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Drainage Report Civil Engineers ● Structural Engineers ● Landscape Architects ● Community Planners ● Land Surveyors Preliminary Stormwater Report PREPARED FOR: Matt Lewis Garrette Custom Homes, Inc. 4802 Tacoma Mall Boulevard Tacoma, WA 98409 PROJECT: The Reserve at Palisades Yelm, Washington 2220348.10 PREPARED BY: Allyson Burket Project Engineer REVIEWED BY: J. Matthew Weber, PE Principal DATE: August 2024 Preliminary Stormwater Report PREPARED FOR: Matt Lewis Garrette Custom Homes, Inc. 4802 Tacoma Mall Boulevard Tacoma, WA 98409 PROJECT: The Reserve at Palisades Yelm, Washington 2220348.10 PREPARED BY: Allyson Burket Project Engineer REVIEWED BY: J. Matthew Weber, PE Principal DATE: August 2024 I hereby state that this Stormwater Report for The Reserve at Palisades Plat has been prepared by me or under my supervision and meets the standard of care and expertise that is usual and customary in this community for professional engineers. I understand that City of Yelm does not and will not assume liability for the sufficiency, suitability, or performance of drainage facilities prepared by me. 8/30/2024 The Preliminary Stormwater Report The Reserve at Palisades 2220348.10 Table of Contents Section Page 1.0 Project Overview ............................................................................................................................ 1 2.0 Summary of Minimum Requirements .......................................................................................... 1 2.1 MR 1 – Preparation of Stormwater Site Plans .................................................................... 1 2.2 MR 2 - Construction Stormwater Pollution Prevention ....................................................... 1 2.3 MR 3 – Source Control of Pollution ..................................................................................... 1 2.4 MR 4 – Preservation of Natural Drainage Systems and Outfalls ........................................ 1 2.5 MR 5 – Onsite Stormwater Control ..................................................................................... 1 2.6 MR 6 – Runoff Treatment ................................................................................................... 2 2.7 MR 7 – Flow Control ........................................................................................................... 2 2.8 MR 8 – Wetlands Protection ............................................................................................... 2 2.9 MR 9 – Basin/Watershed Planning ..................................................................................... 2 2.10 MR 10 – Operation and Maintenance ................................................................................. 2 3.0 Existing Conditions ....................................................................................................................... 2 3.1 Soils Reports ....................................................................................................................... 2 4.0 Wells and Septic Systems ............................................................................................................. 2 5.0 Fuel Tanks ...................................................................................................................................... 3 6.0 Sub-Basin Description................................................................................................................... 3 7.0 Analysis of the 100-Year Flood ..................................................................................................... 3 8.0 Aesthetic Considerations for Facilities ....................................................................................... 3 9.0 Facility Sizing and Downstream Analysis ................................................................................... 3 9.1 Conveyance ........................................................................................................................ 3 9.2 Treatment ............................................................................................................................ 3 9.3 Flow Control ........................................................................................................................ 3 9.4 Roof Runoff ......................................................................................................................... 4 10.0 Covenants Dedications, Easements ............................................................................................ 4 11.0 Property Owners Association Articles of Incorporation ............................................................ 4 12.0 Conclusion ...................................................................................................................................... 4 Preliminary Stormwater Report The Reserve at Palisades 2220348.10 Appendices Appendix A Exhibits A-1 ............. Vicinity Map A-2 ............. Existing Conditions A-3 ............. Developed Conditions A-4 ............. NRCS Soil Map A-5 ............. FEMA 100-Year Flood Plain Map Appendix B Facility Sizing B-1 ............. Basin Map B-2 ............. WWHM Report Appendix C Geotechnical Reports Geotechnical Report GeoResources, LLC April 4, 2024 Preliminary Stormwater Report The Reserve at Palisades 1 2220348.10 1.0 Project Overview The following hydrology report summarizes the storm drainage analysis and design for a 39-lot development located at 15036 State Route 507 SE in Yelm, Thurston County, Washington. The land is currently a 9.71-acre property. The project includes the addition of 39 residential lots for single-family homes, a new roadway and sidewalks, sewer, water services, and stormwater facilities to treat and dispose of the project's stormwater. The proposed roadway features and utilities will be extended from Palisades St SE. The 9.71-acre site is located in Section 25, Township 17 North, Range 01 East, W. M. The Thurston County tax parcel number associated with the project is 21725130200. The increased stormwater runoff resulting from the addition of impervious area will be treated and infiltrated in accordance with the most recent Washington State Department of Ecology (DOE) Stormwater Management Manual for Western Washington (SWMMWW). 2.0 Summary of Minimum Requirements This project is subject to the SWMMWW and is a new development that will add more than 10,000 square feet of impervious surfaces; therefore, all Minimum Requirements (MR) apply to this project. 2.1 MR 1 – Preparation of Stormwater Site Plans This report and the project plans represent the Stormwater Site Plan for this project and satisfy MR 1. 2.2 MR 2 - Construction Stormwater Pollution Prevention A Construction Stormwater Pollution Prevention Plan will be prepared with final engineering. 2.3 MR 3 – Source Control of Pollution Pollution source control will be provided for the site by treating the runoff from pollution generating surfaces with a Stormfilter vault. The residential roads should be maintained and cleaned of debris, garbage, and sediment, as required. The Construction SWPPP, addressing MR 3, will be prepared with final engineering. 2.4 MR 4 – Preservation of Natural Drainage Systems and Outfalls The project proposes to infiltrate all stormwater runoff, so all runoff will be retained in the developed condition. There are no natural drainage systems or outfalls to preserve. 2.5 MR 5 – Onsite Stormwater Control This project will meet the Low Impact Development (LID) Performance Standard. The onsite soils have a high infiltration capacity and all runoff will be retained onsite through treatment systems and infiltration facilities. The LID Performance Standard will be met by infiltrating all stormwater runoff from the site. Refer to Section 9.0 for facility sizing. Additionally, all landscaped areas will have amended soils applied per the post construction soil quality and depth BMP T5.13. Preliminary Stormwater Report The Reserve at Palisades 2 2220348.10 2.6 MR 6 – Runoff Treatment Over 5,000 square feet of pollution generating impervious surface (PGIS) will be added as part of these improvements; therefore, runoff treatment is required for this site. Stormwater from the site will be conveyed to a Stormfilter vault before being infiltrated. Final treatment system sizing will be completed with final engineering. 2.7 MR 7 – Flow Control The project exceeds the thresholds for new development projects and must provide flow control. Proposed flow control is achieved with the use of an infiltration pond that will infiltrate 100 percent of runoff. Refer to Section 9.0 for facility sizing. 2.8 MR 8 – Wetlands Protection To our knowledge, no wetlands are located on or adjacent to the site. 2.9 MR 9 – Basin/Watershed Planning To our knowledge, no basin plans exist for the site. The entire City of Yelm and its urban growth area are identified as a highly susceptible critical aquifer recharge area. Treatment of stormwater prior to entering the infiltration pond is proposed via a Stormfilter vault. 2.10 MR 10 – Operation and Maintenance The stormwater system within the right of way will be publicly owned and maintained. The City of Yelm shall be responsible for the operation and maintenance of the public stormwater facilities. An Operation and Maintenance Plan consisting of maintenance checklists for stormwater management will be prepared with final engineering. Operation and maintenance for drainage facilities constructed for each lot shall be the responsibility of the individual owners. 3.0 Existing Conditions The existing site is primarily covered with shrubbery and grass with conifers along the property line and north portion of the site. The topography slopes north to State Route 507 with slopes ranging from 0 to 20 percent. An abandoned house sits on the northern portion of the property. A wet pond and infiltration pond to the northeast is currently used for stormwater management by the neighboring housing development to the east. 3.1 Soils Reports Site soils are identified by the Natural Resources Conservation Service (NRCS) Web Soil Survey as Alderwood gravelly sandy loam and Everett very gravelly sandy loam. GeoResources conducted a site investigation to confirm subsurface soil conditions and establish a design infiltration rate. Soil test holes were dug in the vicinity of the proposed infiltration basin of the project and observations confirm that the soil types match the soil description. A soil log map showing the location of the test holes is included in the geotechnical report. The report recommends a design infiltration rate of 20 inches per hour for facilities within the site’s northeast corner. See Appendix C for the complete GeoResources report. 4.0 Wells and Septic Systems To the best of our knowledge there are no known wells or septic systems on the site. Preliminary Stormwater Report The Reserve at Palisades 3 2220348.10 5.0 Fuel Tanks To the best of our knowledge there are no known wells or septic systems on the site. 6.0 Sub-Basin Description There is a single basin for the developed conditions, which will direct stormwater runoff to the proposed infiltration pond along Palisades Street. The basin will include impervious areas from the proposed site, a portion of State Route (SR) 507, and the existing housing development to the east. Refer to Appendix A-3 for the Developed Basin Map. 7.0 Analysis of the 100-Year Flood Federal Emergency Management Agency (FEMA) mapping does not indicate flooding in the immediate area. Refer to the exhibit in Appendix A-5. 