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2021.0170.PR0006 Tahoma Terra Drainage Report 09-01-2020 Preliminary Drainage Report TAHOMA TERRA MASTER PLAN COMMUNITY PHASE II, DIVISION III YELM, WASHINGTON Project #10182000024 September 1, 2020 Prepared for: Tahoma Terra Holding, LLC PO Box 73790 Puyallup, WA 98373 Prepared by: Ben Enfield, PE Frances Constantino Consulting Engineers 612 Woodland Square Loop SE, Suite 100 Lacey, WA 98503 (360) 292-7230 (360) 292-7231 FAX Tahoma Terra - Phase II, Div. III Preliminary Drainage Report Yelm, WA i PROJECT ENGINEERS CERTIFICATION: I hereby state that this Drainage Report for Tahoma Terra - Phase II, Division III has been prepared by me or under my supervision and meets the standard of care and expertise which is usual and customary in this community for profession engineers. I understand that the City of Yelm does not and will not assume liability for the sufficiency, suitability, or performance of drainage facilities designed by me. ii Tahoma Terra Holding, LLC Tahoma Terra Master Plan Community Phase II, Division III PROJECT #10182000024 TABLE OF CONTENTS 1.0 PROJECT OVERVIEW _________________________________________________ 1 1.1 Pre-developed Conditions ..................................................................................... 1 1.2 Developed Conditions ............................................................................................ 1 2.0 EXISTING CONDITIONS SUMMARY ______________________________________ 1 3.0 OFF-SITE ANALYSIS REPORT __________________________________________ 2 4.0 MINIMUM REQUIREMENTS ____________________________________________ 2 4.1 #1: Preparation of Stormwater Site Plans ............................................................. 3 4.2 #2: Construction Stormwater Pollution Prevention ............................................. 3 4.3 #3: Source Control of Pollution ............................................................................. 3 4.4 #4: Preservation of Natural Drainage Systems and Outfalls ............................... 3 4.5 #5: On-site Stormwater Management .................................................................... 3 4.6 #6: Runoff Treatment ............................................................................................. 3 4.7 #7: Flow Control ..................................................................................................... 4 4.8 #8: Wetlands Protection ......................................................................................... 4 4.9 #9: Operation and Maintenance............................................................................. 4 5.0 STORMWATER CONTROL PLAN ________________________________________ 4 5.1 Existing Site Hydrology ......................................................................................... 4 5.2 Developed Site Hydrology ..................................................................................... 4 5.3 Performance Standards and Goals ....................................................................... 5 5.4 Flow Control System .............................................................................................. 6 5.5 Water Quality System ............................................................................................. 6 6.0 STORMWATER POLLUTION PREVENTION PLAN (SWPPP) __________________ 7 7.0 SPECIAL REPORTS AND STUDIES ______________________________________ 7 8.0 OTHER PERMITS _____________________________________________________ 7 9.0 OPERATION AND MAINTENANCE MANUAL ______________________________ 7 iii APPENDICES Appendix A – Vicinity Map and Site Maps Appendix B – Flowcharts Appendix C – Preliminary Overall Drainage Plan Appendix D – Off-Site Analysis Study Map Appendix E – Hydraulic Calculations Appendix F – Geotechnical Report Appendix G – City of Yelm Letter of Understanding for Stormwater Requirements Tahoma Terra - Phase II, Div. III Preliminary Drainage Report Yelm, Washington KPFF Consulting Engineers P a g e | 1 1.0 PROJECT OVERVIEW This project involves development of Phase II, Division III of the Tahoma Terra Master Plan Development within the City of Yelm. This phase of development proposes 234 single family units, four (4) apartment buildings, and associated site improvements. The project site is located on existing Thurston County parcel numbers: 78640000015, 78640000016, 78640000017, and 78640000018. The total project site area is approximately 46.6 acres. The site is bounded by Tahoma Boulevard SE to the north, and undeveloped and residential land to the east, west, and south. A buffer for Thompson Creek is adjacent to the project site on the eastern property boundary and a wetland buffer is adjacent along the southern property boundary. See the Vicinity Map for reference in Appendix A. 1.1 Pre-developed Conditions The site has an existing high elevation of approximately 405 feet in the center of parcel 78640000018 and an existing low elevation of approximately 330 feet located along the east property line of parcel 78640000015. The site has been previously cleared of vegetation in 2007 from the early phases of the Tahoma Terra Master Plan Development project. Existing stormwater ponds are located in the center of the project site which currently serves the previously constructed Phase II, Division II development north of Tahoma Boulevard. Per the geotechnical report, the soil consists of glacial till with a design infiltration rate of 20 in/hr. The existing site soils are generally suitable for infiltration where sufficient depth is available above the seasonal high groundwater elevation. A geotechnical report is included for reference in Appendix F. There is an east-west ridgeline approximately 55 feet north of the wetland buffer along the south of the property. There are two (2) natural threshold discharge areas located on-site. Runoff southwest of the existing ponds generally sheet flows toward the wetland area south of the project site. Runoff towards the northeastern portion of the project site sheet flows toward the Thompson Creek approximately 220 feet east of the property line. Runoff towards the northwest corner and north of the ridgeline generally flows into the existing ponds and infiltrate into the site soils. Stormwater runoff from adjacent upstream parcels north of the site are collected in catch basins along Tahoma Boulevard and eventually flow into the existing ponds. A Pre-Developed Site Map is included for reference in Appendix A. 1.2 Developed Conditions The proposed project includes the construction of 234 single family lots, four (4) three-story apartment buildings, asphalt roadways, cement concrete sidewalks, retaining walls, stormwater detention, infiltration, and treatment facilities, and utilities such as water, STEP sanitary sewer, storm conveyance, and franchise utilities. Stormwater runoff will be collected on-site by means of catch basins, treated by water quality facilities, and infiltrated on-site or detained and released at pre-developed rates to off-site areas. Roof runoff will be conveyed in a separate roof drain conveyance system directly to flow control facilities. A Developed Site Map is included for reference in Appendix A. 2.0 EXISTING CONDITIONS SUMMARY Stormwater runoff follows the existing topography and generally sheet flows to either one (1) of three (3) locations: the existing constructed storm ponds serving development north of Tahoma Boulevard, the wetland to the south, or Thompson Creek to the east. Tahoma Terra - Phase II, Div. III Preliminary Drainage Report Yelm, Washington KPFF Consulting Engineers P a g e | 2 There is an existing swale just south of Tahoma Boulevard which connects to the existing ponds. A temporary gravel road stretches from Tahoma Boulevard to the existing pond, then splits and continues into the east and west parcels. There is currently one (1) existing storm drainage pipe located on the project site which runs south from Tahoma Boulevard into the existing pond. The entire project site is within a critical aquifer recharge area and nearly half of parcel #78640000015 (east parcel) is within a wellhead protection area. The creek boundary surrounding Thompson Creek is within a flood zone area and a high groundwater hazard area according to the Thurston County GeoData Center’s website. Insight Geologic, Inc. prepared a Geotechnical Report dated February 13, 2018 for this project. The report identified that existing site soils generally consists of glacial till mixed with outwash silt, sand, and gravel. Insight Geologic, Inc. conducted pilot infiltration tests and determined the site conditions are generally feasible for infiltration of surface runoff. The test results are included in the report in Appendix F. 3.0 OFF-SITE ANALYSIS REPORT Currently, runoff leaves the site at multiple locations along the east and southwest property lines where runoff leaves as sheet flow in all locations. Runoff from the east of the project site discharges to the Thompson Creek, whereas runoff from the southwest areas flow towards the wetland area south of the project site. The one-quarter mile markers for both locations are shown in the Off-Site Analysis Study Map located in Appendix D. Runoff from the off-site drainage basin located north of Tahoma Boulevard currently flows through an existing pipe conveyance system and into the existing infiltration ponds. Runoff from this basin will continue to drain into these ponds after completion of this project. There are currently no known off-site water quality, erosion, or slope stability impacts. Off-site drainage impacts will be mitigated by adherence to Washington State Department of Ecology (DOE) requirements as discussed in Section 4.0 of this report. The wetland area adjacent to the site is discussed briefly in Section 4.8 of this report. 4.0 MINIMUM REQUIREMENTS This development is part of the Tahoma Terra Master Plan Community. The stormwater requirements for future phases of this development were memorialized in a Letter of Understanding from the City of Yelm dated May 24, 2016. This letter is included in Appendix G. The letter states that stormwater facilities shall be designed to the 1992 DOE manual except for stormwater treatment facilities which shall be designed to the most current DOE manual at the time of development. City of Yelm Municipal Code (YMC) 13.16.060 adopts the 2019 Washington State Department of Ecology Stormwater Management Manual for Western Washington (DOE Manual). This manual will be utilized for stormwater treatment design. The DOE Manual identifies nine (9) minimum requirements for stormwater management of new development projects. All minimum requirements apply to this project according to DOE Manual Figure 1-3.1, which has been included for reference in Appendix B. A summary of the project classifications and requirements are listed below:  Applicable Minimum Stormwater Requirements: #1 through #9 apply to new and replaced hard surfaces and converted vegetation areas.  Drainage Review Type: Full Drainage Review Tahoma Terra - Phase II, Div. III Preliminary Drainage Report Yelm, Washington KPFF Consulting Engineers P a g e | 3  Stormwater Treatment Requirements: Phosphorus and Enhanced Treatment 4.1 #1: Preparation of Stormwater Site Plans The Stormwater Site Plan for this project. The technical information and analysis necessary for stormwater management of this project has been included within or attached to this report. A Preliminary Overall Drainage Plan has also been included for reference in Appendix C. 4.2 #2: Construction Stormwater Pollution Prevention A preliminary Construction Stormwater Pollution Prevention Plan (CSWPPP) is included with the submittal packet. 4.3 #3: Source Control of Pollution The primary source of pollutants for this project is residential vehicular traffic. Operational source control Best Management Practices (BMPs) are proposed to mitigate pollutants generated by vehicles. These BMPs include promptly containing and cleaning up pollutant leaks and spills, sweeping all appropriate surfaces quarterly or more frequently as needed, cleaning oil, debris, and sludge from all stormwater facilities regularly, and promptly repairing or replacing damaged structures susceptible to pollution leakage. 4.4 #4: Preservation of Natural Drainage Systems and Outfalls There are two (2) historical threshold discharge areas located on-site. These areas are separated by a central drainage area in which runoff flows towards the existing ponds and infiltrates into the site soils. Multiple discharge locations are located in Basin 1A shown in the Pre-Developed Site Map of Appendix A, and eventually combine within one-quarter mile downstream of the site to form a single threshold discharge area. This is also applicable to Basin 3A. See Off-Site Analysis Study Map in Appendix D. 4.5 #5: On-site Stormwater Management The 1992 DOE Manual was utilized for flow control sizing and the most recent version of the DOE Manual was utilized for sizing treatment. See excerpt in Appendix G for City of Yelm’s approval in using the 1992 DOE Manual. Infiltration BMPs are proposed for two on-site basins with adequate separation to seasonal high groundwater. 4.6 #6: Runoff Treatment Runoff treatment will be provided per the most current DOE design standards per the Tahoma Terra Master Plan Community agreements. The current design manual at this time is the 2019 edition. This project requires Phosphorus treatment for pollution generating surfaces for all project basins due to the proximity to Thompson Creek and adjacent wetlands. Enhanced treatment is also required prior to the proposed infiltration ponds (Infiltration Ponds B and C) due to the project site location within a wellhead protection area and prior to the proposed detention pond D due to its location within a category I critical aquifer recharge area. See Figure III-1.1 in Appendix B for process in selecting runoff treatment BMPs. A treatment wet pond has been selected to treat stormwater runoff for the South Basin (Pond A) by using the single event method through StormShed. Bioretention BMP was selected for the North, West, and East basins (Ponds B, C, & D) per Volume V, Chapter 5 of the 2019 DOE Manual. See Section 5.5 of this report for the proposed water quality system. Tahoma Terra - Phase II, Div. III Preliminary Drainage Report Yelm, Washington KPFF Consulting Engineers P a g e | 4 4.7 #7: Flow Control Flow control will be provided per the requirements of the 1992 DOE stormwater manual per the Tahoma Terra Master Plan Community agreements. Two (2) proposed detention ponds and two (2) infiltration ponds shall be used to meet the 1992 version of the DOE Manual flow control requirements. See Section 5.4 of this report for the proposed flow control system. Previous geotechnical work on the site identifies overall groundwater and soil conditions. Additional facility specific geotechnical test pits and testing will be conducted prior to construction permit plan preparation for the new stormwater facilities identified in this plan to confirm facility specific locations. 4.8 #8: Wetlands Protection This project continues to discharge stormwater runoff towards the off-site wetland located south of the site. Wetland fluctuation calculations shall be provided with permit submittals. 4.9 #9: Operation and Maintenance The Operation and Maintenance (O&M) Manual is discussed in Section 9.0 of this report. 5.0 STORMWATER CONTROL PLAN 5.1 Existing Site Hydrology See Section 1.1 of this report for a description of the pre-developed conditions. The pre- developed conditions were modeled in StormShed modeling software as forested land cover. Type “A” soils were selected based on the drainage properties of the existing site soils identified in the geotechnical report. A Pre-Developed Site Map is included for reference in Appendix A. There are two natural threshold discharge areas on-site. The pre-developed basins are delineated based on the 1996 contours generated from the Thurston County GIS map. The pre-developed basins are summarized in Table 1. Table 1 – Summary of Pre-Developed Basins Area (sf) Area (ac) Basin 1A 265,280 6.09 Basin 2A 874,680 20.08 Basin 3A 892,110 20.48 On-Site TOTAL 2,032,070 46.65 Basin 1B 3,110,180 71.4 Basin 2B 2,610 0.06 Basin 3B 13,070 0.30 Basin 4B 29,620 0.68 Off-Site TOTAL 3,155,480 72.44 5.2 Developed Site Hydrology See Section 1.2 of this report for a brief description of the developed conditions. All pervious surfaces were modeled in StormShed as lawn. A Developed Site Map is included for reference in Appendix A. Tahoma Terra - Phase II, Div. III Preliminary Drainage Report Yelm, Washington KPFF Consulting Engineers P a g e | 5 Developed on-site conditions will maintain the two existing threshold discharge areas. The developed basins are summarized in Table 2. Table 2 – Summary of Developed Basins Land Cover Type Area (sf) Area (ac) North Basin (To Pond B) Lawn/Landscape PGPS 526,200 12.08 Sidewalks, Flat PGIS 39,200 0.90 Roof NPGIS 243,500 5.59 Pond(s) - 109,770 2.52 Roads PGIS 104,540 2.40 Parking/Driveway PGIS 0.00 0.00 North Basin SUBTOTAL 1,023,210 23.49 South Basin (To Pond A) Lawn/Landscape PGPS 104,980 2.40 Sidewalks, Flat PGIS 2,610 0.06 Roof NPGIS 38,330 0.88 Pond(s) - 16,120 0.37 Roads PGIS 12,200 0.28 Parking/Driveway PGIS 0.00 0.00 South Basin SUBTOTAL 174,240 4.00 East Basin (To Pond D) Lawn/Landscape NPGPS 164,220 3.77 Sidewalks, Flat PGIS 8,710 0.20 Roof NPGIS 56,190 1.29 Pond(s) - 40,510 0.93 Roads PGIS 25,260 0.58 Parking/Driveway PGIS 26,140 0.60 East Basin SUBTOTAL 321,030 7.37 West Basin (To Pond C) Lawn/Landscape NPGPS 264,840 6.08 Sidewalks, Flat PGIS 27,880 0.64 Roof NPGIS 136,340 3.13 Pond(s) - 17,860 0.41 Roads PGIS 66,210 1.52 Parking/Driveway PGIS 0.00 0.00 West Basin SUBTOTAL 513,130 11.78 On-Site TOTAL 2,031,610 46.64 Off-Site Basin (To Pond B) Total Pervious NPGPS 2,681,550 41.31 Total Impervious PGIS 1,313,330 30.15 Off-Site TOTAL 3,994,880 71.46 StormShed was used to calculate the pre-developed and developed flow rates to determine conformance to flow control requirements. 