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23-105365-ANK SP_TIR_12.27.23TECHNICAL INFORMATION REPORT FOR AnK SNORT PLAT CLIENT: Asgedom Woldetekle 29850 18"' Ave. S Federal Way, WA 98003 Phone: (913) 485-1676 PREPARED BY: Daley-Morrow-Poblete, Inc. 726 Auburn Way North Auburn, WA 98002 Phone: (253) 333-2200 PROJECT No. 22-400 DATE: Oct. 18, 2023 q 4 s~. o t21T I ZONAL STAMP NOT VALID UNLESS SIGNED & DATED TABLE OF CONTENTS DESCRIPTION PAGE SECTION I — PROJECT OVERVIEW Project Overview I Figure 1— TIR Worksheet 2-6 Figure 2 — Vicinity Map 7 Figure 3 — Basin Map 8 Figure 4 — Soils Map 9 SECTION II — CONDITIONS AND REQUIREMENTS SUMMARY Core Requirements 1-3 SECTION III — OFF -SITE ANALYSIS Off -Site Analysis SECTION IV — FLOW CONTROL, LOW IMPACT DEVELOPMENT (LID AND WATER OUALITY FACILITY ANALYSIS AND DESIGN Existing Site Hydrology I Developed Site hydrology I Performance Standards I Flow Control System I Water Quality System I Detention Facility Design 2 - 16 Water Quality Facility Sizing 17 - 23 SECTION V — CONVEYANCE SYSTEM ANALYSIS AND DESIGN SECTION VI — SPECIAL REPORTS AND STUDIES Geotechical Engineering Report, dated 8/28/2023 by GeoResources 1 - 33 SECTION VII — OTHER PERMITS N/A SECTION VIII — C.S.W.P.P.P. ANALYSIS AND DESIGN T.E.S.C. SECTION IX — BOND QUANTITIES FACILITY SUMMARIES AND DECLARATION OF COVENANT Bond Quantities Worksheet To be added Storm Facility Summary Sheet To be added Declaration of Covenant To be added SECTION X — OPERATIONS AND MAINTENANCE MANUAL To be added TIR Appendix A — Off -site Analysis from approved TIR, dated 2/6/2008 by Vikek Environmental Engrs, LLC for Lamb's Gate SECTION I PROJECT OVERVIEW PROJECT OVERVIEW The proposed AnK Short Plat will be constructed on two parcels, with a combined area of approximately 1.7 acre. The parcels are located within a portion of the southwest quarter of Section 4, Township 21 North, Range 4 East, Willamette Meridian, City of Federal Way, Washington. The site access is along 18t" Avenue S, which abuts the western property line of the two parcels. The parcel numbers are 367440-0155 and 367440-0160. The properties to the east, north and south are all single-family residential zone (RS-7.2). However, the property adjacent to the southwest corner of the project site is zoned commercial. There is presently a single-family residential home, which will remain in one of the new lots. There is also a gravel driveway used to access the site. Most of the site is covered with grass, with some trees, mostly along the eastern and southern perimeter of the site. The site slopes from east to west. A portion of the eastern portion of the site is steeper than 40 percent with 10 or more feet of vertical relief. Per page 8 of the Geotechnical Engineering Report in the TIR Appendix B, installation of a retaining wall will eliminate any landslide hazard; therefore, no additional buffer for landslide hazard areas should be imposed by the City of Federal Way. Site soils are classified as Arents and Alderwood gravelly sandy loam by the Soil Conservation Service. It is proposed to subdivide the parcels into 4 lots. The existing house will remain in the new Lot 1. Detention and water quality facilities will be constructed to meet the City of Federal Way's stormwater standards. The said facility will be constructed within the western portion of the property. An access road and utilities with be constructed to service the new lots. The west side of 181t' Avenue S will also be improved as part of the development. U KING COUNTY, WASHINGTON, SURFACE WATER DESIGN MANUAL TECHNICAL INFORMATION REPORT (TIR) WORKSHEET Part 1 PROJECT OWNER AND PROJECT ENGINEER Project Owner A,56LQof1 WOUVEZZW4 Phone (21 VS 5- 16 7 Address 2 SA0 18 r'-1 A V a 12 � 3 L/ ial 9 d Project Engineer;.,. Company 221ZZ a d Phone 1) Part3 TYPE OF PERMIT APPLICATION Land use (e.g.,Subdivision Short Subd. / UPD) ❑ Building (e.g.,M/F / Commercial / SFR) ❑ Clearing and Grading ❑ Right -of -Way Use ❑ Other Part 2 PROJECT LOCATION AND DESCRIPTION Project Name 14Nk 91-lotzr, Pmr DIS-Permitting Permit # Location Township 2I'Al Range 1C (y X Section / Site Address Part 4 OTHER REVIEWS AND PERMITS' ❑ DFW HPA ❑ Shoreline ❑ ❑ ❑ ❑ COE CWA 404 ECY Dam Safety FEMA Floodplain COE Wetlands Management ❑ Structural Rockery/Vault/ ❑ ESA Section 7 ❑ Other Part 5 PLAN AND REPORT INFORMATION Technical Information Report Site Improvement Plan (Engr. Plans) Full Full Type of Drainage Review ❑ Targeted Plan Type (check ❑ (check one): ❑ Simplified one): Modified ❑ Large Project ❑ Simplified Date (include revision ❑ Directed Date (include revision dates): dates): Date of Final: Date of Final: Part 6 SWDM ADJUSTMENT APPROVALS Type (circle one): Standard / Experimental / Blanket Description: (include conditions in TIR Section 2) Approved Adiustment No. Date of Approval: DFW: WA State Dept. of Fish and Wildlife. HPA: hydraulic project approval. COE: (Army) Corps of Engineers. CWA: Clean Water Act. ECY: WA State Dept. of Ecology. FEMA: Federal Emergency Management Agency. ESA: Endangered Species Act. 2021 Surface Water Design Manual 1 Last revised 7/23/2021 KING COUNTY, WASHINGTON, SURFACE WATER DESIGN MANUAL TECHNICAL INFORMATION REPORT (TIR) WORKSHEET Part 7 MONITORING REQUIREMENTS Monitoring Required: Yes / No Start Date: Completion Date: Describe: &Z-4 Re: KCSWDM Adjustment No. Part 8 SITE COMMUNITY AND DRAINAGE BASIN Community Plan : ,Z62) C AL WA � Special District Overlays: Alamo Drainage Basin: Stormwater Requirements: Part 9 OONSITE AND ADJACENT SENSITIVE AREAS ❑ River/Stream ❑ Lake ❑ Wetlands ❑ Closed Depression ❑ Floodolain ❑ Other Part 10 SOILS Soil Type ❑ High Groundwater Table (within 5 feet) ❑ Other ❑ Additional Sheets Attached LJ Steep SlopeIAI m c- Erosion Hazard CC;� a ❑ Landslide Hazard ❑ Coal Mine Hazard ❑ Seismic Hazard ❑ Habitat Protection Slopes A 9, ®X o -xo '�; ❑ Sole Source Aquifer ❑ Seeps/Springs Erosion Potential rZ-/6A/ 2021 Surface Water Design Manual 2 Last revised 7/23/2021 H KING COUNTY, WASHINGTON, SURFACE WATER DESIGN MANUAL TECHNICAL INFORMATION REPORT (TIR) WORKSHEET Part 11 DRAINAGE DESIGN LIMITATIONS REFERENCE ❑ Core 2 - Offsite Analysis ysensitive/Critical Areas ❑ SEPA ❑ LID Infeasibility ❑ Other LJ ❑ Additional Sheets Attached LIMITATION / SITE CONSTRAINT IVOILId- WN1 9�E d01VStRUC7Z0 A&L Part 12 TIR SUMMARY SHEET (provide one TIR Summary Sheet per Threshold Discharge Area) Threshold Discharge Area: (name or description) Core Requirements (all 8 apply): Discharge at Natural Location Number of Natural Discharge Locations: Offsite Analysis Level: 0/ 2 / 3 dated: 200 Flow Control (include facility Level: 1 A 2 / 3 or Exemption Number summary sheet) Flow Control BMPs Conveyance System Spill containment located at: Erosion and Sediment Control / CSWPP/CESCL/ESC Site Supervisor: a At - Construction Stormwater Contact Phone: &10 7-0 CO Pollution Prevention After Hours Phone: Maintenance and Operation Responsibility (circle one): Private / Public If Private, Maintenance Log Required: Yes / No Financial Guarantees and Provided: Yes / No %® �/9c�G'l�� !/- Liability RrC Lt 14 Water Quality (include facility Type (circle one): Basic / Sens. Lake / Enhanced Basic Bog summary sheet) or Exemption No. Landscape Management Plan: Yes / No For Entire Project: Total Replaced Impervious surfaces on the site % of Target Impervious that had a Total New Pervious Surfaces on the site feasible FCBMP Repl. Imp. on site mitigated w/flow control facility implemented Repl. Imp. on site mitigated w/water quality facility ReIA Imp. on site mitigated with FCBMP 2021 Surface Water Design Manual 3 Last revised 7/23/2021 KING COUNTY, WASHINGTON, SURFACE WATER DESIGN MANUAL TECHNICAL INFORMATION REPORT (TIR) WORKSHEET Part 12 TIR SUMMARY SHEET (provide one TIR Summary Sheet per Threshold Discharge Area) Special Requirements (as applicable): Area Specific Drainage Type: CDA / SDO / MDP / BP / LMP / Shared Fac. None Requirements Name: Floodplain/Floodway Delineation Type (circle one): Major / Minor / Exemption / None 100-year Base Flood Elevation (or range): Datum: Flood Protection Facilities Describe: AIIA Source Control Describe land use: A IA (commercial / industrial land use) Describe any structural controls: Oil Control High -use Site: Yes No Treatment BMP: IVA Maintenance Agreement: Yes / No with whom? Other Drainage Structures Describe: Part 13 EROSION AND SEDIMENT CONTROL REQUIREMENTS MINIMUM ESC REQUIREMENTS MINIMUM ESC REQUIREMENTS DURING CONSTRUCTION AFTER CONSTRUCTION learing Limits Stabilize exposed surfaces Yover Measures emove and restore Temporary ESC Facilities U Perimeter Protection Ycleanand remove all silt and debris, ensure YTraffic Area Stabilization operation of Permanent Facilities, restore operation of Flow Control BMP Facilities as // ediment Retention —,%cessary surface Water Collection Flag limits of SAO and open space preservation ® ewatering Control areas ® Other Dust Control Flow Control Protection of Flow Control BMP Facilities (existing and proposed) Maintain BMPs / Manage Project 2021 Surface Water Design Manual Last revised 7/23/2021 4 0 KING COUNTY, WASHINGTON, SURFACE WATER DESIGN MANUAL TECHNICAL INFORMATION REPORT (TIR) WORKSHEET Part 14 STORMWATER FACILITY DESCRIPTIONS (Note: Include Facility Summary and Sketch) Flow Control Type/Description Water Quality Type/Description Detention ❑ Infiltration ❑ Regional Facility ❑ Shared Facility ❑ Flow Control BMPs ❑ Other ❑ Vegetated Flowpath ❑ Wetpool ❑ Filtration ❑ Oil Control ❑ Spill Control ❑ Flow Control BMPs Lif Other Part 15 EASEMENTS/TRACTS Part16 STRUCTURAL ANALYSIS ❑ Drainage Easement ❑ Cast in Place Vault ❑ Covenant ❑ Retaining Wall ❑ Native Growth Protection Covenant ❑ Rockery > 4' High Urract ❑ Structural on Steep Slope ❑ Other ❑ Other Part 17 SIGNATURE OF PROFESSIONAL ENGINEER I I, or a civil engineer under my supervision, have visited the site. Actual site conditions as observed were incorporated into this worksheet and the attached Technical Informa ion Report. To the best of my knowledge the information provided here is accurate. �o�j8 2023 pned/Date 2021 Surface Water Design Manual Last revised 7/23/2021 O CO WtST 302 ST PL Sacajawea. Park I Sacajawea Addle School F1 G, L VICINITY PIAP S 296:ST ry C\I S 298 ST S s 99 PL 299 OT 171- 'S 300 ST S 301, SIT m cu,dj 6 Ac 124 64 &'r = 0, MIA c 761-lit :7 0,03 A C ) 9Aym) Al2 6- A 91, 9 2 14c cc Oe; 12,0 0, 19,4 Ff"8 ,Z;u M, - Q !N iD 0, .££ M aZU .196.8I ZZI «££ CHI aZZI N t i m LryL o Irn Ilm Is 6 I� N o ®o At, X aZZI. — C7 O O N— LO N a� (L ;>U) =)j � w =m Q Q O 3:U (0 C O m Z 9 Jp� rli d�J�'�" N !` a SECTION II CONDITIONS AND REQUIREMENTS SUMMARY CORE REQUIREMENT #l: DISCHARGE AT THE NATURAL LOCATION Site runoff will continue to drain to its natural location. CORE REQUIREMENT #2: OFFSITE ANALYSIS See Section III and TIR Appendix A. CORE REQUIREMENT #3: FLOW CONTROL FACILITIES It is proposed to construct a detention facility within the western portion of the site. Sizing calculations can be found in Section IV. BMPs will also be provided and will be determined as part of the individual building permit process. CORE REQUIREMENT #4: CONVEYANCE SYSTEM Conveyance facilities will be provided. Sizing calculations will be added in the engineering phase of this project. CORE REQUIREMENT #5: CONSTRUCTION STORMWATER POLLUTION PREVENTION Silt fencing, temporary sediment pond, stabilized construction entrance, interceptor ditch and site stabilization will be provided consistent with developments this size. A TESC Plan will be part of the engineering plans. A SWPPP will also be provided and will be included in this TIR during the engineering phase. CORE REQUIREMENT #6: MAINTENANCE AND OPERATIONS See Section X. CORE REQUIREMENT #7: FINANCIAL GUARANTEES AND LIABILITY Will be provided if required by the City of Federal Way. CORE REQUIREMENT #8: WATER QUALITY A water quality facility will be constructed in the southwest corner of the site. See Section IV for the sizing calculations. CORE REQUIREMENT #9: FLOW CONTROL BMPs The following BMPs were considered for this project: Full Dispersion — There is no sufficient area to provide the required native vegetated flowpath and native growth retention area; therefore, this BMP is not feasible. N Full Infiltration — Per the Geotechnical Engineering Report in TIR Section VI, this option is not feasible due to site soils. Limited Infiltration — Per the Geotechnical Engineering Report in TIR Section VI, this option is not feasible due to site soils. Bioretention — Per the Geotechnical Engineering Report in TIR section VI, this option is not feasible due potential for creation saturated conditions. Permeable Pavement - Per page 13 of the Geotechnical Engineering Report in TIR Section VI, permeable pavement could be considered for this project to help with managing stormwater, provided the proposed bottom of facility elevations are within the weathered glacial till soils observed in our explorations, and at least 1 foot in elevation higher than the undisturbed glacial till contact. Due to the shallow cemented soil layer, it does not appear that this can be achieved with certainty; therefore, this BMP is infeasible for this site. Basic Dispersion — Sheet flow basic dispersion will be used for the private driveways. Either splash blocks or gravel filled trenches will be used for some of the roof runoff. This project falls under the Small Lot BMP requirements. Since Lots 2, 3 and 4 are no more than 11,000 sf, BMPs must be implemented for a minimum of 10% of the lot area. Lot 1 is greater than 11,000 sf; therefore, BMPs must be implemented for a minimum of 20% of the lot area. The following table shows the required BMP mitigation for each lot, and how they will be met: Lot Lot Area Required Area to Sheet Flow Disp. Splash Blocks or Tot. Area (st) be Mitigated (sf) (st) Gravel filled Trench Mitigated (10% or 20%) (sf) (sf1 1 14,153 2,831 1,500 1,331 min. 2,831 2 9,863 986 600 386 min. 986 3 9,863 986 600 386 min. 986 4 11,000 1100 600 500 min. 1,100 Since the total mitigation areas will be more than the required mitigation areas, no additional BMPs are required. Note: Roof and driveway areas that will be mitigated are assumed at this time. Actual roof and driveway areas and BMPs will be determined with each building permit. 