8.0 Aesthetic Considerations for Facilities The proposed infiltration facility is located within a proposed stormwater tract. The facility is designed with a maximum storage depth of 5 feet and 3:1 side slopes. Landscaping plans will provide additional foliage around the facility. 9.0 Facility Sizing and Downstream Analysis The stormwater system was sized and analyzed using the latest edition of the Western Washington Hydrology Model (WWHM) continuous modeling software. A conservative infiltration rate of 20 inches per hour was used for design calculations. Proposed impervious surfaces associated with the proposed roads were calculated based on the site plan layout. 9.1 Conveyance Conveyance sizing will be completed with final engineering. 9.2 Treatment Basic treatment will be provided via Stormfilter structures located prior to the infiltration pond. One structure will be sized for The Reserve at Palisades new development ; the other structure will be sized for the existing Palisades West neighborhood to replace the existing wetpond that will be turned into a larger infiltration pond. See the WWHM basin model in Appendix B for preliminary sizing; final sizing will be completed with final engineering. 9.3 Flow Control Flow control will be provided by fully infiltrating stormwater runoff from the site through an infiltration pond. The pond will be 5.0-feet deep with a minimum bottom area of 10,123 square feet. It will be constructed in the open space in Tract F, where an existing combined wet and infiltration pond for the neighboring property is located. The pond will be located adjacent to SR-507. A portion of SR-507, approximately 210 lineal feet of the northeast bound lane, will drain to the shoulder and into the proposed pond. A culvert located approximately 180 feet upstream southwest of the pond limits the amount of SR-507 draining to the pond. This culvert drains to a ditch on the north side of SR-507. The area draining to the pond is included in the pond sizing. Preliminary Stormwater Report The Reserve at Palisades 4 2220348.10 Below is a summary of the contributing areas to the pond. Infiltration Basin Summary Road (ac) Sidewalk (ac) Driveways (ac) Roof (ac) Pervious (ac) Total (ac) Reserve at Palisades 1.48 0.15 0.54 2.47 4.47 9.11 Palisades West 1.39 0.43 0.45 - 4.79 4.05 State Route 507 0.17 - - - 0.18 0.35 The basin is sized in accordance with the SWMMWW and provides the required storage volume. See Appendix B-1 for the site’s basin map. 9.4 Roof Runoff Stormwater for the roof areas will be directed to the site’s infiltration pond through the site’s network of storm pipes and catch basins. 10.0 Covenants Dedications, Easements The storm facilities for the right-of-way improvements shall be publicly owned and maintained. A maintenance agreement should be executed to ensure future maintenance of the facilities. 11.0 Property Owners Association Articles of Incorporation Not applicable. 12.0 Conclusion The proposed project involves site improvements associated with a 39-lot development. The project includes clearing, grading, erosion control, utility improvements, and stormwater management facilities. The site, as proposed, will meet the requirements of the most recent Department of Ecology Stormwater Management Manual for Western Washington (SWMMWW). This report and associated plans have been prepared within the guidelines established by City of Yelm for stormwater management. This analysis is based on data and records either supplied to or obtained by AHBL. These documents are referenced within the text of the analysis. The analysis has been prepared using procedures and practices within the standard accepted practices of the industry. AHBL, Inc. Allyson Burket Project Engineer August 2024 \\ahbl.com\data\Projects\2022\2220348\WORDPROC\Reports\20240830 Rpt (Prelim TIR) 2220348.10.docx Preliminary Stormwater Report The Reserve at Palisades 2220348.10 Appendix A Exhibits A-1 .................... Vicinity Map A-2 .................... Existing Conditions A-3 .................... Developed Conditions A-4 .................... NRCS Soil Map A-5 .................... FEMA 100-Year Flood Plain Map 1200 6th Avenue, Suite 1620, Seattle, WA 98101 206.267.2425 TEL 206.267.2429 FAX THE RESERVE AT PALISADES VICINITY MAP A-1 VICINITY MAP NOT TO SCALE SITE 507 RIDGELINE MIDDLE SCHOOL 507 P A L I S A D E S S T S E CAR T E R L O O P S E LOOP 10 7 T H SE MI L L R D S E MI L L R D S E 107TH LOOP SE MILL POND ELEMENTARY 104TH AVE SE BRIGHTON ST S E S E 10 5 T H A V E P A L I S A D E S S T S E P A L I S A D E S W E S T P A L I S A D E S W E S T Δ 2215 North 30th Street, Suite 300, Tacoma, WA 98403 253.383.2422 TEL 253.383.2572 FAX JOB NO. DATE: THE RESERVE AT PALISADES EXISTING CONDITIONS A-2 2220348.10 8/27/2024 N GRAPHIC SCALE 0 40 80 1" = 40 FEET 20 89 9 . 8 1 ' 87 5 . 5 0 ' 6830 S.F. 24 6273 S.F. 4 6276 S.F. 3 8989 S.F. TRACT A 6950 S.F. 33 5250 S.F. 35 6300 S.F. 34 7075 S.F. 13 7060 S.F. 157112 S.F. 8 22927 S.F. TRACT F 7105 S.F. 9 7097 S.F. 10 7090 S.F. 11 7082 S.F. 127041 S.F. 6 7067 S.F. 14 7052 S.F. 16 4242 S.F. TRACT C 4599 S.F. TRACT B 6825 S.F. 23 6950 S.F. 30 5250 S.F. 28 6300 S.F. 29 6300 S.F. 27 6419 S.F. 19 8385 S.F. 17 6530 S.F. 18 4922 S.F. TRACT D 6607 S.F. 22 9298 S.F. 32 9327 S.F. 31 7943 S.F. 26 7272 S.F. 25 8767 S.F. 21 11213 S.F. 20 6708 S.F. 36 22388 S.F. TRACT E 7120 S.F. 7 6284 S.F. 5 6276 S.F. 2 5917 S.F. 1 79915 S.F. ROW 7149 S.F. 39 6585 S.F. 38 6378 S.F. 37 s s s s s s s s s s s s ss ss s s s s s s s s s ss ss s s ss s ssss s 420 414 416 418 420 418 422 39 0 40 0 41 0 38 4 38 6 38 8 39 2 39 4 39 6 39 8 40 2 40 4 40 6 40 8 41 2 41 4 41 6 40 4 40 6 39 6 39 8 390 382 382 384 384 386388 39 2 394 39 4 360 3 7 0 38 0 380 38 0 3 6 2 364 3 7 2 3 7 4 3 7 6 3 7 8 3 7 8 37 8 3 7 0 3 7 0 38 0 380 39 0 382 38 4 38 6 38 8 392 36 0 3 7 0 358 36 2 36 4 36 6 36 8 3 7 2 35 4 418 410 408 400402404 CB 16 CB 15 CB 14 CB 13 CB 18 CB 17 CB 11 CB 12 CB 10 CB 9 CB 8 CB 6 CB 7 CB 5 CB 1 CB 4CB 3 CB 2 37 LF 8" CPEP @ 0.50% 62 LF 8" CPEP @ 8.68% 71 LF 8" CPEP @ 0.50% 185 LF 8" CPEP @ 1.98% 204 LF 8" CPEP @ 4.89%164 LF 8" CPEP @ 4.89% 115 LF 8" CPEP @ 4.86% 48 LF 8" CPEP @ 4.37% 147 LF 8" CPEP @ 1.97% 62 LF 8" CPEP @ 0.80% 37 LF 8" CPEP @ 0.50% 160 LF 8" CPEP @ 0.50% 37 LF 8" CPEP @ 1.00%37 LF 8" CPEP @ 0.50% 37 LF 8" CPEP @ 0.50% 37 LF 8" CPEP @ 0.59% 34 LF 8" CPEP @ 5.64% 83 LF 12" CPEP @ 21.16% S R 5 0 7 P A L I S A D E S S T S E P A L I S A D E S S T S E P A L I S A D E S W E S T P A L I S A D E S W E S T 10 LF 12" CPEP @ 0.98% 26 LF 12" CPEP @ 8.84% OUTLET TO INFILTRATION POND 2 INLET TO WQ 2 OUTLET FROM WQ 2 CONNECT TO STCB #501 2215 North 30th Street, Suite 300, Tacoma, WA 98403 253.383.2422 TEL 253.383.2572 FAX JOB NO. DATE: THE RESERVE AT PALISADES DEVELOPED CONDITIONS A-3 2220348.10 8/27/2024 N GRAPHIC SCALE 0 40 80 1" = 40 FEET 20 INFILTRATION POND BOTTOM DIM. 191 FT x 53 FT DEPTH 5FT Soil Map—Thurston County Area, Washington Natural Resources Conservation Service Web Soil Survey National Cooperative Soil Survey 7/31/2024 Page 1 of 3 51 9 7 5 2 0 51 9 7 5 7 0 51 9 7 6 2 0 51 9 7 6 7 0 51 9 7 7 2 0 51 9 7 7 7 0 51 9 7 8 2 0 51 9 7 8 7 0 51 9 7 9 2 0 51 9 7 9 7 0 51 9 7 5 2 0 51 9 7 5 7 0 51 9 7 6 2 0 51 9 7 6 7 0 51 9 7 7 2 0 51 9 7 7 7 0 51 9 7 8 2 0 51 9 7 8 7 0 51 9 7 9 2 0 51 9 7 9 7 0 528670 528720 528770 528820 528870 528920 528970 528670 528720 528770 528820 528870 528920 528970 46° 56' 4'' N 12 2 ° 3 7 ' 2 5 ' ' W 46° 56' 4'' N 12 2 ° 3 7 ' 8 ' ' W 46° 55' 49'' N 12 2 ° 3 7 ' 2 5 ' ' W 46° 55' 49'' N 12 2 ° 3 7 ' 8 ' ' W N Map projection: Web Mercator Corner coordinates: WGS84 Edge tics: UTM Zone 10N WGS84 0 100 200 400 600 Feet 0 30 60 120 180 Meters Map Scale: 1:2,250 if printed on A portrait (8.5" x 11") sheet. Soil Map may not be valid at this scale. MAP LEGEND MAP INFORMATION Area of Interest (AOI) Area of Interest (AOI) Soils Soil Map Unit Polygons Soil Map Unit Lines Soil Map Unit Points Special Point Features Blowout Borrow Pit Clay Spot Closed Depression Gravel Pit Gravelly Spot Landfill Lava Flow Marsh or swamp Mine or Quarry Miscellaneous Water Perennial Water Rock Outcrop Saline Spot Sandy Spot Severely Eroded Spot Sinkhole Slide or Slip Sodic Spot Spoil Area Stony Spot Very Stony Spot Wet Spot Other Special Line Features Water Features Streams and Canals Transportation Rails Interstate Highways US Routes Major Roads Local Roads Background Aerial Photography The soil surveys that comprise your AOI were mapped at 1:24,000. Warning: Soil Map may not be valid at this scale. Enlargement of maps beyond the scale of mapping can cause misunderstanding of the detail of mapping and accuracy of soil line placement. The maps do not show the small areas of contrasting soils that could have been shown at a more detailed scale. Please rely on the bar scale on each map sheet for map measurements. Source of Map: Natural Resources Conservation Service Web Soil Survey URL: Coordinate System: Web Mercator (EPSG:3857) Maps from the Web Soil Survey are based on the Web Mercator projection, which preserves direction and shape but distorts distance and area. A projection that preserves area, such as the Albers equal-area conic projection, should be used if more accurate calculations of distance or area are required. This product is generated from the USDA-NRCS certified data as of the version date(s) listed below. Soil Survey Area: Thurston County Area, Washington Survey Area Data: Version 17, Aug 29, 2023 Soil map units are labeled (as space allows) for map scales 1:50,000 or larger. Date(s) aerial images were photographed: May 26, 2023—Aug 14, 2023 The orthophoto or other base map on which the soil lines were compiled and digitized probably differs from the background imagery displayed on these maps. As a result, some minor shifting of map unit boundaries may be evident. Soil Map—Thurston County Area, Washington Natural Resources Conservation Service Web Soil Survey National Cooperative Soil Survey 7/31/2024 Page 2 of 3 Map Unit Legend Map Unit Symbol Map Unit Name Acres in AOI Percent of AOI 2 Alderwood gravelly sandy loam, 8 to 15 percent slopes 10.0 94.7% 32 Everett very gravelly sandy loam, 0 to 8 percent slopes 0.6 5.3% Totals for Area of Interest 10.6 100.0% Soil Map—Thurston County Area, Washington Natural Resources Conservation Service Web Soil Survey National Cooperative Soil Survey 7/31/2024 Page 3 of 3 National Flood Hazard Layer FIRMette 0 500 1,000 1,500 2,000250 Feet Ü SEE FIS REPORT FOR DETAILED LEGEND AND INDEX MAP FOR FIRM PANEL LAYOUT SPECIAL FLOOD HAZARD AREAS Without Base Flood Elevation (BFE) Zone A, V, A99 With BFE or DepthZone AE, AO, AH, VE, AR Regulatory Floodway 0.2% Annual Chance Flood Hazard, Areas of 1% annual chance flood with average depth less than one foot or with drainage areas of less than one square mileZone X Future Conditions 1% Annual Chance Flood HazardZone X Area with Reduced Flood Risk due to Levee. See Notes.Zone X Area with Flood Risk due to LeveeZone D NO SCREEN Area of Minimal Flood Hazard Zone X Area of Undetermined Flood HazardZone D Channel, Culvert, or Storm Sewer Levee, Dike, or Floodwall Cross Sections with 1% Annual Chance 17.5 Water Surface Elevation Coastal Transect Coastal Transect Baseline Profile Baseline Hydrographic Feature Base Flood Elevation Line (BFE) Effective LOMRs Limit of Study Jurisdiction Boundary Digital Data Available No Digital Data Available Unmapped This map complies with FEMA's standards for the use of digital flood maps if it is not void as described below. The basemap shown complies with FEMA's basemap accuracy standards The flood hazard information is derived directly from the authoritative NFHL web services provided by FEMA. This map was exported on 7/31/2024 at 11:57 AM and does not reflect changes or amendments subsequent to this date and time. The NFHL and effective information may change or become superseded by new data over time. This map image is void if the one or more of the following map elements do not appear: basemap imagery, flood zone labels, legend, scale bar, map creation date, community identifiers, FIRM panel number, and FIRM effective date. Map images for unmapped and unmodernized areas cannot be used for regulatory purposes. Legend OTHER AREAS OF FLOOD HAZARD OTHER AREAS GENERAL STRUCTURES OTHER FEATURES MAP PANELS 8 B 20.2 The pin displayed on the map is an approximate point selected by the user and does not represent an authoritative property location. 