5.3 Performance Standards and Goals See section 4.6 and 4.7 for water quality and flow control standards. Tahoma Terra - Phase II, Div. III Preliminary Drainage Report Yelm, Washington KPFF Consulting Engineers P a g e | 6 5.4 Flow Control System Detention and infiltration ponds, including four separate conveyance systems will provide flow control. The existing ponds within the project area, which were constructed in 2007 as part of the Phase II, Division II development project, will be re-constructed to shift location and to take on-site runoff for the North Basin. A new infiltration pond will also be installed to collect runoff for the West Basin. Due to high groundwater conditions, runoff from the East and South basins will be detained in detention ponds rather than infiltrated. The East Basin will have an outfall releasing runoff towards Thompson creek. Runoff from the South Basin will be released towards the existing wetland south of the project site. StormShed, a single-event hydrology software, was used to size the overall detention volumes required for this project. The site conveyance system shall convey all stormwater runoff from proposed improvements including roadways, sidewalks, roofs, landscaping into stormwater facilities by means of catch basins. The conveyance system will be sized to contain the 25-year event below the crown of the pipes and the 100-year event below the finished ground surface and catch basin rim elevations. Conveyance calculations will be included in future submittals. The preliminary sizes of the proposed stormwater facilities are summarized in Table 3. Table 3 – Summary of Stormwater Facilities Live Storage Depth (ft) Volume Required (cf) Volume Provided (cf) South Basin (Pond A) 4.7 31,370 34,530 North Basin (Pond B) 5.7 136,970 168,060 West Basin (Pond C) 5.6 15,530 17,880 East Basin (Pond D) 2.9 65,830 79,630 StormShed flow control results are included for reference in Appendix E. 5.5 Water Quality System This project proposes to use four (4) stormwater treatment facilities to treat all stormwater runoff from pollution generating surfaces. A treatment wetpond was designed to provide Phosphorus treatment for the South Basin. Bioretention facilities were designed to provide both Phosphorus and Enhanced treatments for the North, West, and East Basins. All treatment facilities are located upstream of the detention/infiltration ponds. See Tables 4 and 5 for the wetpond and bioretention sizes provided for each basin. Table 4 – Summary of Wetpond Facilities Volume Required (cf) Volume Provided (cf) South Basin (Facility A) 6,340 7,390 Tahoma Terra - Phase II, Div. III Preliminary Drainage Report Yelm, Washington KPFF Consulting Engineers P a g e | 7 Table 5 – Summary of Bioretention Facilities Volume Required (cf) Volume Provided (cf) North Basin (Facility B) 24,990 29,700 West Basin (Facility C) 2,090 2,300 East Basin (Facility D) 1,060 1,220 See Appendix E for reference of water quality results. 6.0 STORMWATER POLLUTION PREVENTION PLAN (SWPPP) All 13 Elements listed in Volume II, Chapter 2 of the DOE Manual have been addressed to mitigate potential pollution problems. The SWPPP has been included in the submittal for reference. 7.0 SPECIAL REPORTS AND STUDIES No special report or studies or reports have been identified for this project. 8.0 OTHER PERMITS The stormwater management plan for this project is subject only to City of Yelm engineering review. Other permits required for this project include the following:  City of Yelm Residential Building Permit 9.0 OPERATION AND MAINTENANCE MANUAL Operation and maintenance guidelines for proposed stormwater facilities and treatment devices will be included for reference in the final drainage report. A complete O&M Manual will be prepared and approved before the building permit is issued. APPENDIX A Vicinity Map and Site Maps 1 5,762 7/22/2020 Note: Legend Map Created Using GeoData Public Website The information included on this map has been compiled by Thurston County staff from a variety of sources and is subject to change without notice. Additional elements may be present in reality that are not represented on the map. Ortho-photos and other data may not align. The boundaries depicted by these datasets are approximate. This document is not intended for use as a survey product. ALL DATA IS EXPRESSLY PROVIDED ‘AS IS’ AND ‘WITH ALL FAULTS’. Thurston County makes no representations or warranties, express or implied, as to accuracy, completeness, timeliness, or rights to the use of such information. In no event shall Thurston County be liable for direct, indirect, incidental, consequential, special, or tort damages of any kind, including, but not limited to, lost revenues or lost profits, real or anticipated, resulting from the use, misuse or reliance of the information contained on this map. If any portion of this map or disclaimer is missing or altered, Thurston County removes itself from all responsibility from the map and the data contained within. The burden for determining fitness for use lies entirely with the user and the user is solely responsible for understanding the accuracy limitation of the information contained in this map. Authorized for 3rd Party reproduction for personal use only. Scale 1: Published: Feet 2500 500 Contours 2ft 1996 (NGVD 29) Streams Wetland Delineations Verified Delineated Unverified Parcel Boundary Unknown Wetlands Waterbodies Parcel Boundaries Roads - Major Major Roads Ramp I 5; US 101 Roads (Large Scale) Railroads County Border 2020©Thurston County VICINITY MAP Off-Site Basin (71.4 ac) Project Site (46.6 ac) Surface Runoff (typ.) Creek Boundary (typ.) Downstream flow path Wetland Boundary (typ.) 50+0051+00 22+0023+00 24+ 0 0 25+0 0 26+0 0 27+00 28+00 29+00 30+00 31+00 32+00 33+00 34+00 35+00 36+00 37+00 38+00 39+0040+0041+0042+0043+0044+0045+0046+0047+0048+0049+00 10+0029+0030+0031+0032+0033+0034+0035+0036+0037+0038+0039+0040+0041+0042+0043+0044+00125+00 126+00 127+00 128+00 129+00 130+00 145+00 146+00 147+00 148+00 149+00 150+00 165+00 166+00 167+00 168+00 169+00 170+00 190+00191+00192+00193+00194+00200+00201+00202+00203+00204+00210+00211+00102+00 103+00 104+00 105+00 106+00 107+00 108+00 1 0 9+ 0 0 58+00 59+00 60+ 0 0 61 + 0 0 62+ 0 0 63+00 64+00 65+0066+0067+0068+0069+0070+0071+0072+0073+0074+0075+0076+0077+0078+00BASIN 2A (20.08 ACRES) WETLAND TAHOMA BOULEVARD BASIN 3A (20.48 ACRES) BASIN 1A (6.09 ACRES) BASIN 1B (71.4 ACRES) TAHOMA TERRA PHASE II, DIVISION III PREDEVELOPED SITE & BASIN MAP DATE: 9/1/20 BASIN 4B (0.68 ACRES) BASIN 3B (0.30 ACRES) BASIN 2B (0.06 ACRES) NOTE: WETLAND BUFFER 380 3703 8 0 375370380 37 5 3 7 0 50+0051+00 22+0023+00 24+00 25+ 0 0 26+0 0 27+00 28+00 29+00 30+00 31+00 32+00 33+00 34+00 35+00 36+00 37+00 38+00 39+0040+0041+0042+0043+0044+0045+0046+0047+0048+0049+00 10+0029+0030+0031+0032+0033+0034+0035+0036+0037+0038+0039+0040+0041+0042+0043+0044+00125+00 126+00 127+00 128+00 129+00 130+00 145+00 146+00 147+00 148+00 149+00 150+00 165+00 166+00 167+00 168+00 169+00 170+00 190+00191+00192+00193+00194+00200+00201+00202+00203+00204+00210+00211+00102+00 103+00 104+00 105+00 106+00 107+00 108+00 1 0 9+ 0 0 58+00 59+00 60+ 0 0 61 + 0 0 62+ 0 0 63+00 64+00 65+0066+0067+0068+0069+0070+0071+0072+0073+0074+0075+0076+0077+0078+00 WETLAND TAHOMA BOULEVARD EAST BASIN (7.25 ACRES) SOUTH BASIN (4 ACRES) NORTH BASIN (23.5 ACRES) WEST BASIN (11.9 ACRES) TAHOMA TERRA PHASE II, DIVISION III DEVELOPED SITE & BASIN MAP DATE: 9/1/20 AREA (ACRE) LAND COVER NORTH BASIN SOUTH BASIN WEST BASIN EAST BASIN AREA (ACRE) LAND COVER OFF-SITE BASIN OFF-SITE BASIN (71.4 ACRES) WETLAND BUFFER 370 360350 34035 03603 7 0 3 7 0 3 6 0 360 370 370 360 350 3403 5 0 350 APPENDIX B Flowcharts Figure I-3.1: Flow Chart for Determining Requirements for New Development 2019 Stormwater Management Manual for Western Washington Volume I -Chapter 3 -Page 89 Figure I-3.3: Flow Chart for Determining MR #5 Requirements 2019 Stormwater Management Manual for Western Washington Volume I -Chapter 3 -Page 118 Figure III-1.1: Runoff Treatment BMP Selection Flow Chart 2019 Stormwater Management Manual for Western Washington Volume III -Chapter 1 -Page 421 APPENDIX C Preliminary Overall Drainage Plan WETLANDWETLAND BUFFER979899100101102103104105106107108109110111112113114115116117118119120121122123124125126127128129130131132133134135136137138139140141142143144145228229230231232233234221222223224225226227214215216217218219220209208207210211212213205204203202201200199198197196195194193192191190189180179178176175174173172171170169164163162165166167168181182183184185186146147148149150151152153154155156157158159160161206187188PARKPARKPARKPARKSTORM TRACT BSTORM TRACT APRELIMINARY GRADING & DRAINAGE PLANC3.0VERTICAL DATUMNGVD 29PER THURSTON COUNTYHIGH PRECISION NETWORKHORIZONTAL CONTROL:WASHINGTON STATE PLANE,SOUTH ZONE PER TCHPN&THURSTON COUNTY HIGHPRECISION NETWORKTAHOMA BOULEVARDCALL UNDERGROUND LOCATE TWO (2) WORKING DAYS BEFORE YOU DIG 811 SECTION 23, TOWNSHIP 17 NORTH, RANGE 1 EAST, W.M.THURSTON COUNTY, WASHINGTONTAHOMA TERRA PHASE II, DIVISION III 612 Woodland Square Loop, Suite 100 Lacey, WA 98503 360.292.7230 www.kpff.com PREL I M I N A R Y P L A T (NOT F O R C O N S T R U C T I O N )PROF ESSIONA L E N G INEERREGI S T E R EDTOSATEOFWASHING T NBENJA M I N E.A.EN F I ELD9-1-2020 LOCATED ON PROPERTY LINE: SEE DWG C1.2 MATCHLINE: SEE DWG C3.1WETPOND(POND A)DETENTION(POND A)INFILTRATION(POND B)BIORETENTION(POND B)LEGENDPHASE IIDIVISION IIPHASE IIDIVISION I ABDC12345678910111213141516171819202122232425262728293031323334353637383940414243444597464750515253545556575859606162636465676870717273747576777879808182838485868788899091929394959648496669PARKPARKSTORM TRACT CSTORM TRACT DPRELIMINARY GRADING & DRAINAGE PLANC3.1VERTICAL DATUMNGVD 29PER THURSTONCOUNTY HIGHPRECISION NETWORKHORIZONTAL CONTROL:WASHINGTON STATE PLANE,SOUTH ZONE PER TCHPN&THURSTON COUNTY HIGHPRECISION NETWORKCALL UNDERGROUND LOCATE TWO (2) WORKING DAYS BEFORE YOU DIG 811 SECTION 23, TOWNSHIP 17 NORTH, RANGE 1 EAST, W.M.THURSTON COUNTY, WASHINGTONTAHOMA TERRA PHASE II, DIVISION III 612 Woodland Square Loop, Suite 100 Lacey, WA 98503 360.292.7230 www.kpff.com PREL I M I N A R Y P L A T (NOT F O R C O N S T R U C T I O N )PROF ESSIONA L E N G INEERREGI S T E R EDTOSATEOFWASHING T NBENJA M I N E.A.EN F I ELD9-1-2020 TAHOMABOULEVARDLOCATED ON PROPERTY LINE: SEE DWG C1.2MATCHLINE: SEE DWG C3.0 DETENTION(POND D)LEGENDPHASE IIDIVISION IBIORETENTION(POND D)BIORETENTION(POND C)INFILTRATION(POND C) APPENDIX D Off-Site Analysis Study Map Legend Scale 1: 1 6,564 Published: Feet 0 600300 7/22/2020 Map Created Using GeoData Public Website The information included on this map has been compiled by Thurston County staff from a variety of sources and is subject to change without notice. Additional elements may be present in reality that are not represented on the map. Ortho-photos and other data may not align. The boundaries depicted by these datasets are approximate. This document is not intended for use as a survey product. ALL DATA IS EXPRESSLY PROVIDED ‘AS IS’ AND ‘WITH ALL FAULTS’. Thurston County makes no representations or warranties, express or implied, as to accuracy, completeness, timeliness, or rights to the use of such information. In no event shall Thurston County be liable for direct, indirect, incidental, consequential, special, or tort damages of any kind, including, but not limited to, lost revenues or lost profits, real or anticipated, resulting from the use, misuse or reliance of the information contained on this map. If any portion of this map or disclaimer is missing or altered, Thurston County removes itself from all responsibility from the map and the data contained within. The burden for determining fitness for use lies entirely with the user and the user is solely responsible for understanding the accuracy limitation of the information contained in this map. Authorized for 3rd Party reproduction for personal use only. Note: Contours 2ft 1996 (NGVD 29) Streams Wetlands Waterbodies Parcel Boundaries Roads - Major Major Roads Ramp I 5; US 101 Roads (Large Scale) Railroads County Border ©2020 Thurston County OFF-SITE ANALYSIS STUDY MAP Off-Site Basin (71.4 ac) Project Site (46.6 ac) Surface Runoff (typ.) Downstream Flow Path (typ.) Wetland Boundary Creek Boundary Basin 1A Discharge Locations Basin 3A Discharge Location Existing Pond Locations Approximate One-Quarter Mile Downstream of Project Site Existing 36" SD Pipe Low Point APPENDIX E Hydraulic Calculations Appended on: Thursday, August 27, 2020 4:48:46 PM LPOOLCOMPUTE [N-POND] SUMMARY using Puls, 24 hr Storm Event Start of live storage:339 ft Summary Report of all Detention Pond Data Project Precips BASLIST2 [B-Pond] Using [TYPE1a.rac] As [6-month] [24.0] [B-Pond] Using [TYPE1a.rac] As [2 yr 24 hr] [24.0] [B-Pond] Using [TYPE1a.rac] As [10 year] [24.0] [B-Pond] Using [TYPE1a.rac] As [25 year] [24.0] [B-Pond] Using [TYPE1a.rac] As [50 year] [24.0] [B-Pond] Using [TYPE1a.rac] As [100 year] [24.0] [B-Pond] Using [TYPE1a.rac] As [6-month] [24.0] [B-Pond] Using [TYPE1a.rac] As [6-month] [24.0] [B-Pond] Using [TYPE1a.rac] As [2 yr 24 hr] [24.0] [B-Pond] Using [TYPE1a.rac] As [2 yr 24 hr] [24.0] [B-Pond] Using [TYPE1a.rac] As [10 year] [24.0] [B-Pond] Using [TYPE1a.rac] As [10 year] [24.0] [B-Pond] Using [TYPE1a.rac] As [25 year] [24.0] [B-Pond] Using [TYPE1a.rac] As [25 year] [24.0] [B-Pond] Using [TYPE1a.rac] As [50 year] [24.0] [B-Pond] Using [TYPE1a.rac] As [50 year] [24.0] [B-Pond] Using [TYPE1a.rac] As [100 year] [24.0] [B-Pond] Using [TYPE1a.rac] As [100 year] [24.0] Event Match Q (cfs)Peak Q (cfs)Max Depth (ft)Vol (cf)Vol (acft)Time to Empty (hr) 6-month 8.9265 8.5318 0.1094 2003.3315 0.046 0.1667 2 yr 24 hr 1.1847 9.158 0.7475 14164.8761 0.3252 0.1667 10 year 25.9804 11.2592 2.7906 58760.803 1.349 0.1667 25 year 34.0718 12.775 4.1829 94329.0388 2.1655 0.1667 50 year 37.5032 13.4352 4.7704 110656.1021 2.5403 0.1667 100 year 42.8179 14.4602 5.6621 136969.2805 3.1444 0.1667 Event Precip (in) 6-month 1.28 2 yr 24 hr 2.00 10 year 3.00 25 year 3.50 50 year 3.70 100 year 4.00 Page 1 of 4 8/27/2020file://lac01/projects/2020/10182000024%20-%20Tahoma%20Terra%20Div.%207&8%20... North Basin Flow Control Results LSTEND BASLIST [B-Pond] LSTEND Record Id: B-Pond BasinID Event Peak Q (cfs) Peak T (hrs) Peak Vol (ac- cf) Area (ac)Method/Loss Raintype B-Pond 6-month 8.9265 8.00 3.8235 115.15 SBUH TYPE1a.rac B-Pond 2 yr 24 hr 14.8089 8.00 7.3365 115.15 SBUH TYPE1a.rac B-Pond 10 year 25.9804 8.00 13.4283 115.15 SBUH TYPE1a.rac B-Pond 25 year 34.0718 8.00 16.8379 115.15 SBUH TYPE1a.rac B-Pond 50 year 37.5032 8.00 18.254 115.15 SBUH TYPE1a.rac B-Pond 100 year 42.8179 8.00 20.4269 115.15 SBUH TYPE1a.rac B-Pond 6-month 8.9265 8.00 3.8235 115.15 SBUH TYPE1a.rac B-Pond 6-month 8.9265 8.00 3.8235 115.15 SBUH TYPE1a.rac B-Pond 2 yr 24 hr 14.8089 8.00 7.3365 115.15 SBUH TYPE1a.rac B-Pond 2 yr 24 hr 14.8089 8.00 7.3365 115.15 SBUH TYPE1a.rac B-Pond 10 year 25.9804 8.00 13.4283 115.15 SBUH TYPE1a.rac B-Pond 10 year 25.9804 8.00 13.4283 115.15 SBUH TYPE1a.rac B-Pond 25 year 34.0718 8.00 16.8379 115.15 SBUH TYPE1a.rac B-Pond 25 year 34.0718 8.00 16.8379 115.15 SBUH TYPE1a.rac B-Pond 50 year 37.5032 8.00 18.254 115.15 SBUH TYPE1a.rac B-Pond 50 year 37.5032 8.00 18.254 115.15 SBUH TYPE1a.rac B-Pond 100 year 42.8179 8.00 20.4269 115.15 SBUH TYPE1a.rac B-Pond 100 year 42.8179 8.00 20.4269 115.15 SBUH TYPE1a.rac Design Method SBUH Rainfall type TYPE1a.rac Hyd Intv 10.00 min Peaking Factor 484.00 Storm Duration 24.00 hrs Abstraction Coeff 0.20 Pervious Area 73.60 ac DCIA 41.55 ac Pervious CN 68.00 DC CN 98.00 Pervious TC 12.3935 min DC TC 19.9246 min Pervious CN Calc Description SubArea Sub cn Page 2 of 4 8/27/2020file://lac01/projects/2020/10182000024%20-%20Tahoma%20Terra%20Div.%207&8%20... HYDLIST SUMMARY [6-month out] [2 yr 24 hr out] [10 year out] [25 year out] [50 year out] [100 year out] LSTEND STORLIST [N-INF_POND] LSTEND Open spaces, lawns,parks (>75% grass)73.60 ac 68.00 Pervious Composited CN (AMC 2)68.00 Pervious TC Calc Type Description Length Slope Coeff Misc TT Sheet Short prairie grass and lawns. 0.15 100.00 ft 2.0%0.15 2.50 in 11.0851 min Pervious TC 11.0851 min DCI - CN Calc Description SubArea Sub cn Impervious surfaces (pavements, roofs, etc)41.55 ac 98.00 DC Composited CN (AMC 2)98.00 DCI - TC Calc Type Description Length Slope Coeff Misc TT Sheet Smooth Surfaces. 0.011 17.00 ft 2.0%0.011 0.00 in 0.3322 min Shallow Paved 255.00 ft 1.0%0.01 2.0907 min Int Channel Concrete pipe (n=0.012)2297.00 ft 0.4%0.012 14.2546 min Int Channel Concrete pipe (n=0.012)79.00 ft 0.95%0.012 0.3181 min Int Channel Concrete pipe (n=0.012)63.00 ft 0.51%0.012 0.3462 min Int Channel Concrete pipe (n=0.012)436.00 ft 1.2%0.012 1.5621 min Int Channel Concrete pipe (n=0.012)220.00 ft 1.31%0.012 0.7544 min Int Channel Concrete pipe (n=0.012)103.00 ft 3.17%0.012 0.2271 min Pervious TC 19.8854 min HydID Peak Q (cfs)Peak T (hrs)Peak Vol (ac-ft)Cont Area (ac) 6-month out 8.5318 8.17 3.8235 115.15 2 yr 24 hr out 9.158 8.67 7.3365 115.15 10 year out 11.2592 9.67 13.4283 115.15 25 year out 12.775 10.00 16.8379 115.15 50 year out 13.4352 10.17 18.254 115.15 100 year out 14.4602 10.50 20.4317 115.15 Page 3 of 4 8/27/2020file://lac01/projects/2020/10182000024%20-%20Tahoma%20Terra%20Div.%207&8%20... Record Id: N-INF_POND DISCHLIST [D-INF] LSTEND Record Id: D-INF Licensed to: Engenious Systems, Inc. Descrip:Prototype Record Increment 0.10 ft Start El.339.00 ft Max El.345.00 ft Void Ratio 100.00 Length 260.00 ft Width 70.00 ft Length ss1 3.00v:1h Length ss2 3.00v:1h Width ss1 3.00v:1h Width ss2 3.00v:1h Consider wetted surface for infiltration Trap Type Node Infiltration Descrip:Prototype Structure Increment 0.10 ft Start El.339.00 ft Max El.345.00 ft Infiltration rate 20.00 in/hr WP Multiplier 1.00 Page 4 of 4 8/27/2020file://lac01/projects/2020/10182000024%20-%20Tahoma%20Terra%20Div.