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23-101440-UP_ Civil Prelim TIR_03-21-23
1st Avenue Development Land Use Permit Preliminary Technical Information Report March 2023 1st Avenue Development – City of Federal Way i Technical Information Report Prepared for: City of Federal Way Land Use Permit Prepared by: Jeremy Febus, PE Tom Jones Matt Takane, EIT KPFF Consulting Engineers 1601 Fifth Avenue, Suite 1600 Seattle, WA 98101 (206) 622-5822 KPFF Project No. 2100532 March 202 3 03/20/2023 KPFF Consulting Engineers ii This page intentionally left blank. 1st Avenue Development – City of Federal Way iii Table of Contents 1. Project Overview ........................................................................................................................................... 1 2. Conditions and Requirements Summary ................................................................................................... 2 Core Requirement No. 1 – Discharge at the Natural Location ................................................................. 2 Core Requirement No. 2 – Off-Site Analysis ............................................................................................ 2 Core Requirement No. 3 – Flow Control Facilities ................................................................................... 2 Core Requirement No. 4 – Conveyance System ..................................................................................... 2 Core Requirement No. 5 – Construction Stormwater Pollution Prevention ............................................. 2 Core Requirement No. 6 – Maintenance and Operations ........................................................................ 2 Core Requirement No. 7 – Financial Guarantees and Liability ................................................................ 3 Core Requirement No. 8 – Water Quality ................................................................................................ 3 Core Requirement No. 9 – Flow Control BMPS ....................................................................................... 3 Special Requirement No. 1 – Other Adopted Area-Specific Requirements ............................................. 4 Special Requirement No. 2 – Flood Hazard Area Delineation ................................................................. 4 Special Requirement No. 3 – Flood Protection Facilities ......................................................................... 4 Special Requirement No. 4 – Source Controls ........................................................................................ 4 Special Requirement No. 5 – Oil Control ................................................................................................. 4 3. Off-site Analysis ............................................................................................................................................ 4 Task 1: Study Area Definition and Maps ................................................................................................. 4 Task 2: Resource Review ....................................................................................................................... 4 Task 3: Field Inspection .......................................................................................................................... 5 Task 4: Drainage System Description ..................................................................................................... 5 List of Figures Figure 1: Vicinity Map ............................................................................................................................................ 1 Appendices Appendix A – TIR Worksheet Appendix B – Existing Site Conditions Exhibit Appendix C – Downstream Drainage Map Appendix D – Proposed Site Conditions Exhibit Appendix E – Flow Control Calculations Appendix F – Water Quality BioPod Detail and WADOE GULD Documentation Appendix G – Geotechnical Investigation Report KPFF Consulting Engineers iv This page intentionally left blank. 1st Avenue Development – City of Federal Way 1 1. Project Overview The project proposes to construct multi-family residential units on parcel number 172104-9038 totaling approximately 5.999 acres located in Federal Way, Washington. The site improvements will include twenty multifamily residential buildings with associated drive aisles, parking, sidewalks, residential open space, drainage infrastructure and site utility services. The project site is bounded by 1st Avenue South to the west; South 328th St to the north; single-family residence to the east; Westboro Apartments and Condominiums to the south (See Figure 1 – Vicinity Map). The project site currently has an existing one-story building and parking lot with trees and various underbrush along the perimeter of the site. Stormwater runoff generally sheet flows from the north property boundary to the southeast and southwest property boundary in the existing conditions and has low points in the parking lot that discharges offsite to the existing drainage system on 1st Avenue South, South 328th Street, and to the adjacent east parcel. See Appendix B for existing conditions exhibit and Appendix C for downstream drainage exhibits. The proposed drainage improvements include onsite conveyance system, water quality treatment facilities and a detention vault with a flow control structure. The project proposes to outfall to an