Loading...
The URL can be used to link to this page
Your browser does not support the video tag.
Preliminary Drainage Report
Preliminary Drainage and Erosion Control Report for 906 Rhoton Rd. Yelm, WA November 4, 2022 PO Box 12690 Olympia WA 98508 360.705.2474 www.olyeng.com ________________________________________________________________________________ November 2022 Preliminary Drainage and Erosion Control Report 1 COVER SHEET 906 RHOTON RD. Yelm, Washington November 4, 2022 Owner/Applicant Prepared for: MM Rhoton Rd, LLC Contact: Steve McClung PO Box 1189 Buckley, WA 98321 (360) 761-7695 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: 22015 11/4/2022 "I hereby certify that this Preliminary Drainage and Erosion Control Plan and Report and Construction SWPPP for the 906 Rhoton Rd. 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 Tumwater does not and will not assume liability for the sufficiency, suitability, or performance of drainage facilities prepared by me.” ________________________________________________________________________________ November 2022 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 Timing of the Project .......................................................................................................................... 5 SECTION 2 – EXISTING SITE CONDITIONS ......................................................................... 5 Topography ........................................................................................................................................ 5 Ground Cover .................................................................................................................................... 5 Drainage ............................................................................................................................................ 5 Soils ................................................................................................................................................... 6 Critical Areas ..................................................................................................................................... 6 Adjacent Areas .................................................................................................................................. 6 Precipitation Records ......................................................................................................................... 6 Reports and Studies .......................................................................................................................... 6 SECTION 3 – GEOTECHNICAL REPORT .............................................................................. 6 SECTION 4 – WELLS AND SEPTIC SYSTEMS ..................................................................... 6 SECTION 5 – FUEL TANKS .................................................................................................... 6 SECTION 6 – ANALYSIS OF THE 100-YEAR FLOOD .......................................................... 6 SECTION 7 – AESTHETIC CONSIDERATIONS FOR FACILITIES ....................................... 6 SECTION 8 – FACILITY SIZING AND OFF-SITE ANALYSIS ................................................ 7 Proposed Permanent BMP’s ............................................................................................................. 7 Off-Site Analysis ................................................................................................................................ 8 SECTION 9 – COVENANTS, DEDICATIONS, EASEMENTS ................................................ 8 SECTION 10 – PROPERTY OWNERS ASSOCIATION ARTICLES OF INCORPORATION 8 APPENDICES Appendix 1 - Preliminary Drainage Plan Appendix 2 - Preliminary Drainage Calculations Appendix 3 - Soils Report ________________________________________________________________________________ November 2022 Preliminary Drainage and Erosion Control Report 3 SECTION 1 – PROPOSED PROJECT DESCRIPTION Permit The applicant is applying for permits to construct a construction equipment and materials storage yard at this time. An office/warehouse building(s) and an outdoor RV storage area may be proposed in the future. Project Location See Vicinity Map on plans for reference. Site Address: 906 Rhoton Rd. Yelm, WA 98594 Tax Parcel Number(s): 64300800303 Section, Township, Range: Section 19 Township 17 North Range 02 East, W.M. Property Boundaries & Zoning The zoning is Industrial (I). The parcel boundaries are shown on the drainage plans (see Appendix). Project Description The proposal is to construct a construction equipment and materials gravel storage yard. An office/warehouse building(s) with an associated paved and formal parking lot and an outdoor RV storage area may be constructed in the future. 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 for this project (see Appendix). Minimum Requirement #2 – Construction Stormwater Pollution Prevention (SWPP) A Construction Stormwater Pollution Prevention (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. ________________________________________________________________________________ November 2022 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 as the majority of hard surface areas are proposed to be fully infiltrated. The proposed BMP’s are as follows: Lawn and Landscape Areas: • All disturbed and/or new lawn and landscape areas will contain soils meeting the Post-Construction Soil Quality and Depth (BMP T5.13) requirements. Roof Areas: • Not applicable at this time. Any future building(s) will be placed over gravel parking areas and the Bioretention facility (BMP T7.30) has been sized to accommodate that impervious surface area. Therefore, no revised or additional stormwater facilities would be needed to accommodate any future roof area(s). Other Hard Surface Areas: • Stormwater runoff from the new gravel storage yard will be routed to a Bioretention facility (BMP T7.30). • Due to grades, some stormwater runoff from the driveway access immediately off Rhoton Rd. will inadvertently be sheet flow dispersed (BMP T5.12) over adjacent lawn area. • Any future and formal paved parking lot area(s) will be placed over gravel parking areas and the Bioretention facility (BMP T7.30) has been sized to accommodate that impervious surface area. Therefore, no revised or additional stormwater facilities would be needed to accommodate any future parking lot area(s). See Section 8 and the drainage plans for additional information. Minimum Requirement #6 – Runoff Treatment This project will create/replace more than 5,000 square-feet of new total effective pollution-generating hard surface (PGHS) area; therefore, Runoff Treatment is required. See Minimum Requirement #5 above and Section 8 below for additional information along with the WWHM modeling results in the Appendix for the 15-minute water quality flow rate treatment requirement. ________________________________________________________________________________ November 2022 Preliminary Drainage and Erosion Control Report 5 Minimum Requirement #7 – Flow Control This project will have less than 10,000 square-feet of “effective” impervious surface area; will convert less than ¾-acre of vegetation to lawn/landscape; convert less than 2.5-acres of native vegetation to pasture; and cause less than a 0.15-cfs increase in the 100-year flow frequency; therefore, Flow Control is not required. Per WWHM, this project will meet the LID Performance Standard. See Minimum Requirement #5 above and Section 8 below for additional information along with the WWHM modeling results in the Appendix for infiltration trench sizing. 