%207&8%20... Appended on: Thursday, August 27, 2020 4:42:33 PM LPOOLCOMPUTE [N-Pond] SUMMARY using Puls, 24 hr Storm Event Start of live storage:342 ft Summary Report of all Detention Pond Data Project Precips BASLIST2 [B-Pond] Using [TYPE1a.rac] As [6-month] [24.0] [B-Pond] Using [TYPE1a.rac] As [2 yr 24 hr] [24.0] [B-Pond] Using [TYPE1a.rac] As [10 yr] [24.0] [B-Pond] Using [TYPE1a.rac] As [25 year] [24.0] [B-Pond] Using [TYPE1a.rac] As [50 year] [24.0] [B-Pond] Using [TYPE1a.rac] As [100 year] [24.0] [B-Pre] Using [TYPE1a.rac] As [6-month] [24.0] [B-Pond] Using [TYPE1a.rac] As [6-month] [24.0] [B-Pre] Using [TYPE1a.rac] As [2 yr 24 hr] [24.0] [B-Pond] Using [TYPE1a.rac] As [2 yr 24 hr] [24.0] [B-Pre] Using [TYPE1a.rac] As [10 yr] [24.0] [B-Pond] Using [TYPE1a.rac] As [10 yr] [24.0] [B-Pre] Using [TYPE1a.rac] As [25 year] [24.0] [B-Pond] Using [TYPE1a.rac] As [25 year] [24.0] [B-Pre] Using [TYPE1a.rac] As [50 year] [24.0] [B-Pond] Using [TYPE1a.rac] As [50 year] [24.0] [B-Pre] Using [TYPE1a.rac] As [100 year] [24.0] [B-Pond] Using [TYPE1a.rac] As [100 year] [24.0] Event Match Q (cfs)Peak Q (cfs)Max Depth (ft)Vol (cf)Vol (acft)Time to Empty (hr) 6-month 0.00 0.0074 1.1822 5927.249 0.1361 230.1667 2 yr 24 hr 0.00 0.0098 2.0948 11380.0237 0.2612 236.8333 10 yr 0.013 0.0125 3.4112 20714.2411 0.4755 238.50 25 year 0.046 0.0137 4.05 25912.2493 0.5949 240.1667 50 year 0.0607 0.0141 4.2997 28067.0192 0.6443 240.1667 100 year 0.0843 0.0147 4.667 31370.2007 0.7202 240.1667 Event Precip (in) 6-month 1.28 2 yr 24 hr 2.00 10 yr 3.00 25 year 3.50 50 year 3.70 100 year 4.00 Page 1 of 4 8/27/2020file://lac01/projects/2020/10182000024%20-%20Tahoma%20Terra%20Div.%207&8%20... South Basin Flow Control and Treatment Results LSTEND BASLIST [B-Pond] [B-Pre] LSTEND Record Id: B-Pond BasinID Event Peak Q (cfs) Peak T (hrs) Peak Vol (ac- cf) Area (ac)Method/Loss Raintype B-Pond 6-month 0.4264 8.00 0.1455 3.99 SBUH TYPE1a.rac B-Pond 2 yr 24 hr 0.7022 8.00 0.274 3.99 SBUH TYPE1a.rac B-Pond 10 yr 1.2171 8.00 0.4921 3.99 SBUH TYPE1a.rac B-Pond 25 year 1.5583 8.00 0.6131 3.99 SBUH TYPE1a.rac B-Pond 50 year 1.7009 8.00 0.6631 3.99 SBUH TYPE1a.rac B-Pond 100 year 1.9205 8.00 0.7398 3.99 SBUH TYPE1a.rac B-Pre 6-month 0.00 0.00 0.00 0.00 SBUH TYPE1a.rac B-Pond 6-month 0.4264 8.00 0.1455 3.99 SBUH TYPE1a.rac B-Pre 2 yr 24 hr 0.00 0.00 0.00 0.00 SBUH TYPE1a.rac B-Pond 2 yr 24 hr 0.7022 8.00 0.274 3.99 SBUH TYPE1a.rac B-Pre 10 yr 0.013 24.00 0.002 6.086 SBUH TYPE1a.rac B-Pond 10 yr 1.2171 8.00 0.4921 3.99 SBUH TYPE1a.rac B-Pre 25 year 0.046 24.00 0.019 6.086 SBUH TYPE1a.rac B-Pond 25 year 1.5583 8.00 0.6131 3.99 SBUH TYPE1a.rac B-Pre 50 year 0.0607 24.00 0.0303 6.086 SBUH TYPE1a.rac B-Pond 50 year 1.7009 8.00 0.6631 3.99 SBUH TYPE1a.rac B-Pre 100 year 0.0843 24.00 0.0517 6.086 SBUH TYPE1a.rac B-Pond 100 year 1.9205 8.00 0.7398 3.99 SBUH TYPE1a.rac Design Method SBUH Rainfall type TYPE1a.rac Hyd Intv 10.00 min Peaking Factor 484.00 Storm Duration 24.00 hrs Abstraction Coeff 0.20 Pervious Area 2.40 ac DCIA 1.59 ac Pervious CN 68.00 DC CN 98.00 Pervious TC 5.9545 min DC TC 5.00 min Pervious CN Calc Description SubArea Sub cn Page 2 of 4 8/27/2020file://lac01/projects/2020/10182000024%20-%20Tahoma%20Terra%20Div.%207&8%20... Record Id: B-Pre Open spaces, lawns, parks (50-75% grass)2.40 ac 68.00 Pervious Composited CN (AMC 2)68.00 Pervious TC Calc Type Description Length Slope Coeff Misc TT Sheet Short prairie grass and lawns. 0.15 40.00 ft 2.0%0.15 0.00 in 5.3258 min Pervious TC 5.3258 min DCI - CN Calc Description SubArea Sub cn Impervious surfaces (pavements, roofs, etc)1.59 ac 98.00 DC Composited CN (AMC 2)98.00 DCI - TC Calc Type Description Length Slope Coeff Misc TT Sheet Smooth Surfaces. 0.011 17.00 ft 2.0%0.011 0.00 in 0.3322 min Int Channel Concrete pipe (n=0.012)330.00 ft 2.0%0.012 0.9158 min Shallow Paved 285.00 ft 1.0%0.01 2.3367 min Pervious TC 3.5847 min Design Method SBUH Rainfall type TYPE1a.rac Hyd Intv 10.00 min Peaking Factor 484.00 Storm Duration 24.00 hrs Abstraction Coeff 0.20 Pervious Area 6.086 ac DCIA 0.00 ac Pervious CN 42.00 DC CN 0.00 Pervious TC 5.0083 min DC TC 0.00 min Pervious CN Calc Description SubArea Sub cn Wood/forest land (Undisturbed/2nd growth)6.086 ac 42.00 Pervious Composited CN (AMC 2)42.00 Pervious TC Calc Type Description Length Slope Coeff Misc TT Shallow Forest w/ heavy ground litter & meadows (n=0.10) 342.00 ft 12.57%0.1 5.0083 min Pervious TC 5.0083 min Page 3 of 4 8/27/2020file://lac01/projects/2020/10182000024%20-%20Tahoma%20Terra%20Div.%207&8%20... HYDLIST SUMMARY [6-month out] [2 yr 24 hr out] [10 yr out] [25 year out] [50 year out] [100 year out] LSTEND STORLIST [N-DETPOND] LSTEND Record Id: N-DETPOND DISCHLIST [D-CB] LSTEND Record Id: D-CB Licensed to: Engenious Systems, Inc. HydID Peak Q (cfs)Peak T (hrs)Peak Vol (ac-ft)Cont Area (ac) 6-month out 0.0074 24.33 0.1151 3.99 2 yr 24 hr out 0.0098 24.33 0.173 3.99 10 yr out 0.0125 24.33 0.237 3.99 25 year out 0.0137 24.33 0.2646 3.99 50 year out 0.0141 24.33 0.2743 3.99 100 year out 0.0147 24.33 0.288 3.99 Descrip:Prototype Record Increment 0.10 ft Start El.342.00 ft Max El.347.00 ft Void Ratio 100.00 Length 90.00 ft Width 50.00 ft Length ss1 3.00v:1h Length ss2 3.00v:1h Width ss1 3.00v:1h Width ss2 3.00v:1h Consider wetted surface for infiltration Trap Type Node Multiple Orifice Descrip:Prototype Structure Increment 0.10 ft Start El.342.00 ft Max El.347.00 ft Orif Coeff 0.62 Lowest Orif El.342.00 ft Lowest Diam 0.50 in Dist to next 1.50 ft Page 4 of 4 8/27/2020file://lac01/projects/2020/10182000024%20-%20Tahoma%20Terra%20Div.%207&8%20... Appended on: Thursday, August 27, 2020 4:48:08 PM LPOOLCOMPUTE [N-Pond] SUMMARY using Puls, 24 hr Storm Event Start of live storage:333 ft Summary Report of all Detention Pond Data Project Precips BASLIST2 [B-Pond] Using [TYPE1a.rac] As [6-month] [24.0] [B-Pond] Using [TYPE1a.rac] As [2 yr 24 hr] [24.0] [B-Pond] Using [TYPE1a.rac] As [10 year] [24.0] [B-Pond] Using [TYPE1a.rac] As [25 year] [24.0] [B-Pond] Using [TYPE1a.rac] As [50 year] [24.0] [B-Pond] Using [TYPE1a.rac] As [100 year] [24.0] [B-Pre] Using [TYPE1a.rac] As [6-month] [24.0] [B-Pond] Using [TYPE1a.rac] As [6-month] [24.0] [B-Pre] Using [TYPE1a.rac] As [2 yr 24 hr] [24.0] [B-Pond] Using [TYPE1a.rac] As [2 yr 24 hr] [24.0] [B-Pre] Using [TYPE1a.rac] As [10 year] [24.0] [B-Pond] Using [TYPE1a.rac] As [10 year] [24.0] [B-Pre] Using [TYPE1a.rac] As [25 year] [24.0] [B-Pond] Using [TYPE1a.rac] As [25 year] [24.0] [B-Pre] Using [TYPE1a.rac] As [50 year] [24.0] [B-Pond] Using [TYPE1a.rac] As [50 year] [24.0] [B-Pre] Using [TYPE1a.rac] As [100 year] [24.0] [B-Pond] Using [TYPE1a.rac] As [100 year] [24.0] Event Match Q (cfs)Peak Q (cfs)Max Depth (ft)Vol (cf)Vol (acft)Time to Empty (hr) 6-month 0.00 0.00 0.7163 14253.2836 0.3272 236.8333 2 yr 24 hr 0.00 0.00 1.2604 25912.9089 0.5949 245.1667 10 year 0.031 0.00 2.0798 44848.6451 1.0296 248.50 25 year 0.1397 0.00 2.497 55137.9258 1.2658 250.1667 50 year 0.189 0.00 2.6635 59369.5555 1.3629 250.1667 100 year 0.2679 0.00 2.9124 65826.07 1.5112 250.1667 Event Precip (in) 6-month 1.28 2 yr 24 hr 2.00 10 year 3.00 25 year 3.50 50 year 3.70 100 year 4.00 Page 1 of 5 8/27/2020file://lac01/projects/2020/10182000024%20-%20Tahoma%20Terra%20Div.%207&8%20... East Basin Flow Control Results LSTEND BASLIST [B-Pond] [B-Pre] LSTEND Record Id: B-Pond BasinID Event Peak Q (cfs) Peak T (hrs) Peak Vol (ac- cf) Area (ac)Method/Loss Raintype B-Pond 6-month 0.967 8.00 0.3272 7.38 SBUH TYPE1a.rac B-Pond 2 yr 24 hr 1.5932 8.00 0.5949 7.38 SBUH TYPE1a.rac B-Pond 10 year 2.6066 8.00 1.0296 7.38 SBUH TYPE1a.rac B-Pond 25 year 3.239 8.00 1.2658 7.38 SBUH TYPE1a.rac B-Pond 50 year 3.5018 8.00 1.3629 7.38 SBUH TYPE1a.rac B-Pond 100 year 3.9044 8.00 1.5112 7.38 SBUH TYPE1a.rac B-Pre 6-month 0.00 0.00 0.00 0.00 SBUH TYPE1a.rac B-Pond 6-month 0.967 8.00 0.3272 7.38 SBUH TYPE1a.rac B-Pre 2 yr 24 hr 0.00 0.00 0.00 0.00 SBUH TYPE1a.rac B-Pond 2 yr 24 hr 1.5932 8.00 0.5949 7.38 SBUH TYPE1a.rac B-Pre 10 year 0.031 24.00 0.0069 20.48 SBUH TYPE1a.rac B-Pond 10 year 2.6066 8.00 1.0296 7.38 SBUH TYPE1a.rac B-Pre 25 year 0.1397 24.00 0.0639 20.48 SBUH TYPE1a.rac B-Pond 25 year 3.239 8.00 1.2658 7.38 SBUH TYPE1a.rac B-Pre 50 year 0.189 24.00 0.1018 20.48 SBUH TYPE1a.rac B-Pond 50 year 3.5018 8.00 1.3629 7.38 SBUH TYPE1a.rac B-Pre 100 year 0.2679 24.00 0.1738 20.48 SBUH TYPE1a.rac B-Pond 100 year 3.9044 8.00 1.5112 7.38 SBUH TYPE1a.rac Design Method SBUH Rainfall type TYPE1a.rac Hyd Intv 10.00 min Peaking Factor 484.00 Storm Duration 24.00 hrs Abstraction Coeff 0.20 Pervious Area 3.77 ac DCIA 3.61 ac Pervious CN 68.00 DC CN 98.00 Pervious TC 12.927 min DC TC 5.3683 min Pervious CN Calc Description SubArea Sub cn Page 2 of 5 8/27/2020file://lac01/projects/2020/10182000024%20-%20Tahoma%20Terra%20Div.%207&8%20... Record Id: B-Pre Open spaces, lawns, parks (50-75% grass)3.77 ac 68.00 Pervious Composited CN (AMC 2)68.00 Pervious TC Calc Type Description Length Slope Coeff Misc TT Sheet Short prairie grass and lawns. 0.15 100.00 ft 1.8%0.15 2.00 in 12.927 min Pervious TC 12.927 min DCI - CN Calc Description SubArea Sub cn Impervious surfaces (pavements, roofs, etc)3.61 ac 98.00 DC Composited CN (AMC 2)98.00 DCI - TC Calc Type Description Length Slope Coeff Misc TT Sheet Smooth Surfaces. 0.011 17.00 ft 2.0%0.011 0.00 in 0.3714 min Shallow Paved 338.00 ft 1.0%0.01 2.7712 min Int Channel Concrete pipe (n=0.012)802.00 ft 2.0%0.012 2.2258 min Pervious TC 5.3683 min Design Method SBUH Rainfall type TYPE1a.rac Hyd Intv 10.00 min Peaking Factor 484.00 Storm Duration 24.00 hrs Abstraction Coeff 0.20 Pervious Area 20.48 ac DCIA 0.00 ac Pervious CN 42.00 DC CN 0.00 Pervious TC 69.1068 min DC TC 0.00 min Pervious CN Calc Description SubArea Sub cn Wood/forest land (Undisturbed/2nd growth)20.48 ac 42.00 Pervious Composited CN (AMC 2)42.00 Pervious TC Calc Type Description Length Slope Coeff Misc TT Sheet Short prairie grass and lawns. 0.15 628.00 ft 2.67%0.15 2.00 in 48.0143 min Shallow Forest w/ heavy ground litter & meadows (n=0.10) 738.00 ft 3.3%0.1 21.0925 min Pervious TC 69.1068 Page 3 of 5 8/27/2020file://lac01/projects/2020/10182000024%20-%20Tahoma%20Terra%20Div.%207&8%20... HYDLIST SUMMARY [6-month out] [2 yr 24 hr out] [10 year out] [25 year out] [50 year out] [100 year out] LSTEND STORLIST [N-DET_POND] LSTEND Record Id: N-DET_POND DISCHLIST [D-CB] LSTEND Record Id: D-CB min HydID Peak Q (cfs)Peak T (hrs)Peak Vol (ac-ft)Cont Area (ac) 6-month out 0.00 1.50 0.00 7.38 2 yr 24 hr out 0.00 1.00 0.00 7.38 10 year out 0.00 .83 0.00 7.38 25 year out 0.00 .67 0.00 7.38 50 year out 0.00 .67 0.00 7.38 100 year out 0.00 .67 0.00 7.38 Descrip:Prototype Record Increment 0.10 ft Start El.333.00 ft Max El.336.00 ft Void Ratio 100.00 Length 340.00 ft Width 56.00 ft Length ss1 3.00v:1h Length ss2 3.00v:1h Width ss1 3.00v:1h Width ss2 3.00v:1h Consider wetted surface for infiltration Trap Type Node Multiple Orifice Descrip:Prototype Structure Increment 0.10 ft Start El.333.00 ft Max El.336.00 ft Orif Coeff 0.62 Lowest Orif El.333.00 ft Page 4 of 5 8/27/2020file://lac01/projects/2020/10182000024%20-%20Tahoma%20Terra%20Div.%207&8%20... Licensed to: Engenious Systems, Inc. Page 5 of 5 8/27/2020file://lac01/projects/2020/10182000024%20-%20Tahoma%20Terra%20Div.%207&8%20... Appended on: Thursday, August 27, 2020 4:50:11 PM LPOOLCOMPUTE [N-Pond] SUMMARY using Puls, 24 hr Storm Event Start of live storage:338 ft Summary Report of all Detention Pond Data Project Precips BASLIST2 [B-Pond] Using [TYPE1a.rac] As [6-month] [24.0] [B-Pond] Using [TYPE1a.rac] As [2 yr 24 hr] [24.0] [B-Pond] Using [TYPE1a.rac] As [10 year] [24.0] [B-Pond] Using [TYPE1a.rac] As [25 year] [24.0] [B-Pond] Using [TYPE1a.rac] As [50 year] [24.0] [B-Pond] Using [TYPE1a.rac] As [100 year] [24.0] [B-Pond] Using [TYPE1a.rac] As [6-month] [24.0] [B-Pond] Using [TYPE1a.rac] As [6-month] [24.0] [B-Pond] Using [TYPE1a.rac] As [2 yr 24 hr] [24.0] [B-Pond] Using [TYPE1a.rac] As [2 yr 24 hr] [24.0] [B-Pond] Using [TYPE1a.rac] As [10 year] [24.0] [B-Pond] Using [TYPE1a.rac] As [10 year] [24.0] [B-Pond] Using [TYPE1a.rac] As [25 year] [24.0] [B-Pond] Using [TYPE1a.rac] As [25 year] [24.0] [B-Pond] Using [TYPE1a.rac] As [50 year] [24.0] [B-Pond] Using [TYPE1a.rac] As [50 year] [24.0] [B-Pond] Using [TYPE1a.rac] As [100 year] [24.0] [B-Pond] Using [TYPE1a.rac] As [100 year] [24.0] Event Match Q (cfs)Peak Q (cfs)Max Depth (ft)Vol (cf)Vol (acft)Time to Empty (hr) 6-month 1.4605 0.7913 1.0783 1513.3697 0.0347 0.1667 2 yr 24 hr 0.193 1.119 2.2333 3832.4864 0.088 0.1667 10 year 4.0586 1.6831 3.9243 8756.9488 0.201 0.1667 25 year 5.093 1.9982 4.7579 11946.7274 0.2743 0.1667 50 year 5.522 2.1278 5.0832 13340.2914 0.3063 0.1667 100 year 6.1799 2.3234 5.5575 15531.0927 0.3565 0.1667 Event Precip (in) 6-month 1.28 2 yr 24 hr 2.00 10 year 3.00 25 year 3.50 50 year 3.70 100 year 4.00 Page 1 of 4 8/27/2020file://lac01/projects/2020/10182000024%20-%20Tahoma%20Terra%20Div.%207&8%20... West Basin Flow Control Results LSTEND BASLIST [B-Pond] LSTEND Record Id: B-Pond BasinID Event Peak Q (cfs) Peak T (hrs) Peak Vol (ac- cf) Area (ac)Method/Loss Raintype B-Pond 6-month 1.4605 8.00 0.5169 11.78 SBUH TYPE1a.rac B-Pond 2 yr 24 hr 2.4125 8.00 0.9413 11.78 SBUH TYPE1a.rac B-Pond 10 year 4.0586 8.00 1.6323 11.78 SBUH TYPE1a.rac B-Pond 25 year 5.093 8.00 2.0082 11.78 SBUH TYPE1a.rac B-Pond 50 year 5.522 8.00 2.1628 11.78 SBUH TYPE1a.rac B-Pond 100 year 6.1799 8.00 2.3989 11.78 SBUH TYPE1a.rac B-Pond 6-month 1.4605 8.00 0.5169 11.78 SBUH TYPE1a.rac B-Pond 6-month 1.4605 8.00 0.5169 11.78 SBUH TYPE1a.rac B-Pond 2 yr 24 hr 2.4125 8.00 0.9413 11.78 SBUH TYPE1a.rac B-Pond 2 yr 24 hr 2.4125 8.00 0.9413 11.78 SBUH TYPE1a.rac B-Pond 10 year 4.0586 8.00 1.6323 11.78 SBUH TYPE1a.rac B-Pond 10 year 4.0586 8.00 1.6323 11.78 SBUH TYPE1a.rac B-Pond 25 year 5.093 8.00 2.0082 11.78 SBUH TYPE1a.rac B-Pond 25 year 5.093 8.00 2.0082 11.78 SBUH TYPE1a.rac B-Pond 50 year 5.522 8.00 2.1628 11.78 SBUH TYPE1a.rac B-Pond 50 year 5.522 8.00 2.1628 11.78 SBUH TYPE1a.rac B-Pond 100 year 6.1799 8.00 2.3989 11.78 SBUH TYPE1a.rac B-Pond 100 year 6.1799 8.00 2.3989 11.78 SBUH TYPE1a.rac Design Method SBUH Rainfall type TYPE1a.rac Hyd Intv 10.00 min Peaking Factor 484.00 Storm Duration 24.00 hrs Abstraction Coeff 0.20 Pervious Area 6.08 ac DCIA 5.70 ac Pervious CN 68.00 DC CN 98.00 Pervious TC 6.2108 min DC TC 9.3883 min Pervious CN Calc Description SubArea Sub cn Page 2 of 4 8/27/2020file://lac01/projects/2020/10182000024%20-%20Tahoma%20Terra%20Div.%207&8%20... HYDLIST SUMMARY [6-month out] [2 yr 24 hr out] [10 year out] [25 year out] [50 year out] [100 year out] LSTEND STORLIST [N-INF_POND] LSTEND Record Id: N-INF_POND Open spaces, lawns, parks (50-75% grass)6.08 ac 68.00 Pervious Composited CN (AMC 2)68.00 Pervious TC Calc Type Description Length Slope Coeff Misc TT Sheet Short prairie grass and lawns. 0.15 40.00 ft 1.8%0.15 2.00 in 6.2108 min Pervious TC 6.2108 min DCI - CN Calc Description SubArea Sub cn Impervious surfaces (pavements, roofs, etc)5.70 ac 98.00 DC Composited CN (AMC 2)98.00 DCI - TC Calc Type Description Length Slope Coeff Misc TT Sheet Smooth Surfaces. 0.011 17.00 ft 2.0%0.011 0.00 in 0.3714 min Shallow Paved 830.00 ft 1.0%0.01 6.805 min Int Channel Concrete pipe (n=0.012)797.00 ft 2.0%0.012 2.2119 min Pervious TC 9.3883 min HydID Peak Q (cfs)Peak T (hrs)Peak Vol (ac-ft)Cont Area (ac) 6-month out 0.7913 8.50 0.5169 11.78 2 yr 24 hr out 1.119 8.67 0.9413 11.78 10 year out 1.6831 9.00 1.6326 11.78 25 year out 1.9982 9.17 2.0086 11.78 50 year out 2.1278 9.17 2.1638 11.78 100 year out 2.3234 9.17 2.40 11.78 Descrip:Prototype Record Increment 0.10 ft Start El.338.00 ft Max El.344.00 ft Void Ratio 100.00 Page 3 of 4 8/27/2020file://lac01/projects/2020/10182000024%20-%20Tahoma%20Terra%20Div.%207&8%20... DISCHLIST [D-INF] LSTEND Record Id: D-INF Licensed to: Engenious Systems, Inc. Length 57.00 ft Width 20.00 ft Length ss1 3.00v:1h Length ss2 3.00v:1h Width ss1 3.00v:1h Width ss2 3.00v:1h Consider wetted surface for infiltration Trap Type Node Infiltration Descrip:Prototype Structure Increment 0.10 ft Start El.338.00 ft Max El.344.00 ft Infiltration rate 20.00 in/hr WP Multiplier 1.00 Page 4 of 4 8/27/2020file://lac01/projects/2020/10182000024%20-%20Tahoma%20Terra%20Div.