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2021.0275.PR0008 20210520 Rpt (Storm) 2210016.10 (combined)Civil Engineers ● Structural Engineers ● Landscape Architects ● Community Planners ● Land Surveyors Preliminary Stormwater Report PREPARED FOR: Mr. Jerry Schuur Schuur Brothers Construction PO Box 597 Puyallup, WA 98371 PROJECT: Tahoma Boulevard Apartments SPR / SEPA Yelm, Washington 2210016.10 PREPARED BY: Michael Lesmeister, EIT Project Engineer REVIEWED BY: Scott T. Kaul, PE, LEED AP Project Manager DATE: May 2021 Preliminary Stormwater Report PREPARED FOR: Mr. Jerry Schuur Schuur Brothers Construction PO Box 597 Puyallup, WA 98371 PROJECT: Tahoma Boulevard Apartments SPR / SEPA Yelm, Washington 2210016.10 PREPARED BY: Michael Lesmeister, EIT Project Engineer REVIEWED BY: Scott T. Kaul, PE, LEED AP Project Manager DATE: May 2021 I hereby state that this Preliminary Stormwater Report for the Tahoma Boulevard Apartments project has been prepared by me or under my supervision, and meets the standard of care and expertise that is usual and customary in this community for professional engineers. I understand that City of Yelm does not and will not assume liability for the sufficiency, suitability, or performance of drainage facilities prepared by me. 05/20/2021 Preliminary Stormwater Report Tahoma Boulevard Apartments SPR / SEPA 2210016.10 Table of Contents Section Page 1.0 Project Overview ............................................................................................................................ 1 1.1 Purpose and Scope............................................................................................................. 1 1.2 Existing Condition Summary ............................................................................................... 1 1.3 Post-Developed Conditions Summary ................................................................................ 1 2.0 Summary of Minimum Requirements .......................................................................................... 2 2.1 MR 1 – Preparation of Stormwater Site Plans .................................................................... 2 2.2 MR 2 - Construction Stormwater Pollution Prevention ....................................................... 2 2.3 MR 3 – Source Control of Pollution ..................................................................................... 2 2.4 MR 4 – Preservation of Natural Drainage Systems and Outfalls ........................................ 2 2.5 MR 5 – Onsite Stormwater Control ..................................................................................... 2 2.6 MR 6 – Runoff Treatment ................................................................................................... 2 2.7 MR 7 – Flow Control ........................................................................................................... 2 2.8 MR 8 – Wetlands Protection ............................................................................................... 2 2.9 MR 9 – Basin/Watershed Planning ..................................................................................... 3 2.10 MR 10 – Operation and Maintenance ................................................................................. 3 3.0 Wells ................................................................................................................................................ 3 4.0 Septic Tanks ................................................................................................................................... 3 5.0 Fuel Tanks ...................................................................................................................................... 3 6.0 Sub-Basin Description................................................................................................................... 3 7.0 Analysis of the 100-Year Flood ..................................................................................................... 3 8.0 Aesthetic Considerations for Facilities ....................................................................................... 4 9.0 Facility Sizing and Downstream Analysis ................................................................................... 4 9.1 Conveyance ........................................................................................................................ 4 9.2 Treatment ............................................................................................................................ 4 9.3 Flow Control ........................................................................................................................ 4 10.0 Covenants Dedications, Easements ............................................................................................ 4 11.0 Property Owners Association Articles of Incorporation ............................................................ 4 12.0 Conclusion ...................................................................................................................................... 5 Preliminary Stormwater Report Tahoma Boulevard Apartments SPR / SEPA 2210016.10 Appendices Appendix A Exhibits A-1 ............. Vicinity Map A-2 ............. Existing Conditions Map A-3 ............. Developed Conditions Map A-4 ............. NRCS Soil Map A-5 ............. FEMA Flood Rate Map Appendix B Calculations B-1 ............. WWHM Calculations Appendix C Geotechnical Report South Sound Geotechnical Consulting, April 2, 2021 Preliminary Stormwater Report Tahoma Boulevard Apartments SPR / SEPA 1 2210016.10 1.0 Project Overview 1.1 Purpose and Scope This Preliminary Stormwater Report accompanies the civil engineering plans submitted for the Tahoma Boulevard Apartments SPR/SEPA review. The project is located at 15035 Berry Valley Road SE, Yelm, Washington (Parcel No. 21724420200). The project property is approximately 4.99 acres. Refer to Appendix A-1 for a Vicinity Map. This report describes the stormwater facilities designed for the project. The plans and report have been prepared to satisfy all requirements of City of Yelm and the Washington State Department of Ecology 2019 Stormwater Management Manual for Western Washington (SMMWW). 1.2 Existing Condition Summary 1.2.1 Existing Site Features The site is currently vacant, except for a single-family home. Land cover for the remainder of the site consists of pasture and scattered trees and shrubs. The site is relatively flat with gentle slopes running south to north. There are approximately 10 feet of relief between the north and south boundaries. The site is bounded to the north by Tahoma Boulevard, to the east and south by undeveloped land, and to the west by a multi-family project that is under construction (refer to the Wyndstone Project). The site will be accessed from the proposed Road A of the adjacent development. Utilities will be extended from Tahoma Boulevard. 