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Preliminary Drainage Report
Preliminary Drainage and Erosion Control Report for Rainier View Estates Yelm, WA February 9, 2024 PO Box 12690 Olympia WA 98508 360.705.2474 www.olyeng.com ________________________________________________________________________________ February 2024 Preliminary Drainage and Erosion Control Report 1 COVER SHEET RAINIER VIEW ESTATES Yelm, Washington February 9, 2024 Owner/Applicant Prepared for: C & E Developments, LLC Contact: Ashlynne Solseth PO Box 2983 Yelm, WA 98597 (360) 400-0432 Reviewing Agency Jurisdiction: City of Yelm, Washington Project Number: ____________ Project Contact: ____________ (360) 458-8496 Contractor Contact: References WSDOE Stormwater Management Manual for Western Washington (SWMMWW), 2019 edition, with Errata Project Engineer Prepared by: Olympic Engineering, Inc. PO Box 12690 Olympia, WA 98508 (360) 705-2474 Contact: Chris Merritt, PE Project Number: 20046 2/9/2024 "I hereby certify that this Preliminary Drainage and Erosion Control Plan and Report and Construction SWPPP for the Rainier View Estates project has been prepared by me or under my supervision and meets the requirements of the City of Yelm Stormwater Standards and the standards of care and expertise which is usual and customary in this community for professional engineers. I understand that the City of Yelm does not and will not assume liability for the sufficiency, suitability, or performance of drainage facilities prepared by me.” ________________________________________________________________________________ February 2024 Preliminary Drainage and Erosion Control Report 2 TABLE OF CONTENTS COVER SHEET ........................................................................................................................ 1 TABLE OF CONTENTS ........................................................................................................... 2 SECTION 1 – PROPOSED PROJECT DESCRIPTION .......................................................... 3 Permit ................................................................................................................................................ 3 Project Location ................................................................................................................................. 3 Property Boundaries & Zoning ........................................................................................................... 3 Project Description ............................................................................................................................. 3 Minimum Requirements ..................................................................................................................... 3 Runoff Treatment Selections ............................................................................................................. 6 Timing of the Project .......................................................................................................................... 7 SECTION 2 – EXISTING SITE CONDITIONS ......................................................................... 7 Topography ........................................................................................................................................ 7 Ground Cover .................................................................................................................................... 7 Drainage ............................................................................................................................................ 7 Soils ................................................................................................................................................... 7 Critical Areas ..................................................................................................................................... 8 Adjacent Areas .................................................................................................................................. 8 Precipitation Records ......................................................................................................................... 8 Reports and Studies .......................................................................................................................... 8 SECTION 3 – GEOTECHNICAL REPORT .............................................................................. 8 SECTION 4 – WELLS AND SEPTIC SYSTEMS ..................................................................... 8 SECTION 5 – FUEL TANKS .................................................................................................... 8 SECTION 6 – ANALYSIS OF THE 100-YEAR FLOOD .......................................................... 8 SECTION 7 – AESTHETIC CONSIDERATIONS FOR FACILITIES ....................................... 8 SECTION 8 – FACILITY SIZING AND OFF-SITE ANALYSIS ................................................ 9 Off-Site Analysis ................................................................................................................................ 9 SECTION 9 – COVENANTS, DEDICATIONS, EASEMENTS ................................................ 9 SECTION 10 – PROPERTY OWNERS ASSOCIATION ARTICLES OF INCORPORATION 9 APPENDICES Appendix 1 - Preliminary Drainage Plan Appendix 2 - Preliminary Drainage Calculations Appendix 3 - Soils Reports ________________________________________________________________________________ February 2024 Preliminary Drainage and Erosion Control Report 3 SECTION 1 – PROPOSED PROJECT DESCRIPTION Permit The applicant is applying for permits to subdivide a 5.28-acre parcel into 23 residential lots. Project Location See Vicinity Map on plans for reference. Site Address: 9910 Durant St. SE Yelm, WA 98597 Tax Parcel Number(s): 21724420501 Section, Township, Range: Section 24 Township 17 North Range 01 East, W.M. Property Boundaries & Zoning The parcel is zoned R-4. The parcel boundaries are shown on the site/drainage plan (see Appendix). Project Description The proposal is to subdivide a 5.28-acre parcel into 23 residential lots with associated roadway, storm drainage, and public and private utility improvements. 19 lots will contain single-family residences and 4 lots will contain duplexes for 27 total units. Minimum Requirements The Minimum Requirements for stormwater development and redevelopment sites are listed in Section I-2.4 of Volume I of the SWMMWW. The proposed project creates and/or replaces more than 5,000 square-feet of new hard surface area; therefore, the proposed project must address Minimum Requirements #1 through #9. The Minimum Requirements have been addressed as follows: Minimum Requirement #1 – Preparation of Stormwater Site Plans Preliminary Drainage Plans have been prepared (see Appendix). Minimum Requirement #2 – Construction Stormwater Pollution Prevention (C- SWPP) A Construction Stormwater Pollution Prevention (C-SWPP) Plan will be provided with the final Drainage Report. Minimum Requirement #3 – Source Control of Pollution A Permanent Source Control Plan will be provided with the storm drainage maintenance agreement prior to final project approval. ________________________________________________________________________________ February 2024 Preliminary Drainage and Erosion Control Report 4 Minimum Requirement #4 – Preservation of Natural Drainage Systems and Outfalls There are no existing natural drainage systems or outfalls located on or near the subject parcel; therefore, this Minimum Requirement is not applicable. Minimum Requirement #5 – On-Site Stormwater Management This project will meet the LID Performance Standard. The proposed BMPs are as follows: Lawn and Landscape Areas: • All disturbed, roadside planter, stormwater dispersion, and individual lot lawn/landscape areas will contain soils meeting the Post-Construction Soil Quality and Depth (BMP T5.13) requirements. Roof Areas: • Stormwater runoff from the individual lot roof areas will be routed to downspout infiltration trenches (BMP T5.10A) for detention and 100% infiltration. These will be sized per prescriptive sizing methods at the time of building permit application. Other Hard Surface Areas: • Stormwater runoff from the new public roadways will be routed to a bioretention facility (BMP T7.30). • Stormwater runoff from the emergency vehicle turnaround area will be sheet flow dispersed (BMP T5.12) onto adjacent lawn/landscape areas with soils meeting BMP T5.13 requirements. • Stormwater runoff from the individual lot driveway, walkway, and patio areas will be sheet flow dispersed (BMP T5.12) onto adjacent lawn/landscape areas with soils meeting BMP T5.13 requirements. See Minimum Requirements #6 & #7 below and the drainage plans for additional information. Parcel Area: 5.279 ac Existing Development Coverage Land Coverage Table – Pre-Developed (Acres) Pasture 5.259 Gravel Drive 0.020 Total 5.279 ________________________________________________________________________________ February 2024 Preliminary Drainage and Erosion Control Report 5 Proposed Development Coverage Land Coverage Table – Post-Developed (Acres) Roadway1, 2 0.620 Sidewalks1, 2 0.083 Driveways (w/in ROW)1, 2 0.063 Lawn/Landscape (w/in ROW)2 0.196 Roof (assumed on lots)1 1.056 Driveways (assumed on lots)3,4 0.528 Misc. (walkway, patio) (assumed on lots)3,4 0.528 Lawn/Landscape (assumed on lots)3 1.491 Turnaround4 0.025 Lawn/Landscape Open Space Tract)3 0.597 Bioretention Pond 0.092 Total 5.279 1 “Non-effective” hard surface areas as these areas are being fully infiltrated. 2 Contributes to bioretention facility. 3 It has been assumed that each lot, on average, will have a total of 4,000 sf of hard surface coverage (2,000 sf roof, 1,000 sf driveway, 1,000 sf walkway/patios) and the remaining lot area will consist of lawn/landscape. 4 Hard surface areas to be sheet flow dispersed (BMP T5.12). Modeling Notes • When analyzing the difference in the pre- to post-developed runoff rate, the existing ground cover can be used. However, the entire area to be disturbed was modeled as “forest” in the pre-developed scenario for simplicity and for use in analyzing the Low Impact Development standard. • All lawn/landscape areas will meet the Post-Construction Soil Quality and Depth (BMP T5.13) requirements and have been modeled as “pasture” in WWHM. • Stormwater runoff from the individual lot lawn/landscape and dispersed driveway/walkway/patio areas have been routed to a Compost Amended Vegetated Filter Strip (CAVFS) in WWHM to help meet the flow control requirement. See Minimum Requirement #7 above for additional information. • Stormwater runoff from the emergency vehicle turnaround area will be sheet flow dispersed (BMP T5.12) and this area has been modeled as “lawn”. • The bioretention surface area in the model automatically receives rainfall; therefore, the area of the facility has been excluded from the lawn/landscape area. • Quality Geo and Parnell Engineering recommended long-term infiltration rates of 13.4”/hr and 20”/hr, respectively. A 12”/hr rate was used in WWHM for the bioretention facility subgrade. A 12”/hr rate, with a correction factor of 4, was used for the default bioretention soil mix. ________________________________________________________________________________ February 2024 Preliminary Drainage and Erosion Control Report 6 Minimum Requirement #6 – Runoff Treatment This project will create more than 5,000 square-feet of pollution-generating hard surface (PGHS) area; therefore, Runoff Treatment is required. Runoff Treatment Selections Step 1: There are no receiving waters. Step 2: Oil control is not applicable as the proposal is not a high-use site. Step 3: The native soil is not conducive for pollutant control as it does not meet the minimum 1% organic content and minimum 5 meq/100 gram CEC requirements. Step 4: Phosphorus control is not applicable as the project is not located within a watershed determined to be sensitive to phosphorus (e.g. 305(b) waters. Step 5: Enhanced treatment is not required as this project is a single-family residential project and the proposed roadways will have an AADT traffic count well below 7,500. Therefore, Basic Treatment is required. The proposed Bioretention Facility (BMP T7.30) meets both Basic and Enhanced Treatment. See Minimum Requirement #5 above for additional information. Minimum Requirement #7 – Flow Control This project will create more than 10,000 square-feet of “effective” hard surface area and convert more than ¾-acre into lawn/landscape area; therefore, Flow Control is applicable. Per WWHM, this project will meet the LID Performance Standard and Stream Duration requirements. Stormwater runoff from the individual lot lawn/landscape and dispersed driveway/walkway/patio areas have been routed to a Compost Amended Vegetated Filter Strip (CAVFS) in WWHM to help reduce the effective hard surface area and meet the Flow Control requirement. The entire lawn/landscape area on each building lot could be considered to be a CAVFS; however, only one half (32,474 sf) of the total lawn/landscape area (64,948 sf) has been assumed to be the CAVFS area in WWHM to be conservative. Per the WWHM user’s manual, “The CAVFS surface area automatically receives rainfall and produces evapotranspiration. Due to this model input the CAVFS surface area should be excluded from the basin element’s total surface area.”