Loading...
The URL can be used to link to this page
Your browser does not support the video tag.
21-102066-UP-Prel TIR-2021-06-02-V1
PRELIMINARY TECHNICAL INFORMATION REPORT Smith Brothers Farms – Federal Way 34520 9th Avenue South Federal Way, WA 98003 Prepared for: Smith Brothers Farms 26401 79th Ave S Kent, WA 98032 June 2nd, 2021 Our Job No. 21537 06/02/2021 TABLE OF CONTENTS 1.0 PROJECT OVERVIEW Figure 1 – Technical Information Report (TIR) Worksheet Figure 2 – Vicinity Map Figure 3 – Drainage Basins, Subbasins, and Site Characteristics Figure 4 – Soils Map Figure 5 – Assessor’s Map Figure 6 – FEMA Map Figure 7 – Sensitive Area map Figure 8 – Boundary and Topographic Survey 2.0 CONDITIONS AND REQUIREMENTS SUMMARY 2.1 Analysis of the Nine Core Requirements 2.2 Analysis of the Five Special Requirements 3.0 OFF-SITE ANALYSIS 4.0 FLOW CONTROL AND WATER QUALITY FACILITY ANALYSIS AND DESIGN A. Existing Site Hydrology B. Developed Site Hydrology C. Performance Standards D. Flow Control System E. Water Quality System 5.0 CONVEYANCE SYSTEM ANALYSIS AND DESIGN 6.0 SPECIAL REPORTS AND STUDIES 7.0 OTHER PERMITS 8.0 ESC ANALYSIS AND DESIGN 9.0 BOND QUANTITIES, FACILITY SUMMARIES, AND DECLARATION OF COVENANT 10.0 OPERATIONS AND MAINTENANCE MANUAL 1.0 PROJECT OVERVIEW 1.0 PROJECT OVERVIEW This project is located on a 4.4-acre site within a portion of the Southeast quarter of Section 20, Township 21 North, Range 4 East, Willamette Meridian, City of Federal Way, King County, Washington. More particularly, the site is located at the intersection of 9th Avenue South and South 344th Street, comprised of two parcels, 9264800060 and 9264800070. The existing site is mainly moderate to steep slopes and completely forested. Large existing stockpiles create large berms, centralized on the project site. An access/driveway easement (Rec. No. 20001214000125) begins across the private road along 9th Avenue South and loops around the southern half of the site, ending at the southeast corner of the southern parcel. The proposed development includes a 45,040 square foot (sf) building, associated concrete truck docks, asphalt paved parking lot, and vegetation/landscaping. The developed site will be contained within a single basin with approximate area of 4.42 acres. The developed site will contain approximately 75% impervious surface area. Site drainage design is based on the 2016 King County Surface Water Design Manual (KCSWDM), as adopted and amended by the City of Federal Way. The site is within a Conservation Flow Control area and must comply with Level 2 Flow Control. An infiltration gallery is designed to provide flow control for the entire site. Flow Control BMP requirements for the site are met by providing infiltration. The proposed site use is considered commercial, high-use. Enhanced basic water quality and oil treatment are required for stormwater runoff from pollution generating surfaces. Treatment of stormwater from the pavement is proposed using an oil-water separator in addition to a Modular Wetland System, which has general use level designation (GULD) for enhanced treatment per the Department of Ecology (DOE), or equivalent system. Stormwater tributary to the infiltration system will be treated by an oil-water separator and a cartridge filter prior to entering the infiltration facility. The infiltration gallery has been sized to take all runoff from the roof, pavement, and the landscaping that drains to the proposed stormwater facilities up to the 100-year storm. All stormwater runoff will be treated on-site. Infiltration facility requirements set forth in KCSWDM Section 5.2.1 have been met by the proposed facility including groundwater protection, consideration of groundwater level impacts, and all other required standards. Site drainage designed are based on the 2016 King County, Washington Surface Water Design Manual (KCWSWDM). Please refer to Section 4.0 of this TIR for further details regarding the drainage facility design. FIGURE 1 TECHNICAL INFORMATION REPORT (TIR) WORKSHEET KING COUNTY, WASHINGTON, SURFACE WATER DESIGN MANUAL 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 _________________________ DPER Permit # ________________________ Location Township ______________ Range ________________ Section ________________ Site Address __________________________ _____________________________________ Part 3 TYPE OF PERMIT APPLICATION Part 4 OTHER REVIEWS AND PERMITS Landuse (e.g.,Subdivision / Short Subd. / UPD) Building (e.g.,M/F / Commercial / SFR) Clearing and 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 ____________________________________ __________________ Part 6 SWDM ADJUSTMENT APPROVALS Type (circle one): Standard / Experimental / Blanket Description: (include conditions in TIR Section 2) ____________________________________________________________________________________ ____________________________________________________________________________________ ____________________________________________________________________________________ Approved Adjustment No. ______________________ Date of Approval: ______________________ 2016 Surface Water Design Manual 4/24/2016 1 Fedway Associates II LP Smith Brothers Farms 34700 9th Ave South 21 N Federal Way, WA 98003 04 E Benjamin Eldridge SE 1/4 of SEC 20 Barghausen Consulting Engineers 34520 9th Ave South 425-251-6222 Federal Way, WA 98003 05/21/202105/21/2021 N/A KING COUNTY, WASHINGTON, SURFACE WATER DESIGN MANUAL TECHNICAL INFORMATION REPORT (TIR) WORKSHEET Part 7 MONITORING REQUIREMENTS Monitoring Required: Yes / No Start Date: _______________________ Completion Date: _______________________ Describe: _________________________________ _________________________________________ _________________________________________ Re: KCSWDM Adjustment No. ________________ Part 8 SITE COMMUNITY AND DRAINAGE BASIN Community Plan : ____________________________________________________________________ Special District Overlays: ______________________________________________________________ Drainage Basin: _____________________________________________________________________ Stormwater Requirements: ____________________________________________________________ Part 9 ONSITE AND ADJACENT SENSITIVE AREAS River/Stream ________________________ Lake ______________________________ Wetlands ____________________________ Closed Depression ____________________ Floodplain ___________________________ Other _______________________________ _______________________________ Steep Slope __________________________ Erosion Hazard _______________________ Landslide Hazard ______________________ Coal Mine Hazard ______________________ Seismic Hazard _______________________ Habitat Protection ______________________ _____________________________________ Part 10 SOILS Soil Type _________________ _________________ _________________ _________________ Slopes _________________ _________________ _________________ _________________ Erosion Potential _________________ _________________ _________________ _________________ High Groundwater Table (within 5 feet) Other ________________________________ Sole Source Aquifer Seeps/Springs Additional Sheets Attached 2016 Surface Water Design Manual 4/24/2016 2 N/A N/A Hylebos Creek Level 2 flow control, ehanced basic water quality EwC 6-15% inC 5-15% Sk - Seattle Muck W - Water KING COUNTY, WASHINGTON, SURFACE WATER DESIGN MANUAL TECHNICAL INFORMATION REPORT (TIR) WORKSHEET 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) Level: 1 / 2 / 3 or Exemption Number ____________ Flow Control 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: _________________________ 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. ______________________ Landscape Management Plan: Yes / No Special Requirements (as applicable): Area Specific Drainage Requirements Type: CDA / SDO / MDP / BP / LMP / Shared Fac. / None Name: ________________________ Floodplain/Floodway Delineation Type (circle one): Major / Minor / Exemption / None 100-year Base Flood Elevation (or range): ______________ Datum: Flood Protection Facilities Describe: 2016 Surface Water Design Manual 4/24/2016 3 05/21/2021 TBD Site (4.42 acres) N/A 0 KING COUNTY, WASHINGTON, SURFACE WATER DESIGN MANUAL TECHNICAL INFORMATION REPORT (TIR) WORKSHEET Part 12 TIR SUMMARY SHEET (provide one TIR Summary Sheet per Threshold Discharge Area) Source Control (commercial / industrial land use) Describe land use: Describe any structural controls: Oil Control High-use Site: Yes / No Treatment BMP: ________________________________ Maintenance Agreement: Yes / No with