0 SPECIAL REQUIREMENT #l: OTHER ADOPTED AREA -SPECIFIC REQUIREMENTS. N/A SPECIAL REQUIREMENT #2: FLOOD HAZARD AREA DELINEATION N/A SPECIAL REQUIREMENT #3: FLOOD PROTECTION FACILITIES N/A SPECIAL REQUIREMENT #4: SOURCE CONTROL N/A SPECIAL REQUIREMENT #5: OIL CONTROL This project is not a "High Use Site". SECTION III OFF -SITE ANALYSIS OFF -SITE ANALYSIS A project called Lamb's Gate Presbyterian Church was previously approved to be constructed on the project site. The downstream system was verified to be the same as of June 20, 2023. Since there are no changes to the downstream system, the off -site analysis for the said project still applies to AnK Short Plat. Please see the off -site analysis in TIR Appendix A, which was taken from the previously approved TIR for the Lamb's Gate Presbyterian Church project. SECTION Iv FLOW CONTROL AND WATER QUALITY FACILITY ANALYSIS AND DESIGN EXISTING SITE HYDROLOGY (PART A) Runoff sheet flows to the west and discharges not the drainage facilities along 18th Avenue S. DEVELOPED SITE HYDROLOGY (PART B) Runoff from the proposed development will drain into a detention facility. Release from the detention facility will be to the drainage facilities along 18t1' Avenue S. PERFORMANCE STANDARDS (PART C) The project site is within the Conservation Flow Control/Level 2 Flow Control and Enhanced Basic Water Quality Treatment. FLOW CONTROL SYSTEM (PART D) It is proposed to subdivide the property into 4 single-family residential lots. The existing house will remain in Lot 1, but some accessory structures and the gravel driveway will be removed. Since only a new driveway will be added to Lot 1, for the pre -developed condition, landscaped areas and the house area in Lot 1 was modeled as existing. The remaining areas of the development, including the assumed future driveway for Lot 1, was assumed as forested in the pre -developed condition model. The map is page 8 of Section I, shows the area assumptions used in the modeling. Per the detention facility sizing in page 3, it was determined that 14,888 cuft of storage is required. It is proposed to use an underground detention facility by R-tank. 1,039 units of the Triple + Mini (3.5), with a total volume of 14,951 cu.ft., will be used. WATER QUALITY SYSTEM (PART E) Per page 10, treatment flow of 0.0346 cfs is required. It is proposed to use a BioPod Biofilter Underground System. Per page 17, model BPU-461B will be sufficient to handle the flow. WWHM2012 PROJECT REPORT Project Name: ank Site Name: Ank Short Plat Site Address: 29850 18th Ave. S. City : Federal Way Report Date: 10/17/2023 Gage : Seatac Data Start : 1948/10/01 Data End : 2009/09/30 Precip Scale: 1.00 Version Date: 2023/01/27 Version : 4.2.19 Low Flow Threshold for POC 1 : 50 Percent of the 2 Year High Flow Threshold for POC 1: 50 year PREDEVELOPED LAND USE Name : Basin I Bypass: No GroundWater: No Pervious Land Use C, Forest, Mod C, Lawn, Mod Pervious Total Impervious Land Use ROOF TOPS FLAT Impervious Total Basin Total Element Flows To: Surface MITIGATED LAND USE Name : Basin 1 Bypass: No acre 1.52 .18 �—IAND-CCA/l 0 ARCA /Al 1-67-1 -rO C A R C A Oir t- 0 TV 12 t 0 le 1V /V,) 7" IA)et V 0 C-0) 1.7 acre 0.12 <--1-100,5E 0/\) LOT / 70 RE'AlAliAl 0.12 1.82 Interflow Groundwater H GroundWater: No Pervious Land Use C, Lawn, Mod Pervious Total Impervious Land Use ROADS MOD ROOF TOPS FLAT SIDEWALKS MOD Impervious Total Basin Total Element Flows To: Surface Vault 1 acre 1.06 1.06 S F C, /2/-1 Co r ,® E- C 9 / (`), acre ® a 0.44 5 - [xiST1146A/ L07-1 0. 03 C, U1Z6L 0.76 1.82 Interflow Vault 1 Name Vault 1 Width 34 ft. Length 89 ft. Depth: 5.92 ft. Discharge Structure Riser Height: 4.92 ft. Riser Diameter: 18 in. Notch Type: Rectangular Notch Width: 0.011 ft. Notch Height: 1.835 ft. Orifice 1 Diameter: 0.96758 in Element Flows To: Outlet 1 Outlet 2 Groundwater Elevation: 0 ft. g // 0 35 UNI; s Vault Hydraulic Table Stage(feet) Area(ac.) Volume(ac-ft.) Discharge(cfs) Infilt(cfs) 0.0000 0.069 0.000 0.000 0.000 0.0658 0.069 0.004 0.006 0.000 0.1316 0.069 0.009 0.009 0.000 0.1973 0.069 0.013 0.011 0.000 0.2631 0.069 0.018 0.013 0.000 0.3289 0.069 0.022 0.014 0.000 0.3947 0.069 0.027 0.016 0.000 0.4604 0.069 0.032 0.017 0.000 0.5262 0.069 0.036 0.018 0.000 0.5920 0.069 0.041 0.019 0.000 0.6578 0.069 0.045 0.020 0.000 U 0.7236 0.069 0.050 0.021 0.000 0.7893 0.069 0.054 0.022 0.000 0.8551 0.069 0.059 0.023 0.000 0.9209 0.069 0.064 0.024 0.000 0.9867 0.069 0.068 0.025 0.000 1.0524 0.069 0.073 0.026 0.000 1.1182 0.069 0.077 0.026 0.000 1.1840 0.069 0.082 0.027 0.000 1.2498 0.069 0.086 0.028 0.000 1.3156 0.069 0.091 0.029 0.000 1.3813 0.069 0.096 0.029 0.000 1.4471 0.069 0.100 0.030 0.000 1.5129 0.069 0.105 0.031 0.000 1.5787 0.069 0.109 0.031 0.000 1.6444 0.069 0.114 0.032 0.000 1.7102 0.069 0.118 0.033 0.000 1.7760 0.069 0.123 0.033 0.000 1.8418 0.069 0.127 0.034 0.000 1.9076 0.069 0.132 0.035 0.000 1.9733 0.069 0.137 0.035 0.000 2.0391 0.069 0.141 0.036 0.000 2.1049 0.069 0.146 0.036 0.000 2.1707 0.069 0.150 0.037 0.000 2.2364 0.069 0.155 0.038 0.000 2.3022 0.069 0.159 0.038 0.000 2.3680 0.069 0.164 0.039 0.000 2.4338 0.069 0.169 0.039 0.000 2.4996 0.069 0.173 0.040 0.000 2.5653 0.069 0.178 0.040 0.000 2.6311 0.069 0.182 0.041 0.000 2.6969 0.069 0.187 0.041 0.000 2.7627 0.069 0.191 0.042 0.000 2.8284 0.069 0.196 0.042 0.000 2.8942 0.069 0.201 0.043 0.000 2.9600 0.069 0.205 0.043 0.000 3.0258 0.069 0.210 0.044 0.000 3.0916 0.069 0.214 0.044 0.000 3.1573 0.069 0.219 0.045 0.000 3.2231 0.069 0.223 0.047 0.000 3.2889 0.069 0.228 0.049 0.000 3.3547 0.069 0.233 0.051 0.000 3.4204 0.069 0.237 0.053 0.000 3.4862 0.069 0.242 0.056 0.000 3.5520 0.069 0.246 0.058 0.000 3.6178 0.069 0.251 0.061 0.000 3.6836 0.069 0.255 0.063 0.000 3.7493 0.069 0.260 0.066 0.000 3.8151 0.069 0.265 0.069 0.000 3.8809 0.069 0.269 0.071 0.000 3.9467 0.069 0.274 0.074 0.000 4.0124 0.069 0.278 0.077 0.000 4.0782 0.069 0.283 0.080 0.000 4.1440 0.069 0.287 0.083 0.000 4.2098 0.069 0.292 0.087 0.000 4.2756 0.069 0.297 0.090 0.000 4.3413 0.069 0.301 0.094 0.000 4.4071 0.069 0.306 0.097 0.000 4.4729 0.069 0.310 0.101 0.000 4.5387 0.069 0.315 0.121 0.000 4.6044 0.069 0.319 0.126 0.000 4.6702 0.069 0.324 0.132 0.000 4.7360 0.069 0.329 0.137 0.000 4.8018 0.069 0.333 0.142 0.000 4.8676 0.069 0.338 0.148 0.000 4.9333 0.069 0.342 0.177 0.000 4.9991 0.069 0.347 0.506 0.000 5.0649 0.069 0.351 1.026 0.000 5.1307 0.069 0.356 1.668 0.000 5.1964 0.069 0.361 2.387 0.000 5.2622 0.069 0.365 3.138 0.000 5.3280 0.069 0.370 3.874 0.000 5.3938 0.069 0.374 4.550 0.000 5.4596 0.069 0.379 5.129 0.000 5.5253 0.069 0.383 5.589 0.000 5.5911 0.069 0.388 5.930 0.000 5.6569 0.069 0.393 6.182 0.000 5.7227 0.069 0.397 6.506 0.000 5.7884 0.069 0.402 6.761 0.000 5.8542 0.069 0.406 7.007 0.000 5.9200 0.069 0.411 7.244 0.000 5.9858 0.090 0.457 7.474 0.000 ANALYSIS RESULTS Stream Protection Duration Predeveloped Landuse Totals for POC #1 Total Pervious Area:1.7 Total Impervious Area:0.12 Mitigated Landuse Totals for POC #1 Total Pervious Area:1.06 Total Impervious Area:0.76 Flow Frequency Return Periods for Predeveloped. POC #1 Return Period Flow(cfs) 2 year 0.09336 5 year 0.140275 10 year 0.175896 25 year 0.226238 50 year 0.267726 100 year 0.312726 Flow Frequency Return Periods for Mitigated. POC #1 Return Period Flow(cfs) 2 year 0.044013 5 year 0.068368 ■ 10 year 0.089023 25 year 0.121146 50 year 0.150052 100 year 0.18377 Stream Protection Duration Annual Peaks for Predeveloped and Mitigated. POC #1 Year Predeveloped Mitigated 1949 0.145 0.034 1950 0.143 0.043 1951 0.137 0.128 1952 0.065 0.029 1953 0.051 0.034 1954 0.075 0.040 1955 0.097 0.041 1956 0.091 0.048 1957 0.108 0.038 1958 0.071 0.040 1959 0.065 0.035 1960 0.126 0.090 1961 0.083 0.039 1962 0.044 0.028 1963 0.080 0.039 1964 0.088 0.036 1965 0.096 0.041 1966 0.064 0.035 1967 0.153 0.041 1968 0.096 0.035 1969 0.084 0.034 1970 0.084 0.035 1971 0.097 0.042 1972 0.122 0.065 1973 0.060 0.039 1974 0.093 0.040 1975 0.121 0.040 1976 0.087 0.041 1977 0.051 0.027 1978 0.066 0.039 1979 0.070 0.028 1980 0.189 0.083 1981 0.071 0.035 1982 0.158 0.070 1983 0.082 0.041 1984 0.060 0.032 1985 0.062 0.033 1986 0.122 0.055 1987 0.120 0.070 1988 0.048 0.033 1989 0.048 0.031 1990 0.320 0.095 1991 0.200 0.091 1992 0.079 0.040 1993 0.059 0.034 1994 0.034 0.026 1995 0.080 0.042 1996 0.190 0.131 1997 0.133 0.105 1998 0.073 0.034 1999 0.211 0.068 2000 0.087 0.041 2001 0.055 0.026 2002 0.103 0.060 2003 0.132 0.034 2004 0.146 0.127 2005 0.101 0.042 2006 0.099 0.040 2007 0.266 0.243 2008 0.243 0.150 2009 0.139 0.053 Stream Protection Duration Ranked Annual Peaks for Predeveloped and Mitigated. Rank Predeveloped Mitigated 1 0.3200 0.2434 2 0.2656 0.1497 3 0.2428 0.1310 4 0.2107 0.1282 5 0.2000 0.1270 6 0.1899 0.1054 7 0.1886 0.0950 8 0.1581 0.0914 9 0.1531 0.0905 10 0.1459 0.0826 11 0.1446 0.0702 12 0.1431 0.0696 13 0.1393 0.0679 14 0.1371 0.0647 15 0.1327 0.0601 16 0.1320 0.0549 17 0.1260 0.0527 18 0.1218 0.0485 19 0.1218 0.0431 20 0.1212 0.0424 21 0.1199 0.0417 22 0.1079 0.0416 23 0.1025 0.0413 24 0.1006 0.0412 25 0.0992 0.0408 26 0.0973 0.0407 27 0.0969 0.0406 28 0.0958 0.0406 29 0.0957 0.0405 30 0.0931 0.0399 31 0.0913 0.0397 32 0.0876 0.0396 33 0.0874 0.0395 34 0.0874 0.0395 35 0.0845 0.0393 36 0.0840 0.0389 37 0.0826 0.0387 38 0.0824 0.0386 39 0.0804 0.0385 POC #1 H 40 0.0804 0.0358 41 0.0787 0.0352 42 0.0749 0.0349 43 0.0730 0.0349 44 0.0715 0.0348 45 0.0712 0.0348 46 0.0696 0.0339 47 0.0664 0.0338 48 0.0652 0.0337 49 0.0648 0.0336 50 0.0642 0.0335 51 0.0619 0.0335 52 0.0603 0.0327 53 0.0600 0.0326 54 0.0587 0.0317 55 0.0553 0.0307 56 0.0511 0.0290 57 0.0506 0.0276 58 0.0485 0.0275 59 0.0480 0.0273 60 0.0437 0.0260 61 0.0341 0.0258 Stream Protection Duration POC #1 The Facility PASSED The Facility PASSED. Flow(cfs) Predev Mit Percentage Pass/Fail 0.0467 6335 4145 65 Pass 0.0489 5606 3707 66 Pass 0.0511 4986 3377 67 Pass 0.0534 4389 2999 68 Pass 0.0556 3893 2699 69 Pass 0.0578 3482 2458 70 Pass 0.0601 3095 2229 72 Pass 0.0623 2748 1978 71 Pass 0.0645 2421 1734 71 Pass 0.0668 2156 1577 73 Pass 0.0690 1930 1430 74 Pass 0.0712 1728 1307 75 Pass 0.0735 1551 1225 78 Pass 0.0757 1369 1143 83 Pass 0.0779 1231 1023 83 Pass 0.0802 1103 904 81 Pass 0.0824 1007 790 78 Pass 0.0846 917 687 74 Pass 0.0869 820 610 74 Pass 0.0891 730 534 73 Pass 0.0913 657 453 68 Pass 0.0936 587 394 67 Pass 0.0958 528 325 61 Pass 0.0980 468 276 58 Pass 0.1003 416 241 57 Pass 0.1025 368 206 55 Pass 0.1047 323 195 60 Pass 0.1070 279 188 67 Pass 0.1092 250 179 71 Pass 0.1114 222 171 77 Pass 0.1137 195 164 84 Pass 0.1159 174 157 90 Pass 0.1181 156 147 94 Pass 0.1204 146 142 97 Pass 0.1226 121 134 110 Pass 0.1248 106 113 106 Pass 0.1271 93 90 96 Pass 0.1293 76 76 100 Pass 0.1315 67 65 97 Pass 0.1338 59 59 100 Pass 0.1360 55 54 98 Pass 0.1382 47 46 97 Pass 0.1405 44 43 97 Pass 0.1427 40 38 95 Pass 0.1449 36 33 91 Pass 0.1472 34 26 76 Pass 0.1494 33 17 51 Pass 0.1516 29 15 51 Pass 0.1539 25 14 56 Pass 0.1561 22 12 54 Pass 0.1583 21 11 52 Pass 0.1606 21 10 47 Pass 0.1628 20 10 50 Pass 0.1650 19 9 47 Pass 0.1673 18 9 50 Pass 0.1695 17 7 41 Pass 0.1717 15 7 46 Pass 0.1739 15 6 40 Pass 0.1762 15 6 40 Pass 0.1784 15 6 40 Pass 0.1806 15 5 33 Pass 0.1829 14 5 35 Pass 0.1851 13 5 38 Pass 0.1873 12 5 41 Pass 0.1896 11 5 45 Pass 0.1918 9 4 44 Pass 0.1940 8 4 50 Pass 0.1963 8 4 50 Pass 0.1985 8 4 50 Pass 0.2007 7 3 42 Pass 0.2030 7 3 42 Pass 0.2052 7 3 42 Pass 0.2074 7 3 42 Pass 0.2097 7 3 42 Pass 0.2119 6 3 50 Pass 0.2141 5 3 60 Pass 0.2164 5 3 60 Pass 0.2186 5 3 60 Pass 0.2208 5 3 60 Pass 0.2231 5 3 60 Pass 0.2253 5 2 40 Pass 0.2275 5 2 40 Pass 0.2298 5 2 40 Pass 0.2320 5 1 20 Pass 0.2342 5 1 20 Pass 0.2365 5 1 20 Pass 0.2387 5 1 20 Pass 0.2409 5 1 20 Pass 0.2432 3 1 33 Pass 0.2454 3 0 0 Pass 0.2476 3 0 0 Pass 0.2499 3 0 0 Pass 0.2521 3 0 0 Pass 0.2543 3 0 0 Pass 0.2566 3 0 0 Pass 0.2588 2 0 0 Pass 0.2610 2 0 0 Pass 0.2633 2 0 0 Pass 0.2655 2 0 0 Pass 0.2677 1 0 0 Pass Water Quality BMP Flow and Volume for POC #1 On-line facility volume: 0.0686 acre-feet On-line facility target flow: 0.0346 cfs. Adjusted for 15 min: 0.0346 cfs. Off-line facility target flow: 0.0219 cfs. Adjusted for 15 min: 0.0219 cfs. LID Report LID Technique Used for Total Volume Percent Water Quality Percent Comment Treatment? Needs Volume Water Quality Treatment Infiltrated Treated (ac-ft Vault 1 POC N 185.89 0.00 Total Volume Infiltrated 185.89 0.00 0% No Treat. Credit Compliance with LID Standard 8 Duration Analysis Result = Failed Perind and Impind Changes No changes have been made. Volume Infiltration Cumulative Through Volume Facility (ac-ft.) (ac-ft) 0.00 0.00 Volume Infiltration Credit N 0.00 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. 2005-2023; All Rights Reserved. � m -� � � z �, � gg � v s.�x Reduce the size with the R-Tank System, an efficient and versatile underground stormwater storage system. This system will reduce your underground stormwater storage system footprint to resolve a utility conflict or free up space for a future expansion. It will also provide additional options for vehicular loading and cover depths, and deliver greater installation versatility. MMM With five different module configurations, R-Tank provides system height options from 2" to over 7' deep. It also delivers support for HS-20 and HS-25 traffic, with cover depths from 6" to over 16'. 11 Vulfth an unflnikeed array. of system fiampirkI and a 'r_3 ��wo- jeci, at the b'each ',I Light Duty module (30 psi) ° Ideal for applications in green space • Not rated for vehicular traffic ° 12" Minimum cover, 36" maximum cover ° Four internal plates ® '1 HIGH CAPACITY • 95% void internal area STRENGTH • Easily supports traffic loading from parking lots and roads Module options for HS-20 and HS-25 rating with cover depths from 6 inches to 16 feet DESIGN & CONSTRUCTION VERSATILITY • Modules can be combined into various shapes efficiently and effectively use space • Varied height from 2 inches to 7 feet INCREASED INFILTRATION AND EXILFILTRATION • Outer shell is 90% open • Increases groundwater recharge, reducing post - construction discharge volumes EASY TO TRANSPORT • Can be supplied unassembled for reduced delivery costs LIGHTWEIGHT AND QUICK TO INSTALL • Installed by hand; no cranes required • Reduces site access delays RECYCLED CONTENT • Manufactured with recycled polypropylene 13 s;44Milk- .m Amok a a c If`( !tom ®G + I, -- -- Many factors will influence the design of the R-Tank° system. While this list is not intended to be all-inclusive, the following design considerations are worth highlighting: 1. PRE-TREATMENT Removing pollutants from runoff before they enter an underground detention system is the smart way to design & build a system. Trash Guard Plus® (see page 6) is a great tool for this. Be sure the system you select will remove, heavy sediments, gross pollutants (trash) and biodegradable debris. 2. BACKFILL MATERIALS Backfill materials should be stone (<1.5" in diameter) or soil (GW, GP SW or SP per the Unified Soil Classification System). Material must be free from lumps, debris and sharp objects that could cut the geotextile. See the R-Tank° narrative specification section 2.03 for additional information. 3. RUNOFF REDUCTION Most designs incorporate an outlet to drain the system at a controlled rate and/or an overflow to prevent flooding in extreme events. Any infiltration that can be achieved on the site should also be taken advantage of. Consider raising the invert of your outlet or creating a sump to capture and infiltrate the water quality volume whenever possible. TOTAL COVER: 2W MINP3UM AND 84' MAXIMUM. FIRST 12' MUST BE FREE DRAINING BACKFILL (SPEC SECTION 2.03B): STONE <1.5' OR SOIL (USCS CLASS GW, GP, SW OR SPIT ADDITIONAL FILL MAY BE STRUCTURAL FILL (SPEC SECTION 2.03C): STONE OP. SOIL (USCS CLASS SM, SP, SW, ON, GP OR GW) VATH NIAX CLAY CONTENT<70%, MAX 25 % PASSING NO.200 SIEVE, AND MAX PLASTICITY INDEX OF 4.A MIN. 12' COVER MUST BE MAINTAINED BETWEEN BACKFILL EQUIPMENT AND THE TOP OF THE R-TANK"' SYSTEM AT ALL TINES. TOTAL HEIGHT OF TOP BACKFILL SHOULD NOT EXCEED 7'. CONTACT ACF ENVIRONMENTAL IF MORE THAN TOR LESS THAN 20' OF TOP BACKFILL IS REQUIRED (FROM TOP OF TANK TO TOP OF PAVEMENT). UTILITY MARKERS AT CORNERS (IYP.) 4. WATERTABLE While installing R-Tank° below the water table is manageable, a stable base must be created to account for the system's ability to drain water out or limit its ability to enter the system. If a liner is used to prevent ground water from entering, measures must be taken to prevent the system from floating. 