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 construction of the gravel storage yard area will begin in spring 2023 with substantial completion by summer 2023. Timing of the future building(s) and RV storage area are currently unknown. SECTION 2 – EXISTING SITE CONDITIONS Topography Site topography in the western half of the site is flat and topography in the eastern half slopes down to the west at an average slope of approximately 5%. Ground Cover Site vegetation consists mainly of field grass, brush, and Scotch Broom. Drainage See drainage plan and Section 8 below. ________________________________________________________________________________ November 2022 Preliminary Drainage and Erosion Control Report 6 Soils The Natural Resources Conservation Service (NRCS) Soil Survey of Thurston County classifies the on-site soils as Spanaway Gravelly/Stony Sandy Loam (HSG A). A Geotechnical Services Report prepared by Quality Geo NW (see Appendix) indicates the site soils consisting of topsoil overlying sand with silt to depths of at least 7.5’ below-grade. Seasonal groundwater was encountered in a test pit located on the lower western portion of the site at 7’ below-grade. Critical Areas There are no known critical areas (i.e. wetlands, steep slopes, 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. Adjacent Areas The project site is bounded by industrial parcels to the north and east; by Rhoton Rd. to the west; and by a City of Yelm dog park to the south. Precipitation Records Precipitation data is included within the WWHM model. Reports and Studies A Geotechnical Services Report has been prepared by Quality Geo NW, dated April 27, 2022 (see Appendix). SECTION 3 – GEOTECHNICAL REPORT A Geotechnical Services Report has been prepared by Quality Geo NW, dated April 27, 2022 (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 #53067C0353E dated October 16, 2012, portions of the project site and surrounding area are located in Zones AE and X. The City of Yelm was in the process of removing the flood designations from the subject parcel but the status of this is currently unknown. However, city GIS indicates the parcel is outside of any flood zones. SECTION 7 – AESTHETIC CONSIDERATIONS FOR FACILITIES The proposed Bioretention facility (BMP T7.30) will be landscaped. All disturbed pervious areas will be vegetated and/or landscaped and will contain soils that meet the Post- Construction Soil Quality and Depth (BMP T5.13) requirements. ________________________________________________________________________________ November 2022 Preliminary Drainage and Erosion Control Report 7 SECTION 8 – FACILITY SIZING AND OFF-SITE ANALYSIS Parcel Area: 158,487 sf (3.638 ac) Off-Site: 913 sf (0.021 ac) (new access) Project Area: 159,400 sf (3.659 ac) Existing Development Coverage Land Coverage Table – Pre-Developed (Acres) Pasture (off-site) 0.021 Pasture (on-site) 3.638 Total 3.659 Proposed Development Coverage Land Coverage Table – Post-Developed (Acres) Paved Access (off-site) 0.021 Paved Access (on-site) 0.011 Gravel Storage Yard 2.870 Lawn/Landscape 0.757* Total 3.659 *Approximately 0.403-acres of the perimeter lawn/landscape area will contribute runoff to the bioretention facility and this has been reflected in the model. Proposed Permanent BMP’s The following Permanent BMP’s have been incorporated into the design (see drainage plans): 1. BMP T7.30 Bioretention Facility (for gravel storage yard and future roof and RV storage areas) 2. BMP T5.13 Post-Construction Soil Quality and Depth (all disturbed, lawn/landscape, and stormwater dispersion areas) Flow Control & Runoff Treatment Facilities A Bioretention facility (BMP T7.30) will provide treatment and temporary detention of stormwater runoff from all pollution generating hard surface (PGHS) areas. Per WWHM modeling results, this project will treat and infiltrate 100% of the runoff volume. The bioretention facility will provide for over 2’ of freeboard. At a maximum ponding depth of 1’, the facility will draw down in 1.5 hours (1’x12”)/8”/hr = 1.5 hours). See WWHM modeling results in the Appendix for infiltration trench sizing. ________________________________________________________________________________ November 2022 Preliminary Drainage and Erosion Control Report 8 Modeling & Assumptions • Stormwater runoff from the hard surface areas will be infiltrated. These areas are considered “ineffective” and can be excluded from the impervious area threshold determination of Minimum Requirement #7. • All infiltrated areas can be discounted from WWHM when comparing pre- to post-developed runoff rates. • The existing ground cover has been modeled as it currently exists for comparing the pre- to post-developed runoff rates. • For the LID analysis, all areas to be disturbed were modeled as forest. • All lawn/landscape areas that meet the Post-Construction Soil Quality and Depth (BMP T5.13) requirements have been modeled as “pasture”. • An 8”/hr design (corrected Ksat) infiltration rate has been used for the native subgrade beneath the Bioretention facility as recommended in the Geotechnical Services Report. A 12”/hr rate was used for the default bioretention soil mix. • Approximately 0.403-acres of the perimeter lawn/landscape area will contribute runoff to the bioretention facility and this has been reflected in the model. • The bioretention area in the model automatically receives rainfall; therefore, the area of the facility has been excluded from the contributing basin area. Off-Site Analysis Stormwater runoff generated from the new on-site improvements will be fully infiltrated on-site. Stormwater runoff from the Rhoton Rd. frontage currently sheet flows to a shallow roadside ditch with no apparent ultimate outfall point other than full infiltration. There does not appear to be any noticeable stormwater run-on from adjacent parcels. Stromwater runoff will not be directly discharged off-site. Stormwater from a complete failure of the on-site infiltration system may temporarily overflow to the existing ditch along Rhoton Rd. No downstream impacts, including impacts to structures, are anticipated as a result of an emergency overflow. 