whom? ____________________________________ Other Drainage Structures Describe: Part 13 EROSION AND SEDIMENT CONTROL REQUIREMENTS MINIMUM ESC REQUIREMENTS DURING CONSTRUCTION Clearing Limits Cover Measures Perimeter Protection Traffic Area Stabilization Sediment Retention Surface Water Collection Dewatering Control Dust Control Flow Control Protection of Flow Control BMP Facilities (existing and proposed) Maintain BMPs / Manage Project MINIMUM ESC REQUIREMENTS AFTER CONSTRUCTION Stabilize exposed surfaces Remove and restore Temporary ESC Facilities Clean and remove all silt and debris, ensure operation of Permanent Facilities, restore operation of Flow Control BMP Facilities as necessary Flag limits of SAO and open space preservation areas Other ______________________ Part 14 STORMWATER FACILITY DESCRIPTIONS (Note: Include Facility Summary and Sketch) Flow Control Type/Description Water Quality Type/Description Detention Infiltration Regional Facility Shared Facility Flow Control BMPs Other ________________ ________________ ________________ ________________ ________________ ________________ Vegetated Flowpath Wetpool Filtration Oil Control Spill Control Flow Control BMPs Other ________________ ________________ ________________ ________________ ________________ ________________ ________________ 2016 Surface Water Design Manual 4/24/2016 4 Oil/water separator TBD Infiltration Gallery Oil/water separator Modular Wetland Commercial Maintaining clean site, enclosed trash containers, and providing general education to property owner. KING COUNTY, WASHINGTON, SURFACE WATER DESIGN MANUAL TECHNICAL INFORMATION REPORT (TIR) WORKSHEET 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 ______________________________ 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 2016 Surface Water Design Manual 4/24/2016 5 05/21/20216-2-21 FIGURE 2 SITE LOCATION Horizontal: Scale: Vertical: For: Title: VICINITY MAP Job Number N.T.S.N/A 21537 DATE: 5/18/21 Smith Brothers Farms Federal Way, Washington P:\21000s\21537\exhibit\graphics\21537 vmap.cdr REFERENCE: MapQuest (2021) SITE FIGURE 3 DRAINAGE BASINS, SUBBASINS, AND SITE CHARACTERISTICS EXISTING CONDITIONS PLAN C2 SCALE: 1"=40'“”••••••••••••••••NOTGNIHSAWF O ETATS DE RETSIGER FIGURE 4 SOILS MAP Horizontal: Scale: Vertical: For: Title: SOIL SURVEY MAP Job Number N.T.S.N/A 21537 DATE: 5/18/21 Smith Brothers Farms Federal Way, Washington P:\21000s\21537\exhibit\graphics\21537 soil.cdr HSG A B REFERENCE: USDA, Natural Resources Conservation Service LEGEND: InC = Indianola loamy sand, 5-15% slopes SITE EwC = Everett-Alderwood gravelly sandy loams, 6-15% slopes FIGURE 5 ASSESSOR MAP Horizontal: Scale: Vertical: For: Title: ASSESSOR MAP Job Number N.T.S.N/A 21537 DATE: 5/18/21 Smith Brothers Farms Federal Way, Washington P:\21000s\21537\exhibit\graphics\21537 amap.cdr SITE REFERENCE: King County Department of Assessments (Oct. 2020) FIGURE 6 FEMA MAP Horizontal: Scale: Vertical: For: Title: FEMA MAP Job Number N.T.S.N/A 21537 DATE: 5/18/21 Smith Brothers Farms Federal Way, Washington P:\21000s\21537\exhibit\graphics\21537 fema.cdr REFERENCE: Federal Emergency Management Agency (Portion of Map 53033C1250G, Aug. 2020) Areas determined to be outside the 0.2% annual chance floodplain. ZONE X OTHER AREAS LEGEND SITE FIGURE 7 SENSITIVE AREAS MAP Horizontal: Scale: Vertical: For: Title: SENSITIVE AREAS MAP Job Number N.T.S.N/A 21537 DATE: 5/18/21 Smith Brothers Farms Federal Way, Washington P:\21000s\21537\exhibit\graphics\21537 sens.cdr SITE REFERENCE: King County iMAP (2021) 2.0 CONDITIONS AND REQUIREMENTS SUMMARY 2.0 CONDITIONS AND REQUIREMENTS SUMMARY 2.1 Analysis of the Eight Core Requirements CORE REQUIREMENTS HOW PROJECT HAS ADDRESSED REQUIREMENT No. 1: Discharge at Natural Location Currently, all stormwater runoff is infiltrated and maintained with the native soils and vegetation. Stormwater from the developed site will collected onsite via catch basins and conveyed to an infiltration gallery. All stormwater runoff is expected to be infiltrated, however, an overflow structure and tightlined overflow path has been proposed in case of major storm events or plugging within the system. No. 2: Off-Site Analysis The off-site analysis has been included within Section 3.0 of this Technical Information Report. No. 3: Flow Control All runoff for the 100-year post-developed flows will be infiltrated by the proposed infiltration facility. No. 4: Conveyance System The conveyance and backwater analysis will be designed per the 2016 KCSWDM for the proposed storm drainage system and will be included in Section 5.0 of this Technical Information Report at final engineering. No. 5: Erosion and Sediment Control Temporary erosion control measures for this project will include: stabilized construction entrances, perimeter runoff control, cover practices, temporary sedimentation facilities, and construction sequencing. No. 6: Maintenance and Operations The project owner will own and maintain the private drainage facilities for this project. An Operations and Maintenance Manual, if required, will be provided in Section 10.0 of this Technical Information Report. No. 7: Bonds and Liability Bonding is required by King County using the county’s Bond Quantity Worksheet in section 9.0. No. 8: Water Quality The Water Quality Menu followed in accordance with the 2016 KCSWDM required Enhanced Basic water quality treatment for this commercial development. A Modular Wetland System, or equivalent, is being proposed which will provide enhanced treatment per the Department of Ecology. No. 9: Flow Control BMPs All stormwater runoff will be reliably infiltrated and is therefore exempt from this requirement per the 2016 KCSWDM. SPECIAL REQUIREMENTS HOW PROJECT HAS ADDRESSED REQUIREMENT No. 1: Other Adopted Area Specific Requirements This project is located within the Hylebos Creek Drainage basin, part of the Puget Sound Near Shore Watershed. No area specific requirements are noted at this time. No. 2: Floodplain/Floodway Delineation Per the FEMA map panel 53033C1250G, this project is not located within the 500-year floodplain, therefore, there is no flood hazard area delineation required for this project site. No. 3: Flood Protection Facilities This project does not rely on an existing flood protection facility, nor propose to modify or construct a new flood protection facility; therefore, this special requirement does not apply. No. 4: Source Controls This project will provide source controls in accordance with City of Federal Way requirements, which will include at a minimum sweeping the parking lot on a regular basis, covering the trash enclosures, and educating the property owner about proper use of pesticides and fertilizers on this project site. No. 5: Oil Control The site is designated as a high-use site by the standards outlined in the 2016 KCSWDM. Oil control treatment will be provided for the high-use portion of the site from standards outlined in the High-Use menu. A comprehensive facility design will be provided for final engineering review. 3.0 OFF-SITE ANALYSIS 3.0 OFF-SITE ANALYSIS Refer to the Level 1 Off-Site Drainage Analysis constructed by Barghausen Consulting Engineers dated March 21st, 2021 included in this section. LEVEL 1 OFF-SITE DRAINAGE ANALYSIS Smith Brothers Farms – Federal Way 34520 9th Avenue South Federal Way, WA 98003 Prepared for: Smith Brothers Farms 26401 79th Ave S Kent, WA 98032 March 21st, 2021 Our Job No. 21537 TABLE OF CONTENTS TASK 1 STUDY AREA DEFINITION AND MAPS UPSTREAM DRAINAGE ANALYSIS TASK 2 RESOURCE REVIEW TASK 3 FIELD INSPECTION DOWNSTREAM DRAINAGE PROBLEMS REQUIRING SPECIAL ATTENTION CONVEYANCE SYSTEM NUISANCE PROBLEMS (TYPE 1) SEVERE EROSION PROBLEMS (TYPE 2) SEVERE FLOODING PROBLEMS (TYPE 3) TASK 4 DRAINAGE SYSTEM DESCRIPTION AND PROBLEM DESCRIPTIONS TASK 5 MITIGATION OF EXISTING AND POTENTIAL PROBLEMS TASK 1 STUDY AREA DEFINITION AND MAPS TASK 1 STUDY AREA DEFINITION AND MAPS This project is located on a 4.4-acre site within a portion of the Southeast quarter of Section 20, Township 21 North, Range 4 East, Willamette Meridian, City of Federal Way, King County, Washington. More particularly, the site is located at the intersection of 9th Avenue South and South 344th Street, comprised of two parcels, 9264800060 and 9264800070. The existing site is mainly moderate to steep slopes and completely forested. Large stockpiles create large berms, centralized on the project site. An access/driveway easement (Rec. No. 20001214000125) begins across the private road along 9th Avenue South and loops around the southern half of the site, ending