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RS_Civil_Technical_Information_Report_250123_v1
TECHNICAL INFORMATION REPORT FOR Kite Realty Group at 17803 & 17805 108TH AVE SE Renton, WA 98055 January 21, 2025 PREPARED FOR: Kite Realty Group 17803 & 17805 108TH AVE SE RENTON, WA, 98055 PREPARED BY: KIMLEY-HORN 1201 3RD AVE, SUITE 2800 SEATTLE, WA 98101 OFFICE: (206) 607-2600 KHA PROJECT #: 090191000 ©Kimley-Horn and Associates, Inc., 2025 (This sheet was intentionally left blank) PREPARED FOR: JM1 Holdings, LLC. 11805 7th ST NE LAKE STEVENS, WA 98258 PREPARED BY: KIMLEY-HORN AND ASSOCIATES, INC. 1201 THIRD AVENUE, SUITE 2500 SEATTLE, WA 98104 Christopher Miller, P.E. Disclosure Statement: This document, together with the concepts and designs presented herein, as an instrument of service, is intended only for the specific purpose and client for which it was prepared. Reuse of and improper reliance on this document without written authorization and adaptation by Kimley-Horn and Associates, Inc. shall be without liability to Kimley-Horn and Associates, Inc. 11/27/20 2 4 01/22/25 17803 & 17805 108th Ave SE – Kite Realty Group Kimley-Horn and Associates, Inc. Renton, WA Preliminary Stormwater Report January 21, 2025 Page 1 Table of Contents TECHNICAL INFORMATION REPORT WORKSHEET ............................................................................ 3 SECTION A – PROJECT OVERVIEW ..................................................................................................... 4 A.1 SITE LOCATION .................................................................................................................... 4 A.2 EXISTING SITE CONDITIONS ............................................................................................... 4 A.3 EXISTING ON-SITE STORMWATER SYSTEMS .................................................................... 4 A.4 ADJACENT PROPERTIES ..................................................................................................... 4 A.5 PROJECT IMPACT ON ADJACENT AREAS .......................................................................... 4 A.6 PROPOSED SITE CONDITIONS ............................................................................................ 5 SECTION B – CORE REQUIREMENTS .................................................................................................. 5 B.1 APPLICABLE CORE REQUIREMENTS ......................................................................................... 5 TABLE 1 – LAND DISTURBING ACTIVITY ....................................................................................... 5 CR#1: Discharge at the Natural Location .......................................................................................... 5 CR#2: Offsite Analysis ...................................................................................................................... 6 CR#3: Flow Control Facilities ............................................................................................................ 6 CR#4: Conveyance System .............................................................................................................. 6 CR#5: Construction Stormwater Pollution Prevention Plan (CSWPPP).............................................. 6 CR#6: Maintenance and Operations ................................................................................................. 6 CR#7: Financial Guarantees and Liability.......................................................................................... 6 CR#8: Water Quality Facilities .......................................................................................................... 6 CR#9: On-Site BMPs ........................................................................................................................ 7 B.2 APPLICABLE SPECIAL REQUIREMENTS .................................................................................... 8 SR#1: Other Adopted Area-Specific Requirements ........................................................................... 8 SR#2: Flood Hazard Area Delineation............................................................................................... 9 SR#3: Flood Protection Facilities ...................................................................................................... 9 SR#4: Source Controls ..................................................................................................................... 9 SR#5: Oil Control .............................................................................................................................. 9 SR#6: Aquifer Protection Area .......................................................................................................... 9 SECTION C – PRELIMINARY SOILS EVALUATION ............................................................................... 9 SECTION D – CONVEYANCE SYSTEM (CR#4) ..................................................................................... 9 SECTION E – OTHER PERMITS ............................................................................................................ 9 SECTION F – APPENDICES ................................................................................................................. 10 APPENDIX A: MAPS ......................................................................................................................... 10 1. VICINITY MAP ...................................................................................................................... 10 17803 & 17805 108th Ave SE – Kite Realty Group Kimley-Horn and Associates, Inc. Renton, WA Preliminary Stormwater Report January 21, 2025 Page 2 2. FLOOD INSURANCE RATE MAP ......................................................................................... 11 3. PRE-DEVELOPMENT DRAINAGE AREA MAP .................................................................... 12 4. POST-DEVELOPMENT DRAINAGE AREA MAP .................................................................. 13 5. PROPOSED DRAINAGE PLAN ............................................................................................ 14 6. AQUIFER PROTECTION AREA MAP ................................................................................... 15 APPENDIX B: CALCULATIONS ......................................................................................................... 16 1. TEMPORARY EROSION AND SEDIMENT CONTROL CALCULATIONS (TO BE COMPLETED BEFORE FINAL APPLICATION) .............................................................................. 16 APPENDIX C: ADDITIONAL PLANS AND REPORTS ........................................................................ 17 1. GEOTECHNICAL ENGINEERING REPORT ......................................................................... 17 2. NRCS WEB SOIL SURVEY .................................................................................................. 18 3. SWPPP (TO BE COMPLETED BEFORE FINAL APPLICATION) .......................................... 19 17803 & 17805 108th Ave SE – Kite Realty Group Kimley-Horn and Associates, Inc. Renton, WA Preliminary Stormwater Report January 21, 2025 Page 3 TECHNICAL INFORMATION REPORT 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 _Tony Halsey_ Phone _317-713-5653 _ Address _30 S Meridian St, Suite 110 _ _Indianapolis, IN 46204_ Project Engineer _Chris Miller_ Company _Kimley-Horn_ Phone _317-713-5653_ Project Name _Chipotle 108th Ave SE_ CED Permit # ________________________ Location Township ________________ Range __________________ Section _________________ Site Address _17803 & 17805 108th Ave SE_ _Renton, WA 98055_ 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: __________________ __________________ __________________ Plan Type (check one): Date (include revision dates): Date of Final: Full Modified Simplified __________________ __________________ __________________ Full Targeted Simplified Large Project Directed _________________ 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: _Benson_ Special District Overlays: _N/A_ Drainage Basin: _Panther Creek_ Stormwater Requirements: _N/A_ Part 9 ONSITE AND ADJACENT SENSITIVE AREAS River/Stream ________________________ Lake ______________________________ Wetlands ____________________________ Closed Depression ____________________ Floodplain ___________________________ Other _None_ Steep Slope __________________________ Erosion Hazard _______________________ Landslide Hazard ______________________ Coal Mine Hazard ______________________ Seismic Hazard _______________________ Habitat Protection ______________________ _____________________________________ 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 _Alderwood Gravelly Sandy Loam_ Slopes _8-15%_ Erosion Potential _Very low infiltration rate_ _(Ksat = 0.00% - 0.06%)_ 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________________________________ _Not Applicable _ 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) Site property area highlighted in Appendix A Core Requirements (all 8 apply): Discharge at Natural Location Number of Natural Discharge Locations: Offsite Analysis Level: 1 / 2 / 3 dated:__TBD_____________ Flow Control (include facility summary sheet) Standard: __N/A (Exempt)______________________ or Exemption Number: ____________ On-site BMPs: _N/A___________________________ Conveyance System Spill containment located at: ___N/A _______________________ Erosion and Sediment Control / Construction Stormwater Pollution Prevention CSWPP/CESCL/ESC Site Supervisor: _____________________ Contact Phone: _________________________ After Hours Phone: _________________________ 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. ___N/A_________________ 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: N/A Source Control (commercial / industrial land use) Describe land use: N/A Describe any structural controls: N/A Oil Control High-Use Site: Yes / No Treatment BMP: __N/A____________________________ Maintenance Agreement: Yes / No with whom? __N/A________________________________ Other Drainage Structures Describe: 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 ________________ ________________ ________________ ________________ ________________ _Catch Basins_ Vegetated Flowpath Wetpool Filtration Oil Control Spill Control On-site BMPs Other ________________ ________________ ________________ ________________ ________________ ________________ _Not Applicable____ Part 15 EASEMENTS/TRACTS Part 16 STRUCTURAL ANALYSIS Drainage Easement Covenant Native Growth Protection Covenant Tract Other _Not Applicable_ Cast in Place Vault Retaining Wall Rockery > 4′ High Structural on Steep Slope Other _Not Applicable_ 