. Therefore, one-half of the total lawn/landscape area has been excluded from the basin area being routed to the CAFVS. In this situation, the CAVFS is intended to be a flow control facility with infiltration to the underlying soils. A 1”/hr infiltration rate was used in WWHM as recommended by Quality Geo NW for surface infiltration facilities. The bioretention facility will provide just over 2’ of freeboard. At a maximum ponding depth of 1’, the facility will draw down in 4 hours (1’x12”)/3”/hr = 4 hours). ________________________________________________________________________________ February 2024 Preliminary Drainage and Erosion Control Report 7 See Minimum Requirement #5 above for additional information along with the WWHM modeling results in the Appendix. Minimum Requirement #8 – Wetlands Protection There are no known wetlands located on-site or within the immediate vicinity; therefore, this Minimum Requirement is not applicable. Minimum Requirement #9 – Operation and Maintenance A storm drainage maintenance agreement, including a pollution source control plan, will be prepared and recorded prior to final project approval. Optional Guidance #1 – Financial Liability A Financial Guarantee will be provided prior to final project approval, if required. Optional Guidance #2 – Off-Site Analysis and Mitigation See Section 8 below. No downstream impacts are anticipated as a result of this project. Timing of the Project It is anticipated that site work construction will begin in winter/spring 2025 with substantial completion by spring/summer 2025. The timing of individual lot development (e.g. houses) is currently unknown. SECTION 2 – EXISTING SITE CONDITIONS Topography The subject parcels and surrounding areas are generally flat. A slight ridge runs east to west through the middle portion of the parcel and site topography generally slopes down from this ridge to the south, west, and north. The lowest elevation is in the southwest corner of the project site (proposed Bioretention Facility location). Ground Cover Site vegetation consists mainly of field grass with some brush. Drainage See drainage plan and Section 8 below. Soils The Natural Resources Conservation Service (NRCS) Soil Survey of Thurston County classifies the on-site soils as Spanaway Gravely Sandy Loam (HSG A). Per the Geotechnical Consultation report prepared by Quality Geo NW (see Appendix) the soils consist of topsoil overlying gravel with silt and sand to depths of 10’ below-grade. Per the Soils Report prepared by Parnell Engineering (see appendix), gravelly loam overlying an extremely gravelly and cobbled coarse-fine sand were encountered to 14.3’ below-grade. ________________________________________________________________________________ February 2024 Preliminary Drainage and Erosion Control Report 8 Seasonal groundwater was encountered in one test pit at 13.6’ below-grade per the Parnell Engineering soils report. This test pit was located in the lowest point of the site, in the southwest corner. The proposed bioretention facility bottom will be approximately 10.8’ above the seasonal high groundwater elevation. Quality Geo recommended a long-term infiltration rate of up to 13.4”/hr and Parnell Engineering recommended a long-term rate of up to 20”/hr be used. A 12”/hr design rate has been used for the proposed bioretention facility. Per the Quality Geo report, the CEC and organic content of the native soils do not meet the soil suitability criteria for infiltration treatment. Critical Areas There are no known critical areas (i.e. wetlands, landslide hazards, streams, etc.) located on-site or within the immediate vicinity of the site based on review of Thurston County critical areas maps and a site visit. The project is located within a Category I Critical Aquifer Recharge Area (CARA) and a 10-year time of travel zone of a wellhead protection area. Adjacent Areas The project site is bordered by single-family residential to the south, east, and west, and by recently developed apartment buildings to the north. Precipitation Records Precipitation data is included within the WWHM model. Reports and Studies Soils reports have been prepared by Quality Geo NW and Parnell Engineering (see Appendix). SECTION 3 – GEOTECHNICAL REPORT Soils reports have been prepared by Quality Geo NW and Parnell Engineering (see Appendix). SECTION 4 – WELLS AND SEPTIC SYSTEMS There are no known on-site wells or off-site wells within 200-feet of this project’s boundaries. SECTION 5 – FUEL TANKS No fuel tanks were located during a site inspection or during the soils evaluation work. Olympic Engineering reviewed the latest “LUST” list (Leaking Underground Storage Tank) and found no listing for the subject site. SECTION 6 – ANALYSIS OF THE 100-YEAR FLOOD According to FEMA FIRM #53067C0353F dated October 19, 2023, the project site and surrounding area are located in Zone X, an area of minimal flood hazard. SECTION 7 – AESTHETIC CONSIDERATIONS FOR FACILITIES The proposed Bioretention facility (BMP T7.30) will be landscaped. All disturbed pervious ________________________________________________________________________________ February 2024 Preliminary Drainage and Erosion Control Report 9 areas will be vegetated and/or landscaped and will contain soils that meet the Post- Construction Soil Quality and Depth (BMP T5.13) requirements. SECTION 8 – FACILITY SIZING AND OFF-SITE ANALYSIS See Minimum Requirement’s #5-#7 above for information regarding facility sizing. Off-Site Analysis Stormwater runoff generated from the new on-site improvements will be fully infiltrated and/or dispersed on-site. There does not appear to be any noticeable stormwater run-on from adjacent parcels. Due to site grades, and existing surrounding development (e.g. roadways, homes), the proposed bioretention facility does not have a means to provide for emergency overflow to a downstream release point. However, it has been designed to provide 2’ of freeboard. 2’ of freeboard provides an additional 2.7 times the storage volume available in the 1’ working depth of the pond and the side slopes in the freeboard area will have a slightly higher infiltration rate than the BSM; therefore, the pond has adequate capacity to accommodate premature failing/clogging. No downstream impacts, including impacts to structures, are anticipated as a result of this project. Based on the above, a quantitative off-site analysis or mitigation is not warranted. SECTION 9 – COVENANTS, DEDICATIONS, EASEMENTS No easements are required for the storm drainage system components. SECTION 10 – PROPERTY OWNERS ASSOCIATION ARTICLES OF INCORPORATION The property owner will be required to maintain the on-site stormwater systems. Appendix 1 Preliminary Drainage Plan PO B o x 1 2 6 9 0 Ol y m p i a , W A 9 8 5 0 8 36 0 . 7 0 5 . 2 4 7 4 Ww w . o l y e n g . c o m PO B o x 1 2 6 9 0 Ol y m p i a , W A 9 8 5 0 8 36 0 . 7 0 5 . 2 4 7 4 Ww w . o l y e n g . c o m · · · · · · · · · · · · · · · · · · · PO B o x 1 2 6 9 0 Ol y m p i a , W A 9 8 5 0 8 36 0 . 7 0 5 . 2 4 7 4 Ww w . o l y e n g . c o m Appendix 2 Preliminary Drainage Calculations WWHM2012 PROJECT REPORT 20046_020624 2/9/2024 2:11:24 PM Page 2 General Model Information WWHM2012 Project Name: 20046_020624 Site Name: Rainier Vista Site Address: 9910 Durant City:Yelm Report Date: 2/9/2024 Gage:Lake Lawrence Data Start: 1955/10/01 Data End: 2008/09/30 Timestep: 15 Minute Precip Scale: 0.857 Version Date: 2023/01/27 Version: 4.2.19 POC Thresholds Low Flow Threshold for POC1: 50 Percent of the 2 Year High Flow Threshold for POC1: 50 Year 20046_020624 2/9/2024 2:11:24 PM Page 3 Landuse Basin Data Predeveloped Land Use Basin 1 Bypass:No GroundWater:No Pervious Land Use acre A B, Forest, Flat 4.636 A B, Forest, Mod 0.623 Pervious Total 5.259 Impervious Land Use acre DRIVEWAYS FLAT 0.02 Impervious Total 0.02 Basin Total 5.279 20046_020624 2/9/2024 2:11:24 PM Page 4 Mitigated Land Use Durant Drive Bypass:No GroundWater:No Pervious Land Use acre A B, Pasture, Flat 0.196 Pervious Total 0.196 Impervious Land Use acre ROADS FLAT 0.62 DRIVEWAYS FLAT 0.063 SIDEWALKS FLAT 0.083 Impervious Total 0.766 Basin Total 0.962 20046_020624 2/9/2024 2:11:24 PM Page 5 Misc Bypass:Yes GroundWater:No Pervious Land Use acre A B, Pasture, Mod 0.35 A B, Lawn, Flat 0.025 A B, Pasture, Flat 0.247 Pervious Total 0.622 Impervious Land Use acre Impervious Total 0 Basin Total 0.622 20046_020624 2/9/2024 2:11:24 PM Page 6 Lots Bypass:No GroundWater:No Pervious Land Use acre A B, Pasture, Flat 0.746 Pervious Total 0.746 Impervious Land Use acre DRIVEWAYS FLAT 0.528 SIDEWALKS FLAT 0.528 Impervious Total 1.056 Basin Total 1.802 20046_020624 2/9/2024 2:11:24 PM Page 7 Routing Elements Predeveloped Routing 20046_020624 2/9/2024 2:11:24 PM Page 8 Mitigated Routing Bioretention Pond Bottom Length: 90.00 ft. Bottom Width: 35.00 ft. Material thickness of first layer: 1.5 Material type for first layer: SMMWW 12 in/hr Material thickness of second layer: 0 Material type for second layer: Sand Material thickness of third layer: 0 Material type for third layer: GRAVEL Infiltration On Infiltration rate:12 Infiltration safety factor:1 Wetted surface area On Total Volume Infiltrated (ac-ft.):141.235 Total Volume Through Riser (ac-ft.): 0 Total Volume Through Facility (ac-ft.): 141.235 Percent Infiltrated:100 Total Precip Applied to Facility:11.357 Total Evap From Facility:4.653 Underdrain not used Discharge Structure Riser Height:1 ft. Riser Diameter:6 in. Element Flows To: Outlet 1 Outlet 2 Bioretention Hydraulic Table Stage(feet) Area(ac.) Volume(ac-ft.) Discharge(cfs) Infilt(cfs) 0.0000 0.1000 0.0000 0.0000 0.0000 0.0495 0.0997 0.0016 0.0000 0.0000 0.0989 0.0987 0.0033 0.0000 0.0000 0.1484 0.0977 0.0050 0.0001 0.0001 0.1978 0.0968 0.0067 0.0015 0.0015 0.2473 0.0958 0.0084 0.0026 0.0026 0.2967 0.0949 0.0102 0.0042 0.0042 0.3462 0.0939 0.0119 0.0062 0.0062 0.3956 0.0930 0.0137 0.0087 0.0087 0.4451 0.0920 0.0155 0.0117 0.0117 0.4945 0.0911 0.0173 0.0154 0.0154 0.5440 0.0902 0.0192 0.0197 0.0197 0.5934 0.0892 0.0210 0.0247 0.0247 0.6429 0.0883 0.0229 0.0304 0.0304 0.6923 0.0874 0.0248 0.0369 0.0369 0.7418 0.0865 0.0267 0.0443 0.0443 0.7912 0.0855 0.0287 0.0526 0.0526 0.8407 0.0846 0.0307 0.0618 0.0618 0.8901 0.0837 0.0326 0.0719 0.0719 0.9396 0.0828 0.0347 0.0831 0.0831 0.9890 0.0819 0.0367 0.0954 0.0954 1.0385 0.0810 0.0387 0.1088 0.1088 1.0879 0.0801 0.0408 0.1234 0.1234 1.1374 0.0793 0.0429 0.1393 0.1393 1.1868 0.0784 0.0450 0.1564 0.1564 20046_020624 2/9/2024 2:11:24 PM Page 9 1.2363 0.0775 0.0471 0.1748 0.1748 1.2857 0.0766 0.0493 0.1947 0.1947 1.3352 0.0758 0.0515 0.2159 0.2159 1.3846 0.0749 0.0537 0.2386 0.2386 1.4341 0.0740 0.0559 0.2628 0.2628 1.4835 0.0732 0.0581 0.2884 0.2884 1.5000 0.0723 0.0589 0.5042 0.5042 Bioretention Hydraulic Table Stage(feet)Area(ac.)Volume(ac-ft.)Discharge(cfs)To Amended(cfs)Infilt(cfs) 1.5000 0.1000 0.0589 0.0000 0.2188 0.0118 1.5495 0.1010 0.0639 0.0000 0.2188 0.0237 1.5989 0.1020 0.0689 0.0000 0.2332 0.0356 1.6484 0.1029 0.0739 0.0000 0.2404 0.0475 1.6978 0.1039 0.0791 0.0000 0.2476 0.0595 1.7473 0.1049 0.0842 0.0000 0.2548 0.0716 1.7967 0.1059 0.0894 0.0000 0.2620 0.0837 1.8462 0.1069 0.0947 0.0000 0.2692 0.0959 1.8956 0.1079 0.1000 0.0000 0.2764 0.1081 1.9451 0.1089 0.1054 0.0000 0.2837 0.1203 1.9945 0.1099 0.1108 0.0000 0.2909 0.1326 2.0440 0.1110 0.1162 0.0000 0.2981 0.1449 2.0934 0.1120 0.1218 0.0000 0.3053 0.1573 2.1429 0.1130 0.1273 0.0000 0.3125 0.1698 2.1923 0.1140 0.1329 0.0000 0.3197 0.1823 2.2418 0.1151 0.1386 0.0000 0.3269 0.1948 2.2912 0.1161 0.1443 0.0000 0.3341 0.2074 2.3407 0.1171 0.1501 0.0000 0.3413 0.2201 2.3901 0.1182 0.1559 0.0000 0.3486 0.2328 2.4396 0.1192 0.1618 0.0000 0.3558 0.2455 2.4890 0.1203 0.1677 0.0000 0.3630 0.2583 2.5385 0.1213 0.1737 0.0000 0.3646 0.2711 2.5879 0.1224 0.1797 0.0000 0.3646 0.2840 2.6374 0.1235 0.1858 0.0000 0.3646 0.2969 2.6868 0.1245 0.1919 0.0000 0.3646 0.3099 2.7363 0.1256 0.1981 0.0000 0.3646 0.3230 2.7857 0.1267 0.2043 0.0000 0.3646 0.3360 2.8352 0.1278 0.2106 0.0000 0.3646 0.3492 2.8846 0.1289 0.2170 0.0000 0.3646 0.3624 2.9341 0.1299 0.2234 0.0000 0.3646 0.3756 2.9835 0.1310 0.2298 0.0000 0.3646 0.3889 3.0330 0.1321 0.2363 0.0000 0.3646 0.4022 3.0824 0.1332 0.2429 0.6009 0.3646 0.4156 3.1319 0.1343 0.2495 0.6259 0.3646 0.4290 3.1813 0.1355 0.2562 0.6499 0.3646 0.4425 3.2308 0.1366 0.2629 0.6731 0.3646 0.4560 3.2802 0.1377 0.2697 0.6955 0.3646 0.4695 3.3297 0.1388 0.2765 0.7172 0.3646 0.4832 3.3791 0.1399 0.2834 0.7383 0.3646 0.4968 3.4286 0.1411 0.2904 0.7588 0.3646 0.5106 3.4780 0.1422 0.2974 0.7787 0.3646 0.5243 3.5275 0.1433 0.3044 0.7982 0.3646 0.5381 3.5769 0.1445 0.3115 0.8171 0.3646 0.5520 3.6264 0.1456 0.3187 0.8357 0.3646 0.5659 3.6758 0.1468 0.3259 0.8538 0.3646 0.5799 3.7253 0.1479 0.3332 0.8716 0.3646 0.5939 3.7747 0.1491 0.3406 0.8890 0.3646 0.6079 3.8242 0.1502 0.3480 0.9061 0.3646 0.6221 20046_020624 2/9/2024 2:11:24 PM Page 10 3.8736 0.1514 0.3554 0.9229 0.3646 0.6362 3.9231 0.1526 0.3629 0.9393 0.3646 0.6504 3.9725 0.1538 0.3705 0.9555 0.3646 0.6647 4.0220 0.1549 0.3781 0.9714 0.3646 0.6790 4.0714 0.1561 0.3858 0.9871 0.3646 0.6933 4.1209 0.1573 0.3936 1.0025 0.3646 0.7077 4.1703 0.1585 0.4014 1.0177 0.3646 0.7222 4.2198 0.1597 0.4093 1.0326 0.3646 0.7367 4.2692 0.1609 0.4172 1.0473 0.3646 0.7512 4.3187 0.1621 0.4252 1.0619 0.3646 0.7658 4.3681 0.1633 0.4332 1.0762 0.3646 0.7805 4.4176 0.1645 0.4413 1.0904 0.3646 0.7952 4.4670 0.1657 0.4495 1.1043 0.3646 0.8050 4.5000 0.1665 0.4550 1.1181 0.3646 0.0000 20046_020624 2/9/2024 2:11:24 PM Page 11 Surface tention Pond 20046_020624 2/9/2024 2:11:24 PM Page 12 CAVFS CAVFS Length: 3247.00 ft. CAVFS Width:10.00 ft. Gravel thickness: 1 ft. Material thickness of CAVFS layer: 0.666 ft. Slope of CAVFS layer: 0.03 ft. Infiltration On Infiltration rate:1 Infiltration safety factor:1 Total Volume Infiltrated (ac-ft.):188.958 Total Volume Through Riser (ac-ft.): 0.006 Total Volume Through Facility (ac-ft.): 189.179 Percent Infiltrated:99.88 Total Precip Applied to Facility:9.59 Total Evap From Facility:5.816 Outlet Control Overflow Height: 0.5 ft. Overflow width: 1623.5 in. 20046_020624 2/9/2024 2:11:24 PM Page 13 CAVFS SurfaceFS 20046_020624 2/9/2024 2:11:24 PM Page 14 Analysis Results POC 1 + Predeveloped x Mitigated Predeveloped Landuse Totals for POC #1 Total Pervious Area: 5.259 Total Impervious Area: 0.02 Mitigated Landuse Totals for POC #1 Total Pervious Area: 1.564 Total Impervious Area: 1.822 Flow Frequency Method: Log Pearson Type III 17B Flow Frequency Return Periods for Predeveloped. POC #1 Return Period Flow(cfs) 2 year 0.015112 5 year 0.033886 10 year 0.054983 25 year 0.096732 50 year 0.143207 100 year 0.207671 Flow Frequency Return Periods for Mitigated. POC #1 Return Period Flow(cfs) 2 year 0.004102 5 year 0.015236 10 year 0.03205 25 year 0.074078 50 year 0.130493 100 year 0.220868 Annual Peaks 20046_020624 2/9/2024 2:12:26 PM Page 15 Annual Peaks for Predeveloped and Mitigated. POC #1 Year Predeveloped Mitigated 1956 0.034 0.009 1957 0.013 0.014 1958 0.010 0.005 1959 0.010 0.005 1960 0.012 0.003 1961 0.024 0.006 1962 0.008 0.001 1963 0.015 0.014 1964 0.011 0.003 1965 0.011 0.008 1966 0.008 0.001 1967 0.012 0.005 1968 0.008 0.001 1969 0.007 0.001 1970 0.009 0.002 1971 0.038 0.010 1972 0.064 0.018 1973 0.008 0.001 1974 0.019 0.005 1975 0.009 0.002 1976 0.010 0.003 1977 0.011 0.001 1978 0.012 0.008 1979 0.011 0.001 1980 0.009 0.002 1981 0.017 0.010 1982 0.015 0.007 1983 0.019 0.002 1984 0.009 0.003 1985 0.009 0.001 1986 0.014 0.010 1987 0.017 0.009 1988 0.007 0.001 1989 0.007 0.001 1990 0.052 0.086 1991 0.052 0.014 1992 0.008 0.001 1993 0.008 0.001 1994 0.009 0.002 1995 0.033 0.009 1996 0.076 0.016 1997 0.051 0.016 1998 0.020 0.024 1999 0.009 0.001 2000 0.009 0.002 2001 0.011 0.001 2002 0.032 0.007 2003 0.007 0.001 2004 0.297 