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Stormwater Technical Information Report King County Parks – Renton Shop Central Maintenance Facility Replacement Project King County Department of Natural Resources and Parks - Parks and Recreation Division June 16, 2021 DEVELOPMENT ENGINEERING jchavez 12/08/2021 SURFACE WATER UTILITY JFarah 12/08/2021 Stormwater Technical Information Report King County Parks – Renton Shop Central Maintenance Facility Replacement Project June 16, 2021 | i Certificate of Engineer The technical material and data contained in this report for the King County Parks, Renton Shop - Central Maintenance Facility Replacement Project, Stormwater Technical Information Report was prepared under the supervision and direction of the undersigned. _________________________________ Gerald A (Jerry) Bibee, P.E. Senior Water Resources Engineer HDR Engineering, Inc. June 16, 2021 Stormwater Technical Information Report King County Parks – Renton Shop Central Maintenance Facility Replacement Project June 16, 2021 | i Contents 1 Project Overview ................................................................................................................................. 1 1.1 Introduction and Purpose .......................................................................................................... 1 1.1.1 Project Background ...................................................................................................... 1 1.1.2 Existing Project Site and Adjacent Properties Description......................................... 11 1.1.3 Project Redevelopment Proposal Description ........................................................... 11 1.2 Existing Conditions .................................................................................................................. 12 1.2.1 Site Topography, Drainage, Land Cover, Soils, and Groundwater ............................ 12 1.2.2 Existing Drainage Basin and Threshold Discharge Areas ......................................... 13 1.3 Proposed Conditions ............................................................................................................... 15 1.3.1 Site Grading, Drainage, Land Cover, and Soils ......................................................... 15 1.3.2 Proposed Threshold Discharge Areas and Drainage Systems ................................. 15 1.4 Land Cover and Change Summary ......................................................................................... 17 2 Conditions and Requirements Summary .......................................................................................... 18 2.1 Drainage Review Classification for Project ............................................................................. 18 2.2 Core Requirements and Project Applicability .......................................................................... 19 2.2.1 CR #1: Discharge at the Natural Location.................................................................. 19 2.2.2 CR #2: Off-site Analysis ............................................................................................. 20 2.2.3 CR #3: Flow Control Facilities .................................................................................... 20 2.2.4 CR #4: Conveyance System ...................................................................................... 20 2.2.5 CR #5: Construction Stormwater Pollution Prevention .............................................. 21 2.2.6 CR #6: Maintenance and Operations ......................................................................... 21 2.2.7 CR #7: Financial Guarantees and Liability ................................................................. 22 2.2.8 CR #8: Water Quality Facilities .................................................................................. 22 2.2.9 CR #9: On-site BMPs ................................................................................................. 23 2.3 Special Requirements and Project Applicability ...................................................................... 23 2.3.1 SR #1: Other Area Specific Requirements ................................................................ 23 2.3.2 SR #2: Flood Hazard Area Delineation ...................................................................... 24 2.3.3 SR #3: Flood Protection Facilities .............................................................................. 24 2.3.4 SR #4: Source Controls.............................................................................................. 24 2.3.5 SR #5: Oil Control ...................................................................................................... 25 2.3.6 SR #6 Aquifer Protection Area ................................................................................... 26 3 Off-site Analysis ................................................................................................................................ 26 3.1 Downstream Analysis .............................................................................................................. 26 3.1.1 Define and Map the Study Area ................................................................................. 26 3.1.2 Review Available Study Area Information .................................................................. 27 3.1.3 Field Inspect the Study Area ...................................................................................... 28 3.1.4 Describe the Drainage System and Drainage Problems ........................................... 28 4 Flow Control, Low-impact Development, Water Quality, and Infiltration Facilities Analysis and Design ........................................................................................................................................ 28 4.1 Existing Conditions Site Hydrology ......................................................................................... 28 4.2 Proposed Conditions Site Hydrology ...................................................................................... 29 4.3 Stormwater Controls Design Requirements and Performance Standards ............................. 30 4.3.1 Flow Control Facilities ................................................................................................ 30 4.3.2 On-site Low-impact Development BMPs ................................................................... 33 4.3.3 Water Quality Facilities............................................................................................... 33 4.3.4 Infiltration Facilities ..................................................................................................... 34 4.4 Flow Control Facilities Preliminary Analysis and Sizing .......................................................... 36 Stormwater Technical Information Report King County Parks – Renton Shop Central Maintenance Facility Replacement Project ii | June 16, 2021 4.4.1 Detention Vaults Flow Control Storage ...................................................................... 36 4.5 Water Quality Treatment Facilities Analysis, Sizing, and Design Criteria ............................... 37 4.5.1 Detention Vaults Presettling Storage and Surface Area ............................................ 37 4.5.2 Coalescing Plate Oil Water Separators...................................................................... 37 4.5.3 Modular Wetland System Filters ................................................................................ 38 4.6 Infiltration Facilities Analysis, Sizing, and Design Criteria ...................................................... 39 4.6.1 Bioretention Cell ......................................................................................................... 39 4.6.2 Infiltration Gallery ....................................................................................................... 40 5 Conveyance System Analysis and Design ........................................................................................ 41 5.1 Storm Drain System Components and Layout ........................................................................ 41 5.2 Storm Drain System Analysis and Design Criteria .................................................................. 42 6 Special Reports and Studies ............................................................................................................. 47 7 Other Permits .................................................................................................................................... 47 8 Construction Stormwater Pollution Prevention.................................................................................. 48 8.1 Construction Activities and Sequencing .................................................................................. 48 8.2 ESC Plan and BMP Measures ................................................................................................ 49 8.3 SWPPS BMP Measures .......................................................................................................... 51 9 Bond Quantities and Declaration of Covenant .................................................................................. 52 10 Operations and Maintenance Manual ............................................................................................... 52 11 References ........................................................................................................................................ 54 Tables Table 1. Existing Threshold Discharge Areas Land Cover ........................................................................ 17 Table 2. Proposed Threshold Discharge Areas Land Cover ..................................................................... 18 Table 3. Change in Threshold Discharge Areas Land Cover .................................................................... 18 Table 4. Existing Conditions Hydrology Summary ..................................................................................... 29 Table 5. Proposed Conditions Hydrology Summary .................................................................................. 29 Table 6. Detention Vaults Flow Control Storage Sizing ............................................................................. 36 Table 7. Conveyance Storm Drain Hydrologic Analysis, West and East Drainage System ...................... 45 Table 8. Conveyance Storm Drain Hydraulic Analysis, West and East Drainage System ........................ 46 Table 9. CSWPPP Proposed Primary ESC BMP Measures ..................................................................... 50 Table 10. CSWPPP Proposed Primary SWPPS BMP Measures .............................................................. 51 Table 11. Summary of Proposed Stormwater Control Facilities Function and O&M Requirements ......... 52 Figures Figure 1. TIR Worksheet .............................................................................................................................. 2 Figure 2. Site Location and Critical Areas .................................................................................................... 7 Figure 3A. Existing Threshold Discharge Areas, Site Characteristics, and Downstream Flow Paths ................................................................................................................................................ 8 Figure 3B. Proposed Threshold Discharge Areas and Site Characteristics ................................................ 9 Stormwater Technical Information Report King County Parks – Renton Shop Central Maintenance Facility Replacement Project June 16, 2021 | iii Figure 4. Site Soils and Subsurface Characteristics .................................................................................. 10 Figure 5. Proposed On-site Stormwater Control Facilities ......................................................................... 31 Figure 6. Proposed Conveyance Drainage Areas and Storm Drain Systems ........................................... 43 Appendices Appendix A. Project Drainage Review Classification .................................................................................A-1 Appendix B. MGSFlood Hydrologic Analysis for Flow Control, Water Quality Treatment, Bioretention, and Infiltration Facilities ..............................................................................................B-1 Appendix C. Oil-Water Separator Coalescing Plate Pack Sizing and Infiltration Facilities Hydraulic Analysis ........................................................................................................................................... C-1 Appendix D. Storm Drain Conveyance System Hydrologic and Hydraulic Analysis ................................ D-1 Appendix E. Geotechnical Report ..............................................................................................................E-1 Appendix F. Site Improvement Drawings (submitted separately) .............................................................. F-1 Appendix G. O&M Requirement Cut Sheets for Proposed Stormwater Control Facilities ....................... G-1 Stormwater Technical Information Report King County Parks – Renton Shop Central Maintenance Facility Replacement Project iv | June 16, 2021 Acronyms and Abbreviations ac acre bgs below ground surface BMP best management practice CESF chitosan enhanced sand filtration cf cubic foot/feet cfs cubic feet per second CMF Central Maintenance Facility COR City of Renton CR Core Requirement CSWPPP construction stormwater pollution prevention plan ESC erosion and sediment control GIS geographic information system GULD General Use Level Designation LID low-impact development MOU Memorandum of Understanding MWS Modular Wetland System NPDES National Pollutant Discharge Elimination System NPGPS non-pollution generating pervious surface O&M operations and maintenance OWS oil-water separator PGIS pollution generating impervious surface PGPS pollution generating pervious surface PIT pilot infiltration tests REC Recording RMC Renton Municipal Code RSWDM Renton Surface Water Design Manual sf square feet/foot SP Standard Plan SR Special Requirement SWPPS stormwater pollution prevention and spill control TDA threshold discharge area TIR Technical Information Report TPH total petroleum hydrocarbons TSS total suspended solids UIC Underground Injection Control Stormwater Technical Information Report King County Parks – Renton Shop Central Maintenance Facility Replacement Project June 16, 2021 | 1 1 Project Overview 1.1 Introduction and Purpose The purpose of this Technical Information Report (TIR) is to document the stormwater control facilities proposed and their design basis for the King County Department of Natural Resources and Parks – Parks and Recreation Division (King County Parks), Renton Shop - Central Maintenance Facility Replacement Project (Project). It is located within the City of Renton, Washington, generally between NE 3rd and NE 4th Street (to the north), NE 2nd Street and the Renton Transfer and Recycling Station (to the south), Jefferson Avenue NE (to the east), and a self-storage facility (to the west). The City of Renton (City) has lead permitting agency status for the Project, and as such, the facilities are being designed in compliance with the City’s surface water and stormwater requirements, and also for consistency with the City’s NPDES MS4 Phase II Permit. The Project is subject to drainage review under the 2017 City of Renton Surface Water Design Manual (2017 RSWDM). As required by Section 2.3 of that manual, this drainage report has been prepared in accordance with the City’s TIR format. The TIR is consistent with the 90% design of storm drainage improvements to serve proposed site redevelopment improvements. See Sections 1.1.1 through 1.1.3 for the Project background and a description of the existing site and proposed site re-development improvements. The TIR Worksheet, which provides a detailed summary of the Project and its proposed stormwater controls is included as Figure 1. The Project site location is shown in Figure 2. The Project site drainage subbasins, land cover and downstream flow paths for existing and proposed (redeveloped) site conditions are shown in Figures 3A and 3B respectively. Project site soils and subsurface characterization are shown in Figure 4. 1.1.1 Project Background King County Parks consists of more than 200 parks, 175 miles of regional trails, and 215 miles of backcountry trails, totaling more than 28,000 acres of property to operate and maintain. Their headquarters for operations and maintenance (O&M) is located at the Central Maintenance Facility (CMF), 3005 NE 4th Street in Renton (see Figure 2). It also houses the dispatch center for all O&M staff, fleet vehicle and large equipment storage, warehouse and inventory storage, and King County Parks’ event operations. King County Parks - Brenda Bradford206-477-2030201 South Jackson Street #700Seattle, Washington 98104Jim Rhodes, PE / Jerry Bibee, PE HDRLAND USE ID #584394Renton Shop - CMF Replacement3005 NE 4th Street, Renton, WAConditional Use PermitJanuary 15, 2019January 15, 201923N5E16206-826-4689 (Jim) / 253-432-5057 (Jerry)CR #1 - Discharge at Natural Location - Proposed adjustment to TDAs for full on-site infiltrationCR #2 - Off-site Analysis - Proposed adjustment from off-site analysis for full on-site infiltration CR #3 - Flow Control Facilities - Proposed adjustment from duration standard for full on-site infiltrationAugust, 2020Final June 2021JUNE 2021FINAL DRAFTRevised - December 2019Revised - December 2019August, 2020Final June 2021January 2019January 2019 Lower Cedar River City of Renton Surface Water Design Manual (December 2016) Highlands No stormwater operational monitoring for full infiltration;Construction monitoring under NPDES CGSP Possible wetland on parcel east of site On parcels to west and east of site Wellhead (aquifer) protection area - Zone 2 On parcels to south/east of site Arents/Everett underlain byrecessional glacial outwash Low0-2% Zone 2 - Maplewood10-yr capture zoneProposed infiltration (at depth) test wells JUNE 2021FINAL DRAFT Limited existing off-site sheet and concentratedflow paths to off-site infiltration. No off-site stormdrain connections exist or are proposed asidefrom overflow connection to south off-site closeddepression infiltration area for redundancy On-site TDAs P1 and P2 (east-west drainage split for proposed site grades)replace TDAs E1 and E2 (north-south drainage split for existing site grades);Other TDAs (P3 - P6 and E3 - E6 are for off-site drainage areas; all infiltrate) All discharges to infiltration;2 on-site; 1 off-site (overflow) Proposed adjustment forfull infiltrationFC (Level 2) notapplicable for fullinfiltration withoutdownstream surfacewater discharge Peak rate flow control for100 yr design dischargePresettling vault; CP OWSVault with Oil Control Baffle TBD TBD TBD King County Parks JUNE 2021FINAL DRAFT None exist or are required Industrial (Maintenace and Operations Facility) Roofs covering selected materials storage areas; perimeter berms isolating equipment wash pad (to sanitary sewer) King County Parks to maintain facilities Coalescing plate oil-water separators (CP OWS) (3) Pre-setlting and flow control storage vaults (2); Modular Wetland System (MWS)units (5); infiltration galleries overlaying sand filters (2) - See TIR Figure 5 layout Two drainage systems serving TDA P1 and P2 site areas - conveyance stormdrains leading to linear flow control vaults, then through CP OWS, MWS filterunits, to infiltration gallery underlain by sand filter; treated flow collection for re-use See TIR Table 7 for ProposedESC Measures JUNE 2021FINAL DRAFT Conveyance storm drains to presettling and detention (flow control) storage vaults (west and east); CP OWS units (2 - west, 1 - east); MWS filtration units (4 - west, 3 - east); infiltration galleries (west and east); all 100-year design capture, conveyance, storage, treatment, and infiltration. See Figure 5 for proposed stormwater control facilities layout (Final TIR to be signed) Draft TIR dated Janurary 15, 2019 Linear precast vaultsflow control storage TIR Figure 5 Infiltation galleries(100-yr) Collection/pumpingof a portion of treatedrunoff to AG storagetanks for irrigation re-use Rain garden /bioretention cell Linear precast vaultspresettling storage MWS Linear filters;sand filters Coalescing plate OWS Floating oil booms; teerisers; oil control baffles Rain garden / bioretention cell;Infiltration galleries (100-yr) Off-site south parceloverflow path / closeddepression infiltration area Treatment to 100-yrdetention outflow JUNE 2021FINAL DRAFT MWS linear filters June 11, 2021 Pervious Landscaped Areas Compost Soil Amendment DATE FIGURE CITY OF RENTON IT-GIS | PICTOMETRY, KING COUNTY CITY OF RENTON PROJECT LOCATION SITE BOUNDARY POSSIBLE WETLAND WELLHEAD (AQUIFER) PROTECTION AREA (ZONE 2) REGULATED SLOPES PROJECT SITE: KING COUNTY PARKS AND RECREATION RENTON SHOP - CENTRAL MAINTENANCE FACILITY (5.71 ACRES) POSSIBLE WETLAND WELLHEAD (AQUIFER) PROTECTION AREA - ZONE 2 MAPELEWOOD 10-YR CAPTURE ZONE SAND AND GRAVEL MINING PIT SITE (PRIVATE) REGULATED SLOPES SELF STORAGE FACILITY SITE (PRIVATE) KING COUNTY (RENTON) TRANSFER STATION SITE COMMERCIAL SITE (PRIVATE) KING COUNTY INDUSTRIAL SITE JUNE 2021 2RENTON SHOP - CENTRAL MAINTENANCE FACILITY REPLACEMENT AND CRITICAL AREAS SITE LOCATION KING COUNTY PARKS AND RECREATION DATE FIGURE JUNE 2021 3ARENTON SHOP - CENTRAL MAINTENANCE FACILITY REPLACEMENT AND DOWNSTREAM FLOW PATHS AREAS, SITE CHARACTERISTICS, EXISTING THRESHOLD DISCHARGE KING COUNTY PARKS AND RECREATION TDA E3 (EAST, OFF-SITE): 0.52 ACRES TDA E5 (NORTH, OFF-SITE): 0.55 ACRES TDA E4 (SOUTH, OFF-SITE): 4.89 ACRES OFF-SITE CITY STORM DRAIN WITH DOWNSTREAM OUTFALL CONNECTION TO CEDAR RIVER TDA E1 (NORTH): 2.96 ACRES TDA E2 (SOUTH): 2.79 ACRES TDA E6 (WEST): 0.29 ACRES NE 4TH ST NE 3RD S T MONROE AVE NEJEFFERSONAVE NENE 4TH ST NE 2ND ST POLLUTION GENERATING IMPERVIOUS SURFACE (PGIS) NON-POLLUTION GENERATING IMPERVIOUS SURFACES (NPGIS) NON-POLLUTION GENERATING PERVIOUS SURFACE (NPGPS) POLLUTION GENERATING PERVIOUS SURFACE (PGPS) EXISTING THRESHOLD DISCHARGE AREAS (TDA) BOUNDARIES EXISTING DOWNSTREAM FLOW PATH SITE BOUNDARY EXISTING BUILDINGS EXISTING ROADS EXISTING DEPRESSION / INFILTRATION AREA SHEET DRAINAGE FLOW PATH DATE FIGURE JUNE 2021 3BRENTON SHOP - CENTRAL MAINTENANCE FACILITY REPLACEMENT AREAS AND SITE CHARACTERISTICS PROPOSED THRESHOLD DISCHARGE KING COUNTY PARKS AND RECREATION POLLUTION GENERATING IMPERVIOUS SURFACE (PGIS) NON-POLLUTION GENERATING IMPERVIOUS SURFACES (NPGIS) NON-POLLUTION GENERATING PERVIOUS SURFACE (NPGPS) POLLUTION GENERATING PERVIOUS SURFACE (PGPS) THRESHOLD DISCHARGE AREAS (TDA) BOUNDARIES SITE BOUNDARY EXISTING BUILDINGS EXISTING ROADS TDA P3 (EAST, OFF-SITE): 0.48 ACRES TDA P5 (NORTH, OFF-SITE): 0.63 ACRES TDA P4 (SOUTH, OFF-SITE): 4.99 ACRES TDA P2 (EAST): 2.34 ACRES TDA P1 (WEST): 3.21 ACRES TDA P6 (WEST): 0.31 ACRES BUILDING A BUILDING B BUILDING C NE 4TH ST NE 3RD S T MONROE AVE NEJEFFERSONAVE NENE 4TH ST NE 2ND ST DATE FIGURE BORING BORING DEPTH (FT) GROUND SURFACE ELEV (FT, NAVD88) GLACIAL OUTWASH ELEV (FT, NAVD88) DEPTH TO GROUNDWATER BELOW GROUND SURFACE (FT) B-1 27 328.8 NOT AVAILABLE NO WATER ENCOUNTERED B-2 27 329.6 NOT AVAILABLE NO WATER ENCOUNTERED B-3 27 -NOT AVAILABLE NO WATER ENCOUNTERED B-4 27 329.9 NOT AVAILABLE NO WATER ENCOUNTERED B-5 27 329.9 NOT AVAILABLE NO WATER ENCOUNTERED B-6 17 -NOT AVAILABLE NO WATER ENCOUNTERED AB-01 20 330 323 NO WATER ENCOUNTERED AB-02 20 330 324 NO WATER ENCOUNTERED AB-03 15 330 320 NO WATER ENCOUNTERED AB-04 15 330 323 NO WATER ENCOUNTERED SOIL TYPE An SOIL TYPE PITS B-2 AB-03 AB-04 AB-01 AB-02 B-5 B-4 B-1 JUNE 2021 4RENTON SHOP - CENTRAL MAINTENANCE FACILITY REPLACEMENT SUBSURFACE CHARACTERISTICS SITE SOILS AND KING COUNTY PARKS AND RECREATION SOIL TYPE An (ARENTS, EVERETT MATERIAL) SOIL TYPE PITS SITE BORINGS INFILTRATION MONITORING WELL SITE BOUNDARY B-3 NE 3RD S T MONROE AVE NEJEFFERSON AVE NENE 4TH ST NE 2 N D ST BORING GROUND SURFACE ELEV (FT, NAVD88) MAX DEPTH OF WELL (FT) GLACIAL OUTWASH ELEV (FT, NAVD88) DEPTH TO GROUNDWATER BELOW GROUND SURFACE (FT) GROUNDWATER EL (FT, NAVD88) GEOTECH RECOMMENDED SUBGRADE PERMEABILITY (IN/HR) MW-01 325.0 76.5 321 MW-02 325.0 76.5 320 MW-01 MW-02 Stormwater Technical Information Report King County Parks – Renton Shop Central Maintenance Facility Replacement Project June 16, 2021 | 11 King County Parks is redeveloping the existing CMF with a new and improved facility on Parcel No. 1434000012. The existing post-World War II-era facility is aging, is not connected to the City’s sanitary sewer system, and cannot accommodate the planned expansion of staff, equipment, and vehicles. The replacement facility, developed on the same site, will be called the King County Parks - Renton Shop. The Renton Shop will address future service needs, be built to current building and environmental compliance standards, and will accommodate projected future staff growth. The Renton Shop will allow for additional consolidation of other King County Parks maintenance districts to the site, greatly improving the function and space for shop operations, enhancing vehicle and pedestrian safety within the facility with better site circulation and flow, and providing needed office space, meeting rooms, storage and shop space to support planned growth. 1.1.2 Existing Project Site and Adjacent Properties Description The Project site was subdivided into a 5.71-acre (248,672 square foot) parcel from a larger County- owned property in 2016 (REC #20160303900006) and is zoned light industrial. Adjacent land uses include: • North: A former King County Public Health office building recently purchased for redevelopment by Renton Technical College • South: A vehicle and equipment storage yard owned by King County Roads Division • East: The Jefferson Avenue NE access road together with an adjacent vacant private parcel that historically was mined for sand and gravel, and that now accepts fill material under a City grading permit • West: A self-storage business The Project site is generally flat with a slight slope downward from east to west. Along the western property line is a short section of steeper slope extending west to the self-storage business. City critical areas mapping (City of Renton Maps, accessed June 2018) shows this steeper section as a Regulated Slope, between 15 and 25 percent slope. The site is also within the City’s Wellhead Protection Area, Zone 2. The Project site has two existing primary buildings: one houses administrative and supervisory staff, and the other building is for the field crews. There are additional areas for covered storage structures, maintenance and construction laydown yard, fleet vehicle parking, and employee parking. The site is surfaced primarily with gravel and some limited, localized areas of pavement. There are few trees or landscaping with the exception of a small pocket adjacent to the administration building and along the west site boundary. The facility is accessed via a single driveway off the King County- owned private street along the east property line (Jefferson Avenue NE). 1.1.3 Project Redevelopment Proposal Description The Renton Shop will modernize the site and provide additional capacity to meet current and future demand for staff space and equipment/fleet vehicle storage. The Project redevelopment proposal includes the following major construction and improvement features: • Demolition of all existing buildings • Utility work to connect the Project site to the City sanitary sewer system, providing sewer service capacity across the site and to the south, and to relocate, extend, and upsize the water main serving the site along Jefferson Avenue NE Stormwater Technical Information Report King County Parks – Renton Shop Central Maintenance Facility Replacement Project 12 | June 16, 2021 • Storm drainage improvements to serve all Project site and frontage road improvements consistent with the City’s current stormwater management standards, with goals for full infiltration of site runoff after on-site detention storage and robust water quality treatment protective of the City’s underlying aquifer protection zone • Implementation of sustainable low-impact development (LID) on-site stormwater BMPs, including a planted bioretention cell proposed to infiltrate Building A roof runoff • Site preparation for paving (asphalt pavement), building construction, and landscaping • Construction of 3 buildings with area footprints of: - Administration Building A = 16,500 square feet - Shops Building B = 14,500 square feet - Covered Storage Building C = 11,000 square feet • Administration building housing conference room space, supervisor offices, crew workstations, and multiple restrooms • A large equipment and vehicle covered parking area and outdoor wash area • Miscellaneous sheds for chemical storage, such as fuel containers, fertilizers, pesticides, and equipment maintenance fluids • 182 parking spaces for visitors and staff, including five electric vehicle charging spaces and seven accessible (Americans with Disabilities Act Adult Guideline compliant) spaces • Perimeter chain link and security fencing to cordon off the shops, storage, and fleet vehicle and equipment storage area • Improved site circulation for large delivery trucks with the addition of a second driveway off the private access road • Sustainable building design features, such as net zero energy, with an aspirational goal to implement portions of Living Building Challenge, to improve energy efficiency and result in lower life cycle costs than a conventional building design • Space designated on-site for future Administration Building A expansion area The Administration Building A will be oriented to take advantage of the southern exposure and southerly winds to act as natural ventilation and cooling. The Shops Building B is more centrally located on the site. Along the north and west boundaries, a variety of storage areas will include ecology block material storage bins, utility trailers and other equipment parking, and Building C. 1.2 Existing Conditions 1.2.1 Site Topography, Drainage, Land Cover, Soils, and Groundwater The Project site topography is relatively flat, sloping gently to the west from the east site entry at Jefferson Avenue NE (averaging approximately 1 percent) to a low point approximately 400 feet to the east, then sloping gently back up to the west site boundary. The entry access road forms a slight topographic ridge, with site drainage split between the south and north portions of the site. The south site area drains along a shallow swale at a longitudinal slope of less than 0.5 percent to an off-site discharge location along the southeast site boundary. The north portion of the site is Stormwater Technical Information Report King County Parks – Renton Shop Central Maintenance Facility Replacement Project June 16, 2021 | 13 essentially flat (less than 0.5 percent grades in the north-central and northeast site areas) with a few small depressions where some infiltration occurs. A low point exists about midway between the east and west site boundaries. Excess runoff generally flows via sheet drainage to the north where it is dispersed by sheet flows across a vegetated slope on the adjacent parcel to the north. A steeper vegetated slope exists along the west site boundary, typically ranging from 15 to 25 percent or greater. The slopes on the developed (north) portion of the adjacent south King County parcel are generally consistent with site grades, sloping gently to the west to a low point along a drainage swale, then sloping to the south. This King County industrial site to the south, together with the south portion of the Project site, collectively drain and discharge excess runoff to a closed depression (infiltration) area on the undeveloped portion of the that south parcel. On the east side of Jefferson Avenue NE, slopes drop steeply into a deep closed depression area (a prior private sand and gravel mining pit). The site land cover consists of a mix of existing buildings and covered storage/maintenance service areas, with collective roof areas totaling about 19,000 square feet (sf). The remainder of the site consists of paved and other gravel surfaces suitable for truck and maintenance vehicle access throughout the site. A few small pockets of vegetated landscape (trees, shrubs, grass) totaling approximately 1,500 sf exist at the east end of the largest site building. Some container and uncovered bin material storage areas exist along the east, north, and south site boundaries. Slopes to the east and north of the site are primarily vegetated with trees, shrubs, and grasses. Soils within the site area below the gravel or asphalt surfacing layer generally consist of a silty gravel and sand fill material, with variable depths below ground surface (bgs) ranging from 1.5 to 10 feet. That fill material is underlain by native glacial outwash soils - recessional stratified drift, glacial-fluvial deposits (Qpa) (Aspect 2019). Those underlying outwash soils typically consist of medium-dense, well-graded to poorly-graded sands (SW or SP) with gravels and some cobbles. Fines content is low, and therefore those soils are expected to provide significant infiltration potential. For the deepest prior site boring (extending approximately 27 feet bgs), no underlying till or less permeable boundary soil layer was detected and perched or deep groundwater was also not encountered. Two monitoring wells were subsequently installed by Aspect in mid-April 2019 (See Figure 4, MW-01 and MW-02). Groundwater level data collected during that period reported site groundwater levels to be approximately 67 to 68 feet bgs. Seasonal variations in the groundwater levels are expected, but levels in April should be representative of or close to the highest expected annual groundwater levels. 1.2.2 Existing Drainage Basin and Threshold Discharge Areas The Project site is located within the Lower Cedar River drainage basin. As noted previously, existing site drainage does appear to fully infiltrate either on-site or off-site on adjacent parcels. Based on the City’s GIS utilities database (City of Renton 2018), there are currently no existing storm drainage connections to the site from City drainage systems in NE 3rd Street to the north, and NE 1st Street to the south. Those off-site drainage systems, located within City right-of-way, tie together downstream of the site and collectively discharge to a Lower Cedar River outfall. The existing site area and off-site areas surrounding the site, including the adjacent off-site east access road area (Jefferson Avenue NE), are broken down into six threshold discharge areas (TDAs). Since the affected Project areas drain to various on-site and off-site infiltration areas, the TDAs were defined around those infiltration discharge locations, which are different from conventional TDAs definition relating to the manner of downstream surface water discharge Stormwater Technical Information Report King County Parks – Renton Shop Central Maintenance Facility Replacement Project 14 | June 16, 2021 connections within 0.25 mile of project boundaries. The existing condition TDAs including their boundaries, drainage areas and patterns, discharge locations, and available water quality treatment are summarized below and are illustrated in Figure 3A. TDA E1 TDA E1 includes the north portion of the Project site, north of central site access road, together with the north portion (west half) of Jefferson Avenue NE road frontage that currently sheet drains onto the site (see Figure 3A). The TDA E1 tributary drainage area totals 2.96 acres. As described previously, excess runoff from TDA E1 generally sheet flows to the north site boundary with off-site dispersed discharge to existing vegetated slopes along the north-central and northwest portions of the site. The TDA E1 tributary area is classified as both pollution generating impervious surface (PGIS) for westerly paved areas and pollution generating pervious surface (PGPS) for the east graveled area. In accordance with the 2017 RSWDM, those graveled surfaces would typically classify as PGIS, but since they currently partially infiltrate runoff under existing conditions and are being fully retrofitted for treatment controls, they were considered PGPS for purposes of drainage evaluation. This area includes some small areas of non-pollution generating pervious surface (NPGPS) associated with the limited vegetated surfaces. Drainage from TDA E1 does not currently receive water quality treatment other than incidental filtration treatment provided by the off-site vegetated flow path prior to off-site infiltration. TDA E2 TDA E2 includes the south portion of the Project site, south of the central site access road, together with the south portion (west half) of Jefferson Avenue NE road frontage that currently sheet drains onto the site (see Figure 3A). The TDA E2 tributary drainage area totals 2.79 acres. As described previously, drainage from TDA E2 generally sheet flows to the west, then along a shallow drainage swale with off-site discharge across an off-site extension of that swale to the adjacent King County parcel to the south, then along vegetated surfaces to a closed depression/infiltration area on the undeveloped portion of that south parcel. The TDA E2 tributary area is classified as a split between PGIS and PGPS. Drainage from TDA E2 does not currently receive water quality treatment, except for incidental downstream treatment as described for TDA E4 TDA E3 TDA E3 includes that portion of the off-site Jefferson Avenue NE roadway and shoulders fronting and extending south of the Project site that do not sheet drain onto the project site, and alternatively sheet drain onto adjacent parcels to the east and south of the Project site (see Figure 3A). The TDA E3 tributary drainage area totals 0.52 acres. The TDA E3 tributary area is classified as PGIS. Drainage from TDA E3 does not currently receive water quality treatment. TDA E4 TDA E4 includes the off-site area extending south of the Project site that includes the closed depression area west of the King County/Renton Transfer Station (see Figure 3A). The south portion of the existing site delivers excess runoff to that area for infiltration in that depression, beyond that portion that infiltrates through pervious on-site areas. The TDA E4 tributary drainage area totals 4.89 acres. The north developed portion of the TDA E4 tributary area is classified as a split between PGIS and PGPS, and the south and west undeveloped portions are classified as Stormwater Technical Information Report King County Parks – Renton Shop Central Maintenance Facility Replacement Project June 16, 2021 | 15 NPGPS. Drainage from TDA E4 does not currently receive water quality treatment, other than incidental treatment provided along the vegetated portions of the flow path prior to off-site infiltration. TDA E5 TDA E5 includes the off-site vegetated slope area extending north of the Project site that appears to infiltrate runoff from the north portion of the site, beyond that portion that infiltrates through TDA E1 pervious site areas (see Figure 3A). The TDA E5 tributary drainage area totals 0.55 acres. The TDA E5 tributary area is classified as NPGPS. Drainage from TDA E5 does not currently receive water quality treatment, other than incidental treatment provided along the vegetated sheet flow path prior to infiltration. TDA E6 TDA E6 includes the vegetated slope area along the west side of the Project site that appears to infiltrate precipitation that falls directly on that slope area (see Figure 3A). The TDA E6 tributary drainage area totals 0.29 acres. The TDA E6 tributary area is classified as NPGPS. Drainage from TDA E6 does not currently receive water quality treatment, other than incidental treatment provided along the vegetated slope prior to infiltration. 1.3 Proposed Conditions 1.3.1 Site Grading, Drainage, Land Cover, and Soils Proposed improvements associated with Project redevelopment are shown conceptually in 3B and are briefly described as part of the proposed TDAs below. Beyond new administrative, shop, and covered storage buildings (Buildings A, B, and C respectively), walkways, a vegetated bioretention cell, and other vegetated planter areas, the redeveloped site will include new asphalt concrete paving that replaces existing pavements and gravel surfaces. Drainage from the replaced impervious/hard surfaces will be collected conventionally using catch basin inlets installed at low points and along interior and perimeter curbing. Existing buildings and surfacing will be removed and the site will be re-graded. Existing fill materials will be partly removed and replaced with imported select fill materials including drain rock above subgrade in the infiltration gallery areas and pavement base materials. Some reuse of suitable excavated materials as compacted backfill associated with site grading is also expected to minimize the off-site export of excavated materials. 1.3.2 Proposed Threshold Discharge Areas and Drainage Systems The proposed condition TDAs including their boundaries, drainage areas and patterns, discharge locations, and proposed detention storage and water quality treatment are generally summarized below. Please note that the TDA boundaries for proposed site conditions require some adjustment from existing conditions corresponding to required site grading adjustments for site redevelopment improvements. TDA P1 TDA P1 includes primarily the west portion of the redeveloped Project site that will be served by a new on-site drainage system (west drainage system) inclusive of new conveyance systems, detention flow controls, runoff treatment facilities, and infiltration gallery components (see Figure 3B). The TDA P1 tributary drainage area totals 3.21 acres. Drainage from this tributary area will be Stormwater Technical Information Report King County Parks – Renton Shop Central Maintenance Facility Replacement Project 16 | June 16, 2021 collected in catch basins and will be conveyed through various new storm drains that connect to a linear detention vault providing both presettling (permanent pool) storage and active detention storage. Attenuated flows exiting the storage vault will pass through a flow control manhole with orifice flow control to parallel coalescing plate oil-water separators (OWS), then through parallel Modular Wetland units. Discharge from those treatment facilities will be conveyed through perforated dispersal pipes within a drain rock infiltration gallery. The fully treated runoff will then be infiltrated over subgrade soils. The tributary area includes a bioretention cell that will collect roof runoff from the Building A roof, with an overflow connection to the west detention, treatment, and infiltration facilities. TDA P2 TDA P2 includes primarily the east portion of the redeveloped Project site that will be served by a new on-site drainage system (east drainage system) inclusive of new conveyance systems, detention flow controls, runoff treatment facilities, and infiltration gallery components (see Figure 3B). The TDA P2 tributary drainage area totals 2.34 acres. Drainage from this tributary area will be collected in catch basins and will be conveyed through various new storm drains that connect to a linear detention vault providing both presettling (permanent pool) storage and active detention storage. Attenuated flows exiting the storage vault will pass through a flow control manhole with orifice flow control to a coalescing plate oil-water separator (OWS), then through parallel Modular Wetland units. Discharge from those treatment facilities will be conveyed through perforated dispersal pipes within a drain rock infiltration gallery. The fully treated runoff will then be infiltrated over subgrade soils. An emergency overflow storm drain connection is also included that provides connection of the east and west detention vault and treatment systems. TDA P3 TDA P3 is consistent with TDA E3, except for changes in off-site Jefferson Avenue NE shoulder and adjacent slopes land cover associated with proposed linear utility line installations to serve the Project site (see Figure 3B). The TDA P3 tributary drainage area totals 0.48 acres. TDA P3 land cover is expected to include some small adjustments in roadway shoulder PGIS associated with installation of those utility lines. Since those improvements are associated with linear utility lines installation, they should be exempt from stormwater requirements aside from construction stormwater runoff control. TDA P4 TDA P4 is consistent with TDA E4, except for minor change in grading along the south site boundary that slightly adjusts the north TDA limit (see Figure 3B). The TDA P4 tributary drainage area totals 4.99 acres. TDA P4 land cover is expected to slightly increase the pervious area coverage with some limited conversion of PGIS to NPGPS associated with the south site fringe area grading changes. No stormwater control requirements for these small fringe area land cover conversions (from impervious to pervious) are expected. TDA P5 TDA P5 is consistent with TDA E5, except for a minor change in grading along the north site boundary that slightly adjusts the south TDA limit, along with a narrow corridor for other off-site utility improvements extending to and across NE 3rd Street (see Figure 3B). The TDA P5 tributary drainage area totals 0.63 acres. TDA P5 land cover is expected to slightly increase the pervious Stormwater Technical Information Report King County Parks – Renton Shop Central Maintenance Facility Replacement Project June 16, 2021 | 17 area with some limited conversion of PGIS to NPGPS associated with the north site fringe area grading changes. No stormwater control requirements for these small fringe area land cover conversions (from impervious to pervious) are expected. TDA P6 TDA P6 is consistent with TDA E6, except for a minor change in on-site grading along the west site boundary that slightly adjusts the east TDA limit (see Figure 3B). The TDA P6 tributary drainage area totals 0.31 acres. TDA P6 land cover is not expected to change since it is entirely NPGPS. No stormwater control requirements for these small pervious area changes within TDA P6 are expected. 