration as being feasible for this project, and site produced stormwater should be managed onsite through detention, or diverted to a suitable discharge location along SW 12th St. HHJ Const. – Walker’s Renton Subaru, 519 SW 12th Street, Renton, WA December 11, 2024 Geotechnical Engineering Report Z0816 Migizi Group, Inc. Page 10 of 18 The following sections of this report present our specific geotechnical conclusions and recommendations concerning site preparation, spread footings, slab-on-grade floors, subgrade and retaining walls, asphalt pavement, and structural fill. The Washington State Department of Transportation (WSDOT) Standard Specifications and Standard Plans cited herein refer to WSDOT publications M41-10, Standard Specifications for Road, Bridge, and Municipal Construction, and M21-01, Standard Plans for Road, Bridge, and Municipal Construction, respectively. 4.1 Site Preparation Preparation of the project site should involve erosion control, temporary drainage, clearing, stripping, excavations, cutting, subgrade compaction, and filling. Erosion Control: Before new construction begins, an appropriate erosion control system should be installed. This system should collect and filter all surface water runoff through silt fencing. We anticipate a system of berms and drainage ditches around construction areas will provide an adequate collection system. Silt fencing fabric should meet the requirements of WSDOT Standard Specification 9-33.2 Table 6. In addition, silt fencing should embed a minimum of 6 inches below existing grade. An erosion control system requires occasional observation and maintenance. Specifically, holes in the filter and areas where the filter has shifted above ground surface should be replaced or repaired as soon as they are identified. Temporary Drainage: We recommend intercepting and diverting any potential sources of surface or near-surface water within the construction zones before stripping begins. Because the selection of an appropriate drainage system will depend on the water quantity, season, weather conditions, construction sequence, and contractor's methods, final decisions regarding drainage systems are best made in the field at the time of construction. Based on our current understanding of the construction plans, surface, and subsurface conditions, we anticipate that curbs, berms, or ditches placed around the work areas will adequately intercept surface water runoff. As the existing site is covered by non-permeable asphalt, sediment-laden stormwater will quickly flow into the existing stormwater system; preventing stormwater from leaving the project area should be done well ahead of any forecasted heavy precipitation events. Clearing and Stripping: After surface and near-surface water sources have been controlled, sod, topsoil, and root-rich soil should be stripped from the site. Our subsurface explorations indicate that there are no organic-rich soils onsite below the existing asphalt pavement in the vicinity of the proposed site development. Stripping is best performed during a period of dry weather. Site Excavations: Based on our explorations, we expect that the vast majority of project excavations will encounter a layer of non-native structural fill under the existing structure and asphalt pavements, underlain by soft, poorly consolidated fine-grained alluvial soils. Both soil types can be readily excavated utilizing standard excavation equipment. Dewatering: Our explorations encountered groundwater in four of five subsurface boring, with the shallowest groundwater being encountered approximately 8 feet below surrounding grades. We anticipate that an internal system of ditches, sump holes, and pumps will be adequate to HHJ Const. – Walker’s Renton Subaru, 519 SW 12th Street, Renton, WA December 11, 2024 Geotechnical Engineering Report Z0816 Migizi Group, Inc. Page 11 of 18 temporarily dewater shallow excavations. In order to dewater deeper explorations below the regional water table, expensive dewatering equipment, such as well points will need to be utilized. Temporary Cut Slopes: At this time, final designs and construction sequencing have not been completed. To facilitate project planning we provide the following general comments regarding temporary slopes: • All temporary soil slopes associated with site cutting or excavations should be adequately inclined to prevent sloughing and collapse, • Temporary cut slopes in site soils should be no steeper than 1½H:1V, and • Temporary slopes should conform to Washington Industrial Safety and Health Act (WISHA) regulations. These general guidelines are necessarily somewhat conservative (steeper temporary slopes may be possible). As the project progresses, temporary grading plans are developed, final site features are better defined, and a contractor is engaged, MGI may modify these general guidelines to allow steeper slopes. Subgrade Compaction: Exposed subgrades for the foundation of the proposed structure should be compacted to a firm, unyielding state before new concrete or fill soils are placed. Any localized zones of loose granular soils observed within a subgrade should be compacted to a density commensurate with the surrounding soils. In contrast, any organic, soft, or pumping soils observed within a subgrade should be overexcavated and replaced with suitable structural fill material. Site Filling: Our conclusions regarding the reuse of onsite soil and our comments regarding wet- weather filling are presented subsequently. Regardless of soil type, all fill should be placed and compacted according to our recommendations presented in the Structural Fill section of this report. Specifically, building pad fill soil should be compacted to a uniform density of at least 95 percent (based on ASTM:D-1557). Onsite Soils: We offer the following evaluation of these onsite soils in relation to potential use as structural fill: • Non-native Gravelly Sand: Non-native gravelly sand structural fill underlies existing pavement, and most likely the existing Subaru building. This soil may be reused for structural fill, but a geotechnical engineer should first observe the soil prior to reuse. This soil may become difficult to reuse if placed in an over-optimum moisture condition and should be protected with plastic sheeting during forecasted wet weather. • Alluvial Silt and Silty Fine Sand: The alluvial silt and silty sand that underlies the site is highly moisture sensitive and will likely become impossible to reuse during most weather conditions. As observed, soils are currently above optimum moisture content and will not compact adequately unless aerated or cement treated. Reuse is not recommended, and HHJ Const. – Walker’s Renton Subaru, 519 SW 12th Street, Renton, WA December 11, 2024 Geotechnical Engineering Report Z0816 Migizi Group, Inc. Page 12 of 18 this material should only be used for non-structural purposes, such as in landscaping areas. • Coarse-Grained Alluvial Sands and Gravels: Native coarse-grained sands and sands with gravel were encountered at significant depths (greater than 20 feet) below ground surface in most explorations. Coarse-grained soils which underlie the site are relatively impervious to moisture content variations and can be reused as structural fill under most weather conditions. Permanent Slopes: All permanent cut slopes and fill slopes should be adequately inclined to reduce long-term raveling, sloughing, and erosion. We generally recommend that no permanent slopes be steeper than 2H:1V. For all soil types, the use of flatter slopes (such as 2½H:1V) would further reduce long-term erosion and facilitate revegetation. Slope Protection: We recommend that a permanent berm, swale, or curb be constructed along the top edge of all permanent slopes to intercept surface flow. Also, a hardy vegetative groundcover should be established as soon as feasible, to further protect the slopes from runoff water erosion. Alternatively, permanent slopes could be armored with quarry spalls or a geosynthetic erosion mat. 4.2 Spread Footings and Bearing Pads In our opinion, conventional spread footings built atop structural fill bearing pads will provide adequate support for the proposed structures if the subgrade is properly prepared. We offer the following comments and recommendations for spread footing design. Footing Depths and Widths: For frost and erosion protection, the bases of all exterior footings should bear at least 18 inches below adjacent outside grades, whereas the bases of interior footings need bear only 12 inches below the surrounding slab surface level. To reduce post-construction settlements, continuous (wall) and isolated (column) footings should be at least 18 and 24 inches wide, respectively. Bearing Subgrades: Given the poor consolidation of near surface soils in the immediate vicinity of the project area, structural fill bearing pads 3 to 5 feet thick and compacted to a density of at least 95 percent (based on ASTM:D-1557), should underlie all foundation elements on this site. If foundation construction occurs during wet conditions, a geotextile fabric may be necessary between the bearing pad and native soils. We should be consulted if any new foundations are to be placed adjacent to existing foundations. Refer to the Structural Fill section of this report for more detail. In general, before footing concrete is placed, any localized zones of loose soils exposed across the footing subgrades should be compacted to a firm, unyielding condition, and any localized zones of soft, organic, or debris-laden soils should be over-excavated and replaced with suitable structural fill. Lateral Over excavations: Because foundation stresses are transferred outward as well as downward into the bearing soils, all structural fill placed under footings, should extend HHJ Const. – Walker’s Renton Subaru, 519 SW 12th Street, Renton, WA December 11, 2024 Geotechnical Engineering Report Z0816 Migizi Group, Inc. Page 13 of 18 horizontally outward from the edge of each footing. This horizontal distance should be equal to the depth of placed fill. Therefore, placed fill that extends 3 feet below the bottom elevation of the foundation should also extend 3 feet outward, in both directions, from the footing edges. Subgrade Observation: All footing subgrades should consist of firm, unyielding, native soils, or structural fill materials that have been compacted to a density of at least 95 percent (based on ASTM:D-1557). Footings should never be cast atop loose, soft, or frozen soil, slough, debris, existing uncontrolled fill, or surfaces covered by standing water. Bearing Pressures: For static loading purposes, footings that bear on dense, properly prepared structural fill bearing pads can be designed for maximum allowable soil bearing pressures listed in the table on the following page: Bearing Pad Thickness (feet) Allowable Bearing Pressure (psf) 3 1,500 4 2,000 5 2,500 A one-third increase in allowable soil bearing capacity may be used for short-term loads created by seismic or wind related activities. Footing Settlements: Assuming that structural fill soils are compacted to a medium dense or denser state, we estimate that total post-construction settlements of properly designed footings bearing on properly prepared subgrades will not exceed 1 inch under static conditions. Differential settlements for comparably loaded elements may approach one-half of the actual total settlement over horizontal distances of approximately 50 feet. Footing Backfill: We recommend all footing excavations be backfilled on both sides of the footings and stem walls after the concrete has been cured. This will provide erosion protection and lateral load resistance. Only imported structural fill should be used for this purpose, contingent on suitable moisture content at the time of placement. Onsite native fine-grained soils should not be used. Regardless of soil type, all footing backfill soil should be compacted to a density of at least 90 percent (based on ASTM:D-1557). 4.3 Slab-On-Grade Floors In our opinion, soil-supported slab-on-grade floors can be used for the planned structures if the subgrades are properly prepared. We offer the following comments and recommendations concerning slab-on-grade floors. Floor Subbase: Given the poor consolidation of near surface soil observed across the project area, we recommend over-excavation of slab-on-grade floor subgrades to a minimum depth of 2 feet, with placement and thorough compaction of structural fill as a floor subbase. If floor construction occurs during wet conditions, it is likely that a geotextile fabric, placed between the structural fill HHJ Const. – Walker’s Renton Subaru, 519 SW 12th Street, Renton, WA December 11, 2024 Geotechnical Engineering Report Z0816 Migizi Group, Inc. Page 14 of 18 floor subbase and native soils, will be necessary. All subbase fill should be compacted to a density of at least 95 percent (based on ASTM:D-1557). Capillary Break and Vapor Barrier: To retard the upward wicking of moisture beneath the floor slab, we recommend that a capillary break be placed over the floor subbase and beneath the slab vapor barrier. Ideally, this capillary break would consist of a 4-inch-thick layer of pea gravel or other clean, uniform, well-rounded gravel, such as “Gravel Backfill for Drains” per WSDOT Standard Specification 9-03.12(4), but clean angular gravel can be used if it adequately prevents capillary wicking. A manufactured product, such as 5/8 inch minus crushed rock, should not be used as cap break, as the “minus” component of the crushed rock facilitates moisture wicking beneath a poured slab. In addition, a layer of plastic sheeting (such as Crosstuff, Visqueen, or Moistop) should be placed over the capillary break to serve as a vapor barrier. During subsequent casting of the concrete slab, the contractor should exercise care to avoid puncturing this vapor barrier. 4.4 Drainage Systems In our opinion, the proposed structure should be provided with a permanent drainage system to reduce the risk of future moisture problems, given the low permeability nature of the shallow non- native soils which underlie the project area. We offer the following recommendations and comments for drainage design and construction purposes. Perimeter Drains: We recommend that the structure be encircled with a perimeter drain system to collect seepage water. This drain should consist of a 6-inch-diameter perforated pipe within an envelope of pea gravel or washed rock, extending at least 6 inches on all sides of the pipe, and the gravel envelope should be wrapped with filter fabric to reduce migration of fines from the surrounding soils. Ideally, the drain invert would be installed no more than 8 inches above the base of the perimeter footings. Discharge Considerations: If possible, all perimeter drains should discharge to a sewer system, the proposed stormwater facility, or other suitable location by gravity flow. Check valves should be installed along any drainpipes that discharge to a sewer system to prevent sewage backflow into the drain system. If gravity flow is not feasible, a pump system is recommended to discharge any water that enters the drainage system. Runoff Water: Roof- and surface-runoff water should not discharge into the perimeter drain system. Instead, these sources should discharge into separate tightline pipes and be routed away from the structure to a storm drain or other appropriate location. Grading and Capping: Final site grades should slope downward away from the structure so that runoff water will flow by gravity to suitable collection points, rather than ponding near the building. Ideally, the area surrounding the building will be capped with concrete, asphalt, or low- permeability (silty) soils to minimize or preclude surface-water infiltration. HHJ Const. – Walker’s Renton Subaru, 519 SW 12th Street, Renton, WA December 11, 2024 Geotechnical Engineering Report Z0816 Migizi Group, Inc. Page 15 of 18 4.5 Asphalt Pavement Plans call for the eventual replacement of existing asphalt across the project area after major construction operations have been completed. We offer the following comments and recommendations for pavement design and construction. Subgrade Preparation: We recommend over-excavation of pavement subgrades to depths of 12 or 24 inches, based on geotechnical observation, then placement of properly compacted structural fill as pavement subbase. If construction occurs during wet conditions, it is likely that a geotextile fabric, placed between the structural fill pavement subbase and native soils, will be necessary. We recommend a conventional pavement section comprised of an asphalt concrete pavement over a crushed rock base course over a properly prepared (compacted) subgrade or a granular subbase, depending on subgrade conditions during pavement subgrade preparation. All soil subgrades should be thoroughly compacted, then proof-rolled with a loaded dump truck or heavy compactor. Any localized zones of yielding subgrade disclosed during this proof-rolling operation should be over-excavated to a depth of 2 feet and replaced with a suitable structural fill material. All structural fill should be compacted according to our recommendations given in the Structural Fill section. Specifically, the upper 2 feet of soils underlying pavement section should be compacted to at least 95 percent (based on ASTM D-1557), and all soils below 2 feet should be compacted to at least 90 percent. Pavement Materials: We recommend using imported washed crushed rock, such as "Crushed Surfacing Base Course” per WSDOT Standard Specification 9-03.9(3) but with a fines content of less than 5 percent passing the No. 200 Sieve for the asphalt sections base course. Observations made during explorations do not indicate a need for a pavement subbase. We recommend using imported, clean, well-graded sand and gravel such as “Ballast” or “Gravel Borrow” per WSDOT Standard Specifications 9-03.9(1) and 9-03.14, respectively, should a subbase course be needed based on geotechnical observations. Conventional Asphalt Sections: A conventional pavement section typically comprises an asphalt concrete pavement over a crushed rock base course. We recommend using the following conventional pavement sections: Minimum Thickness Pavement Course Parking Areas High Traffic Driveways Asphalt Concrete Pavement 3 inches 4 inches Crushed Rock Base 6 inches 8 inches Granular Fill Subbase (if needed) 12 inches 24 inches Compaction and Observation: All subbase and base course material should be compacted to at least 95 percent of the Modified Proctor maximum dry density (ASTM D-1557), and all asphalt concrete should be compacted to at least 92 percent of the Rice value (ASTM D-2041). We recommend that an MGI representative be retained to observe the compaction of each course before any overlying layer is placed. For the subbase and pavement course, compaction is best HHJ Const. – Walker’s Renton Subaru, 519 SW 12th Street, Renton, WA December 11, 2024 Geotechnical Engineering Report Z0816 Migizi Group, Inc. Page 16 of 18 observed by means of frequent density testing. For the base course, methodology observations and hand-probing are more appropriate than density testing. Pavement Life and Maintenance: No asphalt pavement is maintenance-free. The above-described pavement sections present our minimum recommendations for an average level of performance during a 20-year design life; therefore, an average level of maintenance will likely be required. Furthermore, a 20-year pavement life typically assumes that an overlay will be placed after about 10 years. Thicker asphalt and/or thicker base and subbase courses would offer better long-term performance but would cost more initially; thinner courses would be more susceptible to “alligator” cracking and other failure modes. As such, pavement design can be considered a compromise between a high initial cost and low maintenance costs versus a low initial cost and higher maintenance costs. 4.6 Structural Fill The term "structural fill" refers to any material placed under foundations, retaining walls, slab-on- grade floors, sidewalks, pavements, and other structures. Our comments, conclusions, and recommendations concerning structural fill are presented in the following paragraphs. Materials: Typical structural fill materials include clean sand, gravel, pea gravel, washed rock, crushed rock, well-graded mixtures of sand and gravel (commonly called "gravel borrow" or "pit- run"), and miscellaneous mixtures of silt, sand, and gravel. Import materials meeting WSDOT Standard Specification 9-03.14(1) gravel borrow will be satisfactory for use as structural fill during dry weather. Recycled asphalt, concrete, and glass, which are derived from pulverizing the parent materials, are also potentially useful as structural fill in certain applications. Soils used for structural fill should not contain any organic matter or debris, nor any individual particles greater than about 6 inches in diameter. Fill Placement: Clean sand, gravel, crushed rock, soil mixtures, and recycled materials should be placed in horizontal lifts not exceeding 8 inches in loose thickness, and each lift should be thoroughly compacted with a mechanical compactor. Compaction Criteria: Using the Modified Proctor test (ASTM:D-1557) as a standard, we recommend that structural fill used for various onsite applications be compacted to the following minimum densities: Fill Application Minimum Compaction Footing subgrade and bearing pad Foundation backfill Asphalt pavement base Asphalt pavement subgrade (upper 2 feet) Asphalt pavement subgrade (below 2 feet) 95 percent 90 percent 95 percent 95 percent 90 percent Subgrade Observation and Compaction Testing: Regardless of material or location, all structural fill should be placed over firm, unyielding subgrades prepared in accordance with the Site HHJ Const. – Walker’s Renton Subaru, 519 SW 12th Street, Renton, WA December 11, 2024 Geotechnical Engineering Report Z0816 Migizi Group, Inc. Page 17 of 18 Preparation section of this report. The condition of all subgrades should be observed by geotechnical personnel before filling or construction begins. Also, fill soil compaction should be verified by means of in-place density tests performed during fill placement so that adequacy of soil compaction efforts may be evaluated as earthwork progresses. Soil Moisture Considerations: The suitability of soils used for structural fill depends primarily on their grain-size distribution and moisture content when they are placed. As the "fines" content (that soil fraction passing the U.S. No. 200 Sieve) increases, soils become more sensitive to small changes in moisture content. Soils containing more than about 5 percent fines (by weight) cannot be consistently compacted to a firm, unyielding condition when the moisture content is more than 2 percentage points above or below optimum. For fill placement during wet-weather site work, we recommend using "clean" fill, which refers to soils that have a fines content of 5 percent or less (by weight) based on the soil fraction passing the U.S. No. 4 Sieve. 