1.2.2 Soils The site is mapped by the Natural Resources Conservation Service (NRCS) as 30% Nisqually Loamy Fine Sand and 70% Spanaway Gravelly Sandy Loam. These soils are Hydro logic Group A soils. Erosion potential is low and infiltration is high for these soil types. A Geotechnical Report prepared by South Sound Geotechnical Consulting, dated April 2, 2021, identifies onsite soils as 1 to 2 feet of topsoil and native soil below the topsoil as sand with trace silt to gravelly sand/sandy gravel with trace silt. These findings are consistent with NRCS mapping. This soil type is reported to have formed in glacial outwash and is a suitable receptor for infiltration. An assessment of infiltration potential of site soils was completed using gradation correlations based on Massmann’s equation per Volume 3, Appendix III-A, Method 3 of the 2016 Thurston County Drainage Design and Erosion Control Manual. The calculated rates were consistent with Pilot Infiltration Tests (PIT) completed in outwash soils at other locations in the same vicinity. A design infiltration rate of 26 in/hr was recommended. No groundwater was observed at the time of the investigation. Refer to Appendix C for the full Geotechnical Report. 1.3 Post-Developed Conditions Summary The project consists of the construction of four apartment buildings totaling 68 units. Improvements are to include clearing, grading, erosion control, parking facilities, sidewalks, and stormwater facilities. Water and sewer will be extended from Tahoma Boulevard. Step tanks are proposed as part of the sewer design for the project. Refer to Appendix A-3 for a Developed Conditions Map. Preliminary Stormwater Report Tahoma Boulevard Apartments SPR / SEPA 2 2210016.10 2.0 Summary of Minimum Requirements This project is subject to the SMMWW and is a new development that will add more than 10,000 square feet of impervious surfaces; therefore, all Minimum Requirements (MR) apply to this project. 2.1 MR 1 – Preparation of Stormwater Site Plans This report and the project plans represent the Stormwater Site Plan for this project and satisfy MR 1. 2.2 MR 2 - Construction Stormwater Pollution Prevention A Construction Stormwater Pollution Prevention Plan (SWPPP) will be submitted with final engineering. 2.3 MR 3 – Source Control of Pollution Pollution source control will be provided for the site by separating roof runoff from pollution generating surfaces. The residential roads should be maintained and cleaned of debris, garbage, and sediment, as required. The Construction SWPPP, to be submitted with final engineering, provides details on the control of pollution during construction. 2.4 MR 4 – Preservation of Natural Drainage Systems and Outfalls The project proposes to infiltrate all stormwater runoff, so all r unoff will be retained in the developed condition. There are no natural drainage systems or outfalls to preserve. 2.5 MR 5 – Onsite Stormwater Control This project will meet the Low Impact Development (LID) performance standard. The onsite soils have a high infiltration capacity, and all runoff will be retained onsite through treatment systems and infiltration trenches. The LID performance standard will be met by infiltrating all stormwater runoff from the site. Refer to Section 9.0 for facility sizing. 2.6 MR 6 – Runoff Treatment Over 5,000 square feet of pollution generating impervious surface (PGIS) will be added as part of these improvements; therefore, runoff treatment is required for this site. Stormwater from the parking areas will be conveyed to stormwater treatment filters before being infiltrated. The treatment system was sized using the water quality output of the Western Washington Hydrology Model (WWHM 2012) to meet the SMMWW treatment requirement of at least 91 percent of runoff volume. Refer to Section 9.0 for facility sizing. 2.7 MR 7 – Flow Control The project exceeds the thresholds for new development projects and must provide flow control. Proposed flow control is achieved with the use of infiltration trenches that will infiltrate 100 percent of runoff. Refer to Section 9.0 for facility sizing. 2.8 MR 8 – Wetlands Protection To our knowledge, no wetlands exist on or adjacent to the site. Preliminary Stormwater Report Tahoma Boulevard Apartments SPR / SEPA 3 2210016.10 2.9 MR 9 – Basin/Watershed Planning To our knowledge, no basin plans exist for the site. 2.10 MR 10 – Operation and Maintenance The stormwater system will be privately owned and maintained. An Operation and Maintenance Plan consisting of maintenance checklists for stormwater management will be submitted with final engineering. Site soils are identified by the Soil Conservation Service (SCS) Soil Survey of Thurston County, Washington, as a Spanaway gravelly sandy loam, a Type B soil. This soil is characterized as very deep, somewhat excessively drained, and formed on terraces. Soil test holes were dug in the vicinity of the proposed infiltration bas ins of the project and observations confirm that the soil types match the SCS soil description. A soil log map showing the location of the test holes is included in the geotechnical report. Geotechnical Testing Laboratory observed an infiltration rate of 34.2 in/hr in the west basin and 32.0 in/hr in the east basin. Design rates of 8.55 in/hr and 8.00 in/hr are recommended by Geotechnical Testing Laboratory in the west and east drainage basins, respectively. Refer to Appendix C for the complete Geotechnical Testing Laboratory report. 3.0 Wells One domestic well is located on the subject property. The well is planned to be abandoned as part of this development. The well will be decommissioned according to Thurston County Department of Health and Washington State Department of Health standards. Refer to Appendix A-2, Existing Conditions Map for the approximate location. 4.0 Septic Tanks An existing septic tank and a drain field are located on the subject property. The septic system is planned to be abandoned as part of this development. The system will be decommissioned according to Thurston County Department of Health and Washington State Department of Ecology standards. Refer to Appendix A-2, Existing Conditions Map for the approximate location. 5.0 Fuel Tanks To the best of our knowledge, no fuel tanks were observed at the project site. 6.0 Sub-Basin Description There are two basins in the developed condition, an onsite basin and an offsite basin. Because of the site’s location and topography, it sits slightly below the neighboring property to the south. While runon from the adjacent property is unlikely due to we ll-draining soils, in an effort to be conservative, the adjacent area has been included in the sizing of the development ’s storm facilities. A description of the land use characteristics of the developed basins can be found in Appendix A-3, Developed Conditions Map. 7.0 Analysis of the 100-Year Flood Federal Emergency Management Agency (FEMA) mapping does not indicate flooding in the immediate area. Refer to the exhibit in Appendix A-5. Preliminary Stormwater Report Tahoma Boulevard Apartments SPR / SEPA 4 2210016.10 8.0 Aesthetic Considerations for Facilities The stormwater treatment facilities and drainage basins will be located underground and will not affect the aesthetics of the site. 9.0 Facility Sizing and Downstream Analysis The proposed system was modeled using the latest edition of the WWHM Continuous Modeling Software and was designed according to the standards in the 2019 SMMWW. 9.1 Conveyance Stormwater will be conveyed to the proposed treatment and infiltration facilities thr ough the combination of CPEP storm pipe and catch basins. 9.2 Treatment A 72-inch StormFilter manhole outfitted with seven 27-inch PSorb media cartridges will provide stormwater treatment for this development. Each cartridge provides a treatment rate of 0.041 cfs, for a total treatment rate of 0.29 cfs. This exceeds the required treatment of 0.26 cfs, as determined by WWHM. Refer to Appendix B-1 for the WWHM Calculations. 