1.4 Land Cover and Change Summary A summary of the existing and proposed land cover areas within the TDAs, which classifies the surface areas as PGIS, NPGIS, PGPS, and NPGPS is provided in Tables 1 and 2 respectively. Examples of those surfaces include pavement (PGIS), roofs (NPGIS), existing gravel surfaces (PGPS), and landscape surfaces (NPGPS). Compacted gravel surfaces accessible to traffic are normally considered as PGIS under 2017 RSWDM definition. However, since partial site infiltration is occurring through those surfaces, they have been assessed as PGPS in hydrologic analysis under existing conditions for this project. This is more consistent with the reduced runoff response expected from those surfaces compared to paved impervious surfaces under proposed conditions. Those gravel surfaces are being fully retrofitted with stormwater pre-settling, flow attenuation, and treatment controls through the 100-year event as required in the 2017 RSWDM. Therefore, an alternative determination of PGIS versus PGPS for those surfaces would not affect improvement needs. TDA areas were broken down by surface areas in those various land cover categories for existing and proposed conditions and are shown graphically in Figures 3A and 3B. Table 3 provides a comparative land cover change summary associated with each TDA for the Project site redevelopment. The results comparison for TDA 1 and 2 were combined to be representative of the total site area minus some fringe area effects, since the TDA boundaries for existing and proposed conditions are different. Table 1. Existing Threshold Discharge Areas Land Cover TDA Existing Surface Areas (sf) Total Area (acre) Impervious (%) PGIS NPGIS PGPS NPGPS Impervious Pervious E1 31,699 12,649 83,024 1,482 1.02 1.94 34.4 E2 27,548 6,739 86,971 0 0.79 2.00 28.3 E3 10,963 11,522 0 0 0.52 0 100 E4 33,573 0 57,586 121,166 0.77 4.12 15.8 E5 0 0 0 23,774 0 0.55 0 E6 0 0 0 12,778 0 0.29 0 Totals for Collective TDAs 11.99 25.8 Stormwater Technical Information Report King County Parks – Renton Shop Central Maintenance Facility Replacement Project 18 | June 16, 2021 Table 2. Proposed Threshold Discharge Areas Land Cover TDA Proposed Surface Areas (sf) Total Area (acre) Impervious (%) PGIS NPGIS PGPS NPGPS Impervious Pervious P1 99,800 40,075 0 0 3.21 0 100.0 P2 88,135 0 0 13,700 2.02 0.32 86.5 P3 18,141 2,966 0 0 0.48 0 100 P4 33,319 493 57,586 125,860 0.78 4.21 15.6 P5 0 0 0 27,358 0 0.63 0 P6 0 0 0 13.353 0 0.31 0 Totals for Collective TDAs 11.96 54.3 Table 3. Change in Threshold Discharge Areas Land Cover TDA Comparison Proposed to Existing Surface Areas Change (sf) Total Area Change (acre) Impervious Change (%) PGIS NPGIS PGPS NPGPS Impervious Pervious P1+P2/ E1+E2 128,688 20,687 -169,995 12,218 3.42 -3.62 65.6 P3/E3 7,178 -8,557 0 0 -0.03 0 0 P4/E4 -254 493 0 4,194 0.01 0.10 -0.2 P5/E5 0 0 0 3,585 0 0.08 0 P6/E6 0 0 0 575 0 0.01 0 Total for Collective TDAs -0.03 28.5 2 Conditions and Requirements Summary 2.1 Drainage Review Classification for Project This Project is subject to the City of Renton’s Municipal Code 4-6-030, Drainage (Surface Water) Standards. City Ordinance 5828, effective January 1, 2017, amended that code section to adopt the City of Renton 2017 Surface Water Design Manual (RSWDM) based on the City’s amendments to the 2016 King County Surface Water Design Manual. The 2017 RSWDM is applicable to Renton projects with permit application after the effective date of the updated manual. This Project is required to provide a Full Drainage Review because it meets the following criteria in Section 1.1.1, Figure 1.1.2.A (see Appendix A), and Section 1.1.2.4 of the 2017 RSWDM: • Results in greater than 2,000 square feet of new impervious surface, replaced impervious, or new plus replaced impervious surfaces • Results in greater than 7,000 square feet of land disturbing activity • Constructs or modifies a pipe 12 inches or more in size/depth • Is a redevelopment project proposing improvements of more than $100,000 to an existing high-use site • Is under 50 acres in size Stormwater Technical Information Report King County Parks – Renton Shop Central Maintenance Facility Replacement Project June 16, 2021 | 19 Projects that trigger a Full Drainage Review are required to demonstrate that the project complies with all nine core requirements (CR) and all five special requirements (SR). Sections 2.1 and 2.2 below provide a summary of how the project will comply with these core and special requirements respectively. Where a particular requirement is not specifically applicable to the Project, the basis for that determination is provided. 2.2 Core Requirements and Project Applicability The following 2017 RSWDM Core Requirements (CR) were evaluated for applicability under the Project’s Full Drainage Review requirement. 2.2.1 CR #1: Discharge at the Natural Location All stormwater runoff and surface water from a project must be discharged at a natural location so as not to be diverted onto or away from a downstream property. The Project site stormwater must be discharged in a manner that does not create a significant adverse impact to downstream properties or to off-site drainage facilities. Drainage facilities are defined as constructed or engineered features that collect, convey, store, treat, or otherwise manage surface water or stormwater runoff. Existing drainage discharge from the Project site and east frontage roadway, beyond that portion that currently discharges through infiltration over the relatively flat site, is primarily by sheet flow discharge onto adjacent properties over existing slopes. An off-site drainage channel does exist that extends to the southeast off the Project site. No improved on-site drainage system currently exists. The magnitude of off-site discharges north and south under 100-year event conditions is expected to exceed 1 cubic foot per second (cfs), although off-site discharges from the smaller fringe areas is expected to be significantly lower than that threshold. The proposed drainage system will collect stormwater runoff from the entire Project site and abutting improved east access road area, will store/presettle/attenuate that runoff, will provide oil control and enhanced water quality filtration treatment, and will infiltrate that runoff through on-site drain rock infiltration galleries (two systems, east and west proposed). The Project site native subsurface soils underlying upper elevation zone fill material are classified as glacial outwash and are expected to be well-suited to a full infiltration approach. No off-site surface water discharges or improved storm drainage conveyance systems extending downstream from the Project site are proposed, and therefore, increases in off-site runoff will not occur under this on-site stormwater management approach. Runoff discharged through infiltration is expected to contribute to aquifer storage and downstream interflow and may result in controlled base flow contributions to off-site surface water systems. Review of the City GIS mapping does no show evidence of documented wetlands in close proximity to the Project site that could be indirectly affected by changes in the hydrologic regime. One potential wetland exists in the adjacent parcel gravel pit area to the east of the site, but it is not expected to be affected by the project improvements. Since there would be an increase in Project site infiltration, coupled with a decrease in off-site surface discharges (no surface discharge would result), it is expected that the City could grant a Standard Adjustment from CR #1 (if needed). Stormwater Technical Information Report King County Parks – Renton Shop Central Maintenance Facility Replacement Project 20 | June 16, 2021 2.2.2 CR #2: Off-site Analysis Projects are required to conduct a Level 1 off-site analysis in accordance with Section 1.1.2 of the 2017 RSWDM. That analysis needs to assess potential off-site drainage and water quality impacts associated with the site redevelopment proposal. An exception can be granted if the City determines that there is sufficient information to conclude that a project will not have a significant adverse impact on the downstream and/or upstream drainage system. Given that the Project proposes full runoff containment, enhanced treatment, and infiltration to the 100-year event level-of- protection, and with no off-site surface water discharge, the applicant requests that the City grant an exception to the need for full off-site analysis beyond the preliminary off-site analysis included in Section 3. 2.2.3 CR #3: Flow Control Facilities Projects with land cover changes above certain minimum thresholds, typically with added and/or replaced impervious/hard surfaces exceeding 5,000 square feet, must provide on-site flow control facilities to mitigate the potential impacts of the added stormwater runoff from targeted surfaces in a manner and to levels defined in the 2017 RSWDM. However, there are flow control exemptions that can eliminate or reduce the need for application of CR #3. Based on the City’s Flow Control Application Map in the 2017 RSWDM, and consistent with Project pre-application responses, the City has determined that the Project is subject to flow control criteria defined as the Flow Control Duration Standard – Matching Forested site conditions, but only for areas draining to streams and subject to flow-related water quality problems such as erosion or sedimentation. The Project does not propose off-site surface discharge connections under the full infiltration proposal. Under those conditions, the flow control standard is not applicable, and a Standard Adjustment to CR #3 is therefore being requested from the City. An alternative flow control approach is included that provides up to 100-year event peak rate control in on-site, linear detention vaults to achieve an attenuated discharge rate equivalent to the design capacity of the proposed on- site treatment and infiltration facilities. Under this flow control approach, site conveyance, detention, treatment and infiltration facilities would provide required stormwater control functions and protections up through the 100-year event. The alternative flow control standard, proposed design, and analysis are discussed in more detail in Section 4. 2.2.4 CR #4: Conveyance System All engineered conveyance system elements of the Project must be analyzed, designed, and constructed to provide a minimum level of protection against overtopping, flooding, erosion, and structural failure, with the following criteria applicable for new conveyance systems associated with the Project site redevelopment proposal: • Provide storm drain system and culvert capacities to convey and contain at minimum the 25- year peak flow for developed conditions from on-site tributary areas, and existing conditions from off-site tributary areas. • Check the conveyance capacity up to the proposed conveyance system under 100-year flood flows (overflow above 25-year event permitted) to confirm it does not aggravate an existing severe flooding or erosion problem, and that any overflow is contained on-site and flows to the natural discharge location. Stormwater Technical Information Report King County Parks – Renton Shop Central Maintenance Facility Replacement Project June 16, 2021 | 21 • Where feasible, conveyance systems should be constructed using vegetation-lined channels as opposed to pipe systems, except for required pipe conveyance systems under roadways, driveways, parking areas, and for roof runoff. • Provide conveyance systems outfall energy dissipation (rock pad at minimum); where the discharge is onto a steep slope, a tight-line conveyance system must be constructed to the bottom of slope, with energy dissipation provided at that location. • Provide spill control for new conveyance systems that receive runoff from non-roof pollution generating impervious surfaces (PGIS) consistent with Section 4.2.1.1 of the 2017 RSWDM. • Where on-site pump systems are needed to convey water within the site, those systems need to meet the design criteria requirements of Section 4.2.3 of the 2017 RSWDM. The Project site redevelopment proposal will result in the installation of an on-site gravity collection and conveyance system serving the new and replaced impervious/hard surfaces as well as created pervious vegetated surfaces. This conveyance system is limited to various 12-inch storm drains along with a few, short 18-inch segments that connect to two constructed primary storage, treatment, and infiltration systems, one in the west portion of the site, and the other in the east portion of the site. Those systems are collectively designed for 100-year conveyance capacity without overflow under maintained operations. The conveyance system design standards, proposal, and analysis are discussed in more detail in Section 5. 2.2.5 CR #5: Construction Stormwater Pollution Prevention Since the Project will conduct construction activities (on-site or off-site) that will clear, grade, or otherwise disturb the site, it needs to provide stormwater pollution prevention and spill controls to prevent, reduce, or eliminate, to the maximum extent practical, the discharge of pollutants to on-site or off-site stormwater systems or watercourses. The 2017 RSWDM requires that erosion and sediment controls (ESCs) and stormwater pollution prevention and spill controls (SWPPS) be documented in a construction stormwater pollution prevention plan (CSWPPP). This needs to be completed in accordance with Sections 1.2.5.1 and 1.2.5.3 of the 2017 RSWDM, and in compliance with the expected Project coverage under the NPDES Stormwater General Permit for Construction Activities. Targeted TESC and SWPPS BMPs applicable to the site improvements are part of the preliminary CSWPPP included in Section 8. Those ESC BMPs are consistent with the ECS design plans and stormwater improvement plans. The construction contractor will be required to prepare the final CSWPPP as will be implemented and updated throughout construction.by the contractor. 2.2.6 CR #6: Maintenance and Operations It is expected that King County Parks, as the Project owner and a public agency, will have primary operations and maintenance (O&M) responsibility for the Project’s on-site stormwater improvements. Since the associated off-site frontage road improvements are not within a publicly owned right-of- way, it is expected that King County Parks will also have that O&M responsibility. The proposed drainage facilities will need to be maintained and operated by King County in accordance with the maintenance standards in the 2017 RSWDM - Appendix A, or other proposed unique facilities supplemental maintenance standards approved by the City. Stormwater Technical Information Report King County Parks – Renton Shop Central Maintenance Facility Replacement Project 22 | June 16, 2021 Proper O&M of proposed stormwater control facilities is critical to their proper operation and to avoid on-site and or off-site potential impacts if overflows were to result due to lack of O&M. This is particularly true given the reliance on enhanced water quality treatment systems and full infiltration facilities to manage on-site stormwater discharges and provide required protection of the City’s underlying aquifer. Required maintenance practices for stormwater control facilities are addressed in Section 10. 2.2.7 CR #7: Financial Guarantees and Liability The financial guarantee requirement of the City under Renton Municipal Code (RMC) Section 4-6-030 for all newly constructed or modified drainage systems proposed by a project are not expected to directly apply since the project owner is public agency. King County Parks and the City will need to review how this requirement will be handled for this Project as implemented though an agreement between the County and City. 2.2.8 CR #8: Water Quality Facilities As a redevelopment project, the Project needs to provide water quality facilities to treat the runoff from the new and replaced PGIS and new PGPS areas targeted for treatment that are not fully dispersed, as defined in Section 1.2.8 of the 2017 RSWDM. In accordance with the City’s land use- specific water quality facility requirements described in Section 1.2.8.1 of the 2017 RSWDM, since the Project is an industrially zoned site where more than 50 percent of the on-site runoff that drains to proposed water quality facilities is from an industrial use, then the Enhanced Basic Water Quality Menu (enhanced treatment) applies. The only applicable exception to CR #8 is a reduction in treatment level to the Basic Water Quality Menu (basic treatment) if that runoff is infiltrated in accordance with the requirements of Section 5.2 of the Renton SWDM. This exception does not apply where runoff is infiltrated within 0.25 mile of a fresh water designated for or having an aquatic life use, and where subgrade soils do not meet the groundwater protection standards defined in Section 5.2.1 of the 2017 Renton SWDM. Since the Project is located in the Zone 2 of City’s Aquifer Protection Zone, it is expected that enhanced treatment will be required regardless of whether the Project meets that exception criteria. That level of treatment also provides added protection for the long-term functionality of the proposed on-site infiltration facilities that are located downstream of the enhanced treatment. The water quality requirement for this project will be satisfied by installing various water quality BMPs (i.e., presettling wet pool storage, coalescing plate oil-water separators, and Modular Wetland filters), that individually and collectively satisfy the 2017 RSWDM requirements for enhanced treatment and oil control (see SR #5). Modular Wetland System (MWS) proprietary treatment facilities included in the treatment train also have general use level designation (GULD) approval for enhanced water quality treatment from the Washington State Department of Ecology (Ecology). The water quality facilities are being sized to treat attenuated runoff for up to the 100-year event prior to infiltration, which extends beyond the minimum requirements of the 2017 RSWDM. As noted above, the proposed increase in runoff volume treated will be more protective of the Project’s infiltration facilities and the City’s Aquifer Protection Zone. The Water Qualities Facilities treatment standards and the specific requirements for the Project design are addressed in Section 4. Stormwater Technical Information Report King County Parks – Renton Shop Central Maintenance Facility Replacement Project June 16, 2021 | 23 2.2.9 CR #9: On-site BMPs As a redevelopment project, the Project needs to provide on-site BMPs to mitigate the impacts of stormwater runoff generated from new impervious surfaces, new pervious surfaces, existing impervious surfaces, and replaced impervious surfaces targeted for mitigation in accordance with Section 1.2.9 of the 2017 RSWDM. On-site BMPs are techniques, facilities, and controls for dispersing, infiltrating, and otherwise reducing or preventing development-related increases in site runoff at or near the runoff sources. Beyond reduction in project runoff footprint, on-site BMPs include preservation and use of native vegetated surfaces to fully disperse runoff, use of other pervious surfaces to disperse runoff, roof downspout infiltration, permeable pavements, bioretention cells, and infiltration systems. On-site BMPs are required to be applied in accordance with the requirements and design specifications of each BMP, where determined to be technically feasible, as included in Appendix C, Section C.2 of the 2017 RSWDM. Since the Project proposed to fully infiltrate on-site runoff from the redeveloped site and contributing off-site road frontage areas, it should meet the flow control facility exception criteria provided in Section 1.2.9 of the 2017 RSWDM. That exemption criterion is for impervious surfaces served by an infiltration facility in accordance with flow control facility requirements, the facility implementation requirements, and the design criteria for infiltration facilities as contained in Sections 1.2.3.1, 1.2.3.2, and Section 5.2 respectively, of the 2017 RSWDM. The Project will install bioretention cells on the south side of the site to capture, evapo-transpire, and infiltrate roof runoff from Building A, and to connect that facility in overflow to the proposed west detention vault, treatment BMPs, and infiltration gallery facilities. The On-site BMPs and other stormwater runoff reduction BMP approaches proposed for integration into the Project are addressed in Section 4. 2.3 Special Requirements and Project Applicability The following 2017 RSWDM Special Requirements (SR) were evaluated for Project applicability under the Project’s need for Full Drainage Review. 2.3.1 SR #1: Other Area Specific Requirements Beyond the 2017 RSWDM, the Project needs to maintain consistency with the other adopted regulations and plans within the City of Renton (and King County as the site owner) that apply requirements for controlling drainage on an area-specific basis. Those regulations and plans generally include: • Master Drainage Plans • Basin Plans • Salmon Conservation Plans • Lake Management Plans • Hazard Mitigation Plans • Shared Drainage Facility Plans Based on initial research regarding these types of available plans within the Project vicinity, the following documents were identified: Stormwater Technical Information Report King County Parks – Renton Shop Central Maintenance Facility Replacement Project 24 | June 16, 2021 • King County Department of Natural Resources, Lower Cedar River Basin and Non-Point Pollution Action Plan (King County DNR 1997) – This previous King County-approved basin plan does not appear to contain more current supplemental requirements regarding required basin stormwater management controls than contained in the 2017 RSWDM requirements. • City of Renton, Lower Cedar River Chinook Salmon Habitat Restoration Assessment Plan (Herrera Environmental Consultant 2015) – This salmon conservation plan appears to be focused on riverine habitat project improvement opportunities and recommendations and does not address basin-related stormwater controls. Therefore, it is does not appear to supersede any drainage requirements of the 2017 RSWDM. 2.3.2 SR #2: Flood Hazard Area Delineation Flood hazard areas are composed of the 100-year floodplain, zero-rise flood fringe, zero-rise floodway, and FEMA floodway. If a proposed project contains or is adjacent to a flood hazard area as determined by the City, SR #2 requires the project to determine those flood hazard components that are applicable and delineate them on the project’s site improvement plans and recorded maps. City regulations and restrictions regarding development within a 100-year floodplain are found in the City’s Critical Areas Code under RMC 4-3-050. Review of FEMA regulatory floodplain maps suggest that the Project site does not fall within the regulatory 100-year floodplain or floodway and associated flood hazard areas. Therefore, SR #2 does not apply to the Project. 2.3.3 SR #3: Flood Protection Facilities Flood protection facilities, such as levees and revetments require a high level of confidence in their structural integrity and performance. Proper analysis, design, and construction are necessary to protect against the potentially catastrophic consequences if such facilities should fail. Where applicable, the City can require compliance and conformance with specific code requirements, standards, and outside agency design guidelines for those facilities needing evaluation by a licensed professional engineer. Since the Project is an upland site not directly adjacent to riverine or stream resources and does not rely on existing or proposed flood protection facilities for flood protection, SR #3 does not apply to the Project. 2.3.4 SR #4: Source Controls Source controls are typically required by the City for commercial sites to prevent rainfall from coming into contact with pollutants, thereby reducing the likelihood that pollutants will enter public waterways that could contribute to violation of water quality standards or City stormwater discharge permit limits. Source controls consist of both structural source control measures (i.e., contained concrete pads, roof covers) and non-structural source control measures (i.e., temporary covering of material storage piles, isolating sources of pollutants). Source control BMP needs are dependent on-site activities and operations. The Project site is industrially zoned, with expected activities and operations similar to commercial site uses that require use-specific source controls. In accordance with the 2017 RSWDM and the referenced King County Stormwater Pollution Prevention Manual (King County 2016), structural and Stormwater Technical Information Report King County Parks – Renton Shop Central Maintenance Facility Replacement Project June 16, 2021 | 25 non-structural source control BMPs expected to be applied with the site improvement and operations include: • A-1 – Required BMPs for all Properties with Commercial Activities • A-2 – Storage of Liquid Materials in Stationary Tanks (structural for covered areas) • A-3 – Storage of Liquid Materials in Portable Containers (structural for covered areas) • A-4 – Storage of Soil, Sand, and Other Erodible Materials (structural for covered areas) • A-5 – Storage of Pesticides and Fertilizers (structural for covered areas) • A-11 – Cleaning or Washing of Tools and Equipment (structural for wash pad) • A-17 – Stationary Fueling Operations (for small equipment; vehicle fueling is not proposed) • A-26 – Landscaping Activities and Vegetation Management • A-31 – Vehicle and Equipment Parking and Storage • A-44 – Dust Control for Commercial Operations • A-45 - Maintenance of Public and Private Utility Corridors and Facilities Non-structural source control BMP needs are not required for permit application and are expected to be confirmed through the City review process. 2.3.5 SR #5: Oil Control The Project proposes redevelopment of an existing industrial use for central O&M facilities where the cost of improvements will exceed $100,000. It will also result in the installation of new plus replaced impervious surfaces that exceed 5,000 square feet. Therefore, the site is considered high-use, with oil control required for those impervious, pollution-generating areas of the redeveloped Project site subject to on-site truck traffic, construction/maintenance equipment operations, laydown, and haul in/out, and diesel/stationary equipment use. A truck/equipment washing pad is also planned for the site, however, process discharge from the area would connect separately be to the sanitary sewer system when in use. High-use oil control treatment captures oil and associated pollutants for maintenance removal. The goal of this treatment is no visible sheen in runoff leaving the facility, or less than 10 mg/L total petroleum hydrocarbons (TPH) in the runoff, depending on the oil control facility options used. Oil control options for the Project site, consistent with City requirements for similar installations in public road right-of-way, include coalescing plate oil-water separators and baffled, gravity-type OWSs, typically called American Petroleum Institute (API) OWS. The City does not consider the use of catch basin inserts alone as sufficient for providing oil control. Given the need to preserve and protect the proposed infiltration facilities and the site being in a Zone 2 Aquifer Protection Area, the Project will provide oil control for the entire site to demonstrate full compliance with SR #5. The project will install four coalescing plate OWS – two for the west drainage system runoff, one for the east drainage system runoff, and one for the equipment wash pad discharge. Those oil-control facilities serving the improved west and east stormwater systems are located downstream of presettling and flow control vaults (receiving attenuated site discharges), but upstream of enhanced filtration treatment and infiltration gallery facilities. Stormwater Technical Information Report King County Parks – Renton Shop Central Maintenance Facility Replacement Project 26 | June 16, 2021 The oil control facility treatment standards and the specific requirements for the Project design are addressed in Section 4. 2.3.6 SR #6 Aquifer Protection Area Aquifer protection areas (APA) are identified in accordance with the City RMC 4-3-050. Reference 15-B in the 2017 RSWDM shows that the Project site is located within Zone 2 of the City’s APA. Therefore, SR #6 requires the Project to determine the specific APA components that are applicable and delineate them on the Project’s site improvements plans. Those requirements are expected to include the need to enhanced treatment of all site discharges planned to be infiltrated within the APA. The Project drainage system proposes presettling, oil control, and enhanced filtration treatment facility improvements, sized to treat attenuated discharges from up to the 100-year event from on- site and adjacent off-site road frontage sources. These robust treatment BMP measures are expected to be sufficient to meet the City’s Zone 2 APA requirements. The APA treatment requirements for the Project design are addressed in Section 4. 3 Off-site Analysis 3.1 Downstream Analysis An off-site drainage analysis is typically required to assess existing drainage conditions and problem areas downstream from a project site. It provides information to determine whether supplemental runoff flow control or water quality mitigation is needed beyond that otherwise required under the City’s stormwater minimum requirements. A Level 1 downstream analysis is typically the minimum level of off-site analysis completed, as prescribed in Sections 1.2.2 and Section 2.3.1.1 of the 2017 RSWDM, unless exempted by the City. Since the project proposes to achieve full infiltration of runoff in combination with partial capture, storage and treatment of runoff for sustainable reuse, further off-site analysis beyond the preliminary assessment provided in this section should not be needed. The Level 1 downstream analysis is a qualitative survey of each downstream system and is intended to identify flooding, erosion, and water quality problems and potential wetland impacts. The steps for completing the off-site analysis are described in the following sections. 3.1.1 Define and Map the Study Area Figure 3A provides a map of the Project area showing the site and adjacent off-site TDA drainage areas, land cover, and downstream flow paths for stormwater discharges under existing conditions. The limits of downstream analysis typically extend a minimum of 0.25-mile downstream from the site boundary along the drainage flow paths but can extend up to 1.0-mile if downstream drainage problems are identified. The Project site does not currently include any storm drain improvements or off-site drainage connections beyond surficial flow paths that extend off-site for conveyance of runoff not infiltrated on-site. As such, the existing off-site discharge paths are very limited because of runoff dispersal and infiltration that occurs adjacent to and north and south of the site. The flow path extending south of the site is limited to an earth swale approximately 550 feet in length. It extends from the Stormwater Technical Information Report King County Parks – Renton Shop Central Maintenance Facility Replacement Project June 16, 2021 | 27 southwest site boundary to a closed depression that infiltrates site runoff on the adjacent King County parcel to the south. To the north of the site, residual site runoff that is not infiltrated on-site is understood to be dispersed linearly along the northwest boundary of the site over a 50- to 75-foot length vegetated flow path, where it appears to infiltrate. 3.1.2 Review Available Study Area Information A resources review is required for the Project study area to identify any existing hazards related to flooding, erosion, and water quality problems. This review was based on research conducted on various websites, and through use of the City’s online GIS interactive mapping tool (City of Renton 2018). Basin Plans of Basin Reconnaissance Summary Reports Based on initial research regarding these types of available plans within the Project vicinity, the following documents were identified: • King County Department of Natural Resources, Lower Cedar River Basin and Non-Point Pollution Action Plan (King County DNR 1997) • City of Renton, Lower Cedar River Chinook Salmon Habitat Restoration Assessment Study (Herrera Environmental Consultants 2015) These documents do not provide unique stormwater management guidelines for the Project site beyond those contained in the 2017 RSWDM. Topographic and Aerial Mapping for Site and Adjacent Areas Off-site topographic mapping beyond the limits of the site topographic mapping was reviewed using the City’s online GIS viewer. This information provided confirmation of presence of the closed depression/infiltration area on the adjacent King County parcel south of the site. It also provided information regarding the characteristics of the graded slope areas to the north and west of the site. Google Earth aerial mapping (Google Earth 2018) was also reviewed to provide additional definition on on-site and off-site drainage flow paths and existing land cover. Critical Areas Mapping for Site and Adjacent Areas Information obtained regarding critical areas shown on Figure 2 on or in proximity to the Project site suggest: • The Project site or adjacent area is not within a floodplain or floodway (Zone X) per City of Renton Flood Insurance Rate Map (FIRM), Map Number 53033C0981G (City of Renton 2017a). • The Project site is not mapped to be within a potential landslide hazard, steep slope, or erosion hazard area per the City of Renton online GIS viewer (Renton 2018). There are some regulated slope areas including steep slopes, some exceeding 25 percent, adjacent to and primarily east and west of the site (see Figure 3A for their locations). • No wetlands appear to exist on the site. One potential off-site wetland was identified on a private parcel (gravel pit) to the east of the site, but no other information was found to identify its regulatory status. Stormwater Technical Information Report King County Parks – Renton Shop Central Maintenance Facility Replacement Project 28 | June 16, 2021 • The site is within a wellhead (aquifer) protection area, Zone 2 (Maplewood 10-year capture zone). • No documented drainage complaints were found for the Project site or in close proximity. 3.1.3 Field Inspect the Study Area A drainage field reconnaissance investigation of the site was conducted by HDR staff in February 2019. Findings of that review are incorporated into Section 1 description of existing TDAs and off- site drainage paths. 3.1.4 Describe the Drainage System and Drainage Problems The downstream drainage system is very limited since no downstream surface water connections have currently been identified. The City GIS (City of Renton 2018) also does not identify nearby downstream flooding, erosion, or water quality problems in close proximity to the site. In addition, full on-site infiltration of the redeveloped site and tributary area runoff is proposed with site improvements. Therefore, description and assessment of the downstream drainage paths beyond that included in Section 1 is not needed. 4 Flow Control, Low-impact Development, Water Quality, and Infiltration Facilities Analysis and Design 4.1 Existing Conditions Site Hydrology The Project site falls within the Lower Cedar River Drainage Basin. The site area totals 5.71 acres, and an additional 0.25 acres of the Jefferson Avenue NE frontage (west half) contributes to the site drainage. This Project site and off-site road frontage area is further broken down under existing conditions as 2.96 acres contributing to TDA E1 north site drainage and off-site dispersed discharge to infiltration, 2.79 acres contributing to the TDA E2 south site drainage and off-site discharge to infiltration, and 0.29 acres of TDA E6 with dispersed slope discharge to the west. The remainder of the affected off-site drainage within TDA E3, E4, and E5 discharges to adjacent off-site parcels. The existing TDA boundaries, off-site discharge locations, and downstream flow paths are shown in Figure 3A. Existing land cover within these TDA areas is shown in Table 1 (Section 1.5) The Project area hydrology under existing land cover conditions was analyzed for TDA 1 and 2 using the continuous simulation MGSFlood model to provide an estimate of existing condition peak flows and volumes beyond on-site infiltration that could be potentially be discharged off-site to adjacent parcels. Other TDA discharges do not affect proposed stormwater control facilities and were therefore not analyzed. For this analysis, existing site pervious soils were conservatively assumed to be till, which likely under-simulates on-site infiltration effects that appears to occur through silty sand and gravel fill soils. The existing conditions analysis was run at a 15-minute time step to capture the effects of higher intensity, short duration precipitation along with the expected short lag time in runoff generation from on-site and off-site areas. The resulting recurrence interval peak flow and annual average runoff volume estimates from this analysis are shown in Table 4. Stormwater Technical Information Report King County Parks – Renton Shop Central Maintenance Facility Replacement Project June 16, 2021 | 29 Table 4. Existing Conditions Hydrology Summary TDA Existing Impervious Surface Area (ac) Existing Pervious Surface Area (ac) Simulated Recurrence Interval Event Peak Flow (cfs) Simulated Water Quality Online Design Flow (cfs) Simulated Average Annual Runoff Volume (ac-ft/yr) 2-Year 10-Year 100-Year E1 1.02 1.94 0.6 1.0 2.0 NA 5.4 E2 0.79 2.00 0.4 0.7 1.2 NA 3.4 4.2 Proposed Conditions Site Hydrology The Project will fully re-grade and redevelop the site with associated changes to the site land cover. More of the site area will exhibit fully impervious runoff characteristics (i.e., larger building roof areas, conversion of compacted gravel surfaces to asphalt concrete pavement). Therefore, there will be some expected increases in redeveloped site peak flows and runoff volumes that will need to be accommodated by the proposed on-site stormwater control facilities. The total TDA P1 and P2 area equates closely to the collective on-site and off-site areas for TDA E1 and E2. TDA P1 will drain to the new west drainage system flow control, treatment, and infiltration facilities, whereas TDA P2 will drain to the similar new east drainage system facilities. Proposed land cover within these TDA areas is shown in Table 2 (Section 1.5). For proposed conditions, on- site flow control, treatment, and infiltration facilities are being designed to control and discharge runoff on-site up to the 100-year event without overflow conveyance to off-site drainage systems. The Project area hydrology under proposed TDA land cover conditions was analyzed using the continuous simulation MGSFlood model to provide an estimate of runoff peak flows and volumes. For that analysis, beyond the impervious pavement areas, runoff response from proposed vegetated surfaces were assumed to be from compacted till-grass soils, although amended landscape soils will achieve infiltration benefit. The proposed conditions analysis was run at a shorter 5-minute time step to capture the effects of higher intensity, short duration precipitation with the improved drainage system in runoff generation from impervious (hard) surfaces. The resulting recurrence interval peak flows, water quality (online) flows, and annual average runoff volume estimates from this analysis are shown in Table 5. These estimates are for inflows to the proposed flow control facilities (for water quality flows, detention outflows are also reported). Detention outflows will subsequently be delivered through the water quality treatment and infiltration facilities (through 100-year level). Results demonstrating the detention flow control volume need and targeted design outflows for sizing of treatment and infiltration facilities are summarized separately in Section 4.4 below. Table 5. Proposed Conditions Hydrology Summary TDA New and Replaced Impervious Surface Area (ac) New Pervious Surface Area (ac) Simulated Recurrence Interval Event Peak Flow (cfs) Simulated Water Quality Online Design Flow (cfs) Simulated Average Annual Runoff Volume (ac-ft/yr) 2-Year 10-Year 100-Year P1 3.21 0 1.6 2.4 4.5 0.50 (1) 0.29 (2) 9.2 P2 2.02 0.32 1.0 1.5 3.0 0.32 (1) 0.14 (2) 6.2 Notes: (1) Upstream of detention; (2) Downstream of detention Stormwater Technical Information Report King County Parks – Renton Shop Central Maintenance Facility Replacement Project 30 | June 16, 2021 4.3 Stormwater Controls Design Requirements and Performance Standards The Project will provide collection, conveyance, flow control, water quality treatment, and infiltration improvements to manage stormwater runoff from the site. Figure 5 illustrates those proposed on- site stormwater control facilities as described and analyzed in more detail in the following sections. To comply with the 2017 RSWDM requirements and proposed Standard Adjustments, stormwater controls are being designed in accordance with the following performance standards. 4.3.1 Flow Control Facilities The Project triggers the requirement for CR #3 - Flow Control Facilities as previously described in Section 2.2.3, since a direct discharge exemption does not apply. The Flow Control Duration Standard – Matching Forested site conditions applies in the Project site area, but only for areas that drain to streams and are subject to flow-related water quality problems such as erosion or sedimentation. Since the Project does not propose off-site surface discharge connections under the full infiltration proposal, this flow control standard is not applicable to the site, and a Standard Adjustment to CR #3 is therefore being requested from the City. An alternative flow control approach is being applied that will provide peak rate flow control in on- site, linear detention vaults to achieve an attenuated discharge rate equivalent to the design capacity of the proposed on-site treatment and infiltration facilities. Under this modified flow control approach, site conveyance, detention, treatment and infiltration facilities would provide required functions and protections up through the 100-year event. The proposed flow control facilities need to mitigate the runoff from the targeted developed surfaces within the TDA, inclusive of new and replaced impervious surfaces and pervious surfaces that are not fully dispersed in accordance with the 2017 RSWDM. Full dispersion for the redeveloped Project site is not technically feasible; therefore, targeted surfaces for the Project site include all new and replaced impervious and pervious surfaces within TDA P1 and P2. The hydrologic analysis for proposed conditions in Section 4.2 considers those collective redeveloped site surfaces. 328.617D D D D D D D D D UD UD UD UDD DDDDD UD CO CO CO CO COCO CO CO CO CO CO CO CO CO CO CO CO CO CO CO CO CO CO CO CO CO CO CO CO CO CO CO CO CO UDUDUDUDUDUDUDUDUD CO CO COCO CO COCO CO COCO CO COCO CO COCO CO COCO CO COCO CO COCO CO CO CO CO CO UDUDUDUDUD UD UD UD UD UD UDUD UD UD UD UD CO CO CO CO CO CO CO CO CO CO CO CO CO DATE FIGURE JUNE 2021 5RENTON SHOP - CENTRAL MAINTENANCE FACILITY REPLACEMENT CONTROL FACILITIES PROPOSED ON-SITE STORMWATER KING COUNTY PARKS AND RECREATION BUILDING A BUILDING B BUILDING C CONVEYANCE SYSTEM - EAST CONVEYANCE SYSTEM - WEST BIORETENTION CELL PRESETTLING AND FLOW CONTROL STORAGE COALESCING PLATE OIL-WATER SEPARATOR MODULAR WETLAND SYSTEM UNITS INFILTRATION GALLERY PERFORATED FLOW DISPERSION PIPE ROOF DRAIN SITE BOUNDARYJEFFERSON AVE NEBIORETENTION CELL D UD EAST MODULAR WETLAND SYSTEM UNITS WEST PRESETTLING AND DETENTION STORAGE VAULT WEST COALESCING PLATE OIL-WATER SEPARATOR TDA P1 TDA P2 WEST FLOW CONTROL MH EAST FLOW CONTROL MH EAST COALESCING PLATE OIL-WATER SEPARATOR WEST MODULAR WETLAND SYSTEM UNITS COVERED STORAGE AREA PRIMARY OVERFLOW FROM BIORETENTION CELL WEST INFILTRATION GALLERY EAST INFILTRATION GALLERY EAST PRESETTLING AND DETENTION STORAGE VAULT Stormwater Technical Information Report King County Parks – Renton Shop Central Maintenance Facility Replacement Project June 16, 2021 | 33 4.3.2 On-site Low-impact Development BMPs The Project improvements trigger the requirement for CR #9 - On-site BMPs, or LID BMPs, as previously discussed in Section 2.2.9. However, within TDA P3, a Basic Exemption to this requirement is expected to apply for utility improvements in the off-site road frontage. The Project improvements in TDAs P1 and P2 should also meet this CR since full-infiltration and other LID BMPs will be provided for collective post-developed surfaces as follows: • BMP C2.2 – Full Infiltration: Full infiltration is proposed for all post-developed surfaces runoff in TDA P1 and P2 up to the 100-year event, to be achieved through two proposed on-site infiltration galleries (one in each TDA), with prior presettling and on-site flow control vaults, coalescing plate OWS and Modular Wetland enhanced filtration treatment. Design criteria for this BMP complies with the Full Infiltration On-site BMP minimum design requirements contained in Appendix C, Section C.2 of the 2017 RSWDM. • BMP C2.6 – Bioretention: Runoff from the Building A roof will be discharged into two interconnected bioretention cells to be constructed south of that building. This facility will infiltrate runoff through a planted bioretention soil mix with no underdrains underlying it. An overflow from the bioretention cell will exist at its west end, to allow for conveyance of any flow not infiltrated to the TDA P1 west drainage system detention vault. The design criteria for this BMP complies with the Bioretention On-site BMP minimum design requirements contained in Appendix C, Section C.2 of the 2017 RSWDM. • BMP C2.11 – Perforated Pipe Connection: Large-scale perforated pipe connections are integrated with the infiltration gallery design in a similar manner to this BMP to achieve dispersal of treated runoff over the subgrade area. The design criteria for this BMP complies with the Perforated Pipe Connection On-site BMP minimum design requirements contained in Appendix C, Section C.2 of the 2017 RSWDM. • BMP C2.13 – Soil Amendment: For those areas of the site to remain as previous, re- vegetated soils, new, replaced and disturbed area topsoil will be amended with organic materials (typically compost). The design criteria for this BMP complies with the Soil Amendment On-site BMP minimum design requirements contained in Appendix C, Section C.2 of the 2017 RSWDM. 4.3.3 Water Quality Facilities The Project triggers the requirement for CR #8 – Water Quality as previously described in Section 2.2.8. Since the Project is an industrially zoned site where more than 50 percent of the on-site runoff that drains to proposed water quality facilities is from an industrial use, then the Enhanced Basic Water Quality Menu (enhanced treatment) applies. Also, in accordance with SR #5 – Oil Control, the Project site, or a portion thereof, is expected to be classified by the City as high-use, requiring the application of oil-control BMPs. Enhanced treatment BMPs are required to meet the following performance standards: • 80 percent removal of total suspended solids (TSS) for flows/volumes up to and including the water quality design flow and volume, that represents 91 percent of the annual runoff volume in a typical rainfall year Stormwater Technical Information Report King County Parks – Renton Shop Central Maintenance Facility Replacement Project 34 | June 16, 2021 • Greater than 30 percent reduction of dissolved copper, and greater than 60 percent removal of dissolved zinc for the water quality design flow and volume (based on specific ranges of untreated concentrations) Application of the 2017 RSWDM BMPs from the Enhanced Basic Treatment Menu, selected paired Basic Treatment BMPs in series, or use of proprietary Ecology-approved treatment BMPs for Enhanced Treatment meets those performance standards. This is based on the presumptive approach provided that BMP-specific design criteria as contained in Sections 6.2 through 6.8 of the 2017 RSWDM are adhered to. Water quality oil control BMP requirements for the Project under assumption of a high-use site designation will need to meet the following performance standards: • Removal of oil particles 60 micron and larger for the water quality design event (off-line design flow) • Oil and grease effluent quality of 10 to 15 milligrams per liter for the water quality design event Acceptable oil control BMPs in the 2017 RSWDM for high use sites include baffle-type OWS and coalescing plate OWS. The Project oil control improvements comply with design requirements and criteria for the coalescing plate OWS BMP as contained in Section 6.6.2 of the 2017 RSWDM. The Project needs to provide water quality treatment facilities to mitigate runoff water quality from the new and replaced PGIS and new PGPS that are not fully dispersed. The comprehensive water quality treatment proposed for the Project will include installing various water quality treatment BMPs in series including presettling (wet pool) storage, coalescing plate OWS, and Modular Wetland filters that collectively meet or exceed the 2017 RSWDM requirements for oil control and enhanced treatment. Proprietary treatment facilities included in the treatment train also have GULD approval for enhanced water quality treatment from Ecology. The water quality facilities are being sized to treat attenuated runoff for up to the 100-year event prior to infiltration, which extends beyond the water quality treatment flow/volume requirements in the 2017 RSWDM. The robust water quality treatment level included in the stormwater facilities design targets effective protection of the infiltration galleries function and the City’s underlying aquifer protection needs. 