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21-102929-UP-Drainage Technical Information Report-07-16-2021-V1 Civil Engineers ● Structural Engineers ● Landscape Architects ● Community Planners ● Land Surveyors Technical Information Report PREPARED FOR: Federal Way Public Schools 33330 8th Avenue South Federal Way, WA 98003 PROJECT: Federal Way High School Pre-Apprenticeship Space 30611 16th Avenue South Federal Way, WA 98003 2210134.10 2210134.10PREPARED BY: James A. Daley, EIT Project Engineer REVIEWED BY: Lucas Johnson, PE, LEED AP Project Manager DATE: July 2021 Technical Information Report PREPARED FOR: Federal Way Public Schools 33330 8th Avenue South Federal Way, WA 98003 PROJECT: Federal Way High School Pre-Apprenticeship Space 30611 16th Avenue South Federal Way, WA 98003 2210134.10 2210134.10PREPARED BY: James A. Daley, EIT Project Engineer REVIEWED BY: Lucas Johnson, PE, LEED AP Project Manager DATE: July 2021 I hereby state that this Technical Information Report for the Federal Way High School Pre-Apprenticeship Space project was prepared by me or under my supervision, and meets the standard of care and expertise that is usual and customary in this community for professional engineers. I understand that King County does not and will not assume liability for the sufficiency, suitability, or performance of drainage facilities prepared by me. 07/08/2021 0 Technical Information Report Federal Way High School Pre-Apprenticeship Space i 2210134.10 Table of Contents Section Page 1.0 Project Overview ......................................................................................................................... 1-1 Purpose and Scope.......................................................................................................... 1-1 Existing Conditions........................................................................................................... 1-1 Post-Development Conditions ......................................................................................... 1-2 Section 1.0 Figures Figure 1-1 ......... TIR Worksheet Figure 1-2 ......... Site Location Map Figure 1-3 ......... Drainage Basin and Site Map Figure 1-4 ......... Table A 2.0 Conditions and Requirements Summary ................................................................................. 2-1 Core Requirements .......................................................................................................... 2-1 2.1.1 CR 1 - Discharge at the Natural Location ........................................................... 2-1 2.1.2 CR 2 - Offsite Analysis ........................................................................................ 2-1 2.1.3 CR 3 - Flow Control ............................................................................................ 2-1 2.1.4 CR 4 - Conveyance System ................................................................................ 2-1 2.1.5 CR 5 - Erosion and Sediment Control................................................................. 2-1 2.1.6 CR 6 - Maintenance and Operations .................................................................. 2-1 2.1.7 CR 7 - Financial Guarantees and Liability .......................................................... 2-2 2.1.8 CR 8 - Water Quality ........................................................................................... 2-2 2.1.9 CR 9 – Flow Control Best Management Practices (BMPs) ................................ 2-2 Special Requirements ...................................................................................................... 2-2 2.2.1 SR 1 - Other Adopted Area-Specific Requirements ........................................... 2-2 2.2.2 SR 2 - Floodplain/Floodway Delineation ............................................................. 2-2 2.2.3 SR 3 - Flood Protection Facilities........................................................................ 2-2 2.2.4 SR 4 - Source Control ......................................................................................... 2-2 2.2.5 SR 5 - Oil Control ................................................................................................ 2-3 Section 2.0 Figures Figure 2-1 ......... Flood Insurance Rate Map Figure 2-2 ......... Bioretention Sizing Calculations Technical Information Report Federal Way High School Pre-Apprenticeship Space ii 2210134.10 3.0 Offsite Analysis ........................................................................................................................... 3-1 4.0 Flow Control and Water Quality Facilities Analysis and Design ........................................... 4-1 Flow Control ..................................................................................................................... 4-1 4.1.1 Existing Site Hydrology (Part A) .......................................................................... 4-1 4.1.2 Post Development Site Hydrology (Part B) ......................................................... 4-1 4.1.3 Performance Standards (Part C) ........................................................................ 4-1 4.1.4 Flow Control System (Part D) ............................................................................. 4-1 4.1.5 Water Quality System (Part E) ............................................................................ 4-1 5.0 Conveyance System Analysis and Design ............................................................................... 5-1 Section 5.0 Figures Figure 5-1 ......... Conveyance Calculations 6.0 Special Reports and Studies ..................................................................................................... 6-1 Section 6.0 Figures Figure 6-1 ......... Technical Information Report (Springline Design, LLC, August 1, 2014) Figure 6-2 ......... Geotechnical Engineering Report (Associated Earth Sciences, Inc., February 8, 2021) 7.0 Other Permits .............................................................................................................................. 7-1 8.0 CSWPPP Analysis and Design .................................................................................................. 8-1 ESC Plan Analysis and Design (Part A) .......................................................................... 8-1 8.1.1 ESC Maintenance ............................................................................................... 8-2 8.1.2 ESC Supervisor................................................................................................... 8-2 8.1.3 Documentation .................................................................................................... 8-2 8.1.4 Review Timing ..................................................................................................... 8-2 Stormwater Pollution Prevention and Spill (SWPPS) Plan Design (Part B) .................... 8-2 8.2.1 Pollution and Spill Prevention Source Controls and BMPs ................................ 8-3 8.2.2 Responsible Personnel and Contact Information ............................................... 8-4 8.2.3 Pollution and Spill Prevention Worksheets ......................................................... 8-5 8.2.4 Disposal Methods................................................................................................ 8-5 Section 8.0 Figures Figure 8-1 ......... ESC Maintenance Report Figure 8-2 ......... CSWPP Forms Figure 8-3 ......... Pollution Prevention Inspection Reports, Spill Prevention Monitoring, and Spill Incident Reports Technical Information Report Federal Way High School Pre-Apprenticeship Space iii 2210134.10 9.0 Bond Quantities, Facilities Summaries, and Declarations of Covenant ............................... 9-1 Section 9.0 Figures Figure 9-1 ......... Stormwater Facility Summary Sheet Figure 9-2 ......... Stormwater Facility Sketches Figure 9-3 ......... Declaration of Covenant for Inspection and Maintenance of Stormwater Facilities and BMPs 10.0 Operations and Maintenance Plan .......................................................................................... 10-1 Facility Descriptions ....................................................................................................... 10-1 10.1.1 Bioretention BMP .............................................................................................. 10-1 10.1.2 Conveyance Pipes and Ditches ........................................................................ 10-1 Maintenance Requirements ........................................................................................... 10-1 Section 10.0 Figures Figure 10-1 ....... Maintenance Requirements for Flow Control, Conveyance, and Water Quality Facilities 11.0 Conclusion ................................................................................................................................. 11-1 Technical Information Report Federal Way High School Pre-Apprenticeship Space 2210134.10 Section 1 Project Overview Technical Information Report Federal Way High School Pre-Apprenticeship Space 1-1 2210134.10 1.0 Project Overview Purpose and Scope This report accompanies the civil engineering plans and documents for the Federal Way High School Pre-Apprenticeship Space. Federal Way High School is located at 30611 16th Avenue South, Federal Way, Washington. The location of work is between the Federal Way High School main building to the east and 14th Avenue South to the west, north of South 308th Street. The site is to be accessed via 14th Avenue South. The site is located on Tax Parcel No. 0821049001 in Section 8, Township 21 North, Range 4 East of the Willamette Meridian, city of Federal Way, King County, Washington. Refer to Figure 1-1 for the Technical Information Report (TIR) Worksheet and Figure 1-2 for the Site Location Map. The Federal Way High School Pre-Apprenticeship Space project proposes the construction of a new 1,152-square foot pole barn building, along with associated outdoor student seating, a rain garden, and gravel surfacing. Stormwater generated from the pole barn roof will be collected via downspouts and roof drains and conveyed to a bioretention facility (rain garden). Stormwater generated by other impervious surfaces will maintain existing drainage patterns and flow into an existing catch basin located at the east side of the Pre-Apprenticeship Space site. The Federal Way High School property is completely developed and includes paved roadways and parking lots, landscaped areas, sport/recreation fields and facilities, and a detention pond. Currently the site is a 7,151-square foot landscaped area on the Federal Way High School property. The project proposes 6,915 square feet of new impervious surfaces , including a 1,152-square foot roof, three 50-square foot seating walls, and 5,613 square feet of gravel surfacing. No pollution generating impervious surfaces (PGIS) are proposed for this site. The project site is located in the Lower Puget Sound Drainage Basin. There are no critical areas on or adjacent to the site. All construction proposed has been designed to meet the 2016 King County Surface Water Design Manual (KCSWDM), as adopted by City Federal Way per the Addendum to the King County Surface Water Manual (Addendum), January 8, 2017. Existing Conditions The property is currently fully developed and consists of the Federal Way High School main building, sport/recreational fields and facilities with sidewalks, paved roadways and parking lots, landscaped areas, and a detention pond. In the existing condition, the site and immediate adjacent areas generally slope down from northeast to southwest, with elevations ranging from 467 to 460. The site is located north of an existing parking lot, east of 14th Avenue South, south of existing landscaped areas, and west of the high school main building. Stormwater on the existing site sheet flows to an existing yard drain and existing catch basins. Stormwater is conveyed through pipes to the existing stormwater detention pond. Refer to Figure 1-3 for a Drainage Basin and Site Map. Technical Information Report Federal Way High School Pre-Apprenticeship Space 1-2 2210134.10 Post-Development Conditions The project proposes to construct a new pole barn structure, along with associated student seating walls, gravel surfacing, and a bioretention facility (rain garden). The pole barn will be located in the central-western portion of the project site, with the associated student seating walls in the northeast corner and the bioretention facility on the west side of the site. Stormwater runoff from the roof of the new pole barn will be collected via downspouts and roof drain s and conveyed to a new bioretention facility. Stormwater runoff from the gravel surfacing and seating walls will sheet flow to the existing catch basins and associated existing stormwater facilities. The existing stormwater facilities have been sized to accommodate roughly one additional acre of impervious surfaces. Refer to the attached TIR by Springline Design, LLC (Figure 6-1) detailing the capacity of the existing detention pond. The proposed developed site, including grading and drainage amenities, can be viewed in Figure 1-4. Technical Information Report Federal Way High School Pre-Apprenticeship Space 2210134.10 Section 1.0 Figures Figure 1-1 ......... TIR Worksheet Figure 1-2 ......... Site Location Map Figure 1-3 ......... Drainage Basin and Site Map Figure 1-4 ......... Table A CITY OF RENTON SURFACE WATER DESIGN MANUAL 2017 City of Renton Surface Water Design Manual 12/12/2016 8-A-1 REFERENCE 8-A TECHNICAL INFORMATION REPORT (TIR) WORKSHEET Part 1 PROJECT OWNER AND PROJECT ENGINEER Part 2 PROJECT LOCATION AND DESCRIPTION Project Owner _____________________________ Phone ___________________________________ Address __________________________________ _________________________________________ Project Engineer ___________________________ Company _________________________________ Phone ___________________________________ Project Name __________________________ CED Permit # ________________________ Location Township ________________ Range __________________ Section _________________ Site Address __________________________ _____________________________________ Part 3 TYPE OF PERMIT APPLICATION Part 4 OTHER REVIEWS AND PERMITS  Land Use (e.g., Subdivision / Short Subd.)  Building (e.g., M/F / Commercial / SFR)  Grading  Right-of-Way Use  Other _______________________  DFW HPA  COE 404  DOE Dam Safety  FEMA Floodplain  COE Wetlands  Other ________  Shoreline Management  Structural Rockery/Vault/_____  ESA Section 7 Part 5 PLAN AND REPORT INFORMATION Technical Information Report Site Improvement Plan (Engr. Plans) Type of Drainage Review (check one): Date (include revision dates): Date of Final:  Full  Targeted  Simplified  Large Project  Directed __________________ __________________ __________________ Plan Type (check one): Date (include revision dates): Date of Final:  Full  Modified  Simplified __________________ __________________ __________________ Figure 1-1 33330 8th Avenue South, Federal Way, WA 98003 James A. Daley, EIT AHBL, Inc. (253) 383-2422 Federal Way Public Schools (253) 261-5506 Federal Way High School Pre-Apprenticeship Space 21 N 4 E 8 30611 16th Avenue South Federal Way, WA 98003 X X X Use Process 1 and Engineering Permits July 2021 Version 1July 2021 Version 1 REFERENCE 8: PLAN REVIEW FORMS AND WORKSHEET TECHNICAL INFORMATION REPORT (TIR) WORKSHEET 12/12/2016 2017 City of Renton Surface Water Design Manual 8-A-2 Part 6 SWDM ADJUSTMENT APPROVALS Type (circle one): Standard / Blanket Description: (include conditions in TIR Section 2) ____________________________________________________________________________________ ____________________________________________________________________________________ ____________________________________________________________________________________ Approved Adjustment No. ______________________ Date of Approval: _______________________ Part 7 MONITORING REQUIREMENTS Monitoring Required: Yes / No Start Date: _______________________ Completion Date: _______________________ Describe: _________________________________ _________________________________________ _________________________________________ Re: SWDM 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 ________________________  Lake ______________________________  Wetlands ____________________________  Closed Depression ____________________  Floodplain ___________________________  Other _______________________________ _______________________________  Steep Slope __________________________  Erosion Hazard _______________________  Landslide Hazard ______________________  Coal Mine Hazard ______________________  Seismic Hazard _______________________  Habitat Protection ______________________  _____________________________________ N/A Federal Way High School Lower Puget Sound REFERENCE 8-A: TECHNICAL INFORMATION REPORT (TIR) WORKSHEET TECHNICAL INFORMATION REPORT (TIR) WORKSHEET 2017 City of Renton Surface Water Design Manual 12/12/2016 Ref 8-A-3 Part 10 SOILS Soil Type ______________________ ______________________ ______________________ ______________________ Slopes ________________________ ________________________ ________________________ ________________________ Erosion Potential _________________________ _________________________ _________________________ _________________________  High Groundwater Table (within 5 feet)  Other ________________________________  Sole Source Aquifer  Seeps/Springs  Additional Sheets Attached Part 11 DRAINAGE DESIGN LIMITATIONS REFERENCE  Core 2 – Offsite Analysis_________________  Sensitive/Critical Areas__________________  SEPA________________________________  LID Infeasibility________________________  Other________________________________  _____________________________________ LIMITATION / SITE CONSTRAINT _______________________________________ _______________________________________ _______________________________________ _______________________________________ _______________________________________ _______________________________________  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 summary sheet) Standard: _______________________________ or Exemption Number: ____________ On-site BMPs: _______________________________ Conveyance System Spill containment located at: _____________________________ Erosion and Sediment Control / Construction Stormwater Pollution Prevention CSWPP/CESCL/ESC Site Supervisor: _____________________ Contact Phone: _________________________ After Hours Phone: _________________________ 1-5%, at site MinimalSilty Fine to Medium Sand with Gravel 1 Bioretention TBD REFERENCE 8: PLAN REVIEW FORMS AND WORKSHEET TECHNICAL INFORMATION REPORT (TIR) WORKSHEET 12/12/2016 2017 City of Renton Surface Water Design Manual 8-A-4 Part 12 TIR SUMMARY SHEET (provide one TIR Summary Sheet per Threshold Discharge Area) 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 summary sheet) Type (circle one): Basic / Sens. Lake / Enhanced Basic / Bog or Exemption No. _______________________ Special Requirements (as applicable): Area Specific Drainage Requirements Type: SDO / MDP / BP / 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: N/A Commercial (public school) Conveyance pipes. 236 square foot bioretention (rain garden). No Pollution Generating Surfaces REFERENCE 8-A: TECHNICAL INFORMATION REPORT (TIR) WORKSHEET TECHNICAL INFORMATION REPORT (TIR) WORKSHEET 2017 City of Renton Surface Water Design Manual 12/12/2016 Ref 8-A-5 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  Control Pollutants  Protect Existing and Proposed BMPs/Facilities  Maintain Protective 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 BMPs/Facilities, restore operation of BMPs/Facilities as necessary  Flag limits of sensitive areas and open space preservation areas  Other _______________________ 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  On-site BMPs  Other ________________ ________________ ________________ ________________ ________________ ________________  Vegetated Flowpath  Wetpool  Filtration  Oil Control  Spill Control  On-site BMPs  Other ________________ ________________ ________________ ________________ ________________ ________________ ________________ Part 15 EASEMENTS/TRACTS Part 16 STRUCTURAL ANALYSIS  Drainage Easement  Covenant  Native Growth Protection Covenant  Tract  Other ____________________________  Cast in Place Vault  Retaining Wall  Rockery > 4′ High  Structural on Steep Slope  Other _______________________________ x x x x x x x x x x x x x x x x x Bioretention (rain garden) REFERENCE 8: PLAN REVIEW FORMS AND WORKSHEET TECHNICAL INFORMATION REPORT (TIR) WORKSHEET 12/12/2016 2017 City of Renton Surface Water Design Manual 8-A-6 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 David Nason, PE AHBL Inc. DRAWN BY:DATE:JOB NO.: 2215 North 30th Street, Suite 300 Tacoma, WA 98403 253.383.2422 TEL 253.383.2572 FAX Fairwood Golf and Country Club Improvements Site Location Map James A. Daley 07/2/2021 2210134.10 1-2 Site 2215 North 30th StreetSuite 300Tacoma, WA 98403253.383.2422 TEL253.383.2572 FAXFederal Way High School Pre-Apprenticeship SpaceDrainage Basin and Site MapFigure1-3PROJECT BASIN0.00 AC PERVIOUS0.16 AC IMPERVIOUSBIORETENTION CELL(MANAGES ROOF RUNOFF)PROPOSED BUILDING - 1,152 SFEXISTING CATCH BASIN TOREMAIN, COLLECT RUNOFFFROM GRAVEL SURFACINGEXISTING STORM PIPE,CONVEYS RUNOFF TOEXISTING DETENTIONPOND ON WEST SIDEOF PROJECT PARCEL Table A Proposed Impervious Surface: Fill in all applicable blanks below to list the square footage of all new and existing impervious surface areas on your parcel. When calculating impervious surface areas for buildings do not list the living/useable space square-footage, instead list the building roof square- footage measured to the outside edge of the eve or gutter. Impervious New Existing Total Roof Area (House, Attached Garage, Covered Patio, Covered Deck, sq. ft. sq. ft. sq. ft. Covered Porch) Roof Area (Detached Garage) sq. ft. sq. ft. sq. ft. Roof Area (All Out Buildings) sq. ft. sq. ft. sq. ft. On-site Driveway Area sq. ft. sq. ft. sq. ft. Off-site Driveway Area sq. ft. sq. ft. sq. ft. Walkways / Sidewalks / Stepping Stone Area sq. ft. sq. ft. sq. ft. Uncovered Porch and / or Patios Area sq. ft. sq. ft. sq. ft. Uncovered Decks Area sq. ft. sq. ft. sq. ft. Replaced Impervious Area (Considered New Impervious) sq. ft. sq. ft. sq. ft. All Other Impervious Areas sq. ft. sq. ft. sq. ft. Total New Impervious Surface Area sq. ft. Total Existing Impervious Surface Area sq. ft. Total Impervious Areas sq. ft. Total Clearing Limits, Site Disturbance / Graded Areas (Include Septic Drainfields Primary and Reserve) sq. ft. Total New Pervious Areas [(Total Clearing Limits, Site Disturbance/Graded Areas) – (Total New Impervious Areas)] sq. ft. Total of Excavation Volume Cubic Yard Total of Fill Volume (Exported) Cubic Yard Total of Fill Volume (Imported) Cubic Yard For DPER Staff Use ONLY Parcel Number: Application Number: Approved By: Date: 5,7635,763 6,915 0 6,915 7,151 236 70 (FILL) 0 40 0 1,152 0 1,152 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 Technical Information Report Federal Way High School Pre-Apprenticeship Space 2210134.10 Section 2 Conditions and Requirements Summary Technical Information Report Federal Way High School Pre-Apprenticeship Space 2-1 2210134.10 2.0 Conditions and Requirements Summary Core Requirements 2.1.1 CR 1 - Discharge at the Natural Location The project site currently slopes from north to south. Stormwater drains by means of overland flow to one of two onsite catch basins. The catch basins are connected to an enclosed pipe network that conveys stormwater to an existing detention pond located at the west side of the project parcel. In the developed condition, stormwater from the building roof will be conveyed to a bioretention facility (rain garden) that will overflow to the existing storm pipe system. Runoff generated by other hard surfaces will maintain existing drainage patterns and will be collected by the existing catch basins to remain. Stormwater discharge created by the proposed improvements will not adversely affect downstream properties or drainage systems. 