1:6,000 122°37'36"W 46°56'8"N 122°36'59"W 46°55'43"N Basemap Imagery Source: USGS National Map 2023 Preliminary Stormwater Report Reserve at Palisades 2220348.10 Appendix B Facility Sizing B-1 .................... Basin Map B-2 .................... WWHM Report C A R T E R L O O P S E S R 5 0 7 PALIS A D E S S T S E PA L I S A D E S S T S E s s s s s s s s s s s s ss ss s s s s s s s s s ss ss s s ss s ssss s 420 414 416 418 420 418 422 39 0 40 0 41 0 39 2 3 9 4 39 6 39 8 40 2 40 4 40 6 40 8 41 2 41 4 41 6 414 41 4 416 416 4 0 2 40 4 40 6 39 4 392 41 2 420420 4 1 841 8 414 410 406 408 40 4 406 408 400 396 398 402404 400 40 0 40 0 40240 2 40 2 3 9 2 39 4 380 39 0 37 8 382 38438 6 38 8 360 36 0 3 7 0 362 36 2 364 36 4 366 36 6 3 6 8 3 7 0 380 3 8 0 3 7 2 3 7 4 3 7 6 3 7 8 3 7 8 37 8 3 9 0 3 8 8 360 358358358358 P A L I S A D E S W E S T P A L I S A D E S W E S T THE RESERVE AT PALISADES ROAD 1.48 AC SIDEWALK 0.15 AC 39 LOT DRIVEWAYS (600 SF EA) = 0.54 AC 39 HOMES NO INFILTRATION(2,700 SF EA) =2.47 AC PERVIOUS 4.47 AC TOTAL 9.11 AC PALISADES WEST ROAD 1.39 AC SIDEWALK 0.43 AC DRIVEWAYS 0.45 AC PERVIOUS 4.79AC TOTAL 7.05 AC STATE ROUTE 507 ROAD 0.17 AC PERVIOUS 0.18 AV TOTAL 0.35 AC TOTAL CONTRIBUTING AREA 16.51 AC 2215 North 30th Street, Suite 300, Tacoma, WA 98403 253.383.2422 TEL 253.383.2572 FAX JOB NO. DATE: THE RESERVE AT PALISADES BASIN MAP B-1 2220348.10 8/27/2024 N GRAPHIC SCALE 0 50 100 1" = 50 FEET 25 STATE ROUTE 705 THE RESERVE AT PALISADES PALISADES WEST INFILTRATION POND WATER QUALITY FILTER VAULT FOR RESERVE AT PALISADES WQ#1 WATER QUALITY FILTER VAULT FOR PALISADES WEST WQ#2 WWHM2012 PROJECT REPORT Mattocks(9_11fx)-20iph4ftInfPndwPali-2220348 8/6/2024 11:37:06 AM Page 2 General Model Information Project Name:Mattocks(9_11fx)-20iph4ftInfPndwPali-2220348 Site Name: Site Address: City: Report Date:8/6/2024 Gage:Lake Lawrence Data Start:1955/10/01 Data End:2008/09/30 Timestep:15 Minute Precip Scale:0.000 (adjusted) Version Date:2021/08/18 Version:4.2.18 POC Thresholds Low Flow Threshold for POC1:50 Percent of the 2 Year High Flow Threshold for POC1:50 Year Low Flow Threshold for POC2:50 Percent of the 2 Year High Flow Threshold for POC2:50 Year Mattocks(9_11fx)-20iph4ftInfPndwPali-2220348 8/6/2024 11:37:06 AM Page 3 Landuse Basin Data Predeveloped Land Use Mattocks Bypass:No GroundWater:No Pervious Land Use acre C, Forest, Flat 3 C, Forest, Mod 5.11 C, Forest, Steep 1 Pervious Total 9.11 Impervious Land Use acre Impervious Total 0 Basin Total 9.11 Element Flows To: Surface Interflow Groundwater Mattocks(9_11fx)-20iph4ftInfPndwPali-2220348 8/6/2024 11:37:06 AM Page 4 Palisades Bypass:No GroundWater:No Pervious Land Use acre C, Forest, Flat 2.5 C, Forest, Mod 4.051 C, Forest, Steep 0.5 Pervious Total 7.051 Impervious Land Use acre Impervious Total 0 Basin Total 7.051 Element Flows To: Surface Interflow Groundwater Mattocks(9_11fx)-20iph4ftInfPndwPali-2220348 8/6/2024 11:37:06 AM Page 5 Mitigated Land Use Mattockss Bypass:No GroundWater:No Pervious Land Use acre C, Lawn, Flat 4.489 Pervious Total 4.489 Impervious Land Use acre ROADS FLAT 1.515 ROOF TOPS FLAT 2.417 DRIVEWAYS FLAT 0.537 SIDEWALKS FLAT 0.152 Impervious Total 4.621 Basin Total 9.11 Element Flows To: Surface Interflow Groundwater Trapezoidal Pond 1 Trapezoidal Pond 1 Mattocks(9_11fx)-20iph4ftInfPndwPali-2220348 8/6/2024 11:37:06 AM Page 6 Palisades Bypass:No GroundWater:No Pervious Land Use acre C, Lawn, Flat 4.79 Pervious Total 4.79 Impervious Land Use acre ROADS FLAT 1.387 DRIVEWAYS FLAT 0.448 SIDEWALKS FLAT 0.426 Impervious Total 2.261 Basin Total 7.051 Element Flows To: Surface Interflow Groundwater Trapezoidal Pond 1 Trapezoidal Pond 1 Mattocks(9_11fx)-20iph4ftInfPndwPali-2220348 8/6/2024 11:37:06 AM Page 7 SR 507 Bypass:No GroundWater:No Pervious Land Use acre C, Lawn, Flat 0.18 Pervious Total 0.18 Impervious Land Use acre ROADS FLAT 0.17 Impervious Total 0.17 Basin Total 0.35 Element Flows To: Surface Interflow Groundwater Trapezoidal Pond 1 Trapezoidal Pond 1 Mattocks(9_11fx)-20iph4ftInfPndwPali-2220348 8/6/2024 11:37:06 AM Page 8 Routing Elements Predeveloped Routing Mattocks(9_11fx)-20iph4ftInfPndwPali-2220348 8/6/2024 11:37:06 AM Page 9 Mitigated Routing Trapezoidal Pond 1 Bottom Length:191.04 ft. Bottom Width:53.07 ft. Depth:5 ft. Volume at riser head:1.2387 acre-feet. Infiltration On Infiltration rate:20 Infiltration safety factor:1 Total Volume Infiltrated (ac-ft.):2691.794 Total Volume Through Riser (ac-ft.):0.05 Total Volume Through Facility (ac-ft.):2691.844 Percent Infiltrated:100 Total Precip Applied to Facility:0 Total Evap From Facility:0 Side slope 1:3 To 1 Side slope 2:3 To 1 Side slope 3:3 To 1 Side slope 4:3 To 1 Discharge Structure Riser Height:4 ft. Riser Diameter:12 in. Element Flows To: Outlet 1 Outlet 2 Pond Hydraulic Table Stage(feet)Area(ac.)Volume(ac-ft.)Discharge(cfs)Infilt(cfs) 0.0000 0.232 0.000 0.000 0.000 0.0556 0.234 0.013 0.000 4.693 0.1111 0.236 0.026 0.000 4.693 0.1667 0.238 0.039 0.000 4.693 0.2222 0.240 0.052 0.000 4.693 0.2778 0.242 0.065 0.000 4.693 0.3333 0.244 0.079 0.000 4.693 0.3889 0.245 0.093 0.000 4.693 0.4444 0.247 0.106 0.000 4.693 0.5000 0.249 0.120 0.000 4.693 0.5556 0.251 0.134 0.000 4.693 0.6111 0.253 0.148 0.000 4.693 0.6667 0.255 0.162 0.000 4.693 0.7222 0.257 0.176 0.000 4.693 0.7778 0.259 0.191 0.000 4.693 0.8333 0.261 0.205 0.000 4.693 0.8889 0.263 0.220 0.000 4.693 0.9444 0.265 0.235 0.000 4.693 1.0000 0.267 0.249 0.000 4.693 1.0556 0.269 0.264 0.000 4.693 1.1111 0.271 0.279 0.000 4.693 1.1667 0.273 0.294 0.000 4.693 1.2222 0.275 0.310 0.000 4.693 1.2778 0.277 0.325 0.000 4.693 1.3333 0.279 0.340 0.000 4.693 1.3889 0.281 0.356 0.000 4.693 1.4444 0.283 0.372 0.000 4.693 Mattocks(9_11fx)-20iph4ftInfPndwPali-2220348 8/6/2024 11:37:06 AM Page 10 1.5000 0.285 0.387 0.000 4.693 1.5556 0.287 0.403 0.000 4.693 1.6111 0.289 0.419 0.000 4.693 1.6667 0.291 0.435 0.000 4.693 1.7222 0.293 0.452 0.000 4.693 1.7778 0.295 0.468 0.000 4.693 1.8333 0.297 0.484 0.000 4.693 1.8889 0.299 0.501 0.000 4.693 1.9444 0.301 0.518 0.000 4.693 2.0000 0.303 0.534 0.000 4.693 2.0556 0.305 0.551 0.000 4.693 2.1111 0.307 0.568 0.000 4.693 2.1667 0.309 0.586 0.000 4.693 2.2222 0.311 0.603 0.000 4.693 2.2778 0.313 0.620 0.000 4.693 2.3333 0.315 0.638 0.000 4.693 2.3889 0.317 0.655 0.000 4.693 2.4444 0.319 0.673 0.000 4.693 2.5000 0.321 0.691 0.000 4.693 2.5556 0.324 0.709 0.000 4.693 2.6111 0.326 0.727 0.000 4.693 2.6667 0.328 0.745 0.000 4.693 2.7222 0.330 0.763 0.000 4.693 2.7778 0.332 0.782 0.000 4.693 2.8333 0.334 0.800 0.000 4.693 2.8889 0.336 0.819 0.000 4.693 2.9444 0.338 0.838 0.000 4.693 3.0000 0.341 0.856 0.000 4.693 3.0556 0.343 0.875 0.000 4.693 3.1111 0.345 0.895 0.000 4.693 3.1667 0.347 0.914 0.000 4.693 3.2222 0.349 0.933 0.000 4.693 3.2778 0.351 0.953 0.000 4.693 3.3333 0.354 0.972 0.000 4.693 3.3889 0.356 0.992 0.000 4.693 3.4444 0.358 1.012 0.000 4.693 3.5000 0.360 1.032 0.000 4.693 3.5556 0.362 1.052 0.000 4.693 3.6111 0.364 1.072 0.000 4.693 3.6667 0.367 1.092 0.000 4.693 3.7222 0.369 1.113 0.000 4.693 3.7778 0.371 1.134 0.000 4.693 3.8333 0.373 1.154 0.000 4.693 3.8889 0.376 1.175 0.000 4.693 3.9444 0.378 1.196 0.000 4.693 4.0000 0.380 1.217 0.000 4.693 4.0556 0.382 1.238 0.138 4.693 4.1111 0.384 1.260 0.389 4.693 4.1667 0.387 1.281 0.703 4.693 4.2222 0.389 1.303 1.046 4.693 4.2778 0.391 1.324 1.383 4.693 4.3333 0.393 1.346 1.683 4.693 4.3889 0.396 1.368 1.921 4.693 4.4444 0.398 1.390 2.088 4.693 4.5000 0.400 1.412 2.203 4.693 4.5556 0.403 1.435 2.347 4.693 4.6111 0.405 1.457 2.462 4.693 4.6667 0.407 1.480 2.571 4.693 Mattocks(9_11fx)-20iph4ftInfPndwPali-2220348 8/6/2024 11:37:06 AM Page 11 4.7222 0.409 1.502 2.676 4.693 4.7778 0.412 1.525 2.777 4.693 4.8333 0.414 1.548 2.875 4.693 4.8889 0.416 1.571 2.969 4.693 4.9444 0.419 1.595 3.060 4.693 5.0000 0.421 1.618 3.149 4.693 5.0556 0.423 1.641 3.235 4.693 Mattocks(9_11fx)-20iph4ftInfPndwPali-2220348 8/6/2024 11:37:06 AM Page 12 Analysis Results POC 1 + Predeveloped x Mitigated Predeveloped Landuse Totals for POC #1 Total Pervious Area:16.161 Total Impervious Area:0 Mitigated Landuse Totals for POC #1 Total Pervious Area:9.459 Total Impervious Area:7.052 Flow Frequency Method:Log Pearson Type III 17B Flow Frequency Return Periods for Predeveloped. POC #1 Return Period Flow(cfs) 2 year 1.07459 5 year 2.037329 10 year 2.96857 25 year 4.583619 50 year 6.181825 100 year 8.193076 Flow Frequency Return Periods for Mitigated. POC #1 Return Period Flow(cfs) 2 year 0 5 year 0 10 year 0 25 year 0 50 year 0 100 year 0 Annual Peaks Annual Peaks for Predeveloped and Mitigated. POC #1 Year Predeveloped Mitigated 1956 1.062 0.000 1957 3.770 0.000 1958 0.879 0.000 1959 0.897 0.000 1960 1.802 0.000 1961 0.849 0.000 1962 0.326 0.000 1963 1.735 0.000 1964 0.870 0.000 1965 1.080 0.000 Mattocks(9_11fx)-20iph4ftInfPndwPali-2220348 8/6/2024 11:37:39 AM Page 13 1966 0.608 0.000 1967 0.980 0.000 1968 0.702 0.000 1969 0.464 0.000 1970 0.802 0.000 1971 0.987 0.000 1972 1.583 0.000 1973 0.850 0.000 1974 4.812 0.000 1975 0.981 0.000 1976 1.119 0.000 1977 0.572 0.000 1978 1.097 0.000 1979 0.777 0.000 1980 0.864 0.000 1981 1.788 0.000 1982 0.731 0.000 1983 1.371 0.000 1984 0.911 0.000 1985 0.538 0.000 1986 1.786 0.000 1987 1.302 0.000 1988 0.647 0.000 1989 0.675 0.000 1990 6.859 0.000 1991 2.418 0.000 1992 1.088 0.000 1993 0.407 0.000 1994 0.943 0.000 1995 1.166 0.000 1996 1.485 0.000 1997 1.252 0.000 1998 2.109 0.000 1999 0.738 0.000 2000 0.693 0.000 2001 0.323 0.000 2002 1.300 0.000 2003 0.562 0.000 2004 6.268 0.000 2005 8.598 0.000 2006 2.429 0.000 2007 1.376 0.000 2008 2.662 0.435 Ranked Annual Peaks Ranked Annual Peaks for Predeveloped and Mitigated. POC #1 Rank Predeveloped Mitigated 1 8.5984 0.4349 2 6.8595 0.0000 3 6.2677 0.0000 4 4.8119 0.0000 5 3.7697 0.0000 6 2.6618 0.0000 7 2.4291 0.0000 8 2.4178 0.0000 9 2.1091 0.0000 10 1.8017 0.0000 11 1.7878 0.0000 Mattocks(9_11fx)-20iph4ftInfPndwPali-2220348 8/6/2024 11:37:39 AM Page 14 12 1.7862 0.0000 13 1.7346 0.0000 14 1.5829 0.0000 15 1.4847 0.0000 16 1.3758 0.0000 17 1.3708 0.0000 18 1.3017 0.0000 19 1.2997 0.0000 20 1.2521 0.0000 21 1.1657 0.0000 22 1.1190 0.0000 23 1.0975 0.0000 24 1.0883 0.0000 25 1.0796 0.0000 26 1.0622 0.0000 27 0.9875 0.0000 28 0.9813 0.0000 29 0.9805 0.0000 30 0.9426 0.0000 31 0.9113 0.0000 32 0.8974 0.0000 33 0.8786 0.0000 34 0.8698 0.0000 35 0.8638 0.0000 36 0.8495 0.0000 37 0.8490 0.0000 38 0.8017 0.0000 39 0.7773 0.0000 40 0.7383 0.0000 41 0.7310 0.0000 42 0.7023 0.0000 43 0.6929 0.0000 44 0.6745 0.0000 45 0.6468 0.0000 46 0.6079 0.0000 47 0.5724 0.0000 48 0.5622 0.0000 49 0.5384 0.0000 50 0.4638 0.0000 51 0.4066 0.0000 52 0.3260 0.0000 53 0.3229 0.0000 Mattocks(9_11fx)-20iph4ftInfPndwPali-2220348 8/6/2024 11:37:39 AM Page 15 Duration Flows The Facility PASSED Flow(cfs)Predev Mit Percentage Pass/Fail 0.5373 11138 0 0 Pass 0.5943 8449 0 0 Pass 0.6513 6506 0 0 Pass 