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 17803 & 17805 108th Ave SE – Kite Realty Group Kimley-Horn and Associates, Inc. Renton, WA Preliminary Stormwater Report January 21, 2025 Page 4 SECTION A – PROJECT OVERVIEW A.1 SITE LOCATI ON The 0.85-acre site (on a 3.62 acre parcel) is located along 108th Ave SE between SE Carr Rd and SE 180th St in the City of Renton, King County, Washington. The legal description of the site is as follows: No easements, restrictions, or reservations of record which would be disclosed by title report are shown. Legal description for property was obtained from king county accessors database. Lot Y of King County boundary line adjustment No. L07L0040, according to that boundary line adjustment recorded August 22, 2007 under recording No. 20070822900006, in King County, Washington. A.2 EXISTING SITE CONDITIONS The site contains an existing building of approximately 3,000 square feet. The site is bounded by 108th Avenue to the east, a parking lot to the west, a parking lot entryway to the north, and an adjacent retail development to the south. The entryway separates the north parcel, an onsite landscape buffer runs along the ROW to the east, and a landscape buffer also separates the adjacent parcel to the south. However, the existing site is relatively flat, decreasing in elevation from east to west. The landscape buffers along the north, east, and southern frontages are relatively steep. The portion of the site proposed to be improved contains existing asphalt pavement across the site with some existing concrete beneath an existing drive thru structure. The rest of the remaining site is landscaping with a rock wall supporting the existing landscaping along the northern and southern sides of the site, and the existing site is approximately 80% impervious. Refer to Appendix A for the Pre-Development Drainage Area Map for additional information. A.3 EXISTING ON -SITE STORMWATER SYSTEMS There are existing drainage structures on-site that convey stormwater runoff to the public storm main in 105th Place SE. It can be assumed that all stormwater runoff is collected by these existing structures and carried off-site. Drainage from the roof is not visibly tightlined to the existing stormwater infrastructure and the survey didn’t capture any roof leaders. Thus, it is assumed that the runoff captured from the roof splashes at grade. Refer to the Pre-Development Drainage Area Map in Appendix A for additional information. A.4 ADJACENT PROPERTIES The site is lower than the property to the south. However, grading on the parcel to the south keeps runoff away from subject property by conveying flow into their developed storm infrastructure, minimizing impacts to our drainage calculations. The general drainage patterns and directions will be maintained in the post-development condition. Refer to the Drainage Area Maps in Appendix A for additional information. A.5 PROJECT IMPACT ON ADJACENT AREAS The stormwater design intent of the project is to produce minimal impact on the adjacent properties and public drainage system. The project is not proposing any new stormwater infrastructure, so any additional impacts on adjacent areas will be minimal as the scope of work is limited. 17803 & 17805 108th Ave SE – Kite Realty Group Kimley-Horn and Associates, Inc. Renton, WA Preliminary Stormwater Report January 21, 2025 Page 5 A.6 PROPOSED SITE CONDITIONS The project will redevelop a small site retail development, renovating the existing building and drive thru structures onsite. There will also be additional frontage improvements along 108th St SE to modify the existing sidewalk with additional proposed landscaping and demolition of existing utility infrastructure as needed with the proper replacement in-kind. Site stormwater runoff will be captured on-site by the existing catch basins and will be conveyed to the public storm main in 105th Place SE. The proposed project will disturb approximately 0.15 acres, and the developed site is approximately 75% impervious. See Table 1 – Land Disturbing Activity below for additional information. One at grade curb ramp is proposed to be installed northwest of the existing building, a service ramp is proposed to be installed southeast of the existing building, disturbance of the base course is not anticipated, and the pavement material will be replaced in-kind. Refer to Appendix A for the Post-Development Drainage Area Map for additional information. SECTION B – CORE REQUIREMENTS B.1 APPLICABLE CORE REQUIREMENTS As the site has an existing impervious surface coverage of more than 35%, the proposed project is considered a redevelopment project. The project is not a single-family project, will create more than 2,000 square feet of hard surfaces, and will disturb more than 7,000 square feet of land. Therefore, the project is subject to Full Drainage Review per page 1-14 of the 2022 City of Renton Surface Water Design Manual (SWDM) and must apply some of Core Requirements (CRs) #1 through #9 and some of Special Requirements (SRs) #1 through #5. See below for list of the Core and Special Requirements, the applicability of each to the project, and where additional information regarding compliance to each Core and Special Requirement can be found in this report. See Table 1 below for summary of Land Disturbing Activity for the project. TABLE 1 – LAND DISTURBING ACTIVITY EXISTING IMPERVIOUS SURFACE 0.67 AC NEW IMPERVIOUS SURFACE 0.00 AC REPLACED IMPERVIOUS SURFACE 0.08 AC NATIVE VEGETATION CONVERTED TO LAWN OR LANDSCAPING 0.04 AC TOTAL LAND DISTURBANCE 0.15 AC UNDISTURBED AREA 0.70 AC CR#1: Discharge at the Natural Location The project is required to adhere to CR#1, which states that, “All storm water runoff and surface water from a project must be discharged at the natural location so as not to be diverted onto or away from downstream properties. The manner in which stormwater runoff and surface water are discharged from the project site must not create a significant adverse impact to downhill properties or drainage facilities.” The existing site drainage patterns will be maintained to collect stormwater runoff in the post-developed condition. No adverse impacts to downstream drainage facilities are anticipated – refer to Section D for an Offsite Analysis of the drainage facilities downstream of the site. 17803 & 17805 108th Ave SE – Kite Realty Group Kimley-Horn and Associates, Inc. Renton, WA Preliminary Stormwater Report January 21, 2025 Page 6 CR#2: Offsite Analysis All proposed projects must adhere to CR#2, which states that “projects must submit an offsite analysis report that assesses potential offsite drainage and water quality impacts associated with development of the project site, and that proposes appropriate mitigation of those impacts.” Given the adjustments to our site that are being made, we are planning on performing a level 1 downstream analysis to meet this requirement at a later date. For reference, a level 1 downstream analysis is a qualitative survey of the downstream system and involves defining and mapping the downstream study area, reviewing all available information on the study area, field inspecting the study area, and describing the drainage system and any existing/predicted drainage and water quality problems. CR#3: Flow Control Facilities As the project proposes less than 5,000 square feet of new plus replaced impervious surface, the project is not required to adhere to CR#3. For reference, CR#3 states that, “All proposed projects, including redevelopment projects, must provide on-site flow control facilities to mitigate the impacts of storm and surface water runoff.” CR#4: Conveyance System The project is not required to adhere to CR#4 as we are the proposed improvements are maintaining the existing flow characteristics on site. For reference, CR#4 states that, “All engineered conveyance system elements for proposed projects must be analyzed, designed, and constructed to provide a minimum level of protection against overtopping, flooding, erosion, and structural failure.” Please refer to the Proposed Drainage Area Map located in Appendix A for more information. CR#5: Construction Stormwater Pollution Prevention Plan (CSWPPP) The project shall comply with CR#5. Temporary erosion control plans will be developed for this project site complying with City of Renton and Washington State Department of Ecology requirements. A Construction Stormwater Pollution Prevention Plan (CSWPPP) will be included with the Final Stormwater Report. CR#6: Maintenance and Operations The project is required to adhere to CR#6, which states, “maintenance and operation of all drainage facilities is the responsibility of the applicant or property owner, except those facilities for which the City assumes maintenance and operation,” An operations and maintenance manual will be included with the Final version of this report. CR#7: Financial Guarantees and Liability The project is required to adhere to CR#7, which states, “In accordance with Renton Municipal Code (RMC) 4-6-030, Community and Economic Development (CED) shall require all persons constructing any surface water facilities (including flow control/water quality facilities, conveyance systems, erosion control, and road drainage), to post with the City of Renton a bond, assignment of funds or certified check.” However, this project does not propose construction of any surface water facilities and is thus exempt from CR#7. CR#8: Water Quality Facilities As a redevelopment project that proposes less than 5,000 square feet of new and replaced impervious surface as well as less than ¾ acre of new pollution generating pervious surfaces, the project is not required to adhere to CR#8. For reference, CR#8 states that “All proposed projects, including redevelopment projects, must provide water quality (WQ) facilities to treat the runoff from those new and 17803 & 17805 108th Ave SE – Kite Realty Group Kimley-Horn and Associates, Inc. Renton, WA Preliminary Stormwater Report January 21, 2025 Page 7 replaced pollution-generating impervious surfaces and new pollution-generating pervious surfaces targeted for treatment.” CR#9: On-Site BMPs The project proposes more than 2,000 square feet of new and replaced impervious surface and more than 7,000 square feet of land disturbing activity will occur, therefore this project must abide by CR#9. For reference, CR#9 states that “All proposed projects, including redevelopment projects, must provide on- site BMPs to mitigate the impacts of storm and surface water runoff generated by new impervious surface, new pervious surface, existing impervious surfaces, and replaced impervious surface targeted for mitigation.” As the proposed project site is larger than 22,000 square