at the southeast corner of the southern parcel. The proposed development includes a 45,000 square foot (sf) building, with a 10,000 square foot future building expansion anticipated, with associated truck docks, asphalt paved parking lot, and vegetation/landscaping. The developed site will be contained within a single basin with approximate area of 4.42 acres. The developed site will contain approximately 75% impervious surface area. UPSTREAM DRAINAGE ANALYSIS Based on a site survey, there appears to be no upstream flows onto the site. The project site resides at a higher elevation than the surrounding areas. The adjacent, developed sites have separate storm facilities, approved by the City of Federal Way, which keep stormwater runoff from entering the project site. EXHIBIT A Vicinity Map Horizontal: Scale: Vertical: For: Title: VICINITY MAP Job Number N.T.S.N/A 21537 DATE: 5/18/21 Smith Brothers Farms Federal Way, Washington P:\21000s\21537\exhibit\graphics\21537 vmap.cdr REFERENCE: MapQuest (2021) SITE EXHIBIT B Downstream Drainage Map TASK 2 RESOURCE REVIEW TASK 2 RESOURCE REVIEW · Adopted Basin Plans: The site is part of the Hylebos Creek Drainage Basin per the City of Federal Way Flow Control Applications Map. · Finalized Drainage Studies: This is not applicable. · Basin Reconnaissance Summary Report: This site is located in the Hylebos Creek Drainage Basin per the City of Federal Way Control Applications Map. · Critical Drainage Area Maps: According to the King County Surface Water Design Manual, for commercial developments, Enhanced Basic water quality is required for this project site. In addition, the King County Surface Water Design Manual (KCSWDM) also indicated that Level 2 Flow Control is required as a minimum. · Floodplain and Floodway FEMA maps: Please see the enclosed Exhibit D – FEMA Map utilized for this analysis. Based on our review of the FEMA floodplain map, the site is not located within the floodplain. · Other Off-Site Analysis Reports: The United States Department of Agriculture Soils Conservations Service (SCS) map is also provided. See Exhibit F – Soil Survey Map. · Sensitive Areas Folios: Based on a review of the King County Sensitive Areas Map Folios, there are no known sensitive areas on or adjacent to the project site. · Drainage Problems: This is not applicable. · United States Department of Agriculture King County Soil Survey: Based on the Soils Map for this area, the majority of the site area being developed consists of Everett-Alderwood gravelly, sandy loams (6-15%) and Indianola loamy sand (5-15%). · Migrating River Studies: This is not applicable. · Department of Ecology 303(d) Waters: This area appears to be tributary to West Hylebos Wetlands, and ultimately part of the Hylebos Creek Drainage Basin per the City of Federal Way Flow Control Applications Map. EXHIBIT H FLOW CONTROL APPLICATIONS MAP EXHIBIT C Fife Milton Tacoma DesMoines Edgewood Pacific AuburnFederalWay Kent Hyle b o s C r e e k W a t e r w a y Blai r W a t e r w a y Puyallup R i v e rPuget Sound BayDumas PovertyBay Sit c u m W a t e r w a y CommencementBay LakeSteel Star Lake MirrorLake GenevaLake North Lake Lorene Lake JeaneLake EasterLake Dolloff Lake TroutLake FiveMileLakeLake KillarneyHOY T RD SW MILITARY RD SWEST VALLEY HWYS 288th ST DASH POINT R D DASH PT RDMILITARY RD S21st AVE SWPACIFIC HWYMARINE VIEW DRSW 336th ST NORTHSHORE PK W Y INTERSTATE 5E 11th STHWY 18H W Y 18PACIFIC HWY S28TH AVE SE N C H A N T E D P KW Y 51st AVE SINTERSTATE 51st AVE SPACIFIC HWY SS 320th ST 21st AVE SWS 336th ST1st AVE SS 312th ST SW 320th ST SW 356th ST S 348th ST SR 99S 272nd ST 33rd ST NE Lower PugetSound Basin HylebosCreekBasin MillCreekBasin LowerGreenRiverBasin 0 0.5 10.25 Mile This map is intended for use as a graphical representation only. The City of Federal Way makes no warranty as to its accuracy. Legend Drainage Basin BoundaryStreamsCity LimitsLakes and Wetlands Scale: City of Federal Way Flow ControlApplications Map Map Date: February, 2010SWM DivisionCity of Federal Way33325 8th Ave SPO Box 9718Federal Way, WA 98063(253) 835-2700www.cityoffederalway.com R:\erike\swm\FlowControl\flowcontrol.mxd Flow Control Basic Flow Control Areas Conservation Flow Control Areas Flood Problem Flow Control Areas Major Receiving Waters1. Puget Sound TASK 3 FIELD INSPECTION & TASK 4 DRAINAGE SYSTEM DESCRIPTION AND PROBLEM DESCRIPTIONS TASK 3 FIELD INSPECTION The project site generally drains to the south-west, following the natural topography and ultimately merging with West Hylebos Wetlands Park via existing drainage ditches and drainage structure systems. There are no known problems along the downstream path. DOWNSTREAM DRAINAGE PROBLEMS REQUIRING SPECIAL ATTENTION Conveyance System Nuisance Problems (Type 1) Conveyance system nuisance problems are minor but chronic flooding or erosion problems that result from the overflow of a constructed conveyance system that is substandard or has become undersized as a result of upstream development. Such problems warrant additional attention because of their chronic nature and because they result from the failure of a conveyance system to provide a minimum acceptable level of protection. Based on the resource review, there is little evidence of past conveyance system nuisance problems occurring. Severe Erosion Problems (Type 2) Severe erosion problems are defined as downstream channels, ravines, or slopes with evidence of or potential for erosion/incision, sufficient to pose a sedimentation hazard to downstream conveyance systems or propose a landslide hazard by undercutting adjacent slopes. Severe erosion problems do not include roadway or minor ditch erosion. Based on our site visit, there is no evidence of, or potential for erosion/incision sufficient to pose a sedimentation hazard to downstream conveyance systems evident anywhere along the downstream drainage course. Severe Flooding Problems (Type 3) Severe flooding problems can be caused by conveyance systems overflows of the elevated water surfaces of ponds, lakes, wetlands, or closed depressions. Severe flooding problems are defined as follows: · Flooding of the finished area of a habitable building for runoff events less than or equal to the 100-year event. Examples include flooding of finished floors of homes and commercial or industrial buildings. Flooding in electrical/heating systems and components in the crawlspace or garage of a home. Such problems are referred to as “severe building flooding problems.” · Flooding over all lanes of a roadway or severely impacting a sole access driveway for runoff events less than or equal to the 100-year event. Such problems are referred to as “severe roadway flooding problems.” The FEMA map indicated that the site does not lie with a floodplain, so it is not anticipated that any impact from flooding will occur on the site. TASK 4 DRAINAGE SYSTEM DESCRIPTION AND PROBLEM DESCRIPTIONS Stormwater runoff from the project site will be routed to an on-site conveyance system that will include several catch basins, roof drains, and pipes, which will convey stormwater runoff to the proposed water quality device and infiltration gallery on the south section of the site. The infiltration facility has been sized to reliably infiltrate all expected stormwater runoff up to the 100- year event storm. In the case of overflow, an outlet structure has been proposed to convey water further downstream to the existing drainage system along 9th Avenue South. TASK 5 MITIGATION OF EXISTING AND POTENTIAL PROBLEMS TASK 5 MITIGATION OF EXISTING AND POTENTIAL PROBLEMS The area downstream of this proposed project does not exhibit any potential problems, and this project is not expected to aggravate or create a problem as specified in the problem-specific mitigation requirements. The project will neither aggravate or create a problem as specified in the problem-specific mitigation requirements set forth in Section 1.2.2.1 of the 2016 King County Surface Water Design Manual, as adopted by the City of Federal Way. 4.0 FLOW CONTROL AND WATER QUALITY FACILITY ANALYSIS AND DESIGN 4.0 FLOW CONTROL AND WATER QUALITY FACILITY ANALYSIS AND DESIGN A. Existing Site Hydrology The project site drains to the existing drainage system along 9th Avenue South. Stormwater runoff is infiltrated by the native soils and intercepted by various plant species. B. Developed Site Hydrology Under the developed conditions the developed portion of the site will be approximately 75 percent impervious surface. The developed site area is approximately 4.42 acres total with water quality and flow control