existing City catch basin on 1st Avenue South. See Appendix D for proposed conditions exhibit. This report is being prepared to for the City of Federal Way land use permit. The project is subject to the requirements of the 2021 King County Surface Water Design Manual (KCSWDM) and the City of Federal Way Addendum requirements. Figure 1: Vicinity Map KPFF Consulting Engineers 2 2. Conditions and Requirements Summary The project proposes greater than 2,000 square feet of new plus replaced impervious surface; therefore, a Full Drainage Review is required, that includes complying with all nine core requirements and all five special requirements. CORE REQUIREMENT NO. 1 – DISCHARGE AT THE NATURAL LOCATION The project site currently discharges runoff to the 1st Avenue South drainage system via two 12 -inch storm service connections off the existing 18-inch main. The northeast portion of the site discharges to the South 328th Street drainage system via a 10-inch storm service connection off the existing main. The project site will be regraded to discharge all runoff to the 1st Avenue South drai nage system. CORE REQUIREMENT NO. 2 – OFF -S ITE ANALYSIS A Level 1 downstream analysis is provided in Section 3. CORE REQUIREMENT NO. 3 – FLOW CONTROL The project is located in a Conservation Flow Control area; therefore, the project is required follow the Level 2 flow control standard, which is to match historic durations for 50% of 2-year through 50-year peaks and match historic 2- and 10-year peaks. Existing conditions are modeled as forested. The project is proposing a detention vault with a flow control structure to meet the Level 2 flow control standard. See Appendix E for preliminary detention vault MGSFlood calculations demonstrating compliance with the Level 2 Flow Control requirements. CORE REQUIREMENT NO. 4 – CONVEYANCE SYSTEM The project is providing a new conveyance system to collect and route the onsite runoff to the proposed detention system. The conveyance system will be designed to convey and contain the 25-year peak flow rates and meet requirements of the KCSWDM. CORE REQUIREMENT NO. 5 – EROSION AND SEDIMENT CONTROL Temporary erosion and sediment control (TESC) measures will be implemented during construction. A preliminary TESC plan is provided for this project submittal. It is anticipated that a construction stormwater pollution prevention plan (CSWPPP) will be required for duration of construction activities. The preliminary TESC measures include but will not be limited to silt fence, inlet protection systems, interceptor swales and silt dikes, and portable sediment treatment tanks to manage erosion during construction activities. CORE REQUIREMENT NO. 6 – MAINTENANCE AND OPERATIONS The Owner will be responsible for the onsite drainage facility maintenance and operation. Onsite drainage facilities include catch basins, manholes, storm drain pipe, water quality facilities, and the detention vault and associated flow control structure. Coordination for maintenance responsibilities for the outfall pipe connection to the existing City drainage infrastructure will be determined prior to construction. 1st Avenue Development – City of Federal Way 3 CORE REQUIREMENT NO. 7 – FINANCIAL GUARANTEES AND LIABILITY All drainage facilities constructed or modified for this project will comply with the City’s financial guarantee requirements. CORE REQUIREMENT NO. 8 – WATER QUALITY The project is required to provide water quality facilities and meet the enhanced water quality treatment standard. The Oldcastle BioPod enhanced treatment system (or an approved equal) is being proposed to meet the enhanced water quality treatment requirements. This treatment facility has a general use level designation (GULD) by the Washington State Department of Ecology (WADOE) for enhanced treatment application. The treatment facilities are located upstream of the detention vault and have been preliminarily sized to meet KCSWDM requirements. See Appendix F for the BioPod general detail and WADOE GULD documentation. The final system decision will be made during construction document design and permitting. CORE REQUIREMENT NO. 9 – FLOW CONTROL BMP S This project is required to evaluate flow control Best Management Practice (BMP) to the maximum extent feasible and is subject to Large Lot BMP Requirements, as the project site is greater than 22,000 square feet. The evaluation of Flow Control BMPs is based on the requirements per KCSWDM, Section 1.2.9.2.2 and Appendix C.2. The following is the evaluation of the BMP categories and summary of implementation of BMPs where feasible: • Full Dispersion: Full dispersion is not feasible, as the proposed improvements do not allow for sufficient on-site native vegetated flow paths for full dispersion. • Full infiltration or roof runoff: Full infiltration is not feasible as the project native and fill soils observed were glacial till soils and soils with high fines that have limited infiltration based on geotechnical analysis. Mottled soil was also observed which indicates seasonal fluctuations in groundwaters seepage levels. See Appendix G for geotechnical report. • Full Infiltration, Partial Infiltration, Bioretention or Permeable Pavement: Full infiltration is not feasible as the project native and fill soils observed were glacial till soils and soils with high fines that have limited infiltration based on geotechnical analysis. Mottled soil was also observed