4.3.4 Infiltration Facilities To satisfy CR #1 – Discharge at Natural Locations and avoid the need for a new off-site connection to the City’s storm drainage system(s) downstream from the Project site, full infiltration of redeveloped site area runoff is proposed. Water quality treatment facilities meeting the performance standards described in Section 4.3.3 will precede runoff infiltration into native subgrade (glacial outwash) soils. Peak rate flow control through the 100-year event prior to treatment will attenuate post-development surfaces runoff and reduce the sizing needs of both water quality treatment and infiltration facilities. The infiltration gallery facilities will need to satisfy the design requirements and performance standards contained in Section 5.2 of the 2017 RSWDM that include: • Establishing that adequate depth of permeable soils and separation to high groundwater exists below the bottom of the proposed infiltration facilities, as determined through subsurface exploration boring logs and soil samples characterization and testing. That Stormwater Technical Information Report King County Parks – Renton Shop Central Maintenance Facility Replacement Project June 16, 2021 | 35 minimum depth value is typically a minimum of 3 feet when confirmed by a groundwater mounding analysis, and 5 feet otherwise (satisfied - see geotechnical report). • Confirming subgrade soils design infiltration rates through pilot infiltration tests (PIT) or other equivalent infiltration field testing as approved by the City and applying suitable correction factors to measured infiltration rates in accordance with the 2017 RSWDM (satisfied – see geotechnical report). • Completing a groundwater mounding analysis meeting the requirements of Section 5.2.1 of the 2017 RSWDM for infiltration facilities serving more than 1 acre and with less than 15 feet of separation between the bottom of the proposed facilities and either a restrictive soil layer or groundwater (not required). • Conducting field performance testing on the proposed infiltration facilities during construction with correction factors applied to confirm the design infiltration rate, and if not confirmed, adjust the required size of the infiltration facility (a future construction phase requirement). • Providing 100-year conveyance overflow from the proposed infiltration facility to a suitable off-site drainage connection as a contingency if there is a restriction in infiltration rate due to partial plugging of the facility, unless the City concurs that a further reduction in the design infiltration rate (by one-half) is sufficient to achieve proper infiltration performance up to the 100-year event (provided with stormwater facilities design). • Providing a spill control device upstream from the proposed infiltration facility, typically a tee section with an elevated riser to the overflow elevation (provided with stormwater facilities design). • Providing presettling upstream of the infiltration facility, either as a basic treatment BMP or a presettling pond or vault sized to a minimum of 25 percent of the basic treatment water quality volume requirement (provided with stormwater facilities design). • Protecting infiltration facilities subgrade from erosion and sediment deposition during construction through alternative routing of construction runoff and applying appropriate source control and construction operations BMPs (a future construction phase requirement). • Protecting off-site groundwater from potential water level and quality impacts through controlling possible groundwater mounding effects and providing required water quality treatment prior to infiltration -oil control and basic treatment facilities at minimum for an industrial site (groundwater mounding control is not needed; water quality control provided with stormwater facilities design) • Providing required setbacks of infiltration facilities from any identified steep slope or landslide hazard areas (provided with stormwater facilities design). • Registering any proposed infiltration wells that are classified as Underground Injection Control (UIC) facilities with Ecology, and complying with UIC regulation requirements for their design, installation, and operation (infiltration galleries classified as UIC facilities have been registered through Ecology, and have been designed in accordance with design criteria requirements of Section 5.2.5 of the 2017 RSWDM). Stormwater Technical Information Report King County Parks – Renton Shop Central Maintenance Facility Replacement Project 36 | June 16, 2021 4.4 Flow Control Facilities Preliminary Analysis and Sizing 4.4.1 Detention Vaults Flow Control Storage Peak rate flow control (through the 100-year event) will be provided for TDA P1 and P2 targeted surfaces through the installation of linear, pre-cast, subsurface detention vaults aligned around the perimeter of the two targeted on-site infiltration galleries (in U-shaped configurations). One will be located in the west portion of the site serving TDA P1, and a second in the east portion of the site serving TDA P2. The vaults will be installed on a level grade and will include a presettling (dead) storage component, a flow control storage (active) storage component, and a freeboard (inactive) storage component. The presettling storage component sizing basis is described in Section 4.5.1. The flow control and freeboard storage components sizing basis are described below. Both flow control facilities for TDA P1 and P2 were sized using the MGSFlood continuous simulation hydrologic model and based on the extended precipitation time-series data set for the Puget Sound East, 40-inch MAP Climate Region. The model was run at a 15-minute time step given the relatively small TDA sizes and highly impervious character of the improved site surfaces. Detention outflows were modeled using a single orifice sized to control the 100-year event peak outflow to the target design flow for the proposed downstream water quality treatment and infiltration facilities. A 10-foot interior width vault with a 4.5-foot active storage depth was used for the hydrologic routing analysis consistent with preliminary design layout of the linear vault system. The analysis was conducted using design lengths of the linear vault system of 358 feet for the TDA 1 west drainage system and 326 feet for the TDA 2 east drainage system. Orifice sizes needed to fully utilize the available active storage volume while maximizing peak flow reduction are 3.125-inch-diameter for the TDA 1 west drainage system and 2.25-inch-diameter for the TDA 2 east drainage system. Table 6 summarizes the detention vault simulated inflows, outflows, simulated flow control volume, and estimated freeboard storage volumes for the 100-year event for the tributary impervious and pervious surfaces within each TDA. The supporting MGSFlood modeling reports providing the preliminary design analysis to determine the controlled outflow for the available flow control storage volumes are included in Appendix B. Freeboard storage was computed based on the resulting vault surface area at 1-foot targeted depth. Table 6. Detention Vaults Flow Control Storage Sizing TDA New and Replaced Impervious Surface Area (ac) New Pervious Surface Area (ac) Detention Vault Simulated 100-Year Event Inflow (cfs) Detention Vault Simulated 100-Year Event Outflow (cfs) Detention Vault Required Flow Control (Active) Storage (cf) Detention Vault Freeboard (Inactive) Storage (cf) P1 3.21 0 4.5 0.65 19,690 3,580 P2 2.02 0.32 3.0 0.31 17,930 3,260 Stormwater Technical Information Report King County Parks – Renton Shop Central Maintenance Facility Replacement Project June 16, 2021 | 37 4.5 Water Quality Treatment Facilities Analysis, Sizing, and Design Criteria 4.5.1 Detention Vaults Presettling Storage and Surface Area Presettling storage in the proposed detention vaults within TDAs P1 and P2 improved drainage systems was estimated using the 2017 RSWDM criteria for pretreatment upstream of infiltration facilities (although other downstream treatment is provided). That criteria requires a minimum presettling storage volume equal to 25 percent of the water quality event volume (basic wet pond volume). Based on the MGSFlood modeling analysis (Appendix B), the basic wet pond water quality simulated volume totals 17,666 cubic feet (cf) for TDA 1 west drainage system and 11,576 cf for TDA 2 east drainage system. Therefore, the required presettling (dead) storage volume within each detention vault is: • TDA P1 West Drainage System – presettling storage volume of 4,416 cf, with an average dead storage depth in the detention vault of 1.23 feet. • TDA P2 East Drainage System – presettling storage volume of 2,892 cf, with an average dead storage depth in the detention vault of 0.89 feet. A check was also made to confirm that the presettling storage area meets that required for design of the coalescing plate OWS forebay using 20 sf per 10,000 sf of tributary drainage area. The proposed presettling surface areas of 3,580 sf and 3,260 sf for the respective west and east drainage systems significantly exceed the minimum presettling surface areas required under that criteria of approximately 280 sf and 205 sf respectively. 4.5.2 Coalescing Plate Oil Water Separators Analysis was conducted for preliminary sizing of the proposed coalescing plate OWS consistent with Section 6.6.2.1 of the 2017 RSWDM. The separators are targeted to treat all runoff up through the 100-year event, exceeding the typical water quality event design flow basis. The simulated 100-year detention vault outflow for TDAs P1 and P2, as reported in Table 6, are 0.65 cfs (292 gpm) for the TDA 1 west drainage system, and 0.31 cfs (139 gpm) for the TDA 2 east drainage system. These 100-year design flows were compared to the conventional water quality design flow criteria described in Section 6.2.1 of the 2017 RSWDM based on factored values to continuously simulated off-line water quality flows. The computed detention discharge off-line water quality flows are 0.17 cfs for the TDA P1 west drainage system, and 0.09 cfs for TDA P2 east drainage system (see Appendix B for MGSFlood model output). Those flows were adjusted by the required ratio (k) in the RSWDM Table 6.2.1.A, with a value of 3.5 calculated to be applicable for the City’s 6-month, 24- hour precipitation value of 1.4 inches. The resulting adjusted water quality flows are slightly less than or equivalent to the 100-year detention discharge for both the west and east drainage system. Therefore, the 100-year detention outflows were selected for use as the OWS, enhanced treatment (Modular Wetlands), and infiltration gallery design flows. Based on Figure 6.6.2.B and equation 6-33 of the 2017 RSWDM, the required minimum effective separation surface areas (Ah) of the coalescing plate pack media are 1,055 sf (combined for two units) and 505 sf respectively, for the west and east separators (see Appendix C). The actual plate area would be larger since they are installed inclined, typically between 45 and 60 degrees. The estimate of the required minimum plate pack size is approximately 5 feet in width, 3 feet in length, Stormwater Technical Information Report King County Parks – Renton Shop Central Maintenance Facility Replacement Project 38 | June 16, 2021 and 4 feet in height for a 150-gpm unit. The spacing of required baffles for sediment retention upstream of, and oil retention downstream of the plate pack that creates the OWS forebay and after bay is based on design criteria contained in Section 6.6.2.2 of the 2017 RSWDM. Therefore, the recommended coalescing plate OWS units for each drainage system as included in the stormwater facilities design are: • TDA P1 West Drainage System – two parallel OWS units, each with a capacity of 0.33 cfs (150 gpm), operated with equal flows delivered to each, for a combined capacity of 0.66 (300 gpm). The required minimum effective separation surface area (Ah) of the coalescing plate pack media for each OWS is 530 sf. Discharge from it will be to the downstream filtration (enhanced) treatment, and then to the west infiltration gallery. • TDA P2 East Drainage System – a single OWS unit with capacity of 0.31 cfs (140 gpm). The required minimum effective separation surface area (Ah) of the coalescing plate pack media is 505 sf. Discharge from it will be to the downstream filtration (enhanced) treatment, and then to the east infiltration gallery. • Wash Pad Drainage System - a single OWS unit with capacity of 0.23 cfs (105 gpm). The required minimum effective separation surface area (Ah) of the coalescing plate pack media is 375 sf. Discharge from it will be to sanitary sewer through Industrial Waste Discharge Permit when the wash pad is in use. When the wash pad is not in use, the piping system includes a valve connection with grit chamber and oil control tee, with connection to the west presettling and detention vault, and subsequently to the downstream stormwater treatment and infiltration system. The OWS vault enclosing these OWS components will extend to finish grade, with hatches provided for maintenance access. Shut-off valves are also included on the discharge piping along with elevated tee-style outlets to avoid the discharge of accumulated oils during normal separator operation and facility maintenance. Required venting is also included. Other appurtenant OWS design features will be identified through contractor shop drawing submittals based on the selected coalescing plate OWS supplier product. 4.5.3 Modular Wetland System Filters Enhanced water quality treatment will be provided using multiple Modular Wetland System (MWS) Linear filter units. This proprietary treatment BMP is a horizontal flow media filtration unit contained in a precast concrete vault. It consists of three chambers and uses a wetland media in the primary filtration chamber. A differential design depth across the filter media of 3.4 feet has been applied between the inlet to outlet storm drains to achieve operation at their rated hydraulic treatment capacity. Wetland or other plantings are typically installed in the filtration chamber, although that is not required or proposed for use on this Project. It includes an upstream pretreatment chamber with pretreatment filtration media cells, as well as a downstream discharge chamber. The MWS Linear 2.0 has received Ecology GULD approval (2014) for enhanced water quality treatment. Based on the 100-year detention outflows of 0.65 cfs and 0.31 cfs respectively for the west and east drainage systems, factored up in size by a minimum of 25 percent for potential decrease in hydraulic performance for filter media for mass loading and blinding effects, the following MWS standard unit sizes are recommended for use as included with the stormwater facilities design: • TDA P1 West Drainage System – four parallel MWS-L-4-21 units (4-foot width by 21-foot length) with hydraulic capacity of 0.268 cfs each, for a combined capacity of 1.07 cfs. Three Stormwater Technical Information Report King County Parks – Renton Shop Central Maintenance Facility Replacement Project June 16, 2021 | 39 of the units will be operated collectively (capacity of 0.80 cfs) with a proportional flow to each, and the fourth unit will be isolated by shut-off valve as a redundant clean unit in the event of further reduction in hydraulic performance requiring filter media maintenance. • TDA P2 East Drainage System – three parallel MWS-L-4-17 units (4-foot width by 17-foot length) with hydraulic capacity of 0.206 cfs each, for a combined capacity of 0.62 cfs. Two of the units will be operated collectively (capacity of 0.41 cfs) with a proportional flow to each, and the third unit will be isolated by shut-off valve as a redundant clean unit in the event of further reduction in hydraulic performance requiring filter media maintenance. The redundant MWS unit will be operated by shut-off valve adjustment to provide treatment capacity while the filter media in the other units is replaced. It could also provide supplemental capacity through opening of the shutoff valve if excessive filter media blinding occurs on the primary units prior to their maintenance. Since full treatment of runoff is proposed through the 100-year event, and bypass of untreated flows to the infiltration gallery facilities is not desired, no internal or external high flow bypass is proposed. The MWS unit vaults will extend to finish grade. Because of their required depth and considering Project surfaces above them, use of plantings within the MWS filtration chamber media isn’t possible. Therefore, multiple man-ways access to the three MWS chambers will be provided in each treatment unit to facilitate their inspection and maintenance along with filter media replacement. 4.6 Infiltration Facilities Analysis, Sizing, and Design Criteria 4.6.1 Bioretention Cell A bioretention cell on the south side of Building A is included to intercept drainage from the Building A roof and adjacent impervious surfaces and infiltrate it through an 18” depth of bioretention soil mix into scarified subgrade soils. The bioretention cell will consist of two interconnected, irregular shape cells, with a 6-inch design storage depth, and with a total bottom area of approximately 2,500 sf. A wall will be constructed on the north side, and the south graded slope will also have bioretention soil mix and will be vegetated. An overflow drop inlet catch basins is included at the west end of the bioretention cell. The overflow catch basin with beehive top debris cage will connect via a 12-inch storm drain to the west presettling and detention vault and associated treatment and infiltration facilities. The Building A impervious roof area draining to the bioretention cell totals approximately 16,500 sf, and with perimeter walkways added, totals approximately 18,000 sf. Therefore, the bottom area of the bioretention cell totals approximately 14 percent of the total impervious tributary area, exceeding RSWDM Bioretention BMP minimum cell area criteria (5 percent). The volume criterion in the RSWDM for the Bioretention BMP (0.6 inches over the impervious area in till soils) is also satisfied. The bioretention cell will provide approximately 50 percent more storage volume than that requirement at its 6-inch design depth. To evaluate the hydrologic/hydraulic design performance of the bioretention cell, an MGSFlood model was developed to model the combined impervious area runoff including the direct precipitation over the bioretention cell (totaling 0.52 ac of combined area). The bioretention cell infiltration capacity was analyzed using a 1.5 inch per hour design permeability rate for both the bioretention soil mix (BSM) media and subgrade materials (conservatively at 50% of the allowable 3 Stormwater Technical Information Report King County Parks – Renton Shop Central Maintenance Facility Replacement Project 40 | June 16, 2021 inch per hour permeability for the BSM media). The results confirmed that essentially the full precipitation volume in the long-term simulation would infiltrate (approximately 1.5 acre-feet annually), with minimal overflow (0.2 cfs) simulated to the west drainage storage, treatment and infiltration system, and only beyond about the 10-year event. The MGSFlood model files are included in Appendix B. A more conservative capacity check for the bioretention cell overflow conveyance system was made considering the Rational Method peak inflow (see Section 5), and that flow is still fully contained by the west overflow system. 4.6.2 Infiltration Gallery For discharge of design flows at the terminus of the west and east drainage systems from the collective detention and treatment facilities, infiltration galleries with perforated flow dispersal piping within them are included that overlay the permeable subgrade soils. The required infiltration gallery areas were determined by analysis using Darcy’s Law assuming a design hydraulic conductivity (permeability) rate of 4.0 inches per hour (in/hr). That recommended design permeability is based on a substantially reduced value for possible long-term subgrade occlusion at 20 percent of the design permeability rate (20 in/hr) recommended by the Geotechnical Engineer (Aspect 2019). The Geotechnical Engineer recommendation includes the required permeability rate reduction through application of RSWDM correction factors from significantly higher field-measured rates documented in Project site test wells monitoring. Using a subgrade design permeability of 4 in/hr, and the targeted footprint areas for the west and east infiltration gallery footprints (4,550 sf and 3,950 sf, respectively), a spreadsheet analysis was conducted to determine the required hydraulic design depth within the drain rock infiltration gallery (see Appendix C). Analysis was also conducted using the MGSFlood model (Appendix B), based on 100-year detention outflows, and considering the infiltration gallery as a bioretention facility with a filter media layer (representing possible subgrade partial blinding) assigned with the design permeability value at 4 in/hr. It considered an underlying subgrade permeability of 20 in/hr as recommended by the Geotechnical Engineer (Aspect 2019). The results of that preliminary analysis were assessed, and the higher of the reported hydraulic depth requirements above subgrade from the collective analyses were determined. The infiltration gallery design criteria recommendations include: • TDA P1 West Drainage System – use a subgrade surface area of 4.550 sf at elevation 311.3, operating at a hydraulic grade elevation of 313.3. • TDA P2 East Drainage System – use a subgrade surface area of 3.950 sf at elevation 313.3, operating at a hydraulic grade elevation of 315.3. Some added infiltration design flow reduction will occur with flow routing through the available storage in the drain rock voids above subgrade, but that was conservatively not accounted for in the analysis. Existing groundwater levels are reported by the Geotechnical Engineer to be in excess of 65 feet below existing grade (approximately 45 to 50 feet below the infiltration gallery subgrade). Therefore, a groundwater mounding analysis is not required in accordance with the RSWDM since that is only required for less than 15 feet of depth between subgrade and the highest expected groundwater level. The design of the infiltration galleries (both west and east drainage systems), consistent with the 2017 RSWDM requirements include: • Required inspection and field testing of native subgrade soils infiltration capacity after construction excavation to confirm consistency with the design permeability and Stormwater Technical Information Report King County Parks – Renton Shop Central Maintenance Facility Replacement Project June 16, 2021 | 41 Geotechnical Engineer soils interpretation and recommendations (a future construction phase requirement). • Protection of subgrade from the effects of construction equipment compaction, turbid runoff entry, and fines entrainment during construction (a future construction phase requirement). • Scarification of native subgrade soils to at least 6-inch depth prior to infiltration gallery drain rock materials placement (provided with stormwater facilities design). • Placement of a 2-foot-thick layer of Gravel Backfill for Drywells above the native subgrade (provided with stormwater facilities design). • Placement of a 2-foot layer of Gravel Backfill for Drains over the lower rock layer, within which the 8-inch perforated dispersal discharge piping will be installed in accordance with the design plans (provided with stormwater facilities design). • Installation of a separation geotextile above the upper drain rock layer to inhibit the migration of fines from the cover backfill into the infiltration gallery (provided with stormwater facilities design). A high stage overflow (beyond the west detention vault 100-year stage) from the west to the east detention vault is included with the drainage conveyance design. The emergency overflow will connect to the east and west drainage systems storage, treatment, and infiltration systems. UIC registration of the proposed west and east infiltration galleries through Ecology has been achieved by King County Parks including meeting the required groundwater non-endangerment standard presumptively through design of the infiltration gallery in accordance with the 2017 RSWDM standards and design criteria. This is required since stormwater infiltration galleries using perforated distribution/dispersal pipe systems are classified as Class 5 UIC facilities under Ecology UIC program regulation. 5 Conveyance System Analysis and Design 5.1 Storm Drain System Components and Layout Multiple storm drain conveyance systems will be installed within TDA P1 as part of the west drainage system, and within TDA P2 as part of the east drainage system, as shown in Figure 5. They will collect and convey the improved site runoff to the respective west and east presettling and detention storage vaults, and subsequently through treatment systems to the infiltration galleries. The drainage conveyance systems will consist of segments of new storm drain, typically 12-inch diameter with smooth interior wall, with a few short sections of 18-inch diameter, together with interconnected catch basins (Type 1 and Type 2). Grated inlets at catch basins will be located along flow lines and at low points in the restored finish grade surface. Catch basin are spaced at less than 150 feet (most are less than 100 feet apart), consistent with 2017 RSWDM requirements based on slope. Storm drains (12-inch diameter) also interconnect the detention vaults, flow control/splitter manholes, filtration treatment systems, and infiltration galleries. A network of 8-inch diameter perforated flow dispersal pipe (same as underdrain pipe) is located within each infiltration gallery. Solid wall 8-inch diameter roof drains will also be installed around the Buildings A and B perimeters, discharging directly to either the bioretention cell (Building A), and to the west presettling and Stormwater Technical Information Report King County Parks – Renton Shop Central Maintenance Facility Replacement Project 42 | June 16, 2021 detention vault (Building B). Building foundation drains will also be installed draining to the west presettling and detention vault. The storm drain conveyance systems are proposed to be installed at flow line gradients typically ranging from approximately 0.5 percent to 2.0 percent, with a few short segments having higher slopes. Perforated underdrain pipe in the infiltration galleries will be installed at a slope of 0.2 percent. The depth of storm drain installation to pipe invert elevations typically varies between approximately 4 feet and 8 feet below finish grade. The storm drain outfalls to the presettling and west and east pre-settling and detention vaults are located in the active flow control storage zone to avoid outlet plugging with sediments that can accumulate in the vault bottom, and to provide outfall energy dissipation benefit at elevated detention storage levels. Under maximum flow control storage conditions, tailwater submergence of the new storm drains will occur, but that effect is limited. For full pipe flow conditions associated with submerged tailwater conditions, the required hydraulic gradient to convey up to the 100-year conveyance design flows is less than 0.5 percent. The horizontal and vertical alignments and sizing of the storm drain systems included in the design are shown on the storm drain plan and profile drawings provided with the site improvement plans. 5.2 Storm Drain System Analysis and Design Criteria Hydrologic and hydraulic analysis was completed for storm drain conveyance improvements for each segment of the west and east drainage system that outfalls to the presettling and detention vaults, and for primary storm drain segments interconnecting treatment and infiltration gallery components. Figure 6 shows the breakdown in site drainage areas tributary to the various drainage system inlets including the overland flow paths and computed time of concentrations to each inlet. It also depicts the storm drain network as analyzed. The hydrologic and pipe sizing analysis was completed using an adjusted version of a WSDOT Hydraulics Manual spreadsheet (WSDOT 2019). That analysis tool allows for input of runoff parameters to provide computation of drainage subarea peak flows using the Rational Method, a conservative analysis approach that is appropriate for use for small, highly impervious site areas. Considering the relatively short runoff time of concentration over impervious surfaces to each inlet (limited to 6.3 minutes minimum in the 2017 RSWDM), this spreadsheet provides estimates of peak flows required to be captured and conveyed through the storm drain network. The hydrologic analysis was set up to compute cumulative 25-year and 100-year event peak flow estimates at each drainage system inlet or junction structure, consistent with requirements of Section 4.2.1.2 of the 2017 RSWDM. It also allows for sizing of pipes to convey computed design flows under uniform flow conditions. Table 7 summarizes the results of the hydrologic analysis results for 25-year and 100- year event peak design flows at each catch basin node. The full spreadsheet used for this conveyance design flow computation is included in Appendix D. EVCCC CC C CC CC C CCCCCCCCCCCCCCCC CCC EVEVEV EV EVEVCCC316'316'316'316'318'318'318'318'320'330'320'330' 32 8 '330' 320' 332' 330' 32 8 ' 326' 334' 332'334'336' 328.617D DDDDDDDUDUDUDUDD D D DCOCOCOCOCOCOCOCOCOCOCOCOCOCOCOCOCOCOCOCOCOCOCOCOCOCOCOCOCOCOCOCOCOCOCOCOCOCOCOCOCOCOCOCOCOCOCOCOCOCOCOCOCOCOCOCOCOCOCOCOCOCOCOCOUD UDUDUDUDUDUDUDUDUDUDUDUDCOCOCOCOCOCOCOCOCOCOCOCOCOD-128,113 SFTc = 2.84 MIND-24,876 SFTc = 3.31 MIND-314,294 SFTc = 3.53 MIND-418,488 SFTc = 3.56 MIND-126,286 SFTc = 1.20 MIND-1320,200 SFTc = 2.25 MIND-225,951 SFD-251,610 SFTc = 0.54 MIND-2113,212 SFTc = 1.66 MIND-203,186 SFTc = 0.68 MIND-23950 SFTc = 2.05 MIND-146,516 SFTc = 2.36 MIND-150 SFD-118,389 SFTc = 1.39 MIND-269,662 SFTc = 2.48 MIND-106,522 SFTc = 0.86 MIND-94,413 SFTc = 1.28 MIND-85,010 SFTc = 1.51 MIND-72,774 SFTc = 1.73 MIND-6A7,500 SFTc = 3.85 MIND-624,097 SFTc = 3.84MIND-56,085 SFTc = 3.78 MIND-1818,210 SFTc = 1.49 MIND-1711,001 SFTc = 1.22 MIN1.4%-0.6%1.6%D-190 SF1. 8% 1. 5%7.0 %1. 8 %-2.3%1.8%2.2%1.1 % -1.0%1.0%0.1%1.5%1.5%1. 3% 1.1 % 0. 9 %2.1%5.4%1.8%1.5%DATEFIGUREJUNE 20216RENTON SHOP - CENTRAL MAINTENANCE FACILITY REPLACEMENTAND STORM DRAIN SYSTEMSPROPOSED CONVEYANCE DRAINAGE AREASKING COUNTY PARKS AND RECREATIONTDA 1 (P1) - WESTTDA 2 (P2) - EASTOVERLAND FLOW PATH / SLOPESITE BOUNDARYMWL-2OWS-2FS-2SED-2OWS-1MWL-1FS-1SED-1Feet120600BUILDING ABUILDING BBUILDING CTDA P1(WEST)TDA P2(EAST)BIORETENTIONCELL Stormwater Technical Information Report King County Parks – Renton Shop Central Maintenance Facility Replacement Project June 16, 2021 | 45 Table 7. Conveyance Storm Drain Hydrologic Analysis, West and East Drainage System Upstream Drainage Inlet or Junction Pipe Segment Designation Downstream Drainage Inlet or Junction Tributary Drainage Area to Inlet (ac) Cumulative Conveyance Peak Flow Estimate (cfs) 25-Year 100-Year West Drainage System D-1 SD-1 D-2 0.65 1.59 1.85 D-2 SD-2 D-3 0.11 1.86 2.18 D-3 SD-3 D-4 0.33 2.67 3.12 D-4 SD-4 SED-1 0.42 3.71 4.34 D-5 SD-5 D-6 0.14 0.34 0.40 D-6 SD-6 D-6A 0.55 1.70 1.99 D-10 SD-10 D-9 0.15 0.37 0.43 D-9 SD-9 D-8 0.10 0.62 0.72 D-8 SD-8 D-7 0.12 0.90 1.05 D-7 SD-7 D-6A 0.06 1.06 1.23 D-6A SD-6A SED-1 0.17 3.19 3.72 SED-1 SED-1 FS-1 2.81 0.58 0.65 FS-1 FS-1 OWS-1 2.81 0.58 0.65 OWS-1 OWS-1 MWL-1 2.81 0.58 0.65 East Drainage System D12 SD-12 D-13 0.09 0.21 0.25 D13 SD-13 D-14 0.46 1.35 1.58 D-14 SD-14 D-15 0.15 1.72 2.01 D-20 SD-20 D-21 0.07 0.18 0.21 D-21 SD-21 D-22 0.30 0.93 1.08 D-25 SD-25 D-22 0.04 0.09 0.11 D-22 SD-22 D-23 0.14 1.35 1.58 D-23 SD-23 D-15 0.02 1.40 1.64 D-15 SD-15 SED-2 0.25 3.74 4.37 D-26 SD-26 D-19 0.22 0.55 0.64 D-11 SD-11 D-19 0.19 0.47 0.55 D-17 SD-17 D-18 0.30 0.73 0.86 D-18 SD-18 D-19 0.42 1.76 2.06 D-19 SD-19 SED-2 2.66 2.78 3.25 SED-2 SED-2 FS-2 2.66 0.28 0.31 FS-2 FS-2 OWS-2 2.66 0.28 0.31 OWS-2 OWS-2 MWL-2 2.66 0.28 0.31 Note: Refer to Figure 6 for drainage inlet/junction, pipe segment, and drainage area designations To confirm the sizing adequacy of the recommended storm drain conveyance system improvements, an adjusted version of the King County Backwater Analysis (spreadsheet) Model was used (King County 2016). This tool allows for computation of the water surface headwater elevations (hydraulic grade elevations) at system inlet and junction structures throughout the storm drain system while considering the tailwater (backwater) effects at drainage system hydraulic controls (e.g., at outfalls to presetting and detention vaults and at treatment units). For storm drain outfalls to the pre-settling and detention vaults, those tailwater control elevations were selected to be the peak 25-year or 100- Stormwater Technical Information Report King County Parks – Renton Shop Central Maintenance Facility Replacement Project 46 | June 16, 2021 year water level computed in the detention vault based on the MGSFlood hydrologic analysis used for detention storage analysis (Appendix B). Therefore, the hydraulic backwater analysis conservatively assumes coincident timing of the expected peak detention storage stage with peak inflows from each drainage system. Other key assumptions applied for the hydraulic analysis are unobstructed flow in pipe systems, smooth interior wall pipe materials (Manning’s n value of 0.014 or less), and adequate grate inlet hydraulic capacity consistent with the subarea design flows estimated for each inlet. The hydraulic analysis was initially conducted for a 25-year event tailwater condition in the presettling and detention vaults combined with 25-year peak inflow to check for full containment of runoff without overflow above catch basin rim elevations. A further check was made for the 100-year event tailwater condition combined with the 100-year peak inflow, to also assess if overflows could occur under that more conservative analysis condition. The key results of those hydraulic analyses are shown in Table 8, conservatively for the 100-year event analysis conditions and assumptions. The results show full containment of the computed hydraulic profile at all drainage system inlets and junctions based on normal drainage system operations. Those results fully satisfy conveyance hydraulic design requirements in Section 4.2.1.2 of the 2017 RSWDM. The full spreadsheet backwater hydraulic analysis for both 25-year and 100-year event conditions is included in Appendix D. Table 8. Conveyance Storm Drain Hydraulic Analysis, West and East Drainage System Downstream Drainage Inlet or Junction Pipe Segment Designation Upstream Drainage Inlet or Junction 100-Year Hydraulic Grade Line Elevations (ft NAVD) Rim Elevation (ft) Rim Elevation to Headwater Elevation Depth (ft) Downstream Tailwater Upstream Headwater West Drainage System MWL-1 OWS-1 OWS-1 318.04 318.93 328.95 10.0 OWS-1 FS-1 FS-1 318.93 319.35 329.00 9.7 FS-1 SED-1 SED-1 319.35 324.90 329.00 4.1 SED-1 SD-6A D-6A 324.90 325.69 327.55 1.9 SED-1 SD-4 D-4 324.90 325.88 328.21 2.3 D-4 SD-3 D-3 325.88 326.71 328.20 1.5 D-3 SD-2 D-2 326.71 327.28 328.42 1.1 D-2 SD-1 D-1 327.28 327.56 328.50 0.9 D-6A SD-6 D-6 325.69 325.93 327.26 1.3 D-6 SD-5 D-5 325.93 325.95 328.31 2.4 D-6A SD-7 D-7 325.69 325.80 328.30 2.5 D-7 SD-8 D-8 325.80 325.90 329.00 3.1 D-8 SD-9 D-9 325.90 325.96 329.45 3.5 D-9 SD-10 D-10 325.96 325.98 329.60 3.6 East Drainage System MWL-2 OWS-2 OWS-2 319.63 320.43 331.95 11.5 OWS-2 FS-2 FS-2 320.43 320.87 331.88 11.0 FS-2 SED-2 SED-2 320.87 326.40 332.03 5.6 SED-2 SD-15 D-15 326.40 327.47 330.51 3.0 D-15 SD-23 D-23 327.47 327.51 330.52 2.8 D-23 SD-22 D-22 327.51 327.69 330.46 2.3 D-22 SD-21 D-21 327.69 328.23 330.49 2.3 Stormwater Technical Information Report King County Parks – Renton Shop Central Maintenance Facility Replacement Project June 16, 2021 | 47 D-21 SD-20 D-20 328.23 328.24 330.50 2.3 D-22 SD-25 D-25 327.69 328.17 331.42 3.3 D-15 SD-14 D-14 327.47 327.60 329.70 2.1 D-14 SD-13 D-13 327.60 327.79 329.62 1.8 D-13 SD-12 D-12 327.79 327.79 329.72 1.9 SED-2 SD-19 D-19 326.40 328.25 330.22 2.0 D-19 SD-18 D-18 328.25 328.47 329.68 1.2 D-18 SD-17 D-17 328.47 328.50 329.65 1.2 D-19 SD-11 D-11 328.25 328.27 329.65 1.4 D-19 SD-26 D-26 328.25 328.27 329.89 1.6 Note: Refer to Figure 6 for drainage inlet/junction, and pipe segment designations 6 Special Reports and Studies A geotechnical site investigation, evaluation, and report has been completed (Aspect 2018). Further geotechnical explorations and infiltration monitoring wells were installed and monitored in 2019, with findings reported in an updated report (Aspect 2019), as is included in Appendix E. No other special study needs and reports associated with the design of site drainage improvements have been identified at this time. 7 Other Permits A list of permits, approvals, and notifications expected to be required for Project implementation includes: City of Renton • Administrative Conditional Use Permit (CUP) Modification • Site Plan Review • Demolition Permit • Grade and Fill Permit • Building Permit – Commercial/Multi-family • Civil Construction Permit • Sign Permit • Utility Construction Permit Renton Regional Fire Authority • Fire Alarm Installation Approval • Sprinkler Suppression System Installation Approval Stormwater Technical Information Report King County Parks – Renton Shop Central Maintenance Facility Replacement Project 48 | June 16, 2021 Seattle King County Public Health Department • Wastewater Tank Abandonment Report King County Parks and Recreation • SEPA Environmental Checklist Washington Department of Ecology • NPDES Construction General Stormwater Permit Coverage Puget Sound Clean Air Agency • Notice of Construction 8 Construction Stormwater Pollution Prevention This TIR section includes a description of the conceptual Temporary Erosion and Sedimentation Control (TESC) plan and proposed Erosion and Sediment Control (ESC) and Stormwater Pollution Prevention and Spill Control (SWPPS) BMPs as components of the Construction Stormwater Pollution Prevention Plan (CSWPPP). This CSWPPP will be adjusted as needed after County and City agreement is achieved regarding required construction stormwater control facilities. The CSWPPP will then be further updated by the contractor as part of construction submittals. The BMPs to be applied are consistent with Appendix D of the 2017 RSWDM, CR #5 – Construction Stormwater Pollution Prevention, and City of Renton Standard Plans (COR SP). A copy of the CSWPPP document must be maintained on-site and available for City staff access and review during construction. The contractor will be required to implement required BMPs, provide TESC construction oversight, conduct required monitoring and reporting, provide construction stormwater permit compliance, and provide ongoing updates to the CSWPPP consistent with their means/methods of construction. 8.1 Construction Activities and Sequencing The Project will provide full redevelopment of the site including the following key land disturbing construction activities including application of proposed ESC and SWPPS control measures: • Install ESC and SWPPPS control BMP measures including perimeter protection, construction vehicle access entrance and track-out controls temporary conveyance facilities, sedimentation ponds or tanks, and construction runoff temporary pumping, treatment and discharge facilities. • Demolish existing buildings and other above ground material storage facilities. • Remove underground storage tanks, an existing drain field, and any associated contaminated soils encountered for covered storage and testing prior to off-site disposal. • Re-grade the site including major excavation and compacted fill placement. • Install stormwater conveyance, flow control/detention, treatment, and infiltration facilities. Stormwater Technical Information Report King County Parks – Renton Shop Central Maintenance Facility Replacement Project June 16, 2021 | 49 • Import select backfill materials for on-site and off-site utility installations and as the base for new pavements and building foundations. • Stockpile and manage excavated materials on-site for partial reuse and off-site export of excess material for compliant disposal. Cover stockpiles when not being actively managed. • Re-vegetate and fully stabilize disturbed areas beyond the new building and pavement limits. The targeted construction sequencing is as follows: • Establish earthwork limits and install temporary construction fencing • Install ESC BMPs • Implement ESC surface water conveyance, detention, treatment, and discharge at the natural location • Establish SWPPS control measures • Perform building demolition for existing structures, abatement, dust control, transport and disposal of materials • Remove or abandon existing underground storage tanks • Construct sewer system connection to the City of Renton sanitary sewer main • Install temporary sewer connection between buildings and excavate and remove existing septic system. • Install temporary shoring and dewatering system for underground utilities and stormwater infrastructure construction, if need for control of any perched groundwater encountered • Construct Buildings B and C • Install site paving, and amend and stabilized soils around buildings and parking lots • Construct Building A • Complete site paving installation and the remainder of soil stabilization 8.2 ESC Plan and BMP Measures A TESC plan and proper contractor implementation of that plan is needed to meet the COR required ESC performance standards and comply with NPDES Construction Stormwater General Permit conditions. A Project-specific TESC plan is included with the site improvement drawings and illustrates the specific type and location of ESC BMPs proposed for contractor implementation. Table 9 summarizes the primary ESC BMP measures proposed for application within the various ESC categories for anticipated Project construction activities, based on guidance and criteria provided in Appendix D of the 2017 RSWDM. These primary ESC measures are identified on the Erosion Control Plans included as part of the Site Improvement Plans. Where applicable, ESC measures have been specified in accordance with COR Standard Plans (SP). Other WSDOT Standard Plan details are also proposed for use as part of the ESC design. Stormwater Technical Information Report King County Parks – Renton Shop Central Maintenance Facility Replacement Project 50 | June 16, 2021 Table 9. CSWPPP Proposed Primary ESC BMP Measures ESC Category Applicable ESC Measure from 2017 RSWDM Appendix D (COR SP No.) Site Application of Proposed ESC Measures 1. Clearing Limits Stake and wire fence (212.00) or high visibility plastic fence Clearing, vegetation preservation, and critical area limits 2. Cover Measures Surface roughening (213.00) Slopes installation of nets/blankets (213.20) Plastic covering (213.30) Straw wattles (215.00) Temporary and permanent seeding Compost blankets Graded slopes erosion control Restored slope areas Temporary stockpile cover Perimeter slopes sheet flow areas Disturbed soils vegetative stabilization Graded slopes temporary erosion protection 3. Perimeter Protection Temporary chain link fence/gate Silt fence (214.00, 214.10) Vegetated strip Perimeter construction area security Perimeter linear sediment retention Perimeter sheet flow sediment removal 4. Traffic Area Stabilization Stabilized construction entrance (215.10) Wheel wash (215.00) Construction vehicles site entrance/exit Construction vehicles site exit 5. Sediment Retention Sediment trap (211.00) Sediment pond (216.00, 216.10) Storm drain inlet protection (216.30) Curb inlet protection (216.40, 216.50) Outlet of ditch and swales conveyances Runoff collection and treatment area Storm drain inlet catch basin inserts Existing curb inlets (side inlet, grate) 6. Surface Water Collection Interceptor conveyance pipe Interceptor dike and swale (217.00, 217.10) Pipe slope drain (217.30) Ditch check dam (217.40) Outlet protection Temporary site conveyance drains Slopes drainage intercept conveyance Conveyance drains down slopes Along swale and ditch conveyances At temporary drain outlets 7. Dewatering Control Temporary wells, sumps, pumps, sedimentation tanks, and discharge control (if perched groundwater is encountered) Deep excavations and UST removal areas 8. Dust Control Metered hydrant and truck watering Site-wide disturbed area 9. Flow Control Temporary flow equalization ponds and tanks Upstream of discharge to infiltration 10. Protect Existing and Proposed Stormwater Facilities and On-site BMPs Protect and restore ESC BMPs function ESC BMPs damage protection Protect infiltration surfaces Site-wide disturbed area Site-wide disturbed area Construction/permanent infiltration areas 11. Maintain Protective BMPs Maintain and repair ESC BMPs Remove ESC BMPs, stabilize surfaces Site-wide disturbed area ESC BMP placement locations 12. Manage the Project CESCL inspection, monitoring, reporting CSWPPP updating Site-wide disturbed area Contractor updates, maintain on-site Note: COR SP No. = City of Renton Standard Plan number reference The Contractor will be required to assign an ESC supervisor to the Project. The ESC supervisor must be a certified professional in ESC or a Certified Erosion and Sediment Control Lead. The ESC supervisor will be responsible for the inspection, maintenance, and performance review of all ESC measures, as well as maintaining compliance with NPDES Construction Stormwater Permit conditions and associated monitoring and reporting to Ecology. Stormwater Technical Information Report King County Parks – Renton Shop Central Maintenance Facility Replacement Project June 16, 2021 | 51 8.3 SWPPS BMP Measures The SWPPS plan proposes site construction activities and control measures intended to prevent pollutants from coming into contact with site drainage, surface water, or groundwater. Table 10 summarizes the primary SWPPS BMP measures expected to be needed for anticipated Project construction activities, based on guidance and criteria provided in Appendix D of the 2017 Renton SWDM. Table 10. CSWPPP Proposed Primary SWPPS BMP Measures SWPPS Category Applicable SWPPS Measure from 2017 RSWDM Appendix D Site Application of Proposed SWPPS Measures Follow effective pollutant handling and disposal procedures Concrete handling, washout facilities Saw-cutting runoff controls Site-wide good housekeeping practices Site-side for construction concrete washoff and washout containment Provide cover and containment for materials, fuel and other pollutants Materials delivery, storage and containment Mobile construction equipment refueling at designated, fully contained site areas Site spill response kits Temporary covered bins for contaminated soils storage/removal Maximize pollutant control and minimize pollutant sources Construction stormwater filtration treatment Chitosan enhanced sand filtration construction runoff treatment system at southeast corner of site Protect from spills and drips of petroleum products and other pollutants Maintain protective BMPs Designated construction vehicles parking area with drip pans, oil booms Avoid over-application or untimely application of chemicals and fertilizers Manage the project Do not use chemical additives for soil stabilization Prevent or treat contamination of stormwater runoff by pH modifying sources Concrete handling and washout facilities, pH control for high pH water Concrete washoff and washout containment; CO2 sparging or compost sock filtration (if needed) Given the large amount of earthwork on this Project, it is expected that construction stormwater filtration treatment of site runoff during construction will be required. This treatment is proposed to be a chitosan enhanced sand filtration (CESF) system, located downstream from the sedimentation pond at the southeast corner of the site (the contractor may propose alternative BMPs). This treatment system, which has Ecology GULD approval for construction runoff treatment, includes various components including pumping, flocculation/settling, sediment/sludge storage tanks, pressure sand filtration pods, recycle through treatment (as needed), and discharge facilities. It is assumed that discharge from this process will be to the south-side swale that exits the site and flows to a closed depression/infiltration area on the south King County parcel. The construction runoff treatment needs and contractor responsibilities, including preparation of the phased ESC plan and CSWPPP update is identified in the Project specifications. Stormwater Technical Information Report King County Parks – Renton Shop Central Maintenance Facility Replacement Project 52 | June 16, 2021 9 Bond Quantities and Declaration of Covenant Bond Quantities Worksheets have been developed and provided separately to King County Parks. Declaration of Covenant for City of Renton site access for inspection during construction are expected to be completed and executed between King County Parks and the City of Renton. 