0.200 2005 0.067 0.273 2006 0.212 0.055 2007 0.096 0.029 2008 0.013 0.009 Ranked Annual Peaks Ranked Annual Peaks for Predeveloped and Mitigated. POC #1 20046_020624 2/9/2024 2:12:26 PM Page 16 Rank Predeveloped Mitigated 1 0.2973 0.2733 2 0.2116 0.1998 3 0.0957 0.0859 4 0.0761 0.0554 5 0.0672 0.0291 6 0.0636 0.0245 7 0.0519 0.0179 8 0.0516 0.0163 9 0.0509 0.0159 10 0.0381 0.0143 11 0.0338 0.0142 12 0.0328 0.0138 13 0.0324 0.0101 14 0.0238 0.0099 15 0.0199 0.0097 16 0.0193 0.0093 17 0.0190 0.0091 18 0.0170 0.0089 19 0.0168 0.0088 20 0.0155 0.0081 21 0.0153 0.0075 22 0.0145 0.0073 23 0.0129 0.0067 24 0.0127 0.0060 25 0.0124 0.0055 26 0.0116 0.0050 27 0.0116 0.0047 28 0.0112 0.0047 29 0.0112 0.0031 30 0.0109 0.0031 31 0.0106 0.0030 32 0.0106 0.0026 33 0.0103 0.0025 34 0.0102 0.0025 35 0.0096 0.0021 36 0.0094 0.0019 37 0.0092 0.0017 38 0.0091 0.0016 39 0.0090 0.0015 40 0.0087 0.0014 41 0.0087 0.0011 42 0.0086 0.0011 43 0.0085 0.0008 44 0.0085 0.0008 45 0.0082 0.0008 46 0.0082 0.0008 47 0.0081 0.0008 48 0.0081 0.0007 49 0.0079 0.0007 50 0.0075 0.0007 51 0.0072 0.0006 52 0.0068 0.0006 53 0.0067 0.0006 20046_020624 2/9/2024 2:12:26 PM Page 17 LID Duration Flows The Facility PASSED Flow(cfs) Predev Mit Percentage Pass/Fail 0.0012 53412 548 1 Pass 0.0013 50290 519 1 Pass 0.0013 47577 499 1 Pass 0.0014 45068 476 1 Pass 0.0015 42652 448 1 Pass 0.0015 40496 423 1 Pass 0.0016 38452 402 1 Pass 0.0017 36482 389 1 Pass 0.0017 34623 374 1 Pass 0.0018 32969 363 1 Pass 0.0019 31352 351 1 Pass 0.0019 29773 336 1 Pass 0.0020 28416 322 1 Pass 0.0020 27115 305 1 Pass 0.0021 25870 297 1 Pass 0.0022 24718 282 1 Pass 0.0022 23584 273 1 Pass 0.0023 22525 262 1 Pass 0.0024 21540 257 1 Pass 0.0024 20610 252 1 Pass 0.0025 19663 243 1 Pass 0.0026 18826 235 1 Pass 0.0026 18046 229 1 Pass 0.0027 17274 225 1 Pass 0.0027 16494 222 1 Pass 0.0028 15804 208 1 Pass 0.0029 15145 206 1 Pass 0.0029 14468 199 1 Pass 0.0030 13795 188 1 Pass 0.0031 13150 184 1 Pass 0.0031 12561 177 1 Pass 0.0032 12004 174 1 Pass 0.0033 11521 172 1 Pass 0.0033 10980 169 1 Pass 0.0034 10502 165 1 Pass 0.0035 10028 161 1 Pass 0.0035 9593 155 1 Pass 0.0036 9131 154 1 Pass 0.0036 8712 149 1 Pass 0.0037 8300 146 1 Pass 0.0038 7887 142 1 Pass 0.0038 7527 138 1 Pass 0.0039 7172 134 1 Pass 0.0040 6826 128 1 Pass 0.0040 6523 125 1 Pass 0.0041 6187 125 2 Pass 0.0042 5888 122 2 Pass 0.0042 5596 121 2 Pass 0.0043 5311 120 2 Pass 0.0044 5057 119 2 Pass 0.0044 4795 114 2 Pass 0.0045 4572 109 2 Pass 0.0045 4356 107 2 Pass 20046_020624 2/9/2024 2:12:26 PM Page 18 0.0046 4161 105 2 Pass 0.0047 3940 104 2 Pass 0.0047 3741 100 2 Pass 0.0048 3553 96 2 Pass 0.0049 3382 93 2 Pass 0.0049 3221 93 2 Pass 0.0050 3063 89 2 Pass 0.0051 2901 87 2 Pass 0.0051 2782 85 3 Pass 0.0052 2637 84 3 Pass 0.0052 2496 84 3 Pass 0.0053 2394 81 3 Pass 0.0054 2284 78 3 Pass 0.0054 2184 78 3 Pass 0.0055 2087 75 3 Pass 0.0056 1992 74 3 Pass 0.0056 1905 74 3 Pass 0.0057 1822 73 4 Pass 0.0058 1741 72 4 Pass 0.0058 1682 72 4 Pass 0.0059 1605 72 4 Pass 0.0060 1540 71 4 Pass 0.0060 1472 70 4 Pass 0.0061 1414 70 4 Pass 0.0061 1361 68 4 Pass 0.0062 1292 68 5 Pass 0.0063 1236 68 5 Pass 0.0063 1172 68 5 Pass 0.0064 1112 67 6 Pass 0.0065 1067 65 6 Pass 0.0065 1020 65 6 Pass 0.0066 981 65 6 Pass 0.0067 939 65 6 Pass 0.0067 900 63 7 Pass 0.0068 849 63 7 Pass 0.0069 819 62 7 Pass 0.0069 778 61 7 Pass 0.0070 744 60 8 Pass 0.0070 719 60 8 Pass 0.0071 689 59 8 Pass 0.0072 667 59 8 Pass 0.0072 640 58 9 Pass 0.0073 620 56 9 Pass 0.0074 598 55 9 Pass 0.0074 577 55 9 Pass 0.0075 559 55 9 Pass 0.0076 541 53 9 Pass 20046_020624 2/9/2024 2:12:44 PM Page 19 Duration Flows The Facility PASSED Flow(cfs) Predev Mit Percentage Pass/Fail 0.0076 541 53 9 Pass 0.0089 294 39 13 Pass 0.0103 183 28 15 Pass 0.0117 132 26 19 Pass 0.0130 103 24 23 Pass 0.0144 88 16 18 Pass 0.0158 73 13 17 Pass 0.0171 59 10 16 Pass 0.0185 52 8 15 Pass 0.0199 44 8 18 Pass 0.0213 39 7 17 Pass 0.0226 38 7 18 Pass 0.0240 36 7 19 Pass 0.0254 34 6 17 Pass 0.0267 33 6 18 Pass 0.0281 31 6 19 Pass 0.0295 29 5 17 Pass 0.0308 28 5 17 Pass 0.0322 27 5 18 Pass 0.0336 22 5 22 Pass 0.0350 20 4 20 Pass 0.0363 20 4 20 Pass 0.0377 20 4 20 Pass 0.0391 18 4 22 Pass 0.0404 15 4 26 Pass 0.0418 15 4 26 Pass 0.0432 15 4 26 Pass 0.0446 13 4 30 Pass 0.0459 10 4 40 Pass 0.0473 10 4 40 Pass 0.0487 10 4 40 Pass 0.0500 10 4 40 Pass 0.0514 9 4 44 Pass 0.0528 7 4 57 Pass 0.0541 6 4 66 Pass 0.0555 6 3 50 Pass 0.0569 6 3 50 Pass 0.0583 6 3 50 Pass 0.0596 6 3 50 Pass 0.0610 6 3 50 Pass 0.0624 6 3 50 Pass 0.0637 5 3 60 Pass 0.0651 5 3 60 Pass 0.0665 5 3 60 Pass 0.0678 4 3 75 Pass 0.0692 4 3 75 Pass 0.0706 4 3 75 Pass 0.0720 4 3 75 Pass 0.0733 4 3 75 Pass 0.0747 4 3 75 Pass 0.0761 3 3 100 Pass 0.0774 3 3 100 Pass 0.0788 3 3 100 Pass 20046_020624 2/9/2024 2:12:44 PM Page 20 0.0802 3 3 100 Pass 0.0815 3 3 100 Pass 0.0829 3 3 100 Pass 0.0843 3 3 100 Pass 0.0857 3 3 100 Pass 0.0870 3 2 66 Pass 0.0884 3 2 66 Pass 0.0898 3 2 66 Pass 0.0911 3 2 66 Pass 0.0925 3 2 66 Pass 0.0939 3 2 66 Pass 0.0952 3 2 66 Pass 0.0966 2 2 100 Pass 0.0980 2 2 100 Pass 0.0994 2 2 100 Pass 0.1007 2 2 100 Pass 0.1021 2 2 100 Pass 0.1035 2 2 100 Pass 0.1048 2 2 100 Pass 0.1062 2 2 100 Pass 0.1076 2 2 100 Pass 0.1090 2 2 100 Pass 0.1103 2 2 100 Pass 0.1117 2 2 100 Pass 0.1131 2 2 100 Pass 0.1144 2 2 100 Pass 0.1158 2 2 100 Pass 0.1172 2 2 100 Pass 0.1185 2 2 100 Pass 0.1199 2 2 100 Pass 0.1213 2 2 100 Pass 0.1227 2 2 100 Pass 0.1240 2 2 100 Pass 0.1254 2 2 100 Pass 0.1268 2 2 100 Pass 0.1281 2 2 100 Pass 0.1295 2 2 100 Pass 0.1309 2 2 100 Pass 0.1322 2 2 100 Pass 0.1336 2 2 100 Pass 0.1350 2 2 100 Pass 0.1364 2 2 100 Pass 0.1377 2 2 100 Pass 0.1391 2 2 100 Pass 0.1405 2 2 100 Pass 0.1418 2 2 100 Pass 0.1432 2 2 100 Pass 20046_020624 2/9/2024 2:12:44 PM Page 21 Water Quality Water Quality BMP Flow and Volume for POC #1 On-line facility volume: 0 acre-feet On-line facility target flow: 0 cfs. Adjusted for 15 min: 0 cfs. Off-line facility target flow: 0 cfs. Adjusted for 15 min: 0 cfs. 20046_020624 2/9/2024 2:12:44 PM Page 22 LID Report 20046_020624 2/9/2024 2:13:04 PM Page 23 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. 20046_020624 2/9/2024 2:13:04 PM Page 24 Appendix Predeveloped Schematic 20046_020624 2/9/2024 2:13:05 PM Page 25 Mitigated Schematic Appendix 3 Soils Reports Quality Geo NW, PLLC Serving All of Washington & Oregon | Geotechnical Investigations & Engineering Consultation Phone: 360-878-9705| Web: qualitygeonw.com | Mail: 4631 Whitman Ln SE, Ste D, Lacey, WA 98513 11/13/2023 C&E Development, LLC Attn: Eric Peterson Subject: Durant St SE - Geotechnical Consultation 9910 Durant St SE, Yelm, WA QG Project No.: QG23-187 Dear Client, At your request, Quality Geo NW, PLLC (QG) has completed a soils investigation of the above- referenced project. The investigation was performed in accordance with our proposal for professional services. We would be pleased to continue our role as your geotechnical consultant of record during the project planning and construction phases, as local inspection firms have not been found to be as familiar or reliably experienced with geotechnical design. This may include soil subgrade inspections, periodic review of special inspection reports, or supplemental recommendations if changes occur during construction. We will happily meet with you at your convenience to discuss these and other additional Time & Materials services. We thank you for the opportunity to be of service on this project and trust this report satisfies your project needs currently. QG wishes you the best while completing the project. Respectfully Submitted, Quality Geo NW, PLLC Luke Preston McCann, L.E.G. Ray Gean II Owner + Principal Staff Geologist/Project Manager Durant St. Geo Quality Geo NW, PLLC 11/13/2023 Project # QG23-187 2 SOILS REPORT DURANT ST GEO 9910 DURANT ST. SE YELM, WA C&E Development, LLC Attn: Eric Peterson Prepared by: Approved by: Ray Gean II Luke Preston McCann, L.E.G. Staff Geologist/Project Manager Principal Licensed Engineering Geologist Quality Geo NW, PLLC Geotechnical Investigation & Engineering Consultation Phone: 360-878-9750| Web: qualitygeonw.com Mail: 4631 Whitman Ln SE, Ste D, Lacey, WA 98513 11/13/2023 QG Project # QG23-187 Copyright © 2023 Quality Geo NW, PLLC All Rights Reserved 11/13/2023 Durant St. Geo Quality Geo NW, PLLC 11/13/2023 Project # QG23-187 3 TABLE OF CONTENTS 1.0 INTRODUCTION ...............................................................................................................4 1.1 PROJECT DESCRIPTION ............................................................................................................................. 4 1.2 FIELD WORK ................................................................................................................................................ 4 2.0 EXISTING SITE CONDITIONS ........................................................................................5 2.1 AREA GEOLOGY .......................................................................................................................................... 5 2.2 SITE & SURFACE CONDITIONS ................................................................................................................ 5 2.3 SOIL LOG ....................................................................................................................................................... 5 SURFACE WATER AND GROUNDWATER CONDITIONS ............................................................................... 6 3.0 GEOTECHNICAL RECOMMENDATIONS .....................................................................7 3.1 SHALLOW FOUNDATION RECOMMENDATIONS ................................................................................. 7 3.1.1 BUILDING SLAB ON GRADE FLOOR ............................................................................................. 8 3.2 INFILTRATION RATE DETERMINATION ................................................................................................ 9 3.2.1 GRADATION ANALYSIS METHODS & RESULTS ......................................................................... 9 3.2.2 TREATMENT POTENTIAL .............................................................................................................. 11 3.2.3 DRAINAGE RECOMMENDATIONS ............................................................................................... 11 3.3 LATERAL SOIL & CONCRETE FOUNDATION CONSIDERATIONS ............................................ 11 3.4 SEISMIC DESIGN PARAMETERS AND LIQUEFACTION ............................................................... 12 4.0 CONSTRUCTION RECOMMENDATIONS ...................................................................14 4.1 EARTHWORK ............................................................................................................................................. 14 4.1.1 GRADING & EXCAVATION ............................................................................................................ 14 4.1.2 SUBGRADE EVALUATION & PREPARATION ............................................................................ 14 4.1.3 SITE PREPARATION, EROSION CONTROLL, WET WEATHER............................................... 14 4.2 STRUCTURAL FILL MATERIALS AND COMPACTION ....................................................................... 15 4.2.1 MATERIALS ...................................................................................................................................... 15 4.2.2 FILL PLACEMENT AND COMPACTION ...................................................................................... 16 4.3 TEMPORARY EXCAVATIONS AND TRENCHES .................................................................................. 16 5.0 SPECIAL INSPECTION ...................................................................................................18 6.0 LIMITATIONS ..................................................................................................................19 Region & Vicinity Maps ................................................................................................................ 20 Exploration Map ............................................................................................................................. 21 Exploration Logs ............................................................................................................................ 22 Laboratory Results ......................................................................................................................... 28 Durant St. Geo Quality Geo NW, PLLC 11/13/2023 Project # QG23-187 4 1.0 INTRODUCTION This report presents the findings and recommendations of Quality Geo NW’s (QG) soil investigation conducted in support of new site surface improvements. 1.1 PROJECT DESCRIPTION QG understands the project entails new construction within a presently undeveloped parcel. QG has been contracted to perform a soils investigation of the proposed site to provide stormwater and earthwork recommendations. 1.2 FIELD WORK Site exploration activities were performed on 10/5/2023. Exploration locations were marked in the field by a QG Staff Geologist with respect to the provided map and cleared for public conductible utilities. Our exploration location was selected by an QG Project Geologist prior to field work to provide safest access to relevant soil conditions. The geologist directed the advancement of 6 excavated test pit (TP). The test pit was advanced within the vicinity of the anticipated development footprint areas, to a maximum depth of 10 feet below present grade in general accordance with equipment capabilities and specified contract depth. During the exploration QG logged each soil horizon that was encountered, and field classified them in accordance with the Unified Soil Classification System (USCS). Representative soil samples were collected from each unit, identified according to boring location and depth, placed in plastic bags to protect against moisture loss, and were transported to the office for supplemental classification and laboratory tests. Durant St. Geo Quality Geo NW, PLLC 11/13/2023 Project # QG23-187 5 2.0 EXISTING SITE CONDITIONS 2.1 AREA GEOLOGY The Washington Geologic Information Portal (WGIP) maintained by the Department of Natural Resources Division of Geology and Earth Resources provides 1:100,000-scale geologic mapping of the region. The subject site is mapped as continental glacial drift deposits (Qgog). The unit is described as, “Recessional and proglacial, stratified pebble, cobble, and boulder gravel deposited in meltwater streams and their deltas; locally contains ice-contact deposits.” The WGIP Map also offers layers of mapped geohazard conditions within the state. According to the regional-scale interactive map, no known geohazards are mapped for the site. The United States Department of Agriculture portal (USDA) provides a soil mapping of the region. The soils on site are mapped as Spanaway Gravelly Sandy loam (110,111), which is formed as terraces and outwash plains derived from volcanic ash over gravelly outwash deposits. The deposits are described as gravelly sandy loam from 0 to 15 inches, very gravelly loam from 15 to 20 inches, and extremely gravelly sand from 20 to 60 inches. Depth to restrictive feature is more than 80 inches. Capacity of the most limiting layer to transmit water (Ksat) is high (01.98 to 5.95 in/hr). Depth to water table is more than 80 inches. 