which indicates seasonal fluctuations in groundwaters seepage levels. See Appendix G for geotechnical report. • Basic Dispersion: Basic dispersion will be applied to roof downspouts use splash blocks and vegetated flows paths where feasible. • Reduced Impervious Surface Credit: Reduced impervious surface techniques will be evaluated where possible. • Native Growth Retention Credit: Native growth retention will be evaluated and retained where possible. Proposed improvements and grading activities may limit the available native growth retention areas onsite. • Post Amended Soils: Post Amended soils will be applied to landscape areas onsite. • Perforated Pipe Connection: Perforated pipe connection are not recommended due to restrictive infiltration glacial till soils onsite. KPFF Consulting Engineers 4 SPECIAL REQUIREMENT NO. 1 – OTHER ADOPTED AREA -SPECIFIC REQUIRE MENTS This project is located within a five-year capture zone as designated by the Lakehaven Water and Sewer District. Capture zones are designeated as critical aquifer recharge areas in the City of Federal Way. A Hazardous Materials Inventory Statement—Critical Aquifer Recharge and Wellhead Protection Areas (enclosed) will be submitted with the application. SPECIAL REQUIREMENT NO. 2 – FLOOD HAZARD AREA DELINEATION No flood hazard areas are located within the proposed site. SPECIAL REQUIREMENT NO. 3 – FLOOD PROTECTION FACIL ITIES The project does not contain a stream that has an existing flood protection facility. The project also does not propose to construct new or to modify an existing flood protection facility. SPECIAL REQUIREMENT NO. 4 – SOURCE CONTROL S Source control BMPs are anticipated to be implemented during construction activities. The contractor shall be responsible for monitoring stormwater runoff during construction activities and implement appropriate source control BMPs to prevent illicit discharges. It is not anticipated that permanent Source Control BMPs will be required for this project. SPECIAL REQUIREMENT NO. 5 – OIL CONTROL This project does not qualify as a high-use site; therefore, no oil controls are required. 3. Off-site Analysis TASK 1: STUDY AREA DEFINITION AND MAPS A Level 1 downstream analysis has been performed for this project in accordance with the KCSWDM. The analysis consists of a project mapping investigation, a field investigation of the site, and a verification of the downstream conveyance path. The study area extends to a point approximately a quarter mile downstream of the project site. Refer to Appendix C for the downstream drainage map. TASK 2: RESOURCE REVIEW The following resources were reviewed for this project: • City of Federal Way record drawings and inspection documents. • City of Federal Way GIS maps. • Project Site Survey 1st Avenue Development – City of Federal Way 5 TASK 3: FIELD INSPECTION A field inspection for a quarter mile downstream of the site will be conducted after the Land Use Process III submittal. From Google Maps Street View dated October 2022, downstream drainage components visible from the surface along 1st Avenue South appeared to be consistent with available survey information and from the City GIS maps and record drawings. There were no drainage concerns documented at the time of the Land Use Process III submittal. There was limited access to the drainage system that runs thr ough the private residential development. TASK 4: DRAINAGE SYSTEM DESCRIPTION Upstream Analysis The upstream drainage system consists of a piped conveyance system that collects roadway runoff along 1st Avenue South. There is a separate drainage system on South 328th Street consisting of a piped conveyance system that collects roadway runoff on South 328th Street and runoff from parcel 169730-0000, north of the project site. Downstream Analysis The project proposes to regrade the site and route all onsite runoff to the 1st Avenue South drainage system. The existing drainage system on 1st Avenue South continues to flow south and through an existing multifamily residential development on parcel 182104-9035. See Appendix C for downstream drainage map. There were no existing or potential drainage, flooding, or erosion issues identified during the review of available resources. 1st Avenue Development – City of Federal Way Appendix A Appendix A TIR Worksheet KING COUNTY, WASHINGTON, SURFACE WATER DESIGN MANUAL TECHNICAL INFORMATION REPORT (TIR) WORKSHEET Part 1 PROJECT OWNER AND PROJECT ENGINEER Project Owner Phone _____ Address Project Engineer Company ____ Phone _______ Part 2 PROJECT LOCATION AND DESCRIPTION Project Name _ DLS-Permitting Permit #_____ Location Township Range _ Section _ Site Address _______ Part 3 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 4 OTHER REVIEWS AND PERMITS1 □ DFW HPA □ COE CWA 404 □ ECY Dam Safety □ FEMA Floodplain □ COE Wetlands □ Other _________ □ Shoreline Management □ Structural Rockery/Vault/______ □ ESA Section 7 Part 5 PLAN AND REPORT INFORMATION Technical Information Report Type of Drainage Review (check one): Date (include revision dates): Date of Final: □ □ □ □ □ Full Targeted Simplified Large Project Directed Site Improvement Plan (Engr. Plans) Plan Type (check one): Date (include revision dates): Date of Final: □ Full □ Modified □ Simplified Part 6 SWDM ADJUSTMENT APPROVALS Type (circle one): Standard / Experimental /Blanket Description: (include conditions in TIR Section 2) Approved Adjustment No._ _ Date of Approval: __________________________ 1 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 1st Avenue Development Tom Jones KPFF Consulting Engineers 206-622-5822 Lakehaven Water & Sewer 21 4 17 32818 1st Ave S NA FW 1st Avenue Development LLC (206) 957-0496 411 1st Avenue South, Suite 650 Seattle, WA 98104 KING COUNTY, WASHINGTON, SURFACE WATER DESIGN MANUAL TECHNICAL INFORMATION REPORT (TIR) WORKSHEET Part 7 MONITORING REQUIREMENTS Monitoring Required: Yes / No Start Date: Describe: Completion Date:Re: KCSWDM Adjustment No. Part 8 SITE COMMUNITY AND DRAINAGE BASIN Community Plan :________________________________ Special District Overlays:_________________________ Drainage Basin:__________________________________ Stormwater Requirements: _______________________ Part 9 ONSITE AND ADJACENT SENSITIVE AREAS □ River/Stream □Steep Slope □ Lake □Erosion Hazard □ Wetlands □Landslide Hazard □ Closed Depression □Coal Mine Hazard □ Floodplain □Seismic Hazard □ Other □Habitat Protection □ Part 10 SOILS Soil Type Slopes Erosion Potential □ High Groundwater Table (within 5 feet) □ Sole Source Aquifer □ Other ______________ _______________________ □ Seeps/Springs □ Additional Sheets Attached 2021 Surface Water Design Manual 2 Last revised 7/23/2021 Erosion potential during construction to be addressed with ESC measures. Glacial till and fill soil with high percentage soil fines. Mottled soils indicating groundwater table fluctations. Exist slopes are generally with 0%-15%, and slope from North PL to South PL Level 2 Conservation Flow Control Requirement and Enhanced WQ Treatment Five-year Capture Zone KING COUNTY, WASHINGTON, SURFACE WATER DESIGN MANUAL TECHNICAL INFORMATION REPORT (TIR) WORKSHEET Part 11 DRAINAGE DESIGN LIMITATIONS REFERENCE LIMITATION / SITE CONSTRAINT □ Core 2 - Offsite Analysis____________________ _________________________________ □ Sensitive/Critical Areas _____________________ _________________________________ □ SEPA _____________________________________ _________________________________ □ LID Infeasibility____________________________ _________________________________ □ Other _____________________________________ _________________________________ □ □ Additional Sheets Attached 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: 1 / 2 / 3 dated: Flow Control (include facility Level: 1 / 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: Construction Stormwater Pollution Prevention Contact Phone: After Hours Phone: Maintenance and Operation Responsibility (circle one): Private / Public If Private, Maintenance Log Required: Yes / No Financial Guarantees and Liability Provided: Yes / No 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 feasible FCBMP Total New Pervious Surfaces on the site Repl. Imp. on site mitigated w/flow control facility implemented Repl. Imp. on site mitigated w/water quality facility Repl. Imp. on site mitigated with FCBMP 2021 Surface Water Design Manual 3 Last revised 7/23/2021 TO BE PROVIDED TBD Flow Control BMPs glacial till and fill soils limiting infiltration BMPs onsite area 5.868 acres Detention Vault XXXX XXXX XXXX XXXX XXXX XXXX 3 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 Requirements Type: CDA / SDO / MDP / BP / LMP / Shared Fac. / None Name: Floodplain/Floodway Delineation Type (circle one): Major / Minor / Exemption / None 100-year Base Flood Elevation (or range): Datum: Flood Protection Facilities Describe: Source Control (commercial / industrial land use) Describe land use: Describe any structural controls: Oil Control High-use Site: Yes / No Treatment BMP: Maintenance Agreement: Yes / No with whom? Other Drainage Structures Describe: Part 13 EROSION AND SEDIMENT CONTROL REQUIREMENTS MINIMUM ESC REQUIREMENTS DURING CONSTRUCTION ^ Clearing Limits ^ Cover Measures ^ Perimeter Protection ^ Traffic Area Stabilization ^ Sediment Retention ^ Surface Water Collection ^ Dewatering Control ^ Dust Control ^ Flow Control ^ Protection of Flow Control BMP Facilities (existing and proposed) ^ Maintain BMPs / Manage Project MINIMUM ESC REQUIREMENTS AFTER CONSTRUCTION ^ Stabilize exposed surfaces ^ Remove and restore Temporary ESC Facilities ^ Clean and remove all silt and debris, ensure operation of Permanent Facilities, restore operation of Flow Control BMP Facilities as necessary ^ Flag limits of SAO and open space preservation areas ^ Other 2021 Surface Water Design Manual 4 Last revised 7/23/2021 None. 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 □Vegetated Flowpath □ Infiltration □Wetpool □ Regional Facility □Filtration □ Shared Facility □Oil Control □ Flow Control BMPs □Spill Control □ Other □Flow Control BMPs □Other Part 15 EASEMENTS/TRACTS Part 16 STRUCTURAL ANALYSIS □ Drainage Easement □ Cast in Place Vault □ Covenant □ Retaining Wall □ Native Growth Protection Covenant □ Rockery > 4’ High □ Tract □ Structural on Steep Slope □ Other □ Other Part 17 SIGNATURE OF PROFESSIONAL ENGINEER 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 Information Report. To the best of my knowledge the information provided here is accurate. Signed/Date 2021 Surface Water Design Manual 5 Last revised 7/23/2021 N/A Old Castle BioPod Detention Vault basic dispersion downspout splash block Jeremy Febus, PE 03/20/2023 1st Avenue Development – City of Federal Way Appendix B Appendix B Existing Site Conditions Map EXISTING STORMWATER RUNOFF OUTFALLS VIA PIPED CONVEYANCE SYSTEM INTO ADJACENT EAST PROPERTY EXISTING STORMWATER