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TIR-4330 Reference_Only.pdf
©2025 D. R. STRONG Consulting Engineers Inc. TECHNICAL INFORMATION REPORT for SOLERRA 10823, 10815, and 10824 145th Pl SE Renton, Washington DRS Project No. 23033 King County File No. STRV24-0008 Owner/Applicant Tri pointe Homes 15900 SE Eastgate Way, Suite 300 Bellevue, WA 98008 (425) 452-0344 Report Prepared by D. R. STRONG Consulting Engineers, Inc. 620 7th Avenue Kirkland WA 98033 (425) 827-3063 Report Issue Date July 3, 2025 㜭㌭㈵ ©2025 D. R. STRONG Consulting Engineers Inc. Solerra Page i of ii Technical Information Report King County TECHNICAL INFORMATION REPORT SOLERRA TABLE OF CONTENTS SECTION I ...................................................................................................................... 1 Project Overview ......................................................................................................... 1 Predeveloped Site Conditions ..................................................................................... 1 Developed Site Conditions .......................................................................................... 1 Natural Drainage System Functions ............................................................................ 2 SECTION II ................................................................................................................... 13 Conditions and Requirements Summary ................................................................... 13 SECTION III .................................................................................................................. 16 Off-Site Analysis ........................................................................................................ 16 Task 1: Define and Map the Study Area .................................................................... 16 Task 2: Resource Review .......................................................................................... 16 Task 3: Field Inspection ............................................................................................. 25 Task 4: Drainage System Description and Problem Descriptions .............................. 26 Task 5: Mitigation of Existing or Potential Problems .................................................. 27 SECTION IV .................................................................................................................. 31 Flow Control and Water Quality Facility Analysis and Design ................................... 31 Existing Site Hydrology (Part A) ............................................................................. 31 Developed Site Area Hydrology (PART B) ............................................................. 35 Performance Standards (Part C) ............................................................................... 37 Flow Control System (Part D) .................................................................................... 37 Flow Control BMP Selection ................................................................................... 37 Flow Control Facility Design Output ....................................................................... 39 Water Quality Treatment System (Part E) ................................................................. 39 SECTION V ................................................................................................................... 41 Conveyance System Analysis and Design ................................................................ 41 SECTION VI .................................................................................................................. 50 Special Reports and Studies ..................................................................................... 50 SECTION VII ................................................................................................................. 51 Other Permits, Variances and Adjustments ............................................................... 51 SECTION VIII ................................................................................................................ 52 ESC Plan Analysis and Design (Part A) .................................................................... 52 SWPPS Plan Design (Part B) .................................................................................... 53 ©2025 D. R. STRONG Consulting Engineers Inc. Solerra Page ii of ii Technical Information Report King County SECTION IX .................................................................................................................. 54 Bond Quantities, Facility Summaries, and Declaration of Covenant .......................... 54 SECTION X ................................................................................................................... 55 Operations and Maintenance Manual ........................................................................ 55 APPENDIX A ................................................................................................................ 56 WWHM Output .......................................................................................................... 56 APPENDIX B ................................................................................................................ 57 Geotechnical Report .................................................................................................. 57 List of Figures Figure 1 TIR Worksheet .................................................................................................. 3 Figure 2 Vicinity Map ....................................................................................................... 8 Figure 3 Drainage Basins, Subbasins, and Site Characteristics Map.............................. 9 Figure 4 Soils ................................................................................................................ 10 Figure 5 Streams and 100-Year Floodplains and Floodway .......................................... 18 Figure 6 Wetlands ......................................................................................................... 19 Figure 7 Erosion Hazard Areas ..................................................................................... 20 Figure 8 Landslide Hazard Areas .................................................................................. 21 Figure 9 Seismic Hazard Areas ..................................................................................... 22 Figure 10 FEMA – Flood Insurance Rate Map .............................................................. 23 Figure 11 Drainage Complaints ..................................................................................... 24 Figure 12 Offsite Analysis Downstream Map ................................................................ 28 Figure 13 Offsite Analysis Downstream Table .............................................................. 29 Figure 14 Predevelopment Area Map............................................................................ 33 Figure 15 Existing Site Conditions................................................................................. 34 Figure 16 Developed Area Map .................................................................................... 36 Figure 17 Detention & Water Quality Facility Details ..................................................... 40 Figure 18 Backwater Map ............................................................................................. 42 ©2025 D. R. STRONG Consulting Engineers Inc. Solerra Page 1 Technical Information Report King County SECTION I PROJECT OVERVIEW The Project is the subdivision of 8 existing parcels into 22 single-family residential lots per the King County subdivision process. The parcels are zoned R4 and sums up to a total site area of 5.46 acres. The Tax Parcel Number is 032305-9256, 9276, 9277, 9278, 9279, 9027, 9280 & 032305TRCT . The Project location is 10823, 10815, 10824 145th Pl SE Renton, WA. The Project will meet the drainage requirements of the 2021 King County Surface Water Design Manual (2021 KCSWDM). PREDEVELOPED SITE CONDITIONS The total existing Site area is approximately 237,888 S.F. (5.46 AC). The Site is currently developed with four single-family residences, sheds, barns, a long asphalt driveway providing access to three single-family residences and associated gravel driveways. The majority of the Site is comprised of open spaces covered by lawn with trees scattered around the property. All surface runoff on the Site slopes towards the northeast and exits the Site at one Natural Discharge Location (NDL) near the northeast corner of the Site. Therefore, for purposes of this analysis, the Site will be considered to be within one Threshold Discharge Area (TDA) and all runoff will be conveyed to the northeast. Currently, the surface runoff sheet flows into drainage ditches along the existing access road. These roadside ditches then convey the existing runoff through culverts before discharging to the existing King County detention pond. The existing King County detention pond has about 11,170 c.f. of live storage volume. This project is proposing to decommission this existing pond and replace it with the proposed detention vault since all of the area currently draining to the detention pond will be a part of the project’s target surface area. Figure 3 shows the layout of the on -site basins. Section III describes Site runoff characteristics and downstream conditions. For the purpose of hydrologic calculations, the Project area was modeled as C, Forest, Mod in predeveloped site conditions. DEVELOPED SITE CONDITIONS The applicant is seeking approval to develop 5.46 AC. with 22 lots with lot sizes ranging from approximately 6,142 S.F. to 12,327 S.F. All existing improvements will be demolished or removed during plat construction. Impervious areas will consist of 22 single-family residences rooftops combined with their driveways, portions of the Tracts, the proposed subdivision right-of-way, and frontage improvements along NE 16th St and NE Sunset Blvd. In addition, there is approximately 2,273 S.F. of impervious area near the plat entrance at the intersection of NE 16 St and Lyon s Pl NE that will bypass the detention facility. 2,273 S.F. of the upstream NE Sunset Blvd frontage improvement area will be treatment/mitigation trade for the bypass area. All remaining area of the developed Site will consist of landscaping and lawn area. The Project is located in a Conservation Flow Control area and is required to provide Level 2 Flow Control and Basic Water Quality treatment per the 2021 KCSWDM. All runoff will be collected and conveyed to the proposed combined detention/wet vault in Tract C ©2025 D. R. STRONG Consulting Engineers Inc. Solerra Page 2 Technical Information Report King County of the proposed subdivision to accommodate basic water quality requirements. Although the project is located in a Conservation Flow Control area, there were several complaints related to flooding near Greenes Creek from citizens living at parcel 177640 -0020. Therefore, a Type 3 Drainage Problem Severe Flooding Problem has been identified downstream. Thus, the project will apply the historic site conditions Level 3 f low control standard to this Project. This is outlined in Table 1.2.3.A of the Manual. A s stated in Section 1.2.3.1(C) of the Manual, “If the Level 3 flow control standard is implemented onsite, no additional measures are required to prevent aggravation of the three types of downstream drainage problems described in Core Requirement #2.” Fu rthermore, as mentioned above, the current existing conditions drain to an existing detention pond meeting previous stormwater code requirements. The 100-year peak flow from this existing detention facility is approximately 2.50 cfs. The proposed project will lower the 100-year peak flow to 0.55 cfs. This significant reduction in released peak flows from the project site will assist in reducing the frequency, depth, and/or duration of the current drainage problems. Please see Section IV for more details. NATURAL DRAINAGE SYSTEM FUNCTIONS The Site is contained within one Threshold Discharge Area (TDA) with one Natural Discharge Areas (NDA) with one Natural Discharge Location (NDL). TDA is approximately 237,888 S.F. (5.46 AC) and the NDL is located near the northeast corner of the Site. The downstream report is included in Section III. A review of the SCS soils map for the area (see Figure 4, Soils) indicates Alde rwood gravelly sandy loam with 8 to 15 percent slopes (AgC ). Per the Manual, this soil type is classified as “Till” material. The SCS Soil series descriptions follow Figure 4. In evaluating the upstream area, we reviewed the area topography from King County iMap, City of Renton Mapping Application, and a field topographic survey. There is a small area of upstream runoff that will sheet flow onto the property . The plat to the west, Concord Place, will generate 6,465 s.f. of upstream area which lies east of their interceptor trench, whereas Tax Parcel Numbers 0323059254 & 0323059255 will generate approximately 22,261 s.f. of upstream area. The total upstream area is 28,726 s.f., of which 3,100 s.f. is roof area. This will be modeled as flow through area for the proposed detention facility. ©2025 D. R. STRONG Consulting Engineers Inc. Solerra Page 3 Technical Information Report King County FIGURE 1 TIR WORKSHEET King County Department of Development and Environmental Services TECHNICAL INFORMATION REPORT (TIR) WORKSHEET Part 1 PROJECT OWNER AND PROJECT ENGINEER Part 2 PROJECT LOCATION AND DESCRIPTION Project Owner: Tri Pointe Homes Phone: (425) 452-0344 Address: 15900 SE Eastgate Way, Suite 300 Bellevue, WA 98008 Project Engineer: Yoshio L. Piediscalzi, P.E. Company: D. R. STRONG Consulting Engineers Inc. Phone: (425) 827-3063 Project Name: Solerra Permit#: STRV24-0008 Location: Township: 23 South Range: 05 East Section: 3 Site Address: 10823, 10815, 10824 145th Pl SE Renton, Washington. Part 3 TYPE OF PERMIT APPLICATION Part 4 OTHER REVIEWS AND PERMITS Landuse (e.g.,Subdivision / Short Subd. / UPD Building (e.g.,M/F / Commercial / SFR) Clearing and Grading Right-of-Way Use Other: DFW HPA Shoreline Management COE 404 Structural DOE Dam Safety /Rockery/Vault FEMA Floodplain ESA Section 7 COE Wetlands Other: Part 5 PLAN AND REPORT INFORMATION Technical Information Report Full Type of Drainage Review Targeted (check one): Simplified Large Project Directed Date (include revision July 27, 2023 dates): Date of Final: September 6, 2024 Site Improvement Plan (Engr. Plans) Plan Type (check Full one): Modified Simplified Date (include revision July 27, 2023 dates): Date of Final: September 6, 2024 ©2025 D. R. STRONG Consulting Engineers Inc. Solerra Page 4 Technical Information Report King County Part 6 ADJUSTMENT APPROVALS Type (circle one): Standard / Experimental / 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: KCSWDM Adjustment No. Part 8 SITE COMMUNITY AND DRAINAGE BASIN Community Plan: New Castle Community Plan Special District Overlays: None Drainage Basin: May Creek Basin Stormwater Requirements: Level 2 w/ Basic WQ Treatment 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 ©2025 D. R. STRONG Consulting Engineers Inc. Solerra Page 5 Technical Information Report King County Part 10 SOILS Soil Type Alderwood (AgC) Slopes 8-15% Erosion Potential Slight High Groundwater Table (within 5 feet) Sole Source Aquifer Other Seeps/Springs Additional Sheets Attached Part 11 DRAINAGE DESIGN LIMITATIONS REFERENCE Core Requirement #2 – Offsite Analysis Sensitive/ Critical Areas SEPA LID Infeasibility Other Additional Sheet Attached LIMITATION / SITE CONSTRAINT None Part 12 TIR SUMMARY SHEET (Provide one TIR Summary Sheet per Threshold Discharge Area) Threshold Discharge Area: The Site is comprised of one TDA (One drainage facility) (name or description) Core Requirements (all 9 apply): Discharge at Natural Location Number of Natural Discharge Locations: 1 Offsite Analysis Level: 1 / 2 / 3 dated: May 22, 2023 and January 19th, 2024 Flow Control Level: 1 / 2 / 3 (Type 3 downstream drainage problems) or Exemption Number (include facility summary sheet) Flow Control BMPS: TBD Conveyance System Spill containment located at: TBD Erosion and Sediment Control/ CSWPP/CESCL/ESC Site Supervisor: TBD Construction Stormwater Contact Phone: TBD Pollution Prevention After Hours Phone: TBD Maintenance and Operation Responsibility (circle one): Private / Public If Private, Maintenance Log Required: Yes / No Financial Guarantees and Liability Provided: Yes / No Water Quality Type: Basic / Sens Lake / Enhanced Basic / Bog (include facility summary sheet) or exemption No. Landscape Management Plan: Yes / No ©2025 D. R. STRONG Consulting Engineers Inc. Solerra Page 6 Technical Information Report King County Special Requirements (as applicable) Area Specific Drainage Type: CDA / SDO / MDP / BP / LMP / Shared Fac./ None Requirements Name: Floodplain/Floodway Delineation Type: (circle one): Major / Minor / Exemption / None 100-year Base Flood Elevation (or range): Datum: Flood Protection Facilities Describe: None required or provided Source Control Describe Land use: Residential (comm. / industrial land use) Describe any structural controls: None required or provided Oil Control High-use Site: Yes / No Treatment BMP: Maintenance Agreement: Yes / No with whom? Other Drainage Structures Describe: Runoff generated by impervious surfaces will be collected and conveyed to the detention facility located in Tract C. Part 13 EROSION AND SEDIMENT CONTROL REQUIREMENTS MINIMUM ESC REQUIREMENTS DURING CONSTRUCTION Clearing Limits Cover Measures Perimeter Protection Traffic Area Stabilization Sediment Retention Surface Water Collection Dewatering Control Dust control Flow Control Protection of Flow Control BMP Facilities (existing and proposed) Maintain BMPs / Manage Project MINIMUM ESC REQUIREMENTS AFTER CONSTRUCTION Stabilize Exposed Surfaces Remove and Restore Temporary ESC Facilities Clean and Remove All Silt and Debris, ensure operation of Permanent Facilities, restore operation of Flow Control BMP Facilities as necessary Flag Limits of SAO and open space Preservation areas Other ©2025 D. R. STRONG Consulting Engineers Inc. Solerra Page 7 Technical Information Report King County Part 14 STORMWATER FACILITY DESCRIPTIONS (Note: Include Facility Summary and Sketch Flow Control Type/Description Water Quality Type/Description Detention Infiltration Regional Facility Shared Facility Flow Control BMPs Other Vault Restricted Footprint Biofiltration Wetpool Media Filtration Oil Control Spill Control Flow Control BMPs Other Wet Vault Part 15 EASEMENTS/TRACTS Part 16 STRUCTURAL ANALYSIS Drainage Easement Covenant Native Growth Protection Covenant Tract Other: Cast in Place Vault Retaining Wall Rockery > 4’ High Structural on Steep Slope Other: Part 17 SIGNATURE OF PROFESSIONAL ENGINEER I, or a civil engineer under my supervision, have visited the site. Actual site conditions as observed were incorporated into this worksheet and the attached Technical Information Report. To the best of my knowledge the information provided here is accurate. Signed/Date 7-3-25 ©2025 D. R. STRONG Consulting Engineers Inc. Solerra Page 8 Technical Information Report King County FIGURE 2 VICINITY MAP The information included on this map has been compiled by King County staff from a variety of sources and is subject to chang e without notice. King County makes no representations or warranties, express or implied, as to accuracy, completeness, timeliness, or rights to the use of such information. King County shall not be liable for any general, special, indirect, incidental, or consequential damages including, but not limited to, lost revenues or lost profits resulting from the use or misuse of the information contained on this map. Any sale of this map or information on this map is prohibited except by written permission of King County. Site ©2025 D. R. STRONG Consulting Engineers Inc. Solerra Page 9 Technical Information Report King County FIGURE 3 DRAINAGE BASINS, SUBBASINS, AND SITE CHARACTERISTICS MAP GRAPHIC SCALE 0 40 80 160 1 INCH=80 FT. ©2025 D. R. STRONG Consulting Engineers Inc. Solerra Page 10 Technical Information Report King County FIGURE 4 SOILS ©2025 D. R. STRONG Consulting Engineers Inc. Solerra Page 11 Technical Information Report King County AgC—Alderwood gravelly sandy loam, 8 to 15 percent slopes Map Unit Setting • National map unit symbol: 2t626 • Elevation: 50 to 800 feet • Mean annual precipitation: 20 to 60 inches • Mean annual air temperature: 46 to 52 degrees F • Frost-free period: 160 to 240 days • Farmland classification: Prime farmland if irrigated Map Unit Composition • Alderwood and similar soils: 85 percent • Minor components: 15 percent • Estimates are based on observations, descriptions, and transects of the mapunit. Description of Alderwood Setting • Landform: Ridges, hills • Landform position (two-dimensional): Shoulder • Landform position (three-dimensional): Nose slope, talf • Down-slope shape: Linear, convex • Across-slope shape: Convex • Parent material: Glacial drift and/or glacial outwash over dense glaciomarine deposits Typical profile • A - 0 to 7 inches: gravelly sandy loam • Bw1 - 7 to 21 inches: very gravelly sandy loam • Bw2 - 21 to 30 inches: very gravelly sandy loam • Bg - 30 to 35 inches: very gravelly sandy loam • 2Cd1 - 35 to 43 inches: very gravelly sandy loam • 2Cd2 - 43 to 59 inches: very gravelly sandy loam Properties and qualities • Slope: 8 to 15 percent • Depth to restrictive feature: 20 to 39 inches to densic material • Natural drainage class: Moderately well drained • Capacity of the most limiting layer to transmit water (Ksat): Very low to moderately low (0.00 to 0.06 in/hr) • Depth to water table: About 18 to 37 inches • Frequency of flooding: None • Frequency of ponding: None • Available water storage in profile: Very low (about 2.7 inches) Interpretive groups • Land capability classification (irrigated): None specified • Land capability classification (nonirrigated): 4s • Hydrologic Soil Group: B • Ecological site: F002XA004WA - Puget Lowlands Forest ©2025 D. R. STRONG Consulting Engineers Inc. Solerra Page 12 Technical Information Report King County • Forage suitability group: Limited Depth Soils (G002XF303WA), Limited Depth Soils (G002XN302WA), Limited Depth Soils (G002XS301WA) • Other vegetative classification: Limited Depth Soils (G002XF303WA), Limited Depth Soils (G002XN302WA), Limited Depth Soils (G002XS301WA) • Hydric soil rating: No Minor Components Everett • Percent of map unit: 5 percent • Landform: Kames, eskers, moraines • Landform position (two-dimensional): Shoulder, footslope • Landform position (three-dimensional): Crest, base slope • Down-slope shape: Convex • Across-slope shape: Convex • Hydric soil rating: No Indianola • Percent of map unit: 5 percent • Landform: Eskers, kames, terraces • Landform position (three-dimensional): Tread • Down-slope shape: Linear • Across-slope shape: Linear • Hydric soil rating: No Shalcar • Percent of map unit: 3 percent • Landform: Depressions • Landform position (three-dimensional): Dip • Down-slope shape: Concave • Across-slope shape: Concave • Hydric soil rating: Yes Norma • Percent of map unit: 2 percent • Landform: Depressions, drainageways • Landform position (three-dimensional): Dip • Down-slope shape: Concave, linear • Across-slope shape: Concave • Hydric soil rating: Yes ©2025 D. R. STRONG Consulting Engineers Inc. Solerra Page 13 Technical Information Report King County SECTION II CONDITIONS AND REQUIREMENTS SUMMARY The Project must comply with the following Core and Special Requirements: • C.R. #1 – Discharge at the Natural Location: There is NDL on Site. The NDL for the TDA is along the northern property line near the northeast corner of the Site. The detention facility shall be designed to match the predeveloped flow. • C.R. #2 – Offsite Analysis: An offsite analysis is included in Section III. The Analysis describes the Site’s runoff pattern in detail. • C.R. #3 – Flow Control: The Project is located in a Conservation Flow Control Area. A detention vault/wetvault will provide flow control as required for 22 lots from the Site. The Project is required to match durations for 50% of the two-year peak flow up to the full 50-year peak flow. Also match developed peak discharge rates to predeveloped peak discharge rates for the 2-year and 10-year return periods (2021 KCSWDM, Sec. 1.2.). However, as discussed in Section I, the Project will adhere to Flood Problem Flow Control Standards due to the drainage complaints downstream. • C.R. #4 – Conveyance System: New pipe systems and ditches/channels are required to be designed with sufficient capacity to convey and contain (at minimum) the 25-year peak flow, assuming developed conditions for onsite tributary areas and existing conditions for any offsite tributary areas. Pipe system structures and ditches/channels may overtop for runoff events that exceed the 25 -year design capacity, provided the overflow from a 100-year runoff event does not create or aggravate a “severe flooding problem” or “severe erosion problem” as defined in C.R. #2. Any overflow occurring onsite for runoff events up to and including the 100-year event must discharge at the natural location for the project Site. In residential subdivisions, such overflow must be contained within an onsite drainage easement, tract, covenant or public right-of-way. The proposed conveyance system was analyzed using the KCBW program, and is capable of conveying the 100 -year peak storm without overtopping any structures or channels. This analysis has been performed and is included in Section V of this report. • C.R. #5 – Erosion and Sediment Control: The Project provides the 13 minimum ESC measures. A SWPPP will be prepared at time of construction plan preparation. • C.R. #6 – Maintenance and Operations: Maintenance of the proposed storm drainage facilities will be the responsibility of the County. An Operation and Maintenance Manual has been included in Section X of this report. • C.R. #7 – Financial Guarantees and Liability: Prior to commencing construction, the Applicant must post a drainage facilities restoration and Site stabilization financial guarantee. For any constructed or modified drainage facilities to be maintained and operated by the City, the Applicant must: 1) Post a drainage defect and maintenance financial guarantee for a period of two years, and 2) Maintain the drainage facilities during the two-year period following posting of the drainage defect and maintenance financial guarantee. ©2025 D. R. STRONG Consulting Engineers Inc. Solerra Page 14 Technical Information Report King County • C.R. #8 – Water Quality: The Project is located in the Basic Water Quality Treatment area. A wetvault will accommodate the basic water quality requirements. • C.R. #9 – Flow Control BMP’s: The Project must meet the Flow Control BMP requirements as specified in the Manual. A BMP infeasibility criteria breakdown for Lots less than 22,000 S.F. in size in the order specified by the 2021 KCSWDM is as follows: Flow Control BMP Evaluation for Lots • Full Dispersion: Full dispersion is not feasible on this Site due to lack of native vegetated areas on the project Site that are both a.) not constrained by critical areas and b.) meet the flowpath slope and length requirements as specified in the Manual. • Full Infiltration: Per the Geotechnical Report, infiltration is infeasible for the project Site due to existing soil conditions. • Limited Infiltration: Per the Geotechnical Report, infiltration is not feasible for the project Site due to existing soil conditions. • Bioretention: Per the Geotechnical Report, infiltration is not feasible for the project Site due to existing soil conditions. • Permeable Pavement: Per the Geotechnical Report, infiltration is not feasible for the project Site due to existing soil conditions. • Basic Dispersion: Basic Dispersion is feasible for all lots. There will be no sizing credit taken for the detention vault. Basic Dispersion will be shown on the building permit plans. • Reduced Impervious Surface Credit: The reduced impervious surface credit is proposed to reduce allowable impervious areas of the lots which will be subsequently discharged via perforated pipe connections. The restricted footprint of each lot will be recorded via a covenant to assure compliance with the Manual. Please see BMP Table Below. Flow Control BMP Evaluation for plat infrastructure improvements • Full Dispersion: Full dispersion is not feasible on this Site due to lack of native vegetated areas on the project Site that are both a.) not constrained by critical areas and b.) meet the flowpath slope and length requirements as specified in the Manual. • Full Infiltration: Per the Geotechnical Report, infiltration is infeasible for the project Site due to existing soil conditions. • Limited Infiltration: Per the Geotechnical Report, infiltration is not feasible for the project Site due to existing soil conditions. • Bioretention: Per the Geotechnical Report, infiltration is not feasible for the project Site due to existing soil conditions. ©2025 D. R. STRONG Consulting Engineers Inc. Solerra Page 15 Technical Information Report King County • Permeable Pavement: Per the Geotechnical Report, infiltration is not feasible for the project Site due to existing soil conditions. • Basic Dispersion: The tracts will sheet flow disperse through the downsream 