5.0 RECOMMENDED ADDITIONAL SERVICES Because the future performance and integrity of the structural elements will depend largely on proper site preparation, drainage, fill placement, and construction procedures, monitoring and testing by experienced geotechnical personnel should be considered an integral part of the construction process. Subsequently, we recommend that MGI be retained to provide the following post-report services: • Review all construction plans and specifications to verify that our design criteria presented in this report have been properly integrated into the design, • Prepare a letter summarizing all review comments (if required), • Check all completed subgrades for footings and slab-on-grade floors before concrete is poured, in order to verify their bearing capacity, and, • Prepare a post-construction letter summarizing all field observations, inspections, and test results (if required). HHJ Const. – Walker’s Renton Subaru, 519 SW 12th Street, Renton, WA December 11, 2024 Geotechnical Engineering Report Z0816 Migizi Group, Inc. Page 18 of 18 6.0 CLOSURE The conclusions and recommendations presented in this report are based, in part, on the explorations that we observed for this study; therefore, if variations in the subgrade conditions are observed at a later time, we may need to modify this report to reflect those changes. Also, because the future performance and integrity of the project elements depend largely on proper initial site preparation, drainage, and construction procedures, monitoring and testing by experienced geotechnical personnel should be considered an integral part of the construction process. MGI is available to provide geotechnical monitoring of soils throughout construction. We appreciate the opportunity to be of service on this project. If you have any questions regarding this report or any aspects of the project, please feel free to contact our office. Respectfully submitted, MIGIZI GROUP, INC. Randall V. Conger-Best, L.G. James E. Brigham, P.E. Senior Staff Geologist Senior Principal Engineer APPROXIMATE SITE LOCATION P.O. Box 44840 Tacoma, WA 98448 Location Job Number Figure DateTitle 519 SW 12th Street Renton, WA 98057 Topographic and Location Map 1 12/01/24 Z0816 222000mmm 666000fffttt +– 47.46835 -122.22446 Degrees JOB NO. PROJECT: SHEET TITLE: FILE: FIGURE: SCALE: DATE: CHECKED BY: DRAWN BY: DESIGNER: Migizi Group, Inc. PO Box 44840 Tacoma, WA 98448 253-537-9400 253-537-9401 fax www.migizigroup.com 519 SW 12th Street Renton, WA 98057 Site and Exploration Plan Nov. 08, 2024 JEB RVCB RVCB Z0816 NTS 2 Fig2.dwg APPENDIX A SOIL CLASSIFICATION CHART AND KEY TO TEST DATA LOGS OF BORINGS CLAYEY GRAVELS, POORLY GRADED GRAVEL-SAND-CLAY MIXTURES SILTS AND CLAYS CO A R S E G R A I N E D S O I L S Mo r e t h a n H a l f > # 2 0 0 s i e v e LIQUID LIMIT LESS THAN 50 LIQUID LIMIT GREATER THAN 50 CLEAN GRAVELS WITH LITTLE OR NO FINES GRAVELS WITH OVER 15% FINES CLEAN SANDS WITH LITTLE OR NO FINESMORE THAN HALF COARSE FRACTION IS SMALLER THAN NO. 4 SIEVE MORE THAN HALF COARSE FRACTION IS LARGER THAN NO. 4 SIEVE INORGANIC SILTS, MICACEOUS OR DIATOMACIOUS FINE SANDY OR SILTY SOILS, ELASTIC SILTS ORGANIC CLAYS AND ORGANIC SILTY CLAYS OF LOW PLASTICITY OH INORGANIC SILTS AND VERY FINE SANDS, ROCK FLOUR,SILTY OR CLAYEY FINE SANDS, OR CLAYEY SILTS WITH SLIGHT PLASTICITY CH SILTY GRAVELS, POORLY GRADED GRAVEL-SAND-SILT MIXTURES SANDS SILTS AND CLAYS Figure A-1 INORGANIC CLAYS OF LOW TO MEDIUM PLASTICITY, GRAVELLY CLAYS, SANDY CLAYS, SILTY CLAYS,LEAN CLAYS E3RA R-Value Sieve Analysis Swell Test Cyclic Triaxial Unconsolidated Undrained Triaxial Torvane Shear Unconfined Compression (Shear Strength, ksf) Wash Analysis (with % Passing No. 200 Sieve) Water Level at Time of Drilling Water Level after Drilling(with date measured) RV SA SW TC TX TV UC (1.2) WA (20) Modified California Split Spoon Pushed Shelby Tube Auger Cuttings Grab Sample Sample Attempt with No Recovery Chemical Analysis Consolidation Compaction Direct Shear Permeability Pocket Penetrometer CA CN CP DS PM PP PtHIGHLY ORGANIC SOILS TYPICAL NAMES GRAVELS ORGANIC CLAYS OF MEDIUM TO HIGH PLASTICITY, ORGANIC SILTS WELL GRADED GRAVELS, GRAVEL-SAND MIXTURES MAJOR DIVISIONS PEAT AND OTHER HIGHLY ORGANIC SOILS WELL GRADED SANDS, GRAVELLY SANDS POORLY GRADED SANDS, GRAVELLY SANDS SILTY SANDS, POOORLY GRADED SAND-SILT MIXTURES CLAYEY SANDS, POORLY GRADED SAND-CLAY MIXTURES POORLY GRADED GRAVELS, GRAVEL-SAND MIXTURES SOIL CLASSIFICATION CHART AND KEY TO TEST DATA GW GP GM GC SW SP SM SC ML FI N E G R A I N E D S O I L S Mo r e t h a n H a l f < # 2 0 0 s i e v e LG D A N N N N 0 2 G I N T U S L A B . G P J 1 1 / 4 / 0 5 INORGANIC CLAYS OF HIGH PLASTICITY, FAT CLAYS CL OL MH SANDS WITH OVER 15% FINES Migizi Group, Inc. SS S-1 SS S-2 SS S-3 SS S-4 20.8 20.3 16.8 14.0 12.0 11.5 5-3-2 (5) 1-2-8 (10) 5-7-9 (16) 3-3-5 (8) GP SP ML SP GP SP 0.3 0.7 4.3 7.0 9.0 9.5 Asphalt (GP) 5/8 inch minus crushed rock (Moist, Dense)Imported crushed surfacing base course (SP) Brown gravelly sand (Moist, Medium Dense)Imported asphalt section subbase (ML) Gray silt with gravel and sand (Moist, Very Soft) (SP) Brown gravelly sand (Moist, Medium Dense) (GP) Gray gravel with sand (Moist, Medium Dense) Coarse-grained lens (SP) Dark gray medium to coarse sand with fine gravel (Moist, Loose) NOTES LOGGED BY RVCB DRILLING METHOD Track Mounted Drill Rig DRILLING CONTRACTOR Holocene Drilling GROUND WATER LEVELS: CHECKED BY JEB DATE STARTED 11/4/24 COMPLETED 11/4/24 AT TIME OF DRILLING 10.00 ft / Elev 11.00 ft AT END OF DRILLING --- AFTER DRILLING --- HOLE SIZE 4.25" HSAGROUND ELEVATION 21 ft SA M P L E T Y P E NU M B E R DE P T H (f t ) 0.0 2.5 5.0 7.5 10.0 (Continued Next Page) PAGE 1 OF 2 Figure A-2 BORING NUMBER B-1 CLIENT HHJ Construction PROJECT NUMBER Z0816 PROJECT NAME Walker's Renton Subaru PROJECT LOCATION 519 SW 12th Street, Renton WA CO P Y O F G E N E R A L B H / T P L O G S - F I G U R E . G D T - 1 1 / 2 6 / 2 4 1 2 : 4 0 - C : \ U S E R S \ J E S S I C A B I Z A K \ D E S K T O P \ T E S T P I T S A N D B O R I N G S - G I N T \ Z 0 8 1 6 \ Z 0 8 1 6 B O R I N G L O G . G P J Migizi Group, Inc. PO Box 44840 Tacoma, WA 98448 Telephone: 253-537-9400 RE C O V E R Y ( i n ) (R Q D ) BL O W CO U N T S (N V A L U E ) U. S . C . S . GR A P H I C LO G MATERIAL DESCRIPTION SS S-5 SS S-6 5.0 3.0 -0.5 1-0-1 (1) 11-10-7 (17) SP ML SP 16.0 18.0 21.5 (SP) Dark gray medium to coarse sand with fine gravel (Moist, Loose) (continued) Grades to medium to coarse sand (ML) Gray fine sandy silt (Moist, Very Soft) (SP) Gray coarse sand with fine gravel (Moist, Medium Dense) Observed zone of heaving sands Bottom of borehole at 21.5 feet. SA M P L E T Y P E NU M B E R DE P T H (f t ) 12.5 15.0 17.5 20.0 PAGE 2 OF 2 Figure A-2 BORING NUMBER B-1 CLIENT HHJ Construction PROJECT NUMBER Z0816 PROJECT NAME Walker's Renton Subaru PROJECT LOCATION 519 SW 12th Street, Renton WA CO P Y O F G E N E R A L B H / T P L O G S - F I G U R E . G D T - 1 1 / 2 6 / 2 4 1 2 : 4 0 - C : \ U S E R S \ J E S S I C A B I Z A K \ D E S K T O P \ T E S T P I T S A N D B O R I N G S - G I N T \ Z 0 8 1 6 \ Z 0 8 1 6 B O R I N G L O G . G P J Migizi Group, Inc. PO Box 44840 Tacoma, WA 98448 Telephone: 253-537-9400 RE C O V E R Y ( i n ) (R Q D ) BL O W CO U N T S (N V A L U E ) U. S . C . S . GR A P H I C LO G MATERIAL DESCRIPTION SS S-1 SS S-2 SS S-3 SS S-4 29.8 29.3 28.0 23.0 21.0 3-2-1 (3) 1-0-0 (0) 15-9-9 (18) 13-7-2 (9) GP SP ML SP SP 0.3 0.7 2.0 7.0 9.0 Asphalt (GP) 5/8 inch minus crushed rock (Moist, Dense)Imported crushed surfacing base course (SP) Brown gravelly sand (Moist, Medium Dense)Imported asphalt section subbase (ML) Mottled brown/gray silt with fine sand (Moist, Very Soft) (SP) Brown/gray sand with gravel (Moist, Loose) (SP) Gray fine to medium sand (Moist, Loose) NOTES LOGGED BY RVCB DRILLING METHOD Track Mounted Drill Rig DRILLING CONTRACTOR Holocene Drilling GROUND WATER LEVELS: CHECKED BY JEB DATE STARTED 11/4/24 COMPLETED 11/4/24 AT TIME OF DRILLING 14.00 ft / Elev 16.00 ft AT END OF DRILLING --- AFTER DRILLING --- HOLE SIZE 4.25" HSAGROUND ELEVATION 30 ft SA M P L E T Y P E NU M B E R DE P T H (f t ) 0.0 2.5 5.0 7.5 10.0 (Continued Next Page) PAGE 1 OF 3 Figure A-3 BORING NUMBER B-2 CLIENT HHJ Construction PROJECT NUMBER Z0816 PROJECT NAME Walker's Renton Subaru PROJECT LOCATION 519 SW 12th Street, Renton WA CO P Y O F G E N E R A L B H / T P L O G S - F I G U R E . G D T - 1 1 / 2 6 / 2 4 1 2 : 4 0 - C : \ U S E R S \ J E S S I C A B I Z A K \ D E S K T O P \ T E S T P I T S A N D B O R I N G S - G I N T \ Z 0 8 1 6 \ Z 0 8 1 6 B O R I N G L O G . G P J Migizi Group, Inc. PO Box 44840 Tacoma, WA 98448 Telephone: 253-537-9400 RE C O V E R Y ( i n ) (R Q D ) BL O W CO U N T S (N V A L U E ) U. S . C . S . GR A P H I C LO G MATERIAL DESCRIPTION SS S-5 SS S-6 15.0 6.0 1-0-1 (1) 2-1-2 (3) SP ML SP 15.0 24.0 (SP) Gray fine to medium sand (Moist, Loose) (continued) (ML) Gray organic-rich silt with fine sand (Moist, Very Soft) (SP) Gray fine to medium gravelly coarse sand (Moist, Medium Dense) SA M P L E T Y P E NU M B E R DE P T H (f t ) 12.5 15.0 17.5 20.0 22.5 25.0 (Continued Next Page) PAGE 2 OF 3 Figure A-3 BORING NUMBER B-2 CLIENT HHJ Construction PROJECT NUMBER Z0816 PROJECT NAME Walker's Renton Subaru PROJECT LOCATION 519 SW 12th Street, Renton WA CO P Y O F G E N E R A L B H / T P L O G S - F I G U R E . G D T - 1 1 / 2 6 / 2 4 1 2 : 4 0 - C : \ U S E R S \ J E S S I C A B I Z A K \ D E S K T O P \ T E S T P I T S A N D B O R I N G S - G I N T \ Z 0 8 1 6 \ Z 0 8 1 6 B O R I N G L O G . G P J Migizi Group, Inc. PO Box 44840 Tacoma, WA 98448 Telephone: 253-537-9400 RE C O V E R Y ( i n ) (R Q D ) BL O W CO U N T S (N V A L U E ) U. S . C . S . GR A P H I C LO G MATERIAL DESCRIPTION SSS-7 SS S-8 1.0 -1.0 -1.5 12-10-20(30) 16-21-21 (42) SP SP GP 29.0 31.0 31.5 (SP) Gray fine to medium gravelly coarse sand (Moist, Medium Dense) (continued) (SP) Gray medium to coarse sand (Moist, Dense) (GP) Gray medium gravel (Moist, Dense) Bottom of borehole at 31.5 feet. SA M P L E T Y P E NU M B E R DE P T H (f t ) 27.5 30.0 PAGE 3 OF 3 Figure A-3 BORING NUMBER B-2 CLIENT HHJ Construction PROJECT NUMBER Z0816 PROJECT NAME Walker's Renton Subaru PROJECT LOCATION 519 SW 12th Street, Renton WA CO P Y O F G E N E R A L B H / T P L O G S - F I G U R E . G D T - 1 1 / 2 6 / 2 4 1 2 : 4 0 - C : \ U S E R S \ J E S S I C A B I Z A K \ D E S K T O P \ T E S T P I T S A N D B O R I N G S - G I N T \ Z 0 8 1 6 \ Z 0 8 1 6 B O R I N G L O G . G P J Migizi Group, Inc. PO Box 44840 Tacoma, WA 98448 Telephone: 253-537-9400 RE C O V E R Y ( i n ) (R Q D ) BL O W CO U N T S (N V A L U E ) U. S . C . S . GR A P H I C LO G MATERIAL DESCRIPTION SS S-1 SS S-2 SS S-3 SS S-4 29.8 29.3 28.0 19.0 4-2-2 (4) 2-2-1 (3) 1-0-0 (0) 0 GP SP ML SP 0.3 0.7 2.0 11.0 Asphalt (GP) 5/8 inch minus crushed rock (Moist, Dense)Imported crushed surfacing base course (SP) Brown gravelly sand (Moist, Medium Dense)Imported asphalt section subbase (ML) Gray silt with fine sand (Moist, Very Soft) (SP) Gray fine to medium sand (Moist, Loose) NOTES LOGGED BY RVCB DRILLING METHOD Track Mounted Drill Rig DRILLING CONTRACTOR Holocene Drilling GROUND WATER LEVELS: CHECKED BY JEB DATE STARTED 11/4/24 COMPLETED 11/4/24 AT TIME OF DRILLING 10.00 ft / Elev 20.00 ft AT END OF DRILLING --- AFTER DRILLING --- HOLE SIZE 4.25" HSAGROUND ELEVATION 30 ft SA M P L E T Y P E NU M B E R DE P T H (f t ) 0.0 2.5 5.0 7.5 10.0 (Continued Next Page) PAGE 1 OF 3 Figure A-4 BORING NUMBER B-3 CLIENT HHJ Construction PROJECT NUMBER Z0816 PROJECT NAME Walker's Renton Subaru PROJECT LOCATION 519 SW 12th Street, Renton WA CO P Y O F G E N E R A L B H / T P L O G S - F I G U R E . G D T - 1 1 / 2 6 / 2 4 1 2 : 4 0 - C : \ U S E R S \ J E S S I C A B I Z A K \ D E S K T O P \ T E S T P I T S A N D B O R I N G S - G I N T \ Z 0 8 1 6 \ Z 0 8 1 6 B O R I N G L O G . G P J Migizi Group, Inc. PO Box 44840 Tacoma, WA 98448 Telephone: 253-537-9400 RE C O V E R Y ( i n ) (R Q D ) BL O W CO U N T S (N V A L U E ) U. S . C . S . GR A P H I C LO G MATERIAL DESCRIPTION SS S-5 SS S-6 10.0 7.0 3-2-3 (5) 1-1-0 (1) SP ML SP 20.0 23.0 (SP) Gray fine to medium sand (Moist, Loose) (continued) (ML) Gray organic-rich silt (Moist, Very Soft) (SP) Gray fine to medium gravelly coarse sand (Moist, Loose) SA M P L E T Y P E NU M B E R DE P T H (f t ) 12.5 15.0 17.5 20.0 22.5 25.0 (Continued Next Page) PAGE 2 OF 3 Figure A-4 BORING NUMBER B-3 CLIENT HHJ Construction PROJECT NUMBER Z0816 PROJECT NAME Walker's Renton Subaru PROJECT LOCATION 519 SW 12th Street, Renton WA CO P Y O F G E N E R A L B H / T P L O G S - F I G U R E . G D T - 1 1 / 2 6 / 2 4 1 2 : 4 0 - C : \ U S E R S \ J E S S I C A B I Z A K \ D E S K T O P \ T E S T P I T S A N D B O R I N G S - G I N T \ Z 0 8 1 6 \ Z 0 8 1 6 B O R I N G L O G . G P J Migizi Group, Inc. PO Box 44840 Tacoma, WA 98448 Telephone: 253-537-9400 RE C O V E R Y ( i n ) (R Q D ) BL O W CO U N T S (N V A L U E ) U. S . C . S . GR A P H I C LO G MATERIAL DESCRIPTION SSS-7 SS S-8 3.0 -1.0 -1.5 7-2-7(9) 7-16-20 (36) SP SP SP 27.0 31.0 31.5 (SP) Gray fine to medium gravelly coarse sand (Moist, Loose) (continued) Soils grade to medium dense (SP) Gray medium to coarse sand (Moist, Dense) (SP) Brown coarse sandy fine to medium gravel (Moist, Dense) Bottom of borehole at 31.5 feet. SA M P L E T Y P E NU M B E R DE P T H (f t ) 27.5 30.0 PAGE 3 OF 3 Figure A-4 BORING NUMBER B-3 CLIENT HHJ Construction PROJECT NUMBER Z0816 PROJECT NAME Walker's Renton Subaru PROJECT LOCATION 519 SW 12th Street, Renton WA CO P Y O F G E N E R A L B H / T P L O G S - F I G U R E . G D T - 1 1 / 2 6 / 2 4 1 2 : 4 0 - C : \ U S E R S \ J E S S I C A B I Z A K \ D E S K T O P \ T E S T P I T S A N D B O R I N G S - G I N T \ Z 0 8 1 6 \ Z 0 8 1 6 B O R I N G L O G . G P J Migizi Group, Inc. PO Box 44840 Tacoma, WA 98448 Telephone: 253-537-9400 RE C O V E R Y ( i n ) (R Q D ) BL O W CO U N T S (N V A L U E ) U. S . C . S . GR A P H I C LO G MATERIAL DESCRIPTION SS S-1 SS S-2 SS S-3 SS S-4 29.8 29.3 26.5 23.5 19-22-13 (35) 6-5-5 (10) 2-0-1 (1) 1-0-0 (0) GP SP SP ML 0.3 0.7 3.5 6.5 Asphalt (GP) 5/8 inch minus crushed rock (Moist, Dense)Imported crushed surfacing base course (SP) Brown gravelly sand (Moist, Medium Dense)Imported asphalt section subbase (SP) Brown gravelly sand (Moist, Loose) Imported trench backfill soils (ML) Gray silt with fine sand (Moist, Very Soft) Soils grade to fine sandy silt NOTES LOGGED BY RVCB DRILLING METHOD Track Mounted Drill Rig DRILLING CONTRACTOR Holocene Drilling GROUND WATER LEVELS: CHECKED BY JEB DATE STARTED 11/5/24 COMPLETED 11/5/24 AT TIME OF DRILLING --- AT END OF DRILLING --- AFTER DRILLING --- HOLE SIZE 4.25" HSAGROUND ELEVATION 30 ft SA M P L E T Y P E NU M B E R DE P T H (f t ) 0.0 2.5 5.0 7.5 10.0 (Continued Next Page) PAGE 1 OF 3 Figure A-5 BORING NUMBER B-4 CLIENT HHJ Construction PROJECT NUMBER Z0816 PROJECT NAME Walker's Renton Subaru PROJECT LOCATION 519 SW 12th Street, Renton WA CO P Y O F G E N E R A L B H / T P L O G S - F I G U R E . G D T - 1 1 / 2 6 / 2 4 1 2 : 4 0 - C : \ U S E R S \ J E S S I C A B I Z A K \ D E S K T O P \ T E S T P I T S A N D B O R I N G S - G I N T \ Z 0 8 1 6 \ Z 0 8 1 6 B O R I N G L O G . G P J Migizi Group, Inc. PO Box 44840 Tacoma, WA 98448 Telephone: 253-537-9400 RE C O V E R Y ( i n ) (R Q D ) BL O W CO U N T S (N V A L U E ) U. S . C . S . GR A P H I C LO G MATERIAL DESCRIPTION SS S-5 SS S-6 16.0 9.0 5.0 0 0-0-5 (5) ML ML SP-SM SP 14.0 21.0 25.0 (ML) Gray silt with fine sand (Moist, Very Soft) (continued) (ML) Gray organic-rich silt with fine sand (Moist, Very Soft) Soils grade to firm (SP-SM) Fine to coarse sand with silt (Moist, Medium Dense) (SP) Gray medium to coarse sand with fine gravel (Moist, Dense) SA M P L E T Y P E NU M B E R DE P T H (f t ) 12.5 15.0 17.5 20.0 22.5 25.0 (Continued Next Page) PAGE 2 OF 3 Figure A-5 BORING NUMBER B-4 CLIENT HHJ Construction PROJECT NUMBER Z0816 PROJECT NAME Walker's Renton Subaru PROJECT LOCATION 519 SW 12th Street, Renton WA CO P Y O F G E N E R A L B H / T P L O G S - F I G U R E . G D T - 1 1 / 2 6 / 2 4 1 2 : 4 0 - C : \ U S E R S \ J E S S I C A B I Z A K \ D E S K T O P \ T E S T P I T S A N D B O R I N G S - G I N T \ Z 0 8 1 6 \ Z 0 8 1 6 B O R I N G L O G . G P J Migizi Group, Inc. PO Box 44840 Tacoma, WA 98448 Telephone: 253-537-9400 RE C O V E R Y ( i n ) (R Q D ) BL O W CO U N T S (N V A L U E ) U. S . C . S . GR A P H I C LO G MATERIAL DESCRIPTION SSS-7 SS S-8 -1.0 -1.5 1-7-17(24) 10-21-30 (51) SP GP 31.0 31.5 (SP) Gray medium to coarse sand with fine gravel (Moist, Dense) (continued) Soils grade to medium to coarse gravel (GP) Gray/brown coarse sandy fine to coarse gravel (Moist, Dense) Bottom of borehole at 31.5 feet. SA M P L E T Y P E NU M B E R DE P T H (f t ) 27.5 30.0 PAGE 3 OF 3 Figure A-5 BORING NUMBER B-4 CLIENT HHJ Construction PROJECT NUMBER Z0816 PROJECT NAME Walker's Renton Subaru PROJECT LOCATION 519 SW 12th Street, Renton WA CO P Y O F G E N E R A L B H / T P L O G S - F I G U R E . G D T - 1 1 / 2 6 / 2 4 1 2 : 4 0 - C : \ U S E R S \ J E S S I C A B I Z A K \ D E S K T O P \ T E S T P I T S A N D B O R I N G S - G I N T \ Z 0 8 1 6 \ Z 0 8 1 6 B O R I N G L O G . G P J Migizi Group, Inc. PO Box 44840 Tacoma, WA 98448 Telephone: 253-537-9400 RE C O V E R Y ( i n ) (R Q D ) BL O W CO U N T S (N V A L U E ) U. S . C . S . GR A P H I C LO G MATERIAL DESCRIPTION SS S-1 SS S-2 SS S-3 SS S-4 29.8 29.3 27.5 22.0 20.0 1-1-1 (2) 1-2-1 (3) 1-1-1 (2) 1-0-1 (1) GP SP ML ML SP-SM 0.3 0.7 2.5 8.0 10.0 Asphalt (GP) 5/8 inch minus crushed rock (Moist, Dense)Imported crushed surfacing base course (SP) Brown gravelly sand (Moist, Medium Dense)Imported asphalt section subbase (ML) Mottled brown/gray silt with fine sand (Moist, Very Soft) (ML) Mottled brown fine sandy silt (Moist, Very Soft) (SP-SM) Gray medium to coarse sand with silt (Moist, Loose) NOTES LOGGED BY RVCB DRILLING METHOD Track Mounted Drill Rig DRILLING CONTRACTOR Holocene Drilling GROUND WATER LEVELS: CHECKED BY JEB DATE STARTED 11/5/24 COMPLETED 11/5/24 AT TIME OF DRILLING 8.00 ft / Elev 22.00 ft AT END OF DRILLING --- AFTER DRILLING --- HOLE SIZE 4.25" HSAGROUND ELEVATION 30 ft SA M P L E T Y P E NU M B E R DE P T H (f t ) 0.0 2.5 5.0 7.5 10.0 (Continued Next Page) PAGE 1 OF 3 Figure A-6 BORING NUMBER B-5 CLIENT HHJ Construction PROJECT NUMBER Z0816 PROJECT NAME Walker's Renton Subaru PROJECT LOCATION 519 SW 12th Street, Renton WA CO P Y O F G E N E R A L B H / T P L O G S - F I G U R E . G D T - 1 1 / 2 6 / 2 4 1 2 : 4 0 - C : \ U S E R S \ J E S S I C A B I Z A K \ D E S K T O P \ T E S T P I T S A N D B O R I N G S - G I N T \ Z 0 8 1 6 \ Z 0 8 1 6 B O R I N G L O G . G P J Migizi Group, Inc. PO Box 44840 Tacoma, WA 98448 Telephone: 253-537-9400 RE C O V E R Y ( i n ) (R Q D ) BL O W CO U N T S (N V A L U E ) U. S . C . S . GR A P H I C LO G MATERIAL DESCRIPTION SS S-5 SS S-6 17.0 9.0 0 2-8-16 (24) SP-SM ML SP 13.0 21.0 (SP-SM) Gray medium to coarse sand with silt (Moist, Loose) (continued) (ML) Gray/brown organic-rich silt with fine sand (Moist, Very Soft) (SP) Gray fine gravelly coarse sand (Moist, Medium Dense) SA M P L E T Y P E NU M B E R DE P T H (f t ) 12.5 15.0 17.5 20.0 22.5 25.0 (Continued Next Page) PAGE 2 OF 3 Figure A-6 BORING NUMBER B-5 CLIENT HHJ Construction PROJECT NUMBER Z0816 PROJECT NAME Walker's Renton Subaru PROJECT LOCATION 519 SW 12th Street, Renton WA CO P Y O F G E N E R A L B H / T P L O G S - F I G U R E . G D T - 1 1 / 2 6 / 2 4 1 2 : 4 0 - C : \ U S E R S \ J E S S I C A B I Z A K \ D E S K T O P \ T E S T P I T S A N D B O R I N G S - G I N T \ Z 0 8 1 6 \ Z 0 8 1 6 B O R I N G L O G . G P J Migizi Group, Inc. PO Box 44840 Tacoma, WA 98448 Telephone: 253-537-9400 RE C O V E R Y ( i n ) (R Q D ) BL O W CO U N T S (N V A L U E ) U. S . C . S . GR A P H I C LO G MATERIAL DESCRIPTION SSS-7 SS S-8 4.0 3.0 0.0 -1.0 -1.5 7-5-13(18) 7-14-21 (35) SP SP SP SP GP 26.0 27.0 30.0 31.0 31.5 (SP) Gray fine gravelly coarse sand (Moist, Medium Dense) (continued) (SP) Gray medium to coarse sand (Moist, Medium Dense) (SP) Gray coarse sand with trace fine gravel (Moist, Dense) (SP) Gray medium to coarse sand (Moist, Dense) (GP) Gray coarse sandy fine gravel (Moist, Dense) Bottom of borehole at 31.5 feet. SA M P L E T Y P E NU M B E R DE P T H (f t ) 27.5 30.0 PAGE 3 OF 3 Figure A-6 BORING NUMBER B-5 CLIENT HHJ Construction PROJECT NUMBER Z0816 PROJECT NAME Walker's Renton Subaru PROJECT LOCATION 519 SW 12th Street, Renton WA CO P Y O F G E N E R A L B H / T P L O G S - F I G U R E . G D T - 1 1 / 2 6 / 2 4 1 2 : 4 0 - C : \ U S E R S \ J E S S I C A B I Z A K \ D E S K T O P \ T E S T P I T S A N D B O R I N G S - G I N T \ Z 0 8 1 6 \ Z 0 8 1 6 B O R I N G L O G . G P J Migizi Group, Inc. PO Box 44840 Tacoma, WA 98448 Telephone: 253-537-9400 RE C O V E R Y ( i n ) (R Q D ) BL O W CO U N T S (N V A L U E ) U. S . C . S . GR A P H I C LO G MATERIAL DESCRIPTION Technical Information Report Walker Subaru Service Center 2240819.10 Appendix E Non-Structural BMPs A-1 .................... Required Best Management