%207&8%20... WWHM2012 PROJECT REPORT NORTH BASIN TREATMENT RESULTS 7&8 NB 8/31/2020 4:43:40 PM Page 2 General Model Information Project Name:7&8 NB Site Name: Site Address: City: Report Date:8/31/2020 Gage:Eaton Creek Data Start:1955/10/01 Data End:2011/09/30 Timestep:15 Minute Precip Scale:1.00 Version Date:2016/02/25 Version:4.2.12 POC Thresholds Low Flow Threshold for POC1:50 Percent of the 2 Year High Flow Threshold for POC1:50 Year 7&8 NB 8/31/2020 4:43:40 PM Page 3 Landuse Basin Data Predeveloped Land Use Basin 1 Bypass:No GroundWater:No Pervious Land Use acre A B, Forest, Mod 94.95 Pervious Total 94.95 Impervious Land Use acre Impervious Total 0 Basin Total 94.95 Element Flows To: Surface Interflow Groundwater 7&8 NB 8/31/2020 4:43:40 PM Page 4 Mitigated Land Use Basin 1 Bypass:No GroundWater:No Pervious Land Use acre A B, Lawn, Flat 53.4 Pervious Total 53.4 Impervious Land Use acre ROADS FLAT 41.55 Impervious Total 41.55 Basin Total 94.95 Element Flows To: Surface Interflow Groundwater Surface retention 1 Surface retention 1 7&8 NB 8/31/2020 4:43:40 PM Page 6 Mitigated Routing Bioretention 1 Bottom Length: 158.08 ft. Bottom Width: 158.08 ft. Material thickness of first layer: 1.5 Material type for first layer: SMMWW 12 in/hr Material thickness of second layer: 2 Material type for second layer: GRAVEL Material thickness of third layer: 0 Material type for third layer: GRAVEL Underdrain used Underdrain Diameter (feet):2 Orifice Diameter (in.):24 Offset (in.):0 Flow Through Underdrain (ac-ft.):7243.402 Total Outflow (ac-ft.):7929.351 Percent Through Underdrain:91.35 Discharge Structure Riser Height:1 ft. Riser Diameter:36 in. Element Flows To: Outlet 1 Outlet 2 Bioretention Hydraulic Table Stage(feet)Area(ac.)Volume(ac-ft.)Discharge(cfs)Infilt(cfs) 0.0000 0.7362 0.0000 0.0000 0.0000 0.0604 0.7335 0.0079 0.0000 0.0000 0.1209 0.7305 0.0159 0.0009 0.0000 0.1813 0.7276 0.0239 0.0038 0.0000 0.2418 0.7246 0.0320 0.0096 0.0000 0.3022 0.7217 0.0401 0.0192 0.0000 0.3626 0.7187 0.0482 0.0228 0.0000 0.4231 0.7158 0.0564 0.0329 0.0000 0.4835 0.7128 0.0646 0.0514 0.0000 0.5440 0.7099 0.0728 0.0751 0.0000 0.6044 0.7070 0.0811 0.0941 0.0000 0.6648 0.7040 0.0894 0.1043 0.0000 0.7253 0.7011 0.0978 0.1396 0.0000 0.7857 0.6982 0.1062 0.1812 0.0000 0.8462 0.6953 0.1146 0.2295 0.0000 0.9066 0.6924 0.1231 0.2296 0.0000 0.9670 0.6895 0.1316 0.2848 0.0000 1.0275 0.6867 0.1401 0.3474 0.0000 1.0879 0.6838 0.1487 0.4177 0.0000 1.1484 0.6809 0.1573 0.4418 0.0000 1.2088 0.6781 0.1659 0.4958 0.0000 1.2692 0.6752 0.1746 0.5822 0.0000 1.3297 0.6723 0.1834 0.6770 0.0000 1.3901 0.6695 0.1921 0.7419 0.0000 1.4505 0.6667 0.2009 0.7806 0.0000 1.5110 0.6638 0.2090 0.8931 0.0000 1.5714 0.6610 0.2170 1.0148 0.0000 1.6319 0.6582 0.2251 1.1394 0.0000 1.6923 0.6554 0.2333 1.1459 0.0000 7&8 NB 8/31/2020 4:43:40 PM Page 7 1.7527 0.6525 0.2414 1.2867 0.0000 1.8132 0.6497 0.2496 1.4373 0.0000 1.8736 0.6469 0.2579 1.5978 0.0000 1.9341 0.6441 0.2661 1.6432 0.0000 1.9945 0.6414 0.2744 1.7354 0.0000 2.0549 0.6386 0.2828 1.7354 0.0000 2.1154 0.6358 0.2912 1.7354 0.0000 2.1758 0.6330 0.2996 1.7354 0.0000 2.2363 0.6303 0.3080 1.7354 0.0000 2.2967 0.6275 0.3165 1.7354 0.0000 2.3571 0.6248 0.3250 1.7354 0.0000 2.4176 0.6220 0.3336 1.7354 0.0000 2.4780 0.6193 0.3422 1.7354 0.0000 2.5385 0.6166 0.3508 1.7354 0.0000 2.5989 0.6138 0.3595 1.7354 0.0000 2.6593 0.6111 0.3682 1.7354 0.0000 2.7198 0.6084 0.3769 1.7354 0.0000 2.7802 0.6057 0.3857 1.7354 0.0000 2.8407 0.6030 0.3945 1.7354 0.0000 2.9011 0.6003 0.4033 1.7354 0.0000 2.9615 0.5976 0.4122 1.7354 0.0000 3.0220 0.5949 0.4212 1.7354 0.0000 3.0824 0.5922 0.4301 1.7354 0.0000 3.1429 0.5896 0.4391 1.7354 0.0000 3.2033 0.5869 0.4481 1.7354 0.0000 3.2637 0.5843 0.4572 1.7354 0.0000 3.3242 0.5816 0.4663 1.7354 0.0000 3.3846 0.5790 0.4755 1.7354 0.0000 3.4451 0.5763 0.4846 1.7354 0.0000 3.5000 0.5737 0.4930 1.7354 0.0000 Bioretention Hydraulic Table Stage(feet)Area(ac.)Volume(ac-ft.)Discharge(cfs)To Amended(cfs)Infilt(cfs) 3.5000 0.7362 0.4930 0.0000 7.2212 0.0000 3.5604 0.7392 0.5376 0.0000 7.2212 0.0000 3.6209 0.7422 0.5824 0.0000 7.5009 0.0000 3.6813 0.7452 0.6273 0.0000 7.7806 0.0000 3.7418 0.7482 0.6724 0.0000 8.0602 0.0000 3.8022 0.7512 0.7178 0.0000 8.3399 0.0000 3.8626 0.7542 0.7633 0.0000 8.6196 0.0000 3.9231 0.7572 0.8089 0.0000 8.8993 0.0000 3.9835 0.7603 0.8548 0.0000 9.1790 0.0000 4.0440 0.7633 0.9008 0.0000 9.4587 0.0000 4.1044 0.7663 0.9471 0.0000 9.7384 0.0000 4.1648 0.7694 0.9935 0.0000 10.018 0.0000 4.2253 0.7724 1.0401 0.0000 10.298 0.0000 4.2857 0.7755 1.0868 0.0000 10.577 0.0000 4.3462 0.7786 1.1338 0.0000 10.857 0.0000 4.4066 0.7816 1.1809 0.0000 11.137 0.0000 4.4670 0.7847 1.2283 0.0000 11.417 0.0000 4.5275 0.7878 1.2758 0.1450 11.696 0.0000 4.5879 0.7909 1.3235 0.8294 11.976 0.0000 4.6484 0.7940 1.3714 1.8167 12.256 0.0000 4.7088 0.7971 1.4195 3.0294 12.535 0.0000 4.7692 0.8002 1.4677 4.4267 12.815 0.0000 4.8297 0.8033 1.5162 5.9785 13.095 0.0000 4.8901 0.8064 1.5648 7.6592 13.374 0.0000 4.9505 0.8095 1.6137 9.4443 13.654 0.0000 7&8 NB 8/31/2020 4:43:40 PM Page 8 5.0110 0.8126 1.6627 11.309 13.934 0.0000 5.0714 0.8158 1.7119 13.230 14.213 0.0000 5.1319 0.8189 1.7613 15.180 14.493 0.0000 5.1923 0.8221 1.8109 17.134 14.773 0.0000 5.2527 0.8252 1.8607 19.067 15.053 0.0000 5.3132 0.8284 1.9107 20.953 15.332 0.0000 5.3736 0.8316 1.9608 22.769 15.612 0.0000 5.4341 0.8347 2.0112 24.492 15.892 0.0000 5.4945 0.8379 2.0617 26.102 16.171 0.0000 5.5000 0.8382 2.0663 27.584 16.197 0.0000 7&8 NB 9/1/2020 10:39:18 AM Page 10 Analysis Results POC 1 + Predeveloped x Mitigated Predeveloped Landuse Totals for POC #1 Total Pervious Area:94.95 Total Impervious Area:0 Mitigated Landuse Totals for POC #1 Total Pervious Area:53.4 Total Impervious Area:41.55 Flow Frequency Method:Log Pearson Type III 17B Flow Frequency Return Periods for Predeveloped. POC #1 Return Period Flow(cfs) 2 year 0.129099 5 year 0.366403 10 year 0.684701 25 year 1.420451 50 year 2.357994 100 year 3.811103 Flow Frequency Return Periods for Mitigated. POC #1 Return Period Flow(cfs) 2 year 13.549217 5 year 19.280005 10 year 23.365731 25 year 28.853128 50 year 33.175409 100 year 37.697906 Annual Peaks Annual Peaks for Predeveloped and Mitigated. POC #1 Year Predeveloped Mitigated 1956 1.395 12.513 1957 0.076 26.245 1958 0.076 8.882 1959 0.107 13.020 1960 0.076 15.496 1961 1.235 8.123 1962 0.076 8.776 1963 0.432 24.913 1964 0.180 14.422 1965 0.137 16.390 7&8 NB 9/1/2020 10:39:59 AM Page 18 Appendix Predeveloped Schematic 7&8 NB 9/1/2020 10:40:01 AM Page 19 Mitigated Schematic 7&8 NB 8/31/2020 4:43:43 PM Page 25 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. 2005-2020; 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 WWHM2012 PROJECT REPORT EAST BASIN TREATMENT RESULTS MF East 8/31/2020 3:49:59 PM Page 2 General Model Information Project Name:MF East Site Name: Site Address: City: Report Date:8/31/2020 Gage:Eaton Creek Data Start:1955/10/01 Data End:2011/09/30 Timestep:15 Minute Precip Scale:1.000 Version Date:2018/10/10 Version:4.2.16 POC Thresholds Low Flow Threshold for POC1:50 Percent of the 2 Year High Flow Threshold for POC1:50 Year MF East 8/31/2020 3:49:59 PM Page 3 Landuse Basin Data Predeveloped Land Use Basin 1 Bypass:No GroundWater:No Pervious Land Use acre A B, Forest, Mod 3.77 Pervious Total 3.77 Impervious Land Use acre Impervious Total 0 Basin Total 3.77 Element Flows To: Surface Interflow Groundwater MF East 8/31/2020 3:49:59 PM Page 4 Mitigated Land Use Basin 1 Bypass:No GroundWater:No Pervious Land Use acre A B, Lawn, Flat 3.77 Pervious Total 3.77 Impervious Land Use acre ROADS FLAT 0.582 ROOF TOPS FLAT 1.29 DRIVEWAYS FLAT 0.603 SIDEWALKS FLAT 0.203 Impervious Total 2.678 Basin Total 6.448 Element Flows To: Surface Interflow Groundwater Surface retention 1 Surface retention 1 MF East 8/31/2020 3:49:59 PM Page 6 Mitigated Routing Bioretention 1 Bottom Length: 46.01 ft. Bottom Width: 46.01 ft. Material thickness of first layer: 1.5 Material type for first layer: SMMWW 12 in/hr Material thickness of second layer: 1.5 Material type for second layer: GRAVEL Material thickness of third layer: 0 Material type for third layer: GRAVEL Underdrain used Underdrain Diameter (feet):0.5 Orifice Diameter (in.):6 Offset (in.):0 Flow Through Underdrain (ac-ft.):474.082 Total Outflow (ac-ft.):516.632 Percent Through Underdrain:91.76 Discharge Structure Riser Height:0.5 ft. Riser Diameter:24 in. Element Flows To: Outlet 1 Outlet 2 Bioretention Hydraulic Table Stage(feet)Area(ac.)Volume(ac-ft.)Discharge(cfs)Infilt(cfs) 0.0000 0.0941 0.0000 0.0000 0.0000 0.0440 0.0939 0.0005 0.0000 0.0000 0.0879 0.0931 0.0010 0.0000 0.0000 0.1319 0.0923 0.0015 0.0000 0.0000 0.1758 0.0916 0.0020 0.0002 0.0000 0.2198 0.0908 0.0025 0.0004 0.0000 0.2637 0.0900 0.0030 0.0008 0.0000 0.3077 0.0893 0.0036 0.0013 0.0000 0.3516 0.0885 0.0041 0.0020 0.0000 0.3956 0.0878 0.0046 0.0029 0.0000 0.4396 0.0870 0.0052 0.0040 0.0000 0.4835 0.0863 0.0057 0.0054 0.0000 0.5275 0.0856 0.0063 0.0070 0.0000 0.5714 0.0848 0.0068 0.0083 0.0000 0.6154 0.0841 0.0074 0.0088 0.0000 0.6593 0.0834 0.0080 0.0110 0.0000 0.7033 0.0826 0.0086 0.0134 0.0000 0.7473 0.0819 0.0091 0.0161 0.0000 0.7912 0.0812 0.0097 0.0190 0.0000 0.8352 0.0805 0.0103 0.0196 0.0000 0.8791 0.0797 0.0109 0.0224 0.0000 0.9231 0.0790 0.0115 0.0260 0.0000 0.9670 0.0783 0.0122 0.0299 0.0000 1.0110 0.0776 0.0128 0.0343 0.0000 1.0549 0.0769 0.0134 0.0370 0.0000 1.0989 0.0762 0.0140 0.0389 0.0000 1.1429 0.0755 0.0147 0.0439 0.0000 1.1868 0.0748 0.0153 0.0493 0.0000 1.2308 0.0741 0.0160 0.0551 0.0000 MF East 8/31/2020 3:49:59 PM Page 7 1.2747 0.0734 0.0167 0.0613 0.0000 1.3187 0.0728 0.0173 0.0613 0.0000 1.3626 0.0721 0.0180 0.0678 0.0000 1.4066 0.0714 0.0187 0.0748 0.0000 1.4505 0.0707 0.0194 0.0821 0.0000 1.4945 0.0701 0.0201 0.0899 0.0000 1.5385 0.0694 0.0207 0.0934 0.0000 1.5824 0.0687 0.0213 0.0981 0.0000 1.6264 0.0681 0.0220 0.1068 0.0000 1.6703 0.0674 0.0226 0.1159 0.0000 1.7143 0.0668 0.0233 0.1254 0.0000 1.7582 0.0661 0.0240 0.1339 0.0000 1.8022 0.0655 0.0246 0.1354 0.0000 1.8462 0.0648 0.0253 0.1458 0.0000 1.8901 0.0642 0.0260 0.2451 0.0000 1.9341 0.0635 0.0267 0.2451 0.0000 1.9780 0.0629 0.0274 0.2451 0.0000 2.0220 0.0623 0.0281 0.2451 0.0000 2.0659 0.0616 0.0288 0.2451 0.0000 2.1099 0.0610 0.0295 0.2451 0.0000 2.1538 0.0604 0.0303 0.2451 0.0000 2.1978 0.0598 0.0310 0.2451 0.0000 2.2418 0.0592 0.0317 0.2451 0.0000 2.2857 0.0585 0.0325 0.2451 0.0000 2.3297 0.0579 0.0332 0.2451 0.0000 2.3736 0.0573 0.0340 0.2451 0.0000 2.4176 0.0567 0.0347 0.2451 0.0000 2.4615 0.0561 0.0355 0.2451 0.0000 2.5055 0.0555 0.0363 0.2451 0.0000 2.5495 0.0549 0.0371 0.2451 0.0000 2.5934 0.0543 0.0379 0.2451 0.0000 2.6374 0.0538 0.0387 0.2451 0.0000 2.6813 0.0532 0.0395 0.2451 0.0000 2.7253 0.0526 0.0403 0.2451 0.0000 2.7692 0.0520 0.0411 0.2451 0.0000 2.8132 0.0514 0.0419 0.2451 0.0000 2.8571 0.0509 0.0427 0.2451 0.0000 2.9011 0.0503 0.0436 0.2451 0.0000 2.9451 0.0497 0.0444 0.2451 0.0000 2.9890 0.0492 0.0453 0.2451 0.0000 3.0000 0.0486 0.0455 0.2451 0.0000 Bioretention Hydraulic Table Stage(feet)Area(ac.)Volume(ac-ft.)Discharge(cfs)To Amended(cfs)Infilt(cfs) 3.0000 0.0941 0.0455 0.0000 0.1470 0.0000 3.0440 0.0948 0.0496 0.0000 0.1470 0.0000 3.0879 0.0956 0.0538 0.0000 0.1557 0.0000 3.1319 0.0964 0.0581 0.0000 0.1600 0.0000 3.1758 0.0972 0.0623 0.0000 0.1643 0.0000 3.2198 0.0980 0.0666 0.0000 0.1686 0.0000 3.2637 0.0988 0.0709 0.0000 0.1729 0.0000 3.3077 0.0996 0.0753 0.0000 0.1772 0.0000 3.3516 0.1004 0.0797 0.0000 0.1815 0.0000 3.3956 0.1012 0.0841 0.0000 0.1858 0.0000 3.4396 0.1020 0.0886 0.0000 0.1901 0.0000 3.4835 0.1028 0.0931 0.0000 0.1944 0.0000 3.5275 0.1036 0.0976 0.0967 0.1987 0.0000 3.5714 0.1044 0.1022 0.4049 0.2030 0.0000 MF East 8/31/2020 3:49:59 PM Page 8 3.6154 0.1052 0.1068 0.8304 0.2074 0.0000 3.6593 0.1061 0.1114 1.3452 0.2117 0.0000 3.7033 0.1069 0.1161 1.9330 0.2160 0.0000 3.7473 0.1077 0.1208 2.5809 0.2203 0.0000 3.7912 0.1085 0.1256 3.2771 0.2246 0.0000 3.8352 0.1094 0.1304 4.0103 0.2289 0.0000 3.8791 0.1102 0.1352 4.7689 0.2332 0.0000 3.9231 0.1111 0.1401 5.5408 0.2375 0.0000 3.9670 0.1119 0.1450 6.3140 0.2418 0.0000 4.0000 0.1125 0.1487 7.0765 0.2451 0.0000 MF East 8/31/2020 3:49:59 PM Page 10 Analysis Results POC 1 + Predeveloped x Mitigated Predeveloped Landuse Totals for POC #1 Total Pervious Area:3.77 Total Impervious Area:0 Mitigated Landuse Totals for POC #1 Total Pervious Area:3.77 Total Impervious Area:2.678 Flow Frequency Method:Log Pearson Type III 17B Flow Frequency Return Periods for Predeveloped. POC #1 Return Period Flow(cfs) 2 year 0.010034 5 year 0.028479 10 year 0.053218 25 year 0.110405 50 year 0.183275 100 year 0.296218 Flow Frequency Return Periods for Mitigated. POC #1 Return Period Flow(cfs) 2 year 1.018204 5 year 1.482186 10 year 1.826137 25 year 2.303263 50 year 2.690175 100 year 3.104605 Annual Peaks Annual Peaks for Predeveloped and Mitigated. POC #1 Year Predeveloped Mitigated 1956 0.108 0.921 1957 0.006 1.928 1958 0.006 0.746 1959 0.008 1.024 1960 0.006 1.178 1961 0.096 0.607 1962 0.006 0.739 1963 0.034 2.256 1964 0.014 1.086 1965 0.011 1.255 MF East 8/31/2020 3:50:50 PM Page 18 Appendix Predeveloped Schematic MF East 8/31/2020 3:50:59 PM Page 19 Mitigated Schematic MF East 8/31/2020 3:51:08 PM Page 30 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. 2005-2020; 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 WWHM2012 PROJECT REPORT WEST BASIN TREATMENT RESULTS MF West 8/31/2020 3:27:34 PM Page 2 General Model Information Project Name:MF West Site Name: Site Address: City: Report Date:8/31/2020 Gage:Eaton Creek Data Start:1955/10/01 Data End:2011/09/30 Timestep:15 Minute Precip Scale:1.000 Version Date:2018/10/10 Version:4.2.16 POC Thresholds Low Flow Threshold for POC1:50 Percent of the 2 Year High Flow Threshold for POC1:50 Year MF West 8/31/2020 3:27:34 PM Page 3 Landuse Basin Data Predeveloped Land Use Basin 1 Bypass:No GroundWater:No Pervious Land Use acre A B, Forest, Mod 11.37 Pervious Total 11.37 Impervious Land Use acre Impervious Total 0 Basin Total 11.37 Element Flows To: Surface Interflow Groundwater MF West 8/31/2020 3:27:34 PM Page 4 Mitigated Land Use Basin 1 Bypass:No GroundWater:No Pervious Land Use acre A B, Lawn, Flat 6.08 Pervious Total 6.08 Impervious Land Use acre ROADS FLAT 1.52 ROOF TOPS FLAT 3.13 SIDEWALKS FLAT 0.64 Impervious Total 5.29 Basin Total 11.37 Element Flows To: Surface Interflow Groundwater Surface retention 1 Surface retention 1 MF West 8/31/2020 3:27:34 PM Page 6 Mitigated Routing Bioretention 1 Bottom Length: 64.67 ft. Bottom Width: 64.67 ft. Material thickness of first layer: 1.5 Material type for first layer: SMMWW 12 in/hr Material thickness of second layer: 2 Material type for second layer: GRAVEL Material thickness of third layer: 0 Material type for third layer: GRAVEL Underdrain used Underdrain Diameter (feet):0.5 Orifice Diameter (in.):6 Offset (in.):0 Flow Through Underdrain (ac-ft.):931.916 Total Outflow (ac-ft.):1016.912 Percent Through Underdrain:91.64 Discharge Structure Riser Height:0.5 ft. Riser Diameter:24 in. Element Flows To: Outlet 1 Outlet 2 Bioretention Hydraulic Table Stage(feet)Area(ac.)Volume(ac-ft.)Discharge(cfs)Infilt(cfs) 0.0000 0.1685 0.0000 0.0000 0.0000 0.0495 0.1676 0.0011 0.0000 0.0000 0.0989 0.1664 0.0022 0.0000 0.0000 0.1484 0.1653 0.0033 0.0001 0.0000 0.1978 0.1641 0.0044 0.0004 0.0000 0.2473 0.1630 0.0056 0.0010 0.0000 0.2967 0.1618 0.0067 0.0020 0.0000 0.3462 0.1607 0.0078 0.0034 0.0000 0.3956 0.1595 0.0090 0.0053 0.0000 0.4451 0.1584 0.0102 0.0077 0.0000 0.4945 0.1573 0.0114 0.0103 0.0000 0.5440 0.1561 0.0126 0.0107 0.0000 0.5934 0.1550 0.0138 0.0142 0.0000 0.6429 0.1539 0.0150 0.0185 0.0000 0.6923 0.1528 0.0162 0.0234 0.0000 0.7418 0.1517 0.0174 0.0246 0.0000 0.7912 0.1506 0.0187 0.0290 0.0000 0.8407 0.1495 0.0199 0.0353 0.0000 0.8901 0.1484 0.0212 0.0425 0.0000 0.9396 0.1473 0.0225 0.0468 0.0000 0.9890 0.1462 0.0238 0.0504 0.0000 1.0385 0.1451 0.0251 0.0592 0.0000 1.0879 0.1440 0.0264 0.0688 0.0000 1.1374 0.1430 0.0277 0.0779 0.0000 1.1868 0.1419 0.0290 0.0793 0.0000 1.2363 0.1408 0.0304 0.0907 0.0000 1.2857 0.1398 0.0317 0.1030 0.0000 1.3352 0.1387 0.0331 0.1164 0.0000 1.3846 0.1376 0.0345 0.1189 0.0000 MF West 8/31/2020 3:27:34 PM Page 7 1.4341 0.1366 0.0359 0.1306 0.0000 1.4835 0.1355 0.0373 0.1459 0.0000 1.5330 0.1345 0.0385 0.1623 0.0000 1.5824 0.1334 0.0398 0.1708 0.0000 1.6319 0.1324 0.0411 0.1796 0.0000 1.6813 0.1314 0.0424 0.1981 0.0000 1.7308 0.1303 0.0438 0.2176 0.0000 1.7802 0.1293 0.0451 0.2344 0.0000 1.8297 0.1283 0.0464 0.2382 0.0000 1.8791 0.1273 0.0478 0.2599 0.0000 1.9286 0.1263 0.0492 0.2828 0.0000 1.9780 0.1253 0.0505 0.4841 0.0000 2.0275 0.1243 0.0519 0.4841 0.0000 2.0769 0.1233 0.0533 0.4841 0.0000 2.1264 0.1223 0.0547 0.4841 0.0000 2.1758 0.1213 0.0561 0.4841 0.0000 2.2253 0.1203 0.0576 0.4841 0.0000 2.2747 0.1193 0.0590 0.4841 0.0000 2.3242 0.1183 0.0605 0.4841 0.0000 2.3736 0.1173 0.0619 0.4841 0.0000 2.4231 0.1164 0.0634 0.4841 0.0000 2.4725 0.1154 0.0649 0.4841 0.0000 2.5220 0.1144 0.0664 0.4811 0.0000 2.5714 0.1135 0.0679 0.4841 0.0000 2.6209 0.1125 0.0694 0.4841 0.0000 2.6703 0.1116 0.0709 0.4841 0.0000 2.7198 0.1106 0.0725 0.4841 0.0000 2.7692 0.1097 0.0740 0.4841 0.0000 2.8187 0.1087 0.0756 0.4841 0.0000 2.8681 0.1078 0.0771 0.4841 0.0000 2.9176 0.1069 0.0787 0.4841 0.0000 2.9670 0.1059 0.0803 0.4841 0.0000 3.0165 0.1050 0.0819 0.4841 0.0000 3.0659 0.1041 0.0836 0.4841 0.0000 3.1154 0.1032 0.0852 0.4841 0.0000 3.1648 0.1023 0.0868 0.4841 0.0000 3.2143 0.1014 0.0885 0.4841 0.0000 3.2637 0.1005 0.0901 0.4841 0.0000 3.3132 0.0996 0.0918 0.4841 0.0000 3.3626 0.0987 0.0935 0.4841 0.0000 3.4121 0.0978 0.0952 0.4841 0.0000 3.4615 0.0969 0.0969 0.4841 0.0000 3.5000 0.0960 0.0983 0.4841 0.0000 Bioretention Hydraulic Table Stage(feet)Area(ac.)Volume(ac-ft.)Discharge(cfs)To Amended(cfs)Infilt(cfs) 3.5000 0.1685 0.0983 0.0000 0.2904 0.0000 3.5495 0.1697 0.1066 0.0000 0.2904 0.0000 3.5989 0.1708 0.1150 0.0000 0.3096 0.0000 3.6484 0.1720 0.1235 0.0000 0.3192 0.0000 3.6978 0.1732 0.1321 0.0000 0.3287 0.0000 3.7473 0.1744 0.1407 0.0000 0.3383 0.0000 3.7967 0.1756 0.1493 0.0000 0.3479 0.0000 3.8462 0.1768 0.1580 0.0000 0.3575 0.0000 3.8956 0.1780 0.1668 0.0000 0.3670 0.0000 3.9451 0.1792 0.1756 0.0000 0.3766 0.0000 3.9945 0.1804 0.1845 0.0000 0.3862 0.0000 4.0440 0.1816 0.1935 0.1956 0.3958 0.0000 MF West 8/31/2020 3:27:34 PM Page 8 4.0934 0.1828 0.2025 0.6052 0.4053 0.0000 4.1429 0.1840 0.2115 1.1428 0.4149 0.0000 4.1923 0.1852 0.2207 1.7799 0.4245 0.0000 4.2418 0.1865 0.2299 2.4970 0.4341 0.0000 4.2912 0.1877 0.2391 3.2771 0.4436 0.0000 4.3407 0.1889 0.2484 4.1040 0.4532 0.0000 4.3901 0.1902 0.2578 4.9611 0.4628 0.0000 4.4396 0.1914 0.2672 5.8312 0.4724 0.0000 4.4890 0.1926 0.2767 6.6973 0.4819 0.0000 4.5000 0.1929 0.2788 7.5423 0.4841 0.0000 MF West 8/31/2020 3:27:34 PM Page 10 Analysis Results POC 1 + Predeveloped x Mitigated Predeveloped Landuse Totals for POC #1 Total Pervious Area:11.37 Total Impervious Area:0 Mitigated Landuse Totals for POC #1 Total Pervious Area:6.08 Total Impervious Area:5.29 Flow Frequency Method:Log Pearson Type III 17B Flow Frequency Return Periods for Predeveloped. POC #1 Return Period Flow(cfs) 2 year 0.010034 5 year 0.028479 10 year 0.053218 25 year 0.110405 50 year 0.183275 100 year 0.296218 Flow Frequency Return Periods for Mitigated. POC #1 Return Period Flow(cfs) 2 year 1.939755 5 year 2.752327 10 year 3.330403 25 year 4.105527 50 year 4.715217 100 year 5.352461 Annual Peaks Annual Peaks for Predeveloped and Mitigated. POC #1 Year Predeveloped Mitigated 1956 0.108 1.745 1957 0.006 3.491 1958 0.006 1.392 1959 0.008 1.920 1960 0.006 2.184 1961 0.096 1.182 1962 0.006 1.427 1963 0.034 3.918 1964 0.014 2.084 1965 0.011 2.302 MF West 8/31/2020 3:28:04 PM Page 16 LID Report MF West 8/31/2020 3:28:26 PM Page 18 Appendix Predeveloped Schematic MF West 8/31/2020 3:28:34 PM Page 19 Mitigated Schematic MF West 8/31/2020 3:28:43 PM Page 30 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. 