10 Operations and Maintenance Manual A full Operations and Maintenance (O&M) Manual or Plan is typically not required for public agency projects where standard stormwater control facilities are installed, but is required for privately installed, operated, and maintained facilities. The stormwater conveyance, detention/flow control, treatment, infiltration facilities proposed for use at the site will be maintained by King County in accordance with the 2017 RSWDM, Appendix A - Maintenance Requirements for Flow Control, Conveyance, and Water Quality Facilities. Table 11 provides the grouping and O&M classification of Project stormwater control facilities (standard, non-standard, proprietary), along with a description of their intended function, their recommended inspection and maintenance frequency, and a reference to facility-specific O&M guideline cut sheets. The O&M cut sheets for standard stormwater facilities from the 2017 RSWDM are provided in Appendix G. Where non-standard and/or proprietary stormwater treatment facilities or equipment are proposed for use (e.g., coalescing plate OWS, MWS Linear filters), potential supplier recommended O&M needs, procedures, and frequency are also included in Appendix G. Stormwater control facilities operations will include management of shut-off valves operation for redundant treatment facilities operation during media replacement. Those specifics will be provided as part of construction submittals after County and City agreement is achieved regarding the proposed stormwater control facilities design and O&M requirements. Table 11. Summary of Proposed Stormwater Control Facilities Function and O&M Requirements Stormwater Control Facility Standard, Non-Standard, Proprietary Facility Description and Function O&M Requirements Recommended Minimum Inspection/ Maintenance Frequency (1, 2) Appendix G O&M Cut Sheet Reference Guide Conveyance System Components Catch Basins and Manholes Standard Collect concentrated runoff from site surfaces for intercept with storm drains Monthly during wet season No. 5 Conveyance Pipes and Ditches Standard Conveys intercepted site runoff in storm drains and connects other treatment and infiltration facilities Monthly during wet season No. 6 Debris Barriers / Trash Racks Standard Limits debris entry into storm drain system at pipe culvert inlets Monthly during wet season No. 7 Catch Basin Insert Standard Controls sediment inputs to storm drain system at catch basin inlets Monthly during wet season No. 24 Rock Pad BMP Standard Erosion protects storm drain outfalls Monthly during wet season No. 33 Stormwater Technical Information Report King County Parks – Renton Shop Central Maintenance Facility Replacement Project June 16, 2021 | 53 Flow Control / Detention System Components Detention Tanks and Vaults Standard Provides active storage to reduce peak inflows to design outflows consistent with downstream treatment and infiltration facilities design Monthly during wet season No. 3 Control Structure / Flow Restrictor Standard Provides detention vault outlet flow restriction and splitting for delivery of design flows to downstream treatment and infiltration facilities Monthly during wet season No. 4 Water Quality Treatment System Components Wet / Pre- Settling Vault Standard Intercepts and settles out large size- fraction sediments in pre-settling / detention vault upstream of treatment facilities to protect their function and reduce their maintenance needs Monthly during wet season No. 17 Coalescing Plate OWS Standard, Proprietary Provides required oil control and containment consistent with required function and performance; periodic oils and other floatables removal required Monthly during wet season No. 23 Contech Vortclarex CP OWS included Cartridge Filter System (MWS Linear) Non-Standard, Proprietary Provides required enhanced treatment of runoff for targeted TSS and dissolved metals removal media biofiltration processes to meet groundwater and aquifer protections Monthly during wet season No. 21 Bio Clean MWS Linear included Infiltration System Components Infiltration Facilities / Gallery Standard Provides for full recharge (through 100-year event) of treated site runoff Semi-Annual No. 2 Gravel-Filled Dispersion Trench Standard Provides for well-distributed recharge of treated site runoff across infiltration galleries Semi-Annual (not accessible for maintenance) No. 27 Flow Control (LID) BMP Components Soil Amendment Standard Provides source control of runoff, reducing the flow rate and volume of runoff discharged to the storm drain and infiltration systems Semi-Annual No. 38 Bioretention / Rain Garden Standard Provides for treatment and infiltration of runoff from rooftop areas connected to bioretention cell, thus reducing the flow rate and volume of runoff discharged to the storm drain system and infiltration systems Semi-Annual No. 31, No. 37 Notes: (1) Adjust inspection frequency to also occur after all significant storm events, typically exceeding 0.25 inches of precipitation within a 24-hour period. (2) Adjust maintenance frequency consistent with thresholds for sediment accumulation as noted in Appendix G O&M cut sheets. Stormwater Technical Information Report King County Parks – Renton Shop Central Maintenance Facility Replacement Project 54 | June 16, 2021 11 References Aspect Consultants 2019. Geotechnical Evaluation – 30 Percent Design. King County Parks and Recreation Division - Renton Shop. Prepared for HDR Architecture, Inc. May 31, 2019. City of Renton 2018. City of Renton Online GIS viewer, http://rp.rentonwa.gov/HTML5Public/Index.HTML?viewer=CORMaps. Accessed December 2018. City of Renton 2017. City of Renton Surface Water Design Manual. City of Renton Public Works Department, Surface Water Utility. December 12, 2016 (Effective January 1, 2017). City of Renton 2017a. FEMA Flood Insurance Rate Map (FIRM), King County, Washington and Incorporated Areas, City of Renton Map No. 5033C0981G (Preliminary). Revised September 15, 2017. Google Earth Pro 2018. Aerial Imaging and Mapping Viewer of City of Renton. Accessed December 2018. Herrera Environmental Consultants 2015. Lower Cedar River Chinook Salmon Habitat Restoration Assessment Study, Habitat Restoration Site Potential and Feasibility Analysis Report. Prepared for the City of Renton. November 5, 2015. King County 2016. King County Surface Water Design Manual. King County Department of Natural Resources and Parks. April 24, 2016. King County 2016. King County Stormwater Pollution Prevention Manual. King County Department of Natural Resources and Parks. April 2016. King County 1997. Lower Cedar River Basin and Nonpoint Pollution Action Plan. Prepared in Coordination with City of Renton and Washington State Department of Ecology. Adopted by Metropolitan King County Council July 1997. WSDOT 2019. Washington State Department of Transportation. Hydraulics Manual, M23-03.06. Environmental and Engineering Programs. April 2019. Stormwater Technical Information Report King County Parks – Renton Shop Central Maintenance Facility Replacement Project June 16, 2021 | A-1 Appendix A. Project Drainage Review Classification Stormwater Technical Information Report King County Parks – Renton Shop Central Maintenance Facility Replacement Project June 16, 2021 | B-1 Appendix B. MGSFlood Hydrologic Analysis for Flow Control, Water Quality Treatment, Bioretention, and Infiltration Facilities MGS FLOOD PROJECT REPORT West (P1) TDA Model Take-Off Values PRE-DEVELOPED INPUT: Impervious = 3.1771 acres Till Grass = 0.0340 acres POST-DEVELOPED INPUT: Impervious = 3.2111 acres ——————————————————————— MGS FLOOD PROJECT REPORT Program Version: MGSFlood 4.46 Program License Number: 200510004 Project Simulation Performed on: 08/16/2019 11:11 AM Report Generation Date: 08/16/2019 11:11 AM ————————————————————————————————— Input File Name: 90%_TDA_Deli_TDA_West_Pond.fld Project Name: King County CMF Analysis Title: TDA 1 – West (P1) Comments: ———————————————— PRECIPITATION INPUT ———————————————— Computational Time Step (Minutes): 5 Extended Precipitation Time Series Selected Climatic Region Number: 3 Full Period of Record Available used for Routing Precipitation Station : 95004005 Puget West 40 in_5min 10/01/1939-10/01/2097 Evaporation Station : 951040 Puget West 40 in MAP Evaporation Scale Factor : 0.750 HSPF Parameter Region Number: 1 HSPF Parameter Region Name : USGS Default ********** Default HSPF Parameters Used (Not Modified by User) *************** ********************** WATERSHED DEFINITION *********************** Predevelopment/Post Development Tributary Area Summary Predeveloped Post Developed Total Subbasin Area (acres) 3.211 3.211 Area of Links that Include Precip/Evap (acres) 0.000 0.104 Total (acres) 3.211 3.316 ----------------------SCENARIO: PREDEVELOPED Number of Subbasins: 1 ---------- Subbasin : Subbasin 1 ---------- -------Area (Acres) -------- Till Grass 0.034 Impervious 3.177 ---------------------------------------------- Subbasin Total 3.211 ----------------------SCENARIO: POSTDEVELOPED Number of Subbasins: 1 ---------- Subbasin : Subbasin 1 ---------- -------Area (Acres) -------- Impervious 3.211 ---------------------------------------------- Subbasin Total 3.211 ************************* LINK DATA ******************************* ----------------------SCENARIO: PREDEVELOPED Number of Links: 1 ------------------------------------------ Link Name: New Channel Lnk1 Link Type: Open Channel Downstream Link: None ----------Left Overbank Upper Sideslope (z) : 0.500 Upper Width (ft) : 3.000 Middle Sideslope (z) : 10.000 Middle Width (ft) : 10.000 Mannings n : 0.040 ----------Main Channel Lower Sideslope Left (z) : 0.500 Lower Width Left (ft) : 3.000 Lower Sideslope Right (z) : 0.500 Lower Width Right (ft) : 3.000 Mannings n : 0.024 Base Width (ft) : 10.0 Elevation (ft) : 100.00 Channel Slope (ft/ft) : 0.020 Channel Length (ft) : 1000.0 ----------Right Overbank Upper Sideslope (z) : 0.500 Upper Width (ft) : 3.000 Middle Sideslope (z) : 10.000 Middle Width (ft) : 10.000 Mannings n : 0.040 Massmann Infiltration Option Used Hydraulic Conductivity (in/hr) : 0.0 Depth to Water Table (ft) : 100.0 Bio-Fouling Potential : Low Maintenance : Average or Better ************************* LINK DATA ******************************* ----------------------SCENARIO: POSTDEVELOPED Number of Links: 2 ------------------------------------------ Link Name: Detention Vault Link Type: Structure Downstream Link Name: Infiltration Gallery Prismatic Pond Option Used Pond Floor Elevation (ft) : 319.50 Riser Crest Elevation (ft) : 325.00 Max Pond Elevation (ft) : 326.00 Storage Depth (ft) : 5.50 Pond Bottom Length (ft) : 358.0 Pond Bottom Width (ft) : 10.0 Pond Side Slopes (ft/ft) : L1= 0.00 L2= 0.00 W1= 0.00 W2= 0.00 Bottom Area (sq-ft) : 3580. Area at Riser Crest El (sq-ft) : 3,580. (acres) : 0.082 Volume at Riser Crest (cu-ft) : 19,690. (ac-ft) : 0.452 Area at Max Elevation (sq-ft) : 3580. (acres) : 0.082 Vol at Max Elevation (cu-ft) : 23,270. (ac-ft) : 0.534 Massmann Infiltration Option Used Hydraulic Conductivity (in/hr) : 0.00 Depth to Water Table (ft) : 0.00 Bio-Fouling Potential : Low Maintenance : Average or Better Riser Geometry Riser Structure Type : Circular Riser Diameter (in) : 12.00 Common Length (ft) : 0.000 Riser Crest Elevation : 325.00 ft Hydraulic Structure Geometry Number of Devices: 1 ---Device Number 1 --- Device Type : Circular Orifice Control Elevation (ft) : 319.50 Diameter (in) : 3.25 Orientation : Vertical Elbow : No ------------------------------------------ Link Name: Infiltration Gallery Link Type: Bioretention Facility Downstream Link: None Base Elevation (ft) : 311.50 Riser Crest Elevation (ft) : 313.50 Storage Depth (ft) : 2.00 Bottom Length (ft) : 111.0 Bottom Width (ft) : 41.0 Side Slopes (ft/ft) : L1= 0.00 L2= 0.00 W1= 0.00 W2= 0.00 Bottom Area (sq-ft) : 4551. Area at Riser Crest El (sq-ft) : 4,551. (acres) : 0.104 Volume at Riser Crest (cu-ft) : 9,239. (ac-ft) : 0.212 Infiltration on Bottom only Selected Soil Properties Biosoil Thickness (ft) : 0.10 Biosoil Saturated Hydraulic Conductivity (in/hr) : 4.00 Biosoil Porosity (Percent) : 30.00 Maximum Elevation of Bioretention Soil : 313.50 Native Soil Hydraulic Conductivity (in/hr) : 20.00 Riser Geometry Riser Structure Type : Circular Riser Diameter (in) : 6.00 Common Length (ft) : 0.000 Riser Crest Elevation : 313.50 ft Hydraulic Structure Geometry Number of Devices: 0 POC AT SUB-BASIN **********************FLOOD FREQUENCY AND DURATION STATISTICS******************* ----------------------SCENARIO: PREDEVELOPED Number of Subbasins: 1 Number of Links: 1 ----------------------SCENARIO: POSTDEVELOPED Number of Subbasins: 1 Number of Links: 2 ***********Groundwater Recharge Summary ************* Recharge is computed as input to Perlnd Groundwater Plus Infiltration in Structures Total Predeveloped Recharge During Simulation Model Element Recharge Amount (ac-ft) ----------------------------------------------------------------------------------------------- Subbasin: Subbasin 1 4.024 Link: New Channel Lnk1 0.000 _____________________________________ Total: 4.024 Total Post Developed Recharge During Simulation Model Element Recharge Amount (ac-ft) ----------------------------------------------------------------------------------------------- Subbasin: Subbasin 1 0.000 Link: Detention Vault Not Computed Link: Infiltration Gallery Not Computed _____________________________________ Total: 0.000 Total Predevelopment Recharge is Greater than Post Developed Average Recharge Per Year, (Number of Years= 158) Predeveloped: 0.025 ac-ft/year, Post Developed: 0.000 ac-ft/year ***********Water Quality Facility Data ************* ----------------------SCENARIO: PREDEVELOPED Number of Links: 1 ********** Link: New Channel Lnk1 ********** Infiltration/Filtration Statistics-------------------- Inflow Volume (ac-ft): 1444.43 Inflow Volume Including PPT-Evap (ac-ft): 1444.43 Total Runoff Infiltrated (ac-ft): 0.00, 0.00% Total Runoff Filtered (ac-ft): 0.00, 0.00% Primary Outflow To Downstream System (ac-ft): 1447.56 Secondary Outflow To Downstream System (ac-ft): 0.00 Percent Treated (Infiltrated+Filtered)/Total Volume: 0.00% ----------------------SCENARIO: POSTDEVELOPED Number of Links: 2 ***********Compliance Point Results ************* Scenario Predeveloped Compliance Link: New Channel Lnk1 Scenario Postdeveloped Compliance Subbasin: Subbasin 1 *** Point of Compliance Flow Frequency Data *** Recurrence Interval Computed Using Gringorten Plotting Position Predevelopment Runoff Postdevelopment Runoff Tr (Years) Discharge (cfs) Tr (Years) Discharge (cfs) ---------------------------------------------------------------------------------------------------------------------- 2-Year 1.305 2-Year 1.599 5-Year 1.652 5-Year 2.015 10-Year 1.864 10-Year 2.370 25-Year 2.257 25-Year 2.803 50-Year 2.888 50-Year 3.496 100-Year 3.777 100-Year 4.471 200-Year 4.091 200-Year 4.833 ** Record too Short to Compute Peak Discharge for These Recurrence Intervals POC AT DETENTION VAULT **********************FLOOD FREQUENCY AND DURATION STATISTICS******************* ----------------------SCENARIO: PREDEVELOPED Number of Subbasins: 1 Number of Links: 1 ----------------------SCENARIO: POSTDEVELOPED Number of Subbasins: 1 Number of Links: 2 ********** Link: Detention Vault ********** Link WSEL Stats WSEL Frequency Data(ft) (Recurrence Interval Computed Using Gringorten Plotting Position) Tr (yrs) WSEL Peak (ft) ====================================== 1.05-Year 320.736 1.11-Year 320.854 1.25-Year 321.115 2.00-Year 321.663 3.33-Year 322.166 5-Year 322.497 10-Year 323.160 25-Year 323.888 50-Year 324.666 100-Year 324.929 ***********Groundwater Recharge Summary ************* Recharge is computed as input to Perlnd Groundwater Plus Infiltration in Structures Total Predeveloped Recharge During Simulation Model Element Recharge Amount (ac-ft) ----------------------------------------------------------------------------------------------- Subbasin: Subbasin 1 4.024 Link: New Channel Lnk1 0.000 _____________________________________ Total: 4.024 Total Post Developed Recharge During Simulation Model Element Recharge Amount (ac-ft) ----------------------------------------------------------------------------------------------- Subbasin: Subbasin 1 0.000 Link: Detention Vault 0.000 Link: Infiltration Gallery Not Computed _____________________________________ Total: 0.000 Total Predevelopment Recharge is Greater than Post Developed Average Recharge Per Year, (Number of Years= 158) Predeveloped: 0.025 ac-ft/year, Post Developed: 0.000 ac-ft/year ***********Water Quality Facility Data ************* ----------------------SCENARIO: PREDEVELOPED Number of Links: 1 ********** Link: New Channel Lnk1 ********** Infiltration/Filtration Statistics-------------------- Inflow Volume (ac-ft): 1444.43 Inflow Volume Including PPT-Evap (ac-ft): 1444.43 Total Runoff Infiltrated (ac-ft): 0.00, 0.00% Total Runoff Filtered (ac-ft): 0.00, 0.00% Primary Outflow To Downstream System (ac-ft): 1447.56 Secondary Outflow To Downstream System (ac-ft): 0.00 Percent Treated (Infiltrated+Filtered)/Total Volume: 0.00% ----------------------SCENARIO: POSTDEVELOPED Number of Links: 2 ********** Link: Detention Vault ********** Basic Wet Pond Volume (91% Exceedance): 17666. cu-ft Computed Large Wet Pond Volume, 1.5*Basic Volume: 26500. cu-ft Infiltration/Filtration Statistics-------------------- Inflow Volume (ac-ft): 1452.50 Inflow Volume Including PPT-Evap (ac-ft): 1452.50 Total Runoff Infiltrated (ac-ft): 0.00, 0.00% Total Runoff Filtered (ac-ft): 0.00, 0.00% Primary Outflow To Downstream System (ac-ft): 1452.86 Secondary Outflow To Downstream System (ac-ft): 0.00 Percent Treated (Infiltrated+Filtered)/Total Volume: 0.00% ***********Compliance Point Results ************* Scenario Predeveloped Compliance Link: New Channel Lnk1 Scenario Postdeveloped Compliance Link: Detention Vault *** Point of Compliance Flow Frequency Data *** Recurrence Interval Computed Using Gringorten Plotting Position Predevelopment Runoff Postdevelopment Runoff Tr (Years) Discharge (cfs) Tr (Years) Discharge (cfs) ---------------------------------------------------------------------------------------------------------------------- 2-Year 1.305 2-Year 0.401 5-Year 1.652 5-Year 0.477 10-Year 1.864 10-Year 0.529 25-Year 2.257 25-Year 0.581 50-Year 2.888 50-Year 0.632 100-Year 3.777 100-Year 0.649 200-Year 4.091 200-Year 0.651 ** Record too Short to Compute Peak Discharge for These Recurrence Intervals **** Flow Duration Performance **** Excursion at Predeveloped 50%Q2 (Must be Less Than or Equal to 0%): -100.0% PASS Maximum Excursion from 50%Q2 to Q2 (Must be Less Than or Equal to 0%): -99.9% PASS Maximum Excursion from Q2 to Q50 (Must be less than 10%): -88.8% PASS Percent Excursion from Q2 to Q50 (Must be less than 50%): 0.0% PASS ------------------------------------------------------------------------------------------------- MEETS ALL FLOW DURATION DESIGN CRITERIA: PASS ------------------------------------------------------------------------------------------------- POC AT DETENTION VAULT **********************FLOOD FREQUENCY AND DURATION STATISTICS******************* ----------------------SCENARIO: PREDEVELOPED Number of Subbasins: 1 Number of Links: 1 ----------------------SCENARIO: POSTDEVELOPED Number of Subbasins: 1 Number of Links: 2 ********** Link: Infiltration Gallery ********** Link WSEL Stats WSEL Frequency Data(ft) (Recurrence Interval Computed Using Gringorten Plotting Position) Tr (yrs) WSEL Peak (ft) ====================================== 1.05-Year 311.513 1.11-Year 311.513 1.25-Year 311.515 2.00-Year 311.517 3.33-Year 311.590 5-Year 311.717 10-Year 312.040 25-Year 312.544 50-Year 312.994 100-Year 313.522 ***********Groundwater Recharge Summary ************* Recharge is computed as input to Perlnd Groundwater Plus Infiltration in Structures Total Predeveloped Recharge During Simulation Model Element Recharge Amount (ac-ft) ----------------------------------------------------------------------------------------------- Subbasin: Subbasin 1 4.024 Link: New Channel Lnk1 0.000 _____________________________________ Total: 4.024 Total Post Developed Recharge During Simulation Model Element Recharge Amount (ac-ft) ----------------------------------------------------------------------------------------------- Subbasin: Subbasin 1 0.000 Link: Detention Vault Not Computed Link: Infiltration Gallery 1496.410 _____________________________________ Total: 1496.410 Total Predevelopment Recharge is Less than Post Developed Average Recharge Per Year, (Number of Years= 158) Predeveloped: 0.025 ac-ft/year, Post Developed: 9.471 ac-ft/year ***********Water Quality Facility Data ************* ----------------------SCENARIO: PREDEVELOPED Number of Links: 1 ********** Link: New Channel Lnk1 ********** Infiltration/Filtration Statistics-------------------- Inflow Volume (ac-ft): 1444.43 Inflow Volume Including PPT-Evap (ac-ft): 1444.43 Total Runoff Infiltrated (ac-ft): 0.00, 0.00% Total Runoff Filtered (ac-ft): 0.00, 0.00% Primary Outflow To Downstream System (ac-ft): 1447.56 Secondary Outflow To Downstream System (ac-ft): 0.00 Percent Treated (Infiltrated+Filtered)/Total Volume: 0.00% ----------------------SCENARIO: POSTDEVELOPED Number of Links: 2 ********** Link: Infiltration Gallery********** Infiltration/Filtration Statistics-------------------- Inflow Volume (ac-ft): 1452.86 Inflow Volume Including PPT-Evap (ac-ft): 1496.41 Total Runoff Infiltrated (ac-ft): 1496.41, 100.00% Total Runoff Filtered (ac-ft): 0.00, 0.00% Primary Outflow To Downstream System (ac-ft): 0.08 Secondary Outflow To Downstream System (ac-ft): 0.00 Percent Treated (Infiltrated+Filtered)/Total Volume: 100.00% ***********Compliance Point Results ************* Scenario Predeveloped Compliance Link: New Channel Lnk1 Scenario Postdeveloped Compliance Link: Infiltration Gallery *** Point of Compliance Flow Frequency Data *** Recurrence Interval Computed Using Gringorten Plotting Position Predevelopment Runoff Postdevelopment Runoff Tr (Years) Discharge (cfs) Tr (Years) Discharge (cfs) ---------------------------------------------------------------------------------------------------------------------- 2-Year 1.305 2-Year 0.000 5-Year 1.652 5-Year 0.000 10-Year 1.864 10-Year 0.000 25-Year 2.257 25-Year 0.000 50-Year 2.888 50-Year 0.000 100-Year 3.777 100-Year 3.476E-02 200-Year 4.091 200-Year 0.130 ** Record too Short to Compute Peak Discharge for These Recurrence Intervals **** Flow Duration Performance **** Excursion at Predeveloped 50%Q2 (Must be Less Than or Equal to 0%): -100.0% PASS Maximum Excursion from 50%Q2 to Q2 (Must be Less Than or Equal to 0%): -99.9% PASS Maximum Excursion from Q2 to Q50 (Must be less than 10%): -88.8% PASS Percent Excursion from Q2 to Q50 (Must be less than 50%): 0.0% PASS ------------------------------------------------------------------------------------------------- MEETS ALL FLOW DURATION DESIGN CRITERIA: PASS ------------------------------------------------------------------------------------------------- **** LID Duration Performance **** Excursion at Predeveloped 8%Q2 (Must be Less Than 0%): -100.0% PASS Maximum Excursion from 8%Q2 to 50%Q2 (Must be Less Than 0%): -100.0% PASS ------------------------------------------------------------------------------------------------- MEETS ALL LID DURATION DESIGN CRITERIA: PASS ------------------------------------------------------------------------------------------------- WATER QUALITY DATA INFLOW TO DETENTION: On-line discharge rate (cfs) = 0.503 Off-line discharge rate (cfs) = 0.284 OUTFLOW FROM DETENTION: On-line discharge rate (cfs) = 0.287 Off-line discharge rate (cfs) = 0.173 MGS FLOOD PROJECT REPORT East (P2) TDA Model Take-Off Values PRE-DEVELOPED INPUT: Impervious = 2.3379 acres POST-DEVELOPED INPUT: Impervious = 2.0233 acres Till Grass = 0.3145 acres ————————————————————————————————— MGS FLOOD PROJECT REPORT Program Version: MGSFlood 4.46 Program License Number: 200510004 Project Simulation Performed on: 08/16/2019 10:44 AM Report Generation Date: 08/16/2019 10:45 AM ————————————————————————————————— Input File Name: 90%_TDA_Deli_TDA_East_08152019.fld Project Name: King County CMF Analysis Title: TDA 2 - East (P2) Comments: ———————————————— PRECIPITATION INPUT ———————————————— Computational Time Step (Minutes): 5 Extended Precipitation Time Series Selected Climatic Region Number: 3 Full Period of Record Available used for Routing Precipitation Station : 95004005 Puget West 40 in_5min 10/01/1939-10/01/2097 Evaporation Station : 951040 Puget West 40 in MAP Evaporation Scale Factor : 0.750 HSPF Parameter Region Number: 1 HSPF Parameter Region Name : USGS Default ********** Default HSPF Parameters Used (Not Modified by User) *************** ********************** WATERSHED DEFINITION *********************** Predevelopment/Post Development Tributary Area Summary Predeveloped Post Developed Total Subbasin Area (acres) 2.338 2.338 Area of Links that Include Precip/Evap (acres) 0.000 0.091 Total (acres) 2.338 2.429 ----------------------SCENARIO: PREDEVELOPED Number of Subbasins: 1 ---------- Subbasin : Subbasin 1 ---------- -------Area (Acres) -------- Impervious 2.338 ---------------------------------------------- Subbasin Total 2.338 ----------------------SCENARIO: POSTDEVELOPED Number of Subbasins: 1 ---------- Subbasin : Subbasin 1 ---------- -------Area (Acres) -------- Till Grass 0.315 Impervious 2.023 ---------------------------------------------- Subbasin Total 2.338 ************************* LINK DATA ******************************* ----------------------SCENARIO: PREDEVELOPED Number of Links: 1 ------------------------------------------ Link Name: New Channel Lnk1 Link Type: Open Channel Downstream Link: None ----------Left Overbank Upper Sideslope (z) : 0.500 Upper Width (ft) : 3.000 Middle Sideslope (z) : 10.000 Middle Width (ft) : 10.000 Mannings n : 0.040 ----------Main Channel Lower Sideslope Left (z) : 0.500 Lower Width Left (ft) : 3.000 Lower Sideslope Right (z) : 0.500 Lower Width Right (ft) : 3.000 Mannings n : 0.024 Base Width (ft) : 10.0 Elevation (ft) : 100.00 Channel Slope (ft/ft) : 0.020 Channel Length (ft) : 1000.0 ----------Right Overbank Upper Sideslope (z) : 0.500 Upper Width (ft) : 3.000 Middle Sideslope (z) : 10.000 Middle Width (ft) : 10.000 Mannings n : 0.040 Massmann Infiltration Option Used Hydraulic Conductivity (in/hr) : 0.0 Depth to Water Table (ft) : 100.0 Bio-Fouling Potential : Low Maintenance : Average or Better ************************* LINK DATA ******************************* ----------------------SCENARIO: POSTDEVELOPED Number of Links: 2 ------------------------------------------ Link Name: Detention Vault Link Type: Structure Downstream Link Name: Infiltration Gallery Prismatic Pond Option Used Pond Floor Elevation (ft) : 321.00 Riser Crest Elevation (ft) : 326.50 Max Pond Elevation (ft) : 327.50 Storage Depth (ft) : 5.50 Pond Bottom Length (ft) : 326.0 Pond Bottom Width (ft) : 10.0 Pond Side Slopes (ft/ft) : L1= 0.00 L2= 0.00 W1= 0.00 W2= 0.00 Bottom Area (sq-ft) : 3260. Area at Riser Crest El (sq-ft) : 3,260. (acres) : 0.075 Volume at Riser Crest (cu-ft) : 17,930. (ac-ft) : 0.412 Area at Max Elevation (sq-ft) : 3260. (acres) : 0.075 Vol at Max Elevation (cu-ft) : 21,190. (ac-ft) : 0.486 Constant Infiltration Option Used Infiltration Rate (in/hr): 0.00 Riser Geometry Riser Structure Type : Circular Riser Diameter (in) : 12.00 Common Length (ft) : 0.000 Riser Crest Elevation : 326.50 ft Hydraulic Structure Geometry Number of Devices: 1 ---Device Number 1 --- Device Type : Circular Orifice Control Elevation (ft) : 321.00 Diameter (in) : 2.25 Orientation : Vertical Elbow : No ------------------------------------------ Link Name: Infiltration Gallery Link Type: Bioretention Facility Downstream Link: None Base Elevation (ft) : 313.50 Riser Crest Elevation (ft) : 315.50 Storage Depth (ft) : 2.00 Bottom Length (ft) : 86.0 Bottom Width (ft) : 46.0 Side Slopes (ft/ft) : L1= 0.00 L2= 0.00 W1= 0.00 W2= 0.00 Bottom Area (sq-ft) : 3956. Area at Riser Crest El (sq-ft) : 3,956. (acres) : 0.091 Volume at Riser Crest (cu-ft) : 8,031. (ac-ft) : 0.184 Infiltration on Bottom only Selected Soil Properties Biosoil Thickness (ft) : 0.10 Biosoil Saturated Hydraulic Conductivity (in/hr) : 4.00 Biosoil Porosity (Percent) : 30.00 Maximum Elevation of Bioretention Soil : 315.50 Native Soil Hydraulic Conductivity (in/hr) : 20.00 Riser Geometry Riser Structure Type : Circular Riser Diameter (in) : 12.00 Common Length (ft) : 0.000 Riser Crest Elevation : 315.50 ft Hydraulic Structure Geometry Number of Devices: 0 POC AT SUB-BASIN **********************FLOOD FREQUENCY AND DURATION STATISTICS******************* ----------------------SCENARIO: PREDEVELOPED Number of Subbasins: 1 Number of Links: 1 ----------------------SCENARIO: POSTDEVELOPED Number of Subbasins: 1 Number of Links: 2 ***********Groundwater Recharge Summary ************* Recharge is computed as input to Perlnd Groundwater Plus Infiltration in Structures Total Predeveloped Recharge During Simulation Model Element Recharge Amount (ac-ft) ----------------------------------------------------------------------------------------------- Subbasin: Subbasin 1 0.000 Link: New Channel Lnk1 0.000 _____________________________________ Total: 0.000 Total Post Developed Recharge During Simulation Model Element Recharge Amount (ac-ft) ----------------------------------------------------------------------------------------------- Subbasin: Subbasin 1 37.226 Link: Detention Vault Not Computed Link: Infiltration Gallery Not Computed _____________________________________ Total: 37.226 Total Predevelopment Recharge is Less than Post Developed Average Recharge Per Year, (Number of Years= 158) Predeveloped: 0.000 ac-ft/year, Post Developed: 0.236 ac-ft/year ***********Water Quality Facility Data ************* ----------------------SCENARIO: PREDEVELOPED Number of Links: 1 ********** Link: New Channel Lnk1 ********** Infiltration/Filtration Statistics-------------------- Inflow Volume (ac-ft): 1057.52 Inflow Volume Including PPT-Evap (ac-ft): 1057.52 Total Runoff Infiltrated (ac-ft): 0.00, 0.00% Total Runoff Filtered (ac-ft): 0.00, 0.00% Primary Outflow To Downstream System (ac-ft): 1059.83 Secondary Outflow To Downstream System (ac-ft): 0.00 Percent Treated (Infiltrated+Filtered)/Total Volume: 0.00% ----------------------SCENARIO: POSTDEVELOPED Number of Links: 2 ***********Compliance Point Results ************* Scenario Predeveloped Compliance Link: New Channel Lnk1 Scenario Postdeveloped Compliance Subbasin: Subbasin 1 *** Point of Compliance Flow Frequency Data *** Recurrence Interval Computed Using Gringorten Plotting Position Predevelopment Runoff Postdevelopment Runoff Tr (Years) Discharge (cfs) Tr (Years) Discharge (cfs) ---------------------------------------------------------------------------------------------------------------------- 2-Year 0.958 2-Year 1.036 5-Year 1.209 5-Year 1.319 10-Year 1.365 10-Year 1.545 25-Year 1.653 25-Year 1.809 50-Year 2.040 50-Year 2.259 100-Year 2.482 100-Year 3.001 200-Year 2.842 200-Year 3.190 ** Record too Short to Compute Peak Discharge for These Recurrence Intervals POC AT DETENTION VAULT **********************FLOOD FREQUENCY AND DURATION STATISTICS******************* ----------------------SCENARIO: PREDEVELOPED Number of Subbasins: 1 Number of Links: 1 ----------------------SCENARIO: POSTDEVELOPED Number of Subbasins: 1 Number of Links: 2 ********** Link: Detention Vault ********** Link WSEL Stats WSEL Frequency Data(ft) (Recurrence Interval Computed Using Gringorten Plotting Position) Tr (yrs) WSEL Peak (ft) ====================================== 1.05-Year 322.215 1.11-Year 322.359 1.25-Year 322.532 2.00-Year 323.079 3.33-Year 323.507 5-Year 323.891 10-Year 324.518 25-Year 325.386 50-Year 325.939 100-Year 326.397 ***********Groundwater Recharge Summary ************* Recharge is computed as input to Perlnd Groundwater Plus Infiltration in Structures Total Predeveloped Recharge During Simulation Model Element Recharge Amount (ac-ft) ----------------------------------------------------------------------------------------------- Subbasin: Subbasin 1 0.000 Link: New Channel Lnk1 0.000 _____________________________________ Total: 0.000 Total Post Developed Recharge During Simulation Model Element Recharge Amount (ac-ft) ----------------------------------------------------------------------------------------------- Subbasin: Subbasin 1 37.226 Link: Detention Vault 0.000 Link: Infiltration Gallery Not Computed _____________________________________ Total: 37.226 Total Predevelopment Recharge is Less than Post Developed Average Recharge Per Year, (Number of Years= 158) Predeveloped: 0.000 ac-ft/year, Post Developed: 0.236 ac-ft/year ***********Water Quality Facility Data ************* ----------------------SCENARIO: PREDEVELOPED Number of Links: 1 ********** Link: New Channel Lnk1 ********** Infiltration/Filtration Statistics-------------------- Inflow Volume (ac-ft): 1057.52 Inflow Volume Including PPT-Evap (ac-ft): 1057.52 Total Runoff Infiltrated (ac-ft): 0.00, 0.00% Total Runoff Filtered (ac-ft): 0.00, 0.00% Primary Outflow To Downstream System (ac-ft): 1059.83 Secondary Outflow To Downstream System (ac-ft): 0.00 Percent Treated (Infiltrated+Filtered)/Total Volume: 0.00% ----------------------SCENARIO: POSTDEVELOPED Number of Links: 2 ********** Link: Detention Vault ********** Basic Wet Pond Volume (91% Exceedance): 11567. cu-ft Computed Large Wet Pond Volume, 1.5*Basic Volume: 17351. cu-ft Infiltration/Filtration Statistics-------------------- Inflow Volume (ac-ft): 982.78 Inflow Volume Including PPT-Evap (ac-ft): 982.78 Total Runoff Infiltrated (ac-ft): 0.00, 0.00% Total Runoff Filtered (ac-ft): 0.00, 0.00% Primary Outflow To Downstream System (ac-ft): 982.77 Secondary Outflow To Downstream System (ac-ft): 0.00 Percent Treated (Infiltrated+Filtered)/Total Volume: 0.00% ***********Compliance Point Results ************* Scenario Predeveloped Compliance Link: New Channel Lnk1 Scenario Postdeveloped Compliance Link: Detention Vault *** Point of Compliance Flow Frequency Data *** Recurrence Interval Computed Using Gringorten Plotting Position Predevelopment Runoff Postdevelopment Runoff Tr (Years) Discharge (cfs) Tr (Years) Discharge (cfs) ---------------------------------------------------------------------------------------------------------------------- 2-Year 0.958 2-Year 0.190 5-Year 1.209 5-Year 0.226 10-Year 1.365 10-Year 0.250 25-Year 1.653 25-Year 0.280 50-Year 2.040 50-Year 0.297 100-Year 2.482 100-Year 0.311 200-Year 2.842 200-Year 0.687 ** Record too Short to Compute Peak Discharge for These Recurrence Intervals **** Flow Duration Performance **** Excursion at Predeveloped 50%Q2 (Must be Less Than or Equal to 0%): -99.9% PASS Maximum Excursion from 50%Q2 to Q2 (Must be Less Than or Equal to 0%): -99.7% PASS Maximum Excursion from Q2 to Q50 (Must be less than 10%): -91.6% PASS Percent Excursion from Q2 to Q50 (Must be less than 50%): 0.0% PASS ------------------------------------------------------------------------------------------------- MEETS ALL FLOW DURATION DESIGN CRITERIA: PASS ------------------------------------------------------------------------------------------------- **** LID Duration Performance **** Excursion at Predeveloped 8%Q2 (Must be Less Than 0%): -11.9% PASS Maximum Excursion from 8%Q2 to 50%Q2 (Must be Less Than 0%): -28.0% PASS ------------------------------------------------------------------------------------------------- MEETS ALL LID DURATION DESIGN CRITERIA: PASS ------------------------------------------------------------------------------------------------- POC AT INFILTRATION GALLERY **********************FLOOD FREQUENCY AND DURATION STATISTICS******************* ----------------------SCENARIO: PREDEVELOPED Number of Subbasins: 1 Number of Links: 1 ----------------------SCENARIO: POSTDEVELOPED Number of Subbasins: 1 Number of Links: 2 ********** Link: Infiltration Gallery ********** Link WSEL Stats WSEL Frequency Data(ft) (Recurrence Interval Computed Using Gringorten Plotting Position) Tr (yrs) WSEL Peak (ft) ====================================== 1.05-Year 313.507 1.11-Year 313.508 1.25-Year 313.509 2.00-Year 313.510 3.33-Year 313.511 5-Year 313.512 10-Year 313.514 25-Year 313.515 50-Year 313.516 100-Year 313.517 ***********Groundwater Recharge Summary ************* Recharge is computed as input to Perlnd Groundwater Plus Infiltration in Structures Total Predeveloped Recharge During Simulation Model Element Recharge Amount (ac-ft) ----------------------------------------------------------------------------------------------- Subbasin: Subbasin 1 0.000 Link: New Channel Lnk1 0.000 _____________________________________ Total: 0.000 Total Post Developed Recharge During Simulation Model Element Recharge Amount (ac-ft) ----------------------------------------------------------------------------------------------- Subbasin: Subbasin 1 37.226 Link: Detention Vault Not Computed Link: Infiltration Gallery 1019.622 _____________________________________ Total: 1056.848 Total Predevelopment Recharge is Less than Post Developed Average Recharge Per Year, (Number of Years= 158) Predeveloped: 0.000 ac-ft/year, Post Developed: 6.689 ac-ft/year ***********Water Quality Facility Data ************* ----------------------SCENARIO: PREDEVELOPED Number of Links: 1 ********** Link: New Channel Lnk1 ********** Infiltration/Filtration Statistics-------------------- Inflow Volume (ac-ft): 1057.52 Inflow Volume Including PPT-Evap (ac-ft): 1057.52 Total Runoff Infiltrated (ac-ft): 0.00, 0.00% Total Runoff Filtered (ac-ft): 0.00, 0.00% Primary Outflow To Downstream System (ac-ft): 1059.83 Secondary Outflow To Downstream System (ac-ft): 0.00 Percent Treated (Infiltrated+Filtered)/Total Volume: 0.00% ----------------------SCENARIO: POSTDEVELOPED Number of Links: 2 ********** Link: Infiltration Gallery ********** Infiltration/Filtration Statistics-------------------- Inflow Volume (ac-ft): 982.77 Inflow Volume Including PPT-Evap (ac-ft): 1019.62 Total Runoff Infiltrated (ac-ft): 1019.62, 100.00% Total Runoff Filtered (ac-ft): 0.00, 0.00% Primary Outflow To Downstream System (ac-ft): 0.00 Secondary Outflow To Downstream System (ac-ft): 0.00 Percent Treated (Infiltrated+Filtered)/Total Volume: 100.00% ***********Compliance Point Results ************* Scenario Predeveloped Compliance Link: New Channel Lnk1 Scenario Postdeveloped Compliance Link: Infiltration Gallery *** Point of Compliance Flow Frequency Data *** Recurrence Interval Computed Using Gringorten Plotting Position Predevelopment Runoff Postdevelopment Runoff Tr (Years) Discharge (cfs) Tr (Years) Discharge (cfs) ---------------------------------------------------------------------------------------------------------------------- 2-Year 0.958 2-Year 0.000 5-Year 1.209 5-Year 0.000 10-Year 1.365 10-Year 0.000 25-Year 1.653 25-Year 0.000 50-Year 2.040 50-Year 0.000 100-Year 2.482 100-Year 0.000 200-Year 2.842 200-Year 0.000 ** Record too Short to Compute Peak Discharge for These Recurrence Intervals **** Flow Duration Performance **** Excursion at Predeveloped 50%Q2 (Must be Less Than or Equal to 0%): 0.0% PASS Maximum Excursion from 50%Q2 to Q2 (Must be Less Than or Equal to 0%): 0.0% PASS Maximum Excursion from Q2 to Q50 (Must be less than 10%): 0.0% PASS Percent Excursion from Q2 to Q50 (Must be less than 50%): 0.0% PASS ------------------------------------------------------------------------------------------------- MEETS ALL FLOW DURATION DESIGN CRITERIA: PASS ------------------------------------------------------------------------------------------------- **** LID Duration Performance **** Excursion at Predeveloped 8%Q2 (Must be Less Than 0%): 0.0% PASS Maximum Excursion from 8%Q2 to 50%Q2 (Must be Less Than 0%): 0.0% PASS ------------------------------------------------------------------------------------------------- MEETS ALL LID DURATION DESIGN CRITERIA: PASS ------------------------------------------------------------------------------------------------- WATER QUALITY DATA INFLOW TO DETENTION: On-line discharge rate (cfs) = 0.317 Off-line discharge rate (cfs) = 0.178 OUTFLOW FROM DETENTION: On-line discharge rate (cfs) = 0.142 Off-line discharge rate (cfs) = 0.087 MGS FLOOD PROJECT REPORT Bioretention Cell Model for Building A and Adjacent Surfaces Including Bioretention Cell —————————————————————— MGS FLOOD PROJECT REPORT Program Version: MGSFlood 4.46 Program License Number: 200510004 Project Simulation Performed on: 08/22/2019 11:27 AM Report Generation Date: 08/22/2019 11:28 AM ————————————————————————————————— Input File Name: BioretentionCell.fld Project Name: King County CMF Analysis Title: Bioretention Cell Comments: ———————————————— PRECIPITATION INPUT ———————————————— Computational Time Step (Minutes): 5 Extended Precipitation Time Series Selected Climatic Region Number: 3 Full Period of Record Available used for Routing Precipitation Station : 95004005 Puget West 40 in_5min 10/01/1939-10/01/2097 Evaporation Station : 951040 Puget West 40 in MAP Evaporation Scale Factor : 0.750 HSPF Parameter Region Number: 1 HSPF Parameter Region Name : USGS Default ********** Default HSPF Parameters Used (Not Modified by User) *************** ********************** WATERSHED DEFINITION *********************** Predevelopment/Post Development Tributary Area Summary Predeveloped Post Developed Total Subbasin Area (acres) 0.520 0.519 Area of Links that Include Precip/Evap (acres) 0.000 0.057 Total (acres) 0.520 0.576 ----------------------SCENARIO: PREDEVELOPED Number of Subbasins: 1 ---------- Subbasin : Subbasin 1 ---------- -------Area (Acres) -------- Impervious 0.520 ---------------------------------------------- Subbasin Total 0.520 ----------------------SCENARIO: POSTDEVELOPED Number of Subbasins: 1 ---------- Subbasin : Subbasin 1 ---------- -------Area (Acres) -------- Impervious 0.519 ---------------------------------------------- Subbasin Total 0.519 ************************* LINK DATA ******************************* ----------------------SCENARIO: PREDEVELOPED Number of Links: 1 ------------------------------------------ Link Name: New Channel Lnk1 Link Type: Open Channel Downstream Link: None ----------Left Overbank Upper Sideslope (z) : 0.500 Upper Width (ft) : 3.000 Middle Sideslope (z) : 10.000 Middle Width (ft) : 10.000 Mannings n : 0.040 ----------Main Channel Lower Sideslope Left (z) : 0.500 Lower Width Left (ft) : 3.000 Lower Sideslope Right (z) : 0.500 Lower Width Right (ft) : 3.000 Mannings n : 0.024 Base Width (ft) : 10.0 Elevation (ft) : 100.00 Channel Slope (ft/ft) : 0.020 Channel Length (ft) : 1000.0 ----------Right Overbank Upper Sideslope (z) : 0.500 Upper Width (ft) : 3.000 Middle Sideslope (z) : 10.000 Middle Width (ft) : 10.000 Mannings n : 0.040 Massmann Infiltration Option Used Hydraulic Conductivity (in/hr) : 0.0 Depth to Water Table (ft) : 100.0 Bio-Fouling Potential : Low Maintenance : Average or Better ************************* LINK DATA ******************************* ----------------------SCENARIO: POSTDEVELOPED Number of Links: 2 ------------------------------------------ Link Name: Bioretention Cell Link Type: Bioretention Facility Downstream Link Name: New Copy Lnk1 Base Elevation (ft) : 328.00 Riser Crest Elevation (ft) : 328.50 Storage Depth (ft) : 0.50 Bottom Length (ft) : 555.6 Bottom Width (ft) : 4.5 Side Slopes (ft/ft) : L1= 3.00 L2= 3.00 W1= 3.00 W2= 3.00 Bottom Area (sq-ft) : 2500. Area at Riser Crest El (sq-ft) : 4,189. (acres) : 0.096 Volume at Riser Crest (cu-ft) : 2,797. (ac-ft) : 0.064 Infiltration on Bottom only Selected Soil Properties Biosoil Thickness (ft) : 1.50 Biosoil Saturated Hydraulic Conductivity (in/hr) : 1.50 Biosoil Porosity (Percent) : 30.00 Maximum Elevation of Bioretention Soil : 328.50 Native Soil Hydraulic Conductivity (in/hr) : 1.50 Riser Geometry Riser Structure Type : Circular Riser Diameter (in) : 24.00 Common Length (ft) : 25.130 Riser Crest Elevation : 328.50 ft Hydraulic Structure Geometry Number of Devices: 0 ------------------------------------------ Link Name: New Copy Lnk1 Link Type: Copy Downstream Link: None POC AT BIORETENTION CELL **********************FLOOD FREQUENCY AND DURATION STATISTICS******************* ----------------------SCENARIO: PREDEVELOPED Number of Subbasins: 1 Number of Links: 1 ----------------------SCENARIO: POSTDEVELOPED Number of Subbasins: 1 Number of Links: 2 ********** Link: Bioretention Cell ********** Link WSEL Stats WSEL Frequency Data(ft) (Recurrence Interval Computed Using Gringorten Plotting Position) Tr (yrs) WSEL Peak (ft) ====================================== 1.05-Year 328.080 1.11-Year 328.106 1.25-Year 328.135 2.00-Year 328.227 3.33-Year 328.295 5-Year 328.399 10-Year 328.479 25-Year 328.534 50-Year 328.541 100-Year 328.543 ***********Groundwater Recharge Summary ************* Recharge is computed as input to Perlnd Groundwater Plus Infiltration in Structures Total Predeveloped Recharge During Simulation Model Element Recharge Amount (ac-ft) ----------------------------------------------------------------------------------------------- Subbasin: Subbasin 1 0.000 Link: New Channel Lnk1 0.000 _____________________________________ Total: 0.000 Total Post Developed Recharge During Simulation Model Element Recharge Amount (ac-ft) ----------------------------------------------------------------------------------------------- Subbasin: Subbasin 1 0.000 Link: Bioretention Cell 261.899 Link: New Copy Lnk1 Not Applicable _____________________________________ Total: 261.899 Total Predevelopment Recharge is Less than Post Developed Average Recharge Per Year, (Number of Years= 158) Predeveloped: 0.000 ac-ft/year, Post Developed: 1.658 ac-ft/year ***********Water Quality Facility Data ************* ----------------------SCENARIO: PREDEVELOPED Number of Links: 1 ********** Link: New Channel Lnk1 ********** Infiltration/Filtration Statistics-------------------- Inflow Volume (ac-ft): 234.99 Inflow Volume Including PPT-Evap (ac-ft): 234.99 Total Runoff Infiltrated (ac-ft): 0.00, 0.00% Total Runoff Filtered (ac-ft): 0.00, 0.00% Primary Outflow To Downstream System (ac-ft): 235.50 Secondary Outflow To Downstream System (ac-ft): 0.00 Percent Treated (Infiltrated+Filtered)/Total Volume: 0.00% ----------------------SCENARIO: POSTDEVELOPED Number of