0.7083 4927 0 0 Pass 0.7654 3838 0 0 Pass 0.8224 3024 0 0 Pass 0.8794 2397 0 0 Pass 0.9364 1911 0 0 Pass 0.9934 1526 0 0 Pass 1.0504 1240 0 0 Pass 1.1074 984 0 0 Pass 1.1645 766 0 0 Pass 1.2215 590 0 0 Pass 1.2785 452 0 0 Pass 1.3355 332 0 0 Pass 1.3925 290 0 0 Pass 1.4495 232 0 0 Pass 1.5066 194 0 0 Pass 1.5636 180 0 0 Pass 1.6206 165 0 0 Pass 1.6776 154 0 0 Pass 1.7346 135 0 0 Pass 1.7916 119 0 0 Pass 1.8487 105 0 0 Pass 1.9057 91 0 0 Pass 1.9627 80 0 0 Pass 2.0197 75 0 0 Pass 2.0767 70 0 0 Pass 2.1337 60 0 0 Pass 2.1907 54 0 0 Pass 2.2478 45 0 0 Pass 2.3048 38 0 0 Pass 2.3618 30 0 0 Pass 2.4188 21 0 0 Pass 2.4758 16 0 0 Pass 2.5328 13 0 0 Pass 2.5899 10 0 0 Pass 2.6469 9 0 0 Pass 2.7039 7 0 0 Pass 2.7609 7 0 0 Pass 2.8179 7 0 0 Pass 2.8749 7 0 0 Pass 2.9319 7 0 0 Pass 2.9890 6 0 0 Pass 3.0460 6 0 0 Pass 3.1030 6 0 0 Pass 3.1600 6 0 0 Pass 3.2170 6 0 0 Pass 3.2740 6 0 0 Pass 3.3311 6 0 0 Pass 3.3881 6 0 0 Pass 3.4451 5 0 0 Pass 3.5021 5 0 0 Pass Mattocks(9_11fx)-20iph4ftInfPndwPali-2220348 8/6/2024 11:37:39 AM Page 16 3.5591 5 0 0 Pass 3.6161 5 0 0 Pass 3.6731 5 0 0 Pass 3.7302 5 0 0 Pass 3.7872 4 0 0 Pass 3.8442 4 0 0 Pass 3.9012 4 0 0 Pass 3.9582 4 0 0 Pass 4.0152 4 0 0 Pass 4.0723 4 0 0 Pass 4.1293 4 0 0 Pass 4.1863 4 0 0 Pass 4.2433 4 0 0 Pass 4.3003 4 0 0 Pass 4.3573 4 0 0 Pass 4.4143 4 0 0 Pass 4.4714 4 0 0 Pass 4.5284 4 0 0 Pass 4.5854 4 0 0 Pass 4.6424 4 0 0 Pass 4.6994 4 0 0 Pass 4.7564 4 0 0 Pass 4.8135 3 0 0 Pass 4.8705 3 0 0 Pass 4.9275 3 0 0 Pass 4.9845 3 0 0 Pass 5.0415 3 0 0 Pass 5.0985 3 0 0 Pass 5.1555 3 0 0 Pass 5.2126 3 0 0 Pass 5.2696 3 0 0 Pass 5.3266 3 0 0 Pass 5.3836 3 0 0 Pass 5.4406 3 0 0 Pass 5.4976 3 0 0 Pass 5.5547 3 0 0 Pass 5.6117 3 0 0 Pass 5.6687 3 0 0 Pass 5.7257 3 0 0 Pass 5.7827 3 0 0 Pass 5.8397 3 0 0 Pass 5.8967 3 0 0 Pass 5.9538 3 0 0 Pass 6.0108 3 0 0 Pass 6.0678 3 0 0 Pass 6.1248 3 0 0 Pass 6.1818 3 0 0 Pass Mattocks(9_11fx)-20iph4ftInfPndwPali-2220348 8/6/2024 11:37:39 AM Page 17 Water Quality Water Quality BMP Flow and Volume for POC #1 On-line facility volume:1.7287 acre-feet On-line facility target flow:1.5145 cfs. Adjusted for 15 min:1.5145 cfs. Off-line facility target flow:0.8327 cfs. Adjusted for 15 min:0.8327 cfs. FULL SITE RESERVE AT PALISADES WQ #1 PALISADES WQ REPLACEMENT WQ #2 0.544 cfs offline Treat with Basic WQ: 0.025 cfs/ 27" SF cartridge 22 Stormfilter 27" cartridges; or, 0.05 cfs/ BF 515 cartridge 11 Bayfilter 515 cartridges; or, 0.1 cfs/BF 545 cartridges 6 Bayfilter 545 cartridges 0.2954 cfs offline Treat with Basic WQ: 0.025 cfs/ 27" SF cartridge 12 Stormfilter 27" cartridges; or, 0.05 cfs/ BF 515 cartridge 6 Bayfilter 515 cartridges; or, 0.1 cfs/BF 545 cartridges 3 Bayfilter 545 cartridges Mattocks(9_11fx)-20iph4ftInfPndwPali-2220348 8/6/2024 11:37:39 AM Page 18 LID Report Mattocks(9_11fx)-20iph4ftInfPndwPali-2220348 8/6/2024 11:37:54 AM Page 19 POC 2 POC #2 was not reported because POC must exist in both scenarios and both scenarios must have been run. Mattocks(9_11fx)-20iph4ftInfPndwPali-2220348 8/6/2024 11:37:54 AM Page 20 Model Default Modifications Total of 0 changes have been made. PERLND Changes No PERLND changes have been made. IMPLND Changes No IMPLND changes have been made. Mattocks(9_11fx)-20iph4ftInfPndwPali-2220348 8/6/2024 11:37:54 AM Page 21 Appendix Predeveloped Schematic Mattocks(9_11fx)-20iph4ftInfPndwPali-2220348 8/30/2024 9:40:27 AM Page 24 Mitigated Schematic Mattocks(9_11fx)-20iph4ftInfPndwPali-2220348 8/6/2024 11:37:57 AM Page 33 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. 2005-2024; 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 Preliminary Stormwater Report Reserve at Palisades 2220348.10 Appendix C Geotechnical Reports Geotechnical Report GeoResources, LLC April 4, 2024 August 22, 2024 Garrette Custom Homes 11815 NE 99th St #1200 Vancouver, Washington 98682 Attn: Kimberly Johnson KimberlyJ@BuildGCH.com Soils Report Proposed Residential Plat xxx – Palisades Street SE Yelm, Washington PN: 21725130200 Doc ID: GCH.MattocksPlat.SR INTRODUCTION This Soils Report presents the results of our literature review, subsurface explorations, laboratory testing, and provides geotechnical conclusions and recommendations regarding the feasibility of onsite stormwater infiltration for the proposed residential plat to be constructed at the above referenced parcel in the City of Yelm, Washington. The general location of the site is shown on the attached Site Location Map, Figure 1. Our understanding of the project is based on our conversations with you; our review of the Preliminary Site Plan prepared by AHBL on November 14, 2023; our January 9 and February 7, 2024 site visits and subsurface explorations; our understanding of the City of Yelm (the City) development codes; and our experience in the site area. The site is currently undeveloped. You propose to construct a 39-lot residential plat with a paved shared access roadway and associated utilities. We anticipate that the proposed residences will be one- to two-story, wood-framed structures supported by conventional shallow foundations. A copy of the Preliminary Site Plan is included in the attached Site & Exploration Plan, Figure 2. Because of the amount of proposed hard surfacing associated with the development, the City will require a Soils Report be prepared in accordance with the adopted 2019 Stormwater Management Manual for Western Washington (SWMMWW). PURPOSE & SCOPE The purpose of our scope services was to evaluate the surface and subsurface conditions across the site as a basis for providing stormwater infiltration recommendations and design criteria for the proposed residential plat. Specifically, the scope of services for this project included the following: 1. Reviewing the available geologic, hydrogeologic, and geotechnical data for the site area; 2. Exploring surface and subsurface conditions across the site by excavating 19 test pits and 1 hand auger at select locations and installing shallow (less than 10 feet) groundwater monitoring standpipes in 3 of the test pits; GCH.MattocksPlat.SR_July2024 August 22, 2024 page | 2 3. While onsite, performing one small-scale Pilot Infiltration Test (PIT) in accordance with the 2019 SWMMWW in a location specified by the civil engineer; 4. Describing surface and subsurface conditions, including soil type, depth to groundwater, and an estimate of seasonal high groundwater levels based on wet season groundwater monitoring; 5. Providing our opinion about the feasibility of onsite infiltration in accordance with the 2019 SWMMWW, including a preliminary design infiltration rate based on infiltration testing, as applicable; and, 6. Preparing this written Soils Report summarizing our site observations and conclusions, and our recommendations and design criteria, along with the supporting data. The above scope of work was summarized in our Proposal for Geotechnical Engineering Services dated December 21, 2023. We received your emailed authorization to proceed on December 26, 2023. SITE CONDITIONS Surface Conditions The site consists of a single unaddressed tax parcel located in the City of Yelm, Washington. The site is generally rectangular in shape, measures about 400 feet wide (east to west) by about 890 to 1,185 feet long (north to south), and encompasses approximately 9.71 acres. The site is bounded by State Route 507 to the north and existing single-family residential development to the east, south, and west. Access to the site is gained from Palisades Street Southeast in the southeast portion of the site. The site is located on the northern margins of the Yelm glacial upland area. Our site description is based on 2-foot elevation contours shown on the Thurston County online Show Me Everything map and our site observations. A storm pond for the residential plat east of the site occupies the northern corner of the site. South of the storm pond and SR 507, the ground surface slopes up to the south at about 18 to 20 percent. The central portion of the site slopes up to the southeast at 5 to 10 percent, and then levels in the southern portion to about 2 percent. Total topographic relief across the site is on the order of 62 feet. Existing site conditions and topography are shown on the attached Site & Exploration Plan, Figure 2 and Site Vicinity Map, Figure 3. Vegetation consists of Douglas fir trees scattered across the site with a dense understory of grasses, Scotch broom, Himalayan blackberries, and other low growing shrubs. No standing water or groundwater springs were observed at the ground surface at the time of our site visit. We did observe some water ponded in the stormwater pond, as it was raining during our January 9, 2024 site visit. We did not observe signs of slope instability or soil erosion at the time of our site visit. Site Soils The USDA Natural Resource Conservation Service (NRCS) Web Soil Survey maps the surficial soils at the site as Alderwood gravelly sandy loam (2) and Everett very gravelly sandy loam (32). Detailed descriptions of these soils are included below, and an excerpt of the referenced NRCS map for the site and adjacent areas is attached as Figure 4. • Alderwood gravelly sandy loam (2): Mapped throughout the majority of the site, these soils are derived from glacial drift and/or glacial outwash over dense glaciomarine deposits and are GCH.MattocksPlat.SR_July2024 August 22, 2024 page | 3 included in hydrologic soil group B. Type 2 soils form on slopes of 8 to 15 percent and are listed as a “slight” erosion hazard when exposed. • Everett very gravelly sandy loam (32): Mapped in the northeastern corner of the site, these soils are derived from sandy and gravelly glacial outwash and are included in hydrologic soil group A. Type 32 soils form on slopes of 0 to 8 percent and are listed as a “slight” erosion hazard when exposed. Site Geology Based on our review of the Geologic Map of the Centralia Quadrangle, Washington (Schasse, 1987), the site is located in an area mapped as being underlain by Vashon till (Qdvt) and Vashon outwash gravel (Qdvg). No landslides, colluvial/alluvial fans, or other deposits of mass wastage are mapped on or within the site vicinity. Detailed descriptions of the mapped geologic units are included below, and an excerpt of the referenced geologic map is attached as Figure 5. • Vashon outwash gravel (Qdvg): Recessional outwash was deposited during the end stages of the Vashon Stade of the Fraser Glaciation, approximately 12,000 to 15,000 years ago by meltwater streams flowing from the retreating continental ice mass. Recessional outwash typically consists of well graded, lightly stratified to locally cross-bedded mixtures of sand and gravel. This unit is considered normally consolidated, offers moderate strength characteristics when undisturbed, and is loose near the surface and increases in density with depth. The infiltration potential of recessional outwash is generally favorable. • Vashon glacial till (Qdvt): Glacial till typically consists of a heterogeneous mixture of clay, silt, sand, and gravel deposited at the base of the continental ice mass and is subsequently over-ridden. Accordingly, these deposits are considered to be overconsolidated and typically offer high strength and low compressibility characteristics, where undisturbed. Infiltration potential within glacial till is generally limited due to its overconsolidated and fine-grained nature. Subsurface Explorations On January 9, 2024, we visited the site and monitored the excavation of 12 test pits to depths of about 5.0 to 10.0 feet below the existing ground surface. We also performed a small-scale Pilot Infiltration Test (PIT) in test pit TP-1 at a depth of 