being provided for this area. Runoff from pollution generating surfaces will receive water quality treatment before infiltration. The proposed gallery will infiltrate 100% of developed drainage basin, with an overflow structure being proposed in the event of unprecedented storm events or reduced performance of the facility due to a buildup of sediment. C. Performance Standards This site is located within unincorporated King County for flow control and water quality purposes. Level 2 flow control is required as well as enhanced basic water quality and oil spill protection, per KCSWDM groundwater protection requirements. The Uniform Flow Analysis will be used for pipe conveyance, for the preliminary design of proposed pipe systems. Detailed conveyance calculations will be provided with the final copy of this report. D. Flow Control System Runoff from the entire proposed development is designed to infiltrate within an infiltration gallery located on the south side of the project, just south of the dock high loading. The infiltration gallery is designed to infiltrate the 100-year event. Water quality facility, Contech or equivalent, is designed for installation immediately upstream of the infiltration gallery to provide removal of suspended solids prior to entering the infiltration facility. The infiltration gallery basic information is summarized below: Tributary Area (ac) Length (ft) Width (ft) Depth (ft) Long-Term Design Infiltration rate (in/hr)* Infiltration Gallery 4.42 250 70 6 1.00 *Infiltration rates are based on the Geotechnical Report in Section 6. E. Water Quality System The infiltration gallery system will include an oil-water separator vault located upstream of the facility to remove oil and suspended solids prior to Enhanced basic water quality treatment. A Modular Wetland Systems (MWS) vault, or approved equivalent, is proposed downstream of the oil-water separator vault to provide enhanced treatment of the runoff prior to infiltration. Refer to the Geotechnical report in Section 6 for more soil information. Sizing for the various treatment systems will be provided during final engineering review for this project. DEVELOPED BASIN MAP DETENTION AND INFILTRATION SIZING CALCULATIONS INFILTRATION AND SIZING CALCULATIONS WWHM2012 PROJECT REPORT INFILTRATION FACILITY 21537-INFIL-FC 5/17/2021 10:28:28 AM Page 2 General Model Information Project Name:21537-INFIL-FC Site Name:Smith Bros Farms Site Address:34520 9TH AVE SOUTH City:Federal Way Report Date:5/17/2021 Gage:Seatac Data Start:1948/10/01 Data End:2009/09/30 Timestep:15 Minute Precip Scale:1.000 Version Date:2018/03/02 Version:4.2.14 POC Thresholds Low Flow Threshold for POC1:50 Percent of the 2 Year High Flow Threshold for POC1:50 Year 21537-INFIL-FC 5/17/2021 10:28:28 AM Page 3 Landuse Basin Data Predeveloped Land Use Basin 1 Bypass:No GroundWater:No Pervious Land Use acre C, Forest, Flat 4.42 Pervious Total 4.42 Impervious Land Use acre Impervious Total 0 Basin Total 4.42 Element Flows To: Surface Interflow Groundwater 21537-INFIL-FC 5/17/2021 10:28:28 AM Page 4 Mitigated Land Use Basin 1 Bypass:No GroundWater:No Pervious Land Use acre C, Lawn, Flat 1.1 Pervious Total 1.1 Impervious Land Use acre ROOF TOPS FLAT 0.9 PARKING FLAT 2.42 Impervious Total 3.32 Basin Total 4.42 Element Flows To: Surface Interflow Groundwater Gravel Trench Bed 1 Gravel Trench Bed 1 21537-INFIL-FC 5/17/2021 10:28:28 AM Page 6 Mitigated Routing Gravel Trench Bed 1 Bottom Length:250.00 ft. Bottom Width:65.00 ft. Trench bottom slope 1:0 To 1 Trench Left side slope 0:0 To 1 Trench right side slope 2:0 To 1 Material thickness of first layer:6 Pour Space of material for first layer:0.4 Material thickness of second layer:0 Pour Space of material for second layer:0 Material thickness of third layer:0 Pour Space of material for third layer:0 Infiltration On Infiltration rate:1 Infiltration safety factor:1 Total Volume Infiltrated (ac-ft.):608.941 Total Volume Through Riser (ac-ft.):0 Total Volume Through Facility (ac-ft.):608.941 Percent Infiltrated:100 Total Precip Applied to Facility:0 Total Evap From Facility:0 Discharge Structure Riser Height:6 ft. Riser Diameter:18 in. Element Flows To: Outlet 1 Outlet 2 Gravel Trench Bed Hydraulic Table Stage(feet)Area(ac.)Volume(ac-ft.)Discharge(cfs)Infilt(cfs) 0.0000 0.373 0.000 0.000 0.000 0.0667 0.373 0.009 0.000 0.376 0.1333 0.373 0.019 0.000 0.376 0.2000 0.373 0.029 0.000 0.376 0.2667 0.373 0.039 0.000 0.376 0.3333 0.373 0.049 0.000 0.376 0.4000 0.373 0.059 0.000 0.376 0.4667 0.373 0.069 0.000 0.376 0.5333 0.373 0.079 0.000 0.376 0.6000 0.373 0.089 0.000 0.376 0.6667 0.373 0.099 0.000 0.376 0.7333 0.373 0.109 0.000 0.376 0.8000 0.373 0.119 0.000 0.376 0.8667 0.373 0.129 0.000 0.376 0.9333 0.373 0.139 0.000 0.376 1.0000 0.373 0.149 0.000 0.376 1.0667 0.373 0.159 0.000 0.376 1.1333 0.373 0.169 0.000 0.376 1.2000 0.373 0.179 0.000 0.376 1.2667 0.373 0.189 0.000 0.376 1.3333 0.373 0.199 0.000 0.376 1.4000 0.373 0.208 0.000 0.376 1.4667 0.373 0.218 0.000 0.376 1.5333 0.373 0.228 0.000 0.376 21537-INFIL-FC 5/17/2021 10:28:28 AM Page 7 1.6000 0.373 0.238 0.000 0.376 1.6667 0.373 0.248 0.000 0.376 1.7333 0.373 0.258 0.000 0.376 1.8000 0.373 0.268 0.000 0.376 1.8667 0.373 0.278 0.000 0.376 1.9333 0.373 0.288 0.000 0.376 2.0000 0.373 0.298 0.000 0.376 2.0667 0.373 0.308 0.000 0.376 2.1333 0.373 0.318 0.000 0.376 2.2000 0.373 0.328 0.000 0.376 2.2667 0.373 0.338 0.000 0.376 2.3333 0.373 0.348 0.000 0.376 2.4000 0.373 0.358 0.000 0.376 2.4667 0.373 0.368 0.000 0.376 2.5333 0.373 0.378 0.000 0.376 2.6000 0.373 0.388 0.000 0.376 2.6667 0.373 0.397 0.000 0.376 2.7333 0.373 0.407 0.000 0.376 2.8000 0.373 0.417 0.000 0.376 2.8667 0.373 0.427 0.000 0.376 2.9333 0.373 0.437 0.000 0.376 3.0000 0.373 0.447 0.000 0.376 3.0667 0.373 0.457 0.000 0.376 3.1333 0.373 0.467 0.000 0.376 3.2000 0.373 0.477 0.000 0.376 3.2667 0.373 0.487 0.000 0.376 3.3333 0.373 0.497 0.000 0.376 3.4000 0.373 0.507 0.000 0.376 3.4667 0.373 0.517 0.000 0.376 3.5333 0.373 0.527 0.000 0.376 3.6000 0.373 0.537 0.000 0.376 3.6667 0.373 0.547 0.000 0.376 3.7333 0.373 0.557 0.000 0.376 3.8000 0.373 0.567 0.000 0.376 3.8667 0.373 0.577 0.000 0.376 3.9333 0.373 0.586 0.000 0.376 4.0000 0.373 0.596 0.000 0.376 4.0667 0.373 0.606 0.000 0.376 4.1333 0.373 0.616 0.000 0.376 4.2000 0.373 0.626 0.000 0.376 4.2667 0.373 0.636 0.000 0.376 4.3333 0.373 0.646 0.000 0.376 4.4000 0.373 0.656 0.000 0.376 4.4667 0.373 0.666 0.000 0.376 4.5333 0.373 0.676 0.000 0.376 4.6000 0.373 0.686 0.000 0.376 4.6667 0.373 0.696 0.000 0.376 4.7333 0.373 0.706 0.000 0.376 4.8000 0.373 0.716 0.000 0.376 4.8667 0.373 0.726 0.000 0.376 4.9333 0.373 0.736 0.000 0.376 5.0000 0.373 0.746 0.000 0.376 5.0667 0.373 0.756 0.000 0.376 5.1333 0.373 0.766 0.000 0.376 5.2000 0.373 0.775 0.000 0.376 5.2667 0.373 0.785 0.000 0.376 5.3333 0.373 0.795 0.000 0.376 5.4000 0.373 0.805 0.000 0.376 21537-INFIL-FC 5/17/2021 10:28:28 AM Page 8 5.4667 0.373 0.815 0.000 0.376 5.5333 0.373 0.825 0.000 0.376 5.6000 0.373 0.835 0.000 0.376 5.6667 0.373 0.845 0.000 0.376 5.7333 0.373 0.855 0.000 0.376 5.8000 0.373 0.865 0.000 0.376 5.8667 0.373 0.875 0.000 0.376 5.9333 0.373 0.885 0.000 0.376 6.0000 0.373 0.895 0.000 0.376 21537-INFIL-FC 5/17/2021 10:28:29 AM Page 11 Appendix Predeveloped Schematic 21537-INFIL-FC 5/17/2021 10:28:30 AM Page 12 Mitigated Schematic 21537-INFIL-FC 5/17/2021 10:28:32 AM Page 25 Disclaimer Legal Notice This program and accompanying documentation is provided 'as-is' without warranty of any kind. The entire risk regarding the performance and results of this program is assumed by the user. Clear Creek Solutions, Inc. disclaims all warranties, either expressed or implied, including but not limited to implied warranties of program and accompanying documentation. In no event shall Clear Creek Solutions, Inc. be liable for any damages whatsoever (including without limitation to damages for loss of business profits, loss of business information, business interruption, and the like) arising out of the use of, or inability to use this program even if Clear Creek Solutions, Inc. has been advised of the possibility of such damages. Clear Creek Solutions, Inc. 6200 Capitol Blvd. Ste F Olympia, WA. 98501 Toll Free 1(866)943-0304 Local (360)943-0304 www.clearcreeksolutions.com 5.0 CONVEYANCE SYSTEM ANALYSIS AND DESIGN 5.0 CONVEYANCE SYSTEM ANALYSIS AND DESIGN The on-site conveyance system will be designed in accordance with the 2016 KCWSWDM. The proposed conveyance system for this project is curb, gutter, catch basins, and storm drainage pipe. The conveyance system sizing utilizes the SBUH method with a Manning’s “n” value of 0.012 for the pipe sizing calculations. Conveyance calculations will be provided during final engineering. 