Links: 2 ********** Link: Bioretention Cell ********** Infiltration/Filtration Statistics-------------------- Inflow Volume (ac-ft): 234.76 Inflow Volume Including PPT-Evap (ac-ft): 261.90 Total Runoff Infiltrated (ac-ft): 261.90, 100.00% Total Runoff Filtered (ac-ft): 0.00, 0.00% Primary Outflow To Downstream System (ac-ft): 0.25 Secondary Outflow To Downstream System (ac-ft): 0.00 Percent Treated (Infiltrated+Filtered)/Total Volume: 100.00% ***********Compliance Point Results ************* Scenario Predeveloped Compliance Link: New Channel Lnk1 Scenario Postdeveloped Compliance Link: Bioretention Cell *** Point of Compliance Flow Frequency Data *** Recurrence Interval Computed Using Gringorten Plotting Position Predevelopment Runoff Postdevelopment Runoff Tr (Years) Discharge (cfs) Tr (Years) Discharge (cfs) ---------------------------------------------------------------------------------------------------------------------- 2-Year 0.213 2-Year 0.000 5-Year 0.269 5-Year 0.000 10-Year 0.303 10-Year 0.000 25-Year 0.367 25-Year 0.136 50-Year 0.453 50-Year 0.181 100-Year 0.552 100-Year 0.193 200-Year 0.606 200-Year 0.235 ** Record too Short to Compute Peak Discharge for These Recurrence Intervals **** Flow Duration Performance **** Excursion at Predeveloped 50%Q2 (Must be Less Than or Equal to 0%): -99.0% PASS Maximum Excursion from 50%Q2 to Q2 (Must be Less Than or Equal to 0%): -98.6% PASS Maximum Excursion from Q2 to Q50 (Must be less than 10%): -91.6% PASS Percent Excursion from Q2 to Q50 (Must be less than 50%): 0.0% PASS ------------------------------------------------------------------------------------------------- MEETS ALL FLOW DURATION DESIGN CRITERIA: PASS ------------------------------------------------------------------------------------------------- **** LID Duration Performance **** Excursion at Predeveloped 8%Q2 (Must be Less Than 0%): -99.9% PASS Maximum Excursion from 8%Q2 to 50%Q2 (Must be Less Than 0%): -99.0% PASS ------------------------------------------------------------------------------------------------- MEETS ALL LID DURATION DESIGN CRITERIA: PASS ------------------------------------------------------------------------------------------------- Stormwater Technical Information Report King County Parks – Renton Shop Central Maintenance Facility Replacement Project June 16, 2021 | C-1 Appendix C. Oil-Water Separator Coalescing Plate Pack Sizing and Infiltration Facilities Hydraulic Analysis King County Parks Central Maintenance Facility Replacement Project Height (ft) Width (ft) Length (ft) Required No. of Plates P1 (West)0.65 2 0.33 528 4.0 5.0 3.0 36 P2 (East)0.31 1 0.31 504 4.0 5.0 3.0 36 Wash Pad 0.23 1 0.23 374 3.0 5.0 3.0 27 Ah = Required horizontal (projected) surface area of coalescing plate media, sf Oil Control Design Flows and Preliminary Sizing for Oil-Water Separator Coalescing Plate Packs TDA or Drainage Subarea Coalescing Plant Oil- Water Separator Design Flow, Q (cfs) Computed Effective (Horizontal) Surface Area of Required CP Media, Ah (sf) Approximate Coalescing Plate Pack Size Q = Water quality treatment design flow, cfs Number of Units Required Design Flow Each Unit (cfs) Elevation Total AreaAreabAreaperimRock Voids Storage Rock Voids StorageibiperimInfiltration Discharge Overflow StageAreab(feet) (sf) (sf) (sf) (cu ft) (ac-ft) (feet/foot) (in/hr) (cfs) (cfs) (feet) (ac) Notes326.50 2,500 2,500 0 0 0.00 1.00 1.00 0.09 0.0 0.00 0.057 Permeable subgrade at El 326.5326.75 2,500 2,500 0 0 0.00 1.17 1.08 0.10 0.0 0.25 0.057 Bioretention media layer (assumed K = 1.5 in/hr)327.00 2,500 2,500 0 0 0.00 1.33 1.17 0.12 0.0 0.50 0.057 Bioretention media layer (assumed K = 1.5 in/hr)327.25 2,500 2,500 0 0 0.00 1.50 1.25 0.13 0.0 0.75 0.057 Bioretention media layer (assumed K = 1.5 in/hr)327.50 2,500 2,500 0 0 0.00 1.67 1.33 0.14 0.0 1.00 0.057 Bioretention media layer (assumed K = 1.5 in/hr)327.75 2,500 2,500 0 0 0.00 1.83 1.42 0.16 0.0 1.25 0.057 Bioretention media layer (assumed K = 1.5 in/hr)328.00 2,500 2,500 0 0 0.00 2.00 1.50 0.17 0.0 1.50 0.057 Surface of rain garden El 328.0328.25 2,500 2,500 0 0 0.00 2.17 1.58 0.19 0.0 1.75 0.057 Ponding depth = 0.25 ft328.50 2,500 2,500 0 0 0.00 2.33 1.67 0.20 0.0 2.00 0.057 Ponding depth = 0.5 ft; West Overflow at CB D1 w/4' dia debris cage328.60 2,500 2,500 0 0 0.00 2.40 1.70 0.21 0.9 2.10 0.057 Pond depth = 0.6 ft328.70 2,500 2,500 0 0 0.00 2.47 1.73 0.21 2.7 2.20 0.057 Ponding depth = 0.7 ft; South emergency overflow above El 328.7Infiltration Flow Using Darcy EquationQ=kiABioretention Media Design Permeability, k=1.50in/hrOverflowQ=CLH^1.5k=3.472E-05ft/sC=3.0ib= (water depth+media depth)/media depthL = 10.0 feetiperim= (water depth/2+media depth)/media depthCrest Elevation 328.50 feetAssumed Media Depth at Design Permeability =1.5feetFilter Surface Area=2,500sfac = acreac ft = acre feetAreab = area bottomAreaperim = area perimetercfs = cubic feet per secondcu ft = cubic feetft/s = feet per secondIb = hydraulic gradient bottomIperim = hydraulic gradient perimeterin/hr = inches per hoursf = square feetKing County Parks, Renton Shop - Central Maintenance Facility Replacement ProjectStormwater Infiltration Analysis - TDA P1, Building A - West Water Treatment System Bioretention Cell1 of 1 Elevation Total AreaAreabAreaperimRock Voids Storage Rock Voids StorageibiperimInfiltration Discharge Overflow StageAreab(feet) (sf) (sf) (sf) (cu ft) (ac-ft) (feet/foot) (in/hr) (cfs) (cfs) (feet) (ac) Notes311.50 4,550 4,550 0 0 0.00 1.00 1.00 0.42 0.0 0.00 0.104 Subgrade (Elev 311.5)311.75 4,550 4,550 0 341 0.01 1.13 1.06 0.47 0.0 0.25 0.104 Gravel Backfill for Drywells312.00 4,550 4,550 0 683 0.02 1.25 1.13 0.53 0.0 0.50 0.104 Gravel Backfill for Drywells312.25 4,550 4,550 0 1,024 0.02 1.38 1.19 0.58 0.0 0.75 0.104 Gravel Backfill for Drywells312.50 4,550 4,550 0 1,365 0.03 1.50 1.25 0.63 0.0 1.00 0.104 Gravel Backfill for Drywells312.75 4,550 4,550 0 1,706 0.04 1.63 1.31 0.68 0.0 1.25 0.104 Gravel Backfill for Drywells313.00 4,550 4,550 0 2,048 0.05 1.75 1.38 0.74 0.0 1.50 0.104 Gravel Backfill for Drywells313.25 4,550 4,550 0 2,389 0.05 1.88 1.44 0.79 0.0 1.75 0.104 Gravel Backfill for Drywells313.50 4,550 4,550 0 2,730 0.06 2.00 1.50 0.84 0.0 2.00 0.104 Top of Gravel Backfill for Drywells (Elev 313.5)Infiltration Flow Using Darcy EquationQ=kiASubgrade Design Permeability, k= 4.00 in/hrOverflow Q=CLH^1.5k= 9.259E-05 ft/sC= 0.0ib= (water depth+media depth)/media depthL = 0.0 feetiperim= (water depth/2+media depth)/media depthCrest Elevation 0.00 feetAssumed Media Depth at Design Permeability = 2 feetFilter Surface Area= 4550 sfac = acreac ft = acre feetAreab = area bottomAreaperim = area perimetercfs = cubic feet per secondcu ft = cubic feetft/s = feet per secondIb = hydraulic gradient bottomIperim = hydraulic gradient perimeterin/hr = inches per hoursf = square feetKing County Parks, Renton Shop - Central Maintenance Facility Replacement ProjectStormwater Treatment System Infiltration Analysis - TDA P1 West Water Treatment System Infiltration Gallery1 of 1 Elevation Total AreaAreabAreaperimRock Voids Storage Rock Voids StorageibiperimInfiltration Discharge Overflow StageAreab(feet) (sf) (sf) (sf) (cu ft) (ac-ft) (feet/foot) (in/hr) (cfs) (cfs) (feet) (ac) Notes313.50 3,950 3,950 0 0 0.00 1.00 1.00 0.37 0.0 0.00 0.091 Subgrade (Elev 313.5)313.75 3,950 3,950 0 296 0.01 1.13 1.06 0.41 0.0 0.25 0.091 Gravel Backfill for Drywells314.00 3,950 3,950 0 593 0.01 1.25 1.13 0.46 0.0 0.50 0.091 Gravel Backfill for Drywells314.25 3,950 3,950 0 889 0.02 1.38 1.19 0.50 0.0 0.75 0.091 Gravel Backfill for Drywells314.50 3,950 3,950 0 1,185 0.03 1.50 1.25 0.55 0.0 1.00 0.091 Gravel Backfill for Drywells314.75 3,950 3,950 0 1,481 0.03 1.63 1.31 0.59 0.0 1.25 0.091 Gravel Backfill for Drywells315.00 3,950 3,950 0 1,778 0.04 1.75 1.38 0.64 0.0 1.50 0.091 Gravel Backfill for Drywells315.25 3,950 3,950 0 2,074 0.05 1.88 1.44 0.69 0.0 1.75 0.091 Gravel Backfill for Drywells315.50 3,950 3,950 0 2,370 0.05 2.00 1.50 0.73 0.0 2.00 0.091 Top of Gravel Backfill for Drywells (Elev 315.5)Infiltration Flow Using Darcy EquationQ=kiASubgrade Design Permeability, k= 4.00 in/hrOverflow Q=CLH^1.5k= 9.259E-05 ft/sC= 0.0ib= (water depth+media depth)/media depthL = 0.0 feetiperim= (water depth/2+media depth)/media depthCrest Elevation 0.00 feetAssumed Media Depth at Design Permeability = 2 feetFilter Surface Area= 3950 sfac = acreac ft = acre feetAreab = area bottomAreaperim = area perimetercfs = cubic feet per secondcu ft = cubic feetft/s = feet per secondIb = hydraulic gradient bottomIperim = hydraulic gradient perimeterin/hr = inches per hoursf = square feetKing County Parks, Renton Shop - Central Maintenance Facility Replacement ProjectStormwater Treatment System Infiltration Analysis - TDA P2 East Water Treatment System Infiltration Gallery1 of 1 Stormwater Technical Information Report King County Parks – Renton Shop Central Maintenance Facility Replacement Project June 16, 2021 | D-1 Appendix D. Storm Drain Conveyance System Hydrologic and Hydraulic Analysis King County Parks Central Maintenance Facility Replacement ProjectConveyance CalcsMRI = 2510094727ar = 2.666/11/2021br = 0.65Pavement thickness = 0.00 ftPipe thickness = 0.25 ftINLETS:DISCHARGE/FLOW CALCULATION:INLET INFORMATION:PIPE INFORMATION:CHECKS:DrainageStructure Pipe NumberToDrainage StructureLength Area Calc. Area A C C*A Cumm. C*A SurfaceSlope(So)SurfaceKRSurface VelocityVTc TtPipeTtSurfaceTc used (6.3 <=Tc<=100)ar br ir Pr Ir Q(CFS)Inlet Rim Outlet Rim Inlet InvertOutlet InvertInlet CoverOutlet CoverPipe DiameterPipe LengthRoughness Coefficient (Manning's n)Slope Pipe Area Vel Capacity Qfull Structure TypeVelocity CheckCapacity CheckInlet Cover CheckOutlet Cover check# # FTFT2Acre Acre AcreAcre PercentMinute Minute MinuteInches in/hr CFS FT FT FT FTFT FT FT FTFT/FTFT2FPS CFSfrom to3.4D-1 D-1 D-2 392 28,113 0.65 0.65 0.90 0.58 0.58 0.015 20.00 2.45 2.84 0.17 2.67 6.30 2.66 0.65 0.80 3.40 2.73 1.59 328.50 328.42 324.50 324.202.75 2.971.0 40.00 0.013 0.75% 0.785 3.929 3.085CB1OK OK OK OKD-2 D-2 D-3 103 4,862 0.11 0.11 0.90 0.10 0.68 0.010 20.00 2.00 3.20 0.370.11 6.30 2.66 0.65 0.80 3.40 2.73 1.86 328.42 328.20 324.20 322.802.97 4.151.0 112.00 0.013 1.25% 0.785 5.072 3.983CB1OK OK OK OKD-3 D-3 D-4 130 14,294 0.33 0.33 0.90 0.30 0.98 0.014 20.00 2.37 3.49 0.28 0.92 6.30 2.66 0.65 0.80 3.40 2.73 2.67 328.20 328.21 322.80 322.314.15 4.651.0 66.00 0.013 0.74% 0.785 3.909 3.070CB2-48OK OK OK OKD-4 D-4 SED-1 201 18,488 0.42 0.42 0.90 0.38 1.36 0.010 20.00 2.00 3.53 0.05 1.68 6.30 2.66 0.65 0.80 3.40 2.73 3.71 328.21 327.80 322.31 322.204.65 4.351.0 12.00 0.013 0.92% 0.785 4.343 3.411CB2-48OK OK OK OKD-5 D-5 D-6 175 6,085 0.14 0.14 0.90 0.13 0.13 0.006 20.00 1.55 2.24 0.361.88 6.30 2.66 0.65 0.80 3.40 2.73 0.34 328.31 327.26 323.14 322.503.92 3.511.0 85.00 0.013 0.75% 0.785 3.936 3.092CB2-48OK OK OK OKD-6 D-6 D-6A 235 24,097 0.55 0.55 0.90 0.50 0.62 0.016 20.00 2.53 2.30 0.06 1.55 6.30 2.66 0.65 0.80 3.40 2.73 1.70 327.26 327.55 322.50 321.903.51 4.401.0 24.00 0.013 2.50% 0.785 7.173 5.633CB1OK OK OK OKD-10 D-10 D-9 63 6,522 0.15 0.15 0.90 0.13 0.13 0.009 20.00 1.90 0.86 0.300.55 6.30 2.66 0.65 0.80 3.40 2.73 0.37 329.60 329.45 324.85 324.323.50 3.881.0 71.00 0.013 0.75% 0.785 3.919 3.078CB1OK OK OK OKD-9 D-9 D-8 61 4,413 0.10 0.10 0.90 0.09 0.23 0.011 20.00 2.10 1.28 0.420.48 6.30 2.66 0.65 0.80 3.40 2.73 0.62 329.45 329.00 324.32 323.563.88 4.191.0 100.00 0.013 0.76% 0.785 3.955 3.106CB2-48OK OK OK OKD-8 D-8 D-7 98 5,010 0.12 0.12 0.90 0.10 0.33 0.013 20.00 2.28 1.51 0.230.72 6.30 2.66 0.65 0.80 3.40 2.73 0.90 329.00 328.30 323.56 323.164.19 3.891.0 54.00 0.013 0.74% 0.785 3.904 3.066CB2-48OK OK OK OKD-7 D-7 D-6A 111 2,774 0.06 0.06 0.90 0.06 0.39 0.015 20.00 2.45 1.73 0.230.76 6.30 2.66 0.65 0.80 3.40 2.73 1.06 328.30 327.55 323.16 322.753.89 3.551.0 54.00 0.013 0.76% 0.785 3.953 3.104CB2-48OK OK OK OKD-6A D-6A SED-1 167 7,500 0.17 0.17 0.90 0.15 1.17 0.015 20.00 2.45 2.32 0.021.14 6.30 2.66 0.65 0.80 3.40 2.73 3.19 327.55 327.80 321.90 321.504.40 5.051.0 10.00 0.013 4.00% 0.785 9.073 7.126CB2-48OK OK OK OKSED-1 SED-1 FS-1 - - - - - - - - - - - - - - - - - - - 0.58 329.00 328.95 319.50 319.408.25 8.301.0 7.00 0.013 1.43% 0.785 5.422 4.258CB2-48OK OK OK OKFS-1 FS-1 OWS-1 - - - - - - - - - - - - - - - - - - - 0.58 329.00 328.95 318.65 318.559.10 9.151.0 17.00 0.013 0.59% 0.785 3.479 2.733MH1-48OK OK OK OKOWS-1 OWS MWL-1 - - - - - - - - - - - - - - - - - - - 0.58 328.95 328.70 318.22 318.049.48 9.411.0 21.00 0.013 0.86% 0.785 4.200 3.299MH1-48OK OK OK OKD12 D-12 D13 113 3,741 0.09 0.09 0.90 0.08 0.08 0.010 20.00 2.00 1.20 0.260.94 6.30 2.66 0.65 0.80 3.40 2.73 0.21 329.72 329.62 325.30 324.503.17 3.871.0 73.00 0.013 1.10% 0.785 4.758 3.737CB1OK OK OK OKD13 D-13 D-14 132 20,200 0.46 0.46 0.90 0.42 0.49 0.011 20.00 2.10 2.25 0.49 1.05 6.30 2.66 0.65 0.80 3.40 2.73 1.35 329.62 329.70 324.50 323.653.87 4.801.0 114.00 0.013 0.74% 0.785 3.902 3.065CB2-48OK OK OK OKD-14 D-14 D-15 11 6,516 0.15 0.15 0.90 0.13 0.63 0.018 20.00 2.68 2.36 0.120.07 6.30 2.66 0.65 0.80 3.40 2.73 1.72 329.70 330.51 323.65 323.464.80 5.801.0 27.00 0.013 0.72% 0.785 3.849 3.023CB2-48OK OK OK OKD-20 D-20 D-21 53 3,186 0.07 0.07 0.90 0.07 0.07 0.023 20.00 3.03 0.68 0.390.29 6.30 2.66 0.65 0.80 3.40 2.73 0.18 330.50 330.49 326.00 325.513.25 3.731.0 82.00 0.013 0.60% 0.785 3.514 2.760CB1OK OK OK OKD-21 D-21 D-22 144 13,212 0.30 0.30 0.90 0.27 0.34 0.015 20.00 2.45 1.66 0.25 0.98 6.30 2.66 0.65 0.80 3.40 2.73 0.93 330.49 330.46 325.51 325.053.73 4.161.0 52.00 0.013 0.60% 0.785 3.514 2.760CB1OK OK OK OKD-25 D-25 D-22 62 1,610 0.04 0.04 0.90 0.03 0.03 0.018 20.00 2.68 0.54 0.150.39 6.30 2.66 0.65 0.80 3.40 2.73 0.09 331.42 330.46 327.50 325.052.67 4.161.0 44.00 0.013 1.13% 0.785 4.822 3.787CB1OK OK OK OKD-22 D-22 D-23 67 5,951 0.14 0.14 0.90 0.12 0.50 0.018 20.00 2.68 2.01 0.350.42 6.30 2.66 0.65 0.80 3.40 2.73 1.35 330.46 330.52 325.05 324.504.16 4.771.0 76.00 0.013 0.64% 0.785 3.629 2.850CB2-48OK OK OK OKD-23 D-23 D-15 74 838 0.02 0.02 0.90 0.02 0.51 0.023 20.00 3.03 2.05 0.04 0.41 6.30 2.66 0.65 0.80 3.40 2.73 1.40 330.52 330.51 324.57 323.304.70 5.961.0 10.00 0.013 0.67% 0.785 3.713 2.916CB2-48OK OK OK OKD-15 D-15 SED2 165 11,001 0.25 0.25 0.90 0.23 1.37 0.009 20.00 1.90 2.40 0.03 1.45 6.30 2.66 0.65 0.80 3.40 2.73 3.74 330.51 330.30 323.30 322.005.96 7.051.0 11.00 0.013 1.41% 0.785 5.387 4.231CB2-48OK OK OK OKD-26 D-26 D-19 650 9,662 0.22 0.22 0.90 0.20 0.20 0.053 20.00 4.60 2.50 0.152.35 6.30 2.66 0.65 0.80 3.40 2.73 0.55 329.89 330.22 324.89 324.153.75 4.821.0 49.00 0.013 1.51% 0.785 5.574 4.378CB1OK OK OK OKD-11 D-11 D19 212 8,389 0.19 0.19 0.90 0.17 0.17 0.019 20.00 2.76 1.36 0.081.28 6.30 2.66 0.65 0.80 3.40 2.73 0.47 329.65 330.22 324.65 324.153.75 4.821.0 29.00 0.013 1.74% 0.785 5.984 4.700CB1OK OK OK OKD-17 D-17 D-18 195 12,976 0.30 0.30 0.90 0.27 0.27 0.022 20.00 2.97 1.22 0.13 1.10 6.30 2.66 0.65 0.80 3.40 2.73 0.73 329.65 329.68 325.75 325.232.65 3.201.0 40.00 0.013 1.30% 0.785 5.172 4.062CB1OK OK OK OKD-18 D-18 D-19 190 18,210 0.42 0.42 0.90 0.38 0.64 0.018 20.00 2.68 1.49 0.27 1.18 6.30 2.66 0.65 0.80 3.40 2.73 1.76 329.68 330.22 325.23 325.003.20 3.971.0 49.00 0.013 0.46% 0.785 3.077 2.416CB1OK OK OK OK- D-19D-19SED-20- 0.000.000.900.001.020.01820.002.682.530.030.006.302.660.650.803.402.732.78330.22330.11324.15324.054.824.811.08.000.0131.20%0.7854.9693.903CB2-48OKOKOKOKSED-2SED-2FS-2-------------------0.28332.03331.91321.00320.929.789.741.06.500.0131.23%0.7855.0313.951MH1-48OKOKOKOKFS-2 FS-2 OWS-2 - - - - - - - - - - - - - - - - - - - 0.28 331.88 331.87 320.18 320.0710.45 10.551.0 10.40 0.013 1.06% 0.785 4.670 3.668MH1-48OK OK OK OKOWS-2 OWS-2 MWL-2 - - - - - - - - - - - - - - - - - - - 0.28 331.95 332.02 319.74 319.6310.96 11.141.0 13.50 0.013 0.81% 0.785 4.083 3.207MH1-48OK OK OK OKEAST BASINWEST BASINC:\Users\DCISAKOWSK\projects\CFM\Permit\KC PARKS CMF_Conveyance_20210611.xls | Conveyance -25yr (Works)Printed 6/16/2021 King County Parks Central Maintenance Facility Replacement ProjectConveyance CalcsMRI = 10010094727ar = 2.616/11/2021br = 0.63Pavement thickness = 0.00 ftPipe thickness = 0.25 ftINLETS:DISCHARGE/FLOW CALCULATION:INLET INFORMATION:PIPE INFORMATION:CHECKS:DrainageStructure Pipe NumberToDrainage StructureLength Area Calc. Area A C C*A Cumm. C*A SurfaceSlope(So)SurfaceKRSurface VelocityVTc TtPipeTtSurfaceTc used (6.3 <=Tc<=100)ar br ir Pr Ir Q(CFS)Inlet Rim Outlet Rim Inlet InvertOutlet InvertInlet CoverOutlet CoverPipe DiameterPipe LengthRoughness Coefficient (Manning's n)Slope Pipe Area Vel Capacity Qfull Structure TypeVelocity CheckCapacity CheckInlet Cover CheckOutlet Cover check# # FTFT2Acre Acre AcreAcre PercentMinute Minute MinuteInches in/hr CFS FT FT FT FTFT FT FT FTFT/FTFT2FPS CFSfrom to3.9D-1 D-1 D-2 392 28,113 0.65 0.65 0.90 0.58 0.58 0.015 20.00 2.45 2.84 0.17 2.67 6.30 2.61 0.63 0.82 3.90 3.19 1.85 328.50 328.42 324.50 324.202.75 2.971.0 40.00 0.013 0.75% 0.785 3.929 3.085CB1OK OK OK OKD-2 D-2 D-3 103 4,862 0.11 0.11 0.90 0.10 0.68 0.010 20.00 2.00 3.20 0.370.11 6.30 2.61 0.63 0.82 3.90 3.19 2.18 328.42 328.20 324.20 322.802.97 4.151.0 112.00 0.013 1.25% 0.785 5.072 3.983CB1OK OK OK OKD-3 D-3 D-4 130 14,294 0.33 0.33 0.90 0.30 0.98 0.014 20.00 2.37 3.49 0.28 0.92 6.30 2.61 0.63 0.82 3.90 3.19 3.12 328.20 328.21 322.80 322.314.15 4.651.0 66.00 0.013 0.74% 0.785 3.909 3.070CB2-48OK OK OK OKD-4 D-4 SED-1 201 18,488 0.42 0.42 0.90 0.38 1.36 0.010 20.00 2.00 3.53 0.05 1.68 6.30 2.61 0.63 0.82 3.90 3.19 4.34 328.21 327.80 322.31 322.204.65 4.351.0 12.00 0.013 0.92% 0.785 4.343 3.411CB2-48OK OK OK OKD-5 D-5 D-6 175 6,085 0.14 0.14 0.90 0.13 0.13 0.006 20.00 1.55 2.24 0.361.88 6.30 2.61 0.63 0.82 3.90 3.19 0.40 328.31 327.26 323.14 322.503.92 3.511.0 85.00 0.013 0.75% 0.785 3.936 3.092CB2-48OK OK OK OKD-6 D-6 D-6A 235 24,097 0.55 0.55 0.90 0.50 0.62 0.016 20.00 2.53 2.30 0.06 1.55 6.30 2.61 0.63 0.82 3.90 3.19 1.99 327.26 327.55 322.50 321.903.51 4.401.0 24.00 0.013 2.50% 0.785 7.173 5.633CB1OK OK OK OKD-10 D-10 D-9 63 6,522 0.15 0.15 0.90 0.13 0.13 0.009 20.00 1.90 0.86 0.300.55 6.30 2.61 0.63 0.82 3.90 3.19 0.43 329.60 329.45 324.85 324.323.50 3.881.0 71.00 0.013 0.75% 0.785 3.919 3.078CB1OK OK OK OKD-9 D-9 D-8 61 4,413 0.10 0.10 0.90 0.09 0.23 0.011 20.00 2.10 1.28 0.420.48 6.30 2.61 0.63 0.82 3.90 3.19 0.72 329.45 329.00 324.32 323.563.88 4.191.0 100.00 0.013 0.76% 0.785 3.955 3.106CB2-48OK OK OK OKD-8 D-8 D-7 98 5,010 0.12 0.12 0.90 0.10 0.33 0.013 20.00 2.28 1.51 0.230.72 6.30 2.61 0.63 0.82 3.90 3.19 1.05 329.00 328.30 323.56 323.164.19 3.891.0 54.00 0.013 0.74% 0.785 3.904 3.066CB2-48OK OK OK OKD-7 D-7 D-6A 111 2,774 0.06 0.06 0.90 0.06 0.39 0.015 20.00 2.45 1.73 0.230.76 6.30 2.61 0.63 0.82 3.90 3.19 1.23 328.30 327.55 323.16 322.753.89 3.551.0 54.00 0.013 0.76% 0.785 3.953 3.104CB2-48OK OK OK OKD-6A D-6A SED-1 167 7,500 0.17 0.17 0.90 0.15 1.17 0.015 20.00 2.45 2.32 0.021.14 6.30 2.61 0.63 0.82 3.90 3.19 3.72 327.55 327.80 321.90 321.504.40 5.051.0 10.00 0.013 4.00% 0.785 9.073 7.126CB2-48OK OK OK OKSED-1 SED-1 FS-1 - - - - - - - - - - - - - - - - - - - 0.65 329.00 328.95 319.50 319.408.25 8.301.0 7.00 0.013 1.43% 0.785 5.422 4.258CB2-48OK OK OK OKFS-1 FS-1 OWS-1 - - - - - - - - - - - - - - - - - - - 0.65 329.00 328.95 318.65 318.559.10 9.151.0 17.00 0.013 0.59% 0.785 3.479 2.733MH1-48OK OK OK OKOWS-1 OWS MWL-1 - - - - - - - - - - - - - - - - - - - 0.65 328.95 328.70 318.22 318.049.48 9.411.0 21.00 0.013 0.86% 0.785 4.200 3.299MH1-48OK OK OK OKD12 D-12 D13 113 3,741 0.09 0.09 0.90 0.08 0.08 0.010 20.00 2.00 1.20 0.260.94 6.30 2.61 0.63 0.82 3.90 3.19 0.25 329.72 329.62 325.30 324.503.17 3.871.0 73.00 0.013 1.10% 0.785 4.758 3.737CB1OK OK OK OKD13 D-13 D-14 132 20,200 0.46 0.46 0.90 0.42 0.49 0.011 20.00 2.10 2.25 0.49 1.05 6.30 2.61 0.63 0.82 3.90 3.19 1.58 329.62 329.70 324.50 323.653.87 4.801.0 114.00 0.013 0.74% 0.785 3.902 3.065CB2-48OK OK OK OKD-14 D-14 D-15 11 6,516 0.15 0.15 0.90 0.13 0.63 0.018 20.00 2.68 2.36 0.120.07 6.30 2.61 0.63 0.82 3.90 3.19 2.01 329.70 330.51 323.65 323.464.80 5.801.0 27.00 0.013 0.72% 0.785 3.849 3.023CB2-48OK OK OK OKD-20 D-20 D-21 53 3,186 0.07 0.07 0.90 0.07 0.07 0.023 20.00 3.03 0.68 0.390.29 6.30 2.61 0.63 0.82 3.90 3.19 0.21 330.50 330.49 326.00 325.513.25 3.731.0 82.00 0.013 0.60% 0.785 3.514 2.760CB1OK OK OK OKD-21 D-21 D-22 144 13,212 0.30 0.30 0.90 0.27 0.34 0.015 20.00 2.45 1.66 0.25 0.98 6.30 2.61 0.63 0.82 3.90 3.19 1.08 330.49 330.46 325.51 325.053.73 4.161.0 52.00 0.013 0.60% 0.785 3.514 2.760CB1OK OK OK OKD-25 D-25 D-22 62 1,610 0.04 0.04 0.90 0.03 0.03 0.018 20.00 2.68 0.54 0.150.39 6.30 2.61 0.63 0.82 3.90 3.19 0.11 331.42 330.46 327.50 325.052.67 4.161.0 44.00 0.013 1.13% 0.785 4.822 3.787CB1OK OK OK OKD-22 D-22 D-23 67 5,951 0.14 0.14 0.90 0.12 0.50 0.018 20.00 2.68 2.01 0.350.42 6.30 2.61 0.63 0.82 3.90 3.19 1.58 330.46 330.52 325.05 324.504.16 4.771.0 76.00 0.013 0.64% 0.785 3.629 2.850CB2-48OK OK OK OKD-23 D-23 D-15 74 838 0.02 0.02 0.90 0.02 0.51 0.023 20.00 3.03 2.05 0.04 0.41 6.30 2.61 0.63 0.82 3.90 3.19 1.64 330.52 330.51 324.57 323.304.70 5.961.0 10.00 0.013 0.67% 0.785 3.713 2.916CB2-48OK OK OK OKD-15 D-15 SED2 165 11,001 0.25 0.25 0.90 0.23 1.37 0.009 20.00 1.90 2.40 0.03 1.45 6.30 2.61 0.63 0.82 3.90 3.19 4.37 330.51 330.30 323.30 322.005.96 7.051.0 11.00 0.013 1.41% 0.785 5.387 4.231CB2-48OK OK OK OKD-26 D-26 D-19 650 9,662 0.22 0.22 0.90 0.20 0.20 0.053 20.00 4.60 2.50 0.152.35 6.30 2.61 0.63 0.82 3.90 3.19 0.64 329.89 330.22 324.89 324.153.75 4.821.0 49.00 0.013 1.51% 0.785 5.574 4.378CB1OK OK OK OKD-11 D-11 D19 212 8,389 0.19 0.19 0.90 0.17 0.17 0.019 20.00 2.76 1.36 0.081.28 6.30 2.61 0.63 0.82 3.90 3.19 0.55 329.65 330.22 324.65 324.153.75 4.821.0 29.00 0.013 1.74% 0.785 5.984 4.700CB1OK OK OK OKD-17 D-17 D-18 195 12,976 0.30 0.30 0.90 0.27 0.27 0.022 20.00 2.97 1.22 0.13 1.10 6.30 2.61 0.63 0.82 3.90 3.19 0.86 329.65 329.68 325.75 325.232.65 3.201.0 40.00 0.013 1.30% 0.785 5.172 4.062CB1OK OK OK OKD-18 D-18 D-19 190 18,210 0.42 0.42 0.90 0.38 0.64 0.018 20.00 2.68 1.49 0.27 1.18 6.30 2.61 0.63 0.82 3.90 3.19 2.06 329.68 330.22 325.23 325.003.20 3.971.0 49.00 0.013 0.46% 0.785 3.077 2.416CB1OK OK OK OK- D-19D-19SED-20- 0.000.000.900.001.020.01820.002.682.530.030.006.302.610.630.823.903.193.25330.22330.11324.15324.054.824.811.08.000.0131.20%0.7854.9693.903CB2-48OKOKOKOKSED-2SED-2FS-2-------------------0.31332.03331.91321.00320.929.789.741.06.500.0131.23%0.7855.0313.951MH1-48OKOKOKOKFS-2 FS-2 OWS-2 - - - - - - - - - - - - - - - - - - - 0.31 331.88 331.87 320.18 320.0710.45 10.551.0 10.40 0.013 1.06% 0.785 4.670 3.668MH1-48OK OK OK OKOWS-2 OWS-2 MWL-2 - - - - - - - - - - - - - - - - - - - 0.31 331.95 332.02 319.74 319.6310.96 11.141.0 13.50 0.013 0.81% 0.785 4.083 3.207MH1-48OK OK OK OKEAST BASINWEST BASINC:\Users\DCISAKOWSK\projects\CFM\Permit\KC PARKS CMF_Conveyance_20210611.xls | Conveyance -25yr (Works)Printed 6/16/2021 25YR Storm1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 1617 18 19 20 21 22Q(CFS)Length(FT)Pipe Size(FT)"n" Value Outlet ElevationInlet ElevationBarrel Area(SF)Barrel Velocity (FT/S)Barrel Velocity Head(FT)TW Elevation(FT)Friction Loss (FT)Entrance HGL Elevation(FT)Entrance Head Loss(FT)Exit Head Loss(FT)Outlet Control Elevation(FT)Inlet Control Elevation(FT)Outlet ConditionsInlet ConditionQ/AD0.5≤3.5Form 2 Unsubmerged AnalysisHW UnsubmergedSubmerged AnalysisHW SubmergedApproach Velocity Head(FT)Bend Head Loss(FT)Junction Head Loss(FT)HW Elevation(FT)RIMElevation(FT)RIMElevation - HW(FT)OWS-1 MWL-1 0.580 21.00 1.00 0.014 318.04 318.22 0.785 0.739 0.008 318.04 0.006 318.046 0.004 0.008 318.927 318.927 Unsubmerged Unsubmerged 0.739 0.009 0.009 0.707 0.707 0.008 0.011 0.000 318.93 328.95 10.02FS-1 OWS-1 0.580 17.00 1.00 0.014 318.55 318.65 0.785 0.739 0.008 318.93 0.005 318.935 0.004 0.008 319.352 319.352 Unsubmerged Unsubmerged 0.739 0.009 0.009 0.702 0.702 0.008 0.011 0.000 319.35 329.00 9.65SED-1 FS-1 0.580 7.00 1.00 0.014 319.40 319.50 0.785 0.739 0.008 319.35 0.002 319.356 0.004 0.008 320.207 320.207 Unsubmerged Unsubmerged 0.739 0.009 0.009 0.707 0.707 0.256 0.000 0.000 324.90 329.00 4.10D-6A SED-1 3.186 10.00 1.00 0.014 321.50 321.90 0.785 4.058 0.256 324.90 0.092 324.992 0.128 0.256 325.376 325.376 Submerged Submerged 4.058 0.051 0.051 0.872 0.872 0.028 0.035 0.100 325.48 327.55 2.07D-4 SED-1 3.714 12.00 1.00 0.014 322.20 322.31 0.785 4.732 0.348 324.90 0.150 325.050 0.174 0.348 325.571 325.571 Submerged Submerged 4.732 0.059 0.059 0.890 0.890 0.180 0.225 0.000 325.62 328.21 2.59D-3 D-4 2.670 66.00 1.00 0.014 322.31 322.80 0.785 3.401 0.180 325.62 0.426 326.042 0.090 0.180 326.312 326.312 Submerged Submerged 3.401 0.042 0.042 0.842 0.842 0.087 0.000 0.000 326.22 328.20 1.98D-2 D-3 1.863 112.00 1.00 0.014 322.80 324.20 0.785 2.373 0.087 326.22 0.352 326.576 0.044 0.087 326.707 326.707 Submerged Submerged 2.373 0.030 0.030 0.790 0.790 0.064 0.000 0.000 326.64 328.42 1.78D-1 D-2 1.588 40.00 1.00 0.014 324.20 324.50 0.785 2.023 0.064 326.64 0.091 326.735 0.032 0.064 326.831 326.831 Submerged Submerged 2.023 0.025 0.025 0.767 0.767 0.073 0.092 0.000 326.85 328.50 1.65D-6 D-6A 1.705 24.00 1.00 0.014 321.90 322.50 0.785 2.172 0.073 325.48 0.063 325.546 0.037 0.073 325.655 325.655 Submerged Submerged 2.172 0.027 0.027 0.780 0.780 0.003 0.004 0.000 325.66 327.26 1.60D-5 D-6 0.344 85.00 1.00 0.014 322.50 323.14 0.785 0.438 0.003 325.66 0.009 325.665 0.001 0.003 325.670 325.670 Submerged Submerged 0.438 0.005 0.005 0.688 0.688 0.000 0.000 0.000 325.67 328.31 2.64D-7 D-6A 1.057 54.00 1.00 0.014 322.75 323.16 0.785 1.347 0.028 325.48 0.055 325.537 0.014 0.028 325.579 325.579 Submerged Submerged 1.347 0.017 0.017 0.738 0.738 0.020 0.000 0.000 325.56 328.30 2.74D-8 D-7 0.901 54.00 1.00 0.014 323.16 323.56 0.785 1.147 0.020 325.56 0.040 325.598 0.010 0.020 325.629 325.629 Submerged Submerged 1.147 0.014 0.014 0.725 0.725 0.010 0.000 0.011 325.63 329.00 3.37D-9 D-8 0.618 100.00 1.00 0.014 323.56 324.32 0.785 0.787 0.010 325.63 0.035 325.665 0.005 0.010 325.679 325.679 Submerged Submerged 0.787 0.010 0.010 0.710 0.710 0.003 0.000 0.000 325.68 329.45 3.77D-10 D-9 0.368 71.00 1.00 0.014 324.32 324.85 0.785 0.469 0.003 325.68 0.009 325.684 0.002 0.003 325.690 325.544 Submerged Unsubmerged 0.469 0.006 0.006 0.694 0.694 0.000 0.000 0.000 325.69 329.60 3.91OWS-2 MWL-2 0.280 13.50 1.00 0.014 319.63 319.74 0.785 0.357 0.002 319.63 0.000 319.630 0.001 0.002 320.425 320.425 Unsubmerged Unsubmerged 0.357 0.004 0.004 0.685 0.685 0.002 0.002 0.000 320.43 331.95 11.52FS-2 OWS-2 0.280 10.40 1.00 0.014 320.07 320.18 0.785 0.357 0.002 320.43 0.000 320.426 0.001 0.002 320.868 320.868 Unsubmerged Unsubmerged 0.357 0.004 0.004 0.688 0.688 0.002 0.002 0.000 320.87 331.88 11.01SED-2 FS-2 0.280 6.50 1.00 0.014 320.92 321.00 0.785 0.357 0.002 320.87 0.000 320.869 0.001 0.002 321.685 321.685 Unsubmerged Unsubmerged 0.357 0.004 0.004 0.685 0.685 0.353 0.000 0.000 326.40 332.03 5.63D-15 SED2 3.743 11.00 1.00 0.014 322.00 323.30 0.785 4.768 0.353 326.40 0.055 326.455 0.176 0.353 326.985 326.985 Submerged Submerged 4.768 0.060 0.060 0.912 0.912 0.075 0.093 0.179 327.18 330.51 3.33D-23 D-15 1.401 10.00 1.00 0.014 323.30 324.57 0.785 1.784 0.049 327.18 0.007 327.190 0.025 0.049 327.264 327.264 Submerged Submerged 1.784 0.022 0.022 0.760 0.760 0.046 0.000 0.000 327.22 330.52 3.30D-22 D-23 1.353 76.00 1.00 0.014 324.50 325.05 0.785 1.724 0.046 327.22 0.050 327.268 0.023 0.046 327.337 327.337 Submerged Submerged 1.724 0.022 0.022 0.757 0.757 0.022 0.027 0.003 327.35 330.46 3.11D-21 D-22 0.926 52.00 1.00 0.014 325.05 327.50 0.785 1.180 0.022 327.35 0.016 327.361 0.011 0.022 327.394 328.224 Submerged Unsubmerged 1.180 0.015 0.015 0.724 0.724 0.001 0.000 0.000 328.22 330.49 2.27D-20 D-21 0.180 82.00 1.00 0.014 325.51 326.00 0.785 0.229 0.001 328.22 0.001 328.224 0.000 0.001 328.226 328.226 Submerged Submerged 0.229 0.003 0.003 0.682 0.682 0.000 0.000 0.000 328.23 330.50 2.27D-25 D-22 0.091 44.00 1.00 0.014 325.05 327.50 0.785 0.116 0.000 327.35 0.000 327.345 0.000 0.000 327.345 328.173 Submerged Unsubmerged 0.116 0.001 0.001 0.673 0.673 0.000 0.000 0.000 328.17 331.42 3.25D-14 D-15 1.720 27.00 1.00 0.014 323.46 323.65 0.785 2.192 0.075 327.18 0.029 327.211 0.037 0.075 327.323 327.323 Submerged Submerged 2.192 0.027 0.027 0.781 0.781 0.046 0.000 0.000 327.28 329.70 2.42D13 D-14 1.352 114.00 1.00 0.014 323.65 324.50 0.785 1.723 0.046 327.28 0.075 327.352 0.023 0.046 327.421 327.421 Submerged Submerged 1.723 0.022 0.022 0.754 0.754 0.001 0.000 0.000 327.42 329.62 2.20D12 D13 0.211 73.00 1.00 0.014 324.50 325.30 0.785 0.269 0.001 327.42 0.001 327.421 0.001 0.001 327.423 327.423 Submerged Submerged 0.269 0.003 0.003 0.684 0.684 0.000 0.000 0.000 327.42 329.72 2.30D-19 SED-2 2.781 8.00 1.00 0.014 324.05 324.15 0.785 3.543 0.195 326.40 0.022 326.422 0.097 0.195 326.715 326.715 Submerged Submerged 3.543 0.044 0.044 0.850 0.850 0.078 0.098 1.024 327.76 330.22 2.46D-18 D-19 1.762 49.00 1.00 0.014 325.00 325.23 0.785 2.244 0.078 327.76 0.055 327.813 0.039 0.078 327.930 327.930 Submerged Submerged 2.244 0.028 0.028 0.784 0.784 0.014 0.000 0.000 327.92 329.68 1.76D-17 D-18 0.733 40.00 1.00 0.014 325.23 325.75 0.785 0.934 0.014 327.92 0.008 327.924 0.007 0.014 327.945 327.945 Submerged Submerged 0.934 0.012 0.012 0.710 0.710 0.006 0.000 0.000 327.94 329.65 1.71D-11 D19 0.474 29.00 1.00 0.014 324.15 324.65 0.785 0.604 0.006 327.76 0.002 327.760 0.003 0.006 327.769 327.769 Submerged Submerged 0.604 0.008 0.008 0.701 0.701 0.000 0.000 0.000 327.77 329.65 1.88D-26 D-19 0.546 49.00 1.00 0.014 324.15 324.89 0.785 0.695 0.008 327.76 0.005 327.763 0.004 0.008 327.775 327.775 Submerged Submerged 0.695 0.009 0.009 0.705 0.705 0.000 0.000 0.000 327.77 329.89 2.12EAST BASINBACKWATER CALCULATIONS(King County Parks Central Maintenance Facility Replacement Project)PipeSegmentCB to CBWEST BASINC:\Users\DCISAKOWSK\projects\CFM\Permit\KC PARKS CMF_Conveyance_20210611.xls Backwater Analysis 6.111Printed 6/17/2021 100YR Storm1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 1617 18 19 20 21 22Q(CFS)Length(FT)Pipe Size(FT)"n" Value Outlet ElevationInlet ElevationBarrel Area(SF)Barrel Velocity (FT/S)Barrel Velocity Head(FT)TW Elevation(FT)Friction Loss (FT)Entrance HGL Elevation(FT)Entrance Head Loss(FT)Exit Head Loss(FT)Outlet Control Elevation(FT)Inlet Control Elevation(FT)Outlet ConditionsInlet ConditionQ/AD0.5≤3.5Form 2 Unsubmerged AnalysisHW UnsubmergedSubmerged AnalysisHW SubmergedApproach Velocity Head(FT)Bend Head Loss(FT)Junction Head Loss(FT)HW Elevation(FT)RIMElevation(FT)RIMElevation - HW(FT)OWS-1 MWL-1 0.580 21.00 1.00 0.014 318.04 318.22 0.785 0.739 0.008 318.04 0.006 318.046 0.004 0.008 318.927 318.927 Unsubmerged Unsubmerged 0.739 0.009 0.009 0.707 0.707 0.008 0.011 0.000 318.93 328.95 10.02FS-1 OWS-1 0.580 17.00 1.00 0.014 318.55 318.65 0.785 0.739 0.008 318.93 0.005 318.935 0.004 0.008 319.352 319.352 Unsubmerged Unsubmerged 0.739 0.009 0.009 0.702 0.702 0.008 0.011 0.000 319.35 329.00 9.65SED-1 FS-1 0.580 7.00 1.00 0.014 319.40 319.50 0.785 0.739 0.008 319.35 0.002 319.356 0.004 0.008 320.207 320.207 Unsubmerged Unsubmerged 0.739 0.009 0.009 0.707 0.707 0.349 0.000 0.000 324.90 329.00 4.10D-6A SED-1 3.720 10.00 1.00 0.014 321.50 321.90 0.785 4.739 0.349 324.90 0.125 325.025 0.174 0.349 325.548 325.548 Submerged Submerged 4.739 0.059 0.059 0.907 0.907 0.038 0.048 0.136 325.69 327.55 1.86D-4 SED-1 4.337 12.00 1.00 0.014 322.20 322.31 0.785 5.525 0.474 324.90 0.204 325.104 0.237 0.474 325.815 325.815 Submerged Submerged 5.525 0.069 0.069 0.930 0.930 0.245 0.306 0.000 325.88 328.21 2.33D-3 D-4 3.118 66.00 1.00 0.014 322.31 322.80 0.785 3.972 0.245 325.88 0.581 326.458 0.122 0.245 326.825 326.825 Submerged Submerged 3.972 0.050 0.050 0.871 0.871 0.119 0.000 0.000 326.71 328.20 1.49D-2 D-3 2.175 112.00 1.00 0.014 322.80 324.20 0.785 2.771 0.119 326.71 0.480 327.186 0.060 0.119 327.364 327.364 Submerged Submerged 2.771 0.035 0.035 0.810 0.810 0.087 0.000 0.000 327.28 328.42 1.14D-1 D-2 1.854 40.00 1.00 0.014 324.20 324.50 0.785 2.362 0.087 327.28 0.125 327.402 0.043 0.087 327.532 327.532 Submerged Submerged 2.362 0.029 0.029 0.784 0.784 0.100 0.125 0.000 327.56 328.50 0.94D-6 D-6A 1.991 24.00 1.00 0.014 321.90 322.50 0.785 2.536 0.100 325.69 0.086 325.780 0.050 0.100 325.930 325.930 Submerged Submerged 2.536 0.032 0.032 0.799 0.799 0.004 0.005 0.000 325.93 327.26 1.33D-5 D-6 0.401 85.00 1.00 0.014 322.50 323.14 0.785 0.511 0.004 325.93 0.012 325.943 0.002 0.004 325.949 325.949 Submerged Submerged 0.511 0.006 0.006 0.692 0.692 0.000 0.000 0.000 325.95 328.31 2.36D-7 D-6A 1.235 54.00 1.00 0.014 322.75 323.16 0.785 1.573 0.038 325.69 0.075 325.769 0.019 0.038 325.826 325.826 Submerged Submerged 1.573 0.020 0.020 0.750 0.750 0.028 0.000 0.000 325.80 328.30 2.50D-8 D-7 1.052 54.00 1.00 0.014 323.16 323.56 0.785 1.340 0.028 325.80 0.054 325.852 0.014 0.028 325.894 325.894 Submerged Submerged 1.340 0.017 0.017 0.734 0.734 0.013 0.000 0.014 325.90 329.00 3.10D-9 D-8 0.721 100.00 1.00 0.014 323.56 324.32 0.785 0.919 0.013 325.90 0.047 325.943 0.007 0.013 325.962 325.962 Submerged Submerged 0.919 0.011 0.011 0.717 0.717 0.005 0.000 0.000 325.96 329.45 3.49D-10 D-9 0.430 71.00 1.00 0.014 324.32 324.85 0.785 0.548 0.005 325.96 0.012 325.970 0.002 0.005 325.977 325.977 Submerged Submerged 0.548 0.007 0.007 0.698 0.698 0.000 0.000 0.000 325.98 329.60 3.62OWS-2 MWL-2 0.280 13.50 1.00 0.014 319.63 319.74 0.785 0.357 0.002 319.63 0.000 319.630 0.001 0.002 320.425 320.425 Unsubmerged Unsubmerged 0.357 0.004 0.004 0.685 0.685 0.002 0.002 0.000 320.43 331.95 11.52FS-2 OWS-2 0.280 10.40 1.00 0.014 320.07 320.18 0.785 0.357 0.002 320.43 0.000 320.426 0.001 0.002 320.868 320.868 Unsubmerged Unsubmerged 0.357 0.004 0.004 0.688 0.688 0.002 0.002 0.000 320.87 331.88 11.01SED-2 FS-2 0.280 6.50 1.00 0.014 320.92 321.00 0.785 0.357 0.002 320.87 0.000 320.869 0.001 0.002 321.685 321.685 Unsubmerged Unsubmerged 0.357 0.004 0.004 0.685 0.685 0.481 0.000 0.000 326.40 332.03 5.63D-15 SED2 4.370 11.00 1.00 0.014 322.00 323.30 0.785 5.567 0.481 326.40 0.076 326.476 0.241 0.481 327.198 327.198 Submerged Submerged 5.567 0.069 0.069 0.952 0.952 0.102 0.127 0.244 327.47 330.51 3.04D-23 D-15 1.636 10.00 1.00 0.014 323.30 324.57 0.785 2.084 0.067 327.47 0.010 327.477 0.034 0.067 327.578 327.578 Submerged Submerged 2.084 0.026 0.026 0.776 0.776 0.063 0.000 0.000 327.51 330.52 3.01D-22 D-23 1.580 76.00 1.00 0.014 324.50 325.05 0.785 2.013 0.063 327.51 0.068 327.583 0.031 0.063 327.678 327.678 Submerged Submerged 2.013 0.025 0.025 0.772 0.772 0.029 0.037 0.004 327.69 330.46 2.77D-21 D-22 1.082 52.00 1.00 0.014 325.05 327.50 0.785 1.378 0.029 327.69 0.022 327.710 0.015 0.029 327.755 328.234 Submerged Unsubmerged 1.378 0.017 0.017 0.734 0.734 0.001 0.000 0.000 328.23 330.49 2.26D-20 D-21 0.210 82.00 1.00 0.014 325.51 326.00 0.785 0.268 0.001 328.23 0.001 328.234 0.001 0.001 328.236 328.236 Submerged Submerged 0.268 0.003 0.003 0.684 0.684 0.000 0.000 0.000 328.24 330.50 2.26D-25 D-22 0.106 44.00 1.00 0.014 325.05 327.50 0.785 0.135 0.000 327.69 0.000 327.689 0.000 0.000 327.689 328.174 Submerged Unsubmerged 0.135 0.002 0.002 0.674 0.674 0.000 0.000 0.000 328.17 331.42 3.25D-14 D-15 2.009 27.00 1.00 0.014 323.46 323.65 0.785 2.559 0.102 327.47 0.039 327.506 0.051 0.102 327.659 327.659 Submerged Submerged 2.559 0.032 0.032 0.800 0.800 0.063 0.000 0.000 327.60 329.70 2.10D13 D-14 1.579 114.00 1.00 0.014 323.65 324.50 0.785 2.012 0.063 327.60 0.102 327.698 0.031 0.063 327.793 327.793 Submerged Submerged 2.012 0.025 0.025 0.769 0.769 0.002 0.000 0.000 327.79 329.62 1.83D12 D13 0.247 73.00 1.00 0.014 324.50 325.30 0.785 0.314 0.002 327.79 0.002 327.793 0.001 0.002 327.795 327.795 Submerged Submerged 0.314 0.004 0.004 0.686 0.686 0.000 0.000 0.000 327.79 329.72 1.93D-19 SED-2 3.248 8.00 1.00 0.014 324.05 324.15 0.785 4.137 0.266 326.40 0.030 326.430 0.133 0.266 326.829 326.829 Submerged Submerged 4.137 0.052 0.052 0.880 0.880 0.107 0.133 1.396 328.25 330.22 1.97D-18 D-19 2.057 49.00 1.00 0.014 325.00 325.23 0.785 2.620 0.107 328.25 0.075 328.326 0.053 0.107 328.486 328.486 Submerged Submerged 2.620 0.033 0.033 0.803 0.803 0.018 0.000 0.000 328.47 329.68 1.21D-17 D-18 0.856 40.00 1.00 0.014 325.23 325.75 0.785 1.090 0.018 328.47 0.011 328.478 0.009 0.018 328.506 328.506 Submerged Submerged 1.090 0.014 0.014 0.718 0.718 0.008 0.000 0.000 328.50 329.65 1.15D-11 D19 0.553 29.00 1.00 0.014 324.15 324.65 0.785 0.705 0.008 328.25 0.003 328.255 0.004 0.008 328.266 328.266 Submerged Submerged 0.705 0.009 0.009 0.706 0.706 0.000 0.000 0.000 328.27 329.65 1.38D-26 D-19 0.637 49.00 1.00 0.014 324.15 324.89 0.785 0.812 0.010 328.25 0.007 328.259 0.005 0.010 328.274 328.274 Submerged Submerged 0.812 0.010 0.010 0.711 0.711 0.000 0.000 0.000 328.27 329.89 1.62EAST BASINBACKWATER CALCULATIONS(King County Parks Central Maintenance Facility Replacement Project)PipeSegmentCB to CBWEST BASINC:\Users\DCISAKOWSK\projects\CFM\Permit\KC PARKS CMF_Conveyance_20210611.xls Backwater Analysis 6.111Printed 6/17/2021 Stormwater Technical Information Report King County Parks – Renton Shop Central Maintenance Facility Replacement Project June 16, 2021 | E-1 Appendix E. Geotechnical Report GEOTECHNICAL EVALUATION King County Parks and Recreation Division – Renton Shop 3005 4th Street NE Renton, Washington Prepared for: Mr. Christopher Walling, Project Manager HDR Architecture, Inc. Project No. 170383 September 9, 2020 FINAL e a r t h w a t e r+ppeecctt C O N S U L T I N G earth +w ater Aspect Consulting, LLC 710 2nd Avenue Suite 550 Seattle, WA 98104 206.328.7443 www.aspectconsulting.com V:\170383 King County Parks Central Maintenance Facility #E00491E17\Deliverables\Final Geotechnical Report\Renton Shop_GeoRpt_2020909_FINAL.docx GEOTECHNICAL EVALUATION King County Parks and Recreation Division – Renton Shop 3005 4th Street NE Renton, Washington Prepared for: Mr. Christopher Walling, Project Manager HDR Architecture, Inc. Project No. 170383 September 9, 2020 FINAL Aspect Consulting, LLC Mark Swank, LG, LEG Senior Engineering Geologist mswank@aspectconsulting.com Engineering Geology Henry H. Haselton, PE, PMP Principal Geotechnical Engineer hhaselton@aspectconsulting.com Geotechnical Engineering John Knutson, PE Principal Water Resources Engineer jknutson@aspectconsulting.com Stormwater Engineering 9/9/2020 9/9/2020 9/9/2020 ASPECT CONSULTING PROJECT NO. 170383 SEPTEMBER 9, 2020 FINAL i i Contents 1 Introduction ................................................................................................. 1 1.1 General ...................................................................................................... 1 1.2 Scope of Services ..................................................................................... 1 1.3 Project Description ................................................................................... 2 2 Site Conditions ............................................................................................ 4 2.1 Site Description ......................................................................................... 4 2.2 Critical Areas ............................................................................................. 5 2.3 Geologic Setting ....................................................................................... 5 2.3.1 Geology ............................................................................................... 5 2.3.2 Faults and Seismicity .......................................................................... 6 2.3.3 Geologic and Seismic Hazards ........................................................... 6 2.4 Site Reconnaissance ................................................................................. 8 2.5 Subsurface Conditions ............................................................................. 8 2.5.1 Previous Subsurface Explorations ..................................................... 8 2.5.2 Aspect Consulting Subsurface Explorations ..................................... 9 2.5.3 Soil Infiltration Rates ........................................................................ 11 3 Conclusions and Recommendations ....................................................... 13 3.1 General .................................................................................................... 13 3.2 Seismic Design Criteria .......................................................................... 14 3.3 Foundation Design ................................................................................. 14 3.3.1 Shallow Foundations ........................................................................ 14 3.4 Floor Slabs and Modulus of Subgrade Reaction .................................. 15 3.5 Pavement Design .................................................................................... 16 3.6 Stormwater Management Design ......................................................... 16 3.6.1 Steep Slope Setback and Groundwater Considerations ................ 16 3.6.2 Infiltration Test Analyses and Infiltration Gallery Design ............... 17 3.6.3 Water Quality Treatment and Underground Injection Control ....... 19 4 Construction Considerations .................................................................... 20 4.1 General .................................................................................................... 20 4.2 Site Preparation ...................................................................................... 20 4.3 Proof Rolling and Subgrade Verification............................................... 20 4.4 Wet Weather Conditions ........................................................................ 21 4.5 Excavation ............................................................................................... 21 4.5.1 General .............................................................................................. 21 4.5.2 Trenches ............................................................................................ 21 4.5.3 Temporary and Permanent Slopes .................................................. 22 ASPECT CONSULTING ii FINAL PROJECT NO. 170383 SEPTEMBER 9, 2020 4.6 Structural Fill Materials and Compaction ............................................. 22 4.7 Ground Moisture .................................................................................... 24 4.7.1 General .............................................................................................. 24 4.7.2 Perimeter Footing Drains ................................................................. 24 4.8 Construction-Phase Stormwater Considerations ................................. 24 4.8.1 Protection and Verification of Infiltration Receptor Soils ............... 24 4.8.2 Geotextiles for Stormwater Drainage .............................................. 25 5 Project Design and Construction Monitoring .......................................... 26 6 References .................................................................................................. 27 7 Limitations ................................................................................................. 29 List of Tables Table 1. Summary of Site Conditions ....................................................................4 Table 2. Geologic and Seismic Hazards Potentially Affecting the Site ..................7 Table 3. Field Infiltration Test Results ................................................................. 12 Table 4. 2018 IBC Seismic Design Parameters .................................................. 14 Table 5. Spread Footing Foundation Design Recommendationsa ....................... 15 Table 6. Preliminary Pavement Section .............................................................. 16 Table 7. Infiltration Analyses Results and Design Parametersa .......................... 18 Table 8. Fill Type and Compaction Requirements .............................................. 