9.3 Flow Control An underground infiltration gallery will infiltrate all runoff onsite, which meets both the duration and LID performance standards. Refer to Appendix B-1 for the WWHM Calculations and model setup. The infiltration gallery was designed to have a bottom area of 2,500 square feet and a depth of 4 feet of washed rock to provide void space. Two 12-inch perforated pipes spaced at 10 feet off- center will distribute stormwater within the system. Long-term native soil infiltration rates onsite were determined to be 26 in/hr. 10.0 Covenants Dedications, Easements No covenants, dedications, or easements are proposed. 11.0 Property Owners Association Articles of Incorporation Not applicable. Preliminary Stormwater Report Tahoma Boulevard Apartments SPR / SEPA 5 2210016.10 12.0 Conclusion The proposed project involves site improvements associated with the 68-unit apartment complex. The project includes clearing, grading, erosion control, utility improvements, and stormwater management facilities. The site, as proposed, will meet the requirements of the 201 9 Washington State Department of Ecology Stormwater Management Manual for Western Washington (SMMWW). This report and associated plans have been prepared within the guidelines established by City of Yelm for stormwater management. This analysis is based on data and records either supplied to or obtained by AHBL. These documents are referenced within the text of the analysis. The analysis has been prepared using procedures and practices within the standard accepted practices of the industry. AHBL, Inc. Michael Lesmeister, EIT Project Engineer ML/lsk May 2021 Q:\2021\2210016\WORDPROC\Reports\20210520 Rpt (Storm) 2210016.10.docx Preliminary Stormwater Report Tahoma Boulevard Apartments SPR / SEPA 2210016.10 Appendix A Exhibits A-1....................Vicinity Map A-2....................Existing Conditions Map A-3....................Developed Conditions Map A-4....................NRCS Soil Map A-5....................FEMA Flood Rate Map 2215 North 30th Street, Suite 300, Tacoma, WA 98403 253.383.2422 TEL 253.383.2572 FAX JOB NO. DATE: TAHOMA BLVD APARTMENTS VICINITY MAP A-1 2210016.10 5/19/2021 1ST S T S VICINITY MAP SCALE: 1" = 1/4 MILE (1,320') SITE TAHOMA BLVD SE BERRY VALLEY RD SE E Y E L M A V E C O A T E S A V E NW LONGMIRE ST SECULLENS RD SE93RD AVE SE CRYSTAL SPRINGS ST NWTORNADO ALLEY WELL HOUSE APPROXIMATE LOCATION OF EXISTING SEPTIC DRAIN FIELD 1 2 3 4 TEL www.ahbl.comWEBTELwww.ahbl.comWEBTELwww.ahbl.comWEB 2215 North 30th Street, Suite 300 Tacoma, WA 98403 253.383.2422TEL www.ahbl.comWEB TACOMA SEATTLE SPOKANE TRI-CITIES Know what's below. before you dig.Call R 253.383.2572 FAX 6 SKML/EAML/EA 5/18/2021 SEPA AND SITE PLAN REVIEW 2210016.10 PO BOX 597 PUYALLUP, WA 98371 JERRY SCHUUR SCHUUR BROTHERS CONSTRUCTION TAHOMA BOULEVARD APARTMENTS A PORTION OF THE NW 1/4 OF THE SE 1/4 OF SEC. 24, TWN. 17 N., RGE. 01 E. W.M. CITY OF YELM, THURSTON COUNTY, WASHINGTON. TAHOMA BOULEVARD APARTMENTS DATE: May 19, 2021 FILENAME: Q:\2021\2210016\10_CIV\CAD\EXHIBITS\Existing Conditions Map.dwg C0.2 2 EXISTING CONDITIONS N GRAPHIC SCALE 0 40 80 1" = 40 FEET 20 THE EAST HALF OF THE NORTHWEST QUARTER OF THE NORTHWEST QUARTER OF THE SOUTHEAST QUARTER OF SECTION 24, TOWNSHIP 17 NORTH, RANGE 1 EAST, W.M. EXCEPT COUNTY ROADS; EXCEPT PORTION TAKEN FOR BERRY VALLEY ROAD PER AUDITOR'S FILE NO. 3980984. SITUATE IN THURSTON COUNTY, STATE OF WASHINGTON. LEGAL DESCRIPTION TAHO M A B L V D ROAD A TAHOMA BOULEVARD SECivil EngineersStructural EngineersLandscape ArchitectsCommunity PlannersLand SurveyorsNeighborsTAHOMA BLVD. APARTMENTS2210016.10NGRAPHIC SCALE0601201" = 60 FEET30BLDG. ABLDG. BBLDG. CBLDG. DROAD ATAHOMA BLVD NESITE DATASITE AREA: 4.99 ACSITE COVER:ROOF: 0.79 ACSIDEWALK:0.26 ACPAVEMENT: 1.89 ACLANDSCAPE:2.05 ACRUN-ON BASIN:PASTURE:1.20 ACPARCEL #: 21724420200ADDRESS: 15035 BERRY VALLEY RD SEONSITE BASINRUN-ON BASININFILTRATION GALLERY2,500 SF FOOTPRINT(125' X 20' X 4')12" PVC PERF10' O.C.12" PVC MANIFOLD72" STORMFILTER Soil Map—Thurston County Area, Washington Natural Resources Conservation Service Web Soil Survey National Cooperative Soil Survey 5/19/2021 Page 1 of 3519897051989905199010519903051990505199070519909051991105199130519915051991705199190519897051989905199010519903051990505199070519909051991105199130519915051991705199190528820528840528860528880528900528920528940528960528980 528820 528840 528860 528880 528900 528920 528940 528960 528980 46° 56' 44'' N 122° 37' 16'' W46° 56' 44'' N122° 37' 9'' W46° 56' 37'' N 122° 37' 16'' W46° 56' 37'' N 122° 37' 9'' WN Map projection: Web Mercator Corner coordinates: WGS84 Edge tics: UTM Zone 10N WGS84 0 50 100 200 300 Feet 0 15 30 60 90 Meters Map Scale: 1:1,080 if printed on A portrait (8.5" x 11") sheet. Soil Map may not be valid at this scale. MAP LEGEND MAP INFORMATION Area of Interest (AOI) Area of Interest (AOI) Soils Soil Map Unit Polygons Soil Map Unit Lines Soil Map Unit Points Special Point Features Blowout Borrow Pit Clay Spot Closed Depression Gravel Pit Gravelly Spot Landfill Lava Flow Marsh or swamp Mine or Quarry Miscellaneous Water Perennial Water Rock Outcrop Saline Spot Sandy Spot Severely Eroded Spot Sinkhole Slide or Slip Sodic Spot Spoil Area Stony Spot Very Stony Spot Wet Spot Other Special Line Features Water Features Streams and Canals Transportation Rails Interstate Highways US Routes Major Roads Local Roads Background Aerial Photography The soil surveys that comprise your AOI were mapped at 1:24,000. Warning: Soil Map may not be valid at this scale. Enlargement of maps beyond the scale of mapping can cause misunderstanding of the detail of mapping and accuracy of soil line placement. The maps do not show the small areas of contrasting soils that could have been shown at a more detailed scale. Please rely on the bar scale on each map sheet for map measurements. Source of Map: Natural Resources Conservation Service Web Soil Survey URL: Coordinate System: Web Mercator (EPSG:3857) Maps from the Web Soil Survey are based on the Web Mercator projection, which preserves direction and shape but distorts distance and area. A projection that preserves area, such as the Albers equal-area conic projection, should be used if more accurate calculations of distance or area are required. This product is generated from the USDA-NRCS certified data as of the version date(s) listed below. Soil Survey Area: Thurston County Area, Washington Survey Area Data: Version 14, Jun 4, 2020 Soil map units are labeled (as space allows) for map scales 1:50,000 or larger. Date(s) aerial images were photographed: Jul 18, 2020—Jul 20, 2020 The orthophoto or other base map on which the soil lines were compiled and digitized probably differs from the background imagery displayed on these maps. As a result, some minor shifting of map unit boundaries may be evident. Soil Map—Thurston County Area, Washington Natural Resources Conservation Service Web Soil Survey National Cooperative Soil Survey 5/19/2021 Page 2 of 3 Map Unit Legend Map Unit Symbol Map Unit Name Acres in AOI Percent of AOI 74 Nisqually loamy fine sand, 3 to 15 percent slopes 1.4 30.3% 110 Spanaway gravelly sandy loam, 0 to 3 percent slopes 3.2 69.7% Totals for Area of Interest 4.7 100.0% Soil Map—Thurston County Area, Washington Natural Resources Conservation