2005-2020; 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 APPENDIX F Geotechnical Report 1015 East 4th Avenue, Olympia, Washington 98506 Phone: 360.754.2128 Fax: 360.754.9299 February 13, 2018 Sound Built Homes PO Box 73790 Puyallup, Washington 98296 Attention: John Harkness Report Update Stormwater Infiltration Evaluation Tahoma Terra Yelm, Washington Project No. 362-004-01 INTRODUCTION Insight Geologic is pleased to provide this report of our services to evaluate stormwater infiltration at the Tahoma Terra residential development in Yelm, Washington. The location of the site is shown relative to surrounding physical features in the Vicinity Map, Figure 1. The temporary stormwater infiltration area consists of a regional pond installed in about 2007. Additional pond locations will be investigated as a part of this study. The City of Yelm is requesting an evaluation of pond performance as well as treatment efficiancy. The proposed stormwater facilities are to receive runoff from other phases of the residential development and infiltrate the water to the subsurface. Our services were conducted in general accordance with the Washington State Department of Ecology 2005 Stormwater Manual as adopted by the City of Yelm. Our services were performed in general accordance with our proposal dated October 17, 2016 and authorized on October 20, 2016. SCOPE OF SERVICES The objective of our services was to explore the subsurface site conditions as a basis for developing recommendations for: 1) stormwater infiltration rates and 2) seasonal high groundwater conditions. Our specific scope of services included the following tasks: 1. Review available information for the subsurface conditions including geologic maps and previous reports conducted for the development. 2. Coordinate the location and clearance of underground utilities in the area of our proposed explorations. We contacted the “One Call” utility locating service to coordinate the clearance of publicly owned utilities within right-of-way’s. 3. Drill four (4) exploratory borings at the stormwater pond locations using a track-mounted drilling Sound Built Homes – Tahoma Terra Stormwater Infiltration Evaluation Report Update February 13, 2018 File No. 362−004−01 3 Insight Geologic, Inc. rig. The borings were drilled to depths of between 21.5 and 40.5 feet below ground surface (bgs). 4. Install four (4) groundwater monitoring wells in the borings to evaluate winter groundwater elevations through the winter season. 5. Install a monitoring point within the stormwater pond to record stormwater depth and infiltration rates for a winter season. 6. Conduct groundwater monitoring through the winter season to evaluate high groundwater elevations and groundwater flow direction. We installed a data-logging pressure transducer in each of the monitoring wells to maintain a continuous record of the site groundwater elevations. We also visited the site once per week to take manual measurements and check that our equipment had not been tampered with and was operational. 7. Monitor water quality at both the stormwater infiltration pond and monitoring well MW-2 installed adjacent to the pond. We collected two samples for the analysis of heavy metals including arsenic, cadmium, chromium, lead, mercury and copper using EPA 7000 series methodology, total petroleum hydrocarbons using Ecology Method NWTPH-HCID, total organic content, total nitrogen, and total phosphorus. 8. Prepare a report that includes our groundwater monitoring data, chemical analytical data and infiltration rates as measured through the winter season. FINDINGS Surface Conditions The project site is situated at elevations between approximately 330 and 390 feet above mean sea level (MSL) and is presently undeveloped. The property is bounded by undeveloped and residential land to the south, west, and east, and Tahoma Boulevard SE to the north. Thompson Creek is adjacent to the eastern property boundary. The subject site generally slopes down from the northwest to the south and east. Site development has created a depression along the northcentral portion of the site and significant reworking of a high point in the southeast corner of the site has occurred. The property has been previously cleared of vegetation with regrowth predominantly consisting of Alder trees, scotch broom and blackberries. The eastern half of the site has been utilized as a sand and gravel borrow and processing area during the construction of previous phases of the Tahoma Terra development to the north and northeast. A temporary stormwater infiltration area consisting of a regional pond was installed in the northcentral portion of the site in 2007, which infiltrates stormwater from the initial phases of the Tahoma Terra development. Geology Based on our review of available published geologic maps, the majority of the site is underlain by Vashon glacial till (Qgt). This material is described as consisting of a dense, unsorted, mixture of silt, gravel, and sand. Based on project work completed in the area by Insight Geologic, the glacial till unit is weakly compacted in this area and often consists of loose to moderately dense recessional outwash silt, sand, and gravel. These materials were deposited at the terminus of the ice sheet and have been subjected to erosion by meltwater streams as the ice melted. As part of recent residential development in the area, the surficial sands and gravels have been Sound Built Homes – Tahoma Terra Stormwater Infiltration Evaluation Report Update February 13, 2018 File No. 362−004−01 4 Insight Geologic, Inc. extensively mined for use as fill. Finer materials from the gravel mining operation were graded to the current site conditions and represent several feet of fill in some areas of the site. Subsurface Explorations We explored subsurface conditions at the site on November 9, 2016 by advancing four exploratory borings and subsequently installing four monitoring wells in the locations as shown on the Site Plan, Figure 2. The borings were completed by Holocene Drilling using a track-mounted BK-81 hollow stem auger drilling rig. A geologist from Insight Geologic monitored the explorations and maintained a log of the conditions encountered. The borings were completed at depths of between 21.5 and 40.5 feet bgs. Three hand augers were completed within the stormwater infiltration pond on January 24, 2018 to a depth of 2 feet bgs. The soils were visually classified in general accordance with the system described in ASTM D2487-06. The exploration logs are contained in Attachment A. The monitoring wells consist of 2-inch diameter casing and screen. The wells were installed with tamper resistant steel covers, flush with the surrounding grade. The monitoring well construction details are included in Attachment A. For the purposes of this report, groundwater elevations were based on estimated ground surface elevations derived from survey data provided by Sound Built Homes. Datalogging pressure transducers were installed in the completed wells and were programmed to collect groundwater readings at 6-hour intervals during the monitoring period. In addition, in January 31, 2017, a transducer was installed in a pre-existing monitoring well identified as MW-1A and within a monitoring point within the stormwater infiltration pond (identified as Pond) in the central portion of the site. Locations of monitoring well MW-1A and the Pond location are shown of Figure 2. The stormwater infiltration pond transducer was programmed to collect groundwater readings at 15-minute intervals during the monitoring period to record stormwater depth and infiltration rates. Manual groundwater measurements were collected on a weekly basis during the monitoring period. Groundwater monitoring data for both the manual measurements and the transducer data are contained in Attachment B. Groundwater hydrographs for the monitoring wells are shown in Figures 4 through 9. Soil Conditions Soil conditions across the site were variable both laterally and vertically due to the interbedded nature of the recessional deposits and the former mining activities that have occurred at the site. Boring MW-1 was completed at a depth of 21.5 feet bgs and encountered 4 feet of brown gravel with sand (GP) in a loose and moist condition, overlying 5.5 feet of gray sand with silt (SP-SM) in a loose and moist to wet condition. The lower 12 feet of the boring consisted of gray sand (SP) in a medium dense and wet condition. Boring MW-2 was completed at a depth of 40.5 feet bgs and consisted of 4 feet of brown sand (SP) in a loose and moist condition, overlying 5 feet of brown sandy silt (ML) in a stiff and moist condition. Underlying the silt unit, we encountered 13 feet of brown silty sand (SM) in a loose to medium dense Sound Built Homes – Tahoma Terra Stormwater Infiltration Evaluation Report Update February 13, 2018 File No. 362−004−01 5 Insight Geologic, Inc. and moist condition. At a depth of 22 feet bgs, we encountered 6.5 feet of brown gravel (GP) in a very dense and moist to wet condition. Underlying this gravel unit, we encountered 11 feet of sand with gravel in a very dense and wet condition. The boring was terminated at gray sand with gravel and silt (SP-SM) in a very dense and moist condition that was interpreted to be glacial till. Boring MW-3 was completed at a depth of 26.5 feet bgs and consisted of 4 feet of brown silty sand with gravel (SM) in a loose and moist condition, overlying 5 feet of brown silt with sand (ML) in a soft and moist condition. Underlying the silt unit, we encountered 14 feet of brown silty sand (SM) in a loose to medium dense and moist to wet condition. The boring was terminated at gray sand with gravel and silt (SP-SM) in a dense and moist condition that was interpreted to be glacial till. Boring MW-4 was completed at a depth of 26.5 feet bgs and consisted of 3 feet of brown sand (SP) in a loose and moist condition, overlying 6 feet of brown silt (ML) in a soft and moist condition. Underlying the silt unit, we encountered 5.5 feet of brown silty sand (SM) in a medium dense and moist to wet condition that graded to gray sand with silt (SP-SM) in a medium dense and wet condition at 14.5 feet bgs. At a depth of 20 feet bgs, we encountered brown silt (ML) in a very stiff and wet condition that extended to the base of the boring. Groundwater Conditions Groundwater was encountered in each of the four monitoring wells during installation on-site. We measured the depth to groundwater in the monitoring wells at between about 5.5 and 24.8 feet bgs at the beginning of the monitoring period in late-November 2016. Groundwater elevations in the monitoring well network did not appear to fluctuate greatly over the monitoring period. However, the amplitude of fluctuations varied across the site. Generally, groundwater elevations were between 227 and 241 feet MSL and individual wells fluctuated between 6.89 feet in MW-4 to 1.95 feet in MW-1. At the highest point, which occurred between March 15 and 22, 2017, high groundwater ranged from about 3.55 feet bgs in well MW-1 to 20.44 feet bgs in MW-2. A summary of groundwater measurements is shown in Table 1, below. Table 1. Summary of Measured Groundwater Levels Well Number Top of Well Casing Elevation Depth to Groundwater (feet below ground surface) Low High MW - 1 335 5.50 3.55 MW - 1A 349 16.81 11.53 MW - 2 353 24.85 20.44 MW - 3 350 13.25 7.80 MW - 4 345 10.69 3.80 Laboratory Testing We selected eleven soil samples for gradation analyses in general accordance with ASTM D422 to define soil class and obtain parameters for stormwater infiltration calculations. Our geotechnical laboratory test results are provided in Attachment C. Sound Built Homes – Tahoma Terra Stormwater Infiltration Evaluation Report Update February 13, 2018 File No. 362−004−01 6 Insight Geologic, Inc. ENVIRONMENTAL SAMPLING Water samples were collected from the stormwater infiltration pond inlet pipe, monitoring wells MW-2 and MW-1A for laboratory analysis. The water sample collected from monitoring well MW-1A is representative of groundwater upgradient of the stormwater infiltration pond. The water sample collected from monitoring well MW-2 is representative of groundwater beneath the existing stormwater infiltration pond. The water sample collected from the stormwater infiltration pond inlet pipe (Pond) is representative of influent water to the pond. Water samples were collected using Department of Ecology stormwater sampling methodology and low flow sampling methodology, respectively. Samples were transported to Libby Environmental in Olympia, Washington for the analysis of heavy metals including arsenic, cadmium, chromium, lead, mercury, and copper using EPA 7000 series methodology, and total petroleum hydrocarbons using Ecology Method NWTPH-HCID. Water Management Laboratories in Tacoma, Washington, conducted analyses for total organic nitrogen content, total nitrogen and total phosphorus. Copper was detected at a concentration of 102 and 26 micrograms per liter (µg/L) in monitoring wells MW-1A and MW-2, respectively. Lead was detected at a concentration of 9.6 µg/L and chromium was detected at a concentration of 22 µg/L in monitoring well MW-1A. Total phosphorus was detected at concentrations of 2.2, 0.09 and 0.4 milligrams per liter (mg/L) in monitoring well MW-2, Pond and MW- 1A, respectively. Total Nitrogen was detected at a concentration of 28.4 mg/L and total organic nitrogen was detected at a concentration of 1.5 mg/L in monitoring well MW-1A. No other analytes were detected at concentrations above method detection limits in the water samples. A summary of analytes detected is presented in Table 2. Laboratory reports from Libby Environmental and Water Management Laboratories are contained in Attachment C. Table 2. Summary of Detected Analytes Water Sample Date Sampled Metals by EPA Method 7010/7470 Series (µg/L) Phosphorus by EPA Method 300.0 (mg/L) Nitrogen (mg/L) Lead Chromium Copper Total Organic Total MW - 1A 1/24/2018 9.6 11.53 102 0.4 1.5 28.4 MW - 2 3/9/2017 <5.0 <5.0 26 2.2 <1.0 <1.5 Pond 3/9/2017 <5.0 <5.0 <5.0 0.09 <1.0 <1.4 STORMWATER INFILTRATION Monitoring Wells/Stormwater Infiltration Pond We completed a stormwater infiltration rate evaluation in general accordance with the Washington State Department of Ecology Stormwater Manual for Western Washington (2005 ESW Manual) as adopted by the City of Yelm. For the purposes of this evaluation, we selected Method 2 “ASTM Gradation Testing at Full Scale Infiltration Facilities” to estimate the long-term design infiltration rates at the site. Method 2 is based on the D10 results of the ASTM grain-size distribution analyses to estimate long-term design infiltration rates. The Method 2 values are listed in Table 3.8 of Volume III of the 2005 ESW Manual. To better identify infiltration rates for soils having D10 values which lie between the values listed in the table, we have plotted those values graphically and calculated a best- fit line to the data. The equation for the best fit line is y = 23.3x – 0.5, where “y” is the infiltration rate Sound Built Homes – Tahoma Terra Stormwater Infiltration Evaluation Report Update February 13, 2018 File No. 362−004−01 7 Insight Geologic, Inc. in inches per hour and “x” is the D10 value as determined by the ASTM gradation testing. By substituting our D10 sample values for “x” in the equation, we are able to calculate design infiltration rates (Fdesign) for each analyzed sample. For samples with a D10 value that was not able to be evaluated using the simple method the infiltration rate was evaluated using the Method 3 “Soil Grain Size Analysis Method” of the 2014 Washington State Department of Ecology Stormwater Manual for Western Washington (2014 Manual). The 2014 Manual utilizes the relationship between the D10, D60, and D90 results of the ASTM grain-size distribution analyses, along with site specific correction factors to estimate long-term design infiltration rates of each infiltration facility. Based on our analyses, we estimate that the long-term design infiltration rate (Fdesign) is 0.2 inches per hour within soils located above the observed winter high groundwater table and in the area of MW-2. The Fdesign is 3.1 inches per hour for soils located within the base of the stormwater infiltration pond, based on the average of the calculated rates. We have observed that groundwater is present near ground surface in the areas of MW-1, MW-3 and MW-4 and as a result, stormwater infiltration is likely infeasible at those locations. In addition, these infiltration rates do not take into account mounding effects, which could occur beneath the stormwater facility. The results of our stormwater infiltration evaluation are presented in Table 3, below. Table 3. Design Infiltration Rates Exploration Location Unit Depth Range (feet) D10 Value Design Infiltration Rate (inches per hour) MW-1 * SW-SM * 5.0 – 6.5 * 0.08 * Infeasible due to high groundwater table * MW-1 * SP * 10.0 – 11.5 * 0.2 * MW-2 ML 5.0 – 6.5 -- 0.1 MW-2 SM 10.0 – 16.5 -- 0.2 MW-3 ML 5.0 – 6.5 -- 0.1 MW-3 * SM * 10.0 – 16.5 * 0.07 * Infeasible due to high groundwater table * MW-4 * ML * 5.0 – 6.5 * -- Infeasible due to high groundwater table * HA-1 GP 1.5 0.18 3.7 HA-2 GP 1.0 0.18 3.7 HA-3 GP-GM 1.0 0.1 1.8 * Sample location is below the winter high groundwater level resulting in an infeasible infiltration rate Stormwater Treatment Pond Stormwater treatment pond water levels were monitored from February 1, 2017 to June 1, 2017. During this period, six storm events that retained water within the treatment pond were evaluated to determine the stormwater infiltration rate of the treatment pond. Infiltration rates observed are for the conditions presently existing within the treatment pond, which includes vegetative growth and buildup of sediments. The stormwater overflow height is located approximately 5 feet above the base of the