feet, per Section 1.2.9.2.2 of the SWDM the project must apply on-site BMPs as specified in the requirements of that section and outlined below: C.2.1 – Full Dispersion: Full Dispersion is infeasible on our site given that the improvements on the eastern frontage above the proposed retaining wall will result in slopes greater than 15%, fulfilling the infeasibility criteria listed for this section in the SWDM. C2.2 – Full Infiltration: Full infiltration is infeasible as per the NRCS web soil survey and supporting information from the geotechnical report, the infiltration rate is low on site. This doesn’t fulfill the requirement to “fully and reliably infiltrate runoff into the ground” as specified in this section. C2.3 – Limited Infiltration: Limited Infiltration is infeasible as well given the soil makeup referenced in the NRCS web soil survey and the geotechnical report as both sources indicate low infiltration rates for the native soil on site. C2.4 – Basic Dispersion: Basic Dispersion is infeasible as our site is unable to properly incorporate a vegetated flow path given the minimal site improvements and space available on site for such a path. C2.5 – Farmland Dispersion: This BMP does not apply to the City of Renton, and thus our site is exempt from needing to apply this BMP. C2.6 – Bioretention: Bioretention is infeasible on our site due to the infeasibility criterion #5 which states that bioretention is deemed impractical “where there is a lack of usable space for bioretention facilities at re-development sites, or where there is insufficient space within the existing public right-of-way on public road projects”. Given the limited scope and space available on the site, this project falls into this criterion and is thus exempt. 17803 & 17805 108th Ave SE – Kite Realty Group Kimley-Horn and Associates, Inc. Renton, WA Preliminary Stormwater Report January 21, 2025 Page 8 C2.7 – Permeable Pavement: Permeable Pavement is infeasible to incorporate on site given the fact that installation of such pavement would occur “within 50 feet from the top of slopes that are greater than 20%”. Given that the proposed slopes on the eastern frontage have slopes in exceedance of 20%, this project fulfills criterion 12, exempting the project from the usage of permeable pavement. C2.8 – Rainwater Harvesting: Rainwater Harvesting does not apply to this project as there are no changes to the existing storm infrastructure on site. C2.9 – Reduced Impervious Surface Credit: The Reduced Impervious Credit is not applicable to this project. C2.10 – Native Growth Retention Credit: The Native Growth Retention Credit is not applicable to this project given the proposed improvements. C2.11 – Perforated Pipe Connection: Perforated Pipe Connections are infeasible because the soil on site has a low infiltration rate as mentioned earlier. C2.12 – Rain Gardens: Rain Gardens are infeasible on site citing the same criterion listed in section C2.6 mentioned earlier. The City of Renton SWDM dictates that Rain Gardens apply to these same infeasibility criteria. C2.13 – Soil Amendment: Native soil retention and reuse will be used on site to the maximum extent feasible. C2.14 – Tree Retention Credit: Existing trees on site will be protected in place and retained to the maximum extent feasible. There are no existing trees within the project limits of disturbance that are proposed to be removed. C2.15 – Vegetated Roofs: Vegetated Roofs do not apply to our project as the existing building has minimal renovations to the existing structure, preserving the existing runoff characteristics. B.2 APPLICABLE SPECIAL REQUIREMENTS SR#1: Other Adopted Area-Specific Requirements Copies of all adopted basin plans, Salmon Conservation Plans (SCPs), Hazard Mitigation Plans, and Lake Management Plans will be obtained from the City of Renton and reviewed for compliance in the Final Drainage Report. 17803 & 17805 108th Ave SE – Kite Realty Group Kimley-Horn and Associates, Inc. Renton, WA Preliminary Stormwater Report January 21, 2025 Page 9 SR#2: Flood Hazard Area Delineation The proposed project is not within or adjacent to a flood hazard area, so SR#2 is not applicable to the project. See Appendix A for the project site Flood Map. SR#3: Flood Protection Facilities The proposed project is not a flood protection facility and doesn’t require additional flood mitigation. Thus, SR#3 is not applicable to this site. SR#4: Source Controls The project is not a commercial building and does not require a commercial site development permit and is thus exempt from SR#4. For reference, SR#4 states that “When applicable per the Stormwater Pollution Prevention Manual, structural source control measures, such as car wash pads or dumpster area roofing, shall be applied to the entire site containing the proposed project, not just the project site.” Additionally, the project will generate 102 new daily trips but is under the high use threshold (100 trips/1000 square feet of building area) as we have 3,000 square feet of building area which rounds out to 34 daily trips/1000 square feet of building area. SR#5: Oil Control The project does not have high-use characteristics and is not proposed to be a high-use site. Thus, the project is not required to adhere to SR#5. For reference, SR#5 states that “Projects proposing to develop or redevelop a high-use site must provide oil controls in addition to any other water quality controls required by this manual.” This project is not a high use site, so SR#5 is not applicable. SR#6: Aquifer Protection Area The project site is not within an Aquifer Protection Area (APA), so SR#6 is not applicable to the project. Refer to Appendix A for the APA Map. SECTION C – PRELIMINARY SOILS EVALUATION A soil survey retrieved from the NRCS Web Soil Survey has been included with this report in addition to a geotechnical report as well. Generally, the soils on site consist of a singular layer of Alderwood gravelly sandy loam with slopes ranging from 8 to 15 percent according to the NRCS survey. Conversely, the geotechnical report soil borings indicate a large presence of Vashon till which is described as “an unsorted deposit (diamict) of clay, silt, sand and gravel that has been glacially transported and deposited. However, in both cases, the soil infiltration rate is low, making infiltration infeasible as described earlier. It is also good to note that there was relatively high drainage seepage present in the soil boring labeled “#3”, so it is important to be weary of this item. Refer to Appendix C for both reports. SECTION D – CONVEYANCE SYSTEM (CR#4) Per Section 1.2.4.2 of the SWDM, existing stormwater pipe systems must be analyzed and shown to have sufficient capacity to convey and contain (at minimum) the 25-year peak flow assuming developed conditions for onsite tributary areas and existing conditions for any offsite tributary areas. An analysis demonstrating satisfaction of this requirement will be included with the Final version of this report. SECTION E – OTHER PERMITS Construction of this project and its stormwater facilities will require the following additional permits: Construction Stormwater General Permit – Washington Department of Ecology Status: Not yet submitted 17803 & 17805 108th Ave SE – Kite Realty Group Kimley-Horn and Associates, Inc. Renton, WA Preliminary Stormwater Report January 21, 2025 Page 10 SECTION F – APPENDICES APPENDIX A: MAPS 1. VICINITY MAP IN COMPLIANCE WITH CITY OF RENTON STANDARDS PROJECT SITE NORTH 10 8 T H A V E S E VICINITY MAP OF SITE 17803 & 17805 108th Ave SE – Kite Realty Group Kimley-Horn and Associates, Inc. Renton, WA Preliminary Stormwater Report January 21, 2025 Page 11 2. FLOOD INSURANCE RATE MAP SITE LOCATION 17803 & 17805 108th Ave SE – Kite Realty Group Kimley-Horn and Associates, Inc. Renton, WA Preliminary Stormwater Report January 21, 2025 Page 12 3. PRE-DEVELOPMENT DRAINAGE AREA MAP IN COMPLIANCE WITH CITY OF RENTON STANDARDS NORTH PR E L I M I N A R Y - N O T F O R C O N S T R U C T I O N 17803 & 17805 108th Ave SE – Kite Realty Group Kimley-Horn and Associates, Inc. Renton, WA Preliminary Stormwater Report January 21, 2025 Page 13 4. POST-DEVELOPMENT DRAINAGE AREA MAP IN COMPLIANCE WITH CITY OF RENTON STANDARDS NORTH PR E L I M I N A R Y - N O T F O R C O N S T R U C T I O N 17803 & 17805 108th Ave SE – Kite Realty Group Kimley-Horn and Associates, Inc. Renton, WA Preliminary Stormwater Report January 21, 2025 Page 14 5. PROPOSED DRAINAGE PLAN 389.18 389.18 388.45 389.30 388.36389.18 399.37 399.44 399.59 399.65 399.48 399.53 393.51 TW 393.50 TW 391.10 TW 393.15 TW 391.95 BW 390.13 BW 390.66 BW 390.22 BW 390.10 389.70 ME 390.02 389.47 ME 389.80 ME 390.11390.09 389.54 ME 391.35 ME390.95 ME 388.21 ME 385.58 ME 386.56 ME 385.21 ME IN COMPLIANCE WITH CITY OF RENTON STANDARDS GRADING & DRAINAGE NOTES 1.ADA ACCESSIBLE SPACES ARE DESIGNED TO HAVE A MAXIMUM SLOPE OF 2.0% IN ANY DIRECTION. 2.THE PROPOSED ACCESSIBLE PATH SIDEWALKS AROUND THE BUILDING AND ALONG THE PROPERTY FRONTAGES SHALL HAVE A MAXIMUM 2% CROSS SLOPE AND 5% LONGITUDINAL SLOPE. 3.CONTRACTOR TO VERIFY DEPTH OF EXISTING UNDERGROUND UTILITIES PRIOR TO PLACEMENT OF ANY PAVEMENT AND NOTIFY KIMLEY-HORN IF ANY CONFLICTS EXIST. 