Service Web Soil Survey National Cooperative Soil Survey 5/19/2021 Page 3 of 3 National Flood Hazard Layer FIRMette 0 500 1,000 1,500 2,000250 Feet Ü SEE FIS REPORT FOR DETAILED LEGEND AND INDEX MAP FOR FIRM PANEL LAYOUT SPECIAL FLOOD HAZARD AREAS Without Base Flood Elevation (BFE) Zone A, V, A99 With BFE or DepthZone AE, AO, AH, VE, AR Regulatory Floodway 0.2% Annual Chance Flood Hazard, Areas of 1% annual chance flood with average depth less than one foot or with drainage areas of less than one square mileZone X Future Conditions 1% Annual Chance Flood HazardZone X Area with Reduced Flood Risk due to Levee. See Notes.Zone X Area with Flood Risk due to LeveeZone D NO SCREEN Area of Minimal Flood Hazard Zone X Area of Undetermined Flood HazardZone D Channel, Culvert, or Storm Sewer Levee, Dike, or Floodwall Cross Sections with 1% Annual Chance 17.5 Water Surface Elevation Coastal Transect Coastal Transect Baseline Profile Baseline Hydrographic Feature Base Flood Elevation Line (BFE) Effective LOMRs Limit of Study Jurisdiction Boundary Digital Data Available No Digital Data Available Unmapped This map complies with FEMA's standards for the use of digital flood maps if it is not void as described below. The basemap shown complies with FEMA's basemap accuracy standards The flood hazard information is derived directly from the authoritative NFHL web services provided by FEMA. This map was exported on 5/19/2021 at 12:37 PM and does not reflect changes or amendments subsequent to this date and time. The NFHL and effective information may change or become superseded by new data over time. This map image is void if the one or more of the following map elements do not appear: basemap imagery, flood zone labels, legend, scale bar, map creation date, community identifiers, FIRM panel number, and FIRM effective date. Map images for unmapped and unmodernized areas cannot be used for regulatory purposes. Legend OTHER AREAS OF FLOOD HAZARD OTHER AREAS GENERAL STRUCTURES OTHER FEATURES MAP PANELS 8 B 20.2 The pin displayed on the map is an approximate point selected by the user and does not represent an authoritative property location. 1:6,000 122°37'29"W 46°56'55"N 122°36'52"W 46°56'31"N Basemap: USGS National Map: Orthoimagery: Data refreshed October, 2020 SITE Preliminary Stormwater Report Tahoma Boulevard Apartments SPR / SEPA 2210016.10 Appendix B Calculations B-1....................WWHM Calculations WWHM2012 PROJECT REPORT Infiltration 5/19/2021 9:44:38 AM Page 2 General Model Information Project Name:Infiltration Site Name:Tahoma Blvd Apartments Site Address:15035 Berry Valley Rd SE City:Yelm Report Date:5/19/2021 Gage:Eaton Creek Data Start:1955/10/01 Data End:2011/09/30 Timestep:15 Minute Precip Scale:0.857 Version Date:2019/09/13 Version:4.2.17 POC Thresholds Infiltration 5/19/2021 9:44:38 AM Page 3 Landuse Basin Data Predeveloped Land Use Infiltration 5/19/2021 9:44:38 AM Page 4 Mitigated Land Use Onsite Basin Bypass:No GroundWater:No Pervious Land Use acre A B, Pasture, Flat 2.05 Pervious Total 2.05 Impervious Land Use acre ROOF TOPS FLAT 0.79 SIDEWALKS FLAT 0.26 PARKING FLAT 1.89 Impervious Total 2.94 Basin Total 4.99 Element Flows To: Surface Interflow Groundwater Infiltration Gallery Infiltration Gallery Infiltration 5/19/2021 9:44:38 AM Page 5 Offsite Basin Bypass:No GroundWater:No Pervious Land Use acre A B, Pasture, Flat 1.2 Pervious Total 1.2 Impervious Land Use acre Impervious Total 0 Basin Total 1.2 Element Flows To: Surface Interflow Groundwater Infiltration Gallery Infiltration Gallery Infiltration 5/19/2021 9:44:38 AM Page 6 Routing Elements Predeveloped Routing Infiltration 5/19/2021 9:44:38 AM Page 7 Mitigated Routing Infiltration Gallery Bottom Length:300.00 ft. Bottom Width:8.00 ft. Trench bottom slope 1:0 To 1 Trench Left side slope 0:0 To 1 Trench right side slope 2:0 To 1 Material thickness of first layer:4 Pour Space of material for first layer:0.33 Material thickness of second layer:0 Pour Space of material for second layer:0 Material thickness of third layer:0 Pour Space of material for third layer:0 Infiltration On Infiltration rate:26 Infiltration safety factor:1 Total Volume Infiltrated (ac-ft.):459.504 Total Volume Through Riser (ac-ft.):0.008 Total Volume Through Facility (ac-ft.):459.511 Percent Infiltrated:100 Total Precip Applied to Facility:0 Total Evap From Facility:0 Discharge Structure Riser Height:4 ft. Riser Diameter:12 in. Element Flows To: Outlet 1 Outlet 2 Gravel Trench Bed Hydraulic Table Stage(feet)Area(ac.)Volume(ac-ft.)Discharge(cfs)Infilt(cfs) 0.0000 0.055 0.000 0.000 0.000 0.0444 0.055 0.000 0.000 1.444 0.0889 0.055 0.001 0.000 1.444 0.1333 0.055 0.002 0.000 1.444 0.1778 0.055 0.003 0.000 1.444 0.2222 0.055 0.004 0.000 1.444 0.2667 0.055 0.004 0.000 1.444 0.3111 0.055 0.005 0.000 1.444 0.3556 0.055 0.006 0.000 1.444 0.4000 0.055 0.007 0.000 1.444 0.4444 0.055 0.008 0.000 1.444 0.4889 0.055 0.008 0.000 1.444 0.5333 0.055 0.009 0.000 1.444 0.5778 0.055 0.010 0.000 1.444 0.6222 0.055 0.011 0.000 1.444 0.6667 0.055 0.012 0.000 1.444 0.7111 0.055 0.012 0.000 1.444 0.7556 0.055 0.013 0.000 1.444 0.8000 0.055 0.014 0.000 1.444 0.8444 0.055 0.015 0.000 1.444 0.8889 0.055 0.016 0.000 1.444 0.9333 0.055 0.017 0.000 1.444 0.9778 0.055 0.017 0.000 1.444 1.0222 0.055 0.018 0.000 1.444 Infiltration 5/19/2021 9:44:38 AM Page 8 1.0667 0.055 0.019 0.000 1.444 1.1111 0.055 0.020 0.000 1.444 1.1556 0.055 0.021 0.000 1.444 1.2000 0.055 0.021 0.000 1.444 1.2444 0.055 0.022 0.000 1.444 1.2889 0.055 0.023 0.000 1.444 1.3333 0.055 0.024 0.000 1.444 1.3778 0.055 0.025 0.000 1.444 1.4222 0.055 0.025 0.000 1.444 1.4667 0.055 0.026 0.000 1.444 1.5111 0.055 0.027 0.000 1.444 1.5556 0.055 0.028 0.000 1.444 1.6000 0.055 0.029 0.000 1.444 1.6444 0.055 0.029 0.000 1.444 1.6889 0.055 0.030 0.000 1.444 1.7333 0.055 0.031 0.000 1.444 1.7778 0.055 0.032 0.000 1.444 1.8222 0.055 0.033 0.000 1.444 1.8667 0.055 0.033 0.000 1.444 1.9111 0.055 0.034 0.000 1.444 1.9556 0.055 0.035 0.000 1.444 2.0000 0.055 0.036 0.000 1.444 2.0444 0.055 0.037 0.000 1.444 2.0889 0.055 0.038 0.000 1.444 2.1333 0.055 0.038 0.000 1.444 2.1778 0.055 0.039 0.000 1.444 2.2222 0.055 0.040 0.000 1.444 2.2667 0.055 0.041 0.000 1.444 2.3111 0.055 0.042 0.000 1.444 2.3556 0.055 0.042 0.000 1.444 2.4000 0.055 0.043 0.000 1.444 2.4444 0.055 0.044 0.000 1.444 2.4889 0.055 0.045 0.000 1.444 2.5333 0.055 0.046 0.000 1.444 2.5778 0.055 0.046 0.000 1.444 2.6222 0.055 0.047 0.000 1.444 2.6667 0.055 0.048 0.000 1.444 2.7111 0.055 0.049 0.000 1.444 2.7556 0.055 0.050 0.000 1.444 2.8000 0.055 0.050 0.000 1.444 2.8444 0.055 0.051 0.000 1.444 2.8889 0.055 0.052 0.000 1.444 2.9333 0.055 0.053 0.000 1.444 2.9778 0.055 0.054 0.000 1.444 3.0222 0.055 0.054 0.000 1.444 3.0667 0.055 0.055 0.000 1.444 3.1111 0.055 0.056 0.000 1.444 3.1556 0.055 0.057 0.000 1.444 3.2000 0.055 0.058 0.000 1.444 3.2444 0.055 0.059 0.000 1.444 3.2889 0.055 0.059 0.000 1.444 3.3333 0.055 0.060 0.000 1.444 3.3778 0.055 0.061 0.000 1.444 3.4222 0.055 0.062 0.000 1.444 3.4667 0.055 0.063 0.000 1.444 3.5111 0.055 0.063 0.000 1.444 3.5556 0.055 0.064 0.000 1.444 3.6000 0.055 0.065 0.000 1.444 Infiltration 5/19/2021 9:44:38 AM Page 9 3.6444 0.055 0.066 0.000 1.444 3.6889 0.055 0.067 0.000 1.444 3.7333 0.055 0.067 0.000 1.444 3.7778 0.055 0.068 0.000 1.444 3.8222 0.055 0.069 0.000 1.444 3.8667 0.055 0.070 0.000 1.444 3.9111 0.055 0.071 0.000 1.444 3.9556 0.055 0.071 0.000 1.444 4.0000 0.055 