Practices (BMPs) for all Properties with Commercial Activities A-8 .................... Storage or Solid and Food Wastes (Including Cooking Grease) A-45 .................. Maintenance of Public and Private Utility Corridors and Facilities Stormwater Pollution Prevention Manual King County Stormwater Services 17 July 2021 A-1: Required BMPs for All Properties with Commercial Activities The following best management practices (BMPs) are required for all commercial, industrial, agricultural, public, and residential properties with commercial activities in unincorporated King County. In addition to implementing required BMPs listed herein, property owners must maintain drainage facilities to meet King County Standards, as required by King County Code 9.04.120. BMPs are required by King County Water Quality Code 9.12. If the BMPs included here are not enough to prevent contamination of stormwater, you will be required to take additional measures. Required BMPs Clean and Maintain Stormwater Drainage System • Evaluate the condition of the catch basin by checking the amount of sediment in the bottom of the catch basin (sump). Catch basins must be cleaned out when the solids, trash and debris in the sump reaches one–half of the depth between the bottom of the sump and the bottom of the lowest inflow or outflow pipe connected to the catch basin or is at least 6 inches below this point. • Clean and maintain catch basins annually. Sites with activities generating sediments and other debris will have to inspect and clean out their catch basins more often. Frequent sweeping of paved parking and storage areas will save time and money in maintaining the stormwater drainage system. • Hire a professional drainage contractor to inspect and maintain your stormwater drainage system or clean the system yourself. If there is sediment or other debris in the drainage pipes, then a professional contractor must be hired to flush or jet out the pipes. Confined space entry should only be conducted by individuals trained to do so. For information on confined spaces refer to www.osha.gov/confined-spaces • Soak up small amounts of floating oil with absorbent pads. The pads and nonhazardous sediments can be bagged up and disposed of as solid waste. Up to one cubic yard of nonhazardous solid material may be disposed of as solid waste in your regular garbage. For additional information please call King County Solid Waste Division at 206-477-4466. If you exceed this threshold hire a professional drainage contractor. For information on how to use absorbent pads please watch Seattle Public Utility’s video How to Use Your Spill Kit (https://www.youtube.com/watch?v=NeH98Rx7dOE). • All of the solids and stagnant water collected from catch basin sumps must be disposed of properly. None of the sump contents can be flushed into the catch basin outflow pipe. Contractors who perform catch basin clean-out services are required to follow appropriate disposal requirements. Stormwater Pollution Prevention Manual King County Stormwater Services 18 July 2021 • Other components of the stormwater drainage system (e.g., ponds, tanks, and bioswales) must also be maintained. If this maintenance is beyond your ability, contractors are available to complete this work. Label All Storm Drain Inlets on Your Property • Stencil or apply catch basin/storm drain markers adjacent to storm drains to help prevent the improper disposal of pollutants. If the catch basin grate is stamped with warnings against polluting, then additional marking may not be required if there is no evidence of pollutants being dumped or washed into the storm drain. • When painting stencils or installing markers, temporarily block the storm drain inlet so that no pollutants are discharged from labelling activities. • Maintain the legibility of markers and signs. • Contact King County Stormwater Services at 206-477-4811 for a free stencil or catch basin marker. Eliminate Illicit Connections to the Storm Drainage System • Connections to the stormwater drainage system that convey substances other than stormwater are prohibited. • Illicit connections must be removed immediately, permanently plugged or re–plumbed. • If the connection is re-plumbed, the line must discharge to the proper receiver, such as the sanitary sewer, a septic system, an on–site treatment system, or a holding tank for off–site disposal. There are restrictions on what can be disposed of to the sanitary sewer and septic systems. Contact your sewer authority or Public Health – Seattle and King County. • Unknown connections may require additional investigation to determine where all stormwater and non–stormwater discharges go. This may include smoke, dye or chemical testing, or closed-circuit television inspection. Contact King County Stormwater Services at 206-477-4811 for further assistance. Maintain Drainage Facilities • Drainage facilities must meet the standards and requirements set forth in King County’s Surface Water Design Manual for continual performance, operation, and maintenance. Additional Information • Stormwater Pollution Prevention Manual, Chapter 5: Information Sheets o Catch Basin Inserts o Disposal o Drainage Maintenance Contractors o Oil/Water Separator Contact King County Stormwater Services at 206-477-4811 or visit kingcounty.gov/stormwater for stencils, catch basin markers, assistance with determining if you have an illicit connection or any further questions. Stormwater Pollution Prevention Manual King County Stormwater Services 35 July 2021 A-8: Storage of Solid Waste and Food Wastes (Including Cooking Grease) The following best management practices (BMPs) apply to garbage dumpsters, trash compactors and outdoor waste containers (e.g., cooking oil/grease receptacles). Potential pollutants include but are not limited to fecal coliform bacteria, hydrocarbons, metals, nutrients, oil and grease, oxygen demanding substances, PCBs, pH, sediment, and other pollutants. BMPs are required by King County Water Quality Code 9.12. If the BMPs included here are not enough to prevent contamination of stormwater, you will be required to take additional measures. Required BMPs • Store wastes in leak-proof containers with solid lids (e.g., dumpsters and trash compactors). No rainwater should be able to enter the container and no fluids should be leaking out. • Keep all waste receptacles (e.g., dumpsters, garbage cans, used cooking oil/grease containers) closed except when adding waste. • Leaking outdoor waste containers must be repaired or replaced. Contact your waste hauler for replacements if the container is leased. • Trash compactor wastewater must be discharged to the sanitary sewer, septic system or collected and hauled off-site for proper disposal. It must not be discharged to ground, stormwater drainage systems, surface waters or groundwater. • Trash compactor drain lines should be connected to the sanitary sewer or septic system. If a connection is not possible, collect the wastewater in a dead-end sump or similar device. The wastewater containment must be easily inspected, maintained, and pumped out for proper disposal. • Used cooking oil/grease containers should be labeled with their contents and have a secured lid. • While oil/grease containers are not required to have secondary containment, they should be located and/or secured such that they can’t be tipped over. • Clean up any spills immediately using absorbent material or scraping it up. Grease cannot be left on the ground. • Have spill cleanup materials nearby. • Use a lid or cover when transporting cooking oil/grease containers from kitchens to outside grease containers to prevent contents from spilling. • Ensure that drip pans or absorbent materials are used whenever grease containers are emptied by vacuum trucks or other means. Stormwater Pollution Prevention Manual King County Stormwater Services 36 July 2021 • Dispose of collected cooking oil/grease as garbage if it is not being recycled. Do not dispose of fats, oils, or grease (FOG) into the sanitary sewer, septic system, or stormwater drainage system. Required Routine Maintenance • Keep the area around the grease container clean and free of debris. • Check storage containers frequently for leaks and to ensure that lids are secure. • Regularly check for loose debris in the waste container storage area and sweep if the area is paved. After sweeping, the waste storage area may be hosed down—without the use of soaps, detergents, or other chemicals—if there are no accumulations of oil and grease present and the rinse water is not discharged to a stormwater drainage system or surface water. The rinse water can infiltrate to ground or be discharged to a sanitary sewer. • Do not hose down or apply soaps, detergents, or other chemicals to waste storage areas with accumulated oil and grease. Oily wastewater can clog stormwater drainage systems and sanitary sewer lines. Contact a service provider to remove and properly dispose of oil and grease accumulations. • If cleaning or rinsing waste containers, dispose of all wastewater into the sanitary sewer. If sanitary sewer is not available, then store the wastewater in a holding tank, dead-end sump, or truck it off-site to an approved disposal location. Additional Information • Stormwater Pollution Prevention Manual, Chapter 3: Commercial and Multifamily BMPs o A-31: Parking Lots, Driveways and Outside Storage Areas • Stormwater Pollution Prevention Manual, Chapter 5: Information Sheets o Disposal o Drainage Maintenance Contractors For more information or assistance contact the King County Stormwater Services at 206–477–4811 and visit kingcounty.gov/stormwater. Stormwater Pollution Prevention Manual King County Stormwater Services 107 July 2021 A-45: Maintenance of Public and Private Utility Corridors and Facilities The following best management practices (BMPs) apply to maintenance activities associated with the transmission and distribution of public and private utilities such as petroleum products, natural gas, water, sewage, and electrical power. This includes the maintenance of underground utility vaults, pump stations, and similar facilities. Potential pollutants can include but are not limited to hydrocarbons, metals, nutrients, oil and grease, oxygen demanding substances, PCBs, pH, sediment, and other pollutants. BMPs are required by King County Water Quality Code (KCC 9.12). If the BMPs included here are not enough to prevent contamination of stormwater, you will be required to take additional measures. Required BMPs • Minimize the amount of herbicides and other pesticides used to maintain access roads and facilities. • Stabilize access roads or areas of bare ground with gravel, crushed rock, or another method to prevent erosion. Use and manage vegetation to minimize bare ground/soils that may be susceptible to erosion. • Provide stormwater drainage for roads and maintenance areas. Grade roads with a crown or slope to minimize the potential for erosion from runoff. Provide ditches, swales, and culverts to convey stormwater runoff. • Keep ditches and culverts properly clear to reduce the possibility of the drainage becoming plugged or blocked, which could cause overflows and erosion. • Check utility vaults or other underground structures for oil prior to pumping out any collected water. Contaminated water must be collected for proper disposal. Small amounts of oil may be captured with absorbent material. Never discharge contaminated water, including oil, sediment, or high or low pH, to stormwater drainage systems, stormwater drainage facilities or surface waters. • When removing water and/or sediment from electrical transformer vaults, determine from records or testing if the transformers contain PCBs. Properly dispose of accumulated water and sediment from these vaults. • Clean up any debris or spilled material immediately after completing maintenance and repair activities. Additional Information • Stormwater Pollution Prevention Manual, Chapter 3: Commercial and Multifamily BMPs o A-3: Storage of Liquid Materials in Portable Containers o A-5: Storage and Use of Pesticides and Fertilizers o A-22: Painting, Finishing and Coating of Vehicles, Products and Equipment Stormwater Pollution Prevention Manual King County Stormwater Services 108 July 2021 o A-26: Landscaping Activities, Vegetation Management, and Irrigation • King County Surface Water Design Manual, Appendix D: Erosion and Sediment Control Standards • Work in public road right of ways requires permission from King County Utility Inspection Program, call 206-296-8122. For more information or assistance contact the King County Stormwater Services at 206–477–4811 and visit kingcounty.gov/stormwater. Technical Information Report Walker Subaru Service Center 2240819.10 Appendix F Construction Stormwater Pollution Prevention Plan Civil Engineers ● Structural Engineers ● Landscape Architects ● Community Planners ● Land Surveyors Construction Stormwater Pollution Prevention Plan PREPARED FOR: ADF Properties, LLC 15007 Woodinville-Redmond Rd, Suite A Woodinville, WA 98072 PROJECT: Walker Subaru Service Center Renton, WA 2240819.10 PREPARED BY: Nathan Kaser Project Engineer REVIEWED BY: Scott T. Kaul, PE, LEED AP Principal DATE: January 2026 Revised April 2026 Construction Stormwater Pollution Prevention Plan PREPARED FOR: ADF Properties, LLC 15007 Woodinville-Redmond Rd, Suite A Woodinville, WA 98072 PROJECT: Walker Subaru Service Center Renton, WA 2240819.10 PREPARED BY: Nathan Kaser Project Engineer REVIEWED BY: Scott T. Kaul, PE, LEED AP Principal DATE: January 2026 Revised April 2026 I hereby state that this Construction Stormwater Pollution Prevention Plan for Walker Subaru Service Center has been prepared by me or under my supervision and meets the standard of care and expertise that is usual and customary in this community for professional engineers. I understand that City of Renton does not and will not assume liability for the sufficiency, suitability, or performance of drainage facilities prepared by me. 04/08/2026 Construction Stormwater Pollution Prevention Plan Walker Subaru Service Center 2240819.10 Table of Contents Section Page 1.0 Introduction .................................................................................................................................... 1 2.0 Project Description ........................................................................................................................ 2 3.0 Erosion Control Specialist ............................................................................................................ 2 4.0 Existing Site Conditions ................................................................................................................ 2 4.1 Existing Cover ..................................................................................................................... 2 4.2 Topography and Drainage .................................................................................................. 3 4.3 100-Year Flood Analysis ..................................................................................................... 3 5.0 Adjacent Areas ............................................................................................................................... 3 6.0 Critical Areas .................................................................................................................................. 3 7.0 Soils ................................................................................................................................................. 3 8.0 Erosion Problem Areas ................................................................................................................. 3 9.0 Construction Stormwater Pollution Prevention Elements ......................................................... 3 9.1 Mark Clearing Limits ........................................................................................................... 3 9.2 Cover Measures .................................................................................................................. 4 9.3 Perimeter Protection ........................................................................................................... 4 9.4 Traffic Area Stabilization ..................................................................................................... 5 9.5 Sediment Retention............................................................................................................. 5 9.6 Surface Water Collection .................................................................................................... 5 9.7 Dewatering Control ............................................................................................................. 5 9.8 Dust Control ........................................................................................................................ 5 9.9 Flow Control ........................................................................................................................ 5 9.10 Protect Existing and Proposed Stormwater Facilities and Onsite BMPs ............................ 5 9.11 Pollutants ............................................................................................................................ 6 9.12 Maintain Protective BMPs ................................................................................................... 7 9.13 Manage the Project ........................................................................................................... 10 10.0 Construction Sequence ............................................................................................................... 10 11.0 Construction Schedule ................................................................................................................ 11 Construction Stormwater Pollution Prevention Plan Walker Subaru Service Center 2240819.10 Appendices Appendix A Exhibits A-1 ............Vicinity Map A-2 ............Existing Conditions Map A-3 ............FEMA Flood Insurance Rate Map A-4 ............NRCS Soil Map A-5 ............Critical Areas Map Appendix B Exhibits B-1 ............TESC Plans B-2 ............Select Pollution Prevention Measures Appendix C Inspection and Maintenance Report Appendix D Engineering Calculations Construction Stormwater Pollution Prevention Plan Walker Subaru Service Center 1 2240819.10 1.0 Introduction In 1972, Congress passed the Federal Water Pollution Control Act (FWPCA), also known as the Clean Water Act (CWA), to restore and maintain the quality of the nation's waterways. The ultimate goal was to ensure that rivers and streams were fishable, swimmable, and drinkable. In 1987, the Water Quality Act (WQA) added provisions to the CWA that allowed the EPA to govern stormwater discharges from construction sites. In 1998, the EPA published the final notice for General Permits for Storm Water Discharges from Construction Activities Disturbing 5 Acres or Greater (63 Federal Register 7898, February 14, 1998). The general permit includes provisions for development of a Stormwater Pollution Prevention Plan (SWPPP) to maximize the potential benefits of pollution prevention and sediment and erosion control measures at construction sites. Development, implementation, and maintenance of the Construction SWPPP will provide the selected general contractor with the framework for reducing soil erosion and minimizing pollutants in stormwater during construction. The Construction SWPPP will: • Define the characteristics of the site and the type of construction that will occur. • Describe the practices that will be implemented to control erosion and the release of pollutants in stormwater. • Create an implementation schedule to ensure that the practices described in this Construction SWPPP are, in fact, implemented; and to evaluate the plan's effectiveness in reducing erosion, sediment, and pollutant levels in stormwater discharged from the site. • Describe the final stabilization/termination design to minimize erosion and prevent stormwater impacts after construction is complete. This Construction SWPPP includes the following: • Identification of the Certified Erosion and Sedimentation Control Lead (CESCL) with a description of this person's duties. • Identification of the Stormwater Pollution Prevention Team (SWPP Team) that will assist in implementation of the Construction SWPPP during construction. • Description of the existing site conditions, including existing land use for the site, soil types at the site, as well as the location of surface waters that are located on or next to the site. • Identification of the body or bodies of water that will receive runoff from the construction site, including the ultimate body of water that receives the stormwater. • Identification of drainage areas and potential stormwater contaminants. • Description of stormwater management controls and various Best Management Practices (BMPs) necessary to reduce erosion, sediment, and pollutants in stormwater discharge. • Description of the facility monitoring plan and how controls will be coordinated with construction activities. • Description of the implementation schedule and provisions for amendment of the plan. Construction Stormwater Pollution Prevention Plan Walker Subaru Service Center 2 2240819.10 2.0 Project Description This Construction SWPPP accompanies the civil engineering plans submitted for a site development permit for the Walker Subaru Service Center project. This 2.13-acre property is located in the Northwest Quarter of Section 19, Township 23 North, Range 5 East, Willamette Meridian, Renton, King County, Washington. Refer to Appendix A-1 for the Vicinity Map. The Walker Subaru Service Center project is located on Parcel 3340404265, totaling approximately 2.13 acres, with the proposed disturbed area totaling approximately 1.20 acres. The proposed project is for a building addition of approximately 14,450 square feet onto the existing Subaru facility. The project also includes relocating stormwater, water, sanitary sewer, and dry utilities. 