5. CONSTRUCTION LOADS Construction loads are often the heaviest loads the system will experience. Care must be taken during back -filling and compaction (see specification section 3.05), and post -installation construction traffic should be routed around the system (Install Guide step 12). 6. LATERAL LOADS As systems get deeper, the loads acting on the sides of the tank increase. While vertical loads often control the design, lateral loads should also be considered. 7. R-TANK MODULES Selecting the right module for your application is critical. See page 3 and the specs on the back of this brochure, for details. Our team is also here to help! 8. LOAD MODELING A safety factor of >1.75 is required when designing an R-Tank System using the AASHTO LRFD Bridge Design Specifications. It is also necessary to run your own loading model with specific site requirements. Example models can be found in our Tech Note on loading capabilities, and minimum cover requirements can be found in the specs on the back of this brochure. NOTES: 1. FOR COMPLETE MODULE DATA, SEE APPROPRIATE R-TANK-MODULE SHEET. 2. INSTALLATIONS PER THIS DETAIL MEET GUIDELINES OF HL-93 LOADING PER THE AASHTO LRFD BRIDGE DESIGN SPECIFICATIONS, CUSTOMARY U.S. UNITS, 7TH EDITION, 2014 WITH 2O15 AND 2016 INTERIM REVISIONS. 3. PRE-TREATMENT STRUCTURES NOT SHOWN. 4. FOR INFILTRATION APPLICATIONS, GEOTEXTILE ENVELOPING R-TANKSHALL BE ACF M200(PER SPEC SECTION 2.02A) AND BASE SHALL BE 4- MIN. UNCOMPACTEO FREE DRAWING BACKFILL (SPEC SECTION 2.03A) TO PROVIDE A LEVEL BASE. SURFACE MUST BE SMOOTH, FREE OF LUMPS OR DEBRIS, AND EXTEND T BEYOND R-TANK- FOOTPRINT. GEOGRID (ACF BX-12 OR EQUAL) PLACED 12-ABOVE THE R-TANK- SYSTEM. OVERLAP ADJACENT PANELS BY 18' MIN. GEOGRID SHOULD EXTEND X SEYONDTHE EXCAVATION FOOTPRINT. -PAVED SURFACE �36'(0.911m)AIIN. COVER FROM FINISH OFTMl GRADE TO OTO TOP OFTANK: Ic ST, (0.51 mj MIN. .1 (03QJbi.�I'`IId e I�I1�IE IEI Iyl��nT OPTIONAL LAI-I1-11 -II IL i� OVERFLOW 111 II IIL71I III711 _ III II-IIL IB PIPE INLET PIPE ! �' ��' II I I_IIE�lE __II_ ifl carter anm� IIFIII It III II JII 111 W-L-111 IC Hun �I I -III �1e161i T ��T III _II REV), .. 1�11 SICyl y1_ 61 IH 16(I _1 I 1 OPTIONAL H " - I I III III III III L.- OUTLET 4�L311_ Hir-il II III ] I' -II I r��Tlli�IHjml�I nI�Ii�-li1 il}Tl6lT�dll�➢l#11iF � 11fi�117N ¢I1�uIuII=�C11116EI PTIlFJTI�Illll 1I6FIIE1I�C11=1 1I1C IIFIIII I-TI IIIEIII I lf(fi �=! IG[[�II1�HIl I�Ia]��II E1I61 I II ld-Il �I PIPE ��Il 3'(0.08mHIN ��L1II I I' IuJP IcnIY�OI �I Ilrt JI�Ir �!- L�L�EIBIIMII�I�J I�i�iJ� n._,III'ETC-JI1�1�1�1CT�i-1C1�1L�161 T.1rr,�l �II�,'I�J ul�ll'Jr(F�I 24(0.61 m) R-TANK- UNITS WRAPPED IN 8 OZ. NONWOVEN GEOTEXTILE(OR EQUAL) BASE:WMIN. BEDDING MATERIAL (SPEC SECTION SIDE BACKFILL 24" MIN. OF FREE DRAINING LOAD RATING: 33.4 PSI (MODULE ONLY) 2.03A) MAY BE STONE (<15) OR SOIL (USCS CLASS GWJ, BACKFILL (SPEC SECTION 2.038): STONE 17.5' SUBGRADE /EXCAVATION LWE: COI.IPACT PER GP, SW OR SP). MUST BE FREE OF LUMPS AND DEBRIS, OR SOIL (USCS CLASS GW, OF, SW OR SP). AND EXTEND 2' BEYOND R-TAN K`�'0. COMPACT PER MUST BE FREE FROM LUMPS, DEBRIS AND SPEC SECTION 3.02 D. A BEARING CAPACITY SPEC SECTION 3.03 A. NATIVE SOILS MAY BE USED IF OTHER SHARP OBJECTS. SPREAD EVENLYTO OF2,000 PSF MUST BE ACHIEVED PRIOR. TO THEY MEET THE REQUIREMENTS OF SPEC SECTION PREVENT R-TANK' MOVEniENT. COMPACT INSTALLING R-TANKI 2.03AAND ARE ACCEPTED BYOWNER'S ENGINEER. SIDE BACKFILL WITH POWERED MECHANICAL CO!.I FACTOR IN 12' LIFTS (PER SPEC SECTION 3.05 A2). I , 1. �� r� n r ` p ,{ rn �' p ��i s As much of the nation's Gray Infrastructure continues to decay, new concepts for rebuilding it are emerging through Green Infrastructure (GI) and Low Impact Development (LID). This type of reconstruction moves beyond traditional systems that do one thing well, to systems that accomplish multiple objectives simultaneously. ACF Environmental has several technologies that dovetail with the goals of LID and GI and can play a significant role in the redevelopment process. fi DA o AlI Pipe and stone are used in traditional systems to move and store runoff. R-Tank accomplishes the same purpose with several additional benefits. PERMEABLE PAVEMENTS Traditional pavements move vehicles efficiently, but are easily damaged by stormwater. ACF Environmental specializes in permeable pavements that handle traffic loads, while providing surface infiltration rates 10x higher than traditional pervious pavements, helping reduce the expense of long-term maintenance. 410 JFOCALPOINT Traditional landscaping adds aesthetic value to projects, but has more potential. Many developers turn to bioretention, but are forced to surrender massive land areas and dedicate significant future funds to maintenance. FocalPoint reduces the space requirements and maintenance costs of bioretention by up to 90% while providing similar pollutant removal. • Stores and moves runoff Moves water slowly, increasing time of concentration • Open system encourages infiltration • Fully accessible for maintenance • Stores 138% more water than stone • Maximizes storage potential of GI practices • Easily handles traffic loads • Ships flat to reduce site disturbance Handles all vehicular loads • Drains ten times faster than competing pervious pavements • Reduces long-term maintenance costs Encourages infiltration Pair with R-Tank° to maximize water storage and transport • Adds aesthetic value to properties Cleans runoff to improve water quality ° Reduces space requirements and maintenance costs of traditional bioretention systems Encourages infiltration to reduce volume of water discharged Pairs with R-Tank° to maximize water storage and transport R-Tank maximizes the storage capabilities of bioretention and permeable pavement systerns. N ki �A CO:Dal Module Width Length Height Volume Capacity Weight' Module Width Length Height Volume Capacity Weight (Ibs) (segments) (in) (in) (inIft) (cf) (cf) (Ibs) (Segments) (in) (in) (in/ft) (cf) (cf) Mini 15.75 28.15 9.45"/0.79' 2.42 2.30 10.1/10.9 Single (1) 15.75 28.15 9.45"/0.79' 2.42 2.30 10.95 Single (1) 15.75 1 28.15 i 17.32"/1.44' 4.44 4.22 15.7/17.3 Double (2) 15.75 28.15 18.12"11.51' 4.64 4.41 19.58 Single + Mini (1.5) 1535 i 28.15 25,98"/2.17' 6.67 6.33 .23.6/25.9 Triple (3) 15.75 i 28.15 26.79"/2.23' i 6.86 6.52 28.21 Double (2) 15.75 28.15 33.86"/2.82' 8.69 8.25 29.1/32.3 Quad (4) 15.75 28.15 i 35.46"/2.96' 9.08 8.63 36.84 Double + Mini (2.5): 15.75 28.15 42.52"/3.54' 10.91 10.36 37.0/41.0 Pent (5) 15.75 i 28.15 44.13'/3.68' 11.30 10.74 45.47 50.39"/4.20' 12.93 12.28 42.5/47.4 Hex,6, 57 2:..Jl 52 "/14.4 13-.52 54.10 I e �(3)M 57 2 8�1 55 5� 3 9 1 12 84 S, 1 - 5 5 0 0' 1 5 5 1 Triple + W, (3 5) 1575 28 1 /4.92' 15 4.i� 56 /�6.0 15.75 2 5 6.847 5 2 574 4:9 62.73 -------------- - a : _T572��6 -93'1-5.5-8' 62�A 15.75 2815 70.14"/5.85' 17.96 17.06 71.36 Quad (4) 5.7 Octo (8) 0 Quad + Mini (4.5) 15.75 28.15 75.59"/6.30' 19.39 18.42 63.8f7l.0 Nono (9) 15.75 28.15 78.81"/6.57' 20.18 19.17 79.99 Pent (5) 15.75 28.15 83.46"/6.96' 21.41 20.34 769.3f77.4 Decka (10) 15.75 28.15 87.48"R.29' 22,40 21.28 88.62 *Weights shown are for LD/HD modules. '-- 4,St' 7'1115 Module Width i Length i Height Volume Capacity Weight Module Width Length Height Volume Capacity Weight (Segments) (in) (in) (in/ft) (cf) (cf) (Ibs) (Segments) (in) (in) (in) (cf) (cf) (Ibs) Single (1) 23.62 i 23.62 1417"/1.18' 4.57 4.35 21.2 Single (1) 19.68 23.62 1,97 0.53 0.48 4 Double (2) 23.62 23.62 27.17'/2.26' t 8.77 8.33 39.0 Double (2) 19.68 23.62 3.94 1.06 0.95 8 Triple (3) 23.62 23.62 40.16'/3.35' 12.97 12.32s 56.8 Triple (3) 19.68 23.62 5.91 1.59 1.43 12 Quad (4) 23.62 23.62 5315"/4.43' 17.16 16.30 74.6 Quad (4) a 19.68 23.62 7.87 2.12 1.91 16 Pent (5) 23.62 23.62 66.14"/5.5' 21.35 s 20.29 92.4 Pent (5) 19.68 23.62 9.84 2.65 2.38 20 Note: XD modules may be stacked up to 10'tall (60 layers). q sm- Item Description Value Va ue Value Value Value Vold Area Volume available for water storage 95% 95% 95% 95% 90% Surface Area Vold 16 of exterior available for infiltration 90% 90% 90% 90% 90% Compressive Strength ASTM D 2412/ASTM F 2318 30.0 psi 33.4 psi 42.9 psi 134.2 psi 320 psi Unit Weight Weight of plastic per cubic foot of tank 3.29 Ibs/cf 3.62 Ibs/cf 3.96 Ibs/cf 4.33 lbs/cf 7.55 Ibs/cf Rib Thickness Thickness of load -bearing members 0.18, 0.18" 0.181, Service Temperature Safe temperature range for use -14-1670 F -14-1670 F -14-1670 F -14-1670 F -14-1670 F Recycled Content Use of recycled polypropylene 100% 100% 100% 100% 100% Minimum Cover Cover required for HS-20 loading Not traffic rated 20" 181, 12"-14" 61, Cover required for HS-25 loading Not traffic rated 24" 181, 15"-17 6" Maximum Cover Maximum allowable cover depth 36" 6.99' 9.99, 5.0' 16.7' OUTLET, 018.00" MAXIMUM I 4 It ALTERNATE SIDE PIPE LOCATION UNDERDRAIN OUTLET ORIFICE BYPASS WEIR ALTERNATE SIDE PIPE LOCATION--_` A INLET WINDOW A DRAIN DOWN DEVICE Ell DIMENSION B DIMENSION 6.00" TYPICAL C DIMENSION WALL THICKNESS s 'f` .2a :T ; �.� " '`T F :� 'a•:4' �'t' N 04.00" PVC SLOTTED ;.i'. +r,•JJJ"="r •� .� • ".I,i UNDERDRAIN PIPE At DIMENSION '';V•i;'w-'y`;e.' ::x':g1%:,w. A DIh1ENSI0N INLET, 018.00" },tAXIMUM I r 1 I' J PLAN VIEW j TOP SLAB NOT SHOWN IN THIS VIEW FOR CLARITY, ACCESS COVERS SHOWN IN PHANTOM. INLET/OUTLET ACCESS COVER & RISER, SIZE, QUANTITY & LOCATION MAY VARY. DIVIDER WALL INLET, NEARSIDE BYPASS WEIR - INLET WINDOW 2.2' [26.001 UNDERDRAIN OUTLET DROP ORIFICE, FARSIDE RECOMMENDED, OUTLET, FARSIDE, 6" MINIMUM. (AT FLOOR) Uu�t DRAIN DOWN DEVICE 036.00" ACCESS COVER & RISER ! 5,00' 2.00" MULCH MINIMUM _` .••rr:'it r„t, i:';�i`v,ti;\...:;:kf.:?i:`;,'.�r`•l�`t'tirf+t%••i L_.:r ly, t':,`:w :J�'... � f ii;�bti'•Inta-.l.%S„rr.?:f. 16.00' StOffllMiXn' ..cyi .:r�. ..Zr %pit;: .?ts':;?snt� }�'i`y`•``•y=��._`,".. MEDIA 6.00" DRAIN ROCK SECTION A -A 04.00" PVC SLOTTED UNDERDRAIN PIPE F MODEL VAULT SIZE' (ID) VAULT FOOTPRINT' (OD) TREATMENT FLOW CAPACITY (GPMICFS) A pIM _•.__..---- B DIM C DIM _... Al DIM 61 DIM .._._. _ _...(INA.GULD 1.6 GPMISZ ). 1.8 GPMISF _(NJCAT) BPUA61B 4' 6' 135' 7' 25.6 / 0.057 __28.8 / O.M4— BPU-481B 4'- _ 8' f3-- 5' 9' 38.4 / 0.086 43.2 / 0.096 BPUA121B 4' 12' 13 5' 13' 64.0/0.143 72.0/0.160 BPU-661B 6' 6' 1.5' 7' 7' 38.410.086 43.210.096 BPU-681B 6' 8' 1.5' 7' 9' 57,6 / 0,128 64,810,144 BPU-6121B 6' 12, 2' 7' 13' 91.2 / 0.203 102.6 / 0.229 BPU-8121B 8' 12' 2' 1 9' 13' 121.610.271 136.910.305 BPU-8161B 8' 16' 2' 9' 17' 172.8 / 0.385 194.4 / 0.433 SITE SPECIFIC DATA Structure ID Model Size Orientation (Left or Right) Treatment Flow Rate (cfs) Peak Flow Rate (cfs) Rim Elevation Pipe Data Pipe Location Pipe Size Pipe Type Invert (Fmn(wsde) Elevation Inlet Outlet T All Dimensions are nominal, ID=Inside Dimension, OD=Outside Dimension. 2 Treartment flow capacity at 1.6 gpm/sf media surface area based on an WA Ecology GULD Approval for Basic, Enhanced & Phosphorus. 3 Treatment flow capacity at 1.8 gpm/sf media surface area based on an NJCAT Verification & US Patents Pending NJ DEP Certification. a TM 7n '�� 1 - � Infrastructure" 1 ! /rj] (IJ]r'�j �A 7 a (�'jjj ° AC�CyO,MPANY • �1 a n 11 �>SY f! kr.1 71iS DOrU1<IFrlSifi PROPERTYOFOL[CASTLEYF R4STRMTMF,UR:. ITISSUB)nTTEDFORREFEKWEWRPXESO,�l.Y MUSKUUMT EE ;\ E�J USEDIN ANYViAY11MR:OLB TO Tk I �TERESTS CfSAU C0'12XNY.00PYW4T@iil20IXL1"hSTLE L`iFR}STRUCit� E,INO. AUMHTS RESERVED. Biorele lion/ i/ I Iy I ' DRAWING N0. REV ECO EC0-0169 DATE Bioriltraiion �Lf W�l l% 21 I IQ ✓ tjc4o o BPU-IB C CJS 3 6 20 PPS 3/9/20 SHEET 2 OF wmw� WASNIN6T ON STATE O EP ANT IIENT OE ECOLOGY July 2018 GENERAL USE LEVEL DESIGNATION FOR BASIC (TSS), DISSOLVED METALS (ENHANCED), AND PHOSPHORUS TREATMENT For Oldcastle Infrastructure, Inc.'s The BioPodTM Biofilter (Formerly the TreePod Biofilter) ■ m Applicant: Oldcastle Infrastructure, Inc. Applicant's Address: 360 Sutton Place Santa Rosa, CA 95407 Application Documents: Technical Evaluation Report TreePodTMBioFilter System Performance Certification Project, Prepared for Oldeastle, Inc., Prepared by Herrera Environmental Consultants, Inc. February 2018 Technical Memorandum: Response to Board of External Reviewers' Comments on the Technical Evaluation Report for the TreePodTMBiofilter System Performance Certification Project, Oldcastle, Inc. and Herrera Environmental Consultants, Inc., February 2018 Technical Memorandum: Response to Board of External Reviewers' Comments oil the Technical Evaluation Report for the TreePodTMBiofilter System Performance Certification Project, Oldcastle, Inc. and Herrera Environmental Consultants, Inc., January 2018 Application for Pilot Use Level Designation, TreePodTM Biofilter — Stormwater Treatment System, Oldcastle Stormwater Solutions, May 2016 Emerging Stormwater Treatment Technologies Application for Certification: The TreePodTM Biofilter, Oldcastle Stormwater Solutions, April 2016 Applicant's Use Level Request: • General Use Level Designation as a Basic, Enhanced, and Phosphorus Treatment device in accordance with Ecology's Stormwater Management Manual for Western Washington Applicant's Performance Claims: Based on results from laboratory and field-testing, the applicant claims the BioPodTM Biofilter operating at a hydraulic loading rate of 153 inches per hour is able to remove: • 80% of Total Suspended Solids (TSS) for influent concentrations greater than 100 mg/L and achieve a 20 mg/L effluent for influent concentrations less than 100 mg/L. • 60% dissolved zinc for influent concentrations 0.02 to 0.3 mg/L. ® 30% dissolved copper for influent concentrations 0.005 to 0.02 mg/L. C 50% or greater total phosphorus for influent concentrations 0.1 to 0.5 mg/L. E Ecology's Recommendations: Ecology finds that: • Oldcastle Infrastructure, Inc. has shown Ecology, through laboratory and field testing, that the BioPodTM Biofilter is capable of attaining Ecology's Basic, Total Phosphorus, and Enhanced treatment goals. Findings of Fact: Field Testing 1. Herrera Environmental Consultants, Inc. conducted monitoring of the BioPodTM Biofilter at the Lake Union Ship Canal Test Facility in Seattle Washington between November 2016 and April 2018. Herrera collected flow -weight composite samples during 14 separate storm events and peak flow grab samples during 3 separate storm events. The system was sized at an infiltration rate of 153 inches per hour or a hydraulic loading rate of 1.6 gpm/ft2. 2. The D50 of the influent PSD ranged from 3 to 292 microns, with an average D50 of 28 microns. 3. Influent TSS concentrations ranged from 17 mg/L to 666 mg/L, with a mean concentration of 98 mg/L. For all samples (influent concentrations above and below 100 mg/L) the bootstrap estimate of the lower 95 percent confidence limit (LCL 95) of the mean TSS reduction was 84% and the bootstrap estimate of the upper 95 percent confidence limit (UCL95) of the mean TSS effluent concentration was 8.2 mg/L. 4. Dissolved copper influent concentrations from the 17 events ranged from 9.0 µg/L to 21.1 µg/L. The 21.1 µg/L data point was reduced to 20.0 µg/L, the upper limit to the TAPE allowed influent concentration range, prior to calculating the pollutant removal. A bootstrap estimate of the LCL95 of the mean dissolved copper reduction was 35%. 