0.072 0.000 1.444 Infiltration 5/19/2021 9:44:38 AM Page 10 Analysis Results POC 1 POC #1 was not reported because POC must exist in both scenarios and both scenarios must have been run. Infiltration 5/19/2021 9:44:38 AM Page 11 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. Infiltration 5/19/2021 9:44:38 AM Page 12 Appendix Predeveloped Schematic Infiltration 5/19/2021 9:44:40 AM Page 13 Mitigated Schematic Infiltration 5/19/2021 9:44:41 AM Page 14 Predeveloped UCI File Infiltration 5/19/2021 9:44:41 AM Page 15 Mitigated UCI File RUN GLOBAL WWHM4 model simulation START 1955 10 01 END 2011 09 30 RUN INTERP OUTPUT LEVEL 3 0 RESUME 0 RUN 1 UNIT SYSTEM 1 END GLOBAL FILES <File> <Un#> <-----------File Name------------------------------>*** <-ID-> *** WDM 26 Infiltration.wdm MESSU 25 MitInfiltration.MES 27 MitInfiltration.L61 28 MitInfiltration.L62 END FILES OPN SEQUENCE INGRP INDELT 00:15 PERLND 4 IMPLND 4 IMPLND 8 IMPLND 11 RCHRES 1 END INGRP END OPN SEQUENCE DISPLY DISPLY-INFO1 # - #<----------Title----------->***TRAN PIVL DIG1 FIL1 PYR DIG2 FIL2 YRND END DISPLY-INFO1 END DISPLY COPY TIMESERIES # - # NPT NMN *** 1 1 1 END TIMESERIES END COPY GENER OPCODE # # OPCD *** END OPCODE PARM # # K *** END PARM END GENER PERLND GEN-INFO <PLS ><-------Name------->NBLKS Unit-systems Printer *** # - # User t-series Engl Metr *** in out *** 4 A/B, Pasture, Flat 1 1 1 1 27 0 END GEN-INFO *** Section PWATER*** ACTIVITY <PLS > ************* Active Sections ***************************** # - # ATMP SNOW PWAT SED PST PWG PQAL MSTL PEST NITR PHOS TRAC *** 4 0 0 1 0 0 0 0 0 0 0 0 0 END ACTIVITY PRINT-INFO <PLS > ***************** Print-flags ***************************** PIVL PYR # - # ATMP SNOW PWAT SED PST PWG PQAL MSTL PEST NITR PHOS TRAC ********* 4 0 0 4 0 0 0 0 0 0 0 0 0 1 9 END PRINT-INFO PWAT-PARM1 Infiltration 5/19/2021 9:44:41 AM Page 16 <PLS > PWATER variable monthly parameter value flags *** # - # CSNO RTOP UZFG VCS VUZ VNN VIFW VIRC VLE INFC HWT *** 4 0 0 0 0 0 0 0 0 0 0 0 END PWAT-PARM1 PWAT-PARM2 <PLS > PWATER input info: Part 2 *** # - # ***FOREST LZSN INFILT LSUR SLSUR KVARY AGWRC 4 0 5 1.5 400 0.05 0.3 0.996 END PWAT-PARM2 PWAT-PARM3 <PLS > PWATER input info: Part 3 *** # - # ***PETMAX PETMIN INFEXP INFILD DEEPFR BASETP AGWETP 4 0 0 2 2 0 0 0 END PWAT-PARM3 PWAT-PARM4 <PLS > PWATER input info: Part 4 *** # - # CEPSC UZSN NSUR INTFW IRC LZETP *** 4 0.15 0.5 0.3 0 0.7 0.4 END PWAT-PARM4 PWAT-STATE1 <PLS > *** Initial conditions at start of simulation ran from 1990 to end of 1992 (pat 1-11-95) RUN 21 *** # - # *** CEPS SURS UZS IFWS LZS AGWS GWVS 4 0 0 0 0 3 1 0 END PWAT-STATE1 END PERLND IMPLND GEN-INFO <PLS ><-------Name-------> Unit-systems Printer *** # - # User t-series Engl Metr *** in out *** 4 ROOF TOPS/FLAT 1 1 1 27 0 8 SIDEWALKS/FLAT 1 1 1 27 0 11 PARKING/FLAT 1 1 1 27 0 END GEN-INFO *** Section IWATER*** ACTIVITY <PLS > ************* Active Sections ***************************** # - # ATMP SNOW IWAT SLD IWG IQAL *** 4 0 0 1 0 0 0 8 0 0 1 0 0 0 11 0 0 1 0 0 0 END ACTIVITY PRINT-INFO <ILS > ******** Print-flags ******** PIVL PYR # - # ATMP SNOW IWAT SLD IWG IQAL ********* 4 0 0 4 0 0 0 1 9 8 0 0 4 0 0 0 1 9 11 0 0 4 0 0 0 1 9 END PRINT-INFO IWAT-PARM1 <PLS > IWATER variable monthly parameter value flags *** # - # CSNO RTOP VRS VNN RTLI *** 4 0 0 0 0 0 8 0 0 0 0 0 11 0 0 0 0 0 END IWAT-PARM1 IWAT-PARM2 <PLS > IWATER input info: Part 2 *** # - # *** LSUR SLSUR NSUR RETSC 4 400 0.01 0.1 0.1 Infiltration 5/19/2021 9:44:41 AM Page 17 8 400 0.01 0.1 0.1 11 400 0.01 0.1 0.1 END IWAT-PARM2 IWAT-PARM3 <PLS > IWATER input info: Part 3 *** # - # ***PETMAX PETMIN 4 0 0 8 0 0 11 0 0 END IWAT-PARM3 IWAT-STATE1 <PLS > *** Initial conditions at start of simulation # - # *** RETS SURS 4 0 0 8 0 0 11 0 0 END IWAT-STATE1 END IMPLND SCHEMATIC <-Source-> <--Area--> <-Target-> MBLK *** <Name> # <-factor-> <Name> # Tbl# *** Onsite Basin*** PERLND 4 2.05 RCHRES 1 2 PERLND 4 2.05 RCHRES 1 3 IMPLND 4 0.79 RCHRES 1 5 IMPLND 8 0.26 RCHRES 1 5 IMPLND 11 1.89 RCHRES 1 5 Offsite Basin*** PERLND 4 1.2 RCHRES 1 2 PERLND 4 1.2 RCHRES 1 3 ******Routing****** END SCHEMATIC NETWORK <-Volume-> <-Grp> <-Member-><--Mult-->Tran <-Target vols> <-Grp> <-Member-> *** <Name> # <Name> # #<-factor->strg <Name> # # <Name> # # *** <-Volume-> <-Grp> <-Member-><--Mult-->Tran <-Target vols> <-Grp> <-Member-> *** <Name> # <Name> # #<-factor->strg <Name> # # <Name> # # *** END NETWORK RCHRES GEN-INFO RCHRES Name Nexits Unit Systems Printer *** # - #<------------------><---> User T-series Engl Metr LKFG *** in out *** 1 Infiltration Gal-006 2 1 1 1 28 0 1 END GEN-INFO *** Section RCHRES*** ACTIVITY <PLS > ************* Active Sections ***************************** # - # HYFG ADFG CNFG HTFG SDFG GQFG OXFG NUFG PKFG PHFG *** 1 1 0 0 0 0 0 0 0 0 0 END ACTIVITY PRINT-INFO <PLS > ***************** Print-flags ******************* PIVL PYR # - # HYDR ADCA CONS HEAT SED GQL OXRX NUTR PLNK PHCB PIVL PYR ********* 1 4 0 0 0 0 0 0 0 0 0 1 9 END PRINT-INFO HYDR-PARM1 Infiltration 5/19/2021 9:44:41 AM Page 18 RCHRES Flags for each HYDR Section *** # - # VC A1 A2 A3 ODFVFG for each *** ODGTFG for each FUNCT for each FG FG FG FG possible exit *** possible exit possible exit * * * * * * * * * * * * * * *** 1 0 1 0 0 4 5 0 0 0 0 0 0 0 0 2 2 2 2 2 END HYDR-PARM1 HYDR-PARM2 # - # FTABNO LEN DELTH STCOR KS DB50 *** <------><--------><--------><--------><--------><--------><--------> *** 1 1 0.06 0.0 0.0 0.5 0.0 END HYDR-PARM2 HYDR-INIT RCHRES Initial conditions for each HYDR section *** # - # *** VOL Initial value of COLIND Initial value of OUTDGT *** ac-ft for each possible exit for each possible exit <------><--------> <---><---><---><---><---> *** <---><---><---><---><---> 1 0 4.0 5.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 END HYDR-INIT END RCHRES SPEC-ACTIONS END SPEC-ACTIONS FTABLES FTABLE 1 92 5 Depth Area Volume Outflow1 Outflow2 Velocity Travel Time*** (ft) (acres) (acre-ft) (cfs) (cfs) (ft/sec) (Minutes)*** 0.000000 0.055096 0.000000 0.000000 0.000000 0.044444 0.055096 0.000808 0.000000 1.444444 0.088889 0.055096 0.001616 0.000000 1.444444 0.133333 0.055096 0.002424 0.000000 1.444444 0.177778 0.055096 0.003232 0.000000 1.444444 0.222222 0.055096 0.004040 0.000000 1.444444 0.266667 0.055096 0.004848 0.000000 1.444444 0.311111 0.055096 0.005657 0.000000 1.444444 0.355556 0.055096 0.006465 0.000000 1.444444 0.400000 0.055096 0.007273 0.000000 1.444444 0.444444 0.055096 0.008081 0.000000 1.444444 0.488889 0.055096 0.008889 0.000000 1.444444 0.533333 0.055096 0.009697 0.000000 1.444444 0.577778 0.055096 0.010505 0.000000 1.444444 0.622222 0.055096 0.011313 0.000000 1.444444 0.666667 0.055096 0.012121 0.000000 1.444444 0.711111 0.055096 0.012929 0.000000 1.444444 0.755556 0.055096 0.013737 0.000000 1.444444 0.800000 0.055096 0.014545 0.000000 1.444444 0.844444 0.055096 0.015354 0.000000 1.444444 0.888889 0.055096 0.016162 0.000000 1.444444 0.933333 0.055096 0.016970 0.000000 1.444444 0.977778 0.055096 0.017778 0.000000 1.444444 1.022222 0.055096 0.018586 0.000000 1.444444 1.066667 0.055096 0.019394 0.000000 1.444444 1.111111 0.055096 0.020202 0.000000 1.444444 1.155556 0.055096 0.021010 0.000000 1.444444 1.200000 0.055096 0.021818 0.000000 1.444444 1.244444 0.055096 0.022626 0.000000 1.444444 1.288889 0.055096 0.023434 0.000000 1.444444 1.333333 0.055096 0.024242 0.000000 1.444444 1.377778 0.055096 0.025051 0.000000 1.444444 1.422222 0.055096 0.025859 0.000000 