25’ of pervious strip prior to being collected by the proposed right-of-way improvements. • Soil Amendment is proposed to be utilized for all disturbed pervious areas on site. • S.R. #1 – Other Adopted Area-Specific Requirements: Not applicable for this Project. • S.R. #2 – Floodplain/Floodway Delineation: Not applicable for this Project. • S.R. #3 – Flood Protection Facilities: Not applicable for this Project. • S.R. #4 – Source Control: Not applicable for this Project. S.R. #5 – Oil Control: Not applicable for this Project. BMP TABLE ©2025 D. R. STRONG Consulting Engineers Inc. Solerra Page 16 Technical Information Report King County SECTION III OFF-SITE ANALYSIS An offsite Level One Downstream Analysis was prepared by D.R. STRONG Consulting Engineers Inc. and is included in this Section. TASK 1: DEFINE AND MAP THE STUDY AREA This Offsite Analysis was prepared in accordance with Core Requirement #2, Section 1.2.2 of the 2021 KCSWDM. The Site is located at 10823, 10815, 10824 145th Pl SE Renton, WA. See Figures 2 through 11 for maps of the study area. TASK 2: RESOURCE REVIEW • Adopted Basin Plans: Final Adopted May Creek Basin Plan (April 23, 2001) • Floodplain/Floodway (FEMA) Map: No floodplains exist on site, See Figure 10. • Other Offsite Analysis Reports: None are applicable to this site. • Sensitive Areas Folio Maps: See Figures 4-8 for documentation of the distance downstream from the proposed project to the nearest critical areas. Included, are sections of the King County Sensitive Areas Folio which indicate the following: • Figure 5 Streams and 100-Year Floodplains and Floodway: There is one Type 3 stream, Greenes Creek to the north, within one mile of the Site. A 100-year floodplain is within one mile of the Site where Greenes Creek outlets to May Creek north of the Site. • Figure 6 Wetlands: There are two wetlands along the downstream path. • Figure 7 Erosion Hazard: There are no mapped Erosion Hazard Areas within one mile of the Site along the downstream path. • Figure 8 Landslide Hazard: There are no mapped Landslide Hazard Areas within one mile of the Site along the downstream path. • Figure 9 Seismic Hazard: There are no mapped Seismic Hazard Areas within one mile of the Site along the downstream path. • DNRP Drainage Complaints and Studies: As shown in Figure 11, there is one complaint within the last ten years that has since been closed. Complaint 1991 -0619 was a comment on increased flow in seasonal creek (Greenes Creek). The complaint was closed in May of 2019. Several other drainage complaints have been filed along the downstream paths but are not within the last ten years or are not applicable to the level one downstream analysis. There were several drainage complaints submitted as public comments during the public comment period. Several of these complaints were from the citizens living at parcel 177640-0020. As a result of the downstream flooding concerns, the detention facility has been sized to meet Level 3 flow control standards. • Road Drainage Problems: Road Maintenance noted a “few clogged pipes and ditch issues” along 147th Ave SE that caused water to go over the roadway on occasion . ©2025 D. R. STRONG Consulting Engineers Inc. Solerra Page 17 Technical Information Report King County • USDA King County Soils Survey: See Figure 4. • Wetlands Inventory: The wetland inventory revealed no additional wetlands within the downstream path. • Migrating River Studies: None are applicable to the site. • Washington State Department of Ecology's latest published Clean Water Act Section 303d list of polluted waters: The presumed receiving body of water, May Creek, has Category 5 listing relating to bioassessment, bacteria, and temperature. See Section 5 for mitigation. • King County Designated Water Quality Problems: None at this time. • Adopted Stormwater Compliance Plans: None at this time. • Basin Reconnaissance Summary Reports: None at this time. ©2025 D. R. STRONG Consulting Engineers Inc. Solerra Page 18 Technical Information Report King County FIGURE 5 STREAMS AND 100-YEAR FLOODPLAINS AND FLOODWAY Site ©2025 D. R. STRONG Consulting Engineers Inc. Solerra Page 19 Technical Information Report King County FIGURE 6 WETLANDS Site ©2025 D. R. STRONG Consulting Engineers Inc. Solerra Page 20 Technical Information Report King County FIGURE 7 EROSION HAZARD AREAS Site ©2025 D. R. STRONG Consulting Engineers Inc. Solerra Page 21 Technical Information Report King County FIGURE 8 LANDSLIDE HAZARD AREAS Site ©2025 D. R. STRONG Consulting Engineers Inc. Solerra Page 22 Technical Information Report King County FIGURE 9 SEISMIC HAZARD AREAS Site ©2025 D. R. STRONG Consulting Engineers Inc. Solerra Page 23 Technical Information Report King County FIGURE 10 FEMA – FLOOD INSURANCE RATE MAP Site ©2025 D. R. STRONG Consulting Engineers Inc. Solerra Page 24 Technical Information Report King County FIGURE 11 DRAINAGE COMPLAINTS Site ©2025 D. R. STRONG Consulting Engineers Inc. Solerra Page 25 Technical Information Report King County TASK 3: FIELD INSPECTION UPSTREAM TRIBUTARY AREA In evaluating the upstream area, we reviewed the area topography from King County iMap, City of Renton Mapping Application and a field topographic survey. There is a small area of upstream runoff that will sheet flow onto the property. The plat to the west, Concord Place and adjacent parcels will generate approximately 28,726 s.f. of upstream area. Approximately 3,100 s.f. of this upstream area is roof are a. This will be modeled as flow through area for the proposed detention facility. GENERAL ONSITE AND OFFSITE DRAINAGE DESCRIPTION The Site is contained within one TDA with one NDA with one NDL. The TDA is approximately 237,888 S.F. (5.46 AC) and the NDL is located along the northern property line near the northeast corner of the Site. Runoff generated in the TDA exits the site as sheet flow at point “A1” located at the northeast corner of the Site. After leaving the Site, runoff is collected at the existing detention pond at the corner of NE 16 th Street and Lyons Pl NE and conveyed in an easterly direction before entering the existing conveyance system in Lyons Ave NE. Runoff then flows north in Lyons Ave NE before entering Greenes Creek and the associated wetland on the north side of NE 17 th Street. Greenes Creek continues north approximately 0.75 miles until it converges with May Creek. May Creek eventually outlets to Lake Washington approximately 4 miles northwest of the Site. ©2025 D. R. STRONG Consulting Engineers Inc. Solerra Page 26 Technical Information Report King County TASK 4: DRAINAGE SYSTEM DESCRIPTION AND PROBLEM DESCRIPTIONS DRAINAGE SYSTEM DESCRIPTION The downstream analysis is further illustrated and detailed in Figures 12 and 13, the Downstream Map, Downstream Photos and Downstream Table. The drainage area is located within the May Creek basin. The drainage area was evaluated by reviewing available resources, and by conducting a field reconnaissance on May 22, 2023 under partly cloudy conditions as well as January 19th, 2024 under mostly cloudy conditions. DOWNSTREAM PATH TDA Point “A1” is the NDL for the TDA. It is located along the northern property line near the northeast corner of the Site. (±0’) From Point “A1” to Point “B1,” runoff flows in a northerly direction as sheet flow. No flow observed. (±0’-11) Point “B1”, runoff is collected in a detention pond at the corner of NE 16 th Street and Lyons Pl NE and routed to the pond intake inlet. No flow observed. (±11’) From Point “B1” to Point “C1,” runoff is conveyed in a northerly direction via a 12” diameter corrugated metal pipe (CMP). No flow observed. (±11’-38’) Point “C1”, runoff enters a Type 2 catch basin located in the northern portion of the detention pond. No flow observed. (±38’) From Point “C1” to Point “D1,” runoff is conveyed in a northeasterly direction via an 18” diameter CMP. No flow observed. (±38’-92’) Point “D1”, runoff enters a Type 2 catch basin located in the property immediately north of the detention pond. No flow observed. (±92’) From Point “D1” to Point “E1,” runoff is conveyed in a northeasterly direction via an 18” diameter pipe. No flow observed. (±92’-104’) Point “E1”, runoff enters a Type 2 catch basin located in the property immediately north of the detention pond. No flow observed. (±104’) From Point “E1” to Point “F1,” flow is conveyed in a southeasterly direction via an 18” diameter pipe. No flow observed. (±104’-120’) Point “F1”, runoff enters a Type 2 catch basin located in the property immediately east of the detention pond. No flow observed. (±120’) From Point “F1” to Point “G1,” flow is conveyed in an easterly direction via an 18” diameter pipe. No flow observed. (±120’-241’) Point “G1”, runoff enters a Type 2 catch basin located in the middle of Lyons Avenue NE No flow observed. (±241’) From Point “G1” to Point “H1,” flow is conveyed in a northerly direction via a 24” diameter CMP. No flow observed. (±241’-433’) ©2025 D. R. STRONG Consulting Engineers Inc. Solerra Page 27 Technical Information Report King County Point “H1”, runoff outlets to Greenes Creek and the associated wetland, approximately 38’ north of NE 17th Street and Lyons Avenue NE. Flow was observed. (±433’) From Point “H1” to Point “I1”, runoff heads north as channel flow through Greenes Creek. No flow was observed. (±433’-1,320’) Point “I1”, the downstream path reaches the quarter mile mark . Greenes Creek continues approximately 0.5 miles until it converges with May Creek. May Creek eventually outlets to Lake Washington approximately 3.8 northwest of the Site. TASK 5: MITIGATION OF EXISTING OR POTENTIAL PROBLEMS A review of the King County Water and Land Resources Division – Drainage Services Section Documented Drainage Complaints within one mile of the downstream flow paths revealed one complaint within the last ten years that has since been closed. Complaint 1991-0619 was a comment on increased flow in seasonal creek (Greenes Creek). The complaint was closed in May of 2019. Several other drainage complaints have been filed along the downstream paths but are not within the last ten years or are not applicable to the level one downstream analysis. There were several drainage complaints submitted as public comments during the public comment period. Several of these complaints were from the citizens living at parcel 177640 -0020. As a result of the downstream flooding concerns, the detention facility has been sized to meet Level 3 flow control standards. Although the project is located in a Conservation Flow Control area, there were several complaints related to flooding near Greenes Creek from citizens living at parcel 177640 - 0020. Therefore, a Type 3 Drainage Problem Severe Flooding Problem has been identified downstream. Thus, the project will apply the historic site conditions Level 3 f low control standard to this Project. This is outlined in Table 1.2.3.A of the Manual. As stated in Section 1.2.3.1(C) of the Manual, “If the Level 3 flow control st andard is implemented onsite, no additional measures are required to prevent aggravation of the three types of downstream drainage problems described in Core Requirement #2.” Furthermore, as mentioned in Section I, the current existing conditions drain to an existing detention pond meeting previous stormwater code requirements. The 100-year peak flow from this existing detention facility is approximately 2.50 cfs. The proposed project will lower th e 100-year peak flow to 0.55 cfs. This significant reduction in released peak flows from the project site will assist in reducing the frequency, depth, and/or duration of the current drainage problems. Please see Section IV for more details. The project drains to May Creek which has been assessed with Category 5 listings relating to bioassessment, bacteria, and temperature. However, mitigation is not required due the Project proximity to the assessed water body (greater than ¼ mile). ©2025 D. R. STRONG Consulting Engineers Inc. Solerra Page 28 Technical Information Report King County FIGURE 12 OFFSITE ANALYSIS DOWNSTREAM MAP GRAPHIC SCALE 0 175 350 700 1 INCH 350 FT. *All photos taken January 19th, 2024 Photo 1: Photo 2: Photo 3: Photo 4: Photo 5: Photo 6: Photo 7: Photo 8: Photo 9: Photo 10: Photo 11: Photo 12: Photo 13: Photo 14: Photo 15: Photo 16: Photo 17: ©2025 D. R. STRONG Consulting Engineers Inc. Solerra Page 29 Technical Information Report King County FIGURE 13 OFFSITE ANALYSIS DOWNSTREAM TABLE TDA Symbol Drainage Component Type, Name, and Size Drainage Component Description Slope Distance From site Discharge Existing Problems Potential Problems Observations of field inspector resource reviewer, or resident See map Type: sheet flow, swale, Stream, channel, pipe, Pond; Size: diameter Surface area drainage basin, vegetation, cover, depth, type of sensitive area, volume % 1/4 mile = 1,320 feet Constrictions, under capacity, ponding, overtopping, flooding, habitat or organism destruction, scouring, bank sloughing, sedimentation, incision, other erosion Tributary area, likelihood of problem, overflow pathways, potential impacts. A1 Natural Discharge Location Runoff exits Site near the northeast property corner as sheet flow 0’ None Observed None Anticipated No flow observed A1-B1 Northerly sheet flow Sheet flow native vegetation None Observed None Anticipated No flow observed B1 Detention pond Type 2 inlet CB Southern portion of detention pond 11’ None Observed None Anticipated No flow observed B1-C1 Northerly pipe flow 12” CMP None Observed None Anticipated No flow observed C1 Type 2 CB Type 2 inlet CB Northern portion of detention pond ±38’ None Observed None Anticipated No flow observed. C1-D1 Northeasterly pipe flow 18” CMP None Observed None Anticipated No flow observed D1 Type 2 CB Type 2 Inlet CB Property north of detention pond ±92’ None Observed None Anticipated No flow observed D1-E1 Southerly pipe flow 18” Pipe None Observed None Anticipated No flow observed E1 Type 2 CB Type 2 Inlet CB Property north of detention pond ±104’ None Observed None Anticipated No flow observed E1-F1 Southeasterly pipe flow 18” Pipe None Observed None Anticipated No flow observed F1 Type 2 CB Type 2 Inlet CB Property east of detention pond ±120’ None Observed None Anticipated No flow observed F1-G1 Easterly pipe flow 18” Pipe None Observed None Anticipated No flow observed ©2025 D. R. STRONG Consulting Engineers Inc. Solerra Page 30 Technical Information Report King County G1 Type 2 CB Type 2 Inlet CB Middle of Lyons Ave NE ±241’ None Observed None Anticipated No flow observed G1-H1 Northerly pipe flow 24” CMP None Observed None Anticipated No flow observed H1 Outlet to Greenes Creek 24” CMP ±433’ None Observed None Anticipated Flow observed H1-I1 Northerly channel flow Greenes Creek and wetland None Observed None Anticipated No flow observed I1 End of quarter mile path Greenes Creek ±1,320’ None Observed None Anticipated No flow observed ©2025 D. R. STRONG Consulting Engineers Inc. Solerra Page 31 Technical Information Report King County SECTION IV FLOW CONTROL AND WATER QUALITY FACILITY ANALYSIS AND DESIGN EXISTING SITE HYDROLOGY (PART A) WWHM was used to model the peak runoff from the Site. Per Table 3.2.2.b of the Manual the soil type is modeled as “C, Forest, Mod” for the Alderwood gravelly sandy loam SCS classification as shown in Figure 4. Soils. The drainage basin in the predeveloped condition shall consist of the TDA modeled as “Forest.” Results of the WWHM analysis are included in this section. The project also analyzed the existing site conditions due to the downstream concerns. The results are shown below. TDA (Historic Site Conditions Including Upstream Area) OUTPUT Flow PREDEVELOPED Flow(cfs) 0501 15m 2 Year = 0.3332 5 Year = 0.5562 10 Year = 0.7311 25 Year = 0.9829 50 Year = 1.1929 100 Year = 1.4221 ©2025 D. R. STRONG Consulting Engineers Inc. Solerra Page 32 Technical Information Report King County TDA (Existing Site Conditions) OUTPUT Flow PREDEVELOPED Flow(cfs) 0501 15m 2 Year = 1.0453 5 Year = 1.5941 10 Year = 1.9875 25 Year = 2.5146 50 Year = 2.9272 100 Year = 3.3560 ©2025 D. R. STRONG Consulting Engineers Inc. Solerra Page 33 Technical Information Report King County FIGURE 14 PREDEVELOPMENT AREA MAP GRAPHIC SCALE 0 40 80 160 1 INCH=80 FT. ©2025 D. R. STRONG Consulting Engineers Inc. Solerra Page 34 Technical Information Report King County FIGURE 15 EXISTING SITE CONDITIONS GRAPHIC SCALE 0 40 80 160 1 INCH=80 FT. ©2025 D. R. STRONG Consulting Engineers Inc. Solerra Page 35 Technical Information Report King County DEVELOPED SITE AREA HYDROLOGY (PART B) WWHM was used to model the developed peak runoff from the Site. The soil types are unchanged from the pre-developed conditions. Results of the WWHM analysis are included in this section. The drainage basin in the mitigated condition shall consist of the TDA. TDA OUTPUT Flow DEVELOPED Flow(cfs) 0701 15m 2 Year = 1.7614 5 Year = 2.3777 10 Year = 2.8184 25 Year = 3.4134 50 Year = 3.8852 100 Year = 4.3819 ©2025 D. R. STRONG Consulting Engineers Inc. Solerra Page 36 Technical Information Report King County FIGURE 16 DEVELOPED AREA MAP GRAPHIC SCALE 0 40 80 160 1 INCH=80 FT. ©2025 D. R. STRONG Consulting Engineers Inc. Solerra Page 37 Technical Information Report King County PERFORMANCE STANDARDS (PART C) The Project is required to adhere to Level 2 Flow Control criteria. The Level 2 performance criteria requires that the developed condition’s durations must match the predeveloped durations ranging from 50% of the two-year peak flow up to the full 50-year peak flow and also match developed peak discharge rates to predeveloped peak discharge rates for the 2-year and 10-year return periods (2021 KCSWDM, Sec. 1.2). Although the project is located in a Conservation Flow Control area, there were several complaints related to flooding near Greenes Creek from citizens living at parcel 177640 -0020. Therefore, a Type 3 Drainage Problem Severe Flooding Problem has been identified downstream. Thus, the project will apply the historic site conditions Level 3 flow control standard to this Project. This is outlined in Table 1.2.3.A of the Manual. As stated in Sectio n 1.2.3.1(C) of the Manual, “If the Level 3 flow control standard is implemented onsite, no additional measures are required to prevent aggravation of the three types of downstream drainage problems described in Core Requirement #2.” Furthermore, as ment ioned in Section I, the current existing conditions drain to an existing detention pond meeting previous stormwater code requirements. The 100-year peak flow from this existing detention facility is approximately 2.50 cfs. Please see the WWHM output for full analysis on existing detention pond. The proposed project will lower the 100-year peak flow to 0.55 cfs. This significant reduction in released peak flows from the project site will assist in reducing the frequency, depth, and/or duration of the cur rent drainage problems. Furthermore, in reviewing the public comments, KCDOT roads maintenance issues, and reviewing all of the past drainage complaints, the downstream issues are a capacity concern and maintenance issue. Therefore, the reduction in peak flows will significantly help/reduce any drainage problem near parcel 177640-0020. See Appendix A for WWHM output showing compliance. The Basic Water Quality Treatment is designed to achieve 80% removal of total suspended solids (TSS) for flows up to and including the WQ design flow or volume (defined in Section 6.2.1, p. 6-17). Conveyance criteria for the Project require that all new pipes be designed to convey and contain (at minimum) the 25-year peak flow. The conveyance system design has been analyzed and is provided in Section V of this report. FLOW CONTROL SYSTEM (PART D) The Site will utilize a detention vault/wetvault meeting the Level 3 Flow Control Criteria. A detention vault/wetvault will provide flow control as required for 22 lots from the Site. WWHM was used to size the detention facility, utilizing 15-minute time steps. The detention vault/wetvault design information is included in this section. FLOW CONTROL BMP SELECTION Subdivision projects are required to mitigate for impervious surface per the requirements laid out in Section 1.2.9.2 of the 2021 KCSWDM. The project falls under the “Small Lot BMP Requirements” due to the area of all proposed lots being less than 22,000 S.F. A BMP list evaluating applicable BMPs in order of preference as specified in the Manual can be found in Section II, Conditions and Requirements under Core Requirement #9. ©2025 D. R. STRONG Consulting Engineers Inc. Solerra Page 38 Technical Information Report King County After analysis of the available BMPs, the project is proposing the Reduced Impervious Surface Credit BMP to meet the requirements of the Manual. In Section 1.2.9.2.1.5, the Manual specifies that “BMPs must be implemented, at minimum, for an impervious area equal to at least 10% of the site/lot for site/lot sizes up to 11,000 sf and at least 20% of the site/lot sizes between 11,000 and 22,000 square feet […]” The project will be implementing the Reduced Impervious Surface Credit per the design requirements laid out in Appendix C of the Manual, Section C.2.9. Per the requirements set forth in the Manual, all areas proposed to be mitigated will be directed towards the proposed detention facilities via a perforated pipe connection. Additionally, a restricted footprint table will be added to the final plat, and co venants will be submitted with individual building permits. Subdivision project are also required to evaluate flow control BMPs for plat infrastructure improvements. As discussed in Section II, all flow control BMPs for plat infrastructure are infeasible. ©2025 D. R. STRONG Consulting Engineers Inc. Solerra Page 39 Technical Information Report King County FLOW CONTROL FACILITY DESIGN OUTPUT See Appendix A for WWHM output. TDA WATER QUALITY TREATMENT SYSTEM (PART E) The Project is located in the Basic Water Quality Treatment area. The treatment goal is 80% removal of total suspend solids for a typical rainfall year, assuming typical pollutant concentration in urban runoff. The project will utilize a detention vault/wetvault to accommodate the Basic water quality requirements. The required dead storage volume is 2 4,245 and the provided dead storage volume is 27,500. See Figure 17 for more details. ©2025 D. R. STRONG Consulting Engineers Inc. Solerra Page 40 Technical Information Report King County FIGURE 17 DETENTION & WATER QUALITY FACILITY DETAILS GRAPHIC SCALE 0 5 10 20 1 INCH = 10 FT. ©2025 D. R. STRONG Consulting Engineers Inc. Solerra Page 41 Technical Information Report King County SECTION V CONVEYANCE SYSTEM ANALYSIS AND DESIGN Per C.R. #4 of the 2021 KCSWDM, the conveyance system must be analyzed and designed for existing tributary and developed on site runoff from the proposed project. Pipe systems shall be designed to convey the 100-year design storm. The Rational Method will be used to calculate the Q-Ratio for each pipe node. A conveyance system consisting primarily of pipes and catch basins was designed for the Project. Onsite runoff from PGIS will be collected by multiple catch basins. Pipes are typically 12, and 18-inch diameter LCPE material. The proposed conveyance system meets all requirements set forth by the Manual. The tailwater conditions were assumed to be the 100-year storm stage elevation in the proposed detention vault . The backwater analysis includes the proposed storm network in SR900. The downstream pipe from detention vault has a capacity to convey a flow rate of 5.86 cfs while the unmitigated/developed 100-year peak flow by WWHM is 4.37 cfs. Please see below for FlowMaster Calculations of the downstream pipe. V = (k/n)*[(A/P)^(2/3)]*[S^(1/2)] V= 7.456747 ft/s Q = V * A Q= 5.856511 ft3/s k = unit conversion factor A = flow area of pipe P = wetted perimeter S = slope V= velocity in pipe Q = discharge rate n = mannings n = 0.012 pipe diameter = 1.00 ft P = pipe circumference = 2πr = 3.14159 ft k = 1.49 A = πr^2 = 0.785398 ft2 S = 0.0229 ft/ft ©2025 D. R. STRONG Consulting Engineers Inc. Solerra Page 42 Technical Information Report King County FIGURE 18 BACKWATER MAP GRAPHIC SCALE 0 40 80 160 1 INCH = 80 FT. Storm Water Runoff Variables: A=Total of Subasin and Tributary Areas C=Runoff Coefficient (the anticipated proportion of rainfall volume that runs off the area) see 2016 KCSWM Table 3.2.1A CC=Composite Runoff Coefficient CC=S(Cn*An)/ATotal Tc=Time of Concentration (Typically 6.3 minutes which is the minimum value used in calculations)6.3 R=design return frequency iR=Unit peak rainfall intensity factor iR=(aR)(Tc)^(-bR) aR,bR=coefficients from '16 KCSWM Table 3.2.1.B used to adjust the equation for the design storm IR=Peak rainfall intensity factor for a storm of return frequency 'R' IR=PR*iR PR=total precipitation (inches) for the 24-hour storm event for the given frequency. See Issopluvial Maps in 2016 KCSWM Figures 3.2.1.A - D QR=peak flow (cfs) for a storm of return frequency 'R' QR=CC*iR*A The Q-Ratio describes the ratio of the tributary flow to the main upstream flow. R=100 -year storm aR=2.61 bR=0.63 PR=4 inches Conveyance System Variables: d=pipe diameter n=Manning's Number l=length of pipe Pipe Structures Subasins &A A C CC Tc iR IR QR SQR Q - d Material n l Slope invert invert over-Q V Bend CB Tributaries subasin Ratio in out flow Full Full Dia elev.Flow Flow FROM CB To CB sf Ac Ac Min.cfs cfs in ft %ft ft ft cfs fps CB#10 TO VAULT INLET 10 10 9 10 5277 0.12 0.77 6.3 0.82 3.27 0.31 0.31 0.00 12 LCPE 0.012 35 0.51 465.10 464.92 468.10 2.77 3.53 124 2 9 9 8 9 206 0.00 0.77 6.5 0.81 3.22 0.01 0.32 0.04 12 LCPE 0.012 124 4.22 464.92 459.71 469.55 7.95 10.12 60 2 8 8 7 8 2697 0.06 0.77 6.7 0.79 3.16 0.15 0.47 0.47 12 LCPE 0.012 17 2.56 459.71 459.28 462.71 6.20 7.89 70 2 7 7 6 7 29587 0.68 0.47 6.7 0.79 3.15 1.01 1.47 2.15 12 LCPE 0.012 126 2.24 459.28 456.46 462.28 5.80 7.38 72 2 6 6 5 6 20514 0.47 0.57 7.0 0.77 3.07 0.82 2.30 0.56 12 LCPE 0.012 24 0.49 456.46 456.34 459.46 2.72 3.46 87 2 5 5 4 5 37354 0.86 0.44 7.1 0.76 3.04 1.16 3.45 0.50 12 LCPE 0.012 198 2.50 456.34 451.41 459.47 6.11 7.78 90 2 RUN 104-4 36696 0.84 0.55 4 4 3 4 33604 0.77 0.57 4 4 3 4 70300 1.61 0.56 7.5 0.73 2.93 2.64 6.10 0.77 12 LCPE 0.012 156 2.96 451.41 446.79 454.53 6.66 8.48 0 2 RUN 103-3 24863 0.57 0.58 3 3 2 3 25467 0.58 0.58 3 3 2 3 50330 1.16 0.58 7.8 0.71 2.85 1.91 8.01 0.31 18 LCPE 0.012 97 8.06 446.79 438.94 450.37 32.40 18.34 22 2 2 2 1 2 6209 0.14 0.69 7.9 0.71 2.83 0.28 8.29 0.04 18 LCPE 0.012 66 13.01 438.94 430.4 442.44 41.15 23.29 22 2 RUN 201-1 31222 0.72 0.58 1 1 VAULT INLET 1 14095 0.32 0.37 1 1 VAULT INLET 1 45317 1.04 0.51 8.0 0.71 2.82 1.50 9.79 0.18 18 LCPE 0.012 29 19.47 430.40 424.7 438.19 50.34 28.49 83 4 CB#103 TO CB#3 103 103 3 103 24863 0.57 0.58 6.3 0.82 3.27 1.09 1.09 0.00 12 LCPE 0.012 24 0.49 447.41 447.29 450.41 2.72 3.46 0 2 CB#104 TO CB#4 104 104 4 104 36696 0.84 0.55 6.3 0.82 3.27 1.50 1.50 0.00 12 LCPE 0.012 24 0.49 451.53 451.41 454.53 2.72 3.46 0 2 CB#201 TO CB#1 201 201 101 201 5877 0.13 0.77 6.3 0.82 3.27 0.34 0.34 0.00 12 LCPE 0.012 28 6.50 436.96 435.17 439.96 9.87 12.57 0 2 101 101 1 101 25345 0.58 0.53 6.3 0.82 3.26 1.01 1.35 2.96 12 LCPE 0.012 24 4.14 435.17 434.18 438.17 7.87 10.02 48 2 31222 0.72 0.58 ©2025 D. R. STRONG Consulting Engineers Inc. Solerra Page 43 Technical Information Report King County BACKWATER ANALYSIS Section VIII FLOW DATA L>C -Critical Depth (ft) DN -Normal Depth (ft) T W -Tailwater Depth (ft) DO -Outlet Depth (ft) DE - Entrance Depth (ft) H W O -Headwater (ft) assuming Outlet Control HWI -Headwater (ft) assuming Inlet Control DXN - Distance (expressed as a fraction of the pipe length) from the outlet to where the flow profile intersects with normal depth. DXN will equal one under full-flow conditions and will equal zero when a hydraulic jump occurs at the outlet or when normal depth equals zero (normal depth w!** equal zero when the pipe grade is flat or re ersed). COEFFIC1ENTS/INLET DATA KE -Entrance Coefficient under Outlet Control KB -Bend Loss Coefficient KJ -Junction Loss Coefficient K -Inlet Control Equation parameter M -Inlet Control Equation parameter C -Inlet Control Equation parameter ' ( Y - Inlet Control Equation parameter Q-Ratio Ratio of tributary flow to main upstream flow of Q3/Q1 \ Junction Q, VBH - Barrel Velocity Head (ft) based on the average velocity determined by V=Q/Afull VUH -Upstream Velocity Head (ft) based on an inputted velocity. EHU-Upstream Energy Head (ft) available after bend losses and junction losses have been subtracted from VUH. VCH -Critical Depth Velocity Head (ft) VNH -Normal Depth Velocity Head (ft) VEH -Entrance Depth Velocity Head (ft) VOH -Outlet Depth Velocity Head (ft) vm-4 KCBW User’s Guide March 15. 