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 Box 12690Olympia, WA 98508360.705.2474 officewww.olyeng.com Appendix 2 Preliminary Drainage Calculations WWHM2012 PROJECT REPORT 22015_110322 LID 11/4/2022 10:49:19 AM Page 2 General Model Information Project Name:22015_110322 LID Site Name:MM Rhoton Site Address:906 Rhoton Rd. SE City:Yelm Report Date:11/4/2022 Gage:Lake Lawrence Data Start:1955/10/01 Data End:2008/09/30 Timestep:15 Minute Precip Scale:0.857 Version Date:2019/09/13 Version:4.2.17 POC Thresholds Low Flow Threshold for POC1:50 Percent of the 2 Year High Flow Threshold for POC1:50 Year 22015_110322 LID 11/4/2022 10:49:19 AM Page 3 Landuse Basin Data Predeveloped Land Use Basin 1 Bypass:No GroundWater:No Pervious Land Use acre A B, Forest, Flat 3.659 Pervious Total 3.659 Impervious Land Use acre Impervious Total 0 Basin Total 3.659 Element Flows To: Surface Interflow Groundwater 22015_110322 LID 11/4/2022 10:49:19 AM Page 4 Mitigated Land Use Basin 1 Bypass:No GroundWater:No Pervious Land Use acre A B, Pasture, Steep 0.403 Pervious Total 0.403 Impervious Land Use acre PARKING FLAT 2.902 Impervious Total 2.902 Basin Total 3.305 Element Flows To: Surface Interflow Groundwater Surface retention 1 Surface retention 1 22015_110322 LID 11/4/2022 10:49:19 AM Page 5 Basin 2 Bypass:Yes GroundWater:No Pervious Land Use acre A B, Pasture, Mod 0.1 A B, Pasture, Flat 0.115 Pervious Total 0.215 Impervious Land Use acre Impervious Total 0 Basin Total 0.215 Element Flows To: Surface Interflow Groundwater 22015_110322 LID 11/4/2022 10:49:19 AM Page 6 Routing Elements Predeveloped Routing 22015_110322 LID 11/4/2022 10:49:19 AM Page 7 Mitigated Routing Bioretention 1 Bottom Length: 207.00 ft. Bottom Width: 16.00 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:8 Infiltration safety factor:1 Wetted surface area On Total Volume Infiltrated (ac-ft.):518.268 Total Volume Through Riser (ac-ft.):0 Total Volume Through Facility (ac-ft.):518.268 Percent Infiltrated:100 Total Precip Applied to Facility:14.713 Total Evap From Facility:5.993 Underdrain not used Discharge Structure Riser Height:1 ft. Riser Diameter:0.5 in. Element Flows To: Outlet 1 Outlet 2 Bioretention Hydraulic Table Stage(feet)Area(ac.)Volume(ac-ft.)Discharge(cfs)Infilt(cfs) 325.00 0.1240 0.0000 0.0000 0.0000 325.04 0.1227 0.0013 0.0000 0.0000 325.08 0.1214 0.0027 0.0000 0.0000 325.12 0.1201 0.0041 0.0000 0.0000 325.15 0.1189 0.0055 0.0000 0.0007 325.19 0.1176 0.0069 0.0000 0.0062 325.23 0.1164 0.0084 0.0000 0.0098 325.27 0.1151 0.0099 0.0000 0.0144 325.31 0.1138 0.0114 0.0000 0.0203 325.35 0.1126 0.0129 0.0000 0.0275 325.38 0.1113 0.0144 0.0000 0.0362 325.42 0.1101 0.0160 0.0000 0.0464 325.46 0.1088 0.0176 0.0000 0.0583 325.50 0.1076 0.0192 0.0000 0.0720 325.54 0.1063 0.0208 0.0000 0.0876 325.58 0.1051 0.0224 0.0000 0.1053 325.62 0.1039 0.0241 0.0000 0.1251 325.65 0.1026 0.0258 0.0000 0.1472 325.69 0.1014 0.0275 0.0000 0.1717 325.73 0.1001 0.0292 0.0000 0.1988 325.77 0.0989 0.0310 0.0000 0.2286 325.81 0.0977 0.0327 0.0000 0.2611 325.85 0.0965 0.0345 0.0000 0.2966 325.88 0.0952 0.0363 0.0000 0.3352 325.92 0.0940 0.0382 0.0000 0.3770 22015_110322 LID 11/4/2022 10:49:19 AM Page 8 325.96 0.0928 0.0400 0.0000 0.4221 326.00 0.0916 0.0419 0.0000 0.4707 326.04 0.0904 0.0438 0.0000 0.5229 326.08 0.0892 0.0457 0.0000 0.5789 326.12 0.0880 0.0477 0.0000 0.6388 326.15 0.0868 0.0497 0.0000 0.7027 326.19 0.0856 0.0517 0.0000 0.7708 326.23 0.0844 0.0537 0.0000 0.8433 326.27 0.0832 0.0557 0.0000 0.9201 326.31 0.0820 0.0578 0.0000 0.9488 326.35 0.0808 0.0598 0.0000 0.9590 326.38 0.0796 0.0619 0.0000 0.9692 326.42 0.0784 0.0641 0.0000 0.9794 326.46 0.0772 0.0662 0.0000 0.9897 326.50 0.0760 0.0684 0.0000 1.0000 Bioretention Hydraulic Table Stage(feet)Area(ac.)Volume(ac-ft.)Discharge(cfs)To Amended(cfs)Infilt(cfs) 1.5000 0.1240 0.0684 0.0000 0.9200 0.0103 1.5385 0.1252 0.0732 0.0000 0.9200 0.0206 1.5769 0.1265 0.0780 0.0000 0.9672 0.0310 1.6154 0.1278 0.0829 0.0000 0.9908 0.0414 1.6538 0.1291 0.0878 0.0000 1.0144 0.0517 1.6923 0.1304 0.0928 0.0000 1.0379 0.0621 1.7308 0.1317 0.0979 0.0000 1.0615 0.0726 1.7692 0.1330 0.1030 0.0000 1.0851 0.0830 1.8077 0.1343 0.1081 0.0000 1.1087 0.0935 1.8462 0.1356 0.1133 0.0000 1.1323 0.1040 1.8846 0.1369 0.1185 0.0000 1.1559 0.1145 1.9231 0.1382 0.1238 0.0000 1.1795 0.1250 1.9615 0.1395 0.1292 0.0000 1.2031 0.1356 2.0000 0.1408 0.1346 0.0000 1.2267 0.1461 2.0385 0.1421 0.1400 0.0000 1.2503 0.1567 2.0769 0.1434 0.1455 0.0000 1.2738 0.1673 2.1154 0.1447 0.1510 0.0000 1.2974 0.1779 2.1538 0.1460 0.1566 0.0000 1.3210 0.1886 2.1923 0.1473 0.1623 0.0000 1.3446 0.1992 2.2308 0.1487 0.1679 0.0000 1.3682 0.2099 2.2692 0.1500 0.1737 0.0000 1.3918 0.2206 2.3077 0.1513 0.1795 0.0000 1.4154 0.2314 2.3462 0.1526 0.1853 0.0000 1.4390 0.2421 2.3846 0.1540 0.1912 0.0000 1.4626 0.2529 2.4231 0.1553 0.1972 0.0000 1.4862 0.2636 2.4615 0.1566 0.2032 0.0000 1.5097 0.2744 2.5000 0.1580 0.2092 0.0000 1.5333 0.2853 2.5385 0.1593 0.2153 0.0011 1.5333 0.2961 2.5769 0.1607 0.2215 0.0015 1.5333 0.3070 2.6154 0.1620 0.2277 0.0019 1.5333 0.3179 2.6538 0.1634 0.2339 0.0021 1.5333 0.3288 2.6923 0.1647 0.2403 0.0024 1.5333 0.3397 2.7308 0.1661 0.2466 0.0026 1.5333 0.3506 2.7692 0.1674 0.2530 0.0028 1.5333 0.3616 2.8077 0.1688 0.2595 0.0030 1.5333 0.3726 2.8462 0.1702 0.2660 0.0032 1.5333 0.3836 2.8846 0.1715 0.2726 0.0034 1.5333 0.3946 2.9231 0.1729 0.2792 0.0036 1.5333 0.4056 2.9615 0.1742 0.2859 0.0037 1.5333 0.4167 3.0000 0.1756 0.2926 0.0039 1.5333 0.4277 22015_110322 LID 11/4/2022 10:49:19 AM Page 9 3.0385 0.1770 0.2994 0.0040 1.5333 0.4388 3.0769 0.1784 0.3062 0.0042 1.5333 0.4500 3.1154 0.1797 0.3131 0.0043 1.5333 0.4611 3.1538 0.1811 0.3200 0.0044 1.5333 0.4723 3.1923 0.1825 0.3270 0.0045 1.5333 0.4834 3.2308 0.1839 0.3341 0.0047 1.5333 0.4946 3.2692 0.1853 0.3412 0.0048 1.5333 0.5058 3.3077 0.1867 0.3483 0.0049 1.5333 0.5171 3.3462 0.1881 0.3555 0.0050 1.5333 0.5283 3.3846 0.1895 0.3628 0.0051 1.5333 0.5396 3.4231 0.1909 0.3701 0.0053 1.5333 0.5509 3.4615 0.1923 0.3775 0.0054 1.5333 0.5622 3.5000 0.1937 0.3849 0.0055 1.5333 0.5622 3.5000 0.1937 0.3849 0.0056 1.5333 0.0000 22015_110322 LID 11/4/2022 10:49:19 AM Page 10 Surface retention 1 Element Flows To: Outlet 1 Outlet 2 Bioretention 1 22015_110322 LID 11/4/2022 10:49:19 AM Page 11 Analysis Results POC 1 + Predeveloped x Mitigated Predeveloped Landuse Totals for POC #1 Total Pervious Area:3.659 Total Impervious Area:0 Mitigated Landuse Totals for POC #1 Total Pervious Area:0.618 Total Impervious Area:2.902 Flow Frequency Method:Log Pearson Type III 17B Flow Frequency Return