5. Dissolved zinc influent concentrations from the 17 events ranged from 26.1 µg/L to 43.3 µg/L. A bootstrap estimate of the LCL95 of the mean dissolved zinc reduction was 71%. 6. Total phosphorus influent concentrations from the 17 events ranged from 0.064 mg/L to 1.56 mg/L. All influent data greater than 0.5 mg/L were reduced to 0.5 mg/L, the upper limit to the TAPE allowed influent concentration range, prior to calculating the pollutant removal. A bootstrap estimate of the LCL95 of the mean total phosphorus reduction was 64%. 7. The system experienced rapid sediment loading and needed to be maintained after 1.5 months. Monitoring personnel observed similar sediment loading issues with other systems evaluated at the Test Facility. The runoff from the Test Facility may not be indicative of maintenance requirements for all sites. Laboratory Testing 1. Good Harbour Laboratories (GHL) conducted laboratory testing at their site in Mississauga, Ontario in October 2017 following the New Jersey Department of Environmental Protection Laboratory Protocol for Filtration MTDs. The testing evaluated a 4-foot by 6-foot standard biofiltration chamber and inlet contour rack with bypass weir. The test sediment used during the testing was custom blended by GHL using various commercially available silica sands, which had an average d50 of 69 µm. Based on the lab test results: 'Z� a. GHL evaluated removal efficiency over 15 events at a Maximum Treatment Flow Rate (MTFR) of 37.6 gpm, which corresponds to a MTFR to effective filtration treatment area ratio of 1.80 gpm/ft2. The system, operating at 100% of the MTFR with an average influent concentration of 201.3 mg/L, had an average removal efficiency of 99 percent. b. GHL evaluated sediment mass loading capacity over an additional 16 events using an influent SSC concentration of 400 mg/L. The first 11 runs were evaluated at 100% of the MTFR. The BioPod began to bypass, so the remaining 5 runs were evaluated at 90% of the MTFR. The total mass of the sediment captured was 245.0 lbs and the cumulative mass removal efficiency was 96.3%. 2. Herrera Environmental Consultants Inc. conducted laboratory testing in September 2014 at the Seattle University Engineering Laboratory. The testing evaluated the flushing characteristics, hydraulic conductivity, and pollutant removal ability of twelve different media blends. Based on this testing, Oldcastle Infrastructure, Inc. selected one media blend, Mix 8, for inclusion in their TAPE evaluation of the BioPodTM Biofilter. a. Herrera evaluated Mix 8 in an 8-inch diameter by 36-inch tall polyvinyl chloride (PVC) column. The column contained 18-inches of Mix 8 on top of 6-inches of pea gravel. The BioPod will normally include a 3-inch mulch layer on top of the media layer; however, this was not included in the laboratory testing. b. Mix 8 has a hydraulic conductivity of 218 inches per hour; however, evaluation of the pollutant removal ability of the media was based on an infiltration rate of 115 inches per hour. The media was tested at 75%, 100%, and 125% of the infiltration rate. Based on the lab test results: • The system was evaluated using natural stormwater. The dissolved copper and dissolved zinc concentrations in the natural stormwater were lower than the TAPE influent standards; therefore, the stormwater was spiked with 66.4 mL of 100 mg/L Cu solution and 113.6 mL of 1,000 mg/L Zn solution. • The BioPod removed an average of 81 % of TSS, with a mean influent concentration of 48.4 mg/L and a mean effluent concentration of 9.8 mg/L. • The BioPod removed an average of 94% of dissolved copper, with a mean influent concentration of 10.6 µg/L and a mean effluent concentration of 0.6 µg/L. • The BioPod removed an average of 97% of dissolved zinc, with a mean influent concentration of 117 µg/L and a mean effluent concentration of 4 µg/L. • The BioPod removed an average of 97% of total phosphorus, with a mean influent concentration of 2.52 mg/L and a mean effluent concentration of 0.066 mg/L. When total phosphorus influent concentrations were capped at the TAPE upper limit of 0.5 mg/L, calculations showed an average removal of 87%. Other BioPod Related Issues to be Addressed By the Company: 1. Conduct hydraulic testing to obtain information about maintenance requirements on a site with runoff that is more typical of the Pacific Northwest. Technology Description: Download at hops :Holdcastleprecast. com/stormwater/bioretention- biofiltration-applications/bioretention-biofiltration- solutions/ Contact Information: Applicant: Chris Demarest Oldcastle Infrastructure, Inc. (925) 667-7100 Chris.demarest@oldcastle.com Applicant website: htips://oldcastleprecast.com/stormwater/ Ecology web link: kgs:Hecologa. og v/Regulations-Permits/Guidance-technical assistance/Stormwater-permittee-uuidance-resources/Emeraina-stormwater-treatment- technologies Ecology: Douglas C. Howie, P.E. Department of Ecology Water Quality Program (360) 407-6444 douglas.howieAecy.wa.gov Revision History Date Revision March 2018 GULD granted for Basic Treatment March 2018 Provisional GULD granted for Enhanced and Phosphorus Treatment June 2016 PULD Granted April 2018 GULD for Basic and Provisional GULD for Enhanced and Phosphorus granted, changed name to BioPod from TreePod July 2018 GULD for Enhanced and Phosphorus granted SECTION V CONVEYANCE SYSTEM ANALYSIS AND DESIGN CONVEYANCE SYSTEM ANALYSIS AND DESIGN Analysis and design of any proposed conveyance systems will be provided during the engineering design phase. SECTION VI SPECIAL REPORTS AND STUDIES �EORESOURCES """ earth science & geotechnical engineering 4809 Pacific Hwy. E. I Fife, Washington 98424 1 253.896.1011 ( www. georesources. rocks Asegedom Woldetekle 28950 - 181h Avenue South Federal Way, Washington 98003 August 28, 2023 Updated Geotechnical Engineering Report Proposed Short Plat 29850 - 18th Avenue South Federal Way, Washington PN: 3674400-155,-160 Doc ID: Woldetekle18thAveS.RG INTRODUCTION This Updated Geotechnical Engineering Report summarizes our site observations, subsurface explorations, laboratory testing and engineering analyses, and provides geotechnical recommendations and design criteria for the proposed short plat to be constructed at 29850 - 18th Avenue South in Federal Way, Washington. The approximate location of the site shown on the Site Location Map, Figure 1. Our understanding of the project is based on our conversations with Svetlana Poblete; our previous work at the site; our review of the Preliminary Site Plan prepared by DMP Inc. dated April 21, 2023; our July 3, 2023, site visit and additional explorations, our previous work at the site; and our experience with City of Federal Way development codes. We previously completed a Revised Geotechnical Engineering Report for the site dated September 22, 2011. Because the report is older than 5 years, the report needs to be updated. Furthermore, a retaining wall is now proposed on the eastern property boundary, and the City of Federal Way development codes have changed, necessitating an updated report. Based on the topography obtained on the King County iMap, and the Preliminary Site Plan, we anticipate the proposed wall will be a concrete cast -in -place retaining wall. The proposed plat layout is presented on the Site & Exploration Plan, Figure 2. PURPOSE & SCOPE The purpose of our services was to evaluate the surface and subsurface conditions across the site as a basis for addressing the City of Federal Way development codes as well as providing geotechnical recommendations and design criteria for the proposed short plat. Specifically, the scope of services for this project included the following: 1. Reviewing the available geologic, hydrogeologic, and geotechnical data for the site area; 2. Performing two hand borings with porter sampling in the eastern portion of the site; and, 3. Updating our previously written Revised Geotechnical Engineering Report with the new development codes, specifically, updating to the 2018 IBC, and summarizing our site observations, conclusions, and our geotechnical recommendations and design criteria, along with the supporting data. 9 Woldeteklel 8thAveS.RG August 28, 2023 page 12 The above scope of work was summarized in our Proposal for Geotechnical Engineering Services dated June 14, 2023. We received written authorization to proceed June 19, 2023. SITE CONDITIONS Surface Conditions The site consists of two contiguous tax parcels located at 29850 - 18th Avenue South in Federal Way, Washington. According to the provided Site Plan and King County iMap, the parcels, when combined, are irregular in shape, measures approximately 180 feet wide (north to south) by approximately 405 to 460 feet long (east to west) and encompasses approximately 1.73 acres. The site is bounded by existing residential development to the north, east, and south, and by 181h Avenue South to the west. According to topographic information obtained from King County iMap and our site observations, the ground surface of the site generally slopes up to the east from 18th Avenue South, From 18th Avenue South, the ground surface slopes up to the east at approximately 15 to 20 percent over a topographic relief of approximately 10 feet. In the central and eastern portions of the site, the ground surface slopes up to the west at approximately 2 to 5 percent. Along the eastern extent of the site, the ground surface slopes steeply up to the west at approximately 40 to 60 percent over a topographic relief of approximately 20 feet. The total topographic relief of the site is on the order of 40 feet. The existing site layout and topography is shown on the Site Vicinity Map, Figure 3. Vegetation across the flatter cleared area of the site generally consists of maintained grass lawn and typical residential landscaping. The eastern slope is vegetated with mixed conifers and scattered deciduous trees. No seeps, springs, or standing water was observed during our site reconnaissance. No signs of erosion or slope instability were observed during our site visit. Site Soils The USDA Natural Resource Conservation Service (NRCS) Web Soil Survey for King County indicates the site soils are Alderwood gravelly sandy loam (AgC and AgD) soils and Arents, Alderwood material (AmB). An excerpt of the soils map for this area is provided as Figure 4. • Alderwood gravellysandyloam (AgC and AgD): The Alderwood soils are derived from glacial drift and/or glacial outwash over dense glaciomarine deposits and are included in hydrologic soils group B. The AgC soils are mapped as underlying the southwest corner of the site, form on slopes of 8 to 15 percent, and are considered to have a "moderate" erosion hazard when exposed. The AgD soils are mapped as underlying the eastern portion of the site, form on slopes of 15 to 30 percent, and are considered to have a "moderate to severe" erosion hazard when exposed. • Arents, Alderwood material (AmD): The Arents soils are mapped as underlying the majority of the site These soils are derived from basal till, form on slopes of 0 to 6 percent, are considered to have a "slight" erosion hazard when exposed, and are included in hydrologic soils group B/ D. Site Geology The Lidar-revised geologic map of the Poverty Bay 7.5' quadrangle, King and Pierce Counties, Washington (Tabor et al, 2014) maps the site geology as being underlain by Glacial Till (Qvt) with GEORESOURCES earth science & geotechnical engineering 017- Woldeteklel 8thAveS.RG August 28, 2023 page 13 Advance Outwash Deposits (Qva) being mapped to the west of the site. No landslides, mass wastage deposits, or alluvial fans are mapped on or within the site vicinity. An excerpt of the above referenced geologic map is attached as Figure 5 and detailed descriptions of the geologic units mapped in the site area are included below. • Glacial till (Ovt): Glacial till typically consists of a heterogeneous mixture of clay, silt, and sand, and gravel that was deposited at the base of the prehistoric continental glacial ice mass and was subsequently over -ridden. As such, glacial till is considered over -consolidated and exhibits high strength and low compressibility characteristics where undisturbed. Infiltration feasibility in these soils is generally poor. • Advance outwash (Qva): Advance outwash was deposited by meltwater stream emanating from the advancing ice mass and generally consists of well graded, lightly stratified to locally cross - bedded mixtures of sand and gravel. These soils are considered to be over -consolidated and offer moderate to high strength characteristics when undisturbed. Infiltration potential is generally favorable based on grain size but can vary. We reviewed both the WA Department of Natural Resources (WA DNR) 2017 Landslide Compilation and the Landslide Inventory datasets forthe site vicinity. The Landslide Inventory dataset maps landslide landforms based on criteria provided in the Protocol for Landslide Mapping from LiDAR Data in Washington State (Slaughter, et al, 2017) and the Oregon Department of Geology and Mineral Industries (DOGAMI) protocol described in Special Paper 42 (Burns and Madin, 2009. The WA DNR Landslide inventory does not map the site for "moderate" or "high" susceptibly to shallow or deep landslides. No landslides are mapped within 300 feet of the subject site. Subsurface Explorations On July 28, 2011, a representative from GeoResources, LLC (GeoResources) visited the site and monitored the excavation of five test pits to depths of approximately 7 to 12 feet below the existing ground surface, logged the subsurface conditions encountered in each test pit, and obtained representative soil samples. The test pits were excavated by a small track -mounted excavator operated by a licensed earthwork contractor working under subcontract for GeoResournces. The number and location of our test pits were selected in the field based on project information provided by you at the time of excavation, our understanding of the proposed development, consideration for underground utilities, existing site conditions, and current site usage. On July 3, 2023, we returned to the site and excavated two hand borings to depths of 4%2 to 5'/2 feet below the existing grades, where refusal conditions were encountered. Our field representatives logged the subsurface conditions encountered in each exploration and obtained representative soil samples. The locations, and depths of our hand boring explorations were selected based on our understanding of the location of the proposed retaining wall and were adjusted in the field based on consideration for underground utilities, existing site conditions, site access limitations, and encountered stratigraphy. Field representatives from our office completed logs of the subsurface conditions encountered, obtained representative soil samples, and observed pertinent site features. Representative soil samples obtained from the explorations were placed in sealed plastic bags and taken to our laboratory for further examination and testing as deemed necessary. Relatively disturbed, but representative, soil samples were obtained at selected depths using portable Porter soil sampling equipment. The hand -operated equipment consists of a 1.4-inch G E 0 R E S 0 U R C E S earth science &. geotechnical engineering Woldeteklel8thAVeS.RG August 28, 2023 page 14 outside -diameter (1.0 inch