2.2 SITE & SURFACE CONDITIONS The site is rectangular in shape and flat, at about the same elevation as the adjacent road. It is vegetated with grasses and small shrubs, with some mature trees. The site is currently undeveloped. There is no surface water on site. 2.3 SOIL LOG Site soil conditions were generally consistent across the property. Representative lab samples were collected from TP-1and TP-2. Soil conditions on site were as follows: • 0’ to 0.5’ – Topsoil: A layer of light brown topsoil overrides the site. This soil is loose and moist, with a high organic content and no cobbles. • 0.5’ to 8.0’ – Poorly Graded Gravel with Silt and Sand (GP-GM) Beneath the topsoil is a layer of tan poorly graded gravel with silt and sand layer. This layer is medium dense to dense and contains no organic content and cobbles measuring up to 12 inches. There is no evidence of oxidation throughout the layer in the form of mottling. Durant St. Geo Quality Geo NW, PLLC 11/13/2023 Project # QG23-187 6 SURFACE WATER AND GROUNDWATER CONDITIONS No active surface water features are present on site. In the near vicinity, Thompson Creek is located approximately 2200 feet west of the parcel. Based on well logs made publicly available by the WA Department of Ecology, the groundwater table is reported to exist at approximately 35 feet beneath the entire site. QG’s scope of work did not include determination or monitoring of seasonal groundwater elevation variations, formal documentation of wet season site conditions, or conclusive measurement of groundwater elevations at depths past the extent feasible for explorations at the time of the field explorations. Durant St. Geo Quality Geo NW, PLLC 11/13/2023 Project # QG23-187 7 3.0 GEOTECHNICAL RECOMMENDATIONS 3.1 SHALLOW FOUNDATION RECOMMENDATIONS Assuming site preparation is completed as described above, we recommend the following: • Subgrade Preparation QG recommends excavating and clearing any loose or organic cover soils, including the overriding layer of topsoil where necessary, from areas of proposed pavement construction, down to firm bearing conditions and benching the final bottom of subgrade elevation flat. Excavations should be performed with a smooth blade bucket to limit disturbance of subgrade soils. Vibratory compaction methods are suitable for densification of the non-organic native soils. After excavations have been completed to the planned subgrade elevations, but before placing fill or structural elements, the exposed subgrade should be evaluated under the periodic guidance of a QG representative. Any areas that are identified as being soft or yielding during subgrade evaluation should be brought to the attention of the geotechnical engineer. Where over excavation is performed below a structure, the over excavation area should extend beyond the outside of the footing a distance equal to the depth of the over excavation below the footing. The over-excavated areas should be backfilled with properly compacted structural fill. The proposed buildings may utilize either stepped or continuous footings with slab-on-grade elements. For continuous footing elements, upon reaching bearing strata, we recommend benching foundation lines flat. Continuous perimeter and strip foundations may be stepped as needed to accommodate variations in final subgrade level. We also recommend maximum steps of 18 inches with spacing of at least 5 feet be constructed unless specified otherwise by the design engineer. Structural fill may then be placed as needed to reestablish final foundation grade. • Allowable Bearing Capacity: Up to 1,500 pounds per square foot (psf) for foundations placed on compacted native soil or approved structural fill soils placed in accordance with the recommendations of Section 4.2. Bearing capacities, at or below 1,500 psf may eliminate the need for additional inspection requirements if approved by the county. The allowable bearing capacity may be increased by 1/3 for transient loading due to wind and seismic events. • Minimum Footing Depth: For a shallow perimeter and spread footing system, all exterior footings shall be embedded a minimum of 18 inches and all interior footings shall be embedded a minimum of 12 inches Durant St. Geo Quality Geo NW, PLLC 11/13/2023 Project # QG23-187 8 below the lowest adjacent finished grade, but not less than the depth required by design. However, all footings must also penetrate to the prescribed bearing stratum cited above. Minimum depths are referenced per IBC requirements for frost protection; other design concerns may dictate greater values be applied. • Minimum Footing Width: Footings should be proportioned to meet the stated bearing capacity and/or the IBC 2018 (or current) minimum requirements. For a shallow perimeter and spread footing system, continuous strip footings should be a minimum of 16 inches wide and interior or isolated column footings should be a minimum of 24 inches wide. • Estimated Settlements: All concrete settles after placement. We estimate that the maximum settlements will be on the order of 0.5 inch, or less, with a differential settlement of ½ inch, or less, over 50 linear feet. Settlement is anticipated to occur soon after the load is applied during construction. 3.1.1 BUILDING SLAB ON GRADE FLOOR QG anticipates that slab-on-grade floors are planned for the interior of the proposed building. Based on typical construction practices, we assume finished slab grade will be similar to or marginally above present grade for the below recommendations. If floor grades are planned to be substantially raised or lowered from existing grade, QG should be contacted to provide revised or alternative recommendations. • Capillary Break: A capillary break will be helpful to maintain a dry slab floor and reduce the potential for floor damage resulting from shallow perched water inundation. To provide a capillary moisture break, a 6-inch thick, properly compacted granular mat consisting of open-graded, free- draining angular aggregate is recommended below floor slabs. To provide additional slab structural support, or to substitute for a structural fill base pad where specified, QG recommends the capillary break should consist of crushed rock all passing the 1-inch sieve and no more than 3 percent (by weight) passing the U.S. No. #4 sieve, compacted in accordance with Section 5.2.2 of this report. • Vapor Barrier: A vapor retarding membrane such as 10 mil polyethylene film should be placed beneath all floor slabs to prevent transmission of moisture where floor coverings may be affected. Care should be taken during construction not to puncture or damage the membrane. To protect the membrane, a layer of sand no more than 2 inches thick may be placed over the membrane if Durant St. Geo Quality Geo NW, PLLC 11/13/2023 Project # QG23-187 9 desired. If excessive relict organic fill material is discovered at any location, additional sealant or more industrial gas barriers may be required to prevent off-gassing of decaying material from infiltrating the new structure. These measures shall be determined by the structural engineer to meet local code requirements as necessary. • Structural Design Considerations: QG assumes the design and specifications of slabs will be assessed by the project design engineer. We suggest a minimum unreinforced concrete structural section of 4.0 inches be considered to help protect against cracking and localized settlement, especially where larger equipment or localized loads are anticipated. It is generally recommended that any floor slabs and annular exterior concrete paving subject to vehicular loading be designed to incorporate reinforcing. Additionally, some level of reinforcing, such as a wire mesh may be desirable to prolong slab life due to the overwhelming presence of such poor underlying soils. It should be noted that QG does not express any guarantee or warranty for proposed slab sections. 3.2 INFILTRATION RATE DETERMINATION QG understands the design of on-site stormwater controls are pending the results of this study to confirm design parameters and interpreted depths to perched seasonal groundwater and restrictive soil features. 3.2.1 GRADATION ANALYSIS METHODS & RESULTS During test pit excavations for general site investigation, QG additionally collected representative samples of native soil deposits among potential infiltration strata and depths. Representative soil samples were selected from TP-1 and TP-2 to characterize the local infiltration conditions. We understand the project will be subject to infiltration design based on the Washington Department of Ecology Stormwater Management Manual for Western Washington (DoE SMMWW). For initial site infiltration characterization within the scope of this study, laboratory gradation analyses were completed including sieve and hydrometer tests for stormwater design characterization and rate determination to supplement field observations. Results of laboratory testing in terms of rate calculation are summarized below. Laboratory results were interpreted to recommended design inputs in accordance with methods of the City of Lacey 2022 Stormwater Design Manual. Gradation results were applied to the Massmann (2003) equation (1) to calculate Ksat representing the initial saturated hydraulic conductivity. Durant St. Geo Quality Geo NW, PLLC 11/13/2023 Project # QG23-187 10 (1) log10(Ksat) = -1.57 + 1.90*D10 + 0.015*D60 - 0.013*D90 - 2.08*ff Corrected Ksat values presented below are a product of the initial Ksat and correction factor CFT. For a generalized site-wide design situation, we have applied a site variability factor of CFv = 0.7 along with typical values of CFt = 0.4 (for the Grain Size Method) and CFm = 0.9 (assuming standard influent control). (2) CFT = CFv x CFt x CFm = 0.7 x 0.4 x 0.9 = 0.25 Results were cross-referenced with test pit logs to determine the validity and suitability of unique materials as an infiltration receptor. Additional reduction factors were applied for practical rate determination based on our professional judgement. Table 1. Results Of Massmann Analysis TP # Sample Depth (BPG) Unit Extent (ft) Soil Type D10 D60 D90 Fines (%) Ksat (in/hr) CorrectedKsat (in/hr) LT Design Infiltration Rate(in/hr) Cation Exchange Capacity (meq/100g) Organic Content % 1 4.0ft 0.5 to 8.0 GP-GM 0.392 15.61 27.96 5.7 119.78 29.94 20.0 5.6 1.3 2 6.0ft 1.5 to 10.0 GP 0.303 10.97 38.05 4.7 53.62 13.4 13.4 3.4 0.9 In-ground infiltration structures are required to maintain a minimum of 5-feet separation from restrictive soil & perched water features. During QG’s field investigation no groundwater was encountered. Available well logs do not indicate the potential for shallow groundwater. The required separation appears to be achievable across the site. At this time, QG does not recommend mounding analysis due to the generally suitable site conditions. For in-ground infiltration galleries, we recommend a maximum design rate of up to 13.4 inches/hour be considered. For any shallow infiltration features such as rain gardens, pervious pavement or swales, we recommend the designer consider a reduced rate of 1.0 inches per hour which is typically suitable and considers potential reductions from compaction during construction. QG recommends the facility designer review these results and stated assumptions per reference literature to ensure applicability with the proposed development, level of anticipated controls, and long- term maintenance plan. The designer may make reasonable adjustments to correction factors and the resulting design values based on these criteria to ensure design and operational intent is met. We recommend that we be contacted if substantial changes to rate determination are considered. Durant St. Geo Quality Geo NW, PLLC 11/13/2023 Project # QG23-187 11 3.2.2 TREATMENT POTENTIAL Depending on stormwater and runoff sources, some stormwater features, such as rain gardens or pervious pavements may require treatment. Stormwater facilities utilizing native soils as treatment media typically require Cation Exchange Capacities (CEC) of greater than 5 milliequivalents per 100grams (meq/100g) and organic contents greater than 1% (this may vary depending on local code). The GP-GM soils across the site do meet these requirements. However, the GP soils across the site do not meet the minimum requirements. 3.2.3 DRAINAGE RECOMMENDATIONS QG recommends proper drainage controls for stormwater runoff during and after site development to protect the site. The ground surface adjacent to structures should be sloped to drain away at a 5% minimum to prevent ponding of water adjacent to them. Foundations shall incorporate a wraparound footing drain composed of imported clean granular drain rock. There shall be a perforated drainpipe connected around the perimeter of the footing drain (within the rock) graded to gravity drain to an outfall pipe, to allow any accumulated water to be released to an approved drainage feature or location. The outfall point must be lower in elevation than the lowest point of possible water accumulation in the mat fill, so as to allow any captured water within the mat or crawlspace to completely drain away from the building footprint preventing standing water from accumulating. QG recommends all stormwater catchments (new or existing) be tightlined (piped) away from structures to an existing catch basin, stormwater system, established channel, or approved outfall to be released using appropriate energy-dissipating features at the outfall to minimize point erosion. Roof and footing drains should be tightlined separately or should be gathered in an appropriately sized catch basin structure and redistributed collectively. If storm drains are incorporated for impervious flatworks (driveways, sidewalks, etc.) collected water should also be discharged according to the above recommendations. 