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HomeMy WebLinkAboutRoberts_SP_TIR TECHNICAL INFORMATION REPORT CITY OF RENTON For Roberts Short Plat Parcel# 14634000052 154th Avenue SE Renton, WA 98059 October 22, 2025 Revised March 2, 2026 Prepared For: Scott Roberts 13801 156th AVE SE Renton, WA 98059 Civil Engineering & Development Services 1700 NW Gilman BLVD, Suite 200; Issaquah, WA 98027 (425) 821-5038 Email: Info@G2CIVIL.COM Roberts Short Plat Technical Information Report July 18, 2025 Page i CONTENTS SECTION I: PROJECT OVERVIEW .................................................................................................... 5 SECTION II: CORE AND SPECIAL REQUIREMENTS SUMMARY ...................................................... 10 SECTION III: OFFSITE ANALYSIS ................................................................................................... 12 SECTION IV: FLOW CONTROL AND WATER QUALITY FACILITY ANALYSIS AND DESIGN ............... 16 SECTION V: CONVEYANCE SYSTEM ANALYSIS AND DESIGN ........................................................ 19 SECTION VI: SPECIAL REPORTS AND STUDIES .............................................................................. 20 SECTION VII: OTHER PERMITS ..................................................................................................... 20 SECTION VIII: CSWPP ANALYSIS AND DESIGN ............................................................................. 20 SECTION IX: BOND QUANTITIES, FACILITY SUMMARIES, AND DECLARATION OF COVENANT ..... 21 SECTION X: OPERATIONS AND MAINTENANCE MANUAL ............................................................ 21 FIGURES Figure 1 – TIR Worksheet Figure 2 – Vicinity Map Figure 3 – Soils Map Figure 4 – Existing Conditions Map Figure 5 – Developed Conditions Map Figure 6 – Flow Chart for Drainage Review Figure 7 – Downstream Mapping APPENDICIES Appendix A – Flow Control Related WWHM Analysis Appendix B – Geotechnical Report Appendix C – Operations & Maintenance Manual Appendix D – Arborist Report Appendix E – Water Quality Related WWHM Analysis CITY OF RENTON SURFACE WATER DESIGN MANUAL 2022 City of Renton Surface Water Design Manual 6/22/2022 8-A-1 REFERENCE 8-A TECHNICAL INFORMATION REPORT (TIR) WORKSHEET Part 1 PROJECT OWNER AND PROJECT ENGINEER Part 2 PROJECT LOCATION AND DESCRIPTION Project Owner _____________________________ Phone ___________________________________ Address __________________________________ _________________________________________ Project Engineer ___________________________ Company _________________________________ Phone ___________________________________ Project Name __________________________ CED Permit # ________________________ Location Township ________________ Range __________________ Section _________________ Site Address __________________________ _____________________________________ Part 3 TYPE OF PERMIT APPLICATION Part 4 OTHER REVIEWS AND PERMITS  Land Use (e.g., Subdivision / Short Subd.)  Building (e.g., M/F / Commercial / SFR)  Grading  Right-of-Way Use  Other _______________________  DFW HPA  COE 404  DOE Dam Safety  FEMA Floodplain  COE Wetlands  Other ________  Shoreline Management  Structural Rockery/Vault/_____  ESA Section 7 Part 5 PLAN AND REPORT INFORMATION Technical Information Report Site Improvement Plan (Engr. Plans) Type of Drainage Review (check one): Date (include revision dates): Date of Final:  Full  Targeted  Simplified  Large Project  Directed __________________ __________________ __________________ Plan Type (check one): Date (include revision dates): Date of Final:  Full  Modified  Simplified __________________ __________________ __________________ REFERENCE 8: PLAN REVIEW FORMS AND WORKSHEET TECHNICAL INFORMATION REPORT (TIR) WORKSHEET 6/22/2022 2022 City of Renton Surface Water Design Manual 8-A-2 Part 6 SWDM ADJUSTMENT APPROVALS Type (circle one): Standard / Blanket Description: (include conditions in TIR Section 2) ____________________________________________________________________________________ ____________________________________________________________________________________ ____________________________________________________________________________________ Approved Adjustment No. ______________________ Date of Approval: _______________________ Part 7 MONITORING REQUIREMENTS Monitoring Required: Yes / No Start Date: _______________________ Completion Date: _______________________ Describe: _________________________________ _________________________________________ _________________________________________ Re: SWDM Adjustment No. ________________ Part 8 SITE COMMUNITY AND DRAINAGE BASIN Community Plan: ____________________________________________________________________ Special District Overlays: ______________________________________________________________ Drainage Basin: _____________________________________________________________________ Stormwater Requirements: _____________________________________________________________ Part 9 ONSITE AND ADJACENT SENSITIVE AREAS  River/Stream ________________________  Lake ______________________________  Wetlands ____________________________  Closed Depression ____________________  Floodplain ___________________________  Other _______________________________ _______________________________  Steep Slope __________________________  Erosion Hazard _______________________  Landslide Hazard ______________________  Coal Mine Hazard ______________________  Seismic Hazard _______________________  Habitat Protection ______________________  _____________________________________ REFERENCE 8-A: TECHNICAL INFORMATION REPORT (TIR) WORKSHEET TECHNICAL INFORMATION REPORT (TIR) WORKSHEET 2022 City of Renton Surface Water Design Manual 6/22/2022 Ref 8-A-3 Part 10 SOILS Soil Type ______________________ ______________________ ______________________ ______________________ Slopes ________________________ ________________________ ________________________ ________________________ Erosion Potential _________________________ _________________________ _________________________ _________________________  High Groundwater Table (within 5 feet)  Other ________________________________  Sole Source Aquifer  Seeps/Springs  Additional Sheets Attached Part 11 DRAINAGE DESIGN LIMITATIONS REFERENCE  Core 2 – Offsite Analysis_________________  Sensitive/Critical Areas__________________  SEPA________________________________  LID Infeasibility________________________  Other________________________________  _____________________________________ LIMITATION / SITE CONSTRAINT _______________________________________ _______________________________________ _______________________________________ _______________________________________ _______________________________________ _______________________________________  Additional Sheets Attached Part 12 TIR SUMMARY SHEET (provide one TIR Summary Sheet per Threshold Discharge Area) Threshold Discharge Area: (name or description) Core Requirements (all 9 apply): Discharge at Natural Location Number of Natural Discharge Locations: Offsite Analysis Level: 1 / 2 / 3 dated:__________________ Flow Control (include facility summary sheet) Standard: _______________________________ or Exemption Number: ____________ Conveyance System Spill containment located at: _____________________________ Erosion and Sediment Control / Construction Stormwater Pollution Prevention CSWPP/CESCL/ESC Site Supervisor: _____________________ Contact Phone: _________________________ After Hours Phone: _________________________ Maintenance and Operation Responsibility (circle one): Private / Public If Private, Maintenance Log Required: Yes / No Financial Guarantees and Liability Provided: Yes / No SECTION I: PROJECT OVERVIEW Existing Conditions: The project site is located between SE 3rd Street and SE 4th Street on 154th Avenue SE and is currently not addressed, King County Parcel # 146340-0052. The property is rectangular in shape and is located on the east side of 154th Avenue SE (See Figure 2 - Vicinity Map below). The property is bordered along the north, south, and east by single family residences. The project parcel area is approximately 1.26 acres and is presently undeveloped except for a stable and fenced horse-riding area. The site slopes from east to west at an average slope of 5% with variations ranging from flat to 30%. Vegetation on the site consists of mature trees and brush. Developed Conditions: Project site improvements consist of onsite and offsite infrastructure improvements to support the future construction of 4 single family residential building lots and new shared access road. Frontage improvements will include the installation of an 8’ wide planter strip, a 5’ wide sidewalk with curb and gutter, and half street paving along 154th Avenue SE. Tree retention in accordance with City of Renton requirements will result in portions of the finished project site remaining in a forested condition, while the remainder will be developed with typical residential landscaping. Stormwater management will utilize the infiltrative properties of the underlying soils to meet flow control requirements. Figure 2 – Vicnity Map Soils: The USDA Web Soils Survey map indicates that the site is underlain entirely by AgC (Alderwood) soils. A site-specific geotechnical engineering report has been prepared by the Riley Group, which is included in Appendix B of this report. The report identifies several variations in the soils that include Ground Moraine Deposits and nearby Vashon Recessional Deposits (Qgt and Qpa, respectively.) The moraine deposits are similar to lodgment till, but looser and more fractured, making the upper stratus appropriate for infiltration. Figure 3 – Soils Map Figure 4 – Existing Conditions Map Figure 5 – Developed Conditions Map Figure 6 – Flow Chart for Drainage Review SECTION II: CORE AND SPECIAL REQUIREMENTS SUMMARY Per Figure 1.1.2.A from the 2022 City of Renton Surface Water Design Manual the project is subject to a Full Drainage Review which includes addressing Core Requirements 1 through 9 and Special Requirements 1 through 6: 1. Core Req. #1 – Discharge at natural location A field review of the site-specific topography indicates that the project area currently sheet flows from east to west to the right of way, thence to the south. Runoff generated within the developed project will follow this pattern, discharging to the natural location situated downstream to the south of the project site. 2. Core Req. #2 – Offsite Analysis An off-site analysis has been performed as a Level 1 analysis, revealing no downstream constraints in the stormwater conveyance system, refer to Section III for detailed information. 3. Core Req. #3 – Flow Control The project site is mapped as a Level 2 or Durations flow control area (consistent with most of King County). Level 2 Flow control limits the developed site runoff rates and durations to those that would have been experienced in the historical, undeveloped condition of the site (forested). Flow control will be achieved by implementing various infiltration facilities including an underground chamber system along the frontage and individual infiltration trenches for the future residences. Please see Section IV for specific design criteria and facility sizing. 4. Core Req. #4 – Conveyance System Runoff from the proposed 20’ private access road will be collected within a vertical curb along the south side of the road where it is collected and conveyed to water quality and infiltration facilities. The short conveyance system will be sized to adequately convey the required runoff rates as determined for given design storms. Please see Section V for specific calculations of the required conveyance capacity of the system. 5. Core Req. #5 – Construction Stormwater Pollution Prevention An erosion and sediment control plan is not relevant to the current preliminary short plat design, but will be provided with the construction design work to minimize soil erosion and control sedimentation during the proposed site construction. 6. Core Req. #6 – Maintenance and Operations The on-site stormwater system will be maintained by the homeowners. The off-site conveyance systems will be maintained by the City of Renton. Refer to Appendix C. 7. Core Req. #7 – Financial Guarantees & Liability Financial Guarantee & Liability commitments between the property developer and the City of Renton will be established at the time of permit issuance. 8. Core Req. #8 – Water Quality Facilities The project will result in approximately 7,035 square feet of new pollution generating impervious surfaces, which is greater than the exemption allowance of 5,000 SF, therefore water quality treatment is required. The project is not commercial, industrial, or multifamily related and will not create a road with over 7500 daily trips. In accordance with the 2022 City of Renton Surface Water Design Manual, Basic Water quality treatment is required. Water Quality treatment for the runoff generated by the private access drive pollution generating impervious surfaces will be provided by a Contech Stormwater Management Cartridge Catch basin. Runoff generated by the PGIS related to the required frontage improvements will be routed into a raingarden between the curb and sidewalk, in the 8’ wide landscaping strip for water quality treatment, refer to Section IV for additional discussion and sizing criteria. 9. Core Req. #9 – On-Site BMPs The project will utilize the LID analysis to satisfy this requirement. The proposed flow control facilities are designed to provide nearly full infiltration, making additional BMP’s related to the short plat development unnecessary. However, the frontage improvements will utilize a raingarden to provide water quality and flow control for the frontage improvements. A passing LID standard is represented in the WWHM output report in Appendix C of this report. The future residences will be required to provide lot specific BMP’s, which have been identified as infiltration trenches. Refer to Section IV for more detail. 10. Special Req. #1 – Other Adopted Area-Specific Requirements The 2022 City of Renton SWDM was reviewed and there are no additional requirements. 11. Special Req. #2 – Flood Hazard Area Delineation Per City of Renton mapping the site does not lie within a floodplain, zero-rise flood fringe, zero-rise floodway, or FEMA floodway. 12. Special Req. #3 – Flood Protection Facilities No flood protection facilities are associated with this project. 13. Special Req. #4 – Source Controls Source Controls of pollution are not warranted for this project as it is not high density or commercial. 14. Special Req. #5 – Oil Control This project is not considered high-use therefore oil control is not applicable to this project. 15. Special Req. #6 – Aquifer Protection Area Per City of Renton GIS mapping, the project is outside of the wellhead protection area zones. SECTION III: OFFSITE ANALYSIS A field review of the downstream conditions was performed on March 14, 2025. The weather was overcast and damp; the temperature was approximately 48 degrees. A visual reconnaissance was performed utilizing information obtained from the City of Renton GIS Mapping. Please refer to storm drainage mapping exhibits that follow for a depiction of the downstream drainage conditions. Upstream: The undeveloped portion of the existing property to the north of site sheet flows from northeast to southwest across the site and into the Toledo Avenue SE right of way. Runoff generated by this area is negligible and will not require additional attention. Downstream: The site runoff sheet flows to the existing Toledo / 154th Ave SE right of way where it enters and existing type 1 storm catch basin located in a local low area outside of the paved street (see photo below, left). Runoff is conveyed south via a 12” storm pipe for 116 feet and outlets to an existing 12-18” deep ditch. The runoff flows south within the ditch for approximately 235 feet before entering an 18” polyethylene pipe with debris barrier (below right). This inlet conveys runoff south through a newer development via the 18” pipe for approximately 365 feet, bypassing the onsite flow control facility and discharging to an existing grass lined ditch (next page, left). The water flows south within the ditch for about 94 feet before the water inlets into an existing culvert continuing south for 40 feet before discharging to an existing ditch. The runoff continues through a series of culverts and ditches (right) along the east side of 154th Ave SE for another 460 feet to SE 142nd Street. The runoff disappears from the ditch at this point (lower right), which coincides with the required ¼ mile point of the downstream analysis where field reconnaissance was terminated. Figure 7 – Downstream Mapping (City of Renton GIS) Downstream Concerns & Effects of Proposed Project: Drainage from the developed site will be infiltrated onsite with an overflow to the public conveyance system within 154th Ave SE. Significant impacts to the downstream system are not anticipated, as a result of the proposed development. The offsite analysis revealed no signs of deficiency and appears to be capable of conveying the runoff adequately. Resource Review: The following list from the 2021 KCSWDM Resource Review was reviewed: Basin Plan - There is no known Adopted Basin Plan for this area. SITE Floodplain Map – Per FEMA Flood Map Number 53033C0982G the site is located outside the floodplains. Other Offsite Analysis Reports - No additional other reports were reviewed in preparation of this report. Sensitive Areas - The City of Renton Critical Areas Map was reviewed and there are some regulated slopes onsite that are >15% but </= 25%, otherwise there are no sensitive areas on- site. Downstream Complaints – Per City of Renton mapping there are no known downstream drainage complaints. Road Drainage – Per City of Renton mapping there are no known downstream drainage complaints. King County Soils Survey - The existing on-site soils are AgC – gravelly sandy loam per the US Department of Agriculture. Wetlands Inventory - There are no wetlands on or adjacent to the site per City of Renton GIS. Migrating River Studies - There are no known migrating rivers in the resource review area. Section 303d list of polluted waters – Based on the Water Quality Assessment link on the DOE website, there are no known waters with contamination in the vicinity of the site. KC designated water quality problems - There are no known water quality problems within the area. Stormwater compliance plans - Not applicable to this project. SECTION IV: FLOW CONTROL & WATER QUALITY FACILITY ANALYSIS & DESIGN Flow Control: A formal flow control facility is required for the project site based on Section 1.2.3 of the City of Renton Surface Water Design Manual (SWDM). According to the Flow Control Application Map in the City of Renton GIS maps, the project site is located within the Flow Control Duration Standard (Forested Conditions). This flow control standard requires that the modeled stormwater runoff from the developed project match the runoff flow and durations of the same area prior to all development in the region. This is typically a forested condition. The project area is defined as the parcel area and any offsite areas that will be modified directly by the project. For this project, the offsite area consists of the frontage improvements. Tabulation of the site and project areas is provided below. The developed project will result in new impervious surfaces consisting of road pavement and sidewalk pavement onsite and along the project frontage. For model purposes, the full buildout of the houses has been included, adding driveways and roof areas. Onsite BMP’s often modify how each new impervious area is modeled. The target areas and any BMP modifications that are applied are provided in the table below. A hydrologic analysis of the site was completed in order to size the required on-site detention and water quality treatment necessary to account for the increase in the peak storm water release rate for the developed site. The site was analyzed for the pre-developed and developed conditions under the Western Washington Hydrology Model (WWHM) using the WWHM2012 Version 4.2.19 software developed for the Department of Ecology. The analysis utilizes 15 minute time steps and shows compliance with the durations flow control requirements. SF AC flat 10,301 0.236 moderate 39,311 0.902 steep 10,318 0.237 59,930 1.376 Parcel Project Area Frontage 1.260 0.116 1.376 54,893 5,037 59,930 Total Site Areas SF AC SF MIT % EFF IA LAWN 8,843 0.203 0.203 0.000 flat 2,412 0.055 onsite 6,346 moderate 6,431 0.148 offsite 2,497 steep - 0.000 731 0.017 Total 8,843 0.203 12,000 0.275 0.275 0.000 2,210 0.051 0.051 0.000 Total Impervious 23,784 0.546 Lawn 36,146 0.830 0.529 0.000 Target Surfaces Area Breakdown AC DRIVEWAY ROOF Sidewalk 0.146 0.057 ROAD Road Area by Slope The model was broken up into three sub-basins that connect to the point of compliance to reflect the future roofs infiltrating through separate trenches, the onsite road and driveways infiltrating through a Stormtech Chamber system along the frontage and the frontage improvements utilizing a raingarden between the curb and sidewalk. See WWHM Schematic below for model representation of this arrangement. Basin 1 - Roof Infiltration: The roof areas have been assumed to be approximately 3,000 square feet each. A single infiltration trench was modeled to represent the sum of all four target surfaces. The modeled trenches achieve 100% infiltration of the runoff from the roof areas. The modeled infiltration trench is represented on the stormwater plan, divided into even sections on each proposed lot. The exact design of the trenches will be provided as part of the future building permit for each residence. Any roof surface that is not fully infiltrated may result in modification of the full flow control system and should be avoided. Basin 2 - Onsite Target Surfaces: Except for the roof areas addressed above, the remainder of the project site is designed to infiltrate along the project frontage, utilizing a StormTech Chamber system to maximize the available volume for storage and the infiltrative properties of the soils below. The Geotechnical engineering report provides a design infiltration rate of 1.56 inches per hour, however there was also a test pit in the northwest corner of the parcel where groundwater seepage was observed. The access road construction will provide a barrier for the observed groundwater to prevent it from impacting the infiltration facilities, but the chamber system is being utilized to maintain 1’ of separation between the facilities and the observed groundwater depth as a precautionary measure. The chambers were modeled with a control structure to discharge runoff during larger storm events. This outlet was sized to comply with the Durations Flow Control requirements. Please see the full WWHM Report in Appendix C. Basin 3 - Frontage Improvements: Runoff generated by the increased road width and sidewalk in the right of way will flow into a landscape strip raingarden facility. The width of the raingarden and available length provide 100% infiltration of the modeled runoff. An overflow pipe will be provided to connect to the public stormwater conveyance system should flows exceeding the 100-year storm event be experienced. Water Quality: The proposed development will create approximately 8,843 square feet of new pollution generating surfaces, exceeding the exemption threshold of 5,000 square feet. Therefore, water quality treatment is required for this project. In accordance with the Renton Surface Water Manual, all areas are subject to basic water quality unless projects are high density or industrial, which this project is not. Water quality treatment will be designed, following the same sub-basin format used for the flow control design, addressing the future roofs, onsite access road and frontage improvements separately. The runoff generated by the future roof areas that will be infiltrated do not qualify as a pollution generating surface, so no water quality treatment is necessary prior to infiltration. Runoff from the internal access road will be collected and routed through a Contech Stormfilter unit. The unit is expected to be contained within a type 2 manhole, but the exact number of internal filters will be determined to accommodate the runoff flow rates calculated using WWHM for Basin 2 (0.0419 cfs) as an inline facility in the Roberts Water Quality WWHM analysis, please refer to the WWHM report in Appendix E. The frontage improvements consist of road widening and a portion of the access road that is in the Right of Way for pollution generating surfaces however, the sidewalk and raingarden areas are also tributary to the overall runoff and have been included in the analysis. The pollution generating surface calculated for this area is approximately 2,497 square feet. The runoff generated in this area will collect in the newly constructed gutter and be allowed to flow through the curb in a series of openings, where the runoff will percolate through the soils of a constructed raingarden prior to infiltration. The raingarden was designed within WWHM using the available area in the landscape strip and then verified as adequate using the design specifications provided in the KCSWDM. The modeled volume of runoff for water quality design for this area is 0.0088 acre-feet or 383 cubic feet. The raingarden provided is 8’ wide, 130’ long and 6” deep (below 6” freeboard) for a provided volume of 406 cubic feet (width modified to account for side slopes resulting in a 5’ bottom averaging to 6.25’ width). This volume exceeds that of the runoff volume required. The raingarden will contain an overflow outlet connecting to the onsite overflow outlet pipe, connecting both to the offsite stormwater conveyance system. SECTION V: CONVEYANCE SYSTEM ANALYSIS AND DESIGN The on-site drainage conveyance system for the proposed development is planned to be constructed of a series of catch basins interconnected with PVC pipe. The on-site drainage conveyance system will collect runoff at the low point of the onsite access road and convey the runoff through a 12” pipe to the infiltration facilities. This conveyance has been analyzed to verify flow capacity during the 100-year storm event. WWHM provides the flow rate as the inflow (line 702) for basin 2 of the water quality model. This model was used because it treated each sub- basin as an individual basin, providing the needed information for conveyance. 