6.0 SPECIAL REPORTS AND STUDIES 6.0 SPECIAL REPORTS AND STUDIES Special reports for this project include: • Draft Geotechnical Engineering Report prepared by Terra Associates, Inc. – December 9th, 2020. • Soundview Consultant LLC’s Site Findings/USFWS NWI/DNR Stream Typing. • Trip Generation Estimates & Concurrency Application prepared by TENW – January 14th, 2021. 1 Scott Hougham From:Matt DeCaro <matt@soundviewconsultants.com> Sent:Friday, November 20, 2020 10:03 AM To:Andrew Coates Cc:Scott Hougham; Kim Schoenfelder; ProjectTeam Subject:SVC's Reconnaissance Findings - 9th Avenue South (SVC#1199.0007) Attachments:USFWS NWI.pdf; DNR Stream Typing.pdf Good morning Andrew, On November 4 and 18, 2020, Soundview Consultants (SVC) completed a feasibility reconnaissance of the 4.4-acre site that Smith Brothers Farms is looking to purchase on 9th Avenue South in Federal Way (King County Tax Parcel Numbers 9264800070 and 9264800060). The findings of our site reconnaissance are summarized below. · General Site Conditions – It seems that the entire site was cleared, graded, and prepped for development decades ago (around 2000?). Based on our observations, a few stormwater ponds were constructed along the roadway, the southern parcel was cut down, and the northern parcel was raised (currently it sits approximately 30 feet higher than the southern parcel). Soils on the south parcel appear to be exposed subsoil (mixed glacial till – sand, gravel, rocks) while soils on the northern parcel appear to be compacted fill from that cut. · Onsite Wetland Absence – No regulated wetlands were identified on the subject property. The site contains gravelly, well-drained soils dominated by an upland, invasive plant community. · Offsite Wetland Findings – One offsite wetland was observed approximately 150 feet to the southwest of the subject property, on the opposite side of 9th Avenue South. This is likely a Category II or III wetland, and its buffer likely terminates at the road edge which constitutes a “permanently altered buffer” under Federal Way Revised Code. · Offsite Stream Findings – One offsite stream is located approximately 150 to 200 feet southeast of the subject property. The buffer will not encumber this project site. · Research Finding – Several resources including the DNR water typing map and USFWS National Wetland Inventory (see attached) map a stream on the subject property. We found absolutely no evidence of a stream onsite, it appears the stream is mapped in error. The City of Federal Way critical areas map accurately shows the offsite stream about 200 feet to the southeast. · Summary – The subject property appears to be unencumbered by any wetlands, streams, regulated habitat areas, or associated buffers. · Disclaimer – SVC’s findings are based on conditions present at the time of the reconnaissance and considered preliminary until validated by the City of Federal Way through their formal wetland and habitat review process. Please let me know if you have questions. The City will likely require a formal critical areas report if a land use is proposed; note also that Federal Way has a “critical areas verification” process that can be pursued at any time, with or without a land use application. Matt DeCaro Associate Principal Soundview Consultants LLC a: 2907 Harborview Drive, Suite D, Gig Harbor, WA 98335 e: matt@soundviewconsultants.com w: soundviewconsultants.com p: 253.514.8952 ext. 025 DNR Stream Typing © 2020 Microsoft Corporation © 2020 Maxar ©CNES (2020) Distribution Subject PropertyDNR - Stream Typing - Watercourses U, unknown 11/3/2020, 2:24:14 PM 0 280 560140ft 0 80 16040m 1:4,514 Soundview Consultants © 2020 Microsoft Corporation, © 2020 Maxar, ©CNES (2020) Distribution Airbus DS, © 2020 HERE | WDFW | These data were collected by WDFW staff with contributions from the North Olympic Salmon Coalition and the Friends of the San Juans. | Source: USDA USFWS NWI U.S. Fish and Wildlife Service, National Standards and Support Team, Subject Property Wetlands Estuarine and Marine Deepwater Estuarine and Marine Wetland Freshwater Emergent Wetland Freshwater Forested/Shrub Wetland Freshwater Pond Lake Other 11/3/2020, 2:26:21 PM 0 280 560140ft 0 80 16040m 1:4,514 Soundview Consultants © 2020 Microsoft Corporation, © 2020 Maxar, ©CNES (2020) Distribution Airbus DS, © 2020 HERE | WDFW | These data were collected by WDFW staff with contributions from the North Olympic Salmon Coalition and the Friends of the San Juans. | Source: USDA TENW Transportation Engineering NorthWest Transportation Planning | Design | Traffic Impact & Operations 11400 SE 8th Street, Suite 200, Bellevue, WA 98004 | Office (425) 889-6747 MEMORANDUM DATE:January 14, 2021 TO:Sarady Long City of Federal Way FROM:Jeff Schramm / Curtis Chin, P.E. TENW SUBJECT:Trip Generation Estimate Smith Brothers Farms TENW Project No. 2020-249 This memorandum documents the trip generation estimate for the proposed Smith Brothers Farms project located at 34520 9th Avenue S in the City of Federal Way (see vicinity map in Attachment A). This memo includes a project description and project trip generation estimate. Project Description The proposed Smith Brothers Farms project would include development of an up to 58,000 square foot (SF) warehouse building for the storage and distribution of dairy products on a currently vacant site. Vehicular access to the project would be provided via one full access driveways on 9th Avenue S and one full access driveway on S 344th Street. A preliminary site plan is included in Attachment B. Trip Generation The trip generation estimates for the proposed Smith Brothers Farms project were based on methodology documented in the Institute of Transportation Engineers (ITE) Trip Generation Manual, 10th Edition for Land Use Code (LUC) 150 (Warehousing). Other land use categories were considered such as LUC 157 (High- Cube Cold Storage Warehouse). However, due to the size of the proposed warehouse the use of LUC 157 was determined to be not appropriate. In addition, the use of LUC 157 would result in less project trips. Therefore, LUC 150 was considered the most appropriate land use and may provide a conservative trip generation estimate. Table 1 summarizes the weekday trip generation estimates for daily, AM peak hour, and PM peak hour for the proposed project, as well as the Saturday peak hour trip generation. The detailed trip generation estimates are included in Attachment C. Trip Generation EstimateSmith Brothers Farms TENW January 14, 2021 Page 2 Table 1 Smith Brothers Farms – Trip Generation Summary New Trips Generated (PASSENGER VEHICLES) New Trips Generated (TRUCKS ONLY) Total Trips Generated (ALL VEHICLES) Time Period In Out Total In Out Total In Out Total Weekday: Daily 51 51 102 17 18 35 68 69 137 AM Peak Hour 24 7 31 1 0 1 25 7 32 PM Peak Hour 8 25 33 1 1 2 9 26 35 Saturday Peak Hour ------2 1 3 As shown in Table 1, the proposed Smith Brothers Farms project is estimated to generate 137 new weekday daily trips, with 32 new weekday AM peak hour trips (25 entering, 7 exiting), and 35 new weekday PM peak hour trips (9 entering, 26 exiting). The Saturday peak hour trip generation is estimated to be 3 trips. Since the project is estimated to generate less than 100 peak hour trips, the project would not be considered a major new development and a TIA would not be required. Also note that this trip generation information will be used for the project traffic concurrency application. If you have any questions regarding the information presented in this memorandum, please contact Curtis at chin@tenw.com. cc: Andrew Coates, KGIP Dustin Highland, Smith Brothers Farms, Inc. Attachments Trip Generation EstimateSmith Brothers Farms ATTACHMENT A Vicinity Map Trip Generation EstimateSmith Brothers Farms ATTACHMENT B Preliminary Site Plan Trip Generation EstimateSmith Brothers Farms ATTACHMENT C Trip Generation Calculations ITE Land Use Units 1 LUC 2 In Out Trip Rate 2 In Out Total Truck Trip Rate 2 In Out Enter Exit Total Enter Exit Total Daily Proposed Use: Warehousing 58,000 GFA 150 50%50%T = 1.58(X)+45.54 68 69 137 0.60 50%50%17 18 35 51 51 102 Daily Trips = 68 69 137 17 18 35 51 51 102 AM Peak Hour Proposed Use: Warehousing 58,000 GFA 150 77%23%T = 0.12(X)+25.32 25 7 32 0.02 52%48%1 0 1 24 7 31 AM Peak Hour Trips = 25 7 32 1 0 1 24 7 31 PM Peak Hour Proposed Use: Warehousing 58,000 GFA 150 27%73%T = 0.12(X)+27.82 9 26 35 0.03 52%48%1 1 2 8 25 33 PM Peak Hour Trips = 9 26 35 1 1 2 8 25 33 Saturday Peak Hour Proposed Use: Warehousing 3 58,000 GFA 150 64% 36% 0.05 2 1 3 - - - - - -- - - Saturday Peak Hour Trips = 2 1 3 - - - - - - Notes: 2 Land Use Code and trip rates based on ITE Trip Generation Manual, 10th Edition, 2017. 