1.444444 1.466667 0.055096 0.026667 0.000000 1.444444 1.511111 0.055096 0.027475 0.000000 1.444444 1.555556 0.055096 0.028283 0.000000 1.444444 1.600000 0.055096 0.029091 0.000000 1.444444 1.644444 0.055096 0.029899 0.000000 1.444444 1.688889 0.055096 0.030707 0.000000 1.444444 1.733333 0.055096 0.031515 0.000000 1.444444 1.777778 0.055096 0.032323 0.000000 1.444444 1.822222 0.055096 0.033131 0.000000 1.444444 Infiltration 5/19/2021 9:44:41 AM Page 19 1.866667 0.055096 0.033939 0.000000 1.444444 1.911111 0.055096 0.034747 0.000000 1.444444 1.955556 0.055096 0.035556 0.000000 1.444444 2.000000 0.055096 0.036364 0.000000 1.444444 2.044444 0.055096 0.037172 0.000000 1.444444 2.088889 0.055096 0.037980 0.000000 1.444444 2.133333 0.055096 0.038788 0.000000 1.444444 2.177778 0.055096 0.039596 0.000000 1.444444 2.222222 0.055096 0.040404 0.000000 1.444444 2.266667 0.055096 0.041212 0.000000 1.444444 2.311111 0.055096 0.042020 0.000000 1.444444 2.355556 0.055096 0.042828 0.000000 1.444444 2.400000 0.055096 0.043636 0.000000 1.444444 2.444444 0.055096 0.044444 0.000000 1.444444 2.488889 0.055096 0.045253 0.000000 1.444444 2.533333 0.055096 0.046061 0.000000 1.444444 2.577778 0.055096 0.046869 0.000000 1.444444 2.622222 0.055096 0.047677 0.000000 1.444444 2.666667 0.055096 0.048485 0.000000 1.444444 2.711111 0.055096 0.049293 0.000000 1.444444 2.755556 0.055096 0.050101 0.000000 1.444444 2.800000 0.055096 0.050909 0.000000 1.444444 2.844444 0.055096 0.051717 0.000000 1.444444 2.888889 0.055096 0.052525 0.000000 1.444444 2.933333 0.055096 0.053333 0.000000 1.444444 2.977778 0.055096 0.054141 0.000000 1.444444 3.022222 0.055096 0.054949 0.000000 1.444444 3.066667 0.055096 0.055758 0.000000 1.444444 3.111111 0.055096 0.056566 0.000000 1.444444 3.155556 0.055096 0.057374 0.000000 1.444444 3.200000 0.055096 0.058182 0.000000 1.444444 3.244444 0.055096 0.058990 0.000000 1.444444 3.288889 0.055096 0.059798 0.000000 1.444444 3.333333 0.055096 0.060606 0.000000 1.444444 3.377778 0.055096 0.061414 0.000000 1.444444 3.422222 0.055096 0.062222 0.000000 1.444444 3.466667 0.055096 0.063030 0.000000 1.444444 3.511111 0.055096 0.063838 0.000000 1.444444 3.555556 0.055096 0.064646 0.000000 1.444444 3.600000 0.055096 0.065455 0.000000 1.444444 3.644444 0.055096 0.066263 0.000000 1.444444 3.688889 0.055096 0.067071 0.000000 1.444444 3.733333 0.055096 0.067879 0.000000 1.444444 3.777778 0.055096 0.068687 0.000000 1.444444 3.822222 0.055096 0.069495 0.000000 1.444444 3.866667 0.055096 0.070303 0.000000 1.444444 3.911111 0.055096 0.071111 0.000000 1.444444 3.955556 0.055096 0.071919 0.000000 1.444444 4.000000 0.055096 0.072727 0.000000 1.444444 4.044444 0.055096 0.075176 0.099321 1.444444 END FTABLE 1 END FTABLES EXT SOURCES <-Volume-> <Member> SsysSgap<--Mult-->Tran <-Target vols> <-Grp> <-Member-> *** <Name> # <Name> # tem strg<-factor->strg <Name> # # <Name> # # *** WDM 2 PREC ENGL 0.857 PERLND 1 999 EXTNL PREC WDM 2 PREC ENGL 0.857 IMPLND 1 999 EXTNL PREC WDM 1 EVAP ENGL 0.76 PERLND 1 999 EXTNL PETINP WDM 1 EVAP ENGL 0.76 IMPLND 1 999 EXTNL PETINP END EXT SOURCES EXT TARGETS <-Volume-> <-Grp> <-Member-><--Mult-->Tran <-Volume-> <Member> Tsys Tgap Amd *** <Name> # <Name> # #<-factor->strg <Name> # <Name> tem strg strg*** END EXT TARGETS MASS-LINK <Volume> <-Grp> <-Member-><--Mult--> <Target> <-Grp> <-Member->*** Infiltration 5/19/2021 9:44:41 AM Page 20 <Name> <Name> # #<-factor-> <Name> <Name> # #*** MASS-LINK 2 PERLND PWATER SURO 0.083333 RCHRES INFLOW IVOL END MASS-LINK 2 MASS-LINK 3 PERLND PWATER IFWO 0.083333 RCHRES INFLOW IVOL END MASS-LINK 3 MASS-LINK 5 IMPLND IWATER SURO 0.083333 RCHRES INFLOW IVOL END MASS-LINK 5 END MASS-LINK END RUN Infiltration 5/19/2021 9:44:41 AM Page 21 Predeveloped HSPF Message File Infiltration 5/19/2021 9:44:41 AM Page 22 Mitigated HSPF Message File ERROR/WARNING ID: 341 6 DATE/TIME: 1992/11/24 6: 0 RCHRES: 1 The volume of water in this reach/mixed reservoir is greater than the value in the "volume" column of the last row of RCHTAB(). To continue the simulation the table has been extrapolated, based on information contained in the last two rows. This will usually result in some loss of accuracy. If depth is being calculated it will also cause an error condition. Relevant data are: NROWS V1 V2 VOL 92 3168.0 3274.7 3517.2 ERROR/WARNING ID: 341 5 DATE/TIME: 1992/11/24 6: 0 RCHRES: 1 Calculation of relative depth, using Newton's method of successive approximations, converged to an invalid value (not in range 0.0 to 1.0). Probably ftable was extrapolated. If extrapolation was small, no problem. Remedy; extend ftable. Relevant data are: A B C RDEP1 RDEP2 COUNT 0.0000E+00 4800.0 -1.571E+04 3.2736 3.2736E+00 2 Infiltration 5/19/2021 9:44:41 AM Page 23 Disclaimer Legal Notice This program and accompanying documentation are provided 'as-is' without warranty of any kind. The entire risk regarding the performance and results of this program is assumed by End User. Clear Creek Solutions Inc. and the governmental licensee or sublicensees disclaim all warranties, either expressed or implied, including but not limited to implied warranties of program and accompanying documentation. In no event shall Clear Creek Solutions Inc. be liable for any damages whatsoever (including without limitation to damages for loss of business profits, loss of business information, business interruption, and the like) arising out of the use of, or inability to use this program even if Clear Creek Solutions Inc. or their authorized representatives have been advised of the possibility of such damages. Software Copyright © by : Clear Creek Solutions, Inc. 2005-2021; All Rights Reserved. Clear Creek Solutions, Inc. 6200 Capitol Blvd. Ste F Olympia, WA. 98501 Toll Free 1(866)943-0304 Local (360)943-0304 www.clearcreeksolutions.com Preliminary Stormwater Report Tahoma Boulevard Apartments SPR / SEPA 2210016.10 Appendix C Geotechnical Report South Sound Geotechnical Consulting, April 2, 2021 South Sound Geotechnical Consulting P.O. Box 39500, Lakewood, WA 98496 (253) 973-0515 April 2, 2021 Schuur Brothers Construction P.O. Box 597 Puyallup, WA 9837 Attention: Mr. Jerry Schuur Subject: Geotechnical Engineering Report – Infiltration Assessment Tahoma Boulevard Apartments 15035 Berry Valley Rd NW Yelm, Washington SSGC Project No. 21013 Mr. Schuur, South Sound Geotechnical Consulting (SSGC) has completed an infiltration assessment on the above addressed lot in Yelm, Washington. Our scope of services included completion of five test pits, laboratory testing, engineering analyses, and preparation of this report. Site Conditions A new four apartment building complex is planned on the approximate 5-acre parcel located south of Berry Valley Road NW and Tahoma Boulevard, in Yelm. The western property boundary is bordered by Durant Street SE. The property is currently occupied with one single family residence in the northern portion. Most of the site is covered with field grasses with isolated trees. Overall, the property is generally level with about 8 feet of elevation change based on Google Earth satellite imagery. Subsurface Conditions Subsurface conditions on the lots were characterized by completing five test pits on February 21, 2021. Test pits were advanced to depths between 5 and 10 feet below existing ground surface. Approximate locations of the explorations are shown on Figure 1, Exploration Plan. A summary description of observed subgrade conditions