100 Year = 0.4525 The conveyance calculations were performed using Manning’s Equation to determine the maximum capacity of a 12” PVC pipe sloped at 1.0% is 5.53 cfs, which is greater than the unmitigated 100-year flow from the developed, unmitigated runoff flow rate of 0.45 cfs. Calculations performed courtesy of Free Online Manning Pipe Flow Calculator SECTION VI: SPECIAL REPORTS AND STUDIES • Geotechnical Engineering Study; The Riley Group, Inc.; April 16, 2025 SECTION VII: OTHER PERMITS The project is subject to administrative review at the City of Renton, for which this preliminary Technical Information Report is authored. Subsequently, a Civil Site Development permit and a Right-of-Way Use Permit for the short plat infrastructure will be acquired. Once constructed, a Final Short Plat must be recorded. Subsequently, individual Single-Family Residential Building Permits from the City of Renton will be required. Utility permits to construct the water system will be required from Water District 90. SECTION VII: CSWPP ANALYSIS AND DESIGN Several standard Best Management Practices (BMP’s) will be utilized by the contractor to minimize the amount of erosion and sedimentation that may be perpetuated by the construction of the site. The thirteen erosion and sedimentation control measures are outlined below: Clearing Limits- Prior to any site clearing, the areas to remain undisturbed during the project construction shall be physically marked on the project site. The clearing limits are delineated on the TESC Plan as the area to be disturbed. Tree Protection fencing is proposed for the retained trees. Cover Measures- Temporary and permanent cover measures should be provided when necessary to protect disturbed areas. Materials will be stockpiled on-site and will be covered with plastic sheeting per 2022 CORSWDM D.2.1.2.4 when necessary. Perimeter Protection- Silt fencing per 2022 CORSWDM D.2.1.3.1 shall be used downstream of all disturbed areas to filter sediment from sheet flow. Traffic Area Stabilization- The current entrances and parking areas shall be utilized for construction purposes. Sediment Retention- A sediment trap has been designed and located at the low point of the project site. In addition, a filter fence will be installed along the downgradient perimeter of the property. Catch basin filters will be installed in new and downstream catch basins. A note is provided on the TESC and SWPP Plan to maintain existing vegetation to the maximum extent possible. These safeguards are anticipated to provide sufficient control of sediment transport during construction. Surface Water Collection- Surface water will be collected in a series of interceptor ditches and routed to a sediment trap before discharge to the off-site system. Dewatering Control- Although dewatering is not anticipated, a note will be provided on TESC/SWPP to alert the contractor that perched groundwater may be encountered (based on the site geotechnical report). Dust Control- Dust control will be implemented per 2022 CORSWDM Table D.2.1.8.A when necessary. Flow Control- A sediment trap has been designed to control sediment onsite during construction. When completed the detention/water quality vault will be used for temporary and long-term flow control. A full cleaning of the stormwater vault will be required prior to completion of the civil construction permit. Control Pollutants- No pollutants will be stored onsite, but a spill kit shall be retained onsite in case of any fuel spills from construction equipment. Protect Existing and Proposed Flow Control BMPs- Tree #101, 107, 108, 118, 119, 120, 121, & 124 shall be retained and protected throughout the construction of the project. Maintain BMPs- TESC/SWPP Plan BMPs shall be maintained and repaired as needed throughout construction. All disturbed areas of the project site shall be vegetated or otherwise permanently stabilized once completed. Manage the Project- The TESC plan shall be retained onsite or within reasonable access to the site. Prior to commencing construction, a contract for a CESCL will be established. SECTION IX: BOND QUANTITIES, FACILITY SUMMARIES, AND DECLARATION OF COVENANT Bond Quantity Worksheet – Appendix F Declaration of Covenant for Privately Maintained Flow Control and Water Quality Features – Appendix G Flow Control and Water Quality Facility Summary Sheet and Sketch – Appendix H SECTION X: OPERATIONS AND MAINTENANCE MANUAL A draft Operations & Maintenance Manual is provided in Appendix B. Roberts Short Plat Technical Information Report APPENDIX A FLOW CONTROL RELATED WWHM HYDROLOGIC ANALYSIS WWHM2012 PROJECT REPORT Roberts SP Infiltration cells 2/25/2026 4:13:35 PM Page 2 General Model Information WWHM2012 Project Name:Roberts SP Infiltration cells Site Name:Roberts Short Plat Site Address:154th Ave SE City:Renton Report Date:2/25/2026 Gage:Seatac Data Start:1948/10/01 Data End:2009/09/30 Timestep:15 Minute Precip Scale:1.000 Version Date:2025/05/13 Version:4.3.2 POC Thresholds Low Flow Threshold for POC1:50 Percent of the 2 Year High Flow Threshold for POC1:50 Year Roberts SP Infiltration cells 2/25/2026 4:13:35 PM Page 3 Landuse Basin Data Predeveloped Land Use Basin 1 Bypass:No GroundWater:No Pervious Land Use acre C, Forest, Flat 0.236 C, Forest, Mod 0.902 C, Forest, Steep 0.237 Pervious Total 1.375 Impervious Land Use acre Impervious Total 0 Basin Total 1.375 Element Flow Componants: Surface Interflow Groundwater Componant Flows To: POC 1 POC 1 Roberts SP Infiltration cells 2/25/2026 4:13:35 PM Page 4 Mitigated Land Use Basin 1 Bypass:No GroundWater:No Pervious Land Use acre Pervious Total 0 Impervious Land Use acre ROOF TOPS FLAT 0.275 Impervious Total 0.275 Basin Total 0.275 Element Flow Componants: Surface Interflow Groundwater Componant Flows To: Gravel Trench Bed 1 Gravel Trench Bed 1 Roberts SP Infiltration cells 2/25/2026 4:13:35 PM Page 5 Basin 2 Bypass:No GroundWater:No Pervious Land Use acre C, Lawn, Flat 0.83 Pervious Total 0.83 Impervious Land Use acre ROADS MOD 0.148 DRIVEWAYS FLAT 0.051 Impervious Total 0.199 Basin Total 1.029 Element Flow Componants: Surface Interflow Groundwater Componant Flows To: StormTech 2 StormTech 2 Roberts SP Infiltration cells 2/25/2026 4:13:35 PM Page 6 Basin 3 Bypass:No GroundWater:No Pervious Land Use acre Pervious Total 0 Impervious Land Use acre ROADS FLAT 0.055 SIDEWALKS FLAT 0.017 Impervious Total 0.072 Basin Total 0.072 Element Flow Componants: Surface Interflow Groundwater Componant Flows To: Gravel Trench Bed 2 Gravel Trench Bed 2 Roberts SP Infiltration cells 2/25/2026 4:13:35 PM Page 7 Routing Elements Predeveloped Routing Roberts SP Infiltration cells 2/25/2026 4:13:35 PM Page 8 Mitigated Routing Gravel Trench Bed 1 Bottom Length:240.00 ft. Bottom Width:5.60 ft. Trench bottom slope 1:0 To 1 Trench Left side slope 0:0 To 1 Trench right side slope 2:0 To 1 Material thickness of first layer:1 Pour Space of material for first layer:0.33 Material thickness of second layer:1 Pour Space of material for second layer:0.33 Material thickness of third layer:1 Pour Space of material for third layer:0.33 Infiltration On Infiltration rate:1.56 Infiltration safety factor:1 Wetted surface area On Total Volume Infiltrated (ac-ft.):43.147 Total Volume Through Riser (ac-ft.):0.002 Total Volume Through Facility (ac-ft.):43.149 Percent Infiltrated:100 Total Precip Applied to Facility:0 Total Evap From Facility:0 Discharge Structure Riser Height:3.5 ft. Riser Diameter:6 in. Orifice 1 Diameter:0.500 in.Elevation:3 ft. Element Outlets: Outlet 1 Outlet 2 Outlet Flows To: Gravel Trench Bed Hydraulic Table Stage(feet)Area(ac.)Volume(ac-ft.)Discharge(cfs)Infilt(cfs) 0.0000 0.030 0.000 0.000 0.000 0.0444 0.030 0.000 0.000 0.048 0.0889 0.030 0.000 0.000 0.048 0.1333 0.030 0.001 0.000 0.048 0.1778 0.030 0.001 0.000 0.048 0.2222 0.030 0.002 0.000 0.048 0.2667 0.030 0.002 0.000 0.048 0.3111 0.030 0.003 0.000 0.048 0.3556 0.030 0.003 0.000 0.048 0.4000 0.030 0.004 0.000 0.048 0.4444 0.030 0.004 0.000 0.048 0.4889 0.030 0.005 0.000 0.048 0.5333 0.030 0.005 0.000 0.048 0.5778 0.030 0.005 0.000 0.048 0.6222 0.030 0.006 0.000 0.048 0.6667 0.030 0.006 0.000 0.048 0.7111 0.030 0.007 0.000 0.048 0.7556 0.030 0.007 0.000 0.048 0.8000 0.030 0.008 0.000 0.048 0.8444 0.030 0.008 0.000 0.048 0.8889 0.030 0.009 0.000 0.048 Roberts SP Infiltration cells 2/25/2026 4:13:35 PM Page 9 0.9333 0.030 0.009 0.000 0.048 0.9778 0.030 0.010 0.000 0.048 1.0222 0.030 0.010 0.000 0.048 1.0667 0.030 0.010 0.000 0.048 1.1111 0.030 0.011 0.000 0.048 1.1556 0.030 0.011 0.000 0.048 1.2000 0.030 0.012 0.000 0.048 1.2444 0.030 0.012 0.000 0.048 1.2889 0.030 0.013 0.000 0.048 1.3333 0.030 0.013 0.000 0.048 1.3778 0.030 0.014 0.000 0.048 1.4222 0.030 0.014 0.000 0.048 1.4667 0.030 0.014 0.000 0.048 1.5111 0.030 0.015 0.000 0.048 1.5556 0.030 0.015 0.000 0.048 1.6000 0.030 0.016 0.000 0.048 1.6444 0.030 0.016 0.000 0.048 1.6889 0.030 0.017 0.000 0.048 1.7333 0.030 0.017 0.000 0.048 1.7778 0.030 0.018 0.000 0.048 1.8222 0.030 0.018 0.000 0.048 1.8667 0.030 0.019 0.000 0.048 1.9111 0.030 0.019 0.000 0.048 1.9556 0.030 0.019 0.000 0.048 2.0000 0.030 0.020 0.000 0.048 2.0444 0.030 0.020 0.000 0.048 2.0889 0.030 0.021 0.000 0.048 2.1333 0.030 0.021 0.000 0.048 2.1778 0.030 0.022 0.000 0.048 2.2222 0.030 0.022 0.000 0.048 2.2667 0.030 0.023 0.000 0.048 2.3111 0.030 0.023 0.000 0.048 2.3556 0.030 0.024 0.000 0.048 2.4000 0.030 0.024 0.000 0.048 2.4444 0.030 0.024 0.000 0.048 2.4889 0.030 0.025 0.000 0.048 2.5333 0.030 0.025 0.000 0.048 2.5778 0.030 0.026 0.000 0.048 2.6222 0.030 0.026 0.000 0.048 2.6667 0.030 0.027 0.000 0.048 2.7111 0.030 0.027 0.000 0.048 2.7556 0.030 0.028 0.000 0.048 2.8000 0.030 0.028 0.000 0.048 2.8444 0.030 0.029 0.000 0.048 2.8889 0.030 0.029 0.000 0.048 2.9333 0.030 0.029 0.000 0.048 2.9778 0.030 0.030 0.000 0.048 3.0222 0.030 0.031 0.001 0.048 3.0667 0.030 0.033 0.001 0.048 3.1111 0.030 0.034 0.002 0.048 3.1556 0.030 0.035 0.002 0.048 3.2000 0.030 0.037 0.003 0.048 3.2444 0.030 0.038 0.003 0.048 3.2889 0.030 0.039 0.003 0.048 3.3333 0.030 0.041 0.003 0.048 3.3778 0.030 0.042 0.004 0.048 3.4222 0.030 0.044 0.004 0.048 3.4667 0.030 0.045 0.004 0.048 Roberts SP Infiltration cells 2/25/2026 4:13:35 PM Page 10 3.5111 0.030 0.046 0.011 0.048 3.5556 0.030 0.048 0.074 0.048 3.6000 0.030 0.049 0.165 0.048 3.6444 0.030 0.050 0.261 0.048 3.6889 0.030 0.052 0.337 0.048 3.7333 0.030 0.053 0.383 0.048 3.7778 0.030 0.055 0.421 0.048 3.8222 0.030 0.056 0.453 0.048 3.8667 0.030 0.057 0.483 0.048 3.9111 0.030 0.059 0.511 0.048 3.9556 0.030 0.060 0.538 0.048 4.0000 0.030 0.061 0.563 0.048 Roberts SP Infiltration cells 2/25/2026 4:13:35 PM Page 11 StormTech 2 Chamber Model:740 Dimensions Max Row Length:110 Number of Chambers:28 Number of Endcaps:4 Top Stone Depth:12 Bottom Stone Depth:6 Infiltration On Infiltration rate:1.56 Infiltration safety factor:1 Wetted surface area On Total Volume Infiltrated (ac-ft.):94.152 Total Volume Through Riser (ac-ft.):3.271 Total Volume Through Facility (ac-ft.):97.423 Percent Infiltrated:96.64 Total Precip Applied to Facility:0 Total Evap From Facility:0 Discharge Structure Riser Height:2.5 ft. Riser Diameter:6 in. Orifice 1 Diameter:1.500 in.Elevation:0.15 ft. Orifice 2 Diameter:0.750 in.Elevation:0.75 ft. Orifice 3 Diameter:0.750 in.Elevation:2 ft. Element Flow Outlets: Outlet 1 Outlet 2 Outlets Flow To: StormTech Hydraulic Table Stage(feet)Area(ac.)Volume(ac-ft.)Discharge(cfs)Infilt(cfs) 0.0000 0.021 0.000 0.000 0.000 0.0833 0.023 0.000 0.000 0.036 0.1667 0.023 0.001 0.007 0.036 0.2500 0.023 0.002 0.019 0.036 0.3333 0.023 0.002 0.026 0.036 0.4167 0.023 0.003 0.031 0.036 0.5000 0.023 0.004 0.036 0.036 0.5833 0.023 0.005 0.040 0.036 0.6667 0.023 0.007 0.043 0.036 0.7500 0.023 0.009 0.047 0.036 0.8333 0.023 0.010 0.054 0.036 0.9167 0.023 0.012 0.059 0.036 1.0000 0.023 0.013 0.063 0.036 1.0833 0.023 0.015 0.067 0.036 1.1667 0.023 0.016 0.071 0.036 1.2500 0.023 0.018 0.074 0.036 1.3333 0.023 0.019 0.078 0.036 1.4167 0.023 0.021 0.081 0.036 1.5000 0.023 0.022 0.084 0.036 1.5833 0.023 0.024 0.087 0.036 1.6667 0.023 0.025 0.089 0.036 1.7500 0.023 0.026 0.092 0.036 1.8333 0.023 0.028 0.095 0.036 1.9167 0.023 0.029 0.097 0.036 2.0000 0.023 0.031 0.100 0.036 Roberts SP Infiltration cells 2/25/2026 4:13:35 PM Page 12 2.0833 0.023 0.032 0.106 0.036 2.1667 0.023 0.033 0.111 0.036 2.2500 0.023 0.034 0.114 0.036 2.3333 0.023 0.036 0.118 0.036 2.4167 0.023 0.037 0.121 0.036 2.5000 0.023 0.038 0.124 0.036 2.5833 0.023 0.039 0.251 0.036 2.6667 0.023 0.040 0.428 0.036 2.7500 0.023 0.041 0.522 0.036 2.8333 0.023 0.042 0.590 0.036 2.9167 0.023 0.043 0.646 0.036 3.0000 0.023 0.043 0.698 0.036 3.0833 0.023 0.044 0.745 0.036 3.1667 0.023 0.045 0.789 0.036 3.2500 0.023 0.046 0.830 0.036 3.3333 0.023 0.046 0.869 0.036 3.4167 0.023 0.047 0.907 0.036 3.5000 0.023 0.048 0.943 0.036 3.5833 0.023 0.048 0.977 0.036 3.6667 0.023 0.049 1.010 0.038 3.7500 0.023 0.050 1.042 0.038 3.8333 0.023 0.051 1.073 0.038 3.9167 0.023 0.051 1.104 0.038 4.0000 0.023 0.052 1.133 0.038 Roberts SP Infiltration cells 2/25/2026 4:13:35 PM Page 13 Gravel Trench Bed 2 Bottom Length:147.40 ft. Bottom Width:8.80 ft. Trench bottom slope 1:0 To 1 Trench Left side slope 0:0 To 1 Trench right side slope 2:0 To 1 Material thickness of first layer:1.5 Pour Space of material for first layer:0.33 Material thickness of second layer:0 Pour Space of material for second layer:0 Material thickness of third layer:0 Pour Space of material for third layer:0 Infiltration On Infiltration rate:1.56 Infiltration safety factor:1 Wetted surface area On Total Volume Infiltrated (ac-ft.):11.175 Total Volume Through Riser (ac-ft.):0 Total Volume Through Facility (ac-ft.):11.175 Percent Infiltrated:100 Total Precip Applied to Facility:0 Total Evap From Facility:0 Discharge Structure Riser Height:0 ft. Riser Diameter:0 in. Element Outlets: Outlet 1 Outlet 2 Outlet Flows To: Gravel Trench Bed Hydraulic Table Stage(feet)Area(ac.)Volume(ac-ft.)Discharge(cfs)Infilt(cfs) 0.0000 0.029 0.000 0.000 0.000 0.0167 0.029 0.000 0.000 0.046 0.0333 0.029 0.000 0.000 0.046 0.0500 0.029 0.000 0.000 0.046 0.0667 0.029 0.000 0.000 0.046 0.0833 0.029 0.000 0.000 0.046 0.1000 0.029 0.001 0.000 0.046 0.1167 0.029 0.001 0.000 0.046 0.1333 0.029 0.001 0.000 0.046 0.1500 0.029 0.001 0.000 0.046 0.1667 0.029 0.001 0.000 0.046 0.1833 0.029 0.001 0.000 0.046 0.2000 0.029 0.002 0.000 0.046 0.2167 0.029 0.002 0.000 0.046 0.2333 0.029 0.002 0.000 0.046 0.2500 0.029 0.002 0.000 0.046 0.2667 0.029 0.002 0.000 0.046 0.2833 0.029 0.002 0.000 0.046 0.3000 0.029 0.002 0.000 0.046 0.3167 0.029 0.003 0.000 0.046 0.3333 0.029 0.003 0.000 0.046 0.3500 0.029 0.003 0.000 0.046 0.3667 0.029 0.003 0.000 0.046 0.3833 0.029 0.003 0.000 0.046 Roberts SP Infiltration cells 2/25/2026 4:13:35 PM Page 14 0.4000 0.029 0.003 0.000 0.046 0.4167 0.029 0.004 0.000 0.046 0.4333 0.029 0.004 0.000 0.046 0.4500 0.029 0.004 0.000 0.046 0.4667 0.029 0.004 0.000 0.046 0.4833 0.029 0.004 0.000 0.046 0.5000 0.029 0.004 0.000 0.046 0.5167 0.029 0.005 0.000 0.046 0.5333 0.029 0.005 0.000 0.046 0.5500 0.029 0.005 0.000 0.046 0.5667 0.029 0.005 0.000 0.046 0.5833 0.029 0.005 0.000 0.046 0.6000 0.029 0.005 0.000 0.046 0.6167 0.029 0.006 0.000 0.046 0.6333 0.029 0.006 0.000 0.046 0.6500 0.029 0.006 0.000 0.046 0.6667 0.029 0.006 0.000 0.046 0.6833 0.029 0.006 0.000 0.046 0.7000 0.029 0.006 0.000 0.046 0.7167 0.029 0.007 0.000 0.046 0.7333 0.029 0.007 0.000 0.046 0.7500 0.029 0.007 0.000 0.046 0.7667 0.029 0.007 0.000 0.046 0.7833 0.029 0.007 0.000 0.046 0.8000 0.029 0.007 0.000 0.046 0.8167 0.029 0.008 0.000 0.046 0.8333 0.029 0.008 0.000 0.046 0.8500 0.029 0.008 0.000 0.046 0.8667 0.029 0.008 0.000 0.046 0.8833 0.029 0.008 0.000 0.046 0.9000 0.029 0.008 0.000 0.046 0.9167 0.029 0.009 0.000 0.046 0.9333 0.029 0.009 0.000 0.046 0.9500 0.029 0.009 0.000 0.046 0.9667 0.029 0.009 0.000 0.046 0.9833 0.029 0.009 0.000 0.046 1.0000 0.029 0.009 0.000 0.046 1.0167 0.029 0.010 0.000 0.046 1.0333 0.029 0.010 0.000 0.046 1.0500 0.029 0.010 0.000 0.046 1.0667 0.029 0.010 0.000 0.046 1.0833 0.029 0.010 0.000 0.046 1.1000 0.029 0.010 0.000 0.046 1.1167 0.029 0.011 0.000 0.046 1.1333 0.029 0.011 0.000 0.046 1.1500 0.029 0.011 0.000 0.046 1.1667 0.029 0.011 0.000 0.046 1.1833 0.029 0.011 0.000 0.046 1.2000 0.029 0.011 0.000 0.046 1.2167 0.029 0.012 0.000 0.046 1.2333 0.029 0.012 0.000 0.046 1.2500 0.029 0.012 0.000 0.046 1.2667 0.029 0.012 0.000 0.046 1.2833 0.029 0.012 0.000 0.046 1.3000 0.029 0.012 0.000 0.046 1.3167 0.029 0.012 0.000 0.046 1.3333 0.029 0.013 0.000 0.046 1.3500 0.029 0.013 0.000 0.046 Roberts SP Infiltration cells 2/25/2026 4:13:35 PM Page 15 1.3667 0.029 0.013 0.000 0.046 1.3833 0.029 0.013 0.000 0.046 1.4000 0.029 0.013 0.000 0.046 1.4167 0.029 0.013 0.000 0.046 1.4333 0.029 0.014 0.000 0.046 1.4500 0.029 0.014 0.000 0.046 1.4667 0.029 0.014 0.000 0.046 1.4833 0.029 0.014 0.000 0.046 1.5000 0.029 0.014 0.000 0.046 Roberts SP Infiltration cells 2/25/2026 4:13:35 PM Page 16 Analysis Results POC 1 + Predeveloped x Mitigated Predeveloped Landuse Totals for POC #1 Total Pervious Area:1.375 Total Impervious Area:0 Mitigated Landuse Totals for POC #1 Total Pervious Area:0.83 Total Impervious Area:0.546 Flow Frequency Method:Log Pearson Type III 17B Flow Frequency Return Periods for Predeveloped. POC #1 Return Period Flow(cfs) 2 year 0.044178 5 year 0.071676 10 year 0.089235 25 year 0.11003 50 year 0.124387 100 year 0.137765 Flow Frequency Return Periods for Mitigated. POC #1 Return Period Flow(cfs) 2 year 0.036905 5 year 0.055272 10 year 0.067332 25 year 0.082263 50 year 0.093114 100 year 0.103716 Annual Peaks Annual Peaks for Predeveloped and Mitigated. POC #1 Year Predeveloped Mitigated 1949 0.050 0.047 1950 0.058 0.061 1951 0.095 0.050 1952 0.031 0.023 1953 0.025 0.016 1954 0.036 0.027 1955 0.061 0.039 1956 0.048 0.032 1957 0.040 0.041 1958 0.043 0.025 Roberts SP Infiltration cells 2/25/2026 4:14:04 PM Page 17 1959 0.037 0.019 1960 0.066 0.043 1961 0.036 0.036 1962 0.023 0.018 1963 0.032 0.036 1964 0.043 0.034 1965 0.030 0.038 1966 0.028 0.028 1967 0.066 0.049 1968 0.038 0.038 1969 0.037 0.036 1970 0.031 0.030 1971 0.034 0.037 1972 0.073 0.055 1973 0.033 0.021 1974 0.035 0.033 1975 0.051 0.042 1976 0.036 0.031 1977 0.005 0.023 1978 0.031 0.037 1979 0.018 0.029 1980 0.083 0.049 1981 0.027 0.037 1982 0.058 0.065 1983 0.047 0.037 1984 0.030 0.024 1985 0.017 0.033 1986 0.077 0.047 1987 0.067 0.051 1988 0.027 0.013 1989 0.017 0.018 1990 0.154 0.117 1991 0.084 0.079 1992 0.035 0.029 1993 0.034 0.014 1994 0.012 0.007 1995 0.047 0.028 1996 0.108 0.057 1997 0.087 0.057 1998 0.023 0.030 1999 0.089 0.062 2000 0.035 0.040 2001 0.006 0.021 2002 0.039 0.048 2003 0.056 0.037 2004 0.067 0.093 2005 0.047 0.040 2006 0.052 0.036 2007 0.116 0.079 2008 0.146 0.102 2009 0.068 0.052 Ranked Annual Peaks Ranked Annual Peaks for Predeveloped and Mitigated. POC #1 Rank Predeveloped Mitigated 1 0.1545 0.1168 2 0.1460 0.1021 3 0.1162 0.0932 Roberts SP Infiltration cells 2/25/2026 4:14:04 PM Page 18 4 0.1077 0.0794 5 0.0947 0.0786 6 0.0887 0.0649 7 0.0869 0.0623 8 0.0837 0.0607 9 0.0827 0.0570 10 0.0767 0.0565 11 0.0725 0.0554 12 0.0684 0.0519 13 0.0674 0.0508 14 0.0667 0.0502 15 0.0663 0.0490 16 0.0661 0.0489 17 0.0612 0.0482 18 0.0582 0.0474 19 0.0581 0.0473 20 0.0560 0.0434 21 0.0521 0.0416 22 0.0509 0.0412 23 0.0495 0.0400 24 0.0485 0.0397 25 0.0475 0.0386 26 0.0474 0.0378 27 0.0472 0.0375 28 0.0435 0.0370 29 0.0432 0.0370 30 0.0404 0.0370 31 0.0391 0.0368 32 0.0376 0.0367 33 0.0372 0.0363 34 0.0367 0.0359 35 0.0363 0.0357 36 0.0363 0.0355 37 0.0358 0.0339 38 0.0353 0.0333 39 0.0350 0.0330 40 0.0346 0.0324 41 0.0342 0.0308 42 0.0337 0.0301 43 0.0331 0.0296 44 0.0317 0.0295 45 0.0312 0.0290 46 0.0309 0.0283 47 0.0308 0.0277 48 0.0297 0.0270 49 0.0296 0.0254 50 0.0284 0.0241 51 0.0272 0.0227 52 0.0271 0.0225 53 0.0246 0.0209 54 0.0234 0.0207 55 0.0225 0.0194 56 0.0183 0.0181 57 0.0173 0.0175 58 0.0172 0.0161 59 0.0115 0.0141 60 0.0065 0.0132 61 0.0053 0.0074 Roberts SP Infiltration cells 2/25/2026 4:14:04 PM Page 19 Roberts SP Infiltration cells 2/25/2026 4:14:04 PM Page 20 Duration Flows The Facility PASSED Flow(cfs)Predev Mit Percentage Pass/Fail 0.0221 15543 2468 15 Pass 0.0231 14112 2342 16 Pass 0.0242 12878 2209 17 Pass 0.0252 11736 2094 17 Pass 0.0262 10652 1968 18 Pass 0.0273 9708 1872 19 Pass 0.0283 8908 1768 19 Pass 0.0293 8158 1693 20 Pass 0.0304 7467 1590 21 Pass 0.0314 6842 1512 22 Pass 0.0324 6305 1427 22 Pass 0.0335 5831 1334 22 Pass 0.0345 5401 1259 23 Pass 0.0355 5014 1195 23 Pass 0.0366 4650 1114 23 Pass 0.0376 4291 1018 23 Pass 0.0386 3961 927 23 Pass 0.0397 3690 866 23 Pass 0.0407 3474 789 22 Pass 0.0417 3230 712 22 Pass 0.0428 3003 647 21 Pass 0.0438 2791 599 21 Pass 0.0448 2603 532 20 Pass 0.0459 2425 461 19 Pass 0.0469 2227 408 18 Pass 0.0479 2069 364 17 Pass 0.0490 1926 344 17 Pass 0.0500 1767 326 18 Pass 0.0510 1644 305 18 Pass 0.0521 1531 294 19 Pass 0.0531 1396 286 20 Pass 0.0541 1272 276 21 Pass 0.0552 1178 262 22 Pass 0.0562 1098 254 23 Pass 0.0572 1039 243 23 Pass 0.0583 981 237 24 Pass 0.0593 929 229 24 Pass 0.0603 875 219 25 Pass 0.0614 821 208 25 Pass 0.0624 769 199 25 Pass 0.0634 724 190 26 Pass 0.0645 680 182 26 Pass 0.0655 638 170 26 Pass 0.0665 584 163 27 Pass 0.0676 541 160 29 Pass 0.0686 510 156 30 Pass 0.0696 475 150 31 Pass 0.0707 448 147 32 Pass 0.0717 399 139 34 Pass 0.0727 364 134 36 Pass 0.0738 335 126 37 Pass 0.0748 309 121 39 Pass 0.0758 282 115 40 Pass Roberts SP Infiltration cells 2/25/2026 4:14:04 PM Page 21 0.0769 254 108 42 Pass 0.0779 226 98 43 Pass 0.0789 202 89 44 Pass 0.0800 174 85 48 Pass 0.0810 160 81 50 Pass 0.0820 142 79 55 Pass 0.0831 127 75 59 Pass 0.0841 108 72 66 Pass 0.0851 98 68 69 Pass 0.0862 87 67 77 Pass 0.0872 76 63 82 Pass 0.0882 73 62 84 Pass 0.0893 67 57 85 Pass 0.0903 58 50 86 Pass 0.0913 48 44 91 Pass 0.0924 45 38 84 Pass 0.0934 39 33 84 Pass 0.0944 34 31 91 Pass 0.0955 30 27 90 Pass 0.0965 29 25 86 Pass 0.0975 24 20 83 Pass 0.0986 21 15 71 Pass 0.0996 19 12 63 Pass 0.1006 18 11 61 Pass 0.1017 16 8 50 Pass 0.1027 14 7 50 Pass 0.1037 12 6 50 Pass 0.1048 12 6 50 Pass 0.1058 7 6 85 Pass 0.1068 7 5 71 Pass 0.1079 6 5 83 Pass 0.1089 5 4 80 Pass 0.1099 5 4 80 Pass 0.1110 5 4 80 Pass 0.1120 5 3 60 Pass 0.1130 5 3 60 Pass 0.1141 4 3 75 Pass 0.1151 4 1 25 Pass 0.1161 4 1 25 Pass 0.1172 3 0 0 Pass 0.1182 3 0 0 Pass 0.1192 3 0 0 Pass 0.1203 3 0 0 Pass 0.1213 3 0 0 Pass 0.1223 3 0 0 Pass 0.1234 3 0 0 Pass 0.1244 3 0 0 Pass Roberts SP Infiltration cells 2/25/2026 4:14:04 PM Page 22 Water Quality Water Quality BMP Flow and Volume for POC #1 On-line facility volume:0 acre-feet On-line facility target flow:0 cfs. Adjusted for 15 min:0 cfs. Off-line facility target flow:0 cfs. Adjusted for 15 min:0 cfs. Roberts SP Infiltration cells 2/25/2026 4:14:04 PM Page 23 LID Report Roberts SP Infiltration cells 2/25/2026 4:14:25 PM Page 24 Model Default Modifications Total of 0 changes have been made. PERLND Changes No PERLND changes have been made. IMPLND Changes No IMPLND changes have been made. Roberts SP Infiltration cells 2/25/2026 4:14:25 PM Page 25 Appendix Predeveloped Schematic Roberts SP Infiltration cells 2/25/2026 4:14:26 PM Page 26 Mitigated Schematic Roberts SP Infiltration cells 2/25/2026 4:14:28 PM Page 27 Predeveloped UCI File RUN GLOBAL WWHM4 model simulation START 1948 10 01 END 2009 09 30 RUN INTERP OUTPUT LEVEL 3 0 RESUME 0 RUN 1 UNIT SYSTEM 1 END GLOBAL FILES <File> <Un#> <-----------File Name------------------------------>*** <-ID-> *** WDM 26 Roberts SP Infiltration cells.wdm MESSU 25 PreRoberts SP Infiltration cells.MES 27 PreRoberts SP Infiltration cells.L61 28 PreRoberts SP Infiltration cells.L62 30 POCRoberts SP Infiltration cells1.dat END FILES OPN SEQUENCE INGRP INDELT 00:15 PERLND 10 PERLND 11 PERLND 12 COPY 501 DISPLY 1 END INGRP END OPN SEQUENCE DISPLY DISPLY-INFO1 # - #<----------Title----------->***TRAN PIVL DIG1 FIL1 PYR DIG2 FIL2 YRND 1 Basin 1 MAX 1 2 30 9 END DISPLY-INFO1 END DISPLY COPY TIMESERIES # - # NPT NMN *** 1 1 1 501 1 1 END TIMESERIES END COPY GENER OPCODE # # OPCD *** END OPCODE PARM # # K *** END PARM END GENER PERLND GEN-INFO <PLS ><-------Name------->NBLKS Unit-systems Printer *** # - # User t-series Engl Metr *** in out *** 10 C, Forest, Flat 1 1 1 1 27 0 11 C, Forest, Mod 1 1 1 1 27 0 12 C, Forest, Steep 1 1 1 1 27 0 END GEN-INFO *** Section PWATER*** ACTIVITY <PLS > ************* Active Sections ***************************** # - # ATMP SNOW PWAT SED PST PWG PQAL MSTL PEST NITR PHOS TRAC *** 10 0 0 1 0 0 0 0 0 0 0 0 0 11 0 0 1 0 0 0 0 0 0 0 0 0 12 0 0 1 0 0 0 0 0 0 0 0 0 END ACTIVITY Roberts SP Infiltration cells 2/25/2026 4:14:28 PM Page 28 PRINT-INFO <PLS > ***************** Print-flags ***************************** PIVL PYR # - # ATMP SNOW PWAT SED PST PWG PQAL MSTL PEST NITR PHOS TRAC ********* 10 0 0 4 0 0 0 0 0 0 0 0 0 1 9 11 0 0 4 0 0 0 0 0 0 0 0 0 1 9 12 0 0 4 0 0 0 0 0 0 0 0 0 1 9 END PRINT-INFO PWAT-PARM1 <PLS > PWATER variable monthly parameter value flags *** # - # CSNO RTOP UZFG VCS VUZ VNN VIFW VIRC VLE INFC HWT *** 10 0 0 0 0 0 0 0 0 0 0 0 11 0 0 0 0 0 0 0 0 0 0 0 12 0 0 0 0 0 0 0 0 0 0 0 END PWAT-PARM1 PWAT-PARM2 <PLS > PWATER input info: Part 2 *** # - # ***FOREST LZSN INFILT LSUR SLSUR KVARY AGWRC 10 0 4.5 0.08 400 0.05 0.5 0.996 11 0 4.5 0.08 400 0.1 0.5 0.996 12 0 4.5 0.08 400 0.15 0.5 0.996 END PWAT-PARM2 PWAT-PARM3 <PLS > PWATER input info: Part 3 *** # - # ***PETMAX PETMIN INFEXP INFILD DEEPFR BASETP AGWETP 10 0 0 2 2 0 0 0 11 0 0 2 2 0 0 0 12 0 0 2 2 0 0 0 END PWAT-PARM3 PWAT-PARM4 <PLS > PWATER input info: Part 4 *** # - # CEPSC UZSN NSUR INTFW IRC LZETP *** 10 0.2 0.5 0.35 6 0.5 0.7 11 0.2 0.5 0.35 6 0.5 0.7 12 0.2 0.3 0.35 6 0.3 0.7 END PWAT-PARM4 PWAT-STATE1 <PLS > *** Initial conditions at start of simulation ran from 1990 to end of 1992 (pat 1-11-95) RUN 21 *** # - # *** CEPS SURS UZS IFWS LZS AGWS GWVS 10 0 0 0 0 2.5 1 0 11 0 0 0 0 2.5 1 0 12 0 0 0 0 2.5 1 0 END PWAT-STATE1 END PERLND IMPLND GEN-INFO <PLS ><-------Name-------> Unit-systems Printer *** # - # User t-series Engl Metr *** in out *** END GEN-INFO *** Section IWATER*** ACTIVITY <PLS > ************* Active Sections ***************************** # - # ATMP SNOW IWAT SLD IWG IQAL *** END ACTIVITY PRINT-INFO <ILS > ******** Print-flags ******** PIVL PYR # - # ATMP SNOW IWAT SLD IWG IQAL ********* END PRINT-INFO IWAT-PARM1 <PLS > IWATER variable monthly parameter value flags *** Roberts SP Infiltration cells 2/25/2026 4:14:28 PM Page 29 # - # CSNO RTOP VRS VNN RTLI *** END IWAT-PARM1 IWAT-PARM2 <PLS > IWATER input info: Part 2 *** # - # *** LSUR SLSUR NSUR RETSC END IWAT-PARM2 IWAT-PARM3 <PLS > IWATER input info: Part 3 *** # - # ***PETMAX PETMIN END IWAT-PARM3 IWAT-STATE1 <PLS > *** Initial conditions at start of simulation # - # *** RETS SURS END IWAT-STATE1 END IMPLND SCHEMATIC <-Source-> <--Area--> <-Target-> MBLK *** <Name> # <-factor-> <Name> # Tbl# *** Basin 1*** PERLND 10 0.236 COPY 501 12 PERLND 10 0.236 COPY 501 13 PERLND 11 0.902 COPY 501 12 PERLND 11 0.902 COPY 501 13 PERLND 12 0.237 COPY 501 12 PERLND 12 0.237 COPY 501 13 ******Routing****** END SCHEMATIC NETWORK <-Volume-> <-Grp> <-Member-><--Mult-->Tran <-Target vols> <-Grp> <-Member-> *** <Name> # <Name> # #<-factor->strg <Name> # # <Name> # # *** COPY 501 OUTPUT MEAN 1 1 48.4 DISPLY 1 INPUT TIMSER 1 <-Volume-> <-Grp> <-Member-><--Mult-->Tran <-Target vols> <-Grp> <-Member-> *** <Name> # <Name> # #<-factor->strg <Name> # # <Name> # # *** END NETWORK RCHRES GEN-INFO RCHRES Name Nexits Unit Systems Printer *** # - #<------------------><---> User T-series Engl Metr LKFG *** in out *** END GEN-INFO *** Section RCHRES*** ACTIVITY <PLS > ************* Active Sections ***************************** # - # HYFG ADFG CNFG HTFG SDFG GQFG OXFG NUFG PKFG PHFG *** END ACTIVITY PRINT-INFO <PLS > ***************** Print-flags ******************* PIVL PYR # - # HYDR ADCA CONS HEAT SED GQL OXRX NUTR PLNK PHCB PIVL PYR ********* END PRINT-INFO HYDR-PARM1 RCHRES Flags for each HYDR Section *** # - # VC A1 A2 A3 ODFVFG for each *** ODGTFG for each FUNCT for each FG FG FG FG possible exit *** possible exit possible exit * * * * * * * * * * * * * * *** END HYDR-PARM1 Roberts SP Infiltration cells 2/25/2026 4:14:28 PM Page 30 HYDR-PARM2 # - # FTABNO LEN DELTH STCOR KS DB50 *** <------><--------><--------><--------><--------><--------><--------> *** END HYDR-PARM2 HYDR-INIT RCHRES Initial conditions for each HYDR section *** # - # *** VOL Initial value of COLIND Initial value of OUTDGT *** ac-ft for each possible exit for each possible exit <------><--------> <---><---><---><---><---> *** <---><---><---><---><---> END HYDR-INIT END RCHRES SPEC-ACTIONS END SPEC-ACTIONS FTABLES END FTABLES EXT SOURCES <-Volume-> <Member> SsysSgap<--Mult-->Tran <-Target vols> <-Grp> <-Member-> *** <Name> # <Name> # tem strg<-factor->strg <Name> # # <Name> # # *** WDM 2 PREC ENGL 1 PERLND 1 999 EXTNL PREC WDM 2 PREC ENGL 1 IMPLND 1 999 EXTNL PREC WDM 1 EVAP ENGL 0.76 PERLND 1 999 EXTNL PETINP WDM 1 EVAP ENGL 0.76 IMPLND 1 999 EXTNL PETINP END EXT SOURCES EXT TARGETS <-Volume-> <-Grp> <-Member-><--Mult-->Tran <-Volume-> <Member> Tsys Tgap Amd *** <Name> # <Name> # #<-factor->strg <Name> # <Name> tem strg strg*** COPY 501 OUTPUT MEAN 1 1 48.4 WDM 501 FLOW ENGL REPL END EXT TARGETS MASS-LINK <Volume> <-Grp> <-Member-><--Mult--> <Target> <-Grp> <-Member->*** <Name> <Name> # #<-factor-> <Name> <Name> # #*** MASS-LINK 12 PERLND PWATER SURO 0.083333 COPY INPUT MEAN END MASS-LINK 12 MASS-LINK 13 PERLND PWATER IFWO 0.083333 COPY INPUT MEAN END MASS-LINK 13 END MASS-LINK END RUN Roberts SP Infiltration cells 2/25/2026 4:14:28 PM Page 31 Mitigated UCI File RUN GLOBAL WWHM4 model simulation START 1948 10 01 END 2009 09 30 RUN INTERP OUTPUT LEVEL 3 0 RESUME 0 RUN 1 UNIT SYSTEM 1 END GLOBAL FILES <File> <Un#> <-----------File Name------------------------------>*** <-ID-> *** WDM 26 Roberts SP Infiltration cells.wdm MESSU 25 MitRoberts SP Infiltration cells.MES 27 MitRoberts SP Infiltration cells.L61 28 MitRoberts SP Infiltration cells.L62 30 POCRoberts SP Infiltration cells1.dat END FILES OPN SEQUENCE INGRP INDELT 00:15 IMPLND 4 PERLND 16 IMPLND 2 IMPLND 5 IMPLND 1 IMPLND 8 RCHRES 1 RCHRES 2 RCHRES 3 COPY 1 COPY 501 DISPLY 1 END INGRP END OPN SEQUENCE DISPLY DISPLY-INFO1 # - #<----------Title----------->***TRAN PIVL DIG1 FIL1 PYR DIG2 FIL2 YRND 1 Gravel Trench Bed 1 MAX 1 2 30 9 END DISPLY-INFO1 END DISPLY COPY TIMESERIES # - # NPT NMN *** 1 1 1 501 1 1 