23 List of Figures 1 Site Location Map 2 Site and Exploration Plan 3 Critical Areas Map List of Appendices A Aspect Soil Exploration Logs B Vibrating-Wire Piezometers Hydrograph C Laboratory Test Results D Stormwater Infiltration Analysis E King County May 22, 2017, Preliminary Geotechnical Design Report – Subsurface Explorations F Report Limitations and Guidance for Use ASPECT CONSULTING PROJECT NO. 170383 SEPTEMBER 9, 2020 FINAL 1 1 1 Introduction 1.1 General This report summarizes Aspect Consulting, LLC’s (Aspect) Geotechnical Evaluation for the King County (County) Parks and Recreation Division’s (Parks) Renton Shop located at 3005 4th Street NE in Renton, Washington (Site). We performed our services in accordance with our agreed-upon scope of work and signed contract dated January 18, 2018, and additional contract amendments. The Site location is shown on Figure 1, Site Location Map. This report presents the following sections: 1. Introduction – describing scope of services and the project 2. Site Conditions – describing critical areas, geologic setting, site reconnaissance, and subsurface conditions 3. Conclusion and Recommendations – summarizing design recommendations for seismic, foundation, floor slabs, pavement design, and stormwater management 4. Construction Considerations – general recommendations for Site prep, proof rolling, working in wet weather conditions, excavation, structural fill, ground moisture, and construction-phase stormwater considerations 5. Project Design and Construction Monitoring Appendices A–F, including: Appendix A – Aspect Soil Exploration Logs Appendix B – Vibrating Wire Piezometers Hydrograph Appendix C – Laboratory Test Results Appendix D – Stormwater Infiltration Analyses Appendix E – King County May 22, 2017 Preliminary Geotechnical Design Report – Subsurface Explorations Appendix F – Report Limitations and Guidance for Use 1.2 Scope of Services Our scope of services included a literature review, Site reconnaissance, geotechnical and environmental subsurface explorations, stormwater infiltration evaluations, laboratory testing, and critical areas and geotechnical engineering assessments of the Site. This report includes: Site and project descriptions ASPECT CONSULTING 2 FINAL PROJECT NO. 170383 SEPTEMBER 9, 2020 A discussion of the data-review findings, including opinions regarding the effects of relevant geologic and seismic hazards and possible past Site activities on future development Distribution and characteristics of the shallow subsurface soils and groundwater conditions (explorations shown on Figure 2, Site and Exploration Map) Geotechnical and environmental exploration logs and a Site plan showing approximate exploration locations Deep infiltration well installations, testing, and analyses Geotechnical and environmental laboratory test results An assessment of relevant critical area (geohazard and aquifer protection) considerations, and preliminary recommendations for seismic design, earthwork, shoring, foundation support, slabs-on-grade support, retaining walls, stormwater infiltration, pavement design, and related geotechnical construction recommendations Review of the alternatives and the geotechnical feasibility, risk factor, and cost input Translating requirements from the County’s preliminary geotechnical report, which references Washington State Department of Transportation (WSDOT) specifications into CSI-based language per County specifications 1.3 Project Description The Renton Shop Facility plays a critical role in Parks’ ability to adequately and efficiently serve the regional trails, back country trails, and parks throughout the County. This facility functions as the headquarters for the Parks’ Operations & Maintenance (O&M) Section and acts as the dispatch center for the centralized work crews supporting the entire system. The Site consists of several small facilities, parking areas, and yard storage areas, providing work space for the O&M staff, warehousing/inventory, and Parks’ emergency operations center. The Renton Shop Facility Design (Project) will design and construct facilities large enough to accommodate future growth of Parks’ O&M Section. Preliminary designs, feasibility analyses, and preliminary permit application processes were completed with the City of Renton (City) based upon the previous anticipated needs from 2009 to 2014. Site redevelopment, new utilities, and new facilities are necessary to accommodate the current and future operations and the work space for employees over the next 25 to 30 years. The Project is intended to create a functionally efficient Site, with a combined 40,000 to 60,000 square feet (ft2) of total enclosed facilities. Proposed facilities include: Building CA is the main building along the south property line and will contain crew work spaces, locker rooms, restrooms, workshop areas, offices, storage, training/conference rooms, and accessory support spaces. The building is shown as a two-story structure with high and low roof lines and a glass mezzanine. Building SH is a large, single-level shop building in the center of the Site that also includes covered parking for equipment adjacent on its west side. The ASPECT CONSULTING PROJECT NO. 170383 SEPTEMBER 9, 2020 FINAL 3 3 structure has a large open area for maintenance work and a high roof with roll-up gates. Building ST is a combined covered materials storage and parking area along the west property line. Uncovered material storage bins and parking areas are planned along the property boundaries and surrounding the buildings. Below-ground stormwater facilities identified on Figure 2 as the West Side Stormwater Management Facility and East Side Stormwater Management Facility will manage on-Site stormwater with a series of trenches discharging into the receptor soil at 10 to 15 below the existing ground surface (bgs). Per the County’s 2015 Strategic Climate Action Plan and the most current adopted Green Building and Sustainable Development Ordinance #17709, the Project must be designed and constructed to meet the requirements of LEED™ Platinum certification by the United States Green Building Council (USGBC) as a base requirement. The Project may also achieve design to achieve Net Zero certification or Petal certification by the International Living Future Institute—if the County decides to pursue this certification. ASPECT CONSULTING 4 FINAL PROJECT NO. 170383 SEPTEMBER 9, 2020 2 Site Conditions 2.1 Site Description Site details are provided in Table 1 below. Table 1. Summary of Site Conditions Detail Description Location Parcel 143400-0012 with a legal Site address listed as 3003 4th Street NE, Renton, Washington Existing conditions The roughly rectangular 5.71-acre Site is currently the County’s active Central Maintenance Facility. Three buildings consisting of offices and maintenance garages are situated in the western portion of the property and the eastern portion is primarily open lots paved with asphalt or gravel. A driveway traverses east-west through the middle of the Site and a small building is on the located on the south side of it, near the center of the property. Current ground cover The Site is primarily open, paved and unpaved lots. Limited landscaping is planted near the front of one of the Site buildings and consists of a few deciduous trees, plants, and small shrubs. The perimeter of the Site on the north, west, and south sides consists of larger deciduous type trees, weeds, and shrubs. Site topography The ground surface is relatively flat with elevation (EL, North American Vertical Datum 1988 [NAVD88]) between approximately EL 325 feet and EL 330 feet, sloping gradually down to the west. Steeper slopes are along the western and north-western property boundaries. Adjacent Properties The Site is bounded, for a distance of 150 feet beyond the Site’s perimeter and proposed easement, by: North Side: Renton Housing Authority Residential Property (Parcel 1623059120), AM-PM Convenience Store and Gas Station (Parcel 1623059115) and the currently vacant King County Public Health Offices (Parcel 1623059130). East Side: An asphalt paved access road (Parcel 1434000010) for other County facilities in the area is directly adjacent to the planned Maintenance Facility. In addition, there is an approximate 50-foot-deep depression that was previously used to mine sand and gravel (Parcel 1623059059). South Side: County property (Parcel 1434000020) that includes a gravel- surfaced equipment storage area and other undeveloped property with natural vegetation. West Side: Commercial properties (Parcels 1623059144 and 1623059143) that include office and storage facilities. The City has issued a preliminary building permit for Parcel 1623059144 to remove an existing building and add a new three-story building totaling approximately 58,350 ft2. ASPECT CONSULTING PROJECT NO. 170383 SEPTEMBER 9, 2020 FINAL 5 5 2.2 Critical Areas The City's Maps (COR, 2018), an online GIS portal, was reviewed for potential Critical Areas at the Site that consider aquifer protection area zones, coalmines, erosion hazards, flood zones, landslides, regulated slopes and shorelines, wetlands, and seismic hazards. Specific geologic hazards identified in the Renton Municipal Code (RMC) Section 4-3- 050 include Steep Slopes, Landslides, Erosion, Seismic and Coal Mines. Based on the City’s data, the Critical Areas are shown on Figure 3, Critical Areas Map and include: The Site and surrounding area is within the Aquifer Protection Area and designated within Zone 2. According to the Washington State Wellhead Protection Program Guidance Document (DOH, 2010): o Zone 2: The 5-year time-of-travel boundary for groundwater. Zone 2 is managed to control potential chemical contaminants. All potential contaminant sources must be addressed with emphasis on pollution prevention and risk reduction. Zone 2 provides information local planners use to site future "high risk" and "medium risk" potential contaminant sources. Aquifer Protection Area Zone 2 designation requires: (a) The consideration of liners under stormwater facilities to protect groundwater quality. Liners are not practical at the site and are not being required by the City. (b) Water quality treatment prior to stormwater infiltration, or soil conditions that meet City stormwater treatability criteria. Water quality treatment Best Management Practices (BMPs) are planned for the site, however soils below the planned infiltration facilities do possess some treatability characteristics, which will help protect groundwater quality. Portions of the northwest and western property boundary are within the Regulated Slopes classified as 1) >15 percent to ≤25 percent or 2) >25 percent to ≤40 percent (Sensitive) identified within the City’s Critical Areas. A narrow strip at the slope toe is classified as greater than 40 percent to less than or equal to 90 percent (Protected). 2.3 Geologic Setting 2.3.1 Geology Based on our review of the geologic map (Mullineaux, 1965), the Site is underlain by Pleistocene Vashon Stade recessional stratified drift, glaciofluvial deposits (Qpa). The glaciofluvial deposits consist chiefly of well-sorted sand and gravel. The unit is subdivided according to origin and topographic form with outwash along the Cedar River valley, sandy gravels containing cobbles in the easternmost terraces that grades to interbedded sand and gravel in Renton and to sand near the north edge of quadrangle. ASPECT CONSULTING 6 FINAL PROJECT NO. 170383 SEPTEMBER 9, 2020 2.3.2 Faults and Seismicity The Site is located within the Puget Lowland physiographic province, an area of active seismicity that is subject to earthquakes on shallow crustal faults and deeper subduction zone earthquakes. The Site area lies about 2.2 miles southwest of the southern boundary of a concealed trace of the Seattle fault zone, which consists of shallow crustal tectonic structures that are considered active (evidence for movement within the Holocene [since about 15,000 years ago]) and is believed to be capable of producing earthquakes of magnitude 7.3 or greater. The recurrence interval of earthquakes on this fault zone is believed to be on the order of 1,000 years or more. The most recent large earthquake on the Seattle fault occurred about 1,100 years ago (Pratt et al., 2015). There are also several other shallow crustal faults in the region capable of producing earthquakes and strong ground shaking. The Site area also lies within the zone of strong ground shaking from earthquakes associated with the Cascadia Subduction Zone (CSZ). Subduction zone earthquakes occur due to rupture between the subducting oceanic plate and the overlying continental plate. The CSZ can produce earthquakes up to magnitude 9.3, and the recurrence interval is thought to be on the order of about 500 years. A recent study estimates the most recent subduction zone earthquake occurred on January 26, 1700 (Atwater et al., 2015). Deep intraslab earthquakes, which occur from tensional rupture of the sinking oceanic plate, are also associated with the CSZ. An example of this type of seismicity is the 2001 Nisqually earthquake. Deep intraslab earthquakes typically are magnitude 7.5 or less and occur approximately every 10 to 30 years. 2.3.3 Geologic and Seismic Hazards Geologic and seismic hazards are defined as those conditions associated with the geologic and seismic environment that could influence existing and/or proposed improvements. In general, the geologic and seismic hazards most commonly associated with the physical and chemical characteristics of near-surface soil, rock, and groundwater include the following. Those shown in bold are the geologic and seismic hazards that could affect the Project area’s development and should be considered during the planning process. Geologic Hazards • Slope stability • Adverse soils • Hydrogeology and groundwater • Subsurface voids • Hydrology and drainage • Hazardous minerals and gases • Volcanic hazards • Land subsidence • Erosion and sedimentation ASPECT CONSULTING PROJECT NO. 170383 SEPTEMBER 9, 2020 FINAL 7 7 Seismic Hazards • Liquefaction • Lateral spreading • Fault ground rupture • Ground shaking • Tsunamis • Earthquake-induced landslides • Seiches Specific hazards identified above in bold are presented in Table 2 below. The “Level of Concern” is a qualitative assessment based on our engineering geology and geotechnical engineering judgment. Where noted with footnotes, the terminology is taken from a specific source (e.g., webviewer; DNR, 2018). Table 2. Geologic and Seismic Hazards Potentially Affecting the Site Geologic and Seismic Hazard Examples Level of Concern Adverse Soils Artificial Fill Expansive Soil, Compressible Soil, Organic-Rich Soil, Sensitive Clay Low to Moderate, Site was graded and filled in areas and is an active maintenance facility with possible buried debris and two underground storage tanks (USTs) near the former fueling station in the center of the Site. None to Low Hydrology and Drainage Floodinga Seiches or Standing Water Not in FEMA 100-year flood plain None to Low Slope Stability Landslides and Existing Slope Movements Low, exception along west property boundary Hydrogeology and Groundwater Shallow or artesian groundwater Seepage Permeability or percolation Low None to Low Low Subsurface Voids Abandoned coal minesb Low, the nearest mapped hazard zone is 0.5 miles southwest of the Site Seismic Hazards Cascadia M9.0 scenarioa Crustal – Seattle FZ M7.2 scenarioa Local Fault Rupture Liquefactiona MMIc 7 MMIc 9 None to Low Very Low Notes: a – DNR webviewer: https://geologyportal.dnr.wa.gov/ b – City of Renton webviewer: http://rp.rentonwa.gov/HTML5Public/Index.HTML?viewer=CORMaps/ (King County, 2018b) c – MMI = Modified Mercalli Intensity Scale: http://resilience.abag.ca.gov/shaking/mmi/ The primary geologic hazards that may require further evaluation during engineering design are related to potential fill and debris. The primary seismic hazard that could ASPECT CONSULTING 8 FINAL PROJECT NO. 170383 SEPTEMBER 9, 2020 impact the Site is ground shaking from a Cascadia earthquake or Seattle fault zone earthquake. 2.4 Site Reconnaissance We performed our geotechnical site reconnaissance of the Site on February 15, 2018. The weather was cool and windy with no measurable precipitation, though about 0.25 inches of rain had fallen on the Site during the two prior days. Much of the Site is unpaved gravel lot with impervious surfaces, including the four buildings and the driveway that leads west from Jefferson Avenue NE into the Site. Sparse vegetation is adjacent to the buildings and trees line the north and west property boundaries. Topographically, the ground surface at the Site is relatively flat, with only about 5 feet of elevation difference from the west boundary of the parcel to the east boundary, a distance of approximately 600 feet, and no apparent elevation change across the 400 feet from the north to the south. A few shallow depressions (<1 inch) with standing water were observed.in low spots on the concrete slabs and mud pits in two shallow, unpaved low spots. We did not observe indications of concentrated surface flows across the Site, areas of groundwater seepage from the western slopes, or of recent or ongoing soil erosion. 2.5 Subsurface Conditions 2.5.1 Previous Subsurface Explorations The County performed six geotechnical borings on April 13, 2017, as part of their preliminary geotechnical evaluation of the Site (Appendix E). Borings B-1 through B-5 were drilled to 26.5 feet bgs at the Site (Parcel No. 1434000012) and boring B-6 to 16.5 feet bgs for a proposed utility easement located along the west side of the adjacent property to the north (Parcel No. 1623059130) (Figure 2, Site and Exploration map). The soils encountered were generally consistent throughout the Site and consisted of: GROUND SURFACE: Ground Surface to up to 0.5 feet bgs, crushed gravel surfacing mixed with sand and silt was encountered in borings B-1 through B-5. Boring B-6 encountered a few inches of topsoil and organic matter. FILL: From between 1.5 and 5 feet bgs, silty sand and mixtures of sand and gravel were encountered in the borings with the exception of B-2, where no fill was observed. The fill material was medium dense to dense immediately beneath the crushed gravel surface and graded to loose with depth. GLACIAL OUTWASH DEPOSITS (Qpa): Outwash deposits were encountered in the borings to the total exploration depths (26.5 feet bgs). The soils typically consisted of interbedded mixtures of medium dense poorly graded mixtures of sand and gravel, including some cobbles and boulders. The previous report (Appendix E) also noted potential oversized materials may be present and it is difficult to determine the percentage of cobbles and, potentially boulders, in the underlying soil deposits. However, cobbles were observed and will likely be encountered during construction, potentially with occasional small boulders. ASPECT CONSULTING PROJECT NO. 170383 SEPTEMBER 9, 2020 FINAL 9 9 In addition, the County’s report also identified that two test pits were excavated to between 4.5 to 5.5 feet bgs during previous [no date stated] exploration of the DNRP Maintenance Complex property. These test pits encountered approximately 2 to 2.5 feet of medium dense to dense gravelly sand fill overlying medium dense to dense native sand and gravel outwash deposits, to the total excavated depths. 2.5.2 Aspect Consulting Subsurface Explorations Subsurface conditions have been explored by Aspect during three exploration programs. The programs included: On April 15 through 17, 2019, drilling two sonic borings (designated MW-01 and MW-02) within the footprints of the West Side and East Side Stormwater Management Facilities (see Figure 2) to depths of 75 feet bgs to install deep infiltration test wells. On April 13, 2018, drilling four hollow-stem auger (HSA) borings (designated AB-01 through AB-04) to depths of 26.5 feet bgs within or in the vicinity of Building CA and Building SH footprints for geotechnical purposes. On February 16, 2018, advancing four 15- to 20-foot bgs direct-push probes (designated AB-05 through AB-08) around the perimeter of two decommissioned USTs for environmental purposes. The explorations were logged and soil samples collected by a geologist on the Aspect staff. Exploration logs summarizing the subsurface conditions are presented in Appendix A. Observations and tests were performed in general accordance with ASTM International (ASTM) D2488, Standard Practice for Description and Identification of Soils (Visual-Manual Procedure; ASTM, 2017). The terminology used in the soil classifications and other modifiers are defined and presented on the attached Exploration Log Key included in Appendix A. 2.5.2.1 Soils The summary of the subsurface units below the existing ground surface encountered in the borings are as follows: GROUND SURFACE Ground Surface to up to 0.5 bgs feet, crushed gravel surfacing mixed with sand and silt was encountered in the borings. FILL Between 1 and 4 feet of fill was encountered in the infiltration test well borings (MW-01 and MW-02) and geotechnical borings (AB-01 through AB-04) consisting of loose to medium dense silty sand (SM) with gravel, sand with gravel (SP), and GRAVEL with sand (GP). Between 7 and 10 feet of fill was encountered in the environmental direct-push probes (AB-05 through AB-08) consisting of brown, silty gravel (GM) with sand and cobbles. The upper fill layer contains some construction debris and the soil color transitioned to gray and tan with depth. ASPECT CONSULTING 10 FINAL PROJECT NO. 170383 SEPTEMBER 9, 2020 GLACIAL OUTWASH DEPOSITS (Qpa) Glacial outwash deposits were encountered in the borings underlying the fill to the maximum exploration depth in MW-02 to 76.5 feet bgs. The subsurface stratigraphy consists of interbedded coarse-grained deposits of gray and brown silty sand (SM), sand with silt (SP -SM and SW-SM), sand with silt and gravel (SP -SM and SW-SM), well-graded and poorly-graded sand (SW and SP) with variable gravel content, silty gravel with sand (GM), and gravel with sand and cobbles (GP and GW). A 1-foot thick layer of gravelly silt with sand (ML) was observed at 35 feet bgs in MW-02. The coarse-grained deposits were medium dense to very dense with N- values between 23 and 68 blows per foot (bpf). 2.5.2.2 Groundwater Groundwater was not observed in Aspect’s geotechnical direct-push borings (maximum depth of 26.5 feet) or in the County’s previous borings (maximum depth 26.5 feet) during previous field explorations. Installation of two deep infiltration test wells included overdrilling to determine the groundwater elevation below the Site. Vibrating-wire piezometers were installed in April 2019 at approximately 75 feet bgs and initially recorded groundwater levels at 30-minute intervals from installation through October 2019. Beginning in November 2019 through March 2020, groundwater readings were recorded at 6-hour intervals. Based on readings from April 2019 through March 2020 (Appendix B), the groundwater fluctuated between 65.5 feet bgs (EL 259.6 feet) and 67.5 feet bgs (EL 254.8 feet), over 50 feet below the bottom of the planned stormwater infiltration facilities. No noticeable impacts to the groundwater table were recorded during or within 6 days post stormwater infiltration tests. Groundwater depths will fluctuate due to variations in rainfall, irrigation, and the season. Generally higher in the wet season from late-November to May and lower in the dry season from June to early-November. 2.5.2.3 Environmental Contamination During the direct-push explorations AB-05 through AB-06, soil samples were subjected to field screening for hydrocarbon contamination. Field screening consisted of visual and olfactory screening and screening the samples with a photoionization detector (PID). No visual, olfactory, or PID field indications of contamination were observed. A soil sample from each of the four borings was collected at a depth at or below the presumed depth of the bottom of the USTs and submitted to an accredited analytical laboratory for detection and quantification of contamination (Appendix C). The laboratory analyzed each sample for gasoline-range organics (by method NWTPH-G) and diesel- and oil-range organics (method NWTPH-Dx). None of the analytes were detected at the reporting detection limits. ASPECT CONSULTING PROJECT NO. 170383 SEPTEMBER 9, 2020 FINAL 11 11 2.5.3 Soil Infiltration Rates Soil infiltration rates were estimated using in situ field testing. Due to the existing receptor soil depth, performing large-scale pilot infiltration tests (PITs) per the City’s Surface Water Design Manual (COR, 2016) was deemed impractical because of the required excavation sizes. Aspect requested and was approved by the City to use infiltration test wells (in lieu of PITs) within the footprints of two of the four proposed stormwater systems. Measured infiltration rates were adjusted to account for the approximate water depths within the planned infiltration trenches and safety factors were applied to the adjusted rates, as required by the City’s standards. Infiltration testing was in general conformance with the United States Bureau of Reclamation (USBR)Well Permeameter Method (USBR, 1989). The measured infiltration results indicate that the Site receptor soil has a high infiltration capacity with an allowed design infiltration rate of 20 inches per hour (maximum allowed by the City) for infiltration trenches. Sandy soils are highly susceptible to plugging by stormwater sediments and the reduction in long-term infiltration rates should be considered in the design of the stormwater system. Typical stormwater treatment BMPs are allowed to bypass flows above the water quality flow that could introduce some untreated, potentially sediment-containing, stormwater into the infiltration system. This is particularly true for this Site, which intends to retain and infiltrate all runoff up to and including the 100-year storm on the Site. The need for sediment-control BMPs for bypass flows, or an additional safety factor on the design infiltration rate, should be considered by the stormwater designer to enhance the functional life of the infiltration system. Additional infiltration test well installation details are provided in Appendix D. 2.5.3.1 Deep Well Infiltration Tests The infiltration rates of the planned receptor soil (proposed to be at depths of 10 feet to 15 feet bgs) were tested in 6-inch-diameter monitoring wells screened from 13 feet to 23 feet bgs in MW-01 and from 15 feet to 25 feet bgs in MW-02, both within the target infiltration receptor soil. We conducted two two-phase infiltration tests in general accordance with the USBR Well Permeameter Method (USBR, 1989); consisting of a constant head test (Phase 1) and falling head test (Phase 2). Due to the high permeability of the Site’s receptor soils and access to finite water source from 5,000-gallon water trucks, producing, maintaining, and measuring constant head levels during the tests were a challenge. Rather than measuring stepped water levels and rates, the tests consisted of using the maximum allowable flow rates the equipment was capable of providing, which was between 90 and 140 gallons per minute (gpm). Table 3 below provides the constant head test details. ASPECT CONSULTING 12 FINAL PROJECT NO. 170383 SEPTEMBER 9, 2020 Table 3. Field Infiltration Test Results Monitoring Well Time Interval (hr) Flow Rates (gpm) Constant Head (ft ht) Total (gal) MW-01 1.5 84 7.6 13,210 0.5 97 7.8 0.5 115 9.3 MW-02 0.5 120 6.2 27,700 3.25 120 5.1 The Phase 2 falling head tests recorded rapid drops in head once the water source was shut-off, with 50 to 80 percent recovery within 2 minutes and 95 percent or greater within 5 minutes. Evidence of post-test perched groundwater was not observed in the infiltration test wells, suggesting no discernable presence of restrictive soil layers or related mounding of the water used during the tests. In addition, the vibrating-wire piezometers data recorded during the tests and for 6 days after were analyzed for fluctuations in the groundwater elevation that could be attributed to the test. No significant groundwater mounding response was observed, indicating that the groundwater likely has ample capacity to absorb infiltrated stormwater. 2.5.3.2 Soil Treatability Tests We understand the proposed plan is to implement stormwater treatment BMPs prior to infiltration. To evaluate the receptor soil for treatment functions to increase groundwater quality protection, soil samples from MW-01 at 20 feet bgs and MW-02 at 35 feet bgs were tested for cation exchange capacity (CEC) and organic matter percentage. For the soil to count as stormwater treatment within a designated Aquifer Protection Zone, City standards require that at least the first two feet of soil below an infiltration facility to: (1) have a CEC of at least 5.0 milliequivalents/100 grams of soil (meq/100g); (2) have an Organic Matter Content of 1 percent or greater by dry weight (for soil fraction passing the #40 sieve); (3) have measured infiltration rates less than or equal to 9 inches per hour, and meet specific soil gradation requirements (Section 5.2 of the 2016 City Surface Water Design Manual; COR, 2016). The CEC and organic percentage results for the samples taken were 4.2 meq/100g of soil and 1.6 percent in MW-01 and 5.0 meq/100g of soil and 1 percent in MW-02. The sample from MW-01 is slightly below the CEC minimum 5 meq/100 grams requirement while the organic content is greater than the minimum. The sample from MW-02 is equivalent to or above both minimum requirements. While the Site soil does have a measured infiltration rates significantly higher than 9 inches per hour, the soil does have the ability to provide some treatment of infiltrating stormwater through filtration, cation exchange, and adsorption, which will enhance the protection of groundwater quality when compared to the planned basic treatment BMPs alone. ASPECT CONSULTING PROJECT NO. 170383 SEPTEMBER 9, 2020 FINAL 13 13 3 Conclusions and Recommendations 3.1 General Based on our geotechnical evaluation of the Site, including data review, Site reconnaissance, subsurface explorations, and laboratory testing, the following key preliminary findings and conclusions should be included in further evaluating the Site: The upper soils encountered in the explorations within the anticipated foundation excavation depths are medium dense to dense sand and gravel soils. The fill and glacial outwash deposits may contain cobbles and boulders that could be encountered during earthwork and require removal. The area surrounding the two decommissioned USTs near the former fueling station in the center of the Site did not have indications of contaminated soil. Although no field or laboratory indications of product release from the USTs were measured or observed, the steel USTs could have leaked while they were in service. Because the soils around and below the USTs are coarse-grained and permeable, any release from the USTs would have migrated vertically. If the tanks will be removed as part of the construction, we recommend field screening the soil directly under the tanks for indications of contamination and, if detected, completing additional analytical laboratory tests. Shallow spread footings are an appropriate foundation type for Buildings CA, SH, and ST. Glacial outwash sands and sandy gravels are generally well suited for stormwater infiltration. The Site’s designation as an Aquifer Protection Area Zone 2 requires water quality treatment prior to infiltrating stormwater. While water quality treatment is required prior to infiltration, chemical testing indicates that the soil does have the ability to provide some treatment of infiltrating stormwater through filtration, cation exchange, and adsorption. Groundwater was encountered in our explorations at approximately 67 feet bgs and monitored for approximately 1 year. Based on these data, the separation between the bottom of the stormwater facility and the top of groundwater is greater than 50 feet, using a soil receptor depth of 15 feet bgs. From a geotechnical perspective, typical activities associated with Site development, such as clearing and grading, utility placement, and building construction will have no adverse impacts on surrounding properties, provided County and/or other regulatory requirements for design and construction are implemented. We anticipate cuts and fills will generally be less than 4 feet over most of the Site, with the exception of the planned stormwater trenches to about 15 feet bgs. From a geotechnical perspective, earthwork excavation using conventional equipment will be feasible during construction. ASPECT CONSULTING 14 FINAL PROJECT NO. 170383 SEPTEMBER 9, 2020 3.2 Seismic Design Criteria Inertial seismic forces are expected to affect the Site and structures. Appropriate design of structures in accordance with the current version of the International Building Code (IBC) with State of Washington amendments will mitigate seismic hazards. The IBC requires design for a “Maximum Considered Earthquake (MCE)” with a 2 percent probability of exceedance (PE) in 50 years (2,475-year return period; IBC, 2015). The U.S. Geological Survey (USGS) has completed probabilistic ground motion studies and maps for Washington (USGS, 2014). Current IBC design methodologies express the effects of site-specific subsurface conditions on the ground motion response in terms of the “site class.” The site class can be correlated to the average standard penetration resistance (SPT) in the upper 100 feet of the soil profile. Based on the results of the previous subsurface exploration program and using the 2015 IBC criteria, we recommend the Site be characterized by a Seismic Site Class D. Based on the Site’s latitude and longitude (47.488°N, 122.178°W), the code-based seismic design criteria, in accordance with the 2015 IBC, are summarized in Table 4. Table 4. 2018 IBC Seismic Design Parameters Parameter Short Period 1 Second Maximum Credible Earthquake Spectral Acceleration Ss = 1.42 g S1 = 0.53 g Site Class D Site Coefficient Fa = 1.00 Fv = 1.56 Adjusted Spectral Acceleration SMS = 1.42 g SM1 = 0.80 g Design Spectral Response Acceleration Parameters SDS = 0.94 g SD1 = 0.53 g Design Spectral Peak Ground Acceleration 0.58 g Notes: g = acceleration due to gravity 3.3 Foundation Design 3.3.1 Shallow Foundations Based on our observations of the subsurface conditions at the Site, shallow foundations on spread or strip footings may be used for building support. We recommend the footings bear directly on sandy and gravelly, medium dense to dense Qpa soil deposits, if exposed by grading, or the footings should be overexcavated by 18 to 24 inches and replaced with compacted structural fill. The structural fill below the footings should extend beyond the edges of the footings by a distance equal to the thickness of the structural fill. The exposed subgrade surface of all footings should be evaluated by a qualified geotechnical engineer. Design parameters are provided in Table 5. ASPECT CONSULTING PROJECT NO. 170383 SEPTEMBER 9, 2020 FINAL 15 15 Table 5. Spread Footing Foundation Design Recommendationsa Design Item Design Information Structures Renton Shop Buildings Bearing Material Qpa deposits or 18 to 24 inches of compacted structural fill placed over approved subgrade Allowable Bearing Pressurea 2,500 pounds per square foot (psf) Minimum Embedment Depthb,c 18 inches Total Estimated Settlement Differential Settlement Less than 1 inch Less than 0.5 inches between adjacent footings Notes: a) Designs are based on the subsurface conditions encountered in the explorations and assumes the recommendations in the Construction Considerations Section will be adhered to. b) For preliminary information related to minimum depth of footing for frost action. Does not infer or indicate depth to bearing strata. Will be updated at final design. c) The recommended allowable bearing pressure applies to the total of dead plus long-term-live loads. Allowable bearing pressures may be increased by one-third (⅓) for seismic and wind loads. For use in design, an ultimate coefficient of friction of 0.45 may be assumed along the interface between the base of a cast-in-place concrete footing and the subgrade soils. An ultimate passive earth pressure of 450 pounds per cubic foot (pcf) may be assumed for structural fill replacement or gravel soils adjacent to below-grade elements. The upper 1 foot of passive resistance should be neglected in design. The recommended coefficient of friction and passive pressure values are ultimate values that do not include a safety factor. We recommend applying a factor of safety of at least 1.5 in design for determining allowable values for coefficient of friction and passive pressure. 3.4 Floor Slabs and Modulus of Subgrade Reaction Concrete slabs-on-grade should be designed in accordance with the American Concrete Institute (ACI) Committee’s 360R-10 Guide to Design of Slabs-on-Ground (ACI, 2010). For slabs that are designed as beam-on-elastic foundation, a modulus of vertical subgrade reaction of 150 pounds per cubic inch (pci) may be utilized. Satisfactory support for building floor slabs can be obtained from the sandy and gravelly, medium dense to dense Qpa soil subgrades or the 18 to 24 inches of structural fill replacement and be prepared in accordance with our recommendations presented in the Site Preparation and/or Wet- Weather/Wet-Soil Conditions sections of this report (Sections 4.2 and 4.4, respectively). A minimum 6-inch-thick layer of imported granular material should be placed and compacted over the prepared subgrade. Imported granular material should be composed of crushed rock or crushed gravel that is relatively well-graded between coarse and fine, contains no deleterious materials, has a maximum particle size of 1 inch, and has less than 5 percent by dry weight passing the US Standard No. 200 Sieve. ASPECT CONSULTING 16 FINAL PROJECT NO. 170383 SEPTEMBER 9, 2020 3.5 Pavement Design Traffic volume estimates and loading patterns were not provided at the time of this report. We anticipate that parking and ancillary access drives will primarily be paved with hot mix asphalt (HMA) pavement. Without traffic volume information to complete a pavement design, the general pavement section recommendation is in accordance with the King County Roads Standards (King County, 2016). Work should be performed in accordance with King County Standard Specifications (KCSS) Section 32 12 16 - Asphalt Paving (King County, 2018a). The main drive lanes entering and leaving the Site and areas of the buildings where maintenance vehicles will frequently be using, including loading ramps, should consider more robust HMA pavement sections or using portland cement concrete (PCC). For planning purposes pavement sections are shown in Table 6 below. Table 6. Preliminary Pavement Section Material Parking areas and ancillary drive lanes Loading ramps and main drive lanes HMA HMA PCC HMA CLASS ½” (wearing course) 2 2 inches HMA CLASS ½” (leveling course) 2 3.5 PCC 8 CSBC 8.5 12 6 3.6 Stormwater Management Design The general coarse-grained soil uniformity encountered in Aspect’s and the County’s previous explorations underlying the Site below approximately 10 to 15 feet bgs provides an opportunity to install infiltration trenches for on-Site stormwater management. Infiltration trench galleries will be designed at four locations at the Site. Due to the design soil receptor depth, performing large-scale PITs per the City (COR, 2016) was deemed impractical because of the required excavation sizes. Aspect requested and was approved by the City to use deep infiltration test wells to measure receptor soil infiltration rates within the footprints of two of the four proposed infiltration galleries. 3.6.1 Steep Slope Setback and Groundwater Considerations The City requires infiltration facilities consider the effects of stormwater injection on slope stability and groundwater aquifers from the injection point. Per Table 6.2.3.A Setback Requirements within the City’s Surface Water Design Manual (COR, 2016), Geotechnical Setbacks are to consider: Facilities are not allowed on slopes >25 percent (4:1). A geotechnical analysis and report are required if located within 200 feet of a steep slope hazard area or landslide hazard or if the facility is located within a setback distance from top of ASPECT CONSULTING PROJECT NO. 170383 SEPTEMBER 9, 2020 FINAL 17 17 slope equal to the total vertical height of a slope area that is steeper than 15 percent. The geotechnical analysis must consider cumulative impacts from the project and surrounding areas under full built-out conditions. The facility design water surface should be a minimum of 200 feet from any steep slope hazard area or landslide hazard. Upon analysis and approval of a licensed geotechnical engineer or engineering geologist, this setback may be reduced to 50 feet. The geotechnical analysis must consider cumulative impacts from the project and surrounding areas under full built-out conditions. The facility design water surface should be set back a minimum distance from top of slope equal to the total vertical height of a slope area that is steeper than 15 percent. Upon analysis and approval of a licensed geotechnical engineer or engineering geologist, this setback may be reduced to 50 feet. The geotechnical analysis must consider cumulative impacts from the project and surrounding areas under full built-out conditions. The proposed location for the stormwater management facility on the Site’s west side will be adjacent to a channel and approximately 50 feet from Regulated Slopes classified as 1) >15 percent to ≤25 percent or 2) >25 percent to ≤40 percent (Sensitive Slope) identified within the City’s Critical Areas. The facility will also be approximately 125 feet from a small, narrow strip at the slope toe shown as Regulated Slopes classified as greater than 40 percent to less than or equal to 90 percent (Protected). Since the proposed stormwater management facility soil receptor will be 10 feet to 15 feet bgs (EL 315 feet [Sheet UD-204; HDR, 2019]), the injection surface will be at the same elevation to 5 feet below the base of the adjacent channel at EL 315 to 320 feet. In our opinion, stormwater injection below El 315 feet will not affect slope stability within or surrounding the Site and the facility’s proposed location of 50 feet from the top of slope is suitable. The City of Renton’s Surface Water Design Manual (COR, 2016) requires groundwater investigations, including: Mounding analyses for infiltration facilities that serve 1 acre or more of tributary area and have less than 15 feet of separation to a restrictive layer or groundwater table Investigating the groundwater regime for flow control design if within 50 feet from the facility base The groundwater depths recorded in the piezometers (see Appendix B) were greater than 50 feet below the injection point. Therefore, mounding analyses and additional assessment of the groundwater regime are not necessary for the proposed stormwater management facilities. 3.6.2 Infiltration Test Analyses and Infiltration Gallery Design Full-scale infiltration design recommendations have been developed to account for: (a) the MW-01 and MW-02 infiltration test results; (b) standard safety factors; (c) the level of variability and uncertainty in site soils; (d) the potential to encounter perched water ASPECT CONSULTING 18 FINAL PROJECT NO. 170383 SEPTEMBER 9, 2020 above the receptor soil; and (e) additional allowance for the long-term reduction in hydraulic conductivity due to biofouling or plugging with sediment. The Well Permeameter Method (USBR 7300-89; 1989) was used to measure infiltration flow rates and estimate the bulk hydraulic conductivity for the receptor soil. Test results were also used to estimate the design infiltration rates for the proposed infiltration trench gallery stormwater management facilities. The infiltration rates measured during infiltration testing were derived by dividing the constant flow rate by the approximate surface area being infiltrated across (surface area of the submerged 10-inch-diameter borehole outside the 6 inch-diameter well screen). The measured infiltration rates were reduced to account for the lower operating head expected in the infiltration trench galleries, and further reduced to account for safety factors specified in the City standards. The initial estimates of design infiltration rates exceeded the City’s maximum allowed rate of 20 inches per hour (in/hr). Table 7 provides the design infiltration results for MW-01 and MW-02. Table 7. Infiltration Analyses Results and Design Parametersa Parameter Unit MW-01 MW-02 IMeasured Unit in/hr/ft 53 167 Measured infiltration rate on per foot of head basis. HFacility ft 1.5 1.5 Assumed average head in proposed infiltration facility. IMeasured Facility in/hr 79.80 250.73 Measured infiltration rate, adjusted for proposed facility head. FTesting -- 0.5 0.5 Correction factor accounting for uncertainty in testing method. FGeometrya -- 1 1 Correction factor accounting for influence of facility geometry1. FPlugging -- 0.85 0.85 Correction factor accounting for reduction in filtration rate over the long term due to plugging of soils. IDesign in/hr 33.91 106.56 IDesign = IMeasured Facility x FTesting x FGeometry x FPlugging IDesign Final in/hr 20.00 20.00 Final design infiltration rate must not exceed 20 in/hr per City of Renton Surface Water Design Manual Section 5.2.1. Notes: a) FGeometry = 4 D/W + 0.05 = 7.38 where, D = depth from bottom of the proposed facility to the maximum wet-season water table ~ 55 ft, and W = width of facility ~ 30 ft. FGeometry must be not greater than 1.0. Due to the Site’s subsurface soil uniformity, similar groundwater depth/elevations, and comparable infiltration test parameters and results, additional infiltration tests are not recommended to further characterize conditions. City standards allow stormwater design to proceed using the maximum infiltration rate permissible in the City’s Surface Water Design Manual (20 inches per hour). However, as discussed above, Aspect notes that sandy soils are highly susceptible to plugging by stormwater sediments. Typical stormwater treatment BMPs are allowed to bypass flows above the water quality flow, which could introduce some untreated, potentially ASPECT CONSULTING PROJECT NO. 170383 SEPTEMBER 9, 2020 FINAL 19 19 sediment-containing stormwater into the infiltration system. This is particularly true for this Site, which intends to retain and infiltrate all runoff up to and including the 100-year storm on the Site. Therefore, the need for sediment control BMPs for bypass flows, or an additional safety factor on the design infiltration rate, should be considered by the stormwater designer to enhance the functional life of the infiltration system. 3.6.3 Water Quality Treatment and Underground Injection Control As required by the City, stormwater runoff should be treated prior to discharging to the infiltration system. Aspect recommends including pretreatment (sediment, floatables, and oil) for water quality BMP overflows during larger storm events since this otherwise untreated water will be directed into the infiltration system rather than to off-Site drainage systems or surface waters for up to and including the 100-year storm event. Infiltration trench galleries that contain perforated pipe will be considered Underground Injection Control (UIC) facilities under Washington State’s UIC program and will require registration with the Washington State Department of Ecology (Ecology) prior to being put into use. Based on the City’s standards (5.2.1 of the 2017 City of Renton Surface Water Design Manual), UIC wells must be registered and registration documentation must be provided to the City prior to stormwater plan review and/or approval. Typically, Ecology requires UIC facilities to be registered during the design process, and then updated based on construction as-builts. This process allows: (1) Ecology to review the UIC design and comment if they deem necessary; (2) the designer to address any comments prior to construction; and (3) the registration to be updated to reflect as- constructed conditions. Aspect can assist in the UIC registration process if needed. ASPECT CONSULTING 20 FINAL PROJECT NO. 170383 SEPTEMBER 9, 2020 4 Construction Considerations 4.1 General Earthwork is typically most economical when performed under dry weather conditions. Appropriate erosion control measures should be implemented prior to beginning earthwork activities in accordance with the local regulations. In our opinion, excavation can generally be accomplished using standard excavation equipment. While not directly observed in Aspect’s subsurface explorations, the presence of potential obstructions, such as small boulders, buried logs, or other debris, in the fill or other deposits should be anticipated. 4.2 Site Preparation Site preparation within the proposed construction footprint should include removal of fill and soils containing roots, organics, debris, and any other deleterious materials in accordance with KCSS Section 31 10 00 – Site Clearing, KCSS Section 31 22 00 – Grading, KCSS Section 31 23 00 – Excavation & Fill, and KCSS Section 31 23 12 – Subgrade Preparation (King County, 2018a). The contractor must use care during Site preparation and excavation operations, so that any bearing surfaces are not disturbed. If disturbance does occur, the disturbed material should be removed to expose undisturbed material or be compacted in place to acceptable criteria as determined by the geotechnical engineer. All footing excavations should be trimmed neat and the bottom of the excavation should be carefully prepared. All loose or softened soil should be removed from the footing excavation or compacted in place prior to placing reinforcing steel bars. We recommend the footing excavations be observed by the geotechnical engineer to assess the presence of fill, evaluate the subgrade condition, and provide depths of overexcavation and replacement with structural fill prior to placing steel and concrete to verify the recommendations in this report have been followed. The subgrade under the HMA pavement section areas should be prepared by scarifying, moisture conditioning, and recompacting a minimum of 12 inches below the bottom of the base course. Materials generated during earthwork should be transported off the Site or stockpiled in areas designated by the owner’s representative. 4.3 Proof Rolling and Subgrade Verification Following Site preparation, subgrade to support structural fill, footings, floor slabs, pavements, hardscapes, and any other structures should be evaluated either by proof rolling or another method of subgrade verification. The subgrade should be proof rolled, per KCSS Section 31 22 00 – Grading, with a fully loaded tandem dump truck with a minimum total gross vehicle weight of 44,000 pounds or articulated dump truck to identify unsuitable areas. If evaluation of the subgrades occurs during wet conditions, or if proof rolling the subgrades will result in disturbance, they should be evaluated by Aspect using a steel foundation probe. We recommend that Aspect be retained to observe the proof rolling and perform the subgrade verifications. Unsuitable areas identified during the field evaluation should be compacted to a firm condition or be excavated and ASPECT CONSULTING PROJECT NO. 170383 SEPTEMBER 9, 2020 FINAL 21 21 replaced with structural fill meeting requirements of KCSS Section 31 23 00 – Excavation and Fill. 4.4 Wet Weather Conditions If earthwork is to be performed or fill is to be placed in wet weather or under wet conditions, when soil moisture content is above optimum and difficult to control, the following recommendations apply: Contractor is responsible for recognizing inclement weather occurs during the construction season, and the contractor is responsible for protecting the moisture condition of soils during the construction phase. Earthwork should be performed in small areas to minimize exposure. Structural fill placed during wet weather should consist of material meeting the criteria for Granular Borrow as specified in KCSS 31 23 00, Part 2 Products, 2.1 Material, F. Excavation or the removal of unsuitable soils should be followed promptly by the placement and compaction of the specified structural fill. The size, type, and access of construction equipment used may have to be limited to prevent soil disturbance. The ground surface within the construction area should be graded to promote runoff of surface water away from the slopes and to prevent water ponding. The ground surface within the construction area should be properly covered and under no circumstances should be left uncompacted and/or exposed to moisture. Soils that become too wet for compaction should be removed and replaced with specified structural fill. Excavation and placement of fill should be observed by the geotechnical engineer to verify that all unsuitable materials are removed prior to placement, compaction requirements are met, and site drainage is appropriate. Erosion and sedimentation control should be implemented in accordance with BMPs. 4.5 Excavation 4.5.1 General The near-surface soils at the Site can be excavated with conventional earthwork equipment. Sloughing and caving should be anticipated in loose, noncohesive materials. Aspect should be retained to review the grading and utility plans when they become available for comparison with encountered field conditions; additional work may be required to better define the impact on the Project. 