2.1.2 CR 2 - Offsite Analysis An offsite analysis is required for this project and is discussed in Section 3.0. 2.1.3 CR 3 - Flow Control This project proposes 6,915 square feet (0.16 acre) of new non-pollution generating impervious (NPGIS) surfaces. The existing stormwater detention pond was designed with the capacity for an additional 0.94 acre of impervious surfaces in the case of redevelopment. This project proposes to use the additional capacity. Post-redevelopment will leave the pond with an additional capacity of 0.78 acre of impervious surfaces for future redevelopment. Because of this, flow control measures are not required. Refer to page 23 of the 2014 Federal Way High School TIR, Section IV – Flow Control and Water Quality Facility Analysis and Design (Figure 6-1 in this report). 2.1.4 CR 4 - Conveyance System The proposed conveyance systems for this project are composed of underground piped. The design and calculations for the proposed conveyance systems are included in Section 5.0. The conveyance systems meet all requirements for new systems outlined in Section 1.2.4.1 of the KCSWDM. 2.1.5 CR 5 - Erosion and Sediment Control An erosion and sediment control plan was developed for this site in accordance with the KCSWDM and to conform to the requirements of the National Pollutant Discharge Elimination System (NPDES) Construction Stormwater General Permit, issued by the Department of Ecology (DOE). The full erosion and sediment control plan is described in Section 8.0 and is depicted on the project drawings. 2.1.6 CR 6 - Maintenance and Operations The onsite drainage facilities will be privately maintained by Federal Way Public Schools. An Operations and Maintenance Manual is provided in Section 10.0. Technical Information Report Federal Way High School Pre-Apprenticeship Space 2-2 2210134.10 2.1.7 CR 7 - Financial Guarantees and Liability The owner and contractor will obtain all necessary permits required by City of Federal Way prior to the beginning of construction. Federal Way Public Schools is exempt from typical bonding requirements because it is a public agency. Because of this, a Bond Quantity Worksheet is not required and has not been prepared. 2.1.8 CR 8 - Water Quality The proposed project does not include PGIS, and therefore water treatment is not required. 2.1.9 CR 9 – Flow Control Best Management Practices (BMPs) The Federal Way High School Pre-Apprenticeship Space site is classified as a Large Lot BMP per Section 1.2.9.2.2 of the KCSWDM. Below is a summary of the flow control BMPs that were considered. 1. Full Dispersion – This BMP is infeasible because there is insufficient area available to disperse stormwater. 2. Full Infiltration of Roof Runoff – Onsite soils consist of glacial till, which is not suitable for stormwater infiltration. This BMP is infeasible because of the poorly infiltrating soils. 3. Bioretention – A bioretention cell is proposed to manage stormwater from the building roof. Refer to Figure 2-2 for Bioretention Sizing Calculations. Refer to Section 4.0 for more information on the proposed bioretention facility. No further flow control BMPs ar e required. Special Requirements 2.2.1 SR 1 - Other Adopted Area-Specific Requirements To our knowledge, no other adopted area-specific requirements are applicable to the project site. 2.2.2 SR 2 - Floodplain/Floodway Delineation Federal Emergency Management Agency (FEMA) Flood Insurance Rate Map No. 53033C1230G was reviewed for this project. It indicates that the project site is within a Zone X area. This area is determined to be outside of the 500-year floodplain. Refer to Figure 2-1 for the Flood Insurance Rate Map. 2.2.3 SR 3 - Flood Protection Facilities The project site does not contain, nor is it adjacent to, any existing flood protection facilities. Project improvements do not include flood protection measures. 2.2.4 SR 4 - Source Control The King County Stormwater Pollution Prevention Manual (KCSPPM) will be referenced for source control measures, in addition to erosion and sediment control measures, during construction. For construction source controls, see Section 8.0, CSWPPP Analysis and Design. For post-construction source controls, see Section 10.0, Operations and Maintenance Plan. Technical Information Report Federal Way High School Pre-Apprenticeship Space 2-3 2210134.10 2.2.5 SR 5 - Oil Control The project site is not considered a high-use site. Therefore, it is not subject to oil control requirements. Technical Information Report Federal Way High School Pre-Apprenticeship Space 2210134.10 Section 2.0 Figures Figure 2-1 ......... Flood Insurance Rate Map Figure 2-2 ......... Bioretention Sizing Calculations Civil Engineers Structural Engineers Landscape Architects Community Planners Land Surveyors Neighbors TACOMA 2215 North 30th Street Suite 300 Tacoma, WA 98403-3350 253.383.2422 TEL www.ahbl.com Project__________________________ Subject _________________________ With/To_________________________ Address_________________________ Date____________________________ Project No.______________________ Phone__________________________ FAX # _________________________ # Faxed Pages ___________________ By_____________________________ Page _____ of _____ Calculations Fax Memorandum Meeting Minutes Telephone Memo Please contact AHBL with any questions, comments, or concerns about the above calculations. Thank you. 1. Bioretention sized per section 1.2.9.2.1 of the KCSWDM: - The project is within the Urban Growth Area (UGA) - On-site soils are described as till soils per the USDA soils data - Bioretention volume based on 0.6 inches of equivalent storage depth 2. Area draining to bioretention ~ 1152 sf - Bioretention Volume = (1152 sf)*(0.6 inch)*(1 ft/ 12 inch) = 57.60 CF 3. The bioretention facility will be 1 foot deep with a bottom area of 6.5' x 13.5' and a top area of 12.5' x 19.5'. The bioretention facility has a capacity of 60 cubic feet. Technical Information Report Federal Way High School Pre-Apprenticeship Space 2210134.10 Section 3 Offsite Analysis Technical Information Report Federal Way High School Pre-Apprenticeship Space 3-1 2210134.10 3.0 Offsite Analysis An offsite analysis was performed by Springline Design, LLC as part of the recent Federal Way High School construction project. Refer to the Springline Design TIR, Section III, in Figure 6-1 of this report. The analysis has been reviewed by AHBL and is confirmed as accurate. Technical Information Report Federal Way High School Pre-Apprenticeship Space 2210134.10 Section 4 Flow Control and Water Quality Facilities Analysis and Design Technical Information Report Federal Way High School Pre-Apprenticeship Space 4-1 2210134.10 4.0 Flow Control and Water Quality Facilities Analysis and Design Flow Control 4.1.1 Existing Site Hydrology (Part A) The existing site drains by means of overland flow to an existing yard drain and catch basin located within the project limits. Stormwater is conveyed in an enclosed pipe network to the existing detention pond located along the west side of the project parcel. 4.1.2 Post Development Site Hydrology (Part B) The new Pre-Apprenticeship Space will replace an existing landscaped area. A network of roof downspouts and roof drains will be installed to capture runoff generated by the pole barn roof and convey it to the proposed bioretention facility. Runoff generated by other hard surfaces will maintain the current flow path and will flow into the existing catchment structures located in the project limits. A bioretention facility is proposed to provide flow control for the pole barn roof. The bioretention facility was sized using the guidelines in the KCSWDM. Refer to Figure 2-2 for Bioretention Sizing Calculations. 4.1.3 Performance Standards (Part C) Flow control is provided by an existing stormwater detention pond located along the west side of the project parcel. The project will apply flow control BMPs in the form of a bioretention facility to meet Core Requirement (CR) 9. As discussed further in Section 5.0, the proposed conveyance system was designed to convey the 100-year, 24-hour design storm event (refer to Figure 5-1 for conveyance calculations). No pollution generating surfaces are proposed, and therefore water treatment will not be provided. 4.1.4 Flow Control System (Part D) As discussed in Section 2.1.9, the project proposes a bioretention facility as a flow control BMP. Refer to Figure 2-2 for Bioretention Sizing Calculations and Figure 9-2 for a sketch and location of the proposed bioretention facility. 4.1.5 Water Quality System (Part E) As discussed in Section 2.1.8, the project is exempt from water quality requirements. The project will not add pollution generating surfaces. Technical Information Report Federal Way High School Pre-Apprenticeship Space 2210134.10 Section 5 Conveyance System Analysis and Design Technical Information Report Federal Way High School Pre-Apprenticeship Space 5-1 2210134.10 5.0 Conveyance System Analysis and Design Based on Section 1.2.4.1 of the KCSWDM, the pipe system was designed to convey and contain at least the peak runoff rate of the 25-year design storm and the 100-year storm event without creating or aggravating a severe flooding or erosion problem. The new conveyance line is a 6-inch pipe with at least a 0.5 percent slope. The size, material, and slope of the pipes chosen are sufficient to convey the 100-year, 24-hour storm. A conveyance analysis was completed using StormSHED2G software and the Santa Barbara Urban Hydrograph (SBUH) method. Refer to Figure 5-1 for the Conveyance Calculations. Technical Information Report Federal Way High School Pre-Apprenticeship Space 2210134.10 Section 5.0 Figures Figure 5-1 ......... Conveyance Calculations Project: Federal Way High School Pre-Apprenticeship Space Project No.: 2210134.10 Subject: Conveyance Calculations Date: 07.03.2021 By: Lucas Johnson The Lake City Community Church expansion project stormwater conveyance system has been designed to convey the 25-year, 24-hour peak flowrate. This flowrate was calculated with StormShed2G™ software, using the Santa Barbara Urban Hydrograph (SBUH) method. The following parameters were used in the design of the stormwater conveyance system: Design storms: 100-year, 24-hour Rainfall values: 4.2 inches (KCSWDM Figure 3.2.1.D) Methodology: Santa Barbara Urban Hydrograph (SBUH) Rainfall distribution: Type 1A (per USDA Urban Hydrology for Small Watersheds TR-55 Figure B-2) Curve Numbers: Impervious surfaces – 98 Pervious surfaces – NA Manning’s coefficient: 0.012 (PVC pipe) Appended on: 06:58:50 Saturday, July 03, 2021 DEV Event Summary Event Peak Q (cfs) Peak T (hrs) Hyd Vol (acft) Area (ac) Method Raintype 100 year 0.0288 8.00 0.0099 0.0300 SBUH TYPE1A Record Id: DEV Design Method SBUH Rainfall type TYPE1A Hyd Intv 10.00 min Peaking Factor 484.00 Abstraction Coeff 0.20 Pervious Area (AMC 2) 0.00 ac DCIA 0.03 ac Pervious CN 0.00 DC CN 98.00 Pervious TC 0.00 min DC TC 5.00 min Directly Connected CN Calc Description SubArea Sub cn Impervious surfaces (pavements, roofs, etc) 0.03 ac 98.00 DC Composited CN (AMC 2) 98.00 Directly Connected TC Calc Type Description Length Slope Coeff Misc TT Fixed 5.00 min Directly Connected TC 5.00min Licensed to: AHBL Project Description Friction Method Manning Formula Solve For Normal Depth Input Data Roughness Coefficient 0.012 Channel Slope 0.00500 ft/ft Diameter 0.50 ft Discharge 0.03 ft³/s Results Normal Depth 0.09 ft Flow Area 0.02 ft² Wetted Perimeter 0.43 ft Hydraulic Radius 0.05 ft Top Width 0.38 ft Critical Depth 0.08 ft Percent Full 17.5 % Critical Slope 0.00640 ft/ft Velocity 1.24 ft/s Velocity Head 0.02 ft Specific Energy 0.11 ft Froude Number 0.89 Maximum Discharge 0.46 ft³/s Discharge Full 0.43 ft³/s Slope Full 0.00002 ft/ft Flow Type SubCritical GVF Input Data Downstream Depth 0.00 ft Length 0.00 ft Number Of Steps 0 GVF Output Data Upstream Depth 0.00 ft Profile Description Profile Headloss 0.00 ft Average End Depth Over Rise 0.00 % Normal Depth Over Rise 17.53 % Downstream Velocity Infinity ft/s FWHS Pre-Apprenticeship Space 7/3/2021 7:04:36 AM Bentley Systems, Inc. Haestad Methods Solution CenterBentley FlowMaster V8i (SELECTseries 1) [08.11.01.03] 27 Siemons Company Drive Suite 200 W Watertown, CT 06795 USA +1-203-755-1666 2of1Page Proposed pipes have capacity to convey 100-year 24-hour storm. GVF Output Data Upstream Velocity Infinity ft/s Normal Depth 0.09 ft Critical Depth 0.08 ft Channel Slope 0.00500 ft/ft Critical Slope 0.00640 ft/ft FWHS Pre-Apprenticeship Space 7/3/2021 7:04:36 AM Bentley Systems, Inc. Haestad Methods Solution CenterBentley FlowMaster V8i (SELECTseries 1) [08.11.01.03] 27 Siemons Company Drive Suite 200 W Watertown, CT 06795 USA +1-203-755-1666 2of2Page Technical Information Report Federal Way High School Pre-Apprenticeship Space 2210134.10 Section 6 Special Reports and Studies Technical Information Report Federal Way High School Pre-Apprenticeship Space 6-1 2210134.10 6.0 Special Reports and Studies A Technical Information Report (TIR) was prepared by Springline Design, LLC, dated August 1, 2014, which is included as Figure 6-1 of this report. The 2014 TIR was prepared for the recently constructed Federal Way High School and describes the extra capacity provided by the existing pond, the storm drainage system located downstream from the project site, and other relevant information. A Geotechnical Engineering Report was prepared by Associated Earth Sciences, Inc., dated February 8, 2021, which is included as Figure 6-2. Technical Information Report Federal Way High School Pre-Apprenticeship Space 2210134.10 Section 6.0 Figures Figure 6-1 ......... Technical Information Report (Springline Design, LLC, August 1, 2014) Figure 6-2 ......... Geotechnical Engineering Report (Associated Earth Sciences, Inc., February 8, 2021) TECHNICAL INFORMATION REPORT Project: Federal Way High School 30611 16th Ave S Federal Way, WA 98003 Prepared For: SRG Partnership, Inc. 110 Union Street, Suite 300 Seattle, WA 98101 Fed. Way Proj. #13-101307-00-PC Prepared By: Max Berde, PE Reviewed By: Marc Errichetti, PE Date: August 1, 2014 Federal Way High School Page 2 Project No. 13003 Springline Design LLC TABLE OF CONTENTS Section No. Subject Page No. SECTION I PROJECT OVERVIEW .....................................................................4 SECTION II CONDITIONS AND REQUIREMENTS SUMMARY...................14 SECTION III OFFSITE ANALYSIS......................................................................16 SECTION IV FLOW CONTROL AND WATER QUALITY FACILITY ANALYSIS AND DESIGN..........................................23 SECTION V CONVEYANCE SYSTEM ANALYSIS AND DESIGN................30 SECTION VI SPECIAL REPORTS AND STUDIES.............................................30 SECTION VII OTHER PERMITS ...........................................................................34 SECTION VIII EROSION AND SEDIMENT CONTROL ......................................34 SECTION IX BOND QUANTITIES ......................................................................35 SECTION X OPERATIONS AND MAINTENANCE MANUAL.......................35 LIST OF FIGURES FIGURE 1 VICINITY MAP.................................................................................7 FIGURE 2 TIR WORKSHEET ............................................................................8 FIGURE 3 EXISTING SITE SOIL CONDITIONS ...........................................11 FIGURE 4 EXISTING LAND COVER .............................................................12 FIGURE 5 DEVELOPED LAND COVER ........................................................13 FIGURE 6 DOWNSTREAM STUDY AREA....................................................18 FIGURE 7 OFFSITE ANALYSIS MAP............................................................19 FIGURE 8 FLOW CONTROL TRADE AREAS...............................................26 FIGURE 9 FLOW CONTROL BMP TARGETED AREAS..............................27 FIGURE 10 BIORETENTION CATCHMENT AREAS.....................................29 FIGURE 11 BACKWATER ANALYSIS ............................................................33 Federal Way High School Page 3 Project No. 13003 Springline Design LLC LIST OF APPENDIXES APPENDIX A WATER QUALITY AND FLOW CONTROL CALCULATIONS APPENDIX B OPERATION AND MAINTENANCE MANUAL APPENDIX C BACKWATER ANALYSIS TABLES APPENDIX D SEDIMENT POND SIZING Federal Way High School Page 4 Project No. 13003 Springline Design LLC SECTION I – PROJECT OVERVIEW General Description: This project consists of the demolition and reconstruction of Federal Way High School (FWHS) on the existing school site. See Figure 1 for a vicinity map of the project area. The new school construction will be completed in stages by a single contractor such that the school grounds can remain occupied and operational throughout the redevelopment. A separate early site work contract is intended to be awarded in early summer of 2014 to allow for dry weather construction of the project detention pond and portions of the proposed storm drain system. ROW improvements for the project include improvements to S 304th Street and S 308th Street to the north and south of the site. On the south margin of S 304th Street, curb, gutter, sidewalk and a landscape strip will be constructed. On the north margin of S 308th Street, from the west property line east to 14th Ave South, curb, gutter, sidewalk and a landscape strip will be constructed. Storm drainage improvements will be constructed in both right-of-ways. This TIR includes details of the stormwater management for the completed project including flow control and water quality analysis, erosion and sediment control, the TIR worksheet, and operation and maintenance manual. Existing Conditions: ROW: Existing conditions in the S 304th Street ROW consist of approximately 32 feet of pavement with no curb or gutter. Runoff sheet flows from the crowned roadway to unimproved gravel and grass shoulders on each side of the road, following the grade of the road to the west. At the very west end of the site frontage is located the upstream end of a 12” ROW storm main which heads west. Existing conditions in the S 308th Street ROW consist of approximately 36 feet of pavement. The portion of the ROW from west property line to 14th Ave South sheet flows to a series of ditch and culverts segments along the north side of the ROW, following the grade of the road to the west. Culvert sizes increase to the west, with the westernmost culvert being a 24” pipe. The portion of the ROW from 14th Ave South to Pacific Highway 99 drains via curb and gutter to an existing 12” storm main on the north side of S 308th Street. This 12” storm drain line follows the grade of the road to the west and discharges to the existing ditch system described above. Federal Way High School Page 5 Project No. 13003 Springline Design LLC Project Site: Existing conditions in the 38.46 acre project site consist of the developed high school campus with existing school district buildings, paved and gravel parking lots, tennis courts, and sports fields. The site is bounded on the west by single-family residential lots, on the north by S. 304th Street, on the east by 16th Ave South and Pacific Highway 99, and to the south by S. 308th Street. The existing school building, including gymnasium, is located in the southeastern quadrant of the site. In the northeast quadrant of the site is a former King County pool building. A school district food services building is located on the southern portion of the site, and Memorial Stadium is located on west central portion of the property. To the west of Memorial Stadium is existing lawn/landscaping and sports fields. The site generally slopes to the south and west from a high point of around 489 feet at the northeast corner to 436 feet at the southeast corner. Total elevation change across the site is approximately 53 feet with slopes generally ranging between 2% and 10%. Existing site drainage is largely collected and conveyed by existing onsite drainage systems consisting of swales, catch basins, area drains, collection structures and pipes. The site has five main subbasins which discharge to the ditch system along the north side of S. 308th Street: Central Kitchen Memorial Stadium/Fields Stadium Parking Southeast School/Parking Northeast School/Parking In addition to the above subbasins, the site has one additional subbasin comprising the Softball Field, which discharges to the storm drain system located at the west end of S. 304th St: Both the S. 308th and the S. 304th ROW drainage systems discharge to Cold Creek to the northwest. See Table 1 below for a summary of existing land cover. See Figure 4 for a graphic representation of existing land cover. Table 1 – Existing Site Land Use Rooftop (Acres) Paving (Acres) Underdrained Fields (Acres) Landscape/ Grass (Acres) Right- of-Way (Acres) Total (Acres) 4.65 6.74 3.48 14.62 0.51 30.00 Federal Way High School Page 6 Project No. 13003 Springline Design LLC Developed Conditions: The developed project includes construction of a new school building and associated plaza areas, loading areas and parking lots on the eastern portion of the site. Additionally, new tennis courts and sports fields will be constructed on the northern portion of the property, and a detention pond will be constructed along the western margin of the site. Memorial Stadium, the Stadium Parking lot, and the Central Kitchen improvements will remain as existing in the developed condition, and their subbasins will continue to discharge to the downstream storm system independently of the developed project. Site runoff will be collected via swales, catch basins, and other collection structures, and will be conveyed via tightline piping to water quality treatment and detention facilities. A detention pond on the western portion of the site will provide Level 3 flow control for targeted surfaces. Upstream of the detention facility, bioretention (raingardens) will provide Enhanced Basic water quality treatment to targeted PGIS surfaces. Flow discharging from the detention pond will be conveyed to the existing City of Federal Way storm drainage system within the S. 308th St. ROW. See Table 2 below for developed site land use summary. See Figure 5 for a graphic representation of developed land cover. Table 2 – Developed Site Land Use Rooftop (Acres) PGIS (Acres) Non- PGIS (Acres) Overlay Ex. Pavement (Acres) Pond (Acres) Underdrained Fields (Acres) Landscape/ Grass (Acres) Total (Acres) 3.05 4.40* 2.89 2.14 1.63 5.64 10.25 30.00 * includes PGIS area (0.51 acres) of ROW improvements S 304nd Street ROW: Right-of-way improvements for S 304th St include construction of curb, gutter, sidewalk and landscape strip on the south side of the ROW for the full site frontage. Associated storm drainage improvements include installation of catch basins and a storm drain main along the proposed curb and gutter. Flow control for S 304th St ROW improvements will be provided in the on site detention system, via a mitigation trade of other non-targeted areas for targeted ROW surfaces. Water quality treatment will be provided by a bioretention area (raingarden) which is located just south of the 304th ROW on the school site. S 308th Street ROW: Right-of-way improvements for S 308th St include construction of curb, gutter, sidewalk and landscape strip on the north side of the ROW from the west property line to14th Ave Federal Way High School Page 7 Project No. 13003 Springline Design LLC S. Storm drainage improvements include installation of catch basins and conveyance along the proposed curb and gutter to replace the existing ditch. Flow control for S 308th St ROW improvements will be provided in the on site detention system, via a mitigation trade of other non-targeted areas for targeted ROW surfaces. Water quality treatment will be provided in the South 304th St raingarden, via a mitigation trade of non-target areas within the 304th St ROW, for targeted S. 308th St surfaces. FIGURE 1 – VICINITY MAP Project Site Federal Way High School Page 8 Project No. 13003 Springline Design LLC FIGURE 2 TECHNICAL INFORMATION REPORT (TIR) WORKSHEET Part 1 PROJECT OWNER AND PROJECT ENGINEER Part 2 PROJECT LOCATION AND DESCRIPTION Project Owner : Federal Way Public Schools School District #210 Address : 31405 18th Ave