transducer. Sound Built Homes – Tahoma Terra Stormwater Infiltration Evaluation Report Update February 13, 2018 File No. 362−004−01 8 Insight Geologic, Inc. At its highest point, which occurred on February 9, 2017, a maximum retention depth of 4.33 feet was recorded. Infiltration rates measured during the final drawdown for each event ranged from 0.7 to 0.4 inches per hour. A summary of groundwater measurements is shown in Table 4, below. Table 4. Summary of Infiltration Rates per Event Rainfall Event Event Date Observed Stormwater Level (feet) Infiltration Rate (inches per hour) Event - 1 2/9/2017 4.33 0.7 Event - 2 2/21/2017 2.32 0.4 Event - 3 3/18/2017 2.72 0.4 Event - 4 3/29/2017 2.08 0.4 Event - 5 5/4/2017 2.40 0.4 Event - 6 5/16/2017 2.01 0.6 OPINION We have performed an evaluation of groundwater conditions for Sound Built Homes at the Tahoma Terra residential development in Yelm, Washington. Groundwater elevations beneath the site were monitored for the period between November 23, 2016 and April 25, 2017. The peak groundwater elevation measured in the monitoring well network was about 341 feet MSL in MW-4 or about 3.8 feet bgs at that location. Shallow groundwater was also measured at MW-1 (3.6 feet) and MW-3 (7.8 feet) during our monitoring period. The deepest groundwater occurs in the area of the existing stormwater pond at depths of 11 feet in MW-1A and 20 feet in MW-2. High winter groundwater levels in the areas of MW-1, MW-3 and MW-4 will result in low stormwater infiltration rates in these areas. Where winter groundwater levels are deeper, as in the central portion of the site near MW-2 and the existing stormwater infiltration pond, the infiltration rate in the soils is low due to the very high fraction of fines. The calculated design infiltration rate of in this area is 0.1 to 0.2 inches per hour. This rate does not account for mounding effects that may occur beneath the infiltration areas. Infiltration rates within the existing stormwater infiltration pond were measured for 4 months and multiple storm events. Infiltration rates for the stormwater pond ranged from 0.4 to 0.7 inches per hour. Removal of accumulated fine sediment in the base of the stormwater pond would likely result in an increase in the infiltration rate. LIMITATIONS We have prepared this report for use by Sound Built Homes and their authorized agents. This report may be made available to regulatory agencies. Within the limitations of scope, schedule and budget, our services have been executed in accordance with generally accepted practices in this area at the time this report was prepared. No warranty or other conditions, express or implied, should be understood. Sound Built Homes – Tahoma Terra Stormwater Infiltration Evaluation Report Update February 13, 2018 File No. 362−004−01 9 Insight Geologic, Inc. Please refer to the Attachment D titled “Report Limitations and Guidelines for Use” for additional information pertaining to use of this report. __________________________ We appreciate the opportunity to be of service to you on this project. Please contact us if you have questions or require additional information. Respectfully Submitted, Insight Geologic, Inc. William E. Halbert, L.E.G., L.HG. Principal Attachments Insight Geologic, Inc. FIGURES Ye1><ri. Flame I � _ � I 510• �_�': � �:`-�_-�. � j- I �; ' � ' �.-.r. �irBwy . ' Sao I '•, Ath - Fie di CD l '.- r • c -240 _ } +" V � ' 124 ► 24 ii Towe .] Goif Coerse -So q mcxenZfe Lake r •— -- ¢ l� -� _Oso `�' • _ '� l�� 5(17 •� rr 1 �� •ll�j 5 1 �__� �� I. ark / � 475 '`��yl'I yI11+ � � ^ • 'S.J J, r�� • i—• .'GFINti�- am Source: Maptech, Inc. MCKENNA & TENALQUOT PRAIRIE, WASHINGTON 7.5 MINUTE QUADRANGLE Year Created 1990 TAHOMA TERRA SCALE: 1: 24000 YELM, WASHINGTON Figure 1 INSIGHT GEOLOGIC, INC. Vicinity Map 2 pi II� _% —Iry 1 TAHOMA BL VD i p, d KA -2 OND W - A MW -4 Source: Thurston County GeoData Center INSIGHT GEOLOGIC, INC. X14 0 125 250 SCALE: 1" = 250' LEGEND: �- HA -1 APPROXIMATE HAND AUGER LOCATION ® POND APPROXIMATE POND SAMPLE LOCATION PP MW -1 APPROXIMATE WELL LOCATION APPROXIMATE PROJECT BOUNDARY TAHOMA TERRA YELM, WASHINGTON Figure 2 Site Plan / t/ / I / l l TAHOMA BLVD ltlwv� vv v vv ��i vv �I)/ /� MW -L �� A`I 4 ii�� ` MYYW -1 ) AAA 7 3 v 33 �— �� 3.34 // HA -1 —s\l \ HA -2 �•-- `✓ \ 3 --- PON ID 3 I / / ill%%Off 1A1\U �� lf1�I rlllll l\ vAvv��` VAAV1 � 33 MW -1A _ . 33 � �Vv Av� 9 � } 1/ v� 1f 11 l � ter\"— �� 344 MW-3/�— ! MW -4 Source: Sound Built Homes i \\UV / Source: Sound Built Homes 0 125 250 SCALE: 1" = 250' i PrP:nln. HiQ -1 APPROXIMATE HAND AUGER LOCATION • POND APPROXIMATE POND SAMPLE LOCATION MWA APPROXIMATE WELL LOCATION APPROXIMATE GROUNDWATER CONTOUR AND ELEVATION APPROXIMATE DIRECTION OF GROUNDWATER FLOW --- APPROXIMATE PROJECT BOUNDARY TAHOMA TERRA YELM, WASHINGTON Figure 3 INSIGHT GEOLOGIC, INC. �c�� Groundwater Elevation and Flow Map \\UV � lv 0 125 250 SCALE: 1" = 250' i PrP:nln. HiQ -1 APPROXIMATE HAND AUGER LOCATION • POND APPROXIMATE POND SAMPLE LOCATION MWA APPROXIMATE WELL LOCATION APPROXIMATE GROUNDWATER CONTOUR AND ELEVATION APPROXIMATE DIRECTION OF GROUNDWATER FLOW --- APPROXIMATE PROJECT BOUNDARY TAHOMA TERRA YELM, WASHINGTON Figure 3 INSIGHT GEOLOGIC, INC. �c�� Groundwater Elevation and Flow Map \\UV 0 125 250 SCALE: 1" = 250' i PrP:nln. HiQ -1 APPROXIMATE HAND AUGER LOCATION • POND APPROXIMATE POND SAMPLE LOCATION MWA APPROXIMATE WELL LOCATION APPROXIMATE GROUNDWATER CONTOUR AND ELEVATION APPROXIMATE DIRECTION OF GROUNDWATER FLOW --- APPROXIMATE PROJECT BOUNDARY TAHOMA TERRA YELM, WASHINGTON Figure 3 INSIGHT GEOLOGIC, INC. �c�� Groundwater Elevation and Flow Map Figure 4 Hydrograph MW−1 32732933133333533733934134310/17/2016 11/16/2016 12/16/2016 1/15/2017 2/14/2017 3/16/2017 4/15/2017 5/15/2017Groundwater Elevation (Feet)DateTransducer DataManual Data Figure 5 Hydrograph MW−1A 32732933133333533733934134310/17/2016 11/16/2016 12/16/2016 1/15/2017 2/14/2017 3/16/2017 4/15/2017 5/15/2017Groundwater Elevation (Feet)DateTransducer DataManual Data Figure 6 Hydrograph MW−2 32732933133333533733934134310/17/2016 11/16/2016 12/16/2016 1/15/2017 2/14/2017 3/16/2017 4/15/2017 5/15/2017Groundwater Elevation (Feet)DateTransducer DataManual Data Figure 7 Hydrograph MW−3 32732933133333533733934134310/17/2016 11/16/2016 12/16/2016 1/15/2017 2/14/2017 3/16/2017 4/15/2017 5/15/2017Groundwater Elevation (Feet)DateTransducer DataManual Data Figure 8 Hydrograph MW−4 32732933133333533733934134310/17/2016 11/16/2016 12/16/2016 1/15/2017 2/14/2017 3/16/2017 4/15/2017 5/15/2017Groundwater Elevation (Feet)DateTransducer DataManual Data Figure 9 Hydrograph Stormwater Pond 012345671/15/2017 2/14/2017 3/16/2017 4/15/2017 5/15/2017 6/14/2017Stormwater Pond Depth (Feet)DateTransducer Data Insight Geologic, Inc. ATTACHMENT A EXPLORATION LOGS SOIL CLASSIFICATION CHART MAJOR DIVISIONS SYMBOLS GROUP NAME CC CEMENT CONCRETE OC ORGANIC COMPOUND G GW WELL -GRADED GRAVEL, CR GRAVEL CLEAN TS TOPSOIL/SOD/DUFF FINE TO COARSE GRAVEL TX TRIAXIAL COMPRESSION AND GRAVEL GP POORLY GRADED GRAVEL GRAVELLY <5% FINES SOILS MORE THAN 50% COARSE OF COARSE GRAVEL GM SILTY GRAVEL GRAINED FRACTION WITH FINES GC CLAYEY GRAVEL SOILS RETAINED ONNO. 4SIM 12% FINES WELL -GRADED SAND, SAND CLEAN SW FINE TO COARSE SAND MORE THAN 50% RETAINED ON AND SAND NO. 200 SIEVE SANDY -5% FINES SP POORLY GRADED SAND SOILS MORE THAN 50% OF COARSE SAND SM SILTY SAND FRACTION WITH FINES PASSING NO.4 SIEVE >12% FINES SC CLAYEY SAND SILTS ML SILT AND INORGANIC CL CLAY FINE CLAYS GRAINED ORGANIC SILT, SOILS LIQUID LIMITOL LESS THAN 50 ORGANIC 1 1 1 1 1 1 ORGANIC CLAY SILT OF HIGH PLASTICITY, SILTS MH MORE THAN 50% AND INORGANIC ELASTIC SILT CH CLAY OF HIGH PLASTICITY, PASSING NO. 200 SIEVE CLAYS FAT CLAY LIQUID LIMIT �� ORGANIC CLAY, 50 OR MORE ORGANIC ,�, � i OH ORGANIC SILT HIGHLY ORGANIC SOILS PT PEAT 70 60 k 50 W O 40 U 1= 30 Q J a 20 10 0 10 20 30 40 50 60 70 80 90 100 LIQUID LIMIT SOIL MOISTURE MODIFIERS: DRY - ABSENCE OF MOISTURE, DUSTY, DRY TO THE TOUCH MOIST - DAMP, BUT NO VISIBLE WATER WET - VISIBLE FREE WATER OR SATURATED, USUALLY SOIL IS OBTAINED BELOW WATER TABLE INSIGHT GEOLOGIC. INC. ADDITIONAL MATERIAL SYMBOLS SYMBOLS TYPICAL DESCRIPTION AL ATTERBERG LIMITS CC CEMENT CONCRETE OC ORGANIC COMPOUND AC ASPHALT CONCRETE COMPACTION TEST CR CRUSHED ROCK/ QUARRY SPALLS PP POCKET PENETROMETER TS TOPSOIL/SOD/DUFF GROUNDWATER EXPLORATION SYMBOLS MEASURED GROUNDWATER LEVEL IN EXPLORATION, WELL, OR PIEZOMETER GROUNDWATER OBSERVED AT TIME OF EXPLORATION PERCHED WATER OBSERVED AT TIME OF EXPLORATION MEASURED FREE PRODUCT IN WELL OR PIEZOMETER STRATIGRAPHIC CONTACT APPROXIMATE CONTACT BETWEEN SOIL STRATA OR GEOLOGIC UNIT --- APPROXIMATE LOCATION OF SOIL STRATA CHANGE WITHIN GEOLOGIC SOIL UNIT APPROXIMATE GRADUAL CHANGE BETWEEN SOIL STRATA OR GEOLOGIC SOIL UNIT APPROXIMATE GRADUAL CHANGE OF SOIL STRATA WITHIN GEOLOGIC SOIL UNIT LABORATORY/ FIELD TEST CLASSIFICATIONS %F PERECENT FINES MD MOISTURE CONTENT AND AL ATTERBERG LIMITS DRY DENSITY CA CHEMICAL ANALYSIS OC ORGANIC COMPOUND CP LABORATORY PM PERMEABILITY OR COMPACTION TEST HYDRAULIC CONDUCTIVITY CS CONSOLIDATION TEST PP POCKET PENETROMETER DS DIRECT SHEAR SA SIEVE ANALYSIS HA HYDROMETER ANALYSIS TX TRIAXIAL COMPRESSION MC MOISTURE CONTENT UC UNCONFINED COMPRESSION VS VANE SHEAR SAMPLER SYMBOLS 2.4 INCH I.D. SPLIT BARREL ® SHELBY TUBE DIRECT -PUSH ® PISTON STANDARD PENETRATION TEST ® BULK OR GRAB SHEEN CLASSIFICATIONS NS NO VISIBLE SHEEN SS SLIGHT SHEEN MS MODERATE SHEEN HIS HEAVYSHEEN NT NOT TESTED Key to Exploration Logs MW -1 z REMARKS AND WELL w LU o s u LITHOLOGY SOIL DESCRIPTION LABORATORY LL CONSTRUCTION a�a a o _�� U) > TEST RESULTS 0 Brown fine to coarse gravel with fine to coarse C7 sand, medium dense, moist c' .2- F5 U U 1 18/8 9 2 Gray fine to coarse sand with silt, loose, moist U o to wet > c) _ - 10 2 18/18 22 Gray fine to coarse sand with fine gravel, medium dense, wet m cB U C/) 3 18/18 15 Grades to orange -brown U o > C) Il 20 4 18/0 12 Grades to light brown fine to medium sand Groundwater encountered at 8 feet 30 40 50 LEGEND: PROJECT NO.: 362-004-01 DATE: NOVEMBER 9, 2016 TOTAL DEPTH: 21.5 FEET DOE WELL NO.: BJU-173 DRILLING CONTRACTOR: HOLOCENE DRILLING DRILLING EQUIPMENT: MOBILE BK -81 TAHOMA TERRA DRILLING METHOD: HOLLOW -STEM AUGER LOGGED BY: KEVIN VANDEHEY YELM, WASHINGTON INSIGHT GEOLOGIC, INC. Exploration Log MW -1 MW -2 F: w w w e t z� REMARKS AND WELL P a 1 ago =o r LITHOLOGY SOIL DESCRIPTION LABORATORY CONSTRUCTION W LL �� w > TEST RESULTS o Brown fine to coarse sand, loose, moist Light brown sandy silt, stiff, moist 1 18/16 9 J a Light brown fine silty sand, medium dense, 10 2 18/16 13 moist U _0) U 2 U 3 18/16 8Grades to loose m 20 4 18/16 14 Grades to fine to medium sand, medium dense Brown fine to coarse gravel with fine to coarse sand, medium dense to very dense, moist to 5 12/0 50/6" _ wet TM Dark brown fine to coarse sand with fine to 30 coarse gravel, very dense, wet ami IIII IIII 6 14/14 50/2" N IIII U) � IIII IIII 7 18/18 52 Gray fine to coarse sand with fine to coarse 8 3/3 50/3" - gravel and silt (till) SP -SM 40 ,:.•: Groundwater encountered at 25.5 feet 50 LEGEND: PROJECT NO.: 362-004-01 DATE: NOVEMBER 9, 2016 TOTAL DEPTH: 40.5 FEET DOE WELL NO.: BJU-174 DRILLING CONTRACTOR: HOLOCENE DRILLING DRILLING EQUIPMENT: MOBILE BK -81 TAHOMA TERRA DRILLING METHOD: HOLLOW -STEM AUGER LOGGED BY: KEVIN VANDEHEY YELM, WASHINGTON INSIGHT GEOLOGIC, INC. _ Exploration Log MW -2 MW -3 F: P w w w e t z� REMARKS AND WELL P a 1 ago =o r LITHOLOGY SOIL DESCRIPTION LABORATORY CONSTRUCTION W LL �� w > TEST RESULTS 0 Brown silty fine to coarse sand with fine to coarse gravel, loose, moist c _a � Light brown silt with sand, soft, moist co U a) 1 18/10 3 U g U o dami - m 2 18/16 9 Light brown fine to medium silty sand, loose, 10 moist Grades to medium dense, wet IIII c CU 3 18/16 11 IIIIo IIII U o 4 18/14 7 Grades to loose A20 Gray fine to coarse sand with fine to coarse 5 18/1138 0- gravel and silt, dense, moist (till) Groundwater encountered at 14 feet 30 40 50 LEGEND: PROJECT NO.: 362-004-01 DATE: NOVEMBER 9, 2016 TOTAL DEPTH: 26.5 FEET DOE WELL NO.: BJU-175 DRILLING CONTRACTOR: HOLOCENE DRILLING DRILLING EQUIPMENT: MOBILE BK -81 TAHOMA TERRA DRILLING METHOD: HOLLOW -STEM AUGER LOGGED BY: KEVIN VANDEHEY YELM, WASHINGTON INSIGHT GEOLOGIC, INC. Exploration Log MW -3 MW -4 z REMARKS AND WELL w a LITHOLOGY SOIL DESCRIPTION LABORATORY LU o s u LL CONSTRUCTION a�a a o _�� U) > TEST RESULTS 0 Brown fine to coarse sand, loose, moist c') CY) a Cn .2 U Light brown silt with fine sand, soft, moist Cj 1 18/12 3 U o CL m Light brown fine to medium silty sand, medium 10 2 18/13 11 dense, moist to wet IIII =IIIIc IIIICU 3 18/0 16 L IIII IIII 204 IL IIII 18/18 23 Light brown silt, very stiff, wet III IIII 5 18/18 27 Groundwater encountered at 13.2 feet 30 40 50 LEGEND: PROJECT NO.: 362-004-01 DATE: NOVEMBER 10, 2016 TOTAL DEPTH: 26.5 FEET DOE WELL NO.: BJU-176 DRILLING CONTRACTOR: HOLOCENE DRILLING DRILLING EQUIPMENT: MOBILE BK -81 TAHOMA TERRA DRILLING METHOD: HOLLOW -STEM AUGER LOGGED BY: KEVIN VANDEHEY YELM, WASHINGTON INSIGHT GEOLOGIC, INC. Exploration Log MW -4 HA -1 DEPTH REMARKS AND (FT) U.S.C.S. LITHOLOGY SOIL DESCRIPTION LABORATORY TEST RESULTS 0 Brown coarse gravel with sand, loose, moist 1 0_ C� 11i H 2 Groundwater not encountered 3 4 5 LEGEND: PROJECT NO.: 362-004-01 DATE: JANUARY 24, 2018 TOTAL DEPTH: 2FEET DRILLING METHOD: HAND AUGER LOGGED BY: KEVIN VANDEHEY TAHOMA TERRA YELM, WASHINGTON INSIGHT GEOLOGIC, INC. Exploration Log HA -1 HA -2 DEPTH REMARKS AND (FT) U.S.C.S. LITHOLOGY SOIL DESCRIPTION LABORATORY TEST RESULTS 0 Brown coarse gravel with sand, loose, moist 1 0_ C� 11i H 2 Groundwater not encountered 3 4 5 LEGEND: PROJECT NO.: 362-004-01 DATE: JANUARY 24, 2018 TOTAL DEPTH: 2FEET DRILLING METHOD: HAND AUGER LOGGED BY: KEVIN VANDEHEY TAHOMA TERRA YELM, WASHINGTON INSIGHT GEOLOGIC, INC. Exploration Log HA -2 HA -3 DEPTH REMARKS AND (FT) U.S.C.S. LITHOLOGY SOIL DESCRIPTION LABORATORY TEST RESULTS 0 7, vTx xi Brown fine to coarse gravel with fine to medium sand and silt, loose, moist 1 � 0_ C� 2 Groundwater not encountered 3 4 5 LEGEND: PROJECT NO.: 362-004-01 DATE: JANUARY 24, 2018 TOTAL DEPTH: 2FEET DRILLING METHOD: HAND AUGER LOGGED BY: KEVIN VANDEHEY TAHOMA TERRA YELM, WASHINGTON INSIGHT GEOLOGIC, INC. Exploration Log HA -3 Insight Geologic, Inc. ATTACHMENT B GROUNDWATER MONITORING DATA Project ID: Tahoma Terra 362‐004‐01 Location: MW‐1 LEVEL UNIT: ft Offset: 0.000000 ft TEMPERATURE UNIT: °C Date Time ms LEVEL TEMP Elevation Manual 11/23/2016 12:00:00 11/23/2016 12:00 327.5 12/1/2016 0:00:00 12/1/2016 0:00 14.131 13.7 327.831 12/1/2016 6:00:00 12/1/2016 6:00 14.101 13.7 327.801 12/1/2016 12:00:00 12/1/2016 12:00 14.075 13.7 327.775 12/1/2016 18:00:00 12/1/2016 18:00 14.057 13.7 327.757 12/2/2016 0:00:00 12/2/2016 0:00 14.043 13.7 327.743 12/2/2016 6:00:00 12/2/2016 6:00 14.006 13.7 327.706 12/2/2016 12:00:00 12/2/2016 12:00 13.985 13.7 327.685 12/2/2016 18:00:00 12/2/2016 18:00 14.054 13.7 327.754 12/3/2016 0:00:00 12/3/2016 0:00 14.071 13.7 327.771 12/3/2016 6:00:00 12/3/2016 6:00 14.008 13.7 327.708 12/3/2016 12:00:00 12/3/2016 12:00 13.967 13.7 327.667 12/3/2016 18:00:00 12/3/2016 18:00 13.95 13.7 327.65 12/4/2016 0:00:00 12/4/2016 0:00 14.051 13.7 327.751 12/4/2016 6:00:00 12/4/2016 6:00 14.305 13.7 328.005 12/4/2016 12:00:00 12/4/2016 12:00 14.303 13.7 328.003 328 12/4/2016 18:00:00 12/4/2016 18:00 14.287 13.7 327.987 12/5/2016 0:00:00 12/5/2016 0:00 14.2 13.7 327.9 12/5/2016 6:00:00 12/5/2016 6:00 14.189 13.7 327.889 12/5/2016 12:00:00 12/5/2016 12:00 14.187 13.7 327.887 12/5/2016 18:00:00 12/5/2016 18:00 14.21 13.7 327.91 12/6/2016 0:00:00 12/6/2016 0:00 14.19 13.7 327.89 12/6/2016 6:00:00 12/6/2016 6:00 14.2 13.7 327.9 12/6/2016 12:00:00 12/6/2016 12:00 14.191 13.7 327.891 12/6/2016 18:00:00 12/6/2016 18:00 14.173 13.7 327.873 12/7/2016 0:00:00 12/7/2016 0:00 14.164 13.7 327.864 12/7/2016 6:00:00 12/7/2016 6:00 14.143 13.7 327.843 12/7/2016 12:00:00 12/7/2016 12:00 14.081 13.7 327.781 12/7/2016 18:00:00 12/7/2016 18:00 14.07 13.7 327.77 12/8/2016 0:00:00 12/8/2016 0:00 14.07 13.7 327.77 12/8/2016 6:00:00 12/8/2016 6:00 14.052 13.7 327.752 12/8/2016 12:00:00 12/8/2016 12:00 14 13.7 327.7 12/8/2016 18:00:00 12/8/2016 18:00 14.057 13.7 327.757 12/9/2016 0:00:00 12/9/2016 0:00 14.085 13.7 327.785 12/9/2016 6:00:00 12/9/2016 6:00 14.03 13.7 327.73 12/9/2016 12:00:00 12/9/2016 12:00 14.004 13.7 327.704 12/9/2016 18:00:00 12/9/2016 18:00 14.048 13.7 327.748 MW‐11 of 13 NOTE: 306 PAGES OF MONITORING WELL LOGS WERE REMOVED FROM THIS REPORT. REFERENCE ORIGINAL REPORT FOR ALL PAGES. Insight Geologic, Inc. ATTACHMENT C LABORATORY ANALYSES RESULTS Job Name:Tahoma Terra Sample Location:MW-1 Job Number:362-004-01 Sample Name:MW-1 5.0'-6.5' Date Tested:12/9/16 Depth:5 - 6.5 Feet Tested By:Kevin Vandehey 15.0% Percent Percent by Sieve Size Passing Size Fraction Weight 3.0 in. (75.0)100.0 Coarse Gravel 0.0 1.5 in. (37.5)100.0 Fine Gravel 3.5 3/4 in. (19.0)100.0 3/8 in. (9.5-mm) 100.0 Coarse Sand 2.6 No. 4 (4.75-mm) 96.5 Medium Sand 47.0 No. 10 (2.00-mm) 94.0 Fine Sand 38.0 No. 20 (.850-mm) 85.0 No. 40 (.425-mm) 46.9 Fines 9.0 No. 60 (.250-mm) 32.9 Total 100.0 No. 100 (.150-mm) 23.9 No. 200 (.075-mm) 9.0 LL - - PL - - Pl - - D10 0.08 D30 0.21 D60 0.54 D90 1.50 Cc 1.02 Cu 6.75 ASTM Classification Group Name:Well-Graded Sand with Silt Symbol:SW-SM Gradation Analysis Summary Data Moisture Content (%) Job Name:Tahoma Terra Sample Location:MW-1 Job Number:362-004-01 Sample Name:MW-1 10.0'-11.5' Date Tested:12/9/16 Depth:10 - 11.5 Feet Tested By:Kevin Vandehey 19.1% Percent Percent by Sieve Size Passing Size Fraction Weight 3.0 in. (75.0)100.0 Coarse Gravel 2.4 1.5 in. (37.5)100.0 Fine Gravel 16.2 3/4 in. (19.0)97.6 3/8 in. (9.5-mm) 87.8 Coarse Sand 6.2 No. 4 (4.75-mm) 81.4 Medium Sand 41.0 No. 10 (2.00-mm) 75.1 Fine Sand 32.4 No. 20 (.850-mm) 61.8 No. 40 (.425-mm) 34.1 Fines 1.7 No. 60 (.250-mm) 15.9 Total 100.0 No. 100 (.150-mm) 5.5 No. 200 (.075-mm) 1.7 LL - - PL - - Pl - - D10 0.2 D30 0.4 D60 0.8 D90 