inside -diameter) split -spoon sampler connected to extension rods of the same diameter as the barrel. The Porter sampling method consists of driving the sampler 18-inches into the soil with a 45-pound weight, with a drop of 18 inches. The number of blows required to drive the sampler through each 6-inch interval is counted, and the total number of blows struck during the final 12 inches is recorded as the Porter Penetration Test (PPT). If a total of 50 blows are recorded within any 6-inch interval (refusal), the driving is stopped, and the blow counts are recorded as 50 blows for the actual distance the sampler was driven. The resulting PPT values indicate the relative density of granular soils and the consistency of cohesive soils, and the energy and size of the test are correlated to approximately match the values that would be obtained from a Standard Penetration Test. The subsurface explorations excavated as part of this evaluation indicate the subsurface conditions at specific locations only, as actual subsurface conditions can vary across the site. Furthermore, the nature and extent of such variation would not become evident until additional explorations are performed or until construction activities have begun. The soil densities presented on the test pit logs are based on the difficulty of excavation and our experience. Representative soil samples obtained from the explorations were placed in sealed plastic bags and taken to our laboratory for further examination and testing as deemed necessary. The number and approximate locations of our test pits are shown on the Site & Exploration Plan, Figure 2. The locations depicted were determined by pacing or taping from existing site features and reference points; as such, the locations should only be considered as accurate as implied by the method of measurement. The soils encountered were visually classified in accordance with the Unified Soil Classification System (USCS) and ASTM D2488. The USCS is included in Appendix A as Figure A-1, while the descriptive logs of our test pits are included as Figures A-2 through A-3. TABLE 1: APPROXIMATE LOCATIONS, ELEVATIONS, AND DEPTHS OF EXPLORATIONS Surface Termination Termination Test Pit Functional Location Elevation' Depth Elevation' Number ` (feet) (feet) (feet) TP-1 Southeast portion of site 465 7'/2 457%z TP-2 Central portion of site 462 81/2 453%2 TP-3 Northeast portion of site 465 7 458 TP-4 Central portion of site 461 12 449 TP-5 Northwest portion of site 458 10'/z 447'/z 1113-1 Northeast corner of site 475 5%z 469% HB-2 Eastern portion of site 480 41/2 475%2 Notes: 1 = Surface elevations estimated by interpolating between contours on King County Map (NAVD88) Subsurface Conditions At the location of our explorations, we encountered somewhat uniform subsurface conditions that, in our opinion, generally confirmed the mapped stratigraphy. In general, we observed topsoil mantling weathered glacial till, underlain by undisturbed glacial till. These different soil layers are GEGRESOURCES earth science & geotechnical engineering Woldeteklel8thAVeS. RG August 28, 2023 page 15 described below, and Table 2, below, summarizes the approximate thicknesses, depths, and elevations of selected soil layers. Logs of explorations are available in Appendix A. • Topsoil: At the locations explored, we encountered approximately Yz to 2Yz feet of topsoil. • Weathered Glacial Till: Underlying the topsoil in all explorations except for test pits TP-1, we encountered approximately 1Yz to 3 feet of brown silty sand with variable amounts of gravel in a loose to medium dense, moist condition. We interpret these soils to be weathered glacial till. • Glacial till: Underlying the topsoil and weathered glacial till encountered in all other explorations, we encountered grey gravelly silty sand in a dense to very dense, moist condition. We interpret these soils to be glacial till. The glacial till was encountered to the full depth explored in all explorations. TABLE 2: APPROXIMATE THICKNESS, DEPTHS, AND ELEVATION OF SOIL TYPES ENCOUNTERED Thickness of Thickness of Weathered Depth to Elevation of Glacial Exploration Topsoil Glacial Till ' Undisturbed Till Number (feet) ,- (feet) Glacial Till (feet) (feet) TP -1 NE 2 2 463 TP-2 1 Yz 13/a 3'/a 4583/a TP-3 Y2 3 3'/2 461 Yz TP-4 1 23/a 33/a 457Ya TP-5 Yz 3Ya 33/a 454Ya H B-1 2Y2 1 Yz 4 471 H B-2 1 Yz 1 Yz 3 477 Notes: = Surface elevations estimated by interpolating between contours obtained from King County iMap (NAVD88) NE=Not Encountered Laboratory Testing Geotechnical laboratory tests were performed on select samples retrieved from our explorations to estimate index engineering properties of the soils encountered. Laboratory testing included visual soil classification per ASTM D2488 and ASTM D2487, moisture content determinations per ASTM D2216, and grain size analyses per ASTM D6913 standard procedures. The results of the laboratory tests are included in Appendix B and summarized below in Table 3. GEORESOURCES earth science & geotechnical engineering Woldetekle18thAveS. RG August 28, 2023 page 16 TABLE I LARORATORV TEST RESULTS FOR ON -SITE SOILS Gravel Sand Silt/Clay Sample Soil Type Content Content Content Dio Ratio (percent) (percent) (percent) TP-3, S-1, D: % -3' SM 26.9 56.1 17.0 <0.075 TP-5, S-1, D:'/z -2%z' SM 32.2 52.9 14.9 <0.075 HB-1, S-4, D: 4%z' SM 23.5 50.1 1 26.4 1 <0.075 Groundwater Conditions No groundwater seepage was observed at the time the test pits and hand borings were excavated; however, the explorations were excavated during the dry season months. Orange iron oxide staining, otherwise known as mottling, which can be evidence of a perched groundwater table was observed in test pit TP-4 and test pit TP-5 at approximately 2%z and 2 feet below ground surface respectively. The stratigraphy observed at each test pit typically creates the conditions for the development of perched groundwater following wet weather. Perched groundwater develops when the vertical and/or horizontal infiltration of stormwater runoff is slowed or impeded by a soil with low permeability, such as the undisturbed glacial till observed at each test pit. Accordingly, soil conditions that consist of relatively permeable soils overlying relatively impermeable soils near the surface are typically necessary. Perched groundwater tables, by definition, are located within a shallow unconfined aquifer that overlies an aquitard. Perched groundwater tables are typically limited in thickness and can vary widely in lateral extent. Relatively rapid fluctuations of groundwater levels should be expected with seasonality and precipitation events, which may include complete dehydration of the aquifer during the dry season. CONCLUSIONS AND RECOMMENDATIONS Based on the results of our data review, site reconnaissance, subsurface explorations and our experience in the area, it is our opinion that site is suitable for the proposed development from a geotechnical standpoint. Pertinent updated conclusions and geotechnical recommendations regarding the design and construction of the proposed development, consistent with the current building code and stormwater manual are presented below. The City of Federal Way Critical Areas Ordinance for Geologically Hazardous Areas state "geologically hazardous areas shall mean areas that, because of their susceptibility to erosion, landsliding, seismic or other geological events, are not suited to siting commercial, residential or industrial development consistent with public health or safety concerns." Applicable sections of the Federal Way Revised Code are included below in italics, and our analysis immediately follows. Based on our site reconnaissance and literature review, we do not interpret the site to be located in a Geologically Hazardous Area. Erosion Hazard Areas per Federal Way Revised Code The FWRC, Chapter 19.05.070.G(1) defines erosion hazard areas as: "those areas identified by the U.S. Department of Agriculture's (USDA) Natural Resource Conservation Service (NRCS) as having a moderate to severe or severe to very GE©RESOURCES earth science & geotechnical engineering Woldetekle18thAveS.RG August 28, 2023 page (7 severe rill and inter -rill erosion hazard due to natural agents such as wind, rain, splash, frost action or stream flow; those areas containing the following group of soils when they occur on slopes of 15 percent or greater. Alderwood-Kitsap ('AkF'g, Alderwood gravelly sandy loam ('AgD'9, Kitsap silt loam ("KpD'), Everett ("EvD'g, and Indianola ("InD'9, and those areas impacted by shore land and/or stream bank erosion" The site soils are mapped as Alderwood gravelly sandy loam (AgC and AgD) and Arents, Alderwood material (AmB) being mapped upslope from the site. The site is not impacted by shoreline or subject to stream bank erosion. The AmB soils on the flatter portion of the site are listed as having a "slight" erosion hazard. The AgD soils, mapped on the sloping, eastern portion of the site do meet the "moderate to severe" designation. However, as stated, the eastern slopes were well vegetated, and we did not observe signs of erosion at the site. Therefore, it is our opinion that while the site meets the technical definition of an erosion hazard, the site does not have an actual erosion hazard at the site. Conventional construction BMP's should be installed prior to any construction and should provide adequate erosion control for the disturbed areas of the site. It is critical that the installed erosion control measures be monitored and maintained, and if necessary modified based on changing site conditions. In the event that the site is not worked for 7 days or more, the disturbed areas should be adequately erosion protected and maintained in the event of a significant storm event. This may include the use of plastic sheeting or mulch. Erosion control should specifically include the installation of silt fencing along the downslope and side slopes of the active construction area. Straw waddles and berms may also be necessary. We have not been provided with a copy of the proposed Temporary Erosion and Sediment Control (TESL) plan at this time. However, provided standard BMP's are installed prior to beginning construction, the potential for erosion or sediment leaving the site should be minimal. Landslide Hazard Areas per Federal Way Revised Code The FWRC, Chapter 19.05.070.G(2) defines landslide hazard areas as "those areas potentially subject to episodic downslope movement of a mass of soil or rock including but not limited to the following areas."These are typically characterized as having the following indicators: a. Any area with a combination of.• i. Slopes greater than 15 percent, ii. Permeable sediment overlying a relatively impermeable sediment or bedrock; iii. Springs or groundwater seeps. b. Any area which has shown movement during the Holocene epoch, from 10,000 years ago to the present, or which is underlain by mass wastage debris of that epoch. c. Any area potentially unstable as a result of rapid stream incision, stream bank erosion or undercutting by wave action. d. Any area located in a ravine or on an active alluvial fan, presently or potentially subject to inundation by debris flows or flooding. e. Those areas mapped as Class U (unstable), UOS (unstable old slides), and URS (unstable recent slides) by the Department of Ecology's Coastal Zone Atlas. G E 0 R E S 0 U R C E S earth science & geotechnical engineering Woldeteklel 8thAveS.RG August 28, 2023 page 18 f. Areas designated as quaternary slumps, earthflows, mudflows, lahars, or landslides on maps published by the U.S. Geological Survey or Washington State Department of Natural Resources. g. Slopes having gradients greater than 80 percent subject to rockfall during seismic shaking h. Any area with a slope of 40 percent or steeper and with a vertical relief of 10 or more feet except areas composed of consolidated rock. A slope is delineated by establishing its toe and top and is measured by averaging the inclination over at least 10 feet of vertical relief. The east portion of the site contains slopes steeper than 15 percent, however we do not interpret the site to be underlain by an adverse geologic contact. No seeps or springs were noted on the slope or on any other portion of the site. No areas on the site were observed or are mapped as having shown movement during the Holocene epoch or is underlain by mass wastage debris of that epoch. As stated, the site is not mapped along a shoreline or streambank. No areas of alluvial fans are mapped nor were any alluvial fans noted in the vicinity of the site at the time of our past site visits. The site is not covered by the Department of Ecology Coastal Atlas, however we would interpret the site to be mapped as "stable". The site's slopes are not steeper than 80 percent or subject to rock fall during seismic shaking. A portion of the slope on the eastern portion of the site is steeper than 40 percent with 10 or more feet of vertical relief. However, a retaining wall will be constructed in this area, effectively eliminating the hazard. Based on our observations and literature review, the site does have one of the above listed indicators (areas steeper than 40 percent with 10 or more feet of vertical relief). However, as stated, a retaining wall will be constructed in this area, and the slope was well vegetated at the time of our site visit. Therefore, no additional buffer for landslide hazard areas should be imposed by the City of Federal Way. Seismic Hazards per Federal Way Revised Code Earthquake -induced geologic hazards per City of Federal Way Revised Code (2016 FWRC), Chapter 19.05.070.G(3) may include liquefaction, lateral spreading, slope instability, and ground surface fault rupture. Based on our review of the Liquefaction Susceptibility Map of King County, Washington (Palmer, et al, 2004), included as Figure 6, the site is within an area mapped as having a ,'very low" susceptibility to liquefaction. In our opinion, the potential for liquefaction and lateral spreading is not significant because of the consolidated nature of the on -site soils. We also reviewed the Washington State Department of Natural Resources Geologic Information Portal Fault Hazards map, Figure 7. The Tacoma fault zone is located approximately 675 feet north of the site. No evidence of lateral spreading, slope instability, or ground surface fault rupture were observed at the site. It is our opinion that provided the proposed development is adequately designed and constructed, the development should not have any greater seismic risk than other similarly designed structures in the area. Seismic Design The site is located in the Puget Sound region of western Washington, which is seismically active. Seismicity in this region is attributed primarily to the interaction between the Pacific, Juan de Fuca and North American plates. The Juan de Fuca plate is subducting beneath the North American plate at the Cascadia Subduction Zone (CSZ). This produces both intercrustal (between plates) and GEORESOURCES earth science & geotechnical engineering Woldeteklel 8thAveS. RG August 28, 2023 Page 19 intracrustal (within a plate) earthquakes. In the following sections we discuss the design criteria and potential hazards associated with the regional seismicity. Seismic Site Class