3 No data available regarding Saturday truck trips. 1 GFA = Gross Floor Area. Smith Brothers Farms - Federal Way Trip Generation Summary Directional Distribution Directional DistributionTrips Generated Truck Trip Generation Non-Truck Trip Generation 1/14/2021 7.0 OTHER PERMITS 7.0 OTHER PERMITS The City of Federal Way will be the governing body for the storm drainage. A building permit and grading permit will be required from the City of Federal Way for the development of the on-site drainage and roadway facilities. These permits and all other permit applications required will be provided during final engineering. Other permits required for this development include: • SEPA Determination • NPDES Permit from the Department of Ecology • Site Development Permit from the City of Federal Way • Building Permit from the City of Federal Way • Water main extension and sewer service permits from Lakehaven Water and Sewer District. 8.0 ESC ANALYSIS AND DESIGN 8.0 ESC ANALYSIS AND DESIGN This project is proposing to clear and grade the portion of the site to be developed and construct a building with truck docks and associated parking. All expected stormwater runoff from the developed area will be routed into a sediment pond via temporary v-ditches prior to discharge downstream. There will be silt fence around the entire perimeter of the site, along with a construction entrance installed from South 344th Street. The clearing limits will be contained within the property boundary. Temporary v-ditches with rock check dams routing stormwater to a temporary sediment pond will control erosion and sediment on site during construction. A. Erosion and Sediment Control (ESC) Plan Analysis and Design The Clear and Grade plans consist of erosion and sediment control plans, prepared in accordance with the 2016 King County Surface Water Design Manual, and standard industry practices throughout the construction process to limit the amount of sediment traveling into the downstream systems. BMPs that are proposed include a rocked construction entrance, silt fence where needed, straw mulch for the areas that reach final grade in the lot areas, V-ditches with rock check dams, sediment traps, and hydro seeding. The project involves more than 3 acres of ground disturbance, so a temporary sediment pond is an appropriate BMP for sediment removal from this construction project. A temporary sediment pond will be used with v-ditches for surface water control, silt fence for perimeter protection, and a stabilized construction entrance to reduce the amount of sediment transported onto paved roads by vehicles or equipment. The following outline summarizes the sediment trap sizing. The 2-year peak (15-minute time step) flow was used for calculating the required surface area. The total disturbance area is approximately 4.4 acres defined by a single basin. There is a non-functioning pond in the southwest portion of the site, that will be utilized as the temporary sediment pond for the entire project. The temporary sediment traps were sized using the following equation from the 2016 KCSWD manual: S.A. = 2 x Q2/0.00096 = 2,080 square feet per cfs of inflow Q2 = CIRA The flow for the entire basin is outlined in the table below and was calculated using WWHM: S.A. = 2 x 1.336/0.00096 = 2,779 sf S.A. Required = 2,779 sf S.A. Provided = 3,804 sf Basin Tributary Area (AC) Q2 (CFS) SA Required (SF) SA Provided (SF) 1 4.42 1.336 2,779 3,804 Refer to Basin area map on next sheet. B. Stormwater Pollution Prevention and Spill (SWPPS) Plan Design A Stormwater Pollution Prevention and Spill Site Plan has been prepared for the Smith Brothers Farms site as part of the Early Clear and Grade plans. This is a site-specific plan that outlines the project scope of work and presents a comprehensive plan to prevent, respond to, and report spills or releases to the environment. It also provides suggested locations for: • equipment parking/maintenance areas • chemical storage areas with secondary containment • construction materials and construction waste storage areas • truck wheel washout areas This plan also provides general locations of erosion control measures such as silt fencing, sediment pond, construction entrance, and clearing limits. Potential Spill Sources or Releases Potential spill sources during construction will include materials and equipment brought on-site. Potential spill sources include: fueling, lubricating oil, hydraulic oil, backhoes, bulldozers, water trucks, support trucks, lighting units, pumps, and generators. Equipment staging and maintenance areas for fueling, hazardous materials, and hazardous waste materials have been designated on the SWPPS. Construction debris will be present during demolition of the existing on-site buildings. No fuel tanks, gasoline, oils and hydraulic fuels will be stored on-site. Control Pollutants Pollutants other than sediment will be controlled as part of the implemented SWPPS plan. Maintenance and repair of heavy equipment and vehicles that may result in discharge or spillage of pollutants to the ground or surface water runoff will be conducted using spill prevention measures. Contaminated surfaces will be cleaned immediately following any discharge or spill incident. Spills will be reported within 24 hours. Emergency repairs may be performed on-site using temporary plastic placed beneath and, if raining, over the vehicle. Concrete truck chutes and pumps shall be washed out only into formed areas awaiting installation of concrete or asphalt. Unused concrete remaining in the truck and pump shall be returned to the originating batch plant for recycling. Hand tools including, but not limited to, screeds, shovels, rakes and trowels shall be washed off only into formed areas awaiting installation of concrete or asphalt. When no formed areas are available, wash water and leftover product shall be contained in a lined container or in a sump designed to receive the materials. Contained concrete shall be disposed of in manner that does not violate groundwater or surface water quality standards. Recommended BMP’s include Concrete Handling (BMP C151) Spill Prevention and Containment The following is a list of BMP’s that will be used for the project. • Store and maintain equipment in a designated area. • Reduce the amount of hazardous materials and waste by substituting non-hazardous or less hazardous materials. • Use secondary containment (drain pan) to catch spills when removing or changing fluids. • Use proper equipment (pumps, funnels) to transfer fluids • Keep spill kits readily accessible. • Check incoming vehicles for leaking oil and fluids. • Transfer used fluids and oil filters to waste or recycling drums. • Inspect equipment immediately, if necessary. • Implement a preventative maintenance schedule for equipment and vehicles. • Perform fueling in designated fueling area. • Do not “top-off” tanks • Use secondary containment (drain pan) to catch spills. • Keep spill kits readily accessible. • Inspect fueling areas routinely for leaks and spills. • Monitor pollution prevention BMP’s and maintain records/reports of all inspections using the worksheets at the end of this section. Spill Response Response in the first 15 minutes is critical to minimize the impacts to human health and the environment and to minimize property damage and cleanup costs. The contractor will respond immediately to spills and regulated materials. Spill response equipment shall be stored in spill response kits located in a clearly marked and accessible area. The standard approach toward spill response will be as follows: • Stop operations. • Stop the source of the spill. • Use appropriate materials to absorb, berm, or cover the area to prevent further contamination. • Notify the construction manager. • Determine the method of clean up required. All methods shall comply with the state or local requirements to spill response. • Contact a cleanup response firm if necessary. Contact Personnel The designated personnel responsible for managing, implementing and maintaining this SWPPS plan include: Smith Brothers Farms – TBD CECL – TBD The contractor – TBD A SWPPP report has also been prepared following the Department of Ecology (Ecology) format and will be kept on-site during all construction activities. The SWPPP report includes a narrative discussion of construction BMP’s that will be implemented during construction, based on the 12 required elements as defined by Ecology. The SWPPP report also outlines inspection, monitoring, and reporting requirements to meet the requirements of the NPDES permit. 