is provided below with logs of the test pits in Appendix A. Soil Conditions Topsoil was observed below the surface in the test pits and extended to depths between about 1.5 to 2 feet. Native soil below the topsoil consisted of sand with trace silt to gravelly sand/sandy gravel with trace silt. These soils extended to the termination depth of the test pits. Caving of sidewall soils limited depth of excavation in several of the test pits. Infiltration Assessment SSGC Tahoma Boulevard Apartments Yelm, Washington SSGC Project No. 21013 April 2, 2021 2 Groundwater Conditions Groundwater was not observed in the test pits at the time of excavation. Evidence of mottling or other indicators of seasonally perched groundwater was not observed. Seasonal high groundwater levels are not anticipated to affect these lots. Groundwater levels will vary throughout the year based on seasonal precipitation and on- and off-site drainage patterns. Geologic Setting Soils over most of the site consist of “Spanaway gravelly sandy loam” per the USDA Soil Conservation Service map of Thurston County. A small area of the northern portion is mapped as “Nisqually loamy fine sand”. Both soils reportedly formed in glacial outwash. Native soils observed in the test pits appear to conform to the mapped soil types. Infiltration Characteristics Assessment of infiltration potential of site soils was completed using gradation correlations based on Massmann’s equation per Volume 3, Appendix III-A, Method 3 of the 2016 Thurston County Drainage Design and Erosion Control Manual. Spanaway gravelly sandy loam is considered a Type A hydrologic soil per the Soil Conservation Service. Results of the correlations are provided in Table 1. Table 1. Infiltration Rates Test Pit Number, and Depth (ft) Soil Type Calculated Infiltration Rate (in/hr) Corrected Infiltration Rate (in/hr) Correction Factors* (Fg/Ft/Fp) TP-1, 4 ft Outwash 60 21 (1.0/0.4/0.9) TP-4, 9 ft Outwash 86 31 (1.0/0.4/0.9) * Correction Factors from the 2016 Thurston County Drainage Design and Erosion Control Manual. Calculated infiltration rates are considered appropriate for the outwash soil tested. Pilot Infiltration Tests (PIT) completed in outwash soils at other locations in the area show infiltration rates similar to the above calculated rates. We recommend averaging the two rates for a long-term design rate of 26 inches per hour (in/hr) for design of infiltration facilities placed in the outwash soil. Seasonal groundwater levels or impermeable soils at depth should not adversely affect infiltration facilities located within 4 feet of the surface. Cation Exchange Capacity (CEC) and organic content tests were completed on a sample of the outwash. Test results are summarized in Table 2. Infiltration Assessment Tahoma Boulevard Apartments Yelm, Washington SSGC Project No. 21013 April 2, 2021 Table 2. CEC and Organic Content Results SSGC Test Location, CEC Results CEC Required* Organic Content Organic Sample ID, Depth (milliequivalents) (milliequivalents) Results (%) Content Required* (%) TP -5, S-1, 5 feet 7.9 > 5 1.26 > 1.0 * Per the 2016 Thurston County Drainage Design and Erosion Control Manual CEC and organic content results of the tested sample satisfy county requirements. The sample tested was collected at a depth near or below the anticipated depth of infiltration facilities. Although CEC and organic content can vary in outwash soils, soils appeared generally consistent across the site. REPORT CONDITIONS This report has been prepared for the exclusive use of Schuur Brothers Construction for specific application to the project discussed and has been prepared in accordance with generally accepted geotechnical engineering practices in the area. No warranties, either express or implied, are intended or made. The analysis and recommendations presented in this report are based on observed soil conditions and test results at the indicated locations, and from other geologic information discussed. This report does not reflect variations that may occur across the project limits, or due to the modifying effects of drainage patterns or weather. The scope of services for this project does not include any environmental or biological assessment of the site including identification or prevention of pollutants, hazardous materials, or conditions. Other studies should be completed if the owner is concerned about the potential for contamination or pollution. We appreciate the opportunity to work with you on this project. Please contact us if additional information is required or we can be of further assistance. Respectfully, South Sound Geotechnical Consulting Timothy H. Roberts, P.E. Member/Geotechnical Engineer Attachments: Figure 1. Exploration Plan Appendix A — Field Exploration Procedures Appendix B — Laboratory Testing and Results Unified Soils Classification System 3 N South Sound Geotechnical Consulting P.O. Box 39500 Lakewood, WA 98496 (253) 973-0515 Figure 1 – Exploration Plan Tahoma Boulevard Apartments Yelm, WA SSGC Project #21013 Approximate Test Pit Location PIT - 1 TP - 1 Scale: NTS Base map from drawing titled, “Tahoma Blvd Apartments, Conceptual Site Plan”, by AHBL, dated 1/13/21. Legend TP-2 TP-1 TP-3 TP-5 TP-4 Infiltration Assessment SSGC Tahoma Boulevard Apartments Yelm, Washington SSGC Project No. 21013 April 2, 2021 4 Appendix A Field Exploration Procedures Infiltration Assessment SSGC Tahoma Boulevard Apartments Yelm, Washington SSGC Project No. 21013 April 2, 2021 5 Field Exploration Procedures Our field exploration for this project included five test pits completed on February 21, 2021. Approximate locations of the explorations are shown on Figure 1, Exploration Plan. The exploration locations were determined by pacing from site features. Ground surface elevations referenced on the logs were inferred from Google Earth satellite imagery. Exploration locations and elevations should be considered accurate only to the degree implied by the means and methods used. A client provided excavator/operator dug the test pits. Soil samples were collected and stored in moisture tight for further assessment and laboratory testing. Explorations were backfilled with excavated soils and tamped when completed. Please note that backfill in the explorations will likely settle with time. Backfill located in building areas should be re-excavated and recompacted, or replaced with structural fill. The following logs indicate the observed lithology of soils and other materials observed in the explorations at the time of excavation. Where a soil contact was observed to be gradational, our log indicates the average contact depth. Our logs also indicate the approximate depth to groundwater (where observed at the time of excavation), along with sample numbers and approximate sample depths. Soil descriptions on the logs are based on the Unified Soil Classification System. Project: Tahoma Boulevard Apartments SSGC Job # 21013 TEST PIT LOGS PAGE 1 OF 2 Location: 15035 Berry Valley Rd NW, Yelm, WA TEST PIT LOGS FIGURE A-1 South Sound Geotechnical Consulting TP-1 TO TP-5 Logged by: THR Test Pit TP-1 Depth (feet) Material Description 0 – 2 2 – 10 Topsoil SAND with trace silt and occasional gravel: Loose to medium dense, moist, brown. (SP)(Outwash)(Sample S-1 @ 4 feet; Sample S-2 @ 7.5 feet) Test pit completed at approximately 10 feet on 2/21/21. Groundwater not observed at time of excavation. Approximate surface