3.0 Erosion Control Specialist The contractor shall appoint a certified erosion and sediment control lead (CESCL) for the project. The duties of the CESCL include: • Maintaining files onsite at all times, which includes the Construction SWPPP and any associated permits and plans. • Directing BMP installation, inspection, maintenance, modification, and removal. • Updating all project drawings and the Construction SWPPP with changes made. • Keeping daily logs and inspection reports. • Facilitate, participate in, and take corrective actions resulting from inspections performed by outside agencies or the owner. • To aid in the implementation of the Construction SWPPP, the members of the SWPP Team include the following: the contractor, the CESCL, the City of Renton Inspector, AHBL, and a project geotechnical engineering consultant. The general contractor will ensure all housekeeping and monitoring procedures are implemented, while the CESCL will ensure the integrity of the structural BMPs. The City of Renton Inspector, a project geotechnical engineering consultant, the CESCL, and AHBL will observe construction and erosion control practices and recommend revisions or additions to the SWPPP and drawings. 4.0 Existing Site Conditions 4.1 Existing Cover The existing condition is a developed site consisting of the Subaru Service Building and parking. Existing Vegetation/Cover: Most of the existing site is impervious. The existing building and paved parking make up a majority of the site. The existing stormwater swale and pond, along with a few landscape islands, are the only vegetated cover. There are four driveways accessing the site, two from the north end and two from the west end. An existing 8-inch sanitary sewer main runs along the south side of the existing building with an existing manhole located near the southeast corner of the building. An existing 6-inch water main runs along the south side of the existing building. Power and other utilities also run south of the existing building. Refer to Appendix A-2 for the Existing Conditions Map. Construction Stormwater Pollution Prevention Plan Walker Subaru Service Center 3 2240819.10 4.2 Topography and Drainage The site is relatively flat and collects all stormwater via catch basins at low points. The site directs stormwater to the existing bioswale/pond at the south end of the site. Refer to Appendix A-2 for the Existing Conditions Map. 4.3 100-Year Flood Analysis To our knowledge, no floodplains are associated with the project site. Refer to Appendix A-3 for the FEMA Flood Map. 5.0 Adjacent Areas The project site is surrounded by commercial development. There are other automotive businesses to the north and east, large areas of impervious surfaces. The site is bounded by SW 12th St to the north and Seneca Ave SW to the west. To the south, the site is adjacent to I-405. 6.0 Critical Areas To our knowledge, the project does not lie within a critical drainage area. Refer to Appendix A-5 for the Critical Areas Map. 7.0 Soils The Natural Resources Conservation Service (NRCS) soil map identifies the site soils as Urban land (Ur). Refer to Appendix A-4 for the NRCS Soil Map. The site is almost entirely impervious surface. A Geotechnical Report prepared by Migizi Group, Inc. confirms that the site consists of typical asphalt sections. They state that the underlying soils consist of very soft silts and sands 5 to 11 feet thick and medium dense sands and gravels below that. 8.0 Erosion Problem Areas To our knowledge, the project site does not have any erosion problem areas. Refer to Exhibit A-5 for the Critical Areas Map. 9.0 Construction Stormwater Pollution Prevention Elements The purpose of this section is to describe how each of the 12 Construction Stormwater Pollution Prevention elements has been addressed and to identify the type and location of BMPs used to satisfy the required element. If an element is not applicable to the project, a reason is provided. Additional supplementary stormwater pollution prevention standards have been included in Appendix B-2. These supplemental resources may be used in the event that approved pollution prevention is not adequate, in addition to other methods identified in the 2022 City of Renton Surface Water Design Manual (Storm Manual). 9.1 Mark Clearing Limits Prior to beginning land disturbing activities, clearing limits will be marked with high visibility plastic or metal fence or silt fencing. Construction Stormwater Pollution Prevention Plan Walker Subaru Service Center 4 2240819.10 9.2 Cover Measures Because source control is the most important form of erosion control, construction practices must adhere to stringent cover requirements. More specifically, during the period of May 1 through September 30, the contractor will not be allowed to leave soils unprotected for more than 7 days, and immediate seeding will be required for areas brought to finish grade with no further work planned for the next 30 days. Areas to be paved may be armored with crushed rock subbase in place of other stabilizing measures. During the period of October 1 through April 30, all disturbed soil areas will be covered or stabilized within two days or 24 hours when a major storm event is predicted. Cover measures may include mulching, netting, plastic sheeting, erosion control blankets, or free draining material. The extent of clearing shall be limited to the amount of land that can be covered or stabilized within 24 hours. Soil stockpiles shall be stabilized by plastic covering or surrounded by filter fabric fence. The contractor has the option of providing all required material for cover measures onsite at all times or prepare a plan of action to submit to the City Renton. A plan of action shall contain the following: • Contractor’s name, address, phone number, and emergency phone number. • Alternate contact with above information. • Clearly defined plan of action designed to prevent offsite migration of sediments, which will be implemented in the event that a major storm is predicted or offsite erosion is observed by the contractor, their employees, or the City. • Description of materials to be used for cover and means by which it will be placed. List equipment to be used or number of personnel anticipated to be used to spread material. • Vendor or supplier of materials to be used. List two alternates and include phone numbers. • Means and timeframe for cleanup of any materials that escape offsite and for repairs to the natural system if damages have occurred. For the ESC facilities to function properly, they must be maintained and sediment removed on a regular basis. Inspection and sediment removal shall be performed on all ESC facilities, as necessary. Temporary and permanent seeding and plastic sheeting may be used to reduce erosion of exposed soils on slopes. 9.3 Perimeter Protection Silt fence is proposed along the property line where improvements are being made to adequately prevent sediment transport. Silt fence will be the primary method of sediment retention. D2.1.3.1 Silt Fence. Construction Stormwater Pollution Prevention Plan Walker Subaru Service Center 5 2240819.10 9.4 Traffic Area Stabilization The existing concrete driveways will act as the stabilized construction entrance and will be used to prevent the transport of sediment onto the adjacent paved surfaces. If sediment is transported onto the road surface, the road shall be cleaned each day by shoveling or sweeping prior to washing. Sediment removal by washing alone will not be allowed. If sediment is tracked from the site, the City may require stabilization of internal roads and car parking areas to contain the sediment or require the installation of a wheel washbasin. A 6-inch depth of 2- to 4-inch crushed rock, gravel base, or crushed surfacing base course should be applied to areas that are used as parking areas where stabilization may be problematic. Offsite parking can be used to prevent sediment tracking during demolition and resurfacing of the site. The replacement and stabilization of onsite surfacing can be completed first so that it can be used while building improvements are being made. 9.5 Sediment Retention Perimeter protection will provide adequate sediment retention for the site. Retained catch basins will be equipped with inlet protection prior to beginning construction activities. When proposed storm facilities are completed, they are to be equipped with inlet protection throughout the remainder of construction to prevent sediment from entering the City system. 9.6 Surface Water Collection Existing and new on-site storm systems with inlet protection will collect water during construction. During construction, runoff will be directed toward the existing bioswale via interceptor ditches. The existing bioswale will be used as a temporary sediment trap. 9.7 Dewatering Control Dewatering is not anticipated for this project. Dewatering discharge shall be filtered prior to discharge to the storm system. 9.8 Dust Control Water should be used as dust control if exposed soils become dry to the point where wind transports dust. The contractor may obtain approval from the City to use an alternate method of dust control listed in Appendix D of the Storm Manual. 9.9 Flow Control Flow speed is expected to be low on this site due to slopes. Runoff will be directed toward the existing bioswale via interceptor ditches. The existing bioswale will be used as a temporary sediment trap. Silt fences will also be installed along the perimeter of the site to provide enough flow control to prevent increases in runoff that could result in erosion. 9.10 Protect Existing and Proposed Stormwater Facilities and Onsite BMPs All existing stormwater facilities shall be protected to the maximum extent feasible to prevent sediment from entering or otherwise affecting the functionality of the system. Care should be taken to protect sedimentation from entering the existing detention pond. Construction Stormwater Pollution Prevention Plan Walker Subaru Service Center 6 2240819.10 9.11 Pollutants The contractor shall be responsible for controlling pollutants at the work site. Key elements, such as centralized areas for equipment and concrete truck washing, and temporary storage of debris and other stockpiled materials, are the responsibility of the contractor. All pollutants, including waste materials and demolition debris, that occur onsite shall be handled and disposed of in a manner that does not cause contamination of stormwater. Woody debris may be chopped and spread onsite. Cover, containment, and protection from vandalism shall be provided for all chemicals, liquid products, petroleum products, and non-inert wastes present on the site (see Chapter 173-304 WAC for the definition of inert waste). Onsite fueling tanks shall include secondary containment. Maintenance and repair of heavy equipment and vehicles involving oil changes, hydraulic system drain down, solvent and degreasing cleaning operations, fuel tank drain down and removal, and other activities which may result in discharge or spillage of pollutants to the ground or into stormwater runoff must be conducted using spill prevention measures, such as drip pans. Contaminated surfaces shall be cleaned immediately following any discharge or spill incident. Emergency repairs may be performed onsite using temporary plastic placed beneath and, if raining, over the vehicle. Wheel wash or tire bath wastewater shall be discharged to a separate onsite treatment system or to the sanitary sewer. Application of agricultural chemicals, including fertilizers and pesticides, shall be conducted in a manner and at application rates that will not result in loss of chemical to stormwater runoff. Manufacturers’ recommendations for application rates and procedures shall be followed. BMPs shall be used to prevent or treat contamination of stormwater runoff by pH modifying sources. These sources include, but are not limited to, bulk cement, cement kiln dust, fly ash, new concrete washing and curing waters, waste streams generated from concrete grinding and sawing, exposed aggregate processes, and concrete pumping and mixer washout waters. Stormwater discharges shall not cause or contribute to a violation of the water quality standard for pH in the receiving water. Construction sites with significant concrete work shall adjust the pH of stormwater if necessary to prevent violations of water quality standards. Table 1 below lists several pollutants that are commonly found on construction sites that have the potential to contaminate storm runoff. These pollutants will be present mainly in areas of building and pavement construction. The contractor and CESCL will be responsible for identifying areas where these pollutants are being used and will monitor runoff coming from these areas. Pollutant sources will be covered with plastic if contaminated runoff is observed from these areas. If contaminated runoff is found in the soils, the CESCL will direct the contractor to remove the polluted water/soil and dispose of it in an approved area offsite. Construction Stormwater Pollution Prevention Plan Walker Subaru Service Center 7 2240819.10 Table 1 – Potential Construction Site Stormwater Pollutants Trade Name Material Chemical/Physical Description (1) Stormwater Pollutants (1) Pesticides (insecticides, fungicides, herbicide, rodenticides) Various colored to colorless liquid, powder, pellets, or grains Chlorinated hydrocarbons, organophosphates, carbamates, arsenic Fertilizer Liquid or solid grains Nitrogen, phosphorous Plaster White granules or powder Calcium sulphate, calcium carbonate, sulfuric acid Cleaning solvents Colorless, blue, or yellow-green liquid Perchloroethylene, methylene chloride, trichloroethylene, petroleum distillates Asphalt Black solid Oil, petroleum distillates Concrete White solid Limestone, sand Glue, adhesives White or yellow liquid Polymers, epoxies Paints Various colored liquid Metal oxides, stoddard solvent, talc, calcium carbonate, arsenic Curing compounds Creamy white liquid Naphtha Wastewater from construction equipment washing Water Soil, oil & grease, solids Wood preservatives Clear amber or dark brown liquid Stoddard solvent, petroleum distillates, arsenic, copper, chromium Hydraulic oil/fluids Brown oily petroleum hydrocarbon Mineral oil Gasoline Colorless, pale brown or pink petroleum hydrocarbon Benzene, ethyl benzene, toluene, xylene, MTBE Diesel fuel Clear, blue-green to yellow liquid Petroleum distillate, oil & grease, naphthalene, xylenes Kerosene Pale yellow liquid petroleum hydrocarbon Coal oil, petroleum distillates Antifreeze/coolant Clear green/yellow liquid Ethylene glycol, propylene glycol, heavy metals (copper, lead, zinc) Erosion Solid Particles Soil, Sediment (1) Data obtained from MSDS when available. 9.12 Maintain Protective BMPs Maintain and repair all silt fencing and inlet protection as needed to ensure continued performance. Remove all temporary erosion and sediment control BMPs prior to final construction approval or within 30 days after achieving final site stabilization. Permanently stabilize disturbed soils and vegetation resulting from removal of erosion and sediment control BMPs. For the ESC facilities to function properly, they must be maintained and sediment removed on a regular basis. Inspection and sediment removal shall be performed on all ESC facilities as described in the following inspection schedule. Erosion control facilities shall not be allowed to fall into disrepair. All ESC facilities shall be inspected, at a minimum, according to the following schedule. • Dry Season: Once a week. • Wet Season: Daily and after every storm event that produces runoff. Construction Stormwater Pollution Prevention Plan Walker Subaru Service Center 8 2240819.10 Needed repairs shall be made within 24 hours or immediately, if possible. If necessary, the Engineer of Record, CESCL, or City will instruct the contractor to provide additional facilities as warranted during field inspections. The following inspection/maintenance schedules shall be used to ensure the ESC facilities are functioning as designed: Construction Entrance • The existing paved driveways from the west will be used as construction entrances. • Any sediment tracked offsite shall be swept back onsite before it can enter storm facilities within the right of way. • The construction entrance shall be inspected once a week during the dry season and after every rainfall event during the wet season. If the entrance is not preventing sediment from being tracked onto adjacent pavement, then alternate measures to keep the pavement free of sediment shall be used. This may include street sweeping, or the installation of a wheel wash. • If vehicles are entering or exiting the site at points other than the approved entrance, temporary fencing shall be installed to control traffic. Temporary and Permanent Seeding • Seeding may be used throughout the project on disturbed areas. During the dry season, areas that have reached final grade or are not being actively worked, shall be seeding within seven days. Seeded areas shall be supplied with adequate moisture, but not watered to the extent that it causes runoff. • During the wet season, all disturbed areas not being actively worked shall be seeded or stabilized with mulch or plastic sheeting. • To prevent seed from being washed away, confirm that all other approved erosion/ sedimentation control facilities have been installed and are functioning properly. • Any seeded areas that fail to establish 80 percent cover (100 percent cover for areas that receive sheet or concentrated flows) shall be reseeded. If reseeding is ineffective, an alternate method shall be used. • Seeded areas shall be inspected after every rainfall event during the wet season. Any areas that experience erosion shall be reseeded and protected by mulch. If the erosion problem is drainage related, the problem shall be fixed and the eroded area reseeded and protected by mulch. • Seeding shall not be used in areas subject to heavy vehicular traffic. Mulching • Mulching shall be inspected once a week during the dry season and after every rainfall event during the wet season. • Mulch shall be inspected to verify that the proper thickness is being maintained, if applicable. Construction Stormwater Pollution Prevention Plan Walker Subaru Service Center 9 2240819.10 • Any areas that experience erosion shall be remulched and/or protected with a net or blanket. If the erosion problem is drainage related, the problem shall be fixed and the eroded area remulched. Plastic Covering • Plastic sheeting shall be inspected once a week during both the wet and dry season. • Torn sheets must be replaced and open seams repaired. • If the plastic begins to deteriorate due to ultraviolet radiation, it must be completely removed and replaced. • When the plastic is no longer needed, it shall be completely removed. • If tires are used to weigh down the plastic sheeting, they must be disposed of properly. Inlet Protection • Catch basin filter inserts shall be inspected frequently, especially after storm events. If the filter becomes clogged, it should be cleaned or replaced. • Inserts shall be replaced when tears are detected. Silt Fence • Any damage shall be repaired immediately. • If concentrated flows are evident uphill of the fence, they must be intercepted and conveyed to a sediment pond. • Check the uphill side of the fence for signs of the fence clogging and acting as a barrier to flow and causing channelization of flows parallel to the fence. If this occurs, replace the fence or remove the trapped sediment. • Sediment deposits shall be removed when the deposit reaches approximately one-third the height of the silt fence or a second silt fence shall be installed. • If the filter fabric (geotextile) has deteriorated due to ultraviolet breakdown, it shall be replaced. If the erosion control facilities are damaged, or if the Engineer of Record, CESCL, or the City determines that existing controls are inadequate, the contractor shall install additional measures as required. The maintenance inspection report will be made after each inspection. Copies of the report forms to be completed by the CESCL are included in Appendix C of this Construction SWPPP. Completed forms will be provided to the City Inspector and will also be maintained onsite during the entire construction project. If construction activities or design modifications are made to the site plan that could impact stormwater, or if the Engineer of Record, CESCL, or City Inspector determines that the measures are not adequate to prevent erosion and the discharge of sediment from the site (based on turbidity measurements), this Construction SWPPP will be amended appropriately. The amended Construction SWPPP will have a description of the new activities that contribute to the increased pollutant loading and the planned source control activities. Construction Stormwater Pollution Prevention Plan Walker Subaru Service Center 10 2240819.10 9.13 Manage the Project The following practices will be required during construction to properly manage activities: • Comply with seasonal work limitations. • Inspect, maintain, and repair BMPs. • Identify a CESCL. • Maintain the Construction SWPPP onsite at all times, including narrative and plans. Erosion control procedures, as described in this Construction SWPPP and illustrated on the design plans, if properly implemented, should mitigate anticipated erosion effects from the proposed filling on the project site. The success of erosion control measures is usually related to the contractor’s attention to maintenance of such measures. However, in some instances, even with proper attention being paid to erosion control, measures such as those shown on the plans are unable to prevent the discharge of turbid water. In this event, secondary measures may be required such as Construction Stormwater Chemical Treatment or Construction Stormwater Filtration. Additional cover measures may be implemented, including Sodding or Polyacrylamide for Soil Erosion Protection. Descriptions of the above-listed BMPs are provided in the Storm Manual. 