Based on our observations and the subsurface units mapped at the site, we interpret the structural site conditions to correspond to a seismic Site Class "C" for the onsite soils in accordance with the 2018 IBC (International Building Code) documents and ASCE 7-16 Chapter 20 Table 20.3-1. This is based on our range of blow counts for the soils encountered at the site. These conditions are assumed to be representative for the subsurface across the site. Design Parameters The U.S. Geological Survey (USGS) completed probabilistic seismic hazard analyses (PSHA) for the entire country in November 1996, which were updated and republished in 2002 and 2008. We used the ATC Hazard by Location website to estimate seismic design parameters at the site. Table 4, below, summarizes the recommended design parameters. TABLE 4: ASCE 7-16 PARAMETERS FOR DESIGN OF SEISMIC STRUCTURES Spectral Response Acceleration (SRA) and Site Coefficients Short Period Mapped SRA SS = 1.334g Site Coefficients (Site Class C) Fa = 1.200 Maximum Considered Earthquake SRA SMs = 1.6019 Design SRA Sys = 1.068g Peak Ground Acceleration The mapped peak ground acceleration (PGA) for this site is 0.564g. To account for site class, the PGA is multiplied by a site amplification factor (FPGA) of 1.2. The resulting site modified peak ground acceleration (PGAM) is 0.677g. In general, estimating seismic earth pressures (kh) by the Mononobe-Okabe method are taken as 50 percent of the PGAM, which would be 0.339g. Foundation Support Based on the subsurface conditions encountered at our test pit and hand boring locations and our understanding of the proposed development, we recommend that spread footings bear directly on the dense native weathered and undisturbed glacial till soils. Bearing Surface Preparation The soil at the base of the foundation excavations should be disturbed as little as possible. All loose, soft, or unsuitable material should be removed. Where materials are over -excavated below a footing bearing surface, the excavated materials should be replaced with structural fill or controlled density fill (CDF). Removal of unsuitable soils, if encountered, below the footings should extend beyond the foundation edges 1 foot horizontally for every 1 foot of vertical excavation. If prepared bearing surfaces remain open for an extended time, we recommend they be protected by placing a GEORESOURCES earth science & geotechnical engineering Wo I d ete kl e 18t hAveS. RG August 28, 2023 page 1 10 rat slab of CDF or a 4 to 6 inch lift of crushed rock. A representative from our firm should observe the foundation excavations to determine if suitable bearing surfaces have been prepared. Spread Footing Design For the single-family residences, we recommend a minimum width of 24 inches for isolated footings and at least 16 inches for continuous wall footings. All footing elements should be embedded at least 18 inches below grade for frost protection. Lateral loads may be resisted by friction on the base of footings and floor slabs and as passive pressure on the sides of footings. Lateral loads may be resisted by a combination of base friction and passive pressure against the footings. Spread footing design parameters are provided in Table 5, below. The bearing capacity provided below includes a factor of safety of 3.0 and the passive earth pressure includes a factor of safety of 1.5 to limit lateral deflections. Disturbance of the foundation bearing surface during construction could result in larger settlements than estimated herein. The allowable bearing value may be increased by one-third for transient loads such as those induced by seismic events or wind loads. The estimated settlement is based on typical residential loads. TABLE 5: SPREAD FOOTING DESIGN PARAMETERS Parameter Value FS Allowable Bearing Pressure (psf) 2,000 3.0 Allowable Coefficient of Friction 0.35 1.5 Allowable Passive Pressure (pcf) 300 1.5 Minimum footing Width - Isolated (inches) 24 -- Minimum footing Width - Strip (inches) 16 -- Estimated Total Settlement (inches) < 1 -- Estimated Differential Settlement Over 50 feet (inches) < %2 -- Floor Slab Support Slab -on -grade floors, where constructed, should be supported on the still native soils or on structural fill prepared as described in the "Structural Fill" section of this report. Any areas of old fill material, if encountered, should be evaluated during grading activity for suitability of structural support. Areas of significant organic debris should be removed. We recommend that floor slabs be directly underlain by a minimum of 4-inch-thick pea gravel or washed 5/8-inch crushed rock and should contain less than 2 percent fines. This layer should be placed and compacted to an unyielding condition. A synthetic vapor retarder is recommended to control moisture migration through the slabs. This is of particular importance where moisture migration through the slab is an issue, such as where adhesives are used to anchor carpet or tile to the slab. -- GEORESOURCES earth science & geotechnical engineering Woldetekle18thAveS. RG August 28, 2023 page 1 11 A subgrade modulus of 200 pounds per cubic inch may be used for floor slab design. We estimate that settlement of the floor slabs designed and constructed as recommended, will be 1/2 inch or less over a span of 50 feet. Subgrade/Basement Walls The lateral pressures acting on retaining walls (such as basement or grade separation walls) will depend upon the nature and density of the soil behind the wall as well as the presence or absence of hydrostatic pressure. Below we provide recommended design values and drainage recommendations for retaining walls. Design Values For walls backfilled with granular well -drained soil such as gravel backfill for walls or permeable ballast, we provided the appropriate active and at -rest equivalent fluid pressures in Table 6 below. If walls taller than 6 feet are required, as seismic surcharge should be included where required by the code. If walls will be constructed with a backslope and will be braced or otherwise restrained against movement, we should be notified so that we can evaluate the anticipated conditions and recommend an appropriate at -rest earth pressure. TABLE 6: LATERAL EARTH PRESSURES Backfill Material Lateral Earth Pressure Gravel backfill for Permeable Ballast Native Undisturbed Condition, equivalent q fluid density(PCF) Walls (WSDOT 9- (WSDOT 9-03.9(2)) Glacial Till 03.12(2)) At -rest, level backslope 55 45 58 Active, level backslope 35 27 37 Active, 3H:1 V backslope 48 32 50 Active, 2H:lV backslope 55 36 57 Seismic Surcharge 15H 11 H 16H Lateral loads may be resisted by friction on the base of footings and as passive pressure on the sides of footings and the buried portion of the wall, as described in the "Foundation Support" section of this report. Wall Drainage Adequate drainage behind retaining structures is imperative. Positive drainage which controls the development of hydrostatic pressure can be accomplished by placing a zone of drainage behind the walls. Granular drainage material should contain less than 2 percent fines and at least 30 percent retained on the US No. 4 sieve. G E 0 R E S 0 U R C E S earth science & geotechnical engineering Woldeteklel 8thAveS.RG August 28, 2023 page l 12 A minimum 4 inch diameter perforated or slotted PVC pipe should be placed in the drainage zone along the base and behind the wall to provide an outlet for accumulated water and direct accumulated water to an appropriate discharge location. We recommend that a nonwoven geotextile filter fabric be placed between the soil drainage material and the remaining wall backfill to reduce silt migration into the drainage zone. The infiltration of silt into the drainage zone can, with time, reduce the permeability of the granular material. The filter fabric should be placed such that it fully separates the drainage material and the backfill, and should be extended over the top of the drainage zone. Typical wall drainage and backfilling details are shown on Figure 8. A soil drainage zone should extend horizontally at least 18 inches from the back of the wall. The drainage zone should also extend from the base of the wall to within 1 foot of the top of the wall. The soil drainage zone should be compacted to approximately 90 percent of the maximum dry density (MDD), as determined in accordance with ASTM D1557. Over -compaction should be avoided as this can lead to excessive lateral pressures on the wall. A geocomposite drain mat may also be used instead of free draining soils, provided it is installed in accordance with the manufacturer's instructions. Temporary Excavations All job site safety issues and precautions are the responsibility of the contractor providing services/work. The following cut/fill slope guidelines are provided for planning purposes only. Temporary cut slopes will likely be necessary during grading operations or utility installation. All excavations at the site associated with confined spaces, such as utility trenches and retaining walls, must be completed in accordance with local, state, or federal requirements including Washington Administrative Code (WAC) and Washington Industrial Safety and Health Administration (WISHA). Excavation, trenching, and shoring is covered under WAC 296-155 Part N. Based on WAC 296-155-66401, it is our opinion that the weathered till encountered in our explorations would be classified as Type C soils and the undisturbed glacial till would be classified as Type A soils. According to WAC 296-155-66403, for temporary excavations of less than 20 feet in depth, the side slopes in Type A should be sloped at a maximum inclination of 3/4H:1 V or flatter from the toe to top of the slope, and side slopes in Type C soils should have a maximum inclination of 1�/2H:1V. All exposed slope faces should be covered with a durable reinforced plastic membrane during construction to prevent slope raveling and rutting during periods of precipitation. These guidelines assume that all surface loads are kept at a minimum distance of at least one half the depth of the cut away from the top of the slope and that significant seepage is not present on the slope face. Flatter cut slopes will be necessary where significant raveling or seepage occurs, or if construction materials will be stockpiled along the slope crest. Where it is not feasible to slope the site soils back at these inclinations, a retaining structure should be considered. Retaining structures greater than 4-feet in height (bottom of footing to top of structure) or that have slopes of greater than 15 percent above them, should be engineered per Washington Administrative Code (WAC 51-16-080 item 5). This information is provided solely for the benefit of the owner and other design consultants and should not be construed to imply that GeoResources assumes responsibility for job site safety. It is understood that job site safety is the sole responsibility of the project contractor. GEORESOURCES earth science & geotechnical engineering Woldeteklel 8thAveS. RG August 28, 2023 page 113 Site Drainage All ground surfaces, pavements and sidewalks at the site should be sloped to direct surface water away from the structures, property lines, and slopes. Surface water runoff should be controlled by a system of curbs, berms, drainage swales, and or catch basins, and conveyed to an appropriate discharge point. We recommend that footing drains are installed for the residence in accordance with IBC 1805.4.2, and basement walls (if utilized) have a wall drain as describe above. The roof drain should not be connected to the footing drain. Stormwater Infiltration The soils at the site consist of weathered glacial till mantling undisturbed glacial till, which is considered an impermeable surface. Because of the indurate nature of the undisturbed glacial till, deep infiltration at the site is not feasible. Low Impact Development (LID) BMPs such as bioretention and/or permeable pavement is not feasible where the seasonal high groundwater or an underlying impermeable/low permeability layer (hardpan) would create saturated conditions within 1 foot of the bottom of the lowest gravel base course. Based on our explorations throughout the project site, permeable pavement could be considered for this project to help with managing stormwater, provided the proposed bottom of facility elevations are within the weathered glacial till soils observed in our explorations, and at least 1 foot in elevation higher than the undisturbed glacial till contact. Design Infiltration Rate for Infiltration Systems & LID BMPs We completed a soil gradation analysis of a representative sample of the weathered glacial till soils at test pits TP-3 and TP-5 in accordance with ASTM D6913. For a preliminary design infiltration rate, we used the Soil Grain Size Method derived from the Massmann equation to determine the preliminary measured rate of the weathered glacial till soils encountered at the site. We applied correction factors to the measured infiltration rate in general accordance with the correction factors presented in the 2021 KCSWDM. The correction factors applied were for test method (0.4 for the Soil Grain Size Method), facility geometry (0.25) and plugging (0.7). After applying the appropriate correction factors to the preliminary measured rate, we recommend a design infiltration rate of 0.7 inches per hour be used for infiltration systems and BMPs founded in the weathered glacial till soils encountered at the site. In -situ infiltration testing in accordance with the 2021 KCSWDM should be completed once a final location and bottom elevation is determined for any infiltration system. Construction Considerations Appropriate design, construction and maintenance measures will be required to ensure the infiltration rate can be effectively maintained overtime. Stormwater Best Management Practices (BMPs) in accordance with the 2021 KCSWDM should be included in the project plans and specifications to minimize the potential forfines contamination of Low Impact Development BMPs or infiltration systems utilized at the site. If an overflow is incorporated into the final design of an infiltration system, we recommend the overflow be connected to an existing stormwater system or directed to another discharge point away from any existing or proposed structures. Suspended solids could clog the underlying soil and reduce the infiltration rate of the facilities. Additional measures may also be taken during construction to minimize the potential of fines GEORESOURCES earth science & geotechnical engineering ■ Woldetekle18thAveS. RG August 28, 2023 page 114 contamination of the proposed infiltration system, such as utilizing an alternative storm water management location during construction or leaving the bottom of the permanent systems 1 to 2 feet high, and subsequently excavating to the finished grade once the site soils have been stabilized. All contractors working on the site (builders and subcontractors) should divert sediment laden stormwater away from proposed infiltration facilities during construction and landscaping activities. No concrete trucks should be washed or cleaned, and washout areas should not be within the vicinity of the proposed infiltration facilities. Permanent Cut and Fill Slopes Permanent slopes in