elevation: 347 feet Test Pit TP-2 Depth (feet) Material Description 0 – 1.5 1.5 – 5 Topsoil Gravelly SAND/Sandy GRAVEL with cobbles and trace silt: Loose, moist, brown to gray. (SP/GP)(Outwash) Test pit completed at approximately 5 feet on 2/21/21 due to caving. Groundwater not observed at time of excavation. Approximate surface elevation: 348 feet Test Pit TP-3 Depth (feet) Material Description 0 – 1.5 1.5 – 9 Topsoil Gravelly SAND/Sandy GRAVEL with cobbles and trace silt, boulder: Loose to medium dense, moist, brown. (SP)(Outwash) Test pit completed at approximately 9 feet on 2/21/21 due to caving. Groundwater not observed at time of excavation. Approximate surface elevation: 348 feet Project: Tahoma Boulevard Apartments SSGC Job # 21013 TEST PIT LOGS PAGE 2 OF 2 Location: 15035 Berry Valley Rd NW, Yelm, WA TEST PIT LOGS FIGURE A-1 South Sound Geotechnical Consulting TP-1 TO TP-5 Logged by: THR Test Pit TP-4 Depth (feet) Material Description 0 – 1.5 2 – 9.5 Topsoil Gravelly SAND with trace silt: Loose to medium dense, moist, brown. (SP)(Outwash)(Sample S-1 @ 4 feet; Sample S-2 @ 9 feet) Test pit completed at approximately 9.5 feet on 2/21/21 due to caving. Groundwater not observed at time of excavation. Approximate surface elevation: 350 feet Test Pit TP-5 Depth (feet) Material Description 0 – 2 2 – 10 Topsoil SAND with trace silt and occasional gravel: Loose to medium dense, moist, brown. (SP)(Outwash)(Sample S-1 @ 6 feet) Test pit completed at approximately 10 feet on 2/21/21. Groundwater not observed at time of excavation. Approximate surface elevation: 345 feet Infiltration Assessment SSGC Tahoma Boulevard Apartments Yelm, Washington SSGC Project No. 21013 April 2, 2021 6 Appendix B Laboratory Testing and Results Infiltration Assessment SSGC Tahoma Boulevard Apartments Yelm, Washington SSGC Project No. 21013 April 2, 2021 7 Laboratory Testing Organic content and cation exchange capacity (CEC) testing on a sample from the base of the PIT test hole was completed by Northwest Agricultural Consultants of Kennewick, Washington. Gradation tests were completed by Construction Testing Laboratories (CTL) of Puyallup, Washington. Results of the laboratory testing are included in this appendix. Report shall not be reproduced except in full without the written approval of the Laboratory. Report pertains only to the material tested.Tested By: R Rowden Checked By: C Pedersen Particle Size Distribution Report ASTM C117/C136 PERCENT FINER0 10 20 30 40 50 60 70 80 90 100 GRAIN SIZE - mm. 0.0010.010.1110100 % +3"Coarse % Gravel Fine Coarse Medium % Sand Fine Silt % Fines Clay 0 2 6 2 35 51 46 in.3 in.2 in.1½ in.1 in.¾ in.½ in.3/8 in.#4#10#20#30#40#60#100#140#200SIEVE PERCENT SPEC.*PASS? SIZE FINER PERCENT (X=NO) Material Description Atterberg Limits Classification Remarks Source of Sample: TP-1 Sample Number: 21-221 Date: Client: Project: Project No:Figure Grab Sample, S-1 Sampled at 4'1" 3/4" 1/2" 3/8" #4 #8 #16 #30 #50 #100 #200 100 98 96 94 92 90 87 77 30 7 3.6 SP Report: 02 Sampled By: Client South Sound Geotechnical Tahoma (21013) 9015 PL=LL=PI= USCS=AASHTO= *(no specification provided) 02-22-21 Construction Testing Laboratories 400 Valley Ave. NE, Suite #102 Puyallup WA, 98372 Tel. (253) 383-8778 Report shall not be reproduced except in full without the written approval of the Laboratory. Report pertains only to the material tested.Tested By: R Rowden Checked By: C Pedersen Particle Size Distribution Report ASTM C117/C136 PERCENT FINER0 10 20 30 40 50 60 70 80 90 100 GRAIN SIZE - mm. 0.0010.010.1110100 % +3"Coarse % Gravel Fine Coarse Medium % Sand Fine Silt % Fines Clay 0 11 30 9 37 10 36 in.3 in.2 in.1½ in.1 in.¾ in.½ in.3/8 in.#4#10#20#30#40#60#100#140#200SIEVE PERCENT SPEC.*PASS? SIZE FINER PERCENT (X=NO) Material Description Atterberg Limits Classification Remarks Source of Sample: TP-4 Sample Number: 21-220 Date: Client: Project: Project No:Figure Grab Sample, S-1 Sampled at 9'2" 1" 3/4" 1/2" 3/8" #4 #8 #16 #30 #50 #100 #200 100 91 89 78 73 59 52 42 21 8 4 3.2 SP Report: 01 Sampled By: Client South Sound Geotechnical Tahoma (21013) 9015 PL=LL=PI= USCS=AASHTO= *(no specification provided) 02-22-21 Construction Testing Laboratories 400 Valley Ave. NE, Suite #102 Puyallup WA, 98372 Tel. (253) 383-8778 2545 W Falls Avenue Kennewick, WA 99336 509.783.7450 www.nwag.com lab@nwag.com Sample ID Organic Matter Cation Exchange Capacity TP-5, S-1 @ 5’ 1.26% 7.9 meq/100g Method ASTM D2974 EPA 9081 South Sound Geotechnical Consulting PO Box 39500 Lakewood, WA 98496 Report: 54768-1-1 Date: March 31, 2021 Project No: 21013 Project Name: Tahoma Apts UNIFIED SOIL CLASSIFICATION SYSTEM Criteria for Assigning Group Symbols and Group Names Using Laboratory TestsA Soil Classification Group Symbol Group NameB Coarse Grained Soils More than 50% retained on No. 200 sieve Gravels More than 50% of coarse fraction retained on No. 4 sieve Clean Gravels Less than 5% finesC Cu  4 and 1  Cc  3E GW Well-graded gravelF Cu  4 and/or 1  Cc  3E GP Poorly graded gravelF Gravels with Fines More than 12% finesC Fines classify as ML or MH GM Silty gravelF,G, H Fines classify as CL or CH GC Clayey gravelF,G,H Sands 50% or more of coarse fraction passes No. 4 sieve Clean Sands Less than 5% finesD Cu  6 and 1  Cc  3E SW Well-graded sandI Cu  6 and/or 1  Cc  3E SP Poorly graded sandI Sands with Fines More than 12% finesD Fines classify as ML or MH SM Silty sandG,H,I Fines Classify as CL or CH SC Clayey sandG,H,I Fine-Grained Soils 50% or more passes the No. 200 sieve Silts and Clays Liquid limit less than 50 inorganic PI  7 and plots on or above “A” lineJ CL Lean clayK,L,M PI  4 or plots below “A” lineJ ML SiltK,L,M organic Liquid limit - oven dried  0.75 OL Organic clayK,L,M,N Liquid limit - not dried Organic siltK,L,M,O Silts and Clays Liquid limit 50 or more inorganic PI plots on or above “A” line CH Fat clayK,L,M PI plots below “A” line MH Elastic SiltK,L,M organic Liquid limit - oven dried  0.75 OH Organic clayK,L,M,P Liquid limit - not dried Organic siltK,L,M,Q Highly organic soils Primarily organic matter, dark in color, and organic odor PT Peat A Based on the material passing the 3-in. (75-mm) sieve B If field sample contained cobbles or boulders, or both, add “with cobbles or boulders, or both” to group name. C Gravels with 5 to 12% fines require dual symbols: GW -GM well-graded gravel with silt, GW -GC well-graded gravel with clay, GP-GM poorly graded gravel with silt, GP-GC poorly graded gravel with clay. D Sands with 5 to 12% fines require dual symbols: SW -SM well-graded sand with silt, SW -SC well-graded sand with clay, SP-SM poorly graded sand with silt, SP-SC poorly graded sand with clay E Cu = D60/D10 Cc = 6010 2 30 DxD )(D F If soil contains  15% sand, add “with sand” to group name. G If fines classify as CL-ML, use dual symbol GC-GM, or SC-SM. HIf fines are organic, add “with organic fines” to group name. I If soil contains  15% gravel, add “with gravel” to group name. J If Atterberg limits plot in shaded area, soil is a CL-ML, silty clay. K If soil contains 15 to 29% plus No. 200, add “with sand” or “with gravel,” whichever is predominant. L If soil contains  30% plus No. 200 predominantly sand, add “sandy” to group name. M If soil contains  30% plus No. 200, predominantly gravel, add “gravelly” to group name. N PI  4 and plots on or above “A” line. O PI  4 or plots below “A” line. P PI plots on or above “A” line. Q PI plots below “A” line.