S Federal Way, WA 98003 Phone : 253 945 2000 Project Engineer: Marc Errichetti, PE Company: Springline Design, LLC Address/Phone: 206 957 8311 Project Name : Federal Way High School Location : 30611 16th Ave S Township 21N Range 4E Section 8 Part 3 TYPE OF PERMIT APPLICATION Part 4 OTHER REVIEWS AND PERMITS Subdivison Short Subdivision Grading Commercial Other _______________________ _______________________________ DFW HPA Shoreline Management COE 404 Rockery DOE Dam Safety Structural Vaults FEMA Floodplain Other COE Wetlands Part 5 SITE COMMUNITY AND DRAINAGE BASIN Community City of Federal Way Drainage Basin Lower Puget Sound Basin Part 6 SITE CHARACTERISTICS River ________________________________ Stream ___________________________ Critical Stream Reach Depressions/Swales Lake Steep Slopes ______________________ Floodplain ______________________ Wetlands Seeps/Springs High Groundwater Table Groundwater Recharge Other __________________________ Federal Way High School Page 9 Project No. 13003 Springline Design LLC Part 7 SOILS Soil Type Ardents, Alderwood _________________ _________________ _________________ Slopes 0% to 10% _________________ _________________ _________________ Erosion Potential Moderate _________________ _________________ _________________ Erosive Velocities _________________ _________________ _________________ _________________ Additional Sheets Attached Part 8 DEVELOPMENT LIMITATIONS REFERENCE ______________________________ ______________________________ ______________________________ ______________________________ ______________________________ ______________________________ Additional Sheets Attached LIMITATION/SITE CONSTRAINT _______________________________________ _______________________________________ _______________________________________ _______________________________________ _______________________________________ _______________________________________ Part 9 ESC REQUIREMENTS MINIMUM ESC REQUIREMENTS DURING CONSTRUCTION Sedimentation Facilities Stabilized Construction Entrance Perimeter Runoff Control Clearing and Grading Restrictions Cover Practices Construction Sequence Other MINIMUM ESC REQUIREMENTS AFTER CONSTRUCTION Stabilize Exposed Surface Remove and Restore Temporary ESC Facilities Clean and Remove All Silt and Debris Ensure Operation of Permanent Facilities Flag Limits of SAO and open space preservation areas Other Federal Way High School Page 11 Project No. 13003 Springline Design LLC FIGURE 3 – EXISTING SITE SOIL CONDITIONS Project Site Till soils Federal Way High School Page 14 Project No. 13003 Springline Design LLC SECTION II – CONDITIONS AND REQUIREMENTS SUMMARY Core and Special Requirements are listed below along with a discussion of their applicability to this project. Core Requirements: Req. #1 Discharge at Natural Location: Site and ROW: Existing TDA’s will be maintained. Req. #2 Offsite Analysis: See Section III. Req. #3 Flow Control: Site: Flood Problem Area flow control is required and is being provided through the use of an onsite detention pond. Onsite flow control BMPs are provided with the use of bioretention areas. ROW: Flood Problem Area flow control is required for the S. 304th St and S. 308th St ROW improvements and is being provided by the onsite detention pond and mitigation area trades. Req. #4 Conveyance System: Site and ROW: New conveyance systems will be implemented to meet this requirement. Req. #5 Erosion and Sediment Control: Site and ROW: Construction ESC systems will be implemented to meet this requirement. Req. #6 Maintenance and Operations: Site: FWPS will be responsible for maintenance and operations of site stormwater systems. ROW: Public facilities will be owned and maintained by the City. Easements will be provided for public facilities located onsite, as required. Req. #7 Financial Guarantees: Site and ROW: A financial guarantee may be necessary for this project. Federal Way High School Page 15 Project No. 13003 Springline Design LLC Req. #8 Water Quality: Site and ROW: Enhanced Basic water quality treatment is required for the site and right-of-way and is being provided by bioretention treatment areas sized per DOE requirements. In accordance with FWRC Section 19.20.120, “Nonconforming Water Quality Improvements,” all new and existing pollution generating surfaces within the site will be treated by a water quality facility. Special Requirements: Req. #1 Area Specific Requirements: No area specific requirements are applicable to this project. Req. #2: Floodplain/Floodway Delineation Project is not adjacent to any floodplains or floodways. Req. #3 Flood Protection Facilities: Project is not adjacent to applicable area and will not affect any applicable facility. Req. #4 Source Controls: Project is a school project and will provide appropriate source controls when required. Req. #5 Oil Control: There will be no high use areas and therefore oil control is not required. Federal Way High School Page 16 Project No. 13003 Springline Design LLC SECTION III – OFFSITE ANALYSIS Task 1 – Study Area Definition and Maps Maps of the project site and surrounding area were obtained from the King County GIS website. Topographical site information is from the topographical survey for the project and from the King County iMAP. Storm drainage system maps were compiled from Federal Way GIS maps and as-built plans. Aerial images were obtained from Google Maps. Task 2 – Resource Review The Federal Way Public Works Department was contacted regarding the resources listed in section 2.3.1.1 of the 1999 Addendum to KCSWDM. The following is a summary of the resource review: Adopted Basin Plans o Basin Name: Lower Puget Sound Basin (per City of Federal Federal Way Flow Control Applications Map) Finalized Drainage Studies o TIRs from surrounding projects were reviewed. Basin Reconnaissance Summary Reports o None completed to our knowledge. Floodplain/Floodway (FEMA) Maps o The site is not within a floodplain or floodway per FEMA mapping. Other Offsite Analysis Reports o No problems identified. Environmentally Sensitive Areas Map o No environmentally sensitive areas identified on or adjacent to site. Road Drainage Problems o None to our knowledge. USDA Soils Survey o A geotech report has been completed and site soils are primarily glacial till. Wetlands Inventory Maps o No mapped wetlands located on or directly adjacent to site. o Nearest mapped wetlands located approximately 500 feet southwest of the site bordering Easter Lake. Federal Way High School Page 17 Project No. 13003 Springline Design LLC Task 3 – Field Inspection A Level 1 downstream analysis was performed in the morning of September 13, 2013. Weather conditions during the downstream analysis consisted of overcast skies and temperatures of 64-70 degrees F. On-site land use and topography was confirmed and downstream land use was identified as a combination of asphalt streets and forested areas. Refer to Figures 6 and 7 and the Off-Site Analysis Drainage System Tables following this section for detailed information. Runoff from the site discharges into the City of Federal Way conveyance system at several points along the existing ditch that runs along the north side of S 308th Street, and at the northwest corner of the site. All site discharges flow west to 10th Avenue South where the system flows north to where it is discharged in Cold Creek. The storm drain pipes in the closed system were in good condition. Task 4 – Drainage System Description and Problem Description Based on correspondence with the City of Federal Public Works Department, the only known problem with the downstream system is several sections of 36” CMP pipe draining to Cold Creek with the “bottom rusted out of them and are in bad condition” north of Dash Point Road. Task 5 – Mitigation of Existing or Potential Problems Based on the observations made during the field inspection and the requirements for the design of the proposed drainage systems, no negative impacts to the downstream system are anticipated, as flows from the site in the redeveloped condition will be greatly reduced both in duration and peak. Page 1 of 3 OFF-SITE ANALYSIS DRAINAGE SYSTEM TABLE SURFACE WATER DESIGN MANUAL, CORE REQUIREMENT #2 Basin:Federal Way High School Subbasin Name:N/A Subbasin Number:N/A Symbol Drainage Component Type, Name, and Size Drainage Component Description Slope Distance from site discharge Existing Problems Potential Problems Observations of field inspector, resource reviewer, or resident see map Type: sheet flow, swale, stream, channel, pipe, pond; Size: diameter, surface area drainage basin, vegetation, cover, depth, type of sensitive area, volume %1/4 ml = 1,320 ft.constrictions, under capacity, ponding, overtopping, flooding, habitat or organism destruction, scouring, bank sloughing, sedimentation, incision, other erosion tributary area, likelihood of problem, overflow pathways, potential impacts #1 SDMH Circular grate 18” CONC (W) 18” CONC (E) 18” CONC (N) N/A (adjacent to site) CONC (W) good condition CONC (E) sediment and rock observed at invert CONC (N) mineral deposits observed at invert of pipe #2 18” Storm Drain 18” Concrete Pipe 6.7% #3 Catch Basin Type 1 Rectangular grate 18” CONC (W) 18” CONC (E) 18” CONC (S) N/A 12 ft. 18” CONC (W) good condition 18” CONC (E) good condition Sump full of non-moving water #4 18” Storm Drain 18” Concrete Pipe 6.5% Brick headwall in good condition Pipe clear of debris and in good condition #5 24” Storm Drain 24” Concrete Pipe 1.0% Rip rap headwall in good condition Pipe clear of debris and in good condition #6 Catch Basin Type 2 - 72” with “Snout” Debris Guard Rectangular grate 18” CONC (W) 24” CONC (E) 18” CONC (S) 12” IP (NE) N/A 196 ft. Structure full of non-moving water to invert of 12” IP (NE) #6i 12” Storm Drain 12” IP N/A Good condition Page 2 of 3 Symbol Drainage Component Type, Name, and Size Drainage Component Description Slope Distance from site discharge Existing Problems Potential Problems Observations of field inspector, resource reviewer, or resident see map Type: sheet flow, swale, stream, channel, pipe, pond; Size: diameter, surface area drainage basin, vegetation, cover, depth, type of sensitive area, volume %1/4 ml = 1,320 ft.constrictions, under capacity, ponding, overtopping, flooding, habitat or organism destruction, scouring, bank sloughing, sedimentation, incision, other erosion tributary area, likelihood of problem, overflow pathways, potential impacts #7 30” Storm Drain 30” CPP 1.0% #8 Catch Basin Type 2-84” With flat top high lake level and overflow weir vaned grate. 30” CONC(W) 24” CONC (N) 30” CPP (S) N/A 242 ft. Structure partially filled with non- moving water. #9 30” Storm Drain 30” CONC 0.5% #10 Manhole Type 2 -54” 30” CONC (W) 30” CONC (E) N/A 458 ft. Locking lid. #11 30” Storm Drain 30” CONC 0.5% #12 Manhole Type 2 – 54” 30” CONC (W) 30” CONC (E) N/A 674 ft. No sediment observed. #13 30” Storm Drain 30” CONC 0.5% #14 Manhole Type 2 – 72” 30” CONC (E) 24” CONC (N) 24” CONC (S) N/A 744 ft. #15 24” Storm Drain 24” CONC 1.6% #16 Manhole Type 1 – 48” 24” CONC (N) 24” CONC (S) N/A 785 ft. No debris or sediment observed. Pipes in good condition. Page 3 of 3 Symbol Drainage Component Type, Name, and Size Drainage Component Description Slope Distance from site discharge Existing Problems Potential Problems Observations of field inspector, resource reviewer, or resident see map Type: sheet flow, swale, stream, channel, pipe, pond; Size: diameter, surface area drainage basin, vegetation, cover, depth, type of sensitive area, volume %1/4 ml = 1,320 ft.constrictions, under capacity, ponding, overtopping, flooding, habitat or organism destruction, scouring, bank sloughing, sedimentation, incision, other erosion tributary area, likelihood of problem, overflow pathways, potential impacts #17 24” Storm Drain 24” CONC 1.6% #18 Manhole Type 1 – 48” 24” CONC (N) 24” CONC (S) N/A 987 ft. No debris or sediment observed. Pipes in good condition. #19 24” Storm 24” CONC 1.6% #20 Manhole Type 1 – 48” 24” CONC N/A 1162 ft. No debris or sediment observed. Pipes in good condition. #21 24” Storm Drain 24” CONC 1.6% #22 Catch Basin Type 2 – 54”18” CONC (SE) 24” CONC (S) 30” CONC (NW) 8” CONC (SE) N/A 1337 ft. Locking solid lid. #23 30” Storm Drain 30” CONC Federal Way High School Page 23 Project No. 13003 Springline Design LLC SECTION IV – FLOW CONTROL AND WATER QUALITY FACILITY ANALYSIS AND DESIGN Flow Control: Flow Control BMPs Per the requirements of Section 5.2 of the 2009 King County Surface Water Design Manual (KCSWDM), the project is required to implement Flow Control BMP’s. In the redeveloped condition the site is classified as Large Lot High Impervious,per Section 5.2.1.2 of the KCSWDM. As such, 100% of targeted surfaces must be served by a Flow Control BMP. Per footnote #3 on page 5-7 of the KCSWDM, the targeted surface for projects on large lots (>22,000 SF) is comprised of all new impervious surfaces. See Figure 9 for a depiction of targeted surfaces, totaling 3.7 acres. Bioretention areas (Rain Gardens) have been implemented in several areas of the site to meet this Flow Control BMP requirement. Surface water runoff which drains to the rain gardens are subsequently be conveyed to the detention pond. Per the credits listed in Table 5.2.2.A of the KCSWDM, impervious surfaces which are served by the rain gardens are modeled as 50% impervious and 50% till grass for design of the formal downstream flow control facility. Formal Flow Control Facility Per the requirements of Section 1.2.3 of the 2009 King County Surface Water Design Manual (KCSWDM) and the City of Federal Way Flow Control Applications Map, the project is required to provide formal flow control facilities that meet the requirements of Flood Problem Flow Control (Level 3 Flow Control). Level 3 flow control is required to mitigate for all new or replaced impervious surfaces. As the project will not be converting any native forested areas to pervious surfaces, all developed pervious areas are non targeted, and these areas will be modeled as pervious in both the predeveloped and developed condition. Level 3 Flow Control:Apply the Level 2 flow control standard,AND match the developed 100-year peak discharge rate to the predeveloped 100-year peak discharge rate. If the Flood Problem Flow Control Area is located within a Conservation Flow Control Area and does not drain entirely by non-erodible manmade conveyance to a major receiving body, then historic site conditions shall be assumed as the predeveloped condition except for the purposes of matching 100-year peak discharge rates. For the purposes of matching 100-year peak discharge rates,existing site conditions may be assumed. Level 2 Flow Control: Match developed discharge durations to predeveloped durations for the range of predeveloped discharge rates from 50% of the 2-year Federal Way High School Page 24 Project No. 13003 Springline Design LLC peak flow up to the full 50-year peak flow. Also match developed peak discharge rates to predeveloped peak discharge rates for the 2- and 10- year return periods. In the developed condition, runoff from flow control targeted surfaces will be collected and conveyed to a detention facility on the west side of the site. Due to the topography of the site, flow control targeted surfaces at the southern margin of the site cannot be reasonably conveyed to the proposed detention facility. In addition, due to space constraints, provision of separate flow control facilities for the ROW’s is not reasonably feasible. Accordingly, per section 1.2.3.2.G of the KCSWDM, a mitigation trade is proposed to provide flow control for these areas, which will bypass the detention facility. In trade for these areas, the proposed onsite storm drainage system will include the collection and conveyance to the detention pond of areas which are not targeted for flow control. However, due to the configuration of the proposed bypass areas and the available areas for mitigation trades, implementation of the trade will result in the provision of mitigation for an additional 0.94 acres of impervious area beyond that which is “targeted” for required mitigation by the proposed redevelopment. In short, the project will be “banking” mitigation in the proposed pond for an additional 0.94 acres of impervious area which may be developed at a later date. See Table 4 below for a summary of the flow control mitigation trade areas. See Figure 8 for a depiction of the mitigation trade areas. Table 4 – Flow Control Mitigation Trade Areas Developed Surface Area (Acres) Non-Target Areas to Flow Control (+) 1.86 Target Areas Bypassing Flow Control (-) 0.92 Net “Additional” Mitigation Trade Area To Flow Control (+) 0.94 Per table 3.2.2.C of the KCSWDM, field areas that include an underdrain collection system (e.g. grass or synthetic turf sports field) are modeled as 75% grass and 25% impervious. Per the credits listed in Table 5.2.2.A of the KCSWDM, impervious surfaces which are served by the rain gardens are modeled as 50% impervious and 50% till grass for design of the formal downstream flow control facility. See Table 5 below for a summary of the targeted areas for flow control. This includes the net “additional” mitigation trade area outlined above. See Figure 5 in Section 1 for a graphic representation of developed land cover. Federal Way High School Page 25 Project No. 13003 Springline Design LLC Table 5 – Targeted Areas Summary Developed Surface Area (Acres) Effective Impervious (Acres) Effective Pervious (Acres) Building 3.05 3.05 --- PGIS with Bioretention (50% Pervious/50% Impervious)4.68 2.34 2.34 Non-PGIS 2.89 2.89 --- Proposed Underdrained Turf (75% Pervious/25% Impervious)5.64 1.41 4.23 Pond (100% Impervious)1.63 1.63 --- Net “Additional” Flow Control Mitigation Trade Area 0.94 0.94 --- Total Target Areas for Flow Control 12.26 6.57 In addition to the targeted areas summarized in Table 5, the developed condition includes 10.25 acres of non-targeted landscape area; this non targeted area will be modeled as till grass in both the predeveloped and developed condition. See Table 6 below for the facility sizing inputs and flow rate comparison based on the above. See Appendix A for KCRTS routing summaries. Table 6 – Detention Facility Sizing Data Impervious (Acres) Till Forest (Acres) Till Grass (Acres) Total Area (Acres) 2-year Peak Discharge Rate (cfs) 10-year Peak Discharge Rate (cfs) 100-year Peak Discharge Rate (cfs) Predeveloped --- 18.83 10.25 29.08 1.03 1.94 9.24* Developed Targeted Areas 12.26 --- 6.57 29.08 0.52 1.28 2.53Developed Non-Targeted Areas --- --- 10.25 * Per KCSWDM,existing site condition used for 100-year pre-developed condition. See Section 1, Table 1. A flow control system consisting of a 250,000 cubic foot detention pond will be constructed to provide Level 3 Flow Control onsite before discharging detained stormwater to the downstream City of Federal Way storm drainage system. S 304th and 308th Streets ROW Flow control for right-of-way improvements are implemented as described in mitigation trade area summarized in Table 4 and facility sizing in Table 6 above. TTTTT Federal Way High School Page 28 Project No. 13003 Springline Design LLC Water Quality General Per the City of Federal Way, this project is required to provide Enhanced Basic water quality treatment for all existing and proposed pollution generation impervious surfaces (PGIS). This requirement is being met through the use of bioretention areas (rain gardens) to filter and treat runoff. Design and sizing of bioretention areas is in accordance with the Department of Ecology Stormwater Management Manual for Western Washington. Bioretention areas are designed with 18” of bioretention material and are underdrained, with a maximum ponding depth of 12” and maximum drawdown time of 24 hours following a storm event. Sizing of the facilities was done with the Western Washington Hydrology Model (WWHM) to filter 91% of the runoff volume, per DOE standards. Site: The proposed improvements result in approximately 7.62 acres of targeted surfaces, comprising new and/or replaced pollution generating impervious surface (PGIS), and landscape areas draining across PGIS. S 304th and 308th Streets ROW The proposed improvements to the right-of-ways will add approximately 0.91 acres of new and replaced PGIS and landscape draining to the ROW. Due to limited space in the 308th ROW, and in order to limit impacts to existing Stadium Parking and Central Kitchen facilities adjacent to that ROW, a single ROW water quality treatment facility is proposed, to be located adjacent to S. 304th St. A catch basin in the S 304th St ROW will collect runoff from the ROW and convey it to a bioretention facility adjacent to the ROW. The bioretention facility will treat an area equivalent to the sum of the target surfaces in the S 304th and S 308th Streets right-of- ways (0.91 acres). Treated runoff from the bioretention facility will then be discharged to the downstream S. 304th ROW drainage system. See Figure 10 for bioretention catchment areas, sizes, and locations. See Appendix A for bioretention sizing calculations. Federal Way High School Page 30 Project No. 13003 Springline Design LLC SECTION V – CONVEYANCE SYSTEM DESIGN AND ANALYSIS The on-site and ROW drainage will be served by a collection and conveyance system consisting of pipes and catch basins. Pipes are sloped at a minimum 0.5% with catch basins at every juncture. For the purposes of design, a backwater analysis was performed on this system. Flows were derived through the rational method for use in the backwater analysis. No overtopping of this system occurs during the 25-year event. The spreadsheet for the pipe flows and layout and 25-year event backwater analysis are included in Appendix C. See Figures 11A – 11C following this section for conveyance system and basin area diagrams. SOUTH308THSTREETESOUTH 16THAVESOUTHPACIFICHIGHWAY99PACIFICHIGHWAY99PACIFICHIGHWAY99TTT SOUTH304THSTREETSOUTH304THSTREETSOUTH304THSTREET16THAVESOUTH13THPLSOUTHT Federal Way High School Page 34 Project No. 13003 Springline Design LLC SECTION VI – SPECIAL REPORTS AND STUDIES A geotechnical report for the site was completed. SECTION VII – OTHER PERMITS Federal Way Public Schools will be filing a Washington State Department of Ecology NPDES Notice of Intent. SECTION VIII – EROSION AND SEDIMENT CONTROL ESC Measures are being addressed as follows: Clearing Limits: Clearing limits are being delineated by perimeter silt fencing and/or chain link fencing. Cover Measures: Temporary cover shall be installed if an area is to remain unworked for more than seven days during the dry season (May 1 to September 30) or for more than two consecutive working days during the wet season (October 1 to April 30). Any area to remain unworked for more than 30 days shall be seeded or sodded, unless the City determines that winter weather makes vegetation establishment infeasible. Perimeter Protection: Perimeter protection will be implemented by silt fencing around the site perimeter where drainage paths require. Traffic Area Stabilization: Stabilized areas will be used for construction traffic. Sediment Retention: The proposed detention pond will be utilized as a sediment pond during construction. See Appendix D for sediment pond sizing. Surface Water Control: Surface water will be collected and conveyed via swales with check dams as necessary. Dust Control: Dust control, if required, will be provided through the limited use of water trucks. Federal Way High School Page 35 Project No. 13003 Springline Design LLC SECTION IX – BOND QUANTITIES A bond quantity worksheet for the proposed site improvements will be completed at a later date. SECTION X – OPERATIONS AND MAINTENANCE MANUAL An operation and maintenance manual is provided in Appendix B, outlining the required regular maintenance necessary for the detention pond and rain gardens to be performed by Federal Way Public Schools for the site improvements. APPENDIX A – FLOW CONTROL AND WATER QUALITY CALCULATIONS FLOW CONTROL SUMMARY OF KCRTS INPUTS EXISTING (HISTORIC) CONDITIONS: (FOR FLOW CONTROL OTHER THAN 100 YEAR PEAK) EXISTING (HISTORIC) CONDITION EXISTING (CURRENT) CONDITIONS: (FOR 100 YEAR PEAK FLOW CONTROL) EXISTING (CURRENT) CONDITION DEVELOPED CONDITIONS: DEVELOPED CONDITION MITIGATED CONDITION (POND OUTFLOW) DETENTION POND (STAGE DISCHARGE STORAGE SETUP): DURATION COMPARISON ANALYSIS WATER QUALITY Federal Way High School Page 1 of 8 Project No. 13003 Springline Design LLC Bioretention/Rain Garden #1 Federal Way High School Page 2 of 8 Project No. 13003 Springline Design LLC Bioretention/Rain Garden #2 Federal Way High School Page 3 of 8 Project No. 13003 Springline Design LLC Bioretention/Rain Garden #3 Federal Way High School Page 4 of 8 Project No. 13003 Springline Design LLC Bioretention/Rain Garden #4 Federal Way High School Page 5 of 8 Project No. 13003 Springline Design LLC Bioretention/Rain Garden #5 Federal Way High School Page 6 of 8 Project No. 13003 Springline Design LLC Bioretention/Rain Garden #6 Federal Way High School Page 7 of 8 Project No. 13003 Springline Design LLC Bioretention/Rain Garden #7 Federal Way High School Page 8 of 8 Project No. 13003 Springline Design LLC Bioretention/Rain Garden #8 APPENDIX B – OPERATIONS AND MAINTENANCE MANUAL APPENDIX C – BACKWATER ANALYSIS CONVEYANCE INPUTS AND LAYOUT DATA Project Name:Federal Way High School Event Parameters:Runoff Coefficients: Job Number:13003 Event PR aR bR Tc iR IR C impervious 0.90 Designed By:MEB in unitless unitless min unitless in/hr C pervious 0.25 25-yr, 24-hr 3.5 2.66 0.65 10 0.60 2.08 100-yr, 24-hr 4.3 2.61 0.63 10 0.61 2.63 CB CB Impervious Pervious Total Total C IR, 25-yr Q25-yr Q25-yr IR,100-yr Q100-yr Q100-yr Length Pipe Size Mannings "n" Mannings "n" Downstream Downstream Upstream Upstream Pipe Downstream Upstream Area Area Area Area Surface Total Surface Total Uniform Flow Backwater Invert Rim Invert Rim Slope sf sf sf ac unitless in/hr cfs cfs in/hr cfs cfs ft in unitless unitless % CB 1.1 CB 1.2 5,000 0 5,000 0.11 0.90 2.08 0.22 2.29 2.63 0.27 6.60 245.0 24 0.014 0.012 429.65 433.35 430.88 439.00 0.50% CB 1.2 CB 1.3 (FCS) 0 0 0 0.00 0.00 2.08 0.00 2.07 2.63 0.00 6.33 8.0 24 0.014 0.012 430.88 439.00 430.92 441.50 0.50% CB 1.3 (FCS)INLET #1 0 77,463 77,463 1.78 0.25 2.08 0.93 2.07 2.63 1.17 6.33 34.0 24 0.014 0.012 431.00 439.00 431.00 440.00 0.00% PIPE OUTLET #2 CB 2.1 0 0 0.00 0.00 2.08 0.00 23.21 2.63 0.00 29.30 53.0 24 0.014 0.012 436.00 439.00 437.90 444.00 3.58% CB 2.1 CB 2.2 0 0 0.00 0.00 2.08 0.00 23.21 2.63 0.00 29.30 129.0 24 0.014 0.012 437.90 444.00 439.93 444.50 1.57% CB 2.2 CB 2.3 0 0 0.00 0.00 2.08 0.00 23.21 2.63 0.00 29.30 131.0 24 0.014 0.012 439.93 444.50 441.96 447.50 1.55% CB 2.3 CB 2.4 0 0 0.00 0.00 2.08 0.00 23.21 2.63 0.00 29.30 63.0 24 0.014 0.012 441.96 447.50 445.23 457.00 5.19% CB 2.4 CB 2.5 0 0 0.00 0.00 2.08 0.00 23.21 2.63 0.00 29.30 151.0 24 0.014 0.012 445.23 457.00 447.50 459.20 1.50% CB 2.5 CB 2.6 10,000 9,525 19,525 0.45 0.58 2.08 0.54 22.50 2.63 0.69 28.40 221.0 24 0.014 0.012 447.50 459.20 450.82 464.05 1.50% CB 2.6 CB 2.7 2,000 17,626 19,626 0.45 0.32 2.08 0.30 6.51 2.63 0.37 8.22 217.0 24 0.014 0.012 450.82 464.05 451.91 461.80 0.50% CB 2.7 CB 2.8 0 0 0.00 0.00 2.08 0.00 2.89 2.63 0.00 3.65 210.0 18 0.014 0.012 452.41 461.80 453.46 458.50 0.50% CB 2.8 CB 2.9 20,000 3,254 23,254 0.53 0.81 2.08 0.90 2.37 2.63 1.14 3.00 106.0 12 0.014 0.012 453.96 458.50 456.32 461.30 2.23% CB 2.9 CB 2.10 7,200 306 7,506 0.17 0.87 2.08 0.31 1.47 2.63 0.40 1.86 125.0 12 0.014 0.012 456.32 461.30 457.74 461.00 1.14% CB 2.10 CB 2.11 11,100 8,535 19,635 0.45 0.62 2.08 0.58 1.16 2.63 0.73 1.46 73.0 8 0.014 0.012 458.07 461.00 458.57 460.60 0.68% CB 2.11 CB 2.12 11,300 7,796 19,096 0.44 0.63 2.08 0.58 0.58 2.63 0.73 0.73 218.0 8 0.014 0.012 458.57 460.60 459.67 464.50 0.50% CB 2.5 CB 22.1 0 5,928 5,928 0.14 0.25 2.08 0.07 0.71 2.63 0.09 0.90 65.0 8 0.014 0.012 448.83 459.20 455.00 458.00 9.49% PIPE OUTLET #3 CB 22.2 11,675 11,690 23,365 0.54 0.57 2.08 0.64 0.64 2.63 0.81 0.81 49.0 8 0.014 0.012 457.00 457.50 457.25 458.15 0.51% CB 2.6 CB 4.1 55,000 1,340 56,340 1.29 0.88 2.08 2.38 5.12 2.63 3.01 6.47 90.0 12 0.014 0.012 450.82 464.05 460.00 463.50 10.20% PIPE OUTLET #4 CB 4.2 19,000 1,590 20,590 0.47 0.85 2.08 0.84 2.29 2.63 1.06 2.89 79.0 12 0.014 0.012 463.00 463.50 465.50 468.20 3.16% CB 4.2 CB 4.3 23,000 1,211 24,211 0.56 0.87 2.08 1.00 1.45 2.63 1.27 1.83 67.0 8 0.014 0.012 465.50 468.20 468.50 471.80 4.48% PIPE OUTLET #5 CB 5.1 10,000 1,485 11,485 0.26 0.82 2.08 0.45 0.45 2.63 0.57 0.57 57.0 8 0.014 0.012 463.00 463.50 463.60 466.50 1.05% CB 2.6 CB 6.1 0 0 0 0.00 0.00 2.08 0.00 10.32 2.63 0.00 13.02 318.0 18 0.014 0.012 450.82 464.05 457.00 465.50 1.94% CB 6.1 CB 6.2 0 0 0 0.00 0.00 2.08 0.00 1.31 2.63 0.00 1.65 292.0 12 0.014 0.012 457.00 465.50 468.00 478.00 3.77% CB 6.2 CB 6.3 0 0 0 0.00 0.00 2.08 0.00 1.31 2.63 0.00 1.65 59.0 12 0.014 0.012 468.00 478.00 472.00 482.10 6.78% CB 6.3 CB 6.4 30,400 0 30,400 0.70 0.90 2.08 1.31 1.31 2.63 1.65 1.65 83.0 8 0.014 0.012 472.00 482.10 480.00 483.00 9.64% CB 6.1 CB 7.1 9,000 3,087 12,087 0.28 0.73 2.08 0.42 1.21 2.63 0.54 1.53 242.0 12 0.014 0.012 457.50 465.50 460.00 465.00 1.03% PIPE OUTLET #9 CB 7.2 17,000 4,791 21,791 0.50 0.76 2.08 0.79 0.79 2.63 1.00 1.00 20.0 8 0.014 0.012 464.00 465.00 464.10 465.70 0.50% CB 6.1 CB 8.1 1,381 0 1,381 0.03 0.90 2.08 0.06 1.52 2.63 0.08 1.92 39.0 8 0.014 0.012 457.00 465.50 462.00 465.50 12.82% CB 8.1 CB 8.2 4,688 0 4,688 0.11 0.90 2.08 0.20 0.77 2.63 0.25 0.98 63.0 8 0.014 0.012 462.00 465.50 462.66 466.50 1.05% CB 8.2 CB 8.3 4,868 0 4,868 0.11 0.90 2.08 0.21 0.57 2.63 0.26 0.72 63.0 8 0.014 0.012 462.66 466.50 463.32 466.50 1.05% CB 8.3 CB 8.4 8,386 0 8,386 0.19 0.90 2.08 0.36 0.36 2.63 0.46 0.46 58.0 8 0.014 0.012 463.32 466.50 463.93 466.80 1.05% CB 8.1 CB 8.5 7,903 0 7,903 0.18 0.90 2.08 0.34 0.69 2.63 0.43 0.87 39.0 8 0.014 0.012 462.00 465.50 462.82 466.50 2.10% CB 8.5 CB 8.6 8,168 0 8,168 0.19 0.90 2.08 0.35 0.35 2.63 0.44 0.44 51.0 8 0.014 0.012 462.82 466.50 463.37 466.50 1.08% CB 6.1 CB 9.1 30,000 24,625 54,625 1.25 0.61 2.08 1.59 6.27 2.63 2.00 7.92 89.0 18 0.014 0.012 457.00 465.50 462.00 465.50 5.62% CB CB Impervious Pervious Total Total C IR, 25-yr Q25-yr Q25-yr IR,100-yr Q100-yr Q100-yr Length Pipe Size Mannings "n" Mannings "n" Downstream Downstream Upstream Upstream Pipe Downstream Upstream Area Area Area Area Surface Total Surface Total Uniform Flow Backwater Invert Rim Invert Rim Slope sf sf sf ac unitless in/hr cfs cfs in/hr cfs cfs ft in unitless unitless % CB 6.2 CB 10.1 0 0 0 0.00 0.00 2.08 0.00 1.25 2.63 0.00 1.58 60.0 8 0.014 0.012 468.00 478.00 469.00 477.00 1.67% CB 10.1 CB 10.2 0 7,450 7,450 0.17 0.25 2.08 0.09 1.25 2.63 0.11 1.58 86.0 8 0.014 0.012 469.00 477.00 470.50 473.50 1.74% CB 10.2 CB 10.3 0 80,000 105,400 2.42 0.19 2.08 0.96 0.96 2.63 1.21 1.21 64.0 8 0.014 0.012 470.50 473.50 471.00 474.00 0.78% PIPE OUTLET #8 CB 10.4 4,850 0 4,850 0.11 0.90 2.08 0.21 0.21 2.63 0.26 0.26 51.0 8 0.014 0.012 475.80 476.50 480.00 484.00 8.24% PIPE OUTLET #6 CB 11.1 12,000 2,566 14,566 0.33 0.79 2.08 0.55 2.57 2.63 0.69 3.24 101.0 12 0.014 0.012 464.00 464.50 465.50 468.80 1.49% CB 11.1 CB 11.2 10,000 2,725 12,725 0.29 0.76 2.08 0.46 2.02 2.63 0.58 2.55 72.0 8 0.014 0.012 465.50 468.80 469.50 472.30 5.56% CB 11.2 CB 11.3 12,000 6,750 18,750 0.43 0.67 2.08 0.60 1.56 2.63 0.75 1.96 70.0 8 0.014 0.012 469.50 472.30 472.50 475.50 4.29% CB 11.3 CB 11.4 0 960 960 0.02 0.25 2.08 0.01 0.96 2.63 0.01 1.21 70.0 8 0.014 0.012 472.50 475.50 476.00 480.50 5.00% CB 11.4 CB 11.5 22,000 0 22,000 0.51 0.90 2.08 0.95 0.95 2.63 1.20 1.20 14.0 8 0.014 0.012 476.00 480.50 476.50 480.00 3.57% PIPE OUTLET #7 CB 12.1 0 0 0 0.00 0.00 2.08 0.00 2.12 2.63 0.00 2.67 42.0 12 0.014 0.012 464.00 464.50 465.00 467.50 2.38% CB 12.1 CB 12.2 49,163 0 49,163 1.13 0.90 2.08 2.12 2.12 2.63 2.67 2.67 120.0 8 0.014 0.012 465.00 467.50 473.50 479.00 7.08% CB 2.7 CB 13.1 2,300 12,700 15,000 0.34 0.35 2.08 0.25 3.32 2.63 0.32 4.19 129.0 12 0.014 0.012 452.91 461.80 456.20 461.20 2.55% CB 13.1 CB 13.2 29,000 13,755 42,755 0.98 0.69 2.08 1.41 3.07 2.63 1.78 3.88 125.0 12 0.014 0.012 456.20 461.20 459.20 464.20 2.40% CB 13.2 CB 13.3 34,000 16,155 50,155 1.15 0.69 2.08 1.66 1.66 2.63 2.09 2.09 109.0 12 0.014 0.012 459.20 464.20 460.29 463.50 1.00% CB 13.3 CB 13.4 45,000 8,302 53,302 1.22 0.80 2.08 2.04 2.04 2.63 2.57 2.57 117.0 12 0.014 0.012 460.29 463.50 462.00 466.00 1.46% PIPE OUTLET #8 CB 21.1 1,382 0 1,382 0.03 0.90 2.08 0.06 0.06 2.63 0.08 0.08 58.0 8 0.014 0.012 452.50 453.50 453.80 456.80 2.24% CB 2.8 CB 17.1 11,516 2,000 13,516 0.31 0.80 2.08 0.52 0.52 2.63 0.66 0.66 77.0 8 0.014 0.012 456.23 458.50 457.00 459.00 1.00% S 308th Street ROW EX CB #1 CB 14.1 964 0 964 0.02 0.90 2.08 0.04 6.01 2.63 0.05 7.59 26.0 30 0.014 0.012 429.00 433.42 429.65 433.35 2.50% CB 14.1 CB 14.2 7,040 0 7,040 0.16 0.90 2.08 0.30 5.97 2.63 0.38 7.53 91.0 24 0.014 0.012 429.65 433.35 430.14 432.68 0.54% CB 14.2 CB 14.3 30,054 0 30,054 0.69 0.90 2.08 1.29 4.02 2.63 1.63 5.07 52.0 18 0.014 0.012 430.14 432.68 430.43 432.47 0.56% CB 14.3 CB 14.4 4,213 0 4,213 0.10 0.90 2.08 0.18 2.72 2.63 0.23 3.43 8.0 18 0.014 0.012 430.43 432.47 430.50 432.41 0.87% CB 14.4 CB 14.5 5,929 0 5,929 0.14 0.90 2.08 0.26 2.54 2.63 0.32 3.21 109.0 12 0.014 0.012 430.50 432.41 432.00 434.72 1.38% CB 14.5 CB 14.6 3,475 0 3,475 0.08 0.90 2.08 0.15 2.28 2.63 0.19 2.88 174.0 12 0.014 0.012 432.00 434.72 441.00 444.72 5.17% CB 14.6 CB 14.7 22,337 0 22,337 0.51 0.90 2.08 0.96 0.96 2.63 1.21 1.21 100.0 12 0.014 0.012 441.00 444.72 447.00 450.85 6.00% CB 14.1 CB 15.1 30,000 30,000 60,000 1.38 0.58 2.08 1.65 1.65 2.63 2.08 2.08 58.0 8 0.014 0.012 430.14 432.68 434.50 437.50 7.52% CB 14.5 CB 16.1 25,100 0 25,100 0.58 0.90 2.08 1.08 1.08 2.63 1.36 1.36 50.0 8 0.014 0.012 441.00 444.72 442.50 445.50 3.00% CB 14.6 CB 16.2 0 2,700 2,700 0.06 0.25 2.08 0.03 0.09 2.63 0.04 0.12 33.0 8 0.014 0.012 447.33 450.85 450.00 454.00 8.09% S 304th Street ROW CB 18.2 CB 18.3 10,667 0 10,667 0.24 0.90 2.08 0.46 1.32 2.63 0.58 1.67 102.0 12 0.014 0.012 444.00 447.39 451.43 456.43 7.28% CB 18.3 CB 18.4 6,861 0 6,861 0.16 0.90 2.08 0.30 0.87 2.63 0.37 1.09 297.0 12 0.014 0.012 451.43 456.43 467.68 472.68 5.47% CB 18.4 CB 18.5 6,694 0 6,694 0.15 0.90 2.08 0.29 0.57 2.63 0.36 0.72 197.0 12 0.014 0.012 467.68 472.68 473.53 478.53 2.97% CB 18.5 CB 18.6 6,537 6,537 0.15 0.90 2.08 0.28 0.28 2.63 0.36 0.36 197.0 12 0.014 0.012 473.53 478.53 478.25 483.26 2.40% CB 18.6 CB 18.7 1,826 0 1,826 0.04 0.90 2.08 0.08 0.08 2.63 0.10 0.10 196.0 12 0.014 0.012 478.25 483.26 480.25 488.25 1.02% CB 18.1 CB 19.1 0 2,933 2,933 0.07 0.25 2.08 0.04 1.36 2.63 0.04 1.72 42.0 8 0.014 0.012 439.30 443.94 441.50 444.50 5.24% PIPE OUTLET #10 CB 18.2 0 0 0 0.00 0.90 2.08 0.00 1.32 2.63 0.00 1.67 27.0 8 0.014 0.012 443.50 444.50 444.00 447.39 1.85% BACKWATER CALCULATION SPREADSHEET - 25 YEAR Project Name:FWHS Designed By:MEB Job Number:13003 Storm Event:25-yr, 24-hr Conveyance System Information Outlet Control Inlet Control Headwater Summation Overtopping Check Pipe Segment Surface Total Length Pipe "n" Down- Down- Up- Up- Pipe Barrel Barrel Critical TW TW Barrel Friction Entrance Entrance Entrance Exit Outlet Inlet Inlet Control Approach Bend Bend Q1 Q3 V1 Junction Head HW (HW - Rim) Over- CB/MH # CB/MH # Flow Flow L Size value Stream Stream Stream Stream Slope Velocity Velocity Depth Elev. Check Hyd. Loss HGL Ke Head Head Control Control Control HW Veloctiy Kb Head Head Loss Elev. Clearance topping Down Up Q Qtot D Invert Rim Invert Rim Head Rad.Elev.Loss Loss Elev.HW/D Elev.Elev.Head Loss Loss Total Check CFS CFS FT IN FT FT FT FT % FPS FT FT FT FT FT FT FT FT FT FT FT FT FT FT FT CFS CFS FPS FT FT FT FT CB 1.1 CB 1.2 0.22 2.29 245.0 24 0.012 429.65 433.35 430.88 439.00 0.50% 0.73 0.01 1.80 432.14 432.14 0.50 0.02 432.88 0.50 0.00 0.01 432.89 0.50 431.88 432.89 0.01 0.64 0.01 2.07 0.73 0.01 432.89 -6.11 Okay CB 1.2 CB 1.3 (FCS) 0.00 2.07 8.0 24 0.012 430.88 439.00 430.92 441.50 0.50% 0.66 0.01 1.80 432.89 432.89 0.50 0.00 432.92 0.50 0.00 0.01 432.93 0.50 431.92 432.93 0.01 1.32 0.01 2.07 0.66 0.01 432.93 -8.57 Okay CB 1.3 (FCS) INLET #1 0.93 2.07 34.0 24 0.012 431.00 439.00 431.00 440.00 0.00% 0.66 0.01 1.80 432.93 432.93 0.50 0.00 433.00 0.50 0.00 0.01 433.01 1.10 433.20 433.20 0.00 0.00 23.21 0.66 433.20 -6.80 Okay PIPE OUTLET #2 CB 2.1 0.00 23.21 53.0 24 0.012 436.00 439.00 437.90 444.00 3.58% 7.39 0.85 1.75 431.00 437.88 0.50 0.47 439.90 0.50 0.42 0.85 441.17 1.80 441.50 441.50 0.85 0.12 0.10 23.21 7.39 0.10 440.75 -3.25 Okay CB 2.1 CB 2.2 0.00 23.21 129.0 24 0.012 437.90 444.00 439.93 444.50 1.57% 7.39 0.85 1.75 440.75 440.75 0.50 1.15 441.93 0.50 0.42 0.85 443.20 1.80 443.53 443.53 0.85 0.48 0.41 23.21 7.39 0.41 443.09 -1.41 Okay CB 2.2 CB 2.3 0.00 23.21 131.0 24 0.012 439.93 444.50 441.96 447.50 1.55% 7.39 0.85 1.75 443.09 443.09 0.50 1.17 444.26 0.50 0.42 0.85 445.53 1.80 445.56 445.56 0.85 0.00 23.21 7.39 444.71 -2.79 Okay CB 2.3 CB 2.4 0.00 23.21 63.0 24 0.012 441.96 447.50 445.23 457.00 5.19% 7.39 0.85 1.75 444.71 444.71 0.50 0.56 447.23 0.50 0.42 0.85 448.50 1.80 448.83 448.83 0.85 0.00 23.21 7.39 447.98 -9.02 Okay CB 2.4 CB 2.5 0.00 23.21 151.0 24 0.012 445.23 457.00 447.50 459.20 1.50% 7.39 0.85 1.75 447.98 447.98 0.50 1.35 449.50 0.50 0.42 0.85 450.77 1.80 451.10 451.10 0.80 1.32 1.12 22.50 0.71 7.39 0.02 1.14 451.44 -7.76 Okay CB 2.5 CB 2.6 0.54 22.50 221.0 24 0.012 447.50 459.20 450.82 464.05 1.50% 7.16 0.80 1.75 451.44 451.44 0.50 1.86 453.30 0.50 0.40 0.80 454.50 1.80 454.42 454.50 0.07 0.00 6.51 15.44 7.16 0.71 0.71 455.14 -8.91 Okay CB 2.6 CB 2.7 0.30 6.51 217.0 24 0.012 450.82 464.05 451.91 461.80 0.50% 2.07 0.07 1.12 455.14 455.14 0.50 0.15 455.29 0.50 0.03 0.07 455.39 0.75 453.41 455.39 0.04 0.00 2.89 3.32 2.07 0.04 0.04 455.39 -6.41 Okay CB 2.7 CB 2.8 0.00 2.89 210.0 18 0.012 452.41 461.80 453.46 458.50 0.50% 1.64 0.04 0.74 455.39 455.39 0.38 0.14 455.52 0.50 0.02 0.04 455.58 0.60 454.36 455.58 0.14 1.32 0.05 2.37 0.52 1.64 0.01 0.06 455.50 -3.00 Okay CB 2.8 CB 2.9 0.90 2.37 106.0 12 0.012 453.96 458.50 456.32 461.30 2.23% 3.02 0.14 0.65 455.50 455.50 0.25 0.40 457.32 0.50 0.07 0.14 457.53 0.75 457.07 457.53 0.05 1.32 0.19 1.47 3.02 0.19 457.67 -3.63 Okay CB 2.9 CB 2.10 0.31 1.47 125.0 12 0.012 456.32 461.30 457.74 461.00 1.14% 1.88 0.05 0.57 457.67 457.67 0.25 0.18 458.74 0.50 0.03 0.05 458.82 0.65 458.39 458.82 0.17 0.48 0.03 1.16 1.88 0.03 458.68 -2.32 Okay CB 2.10 CB 2.11 0.58 1.16 73.0 8 0.012 458.07 461.00 458.57 460.60 0.68% 3.32 0.17 0.52 458.68 458.68 0.17 0.57 459.25 0.50 0.09 0.17 459.50 0.50 458.90 459.50 0.04 0.48 0.08 0.58 3.32 0.08 459.54 -1.06 Okay CB 2.11 CB 2.12 0.58 0.58 218.0 8 0.012 458.57 460.60 459.67 464.50 0.50% 1.66 0.04 0.36 459.54 459.54 0.17 0.42 460.34 0.50 0.02 0.04 460.40 0.50 460.00 460.40 0.00 0.00 1.66 460.40 -4.10 Okay CB 2.5 CB 22.1 0.07 0.71 65.0 8 0.012 448.83 459.20 455.00 458.00 9.49% 2.04 0.06 0.40 451.44 451.44 0.17 0.19 455.67 0.50 0.03 0.06 455.76 0.50 455.33 455.76 0.05 1.32 0.09 0.64 2.04 0.09 455.80 -2.20 Okay PIPE OUTLET #3 CB 22.2 0.64 0.64 49.0 8 0.012 457.00 457.50 457.25 458.15 0.51% 1.84 0.05 0.38 457.50 457.52 0.17 0.12 457.92 0.50 0.03 0.05 458.00 0.50 457.58 458.00 0.00 0.00 1.84 458.00 -0.15 Caution CB 2.6 CB 4.1 2.38 5.12 90.0 12 0.012 450.82 464.05 460.00 463.50 10.20% 6.52 0.66 0.66 455.14 455.14 0.25 1.58 461.00 0.50 0.33 0.66 461.99 0.50 460.50 461.99 0.13 1.32 0.87 2.29 6.52 0.87 462.73 -0.77 Okay PIPE OUTLET #4 CB 4.2 0.84 2.29 79.0 12 0.012 463.00 463.50 465.50 468.20 3.16% 2.92 0.13 0.64 462.73 463.82 0.25 0.28 466.50 0.50 0.07 0.13 466.70 0.50 466.00 466.70 0.27 0.00 1.45 2.92 466.43 -1.77 Okay CB 4.2 CB 4.3 1.00 1.45 67.0 8 0.012 465.50 468.20 468.50 471.80 4.48% 4.16 0.27 0.56 466.43 466.43 0.17 0.82 469.17 0.50 0.13 0.27 469.57 0.50 468.83 469.57 0.03 0.00 0.45 4.16 469.54 -2.26 Okay PIPE OUTLET #5 CB 5.1 0.45 0.45 57.0 8 0.012 463.00 463.50 463.60 466.50 1.05% 1.28 0.03 0.31 463.50 463.50 0.17 0.07 464.27 0.50 0.01 0.03 464.31 0.50 463.93 464.31 0.00 0.00 1.28 464.31 -2.19 Okay CB 2.6 CB 6.1 0.00 10.32 318.0 18 0.012 450.82 464.05 457.00 465.50 1.94% 5.84 0.53 1.23 455.14 455.14 0.38 2.60 458.50 0.50 0.26 0.53 459.29 0.50 457.75 459.29 0.04 1.32 0.70 1.31 9.01 5.84 0.66 1.36 460.61 -4.89 Okay CB 6.1 CB 6.2 0.00 1.31 292.0 12 0.012 457.00 465.50 468.00 478.00 3.77% 1.67 0.04 0.48 460.61 460.61 0.25 0.33 469.00 0.50 0.02 0.04 469.06 0.50 468.50 469.06 0.04 0.48 0.02 1.31 1.25 1.67 0.02 0.04 469.07 -8.93 Okay CB 6.2 CB 6.3 0.00 1.31 59.0 12 0.012 468.00 478.00 472.00 482.10 6.78% 1.67 0.04 0.48 469.07 469.07 0.25 0.07 473.00 0.50 0.02 0.04 473.06 0.50 472.50 473.06 0.22 0.00 1.31 1.67 472.85 -9.25 Okay CB 6.3 CB 6.4 1.31 1.31 83.0 8 0.012 472.00 482.10 480.00 483.00 9.64% 3.75 0.22 0.54 472.85 472.85 0.17 0.82 480.67 0.50 0.11 0.22 480.99 0.50 480.33 480.99 0.00 0.00 3.75 480.99 -2.01 Okay CB 6.1 CB 7.1 0.42 1.21 242.0 12 0.012 457.50 465.50 460.00 465.00 1.03% 1.55 0.04 0.46 460.61 460.61 0.25 0.24 461.00 0.50 0.02 0.04 461.06 0.50 460.50 461.06 0.08 0.00 0.79 1.55 460.98 -4.02 Okay PIPE OUTLET #9 CB 7.2 0.79 0.79 20.0 8 0.012 464.00 465.00 464.10 465.70 0.50% 2.26 0.08 0.42 460.98 464.54 0.17 0.07 464.77 0.50 0.04 0.08 464.89 0.50 464.43 464.89 0.00 0.00 2.26 464.89 -0.81 Okay CB 6.1 CB 8.1 0.06 1.52 39.0 8 0.012 457.00 465.50 462.00 465.50 12.82% 4.37 0.30 0.58 460.61 460.61 0.17 0.53 462.67 0.50 0.15 0.30 463.11 0.50 462.33 463.11 0.08 1.32 0.39 0.77 0.69 4.37 0.15 0.54 463.58 -1.92 Okay CB 8.1 CB 8.2 0.20 0.77 63.0 8 0.012 462.00 465.50 462.66 466.50 1.05% 2.21 0.08 0.42 463.58 463.58 0.17 0.22 463.80 0.50 0.04 0.08 463.91 0.50 462.99 463.91 0.04 1.32 0.10 0.57 2.21 0.10 463.97 -2.53 Okay CB 8.2 CB 8.3 0.21 0.57 63.0 8 0.012 462.66 466.50 463.32 466.50 1.05% 1.64 0.04 0.36 463.97 463.97 0.17 0.12 464.09 0.50 0.02 0.04 464.15 0.50 463.65 464.15 0.02 0.00 0.36 1.64 464.13 -2.37 Okay CB 8.3 CB 8.4 0.36 0.36 58.0 8 0.012 463.32 466.50 463.93 466.80 1.05% 1.03 0.02 0.28 464.13 464.13 0.17 0.04 464.60 0.50 0.01 0.02 464.62 0.50 464.26 464.62 0.06 0.00 0.69 1.03 464.56 -2.24 Okay CB 8.1 CB 8.5 0.34 0.69 39.0 8 0.012 462.00 465.50 462.82 466.50 2.10% 1.98 0.06 0.39 464.56 464.56 0.17 0.11 464.67 0.50 0.03 0.06 464.76 0.50 463.15 464.76 0.02 0.48 0.03 0.35 1.98 0.03 464.77 -1.73 Okay CB 8.5 CB 8.6 0.35 0.35 51.0 8 0.012 462.82 466.50 463.37 466.50 1.08% 1.01 0.02 0.27 464.77 464.77 0.17 0.04 464.81 0.50 0.01 0.02 464.83 0.50 463.70 464.83 1.32 0.02 0.00 1.01 0.02 464.85 -1.65 Okay CB 6.1 CB 9.1 1.59 6.27 89.0 18 0.012 457.00 465.50 462.00 465.50 5.62% 3.55 0.20 0.96 460.61 460.61 0.38 0.27 463.50 0.50 0.10 0.20 463.79 0.50 462.75 463.79 0.00 0.00 3.55 463.79 -1.71 Okay CB 6.2 CB 10.1 0.00 1.25 60.0 8 0.012 468.00 478.00 469.00 477.00 1.67% 3.60 0.20 0.53 455.14 468.60 0.17 0.55 469.67 0.50 0.10 0.20 469.97 0.50 469.33 469.97 0.20 0.48 0.10 1.25 3.60 0.10 469.86 -7.14 Okay CB 10.1 CB 10.2 0.09 1.25 86.0 8 0.012 469.00 477.00 470.50 473.50 1.74% 3.60 0.20 0.53 469.86 469.86 0.17 0.78 471.17 0.50 0.10 0.20 471.47 0.50 470.83 471.47 0.12 0.48 0.10 0.96 3.60 0.10 471.45 -2.05 Okay CB 10.2 CB 10.3 0.96 0.96 64.0 8 0.012 470.50 473.50 471.00 474.00 0.78% 2.74 0.12 0.46 471.45 471.45 0.17 0.34 471.79 0.50 0.06 0.12 471.96 0.50 471.33 471.96 0.01 0.00 0.21 2.74 471.96 -2.04 Okay PIPE OUTLET #8 CB 10.4 0.21 0.21 51.0 8 0.012 475.80 476.50 480.00 484.00 8.24% 0.60 0.01 0.21 471.96 476.24 0.17 0.01 480.67 0.50 0.00 0.01 480.68 0.50 480.33 480.68 0.00 0.00 0.60 480.68 -3.32 Okay PIPE OUTLET #6 CB 11.1 0.55 2.57 101.0 12 0.012 464.00 464.50 465.50 468.80 1.49% 3.27 0.17 0.68 464.50 464.84 0.25 0.44 466.50 0.50 0.08 0.17 466.75 0.50 466.00 466.75 0.52 0.48 0.08 2.02 3.27 0.08 466.31 -2.49 Okay CB 11.1 CB 11.2 0.46 2.02 72.0 8 0.012 465.50 468.80 469.50 472.30 5.56% 5.79 0.52 0.63 466.31 466.31 0.17 1.70 470.17 0.50 0.26 0.52 470.95 0.50 469.83 470.95 0.31 0.00 1.56 5.79 470.64 -1.66 Okay CB 11.2 CB 11.3 0.60 1.56 70.0 8 0.012 469.50 472.30 472.50 475.50 4.29% 4.46 0.31 0.56 470.64 470.64 0.17 0.98 473.17 0.50 0.15 0.31 473.63 0.50 472.83 473.63 0.12 0.00 0.96 4.46 473.51 -1.99 Okay CB 11.3 CB 11.4 0.01 0.96 70.0 8 0.012 472.50 475.50 476.00 480.50 5.00% 2.75 0.12 0.41 473.51 473.51 0.17 0.37 476.67 0.50 0.06 0.12 476.84 0.50 476.33 476.84 0.11 0.00 0.95 2.75 476.73 -3.77 Okay CB 11.4 CB 11.5 0.95 0.95 14.0 8 0.012 476.00 480.50 476.50 480.00 3.57% 2.71 0.11 0.40 476.73 476.73 0.17 0.07 477.17 0.50 0.06 0.11 477.34 0.50 476.83 477.34 1.32 0.15 0.00 2.71 0.15 477.49 -2.51 Okay PIPE OUTLET #7 CB 12.1 0.00 2.12 42.0 12 0.012 464.00 464.50 465.00 467.50 2.38% 2.70 0.11 0.33 464.50 464.67 0.25 0.13 466.00 0.50 0.06 0.11 466.17 0.50 465.50 466.17 0.57 0.48 0.05 2.12 2.70 0.05 465.65 -1.85 Okay FWHS - Backwater Conveyance Calculation-Ph2 Permit.xls 7/30/2014 Conveyance System Information Outlet Control Inlet Control Headwater Summation Overtopping Check Pipe Segment Surface Total Length Pipe "n" Down- Down- Up- Up- Pipe Barrel Barrel Critical TW TW Barrel Friction Entrance Entrance Entrance Exit Outlet Inlet Inlet Control Approach Bend Bend Q1 Q3 V1 Junction Head HW (HW - Rim) Over- CB/MH # CB/MH # Flow Flow L Size value Stream Stream Stream Stream Slope Velocity Velocity Depth Elev. Check Hyd. Loss HGL Ke Head Head Control Control Control HW Veloctiy Kb Head Head Loss Elev. Clearance topping Down Up Q Qtot D Invert Rim Invert Rim Head Rad.Elev.Loss Loss Elev.HW/D Elev.Elev.Head Loss Loss Total Check CFS CFS FT IN FT FT FT FT % FPS FT FT FT FT FT FT FT FT FT FT FT FT FT FT FT CFS CFS FPS FT FT FT FT CB 12.1 CB 12.2 2.12 2.12 120.0 8 0.012 465.00 467.50 473.50 479.00 7.08% 6.07 0.57 0.33 465.65 465.65 0.17 3.12 474.17 0.50 0.29 0.57 475.02 0.50 473.83 475.02 1.32 0.75 0.00 6.07 0.75 475.78 -3.22 Okay CB 2.7 CB 13.1 0.25 3.32 129.0 12 0.012 452.91 461.80 456.20 461.20 2.55% 4.23 0.28 0.33 455.39 455.39 0.25 0.95 457.20 0.50 0.14 0.28 457.62 0.50 456.70 457.62 0.24 1.32 0.37 3.07 4.23 0.37 457.75 -3.45 Okay CB 13.1 CB 13.2 1.41 3.07 125.0 12 0.012 456.20 461.20 459.20 464.20 2.40% 3.91 0.24 0.33 457.75 457.75 0.25 0.79 460.20 0.50 0.12 0.24 460.56 0.50 459.70 460.56 0.07 0.00 1.66 3.91 460.49 -3.71 Okay CB 13.2 CB 13.3 1.66 1.66 109.0 12 0.012 459.20 464.20 460.29 463.50 1.00% 2.11 0.07 0.33 460.49 460.49 0.25 0.20 461.29 0.50 0.03 0.07 461.39 0.50 460.79 461.39 0.00 0.00 2.11 461.39 -2.11 Okay CB 13.3 CB 13.4 2.04 2.04 117.0 12 0.012 460.29 463.50 462.00 466.00 1.46% 2.59 0.10 0.33 461.39 461.39 0.25 0.32 463.00 0.50 0.05 0.10 463.16 0.50 462.50 463.16 0.00 0.00 0.06 2.59 463.16 -2.84 Okay PIPE OUTLET #8 CB 21.1 0.06 0.06 58.0 8 0.012 452.50 453.50 453.80 456.80 2.24% 0.17 0.00 0.33 452.50 453.00 0.17 0.00 454.47 0.50 0.00 0.00 454.47 0.50 454.13 454.47 0.00 0.00 0.17 454.47 -2.33 Okay CB 2.8 CB 17.1 0.52 0.52 77.0 8 0.012 456.23 458.50 457.00 459.00 1.00% 1.49 0.03 0.33 455.50 456.73 0.17 0.12 457.67 0.50 0.02 0.03 457.72 0.50 457.33 457.72 1.32 0.05 0.00 1.49 0.05 457.76 -1.24 Okay S 308th Street ROW EX CB #1 CB 14.1 0.04 6.01 26.0 30 0.012 429.00 433.42 429.65 433.35 2.50% 1.22 0.02 0.94 429.50 430.72 0.63 0.00 432.15 0.50 0.01 0.02 432.18 0.50 430.90 432.18 0.06 0.00 5.97 2.29 1.22 0.01 0.01 432.14 -1.21 Okay CB 14.1 CB 14.2 0.30 5.97 91.0 24 0.012 429.65 433.35 430.14 432.68 0.54% 1.90 0.06 0.94 432.14 432.14 0.50 0.05 432.19 0.50 0.03 0.06 432.27 0.50 431.14 432.27 0.08 0.00 4.02 1.65 1.90 0.02 0.02 432.21 -0.47 Caution CB 14.2 CB 14.3 1.29 4.02 52.0 18 0.012 430.14 432.68 430.43 432.47 0.56% 2.27 0.08 0.86 432.21 432.21 0.38 0.06 432.27 0.50 0.04 0.08 432.39 0.50 431.18 432.39 0.04 0.00 2.72 2.27 432.36 -0.11 Caution CB 14.3 CB 14.4 0.18 2.72 8.0 18 0.012 430.43 432.47 430.50 432.41 0.87% 1.54 0.04 0.75 432.36 432.36 0.38 0.00 432.36 0.50 0.02 0.04 432.42 0.50 431.25 432.42 0.16 0.00 2.54 1.54 432.25 -0.16 Caution CB 14.4 CB 14.5 0.26 2.54 109.0 12 0.012 430.50 432.41 432.00 434.72 1.38% 3.23 0.16 0.82 432.25 432.25 0.25 0.47 433.00 0.50 0.08 0.16 433.24 0.50 432.50 433.24 0.13 0.00 2.28 3.23 433.11 -1.61 Okay CB 14.5 CB 14.6 0.15 2.28 174.0 12 0.012 432.00 434.72 441.00 444.72 5.17% 2.91 0.13 0.79 433.11 433.11 0.25 0.61 442.00 0.50 0.07 0.13 442.20 0.50 441.50 442.20 0.02 0.00 0.96 1.17 2.91 0.08 0.08 442.26 -2.46 Okay CB 14.6 CB 14.7 0.96 0.96 100.0 12 0.012 441.00 444.72 447.00 450.85 6.00% 1.22 0.02 0.41 442.26 442.26 0.25 0.06 448.00 0.50 0.01 0.02 448.03 0.50 447.50 448.03 0.00 0.96 1.22 448.03 -2.82 Okay CB 14.1 CB 15.1 1.65 1.65 58.0 8 0.012 430.14 432.68 434.50 437.50 7.52% 4.73 0.35 0.62 432.21 432.21 0.17 0.92 435.17 