11.0 Cc 0.9 Cu 4.0 ASTM Classification Group Name:Poorly-Graded Sand with Gravel Symbol:SP Gradation Analysis Summary Data Moisture Content (%) Job Name:Tahoma Terra Sample Location:MW-2 Job Number:362-004-01 Sample Name:MW-2 5.0'-6.5' Date Tested:12/9/16 Depth:5 - 6.5 Feet Tested By:Kevin Vandehey 13.3% Percent Percent by Sieve Size Passing Size Fraction Weight 3.0 in. (75.0)100.0 Coarse Gravel 0.0 1.5 in. (37.5)100.0 Fine Gravel 0.0 3/4 in. (19.0)100.0 3/8 in. (9.5-mm) 100.0 Coarse Sand 0.0 No. 4 (4.75-mm) 100.0 Medium Sand 1.0 No. 10 (2.00-mm) 100.0 Fine Sand 48.0 No. 20 (.850-mm) 99.7 No. 40 (.425-mm) 99.0 Fines 51.0 No. 60 (.250-mm) 98.2 Total 100.0 No. 100 (.150-mm) 96.0 No. 200 (.075-mm) 51.0 LL - - PL - - Pl - - D10 0.00 D30 0.00 D60 0.09 D90 0.14 Cc - - Cu - - ASTM Classification Group Name:Sandy Silt Symbol:ML Moisture Content (%) Gradation Analysis Summary Data Job Name:Tahoma Terra Sample Location:MW-2 Job Number:362-004-01 Sample Name:MW-2 10.0'-11.5' Date Tested:12/9/16 Depth:10 - 11.5 Feet Tested By:Kevin Vandehey 8.3% Percent Percent by Sieve Size Passing Size Fraction Weight 3.0 in. (75.0)100.0 Coarse Gravel 0.0 1.5 in. (37.5)100.0 Fine Gravel 0.0 3/4 in. (19.0)100.0 3/8 in. (9.5-mm) 100.0 Coarse Sand 0.1 No. 4 (4.75-mm) 100.0 Medium Sand 0.5 No. 10 (2.00-mm) 99.9 Fine Sand 70.1 No. 20 (.850-mm) 99.8 No. 40 (.425-mm) 99.4 Fines 29.3 No. 60 (.250-mm) 98.1 Total 100.0 No. 100 (.150-mm) 83.4 No. 200 (.075-mm) 29.3 LL - - PL - - Pl - - D10 0.00 D30 0.08 D60 0.11 D90 0.17 Cc - - Cu - - ASTM Classification Group Name:Silty Sand Symbol:SM Gradation Analysis Summary Data Moisture Content (%) Job Name:Tahoma Terra Sample Location:MW-2 Job Number:362-004-01 Sample Name:MW-2 15.0'-16.5' Date Tested:12/9/16 Depth:15 - 16.5 Feet Tested By:Kevin Vandehey 12.0% Percent Percent by Sieve Size Passing Size Fraction Weight 3.0 in. (75.0)100.0 Coarse Gravel 0.0 1.5 in. (37.5)100.0 Fine Gravel 0.0 3/4 in. (19.0)100.0 3/8 in. (9.5-mm) 100.0 Coarse Sand 0.0 No. 4 (4.75-mm) 100.0 Medium Sand 0.3 No. 10 (2.00-mm) 100.0 Fine Sand 66.5 No. 20 (.850-mm) 99.9 No. 40 (.425-mm) 99.6 Fines 33.1 No. 60 (.250-mm) 92.9 Total 100.0 No. 100 (.150-mm) 92.5 No. 200 (.075-mm) 33.1 LL - - PL - - Pl - - D10 0.00 D30 0.07 D60 0.10 D90 0.15 Cc - - Cu - - ASTM Classification Group Name:Silty Sand Symbol:SM Moisture Content (%) Gradation Analysis Summary Data Job Name:Tahoma Terra Sample Location:MW-3 Job Number:362-004-01 Sample Name:MW-3 5.0'-6.5' Date Tested:12/9/16 Depth:5 - 6.5 Feet Tested By:Kevin Vandehey 25.1% Percent Percent by Sieve Size Passing Size Fraction Weight 3.0 in. (75.0)100.0 Coarse Gravel 0.0 1.5 in. (37.5)100.0 Fine Gravel 2.6 3/4 in. (19.0)100.0 3/8 in. (9.5-mm) 98.0 Coarse Sand 0.5 No. 4 (4.75-mm) 97.4 Medium Sand 3.9 No. 10 (2.00-mm) 96.9 Fine Sand 12.2 No. 20 (.850-mm) 95.2 No. 40 (.425-mm) 93.0 Fines 80.7 No. 60 (.250-mm) 90.6 Total 100.0 No. 100 (.150-mm) 88.3 No. 200 (.075-mm) 80.7 LL - - PL - - Pl - - D10 0.00 D30 0.00 D60 0.00 D90 0.22 Cc - - Cu - - ASTM Classification Group Name:Silt with Sand Symbol:ML Moisture Content (%) Gradation Analysis Summary Data Job Name:Tahoma Terra Sample Location:MW-3 Job Number:362-004-01 Sample Name:MW-3 10.0'-11.5' Date Tested:12/9/16 Depth:10 - 11.5 Feet Tested By:Kevin Vandehey 18.1% Percent Percent by Sieve Size Passing Size Fraction Weight 3.0 in. (75.0)100.0 Coarse Gravel 0.0 1.5 in. (37.5)100.0 Fine Gravel 0.0 3/4 in. (19.0)100.0 3/8 in. (9.5-mm) 100.0 Coarse Sand 0.0 No. 4 (4.75-mm) 100.0 Medium Sand 1.2 No. 10 (2.00-mm) 100.0 Fine Sand 72.4 No. 20 (.850-mm) 99.9 No. 40 (.425-mm) 98.8 Fines 26.3 No. 60 (.250-mm) 92.7 Total 100.0 No. 100 (.150-mm) 70.0 No. 200 (.075-mm) 26.3 LL - - PL - - Pl - - D10 0.00 D30 0.08 D60 0.14 D90 0.30 Cc - - Cu - - ASTM Classification Group Name:Silty Sand Symbol:SM Gradation Analysis Summary Data Moisture Content (%) Job Name:Tahoma Terra Sample Location:MW-3 Job Number:362-004-01 Sample Name:MW-3 15.0'-16.5' Date Tested:12/9/16 Depth:15 - 16.5 Feet Tested By:Kevin Vandehey 22.8% Percent Percent by Sieve Size Passing Size Fraction Weight 3.0 in. (75.0)100.0 Coarse Gravel 0.0 1.5 in. (37.5)100.0 Fine Gravel 0.8 3/4 in. (19.0)100.0 3/8 in. (9.5-mm) 99.2 Coarse Sand 0.0 No. 4 (4.75-mm) 99.2 Medium Sand 5.7 No. 10 (2.00-mm) 99.2 Fine Sand 80.4 No. 20 (.850-mm) 98.7 No. 40 (.425-mm) 93.5 Fines 13.1 No. 60 (.250-mm) 71.0 Total 100.0 No. 100 (.150-mm) 41.0 No. 200 (.075-mm) 13.1 LL - - PL - - Pl - - D10 0.07 D30 0.12 D60 0.21 D90 0.38 Cc 0.98 Cu 3.00 ASTM Classification Group Name:Silty Sand Symbol:SM Moisture Content (%) Gradation Analysis Summary Data Job Name:Tahoma Terra Sample Location:HA-1 Job Number:362-004-01 Sample Name:HA-1 1.5' Date Tested:1/29/18 Depth:1.5 Ft Tested By:Kevin Vandehy 5.7% Percent Percent by Sieve Size Passing Size Fraction Weight 3.0 in. (75.0)100.0 Coarse Gravel 63.6 1.5 in. (37.5)52.4 Fine Gravel 4.7 3/4 in. (19.0)36.4 3/8 in. (9.5-mm) 33.0 Coarse Sand 1.2 No. 4 (4.75-mm) 31.7 Medium Sand 8.2 No. 10 (2.00-mm) 30.5 Fine Sand 18.7 No. 20 (.850-mm) 28.4 No. 40 (.425-mm) 22.3 Fines 3.6 No. 60 (.250-mm) 14.2 Total 100.0 No. 100 (.150-mm) 8.0 No. 200 (.075-mm) 3.6 LL - - PL - - Pl - - D10 0.18 D30 1.70 D60 43.00 D90 65.00 Cc 0.37 Cu 238.89 ASTM Classification Group Name:Poorly Graded Gravel with Sand Symbol:GP Gradation Analysis Summary Data Moisture Content (%) Job Name:Tahoma Terra Sample Location:HA-2 Job Number:362-004-01 Sample Name:HA-2 1.0' Date Tested:1/29/18 Depth:1 Ft Tested By:Kevin Vandehy 6.1% Percent Percent by Sieve Size Passing Size Fraction Weight 3.0 in. (75.0)100.0 Coarse Gravel 60.3 1.5 in. (37.5)57.5 Fine Gravel 9.0 3/4 in. (19.0)39.7 3/8 in. (9.5-mm) 31.9 Coarse Sand 0.4 No. 4 (4.75-mm) 30.7 Medium Sand 3.9 No. 10 (2.00-mm) 30.3 Fine Sand 22.8 No. 20 (.850-mm) 29.4 No. 40 (.425-mm) 26.4 Fines 3.6 No. 60 (.250-mm) 16.3 Total 100.0 No. 100 (.150-mm) 8.0 No. 200 (.075-mm) 3.6 LL - - PL - - Pl - - D10 0.18 D30 1.70 D60 40.00 D90 65.00 Cc 0.40 Cu 222.22 ASTM Classification Group Name:Poorly Graded Gravel with Sand Symbol:GP Gradation Analysis Summary Data Moisture Content (%) Job Name:Tahoma Terra Sample Location:HA-3 Job Number:362-004-01 Sample Name:HA-3 1.0' Date Tested:1/29/18 Depth:1 Ft Tested By:Kevin Vandehy 6.4% Percent Percent by Sieve Size Passing Size Fraction Weight 3.0 in. (75.0)100.0 Coarse Gravel 38.9 1.5 in. (37.5)81.5 Fine Gravel 18.7 3/4 in. (19.0)61.1 3/8 in. (9.5-mm) 49.0 Coarse Sand 4.1 No. 4 (4.75-mm) 42.4 Medium Sand 11.4 No. 10 (2.00-mm) 38.3 Fine Sand 19.9 No. 20 (.850-mm) 33.4 No. 40 (.425-mm) 26.9 Fines 7.0 No. 60 (.250-mm) 21.8 Total 100.0 No. 100 (.150-mm) 14.6 No. 200 (.075-mm) 7.0 LL - - PL - - Pl - - D10 0.10 D30 0.59 D60 18.00 D90 51.00 Cc 0.19 Cu 180.00 ASTM Classification Group Name:Poorly Graded Gravel with Sand and Silt Symbol:GP-GM Gradation Analysis Summary Data Moisture Content (%) 01020304050607080901000.0010.010.11101001000Percent Passing by Weight Grain Size in MillimetersU.S. Standard Sieve SizeMW-1 5.0'-6.5'MW-1 10.0'-11.5'MW-2 5.0'-6.5'MW-2 10.0'-11.5'COBBLESGRAVELSILT OR CLAYSANDCOARSEMEDIUMFINECOARSEFINE3" 1.5" 3/4" 3/8" #4 #10 #20 #40 #60 #100 #200Graph 1Gradation Analysis ResultsTAHOMA TERRA YELM, WASHINGTON 01020304050607080901000.0010.010.11101001000Percent Passing by Weight Grain Size in MillimetersU.S. Standard Sieve SizeMW-2 15.0'-16.5'MW-3 5.0'-6.5'MW-3 10.0'-11.5'MW-3 15.0'-16.5'COBBLESGRAVELSILT OR CLAYSANDCOARSEMEDIUMFINECOARSEFINE3" 1.5" 3/4" 3/8" #4 #10 #20 #40 #60 #100 #200Graph 2Gradation Analysis ResultsTAHOMA TERRA YELM, WASHINGTON 01020304050607080901000.0010.010.11101001000Percent Passing by Weight Grain Size in MillimetersU.S. Standard Sieve SizeHA-1 1.5'HA-2 1.0'HA-3 1.0'COBBLESGRAVELSILT OR CLAYSANDCOARSEMEDIUMFINECOARSEFINE3" 1.5" 3/4" 3/8" #4 #10 #20 #40 #60 #100 #200Graph 3Gradation Analysis ResultsTAHOMA TERRAYELM, WASHINGTON Phone (360) 352-2110 • Fax (360) 352-4154 • libbyenv@aol.com Libby Environmental, Inc. 4139 Libby Road NE • Olympia, WA 98506-2518 March 20, 2017 Bill Halbert Insight Geologic, Inc. 1015 East Fourth Ave Olympia, WA 98506 Dear Mr. Halbert: Please find enclosed the analytical data report for the Tahoma Terra Project located in Yelm, Washington. The results of the analyses are summarized in the attached tables. Applicable detection limits and QA/QC data are included. The sample(s) will be disposed of in 30 days unless we are contacted to arrange long term storage. Libby Environmental, Inc. appreciates the opportunity to have provided analytical services for this project. If you have any further questions about the data report, please give me a call. It was a pleasure working with you on this project, and we are looking forward to the next opportunity to work together. Sincerely, Sherry L. Chilcutt Senior Chemist Libby Environmental, Inc. Libby Environmental, Inc. 4139 Libby Road NE Ph: 360-352-2110 Olympia, WA 98506 _ Fax: 360-352-4154 Client: TV\ ( 1'11'\k.d---(;Ll> fo~ ,·u =u fi'.Jl II. Address: /0/~ ~-s:i -, vr--l1-vv Chain of Custody Record Date: .1/ f/ / -=r Project Ma~~~er: f?,/ / kk.J L., r 1-Project Name: lA A-~""" ... "'f~f r c.. www.LibbyEnvironmental.com Paqe: J of ) I Citv: t:J/tA ~.101 ~ State: LI/Jit~ Zip: .1/Yl!Jb Location: 4 -tJ I'V\_ City, State: lA/ )a.. Phone: ~ ti.J-.J-~-~1-1,-/ 1--V Fax: 3 60 -9-s-LJ-7 t--"V7 Collector~(J~n;,n = .. D t:t!.v.l' )...J /1/ Date of Collection: •Jff /1 =;--Client Proiect # :J (;;Z-oo'·(..-D l 1 JJA w-2-2 -P~rn./\ 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 Reli;;::d ftlttl/'J ReTinquished by: II Relinquished by: Depth Time Sample Type ~ lw~.Jv--I z,;JD I Wwl_q_r Date I Time '3/t~/ 1q 1 s~:l6 Date I Time Date I Time '--.---71-Em a i I: i11 If IJ-I)::f:n <;. 1 DV'Jvt-('.., lfJ '/ o 6t, u , ( 1J Jv\ Container Type A,.,._b.t.,/ lA ... Jx.r 1')4 I I I I I r>< I'X1 I I I I I . lX R275-ed bl /' ;}_ . Date 1 Time 1 Sample Rec.$!,pt ~ ~ .J/q/17 t).'f,l? ; Received by:V -Date I Time Received by: Date I Time Temp. oC Seals Intact? ?iYJ N N/A Total Number of I'"' LJ Containers Field Notes Remarks: --\ TAT: 24HR 48HR ~:.DA'6 LEGAL ACTION CLAUSE: In the event of default of payment and/or failure to pay, Client agrees to pay the costs of collection including court costs and reasonable attorney fees to be determined by a cout of law. Distribution: White-Lab, Yellow-File, Pink -~nator Libby Environmental, Inc.4139 Libby Road NE Olympia, WA 98506 TAHOMA TERRA PROJECT Phone: (360) 352-2110 Insight Geologic FAX: (360) 352-4154 Yelm, Washington Email: libbyenv@aol.com Libby Project # L170309-2 Client Project # 362-004-01 Sample Date Surrogate Gasoline Diesel Oil Number Analyzed Recovery (%)(µg/l)(µg/l)(µg/l) Method Blank 3/10/17 104 nd nd nd MW-2 3/10/17 97 nd nd nd Pond 3/10/17 111 nd nd nd Pond Dup 3/10/17 102 nd nd nd Practical Quantitation Limit 200 500 500 "nd" Indicates not detected at listed detection limits. "D" Indicates detected above the listed detection limit. "int" Indicates that interference prevents determination. Hydrocarbon Identification by NWTPH-HCID for Water ANALYSES PERFORMED BY: Kodey Eley ACCEPTABLE RECOVERY LIMITS FOR SURROGATE (2-F Biphenyl): 65% TO 135% Page 1 of 7 Libby Environmental, Inc.4139 Libby Road NE Olympia, WA 98506 TAHOMA TERRA PROJECT Phone: (360) 352-2110 Insight Geologic FAX: (360) 352-4154 Yelm, Washington Email: libbyenv@aol.com Libby Project # L170309-2 Client Project # 362-004-01 Sample Date Lead Cadmium Chromium Arsenic Number Analyzed µg/L µg/L µg/L µg/L Method Blank 3/12/17 nd nd nd nd MW-2 3/12/17 nd nd nd nd Pond 3/12/17 nd nd nd nd Pond Dup 3/12/17 nd nd nd nd Practical Quantitation Limit 5.0 0.5 5.0 3.0 Analyses of Total Metals in Water by EPA Method 7010 Series "nd" Indicates not detected at the listed detection limits. ANALYSES PERFORMED BY: Dirk Peterson Page 2 of 7 Libby Environmental, Inc.4139 Libby Road NE Olympia, WA 98506 TAHOMA TERRA PROJECT Phone: (360) 352-2110 Insight Geologic FAX: (360) 352-4154 Yelm, Washington Email: libbyenv@aol.com Libby Project # L170309-2 Client Project # 362-004-01 Sample Date Lead Cadmium Chromium Arsenic Number Analyzed (% Recovery)(% Recovery)(% Recovery)(% Recovery) LCS 3/12/17 86%88%94%112% Pond MS 3/12/17 104%118%81%117% Pond MSD 3/12/17 94%112%80%111% RPD 3/12/17 10%5%1%5% QA/QC for Metals in Water by EPA Method 7010 Series ACCEPTABLE RECOVERY LIMITS FOR MATRIX SPIKES: 75%-125% ACCEPTABLE RPD IS 20% ANALYSES PERFORMED BY: Dirk Peterson Page 3 of 7 Libby Environmental, Inc.4139 Libby Road NE Olympia, WA 98506 TAHOMA TERRA PROJECT Phone: (360) 352-2110 Insight Geologic FAX: (360) 352-4154 Yelm, Washington Email: libbyenv@aol.com Libby Project # L170309-2 Client Project # 362-004-01 Sample Date Mercury Number Analyzed µg/L Method Blank 3/16/17 nd MW-2 3/16/17 nd Pond 3/16/17 nd Pond Dup 3/16/17 nd Practical Quantitation Limit 0.5 Analyses of Total Mercury in Water by EPA Method 7470 "nd" Indicates not detected at the listed detection limits. ANALYSES PERFORMED BY: Jamie Deyman Page 4 of 7 Libby Environmental, Inc.4139 Libby Road NE Olympia, WA 98506 TAHOMA TERRA PROJECT Phone: (360) 352-2110 Insight Geologic FAX: (360) 352-4154 Yelm, Washington Email: libbyenv@aol.com Libby Project # L170309-2 Client Project # 362-004-01 Sample Date Mercury Number Analyzed (% Recovery) LCS 3/16/17 92% Pond MS 3/16/17 114% Pond MSD 3/16/17 124% RPD 3/16/17 8% ACCEPTABLE RPD IS 20% ANALYSES PERFORMED BY: Jamie Deyman QA/QC for Mercury by EPA Method 7470 ACCEPTABLE RECOVERY LIMITS FOR MATRIX SPIKES: 75%-125% Page 5 of 7 Libby Environmental, Inc.4139 Libby Road NE Olympia, WA 98506 TAHOMA TERRA PROJECT Phone: (360) 352-2110 Insight Geologic FAX: (360) 352-4154 Yelm, Washington Email: libbyenv@aol.com Libby Project # L170309-2 Client Project # 362-004-01 Sample Date Copper Number Analyzed (ug/l) Method Blank 3/12/17 nd MW-2 3/12/17 26 Pond 3/12/17 nd Pond Dup 3/12/17 nd Practical Quantitation Limit 5.0 Analyses of Total Copper in Water by EPA Method 7010 Series "nd" Indicates not detected at the listed detection limits. ANALYSES PERFORMED BY: Dirk Peterson Page 6 of 7 Libby Environmental, Inc.4139 Libby Road NE Olympia, WA 98506 TAHOMA TERRA PROJECT Phone: (360) 352-2110 Insight Geologic FAX: (360) 352-4154 Yelm, Washington Email: libbyenv@aol.com Libby Project # L170309-2 Client Project # 362-004-01 Sample Date Copper Number Analyzed (% Recovery) LCS 3/12/17 90% L170311-8 MS 3/12/17 82% L170311-8 MSD 3/12/17 85% RPD 3/12/17 4% QA/QC for Copper in Water by EPA Method 7010 Series ACCEPTABLE RPD IS 20% ACCEPTABLE RECOVERY LIMITS FOR MATRIX SPIKES: 75%-125% ANALYSES PERFORMED BY: Dirk Peterson Page 7 of 7 March 18, 2017 Insight Geologic, Inc. 1015 East 4th Avenue Olympia, WA 98506 Attn: Bill Halbert Dear Sir: Results of analysis of one non -drinking water sample taken by Kevin Vandehey on 03-09-1.7 at 1:15 p.m. and received on 03-09-17 at 2:15 p.m. are as follows: Project: Tahoma Terra Phases 7 & 8 Sample Identification: MW -2 Tests Results Total Organic Nitrogen (mg/L) < 1.0* Total Nitrogen (mg/ L) < 1.5* Total Phosphorus (mg/L) 2.2 Results of analysis of one surface water sample taken by Kevin Vandehey on 03-09-17 at 12:30 p.m. and received on 03-09-17 at 2:15 p.m. are as follows: Sample Identification: Pond Tests Results Total Organic Nitrogen (mg/ L) < 1.0* Total Nitrogen (mg/L) < 1.4* Total Phosphorus (mg/L) 0.09 * < is less than Lab Number: 08964771 Insight Geologic, Inc. March 18, 2017 Page 2 Samples were analyzed according to Standard Methods for the Examination of Water and Wastewater, 21St Edition and EPA Method 300. 0, Revision 2.1: Determination of Inorganic Anions in Water by Ion Chromatography. Chain of custody record is enclosed. Sincerely, Josh Hird Chemist JH:lcp Enclosure R: \COMM\INSIGHTGEOLOGIC3-9 ❑ a LU U p w Z ?" H' z w V o w It z� - a.: IL n 01, Q LU � Lii � O H H * * °w * w w W J' 9 "V W W co Cl) o > 0 v z LU D w cr. z o a _U � C ❑ 2A V ` � S:e� u H pp NLO �r ^ 4j CO O wa .ate L, C H m m CA ae ~ 1:1 - u. �0 o XR w wun IQ c cV Z w Z W W m VN O o Lo a3H10 c Ul m x v LL W W a O Q 0 ' --0 C r 31SbMW H W OC U Q C- W 00 O a31b'M R Lo `-� Sa3NIVIN00 30 # LL Z Y OO O cc ~ Q # 3�ldKVS r N M zt LO co h co 8? (� W w Phone (360) 352-2110 • Fax (360) 352-4154 • libbyenv@aol.com Libby Environmental, Inc. 4139 Libby Road NE • Olympia, WA 98506-2518 January 30, 2018 Bill Halbert Insight Geologic, Inc. 1015 East Fourth Ave Olympia, WA 98506 Dear Mr. Halbert: Please find enclosed the analytical data report for the Tahoma Terra Project located in Yelm, Washington. The results of the analyses are summarized in the attached tables. Applicable detection limits and QA/QC data are included. The sample(s) will be disposed of in 30 days unless we are contacted to arrange long term storage. Libby Environmental, Inc. appreciates the opportunity to have provided analytical services for this project. If you have any further questions about the data report, please give me a call. It was a pleasure working with you on this project, and we are looking forward to the next opportunity to work together. Sincerely, Sherry L. Chilcutt Senior Chemist Libby Environmental, Inc. Libby Environmental, Inc~ Chain of Custody Record www.LibbyEnvironmental.com 4139 Libby Road NE Ph: 360-352-2110 Olympia, WA 98506 Fax: 360-352-4154 Date: I / 1-Jj /Jq PaQe: of J , I Client:fY\~~-"'~j.--bto/ou ,·u Project Man~Qer: I a,'/ I /J.,..J b i> ./ ,.r Address: iO/t;" fi""'si 41!::-tivl/ Project Name: -:r;,. 1. ~~ '1-t r Y ~ City: 0 /"/)Jrn.fJ ~~-State: Wf\ Zip: '}~1,-D{., Location: &..P) yv-v----' City, State: 111/14-.-:77 , . Phone: 7 L. () ·--=J-I)ZJ-2/ 2---~ Fax: 1 ~D ·· ::Jt:Z-1" q Z.Ji '1 Collector: J J:.., v, ~ /)Ci ~ ,L,,...J, Date of Colle.ction: ~ // 2 £//;~ Client Project # 3 t, '2--C> o i-f -o I Email: /3,/J jjQ Tn~J'v.h--1 (;~o/o1·~ ,..L 6Qv 7 'I Sample Number Sample I Container Depth I Time I Type Type Field Notes 1 m,v,J A lV. ~I II ,?::3d tJ;~ k.r I /!). W'l J,.., / x' I I I I I I lx 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 Rei~~~;~// ~~:;;;ime I~;.,-, Receiv7 /Yf0 '--mple Receipt y N Remarks: Re~isfied by: -~-'7r-' 17ate 1 Time Rece~ Date I Time I Temp. oc Relinquished by: Date I Time Received by: Date /Time ~.:.. LEGAL ACTION CLAUSE: In the event of default of payment ancVor failure to pay, Client agrees to pay the costs of colf~lk>n including court costs and reasonable attorney fees to be determined by a cout of law. Seals Intact? Total Number of Containers Y N N/A .........