9.0 BOND QUANTITIES, FACILITY SUMMARIES, AND DECLARATIONS OF COVENANT 9.0 BOND QUANTITIES, FACILITY SUMMARIES, AND DECLARATION OF COVENANT Appropriate bond quantity worksheets and facility summary forms will be included within the final engineering review submittals. 10.0 OPERATIONS AND MAINTENANCE MANUAL 10.0 OPERATIONS AND MAINTENANCE MANUAL The following pages of this report are the maintenance checklists for the various stormwater facilities around the project site. Please use these pages as guidance when performing maintenance around the site which should occur at a minimum every fall and spring, as well as after every storm event exceeding 1 inch of precipitation in 24 hours. An Operations and Maintenance Manual will be provided during final engineering. APPENDIX A MAINTENANCE REQUIREMENTS FOR FLOW CONTROL, CONVEYANCE, AND WQ FACILITIES NO. 2 – INFILTRATION FACILITIES Maintenance Component Defect or Problem Conditions When Maintenance Is Needed Results Expected When Maintenance Is Performed Site Trash and debris 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. Infiltration Pond, Top or Side Slopes of Dam, Berm or Embankment Rodent holes Any evidence of rodent holes if facility is acting as a dam or berm, or any evidence of water piping through dam or berm via rodent holes. Rodents removed or destroyed and dam or berm repaired. Tree growth Tree growth threatens integrity of dams, berms or slopes, does not allow maintenance access, or interferes with maintenance activity. If trees are not a threat to dam, berm, or embankment integrity or not interfering with access or maintenance, they do not need to be removed. Trees do not hinder facility performance or maintenance activities. Erosion Eroded damage over 2 inches deep where cause of damage is still present or where there is potential for continued erosion. Any erosion observed on a compacted slope. Slopes stabilized using appropriate erosion control measures. If erosion is occurring on compacted slope, a licensed civil engineer should be consulted to resolve source of erosion. Settlement Any part of a dam, berm or embankment that has settled 4 inches lower than the design elevation. Top or side slope restored to design dimensions. If settlement is significant, a licensed civil engineer should be consulted to determine the cause of the settlement. Infiltration Pond, Tank, Vault, Trench, or Small Basin Storage Area Sediment accumulation If two inches or more sediment is present or a percolation test indicates facility is working at or less than 90% of design. Facility infiltrates as designed. Liner damaged (If Applicable) Liner is visible or pond does not hold water as designed. Liner repaired or replaced. Infiltration Tank Structure Plugged air vent Any blockage of the vent. Tank or vault freely vents. Tank bent out of shape Any part of tank/pipe is bent out of shape more than 10% of its design shape. Tank repaired or replaced to design. Gaps between sections, damaged joints or cracks or tears in wall A gap wider than ½-inch at the joint of any tank sections or any evidence of soil particles entering the tank at a joint or through a wall. No water or soil entering tank through joints or walls. Infiltration Vault Structure Damage to wall, frame, bottom, and/or top slab Cracks wider than ½-inch, any evidence of soil entering the structure through cracks or qualified inspection personnel determines that the vault is not structurally sound. Vault is sealed and structurally sound. 2016 Surface Water Design Manual – Appendix A 4/24/2016 A-3 APPENDIX A MAINTENANCE REQUIREMENTS FLOW CONTROL, CONVEYANCE, AND WQ FACILITIES NO. 2 – INFILTRATION FACILITIES Maintenance Component Defect or Problem Conditions When Maintenance Is Needed Results Expected When Maintenance Is Performed Inlet/Outlet Pipes Sediment accumulation Sediment filling 20% or more of the pipe. Inlet/outlet pipes clear of sediment. Trash and debris Trash and debris accumulated in inlet/outlet pipes (includes floatables and non-floatables). No trash or debris in pipes. Damaged Cracks wider than ½-inch at the joint of the inlet/outlet pipes or any evidence of soil entering at the joints of the inlet/outlet pipes. No cracks more than ¼-inch wide at the joint of the inlet/outlet pipe. Access Manhole Cover/lid not in place Cover/lid is missing or only partially in place. Any open manhole requires immediate maintenance. Manhole access covered. Locking mechanism not working Mechanism cannot be opened by one maintenance person with proper tools. Bolts cannot be seated. Self-locking cover/lid does not work. Mechanism opens with proper tools. Cover/lid difficult to remove One maintenance person cannot remove cover/lid after applying 80 lbs of lift. Cover/lid can be removed and reinstalled by one maintenance person. Ladder rungs unsafe Missing rungs, misalignment, rust, or cracks. Ladder meets design standards. Allows maintenance person safe access. Large access doors/plate Damaged or difficult to open Large access doors or plates cannot be opened/removed using normal equipment. Replace or repair access door so it can opened as designed. Gaps, doesn't cover completely Large access doors not flat and/or access opening not completely covered. Doors close flat; covers access opening completely. Lifting Rings missing, rusted Lifting rings not capable of lifting weight of door or plate. Lifting rings sufficient to lift or remove door or plate. Infiltration Pond, Tank, Vault, Trench, or Small Basin Filter Bags Plugged Filter bag more than 1/2 full. Replace filter bag or redesign system. Infiltration Pond, Tank, Vault, Trench, or Small Basin Pre-settling Ponds and Vaults Sediment accumulation 6" or more of sediment has accumulated. Pre-settling occurs as designed Infiltration Pond, Rock Filter Plugged High water level on upstream side of filter remains for extended period of time or little or no water flows through filter during heavy rain storms. Rock filter replaced evaluate need for filter and remove if not necessary. Infiltration Pond Emergency Overflow Spillway Rock missing Only one layer of rock exists above native soil in area five square feet or larger, or any exposure of native soil at the top of out flow path of spillway. Rip-rap on inside slopes need not be replaced. Spillway restored to design standards. Tree growth Tree growth impedes flow or threatens stability of spillway. Trees removed. 4/24/2016 2016 Surface Water Design Manual – Appendix A A-4 APPENDIX A MAINTENANCE REQUIREMENTS FOR FLOW CONTROL, CONVEYANCE, AND WQ FACILITIES NO. 4 – CONTROL STRUCTURE/FLOW RESTRICTOR Maintenance Component Defect or Problem Condition When Maintenance is Needed Results Expected When Maintenance is Performed Structure Trash and debris Trash or debris of more than ½ cubic foot which is located immediately in front of the structure opening or is blocking capacity of the structure by more than 10%. No Trash or debris blocking or potentially blocking entrance to structure. Trash or debris in the structure that exceeds 1/3 the depth from the bottom of basin to invert the lowest pipe into or out of the basin. No trash or debris in the structure. Deposits of garbage exceeding 1 cubic foot in volume. No condition present which would attract or support the breeding of insects or rodents. Sediment Sediment exceeds 60% of the depth from the bottom of the structure to the invert of the lowest pipe into or out of the structure or the bottom of the FROP-T section or is within 6 inches of the invert of the lowest pipe into or out of the structure or the bottom of the FROP-T section. Sump of structure contains no sediment. Damage to frame and/or top slab Corner of frame extends more than ¾ inch past curb face into the street (If applicable). Frame is even with curb. Top slab has holes larger than 2 square inches or cracks wider than ¼ inch. Top slab is free of holes and cracks. Frame not sitting flush on top slab, i.e., separation of more than ¾ inch of the frame from the top slab. Frame is sitting flush on top slab. Cracks in walls or bottom Cracks wider than ½ inch and longer than 3 feet, any evidence of soil particles entering structure through cracks, or maintenance person judges that structure is unsound. Structure is sealed and structurally sound. Cracks wider than ½ inch and longer than 1 foot at the joint of any inlet/outlet