4 feet below the ground surface. On February 7, 2024 we returned to the site and monitored the excavation of 7 additional test pits to depths of 9.0 to 12.5 feet below the existing ground surface and advanced one hand auger to a depth of approximately 3.5 feet below the existing ground surface in the existing southern stormwater pond. Our field staff logged the subsurface conditions encountered in each exploration and obtained representative soil samples. The indicated test pit locations were determined by taping or pacing from existing site features and reference points; as such, the locations should only be considered as accurate as implied by the measurement method. Elevations for our test pits and in- situ testing were taken by interpolating between contours from the WA DNR Thurston 2021 DTM 53 LiDAR dataset. The soils encountered were visually classified in accordance with the Unified Soil Classification System (USCS) and ASTM D2488. The USCS is included in Appendix A as Figure A-1, while the descriptive logs of our test pits and hand augers are included as Figures A-2 through A-(. Table 1 below GCH.MattocksPlat.SR_July2024 August 22, 2024 page | 4 summarizes the approximate functional locations, surface elevations, and termination depths of the explorations. The specific number, locations, and depths of our explorations were selected based on the configuration of the proposed development and were adjusted in the field based on consideration for underground utilities, existing site conditions, site access limitations and encountered stratigraphy. The subsurface explorations completed as part of this evaluation indicate the subsurface conditions at specific locations only, as actual subsurface conditions can vary across the site. The nature and extent of such variation would not become evident until additional explorations are performed or until construction activities have begun. TABLE 1: APPROXIMATE LOCATIONS, ELEVATIONS, AND DEPTHS OF EXPLORATIONS Test Pit Number Functional Location Surface Elevation1 (feet) Termination Depth (feet) Termination Elevation (feet) TP-1 Storm Tract F 360 10.0 350.0 TP-2 Northeast portion of Access Roadway 384 6.0 378.0 TP-3 Proposed Lot 18 394 8.0 386.0 TP-4 Proposed Lots 25, 26, 30, & 31 409 6.0 403.0 TP-5 Proposed Lot 23 401 6.0 395.0 TP-6 Proposed Lot 38 420 6.0 414.0 TP-7 Proposed Lot 1 360 7.0 353.0 TP-8 Proposed Lot 4 405 7.0 398.0 TP-9 Center south portion of Access Roadway 407 5.0 402.0 TP-10 Proposed Lot 10 404 5.0 399.0 TP-11 Proposed Lot 4 405 6.0 399.0 TP-12 Proposed Lot 14 396 5.0 391.0 TP-101 Storm Tract F 360 12.5 347.5 TP-102 Tract E 368 11.5 356.5 TP-103 Tract E 370 10.5 359.5 TP-104 Proposed Lot 16 376 9.5 366.5 TP-105 Northern proposed road 380 11.5 368.5 TP-106 Proposed Lot 23 396 9.5 386.5 TP-107 Proposed Lot 29 404 9.0 395.0 HA-1 Existing stormwater facility 357 3.5 353.5 Notes: 1 = Surface elevations estimated by interpolating between contours derived from WA DNR Thurston 2020 LiDAR (Datum: NAVD88) Test Pits The test pits were excavated using a small track-mounted excavator operated by a licensed earthwork contractor working for GeoResources. Our field representative logged the subsurface conditions encountered in each test pit and obtained representative soil samples, which were placed in sealed plastic bags and then taken to our laboratory for further examination and testing as deemed GCH.MattocksPlat.SR_July2024 August 22, 2024 page | 5 necessary. The soil densities presented on the logs were based on the difficulty of excavation and our experience. The test pits were backfilled with excavated soil and tamped in place, but not otherwise compacted. Open standpipe piezometers (OSPs) were installed in three of the test pits. The piezometers consisted of 2-inch PVC pipe, with a perforated or slotted section within the lower 3 feet. The Piezometer installations were backfilled with the native soils and affixed with a threaded cap for future measurement of groundwater levels. Pilot Infiltration Test (PIT) We performed one small-scale pilot infiltration test (PIT) in accordance with Volume III, Appendix A of the 2021 Pierce County Stormwater Management and Site Development Manual. The PIT was completed adjacent to the existing stormwater pond in the northern portion of the site. However, the PIT was performed at 4.0 feet below the ground surface in what was later determined to be fill material. The soils at the elevation the test was performed at generally consisted of sandy silt with gravel, likely placed as part of the construction of the pond berm and previous site grading. After the PIT was completed, we over excavated the test pit an additional 6.0 feet to a final depth of 10.0 feet below ground surface and collected representative soil samples. Soil encountered approximately 6 feet below the ground surface to the full depth explored consisted of poorly graded gravel with limited amounts of silt. Subsurface Conditions At the locations of our test pits, we encountered subsurface conditions that, in our opinion, generally confirm the mapped stratigraphy at the site. Our test pits encountered soils that appeared to be consistent with topsoil and undocumented fill soils overlying glacial till. These soil layers are described below. • Topsoil: Our test pits encountered about 0.25 to 1.0 feet of dark brown topsoil. • Undocumented fill: Underlying the topsoil in test pits TP-1, TP-7, TP-101, and TP-106 we observed 2.5 to 5.5 feet of brown-grey sandy silt and medium brown gravelly silty sand in a moist condition. • Vashon glacial till: Underlying the topsoil and fill soils in test pits TP-2 through TP-12, TP-104, TP- 106, and TP-107, we observed a medium dense to very dense, grey-brown to grey sandy silty gravel and gravelly silty sand in a moist to wet condition to the full depth of exploration. We interpret these soils to be weathered and undisturbed glacial till. • Weathered Advance Outwash: Underlying the topsoil in test pits TP-102, TP-103, and TP-105, we encountered brown silty sand with some gravel in a medium dense, moist condition. We interpret these soils to be weathered advance outwash. • Advance Outwash: Underlying the weathered advance outwash and the undocumented fill in TP- 1 and TP-101, we encountered grey poorly graded sand with silt and gravel, and grey poorly graded gravel in a dense to very dense, moist condition. We interpret these soils to be advance outwash. The advance outwash was encountered to the full depth explored where encountered. GCH.MattocksPlat.SR_July2024 August 22, 2024 page | 6 TABLE 2: APPROXIMATE DEPTHS AND EXLEVATIONS OF ENCOUNTERED SOILS TYPES Exploration Number Thickness of (feet) Depth to Undisturbed Till (feet) Depth to Advance Outwash (feet) Elevation1 of Advance Outwash (feet) Topsoil Fill Weathered Soils TP-1 0.5 5.5 NE NE 6.0 354.0 TP-2 0.5 NE 2.0 2.5 NE NE TP-3 0.75 NE 2.75 3.5 NE NE TP-4 0.75 NE 3.25 4.0 NE NE TP-5 0.5 NE 3.5 4.0 NE NE TP-6 0.5 NE 2.5 3.0 NE NE TP-7 0.5 2.5 NE 3.0 NE NE TP-8 0.5 NE 4.5 5.0 NE NE TP-9 0.75 NE 2.25 3.0 NE NE TP-10 0.75 NE 1.25 2.0 NE NE TP-11 0.5 NE 3.5 4.0 NE NE TP-12 0.75 NE 2.25 3.0 NE NE TP-101 0.75 4.25 NE NE 5.0 355.0 TP-102 1.0 NE 3.25 NE 4.25 363.75 TP-103 1.0 NE 2.5 NE 3.5 366.5 TP-104 0.75 NE 2.25 3.0 NE NE TP-105 1.0 NE 2.5 NE 3.5 376.5 TP-106 1.0 2.25 1.75 5.0 NE NE TP-107 0.5 NE 1.5 2.0 NE NE HA-1 0.25 NE NE NE 0.25 356.75 Notes: 1 = Surface elevations estimated by interpolating between contours derived from WA DNR Thurston 2020 LiDAR (Datum: NAVD88) Laboratory Testing Geotechnical laboratory tests were performed on select samples retrieved from the test pits to estimate index engineering properties of the soils encountered. Laboratory testing included visual soil classification per ASTM D2488 and ASTM D2487, moisture content determinations per ASTM D2216 and grain size analyses per ASTM D6913 standard procedures. Test results are summarized below in Table 3 and graphical output results are included in Appendix B. GCH.MattocksPlat.SR_July2024 August 22, 2024 page | 7 TABLE 3: LABORATORY TEST RESULTS FOR ON-SITE SOILS Sample Soil Type Lab ID Gravel Content (percent) Sand Content (percent) Silt/Clay Content (percent) Moisture Content (percent) TP-1, S-2, D: 4ft ML 104657 20.4 28.2 51.4 22.9 TP-5, S-2, D: 3.5ft GP-GM 104658 56.3 32.8 10.9 10.4 TP-9, S-1, D: 2ft GW-GM 104659 64.0 30.9 5.1 6.4 TP-11, S-1, D: 1ft SM 104660 30.5 49.0 20.5 20.8 TP-8, S-1, D: 2ft SM 104663 39.8 44.5 15.7 15.9 TP-101, S-1, D: 8’ GP 104798 83.4 12.6 4.0 3.4 TP-102, S-2, D; 8.5’ SP-SM 104799 28.4 65.0 6.6 7.3 Groundwater Conditions Groundwater seepage was observed in test pit TP-7 at a depth of 1.5 feet below existing grades at the time of excavation during our first explorations in January 2024. When we returned to the site on February 7, 2024 groundwater seepage was observed in test pit TP-101 at approximately 11 feet below ground surface. Based on the elevations of the encountered groundwater seepage, we anticipate this is an inconsistent seasonal perched groundwater table. The groundwater encountered in test pit TP-101 is likely an unconfined regional groundwater table. As such, we estimate that seasonal high groundwater within the advance outwash is near elevation 349 feet. We anticipate fluctuations in the local groundwater levels will occur in response to precipitation patterns, off-site construction activities, and site utilization. As such, water level observations made at the time of our field investigation may vary from those encountered during the construction phase. We performed groundwater monitoring on a bi-weekly basis between January 16, 2024 and April 29, 2024 to monitor water levels in the 3 open-standpipe piezometers (OSP’s) installed during our January 9, 2024 site visit. Throughout the monitoring duration we did not observe groundwater within the OSP’s, which extended about 10, 6, and 7 feet below the ground surface in OSP-1, OSP-2, and OSP-3, respectively. The locations of the OSP’s are shown on Figure 2. CONCLUSIONS AND RECOMMENDATIONS Based on the results of our data review, site reconnaissance, subsurface explorations, engineering analysis, and our experience in the area, it is our opinion that the on-site management of stormwater runoff is feasible within the advance outwash soils. Further details are provided below. Infiltration Recommendations Test Method The 2019 SWMMWW, Volume V, Section V-5.4 provides three approved methods to estimate the design infiltration rate of site soils: 1) Large-Scale Pilot Infiltration Test, 2) Small-Scale Pilot Infiltration Test, and 3) soil grain size analysis method. Restrictions do apply to the various methods GCH.MattocksPlat.SR_July2024 August 22, 2024 page | 8 based on soil conditions and type of infiltration facility. We used the grain size analysis method to develop a preliminary infiltration rate. Preliminary Design Stormwater Infiltration Rate We completed soil gradation analyses on two representative soil samples from the advance outwash soils in the lower, northern portion of the site per the 2019 SWMMWW, Volume V and in accordance with ASTM D6913. Based on our grain size analysis results, we recommend a preliminary design infiltration rate of 20.0 inches per hour be used for design of infiltration facilities within the gravelly advance outwash in the area of TP-1 and TP-101 and 4.2 inches per hour be used for design of infiltration facilities within the sandy advance outwash observed within test pits TP-102, TP-103, and TP-105. This rate includes factors of safety for site variability and number of tests (CFv = 0.5), test method (CFt = 0.4 for grain size analysis), and