0.50 0.17 0.35 435.69 0.50 434.83 435.69 1.32 0.46 0.00 4.73 0.46 436.15 -1.35 Okay CB 14.5 CB 16.1 1.08 1.08 50.0 8 0.012 441.00 444.72 442.50 445.50 3.00% 3.10 0.15 0.49 442.26 442.26 0.17 0.34 443.17 0.50 0.07 0.15 443.39 0.50 442.83 443.39 0.00 1.32 0.20 0.00 3.10 0.20 443.59 -1.91 Okay CB 14.6 CB 16.2 0.03 0.09 33.0 8 0.012 447.33 450.85 450.00 454.00 8.09% 0.26 0.00 0.52 442.26 447.92 0.17 0.00 450.67 0.50 0.00 0.00 450.67 0.50 450.33 450.67 1.32 0.00 0.00 0.26 0.00 450.67 -3.33 Okay S 304th Street ROW CB 18.2 CB 18.3 0.46 1.32 102.0 12 0.012 444.00 447.39 451.43 456.43 7.28% 1.69 0.04 0.33 445.00 445.00 0.25 0.12 452.43 0.50 0.02 0.04 452.50 0.50 451.93 452.50 0.01 0.00 0.87 1.69 452.49 -3.94 Okay CB 18.3 CB 18.4 0.30 0.87 297.0 12 0.012 451.43 456.43 467.68 472.68 5.47% 1.10 0.02 0.33 452.49 452.49 0.25 0.15 468.68 0.50 0.01 0.02 468.71 0.50 468.18 468.71 0.00 0.00 0.57 1.10 468.71 -3.97 Okay CB 18.4 CB 18.5 0.29 0.57 197.0 12 0.012 467.68 472.68 473.53 478.53 2.97% 0.73 0.01 0.33 468.71 468.71 0.25 0.04 474.53 0.50 0.00 0.01 474.54 0.50 474.03 474.54 0.00 0.00 0.28 0.73 474.54 -3.99 Okay CB 18.5 CB 18.6 0.28 0.28 197.0 12 0.012 473.53 478.53 478.25 483.26 2.40% 0.36 0.00 0.33 474.54 474.54 0.25 0.01 479.25 0.50 0.00 0.00 479.25 0.50 478.75 479.25 0.00 0.08 0.36 479.25 -4.01 Okay CB 18.6 CB 18.7 0.08 0.08 196.0 12 0.012 478.25 483.26 480.25 488.25 1.02% 0.10 0.00 0.33 479.25 479.25 0.25 0.00 481.25 0.50 0.00 0.00 481.25 0.50 480.75 481.25 0.00 0.00 0.10 481.25 -7.00 Okay CB 18.1 CB 19.1 0.04 1.36 42.0 8 0.012 439.30 443.94 441.50 444.50 5.24% 3.90 0.24 0.33 439.30 439.80 0.17 0.45 442.17 0.50 0.12 0.24 442.52 0.50 441.83 442.52 0.00 0.00 3.90 442.52 -1.98 Okay PIPE OUTLET #10 CB 18.2 0.00 1.32 27.0 8 0.012 443.50 444.50 444.00 447.39 1.85% 3.79 0.22 0.33 444.00 444.00 0.17 0.27 444.67 0.50 0.11 0.22 445.00 0.50 444.33 445.00 0.00 0.00 3.79 445.00 -2.39 Okay FWHS - Backwater Conveyance Calculation-Ph2 Permit.xls 7/30/2014 BACKWATER CALCULATION SPREADSHEET - 100 YEAR Project Name:FWHS Designed By:MEB Job Number:13003 Storm Event:100-yr, 24-hr Conveyance System Information Outlet Control Inlet Control Headwater Summation Overtopping Check Pipe Segment Surface Total Length Pipe "n" Down- Down- Up- Up- Pipe Barrel Barrel Critical TW TW Barrel Friction Entrance Entrance Entrance Exit Outlet Inlet Inlet Control Approach Bend Bend Q1 Q3 V1 Junction Head HW (HW - Rim) Over- CB/MH # CB/MH # Flow Flow L Size value Stream Stream Stream Stream Slope Velocity Velocity Depth Elev. Check Hyd. Loss HGL Ke Head Head Control Control Control HW Veloctiy Kb Head Head Loss Elev. Clearance topping Down Up Q Qtot D Invert Rim Invert Rim Head Rad.Elev.Loss Loss Elev.HW/D Elev.Elev.Head Loss Loss Total Check CFS CFS FT IN FT FT FT FT % FPS FT FT FT FT FT FT FT FT FT FT FT FT FT FT FT CFS CFS FPS FT FT FT FT CB 1.1 CB 1.2 0.27 6.60 245.0 24 0.012 429.65 433.35 430.88 439.00 0.50% 2.10 0.07 1.80 432.14 432.14 0.50 0.18 432.88 0.50 0.03 0.07 432.98 0.50 431.88 432.98 0.06 0.64 0.04 6.33 2.10 0.04 432.96 -6.04 Okay CB 1.2 CB 1.3 (FCS) 0.00 6.33 8.0 24 0.012 430.88 439.00 430.92 441.50 0.50% 2.01 0.06 1.80 432.96 432.96 0.50 0.01 432.97 0.50 0.03 0.06 433.06 0.50 431.92 433.06 0.06 1.32 0.08 6.33 2.01 0.08 433.08 -8.42 Okay CB 1.3 (FCS) INLET #1 1.17 6.33 34.0 24 0.012 431.00 439.00 431.00 440.00 0.00% 2.01 0.06 1.80 433.08 433.08 0.50 0.02 433.11 0.50 0.03 0.06 433.20 1.10 433.20 433.20 0.00 0.00 29.30 2.01 433.20 -6.80 Okay PIPE OUTLET #2 CB 2.1 0.00 29.30 53.0 24 0.012 436.00 439.00 437.90 444.00 3.58% 9.33 1.35 1.75 431.00 437.88 0.50 0.76 439.90 0.50 0.68 1.35 441.93 1.80 441.50 441.93 1.35 0.12 0.16 29.30 9.33 0.16 440.74 -3.26 Okay CB 2.1 CB 2.2 0.00 29.30 129.0 24 0.012 437.90 444.00 439.93 444.50 1.57% 9.33 1.35 1.75 440.74 440.74 0.50 1.84 442.58 0.50 0.68 1.35 444.60 1.80 443.53 444.60 1.35 0.48 0.65 29.30 9.33 0.65 443.90 -0.60 Okay CB 2.2 CB 2.3 0.00 29.30 131.0 24 0.012 439.93 444.50 441.96 447.50 1.55% 9.33 1.35 1.75 443.90 443.90 0.50 1.87 445.77 0.50 0.68 1.35 447.79 1.80 445.56 447.79 1.35 0.00 29.30 9.33 446.44 -1.06 Okay CB 2.3 CB 2.4 0.00 29.30 63.0 24 0.012 441.96 447.50 445.23 457.00 5.19% 9.33 1.35 1.75 446.44 446.44 0.50 0.90 447.34 0.50 0.68 1.35 449.36 1.80 448.83 449.36 1.35 0.00 29.30 9.33 448.01 -8.99 Okay CB 2.4 CB 2.5 0.00 29.30 151.0 24 0.012 445.23 457.00 447.50 459.20 1.50% 9.33 1.35 1.75 448.01 448.01 0.50 2.15 450.17 0.50 0.68 1.35 452.19 1.80 451.10 452.19 1.27 1.32 1.78 28.40 0.90 9.33 0.04 1.82 452.74 -6.46 Okay CB 2.5 CB 2.6 0.69 28.40 221.0 24 0.012 447.50 459.20 450.82 464.05 1.50% 9.04 1.27 1.75 452.74 452.74 0.50 2.96 455.70 0.50 0.63 1.27 457.60 1.80 454.42 457.60 0.11 0.00 8.22 19.49 9.04 1.13 1.13 458.62 -5.43 Okay CB 2.6 CB 2.7 0.37 8.22 217.0 24 0.012 450.82 464.05 451.91 461.80 0.50% 2.62 0.11 1.12 458.62 458.62 0.50 0.24 458.87 0.50 0.05 0.11 459.02 0.75 453.41 459.02 0.07 0.00 3.65 4.19 2.62 0.06 0.06 459.02 -2.78 Okay CB 2.7 CB 2.8 0.00 3.65 210.0 18 0.012 452.41 461.80 453.46 458.50 0.50% 2.07 0.07 0.74 459.02 459.02 0.38 0.22 459.24 0.50 0.03 0.07 459.34 0.60 454.36 459.34 0.23 1.32 0.09 3.00 0.66 2.07 0.01 0.10 459.21 0.71 Overtopping!! CB 2.8 CB 2.9 1.14 3.00 106.0 12 0.012 453.96 458.50 456.32 461.30 2.23% 3.82 0.23 0.65 459.21 459.21 0.25 0.64 459.85 0.50 0.11 0.23 460.18 0.75 457.07 460.18 0.09 1.32 0.30 1.86 3.82 0.30 460.40 -0.90 Okay CB 2.9 CB 2.10 0.40 1.86 125.0 12 0.012 456.32 461.30 457.74 461.00 1.14% 2.37 0.09 0.57 460.40 460.40 0.25 0.29 460.68 0.50 0.04 0.09 460.82 0.65 458.39 460.82 0.27 0.48 0.04 1.46 2.37 0.04 460.58 -0.42 Caution CB 2.10 CB 2.11 0.73 1.46 73.0 8 0.012 458.07 461.00 458.57 460.60 0.68% 4.19 0.27 0.52 460.58 460.58 0.17 0.91 461.49 0.50 0.14 0.27 461.90 0.50 458.90 461.90 0.07 0.48 0.13 0.73 4.19 0.13 461.96 1.36 Overtopping!! CB 2.11 CB 2.12 0.73 0.73 218.0 8 0.012 458.57 460.60 459.67 464.50 0.50% 2.10 0.07 0.36 461.96 461.96 0.17 0.68 462.64 0.50 0.03 0.07 462.74 0.50 460.00 462.74 0.00 0.00 2.10 462.74 -1.76 Okay CB 2.5 CB 22.1 0.09 0.90 65.0 8 0.012 448.83 459.20 455.00 458.00 9.49% 2.58 0.10 0.40 452.74 452.74 0.17 0.31 455.67 0.50 0.05 0.10 455.82 0.50 455.33 455.82 0.08 1.32 0.14 0.81 2.58 0.14 455.87 -2.13 Okay PIPE OUTLET #3 CB 22.2 0.81 0.81 49.0 8 0.012 457.00 457.50 457.25 458.15 0.51% 2.32 0.08 0.38 457.50 457.52 0.17 0.19 457.92 0.50 0.04 0.08 458.04 0.50 457.58 458.04 0.00 0.00 2.32 458.04 -0.11 Caution CB 2.6 CB 4.1 3.01 6.47 90.0 12 0.012 450.82 464.05 460.00 463.50 10.20% 8.23 1.05 0.66 458.62 458.62 0.25 2.51 461.13 0.50 0.53 1.05 462.71 0.50 460.50 462.71 0.21 1.32 1.39 2.89 8.23 1.39 463.89 0.39 Overtopping!! PIPE OUTLET #4 CB 4.2 1.06 2.89 79.0 12 0.012 463.00 463.50 465.50 468.20 3.16% 3.68 0.21 0.64 463.89 463.89 0.25 0.44 466.50 0.50 0.11 0.21 466.82 0.50 466.00 466.82 0.43 0.00 1.83 3.68 466.39 -1.81 Okay CB 4.2 CB 4.3 1.27 1.83 67.0 8 0.012 465.50 468.20 468.50 471.80 4.48% 5.26 0.43 0.56 466.39 466.39 0.17 1.31 469.17 0.50 0.21 0.43 469.81 0.50 468.83 469.81 0.04 0.00 0.57 5.26 469.77 -2.03 Okay PIPE OUTLET #5 CB 5.1 0.57 0.57 57.0 8 0.012 463.00 463.50 463.60 466.50 1.05% 1.62 0.04 0.31 463.50 463.50 0.17 0.11 464.27 0.50 0.02 0.04 464.33 0.50 463.93 464.33 0.00 0.00 1.62 464.33 -2.17 Okay CB 2.6 CB 6.1 0.00 13.02 318.0 18 0.012 450.82 464.05 457.00 465.50 1.94% 7.37 0.84 1.23 458.62 458.62 0.38 4.15 462.77 0.50 0.42 0.84 464.04 0.50 457.75 464.04 0.07 1.32 1.11 1.65 11.37 7.37 1.05 2.17 466.13 0.63 Overtopping!! CB 6.1 CB 6.2 0.00 1.65 292.0 12 0.012 457.00 465.50 468.00 478.00 3.77% 2.10 0.07 0.48 466.13 466.13 0.25 0.53 469.00 0.50 0.03 0.07 469.10 0.50 468.50 469.10 0.07 0.48 0.03 1.65 1.58 2.10 0.04 0.07 469.10 -8.90 Okay CB 6.2 CB 6.3 0.00 1.65 59.0 12 0.012 468.00 478.00 472.00 482.10 6.78% 2.10 0.07 0.48 469.10 469.10 0.25 0.11 473.00 0.50 0.03 0.07 473.10 0.50 472.50 473.10 0.35 0.00 1.65 2.10 472.76 -9.34 Okay CB 6.3 CB 6.4 1.65 1.65 83.0 8 0.012 472.00 482.10 480.00 483.00 9.64% 4.73 0.35 0.54 472.76 472.76 0.17 1.31 480.67 0.50 0.17 0.35 481.19 0.50 480.33 481.19 0.00 0.00 4.73 481.19 -1.81 Okay CB 6.1 CB 7.1 0.54 1.53 242.0 12 0.012 457.50 465.50 460.00 465.00 1.03% 1.95 0.06 0.46 466.13 466.13 0.25 0.38 466.51 0.50 0.03 0.06 466.60 0.50 460.50 466.60 0.13 0.00 1.00 1.95 466.47 1.47 Overtopping!! PIPE OUTLET #9 CB 7.2 1.00 1.00 20.0 8 0.012 464.00 465.00 464.10 465.70 0.50% 2.85 0.13 0.42 466.47 466.47 0.17 0.12 466.59 0.50 0.06 0.13 466.78 0.50 464.43 466.78 0.00 0.00 2.85 466.78 1.08 Overtopping!! CB 6.1 CB 8.1 0.08 1.92 39.0 8 0.012 457.00 465.50 462.00 465.50 12.82% 5.51 0.47 0.58 466.13 466.13 0.17 0.84 466.97 0.50 0.24 0.47 467.68 0.50 462.33 467.68 0.12 1.32 0.62 0.98 0.87 5.51 0.24 0.86 468.42 2.92 Overtopping!! CB 8.1 CB 8.2 0.25 0.98 63.0 8 0.012 462.00 465.50 462.66 466.50 1.05% 2.79 0.12 0.42 468.42 468.42 0.17 0.35 468.77 0.50 0.06 0.12 468.95 0.50 462.99 468.95 0.07 1.32 0.16 0.72 2.79 0.16 469.04 2.54 Overtopping!! CB 8.2 CB 8.3 0.26 0.72 63.0 8 0.012 462.66 466.50 463.32 466.50 1.05% 2.06 0.07 0.36 469.04 469.04 0.17 0.19 469.23 0.50 0.03 0.07 469.33 0.50 463.65 469.33 0.03 0.00 0.46 2.06 469.31 2.81 Overtopping!! CB 8.3 CB 8.4 0.46 0.46 58.0 8 0.012 463.32 466.50 463.93 466.80 1.05% 1.31 0.03 0.28 469.31 469.31 0.17 0.07 469.38 0.50 0.01 0.03 469.42 0.50 464.26 469.42 0.10 0.00 0.87 1.31 469.32 2.52 Overtopping!! CB 8.1 CB 8.5 0.43 0.87 39.0 8 0.012 462.00 465.50 462.82 466.50 2.10% 2.50 0.10 0.39 469.32 469.32 0.17 0.17 469.49 0.50 0.05 0.10 469.64 0.50 463.15 469.64 0.03 0.48 0.05 0.44 2.50 0.05 469.66 3.16 Overtopping!! CB 8.5 CB 8.6 0.44 0.44 51.0 8 0.012 462.82 466.50 463.37 466.50 1.08% 1.27 0.03 0.27 469.66 469.66 0.17 0.06 469.72 0.50 0.01 0.03 469.75 0.50 463.70 469.75 1.32 0.03 0.00 1.27 0.03 469.79 3.29 Overtopping!! CB 6.1 CB 9.1 2.00 7.92 89.0 18 0.012 457.00 465.50 462.00 465.50 5.62% 4.48 0.31 0.96 466.13 466.13 0.38 0.43 466.56 0.50 0.16 0.31 467.03 0.50 462.75 467.03 0.00 0.00 4.48 467.03 1.53 Overtopping!! CB 6.2 CB 10.1 0.00 1.58 60.0 8 0.012 468.00 478.00 469.00 477.00 1.67% 4.54 0.32 0.53 458.62 468.60 0.17 0.87 469.67 0.50 0.16 0.32 470.15 0.50 469.33 470.15 0.32 0.48 0.15 1.58 4.54 0.15 469.98 -7.02 Okay CB 10.1 CB 10.2 0.11 1.58 86.0 8 0.012 469.00 477.00 470.50 473.50 1.74% 4.54 0.32 0.53 469.98 469.98 0.17 1.25 471.23 0.50 0.16 0.32 471.71 0.50 470.83 471.71 0.19 0.48 0.15 1.21 4.54 0.15 471.68 -1.82 Okay CB 10.2 CB 10.3 1.21 1.21 64.0 8 0.012 470.50 473.50 471.00 474.00 0.78% 3.46 0.19 0.46 471.68 471.68 0.17 0.54 472.22 0.50 0.09 0.19 472.50 0.50 471.33 472.50 0.01 0.00 0.26 3.46 472.49 -1.51 Okay PIPE OUTLET #8 CB 10.4 0.26 0.26 51.0 8 0.012 475.80 476.50 480.00 484.00 8.24% 0.76 0.01 0.21 472.49 476.24 0.17 0.02 480.67 0.50 0.00 0.01 480.68 0.50 480.33 480.68 0.00 0.00 0.76 480.68 -3.32 Okay PIPE OUTLET #6 CB 11.1 0.69 3.24 101.0 12 0.012 464.00 464.50 465.50 468.80 1.49% 4.13 0.26 0.68 464.50 464.84 0.25 0.71 466.50 0.50 0.13 0.26 466.90 0.50 466.00 466.90 0.83 0.48 0.13 2.55 4.13 0.13 466.20 -2.60 Okay CB 11.1 CB 11.2 0.58 2.55 72.0 8 0.012 465.50 468.80 469.50 472.30 5.56% 7.30 0.83 0.63 466.20 466.20 0.17 2.71 470.17 0.50 0.41 0.83 471.41 0.50 469.83 471.41 0.49 0.00 1.96 7.30 470.92 -1.38 Okay CB 11.2 CB 11.3 0.75 1.96 70.0 8 0.012 469.50 472.30 472.50 475.50 4.29% 5.63 0.49 0.56 470.92 470.92 0.17 1.57 473.17 0.50 0.25 0.49 473.90 0.50 472.83 473.90 0.19 0.00 1.21 5.63 473.72 -1.78 Okay CB 11.3 CB 11.4 0.01 1.21 70.0 8 0.012 472.50 475.50 476.00 480.50 5.00% 3.47 0.19 0.41 473.72 473.72 0.17 0.59 476.67 0.50 0.09 0.19 476.95 0.50 476.33 476.95 0.18 0.00 1.20 3.47 476.76 -3.74 Okay CB 11.4 CB 11.5 1.20 1.20 14.0 8 0.012 476.00 480.50 476.50 480.00 3.57% 3.43 0.18 0.40 476.76 476.76 0.17 0.12 477.17 0.50 0.09 0.18 477.44 0.50 476.83 477.44 1.32 0.24 0.00 3.43 0.24 477.68 -2.32 Okay PIPE OUTLET #7 CB 12.1 0.00 2.67 42.0 12 0.012 464.00 464.50 465.00 467.50 2.38% 3.40 0.18 0.33 464.50 464.67 0.25 0.20 466.00 0.50 0.09 0.18 466.27 0.50 465.50 466.27 0.91 0.48 0.09 2.67 3.40 0.09 465.45 -2.05 Okay CB 12.1 CB 12.2 2.67 2.67 120.0 8 0.012 465.00 467.50 473.50 479.00 7.08% 7.66 0.91 0.33 465.45 465.50 0.17 4.97 474.17 0.50 0.46 0.91 475.53 0.50 473.83 475.53 1.32 1.20 0.00 7.66 1.20 476.73 -2.27 Okay CB 2.7 CB 13.1 0.32 4.19 129.0 12 0.012 452.91 461.80 456.20 461.20 2.55% 5.34 0.44 0.33 459.02 459.02 0.25 1.51 460.54 0.50 0.22 0.44 461.20 0.50 456.70 461.20 0.38 1.32 0.58 3.88 5.34 0.58 461.41 0.21 Overtopping!! CB 13.1 CB 13.2 1.78 3.88 125.0 12 0.012 456.20 461.20 459.20 464.20 2.40% 4.94 0.38 0.33 461.41 461.41 0.25 1.25 462.66 0.50 0.19 0.38 463.23 0.50 459.70 463.23 0.11 0.00 2.09 4.94 463.12 -1.08 Okay CB 13.2 CB 13.3 2.09 2.09 109.0 12 0.012 459.20 464.20 460.29 463.50 1.00% 2.66 0.11 0.33 463.12 463.12 0.25 0.32 463.44 0.50 0.06 0.11 463.60 0.50 460.79 463.60 0.00 0.00 2.66 463.60 0.10 Overtopping!! CB 13.3 CB 13.4 2.57 2.57 117.0 12 0.012 460.29 463.50 462.00 466.00 1.46% 3.27 0.17 0.33 463.60 463.60 0.25 0.52 464.12 0.50 0.08 0.17 464.37 0.50 462.50 464.37 0.00 0.00 0.08 3.27 464.37 -1.63 Okay PIPE OUTLET #8 CB 21.1 0.08 0.08 58.0 8 0.012 452.50 453.50 453.80 456.80 2.24% 0.22 0.00 0.33 451.00 453.00 0.17 0.00 454.47 0.50 0.00 0.00 454.47 0.50 454.13 454.47 0.00 0.22 454.47 -2.33 Okay FWHS - Backwater Conveyance Calculation-Ph2 Permit.xls 7/30/2014 Conveyance System Information Outlet Control Inlet Control Headwater Summation Overtopping Check Pipe Segment Surface Total Length Pipe "n" Down- Down- Up- Up- Pipe Barrel Barrel Critical TW TW Barrel Friction Entrance Entrance Entrance Exit Outlet Inlet Inlet Control Approach Bend Bend Q1 Q3 V1 Junction Head HW (HW - Rim) Over- CB/MH # CB/MH # Flow Flow L Size value Stream Stream Stream Stream Slope Velocity Velocity Depth Elev. Check Hyd. Loss HGL Ke Head Head Control Control Control HW Veloctiy Kb Head Head Loss Elev. Clearance topping Down Up Q Qtot D Invert Rim Invert Rim Head Rad.Elev.Loss Loss Elev.HW/D Elev.Elev.Head Loss Loss Total Check CFS CFS FT IN FT FT FT FT % FPS FT FT FT FT FT FT FT FT FT FT FT FT FT FT FT CFS CFS FPS FT FT FT FT CB 2.8 CB 17.1 0.66 0.66 77.0 8 0.012 456.23 458.50 457.00 459.00 1.00% 1.88 0.05 0.33 459.21 459.21 0.17 0.19 459.40 0.50 0.03 0.05 459.48 0.50 457.33 459.48 1.32 0.07 1.88 0.07 459.56 0.56 Overtopping!! S 308th Street ROW EX CB #1 CB 14.1 0.05 7.59 26.0 30 0.012 429.00 433.42 429.65 433.35 2.50% 1.55 0.04 0.94 429.65 430.72 0.63 0.01 432.15 0.50 0.02 0.04 432.21 0.50 430.90 432.21 0.09 0.00 7.53 6.60 1.55 0.02 0.02 432.14 -1.21 Okay CB 14.1 CB 14.2 0.38 7.53 91.0 24 0.012 429.65 433.35 430.14 432.68 0.54% 2.40 0.09 0.94 432.14 432.14 0.50 0.09 432.22 0.50 0.04 0.09 432.35 0.50 431.14 432.35 0.13 0.00 5.07 2.08 2.40 0.03 0.03 432.25 -0.43 Caution CB 14.2 CB 14.3 1.63 5.07 52.0 18 0.012 430.14 432.68 430.43 432.47 0.56% 2.87 0.13 0.86 432.25 432.25 0.38 0.10 432.36 0.50 0.06 0.13 432.55 0.50 431.18 432.55 0.06 0.00 3.43 2.87 432.49 0.02 Overtopping!! CB 14.3 CB 14.4 0.23 3.43 8.0 18 0.012 430.43 432.47 430.50 432.41 0.87% 1.94 0.06 0.75 432.49 432.49 0.38 0.01 432.50 0.50 0.03 0.06 432.58 0.50 431.25 432.58 0.26 0.00 3.21 1.94 432.32 -0.09 Caution CB 14.4 CB 14.5 0.32 3.21 109.0 12 0.012 430.50 432.41 432.00 434.72 1.38% 4.08 0.26 0.82 432.32 432.32 0.25 0.75 433.07 0.50 0.13 0.26 433.46 0.50 432.50 433.46 0.21 0.00 2.88 4.08 433.25 -1.47 Okay CB 14.5 CB 14.6 0.19 2.88 174.0 12 0.012 432.00 434.72 441.00 444.72 5.17% 3.67 0.21 0.79 433.25 433.25 0.25 0.97 442.00 0.50 0.10 0.21 442.31 0.50 441.50 442.31 0.04 0.00 1.21 1.48 3.67 0.13 0.13 442.41 -2.31 Okay CB 14.6 CB 14.7 1.21 1.21 100.0 12 0.012 441.00 444.72 447.00 450.85 6.00% 1.55 0.04 0.41 442.41 442.41 0.25 0.10 448.00 0.50 0.02 0.04 448.06 0.50 447.50 448.06 0.00 1.21 1.55 448.06 -2.79 Okay CB 14.1 CB 15.1 2.08 2.08 58.0 8 0.012 430.14 432.68 434.50 437.50 7.52% 5.97 0.55 0.62 432.25 432.25 0.17 1.46 435.17 0.50 0.28 0.55 436.00 0.50 434.83 436.00 1.32 0.73 0.00 5.97 0.73 436.73 -0.77 Okay CB 14.5 CB 16.1 1.36 1.36 50.0 8 0.012 441.00 444.72 442.50 445.50 3.00% 3.91 0.24 0.49 442.41 442.41 0.17 0.54 443.17 0.50 0.12 0.24 443.52 0.50 442.83 443.52 0.00 1.32 0.31 0.00 3.91 0.31 443.83 -1.67 Okay CB 14.6 CB 16.2 0.04 0.12 33.0 8 0.012 447.33 450.85 450.00 454.00 8.09% 0.33 0.00 0.52 442.41 447.92 0.17 0.00 450.67 0.50 0.00 0.00 450.67 0.50 450.33 450.67 1.32 0.00 0.00 0.33 0.00 450.67 -3.33 Okay S 304th Street ROW CB 18.2 CB 18.3 0.58 1.67 102.0 12 0.012 444.00 447.39 451.43 456.43 7.28% 2.13 0.07 0.33 445.20 445.20 0.25 0.19 452.43 0.50 0.04 0.07 452.54 0.50 451.93 452.54 0.01 0.00 1.09 2.13 452.52 -3.91 Okay CB 18.3 CB 18.4 0.37 1.09 297.0 12 0.012 451.43 456.43 467.68 472.68 5.47% 1.39 0.03 0.33 452.52 452.52 0.25 0.24 468.68 0.50 0.02 0.03 468.73 0.50 468.18 468.73 0.00 0.00 0.72 1.39 468.72 -3.96 Okay CB 18.4 CB 18.5 0.36 0.72 197.0 12 0.012 467.68 472.68 473.53 478.53 2.97% 0.92 0.01 0.33 468.72 468.72 0.25 0.07 474.53 0.50 0.01 0.01 474.55 0.50 474.03 474.55 0.00 0.00 0.36 0.92 474.55 -3.98 Okay CB 18.5 CB 18.6 0.36 0.36 197.0 12 0.012 473.53 478.53 478.25 483.26 2.40% 0.45 0.00 0.33 474.55 474.55 0.25 0.02 479.25 0.50 0.00 0.00 479.25 0.50 478.75 479.25 0.00 0.10 0.45 479.25 -4.01 Okay CB 18.6 CB 18.7 0.10 0.10 196.0 12 0.012 478.25 483.26 480.25 488.25 1.02% 0.13 0.00 0.33 479.25 479.25 0.25 0.00 481.25 0.50 0.00 0.00 481.25 0.50 480.75 481.25 0.00 0.00 0.13 481.25 -7.00 Okay CB 18.1 CB 19.1 0.04 1.72 42.0 8 0.012 439.30 443.94 441.50 444.50 5.24% 4.92 0.38 0.33 443.30 443.30 0.17 0.72 444.02 0.50 0.19 0.38 444.58 0.50 441.83 444.58 0.00 0.00 4.92 444.58 0.08 Overtopping!! PIPE OUTLET #10 CB 18.2 0.00 1.67 27.0 8 0.012 443.50 444.50 444.00 447.39 1.85% 4.79 0.36 0.33 444.00 444.00 0.17 0.44 444.67 0.50 0.18 0.36 445.20 0.50 444.33 445.20 0.00 0.00 4.79 445.20 -2.19 Okay FWHS - Backwater Conveyance Calculation-Ph2 Permit.xls 7/30/2014 APPENDIX D – SEDIMENT POND SIZING Developed (15-min time series) 2 Year Flow for Sediment Pond Sizing Kirkland | Tacoma | Mount Vernon 425-827-7701 | www.aesgeo.com February 8, 2021 Project No. 20200453E001 Federal Way Public Schools 33330 8th Avenue South Federal Way, Washington 98003 Attention: Mr. Delin Huang Subject: Preliminary Geotechnical Engineering Recommendations Federal Way High School Memorial Field Improvements 1344 South 308th Street Federal Way, Washington Dear Mr. Huang: This letter-report summarizes Associated Earth Sciences, Inc.’s (AESI’s) preliminary geotechnical engineering recommendations for the proposed improvements to the Federal Way High School Memorial Field located at 1344 South 308th Street in Federal Way, Washington. Our recommendations are based on review of our previous work completed on the Federal Way High School site, which has included subsurface explorations, geotechnical engineering studies, and construction monitoring. Our work was completed in accordance with our proposal, dated December 21, 2020. SITE AND PROJECT DESCRIPTION The project site is the Memorial Field athletics field and parking lot at the southwest corner of the existing Federal Way High School property, located at 1344 South 308th Street in Federal Way, Washington (King County Parcel No. 0821049001). The site is shown on the “Vicinity Map,” Figure 1. The parking lot and stadium are roughly rectangular-shaped portions of the high school parcel and are bound to the north by the high school baseball field, to the east by a parking lot and the school building, to the south by South 308th Street, and to the west by existing stormwater ponds and residential development. The football field is surrounded by an athletic track and oriented with its long axis north-south. Grandstands overlook the field from the east and west sides. The existing parking lot is gravel-surfaced, with ingress and egress at the east and west ends of the parking lot. The ground surface is basically flat over most of the parking lot and Federal Way High School Memorial Field Improvements Preliminary Federal Way, Washington Geotechnical Engineering Recommendations February 8, 2021 ASSOCIATED EARTH SCIENCES, INC. NS/ld - 20200453E001-3 Page 2 field and then slopes upward to the east at an inclination of about 2 Horizontal:1 Vertical (2H:1V) on the east side of the field. Overall vertical relief across the site is on the order of 25 feet. Details of the proposed improvements are limited at this time, but the improvements are planned to occur in two phases. The first phase would consist of improvements to the parking area and the second phase would consist of improvements to the stadium and field. Specifically, the proposed improvements include the following: • replacement of several stadium structures, including grandstands, bathrooms, and other accessory structures; • new asphalt pavement in the stadium parking lot; • new pavement of pathways throughout the site; • replacement of track surfaces and artificial turfs; • improvements to infrastructure for site lighting, security, and other systems; and • possibly frontage improvements. The purpose of our work was to use existing subsurface information to develop preliminary geotechnical engineering design recommendations for pavement, foundations, structural fills, and seismic site class per current code requirements. The recommendations contained in the letter-report are considered preliminary. The subsurface conditions that are the basis for the recommendations in the letter-report were extrapolated from site explorations advanced for the neighboring high school project. The assumed subsurface conditions should be verified by site-specific explorations or by observation of exposed subgrades at the time of construction. If differing subsurface conditions are encountered, the conclusions and recommendations contained in this letter-report should be confirmed or changed to reflect the actual conditions encountered. PREVIOUS SUBSURFACE EXPLORATION In order to collect subsurface information at the areas of the proposed improvements, we reviewed our previous study at the site, which included drilling 10 exploration borings on January 2 and 3, 2014 using a hollow-stem auger drilling rig. Our findings and analyses were reported in our geotechnical engineering report titled, “Subsurface Exploration, Geologic Hazards, and Geotechnical Engineering Report, Federal Way High School Replacement,” dated as revised October 31, 2014. Eight of the 2014 exploration borings were drilled at the southeast corner of the parcel near the high school building and two were drilled west of the Memorial Field and parking lot area. The locations of the four nearest exploration borings, EB-4, EB-5, EB-9, and EB-10, are shown on the “Existing Site and Exploration Plan,” Figure 2, and logs of these Federal Way High School Memorial Field Improvements Preliminary Federal Way, Washington Geotechnical Engineering Recommendations February 8, 2021 ASSOCIATED EARTH SCIENCES, INC. NS/ld - 20200453E001-3 Page 3 explorations are included in the Appendix. Additional subsurface explorations were not included in this scope of work. The conclusions and recommendations presented in this letter-report are based on review of our previous exploration borings at the site. The number, locations, and depths of the explorations were completed within site and budgetary constraints. Because of the nature of exploratory work below ground, interpolation of subsurface conditions between field explorations is necessary. It should be noted that differing subsurface conditions may sometimes be present due to the random nature of deposition and the alteration of topography by past grading and/or filling. The nature and extent of any variations between the field explorations may not become fully evident until construction. If variations are observed at that time, it may be necessary to re-evaluate specific recommendations in this letter-report and make appropriate changes. Ground surface elevations and subsurface conditions observed at the exploration boring locations may have been altered by the construction and grading activities that occurred after the exploration during construction of the existing school, and the conditions observed at the time of drilling may no longer be representative of existing conditions. The various types of soil and groundwater elevations, as well as the depths where soil and groundwater characteristics changed, are indicated on the exploration boring logs presented in the Appendix. The depths