pipe or any evidence of soil particles entering structure through cracks. No cracks more than 1/4 inch wide at the joint of inlet/outlet pipe. Settlement/ misalignment Structure has settled more than 1 inch or has rotated more than 2 inches out of alignment. Basin replaced or repaired to design standards. Damaged pipe joints Cracks wider than ½-inch at the joint of the inlet/outlet pipes or any evidence of soil entering the structure at the joint of the inlet/outlet pipes. No cracks more than ¼-inch wide at the joint of inlet/outlet 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. Ladder rungs missing or unsafe Ladder is unsafe due to missing rungs, misalignment, rust, cracks, or sharp edges. Ladder meets design standards and allows maintenance person safe access. FROP-T Section Damage T section is not securely attached to structure wall and outlet pipe structure should support at least 1,000 lbs of up or down pressure. T section securely attached to wall and outlet pipe. Structure is not in upright position (allow up to 10% from plumb). Structure in correct position. Connections to outlet pipe are not watertight or show signs of deteriorated grout. Connections to outlet pipe are water tight; structure repaired or replaced and works as designed. Any holes—other than designed holes—in the structure. Structure has no holes other than designed holes. 2016 Surface Water Design Manual – Appendix A 4/24/2016 A-7 APPENDIX A MAINTENANCE REQUIREMENTS FLOW CONTROL, CONVEYANCE, AND WQ FACILITIES NO. 4 – CONTROL STRUCTURE/FLOW RESTRICTOR Maintenance Component Defect or Problem Condition When Maintenance is Needed Results Expected When Maintenance is Performed Cleanout Gate Damaged or missing Cleanout gate is missing. Replace cleanout gate. Cleanout gate is not watertight. Gate is watertight and works as designed. Gate cannot be moved up and down by one maintenance person. Gate moves up and down easily and is watertight. Chain/rod leading to gate is missing or damaged. Chain is in place and works as designed. Orifice Plate Damaged or missing Control device is not working properly due to missing, out of place, or bent orifice plate. Plate is in place and works as designed. Obstructions Any trash, debris, sediment, or vegetation blocking the plate. Plate is free of all obstructions and works as designed. Overflow Pipe Obstructions Any trash or debris blocking (or having the potential of blocking) the overflow pipe. Pipe is free of all obstructions and works as designed. Deformed or damaged lip Lip of overflow pipe is bent or deformed. Overflow pipe does not allow overflow at an elevation lower than design Inlet/Outlet Pipe Sediment accumulation Sediment filling 20% or more of the pipe. Inlet/outlet pipes clear of sediment. Trash and debris Trash and debris accumulated in inlet/outlet pipes (includes floatables and non-floatables). No trash or debris in pipes. Damaged Cracks wider than ½-inch at the joint of the inlet/outlet pipes or any evidence of soil entering at the joints of the inlet/outlet pipes. No cracks more than ¼-inch wide at the joint of the inlet/outlet pipe. Metal Grates (If Applicable) Unsafe grate opening Grate with opening wider than 7/8 inch. Grate opening meets design standards. Trash and debris Trash and debris that is blocking more than 20% of grate surface. Grate free of trash and debris. footnote to guidelines for disposal Damaged or missing Grate missing or broken member(s) of the grate. Grate is in place and meets design standards. Manhole Cover/Lid Cover/lid not in place Cover/lid is missing or only partially in place. Any open structure requires urgent maintenance. Cover/lid protects opening to structure. Locking mechanism Not Working Mechanism cannot be opened by one maintenance person with proper tools. Bolts cannot be seated. Self-locking cover/lid does not work. Mechanism opens with proper tools. Cover/lid difficult to Remove One maintenance person cannot remove cover/lid after applying 80 lbs. of lift. Cover/lid can be removed and reinstalled by one maintenance person. 4/24/2016 2016 Surface Water Design Manual – Appendix A A-8 APPENDIX A MAINTENANCE REQUIREMENTS FOR FLOW CONTROL, CONVEYANCE, AND WQ FACILITIES NO. 5 – CATCH BASINS AND MANHOLES Maintenance Component Defect or Problem Condition When Maintenance is Needed Results Expected When Maintenance is Performed Structure Sediment Sediment exceeds 60% of the depth from the bottom of the catch basin to the invert of the lowest pipe into or out of the catch basin or is within 6 inches of the invert of the lowest pipe into or out of the catch basin. Sump of catch basin contains no sediment. Trash and debris Trash or debris of more than ½ cubic foot which is located immediately in front of the catch basin opening or is blocking capacity of the catch basin by more than 10%. No Trash or debris blocking or potentially blocking entrance to catch basin. Trash or debris in the catch basin that exceeds 1/3 the depth from the bottom of basin to invert the lowest pipe into or out of the basin. No trash or debris in the catch basin. Dead animals or vegetation that could generate odors that could cause complaints or dangerous gases (e.g., methane). No dead animals or vegetation present within catch basin. Deposits of garbage exceeding 1 cubic foot in volume. No condition present which would attract or support the breeding of insects or rodents. Damage to frame and/or top slab Corner of frame extends more than ¾ inch past curb face into the street (If applicable). Frame is even with curb. Top slab has holes larger than 2 square inches or cracks wider than ¼ inch. Top slab is free of holes and cracks. Frame not sitting flush on top slab, i.e., separation of more than ¾ inch of the frame from the top slab. Frame is sitting flush on top slab. Cracks in walls or bottom Cracks wider than ½ inch and longer than 3 feet, any evidence of soil particles entering catch basin through cracks, or maintenance person judges that catch basin is unsound. Catch basin is sealed and is structurally sound. Cracks wider than ½ inch and longer than 1 foot at the joint of any inlet/outlet pipe or any evidence of soil particles entering catch basin through cracks. No cracks more than 1/4 inch wide at the joint of inlet/outlet pipe. Settlement/ misalignment Catch basin has settled more than 1 inch or has rotated more than 2 inches out of alignment. Basin replaced or repaired to design standards. Damaged pipe joints Cracks wider than ½-inch at the joint of the inlet/outlet pipes or any evidence of soil entering the catch basin at the joint of the inlet/outlet pipes. No cracks more than ¼-inch wide at the joint of inlet/outlet 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. Inlet/Outlet Pipe Sediment accumulation Sediment filling 20% or more of the pipe. Inlet/outlet pipes clear of sediment. Trash and debris Trash and debris accumulated in inlet/outlet pipes (includes floatables and non-floatables). No trash or debris in pipes. Damaged Cracks wider than ½-inch at the joint of the inlet/outlet pipes or any evidence of soil entering at the joints of the inlet/outlet pipes. No cracks more than ¼-inch wide at the joint of the inlet/outlet pipe. 2016 Surface Water Design Manual – Appendix A 4/24/2016 A-9 APPENDIX A MAINTENANCE REQUIREMENTS FLOW CONTROL, CONVEYANCE, AND WQ FACILITIES NO. 5 – CATCH BASINS AND MANHOLES Maintenance Component Defect or Problem Condition When Maintenance is Needed Results Expected When Maintenance is Performed Metal Grates (Catch Basins) Unsafe grate opening Grate with opening wider than 7/8 inch. Grate opening meets design standards. Trash and debris Trash and debris that is blocking more than 20% of grate surface. Grate free of trash and debris. footnote to guidelines for disposal Damaged or missing Grate missing or broken member(s) of the grate. Any open structure requires urgent maintenance. Grate is in place and meets design standards. Manhole Cover/Lid Cover/lid not in place Cover/lid is missing or only partially in place. Any open structure requires urgent maintenance. Cover/lid protects opening to structure. Locking mechanism Not Working Mechanism cannot be opened by one maintenance person with proper tools. Bolts cannot be seated. Self-locking cover/lid does not work. Mechanism opens with proper tools. Cover/lid difficult to Remove One maintenance person cannot remove cover/lid after applying 80 lbs. of lift. Cover/lid can be removed and reinstalled by one maintenance person. 4/24/2016 2016 Surface Water Design Manual – Appendix A A-10 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