END TIMESERIES END COPY GENER OPCODE # # OPCD *** END OPCODE PARM # # K *** END PARM END GENER PERLND GEN-INFO <PLS ><-------Name------->NBLKS Unit-systems Printer *** # - # User t-series Engl Metr *** in out *** 16 C, Lawn, Flat 1 1 1 1 27 0 END GEN-INFO *** Section PWATER*** ACTIVITY <PLS > ************* Active Sections ***************************** # - # ATMP SNOW PWAT SED PST PWG PQAL MSTL PEST NITR PHOS TRAC *** Roberts SP Infiltration cells 2/25/2026 4:14:28 PM Page 32 16 0 0 1 0 0 0 0 0 0 0 0 0 END ACTIVITY PRINT-INFO <PLS > ***************** Print-flags ***************************** PIVL PYR # - # ATMP SNOW PWAT SED PST PWG PQAL MSTL PEST NITR PHOS TRAC ********* 16 0 0 4 0 0 0 0 0 0 0 0 0 1 9 END PRINT-INFO PWAT-PARM1 <PLS > PWATER variable monthly parameter value flags *** # - # CSNO RTOP UZFG VCS VUZ VNN VIFW VIRC VLE INFC HWT *** 16 0 0 0 0 0 0 0 0 0 0 0 END PWAT-PARM1 PWAT-PARM2 <PLS > PWATER input info: Part 2 *** # - # ***FOREST LZSN INFILT LSUR SLSUR KVARY AGWRC 16 0 4.5 0.03 400 0.05 0.5 0.996 END PWAT-PARM2 PWAT-PARM3 <PLS > PWATER input info: Part 3 *** # - # ***PETMAX PETMIN INFEXP INFILD DEEPFR BASETP AGWETP 16 0 0 2 2 0 0 0 END PWAT-PARM3 PWAT-PARM4 <PLS > PWATER input info: Part 4 *** # - # CEPSC UZSN NSUR INTFW IRC LZETP *** 16 0.1 0.25 0.25 6 0.5 0.25 END PWAT-PARM4 PWAT-STATE1 <PLS > *** Initial conditions at start of simulation ran from 1990 to end of 1992 (pat 1-11-95) RUN 21 *** # - # *** CEPS SURS UZS IFWS LZS AGWS GWVS 16 0 0 0 0 2.5 1 0 END PWAT-STATE1 END PERLND IMPLND GEN-INFO <PLS ><-------Name-------> Unit-systems Printer *** # - # User t-series Engl Metr *** in out *** 4 ROOF TOPS/FLAT 1 1 1 27 0 2 ROADS/MOD 1 1 1 27 0 5 DRIVEWAYS/FLAT 1 1 1 27 0 1 ROADS/FLAT 1 1 1 27 0 8 SIDEWALKS/FLAT 1 1 1 27 0 END GEN-INFO *** Section IWATER*** ACTIVITY <PLS > ************* Active Sections ***************************** # - # ATMP SNOW IWAT SLD IWG IQAL *** 4 0 0 1 0 0 0 2 0 0 1 0 0 0 5 0 0 1 0 0 0 1 0 0 1 0 0 0 8 0 0 1 0 0 0 END ACTIVITY PRINT-INFO <ILS > ******** Print-flags ******** PIVL PYR # - # ATMP SNOW IWAT SLD IWG IQAL ********* 4 0 0 4 0 0 4 1 9 2 0 0 4 0 0 0 1 9 5 0 0 4 0 0 0 1 9 Roberts SP Infiltration cells 2/25/2026 4:14:28 PM Page 33 1 0 0 4 0 0 0 1 9 8 0 0 4 0 0 0 1 9 END PRINT-INFO IWAT-PARM1 <PLS > IWATER variable monthly parameter value flags *** # - # CSNO RTOP VRS VNN RTLI *** 4 0 0 0 0 0 2 0 0 0 0 0 5 0 0 0 0 0 1 0 0 0 0 0 8 0 0 0 0 0 END IWAT-PARM1 IWAT-PARM2 <PLS > IWATER input info: Part 2 *** # - # *** LSUR SLSUR NSUR RETSC 4 400 0.01 0.1 0.1 2 400 0.05 0.1 0.08 5 400 0.01 0.1 0.1 1 400 0.01 0.1 0.1 8 400 0.01 0.1 0.1 END IWAT-PARM2 IWAT-PARM3 <PLS > IWATER input info: Part 3 *** # - # ***PETMAX PETMIN 4 0 0 2 0 0 5 0 0 1 0 0 8 0 0 END IWAT-PARM3 IWAT-STATE1 <PLS > *** Initial conditions at start of simulation # - # *** RETS SURS 4 0 0 2 0 0 5 0 0 1 0 0 8 0 0 END IWAT-STATE1 END IMPLND SCHEMATIC <-Source-> <--Area--> <-Target-> MBLK *** <Name> # <-factor-> <Name> # Tbl# *** Basin 1*** IMPLND 4 0.275 RCHRES 1 5 Basin 2*** PERLND 16 0.83 RCHRES 2 2 PERLND 16 0.83 RCHRES 2 3 IMPLND 2 0.148 RCHRES 2 5 IMPLND 5 0.051 RCHRES 2 5 Basin 3*** IMPLND 1 0.055 RCHRES 3 5 IMPLND 8 0.017 RCHRES 3 5 ******Routing****** IMPLND 4 0.275 COPY 1 15 PERLND 16 0.83 COPY 1 12 IMPLND 2 0.148 COPY 1 15 IMPLND 5 0.051 COPY 1 15 PERLND 16 0.83 COPY 1 13 IMPLND 1 0.055 COPY 1 15 IMPLND 8 0.017 COPY 1 15 RCHRES 1 1 COPY 501 17 RCHRES 2 1 COPY 501 17 Roberts SP Infiltration cells 2/25/2026 4:14:28 PM Page 34 RCHRES 3 1 COPY 501 17 END SCHEMATIC NETWORK <-Volume-> <-Grp> <-Member-><--Mult-->Tran <-Target vols> <-Grp> <-Member-> *** <Name> # <Name> # #<-factor->strg <Name> # # <Name> # # *** COPY 501 OUTPUT MEAN 1 1 48.4 DISPLY 1 INPUT TIMSER 1 <-Volume-> <-Grp> <-Member-><--Mult-->Tran <-Target vols> <-Grp> <-Member-> *** <Name> # <Name> # #<-factor->strg <Name> # # <Name> # # *** END NETWORK RCHRES GEN-INFO RCHRES Name Nexits Unit Systems Printer *** # - #<------------------><---> User T-series Engl Metr LKFG *** in out *** 1 Gravel Trench Be-014 2 1 1 1 28 0 1 2 StormTech 2 2 1 1 1 28 0 1 3 Gravel Trench Be-034 2 1 1 1 28 0 1 END GEN-INFO *** Section RCHRES*** ACTIVITY <PLS > ************* Active Sections ***************************** # - # HYFG ADFG CNFG HTFG SDFG GQFG OXFG NUFG PKFG PHFG *** 1 1 0 0 0 0 0 0 0 0 0 2 1 0 0 0 0 0 0 0 0 0 3 1 0 0 0 0 0 0 0 0 0 END ACTIVITY PRINT-INFO <PLS > ***************** Print-flags ******************* PIVL PYR # - # HYDR ADCA CONS HEAT SED GQL OXRX NUTR PLNK PHCB PIVL PYR ********* 1 4 0 0 0 0 0 0 0 0 0 1 9 2 4 0 0 0 0 0 0 0 0 0 1 9 3 4 0 0 0 0 0 0 0 0 0 1 9 END PRINT-INFO HYDR-PARM1 RCHRES Flags for each HYDR Section *** # - # VC A1 A2 A3 ODFVFG for each *** ODGTFG for each FUNCT for each FG FG FG FG possible exit *** possible exit possible exit * * * * * * * * * * * * * * *** 1 0 1 0 0 4 5 0 0 0 0 0 0 0 0 2 2 2 2 2 2 0 1 0 0 4 5 0 0 0 0 0 0 0 0 2 2 2 2 2 3 0 1 0 0 4 5 0 0 0 0 0 0 0 0 2 2 2 2 2 END HYDR-PARM1 HYDR-PARM2 # - # FTABNO LEN DELTH STCOR KS DB50 *** <------><--------><--------><--------><--------><--------><--------> *** 1 1 0.05 0.0 0.0 0.5 0.0 2 2 0.02 0.0 0.0 0.5 0.0 3 3 0.03 0.0 0.0 0.5 0.0 END HYDR-PARM2 HYDR-INIT RCHRES Initial conditions for each HYDR section *** # - # *** VOL Initial value of COLIND Initial value of OUTDGT *** ac-ft for each possible exit for each possible exit <------><--------> <---><---><---><---><---> *** <---><---><---><---><---> 1 0 4.0 5.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 2 0 4.0 5.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 3 0 4.0 5.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 END HYDR-INIT END RCHRES SPEC-ACTIONS Roberts SP Infiltration cells 2/25/2026 4:14:28 PM Page 35 END SPEC-ACTIONS FTABLES FTABLE 1 92 5 Depth Area Volume Outflow1 Outflow2 Velocity Travel Time*** (ft) (acres) (acre-ft) (cfs) (cfs) (ft/sec) (Minutes)*** 0.000000 0.030854 0.000000 0.000000 0.000000 0.044444 0.030854 0.000453 0.000000 0.048533 0.088889 0.030854 0.000905 0.000000 0.048533 0.133333 0.030854 0.001358 0.000000 0.048533 0.177778 0.030854 0.001810 0.000000 0.048533 0.222222 0.030854 0.002263 0.000000 0.048533 0.266667 0.030854 0.002715 0.000000 0.048533 0.311111 0.030854 0.003168 0.000000 0.048533 0.355556 0.030854 0.003620 0.000000 0.048533 0.400000 0.030854 0.004073 0.000000 0.048533 0.444444 0.030854 0.004525 0.000000 0.048533 0.488889 0.030854 0.004978 0.000000 0.048533 0.533333 0.030854 0.005430 0.000000 0.048533 0.577778 0.030854 0.005883 0.000000 0.048533 0.622222 0.030854 0.006335 0.000000 0.048533 0.666667 0.030854 0.006788 0.000000 0.048533 0.711111 0.030854 0.007240 0.000000 0.048533 0.755556 0.030854 0.007693 0.000000 0.048533 0.800000 0.030854 0.008145 0.000000 0.048533 0.844444 0.030854 0.008598 0.000000 0.048533 0.888889 0.030854 0.009051 0.000000 0.048533 0.933333 0.030854 0.009503 0.000000 0.048533 0.977778 0.030854 0.009956 0.000000 0.048533 1.022222 0.030854 0.010408 0.000000 0.048533 1.066667 0.030854 0.010861 0.000000 0.048533 1.111111 0.030854 0.011313 0.000000 0.048533 1.155556 0.030854 0.011766 0.000000 0.048533 1.200000 0.030854 0.012218 0.000000 0.048533 1.244444 0.030854 0.012671 0.000000 0.048533 1.288889 0.030854 0.013123 0.000000 0.048533 1.333333 0.030854 0.013576 0.000000 0.048533 1.377778 0.030854 0.014028 0.000000 0.048533 1.422222 0.030854 0.014481 0.000000 0.048533 1.466667 0.030854 0.014933 0.000000 0.048533 1.511111 0.030854 0.015386 0.000000 0.048533 1.555556 0.030854 0.015838 0.000000 0.048533 1.600000 0.030854 0.016291 0.000000 0.048533 1.644444 0.030854 0.016743 0.000000 0.048533 1.688889 0.030854 0.017196 0.000000 0.048533 1.733333 0.030854 0.017648 0.000000 0.048533 1.777778 0.030854 0.018101 0.000000 0.048533 1.822222 0.030854 0.018554 0.000000 0.048533 1.866667 0.030854 0.019006 0.000000 0.048533 1.911111 0.030854 0.019459 0.000000 0.048533 1.955556 0.030854 0.019911 0.000000 0.048533 2.000000 0.030854 0.020364 0.000000 0.048533 2.044444 0.030854 0.020816 0.000000 0.048533 2.088889 0.030854 0.021269 0.000000 0.048533 2.133333 0.030854 0.021721 0.000000 0.048533 2.177778 0.030854 0.022174 0.000000 0.048533 2.222222 0.030854 0.022626 0.000000 0.048533 2.266667 0.030854 0.023079 0.000000 0.048533 2.311111 0.030854 0.023531 0.000000 0.048533 2.355556 0.030854 0.023984 0.000000 0.048533 2.400000 0.030854 0.024436 0.000000 0.048533 2.444444 0.030854 0.024889 0.000000 0.048533 2.488889 0.030854 0.025341 0.000000 0.048533 2.533333 0.030854 0.025794 0.000000 0.048533 2.577778 0.030854 0.026246 0.000000 0.048533 2.622222 0.030854 0.026699 0.000000 0.048533 2.666667 0.030854 0.027152 0.000000 0.048533 2.711111 0.030854 0.027604 0.000000 0.048533 2.755556 0.030854 0.028057 0.000000 0.048533 2.800000 0.030854 0.028509 0.000000 0.048533 Roberts SP Infiltration cells 2/25/2026 4:14:28 PM Page 36 2.844444 0.030854 0.028962 0.000000 0.048533 2.888889 0.030854 0.029414 0.000000 0.048533 2.933333 0.030854 0.029867 0.000000 0.048533 2.977778 0.030854 0.030319 0.000000 0.048533 3.022222 0.030854 0.031690 0.001011 0.048533 3.066667 0.030854 0.033062 0.001752 0.048533 3.111111 0.030854 0.034433 0.002261 0.048533 3.155556 0.030854 0.035804 0.002676 0.048533 3.200000 0.030854 0.037176 0.003034 0.048533 3.244444 0.030854 0.038547 0.003354 0.048533 3.288889 0.030854 0.039918 0.003646 0.048533 3.333333 0.030854 0.041290 0.003917 0.048533 3.377778 0.030854 0.042661 0.004170 0.048533 3.422222 0.030854 0.044032 0.004408 0.048533 3.466667 0.030854 0.045403 0.004634 0.048533 3.511111 0.030854 0.046775 0.011063 0.048533 3.555556 0.030854 0.048146 0.073971 0.048533 3.600000 0.030854 0.049517 0.165711 0.048533 3.644444 0.030854 0.050889 0.261329 0.048533 3.688889 0.030854 0.052260 0.337842 0.048533 3.733333 0.030854 0.053631 0.383816 0.048533 3.777778 0.030854 0.055002 0.420983 0.048533 3.822222 0.030854 0.056374 0.453121 0.048533 3.866667 0.030854 0.057745 0.483115 0.048533 3.911111 0.030854 0.059116 0.511345 0.048533 3.955556 0.030854 0.060488 0.538091 0.048533 4.000000 0.030854 0.061859 0.563565 0.048533 4.044444 0.030854 0.063230 0.587934 0.048533 END FTABLE 1 FTABLE 2 49 5 Depth Area Volume Outflow1 Outflow2 Velocity Travel Time*** (ft) (acres) (acre-ft) (cfs) (cfs) (ft/sec) (Minutes)*** 0.000000 0.021729 0.000000 0.000000 0.000000 0.083333 0.023017 0.000725 0.000000 0.036206 0.166667 0.023017 0.001450 0.007883 0.036206 0.250000 0.023017 0.002178 0.019308 0.036206 0.333333 0.023017 0.002903 0.026143 0.036206 0.416667 0.023017 0.003630 0.031530 0.036206 0.500000 0.023017 0.004356 0.036122 0.036206 0.583333 0.023017 0.005932 0.040193 0.036206 0.666667 0.023017 0.007503 0.043888 0.036206 0.750000 0.023017 0.009068 0.047295 0.036206 0.833333 0.023017 0.010622 0.054879 0.036206 0.916667 0.023017 0.012168 0.059694 0.036206 1.000000 0.023017 0.013705 0.063925 0.036206 1.083333 0.023017 0.015231 0.067800 0.036206 1.166667 0.023017 0.016743 0.071418 0.036206 1.250000 0.023017 0.018241 0.074832 0.036206 1.333333 0.023017 0.019728 0.078078 0.036206 1.416667 0.023017 0.021198 0.081182 0.036206 1.500000 0.023017 0.022654 0.084162 0.036206 1.583333 0.023017 0.024093 0.087034 0.036206 1.666667 0.023017 0.025513 0.089809 0.036206 1.750000 0.023017 0.026913 0.092497 0.036206 1.833333 0.023017 0.028293 0.095106 0.036206 1.916667 0.023017 0.029651 0.097643 0.036206 2.000000 0.023017 0.030984 0.100114 0.036206 2.083333 0.023017 0.032297 0.106930 0.036206 2.166667 0.023017 0.033582 0.111108 0.036206 2.250000 0.023017 0.034828 0.114808 0.036206 2.333333 0.023017 0.036041 0.118240 0.036206 2.416667 0.023017 0.037222 0.121485 0.036206 2.500000 0.023017 0.038359 0.124586 0.036206 2.583333 0.023017 0.039451 0.251922 0.036206 2.666667 0.023017 0.040484 0.428056 0.036206 2.750000 0.023017 0.041442 0.522758 0.036206 2.833333 0.023017 0.042274 0.590595 0.036206 2.916667 0.023017 0.043060 0.646912 0.036206 3.000000 0.023017 0.043808 0.698020 0.036206 Roberts SP Infiltration cells 2/25/2026 4:14:28 PM Page 37 3.083333 0.023017 0.044533 0.745171 0.036206 3.166667 0.023017 0.045258 0.789181 0.036206 3.250000 0.023017 0.045986 0.830620 0.036206 3.333333 0.023017 0.046711 0.869900 0.036206 3.416667 0.023017 0.047438 0.907336 0.036206 3.500000 0.023017 0.048164 0.943170 0.036206 3.583333 0.023017 0.048890 0.977597 0.036206 3.666667 0.023017 0.049617 1.010773 0.038792 3.750000 0.023017 0.050343 1.042829 0.038792 3.833333 0.023017 0.051070 1.073874 0.038792 3.916667 0.023017 0.051796 1.103999 0.038792 4.000000 0.023017 0.052522 1.133283 0.038792 END FTABLE 2 FTABLE 3 92 5 Depth Area Volume Outflow1 Outflow2 Velocity Travel Time*** (ft) (acres) (acre-ft) (cfs) (cfs) (ft/sec) (Minutes)*** 0.000000 0.029778 0.000000 0.000000 0.000000 0.016667 0.029778 0.000164 0.000000 0.046840 0.033333 0.029778 0.000328 0.000000 0.046840 0.050000 0.029778 0.000491 0.000000 0.046840 0.066667 0.029778 0.000655 0.000000 0.046840 0.083333 0.029778 0.000819 0.000000 0.046840 0.100000 0.029778 0.000983 0.000000 0.046840 0.116667 0.029778 0.001146 0.000000 0.046840 0.133333 0.029778 0.001310 0.000000 0.046840 0.150000 0.029778 0.001474 0.000000 0.046840 0.166667 0.029778 0.001638 0.000000 0.046840 0.183333 0.029778 0.001802 0.000000 0.046840 0.200000 0.029778 0.001965 0.000000 0.046840 0.216667 0.029778 0.002129 0.000000 0.046840 0.233333 0.029778 0.002293 0.000000 0.046840 0.250000 0.029778 0.002457 0.000000 0.046840 0.266667 0.029778 0.002620 0.000000 0.046840 0.283333 0.029778 0.002784 0.000000 0.046840 0.300000 0.029778 0.002948 0.000000 0.046840 0.316667 0.029778 0.003112 0.000000 0.046840 0.333333 0.029778 0.003276 0.000000 0.046840 0.350000 0.029778 0.003439 0.000000 0.046840 0.366667 0.029778 0.003603 0.000000 0.046840 0.383333 0.029778 0.003767 0.000000 0.046840 0.400000 0.029778 0.003931 0.000000 0.046840 0.416667 0.029778 0.004094 0.000000 0.046840 0.433333 0.029778 0.004258 0.000000 0.046840 0.450000 0.029778 0.004422 0.000000 0.046840 0.466667 0.029778 0.004586 0.000000 0.046840 0.483333 0.029778 0.004750 0.000000 0.046840 0.500000 0.029778 0.004913 0.000000 0.046840 0.516667 0.029778 0.005077 0.000000 0.046840 0.533333 0.029778 0.005241 0.000000 0.046840 0.550000 0.029778 0.005405 0.000000 0.046840 0.566667 0.029778 0.005568 0.000000 0.046840 0.583333 0.029778 0.005732 0.000000 0.046840 0.600000 0.029778 0.005896 0.000000 0.046840 0.616667 0.029778 0.006060 0.000000 0.046840 0.633333 0.029778 0.006224 0.000000 0.046840 0.650000 0.029778 0.006387 0.000000 0.046840 0.666667 0.029778 0.006551 0.000000 0.046840 0.683333 0.029778 0.006715 0.000000 0.046840 0.700000 0.029778 0.006879 0.000000 0.046840 0.716667 0.029778 0.007042 0.000000 0.046840 0.733333 0.029778 0.007206 0.000000 0.046840 0.750000 0.029778 0.007370 0.000000 0.046840 0.766667 0.029778 0.007534 0.000000 0.046840 0.783333 0.029778 0.007698 0.000000 0.046840 0.800000 0.029778 0.007861 0.000000 0.046840 0.816667 0.029778 0.008025 0.000000 0.046840 0.833333 0.029778 0.008189 0.000000 0.046840 0.850000 0.029778 0.008353 0.000000 0.046840 0.866667 0.029778 0.008516 0.000000 0.046840 Roberts SP Infiltration cells 2/25/2026 4:14:28 PM Page 38 0.883333 0.029778 0.008680 0.000000 0.046840 0.900000 0.029778 0.008844 0.000000 0.046840 0.916667 0.029778 0.009008 0.000000 0.046840 0.933333 0.029778 0.009172 0.000000 0.046840 0.950000 0.029778 0.009335 0.000000 0.046840 0.966667 0.029778 0.009499 0.000000 0.046840 0.983333 0.029778 0.009663 0.000000 0.046840 1.000000 0.029778 0.009827 0.000000 0.046840 1.016667 0.029778 0.009990 0.000000 0.046840 1.033333 0.029778 0.010154 0.000000 0.046840 1.050000 0.029778 0.010318 0.000000 0.046840 1.066667 0.029778 0.010482 0.000000 0.046840 1.083333 0.029778 0.010646 0.000000 0.046840 1.100000 0.029778 0.010809 0.000000 0.046840 1.116667 0.029778 0.010973 0.000000 0.046840 1.133333 0.029778 0.011137 0.000000 0.046840 1.150000 0.029778 0.011301 0.000000 0.046840 1.166667 0.029778 0.011464 0.000000 0.046840 1.183333 0.029778 0.011628 0.000000 0.046840 1.200000 0.029778 0.011792 0.000000 0.046840 1.216667 0.029778 0.011956 0.000000 0.046840 1.233333 0.029778 0.012120 0.000000 0.046840 1.250000 0.029778 0.012283 0.000000 0.046840 1.266667 0.029778 0.012447 0.000000 0.046840 1.283333 0.029778 0.012611 0.000000 0.046840 1.300000 0.029778 0.012775 0.000000 0.046840 1.316667 0.029778 0.012938 0.000000 0.046840 1.333333 0.029778 0.013102 0.000000 0.046840 1.350000 0.029778 0.013266 0.000000 0.046840 1.366667 0.029778 0.013430 0.000000 0.046840 1.383333 0.029778 0.013594 0.000000 0.046840 1.400000 0.029778 0.013757 0.000000 0.046840 1.416667 0.029778 0.013921 0.000000 0.046840 1.433333 0.029778 0.014085 0.000000 0.046840 1.450000 0.029778 0.014249 0.000000 0.046840 1.466667 0.029778 0.014412 0.000000 0.046840 1.483333 0.029778 0.014576 0.000000 0.046840 1.500000 0.029778 0.014740 0.000000 0.046840 1.516667 0.029778 0.015236 0.000000 0.046840 END FTABLE 3 END FTABLES EXT SOURCES <-Volume-> <Member> SsysSgap<--Mult-->Tran <-Target vols> <-Grp> <-Member-> *** <Name> # <Name> # tem strg<-factor->strg <Name> # # <Name> # # *** WDM 2 PREC ENGL 1 PERLND 1 999 EXTNL PREC WDM 2 PREC ENGL 1 IMPLND 1 999 EXTNL PREC WDM 1 EVAP ENGL 0.76 PERLND 1 999 EXTNL PETINP WDM 1 EVAP ENGL 0.76 IMPLND 1 999 EXTNL PETINP END EXT SOURCES EXT TARGETS <-Volume-> <-Grp> <-Member-><--Mult-->Tran <-Volume-> <Member> Tsys Tgap Amd *** <Name> # <Name> # #<-factor->strg <Name> # <Name> tem strg strg*** RCHRES 1 HYDR RO 1 1 1 WDM 1006 FLOW ENGL REPL RCHRES 1 HYDR O 1 1 1 WDM 1007 FLOW ENGL REPL RCHRES 1 HYDR O 2 1 1 WDM 1008 FLOW ENGL REPL RCHRES 1 HYDR STAGE 1 1 1 WDM 1009 STAG ENGL REPL COPY 1 OUTPUT MEAN 1 1 48.4 WDM 701 FLOW ENGL REPL COPY 501 OUTPUT MEAN 1 1 48.4 WDM 801 FLOW ENGL REPL RCHRES 2 HYDR RO 1 1 1 WDM 1014 FLOW ENGL REPL RCHRES 2 HYDR O 1 1 1 WDM 1015 FLOW ENGL REPL RCHRES 2 HYDR O 2 1 1 WDM 1016 FLOW ENGL REPL RCHRES 2 HYDR STAGE 1 1 1 WDM 1017 STAG ENGL REPL RCHRES 3 HYDR RO 1 1 1 WDM 1018 FLOW ENGL REPL RCHRES 3 HYDR O 1 1 1 WDM 1019 FLOW ENGL REPL RCHRES 3 HYDR O 2 1 1 WDM 1020 FLOW ENGL REPL RCHRES 3 HYDR STAGE 1 1 1 WDM 1021 STAG ENGL REPL END EXT TARGETS Roberts SP Infiltration cells 2/25/2026 4:14:28 PM Page 39 MASS-LINK <Volume> <-Grp> <-Member-><--Mult--> <Target> <-Grp> <-Member->*** <Name> <Name> # #<-factor-> <Name> <Name> # #*** MASS-LINK 2 PERLND PWATER SURO 0.083333 RCHRES INFLOW IVOL END MASS-LINK 2 MASS-LINK 3 PERLND PWATER IFWO 0.083333 RCHRES INFLOW IVOL END MASS-LINK 3 MASS-LINK 5 IMPLND IWATER SURO 0.083333 RCHRES INFLOW IVOL END MASS-LINK 5 MASS-LINK 12 PERLND PWATER SURO 0.083333 COPY INPUT MEAN END MASS-LINK 12 MASS-LINK 13 PERLND PWATER IFWO 0.083333 COPY INPUT MEAN END MASS-LINK 13 MASS-LINK 15 IMPLND IWATER SURO 0.083333 COPY INPUT MEAN END MASS-LINK 15 MASS-LINK 17 RCHRES OFLOW OVOL 1 COPY INPUT MEAN END MASS-LINK 17 END MASS-LINK END RUN Roberts SP Infiltration cells 2/25/2026 4:14:28 PM Page 40 Predeveloped HSPF Message File Roberts SP Infiltration cells 2/25/2026 4:14:28 PM Page 41 Mitigated HSPF Message File Roberts SP Infiltration cells 2/25/2026 4:14:28 PM Page 42 Disclaimer Legal Notice This program and accompanying documentation are provided 'as-is' without warranty of any kind. The entire risk regarding the performance and results of this program is assumed by End User. Clear Creek Solutions Inc. and the governmental licensee or sublicensees disclaim all warranties, either expressed or implied, including but not limited to implied warranties of program and accompanying documentation. In no event shall Clear Creek Solutions Inc. be liable for any damages whatsoever (including without limitation to damages for loss of business profits, loss of business information, business interruption, and the like) arising out of the use of, or inability to use this program even if Clear Creek Solutions Inc. or their authorized representatives have been advised of the possibility of such damages. Software Copyright © by : Clear Creek Solutions, Inc. 2005-2026; All Rights Reserved. Clear Creek Solutions, Inc. 6200 Capitol Blvd. Ste F Olympia, WA. 98501 Toll Free 1(866)943-0304 Local (360)943-0304 www.clearcreeksolutions.com APPENDIX B MAINTENANCE and OPERATIONS MANUAL APPENDIX C GEOTECHNICAL REPORT Corporate Office: 17522 Bothell Way Northeast, Bothell, WA 98011 Tacoma Office: 708 Broadway Suite #100B Tacoma, WA 98402 Phone 425.415.0551 ♦ Fax 425.415.0311 www.riley-group.com GEOTECHNICAL ENGINEERING REPORT PREPARED BY: THE RILEY GROUP, INC. 17522 BOTHELL WAY NORTHEAST BOTHELL, WASHINGTON 98011 PREPARED FOR: KUSHAL VARMA 4159 NORTHWEST WOODGATE AVENUE PORTLAND, WASHINGTON97229 RGI PROJECT NO.2024-344-1 ROBERTS SHORT PLAT 3XXX TOLEDO AVENUE SOUTHEAST RENTON, WASHINGTON APRIL 16, 2025 Corporate Office: 17522 Bothell Way Northeast, Bothell, WA 98011 Tacoma Office: 708 Broadway Suite #100B Tacoma, WA 98402 Phone 425.415.0551 ♦ Fax 425.415.0311 www.riley-group.com April 16, 2025 Kushal Varma 4159 Northwest Woodgate Avenue Portland, Washington97229 Subject: Geotechnical Engineering Report Roberts Short Plat 3XXX Toledo Avenue Southeast Renton, Washington RGI Project No.2024-344-1 Dear Kushal Varma: As requested, The Riley Group, Inc. (RGI) has performed a Geotechnical Engineering Report (GER) for the Roberts Short Plat located at 3XXX Toledo Avenue Southeast, Renton, Washington. Our services were completed in accordance with our proposal dated November 4, 2024 and authorized by you via email on March 5, 2025. The information in this GER is based on our understanding of the proposed construction, and the soil and groundwater conditions encountered in the test pits completed by RGI at the site on March 24, 2025. RGI recommends that you submit the project plans and specifications to RGI for a general review so that we may confirm that the recommendations in this GER are interpreted and implemented properly in the construction documents. RGI also recommends that a representative of our firm be present on site during portions of the project construction to confirm that the soil and groundwater conditions are consistent with those that form the basis for the engineering recommendations in this GER. If you have any questions or require additional information, please contact us. Respectfully submitted, THE RILEY GROUP, INC. 04/16/2025 04/16/2025 Robert K. Teng, PE Kristina M. Weller, PE Project I Engineer Principal Geotechnical Engineer Geotechnical Engineering Report i April 16, 2025 3XXX Toledo Avenue Southeast, Renton, Washington RGI Project No. 2024-344-1 TABLE OF CONTENTS 1.0 INTRODUCTION ............................................................................................................................... 1 2.0 PROJECT DESCRIPTION ............................................................................................................... 1 3.0 FIELD EXPLORATION AND LABORATORY TESTING .......................................................... 1 3.1 FIELD EXPLORATION ................................................................................................................................... 1 3.2 LABORATORY TESTING ................................................................................................................................ 2 4.0 SITE CONDITIONS ........................................................................................................................... 2 4.1 SURFACE .................................................................................................................................................. 2 4.2 GEOLOGY ................................................................................................................................................. 2 4.3 SOILS ....................................................................................................................................................... 2 4.4 GROUNDWATER ........................................................................................................................................ 3 4.5 SEISMIC CONSIDERATIONS ........................................................................................................................... 3 4.6 GEOLOGIC HAZARD AREAS .......................................................................................................................... 4 5.0 DISCUSSION AND RECOMMENDATIONS ................................................................................. 4 5.1 GEOTECHNICAL CONSIDERATIONS ................................................................................................................. 4 5.2 EARTHWORK ............................................................................................................................................. 4 5.2.1 Erosion and Sediment Control ..................................................................................................... 4 5.2.2 Stripping ....................................................................................................................................... 5 5.2.3 Excavations .................................................................................................................................. 6 5.2.4 Site Preparation ........................................................................................................................... 6 5.2.5 Structural Fill ................................................................................................................................ 7 5.2.6 Cut and Fill Slopes ........................................................................................................................ 9 5.2.7 Wet Weather Construction Considerations ................................................................................. 9 5.3 FOUNDATIONS .......................................................................................................................................... 9 5.4 RETAINING WALLS ................................................................................................................................... 10 5.5 SLAB-ON-GRADE CONSTRUCTION ............................................................................................................... 11 5.6 DRAINAGE .............................................................................................................................................. 11 5.6.1 Surface ....................................................................................................................................... 11 5.6.2 Subsurface .................................................................................................................................. 11 5.6.3 Infiltration .................................................................................................................................. 11 5.6.4 Soil Properties for Groundwater Protection .............................................................................. 12 5.7 UTILITIES ................................................................................................................................................ 13 5.8 PAVEMENTS ............................................................................................................................................ 13 6.0 ADDITIONAL SERVICES .............................................................................................................. 14 7.0 LIMITATIONS ................................................................................................................................. 