Periods for Predeveloped. POC #1 Return Period Flow(cfs) 2 year 0.00555 5 year 0.015401 10 year 0.028395 25 year 0.057986 50 year 0.095211 100 year 0.152298 Flow Frequency Return Periods for Mitigated. POC #1 Return Period Flow(cfs) 2 year 0.001002 5 year 0.003686 10 year 0.007601 25 year 0.017002 50 year 0.029133 100 year 0.047884 Annual Peaks 22015_110322 LID 11/4/2022 10:50:10 AM Page 12 Annual Peaks for Predeveloped and Mitigated. POC #1 Year Predeveloped Mitigated 1956 0.018 0.003 1957 0.004 0.003 1958 0.003 0.001 1959 0.003 0.001 1960 0.003 0.001 1961 0.013 0.002 1962 0.003 0.000 1963 0.003 0.004 1964 0.003 0.001 1965 0.003 0.002 1966 0.003 0.000 1967 0.005 0.001 1968 0.003 0.000 1969 0.003 0.000 1970 0.003 0.000 1971 0.024 0.003 1972 0.039 0.006 1973 0.003 0.000 1974 0.010 0.001 1975 0.003 0.000 1976 0.004 0.001 1977 0.003 0.000 1978 0.004 0.002 1979 0.003 0.000 1980 0.003 0.001 1981 0.007 0.003 1982 0.008 0.002 1983 0.003 0.001 1984 0.003 0.001 1985 0.003 0.000 1986 0.007 0.003 1987 0.006 0.002 1988 0.003 0.000 1989 0.003 0.000 1990 0.021 0.011 1991 0.032 0.004 1992 0.003 0.000 1993 0.003 0.000 1994 0.003 0.000 1995 0.018 0.003 1996 0.044 0.005 1997 0.029 0.005 1998 0.007 0.007 1999 0.003 0.000 2000 0.003 0.001 2001 0.003 0.000 2002 0.019 0.002 2003 0.003 0.000 2004 0.185 0.044 2005 0.030 0.021 2006 0.133 0.017 2007 0.057 0.009 2008 0.003 0.002 Ranked Annual Peaks Ranked Annual Peaks for Predeveloped and Mitigated. POC #1 22015_110322 LID 11/4/2022 10:50:10 AM Page 13 Rank Predeveloped Mitigated 1 0.1852 0.0443 2 0.1332 0.0208 3 0.0574 0.0175 4 0.0442 0.0107 5 0.0388 0.0088 6 0.0316 0.0067 7 0.0299 0.0056 8 0.0292 0.0051 9 0.0239 0.0047 10 0.0209 0.0039 11 0.0188 0.0037 12 0.0182 0.0032 13 0.0182 0.0031 14 0.0131 0.0028 15 0.0101 0.0028 16 0.0075 0.0026 17 0.0070 0.0025 18 0.0068 0.0024 19 0.0068 0.0023 20 0.0063 0.0021 21 0.0048 0.0021 22 0.0041 0.0020 23 0.0041 0.0018 24 0.0040 0.0018 25 0.0030 0.0014 26 0.0029 0.0013 27 0.0029 0.0012 28 0.0029 0.0010 29 0.0029 0.0009 30 0.0029 0.0008 31 0.0029 0.0006 32 0.0029 0.0006 33 0.0029 0.0006 34 0.0029 0.0005 35 0.0029 0.0005 36 0.0029 0.0004 37 0.0029 0.0003 38 0.0029 0.0003 39 0.0029 0.0003 40 0.0029 0.0003 41 0.0029 0.0002 42 0.0029 0.0002 43 0.0029 0.0002 44 0.0029 0.0002 45 0.0029 0.0002 46 0.0029 0.0002 47 0.0029 0.0002 48 0.0028 0.0002 49 0.0028 0.0002 50 0.0028 0.0002 51 0.0028 0.0002 52 0.0026 0.0002 53 0.0026 0.0002 22015_110322 LID 11/4/2022 10:50:10 AM Page 14 LID Duration Flows The Facility PASSED Flow(cfs)Predev Mit Percentage Pass/Fail 0.0004 24234 302 1 Pass 0.0005 23361 289 1 Pass 0.0005 22506 278 1 Pass 0.0005 21744 270 1 Pass 0.0005 20963 256 1 Pass 0.0006 20294 243 1 Pass 0.0006 19681 233 1 Pass 0.0006 19105 226 1 Pass 0.0006 18520 214 1 Pass 0.0007 18012 208 1 Pass 0.0007 17486 199 1 Pass 0.0007 16996 191 1 Pass 0.0007 16509 186 1 Pass 0.0008 16026 174 1 Pass 0.0008 15593 166 1 Pass 0.0008 15217 157 1 Pass 0.0008 14793 152 1 Pass 0.0008 14385 145 1 Pass 0.0009 13963 141 1 Pass 0.0009 13531 139 1 Pass 0.0009 13199 132 1 Pass 0.0009 12844 128 0 Pass 0.0010 12467 128 1 Pass 0.0010 12169 124 1 Pass 0.0010 11809 120 1 Pass 0.0010 11513 117 1 Pass 0.0011 11210 113 1 Pass 0.0011 10943 106 0 Pass 0.0011 10660 101 0 Pass 0.0011 10411 97 0 Pass 0.0012 10147 94 0 Pass 0.0012 9913 91 0 Pass 0.0012 9657 88 0 Pass 0.0012 9393 85 0 Pass 0.0012 9190 84 0 Pass 0.0013 8991 83 0 Pass 0.0013 8757 81 0 Pass 0.0013 8532 77 0 Pass 0.0013 8309 77 0 Pass 0.0014 8105 76 0 Pass 0.0014 7919 75 0 Pass 0.0014 7724 73 0 Pass 0.0014 7540 73 0 Pass 0.0015 7328 71 0 Pass 0.0015 7150 69 0 Pass 0.0015 6984 66 0 Pass 0.0015 6819 66 0 Pass 0.0016 6655 66 0 Pass 0.0016 6508 65 0 Pass 0.0016 6356 65 1 Pass 0.0016 6191 65 1 Pass 0.0016 5995 65 1 Pass 0.0017 5847 63 1 Pass 22015_110322 LID 11/4/2022 10:50:10 AM Page 15 0.0017 5681 62 1 Pass 0.0017 5508 62 1 Pass 0.0017 5351 61 1 Pass 0.0018 5207 60 1 Pass 0.0018 5077 60 1 Pass 0.0018 4942 59 1 Pass 0.0018 4787 58 1 Pass 0.0019 4654 58 1 Pass 0.0019 4505 58 1 Pass 0.0019 4388 58 1 Pass 0.0019 4243 56 1 Pass 0.0020 4111 56 1 Pass 0.0020 3962 55 1 Pass 0.0020 3841 51 1 Pass 0.0020 3713 49 1 Pass 0.0020 3579 48 1 Pass 0.0021 3457 48 1 Pass 0.0021 3340 45 1 Pass 0.0021 3219 44 1 Pass 0.0021 3104 43 1 Pass 0.0022 3001 42 1 Pass 0.0022 2894 42 1 Pass 0.0022 2795 41 1 Pass 0.0022 2700 41 1 Pass 0.0023 2594 41 1 Pass 0.0023 2505 41 1 Pass 0.0023 2423 41 1 Pass 0.0023 2325 40 1 Pass 0.0024 2226 40 1 Pass 0.0024 2126 39 1 Pass 0.0024 2018 39 1 Pass 0.0024 1925 38 1 Pass 0.0024 1846 37 2 Pass 0.0025 1760 36 2 Pass 0.0025 1670 36 2 Pass 0.0025 1578 36 2 Pass 0.0025 1493 34 2 Pass 0.0026 1397 34 2 Pass 0.0026 1311 34 2 Pass 0.0026 1227 34 2 Pass 0.0026 1140 33 2 Pass 0.0027 1052 31 2 Pass 0.0027 971 30 3 Pass 0.0027 892 30 3 Pass 0.0027 824 30 3 Pass 0.0028 745 29 3 Pass 0.0028 687 28 4 Pass 22015_110322 LID 11/4/2022 10:50:24 AM Page 16 Duration Flows The Facility PASSED Flow(cfs)Predev Mit Percentage Pass/Fail 0.0028 687 28 4 Pass 0.0037 148 21 14 Pass 0.0046 120 13 10 Pass 0.0056 98 9 9 Pass 0.0065 80 7 8 Pass 0.0074 61 6 9 Pass 0.0084 51 6 11 Pass 0.0093 48 5 10 Pass 0.0102 44 5 11 Pass 0.0112 38 3 7 Pass 0.0121 37 3 8 Pass 0.0130 33 3 9 Pass 0.0140 32 3 9 Pass 0.0149 30 3 10 Pass 0.0158 29 3 10 Pass 0.0168 27 3 11 Pass 0.0177 26 2 7 Pass 0.0186 22 2 9 Pass 0.0196 19 2 10 Pass 0.0205 18 2 11 Pass 0.0214 16 1 6 Pass 0.0224 16 1 6 Pass 0.0233 14 1 7 Pass 0.0243 13 1 7 Pass 0.0252 11 1 9 Pass 0.0261 9 1 11 Pass 0.0271 9 1 11 Pass 0.0280 9 1 11 Pass 0.0289 9 1 11 Pass 0.0299 8 1 12 Pass 0.0308 6 1 16 Pass 0.0317 5 1 20 Pass 0.0327 5 1 20 Pass 0.0336 5 1 20 Pass 0.0345 5 1 20 Pass 0.0355 5 1 20 Pass 0.0364 5 1 20 Pass 0.0373 5 1 20 Pass 0.0383 5 1 20 Pass 0.0392 4 1 25 Pass 0.0401 4 1 25 Pass 0.0411 4 1 25 Pass 0.0420 4 1 25 Pass 0.0429 4 1 25 Pass 0.0439 4 1 25 Pass 0.0448 3 0 0 Pass 0.0457 3 0 0 Pass 0.0467 3 0 0 Pass 0.0476 3 0 0 Pass 0.0485 3 0 0 Pass 0.0495 3 0 0 Pass 0.0504 3 0 0 Pass 0.0513 3 0 0 Pass 22015_110322 LID 11/4/2022 10:50:24 AM Page 17 0.0523 3 0 0 Pass 0.0532 3 0 0 Pass 0.0541 3 0 0 Pass 0.0551 3 0 0 Pass 0.0560 3 0 0 Pass 0.0569 3 0 0 Pass 0.0579 2 0 0 Pass 0.0588 2 0 0 Pass 0.0597 2 0 0 Pass 0.0607 2 0 0 Pass 0.0616 2 0 0 Pass 0.0625 2 0 0 Pass 0.0635 2 0 0 Pass 0.0644 2 0 0 Pass 0.0653 2 0 0 Pass 0.0663 2 0 0 Pass 0.0672 2 0 0 Pass 0.0681 2 0 0 Pass 0.0691 2 0 0 Pass 0.0700 2 0 0 Pass 0.0709 2 0 0 Pass 0.0719 2 0 0 Pass 0.0728 2 0 0 Pass 0.0737 2 0 0 Pass 0.0747 2 0 0 Pass 0.0756 2 0 0 Pass 0.0765 2 0 0 Pass 0.0775 2 0 0 Pass 0.0784 2 0 0 Pass 0.0793 2 0 0 Pass 0.0803 2 0 0 Pass 0.0812 2 0 0 Pass 0.0821 2 0 0 Pass 0.0831 2 0 0 Pass 0.0840 2 0 0 Pass 0.0849 2 0 0 Pass 0.0859 2 0 0 Pass 0.0868 2 0 0 Pass 0.0877 2 0 0 Pass 0.0887 2 0 0 Pass 0.0896 2 0 0 Pass 0.0905 2 0 0 Pass 0.0915 2 0 0 Pass 0.0924 2 0 0 Pass 0.0933 2 0 0 Pass 0.0943 2 0 0 Pass 0.0952 2 0 0 Pass 22015_110322 LID 11/4/2022 10:50:24 AM Page 18 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. 