for potential for siltation and biofouling (CFm = 0.9). Construction Considerations If infiltration facilities are proposed, we recommend that a representative from our firm be onsite at the time of excavation of the proposed stormwater management facilities to verify that the soils encountered during construction are consistent with the soils observed in our subsurface explorations. In-situ infiltration testing shall be performed prior to and at the time of construction to verify the recommended infiltration rate and to determine if a different site-specific infiltration rate would be more appropriate for the site. It should be noted that special care is required during the grading and construction periods to avoid fine sediment contamination. This may be accomplished using an alternative stormwater management location during construction. All contractors, builders, and subcontractors working on the site should be advised to avoid allowing “dirty” stormwater or excess sediment to enter the stormwater facilities during construction and landscaping activities. No concrete trucks should be washed or cleaned in the vicinity of proposed stormwater systems. Suspended solids could clog the underlying soil and reduce the infiltration rate of the facilities. To reduce potential clogging of the infiltration systems, the infiltration system should not be connected to the stormwater runoff system until after construction is complete and the site area is landscaped, paved or otherwise protected. Temporary systems may be utilized throughout construction. Periodic sweeping of the paved areas will help extend the life of the infiltration system. Additional Services The City will likely require in-situ infiltration testing be performed in the area of proposed infiltration facilities. Once the actual size, depth, and location of the gallery has been determined using the preliminary rate provided above, we should perform in-situ Pilot Infiltration Test per the stormwater manual. Our final report will then include the final site and grading plans, updated infiltration rate based on testing, and any additional changes required by the design team. LIMITATIONS We have prepared this report for use by Garrette Custom Homes and other members of the design team for use in the design of a portion of this project. The data used in preparing this report and this report should be provided to prospective contractors for their bidding or estimating purposes only. Our report, conclusions and interpretations are based on our subsurface explorations, data from others GCH.MattocksPlat.SR_July2024 August 22, 2024 page | 9 and limited site reconnaissance, and should not be construed as a warranty of the subsurface conditions. Variations in subsurface conditions are possible between the explorations and may also occur with time. A contingency for unanticipated conditions should be included in the budget and schedule. Sufficient monitoring, testing and consultation should be provided by our firm during construction to confirm that the conditions encountered are consistent with those indicated by the explorations, to provide recommendations for design changes should the conditions revealed during the work differ from those anticipated, and to evaluate whether earthwork and foundation installation activities comply with contract plans and specifications. The scope of our services does not include services related to environmental remediation and construction safety precautions. Our recommendations are not intended to direct the contractor's methods, techniques, sequences or procedures, except as specifically described in our report for consideration in design. If there are any changes in the loads, grades, locations, configurations or type of facilities to be constructed, the conclusions and recommendations presented in this report may not be fully applicable. If such changes are made, we should be given the opportunity to review our recommendations and provide written modifications or verifications, as appropriate.    GCH.MattocksPlat.SR_July2024 August 22, 2024 page | 10 We have appreciated the opportunity to be of service to you on this project. If you have any questions or comments, please do not hesitate to call at your earliest convenience. Respectfully submitted, GeoResources, LLC Davis W. Carlsen, GIT Senior Staff Geologist Kyle E. Billingsley, PE Eric. W. Heller, PE, LG Senior Geotechnical Engineer Senior Geotechnical Engineer DWC:KEB:EWH/dwc Doc ID: GCH.MattocksPlat.SR Attachments: Figure 1: Site Location Map Figure 2: Site & Exploration Plan Figure 3: Site Vicinity Map Figure 4: NRCS Soils Map Figure 5: Geologic Map Appendix A: Subsurface Explorations Appendix B: Laboratory Test Results Appendix C: Infiltration Rate Calculations Approximate Site Location Figure created from the Pierce County Public GIS website (https://matterhornwab.co.pierce.wa.us/publicgis/) Not to Scale Site Location Map Proposed Residential Plat xxx – Palisades Street Southeast Yelm, Washington PN: 21725130200 Doc ID: GCH.MattocksPlat.F Aug 2024 Figure 1 EDED EDED EDED ED ED ED ED ED ED ED ED ED ED ED ED ED @A TP-1 / PIT-1 / OSP-1 HA-1 TP-9 TP-8 TP-6 TP-4 TP-3 TP-2 TP-12 TP-11 TP-10 TP-101TP-102TP-105 TP-103TP-104 TP-106TP-107 TP-7 / OSP-3 TP-5 / OSP-2 Site & Exploration Plan Proposed Residential Plat xxx - Palisades Street Southeast Yelm, Washington PN: 21725130200 Figure 2Doc ID: GCH.MattocksPlat.F August 2024 0 80 160 24040 Feet1 in = 80 ft Legend @A Hand auger ED Infiltration test ED Test pit Preliminary Site Plan prepared by AHBL dated November 14, 2023 µ Approximate Site Location Figure created from the Thurston County online Show Me Everything Map (https://map.co.thurston.wa.us/Html5Viewer/Index.html?viewer=uMap.Main) Not to Scale Site Vicinity Map Proposed Residential Plat xxx – Palisades Street Southeast Yelm, Washington PN: 21725130200 Doc ID: GCH.MattocksPlat.F Aug 2024 Figure 3 Approximate Site Location Figure created from the Web Soil Survey (http://websoilsurvey.sc.egov.usda.gov/App/WebSoilSurvey.aspx) Soil Type Soil Name Parent Material Slopes Erosion Hazard (off -road, off-trail) Hydrologic Soil Group 2 Alderwood gravelly sandy loam Glacial drift and/or glacial outwash over dense glaciomarine deposits 8 to 15 Slight B 32 Everett very gravelly sandy loam Sandy and gravelly glacial outwash 0 to 8 A Not to Scale NRCS Soils Map Proposed Residential Plat xxx – Palisades Street Southeast Yelm, Washington PN: 21725130200 Doc ID: GCH.MattocksPlat.F Aug 2024 Figure 4 Approximate Site Location An excerpt from the Geologic Map of the Centralia Quadrangle, Washington by Schasse, H.W. (1987) Symbol Geologic Unit Qdvg Vashon outwash gravel Qdvt Vashon till Not to Scale Geologic Map Proposed Residential Plat xxx – Palisades Street Southeast Yelm, Washington PN: 21725130200 Doc ID: GCH.MattocksPlat.F Aug 2024 Figure 5 Appendix A Subsurface Explorations SOIL CLASSIFICATION SYSTEM MAJOR DIVISIONS GROUP SYMBOL GROUP NAME COARSE GRAINED SOILS GRAVEL CLEAN GRAVEL GW WELL-GRADED GRAVEL, FINE TO COARSE GRAVEL GP POORLY-GRADED GRAVEL More than 50% Of Coarse Fraction Retained on No. 4 Sieve GRAVEL WITH FINES GM SILTY GRAVEL GC CLAYEY GRAVEL More than 50% Retained on No. 200 Sieve SAND CLEAN SAND SW WELL-GRADED SAND, FINE TO COARSE SAND SP POORLY-GRADED SAND More than 50% Of Coarse Fraction Passes No. 4 Sieve SAND WITH FINES SM SILTY SAND SC CLAYEY SAND FINE GRAINED SOILS SILT AND CLAY INORGANIC ML SILT CL CLAY Liquid Limit Less than 50 ORGANIC OL ORGANIC SILT, ORGANIC CLAY More than 50% Passes No. 200 Sieve SILT AND CLAY INORGANIC MH SILT OF HIGH PLASTICITY, ELASTIC SILT CH CLAY OF HIGH PLASTICITY, FAT CLAY Liquid Limit 50 or more ORGANIC OH ORGANIC CLAY, ORGANIC SILT HIGHLY ORGANIC SOILS PT PEAT NOTES: SOIL MOISTURE MODIFIERS: 1. Field classification is based on visual examination of soil Dry- Absence of moisture, dry to the touch in general accordance with ASTM D2488-90. Moist- Damp, but no visible water 2. Soil classification using laboratory tests is based on ASTM D6913. Wet- Visible free water or saturated, usually soil is obtained from below water table 3. Description of soil density or consistency are based on interpretation of blow count data, visual appearance of soils, and or test data. Unified Soils Classification System Proposed Residential Plat xxx – Palisades Street Southeast Yelm, Washington PN: 21725130200 Doc ID: GCH.MattocksPlat.F Aug 2024 Figure A-1 Test Pit TP-1 / Pilot Infiltration Test PIT-1/OSP-1 Location: Storm Tract F Approximate Elevation: 360 feet (lidar-derived, Thurston 2021 DTM 53, NAVD88) Depth (ft) Soil Type Soil Description 0.0 - 0.5 - Topsoil 0.5 - 1.5 ML Grey-brown sandy gravelly SILT (medium stiff, moist) 1.5 - 6.0 ML Grey sandy SILT with gravel (medium stiff, moist) 6.0 - 10.0 GP Grey GRAVEL with sand and trace silt (dense to very dense, moist) (advance outwash) Pilot Infiltration Test (PIT) performed at 4.0 feet below ground surface (BGS). Measured infiltration rate: 0.0 in/hr Terminated at 10.0 feet below the existing ground surface after completion of PIT. No caving observed at the time of excavation. Mottling observed from 1.0 to 1.5 feet BGS. Open standpipe piezometer installed at 10.0 feet BGS. Test Pit TP-2 Location: Northeast portion of Access Roadway Approximate Elevation: 384 feet (lidar-derived, Thurston 2021 DTM 53, NAVD88) Depth (ft) Soil Type Soil Description 0.0 - 0.5 - Topsoil 0.5 - 2.5 GM Medium brown sandy silty GRAVEL (medium dense to dense, moist) (Weathered till) 2.5 - 6.0 GM Grey sandy silty GRAVEL (dense to very dense, moist) (Undisturbed glacial till) Terminated at 6.0 feet BGS. No caving observed at the time of excavation. Mottling observed at 2.0 feet BGS. No groundwater seepage at time of excavation. Test Pit TP-3 Location: Proposed Lot 18 Approximate Elevation: 394 feet (lidar-derived, Thurston 2021 DTM 53, NAVD88) Depth (ft) Soil Type Soil Description 0.0 - 0.75 - Topsoil 0.75 - 3.5 GM Medium brown sandy silty GRAVEL (medium dense to dense, moist) (Weathered till) 3.5 - 8.0 GM Grey sandy silty GRAVEL (dense to very dense, moist) (Undisturbed glacial till) Terminated at 8.0 feet BGS. No caving observed at the time of excavation. No mottling observed. No groundwater seepage at time of excavation. Logged by: MAE/DEM Excavated on: January 9, 2024 Test Pit Logs Proposed Residential Plat xxx – Palisades Street Southeast Yelm, Washington PN: 21725130200 Doc ID: GCH.MattocksPlat.F Aug 2024 Figure A-2 Test Pit TP-4 Location: Intersecting corners of proposed Lots 25, 26, 30, & 31 Approximate Elevation: 409 feet (lidar-derived, Thurston 2021 DTM 53, NAVD88) Depth (ft) Soil Type Soil Description 0.0 - 0.7 5 - Topsoil 0.75 - 4.0 GM Medium brown sandy silty GRAVEL (medium dense to dense, moist) (Weathered till) 4.0 - 6.0 GM Grey sandy silty GRAVEL (dense to very dense, moist) (Undisturbed glacial till) Terminated at 6.0 feet BGS. No caving observed at the time of excavation. Mottling observed from 4.0 to 5.0 feet BGS. No groundwater seepage at time of excavation. Test Pit TP-5/OSP-2 Location: Proposed Lot 23 Approximate Elevation: 401 feet (lidar-derived, Thurston 2021 DTM 53, NAVD88) Depth (ft) Soil Type Soil Description 0.0 - 0.5 - Topsoil 0.5 - 3.0 GM Medium brown sandy silty GRAVEL (medium dense to dense, moist) (Weathered till) 3.0 - 4.0 GP-GM Grey-brown sandy poorly graded GRAVEL with silt (medium dense to dense, moist) (Weathered till) 4.0 - 6.0 GM Grey sandy silty GRAVEL (dense to very dense, moist) (Undisturbed glacial till) Terminated at 6.0 feet BGS. No caving observed at the time of excavation. No mottling observed. No groundwater seepage at time of excavation. Open