1999 ©2025 D. R. STRONG Consulting Engineers Inc. Solerra Page 44 Technical Information Report King County BACKWATER ANALYSIS RESULTS BACKWATER COMPUTER PROGRAM FOR PIPES Pipe data from file:CB#10 TO VAULT INLET.bwp Surcharge condition at intermediate junctions Tailwater Elevation:437.1 feet Discharge Range:0.979 to 9.79 Step of 0.979 [cfs] Overflow Elevation:468.1 feet Weir:NONE Upstream Velocity:0. feet/sec PIPE NO. 1: 29 LF - 18"CP @ 19.47% OUTLET: 424.70 INLET: 430.40 INTYP: 5 JUNC NO. 1: OVERFLOW-EL: 438.19 BEND: 83 DEG DIA/WIDTH: 4.0 Q-RATIO: 0.18 Q(CFS) HW(FT) HW ELEV. * N-FAC DC DN TW DO DE HWO HWI ******************************************************************************* 0.98 6.72 437.12 * 0.012 0.37 0.15 12.40 12.40 6.71 6.72 0.36 1.96 6.74 437.14 * 0.012 0.53 0.21 12.40 12.40 6.71 6.74 0.59 2.94 6.79 437.19 * 0.012 0.66 0.25 12.40 12.40 6.72 6.79 0.79 3.92 6.86 437.26 * 0.012 0.76 0.29 12.40 12.40 6.73 6.86 0.97 4.89 6.96 437.36 * 0.012 0.86 0.32 12.40 12.40 6.75 6.96 1.15 5.87 7.07 437.47 * 0.012 0.94 0.35 12.40 12.40 6.78 7.07 1.33 6.85 7.20 437.60 * 0.012 1.02 0.38 12.40 12.40 6.81 7.20 1.52 7.83 7.36 437.76 * 0.012 1.09 0.41 12.40 12.40 6.84 7.36 1.70 8.81 7.53 437.93 * 0.012 1.15 0.43 12.40 12.40 6.88 7.53 1.93 9.79 7.73 438.13 * 0.012 1.21 0.45 12.40 12.40 6.92 7.73 2.18 PIPE NO. 2: 65 LF - 18"CP @ 13.01% OUTLET: 430.40 INLET: 438.94 INTYP: 5 JUNC NO. 2: OVERFLOW-EL: 442.44 BEND: 22 DEG DIA/WIDTH: 2.0 Q-RATIO: 0.04 Q(CFS) HW(FT) HW ELEV. * N-FAC DC DN TW DO DE HWO HWI ******************************************************************************* 0.83 0.36 439.30 * 0.012 0.34 0.15 6.72 6.72 0.34 ***** 0.36 1.66 0.56 439.50 * 0.012 0.49 0.21 6.74 6.74 0.49 ***** 0.56 2.49 0.72 439.66 * 0.012 0.60 0.26 6.79 6.79 0.60 ***** 0.72 3.32 0.86 439.80 * 0.012 0.70 0.29 6.86 6.86 0.70 ***** 0.86 4.14 0.98 439.92 * 0.012 0.79 0.33 6.96 6.96 0.79 ***** 0.98 4.97 1.09 440.03 * 0.012 0.86 0.36 7.07 7.07 0.86 ***** 1.09 5.80 1.20 440.14 * 0.012 0.93 0.39 7.20 7.20 0.93 ***** 1.20 6.63 1.31 440.25 * 0.012 1.00 0.41 7.36 7.36 1.00 ***** 1.31 7.46 1.41 440.35 * 0.012 1.06 0.44 7.53 7.53 1.06 ***** 1.41 8.29 1.51 440.45 * 0.012 1.12 0.46 7.73 7.73 1.12 ***** 1.51 ©2025 D. R. STRONG Consulting Engineers Inc. Solerra Page 45 Technical Information Report King County PIPE NO. 3: 97 LF - 18"CP @ 8.06% OUTLET: 438.94 INLET: 446.79 INTYP: 5 JUNC NO. 3: OVERFLOW-EL: 450.37 BEND: 22 DEG DIA/WIDTH: 2.0 Q-RATIO: 0.31 Q(CFS) HW(FT) HW ELEV. * N-FAC DC DN TW DO DE HWO HWI ******************************************************************************* 0.80 0.39 447.18 * 0.012 0.34 0.17 0.36 0.36 0.34 ***** 0.39 1.60 0.57 447.36 * 0.012 0.48 0.23 0.56 0.56 0.48 ***** 0.57 2.40 0.71 447.50 * 0.012 0.59 0.28 0.72 0.72 0.59 ***** 0.71 3.20 0.82 447.61 * 0.012 0.69 0.32 0.86 0.86 0.69 ***** 0.82 4.00 0.91 447.70 * 0.012 0.77 0.36 0.98 0.98 0.77 ***** 0.91 4.81 0.98 447.77 * 0.012 0.85 0.40 1.09 1.09 0.85 ***** 0.98 5.61 1.04 447.83 * 0.012 0.92 0.43 1.20 1.20 0.92 ***** 1.04 6.41 1.09 447.88 * 0.012 0.98 0.46 1.31 1.31 0.98 ***** 1.09 7.21 1.13 447.92 * 0.012 1.04 0.49 1.41 1.41 1.04 ***** 1.13 8.01 1.16 447.95 * 0.012 1.10 0.51 1.51 1.51 1.10 ***** 1.16 PIPE NO. 4: 156 LF - 12"CP @ 2.96% OUTLET: 446.79 INLET: 451.41 INTYP: 5 JUNC NO. 4: OVERFLOW-EL: 454.53 BEND: 0 DEG DIA/WIDTH: 2.0 Q-RATIO: 0.77 Q(CFS) HW(FT) HW ELEV. * N-FAC DC DN TW DO DE HWO HWI ******************************************************************************* 0.61 0.43 451.84 * 0.012 0.33 0.21 0.39 0.39 0.33 ***** 0.43 1.22 0.65 452.06 * 0.012 0.47 0.30 0.57 0.57 0.47 ***** 0.65 1.83 0.84 452.25 * 0.012 0.58 0.36 0.71 0.71 0.58 ***** 0.84 2.44 1.02 452.43 * 0.012 0.67 0.42 0.82 0.82 0.67 ***** 1.02 3.05 1.21 452.62 * 0.012 0.75 0.48 0.91 0.91 0.75 ***** 1.21 3.66 1.46 452.87 * 0.012 0.82 0.53 0.98 0.98 0.82 ***** 1.46 4.27 1.75 453.16 * 0.012 0.87 0.59 1.04 1.04 0.87 ***** 1.75 4.88 2.09 453.50 * 0.012 0.92 0.64 1.09 1.09 0.92 ***** 2.09 5.49 2.47 453.88 * 0.012 0.94 0.70 1.13 1.13 0.94 ***** 2.47 6.10 2.90 454.31 * 0.012 0.96 0.76 1.16 1.16 0.96 ***** 2.90 PIPE NO. 5: 197 LF - 12"CP @ 2.50% OUTLET: 451.41 INLET: 456.34 INTYP: 5 JUNC NO. 5: OVERFLOW-EL: 459.47 BEND: 90 DEG DIA/WIDTH: 2.0 Q-RATIO: 0.50 Q(CFS) HW(FT) HW ELEV. * N-FAC DC DN TW DO DE HWO HWI ******************************************************************************* 0.35 0.32 456.66 * 0.012 0.25 0.17 0.43 0.43 0.25 ***** 0.32 0.69 0.47 456.81 * 0.012 0.35 0.23 0.65 0.65 0.35 ***** 0.47 1.04 0.60 456.94 * 0.012 0.43 0.28 0.84 0.84 0.43 ***** 0.60 1.38 0.72 457.06 * 0.012 0.50 0.33 1.02 1.02 0.50 ***** 0.72 1.73 0.84 457.18 * 0.012 0.56 0.37 1.21 1.21 0.56 ***** 0.84 2.07 0.96 457.30 * 0.012 0.62 0.41 1.46 1.46 0.62 ***** 0.96 2.42 1.08 457.42 * 0.012 0.67 0.44 1.75 1.75 0.67 ***** 1.08 2.76 1.21 457.55 * 0.012 0.72 0.48 2.09 2.09 0.72 ***** 1.21 3.11 1.35 457.69 * 0.012 0.76 0.51 2.47 2.47 0.76 ***** 1.35 3.46 1.52 457.86 * 0.012 0.80 0.54 2.90 2.90 0.80 ***** 1.52 ©2025 D. 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Solerra Page 46 Technical Information Report King County PIPE NO. 6: 24 LF - 12"CP @ 0.49% OUTLET: 456.34 INLET: 456.46 INTYP: 5 JUNC NO. 6: OVERFLOW-EL: 459.46 BEND: 87 DEG DIA/WIDTH: 2.0 Q-RATIO: 0.56 Q(CFS) HW(FT) HW ELEV. * N-FAC DC DN TW DO DE HWO HWI ******************************************************************************* 0.23 0.30 456.76 * 0.012 0.20 0.20 0.32 0.32 0.22 0.30 0.26 0.46 0.44 456.90 * 0.012 0.29 0.28 0.47 0.47 0.36 0.44 0.38 0.69 0.57 457.03 * 0.012 0.35 0.35 0.60 0.60 0.49 0.57 0.48 0.92 0.70 457.16 * 0.012 0.41 0.41 0.72 0.72 0.62 0.70 0.57 1.15 0.83 457.29 * 0.012 0.46 0.46 0.84 0.84 0.74 0.83 0.65 1.38 0.97 457.43 * 0.012 0.50 0.51 0.96 0.96 0.87 0.97 0.73 1.61 1.12 457.58 * 0.012 0.54 0.56 1.08 1.08 1.01 1.12 0.81 1.84 1.29 457.75 * 0.012 0.58 0.61 1.21 1.21 1.14 1.29 0.89 2.07 1.48 457.94 * 0.012 0.62 0.66 1.35 1.35 1.30 1.48 0.97 2.30 1.71 458.17 * 0.012 0.65 0.71 1.52 1.52 1.48 1.71 1.05 PIPE NO. 7: 125 LF - 12"CP @ 2.24% OUTLET: 456.46 INLET: 459.28 INTYP: 5 JUNC NO. 7: OVERFLOW-EL: 462.28 BEND: 72 DEG DIA/WIDTH: 2.0 Q-RATIO: 2.15 Q(CFS) HW(FT) HW ELEV. * N-FAC DC DN TW DO DE HWO HWI ******************************************************************************* 0.15 0.20 459.48 * 0.012 0.16 0.12 0.30 0.30 0.16 ***** 0.20 0.30 0.29 459.57 * 0.012 0.23 0.16 0.44 0.44 0.23 ***** 0.29 0.44 0.37 459.65 * 0.012 0.28 0.19 0.57 0.57 0.28 ***** 0.37 0.59 0.43 459.71 * 0.012 0.32 0.22 0.70 0.70 0.32 ***** 0.43 0.74 0.49 459.77 * 0.012 0.36 0.25 0.83 0.83 0.36 ***** 0.49 0.89 0.54 459.82 * 0.012 0.40 0.27 0.97 0.97 0.40 ***** 0.54 1.03 0.60 459.88 * 0.012 0.43 0.29 1.12 1.12 0.43 ***** 0.60 1.18 0.65 459.93 * 0.012 0.46 0.31 1.29 1.29 0.46 ***** 0.65 1.33 0.70 459.98 * 0.012 0.49 0.33 1.48 1.48 0.49 ***** 0.70 1.48 0.75 460.03 * 0.012 0.52 0.35 1.71 1.71 0.52 ***** 0.75 PIPE NO. 8: 16 LF - 12"CP @ 2.56% OUTLET: 459.28 INLET: 459.71 INTYP: 5 JUNC NO. 8: OVERFLOW-EL: 462.71 BEND: 70 DEG DIA/WIDTH: 2.0 Q-RATIO: 0.47 Q(CFS) HW(FT) HW ELEV. * N-FAC DC DN TW DO DE HWO HWI ******************************************************************************* 0.05 0.10 459.81 * 0.012 0.09 0.07 0.20 0.20 0.09 ***** 0.10 0.09 0.16 459.87 * 0.012 0.13 0.09 0.29 0.29 0.13 ***** 0.16 0.14 0.19 459.90 * 0.012 0.16 0.11 0.37 0.37 0.16 ***** 0.19 0.19 0.23 459.94 * 0.012 0.18 0.12 0.43 0.43 0.18 ***** 0.23 0.23 0.26 459.97 * 0.012 0.20 0.14 0.49 0.49 0.20 ***** 0.26 0.28 0.28 459.99 * 0.012 0.22 0.15 0.54 0.54 0.22 ***** 0.28 0.33 0.31 460.02 * 0.012 0.24 0.16 0.60 0.60 0.24 ***** 0.31 0.37 0.33 460.04 * 0.012 0.26 0.17 0.65 0.65 0.26 ***** 0.33 0.42 0.35 460.06 * 0.012 0.27 0.18 0.70 0.70 0.27 ***** 0.35 0.47 0.38 460.09 * 0.012 0.29 0.19 0.75 0.75 0.29 ***** 0.38 ©2025 D. 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Solerra Page 47 Technical Information Report King County PIPE NO. 9: 123 LF - 12"CP @ 4.22% OUTLET: 459.71 INLET: 464.92 INTYP: 5 JUNC NO. 9: OVERFLOW-EL: 469.55 BEND: 60 DEG DIA/WIDTH: 2.0 Q-RATIO: 0.04 Q(CFS) HW(FT) HW ELEV. * N-FAC DC DN TW DO DE HWO HWI ******************************************************************************* 0.03 0.08 465.00 * 0.012 0.08 0.05 0.10 0.10 0.08 ***** 0.08 0.06 0.12 465.04 * 0.012 0.11 0.07 0.16 0.16 0.11 ***** 0.12 0.10 0.15 465.07 * 0.012 0.13 0.08 0.19 0.19 0.13 ***** 0.15 0.13 0.17 465.09 * 0.012 0.15 0.09 0.23 0.23 0.15 ***** 0.17 0.16 0.20 465.12 * 0.012 0.17 0.10 0.26 0.26 0.17 ***** 0.20 0.19 0.22 465.14 * 0.012 0.18 0.11 0.28 0.28 0.18 ***** 0.22 0.22 0.24 465.16 * 0.012 0.20 0.12 0.31 0.31 0.20 ***** 0.24 0.25 0.26 465.18 * 0.012 0.21 0.13 0.33 0.33 0.21 ***** 0.26 0.29 0.28 465.20 * 0.012 0.22 0.13 0.35 0.35 0.22 ***** 0.28 0.32 0.29 465.21 * 0.012 0.24 0.14 0.38 0.38 0.24 ***** 0.29 PIPE NO.10: 35 LF - 12"CP @ 0.51% OUTLET: 464.92 INLET: 465.10 INTYP: 5 Q(CFS) HW(FT) HW ELEV. * N-FAC DC DN TW DO DE HWO HWI ******************************************************************************* 0.03 0.11 465.21 * 0.012 0.08 0.08 0.08 0.08 0.08 0.11 0.09 0.06 0.15 465.25 * 0.012 0.11 0.11 0.12 0.12 0.11 0.15 0.13 0.09 0.18 465.28 * 0.012 0.13 0.13 0.15 0.15 0.13 0.18 0.16 0.12 0.21 465.31 * 0.012 0.15 0.15 0.17 0.17 0.15 0.21 0.19 0.15 0.24 465.34 * 0.012 0.16 0.16 0.20 0.20 0.16 0.24 0.21 0.18 0.26 465.36 * 0.012 0.18 0.18 0.22 0.22 0.18 0.26 0.23 0.21 0.29 465.39 * 0.012 0.19 0.19 0.24 0.24 0.19 0.29 0.25 0.24 0.31 465.41 * 0.012 0.21 0.21 0.26 0.26 0.21 0.31 0.27 0.28 0.33 465.43 * 0.012 0.22 0.22 0.28 0.28 0.22 0.33 0.29 0.31 0.35 465.45 * 0.012 0.23 0.23 0.29 0.29 0.23 0.35 0.31 BACKWATER COMPUTER PROGRAM FOR PIPES Pipe data from file:CB#103 TO CB#3.bwp Surcharge condition at intermediate junctions Tailwater Elevation:447.95 feet Discharge Range:0.109 to 1.09 Step of 0.109 [cfs] Overflow Elevation:450.41 feet Weir:NONE Upstream Velocity:0. feet/sec PIPE NO. 1: 24 LF - 12"CP @ 0.49% OUTLET: 447.29 INLET: 447.41 INTYP: 5 Q(CFS) HW(FT) HW ELEV. * N-FAC DC DN TW DO DE HWO HWI ******************************************************************************* 0.11 0.55 447.96 * 0.012 0.14 0.14 0.66 0.66 0.55 0.55 0.18 0.22 0.56 447.97 * 0.012 0.20 0.20 0.66 0.66 0.55 0.56 0.26 0.33 0.56 447.97 * 0.012 0.24 0.24 0.66 0.66 0.55 0.56 0.32 0.44 0.57 447.98 * 0.012 0.28 0.28 0.66 0.66 0.55 0.57 0.37 0.54 0.59 448.00 * 0.012 0.31 0.31 0.66 0.66 0.55 0.59 0.42 0.65 0.60 448.01 * 0.012 0.34 0.34 0.66 0.66 0.55 0.60 0.46 0.76 0.62 448.03 * 0.012 0.37 0.37 0.66 0.66 0.55 0.62 0.51 0.87 0.64 448.05 * 0.012 0.40 0.40 0.66 0.66 0.55 0.64 0.55 0.98 0.66 448.07 * 0.012 0.42 0.42 0.66 0.66 0.55 0.66 0.59 1.09 0.70 448.11 * 0.012 0.44 0.45 0.66 0.66 0.56 0.70 0.62 1.20 0.72 448.13 * 0.012 0.47 0.47 0.66 0.66 0.56 0.72 0.66 ©2025 D. 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Solerra Page 48 Technical Information Report King County BACKWATER COMPUTER PROGRAM FOR PIPES Pipe data from file:CB#104 TO CB#4.bwp Surcharge condition at intermediate junctions Tailwater Elevation:454.31 feet Discharge Range:0.15 to 1.5 Step of 0.15 [cfs] Overflow Elevation:454.53 feet Weir:NONE Upstream Velocity:0. feet/sec PIPE NO. 1: 24 LF - 12"CP @ 0.49% OUTLET: 451.41 INLET: 451.53 INTYP: 5 Q(CFS) HW(FT) HW ELEV. * N-FAC DC DN TW DO DE HWO HWI ******************************************************************************* 0.15 2.79 454.32 * 0.012 0.16 0.16 2.90 2.90 2.79 2.79 0.21 0.30 2.78 454.31 * 0.012 0.23 0.23 2.90 2.90 2.78 2.78 0.30 0.45 2.79 454.32 * 0.012 0.28 0.28 2.90 2.90 2.78 2.79 0.38 0.60 2.80 454.33 * 0.012 0.33 0.32 2.90 2.90 2.79 2.80 0.44 0.75 2.81 454.34 * 0.012 0.37 0.36 2.90 2.90 2.79 2.81 0.50 0.90 2.82 454.35 * 0.012 0.40 0.40 2.90 2.90 2.79 2.82 0.56 1.05 2.84 454.37 * 0.012 0.44 0.44 2.90 2.90 2.80 2.84 0.61 1.20 2.86 454.39 * 0.012 0.47 0.47 2.90 2.90 2.80 2.86 0.66 1.35 2.88 454.41 * 0.012 0.50 0.50 2.90 2.90 2.81 2.88 0.71 1.50 2.90 454.43 * 0.012 0.52 0.54 2.90 2.90 2.82 2.90 0.76 1.50 2.90 454.43 * 0.012 0.52 0.54 2.90 2.90 2.82 2.90 0.76 BACKWATER COMPUTER PROGRAM FOR PIPES Pipe data from file:CB#201 TO CB#1.bwp Surcharge condition at intermediate junctions Tailwater Elevation:438.08 feet Discharge Range:0.135 to 1.35 Step of 0.135 [cfs] Overflow Elevation:439.96 feet Weir:NONE Upstream Velocity:0. feet/sec PIPE NO. 1: 23 LF - 12"CP @ 4.14% OUTLET: 434.18 INLET: 435.17 INTYP: 5 JUNC NO. 1: OVERFLOW-EL: 438.17 BEND: 48 DEG DIA/WIDTH: 2.0 Q-RATIO: 2.96 Q(CFS) HW(FT) HW ELEV. * N-FAC DC DN TW DO DE HWO HWI ******************************************************************************* 0.14 2.92 438.09 * 0.012 0.16 0.10 3.90 3.90 2.92 2.92 0.18 0.27 2.91 438.08 * 0.012 0.22 0.13 3.90 3.90 2.91 2.91 0.27 0.41 2.92 438.09 * 0.012 0.27 0.16 3.90 3.90 2.91 2.92 0.34 0.54 2.93 438.10 * 0.012 0.31 0.18 3.90 3.90 2.91 2.93 0.40 0.68 2.93 438.10 * 0.012 0.35 0.20 3.90 3.90 2.92 2.93 0.45 0.81 2.95 438.12 * 0.012 0.38 0.22 3.90 3.90 2.92 2.95 0.51 0.94 2.96 438.13 * 0.012 0.41 0.24 3.90 3.90 2.92 2.96 0.56 1.08 2.97 438.14 * 0.012 0.44 0.26 3.90 3.90 2.93 2.97 0.60 1.22 2.99 438.16 * 0.012 0.47 0.27 3.90 3.90 2.93 2.99 0.65 1.35 3.01 438.18 * 0.012 0.50 0.29 3.90 3.90 2.94 3.01 0.69 ©2025 D. R. STRONG Consulting Engineers Inc. Solerra Page 49 Technical Information Report King County PIPE NO. 2: 27 LF - 12"CP @ 6.50% OUTLET: 435.17 INLET: 436.96 INTYP: 5 Q(CFS) HW(FT) HW ELEV. * N-FAC DC DN TW DO DE HWO HWI ******************************************************************************* 0.03 1.14 438.10 * 0.012 0.08 0.05 2.92 2.92 1.14 1.14 0.07 0.07 1.12 438.08 * 0.012 0.11 0.06 2.91 2.91 1.12 1.12 0.11 0.10 1.13 438.09 * 0.012 0.14 0.08 2.92 2.92 1.13 1.13 0.14 0.14 1.14 438.10 * 0.012 0.16 0.09 2.93 2.93 1.14 1.14 0.17 0.17 1.15 438.11 * 0.012 0.17 0.10 2.93 2.93 1.15 1.15 0.20 0.20 1.16 438.12 * 0.012 0.19 0.10 2.95 2.95 1.16 1.16 0.22 0.24 1.17 438.13 * 0.012 0.21 0.11 2.96 2.96 1.17 1.17 0.24 0.27 1.19 438.15 * 0.012 0.22 0.12 2.97 2.97 1.18 1.19 0.26 0.31 1.21 438.17 * 0.012 0.23 0.13 2.99 2.99 1.20 1.21 0.28 0.34 1.23 438.19 * 0.012 0.25 0.13 3.01 3.01 1.22 1.23 0.30 ©2025 D. R. STRONG Consulting Engineers Inc. Solerra Page 50 Technical Information Report King County SECTION VI SPECIAL REPORTS AND STUDIES The following report and studies have been provided with this submittal. 1. Critical Areas Report – Sewall Wetland Consulting, Inc., June 5, 2023 2. Geotechnical Engineering Study – Earthwork Solutions NW, June 9, 2023 3. School Walkway Analysis – DR Strong, June 5, 2023 ©2025 D. R. STRONG Consulting Engineers Inc. Solerra Page 51 Technical Information Report King County SECTION VII OTHER PERMITS, VARIANCES AND ADJUSTMENTS ©2025 D. R. STRONG Consulting Engineers Inc. Solerra Page 52 Technical Information Report King County SECTION VIII ESC PLAN ANALYSIS AND DESIGN (PART A) The Erosion and Sedimentation Control Design meets the nine minimum requirements: 1. Clearing Limits – Areas to remain undisturbed shall be delineated with a high- visibility plastic fence prior to any Site clearing or grading. 2. Cover Measures – Disturbed Site areas shall be covered with mulch and seeded, as appropriate, for temporary or permanent measures. 3. Perimeter protection – Perimeter protection shall consist of a silt fence down slope of any disturbed areas or stockpiles. 4. Traffic Area Stabilization – A stabilized construction entrance will be located at the point of ingress/egress. 5. Sediment Retention – Surface water collected from disturbed areas of the Site shall be routed through a sediment vault or sediment traps prior to release from the Site. The sediment vault or traps will be installed prior to grading of any contributing area. 6. Surface Water Control –Interceptor berms or swales shall be installed to control and intercept all surface water from disturbed areas. Surface water controls shall be installed concurrently with and/or immediately following rough grading. 7. Dewatering Control – Will be provided as needed. 8. Dust Control – Dust control shall be provided by spraying exposed soils with water until wet. This is required when exposed soils are dry to the point that wind transport is possible which would impact roadways, drainage ways, surface waters, or neighboring residences. 9. Flow Control – Runoff collected in the sediment vault will discharge to the permanent detention vault outfall system. ©2025 D. R. STRONG Consulting Engineers Inc. Solerra Page 53 Technical Information Report King County SWPPS PLAN DESIGN (PART B) Construction activities that could contribute pollutants to surface and storm water include the following, with applicable BMP’s listed for each item: 1. Storage and use of chemicals: Utilize source control, and soil erosion and sedimentation control practices, such as using only recommended amounts of chemical materials applied in the proper manner; neutralizing concrete wash water, and disposing of excess concrete material only in areas prepared for concrete placement, or return to batch plant; disposing of wash -up waters from water-based paints in sanitary sewer; disposing of wastes from oil -based paints, solvents, thinners, and mineral spirits only through a licensed waste management firm, or treatment, storage, and disposal (TSD) facility. 2. Material delivery and storage: Locate temporary storage areas away from vehicular traffic, near the construction entrance, and away from storm drains. Material Safety Data Sheets (MSDS) should be supplied for all materials stored, and chemicals kept in their original labeled containers. Maintenance, fueling, and repair of heavy equipment and vehicles shall be conducted using spill prevention and control measures. Contaminated surfaces shall be cleaned immediately following any spill incident. Provide cover, containment, and protection from vandalism for all chemicals, liquid products, petroleum products, and other potentially hazardous materials. 3. Building demolition: Protect stormwater drainage system from sediment-laden runoff and loose particles. To the extent possible, use dikes, berms, or other methods to protect overland discharge paths from runoff. Street gutter, sidewalks, driveways, and other paved surfaces in the immediate area of demolition must be swept daily to collect and properly dispose of loose debris and garbage. Spray the minimum amount of water to help control windblown fine particles such as concrete, dust, and paint chips. Avoid excessive spraying so that runoff from the Site does not occur, yet dust control is achieved. Oils must never be used for dust control. 4. Sawcutting: Slurry and cuttings shall be vacuumed during the activity to prevent migration offsite and must not remain on permanent concrete or asphalt paving overnight. Collected slurry and cuttings shall be disposed of in a manner that does not violate ground water or surface water quality standards. The complete CSWPPP will be submitted at the time of final engineering. ©2025 D. R. STRONG Consulting Engineers Inc. Solerra Page 54 Technical Information Report King County SECTION IX BOND QUANTITIES, FACILITY SUMMARIES, AND DECLARATION OF COVENANT 1. Bond Quantity Worksheet – is included in this section. 2. The Stormwater Facility Summary Sheet is included in this section 3. Declaration of Covenant– will be provided prior to final engineering approval. 1055 South Grady Way – 6 th Floor | Renton, WA 98057 (425) 430-7200 • • Section I: Project Information • • • Section II: Bond Quantities Worksheets • •Section II.a EROSION CONTROL (Stabilization/Erosion Sediment Control (ESC)) •Section II.b TRANSPORTATION (Street and Site Improvements) •Section II.c DRAINAGE (Drainage and Stormwater Facilities): •Section II.d WATER - ONLY APPLICABLE IF WATER SERVICE IS PROVIDED BY CITY OF RENTON •Section II.e SANITARY SEWER - ONLY APPLICABLE IF SEWER SERVICE IS PROVIDED BY CITY OF RENTON • • • • • • Section III. Bond Worksheet •This section calculates the required Permit Bond for construction permit issuance as well as the required Maintenance Bond for project close-out submittals to release the permit bond on a project. All unit prices include labor, equipment, materials, overhead, profit, and taxes. Complete the 'Quantity' columns for each of the appropriate section(s). Include existing Right-of-Way (ROW), Future Public Improvements and Private Improvements. The 'Quantity Remaining' column is only to be used when a project is under construction. The City allows one (1) bond reduction during the life of the project with the exception of the maintenance period reduction. Excel will auto-calculate and auto-populate the relevant fields and subtotals throughout the document. Only the 'Quantity' columns should need completing. Additional items not included in the lists can be added under the "write-in" sections. Provide a complete description, cost estimate and unit of measure for each write-in item. Note: Private improvements, with the exception of stormwater facilities, are not included in the bond amount calculation, but must be entered on the form. Stormwater facilities (public and private) are required to be included in the bond amount. BOND QUANTITY WORKSHEET INSTRUCTIONS This worksheet is intended to be a "working" copy of the bond quantity worksheet, which will be used throughout all phases of the project, from initial submittal to project close-out approval. Submit this workbook, in its entirety, as follows: The following forms are to be completed by the engineer/developer/applicant as applicable to the project: The Bond Worksheet form will auto-calculate and auto-populate from the information provided in Section I and Section II. This section includes all pertinent information for the project Section II contains a separate spreadsheet TAB for each of the following specialties: (1) electronic copy (.xlsx format) and (1) hard copy of the entire workbook for civil construction permit submittal. Hard copies are to be included as part of the Technical Information Report (TIR). (1) electronic copy (.xlsx format) and (1) hard copy of the entire workbook for final close-out submittal. This section must be completed in its entirety Information from this section auto-populates to all other relevant areas of the workbook Page 1 of 15 Ref 8-H Bond Quantity Worksheet INSTRUCTIONS Version: 4/1/2024 Printed 7/3/2025 1055 South Grady Way – 6 th Floor | Renton, WA 98057 (425) 430-7200 Date Prepared: Name: PE Registration No: Firm Name: Firm Address: Phone No. Email Address: Project Name: Project Owner: CED Plan # (LUA):Phone: CED Permit # (C):Address: Site Address: Street Intersection:Addt'l Project Owner: Parcel #(s):Phone: Address: Clearing and grading greater than or equal to 5,000 board feet of timber? Yes/No:NO Water Service Provided by: If Yes, Provide Forest Practice Permit #:Sewer Service Provided by: SITE IMPROVEMENT BOND QUANTITY WORKSHEET PROJECT INFORMATION KC WATER DISTRICT 90 CITY OF RENTON Clearing and Grading Utility Providers N/A Project Location and Description Project Owner Information Solerra (FKA Buxton) Bellevue, Wa 98008 032305-9056, 9276, 9277, 9278, 9279, 9027 Tri Pointe Homes 425-452-0344 7/3/2025 Prepared by: FOR APPROVALProject Phase 1 yoshio.piediscalzi@drstrong.com Yoshio L. Piediscalzi 53232 DR Strong Consulting Engineers 620 7th Avenue, Kirkland, WA 98033 (425) 827-3063 10823 145th Pl SE, Renton, WA 98059 15900 SE Eastgate Way, Suite 300 Just South of NE 16th St & Lyons Pl NE 302,266.12$ Abbreviated Legal Description: PP ACT 37313764 MOBILE HOME LOT 3 TGW UND INT IN TR X OF KC SHORT PLAT NO 584164 REC NO 8709231174 SD SHORT PLAT DAF - LOT 4 OF KC SHORT PLAT NO 778093 REC NO 7903290830 SD SHORT PLAT BEING A POR OF E 1/2 OF W 1/2 OF SE 1/4 OF SE 1/4 LY NLY OF SUNSET HWY LESS C/M RGTS Total Estimated Construction Costs E A + B + C + D 461,208.03$ Estimated Civil Construction Permit - Construction Costs2 Stormwater (Drainage)C 10,379.23$ As outlined in City Ordinance No. 4345, 50% of the plan review and inspection fees are to be paid at Permit Submittal. The balance is due at Permit Issuance. Significant changes or additional review cycles (beyond 3 cycles) during the review process may result in adjustments to the final review fees. Roadway (Erosion Control + Transportation)D 148,562.68$ Water A -$ Wastewater (Sanitary Sewer)B 7/3/25 Page 2 of 15 Ref 8-H Bond Quantity Worksheet SECTION I PROJECT INFORMATION Version 4/1/2024 Printed 7/3/2025 10.3%2 All prices include labor, equipment, materials, overhead, profit, and taxes. City of Renton Sales Tax is: 1 Select the current project status/phase from the following options: For Approval - Preliminary Data Enclosed, pending approval from the City; For Construction - Estimated Data Enclosed, Plans have been approved for contruction by the City; Project Closeout - Final Costs and Quantities Enclosed for Project Close-out Submittal Page 3 of 15 Ref 8-H Bond Quantity Worksheet SECTION I PROJECT INFORMATION Version 4/1/2024 Printed 7/3/2025 CED Permit #: Unit Reference #Price Unit Quantity Cost Backfill & compaction-embankment ESC-1 7.50$ CY Check dams, 4" minus rock ESC-2 SWDM 5.4.6.3 90.00$ Each 32 2,880.00 Catch Basin Protection ESC-3 145.00$ Each 24 3,480.00 Crushed surfacing 1 1/4" minus ESC-4 WSDOT 9-03.9(3)110.00$ CY Ditching ESC-5 10.50$ CY Excavation-bulk ESC-6 2.30$ CY Fence, silt ESC-7 SWDM 5.4.3.1 5.00$ LF 1062 5,310.00 Fence, Temporary (NGPE)ESC-8 1.75$ LF Geotextile Fabric ESC-9 3.00$ SY Hay Bale Silt Trap ESC-10 0.60$ Each Hydroseeding ESC-11 SWDM 5.4.2.4 0.90$ SY Interceptor Swale / Dike ESC-12 1.15$ LF 1992 2,290.80 Jute Mesh ESC-13 SWDM 5.4.2.2 4.00$ SY Level Spreader ESC-14 2.00$ LF Mulch, by hand, straw, 3" deep ESC-15 SWDM 5.4.2.1 2.90$ SY Mulch, by machine, straw, 2" deep ESC-16 SWDM 5.4.2.1 2.30$ SY Piping, temporary, CPP, 6"ESC-17 13.75$ LF Piping, temporary, CPP, 8"ESC-18 16.00$ LF Piping, temporary, CPP, 12"ESC-19 20.50$ LF 45 922.50 Plastic covering, 6mm thick, sandbagged ESC-20 SWDM 5.4.2.3 4.60$ SY Rip Rap, machine placed; slopes ESC-21 WSDOT 9-13.1(2)51.00$ CY Rock Construction Entrance, 50'x15'x1'ESC-22 SWDM 5.4.4.1 2,050.00$ Each Rock Construction Entrance, 100'x15'x1'ESC-23 SWDM 5.4.4.1 3,675.00$ Each 1 3,675.00 Sediment pond riser assembly ESC-24 SWDM 5.4.5.2 2,525.00$ Each Sediment trap, 5' high berm ESC-25 SWDM 5.4.5.1 22.00$ LF Sed. trap, 5' high, riprapped spillway berm section ESC-26 SWDM 5.4.5.1 80.00$ LF Seeding, by hand ESC-27 SWDM 5.4.2.4 1.15$ SY Sodding, 1" deep, level ground ESC-28 SWDM 5.4.2.5 9.20$ SY Sodding, 1" deep, sloped ground ESC-29 SWDM 5.4.2.5 11.50$ SY TESC Supervisor ESC-30 125.00$ HR 60 7,500.00 Water truck, dust control ESC-31 SWDM 5.4.7 160.00$ HR 28 4,480.00 Unit Reference #Price Unit Quantity Cost EROSION/SEDIMENT SUBTOTAL:30,538.30 SALES TAX @ 10.3%3,145.44 EROSION/SEDIMENT TOTAL:33,683.74 (A) SITE IMPROVEMENT BOND QUANTITY WORKSHEET FOR EROSION & SEDIMENT CONTROL Description No. (A) WRITE-IN-ITEMS Page 4 of 15 Ref 8-H Bond Quantity Worksheet SECTION II.a EROSION_CONTROL Version: 4/01/2024 Printed 7/3/2025 CED Permit #: Existing Future Public Private Right-of-Way Improvements Improvements (D) (E) Description No. Unit Price Unit Quant.Cost Quant.Cost Quant.Cost Quant.Cost GENERAL ITEMS Backfill & Compaction- embankment GI-1 7.00$ CY 1174 8,218.00 Backfill & Compaction- trench GI-2 10.25$ CY 94 963.50 1312 13,448.00 Clear/Remove Brush, by hand (SY)GI-3 1.15$ SY Bollards - fixed GI-4 275.00$ Each Bollards - removable GI-5 520.00$ Each Clearing/Grubbing/Tree Removal GI-6 11,475.00$ Acre Excavation - bulk GI-7 2.30$ CY 1087 2,500.10 Excavation - Trench GI-8 5.75$ CY 49 281.75 1312 7,544.00 Fencing, cedar, 6' high GI-9 23.00$ LF Fencing, chain link, 4'GI-10 44.00$ LF Fencing, chain link, vinyl coated, 6' high GI-11 23.00$ LF Fencing, chain link, gate, vinyl coated, 20' GI-12 1,600.00$ Each Fill & compact - common barrow GI-13 28.75$ CY Fill & compact - gravel base GI-14 31.00$ CY Fill & compact - screened topsoil GI-15 44.75$ CY Gabion, 12" deep, stone filled mesh GI-16 74.50$ SY Gabion, 18" deep, stone filled mesh GI-17 103.25$ SY Gabion, 36" deep, stone filled mesh GI-18 172.00$ SY Grading, fine, by hand GI-19 2.90$ SY Grading, fine, with grader GI-20 2.30$ SY Monuments, 3' Long GI-21 1,025.00$ Each 2 2,050.00 Sensitive Areas Sign GI-22 8.00$ Each Sodding, 1" deep, sloped ground GI-23 9.25$ SY Surveying, line & grade GI-24 975.00$ Day Surveying, lot location/lines GI-25 2,050.00$ Acre Topsoil Type A (imported)GI-26 32.75$ CY Traffic control crew ( 2 flaggers )GI-27 137.75$ HR 40 5,510.00 Trail, 4" chipped wood GI-28 9.15$ SY Trail, 4" crushed cinder GI-29 10.25$ SY Trail, 4" top course GI-30 13.75$ SY Conduit, 2"GI-31 5.75$ LF Wall, retaining, concrete GI-32 63.00$ SF Wall, rockery GI-33 17.25$ SF SUBTOTAL THIS PAGE:19,523.35 20,992.00 (B)(C)(D)(E) SITE IMPROVEMENT BOND QUANTITY WORKSHEET FOR STREET AND SITE IMPROVEMENTS Quantity Remaining (Bond Reduction) (B)(C) Page 5 of 15 Ref 8-H Bond Quantity Worksheet SECTION II.b TRANSPORTATION Version: 4/1/2024 Printed 7/3/2025 CED Permit #: Existing Future Public Private Right-of-Way Improvements Improvements (D) (E) Description No. Unit Price Unit Quant.Cost Quant.Cost Quant.Cost Quant.Cost SITE IMPROVEMENT BOND QUANTITY WORKSHEET FOR STREET AND SITE IMPROVEMENTS Quantity Remaining (Bond Reduction) (B)(C) ROAD IMPROVEMENT/PAVEMENT/SURFACING AC Grinding, 4' wide machine < 1000sy RI-1 34.50$ SY AC Grinding, 4' wide machine 1000-2000sy RI-2 18.25$ SY AC Grinding, 4' wide machine > 2000sy RI-3 11.50$ SY AC Removal/Disposal RI-4 40.00$ SY Barricade, Type III ( Permanent )RI-5 64.25$ LF Guard Rail RI-6 34.50$ LF Curb & Gutter, rolled RI-7 19.50$ LF Curb & Gutter, vertical RI-8 14.25$ LF 445 6,341.25 Curb and Gutter, demolition and disposal RI-9 20.50$ LF Curb, extruded asphalt RI-10 6.25$ LF Curb, extruded concrete RI-11 8.00$ LF Sawcut, asphalt, 3" depth RI-12 3.00$ LF 478 1,434.00 Sawcut, concrete, per 1" depth RI-13 5.00$ LF Sealant, asphalt RI-14 2.25$ LF 478 1,075.50 Shoulder, gravel, 4" thick RI-15 17.25$ SY Sidewalk, 4" thick RI-16 43.50$ SY 297 12,919.50 Sidewalk, 4" thick, demolition and disposal RI-17 37.00$ SY Sidewalk, 5" thick RI-18 47.00$ SY Sidewalk, 5" thick, demolition and disposal RI-19 46.00$ SY Sign, Handicap RI-20 97.00$ Each Striping, per stall RI-21 8.00$ Each Striping, thermoplastic, ( for crosswalk )RI-22 3.50$ SF Striping, 4" reflectorized line RI-23 0.55$ LF Additional 2.5" Crushed Surfacing RI-24 4.15$ SY HMA 1/2" Overlay 1.5" RI-25 16.00$ SY HMA 1/2" Overlay 2"RI-26 20.75$ SY HMA Road, 2", 4" rock, First 2500 SY RI-27 32.25$ SY HMA Road, 2", 4" rock, Qty. over 2500SY RI-28 24.00$ SY HMA