22015_110322 LID 11/4/2022 10:50:24 AM Page 19 LID Report 22015_110322 LID 11/4/2022 10:50:40 AM Page 20 Model Default Modifications Total of 0 changes have been made. PERLND Changes No PERLND changes have been made. IMPLND Changes No IMPLND changes have been made. 22015_110322 LID 11/4/2022 10:50:40 AM Page 21 Appendix Predeveloped Schematic 22015_110322 LID 11/4/2022 10:50:42 AM Page 22 Mitigated Schematic WWHM2012 PROJECT REPORT 22015_110322 11/4/2022 10:42:11 AM Page 2 General Model Information Project Name:22015_110322 Site Name:MM Rhoton Site Address:906 Rhoton Rd. SE City:Yelm Report Date:11/4/2022 Gage:Lake Lawrence Data Start:1955/10/01 Data End:2008/09/30 Timestep:15 Minute Precip Scale:0.857 Version Date:2019/09/13 Version:4.2.17 POC Thresholds Low Flow Threshold for POC1:50 Percent of the 2 Year High Flow Threshold for POC1:50 Year 22015_110322 11/4/2022 10:42:11 AM Page 3 Landuse Basin Data Predeveloped Land Use Basin 1 Bypass:No GroundWater:No Pervious Land Use acre A B, Pasture, Flat 3.659 Pervious Total 3.659 Impervious Land Use acre Impervious Total 0 Basin Total 3.659 Element Flows To: Surface Interflow Groundwater 22015_110322 11/4/2022 10:42:11 AM Page 4 Mitigated Land Use Basin 1 Bypass:No GroundWater:No Pervious Land Use acre A B, Pasture, Steep 0.403 Pervious Total 0.403 Impervious Land Use acre PARKING FLAT 2.902 Impervious Total 2.902 Basin Total 3.305 Element Flows To: Surface Interflow Groundwater Surface retention 1 Surface retention 1 22015_110322 11/4/2022 10:42:11 AM Page 5 Basin 2 Bypass:Yes GroundWater:No Pervious Land Use acre A B, Pasture, Mod 0.1 A B, Pasture, Flat 0.115 Pervious Total 0.215 Impervious Land Use acre Impervious Total 0 Basin Total 0.215 Element Flows To: Surface Interflow Groundwater 22015_110322 11/4/2022 10:42:11 AM Page 6 Routing Elements Predeveloped Routing 22015_110322 11/4/2022 10:42:11 AM Page 7 Mitigated Routing Bioretention 1 Bottom Length: 207.00 ft. Bottom Width: 16.00 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:8 Infiltration safety factor:1 Wetted surface area On Total Volume Infiltrated (ac-ft.):518.268 Total Volume Through Riser (ac-ft.):0 Total Volume Through Facility (ac-ft.):518.268 Percent Infiltrated:100 Total Precip Applied to Facility:14.713 Total Evap From Facility:5.993 Underdrain not used Discharge Structure Riser Height:1 ft. Riser Diameter:0.5 in. Element Flows To: Outlet 1 Outlet 2 Bioretention Hydraulic Table Stage(feet)Area(ac.)Volume(ac-ft.)Discharge(cfs)Infilt(cfs) 325.00 0.1240 0.0000 0.0000 0.0000 325.04 0.1227 0.0013 0.0000 0.0000 325.08 0.1214 0.0027 0.0000 0.0000 325.12 0.1201 0.0041 0.0000 0.0000 325.15 0.1189 0.0055 0.0000 0.0007 325.19 0.1176 0.0069 0.0000 0.0062 325.23 0.1164 0.0084 0.0000 0.0098 325.27 0.1151 0.0099 0.0000 0.0144 325.31 0.1138 0.0114 0.0000 0.0203 325.35 0.1126 0.0129 0.0000 0.0275 325.38 0.1113 0.0144 0.0000 0.0362 325.42 0.1101 0.0160 0.0000 0.0464 325.46 0.1088 0.0176 0.0000 0.0583 325.50 0.1076 0.0192 0.0000 0.0720 325.54 0.1063 0.0208 0.0000 0.0876 325.58 0.1051 0.0224 0.0000 0.1053 325.62 0.1039 0.0241 0.0000 0.1251 325.65 0.1026 0.0258 0.0000 0.1472 325.69 0.1014 0.0275 0.0000 0.1717 325.73 0.1001 0.0292 0.0000 0.1988 325.77 0.0989 0.0310 0.0000 0.2286 325.81 0.0977 0.0327 0.0000 0.2611 325.85 0.0965 0.0345 0.0000 0.2966 325.88 0.0952 0.0363 0.0000 0.3352 325.92 0.0940 0.0382 0.0000 0.3770 22015_110322 11/4/2022 10:42:11 AM Page 8 325.96 0.0928 0.0400 0.0000 0.4221 326.00 0.0916 0.0419 0.0000 0.4707 326.04 0.0904 0.0438 0.0000 0.5229 326.08 0.0892 0.0457 0.0000 0.5789 326.12 0.0880 0.0477 0.0000 0.6388 326.15 0.0868 0.0497 0.0000 0.7027 326.19 0.0856 0.0517 0.0000 0.7708 326.23 0.0844 0.0537 0.0000 0.8433 326.27 0.0832 0.0557 0.0000 0.9201 326.31 0.0820 0.0578 0.0000 0.9488 326.35 0.0808 0.0598 0.0000 0.9590 326.38 0.0796 0.0619 0.0000 0.9692 326.42 0.0784 0.0641 0.0000 0.9794 326.46 0.0772 0.0662 0.0000 0.9897 326.50 0.0760 0.0684 0.0000 1.0000 Bioretention Hydraulic Table Stage(feet)Area(ac.)Volume(ac-ft.)Discharge(cfs)To Amended(cfs)Infilt(cfs) 1.5000 0.1240 0.0684 0.0000 0.9200 0.0103 1.5385 0.1252 0.0732 0.0000 0.9200 0.0206 1.5769 0.1265 0.0780 0.0000 0.9672 0.0310 1.6154 0.1278 0.0829 0.0000 0.9908 0.0414 1.6538 0.1291 0.0878 0.0000 1.0144 0.0517 1.6923 0.1304 0.0928 0.0000 1.0379 0.0621 1.7308 0.1317 0.0979 0.0000 1.0615 0.0726 1.7692 0.1330 0.1030 0.0000 1.0851 0.0830 1.8077 0.1343 0.1081 0.0000 1.1087 0.0935 1.8462 0.1356 0.1133 0.0000 1.1323 0.1040 1.8846 0.1369 0.1185 0.0000 1.1559 0.1145 1.9231 0.1382 0.1238 0.0000 1.1795 0.1250 1.9615 0.1395 0.1292 0.0000 1.2031 0.1356 2.0000 0.1408 0.1346 0.0000 1.2267 0.1461 2.0385 0.1421 0.1400 0.0000 1.2503 0.1567 2.0769 0.1434 0.1455 0.0000 1.2738 0.1673 2.1154 0.1447 0.1510 0.0000 1.2974 0.1779 2.1538 0.1460 0.1566 0.0000 1.3210 0.1886 2.1923 0.1473 0.1623 0.0000 1.3446 0.1992 2.2308 0.1487 0.1679 0.0000 1.3682 0.2099 2.2692 0.1500 0.1737 0.0000 1.3918 0.2206 2.3077 0.1513 0.1795 0.0000 1.4154 0.2314 2.3462 0.1526 0.1853 0.0000 1.4390 0.2421 2.3846 0.1540 0.1912 0.0000 1.4626 0.2529 2.4231 0.1553 0.1972 0.0000 1.4862 0.2636 2.4615 0.1566 0.2032 0.0000 1.5097 0.2744 2.5000 0.1580 0.2092 0.0000 1.5333 0.2853 2.5385 0.1593 0.2153 0.0011 1.5333 0.2961 2.5769 0.1607 0.2215 0.0015 1.5333 0.3070 2.6154 0.1620 0.2277 0.0019 1.5333 0.3179 2.6538 0.1634 0.2339 0.0021 1.5333 0.3288 2.6923 0.1647 0.2403 0.0024 1.5333 0.3397 2.7308 0.1661 0.2466 0.0026 1.5333 0.3506 2.7692 0.1674 0.2530 0.0028 1.5333 0.3616 2.8077 0.1688 0.2595 0.0030 1.5333 0.3726 2.8462 0.1702 0.2660 0.0032 1.5333 0.3836 2.8846 0.1715 0.2726 0.0034 1.5333 0.3946 2.9231 0.1729 0.2792 0.0036 1.5333 0.4056 2.9615 0.1742 0.2859 0.0037 1.5333 0.4167 3.0000 0.1756 0.2926 0.0039 1.5333 0.4277 22015_110322 11/4/2022 10:42:11 AM Page 9 3.0385 0.1770 0.2994 0.0040 1.5333 0.4388 3.0769 0.1784 0.3062 0.0042 1.5333 0.4500 3.1154 0.1797 0.3131 0.0043 1.5333 0.4611 3.1538 0.1811 0.3200 0.0044 1.5333 0.4723 3.1923 0.1825 0.3270 0.0045 1.5333 0.4834 3.2308 0.1839 0.3341 0.0047 1.5333 0.4946 3.2692 0.1853 0.3412 0.0048 1.5333 0.5058 3.3077 0.1867 0.3483 0.0049 1.5333 0.5171 3.3462 0.1881 0.3555 0.0050 1.5333 0.5283 3.3846 0.1895 0.3628 0.0051 1.5333 0.5396 3.4231 0.1909 0.3701 0.0053 1.5333 0.5509 3.4615 0.1923 0.3775 0.0054 1.5333 0.5622 3.5000 0.1937 0.3849 0.0055 1.5333 0.5622 3.5000 0.1937 0.3849 0.0056 1.5333 0.0000 22015_110322 11/4/2022 10:42:11 AM Page 10 Surface retention 1 Element Flows To: Outlet 1 Outlet 2 Bioretention 1 22015_110322 11/4/2022 10:42:11 AM Page 11 Analysis Results POC 1 + Predeveloped x Mitigated Predeveloped Landuse Totals for POC #1 Total Pervious Area:3.659 Total Impervious Area:0 Mitigated