14 LIST OF FIGURES AND APPENDICES Figure 1 ..................................................................................................................... Site Vicinity Map Figure 2 ............................................................................................... Geotechnical Exploration Plan Figure 3 ............................................................................................... Retaining Wall Drainage Detail Figure 4 ................................................................................................... Typical Footing Drain Detail Appendix A .......................................................................... Field Exploration and Laboratory Testing Geotechnical Engineering Report ii April 16, 2025 3XXX Toledo Avenue Southeast, Renton, Washington RGI Project No. 2024-344-1 Executive Summary This Executive Summary should be used in conjunction with the entire Geotechnical Engineering Report (GER) for design and/or construction purposes. It should be recognized that specific details were not included or fully developed in this section, and the GER must be read in its entirety for a comprehensive understanding of the items contained herein. Section 7.0 should be read for an understanding of limitations. RGI’s geotechnical scope of work included the advancement of 5 test pits and 1 pilot infiltration test to approximate depths of 6 to 9.5 feet below existing site grades. Based on the information obtained from our subsurface exploration, the site is suitable for development of the proposed project. The following geotechnical considerations were identified: Soil Conditions: The soils encountered during field exploration include loose to very dense silty sands with varying amounts of gravel and medium dense to dense sands with trace to some silt. Groundwater: Moderate groundwater seepage was encountered during our subsurface exploration at 4.5 feet during test pit TP-5 Foundations: Foundations for the proposed residences may be supported on conventional spread footings bearing on native soil or structural fill. Slab-on-grade: Slab-on-grade floors and slabs can be supported on native soil or structural fill. Geotechnical Engineering Report 1 April 16, 2025 3XXX Toledo Avenue Southeast, Renton, Washington RGI Project No. 2024-344-1 1.0 Introduction This Geotechnical Engineering Report (GER) presents the results of the geotechnical engineering services provided for the Roberts Short Plat in Renton, Washington. The purpose of this evaluation is to assess subsurface conditions and provide geotechnical recommendations for the construction of a 4-lot residential development with associated roads and stormwater facilities. Our scope of services included field explorations, laboratory testing, engineering analyses, and preparation of this GER. The recommendations in the following sections of this GER are based upon our current understanding of the proposed site development as outlined below. If actual features vary or changes are made, RGI should review them in order to modify our recommendations as required. In addition, RGI requests to review the final design drawings when available to verify that our project understanding is correct and that our recommendations have been properly interpreted and incorporated into the project design. 2.0 Project description The project site is located at 3XXX Toledo Avenue Southeast in Renton, Washington. The approximate location of the site is shown on Figure 1. The site is currently a vacant lot with a one lot pad established in the middle-west of the parcel and a concrete pad in the middle-east part of the parcel. We understand that a 4-lot residential development with associated roads and stormwater facilities will be constructed onsite. At the time of preparing this GER, building plans were not available for our review. Based on our experience with similar construction, RGI anticipates that the proposed building will be supported on perimeter walls with bearing loads of two to four kips per linear foot. Slab- on-grade floor loading of 150 pounds per square foot (psf) are expected. 3.0 Field Exploration and Laboratory Testing 3.1 FIELD EXPLORATION On March 24, 2025, RGI observed the excavation of 5 test pits and 1 pilot infiltration test. The approximate exploration locations are shown on Figure 2. Field logs of each exploration were prepared by the geotechnical engineer that continuously observed the excavation. These logs included visual classifications of the materials encountered during excavation as well as our interpretation of the subsurface conditions between samples. The test pits logs included in Appendix A represent an interpretation of the field logs and include modifications based on laboratory observation and analysis of the samples. Geotechnical Engineering Report 2 April 16, 2025 3XXX Toledo Avenue Southeast, Renton, Washington RGI Project No. 2024-344-1 3.2 LABORATORY TESTING During the field exploration, a representative portion of each recovered sample was sealed in containers and transported to our laboratory for further visual and laboratory examination. Selected samples retrieved from the test pits were tested for moisture content and grain size analysis to aid in soil classification and provide input for the recommendations provided in this GER. The results and descriptions of the laboratory tests are enclosed in Appendix A. 4.0 Site Conditions 4.1 SURFACE The subject site is a rectangular-shaped parcel (1463400052) of land approximately 1.26 acres in size. The site is bound to the north by a construction storage yard, to the east and south by residential property, and to the west by Toledo Avenue Southeast. The existing site is vacant land covered by trees and other vegetation. The site is slopes downhill towards the southwest with an overall elevation difference of approximately 21 feet. 4.2 GEOLOGY Review of the Geologic Map of the Renton quadrangle, King County, Washington, by Mullineaux, D.R. (1993) indicates that the soil in the project vicinity is mapped as Ground moraine deposits (Qgt), which is thin ablation till over lodgment till. Lodgment till is generally compact, coherent, unsorted mixture of sand, silt, clay and gravel, commonly termed hardpan. Layer thickness is typically 5 to 30 feet thick. Ablation till, similar, but much less compact and coherent is typically 2 to 10 feet thick. Mapped nearby is Vashon recessional deposits (Qpa) which is sandy pebble and cobble gravel in easternmost terraces grades to interbedded sand and pebble gravel at Renton and to sand at north edge of quadrangle. These descriptions are generally similar to the findings in our field explorations. 4.3 SOILS The soils encountered during field exploration include loose to very dense silty sands with varying amounts of gravel and medium dense to dense sands with some silt. Fill soils were encountered in test pit, TP-4 extending up to 5 feet below the existing grade. More detailed descriptions of the subsurface conditions encountered are presented in the test pits included in Appendix A. Sieve analysis was performed on two selected soil samples. Grain size distribution curves are included in Appendix A. Geotechnical Engineering Report 3 April 16, 2025 3XXX Toledo Avenue Southeast, Renton, Washington RGI Project No. 2024-344-1 4.4 GROUNDWATER Moderate groundwater seepage was encountered at 4.5 feet during our subsurface exploration in test pit TP-5. The groundwater is perched over the top of the dense glacially compacted layer. Surface water was observed puddling near the vicinity of test pit TP-2. It should be recognized that fluctuations of the groundwater table will occur due to seasonal variations in the amount of rainfall, runoff, and other factors not evident at the time the explorations were performed. In addition, perched water can develop within seams and layers contained in fill soils or higher permeability soils overlying less permeable soils following periods of heavy or prolonged precipitation. Therefore, groundwater levels during construction or at other times in the future may be higher or lower than the levels indicated on the logs. Groundwater level fluctuations should be considered when developing the design and construction plans for the project. 4.5 SEISMIC CONSIDERATIONS Based on the International Building Code (IBC), the seismic parameters below may be used for design in accordance with ASCE 7-16. Additional seismic criteria or updated can be obtained from https://ascehazardtool.org/ or similar sites based on the current edition of IBC and ASCE 7 at the time of building permit submittal. Table 1 IBC Parameter Value Site Soil Class1 D2 Short Period Spectral Response Acceleration, SS (g) 1.37 1-Second Period Spectral Response Acceleration, S1 (g) 0.469 1. Note: In general accordance with Chapter 20 of ASCE 7-16, the Site Class is based on the average characteristics of the upper 100 feet of the subsurface profile. 2. Note: ASCE 7-16 require a site soil profile determination extending to a depth of 100 feet for seismic site classification. The current scope of our services does not include the required 100 foot soil profile determination. Test pits extended to a maximum depth of 9.5 feet, and this seismic site class definition considers that very dense soil continues below the maximum depth of the subsurface exploration. Additional exploration to deeper depths would be required to confirm the conditions below the current depth of exploration. Note: In accordance with ASCE 11.4.8, a ground motion hazard analysis is not required for the following cases: • Structures on Site Class E sites with SS greater than or equal to 1.0, provided the site coefficient Fa is taken as equal to that of Site Class C. • Structures on Site Class D sites with S1 greater than or equal to 0.2, provided that the value of the seismic response coefficient Cs is determined by Eq. 12.8-2 for values of T ≤ 1.5Ts and taken as equal to 1.5 times the value computed in accordance with either Eq. 12.8-3 for TL ≥ T > 1.5Ts or Eq. 12.8-4 for T > TL. • Structures on Site Class E sites with S1 greater than or equal to 0.2, provided that T is less than or equal to Ts and the equivalent static force procedure is used for design. The above exceptions do not apply to seismically isolated structures, structures with damping systems or structures designed using the response history procedures of Chapter 16. Liquefaction is a phenomenon where there is a reduction or complete loss of soil strength due to an increase in water pressure induced by vibrations from a seismic event. Liquefaction mainly affects geologically recent deposits of fine-grained sands that are Geotechnical Engineering Report 4 April 16, 2025 3XXX Toledo Avenue Southeast, Renton, Washington RGI Project No. 2024-344-1 below the groundwater table. Soils of this nature derive their strength from intergranular friction. The generated water pressure or pore pressure essentially separates the soil grains and eliminates this intergranular friction, thus reducing or eliminating the soil’s strength. RGI reviewed the results of the field and laboratory testing and assessed the potential for liquefaction of the site’s soil during an earthquake. Since the site is underlain by glacially consolidated material, RGI considers that the possibility of liquefaction during an earthquake is minimal. 4.6 GEOLOGIC HAZARD AREAS Regulated geologically hazardous areas include erosion, landslide, earthquake, or other geological hazards. Based on the King County iMap and City of Renton GIS data, the site contains a regulated slope between 15 and 25 percent. The mapped regulated slope is part of the northeast corner of the existing pad that was cut and shaped to be lower than the surrounding area. Slopes are approximately 5-6 feet in vertical height and are shaped to roughly a 1H:1V. According to the Critical Areas Regulations under Renton Municipal Code (4-3-050B), the slope does not meet the criteria of being greater than 15 feet in vertical rise, and thus is not considered to be a hazard. 5.0 Discussion and Recommendations 5.1 GEOTECHNICAL CONSIDERATIONS Based on the information obtained from our subsurface exploration and our observations onsite, the site is suitable for the proposed construction from a geotechnical standpoint. Foundations for the proposed residences can be supported on conventional spread footings bearing on native soil or structural fill. Slab-on-grade floors and pavements can be similarly supported. Detailed recommendations regarding the above issues and other geotechnical design considerations are provided in the following sections. These recommendations should be incorporated into the final design drawings and construction specifications. 5.2 EARTHWORK Site earthwork is expected to include cuts and fills to provide lot and roadway grade, installation of underground utilities, and preparation of road and sidewalk grades. After stripping, the existing fill soils encountered in the fill pad should be evaluated for removal. 5.2.1 EROSION AND SEDIMENT CONTROL Potential sources or causes of erosion and sedimentation depend on construction methods, slope length and gradient, amount of soil exposed and/or disturbed, soil type, Geotechnical Engineering Report 5 April 16, 2025 3XXX Toledo Avenue Southeast, Renton, Washington RGI Project No. 2024-344-1 construction sequencing and weather. The impacts on erosion-prone areas can be reduced by implementing an erosion and sedimentation control plan. The plan should be designed in accordance with applicable city and/or county standards. RGI recommends the following erosion control Best Management Practices (BMPs):  Scheduling site preparation and grading for the drier summer and early fall months and undertaking activities that expose soil during periods of little or no rainfall  Retaining existing vegetation whenever feasible  Establishing a quarry spall construction entrance  Installing siltation control fencing or anchored straw or coir wattles on the downhill side of work areas  Covering soil stockpiles with anchored plastic sheeting  Revegetating or mulching exposed soils with a minimum 3-inch thickness of straw if surfaces will be left undisturbed for more than one day during wet weather or one week in dry weather  Directing runoff away from exposed soils and slopes  Minimizing the length and steepness of slopes with exposed soils and cover excavation surfaces with anchored plastic sheeting (Graded and disturbed slopes should be tracked in place with the equipment running perpendicular to the slope contours so that the track marks provide a texture to help resist erosion and channeling. Some sloughing and raveling of slopes with exposed or disturbed soil should be expected.)  Decreasing runoff velocities with check dams, straw bales or coir wattles  Confining sediment to the project site  Inspecting and maintaining erosion and sediment control measures frequently (The contractor should be aware that inspection and maintenance of erosion control BMPs is critical toward their satisfactory performance. Repair and/or replacement of dysfunctional erosion control elements should be anticipated.) Permanent erosion protection should be provided by reestablishing vegetation using hydroseeding and/or landscape planting. Until the permanent erosion protection is established, site monitoring should be performed by qualified personnel to evaluate the effectiveness of the erosion control measures. Provisions for modifications to the erosion control system based on monitoring observations should be included in the erosion and sedimentation control plan. 5.2.2 STRIPPING Stripping efforts should include removal of pavements, vegetation, organic materials, and deleterious debris from areas slated for building, pavement, and utility construction. The test pits encountered 4 to 8 inches of topsoil and rootmass. In test pits TP-2, TP-3 and TP- Geotechnical Engineering Report 6 April 16, 2025 3XXX Toledo Avenue Southeast, Renton, Washington RGI Project No. 2024-344-1 4 about an inch of topsoil was encountered followed by about 11 inches of gravel. Deeper areas of stripping may be required in forested or heavily vegetated areas of the site. The existing single pad lot fills encountered in test pit TP-2 should be evaluated for potential removal. During test pit TP-3, also within the pre-existing pad, a large tree root was discovered 2.5 feet down. Material removed from the existing pad may be unsuitable for re-use if more organics are encountered. 5.2.3 EXCAVATIONS All temporary cut slopes associated with the site and utility excavations should be adequately inclined to prevent sloughing and collapse. The site soils consist of loose to very dense silty sands with varying amounts of gravel and medium dense to dense sands with some silt. Accordingly, for excavations more than 4 feet but less than 20 feet in depth, the temporary side slopes should be laid back with a minimum slope inclination of 1.5H:1V (Horizontal:Vertical). If there is insufficient room to complete the excavations in this manner, or excavations greater than 20 feet in depth are planned, using temporary shoring to support the excavations should be considered. For open cuts at the site, RGI recommends:  No traffic, construction equipment, stockpiles or building supplies are allowed at the top of cut slopes within a distance of at least five feet from the top of the cut  Exposed soil along the slope is protected from surface erosion using waterproof tarps and/or plastic sheeting  Construction activities are scheduled so that the length of time the temporary cut is left open is minimized  Surface water is diverted away from the excavation  The general condition of slopes should be observed periodically by a geotechnical engineer to confirm adequate stability and erosion control measures In all cases, however, appropriate inclinations will depend on the actual soil and groundwater conditions encountered during earthwork. Ultimately, the site contractor must be responsible for maintaining safe excavation slopes that comply with applicable OSHA or WISHA guidelines. 5.2.4 SITE PREPARATION RGI anticipates that some areas of loose or soft soil will be exposed upon completion of stripping and grubbing. Proofrolling and subgrade verification should be considered an essential step in site preparation. After stripping, grubbing, removal of unsuitable fill soils, and prior to placement of structural fill, RGI recommends proofrolling building and pavement subgrades and areas to receive structural fill. These areas should moisture conditioned and compacted to a firm and unyielding condition in order to achieve a Geotechnical Engineering Report 7 April 16, 2025 3XXX Toledo Avenue Southeast, Renton, Washington RGI Project No. 2024-344-1 minimum compaction level of 95 percent of the modified proctor maximum dry density as determined by the American Society of Testing and Materials D1557-09 Standard Test Methods for Laboratory Compaction Characteristics of Soil Using Modified Effort (ASTM D1557). Proofrolling and adequate subgrade compaction can only be achieved when the soils are within approximately ± 2 percent moisture content of the optimum moisture content. Soils which appear firm after stripping and grubbing may be proofrolled with a heavy compactor, loaded double-axle dump truck, or other heavy equipment under the observation of an RGI representative. This observer will assess the subgrade conditions prior to filling. The need for or advisability of proofrolling due to soil moisture conditions should be determined at the time of construction. In wet areas it may be necessary to hand probe the exposed subgrades in lieu of proofrolling with mechanical equipment. If fill is placed in areas of the site where existing slopes are steeper than 5:1 (Horizontal:Vertical), the area should be benched to reduce the potential for slippage between existing slopes and fills. Benches should be wide enough to accommodate compaction and earth moving equipment, and to allow placement of horizontal lifts of fill. Subgrade soils that become disturbed due to elevated moisture conditions should be overexcavated to reveal firm, non-yielding, non-organic soils and backfilled with compacted structural fill. In order to maximize utilization of site soils as structural fill, RGI recommends that the earthwork portion of this project be completed during extended periods of warm and dry weather if possible. If earthwork is completed during the wet season (typically November through May) it will be necessary to take extra precautionary measures to protect subgrade soils. Wet season earthwork will require additional mitigative measures beyond that which would be expected during the drier summer and fall months. 5.2.5 STRUCTURAL FILL Once stripping, clearing and other preparing operations are complete, cuts and fills can be made to establish desired building grades. Prior to placing fill, RGI recommends proof- rolling as described above. RGI recommends fill below the foundation and floor slab, behind retaining walls, and below pavement and hardscape surfaces be placed in accordance with the following recommendations for structural fill. The structural fill should be placed after completion of site preparation procedures as described above. The suitability of excavated site soils and import soils for compacted structural fill use will depend on the gradation and moisture content of the soil when it is placed. As the amount of fines (that portion passing the U.S. No. 200 sieve) increases, soil becomes increasingly sensitive to small changes in moisture content and adequate compaction becomes more Geotechnical Engineering Report 8 April 16, 2025 3XXX Toledo Avenue Southeast, Renton, Washington RGI Project No. 2024-344-1 difficult or impossible to achieve. Soils containing more than about 5 percent fines cannot be consistently compacted to a dense, non-yielding condition when the moisture content is more than 2 percent above or below optimum. Optimum moisture content is that moisture that results in the greatest compacted dry density with a specified compactive effort. Non-organic site soils are only considered suitable for structural fill provided that their moisture content is within about two percent of the optimum moisture level as determined by ASTM D1557. Excavated site soils may not be suitable for re-use as structural fill depending on the moisture content and weather conditions at the time of construction. If soils are stockpiled for future reuse and wet weather is anticipated, the stockpile should be protected with plastic sheeting that is securely anchored. Even during dry weather, moisture conditioning (such as, windrowing and drying) of site soils to be reused as structural fill may be required. Even during the summer, delays in grading can occur due to excessively high moisture conditions of the soils or due to precipitation. If wet weather occurs, the upper wetted portion of the site soils may need to be scarified and allowed to dry prior to further earthwork, or may need to be wasted from the site. If on-site soils are or become unusable, it may become necessary to import clean, granular soils to complete site work that meet the grading requirements listed in Table 2 to be used as structural fill. Table 2 Structural Fill Gradation U.S. Sieve Size Percent Passing 4 inches 100 No. 4 sieve 22 to 100 No. 200 sieve 0 to 5* *Based on minus 3/4 inch fraction. Prior to use, an RGI representative should observe and test all materials imported to the site for use as structural fill. Structural fill materials should be placed in uniform loose layers not exceeding 12 inches and compacted to 95 percent of the maximum dry density. The soil’s maximum density and optimum moisture should be determined by ASTM D1557. Placement and compaction of structural fill should be observed by RGI. A representative number of in-place density tests should be performed as the fill is being placed to confirm that the recommended level of compaction is achieved. Geotechnical Engineering Report 9 April 16, 2025 3XXX Toledo Avenue Southeast, Renton, Washington RGI Project No. 2024-344-1 5.2.6 CUT AND FILL SLOPES All permanent cut and fill slopes should be graded with a finished inclination no greater than 2H:1V. Slopes above modular block walls should not exceed 3H:1V. Upon completion of construction, the slope face should be trackwalked, compacted and vegetated, or provided with other physical means to guard against erosion. All fill placed for slope construction should meet the structural fill requirements as described in Section 5.2.5. Final grades at the top of the slopes must promote surface drainage away from the slope crest. Water must not be allowed to flow in an uncontrolled fashion over the slope face. If it is necessary to direct surface runoff towards the slope, it should be controlled at the top of the slope, piped in a closed conduit installed on the slope face, and taken to an appropriate point of discharge beyond the toe of the slope. 5.2.7 WET WEATHER CONSTRUCTION CONSIDERATIONS RGI recommends that preparation for site grading and construction include procedures intended to drain ponded water, control surface water runoff, and to collect shallow subsurface seepage zones in excavations where encountered. It will not be possible to successfully compact the subgrade or utilize on-site soils as structural fill if accumulated water is not drained prior to grading or if drainage is not controlled during construction. Attempting to grade the site without adequate drainage control measures will reduce the amount of on-site soil effectively available for use, increase the amount of select import fill materials required, and ultimately increase the cost of the earthwork phases of the project. Free water should not be allowed to pond on the subgrade soils. RGI anticipates that the use of berms and shallow drainage ditches, with sumps and pumps in utility trenches, will be required for surface water control during wet weather and/or wet site conditions. 5.3 FOUNDATIONS Following site preparation and grading, the foundations for the proposed residences can be supported on conventional spread footings bearing on native soil or structural fill. Loose, organic, or other unsuitable soils may be encountered in the proposed building footprint. If unsuitable soils are encountered, they should be overexcavated and backfilled with structural fill. If a below grade vault is needed, foundations may be designed for the dense native soils provided the vault is at least 8 feet below grade and founded on the dense native soils. Perimeter foundations exposed to weather should be at a minimum depth of 18 inches below final exterior grades. Interior foundations can be constructed at any convenient depth below the floor slab. Finished grade is defined as the lowest adjacent grade within 5 feet of the foundation for perimeter (or exterior) footings and finished floor level for interior footings. Geotechnical Engineering Report 10 April 16, 2025 3XXX Toledo Avenue Southeast, Renton, Washington RGI Project No. 2024-344-1 Table 3 Foundation Design Design Parameter Value Allowable Bearing Capacity – shallow footings Dense native soils at least 8 feet below grade 2,000 psf1 4,000 psf Friction Coefficient 0.30 Passive pressure (equivalent fluid pressure) 250 pcf2 1. psf = pounds per square foot 2. pcf = pounds per cubic foot The allowable foundation bearing pressures apply to dead loads plus design live load conditions. For short-term loads, such as wind and seismic, a 1/3 increase in this allowable capacity may be used. At perimeter locations, RGI recommends not including the upper 12 inches of soil in the computation of passive pressures because they can be affected by weather or disturbed by future grading activity. The passive pressure value assumes the foundation will be constructed neat against competent soil or backfilled with structural fill as described in Section 5.2.5. The recommended base friction value includes a safety factor of about 1.5. With spread footing foundations designed in accordance with the recommendations in this section, maximum total and differential post-construction settlements of 1 inch and 1/2 inch, respectively, should be expected. 5.4 RETAINING WALLS If retaining walls are needed for the residences or for vaults, RGI recommends cast-in-place concrete walls be used. Modular block walls may be used for grade changes in other areas. The magnitude of earth pressure development on retaining walls will partly depend on the quality of the wall backfill. RGI recommends placing and compacting wall backfill as structural fill. Wall drainage will be needed behind the wall face. A typical retaining wall drainage detail is shown in Figure 3. With wall backfill placed and compacted as recommended, level backfill, and drainage properly installed, RGI recommends using the values in the following table for design. Table 4 Retaining Wall Design Design Parameter Value Active Earth Pressure (unrestrained walls) 35 pcf At-rest Earth Pressure (restrained walls) 50 pcf Geotechnical Engineering Report 11 April 16, 2025 3XXX Toledo Avenue Southeast, Renton, Washington RGI Project No. 2024-344-1 For seismic design, an additional uniform load of 7 times the wall height (H) for unrestrained walls and 14H in psf for restrained walls should be applied to the wall surface. Friction at the base of foundations and passive earth pressure will provide resistance to these lateral loads. Values for these parameters are provided in Section 5.3. 