indicated on the logs where conditions changed may represent gradational variations between sediment types in the field. If changes occurred between sample intervals in our borings, they were interpreted. SUBSURFACE CONDITIONS Subsurface conditions at the project site were inferred from the field explorations accomplished for our 2014 study and review of selected applicable geologic literature. The general distribution of geologic units is shown on the exploration logs. The explorations generally encountered native pre-Fraser sediments overlain in some areas by existing fill. Stratigraphy The following sections present more detailed subsurface information organized from the youngest (shallowest) to the oldest (deepest) sediment types. Federal Way High School Memorial Field Improvements Preliminary Federal Way, Washington Geotechnical Engineering Recommendations February 8, 2021 ASSOCIATED EARTH SCIENCES, INC. NS/ld - 20200453E001-3 Page 4 Existing Fill Fill soils (soils not naturally placed) were encountered at the locations of exploration borings EB-9 and EB-10 to depths of 11 and 7 feet below the ground surface, respectively. The fill generally consisted of loose, silty sand with gravel. Portions of the fill contained organic material. We interpret the encountered fill as likely resulting from past grading activities, including the filling of low areas west of the stadium and field. Fill thickness can vary over short distances and may be deeper than observed in our explorations. Due to the variable density and content, the existing fill soils are not suitable for foundation support. Pre-Fraser Deposits In exploration borings EB-4 and EB-5 and underlying the fill in exploration borings EB-9 and EB-10, sediments consisted of medium dense to very dense, silty, fine to medium sand with gravel, siltier areas, silt beds, and trace organics, interpreted as pre-Fraser deposits. The pre-Fraser deposits were placed prior to the Fraser Glaciation and subsequently compacted by the weight of the overlying glacial ice. The upper 3 to 5 feet of the pre-Fraser deposits were of lower density, interpreted as being due to weathering. The pre-Fraser deposits extended to the full depths explored of approximately 15.9 to 21.5 feet, as shown on the exploration logs in the Appendix. The medium dense to very dense material is generally considered suitable for support of light- to heavily-loaded foundations when in an intact, undisturbed condition. This material is moisture- sensitive and susceptible to disturbance when wet. Groundwater We encountered groundwater seepage in exploration borings EB-9 and EB-10 at depths of 10 and 14 feet, respectively. We anticipate that the encountered groundwater likely represents a local groundwater table within the underlying pre-Fraser deposits. We expect that shallow groundwater seepage would likely represent interflow within the existing fill. Interflow occurs when surface water percolates down through the surficial weathered or higher-permeability sediments and becomes perched atop underlying, lower-permeability sediments. It should be noted that the occurrence and level of groundwater seepage at the site may vary in response to such factors as changes in season, precipitation, and site use. The explorations reviewed for this study were completed on January 2 and 3, 2014. PRELIMINARY GEOTECHNICAL DESIGN RECOMMENDATIONS From a geotechnical engineering standpoint, it is our opinion that the site is suitable for the proposed improvements provided the recommendations contained in this letter-report are Federal Way High School Memorial Field Improvements Preliminary Federal Way, Washington Geotechnical Engineering Recommendations February 8, 2021 ASSOCIATED EARTH SCIENCES, INC. NS/ld - 20200453E001-3 Page 5 incorporated into the design and construction of the project. In general, foundations can be supported by medium dense or denser native soils or structural fill, where dense, non-organic existing fill is present under proposed lightly-loaded structures, such as pavement; it may be suitable for structural support provided the subgrade can be compacted to a firm and unyielding condition and with the approval of the geotechnical engineer. The following sections provide preliminary recommendations for seismic site class, site preparation, structural fill, foundations, pavement, and drainage. Seismic Site Class Seismic design shall be in accordance with the 2015 International Building Code (IBC). The native soils at the site are consistent with seismic Site Class “D” as defined in ASCE 7 - Minimum Design Loads for Buildings and Other Structures (2010) as referenced by the 2015 IBC and Site Class “D” seismic design parameters should be used for design. Site Preparation Existing buried utilities, vegetation, topsoil, demolition debris, and any other deleterious materials should be removed where they are located below planned construction areas. All disturbed soils should be removed to expose underlying, undisturbed, native sediments and replaced with structural fill, as needed. All excavations below final grade made for demolition or clearing and grubbing activities should be backfilled, as needed, with structural fill. Erosion and surface water control should be established around the clearing limits to satisfy local requirements. Once clearing and grubbing activities have been completed, existing fill, where encountered, should be addressed. We recommend that existing fill be removed from below areas of planned foundations to expose underlying, undisturbed native sediments, followed by restoration of the planned foundation grade with compacted structural fill. Removal of existing fill should extend laterally beyond the new foundation footprint a minimum of 2 feet. Care should be taken not to disturb support soils of existing foundations, if any will remain. Support soils should be considered those soils within a prism projected downward and outward from existing footings at inclinations of 1H:1V. Where existing fill is removed and replaced with structural fill, conventional shallow foundations may be used for building support. The required depth of removal should be determined in the field based on actual conditions encountered during excavation. Site Disturbance The site soils contained a high percentage of fine-grained material, which makes them moisture- sensitive and subject to disturbance when wet. The contractor must use care during site Federal Way High School Memorial Field Improvements Preliminary Federal Way, Washington Geotechnical Engineering Recommendations February 8, 2021 ASSOCIATED EARTH SCIENCES, INC. NS/ld - 20200453E001-3 Page 6 preparation and excavation operations so that the underlying soils are not softened. If disturbance occurs to soils in structural areas, the softened soils should be removed and the area brought to grade with structural fill. Proof-Rolling Following the recommended clearing, stripping, and any planned excavation, the stripped subgrade within large paving areas should be proof-rolled with heavy, rubber-tired construction equipment, such as a fully-loaded, tandem-axle dump truck. Proof-rolling should be performed prior to structural fill placement or foundation excavation. The proof-roll should be monitored by the geotechnical engineer so that any soft or yielding subgrade soils can be identified. Any soft/loose, yielding soils should be removed to expose firm and unyielding subgrade. The subgrade should then be scarified, adjusted in moisture content, and recompacted to the required density. Proof-rolling should only be attempted if soil moisture contents are at or near optimum moisture content. Proof-rolling of wet subgrades could result in further degradation. Low areas and excavations may then be raised to the planned finished grade with compacted structural fill. Subgrade preparation and selection, placement, and compaction of structural fill should be performed under engineering-controlled conditions in accordance with the project specifications. Structural Fill Placement of structural fill may be necessary to establish desired grades at the site or to backfill utility trenches or around foundations. All references to structural fill in this letter-report refer to subgrade preparation, fill type, and placement and compaction of materials as discussed in this section. If a percentage of compaction is specified under another section of this letter-report the value given in that section should be used. After overexcavation/stripping has been performed to the satisfaction of the geotechnical engineer/engineering geologist, the exposed ground surface should be recompacted to a firm and unyielding condition. If the subgrade contains too much moisture, suitable recompaction may be difficult or impossible to attain and should probably not be attempted. In lieu of recompaction, the area to receive fill should be blanketed with washed rock or quarry spalls to act as a capillary break between the new fill and the wet subgrade. Where the exposed ground remains soft and further overexcavation is impractical, placement of an engineered stabilization fabric may be necessary to prevent contamination of the free-draining layer by silt migration from below. After recompaction of the exposed ground is approved by the geotechnical engineer, or a free-draining rock course is laid, structural fill may be placed to attain desired grades. Federal Way High School Memorial Field Improvements Preliminary Federal Way, Washington Geotechnical Engineering Recommendations February 8, 2021 ASSOCIATED EARTH SCIENCES, INC. NS/ld - 20200453E001-3 Page 7 Structural fill is defined as non-organic soil, acceptable to the geotechnical engineer, placed in maximum 8-inch loose lifts, with each lift being compacted to at least 95 percent of the modified Proctor maximum dry density using ASTM International (ASTM) D-1557 as the standard. Utility trench backfill should be placed and compacted in accordance with applicable municipal codes and standards. The top of the compacted fill should extend horizontally a minimum distance of 3 feet beyond footings or pavement edges before sloping down at an angle no steeper than 2H:1V. Fill slopes should either be overbuilt and trimmed back to final grade or surface-compacted to the specified density. We recommend that a clean, free-draining gravel and/or sand be used in structural areas. Free-draining fill consists of non-organic soil with the amount of fine-grained material limited to 5 percent by weight when measured on the minus No. 4 sieve fraction. Soils in which the amount of fine-grained material (smaller than No. 200 sieve) is greater than approximately 5 percent (measured on the minus No. 4 sieve size) should be considered moisture-sensitive. Portions of the site soils contained significant fine-grained fractions and are considered moisture-sensitive. The use of moisture-sensitive soil in structural fills should be limited to favorable dry weather conditions and non-structural areas such as under landscaping. The contractor should note that any proposed fill soils must be evaluated by AESI prior to their use in fills. This would require that we have a sample of the material at least 3 business days in advance to perform a Proctor test and determine its field compaction standard. A representative from our firm should observe the stripped subgrade and be present during placement of structural fill to monitor the work and perform a representative number of in-place density tests. In this way, the adequacy of the earthwork may be evaluated as filling progresses and any problem areas may be corrected at that time. It is important to understand that taking random compaction tests on a part-time basis will not assure uniformity or acceptable performance of a fill. As such, we are available to aid the owner in developing a suitable monitoring and testing frequency. Foundations In the exploration borings located near the site, suitable bearing soils were observed at depths of about 5 feet in EB-4 and EB-5 east of the site and 8 to 12 feet in EB-9 and EB-10 west of the site. Based on our current understanding of the project, significant foundations are not planned near the western part of the site, where the bearing stratum was encountered relatively deep within the existing detention pond areas. Therefore, we anticipate that any proposed structures can be supported on conventional shallow spread footings. If changes to the proposed improvements include new foundations near the west end of the site, additional field studies Federal Way High School Memorial Field Improvements Preliminary Federal Way, Washington Geotechnical Engineering Recommendations February 8, 2021 ASSOCIATED EARTH SCIENCES, INC. NS/ld - 20200453E001-3 Page 8 may be needed to verify subsurface conditions and depth to bearing soils in the proposed foundation areas. For footings bearing directly on medium dense to dense natural sediments, or on structural fill placed over these materials as described above, we recommend that an allowable foundation soil bearing pressure of 2,500 pounds per square foot (psf) be used for design purposes, including both dead and live loads. An increase of one-third may be used for short-term wind or seismic loading. Perimeter footings should be buried at least 18 inches into the surrounding soil for frost protection. However, all footings must penetrate to the prescribed bearing stratum, and no footing should be founded in or above organic or loose soils. All footings should have a minimum width of 18 inches. It should be noted that the area bound by lines extending downward at 1H:1V from any footing must not intersect another footing or intersect a filled area that has not been compacted to at least 95 percent of ASTM D-1557. In addition, a 1.5H:1V line extending down from any footing must not daylight because sloughing or raveling may eventually undermine the footing. Thus, footings should not be placed near the edge of steps or cuts in the bearing soils. Anticipated settlement of footings founded as described above should be on the order of 1 inch or less. However, disturbed soil not removed from footing excavations prior to footing placement could result in increased settlements. All footing areas should be inspected by AESI prior to placing concrete to verify that the design bearing capacity of the soils has been attained and that construction conforms to the recommendations contained in this letter-report. Such inspections may be required by the City of Federal Way. Perimeter footing drains should be provided, as discussed under the “Drainage Considerations” section of this letter-report. Floor Support Slab-on-grade floors may be used over medium dense or denser native soils, inorganic existing fills soils re-compacted to 95 percent relative compaction, or over structural fill placed as recommended in the “Site Preparation” and “Structural Fill” sections of this letter-report. Slab design can assume a soil subgrade modulus of 200 pounds per cubic inch (pci) for slabs cast over the medium dense, natural sediments, re-compacted existing fill or properly compacted structural fill placed over these materials. Slab-on-grade floors should be cast atop a minimum of 4 inches of washed pea gravel or washed crushed “chip” rock with less than 3 percent passing the U.S. No. 200 sieve to act as a capillary break. The floors should also be protected from dampness by covering the capillary break layer with an impervious moisture barrier at least 10 mils in thickness. Federal Way High School Memorial Field Improvements Preliminary Federal Way, Washington Geotechnical Engineering Recommendations February 8, 2021 ASSOCIATED EARTH SCIENCES, INC. NS/ld - 20200453E001-3 Page 9 Passive Resistance and Friction Factors All backfill around foundation units should be placed per our recommendations for structural fill and as described in the “Structural Fill” section of this letter-report. Lateral loads can be resisted by friction between the foundation and the natural glacial soils or supporting structural fill soils, and by passive earth pressure acting on the buried portions of the foundations. The foundations must be backfilled with structural fill and compacted to at least 95 percent of the maximum dry density to achieve the passive resistance provided below. We recommend the following allowable design parameters: Passive equivalent fluid = 350 pounds per cubic foot Coefficient of friction = 0.35 Drainage Considerations Foundations should be provided with foundation drains placed at the bottom of footing or slab elevation. Drains should consist of rigid, perforated, polyvinyl chloride (PVC) pipe surrounded by washed pea gravel. The drains should be constructed with sufficient gradient to allow gravity discharge away from any proposed buildings. Roof and surface runoff should not discharge into the footing drain system, but should be handled by a separate, rigid, tightline drain. In planning, exterior grades adjacent to walls should be sloped downward away from the proposed structures to achieve surface drainage. Pavement Pavement areas should be prepared in accordance with the “Site Preparation” section of this letter-report. If the stripped native soil or existing fill pavement subgrade can be compacted to 95 percent of ASTM D-1557 and is firm and unyielding, no additional overexcavation is required. Soft or yielding areas should be overexcavated to provide a suitable subgrade and backfilled with structural fill. The pavement sections included in this letter-report section are for driveway and parking areas onsite, and are not applicable to right-of-way improvements. At this time we are not aware of any planned right-of-way improvements; however, if any new paving of public streets is required, we should be allowed to offer situation-specific recommendations. The exposed ground should be recompacted to 95 percent of ASTM D-1557 and proof-rolled in accordance with the “Proof-Rolling” section of this letter-report. If required, structural fill may then be placed to achieve desired subbase grades. After the prepared subgrade is approved by the geotechnical engineer, the overlying pavement in areas of planned passenger car driving and parking can consist of a minimum of 2 inches of asphaltic concrete pavement (ACP) underlain by 4 inches of 1¼-inch crushed surfacing base course. In driveway areas subjected to heavier loads, Federal Way High School Memorial Field Improvements Preliminary Federal Way, Washington Geotechnical Engineering Recommendations February 8, 2021 ASSOCIATED EARTH SCIENCES, INC. NS/ld - 20200453E001-3 Page 10 such as that from delivery trucks or school buses, a minimum pavement section consisting of 3 inches of ACP underlain by 2 inches of 5/8-inch crushed surfacing top course and 4 inches of 1¼-inch crushed surfacing base course is recommended. The crushed rock courses must be compacted to 95 percent of the maximum density, as determined by ASTM D-1557. All paving materials should meet gradation criteria contained in the current Washington State Department of Transportation (WSDOT) Standard Specifications. Depending on construction staging and desired performance, the crushed base course material may be substituted with asphalt treated base (ATB) beneath the final asphalt surfacing. The substitution of ATB should be as follows: 4 inches of crushed rock can be substituted with 3 inches of ATB, and 6 inches of crushed rock may be substituted with 4 inches of ATB. ATB should be placed over a native or structural fill subgrade compacted to a minimum of 95 percent relative density, and a 1½- to 2-inch thickness of crushed rock to act as a working surface. If ATB is used for construction access and staging areas, some rutting and disturbance of the ATB surface should be expected. The general contractor should remove affected areas and replace them with properly compacted ATB prior to final surfacing. LIMITATIONS This letter-report has been prepared for the exclusive use of Federal Way Public Schools and their agents for specific application to this project. Within the limitations of scope, schedule, and budget, our services have been performed in accordance with generally accepted geotechnical engineering practices in effect in this area at the time our letter-report was prepared. No other warranty, express or implied, is made. CLOSURE Our recommendations should be considered preliminary in that project plans and construction details have not been finalized at the time of this letter-report. We are available to provide additional geotechnical consultation as the project design develops and possibly changes from that upon which this letter-report is based. We recommend that AESI perform a final geotechnical review of the plans prior to final design completion. In this way, our earthwork and foundation recommendations may be properly interpreted and implemented in the design. We are also available to provide geotechnical engineering and monitoring services during construction. The integrity of the foundations and pavement depends on proper site preparation and construction procedures. In addition, engineering decisions may have to be made in the field in the event that variations in subsurface conditions become apparent. Construction monitoring Federal Way High School Memorial Field Improvements Preliminary Federal Way, Washington Geotechnical Engineering Recommendations February 8, 2021 ASSOCIATED EARTH SCIENCES, INC. NS/ld - 20200453E001-3 Page 11 services are not part of this current scope of work. If these services are desired, please let us know, and we will prepare a proposal. We have enjoyed working with you on this study and are confident these recommendations will aid in the successful completion of your project. If you should have any questions or require further assistance, please do not hesitate to call. Sincerely, ASSOCIATED EARTH SCIENCES, INC. Kirkland, Washington ______________________________ Nicki Shobert, E.I.T. Kurt D. Merriman, P.E. Project Engineer Senior Principal Engineer Attachments: Figure 1. Vicinity Map Figure 2. Existing Site and Exploration Plan Appendix. Exploration Logs APPENDIX Exploration Logs Technical Information Report Federal Way High School Pre-Apprenticeship Space 2210134.10 Section 7 Other Permits Technical Information Report Federal Way High School Pre-Apprenticeship Space 7-1 2210134.10 7.0 Other Permits Required permits for this project include City of Federal Way Use Process I approval, a City of Federal Way Engineering Permit, and a City of Federal Way Building Permit. No other permits are anticipated requirements. Technical Information Report Federal Way High School Pre-Apprenticeship Space 2210134.10 Section 8 CSWPPP Analysis and Design Technical Information Report Federal Way High School Pre-Apprenticeship Space 8-1 2210134.10 8.0 CSWPPP Analysis and Design The proposed development will comply with guidelines set forth in the KCSWDM. The plan includes erosion/sedimentation control measures designed to prevent sediment -laden runoff from leaving the site or from adversely affecting critical water resources during construction. ESC Plan Analysis and Design (Part A) The erosion potential of the site is influenced by four major factors: soil characteristics, vegetative cover, topography, and climate. Erosion/sedimentation control is achieved by a combination of structural measures, cover measures, and construction practices that are tailored to fit the specific site. The following measures will be used to control erosion/sedimentation processes. These measures comply with the Erosion and Sediment Control Standards in the KCSWDM. • Clearing Limits: Prior to beginning land-disturbing activities, clearing limits will be marked with high-visibility plastic fence or temporary construction fencing. Significant vegetation to remain will be marked and protected by fencing. • Cover Measures: Disturbed areas shall be permanently or temporarily covered, as required in Section D.4.2 of the KCSWDM. Temporary measures include plastic sheeting and mulch. Permanent measures include gravel surfacing and vegetation. • Perimeter Protection: Silt fence will be installed at the perimeter of the disturbed areas to protect them. The silt fence will help to remove sediment from surface water and will provide some flow control. • Traffic Area Stabilization: Existing paved surfaces will be used for a construction entrance; a stabilized construction entrance may be used, if found necessary. Wheel washing and/or street sweeping will be provided, as necessary, to prevent tracking of sediment onto adjacent surfaces. • Sediment Retention: Inlet protection devices will be installed in all existing and new catch basins. Additionally, silt fence will be installed at the perimeter of the disturb ed areas. These measures will assist with sediment retention during construction. • Surface Water Collection: Surface water from the threshold discharge area will sheet flow toward the project boundary or to a catch basin. Inlet protection devices will be installed in all new and existing catch basins and silt fence will be installed at the project boundary. These measures will assist with removing sediment from surface water. The disturbed area within the threshold discharge area is small and does not require large collection devices, such as sediment traps or ponds. • Dewatering Control: Water may be encountered during ground disturbing activities. If water is encountered, the contractor shall remove it and dispose of it in a manner that does not pollute surface water or cause downstream erosion or flooding. Examples of disposal options include use of a sedimentation bag with outfall to a swale for small volumes of localized dewatering or transporting it in a vehicle for legal offsite disposal. • Dust Control: If necessary, the contractor shall spray exposed soils with water to prevent wind transport of soil. Technical Information Report Federal Way High School Pre-Apprenticeship Space 8-2 2210134.10 • Flow Control: The disturbed area within the threshold discharge area is very small , approximately 0.2 acre in size or less. Because of the small nature of the site, the need for formal flow control facilities is not anticipated during construction. The silt fence installed at the perimeter of the site will provide some level of flow control for surface water. No known hazard areas are located on or near the project site. 8.1.1 ESC Maintenance All ESC measures shall be maintained and reviewed on a regular basis, as prescribed in the maintenance requirements of each BMP (see Figure 8-3). 