4.5.2 Trenches Trench cuts should stand relatively vertical to a depth of approximately 4 feet bgs, provided no groundwater seepage is present in the trench walls. Open excavation ASPECT CONSULTING 22 FINAL PROJECT NO. 170383 SEPTEMBER 9, 2020 techniques may be used in the clay, silt, silty sand, and sandy silt, provided the excavation is configured in accordance with the U.S. Occupational Safety and Health Administration (OSHA) requirements, groundwater seepage is not present, and with the understanding that some sloughing may occur. The trenches should be flattened if sloughing occurs or seepage is present. If shallow groundwater is observed during construction, use of a trench shield or other approved temporary shoring is recommended for cuts that extend below groundwater seepage, or if vertical walls are desired for cuts deeper than 4 feet bgs. If dewatering is used, we recommend that the type and design of the dewatering system be the responsibility of the contractor, who is in the best position to choose systems that fit the overall plan of operation. 4.5.3 Temporary and Permanent Slopes With time and the presence of seepage and/or precipitation, the stability of temporary unsupported cut slopes can be significantly reduced. We recommend planning the construction schedule to have excavation occur during the summer months and to minimize the amount of time that the temporary slopes will be unsupported during construction. The contractor should monitor the stability of the temporary cut slopes and adjust the construction schedule and slope inclination accordingly. Vibrations created by traffic and construction equipment may cause caving and raveling of the face of the temporary slopes. At no time should soil stockpiles, equipment, and other loads be placed immediately adjacent to an excavation. In general, shallow surface soils, such as topsoil and unconsolidated soils that will be subject to excavation and sloping on the Site, classify OSHA Soil Classification Type C. These soils are expected to fail at steep angles. Temporary excavation side slopes (cut slopes) are anticipated to stand as steep as 1.5H:1V (Horizontal:Vertical) within the topsoil and unconsolidated soils. The cut slope inclinations estimated above are for planning purposes only and are applicable to excavations without inflowing perched groundwater or runoff. Permanent slopes for the project should have a maximum inclination of 2H:1V. Access roads and pavements should be located at least 5 feet from the top of temporary slopes. Surface water runoff should be collected and directed away from slopes to prevent water from running down the face. 4.6 Structural Fill Materials and Compaction Structural fill, including base rock, should be placed over subgrades that have been prepared in conformance with the Site Preparation and Wet Weather Conditions sections of this report (Sections 4.2 and 4.4, respectively). Source material may be derived from on-site sources or imported. The suitability of excavated soils for reuse as structural fill depends on the gradation and moisture content when it is placed. As the fines percentage (percent passing through a U.S. No. 200 sieve) increases, the soil becomes increasingly sensitive to small changes in moisture content and adequate compaction becomes more difficult. Soil containing more than about 5 percent fines cannot be consistently compacted to a dense, nonyielding condition when the moisture content is greater than 3 to 4 percent above or below optimum. Soil considered for use as structural fill must also be free of organics and other compressible materials. ASPECT CONSULTING PROJECT NO. 170383 SEPTEMBER 9, 2020 FINAL 23 23 Results of laboratory analysis (grain-size analysis) indicate the majority of the excavation soils at the Site will have a fines content below 5 percent (by weight). These materials should be acceptable to reuse as structural fill if properly moisture conditioned and placed and compacted during dry weather. Import fill may be required if earthwork is planned for the wet season. Soil reuse as structural fill should be evaluated during construction on a case-specific basis. General fill specifics are provided in Table 8. Table 8. Fill Type and Compaction Requirements Fill Type KCSS Details Lift Thicknessa and Compaction Requirementsb On-Site Soil KCSS Section 31 23 00, Part 2 Products, 2.1 Material, B – Common 8 to 12 inches Dependent on Application Imported Granular Materials KCSS Section 31 23 00, Part 2 Products, 2.1 Material, D – Select Borrowc 9 inches 95 percent Crushed Aggregate Base KCSS Section 31 11 23, Part 2 Products, 2.1 – Aggregated 9 inches 95 percent Foundation Base Aggregate KCSS Section 31 23 00, Part 2 Products, 2.1 Material, D – Select Borrowc 9 inches 95 percent Trench Backfill KCSS Section 31 23 33, Part 2 Products, 2.1 – Pipe Embedment Materiale KCSS Section 31 23 33, Part 2 Products, 2.5 –Backfill Materialf KCSS Section 31 23 33, Part 2 Products, 2.5 –Backfill Materialg 9 inches 90 percenth 9 inches 90 percenth 9 inches 95 percenti 9 inches 90 percenth Notes: a) Maximum uncompacted thickness b) Maximum dry density, as determined by ASTM D1557 c) Equivalent to WSDOT SS 9-03.14(2) – Select Borrow. Fraction passing the US Standard No. 4 Sieve, less than 5 percent by dry weight should pass the US Standard No. 200 Sieve. d) Equivalent to WSDOT SS 9-03.9(3) – Crushed Surfacing Base Course e) Trench backfill placed beneath, adjacent to, and for at least 6 inches above utility lines (i.e., the pipe embedment zone) f) Within pavement areas or beneath building pads g) Outside of structural improvement areas (e.g., roadway alignments or building pads), trench backfill placed above the pipe zone h) Or per manufacturer / local building department i) Within 2 feet below final grade or pavement ASPECT CONSULTING 24 FINAL PROJECT NO. 170383 SEPTEMBER 9, 2020 4.7 Ground Moisture 4.7.1 General The perimeter ground surface and hardscaping should be sloped to drain away from all structures and away from adjacent slopes. Gutters should be tightlined to a suitable discharge and maintained as free-flowing. Any crawl spaces should be adequately ventilated and sloped to drain to a suitable, exterior discharge. 4.7.2 Perimeter Footing Drains Due to the potential for perched groundwater, Aspect recommends perimeter foundation drains be installed around all proposed structures. The foundation subdrainage system should include a minimum 4-inch-diameter perforated pipe in a drain rock envelope. A nonwoven geotextile filter fabric, such as Mirafi 140N or equivalent, should be used to completely wrap the drain rock envelope, separating it from the native soil and footing backfill materials. The invert of the perimeter drain lines should be placed approximately at the bottom of footing elevation. Also, the subdrainage system should be sealed at the ground surface. The perforated subdrainage pipe should be laid to drain by gravity into a nonperforated, solid pipe and finally connected to the Site drainage stem at a suitable location. Water from downspouts and surface water should be independently collected and routed to a storm sewer or other outlet. This water must not be allowed to enter the bearing soils. 4.8 Construction-Phase Stormwater Considerations 4.8.1 Protection and Verification of Infiltration Receptor Soils In addition to applying construction erosion and sediment controls as required by the City (and potentially the state), Site preparation, grading, and other construction work must: a. Protect infiltration receptor soils from exposure to sediments due to erosion or contact with finer-grained soils, both of which could compromise infiltration rates b. Protect infiltration receptor soils from compaction, which could compromise infiltration rates c. Protect all constructed stormwater drainage facilities from sediment entry during construction d. Include inspection and, if needed, flushing and cleaning of drainage system components to remove any accumulated sediment from the system prior to allowing any flow to enter the infiltration system. Any water used for flushing or cleaning must not be allowed to enter the infiltration system. e. Verify that the drainage area for each infiltration gallery is fully stabilized and erosion resistant prior to allowing any flow into the infiltration galleries Excavation and construction of the infiltration galleries should include ample observation to verify receptor soils are properly protected and are consistent with the soils used to determine the design infiltration rates. Any observations of finer and potentially flow restricting soils in the infiltration gallery area should be reported to the design engineer ASPECT CONSULTING PROJECT NO. 170383 SEPTEMBER 9, 2020 FINAL 25 25 for assessment and determination of whether any design changes or other actions are warranted. 4.8.2 Geotextiles for Stormwater Drainage Geotextiles that will be expected to pass water while being exposed to soil and/or sediments over time, such as those used in stormwater infiltration systems, should be woven monofilament (nonsplit tape) fabric with a relatively high percent open area and relatively small opening size. Needle punched nonwoven materials are not recommended. Geotextiles suitable for drainage pass-through applications would meet specifications similar to: a. Woven monofilament geotextile b. Permittivity per ASTM D4491 of 1.0 sec-1 minimum c. Water flow rate per ASTM D4491 of 150 gpm/ft2 minimum d. Percent open area per CW-02215 of 15% minimum e. Maximum Apparent Opening Size (AOS) per ASTM D4751 of 20 U.S. Std. Sieve (0.84 mm) ASPECT CONSULTING 26 FINAL PROJECT NO. 170383 SEPTEMBER 9, 2020 5 Project Design and Construction Monitoring At the time of this report, site plans, site grading, structural plans, and construction methods have not been finalized, and the recommendations presented herein are based on preliminary project information. Additional work including geotechnical explorations and infiltration tests, engineering analyses, and geotechnical design recommendations will be needed for the selected, preferred alternative development. This report is issued with the understanding that the information and recommendations contained herein will be brought to the attention of the appropriate design team personnel and incorporated into the project plans and specifications, and that the necessary steps will be taken to verify that the contractor and subcontractors carry out such recommendations in the field. We do not direct the contractor’s operations, and we cannot be responsible for the safety of personnel other than our own on the Site; the safety of others is the responsibility of the contractor. The contractor should notify the property owner if he considers any of the recommended actions presented herein unsafe. We are available to provide geotechnical engineering and monitoring services during construction. The integrity of the foundation 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. ASPECT CONSULTING PROJECT NO. 170383 SEPTEMBER 9, 2020 FINAL 27 27 6 References American Concrete Institute (ACI), 2010, Guide to Design of Slabs-on-Ground, Reported by ACI Committee 360, April 2010. ASTM International (ASTM), 2017, 2017 Annual Book of ASTM Standards, West Conshohocken, Pennsylvania. Atwater, B.F., S. Musumi-Rokkaku, K. Satake, Y. Tsuji, K. Ueda, and D.K. Yamaguchi (Atwater et al.), 2015, The orphan tsunami of 1700—Japanese clues to a parent earthquake in North America, 2nd ed.: Seattle, University of Washington Press, U.S. Geological Survey Professional Paper 1707, 135 p. City of Renton (COR), 2016, Surface Water Design Manual, Public Works Department, Surface Water Utility, December 12, 2016. City of Renton (COR), 2018, Maps of Your Community online portal , Website, http://rp.rentonwa.gov/HTML5Public/Index.HTML?viewer=CORMaps, Accessed March 1, 2018. HDR, Inc. (HDR), 2019, King County Parks – Renton Shop, 60 Percent Design Plan Set, KC PARKS Project #1122161, dated January 15, 2019. International Building Code (IBC), 2015, International Building Code. Prepared by International Code Council, January. King County (County), 2016, Road Design and Construction Standards, Department of Transportation, Road Services Division, 18420 Attachment A, revised November 28, 2016. King County (County), 2018a, King County Standard Specifications (KCSS). King County (County), 2018b, King County Interactive Mapping Program (iMap) Web Portal, website https://gismaps.kingcounty.gov/iMap/, Accessed March 1, 2018. Mullineaux, D. R., 1965, Geologic map of the Renton quadrangle, King County, Washington, U.S. Geological Survey, Geologic Quadrangle Map GQ-405, 1 sheet, scale 1:24,000. Pratt, T.L., K.G. Troost, J.K. Odum, and W.J. Stephenson (Pratt et al.), 2015, Kinematics of shallow backthrusts in the Seattle fault zone, Washington State, Geosphere, v. 11, no. 6, p. 1–27, doi:10.1130/GES01179.1. United States Bureau of Reclamation (USBR), 1989, Procedure for Performing Field Permeability Testing by the Well Permeameter Method (USBR 7300-89). United States Geological Survey (USGS), 2014, U.S. Seismic Design Maps, Page Last Modified: January 30, 2017 18:07:40 UTC, Website, http://earthquake.usgs.gov/designmaps/us/application.php, Accessed March 1, 2018. ASPECT CONSULTING 28 FINAL PROJECT NO. 170383 SEPTEMBER 9, 2020 Washington Department of Ecology (Ecology), 2014, Stormwater Management Manual for Western Washington, Publication Numbers 12-10-030, As amended December 2014. Washington Department of Health (DOH), 2010, Washington State Wellhead Protection Program Guidance Document, June 2010. Washington Department of Natural Resources (DNR), 2017, Interactive Geologic Map, Website: https://geologyportal.dnr.wa.gov/, Division of Geology and Earth Resources, Accessed March 1, 2018. Washington State Department of Transportation (WSDOT), 2016, Standard Specifications for Road, Bridge and Municipal Construction, Document M 41-10. ASPECT CONSULTING PROJECT NO. 170383 SEPTEMBER 9, 2020 FINAL 29 29 7 Limitations Work for this project was performed for HDR Architecture, Inc. (Client), and this report was prepared consistent with recognized standards of professionals in the same locality and involving similar conditions, at the time the work was performed. No other warranty, expressed or implied, is made by Aspect Consulting, LLC (Aspect). Recommendations presented herein are based on our interpretation of site conditions, geotechnical engineering calculations, and judgment in accordance with our mutually agreed-upon scope of work. Our recommendations are unique and specific to the project, site, and Client. Application of this report for any purpose other than the project should be done only after consultation with Aspect. Variations may exist between the soil and groundwater conditions reported and those actually underlying the site. The nature and extent of such soil variations may change over time and may not be evident before construction begins. If any soil conditions are encountered at the site that are different from those described in this report, Aspect should be notified immediately to review the applicability of our recommendations. It is the Client's responsibility to see that all parties to this project, including the designer, contractor, subcontractors, and agents, are made aware of this report in its entirety. At the time of this report, design plans and construction methods have not been finalized, and the recommendations presented herein are based on preliminary project information. If project developments result in changes from the preliminary project information, Aspect should be contacted to determine if our recommendations contained in this report should be revised and/or expanded upon. The scope of work does not include services related to construction safety precautions. Site safety is typically the responsibility of the contractor, and our recommendations are not intended to direct the contractor’s site safety methods, techniques, sequences, or procedures. The scope of our work also does not include the assessment of environmental characteristics, particularly those involving potentially hazardous substances in soil or groundwater. All reports prepared by Aspect for the Client apply only to the services described in the Agreement(s) with the Client. Any use or reuse by any party other than the Client is at the sole risk of that party, and without liability to Aspect. Aspect’s original files/reports shall govern in the event of any dispute regarding the content of electronic documents furnished to others. Please refer to Appendix F titled “Report Limitations and Guidelines for Use” for additional information governing the use of this report. i FIGURES ^GIS Path: T:\projec ts_8\KingCountyParksMaintenanc eFac ility_170383\Delivered \ Geotec hnicalReport_30Perc ent\ 01 Site Loc ation Map.m xd || Coord inate System : N AD 1983 StatePlane Washington N orth FIPS 4601 Feet || Date Saved : 5/20/2019 || User: ecrum b aker || Print Date: 5/20/2019 Site Location MapGeotec hnic al Report - 30 Perc entKing County Parks and Rec reation Division – Renton Shop 3005 N E 4th StreetRenton, Washington FIGURE NO.1MAY-2019 PROJECT NO.170292 BY:MWS / KES REVISED BY:EAC 0 2,000 4,000 Feet ! ! ! #! ! ! ! !( W A S H I N G T O N Bellingham Olympia Port Angeles Seattle Spokane Tacoma Wenatchee Yakima ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! # ! ! !( PugetSound LakeWashin gtonElliottBay Auburn Bellevue Burien Covington Des Moines Factoria Federal Way Issaquah Kent Maple Valley Mercer Island Newcastle Renton SammamishSeattle Tukwila White Center Basem ap Layer Cred its || Esri, HERE, Garm in, (c) OpenStreetMap contrib utors, and the GIS user c om m unitySourc es: Esri, HERE, Garm in, Interm ap, inc rem ent P Corp., GEBCO, USGS, FAO, N PS, N RCAN , GeoBase, IGN , Kad aster N L, Ord nance Survey, Esri Japan, METI, Esri China (Hong Kong), (c) OpenStreetMap contrib utors, and theGIS User Com m unity SITE LOCATION SITELOCATION SITELOCATION MW-02 MW-01 AB-02 AB-03 AB-04 AB-01B-1 B-5 B-2 B-4 B-3 AB-06 AB-05 AB-08 AB-07 EAST SIDE STORMWATER MANAGEMENT FACILITY WEST SIDE STORMWATER MANAGEMENT FACILITY CAD Path: Q:\King County\170383 Renton Shop\2019-05 Geotechnical Report-30 Percent\170383-02.dwg 11x17 Landscape || Date Saved: May 20, 2019 2:58pm || User: scuddGeotechnical Report - 30 Percent King County Parks and Recreation Division - Renton Shop 3005 NE 4th StreetRenton, Washington 2 BY:MWS/SCC Site and Exploration Plan May-2019 REVISED BY:-PROJECT NO.170383 FIGURE NO.Feet 060120 Boring Location (Aspect) Boring Location (King County) Monitoring Well Location (Aspect) Direct Push Probe Location (Aspect) Legend Source: Base map provided by King County Department of Natural Resources and Parks, King County Parks-Renton Shop, Draft 60%, 1/15/19. Wellhead Protection Zone 2 West SideStormwaterManagementFacility East SideStormwaterManagementFacility Building SH Building ST Building CA FIGURE NO.3MAY-2019 PROJECT NO.170292 BY:EAC / MW S REVISED BY:- - - Critical Areas MapGeotec hn ic a l Report - 30 Perc en tK in g Coun ty Pa rks a n d Rec rea tion Division – Ren ton Shop3005 N E 4th StreetRen ton , W a shin gton GIS Pa th: T:\projects_ 8\K in gCoun tyPa rksMa in ten a n ceFa cility_ 170383\Delivered\Geotechn ica lReport_ 30Percen t\03 Critica l Area s Ma p.m xd || Coordin a te System : NAD 1983 Sta tePla n e W a shin gton North FIPS 4601 Feet || Da te Sa ved: 5/20/2019 || User: ecrum b a ker || Prin t Da te: 5/20/2019 K in g Coun ty Pa rcel Erosion Ha za rd - High Slope City of Renton >15% & <=25% >25% & <=40% (Sen sitive) >40% & <=90% (Protected) >90% (Protected) Wellhead Protection Area Zones Zon e 1 Zon e 1 Modified Zon e 2 0 200 400 Feet Basemap Layer Credits || Pictometry, King County i APPENDIX A Aspect Soil Exploration Logs ASPECT CONSULTING PROJECT NO. 170383 SEPTEMBER 9, 2020 A-1 1 A. Subsurface Exploration Program The field exploration programs consisted of drilling a total of drilling ten borings (designated MW-01, MW-02, and AB-01 through AB-08) between March 2018 and April 2019. Borings were advanced using sonic, hollow stem auger (HSA), and direct push methods to between 15 feet and 75 feet bgs. The locations of the explorations are shown on Figure 2 and the exploration logs are included in this appendix. An Aspect geologist was present throughout the field exploration program to observe the drilling procedure, assist in sampling, and to prepare descriptive logs of the exploration. Soils were classified in general accordance with ASTM International (ASTM) D2488, Standard Practice for Description and Identification of Soils (Visual-Manual Procedure). The summary exploration logs represent our interpretation of the contents of the field log. The stratigraphic contacts shown on the individual summary logs represent the approximate boundaries between soil types; actual transitions may be more gradual. The subsurface conditions depicted are only for the specific date and locations reported, and therefore, are not necessarily representative of other locations and times. A.1. Soil Borings Two deep infiltration test well borings (designated MW-01 and MW-02) were drilled to 75 feet bgs with rotary sonic methods by Holocene Drilling using a track-mounted Geoprobe 8140LC drill rig equipped with a 140-pound automatic-safety hammer. Samples were obtained continuously below ground surface (bgs) to the depths explored. Select samples were collected using the Standard Penetration Test (SPT) in general accordance with ASTM D1586. The sampler types used are depicted on the exploration logs in this appendix. Four geotechnical borings (designated AB-01 through AB-04) were drilled to 26.5 feet bgs with hollow stem augers by Gregory Drilling using a truck-mounted CME-75 drill rig equipped with a 140-pound automatic-safety hammer. Samples were typically obtained at 2.5 feet to 5 feet intervals below ground surface (bgs) to the depths explored, using the SPT in general accordance with ASTM D1586. Four environment direct push probes (designated AB-05 through AB-08)were advanced to between 15 and 20 feet bgs by Holt Services, Inc. with a Geoprobe 7822D. Samples were collected continuously. The SPT method involves driving a 2-inch-outside-diameter split-barrel sampler with a 140-pound hammer free-falling from a distance of 30 inches. The number of blows for each 6-inch interval is recorded, and the number of blows required to drive the sampler the final 12 inches is known as the Standard Penetration Resistance (“N”) or blow count. The resistance, or N-value, provides a measure of the relative density of granular soils or the relative consistency of cohesive soils. If a total of 50 blows are recorded for a single 6-inch interval, the test is terminated and the blow count is recorded as 50 blows for the ASPECT CONSULTING PROJECT NO. 170383 SEPTEMBER 9, 2020 A-2 total inches of penetration. Samples were placed in labeled plastic jars and taken to a laboratory for further classification. The geotechnical and environmental explorations were backfilled with the bentonite in accordance with Washington State Department of Ecology guidelines. The deep infiltration tests well borings were backfilled by cement grout from 25 to 75 feet bgs, installing a 6-inch diameter monitoring well, and completing with a flush-mounted monument. AI Path: Q:\_ACAD Standards\FIELD REFERENCE\MASTERS\Exploration Log Key-2018.ai // user: jinman // last saved: 09/26/2018“WITH SILT” or “WITH CLAY” means 5 to 15% silt and clay, denoted by a “-“ in the groupname; e.g., SP-SM ● “SILTY” or “CLAYEY” means >15% silt and clay ● “WITH SAND” or “WITHGRAVEL” means 15 to 30% sand and gravel. ● “SANDY” or “GRAVELLY” means >30% sand andgravel. ● “Well-graded” means approximately equal amounts of fine to coarse grain sizes ● “Poorlygraded” means unequal amounts of grain sizes ● Group names separated by “/” means soilcontains layers of the two soil types; e.g., SM/ML. Soils were described and identified in the field in general accordance with the methods described inASTM D2488. Where indicated in the log, soils were classified using ASTM D2487 or otherlaboratory tests as appropriate. Refer to the report accompanying these exploration logs for details. % by Weight Density³SPT² Blows/Foot HighlyOrganicSoilsFine-Grained Soils - 50%1 or More Passes No. 200 SieveCoarse-Grained Soils - More than 50%1 Retained on No. 200 SieveGravels - More than 50%1 of Coarse FractionRetained on No. 4 Sieve15% Fines5% FinesSands - 50%1 or More of Coarse FractionPasses No. 4 SieveSilts and ClaysLiquid Limit Less than 50%Silts and ClaysLiquid Limit 50% or More15% Fines5% FinesWell-graded GRAVELWell-graded GRAVEL WITH SAND Poorly-graded GRAVELPoorly-graded GRAVEL WITH SAND SILTY GRAVEL SILTY GRAVEL WITH SAND CLAYEY GRAVEL CLAYEY GRAVEL WITH SAND Well-graded SAND Well-graded SAND WITH GRAVEL Poorly-graded SANDPoorly-graded SAND WITH GRAVEL SILTY SAND SILTY SAND WITH GRAVEL CLAYEY SANDCLAYEY SAND WITH GRAVEL SILTSANDY or GRAVELLY SILTSILT WITH SANDSILT WITH GRAVEL LEAN CLAYSANDY or GRAVELLY LEAN CLAYLEAN CLAY WITH SANDLEAN CLAY WITH GRAVEL ORGANIC SILT SANDY or GRAVELLY ORGANIC SILTORGANIC SILT WITH SANDORGANIC SILT WITH GRAVEL ELASTIC SILTSANDY or GRAVELLY ELASTIC SILT ELASTIC SILT WITH SAND ELASTIC SILT WITH GRAVEL FAT CLAYSANDY or GRAVELLY FAT CLAYFAT CLAY WITH SANDFAT CLAY WITH GRAVEL ORGANIC CLAYSANDY or GRAVELLY ORGANIC CLAYORGANIC CLAY WITH SAND ORGANIC CLAY WITH GRAVEL PEAT and other mostly organic soils GW GP GM GC SW SP SM SC ML CL OL MH CH OH PT Modifier Organic Chemicals BTEX = Benzene, Toluene, Ethylbenzene, Xylenes TPH-Dx = Diesel and Oil-Range Petroleum HydrocarbonsTPH-G = Gasoline-Range Petroleum HydrocarbonsVOCs = Volatile Organic Compounds SVOCs = Semi-Volatile Organic CompoundsPAHs = Polycyclic Aromatic Hydrocarbon CompoundsPCBs = Polychlorinated Biphenyls GEOTECHNICAL LAB TESTSMC = Natural Moisture ContentGS = Grain Size DistributionFC = Fines Content (% < 0.075 mm)GH = Hydrometer TestAL = Atterberg LimitsC = Consolidation TestStr = Strength TestOC = Organic Content (% Loss by Ignition)Comp = Proctor TestK = Hydraulic Conductivity TestSG = Specific Gravity Test RCRA8 = As, Ba, Cd, Cr, Pb, Hg, Se, Ag, (d = dissolved, t = total) MTCA5 = As, Cd, Cr, Hg, Pb (d = dissolved, t = total)PP-13 = Ag, As, Be, Cd, Cr, Cu, Hg, Ni, Pb, Sb, Se, Tl, Zn (d=dissolved, t=total) CHEMICAL LAB TESTS PID = Photoionization Detector Sheen = Oil Sheen TestSPT2= Standard Penetration TestNSPT = Non-Standard Penetration Test DCPT = Dynamic Cone Penetration Test <1 = Subtrace1 to <5 = Trace5 to 10 = Few Dry = Absence of moisture, dusty, dry to the touch Slightly Moist = Perceptible moistureMoist = Damp but no visible waterVery Moist = Water visible but not free draining Wet = Visible free water, usually from below water table COMPONENT DEFINITIONSDescriptive Term Size Range and Sieve Number Boulders = Larger than 12 inchesCobbles = 3 inches to 12 inches Coarse Gravel = 3 inches to 3/4 inchesFine Gravel = 3/4 inches to No. 4 (4.75 mm)Coarse Sand = No. 4 (4.75 mm) to No. 10 (2.00 mm) Medium Sand = No. 10 (2.00 mm) to No. 40 (0.425 mm) Fine Sand = No. 40 (0.425 mm) to No. 200 (0.075 mm)Silt and Clay = Smaller than No. 200 (0.075 mm) Metals ESTIMATED1 PERCENTAGE MOISTURE CONTENT RELATIVE DENSITY CONSISTENCY GEOLOGIC CONTACTS Very Loose = 0 to 4 ≥2'Loose = 5 to 10 1' to 2'Medium Dense = 11 to 30 3" to 1'Dense = 31 to 50 1" to 3"Very Dense = > 50 < 1" Consistency³ Very Soft =0 to 1 Penetrated >1" easily by thumb. Extrudes between thumb & fingers.Soft =2 to 4 Penetrated 1/4" to 1" easily by thumb. Easily molded.Medium Stiff =5 to 8 Penetrated >1/4" with effort by thumb. Molded with strong pressure.Stiff =9 to 15 Indented ~1/4" with effort by thumb.Very Stiff =16 to 30 Indented easily by thumbnail.Hard => 30 Indented with difficulty by thumbnail. Non-Cohesive or Coarse-Grained Soils SPT² Blows/Foot Observed and Distinct Observed and Gradual Inferred 1. Estimated or measured percentage by dry weight2. (SPT) Standard Penetration Test (ASTM D1586)3. Determined by SPT, DCPT (ASTM STP399) or other field methods. See report text for details. % by Weight Modifier 15 to 25 = Little30 to 45 = Some>50 = Mostly Penetration with 1/2" Diameter Rod Manual Test FIELD TESTS Cohesive or Fine-Grained Soils Exploration Log Key 9 16 15 17 19 23 GS CECOC=1.6%S-1Bulk 1S-2S-3S-4S-5S-612-inch-diameterflush-mountmonumentWell capped with acompression plug VW Piezometerinstalled at 74.75 feetbgs, SN: 1907571 Cement grout 6-inch schedule 40PVC well casing 6-inch, 10-foot length,stainless steel V-wrapwire screen, 0.020-slot 6x9 Colorado silicasand filter pack Threaded stainlesssteel cap Cement grout ASPHALT ASPHALT; (2 inches) GRAVEL WITH SAND (GP); (4 inches) FILL SAND WITH GRAVEL (SP); Medium dense, moist,brown; medium to coarse sand; fine to coarse, subangularto subrounded gravel. GLACIAL OUTWASH DEPOSITS (Qpa) GRAVEL WITH SAND (GP); Medium dense to dense,moist, brown; medium to coarse sand; fine to coarse,subrounded gravel. Grades to fine to coarse sand; fine to coarse, subroundedto rounded gravel; subrounded cobbles. SILTY GRAVEL WITH SAND (GM); Dense, moist, browngray; fine to coarse sand; fine to coarse, subroundedgravel. GRAVEL (GP); Dense, moist, brown gray; few fine tocoarse sand; fine to coarse, subangular gravel. Operator Work Start/Completion Dates Blows/footWater Content (%) MW-01Equipment Legend Contractor 320 315 310 305 300 MW-01 Tests Geoprobe 8140LC Sonic Holocene Drilling Exploration Method(s) See Exploration Log Key for explanationof symbols Exploration Completionand Notes SampleType/ID Depth to Water (Below GS) Liquid Limit Geotechnical Exploration Log Water Level ATD Logged by: DRTApproved by: MWS 05/30/2019 67.29' (Static) Exploration Number No Soil Sample Recovery WaterLevelSheet 1 of 3 Depth(ft) Sampling Method 4/15/2019 to 4/16/2019 Project Address & Site Specific Location 325' (est) 47.48666, -122.17937 (est) Coordinates (Lat,Lon WGS84) Plastic Limit Description 5 10 15 20 25 3005 NE 4th St, Renton, Washington ExplorationLog NEW STANDARD EXPLORATION LOG TEMPLATE P:\GINTW\PROJECTS\KING COUNTY PARKS CFD 170383.GPJ May 31, 2019Top of Casing Elev. (NAVD88) Blows/6" 5 10 15 20 25 Renton Shop Facility Design - 170383 Depth(feet)MaterialType Ground Surface (GS) Elev. (NAVD88) Zach Bailey SampleTypeElev.(feet) Static Water Level 324.75' (est) Autohammer; 140 lb hammer; 30" drop Continuous core 7" ID Grab sample Split Barrel 2" X 1.375" (SPT) 10 20 30 400 50 28 27 26 GSS-7S-8S-9S-10S-11S-12S-13VW Piezometerinstalled at 74.75 feetbgs, SN: 1907571 Cement grout GRAVEL (GP); Dense, moist, brown gray; few fine tocoarse sand; fine to coarse, subangular gravel. (continued) SAND WITH GRAVEL (SP); Dense, moist, brown;medium to coarse sand; little, fine, subangular tosubrounded gravel. SILTY SAND (SM); Very dense, moist, brown;non-plastic silt; fine to medium sand. Operator Work Start/Completion Dates Blows/footWater Content (%) MW-01Equipment Legend Contractor 290 285 280 275 270 MW-01 Tests Geoprobe 8140LC Sonic Holocene Drilling Exploration Method(s) See Exploration Log Key for explanationof symbols Exploration Completionand Notes SampleType/ID Depth to Water (Below GS) Liquid Limit Geotechnical Exploration Log Water Level ATD Logged by: DRTApproved by: MWS 05/30/2019 67.29' (Static) Exploration Number No Soil Sample Recovery WaterLevelSheet 2 of 3 Depth(ft) Sampling Method 4/15/2019 to 4/16/2019 Project Address & Site Specific Location 325' (est) 47.48666, -122.17937 (est) Coordinates (Lat,Lon WGS84) Plastic Limit Description 35 40 45 50 55 3005 NE 4th St, Renton, Washington ExplorationLog NEW STANDARD EXPLORATION LOG TEMPLATE P:\GINTW\PROJECTS\KING COUNTY PARKS CFD 170383.GPJ May 31, 2019Top of Casing Elev. (NAVD88) Blows/6" 35 40 45 50 55 Renton Shop Facility Design - 170383 Depth(feet)MaterialType Ground Surface (GS) Elev. (NAVD88) Zach Bailey SampleTypeElev.(feet) Static Water Level 324.75' (est) Autohammer; 140 lb hammer; 30" drop Continuous core 7" ID Grab sample Split Barrel 2" X 1.375" (SPT) 10 20 30 400 50 S-14S-15S-16Cement grout 6x9 Colorado silicasand filter pack VW Piezometerinstalled at 74.75 feetbgs, SN: 1907571 SILTY SAND (SM); Very dense, moist, brown;non-plastic silt; fine to medium sand. (continued) Grades to medium to coarse sand. Bottom of exploration at 75 ft. bgs. 4/29/2019 4/16/2019 Operator Work Start/Completion Dates Blows/footWater Content (%) MW-01Equipment Legend Contractor 260 255 250 245 240 MW-01 Tests Geoprobe 8140LC Sonic Holocene Drilling Exploration Method(s) See Exploration Log Key for explanationof symbols Exploration Completionand Notes SampleType/ID Depth to Water (Below GS) Liquid Limit Geotechnical Exploration Log Water Level ATD Logged by: DRTApproved by: MWS 05/30/2019 67.29' (Static) Exploration Number No Soil Sample Recovery WaterLevelSheet 3 of 3 Depth(ft) Sampling Method 4/15/2019 to 4/16/2019 Project Address & Site Specific Location 325' (est) 47.48666, -122.17937 (est) Coordinates (Lat,Lon WGS84) Plastic Limit Description 65 70 75 80 85 3005 NE 4th St, Renton, Washington ExplorationLog NEW STANDARD EXPLORATION LOG TEMPLATE P:\GINTW\PROJECTS\KING COUNTY PARKS CFD 170383.GPJ May 31, 2019Top of Casing Elev. (NAVD88) Blows/6" 65 70 75 80 85 Renton Shop Facility Design - 170383 Depth(feet)MaterialType Ground Surface (GS) Elev. (NAVD88) Zach Bailey SampleTypeElev.(feet) Static Water Level 324.75' (est) Autohammer; 140 lb hammer; 30" drop Continuous core 7" ID Grab sample Split Barrel 2" X 1.375" (SPT) 10 20 30 400 50 9 22 24 5 17 29 GSS-1S-2S-3S-4S-5S-6S-7S-812-inch-diameterflush-mountmonumentWell capped with acompression plug VW Piezometerinstalled at 74.6 feetbgs, SN: 1907570 Cement grout 6-inch schedule 40PVC well casing 6-inch, 10-foot length,stainless steel V-wrapwire screen, 0.020-slot 6x9 Colorado silicasand filter pack Threaded stainlesssteel cap Cement grout GRAVEL WITH SAND (GP); (4 inches) FILL GRAVEL WITH SAND (GP); Medium dense, moist, redbrown; medium to coarse sand; fine to coarse, subangularto subrounded gravel; subrounded to rounded cobbles;subtrace organics; burnt wood debris. GLACIAL OUTWASH DEPOSITS (Qpa) GRAVEL WITH SAND (GW); Medium dense to dense,moist, brown gray; medium to coarse sand; fine to coarse,subangular to subrounded gravel; subrounded cobbles. Grades gray, subrounded to rounded cobbles. SAND WITH GRAVEL (SP); Dense, moist, gray; fine tocoarse sand; fine to coarse gravel; subrounded cobbles. GRAVEL WITH SAND (GP); Dense, moist, brown gray;coarse sand; fine to coarse, subrounded gravel. Operator Work Start/Completion Dates Blows/footWater Content (%) MW-02Equipment Legend Contractor 320 315 310 305 300 MW-02 Tests Geoprobe 8140LC Sonic Holocene Drilling Exploration Method(s) See Exploration Log Key for explanationof symbols Exploration Completionand Notes SampleType/ID Depth to Water (Below GS) Liquid Limit Geotechnical Exploration Log Water Level ATD Logged by: DRTApproved by: MWS 05/30/2019 67.88' (Static) Exploration Number WaterLevelSheet 1 of 3 Depth(ft) Sampling Method 4/17/2019 to 4/18/2019 Project Address & Site Specific Location 325' (est) 47.48659, -122.17802 (est) Coordinates (Lat,Lon WGS84) Plastic Limit Description 5 10 15 20 25 3005 NE 4th St, Renton, Washington ExplorationLog NEW STANDARD EXPLORATION LOG TEMPLATE P:\GINTW\PROJECTS\KING COUNTY PARKS CFD 170383.GPJ May 31, 2019Top of Casing Elev. (NAVD88) Blows/6" 5 10 15 20 25 Renton Shop Facility Design - 170383 Depth(feet)MaterialType Ground Surface (GS) Elev. (NAVD88) Zach Bailey SampleTypeElev.(feet) Static Water Level 324.75' (est) Autohammer; 140 lb hammer; 30" drop Continuous core 7" ID Split Barrel 3" X 2.375" (Mod Cal) 10 20 30 400 50 25 23 19 CECOC=1%S-9S-10S-11S-12S-13S-14S-15VW Piezometerinstalled at 74.6 feetbgs, SN: 1907570 Cement Grout GRAVEL WITH SAND (GP); Dense, moist, brown gray;coarse sand; fine to coarse, subrounded gravel.(continued) GRAVELLY SILT WITH SAND (ML); Medium dense todense, moist, tan; fine sand, fine to coarse, subroundedgravel. GRAVEL WITH SAND (GP); Medium dense to dense,moist, brown; coarse sand; fine to coarse, subroundedgravel. SAND WITH GRAVEL (SP); Medium dense, moist, tan;fine sand; fine, subangular to subrounded gravel. GRAVEL WITH SAND (GP); Medium dense, moist, gray;medium to coarse sand; fine to coarse, subangular tosubrounded gravel. Operator Work Start/Completion Dates Blows/footWater Content (%) MW-02Equipment Legend Contractor 290 285 280 275 270 MW-02 Tests Geoprobe 8140LC Sonic Holocene Drilling Exploration Method(s) See Exploration Log Key for explanationof symbols Exploration Completionand Notes SampleType/ID Depth to Water (Below GS) Liquid Limit Geotechnical Exploration Log Water Level ATD Logged by: DRTApproved by: MWS 05/30/2019 67.88' (Static) Exploration Number WaterLevelSheet 2 of 3 Depth(ft) Sampling Method 4/17/2019 to 4/18/2019 Project Address & Site Specific Location 325' (est) 47.48659, -122.17802 (est) Coordinates (Lat,Lon WGS84) Plastic Limit Description 35 40 45 50 55 3005 NE 4th St, Renton, Washington ExplorationLog NEW STANDARD EXPLORATION LOG TEMPLATE P:\GINTW\PROJECTS\KING COUNTY PARKS CFD 170383.GPJ May 31, 2019Top of Casing Elev. (NAVD88) Blows/6" 35 40 45 50 55 Renton Shop Facility Design - 170383 Depth(feet)MaterialType Ground Surface (GS) Elev. (NAVD88) Zach Bailey SampleTypeElev.(feet) Static Water Level 324.75' (est) Autohammer; 140 lb hammer; 30" drop Continuous core 7" ID Split Barrel 3" X 2.375" (Mod Cal) 10 20 30 400 50 S-16S-17S-18S-19Cement grout 6x9 Colorado silicasand filter pack VW Piezometerinstalled at 74.6 feetbgs, SN: 1907570 GRAVEL WITH SAND (GP); Medium dense, moist, gray;medium to coarse sand; fine to coarse, subangular tosubrounded gravel. (continued) SAND (SP); Medium dense, moist, brown; fine to coarsesand; few fine, subangular to subrounded gravel. SAND WITH GRAVEL (SP); Medium dense, moist,brown; fine to coarse sand; fine, subangular to subroundedgravel. SAND (SP); Medium dense, wet, brown; medium tocoarse sand. Bottom of exploration at 76.5 ft. bgs. 4/29/2019 4/17/2019 Operator Work Start/Completion Dates Blows/footWater Content (%) MW-02Equipment Legend Contractor 260 255 250 245 240 MW-02 Tests Geoprobe 8140LC Sonic Holocene Drilling Exploration Method(s) See Exploration Log Key for explanationof symbols Exploration Completionand Notes SampleType/ID Depth to Water (Below GS) Liquid Limit Geotechnical Exploration Log Water Level ATD Logged by: DRTApproved by: MWS 05/30/2019 67.88' (Static) Exploration Number WaterLevelSheet 3 of 3 Depth(ft) Sampling Method 4/17/2019 to 4/18/2019 Project Address & Site Specific Location 325' (est) 47.48659, -122.17802 (est) Coordinates (Lat,Lon WGS84) Plastic Limit Description 65 70 75 80 85 3005 NE 4th St, Renton, Washington ExplorationLog NEW STANDARD EXPLORATION LOG TEMPLATE P:\GINTW\PROJECTS\KING COUNTY PARKS CFD 170383.GPJ May 31, 2019Top of Casing Elev. (NAVD88) Blows/6" 65 70 75 80 85 Renton Shop Facility Design - 170383 Depth(feet)MaterialType Ground Surface (GS) Elev. (NAVD88) Zach Bailey SampleTypeElev.(feet) Static Water Level 324.75' (est) Autohammer; 140 lb hammer; 30" drop Continuous core 7" ID Split Barrel 3" X 2.375" (Mod Cal) 10 20 30 400 50 Classifications of soils in this report are based on visual field and/or laboratory observations, which include density/consistency, moisture condition, grain size, and plasticity estimates and should not be construed to imply field or laboratory testing unless presented herein. Visual-manual and/or laboratory classification methods of ASTM D-2487 and D-2488 were used as an identification guide for the Unified Soil Classification System. Terms Describing Relative Density and Consistency Estimated Percentage Symbols Moisture Content Percentage by Weight SamplerType Sampler Type Description Blows/6" orportion of 6" Component Definitions Size Range and Sieve Number Larger than 12" Descriptive Term Smaller than No. 200 (0.075 mm) 3" to 12" Coarse- Grained Soils Fine- Grained Soils Density Very Loose Loose Medium Dense Dense Very Dense SPT blows/foot 0 to 4 4 to 10 10 to 30 30 to 50 >50 (2) 0 to 2 2 to 4 4 to 8 8 to 15 15 to 30 >30 Consistency Very Soft Soft Medium Stiff Stiff Very Stiff Hard SPT blows/foot(2) 2.0" OD Split-Spoon Sampler(SPT)Continuous Push Non-Standard Sampler Bulk sample 3.0" OD Thin-Wall Tube Sampler (including Shelby tube) Grab Sample Portion not recovered(1)ATD = At time of drilling Static water level (date) Percentage by dry weight (SPT) Standard Penetration Test (ASTM D-1586) In General Accordance with Standard Practice for Description and Identification of Soils (ASTM D-2488) Test Symbols Depth of groundwater(4) (1) (2) (3) Cement grout surface seal Groutseal End cap Filter pack with blank casing section Boulders Silt and Clay Gravel Coarse Gravel Fine Gravel Cobbles Sand Coarse Sand Medium Sand Fine Sand Dry - Absence of moisture, dusty, dry to the touch Slightly Moist - Perceptible moisture Moist - Damp but no visible water Very Moist - Water visible but not free draining Wet - Visible free water, usually from below water table Highly Organic SoilsFine-Grained Soils - 50% or More Passes No. 200 Sieve(1)Coarse-Grained Soils - More than 50% Retained on No. 200 SieveGravels - More than 50% of Coarse Fraction Retained on No. 4 Sieve15% Fines5% FinesSands - 50% or More of Coarse Fraction Passes No. 4 SieveSilts and ClaysLiquid Limit Less than 50Silts and ClaysLiquid Limit 50 or More(5)Combined USCS symbols used for fines between 5% and 15% as estimated in General Accordance with Standard Practice for Description and Identification of Soils (ASTM D-2488)(1)(1)15% Fines5% Fines(5)(5)(5)(5)FC = Fines Content G = Grain Size M = Moisture Content A = Atterberg Limits C = Consolidation DD = Dry Density K = Permeability Str = Shear Strength Env = Environmental PiD = Photoionization No. 4 (4.75 mm) to No. 10 (2.00 mm) No. 10 (2.00 mm) to No. 40 (0.425 mm) No. 40 (0.425 mm) to No. 200 (0.075 mm) 3" to No. 4 (4.75 mm) 3" to 3/4" 3/4" to No. 4 (4.75 mm) No. 4 (4.75 mm) to No. 200 (0.075 mm) Well-graded gravel and gravel with sand, little to no fines Poorly-graded gravel and gravel with sand, little to no fines Silty gravel and silty gravel with sand Clayey gravel and clayey gravel with sand Well-graded sand and sand with gravel, little to no fines Poorly-graded sand and sand with gravel, little to no fines Silty sand and silty sand with gravel Clayey sand and clayey sand with gravel Silt, sandy silt, gravelly silt, silt with sand or gravel Clay of low to medium plasticity; silty, sandy, or gravelly clay, lean clay Organic clay or silt of low plasticity Elastic silt, clayey silt, silt with micaceous or diato- maceous fine sand or silt Clay of high plasticity, sandy or gravelly clay, fat clay with sand or gravel Organic clay or silt of medium to high plasticity Peat, muck and other highly organic soils GW GP GM GC SW SP SM SC ML CL OL MH CH OH PT Trace Slightly (sandy, silty, clayey, gravelly) Sandy, silty, clayey, gravelly) Very (sandy, silty, clayey, gravelly) Modifier <5 5 to 15 15 to 30 30 to 49 Screened casing or Hydrotip with filter pack Bentonitechips FIGURE NO. PROJECT NO.DATE: REVISED BY: DRAWN BY: DESIGNED BY: www.aspectconsulting.com earth + water Exploration Log Key A-1 Q:\_ACAD Standards\Standard Details\Exploration Log Key B1.dwgDetector Grouted Transducer BGS = below ground surface 16 17 16 11 12 11 7 10 14 14 21 17 11 15 14 14 15 18 7 14 13 GS FC=4.1% FC=8.2%S1S2S3S4S5S6S7Exploration backfilledwith 3/8-inch bentonitechips and capped withexcavated soil. FILL SILTY SAND WITH GRAVEL (SM); medium dense,moist, orange-brown; fine to coarse sand; fine, rounded toangular gravel. GLACIAL OUTWASH (Qpa) SAND WITH SILT AND GRAVEL (SP-SM); dense, moist,brown; fine and coarse sand; fine and coarse, subroundedto subangular gravel. GRAVEL WITH SAND (GW); medium dense, moist,brown; fine to coarse sand; fine, subrounded to angulargravel. Becomes fine and coarse, rounded to subangular gravel. SAND WITH GRAVEL (SP); dense, moist, brown; fine tocoarse sand; fine and coarse, subrounded to subangulargravel. Bottom of exploration at 26.5 ft. bgs. Operator Work Start/Completion Dates Blows/footWater Content (%) AB-01Equipment Legend Contractor 325 320 315 310 305 AB-01 Tests Truck-mounted CME75 Hollow-stem auger Gregory Drilling Exploration Method(s) See Exploration Log Key for explanationof symbols Exploration Completionand Notes SampleType/ID Depth to Water (Below GS) Liquid Limit Geotechnical Exploration Log Logged by: JGFApproved by: MWS 05/30/2019 Exploration Number No Soil Sample Recovery WaterLevelSheet 1 of 1 Depth(ft) Sampling Method 4/13/2018 Project Address & Site Specific Location 330' (est) 47.48642, -122.17887 (est) Coordinates (Lat,Lon WGS84) Plastic Limit No Water Encountered Description 5 10 15 20 25 3005 NE 4th St, Renton, Washington. ExplorationLog NEW STANDARD EXPLORATION LOG TEMPLATE P:\GINTW\PROJECTS\KING COUNTY PARKS CFD 170383.GPJ May 31, 2019Top of Casing Elev. (NAVD88) Blows/6" 5 10 15 20 25 Renton Shop Facility Design - 170383 Depth(feet)MaterialType Ground Surface (GS) Elev. (NAVD88) Josh Willets SampleTypeElev.(feet) No Water Encountered NA (est) Autohammer; 140 lb hammer; 30" drop Split Barrel 2" X 1.375" (SPT) 10 20 30 400 50 2 1 4 8 14 13 6 17 19 9 13 13 8 11 12 8 10 13 8 10 13 OC=3% GS FC=4.8%S1S2S3S4S5S6S7Exploration backfilledwith 3/8-inch bentonitechips and capped withexcavated soil. FILL SILTY SAND WITH GRAVEL (SM); loose, moist,orange-brown; fine to coarse sand, fine, rounded toangular gravel. GLACIAL OUTWASH DEPOSITS (Qpa) GRAVEL WITH SAND (GW); medium dense, moist,brown; fine to coarse sand, fine and coarse, subrounded toangular gravel. Becomes dense, very moist, and gray at 7.5 bgs. Becomes medium dense at 10' bgs. Becomes moist at 15' bgs. SAND WITH GRAVEL (SP); medium dense, moist,brown; trace silt; fine to coarse sand; fine and coarse,subrounded to angular gravel. SAND (SP); medium dense, moist, brown; trace silt; fineto coarse sand; fine, subrounded to angular gravel. Bottom of exploration at 26.5 ft. bgs. Operator Work Start/Completion Dates Blows/footWater Content (%) AB-02Equipment Legend Contractor 325 320 315 310 305 AB-02 Tests Truck-mounted CME75 Hollow-stem auger Gregory Drilling Exploration Method(s) See Exploration Log Key for explanationof symbols Exploration Completionand Notes SampleType/ID Depth to Water (Below GS) Liquid Limit Geotechnical Exploration Log Logged by: JGFApproved by: MWS 05/30/2019 Exploration Number No Soil Sample Recovery WaterLevelSheet 1 of 1 Depth(ft) Sampling Method 4/13/2018 Project Address & Site Specific Location 330' (est) 47.48585, -122.17830 (est) Coordinates (Lat,Lon WGS84) Plastic Limit No Water Encountered Description 5 10 15 20 25 3005 NE 4th St, Renton, Washington. ExplorationLog NEW STANDARD EXPLORATION LOG TEMPLATE P:\GINTW\PROJECTS\KING COUNTY PARKS CFD 170383.GPJ May 31, 2019Top of Casing Elev. (NAVD88) Blows/6" 5 10 15 20 25 Renton Shop Facility Design - 170383 Depth(feet)MaterialType Ground Surface (GS) Elev. (NAVD88) Josh Willets SampleTypeElev.