Road, 4", 6" rock, First 2500 SY RI-29 51.75$ SY 809 41,865.75 HMA Road, 4", 6" rock, Qty. over 2500 SY RI-30 42.50$ SY HMA Road, 4", 4.5" ATB RI-31 43.50$ SY Gravel Road, 4" rock, First 2500 SY RI-32 17.25$ SY Gravel Road, 4" rock, Qty. over 2500 SY RI-33 11.50$ SY Thickened Edge RI-34 10.00$ LF SUBTOTAL THIS PAGE:63,636.00 (B)(C)(D)(E) Page 6 of 15 Ref 8-H Bond Quantity Worksheet SECTION II.b TRANSPORTATION Version: 4/1/2024 Printed 7/3/2025 CED Permit #: Existing Future Public Private Right-of-Way Improvements Improvements (D) (E) Description No. Unit Price Unit Quant.Cost Quant.Cost Quant.Cost Quant.Cost SITE IMPROVEMENT BOND QUANTITY WORKSHEET FOR STREET AND SITE IMPROVEMENTS Quantity Remaining (Bond Reduction) (B)(C) PARKING LOT SURFACING No. 2" AC, 2" top course rock & 4" borrow PL-1 24.00$ SY 2" AC, 1.5" top course & 2.5" base course PL-2 32.00$ SY 4" select borrow PL-3 5.75$ SY 1.5" top course rock & 2.5" base course PL-4 16.00$ SY SUBTOTAL PARKING LOT SURFACING: (B)(C)(D)(E) LANDSCAPING & VEGETATION No. Street Trees LA-1 Median Landscaping LA-2 Right-of-Way Landscaping LA-3 Wetland Landscaping LA-4 SUBTOTAL LANDSCAPING & VEGETATION: (B)(C)(D)(E) TRAFFIC & LIGHTING No. Signs TR-1 Street Light System ( # of Poles)TR-2 Traffic Signal TR-3 Traffic Signal Modification TR-4 SUBTOTAL TRAFFIC & LIGHTING: (B)(C)(D)(E) WRITE-IN-ITEMS SUBTOTAL WRITE-IN ITEMS: STREET AND SITE IMPROVEMENTS SUBTOTAL:83,159.35 20,992.00 SALES TAX @ 10.3%8,565.41 2,162.18 STREET AND SITE IMPROVEMENTS TOTAL:91,724.76 23,154.18 (B)(C)(D)(E) Page 7 of 15 Ref 8-H Bond Quantity Worksheet SECTION II.b TRANSPORTATION Version: 4/1/2024 Printed 7/3/2025 CED Permit #: Existing Future Public Private Right-of-Way Improvements Improvements (D) (E) Description No. Unit Price Unit Quant.Cost Quant.Cost Quant.Cost Quant.Cost DRAINAGE (CPE = Corrugated Polyethylene Pipe, N12 or Equivalent) For Culvert prices, Average of 4' cover was assumed. Assume perforated PVC is same price as solid pipe.) Access Road, R/D D-1 30.00$ SY * (CBs include frame and lid) Beehive D-2 103.00$ Each Through-curb Inlet Framework D-3 460.00$ Each CB Type I D-4 1,725.00$ Each 1 1,725.00 1 1,725.00 1 1,725.00 CB Type IL D-5 2,000.00$ Each CB Type II, 48" diameter D-6 3,500.00$ Each for additional depth over 4' D-7 550.00$ FT CB Type II, 54" diameter D-8 4,075.00$ Each for additional depth over 4'D-9 570.00$ FT CB Type II, 60" diameter D-10 4,225.00$ Each for additional depth over 4'D-11 690.00$ FT CB Type II, 72" diameter D-12 6,900.00$ Each for additional depth over 4'D-13 975.00$ FT CB Type II, 96" diameter D-14 16,000.00$ Each for additional depth over 4'D-15 1,050.00$ FT Trash Rack, 12"D-16 400.00$ Each Trash Rack, 15"D-17 470.00$ Each Trash Rack, 18"D-18 550.00$ Each Trash Rack, 21"D-19 630.00$ Each Cleanout, PVC, 4"D-20 170.00$ Each Cleanout, PVC, 6"D-21 195.00$ Each Cleanout, PVC, 8"D-22 230.00$ Each Culvert, PVC, 4" D-23 11.50$ LF Culvert, PVC, 6" D-24 15.00$ LF Culvert, PVC, 8" D-25 17.00$ LF Culvert, PVC, 12" D-26 26.00$ LF Culvert, PVC, 15" D-27 40.00$ LF Culvert, PVC, 18" D-28 47.00$ LF Culvert, PVC, 24"D-29 65.00$ LF Culvert, PVC, 30" D-30 90.00$ LF Culvert, PVC, 36" D-31 150.00$ LF Culvert, CMP, 8"D-32 22.00$ LF Culvert, CMP, 12"D-33 33.00$ LF SUBTOTAL THIS PAGE:1,725.00 1,725.00 1,725.00 (B)(C)(D)(E) SITE IMPROVEMENT BOND QUANTITY WORKSHEET FOR DRAINAGE AND STORMWATER FACILITIES Quantity Remaining (Bond Reduction) (B)(C) Page 8 of 15 Ref 8-H Bond Quantity Worksheet SECTION II.c DRAINAGE Version: 4/1/2024 Printed 7/3/2025 CED Permit #: Existing Future Public Private Right-of-Way Improvements Improvements (D) (E) Description No. Unit Price Unit Quant.Cost Quant.Cost Quant.Cost Quant.Cost SITE IMPROVEMENT BOND QUANTITY WORKSHEET FOR DRAINAGE AND STORMWATER FACILITIES Quantity Remaining (Bond Reduction) (B)(C) DRAINAGE (Continued) Culvert, CMP, 15"D-34 40.00$ LF Culvert, CMP, 18"D-35 47.00$ LF Culvert, CMP, 24"D-36 64.00$ LF Culvert, CMP, 30"D-37 90.00$ LF Culvert, CMP, 36"D-38 150.00$ LF Culvert, CMP, 48"D-39 218.00$ LF Culvert, CMP, 60"D-40 310.00$ LF Culvert, CMP, 72"D-41 400.00$ LF Culvert, Concrete, 8"D-42 48.00$ LF Culvert, Concrete, 12"D-43 55.00$ LF Culvert, Concrete, 15"D-44 89.00$ LF Culvert, Concrete, 18"D-45 100.00$ LF Culvert, Concrete, 24"D-46 120.00$ LF Culvert, Concrete, 30"D-47 145.00$ LF Culvert, Concrete, 36"D-48 175.00$ LF Culvert, Concrete, 42"D-49 200.00$ LF Culvert, Concrete, 48"D-50 235.00$ LF Culvert, CPE Triple Wall, 6" D-51 16.00$ LF Culvert, CPE Triple Wall, 8" D-52 18.00$ LF Culvert, CPE Triple Wall, 12" D-53 27.00$ LF Culvert, CPE Triple Wall, 15" D-54 40.00$ LF Culvert, CPE Triple Wall, 18" D-55 47.00$ LF Culvert, CPE Triple Wall, 24" D-56 64.00$ LF Culvert, CPE Triple Wall, 30" D-57 90.00$ LF Culvert, CPE Triple Wall, 36" D-58 149.00$ LF Culvert, LCPE, 6"D-59 69.00$ LF Culvert, LCPE, 8"D-60 83.00$ LF Culvert, LCPE, 12"D-61 96.00$ LF Culvert, LCPE, 15"D-62 110.00$ LF Culvert, LCPE, 18"D-63 124.00$ LF Culvert, LCPE, 24"D-64 138.00$ LF Culvert, LCPE, 30"D-65 151.00$ LF Culvert, LCPE, 36"D-66 165.00$ LF Culvert, LCPE, 48"D-67 179.00$ LF Culvert, LCPE, 54"D-68 193.00$ LF SUBTOTAL THIS PAGE: (B)(C)(D)(E) Page 9 of 15 Ref 8-H Bond Quantity Worksheet SECTION II.c DRAINAGE Version: 4/1/2024 Printed 7/3/2025 CED Permit #: Existing Future Public Private Right-of-Way Improvements Improvements (D) (E) Description No. Unit Price Unit Quant.Cost Quant.Cost Quant.Cost Quant.Cost SITE IMPROVEMENT BOND QUANTITY WORKSHEET FOR DRAINAGE AND STORMWATER FACILITIES Quantity Remaining (Bond Reduction) (B)(C) DRAINAGE (Continued) Culvert, LCPE, 60"D-69 206.00$ LF Culvert, LCPE, 72"D-70 220.00$ LF Culvert, HDPE, 6"D-71 48.00$ LF Culvert, HDPE, 8"D-72 60.00$ LF Culvert, HDPE, 12"D-73 85.00$ LF Culvert, HDPE, 15"D-74 122.00$ LF Culvert, HDPE, 18"D-75 158.00$ LF Culvert, HDPE, 24"D-76 254.00$ LF Culvert, HDPE, 30"D-77 317.00$ LF Culvert, HDPE, 36"D-78 380.00$ LF Culvert, HDPE, 48"D-79 443.00$ LF Culvert, HDPE, 54"D-80 506.00$ LF Culvert, HDPE, 60"D-81 570.00$ LF Culvert, HDPE, 72"D-82 632.00$ LF Pipe, Polypropylene, 6"D-83 96.00$ LF Pipe, Polypropylene, 8"D-84 100.00$ LF Pipe, Polypropylene, 12"D-85 100.00$ LF Pipe, Polypropylene, 15"D-86 103.00$ LF Pipe, Polypropylene, 18"D-87 106.00$ LF Pipe, Polypropylene, 24"D-88 119.00$ LF Pipe, Polypropylene, 30"D-89 136.00$ LF Pipe, Polypropylene, 36"D-90 185.00$ LF Pipe, Polypropylene, 48"D-91 260.00$ LF Pipe, Polypropylene, 54"D-92 381.00$ LF Pipe, Polypropylene, 60"D-93 504.00$ LF Pipe, Polypropylene, 72"D-94 625.00$ LF Culvert, DI, 6"D-95 70.00$ LF Culvert, DI, 8"D-96 101.00$ LF Culvert, DI, 12"D-97 121.00$ LF 35 4,235.00 Culvert, DI, 15"D-98 148.00$ LF Culvert, DI, 18"D-99 175.00$ LF Culvert, DI, 24"D-100 200.00$ LF Culvert, DI, 30"D-101 227.00$ LF Culvert, DI, 36"D-102 252.00$ LF Culvert, DI, 48"D-103 279.00$ LF Culvert, DI, 54"D-104 305.00$ LF Culvert, DI, 60"D-105 331.00$ LF Culvert, DI, 72"D-106 357.00$ LF SUBTOTAL THIS PAGE:4,235.00 (B)(C)(D)(E) Page 10 of 15 Ref 8-H Bond Quantity Worksheet SECTION II.c DRAINAGE Version: 4/1/2024 Printed 7/3/2025 CED Permit #: Existing Future Public Private Right-of-Way Improvements Improvements (D) (E) Description No. Unit Price Unit Quant.Cost Quant.Cost Quant.Cost Quant.Cost SITE IMPROVEMENT BOND QUANTITY WORKSHEET FOR DRAINAGE AND STORMWATER FACILITIES Quantity Remaining (Bond Reduction) (B)(C) Specialty Drainage Items Ditching SD-1 10.90$ CY Flow Dispersal Trench (1,436 base+)SD-3 32.00$ LF French Drain (3' depth)SD-4 30.00$ LF Geotextile, laid in trench, polypropylene SD-5 3.40$ SY Mid-tank Access Riser, 48" dia, 6' deep SD-6 2,300.00$ Each Pond Overflow Spillway SD-7 18.25$ SY Restrictor/Oil Separator, 12"SD-8 1,320.00$ Each Restrictor/Oil Separator, 15"SD-9 1,550.00$ Each Restrictor/Oil Separator, 18"SD-10 1,950.00$ Each Riprap, placed SD-11 48.20$ CY Tank End Reducer (36" diameter)SD-12 1,375.00$ Each Infiltration pond testing SD-13 143.00$ HR Permeable Pavement SD-14 Permeable Concrete Sidewalk SD-15 Culvert, Box __ ft x __ ft SD-16 SUBTOTAL SPECIALTY DRAINAGE ITEMS: (B)(C)(D)(E) STORMWATER FACILITIES (Include Flow Control and Water Quality Facility Summary Sheet and Sketch) Detention Pond SF-1 Each Detention Tank SF-2 Each Detention Vault SF-3 Each Infiltration Pond SF-4 Each Infiltration Tank SF-5 Each Infiltration Vault SF-6 Each Infiltration Trenches SF-7 Each Basic Biofiltration Swale SF-8 Each Wet Biofiltration Swale SF-9 Each Wetpond SF-10 Each Wetvault SF-11 Each Sand Filter SF-12 Each Sand Filter Vault SF-13 Each Linear Sand Filter SF-14 Each Proprietary Facility SF-15 Each Bioretention Facility SF-16 Each SUBTOTAL STORMWATER FACILITIES: (B)(C)(D)(E) Page 11 of 15 Ref 8-H Bond Quantity Worksheet SECTION II.c DRAINAGE Version: 4/1/2024 Printed 7/3/2025 CED Permit #: Existing Future Public Private Right-of-Way Improvements Improvements (D) (E) Description No. Unit Price Unit Quant.Cost Quant.Cost Quant.Cost Quant.Cost SITE IMPROVEMENT BOND QUANTITY WORKSHEET FOR DRAINAGE AND STORMWATER FACILITIES Quantity Remaining (Bond Reduction) (B)(C) WRITE-IN-ITEMS (INCLUDE ON-SITE BMPs) WI-1 WI-2 WI-3 WI-4 WI-5 WI-6 WI-7 WI-8 WI-9 WI-10 WI-11 WI-12 WI-13 WI-14 WI-15 SUBTOTAL WRITE-IN ITEMS: DRAINAGE AND STORMWATER FACILITIES SUBTOTAL:1,725.00 1,725.00 5,960.00 SALES TAX @ 10.3%177.68 177.68 613.88 DRAINAGE AND STORMWATER FACILITIES TOTAL:1,902.68 1,902.68 6,573.88 (B)(C)(D)(E) Page 12 of 15 Ref 8-H Bond Quantity Worksheet SECTION II.c DRAINAGE Version: 4/1/2024 Printed 7/3/2025 CED Permit #: Existing Future Public Private Right-of-Way Improvements Improvements (D) (E) Description No. Unit Price Unit Quant.Cost Quant.Cost Quant.Cost Quant.Cost Connection to Existing Watermain W-1 3,400.00$ Each Ductile Iron Watermain, CL 52, 4 Inch Diameter W-2 58.00$ LF Ductile Iron Watermain, CL 52, 6 Inch Diameter W-3 65.00$ LF Ductile Iron Watermain, CL 52, 8 Inch Diameter W-4 75.00$ LF Ductile Iron Watermain, CL 52, 10 Inch Diameter W-5 80.00$ LF Ductile Iron Watermain, CL 52, 12 Inch Diameter W-6 145.00$ LF Gate Valve, 4 inch Diameter W-7 1,225.00$ Each Gate Valve, 6 inch Diameter W-8 1,350.00$ Each Gate Valve, 8 Inch Diameter W-9 1,550.00$ Each Gate Valve, 10 Inch Diameter W-10 2,100.00$ Each Gate Valve, 12 Inch Diameter W-11 2,500.00$ Each Fire Hydrant Assembly W-12 5,000.00$ Each Permanent Blow-Off Assembly W-13 1,950.00$ Each Air-Vac Assembly, 2-Inch Diameter W-14 3,050.00$ Each Air-Vac Assembly, 1-Inch Diameter W-15 1,725.00$ Each Compound Meter Assembly 3-inch Diameter W-16 9,200.00$ Each Compound Meter Assembly 4-inch Diameter W-17 10,500.00$ Each Compound Meter Assembly 6-inch Diameter W-18 11,500.00$ Each Pressure Reducing Valve Station 8-inch to 10-inch W-19 23,000.00$ Each WATER SUBTOTAL: SALES TAX @ 10.3% WATER TOTAL: (B)(C)(D)(E) SITE IMPROVEMENT BOND QUANTITY WORKSHEET FOR WATER Quantity Remaining (Bond Reduction) (B)(C) Page 13 of 15 Ref 8-H Bond Quantity Worksheet SECTION II.d WATER Version: 4/1/2024 Printed 7/3/2025 CED Permit #: Existing Future Public Private Right-of-Way Improvements Improvements (D) (E) Description No. Unit Price Unit Quant.Cost Quant.Cost Quant.Cost Quant.Cost Clean Outs SS-1 1,150.00$ Each 22 25,300.00 Grease Interceptor, 500 gallon SS-2 9,200.00$ Each Grease Interceptor, 1000 gallon SS-3 11,500.00$ Each Grease Interceptor, 1500 gallon SS-4 17,200.00$ Each Side Sewer Pipe, PVC. 4 Inch Diameter SS-5 92.00$ LF Side Sewer Pipe, PVC. 6 Inch Diameter SS-6 110.00$ LF 1022 112,420.00 Sewer Pipe, PVC, 8 inch Diameter SS-7 120.00$ LF 53 6,360.00 738 88,560.00 Sewer Pipe, PVC, 12 Inch Diameter SS-8 144.00$ LF Sewer Pipe, DI, 8 inch Diameter SS-9 130.00$ LF Sewer Pipe, DI, 12 Inch Diameter SS-10 150.00$ LF Manhole, 48 Inch Diameter SS-11 6,900.00$ Each 5 34,500.00 1 6,900.00 Manhole, 54 Inch Diameter SS-13 6,800.00$ Each Manhole, 60 Inch Diameter SS-15 7,600.00$ Each Manhole, 72 Inch Diameter SS-17 10,600.00$ Each Manhole, 96 Inch Diameter SS-19 16,000.00$ Each Pipe, C-900, 12 Inch Diameter SS-21 205.00$ LF Outside Drop SS-24 1,700.00$ LS Inside Drop SS-25 1,150.00$ LS Sewer Pipe, PVC, ____ Inch Diameter SS-26 Lift Station (Entire System)SS-27 LS SANITARY SEWER SUBTOTAL:6,360.00 123,060.00 144,620.00 SALES TAX @ 10.3%655.08 12,675.18 14,895.86 SANITARY SEWER TOTAL:7,015.08 135,735.18 159,515.86 (B)(C)(D)(E) SITE IMPROVEMENT BOND QUANTITY WORKSHEET FOR SANITARY SEWER Quantity Remaining (Bond Reduction) (B)(C) Page 14 of 15 Ref 8-H Bond Quantity Worksheet SECTION II.e SANITARY SEWER Version: 4/1/2024 Printed 7/3/2025 1055 South Grady Way – 6 th Floor | Renton, WA 98057 (425) 430-7200 Date: Name:Project Name: PE Registration No:CED Plan # (LUA): Firm Name:CED Permit # (C): Firm Address:Site Address: Phone No.Parcel #(s): Email Address:Project Phase: Site Restoration/Erosion Sediment Control Subtotal (a) Existing Right-of-Way Improvements Subtotal (b)(b)98,739.84$ Future Public Improvements Subtotal (c)158,889.36$ Stormwater & Drainage Facilities (Public & Private) Subtotal (d)(d)10,379.23$ (e) (f) Site Restoration Existing Right-of-Way and Storm Drainage Improvements Maintenance Bond 53,601.69$ Bond Reduction 2 Construction Permit Bond Amount 3 Minimum Bond Amount is $10,000.00 1 Estimate Only - May involve multiple and variable components, which will be established on an individual basis by Development Engineering. 2 The City of Renton allows one request only for bond reduction prior to the maintenance period. Reduction of not more than 70% of the original bond amount, provided that the remaining 30% will cover all remaining items to be constructed. 3 Required Bond Amounts are subject to review and modification by Development Engineering. * Note: The word BOND as used in this document means any financial guarantee acceptable to the City of Renton. ** Note: All prices include labor, equipment, materials, overhead, profit, and taxes. (425) 827-3063 yoshio.piediscalzi@drstrong.com Solerra (FKA Buxton) 10823 145th Pl SE, Renton, WA 98059 032305-9056, 9276, 9277, 9278, 9279, 9027 FOR APPROVAL 620 7th Avenue, Kirkland, WA 98033 192,172.74$ P (a) x 100% SITE IMPROVEMENT BOND QUANTITY WORKSHEET BOND CALCULATIONS 7/3/2025 Yoshio L. Piediscalzi 53232 DR Strong Consulting Engineers R ((b x 150%) + (d x 100%)) S (e) x 150% + (f) x 100% Bond Reduction: Existing Right-of-Way Improvements (Quantity Remaining)2 Bond Reduction: Stormwater & Drainage Facilities (Quantity Remaining)2 T (P +R - S) Prepared by:Project Information CONSTRUCTION BOND AMOUNT */** (prior to permit issuance) EST1 ((b) + (c) + (d)) x 20% -$ MAINTENANCE BOND */** (after final acceptance of construction) 33,683.74$ 98,739.84$ 158,488.99$ 33,683.74$ -$ 10,379.23$ -$ Page 15 of 15 Ref 8-H Bond Quantity Worksheet SECTION III. BOND WORKSHEET Version: 4/1/2024 Printed 7/3/2025 STORMWATER FACILITY SUMMARY SHEET Parcel No. Project Location Retired Parcel No. Detention Infiltration Type # of Type # of Ponds ______Ponds ____Ponds ______ Vaults __1___ Vaults ____ Vaults __1__ Tanks ______ Tanks _____ Tanks ________ TREATMENT SUMMARY FOR TOTAL IMPERVIOUS SURFACES Area % of Total ________________________________________________ Page 1 Water Quality Flow Control Performance StdType # of Facilities Clearing Limit Renton, WA 98059 Basic GENERAL FACILITY INFORMATION: Project includes Landscape Management Plan? yes (include copy with TIR as Appendix) no Declarations of Covenant Leachable Metals Impervious Surface Limit Recording No. DPER Permit No._________________ Date ________________ NPDES Permit No. __________________ 032305-9256, 9276, 9277, 9278, 9279, 9027, 9280, TRCT ( provide one Stormwater Facility Summary Sheet per Natural Discharge Location ) Downstream Drainage Basins: Major Basin Name Immediate Basin Name Cedar River / Lake Washington May Creek 10823, 10815, 10824 145th Pl NE Solerra OVERVIEW: Project Name Redevelopment projects Drainage Facility Landscape Management Plan Conservation Flood Problem (Applies to Commercial parcels only) Total Acreage (ac) If no flow control facility, check one: Project qualifies of KCSWDM Exemption (KCSWDM 1.2.3): Basic Exemption Impervious Surface Exemption for Transportation __________________________________________________ Flow control provided in regional/shared facility per approved approved KCSWDM Adjustment No. ______________________ Shared Facility Name/ Location: __________________________ No flow control required (other, provide justification): Cost Exemption for Parcel Redevelopment projects Direct Discharge Exemption Other Project qualifies for 0.1 cfs Exception per KCSWDM 1.2.3 No flow control required per approved water quality facility(ies) (sq ft) Total Impervious Acreage (ac) Total impervious surface served by KCSWDM Adjustment No. _____________________ Flow Control BMPs flow control facility(ies) (sq ft) PROVIDE FACILITY DETAILS AND FACILITY SKETCH FOR EACH FACILITY ON REVERSE. USE ADDITIONAL SHEET AS NEEDED FOR ADDITIONAL FACILITIES control facility(ies) designed 1990 or later (sq ft) Impervious surface served by pervious surface absorption (sq ft) Impervious surface served by approved Impervious surface served by flow Facility Name/Number _______________________________________Vault 1 Facility Location ___________________________________________Tract C cu.ft. ac.ft. WATER QUALITY FACILITIES Indicate no. of water quality facilities/BMPs for each type: 27,500 regular, wet or continuous inflow yes no Page 2 ______ Oil/water separator baffle coalescing plate ______ Modular Wetland Vault Facility Summary Sheet Sketch: All detention, infiltration and water quality facilities must include a detailed sketch (11"x17" reduced size plan sheets preferred). Combined w/detention ______ Source controls___________________________________ Sand bed depth • Is facility lined? regular linear vault (inches) ____________ If so, what marker issued above liner?______________________________________________________ ______ Pre-settling structure (manufacturer:__________________) ______ Catch basin inserts (Manufacturer:___________________) _____ Pre-settling pond _____ Stormwater wetland ______ Sand Filter basic large _____ Wetpond basic large combined w/detention Design Information Water Quality design flow (cfs) Water Quality treated volume (sandfilter) (cu.ft.) Water Quality storage volume (pre-settling vault) (cu.ft.) Landscape management plan Farm management plan _____ Flow dispersion _____ Filter strip _____ Biofiltration swale ______ High flow bypass structure (e.g., flow-splitter catch basin)__1__ Wetvault (numbered starting with lowest orifice): Project Impervious Acres Served 2.87 ac % of Total Project Impervious Acres served 50.0% No. of Lots Served 22 (ft) (inches in decimal format) No. 1 1.40 No. 2 2.25 No. 3 1.50 No. 4 ______ UIC? yes no UIC Site ID: Volume ac.ft. Live Storage DPER Permit No. XX-XXXX Downstream Drainage Basins: Major Basin Name Cedar River / lake Washington Immediate Basin Name May Creek STORMWATER FACILITY SUMMARY SHEET Project Name Solerra Project Location 10823, 10815, 10824 145th Pl NE (provide one Stormwater Facility Summary Sheet per Natural Discharge Location) Depth (ft) Reservoir Volume Renton, WA 98059 FLOW CONTROL FACILITY: Detention Vault Basin: TDA West No. of Orifices/Restrictions 3 Size of Orifice/Restriction (in.) above natural grade Depth of Reservoir above natural grade New Facility Existing Facility Volume Factor of Safety Dam Safety Regulation (WA State Dept of Ecology): Control Structure location: Interior of vault Type of Control Structure: Riser in vault Riser in Type II CB Weir in Type II CB Live Storage cu.ft. ©2025 D. R. STRONG Consulting Engineers Inc. Solerra Page 55 Technical Information Report King County SECTION X OPERATIONS AND MAINTENANCE MANUAL Excerpts from the 2021 KCSWDM has been included in this Section. APPENDIX A MAINTENANCE REQUIREMENTS FOR FLOW CONTROL, CONVEYANCE, AND WQ FACILITIES 2021 Surface Water Design Manual Appendix A 7/23/2021 A-5 NO. 3 DETENTION TANKS AND VAULTS Maintenance Component Defect or Problem Conditions When Maintenance is Needed Results Expected When Maintenance is Performed Site Trash and debris Any trash and debris which exceed 1 cubic foot per 1,000 square feet (this is about equal to the amount of trash it would take to fill up one standard size office garbage can). In general, there should be no visual evidence of dumping. Trash and debris cleared from site. Noxious weeds Any noxious or nuisance vegetation which may constitute a hazard to County personnel or the public. Noxious and nuisance vegetation removed according to applicable regulations. No danger of noxious vegetation where County personnel or the public might normally be. Contaminants and pollution Any evidence of contaminants or pollution such as oil, gasoline, concrete slurries or paint. Materials removed and disposed of according to applicable regulations. Source control BMPs implemented if appropriate. No contaminants present other than a surface oil film. Grass/groundcover Grass or groundcover exceeds 18 inches in height. Grass or groundcover mowed to a height no greater than 6 inches. Tank or Vault Storage Area Trash and debris Any trash and debris accumulated in vault or tank (includes floatables and non-floatables). No trash or debris in vault. Sediment accumulation Accumulated sediment depth exceeds 10% of the diameter of the storage area for ½ length of storage vault or any point depth exceeds 15% of diameter. Example: 72-inch storage tank would require cleaning when sediment reaches depth of 7 inches for more than ½ length of tank. All sediment removed from storage area. Tank Structure Plugged air vent Any blockage of the vent.Tank or vault freely vents. Tank bent out of shape Any part of tank/pipe is bent out of shape more than 10% of its design shape. Tank repaired or replaced to design. Gaps between sections, damaged joints or cracks or tears in wall A gap wider than ½-inch at the joint of any tank sections or any evidence of soil particles entering the tank at a joint or through a wall. No water or soil entering tank through joints or walls. Vault Structure Damage to wall, frame, bottom, and/or top slab Cracks wider than ½-inch, any evidence of soil entering the structure through cracks or qualified inspection personnel determines that the vault is not structurally sound. Vault is sealed and structurally sound. Inlet/Outlet Pipes Sediment accumulation Sediment filling 20% or more of the pipe.Inlet/outlet pipes clear of sediment. Trash and debris Trash and debris accumulated in inlet/outlet pipes (includes floatables and non-floatables). No trash or debris in pipes. Damaged Cracks wider than ½-inch at the joint of the inlet/outlet pipes or any evidence of soil entering at the joints of the inlet/outlet pipes. No cracks more than ¼-inch wide at the joint of the inlet/outlet pipe. APPENDIX A MAINTENANCE REQUIREMENTS FLOW CONTROL, CONVEYANCE, AND WQ FACILITIES 7/23/2021 2021 Surface Water Design Manual Appendix A A-6 NO. 3 DETENTION TANKS AND VAULTS Maintenance Component Defect or Problem Conditions When Maintenance is Needed Results Expected When Maintenance is Performed Access Manhole Cover/lid not in place Cover/lid is missing or only partially in place. Any open manhole requires immediate maintenance. Manhole access covered. Locking mechanism not working Mechanism cannot be opened by one maintenance person with proper tools. Bolts cannot be seated. Self-locking cover/lid does not work. Mechanism opens with proper tools. Cover/lid difficult to remove One maintenance person cannot remove cover/lid after applying 80 lbs of lift. Cover/lid can be removed and reinstalled by one maintenance person. Ladder rungs unsafe Missing rungs, misalignment, rust, or cracks.Ladder meets design standards. Allows maintenance person safe access. Large access doors/plate Damaged or difficult to open Large access doors or plates cannot be opened/removed using normal equipment. Replace or repair access door so it can opened as designed. Gaps, doesn't cover completely Large access doors not flat and/or access opening not completely covered. Doors close flat; covers access opening completely. Lifting Rings missing, rusted Lifting rings not capable of lifting weight of door or plate. Lifting rings sufficient to lift or remove door or plate. APPENDIX A MAINTENANCE REQUIREMENTS FOR FLOW CONTROL, CONVEYANCE, AND WQ FACILITIES 2021 Surface Water Design Manual Appendix A 7/23/2021 A-7 NO. 4 CONTROL STRUCTURE/FLOW RESTRICTOR Maintenance Component Defect or Problem Condition When Maintenance is Needed Results Expected When Maintenance is Performed Structure Trash and debris Trash or debris of more than ½ cubic foot which is located immediately in front of the structure opening or is blocking capacity of the structure by more than 10%. No Trash or debris blocking or potentially blocking entrance to structure. Trash or debris in the structure that exceeds 1/3 the depth from the bottom of basin to invert the lowest pipe into or out of the basin. No trash or debris in the structure. Deposits of garbage exceeding 1 cubic foot in volume. No condition present which would attract or support the breeding of insects or rodents. Sediment Sediment exceeds 60% of the depth from the bottom of the structure to the invert of the lowest pipe into or out of the structure or the bottom of the FROP-T section or is within 6 inches of the invert of the lowest pipe into or out of the structure or the bottom of the FROP-T section. Sump of structure contains no sediment. Damage to frame and/or top slab Corner of frame extends more than ¾ inch past curb face into the street (If applicable). Frame is even with curb. Top slab has holes larger than 2 square inches or cracks wider than ¼ inch. Top slab is free of holes and cracks. Frame not sitting flush on top slab, i.e., separation of more than ¾ inch of the frame from the top slab. Frame is sitting flush on top slab. Cracks in walls or bottom Cracks wider than ½ inch and longer than 3 feet, any evidence of soil particles entering structure through cracks, or maintenance person judges that structure is unsound. Structure is sealed and structurally sound. Cracks wider than ½ inch and longer than 1 foot at the joint of any inlet/outlet pipe or any evidence of soil particles entering structure through cracks. No cracks more than 1/4 inch wide at the joint of inlet/outlet pipe. Settlement/ misalignment Structure has settled more than 1 inch or has rotated more than 2 inches out of alignment. Basin replaced or repaired to design standards. Damaged pipe joints Cracks wider than ½-inch at the joint of the inlet/outlet pipes or any evidence of soil entering the structure at the joint of the inlet/outlet pipes. No cracks more than ¼-inch wide at the joint of inlet/outlet pipes. Contaminants and pollution Any evidence of contaminants or pollution such as oil, gasoline, concrete slurries or paint. Materials removed and disposed of according to applicable regulations. Source control BMPs implemented if appropriate. No contaminants present other than a surface oil film. Ladder rungs missing or unsafe Ladder is unsafe due to missing rungs, misalignment, rust, cracks, or sharp edges. Ladder meets design standards and allows maintenance person safe access. FROP-T Section Damage T section is not securely attached to structure wall and outlet pipe structure should support at least 1,000 lbs of up or down pressure. T section securely attached to wall and outlet pipe. Structure is not in upright position (allow up to 10% from plumb). Structure in correct position. Connections to outlet pipe are not watertight or show signs of deteriorated grout. Connections to outlet pipe are water tight; structure repaired or replaced and works as designed. Any holes other than designed holes in the structure. Structure has no holes other than designed holes. Cleanout Gate Damaged or missing Cleanout gate is missing.Replace cleanout gate. APPENDIX A MAINTENANCE REQUIREMENTS FLOW CONTROL, CONVEYANCE, AND WQ FACILITIES 7/23/2021 2021 Surface Water Design Manual Appendix A A-8 NO. 4 CONTROL STRUCTURE/FLOW RESTRICTOR Maintenance Component Defect or Problem Condition When Maintenance is Needed Results Expected When Maintenance is Performed Cleanout gate is not watertight.Gate is watertight and works as designed. Gate cannot be moved up and down by one maintenance person. Gate moves up and down easily and is watertight. Chain/rod leading to gate is missing or damaged. Chain is in place and works as designed. Orifice Plate Damaged or missing Control device is not working properly due to missing, out of place, or bent orifice plate. Plate is in place and works as designed. Obstructions Any trash, debris, sediment, or vegetation blocking the plate. Plate is free of all obstructions and works as designed. Overflow Pipe Obstructions Any trash or debris blocking (or having the potential of blocking) the overflow pipe. Pipe is free of all obstructions and works as designed. Deformed or damaged lip Lip of overflow pipe is bent or deformed.Overflow pipe does not allow overflow at an elevation lower than design Inlet/Outlet Pipe Sediment accumulation Sediment filling 20% or more of the pipe.Inlet/outlet pipes clear of sediment. Trash and debris Trash and debris accumulated in inlet/outlet pipes (includes floatables and non-floatables). No trash or debris in pipes. Damaged Cracks wider than ½-inch at the joint of the inlet/outlet pipes or any evidence of soil entering at the joints of the inlet/outlet pipes. No cracks more than ¼-inch wide at the joint of the inlet/outlet pipe. Metal Grates (If Applicable) Unsafe grate opening Grate with opening wider than 7/8 inch.Grate opening meets design standards. Trash and debris Trash and debris