soil should be no steeper than 2H:1 V. Fill slopes constructed on grades that are steeper than 5H:1 V should be constructed in accordance with Appendix J of the 2018 IBC and should utilize proper keying and benching methods. The benches should be 1%z times the width of the equipment used for grading and be a maximum of 3 feet in height. Subsurface drainage may be required in areas where significant seepage is encountered during grading. Collected drainage should be directed to an appropriate discharge point. Surface drainage should be directed away from all slope faces. All permanent slopes should be protected from erosion as soon as feasible after grading is completed. Typical erosion control methods per the 2021 KCSWDM should be sufficient for proposed site grading activities. Additionally, permanent slopes should be planted with a hardy vegetative groundcover, mulched, or armored with quarry spalls as soon as feasible after grading is completed. EARTHWORK RECOMMENDATIONS Site Preparation All structural areas on the site to be graded should be stripped of vegetation, organic surface soils, and other deleterious materials including existing structures, foundations, or abandoned utility lines. Organic topsoil is not suitable for use as structural fill, but may be used for limited depths in non-structural areas. Stripping depths ranging from 6 to 30 inches should be expected to remove these unsuitable soils. Areas of thicker topsoil or organic debris may be encountered in areas of heavy vegetation or depressions. Although not encountered in our borings, areas of fill material may be encountered in the footprint of the existing site improvements. Where placement of fill material is required, the stripped/exposed subgrade areas should be compacted to a firm and unyielding surface prior to placement of any fill. Excavations for debris removal should be backfilled with structural fill compacted to the densities described in the "Structural Fill" section of this report. We recommend that a member of our staff evaluate the exposed subgrade conditions after removal of vegetation and topsoil stripping is completed and prior to placement of structural fill. The exposed subgrade soil should be proof -rolled with heavy rubber -tired equipment during dry weather or probed with a 1/2-inch-diameter steel rod during wet weather conditions. Soft, loose, or otherwise unsuitable areas delineated during proofrolling or probing should be recompacted, if practical, or over -excavated and replaced with structural fill. The depth and extent of overexcavation should be evaluated by our field representative at the time of construction. The areas of old fill material should be evaluated during grading operations to determine if they need mitigation; recompaction or removal. GEORESOURCES earth science & geotechnicat engineering fl Woldeteklel 8thAveS.RG August 28, 2023 page 1 15 Structural Fill All material placed as fill for the proposed wall should be placed as structural fill. Material placed as structural fill should be free of debris, organic matter, trash, and cobbles greater than 4- inches in diameter. The moisture content of the fill material should be adjusted as necessary for proper compaction. Materials The suitability of material for use as structural fill will depend on the gradation and moisture content of the soil. As the amount of fines (material passing US No. 200 sieve) increases, soil becomes increasingly sensitive to small changes in moisture content and adequate compaction becomes more difficult to achieve. During wet weather, we recommend use of well -graded sand and gravel with less than 5 percent (by weight) passing the US No. 200 sieve based on that fraction passing the 3/a-inch sieve, such as Gravel Backfill for Walls (WSDOT 9-03.12(2)). If prolonged dry weather prevails during the wall construction, higher fines content (up to 10 to 12 percent) may be acceptable. Placement and Compaction The appropriate lift thickness will depend on the structural fill characteristics and compaction equipment used, but it is typically limited to 4 to 6 inches for hand operated equipment; thicker lifts may be appropriate for larger equipment. For larger equipment such as a hoe-pac or drum roller, we recommend a maximum loose -lift thickness of 12 inches. Structural fill should be compacted to at least 95 percent of the MDD as determined by the Modified Proctor (ASTM D1557). Additionally, the moisture content should be maintained within 3 percent of the optimum moisture content in accordance with ASTM D1557. Suitability of On -Site Materials as Fill During dry weather construction, the non -organic on -site soil may be considered for use as structural fill, provided it meets the criteria described above in the "Structural Fill" section and can be compacted as recommended. If the soil material is over -optimum in moisture content when excavated, it will be necessary to aerate or dry the soil prior to placement as structural fill. The weathered and undisturbed glacial till soils are generally comparable to "Common Borrow" (WSDOT Standard Specification 9-03.14(3)) material and should be suitable for use as structural fill provided the moisture content is maintained within 2 percent of the optimum moisture level. We recommend that completed graded -areas be restricted from traffic or protected prior to wet weather conditions. The graded areas may be protected by paving, placing asphalt -treated base, a layer of free -draining material such as pit run sand and gravel or clean crushed rock material containing less than 5 percent fines, or some combination of the above. Erosion Control Weathering, erosion and the resulting surficial sloughing and shallow land sliding are natural processes. As noted, no evidence of surficial raveling or sloughing was observed at the site. To manage and reduce the potential for these natural processes, we recommend erosion hazards be mitigated by applying Best Management Practices (BMPs), as outlined in the 2021 KCSWDM. The project civil engineer/designer should prepare a drainage and temporary erosion control plan per the KCSWDM showing which BMPs will be used. GEORESOURCES g earth science & geotechnicaf engineering Woldetekle18thAveS. RG August 28, 2023 page 116 Temporary erosion control BMPs should be installed at the site prior to the beginning of clearing, grading, or other construction activities, and should be updated and maintained throughout construction until final site stabilization is established. Temporary erosion control BMPs may include, but are not limited to: • Silt fencing and appropriate soil stockpiling techniques to prevent silty stormwater from leaving the site, • jute matting, hydroseeding, or plastic covering to protect exposed soils, • Straw wattles, quarry spall armoring, check dams, or other energy attenuation BMPs to slow the flow of stormwater over slopes and within drainage channels, and, • Swales and berms to convey construction stormwater away from any slopes. Erosion protection measures should be in place prior to the start of grading activity on the site. Where native vegetation is removed because of clearing and grading activities, a dense vegetative groundcover, grass lawn, or native vegetation should be reestablished as soon as feasible. Permanent erosion control, such as mulched landscaping areas, groundcovers, hardscaping, or grass lawns, should be established as soon as feasible once final grades have been completed. All permanent erosion control methods should be maintained after construction activities have been completed. LIMITATIONS We have prepared this report for Asegedom Woldetekle and other members of the permitting and design team for use in evaluating a portion of this project. Subsurface conditions described herein are based on our observations of exposed soils on the parcel. This report may be made available to regulatory agencies or others, but this report and conclusions should not be construed as a warranty of subsurface conditions. Subsurface conditions can vary over short distances and can change with time. Variations in subsurface conditions are possible between the explorations and may also occur with time. A contingency for unanticipated conditions should be included in the budget and schedule. Sufficient monitoring, testing and consultation should be provided by our firm during construction to confirm that the conditions encountered are consistent with those indicated by the explorations, to provide recommendations for design changes should the conditions revealed during the work differ from those anticipated, and to evaluate whether earthwork and foundation installation activities comply with contract plans and specifications. The scope of our services does not include services related to environmental remediation and construction safety precautions. Our recommendations are not intended to direct the contractor's methods, techniques, sequences or procedures, except as specifically described in our report for consideration in design. If there are any changes in the loads, grades, locations, configurations or type of facilities to be constructed, the conclusions and recommendations presented in this report may not be fully applicable. If such changes are made, we should be given the opportunity to review our recommendations and provide written modifications or verifications, as appropriate. GEORESOURCES earth science & geotechnical engineering d Woldeteklel8thAVeS.RG August 28, 2023 page 1 17 We have appreciated the opportunity to be of service to you on this project. If you have any questions or comments, please do not hesitate to call at your earliest convenience. Respectfully submitted, GeoResources, LLC Davis W. Carlsen, GIT Senior Staff Geologist Spa%)W I Andrew E. Schnitger, PE Project Engineer DC:AES:EWH/dc DoclD: Woldetekle18thAveS.RG Attachments: Figure 1: Site location Map Figure 2: Site & Exploration Plan Figure 3: Site Vicinity Map Figure 4: NRCS Soils Map Figure 5: Geologic Map Figure 6: Liquefaction Susceptibility Map Figure 7: WA DNR Fault Hazards Map Figure 8: Typical Wall Drainage & Backfill Detail Appendix A- Subsurface Explorations Appendix B - Laboratory Test Results Eric W. Heller, PE, LG Senior Geotechnical Engineer G E 0 R E S 0 U R C E S � earth science w geotechnical engineering k i I � r P � � cl mM63t , S290hSt, - i 1 r- i t. t1 Ofi F u 1 11 A {. i .S316thSi `t s s3a1'A_t J." D Approximate Site Location Figure created from King County Nap website (https://gismaps.kingcounty.gov/iMap/) V E R E GEo� sou c s earth science & geotechnical engineering 4909 Pacific Hwy, E. I Fife, WA 98424 1 253.896.1011 1 w N georesources rocks Not to Scale I Site Location Map Proposed Short Plat 29850 18t" Avenue South Federal Way, Washington PN: 3674400-155, -160 Doc ID: Woldetekle.18thAveS.F Aug 2023 Figure 1 t! !C0J-4-rADLE' 4 i F.SrANCE AGLESv) . _ a � V11N F-10,12- 3G RIGHT OF `ii ATED ,`nt6 CC 1rE i = ..— TY OF FEDERA WAY - (- {�- HE RECORDIN CzF SHORT PLC, % ; F - r# 'z a � LANDSCAPE r.•p ......... HYDRANT z LOT 313 7,706 SF 0 TRACT .4 (ACCESS) Fri AREA, i�,vb� SF iIf _ i y `t. I1 ir*E - -. WALL OR i ®S ROCKERY -- TP tj .E1L F.5RL S i 1 L 5EL __, I � _ -® --- i---- - � I .I! E PROPOSED RELOCATION LOT 1 t LOT i I I ; y_ OF EX, SO I AREA 13,7.3.3 SF 1 E AREA; 8,914 'SF i j � � � AND EMT 1 BLDG. ENV.: ' 9LOG, ENV- I � - - I t ( TO KING j 9.302 3F F I ®2 COUNTY 1 I I ( 15 2 51- F F.' TRACT B r AREA: 13,838 SF i t STOtRIA FACILITY (j/f r NJTE ''` . lip M Za'. dat I Ehd ?ETAL EN SHEID.S ARE TO �-E T 1 - �- -. —_ OUBI Arr rvtc-nkit' r—n n 1 e eryR r1nh1/ DrTC* 01DC r- I �t T CD I IFS E= L (7�) TiE ®. ti ; E, ------��, Pzi — ------ -I ------- ------- P- P-2LEW �., (TO BE ABANDONE )�': I I � LOT 3 F 3�* i I M AREA, 8,914 SF LOT 4 TO BE I I BLDG. ENV., o 4,735 SF 1 EXISTING I EA�OVE[1 1=, � S, 8 4 SF r6j� Efj V-, }( f C3t11LC31rc0 '� P 95FA a� s 7.i317 c;F r !I I .y I a i =L 11 L-----K-K "0EASIDANT FCC PUBLIC SEWER TG BE DEDICATED AND C:UNVE-1ED Tr3 THE NTY ��F FMTMA1 W)AY Not to Scale NOTES: I. � �Site & Exploration Map An excerpt from the ANK Preliminary Short Plat Site Plan by dmp incorporated dated 4/31/2023 WE Proposed Short Plat Number and approximate location of test pits (2011) 29850 - 18th Avenue South s E 0 R E S 0 U R C E S Federal Way, Washington Number and approximate location of hand borings (2023) earth science & geotechnical engineering PN: 3674400-155, -160 4809 Pacific Hwy. E. I Fife, WA 98424 1 253-896.1011 1 www. georesources.rocks Doc ID: Woldetekle.18thAveS.F2 August 2023 Figure 2 ■ Approximate Site Location Figure created from King County Nap website (https://gismaps.kingcounty.gov/iMap/) GEORESOURCES earth science & geotechnical engineering 4809 Pacific Hwy. E. i Fife, WA 99424 I 253896-1011 ( vrww. georesources.rocks Not to Scale Site Vicinity Map Proposed Short Plat 29850 18th Avenue South Federal Way, Washington PN: 3674400-155, -160 Doc ID: Woldetekle.18thAve&F I Aug 2023 1 Figure 3 ?"0 Approximate Site Location Figure created from Web Soil Survey (http://websoilsurvey.sc.egov.usda.gov/App/WebSoi]Survey.aspx) Soil Soil Name Parent Material Slopes Erosion Hazard Hydrologic Type Soils Group AgC Glacial drift and/or glacial 8 to 15 Moderate Alderwood gravelly outwash over dense B Moderate to AgD sandy loam glaciomarine deposits 15 to 30 severe AmB Arents, Alderwood Basal till 0 to 6 Slight B/D material - ww,- wiiiii� GEORESOURCES earth science & geotechnical engineering 4809 Pacific Hwy. E. I fife, WA 98424 1253.896.1011 I www. georesources.rocks Not to Scale MRCS Soils Map Proposed Short Plat 29850 18th Avenue South Federal Way, Washington PN: 3674400-155, -160 Doc ID: Woldetekle.18thAveS.F I Aug 2023 1 Figure 4 Approximate Site Location An excerpt from the Geologic Map of the Poverty Bay 7.5-Minute Quadrangle, Washington by D. B. Booth, H. H. Waldron, and K. G. Troost N 'e S MEMO GEORESOURCES earth science & geotechnical engineering 4809 Pacific H-y. E. I Fite, WA 98424 1253.896A 011 1 www. gearesources.rocks Not to Scale Geologic Map Proposed Short Plat 29850 18t" Avenue South Federal Way, Washington PN: 3674400-155, -160 Doc ID: Woldetekle.18thAveS.F I Aug 2023 1 Figure 5 EXPLANATION i Liq.,fimi. vireFKibilay: HIGH F ' o Lquelitc¢tzi wscepribility: MODERATE to HIGH 3 ysz s Liquclaction s ,vptibilgyc MODERATE f Liquclac6an suazptibilic}. LOW toMODERATE 7„',�, t„ ' LiqucFac6on susceptibility: LOW Liqucrac6onsuscc3tib[ ity: VERY LOW to LOW .3. , Liquefaccoasusccptibaity: VERY LOW ._,yS "„ Peat deposit PL3 t5 fK4 "Ctn2i 4511 �1 tna �^ �F vsa: ri�tin t t Water Approximate Site Location An excerpt from the Liquification Susceptibility Map of King County, Washington by Stephen P. Palmer, Sammantha L. Magsino, Eric L. Bilderback, James L. Poelstra, Derek S. Folger, and Rebecca A. Niggemann (2004) —5—To GEORESOURCES earth science & geotechnical engineering 4909 Pacific Hwy. E. I Fife, WA 98424 I 253.896,1011 ( www- georesources. rocks Not to Scale Liquefaction Susceptibility Map Proposed Short Plat 29850 18th Avenue South Federal Way, Washington PN: 3674400-155, -160 Doc ID: Woldetekle.18thAveS.F I Aug 2023 1 Figure 6 L Seismogenic Folds. Known or Suspected a a534 ft — Vsible fold trace Inferred fold trace ;��`` — n • - Concealed food trace V S 288Eh St x' Active Faults, Known or Suspected 5 — Visible fault trace Tacoma fault zone (class B) > - - Inferred fault trace r Lai�reb,��gd Pa rl, - Concealed fault trace Camelot Park in ` ` v N t rn vs ® r ` S 298tr SE ti S 2 A,tk? St x u� r': `1 • ¢r to vs �" S N4th St r S 304s1t 5t ` v SW Mth St ° v irror Lake s nttt st ' Z 30W1 vc Slev1 Lake Park, a' s S>✓,yy2th St S 3t2tY1 St ; s s _ 1 ari, >t — ;t tctl st :x _ z a S316t1St �� S v c Approximate Site Location An excerpt from the Washington State Department of Natural Resources Geologic Information Portal (https://geologyportal.dnr.wa.gov/) G E 0 R E S 0 U R C E S earth science & geotechnical engineering 4809 Pacific Hwy. E. I Fife, WA 98424 1 53.896,1011 1 www. georesources. rocks Not to Scale Fault Hazards Map Proposed Short Plat 29850 18th Avenue South Federal Way, Washington PN: 3674400-155, -160 Doc ID: Woldetekle.18thAveS.F I Aug 2023 1 Figure 7 SLOPED TO DRAIN ELOW GRADE WALL AWAY FROM STRUCTURE ='t: RAINAGE SAND AND GRAVEL (SEE NOTE 3) �� ( ,�•,:� DAMP PROOFING IMPERVIOUS SOIL PAVEMENT OR 18° HOLES (SEE NOTE 1) WALL BACKFILL FLOOR SLAB SEE NOTE EXCAVATION SLOPE CONTRACTOR'S REPSONSIBILITY & MIN ON SIDES OF PIPE;' Z 2° BELOW z 2 x � a© � r N WASHED PEA GRAVEL/GLEAN CRUSHED GRAVEL ERIMETER / SUBDRAIN PIPE Notes 1. Washed pea gravel/crushed rock beneath floor slab could be 6 hydraulically connected to perimeter/subdrain pipe. Use of 1" diameter weep holes as shown is one applicable method. Crushed gravel should consist of 3/4" minus. Washed pea gravel should consist of 3/8" to No. 8 standard sieve. 