10.0 Construction Sequence The proposed project will be completed in a single phase. A general construction sequence is as follows: 1. Survey and flag clearing limits. 2. Schedule and attend pre-construction meeting with City of Renton. 3. Provide miscellaneous demolition and clear and grub area within clearing limits required for installation of temporary erosion control facilities. All erosion and sediment control facilities shown on the erosion control plan shall be installed prior to or as a first stage of site preparation. 4. Provide construction entrance, silt fence, and inlet protection, as shown on the plans. 5. The contractor shall inspect the erosion control measures weekly and provide repairs, as needed. 6. Provided cover measures, to include armoring, mulching, and hydroseeding, to stabilize denuded areas and prevent the transport of sediment-laden stormwater offsite. 7. Provide storm system, sanitary system, water, and miscellaneous utilities, as shown on the plans. Provide 6-inch vertical and 3-foot horizontal clearance (outside surfaces) between storm drain lines and other utility pipes and conduits. 8. Provide catch basin sediment protection on all catch basins. 9. Fine grade site and pave. Coordinate with the City for required inspections. Construction Stormwater Pollution Prevention Plan Walker Subaru Service Center 11 2240819.10 10. Remove sediment from storm pipes and catch basin sumps. 11. Stabilize all remaining disturbed areas. 12. Coordinate with City of Renton for final inspection. 13. Remove remaining temporary erosion control devices when area has been permanently stabilized with vegetation and removal is approved by the City. 11.0 Construction Schedule Construction is scheduled to begin in the summer of 2026 and continue through fall 2026. This analysis is based on data and records either supplied to or obtained by AHBL, Inc. These documents are referenced within the text of the analysis. The analysis has been prepared using procedures and practices within the standard accepted practices of the industry. We conclude that this project, as proposed, will not create any new problems within the existing downstream drainage system. This project will not noticeably aggravate any existing downstream problems due to either water quality or quantity. AHBL, Inc. Nathan Kaser Project Engineer NK/lsk January 2026 Revised April 2026 Q:\2024\2240819\WORDPROC\Reports\20260408 Rpt (SWPPP) 2240819.10.docx Construction Stormwater Pollution Prevention Plan Walker Subaru Service Center 2240819.10 Appendix A Exhibits A-1 .................... Vicinity Map A-2 .................... Existing Conditions Map A-3 .................... FEMA Flood Insurance Rate Map A-4 .................... NRCS Soil Map A-5 .................... Critical Areas Map 2215 North 30th Street Suite 300 Tacoma, WA 98403 253.383.2422 TEL 253.383.2572 FAX SUNSET HIGHLANDS MIXED USE 2190210.10 VICINITY MAP A-1 NOT TO SCALE VICINITY MAP SUNSET HIGHLANDS - 2230621.10WALKER SUBARU SERVICE CENTER - 2240819.10 2215 North 30th Street, Suite 300, Tacoma, WA 98403 253.383.2422 TEL 253.383.2572 FAX JOB NO. DATE: WALKER SUBARU SERVICE CENTER EXISTING CONDITIONS A-2 2240819.10 2/5/2025 N GRAPHIC SCALE 0 30 60 1" = 30 FEET 15 National Flood Hazard Layer FIRMette 0 500 1,000 1,500 2,000250 Feet Ü SEE FIS REPORT FOR DETAILED LEGEND AND INDEX MAP FOR FIRM PANEL LAYOUT SPECIAL FLOODHAZARD AREAS Without Base Flood Elevation (BFE)Zone A, V, A99With BFE or Depth Zone AE, AO, AH, VE, AR Regulatory Floodway 0.2% Annual Chance Flood Hazard, Areasof 1% annual chance flood with averagedepth less than one foot or with drainageareas of less than one square mile Zone X Future Conditions 1% Annual Chance Flood Hazard Zone X Area with Reduced Flood Risk due to Levee. See Notes.Zone X Area with Flood Risk due to LeveeZone D NO SCREEN Area of Minimal Flood Hazard Zone X Area of Undetermined Flood Hazard Zone D Channel, Culvert, or Storm Sewer Levee, Dike, or Floodwall Cross Sections with 1% Annual Chance 17.5 Water Surface Elevation Coastal Transect Coastal Transect Baseline Profile Baseline Hydrographic Feature Base Flood Elevation Line (BFE) Effective LOMRs Limit of Study Jurisdiction Boundary Digital Data Available No Digital Data Available Unmapped This map complies with FEMA's standards for the use of digital flood maps if it is not void as described below.The basemap shown complies with FEMA's basemapaccuracy standards The flood hazard information is derived directly from theauthoritative NFHL web services provided by FEMA. This mapwas exported on 2/5/2025 at 5:44 PM and does notreflect changes or amendments subsequent to this date andtime. The NFHL and effective information may change orbecome superseded by new data over time. This map image is void if the one or more of the following map elements do not appear: basemap imagery, flood zone labels, legend, scale bar, map creation date, community identifiers, FIRM panel number, and FIRM effective date. Map images for unmapped and unmodernized areas cannot be used for regulatory purposes. Legend OTHER AREAS OF FLOOD HAZARD OTHER AREAS GENERAL STRUCTURES OTHER FEATURES MAP PANELS 8 B 20.2 The pin displayed on the map is an approximatepoint selected by the user and does not representan authoritative property location. 1:6,000 122°13'49"W 47°28'18"N 122°13'11"W 47°27'54"N Basemap Imagery Source: USGS National Map 2023 United States Department of Agriculture A product of the National Cooperative Soil Survey, a joint effort of the United States Department of Agriculture and other Federal agencies, State agencies including the Agricultural Experiment Stations, and local participants Custom Soil Resource Report for King County Area, Washington Natural Resources Conservation Service February 5, 2025 Preface Soil surveys contain information that affects land use planning in survey areas. They highlight soil limitations that affect various land uses and provide information about the properties of the soils in the survey areas. Soil surveys are designed for many different users, including farmers, ranchers, foresters, agronomists, urban planners, community officials, engineers, developers, builders, and home buyers. Also, conservationists, teachers, students, and specialists in recreation, waste disposal, and pollution control can use the surveys to help them understand, protect, or enhance the environment. Various land use regulations of Federal, State, and local governments may impose special restrictions on land use or land treatment. Soil surveys identify soil properties that are used in making various land use or land treatment decisions. The information is intended to help the land users identify and reduce the effects of soil limitations on various land uses. The landowner or user is responsible for identifying and complying with existing laws and regulations. Although soil survey information can be used for general farm, local, and wider area planning, onsite investigation is needed to supplement this information in some cases. Examples include soil quality assessments (http://www.nrcs.usda.gov/wps/ portal/nrcs/main/soils/health/) and certain conservation and engineering applications. For more detailed information, contact your local USDA Service Center (https://offices.sc.egov.usda.gov/locator/app?agency=nrcs) or your NRCS State Soil Scientist (http://www.nrcs.usda.gov/wps/portal/nrcs/detail/soils/contactus/? cid=nrcs142p2_053951). Great differences in soil properties can occur within short distances. Some soils are seasonally wet or subject to flooding. Some are too unstable to be used as a foundation for buildings or roads. Clayey or wet soils are poorly suited to use as septic tank absorption fields. A high water table makes a soil poorly suited to basements or underground installations. The National Cooperative Soil Survey is a joint effort of the United States Department of Agriculture and other Federal agencies, State agencies including the Agricultural Experiment Stations, and local agencies. The Natural Resources Conservation Service (NRCS) has leadership for the Federal part of the National Cooperative Soil Survey. Information about soils is updated periodically. Updated information is available through the NRCS Web Soil Survey, the site for official soil survey information. The U.S. Department of Agriculture (USDA) prohibits discrimination in all its programs and activities on the basis of race, color, national origin, age, disability, and where applicable, sex, marital status, familial status, parental status, religion, sexual orientation, genetic information, political beliefs, reprisal, or because all or a part of an individual's income is derived from any public assistance program. (Not all prohibited bases apply to all programs.) Persons with disabilities who require 2 alternative means for communication of program information (Braille, large print, audiotape, etc.) should contact USDA's TARGET Center at (202) 720-2600 (voice and TDD). To file a complaint of discrimination, write to USDA, Director, Office of Civil Rights, 1400 Independence Avenue, S.W., Washington, D.C. 20250-9410 or call (800) 795-3272 (voice) or (202) 720-6382 (TDD). USDA is an equal opportunity provider and employer. 3 Contents Preface....................................................................................................................2 Soil Map..................................................................................................................5 Soil Map................................................................................................................6 Legend..................................................................................................................7 Map Unit Legend..................................................................................................8 Map Unit Descriptions..........................................................................................8 King County Area, Washington.......................................................................10 Ur—Urban land...........................................................................................10 4 Soil Map The soil map section includes the soil map for the defined area of interest, a list of soil map units on the map and extent of each map unit, and cartographic symbols displayed on the map. Also presented are various metadata about data used to produce the map, and a description of each soil map unit. 5 6 Custom Soil Resource Report Soil Map 52 5 7 4 1 0 52 5 7 4 3 0 52 5 7 4 5 0 52 5 7 4 7 0 52 5 7 4 9 0 52 5 7 5 1 0 52 5 7 5 3 0 52 5 7 5 5 0 52 5 7 5 7 0 52 5 7 5 9 0 52 5 7 4 1 0 52 5 7 4 3 0 52 5 7 4 5 0 52 5 7 4 7 0 52 5 7 4 9 0 52 5 7 5 1 0 52 5 7 5 3 0 52 5 7 5 5 0 52 5 7 5 7 0 52 5 7 5 9 0 558370 558390 558410 558430 558450 558470 558490 558510 558370 558390 558410 558430 558450 558470 558490 558510 47° 28' 8'' N 12 2 ° 1 3 ' 3 1 ' ' W 47° 28' 8'' N 12 2 ° 1 3 ' 2 4 ' ' W 47° 28' 2'' N 12 2 ° 1 3 ' 3 1 ' ' W 47° 28' 2'' N 12 2 ° 1 3 ' 2 4 ' ' W N Map projection: Web Mercator Corner coordinates: WGS84 Edge tics: UTM Zone 10N WGS84 0 45 90 180 270 Feet 0 10 20 40 60 Meters Map Scale: 1:937 if printed on A portrait (8.5" x 11") sheet. Soil Map may not be valid at this scale. MAP LEGEND MAP INFORMATION Area of Interest (AOI) Area of Interest (AOI) Soils Soil Map Unit Polygons Soil Map Unit Lines Soil Map Unit Points Special Point Features Blowout Borrow Pit Clay Spot Closed Depression Gravel Pit Gravelly Spot Landfill Lava Flow Marsh or swamp Mine or Quarry Miscellaneous Water Perennial Water Rock Outcrop Saline Spot Sandy Spot Severely Eroded Spot Sinkhole Slide or Slip Sodic Spot Spoil Area Stony Spot Very Stony Spot Wet Spot Other Special Line Features Water Features Streams and Canals Transportation Rails Interstate Highways US Routes Major Roads Local Roads Background Aerial Photography The soil surveys that comprise your AOI were mapped at 1:24,000. Warning: Soil Map may not be valid at this scale. Enlargement of maps beyond the scale of mapping can cause misunderstanding of the detail of mapping and accuracy of soil line placement. The maps do not show the small areas of contrasting soils that could have been shown at a more detailed scale. Please rely on the bar scale on each map sheet for map measurements. Source of Map: Natural Resources Conservation Service Web Soil Survey URL: Coordinate System: Web Mercator (EPSG:3857) Maps from the Web Soil Survey are based on the Web Mercator projection, which preserves direction and shape but distorts distance and area. A projection that preserves area, such as the Albers equal-area conic projection, should be used if more accurate calculations of distance or area are required. This product is generated from the USDA-NRCS certified data as of the version date(s) listed below. Soil Survey Area: King County Area, Washington Survey Area Data: Version 20, Aug 27, 2024 Soil map units are labeled (as space allows) for map scales 1:50,000 or larger. Date(s) aerial images were photographed: Jul 31, 2022—Aug 8, 2022 The orthophoto or other base map on which the soil lines were compiled and digitized probably differs from the background imagery displayed on these maps. As a result, some minor shifting of map unit boundaries may be evident. Custom Soil Resource Report 7 Map Unit Legend Map Unit Symbol Map Unit Name Acres in AOI Percent of AOI Ur Urban land 2.6 100.0% Totals for Area of Interest 2.6 100.0% Map Unit Descriptions The map units delineated on the detailed soil maps in a soil survey represent the soils or miscellaneous areas in the survey area. The map unit descriptions, along with the maps, can be used to determine the composition and properties of a unit. A map unit delineation on a soil map represents an area dominated by one or more major kinds of soil or miscellaneous areas. A map unit is identified and named according to the taxonomic classification of the dominant soils. Within a taxonomic class there are precisely defined limits for the properties of the soils. On the landscape, however, the soils are natural phenomena, and they have the characteristic variability of all natural phenomena. Thus, the range of some observed properties may extend beyond the limits defined for a taxonomic class. Areas of soils of a single taxonomic class rarely, if ever, can be mapped without including areas of other taxonomic classes. Consequently, every map unit is made up of the soils or miscellaneous areas for which it is named and some minor components that belong to taxonomic classes other than those of the major soils. Most minor soils have properties similar to those of the dominant soil or soils in the map unit, and thus they do not affect use and management. These are called noncontrasting, or similar, components. They may or may not be mentioned in a particular map unit description. Other minor components, however, have properties and behavioral characteristics divergent enough to affect use or to require different management. These are called contrasting, or dissimilar, components. They generally are in small areas and could not be mapped separately because of the scale used. Some small areas of strongly contrasting soils or miscellaneous areas are identified by a special symbol on the maps. If included in the database for a given area, the contrasting minor components are identified in the map unit descriptions along with some characteristics of each. A few areas of minor components may not have been observed, and consequently they are not mentioned in the descriptions, especially where the pattern was so complex that it was impractical to make enough observations to identify all the soils and miscellaneous areas on the landscape. The presence of minor components in a map unit in no way diminishes the usefulness or accuracy of the data. The objective of mapping is not to delineate pure taxonomic classes but rather to separate the landscape into landforms or landform segments that have similar use and management requirements. The delineation of such segments on the map provides sufficient information for the development of resource plans. If intensive use of small areas is planned, however, onsite investigation is needed to define and locate the soils and miscellaneous areas. Custom Soil Resource Report 8 An identifying symbol precedes the map unit name in the map unit descriptions. Each description includes general facts about the unit and gives important soil properties and qualities. Soils that have profiles that are almost alike make up a soil series. Except for differences in texture of the surface layer, all the soils of a series have major horizons that are similar in composition, thickness, and arrangement. Soils of one series can differ in texture of the surface layer, slope, stoniness, salinity, degree of erosion, and other characteristics that affect their use. On the basis of such differences, a soil series is divided into soil phases. Most of the areas shown on the detailed soil maps are phases of soil series. The name of a soil phase commonly indicates a feature that affects use or management. For example, Alpha silt loam, 0 to 2 percent slopes, is a phase of the Alpha series. Some map units are made up of two or more major soils or miscellaneous areas. These map units are complexes, associations, or undifferentiated groups. A complex consists of two or more soils or miscellaneous areas in such an intricate pattern or in such small areas that they cannot be shown separately on the maps. The pattern and proportion of the soils or miscellaneous areas are somewhat similar in all areas. Alpha-Beta complex, 0 to 6 percent slopes, is an example. An association is made up of two or more geographically associated soils or miscellaneous areas that are shown as one unit on the maps. Because of present or anticipated uses of the map units in the survey area, it was not considered practical or necessary to map the soils or miscellaneous areas separately. The pattern and relative proportion of the soils or miscellaneous areas are somewhat similar. Alpha-Beta association, 0 to 2 percent slopes, is an example. An undifferentiated group is made up of two or more soils or miscellaneous areas that could be mapped individually but are mapped as one unit because similar interpretations can be made for use and management. The pattern and proportion of the soils or miscellaneous areas in a mapped area are not uniform. An area can be made up of only one of the major soils or miscellaneous areas, or it can be made up of all of them. Alpha and Beta soils, 0 to 2 percent slopes, is an example. Some surveys include miscellaneous areas. Such areas have little or no soil material and support little or no vegetation. Rock outcrop is an example. Custom Soil Resource Report 9 King County Area, Washington Ur—Urban land Map Unit Composition Urban land:100 percent Estimates are based on observations, descriptions, and transects of the mapunit. Description of Urban Land Interpretive groups Land capability classification (irrigated): None specified Land capability classification (nonirrigated): 8 Hydric soil rating: No Custom Soil Resource Report 10 Q: \ 2 0 2 4 \ 2 2 4 0 8 1 9 \ 1 0 _ C I V \ C A D \ E X H I B I T S \ 2 0 2 5 0 5 0 2 D e v e l o p e d B a s i n M a p - C o p y . d w g 2215 North 30th Street, Suite 300, Tacoma, WA 98403 253.383.2422 TEL 253.383.2572 FAX JOB NO. DATE: WALKER SUBARU SERVICE CENTER CRITICAL AREAS MAP A-5 2240819.10 2/5/2025 REGULATED SLOPES Construction Stormwater Pollution Prevention Plan Walker Subaru Service Center 2240819.10 Appendix B Exhibits B-1 .................... TESC Plans B-2 .................... Select Pollution Prevention Measures GPGP GP GP GP GP GP GP GP GP GP GP GP GP GP GP GP GP GP P P GP GP S0 1 ° 2 3 ' 1 0 " W 2 7 8 . 3 5 ' ( M ) RAMP C/C C/C C/C C/C RAMP 12" MAPLE 12" MAPLE 14" MAPLE 8" UNKNOWN DECIDUOUS DRIVEWAY C/G C/G C/G E/C E/C E/CE/C E/C E/C 6' CLF 6' CLF 6' CLF 0.6' 0.5' NOT PART OF SURVEY (TAX PARCEL NO. 3340404150) NOT PART OF SURVEY (TAX PARCEL NO. 3340404150) GATE 0.3' 0.1' 4.9' 8.0' 6' CLF 7' CLF 6' CLF 6' CLF 6' CLF ANGLE POINT BEARS S84°11'E, 0.6' FROM CALCULATED LOT CORNER 6' CLF 6' CLF 6' CLF 6' CLF 8' CLF E/C E/C E/C E/C 5.1' 9.0' 8.2' 17.5' 3.1' 0.3' 10' CLF GATE 0.3' 0.1' 3X8" UNKNOWN DECIDUOUS GATE E/C E/C 6' CLF 6' CLF 6' CLF STOP BAR C/G C/G C/G C/G 30.0' DRIVEWAY E/C RA/W RA/W RA/W RA/W RA/W RA/W BUILDING FINISH FLOOR AT CENTER OF PED. DOOR LABELED "SPRINKLER ROOM" ELEV=21.95' NAVD 88 BUILDING FINISH FLOOR AT CENTER OF DOUBLE PED. DOOR ELEV=22.03' NAVD 88 E/C E/C E/C E/C E/C CONC. CANOPY COLUMN CONC. CANOPY COLUMN CONC. CANOPY COLUMN CONC. CANOPY COLUMN GATE GATE GATE 4' CLF4' CLF 4' CLF 4' CLF 4' CLF 4' CLF EDGE CANOPY (TYPICAL) EDGE CANOPY (TYPICAL) 12"MAPLE 13" MAPLE 17" MAPLE 11" MAPLE 14" MAPLE GATE 6' CLF "STOP" STEEL POST FOR AERIAL WALKER'S RENTON SUBARU PARTS AND SERVICE CENTER SIGN SERVICE CENTER DIRECTIONS SIGN C/C C/C RAMP E/C C/C C/C RAMP STEEL POST FOR AERIAL SUBARU SIGN 26.9'DRIVEWAY C/G RA/W 6' CLF 6' CLF 6' CLF 6' CLF 6' CLF 6' CLF 6' CLF GATE 6' CLF FENCE TRANSITION 6' CLF/6' STEEL 6' STEEL STORMWATER DETENTION POND 6' CLF 6' CLF 6' CLF 6' CLF 6' CLF 8' CLF 8' CLF 8' CLF 8' CLF 8' CLF 6' CLF 4' CLF 0.7' 1.2' 4.4' 2.8' 1.5' 0.8' 0.8' 1.5' 1.4' 1.0' 2.1' 0.4' 0.9' 1.0' 0.9' UNKNOWN USE CLEANOUT RIM=22.06' UNKNOWN USE CLEANOUT RIM=21.96' 525.46'(C) 117.44' S0 1 ° 2 2 ' 4 2 " W 11 6 . 4 3 ' N77°26'10" E 119.92' N0 1 ° 2 2 ' 4 3 " E 11 6 . 3 8 ' L1 8 L17 S0 9 ° 3 9 ' 1 5 " E 10 5 . 0 4 ' L2 0 L2 1 N77°24'38" E 123.29' 11 4 . 3 4 ' S86°20'10"W 391.52' 25 4 . 8 8 ' L1 0 L1 9 FND 1/2" REBAR AND CAP STAMPED "LS 19635" REBAR BEARS S88°24'33"E, 0.23' FROM THE CALCULATED LOT CORNER VISITED 11/18/2024 A/W A/W 0.7' 0.9' 1.0' 0.8' 3-WAY 6' CLF INTERSECTION BEARS S15°13'E, 6.2' 8'/6' CLF INTERSECTION BEARS S26°55'W, 0.8' FROM THE CALCULATED LOT CORNERGATE 8'/6' CLF INTERSECTION BEARS S79°15'W, 2.9' FROM THE CALCULATED LOT CORNER 75 . 