5.5 SLAB-ON-GRADE CONSTRUCTION RGI recommends that the concrete slab be placed on top of medium dense native soil or structural fill. Immediately below the floor slab, RGI recommends placing a four-inch thick capillary break layer of clean, free-draining sand or gravel that has less than five percent passing the U.S. No. 200 sieve. This material will reduce the potential for upward capillary movement of water through the underlying soil and subsequent wetting of the floor slab. Where moisture by vapor transmission is undesirable, an 8- to 10-millimeter thick plastic membrane should be placed on a 4-inch thick layer of clean gravel. 5.6 DRAINAGE 5.6.1 SURFACE Final exterior grades should promote free and positive drainage away from the building area. Water must not be allowed to pond or collect adjacent to foundations or within the immediate building area. For non-pavement locations, RGI recommends providing a minimum drainage gradient of 3 percent for a minimum distance of 10 feet from the building perimeter. In paved locations, a minimum gradient of 1 percent should be provided unless provisions are included for collection and disposal of surface water adjacent to the structure. 5.6.2 SUBSURFACE RGI recommends installing perimeter foundation drains. A typical footing drain detail is shown on Figure 4. The foundation drains and roof downspouts should be tightlined separately to an approved discharge facility. Subsurface drains must be laid with a gradient sufficient to promote positive flow to a controlled point of approved discharge. 5.6.3 INFILTRATION RGI understands that infiltration is being considered for the onsite disposal of water. Field infiltration test TP-1/IT-1 was completed in the southwest corner of the site as shown in Figure 2. The small-scale Pilot Infiltration Test (PIT) was completed at a depth of approximately 3.5 feet below grade and measured 3 feet by 4 feet. The PIT was conducted in the weathered moraine deposit, a red/gray silty sand with some gravel. The infiltration test was conducted in accordance with the 2022 City of Renton Surface Water Design Manual. Geotechnical Engineering Report 12 April 16, 2025 3XXX Toledo Avenue Southeast, Renton, Washington RGI Project No. 2024-344-1 Table 5 Measured Infiltration Rates Test Location Test Depth (feet) Measured Rate (inches/hour) Design Rate (inches/hour) TP-1/IT-1 3.5 3.9 1.56 The measured rates in the above table should have appropriate factors of safety applied prior to use in design. A Total Correction Factor was applied to the field measured infiltration rate as indicated below for infiltration trench facilities less than 4 feet in width. Idesign = Imeasured X Ftesting X Fgeometry X Fplugging = 3.9 X 0.5 X 1 X 0.8 = 1.56 Where: Idesign The design infiltration rate Imeasured The measured infiltration rate Ftesting Accounts for uncertainties in the test method (Large-scale PIT and Small- scale PIT = 0.50) Fgeometry Accounts for the geometry of the planned facility and the depth to the water table or impervious strata. Fgeometry = (4D/W) + 0.05, D = depth from the bottom of the proposed facility to the maximum wet-season water table or nearest impervious layer, whichever is less, and W = width of the facility. Fgeometry = 1 for facilities less than 4 feet in width Fplugging Accounts for reductions in infiltration rates over long term use due to the plugging of soils. Fplugging = 0.8 for fine sands and loamy sands 5.6.4 SOIL PROPERTIES FOR GROUNDWATER PROTECTION A soil sample from the bottom of the infiltration pit (TP-1/IT-1) was submitted to Northwest Agricultural Consultants laboratory for analysis of Cation Exchange Capacity (CEC) and organic content. An infiltration test was also conducted and rate acquired during the exploration. The infiltration rate, CEC, and organic content were used to evaluate the soil properties required for groundwater protection, per Section 5.2.1 of the 2022 City of Renton Surface Water Design Manual. To meet groundwater protection criteria the CEC must be greater than 5 meq/100g and the organic content must be 1.0 percent or greater. Geotechnical Engineering Report 13 April 16, 2025 3XXX Toledo Avenue Southeast, Renton, Washington RGI Project No. 2024-344-1 Table 6 Soil Property Results Sample Cation Exchange Capacity (meq/100g) Organic Content (percent) TP-1/IT-1 8.2 3.77 The soil sample meets the soil property requirements for CEC and organic content for groundwater protection as shown in Table 6. The second criterion, for sites located outside of groundwater protected areas, is the soil to have a measured infiltration rate less than or equal to 9 inches per hour. TP-1/IT- 1 had a measured infiltration rate of 3.9 inches per hour as shown in Table 5 and meets the second soil property criteria. 5.7 UTILITIES Utility pipes should be bedded and backfilled in accordance with American Public Works Association (APWA) specifications. For site utilities located within the right-of-ways, bedding and backfill should be completed in accordance with City of Renton specifications. At a minimum, trench backfill should be placed and compacted as structural fill, as described in Section 5.2.5. Where utilities occur below unimproved areas, the degree of compaction can be reduced to a minimum of 90 percent of the soil’s maximum density as determined by the referenced ASTM D1557. 5.8 PAVEMENTS Pavement subgrades should be prepared as described in Section 5.2 and as discussed below. Regardless of the relative compaction achieved, the subgrade must be firm and relatively unyielding before paving. The subgrade should be proof-rolled with heavy construction equipment to verify this condition. 5.8.1 FLEXIBLE PAVEMENTS With the pavement subgrade prepared as described above, RGI recommends the following pavement sections for parking and drive areas paved with flexible asphalt concrete surfacing.  For drive areas: 3 inches of Hot Mix Asphalt (HMA) over 6 inches of crushed rock base (CRB) 5.8.2 CONCRETE PAVEMENTS With the pavement subgrade prepared as described above, RGI recommends the following pavement sections for parking and drive areas paved with concrete surfacing. Geotechnical Engineering Report 14 April 16, 2025 3XXX Toledo Avenue Southeast, Renton, Washington RGI Project No. 2024-344-1  For concrete pavement areas: 6 inches of concrete for drive areas and 4 inches for sidewalks over 4 inches of CRB The paving materials used should conform to the WSDOT specifications for HMA, concrete paving, and CRB surfacing (9-03.9(3) Crushed Surfacing). Long-term pavement performance will depend on surface drainage. A poorly-drained pavement section will be subject to premature failure as a result of surface water infiltrating into the subgrade soils and reducing their supporting capability. For optimum pavement performance, surface drainage gradients of no less than 2 percent are recommended. Also, some degree of longitudinal and transverse cracking of the pavement surface should be expected over time. Regular maintenance should be planned to seal cracks when they occur. 6.0 Additional Services RGI is available to provide further geotechnical consultation throughout the design phase of the project. RGI should review the final design and specifications in order to verify that earthwork and foundation recommendations have been properly interpreted and incorporated into project design and construction. RGI is also available to provide geotechnical engineering and construction monitoring services during construction. The integrity of the earthwork and construction depends on proper site preparation and procedures. In addition, engineering decisions may arise in the field in the event that variations in subsurface conditions become apparent. Construction monitoring services are not part of this scope of work. If these services are desired, please let us know and we will prepare a cost proposal. 7.0 Limitations This GER is the property of RGI, Kushal Varma, and its designated agents. Within the limits of the scope and budget, this GER was prepared in accordance with generally accepted geotechnical engineering practices in the area at the time this GER was issued. This GER is intended for specific application to the Roberts Short Plat project in Renton, Washington, and for the exclusive use of Kushal Varma and its authorized representatives. No other warranty, expressed or implied, is made. Site safety, excavation support, and dewatering requirements are the responsibility of others. The scope of services for this project does not include either specifically or by implication any environmental or biological (for example, mold, fungi, bacteria) assessment of the site or identification or prevention of pollutants, hazardous materials or conditions. If the owner is concerned about the potential for such contamination or pollution, we can provide a proposal for these services. Geotechnical Engineering Report 15 April 16, 2025 3XXX Toledo Avenue Southeast, Renton, Washington RGI Project No. 2024-344-1 The analyses and recommendations presented in this GER are based upon data obtained from the explorations performed on site. Variations in soil conditions can occur, the nature and extent of which may not become evident until construction. If variations appear evident, RGI should be requested to reevaluate the recommendations in this GER prior to proceeding with construction. It is the client’s responsibility to see that all parties to the project, including the designers, contractors, subcontractors, are made aware of this GER in its entirety. The use of information contained in this GER for bidding purposes should be done at the contractor’s option and risk. USGS, 2023, Maple Valley, Washington USGS, 2023, Renton, Washington 7.5-Minute Quadrangle Approximate Scale: 1"=1000' 0 500 1000 2000 N Site Vicinity Map Figure 1 04/2025 Corporate Office 17522 Bothell Way Northeast Bothell, Washington 98011 Phone: 425.415.0551 Fax: 425.415.0311 Roberts Short Plat RGI Project Number: 2024-344-1 Date Drawn: Address: 3XXX Toledo Avenue Southeast, Renton, Washington 98059 SITE TP-5 TP-3 TP-4 TP-2 TP-1 IT-1 04/2025 Corporate Office 17522 Bothell Way Northeast Bothell, Washington 98011 Phone: 425.415.0551 Fax: 425.415.0311 Roberts Short Plat RGI Project Number: 2024-344-1 Date Drawn: Address: 3XXX Toledo Avenue Southeast, Renton, Washington 98059 Figure 2 Approximate Scale: 1" = 50' 0 25 50 100 N= Test pit locations by RGI, 03/24/2025 = Site boundary Geotechnical Exploration Plan Incliniations) 12" Over the Pipe 3" Below the Pipe Perforated Pipe 4" Diameter PVC Compacted Structural Backfill (Native or Import) 12" min. Filter Fabric Material 12" Minimum Wide Free-Draining Gravel Slope to Drain (See Report for Appropriate Excavated Slope 04/2025 Corporate Office 17522 Bothell Way Northeast Bothell, Washington 98011 Phone: 425.415.0551 Fax: 425.415.0311 Roberts Short Plat RGI Project Number: 2024-344-1 Date Drawn: Address: 3XXX Toledo Avenue Southeast, Renton, Washington 98059 Retaining Wall Drainage Detail Figure 3 Not to Scale Building Slab Structural Backfill Compacted 04/2025 Corporate Office 17522 Bothell Way Northeast Bothell, Washington 98011 Phone: 425.415.0551 Fax: 425.415.0311 Roberts Short Plat RGI Project Number: 2024-344-1 Date Drawn: Address: 3XXX Toledo Avenue Southeast, Renton, Washington 98059 Typical Foundation Drainage Detail Figure 4 Not to Scale Gravel or Crushed Stone with less than 10% passing No. 4 (4.75mm) Sieve 12" Minimum 4" Perforated Pipe (See Report Text) Approved Filter Membrane Material Geotechnical Engineering Report April 16, 2025 3XXX Toledo Avenue Southeast, Renton, Washington RGI Project No. 2024-344-1 APPENDIX A FIELD EXPLORATION AND LABORATORY TESTING On March 24, 2025, RGI observed field explorations using a rubber tracked excavator. We documented subsurface soil conditions at the site by observing the excavation of 5 test pits to a maximum depth of 9.5 feet below existing grade. The test pit locations are shown on Figure 2. The test pit locations were approximately determined by measurements from existing property lines and paved roads. An engineer from our office observed the field exploration and classified the soil conditions encountered, maintained a log of each test exploration, obtained representative soil samples, and observed pertinent site features. All soil samples were visually classified in accordance with the Unified Soil Classification System (USCS). Representative soil samples obtained from the explorations were placed in closed containers and taken to our laboratory for further examination and testing. As a part of the laboratory testing program, the soil samples were classified in our in house laboratory based on visual observation, texture, plasticity, and the limited laboratory testing described below. Moisture Content Determinations Moisture content determinations were performed in accordance with ASTM D2216-10 Standard Test Methods for Laboratory Determination of Water (Moisture) Content of Soil and Rock by Mass (ASTM D2216) on representative samples obtained from the exploration in order to aid in identification and correlation of soil types. The moisture content of typical sample was measured and is reported on the test pits logs. Grain Size Analysis A grain size analysis indicates the range in diameter of soil particles included in a particular sample. Grain size analyses was determined using D6913-04(2009) Standard Test Methods for Particle-Size Distribution (Gradation) of Soils Using Sieve Analysis (ASTM D6913) on two of the samples. Project Name:Roberts Short Plat Project Number:2024-344-1 Client:Kushal Varma Test Pit No.: TP-1/IT-1 Date(s) Excavated:March 24, 2025 Excavation Method:Test Pit Excavator Type:Rubber tracked excavator Groundwater Level:Not Encountered Test Pit Backfill:Cuttings Logged By RT Bucket Size:24 inch Excavating Contractor:Client Provided Sampling Method(s)Grab Location 3XXX Toledo Avenue Southeast, Renton, Washington Surface Conditions:Wood Chips Total Depth of Excavation:6 feet bgs Approximate Surface Elevation Compaction Method Bucket Tamp US C S S y m b o l SM SM SM Pe r c e n t F i n e s , % Gr a p h i c L o g Wa t e r C o n t e n t , % 15% 13% 13% 11% MATERIAL DESCRIPTION 4 inches of wood chips and rootmass Brown/gray silty SAND with some gravel, medium dense, moist (Fill) Red/gray silty SAND with some gravel, medium dense, moist (Weathered moraine deposit) Becomes dense Gray silty SAND with some gravel, very dense, moist (Moraine deposit) Test pit terminated due to very dense soils at 6 feet bgs De p t h ( f e e t ) 0 5 10 Sa m p l e T y p e El e v a t i o n ( f e e t ) Sheet 1 of 1 The Riley Group, Inc. 17522 Bothell Way NE, Bothell, WA 98011 Project Name:Roberts Short Plat Project Number:2024-344-1 Client:Kushal Varma Test Pit No.: TP-2 Date(s) Excavated:March 24, 2025 Excavation Method:Test Pit Excavator Type:Rubber tracked excavator Groundwater Level:Not Encountered Test Pit Backfill:Cuttings Logged By RT Bucket Size:24 inch Excavating Contractor:Client Provided Sampling Method(s)Grab Location 3XXX Toledo Avenue Southeast, Renton, Washington Surface Conditions:Bare Soil Total Depth of Excavation:9.5 feet bgs Approximate Surface Elevation Compaction Method Bucket Tamp US C S S y m b o l SM Topsoil SM SP SM Pe r c e n t F i n e s , % Gr a p h i c L o g Wa t e r C o n t e n t , % 11% 15% 3% 7% MATERIAL DESCRIPTION 12 inches of gravel, topsoil and rootmass Dark gray silty SAND with some gravel, medium dense, moist (Fill) 6 inches of topsoil Brown silty SAND with trace gravel, loose, moist Gray SAND with trace silt, medium dense, moist (Vashon recessional) Gray silty SAND with some gravel, very dense, moist (Moraine deposit) Test pit terminated due to very dense soils at 9.5 feet bgs De p t h ( f e e t ) 0 5 10 Sa m p l e T y p e El e v a t i o n ( f e e t ) Sheet 1 of 1 The Riley Group, Inc. 17522 Bothell Way NE, Bothell, WA 98011 Project Name:Roberts Short Plat Project Number:2024-344-1 Client:Kushal Varma Test Pit No.: TP-3 Date(s) Excavated:March 24, 2025 Excavation Method:Test Pit Excavator Type:Rubber tracked excavator Groundwater Level:Not Encountered Test Pit Backfill:Cuttings Logged By RT Bucket Size:24 inch Excavating Contractor:Client Provided Sampling Method(s)Grab Location 3XXX Toledo Avenue Southeast, Renton, Washington Surface Conditions:Bare Soil Total Depth of Excavation:7 feet bgs Approximate Surface Elevation Compaction Method Bucket Tamp US C S S y m b o l SM SP SM Pe r c e n t F i n e s , % 18.9% Gr a p h i c L o g Wa t e r C o n t e n t , % 10% 11% MATERIAL DESCRIPTION 12 inches of gravel, topsoil and rootmass Red/tan silty SAND with some gravel, medium dense, moist Large tree root for 12 inches Tan SAND with trace silt, medium dense, moist (Vashon recessional) Gray silty SAND with some gravel, very dense, moist (Moraine deposit) Test pit terminated due to very dense soils 7 feet bgs De p t h ( f e e t ) 0 5 10 Sa m p l e T y p e El e v a t i o n ( f e e t ) Sheet 1 of 1 The Riley Group, Inc. 17522 Bothell Way NE, Bothell, WA 98011 Project Name:Roberts Short Plat Project Number:2024-344-1 Client:Kushal Varma Test Pit No.: TP-4 Date(s) Excavated:March 24, 2025 Excavation Method:Test Pit Excavator Type:Rubber tracked excavator Groundwater Level:Not Encountered Test Pit Backfill:Cuttings Logged By RT Bucket Size:24 inch Excavating Contractor:Client Provided Sampling Method(s)Grab Location 3XXX Toledo Avenue Southeast, Renton, Washington Surface Conditions:Pine Needles Total Depth of Excavation:7.5 feet bgs Approximate Surface Elevation Compaction Method Bucket Tamp US C S S y m b o l SM SM SP SM SM Pe r c e n t F i n e s , % Gr a p h i c L o g Wa t e r C o n t e n t , % 10% 6% 11% MATERIAL DESCRIPTION 12 inches of gravel, topsoil and rootmass Brown/gray silty SAND with some gravel, medium dense, moist Red/brown silty SAND, loose, moist Tan SAND with trace silt, medium dense, moist (Vashon recessional) Becomes dense Gray silty SAND with some gravel, very dense, moist (Moraine deposit) Test pit terminated due to very dense soils at 7.5 feet bgs De p t h ( f e e t ) 0 5 10 Sa m p l e T y p e El e v a t i o n ( f e e t ) Sheet 1 of 1 The Riley Group, Inc. 17522 Bothell Way NE, Bothell, WA 98011 Project Name:Roberts Short Plat Project Number:2024-344-1 Client:Kushal Varma Test Pit No.: TP-5 Date(s) Excavated:March 24, 2025 Excavation Method:Test Pit Excavator Type:Rubber tracked excavator Groundwater Level:Not Encountered Test Pit Backfill:Cuttings Logged By RT Bucket Size:24 inch Excavating Contractor:Client Provided Sampling Method(s)Grab Location 3XXX Toledo Avenue Southeast, Renton, Washington Surface Conditions:Bare Soil Total Depth of Excavation:6 feet bgs Approximate Surface Elevation Compaction Method Bucket Tamp US C S S y m b o l Topsoil SM SP SP-SM SM Pe r c e n t F i n e s , % 1.8% Gr a p h i c L o g Wa t e r C o n t e n t , % 10% 12% MATERIAL DESCRIPTION 8 inches of topsoil and rootmass Red/tan silty SAND, loose. moist Tan SAND with trace silt, medium dense, moist (Vashon recessional) Red/gray SAND with some silt and trace gravel, medium dense, moist to wet (Weathered moraine deposit) Gray silty SAND with trace gravel, dense, wet (Moraine deposit) Moderate seepage at 4.5 feet Test pit terminated due to moderate seepage at 6 feet bgs De p t h ( f e e t ) 0 5 10 Sa m p l e T y p e El e v a t i o n ( f e e t ) Sheet 1 of 1 The Riley Group, Inc. 17522 Bothell Way NE, Bothell, WA 98011 Project Name:Roberts Short Plat Project Number:2024-344-1 Client:Kushal Varma Key to Logs US C S S y m b o l Pe r c e n t F i n e s , % Gr a p h i c L o g Wa t e r C o n t e n t , % MATERIAL DESCRIPTIONDe p t h ( f e e t ) Sa m p l e T y p e El e v a t i o n ( f e e t ) 1 2 3 4 5 6 7 8 COLUMN DESCRIPTIONS 1 Elevation (feet): Elevation (MSL, feet). 2 Depth (feet): Depth in feet below the ground surface. 3 Sample Type: Type of soil sample collected at the depth interval shown. 4 USCS Symbol: USCS symbol of the subsurface material. 5 Graphic Log: Graphic depiction of the subsurface material encountered. 6 MATERIAL DESCRIPTION: Description of material encountered. May include consistency, moisture, color, and other descriptive text. 7 Water Content, %: Water content of the soil sample, expressed as percentage of dry weight of sample. 8 Percent Fines, %: The percent fines (soil passing the No. 200 Sieve) in the sample. WA indicates a Wash Sieve, SA indicates a Sieve Analysis. FIELD AND LABORATORY TEST ABBREVIATIONS CHEM: Chemical tests to assess corrosivity COMP: Compaction test CONS: One-dimensional consolidation test LL: Liquid Limit, percent PI: Plasticity Index, percent SA: Sieve analysis (percent passing No. 200 Sieve) UC: Unconfined compressive strength test, Qu, in ksf WA: Wash sieve (percent passing No. 200 Sieve) MATERIAL GRAPHIC SYMBOLS Gravel Artificial Fill Silty SAND (SM) Poorly graded SAND (SP) Poorly graded SAND with Silt (SP-SM) Topsoil TYPICAL SAMPLER GRAPHIC SYMBOLS Auger sampler Bulk Sample 3-inch-OD California w/ brass rings CME Sampler Grab Sample 2.5-inch-OD Modified California w/ brass liners Pitcher Sample 2-inch-OD unlined split spoon (SPT) Shelby Tube (Thin-walled, fixed head) OTHER GRAPHIC SYMBOLS Water level (at time of drilling, ATD) Water level (after waiting, AW) Minor change in material properties within a stratum Inferred/gradational contact between strata ?Queried contact between strata GENERAL NOTES 1: Soil classifications are based on the Unified Soil Classification System. Descriptions and stratum lines are interpretive, and actual lithologic changes may be gradual. Field descriptions may have been modified to reflect results of lab tests. 2: Descriptions on these logs apply only at the specific boring locations and at the time the borings were advanced. They are not warranted to be representative of subsurface conditions at other locations or times. Sheet 1 of 1 The Riley Group, Inc. 17522 Bothell Way NE, Bothell, WA 98011 THE RILEY GROUP, INC. 17522 Bothell Way NE Bothell, WA 98011 PHONE: (425) 415-0551 FAX: (425) 415-0311 GRAIN SIZE ANALYSIS ASTM D421, D422, D1140, D2487, D6913 PROJECT TITLE Roberts Short Plat SAMPLE ID/TYPE TP-3 PROJECT NO.2024-344 SAMPLE DEPTH 4 feet TECH/TEST DATE TW/RT 3/25/2025 DATE RECEIVED 3/24/2025 WATER CONTENT (Delivered Moisture) Total Weight Of Sample Used For Sieve Corrected For Hygroscopic Moisture Wt Wet Soil & Tare (gm) (w1)1096.3 Weight Of Sample (gm)1000.2 Wt Dry Soil & Tare (gm) (w2)1000.2 Tare Weight (gm) 125.2 Weight of Tare (gm) (w3)125.2 (W6) Total Dry Weight (gm) 875.0 Weight of Water (gm) (w4=w1-w2) 96.1 SIEVE ANALYSIS Weight of Dry Soil (gm) (w5=w2-w3) 875.0 Cumulative Moisture Content (%) (w4/w5)*100 11 Wt Ret (Wt-Tare) (%Retained)% PASS +Tare {(wt ret/w6)*100}(100-%ret) % COBBLES 0.0 12.0"125.2 0.00 0.00 100.00 cobbles % C GRAVEL 1.7 3.0"125.2 0.00 0.00 100.00 coarse gravel % F GRAVEL 23.8 2.5" coarse gravel % C SAND 8.1 2.0"125.2 0.00 0.00 100.00 coarse gravel % M SAND 15.7 1.5"125.2 0.00 0.00 100.00 coarse gravel % F SAND 31.7 1.0" coarse gravel % FINES 18.9 0.75"140.5 15.30 1.75 98.25 fine gravel % TOTAL 100.0 0.50" fine gravel 0.375"281.3 156.10 17.84 82.16 fine gravel D10 (mm)#4 348.6 223.40 25.53 74.47 coarse sand D30 (mm)#10 419.9 294.70 33.68 66.32 medium sand D60 (mm)#20 medium sand Cu #40 557.0 431.80 49.35 50.65 fine sand Cc #60 fine sand #100 755.6 630.40 72.05 27.95 fine sand #200 834.5 709.30 81.06 18.94 fines PAN 1000.2 875.00 100.00 0.00 silt/clay DESCRIPTION Silty SAND with some gravel USCS SM Prepared For: Reviewed By: RT Kushal Varma 0 10 20 3040 50 60 7080 90 100 0.0010.010.11101001000 % P A S S I N G Grain size in millimeters 12"3" 2" 1" .75" .375" #4 #10 #20 #40 #60 #100 #200 THE RILEY GROUP, INC. 17522 Bothell Way NE Bothell, WA 98011 PHONE: (425) 415-0551 FAX: (425) 415-0311 GRAIN SIZE ANALYSIS ASTM D421, D422, D1140, D2487, D6913 PROJECT TITLE Roberts Short Plat SAMPLE ID/TYPE TP-5 PROJECT NO.2024-344 SAMPLE DEPTH 2.5 feet TECH/TEST DATE TW/RT 3/25/2025 DATE RECEIVED 3/24/2025 WATER CONTENT (Delivered Moisture) Total Weight Of Sample Used For Sieve Corrected For Hygroscopic Moisture Wt Wet Soil & Tare (gm) (w1)1032.6 Weight Of Sample (gm)935.8 Wt Dry Soil & Tare (gm) (w2)935.8 Tare Weight (gm) 135.4 Weight of Tare (gm) (w3)135.4 (W6) Total Dry Weight (gm) 800.4 Weight of Water (gm) (w4=w1-w2) 96.8 SIEVE ANALYSIS Weight of Dry Soil (gm) (w5=w2-w3) 800.4 Cumulative Moisture Content (%) (w4/w5)*100 12 Wt Ret (Wt-Tare) (%Retained)% PASS +Tare {(wt ret/w6)*100}(100-%ret) % COBBLES 0.0 12.0"135.4 0.00 0.00 100.00 cobbles % C GRAVEL 4.4 3.0"135.4 0.00 0.00 100.00 coarse gravel % F GRAVEL 15.2 2.5" coarse gravel % C SAND 10.6 2.0"135.4 0.00 0.00 100.00 coarse gravel % M SAND 34.2 1.5"135.4 0.00 0.00 100.00 coarse gravel % F SAND 33.8 1.0" coarse gravel % FINES 1.8 0.75"170.3 34.90 4.36 95.64 fine gravel % TOTAL 100.0 0.50" fine gravel 0.375"216.1 80.70 10.08 89.92 fine gravel D10 (mm)0.19 #4 292.3 156.90 19.60 80.40 coarse sand D30 (mm)0.35 #10 376.9 241.50 30.17 69.83 medium sand D60 (mm)1.3 #20 medium sand Cu 6.8 #40 650.8 515.40 64.39 35.61 fine sand Cc 0.5 #60 fine sand #100 896.9 761.50 95.14 4.86 fine sand #200 921.2 785.80 98.18 1.82 fines PAN 935.8 800.40 100.00 0.00 silt/clay DESCRIPTION SAND with some gravel and trace silt USCS SP Prepared For: Reviewed By: RT Kushal Varma 0 10 20 3040 50 60 7080 90 100 0.0010.010.11101001000 % P A S S I N G Grain size in millimeters 12"3" 2" 1" .75" .375" #4 #10 #20 #40 #60 #100 #200 APPENDIX D ARBORIST REPORT LAYTON TREE CONSULTING, LLC It’s all about trees…… PO BOX 572, SNOHOMISH, WA 98291-0572 * 425-220-5711 * bob@laytontreeconsulting.com ARBORIST REPORT/TREE PLAN Roberts Short Plat 137XX 154th Avenue SE – Short Plat King County Parcel 146340-0052 Renton, WA Report Prepared by: Bob Layton Registered Consulting Arborist #670 Certified Arborist #PN-2714A April 15, 2025 Updated February 20, 2026 Arborist Report – 137XX 154th Ave SE Short Plat - Renton Page 2 Layton Tree Consulting LLC April 15, 2025 Updated February 20, 2026 Table of Contents Assignment.................................................................................................................................................... 3 Description .................................................................................................................................................... 3 Methodology ................................................................................................................................................. 3 Judging Condition...................................................................................................................................... 4 Judging Retention Suitability .................................................................................................................... 4 Observations ................................................................................................................................................. 4 Discussion/Recommendations ...................................................................................................................... 5 Tree Protection Guidelines ............................................................................................................................ 5 Tree Density-Tree Replacement ................................................................................................................... 6 Arborist Disclosure Statement ...................................................................................................................... 