RUNOFF IN VEGETATED AREA OUTFALL VIA SHEETFLOW OFFSITE ALONG PROPERTY LINE ONTO ADJACENT SOUTH PROPERTY EXISTING STORMWATER RUNOFF OUTFALLS VIA PIPED CONVEYANCE SYSTEM INTO 1ST AVE S DRAINAGE SYSTEM EXISTING STORMWATER RUNOFF OUTFALLS VIA PIPED CONVEYANCE SYSTEM INTO S 328TH ST DRAINAGE SYSTEM 1ST AVE SS 328TH S T CHD.APPR.BYDATENO. DESIGNED BY APPROVED BY J O B No. :REVISION DRAWN BY CHECKED BY DATE S C A L E: FEDERAL WAY, WASHINGTON 1ST AVE DEVELOPMENT SHEETCALL TWO BUSINESS DAYS BEFORE YOU DIG 1-800-424-5555 1601 5th Avenue, Suite 1600 Seattle, WA 98101 206.622.5822 www.kpff.com EXISTING CONDITIONS B MSTRAG TJ JSF 03/2023 2100532 AS SHOWN 0 30'60' 1st Avenue Development – City of Federal Way Appendix C Appendix C Downstream Drainage Map CITY OF FEDERAL WAY STORMWATER GIS MAPPROJECT SITEDOWNSTREAM PATH Kin g C ounty, EagleView King C ou nty iMa p Dat e: 1/19 /20 2 3 Not es:±Th e inform a tion in clud e d o n th is ma p h a s b e en comp ile d by K in g Count y s ta ff fr o m a varie ty of so u rc es a nd is sub je ct tochange w ith o ut n o tic e. King C ou n ty mak es n o re p res e nt a tion s or w a rra ntie s, express or imp lie d , a s to ac cu ra cy,comp let e ne s s, time lin ess, o r rig h ts to t he u se o f su ch inf o rma tio n . This d o cu men t is no t int ende d f or u se a s a su rve yproduct. K in g Cou n ty sh a ll n o t be lia ble f or a ny g en eral, spe cial, ind ire ct , incid en ta l, or co n se qu e nt ial d am a ge s in clu d ing ,but n ot limit e d to, lo st re ve nu e s or lo st p rof its re sultin g fro m th e use or misu se of t he inf o rma tio n co ntain e d on th is ma p.An y sa le of th is ma p o r in formation o n t h is m ap is p ro h ibit ed e xce pt by wr it te n p e r missio n o f K ing Co u n ty. Leg end Pa rc els EXIST CB IE 12" CMP= 342.75' PROP SD POC EXIST 18" SD EXIST 54" RCP EXIST 24" RCP EXIST 15" SD 1st Avenue Development – City of Federal Way Appendix D Appendix D Proposed Site Conditions Map ENHANCED WATER QUALITY TREATMENT FACILITY OLD CASTLE BIOPOD STRUCTURE OR EQUIVALENT 87'x110'x12.5' DETENTION VAULT (INTERIOR DIMS) 98,175 CF REQUIRED DETENTION VOLUME 1' FREEBOARD 11' DETENTION STORAGE 0.5' SEDIMENT STORAGE *DIMENSIONS ARE INTERIOR VAULT DIMENSIONS ASSUMED 1' THICK EXTERIOR WALLS 89'x112'x15.5' DETENTION VAULT (EXTERIOR DIMS)1ST AVE SS 328TH S T PROP STORM OUTFALL POC EXIST CB RIM 349.8 IE 342.75 DETENTION VAULT FLOW CONTROL STRUCTURE BUILDING 18 11,702 SF 8-PLEX (A) FFE 357.31 BUILDING 17 11,702 SF 8-PLEX (A) FFE 357.38 BUILDING 13 11,200 SF 8-PLEX (B) BUILDING 14 11,702 SF 8-PLEX (A) FFE 355.90 BUILDING 15 11,702 SF 8-PLEX (A) FFE 355.90 BUILDING 16 10,332 SF 7-PLEX (B) FFE 355.81 BUILDING 10 8,962 SF 6-PLEX BUILDING 11 10,081 SF 7-PLEX (A) BUILDING 4 10,081 SF 7-PLEX (A) BUILDING 12 11,200 SF 8-PLEX (B) BUILDING 9 8,962 SF 6-PLEX BUILDING 8 8,962 SF 6-PLEX BUILDING 7 8,962 SF 6-PLEX BUILDING 6 8,962 SF 6-PLEX BUILDING 5 8,962 SF 6-PLEX BUILDING 3 10,332 SF 7-PLEX (B) FFE 356.43 BUILDING 2 8,962 SF 6-PLEX FFE 356.43 BUILDING 1 2,017 SF FFE 358.50 BUILDING 20 11,702 SF 8-PLEX (A) FFE 357.32 BUILDING 19 10,332 SF 7-PLEX (B) FFE 357.20 FFE 356.25 FFE 355.88 FFE 355.45 FFE 355.10 FFE 355.44 FFE 355.10 FFE 354.90 FFE 354.45 FFE 356.36 FFE 356.06 FFE 356.57 FFE 356.36 FFE 355.58 FFE 355.44 FFE 354.90 FFE 354.45 FFE 354.90 FFE 354.45 FFE 354.90 FFE 354.45 FFE 355.02 FFE 354.57 FFE 355.02 FFE 354.57 FFE 355.90 FFE 354.90 FFE 356.02 FFE 355.02 FFE 355.52 FFE 355.02360357358359361360359361 362 360 357 358359 3603593 5 5 354 3 5 6 3 5 7 358 356357 357 358358 355355356 356357 358 357355 354 356355 354 356355 354 356 355355 355 355 355 355 355 355356 350355 351 35 2 353 35 4 356 357 356 357 35 7 356 357 357 356 357 351352353354354354354350351352353354 354355 353 354 350355349351352353354350348349351350351352353354355 355 3 5 5 3560 15'30' CHD.APPR.BYDATENO. DESIGNED BY APPROVED BY J O B No. :REVISION DRAWN BY CHECKED BY DATE S C A L E: FEDERAL WAY, WASHINGTON 1ST AVE DEVELOPMENT SHEETCALL TWO BUSINESS DAYS BEFORE YOU DIG 1-800-424-5555 1601 5th Avenue, Suite 1600 Seattle, WA 98101 206.622.5822 www.kpff.com PROPOSED CONDITIONS D MSTRAG TJ JSF 03/2023 2100532 AS SHOWN 1st Avenue Development – City of Federal Way Appendix E Appendix E Flow Control Calculations ————————————————————————————————— MGS FLOOD PROJECT REPORT Program Version: MGSFlood 4.58 Program License Number: 200410007 Project Simulation Performed on: 02/09/2023 10:02 PM Report Generation Date: 02/09/2023 10:02 PM ————————————————————————————————— Input File Name: LU Ballys FWTH.fld Project Name: Ballys Vault Size Land Use Analysis Title: Comments: ———————————————— PRECIPITATION INPUT ———————————————— Computational Time Step (Minutes): 15 Extended Precipitation Time Series Selected Full Period of Record Available used for Routing Climatic Region Number: 15 Precipitation Station : 96004005 Puget East 40 in_5min 10/01/1939-10/01/2097 Evaporation Station : 961040 Puget East 40 in MAP Evaporation Scale Factor : 0.750 HSPF Parameter Region Number: 3 HSPF Parameter Region Name : USGS Default ********** Default HSPF Parameters Used (Not Modified by User) *************** ********************** WATERSHED DEFINITION *********************** Predevelopment/Post Development Tributary Area Summary Predeveloped Post Developed Total Subbasin Area (acres) 5.868 5.868 Area of Links that Include Precip/Evap (acres) 0.000 0.000 Total (acres) 5.868 5.868 ----------------------SCENARIO: PREDEVELOPED Number of Subbasins: 1 ---------- Subbasin : Basin 5.868 ac ---------- -------Area (Acres) -------- Till Forest 5.868 ---------------------------------------------- Subbasin Total 5.868 ----------------------SCENARIO: POSTDEVELOPED Number of Subbasins: 1 ---------- Subbasin : Proposed Conditions 69% Imp ---------- -------Area (Acres) -------- Till Grass 1.824 Impervious 4.044 ---------------------------------------------- Subbasin Total 5.868 ************************* LINK DATA ******************************* ----------------------SCENARIO: PREDEVELOPED Number of Links: 0 ************************* LINK DATA ******************************* ----------------------SCENARIO: POSTDEVELOPED Number of Links: 1 ------------------------------------------ Link Name: PROP VAULT Link Type: Structure Downstream Link: None Prismatic Pond Option Used Pond Floor Elevation (ft) : 100.00 Riser Crest Elevation (ft) : 111.00 Max Pond Elevation (ft) : 112.00 Storage Depth (ft) : 11.00 Pond Bottom Length (ft) : 110.0 Pond Bottom Width (ft) : 87.0 Pond Side Slopes (ft/ft) : Z1= 0.00 Z2= 0.00 Z3= 0.00 Z4= 0.00 Bottom Area (sq-ft) : 9570. Area at Riser Crest El (sq-ft) : 9,570. (acres) : 0.220 Volume at Riser Crest (cu-ft) : 105,270. (ac-ft) : 2.417 Area at Max Elevation (sq-ft) : 9570. (acres) : 0.220 Vol at Max Elevation (cu-ft) : 114,840. (ac-ft) : 2.636 Hydraulic Conductivity (in/hr) : 0.00 Massmann Regression Used to Estimate Hydralic Gradient Depth to Water Table (ft) : 100.00 Bio-Fouling Potential : Low Maintenance : Average or Better Riser Geometry Riser Structure Type : Circular Riser Diameter (in) : 12.00 Common Length (ft) : 0.000 Riser Crest Elevation : 111.00 ft Hydraulic Structure Geometry Number of Devices: 3 ---Device Number 1 --- Device Type : Circular Orifice Control Elevation (ft) : 100.00 Diameter (in) : 0.94 Orientation : Horizontal Elbow : No ---Device Number 2 --- Device Type : Circular Orifice Control Elevation (ft) : 106.50 Diameter (in) : 1.13 Orientation : Horizontal Elbow : Yes ---Device Number 3 --- Device Type : Circular Orifice Control Elevation (ft) : 109.50 Diameter (in) : 1.94 Orientation : Horizontal Elbow : Yes **********************FLOOD FREQUENCY AND DURATION STATISTICS******************* ----------------------SCENARIO: PREDEVELOPED Number of Subbasins: 1 Number of Links: 0 ----------------------SCENARIO: POSTDEVELOPED Number of Subbasins: 1 Number of Links: 1 ********** Link: PROP VAULT ********** Link WSEL Stats WSEL Frequency Data(ft) (Recurrence Interval Computed Using Gringorten Plotting Position) Tr (yrs) WSEL Peak (ft) ====================================== 1.05-Year 103.468 1.11-Year 103.843 1.25-Year 104.389 2.00-Year 106.002 3.33-Year 106.924 5-Year 107.818 10-Year 109.403 25-Year 110.070 50-Year 110.284 100-Year 110.851 ***********Groundwater Recharge Summary ************* Recharge is computed as input to Perlnd Groundwater Plus Infiltration in Structures Total Predeveloped Recharge During Simulation Model Element Recharge Amount (ac-ft) ----------------------------------------------------------------------------------------------- Subbasin: Basin 5.868 ac 1011.813 _____________________________________ Total: 1011.813 Total Post Developed Recharge During Simulation Model Element Recharge Amount (ac-ft) ----------------------------------------------------------------------------------------------- Subbasin: Proposed Conditions 222.888 Link: PROP VAULT 0.000 _____________________________________ Total: 222.888 Total Predevelopment Recharge is Greater than Post Developed Average Recharge Per Year, (Number of Years= 158) Predeveloped: 6.404 ac-ft/year, Post Developed: 1.411 ac-ft/year ***********Water Quality Facility Data ************* ----------------------SCENARIO: PREDEVELOPED Number of Links: 0 ----------------------SCENARIO: POSTDEVELOPED Number of Links: 1 ********** Link: PROP VAULT ********** Basic Wet Pond Volume (91% Exceedance): 19740. cu-ft Computed Large Wet Pond Volume, 1.5*Basic Volume: 29610. cu-ft 2-Year Discharge Rate : 0.058 cfs 15-Minute Timestep, Water Quality Treatment Design Discharge On-line Design Discharge Rate (91% Exceedance): 0.58 cfs Off-line Design Discharge Rate (91% Exceedance): 0.32 cfs Infiltration/Filtration Statistics-------------------- Inflow Volume (ac-ft): 2179.98 Inflow Volume Including PPT-Evap (ac-ft): 2179.98 Total Runoff Infiltrated (ac-ft): 0.00, 0.00% Total Runoff Filtered (ac-ft): 0.00, 0.00% Primary Outflow To Downstream System (ac-ft): 2179.52 Secondary Outflow To Downstream System (ac-ft): 0.00 Volume Lost to ET (ac-ft): 0.00 Percent Treated (Infiltrated+Filtered+ET)/Total Volume: 0.00% ***********Compliance Point Results ************* Scenario Predeveloped Compliance Subbasin: Basin 5.868 ac Scenario Postdeveloped Compliance Link: PROP VAULT *** Point of Compliance Flow Frequency Data *** Recurrence Interval Computed Using Gringorten Plotting Position Predevelopment Runoff Postdevelopment Runoff Tr (Years) Discharge (cfs) Tr (Years) Discharge (cfs) ---------------------------------------------------------------------------------------------------------------------- 2-Year 0.125 2-Year 5.752E-02 5-Year 0.204 5-Year 0.102 10-Year 0.275 10-Year 0.127 25-Year 0.348 25-Year 0.207 50-Year 0.444 50-Year 0.221 100-Year 0.481 100-Year 0.255 200-Year 0.749 200-Year 0.258 500-Year 1.109 500-Year 0.262 ** Record too Short to Compute Peak Discharge for These Recurrence Intervals **** Flow