4.TOP OF CURB SHALL BE 6" ABOVE PAVEMENT ELEVATION UNLESS OTHERWISE SPECIFIED. PROPERTY LINE EXISTING CONTOUR PROPOSED MAJOR CONTOUR PROPOSED MINOR CONTOUR GRADE BREAK PROPOSED SPOT ELEVATION EXISTING SEWER CLEANOUT GRADING LEGEND XXX.XX SPOT ELEVATION LEGEND BC BOTTOM OF CURB BW BOTTOM OF WALL HP HIGH POINT LP LOW POINT TC TOP OF CURB TW TOP OF WALL ME MATCH EXISTING SW SIDEWALK GR A D I N G A N D D R A I N A G E P L A N NORTH C5.0 1/22/25 7 12 GRADING AND DRAINAGE PLAN CHIPOTLE 108TH AVE SE PRE L I M I N A R Y 17803 & 17805 108th Ave SE – Kite Realty Group Kimley-Horn and Associates, Inc. Renton, WA Preliminary Stormwater Report January 21, 2025 Page 15 6. AQUIFER PROTECTION AREA MAP SITE LOCATION 17803 & 17805 108th Ave SE – Kite Realty Group Kimley-Horn and Associates, Inc. Renton, WA Preliminary Stormwater Report January 21, 2025 Page 16 APPENDIX B: CALCULATIONS 1. TEMPORARY EROSION AND SEDIMENT CONTROL CALCULATIONS (TO BE COMPLETED BEFORE FINAL APPLICATION) 17803 & 17805 108th Ave SE – Kite Realty Group Kimley-Horn and Associates, Inc. Renton, WA Preliminary Stormwater Report January 21, 2025 Page 17 APPENDIX C : ADDITIONAL PLANS AND REPORTS 1. GEOTECHNICAL ENGINEERING REPORT ________________________________________________ 3213 Eastlake Avenue East, Suite B Seattle, WA 98102 (206) 262-0370 | pangeoinc.com Geotechnical & Earthquake Engineering Consultants January 13, 2025 Project No. 24-497 Tony Halsey, P.E. Kite Realty Group 30 South Meridian Street, Suite 1100 Indianapolis, IN 46204 Subject: Limited Geotechnical Report Proposed Retaining Wall 17803 108th Avenue SE, Renton, WA 98055 Dear Tony: As requested, PanGEO, Inc. completed a geotechnical study to support the design and permitting of the proposed retaining wall at the above-referenced site in Renton, Washington. Our service scope included reviewing readily available geologic and geotechnical data in the vicinity of the project, conducting a reconnaissance of the site, performing limited subsurface investigations, and formulating the conclusions and recommendations presented in this report. Our work was completed in accordance with our proposal for geotechnical engineering services, dated December 20, 2024, and the professional services agreement with you, dated 1/3/2025. SITE & PROJECT DESCRIPTION The subject site is located at 17803 108th Avenue SE, in Renton, Washington, as shown on the attached Figure 1, Vicinity Map. The site is bounded by 108th Avenue SE/Benson Road South to the east, and by commercial properties to the north, west and south, anchored by the Fred Meyer retail store to the west. The project site is currently developed with a one-level at-grade structure that was formerly a Bank of America branch. The structure is surrounded with asphalt parking areas and driveways. The majority of the site is relatively flat, with the exception of the eastern margin of the site that slopes up from the parking lot at an angle of about 2H:1V to the sidewalk of 108th Avenue SE, with a vertical relief of about 12 feet. Limited Geotechnical Report – Proposed Retaining Wall 17803 108th Avenue SE, Renton, WA January 13, 2025 24-497_17803 108th ave se_renton_r_wall.docx 2 PanGEO, Inc. The specific focus of our current study is the slope on the eastern portion of the site. As part of the proposed re-development of the property, we understand that the City of Renton is requiring street improvements along the frontage of the subject property, which includes the addition of a planter strip and widened sidewalk which will extend over the existing slope on the east side of the subject site. As such, a new retaining wall will need to be incorporated into the project to support the new sidewalk, and/or retain the fill soils placed to support the new sidewalk. Plates 1 and 2 below depict current site conditions. Plate 1. Looking north-northeast at the slope on the east side of the property where the proposed retaining wall will be constructed. A portion of the existing bank drive-through structure can be seen on the left side of the photo. Limited Geotechnical Report – Proposed Retaining Wall 17803 108th Avenue SE, Renton, WA January 13, 2025 24-497_17803 108th ave se_renton_r_wall.docx 3 PanGEO, Inc. Plate 2. Looking south along the western sidewalk of 108th Avenue SE. The proposed retaining wall will be located near the toe of the slope shown on the right side of the photo. The conclusions and recommendations outlined in this report are based on our understanding of the proposed project, which is in turn based on the project information provided to us. If the above project description is substantially different from the proposed improvements, or if the project scope changes, PanGEO should be consulted to review the recommendations contained in this study and make modifications, if needed. SUBSURFACE EXPLORATIONS Our subsurface exploration program included advancing four (4) hand borings (PG-1 to PG-4) on December 30, 2024, to explore near-surface soil conditions at the location of the proposed retaining wall and backslope. The boring locations are shown on Figure 2, Site and Exploration Plan, and were measured in the field from existing site features. Limited Geotechnical Report – Proposed Retaining Wall 17803 108th Avenue SE, Renton, WA January 13, 2025 24-497_17803 108th ave se_renton_r_wall.docx 4 PanGEO, Inc. The hand borings were advanced utilizing a post-hole digger and a 4-inch diameter hand auger to depths of up to 4½-feet below the existing ground surface. An engineer from PanGEO performed the explorations and logged the subsurface conditions encountered in the test holes. The relative density of granular soils and the relative consistency of cohesive soils were generally estimated based on the excavation resistance encountered throughout the depth of the exploration, and on the penetration resistance of the soil from a ½-inch diameter steel hand probe. After each test hole was completed, it was backfilled with excavated spoils, and the surface tamped firm. The summary hand boring logs are included in Appendix A at the end of this report. The soil samples were described using the system outlined in Appendix A, Figure A-1. GEOLOGY General geologic information for the project area was obtained by reviewing the Geologic Map of the Renton Quadrangle, King County, Washington (Mullineaux, 1965) and the Geologic Map of the Tacoma 1:100,000-scale Quadrangle, Washington (Schuster et al, 2015). Based on our review, the geologic unit in the vicinity of the site consists of Vashon till – Geologic Map Unit Qgt. Vashon till is described as consisting of an unsorted deposit (diamict) of clay, silt, sand and gravel that has been glacially transported and deposited. This soil has been directly deposited by a glacier and overridden by several thousand feet of glacial ice and is typically dense to very dense. Plate 3 on the following page depicts and excerpt from the geologic map by Schuster et at, 2015. SUBSURFACE CONDITIONS SOIL CONDITIONS Based on the conditions encountered in our test borings, the area of the proposed retaining wall is generally underlain by a relatively thin layer of undocumented fill over medium dense to dense silty and with some gravel, which we interpreted to be the mapped glacial till. A summary of the soil units encountered in the explorations is provided below, and details of the soil conditions encountered in each of the test borings can be found in Appendix A. Limited Geotechnical Report – Proposed Retaining Wall 17803 108th Avenue SE, Renton, WA January 13, 2025 24-497_17803 108th ave se_renton_r_wall.docx 5 PanGEO, Inc. Topsoil: All of the test borings encountered from about 6 to 8 inches of loose, dark brown, silty sand and sandy silt with prevalent organics which we interpreted to be topsoil. Fill: Below the organic-rich topsoil, all of the test borings encountered a relatively thin layer of fill, except boring PG-2, where no fill was encountered. The fill typically consisted of loose to medium dense, silty sand and sandy silt with trace to some gravel and scattered organic matter. In general, near the toe of the slope, the fill extended to about 2½ feet below the ground surface, while near the middle of the slope, at the location of PG-3, about two feet of fill was encountered. Plate 3 – Geology map of the area. The site is located in an area mapped as glacial till (map unit Qgt). (Schuster et al, 2015) SITE Limited Geotechnical Report – Proposed Retaining Wall 17803 108th Avenue SE, Renton, WA January 13, 2025 24-497_17803 108th ave se_renton_r_wall.docx 6 PanGEO, Inc. Drainage Gravel - At the toe of the slope, PG-1 encountered washed drainage rock at a depth from about 1 to 2½ feet below the ground surface. We infer that a drain line may have been installed at the toe of the slope to intercept groundwater seeping from the slope cut to transport the water to a suitable drainage outlet. Glacial Till: Below the topsoil in PG-2, and below the fill in all other borings, we generally encountered a medium dense to dense, silty sand with some gravel that we interpreted to be the mapped glacial till. Due to the medium dense to dense nature of this deposit, and evidence of iron-oxide staining, we inferred that the top of the glacial till deposit encountered in the test borings was weathered, and that the underlying un-weathered soils would become dense to very dense, which his typical of glacial till deposits. Our subsurface descriptions are based on the conditions encountered at the time of our exploration. Soil conditions between our exploration locations may vary from those encountered. The nature and extent of variations between our exploratory locations may not become evident until construction. If variations do appear, PanGEO should be requested to reevaluate the recommendations in this report and to modify or verify them in writing prior to proceeding with earthwork and construction. GROUNDWATER CONDITIONS At the toe of the slope, the test borings encountered groundwater seepage as shallow as 1-foot below the ground surface (see Hand Boring Log – PG-3). All borings encountered soils with iron- oxide stains, which is an indication of groundwater fluctuations within the soil layer. We interpret that the groundwater seepage encountered in PG-3, and the cause of the iron oxide staining in the other borings, is perched water that forms on top of the underlying dense glacial till during wet times of the year. We anticipate that stormwater infiltrates into the ground above the slope, becomes perched on the low permeability till, and then flows downslope to the west, following the contact of the glacial till. We anticipate that a significant amount of groundwater was accumulating at the toe of the slope during original grading of the property, which is the likely reason a drainage measure was installed at the toe of the slope to intercept and collect the groundwater seepage. It may be noted that glacial till deposits also typically contain pockets of clean sand and gravel that can also contain groundwater, which may contribute to seepage once they are excavated into. Limited Geotechnical Report – Proposed Retaining Wall 17803 108th Avenue SE, Renton, WA January 13, 2025 24-497_17803 108th ave se_renton_r_wall.docx 7 PanGEO, Inc. Groundwater levels will change depending on the season, amount of rainfall, surface water runoff, and other factors. Generally, the water level is higher and seepage rates are greater in the wetter, winter months (typically October through May). GEOTECHNICAL RECOMMENDATIONS RETAINING WALL DESIGN Due to the depth of competent bearing soils near the mid-height of the slope (about 4½ feet), in our opinion it will be more cost effective to locate the proposed retaining wall along the toe of the slope, instead of mid-height. Based on the results of our subsurface exploration program and our site reconnaissance, in our opinion a cast-in-place concrete wall located at the toe of the existing slope represents a feasible wall type at the subject site. To limit the wall height, in our opinion, a backslope no steeper than 2H:1V may be constructed behind the wall to support the new frontage improvements. We recommend that the wall be designed to stick up a minimum of 1-foot above the ground surface to account for any