8.1.2 ESC Supervisor The contractor shall designate an Erosion and Sedimentation Control (ESC) supervisor who shall be responsible for maintenance and review of ESC and for compliance w ith all permit conditions relating to ESC. The ESC supervisor must be available for rapid response to ESC problems. The ESC supervisor is required to be a Certified Erosion and Sedimentation Control Lead (CESCL), with demonstrated expertise in ESC to perform these reviews and to be responsible for ESC implementation. 8.1.3 Documentation The ESC supervisor shall review the site at least once a month during the dry season, weekly during the wet season, and within 24 hours of significant storms. Written records o f these reviews shall be kept onsite, with copies submitted to City of Federal Way within 48 hours. If the Department of Development and Environmental Services (DDES) requires that a written record be maintained, a standard ESC Maintenance Report, included here as Figure 8-1, may be used. A copy of all required maintenance reports shall be kept onsite throughout the duration of construction. 8.1.4 Review Timing During the wet season, weekly reviews shall be carried out every six to eight calendar days. During the dry season, monthly reviews shall be carried out within three days of the calendar day for the last inspection (e.g., if an inspection occurred on June 6, then the next inspection must occur between July 3 and July 9). Reviews shall also take place within 24 hours of significant storms. In general, a significant storm is one with more than 0.5 inch of rain in 24 hours or less. Another indication that a storm is "significant" is if gullies form as a result of the runoff. Stormwater Pollution Prevention and Spill (SWPPS) Plan Design (Part B) The below SWPPS Plan shall be completed by the contractor for use during construction of the project. Blanks are intentional as they are part of the contractor’s means and methods. The Stormwater Pollution Prevention and Spill (SWPPS) Plan includes three elements: a site plan, a pollution prevention report, and a spill prevention and cleanup report. This report includes identifying the expected sources of potential pollution and spills that may occur during construction, and works to develop a plan to prevent pollution and spills. It also develops a plan to mitigate spills that may occur. The SWPPS Plan will be kept on-site at all times during construction. The general contractor will be responsible to ensure that subcontractors are aware of the SWPPS Plan and a form or record will be provided stating that all subcontractors have read and agree to the SWPPS Plan. An employee training worksheet is provided for the contractor’s use (see Figure 8-2). Technical Information Report Federal Way High School Pre-Apprenticeship Space 8-3 2210134.10 A SWPPS Site Plan will be developed by the contractor. The SWPPS Site Plan, Pollution Prevention Report, and Spill Prevention and Cleanup Report were preliminarily developed and BMPs were selected based on Section 2.3.1.4 of the KCSWDM and the KCSPPM. 8.2.1 Pollution and Spill Prevention Source Controls and BMPs The sources of pollution and spills are identified below, and the BMPs to be used for each source for prevention of both pollution and spills are listed below: Liquids that will be handled or stored on-site are the following: _________. Containers will be stored as shown on the SWPPS Site Plan and include the following types and sizes: ___________. Tight-fitting lids shall be placed on all containers containing liquids. Containers shall be covered with plastic sheeting during rain events. Drip pans or absorbent materials shall be placed beneath all mounted container taps and at all potential drip and spill locations during filling and unloading of containers. Containers shall be stored such that if a container leaks or spills, the contents will not be discharged, flow, or be washed into the storm drainage system, surface water, or groundwater. Appropriate spill cleanup materials shall be stored and maintained near the container storage area. Storage area shall be swept and cleaned as needed. Area shall not be hosed down such that water drains to the storm drainage system or neighboring areas. Containers shall be checked daily for leaks and spills and replaced, as necessary. All spilled liquids will be collected and disposed of properly. Spill control devices shall be routinely inspected on a weekly basis. Dry pesticides and fertilizers shall be covered with plastic sheeting or stored in a sealed container. Materials shall be stored on pallets or another raised method to prevent contact with stormwater runoff. Alternatively, the materials shall be contained in a manner such that if the container leaks or spills, the contents will not discharge, flow, or be washed into the storm drainage system, surface waters, or groundwater. Maintenance requirements are the same as liquid materials described above. Chemicals that will be handled or stored on-site are the following: _________. Containers will be stored as shown on the SWPPS Site Plan and include the following types and sizes: ___________. BMPs and maintenance requirements are the same as liquids with the addition of the following ______. Soil, sand, and other erodible materials shall be stored on-site in a contractor-designated location. Materials shall be covered with plastic sheeting per standard detail. Perimeter controls shall be constructed as shown on the TESC plan to prevent eroded materials from leaving the project site. Fueling shall not occur on-site. If fueling does occur on-site, the contractor shall develop a containment plan for spills and provide lighting and signage if fueling occurs at night in conformance with the KCSPPM. Maintenance and repair of vehicles shall not occur on-site. If maintenance or repair of vehicles does occur on-site, the contractor shall develop a spill prevention plan in conformance with the KCSPPM. Truck wheel washing shall occur in a controlled manner, such that runoff is collected and disposed of in a legal manner. Rinsing of hand tools shall occur in a designated location, and water for washing shall be collected and disposed of in a legal manner. Technical Information Report Federal Way High School Pre-Apprenticeship Space 8-4 2210134.10 Contaminated soils shall be covered with plastic sheeting or contained to prevent stormwater from carrying pollutants away to surface or ground waters. Appropriate spill cleanup materials, such as brooms, dustpans, vacuum sweepers, etc., shall be stored and maintained near the storage area. Storage area shall be swept and cleaned as needed. Area shall not be hose d down such that water drains to the storm drainage system, groundwater, surface water, or neighboring areas. During concrete and asphalt construction, the contractor shall provide the following BMPs or equivalent measures, methods or practices as requir ed: 1. Drip pans, ground cloths, heavy cardboard, or plywood wherever concrete, asphalt, and asphalt emulsion chunks and drips are likely to fall unintentionally, such as beneath extraction points from mixing equipment. 2. Storm drains shall be covered to prevent concrete and asphalt from entering the storm system. 3. Concrete, concrete slurry, and rinse water shall be contained and collected, and shall not be washed or allowed to discharge into storm drain, ditch, or neighboring parcels. All collected runoff shall be properly disposed of. 4. Contractor shall designate an area where application and mixing equipment cleaning will be conducted. Rinse water and slurry shall be collected, contained, and disposed of in a legal manner. 5. Routine maintenance: the pouring area shall be swept at the end of each day or more frequently if needed. Loose aggregate chunks and dust shall be collected. Areas shall not be hosed down. The contractor may provide the following optional BMPs if the above do not provide adequate source controls: 6. Cover portable mixing equipment with an awning or plastic sheeting to prevent contact with rainfall. 7. Provide catch basin inserts configured for pollutant removal. pH elevated water shall not be discharged from the site. Contractor shall monitor stormwater for pH prior to discharging from the site. Contractor shall implement a pH treatment plan if pH is not within the natural range. 8.2.2 Responsible Personnel and Contact Information The contractor shall designate an ESC Supervisor and post their contact name, company, and phone number and/or email in a readily visible location onsite. [name] with [company] shall be responsible for pollution and spill prevention and cleanup and can be contacted at [phone] or [email] . Contractor shall fill out the attached Pollution Prevention Team Worksheet (see Figure 8-2). Technical Information Report Federal Way High School Pre-Apprenticeship Space 8-5 2210134.10 8.2.3 Pollution and Spill Prevention Worksheets Pollution prevention, BMP implementation reports, material inventory worksheets, pollutant source identification worksheet, and spill/leak report may be found attached as Figure 8-2. 8.2.4 Disposal Methods Contractor shall dispose of contaminated soils and water in a legal manner. Options include the following: _______________. Technical Information Report Federal Way High School Pre-Apprenticeship Space 2210134.10 Section 8.0 Figures Figure 8-1 ......... ESC Maintenance Report Figure 8-2 ......... CSWPP Forms Figure 8-3 ......... Pollution Prevention Inspection Reports, Spill Prevention Monitoring, and Spill Incident Reports KING COUNTY, WASHINGTON, SURFACE WATER DESIGN MANUAL E S C M A I N T E N A N C E R E P O R T Performed By:___________________________ Date:___________________________ Project Name:___________________________ DPER Permit #:___________________________ Clearing Limits Damage OK Problem Visible OK Problem Intrusions OK Problem Other OK Problem Mulch Rills/Gullies OK Problem Thickness OK Problem Other OK Problem Nets/Blankets Rills/Gullies OK Problem Ground Contact OK Problem Other OK Problem Plastic Tears/Gaps OK Problem Other OK Problem Seeding Percent Cover OK Problem Rills/Gullies OK Problem Mulch OK Problem Other OK Problem Sodding Grass Health OK Problem Rills/Gullies OK Problem Other OK Problem Perimeter Protection including Silt Fence Damage OK Problem Sediment Build-up OK Problem Concentrated Flow OK Problem Other OK Problem Flow Control BMP protection Damage OK Problem Sedimentation OK Problem Concentrated Flow OK Problem Rills/Gullies OK Problem Intrusions OK Problem Other OK Problem Brush Barrier Damage OK Problem Sediment Build-up OK Problem Concentrated Flow OK Problem Other OK Problem Vegetated Strip Damage OK Problem Sediment Build-up OK Problem Concentrated Flow OK Problem Other OK Problem Construction Entrance Dimensions OK Problem Sediment Tracking OK Problem Vehicle Avoidance OK Problem Other OK Problem 2016 Surface Water Design Manual – Appendix D CSWPP Forms 4/24/2016 KING COUNTY, WASHINGTON, SURFACE WATER DESIGN MANUAL Wheel Wash Dimensions OK Problem Sed build up or tracking OK……. Problem Other OK Problem Construction Road Stable Driving Surf. OK Problem Vehicle Avoidance OK Problem Other OK Problem Sediment Trap/Pond Sed. Accumulation OK Problem Overtopping OK Problem Inlet/Outlet Erosion OK Problem Other OK Problem Catch Basin/Inlet Protection Sed. Accumulation OK Problem Damage OK Problem Clogged Filter OK Problem Other OK Problem Interceptor Dike/Swale Damage OK Problem Sed. Accumulation OK Problem Overtopping OK Problem Other OK Problem Pipe Slope Drain Damage OK Problem Inlet/Outlet OK Problem Secure Fittings OK Problem Other OK Problem Ditches Damage OK Problem Sed. Accumulation OK Problem Overtopping OK Problem Other OK Problem Outlet Protection Scour OK Problem Other OK Problem Level Spreader Damage OK Problem Concentrated Flow OK Problem Rills/Gullies OK Problem Sed. Accumulation OK Problem Other OK Problem Dewatering Controls Sediment OK.. Problem Dust Control Palliative applied OK Problem Miscellaneous Wet Season Stockpile OK Problem Other OK Problem Comments: Actions Taken: Problems Unresolved: 2016 Surface Water Design Manual – Appendix D CSWPP Forms 4/24/2016 KING COUNTY, WASHINGTON, SURFACE WATER DESIGN MANUAL BMP Implementation Completed by: Title: Date: Develop a plan for implementing each BMP. Describe the steps necessary to implement the BMP (i.e., any construction or design), the schedule for completing those steps (list dates), and the person(s) responsible for implementation. BMPs Description of Action(s) Required for Implementation Scheduled Milestone and Completion Date(s) Person Responsible for Action Good Housekeeping 1. 2. 3 Preventive Maintenance 1. 2. 3. 4. Spill Prevention and Emergency Cleanup 1. 2. 3. Inspections 1. 2. 3. 2016 Surface Water Design Manual – Appendix D CSWPP Forms 4/24/2016 KING COUNTY, WASHINGTON, SURFACE WATER DESIGN MANUAL BMPs Description of Action(s) Required for Implementation Schedule Milestone and Completion Date(s) Person Responsible for Action Source Control BMPs 1. 2. 3 4. 5. 6. 7. 8. Treatment BMPs 1. 2. 3. 4. Emerging technologies 1. 2. Flow Control BMPs 3. 4. 2016 Surface Water Design Manual – Appendix D CSWPP Forms 4/24/2016 KING COUNTY, WASHINGTON, SURFACE WATER DESIGN MANUAL Pollution Prevention Team Completed by: ______________________ Title: ______________________________ Date: ______________________________ Responsible Official: Title: Team Leader: Office Phone: Cell Phone #: Pager #: Responsibilities: (1) Title: Office Phone: Pager #: Cell Phone: Responsibilities: (2) Title: Office Phone: Pager #: Cell Phone #: Responsibilities: 2016 Surface Water Design Manual – Appendix D CSWPP Forms 4/24/2016 KING COUNTY, WASHINGTON, SURFACE WATER DESIGN MANUAL Employee Training Completed by: Title: Date: Describe the annual training of employees on the SWPPP, addressing spill response, good housekeeping, and material management practices. Training Topics 1.) LINE WORKERS Brief Description of Training Program/Materials (e.g., film, newsletter course) Schedule for Training (list dates) Attendees Spill Prevention and Response Good Housekeeping Material Management Practices 2.) P2 TEAM: SWPPP Implementation Monitoring Procedures 2016 Surface Water Design Manual – Appendix D CSWPP Forms 4/24/2016 KING COUNTY, WASHINGTON, SURFACE WATER DESIGN MANUAL List of Significant Spills and Leaks Completed by: Title: Date: List all spills and leaks of toxic or hazardous pollutants that were significant but are not limited to, release of oil or hazardous substances in excess of reportable quantities. Although not required, we suggest you list spills and leaks of non-hazardous materials. Description Response Procedure Date (month/day/ye ar) Location (as indicated on site map) Type of Material Quantit y Sourc e, If Known Reason for Spill/Leak Amount of Material Recovered Material No longer exposed to Stormwater (Yes/No) Preventive Measure Taken 2016 Surface Water Design Manual – Appendix D CSWPP Forms 4/24/2016 KING COUNTY, WASHINGTON, SURFACE WATER DESIGN MANUAL Potential Pollutant Source Identification Completed by: Title: Date: List all potential stormwater pollutants from materials handled, treated, or stored on-site. Potential Stormwater Pollutant Stormwater Pollutant Source Likelihood of pollutant being present in your stormwater discharge. If yes, explain 2016 Surface Water Design Manual – Appendix D CSWPP Forms 4/24/2016 KING COUNTY, WASHINGTON, SURFACE WATER DESIGN MANUAL Material Inventory Completed by: Title: Date: List materials handled, treated, stored, or disposed of at the project site that may potentially be exposed to precipitation or runoff. Quantity (Units) Likelihood of contact with stormwater Past Spill or Used Produced Stored If Yes, describe reason Leak Material Purpose/Location (indicate per/wk. or yr.) Yes No 2016 Surface Water Design Manual – Appendix D CSWPP Forms 4/24/2016 Technical Information Report Federal Way High School Pre-Apprenticeship Space 2210134.10 Section 9 Bond Quantities, Facilities Summaries, and Declarations of Covenant Technical Information Report Federal Way High School Pre-Apprenticeship Space 9-1 2210134.10 9.0 Bond Quantities, Facilities Summaries, and Declarations of Covenant A Stormwater Facility Summary Sheet is provided as Figure 9-1. In addition, Stormwater Facility Sketches are provided as Figure 9-2. Federal Way Public Schools is exempt from typical bonding requirements because it is a public agency. Because of this, a Bond Quantity Worksheet is not required and has not been prepared. Because the drainage facilities are to be privately owned and maintained, a Declaration of Covenant for Inspection and Maintenance of Stormwater Facilities and BMPs is provided as Figure 9-3. Technical Information Report Federal Way High School Pre-Apprenticeship Space 2210134.10 Section 9.0 Figures Figure 9-1 ......... Stormwater Facility Summary Sheet Figure 9-2 ......... Stormwater Facility Sketches Figure 9-3 ......... Declaration of Covenant for Inspection and Maintenance of Stormwater Facilities and BMPs 2016 KING COUNTY SURFACE WATER DESIGN MANUAL, REFERENCE D 4/24/2016 Page 1 STORMWATER FACILITY SUMMARY SHEET DPER Permit No.___________________ (provide one Stormwater Facility Summary Sheet per Natural Discharge Location)Date ___________________ OVERVIEW:NPDES Permit No.___________________ Project Name Parcel No.____________________________ Project Location Retired Parcel No.____________________________ Downstream Drainage Basins:Project includes Landscape Management Plan?yes Major Basin Name ______________________________________________(include copy with TIR as Appendix)no Immediate Basin Name ______________________________________________ GENERAL FACILITY INFORMATION: Leachable Metals Infiltration Impervious Surface Limit Type # of Type # of Type # of facilities Flow Control BMPs Ponds ______ Ponds ______ Ponds ______ Basic Clearing Limit Vaults ______ Tanks ______ Vaults ______ Conservation Drainage Facility Tanks ______ Trenches _____ Tanks ______ Flood Problem Landscape Management Plan If no flow control facility, check one: Project qualifies for KCSWDM Exemption (KCSWDM 1.2.3): Basic Exemption (Applies to Commercial parcels only)Area % of Total Redevelopment projects Cost Exemption for Parcel Redevelopment projects Direct Discharge Exemption Other _____________________ Total impervious surface served by Project qualifies for 0.1 cfs Exception per KCSWDM 1.2.3 flow control facility(ies) (sq ft) Impervious surface served by flow KCSWDM Adjustment No. ___________________control facility(ies) designed 1990 or later (sq ft) approved KCSWDM Adjustment No. __________________ Impervious surface served by Shared Facility Name/Location: _________________________ pervious surface absorption (sq ft) No flow control required (other, provide justification): Impervious surface served by approved ____________________________________________________ water quality facility(ies) (sq ft) Flow Control Performance Std Declarations of Covenant Recording No. Water QualityDetention TREATMENT SUMMARY FOR TOTAL IMPERVIOUS SURFACES ----- Total Impervious Acreage (ac) No flow control required per approved Flow control provided in regional/shared facility per approved PROVIDE FACILITY DETAILS AND FACILITY SKETCH FOR EACH FACILITY ON REVERSE. USE ADDITIONAL SHEETS AS NEEDED FOR ADDITIONAL FACILITIES Impervious Surface Exemption for Transportation Total Acreage (ac) Federal Way High School Pre-Apprenticeship Space 30611 16th Avenue South, Federal Way, WA 98003 2723059014 XLower Puget Sound X 1 acre of impervious surface capacity in existing pond Cold Creek NA 0 0 0 0 0 0 0 0 0 X TBD 0.17 0.17 100 7405 100 7405 100 0 0 0 0 2016 KING COUNTY SURFACE WATER DESIGN MANUAL, REFERENCE D 4/24/2016 Page 2 STORMWATER FACILITY SUMMARY SHEET DPER Permit No.___________________ (provide one Stormwater Facility Summary Sheet per Natural Discharge Location) Project Name Downstream Drainage Basins: Major Basin Name _______________________________ Project Location Immediate Basin Name ___________________________ FLOW CONTROL FACILITY:Basin: Facility Name/Number _______________________________________ New Facility Project Impervious Facility Location ____________________________________________ Existing Facility Acres Served ________ UIC? □ yes □ no UIC Site ID:% of Total Project Impervious cu.ft.Volume Factor Acres Served ________ _____________ ac.ft.____________of Safety _______No. of Lots Served ________ Control Structure location: _______________________________________________ Type of Control Structure:No. of Orifices/Restrictions __________ Riser in vault Size of Orifice/Restriction (in.) No.1 ______ cu.ft. Riser in Type II CB (numbered starting with lowest No.2 ______ ac.ft. Weir in Type II CB orifice): No.3 ______ (inches in decimal format)No.4 ______ WATER QUALITY FACILITIES Design Information Indicate no. of water quality facilities/BMPs for each type:Water Quality design flow (cfs) _______Flow dispersion Water Quality treated volume (sandfilter) (cu.ft.) _______Filter strip Water Quality storage volume (wetpool) (cu.ft.) _______Biofiltration swale regular, wet or Landscape management plan Farm management plan continuous inflow _______Wetvault combined w/detention ______High flow bypass structure (e.g., flow-splitter catch basin) _______Wetpond basic large combined w/detention ______Oil/water separator baffle coalescing plate _______Pre-settling pond ______Storm filter _______Stormwater wetland ______Pre-settling structure (Manufacturer:______________________) _______Sand filter basic large Sand bed depth ______Catch basin inserts (Manufacturer:________________________) regular linear vault (inches)______________Source controls _________________________________________ ● Is facility lined? yes no If so, what marker is used above liner?