Duration Performance **** Excursion at Predeveloped 50%Q2 (Must be Less Than or Equal to 0%): -32.5% PASS Maximum Excursion from 50%Q2 to Q2 (Must be Less Than or Equal to 0%): -9.3% PASS Maximum Excursion from Q2 to Q50 (Must be less than 10%): -60.7% PASS Percent Excursion from Q2 to Q50 (Must be less than 50%): 0.0% PASS ------------------------------------------------------------------------------------------------- MEETS ALL FLOW DURATION DESIGN CRITERIA: PASS ------------------------------------------------------------------------------------------------- 1st Avenue Development – City of Federal Way Appendix F Appendix F Water Quality Bio P od Detail and WADOE GULD Documentation ISOMETRIC VIEW BPU-IB C US Patents Pending THIS DOCUMENT IS THE PROPERTY OF OLDCASTLE INFRASTRUCTURE, INC. IT IS SUBMITTED FOR REFERENCE PURPOSES ONLY AND SHALL NOT BE USED IN ANY WAY INJURIOUS TO THE INTERESTS OF SAID COMPANY. COPYRIGHT © 2020 OLDCASTLE INFRASTRUCTURE, INC. ALL RIGHTS RESERVED. BioPod f Biofilter Underground Vault with Internal Bypass dOldcastle dOldcastle dOldcastle Bioretention/ Biofiltration A PLAN VIEW A SECTION A-A BPU-IB C US Patents PendingSAUDFI1325-0510USAXXXXTHIS DOCUMENT IS THE PROPERTY OF OLDCASTLE INFRASTRUCTURE, INC. IT IS SUBMITTED FOR REFERENCE PURPOSES ONLY AND SHALL NOT BE USED IN ANY WAY INJURIOUS TO THE INTERESTS OF SAID COMPANY. COPYRIGHT © 2020 OLDCASTLE INFRASTRUCTURE, INC. ALL RIGHTS RESERVED. MODEL VAULT SIZE 1 (ID) VAULT FOOTPRINT 1 (OD) TREATMENT FLOW CAPACITY (GPM/CFS) A DIM B DIM C DIM A1 DIM B1 DIM 1.6 GPM/SF (WA GULD2) 1.8 GPM/SF (NJCAT3) BPU-46IB 4'6'1.5'5'7'25.6 / 0.057 28.8 / 0.064 BPU-48IB 4'8'1.5'5'9'38.4 / 0.086 43.2 / 0.096 BPU-412IB 4'12'1.5'5'13'64.0 / 0.143 72.0 / 0.160 BPU-66IB 6'6'1.5'7'7'38.4 / 0.086 43.2 / 0.096 BPU-68IB 6'8'1.5'7'9'57.6 / 0.128 64.8 / 0.144 BPU-612IB 6'12'2'7'13'91.2 / 0.203 102.6 / 0.229 BPU-812IB 8'12'2'9'13'121.6 / 0.271 136.9 / 0.305 BPU-816IB 8'16'2'9'17'172.8 / 0.385 194.4 / 0.433 BioPod f Biofilter Underground Vault with Internal Bypass fFIDSAUXXXXUSADFI11540010FIDSAUXXXXUSADFI11540010 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 (Front or Side)Pipe Size Pipe Type Invert Elevation Inlet Outlet Notes: 1 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 & NJ DEP Certification. Bioretention/ Biofiltration XXXX XXXX XXXX XXXX XXXX XXXX XX" PER PLAN XXXXX XXXX XX" PER PLAN XXX.XX TREATMENT FLOW RATE BASED ON 2-YR RELEASE RATE DOWNSTREAM OF DETENTION FACILITY October 2019 GENERAL USE LEVEL DESIGNATION FOR BASIC (TSS), DISSOLVED METALS (ENHANCED), AND PHOSPHORUS TREATMENT For Oldcastle Infrastructure, Inc.’s The BioPod™ Biofilter (Formerly the TreePod Biofilter) Ecology’s Decision: Based on Oldcastle Infrastructure, Inc. application submissions for the The BioPod™ Biofilter (BioPod), Ecology hereby issues the following use level designation: 1. General Use Level Designation (GULD) for Basic, Enhanced, and Phosphorus Treatment: Sized at a hydraulic loading rate of 1.6 gallons per minute (gpm) per square foot (sq ft) of media surface area. Constructed with a minimum media thickness of 18-inches (1.5-feet). 2. Ecology approves the BioPod at the hydraulic loading rate listed above, to achieve the maximum water quality design flow rate. The water quality design flow rates are calculated using the following procedures: Western Washington: For treatment installed upstream of detention or retention, the water quality design flow rate is the peak 15-minute flow rate as calculated using the latest version of the Western Washington Hydrology Model or other Ecology- approved continuous runoff model. Eastern Washington: For treatment installed upstream of detention or retention, the water quality design flow rate is the peak 15-minute flow rate as calculated using one of the three methods described in Chapter 2.2.5 of the Stormwater Management Manual for Eastern Washington (SWMMEW) or local manual. Entire State: For treatment installed downstream of detention, the water quality design flow rate is the full 2-year release rate of the detention facility. 3. The GULD has no expiration date, but may be amended or revoked by Ecology. Ecology’s Conditions of Use: The BioPod shall comply with these conditions: 1) Applicants shall design, assemble, install, operate, and maintain the BioPod installations in accordance with Oldcastle Infrastructure, Inc.’s applicable manuals and the Ecology Decision. 2) The minimum size filter surface-area for use in Washington is determined by using the design water quality flow rate (as determined in Ecology Decision, Item 3, above) and the Infiltration Rate (as identified in Ecology Decision, Item 1, above). Calculate the required area by dividing the water quality design flow rate (cu-ft/sec) by the Infiltration Rate (converted to ft/sec) to obtain required surface area (sq ft) of the BioPod unit 3) BioPod media shall conform to the specifications submitted to and approved by Ecology 4) Maintenance: The required inspection/maintenance interval for stormwater treatment devices is often dependent on the efficiency of the device and the degree of pollutant loading from a particular drainage basin. Therefore, Ecology does not endorse or recommend a “one size fits all” maintenance cycle for a particular model/size of manufactured filter treatment device. The BioPod is designed for a target maintenance interval of 1 year. Maintenance includes replacing the mulch, assessing plant