erosion that could occur on the backslope behind the wall. Retaining walls should be properly designed to resist the pressure exerted by the soils behind the wall, including a backslope. Proper drainage provisions should also be provided behind the walls to intercept and remove any groundwater from behind the wall. In this particular case, as described above, groundwater seepage is anticipated behind the proposed wall, and therefore adequate drainage provisions are critical, and should not be omitted during the design or construction of the wall. Our geotechnical recommendations for the design and construction of the proposed retaining wall are presented below. Footing Depth and Allowable Bearing Pressure We recommend that the wall footing bears on the undisturbed, medium dense to dense native soils which we estimate is present about 2½ feet below the toe of the slope. As such, the footing will need to be embedded about 2½ feet below the existing pavement elevation, or the soils below the footing should be over-excavated to about 2½ feet below the pavement elevation, and backfilled with properly compacted structural fill or lean-mix concrete (1.5 sack mix, minimum) up to the design footing elevation. We recommend a minimum foundation embedment of 18 inches below final exterior grade. The footings may be designed for a maximum allowable bearing pressure of Limited Geotechnical Report – Proposed Retaining Wall 17803 108th Avenue SE, Renton, WA January 13, 2025 24-497_17803 108th ave se_renton_r_wall.docx 8 PanGEO, Inc. 3,000 psf. For allowable stress design, the recommended allowable bearing pressure may be increased by 1/3 for transient conditions such as wind and seismic loadings. Lateral Earth Pressures Considering the maximum backslope of 2H:1V, the wall should be designed for an earth pressure based upon an equivalent fluid weight of 53 pcf for a wall that is allowed to yield (active condition), and 35 pcf for a wall with a level backslope. For the seismic condition and a 2H:1V wall backslope, we recommend a uniform lateral earth pressure of 15H psf (where H is the height of the below grade portion of the wall) be added to the static pressure for sizing the walls for the ultimate condition. If the wall backfill will be level, we recommend a uniform lateral earth pressure of 10H psf be added for the seismic condition. The recommended lateral pressures assume that adequate wall drainage will be incorporated into the design and construction of the walls to prevent the development of hydrostatic pressure. Lateral Resistance Lateral forces may be resisted by the combination of passive earth pressures acting against the embedded portions of the foundations and by friction acting on the base of the foundations. Passive resistance values may be determined using an equivalent fluid weight of 300 pounds per cubic foot (pcf), which assumes level ground conditions in front of the wall. This value includes a geotechnical factor of safety of at least 1.5 assuming that properly compacted structural fill will be placed adjacent to the sides of the footings. A coefficient of friction of 0.45 may be used to determine the frictional resistance at the base of the footings. This coefficient includes a geotechnical factor of safety of approximately 1.5. Wall Drainage Provisions for permanent control of subsurface water should be incorporated into the design and construction of the new walls, as groundwater seepage is expected behind the proposed wall. For walls constructed with conventional free-draining backfill, a footing drain consisting of a 4-inch diameter perforated pipe embedded in at least 12 inches of washed gravel wrapped with a geotextile fabric should be placed at the base of the new wall footing. We recommend a minimum 12-inch-wide chimney of free draining gravel be placed behind the wall. In addition, prefabricated drainage mats, such as Mirafi 6000 or equivalent, may be installed behind the walls to promote Limited Geotechnical Report – Proposed Retaining Wall 17803 108th Avenue SE, Renton, WA January 13, 2025 24-497_17803 108th ave se_renton_r_wall.docx 9 PanGEO, Inc. wall drainage. The drain can likely be connected to the same outlet as an existing drain we anticipate is located along the toe of the slope. Wall Backfill Wall backfill should consist of free draining granular soils. Imported wall backfill may consist of granular soils such as Gravel Borrow (Section 9.03.14 (1) of the 2024 WSDOT Standard Specifications) or approved equivalent. Wall backfill should be moisture conditioned to within about 3 percent of optimum moisture content, placed in loose, horizontal lifts less than 8 inches in thickness, and systematically compacted to a dense and relatively unyielding condition and to at least 95 percent of the maximum dry density, as determined using test method ASTM D 1557 (Modified Proctor). Within 5 feet of the wall, the backfill should be compacted to 90 percent of the maximum dry density. Wall Foundation Performance Total and differential settlements are anticipated to be within tolerable limits for footings designed and constructed as discussed above. Footing settlement under static loading conditions is estimated to be less than approximately 3/4 inch, and differential settlement along the wall should be less than about ½-inch. Global Stability Provided that the proposed retaining wall is founded on spread footings bearing below the fill soils on medium dense to very dense native soils at the toe of the slope, and the recommendations provided in this report are adhered to in the design and construction of the walls, the retaining walls will meet current code requirements for global stability. PERMANENT SLOPES Provided that the proposed retaining wall is backfilled with free-draining imported gravel borrow (Section 9.03.14 (1) of the 2024 WSDOT Standard Specifications) or approved equivalent, and the fill is adequately compacted as described above for wall backfill, we recommend permanent fill slopes be constructed no steeper than 2H:1V (Horizontal:Vertical). All existing topsoil should be removed from the slope before backfilling, and any existing loose/soft fill soils should be re- Limited Geotechnical Report – Proposed Retaining Wall 17803 108th Avenue SE, Renton, WA January 13, 2025 24-497_17803 108th ave se_renton_r_wall.docx 10 PanGEO, Inc. compacted to a firm condition, or removed, prior to placement on compaction of the granular wall backfill. RETAINING WALL CONSTRUCTION CONSIDERATIONS We offer the following geotechnical considerations related to construction aspects of the proposed cast-in-place retaining wall. Footing Construction Considerations All footing subgrades should be carefully prepared. Any loose soil should be removed from the footing excavations or re-compacted. Footing subgrades should be observed by PanGEO to confirm that the exposed footing subgrade is consistent with the expected conditions and adequate to support the design bearing pressure. As noted above, at the toe of the slope drainage gravel may be encountered during the excavation for the retaining wall footing. We recommend that the drainage gravel be removed below the proposed footing to expose the medium dense to very dense native soils. Footing Subgrade Protection The contractor should be aware that the site soils are sensitive to moisture, and may become disturbed and soft when exposed to inclement weather conditions. If the footing subgrades are exposed to water, it may be necessary to place 3 to 4 inches of clean crushed rock on the prepared footing subgrade, or lean-mix concrete (1.5 sack, minimum), to protect it against moisture and disturbance. Temporary Excavations In general, maximum temporary excavation cuts are expected to be about 12 feet tall. Temporary excavations greater than 4 feet deep should be properly sloped or shored. All temporary excavations should be performed in accordance with Part N of WAC (Washington Administrative Code) 296-155. The contractor is responsible for maintaining safe excavation slopes and/or shoring. For planning purposes, the temporary excavations may be sloped to as steep as 1H:1V (Horizontal:Vertical). The temporary cut slopes should be re-evaluated by a representative of PanGEO during construction based on actual observed soil conditions. Limited Geotechnical Report – Proposed Retaining Wall 17803 108th Avenue SE, Renton, WA January 13, 2025 24-497_17803 108th ave se_renton_r_wall.docx 11 PanGEO, Inc. During periods of precipitation, the temporary cuts should be protected with plastic sheeting. If areas of seepage are encountered during construction, the slopes may need to be flattened or armored with quarry spalls to reduce the potential of face instability. We recommend that traffic, construction equipment, building materials and excavated soil should not be allowed within a distance equal to one-half the slope height from the top of any excavation, or 3-foot minimum. The setback distance of heavy point loads, such as crane or pump truck outriggers, should be evaluated on a case-by-case basis. Temporary Groundwater Control The contractor should be aware that groundwater seepage is expected in the excavation for the wall foundation, especially during wet times of the year. We anticipate that sumps and pumps will be adequate to dewater the wall footing excavation. STRUCTURAL FILL AND COMPACTION Stuctural fill will be needed next to the wall footing, and may be needed below wall footings if over-excavation of unsuitable soils occurs. Structural fill, should be free of organic and inorganic debris, be near the optimum moisture content and be capable of being compacted to the recommendations provided below. The site soils are relatively fine grained and, in our opinion will not be suitable for re-use as structural fill and an imported structural fill will be needed. Fill for use during wet weather should consist of a well graded soil free of organic material with less than 5 percent fines (silt and clay sized particles passing the U.S. 200 sieve). Structural fill should be moisture conditioned to within about 3 percent of optimum moisture content, placed in loose, horizontal lifts less than 8 inches in thickness, and compacted to at least 95 percent maximum density, determined using ASTM D1557 (Modified Proctor). The procedure to achieve proper density of a compacted fill depends on the size and type of compacting equipment, the number of passes, thickness of the lifts being compacted, and certain soil properties. If the excavation to be backfilled is constricted and limits the use of heavy equipment, smaller equipment can be used, but the lift thickness will need to be reduced to achieve the required relative compaction. Generally, loosely compacted soils are