7 Attachments Photos, pages 8 - 15 Tree Summary Table Tree Locator/Conditions Map – Existing Conditions Tree Plan Map City of Renton - Tree Retention and Credit Worksheet City of Renton Tree List Arborist Report – 137XX 154th Ave SE Short Plat - Renton Page 3 Layton Tree Consulting LLC April 15, 2025 Updated February 20, 2026 Assignment Layton Tree Consulting, LLC was asked to compile an Arborist Report for a parcel in Renton. The subject property is located at 137XX 154th Avenue SE, King County Parcel 146340-0052. The purpose of the report is to satisfy City requirements associated with tree retention regulations for the proposed 4-Lot short plat. My assignment is to prepare a written report on present tree conditions, which is to be submitted to the City with the development application materials. This report covers all of the criteria set forth under the City of Renton’s tree regulations, Municipal Code Section 4-4-130 - Tree Retention and Land Clearing Regulations. Date of Field Examination: April 9, 2025 Description 63 trees of ‘significant’ size were identified and assessed on the subject parcel. A ‘significant’ tree as defined by the City is ‘A tree with a caliper of at least six inches (6"), or an alder or cottonwood tree with a caliper of at least eight inches (8"). Trees qualified as dangerous shall not be considered significant. Trees planted within the most recent ten (10) years shall qualify as significant trees, regardless of the actual caliper’. The subject property is vacant. There is a large elevated pad in the middle of the property where the grade was significantly raised in the past. Trees are primarily located on the east and west portions of the property. These are native species of Douglas fir, and one native bigleaf maple. Trees were identified in the field with a numbered aluminum tag, attached to the lower trunk. These tag numbers correspond with the numbers on the attached Tree Summary Table and attached Tree Plan Map. There are six significant neighboring or off-site trees whose crowns or canopies extend onto the subject property. These trees were assessed and are included in this report. These are all Douglas fir. Methodology Each tree in this report was visited. Tree diameters were measured by tape. The tree heights were measured using a Spiegel Relaskop. Each tree was visually examined for defects and vigor. The tree assessment procedure involves the examination of many factors:  The crown or canopy of the tree is examined for current vigor/health by examining the foliage for appropriate color and density, the vegetative buds for color and size, and the branches for structural form and annual shoot growth; and the overall presence of limb dieback and/or any disease issues.  The trunk or main stem of the tree is inspected for decay, which includes cavities, wounds, fruiting bodies of decay (conks or mushrooms), seams, insect pests, bleeding or exudation of sap, callus development, broken or dead tops, structural defects and unnatural leans. Structural defects can include but are not limited to excessive or unnatural leans, crooks, forks with V-shaped crotches, multiple attachments. Arborist Report – 137XX 154th Ave SE Short Plat - Renton Page 4 Layton Tree Consulting LLC April 15, 2025 Updated February 20, 2026  The root collar and exposed surface roots are inspected for the presence of decay, insect damage, as well as if they have been injured or wounded, undermined or exposed, or the original grade has been altered. Judging Condition The three condition categories are described as follows: Good – free of significant structural defects, no disease concerns, minor pest issues, no significant root issues, good structure/form with uniform crown or canopy, foliage of normal color and density, average or normal vigor, will be wind firm if isolated or left as part of a grouping or grove of trees, suitable for its location Fair – minor to moderate structural defects not expected to contribute to a failure in near future, no disease concerns, moderate pest issues, no significant root issues, asymmetric or unbalanced crown or canopy, average or normal vigor, foliage of normal color, moderate foliage density, will be wind firm if left as part of a grouping or grove of trees, cannot be isolated, suitable for its location Poor – major structural defects expected to cause fail in near future, disease or significant pest concerns, obvious irreversible decline due to old age, disease or pests, not suitable for its location The attached tree plan maps indicate the ‘condition rating’ of the subject trees found at the site. The attached Tree Summary Table provides specific information on tree sizes and condition; and drip-line measurements for trees with a potential for retention. Judging Retention Suitability Not all trees necessarily warrant retention. The three retention suitability categories as described in ANSI A300 Part 5 (Standard Practices for the Management of Trees During Site Planning, Site Development and Construction) are as follows: Good – trees are in good health condition and structural stability and have the potential for longevity at the site Fair – trees are in fair health condition and/or have structural defects that can be mitigated with treatment. These trees may require more intense management and monitoring, and may have shorter life-spans than those in the “good” category. Poor – trees are in poor health condition and have significant defects in structure that cannot be mitigated with treatment. These trees can be expected to decline regardless of management. The species or individual tree may possess characteristics that are incompatible or undesirable in landscape settings or be unsuited for the intended use of the site. Observations Subject trees are found on the east and west side of the property. The middle is open with no tree cover. Species composition is Douglas fir, and one bigleaf maple. Trees are even-aged (all about the same age). These are semi-mature specimens, estimated at around 80 years of age. Arborist Report – 137XX 154th Ave SE Short Plat - Renton Page 5 Layton Tree Consulting LLC April 15, 2025 Updated February 20, 2026 The majority of trees are of good vigor with foliage of normal color and density. The majority have sound trunks with no outward indicators of any internal decay issues. Several have old wounds on the lower trunks where they have been hit by equipment in the past. Some of the trees around the perimeter of the raised pad had fills soils placed over their roots many years ago. This does not appear to have had adverse effects on tree health. Tree #62 has an incipient infection of Schweinitizii root and butt rot. This is evident by the presence of fruiting body of the fungus near the base of the tree. Condition is rated as ‘fair-to-poor’. Only three trees were found to be in ‘poor’ condition. These include Trees #12, #15 and #39. Trees #12 and #15 are smaller, suppressed specimens. These have developed poor structural form and are susceptible to failure. Tree #39 has an advanced infection of Porodaedalea pini, red ring rot. This is evident by the presence of multiple fruiting bodies(conks) of the white rot fungus on the lower and mid- trunk. It is susceptible to failure. One tree has recently died, Tree #20. The cause of mortality is unknown. Neighboring/Off-site Trees Trees #101 > #106 are also all Douglas fir. These are similar in size and condition as compared to subject property trees. No concerning issues were observed from the subject property side. Tree conditions range from ‘fair’ to ‘good’. Discussion/Recommendations The proposal is to retain trees on the site perimeter that will not be significantly impacted by the construction of future homes. These are well-positioned for successful retention. See the attached Tree Plan Map. The attached Tree Plan Map indicates the driplines of retained and protected off-site trees, and the recommended location of a tree protection barrier. Position the tree protection barrier a few feet beyond the driplines for optimal protection as shown on the attached map. The cut stumps of removed trees in proximity to tree protection areas shall be grinded down to grade and not pulled to protect the roots of nearby trees. This applies to Trees #58 and #41. Neighboring or off-site trees are not expected to be impacted by the proposal. No work is proposed within a proximity of them. Position a tree protection barrier at +/- 6- feet off the north property line to appropriately protect off-site Trees #101 and #102. The removal of trees from the property is not expected to have adverse effects on trees to remain at the site. Tree Protection Guidelines Tree protection fencing shall be positioned around any retained trees or off-site protected trees prior to site demolition or bringing any heavy equipment onto the site. This will help to define clearing limits and protect soils and surface roots. Existing grades within the fenced areas shall not be altered. Position fencing as shown on the attached tree plan map. Arborist Report – 137XX 154th Ave SE Short Plat - Renton Page 6 Layton Tree Consulting LLC April 15, 2025 Updated February 20, 2026 Any excavation within the driplines of retained trees and/or the neighboring trees shall be monitored by the project arborist so necessary precautions can be taken to minimize overall impacts. Any roots that are damaged outside of the fenced protection area shall be pruned clean at sound tissue prior to backfilling or finishing areas. Sound tissue is where the root is undamaged and the bark is completely intact with the root. This will help roots to seal off potential decay and allow them to sprout new growth. Any disturbed areas at the outer edge of the protection area shall be watered weekly during the dry season of June through September. This will help to create a favorable environment for new root growth and reduce the overall stress associated with root loss and disturbance. Simply finish the landscape within the driplines of retained trees by cutting/hand-pulling any unwanted vegetation and applying a 2 to 4-inch covering of organic mulch/beauty bark. Retain any existing native shrubs. Keep large plantings, irrigation trenches and the construction of hardscapes outside of the driplines of retained trees. Tree Density-Tree Replacement RMC 4-4-130 H. 1. Protected Trees – Retention Required: a. Minimum Tree Retention Requirements: Properties subject to an active land development permit shall retain a minimum of thirty percent (30%) of all significant trees on site. The subject site requires the retention of 30% of significant trees. There are 59 viable significant trees on the property, requiring the retention of 18 trees. Based on the proposed site layout, there are 17 trees that can be feasibly retained. These are well- position for successful retention on the site perimeters. All of these are classified as Priority One trees under Renton’s tree code section. Tree credits to be retained (160) far exceed the required minimum for the property (38). See the attached Tree Retention and Credit Worksheet. No supplemental trees are required to meet the required minimum of 30 tree credits per acre of net buildable area, however; since only 17 trees can be retained, the 18th tree will require replacement. The planting of 12 tree credits is required, see page 3 of the worksheet. This can be achieved by the planting of 12 medium sized trees, or a combination of small, medium and large trees to attain the required credits. Species can be selected from the City’s tree list, also attached. Arborist Report – 137XX 154th Ave SE Short Plat - Renton Page 7 Layton Tree Consulting LLC April 15, 2025 Updated February 20, 2026 Arborist Disclosure Statement Arborists are tree specialists who use their education, knowledge, training and experience to examine and assess trees, recommend measures to enhance the beauty and health of trees, and attempt to reduce the risks associated with living near trees. Clients may choose to accept or disregard the recommendations of the arborist, or to seek additional advice. Arborists cannot detect every condition that could possibly lead to the structural failure of a tree. Trees are living organisms that grow, respond to their environment, mature, decline and sometimes fail in ways we do not fully understand. Conditions are often hidden within trees and below ground. Arborists cannot guarantee that a tree will be healthy and/or safe under all circumstances, or for a specified period of time. Likewise, remedial treatments, like any medicine, cannot be guaranteed. Treatment, pruning and removal of trees may involve considerations beyond the scope of the arborist’s services such as property boundaries, property ownership, site lines, disputes between neighbors, and other issues. Arborists cannot take such considerations into account unless complete and accurate information is disclosed to the arborist. An arborist should then be expected to reasonably rely upon the completeness and accuracy of the information provided. Trees can be managed, but they cannot be controlled. To live near trees is to accept some degree of risk. The only way to eliminate all risk associated with trees is to eliminate all trees. Arborist Report – 137XX 154th Ave SE Short Plat - Renton Page 8 Layton Tree Consulting LLC April 15, 2025 Updated February 20, 2026 Photo Documentation Looking east down north perimeter of property Trees #1 > #5 on west perimeter Arborist Report – 137XX 154th Ave SE Short Plat - Renton Page 9 Layton Tree Consulting LLC April 15, 2025 Updated February 20, 2026 Trees #6 > #10 on west perimeter Trees #6 > #10 on west perimeter Arborist Report – 137XX 154th Ave SE Short Plat - Renton Page 10 Layton Tree Consulting LLC April 15, 2025 Updated February 20, 2026 Upper crowns of trees pictured above Looking west down south perimeter, Tree #28 in foreground Arborist Report – 137XX 154th Ave SE Short Plat - Renton Page 11 Layton Tree Consulting LLC April 15, 2025 Updated February 20, 2026 Trees on west side of property Upper crowns of trees pictured above Arborist Report – 137XX 154th Ave SE Short Plat - Renton Page 12 Layton Tree Consulting LLC April 15, 2025 Updated February 20, 2026 Looking west down south property line, Tree #26 closest to fence Trees on east side of property Arborist Report – 137XX 154th Ave SE Short Plat - Renton Page 13 Layton Tree Consulting LLC April 15, 2025 Updated February 20, 2026 Trees #35 and #36 on south perimeter The lower to mid-trunk of #39 covered with pini conks Arborist Report – 137XX 154th Ave SE Short Plat - Renton Page 14 Layton Tree Consulting LLC April 15, 2025 Updated February 20, 2026 Trees #52, #53 and #54 on north perimeter, fire pit near trees Base of Tree #62, has incipient Schweinitizii infection Arborist Report – 137XX 154th Ave SE Short Plat - Renton Page 15 Layton Tree Consulting LLC April 15, 2025 Updated February 20, 2026 Looking south down east property line, Trees #63 and #105 in foreground Looking north down east property line, Tree #106 in foreground-right Layton Tree Consulting LLC For:Roberts Short Plat Site:137XX 154th AVE SE - Renton Tree Summary Table Date: Average Tree/DBH Height Dripline Retention Tag #Species (inches)(feet)Radius Condition Suitability Comments Proposal 1 Douglas fir 16 72 10 Fair CBC old broken top,foliage somewhat sparse Remove 2 Douglas fir 23 120 14 Good CBC natural, self corrected lean north Remove 3 Douglas fir 24 125 12 Fair-Good CBC foliage somewhat sparse Remove 4 Douglas fir 26 125 12 Good CBC good form and vigor Remove 5 Douglas fir 36 112 16 Good CBC old broken top,good vigor Remove 6 bigleaf maple 23 56 16 Fair-Good CBC somewhat suppressed by firs Remove 7 Douglas fir 40 115 16 Good CBC good form and vigor Remove 8 Douglas fir 31 105 12 Good CBC good form and vigor Remove 9 Douglas fir 11 50 8 Fair CBC somewhat suppressed, decent vigor Remove 10 Douglas fir 31 120 16 Good CBC good form and vigor Remove 11 Douglas fir 18 85 10 Good CBC natural, self corrected lean north Remove 12 Douglas fir 13 30 x Poor Poor suppressed, dead top,decay column Remove 13 Douglas fir 27 115 12 Good CBC good form and vigor Remove 14 Douglas fir 17 65 12 Fair CBC old broken top,foliage somewhat sparse Remove 15 Douglas fir 9 50 x Poor Poor bent top,poor stem taper Remove 16 Douglas fir 32 125 14 Good CBC good form and vigor Remove 17 Douglas fir 25 125 14 Fair CBC sparse top foliage Remove 18 Douglas fir 16 85 10 Fair-Good CBC old broken top,good vigor Remove 19 Douglas fir 30 135 14 Fair CBC foliage somewhat sparse Remove 20 Douglas fir 26 125 x Dead Poor recent dead Remove 21 Douglas fir 22 60 14 Fair CBC old broken top,foliage somewhat sparse, ivy on trunk Remove 22 Douglas fir 18 65 14 Good CBC good form and vigor Remove 23 Douglas fir 33 115 16 Good CBC old broken top,good vigor Remove 24 Douglas fir 26 110 14 Fair-Good CBC top foliage somewhat sparse Remove 25 Douglas fir 33 120 16 Fair-Good CBC asymmetric crown SW,crook in top Remove 26 Douglas fir 23 70 14 Good Good asymmetric crown south, overtopped,good vigor Retain 27 Douglas fir 37 125 14 Good Good asymmetric crown south, good form and vigor Retain 28 Douglas fir 29 118 12 Fair-Good Good top foliage somewhat sparse Retain 29 Douglas fir 28 90 14 Good CBC good form and vigor Remove 30 Douglas fir 27 110 12 Good CBC good form and vigor Remove 31 Douglas fir 32 120 14 Fair-Good Fair top foliage somewhat sparse, asymmetric crown south Retain 32 Douglas fir 22 90 12 Fair-Good Fair old buttress root damage Retain 33 Douglas fir 32 130 16 Fair Fair sparse foliage Retain 34 Douglas fir 26 105 14 Good Good old broken top,good vigor Retain 35 Douglas fir 33 130 16 Fair-Good Fair asymmetric crown south, old root damage Retain 36 Douglas fir 21 100 12 Fair-Good Good old broken top,good vigor Retain 37 Douglas fir 19 80 12 Fair Fair old broken top,decent vigor Retain 38 Douglas fir 27 125 14 Good Good good form and vigor Retain 39 Douglas fir 17 95 x Poor CBC advanced pini infection, sparse foliage Remove 40 Douglas fir 17 75 12 Fair Fair somewhat suppressed, decent vigor Retain 41 Douglas fir 28 120 14 Good CBC good form and vigor Remove 42 Douglas fir 28 115 14 Good CBC good form and vigor Remove 43 Douglas fir 21 85 14 Good CBC good form and vigor Remove 44 Douglas fir 21 80 12 Fair CBC unusual lean south, crooked top Remove 45 Douglas fir 22 100 12 Good CBC old broken top,good vigor Remove 46 Douglas fir 25 120 14 Good CBC good form and vigor Remove 47 Douglas fir 20 95 12 Fair-Good CBC old trunk wound Remove 48 Douglas fir 19 80 10 Fair-Good CBC somewhat suppressed, good vigor Remove 49 Douglas fir 23 90 12 Fair CBC large old trunk wound ,old broken top Remove 50 Douglas fir 30 125 16 Good CBC good form and vigor Remove 51 Douglas fir 22 95 12 Good CBC old broken top,good vigor Remove 52 Douglas fir 28 125 14 Good CBC good form and vigor Remove 53 Douglas fir 34 125 16 Good CBC good form and vigor Remove 54 Douglas fir 28 120 14 Good CBC good form and vigor Remove 55 Douglas fir 17 100 10 Fair-Good CBC decent form,good vigor Remove 56 Douglas fir 23 110 14 Good CBC good form and vigor Remove 57 Douglas fir 24 120 14 Fair-Good CBC old trunk wound Remove 58 Douglas fir 17 60 12 Fair-Good CBC somewhat suppressed, good vigor Remove 4/9/2025 Layton Tree Consulting LLC For:Roberts Short Plat Site:137XX 154th AVE SE - Renton Tree Summary Table Date: Average Tree/DBH Height Dripline Retention Tag #Species (inches)(feet)Radius Condition Suitability Comments Proposal 4/9/2025 59 Douglas fir 28 115 14 Fair-Good Good recent trunk wound, good vigor Retain 60 Douglas fir 14 70 10 Fair Fair crooked top,foliage somewhat sparse, old trunk wound Retain 61 Douglas fir 16 75 12 Fair Fair crooked top,foliage somewhat sparse Retain 62 Douglas fir 22 110 10 Fair-Poor Fair schw infection, slight lean west Retain 63 Douglas fir 24 100 14 Good Good good form and vigor Retain Neighboring/Off-site Trees 101 Douglas fir 26 110 12 Good Good no concerns Protect 102 Douglas fir 18 100 10 Fair Fair sparse foliage Protect 103 Douglas fir 28 115 14 Good Good good form and vigor Protect 104 Douglas fir 12 60 8 Fair Fair suppressed, small live crown Protect 105 Douglas fir 14 65 8 Fair Fair somewhat suppressed, decent vigor Protect 106 Douglas fir 18 75 12 Good Good asymmetric crown south, good vigor Protect Dripline measurements from face of trunk CBC - Compromised by Construction rentonwa.gov/permitcenter | planningcustomerservice@rentonwa.gov | 425-430-7294 10/6/2022 Page 1 of 3 CITY OF RENTON Ι PERMIT CENTER TREE RETENTION AND CREDIT WORKSHEET TREE RETENTION REQUIREMENTS A minimum retention of thirty percent (30%) of all significant trees (as defined in RMC 4-11-200) is required on site. Please complete the form below to verify compliance with minimum tree retention requirements. • Identify total number of trees 6-inch caliper or greater (or alder or cottonwood trees 8-inch caliper or greater) on site: Trees Trees Trees Trees Trees Trees Required Trees Proposed •Deductions – Certain trees are excluded from the retention calculation: o Trees that are high-risk, as defined in RMC 4-11-200: o Trees within existing and proposed public right-of-way: o Trees within wetlands, streams, very high landslide hazards, protected slopes, and associated buffers: •Total remaining trees after deductions: •Required tree retention (30%): •Identify number of trees proposed for retention: •Identify number of trees requested for replacement in lieu of retention (skip page 3 if no tree replacement is requested):Trees TREE CREDIT REQUIREMENTS Tree credit requirements apply at a minimum rate of thirty (30) credits per net acre. Complete the form below to determine minimum tree credit requirements. •Gross area of property in square feet: Square Feet •Deductions: Certain areas are excluded from tree credit calculation: o Existing and proposed public right-of-way: Square Feet o Wetlands, streams, very high landslide hazards, protected slopes, and associated buffers: Square Feet •Total excluded area:Square Feet •Net land area (after deductions) in square feet:Square Feet •Net land area (after deductions) in acres:Acres •Required tree credits:Tree Credits Required rentonwa.gov/permitcenter | planningcustomerservice@rentonwa.gov | 425-430-7294 10/6/2022 Page 2 of 3 TREE RETENTION AND CREDIT WORKSHEET PROPOSED TREE CREDITS Please complete the table below to calculate the total tree credits proposed for your project. Identify the quantity of trees for each tree category, after deducting trees within excluded areas, as shown in the previous section. TREE SIZE TREE CREDITS TREE QUANTITY TOTAL TREE CREDITS RETAINED TREES Preserved tree 6 – 9” caliper 4 Preserved tree 10 – 12” caliper 5 Preserved tree 12 – 15” caliper 6 Preserved tree 16 – 18” caliper 7 Preserved tree 19 – 21” caliper 8 Preserved tree 22 – 24” caliper 9 Preserved tree 25 – 28” caliper 10 Preserved tree 29 – 32” caliper 11 Preserved tree 33 – 36” caliper 12 Preserved tree 37” caliper and greater 13 NEW TREES New small species tree (30' or less at maturity) 0.25 New medium species tree (30' to 50' at maturity) 1 New large species tree (50' or more at maturity) 2 TREE CREDITS PROPOSED: rentonwa.gov/permitcenter | planningcustomerservice@rentonwa.gov | 425-430-7294 10/6/2022 Page 3 of 3 TREE RETENTION AND CREDIT WORKSHEET TREE REPLACEMENT JUSTIFICATION Replacement may be authorized as an alternative to 30% retention provided the removal is the minimum necessary to accomplish the desired purpose and provided the proposal meets one of the following options: a. There are special circumstances related to the size, shape, topography, location, or surroundings of the subject property; or b. The strict application of the code would prevent reasonable use of property; or c. The strict application of the code would prevent compliance with minimum density requirements of the zone; or d. The project is a short plat with four (4) or fewer lots. Please attach a written justification demonstrating compliance with the requirements and criteria as descripted above. TREE REPLACEMENT QUANTITY Tree replacement quantity is determined based on the credit value of the trees proposed for removal. Larger, higher priority trees shall be used for calculation of tree replacement. Identify the quantity of each tree requested to be removed in lieu of 30% retention, based on tree size. List the identification number of each tree, as indicated in the arborist report. TREE SIZE TREE CREDITS TREE QUANTITY TREE INDENTIFICATION # TOTAL TREE CREDITS Tree 37” caliper + 13 Tree 33 – 36” caliper 12 Tree 29 – 32” caliper 11 Tree 25 – 28” caliper 10 Tree 22 – 24” caliper 9 Tree 19 – 21” caliper 8 Tree 16 – 18” caliper 7 Tree 12 – 15” caliper 6 Tree 10 – 12” caliper 5 Tree 6 – 9” caliper 4 REPLACEMENT CREDITS REQUIRED: TREE REPLACEMENT PLANTING Identify the quantity of proposed new replacement trees (minimum size of 2-inch caliper). The total replacement credits proposed should be equal to or greater than the replacement credits required, as shown in the previous section. TREE SIZE TREE CREDITS TREE QUANTITY TOTAL TREE CREDITS New small species tree (30' or less at maturity) 0.25 New medium species tree (30' to 50' at maturity) 1 New large species tree (50' or more at maturity) 2 REPLACEMENT CREDITS PROPOSED: APPENDIX E WATER QUALITY RELATED WWHM ANALYSIS WWHM2012 PROJECT REPORT Roberts Water Quality Onsite 2/28/2026 1:06:36 PM Page 2 General Model Information WWHM2012 Project Name:Roberts Water Quality Onsite Site Name:Roberts Short Plat Site Address:154th Ave SE City:Renton Report Date:2/28/2026 Gage:Seatac Data Start:1948/10/01 Data End:2009/09/30 Timestep:15 Minute Precip Scale:1.000 Version Date:2025/05/13 Version:4.3.2 POC Thresholds Low Flow Threshold for POC1:50 Percent of the 2 Year High Flow Threshold for POC1:50 Year Low Flow Threshold for POC2:50 Percent of the 2 Year High Flow Threshold for POC2:50 Year Low Flow Threshold for POC3:50 Percent of the 2 Year High Flow Threshold for POC3:50 Year Roberts Water Quality Onsite 2/28/2026 1:06:36 PM Page 3 Landuse Basin Data Predeveloped Land Use Basin 1 Bypass:No GroundWater:No Pervious Land Use acre C, Forest, Mod 0.275 Pervious Total 0.275 Impervious Land Use acre Impervious Total 0 Basin Total 0.275 Element Flow Componants: Surface Interflow Groundwater Componant Flows To: POC 1 POC 1 Roberts Water Quality Onsite 2/28/2026 1:06:36 PM Page 4 Basin 2 Bypass:No GroundWater:No Pervious Land Use acre C, Forest, Mod 1.042 Pervious Total 1.042 Impervious Land Use acre Impervious Total 0 Basin Total 1.042 Element Flow Componants: Surface Interflow Groundwater Componant Flows To: POC 2 POC 2 Roberts Water Quality Onsite 2/28/2026 1:06:36 PM Page 5 Basin 3 Bypass:No GroundWater:No Pervious Land Use acre C, Forest, Flat 0.116 Pervious Total 0.116 Impervious Land Use acre Impervious Total 0 Basin Total 0.116 Element Flow Componants: Surface Interflow Groundwater Componant Flows To: POC 3 POC 3 Roberts Water Quality Onsite 2/28/2026 1:06:36 PM Page 6 Mitigated Land Use Basin 1 Bypass:No GroundWater:No Pervious Land Use acre Pervious Total 0 Impervious Land Use acre ROOF TOPS FLAT 0.275 Impervious Total 0.275 Basin Total 0.275 Element Flow Componants: Surface Interflow Groundwater Componant Flows To: Gravel Trench Bed 1 Gravel Trench Bed 1 Roberts Water Quality Onsite 2/28/2026 1:06:36 PM Page 7 Basin 2 Bypass:No GroundWater:No Pervious Land Use acre C, Lawn, Flat 0.83 Pervious Total 0.83 Impervious Land Use acre ROADS MOD 0.148 DRIVEWAYS FLAT 0.051 Impervious Total 0.199 Basin Total 1.029 Element Flow Componants: Surface Interflow Groundwater Componant Flows To: StormTech 2 StormTech 2 Roberts Water Quality Onsite 2/28/2026 1:06:36 PM Page 8 Basin 3 Bypass:No GroundWater:No Pervious Land Use acre Pervious Total 0 Impervious Land Use acre ROADS FLAT 0.055 SIDEWALKS FLAT 0.017 Impervious Total 0.072 Basin Total 0.072 Element Flow Componants: Surface Interflow Groundwater Componant Flows To: Surface retention 1 Surface retention 1 Roberts Water Quality Onsite 2/28/2026 1:06:36 PM Page 9 Routing Elements Predeveloped Routing Roberts Water Quality Onsite 2/28/2026 1:06:36 PM Page 10 Mitigated Routing Gravel Trench Bed 1 Bottom Length:240.00 ft. Bottom Width:5.60 ft. Trench bottom slope 1:0 To 1 Trench Left side slope 0:0 To 1 Trench right side slope 2:0 To 1 Material thickness of first layer:1 Pour Space of material for first layer:0.33 Material thickness of second layer:1 Pour Space of material for second layer:0.33 Material thickness of third layer:1 Pour Space of material for third layer:0.33 Infiltration On Infiltration rate:1.56 Infiltration safety factor:1 Wetted surface area On Total Volume Infiltrated (ac-ft.):43.147 Total Volume Through Riser (ac-ft.):0.002 Total Volume Through Facility (ac-ft.):43.149 Percent Infiltrated:100 Total Precip Applied to Facility:0 Total Evap From Facility:0 Discharge Structure Riser Height:3.5 ft. Riser Diameter:6 in. Orifice 1 Diameter:0.500 in.Elevation:3 ft. Element Outlets: Outlet 1 Outlet 2 Outlet Flows To: Gravel Trench Bed Hydraulic Table Stage(feet)Area(ac.)Volume(ac-ft.)Discharge(cfs)Infilt(cfs) 0.0000 0.030 0.000 0.000 0.000 0.0444 0.030 0.000 0.000 0.048 0.0889 0.030 0.000 0.000 0.048 0.1333 0.030 0.001 0.000 0.048 0.1778 0.030 0.001 0.000 0.048 0.2222 0.030 0.002 0.000 0.048 0.2667 0.030 0.002 0.000 0.048 0.3111 0.030 0.003 0.000 0.048 0.3556 0.030 0.003 0.000 0.048 0.4000 0.030 0.004 0.000 0.048 0.4444 0.030 0.004 0.000 0.048 0.4889 0.030 0.005 