Landuse Totals for POC #1 Total Pervious Area:0.618 Total Impervious Area:2.902 Flow Frequency Method:Log Pearson Type III 17B Flow Frequency Return Periods for Predeveloped. POC #1 Return Period Flow(cfs) 2 year 0.015063 5 year 0.053395 10 year 0.10788 25 year 0.23588 50 year 0.398078 100 year 0.645182 Flow Frequency Return Periods for Mitigated. POC #1 Return Period Flow(cfs) 2 year 0.001002 5 year 0.003686 10 year 0.007601 25 year 0.017002 50 year 0.029133 100 year 0.047884 Annual Peaks Annual Peaks for Predeveloped and Mitigated. POC #1 Year Predeveloped Mitigated 1956 0.037 0.003 1957 0.046 0.003 1958 0.017 0.001 1959 0.015 0.001 1960 0.008 0.001 1961 0.025 0.002 1962 0.003 0.000 1963 0.054 0.004 1964 0.012 0.001 1965 0.026 0.002 22015_110322 11/4/2022 10:42:32 AM Page 12 1966 0.003 0.000 1967 0.019 0.001 1968 0.004 0.000 1969 0.003 0.000 1970 0.004 0.000 1971 0.045 0.003 1972 0.081 0.006 1973 0.006 0.000 1974 0.019 0.001 1975 0.004 0.000 1976 0.012 0.001 1977 0.003 0.000 1978 0.033 0.002 1979 0.003 0.000 1980 0.008 0.001 1981 0.041 0.003 1982 0.030 0.002 1983 0.008 0.001 1984 0.007 0.001 1985 0.003 0.000 1986 0.038 0.003 1987 0.035 0.002 1988 0.003 0.000 1989 0.003 0.000 1990 0.154 0.011 1991 0.056 0.004 1992 0.003 0.000 1993 0.003 0.000 1994 0.004 0.000 1995 0.040 0.003 1996 0.074 0.005 1997 0.068 0.005 1998 0.101 0.007 1999 0.003 0.000 2000 0.008 0.001 2001 0.003 0.000 2002 0.029 0.002 2003 0.005 0.000 2004 0.651 0.044 2005 0.304 0.021 2006 0.254 0.017 2007 0.128 0.009 2008 0.031 0.002 Ranked Annual Peaks Ranked Annual Peaks for Predeveloped and Mitigated. POC #1 Rank Predeveloped Mitigated 1 0.6515 0.0443 2 0.3044 0.0208 3 0.2542 0.0175 4 0.1544 0.0107 5 0.1276 0.0088 6 0.1011 0.0067 7 0.0812 0.0056 8 0.0744 0.0051 9 0.0679 0.0047 10 0.0558 0.0039 11 0.0540 0.0037 22015_110322 11/4/2022 10:42:32 AM Page 13 12 0.0460 0.0032 13 0.0450 0.0031 14 0.0406 0.0028 15 0.0398 0.0028 16 0.0380 0.0026 17 0.0366 0.0025 18 0.0350 0.0024 19 0.0333 0.0023 20 0.0307 0.0021 21 0.0301 0.0021 22 0.0287 0.0020 23 0.0261 0.0018 24 0.0253 0.0018 25 0.0195 0.0014 26 0.0185 0.0013 27 0.0169 0.0012 28 0.0148 0.0010 29 0.0124 0.0009 30 0.0119 0.0008 31 0.0085 0.0006 32 0.0083 0.0006 33 0.0083 0.0006 34 0.0076 0.0005 35 0.0075 0.0005 36 0.0057 0.0004 37 0.0046 0.0003 38 0.0044 0.0003 39 0.0043 0.0003 40 0.0039 0.0003 41 0.0036 0.0002 42 0.0029 0.0002 43 0.0029 0.0002 44 0.0029 0.0002 45 0.0029 0.0002 46 0.0029 0.0002 47 0.0029 0.0002 48 0.0029 0.0002 49 0.0029 0.0002 50 0.0029 0.0002 51 0.0029 0.0002 52 0.0028 0.0002 53 0.0027 0.0002 22015_110322 11/4/2022 10:42:32 AM Page 14 Duration Flows The Facility PASSED Flow(cfs)Predev Mit Percentage Pass/Fail 0.0075 265 6 2 Pass 0.0115 158 3 1 Pass 0.0154 108 3 2 Pass 0.0194 77 2 2 Pass 0.0233 65 1 1 Pass 0.0273 58 1 1 Pass 0.0312 43 1 2 Pass 0.0351 38 1 2 Pass 0.0391 31 1 3 Pass 0.0430 27 1 3 Pass 0.0470 24 0 0 Pass 0.0509 23 0 0 Pass 0.0549 18 0 0 Pass 0.0588 16 0 0 Pass 0.0628 14 0 0 Pass 0.0667 13 0 0 Pass 0.0707 11 0 0 Pass 0.0746 10 0 0 Pass 0.0785 9 0 0 Pass 0.0825 8 0 0 Pass 0.0864 8 0 0 Pass 0.0904 7 0 0 Pass 0.0943 7 0 0 Pass 0.0983 7 0 0 Pass 0.1022 6 0 0 Pass 0.1062 6 0 0 Pass 0.1101 6 0 0 Pass 0.1140 6 0 0 Pass 0.1180 6 0 0 Pass 0.1219 6 0 0 Pass 0.1259 6 0 0 Pass 0.1298 5 0 0 Pass 0.1338 5 0 0 Pass 0.1377 5 0 0 Pass 0.1417 5 0 0 Pass 0.1456 5 0 0 Pass 0.1495 5 0 0 Pass 0.1535 5 0 0 Pass 0.1574 4 0 0 Pass 0.1614 4 0 0 Pass 0.1653 4 0 0 Pass 0.1693 4 0 0 Pass 0.1732 4 0 0 Pass 0.1772 3 0 0 Pass 0.1811 3 0 0 Pass 0.1851 3 0 0 Pass 0.1890 3 0 0 Pass 0.1929 3 0 0 Pass 0.1969 3 0 0 Pass 0.2008 3 0 0 Pass 0.2048 3 0 0 Pass 0.2087 3 0 0 Pass 0.2127 3 0 0 Pass 22015_110322 11/4/2022 10:42:32 AM Page 15 0.2166 3 0 0 Pass 0.2206 3 0 0 Pass 0.2245 3 0 0 Pass 0.2284 3 0 0 Pass 0.2324 3 0 0 Pass 0.2363 3 0 0 Pass 0.2403 3 0 0 Pass 0.2442 3 0 0 Pass 0.2482 3 0 0 Pass 0.2521 3 0 0 Pass 0.2561 2 0 0 Pass 0.2600 2 0 0 Pass 0.2640 2 0 0 Pass 0.2679 2 0 0 Pass 0.2718 2 0 0 Pass 0.2758 2 0 0 Pass 0.2797 2 0 0 Pass 0.2837 2 0 0 Pass 0.2876 2 0 0 Pass 0.2916 2 0 0 Pass 0.2955 2 0 0 Pass 0.2995 2 0 0 Pass 0.3034 2 0 0 Pass 0.3073 1 0 0 Pass 0.3113 1 0 0 Pass 0.3152 1 0 0 Pass 0.3192 1 0 0 Pass 0.3231 1 0 0 Pass 0.3271 1 0 0 Pass 0.3310 1 0 0 Pass 0.3350 1 0 0 Pass 0.3389 1 0 0 Pass 0.3428 1 0 0 Pass 0.3468 1 0 0 Pass 0.3507 1 0 0 Pass 0.3547 1 0 0 Pass 0.3586 1 0 0 Pass 0.3626 1 0 0 Pass 0.3665 1 0 0 Pass 0.3705 1 0 0 Pass 0.3744 1 0 0 Pass 0.3784 1 0 0 Pass 0.3823 1 0 0 Pass 0.3862 1 0 0 Pass 0.3902 1 0 0 Pass 0.3941 1 0 0 Pass 0.3981 1 0 0 Pass 22015_110322 11/4/2022 10:42:32 AM Page 16 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. 22015_110322 11/4/2022 10:42:32 AM Page 17 LID Report 22015_110322 11/4/2022 10:42:57 AM Page 18 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. 22015_110322 11/4/2022 10:42:57 AM Page 19 Appendix Predeveloped Schematic 22015_110322 11/4/2022 10:42:58 AM Page 20 Mitigated Schematic Appendix 3 Soils Report 906 Rhoton Rd Geo - Soils Report Quality Geo NW, PLLC 4/27/2022 Project # QG22-060 2 SOILS REPORT 906 RHOTON RD TPN 64300800303, 906 RHOTON RD SE YELM, WA McClung Construction Attn: Steve McClung 712 Main St. Buckley, WA Prepared by: Approved by: Ray Gean 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 04/27/2022 QG Project # QG22-060 Copyright © 2022 Quality Geo NW, PLLC All Rights Reserved 04/27/2022 906 Rhoton Rd Geo - Soils Report Quality Geo NW, PLLC 4/27/2022 Project # QG22-060 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 2.4 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 IMPERVIOUS PAVEMENT CONSIDERATIONS .................................................................................... 11 4.0 CONSTRUCTION RECOMMENDATIONS ...................................................................13 4.1 EARTHWORK ............................................................................................................................................. 13 4.1.1 GRADING & EXCAVATION ............................................................................................................ 13 4.1.2 SUBGRADE EVALUATION & PREPARATION ............................................................................ 13 4.1.3 SITE PREPARATION, EROSION CONTROLL, WET WEATHER............................................... 13 4.2 STRUCTURAL FILL MATERIALS AND COMPACTION ....................................................................... 14 4.2.1 MATERIALS ...................................................................................................................................... 14 4.2.2 FILL PLACEMENT AND COMPACTION ...................................................................................... 15 4.3 TEMPORARY EXCAVATIONS AND TRENCHES .................................................................................. 