health, removal of trash, and raking the top few inches of engineered media. A BioPod system tested at the Lake Union Ship Canal Test Facility in Seattle, WA required maintenance after 1.5 months, or 6.3% of a water year. Monitoring personnel observed similar maintenance issues with other systems evaluated at the Test Facility. The runoff from the Test Facility may be unusual and maintenance requirements of systems installed at the Test Facility may not be indicative of maintenance requirements for all sites. Test results provided to Ecology from a BioPod System evaluated in a lab following New Jersey Department of Environmental Protection Laboratory Protocol for Filtration MTDs have indicated the BioPod System is capable of longer maintenance intervals. Owners/operators must inspect BioPod systems for a minimum of twelve months from the start of post-construction operation to determine site-specific inspection/maintenance schedules and requirements. Owners/operators must conduct inspections monthly during the wet season, and every other month during the dry season. (According to the SWMMWW, the wet season in western Washington is October 1 to April 30. According to the SWMMEW, the wet season in eastern Washington is October 1 to June 30.) After the first year of operation, owners/operators must conduct inspections based on the findings during the first year of inspections. Conduct inspections by qualified personnel, follow manufacturer’s guidelines, and use methods capable of determining either a decrease in treated effluent flow rate and/or a decrease in pollutant removal ability. 5) Install the BioPod in such a manner that you bypass flows exceeding the maximum operating rate and you will not resuspend captured sediment. 6) Discharges from the BioPod shall not cause or contribute to water quality standards violations in receiving waters. Approved Alternate Configurations BioPod Internal Bypass 1) The BioPod Internal Bypass configuration may be combined with a Curb Inlet, Grated Inlet, and Piped-In Inlet. Water quality flows and peak flows are directed from the curb, overhead grate, or piped inlet to a contoured inlet rack. The inlet rack disperses water quality flows over the top surface of the biofiltration chamber. Excess flows are diverted over an curved bypass weir to the outlet area without passing through the treatment area. Both water quality flows and bypass flows are combined in the outlet area prior to being discharged out of the system. 2) To select a BioPod Internal Bypass unit, the designer must determine the size of the standard unit using the sizing guidance described above. Systems that have an internal bypass, may use the off-line water quality design flow rate. 3) The internal bypass configuration has a maximum flow rate of 900 gallons per minute. Sites where the anticipated flow rate at the treatment device is larger than 900 gpm must use an external bypass, or size the treatment device for the on-line water quality design flow rate. Applicant: Oldcastle Infrastructure, Inc. Applicant’s Address: 7100 Longe St, Suite 100 Stockton, CA 95206 Application Documents: Technical Evaluation Report TreePod™ BioFilter System Performance Certification Project, Prepared for Oldcastle, 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 TreePod™ Biofilter System Performance Certification Project, Oldcastle, Inc. and Herrera Environmental Consultants, Inc., February 2018 Technical Memorandum: Response to Board of External Reviewers’ Comments on the Technical Evaluation Report for the TreePod™ Biofilter System Performance Certification Project, Oldcastle, Inc. and Herrera Environmental Consultants, Inc., January 2018 Application for Pilot Use Level Designation, TreePod™ Biofilter – Stormwater Treatment System, Oldcastle Stormwater Solutions, May 2016 Emerging Stormwater Treatment Technologies Application for Certification: The TreePod™ 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 BioPod™ 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. 50% or greater total phosphorus for influent concentrations 0.1 to 0.5 mg/L. Ecology’s Recommendations: Ecology finds that: Oldcastle Infrastructure, Inc. has shown Ecology, through laboratory and field testing, that the BioPod™ 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 BioPod™ 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: 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 BioPod™ 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 https://oldcastleprecast.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: https://oldcastleprecast.com/stormwater/ Ecology web link: https://ecology.wa.gov/Regulations-Permits/Guidance-technical- assistance/Stormwater-permittee-guidance-resources/Emerging-stormwater-treatment- technologies Ecology: Douglas C. Howie, P.E. Department of Ecology Water Quality Program (360) 407-6444 douglas.howie@ecy.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 September 2018 Changed Address for Oldcastle December 2018 Added minimum media thickness requirement May 2019 Changed language on who must Install and maintain the device from Oldcastle to Applicants August 2019 Added text on sizing using infiltration rate and water quality design flow rate October 2019 Added text describing ability to use off-line design water quality flow rate for sizing due to internal bypass 1st Avenue Development – City of Federal Way Appendix G Appendix G Geotechnical Investigation Report