that is blocking more than 20% of grate surface. Grate free of trash and debris. Damaged or missing Grate missing or broken member(s) of the grate. Grate is in place and meets design standards. Manhole Cover/Lid Cover/lid not in place Cover/lid is missing or only partially in place. Any open structure requires urgent maintenance. Cover/lid protects opening to structure. Locking mechanism Not Working Mechanism cannot be opened by one maintenance person with proper tools. Bolts cannot be seated. Self-locking cover/lid does not work. Mechanism opens with proper tools. Cover/lid difficult to Remove One maintenance person cannot remove cover/lid after applying 80 lbs. of lift. Cover/lid can be removed and reinstalled by one maintenance person. APPENDIX A MAINTENANCE REQUIREMENTS FOR FLOW CONTROL, CONVEYANCE, AND WQ FACILITIES 2021 Surface Water Design Manual Appendix A 7/23/2021 A-9 NO. 5 CATCH BASINS AND MANHOLES Maintenance Component Defect or Problem Condition When Maintenance is Needed Results Expected When Maintenance is Performed Structure Sediment Sediment exceeds 60% of the depth from the bottom of the catch basin to the invert of the lowest pipe into or out of the catch basin or is within 6 inches of the invert of the lowest pipe into or out of the catch basin. Sump of catch basin contains no sediment. Trash and debris Trash or debris of more than ½ cubic foot which is located immediately in front of the catch basin opening or is blocking capacity of the catch basin by more than 10%. No Trash or debris blocking or potentially blocking entrance to catch basin. Trash or debris in the catch basin that exceeds 1/3 the depth from the bottom of basin to invert the lowest pipe into or out of the basin. No trash or debris in the catch basin. Dead animals or vegetation that could generate odors that could cause complaints or dangerous gases (e.g., methane). No dead animals or vegetation present within catch basin. Deposits of garbage exceeding 1 cubic foot in volume. No condition present which would attract or support the breeding of insects or rodents. Damage to frame and/or top slab Corner of frame extends more than ¾ inch past curb face into the street (If applicable). Frame is even with curb. Top slab has holes larger than 2 square inches or cracks wider than ¼ inch. Top slab is free of holes and cracks. Frame not sitting flush on top slab, i.e., separation of more than ¾ inch of the frame from the top slab. Frame is sitting flush on top slab. Cracks in walls or bottom Cracks wider than ½ inch and longer than 3 feet, any evidence of soil particles entering catch basin through cracks, or maintenance person judges that catch basin is unsound. Catch basin is sealed and is structurally sound. Cracks wider than ½ inch and longer than 1 foot at the joint of any inlet/outlet pipe or any evidence of soil particles entering catch basin through cracks. No cracks more than 1/4 inch wide at the joint of inlet/outlet pipe. Settlement/ misalignment Catch basin has settled more than 1 inch or has rotated more than 2 inches out of alignment. Basin replaced or repaired to design standards. Damaged pipe joints Cracks wider than ½-inch at the joint of the inlet/outlet pipes or any evidence of soil entering the catch basin at the joint of the inlet/outlet pipes. No cracks more than ¼-inch wide at the joint of inlet/outlet pipes. Contaminants and pollution Any evidence of contaminants or pollution such as oil, gasoline, concrete slurries or paint. Materials removed and disposed of according to applicable regulations. Source control BMPs implemented if appropriate. No contaminants present other than a surface oil film. Inlet/Outlet Pipe Sediment accumulation Sediment filling 20% or more of the pipe.Inlet/outlet pipes clear of sediment. Trash and debris Trash and debris accumulated in inlet/outlet pipes (includes floatables and non-floatables). No trash or debris in pipes. Damaged Cracks wider than ½-inch at the joint of the inlet/outlet pipes or any evidence of soil entering at the joints of the inlet/outlet pipes. No cracks more than ¼-inch wide at the joint of the inlet/outlet pipe. APPENDIX A MAINTENANCE REQUIREMENTS FLOW CONTROL, CONVEYANCE, AND WQ FACILITIES 7/23/2021 2021 Surface Water Design Manual Appendix A A-10 NO. 5 CATCH BASINS AND MANHOLES Maintenance Component Defect or Problem Condition When Maintenance is Needed Results Expected When Maintenance is Performed Metal Grates (Catch Basins) Unsafe grate opening Grate with opening wider than 7/8 inch.Grate opening meets design standards. Trash and debris Trash and debris that is blocking more than 20% of grate surface. Grate free of trash and debris. Damaged or missing Grate missing or broken member(s) of the grate. Any open structure requires urgent maintenance. Grate is in place and meets design standards. Manhole Cover/Lid Cover/lid not in place Cover/lid is missing or only partially in place. Any open structure requires urgent maintenance. Cover/lid protects opening to structure. Locking mechanism Not Working Mechanism cannot be opened by one maintenance person with proper tools. Bolts cannot be seated. Self-locking cover/lid does not work. Mechanism opens with proper tools. Cover/lid difficult to Remove One maintenance person cannot remove cover/lid after applying 80 lbs. of lift. Cover/lid can be removed and reinstalled by one maintenance person. APPENDIX A MAINTENANCE REQUIREMENTS FOR FLOW CONTROL, CONVEYANCE, AND WQ FACILITIES 2021 Surface Water Design Manual Appendix A 7/23/2021 A-11 NO. 6 CONVEYANCE PIPES AND DITCHES Maintenance Component Defect or Problem Conditions When Maintenance is Needed Results Expected When Maintenance is Performed Pipes Sediment & debris accumulation Accumulated sediment or debris that exceeds 20% of the diameter of the pipe. Water flows freely through pipes. Vegetation/roots Vegetation/roots that reduce free movement of water through pipes. Water flows freely through pipes. Contaminants and pollution Any evidence of contaminants or pollution such as oil, gasoline, concrete slurries or paint. Materials removed and disposed of according to applicable regulations. Source control BMPs implemented if appropriate. No contaminants present other than a surface oil film. Damage to protective coating or corrosion Protective coating is damaged; rust or corrosion is weakening the structural integrity of any part of pipe. Pipe repaired or replaced. Damaged Any dent that decreases the cross section area of pipe by more than 20% or is determined to have weakened structural integrity of the pipe. Pipe repaired or replaced. Ditches Trash and debris Trash and debris exceeds 1 cubic foot per 1,000 square feet of ditch and slopes. Trash and debris cleared from ditches. Sediment accumulation Accumulated sediment that exceeds 20% of the design depth. Ditch cleaned/flushed of all sediment and debris so that it matches design. Noxious weeds Any noxious or nuisance vegetation which may constitute a hazard to County personnel or the public. Noxious and nuisance vegetation removed according to applicable regulations. No danger of noxious vegetation where County personnel or the public might normally be. Contaminants and pollution Any evidence of contaminants or pollution such as oil, gasoline, concrete slurries or paint. Materials removed and disposed of according to applicable regulations. Source control BMPs implemented if appropriate. No contaminants present other than a surface oil film. Vegetation Vegetation that reduces free movement of water through ditches. Water flows freely through ditches. Erosion damage to slopes Any erosion observed on a ditch slope.Slopes are not eroding. Rock lining out of place or missing (If Applicable) One layer or less of rock exists above native soil area 5 square feet or more, any exposed native soil. Replace rocks to design standards. APPENDIX A MAINTENANCE REQUIREMENTS FLOW CONTROL, CONVEYANCE, AND WQ FACILITIES 7/23/2021 2021 Surface Water Design Manual Appendix A A-14 NO. 9 FENCING Maintenance Component Defect or Problem Conditions When Maintenance is Needed Results Expected When Maintenance is Performed Site Erosion or holes under fence Erosion or holes more than 4 inches high and 12- 18 inches wide permitting access through an opening under a fence. No access under the fence. Wood Posts, Boards and Cross Members Missing or damaged parts Missing or broken boards, post out of plumb by more than 6 inches or cross members broken No gaps on fence due to missing or broken boards, post plumb to within 1½ inches, cross members sound. Weakened by rotting or insects Any part showing structural deterioration due to rotting or insect damage All parts of fence are structurally sound. Damaged or failed post foundation Concrete or metal attachments deteriorated or unable to support posts. Post foundation capable of supporting posts even in strong wind. Metal Posts, Rails and Fabric Damaged parts Post out of plumb more than 6 inches.Post plumb to within 1½ inches. Top rails bent more than 6 inches.Top rail free of bends greater than 1 inch. Any part of fence (including post, top rails, and fabric) more than 1 foot out of design alignment. Fence is aligned and meets design standards. Missing or loose tension wire.Tension wire in place and holding fabric. Deteriorated paint or protective coating Part or parts that have a rusting or scaling condition that has affected structural adequacy. Structurally adequate posts or parts with a uniform protective coating. Openings in fabric Openings in fabric are such that an 8-inch diameter ball could fit through. Fabric mesh openings within 50% of grid size. APPENDIX A MAINTENANCE REQUIREMENTS FOR FLOW CONTROL, CONVEYANCE, AND WQ FACILITIES 2021 Surface Water Design Manual Appendix A 7/23/2021 A-15 NO. 10 GATES/BOLLARDS/ACCESS BARRIERS Maintenance Component Defect or Problem Conditions When Maintenance is Needed Results Expected When Maintenance is Performed Chain Link Fencing Gate Damaged or missing members Missing gate.Gates in place. Broken or missing hinges such that gate cannot be easily opened and closed by a maintenance person. Hinges intact and lubed. Gate is working freely. Gate is out of plumb more than 6 inches and more than 1 foot out of design alignment. Gate is aligned and vertical. Missing stretcher bar, stretcher bands, and ties.Stretcher bar, bands, and ties in place. Locking mechanism does not lock gate Locking device missing, non-functioning or does not link to all parts. Locking mechanism prevents opening of gate. Openings in fabric Openings in fabric are such that an 8-inch diameter ball could fit through. Fabric mesh openings within 50% of grid size. Bar Gate Damaged or missing cross bar Cross bar does not swing open or closed, is missing or is bent to where it does not prevent vehicle access. Cross bar swings fully open and closed and prevents vehicle access. Locking mechanism does not lock gate Locking device missing, non-functioning or does not link to all parts. Locking mechanism prevents opening of gate. Support post damaged Support post does not hold cross bar up.Cross bar held up preventing vehicle access into facility. Bollards Damaged or missing Bollard broken, missing, does not fit into support hole or hinge broken or missing. No access for motorized vehicles to get into facility. Does not lock Locking assembly or lock missing or cannot be attached to lock bollard in place. No access for motorized vehicles to get into facility. Boulders Dislodged Boulders not located to prevent motorized vehicle access. No access for motorized vehicles to get into facility. Circumvented Motorized vehicles going around or between boulders. No access for motorized vehicles to get into facility. APPENDIX A MAINTENANCE REQUIREMENTS FLOW CONTROL, CONVEYANCE, AND WQ FACILITIES 7/23/2021 2021 Surface Water Design Manual Appendix A A-16 NO. 11 GROUNDS (LANDSCAPING) Maintenance Component Defect or Problem Conditions When Maintenance is Needed Results Expected When Maintenance is Performed Site Trash or litter Any trash and debris which exceed 1 cubic foot per 1,000 square feet (this is about equal to the amount of trash it would take to fill up one standard size office garbage can). In general, there should be no visual evidence of dumping. Trash and debris cleared from site. Noxious weeds Any noxious or nuisance vegetation which may constitute a hazard to County personnel or the public. Noxious and nuisance vegetation removed according to applicable regulations. No danger of noxious vegetation where County personnel or the public might normally be. Contaminants and pollution Any evidence of contaminants or pollution such as oil, gasoline, concrete slurries or paint. Materials removed and disposed of according to applicable regulations. Source control BMPs implemented if appropriate. No contaminants present other than a surface oil film. Grass/groundcover Grass or groundcover exceeds 18 inches in height. Grass or groundcover mowed to a height no greater than 6 inches. Trees and Shrubs Hazard Any tree or limb of a tree identified as having a potential to fall and cause property damage or threaten human life.A hazard tree identified by a qualified arborist must be removed as soon as possible. No hazard trees in facility. Damaged Limbs or parts of trees or shrubs that are split or broken which affect more than 25% of the total foliage of the tree or shrub. Trees and shrubs with less than 5% of total foliage with split or broken limbs. Trees or shrubs that have been blown down or knocked over. No blown down vegetation or knocked over vegetation. Trees or shrubs free of injury. Trees or shrubs which are not adequately supported or are leaning over, causing exposure of the roots. Tree or shrub in place and adequately supported; dead or diseased trees removed. APPENDIX A MAINTENANCE REQUIREMENTS FOR FLOW CONTROL, CONVEYANCE, AND WQ FACILITIES 2021 Surface Water Design Manual Appendix A 7/23/2021 A-17 NO. 12 ACCESS ROADS Maintenance Component Defect or Problem Condition When Maintenance is Needed Results Expected When Maintenance is Performed Site Trash and debris Trash and debris exceeds 1 cubic foot per 1,000 square feet (i.e., trash and debris would fill up one standards size garbage can). Roadway drivable by maintenance vehicles. Debris which could damage vehicle tires or prohibit use of road. Roadway drivable by maintenance vehicles. Contaminants and pollution Any evidence of contaminants or pollution such as oil, gasoline, concrete slurries or paint. Materials removed and disposed of according to applicable regulations. Source control BMPs implemented if appropriate. No contaminants present other than a surface oil film. Blocked roadway Any obstruction which reduces clearance above road surface to less than 14 feet. Roadway overhead clear to 14 feet high. Any obstruction restricting the access to a 10- to 12 foot width for a distance of more than 12 feet or any point restricting access to less than a 10 foot width. At least 12-foot of width on access road. Road Surface Erosion, settlement, potholes, soft spots, ruts Any surface defect which hinders or prevents maintenance access. Road drivable by maintenance vehicles. Vegetation on road surface Trees or other vegetation prevent access to facility by maintenance vehicles. Maintenance vehicles can access facility. Shoulders and Ditches Erosion Erosion within 1 foot of the roadway more than 8 inches wide and 6 inches deep. Shoulder free of erosion and matching the surrounding road. Weeds and brush Weeds and brush exceed 18 inches in height or hinder maintenance access. Weeds and brush cut to 2 inches in height or cleared in such a way as to allow maintenance access. Modular Grid Pavement Contaminants and pollution Any evidence of contaminants or pollution such as oil, gasoline, concrete slurries or paint. Materials removed and disposed of according to applicable regulations. Source control BMPs implemented if appropriate. No contaminants present other than a surface oil film. Damaged or missing Access surface compacted because of broken on missing modular block. Access road surface restored so road infiltrates. APPENDIX A MAINTENANCE REQUIREMENTS FOR FLOW CONTROL, CONVEYANCE, AND WQ FACILITIES 2021 Surface Water Design Manual Appendix A 7/23/2021 A-23 NO. 17 WETVAULT Maintenance Component Defect or Problem Condition When Maintenance is Needed Results Expected When Maintenance is Performed Site Trash and debris Trash and debris accumulated on facility site.Trash and debris removed from facility site. Treatment Area Trash and debris Any trash and debris accumulated in vault (includes floatables and non-floatables). No trash or debris in vault. Sediment accumulation Sediment accumulation in vault bottom exceeds the depth of the sediment zone plus 6 inches. No sediment in vault. Contaminants and pollution Any evidence of contaminants or pollution such as oil, gasoline, concrete slurries or paint. Materials removed and disposed of according to applicable regulations. Source control BMPs implemented if appropriate. No contaminants present other than a surface oil film. Vault Structure Damage to wall, frame, bottom, and/or top slab Cracks wider than ½-inch, any evidence of soil entering the structure through cracks, vault does not retain water or qualified inspection personnel determines that the vault is not structurally sound. Vault is sealed and structurally sound. Baffles damaged Baffles corroding, cracking, warping and/or showing signs of failure or baffle cannot be removed. Repair or replace baffles or walls to specifications. Ventilation Ventilation area blocked or plugged.No reduction of ventilation area exists. Inlet/Outlet Pipe Sediment accumulation Sediment filling 20% or more of the pipe.Inlet/outlet pipes clear of sediment. Trash and debris Trash and debris accumulated in inlet/outlet pipes (includes floatables and non-floatables). No trash or debris in pipes. Damaged Cracks wider than ½-inch at the joint of the inlet/outlet pipes or any evidence of soil entering at the joints of the inlet/outlet pipes. No cracks more than ¼-inch wide at the joint of the inlet/outlet pipe. Gravity Drain Inoperable valve Valve will not open and close.Valve opens and closes normally. Valve does not seal completely.Valve completely seals closed. Access Manhole Access cover/lid damaged or difficult to open Access cover/lid cannot be easily opened by one person. Corrosion/deformation of cover/lid. Access cover/lid can be opened by one person. Locking mechanism not working Mechanism cannot be opened by one maintenance person with proper tools. Bolts cannot be seated. Self-locking cover/lid does not work. Mechanism opens with proper tools. Cover/lid difficult to remove One maintenance person cannot remove cover/lid after applying 80 lbs of lift. Cover/lid can be removed and reinstalled by one maintenance person. Access doors/plate has gaps, doesn't cover completely Large access doors not flat and/or access opening not completely covered. Doors close flat; covers access opening completely. Lifting Rings missing, rusted Lifting rings not capable of lifting weight of door or plate. Lifting rings sufficient to lift or remove door or plate. Ladder rungs unsafe Missing rungs, misalignment, rust, or cracks.Ladder meets design standards. Allows maintenance person safe access. APPENDIX A MAINTENANCE REQUIREMENTS FOR FLOW CONTROL, CONVEYANCE, AND WQ FACILITIES 2021 Surface Water Design Manual Appendix A 7/23/2021 A-37 NO. 28 NATIVE VEGETATED SURFACE / NATIVE VEGETATED LANDSCAPE BMP Maintenance Component Defect or Problem Condition When Maintenance is Needed Results Expected When Maintenance Is Performed Site Trash and debris Trash and debris accumulated on the native vegetated surface/native vegetated landscape site. Native vegetated surface site free of any trash or debris. Vegetation Native vegetation type Less than two species each of native trees, shrubs, and groundcover occur in the design area. A minimum of two species each of native trees, shrubs, and groundcover is established and healthy. Native vegetated area Less than 90% if the required vegetated area has healthy growth. A minimum of 90% of the required vegetated area has healthy growth. Undesirable vegetation Weeds, blackberry, and other undesirable plants are invading more than 10% of vegetated area. Less than 10% undesirable vegetation occurs in the required native vegetated surface area. Vegetated Area Soil compaction Soil in the native vegetation area compacted.Less than 8% of native vegetation area is compacted. Insufficient area Less than 3.5 square feet of native vegetation area for every 1 square foot of impervious surface. A minimum of 3.5 square feet of native vegetation area for every 1 square foot of impervious surface. Excess slope Slope of native vegetation area greater than 15%. Slope of native growth area does not exceed 15%. Inspection Frequency Annually Inspect native vegetation area for any defects of deficiencies NO. 29 PERFORATED PIPE CONNECTIONS BMP Maintenance Component Defect or Problem Conditions When Maintenance is Needed Results Expected When Maintenance is Performed Preventative Blocking, obstructions Debris or trash limiting flow into perforated pipe system or outfall of BMP is plugged or otherwise nonfunctioning. Outfall of BMP is receiving designed flows from perforated pipe connection. Inflow Inflow impeded Inflow into the perforated pipe is partially or fully blocked or altered to prevent flow from getting into the pipe. Inflow to the perforated pipe is unimpeded. Pipe Trench Area Surface compacted Ground surface over the perforated pipe trench is compacted or covered with impermeable material. Ground surface over the perforated pipe is not compacted and free of any impervious cover. Outflow Outflow impeded Outflow from the perforated pipe into the public drainage system is blocked. Outflow to the public drainage system is unimpeded. Outfall Area Erosion or landslides Existence of the perforated pipe is causing or exasperating erosion or landslides. Perforated pipe system is sealed off and an alternative BMP is implemented. Inspection Frequency Annually and prior to and following significant storms.Perforated pipe system is operating as designed. ©2025 D. R. STRONG Consulting Engineers Inc. Solerra Page 56 Technical Information Report King County APPENDIX A WWHM OUTPUT WWHM2012 PROJECT REPORT Revised Buxton Detention Vault 3/19/2025 11:18:50 AM Page 2 General Model Information WWHM2012 Project Name:Revised Buxton Detention Vault Site Name:Buxton Site Address: City: Report Date:3/19/2025 Gage:Seatac Data Start:1948/10/01 Data End:2009/09/30 Timestep:15 Minute Precip Scale:1.167 Version Date:2024/06/28 Version:4.3.1 POC Thresholds Low Flow Threshold for POC1:50 Percent of the 2 Year High Flow Threshold for POC1:50 Year Revised Buxton Detention Vault 3/19/2025 11:18:50 AM Page 3 Landuse Basin Data Predeveloped Land Use PRE DEV Bypass:No GroundWater:No Pervious Land Use acre C, Forest, Mod 5.73 C, Lawn, Mod 0.588 Pervious Total 6.318 Impervious Land Use acre ROOF TOPS FLAT 0.071 Impervious Total 0.071 Basin Total 6.389 Element Flow Componants: Surface Interflow Groundwater Componant Flows To: POC 1 POC 1 Revised Buxton Detention Vault 3/19/2025 11:18:50 AM Page 4 Mitigated Land Use DEV Bypass:No GroundWater:No Pervious Land Use acre C, Lawn, Flat 3.28 C, Lawn, Mod 0.149 Pervious Total 3.429 Impervious Land Use acre ROADS FLAT 0.719 ROADS MOD 0.1 ROOF TOPS FLAT 1.473 DRIVEWAYS FLAT 0.202 SIDEWALKS FLAT 0.188 SIDEWALKS MOD 0.256 Impervious Total 2.938 Basin Total 6.367 Element Flow Componants: Surface Interflow Groundwater Componant Flows To: Vault 1 Vault 1 Revised Buxton Detention Vault 3/19/2025 11:18:50 AM Page 5 Bypass Bypass:Yes GroundWater:No Pervious Land Use acre C, Lawn, Flat 0.01 Pervious Total 0.01 Impervious Land Use acre ROADS FLAT 0.013 Impervious Total 0.013 Basin Total 0.023 Element Flow Componants: Surface Interflow Groundwater Componant Flows To: POC 1 POC 1 Revised Buxton Detention Vault 3/19/2025 11:18:50 AM Page 6 Routing Elements Predeveloped Routing Revised Buxton Detention Vault 3/19/2025 11:18:50 AM Page 7 Mitigated Routing Vault 1 Width:77 ft. Length:100 ft. Depth:10.9 ft. Discharge Structure Riser Height:9.9 ft. Riser Diameter:18 in. Orifice 1 Diameter:1.670 in.Elevation:0 ft. Orifice 2 Diameter:2.250 in.Elevation:7.1 ft. Orifice 3 Diameter:1.500 in.Elevation:9.25 ft. Element Outlets: Outlet 1 Outlet 2 Outlet Flows To: Vault Hydraulic Table Stage(feet)Area(ac.)Volume(ac-ft.)Discharge(cfs)Infilt(cfs) 0.0000 0.176 0.000 0.000 0.000 0.1211 0.176 0.021 0.026 0.000 0.2422 0.176 0.042 0.037 0.000 0.3633 0.176 0.064 0.045 0.000 0.4844 0.176 0.085 0.052 0.000 0.6056 0.176 0.107 0.058 0.000 0.7267 0.176 0.128 0.064 0.000 0.8478 0.176 0.149 0.069 0.000 0.9689 0.176 0.171 0.074 0.000 1.0900 0.176 0.192 0.079 0.000 1.2111 0.176 0.214 0.083 0.000 1.3322 0.176 0.235 0.087 0.000 1.4533 0.176 0.256 0.091 0.000 1.5744 0.176 0.278 0.095 0.000 1.6956 0.176 0.299 0.098 0.000 1.8167 0.176 0.321 0.102 0.000 1.9378 0.176 0.342 0.105 0.000 2.0589 0.176 0.363 0.108 0.000 2.1800 0.176 0.385 0.111 0.000 2.3011 0.176 0.406 0.114 0.000 2.4222 0.176 0.428 0.117 0.000 2.5433 0.176 0.449 0.120 0.000 2.6644 0.176 0.471 0.123 0.000 2.7856 0.176 0.492 0.126 0.000 2.9067 0.176 0.513 0.129 0.000 3.0278 0.176 0.535 0.131 0.000 3.1489 0.176 0.556 0.134 0.000 3.2700 0.176 0.578 0.136 0.000 3.3911 0.176 0.599 0.139 0.000 3.5122 0.176 0.620 0.141 0.000 3.6333 0.176 0.642 0.144 0.000 3.7544 0.176 0.663 0.146 0.000 3.8756 0.176 0.685 0.149 0.000 3.9967 0.176 0.706 0.151 0.000 4.1178 0.176 0.727 0.153 0.000 4.2389 0.176 0.749 0.155 0.000 4.3600 0.176 0.770 0.158 0.000 Revised Buxton Detention Vault 3/19/2025 11:18:50 AM Page 8 4.4811 0.176 0.792 0.160 0.000 4.6022 0.176 0.813 0.162 0.000 4.7233 0.176 0.834 0.164 0.000 4.8444 0.176 0.856 0.166 0.000 4.9656 0.176 0.877 0.168 0.000 5.0867 0.176 0.899 0.170 0.000 5.2078 0.176 0.920 0.172 0.000 5.3289 0.176 0.942 0.174 0.000 5.4500 0.176 0.963 0.176 0.000 5.5711 0.176 0.984 0.178 0.000 5.6922 0.176 1.006 0.180 0.000 5.8133 0.176 1.027 0.182 0.000 5.9344 0.176 1.049 0.184 0.000 6.0556 0.176 1.070 0.186 0.000 6.1767 0.176 1.091 0.188 0.000 6.2978 0.176 1.113 0.189 0.000 6.4189 0.176 1.134 0.191 0.000 6.5400 0.176 1.156 0.193 0.000 6.6611 0.176 1.177 0.195 0.000 6.7822 0.176 1.198 0.197 0.000 6.9033 0.176 1.220 0.198 0.000 7.0244 0.176 1.241 0.200 0.000 7.1456 0.176 1.263 0.231 0.000 7.2667 0.176 1.284 0.260 0.000 7.3878 0.176 1.305 0.279 0.000 7.5089 0.176 1.327 0.295 0.000 7.6300 0.176 1.348 0.309 0.000 7.7511 0.176 1.370 0.321 0.000 7.8722 0.176 1.391 0.333 0.000 7.9933 0.176 1.413 0.343 0.000 8.1144 0.176 1.434 0.354 0.000 8.2356 0.176 1.455 0.363 0.000 8.3567 0.176 1.477 0.372 0.000 8.4778 0.176 1.498 0.381 0.000 8.5989 0.176 1.520 0.390 0.000 8.7200 0.176 1.541 0.398 0.000 8.8411 0.176 1.562 0.406 0.000 8.9622 0.176 1.584 0.414 0.000 9.0833 0.176 1.605 0.421 0.000 9.2044 0.176 1.627 0.428 0.000 9.3256 0.176 1.648 0.452 0.000 9.4467 0.176 1.669 0.470 0.000 9.5678 0.176 1.691 0.484 0.000 9.6889 0.176 1.712 0.497 0.000 9.8100 0.176 1.734 0.508 0.000 9.9311 0.176 1.755 0.607 0.000 10.052 0.176 1.776 1.470 0.000 10.173 0.176 1.798 2.739 0.000 10.294 0.176 1.819 4.122 0.000 10.416 0.176 1.841 5.336 0.000 10.537 0.176 1.862 6.179 0.000 10.658 0.176 1.884 6.747 0.000 10.779 0.176 1.905 7.231 0.000 10.900 0.176 1.926 7.682 0.000 11.021 0.176 1.948 8.108 0.000 11.142 0.000 0.000 8.511 0.000 Revised Buxton Detention Vault 3/19/2025 11:18:50 AM Page 9 Analysis Results POC 1 + Predeveloped x Mitigated Predeveloped Landuse Totals for POC #1 Total Pervious Area:6.318 Total Impervious Area:0.071 Mitigated Landuse Totals for POC #1 Total Pervious Area:3.439 Total Impervious Area:2.951 Flow Frequency Method:Log Pearson Type III 17B Flow Frequency Return Periods for Predeveloped. POC #1 Return Period Flow(cfs) 2 year 0.33321 5 year 0.55616 10 year 0.731096 25 year 0.982917 50 year 1.192867 100 year 1.422061 Flow Frequency Return Periods for Mitigated. POC #1 Return Period Flow(cfs) 2 year 0.172206 5 year 0.245772 10 year 0.304177 25 year 0.390118 50 year 0.463719 100 year 0.546204 Annual Peaks Annual Peaks for Predeveloped and Mitigated. POC #1 Year Predeveloped Mitigated 1949 0.561 0.136 1950 0.553 0.172 1951 0.541 0.394 1952 0.208 0.117 1953 0.159 0.141 1954 0.248 0.159 1955 0.344 0.164 1956 0.373 0.184 1957 0.381 0.157 1958 0.254 0.162 Revised Buxton Detention Vault 3/19/2025 11:19:23 AM Page 10 1959 0.222 0.141 1960 0.492 0.341 1961 0.271 0.161 1962 0.147 0.111 1963 0.277 0.157 1964 0.335 0.147 1965 0.306 0.171 1966 0.205 0.143 1967 0.598 0.164 1968 0.344 0.144 1969 0.292 0.136 1970 0.285 0.141 1971 0.354 0.169 1972 0.455 0.199 1973 0.198 0.164 1974 0.354 0.165 1975 0.433 0.158 1976 0.307 0.163 1977 0.169 0.119 1978 0.228 0.160 1979 0.121 0.113 1980 0.893 0.354 1981 0.237 0.143 1982 0.610 0.222 1983 0.313 0.163 1984 0.196 0.130 1985 0.131 0.138 1986 0.444 0.191 1987 0.448 0.237 1988 0.178 0.133 1989 0.133 0.131 1990 1.468 0.355 1991 0.778 0.340 1992 0.280 0.163 1993 0.209 0.136 1994 0.110 0.108 1995 0.283 0.170 1996 0.801 0.407 1997 0.530 0.391 1998 0.278 0.137 1999 0.992 0.286 2000 0.277 0.169 2001 0.088 0.108 2002 0.397 0.197 2003 0.577 0.141 2004 0.511 0.405 2005 0.355 0.167 2006 0.350 0.163 2007 1.186 0.528 2008 1.067 0.445 2009 0.520 0.189 Ranked Annual Peaks Ranked Annual Peaks for Predeveloped and Mitigated. POC #1 Rank Predeveloped Mitigated 1 1.4683 0.5279 2 1.1861 0.4455 3 1.0671 0.4069 Revised Buxton Detention Vault 3/19/2025 11:19:23 AM Page 11 4 0.9919 0.4054 5 0.8931 0.3940 6 0.8012 0.3907 7 0.7778 0.3551 8 0.6098 