3.3 LATERAL SOIL & CONCRETE FOUNDATION CONSIDERATIONS The results of QG’s investigation indicate shallow and deep subsurface conditions at the proposed building area consist of generally medium dense to dense silty gravel with sand overlying medium dense to dense silty sand with gravel, and other deposits of variable composition. The finished grade is assumed to be similar to the existing grade. QG understands that the building structures may likely incorporate continuous perimeter grade beams as well as isolated footings, incorporating soil amendment, and underpinning as determined by the structural design team. For lateral support of these structures, the following soil parameters should be considered regarding Durant St. Geo Quality Geo NW, PLLC 11/13/2023 Project # QG23-187 12 any structural fill against these features (ignoring the upper 18 inches, due to freeze/thaw softening, unless covered in concrete or asphalt). Table 2. Lateral Earth Pressures Soil Type Active Pressure (PSF*H) At-Rest Pressure (PSF*H) Seismic Surcharge (PSF*H) Grade Beam Passive Equivalent Fluid Weight (PCF) Grade Beam Coefficient of Friction Existing GM Soils 40 60 12 203** 0.35* New Structural Fill 35 55 10 200** 0.35* * Factor of Safety: 1.5 ** Factor of Safety: 2.0 All concrete foundation elements shall be separated from the native soil with a minimum 12-inch section of approved, imported, granular, structural fill per the requirements of Section 4.2 Structural Fill Materials And Compaction. To ensure adequate friction, no fabric shall be placed between the structural fill and native soils when placed under primary building foundations & grade beams. The proposed buildings may utilize continuous grade beams with slab-on-grade, where appropriate, depending on the chosen development style. For continuous footing elements, upon reaching bearing strata, we recommend benching foundation lines flat. 3.4 SEISMIC DESIGN PARAMETERS AND LIQUEFACTION According to the Liquefaction Susceptibility Map of Seismic Design Maps Portal, the site is identified as having a very low susceptibility. This is generally consistent with the findings of QG’s investigation to date. Liquefaction is a phenomenon typically associated with a subsurface profile of relatively loose, cohesionless soils saturated by groundwater. Under seismic shaking the pore pressure can exceed the soil’s shear resistance and the soil ‘liquefies’, which may result in excessive differential settlements that are damaging to structures and disruptive to exterior improvements. The Washington Interactive Geologic Map - Seismic Site Class Map classifies the project regional vicinity as Site Class C. As is common for Washington, we have concurrently identified the site as Site Class D. The USGS Seismic Design Map Tool was used to determine seismic design coefficients and spectral response accelerations assuming Site Class D, representing a generally stiff soil profile. Parameters in Table 5 were calculated using 2008 USGS hazard data and ASCE 7-16 was referenced for site Peak Ground Acceleration. Durant St. Geo Quality Geo NW, PLLC 11/13/2023 Project # QG23-187 13 Table 3. Seismic Design Parameters Seismic Design Category D D D-Default Reference ASCE 7-10 ASCE 7-16 ASCE 7-16 Risk Category II II II MCER ground motion (period=0.2s) SS 1.251 1.292 1.292 MCER ground motion (period=1.0s) S1 0.499 0.467 0.467 Site-modified spectral acceleration value SMS 1.251 1.292 1.55 Site-modified spectral acceleration value SM1 0.749 NULL NULL Numeric seismic design value at 0.2s SA SDS 0.834 0.861 1.034 Numeric seismic design value at 1.0s SA SD1 0.499 NULL NULL Site amplification factor at 0.2s Fa 1.0 1.0 1.2 Site amplification factor at 1.0s Fv 1.5 NULL NULL Site modified peak ground acceleration PGAM 0.5 0.567 0.618 Based on the findings of this study, the site is generally considered to have a low risk of liquefaction-induced settlement. Durant St. Geo Quality Geo NW, PLLC 11/13/2023 Project # QG23-187 14 4.0 CONSTRUCTION RECOMMENDATIONS 4.1 EARTHWORK 4.1.1 GRADING & EXCAVATION A grading plan was not available to QG at the time of this report. However, based on provided conceptual plans, this study assumes finished site grade will approximate current grade. Therefore, depths referred to in this report are considered roughly equivalent to final depths. Excavations can generally be performed with conventional earthmoving equipment such as bulldozers, scrapers, and excavators. 4.1.2 SUBGRADE EVALUATION & PREPARATION After excavations have been completed to the planned subgrade elevations, but before placing fill or structural elements, the exposed subgrade should be evaluated under the part-time observation and guidance of a QG representative. The special inspection firm should continuously evaluate all backfilling. Any areas that are identified as being soft or yielding during subgrade evaluation should be over excavated to a firm and unyielding condition or to the depth determined by the geotechnical engineer. Where over excavation is performed below a structure, the over excavation area should extend beyond the outside of the footing a distance equal to the depth of the over excavation below the footing. The over-excavated areas should be backfilled with properly compacted structural fill. 4.1.3 SITE PREPARATION, EROSION CONTROLL, WET WEATHER Any silty or organic rich native soils may be moisture-sensitive and become soft and difficult to traverse with construction equipment when wet. During wet weather, the contractor should take measures to protect any exposed soil subgrades, limit construction traffic during earthwork activities, and limit machine use only to areas undergoing active preparation. Once the geotechnical engineer has approved the subgrade, further measures should be implemented to prevent degradation or disturbance of the subgrade. These measures could include, but are not limited to, placing a layer of crushed rock or lean concrete on the exposed subgrade, or covering the exposed subgrade with a plastic tarp and keeping construction traffic off the subgrade. Once the subgrade has been approved, any disturbance because the subgrade was not protected should be repaired by the contractor at no cost to the owner. During wet weather, earthen berms or other methods should be used to prevent runoff from draining into excavations. All runoffs should be collected and disposed of properly. Measures may Durant St. Geo Quality Geo NW, PLLC 11/13/2023 Project # QG23-187 15 also be required to reduce the moisture content of on-site soil in the event of wet weather. These measures can include, but are not limited to, air drying and soil amendment, etc. QG recommends earthwork activities take place during the summer dry season. 4.2 STRUCTURAL FILL MATERIALS AND COMPACTION 4.2.1 MATERIALS All material placed below structures or pavement areas should be considered structural fill. Excavated native soils may be considered suitable for reuse as structural fill on a case-by-case basis. Imported material can also be used as structural fill. Care should be taken by the earthwork contractor during grading to avoid contaminating stockpiled soils that are planned for reuse as structural fill with native organic materials. Frozen soil is not suitable for use as structural fill. Fill material may not be placed on frozen soil. Structural fill material shall be free of deleterious materials, have a maximum particle size of 4 inches, and be compactable to the required compaction level. Imported structural fill material should conform to the WSDOT manual Section 9-03.14(1) Gravel Borrow, or an approved alternative import material. Controlled-density fill (CDF) or lean mix concrete can be used as an alternative to structural fill materials, except in areas where free-draining materials are required or specified. Imported materials utilized for trench back fill shall conform to Section 9-03.19, Trench Backfill, of the most recent edition (at the time of construction) of the State of Washington Department of Transportation Standard Specifications for Road, Bridge, and Municipal Construction (WSDOT Standard Specifications). Imported materials utilized as grade fill beneath roads shall conform to WSDOT Section 9-03.10, Gravel Base. Pipe bedding material should conform to the manufacturer’s recommendations and be worked around the pipe to provide uniform support. Cobbles exposed in the bottom of utility excavations should be covered with pipe bedding or removed to avoid inducing concentrated stresses on the pipe. Soils with fines content near or greater than 10% fines content may likely be moisture sensitive and become difficult to use during wet weather. Care should be taken by the earthwork contractor during grading to avoid contaminating stockpiled soils that are planned for reuse as structural fill with native organic materials. The contractor should submit samples of each of the required earthwork materials to the materials testing lab for evaluation and approval prior to delivery to the site. The samples should be Durant St. Geo Quality Geo NW, PLLC 11/13/2023 Project # QG23-187 16 submitted at least 5 days prior to their delivery and sufficiently in advance of the work to allow the contractor to identify alternative sources if the material proves unsatisfactory. 4.2.2 FILL PLACEMENT AND COMPACTION For lateral and bearing support, structural fill placement below footings shall extend at minimum a distance past each edge of the base of the footing equal to the depth of structural fill placed below the footing [i.e. extending at least a 1H:1V past both the interior and the exterior of the concrete footing]. Prior to placement and compaction, structural fill should be moisture conditioned to within 3 percent of its optimum moisture content. Loose lifts of structural fill shall not exceed 12 inches in thickness. All structural fill shall be compacted to a firm and unyielding condition and to a minimum percent compaction based on its modified Proctor maximum dry density as determined per ASTM D1557. Structural fill placed beneath each of the following shall be compacted to the indicated percent compaction: • Foundation and Floor Slab Subgrades: 95 Percent • Pavement Subgrades & wall backfill (upper 2 feet): 95 Percent • Pavement Subgrades & wall backfill (below 2 feet): 90 Percent • Utility Trenches (upper 4 feet): 95 Percent • Utility Trenches (below 4 feet): 90 Percent A sufficient number of tests should be performed to verify the compaction of each lift. The number of tests required will vary depending on the fill material, its moisture condition and the equipment being used. Initially, more frequent tests will be required while the contractor establishes the means and methods required to achieve proper compaction. Jetting or flooding is not a substitute for mechanical compaction and should not be allowed. 4.3 TEMPORARY EXCAVATIONS AND TRENCHES All excavations and trenches must comply with applicable local, state, and federal safety regulations. Construction site safety is the sole responsibility of the Contractor, who shall also be solely responsible for the means, methods, and sequencing of construction operations. We are providing soil type information solely as a service to our client for planning purposes. Under no circumstances should the information be interpreted to mean that QG is assuming responsibility for construction site safety or the Contractor’s activities; such responsibility is not being implied and should not be inferred. The contractor shall be responsible for the safety of personnel working in utility trenches. Given that steep excavations in native soils may be prone to caving, we recommend all utility trenches, but particularly those greater than 4 feet in depth, be supported in Durant St. Geo Quality Geo NW, PLLC 11/13/2023 Project # QG23-187 17 accordance with state and federal safety regulations. Heavy construction equipment, building materials, excavated soil, and vehicular traffic should not be allowed near the top of any excavation. Temporary excavations and trenches should be protected from the elements by covering them with plastic sheeting or some other similar impermeable material. Sheeting sections should overlap by at least 12 inches and be tightly secured with sandbags, tires, staking, or other means to prevent wind from exposing the soils under the sheeting. Durant St. Geo Quality Geo NW, PLLC 11/13/2023 Project # QG23-187 18 5.0 SPECIAL INSPECTION The recommendations made in this report assume that an adequate program of tests and observations will be made throughout construction to verify compliance with these recommendations. Testing and observations performed during construction should include, but not necessarily be limited to, the following: • Geotechnical plan review and engineering consultation as needed prior to construction phase, • Observations and testing during site preparation, earthwork, structural fill, and pavement section placement, • Consultation on temporary excavation cutslopes and shoring if needed, • Consultation as necessary during construction. QG recommends that a local and reputable materials testing & inspection firm be retained for construction phase testing and observation in accordance with the local code requirements. We also strongly recommend that QG be retained as the project Geotechnical Engineering Firm of Record (GER) during the construction of this project to perform periodic supplementary geotechnical observations and review the special inspectors reports during construction. Our knowledge of the project site and the design recommendations contained herein will be of great benefit in the event that difficulties arise and either modifications or additional geotechnical engineering recommendations are required or desired. We can also, in a timely fashion observe the actual soil conditions encountered during construction, evaluate the applicability of the recommendations presented in this report to the soil conditions encountered, and recommend appropriate changes in design or construction procedures if conditions differ from those described herein. We would be pleased to meet with you at your convenience to discuss the Time & Materials scope and cost for these services. Durant St. Geo Quality Geo NW, PLLC 11/13/2023 Project # QG23-187 19 6.0 LIMITATIONS Upon acceptance and use of this report, and its interpretations and recommendations, the user shall agree to indemnify and hold harmless QG, including its owners, employees and subcontractors, from