a result of poor construction technique or improper moisture content. Soils with high fines contents are particularly susceptible to becoming too wet Limited Geotechnical Report – Proposed Retaining Wall 17803 108th Avenue SE, Renton, WA January 13, 2025 24-497_17803 108th ave se_renton_r_wall.docx 12 PanGEO, Inc. and coarse-grained materials easily become too dry, for proper compaction. Silty or clayey soils with a moisture content too high for adequate compaction should be dried as necessary, or moisture conditioned by mixing with drier materials, or other methods. PERMANENT DRAINAGE CONSIDERATIONS Permanent control of surface water should be incorporated in the final grading design. Adequate surface gradients and drainage systems should be incorporated into the design such that surface runoff is directed away from the wall. Under no circumstances should collected surface water be allowed to discharge behind retaining walls. TEMPORARY & PERMANENT EROSION CONTROL CONSIDERATIONS Surface runoff can be controlled during construction by careful grading practices. This may include the construction of shallow, upgrade perimeter ditches or low earthen or asphalt berms to collect runoff and prevent water from entering the excavation. All collected water should be directed to a positive and permanent discharge system such as a storm sewer. It should be noted that the site soils are prone to surficial erosion. Special care should be taken to avoid surface water on open cut excavations, and exposed slopes should be protected with plastic sheeting. Permanent erosion control measures such as covering exposed ground surfaces with topsoil or mulch, and installing landscaping, should be performed as soon as possible after construction to limit the time the exposed surfaces are susceptible to erosion. LIMITATIONS We have prepared this report for use by Kite Realty Group and the project team. Recommendations contained in this report are based on a review of existing data, a site reconnaissance, the results of our limited subsurface exploration program, and our understanding of the project. The study was performed using a mutually agreed-upon scope of work. Variations in soil conditions may exist between the observed soil type and the actual conditions underlying the site. The nature and extent of soil variations may not be evident until construction occurs. If any soil conditions are encountered at the site that are different from those described in this report, we should be notified immediately to review the applicability of our recommendations. Additionally, we should also be notified to review the applicability of our recommendations if there are any changes in the project scope. Limited Geotechnical Report – Proposed Retaining Wall 17803 108th Avenue SE, Renton, WA January 13, 2025 24-497_17803 108th ave se_renton_r_wall.docx 13 PanGEO, Inc. The scope of our work does not include services related to construction safety precautions. Our recommendations are not intended to direct the contractors’ methods, techniques, sequences or procedures, except as specifically described in our report for consideration in design. Additionally, the scope of our work specifically excludes the assessment of environmental characteristics, particularly those involving hazardous substances. We are not mold consultants nor are our recommendations to be interpreted as being preventative of mold development. A mold specialist should be consulted for all mold-related issues. This report may be used only by the client and for the purposes stated, within a reasonable time from its issuance. Land use, site conditions (both off and on-site), or other factors including advances in our understanding of applied science, may change over time and could materially affect our findings. Therefore, this report should not be relied upon after 24 months from its issuance. PanGEO should be notified if the project is delayed by more than 24 months from the date of this report so that we may review the applicability of our conclusions considering the time lapse. It is the client’s responsibility to see that all parties to this project, including the designer, contractor, subcontractors, etc., are made aware of this report in its entirety. The use of information contained in this report for bidding purposes should be done at the contractor’s option and risk. Any party other than the client who wishes to use this report shall notify PanGEO of such intended use and for permission to copy this report. Based on the intended use of the report, PanGEO may require that additional work be performed and that an updated report be reissued. Noncompliance with any of these requirements will release PanGEO from any liability resulting from the use this report. Within the limitation of scope, schedule and budget, PanGEO engages in the practice of geotechnical engineering and endeavors to perform its services in accordance with generally accepted professional principles and practices at the time the Report or its contents were prepared. No warranty, express or implied, is made. Limited Geotechnical Report – Proposed Retaining Wall 17803 108th Avenue SE, Renton, WA January 13, 2025 24-497_17803 108th ave se_renton_r_wall.docx 14 PanGEO, Inc. We appreciate the opportunity to be of service to you on this project. Please feel free to contact our office with any questions you have regarding our study, this report, or any geotechnical engineering related project issues. Sincerely, PanGEO, Inc. Jon C. Rehkopf, P.E. Principal Geotechnical Engineer jrehkopf@pangeoinc.com ATTACHMENTS Figures Figure 1 – Vicinity Map Figure 2 – Site and Exploration Plan Appendix A Figure A-1 – Terms and Symbols for Boring and Test Pit Logs Figures A-2 through A-5 – Subsurface Exploration Logs PG-1 through PG-4 Limited Geotechnical Report – Proposed Retaining Wall 17803 108th Avenue SE, Renton, WA January 13, 2025 24-497_17803 108th ave se_renton_r_wall.docx PanGEO, Inc. REFERENCES Mullineaux, D.R., 1965, Geologic Map of the Renton Quadrangle, King County, Washington – U.S. Geological Survey Geologic, Quadrangle Map GQ-405, scale 1:24,000. Schuster, J.E., Cabibbo, A.A., Schilter, J.F., and Hubert I.J., 2015, Geologic Map of the Tacoma 1:100,000-scale Quadrangle, Washington – Washington Division of Geology and Earth Resources, Map Series 2015-03, scale 1:100,000. WSDOT, 2024, Standard Specifications for Road, Bridge and Municipal Construction, M 41-10. Washington Administrative Code (WAC), 2013, Chapter 296-155 - Safety Standards for Construction Work, Part N - Excavation, Trenching, and Shoring, Olympia, Washington. 24-497 Proposed Retaining Wall 17803 108th Avenue SE Renton, Washington 1 VICINITY MAP Figure No.Project No. Fi g 1 - V i c i n i t y M a p . g p j 1 / 1 3 / 2 5 ( 1 0 : 3 1 : 4 4 ) Base Map Credit: King County iMAP. Project Site NOT TO SCALE Project Vicinity Project No.Figure No. SITE AND EXPLORATION PLAN 24-497 2 Fi g 2 - S i t e a n d E x p l o r a t i o n P l a n . g p j 1 / 1 3 / 2 5 ( 1 1 : 0 9 : 3 2 ) J C R 0 20 40 1 inch ~ 40 feet Note: Base map modified from site survey prepared by SAM, dated 5/8/2024. 10 8 t h A V E S E Proposed Retaining Wall 17803 108th Avenue SE Renton, Washington PG-1 PG-2 PG-3 PG-4 LEGEND Approximate Location of Subsurface Explorations (PanGEO, 2024) Approximate Location of Proposed Retaining Wall Limits of Subject Site Limited Geotechnical Report – Proposed Retaining Wall 17803 108th Avenue SE, Renton, WA January 13, 2025 24-497_17803 108th ave se_renton_r_wall.docx PanGEO, Inc. APPENDIX A SUBSURFACE EXPLORATION LOGS MOISTURE CONTENT 2-inch OD Split Spoon, SPT (140-lb. hammer, 30" drop) 3.25-inch OD Spilt Spoon (300-lb hammer, 30" drop) Non-standard penetration test (see boring log for details) Thin wall (Shelby) tube Grab Rock core Vane Shear Dusty, dry to the touch Damp but no visible water Visible free water Terms and Symbols for Boring and Test Pit Logs Density SILT / CLAY GRAVEL (<5% fines) GRAVEL (>12% fines) SAND (<5% fines) SAND (>12% fines) Liquid Limit < 50 Liquid Limit > 50 Breaks along defined planes Fracture planes that are polished or glossy Angular soil lumps that resist breakdown Soil that is broken and mixed Less than one per foot More than one per foot Angle between bedding plane and a planenormaltocoreaxis Very Loose Loose Med. Dense Dense Very Dense SPT N-values Approx. Undrained Shear Strength (psf) <4 4 to 10 10 to 30 30 to 50 >50 <2 2 to 4 4 to 8 8 to 15 15 to 30 >30 SPT N-values Units of material distinguished by color and/orcomposition frommaterial unitsabove andbelow Layers of soil typically 0.05 to 1mm thick, max. 1 cm Layer of soil that pinches out laterally Alternating layers of differing soil material Erratic, discontinuous deposit of limited extent Soil with uniform color and composition throughout Approx. Relative Density (%) Gravel Layered: Laminated: Lens: Interlayered: Pocket: Homogeneous: Highly Organic Soils #4 to #10 sieve (4.5 to 2.0 mm) #10 to #40 sieve (2.0 to 0.42 mm) #40 to #200 sieve (0.42 to 0.074 mm) 0.074 to 0.002 mm <0.002 mm UNIFIED SOIL CLASSIFICATION SYSTEM MAJOR DIVISIONS GROUP DESCRIPTIONS Notes: MONITORING WELL <15 15 - 35 35 - 65 65 - 85 85 - 100 GW GP GM GC SW SP SM SC ML CL OL MH CH OH PT TEST SYMBOLS 50%or more passing #200 sieve Groundwater Level at time of drilling (ATD)Static Groundwater Level Cement / Concrete Seal Bentonite grout / seal Silica sand backfill Slotted tip Slough <250 250 - 500 500 - 1000 1000 - 2000 2000 - 4000 >4000 RELATIVE DENSITY / CONSISTENCY Fissured: Slickensided: Blocky: Disrupted: Scattered: Numerous: BCN: COMPONENT DEFINITIONS Dry Moist Wet 1. Soil exploration logs contain material descriptions based on visual observation and field tests using a systemmodified from the Uniform Soil Classification System (USCS). Where necessary laboratory tests have beenconducted (as noted in the "Other Tests" column), unit descriptions may include a classification. Please refer to thediscussions in the report text for a more complete description of the subsurface conditions. 2. The graphic symbols given above are not inclusive of all symbols that may appear on the borehole logs.Other symbols may be used where field observations indicated mixed soil constituents or dual constituent materials. COMPONENT SIZE / SIEVE RANGE COMPONENT SIZE / SIEVE RANGE SYMBOLS Sample/In Situ test types and intervals Silt and Clay Consistency SAND / GRAVEL Very Soft Soft Med. Stiff Stiff Very Stiff Hard Phone: 206.262.0370 Bottom of BoringBoulder: Cobbles: Gravel Coarse Gravel: Fine Gravel: Sand Coarse Sand: Medium Sand: Fine Sand: Silt Clay > 12 inches 3 to 12 inches 3 to 3/4 inches 3/4 inches to #4 sieve Atterberg Limit Test Compaction Tests Consolidation Dry Density Direct Shear Fines Content Grain Size Permeability Pocket Penetrometer R-value Specific Gravity Torvane Triaxial Compression Unconfined Compression Sand 50% or more of the coarse fraction passing the #4 sieve. Use dual symbols (eg. SP-SM) for 5% to 12% fines. for In Situ and Laboratory Testslisted in "Other Tests" column. 