---. ...., TAT: 24HR 48HR(5-DAY\ Distribution: White-Lab, Yellow-File, ~gina?or Libby Environmental, Inc.4139 Libby Road NE Olympia, WA 98506 TAHOMA TERRA PROJECT Phone: (360) 352-2110 Insight Geologic FAX: (360) 352-4154 Yelm, Washington Email: libbyenv@aol.com Libby Project # L180124-4 Client Project # 362-004-01 Sample Date Surrogate Gasoline Diesel Oil Number Analyzed Recovery (%)(µg/L)(µg/L)(µg/L) Method Blank 1/25/18 125 nd nd nd MW-1A 1/25/18 119 nd nd nd MW-1A Dup 1/25/18 120 nd nd nd Practical Quantitation Limit 200 500 500 "nd" Indicates not detected at listed detection limits. "D" Indicates detected above the listed detection limit. "int" Indicates that interference prevents determination. Hydrocarbon Identification by NWTPH-HCID for Water ANALYSES PERFORMED BY: Vanessa Cheang ACCEPTABLE RECOVERY LIMITS FOR SURROGATE (2-F Biphenyl): 65% TO 135% Page 1 of 7 Libby Environmental, Inc.4139 Libby Road NE Olympia, WA 98506 TAHOMA TERRA PROJECT Phone: (360) 352-2110 Insight Geologic FAX: (360) 352-4154 Yelm, Washington Email: libbyenv@aol.com Libby Project # L180124-4 Client Project # 362-004-01 Sample Date Lead Cadmium Chromium Arsenic Number Analyzed (µg/L)(µg/L)(µg/L)(µg/L) Method Blank 1/28/18 nd nd nd nd MW-1A 1/28/18 9.6 nd 22 nd Practical Quantitation Limit 5.0 0.5 5.0 3.0 Analyses of Total Metals in Water by EPA Method 7010 Series "nd" Indicates not detected at the listed detection limits. ANALYSES PERFORMED BY: Dirk Peterson Page 2 of 7 Libby Environmental, Inc.4139 Libby Road NE Olympia, WA 98506 TAHOMA TERRA PROJECT Phone: (360) 352-2110 Insight Geologic FAX: (360) 352-4154 Yelm, Washington Email: libbyenv@aol.com Libby Project # L180124-4 Client Project # 362-004-01 Sample Date Lead Cadmium Chromium Arsenic Number Analyzed (% Recovery)(% Recovery)(% Recovery)(% Recovery) LCS 1/28/18 89%98%108%113% L180124-1 MS 1/28/18 112%85%93%114% L180124-1 MSD 1/28/18 112%88%90%108% RPD 1/28/18 0%3%3%5% ANALYSES PERFORMED BY: Dirk Peterson QA/QC for Total Metals in Water by EPA Method 7010 Series ACCEPTABLE RECOVERY LIMITS FOR MATRIX SPIKES: 75%-125% ACCEPTABLE RPD IS 20% Page 3 of 7 Libby Environmental, Inc.4139 Libby Road NE Olympia, WA 98506 TAHOMA TERRA PROJECT Phone: (360) 352-2110 Insight Geologic FAX: (360) 352-4154 Yelm, Washington Email: libbyenv@aol.com Libby Project # L180124-4 Client Project # 362-004-01 Sample Date Mercury Number Analyzed (µg/L) Method Blank 1/28/18 nd MW-1A 1/28/18 nd MW-1A Dup 1/28/18 nd Practical Quantitation Limit 0.5 Analyses of Total Mercury in Water by EPA Method 7470 "nd" Indicates not detected at the listed detection limits. ANALYSES PERFORMED BY: Sherry Chilcutt Page 4 of 7 Libby Environmental, Inc.4139 Libby Road NE Olympia, WA 98506 TAHOMA TERRA PROJECT Phone: (360) 352-2110 Insight Geologic FAX: (360) 352-4154 Yelm, Washington Email: libbyenv@aol.com Libby Project # L180124-4 Client Project # 362-004-01 Sample Date Mercury Number Analyzed (% Recovery) LCS 1/28/18 101% MW-1A MS 1/28/18 106% MW-1A MSD 1/28/18 111% RPD 1/28/18 5% ANALYSES PERFORMED BY: Sherry Chilcutt QA/QC for Total Mercury by EPA Method 7470 ACCEPTABLE RECOVERY LIMITS FOR MATRIX SPIKES: 75%-125% ACCEPTABLE RPD IS 20% Page 5 of 7 Libby Environmental, Inc.4139 Libby Road NE Olympia, WA 98506 TAHOMA TERRA PROJECT Phone: (360) 352-2110 Insight Geologic FAX: (360) 352-4154 Yelm, Washington Email: libbyenv@aol.com Libby Project # L180124-4 Client Project # 362-004-01 Sample Date Copper Number Analyzed (µg/L) Method Blank 1/28/18 nd MW-1A 1/28/18 102 Practical Quantitation Limit 5.0 Analyses of Total Copper in Water by EPA Method 7010 Series "nd" Indicates not detected at the listed detection limits. ANALYSES PERFORMED BY: Dirk Peterson Page 6 of 7 Libby Environmental, Inc.4139 Libby Road NE Olympia, WA 98506 TAHOMA TERRA PROJECT Phone: (360) 352-2110 Insight Geologic FAX: (360) 352-4154 Yelm, Washington Email: libbyenv@aol.com Libby Project # L180124-4 Client Project # 362-004-01 Sample Date Copper Number Analyzed (% Recovery) LCS 1/28/18 106% L180124-1 MS 1/28/18 87% L180124-1 MSD 1/28/18 92% RPD 1/28/18 6% QA/QC for Total Copper in Soil by EPA Method 7010 Series ACCEPTABLE RECOVERY LIMITS FOR MATRIX SPIKES: 75%-125% ACCEPTABLE RPD IS 20% ANALYSES PERFORMED BY: Dirk Peterson Page 7 of 7 WATER MANAGEMENT LABORATORIES INC. February 3, 2018 Insight Geologic, Inc. 1015 East 4th Avenue Olympia, WA 98506 Attn: Bill Halbert Dear Sir: 1515 80th St. E. Tacoma, WA 98404 (253) 531-3121 Results of analysis of one non -drinking water sample taken by Kevin Vandehey on 01-24-18 at 1:35 p.m. and received on 01-24-18 at 3:00 p.m. are as follows: Project: Tahoma Terra Sample Identification: MW -1A Tests Results Total Organic Nitrogen (mg/ L) 1.5 Total Nitrogen (mg/ L) 28.4 Total Phosphorus (mg/ L) 0.40 Lab Number: 08968703 Samples were analyzed according to Standard Methods for the Examination of Water and Wastewater, 21 st Edition and EPA Method 300. 0, Revision 2.1: Determination of Inorganic Anions in Water by Ion Chromatography. Chain of custody record is enclosed. Sincerely, Christ$er drum Chemist CL:ldt Enclosure R: \ COMM \INSIGHTGEOLO GIC 1-24 Ex E a. A _CW CwC G G I— *p* LU W rs :�C * W 3 LU cc * Zj W r, v intn'C�� 4 Q = 0 m 0 Cl) uj d > z W ::i U w w - z o y IL U �' Z 1/ z�00 rn L? � A � LO w N -tel X H (� a F. w z i Y F H �I W Z ;Zoo (� (n r-4 N W W \ a� m 4 W Wm w m — o z 0 4 H3H10 H cvi co � cn Est LOU- w W a co 0 CL Q c x 31Sb'M W o C ��Z U Q a. M 00 O Lo x hlNt�d t�19 X SE13NIb'1N00 d0 # uj Ia- LL Z Y O Ia., oC o U a OF IN S �s Ilk oWC Insight Geologic, Inc. ATTACHMENT D REPORT LIMITATIONS AND GUIDELINES FOR USE Insight Geologic,Inc. Limitations ATTACHMENT D REPORT LIMITATIONS AND GUIDELINES FOR USE1 This attachment provides information to help you manage your risks with respect to the use of this report. HYDROGEOLOGIC SERVICES ARE PERFORMED FOR SPECIFIC PURPOSES, PERSONS AND PROJECTS This report has been prepared for the exclusive use of Sound Built Homes (Client) and their authorized agents. This report may be made available to regulatory agencies for review. This report is not intended for use by others, and the information contained herein is not applicable to other sites. Insight Geologic structures our services to meet the specific needs of our clients. For example, a hydrogeologic or geologic study conducted for a civil engineer or architect may not fulfill the needs of a construction contractor or even another civil engineer or architect that are involved in the same project. Because each hydrogeologic or geologic study is unique, each hydrogeologic or geologic report is unique, prepared solely for the specific client and project site. Our report is prepared for the exclusive use of our Client. No other party may rely on the product of our services unless we agree in advance to such reliance in writing. This is to provide our firm with reasonable protection against open-ended liability claims by third parties with whom there would otherwise be no contractual limits to their actions. Within the limitations of scope, schedule and budget, our services have been executed in accordance with our Agreement with the Client and generally accepted hydrogeologic practices in this area at the time this report was prepared. This report should not be applied for any purpose or project except the one originally contemplated. A HYDROGEOLOGIC OR GEOLOGIC REPORT IS BASED ON A UNIQUE SET OF PROJECT-SPECIFIC FACTORS Insight Geologic considered a number of unique, project-specific factors when establishing the scope of services for this project and report. Unless Insight Geologic specifically indicates otherwise, do not rely on this report if it was:  not prepared for you,  not prepared for your project,  not prepared for the specific site explored, or  completed before important project changes were made. If important changes are made after the date of this report, Insight Geologic should be given the opportunity to review our interpretations and recommendations and provide written modifications or confirmation, as appropriate. SUBSURFACE CONDITIONS CAN CHANGE This hydrogeologic or geologic report is based on conditions that existed at the time the study was performed. The findings and conclusions of this report may be affected by the passage of time, by manmade events such as construction on or adjacent to the site, or by natural events such as floods, 1 Developed based on material provided by ASFE, Professional Firms Practicing in the Geosciences; www.asfe.org . Insight Geologic,Inc. Limitations earthquakes, slope instability or ground water fluctuations. Always contact Insight Geologic before applying a report to determine if it remains applicable. MOST HYDROGEOLOGIC AND GEOLOGIC FINDINGS ARE PROFESSIONAL OPINIONS Our interpretations of subsurface conditions are based on field observations from widely spaced sampling locations at the site. Site exploration identifies subsurface conditions only at those points where subsurface tests are conducted or samples are taken. Insight Geologic reviewed field and laboratory data and then applied our professional judgment to render an opinion about subsurface conditions throughout the site. Actual subsurface conditions may differ, sometimes significantly, from those indicated in this report. Our report, conclusions and interpretations should not be construed as a warranty of the subsurface conditions. HYDROGEOLOGIC REPORT RECOMMENDATIONS ARE NOT FINAL Do not over-rely on the preliminary recommendations included in this report. These recommendations are not final, because they were developed principally from Insight Geologic’s professional judgment and opinion. Insight Geologic’s recommendations can be finalized only by observing actual subsurface conditions revealed during construction. A HYDROGEOLOGIC OR GEOLOGIC REPORT COULD BE SUBJECT TO MISINTERPRETATION Misinterpretation of this report by other design team members can result in costly problems. You could lower that risk by having Insight Geologic confer with appropriate members of the design team after submitting the report. Also retain Insight Geologic to review pertinent elements of the design team's plans and specifications. Contractors can also misinterpret a hydrogeologic engineering or geologic report. Reduce that risk by having Insight Geologic participate in pre-bid and preconstruction conferences, and by providing construction observation. DO NOT REDRAW THE EXPLORATION LOGS Hydrogeologic engineers and geologists prepare final boring and test pit logs based upon their interpretation of field logs and laboratory data. To prevent errors or omissions, the logs included in a hydrogeologic engineering or geologic report should never be redrawn for inclusion in architectural or other design drawings. Only photographic or electronic reproduction is acceptable, but recognize that separating logs from the report can elevate risk. READ THESE PROVISIONS CLOSELY Some clients, design professionals and contractors may not recognize that the geoscience practices (hydrogeologic engineering or geology) are far less exact than other engineering and natural science disciplines. This lack of understanding can create unrealistic expectations that could lead to disappointments, claims and disputes. Insight Geologic includes these explanatory “limitations” provisions in our reports to help reduce such risks. Please confer with Insight Geologic if you are unclear how these “Report Limitations and Guidelines for Use” apply to your project or site. Insight Geologic,Inc. Limitations HYDROGEOLOGIC, GEOLOGIC AND ENVIRONMENTAL REPORTS SHOULD NOT BE INTERCHANGED The equipment, techniques and personnel used to perform an environmental study differ significantly from those used to perform a hydrogeologic or geologic study and vice versa. For that reason, a hydrogeologic engineering or geologic report does not usually relate any environmental findings, conclusions or recommendations; e.g., about the likelihood of encountering underground storage tanks or regulated contaminants. Similarly, environmental reports are not used to address hydrogeologic or geologic concerns regarding a specific project. TO: Evan Mann, Sound Built Homes Clint Pierpoint, KPFF Ben Enfield, KPFF FROM: William Halbert, LEG DATE: May 1, 2020 SUBJECT: Clarification on Proposed Stormwater Infiltration Rates, Tahoma Terra 7 & 8 Regarding infiltration rates for the existing storm water infiltration pond at the Tahoma Terra 7 & 8 project area, Insight Geologic erred in our report and in our Response to Comments to SCJ. We were under the assumption that the project was operating under Ecology’s 2005 Storm water Manual as adopted by the City of Yelm where the project is located. We understand, after further discussions with KPFF and Sound Built Homes, that the project is actually vested under the 1992 Storm water Manual. Our proposed infiltration rate for the storm water infiltration pond as presented in our report and in our Response to Comments was 3.1 inches per hour. This rate was based on the ASTM gradation method described in the 2005 manual. Previous infiltration rate testing for the infiltration pond using a double ring infiltrometer (allowed under the 1992 Manual) ranged from 3.7 to 180 inches per hour. Infiltration Rates based on Hydrologic Soil Group are presented in Table III 3.1 from the 1992 manual, below. MEMORANDUM 1015 East 4th Avenue Olympia, Washington 98506 Telephone: (360) 754-2128 Fax: (360) 754-9299 Tahoma Terra Phase 7 & 8 May 1, 2020 Page 2 The soils in this area of the site are mapped as Everett Very Gravelly Sandy Loam and are classified as Hydrologic Group A, Outwash Soils. Under the Hydrologic Group classification system the storm water infiltration rate is given as 20 inches per hour which conforms to the high infiltration rates determined by the double ring infiltrometer testing. We trust this clarification meets your requirements. Please contact us if you have additional questions. APPENDIX G City of Yelm Letter of Understanding for Stormwater Requirements City of Yelm Public Works Department Physical Address: 901 Rhoton Road SE Mailing Address: 105 Yelm Ave West Yelm, WA 98597 (360)458-8406 Fax: (360) 458-8417 Web: www.d.yelm.wa.us May 24, 2016 Tahoma Terra Holding, LLC Attn: John Harkness PO Box 73790 Puyallup, WA 98373 Subject: Letter of Understanding —Tahoma Terra Master Plan Community Stormwater Requirements & Vesting Dear Mr. Harkness, The City of Yelm (COY) and Tahoma Terra Holding, LLC (Developer) have a mutual desire to come to an understanding as it pertains to the stormwater management for the continued platting and development of the Tahoma Terra Master Plan Community (MPC). A meeting was conducted between the two parties on May 17, 2016 to coordinate the stormwater permitting requirements for the MPC for Division 2, Phase 2's forthcoming application, as well as future requirements for the MPC. This letter is to memorialize the mutual understanding as it pertains to stormwater regulations and requirements imposed by the COY for the MPC relating to existing stormwater infrastructure and future development or modification of stormwater conveyance, treatment, and detention/infiltration systems. Both parties recognize the complexity of stormwater regulations, and agree that it is in their best interest to develop continuity and engineering predictability for the MPC, and furthermore that the development shall be vested to design all stormwater facilities utilizing the Department of Ecology (DOE) 1992 Stormwater Manual for the Puget Sound Basin for any new or retrofit stormwater facilities within the Tahoma Tera MPC. However, looking for ways to improve stormwater quality discharge prior to infiltration utilizing latest practices shall be strongly considered. Conditions to be met prior to final plat approval of Tahoma Tera Division 2 Phase 2 • Developer is required to conduct water quality monitoring at its existing regional wetpond and infiltration pond to confirm that water quality standards are being achieved. • Developer agrees to conduct a Winter Weather Stormwater Study in 2016-17 to determine flows and depth to ground water and report those results to the City • Developer shall install a minimum of one Ground Water Monitoring Well With the Winter Weather Study as required per the 1992 DOE SWMM near the existing regional facility. • The remaining development of the 198 -lots, which may be phased, will not require any stormwater changes to the existing pond system, unless the as stated monitoring or study of the facility determines it is not meeting the original designed performance requirements. • If modification is needed to the existing ponds, said modifications shall be completed prior to the recording of the final plat of phases 5 and 6. City staff has already reviewed the stormwater system for the current phase and has offered no comments that the regulations in place are not being met. Conditions for all future phases of the Tahoma Terra MPC • If the Developer relocates his/her existing stormwater management pond system south of Tahoma Blvd, any new facilities constructed as replacements will be designed to the most current DOE design standards for water quality, however, maintaining the 1992 manual for retention/detention. This letter of understanding may be revised or revisited in the future if both parties agree that is beneficial to the permitting, development or design of Tahoma Terra MPC. Please feel free to contact me at (360) 458-8412 if you have any questions or require any further clarification of these requirements. Best Regards, Chad A. Bedlington Public Works Manager Cc: Ryan Johnstone, PW Director Grant Beck, P&CD Director Tami Merriman, Associate Planner