2 0 ' PRIVATE INGRESS/EGRESS EASEMENT PER EASEMENT AGREEMENT WITH RIGHTS AND RESPONSIBILITIES AFN 20020612000622 QWEST TELECOMMUNICATIONS EASEMENT PER AFN 20030327000925 PRIVATE INGRESS/EGRESS EASEMENT PER EASEMENT AGREEMENT WITH RIGHTS AND RESPONSIBILITIES AFN 20020612000622 UTILITIES EASEMENT TO THE CITY OF RENTON PER AFN 20010906002177, CITY OF RENTON ORDINANCE 4914 (ENCOMPASSES WHOLE VACATED ALLEY) BUILDING FINISH FLOOR AT CENTER OF BAY DOOR ELEV=21.94' NAVD 88 6' CLF ANGLE POINT BEARS N53°23'W, 1.3' FROM CALCULATED LOT CORNER 8' CLF END BEARS N25°48'W, 1.0' FROM CALCULATED LOT CORNER PSE ELECTRICAL EASEMENT PER AFN 20030128002591 UTILITIES EASEMENT TO THE CITY OF RENTON PER AFN 20010906002177, CITY OF RENTON ORDINANCE 4914 (ENCOMPASSES WHOLE VACATED ALLEY) PSE ELECTRICAL EASEMENT PER AFN 20030128002591 PSE ELECTRICAL EASEMENT PER AFN 20030128002591 UTILITIES EASEMENT TO THE CITY OF RENTON PER AFN 20020207002539, CITY OF RENTON ORDINANCE 4942 (ENCOMPASSES WHOLE VACATED STREET) SE N E C A A V E S W SW 12TH S T SW 13TH S T INTERSTATE 405 EXISTING BUILDING FF: 21.95 FUTURE BUILDING OUTLINE FUTURE BUILDING OUTLINE 22.00 22.00 22.0 0 22.00 22 . 0 0 22.00 23.0 0 23.00 23 . 0 0 22.00 22.0022.00 21.00 21 . 0 0 23 . 0 0 PROTECT EXISTING STORM POND CONTRACTORS TO STABILIZE ALL DISTURBED PORTIONS OF THE SITE USING SEED, MULCH, OR OTHER ENGINEER APPROVED BMP IP (TYP.) AFTER CB INSTALLATION SF CL CL WATER QUALITY STRUCTURE SHALL NOT HAVE ANY SOIL MEDIA INSTALLED PRIOR TO FULL SITE STABILIZATION AND SHALL BE CLEANED PRIOR TO SOIL INSTALLATION WATER QUALITY STRUCTURE SHALL NOT HAVE ANY SOIL MEDIA INSTALLED PRIOR TO FULL SITE STABILIZATION AND SHALL BE CLEANED PRIOR TO SOIL INSTALLATION NO STAGING, CONSTRUCTION PARKING OR STOCKPILING OFFSITE OR IN PUBLIC ROW. ID CD MAINTAIN ACCESS TO GATE FOR NEIGHBORING PROPERTY OWNER DURING CONSTRUCTION OR HAVE AN AGREEMENT IN PLACE THAT ALLOWS FOR ACCESS TO BE CLOSED. CITY OF RENTON IN COMPLIANCE WITH CITY OF RENTON STANDARDS T A C O M A 2215 North 30th Street, Suite 300 Tacoma, WA 98403 253.383.2422TEL 253.383.2572FAX www.ahbl.comWEB S E A T T L E S P O K A N E T R I - C I T I E S WALKER SUBARU SERVICE CENTER PERMIT SET AHBL JOB #2240819.10 54 Know what's below. before you dig.Call R C2 6 0 0 0 6 3 8 LU A 2 5 - 0 0 0 1 7 1 PR 2 5 - 0 0 0 0 3 1 TE D - 4 0 - 4 3 8 8 N GRAPHIC SCALE 0 20 40 1" = 20 FEET 10 TESC LEGEND 16 TEMPORARY EROSION AND SEDIMENT CONTROL PLAN C1.2Q: \ 2 0 2 4 \ 2 2 4 0 8 1 9 \ 1 0 _ C I V \ C A D \ _ F i n a l D e s i g n \ 2 2 4 0 8 1 9 - S H - T E S C . d w g INLET PROTECTION SILT FENCE (MAINTAIN EXISTING) CLEARING LIMITS CONSTRUCTION ENTRANCE (MAINTAIN EXISTING) INTERCEPTOR DITCH CHECK DAM CL SF IP CE SAWCUT LINE CE CE EROSION CONTROL AND SEDIMENT CONTROL (ESC) FACILITIES SHALL NOT BE ALLOWED TO FALL INTO DISREPAIR. ALL ESC FACILITIES SHALL BE INSPECTED AS A MINIMUM, ACCORDING TO THE FOLLOWING SCHEDULE: DRY SEASON: ONCE A WEEK WET SEASON: DAILY, AND AFTER EVERY RAINFALL EVENT PRODUCING RUNOFF. NEEDED REPAIRS SHALL BE MADE WITHIN 24 HOURS OR IMMEDIATELY IF POSSIBLE. INSPECTION SCHEDULE FOR ESC FACILITIES 3 C1.3 2 C1.3 4 C1.3 THE WALKER'S RENTON SUBARU SERVICE DEPARTMENT EXPANSION SITE PLAN REVIEW, CONDITIONAL USE PERMIT, AND MODIFICATION, FILE NO. LUA25-000171, ECF, CU-A, SA-A, MOD, AS DEPICTED IN EXHIBIT 3, IS APPROVED AND IS SUBJECT TO THE FOLLOWING CONDITIONS: 1.THE APPLICANT SHALL COMPLY WITH THE THREE (3) MITIGATION MEASURES INCLUDED AS PART OF THE DETERMINATION OF NON-SIGNIFICANCE - MITIGATED (DNS-M) ISSUED BY THE RENTON ENVIRONMENTAL REVIEW COMMITTEE ON JULY 7, 2025. a.THE PROJECT CONSTRUCTION SHALL COMPLY WITH THE RECOMMENDATIONS FOUND IN THE GEOTECHNICAL ENGINEERING REPORT, PREPARED BY MIGIZI GROUP AND DATED DECEMBER 11, 2024, OR FUTURE ADDENDA. b.THE APPLICANT’S GEOTECHNICAL ENGINEER SHALL REVIEW THE FINAL CONSTRUCTION AND BUILDING PERMIT PLANS TO VERIFY CONSISTENCY WITH THE REPORT RECOMMENDATIONS. A STAMPED LETTER SHALL BE PROVIDED TO THE CITY CONFIRMING THAT THE PLANS MEET THE INTENT OF THE GEOTECHNICAL RECOMMENDATIONS. c.THE APPLICANT SHALL SAMPLE SOIL FOR ARSENIC AND LEAD FOLLOWING THE 2019 TACOMA SMELTER PLUME GUIDANCE. IF LEAD OR ARSENIC ARE FOUND AT CONCENTRATIONS ABOVE THE MODEL TOXICS CONTROL ACT (MTCA) CLEANUP LEVEL, CONSTRUCTION WORKERS AND EMPLOYEES ON-SITE SHALL BE NOTIFIED OF THEIR OCCURRENCE. 2.THE APPLICANT SHALL SUBMIT A REVISED SITE PLAN WITH THE BUILDING PERMIT APPLICATION THAT IDENTIFIES ONE (1) OR MORE REFUSE AND RECYCLABLES ENCLOSURES COMPLIANT WITH THE SIZE REQUIREMENTS IN RMC 4-4-090E.3 OR OBTAIN MODIFICATION APPROVAL TO REDUCE THE MINIMUM SIZE REQUIREMENT. THE REFUSE AND RECYCLING ENCLOSURE(S) SHALL BE SIZED BASED ON THE COMBINED SQUARE FOOTAGE OF BOTH DEALERSHIPS TO ENSURE ADEQUATE SPACE IS PROVIDED. THE REVISED SITE PLAN OR MODIFICATION SHALL BE REVIEWED AND APPROVED BY THE CURRENT PLANNING PROJECT MANAGER PRIOR TO BUILDING PERMIT APPROVAL. 3.THE APPLICANT SHALL PROVIDE DETAILED PLANS FOR A MINIMUM OF SIX (6) BICYCLE PARKING SPACES MEETING THE STANDARDS OF RMC 4-4-080F.11. THE DESIGN, SPECIFICATIONS, AND PLACEMENT OF THE BICYCLE PARKING SPACES SHALL BE SUBMITTED FOR REVIEW AND APPROVAL BY THE CURRENT PLANNING PROJECT MANAGER PRIOR TO CIVIL CONSTRUCTION PERMIT ISSUANCE. 4.THE APPLICANT SHALL SUBMIT A REVISED LANDSCAPE PLAN IDENTIFYING ON-SITE LANDSCAPING THAT TOTALS A MINIMUM OF TWO AND ONE-HALF PERCENT (2.5%) OF THE SITE AREA. THE REVISED LANDSCAPE PLAN SHALL BE REVIEWED AND APPROVED BY THE CURRENT PLANNING PROJECT MANAGER PRIOR TO CIVIL CONSTRUCTION PERMIT ISSUANCE. 5.THE APPLICANT SHALL SUBMIT A LIGHTING PLAN THAT DEMONSTRATES COMPLIANCE WITH RENTON MUNICIPAL CODE AND PROVIDE ENOUGH LIGHT FOR SAFETY BUT DOES NOT PROVIDE EXCESSIVE LIGHT ACROSS THE SITE THAT WOULD IMPACT ADJACENT PROPERTIES AT THE TIME OF CONSTRUCTION PERMIT REVIEW. CONDITIONS OF APPROVAL R-438816 TEMPORARY SEDIMENT TRAP MIN SURFACE AREA: 1501 SF TOP POND: 21.0 6' WIDE SPILLWAY: 20.0 BOTTOM POND: 17.5 USE EXISTING BIOSWALE AS TEMPORARY SEDIMENT TRAP. BIOSWALE OUTLET TO BE PLUGGED/REMOVED PRIOR TO CONSTRUCTION RUNOFF BEING DIRECTED INTO THE SEDIMENT TRAP. CONCRETE WASHOUT AREA, CONTRACTOR TO PROVIDE CONCRETE WASHOUT AS NECESSARY ID CD 2 C1.4 3 C1.4 CITY OF RENTON IN COMPLIANCE WITH CITY OF RENTON STANDARDS T A C O M A 2215 North 30th Street, Suite 300 Tacoma, WA 98403 253.383.2422TEL 253.383.2572FAX www.ahbl.comWEB S E A T T L E S P O K A N E T R I - C I T I E S WALKER SUBARU SERVICE CENTER PERMIT SET AHBL JOB #2240819.10 54 Know what's below. before you dig.Call R C2 6 0 0 0 6 3 8 LU A 2 5 - 0 0 0 1 7 1 PR 2 5 - 0 0 0 0 3 1 TE D - 4 0 - 4 3 8 8 17 TESC NOTES AND DETAILS C1.3Q: \ 2 0 2 4 \ 2 2 4 0 8 1 9 \ 1 0 _ C I V \ C A D \ _ F i n a l De s i g n \ 2 2 4 0 8 1 9 - S H - T E S C - D E T L . d w g 1.BEFORE ANY CONSTRUCTION OR DEVELOPMENT ACTIVITY OCCURS, A PRE-CONSTRUCTION MEETING SHALL BE HELD AMONG THE CITY OF RENTON, HEREBY REFERRED TO AS THE CITY, THE APPLICANT, AND THE APPLICANT’S CONTRACTOR. 2.THE APPLICANT IS RESPONSIBLE FOR OBTAINING THE WASHINGTON STATE DEPARTMENT OF ECOLOGY (ECOLOGY) CONSTRUCTION STORMWATER GENERAL PERMIT, IF IT IS REQUIRED FOR THE PROJECT. THE APPLICANT SHALL PROVIDE THE CITY COPIES OF ALL MONITORING REPORTS PROVIDED TO ECOLOGY ASSOCIATED WITH THE CONSTRUCTION STORMWATER GENERAL PERMIT. 3.THE ESC PLAN SET SHALL INCLUDE AN ESC CONSTRUCTION SEQUENCE DETAILING THE ORDERED STEPS THAT SHALL BE FOLLOWED FROM THE PRE-CONSTRUCTION MEETING TO POST-PROJECT CLEANUP IN ORDER TO FULFILL PROJECT ESC REQUIREMENTS. 4.THE BOUNDARIES OF THE CLEARING LIMITS, SENSITIVE AREAS AND THEIR BUFFERS, AND AREAS OF VEGETATION PRESERVATION AND TREE RETENTION, AS PRESCRIBED ON THE PLAN(S), SHALL BE CLEARLY FLAGGED BY SURVEY TAPE OR FENCING AND PROTECTED IN THE FIELD IN ACCORDANCE WITH APPENDIX D OF THE CITY OF RENTON SURFACE WATER DESIGN MANUAL (RSWDM) PRIOR TO CONSTRUCTION. DURING THE CONSTRUCTION PERIOD, NO DISTURBANCE BEYOND THE CLEARING LIMITS SHALL BE PERMITTED. THE CLEARING LIMITS SHALL BE MAINTAINED BY THE APPLICANT/ESC SUPERVISOR FOR THE DURATION OF CONSTRUCTION. 5.STABILIZED CONSTRUCTION ENTRANCES SHALL BE INSTALLED AT THE BEGINNING OF CONSTRUCTION AND MAINTAINED FOR THE DURATION OF THE PROJECT. ADDITIONAL MEASURES, SUCH AS CONSTRUCTED WHEEL WASH SYSTEMS OR WASH PADS, MAY BE REQUIRED TO ENSURE THAT ALL PAVED AREAS ARE KEPT CLEAN AND TRACK-OUT TO ROAD RIGHT OF WAY DOES NOT OCCUR FOR THE DURATION OF THE PROJECT. IF SEDIMENT IS TRACKED OFFSITE, PUBLIC ROADS SHALL BE CLEANED THOROUGHLY AT THE END OF EACH DAY, OR MORE FREQUENTLY DURING WET WEATHER, AS NECESSARY TO PREVENT SEDIMENT FROM ENTERING WATERS OF THE STATE. 6.WASHOUT FROM CONCRETE TRUCKS SHALL BE PERFORMED OFF-SITE OR IN DESIGNATED CONCRETE WASHOUT AREAS ONLY. DO NOT WASH OUT CONCRETE TRUCKS ONTO THE GROUND, OR TO STORM DRAINS OR OPEN DITCHES. ON-SITE DUMPING OF EXCESS CONCRETE SHALL ONLY OCCUR IN DESIGNATED CONCRETE WASHOUT AREAS. 7.ALL REQUIRED ESC BMPS SHALL BE CONSTRUCTED AND IN OPERATION PRIOR TO LAND CLEARING AND/OR CONSTRUCTION TO PREVENT TRANSPORTATION OF SEDIMENT TO SURFACE WATER, DRAINAGE SYSTEMS AND ADJACENT PROPERTIES. ALL ESC BMPS SHALL BE MAINTAINED IN A SATISFACTORY CONDITION UNTIL SUCH TIME THAT CLEARING AND/OR CONSTRUCTION IS COMPLETE AND POTENTIAL FOR ON-SITE EROSION HAS PASSED. ALL ESC BMPS SHALL BE REMOVED AFTER CONSTRUCTION IS COMPLETED AND THE SITE HAS BEEN STABILIZED TO ENSURE POTENTIAL FOR ON-SITE EROSION DOES NOT EXIST. THE IMPLEMENTATION, MAINTENANCE, REPLACEMENT, ENHANCEMENT, AND REMOVAL OF ESC BMPS SHALL BE THE RESPONSIBILITY OF THE APPLICANT. 8.ANY HAZARDOUS MATERIALS OR LIQUID PRODUCTS THAT HAVE THE POTENTIAL TO POLLUTE RUNOFF SHALL BE DISPOSED OF PROPERLY. 9.THE ESC BMPS DEPICTED ON THIS DRAWING ARE INTENDED TO BE MINIMUM REQUIREMENTS TO MEET ANTICIPATED SITE CONDITIONS. AS CONSTRUCTION PROGRESSES AND UNEXPECTED OR SEASONAL CONDITIONS DICTATE, THE APPLICANT SHALL ANTICIPATE THAT MORE ESC BMPS WILL BE NECESSARY TO ENSURE COMPLETE SILTATION CONTROL ON THE PROPOSED SITE. DURING THE COURSE OF CONSTRUCTION, IT SHALL BE THE OBLIGATION AND RESPONSIBILITY OF THE APPLICANT TO ADDRESS ANY NEW CONDITIONS THAT MAY BE CREATED BY THE ACTIVITIES AND TO PROVIDE ADDITIONAL ESC BMPS, OVER AND ABOVE MINIMUM REQUIREMENTS, AS MAY BE NEEDED, TO PROTECT ADJACENT PROPERTIES AND WATER QUALITY OF THE RECEIVING DRAINAGE SYSTEM. 10.APPROVAL OF THIS PLAN IS FOR ESC ONLY. IT DOES NOT CONSTITUTE AN APPROVAL OF STORM DRAINAGE DESIGN, SIZE NOR LOCATION OF PIPES, RESTRICTORS, CHANNELS, OR STORMWATER FACILITIES. 11.ANY DEWATERING SYSTEM NECESSARY FOR THE CONSTRUCTION OF STORMWATER FACILITIES SHALL BE SUBMITTED TO THE CITY FOR REVIEW AND APPROVAL. 12.ANY AREAS OF EXPOSED SOILS, INCLUDING ROADWAY EMBANKMENTS, THAT WILL NOT BE DISTURBED FOR TWO DAYS DURING THE WET SEASON (OCTOBER 1ST THROUGH APRIL 30TH) OR SEVEN DAYS DURING THE DRY SEASON (MAY 1ST THROUGH SEPTEMBER 30TH) SHALL BE IMMEDIATELY STABILIZED WITH THE APPROVED ESC COVER METHODS (E.G., SEEDING, MULCHING, PLASTIC COVERING, ETC.) IN CONFORMANCE WITH APPENDIX D OF THE RSWDM. 13.WET SEASON ESC REQUIREMENTS APPLY TO ALL CONSTRUCTION SITES BETWEEN OCTOBER 1ST AND APRIL 30TH, UNLESS OTHERWISE APPROVED BY THE CITY. 14.ANY AREA NEEDING ADDITIONAL ESC MEASURES, NOT REQUIRING IMMEDIATE ATTENTION, SHALL BE ADDRESSED WITHIN SEVEN (7) DAYS. 15.THE ESC BMPS ON INACTIVE SITES SHALL BE INSPECTED AND MAINTAINED AT A MINIMUM OF ONCE A MONTH OR WITHIN 24 HOURS FOLLOWING A STORM EVENT. INSPECTION AND MAINTENANCE SHALL OCCUR MORE FREQUENTLY AS REQUIRED BY THE CITY. 16.BEFORE COMMENCEMENT OF ANY CONSTRUCTION ACTIVITY, CATCH BASIN INSERTS PER THE CITY STANDARD PLANS SHALL BE PROVIDED FOR ALL STORM DRAIN INLETS DOWNSLOPE AND WITHIN 500 FEET OF A DISTURBED OR CONSTRUCTION AREA, UNLESS THE RUNOFF THAT ENTERS THE INLET WILL BE CONVEYED TO A SEDIMENT POND OR TRAP. ALL CATCH BASIN INSERTS SHALL BE PERIODICALLY INSPECTED AND REPLACED AS NECESSARY TO ENSURE FULLY FUNCTIONING CONDITION. 17.AT NO TIME SHALL SEDIMENT ACCUMULATION EXCEED 2/3 OF THE CAPACITY OF THE CATCH BASIN SUMP. ALL CATCH BASINS AND CONVEYANCE LINES SHALL BE CLEANED PRIOR TO PAVING. THE CLEANING OPERATION SHALL NOT FLUSH SEDIMENT-LADEN WATER INTO THE DOWNSTREAM SYSTEM. 18.ANY PERMANENT STORMWATER FACILITY USED AS A TEMPORARY SETTLING BASIN SHALL BE MODIFIED WITH THE NECESSARY ESC BMPS AND SHALL PROVIDE ADEQUATE STORAGE CAPACITY. IF THE PERMANENT FACILITY IS TO FUNCTION ULTIMATELY AS AN INFILTRATION SYSTEM, THE TEMPORARY FACILITY SHALL BE ROUGH GRADED SO THAT THE BOTTOM AND SIDES ARE AT LEAST THREE FEET ABOVE THE FINAL GRADE OF THE PERMANENT FACILITY. 19.AREAS DESIGNATED ON THE PLAN(S) CONTAINING EXISTING STORMWATER FACILITIES OR ON-SITE BMPS (AMENDED SOILS, BIORETENTION, PERMEABLE PAVEMENT, ETC.) SHALL BE CLEARLY FENCED AND PROTECTED USING ESC BMPS TO AVOID SEDIMENTATION AND COMPACTION DURING CONSTRUCTION. 20.PRIOR TO THE BEGINNING OF THE WET SEASON (OCTOBER 1ST), ALL DISTURBED AREAS SHALL BE INSPECTED TO IDENTIFY WHICH ONES SHALL BE SODDED OR SEEDED IN PREPARATION FOR THE WINTER RAINS. DISTURBED AREAS SHALL BE SODDED OR SEEDED WITHIN ONE WEEK OF THE BEGINNING OF THE WET SEASON. AN EXHIBIT OF THOSE AREAS TO BE SODDED OR SEEDED AND THOSE AREAS TO REMAIN UNCOVERED SHALL BE SUBMITTED TO THE CITY FOR REVIEW. 21.PRIOR TO FINAL CONSTRUCTION ACCEPTANCE, THE PROJECT SITE SHALL BE STABILIZED TO PREVENT SEDIMENT-LADEN WATER FROM LEAVING THE PROJECT SITE, ALL ESC BMPS SHALL BE REMOVED, AND STORMWATER CONVEYANCE SYSTEMS, FACILITIES, AND ON-SITE BMPS SHALL BE RESTORED TO THEIR FULLY FUNCTIONING CONDITION. ALL DISTURBED AREAS OF THE PROJECT SITE SHALL BE VEGETATED OR OTHERWISE PERMANENTLY STABILIZED. AT A MINIMUM, DISTURBED AREAS SHALL BE SODDED OR SEEDED AND MULCHED TO ENSURE THAT SUFFICIENT COVER WILL DEVELOP SHORTLY AFTER FINAL APPROVAL. MULCH WITHOUT SEEDING IS ADEQUATE FOR SMALL AREAS TO BE LANDSCAPED BEFORE OCTOBER 1ST. 22.ROCKERIES ARE CONSIDERED TO BE A METHOD OF BANK STABILIZATION AND EROSION CONTROL. ROCKERIES SHALL NOT BE CONSTRUCTED TO SERVE AS RETAINING WALLS. ALL ROCKERIES IN CITY ROAD RIGHT-OF-WAY SHALL BE CONSTRUCTED IN ACCORDANCE WITH CITY STANDARDS. ROCKERIES OUTSIDE OF ROAD RIGHT-OF-WAY SHALL BE CONSTRUCTED IN ACCORDANCE WITH THE INTERNATIONAL BUILDING CODE. EROSION CONTROL (ESC) STANDARD PLAN NOTES (PER COR STD 268.00) 1.PLASTIC SHEETING SHALL HAVE A MINIMUM THICKNESS OF 6 MILS AND SHALL MEET THE REQUIREMENTS OF THE STATE STANDARD SPECIFICATIONS SECTION 9-14.5. 2.COVERING SHALL BE INSTALLED AND MAINTAINED TIGHTLY IN PLACE BY USING SANDBAGS OR TIRES ON ROPES WITH A MAXIMUM 10-FOOT GRID SPACING IN ALL DIRECTIONS. ALL SEAMS SHALL BE TAPED OR WEIGHTED DOWN FULL LENGTH AND THERE SHALL BE AT LEAST A 12 INCH OVERLAP OF ALL SEAMS. 3.CLEAR PLASTIC COVERING SHALL BE INSTALLED IMMEDIATELY ON AREAS SEEDED BETWEEN NOVEMBER 1 AND MARCH 31 AND REMAIN UNTIL VEGETATION IS FIRMLY ESTABLISHED. 4.WHEN THE COVERING IS USED ON UN-SEEDED SLOPES, IT SHALL BE KEPT IN PLACE UNTIL THE NEXT SEEDING PERIOD. 5.PLASTIC COVERING SHEET SHALL BE BURIED TWO FEET AT THE TOP OF SLOPES IN ORDER TO PREVENT SURFACE WATER FLOW BENEATH SHEETS. 6.PROPER MAINTENANCE INCLUDES REGULAR CHECKS FOR RIPS AND DISLODGED ENDS. PLASTIC COVERING NOTES: 1 PLASTIC COVERING 2 SILT FENCE 3 STABILIZED CONSTRUCTION ENTRANCE 4 CATCH BASIN INSERT R-438817 CITY OF RENTON IN COMPLIANCE WITH CITY OF RENTON STANDARDS T A C O M A 2215 North 30th Street, Suite 300 Tacoma, WA 98403 253.383.2422TEL 253.383.2572FAX www.ahbl.comWEB S E A T T L E S P O K A N E T R I - C I T I E S WALKER SUBARU SERVICE CENTER PERMIT SET AHBL JOB #2240819.10 54 Know what's below. before you dig.Call R C2 6 0 0 0 6 3 8 LU A 2 5 - 0 0 0 1 7 1 PR 2 5 - 0 0 0 0 3 1 TE D - 4 0 - 4 3 8 8 18 TESC NOTES AND DETAILS CONT. C1.4Q: \ 2 0 2 4 \ 2 2 4 0 8 1 9 \ 1 0 _ C I V \ C A D \ _ F i n a l De s i g n \ 2 2 4 0 8 1 9 - S H - T E S C - D E T L . d w g 10. SEED SHALL NOT BE USED IN AREAS SUBJECT TO WEAR BY CONSTRUCTION TRAFFIC. 3. APPLICATION TO BE 100 LBS/ACRE. SEDIMENT BASINS. AND WETLANDS. 6. FOR SEED BEDS PLANTED BETWEEN OCTOBER 31 AND APRIL 30, ARMORING OF THE 7. BEFORE SEEDING, INSTALL NEEDED SURFACE RUNOFF CONTROL MEASURES SUCH 8. THE SEEDBED SHALL BE FIRM WITH A FAIRLY FINE SURFACE, FOLLOWING SURFACE 9. FERTILIZERS ARE TO BE USED ACCORDING TO SUPPLIERS RECOMMENDATIONS. 5. SEED BEDS PLANTED BETWEEN MAY 1 AND OCTOBER 31 WILL REQUIRE IRRIGATION 4. 500 LBS/ACRE 10-20-20 FERTILIZER, 2000 LBS/ACRE WOOD FIBER CELLULOSE AND AND OTHER MAINTENANCE AS NECESSARY TO FOSTER AND PROTECT THE ROOT SEED BED WILL BE NECESSARY. (E.G., GEOTEXTILES, JUTE MAT, CLEAR PLASTIC AS GRADIENT TERRACES, INTERCEPTOR DIKES, SWALES, LEVEL SPREADERS AND ROUGHENING. PERFORM ALL OPERATIONS ACROSS OR AT RIGHT ANGLES TO THE AMOUNTS USED SHOULD BE MINIMIZED, ESPECIALLY ADJACENT TO WATER BODIES 40 LBS/ACRE SOIL BINDER OR TACKING AGENT TO BE APPLIED WITH SEED MIXTURE. COVERING.) SLOPE. STRUCTURE. NOTES" ON THIS SHEET. HYDROSEEDING NOTES: 2. HYDROSEEDING TO BE THE FOLLOWING MIXTURE: 1. HYDROSEEDING SHALL BE APPLIED IN ACCORDANCE WITH THE "EROSION CONTROL 1.MULCH MATERIALS USED SHALL BE HAY OR STRAW, AND SHALL BE APPLIED AT THE RATE OF 2 TONS/ACRE. (MIN. 2" THICK) 2.MULCHES SHALL BE APPLIED IN ALL AREAS WITH EXPOSED SLOPES GREATER THAN 2:1. 3.MULCHING SHALL BE USED IMMEDIATELY AFTER SEEDING OR IN AREAS WHICH CANNOT BE SEEDED BECAUSE OF THE SEASON. 4.ALL AREAS NEEDING MULCH SHALL BE COVERED BY NOVEMBER 1. MULCHING NOTES: R-438818 1 SEDIMENT TRAP 2 INTERCEPTOR SWALE 3 DITCH CHECK DAMS 4 TREE PROTECTION 1.FROM OCTOBER 1ST THROUGH APRIL 30TH, NO SOILS SHALL BE EXPOSED FOR MORE THAN TWO CONSECUTIVE WORKING DAYS. THIS TWO-DAY REQUIREMENT MAY BE APPLIED AT OTHER TIMES OF THE YEAR IF STORM EVENTS WARRANT MORE CONSERVATIVE MEASURES. 2.EXPOSED SOILS SHALL BE STABILIZED AT THE END OF THE WORKDAY PRIOR TO A WEEKEND, HOLIDAY, OR PREDICTED RAIN EVENT. 3.A WEEKLY MAINTENANCE REPORT IS REQUIRED TO BE SUBMITTED TO CED. WET SEASON NOTES: Construction Stormwater Pollution Prevention Plan Walker Subaru Service Center 2240819.10 Appendix C Inspection and Maintenance Report Construction Stormwater Pollution Prevention Plan Walker Subaru Service Center 2240819.10 Appendix D Engineering Calculations 2215 N. 30th Street, #300 Tacoma, WA 98403 253.383.2422 TEL 253.383.2572 FAX www.ahbl.com Walker Renton Subaru 2240819.10 Engineering Calculations Sediment Trap Sizing D Surface Area SA = 2Q2 / 0.00096 SA = 2(0.7206cfs) / 0.00096 SA = 1501 sf Spillway L = (Q100 / 3.21H3/2)- 2.4H L = (1.465cfs / 3.21(0.2ft)3/2) - 2.4 x 0.2ft L = 4.62 ft (6.0ft min) Technical Information Report Walker Subaru Service Center 2240819.10 Appendix G Stormwater Maintenance Plan Civil Engineers ● Structural Engineers ● Landscape Architects ● Community Planners ● Land Surveyors Stormwater Maintenance Plan PREPARED FOR: ADF Properties, LLC 15007 Woodinville-Redmond Rd, Suite A Woodinville, WA 98072 PROJECT: Walker Subaru Service Center Renton, WA 2240819.10 PREPARED BY: Nathan Kaser Project Engineer REVIEWED BY: Scott T. Kaul, PE, LEED AP Principal DATE: January 2026 Revised April 2026 Stormwater Maintenance Plan PREPARED FOR: ADF Properties, LLC 15007 Woodinville-Redmond Rd, Suite A Woodinville, WA 98072 PROJECT: Walker Subaru Service Center Renton, WA 2240819.10 PREPARED BY: Nathan Kaser Project Engineer REVIEWED BY: Scott T. Kaul, PE, LEED AP Principal DATE: January 2026 Revised April 2026 I hereby state that this Stormwater Maintenance Plan for Walker Subaru Service Center has been prepared by me or under my supervision and meets the standard of care and expertise that is usual and customary in this community for professional engineers. I understand that City of Renton does not and will not assume liability for the sufficiency, suitability, or performance of drainage facilities prepared by me. 04/08/2026 Stormwater Maintenance Plan Walker Subaru Service Center 2240819.10 Table of Contents Section Page 1.0 Introduction .................................................................................................................................... 1 2.0 Responsibility ................................................................................................................................. 1 3.0 Schedule ......................................................................................................................................... 1 4.0 Vegetation Management Plan ....................................................................................................... 1 5.0 Source Control ............................................................................................................................... 1 6.0 Instructions for Person Maintaining Stormwater System .......................................................... 2 7.0 Conclusion ...................................................................................................................................... 2 Stormwater Maintenance Plan Walker Subaru Service Center 2240819.10 Attachments Attachment A Maintenance Guide A-1 ............Maintenance Checklist A-2 ............Site Specific Best Management Practices (BMPs) A-3 ............BioPod Maintenance Guide Attachment B Exhibits B-1 ............Vicinity Map B-2 ............Developed Conditions Stormwater Maintenance Plan Walker Subaru Service Center 1 2240819.10 1.0 Introduction This report presents a maintenance program that meets the requirements of the 2022 City of Renton Surface Water Design Manual (Storm Manual). The private stormwater control facilities associated with the Renton Walker Subaru Service Center site include catch basins, conveyance pipes, detention pond, and pipe discharge. It is vitally important that these facilities are maintained in a timely and conscientious manner to ensure the facilities operate as intended. If the collection, conveyance, or treatment facilities are not adequately inspected and maintained periodically, it could lead to surcharging of the stormwater conveyance network, local flooding, increased erosion potential, and possible groundwater contamination. Siltation, debris, or lack of general maintenance can reduce the performance capabilities of the facilities. 