50% or more of the coarse fraction retained on the #4 sieve. Use dual symbols (eg. GP-GM) for 5% to 12% fines. DESCRIPTIONS OF SOIL STRUCTURES Well-graded GRAVEL Poorly-graded GRAVEL Silty GRAVEL Clayey GRAVEL Well-graded SAND Poorly-graded SAND Silty SAND Clayey SAND SILT Lean CLAY Organic SILT or CLAY Elastic SILT Fat CLAY Organic SILT or CLAY PEAT ATT Comp Con DD DS %F GS Perm PP R SG TV TXC UCC Figure A-1 Project No: 24-497 Project Name: Proposed Retaining Wall Project Loca�on: 17803 108th Ave SE, Renton, Washington Date Excavated: 12/30/2024 24-497 hand boring logs.docx Figure A-2 PanGEO, Inc. Hand Boring Log: PG-1 Approximate ground surface eleva�on: ~390 feet (NAVD 88 ) Approximate Loca�on: 26 feet north of southern rockery, abou t 1’ east of curb at toe of slope Depth (feet ) Material Descrip�on 0 – ½ Loose, moist, dark brown, silty SAND and sandy SILT with some gravel and prevalent organics. [Topsoil] ½ – 1 Loose to medium dense, moist, tan with iron oxide staining, silty SAND with some gravel and trace organics. [Fill] 1 – 2 ½ Washed 7/8-inch diameter rounded drain rock [Fill from apparent drainage system] 2½ Medium dense to dense, silty SAND with some gravel [Glacial Till (Qvt)] - Soil descrip�on based on probing with a ½-inch diameter soil probe through the washed rock. Probe penetra�ons were observed to be less than 2 to 3 inches into the underlying na�ve soil. Photo shows drain rock at ~1 foot below ground surface at bottom of hole. -PG-1 was terminated approximately 2½ feet below ground surface due to caving drain rock. -Light groundwater seepage was observed about 2’ below ground surface. Project No: 24-497 Project Name: Proposed Retaining Wall Project Loca�on: 17803 108th Ave SE, Renton, Washington Date Excavated: 12/30/2024 24-497 hand boring logs.docx Figure A-3 PanGEO, Inc. Hand Boring Log: PG-2 Approximate ground surface eleva�on: ~392 feet (NAVD 88 ) Approximate Loca�on: 28 feet north of southern rockery, abou t 4’ east of curb at toe of slope Depth (feet ) Material Descrip�on 0 – ½ Loose, moist, dark brown, silty SAND and sandy SILT with some gravel and prevalent organics. [Topsoil] ½ - 2 Medium dense to dense, moist, tan with some iron-oxide stains, silty SAND with some gravel [Glacial Till (Qvt)] - Soil probe penetra�on less than 1” into dense silty SAND Photo shows soil sample at ~2 feet below ground surface. -PG-2 was terminated approximately 2 feet below ground surface due to refusal on dense gravelly soils. -No groundwater seepage was observed in test hole. Project No: 24-497 Project Name: Proposed Retaining Wall Project Loca�on: 17803 108th Ave SE, Renton, Washington Date Excavated: 12/30/2024 24-497 hand boring logs.docx Figure A-4 PanGEO, Inc. Hand Boring Log: PG-3 Approximate ground surface eleva�on: ~391 feet (NAVD 88 ) Approximate Loca�on: 20 feet north of former bank sign, about 3’ east of curb at toe of slope Depth (feet ) Material Descrip�on 0 – ½ Loose, moist, dark brown, silty SAND and sandy SILT with some gravel and prevalent organics. [Topsoil] ½ – 2½ Loose to medium dense, moist to wet, tan with iron oxide staining, silty SAND with some gravel and trace organics. [Fill] - Groundwater seepage at 1 foot below ground surface - Some washed rock observed - maybe near drainage line 2½ Medium dense to dense, tan with iron oxide staining, moist to wet, silty SAND with some gravel [Glacial Till (Qvt)] - Soil probe penetra�ons of less than 1 inch @ 2½ feet below ground surface. Photo shows seepage filling hole to about 1 foot below ground surface. -PG-3 was terminated approximately 2½ feet below ground surface due to dense soils and groundwater seepage causing caving of hole. -Heavy groundwater seepage was observed about 1’ below ground surface. Project No: 24-497 Project Name: Proposed Retaining Wall Project Loca�on: 17803 108th Ave SE, Renton, Washington Date Excavated: 12/30/2024 24-497 hand boring logs.docx Figure A-5 PanGEO, Inc. Logged by HKR & JCR Hand Boring Log: PG-4 Approximate ground surface eleva�on: ~395 feet (NAVD 88 ) Approximate Loca�on: 12 feet south of former bank sign, ~12’ east of curb at toe of slope Depth (feet ) Material Descrip�on 0 – 2/3 Loose, moist, dark brown, silty SAND and sandy SILT with some gravel and prevalent organics. [Topsoil] 2/3 – 2 Loose to medium dense, moist, medium to dark brown, sandy SILT with trace gravel and trace to some organics. [Fill] 2 - 4½ Medium dense to dense, moist, tan with heavy iron-oxide stains, silty SAND with some gravel [Glacial Till (Qvt)] - Soil probe penetra�ons about 2” @ 2 feet depth - Gravel content increases around a depth of about 4 feet - Soil probe penetra�on less than 1” @ 4½ feet depth Photo shows soil sample at ~2½ feet below ground surface. -PG-4 was terminated approximately 4½ feet below ground surface due to refusal on dense gravelly soils. -No groundwater seepage was observed in test hole. 17803 & 17805 108th Ave SE – Kite Realty Group Kimley-Horn and Associates, Inc. Renton, WA Preliminary Stormwater Report January 21, 2025 Page 18 2. NRCS WEB SOIL SURVEY 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 December 30, 2024 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 How Soil Surveys Are Made..................................................................................5 Soil Map..................................................................................................................8 Soil Map (Kite Realty Group Renton)...................................................................9 Legend................................................................................................................10 Map Unit Legend (Kite Realty Group Renton)....................................................11 Map Unit Descriptions (Kite Realty Group Renton)............................................11 King County Area, Washington.......................................................................13 AgC—Alderwood gravelly sandy loam, 8 to 15 percent slopes...................13 References............................................................................................................15 4 How Soil Surveys Are Made Soil surveys are made to provide information about the soils and miscellaneous areas in a specific area. They include a description of the soils and miscellaneous areas and their location on the landscape and tables that show soil properties and limitations affecting various uses. Soil scientists observed the steepness, length, and shape of the slopes; the general pattern of drainage; the kinds of crops and native plants; and the kinds of bedrock. They observed and described many soil profiles. A soil profile is the sequence of natural layers, or horizons, in a soil. The profile extends from the surface down into the unconsolidated material in which the soil formed or from the surface down to bedrock. The unconsolidated material is devoid of roots and other living organisms and has not been changed by other biological activity. Currently, soils are mapped according to the boundaries of major land resource areas (MLRAs). MLRAs are geographically associated land resource units that share common characteristics related to physiography, geology, climate, water resources, soils, biological resources, and land uses (USDA, 2006). Soil survey areas typically consist of parts of one or more MLRA. The soils and miscellaneous areas in a survey area occur in an orderly pattern that is related to the geology, landforms, relief, climate, and natural vegetation of the area. Each kind of soil and miscellaneous area is associated with a particular kind of landform or with a segment of the landform. By observing the soils and miscellaneous areas in the survey area and relating their position to specific segments of the landform, a soil scientist develops a concept, or model, of how they were formed. Thus, during mapping, this model enables the soil scientist to predict with a considerable degree of accuracy the kind of soil or miscellaneous area at a specific location on the landscape. Commonly, individual soils on the landscape merge into one another as their characteristics gradually change. To construct an accurate soil map, however, soil scientists must determine the boundaries between the soils. They can observe only a limited number of soil profiles. Nevertheless, these observations, supplemented by an understanding of the soil-vegetation-landscape relationship, are sufficient to verify predictions of the kinds of soil in an area and to determine the boundaries. Soil scientists recorded the characteristics of the soil profiles that they studied. They noted soil color, texture, size and shape of soil aggregates, kind and amount of rock fragments, distribution of plant roots, reaction, and other features that enable them to identify soils. After describing the soils in the survey area and determining their properties, the soil scientists assigned the soils to taxonomic classes (units). Taxonomic classes are concepts. Each taxonomic class has a set of soil characteristics with precisely defined limits. The classes are used as a basis for comparison to classify soils systematically. Soil taxonomy, the system of taxonomic classification used in the United States, is based mainly on the kind and character of soil properties and the arrangement of horizons within the profile. After the soil 5 scientists classified and named the soils in the survey area, they compared the individual soils with similar soils in the same taxonomic class in other areas so that they could confirm data and assemble additional data based on experience and research. The objective of soil mapping is not to delineate pure map unit components; the objective is to separate the landscape into landforms or landform segments that have similar use and management requirements. Each map unit is defined by a unique combination of soil components and/or miscellaneous areas in predictable proportions. Some components may be highly contrasting to the other components of the map unit. The presence of minor components in a map unit in no way diminishes the usefulness or accuracy of the data. The delineation of such landforms and landform segments on the map provides sufficient information for the development of resource plans. If intensive use of small areas is planned, onsite investigation is needed to define and locate the soils and miscellaneous areas. Soil scientists make many field observations in the process