any adverse effects resulting from development and occupation of the subject site. Ultimately, it is the owner’s choice to develop and live in such an area of possible geohazards (which exist in perpetuity across the earth in one form or another), and therefore the future consequences, both anticipated and unknown, are solely the responsibility of the owner. By using this report for development of the subject property, the owner must accept and understand that it is not possible to fully anticipate all inherent risks of development. The recommendations provided above are intended to reduce (but may not eliminate) such risks. This report does not represent a construction specification or engineered plan and shall not be used or referenced as such. The information included in this report should be considered supplemental to the requirements contained in the project plans & specifications and should be read in conjunction with the above referenced information. The selected recommendations presented in this report are intended to inform only the specific corresponding subjects. All other requirements of the above-mentioned items remain valid, unless otherwise specified. Recommendations contained in this report are based on our understanding of the proposed development and construction activities, field observations and explorations, and laboratory test results. It is possible that soil and groundwater conditions could vary and differ between or beyond the points explored. If soil or groundwater conditions are encountered during construction that differ from those described herein, or if the scope of the proposed construction changes from that described in this report, QG should be notified immediately in order to review and provide supplemental recommendations. The findings of this study are limited by the level of scope applied. We have prepared this report in substantial accordance with the generally accepted geotechnical engineering practice as it exists in the subject region. No warranty, expressed or implied, is made. The recommendations provided in this report assume that an adequate program of tests and observations will be conducted by a WABO approved special inspection firm during the construction phase in order to evaluate compliance with our recommendations. This report may be used only by the Client and their design consultants and only for the purposes stated within a reasonable time from its issuance, but in no event later than 18 months from the date of the report. It is the Client's responsibility to ensure that the Designer, Contractor, Subcontractors, etc. are made aware of this report in its entirety. Note that if another firm assumes Geotechnical Engineer of Record responsibilities, they need to review this report and either concur with the findings, conclusions, and recommendations or provide alternate findings, conclusions and recommendation. Land or facility use, on- and off-site conditions, regulations, or other factors may change over time, and additional work may be required. Based on the intended use of the report, QG may recommend that additional work be performed and that an updated report be issued. Non-compliance with any of these requirements by the Client or anyone else will release QG from any liability resulting from the use of this report. The Client, the design consultants, and any unauthorized party, agree to defend, indemnify, and hold harmless QG from any claim or liability associated with such unauthorized use or non-compliance. We recommend that QG be given the opportunity to review the final project plans and specifications to evaluate if our recommendations have been properly interpreted. We assume no responsibility for misinterpretation of our recommendations. Durant St. Geo Quality Geo NW, PLLC 11/13/2023 Project # QG23-187 20 Region & Vicinity Maps REGION VICINITY Quality Geo NW, PLLC Site Region Durant St. Geo Figure 1 Source: Google Imagery, 2023 Scale & Locations are approx. Not for Construction Durant St. Geo Quality Geo NW, PLLC 11/13/2023 Project # QG23-187 21 Exploration Map Figure 2 Source: Thurston Co. GIS, 2023 Scale & Locations are approx. Not for Construction 20 0 SCALE (FEET) Quality Geo NW, PLLC Site Map Durant St. Geo TP-1 Proposed Build Site TP-2 TP-3 TP-6 TP-5 TP-4 Durant St. Geo Quality Geo NW, PLLC 11/13/2023 Project # QG23-187 Quality Geo NW, PLLC Serving All of Washington & Oregon | Geotechnical Investigations & Engineering Consultation Phone: 360-878-9705| Web: qualitygeonw.com | Mail: 4631 Whitman Ln SE, Ste D, Lacey, WA 98513 Exploration Logs Durant St. Geo Quality Geo NW, PLLC 11/13/2023 Project # QG23-187 23 Durant St. Geo Quality Geo NW, PLLC 11/13/2023 Project # QG23-187 24 Durant St. Geo Quality Geo NW, PLLC 11/13/2023 Project # QG23-187 25 Durant St. Geo Quality Geo NW, PLLC 11/13/2023 Project # QG23-187 26 Durant St. Geo Quality Geo NW, PLLC 11/13/2023 Project # QG23-187 27 Durant St Geo Quality Geo NW, PLLC 11/13/2023 Project # QG23-187 28 Laboratory Results Durant St Geo Quality Geo NW, PLLC 11/13/2023 Project # QG23-187 29 Durant Street Plat Soils Report For Evaluating Site Feasibility of Stormwater Infiltration BMP’s Associated with Roof, Driveway and Road Runoff. Site Address: 9910 Durant St. SE, Yelm WA 98597 TPN: 21724420501 Prepared For: C & E Developments LLC PO Box 2983 Yelm, WA 98597 Contact: Casey Peterson (360) 400-0432 cedevelopment05@gmail.com Prepared By: Parnell Engineering, LLC 10623 Hunters Lane S.E. Olympia, WA 98513 Contact: William Parnell, P.E. (360) 491-3243 PE PARNELL ENGINEERING, LLC SOIL EVALUATION REPORT FORM l: GENERAL SITE INFORMATION PROJECTTITLE:Du「antSt「eetPiat SHEE丁:1OFl 胃 PEPROJECTNO,:21106 DA丁E:3I5/2021 PREPAREDBY:W冊amPame=,P.E. 1.SITEADDRESS:9910DurantSt.SE,YeImWA98597 TPN:217244205Ol 2.PROJECTDESCRiPTION:P「oposed211otpIat. 3.SITEDESCRiPTION:The5.52ac「e「ectanguIarshapedprojectsiteiscur「entiyunoccupiedbyany bu=dingst「uctures.SitereiiefisgentIysIopingno巾handsouthf「omthecentraiportionofthesiteonthe eastemhalfofthesiteandgenera=yeasttowestonthewestemhalfofthesite・An8%southweste「lyfacing SIopeliesonthewestemportionofthesite.Elevationsva「yfromahighof355ft.attheeasトCentraIportion Ofthesitetoalowof346ft.atthesouthwestpropertyco「ne「.Sitevegetationconsistsofpastureg「assesand SCOtChbioomonthemajo「ityofthesitewithsomelightdensityt「eesonthewestemquarterofthesite.The PrOjectsiteisboundedtothewestbyDu「antSt「eetSEandresidentiaIp「opertytotheno軸,eaStandsouth. Theon-Siteso=sa「emappedbytheNatu「aIResourceConservationService(NRCS)asawe=-d「ained Spanawaygrave=ysandy10am(11O)formedinvoicanicashove「graveiiyoutwash. 4.SUMMARYOFSOILSWORKPERFORMED:Threetestpitswereexcavatedbyt「ackhoetoamaximum depthof172’’beiowtheexistinggrade.Soilswereinspectedbyente「ingandvisua=yIoggingeachtestpitto adepthoffou「feet.SoiIsbeyondfourfeetwe「einspectedbyexaminingbackhoeta冊gs.Soiisampleswe「e takenfromtestpit#1at24’’&48”and#2at30’’&48’’beIowtheexistinggrade.Grainsizeanalysismethod WaSuSedtodeterminethesuitab冊yofthe「ep「esentativesoiIho「izonsforstormwate「in凧t「ationfac冊es.An initialsaturatedhydraulicconductivity(Ksat)wascaicuiatedandthen「educedbycor「ectionfactors(CFT)to PrOduceanadjusteddesignin輔ration「ateKsatdesignfo「fac冊ysizingpurposes.Testpitso旧Ogdatasheets andg「ainsizeanaIysisdatawithKsatcalculationsareincIudedinthisreport. 5.ADDITIONALSOiLSWORKRECOMMENDED:Additionaisoilsworkshouldnotbenecessaryunless StOrmWaterin刑trationfac冊esa「enotlocatedinthegene「alvicinityofso旧ogtestpits. 6.FiNDINGS:Theon-Sitesoiisa「emappedbyNRCSasaSpanawayg「ave=ysandyloam(110).Testpits 「evealedsoilsconsistentofaSpanawayserieswithstratumsoiisp「o輔ngagraveilyloamoverIyingan extremeIyg「aveIiyandcobbIedcoa「se-finesand.Winte「watertablewaspresentintestpit#1at163”beIow theexistinggrade(lowpointofthesite),Nowinte「wate「tabIeorpossibleindicatorswereobviousintestpits #2.ThesoiigrainsizeanalysismethodresuitedinadjustedKsatdesignvaluesfo「thefo=owingsoil SamPIes:Testpit#1at24’’&48’’beIowtheexistingg「ade-27.67inIhr&22in/h「respectively.Testpit#2at 30’’&48’’belowtheexistingg「ade-20.9inlh「&28in/hr「espectiveiy. CaIcuIationsassumedanin凧trationfac冊ywidthof20ft.andaminimum9ft.separationbetweenthebottom Ofthesto「mwaterin凧trationfaciiityandwinte「wate「tabIe.At20ft.infac冊ywidth,thissepa「ationcanbe 「educedto5什beforeanyadditional「eductioninKsatdesignin凧trationratewouIdbenecessary. 7.RECOMMENDATIONS:TheSpanawayse「iessoilsa「esomewhatexcessiveIydrainedsoiIsfoundon OutwaShpIainsformedinvoIcanicashove「g「aveliyoutwash.ln冊「ationratesaregene「a=yrapidinthe Substratumsoils.G「ainsizeanaIysismethodresuItedinadjustedKsatdesjgnvalues>20inlhr.Fo「theta「geted ChorizonsoiIs言tisrecommendedKsatdesign(F)vaIuesdonotexceed20in/h「.PIease「efe「totheattached SOilg「adationtest「esultswithKsatdesigncaicuiations,aSSOCiatedindividuaIso旧ogdatasheetsandtestpit/so旧og locationmap. Duringconst「uction,Ca「emuStbetakentopreventtheerosionofexposedsoils.Sto「mwate「d「ainagefac冊y in柵rationsurfacesmustbep「operiyp「OteCtedf「omcontaminationbythefine-g「aineduppe「ho「izonso=s andfromcompactionbyconstructionsiteactivities.So=snotp「ope「lyprotectedmaycausestormwate「 drainagein冊「ationfac冊estonotperfo「masintended. Iherebycertifythatlp「eparedthis「epo巾andconductedo「supervisedtheperformanceof「eiatedwork.l Certifythatlamqua晒edtodothiswork.l「ep「esentmywo「ktobecompleteanaccu「atewithintheb :器械P’a SOl-sscIenCe’an器Su-tab一誌芹uSe par 顎騒 の 畿麗 〇番′ SOIL EVALUATION REPORT FORM 2: SOIL LOG INFORMATION PROJECT TITLE: Durant Street Plat SHEET: 1 OF 3 PROJECT NO.: 21106 DATE: 2/24/2021 PREPARED BY: William Parnell, PE SOIL LOG: #1 LOCATION: 15 ft. north and 21 ft. east of the southwest property corner. (see attached site plan map) 1. TYPES OF TEST DONE: Grain size analysis 2. NRCS SOILS SERIES: Spanaway gravelly sandy loam (110) 3. LAND FORM: Outwash plain 4. DEPOSITION HISTORY: Volcanic ash over gravelly outwash 5. HYDROLOGIC SOIL GROUP: A 6. DEPTH OF SEASONAL HW: Unknown 7. CURRENT WATER DEPTH: 163” 8. DEPTH TO RESTRICTIVE HORIZONS: Greater than bottom of hole 9. MISCELLANEOUS: Nearly Level 10. POTENTIAL FOR: EROSION RUNOFF PONDING Slight Slow Minimal 11. SOIL STRATA DESCRIPTION: See Following chart 12. SITE PERCOLATION RATE: See FSP 13. FINDINGS & RECOMMENDATIONS: Roots were present to 26”. Water was present at 163” below the existing grade. Grain size analysis method was completed on soil samples taken at 24” & 48” below the existing grade resulting in adjusted Ksat design values of 27.67 in/hr and 22 in/hr respectively. Use a design infiltration rate < 20 in/hr for stormwater facilities with the infiltration surface area located in the C horizon soils. Soils Strata Description Soil Log #1 Horz Depth Color Texture %CL %ORG CF STR MOT IND CEM ROO <X> FSP A 0”- 20” 10YR2/1 GrLm <15 <12 <30 1SBK - - - fm 2-6 3 Bw 20”- 26” 10YR3/4 ExGrC-FSa <2 - <80 SG - - - fm >20 <20 C1 26”- 78” 10YR5/4 ExGrCob M-FSa <3 - <75 SG - - - - >20 <20 C2 78”-108” 10YR5/2 ExGrCobC- FSa <1 - <85 SG - - - - >20 <20 C3 108”-132” 10YR5/1 ExGrCob C-FSa some stones <2 - <85 SG - - - - >20 <20 C4 132”-170” 10YR5/1 ExGrCob C-MSa some stones <2 - <90 SG - - - - >20 <20 SOIL EVALUATION REPORT FORM 2: SOIL LOG INFORMATION PROJECT TITLE: Durant Street Plat SHEET: 2 OF 3 PROJECT NO.: 21106 DATE: 2/24/2021 PREPARED BY: William Parnell, PE SOIL LOG: #2 LOCATION: 105 ft. north and 45 ft. east of the southwest property corner. (see attached site plan map) 1. TYPES OF TEST DONE: Grain size analysis 2. NRCS SOILS SERIES: Spanaway gravelly sandy loam (110) 3. LAND FORM: Outwash plain 4. DEPOSITION HISTORY: Volcanic ash over gravelly outwash 5. HYDROLOGIC SOIL GROUP: A 6. DEPTH OF SEASONAL HW: Unknown 7. CURRENT WATER DEPTH: Greater than bottom of hole 8. DEPTH TO RESTRICTIVE HORIZONS: Greater than bottom of hole 9. MISCELLANEOUS: Toe of slope, nearly level 10. POTENTIAL FOR: EROSION RUNOFF PONDING Slight Slow Minimal 11. SOIL STRATA DESCRIPTION: See Following chart 12. SITE PERCOLATION RATE: See FSP 13. FINDINGS & RECOMMENDATIONS: Roots were present to 29”. Grain size analysis method was completed on samples taken at 30” & 48” below the existing grade resulting in adjusted Ksat design values of 20.9 in/hr and 28 in/hr respectively. Use a design infiltration rate < 20 in/hr for stormwater facilities with the infiltration surface area located in the C horizon soils. Soils Strata Description Soil Log #2 Horz Depth Color Texture %CL %ORG CF STR MOT IND CEM ROO <X> FSP A 0”- 29” 10YR2/1 GrLm <15 <12 <20 1SBK - - - fm 2-6 3 C1 29”- 80” 10YR4/6 ExGrCob M-FSa some stones <5 - <75 SG - - - - >20 <20 C2 80”- 98” 10YR5/1 ExGrC-FSa some stones <3 - <85 SG - - - - >20 <20 C3 98”-116” 10YR5/4 ExGrM-FSa <1 - <85 SG - - - - >20 <20 C3 116”-170” 10YR5/1 ExGrC-MSa some stones <2 - <90 SG - - - - >20 <20 SOIL EVALUATION REPORT FORM 2: SOIL LOG INFORMATION PROJECT TITLE: Durant Street Plat SHEET: 3 OF 3 PROJECT NO.: 21106 DATE: 2/24/2021 PREPARED BY: William Parnell, PE SOIL LOG: #3 LOCATION: 21 ft. north and 120 ft. east of the southwest property corner. (see attached site plan map) 1. TYPES OF TEST DONE: None 2. NRCS SOILS SERIES: Spanaway gravelly sandy loam (110) 3. LAND FORM: Outwash plain 4. DEPOSITION HISTORY: Volcanic ash over gravelly outwash 5. HYDROLOGIC SOIL GROUP: A 6. DEPTH OF SEASONAL HW: Unknown 7. CURRENT WATER DEPTH: Greater than bottom of hole 8. DEPTH TO RESTRICTIVE HORIZONS: Greater than bottom of hole 9. MISCELLANEOUS: Toe of slope, nearly level 10. POTENTIAL FOR: EROSION RUNOFF PONDING Slight Slow Minimal 11. SOIL STRATA DESCRIPTION: See Following chart 12. SITE PERCOLATION RATE: See FSP 13. FINDINGS & RECOMMENDATIONS: Roots were present to 30”. Use a design infiltration rate < 20 in/hr for stormwater facilities with the infiltration surface area located in the C horizon soils. Soils Strata Description Soil Log #3 Horz Depth Color Texture %CL %ORG CF STR MOT IND CEM ROO <X> FSP A 0”- 30” 10YR2/1 GrLm <15 <12 <20 1SBK - - - fm 2-6 3 C1 30”- 44” 10YR3/6 ExGrCob M-FSa <5 - <70 SG - - - - >20 <20 C2 44”- 66” 10YR4/6 ExGrC-FSa <3 - <85 SG - - - - >20 <20 C3 66”-127” 10YR5/2 ExGrCobC- MSa some stones <1 - <90 SG - - - - >20 <20 C4 127”-172” 10YR5/2 ExGrCob CSa some stones <1 - <90 SG - - - - >20 <20 DurantSt,P!at 100 90 80 くの くの くロ ∈70 」 ○ 言60 掌 主50 の ⊂ 紛40 の く⊃, 宣30 ① 0- 20 10 0 C \ iil i i i I i l 0.001 \ ! ( 雪 1 lTestPit#1at24”l き i i i l き 且 l.samp-el ! i l i l i 雪 雪 i l i き 雪 ! i i 口\ )i l i i i i I l ! ) ! 1 l l N l i 圭 i i 圭 雪 i i 雪 l 圭 l ) i i i ∴ ! 