0.3540 9 0.5981 0.3413 10 0.5775 0.3395 11 0.5611 0.2855 12 0.5525 0.2370 13 0.5408 0.2217 14 0.5303 0.1991 15 0.5198 0.1968 16 0.5109 0.1905 17 0.4917 0.1891 18 0.4546 0.1839 19 0.4478 0.1723 20 0.4439 0.1710 21 0.4333 0.1700 22 0.3966 0.1693 23 0.3809 0.1688 24 0.3725 0.1672 25 0.3548 0.1647 26 0.3541 0.1645 27 0.3538 0.1642 28 0.3499 0.1639 29 0.3438 0.1634 30 0.3435 0.1632 31 0.3347 0.1632 32 0.3126 0.1631 33 0.3070 0.1622 34 0.3057 0.1606 35 0.2915 0.1599 36 0.2847 0.1593 37 0.2834 0.1575 38 0.2798 0.1571 39 0.2780 0.1569 40 0.2770 0.1468 41 0.2767 0.1441 42 0.2707 0.1428 43 0.2544 0.1426 44 0.2484 0.1413 45 0.2372 0.1407 46 0.2279 0.1407 47 0.2217 0.1406 48 0.2093 0.1385 49 0.2082 0.1371 50 0.2049 0.1358 51 0.1977 0.1358 52 0.1957 0.1356 53 0.1778 0.1328 54 0.1685 0.1308 55 0.1593 0.1297 56 0.1467 0.1194 57 0.1326 0.1173 58 0.1309 0.1128 59 0.1214 0.1111 60 0.1103 0.1081 61 0.0877 0.1080 Revised Buxton Detention Vault 3/19/2025 11:19:23 AM Page 12 Revised Buxton Detention Vault 3/19/2025 11:19:23 AM Page 13 Duration Flows The Facility PASSED Flow(cfs)Predev Mit Percentage Pass/Fail 0.1666 10230 9274 90 Pass 0.1770 8731 6628 75 Pass 0.1873 7405 4671 63 Pass 0.1977 6389 2971 46 Pass 0.2081 5484 2115 38 Pass 0.2184 4830 1956 40 Pass 0.2288 4269 1804 42 Pass 0.2392 3724 1708 45 Pass 0.2495 3262 1645 50 Pass 0.2599 2858 1541 53 Pass 0.2703 2485 1447 58 Pass 0.2806 2167 1375 63 Pass 0.2910 1928 1294 67 Pass 0.3014 1719 1219 70 Pass 0.3117 1524 1115 73 Pass 0.3221 1292 1001 77 Pass 0.3325 1174 866 73 Pass 0.3428 1054 704 66 Pass 0.3532 960 561 58 Pass 0.3636 872 480 55 Pass 0.3739 775 422 54 Pass 0.3843 691 345 49 Pass 0.3947 584 261 44 Pass 0.4050 476 189 39 Pass 0.4154 407 140 34 Pass 0.4258 354 98 27 Pass 0.4361 287 71 24 Pass 0.4465 232 58 25 Pass 0.4569 195 53 27 Pass 0.4672 165 47 28 Pass 0.4776 146 42 28 Pass 0.4880 127 37 29 Pass 0.4983 107 30 28 Pass 0.5087 90 15 16 Pass 0.5191 77 6 7 Pass 0.5294 65 0 0 Pass 0.5398 56 0 0 Pass 0.5502 49 0 0 Pass 0.5605 40 0 0 Pass 0.5709 35 0 0 Pass 0.5813 32 0 0 Pass 0.5916 30 0 0 Pass 0.6020 27 0 0 Pass 0.6124 23 0 0 Pass 0.6227 22 0 0 Pass 0.6331 22 0 0 Pass 0.6435 21 0 0 Pass 0.6538 20 0 0 Pass 0.6642 19 0 0 Pass 0.6746 17 0 0 Pass 0.6849 17 0 0 Pass 0.6953 16 0 0 Pass 0.7057 15 0 0 Pass Revised Buxton Detention Vault 3/19/2025 11:19:23 AM Page 14 0.7160 14 0 0 Pass 0.7264 13 0 0 Pass 0.7368 12 0 0 Pass 0.7471 12 0 0 Pass 0.7575 12 0 0 Pass 0.7678 10 0 0 Pass 0.7782 9 0 0 Pass 0.7886 9 0 0 Pass 0.7989 9 0 0 Pass 0.8093 8 0 0 Pass 0.8197 8 0 0 Pass 0.8300 8 0 0 Pass 0.8404 8 0 0 Pass 0.8508 8 0 0 Pass 0.8611 8 0 0 Pass 0.8715 8 0 0 Pass 0.8819 7 0 0 Pass 0.8922 7 0 0 Pass 0.9026 6 0 0 Pass 0.9130 6 0 0 Pass 0.9233 6 0 0 Pass 0.9337 6 0 0 Pass 0.9441 6 0 0 Pass 0.9544 6 0 0 Pass 0.9648 6 0 0 Pass 0.9752 6 0 0 Pass 0.9855 6 0 0 Pass 0.9959 5 0 0 Pass 1.0063 5 0 0 Pass 1.0166 5 0 0 Pass 1.0270 5 0 0 Pass 1.0374 5 0 0 Pass 1.0477 5 0 0 Pass 1.0581 5 0 0 Pass 1.0685 3 0 0 Pass 1.0788 3 0 0 Pass 1.0892 3 0 0 Pass 1.0996 3 0 0 Pass 1.1099 3 0 0 Pass 1.1203 3 0 0 Pass 1.1307 2 0 0 Pass 1.1410 2 0 0 Pass 1.1514 2 0 0 Pass 1.1618 2 0 0 Pass 1.1721 2 0 0 Pass 1.1825 2 0 0 Pass 1.1929 1 0 0 Pass Revised Buxton Detention Vault 3/19/2025 11:19:23 AM Page 15 Water Quality Water Quality BMP Flow and Volume for POC #1 On-line facility volume:0.5552 acre-feet On-line facility target flow:0.5684 cfs. Adjusted for 15 min:0.5684 cfs. Off-line facility target flow:0.3144 cfs. Adjusted for 15 min:0.3144 cfs. Revised Buxton Detention Vault 3/19/2025 11:19:23 AM Page 16 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. Revised Buxton Detention Vault 3/19/2025 11:19:24 AM Page 17 Appendix Predeveloped Schematic Revised Buxton Detention Vault 3/19/2025 11:19:25 AM Page 18 Mitigated Schematic Revised Buxton Detention Vault 3/19/2025 11:19:26 AM Page 19 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 Revised Buxton Detention Vault.wdm MESSU 25 PreRevised Buxton Detention Vault.MES 27 PreRevised Buxton Detention Vault.L61 28 PreRevised Buxton Detention Vault.L62 30 POCRevised Buxton Detention Vault1.dat END FILES OPN SEQUENCE INGRP INDELT 00:15 PERLND 11 PERLND 17 IMPLND 4 COPY 501 DISPLY 1 END INGRP END OPN SEQUENCE DISPLY DISPLY-INFO1 # - #<----------Title----------->***TRAN PIVL DIG1 FIL1 PYR DIG2 FIL2 YRND 1 PRE DEV 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 *** 11 C, Forest, Mod 1 1 1 1 27 0 17 C, Lawn, Mod 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 *** 11 0 0 1 0 0 0 0 0 0 0 0 0 17 0 0 1 0 0 0 0 0 0 0 0 0 END ACTIVITY PRINT-INFO <PLS > ***************** Print-flags ***************************** PIVL PYR Revised Buxton Detention Vault 3/19/2025 11:19:26 AM Page 20 # - # 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 17 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 17 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 17 0 4.5 0.03 400 0.1 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 17 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 17 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 11 0 0 0 0 2.5 1 0 17 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 END GEN-INFO *** Section IWATER*** ACTIVITY <PLS > ************* Active Sections ***************************** # - # ATMP SNOW IWAT SLD IWG IQAL *** 4 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 END PRINT-INFO IWAT-PARM1 <PLS > IWATER variable monthly parameter value flags *** # - # CSNO RTOP VRS VNN RTLI *** 4 0 0 0 0 0 END IWAT-PARM1 IWAT-PARM2 Revised Buxton Detention Vault 3/19/2025 11:19:26 AM Page 21 <PLS > IWATER input info: Part 2 *** # - # *** LSUR SLSUR NSUR RETSC 4 400 0.01 0.1 0.1 END IWAT-PARM2 IWAT-PARM3 <PLS > IWATER input info: Part 3 *** # - # ***PETMAX PETMIN 4 0 0 END IWAT-PARM3 IWAT-STATE1 <PLS > *** Initial conditions at start of simulation # - # *** RETS SURS 4 0 0 END IWAT-STATE1 END IMPLND SCHEMATIC <-Source-> <--Area--> <-Target-> MBLK *** <Name> # <-factor-> <Name> # Tbl# *** PRE DEV*** PERLND 11 5.73 COPY 501 12 PERLND 11 5.73 COPY 501 13 PERLND 17 0.588 COPY 501 12 PERLND 17 0.588 COPY 501 13 IMPLND 4 0.071 COPY 501 15 ******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 HYDR-PARM2 # - # FTABNO LEN DELTH STCOR KS DB50 *** Revised Buxton Detention Vault 3/19/2025 11:19:26 AM Page 22 <------><--------><--------><--------><--------><--------><--------> *** 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 1.167 PERLND 1 999 EXTNL PREC WDM 2 PREC ENGL 1.167 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 MASS-LINK 15 IMPLND IWATER SURO 0.083333 COPY INPUT MEAN END MASS-LINK 15 END MASS-LINK END RUN Revised Buxton Detention Vault 3/19/2025 11:19:26 AM Page 23 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 Revised Buxton Detention Vault.wdm MESSU 25 MitRevised Buxton Detention Vault.MES 27 MitRevised Buxton Detention Vault.L61 28 MitRevised Buxton Detention Vault.L62 30 POCRevised Buxton Detention Vault1.dat END FILES OPN SEQUENCE INGRP INDELT 00:15 PERLND 16 PERLND 17 IMPLND 1 IMPLND 2 IMPLND 4 IMPLND 5 IMPLND 8 IMPLND 9 RCHRES 1 COPY 1 COPY 501 COPY 601 DISPLY 1 END INGRP END OPN SEQUENCE DISPLY DISPLY-INFO1 # - #<----------Title----------->***TRAN PIVL DIG1 FIL1 PYR DIG2 FIL2 YRND 1 Vault 1 MAX 1 2 30 9 END DISPLY-INFO1 END DISPLY COPY TIMESERIES # - # NPT NMN *** 1 1 1 501 1 1 601 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 17 C, Lawn, Mod 1 1 1 1 27 0 END GEN-INFO *** Section PWATER*** Revised Buxton Detention Vault 3/19/2025 11:19:26 AM Page 24 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 17 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 17 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 17 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 17 0 4.5 0.03 400 0.1 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 17 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 17 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 17 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 *** 1 ROADS/FLAT 1 1 1 27 0 2 ROADS/MOD 1 1 1 27 0 4 ROOF TOPS/FLAT 1 1 1 27 0 5 DRIVEWAYS/FLAT 1 1 1 27 0 8 SIDEWALKS/FLAT 1 1 1 27 0 9 SIDEWALKS/MOD 1 1 1 27 0 END GEN-INFO *** Section IWATER*** ACTIVITY <PLS > ************* Active Sections ***************************** # - # ATMP SNOW IWAT SLD IWG IQAL *** 1 0 0 1 0 0 0 2 0 0 1 0 0 0 Revised Buxton Detention Vault 3/19/2025 11:19:26 AM Page 25 4 0 0 1 0 0 0 5 0 0 1 0 0 0 8 0 0 1 0 0 0 9 0 0 1 0 0 0 END ACTIVITY PRINT-INFO <ILS > ******** Print-flags ******** PIVL PYR # - # ATMP SNOW IWAT SLD IWG IQAL ********* 1 0 0 4 0 0 4 1 9 2 0 0 4 0 0 0 1 9 4 0 0 4 0 0 0 1 9 5 0 0 4 0 0 0 1 9 8 0 0 4 0 0 0 1 9 9 0 0 4 0 0 0 1 9 END PRINT-INFO IWAT-PARM1 <PLS > IWATER variable monthly parameter value flags *** # - # CSNO RTOP VRS VNN RTLI *** 1 0 0 0 0 0 2 0 0 0 0 0 4 0 0 0 0 0 5 0 0 0 0 0 8 0 0 0 0 0 9 0 0 0 0 0 END IWAT-PARM1 IWAT-PARM2 <PLS > IWATER input info: Part 2 *** # - # *** LSUR SLSUR NSUR RETSC 1 400 0.01 0.1 0.1 2 400 0.05 0.1 0.08 4 400 0.01 0.1 0.1 5 400 0.01 0.1 0.1 8 400 0.01 0.1 0.1 9 400 0.05 0.1 0.08 END IWAT-PARM2 IWAT-PARM3 <PLS > IWATER input info: Part 3 *** # - # ***PETMAX PETMIN 1 0 0 2 0 0 4 0 0 5 0 0 8 0 0 9 0 0 END IWAT-PARM3 IWAT-STATE1 <PLS > *** Initial conditions at start of simulation # - # *** RETS SURS 1 0 0 2 0 0 4 0 0 5 0 0 8 0 0 9 0 0 END IWAT-STATE1 END IMPLND SCHEMATIC <-Source-> <--Area--> <-Target-> MBLK *** <Name> # <-factor-> <Name> # Tbl# *** DEV*** PERLND 16 3.28 RCHRES 1 2 PERLND 16 3.28 RCHRES 1 3 PERLND 17 0.149 RCHRES 1 2 Revised Buxton Detention Vault 3/19/2025 11:19:26 AM Page 26 PERLND 17 0.149 RCHRES 1 3 IMPLND 1 0.719 RCHRES 1 5 IMPLND 2 0.1 RCHRES 1 5 IMPLND 4 1.473 RCHRES 1 5 IMPLND 5 0.202 RCHRES 1 5 IMPLND 8 0.188 RCHRES 1 5 IMPLND 9 0.256 RCHRES 1 5 Bypass*** PERLND 16 0.01 COPY 501 12 PERLND 16 0.01 COPY 601 12 PERLND 16 0.01 COPY 501 13 PERLND 16 0.01 COPY 601 13 IMPLND 1 0.013 COPY 501 15 IMPLND 1 0.013 COPY 601 15 ******Routing****** PERLND 16 3.28 COPY 1 12 PERLND 17 0.149 COPY 1 12 IMPLND 1 0.719 COPY 1 15 IMPLND 2 0.1 COPY 1 15 IMPLND 4 1.473 COPY 1 15 IMPLND 5 0.202 COPY 1 15 IMPLND 8 0.188 COPY 1 15 IMPLND 9 0.256 COPY 1 15 PERLND 16 3.28 COPY 1 13 PERLND 17 0.149 COPY 1 13 RCHRES 1 1 COPY 501 16 END SCHEMATIC NETWORK <-Volume-> <-Grp> <-Member-><--Mult-->Tran <-Target vols> <-Grp> <-Member-> *** <Name> # <Name> # #<-factor->strg <Name> # # <Name> # # *** COPY 501 OUTPUT MEAN 1 1 48.4 DISPLY 1 INPUT TIMSER 1 <-Volume-> <-Grp> <-Member-><--Mult-->Tran <-Target vols> <-Grp> <-Member-> *** <Name> # <Name> # #<-factor->strg <Name> # # <Name> # # *** END NETWORK RCHRES GEN-INFO RCHRES Name Nexits Unit Systems Printer *** # - #<------------------><---> User T-series Engl Metr LKFG *** in out *** 1 Vault 1 1 1 1 1 28 0 1 END GEN-INFO *** Section RCHRES*** ACTIVITY <PLS > ************* Active Sections ***************************** # - # HYFG ADFG CNFG HTFG SDFG GQFG OXFG NUFG PKFG PHFG *** 1 1 0 0 0 0 0 0 0 0 0 END ACTIVITY PRINT-INFO <PLS > ***************** Print-flags ******************* PIVL PYR # - # HYDR ADCA CONS HEAT SED GQL OXRX NUTR PLNK PHCB PIVL PYR ********* 1 4 0 0 0 0 0 0 0 0 0 1 9 END PRINT-INFO HYDR-PARM1 RCHRES Flags for each HYDR Section *** # - # VC A1 A2 A3 ODFVFG for each *** ODGTFG for each FUNCT for each FG FG FG FG possible exit *** possible exit possible exit * * * * * * * * * * * * * * *** 1 0 1 0 0 4 0 0 0 0 0 0 0 0 0 2 2 2 2 2 END HYDR-PARM1 HYDR-PARM2 Revised Buxton Detention Vault 3/19/2025 11:19:26 AM Page 27 # - # FTABNO LEN DELTH STCOR KS DB50 *** <------><--------><--------><--------><--------><--------><--------> *** 1 1 0.02 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 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 END HYDR-INIT END RCHRES SPEC-ACTIONS END SPEC-ACTIONS FTABLES FTABLE 1 92 4 Depth Area Volume Outflow1 Velocity Travel Time*** (ft) (acres) (acre-ft) (cfs) (ft/sec) (Minutes)*** 0.000000 0.176768 0.000000 0.000000 0.121111 0.176768 0.021409 0.026338 0.242222 0.176768 0.042817 0.037248 0.363333 0.176768 0.064226 0.045619 0.484444 0.176768 0.085634 0.052676 0.605556 0.176768 0.107043 0.058894 0.726667 0.176768 0.128451 0.064515 0.847778 0.176768 0.149860 0.069684 0.968889 0.176768 0.171268 0.074495 1.090000 0.176768 0.192677 0.079014 1.211111 0.176768 0.214085 0.083288 1.332222 0.176768 0.235494 0.087353 1.453333 0.176768 0.256902 0.091238 1.574444 0.176768 0.278311 0.094963 1.695556 0.176768 0.299719 0.098548 1.816667 0.176768 0.321128 0.102007 1.937778 0.176768 0.342536 0.105352 2.058889 0.176768 0.363945 0.108595 2.180000 0.176768 0.385354 0.111743 2.301111 0.176768 0.406762 0.114805 2.422222 0.176768 0.428171 0.117787 2.543333 0.176768 0.449579 0.120696 2.664444 0.176768 0.470988 0.123536 2.785556 0.176768 0.492396 0.126313 2.906667 0.176768 0.513805 0.129030 3.027778 0.176768 0.535213 0.131690 3.148889 0.176768 0.556622 0.134298 3.270000 0.176768 0.578030 0.136857 3.391111 0.176768 0.599439 0.139368 3.512222 0.176768 0.620847 0.141835 3.633333 0.176768 0.642256 0.144259 3.754444 0.176768 0.663664 0.146644 3.875556 0.176768 0.685073 0.148991 3.996667 0.176768 0.706481 0.151301 4.117778 0.176768 0.727890 0.153576 4.238889 0.176768 0.749299 0.155818 4.360000 0.176768 0.770707 0.158028 4.481111 0.176768 0.792116 0.160208 4.602222 0.176768 0.813524 0.162359 4.723333 0.176768 0.834933 0.164481 4.844444 0.176768 0.856341 0.166576 4.965556 0.176768 0.877750 0.168646 5.086667 0.176768 0.899158 0.170690 5.207778 0.176768 0.920567 0.172710 5.328889 0.176768 0.941975 0.174707 5.450000 0.176768 0.963384 0.176681 5.571111 0.176768 0.984792 0.178633 5.692222 0.176768 1.006201 0.180565 5.813333 0.176768 1.027609 0.182475 5.934444 0.176768 1.049018 0.184366 Revised Buxton Detention Vault 3/19/2025 11:19:26 AM Page 28 6.055556 0.176768 1.070426 0.186238 6.176667 0.176768 1.091835 0.188091 6.297778 0.176768 1.113244 0.189926 6.418889 0.176768 1.134652 0.191744 6.540000 0.176768 1.156061 0.193544 6.661111 0.176768 1.177469 0.195328 6.782222 0.176768 1.198878 0.197096 6.903333 0.176768 1.220286 0.198848 7.024444 0.176768 1.241695 0.200585 7.145556 0.176768 1.263103 0.231628 7.266667 0.176768 1.284512 0.260099 7.387778 0.176768 1.305920 0.279404 7.508889 0.176768 1.327329 0.295233 7.630000 0.176768 1.348737 0.309066 7.751111 0.176768 1.370146 0.321558 7.872222 0.176768 1.391554 0.333069 7.993333 0.176768 1.412963 0.343818 8.114444 0.176768 1.434371 0.353955 8.235556 0.176768 1.455780 0.363585 8.356667 0.176768 1.477189 0.372785 8.477778 0.176768 1.498597 0.381615 8.598889 0.176768 1.520006 0.390122 8.720000 0.176768 1.541414 0.398342 8.841111 0.176768 1.562823 0.406307 8.962222 0.176768 1.584231 0.414042 9.083333 0.176768 1.605640 0.421568 9.204444 0.176768 1.627048 0.428903 9.325556 0.176768 1.648457 0.452846 9.446667 0.176768 1.669865 0.470139 9.567778 0.176768 1.691274 0.484330 9.688889 0.176768 1.712682 0.497070 9.810000 0.176768 1.734091 0.508890 9.931111 0.176768 1.755499 0.607382 10.05222 0.176768 1.776908 1.470031 10.17333 0.176768 1.798316 2.739617 10.29444 0.176768 1.819725 4.122008 10.41556 0.176768 1.841134 5.336132 10.53667 0.176768 1.862542 6.179398 10.65778 0.176768 1.883951 6.747620 10.77889 0.176768 1.905359 7.231156 10.90000 0.176768 1.926768 7.682766 11.02111 0.176768 1.948176 8.108087 END FTABLE 1 END FTABLES EXT SOURCES <-Volume-> <Member> SsysSgap<--Mult-->Tran <-Target vols> <-Grp> <-Member-> *** <Name> # <Name> # tem strg<-factor->strg <Name> # # <Name> # # *** WDM 2 PREC ENGL 1.167 PERLND 1 999 EXTNL PREC WDM 2 PREC ENGL 1.167 IMPLND 1 999 EXTNL PREC WDM 1 EVAP ENGL 0.76 PERLND 1 999 EXTNL PETINP WDM 1 EVAP ENGL 0.76 IMPLND 1 999 EXTNL PETINP END EXT SOURCES EXT TARGETS <-Volume-> <-Grp> <-Member-><--Mult-->Tran <-Volume-> <Member> Tsys Tgap Amd *** <Name> # <Name> # #<-factor->strg <Name> # <Name> tem strg strg*** RCHRES 1 HYDR RO 1 1 1 WDM 1002 FLOW ENGL REPL RCHRES 1 HYDR STAGE 1 1 1 WDM 1003 STAG ENGL REPL COPY 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 COPY 601 OUTPUT MEAN 1 1 48.4 WDM 901 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 Revised Buxton Detention Vault 3/19/2025 11:19:26 AM Page 29 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 16 RCHRES ROFLOW COPY INPUT MEAN END MASS-LINK 16 END MASS-LINK END RUN Revised Buxton Detention Vault 3/19/2025 11:19:26 AM Page 30 Predeveloped HSPF Message File Revised Buxton Detention Vault 3/19/2025 11:19:26 AM Page 31 Mitigated HSPF Message File Revised Buxton Detention Vault 3/19/2025 11:19:26 AM Page 32 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. 2005-2025; 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 ©2025 D. R. STRONG Consulting Engineers Inc. Solerra Page 57 Technical Information Report King County APPENDIX B GEOTECHNICAL REPORT EarthSolutionsNWLLC EarthSolutions NW LLC Geotechnical Engineering Construction Observation/Testing Environmental Services 15365 N.E.90th Street,Suite 100 Redmond,WA 98052 (425)449-4704 Fax (425)449-4711 www.earthsolutionsnw.com GEOTECHNICAL ENGINEERING STUDY BUXTON 14506 SOUTHEAST RENTON-ISSAQUAH ROAD AND 10815,10823 AND 10824 –145 PLACE SOUTHEAST KING COUNTY (RENTON),WASHINGTON ES-9205 TH PREPARED FOR ACH DEVELOPMENT GROUP, LLC June 9, 2023 _________________________ Brian C. Snow, L.G. Senior Staff Geologist _________________________ Scott S. Riegel, L.G., L.E.G. Associate Principal Geologist GEOTECHNICAL ENGINEERING STUDY BUXTON 14506 SOUTHEAST RENTON-ISSAQUAH ROAD AND 10815, 10823 AND 10824 – 145TH PLACE SOUTHEAST KING COUNTY (RENTON), WASHINGTON ES-9205 Earth Solutions NW, LLC 15365 Northeast 90th Street, Suite 100 Redmond, Washington 98052 Phone: 425-449-4704 | Fax: 425-449-4711 www.earthsolutionsnw.com 06/09/2023 Geotechnical-Engineering Report Important Information about This Subsurface problems are a principal cause of construction delays, cost overruns, claims, and disputes. While you cannot eliminate all such risks, you can manage them. The following information is provided to help. The Geoprofessional Business Association (GBA) has prepared this advisory to help you – assumedly a client representative – interpret and apply this geotechnical-engineering report as effectively as possible. In that way, you can benefit from a lowered exposure to problems associated with subsurface conditions at project sites and development of them that, for decades, have been a principal cause of construction delays, cost overruns, claims, and disputes. If you have questions or want more information about any of the issues discussed herein, contact your GBA-member geotechnical engineer. Active engagement in GBA exposes geotechnical engineers to a wide array of risk-confrontation techniques that can be of genuine benefit for everyone involved with a construction project. Understand the Geotechnical-Engineering Services Provided for this Report Geotechnical-engineering services typically include the planning, collection, interpretation, and analysis of exploratory data from widely spaced borings and/or test pits. Field data are combined with results from laboratory tests of soil and rock samples obtained from field exploration (if applicable), observations made during site reconnaissance, and historical information to form one or more models of the expected subsurface conditions beneath the site. Local geology and alterations of the site surface and subsurface by previous and proposed construction are also important considerations. Geotechnical engineers apply their engineering training, experience, and judgment to adapt the requirements of the prospective project to the subsurface model(s). Estimates are made of the subsurface conditions that will likely be exposed during construction as well as the expected performance of foundations and other structures being planned and/or affected by construction activities. The culmination of these geotechnical-engineering services is typically a geotechnical-engineering report providing the data obtained, a discussion of the subsurface model(s), the engineering and geologic engineering assessments and analyses made, and the recommendations developed to satisfy the given requirements of the project. These reports may be titled investigations, explorations, studies, assessments, or evaluations. Regardless of the title used, the geotechnical-engineering report is an engineering interpretation of the subsurface conditions within the context of the project and does not represent a close examination, systematic inquiry, or thorough investigation of all site and subsurface conditions. Geotechnical-Engineering Services are Performed for Specific Purposes, Persons, and Projects, and At Specific Times Geotechnical engineers structure their services to meet the specific needs, goals, and risk management preferences of their clients. A geotechnical-engineering study conducted for a given civil engineer will not likely meet the needs of a civil-works constructor or even a different civil engineer. Because each geotechnical-engineering study is unique, each geotechnical-engineering report is unique, prepared solely for the client. Likewise, geotechnical-engineering services are performed for a specific project and purpose. For example, it is unlikely that a geotechnical- engineering study for a refrigerated warehouse will be the same as one prepared for a parking garage; and a few borings drilled during a preliminary study to evaluate site feasibility will not be adequate to develop geotechnical design recommendations for the project. Do not rely on this report if your geotechnical engineer prepared it: • for a different client; • for a different project or purpose; • for a different site (that may or may not include all or a portion of the original site); or • before important events occurred at the site or adjacent to it; e.g., man-made events like construction or environmental remediation, or natural events like floods, droughts, earthquakes, or groundwater fluctuations. Note, too, the reliability of a geotechnical-engineering report can be affected by the passage of time, because of factors like changed subsurface conditions; new or modified codes, standards, or regulations; or new techniques or tools. If you are the least bit uncertain about the continued reliability of this report, contact your geotechnical engineer before applying the recommendations in it. A minor amount of additional testing or analysis after the passage of time – if any is required at all – could prevent major problems. Read this Report in Full Costly problems have occurred because those relying on a geotechnical- engineering report did not read the report in its entirety. Do not rely on an executive summary. Do not read selective elements only. Read and refer to the report in full. You Need to Inform Your Geotechnical Engineer About Change Your geotechnical engineer considered unique, project-specific factors when developing the scope of study behind this report and developing the confirmation-dependent recommendations the report conveys. Typical changes that could erode the reliability of this report include those that affect: • the site’s size or shape; • the elevation, configuration, location, orientation, function or weight of the proposed structure and the desired performance criteria; • the composition of the design team; or • project ownership. As a general rule, always inform your geotechnical engineer of project or site changes – even minor ones – and request an assessment of their impact. The geotechnical engineer who prepared this report cannot accept responsibility or liability for problems that arise because the geotechnical engineer was not informed about developments the engineer otherwise would have considered. Most of the “Findings” Related in This Report Are Professional Opinions Before construction begins, geotechnical engineers explore a site’s subsurface using various sampling and testing procedures. Geotechnical engineers can observe actual subsurface conditions only at those specific locations where sampling and testing is performed. The data derived from that sampling and testing were reviewed by your geotechnical engineer, who then applied professional judgement to form opinions about subsurface conditions throughout the site. Actual sitewide-subsurface conditions may differ – maybe significantly – from those indicated in this report. Confront that risk by retaining your geotechnical engineer to serve on the design team through project completion to obtain informed guidance quickly, whenever needed. This Report’s Recommendations Are Confirmation-Dependent The recommendations included in this report – including any options or alternatives – are confirmation-dependent. In other words, they are not final, because the geotechnical engineer who developed them relied heavily on judgement and opinion to do so. Your geotechnical engineer can finalize the recommendations only after observing actual subsurface conditions exposed during construction. If through observation your geotechnical engineer confirms that the conditions assumed to exist actually do exist, the recommendations can be relied upon, assuming no other changes have occurred. The geotechnical engineer who prepared this report cannot assume responsibility or liability for confirmation-dependent recommendations if you fail to retain that engineer to perform construction observation. This Report Could Be Misinterpreted Other design professionals’ misinterpretation of geotechnical- engineering reports has resulted in costly problems. Confront that risk by having your geotechnical engineer serve as a continuing member of the design team, to: • confer with other design-team members; • help develop specifications; • review pertinent elements of other design professionals’ plans and specifications; and • be available whenever geotechnical-engineering guidance is needed. You should also confront the risk of constructors misinterpreting this report. Do so by retaining your geotechnical engineer to participate in prebid and preconstruction conferences and to perform construction- phase observations. Give Constructors a Complete Report and Guidance Some owners and design professionals mistakenly believe they can shift unanticipated-subsurface-conditions liability to constructors by limiting the information they provide for bid preparation. To help prevent the costly, contentious problems this practice has caused, include the complete geotechnical-engineering report, along with any attachments or appendices, with your contract documents, but be certain to note conspicuously that you’ve included the material for information purposes only. To avoid misunderstanding, you may also want to note that “informational purposes” means constructors have no right to rely on the interpretations, opinions, conclusions, or recommendations in the report. Be certain that constructors know they may learn about specific project requirements, including options selected from the report, only from the design drawings and specifications. Remind constructors that they may perform their own studies if they want to, and be sure to allow enough time to permit them to do so. Only then might you be in a position to give constructors the information available to you, while requiring them to at least share some of the financial responsibilities stemming from unanticipated conditions. Conducting prebid and preconstruction conferences can also be valuable in this respect. Read Responsibility Provisions Closely Some client representatives, design professionals, and constructors do not realize that geotechnical engineering is far less exact than other engineering disciplines. This happens in part because soil and rock on project sites are typically heterogeneous and not manufactured materials with well-defined engineering properties like steel and concrete. That lack of understanding has nurtured unrealistic expectations that have resulted in disappointments, delays, cost overruns, claims, and disputes. To confront that risk, geotechnical engineers commonly include explanatory provisions in their reports. Sometimes labeled “limitations,” many of these provisions indicate where geotechnical engineers’ responsibilities begin and end, to help others recognize their own responsibilities and risks. Read these provisions closely. Ask questions. Your geotechnical engineer should respond fully and frankly. Geoenvironmental Concerns Are Not Covered The personnel, equipment, and techniques used to perform an environmental study – e.g., a “phase-one” or “phase-two” environmental site assessment – differ significantly from those used to perform a geotechnical-engineering study. For that reason, a geotechnical-engineering report does not usually provide environmental findings, conclusions, or recommendations; e.g., about the likelihood of encountering underground storage tanks or regulated contaminants. Unanticipated subsurface environmental problems have led to project failures. If you have not obtained your own environmental information about the project site, ask your geotechnical consultant for a recommendation on how to find environmental risk-management guidance. Obtain Professional Assistance to Deal with Moisture Infiltration and Mold While your geotechnical engineer may have addressed groundwater, water infiltration, or similar issues in this report, the engineer’s services were not designed, conducted, or intended to prevent migration of moisture – including water vapor – from the soil through building slabs and walls and into the building interior, where it can cause mold growth and material-performance deficiencies. Accordingly, proper implementation of the geotechnical engineer’s recommendations will not of itself be sufficient to prevent moisture infiltration. Confront the risk of moisture infiltration by including building-envelope or mold specialists on the design team. Geotechnical engineers are not building-envelope or mold specialists. Copyright 2019 by Geoprofessional Business Association (GBA). Duplication, reproduction, or copying of this document, in whole or in part, by any means whatsoever, is strictly prohibited, except with GBA’s specific written permission. Excerpting, quoting, or otherwise extracting wording from this document is permitted only with the express written permission of GBA, and only for purposes of scholarly research or book review. Only members of GBA may use this document or its wording as a complement to or as an element of a report of any kind. Any other firm, individual, or other entity that so uses this document without being a GBA member could be committing negligent or intentional (fraudulent) misrepresentation. Telephone: 301/565-2733 e-mail: info@geoprofessional.org www.geoprofessional.org June 9, 2023 ES-9205 ACH Development Group, LLC 9675 Southeast 36th Street, Suite 105 Mercer Island, Washington 98040 Attention: Justin Lagers Dear Justin: Earth Solutions NW, LLC (ESNW) is pleased to present this geotechnical report to support the proposed residential construction. Based on the results of our investigation, the proposed construction is feasible from a geotechnical standpoint. Our field observations indicate the site is underlain primarily by dense to very dense glacial till deposits. Typical residential structures for this site can be supported on conventional spread and continuous foundations bearing on undisturbed competent native soil, recompacted native soil, or new structural fill placed directly on a competent subgrade. Competent native soil suitable for foundation support is expected to be encountered beginning at depths of about two to four feet below existing grades across the site. The native glacial till deposits exhibit very poor infiltration characteristics, including high relative density, high fines content, and weak cementation. In our opinion, full infiltration should be considered infeasible from a geotechnical standpoint. This report provides geotechnical analyses and recommendations for the proposed residential development. The opportunity to be of service to you is appreciated. If you have any questions regarding the content of this geotechnical engineering study, please call. Sincerely, EARTH SOLUTIONS NW, LLC Brian C. Snow, L.G. Senior Staff Geologist 15365 N.E. 90th Street, Suite 100 • Redmond, WA 98052 •(425) 449-4704 • FAX (425) 449-4711 Earth Solutions NW LLC Geotechnical Engineering, Construction Observation/Testing and Environmental Services Earth Solutions NW, LLC Table of Contents ES-9205 PAGE INTRODUCTION ................................................................................. 