15 5.0 SPECIAL INSPECTION ...................................................................................................17 6.0 LIMITATIONS ..................................................................................................................18 Region & Vicinity Maps ................................................................................................................ 19 Exploration Map ............................................................................................................................. 20 Exploration Logs ............................................................................................................................ 21 Laboratory Results ......................................................................................................................... 23 906 Rhoton Rd Geo - Soils Report Quality Geo NW, PLLC 4/27/2022 Project # QG22-060 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 the construction of new mixed-use structures within a presently clear large 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 3/24/2022. 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 locations were selected by an QG Staff Geologist prior to field work to provide safest access to relevant soil conditions. The geologist directed the advancement of 2 excavated test pits (TP). The test pits were advanced within the vicinity of the anticipated development footprint areas, to maximum depths of 10.0 feet below present grade (BPG) in general accordance with the specified contract depth. During explorations QG logged each soil horizon we 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 soil laboratory for supplemental classification and other tests. 906 Rhoton Rd Geo - Soils Report Quality Geo NW, PLLC 4/27/2022 Project # QG22-060 5 2.0 EXISTING SITE CONDITIONS 2.1 AREA GEOLOGY QG reviewed available map publications to assess known geologic conditions and hazards present at the site location. 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. Geology of the site location and vicinity consists of continental glacial outwash and gravel (Qgog). The deposits on site are 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 in the vicinity are mapped as Spanaway gravelly sandy loam (110), these are formed by outwash plains and terrace deposits. The parent material for these soils is volcanic ash over gravelly outwash. The soils 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 most limiting layer to transmit water (ksat), is listed as high (1.98 to 5.95 in/hr). Depth to water table is more than 80 inches. 2.2 SITE & SURFACE CONDITIONS The project area is relatively flat, near the same elevation as the adjacent road. The site is currently undeveloped within the parcel and mostly grasses. 2.3 SOIL LOG Site soil conditions were generally identical across the property in the 2 test pits. Representative lab samples were taken from TP-1. Soil conditions on site were as follows: • 0’ to 1.6’ – Topsoil: An overriding 19-inch layer of topsoil was present over the site. • 1.6’ to 10.0’ – Poorly Graded Sand with Silt (SP-SM) Beneath topsoil, native sediments resemble a tan to gray fine sandy outwash, with minimal gravel present and fine sediments, in a typically medium dense to dense condition. Groundwater was encountered at 7-feet within this unit. No groundwater was encountered the other test pit down to maximum depth of 10 feet below present grade. 906 Rhoton Rd Geo - Soils Report Quality Geo NW, PLLC 4/27/2022 Project # QG22-060 6 2.4 SURFACE WATER AND GROUNDWATER CONDITIONS No active surface water features are present on site. In the near vicinity, Yelm Creek is ~2100 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 22 feet beneath the entire site. During our test pit explorations, a possible perched groundwater table was encountered in TP-1 at approximately 7.0 feet below grade. 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. 906 Rhoton Rd Geo - Soils Report Quality Geo NW, PLLC 4/27/2022 Project # QG22-060 7 3.0 GEOTECHNICAL RECOMMENDATIONS 3.1 SHALLOW FOUNDATION RECOMMENDATIONS QG recommends excavating loose or organic cover soils down to firm bearing conditions expected within 1.5 feet from the surface. As the variability in subgrade support between consolidated glacial deposits and weathered medium dense cover soils may result in differential settlement, QG recommends that foundations be placed on compacted native soils wherever, or on firm structural fill installed over these compacted soils to achieve footing grade. 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 thin 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 on 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 906 Rhoton Rd Geo - Soils Report Quality Geo NW, PLLC 4/27/2022 Project # QG22-060 8 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 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 2012 (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. 906 Rhoton Rd Geo - Soils Report Quality Geo NW, PLLC 4/27/2022 Project # QG22-060 9 • 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 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 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 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 the north portion of the site (TP-1) 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. 906 Rhoton Rd Geo - Soils Report Quality Geo NW, PLLC 4/27/2022 Project # QG22-060 10 Laboratory results were interpreted to recommended design inputs in accordance with methods of the 2019 DoE SMMWW. Gradation results were applied to the Massmann (2003) equation (1) to calculate Ksat representing the initial saturated hydraulic conductivity. (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) Correct ed Ksat (in/hr) LT Design Infiltration Rate(in/hr) Cation Exchange Capacity (meq/100g) Organic Content % 1 3.5 1.6 to 7.5 SP-SM 0.075 0.2 0.6 9.79 32.77 8.19 8.00 3.0 1.4 Beneath topsoils, the lower tan to gray outwash soils were observed to generally exhibit minimal fines content and minimal oxidation patterns. The presence of a groundwater at 7 feet below present grade across the site, and the likelihood that this is may be the seasonal high, limit the potential for conventional in-ground infiltration facilities. In-ground infiltration structures are required to maintain a minimum separation from restrictive soil & groundwater features. We recommend the designer pursue shallow infiltration structures instead, such as bio swales, rain gardens, pervious pavements, etc. These features shall penetrate beneath the overriding topsoil but have their bottom infiltrating base no deeper than 4.00 feet below present grade. For shallow infiltration features utilizing treatment media, we recommend a maximum design rate of up to 8.00 inch/hour be considered, which is typically suitable for most shallow infiltration features. This does not consider the potential reductions from compaction during construction. Construction traffic should be prevented from crossing within proposed infiltration areas, in order to limit reduction of the infiltration potential. If traffic can not be minimized, then a significant reduction to the infiltration rate can be anticipated, and additional in-field testing will be required prior to placement of the drainage course. 