2.0 Responsibility The stormwater facilities associated with the Walker Subaru Service Center project are private and maintenance shall be the responsibility of ADF Properties, LLC. 3.0 Schedule Maintenance of the stormwater facilities shall follow the schedule as specified in the Storm Manual. Additional maintenance may be required to respond to unusual storm events or reduced performance of the treatment. A copy of the recommended maintenance schedule is included in Attachment A and may be photocopied and used as inspection records. 4.0 Vegetation Management Plan The attached maintenance schedule provides guidance on vegetation control and management. Irrigation and other maintenance as necessary shall be provided to ensure that vegetation remains viable and that a hardy root structure forms in the first year. Vegetation planting shall be provided as described in the construction documents. 5.0 Source Control Wastes for this development will consist of oil, grease (and other contaminants from cars), sediment, and small quantities of fertilizers and pesticides. The following actions should be taken so that pollution generated onsite will be minimized: 1. Vehicle maintenance, washing, mixing of pesticides, or any other activities that would contribute high concentrations of pollution to the stormwater conveyance system should not be performed in the parking areas. 2. Vegetation along the road edges, including cut and fill slopes, shall be maintained to prevent erosion of the banks. 3. Street sweeping shall be performed to reduce the quantity of sediment being transported to the storm drainage system. 4. The stormwater facilities shall be inspected and maintained per the checklists and BMPs in Attachment A. Stormwater Maintenance Plan Walker Subaru Service Center 2 2240819.10 6.0 Instructions for Person Maintaining Stormwater System Attachment A contains a stormwater facility maintenance schedule. Plan to complete a checklist for all system components per the following schedule: • Monthly from November through April • Once in late summer (preferably September) • After any major storm event Using photocopies of the attached pages, check off the problems that are noted each time the item is inspected. Document comments on problems found and the corrective action taken. The inspection checklist sheets should be kept on file and presented to City of Renton officials upon request. Use the suggested inspection frequency at the left of each item as an inspection guide (see Attachment A-1). When evaluating the operation and maintenance of the stormwater system, a log of activity should be noted. Minimum log information should include the following: • Name • Date • Weather • Problems Observed • Remedial Action Taken 7.0 Conclusion This Stormwater Maintenance Plan is developed for the stormwater facilities associated with the Walker Subaru Service Center project. The maintenance plan has been prepared within the guidelines of the 2022 City of Renton Storm Manual. If this plan is properly implemented, the owner can expect the stormwater conveyance system to function as designed. This analysis is based on data and records either supplied to or obtained by AHBL. These documents are referenced within the text of the analysis. The analysis has been prepared using procedures and practices within the standard accepted practices of the industry. AHBL, Inc. Nathan Kaser Project Engineer NK/lsk January 2026 Revised April 2026 Q:\2024\2240819\WORDPROC\Reports\20260408 Rpt (Maintenance Plan) 2240819.10.docx Stormwater Maintenance Plan Walker Subaru Service Center 2240819.10 Attachment A Maintenance Guide A-1 .................... Maintenance Checklist A-2 .................... Site Specific Best Management Practices (BMPs) A-3 .................... BioPod Maintenance Guide Stormwater Maintenance Plan Walker Subaru Service Center 2240819.10 Operations and Maintenance Manual The Walker Subaru Service Center project is located at 519 SW 12th Street, Renton, WA 98057. Improvements for the site will include construction of a building addition to the existing Subaru facility, parking, utility connections, and stormwater improvements. All other onsite stormwater improvements are to be the responsibility of ADF Properties, LLC. Table 1 below describes each stormwater facility, including what it does and how it works: Table 1. Stormwater Facility Descriptions Stormwater Facility Description Storm Drainage Manholes / Catch Basins Manholes and catch basins collect stormwater from the site and are connected to the storm drainage pipes. Roof Drain Conveys roof runoff from downspouts to detention pond. BioPod Underground Vault Provides enhanced water quality treatment of stormwater via storm mix media before runoff enters the detention pond. Detention Pond Engineered depression storage facility used to retain stormwater onsite. Maintenance of the stormwater system is required to ensure proper functioning of the system. The attached Maintenance Checklists are for your use when inspecting the stormwater facilities. The only checklists included are those that pertain to this project site. The checklists are in a tabular format for ease of use. Each describes the conditions to check for, inspection frequency, and action that needs to be taken if maintenance is required. Stormwater Maintenance Plan Walker Subaru Service Center 2240819.10 Walker Subaru Service Center Inspection Frequencies Asset Preferred Month Interval Storm Drainage Manholes / Catch Basins Annually Roof Drain Annually BioPod Annually Detention Pond Annually Landscaping March through April September through October Semi-annually Stormwater Maintenance Plan Walker Subaru Service Center 2240819.10 Walker Subaru Service Center Maintenance Activity Log DATE FACILITY DEFECT OR PROBLEM ACTION TAKEN CONDITION AFTER MAINTENANCE Inspection and Maintenance Manual High Flow System with StormMixTM Media BioPodTM HF BioPodTM HF High Flow System with StormMixTM Media Page 2 www.oldcastleinfrastructure.com | (888) 965-3227 Rev. 2/2025 6-A-045 | Operations and Maintenance Manual BioPodTM High Flow (HF) Biofilter with StormMixTM Biofiltration Media Desription The BioPod™ HF Biofilter System (BioPod HF) is a storm water biofiltration treatment system used to remove pollutants from storm water runoff. Impervious surfaces and other urban and suburban landscapes generate a variety of pollutants that can enter storm water and contaminate downstream receiving waters unless treatment is provided. The BioPod HF system uses proprietary StormMix™ biofiltration media to capture and retain pollutants including total suspended solids (TSS), metals, nutrients, gross solids, trash and debris. Function The BioPod HF system uses engineered, high-flow rate filter media to remove storm water pollutants, allowing for a smaller footprint than conventional bioretention systems. Contained within a compact precast concrete vault, the BioPod HF system consists of a biofiltration chamber and an optional integrated high-flow bypass. The biofiltration chamber is filled with horizontal layers of aggregate, biofiltration media and mulch. Storm water passes vertically down through the mulch and biofiltration media for treatment. The mulch provides pretreatment by retaining most of the solids or sediment. The biofiltration media provides further treatment by retaining finer sediment and dissolved pollutants. The aggregate allows the media bed to drain evenly for discharge through an underdrain pipe or by infiltration. Inspection & Maintenance Overview State and local regulations require all storm water management systems to be inspected on a regular basis and maintained as necessary to ensure performance and protect downstream receiving waters. Without maintenance, excessive pollutant buildup can limit system performance by reducing the operating capacity of the system and increasing the potential for scouring of pollutants during periods of high flow. The BioPod HF may require periodic irrigation to establish and maintain vegetation. Vegetation will typically become established about two years after planting. Irrigation requirements are ultimately dependent on climate, rainfall and the type of vegetation selected. Inspection & Maintenance Frequency Periodic inspection is essential for consistent system performance and is easily completed. Inspection is typically conducted a minimum of twice per year, but since pollutant transport and deposition varies from site to site, a site-specific maintenance frequency should be established during the first two or three years of operation. BioPodTM HF High Flow System with StormMixTM Media Page 3 www.oldcastleinfrastructure.com | (888) 965-3227 Rev. 2/2025 6-A-045 | Operations and Maintenance Manual Inspection Equipment The following equipment is helpful when conducting BioPod HF inspections: • Recording device (pen and paper form, voice recorder, iPad,etc.) • Suitable clothing (appropriate footwear, gloves, hardhat, safety glasses, etc.) • PPE as required for entry • Traffic control equipment (cones, barricades, signage, flagging, etc.) • Manhole hook or pry bar • Flashlight • Tape measure • Socket Inspection Procedures BioPod HF inspections are visual and are conducted without entering the unit. To complete an inspection, safety measures including traffic control should be deployed before the access covers or tree grates are removed. Once the covers have been removed, the following items should be checked and recorded (see form provided on page 8) to determine whether maintenance is required: • If the BioPod HF unit is equipped with an internal bypass, inspect the inlet chamber and outlet chamber and note whether there are any broken or missing parts. In the unlikely event that internal parts are broken or missing, contact Oldcastle Storm water at (800) 579-8819 to determine appropriate corrective action. • Note whether the curb inlet or inlet pipe is blocked or obstructed. • If the unit is equipped with an internal bypass, observe, quantify and record the accumulation of trash and debris in the inlet chamber. The significance of accumulated trash and debris is a matter of judgment. Often, much of the trash and debris may be removed manually at the time of inspection if a separate maintenance visit is not yet warranted. • If it has not rained within the past 24 hours, note whether standing water is observed in the biofiltration chamber. • Finally, observe, quantify and record presence of invasive vegetation and the amount of trash and debris and sediment load in the biofiltration chamber. Erosion of the mulch and biofiltration media bed should also be recorded. Often, much of the invasive vegetation and trash and debris may be removed manually at the time of inspection if a separate maintenance visit is not yet warranted. Sediment load may be rated light, medium or heavy depending on the conditions. Loading characteristics may be determined as follows: • Light sediment load – sediment is difficult to distinguish among the mulch fibers at the top of the mulch layer; the mulch appears almost new. • Medium sediment load – sediment accumulation is apparent and may be concentrated in some areas; probing the mulch layer reveals lighter sediment loads under the top 1” of mulch. • Heavy sediment load – sediment is readily apparent across the entire top of the mulch layer; individual mulch fibers are difficult to distinguish; probing the mulch layer reveals heavy sediment load under the top 1” of mulch. BioPodTM HF High Flow System with StormMixTM Media Page 4 www.oldcastleinfrastructure.com | (888) 965-3227 Rev. 2/2025 6-A-045 | Operations and Maintenance Manual Maintenance Indicators Mulch acts as a prefilter to protect the StormMix™ media from sediment loading and subsequent loss of hydraulic capacity. As runoff carries sediment into the BioPod HF, the sediment will accumulate on top of the mulch layer and then, over time, begin to work its way down through the mulch and eventually into the media bed. Mulch replacement should be performed when the mulch layer is full of sediment but the StormMix media is still relatively clean. Maintenance personnel should observe sediment accumulation on the surface of the mulch layer and then dig down into the mulch and potentially into the media bed to the point where the mulch or media appears relatively clean. The sediment penetration depth can be used to rate the sediment load and determine maintenance requirements as follows: Sediment Conditions Inspection Rating Maintenance Requirements Little visible sediment Light sediment load None Sediment on mulch surface only Light sediment load None Sediment throughout mulch layer Medium sediment load Minor maintenance Sediment less than 3” into media layer Medium sediment load Minor maintenance Sediment less more 3” into media layer Heavy sediment load Full maintenance Standing water on top of media layer Heavy sediment load Full maintenance BioPodTM HF BioPodTM HF High Flow System with StormMixTM Media Page 5 www.oldcastleinfrastructure.com | (888) 965-3227 Rev. 2/2025 6-A-045 | Operations and Maintenance Manual The following photographs help illustrate these conditions. Light Sediment Load • Little visible sediment or light sediment on mulch surface only • Mulch layer appears relatively fresh, open, and fibrous • No maintenance required Heavy Sediment Load • Thick sediment throughout mulch layer and more than 3” into top of the media bed • Digging down more than 6” below the top of the mulch layer reveals heavy sediment accumulation • Full maintenance required Heavy Sediment Load • Thick sediment and standing water on surface of mulch layer more than 24 hours after a storm event • Full maintenance required Medium Sediment Load • Thick sediment throughout mulch layer and up to 3” into top of media layer • Digging down 3” to 6” below the top of the mulch reveals relatively clean media with little sediment accumulation • Minor maintenance required BioPodTM HF High Flow System with StormMixTM Media Page 6 www.oldcastleinfrastructure.com | (888) 965-3227 Rev. 2/2025 6-A-045 | Operations and Maintenance Manual Maintenance should be scheduled if any of the following conditions are identified during inspection: • The concrete structure is damaged or the tree grate or access cover is damaged or missing • The inlet obstructed • Standing water is observed in the biofiltration chamber more than 24 hours after a rainfall event (use discretion if the BioPod HF is located downstream of a storage system that attenuates flow) • Trash and debris in the inlet chamber cannot be easily removed at the time of inspection • Trash and debris, invasive vegetation or sediment load in the biofiltration chamber is heavy or excessive erosion has occurred Maintenance Equipment • Suitable clothing (appropriate footwear, gloves, hardhat, safety glasses, etc.) • PPE as required for entry • Traffic control equipment (cones, barricades, signage, flagging, etc.) • Manhole hook or pry bar • Flashlight • Tape measure • Rake, hoe, shovel and broom • Bucket • Pruners • Vacuum truck (optional) • Socket Maintenance Procedures Maintenance should be conducted during dry weather when no flows are entering the system. In most cases, maintenance may be conducted without entering. Entry may be required to maintain depending on system depth. Once safety measures such as traffic control are deployed, the access covers may be removed and the following activities may be conducted to complete maintenance: • Remove all trash and debris from the inlet chamber manually or by using a vacuum truck as required. • Remove all trash and debris and invasive vegetation from the biofiltration chamber manually or by using a vacuum truck as required. • If the sediment load is medium or light but erosion of the biofiltration media bed is evident, redistribute the mulch with a rake or replace missing mulch as appropriate. If erosion persists, rocks may be placed in the eroded area to help dissipate energy and prevent recurring erosion. • If the sediment load is heavy, remove the mulch layer using a hoe, rake, shovel and bucket, or by using a vacuum truck as required. If the sediment load is particularly heavy, inspect the surface of the biofiltration media once the mulch has been removed. If the media appears clogged with sediment, remove and replace one or two inches of biofiltration media prior to replacing the mulch* layer. • Prune vegetation as appropriate and replace damaged or dead plants as required. • Replace the tree grate and/or access covers and sweep the area around the BioPod HF to leave the site clean. • All material removed from the BioPod HF during maintenance must be disposed of in accordance with local environmental regulations. In most cases, the material may be handled in the same manner as disposal of material removed from sumped catch basins or manholes. BioPodTM HF High Flow System with StormMixTM Media Page 7 www.oldcastleinfrastructure.com | (888) 965-3227 Rev. 2/2025 6-A-045 | Operations and Maintenance Manual * NoFloat cypress mulch should be used in the BioPod HF. Timely replacement of the mulch layer according to the maintenance indicators described above should protect the biofiltration media below the mulch layer from clogging due to sediment accumulation. However, whenever the mulch is replaced, the BioPod HF should be visited 24 hours after the next major storm event to ensure that there is no standing water in the biofiltration chamber. Standing water indicates that the biofiltration media below the mulch layer is clogged and must be replaced. Please contact Oldcastle Infrastructure at (800) 579-8819 to purchase the proprietary StormMix™ biofiltration media. Biopod HF Planter Biopod HF Tree BioPodTM HF High Flow System with StormMixTM Media Page 8 www.oldcastleinfrastructure.com | (888) 965-3227 Rev. 2/2025 6-A-045 | Operations and Maintenance Manual BioPod HF Inspection & Maintenance Log BioPod HF Model Inspection Date Location Good Light Yes Yes Yes Yes Yes Yes YES - Schedule Maintenance Damaged Medium No No No No No No NO - Schedule Re-Inspection Missing Heavy Condition of Internal Components Curb Inlet Blocked Standing Water in Biofiltration Chamber Trash and Debris in Inlet Chamber Trash and Debris in Biofiltration Chamber Invasive Vegetation in Biofiltration Chamber Sediment in Biofiltration Chamber Erosion in Biofiltration Chamber Maintenance Requirements NOTES: NOTES: NOTES: NOTES: NOTES: NOTES: NOTES: NOTES: BioPodTM HF High Flow System with StormMixTM Media Page 9 www.oldcastleinfrastructure.com | (888) 965-3227 Rev. 2/2025 6-A-045 | Operations and Maintenance Manual BioPodTM HF High Flow System with StormMixTM Media Page 10 www.oldcastleinfrastructure.com | (888) 965-3227 Rev. 2/2025 6-A-045 | Operations and Maintenance Manual BioPodTM HF High Flow System with StormMixTM Media Page 11 www.oldcastleinfrastructure.com | (888) 965-3227 Rev. 2/2025 6-A-045 | Operations and Maintenance Manual Trusted partnerships. Full scale solutions.www.oldcastleinfrastructure.com | (888) 965-3227 Stormwater Maintenance Plan Walker Subaru Service Center 2240819.10 Attachment B Exhibits B-1 .................... Vicinity Map B-2 .................... Developed Conditions 2215 North 30th Street Suite 300 Tacoma, WA 98403 253.383.2422 TEL 253.383.2572 FAX SUNSET HIGHLANDS MIXED USE 2190210.10 VICINITY MAP B-1 NOT TO SCALE VICINITY MAP SUNSET HIGHLANDS - 2230621.10WALKER SUBARU SERVICE CENTER - 2240819.10 GPGP GP GP GP GP GP GP GP GP GP GP GP GP GP GP GP GP GP P P GP GP S0 1 ° 2 3 ' 1 0 " W 2 7 8 . 3 5 ' ( M ) RAMP C/C C/C C/C C/C RAMP 12" MAPLE 12" MAPLE 14" MAPLE 8" UNKNOWN DECIDUOUS DRIVEWAY C/G C/G C/G E/C E/C E/CE/C E/C E/C 6' CLF 6' CLF 6' CLF 0.6' 0.5' NOT PART OF SURVEY (TAX PARCEL NO. 3340404150) NOT PART OF SURVEY (TAX PARCEL NO. 3340404150) GATE 0.3' 0.1' 4.9' 8.0' 6' CLF 7' CLF 6' CLF 6' CLF 6' CLF ANGLE POINT BEARS S84°11'E, 0.6' FROM CALCULATED LOT CORNER 6' CLF 6' CLF 6' CLF 6' CLF 8' CLF E/C E/C E/C E/C 5.1' 9.0' 8.2' 17.5' 3.1' 0.3' 10' CLF GATE 0.3' 0.1' 3X8" UNKNOWN DECIDUOUS GATE E/C E/C 6' CLF 6' CLF 6' CLF STOP BAR C/G C/G C/G C/G 30.0' DRIVEWAY E/C RA/W RA/W RA/W RA/W RA/W RA/W BUILDING FINISH FLOOR AT CENTER OF PED. DOOR LABELED "SPRINKLER ROOM" ELEV=21.95' NAVD 88 BUILDING FINISH FLOOR AT CENTER OF DOUBLE PED. DOOR ELEV=22.03' NAVD 88 E/C E/C E/C E/C E/C CONC. CANOPY COLUMN CONC. CANOPY COLUMN CONC. CANOPY COLUMN CONC. CANOPY COLUMN GATE GATE GATE 4' CLF4' CLF 4' CLF 4' CLF 4' CLF 4' CLF EDGE CANOPY (TYPICAL) EDGE CANOPY (TYPICAL) 12"MAPLE 13" MAPLE 17" MAPLE 11" MAPLE 14" MAPLE GATE 6' CLF "STOP" STEEL POST FOR AERIAL WALKER'S RENTON SUBARU PARTS AND SERVICE CENTER SIGN SERVICE CENTER DIRECTIONS SIGN C/C C/C RAMP E/C C/C C/C RAMP STEEL POST FOR AERIAL SUBARU SIGN 26.9'DRIVEWAY C/G RA/W 6' CLF 6' CLF 6' CLF 6' CLF 6' CLF 6' CLF 6' CLF GATE 6' CLF FENCE TRANSITION 6' CLF/6' STEEL 6' STEEL STORMWATER DETENTION POND 6' CLF 6' CLF 6' CLF 6' CLF 6' CLF 8' CLF 8' CLF 8' CLF 8' CLF 8' CLF 6' CLF 4' CLF 0.7' 1.2' 4.4' 2.8' 1.5' 0.8' 0.8' 1.5' 1.4' 1.0' 2.1' 0.4' 0.9' 1.0' 0.9' UNKNOWN USE CLEANOUT RIM=22.06' UNKNOWN USE CLEANOUT RIM=21.96' 525.46'(C) 117.44' S0 1 ° 2 2 ' 4 2 " W 11 6 . 4 3 ' N77°26'10" E 119.92' N0 1 ° 2 2 ' 4 3 " E 11 6 . 3 8 ' L1 8 L17 S0 9 ° 3 9 ' 1 5 " E 1 0 5 . 0 4 ' L2 0 L2 1 N77°24'38" E 123.29' 11 4 . 3 4 ' S86°20'10"W 391.52' 25 4 . 8 8 ' L1 0 L1 9 FND 1/2" REBAR AND CAP STAMPED "LS 19635" REBAR BEARS S88°24'33"E, 0.23' FROM THE CALCULATED LOT CORNER VISITED 11/18/2024 A/W A/W 0.7' 0.9' 1.0' 0.8' 3-WAY 6' CLF INTERSECTION BEARS S15°13'E, 6.2' GATE 8'/6' CLF INTERSECTION BEARS S79°15'W, 2.9' FROM THE CALCULATED LOT CORNER 75 . 