_____________________________________________________ Facility Summary Sheet Sketch: All detention, infiltration and water quality facilities must include a detailed sketch (11"x17" reduced size plan sheets preferred). Dam Safety Regulations (WA State Dept of Ecology): Reservoir Volume above natural grade Depth of Reservoir above natural grade (ft) Live Storage Volume Live Storage Depth (ft) XBIORETENTION (rain garden) West end of site X 1 0 0 N/A N/A N/A 0.17 100% Lower Puget Sound 60 X 0.5 Federal Way High School Pre-Apprenticeship Space 30611 16th Avenue South, Federal Way, WA 98003 Cold Creek NA 0 0 0 0 0 0 0 0 0 0 0 0 0 0 EXISTING FEDERAL WAY HIGH SCHOOL EXISTING FEDERAL WAY HIGH SCHOOL PROPOSED POLE BARN FFE = 462.67 EXISTING 12" PVC STORM PIPE CONNECT STORM PIPE TO EXISTING WITH INSERTA-TEE. CONTRACTOR SHALL POTHOLE AND FIELD VERIFY EXISTING PIPE LOCATION AND INVERT ELEVATION PRIOR TO CONSTRUCTION. IE: 453.90± 7 LF 6" PVC SDR35 @ 61.0% CB 01 TYPE 1 WITH LOCKING HERRINGBONE GRATE N: 122838.87 E: 1272744.54 RIM: 461.17 IE: 458.17 6" NE IE: 458.17 6" SW 6.50' 13.50' RAIN GARDEN WITH MINIMUM LIVE STORAGE VOLUME OF 50 CF CONNECT BUILDING DOWNSPOUTS TO RAIN GARDEN WITH 4" PVC SDR35 PIPE SLOPED AT 0.5% MIN (TYP)46546446 3 462 462461462462 4614 C4.1 ROOF DRAIN CONNECTION 6" IE: 460.67 ROOF DRAIN CONNECTION 6" IE: 460.67 Sheet No. Designed by:Drawn by:Checked by: Sheet Title: Revisions: Project Title: Issue Set & Date: Client: Project No. 2215 North 30th Street, Suite 300 Tacoma, WA 98403 T A C O M A SEATTLE SPOKANE TRI-CITIES 253.383.2422 TEL 253.383.2572 FAX www.ahbl.com WEB FEDERAL WAY HIGH SCHOOL PRE-APPRENTICESHIP SPACE A PORTION OF THE NE 1/4 OF THE NE 1/4 OF SEC. 08, TWN. 21 N., RGE. 04 E. W.M. CITY OF FEDERAL WAY, KING COUNTY, WASHINGTON. FEDERAL WAY HIGH SCHOOL PRE-APPRENTICESHIP SPACE FEDERAL WAY PUBLIC SCHOOLS 33330 8TH AVENUE SOUTH FEDERAL WAY, WA 98003 STEPHEN NUTT 2210134 PERMIT SET 07.12.2021 JAD LDJJAD 9Know what's below. before you dig.Call R CITY ENGINEER DATE CITY OF FEDERAL WAY PERMIT NO.:16-105024-00-CO 8 C4.0 GRAPHIC SCALE 0 10 20 1" = 10 FEET 5 N STORM DRAINAGE AND UTILITY PLAN 1.PROOF OF LIABILITY INSURANCE SHALL BE SUBMITTED TO THE CITY PRIOR TO THE PRECONSTRUCTION MEETING. 2.ALL PIPE AND APPURTENANCES SHALL BE LAID ON A PROPERLY PREPARED FOUNDATION IN ACCORDANCE WITH WSDOT 7-02.3(1). THIS SHALL INCLUDE LEVELING AND COMPACTING THE TRENCH BOTTOM, THE TOP OF FOUNDATION MATERIAL, AND REQUIRED PIPE BEDDING, TO A UNIFORM GRADE SO THAT THE ENTIRE PIPE IS SUPPORTED BY A UNIFORMLY DENSE UNYIELDING BASE. 3.STEEL PIPE SHALL BE GALVANIZED AND HAVE ASPHALT TREATMENT #1 OR BETTER INSIDE AND OUTSIDE. 4.ALL DRAINAGE STRUCTURES, SUCH AS CATCH BASINS AND MANHOLES, NOT LOCATED WITHIN A TRAVELED ROADWAY OR SIDEWALK SHALL HAVE SOLID LOCKING LIDS. ALL DRAINAGE STRUCTURES ASSOCIATED WITH A PERMANENT RETENTION/DETENTION FACILITY SHALL HAVE SOLID LOCKING LIDS. 5.ALL CATCH BASIN GRATES SHALL CONFORM TO CFW DRAWING NUMBERS 4-1, 4-2, 4-3, 4-4 OR 4-5. 6.ALL DRIVEWAY CULVERTS LOCATED WITHIN THE RIGHT-OF-WAY SHALL BE OF SUFFICIENT LENGTH TO PROVIDE A MINIMUM 3:1 SLOPE FROM THE EDGE OF THE DRIVEWAY TO THE BOTTOM OF THE DITCH. CULVERTS SHALL HAVE BEVELED END SECTIONS TO MATCH THE SIDE SLOPES. 7.ROCK FOR EROSION PROTECTION OF DITCHES, CHANNELS AND SWALES, WHERE REQUIRED, MUST BE OF SOUND QUARRY ROCK, PLACED TO A DEPTH OF ONE FOOT AND MUST MEET THE FOLLOWING SPECIFICATIONS: 4"-8" ROCK/40%-70% PASSING; 2"-4" ROCK/30%-40% PASSING; AND -2" ROCK/10%-20% PASSING. INSTALLATION SHALL BE IN ACCORDANCE WITH KCRS DRAWING NUMBER 51 OR AS AMENDED BY THE APPROVED PLANS. RECYCLED ASPHALT OR CONCRETE RUBBLE SHALL NOT BE USED. 8.LOTS NOT APPROVED FOR INFILTRATION SHALL BE PROVIDED WITH DRAINAGE OUTLETS (STUB-OUTS). STUB-OUTS SHALL CONFORM TO THE FOLLOWING: A.EACH OUTLET SHALL BE SUITABLY LOCATED AT THE LOWEST ELEVATION ON THE LOT, SO AS TO SERVICE ALL FUTURE ROOF DOWNSPOUTS AND FOOTING DRAINS, DRIVEWAYS, YARD DRAINS, AND ANY OTHER SURFACE OR SUBSURFACE DRAINS NECESSARY TO RENDER THE LOTS SUITABLE FOR THEIR INTENDED USE. EACH OUTLET SHALL HAVE FREE-FLOWING, POSITIVE DRAINAGE TO AN APPROVED STORMWATER CONVEYANCE SYSTEM OR TO AN APPROVED OUTFALL LOCATION. B.OUTLETS ON EACH LOT SHALL BE LOCATED WITH A FIVE-FOOT HIGH, 2 X 4 STAKE MARKED "STORM". THE STUBOUT SHALL EXTEND ABOVE SURFACE LEVEL, BE VISIBLE AND BE SECURED TO THE STAKE. C.PIPE MATERIAL SHALL CONFORM TO UNDERDRAIN SPECIFICATIONS DESCRIBED IN KCRS 7.04 AND, IF NONMETALLIC, THE PIPE SHALL CONTAIN WIRE OR OTHER ACCEPTABLE DETECTION. D.DRAINAGE EASEMENTS ARE REQUIRED FOR DRAINAGE SYSTEMS DESIGNED TO CONVEY FLOWS THROUGH INDIVIDUAL LOTS. E.THE APPLICANT/CONTRACTOR IS RESPONSIBLE FOR COORDINATING THE LOCATIONS OF ALL STUB-OUT CONVEYANCE LINES WITH RESPECT TO THE UTILITIES (I.E. POWER, GAS, TELEPHONE, TELEVISION). F.ALL INDIVIDUAL STUB-OUTS SHALL BE PRIVATELY OWNED AND MAINTAINED BY THE LOT HOMEOWNER. CITY OF FEDERAL WAY DRAINAGE NOTES: LEGEND BUILDING OUTLINE EXISTING MINOR CONTOURS EXISTING MAJOR CONTOURS PROPOSED MINOR CONTOUR PROPOSED MAJOR CONTOUR CATCH BASIN TYPE 1 DOWNSPOUT CONNECTION STORM DRAINAGE PIPING BIORETENTION FACILITY PERFORATED UNDERDRAIN ROCK OUTFALL PROTECTION 101 100 1 C4.1 2 C4.1 4 C4.1 3 C4.1 5 C4.1 Sheet No. Designed by:Drawn by:Checked by: Sheet Title: Revisions: Project Title: Issue Set & Date: Client: Project No. 2215 North 30th Street, Suite 300 Tacoma, WA 98403 T A C O M A SEATTLE SPOKANE TRI-CITIES 253.383.2422 TEL 253.383.2572 FAX www.ahbl.com WEB FEDERAL WAY HIGH SCHOOL PRE-APPRENTICESHIP SPACE A PORTION OF THE NE 1/4 OF THE NE 1/4 OF SEC. 08, TWN. 21 N., RGE. 04 E. W.M. CITY OF FEDERAL WAY, KING COUNTY, WASHINGTON. FEDERAL WAY HIGH SCHOOL PRE-APPRENTICESHIP SPACE FEDERAL WAY PUBLIC SCHOOLS 33330 8TH AVENUE SOUTH FEDERAL WAY, WA 98003 STEPHEN NUTT 2210134 PERMIT SET 07.12.2021 JAD LDJJAD 9Know what's below. before you dig.Call R CITY ENGINEER DATE CITY OF FEDERAL WAY PERMIT NO.:16-105024-00-CO 9 C4.1 STORM DRAINAGE DETAILS POLE BARN STRUCTURE 0.5% (MIN) DOWNSPOUT OR RAIN LEADER. REFER TO ARCHITECTURAL DRAWINGS. PROVIDE FITTINGS AS REQUIRED PVC CAP. CUT HOLE IN CAP TO ALLOW DOWNSPOUT / RAIN LEADER TO PENETRATE WITH 18" CLEARANCE FINISHED GRADE 2" (MIN)4"±BIORETENTION FACILITY NOTES 1.CONTRACTOR SHALL EXCAVATE TO SUBGRADE OF BIORETENTION FACILITY. 2.PROVIDE BIORETENTION SOIL MIX (BSM) PER REFERENCE 11-C OF THE KING COUNTY SURFACE WATER DESIGN MANUAL. 3.BIORETENTION SOIL MIX (BSM) SHALL NOT BE PLACED UNTIL AFTER SITE PAVING. 4.DO NOT PLACE WHEN SOIL IS SATURATED OR SUBJECT TO WATER WITHIN 48 HRS. COVER ON SITE SOILS TO PREVENT WETTING OR SATURATION. TEST SOIL FERTILITY AND MICRONUTRIENTS AND, IF NECESSARY, AMEND MIXTURE TO CREATE OPTIMUM CONDITIONS FOR PLANT ESTABLISHMENT AND EARLY GROWTH AT RATES RECOMMENDED BY AN INDEPENDENT LAB SOIL TEST. 5.SUBGRADE PREPARATION: SCARIFY SUB-SOILS IN TWO DIRECTIONS TO A DEPTH OF 6". THE ENTIRE AREA SHOULD BE DISTURBED BY SCARIFICATION AND BSM APPLIED TO SCARIFIED SURFACE. NO CONSTRUCTION VEHICLES SHALL DRIVE ON NATIVE SOILS AT INFILTRATION ELEVATION OR ON BIORETENTION SOILS. 6.DO NOT COMPACT SUBGRADE 7.NO CONSTRUCTION TRAFFIC SHALL BE ALLOWED TO DRIVE WITHIN BIORETENTION FACILITY 8.QUARRY SPALLS ARE TO BE PER WSDOT SPEC. 9-13.1(5). THICKNESS SHALL BE 8" MINIMUM AND AREA SHALL BE APPROXIMATELY 10 SF AT EACH INLET. 9.THE BIORETENTION FACILITY HAS BEEN SIZED TO TREAT 1,152 SF (REFER TO CALCULATIONS INCLUDED IN SECTION 2 OF THE TIR). 10.SEE LANDSCAPING PLAN FOR PLANTING DETAILS 3:1 M A X BIORETENTION SOIL MIX PER REFERENCE 11-C OF THE KCSWDM 18" MINTOP WIDTH: 14.5 461.17 UNDISTURBED NATIVE SOIIL SEE GRADING SHEET SEE GRADING SHEET BOTTOM WIDTH: 8.5' 6" FREEBOARD FRAME AND VANED GRATE RECTANGULAR ADJUSTMENT SECTION 3"4" MI N. ( T Y P.) 34" 5" #3 BAR EACH WAY SEE NOTE 1 #3 BAR EACH CORNER #3 BAR EACH CORNER 18" MIN. 26"(SEE N O T E 6) 22 " (S E E N O T E 6 )4"44"21" MIN.24" 30 " 20" 5" 6" OR 12" ONE #3 BAR HOOP FOR 6" HEIGHT TWO #3 BAR HOOPS FOR 12" HEIGHT ALTERNATIVE PRECAST BASE SECTION #3 BAR EACH SIDE SECTION B-B #3 BAR HOOP *CORRUGATED POLYETHYLENE STORM SEWER PIPE NOTE: 1.AS ACCEPTABLE ALTERNATIVES TO THE REBAR SHOWN IN THE PRECAST BASE SECTION, FIBERS (PLACED ACCORDING TO THE STANDARD SPECIFICATIONS), OR WIRE MESH HAVING A MINIMUM AREA OF 0.12 SQUARE INCHES PER FOOT SHALL BE USED WITH THE MINIMUM REQUIRED REBAR SHOWN IN THE ALTERNATIVE PRECAST BASE SECTION. WIRE MESH SHALL NOT BE PLACED IN THE KNOCKOUTS. 2.THE KNOCKOUT DIAMETER SHALL NOT BE GREATER THAN 20". KNOCKOUTS SHALL HAVE A WALL THICKNESS OF 2" MINIMUM TO 2.5" MAXIMUM. PROVIDE A 1.5" MINIMUM GAP BETWEEN THE KNOCKOUT WALL AND THE OUTSIDE OF THE PIPE. AFTER THE PIPE IS INSTALLED, FILL THE GAP WITH JOINT MORTAR IN ACCORDANCE WITH STANDARD SPECIFICATION 9-04.3. 3.THE MAXIMUM DEPTH FROM THE FINISHED GRADE TO THE LOWEST PIPE INVERT SHALL BE 5'. 4.THE FRAME AND GRATE MAY BE INSTALLED WITH THE FLANGE UP OR DOWN. THE FRAME MAY BE CAST INTO THE ADJUSTMENT SECTION. 5.THE PRECAST BASE SECTION MAY HAVE A ROUNDED FLOOR, AND THE WALLS MAY BE SLOPED AT A RATE OF 1:24 OR STEEPER. 6.THE OPENING SHALL BE MEASURED AT THE TOP OF THE PRECAST BASE SECTION. 7.ALL PICKUP HOLES SHALL BE GROUTED FULL AFTER THE BASIN HAS BEEN PLACED. PIPE ALLOWANCES PIPE MATERIAL MAXIMUM INSIDE DIAMETER REINFORCED OR PLAIN CONCRETE 12" ALL METAL PIPE 15" *CPSSP (STD. SPEC. 9-05.20)12" SOLID WALL PVC (STD. SPEC. 9-05.12(1))15" PROFILE WALL PVC (STD. SPEC. 9-05.12(2))15" NOTES: 1.BACKFILL MATERIAL SHALL NOT HAVE ROCKS OR PARTICLES LARGER THAN 1" WITHIN 12" OF THE PIPE. BACKFILL MATERIAL SHALL BE PLACED IN 8" MAXIMUM LOOSE LIFTS AND COMPACTED TO 95% MAXIMUM DRY DENSITY PER MODIFIED PROCTOR TEST (ASTM D-1557). 2.CONSTRUCT ALL STORM AND ROOF DRAINS IN CONFORMANCE WITH THIS DETAIL UNLESS NOTED OTHERWISE ON THE PLANS. 3.ALL TRENCH EXCAVATIONS SHALL BE SLOPED, SHORED, SHEETED, BRACED, OR OTHERWISE SUPPORTED IN COMPLIANCE WITH OSHA REGULATIONS AND LOCAL ORDINANCES. 4.IF ORGANIC MATERIAL IS ENCOUNTERED DURING UTILITY EXCAVATION, OVEREXCAVATE TRENCH TO INCREASE PIPE BEDDING DEPTH TO 18" OR MORE AS REQUIRED TO COMPACT BEDDING TO FIRM AND UNYIELDING CONDITION. BACKFILL WITH BANK RUN GRAVEL FOR TRENCH BACKFILL PER WSDOT 9-03.19 OR SUITABLE NATIVE MATERIAL 0.15 x DIA OR 4" MIN PAVEMENT, BASE COURSE AND SUBBASE PER PAVING SHEETS 8" TYP RIGID (DI, CONC) FLEXIBLE (CPEP, CMP, PVC) PIPE AS SPECIFIED ON PLAN OR SPECS 1.5 x I.D. + 18" 24" MIN PIPE BEDDING PER WSDOT 9-03.12, (3)6"DIA6" MIN 1 NOT TO SCALE CATCH BASIN TYPE 1 2 NOT TO SCALE TRENCH SECTION 4 NOT TO SCALE BIORETENTION FACILITY 3 NOT TO SCALE DOWNSPOUT CONNECTION BOTTOM ELEV: 460.67 6" PONDING DEPTH TOP OF POND ELEV: 461.67 OVERFLOW RIM ELEV: 461.17 OUTLET PROTECTION PER PLAN INLET PIPE PER PLAN 6"Ø PERFORATED PVC SDR35 SLOPED AT 0.5% MIN. 18" MIN. 6" MIN UNDERDRAIN BEDDING PER WSDOT 9-03.12(4), GRAVEL BACKFILL FOR DRAINS. INLET P I P E INLET/OUTFALL PIPE OUTFALL P I P E *8' 2'DIA. + 4'PLAN SECTION * UNLESS OTHERWISE NOTED ON PLANS EXISTING AND/OR FINISHED GROUND 4" MIN. FACE QUARRY ROCK 12" MIN. DEPTH (12"Ø PIPE) 18" MIN. DEPTH (15"-18"Ø PIPE) 24" MIN. ( 24"-30"Ø PIPE) 5 NOT TO SCALE ROCK OUTFALL PROTECTION RECORDING REQUESTED BY AND WHEN RECORDED MAIL TO: DECLARATION OF COVENANT FOR MAINTENANCE AND INSPECTION OF FLOW CONTROL BMPS Grantor: Grantee: King County Legal Description: Additional Legal(s) on: Assessor's Tax Parcel ID#: IN CONSIDERATION of the approved King County (check one of the following) residential building permit, commercial building permit, clearing and grading permit, subdivision permit, or short subdivision permit for Application No. ____________________ relating to the real property ("Property") described above, the Grantor(s), the owner(s) in fee of that Property, hereby covenants(covenant) with King County, a political subdivision of the state of Washington, and its municipal successors in interest and assigns ("King County" and "the County", or "its municipal successor"), that he/she(they) will observe, consent to, and abide by the conditions and obligations set forth and described in Paragraphs 1 through 8 below with regard to the Property. Grantor(s) hereby grants(grant), covenants(covenant), and agrees(agree) as follows: 1 Federal Way High School Pre-Apprenticeship Space NE 1/4 OF NE 1/4 OF SEC 8-21-4 LESS CO RDS TGW POR OF NW 1/4 OF NW 1/4 . N/A 0821049001 x NW 1/4 OF SEC 9-21-4 LY WLY OF 16TH AVE S & OF PACIFIC HWY S TGW POR OF VAC 16TH AVE S LESS RD (ROW DEDICATION PER CITY OF FEDERAL WAY REC #20190329000115 & #20190329000116) . 1. Grantor(s) or his/her(their) successors in interest and assigns ("Owners") shall retain, uphold, and protect the stormwater management devices, features, pathways, limits, and restrictions, known as flow control best management practices ("BMPs"), shown on the approved Flow Control BMP Site Plan for the Property attached hereto and incorporated herein as Exhibit A. 2. The Owners shall at their own cost, operate, maintain, and keep in good repair, the Property's BMPs as described in the approved Design and Maintenance Details for each BMP attached hereto and incorporated herein as Exhibit B. 3. King County shall provide at least 30 days written notice to the Owners that entry on the Property is planned for the inspection of the BMPs. After the 30 days, the Owners shall allow King County to enter for the sole purpose of inspecting the BMPs. In lieu of inspection by the County, the Owners may elect to engage a licensed civil engineer registered in the state of Washington who has expertise in drainage to inspect the BMPs and provide a written report describing their condition. If the engineer option is chosen, the Owners shall provide written notice to the Director of the Water and Land Resources Division or its municipal successor in interest ("WLR") within fifteen days of receiving the County's notice of inspection. Within 30 days of giving this notice, the Owners, or the engineer on behalf of the Owners, shall provide the engineer's report to WLR. If the report is not provided in a timely manner as specified above, the County may inspect the BMPs without further notice. 4. If King County determines from its inspection, or from an engineer's report provided in accordance with Paragraph 3, that maintenance, repair, restoration, and/or mitigation work is required for the BMPs, WLR shall notify the Owners of the specific maintenance, repair, restoration, and/or mitigation work (Work) required under Title 9 of the King County Code ("KCC"). WLR shall also set a reasonable deadline for completing the Work or providing an engineer's report that verifies completion of the Work. After the deadline has passed, the Owners shall allow the County access to re-inspect the BMPs unless an engineer's report has been provided verifying completion of the Work. If the work is not 2 completed properly within the time frame set by WLR, King County may initiate an enforcement action. Failure to properly maintain the BMPs is a violation of KCC Chapter 9.04 and may subject the Owners to enforcement under the KCC, including fines and penalties. 5. Apart from performing routine landscape maintenance, the Owners are hereby required to obtain written approval from WLR before performing any alterations or modifications to the BMPs. 6. Any notice or approval required to be given by one party to the other under the provisions of this Declaration of Covenant shall be effective upon personal delivery to the other party, or after three (3) days from the date that the notice or approval is mailed with delivery confirmation to the current address on record with each Party. The parties shall notify each other of any change to their addresses. 7. This Declaration of Covenant is intended to promote the efficient and effective management of surface water drainage on the Property, and it shall inure to the benefit of all the citizens of King County and its municipal successors and assigns. This Declaration of Covenant shall run with the land and be binding upon Grantor(s), and Grantor's(s') successors in interest and assigns. 8. This Declaration of Covenant may be terminated by execution of a written agreement by the Owners and King County that is recorded by King County in its real property records. 3 IN WITNESS WHEREOF, this Declaration of Covenant for the Maintenance and Inspection of Flow Control BMPs is executed this _____ day of ____________________, 20_____. GRANTOR, owner of the Property GRANTOR, owner of the Property STATE OF WASHINGTON ) COUNTY OF KING )ss. On this day personally appeared before me: , to me known to be the individual(s) described in and who executed the within and foregoing instrument and acknowledged that they signed the same as their free and voluntary act and deed, for the uses and purposes therein stated. Given under my hand and official seal this _____ day of ____________________, 20_____. Printed name Notary Public in and for the State of Washington, residing at My appointment expires 4 Technical Information Report Federal Way High School Pre-Apprenticeship Space 2210134.10 Section 10 Operations and Maintenance Plan Technical Information Report Federal Way High School Pre-Apprenticeship Space 10-1 2210134.10 10.0 Operations and Maintenance Plan The drainage facilities detailed in this report will be privately owned and maintained. Facility Descriptions 10.1.1 Bioretention BMP This project proposes a bioretention facility, which will provide flow control for stormwater, if maintained properly. To function as intended, the bioretention facility must be clear of trash and debris and contain healthy, water tolerant plants. The facility should be inspected annually and after large storms to ensure that it is functioning properly. 10.1.2 Conveyance Pipes and Ditches Pipes transport stormwater runoff from the roof to the proposed bioretention facility. To work properly, pipes must be kept free of silt and other debris. If pipes become blocked, surface flooding could occur. Maintenance Requirements Refer to Figure 10-1 for a copy of the Maintenance Requirements for Flow Control, Conveyance, and Water Quality Facilities. Technical Information Report Federal Way High School Pre-Apprenticeship Space 2210134.10 Section 10.0 Figures Figure 10-1 ....... Maintenance Requirements for Flow Control, Conveyance, and Water Quality Facilities APPENDIX A MAINTENANCE REQUIREMENTS FOR FLOW CONTROL, CONVEYANCE, AND WQ FACILITIES NO. 6 – CONVEYANCE PIPES AND DITCHES Maintenance Component Defect or Problem Conditions When Maintenance is Needed Results Expected When Maintenance is Performed Pipes Sediment & debris accumulation Accumulated sediment or debris that exceeds 20% of the diameter of the pipe. Water flows freely through pipes. Vegetation/roots Vegetation/roots that reduce free movement of water through pipes. Water flows freely through pipes. Contaminants and pollution Any evidence of contaminants or pollution such as oil, gasoline, concrete slurries or paint. Materials removed and disposed of according to applicable regulations. Source control BMPs implemented if appropriate. No contaminants present other than a surface oil film. Damage to protective coating or corrosion Protective coating is damaged; rust or corrosion is weakening the structural integrity of any part of pipe. Pipe repaired or replaced. Damaged Any dent that decreases the cross section area of pipe by more than 20% or is determined to have weakened structural integrity of the pipe. Pipe repaired or replaced. Ditches Trash and debris Trash and debris exceeds 1 cubic foot per 1,000 square feet of ditch and slopes. Trash and debris cleared from ditches. Sediment accumulation Accumulated sediment that exceeds 20% of the design depth. Ditch cleaned/flushed of all sediment and debris so that it matches design. Noxious weeds Any noxious or nuisance vegetation which may constitute a hazard to County personnel or the public. Noxious and nuisance vegetation removed according to applicable regulations. No danger of noxious vegetation where County personnel or the public might normally be. Contaminants and pollution Any evidence of contaminants or pollution such as oil, gasoline, concrete slurries or paint. Materials removed and disposed of according to applicable regulations. Source control BMPs implemented if appropriate. No contaminants present other than a surface oil film. Vegetation Vegetation that reduces free movement of water through ditches. Water flows freely through ditches. Erosion damage to slopes Any erosion observed on a ditch slope. Slopes are not eroding. Rock lining out of place or missing (If Applicable) One layer or less of rock exists above native soil area 5 square feet or more, any exposed native soil. Replace rocks to design standards. 2016 Surface Water Design Manual – Appendix A 4/24/2016 A-11 APPENDIX A MAINTENANCE REQUIREMENTS FLOW CONTROL, CONVEYANCE, AND WQ FACILITIES NO. 11 – GROUNDS (LANDSCAPING) Maintenance Component Defect or Problem Conditions When Maintenance is Needed Results Expected When Maintenance is Performed Site Trash or litter Any trash and debris which exceed 1 cubic foot per 1,000 square feet (this is about equal to the amount of trash it would take to fill up one standard size office garbage can). In general, there should be no visual evidence of dumping. Trash and debris cleared from site. Noxious weeds Any noxious or nuisance vegetation which may constitute a hazard to County personnel or the public. Noxious and nuisance vegetation removed according to applicable regulations. No danger of noxious vegetation where County personnel or the public might normally be. Contaminants and pollution Any evidence of contaminants or pollution such as oil, gasoline, concrete slurries or paint. Materials removed and disposed of according to applicable regulations. Source control BMPs implemented if appropriate. No contaminants present other than a surface oil film. Grass/groundcover Grass or groundcover exceeds 18 inches in height. Grass or groundcover mowed to a height no greater than 6 inches. Trees and Shrubs Hazard Any tree or limb of a tree identified as having a potential to fall and cause property damage or threaten human life. A hazard tree identified by a qualified arborist must be removed as soon as possible. No hazard trees in facility. Damaged Limbs or parts of trees or shrubs that are split or broken which affect more than 25% of the total foliage of the tree or shrub. Trees and shrubs with less than 5% of total foliage with split or broken limbs. Trees or shrubs that have been blown down or knocked over. No blown down vegetation or knocked over vegetation. Trees or shrubs free of injury. Trees or shrubs which are not adequately supported or are leaning over, causing exposure of the roots. Tree or shrub in place and adequately supported; dead or diseased trees removed. 4/24/2016 2016 Surface Water Design Manual – Appendix A A-16 Technical Information Report Federal Way High School Pre-Apprenticeship Space 2210134.10 Section 11 Conclusion Technical Information Report Federal Way High School Pre-Apprenticeship Space 11-1 2210134.10 11.0 Conclusion The Federal Way High School Pre-Apprenticeship Space site was designed to meet the 2016 King County Surface Water Design Manual (KCSWDM), as adopted by the City Federal Way per the Addendum to the King County Surface Water Manual (Addendum), January 8, 2017. The site incorporates conveyance and bioretention facilities to manage stormwater generated from the site. Stormwater calculations and modeling conform to King County standards. It was determined using these criteria that: • The bioretention facility was sized properly. • Pipe networks are designed to be of adequate size to effectively convey the 25-year storm event and to contain the 100-year storm event. This analysis is based on data and records either supplied to or obtained by AHBL. These documents are referenced within the text of the analysis. The analysis was prepared using procedures and practices within the standard accepted practices of the industry. We conclude that this project, as schematically represented, will not create any new problems within the downstream drainage system. This project will not noticeably aggravate any existing downstream problems due to either water quality or quantity. AHBL, Inc. James A. Daley, EIT Project Engineer JAD/lsk July 2021 Q:\2021\2210134\WORDPROC\Reports\20210708 Rpt (TIR) 2210134.10.docx