of producing a soil map. The frequency of observation is dependent upon several factors, including scale of mapping, intensity of mapping, design of map units, complexity of the landscape, and experience of the soil scientist. Observations are made to test and refine the soil-landscape model and predictions and to verify the classification of the soils at specific locations. Once the soil-landscape model is refined, a significantly smaller number of measurements of individual soil properties are made and recorded. These measurements may include field measurements, such as those for color, depth to bedrock, and texture, and laboratory measurements, such as those for content of sand, silt, clay, salt, and other components. Properties of each soil typically vary from one point to another across the landscape. Observations for map unit components are aggregated to develop ranges of characteristics for the components. The aggregated values are presented. Direct measurements do not exist for every property presented for every map unit component. Values for some properties are estimated from combinations of other properties. While a soil survey is in progress, samples of some of the soils in the area generally are collected for laboratory analyses and for engineering tests. Soil scientists interpret the data from these analyses and tests as well as the field-observed characteristics and the soil properties to determine the expected behavior of the soils under different uses. Interpretations for all of the soils are field tested through observation of the soils in different uses and under different levels of management. Some interpretations are modified to fit local conditions, and some new interpretations are developed to meet local needs. Data are assembled from other sources, such as research information, production records, and field experience of specialists. For example, data on crop yields under defined levels of management are assembled from farm records and from field or plot experiments on the same kinds of soil. Predictions about soil behavior are based not only on soil properties but also on such variables as climate and biological activity. Soil conditions are predictable over long periods of time, but they are not predictable from year to year. For example, soil scientists can predict with a fairly high degree of accuracy that a given soil will have a high water table within certain depths in most years, but they cannot predict that a high water table will always be at a specific level in the soil on a specific date. After soil scientists located and identified the significant natural bodies of soil in the survey area, they drew the boundaries of these bodies on aerial photographs and Custom Soil Resource Report 6 identified each as a specific map unit. Aerial photographs show trees, buildings, fields, roads, and rivers, all of which help in locating boundaries accurately. Custom Soil Resource Report 7 Soil Map The soil map section includes the soil map for the defined area of interest, a list of soil map units on the map and extent of each map unit, and cartographic symbols displayed on the map. Also presented are various metadata about data used to produce the map, and a description of each soil map unit. 8 9 Custom Soil Resource Report Soil Map (Kite Realty Group Renton) 52 5 4 6 9 0 52 5 4 7 0 0 52 5 4 7 1 0 52 5 4 7 2 0 52 5 4 7 3 0 52 5 4 7 4 0 52 5 4 7 5 0 52 5 4 6 9 0 52 5 4 7 0 0 52 5 4 7 1 0 52 5 4 7 2 0 52 5 4 7 3 0 52 5 4 7 4 0 52 5 4 7 5 0 560450 560460 560470 560480 560490 560500 560510 560520 560530 560540 560550 560560 560450 560460 560470 560480 560490 560500 560510 560520 560530 560540 560550 560560 47° 26' 36'' N 12 2 ° 1 1 ' 5 3 ' ' W 47° 26' 36'' N 12 2 ° 1 1 ' 4 8 ' ' W 47° 26' 34'' N 12 2 ° 1 1 ' 5 3 ' ' W 47° 26' 34'' N 12 2 ° 1 1 ' 4 8 ' ' W N Map projection: Web Mercator Corner coordinates: WGS84 Edge tics: UTM Zone 10N WGS84 0 25 50 100 150 Feet 0 5 10 20 30 Meters Map Scale: 1:531 if printed on A landscape (11" x 8.5") 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 10 Map Unit Legend (Kite Realty Group Renton) Map Unit Symbol Map Unit Name Acres in AOI Percent of AOI AgC Alderwood gravelly sandy loam, 8 to 15 percent slopes 1.1 100.0% Totals for Area of Interest 1.1 100.0% Map Unit Descriptions (Kite Realty Group Renton) 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 Custom Soil Resource Report 11 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. 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 12 King County Area, Washington AgC—Alderwood gravelly sandy loam, 8 to 15 percent slopes Map Unit Setting National map unit symbol: 2t626 Elevation: 50 to 800 feet Mean annual precipitation: 20 to 60 inches Mean annual air temperature: 46 to 52 degrees F Frost-free period: 160 to 240 days Farmland classification: Prime farmland if irrigated Map Unit Composition Alderwood and similar soils:85 percent Minor components:15 percent Estimates are based on observations, descriptions, and transects of the mapunit. Description of Alderwood Setting Landform:Hills, ridges Landform position (two-dimensional):Shoulder Landform position (three-dimensional):Nose slope, talf Down-slope shape:Convex, linear Across-slope shape:Convex Parent material:Glacial drift and/or glacial outwash over dense glaciomarine deposits Typical profile A - 0 to 7 inches: gravelly sandy loam Bw1 - 7 to 21 inches: very gravelly sandy loam Bw2 - 21 to 30 inches: very gravelly sandy loam Bg - 30 to 35 inches: very gravelly sandy loam 2Cd1 - 35 to 43 inches: very gravelly sandy loam 2Cd2 - 43 to 59 inches: very gravelly sandy loam Properties and qualities Slope:8 to 15 percent Depth to restrictive feature:20 to 39 inches to densic material Drainage class:Moderately well drained Capacity of the most limiting layer to transmit water (Ksat):Very low to moderately low (0.00 to 0.06 in/hr) Depth to water table:About 18 to 37 inches Frequency of flooding:None Frequency of ponding:None Available water supply, 0 to 60 inches: Very low (about 2.7 inches) Interpretive groups Land capability classification (irrigated): None specified Land capability classification (nonirrigated): 4s Hydrologic Soil Group: B Ecological site: F002XA004WA - Puget Lowlands Forest Forage suitability group: Limited Depth Soils (G002XN302WA), Limited Depth Soils (G002XS301WA), Limited Depth Soils (G002XF303WA) Custom Soil Resource Report 13 Other vegetative classification: Limited Depth Soils (G002XN302WA), Limited Depth Soils (G002XS301WA), Limited Depth Soils (G002XF303WA) Hydric soil rating: No Minor Components Indianola Percent of map unit:5 percent Landform:Terraces, kames, eskers Landform position (three-dimensional):Tread Down-slope shape:Linear Across-slope shape:Linear Hydric soil rating: No Everett Percent of map unit:5 percent Landform:Kames, moraines, eskers Landform position (two-dimensional):Shoulder, footslope Landform position (three-dimensional):Base slope, crest Down-slope shape:Convex Across-slope shape:Convex Hydric soil rating: No Shalcar Percent of map unit:3 percent Landform:Depressions Landform position (three-dimensional):Dip Down-slope shape:Concave Across-slope shape:Concave Hydric soil rating: Yes Norma Percent of map unit:2 percent Landform:Drainageways, depressions Landform position (three-dimensional):Dip Down-slope shape:Linear, concave Across-slope shape:Concave Hydric soil rating: Yes Custom Soil Resource Report 14 References American Association of State Highway and Transportation Officials (AASHTO). 2004. Standard specifications for transportation materials and methods of sampling and testing. 24th edition. American Society for Testing and Materials (ASTM). 2005. Standard classification of soils for engineering purposes. ASTM Standard D2487-00. Cowardin, L.M., V. Carter, F.C. Golet, and E.T. LaRoe. 1979. Classification of wetlands and deep-water habitats of the United States. U.S. Fish and Wildlife Service FWS/OBS-79/31. Federal Register. July 13, 1994. Changes in hydric soils of the United States. Federal Register. September 18, 2002. Hydric soils of the United States. Hurt, G.W., and L.M. Vasilas, editors. Version 6.0, 2006. Field indicators of hydric soils in the United States. National Research Council. 1995. Wetlands: Characteristics and boundaries. Soil Survey Division Staff. 1993. Soil survey manual. Soil Conservation Service. U.S. Department of Agriculture Handbook 18. http://www.nrcs.usda.gov/wps/portal/ nrcs/detail/national/soils/?cid=nrcs142p2_054262 Soil Survey Staff. 1999. Soil taxonomy: A basic system of soil classification for making and interpreting soil surveys. 2nd edition. Natural Resources Conservation Service, U.S. Department of Agriculture Handbook 436. http:// www.nrcs.usda.gov/wps/portal/nrcs/detail/national/soils/?cid=nrcs142p2_053577 Soil Survey Staff. 2010. Keys to soil taxonomy. 11th edition. U.S. Department of Agriculture, Natural Resources Conservation Service. http:// www.nrcs.usda.gov/wps/portal/nrcs/detail/national/soils/?cid=nrcs142p2_053580 Tiner, R.W., Jr. 1985. Wetlands of Delaware. U.S. Fish and Wildlife Service and Delaware Department of Natural Resources and Environmental Control, Wetlands Section. United States Army Corps of Engineers, Environmental Laboratory. 1987. Corps of Engineers wetlands delineation manual. Waterways Experiment Station Technical Report Y-87-1. United States Department of Agriculture, Natural Resources Conservation Service. National forestry manual. http://www.nrcs.usda.gov/wps/portal/nrcs/detail/soils/ home/?cid=nrcs142p2_053374 United States Department of Agriculture, Natural Resources Conservation Service. National range and pasture handbook. http://www.nrcs.usda.gov/wps/portal/nrcs/ detail/national/landuse/rangepasture/?cid=stelprdb1043084 15 United States Department of Agriculture, Natural Resources Conservation Service. National soil survey handbook, title 430-VI. http://www.nrcs.usda.gov/wps/portal/ nrcs/detail/soils/scientists/?cid=nrcs142p2_054242 United States Department of Agriculture, Natural Resources Conservation Service. 2006. Land resource regions and major land resource areas of the United States, the Caribbean, and the Pacific Basin. U.S. Department of Agriculture Handbook 296. http://www.nrcs.usda.gov/wps/portal/nrcs/detail/national/soils/? cid=nrcs142p2_053624 United States Department of Agriculture, Soil Conservation Service. 1961. Land capability classification. U.S. Department of Agriculture Handbook 210. http:// www.nrcs.usda.gov/Internet/FSE_DOCUMENTS/nrcs142p2_052290.pdf Custom Soil Resource Report 16 17803 & 17805 108th Ave SE – Kite Realty Group Kimley-Horn and Associates, Inc. Renton, WA Preliminary Stormwater Report January 21, 2025 Page 19 3. SWPPP (TO BE COMPLETED BEFORE FINAL APPLICATION)