0.000 0.048 0.5333 0.030 0.005 0.000 0.048 0.5778 0.030 0.005 0.000 0.048 0.6222 0.030 0.006 0.000 0.048 0.6667 0.030 0.006 0.000 0.048 0.7111 0.030 0.007 0.000 0.048 0.7556 0.030 0.007 0.000 0.048 0.8000 0.030 0.008 0.000 0.048 0.8444 0.030 0.008 0.000 0.048 0.8889 0.030 0.009 0.000 0.048 Roberts Water Quality Onsite 2/28/2026 1:06:36 PM Page 11 0.9333 0.030 0.009 0.000 0.048 0.9778 0.030 0.010 0.000 0.048 1.0222 0.030 0.010 0.000 0.048 1.0667 0.030 0.010 0.000 0.048 1.1111 0.030 0.011 0.000 0.048 1.1556 0.030 0.011 0.000 0.048 1.2000 0.030 0.012 0.000 0.048 1.2444 0.030 0.012 0.000 0.048 1.2889 0.030 0.013 0.000 0.048 1.3333 0.030 0.013 0.000 0.048 1.3778 0.030 0.014 0.000 0.048 1.4222 0.030 0.014 0.000 0.048 1.4667 0.030 0.014 0.000 0.048 1.5111 0.030 0.015 0.000 0.048 1.5556 0.030 0.015 0.000 0.048 1.6000 0.030 0.016 0.000 0.048 1.6444 0.030 0.016 0.000 0.048 1.6889 0.030 0.017 0.000 0.048 1.7333 0.030 0.017 0.000 0.048 1.7778 0.030 0.018 0.000 0.048 1.8222 0.030 0.018 0.000 0.048 1.8667 0.030 0.019 0.000 0.048 1.9111 0.030 0.019 0.000 0.048 1.9556 0.030 0.019 0.000 0.048 2.0000 0.030 0.020 0.000 0.048 2.0444 0.030 0.020 0.000 0.048 2.0889 0.030 0.021 0.000 0.048 2.1333 0.030 0.021 0.000 0.048 2.1778 0.030 0.022 0.000 0.048 2.2222 0.030 0.022 0.000 0.048 2.2667 0.030 0.023 0.000 0.048 2.3111 0.030 0.023 0.000 0.048 2.3556 0.030 0.024 0.000 0.048 2.4000 0.030 0.024 0.000 0.048 2.4444 0.030 0.024 0.000 0.048 2.4889 0.030 0.025 0.000 0.048 2.5333 0.030 0.025 0.000 0.048 2.5778 0.030 0.026 0.000 0.048 2.6222 0.030 0.026 0.000 0.048 2.6667 0.030 0.027 0.000 0.048 2.7111 0.030 0.027 0.000 0.048 2.7556 0.030 0.028 0.000 0.048 2.8000 0.030 0.028 0.000 0.048 2.8444 0.030 0.029 0.000 0.048 2.8889 0.030 0.029 0.000 0.048 2.9333 0.030 0.029 0.000 0.048 2.9778 0.030 0.030 0.000 0.048 3.0222 0.030 0.031 0.001 0.048 3.0667 0.030 0.033 0.001 0.048 3.1111 0.030 0.034 0.002 0.048 3.1556 0.030 0.035 0.002 0.048 3.2000 0.030 0.037 0.003 0.048 3.2444 0.030 0.038 0.003 0.048 3.2889 0.030 0.039 0.003 0.048 3.3333 0.030 0.041 0.003 0.048 3.3778 0.030 0.042 0.004 0.048 3.4222 0.030 0.044 0.004 0.048 3.4667 0.030 0.045 0.004 0.048 Roberts Water Quality Onsite 2/28/2026 1:06:36 PM Page 12 3.5111 0.030 0.046 0.011 0.048 3.5556 0.030 0.048 0.074 0.048 3.6000 0.030 0.049 0.165 0.048 3.6444 0.030 0.050 0.261 0.048 3.6889 0.030 0.052 0.337 0.048 3.7333 0.030 0.053 0.383 0.048 3.7778 0.030 0.055 0.421 0.048 3.8222 0.030 0.056 0.453 0.048 3.8667 0.030 0.057 0.483 0.048 3.9111 0.030 0.059 0.511 0.048 3.9556 0.030 0.060 0.538 0.048 4.0000 0.030 0.061 0.563 0.048 Roberts Water Quality Onsite 2/28/2026 1:06:36 PM Page 13 StormTech 2 Chamber Model:740 Dimensions Max Row Length:110 Number of Chambers:28 Number of Endcaps:4 Top Stone Depth:12 Bottom Stone Depth:6 Infiltration On Infiltration rate:1.56 Infiltration safety factor:1 Wetted surface area On Total Volume Infiltrated (ac-ft.):94.152 Total Volume Through Riser (ac-ft.):3.271 Total Volume Through Facility (ac-ft.):97.423 Percent Infiltrated:96.64 Total Precip Applied to Facility:0 Total Evap From Facility:0 Discharge Structure Riser Height:2.5 ft. Riser Diameter:6 in. Orifice 1 Diameter:1.500 in.Elevation:0.15 ft. Orifice 2 Diameter:0.750 in.Elevation:0.75 ft. Orifice 3 Diameter:0.750 in.Elevation:2 ft. Element Flow Outlets: Outlet 1 Outlet 2 Outlets Flow To: StormTech Hydraulic Table Stage(feet)Area(ac.)Volume(ac-ft.)Discharge(cfs)Infilt(cfs) 0.0000 0.021 0.000 0.000 0.000 0.0833 0.023 0.000 0.000 0.036 0.1667 0.023 0.001 0.007 0.036 0.2500 0.023 0.002 0.019 0.036 0.3333 0.023 0.002 0.026 0.036 0.4167 0.023 0.003 0.031 0.036 0.5000 0.023 0.004 0.036 0.036 0.5833 0.023 0.005 0.040 0.036 0.6667 0.023 0.007 0.043 0.036 0.7500 0.023 0.009 0.047 0.036 0.8333 0.023 0.010 0.054 0.036 0.9167 0.023 0.012 0.059 0.036 1.0000 0.023 0.013 0.063 0.036 1.0833 0.023 0.015 0.067 0.036 1.1667 0.023 0.016 0.071 0.036 1.2500 0.023 0.018 0.074 0.036 1.3333 0.023 0.019 0.078 0.036 1.4167 0.023 0.021 0.081 0.036 1.5000 0.023 0.022 0.084 0.036 1.5833 0.023 0.024 0.087 0.036 1.6667 0.023 0.025 0.089 0.036 1.7500 0.023 0.026 0.092 0.036 1.8333 0.023 0.028 0.095 0.036 1.9167 0.023 0.029 0.097 0.036 2.0000 0.023 0.031 0.100 0.036 Roberts Water Quality Onsite 2/28/2026 1:06:36 PM Page 14 2.0833 0.023 0.032 0.106 0.036 2.1667 0.023 0.033 0.111 0.036 2.2500 0.023 0.034 0.114 0.036 2.3333 0.023 0.036 0.118 0.036 2.4167 0.023 0.037 0.121 0.036 2.5000 0.023 0.038 0.124 0.036 2.5833 0.023 0.039 0.251 0.036 2.6667 0.023 0.040 0.428 0.036 2.7500 0.023 0.041 0.522 0.036 2.8333 0.023 0.042 0.590 0.036 2.9167 0.023 0.043 0.646 0.036 3.0000 0.023 0.043 0.698 0.036 3.0833 0.023 0.044 0.745 0.036 3.1667 0.023 0.045 0.789 0.036 3.2500 0.023 0.046 0.830 0.036 3.3333 0.023 0.046 0.869 0.036 3.4167 0.023 0.047 0.907 0.036 3.5000 0.023 0.048 0.943 0.036 3.5833 0.023 0.048 0.977 0.036 3.6667 0.023 0.049 1.010 0.038 3.7500 0.023 0.050 1.042 0.038 3.8333 0.023 0.051 1.073 0.038 3.9167 0.023 0.051 1.104 0.038 4.0000 0.023 0.052 1.133 0.038 Roberts Water Quality Onsite 2/28/2026 1:06:36 PM Page 15 Bioretention 1 Bottom Length: 134.00 ft. Bottom Width: 2.00 ft. Material thickness of first layer: 0.25 Material type for first layer: SMMWW 12 in/hr Material thickness of second layer: 0.5 Material type for second layer: Sand Material thickness of third layer: 1.5 Material type for third layer: GRAVEL Infiltration On Infiltration rate:1.56 Infiltration safety factor:1 Wetted surface area On Total Volume Infiltrated (ac-ft.):11.589 Total Volume Through Riser (ac-ft.):0 Total Volume Through Facility (ac-ft.):11.589 Percent Infiltrated:100 Total Precip Applied to Facility:1.627 Total Evap From Facility:1.353 Underdrain not used Discharge Structure Riser Height:0 ft. Riser Diameter:0 in. Element Outlets: Outlet 1 Outlet 2 Outlet Flows To: Bioretention Hydraulic Table Stage(feet)Area(ac.)Volume(ac-ft.)Discharge(cfs)Infilt(cfs) 0.0000 0.0525 0.0000 0.0000 0.0000 0.0275 0.0519 0.0001 0.0000 0.0000 0.0549 0.0513 0.0002 0.0000 0.0000 0.0824 0.0507 0.0003 0.0000 0.0000 0.1099 0.0501 0.0004 0.0000 0.0000 0.1374 0.0495 0.0005 0.0000 0.0000 0.1648 0.0489 0.0006 0.0000 0.0000 0.1923 0.0483 0.0007 0.0000 0.0000 0.2198 0.0477 0.0008 0.0000 0.0021 0.2473 0.0470 0.0010 0.0000 0.0026 0.2747 0.0464 0.0011 0.0000 0.0039 0.3022 0.0458 0.0012 0.0000 0.0063 0.3297 0.0452 0.0013 0.0000 0.0068 0.3571 0.0446 0.0015 0.0000 0.0100 0.3846 0.0440 0.0016 0.0000 0.0137 0.4121 0.0434 0.0018 0.0000 0.0150 0.4396 0.0428 0.0019 0.0000 0.0187 0.4670 0.0422 0.0021 0.0000 0.0217 0.4945 0.0416 0.0023 0.0000 0.0246 0.5220 0.0411 0.0024 0.0000 0.0254 0.5495 0.0405 0.0026 0.0000 0.0263 0.5769 0.0399 0.0028 0.0000 0.0271 0.6044 0.0393 0.0030 0.0000 0.0280 0.6319 0.0387 0.0032 0.0000 0.0288 0.6593 0.0381 0.0034 0.0000 0.0297 0.6868 0.0375 0.0036 0.0000 0.0305 Roberts Water Quality Onsite 2/28/2026 1:06:36 PM Page 16 0.7143 0.0369 0.0038 0.0000 0.0314 0.7418 0.0363 0.0041 0.0000 0.0323 0.7692 0.0358 0.0043 0.0000 0.0331 0.7967 0.0352 0.0045 0.0000 0.0340 0.8242 0.0346 0.0048 0.0000 0.0348 0.8516 0.0340 0.0050 0.0000 0.0357 0.8791 0.0334 0.0053 0.0000 0.0366 0.9066 0.0329 0.0056 0.0000 0.0375 0.9341 0.0323 0.0058 0.0000 0.0383 0.9615 0.0317 0.0061 0.0000 0.0392 0.9890 0.0311 0.0064 0.0000 0.0401 1.0165 0.0306 0.0067 0.0000 0.0410 1.0440 0.0300 0.0070 0.0000 0.0419 1.0714 0.0294 0.0073 0.0000 0.0427 1.0989 0.0289 0.0076 0.0000 0.0436 1.1264 0.0283 0.0079 0.0000 0.0445 1.1538 0.0277 0.0083 0.0000 0.0454 1.1813 0.0272 0.0086 0.0000 0.0463 1.2088 0.0266 0.0089 0.0000 0.0472 1.2363 0.0260 0.0093 0.0000 0.0481 1.2637 0.0255 0.0096 0.0000 0.0490 1.2912 0.0249 0.0100 0.0000 0.0499 1.3187 0.0244 0.0104 0.0000 0.0508 1.3462 0.0238 0.0107 0.0000 0.0517 1.3736 0.0233 0.0111 0.0000 0.0526 1.4011 0.0227 0.0115 0.0000 0.0535 1.4286 0.0222 0.0119 0.0000 0.0544 1.4560 0.0216 0.0123 0.0000 0.0553 1.4835 0.0211 0.0127 0.0000 0.0563 1.5110 0.0205 0.0131 0.0000 0.0572 1.5385 0.0200 0.0135 0.0000 0.0581 1.5659 0.0194 0.0139 0.0000 0.0590 1.5934 0.0189 0.0144 0.0000 0.0599 1.6209 0.0183 0.0148 0.0000 0.0609 1.6484 0.0178 0.0153 0.0000 0.0618 1.6758 0.0172 0.0157 0.0000 0.0627 1.7033 0.0167 0.0162 0.0000 0.0636 1.7308 0.0162 0.0166 0.0000 0.0646 1.7582 0.0156 0.0171 0.0000 0.0655 1.7857 0.0151 0.0176 0.0000 0.0664 1.8132 0.0145 0.0181 0.0000 0.0674 1.8407 0.0140 0.0186 0.0000 0.0683 1.8681 0.0135 0.0191 0.0000 0.0693 1.8956 0.0129 0.0196 0.0000 0.0702 1.9231 0.0124 0.0201 0.0000 0.0712 1.9505 0.0119 0.0206 0.0000 0.0721 1.9780 0.0114 0.0211 0.0000 0.0730 2.0055 0.0108 0.0216 0.0000 0.0740 2.0330 0.0103 0.0222 0.0000 0.0750 2.0604 0.0098 0.0227 0.0000 0.0759 2.0879 0.0093 0.0233 0.0000 0.0769 2.1154 0.0087 0.0239 0.0000 0.0778 2.1429 0.0082 0.0244 0.0000 0.0788 2.1703 0.0077 0.0250 0.0000 0.0798 2.1978 0.0072 0.0256 0.0000 0.0807 2.2253 0.0067 0.0262 0.0000 0.0817 2.2500 0.0062 0.0267 0.0000 0.0826 Bioretention Surface Hydraulic Table Roberts Water Quality Onsite 2/28/2026 1:06:36 PM Page 17 Stage(feet)Area(ac.)Volume(ac-ft.)Discharge(cfs)To Amended(cfs)Infilt(cfs) 2.2500 0.0525 0.0267 0.0000 0.0895 0.0010 2.2775 0.0531 0.0281 0.0000 0.0895 0.0019 2.3049 0.0537 0.0296 0.0000 0.0926 0.0029 2.3324 0.0543 0.0311 0.0000 0.0958 0.0039 2.3599 0.0550 0.0326 0.0000 0.0990 0.0049 2.3874 0.0556 0.0341 0.0000 0.1021 0.0059 2.4148 0.0562 0.0357 0.0000 0.1053 0.0068 2.4423 0.0568 0.0372 0.0000 0.1084 0.0078 2.4698 0.0575 0.0388 0.0000 0.1116 0.0088 2.4973 0.0581 0.0404 0.0000 0.1148 0.0089 2.5000 0.0581 0.0405 0.0000 0.1151 0.0000 Roberts Water Quality Onsite 2/28/2026 1:06:36 PM Page 18 Analysis Results POC 1 + Predeveloped x Mitigated Predeveloped Landuse Totals for POC #1 Total Pervious Area:0.275 Total Impervious Area:0 Mitigated Landuse Totals for POC #1 Total Pervious Area:0 Total Impervious Area:0.275 Flow Frequency Method:Log Pearson Type III 17B Flow Frequency Return Periods for Predeveloped. POC #1 Return Period Flow(cfs) 2 year 0.008188 5 year 0.013417 10 year 0.016779 25 year 0.020778 50 year 0.023549 100 year 0.026136 Flow Frequency Return Periods for Mitigated. POC #1 Return Period Flow(cfs) 2 year 0 5 year 0 10 year 0 25 year 0 50 year 0 100 year 0 Annual Peaks Annual Peaks for Predeveloped and Mitigated. POC #1 Year Predeveloped Mitigated 1949 0.009 0.000 1950 0.011 0.000 1951 0.018 0.000 1952 0.006 0.000 1953 0.005 0.000 1954 0.007 0.000 1955 0.011 0.000 1956 0.009 0.000 1957 0.007 0.000 1958 0.008 0.000 Roberts Water Quality Onsite 2/28/2026 1:10:42 PM Page 19 1959 0.007 0.000 1960 0.012 0.000 1961 0.007 0.000 1962 0.004 0.000 1963 0.006 0.000 1964 0.008 0.000 1965 0.005 0.000 1966 0.005 0.000 1967 0.013 0.000 1968 0.007 0.000 1969 0.007 0.000 1970 0.006 0.000 1971 0.006 0.000 1972 0.014 0.000 1973 0.006 0.000 1974 0.007 0.000 1975 0.009 0.000 1976 0.007 0.000 1977 0.001 0.000 1978 0.006 0.000 1979 0.003 0.000 1980 0.016 0.000 1981 0.005 0.000 1982 0.010 0.000 1983 0.009 0.000 1984 0.005 0.000 1985 0.003 0.000 1986 0.014 0.000 1987 0.012 0.000 1988 0.005 0.000 1989 0.003 0.000 1990 0.030 0.000 1991 0.016 0.000 1992 0.006 0.000 1993 0.006 0.000 1994 0.002 0.000 1995 0.009 0.000 1996 0.021 0.000 1997 0.016 0.000 1998 0.004 0.000 1999 0.018 0.000 2000 0.006 0.000 2001 0.001 0.000 2002 0.007 0.000 2003 0.011 0.000 2004 0.012 0.004 2005 0.009 0.000 2006 0.010 0.000 2007 0.022 0.000 2008 0.027 0.002 2009 0.013 0.000 Ranked Annual Peaks Ranked Annual Peaks for Predeveloped and Mitigated. POC #1 Rank Predeveloped Mitigated 1 0.0297 0.0040 2 0.0273 0.0021 3 0.0224 0.0000 Roberts Water Quality Onsite 2/28/2026 1:10:42 PM Page 20 4 0.0208 0.0000 5 0.0179 0.0000 6 0.0176 0.0000 7 0.0160 0.0000 8 0.0160 0.0000 9 0.0157 0.0000 10 0.0140 0.0000 11 0.0136 0.0000 12 0.0127 0.0000 13 0.0126 0.0000 14 0.0124 0.0000 15 0.0123 0.0000 16 0.0115 0.0000 17 0.0112 0.0000 18 0.0111 0.0000 19 0.0108 0.0000 20 0.0104 0.0000 21 0.0096 0.0000 22 0.0094 0.0000 23 0.0093 0.0000 24 0.0090 0.0000 25 0.0090 0.0000 26 0.0089 0.0000 27 0.0086 0.0000 28 0.0082 0.0000 29 0.0080 0.0000 30 0.0072 0.0000 31 0.0072 0.0000 32 0.0071 0.0000 33 0.0070 0.0000 34 0.0069 0.0000 35 0.0069 0.0000 36 0.0068 0.0000 37 0.0067 0.0000 38 0.0066 0.0000 39 0.0064 0.0000 40 0.0063 0.0000 41 0.0062 0.0000 42 0.0062 0.0000 43 0.0060 0.0000 44 0.0058 0.0000 45 0.0056 0.0000 46 0.0056 0.0000 47 0.0055 0.0000 48 0.0055 0.0000 49 0.0053 0.0000 50 0.0053 0.0000 51 0.0050 0.0000 52 0.0049 0.0000 53 0.0045 0.0000 54 0.0042 0.0000 55 0.0039 0.0000 56 0.0034 0.0000 57 0.0032 0.0000 58 0.0032 0.0000 59 0.0021 0.0000 60 0.0011 0.0000 61 0.0010 0.0000 Roberts Water Quality Onsite 2/28/2026 1:10:42 PM Page 21 Roberts Water Quality Onsite 2/28/2026 1:10:42 PM Page 22 Duration Flows The Facility PASSED Flow(cfs)Predev Mit Percentage Pass/Fail 0.0041 17075 0 0 Pass 0.0043 15488 0 0 Pass 0.0045 14067 0 0 Pass 0.0047 12799 0 0 Pass 0.0049 11567 0 0 Pass 0.0051 10517 0 0 Pass 0.0053 9561 0 0 Pass 0.0055 8750 0 0 Pass 0.0057 8031 0 0 Pass 0.0059 7347 0 0 Pass 0.0061 6733 0 0 Pass 0.0063 6190 0 0 Pass 0.0065 5726 0 0 Pass 0.0066 5309 0 0 Pass 0.0068 4924 0 0 Pass 0.0070 4569 0 0 Pass 0.0072 4235 0 0 Pass 0.0074 3951 0 0 Pass 0.0076 3643 0 0 Pass 0.0078 3388 0 0 Pass 0.0080 3133 0 0 Pass 0.0082 2915 0 0 Pass 0.0084 2704 0 0 Pass 0.0086 2490 0 0 Pass 0.0088 2314 0 0 Pass 0.0090 2136 0 0 Pass 0.0092 1972 0 0 Pass 0.0094 1824 0 0 Pass 0.0096 1702 0 0 Pass 0.0098 1577 0 0 Pass 0.0100 1442 0 0 Pass 0.0102 1327 0 0 Pass 0.0104 1232 0 0 Pass 0.0106 1151 0 0 Pass 0.0108 1086 0 0 Pass 0.0110 1020 0 0 Pass 0.0112 950 0 0 Pass 0.0114 887 0 0 Pass 0.0116 824 0 0 Pass 0.0118 764 0 0 Pass 0.0120 725 0 0 Pass 0.0122 674 0 0 Pass 0.0123 626 0 0 Pass 0.0125 589 0 0 Pass 0.0127 549 0 0 Pass 0.0129 506 0 0 Pass 0.0131 469 0 0 Pass 0.0133 427 0 0 Pass 0.0135 388 0 0 Pass 0.0137 356 0 0 Pass 0.0139 329 0 0 Pass 0.0141 298 0 0 Pass 0.0143 270 0 0 Pass Roberts Water Quality Onsite 2/28/2026 1:10:42 PM Page 23 0.0145 242 0 0 Pass 0.0147 218 0 0 Pass 0.0149 198 0 0 Pass 0.0151 176 0 0 Pass 0.0153 152 0 0 Pass 0.0155 130 0 0 Pass 0.0157 119 0 0 Pass 0.0159 104 0 0 Pass 0.0161 95 0 0 Pass 0.0163 84 0 0 Pass 0.0165 74 0 0 Pass 0.0167 69 0 0 Pass 0.0169 61 0 0 Pass 0.0171 53 0 0 Pass 0.0173 46 0 0 Pass 0.0175 39 0 0 Pass 0.0177 29 0 0 Pass 0.0179 25 0 0 Pass 0.0180 22 0 0 Pass 0.0182 20 0 0 Pass 0.0184 17 0 0 Pass 0.0186 14 0 0 Pass 0.0188 12 0 0 Pass 0.0190 9 0 0 Pass 0.0192 7 0 0 Pass 0.0194 7 0 0 Pass 0.0196 7 0 0 Pass 0.0198 6 0 0 Pass 0.0200 6 0 0 Pass 0.0202 6 0 0 Pass 0.0204 6 0 0 Pass 0.0206 6 0 0 Pass 0.0208 5 0 0 Pass 0.0210 5 0 0 Pass 0.0212 5 0 0 Pass 0.0214 5 0 0 Pass 0.0216 5 0 0 Pass 0.0218 5 0 0 Pass 0.0220 5 0 0 Pass 0.0222 4 0 0 Pass 0.0224 4 0 0 Pass 0.0226 3 0 0 Pass 0.0228 3 0 0 Pass 0.0230 3 0 0 Pass 0.0232 3 0 0 Pass 0.0234 3 0 0 Pass 0.0235 3 0 0 Pass Roberts Water Quality Onsite 2/28/2026 1:10:42 PM Page 24 Water Quality Water Quality BMP Flow and Volume for POC #1 On-line facility volume:0 acre-feet On-line facility target flow:0 cfs. Adjusted for 15 min:0 cfs. Off-line facility target flow:0 cfs. Adjusted for 15 min:0 cfs. Roberts Water Quality Onsite 2/28/2026 1:10:42 PM Page 25 POC 2 + Predeveloped x Mitigated Predeveloped Landuse Totals for POC #2 Total Pervious Area:1.042 Total Impervious Area:0 Mitigated Landuse Totals for POC #2 Total Pervious Area:0.83 Total Impervious Area:0.199 Flow Frequency Method:Log Pearson Type III 17B Flow Frequency Return Periods for Predeveloped. POC #2 Return Period Flow(cfs) 2 year 0.031026 5 year 0.050838 10 year 0.063578 25 year 0.078731 50 year 0.089228 100 year 0.099032 Flow Frequency Return Periods for Mitigated. POC #2 Return Period Flow(cfs) 2 year 0.036864 5 year 0.055124 10 year 0.0671 25 year 0.081915 50 year 0.092676 100 year 0.103185 Annual Peaks Annual Peaks for Predeveloped and Mitigated. POC #2 Year Predeveloped Mitigated 1949 0.036 0.047 1950 0.042 0.061 1951 0.068 0.050 1952 0.021 0.023 1953 0.017 0.016 1954 0.026 0.027 1955 0.042 0.039 1956 0.034 0.032 1957 0.027 0.041 1958 0.030 0.025 1959 0.026 0.019 Roberts Water Quality Onsite 2/28/2026 1:11:16 PM Page 26 1960 0.047 0.043 1961 0.026 0.036 1962 0.016 0.018 1963 0.022 0.036 1964 0.031 0.034 1965 0.021 0.038 1966 0.020 0.028 1967 0.048 0.049 1968 0.027 0.038 1969 0.026 0.036 1970 0.021 0.030 1971 0.024 0.037 1972 0.051 0.055 1973 0.023 0.021 1974 0.025 0.033 1975 0.035 0.042 1976 0.025 0.031 1977 0.004 0.023 1978 0.021 0.037 1979 0.013 0.029 1980 0.061 0.049 1981 0.019 0.037 1982 0.039 0.065 1983 0.034 0.037 1984 0.020 0.024 1985 0.012 0.033 1986 0.053 0.047 1987 0.047 0.051 1988 0.019 0.013 1989 0.012 0.018 1990 0.112 0.117 1991 0.060 0.079 1992 0.024 0.029 1993 0.024 0.014 1994 0.008 0.007 1995 0.034 0.028 1996 0.079 0.057 1997 0.061 0.057 1998 0.015 0.030 1999 0.067 0.062 2000 0.024 0.040 2001 0.004 0.021 2002 0.027 0.048 2003 0.041 0.037 2004 0.044 0.089 2005 0.032 0.040 2006 0.037 0.036 2007 0.085 0.079 2008 0.104 0.100 2009 0.048 0.052 Ranked Annual Peaks Ranked Annual Peaks for Predeveloped and Mitigated. POC #2 Rank Predeveloped Mitigated 1 0.1123 0.1168 2 0.1035 0.1001 3 0.0849 0.0894 4 0.0787 0.0794 Roberts Water Quality Onsite 2/28/2026 1:11:16 PM Page 27 5 0.0678 0.0786 6 0.0666 0.0649 7 0.0607 0.0623 8 0.0606 0.0607 9 0.0596 0.0570 10 0.0532 0.0565 11 0.0515 0.0554 12 0.0483 0.0519 13 0.0476 0.0508 14 0.0469 0.0502 15 0.0468 0.0490 16 0.0437 0.0489 17 0.0424 0.0482 18 0.0422 0.0474 19 0.0409 0.0473 20 0.0393 0.0434 21 0.0365 0.0416 22 0.0357 0.0412 23 0.0352 0.0400 24 0.0340 0.0397 25 0.0340 0.0386 26 0.0336 0.0378 27 0.0325 0.0375 28 0.0312 0.0370 29 0.0304 0.0370 30 0.0274 0.0370 31 0.0274 0.0368 32 0.0268 0.0367 33 0.0264 0.0363 34 0.0261 0.0359 35 0.0261 0.0357 36 0.0257 0.0355 37 0.0253 0.0339 38 0.0251 0.0333 39 0.0243 0.0330 40 0.0237 0.0324 41 0.0236 0.0308 42 0.0236 0.0301 43 0.0228 0.0296 44 0.0220 0.0295 45 0.0213 0.0290 46 0.0212 0.0283 47 0.0209 0.0277 48 0.0207 0.0270 49 0.0202 0.0254 50 0.0199 0.0241 51 0.0190 0.0227 52 0.0185 0.0225 53 0.0172 0.0209 54 0.0160 0.0207 55 0.0149 0.0194 56 0.0129 0.0181 57 0.0123 0.0175 58 0.0120 0.0161 59 0.0080 0.0141 60 0.0042 0.0132 61 0.0037 0.0074 Roberts Water Quality Onsite 2/28/2026 1:11:16 PM Page 28 Roberts Water Quality Onsite 2/28/2026 1:11:16 PM Page 29 Duration Flows The Duration Matching Failed Flow(cfs)Predev Mit Percentage Pass/Fail 0.0155 17079 3482 20 Pass 0.0163 15496 3343 21 Pass 0.0170 14070 3230 22 Pass 0.0177 12805 3112 24 Pass 0.0185 11567 3001 25 Pass 0.0192 10523 2915 27 Pass 0.0200 9561 2800 29 Pass 0.0207 8752 2680 30 Pass 0.0215 8046 2565 31 Pass 0.0222 7347 2455 33 Pass 0.0230 6740 2366 35 Pass 0.0237 6192 2269 36 Pass 0.0244 5730 2177 37 Pass 0.0252 5309 2091 39 Pass 0.0259 4924 2007 40 Pass 0.0267 4569 1921 42 Pass 0.0274 4237 1861 43 Pass 0.0282 3951 1781 45 Pass 0.0289 3645 1713 46 Pass 0.0297 3388 1652 48 Pass 0.0304 3133 1582 50 Pass 0.0311 2917 1525 52 Pass 0.0319 2706 1470 54 Pass 0.0326 2490 1410 56 Pass 0.0334 2314 1339 57 Pass 0.0341 2136 1285 60 Pass 0.0349 1972 1239 62 Pass 0.0356 1825 1188 65 Pass 0.0364 1702 1130 66 Pass 0.0371 1577 1068 67 Pass 0.0379 1442 995 69 Pass 0.0386 1325 930 70 Pass 0.0393 1232 883 71 Pass 0.0401 1147 840 73 Pass 0.0408 1086 781 71 Pass 0.0416 1020 724 70 Pass 0.0423 947 673 71 Pass 0.0431 886 637 71 Pass 0.0438 824 596 72 Pass 0.0446 760 545 71 Pass 0.0453 725 501 69 Pass 0.0460 674 454 67 Pass 0.0468 623 414 66 Pass 0.0475 589 375 63 Pass 0.0483 549 357 65 Pass 0.0490 506 341 67 Pass 0.0498 469 329 70 Pass 0.0505 427 310 72 Pass 0.0513 388 305 78 Pass 0.0520 356 294 82 Pass 0.0527 328 289 88 Pass 0.0535 298 283 94 Pass 0.0542 270 276 102 Pass 0.0550 241 263 109 Pass Roberts Water Quality Onsite 2/28/2026 1:11:16 PM Page 30 0.0557 218 257 117 Fail 0.0565 198 252 127 Fail 0.0572 173 243 140 Fail 0.0580 152 239 157 Fail 0.0587 130 233 179 Fail 0.0594 119 226 189 Fail 0.0602 104 219 210 Fail 0.0609 95 210 221 Fail 0.0617 83 205 246 Fail 0.0624 74 197 266 Fail 0.0632 69 192 278 Fail 0.0639 61 185 303 Fail 0.0647 53 180 339 Fail 0.0654 46 172 373 Fail 0.0661 39 168 430 Fail 0.0669 29 160 551 Fail 0.0676 25 159 636 Fail 0.0684 22 156 709 Fail 0.0691 20 151 755 Fail 0.0699 17 147 864 Fail 0.0706 14 146 1042 Fail 0.0714 12 138 1150 Fail 0.0721 8 134 1675 Fail 0.0728 7 130 1857 Fail 0.0736 7 125 1785 Fail 0.0743 7 120 1714 Fail 0.0751 6 117 1950 Fail 0.0758 6 113 1883 Fail 0.0766 6 107 1783 Fail 0.0773 6 102 1700 Fail 0.0781 6 94 1566 Fail 0.0788 5 88 1760 Fail 0.0795 5 83 1660 Fail 0.0803 5 81 1620 Fail 0.0810 5 78 1560 Fail 0.0818 5 77 1540 Fail 0.0825 5 75 1500 Fail 0.0833 5 73 1460 Fail 0.0840 4 71 1775 Fail 0.0848 4 67 1675 Fail 0.0855 3 64 2133 Fail 0.0862 3 63 2100 Fail 0.0870 3 59 1966 Fail 0.0877 3 56 1866 Fail 0.0885 3 51 1700 Fail 0.0892 3 47 1566 Fail The development has an increase in flow durations from 1/2 Predeveloped 2 year flow to the 2 year flow or more than a 10% increase from the 2 year to the 50 year flow. Roberts Water Quality Onsite 2/28/2026 1:11:16 PM Page 31 Water Quality Water Quality BMP Flow and Volume for POC #2 On-line facility volume:0.0589 acre-feet On-line facility target flow:0.0419 cfs. Adjusted for 15 min:0.0419 cfs. Off-line facility target flow:0.0232 cfs. Adjusted for 15 min:0.0232 cfs. Roberts Water Quality Onsite 2/28/2026 1:11:16 PM Page 32 POC 3 + Predeveloped x Mitigated Predeveloped Landuse Totals for POC #3 Total Pervious Area:0.116 Total Impervious Area:0 Mitigated Landuse Totals for POC #3 Total Pervious Area:0 Total Impervious Area:0.072 Flow Frequency Method:Log Pearson Type III 17B Flow Frequency Return Periods for Predeveloped. POC #3 Return Period Flow(cfs) 2 year 0.00341 5 year 0.005356 10 year 0.006459 25 year 0.007627 50 year 0.00835 100 year 0.008965 Flow Frequency Return Periods for Mitigated. POC #3 Return Period Flow(cfs) 2 year 0 5 year 0 10 year 0 25 year 0 50 year 0 100 year 0 Annual Peaks Annual Peaks for Predeveloped and Mitigated. POC #3 Year Predeveloped Mitigated 1949 0.003 0.000 1950 0.004 0.000 1951 0.008 0.000 1952 0.002 0.000 1953 0.002 0.000 1954 0.003 0.000 1955 0.005 0.000 1956 0.004 0.000 1957 0.003 0.000 1958 0.003 0.000 1959 0.003 0.000 Roberts Water Quality Onsite 2/28/2026 1:12:17 PM Page 33 1960 0.005 0.000 1961 0.003 0.000 1962 0.002 0.000 1963 0.002 0.000 1964 0.003 0.000 1965 0.002 0.000 1966 0.002 0.000 1967 0.005 0.000 1968 0.003 0.000 1969 0.003 0.000 1970 0.002 0.000 1971 0.002 0.000 1972 0.006 0.000 1973 0.003 0.000 1974 0.003 0.000 1975 0.004 0.000 1976 0.003 0.000 1977 0.000 0.000 1978 0.002 0.000 1979 0.001 0.000 1980 0.005 0.000 1981 0.002 0.000 1982 0.004 0.000 1983 0.004 0.000 1984 0.002 0.000 1985 0.001 0.000 1986 0.006 0.000 1987 0.005 0.000 1988 0.002 0.000 1989 0.001 0.000 1990 0.011 0.000 1991 0.007 0.000 1992 0.003 0.000 1993 0.003 0.000 1994 0.001 0.000 1995 0.004 0.000 1996 0.008 0.000 1997 0.007 0.000 1998 0.002 0.000 1999 0.006 0.000 2000 0.003 0.000 2001 0.000 0.000 2002 0.003 0.000 2003 0.004 0.000 2004 0.005 0.000 2005 0.003 0.000 2006 0.004 0.000 2007 0.008 0.000 2008 0.010 0.000 2009 0.005 0.000 Ranked Annual Peaks Ranked Annual Peaks for Predeveloped and Mitigated. POC #3 Rank Predeveloped Mitigated 1 0.0109 0.0000 2 0.0105 0.0000 3 0.0081 0.0000 4 0.0080 0.0000 Roberts Water Quality Onsite 2/28/2026 1:12:17 PM Page 34 5 0.0075 0.0000 6 0.0067 0.0000 7 0.0066 0.0000 8 0.0063 0.0000 9 0.0059 0.0000 10 0.0056 0.0000 11 0.0053 0.0000 12 0.0052 0.0000 13 0.0051 0.0000 14 0.0051 0.0000 15 0.0048 0.0000 16 0.0047 0.0000 17 0.0046 0.0000 18 0.0042 0.0000 19 0.0041 0.0000 20 0.0040 0.0000 21 0.0038 0.0000 22 0.0037 0.0000 23 0.0037 0.0000 24 0.0037 0.0000 25 0.0037 0.0000 26 0.0034 0.0000 27 0.0034 0.0000 28 0.0034 0.0000 29 0.0032 0.0000 30 0.0030 0.0000 31 0.0029 0.0000 32 0.0029 0.0000 33 0.0029 0.0000 34 0.0029 0.0000 35 0.0029 0.0000 36 0.0028 0.0000 37 0.0028 0.0000 38 0.0027 0.0000 39 0.0026 0.0000 40 0.0026 0.0000 41 0.0025 0.0000 42 0.0025 0.0000 43 0.0025 0.0000 44 0.0024 0.0000 45 0.0024 0.0000 46 0.0024 0.0000 47 0.0023 0.0000 48 0.0023 0.0000 49 0.0023 0.0000 50 0.0022 0.0000 51 0.0021 0.0000 52 0.0021 0.0000 53 0.0019 0.0000 54 0.0018 0.0000 55 0.0015 0.0000 56 0.0014 0.0000 57 0.0013 0.0000 58 0.0013 0.0000 59 0.0009 0.0000 60 0.0005 0.0000 61 0.0003 0.0000 Roberts Water Quality Onsite 2/28/2026 1:12:17 PM Page 35 Roberts Water Quality Onsite 2/28/2026 1:12:17 PM Page 36 Duration Flows The Facility PASSED Flow(cfs)Predev Mit Percentage Pass/Fail 0.0017 17554 0 0 Pass 0.0018 16166 0 0 Pass 0.0018 14970 0 0 Pass 0.0019 13856 0 0 Pass 0.0020 12818 0 0 Pass 0.0020 11815 0 0 Pass 0.0021 10904 0 0 Pass 0.0022 10125 0 0 Pass 0.0022 9394 0 0 Pass 0.0023 8731 0 0 Pass 0.0024 8147 0 0 Pass 0.0024 7597 0 0 Pass 0.0025 7063 0 0 Pass 0.0026 6592 0 0 Pass 0.0026 6149 0 0 Pass 0.0027 5781 0 0 Pass 0.0028 5437 0 0 Pass 0.0028 5097 0 0 Pass 0.0029 4808 0 0 Pass 0.0030 4526 0 0 Pass 0.0030 4254 0 0 Pass 0.0031 4017 0 0 Pass 0.0032 3784 0 0 Pass 0.0032 3551 0 0 Pass 0.0033 3339 0 0 Pass 0.0034 3138 0 0 Pass 0.0035 2952 0 0 Pass 0.0035 2787 0 0 Pass 0.0036 2599 0 0 Pass 0.0037 2449 0 0 Pass 0.0037 2308 0 0 Pass 0.0038 2162 0 0 Pass 0.0039 2027 0 0 Pass 0.0039 1898 0 0 Pass 0.0040 1790 0 0 Pass 0.0041 1688 0 0 Pass 0.0041 1586 0 0 Pass 0.0042 1483 0 0 Pass 0.0043 1381 0 0 Pass 0.0043 1292 0 0 Pass 0.0044 1221 0 0 Pass 0.0045 1155 0 0 Pass 0.0045 1098 0 0 Pass 0.0046 1048 0 0 Pass 0.0047 997 0 0 Pass 0.0047 930 0 0 Pass 0.0048 883 0 0 Pass 0.0049 837 0 0 Pass 0.0049 789 0 0 Pass 0.0050 743 0 0 Pass 0.0051 713 0 0 Pass 0.0051 668 0 0 Pass 0.0052 630 0 0 Pass Roberts Water Quality Onsite 2/28/2026 1:12:17 PM Page 37 0.0053 596 0 0 Pass 0.0053 566 0 0 Pass 0.0054 539 0 0 Pass 0.0055 497 0 0 Pass 0.0055 473 0 0 Pass 0.0056 434 0 0 Pass 0.0057 399 0 0 Pass 0.0057 366 0 0 Pass 0.0058 348 0 0 Pass 0.0059 323 0 0 Pass 0.0059 296 0 0 Pass 0.0060 272 0 0 Pass 0.0061 256 0 0 Pass 0.0061 235 0 0 Pass 0.0062 217 0 0 Pass 0.0063 195 0 0 Pass 0.0063 180 0 0 Pass 0.0064 158 0 0 Pass 0.0065 145 0 0 Pass 0.0065 129 0 0 Pass 0.0066 119 0 0 Pass 0.0067 109 0 0 Pass 0.0067 97 0 0 Pass 0.0068 91 0 0 Pass 0.0069 82 0 0 Pass 0.0069 76 0 0 Pass 0.0070 69 0 0 Pass 0.0071 61 0 0 Pass 0.0071 54 0 0 Pass 0.0072 48 0 0 Pass 0.0073 41 0 0 Pass 0.0073 38 0 0 Pass 0.0074 33 0 0 Pass 0.0075 27 0 0 Pass 0.0075 22 0 0 Pass 0.0076 21 0 0 Pass 0.0077 20 0 0 Pass 0.0077 19 0 0 Pass 0.0078 17 0 0 Pass 0.0079 13 0 0 Pass 0.0079 12 0 0 Pass 0.0080 8 0 0 Pass 0.0081 4 0 0 Pass 0.0081 3 0 0 Pass 0.0082 3 0 0 Pass 0.0083 3 0 0 Pass 0.0084 3 0 0 Pass Roberts Water Quality Onsite 2/28/2026 1:12:17 PM Page 38 Water Quality Water Quality BMP Flow and Volume for POC #3 On-line facility volume:0.0088 acre-feet On-line facility target flow:0.0116 cfs. Adjusted for 15 min:0.0116 cfs. Off-line facility target flow:0.0066 cfs. Adjusted for 15 min:0.0066 cfs. Roberts Water Quality Onsite 2/28/2026 1:12:17 PM Page 39 Model Default Modifications Total of 0 changes have been made. PERLND Changes No PERLND changes have been made. IMPLND Changes No IMPLND changes have been made. Roberts Water Quality Onsite 2/28/2026 1:12:18 PM Page 40 Appendix Predeveloped Schematic Roberts Water Quality Onsite 2/28/2026 1:12:19 PM Page 41 Mitigated Schematic Roberts Water Quality Onsite 2/28/2026 1:12:21 PM Page 42 Predeveloped UCI File RUN GLOBAL WWHM4 model simulation START 1948 10 01 END 2009 09 30 RUN INTERP OUTPUT LEVEL 3 0 RESUME 0 RUN 1 UNIT SYSTEM 1 END GLOBAL FILES <File> <Un#> <-----------File Name------------------------------>*** <-ID-> *** WDM 26 Roberts Water Quality Onsite.wdm MESSU 25 PreRoberts Water Quality Onsite.MES 27 PreRoberts Water Quality Onsite.L61 28 PreRoberts Water Quality Onsite.L62 30 POCRoberts Water Quality Onsite1.dat 31 POCRoberts Water Quality Onsite2.dat 32 POCRoberts Water Quality Onsite3.dat END FILES OPN SEQUENCE INGRP INDELT 00:15 PERLND 11 PERLND 10 COPY 501 COPY 502 COPY 503 DISPLY 1 DISPLY 2 DISPLY 3 END INGRP END OPN SEQUENCE DISPLY DISPLY-INFO1 # - #<----------Title----------->***TRAN PIVL DIG1 FIL1 PYR DIG2 FIL2 YRND 1 Basin 1 MAX 1 2 30 9 2 Basin 2 MAX 1 2 31 9 3 Basin 3 MAX 1 2 32 9 END DISPLY-INFO1 END DISPLY COPY TIMESERIES # - # NPT NMN *** 1 1 1 501 1 1 502 1 1 503 1 1 END TIMESERIES END COPY GENER OPCODE # # OPCD *** END OPCODE PARM # # K *** END PARM END GENER PERLND GEN-INFO <PLS ><-------Name------->NBLKS Unit-systems Printer *** # - # User t-series Engl Metr *** in out *** 11 C, Forest, Mod 1 1 1 1 27 0 10 C, Forest, Flat 1 1 1 1 27 0 END GEN-INFO *** Section PWATER*** Roberts Water Quality Onsite 2/28/2026 1:12:21 PM Page 43 ACTIVITY <PLS > ************* Active Sections ***************************** # - # ATMP SNOW PWAT SED PST PWG PQAL MSTL PEST NITR PHOS TRAC *** 11 0 0 1 0 0 0 0 0 0 0 0 0 10 0 0 1 0 0 0 0 0 0 0 0 0 END ACTIVITY PRINT-INFO <PLS > ***************** Print-flags ***************************** PIVL PYR # - # ATMP SNOW PWAT SED PST PWG PQAL MSTL PEST NITR PHOS TRAC ********* 11 0 0 4 0 0 0 0 0 0 0 0 0 1 9 10 0 0 4 0 0 0 0 0 0 0 0 0 1 9 END PRINT-INFO PWAT-PARM1 <PLS > PWATER variable monthly parameter value flags *** # - # CSNO RTOP UZFG VCS VUZ VNN VIFW VIRC VLE INFC HWT *** 11 0 0 0 0 0 0 0 0 0 0 0 10 0 0 0 0 0 0 0 0 0 0 0 END PWAT-PARM1 PWAT-PARM2 <PLS > PWATER input info: Part 2 *** # - # ***FOREST LZSN INFILT LSUR SLSUR KVARY AGWRC 11 0 4.5 0.08 400 0.1 0.5 0.996 10 0 4.5 0.08 400 0.05 0.5 0.996 END PWAT-PARM2 PWAT-PARM3 <PLS > PWATER input info: Part 3 *** # - # ***PETMAX PETMIN INFEXP INFILD DEEPFR BASETP AGWETP 11 0 0 2 2 0 0 0 10 0 0 2 2 0 0 0 END PWAT-PARM3 PWAT-PARM4 <PLS > PWATER input info: Part 4 *** # - # CEPSC UZSN NSUR INTFW IRC LZETP *** 11 0.2 0.5 0.35 6 0.5 0.7 10 0.2 0.5 0.35 6 0.5 0.7 END PWAT-PARM4 PWAT-STATE1 <PLS > *** Initial conditions at start of simulation ran from 1990 to end of 1992 (pat 1-11-95) RUN 21 *** # - # *** CEPS SURS UZS IFWS LZS AGWS GWVS 11 0 0 0 0 2.5 1 0 10 0 0 0 0 2.5 1 0 END PWAT-STATE1 END PERLND IMPLND GEN-INFO <PLS ><-------Name-------> Unit-systems Printer *** # - # User t-series Engl Metr *** in out *** END GEN-INFO *** Section IWATER*** ACTIVITY <PLS > ************* Active Sections ***************************** # - # ATMP SNOW IWAT SLD IWG IQAL *** END ACTIVITY PRINT-INFO <ILS > ******** Print-flags ******** PIVL PYR # - # ATMP SNOW IWAT SLD IWG IQAL ********* END PRINT-INFO IWAT-PARM1 Roberts Water Quality Onsite 2/28/2026 1:12:21 PM Page 44 <PLS > IWATER variable monthly parameter value flags *** # - # CSNO RTOP VRS VNN RTLI *** END IWAT-PARM1 IWAT-PARM2 <PLS > IWATER input info: Part 2 *** # - # *** LSUR SLSUR NSUR RETSC END IWAT-PARM2 IWAT-PARM3 <PLS > IWATER input info: Part 3 *** # - # ***PETMAX PETMIN END IWAT-PARM3 IWAT-STATE1 <PLS > *** Initial conditions at start of simulation # - # *** RETS SURS END IWAT-STATE1 END IMPLND SCHEMATIC <-Source-> <--Area--> <-Target-> MBLK *** <Name> # <-factor-> <Name> # Tbl# *** Basin 1*** PERLND 11 0.275 COPY 501 12 PERLND 11 0.275 COPY 501 13 Basin 2*** PERLND 11 1.042 COPY 502 12 PERLND 11 1.042 COPY 502 13 Basin 3*** PERLND 10 0.116 COPY 503 12 PERLND 10 0.116 COPY 503 13 ******Routing****** END SCHEMATIC NETWORK <-Volume-> <-Grp> <-Member-><--Mult-->Tran <-Target vols> <-Grp> <-Member-> *** <Name> # <Name> # #<-factor->strg <Name> # # <Name> # # *** COPY 501 OUTPUT MEAN 1 1 48.4 DISPLY 1 INPUT TIMSER 1 COPY 502 OUTPUT MEAN 1 1 48.4 DISPLY 2 INPUT TIMSER 1 COPY 503 OUTPUT MEAN 1 1 48.4 DISPLY 3 INPUT TIMSER 1 <-Volume-> <-Grp> <-Member-><--Mult-->Tran <-Target vols> <-Grp> <-Member-> *** <Name> # <Name> # #<-factor->strg <Name> # # <Name> # # *** END NETWORK RCHRES GEN-INFO RCHRES Name Nexits Unit Systems Printer *** # - #<------------------><---> User T-series Engl Metr LKFG *** in out *** END GEN-INFO *** Section RCHRES*** ACTIVITY <PLS > ************* Active Sections ***************************** # - # HYFG ADFG CNFG HTFG SDFG GQFG OXFG NUFG PKFG PHFG *** END ACTIVITY PRINT-INFO <PLS > ***************** Print-flags ******************* PIVL PYR # - # HYDR ADCA CONS HEAT SED GQL OXRX NUTR PLNK PHCB PIVL PYR ********* END PRINT-INFO HYDR-PARM1 RCHRES Flags for each HYDR Section *** Roberts Water Quality Onsite 2/28/2026 1:12:21 PM Page 45 # - # VC A1 A2 A3 ODFVFG for each *** ODGTFG for each FUNCT for each FG FG FG FG possible exit *** possible exit possible exit * * * * * * * * * * * * * * *** END HYDR-PARM1 HYDR-PARM2 # - # FTABNO LEN DELTH STCOR KS DB50 *** <------><--------><--------><--------><--------><--------><--------> *** END HYDR-PARM2 HYDR-INIT RCHRES Initial conditions for each HYDR section *** # - # *** VOL Initial value of COLIND Initial value of OUTDGT *** ac-ft for each possible exit for each possible exit <------><--------> <---><---><---><---><---> *** <---><---><---><---><---> END HYDR-INIT END RCHRES SPEC-ACTIONS END SPEC-ACTIONS FTABLES END FTABLES EXT SOURCES <-Volume-> <Member> SsysSgap<--Mult-->Tran <-Target vols> <-Grp> <-Member-> *** <Name> # <Name> # tem strg<-factor->strg <Name> # # <Name> # # *** WDM 2 PREC ENGL 1 PERLND 1 999 EXTNL PREC WDM 2 PREC ENGL 1 IMPLND 1 999 EXTNL PREC WDM 1 EVAP ENGL 0.76 PERLND 1 999 EXTNL PETINP WDM 1 EVAP ENGL 0.76 IMPLND 1 999 EXTNL PETINP END EXT SOURCES EXT TARGETS <-Volume-> <-Grp> <-Member-><--Mult-->Tran <-Volume-> <Member> Tsys Tgap Amd *** <Name> # <Name> # #<-factor->strg <Name> # <Name> tem strg strg*** COPY 501 OUTPUT MEAN 1 1 48.4 WDM 501 FLOW ENGL REPL COPY 502 OUTPUT MEAN 1 1 48.4 WDM 502 FLOW ENGL REPL COPY 503 OUTPUT MEAN 1 1 48.4 WDM 503 FLOW ENGL REPL END EXT TARGETS MASS-LINK <Volume> <-Grp> <-Member-><--Mult--> <Target> <-Grp> <-Member->*** <Name> <Name> # #<-factor-> <Name> <Name> # #*** MASS-LINK 12 PERLND PWATER SURO 0.083333 COPY INPUT MEAN END MASS-LINK 12 MASS-LINK 13 PERLND PWATER IFWO 0.083333 COPY INPUT MEAN END MASS-LINK 13 END MASS-LINK END RUN Roberts Water Quality Onsite 2/28/2026 1:12:21 PM Page 46 Mitigated UCI File RUN GLOBAL WWHM4 model simulation START 1948 10 01 END 2009 09 30 RUN INTERP OUTPUT LEVEL 3 0 RESUME 0 RUN 1 UNIT SYSTEM 1 END GLOBAL FILES <File> <Un#> <-----------File Name------------------------------>*** <-ID-> *** WDM 26 Roberts Water Quality Onsite.wdm MESSU 25 MitRoberts Water Quality Onsite.MES 27 MitRoberts Water Quality Onsite.L61 28 MitRoberts Water Quality Onsite.L62 30 POCRoberts Water Quality Onsite1.dat 31 POCRoberts Water Quality Onsite2.dat 32 POCRoberts Water Quality Onsite3.dat END FILES OPN SEQUENCE INGRP INDELT 00:15 IMPLND 4 PERLND 16 IMPLND 2 IMPLND 5 IMPLND 1 IMPLND 8 RCHRES 1 RCHRES 2 GENER 4 RCHRES 3 RCHRES 4 COPY 1 COPY 501 COPY 2 COPY 502 COPY 3 COPY 503 DISPLY 1 DISPLY 2 DISPLY 3 END INGRP END OPN SEQUENCE DISPLY DISPLY-INFO1 # - #<----------Title----------->***TRAN PIVL DIG1 FIL1 PYR DIG2 FIL2 YRND 1 Gravel Trench Bed 1 MAX 1 2 30 9 2 StormTech 2 MAX 1 2 31 9 3 Surface retention 1 MAX 1 2 32 9 END DISPLY-INFO1 END DISPLY COPY TIMESERIES # - # NPT NMN *** 1 1 1 501 1 1 2 1 1 502 1 1 3 1 1 503 1 1 END TIMESERIES END COPY GENER OPCODE # # OPCD *** 4 24 Roberts Water Quality Onsite 2/28/2026 1:12:21 PM Page 47 END OPCODE PARM # # K *** 4 0. END PARM END GENER PERLND GEN-INFO <PLS ><-------Name------->NBLKS Unit-systems Printer *** # - # User t-series Engl Metr *** in out *** 16 C, Lawn, Flat 1 1 1 1 27 0 END GEN-INFO *** Section PWATER*** ACTIVITY <PLS > ************* Active Sections ***************************** # - # ATMP SNOW PWAT SED PST PWG PQAL MSTL PEST NITR PHOS TRAC *** 16 0 0 1 0 0 0 0 0 0 0 0 0 END ACTIVITY PRINT-INFO <PLS > ***************** Print-flags ***************************** PIVL PYR # - # ATMP SNOW PWAT SED PST PWG PQAL MSTL PEST NITR PHOS TRAC ********* 16 0 0 4 0 0 0 0 0 0 0 0 0 1 9 END PRINT-INFO PWAT-PARM1 <PLS > PWATER variable monthly parameter value flags *** # - # CSNO RTOP UZFG VCS VUZ VNN VIFW VIRC VLE INFC HWT *** 16 0 0 0 0 0 0 0 0 0 0 0 END PWAT-PARM1 PWAT-PARM2 <PLS > PWATER input info: Part 2 *** # - # ***FOREST LZSN INFILT LSUR SLSUR KVARY AGWRC 16 0 4.5 0.03 400 0.05 0.5 0.996 END PWAT-PARM2 PWAT-PARM3 <PLS > PWATER input info: Part 3 *** # - # ***PETMAX PETMIN INFEXP INFILD DEEPFR BASETP AGWETP 16 0 0 2 2 0 0 0 END PWAT-PARM3 PWAT-PARM4 <PLS > PWATER input info: Part 4 *** # - # CEPSC UZSN NSUR INTFW IRC LZETP *** 16 0.1 0.25 0.25 6 0.5 0.25 END PWAT-PARM4 PWAT-STATE1 <PLS > *** Initial conditions at start of simulation ran from 1990 to end of 1992 (pat 1-11-95) RUN 21 *** # - # *** CEPS SURS UZS IFWS LZS AGWS GWVS 16 0 0 0 0 2.5 1 0 END PWAT-STATE1 END PERLND IMPLND GEN-INFO <PLS ><-------Name-------> Unit-systems Printer *** # - # User t-series Engl Metr *** in out *** 4 ROOF TOPS/FLAT 1 1 1 27 0 2 ROADS/MOD 1 1 1 27 0 5 DRIVEWAYS/FLAT 1 1 1 27 0 1 ROADS/FLAT 1 1 1 27 0 8 SIDEWALKS/FLAT 1 1 1 27 0 END GEN-INFO Roberts Water Quality Onsite 2/28/2026 1:12:21 PM Page 48 *** Section IWATER*** ACTIVITY <PLS > ************* Active Sections ***************************** # - # ATMP SNOW IWAT SLD IWG IQAL *** 4 0 0 1 0 0 0 2 0 0 1 0 0 0 5 0 0 1 0 0 0 1 0 0 1 0 0 0 8 0 0 1 0 0 0 END ACTIVITY PRINT-INFO <ILS > ******** Print-flags ******** PIVL PYR # - # ATMP SNOW IWAT SLD IWG IQAL ********* 4 0 0 4 0 0 4 1 9 2 0 0 4 0 0 0 1 9 5 0 0 4 0 0 0 1 9 1 0 0 4 0 0 0 1 9 8 0 0 4 0 0 0 1 9 END PRINT-INFO IWAT-PARM1 <PLS > IWATER variable monthly parameter value flags *** # - # CSNO RTOP VRS VNN RTLI *** 4 0 0 0 0 0 2 0 0 0 0 0 5 0 0 0 0 0 1 0 0 0 0 0 8 0 0 0 0 0 END IWAT-PARM1 IWAT-PARM2 <PLS > IWATER input info: Part 2 *** # - # *** LSUR SLSUR NSUR RETSC 4 400 0.01 0.1 0.1 2 400 0.05 0.1 0.08 5 400 0.01 0.1 0.1 1 400 0.01 0.1 0.1 8 400 0.01 0.1 0.1 END IWAT-PARM2 IWAT-PARM3 <PLS > IWATER input info: Part 3 *** # - # ***PETMAX PETMIN 4 0 0 2 0 0 5 0 0 1 0 0 8 0 0 END IWAT-PARM3 IWAT-STATE1 <PLS > *** Initial conditions at start of simulation # - # *** RETS SURS 4 0 0 2 0 0 5 0 0 1 0 0 8 0 0 END IWAT-STATE1 END IMPLND SCHEMATIC <-Source-> <--Area--> <-Target-> MBLK *** <Name> # <-factor-> <Name> # Tbl# *** Basin 1*** IMPLND 4 0.275 RCHRES 1 5 Basin 2*** Roberts Water Quality Onsite 2/28/2026 1:12:21 PM Page 49 PERLND 16 0.83 RCHRES 2 2 PERLND 16 0.83 RCHRES 2 3 IMPLND 2 0.148 RCHRES 2 5 IMPLND 5 0.051 RCHRES 2 5 Basin 3*** IMPLND 1 0.055 RCHRES 3 5 IMPLND 8 0.017 RCHRES 3 5 ******Routing****** IMPLND 4 0.275 COPY 1 15 PERLND 16 0.83 COPY 2 12 IMPLND 2 0.148 COPY 2 15 IMPLND 5 0.051 COPY 2 15 PERLND 16 0.83 COPY 2 13 IMPLND 1 0.055 COPY 3 15 IMPLND 8 0.017 COPY 3 15 RCHRES 3 1 RCHRES 4 8 RCHRES 1 1 COPY 501 17 RCHRES 2 1 COPY 502 17 RCHRES 4 1 COPY 503 17 RCHRES 3 1 COPY 503 17 END SCHEMATIC NETWORK <-Volume-> <-Grp> <-Member-><--Mult-->Tran <-Target vols> <-Grp> <-Member-> *** <Name> # <Name> # #<-factor->strg <Name> # # <Name> # # *** COPY 501 OUTPUT MEAN 1 1 48.4 DISPLY 1 INPUT TIMSER 1 COPY 502 OUTPUT MEAN 1 1 48.4 DISPLY 2 INPUT TIMSER 1 COPY 503 OUTPUT MEAN 1 1 48.4 DISPLY 3 INPUT TIMSER 1 GENER 4 OUTPUT TIMSER .0011111 RCHRES 3 EXTNL OUTDGT 1 <-Volume-> <-Grp> <-Member-><--Mult-->Tran <-Target vols> <-Grp> <-Member-> *** <Name> # <Name> # #<-factor->strg <Name> # # <Name> # # *** END NETWORK RCHRES GEN-INFO RCHRES Name Nexits Unit Systems Printer *** # - #<------------------><---> User T-series Engl Metr LKFG *** in out *** 1 Gravel Trench Be-014 2 1 1 1 28 0 1 2 StormTech 2 2 1 1 1 28 0 1 3 Surface retentio-037 3 1 1 1 28 0 1 4 Bioretention 1 2 1 1 1 28 0 1 END GEN-INFO *** Section RCHRES*** ACTIVITY <PLS > ************* Active Sections ***************************** # - # HYFG ADFG CNFG HTFG SDFG GQFG OXFG NUFG PKFG PHFG *** 1 1 0 0 0 0 0 0 0 0 0 2 1 0 0 0 0 0 0 0 0 0 3 1 0 0 0 0 0 0 0 0 0 4 1 0 0 0 0 0 0 0 0 0 END ACTIVITY PRINT-INFO <PLS > ***************** Print-flags ******************* PIVL PYR # - # HYDR ADCA CONS HEAT SED GQL OXRX NUTR PLNK PHCB PIVL PYR ********* 1 4 0 0 0 0 0 0 0 0 0 1 9 2 4 0 0 0 0 0 0 0 0 0 1 9 3 4 0 0 0 0 0 0 0 0 0 1 9 4 4 0 0 0 0 0 0 0 0 0 1 9 END PRINT-INFO HYDR-PARM1 RCHRES Flags for each HYDR Section *** # - # VC A1 A2 A3 ODFVFG for each *** ODGTFG for each FUNCT for each Roberts Water Quality Onsite 2/28/2026 1:12:21 PM Page 50 FG FG FG FG possible exit *** possible exit possible exit * * * * * * * * * * * * * * *** 1 0 1 0 0 4 5 0 0 0 0 0 0 0 0 2 2 2 2 2 2 0 1 0 0 4 5 0 0 0 0 0 0 0 0 2 2 2 2 2 3 0 1 0 0 4 5 6 0 0 0 1 0 0 0 2 1 2 2 2 4 0 1 0 0 4 5 0 0 0 0 0 0 0 0 2 2 2 2 2 END HYDR-PARM1 HYDR-PARM2 # - # FTABNO LEN DELTH STCOR KS DB50 *** <------><--------><--------><--------><--------><--------><--------> *** 1 1 0.05 0.0 0.0 0.5 0.0 2 2 0.02 0.0 0.0 0.5 0.0 3 3 0.01 0.0 0.0 0.0 0.0 4 4 0.03 0.0 0.0 0.0 0.0 END HYDR-PARM2 HYDR-INIT RCHRES Initial conditions for each HYDR section *** # - # *** VOL Initial value of COLIND Initial value of OUTDGT *** ac-ft for each possible exit for each possible exit <------><--------> <---><---><---><---><---> *** <---><---><---><---><---> 1 0 4.0 5.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 2 0 4.0 5.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 3 0 4.0 5.0 6.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 4 0 4.0 5.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 END HYDR-INIT END RCHRES SPEC-ACTIONS *** User-Defined Variable Quantity Lines *** addr *** <------> *** kwd varnam optyp opn vari s1 s2 s3 tp multiply lc ls ac as agfn *** <****> <----> <----> <-> <----><-><-><-><-><--------> <><-> <><-> <--> *** UVQUAN vol4 RCHRES 4 VOL 4 UVQUAN v2m4 GLOBAL WORKSP 3 3 UVQUAN vpo4 GLOBAL WORKSP 4 3 UVQUAN v2d4 GENER 4 K 1 3 *** User-Defined Target Variable Names *** addr or addr or *** <------> <------> *** kwd varnam ct vari s1 s2 s3 frac oper vari s1 s2 s3 frac oper <****> <----><-> <----><-><-><-> <---> <--> <----><-><-><-> <---> <--> UVNAME v2m4 1 WORKSP 3 1.0 QUAN UVNAME vpo4 1 WORKSP 4 1.0 QUAN UVNAME v2d4 1 K 1 1.0 QUAN *** opt foplop dcdts yr mo dy hr mn d t vnam s1 s2 s3 ac quantity tc ts rp <****><-><--><><-><--> <> <> <> <><><> <----><-><-><-><-><--------> <> <-><-> GENER 4 v2m4 = 1237.27 *** Compute remaining available pore space GENER 4 vpo4 = v2m4 GENER 4 vpo4 -= vol4 *** Check to see if VPORA goes negative; if so set VPORA = 0.0 IF (vpo4 < 0.0) THEN GENER 4 vpo4 = 0.0 END IF *** Infiltration volume GENER 4 v2d4 = vpo4 END SPEC-ACTIONS FTABLES FTABLE 1 92 5 Depth Area Volume Outflow1 Outflow2 Velocity Travel Time*** (ft) (acres) (acre-ft) (cfs) (cfs) (ft/sec) (Minutes)*** 0.000000 0.030854 0.000000 0.000000 0.000000 0.044444 0.030854 0.000453 0.000000 0.048533 0.088889 0.030854 0.000905 0.000000 0.048533 0.133333 0.030854 0.001358 0.000000 0.048533 0.177778 0.030854 0.001810 0.000000 0.048533 0.222222 0.030854 0.002263 0.000000 0.048533 Roberts Water Quality Onsite 2/28/2026 1:12:21 PM Page 51 0.266667 0.030854 0.002715 0.000000 0.048533 0.311111 0.030854 0.003168 0.000000 0.048533 0.355556 0.030854 0.003620 0.000000 0.048533 0.400000 0.030854 0.004073 0.000000 0.048533 0.444444 0.030854 0.004525 0.000000 0.048533 0.488889 0.030854 0.004978 0.000000 0.048533 0.533333 0.030854 0.005430 0.000000 0.048533 0.577778 0.030854 0.005883 0.000000 0.048533 0.622222 0.030854 0.006335 0.000000 0.048533 0.666667 0.030854 0.006788 0.000000 0.048533 0.711111 0.030854 0.007240 0.000000 0.048533 0.755556 0.030854 0.007693 0.000000 0.048533 0.800000 0.030854 0.008145 0.000000 0.048533 0.844444 0.030854 0.008598 0.000000 0.048533 0.888889 0.030854 0.009051 0.000000 0.048533 0.933333 0.030854 0.009503 0.000000 0.048533 0.977778 0.030854 0.009956 0.000000 0.048533 1.022222 0.030854 0.010408 0.000000 0.048533 1.066667 0.030854 0.010861 0.000000 0.048533 1.111111 0.030854 0.011313 0.000000 0.048533 1.155556 0.030854 0.011766 0.000000 0.048533 1.200000 0.030854 0.012218 0.000000 0.048533 1.244444 0.030854 0.012671 0.000000 0.048533 1.288889 0.030854 0.013123 0.000000 0.048533 1.333333 0.030854 0.013576 0.000000 0.048533 1.377778 0.030854 0.014028 0.000000 0.048533 1.422222 0.030854 0.014481 0.000000 0.048533 1.466667 0.030854 0.014933 0.000000 0.048533 1.511111 0.030854 0.015386 0.000000 0.048533 1.555556 0.030854 0.015838 0.000000 0.048533 1.600000 0.030854 0.016291 0.000000 0.048533 1.644444 0.030854 0.016743 0.000000 0.048533 1.688889 0.030854 0.017196 0.000000 0.048533 1.733333 0.030854 0.017648 0.000000 0.048533 1.777778 0.030854 0.018101 0.000000 0.048533 1.822222 0.030854 0.018554 0.000000 0.048533 1.866667 0.030854 0.019006 0.000000 0.048533 1.911111 0.030854 0.019459 0.000000 0.048533 1.955556 0.030854 0.019911 0.000000 0.048533 2.000000 0.030854 0.020364 0.000000 0.048533 2.044444 0.030854 0.020816 0.000000 0.048533 2.088889 0.030854 0.021269 0.000000 0.048533 2.133333 0.030854 0.021721 0.000000 0.048533 2.177778 0.030854 0.022174 0.000000 0.048533 2.222222 0.030854 0.022626 0.000000 0.048533 2.266667 0.030854 0.023079 0.000000 0.048533 2.311111 0.030854 0.023531 0.000000 0.048533 2.355556 0.030854 0.023984 0.000000 0.048533 2.400000 0.030854 0.024436 0.000000 0.048533 2.444444 0.030854 0.024889 0.000000 0.048533 2.488889 0.030854 0.025341 0.000000 0.048533 2.533333 0.030854 0.025794 0.000000 0.048533 2.577778 0.030854 0.026246 0.000000 0.048533 2.622222 0.030854 0.026699 0.000000 0.048533 2.666667 0.030854 0.027152 0.000000 0.048533 2.711111 0.030854 0.027604 0.000000 0.048533 2.755556 0.030854 0.028057 0.000000 0.048533 2.800000 0.030854 0.028509 0.000000 0.048533 2.844444 0.030854 0.028962 0.000000 0.048533 2.888889 0.030854 0.029414 0.000000 0.048533 2.933333 0.030854 0.029867 0.000000 0.048533 2.977778 0.030854 0.030319 0.000000 0.048533 3.022222 0.030854 0.031690 0.001011 0.048533 3.066667 0.030854 0.033062 0.001752 0.048533 3.111111 0.030854 0.034433 0.002261 0.048533 3.155556 0.030854 0.035804 0.002676 0.048533 3.200000 0.030854 0.037176 0.003034 0.048533 3.244444 0.030854 0.038547 0.003354 0.048533 3.288889 0.030854 0.039918 0.003646 0.048533 3.333333 0.030854 0.041290 0.003917 0.048533 Roberts Water Quality Onsite 2/28/2026 1:12:21 PM Page 52 3.377778 0.030854 0.042661 0.004170 0.048533 3.422222 0.030854 0.044032 0.004408 0.048533 3.466667 0.030854 0.045403 0.004634 0.048533 3.511111 0.030854 0.046775 0.011063 0.048533 3.555556 0.030854 0.048146 0.073971 0.048533 3.600000 0.030854 0.049517 0.165711 0.048533 3.644444 0.030854 0.050889 0.261329 0.048533 3.688889 0.030854 0.052260 0.337842 0.048533 3.733333 0.030854 0.053631 0.383816 0.048533 3.777778 0.030854 0.055002 0.420983 0.048533 3.822222 0.030854 0.056374 0.453121 0.048533 3.866667 0.030854 0.057745 0.483115 0.048533 3.911111 0.030854 0.059116 0.511345 0.048533 3.955556 0.030854 0.060488 0.538091 0.048533 4.000000 0.030854 0.061859 0.563565 0.048533 4.044444 0.030854 0.063230 0.587934 0.048533 END FTABLE 1 FTABLE 2 49 5 Depth Area Volume Outflow1 Outflow2 Velocity Travel Time*** (ft) (acres) (acre-ft) (cfs) (cfs) (ft/sec) (Minutes)*** 0.000000 0.021729 0.000000 0.000000 0.000000 0.083333 0.023017 0.000725 0.000000 0.036206 0.166667 0.023017 0.001450 0.007883 0.036206 0.250000 0.023017 0.002178 0.019308 0.036206 0.333333 0.023017 0.002903 0.026143 0.036206 0.416667 0.023017 0.003630 0.031530 0.036206 0.500000 0.023017 0.004356 0.036122 0.036206 0.583333 0.023017 0.005932 0.040193 0.036206 0.666667 0.023017 0.007503 0.043888 0.036206 0.750000 0.023017 0.009068 0.047295 0.036206 0.833333 0.023017 0.010622 0.054879 0.036206 0.916667 0.023017 0.012168 0.059694 0.036206 1.000000 0.023017 0.013705 0.063925 0.036206 1.083333 0.023017 0.015231 0.067800 0.036206 1.166667 0.023017 0.016743 0.071418 0.036206 1.250000 0.023017 0.018241 0.074832 0.036206 1.333333 0.023017 0.019728 0.078078 0.036206 1.416667 0.023017 0.021198 0.081182 0.036206 1.500000 0.023017 0.022654 0.084162 0.036206 1.583333 0.023017 0.024093 0.087034 0.036206 1.666667 0.023017 0.025513 0.089809 0.036206 1.750000 0.023017 0.026913 0.092497 0.036206 1.833333 0.023017 0.028293 0.095106 0.036206 1.916667 0.023017 0.029651 0.097643 0.036206 2.000000 0.023017 0.030984 0.100114 0.036206 2.083333 0.023017 0.032297 0.106930 0.036206 2.166667 0.023017 0.033582 0.111108 0.036206 2.250000 0.023017 0.034828 0.114808 0.036206 2.333333 0.023017 0.036041 0.118240 0.036206 2.416667 0.023017 0.037222 0.121485 0.036206 2.500000 0.023017 0.038359 0.124586 0.036206 2.583333 0.023017 0.039451 0.251922 0.036206 2.666667 0.023017 0.040484 0.428056 0.036206 2.750000 0.023017 0.041442 0.522758 0.036206 2.833333 0.023017 0.042274 0.590595 0.036206 2.916667 0.023017 0.043060 0.646912 0.036206 3.000000 0.023017 0.043808 0.698020 0.036206 3.083333 0.023017 0.044533 0.745171 0.036206 3.166667 0.023017 0.045258 0.789181 0.036206 3.250000 0.023017 0.045986 0.830620 0.036206 3.333333 0.023017 0.046711 0.869900 0.036206 3.416667 0.023017 0.047438 0.907336 0.036206 3.500000 0.023017 0.048164 0.943170 0.036206 3.583333 0.023017 0.048890 0.977597 0.036206 3.666667 0.023017 0.049617 1.010773 0.038792 3.750000 0.023017 0.050343 1.042829 0.038792 3.833333 0.023017 0.051070 1.073874 0.038792 3.916667 0.023017 0.051796 1.103999 0.038792 4.000000 0.023017 0.052522 1.133283 0.038792 Roberts Water Quality Onsite 2/28/2026 1:12:21 PM Page 53 END FTABLE 2 FTABLE 4 83 5 Depth Area Volume Outflow1 Outflow2 Velocity Travel Time*** (ft) (acres) (acre-ft) (cfs) (cfs) (ft/sec) (Minutes)*** 0.000000 0.052485 0.000000 0.000000 0.000000 0.027473 0.051930 0.000081 0.000000 0.000000 0.054945 0.051315 0.000168 0.000000 0.000000 0.082418 0.050702 0.000261 0.000000 0.000000 0.109890 0.050089 0.000361 0.000000 0.000000 0.137363 0.049478 0.000468 0.000000 0.000000 0.164835 0.048868 0.000581 0.000000 0.000000 0.192308 0.048259 0.000700 0.000000 0.000000 0.219780 0.047651 0.000827 0.000000 0.002083 0.247253 0.047045 0.000959 0.000000 0.002589 0.274725 0.046440 0.001081 0.000000 0.003884 0.302198 0.045836 0.001209 0.000000 0.006302 0.329670 0.045233 0.001343 0.000000 0.006801 0.357143 0.044632 0.001482 0.000000 0.010000 0.384615 0.044032 0.001627 0.000000 0.013682 0.412088 0.043433 0.001778 0.000000 0.015044 0.439560 0.042836 0.001935 0.000000 0.018670 0.467033 0.042239 0.002098 0.000000 0.021696 0.494505 0.041644 0.002267 0.000000 0.024567 0.521978 0.041050 0.002441 0.000000 0.025413 0.549451 0.040458 0.002622 0.000000 0.026261 0.576923 0.039866 0.002808 0.000000 0.027110 0.604396 0.039276 0.003001 0.000000 0.027962 0.631868 0.038687 0.003199 0.000000 0.028816 0.659341 0.038100 0.003403 0.000000 0.029671 0.686813 0.037513 0.003613 0.000000 0.030529 0.714286 0.036928 0.003830 0.000000 0.031389 0.741758 0.036344 0.004052 0.000000 0.032250 0.769231 0.035762 0.004289 0.000000 0.033114 0.796703 0.035180 0.004532 0.000000 0.033979 0.824176 0.034600 0.004781 0.000000 0.034847 0.851648 0.034021 0.005037 0.000000 0.035716 0.879121 0.033444 0.005299 0.000000 0.036587 0.906593 0.032867 0.005568 0.000000 0.037461 0.934066 0.032292 0.005842 0.000000 0.038336 0.961538 0.031718 0.006123 0.000000 0.039213 0.989011 0.031146 0.006411 0.000000 0.040092 1.016484 0.030574 0.006704 0.000000 0.040973 1.043956 0.030004 0.007005 0.000000 0.041856 1.071429 0.029435 0.007311 0.000000 0.042742 1.098901 0.028867 0.007624 0.000000 0.043629 1.126374 0.028301 0.007944 0.000000 0.044518 1.153846 0.027736 0.008270 0.000000 0.045409 1.181319 0.027172 0.008602 0.000000 0.046301 1.208791 0.026609 0.008941 0.000000 0.047196 1.236264 0.026048 0.009286 0.000000 0.048093 1.263736 0.025488 0.009638 0.000000 0.048992 1.291209 0.024929 0.009996 0.000000 0.049893 1.318681 0.024371 0.010361 0.000000 0.050796 1.346154 0.023815 0.010733 0.000000 0.051700 1.373626 0.023260 0.011111 0.000000 0.052607 1.401099 0.022706 0.011495 0.000000 0.053515 1.428571 0.022153 0.011886 0.000000 0.054426 1.456044 0.021601 0.012284 0.000000 0.055339 1.483516 0.021051 0.012689 0.000000 0.056253 1.510989 0.020502 0.013100 0.000000 0.057170 1.538462 0.019955 0.013517 0.000000 0.058088 1.565934 0.019408 0.013942 0.000000 0.059008 1.593407 0.018863 0.014373 0.000000 0.059931 1.620879 0.018319 0.014810 0.000000 0.060855 1.648352 0.017776 0.015255 0.000000 0.061781 1.675824 0.017235 0.015706 0.000000 0.062710 1.703297 0.016695 0.016164 0.000000 0.063640 1.730769 0.016156 0.016629 0.000000 0.064572 1.758242 0.015618 0.017100 0.000000 0.065506 Roberts Water Quality Onsite 2/28/2026 1:12:21 PM Page 54 1.785714 0.015082 0.017578 0.000000 0.066442 1.813187 0.014546 0.018063 0.000000 0.067380 1.840659 0.014012 0.018555 0.000000 0.068320 1.868132 0.013480 0.019054 0.000000 0.069262 1.895604 0.012948 0.019559 0.000000 0.070206 1.923077 0.012418 0.020071 0.000000 0.071152 1.950549 0.011889 0.020590 0.000000 0.072100 1.978022 0.011361 0.021116 0.000000 0.073050 2.005495 0.010835 0.021649 0.000000 0.074002 2.032967 0.010309 0.022189 0.000000 0.074955 2.060440 0.009785 0.022736 0.000000 0.075911 2.087912 0.009263 0.023290 0.000000 0.076869 2.115385 0.008741 0.023850 0.000000 0.077828 2.142857 0.008221 0.024418 0.000000 0.078790 2.170330 0.007702 0.024992 0.000000 0.079754 2.197802 0.007184 0.025574 0.000000 0.080719 2.225275 0.006668 0.026162 0.000000 0.081687 2.250000 0.006152 0.028404 0.000000 0.082559 END FTABLE 4 FTABLE 3 11 6 Depth Area Volume Outflow1 Outflow2 Outflow3 Velocity Travel Time*** (ft) (acres) (acre-ft) (cfs) (cfs) (cfs) (ft/sec) (Minutes)*** 0.000000 0.006152 0.000000 0.000000 0.000000 0.000971 0.027473 0.053103 0.001450 0.000000 0.089476 0.000971 0.054945 0.053721 0.002918 0.000000 0.092638 0.001944 0.082418 0.054341 0.004402 0.000000 0.095800 0.002920 0.109890 0.054962 0.005904 0.000000 0.098961 0.003897 0.137363 0.055585 0.007422 0.000000 0.102123 0.004876 0.164835 0.056208 0.008958 0.000000 0.105285 0.005857 0.192308 0.056833 0.010510 0.000000 0.108447 0.006840 0.219780 0.057459 0.012080 0.000000 0.111608 0.007825 0.247253 0.058087 0.013668 0.000000 0.114770 0.008812 0.250000 0.058150 0.013827 0.000000 0.115086 0.008910 END FTABLE 3 END FTABLES EXT SOURCES <-Volume-> <Member> SsysSgap<--Mult-->Tran <-Target vols> <-Grp> <-Member-> *** <Name> # <Name> # tem strg<-factor->strg <Name> # # <Name> # # *** WDM 2 PREC ENGL 1 PERLND 1 999 EXTNL PREC WDM 2 PREC ENGL 1 IMPLND 1 999 EXTNL PREC WDM 1 EVAP ENGL 0.76 PERLND 1 999 EXTNL PETINP WDM 1 EVAP ENGL 0.76 IMPLND 1 999 EXTNL PETINP WDM 2 PREC ENGL 1 RCHRES 3 EXTNL PREC WDM 1 EVAP ENGL 0.5 RCHRES 3 EXTNL POTEV WDM 1 EVAP ENGL 0.76 RCHRES 4 EXTNL POTEV END EXT SOURCES EXT TARGETS <-Volume-> <-Grp> <-Member-><--Mult-->Tran <-Volume-> <Member> Tsys Tgap Amd *** <Name> # <Name> # #<-factor->strg <Name> # <Name> tem strg strg*** RCHRES 1 HYDR RO 1 1 1 WDM 1006 FLOW ENGL REPL RCHRES 1 HYDR O 1 1 1 WDM 1007 FLOW ENGL REPL RCHRES 1 HYDR O 2 1 1 WDM 1008 FLOW ENGL REPL RCHRES 1 HYDR STAGE 1 1 1 WDM 1009 STAG ENGL REPL COPY 1 OUTPUT MEAN 1 1 48.4 WDM 701 FLOW ENGL REPL COPY 501 OUTPUT MEAN 1 1 48.4 WDM 801 FLOW ENGL REPL RCHRES 2 HYDR RO 1 1 1 WDM 1014 FLOW ENGL REPL RCHRES 2 HYDR O 1 1 1 WDM 1015 FLOW ENGL REPL RCHRES 2 HYDR O 2 1 1 WDM 1016 FLOW ENGL REPL RCHRES 2 HYDR STAGE 1 1 1 WDM 1017 STAG ENGL REPL COPY 2 OUTPUT MEAN 1 1 48.4 WDM 702 FLOW ENGL REPL COPY 502 OUTPUT MEAN 1 1 48.4 WDM 802 FLOW ENGL REPL RCHRES 4 HYDR RO 1 1 1 WDM 1022 FLOW ENGL REPL RCHRES 4 HYDR O 1 1 1 WDM 1023 FLOW ENGL REPL RCHRES 4 HYDR O 2 1 1 WDM 1024 FLOW ENGL REPL Roberts Water Quality Onsite 2/28/2026 1:12:21 PM Page 55 RCHRES 4 HYDR STAGE 1 1 1 WDM 1025 STAG ENGL REPL RCHRES 3 HYDR STAGE 1 1 1 WDM 1026 STAG ENGL REPL RCHRES 3 HYDR O 1 1 1 WDM 1027 FLOW ENGL REPL COPY 3 OUTPUT MEAN 1 1 48.4 WDM 703 FLOW ENGL REPL COPY 503 OUTPUT MEAN 1 1 48.4 WDM 803 FLOW ENGL REPL END EXT TARGETS MASS-LINK <Volume> <-Grp> <-Member-><--Mult--> <Target> <-Grp> <-Member->*** <Name> <Name> # #<-factor-> <Name> <Name> # #*** MASS-LINK 2 PERLND PWATER SURO 0.083333 RCHRES INFLOW IVOL END MASS-LINK 2 MASS-LINK 3 PERLND PWATER IFWO 0.083333 RCHRES INFLOW IVOL END MASS-LINK 3 MASS-LINK 5 IMPLND IWATER SURO 0.083333 RCHRES INFLOW IVOL END MASS-LINK 5 MASS-LINK 8 RCHRES OFLOW OVOL 2 RCHRES INFLOW IVOL END MASS-LINK 8 MASS-LINK 12 PERLND PWATER SURO 0.083333 COPY INPUT MEAN END MASS-LINK 12 MASS-LINK 13 PERLND PWATER IFWO 0.083333 COPY INPUT MEAN END MASS-LINK 13 MASS-LINK 15 IMPLND IWATER SURO 0.083333 COPY INPUT MEAN END MASS-LINK 15 MASS-LINK 17 RCHRES OFLOW OVOL 1 COPY INPUT MEAN END MASS-LINK 17 END MASS-LINK END RUN Roberts Water Quality Onsite 2/28/2026 1:12:21 PM Page 56 Predeveloped HSPF Message File Roberts Water Quality Onsite 2/28/2026 1:12:21 PM Page 57 Mitigated HSPF Message File Roberts Water Quality Onsite 2/28/2026 1:12:21 PM Page 58 Disclaimer Legal Notice This program and accompanying documentation are provided 'as-is' without warranty of any kind. The entire risk regarding the performance and results of this program is assumed by End User. Clear Creek Solutions Inc. and the governmental licensee or sublicensees disclaim all warranties, either expressed or implied, including but not limited to implied warranties of program and accompanying documentation. In no event shall Clear Creek Solutions Inc. be liable for any damages whatsoever (including without limitation to damages for loss of business profits, loss of business information, business interruption, and the like) arising out of the use of, or inability to use this program even if Clear Creek Solutions Inc. or their authorized representatives have been advised of the possibility of such damages. Software Copyright © by : Clear Creek Solutions, Inc. 2005-2026; All Rights Reserved. Clear Creek Solutions, Inc. 6200 Capitol Blvd. Ste F Olympia, WA. 98501 Toll Free 1(866)943-0304 Local (360)943-0304 www.clearcreeksolutions.com