1 General .................................................................................... 1 Project Description ................................................................. 2 SITE CONDITIONS ............................................................................. 2 Surface ..................................................................................... 2 Subsurface .............................................................................. 3 Topsoil and Fill ............................................................. 3 Native Soil ..................................................................... 3 Geologic Setting ........................................................... 4 Groundwater ................................................................. 4 Geologically Hazardous Areas Review ................................. 4 DISCUSSION AND RECOMMENDATIONS ....................................... 4 General .................................................................................... 4 Site Preparation and Earthwork ............................................. 5 Temporary Erosion Control ......................................... 5 Excavations and Slopes .............................................. 6 Structural Fill ................................................................ 6 In-situ and Imported Soil ............................................. 7 Wet-Season Grading .................................................... 7 Subgrade Preparation .................................................. 7 Void Space Restoration ............................................... 8 Foundations ............................................................................ 8 Retaining Walls ....................................................................... 9 Seismic Design ....................................................................... 10 Slab-on-Grade Floors ............................................................. 11 Utility Support and Trench Backfill ....................................... 11 Preliminary Pavement Sections ............................................. 11 Drainage................................................................................... 12 Preliminary Infiltration Feasibility ............................... 12 LIMITATIONS ...................................................................................... 13 Additional Services ................................................................. 13 Earth Solutions NW, LLC Table of Contents Cont’d ES-9205 GRAPHICS Plate 1 Vicinity Map Plate 2 Test Pit Location Plan Plate 3 Retaining Wall Drainage Detail Plate 4 Footing Drain Detail APPENDICES Appendix A Subsurface Exploration Test Pit Logs Appendix B Laboratory Test Results Earth Solutions NW, LLC GEOTECHNICAL ENGINEERING STUDY BUXTON 14506 SOUTHEAST RENTON-ISSAQUAH ROAD AND 10815, 10823 AND 10824 – 145TH PLACE SOUTHEAST KING COUNTY (RENTON), WASHINGTON ES-9205 INTRODUCTION General This geotechnical engineering study (study) was prepared for the proposed residential construction to be located along the east and west sides of 145th Place Southeast, north of the intersection with Renton Issaquah Road Southeast, in the Renton area of unincorporated King County, Washington. To fulfill our scope of services, the following were completed: Subsurface exploration to characterize the soil and groundwater conditions. Laboratory testing of representative soil sample collected on site. Preliminary infiltration feasibility evaluation based on our field observations and laboratory analyses. Engineering analyses and recommendations for the proposed residential construction. Preparation of this report. The following documents and resources were reviewed as part of our report preparation: Site Layout Drawing, provided by the client, undated. Geologic Map of King County, compiled by Booth, D.B., Troost, K.G., and Wisher, A.P., dated March 2007. Web Soil Survey (WSS) online resource, maintained by the Natural Resources Conservation Service (NRCS) under the United States Department of Agriculture (USDA). Soil Survey of King County Area, Washington, by Snyder, D.E., Gale, P.S., and Pringle, R.F., United States Department of Agriculture, Soil Conservation Service, Issued November 1973. Faults and Earthquakes in Washington State, by Czajkowski and Bowman, endorsed by the Washington State Department of Natural Resources, dated 2014. ACH Development Group, LLC ES-9205 June 9, 2023 Page 2 Earth Solutions NW, LLC King County Landslide Hazard Areas, Map 12-1, prepared by Tetra Tech, Inc. and endorsed by the King County Flood Control District, dated May 2010. King County Liquefaction Susceptibility, Map 11-5, prepared by Tetra Tech, Inc. and endorsed by the King County Flood Control District, dated May 2010. King County Code (KCC) Title 21A. King County Surface Water Design Manual, 2021. Project Description The subject site is located along the east and west sides of 145th Place Southeast, north of the intersection with Renton Issaquah Road Southeast, in the Renton area of unincorporated King County, Washington. Based on review of the referenced preliminary site plan, we understand the properties will be further subdivided into 22 new residential lots and associated improvements, including a storm drainage tract (Tract C) in the northeastern corner of the site. Access will be provided by a new road extension off the Northeast 16th Street/Lyons Place Northeast intersection. We understand site grading will likely include grade cuts on the western half of the project area and fills on the eastern half. We anticipate mass grading will likely be limited to cuts and fills on the order of about 10 feet. At the time of report submission, specific building load values were not available for review; however, we anticipate the typical two to three story residential structures will consist of relatively lightly loaded wood framing supported on conventional foundations. Based on our experience with similar developments, we estimate wall loads of about 2 to 3 kips per linear foot and slab- on-grade and column loading of 150 pounds per square foot (psf) will be incorporated into the final design. If the above design assumptions either change or are incorrect, ESNW should be contacted to review the recommendations provided in this report. ESNW should be contacted to review the final design to confirm that our geotechnical recommendations have been incorporated into the final plans. SITE CONDITIONS Surface The subject site is located along the east and west sides of 145th Place Southeast, north of the intersection with Renton Issaquah Road Southeast, in the Renton area of unincorporated King County, Washington. The project area consists of seven adjoining tax parcels (King County Parcel Nos. 032305-9027, -9279, -9280, -9256, -9276, -9277, & -9278) totaling roughly 4.77 acres of land, of which four parcels are occupied by single family residences and associated improvements. Remaining parcels are undeveloped and vacant. The approximate site location is depicted on Plate 1 (Vicinity Map). ACH Development Group, LLC ES-9205 June 9, 2023 Page 3 Earth Solutions NW, LLC Per the referenced site layout, topography across the development envelope descends gently to the north-northeast for a total of about 40 feet of vertical relief. The site is generally surrounded by existing residential development and is bordered to the south by Southeast Renton Issaquah Road. Subsurface A representative of ESNW observed, logged, and sampled eight test pits on April 28, 2023, advanced at accessible locations within the property boundaries using a mini-trackhoe and operator retained by ESNW. The test pits were completed to assess and classify the site soils and to characterize the groundwater conditions within areas proposed for new development. The maximum exploration depth was approximately nine-and-one-half feet below the existing ground surface (bgs), and all test pits were terminated in undisturbed native soil deposits. The approximate locations of the test pits are depicted on Plate 2 (Test Pit Location Plan). Please refer to the test pit logs provided in Appendix A for a more detailed description of subsurface conditions. Representative soil samples collected at our exploration sites were analyzed in general accordance with Unified Soil Classification System (USCS) and USDA methods and procedures. Topsoil and Fill Topsoil was observed within the upper approximately 8 to 10 inches of existing grades at the test locations. A relic topsoil horizon, underlying a relatively thin layer of fill, was encountered at TP- 6; the topsoil and fill at TP-6 extended to roughly one-and-one-half feet bgs. It is possible that deeper or shallower pockets of topsoil are present in localized areas across the site. The topsoil was characterized by its dark brown color, the presence of fine organic material, and small root intrusions. Fill was encountered at two test locations (TP-3 and TP-6) extending to a maximum of observed depth of about two feet bgs. In general, the fill consisted of silty sand with variable gravel in a loose to medium dense and moist condition. Native Soil Underlying the topsoil and fill, weathered native soils consisting primarily of silty sand with gravel (USCS:SM) extended to depths of roughly two to four feet bgs. Below the weathered soil horizon, the native silty sand with gravel transitioned to a relatively dense and unweathered condition. Weakly cemented unweathered soils were noted at nearly all exploration locations below depths of about two to four feet. The native soils were characterized as being representative of glacial till deposits. At TP-7, an anomalous layer of relatively clean gravel and sand was encountered below about four-and-one-half feet bgs. Similar soil layers were not observed within any other exploration. ACH Development Group, LLC ES-9205 June 9, 2023 Page 4 Earth Solutions NW, LLC Laboratory analyses of representative soil samples indicate the native silty sand with gravel deposits contain roughly 13 to 30 percent fines by weight, and the native soils were primarily in a moist condition at the time of exploration. Geologic Setting Geologic mapping of the area identifies Vashon subglacial till deposits (Qvt) as the primary geologic unit underlying the site. Glacial till typically consists of a non-sorted mixture of clay, silt, sand, and gravel in variable amounts, deposited directly beneath the glacier as it advanced over bedrock and older deposits. Glacial till typically possesses high strength characteristics resulting from consolidation by glacial overburden. The online WSS resource identifies Alderwood gravelly sandy loam, 8 to 15 percent slopes (Map Unit Symbol: AgC), as the sole soil unit surfacing the subject site. Alderwood series soils are found on hill landforms atop glacial drift deposits, formed beneath conifer trees, and are characterized in the referenced USDA soil survey with medium runoff and a moderate hazard of water erosion. In our opinion, the native soils observed at the test locations are representative of glacial till deposits and are consistent with the mapping resources outlined in this section. Groundwater Light groundwater seepage was observed at one test location (TP-5) during the April 2023 exploration, expressing as discrete zones of perched groundwater at depths of four and eight feet bgs. Zones of perched groundwater seepage are common within glacial till deposits and should be expected within site excavations at depth, particularly during the wet season. Groundwater seepage rates and elevations may fluctuate depending on many factors, including precipitation duration and intensity, the time of year, and soil conditions. In general, groundwater flow rates are higher during the winter, spring, and early summer months. Geologically Hazardous Areas Review ESNW reviewed the available online King County hazard mapping (iMap), as well as Title 21A of the King County Code, to determine if erosion, landslide, or seismic hazard areas exist on or near the subject site. Based on our review, the site does not contain areas meeting definition criteria for geologic hazard areas, nor does it contain mapped geologic hazards. DISCUSSION AND RECOMMENDATIONS General In our opinion, typical residential construction up to three stories in height is feasible from a geotechnical standpoint. The primary geotechnical considerations associated with the proposed project include earthwork, temporary excavations, structural fill requirements, subgrade preparation, retaining wall foundation support, slab-on-grade support, utility support and trench backfill, drainage, and stormwater management. ACH Development Group, LLC ES-9205 June 9, 2023 Page 5 Earth Solutions NW, LLC The proposed residential structures may be supported on conventional continuous and spread footing foundations bearing on competent native soil, recompacted native soil, or new structural fill placed directly on a competent subgrade. In general, we expect competent native soil suitable for support of foundations will likely be encountered about two to four feet below existing grades. Where loose or unsuitable soil conditions are exposed at foundation subgrade elevations, compaction of the soil to the specifications of structural fill, or overexcavation and replacement with suitable structural fill will likely be necessary. An ESNW representative should be contacted to confirm suitability of foundation subgrades at the time of construction. If deemed necessary, the undisturbed weathered native soils may be compacted in-situ provided the soil is at or slightly above the optimum moisture content. Where encountered, fill intended for reuse as structural fill must be primarily free of organic and deleterious material and should be evaluated by ESNW at the time of construction. This study has been prepared for the exclusive use of ACH Development Group, LLC., and its representatives. A warranty is neither expressed nor implied. This study has been prepared in a manner consistent with the level of care and skill ordinarily exercised by other members of the profession currently practicing under similar conditions in this area. Site Preparation and Earthwork Site preparation activities should consist of installing temporary erosion control measures and performing site stripping within the designated clearing limits. Subsequent earthwork activities may involve additional mass grading and utility installations. Temporary Erosion Control The following temporary erosion and sediment control (TESC) Best Management Practices (BMPs) should be considered: Temporary construction entrances and drive lanes, consisting of at least six inches of quarry spalls, should be considered to both minimize off-site soil tracking and provide stable surfaces at site entrances. Placing geotextile fabric underneath the quarry spalls will provide greater stability, if needed. Silt fencing should be placed around the appropriate portions of the site perimeter. When not in use, soil stockpiles should be covered or otherwise protected to reduce the potential for soil erosion, especially during periods of wet weather. Temporary measures for controlling surface water runoff, such as interceptor trenches, sumps, or interceptor swales, should be installed prior to beginning earthwork activities. Dry soils disturbed during construction should be wetted to reduce dust and airborne soil erosion. ACH Development Group, LLC ES-9205 June 9, 2023 Page 6 Earth Solutions NW, LLC Additional TESC BMPs, as specified by the project civil engineer and indicated on the plans, should be incorporated into construction activities. TESC BMPs may be modified during construction as site conditions require and as approved by the site erosion control lead. Excavations and Slopes Based on the soil conditions observed at the exploration locations, excavation activities are likely to expose loose to medium dense native soils within the upper four feet of existing grades, becoming dense to very dense at depth. The following Federal Occupation Safety and Health Administration and Washington Industrial Safety and Health Act soil classifications and maximum allowable temporary slope inclinations may be used: Areas exposing groundwater seepage 1.5H:1V (Type C) Loose soil and fill 1.5H:1V (Type C) Medium dense to dense soil 1H:1V (Type B) Dense to very dense “hardpan” native soil 0.75H:1V (Type A) Groundwater seepage should be anticipated during excavation activities, particularly if excavations take place during the wet season. An ESNW representative should observe temporary excavations to evaluate the presence of groundwater seepage. If seepage is not observed, steeper temporary slope inclinations may be feasible, particularly where “hardpan” native soil is exposed within relatively large, open excavations. An ESNW representative should observe temporary and permanent slopes to confirm the slope inclinations are suitable for the exposed soil conditions and to provide additional excavation and slope recommendations, as necessary. If the recommended temporary slope inclinations cannot be achieved, temporary shoring may be necessary to support excavations. Permanent slopes should be planted with vegetation to both enhance stability and minimize erosion and should maintain a gradient of 2H:1V or flatter. Structural Fill Structural fill is defined as compacted soil placed in foundation, slab-on-grade, roadway, permanent slope, retaining wall, and utility trench backfill areas. Structural fill placed and compacted during site grading activities should meet the following specifications and guidelines: Structural fill material Granular soil Moisture Content At or slightly above optimum Relative compaction (minimum) 95 percent (Modified Proctor) Loose lift thickness (maximum) 12 inches ACH Development Group, LLC ES-9205 June 9, 2023 Page 7 Earth Solutions NW, LLC The existing soil may not be suitable for use as structural fill unless the soil is at (or slightly above) the optimum moisture content at the time of placement and compaction. Soil shall not be placed dry of the optimum moisture content and should be evaluated by ESNW during construction. With respect to underground utility installations and backfill, local jurisdictions may dictate the soil type(s) and compaction requirements. Unsuitable material or debris must be removed from structural areas if encountered. In-situ and Imported Soil The in-situ soils encountered at the subject site have a high sensitivity to moisture and were generally in a moist condition at the time of exploration. Soils anticipated to be exposed on site will degrade rapidly if exposed to wet weather and construction traffic. Compaction of the soils to the levels necessary for use as structural fill may be difficult or impossible during wet weather conditions. Soils encountered during site excavations that are excessively over the optimum moisture content will likely require aeration or treatment prior to placement and compaction. Conversely, soils that are substantially below the optimum moisture content will require moisture conditioning through the addition of water prior to use as structural fill. An ESNW representative should determine the suitability of in-situ soils for use as structural fill at the time of construction. Imported soil intended for use as structural fill should be evaluated by ESNW during construction. The imported soil must be workable to the optimum moisture content, as determined by the Modified Proctor Method (ASTM D1557), at the time of placement and compaction. During wet weather conditions, imported soil intended for use as structural fill should consist of a well-graded, granular soil with a fines content of 5 percent or less (where the fines content is defined as the percent passing the Number 200 sieve, based on the minus three-quarter-inch fraction). Wet-Season Grading Earthwork activities that occur during the wet season may require additional measures to protect both structural subgrades and soil intended for use as structural fill. Site-specific recommendations can be provided at the time of construction and may include leaving cut areas several inches above design subgrade elevations, covering working surfaces with crushed rock, protecting structural fill soil from adverse moisture conditions, and additional TESC recommendations. ESNW can assist in obtaining a wet season grading permit if required by the governing jurisdiction. Subgrade Preparation Following site stripping, ESNW should observe the subgrade to confirm soil conditions are as anticipated and to provide supplementary recommendations for subgrade preparation, as necessary. In general, foundation subgrades on native cut surfaces should be compacted in-situ to a minimum depth of one foot below the design subgrade elevation. Uniform compaction of structural fill and the foundation and slab subgrade areas will establish a relatively consistent subgrade condition below the foundation and slab elements. Supplementary recommendations for subgrade improvement may be provided at the time of construction and would likely include further mechanical compaction or overexcavation and replacement with suitable structural fill. ACH Development Group, LLC ES-9205 June 9, 2023 Page 8 Earth Solutions NW, LLC Void Space Restoration The process of removing the existing structures may produce voids where existing foundations are removed and where crawl space or deeper foundation areas may have been present. Complete restoration of voids from old foundation areas must be executed as part of the subgrade preparation activities. The following guidelines for preparing subgrade areas should be incorporated into the final design: Where voids and related demolition disturbances extend below planned subgrade elevations, restoration of these areas should be completed. Structural fill should be used to restore voids or unstable areas resulting from the removal of existing structural elements. Recompact, or overexcavate and replace, areas of existing fill exposed at the design subgrade elevations. Overexcavations should extend into competent native soils and structural fill should be utilized to restore subgrade elevations, as necessary. ESNW should confirm subgrade conditions, as well as the required level of recompaction and/or overexcavation and replacement, during site preparation activities. ESNW should also evaluate the overall suitability of prepared subgrade areas following site preparation activities. Foundations Typical two to three story residential structures constructed on this site can be supported on conventional spread and continuous footings bearing on competent (undisturbed) native soil, recompacted native soil, or new structural fill placed directly on a competent subgrade. Provided site earthwork activities are completed in accordance with our recommendations, suitable soil conditions should be exposed beginning at depths of about two to four feet bgs. Due to the high moisture sensitivity of the site soils, foundation subgrade areas should be protected from wet weather or areas of remediation should be anticipated; a layer of crushed rock can be considered to protect foundation subgrade areas. If structural building pads are disturbed during wet weather, remediation measures such as overexcavation and replacement with rock may be necessary in some areas. An ESNW representative should be requested to confirm suitability of foundation subgrades at the time of construction. Provided the structure(s) will be supported as described above, the following parameters may be used for design of the new foundations: Allowable soil bearing capacity 2,500 psf Passive earth pressure 300 pcf Coefficient of friction 0.40 ACH Development Group, LLC ES-9205 June 9, 2023 Page 9 Earth Solutions NW, LLC A one-third increase in the allowable soil bearing capacity can be assumed for short-term wind and seismic loading conditions. The passive earth pressure and coefficient of friction values include a safety factor of 1.5. With structural loading as expected, total settlement in the range of one inch is anticipated, with differential settlement of about one-half inch. Most of the anticipated settlement should occur during construction as dead loads are applied. Retaining Walls Retaining walls must be designed to resist earth pressures and applicable surcharge loads. The following parameters may be used for retaining wall design: Active earth pressure (unrestrained condition) 32 pcf At-rest earth pressure (restrained condition) 52 pcf Traffic surcharge (passenger vehicles) 70 psf (rectangular distribution) Passive earth pressure 350 pcf Coefficient of friction 0.40 Seismic surcharge 8H psf* * Where H equals the retained height (in feet). The passive earth pressure and coefficient of friction values include a safety factor of 1.5. Additional surcharge loading from adjacent foundations, sloped backfill, or other loads should be included in the retaining wall design. Retaining walls should be backfilled with free-draining material that extends along the height of the wall and a distance of at least 18 inches behind the wall. The upper 12 inches of the wall backfill may consist of a less permeable soil, if desired. Drainage should be provided behind retaining walls such that hydrostatic pressures do not develop. If drainage is not provided, hydrostatic pressures should be included in the wall design. A perforated drainpipe should be placed along the base of the wall and connected to an approved discharge location. A typical retaining wall drainage detail is provided on Plate 3. ACH Development Group, LLC ES-9205 June 9, 2023 Page 10 Earth Solutions NW, LLC Seismic Design The 2018 International Building Code (2018 IBC) recognizes the most recent edition of the Minimum Design Loads for Buildings and Other Structures manual (ASCE 7-16) for seismic design, specifically with respect to earthquake loads. Based on the soil conditions encountered at the test pit locations, the parameters and values provided below are recommended for seismic design per the 2018 IBC. Parameter Value Site Class C* Mapped short period spectral response acceleration, SS (g) 1.396 Mapped 1-second period spectral response acceleration, S1 (g) 0.478 Short period site coefficient, Fa 1.2 Long period site coefficient, Fv 1.5 Adjusted short period spectral response acceleration, SMS (g) 1.675 Adjusted 1-second period spectral response acceleration, SM1 (g) 0.718 Design short period spectral response acceleration, SDS (g) 1.117 Design 1-second period spectral response acceleration, SD1 (g) 0.478 * Assumes very dense soil conditions, encountered to a maximum depth of