1 ) i i i 1 l i 〉 l i l 雪 き ! l i i ! i i i 圭 ! i i -i l 100 10 1Sam el O.1 0.01 bb GnqveI ふ}研1 l s′I′ C句, Coa左沌 ん細高層肋 i 勅e Ksat Ca看culations Test pit#1 - SamPle #1 taken at 24一一below the existing g「ade Soii Gradation Test Re uIts: DlO こ 0.3 D60 = 3,3 D90 = 22.0 価nesこ 0.0141 loglO (Ksat) =一1.57 + 1.90 (DlO) + 0.015 (D60) - 0.013 (D90) - 2.08 (ffines) ioglO(Ksat) =-1.57+ 1.90 (0.3) +0.015(3.3)-0.013(22.0)-2.08 (0.0141) loglO (Ksat) = -1.2658 Ksat = 0.0542 cmls Ksat= 0.0542 cm/s x O.3937 in/cm X 60s/min X60 min川r Ksat= 76.85 in/hr Finai Desiqn Inf靴「ation Rate Calcuiation : idesiqn/F) Idesign = lmeasured X Ftesting x Fgeometry x FpIugging imeasu「ed = Ksat = 76.85 in/h「 Ftesting = 0,40 Fgeometry= 4DAV + 0.05 Where: D = Depth from the bottom ofthe p「oposed fac帥ty to the O.25 5 Fgeometry≦ 1.O maximum wet season water tabIe, nea「eSt impervious Iayer, O「 SO旧exturai change, Whicheve「 is less. Assume D > 11 feet. Fg∞metry= 4(11/20) + 0.05 W = Width offac帥ty Assume W = 20 feet Fgeometry= 2.25 Use Fgeometry= 1.O FpIugging= 0.7 fo「 loams and sandy loams, 0.8 fo「 loamy sands o「fine sands, 0.9 for medium Sands, 1.O for coa「se sands o「 cobbIes o「 any soiI type with in輔ration fac帥ty p「eceded by a specific wate「 qua=ty fac冊Y. Use Fplugging = 0.9 !design = 76.85 xO.4 x l.Ox O.9 = 27.67 inIh「 Use idesign(F)S20 in/hr DurantSt.Plat 100 90 80 の くの く0 ∈70 」 ○ 言60 筆 舌50 ○) ⊂ 紛40 の く⊃. 宣30 ① 直20 10 0 C =i I i曇 i) il i 0.001 1 i ( ○獲〇〇一〇Ⅲ○○星星田 TestPit#1at48’l \ i l き ( ● Sample2 i 雪 i l l i 圭雪 l l l l ( ) 1 き ) i雪 ! l 雪 i i ( i i 1 ! i l 1 ! ! き ( l ! i ) 雪 雪 i 1 ) 雪 = i 100 10 1Sample2 0.1 0.01 bb G月のveI くわnd l s′I′ Cゆ Coar∫e 胸-1励 I 勅e Ksat Caicuiations Test pit#1 - SamPle #1 taken at 48'一beIowthe existjng grade Soil G「adation Test Resuits: DlO こ 0.26 D60 = 5.8 D90 = 24.0 塙nesこ 0.0308 IoglO (Ksat) = -1.57 + 1・90 (DlO) + 0.015 (D60) - 0.013 (D90)一2.08 (ffines) ioglO(庵at)=-1,57十1.90(0.26)十0.015 (5.8)-0.013 (24.0)-2.08 (0.0308) loglO (Ksat) = -1.3651 Ksatこ0.0431 cm/s Ksat= 0.0431 cm/s x O.3937 in/cm X 60s/min X 60 minlh「 Ksat= 61.15 inlhr Final Desian lnfiltration Rate CaIcuiation : ides gn田 Idesign = Imeasu「ed x Ftes師g X Fgeometry x Fplugging imeasu「ed = Ksat = 61.15 in/h「 Ftesting = 0.40 Fgeomet「y= 4DAV + 0.05 Where: D = Depth f「om the bottom ofthe p「oposed faciIity to the O.25 ≦ Fg∞metry≦ 1.O maximum wet season water tabIe, nea「eSt impervious iayer, Or SO旧extural change, Whicheve「 is Iess. Assume D > 9 feet, Fgeometry= 4(9/20) + 0・05 W = VVIdth of fac=ity. Assume W = 20 feet Fgeometry= 1,85 Use Fg∞metry= 1.O Fplugging= 0.7 fo「 loams and sandy Ioams, 0.8 fo「 Ioamy sands o「 fine sands, 0.9 fo「 medium Sands, 1.O for coarse sands o「 oobbIes or any soil type with in航ration fac掴ty p「eceded by a specific water quaiity fac=ity. Use FpIugging = 0.9 idesign=61.15xO.4xl,OxO.9=22 in仙r Use ldesign(F)≦20 in/h「 DurantSt.Piat 100 90 80 ∽ ∽ の ∈70 」 ○ 言60 掌 主50 ① ⊂ 次40 (○ ○. 垂30 ① 凸。 20 10 0 C l 1 卜 i i i 当 i i 圭 i 0.001 i \ i l i l l i lll i ( TestPit#2at30 = l l l i ● SampIe3 = 事 i ( = 雪 l i l l ! i i ! l ( i i l i l 曇 i i i 圭 i i i l i 100 10 1Sample3 0.1 0.01 bb G竹VeI あれd i 洲 C佃y Coo硲e 偽di~′m i 勅e Ksat Calcutations Test pit#2 - SamPle #3 taken at 30一’below the existing g「ade So= Gradation Test ResuIts: D「O = 0.21 D60 = 6.5 D90 = 17.5 怖nesこ 0.0413 ioglO (Ksat) = -1.57 + 1.90 (DlO) + 0.015 (D60)一0.013 (D90) - 2.08 (ffines) IoglO(Ksat)=-1.57+ 1.90 (0.21)+0,015 (6.5)-0.013 (17.5)-2.08 (0.0413) IoglO (Ksat) =一1.3869 Ksat = 0.0410 cm/s Ksat= 0,0410 cm/s x O.3937 in/cm X 60sImin X 60 min/h「 Ksat= 58,15 in/h「 Final Desian lnf冊「ation Rate Ca看cu看ation : Idesiqn/FI ldesign = imeasured X Ftesting X Fgeometry x FpIugging lmeasu「ed = Ksat = 58.15 in仙「 Ftesting = 0.40 Fgeometry= 4D/W + 0.05 Whe「e: D = Depth f「om the bottom ofthe p「oposed fac掴ty to the O.25 ≦ Fgeometry三1.O maximum wet season wate「 tabie, nea「eSt impervious layer, O「 SO旧extu「ai change, Whicheve「 is less. Assume D > 10.5 feet. Fgeometry= 4(10.5/20) + 0.05 W= Width offacility. AssumeW = 20 feet Fgeometry= 2.15 Use Fgeometry= 1.O Fplugging= 0,7 fo「 loams and sandy loams, 0.8 for Ioamy sands or師e sands, 0.9 for medium Sands, 1.O for coa「se sands o「 ∞bbIes o「 any soiI type with in靴ration fac掴ty preceded by a specific water qua=ty fac掴ty. Use FpIngging = 0.9 1design = 58.15 xO.4 x l.O xO.9 = 20.9 in/hr Use Idesign(F)≦20 inlhr DurantSt.Plat 100 90 80 く∩ くの くe ∈70 」 ○ 言60 筆 舌50 ⊂)) ⊂ 総40 くロ ⊂し 宣30 o) 直20 10 0 C i i i 〔 i i i l i i! i i き i き 0.001 \ l 圭 i l 雪 i 圭 l l l 圭 S○○Ⅲ ⅢSOO TestPit#2at481i 呈 雪 i ! i き 圭 き l i l i き ● Sample4 i 雪 漢 ) ( l i l i i l l l i ! i l i i ! 曇 雪 ) i i i i i l l 「 i i ! \ i i \ l i i き 雪 ○○" l i 雪 l i = l 100 10 1Sample4 0.1 0.01 bb Sand l s誰 Cんy Coor∫e 旅di~′m l 勅e Ksat Calcu看ations Test pit#2 - SamPle紺taken at 48"’below the existing grade Soii G「adation Test Resuits: DlOこ 0.27 D60 = 6.O D90こ18.0 楠nesこ 0.0286 ioglO (Ksat) = -1・57 + 1.90 (DlO) + 0.015 (D60) - 0.013 (D90) - 2.08 (ffines) iog「O(Ksat)こ-1.57十1.90 (0.27)十0.015 (6.0)-0.013(18.0)-2.08 (0.0286) iog「O (Ksat) = -1.2605 Ksat = 0.0549 cm/s Ksat= 0.0549 cm/s x O.3937 in/cm X 60s/min X 60 min/h「 Ksat= 77.8 in/hr Finai Desian Infiitration Rate Caicu!ation : ldesian/FI Idesign = 1measured X Ftesting X Fgeometry x Fplugging lmeasured = Ksat = 77.8 inIh「 Ftesting = 0.40 Fgeometry= 4DAV + 0.05 Where: D = Depth f「om the bottom ofthe p「oposed fac掴ty to the O.25 ≦ Fg∞metry≦ 1.O maximum wet season water table, nea「eSt impervious Iaye「, Or SO旧extu「al change, Whicheve「 is less. Assume D > 9 feet. Fgeometry= 4(9/20) + 0.05 W = Width offac掴ty. Assume W = 20 feet Fgeometry= 1.85 Use Fgeomet「y= 1.O Fpiugging= 0.7 for Ioams and sandyloams, 0.8 for loamy sands or fine sands, 0.9 fo「 medium Sands, 1.O for coa「se sands o「 cobbles or any soil type with inf冊ration fac=ity preceded by a spec楯c wate「 quaIity fac掴ty. Use Fplugging = 0.9 1design = 77.8 x O.4 x l.O x O.9 = 28.O in/hr Use Idesign(F)≦20 in/hr 一一一二へ_○○ ∠-臆_、__ /￣￣￣￣￣o/′//星田 各軍 N O129’21’’E 2J127 United States Department of Agriculture A product of the National Cooperative Soil Survey, a joint effort of the United States Department of Agriculture and other Federal agencies, State agencies including the Agricultural Experiment Stations, and local participants Custom Soil Resource Report for Thurston County Area, Washington 9910 Durant St SE Natural Resources Conservation Service February 6, 2024 Preface Soil surveys contain information that affects land use planning in survey areas. They highlight soil limitations that affect various land uses and provide information about the properties of the soils in the survey areas. Soil surveys are designed for many different users, including farmers, ranchers, foresters, agronomists, urban planners, community officials, engineers, developers, builders, and home buyers. Also, conservationists, teachers, students, and specialists in recreation, waste disposal, and pollution control can use the surveys to help them understand, protect, or enhance the environment. Various land use regulations of Federal, State, and local governments may impose special restrictions on land use or land treatment. Soil surveys identify soil properties that are used in making various land use or land treatment decisions. The information is intended to help the land users identify and reduce the effects of soil limitations on various land uses. The landowner or user is responsible for identifying and complying with existing laws and regulations. Although soil survey information can be used for general farm, local, and wider area planning, onsite investigation is needed to supplement this information in some cases. Examples include soil quality assessments (http://www.nrcs.usda.gov/wps/ portal/nrcs/main/soils/health/) and certain conservation and engineering applications. For more detailed information, contact your local USDA Service Center (https://offices.sc.egov.usda.gov/locator/app?agency=nrcs) or your NRCS State Soil Scientist (http://www.nrcs.usda.gov/wps/portal/nrcs/detail/soils/contactus/? cid=nrcs142p2_053951). Great differences in soil properties can occur within short distances. Some soils are seasonally wet or subject to flooding. Some are too unstable to be used as a foundation for buildings or roads. Clayey or wet soils are poorly suited to use as septic tank absorption fields. A high water table makes a soil poorly suited to basements or underground installations. The National Cooperative Soil Survey is a joint effort of the United States Department of Agriculture and other Federal agencies, State agencies including the Agricultural Experiment Stations, and local agencies. The Natural Resources Conservation Service (NRCS) has leadership for the Federal part of the National Cooperative Soil Survey. Information about soils is updated periodically. Updated information is available through the NRCS Web Soil Survey, the site for official soil survey information. The U.S. Department of Agriculture (USDA) prohibits discrimination in all its programs and activities on the basis of race, color, national origin, age, disability, and where applicable, sex, marital status, familial status, parental status, religion, sexual orientation, genetic information, political beliefs, reprisal, or because all or a part of an individual's income is derived from any public assistance program. (Not all prohibited bases apply to all programs.) Persons with disabilities who require 2 alternative means for communication of program information (Braille, large print, audiotape, etc.) should contact USDA's TARGET Center at (202) 720-2600 (voice and TDD). To file a complaint of discrimination, write to USDA, Director, Office of Civil Rights, 1400 Independence Avenue, S.W., Washington, D.C. 20250-9410 or call (800) 795-3272 (voice) or (202) 720-6382 (TDD). USDA is an equal opportunity provider and employer. 3 Contents Preface....................................................................................................................2 How Soil Surveys Are Made..................................................................................5 Soil Map..................................................................................................................8 Soil Map................................................................................................................9 Legend................................................................................................................10 Map Unit Legend................................................................................................11 Map Unit Descriptions.........................................................................................11 Thurston County Area, Washington................................................................13 110—Spanaway gravelly sandy loam, 0 to 3 percent slopes......................13 111—Spanaway gravelly sandy loam, 3 to 15 percent slopes....................13 4 How Soil Surveys Are Made Soil surveys are made to provide information about the soils and miscellaneous areas in a specific area. They include a description of the soils and miscellaneous areas and their location on the landscape and tables that show soil properties and limitations affecting various uses. Soil scientists observed the steepness, length, and shape of the slopes; the general pattern of drainage; the kinds of crops and native plants; and the kinds of bedrock. They observed and described many soil profiles. A soil profile is the sequence of natural layers, or horizons, in a soil. The profile extends from the surface down into the unconsolidated material in which the soil formed or from the surface down to bedrock. The unconsolidated material is devoid of roots and other living organisms and has not been changed by other biological activity. Currently, soils are mapped according to the boundaries of major land resource areas (MLRAs). MLRAs are geographically associated land resource units that share common characteristics related to physiography, geology, climate, water resources, soils, biological resources, and land uses (USDA, 2006). Soil survey areas typically consist of parts of one or more MLRA. The soils and miscellaneous areas in a survey area occur in an orderly pattern that is related to the geology, landforms, relief, climate, and natural vegetation of the area. Each kind of soil and miscellaneous area is associated with a particular kind of landform or with a segment of the landform. By observing the soils and miscellaneous areas in the survey area and relating their position to specific segments of the landform, a soil scientist develops a concept, or model, of how they were formed. Thus, during mapping, this model enables the soil scientist to predict with a considerable degree of accuracy the kind of soil or miscellaneous area at a specific location on the landscape. Commonly, individual soils on the landscape merge into one another as their characteristics gradually change. To construct an accurate soil map, however, soil scientists must determine the boundaries between the soils. They can observe only a limited number of soil profiles. Nevertheless, these observations, supplemented by an understanding of the soil-vegetation-landscape relationship, are sufficient to verify predictions of the kinds of soil in an area and to determine the boundaries. Soil scientists recorded the characteristics of the soil profiles that they studied. They noted soil color, texture, size and shape of soil aggregates, kind and amount of rock fragments, distribution of plant roots, reaction, and other features that enable them to identify soils. After describing the soils in the survey area and determining their properties, the soil scientists assigned the soils to taxonomic classes (units). Taxonomic classes are concepts. Each taxonomic class has a set of soil characteristics with precisely defined limits. The classes are used as a basis for comparison to classify soils systematically. Soil taxonomy, the system of taxonomic classification used in the United States, is based mainly on the kind and character of soil properties and the arrangement of horizons within the profile. After the soil 5 scientists classified and named the soils in the survey area, they compared the individual soils with similar soils in the same taxonomic class in other areas so that they could confirm data and assemble additional data based on experience and research. The objective of soil mapping is not to delineate pure map unit components; the objective is to separate the landscape into landforms or landform segments that have similar use and management requirements. Each map unit is defined by a unique combination of soil components and/or miscellaneous areas in predictable proportions. Some components may be highly contrasting to the other components of the map unit. The presence of minor components in a map unit in no way diminishes the usefulness or accuracy