standpipe piezometer installed at 5.0 feet BGS. Test Pit TP-6 Location: Proposed Lot 38 Approximate Elevation: 420 feet (lidar-derived, Thurston 2021 DTM 53, NAVD88) Depth (ft) Soil Type Soil Description 0.0 - 0.5 - Topsoil 0.5 - 2.5 GM Medium brown sandy silty GRAVEL (medium dense to dense, moist) (Weathered till) 2.5 - 3.0 SM Grey-brown silty SAND (medium dense to dense, moist) (Weathered till) 3.0 - 6.0 GM Grey sandy silty GRAVEL (dense to very dense, moist) (Undisturbed glacial till) Terminated at 6.0 feet BGS. No caving observed at the time of excavation. No mottling observed. No groundwater seepage at time of excavation. Logged by: MAE Excavated on: January 9, 2024 Test Pit Logs Proposed Residential Plat xxx – Palisades Street Southeast Yelm, Washington PN: 21725130200 Doc ID: GCH.MattocksPlat.F Aug 2024 Figure A-3 Test Pit TP-7/OSP-3 Location: Proposed Lot 1 Approximate Elevation: 360 feet (lidar-derived, Thurston 2021 DTM 53, NAVD88) Depth (ft) Soil Type Soil Description 0.0 - 0.5 - Topsoil 0.5 - 3.0 GM Medium brown sandy silty GRAVEL (medium dense to dense, moist) (Fill) 3.0 - 7.0 GM Grey sandy silty GRAVEL (dense to very dense, moist) (Undisturbed glacial till) Terminated at 7.0 feet BGS. No caving observed at the time of excavation. No mottling observed. Slow groundwater seepage observed at about 1.5 feet below existing grades. Open standpipe piezometer installed at 5.5 feet BGS. Test Pit TP-8 Location: Proposed Lot 4 Approximate Elevation: 405 feet (lidar-derived, Thurston 2021 DTM 53, NAVD88) Depth (ft) Soil Type Soil Description 0.0 - 0.5 - Topsoil 0.5 - 5.0 SM Medium brown gravelly silty SAND (medium dense to dense, moist) (Weathered till) 5.0 - 7.0 GM Grey sandy silty GRAVEL (dense to very dense, moist) (Undisturbed glacial till) Terminated at 7.0 feet BGS. No caving observed at the time of excavation. No mottling observed. No groundwater seepage observed at time of excavation. Test Pit TP-9 Location: Center south portion of Access Roadway Approximate Elevation: 407 feet (lidar-derived, Thurston 2021 DTM 53, NAVD88) Depth (ft) Soil Type Soil Description 0.0 - 0.7 5 - Topsoil 0.75 - 1.5 GM Medium brown sandy silty GRAVEL (medium dense to dense, moist) (Weathered till) 1.5 - 3.0 GW-GM Grey-brown sandy well-graded GRAVEL with silt (medium dense to dense, moist) (Weathered glacial till) 3.0 - 5.0 GM Grey sandy silty GRAVEL (dense to very dense, moist) (Undisturbed glacial till) Terminated at 5.0 feet BGS. No caving observed at the time of excavation. No mottling observed. No groundwater seepage observed at time of excavation. Logged by: MAE Excavated on: January 9, 2024 Test Pit Logs Proposed Residential Plat xxx – Palisades Street Southeast Yelm, Washington PN: 21725130200 Doc ID: GCH.MattocksPlat.F Aug 2024 Figure A-4 Test Pit TP-10 Location: Proposed Lot 10 Approximate Elevation: 404 feet (lidar-derived, Thurston 2021 DTM 53, NAVD88) Depth (ft) Soil Type Soil Description 0.0 - 0.7 5 - Topsoil 0.75 - 2.0 SM Grey-brown silty SAND (medium dense to dense, moist) (Weathered glacial till) 2.0 - 5.0 GM Grey sandy silty GRAVEL (dense to very dense, moist) (Undisturbed glacial till) Terminated at 5.0 feet BGS. No caving observed at the time of excavation. No mottling observed. No groundwater seepage at time of excavation. Test Pit TP-11 Location: Proposed Lot 4 Approximate Elevation: 405 feet (lidar-derived, Thurston 2021 DTM 53, NAVD88) Depth (ft) Soil Type Soil Description 0.0 - 0.5 - Topsoil 0.5 - 4.0 SM Medium brown gravelly silty SAND (medium dense to dense, moist) (Weathered till) 4.0 - 6.0 GM Grey sandy silty GRAVEL (dense to very dense, moist) (Undisturbed glacial till) Terminated at 6.0 feet BGS. No caving observed at the time of excavation. No mottling observed. No groundwater seepage at time of excavation. Test Pit TP-12 Location: Proposed Lot 14 Approximate Elevation: 396 feet (lidar-derived, Thurston 2021 DTM 53, NAVD88) Depth (ft) Soil Type Soil Description 0.0 - 0.7 5 - Topsoil 0.75 - 3.0 GM Medium brown sandy silty GRAVEL (medium dense to dense, moist) (Weathered till) 3.0 - 5.0 GM Grey sandy silty GRAVEL (dense to very dense, moist) (Undisturbed glacial till) Terminated at 5.0 feet BGS. No caving observed at the time of excavation. No mottling observed. No groundwater seepage observed at time of excavation. Logged by: MAE Excavated on: January 9, 2024 Test Pit Logs Proposed Residential Plat xxx – Palisades Street Southeast Yelm, Washington PN: 21725130200 Doc ID: GCH.MattocksPlat.F Aug 2024 Figure A-5 Test Pit TP-101 Location: Tract E Approximate Elevation: 360 feet (lidar-derived, Thurston 2021 DTM 53, NAVD88) Depth (ft) Soil Type Soil Description 0.0 - 0.75 - Topsoil 0.75 - 5 ML Brown-grey sandy SILT with some gravel (stiff, moist) (undocumented fill) 5 - 12.5 GP Grey GRAVEL with sand and trace silt (dense to very dense, moist) (advance outwash) Terminated at 12.5 feet BGS. No caving observed at the time of excavation. No mottling observed. Slow groundwater seepage observed at approximately 11 feet BGS Test Pit TP-102 Location: Proposed Tract D Approximate Elevation: 368 feet (lidar-derived, Thurston 2021 DTM 53, NAVD88) Depth (ft) Soil Type Soil Description 0.0 - 1.0 - Topsoil 1.0 - 4.25 SM Brown silty SAND with some gravel (medium dense, moist) (weathered advance outwash) 4.25 - 11.5 SP-SM Grey gravelly poorly graded SAND with some silt, occasional thin silt lenses (dense, moist) (advance outwash) Terminated at 11.5 feet BGS. No caving observed at the time of excavation. No mottling observed. No groundwater seepage at time of excavation. Logged by: DC Excavated on: February 7, 2024 Test Pit Logs Proposed Residential Plat xxx – Palisades Street Southeast Yelm, Washington PN: 21725130200 Doc ID: GCH.MattocksPlat.F Aug 2024 Figure A-6 Test Pit TP-103 Location: Proposed Tract D Approximate Elevation: 370 feet (lidar-derived, Thurston 2021 DTM 53, NAVD88) Depth (ft) Soil Type Soil Description 0.0 - 1.0 - Topsoil 1.0 - 3.5 SM Brown silty SAND with some gravel (medium dense, moist) (weathered advance outwash) 3.5 - 10.5 GM Grey sandy silty GRAVEL (dense to very dense, moist) (advance outwash) Terminated at 10.5 feet BGS. No caving observed at the time of excavation. No mottling observed. No groundwater seepage at time of excavation Test Pit TP-104 Location: Proposed Tract D Approximate Elevation: 376 feet (lidar-derived, Thurston 2021 DTM 53, NAVD88) Depth (ft) Soil Type Soil Description 0.0 - 0.75 - Topsoil 0.75 - 3.0 SM Brown gravelly silty SAND (medium dense, moist) (weathered glacial till) 3.0 - 9.5 SM Grey gravelly silty SAND (very dense, moist) (glacial till) Terminated at 9.5 feet BGS. No caving observed at the time of excavation. Mottling observed at approximately 2.5 feet BGS. No groundwater seepage at time of excavation. Refusal in excavation Logged by: DC Excavated on: February 7, 2024 Test Pit Logs Proposed Residential Plat xxx – Palisades Street Southeast Yelm, Washington PN: 21725130200 Doc ID: GCH.MattocksPlat.F Aug 2024 Figure A-7 Test Pit TP-105 Location: Northern road area Approximate Elevation: 380 feet (lidar-derived, Thurston 2021 DTM 53, NAVD88) Depth (ft) Soil Type Soil Description 0.0 - 1.0 - Topsoil 1.0 - 3.5 SM Brown silty SAND with some gravel (medium dense, moist) (weathered advance outwash) 3.5 - 7.5 SM Grey fine silty SAND with some gravel (medium dense, moist) (advance outwash) 7.5 - 11.5 GM Grey sandy silty GRAVEL (dense to very dense, moist) (advance outwash) Terminated at 11.5 feet BGS. No caving observed at the time of excavation. Slight mottling observed at 7 feet BGS. No groundwater seepage at time of excavation Test Pit TP-106 Location: Proposed Lot 22 Approximate Elevation: 396 feet (lidar-derived, Thurston 2021 DTM 53, NAVD88) Depth (ft) Soil Type Soil Description 0.0 - 1.0 - Topsoil 1.0 - 3.25 SM Browns silty SAND with some gravel, buried debris (loose to medium dense) (undocumented fill) 3.25 - 5.0 SM Brown gravelly silty SAND (medium dense, moist) (weathered glacial till) 5.0 - 9.5 SM Grey gravelly silty SAND (very dense, moist) (glacial till) Terminated at 9.5 feet BGS. No caving observed at the time of excavation. Mottling observed at approximately 4.5 feet BGS. No groundwater seepage at time of excavation. Refusal in excavation Logged by: DC Excavated on: February 7, 2024 Test Pit Logs Proposed Residential Plat xxx – Palisades Street Southeast Yelm, Washington PN: 21725130200 Doc ID: GCH.MattocksPlat.F Aug 2024 Figure A-8 Test Pit TP-107 Location: Proposed lot 29 Approximate Elevation: 404 feet (lidar-derived, Thurston 2021 DTM 53, NAVD88) Depth (ft) Soil Type Soil Description 0.0 - 0.5 - Topsoil 0.5 - 2.0 SM Brown gravelly silty SAND (medium dense, moist) (weathered glacial till) 2.0 - 9.0 SM Grey gravelly silty SAND (very dense, moist) (glacial till) Terminated at 9.0 feet BGS. No caving observed at the time of excavation. Slight mottling observed at 2 feet BGS. No groundwater seepage at time of excavation Logged by: DC Excavated on: February 7, 2024 Test Pit Logs Proposed Residential Plat xxx – Palisades Street Southeast Yelm, Washington PN: 21725130200 Doc ID: GCH.MattocksPlat.F Aug 2024 Figure A-9 Hand Auger HA-1 Location: Existing stormwater facility Approximate Elevation: 357 feet (lidar-derived, Thurston 2021 DTM 53, NAVD88) Depth (ft) Soil Type Soil Description 0.0 - 0.25 - Topsoil 0.25 - 3.5 GM Grey silty GRAVEL with some sand (very dense, moist) (advance outwash) Terminated at 3.5 feet BGS. No caving observed at the time of excavation. No mottling observed at time of excavation No groundwater seepage at time of excavation Logged by: DC Excavated on: February 7, 2024 Test Pit Logs Proposed Residential Plat xxx – Palisades Street Southeast Yelm, Washington PN: 21725130200 Doc ID: GCH.MattocksPlat.F Aug 2024 Figure A-10 Appendix B Laboratory Test Results Th e s e r e s u l t s a r e f o r t h e e x c l u s i v e u s e o f t h e c l i e n t f o r w h o m t h e y w e r e o b t a i n e d . T h e y a p p l y o n l y t o t h e s a m p l e s t e s t e d a n d a r e n o t i n d i c i t i v e o f a p p a r e n t l y i d e n t i c a l s a m p l e s . Tested By: Checked By: Particle Size Distribution Report PE R C E N T F I N E R 0 10 20 30 40 50 60 70 80 90 100 GRAIN SIZE - mm. 0.0010.010.1110100 % +3"Coarse % Gravel Fine Coarse Medium % Sand Fine Silt % Fines Clay 0.0 13.2 7.2 2.8 6.7 18.7 51.4 6 i n . 3 i n . 2 i n . 1½ i n . 1 i n . ¾ i n . ½ i n . 3/ 8 i n . #4 #1 0 #2 0 #3 0 #4 0 #6 0 #1 0 0 #1 4 0 #2 0 0 Test Results (ASTM D 6913 & ASTM D 1140) Opening Percent Spec.*Pass? Size Finer (Percent)(X=Fail) Material Description Atterberg Limits (ASTM D 4318) Classification Coefficients Date Received:Date Tested: Tested By: Checked By: Title: Date Sampled:Location: TP-1, S-2 Sample Number: 104657 Depth: 4' Client: Project: Project No:Figure Sandy SILT with gravel (ML) 2.0 1.5 1.25 1 .75 .5 0.375 #4 #10 #20 #40 #60 #100 #200 100.0 91.2 91.2 91.2 86.8 84.1 82.6 79.6 76.8 74.0 70.1 65.8 60.5 51.4 NP NV NP ML A-4(0) 23.0729 15.8081 0.1443 Natural Moisture: 22.9% 1/9/24 1/18/24 MAW KEB PM 1/9/24 Garrette Custom Homes Proposed Residential Plat GarretteCustomHomes.MattocksPlat PL=LL=PI= USCS (D 2487)=AASHTO (M 145)= D90=D85=D60= D50=D30=D15= D10=Cu=Cc= Remarks *(no specification provided) GeoResources, LLC Fife, WA B-1 Th e s e r e s u l t s a r e f o r t h e e x c l u s i v e u s e o f t h e c l i e n t f o r w h o m t h e y w e r e o b t a i n e d . T h e y a p p l y o n l y t o t h e s a m p l e s t e s t e d a n d a r e n o t i n d i c i t i v e o f a p p a r e n t l y i d e n t i c a l s a m p l e s . Tested By: Checked By: Particle Size Distribution Report PE R C E N T F I N E R 0 10 20 30 40 50 60 70 80 90 100 GRAIN SIZE - mm. 0.0010.010.1110100 % +3"Coarse % Gravel Fine Coarse Medium % Sand Fine Silt % Fines Clay 0.0 32.6 23.7 9.2 12.8 10.8 10.9 6 i n . 