nine-and-one-half feet bgs during the April 2023 field exploration, remain very dense to at least 100 feet bgs. Based on our experience with the project geologic setting (glacial till) across the Puget Sound region, soil conditions are likely consistent with this assumption. Liquefaction is a phenomenon that can occur within a soil profile as a result of an intense ground shaking or loading condition. Most commonly, liquefaction is caused by ground shaking during an earthquake. Soil profiles that are loose, cohesionless, and present below the groundwater table are most susceptible to liquefaction. During the ground shaking, the soil contracts, and porewater pressure increases. The increased porewater pressure occurs quickly and without sufficient time to dissipate, resulting in water flowing upward to the ground surface and a liquefied soil condition. Soil in a liquefied condition possesses very little shear strength in comparison to the drained condition, which can result in a loss of foundation support for structures. In our opinion, and consistent with regional liquefaction susceptibility mapping, site susceptibility to liquefaction may be considered very low to negligible. The relatively consistent density of the native soils and the absence of a uniformly established, shallow groundwater table were the primary bases for this opinion. ACH Development Group, LLC ES-9205 June 9, 2023 Page 11 Earth Solutions NW, LLC Slab-on-Grade Floors Slab-on-grade floors should be supported on a firm and unyielding subgrade consisting of competent native soil or at least 12 inches of new structural fill. Unstable or yielding areas of the subgrade should be recompacted or overexcavated and replaced with suitable structural fill prior to slab construction. A capillary break consisting of a minimum of four inches of free-draining crushed rock or gravel should be placed below the slab. The free-draining material should have a fines content of 5 percent or less defined as the percent passing the number 200 sieve, based on the minus three- quarter-inch fraction. In areas where slab moisture is undesirable, installation of a vapor barrier below the slab should be considered. If used, the vapor barrier should consist of a material specifically designed to function as a vapor barrier and should be installed in accordance with the manufacturer’s specifications. Utility Support and Trench Backfill The soils observed at the subsurface exploration locations are generally suitable for support of utilities. Use of the native soil as structural backfill in the utility trench excavations will depend on the in-situ moisture content at the time of placement and compaction. If native soil is placed below the optimum moisture content, settlement will likely occur once wet weather impacts the trenches. As such, backfill soils should be properly moisture conditioned, as necessary, to ensure acceptability of the soil moisture content at the time of placement and compaction. Native soil will be difficult or impossible to use as utility trench backfill during extended wet weather conditions. In this respect, moisture conditioning or treatment of the soils may be necessary at some locations prior to use as structural fill. Utility trench backfill should be placed and compacted to the specifications of structural fill provided in this report or to the applicable requirements of the presiding jurisdiction. Preliminary Pavement Sections The performance of site pavements is largely related to the condition of the underlying subgrade. To ensure adequate pavement performance, the subgrade should be in a firm and unyielding condition when subjected to proof rolling with a loaded dump truck. Structural fill in pavement areas should be compacted to the specifications previously detailed in this report. Soft, wet, or otherwise unsuitable or yielding subgrade conditions will require remedial measures, such as overexcavation and/or placement of thick crushed rock or structural fill sections, prior to paving. We anticipate new pavement sections will be subjected primarily to passenger vehicle traffic. For lightly loaded pavement areas subjected primarily to passenger vehicles, the following preliminary pavement sections may be considered: A minimum of two inches of hot-mix asphalt (HMA) placed over four inches of crushed rock base (CRB). A minimum of two inches of HMA placed over three inches of asphalt-treated base (ATB). ACH Development Group, LLC ES-9205 June 9, 2023 Page 12 Earth Solutions NW, LLC An ESNW representative should be requested to observe subgrade conditions prior to placement of CRB or ATB. As necessary, supplemental recommendations for achieving subgrade stability and drainage can be provided. Final pavement design recommendations, including recommendations for heavy traffic areas, access roads, and frontage improvement areas, can be provided once final traffic loading has been determined. Road standards utilized by the governing jurisdiction may supersede the recommendations provided in this report. The HMA, ATB, and CRB materials should conform to WSDOT specifications. All soil base material should be compacted to a relative compaction of 95 percent, based on the laboratory maximum dry density as determined by ASTM D1557. If on-site roads will be constructed with an inverted crown, additional drainage measures may be recommended to assist in maintaining road subgrade and pavement stability. Drainage Groundwater seepage will likely be encountered within site excavations depending on the time of year grading operations take place. Given the observed geologic conditions on site, groundwater flow rates (if present) are expected to be relatively light. Temporary measures to control surface water runoff and groundwater during construction would likely involve passive elements such as interceptor trenches, interceptor swales, and sumps. ESNW should be consulted during preliminary grading to identify areas of seepage and provide recommendations to reduce the potential for seepage-related instability. Finish grades must be designed to direct surface drain water away from structures and slopes. Water must not be allowed to pond adjacent to structures or slopes. In our opinion, a foundation drain should be installed along building perimeter footings. A typical foundation drain detail is provided on Plate 4. Preliminary Infiltration Feasibility In general, the native glacial till soils exhibit very poor infiltration characteristics, including high relative density, high fines content, and weak cementation, and in our opinion, full infiltration should be considered infeasible from a geotechnical standpoint. If necessary to satisfy project objectives, limited infiltration applications may be feasible within the upper weathered soil horizon. However, given the anticipated grade modifications (considerable grade cuts and fills), it is unlikely that the upper weathered soils will remain in an undisturbed condition, precluding the design and implementation of shallow LID elements. ACH Development Group, LLC ES-9205 June 9, 2023 Page 13 Earth Solutions NW, LLC LIMITATIONS This study has been prepared for the exclusive use of ACH Development Group, LLC, and its representatives. The recommendations and conclusions provided in this study are professional opinions consistent with the level of care and skill that is typical of other members in the profession currently practicing under similar conditions in this area. A warranty is neither expressed nor implied. Variations in the soil and groundwater conditions observed at the exploration locations may exist and may not become evident until construction. ESNW should reevaluate the conclusions provided in this study if variations are encountered. Additional Services ESNW should have an opportunity to review final project plans with respect to the geotechnical recommendations provided in this report. ESNW should also be retained to provide testing and consultation services as needed during design and construction phases of the project. Drawn CAM Checked BCS Date June 2023 Date 06/09/2023 Proj.No.9205 Plate 1 Geotechnical Engineering,Construction Observation/Testing and Environmental Services Earth Solutions NWLLCEarthSolutionsNWLLC EarthSolutions NW LLC Vicinity Map Buxton King County (Renton),Washington Reference: King County,Washington OpenStreetMap.org NORTH NOTE:This plate may contain areas of color.ESNW cannot be responsible for any subsequent misinterpretation of the information resulting from black &white reproductions of this plate. Renton SITE Newcastle Plate Proj.No. Date Checked Drawn Earth Solutions NWLLC Geotechnical Engineering, Construction Observation/Testing and Environmental Services Earth Solutions NWLLC Earth Solutions NW LLC TP-1 TP-2 TP-3 TP-4 TP-5 TP-6 TP-7 TP-8 n.e.16th street lyons place n.e. re n t o n i s s a q u a h r o a d s .e . 1 2 3 4 5 6 7 8 9 10 Tract A Recreation 11 12 13 Tract B Utilies,Fire & Pedestrian Access 14 15 16 17 18 19 20 21 22 Tract C Storm Drainage & Recreation 470 470 460 460 450 450 440 440 430 460 460 0 75 150 300 Sc ale in Feet1"=150' NOTE:This plate may contain areas of color.ESNW cannot be responsible for any subsequent misinterpretation of the information resulting from black &white reproductions of this plate. NOTE:The graphics shown on this plate are not intended for design purposes or precise scale measurements,but only to illustrate the approximate test locations relative to the approximate locations of existing and /or proposed site features.The information illustrated is largely based on data provided by the client at the time of our study.ESNW cannot be responsible for subsequent design changes or interpretation of the data by others. LEGEND Approximate Location of ESNW Test Pit,Proj.No. ES-9205,April 2023 Subject Site Existing Building Proposed Lot Number TP-1 NORTH 21 Test Pit Location Plan Buxton King County (Renton), Washington CAM BCS 06/09/2023 9205 2 Geotechnical Engineering,Construction Observation/Testing and Environmental Services Drawn CAM Checked BCS Date June 2023 Date 06/09/2023 Proj.No.9205 Plate 3 Earth Solutions NWLLCEarthSolutionsNWLLC EarthSolutions NW LLC NOTES: Free-draining Backfill should consist of soil having less than 5 percent fines. Percent passing No.4 sieve should be 25 to 75 percent. Sheet Drain may be feasible in lieu of Free-draining Backfill,per ESNW recommendations. Drain Pipe should consist of perforated, rigid PVC Pipe surrounded with 1-inch Drain Rock. LEGEND: Free-draining Structural Backfill 1-inch Drain Rock 18"Min. Structural Fill Perforated Rigid Drain Pipe (Surround in Drain Rock) SCHEMATIC ONLY -NOT TO SCALE NOT A CONSTRUCTION DRAW ING Retaining Wall Drainage Detail Buxton King County (Renton),Washington Geotechnical Engineering,Construction Observation/Testing and Environmental Services Drawn CAM Checked BCS Date June 2023 Date 06/09/2023 Proj.No.9205 Plate 4 Earth Solutions NWLLCEarthSolutionsNWLLC EarthSolutions NW LLC Slope Perforated Rigid Drain Pipe (Surround in Drain Rock) 18"Min. NOTES: Do NOT tie roof downspouts to Footing Drain. Surface Seal to consist of 12"of less permeable,suitable soil.Slope away from building. LEGEND: Surface Seal:native soil or other low-permeability material. 1-inch Drain Rock SCHEMATIC ONLY -NOT TO SCALE NOT A CONSTRUCTION DRAW ING Footing Drain Detail Buxton King County (Renton),Washington Earth Solutions NW, LLC Appendix A Subsurface Exploration Test Pit Logs ES-9205 Subsurface conditions on site were explored on April 28, 2023, by advancing eight test pits using a machine and an operator retained by ESNW. The approximate locations of the test pits are illustrated on Plate 2 of this study. The test pit logs are provided in this Appendix. The test pits were advanced to a maximum depth of about nine-and-one-half feet bgs. The final logs represent the interpretations of the field logs and the results of laboratory analyses. The stratification lines on the logs represent the approximate boundaries between soil types. In actuality, the transitions may be more gradual. > 12% Fines < 5% Fines Highly Organic Soils Silts and Clays Liquid Limit 50 or More Silts and Clays Liquid Limit Less Than 50 Fine-Grained Soils - 50% or More Passes No. 200 Sieve Coarse-Grained Soils - More Than 50% Retained on No. 200 Sieve Sands - 50% or More of Coarse Fraction Passes No. 4 Sieve Gravels - More Than 50% of Coarse Fraction Retained on No. 4 Sieve > 12% Fines < 5% Fines GW GP GM GC SW SP SM SC ML CL OL MH CH OH PT Well-graded gravel with or without sand,little to no fines Poorly graded gravel with or without sand,little to no fines Silty gravel with or without sand Clayey gravel with or without sand Well-graded sand with or without gravel,little to no fines Poorly graded sand with or without gravel,little to no fines Silty sand with or without gravel Clayey sand with or without gravel Silt with or without sand or gravel;sandy or gravelly silt Clay of low to medium plasticity;lean clay with or without sand or gravel; sandy or gravelly lean clay Organic clay or silt of low plasticity Elastic silt with or without sand or gravel;sandy or gravelly elastic silt Clay of high plasticity; fat clay with or without sand or gravel;sandy or gravelly fat clay Organic clay or silt of medium to high plasticity Peat,muck,and other highly organic soils EEaarrtthh SSoolluuttiioonnss NNWW LLC Geotechnical Engineering,Construction Observation/Testing and Environmental Services EXPLORATION LOG KEY Fill FILL Made Ground Classifications of soils in this geotechnical report and as shown on the exploration logs are based on visual field and/or laboratory observations,which include density/consistency,moisture condition,grain size,and plasticity estimates,and should not be construed to imply field or laboratory testing unless presented herein. Visual-manual and/or laboratory classification methods of ASTM D2487 and D2488 were used as an identification guide for the Unified Soil Classification System. Terms Describing Relative Density and Consistency Coarse-Grained Soils: Fine-Grained Soils: SPT blows/foot SPT blows/foot Test Symbols &Units Fines =Fines Content (%) MC =Moisture Content (%) DD =Dry Density (pcf) Str =Shear Strength (tsf) PID =Photoionization Detector (ppm) OC =Organic Content (%) CEC =Cation Exchange Capacity (meq/100 g) LL =Liquid Limit (%) PL =Plastic Limit (%) PI =Plasticity Index (%) Component Definitions Descriptive Term Size Range and Sieve Number Smaller than No.200 (0.075 mm) Boulders Modifier Definitions Percentage by Weight (Approx.) <5 5 to 14 15 to 29 >30_ Modifier Trace (sand,silt,clay,gravel) Slightly (sandy,silty,clayey,gravelly) Sandy,silty,clayey,gravelly Very (sandy,silty,clayey,gravelly) Moisture Content Dry -Absence of moisture,dusty,dry to the touch Damp -Perceptible moisture,likely below optimum MC Moist -Damp but no visible water,likely at/near optimum MC Wet -Water visible but not free draining, likely above optimum MC Saturated/Water Bearing -Visible free water,typically below groundwater table Symbols Cement grout surface seal Bentonite chips Grout seal Filter pack with blank casing section Screened casing or Hydrotip with filter pack End cap ATD =At time of drilling Static water level (date) _>50 Density Very Loose Loose Medium Dense Dense Very Dense Consistency Very Soft Soft Medium Stiff Stiff Very Stiff Hard <4 4 to 9 10 to 29 30 to 49 <2 2 to 3 4 to 7 8 to 14 15 to 29 _>30 EEaarrtthh NNWWLLC EarthSolutions NW LLC Cobbles Gravel Coarse Gravel Fine Gravel Sand Coarse Sand Medium Sand Fine Sand Silt and Clay Larger than 12" 3"to 12" 3"to No.4 (4.75 mm) 3"to 3/4" 3/4"to No.4 (4.75 mm) No.4 (4.75 mm)to No.200 (0.075 mm) No.4 (4.75 mm)to No.10 (2.00 mm) No.10 (2.00 mm)to No.40 (0.425 mm) No.40 (0.425 mm)to No.200 (0.075 mm) 457.3 451.0 GB GB GB MC = 11.5 MC = 12.9 MC = 12.8 TPSL SM Dark brown TOPSOIL Brown silty SAND with gravel, medium dense, moist (weathered till) -probed 6" -becomes gray, dense -light iron oxide staining -probed 3", becomes very dense, weakly cemented (unweathered till) Test pit terminated at 7.0 feet below existing grade. No groundwater encountered during excavation. No caving observed. LIMITATIONS: Ground elevation (if listed) is approximate; the test location was not surveyed. Coordinates are approximate and based on the WGS84 datum. Do not rely on this test log as a standalone document. Refer to the text of the geotechnical report for a complete understanding of subsurface conditions. 0.7 7.0 DE P T H (f t ) 0.0 2.5 5.0 SA M P L E T Y P E NU M B E R EXCAVATION CONTRACTOR NW Excavating DATE STARTED 4/28/23 COMPLETED 4/28/23 GROUND WATER LEVEL: GROUND ELEVATION 458 ft LATITUDE 47.50483 LONGITUDE -122.14639 LOGGED BY BCS CHECKED BY SSR NOTES SURFACE CONDITIONS Grass AT TIME OF EXCAVATIONAT TIME OF EXCAVATION AFTER EXCAVATION PAGE 1 OF 1 TEST PIT NUMBER TP-1 PROJECT NUMBER ES-9205 PROJECT NAME Buxton GE N E R A L B H / T P / W E L L - 9 2 0 5 . G P J - G I N T U S . G D T - 6 / 9 / 2 3 Earth Solutions NW, LLC 15365 N.E. 90th Street, Suite 100 Redmond, Washington 98052 Telephone: 425-449-4704 Fax: 425-449-4711 TESTS U. S . C . S . MATERIAL DESCRIPTION GR A P H I C LO G 453.3 449.0 GB GB MC = 18.4 MC = 9.9 TPSL SM Dark brown TOPSOIL Tan silty SAND with gravel, loose, wet (weathered till) -probed 16" -light iron oxide staining -becomes gray, dense to very dense, moist -weakly cemented (unweathered till) Test pit terminated at 5.0 feet below existing grade. No groundwater encountered during excavation. No caving observed. LIMITATIONS: Ground elevation (if listed) is approximate; the test location was not surveyed. Coordinates are approximate and based on the WGS84 datum. Do not rely on this test log as a standalone document. Refer to the text of the geotechnical report for a complete understanding of subsurface conditions. 0.7 5.0 DE P T H (f t ) 0.0 2.5 5.0 SA M P L E T Y P E NU M B E R EXCAVATION CONTRACTOR NW Excavating DATE STARTED 4/28/23 COMPLETED 4/28/23 GROUND WATER LEVEL: GROUND ELEVATION 454 ft LATITUDE 47.50513 LONGITUDE -122.14622 LOGGED BY BCS CHECKED BY SSR NOTES SURFACE CONDITIONS Grass AT TIME OF EXCAVATIONAT TIME OF EXCAVATION AFTER EXCAVATION PAGE 1 OF 1 TEST PIT NUMBER TP-2 PROJECT NUMBER ES-9205 PROJECT NAME Buxton GE N E R A L B H / T P / W E L L - 9 2 0 5 . G P J - G I N T U S . G D T - 6 / 9 / 2 3 Earth Solutions NW, LLC 15365 N.E. 90th Street, Suite 100 Redmond, Washington 98052 Telephone: 425-449-4704 Fax: 425-449-4711 TESTS U. S . C . S . MATERIAL DESCRIPTION GR A P H I C LO G 449.6 448.0 444.5 GB GB MC = 15.3 MC = 10.9 TPSL SM SM Dark brown TOPSOIL and SOD (Fill) Brown silty SAND, loose, moist to wet (Fill) -scattered minor organics -probed 24" Brown silty SAND with gravel, medium dense, moist (weathered till) -light iron oxide staining -becomes gray, dense to very dense, weakly cemented (unweathered till) Test pit terminated at 5.5 feet below existing grade. No groundwater encountered during excavation. No caving observed. LIMITATIONS: Ground elevation (if listed) is approximate; the test location was not surveyed. Coordinates are approximate and based on the WGS84 datum. Do not rely on this test log as a standalone document. Refer to the text of the geotechnical report for a complete understanding of subsurface conditions. 0.4 2.0 5.5 DE P T H (f t ) 0.0 2.5 5.0 SA M P L E T Y P E NU M B E R EXCAVATION CONTRACTOR NW Excavating DATE STARTED 4/28/23 COMPLETED 4/28/23 GROUND WATER LEVEL: GROUND ELEVATION 450 ft LATITUDE 47.50547 LONGITUDE -122.14608 LOGGED BY BCS CHECKED BY SSR NOTES SURFACE CONDITIONS Grass AT TIME OF EXCAVATIONAT TIME OF EXCAVATION AFTER EXCAVATION PAGE 1 OF 1 TEST PIT NUMBER TP-3 PROJECT NUMBER ES-9205 PROJECT NAME Buxton GE N E R A L B H / T P / W E L L - 9 2 0 5 . G P J - G I N T U S . G D T - 6 / 9 / 2 3 Earth Solutions NW, LLC 15365 N.E. 90th Street, Suite 100 Redmond, Washington 98052 Telephone: 425-449-4704 Fax: 425-449-4711 TESTS U. S . C . S . MATERIAL DESCRIPTION GR A P H I C LO G 443.3 434.5 GB GB GB MC = 15.1 MC = 10.6 Fines = 23.9 MC = 12.2 TPSL SM Dark brown TOPSOIL Brown silty SAND with gravel, loose, moist to wet (weathered till) -probed 20" -becomes gray, dense to very dense, moist -weakly cemented (unweathered till) [USDA Classification: gravelly sandy LOAM] Test pit terminated at 9.5 feet below existing grade. No groundwater encountered during excavation. No caving observed. LIMITATIONS: Ground elevation (if listed) is approximate; the test location was not surveyed. Coordinates are approximate and based on the WGS84 datum. Do not rely on this test log as a standalone document. Refer to the text of the geotechnical report for a complete understanding of subsurface conditions. 0.7 9.5 DE P T H (f t ) 0.0 2.5 5.0 7.5 SA M P L E T Y P E NU M B E R EXCAVATION CONTRACTOR NW Excavating DATE STARTED 4/28/23 COMPLETED 4/28/23 GROUND WATER LEVEL: GROUND ELEVATION 444 ft LATITUDE 47.50602 LONGITUDE -122.14615 LOGGED BY BCS CHECKED BY SSR NOTES SURFACE CONDITIONS Grass AT TIME OF EXCAVATIONAT TIME OF EXCAVATION AFTER EXCAVATION PAGE 1 OF 1 TEST PIT NUMBER TP-4 PROJECT NUMBER ES-9205 PROJECT NAME Buxton GE N E R A L B H / T P / W E L L - 9 2 0 5 . G P J - G I N T U S . G D T - 6 / 9 / 2 3 Earth Solutions NW, LLC 15365 N.E. 90th Street, Suite 100 Redmond, Washington 98052 Telephone: 425-449-4704 Fax: 425-449-4711 TESTS U. S . C . S . MATERIAL DESCRIPTION GR A P H I C LO G 445.2 436.5 GB GB MC = 16.5 Fines = 21.4 MC = 11.8 Fines = 22.6 TPSL SM Dark brown TOPSOIL Brown silty SAND with gravel, medium dense, moist to wet (weathered till) -probed 5" [USDA Classification: very gravelly sandy LOAM] -light iron oxide staining -becomes gray, dense, moist, weakly cemented (unweathered till) -light groundwater seepage -light groundwater seepage [USDA Classification: gravelly sandy LOAM] Test pit terminated at 9.5 feet below existing grade. Groundwater seepage encountered at 4.0 and 8.0 feet during excavation. No caving observed. LIMITATIONS: Ground elevation (if listed) is approximate; the test location was not surveyed. Coordinates are approximate and based on the WGS84 datum. Do not rely on this test log as a standalone document. Refer to the text of the geotechnical report for a complete understanding of subsurface conditions. 0.8 9.5 DE P T H (f t ) 0.0 2.5 5.0 7.5 SA M P L E T Y P E NU M B E R EXCAVATION CONTRACTOR NW Excavating DATE STARTED 4/28/23 COMPLETED 4/28/23 GROUND WATER LEVEL: GROUND ELEVATION 446 ft LATITUDE 47.50613 LONGITUDE -122.14638 LOGGED BY BCS CHECKED BY SSR NOTES SURFACE CONDITIONS Grass AT TIME OF EXCAVATIONAT TIME OF EXCAVATION AFTER EXCAVATION PAGE 1 OF 1 TEST PIT NUMBER TP-5 PROJECT NUMBER ES-9205 PROJECT NAME Buxton GE N E R A L B H / T P / W E L L - 9 2 0 5 . G P J - G I N T U S . G D T - 6 / 9 / 2 3 Earth Solutions NW, LLC 15365 N.E. 90th Street, Suite 100 Redmond, Washington 98052 Telephone: 425-449-4704 Fax: 425-449-4711 TESTS U. S . C . S . MATERIAL DESCRIPTION GR A P H I C LO G 454.3 453.5 445.5 GB GB GB MC = 19.8 MC = 9.4 MC = 11.0 SM TPSL SM Gray silty SAND with gravel, medium dense, moist (Fill) Dark brown relic TOPSOIL and SOD Brown silty SAND with gravel, medium dense, wet (weathered till) -probed 10" -becomes gray, dense to very dense, moist -weakly cemented (unweathered till) Test pit terminated at 9.5 feet below existing grade. No groundwater encountered during excavation. No caving observed. LIMITATIONS: Ground elevation (if listed) is approximate; the test location was not surveyed. Coordinates are approximate and based on the WGS84 datum. Do not rely on this test log as a standalone document. Refer to the text of the geotechnical report for a complete understanding of subsurface conditions. 0.8 1.5 9.5 DE P T H (f t ) 0.0 2.5 5.0 7.5 SA M P L E T Y P E NU M B E R EXCAVATION CONTRACTOR NW Excavating DATE STARTED 4/28/23 COMPLETED 4/28/23 GROUND WATER LEVEL: GROUND ELEVATION 455 ft LATITUDE 47.50541 LONGITUDE -122.14702 LOGGED BY BCS CHECKED BY SSR NOTES SURFACE CONDITIONS Graded Soil AT TIME OF EXCAVATIONAT TIME OF EXCAVATION AFTER EXCAVATION PAGE 1 OF 1 TEST PIT NUMBER TP-6 PROJECT NUMBER ES-9205 PROJECT NAME Buxton GE N E R A L B H / T P / W E L L - 9 2 0 5 . G P J - G I N T U S . G D T - 6 / 9 / 2 3 Earth Solutions NW, LLC 15365 N.E. 90th Street, Suite 100 Redmond, Washington 98052 Telephone: 425-449-4704 Fax: 425-449-4711 TESTS U. S . C . S . MATERIAL DESCRIPTION GR A P H I C LO G 459.3 455.5 454.0 452.5 GB GB GB MC = 17.2 Fines = 30.2 MC = 3.4 MC = 8.5 TPSL SM GW SP Dark brown TOPSOIL Brown silty SAND with gravel, medium dense, wet -minor charcoal -probed 10" [USDA Classification: very gravelly fine sandy LOAM] -becomes gray, dense, moist Gray well-graded GRAVEL with sand, dense, damp Gray poorly graded SAND, dense, damp to moist Test pit terminated at 7.5 feet below existing grade. No groundwater encountered during excavation. No caving observed. LIMITATIONS: Ground elevation (if listed) is approximate; the test location was not surveyed. Coordinates are approximate and based on the WGS84 datum. Do not rely on this test log as a standalone document. Refer to the text of the geotechnical report for a complete understanding of subsurface conditions. 0.7 4.5 6.0 7.5 DE P T H (f t ) 0.0 2.5 5.0 7.5 SA M P L E T Y P E NU M B E R EXCAVATION CONTRACTOR NW Excavating DATE STARTED 4/28/23 COMPLETED 4/28/23 GROUND WATER LEVEL: GROUND ELEVATION 460 ft LATITUDE 47.50509 LONGITUDE -122.14698 LOGGED BY BCS CHECKED BY SSR NOTES SURFACE CONDITIONS Grass AT TIME OF EXCAVATIONAT TIME OF EXCAVATION AFTER EXCAVATION PAGE 1 OF 1 TEST PIT NUMBER TP-7 PROJECT NUMBER ES-9205 PROJECT NAME Buxton GE N E R A L B H / T P / W E L L - 9 2 0 5 . G P J - G I N T U S . G D T - 6 / 9 / 2 3 Earth Solutions NW, LLC 15365 N.E. 90th Street, Suite 100 Redmond, Washington 98052 Telephone: 425-449-4704 Fax: 425-449-4711 TESTS U. S . C . S . MATERIAL DESCRIPTION GR A P H I C LO G 465.1 457.0 GB GB GB MC = 9.8 Fines = 16.7 MC = 6.4 Fines = 13.4 MC = 6.8 TPSL SM Dark brown TOPSOIL Brown silty SAND with gravel, loose, moist (weathered till) -probed 24" [USDA Classification: gravelly loamy SAND] -becomes gray, medium dense to dense (unweathered till) [USDA Classification: very gravelly sandy LOAM] Test pit terminated at 9.0 feet below existing grade. No groundwater encountered during excavation. No caving observed. LIMITATIONS: Ground elevation (if listed) is approximate; the test location was not surveyed. Coordinates are approximate and based on the WGS84 datum. Do not rely on this test log as a standalone document. Refer to the text of the geotechnical report for a complete understanding of subsurface conditions. 0.9 9.0 DE P T H (f t ) 0.0 2.5 5.0 7.5 SA M P L E T Y P E NU M B E R EXCAVATION CONTRACTOR NW Excavating DATE STARTED 4/28/23 COMPLETED 4/28/23 GROUND WATER LEVEL: GROUND ELEVATION 466 ft LATITUDE 47.50478 LONGITUDE -122.14699 LOGGED BY BCS CHECKED BY SSR NOTES SURFACE CONDITIONS Grass AT TIME OF EXCAVATIONAT TIME OF EXCAVATION AFTER EXCAVATION PAGE 1 OF 1 TEST PIT NUMBER TP-8 PROJECT NUMBER ES-9205 PROJECT NAME Buxton GE N E R A L B H / T P / W E L L - 9 2 0 5 . G P J - G I N T U S . G D T - 6 / 9 / 2 3 Earth Solutions NW, LLC 15365 N.E. 90th Street, Suite 100 Redmond, Washington 98052 Telephone: 425-449-4704 Fax: 425-449-4711 TESTS U. S . C . S . MATERIAL DESCRIPTION GR A P H I C LO G Earth Solutions NW, LLC Appendix B Laboratory Test Results ES-9205 0 5 10 15 20 25 30 35 40 45 50 55 60 65 70 75 80 85 90 95 100 0.0010.010.1110100 3 D100 140 Specimen Identification 1 fine 6 HYDROMETER 304 23.9 21.4 22.6 30.2 16.7 101/2 COBBLES Specimen Identification 4 coarse 20 401.5 8 14 USDA: Gray Gravelly Sandy Loam. USCS: SM with Gravel. USDA: Brown Very Gravelly Sandy Loam. USCS: SM with Gravel. USDA: Gray Gravelly Sandy Loam. USCS: SM with Gravel. USDA: Brown Very Gravelly Fine Sandy Loam. USCS: SM with Gravel. USDA: Brown Gravelly Loamy Sand. USCS: SM with Gravel. 6 60 PE R C E N T F I N E R B Y W E I G H T D10 0.109 0.182 0.123 0.176 0.51 3.447 0.676 1.81 0.714 GRAIN SIZE DISTRIBUTION 100 LL TP-04 TP-05 TP-05 TP-07 TP-08 3/4 U.S. SIEVE OPENING IN INCHES U.S. SIEVE NUMBERS GRAVEL SAND 37.5 37.5 19 37.5 37.5 %Silt TP-04 TP-05 TP-05 TP-07 TP-08 2 2003 Cc CuClassification %Clay 16 PID60 D30 coarse SILT OR CLAYfinemedium GRAIN SIZE IN MILLIMETERS 3/8 50 4.5ft. 2.0ft. 9.5ft. 1.5ft. 2.5ft. 4.50ft. 2.00ft. 9.50ft. 1.50ft. 2.50ft. PL PROJECT NUMBER ES-9205 PROJECT NAME Buxton GR A I N S I Z E U S D A E S - 9 2 0 5 B U X T O N . G P J G I N T U S L A B . G D T 6 / 2 / 2 3 Earth Solutions NW, LLC 15365 N.E. 90th Street, Suite 100 Redmond, Washington 98052 Telephone: 425-449-4704 Fax: 425-449-4711 0 5 10 15 20 25 30 35 40 45 50 55 60 65 70 75 80 85 90 95 100 0.0010.010.1110100 3 D100 140 Specimen Identification 1 fine 6 HYDROMETER 304 13.4 101/2 COBBLES Specimen Identification 4 coarse 20 401.5 8 14 USDA: Gray Very Gravelly Sandy Loam. USCS: SM with Gravel. 6 60 PE R C E N T F I N E R B Y W E I G H T D10 0.25.542 GRAIN SIZE DISTRIBUTION 100 LL TP-08 3/4 U.S. SIEVE OPENING IN INCHES U.S. SIEVE NUMBERS GRAVEL SAND 37.5 %Silt TP-08 2 2003 Cc CuClassification %Clay 16 PID60 D30 coarse SILT OR CLAYfinemedium GRAIN SIZE IN MILLIMETERS 3/8 50 5.0ft. 5.00ft. PL PROJECT NUMBER ES-9205 PROJECT NAME Buxton GR A I N S I Z E U S D A E S - 9 2 0 5 B U X T O N . G P J G I N T U S L A B . G D T 6 / 2 / 2 3 Earth Solutions NW, LLC 15365 N.E. 90th Street, Suite 100 Redmond, Washington 98052 Telephone: 425-449-4704 Fax: 425-449-4711 Earth Solutions NW, LLC Report Distribution ES-9205 EMAIL ONLY ACH Development Group, LLC 9675 Southeast 36th Street, Suite 105 Mercer Island, Washington 98040 Attention: Justin Lagers