of the data. The delineation of such landforms and landform segments on the map provides sufficient information for the development of resource plans. If intensive use of small areas is planned, onsite investigation is needed to define and locate the soils and miscellaneous areas. Soil scientists make many field observations in the process of producing a soil map. The frequency of observation is dependent upon several factors, including scale of mapping, intensity of mapping, design of map units, complexity of the landscape, and experience of the soil scientist. Observations are made to test and refine the soil-landscape model and predictions and to verify the classification of the soils at specific locations. Once the soil-landscape model is refined, a significantly smaller number of measurements of individual soil properties are made and recorded. These measurements may include field measurements, such as those for color, depth to bedrock, and texture, and laboratory measurements, such as those for content of sand, silt, clay, salt, and other components. Properties of each soil typically vary from one point to another across the landscape. Observations for map unit components are aggregated to develop ranges of characteristics for the components. The aggregated values are presented. Direct measurements do not exist for every property presented for every map unit component. Values for some properties are estimated from combinations of other properties. While a soil survey is in progress, samples of some of the soils in the area generally are collected for laboratory analyses and for engineering tests. Soil scientists interpret the data from these analyses and tests as well as the field-observed characteristics and the soil properties to determine the expected behavior of the soils under different uses. Interpretations for all of the soils are field tested through observation of the soils in different uses and under different levels of management. Some interpretations are modified to fit local conditions, and some new interpretations are developed to meet local needs. Data are assembled from other sources, such as research information, production records, and field experience of specialists. For example, data on crop yields under defined levels of management are assembled from farm records and from field or plot experiments on the same kinds of soil. Predictions about soil behavior are based not only on soil properties but also on such variables as climate and biological activity. Soil conditions are predictable over long periods of time, but they are not predictable from year to year. For example, soil scientists can predict with a fairly high degree of accuracy that a given soil will have a high water table within certain depths in most years, but they cannot predict that a high water table will always be at a specific level in the soil on a specific date. After soil scientists located and identified the significant natural bodies of soil in the survey area, they drew the boundaries of these bodies on aerial photographs and Custom Soil Resource Report 6 identified each as a specific map unit. Aerial photographs show trees, buildings, fields, roads, and rivers, all of which help in locating boundaries accurately. Custom Soil Resource Report 7 Soil Map The soil map section includes the soil map for the defined area of interest, a list of soil map units on the map and extent of each map unit, and cartographic symbols displayed on the map. Also presented are various metadata about data used to produce the map, and a description of each soil map unit. 8 9 Custom Soil Resource Report Soil Map 51 9 8 8 4 0 51 9 8 8 6 0 51 9 8 8 8 0 51 9 8 9 0 0 51 9 8 9 2 0 51 9 8 9 4 0 51 9 8 9 6 0 51 9 8 9 8 0 51 9 8 8 4 0 51 9 8 8 6 0 51 9 8 8 8 0 51 9 8 9 0 0 51 9 8 9 2 0 51 9 8 9 4 0 51 9 8 9 6 0 51 9 8 9 8 0 528740 528760 528780 528800 528820 528840 528860 528880 528900 528920 528940 528960 528740 528760 528780 528800 528820 528840 528860 528880 528900 528920 528940 528960 46° 56' 37'' N 12 2 ° 3 7 ' 2 0 ' ' W 46° 56' 37'' N 12 2 ° 3 7 ' 9 ' ' W 46° 56' 32'' N 12 2 ° 3 7 ' 2 0 ' ' W 46° 56' 32'' N 12 2 ° 3 7 ' 9 ' ' W N Map projection: Web Mercator Corner coordinates: WGS84 Edge tics: UTM Zone 10N WGS84 0 50 100 200 300Feet 0 15 30 60 90Meters Map Scale: 1:1,110 if printed on A landscape (11" x 8.5") sheet. Soil Map may not be valid at this scale. MAP LEGEND MAP INFORMATION Area of Interest (AOI) Area of Interest (AOI) Soils Soil Map Unit Polygons Soil Map Unit Lines Soil Map Unit Points Special Point Features Blowout Borrow Pit Clay Spot Closed Depression Gravel Pit Gravelly Spot Landfill Lava Flow Marsh or swamp Mine or Quarry Miscellaneous Water Perennial Water Rock Outcrop Saline Spot Sandy Spot Severely Eroded Spot Sinkhole Slide or Slip Sodic Spot Spoil Area Stony Spot Very Stony Spot Wet Spot Other Special Line Features Water Features Streams and Canals Transportation Rails Interstate Highways US Routes Major Roads Local Roads Background Aerial Photography The soil surveys that comprise your AOI were mapped at 1:24,000. Warning: Soil Map may not be valid at this scale. Enlargement of maps beyond the scale of mapping can cause misunderstanding of the detail of mapping and accuracy of soil line placement. The maps do not show the small areas of contrasting soils that could have been shown at a more detailed scale. Please rely on the bar scale on each map sheet for map measurements. Source of Map: Natural Resources Conservation Service Web Soil Survey URL: Coordinate System: Web Mercator (EPSG:3857) Maps from the Web Soil Survey are based on the Web Mercator projection, which preserves direction and shape but distorts distance and area. A projection that preserves area, such as the Albers equal-area conic projection, should be used if more accurate calculations of distance or area are required. This product is generated from the USDA-NRCS certified data as of the version date(s) listed below. Soil Survey Area: 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. Custom Soil Resource Report 10 Map Unit Legend Map Unit Symbol Map Unit Name Acres in AOI Percent of AOI 110 Spanaway gravelly sandy loam, 0 to 3 percent slopes 3.7 65.8% 111 Spanaway gravelly sandy loam, 3 to 15 percent slopes 1.9 34.2% Totals for Area of Interest 5.6 100.0% Map Unit Descriptions The map units delineated on the detailed soil maps in a soil survey represent the soils or miscellaneous areas in the survey area. The map unit descriptions, along with the maps, can be used to determine the composition and properties of a unit. A map unit delineation on a soil map represents an area dominated by one or more major kinds of soil or miscellaneous areas. A map unit is identified and named according to the taxonomic classification of the dominant soils. Within a taxonomic class there are precisely defined limits for the properties of the soils. On the landscape, however, the soils are natural phenomena, and they have the characteristic variability of all natural phenomena. Thus, the range of some observed properties may extend beyond the limits defined for a taxonomic class. Areas of soils of a single taxonomic class rarely, if ever, can be mapped without including areas of other taxonomic classes. Consequently, every map unit is made up of the soils or miscellaneous areas for which it is named and some minor components that belong to taxonomic classes other than those of the major soils. Most minor soils have properties similar to those of the dominant soil or soils in the map unit, and thus they do not affect use and management. These are called noncontrasting, or similar, components. They may or may not be mentioned in a particular map unit description. Other minor components, however, have properties and behavioral characteristics divergent enough to affect use or to require different management. These are called contrasting, or dissimilar, components. They generally are in small areas and could not be mapped separately because of the scale used. Some small areas of strongly contrasting soils or miscellaneous areas are identified by a special symbol on the maps. If included in the database for a given area, the contrasting minor components are identified in the map unit descriptions along with some characteristics of each. A few areas of minor components may not have been observed, and consequently they are not mentioned in the descriptions, especially where the pattern was so complex that it was impractical to make enough observations to identify all the soils and miscellaneous areas on the landscape. The presence of minor components in a map unit in no way diminishes the usefulness or accuracy of the data. The objective of mapping is not to delineate pure taxonomic classes but rather to separate the landscape into landforms or landform segments that have similar use and management requirements. The delineation of such segments on the map provides sufficient information for the development of resource plans. If intensive use of small areas is planned, however, Custom Soil Resource Report 11 onsite investigation is needed to define and locate the soils and miscellaneous areas. An identifying symbol precedes the map unit name in the map unit descriptions. Each description includes general facts about the unit and gives important soil properties and qualities. Soils that have profiles that are almost alike make up a soil series. Except for differences in texture of the surface layer, all the soils of a series have major horizons that are similar in composition, thickness, and arrangement. Soils of one series can differ in texture of the surface layer, slope, stoniness, salinity, degree of erosion, and other characteristics that affect their use. On the basis of such differences, a soil series is divided into soil phases. Most of the areas shown on the detailed soil maps are phases of soil series. The name of a soil phase commonly indicates a feature that affects use or management. For example, Alpha silt loam, 0 to 2 percent slopes, is a phase of the Alpha series. Some map units are made up of two or more major soils or miscellaneous areas. These map units are complexes, associations, or undifferentiated groups. A complex consists of two or more soils or miscellaneous areas in such an intricate pattern or in such small areas that they cannot be shown separately on the maps. The pattern and proportion of the soils or miscellaneous areas are somewhat similar in all areas. Alpha-Beta complex, 0 to 6 percent slopes, is an example. An association is made up of two or more geographically associated soils or miscellaneous areas that are shown as one unit on the maps. Because of present or anticipated uses of the map units in the survey area, it was not considered practical or necessary to map the soils or miscellaneous areas separately. The pattern and relative proportion of the soils or miscellaneous areas are somewhat similar. Alpha-Beta association, 0 to 2 percent slopes, is an example. An undifferentiated group is made up of two or more soils or miscellaneous areas that could be mapped individually but are mapped as one unit because similar interpretations can be made for use and management. The pattern and proportion of the soils or miscellaneous areas in a mapped area are not uniform. An area can be made up of only one of the major soils or miscellaneous areas, or it can be made up of all of them. Alpha and Beta soils, 0 to 2 percent slopes, is an example. Some surveys include miscellaneous areas. Such areas have little or no soil material and support little or no vegetation. Rock outcrop is an example. Custom Soil Resource Report 12 Thurston County Area, Washington 110—Spanaway gravelly sandy loam, 0 to 3 percent slopes Map Unit Setting National map unit symbol: 2ndb6 Elevation: 330 to 1,310 feet Mean annual precipitation: 35 to 65 inches Mean annual air temperature: 50 degrees F Frost-free period: 150 to 200 days Farmland classification: Prime farmland if irrigated Map Unit Composition Spanaway and similar soils:100 percent Estimates are based on observations, descriptions, and transects of the mapunit. Description of Spanaway Setting Landform:Terraces, outwash plains Parent material:Volcanic ash over gravelly outwash Typical profile H1 - 0 to 15 inches: gravelly sandy loam H2 - 15 to 20 inches: very gravelly loam H3 - 20 to 60 inches: extremely gravelly sand Properties and qualities Slope:0 to 3 percent Depth to restrictive feature:More than 80 inches Drainage class:Somewhat excessively drained Capacity of the most limiting layer to transmit water (Ksat):High (1.98 to 5.95 in/hr) Depth to water table:More than 80 inches Frequency of flooding:None Frequency of ponding:None Available water supply, 0 to 60 inches: Low (about 3.8 inches) Interpretive groups Land capability classification (irrigated): 3s Land capability classification (nonirrigated): 3s Hydrologic Soil Group: A Ecological site: R002XA006WA - Puget Lowlands Prairie Forage suitability group: Droughty Soils (G002XS401WA) Other vegetative classification: Droughty Soils (G002XS401WA) Hydric soil rating: No 111—Spanaway gravelly sandy loam, 3 to 15 percent slopes Map Unit Setting National map unit symbol: 2ndb7 Custom Soil Resource Report 13 Elevation: 330 to 1,310 feet Mean annual precipitation: 35 to 65 inches Mean annual air temperature: 50 degrees F Frost-free period: 150 to 200 days Farmland classification: Farmland of statewide importance Map Unit Composition Spanaway and similar soils:100 percent Estimates are based on observations, descriptions, and transects of the mapunit. Description of Spanaway Setting Landform:Terraces, outwash plains Parent material:Volcanic ash over gravelly outwash Typical profile H1 - 0 to 15 inches: gravelly sandy loam H2 - 15 to 20 inches: very gravelly sandy loam H3 - 20 to 60 inches: extremely gravelly sand Properties and qualities Slope:3 to 15 percent Depth to restrictive feature:More than 80 inches Drainage class:Somewhat excessively drained Capacity of the most limiting layer to transmit water (Ksat):High (1.98 to 5.95 in/hr) Depth to water table:More than 80 inches Frequency of flooding:None Frequency of ponding:None Available water supply, 0 to 60 inches: Low (about 3.8 inches) Interpretive groups Land capability classification (irrigated): 3e Land capability classification (nonirrigated): 4s Hydrologic Soil Group: A Ecological site: R002XA006WA - Puget Lowlands Prairie Forage suitability group: Droughty Soils (G002XS401WA) Other vegetative classification: Droughty Soils (G002XS401WA) Hydric soil rating: No Custom Soil Resource Report 14