2 0 ' PRIVATE INGRESS/EGRESS EASEMENT PER EASEMENT AGREEMENT WITH RIGHTS AND RESPONSIBILITIES AFN 20020612000622 QWEST TELECOMMUNICATIONS EASEMENT PER AFN 20030327000925 PRIVATE INGRESS/EGRESS EASEMENT PER EASEMENT AGREEMENT WITH RIGHTS AND RESPONSIBILITIES AFN 20020612000622 UTILITIES EASEMENT TO THE CITY OF RENTON PER AFN 20010906002177, CITY OF RENTON ORDINANCE 4914 (ENCOMPASSES WHOLE VACATED ALLEY) BUILDING FINISH FLOOR AT CENTER OF BAY DOOR ELEV=21.94' NAVD 88 6' CLF ANGLE POINT BEARS N53°23'W, 1.3' FROM CALCULATED LOT CORNER 8' CLF END BEARS N25°48'W, 1.0' FROM CALCULATED LOT CORNER PSE ELECTRICAL EASEMENT PER AFN 20030128002591 UTILITIES EASEMENT TO THE CITY OF RENTON PER AFN 20010906002177, CITY OF RENTON ORDINANCE 4914 (ENCOMPASSES WHOLE VACATED ALLEY) PSE ELECTRICAL EASEMENT PER AFN 20030128002591 PSE ELECTRICAL EASEMENT PER AFN 20030128002591 UTILITIES EASEMENT TO THE CITY OF RENTON PER AFN 20020207002539, CITY OF RENTON ORDINANCE 4942 (ENCOMPASSES WHOLE VACATED STREET) SE N E C A A V E S W SW 12TH S T SW 13TH S T INTERSTATE 405 CB #6 CB #5 CB #4 CB #3 CB #2 CB #1 BLDG ADDITION FF: 21.95 CB #7 EXIST. CB1 EXIST. CB3 EXISTING BUILDING FF: 21.95BLDG ADDITION EXIST. CB4 61 LF 8" DI CL52 @ 0.25% 89 LF 8" CPEP @ 0.25% 57 LF 8" CPEP @ 0.25% 86 LF 8" CPEP @ 0.46% 57 LF 8" DI CL52 @ 0.25% 28 LF 8" DI CL52 @ 0.25% 130 LF 6" PVC SDR-35 @ 0.25% 16 LF 6" PVC SDR-35 @ 0.25% 16+10 10+00 11 + 0 0 12 + 0 0 13 + 0 0 14+00 15+00 16+00 STORM RUN 1 SHEET C3.4 20+ 0 0 20+ 4 7 30 + 0 0 31 + 0 0 3 1 + 5 0 STORM RUN 3 SHEET C3.4 STORM RUN 2 SHEET C3.4 CO #3 91 LF 6" PVC SDR-35 @ 0.50% CO #4 128 LF 6" PVC SDR-35 @ 1.13% CO #5 9 LF 6" PVC SDR-35 @ 0.50% CO #6 103 LF 6" PVC SDR-35 @ 0.25% 108 LF 6" PVC SDR-35 @ 1.51% CO #7 13 LF 6" PVC SDR-35 @ 0.50% CO #2 CO #1 69 LF 8" CPEP @ 0.26% 18 LF 8" CPEP @ 1.48% IE: 17.55 8" (W) IE: 17.00 6" (W) EXISTING STORM PIPE TO REMAIN EXISTING STORM PIPE TO REMAIN CB #8 APPROX. POND BOTTOM EG: 16.50 EXISTING DETENTION POND TO REMAIN 21 LF 6" PVC SDR-35 @ 0.25% 22.00 22.00 22.00 22 . 0 0 23.0 0 23 . 0 0 23 . 0 0 23 . 0 0 21.00 2 1 . 0 0 22.00 22 . 0 0 22.00 22.0022.00 CONNECT EXISTING BUILDING ROOF DRAINS, CONTRACTOR TO POTHOLE AND VERIFY DEPTH PRIOR TO CONSTRUCTION. CONNECT EXISTING BUILDING ROOF DRAINS, CONTRACTOR TO POTHOLE AND VERIFY DEPTH PRIOR TO CONSTRUCTION. OUTLET PROTECTION 2 C3.5 EXISTING POND TO BE REFRESHED. REMOVE ALL DEBRIS AND SEDIMENT BUILD-UP. REMOVE ALL NOXIOUS WEEDS. POND OUTLET TO BE CLEARED AND CLEANED. EXISTING STORM PIPE TO REMAIN STA:12+50.33, 0.00' EXIST. CB2 STORM STRUCTURE TABLE STRUCTURE NAME CB #1 TYPE 1 N 173874.77 E 1296386.65 CB #2 TYPE 1 N 173790.74 E 1296405.48 CB #3 TYPE 1 N 173778.29 E 1296350.24 CB #4 TYPE 1 N 173758.79 E 1296263.78 CB #5 TYPE 1 N 173795.86 E 1296220.61 CB #6 TYPE 1 N 173815.39 E 1296240.61 CB #7 48" TYPE 2 W/ SUMP PUMP 0.4CFS @ 5' TDH N 173835.29 E 1296174.69 CB #8 6x12 BIOPOD UNDERGROUND VAULT N 173792.17 E 1296477.46 CO #1 CO N 173976.94 E 1296166.26 STRUCTURE DETAILS RIM = 21.59 IE = 18.90 (8" S) IE = 18.90 (8" NE) RIM = 21.60 IE = 18.50 (8" W) IE = 18.50 (8" N) IE = 18.50 (8" E) RIM = 21.60 IE = 18.64 (8" W) IE = 18.64 (8" E) RIM = 21.60 IE = 18.86 (8" NW) IE = 18.86 (8" E) RIM = 21.66 IE = 19.00 (8" NW) IE = 19.00 (8" SE) IE = 19.00 (8" NE) RIM = 21.40 IE = 19.07 (8" SW) RIM = 21.17 IE = 19.15 (8" SE) IE = 19.32 (6" NE) IE = 19.32 (6" NW) IE = 18.50 (8" N) RIM = 22.93 IE = 18.32 (8" W) IE = 17.82 (8" E) RIM = 21.37 IE = 19.68 (6" S) STORM STRUCTURE TABLE STRUCTURE NAME CO #2 CO N 173847.01 E 1296163.19 CO #3 CO N 173855.79 E 1296253.46 CO #4 CO N 173766.96 E 1296273.50 CO #5 CO N 173795.13 E 1296398.36 CO #6 CO N 173804.01 E 1296396.36 CO #7 CO N 173909.80 E 1296372.49 EXIST. CB1 EXISTING TYPE 1 N 173898.95 E 1296401.89 EXIST. CB2 EXISTING TYPE 1 N 174067.99 E 1296401.66 EXIST. CB3 EXISTING TYPE 1 N 173985.44 E 1296176.98 STRUCTURE DETAILS RIM = 21.38 IE = 19.36 (6" N) IE = 19.36 (6" SE) RIM = 21.95 IE = 19.22 (6" S) RIM = 21.85 IE = 18.76 (6" E) IE = 18.76 (6" N) RIM = 21.85 IE = 17.31 (6" N) IE = 17.31 (6" W) RIM = 21.90 IE = 17.26 (6" E) IE = 17.26 (6" S) IE = 17.26 (6" N) RIM = 21.89 IE = 18.90 (6" S) IE = 18.90 (6" E) RIM = 21.31 IE = 19.00 (8" SW) IE = 19.00 (8" N) RIM = 21.46 IE = 19.69 (8" S) RIM = 21.20 IE = 18.75 (8" S) IE = 18.88 (12" NE) IE = 18.77 (6" E) STRUCTURE NAME CITY OF RENTON IN COMPLIANCE WITH CITY OF RENTON STANDARDS T A C O M A 2215 North 30th Street, Suite 300 Tacoma, WA 98403 253.383.2422TEL 253.383.2572FAX www.ahbl.comWEB S E A T T L E S P O K A N E T R I - C I T I E S WALKER SUBARU SERVICE CENTER PERMIT SET AHBL JOB #2240819.10 54 Know what's below. before you dig.Call R C2 6 0 0 0 6 3 8 LU A 2 5 - 0 0 0 1 7 1 PR 2 5 - 0 0 0 0 3 1 TE D - 4 0 - 4 3 8 8 N GRAPHIC SCALE 0 20 40 1" = 20 FEET 10 HELD COMPUTED NAD 83/91, WASHINGTON STATE PLANE, NORTH ZONE, GRID BEARING OF NORTH 89°43'16" WEST BETWEEN A MONUMENT FOUND AT THE INTERSECTION OF LIND AVE. SW AND SW 16TH ST., BEING CITY OF RENTON CONTROL ID. 1895, TO A MONUMENT FOUND ON ALONG THE NORTHERLY MARGIN OF SW 16TH ST. AT A BRIDGE CROSSING OF SPRINGBROOK CREEK, BEING CITY OF RENTON CONTROL ID. 1891, RESPECTIVELY. NAD 83/91, WASHINGTON STATE PLANE, NORTH ZONE, AS DEFINED BY THE CITY OF RENTON PUBLISHED HORIZONTAL CONTROL NETWORK UNIT OF MEASUREMENT IS U.S. SURVEY FEET ALL DISTANCES SHOWN ARE GROUND A COMBINED GRID SCALE FACTOR OF 0.999987504615 (GRID TO GROUND) WAS HELD AT CITY OF RENTON CONTROL ID. 1895 NAVD 88 (AS DEFINED BY THE PUBLISHED CITY OF RENTON VERTICAL BENCHMARK NETWORK) (NGS2018 GEOID - USED) PROJECT PRIMARY BENCHMARK: CITY OF RENTON CONTROL ID. 1895 PUBLISHED ELEVATION: 25.702' NAVD 88 DESCRIPTION: ENCASED 3" BRASS DISK W/PUNCH LOCATED AT THE INTERSECTION OF LIND AVE. SW AND SW 16TH ST. PROJECT SECONDARY BENCHMARK: CITY OF RENTON CONTROL ID. 1891 PUBLISHED ELEVATION: 24.1568' NAVD 88 OBSERVED ELEVATION: 24.06' NAVD 88 DESCRIPTION: MONUMENT FOUND ALONG THE NORTHERLY MARGIN OF SW 16TH ST. AT A BRIDGE CROSSING OF SPRINGBROOK CREEK. SITE BENCHMARK OBSERVED ELEVATION: 27.41' NAVD 88 DESCRIPTION: ENCASED 1 7/8" BRASS DISK W/PUNCH AT THE INTERSECTION OF SW GRADY WAY AND SENECA AVE. SW BASIS OF BEARING HORIZONTAL DATUM VERTICAL DATUM 23 STORM PLAN C3.3Q: \ 2 0 2 4 \ 2 2 4 0 8 1 9 \ 1 0 _ C I V \ C A D \ _ F i n a l D e s i g n \ 2 2 4 0 8 1 9 - S H - S T R M . d w g 1.PROVIDE 4" PERFORATED FOUNDATION DRAINS AROUND BUILDING FOUNDATION. CONNECT TO STORM SYSTEM. 2.PROVIDE 6" PVC SDR-35 ROOF DRAIN LINES AT 0.5% MINIMUM SLOPE UNLESS OTHERWISE NOTED. 3.PROVIDE HERRINGBONE GRATE INLETS FOR ALL CATCH BASINS PER WSDOT STANDARD PLAN B30.50.03 UNLESS OTHERWISE NOTED. 4.CONTRACTOR SHALL COORDINATE AND CONFIRM DOWNSPOUT ROOF DRAIN LOCATIONS WITH BUILDING PLANS PRIOR TO CONSTRUCTION. DOWNSPOUTS SHALL BE COORDINATED WITH FOOTING CONSTRUCTION TO ENSURE ADEQUATE COVER. STORM NOTES 1 C3.6 R-438823 Technical Information Report Walker Subaru Service Center 2240819.10 Appendix H OWS Design Memo Page 1 of 1 TO: City of Renton DATE: January 16, 2026 FROM: Nate Kaser, Project Engineer Tacoma - (253) 383-2422 PROJECT NO.: 2240819.10 PROJECT NAME: Walker Subaru Service Center SUBJECT: Renton Walker Subaru – Oil/Water Separator Sizing Calculations This Project Memo justifies the sizing calculations for the oil/water separators proposed for the Walker Subaru Service Center project. Four wet bays in the maintenance area will be served by a trench drain. The drive-through waiting area will be served by a trench drain. Any flows entering the drains will pass through an oil/water separator prior to discharging to the sanitary sewer. One oil/water separator will serve the four maintenance bays and another will serve the drive-through waiting area. The maintenance areas are fully covered and will not receive any stormwater runoff. The largest possible flows to the oil/water separator will occur if all four wet bays are operated simultaneously. Each area will be equipped with a single hose. Flow from a hose can be conservatively estimated at 9 gpm (for a pressure of 40 psi with a 75-foot long, 0.5-inch diameter garden hose). A residence time of 45 minutes is required for oil/water separators for this application, per the King County Waste Treatment Division. The design flow rate of 9 gpm for 45 minutes gives a minimum volume of 1,620 gallons. The next largest available size of oil/water separator is the 5106-SA Oil/Water Separator by Oldcastle, which has a 1,750-gallon capacity. This model is equivalent to the 264-CPS Oil/Water Separator model by Oldcastle, which has a treatment rate of 47 gpm. The drive-through waiting area will be equipped with a single hose. With a design flow rate of 9 gpm for 45 minutes, the minimum volume required will be 405 gallons. The Oldcastle 253-CPS Oil/Water Separator can treat 27 gpm, or the Oldcastle 660-SA-550 Oil/Water Separator with a 550-gallon capacity would provide adequate treatment. The cut sheets of all four products are included with the memo. NK/lsk Enclosures: Oldcastle 1,750-Gallon Cut Sheet Oldcastle 47 gpm Cut Sheet Oldcastle 550-Gallon Cut Sheet Oldcastle 27 gpm Cut Sheet King County Fact Sheet Q:\2024\2240819\WORDPROC\Reports\20260116 Memo (OWS Rpt) 2240819.10.docx oldcastleprecast.com/wilsonville File Name: PO Box 323, Wilsonville, Oregon 97070-0323 Tel: (503) 682-2844 Fax: (503) 682-2657 Issue Date: 5106-SA-1750 2016 020-5106-SA-1750 5106-SA-1750 OIL / WATER SEPARATOR 1750 GALLON - API STYLE 5106-SA-1750 16.0 TOP No. 5106-T-SA BASE ASSEMBLY No. 5106-B-SA "IAPMO Listed" Issue Date: File Name: PO Box 323, Wilsonville, Oregon 97070-0323 Tel: (503) 682-2844 Fax: (503) 682-2657 oldcastleprecast.com/wilsonville 5106-SA-1750 2016 020-5106-SA-1750 5106-SA-1750 OIL / WATER SEPARATOR 1750 GALLON - API STYLE 5106-SA-1750 16.1 SECTION AA PLAN VIEW A A oldcastleprecast.com/wilsonville File Name: PO Box 323, Wilsonville, Oregon 97070-0323 Tel: (503) 682-2844 Fax: (503) 682-2657 Issue Date: 264-CPS 2018 020-264CPS 264-CPS OIL / WATER SEPARATOR COALESCING - 47 GPM 264-CPS 5.0 COVER with ADJUSTABLE FRAME No. 264P ASSEMBLY BASE ASSEMBLY No. 264-CPS-B OPTIONAL TOP - HEAVY TRAFFIC No. 264-T-CPS-HD A A PLAN VIEW SECTION AA Issue Date: File Name: PO Box 323, Wilsonville, Oregon 97070-0323 Tel: (503) 682-2844 Fax: (503) 682-2657 oldcastleprecast.com/wilsonville 264-CPS 2018 020-264CPS 264-CPS OIL / WATER SEPARATOR COALESCING - 47 GPM 264-CPS 5.1 oldcastleprecast.com/wilsonville File Name: PO Box 323, Wilsonville, Oregon 97070-0323 Tel: (503) 682-2844 Fax: (503) 682-2657 Issue Date: 660-SA-550 2016 020-660SA-550 660-SA-550 OIL / WATER SEPARATOR 550 GALLON - API STYLE 660-SA-550 14.0 TOP No. 660-T-SA BASE ASSEMBLY No. 660-B-SA OPTIONAL TOP - HEAVY TRAFFIC No. 660-T-SA-HD "IAPMO Listed" A A PLAN VIEW TOP VIEW SECTION AA Issue Date: File Name: PO Box 323, Wilsonville, Oregon 97070-0323 Tel: (503) 682-2844 Fax: (503) 682-2657 oldcastleprecast.com/wilsonville 660-SA-550 2016 020-660SA-550 660-SA-550 OIL / WATER SEPARATOR 550 GALLON - API STYLE 660-SA-550 14.1 oldcastleprecast.com/wilsonville File Name: PO Box 323, Wilsonville, Oregon 97070-0323 Tel: (503) 682-2844 Fax: (503) 682-2657 Issue Date: 253-CPS 2018 020-253CPS 253-CPS OIL / WATER SEPARATOR COALESCING - 27 GPM 253-CPS 4.0 COVER with ADJUSTABLE FRAME No. 25P ASSEMBLY BASE ASSEMBLY No. 253-B-CPS OPTIONAL TOP - HEAVY TRAFFIC No. 253-T-CPS-HD PLAN VIEW SECTION AA A Issue Date: File Name: PO Box 323, Wilsonville, Oregon 97070-0323 Tel: (503) 682-2844 Fax: (503) 682-2657 oldcastleprecast.com/wilsonville 253-CPS 2018 020-253CPS 253-CPS OIL / WATER SEPARATOR COALESCING - 27 GPM 253-CPS 4.1 A INDUSTRIAL WASTE PROGRAMPartering with Industriesto Prevent Pollution MISSION STATEMENT The mission of the Industrial Waste Program is to protect the environment, public health, biosolids quality, and King County’s regional sewerage systems. We work cooperatively with our customers as we regulate industrial discharges, provide technical assistance, and monitor the regional sewerage system. INTRODUCTION For businesses that generate oily wastewater from use of petroleum products, an oil/water separator can be an effective and economical means to treat wastewater to an acceptable level for discharge to the King County sanitary sewer system. Because oil and water do not mix well, and as oil “floats” due to being lighter than water, effective treatment can be achieved if the correct oil/water separator is installed, routine maintenance is adhered to, and the separation of oil and water is not compromised by the excessive use of certain chemicals. This fact sheet is designed to provide information for businesses that currently have an oil/water separator or are considering the purchase of an oil/water separator. WHAT IS AN OIL/WATER SEPARATOR? Standard baffle oil/water (O/W) separators are large-capacity, underground cement vaults installed between a drain and the connecting sewer pipe. These vaults are designed with baffles to trap sediments and retain floating oils. The large capacity of the vaults slows down the wastewater, allowing oil to float to the surface and solid material to settle out (Figure 1). Another popular design is the coalescing plate separator (CPS), which businesses can install above or below ground. It has a smaller capacity and employs a series of oil-attracting plates. Oil droplets collect and float to the surface, where they can be skimmed off or removed mechanically (Figure 2). FACT SHEET: THE OIL/WATER SEPARATOR HOW TO SELECT AND MAINTAIN AN OIL/WATER SEPARATOR 1 Topic overview Introduction What is an oil/water separator? Who needs an oil/water separator? What are the installation guidelines? How do businesses inspect the O/W separator to know when it is dirty? Who do businesses call to clean out an O/W separator? What can businesses do to maintain their oil/water separators? What should and should not go through a separator? How do businesses choose a tank-cleaning company? For further information Solids drop out in the inlet weir Oily water passes through the Coalescing plates Inspection Plates Sampling tee or 90° elbow 6” below fluid level. Sludge Retainer Weir Inlet from drainBaffles Oil FilmOutlet to Sewer May be installed above or below ground 2 WHO NEEDS AN OIL/WATER SEPARATOR? Any business that plans to discharge oily or sediment-laden wastewater to the sewer must install, use and maintain an oil/water separator. Businesses that typically need oil/water separators include: • Quick-lube stations • Transportation fueling facilities; • Vehicle/heavy equipment repair; and • Businesses using steam or pressure washers. WHAT ARE THE INSTALLATION GUIDELINES? Some local sewer agencies in King County approve separators in their areas, so requestors must first determine whether they will be working with the county. Before installing an oil/water separator, the sewer contractor should submit all plans to the local sewer utility or King County for review. Businesses will need a letter approving the design and allowing discharge of wastewater from the properly installed tank. When submitting pl ans, include the following information: • Name and address of the facility, and the phone number and mailing address of the person legally responsible for operation and maintenance. • Drawing of the oil/water separator with capacities and dimensions. The outlet to the sewer must have a sampling “T” installed. (See Figure 1.) • Site map detailing all drains and the separator location. Indicate if any drainage is from rainwater runoff; this should be kept to a maximum of 200 square feet. KCIW can make exceptions based on specific needs or situation. • Location of the water sources and maximum water flows, in gallons per minute (gpm) from all potential service areas and equipment discharging to the oil/water separator. King County has capacity guidelines for standard oil/water separators to hold the maximum discharge flow for 45 minutes, e.g., a 20-gpm flow would require a 900-gallon separator. For more information on specifications and approval, call KCIW at 206-477-5300. Remove floating oils. Use pads, skimmers or do it manually. Inlet from drain COALESCING PLATE SEPARATOR (CPS) VAULT O/W SEPARATOR FIGURE 2 FIGURE 1 3 HOW DO BUSINESSES INSPECT THE O/W SEPARATOR TO KNOW WHEN IT IS DIRTY? Many think that if it is still draining, it’s working; but like any “filter” an O/W separator needs occasional cleaning. A separator’s efficiency is most affected by settled solids or sludge and oils. King County recommends that businesses inspect an O/W separator at least every six months. Steps to inspect are: • Open the inspection plates with a screwdriver and look in each chamber. Make sure the outlet chamber (usually the side closest to the street has a sampling “T.” It should have at least a six inch extension below the water surface. • Take a long stick that will reach the bottom (about 8 feet). Any resistance in pushing through to the bottom will indicate a sludge buildup. Service the O/W separator when the buildup is about 8 inches deep in the inlet chamber (typically the one closest to the drain). • Measure oil floating on top of the water. When there are two inches or more of oil in any chamber, it should be removed. Older oil has a chance of becoming emulsified. • For coalescing plate separators, it is critical to remove and clean the plates before they get “blinded” or coated with silt or solids. This will allow oils to pass through to the sewer, possibly exceeding King County’s discharge limits of 100 parts per million (ppm) for nonpolar Fats, Oils, and Grease (FOG). BUSINESSES SHOULD NEVER USE A SEPTIC TANK SERVICE TO CLEAN THEIR O/W SEPARATORS OR CATCH BASINS. Since vendors may have different requirements and/ or treatment methods, costs could vary. Fees can include: • Lab analysis from a sample of the separator’s contents • Wastewater disposal charges HOW DO BUSINESSES CHOOSE A TANK-CLEANING COMPANY? Businesses should choose a reliable vendor by making sure that its equipment is right for the situation. Some equipment requires that incoming sludge to be a pumpable slurry. A lot of water may be needed to break up compacted sludge and to rinse out the truck’s tank at the treatment facility. Both steps will involve extra time and expense. Make sure the vendor vacuums out all of the sludge in each chamber. Businesses should inspect and then fill up the separator with clean water before they begin discharging. WHAT SHOULD AND SHOULD NOT GO THROUGH A SEPARATOR? • Antifreeze, degreasers, and detergents will emulsify (break up) oil into small droplets so the oil doesn’t float to the surface. • Fuels, alcohols or solvents not only can emulsify oil, but accumulated vapors can pose a threat to line workers at the pump stations or treatment plant. • Concentrated amounts of oily products can overload the baffles or plates and pass through to the sewer. The smaller capacity of coalescing units may have more turbulent flows. This “flushing” action, combined with a concentration of any emulsifier, can wash off the residual oils clinging to plates and release large amounts of emulsified oils to the sewer. Floating oils that are not skimmed from the surface of the separator will eventually become emulsified and appear to have a lighter color. Any use of emulsifiers could result in a violation of King County’s nonpolar FOG (Fats, Oils, and Grease) limits of 100 ppm (equivalent to one teaspoon of oil to13 gallons of water). WHO DO BUSINESSES CALL TO CLEAN OUT AN O/W SEPARATOR? There are firms that specialize in pumping out and cleaning O/W separators. Search for these companies online under “Tanks – Cleaning.” These firms have special vacuum trucks that pump out materials with the consistency of anything from liquid slurry to solid dirt. The bulk liquid is shipped to a licensed treatment facility where the oils, solids and heavy metals are treated and removed from the water before being discharged to the sewer. 4 FIGURE 3 WHAT CAN BUSINESSES DO TO MAINTAIN THEIR OIL/WATER SEPARATORS? Businesses can save maintenance costs by diverting oils and sludge out of their separators. The sooner oils are removed, the less the chance they will become emulsified. Oils that are freefloating should be carefully pumped out. Businesses should store this oil in a separate drum and consult their vendors on how to properly dispose of it. Cleaners may contain certain chemicals that, when mixed with the oil, could make it a hazardous waste. Another way to remove oil is to use absorbent pads or socks, which float on top of the water and attract only oil. Place the pads in the inlet chamber to trap the oils before the they get a chance to migrate. Remove the pads often before they are saturated. These pads can be wrung out and reused if handled properly. Absorbent products are available at most chemical and safety supply stores. Sludge is oily dirt that builds up on the bottom of the separator. Sludges are expensive to dispose of and difficult to clean out. A catch basin, installed before the separator, can be shoveled out and will trap solids before they wash into the separator (Figure 3). This can be very helpful to businesses cleaning muddy equipment. The sludge should be collected in a drum and tested to determine proper disposal methods. Sludges and other wastes may not be considered “hazardous wastes,” but they may not be acceptable for garbage disposal. O/W separators are not designed to treat heavy metal-bearing wastewater. This type of discharge will require chemical treatment or special equipment for an acceptable discharge. Some potential examples of heavy metal-bearing wastewater: •Hot tank and cabinet washer solutions from auto repair or machine shops •Pressure-wash water from ship and boat yards •ANY metal finishing, plating or metal recovery water •Water-soluble machine coolant FOR FURTHER INFORMATION: For information on solid waste disposal guide lines, call King County Waste Characterization at 206-296-4633 (within Seattle) or 206-296-4466 (King County outside of Seattle). For further information on Fats, Oils and Grease (FOG) and to download this fact sheet, go to: https://kingcounty.gov/en/dept/dnrp/waste- services/wastewater-treatment/sewer-system- services/industrial-waste/wastewater- discharge-limits-regulations. Call the contact information below for hard copies. Published by the King County Industrial Waste Program 201 S. Jackson St. Room 513 Seattle WA 98104-3855 Ph: 206-477-5300 Alternate Formats Available Voice: 206-477-5300 or TTY Relay: 711 Removable trench grate Clean out before sludge/dirt gets to pipe level Shop floor Water Level CATCH BASIN for high dirt/sludge discharges Install before the separator To O/W Separator