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 906 Rhoton Rd Geo - Soils Report Quality Geo NW, PLLC 4/27/2022 Project # QG22-060 11 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. 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 soils directly beneath the topsoil did not meet the minimum treatment standards. 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. 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 waters should also be discharged according to the above recommendations. Based on our observations of a shallow groundwater table, appropriate measures should be taken by the site designer to consider and allow for an adequate emergency outfall location in the event of future record stormwater fall that cannot be anticipated. 3.3 IMPERVIOUS PAVEMENT CONSIDERATIONS QG anticipates most pavements will be constructed of flexible Hot Mix Asphalt surfacing, with thickened sections for anticipated heavy load areas. The main entrance/exit drive will likely experience different traffic volumes than the far end of the pavement areas. As a result, consideration could be given to increasing the pavement section in the main entrance/exit drive. Pavement sections presented in the above table should not be used for areas which experience repeated truck traffic/parking, equipment or truck parking areas, entrances and exit aprons, or contain trash dumpster loading zones. In these areas, a Portland Cement Concrete (PCC) pavement should be used, as opposed to HMA. 906 Rhoton Rd Geo - Soils Report Quality Geo NW, PLLC 4/27/2022 Project # QG22-060 12 One of the important considerations in designing a high quality and durable pavement is providing adequate drainage. Design of drainage for the proposed pavement section is outside of QG ’s scope of work at this time. It is important that bird baths (leeching basins) and surface waves are not created during construction of the HMA layer. A proper slope should also be allowed, and drainage should be provided along the edges of pavements and around catch basins to prevent accumulation of free water within the base course, which otherwise may result in subgrade softening and pavement deterioration under exposure and repeated traffic conditions. All pavements require regular maintenance and repair in order to maintain the serviceability of the pavement. These repairs and maintenance are due to normal wear and tear of the pavement surface and are required in order to extend the serviceability life of the pavement. However, after 10 years of service, a normal pavement structure is likely to deteriorate to a point where pavement rehabilitation may be required to maintain the serviceability. The deterioration is more likely if the pavement is constructed over poor subgrade soils or in area of higher traffic volumes. Rigid pavement components are commonly utilized for portions of accesses and ancillary exterior improvements. The project civil designer may re-evaluate the below general recommendations for pavement thicknesses and base sections, if necessary, to ensure proper application to a given structure and use. QG recommends that we be contacted for further consultation if the below sections are proposed to be reduced. Concrete driveway aprons and curb alignments, if utilized, should consist of a minimum 6-inch thickness of unreinforced concrete pavement over structural base fill. Base thickness should correspond to related location and anticipated traffic loading. For light traffic areas, a 6-inch minimum base thickness (total 12-inch section) can be applied. For heavy traffic zones, we recommend allotting a 12- inch minimum base section beneath the pavement, or the incorporation of reinforcing steel in the concrete. Concrete sidewalks, walkways and patios if present may consist of a minimum 4-inch section of plain concrete (unreinforced) installed over a 6-inch minimum compacted base of crushed rock. At locations where grade has been raised with structural fill, a 4-inch minimum crushed rock section may be used. Flatworks should employ frequent joint controls to limit cracking potential. 906 Rhoton Rd Geo - Soils Report Quality Geo NW, PLLC 4/27/2022 Project # QG22-060 13 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 an 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 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 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 906 Rhoton Rd Geo - Soils Report Quality Geo NW, PLLC 4/27/2022 Project # QG22-060 14 also be required to reduce the moisture content of on-site soils 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 utilize 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 906 Rhoton Rd Geo - Soils Report Quality Geo NW, PLLC 4/27/2022 Project # QG22-060 15 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 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 906 Rhoton Rd Geo - Soils Report Quality Geo NW, PLLC 4/27/2022 Project # QG22-060 16 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 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. 906 Rhoton Rd Geo - Soils Report Quality Geo NW, PLLC 4/27/2022 Project # QG22-060 17 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. 906 Rhoton Rd Geo - Soils Report Quality Geo NW, PLLC 4/27/2022 Project # QG22-060 18 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. 906 Rhoton Rd Geo - Soils Report Quality Geo NW, PLLC 4/27/2022 Project # QG22-060 19 Region & Vicinity Maps REGION VICINITY Quality Geo NW, PLLC Site Region 906 Rhoton Rd Figure 1 Source: Google Imagery, 2022 Scale & Locations are approx. Not for Construction 906 Rhoton Rd Geo - Soils Report Quality Geo NW, PLLC 4/27/2022 Project # QG22-060 20 Exploration Map Figure 2 Source: Thurston Co. GIS, 2022 Scale & Locations are approx. Not for Construction 140 0 SCALE (FEET) Quality Geo NW, PLLC Site Map 906 Rhoton Rd TP-1 TP-2 906 Rhoton Rd Geo - Soils Report Quality Geo NW, PLLC 4/27/2022 Project # QG22-060 21 Exploration Logs 906 Rhoton Rd Geo - Soils Report Quality Geo NW, PLLC 4/27/2022 Project # QG22-060 22 906 Rhoton Rd Geo - Soils Report Quality Geo NW, PLLC 4/27/2022 Project # QG22-060 23 Laboratory Results 906 Rhoton Rd Geo - Soils Report Quality Geo NW, PLLC 4/27/2022 Project # QG22-060 24