3 i n . 2 i n . 1½ i n . 1 i n . ¾ i n . ½ i n . 3/ 8 i n . #4 #1 0 #2 0 #3 0 #4 0 #6 0 #1 0 0 #1 4 0 #2 0 0 Test Results (ASTM D 6913 & ASTM D 1140) Opening Percent Spec.*Pass? Size Finer (Percent)(X=Fail) Material Description Atterberg Limits (ASTM D 4318) Classification Coefficients Date Received:Date Tested: Tested By: Checked By: Title: Date Sampled:Location: TP-5, S-2 Sample Number: 104658 Depth: 3.5' Client: Project: Project No:Figure Poorly graded GRAVEL with silt and sand (GP-GM) 2.0 1.5 1.25 1 .75 .5 0.375 #4 #10 #20 #40 #60 #100 #200 100.0 93.8 89.6 76.8 67.4 58.3 55.6 43.7 34.5 27.9 21.7 17.5 14.2 10.9 NP NV NP GP-GM A-1-a 32.0590 29.0710 13.9775 6.6497 1.0999 0.1709 Natural Moisture: 10.4% 1/9/24 1/18/24 MAW KEB PM 1/9/24 Garrette Custom Homes Proposed Residential Plat GarretteCustomHomes.MattocksPlat PL=LL=PI= USCS (D 2487)=AASHTO (M 145)= D90=D85=D60= D50=D30=D15= D10=Cu=Cc= Remarks *(no specification provided) GeoResources, LLC Fife, WA B-2 Th e s e r e s u l t s a r e f o r t h e e x c l u s i v e u s e o f t h e c l i e n t f o r w h o m t h e y w e r e o b t a i n e d . T h e y a p p l y o n l y t o t h e s a m p l e s t e s t e d a n d a r e n o t i n d i c i t i v e o f a p p a r e n t l y i d e n t i c a l s a m p l e s . Tested By: Checked By: Particle Size Distribution Report PE R C E N T F I N E R 0 10 20 30 40 50 60 70 80 90 100 GRAIN SIZE - mm. 0.0010.010.1110100 % +3"Coarse % Gravel Fine Coarse Medium % Sand Fine Silt % Fines Clay 0.0 39.8 24.2 7.0 11.9 12.0 5.1 6 i n . 3 i n . 2 i n . 1½ i n . 1 i n . ¾ i n . ½ i n . 3/ 8 i n . #4 #1 0 #2 0 #3 0 #4 0 #6 0 #1 0 0 #1 4 0 #2 0 0 Test Results (ASTM D 6913 & ASTM D 1140) Opening Percent Spec.*Pass? Size Finer (Percent)(X=Fail) Material Description Atterberg Limits (ASTM D 4318) Classification Coefficients Date Received:Date Tested: Tested By: Checked By: Title: Date Sampled:Location: TP-9, S-1 Sample Number: 104659 Depth: 2' Client: Project: Project No:Figure Well-graded GRAVEL with silt and sand (GW-GM) 2.0 1.5 1.25 1 .75 .5 0.375 #4 #10 #20 #40 #60 #100 #200 100.0 87.1 67.1 64.0 60.2 48.4 44.7 36.0 29.0 22.9 17.1 12.1 8.5 5.1 NP NV NP GW-GM A-1-a 39.3352 37.3647 18.8871 13.6053 2.3410 0.3411 0.1903 99.25 1.52 Natural Moisture: 6.4% 1/9/24 1/18/24 MAW KEB PM 1/9/24 Garrette Custom Homes Proposed Residential Plat GarretteCustomHomes.MattocksPlat PL=LL=PI= USCS (D 2487)=AASHTO (M 145)= D90=D85=D60= D50=D30=D15= D10=Cu=Cc= Remarks *(no specification provided) GeoResources, LLC Fife, WA B-3 Th e s e r e s u l t s a r e f o r t h e e x c l u s i v e u s e o f t h e c l i e n t f o r w h o m t h e y w e r e o b t a i n e d . T h e y a p p l y o n l y t o t h e s a m p l e s t e s t e d a n d a r e n o t i n d i c i t i v e o f a p p a r e n t l y i d e n t i c a l s a m p l e s . Tested By: Checked By: Particle Size Distribution Report PE R C E N T F I N E R 0 10 20 30 40 50 60 70 80 90 100 GRAIN SIZE - mm. 0.0010.010.1110100 % +3"Coarse % Gravel Fine Coarse Medium % Sand Fine Silt % Fines Clay 0.0 7.0 23.5 10.6 16.2 22.2 20.5 6 i n . 3 i n . 2 i n . 1½ i n . 1 i n . ¾ i n . ½ i n . 3/ 8 i n . #4 #1 0 #2 0 #3 0 #4 0 #6 0 #1 0 0 #1 4 0 #2 0 0 Test Results (ASTM D 6913 & ASTM D 1140) Opening Percent Spec.*Pass? Size Finer (Percent)(X=Fail) Material Description Atterberg Limits (ASTM D 4318) Classification Coefficients Date Received:Date Tested: Tested By: Checked By: Title: Date Sampled:Location: TP-11, S-1 Sample Number: 104660 Depth: 1' Client: Project: Project No:Figure Silty SAND with gravel (SM) 1.25 1 .75 .5 0.375 #4 #10 #20 #40 #60 #100 #200 100.0 95.9 93.0 86.0 82.0 69.5 58.9 50.4 42.7 35.1 27.8 20.5 NP NV NP SM A-1-b 15.8019 11.8879 2.2367 0.8152 0.1770 Natural Moisture: 20.8% 1/9/24 1/18/24 MAW KEB PM 1/9/24 Garrette Custom Homes Proposed Residential Plat GarretteCustomHomes.MattocksPlat PL=LL=PI= USCS (D 2487)=AASHTO (M 145)= D90=D85=D60= D50=D30=D15= D10=Cu=Cc= Remarks *(no specification provided) GeoResources, LLC Fife, WA B-4 Th e s e r e s u l t s a r e f o r t h e e x c l u s i v e u s e o f t h e c l i e n t f o r w h o m t h e y w e r e o b t a i n e d . T h e y a p p l y o n l y t o t h e s a m p l e s t e s t e d a n d a r e n o t i n d i c i t i v e o f a p p a r e n t l y i d e n t i c a l s a m p l e s . Tested By: Checked By: Particle Size Distribution Report PE R C E N T F I N E R 0 10 20 30 40 50 60 70 80 90 100 GRAIN SIZE - mm. 0.0010.010.1110100 % +3"Coarse % Gravel Fine Coarse Medium % Sand Fine Silt % Fines Clay 0.0 16.1 23.7 12.1 16.5 15.9 15.7 6 i n . 3 i n . 2 i n . 1½ i n . 1 i n . ¾ i n . ½ i n . 3/ 8 i n . #4 #1 0 #2 0 #3 0 #4 0 #6 0 #1 0 0 #1 4 0 #2 0 0 Test Results (ASTM D 6913 & ASTM D 1140) Opening Percent Spec.*Pass? Size Finer (Percent)(X=Fail) Material Description Atterberg Limits (ASTM D 4318) Classification Coefficients Date Received:Date Tested: Tested By: Checked By: Title: Date Sampled:Location: TP-8, S-1 Sample Number: 104663 Depth: 2' Client: Project: Project No:Figure Silty SAND with gravel (SM) 1.25 1 .75 .5 0.375 #4 #10 #20 #40 #60 #100 #200 100.0 93.1 83.9 74.9 71.9 60.2 48.1 39.2 31.6 25.7 20.8 15.7 NP NV NP SM A-1-b 23.1091 19.7827 4.7072 2.3489 0.3707 Natural Moisture: 15.9% 1/9/24 1/18/24 MAW KEB PM 1/9/24 Garrette Custom Homes Proposed Residential Plat GarretteCustomHomes.MattocksPlat PL=LL=PI= USCS (D 2487)=AASHTO (M 145)= D90=D85=D60= D50=D30=D15= D10=Cu=Cc= Remarks *(no specification provided) GeoResources, LLC Fife, WA B-5 Th e s e r e s u l t s a r e f o r t h e e x c l u s i v e u s e o f t h e c l i e n t f o r w h o m t h e y w e r e o b t a i n e d . T h e y a p p l y o n l y t o t h e s a m p l e s t e s t e d a n d a r e n o t i n d i c i t i v e o f a p p a r e n t l y i d e n t i c a l s a m p l e s . Tested By: Checked By: Particle Size Distribution Report PE R C E N T F I N E R 0 10 20 30 40 50 60 70 80 90 100 GRAIN SIZE - mm. 0.0010.010.1110100 % +3"Coarse % Gravel Fine Coarse Medium % Sand Fine Silt % Fines Clay 0.0 69.6 13.8 2.4 5.0 5.2 4.0 6 i n . 3 i n . 2 i n . 1½ i n . 1 i n . ¾ i n . ½ i n . 3/ 8 i n . #4 #1 0 #2 0 #3 0 #4 0 #6 0 #1 0 0 #1 4 0 #2 0 0 Test Results (ASTM D 6913 & ASTM D 1140) Opening Percent Spec.*Pass? Size Finer (Percent)(X=Fail) Material Description Atterberg Limits (ASTM D 4318) Classification Coefficients Date Received:Date Tested: Tested By: Checked By: Title: Date Sampled:Location: TP-101, S-1 Sample Number: 104798 Depth: 8' Client: Project: Project No:Figure Poorly graded GRAVEL (GP) 3.0 2.5 2.0 1.5 1.25 1 .75 .5 0.375 #4 #10 #20 #40 #60 #100 #200 100.0 79.2 68.0 47.1 44.9 34.9 30.4 23.7 20.8 16.6 14.2 11.6 9.2 7.3 5.7 4.0 NP NV NP GP A-1-a 70.5107 67.5324 45.7374 40.3640 18.3467 2.8544 0.5352 85.46 13.75 Natural Moisture: 3.4% 2/7/24 2/15/24 MAW KEB PM 2/7/24 Garrette Custom Homes Proposed Residential Plat GarretteCustomHomes.MattocksPlat PL=LL=PI= USCS (D 2487)=AASHTO (M 145)= D90=D85=D60= D50=D30=D15= D10=Cu=Cc= Remarks *(no specification provided) GeoResources, LLC Fife, WA B-6 Th e s e r e s u l t s a r e f o r t h e e x c l u s i v e u s e o f t h e c l i e n t f o r w h o m t h e y w e r e o b t a i n e d . T h e y a p p l y o n l y t o t h e s a m p l e s t e s t e d a n d a r e n o t i n d i c i t i v e o f a p p a r e n t l y i d e n t i c a l s a m p l e s . Tested By: Checked By: Particle Size Distribution Report PE R C E N T F I N E R 0 10 20 30 40 50 60 70 80 90 100 GRAIN SIZE - mm. 0.0010.010.1110100 % +3"Coarse % Gravel Fine Coarse Medium % Sand Fine Silt % Fines Clay 0.0 10.7 17.7 7.1 20.4 37.5 6.6 6 i n . 3 i n . 2 i n . 1½ i n . 1 i n . ¾ i n . ½ i n . 3/ 8 i n . #4 #1 0 #2 0 #3 0 #4 0 #6 0 #1 0 0 #1 4 0 #2 0 0 Test Results (ASTM D 6913 & ASTM D 1140) Opening Percent Spec.*Pass? Size Finer (Percent)(X=Fail) Material Description Atterberg Limits (ASTM D 4318) Classification Coefficients Date Received:Date Tested: Tested By: Checked By: Title: Date Sampled:Location: TP-102, S-2 Sample Number: 104799 Depth: 8.5' Client: Project: Project No:Figure Poorly graded SAND with silt and gravel (SP-SM) 1.25 1 .75 .5 0.375 #4 #10 #20 #40 #60 #100 #200 100.0 91.2 89.3 83.3 78.3 71.6 64.5 56.2 44.1 27.5 14.2 6.6 NP NV NP SP-SM A-1-b 23.7022 13.8854 1.2172 0.5534 0.2702 0.1565 0.1127 10.80 0.53 Natural Moisture: 7.3% 2/7/24 2/15/24 MAW KEB PM 2/7/24 Garrette Custom Homes Proposed Residential Plat GarretteCustomHomes.MattocksPlat PL=LL=PI= USCS (D 2487)=AASHTO (M 145)= D90=D85=D60= D50=D30=D15= D10=Cu=Cc= Remarks *(no specification provided) GeoResources, LLC Fife, WA B-7 Appendix C Infiltration Rate Analysis Soil Grain Size Analysis Method Procudure based on 2019 SWMMWW, Volume V, Chapter 5, V-5.4 K sat = 10^(-1.57 + 1.90D10 + 0.015D60 - 0.013D90 - 2.08Ffines)(provides Ksat in cm/s) K sat = [10^(-1.57 + 1.90D10 + 0.015D60 - 0.013D90 - 2.08Ffines)]*1417 (provides Ksat in in/hr) I.D.Expl.Depth (ft) Layer Thickness (ft) D10 D60 D90 Ffines Individual Ksat (cm/s) Equivalent Ksat (in/hr) 104798 TP-101 8 0.535 45.737 70.511 0.040 0.136 192.518 Effective Average Hydraulic Conductivity, K equiv 192.518 Har. Mean Based on either:192.518 Lowest 1)Average Ksat determined using harmonic mean 192.000 To Use 2)Lowest conductive layer, if within 5ft of bottom of pond Site variability and number of tests (CFv) 0.25 to 1.0 Factor to use for calculations 0.5 Test Method (CFt) 0.75 0.5 0.4 Factor to use for calculations 0.4 Siltation and bio-buildup (CFm) 0.90 Factor to use for calculations 0.9 Idesign = Imeasured * Ftesting * Fgeometry *Fplugging 34.56 in/hr Preliminary Design Value 20.00 in/hr April 2024 Figure C-1 2019 Stormwater Management Manual for Western Washington Garrette Custom Homes - Mattocks Plat Yelm, Washington Massman Calculation Sheet Proposed Residential Plat Sample Information Sieve Data Unfactored Rate Yelm, Washington PN: 21725130200 DocID: GCH.MattocksPlat.ksat kequiv= Large-scale PIT 90% of design capacity Small-scale PIT Other small-scale (e.g. Double ring, falling head) & Grain Size Infiltration Rate Analysis - Shallow Facilities xxx - Palisades Street Southeast Soil Grain Size Analysis Method Procudure based on 2019 SWMMWW, Volume V, Chapter 5, V-5.4 K sat = 10^(-1.57 + 1.90D10 + 0.015D60 - 0.013D90 - 2.08Ffines)(provides Ksat in cm/s) K sat = [10^(-1.57 + 1.90D10 + 0.015D60 - 0.013D90 - 2.08Ffines)]*1417 (provides Ksat in in/hr) I.D.Expl.Depth (ft) Layer Thickness (ft) D10 D60 D90 Ffines Individual Ksat (cm/s) Equivalent Ksat (in/hr) 104799 TP-102 8.5 0.113 1.217 23.702 0.066 0.016 23.353 Effective Average Hydraulic Conductivity, K equiv 23.353 Har. Mean Based on either:23.353 Lowest 1)Average Ksat determined using harmonic mean 23.353 To Use 2)Lowest conductive layer, if within 5ft of bottom of pond Site variability and number of tests (CFv) 0.25 to 1.0 Factor to use for calculations 0.5 Test Method (CFt) 0.75 0.5 0.4 Factor to use for calculations 0.4 Siltation and bio-buildup (CFm) 0.90 Factor to use for calculations 0.9 Idesign = Imeasured * Ftesting * Fgeometry *Fplugging 4.20 in/hr Preliminary Design Value 4.20 in/hr April 2024 Figure C-2 xxx - Palisades Street Southeast Yelm, Washington PN: 21725130200 DocID: GCH.MattocksPlat.ksat Infiltration Rate Analysis - Shallow Facilities Proposed Residential Plat 2019 Stormwater Management Manual for Western Washington Garrette Custom Homes - Mattocks Plat Yelm, Washington Massman Calculation Sheet kequiv= Sample Information Sieve Data Unfactored Rate 90% of design capacity Large-scale PIT Small-scale PIT Other small-scale (e.g. Double ring, falling head) & Grain Size