2. Wall backfill should meet WSDOT Gravel Backfill for walls Specification 9-03-12(2). 3. Drainage sand and gravel backfill within 18" of wall should be compacted with hand -operated equipment. Heavy equipment should not be used for backfill, as such equipment operated near the wall could increase lateral earth pressures and possibly damage the wall. The table below presents the drainage sand and gravel gradation. 4. All wall back fill should be placed in layers not exceeding 4" loose thickness for light equipment and 8" for heavy equipment and should be densely compacted. Beneath paved or sidewalk areas, compact to at least 95% Modified Proctor maximum density (ASTM: 01557-70 Method C). In landscaping areas, compact to 90% minimum. 5. Drainage sand and gravel may be replaced with a geocomposite core sheet drain placed against the wall and connected to the subdrain pipe. The geocomposite core sheet should have a minimum transmissivity of 3.0 gallons/minute/foot when tested under a gradient of 1.0 according to ASTM 04716. ON G E 0 R E S 0 U R C E S earth science & geotechnical engineering 4909 Pacific Hwy. E. I Fife, WA 99424 1 253.596A 011 1 www. georesources.racks RETARDER The subdrain should consist of 4" diameter (minimum), slotted or perforated plastic pipe meeting the requirements of AASHTO M 304; 1/8-inch maximum slot width; 3/16- to 3/8- inch perforated pipe holes in the lower half of pipe, with lower third segment unperforated for water flow; tight joints; sloped at a minimum of 6"/100' to drain; cleanouts to be provided at regular intervals. 7. Surround subdrain pipe with 8 inches (minimum) of washed pea gravel (2" below pipe" or 5/8" minus clean crushed gravel. Washed pea gravel to be graded from 3/8-inch to No.8 standard sieve. 8. See text for floor slab subgrade preparation. Materials Drainage Sand and Gravel 3/4" Minus Crushed Gravel Sieve Size % Passing by Weight 3/a' 100 No4 28-56 No8 20-50 No50 3-12 No 100 0-2 Sieve Size % Passing by Weight 3/" 100 /z" 75 - 100 /a" 0-25 No 100 0-2 (by wet sieving) (non -plastic) Typical Wall Drainage & Backfill Detail Proposed Short Plat 29850 18th Avenue South Federal Way, Washington PN: 3674400-155, -160 Doc ID: Woldetekle.18thAveS.F I Aug 2023 1 Figure 8 Appendix Subsurface Explorations ■ Test Pit TP-1 Location: SE corner of proposed building Depth feet Soil Type Soil Description 0 - 2 SM Brown silty fine sand with gravel, scattered roots (loose, moist) (Weathered Native soils) 2 - 7% SM Gray silty SAND with gravel, cemented (dense to very dense, moist) (Glacial Till) Terminated at 7'/2 feet below ground -surface. No -caving observed. No groundwater seepage or significant mottling observed Test Pit TP-2 Location: North of proposed building Depth feet Soil Type Soil Description 0 - 1'/2 - Topsoil 1'/2 - 3'/ SM Brown silty fine sand with gravel, scattered roots (loose, moist) (Weathered Native soils) 3'/a - 8% SM Gray silty SAND with gravel, cemented (dense to very dense, moist) (Glacial Till) Terminated at 8%2 feet below ground surface. No caving observed. No groundwater seepage or significant mottling observed Test Pit TP-3 Location: NE portion of site, between proposed parking area and toe of slope Depth feet Soil Type Soil Description 0 - %2 - Topsoil %2 - 3% SM Brown silty fine sand with gravel, scattered roots (loose, moist) (Weathered Native soils) 3'/2 - 7 SM Gray silty SAND with gravel, cemented (very dense, moist) (Glacial Till) Terminated at 7 feet below ground surface. No caving observed. No groundwater seepage or significant mottling observed Logged by R. M. Hadley Excavated on: July 28, 2011 Test Pit Logs GeoResources, LLC Proposed Church Improvements 5007 Pacific Highway East, Suite 16 29850 —18th Avenue South Fife, Washington 98424 Federal Way, Washington Phone: 253-896-1011 Fax: 253-896-2633 JOB Lamb'sGate.18thAveS.TP I August 2011 Figure 6a 0 Test Pit TP-4 Location: E portion of round -a -bout, proposed drywell Depth (feet) Soil Type Soil Description 0 1 - 1 - 2%2 - SM Crushed rock, fill over topsoil Brown silty fine sand with gravel, scattered roots (loose, moist) (Weathered Native soils) 2%2 - 33/ SM Gray mottled silty SAND with gravel, cemented (dense, moist) (Weathered Glacial Till) 33/ - 8%2 SM Gray silty SAND with gravel, cemented (very dense, moist) (Glacial Till) 8'/2 - 10 SP Gray SAND with silt (dense. Moist) (interbeds of Advance sand?) 10 - 12 SM Gray silty SAND with gravel, cemented (very dense, moist) (Glacial Till) Terminated at 12 feet below ground surface. No caving observed. No groundwater seepage observed, mottling below 2'/ feet depth. Test Pit TP-5 Location: proposed drywell Depth (feet) Soil Type Soil Description 0 - '/2 - Topsoil '/2 - 2 SM Brown silty fine sand with gravel, scattered roots (loose, moist) (Weathered Native soils) 2 - 3% SM Light brown to gray minor mottling silty SAND with gravel, cemented, no roots (dense, moist) (Weathered Glacial Till) 3% - 10% SM Gray silty SAND with gravel, cemented (dense to very dense, moist) (Glacial Till) Terminated at 10'/ feet below ground surface. No caving observed. No groundwater seepage or significant mottling observed Logged by: R. M. Hadley GeoResources, LLG 5007 Pacific Highway East, Suite 16 Fife, Washington 98424 Phone: 253-896-1011 Fax: 253-896-2633 Excavated on: July 28, 2011 Test Pit Logs Proposed Church Improvements 29850 —18th Avenue South Federal Way, Washington JOB Lamb'sGate.18thAveS.TP I August 2011 1 Figure 6b ■ ® LOG OF BORING HB-1 G E O R E S O U R C E S 29850 18th Avenue South, Federal Way earth science & geotechnical engineering Federal Way WA 1. Refer to log key for definition of symbols, abbreviations, and codes Drilling Company: GeoResources Logged By: KLR 2. USCS disination is based on visual manual classification Drilling Method: Hand Auger Drilling Date: 07/03/2023 and selected lab testing 3. Groundwater level, if indicated, is for the date shown and may vary Drilling Rig: Datum: NAVD88 4. NE = Not Encountered Sampler Type: Porter Sampler Elevation: 475' S.ATD = At Time of Drilling Hammer Type: Donut Termination Depth: 5.5' Hammer Weight: 40lbs Latitude: Notes: Longitude: Test Results c o Exploration p o `w a o Plastic Limit Liquid Limit 3 a m y ,� I notes Soil description o E E % Fines (<0.075mm) O o w m „° v�i %Water Content • o w a C0 Penetration - ♦ (blows per foot) 0 475 NE Topsoil 1 474 2 473 . ... ... ... ... ... ... ... ...................................................... ...................................................... ...................................................... ...................................................... ...................................................... ...................................................... ...................................................... ...................................................... . 10 Brown silty SAND (medium dense, moist) (SM) (weathered glacial till) $TT 14 3 472 gravel content increases 4 471 10 ..................................................... . •. ♦............. Gray silty SAND w/ gravel (dense, moist) (SM) (undisturbed glacial till) 17 27 5 470 (Termination Depth - 0710312023) 6 469 QTopsoil Silty sand f Sheet 1 of 1 JOB: Wodletekle.18thAveS I FIG. .000.0=� LOG OF BORING HB-2 G E O R E S O U R C E S 29850 18th Avenue South, Federal Way earth science & geotechnical engineering Federal Way WA 1. Refer to log key for definition of symbols, abbreviations, and codes Drilling Company: GeoResources Logged By: KLR 2. USCS disination is based on visual manual classification Drilling Method: Hand Auger Drilling Date: 07/03/2023 and selected lab testing 3. Groundwater level, if indicated, is for the date shown and may vary Drilling Rig: Datum: NAVD88 4. NE = Not Encountered Sampler Type: Porter Sampler Elevation: 480' S. ATD = At Time of Drilling Hammer Type: Donut Termination Depth: 4.5' Hammer Weight: 40lbs Latitude: Notes: Longitude: c Test Results `v Y Y o loration Ex p Soil description 'o o `m o- g a E% Plastic Fines Limit (10.075mm) Liquid Limit 3 �� O o v " w notes al ,� vTi 95 Water Content • L a N l7 Penetration - ♦ (blows per foot) 0 480 NE Topsoil ... ...................................................... 1 479 17 Brown silty SAND w/ grave I.(medium dense, moist) (SM) (weathered glacial till) 16 15 2 478 3 477 14 Gray silty SAND w/ gravel (dense, moist) (SM) (undisturbed gla Clal till) 27 33 ... 4 476 (Termination Depth - 0710312023) 5 475 6 474 10 Topsoil Silty sand Sheet t of 1 JOB: Wodletekle.18thAveS FIG. N Appendix B Laboratory Test Results Particle Size Distribution Report 100 109 NUNN III 90 a0 I IN 1 0 70 MM m n 60 Z m Z LL Z 50 W D U � W 40 CIJ a m X 30 20' � 10 111 N Q:110111111 o GRAIN SIZE - mm. c % Gravel % Sand % Fines o °fO+3.. Coarse Fine Coarse Medium Fine Silt Clay 0.0 0.0 32.2 14.8 16.7 21.4 14.9 c CU Material Description tv 0 .2! Atterbera Limits .2 PL= LL= PI= c °c Coefficients D85:8.0936 D60= 3A417 D50=1.4918 D30= 0.2743 D15= 0.076I D10= Cu Cc Classification USCS= AASHTO= Remarks n F.M. 3.49 a� E m � nos specification provided) ( P P � o Sample Number: 0902847 B Depth: .5'-2.5' Date: 8-2-11 Location: TP 5 C GeoResources, LLC Client: Lambs Gate 0 in Project: Proposed Lam's Gate Pres. Church Improvements m Fife WA Pro ect No: LamVsGate.18thAveS Figure SIEVE SIZE PERCENT FINER SPEC: PERCENT PASS? (X=NO) .75 100.0 .5 91.4 .3125 84.6 #4 67.8 #IO 53.0 #20 44.2 #40 36.3 #60 28.5 #100 20.9 #200 14.9 Tested By: CRO Checked By: RMH SECTION VII OTHER PERMITS SECTION VIII .IMMAill''ll ' , - T.E.S.C. Silt fencing, temporary sediment pond, stabilized construction entrance, interceptor ditch and site stabilization will be provided consistent with developments this size. A TESC Plan will be part of the engineering plans. A SWPPP will also be provided and will be included in this TIR during the engineering phase. 0 SECTION IX BOND QUANTITIES, FACILITY SUMMARIES AND DECLARATION OF COVENANT 16 o3m AMED SECTION X OPERATIONS AND MAINTENANCE MANUAL —6) � A 0z9e,a', , i s i TIR Appendix A Off -site Analysis from approved TIR, dated 2/6/2008 by Vikek Environmental Engrs, LLC for Lamb's Gate TIR SECTION 3 OFFSITE ANALYSIS The existing and proposed property lines are shown on the attached engineering plans. The site location is identified in figure 1. Offsite areas are shown in figure S with the associated downstream conveyance system for more than 1/4 mile. Flow released from the detention facility is discharged into a new 12 - inch pipeline along 18th Avenue North East. Through this pipe, runoff is conveyed in a slightly northwesterly direction through pipes of the following diameters; 12 inches across Highway 99, 30 inches and 24 inches along the west side of Highway 99 and several other pipes before discharging into Redondo Creek after more than 1/4 mile downstream. Complete detail is provided in the enclosed Offsite Analysis Drainage System Table. CITY OF FEDERAL WAY SWM ATLAS - Map Date: March 2002 (Reprinted: February, 2003) W - 1273268, 4.31 03 f 7 1,101; W 4 J. 129624 wig !: W-K; zm2 Lj 2" i . . . . . . . . . . . . . . . . . . . . . . . . . f fd.. / 0 fOf2 2 All, 29A 0 2 13 NETT 'SOONL�VIEW 29600 t 29M ---jECT SITE 19 119 R-F 201 2M' 2al -�NDVEW7P- Ff. C\f 78 Uj SITE ADDRESS: CO) Vik-ek Environmental Engineers, LLC 29805I 81h AVENUE SOUTH P. O. Box 85122 FEDERAL WAy, WASHINGTON 98003 Seattle, Washington 98145-1122 JOB NO. 11 1403-LG Figure - 5, Downstream Conveyance Svstem .TA v C n 0 O 0) Zl o C O L O Y O L: ca aa) �. 0 a P, �cvg'roQ ) u j o aq 0��= n. 0 N MO b CC 21 tt^j�� Pa y0 - a) o ' L. :� •+ x 5 as N N o N a m�o z z z N � CCU C G Md U � � r U a) N .0 0 2.9 N wa 0?�NZ a) a) z Q) z 0 0 o an W 0 z Iz Iz0 0 Iz Iz z +z Iz Iz a Qf °' rn o N 3 V L. N CV p N to y C Ci 11 M 4.. .� � N rn �D O� t-• Ooi N M Q, Z a a� M n n n n n n wj c ;p W O o o O� O O O O p CL a, _ t-- t` t` r- Q�w> ca 0oLT PL� y 4 $GO 3:4 cn U) cis to cis `� _N o\ w o�tn U C var asP, P, rn �+ + yv, C � O N � � M N ;� 3 0c30 ,.-� U 00 .-. +� � O � Q. mod�++ N .� N ++ ic�l 2 00 WJ � + k � 3 O� N i N v to CL bA a � a a y b0 01 N U�~a z z W W o W W o rn N O m v �(0 .� N°) p ° NLL M d �n �b CAI � N M v1 0 n 9 I0? O Fi a i roro1 4 O O co cisCdd O Cl) W O In N O cad U w 0 � 0 8 QA, a, �; 0 a. a 9 L6 rA a fl n s, Z U z O 'd +' s0, U O sO U �+ "j p d O sO o cC p 'd Q 0 i, Z d r0 G A 0 O p N O O N O O O O N O O p O d O bA O d Q 'd G O ri A !lljjggp o w o 0 0 M O\ O O d d C. N M n n n n n n M M Cfl M M M O C O b cd� cnd cd cd cdd id id cd l) o O a, p p N It ai ai u n c4 o ss �3 0 ° Q' as o ON ° o0 4. 00 oo a�i oo b to to '7M ai m o t v, i o v' N 0 o cd w 3CC3 b w 3Cd b w 3 w 3 m Cn rn RESOURCE REVIEW: The site is within the Lower Puget Sound Drainage Basin and drains to Puget Sound through Redondo Creek. Resources reviewed for this report includes the following; ® Wetlands Inventory Maps : There are no Wetlands on the site or draining into it. ® Sensitive Area Map Folios: No sensitive area is indicated. ® Floodplain(FEMA) maps: No floodplain area is indicated on site. ® Critical Drainage Area Maps: The site is located in Lower Puget Sound Drainage Basin. FIELD INSPECTION: Field inspection was completed in 2005. Please see Figure 5. Runoff from the site drains generally southwesterly and then northerly as previously described in the preceding section. DRAINAGE SYSTEM DESCRIPTION AND PROBLEM DESCRIPTIONS: Details of the existing drainage system are shown in Figure 5. They are no significant offsite runoff draining into the site. Upstream runoff is intercepted by existing conveyance facilities and then conveyed downstream to existing drainage conveyance facilities along on 181' Avenue South. Runoff and overflows from the proposed detention will discharge onto the proposed pipeline as shown on the plans. MITIGATION There are no identifiable drainage problems, therefore no mitigation is proposed.