(feet) No Water Encountered NA (est) Autohammer; 140 lb hammer; 30" drop Split Barrel 2" X 1.375" (SPT) 10 20 30 400 50 8 13 9 8 12 18 8 13 14 10 13 15 12 18 19 10 12 13 13 22 15 OC=0.8% GS FC=5.3%S1S2S3S4S5S6S7Exploration backfilledwith 3/8-inch bentonitechips and capped withexcavated soil. FILL SILTY SAND WITH GRAVEL (SM); loose, moist,orange-brown; fine to coarse sand; fine, rounded toangular gravel. GLACIAL OUTWASH DEPOSITS (Qpa) SAND WITH GRAVEL (SP); medium dense, moist,brown; trace silt; fine to coarse sand; fine and coarse,rounded to subangular gravel. GRAVEL WITH SAND (GW); dense, moist, brown, withcobbles; trace silt; fine to coarse sand; fine and coarse,rounded to subangular gravel. SILTY SAND (SM); medium dense, brown, moist; fine tomedium sand. SAND WITH SILT AND GRAVEL (SP-SM); mediumdense, brown, moist; fine to coarse sand; fine and coarse,subrounded to subangular gravel. Becomes dense and very moist at 15' bgs. SAND WITH SILT (SP-SM); medium dense, brown,moist; fine to coarse sand; trace fine, subrounded tosubangular gravel. SAND WITH SILT AND GRAVEL (SP-SM); dense,brown, moist; fine to coarse sand; fine and coarse,subrounded to subangular gravel. Bottom of exploration at 26.5 ft. bgs. Operator Work Start/Completion Dates Blows/footWater Content (%) AB-03Equipment Legend Contractor 325 320 315 310 305 AB-03 Tests Truck-mounted CME75 Hollow-stem auger Gregory Drilling Exploration Method(s) See Exploration Log Key for explanationof symbols Exploration Completionand Notes SampleType/ID Depth to Water (Below GS) Liquid Limit Geotechnical Exploration Log Logged by: JGFApproved by: MWS 05/30/2019 Exploration Number No Soil Sample Recovery WaterLevelSheet 1 of 1 Depth(ft) Sampling Method 4/13/2018 Project Address & Site Specific Location 330' (est) 47.48606, -122.17942 (est) Coordinates (Lat,Lon WGS84) Plastic Limit No Water Encountered Description 5 10 15 20 25 3005 NE 4th St, Renton, Washington. ExplorationLog NEW STANDARD EXPLORATION LOG TEMPLATE P:\GINTW\PROJECTS\KING COUNTY PARKS CFD 170383.GPJ May 31, 2019Top of Casing Elev. (NAVD88) Blows/6" 5 10 15 20 25 Renton Shop Facility Design - 170383 Depth(feet)MaterialType Ground Surface (GS) Elev. (NAVD88) Josh Willets SampleTypeElev.(feet) No Water Encountered NA (est) Autohammer; 140 lb hammer; 30" drop Split Barrel 2" X 1.375" (SPT) 10 20 30 400 50 7 11 17 6 11 15 8 15 22 8 22 24 12 15 18 15 35 33 14 20 18 GS FC=3.4% FC=4.3%S1S2S3S4S5S6S7Exploration backfilledwith 3/8-inch bentonitechips and capped withexcavated soil. FILL SILTY SAND WITH GRAVEL (SM); medium dense,moist, orange-brown; fine to coarse sand; fine, rounded toangular gravel. GLACIAL OUTWASH DEPOSITS (Qpa) GRAVEL WITH SAND (GP); medium dense, moist,brown; fine to coarse sand; fine and coarse, subrounded tosubangular gravel. SAND WITH GRAVEL (SP); medium dense, moist,brown; trace silt; fine to coarse sand; fine and coarse,subrounded to subangular gravel. GRAVEL WITH SAND (GP); dense, moist, brown; fine tocoarse sand; fine and coarse, subrounded to subangulargravel. SAND WITH GRAVEL (SP); dense, moist, brown; tracesilt; fine to coarse sand; fine and coarse, subrounded tosubangular gravel. Becomes very dense at 20' bgs; blows elevated due togravel. Becomes dense at 25' bgs. Bottom of exploration at 26.5 ft. bgs. Operator Work Start/Completion Dates Blows/footWater Content (%) AB-04Equipment Legend Contractor 325 320 315 310 305 AB-04 Tests Truck-mounted CME75 Hollow-stem auger Gregory Drilling Exploration Method(s) See Exploration Log Key for explanationof symbols Exploration Completionand Notes SampleType/ID Depth to Water (Below GS) Liquid Limit Geotechnical Exploration Log Logged by: JGFApproved by: MWS 05/30/2019 Exploration Number No Soil Sample Recovery WaterLevelSheet 1 of 1 Depth(ft) Sampling Method 4/13/2018 Project Address & Site Specific Location 330' (est) 47.48637, -122.17945 (est) Coordinates (Lat,Lon WGS84) Plastic Limit No Water Encountered Description 5 10 15 20 25 3005 NE 4th St, Renton, Washington. ExplorationLog NEW STANDARD EXPLORATION LOG TEMPLATE P:\GINTW\PROJECTS\KING COUNTY PARKS CFD 170383.GPJ May 31, 2019Top of Casing Elev. (NAVD88) Blows/6" 5 10 15 20 25 Renton Shop Facility Design - 170383 Depth(feet)MaterialType Ground Surface (GS) Elev. (NAVD88) Josh Willets SampleTypeElev.(feet) No Water Encountered NA (est) Autohammer; 140 lb hammer; 30" drop Split Barrel 2" X 1.375" (SPT) 10 20 30 400 50 AB-01-12NWTPH-Dx,NWTPH-G PID=0 Sheen=None PID=0 Sheen=None PID=0 Sheen=None PID=0 Sheen=None PID=0 Sheen=None PID=0 Sheen=None PID=0 PID=0 Sheen=None PID=0 Sheen=None PID=0 Sheen=None Exploration backfilledwith 3/8-inch bentonitechips and capped withexcavated soil.Vacuum excavated to5 ft bgs FILL SILTY GRAVEL WITH SAND (GM); wet to moist, brown;fine to coarse sand; rounded cobbles. Becomes slightly moist. GLACIAL OUTWASH DEPOSITS (Qpa) SAND WITH SILT AND GRAVEL (SW-SM); moist, gray;fine to coarse sand; fine to coarse gravel. Bottom of exploration at 20 ft. bgs. Operator Work Start/Completion Dates AnalyticalSample Number &Lab Test(s) AB-05Equipment Legend Contractor 325 320 315 310 305 AB-05 Field Tests Geoprobe 7822D Direct push Holt Drilling Exploration Method(s) See Exploration Log Key for explanationof symbols Exploration Completionand Notes SampleType/ID Depth to Water (Below GS) Environmental Exploration Log Logged by: MvApproved by: MWS 03/12/18 Exploration Number No Soil Sample Recovery WaterLevelSheet 1 of 1 Depth(ft) Sampling Method 2/16/2018 Project Address & Site Specific Location 330' (est) 47.48615, -122.17895 (est) Coordinates (Lat,Lon WGS84) No Water Encountered Description 5 10 15 20 25 3005 NE 4th St, Renton, SW corner of canopy ExplorationLog NEW STANDARD EXPLORATION LOG TEMPLATE P:\GINTW\PROJECTS\KING COUNTY PARKS CFD 170383.GPJ May 31, 2019Top of Casing Elev. (NAVD88) 5 10 15 20 25 Renton Shop Facility Design - 170383 Depth(feet)MaterialType Ground Surface (GS) Elev. (NAVD88) Mike SampleTypeElev.(feet) No Water Encountered NA (est) Percussion hammer Continuous core 1.5" ID Grab sample AB-02-7NWTPH-Dx,NWTPH-G PID=0 Sheen=None PID=0 Sheen=None PID=0 Sheen=None PID=0 Sheen=None PID=0 Sheen=None PID=0 Sheen=None PID=0 Sheen=None PID=0 Sheen=None PID=0 Exploration backfilledwith 3/8-inch bentonitechips and capped withexcavated soil.Vacuum excavated to5 ft bgs FILL SILTY GRAVEL WITH SAND (GM); moist to wet, brown;fine to coarse sand; fine to coarse gravel; roundedcobbles. Becomes slightly moist. GLACIAL OUTWASH DEPOSITS (Qpa) SAND WITH SILT (SW-SM); moist, gray; fine to coarsesand; few percent gravel. SAND WITH SILT (SP-SM); moist, gray; fine to mediumsand; few gravel. Bottom of exploration at 20 ft. bgs. Operator Work Start/Completion Dates AnalyticalSample Number &Lab Test(s) AB-06Equipment Legend Contractor 325 320 315 310 305 AB-06 Field Tests Geoprobe 7822D Direct push Holt Drilling Exploration Method(s) See Exploration Log Key for explanationof symbols Exploration Completionand Notes SampleType/ID Depth to Water (Below GS) Environmental Exploration Log Logged by: MvApproved by: MWS 03/12/18 Exploration Number No Soil Sample Recovery WaterLevelSheet 1 of 1 Depth(ft) Sampling Method 2/16/2018 Project Address & Site Specific Location 330' (est) 47.48621, -122.17898 (est) Coordinates (Lat,Lon WGS84) No Water Encountered Description 5 10 15 20 25 3005 NE 4th St, Renton, NW corner of canopy ExplorationLog NEW STANDARD EXPLORATION LOG TEMPLATE P:\GINTW\PROJECTS\KING COUNTY PARKS CFD 170383.GPJ May 31, 2019Top of Casing Elev. (NAVD88) 5 10 15 20 25 Renton Shop Facility Design - 170383 Depth(feet)MaterialType Ground Surface (GS) Elev. (NAVD88) Mike SampleTypeElev.(feet) No Water Encountered NA (est) Percussion hammer Continuous core 1.5" ID Grab sample AB-03-12NWTPH-Dx,NWTPH-G PID=0 Sheen=None PID=0 Sheen=None PID=0 Sheen=None PID=0 Sheen=None PID=0 Sheen=None PID=0 Sheen=None PID=0 Sheen=None PID=0 Exploration backfilledwith 3/8-inch bentonitechips and capped withexcavated soil.Vacuum excavated to5 ft bgs FILL SILTY GRAVEL WITH SAND (GM); wet to moist, brown;fine to coarse gravel; fine to coarse sand GLACIAL OUTWASH DEPOSITS (Qpa) SAND WITH SILT (SW-SM); moist, gray; fine to coarsesand; few gravel. Bottom of exploration at 15 ft. bgs. Operator Work Start/Completion Dates AnalyticalSample Number &Lab Test(s) AB-07Equipment Legend Contractor 325 320 315 310 305 AB-07 Field Tests Geoprobe 7822D Direct push Holt Drilling Exploration Method(s) See Exploration Log Key for explanationof symbols Exploration Completionand Notes SampleType/ID Depth to Water (Below GS) Environmental Exploration Log Logged by: MvApproved by: MWS 03/12/18 Exploration Number No Soil Sample Recovery WaterLevelSheet 1 of 1 Depth(ft) Sampling Method 2/16/2018 Project Address & Site Specific Location 330' (est) 47.48620, -122.17884 (est) Coordinates (Lat,Lon WGS84) No Water Encountered Description 5 10 15 20 25 3005 NE 4th St, Renton, NE corner of canopy ExplorationLog NEW STANDARD EXPLORATION LOG TEMPLATE P:\GINTW\PROJECTS\KING COUNTY PARKS CFD 170383.GPJ May 31, 2019Top of Casing Elev. (NAVD88) 5 10 15 20 25 Renton Shop Facility Design - 170383 Depth(feet)MaterialType Ground Surface (GS) Elev. (NAVD88) Mike SampleTypeElev.(feet) No Water Encountered NA (est) Percussion hammer Continuous core 1.5" ID Grab sample AB-04-12NWTPH-Dx,NWTPH-G PID=0 Sheen=None PID=0 Sheen=None PID=0 Sheen=None PID=0 Sheen=None PID=0 Sheen=None PID=0 Sheen=None PID=0 Sheen=None PID=0 Sheen=None PID=0 Sheen=None Exploration backfilledwith 3/8-inch bentonitechips and capped withexcavated soil.Vacuum excavated to5 ft bgs FILL SILTY GRAVEL WITH SAND (GM); wet to moist, brown;fine to coarse sand; fine to coarse gravel; containsconstruction debris. Becomes slighlty moist; becomes gray, tan, brown GLACIAL OUTWASH DEPOSITS (Qpa) SAND WITH SILT (SW-SM); moist, gray; fine to coarsesand; few gravel. Bottom of exploration at 15 ft. bgs. Operator Work Start/Completion Dates AnalyticalSample Number &Lab Test(s) AB-08Equipment Legend Contractor 325 320 315 310 305 AB-08 Field Tests Geoprobe 7822D Direct push Holt Drilling Exploration Method(s) See Exploration Log Key for explanationof symbols Exploration Completionand Notes SampleType/ID Depth to Water (Below GS) Environmental Exploration Log Logged by: MvApproved by: MWS 03/12/18 Exploration Number No Soil Sample Recovery WaterLevelSheet 1 of 1 Depth(ft) Sampling Method 2/16/2018 Project Address & Site Specific Location 330' (est) 47.48618, -122.17884 (est) Coordinates (Lat,Lon WGS84) No Water Encountered Description 5 10 15 20 25 3005 NE 4th St, Renton, SE corner of canopy ExplorationLog NEW STANDARD EXPLORATION LOG TEMPLATE P:\GINTW\PROJECTS\KING COUNTY PARKS CFD 170383.GPJ May 31, 2019Top of Casing Elev. (NAVD88) 5 10 15 20 25 Renton Shop Facility Design - 170383 Depth(feet)MaterialType Ground Surface (GS) Elev. (NAVD88) Mike SampleTypeElev.(feet) No Water Encountered NA (est) Percussion hammer Continuous core 1.5" ID Grab sample 1 APPENDIX B Vibrating-Wire Piezometers Hydrograph 64.0 65.0 66.0 67.0 68.0 69.0 70.0 71.0 72.0 03/06/1904/05/1905/05/1906/04/1907/04/1908/03/1909/02/1910/02/1911/01/1912/01/1912/31/1901/30/2002/29/2003/30/2004/29/20Depth of Water (ft. bgs)Date King County Parks and Recreation Division –Renton Shop VW Piezometers MW-01 MW-02 Depth 50 feet below soil receptor 1 APPENDIX C Laboratory Test Results ASPECT CONSULTING PROJECT NO. 170383 SEPTEMBER 9, 2020 C-1 1 C. Laboratory Test Results A laboratory testing program was developed to determine index and engineering properties of materials and to determine the concentrations of potential contaminants at the Site. Soil samples used in the testing program were collected from the soil borings. The tests performed and the procedures followed are outlined below. C.1. Soil Classification Soil samples from the explorations were visually classified in the field and then taken to our office where the classifications were verified in a relatively controlled environment. Field and laboratory observations include density/consistency, moisture condition, and grain-size and plasticity estimates. The classifications of selected samples were checked by grain-size analysis and plasticity index testing. Classifications were made in general accordance with the Unified Soil Classification System (USCS), ASTM D2488. C.2. Moisture-Content Determination Moisture contents were determined for samples recovered in the explorations in general accordance with ASTM D2216, as soon as possible following their arrival to the laboratory. Moisture contents are shown on the exploration logs and shown in this appendix. Water content determination was also completed as part of other tests conducted and is shown with the results of those tests. C.3. Grain-Size Analyses Grain-size analysis was conducted in accordance with ASTM D6913 on selected soil samples collected from the soil borings. The results of the tests are presented in this appendix, plotting percent finer by weight versus grain size and on the boring logs. C.4. Organic Content Organic contents of select samples were tested in general accordance with ASTM D 2974 in a muffle furnace. The organic content is the percentage by weight of oven-dried organic matter (pre-burn dry weight minus post-burn dry weight) divided by the total oven-dried sample weight. The results of the tests are presented in this appendix. C.5. Cation Exchange Capacity The cation exchange capacity (CEC) is the exchangeable cations that a soil can adsorb. Units are milliequivalents per 100 grams of soil. Soils with a CEC of 5 milliequivalents at pH 7 will have a CEC less than 5 milliequivalents when the pH is less 7. The CEC of the treatment soil must be equal to or greater than 5 milliequivalents per100 grams dry soil per USEPA Method 9081. The results of the tests are presented in this appendix. ASPECT CONSULTING PROJECT NO. 170383 SEPTEMBER 9, 2020 C-2 C.6. Analytical Tests One soil sample from each of the four direct-push explorations were submitted to an accredited analytical laboratory for detection and quantification of contamination. The selected samples were collected at a depth at or below the presumed bottom of the USTs. Samples were collected in general conformance with EPA Method 5030 and with applicable industry practices. The laboratory analyzed each sample for gasoline-range organics (by method NWTPH- G) and diesel- and oil-range organics (method NWTPH-Dx). The laboratory report is included in this appendix. Test(s) Performed:Test(s) Performed: X X Respectfully Submitted, Laboratory Technician Atterberg Limits Moisture Content Cation Exchange Capacity Specific Gravity, Coarse Specific Gravity, Fine Hydrometer Analysis Proctor Sand Equivalent Fracture Count Organic Content WSDOT Degradation Bulk Density & Voids Corporate ~ 777 Chrysler Drive • Burlington, WA 98233 • Phone (360) 755-1990 • Fax (360) 755-1980 Regional Offices: Olympia ~ 360.534.9777 Bellingham ~ 360.647.6061 Silverdale ~ 360.698.6787 Tukwila ~ 206.241.1974 Visit our website: www.mtc-inc.net Meghan Blodgett-Carrillo If you have any questions concerning the test results, the procedures used, or if we can be of any further assistance please call on us at the number below. See Report See Reports Materials Testing & Consulting, Inc. Geotechnical Engineering • Special Inspection • Materials Testing • Environmental Consulting Test Results Seattle, WA 98104 Dustin Taylor May 10, 2019 18B011-16 B19-0284 & 0285 Project #: Parks Central MaintenanceAddress: As requested MTC, Inc. has performed the following test(s) on the sample referenced above. The testing was performed in accordance with current applicable AASHTO or ASTM standards as indicated below. The results obtained in our laboratory were as follows below or on the attached pages: Test Results Client: Sample #: Date: Project: Aspect Consulting 710 2nd Ave., Suite 550 Attn: Sulfate SoundnessSieve Analysis Revised on:Date sampled:April 15, 2019 Project:Parks Central Maintenance Client: Project #:18B011-16 Date Received:May 3, 2019 Sampled by: Date Tested:May 7, 2019 Tested by: Sample #Location Tare Wet + Tare Dry + Tare Wgt. Of Moisture Wgt. Of Soil % Moisture B19-0284 MW-01 Bulk 2 @ 20'718.8 3855.8 3817.4 38.4 3098.6 1.2% B19-0285 MW-02 Bulk 7 @ 35'763.6 3257.3 3201.5 55.8 2437.9 2.3% 0.0 0.0 #DIV/0! 0.0 0.0 #DIV/0! 0.0 0.0 #DIV/0! 0.0 0.0 #DIV/0! 0.0 0.0 #DIV/0! 0.0 0.0 #DIV/0! 0.0 0.0 #DIV/0! 0.0 0.0 #DIV/0! Sample #Location Tare % Organics B19-0284 MW-01 Bulk 2 @ 20'68.1 1.6% B19-0285 MW-02 Bulk 7 @ 35'68.6 1.0% #DIV/0! #DIV/0! #DIV/0! #DIV/0! #DIV/0! #DIV/0! #DIV/0! #DIV/0! Reviewed by: Meghan Blodgett-Carrillo Visit our website: www.mtc-inc.net All results apply only to actual locations and materials tested. As a mutual protection to clients, the public and ourselves, all reports are submitted as the confidential property of clients, and authorization for publication of statements, conclusions or extracts from or regarding our reports is reserved pending our written approval. Materials Testing & Consulting, Inc. Geotechnical Engineering • Special Inspection • Materials Testing • Environmental Consulting 106.8 106.2 Moisture Content - AASHTO T-265 Organic Content - AASHTO T-267 Soil + Tare, Pre-Ignition Soil + Tare, Post Ignition Aspect Consulting Client Corporate ~ 777 Chrysler Drive • Burlington, WA 98233 • Phone (360) 755-1990 • Fax (360) 755-1980 Regional Offices: Olympia ~ 360.534.9777 Bellingham ~ 360.647.6111 Silverdale ~ 360.698.6787 Tukwila ~ 206.241.1974 A. Eifrig 108.2 107.8 MATERIALS TESTING 777 CHRYSLER DR Burlington , WA 98233 5/6/2019 Soil PARKS CENTRAL MAINTENANCE B19-0284 MW-01 BULK 2 AT 20FT S19-06743 Date Received: Grower: Sampled By: Field: Laboratory #: Test Results Customer Account #: Customer Sample ID: Other Tests: Cation Exchange meq/100gCEC 4.2 pH 1:1 E.C. 1:1 m.mhos/cm Est Sat Paste E.C. m.mhos/cm Effervescence Lbs/Acre Ammonium - N mg/kg %Organic Matter W.B.ENR: This is your Invoice #:B.Thyssen, CPReviewed by:S19-06743 Account #234500 We make every effort to provide an accurate analysis of your sample. For reasonable cause we will repeat tests, but because of factors beyond our control in sampling procedures and the inherent variability of soil, our liability is limited to the price of the tests. Recommendations are to be used as general guides and should be modified for specific field conditions and situations. Note: "u" indicates that the element was analyzed for but not detected MATERIALS TESTING 777 CHRYSLER DR Burlington , WA 98233 5/6/2019 Soil PARKS CENTRAL MAINTENANCE B19-0285 MW-02 BULK 7 AT 35 FT S19-06744 Date Received: Grower: Sampled By: Field: Laboratory #: Test Results Customer Account #: Customer Sample ID: Other Tests: Cation Exchange meq/100gCEC 5.0 pH 1:1 E.C. 1:1 m.mhos/cm Est Sat Paste E.C. m.mhos/cm Effervescence Lbs/Acre Ammonium - N mg/kg %Organic Matter W.B.ENR: This is your Invoice #:B.Thyssen, CPReviewed by:S19-06744 Account #234500 We make every effort to provide an accurate analysis of your sample. For reasonable cause we will repeat tests, but because of factors beyond our control in sampling procedures and the inherent variability of soil, our liability is limited to the price of the tests. Recommendations are to be used as general guides and should be modified for specific field conditions and situations. Note: "u" indicates that the element was analyzed for but not detected FRIEDMAN & BRUYA, INC. _________________________________________________ ENVIRONMENTAL CHEMISTS James E. Bruya, Ph.D. 3012 16th Avenue West Yelena Aravkina, M.S. Seattle, WA 98119-2029 Michael Erdahl, B.S. (206) 285-8282 Arina Podnozova, B.S. fbi@isomedia.com Eric Young, B.S. www.friedmanandbruya.com February 22, 2018 Matthew Vonder-Ahe, Project Manager Aspect Consulting, LLC 350 Madison Ave. N. Bainbridge Island, WA 98110-1810 Dear Mr Vonder-Ahe: Included are the results from the testing of material submitted on February 16, 2018 from the KCPCFM 170383, F&BI 802285 project. There are 6 pages included in this report. Any samples that may remain are currently scheduled for disposal in 30 days. If you would like us to return your samples or arrange for long term storage at our offices, please contact us as soon as possible. We appreciate this opportunity to be of service to you and hope you will call if you have any questions. Sincerely, FRIEDMAN & BRUYA, INC. Michael Erdahl Project Manager Enclosures c: data@aspectconsulting.com ASP0222R.DOC FRIEDMAN & BRUYA, INC. _________________________________________________ ENVIRONMENTAL CHEMISTS 1 CASE NARRATIVE This case narrative encompasses samples received on February 16, 2018 by Friedman & Bruya, Inc. from the Aspect Consulting, LLC KCPCFM 170383, F&BI 802285 project. Samples were logged in under the laboratory ID’s listed below. Laboratory ID Aspect Consulting, LLC 802285 -01 AB-02-7 802285 -02 AB-01-12 802285 -03 AB-03-12 802285 -04 AB-04-12 802285 -05 Trip Blank All quality control requirements were acceptable. FRIEDMAN & BRUYA, INC. _________________________________________________ ENVIRONMENTAL CHEMISTS 2 Date of Report: 02/22/18 Date Received: 02/16/18 Project: KCPCFM 170383, F&BI 802285 Date Extracted: 02/20/18 Date Analyzed: 02/20/18 RESULTS FROM THE ANALYSIS OF SOIL SAMPLES FOR TOTAL PETROLEUM HYDROCARBONS AS GASOLINE USING METHOD NWTPH-Gx Results Reported on a Dry Weight Basis Results Reported as mg/kg (ppm) Surrogate Sample ID Gasoline Range (% Recovery) Laboratory ID (Limit 58-139) AB-02-7 <5 99 802285-01 AB-01-12 <5 97 802285-02 AB-03-12 <5 98 802285-03 AB-04-12 <5 95 802285-04 Method Blank <5 95 08-340 MB2 FRIEDMAN & BRUYA, INC. _________________________________________________ ENVIRONMENTAL CHEMISTS 3 Date of Report: 02/22/18 Date Received: 02/16/18 Project: KCPCFM 170383, F&BI 802285 Date Extracted: 02/19/18 Date Analyzed: 02/19/18 RESULTS FROM THE ANALYSIS OF SOIL SAMPLES FOR TOTAL PETROLEUM HYDROCARBONS AS DIESEL AND MOTOR OIL USING METHOD NWTPH-Dx Results Reported on a Dry Weight Basis Results Reported as mg/kg (ppm) Surrogate Sample ID Diesel Range Motor Oil Range (% Recovery) Laboratory ID (C10-C25) (C25-C36) (Limit 48-168) AB-02-7 <50 <250 101 802285-01 AB-01-12 <50 <250 97 802285-02 AB-03-12 <50 <250 108 802285-03 AB-04-12 <50 <250 109 802285-04 Method Blank <50 <250 101 08-375 MB FRIEDMAN & BRUYA, INC. _________________________________________________ ENVIRONMENTAL CHEMISTS 4 Date of Report: 02/22/18 Date Received: 02/16/18 Project: KCPCFM 170383, F&BI 802285 QUALITY ASSURANCE RESULTS FOR THE ANALYSIS OF SOIL SAMPLES FOR TPH AS GASOLINE USING METHOD NWTPH-Gx Laboratory Code: 802300-01 (Duplicate) Analyte Reporting Units Sample Result (Wet Wt) Duplicate Result (Wet Wt) RPD (Limit 20) Gasoline mg/kg (ppm) <5 <5 nm Laboratory Code: Laboratory Control Sample Analyte Reporting Units Spike Level Percent Recovery LCS Acceptance Criteria Gasoline mg/kg (ppm) 20 95 71-131 FRIEDMAN & BRUYA, INC. _________________________________________________ ENVIRONMENTAL CHEMISTS 5 Date of Report: 02/22/18 Date Received: 02/16/18 Project: KCPCFM 170383, F&BI 802285 QUALITY ASSURANCE RESULTS FROM THE ANALYSIS OF SOIL SAMPLES FOR TOTAL PETROLEUM HYDROCARBONS AS DIESEL EXTENDED USING METHOD NWTPH-Dx Laboratory Code: 802289-01 (Matrix Spike) Analyte Reporting Units Spike Level Sample Result (Wet Wt) Percent Recovery MS Percent Recovery MSD Acceptance Criteria RPD (Limit 20) Diesel Extended mg/kg (ppm) 5,000 <50 90 94 73-135 4 Laboratory Code: Laboratory Control Sample Analyte Reporting Units Spike Level Percent Recovery LCS Acceptance Criteria Diesel Extended mg/kg (ppm) 5,000 80 74-139 FRIEDMAN & BRUYA, INC. _________________________________________________ ENVIRONMENTAL CHEMISTS 6 Data Qualifiers & Definitions a - The analyte was detected at a level less than five times the reporting limit. The RPD results may not provide reliable information on the variability of the analysis. b - The analyte was spiked at a level that was less than five times that present in the sample. Matrix spike recoveries may not be meaningful. ca - The calibration results for the analyte were outside of acceptance criteria. The value reported is an estimate. c - The presence of the analyte may be due to carryover from previous sample injections. cf - The sample was centrifuged prior to analysis. d - The sample was diluted. Detection limits were raised and surrogate recoveries may not be meaningful. dv - Insufficient sample volume was available to achieve normal reporting limits. f - The sample was laboratory filtered prior to analysis. fb - The analyte was detected in the method blank. fc - The compound is a common laboratory and field contaminant. hr - The sample and duplicate were reextracted and reanalyzed. RPD results were still outside of control limits. Variability is attributed to sample inhomogeneity. hs - Headspace was present in the container used for analysis. ht – The analysis was performed outside the method or client-specified holding time requirement. ip - Recovery fell outside of control limits. Compounds in the sample matrix interfered with the quantitation of the analyte. j - The analyte concentration is reported below the lowest calibration standard. The value reported is an estimate. J - The internal standard associated with the analyte is out of control limits. The reported concentration is an estimate. jl - The laboratory control sample(s) percent recovery and/or RPD were out of control limits. The reported concentration should be considered an estimate. js - The surrogate associated with the analyte is out of control limits. The reported concentration should be considered an estimate. lc - The presence of the analyte is likely due to laboratory contamination. L - The reported concentration was generated from a library search. nm - The analyte was not detected in one or more of the duplicate analyses. Therefore, calculation of the RPD is not applicable. pc - The sample was received with incorrect preservation or in a container not approved by the method. The value reported should be considered an estimate. ve - The analyte response exceeded the valid instrument calibration range. The value reported is an estimate. vo - The value reported fell outside the control limits established for this analyte. x - The sample chromatographic pattern does not resemble the fuel standard used for quantitation. 1 APPENDIX D Stormwater Infiltration Analysis ASPECT CONSULTING PROJECT NO. 170383 SEPTEMBER 9, 2020 D-1 1 D. Stormwater Infiltration Analyses As part of our stormwater infiltration analyses for the Site, the infiltration potential was estimated using well permeameter testing (USBR, 1989) in infiltration wells. The infiltration tests were performed within and near the area where the proposed infiltration trench galleries are planned. D.1. Infiltration Well Tests Infiltration test wells MW-01 and MW-02 were constructed by drilling two 10-inch- diameter 75-foot deep borings, placing vibrating-wire piezometers at the bottoms, backfilling the boreholes with grout to approximately 26 feet bgs, and installing the well casings. The wells consist of 6-inch diameter Schedule 40 polyvinyl chloride (PVC) casing and a 10-foot-long steel V-wrap wire screen with 0.020-slots. The filter pack encasing the screens is 6x9 Colorado Silica sand (see Appendix A for Boring Logs). The test wells penetrate 10 feet into an approximately 53-foot relatively uniform stratigraphy of unsaturated receptor soils consisting primarily of sandy and gravelly glacial outwash deposits (Qpa) with low fines content. The bottom of the receptor soils are bound by the top of the regional, unconfined aquifer. Infiltration tests generally followed the procedure outlined in the U.S. Bureau of Reclamation Well Permeameter method (USBR,7300-89). The infiltration tests were performed on MW-01 between 13 feet and 23 feet bgs on April 22, 2019 and on MW-02 between 15 feet and 25 feet bgs. The test protocols consist of a constant head test (Phase 1) and falling head test (Phase 2). The standard test procedure includes: 1. Adding water to the test well to maintain a constant hydraulic head in the well. 2. Monitoring the flow rates and total water added with a flow meter. 3. Monitoring water levels within the test well with a pressure transducer. 4. Adjusting water flow rates until the water level in the well is constant (less than 5 percent variation), or for a minimum of 4 hours. 5. Once the constant rate is achieved or the minimum duration reached, Phase 1 is complete and Phase 2 is begun. The water source is shut off and the water levels monitored until it has fallen to less than 5 percent of the total head targeted during the constant rate portion of the test. Due to the high permeability of the receptor soils and access to finite water sources from 5,000-gallon water trucks, producing, maintaining, and measuring constant head levels during the tests were a challenge. Rather than measuring stepped water levels and rates, the tests consisted of using the maximum allowable flow rates the equipment was capable ASPECT CONSULTING PROJECT NO. 170383 SEPTEMBER 9, 2020 D-2 of providing, which was between 90 and 140 gallons per minute (gpm). The groundwater response to testing was continuously monitored using vibrating wire piezometers installed in the groundwater below the test wells. Table 3 in Section 2.5.3 provides the constant head test flowrates and heads. The test data are shown in the attached Figures D1 and D2 and in Table D1 below. D.1.1. Infiltration Well Test Results The infiltration well test data were analyzed using the USBR Well Permeameter equation for Condition I, resulting in estimates of the bulk saturated hydraulic conductivity of the infiltration receptor soil. Table D1. Infiltration Test Results and Well Permeameter Variables Variablea MW-01 MW-02 Q, gpm 90 118 Q, cfs 0.20 0.26 Q, ft3/day 17,280 22,464 H, ft 7.81 5.00 r, ft 0.42 0.42 Tu, ft 67 68 T, °C 11 12 µT 0.001271 0.001236 µ20 0.001003 0.001003 V 1.2671984 1.23230309 Kb, ft/day 168 468 Notes: a) Refer to USBR 7300-89 for more detail on the Well Permeameter method, equations, and variables. No discernable groundwater response was measured during or after infiltration testing. The results of translating the infiltration well test results into design infiltration rates for infiltration trench galleries including safety factors, is described in Section 3.6 of the Geotechnical Report. Attachments Figure D1 – MW-01 Borehole Injection Test Results Figure D2 – MW-02 Borehole Injection Test Results 0.0 1.0 2.0 3.0 4.0 5.0 6.0 7.0 8.0 9.0 10.0 0 10 20 30 40 50 60 70 80Head of Water (feet)Elapsed Time (minutes) King County Parks Central Maintenance Facility Infiltration Well Testing MW-01 Constant Head Test Data Selected for Analysis Figure C1 0.0 1.0 2.0 3.0 4.0 5.0 6.0 7.0 0 25 50 75 100 125 150 175 200Head of Water (feet)Elapsed Time (minutes) King County Parks Central Maintenance Facility Infiltration Well Testing MW-02 Constant Head Test Data Selected for Analysis Figure C2 1 APPENDIX E King County May 22, 2017 Preliminary Geotechnical Design Report – Subsurface Explorations Department of Transportation Road Services Division Mailstop: RSD-TR-0100 | 155 Monroe Avenue NE, Bldg. D, Renton, WA 98056-4199 206-477-8100 | maint.roads@kingcounty.gov | www.kingcounty.gov/roads DATE: May 24, 2017 TO: Brenda Bradford, Architect, Capital Project Management, King County Department of Natural Resources and Parks VIA: Alan Corwin, P.E., Engineer IV, Materials Lab Unit, Road Services Division, King County Department of Transportation FROM: Timothy Hyden, Engineer III, Materials Lab Unit, Road Services Division, King County Department of Transportation RE: Addenda No. 1 Project No. 1122161 – Preliminary Geotechnical Design Report New King County DNRP Central Maintenance Facility 3005 NE 4th Street, Renton, Washington As discussed, this letter is submitted as Addenda No. 1 to our Preliminary Geotechnical Design Report for the referenced project originally dated May 11, 2017. 1) The title for Section 4.4 should be changed from “Wellhead Protection Area Zones” to “Wellhead Protection Area Zones (Aquifer Protection Area)”, as the City of Renton Critical Areas Ordinance uses both terms interchangeably. 2) Add the following paragraph to the end of Section 5.4.1: In addition to the types of materials to be used for fill, the City of Renton Municipal Code (4-4-060N) should be reviewed for other grading restrictions related to fill slope locations, benching of fill slopes and submittal of a Source Statement to preclude the import and use of contaminated fill soils. Should you have questions, require clarification or desire additional information, please contact Tim Hyden (206-477-0983) or Alan Corwin (206-296-7711) at your convenience. cc: Bing Subelbia, Project Program Manager IV tQ King County DATE: TO: VIA: Department of Transportation Road Services Division May 11 , 2017 Brenda Bradford, Architect, Capital Project Management, King County Department of Natural Resources and Parks ~n. P.E., Engineer IV, Materials Lab Unit, R~a~~ices Division, King County Department of Transportation . FROM:~ Hyden, Engineer Ill, Materials Lab Unit, Road Services Division, King County Department of Transportation RE: Project No. 1122161 -Preliminary Geotechnical Design Report New King County DNRP Central Maintenance Facility 3005 NE 4th Street, Renton, Washington -As requested, we have completed a preliminary geotechnical engineering study for the new King County DNRP Central Maintenance Facility to be located in Renton, Washington. Our work was performed and this report prepared to addresses the items included with the approved scope of work as detailed by our proposal and cost estimate dated March 17, 2017. This report summarizes the results of our site reconnaissance, literature review, subsurface exploration, critical area and geologic hazards evaluation, and provides recommendations for development, design and construction. Should you have questions, require clarification or desire additional information, please contact Tim Hyden (206-4 77-0983) or Alan Corwin (206-296-7711) at your convenience. cc: Bing Subelbia, Project Program Manager IV Mailstop: RSD -TR-0100 I 155 Monroe Avenue NE, Bldg. D, Renton, WA 98056-4199 206-477-8100 I maint.roads@kingcounty.gov I www.kingcounty.gov/roads TABLE OF CONTENTS (Page 1 of 2) Project No. 1121161 -Preliminary Geotechnical Design Report New King County DNRP Central Maintenance Facility 3005 NE 4th Street, Renton, Washington SECTION 1 -INTRODUCTION ........................................................................................................ 1 SECTION 2 -PROJECT OVERVIEW ............................................................................................. 1 SECTION 2.1 -SITE DESCRIPTION ........................................................................................... 1 SECTION 2.2 -PLANNED DEVELOPMENT ............................................................................... 1 SECTION 2.3-ADJACENT PROPERTIES ................................................................................. 2 SECTION 3 -SURFACE AND SUBSURFACE CONDITIONS ...................................................... 2 SECTION 3.1 -GEOLOGIC RECONNAISSANCE AND MAPPING ............................................ 2 SECTION 3.2-SUBSURFACE EXPLORATION ......................................................................... 3 Subsection 3.2.1 -Borings 8-1 through B-5 ............................................................................. 3 Subsection 3.2.2-Boring 8-6 .................................................................................................. 4 Subsection 3.2.3-Oversize Materia/s ...................................................................................... 4 SECTION 3.3-SITE SPECIFIC BORING LOCATIONS ............................................................. 4 SECTION 3.4 -PREVIOUS EXPLORATION .............................................................................. .4 SECTION 3.5 GROUNDWATER ............................................................................................... 4 SECTION 4 -CRITICAL AREA IDENTIFICATION ........................................................................ 5 SECTION 4.1 -SENSITIVE SLOPES .......................................................................................... 5 SECTION 4.2 -PROTECTED SLOPES ....................................................................................... 6 SECTION 4.3-DETERMINATION OF REGULATED SLOPE LOCATIONS ................................ 6 SECTION 4.4 -WELLHEAD PROTECTION ZONES ................................................................... 6 SECTION 5 -ANALYSIS, CONCLUSIONS AND RECOMMENDATION ...................................... 6 SECTION 5.1-TEMPORARY EROSION AND SEDIMENTATION CONTROL. .......................... 6 SECTION 5.2 -STORMWATER INFILTRATION ......................................................................... 7 SECTION 5.3-SUBGRADE PREPARATION ............................................................................. 8 SECTION 5.4 -FILL FOR SITE GRADING .................................................................................. 8 Subsection 5.4.1 -Fill Materials ............................................................................................... 8 Subsection 5.4.2-Fill/Backfill Moisture Content and Compaction Leve/ ................................. 8 SECTION 5.5-UTILITY CONSTRUCTION ................................................................................. 9 SECTION 5.6-EXCAVATION SAFETY ...................................................................................... 9 SECTION 5.7 -SHALLOW FOUNDATIONS BEARING CAPACITY ............................................ 9 SECTION 5.8 -SHALLOW FOUNDATION SETTLEMENT ....................................................... 10 SECTION 5.9-ALTERNATE FOUNDATION/SLAB BEARING SURFACE PREP .................... 10 TABLE OF CONTENTS (Page 2 of 2) Project No. 1121161 -Preliminary Geotechnical Design Report New King County DNRP Central Maintenance Facility 3005 NE 4th Street, Renton, Washington SECTION 5.10-SEISMIC DESIGN CONSIDERATIONS .......................................................... 10 Subsection 5.10.1-Seismic Ground Motion Values .............................................................. 10 Subsection 5.10.2-Seismic Hazard Areas ............................................................................ 11 Subsection 5. 10.3 -Liquefaction ............................................................................................ 11 Subsection 5.10.4-Seismically Induced Landslides ............................................................. 11 Subsection 5.10.5-Ground Rupture ...................................................................................... 11 SECTION 6.0-ASPHALT PAVING .............................................................................................. 12 SECTION 7 .0 -CLOSURE ............................................................................................. : .............. 12 SECTION 8.0 -REFERENCES ..................................................................................................... 13 LIST OF FIGURES FIGURE 1: FIGURE 1 -VICINITY MAP FIGURE 2: FIGURE 2 -BORING LOCATION PLAN FIGURE 3: FIGURE 3 -CRITICAL AREAS APPENDICES APPENDIX A-BORING LOGS AND LABORATORY TEST REPORTS Project No. 1122161 -Preliminary Geotechnical Design Report New King County DNRP Central Maintenance Facility 3005 NE 4th Street, Renton, Washington (Page 1 of 14) 1.0 INTRODUCTION As requested, we have completed a preliminary geotechnical engineering investigation for the new King County Department of Natural Resources and Parks Central Maintenance Facility. This report was prepared to characterize site, soil and groundwater conditions for project planning and preliminary design. The types, size and locations of specific structures or improvements have not yet been fully determined. As the project progresses, additional field exploration, engineering analysis and recommendations for design and construction may be needed. 2.0 PROJECT OVERVIEW 2.1 Site Description The subject property at 3005 NE 4th Street (Parcel 1434000012) is approximately 5 acres with dimensions on the order of 600 lineal feet, east to west, and 420 lineal feet, north to south. The property is relatively flat with approximately 5 feet of relief sloping downward from east to west. In addition, along the western property line, there is a steep downward slope to the adjacent property. Currently, offices, maintenance structures and other ancillary buildings are on the DNRP Central Maintenance Facility site. Portions of the site without structures are covered with asphalt pavement, gravel surfacing and landscaping. In addition to the subject property, negotiations are underway for an easement on the adjacent property to the north located at 3001 NE 4th Street (Parcel 1623059130). The easement will be along the west border of the property and is intended to provide access to utilities off NE 4th Street. The planned easement area is currently undeveloped, with a gentle east to west downward slope and covered with small trees, scrub brush and grasses. A site vicinity map is attached as Figure 1. 2.2 Planned Development Current plans are to demolish most of the existing structures and construct new facilities. The new office and maintenance buildings may be up to three stories in height. Shallow spread footing foundations are planned and foundation loads are anticipated to be relatively light. Preliminary plans indicate the new buildings will likely be located on the eastern half of the property. Covered and uncovered materials storage buildings, a sawmill shelter and, possibly, a retaining wall may be constructed along the west side of the property. Site areas Mailstop: RSD-TR-0100 I 155 Monroe Avenue NE, Bldg. D, Renton, WA 98056-4199 206-477-8100 I maint.roads@kingcounty.gov I www.kingcounty.gov/roads Job No. 1121161 -Preliminary Geotechnical Design Report King County DNRP Maintenance Facility, Renton, WA May 11, 2017 Page 2 of 14 where building construction is not planned will primarily be used for parking and landscaping, and stormwater retention and/or infiltration facilities are being considered. 2.3 Adjacent Properties For a distance of 150 feet beyond the site perimeter and proposed easement, natural and man-made features include the following: North Side: Renton Housing Authority Residential Property (Parcel 1623059120), AM PM Convenience Store and Gas Station (Parcel 1623059115) and the currently vacant King County Public Health Offices (Parcel 1623059130). Surfaces surrounding the occupied structures on these three properties include asphalt/concrete pavement and landscaped areas. In addition, a section of NE 3rd Street, a City of Renton roadway, is within the 150-foot zone. East Side: An asphalt paved access road (Parcel 1434000010) for other King County facilities in the area is directly adjacent to the planned DNRP Maintenance Facility. In addition, there is an approximate 50 foot deep depression that was previously used to mine sand and gravel (Parcel 1623059059). This parcel has an active City of Renton grading permit (No. B 16005811) and contains regulated steep slopes and a designated wetland area. South Side: The property to the south (Parcel 1434000020) is owned by King County and includes a gravel surfaced equipment storage area and other undeveloped property with natural vegetation. West Side: Commercial properties (Parcels 1623059144 and 1623059143) that include office and storage facilities, essentially surrounded by asphalt surfacing. The City of Renton has issued a preliminary building permit for Parcel 1623059144 to remove an existing building and add a new three-story building totaling approximately 58,350 square feet. 3.0 3.1 SURFACE AND SUBSURFACE CONDITIONS Geologic Reconnaissance and Mapping The project area is located in the Puget Lowland, bounded by the Olympic Mountains to the west, and the Cascade Mountains to the east, in the bluff area of the Renton Highlands north of the Cedar River Valley. The topography in the Puget Sound Basin was created by repeated glacial advancement and retreat, and postglacial processes. Review of the 1965 USGS Geologic Map of the Renton Quadrangle shows Recessional Stratified Drift as the single geologic unit within the project site boundaries and adjacent properties. On a geologic time scale, this unit originates from the Upper Pleistocene series of the Quaternary Period and is summarily described as follows: Recessional Stratified Drift (Qpa): Sandy pebble and cobble gravel in easternmost terraces, grades to interbedded sand and pebble gravel at Renton and to sand at north edge of quadrangle. Job No. 1121161 -Preliminary Geotechnica/ Design Report King County DNRP Maintenance Facility, Renton, WA May 11, 2017 Page 3 of 14 During our site reconnaissance, outwash gravels and sands were visible along the western property boundary slope and on the side-slopes of the inactive sand and gravel mining pit located east of the property. Based on the noted soil exposures, review of published literature and subsurface exploration, we anticipate outwash sands and gravels underlie the entire planned project area to a depth of 30 feet or more below the existing ground surface {bgs). 3.2 Subsurface Exploration Site-specific soil and groundwater conditions were explored on April 13, 2017 by completing a total of 6 geotechnical test borings. Holocene Drilling completed the borings using a Diedrich D-50 track-mounted drill rig by advancing 8-inch nominal outside diameter hollow- stem auger. Five of the borings were completed to a depth of 26.5 feet bgs in the existing DNRP Maintenance Complex (Parcel No. 1434000012) and one boring was completed to a depth of 16.5 feet bgs for the proposed utility easement to be located along the west side of the adjacent property to the north (Parcel No. 1623059130). Standard Penetration Tests (SPT) were performed at 2.5-foot intervals to a depth of 10-feet bgs and at 5.0-foot intervals thereafter to the boring termination depths. The SPT provides a measure of compaction or relative density of granular soils, and consistency or stiffness of cohesive fine-grained soils. Disturbed but representative soil samples were collected, when retrieved, at each SPT testing interval, and returned to our laboratory for further evaluation and testing. Soils classified during subsurface site exploration were generally consistent with those described by the referenced geologic mapping. A summary of the subsurface soil profile encountered during our investigation is provided below: 3.2.1 Borings B-1 through B-5 Soils encountered during drilling were generally consistent throughout the site. Gravel surfacing mixed with sand and silt in a medium dense to very dense state was encountered from the existing ground surface to depths of approximately 0.25 to 0.50 feet. Silty sand and mixtures of sand and gravel, interpreted as man-made fill, were encountered below the gravel surfacing to depths of about 2.5 to 5.0 feet bgs in Borings B-1, B-3, B-4 and B-5. Predominantly, the fill material was in a loose condition with respect to relative density. However, just below the gravel surfacing near the ground surface, the fill ranged from medium dense to very dense, likely due to compaction from traffic and periodic gravel surfacing maintenance. At Boring B-2 and below the fill from Borings B-1, B-3, B-4 and B-5, the soils predominantly consisted of medium dense mixed sands and gravels sandy gravels to depths ranging from about 15 to 22.5 feet bgs. The underlying soil horizon predominantly consisted of medium dense, poorly graded, fine to medium grained sands interspersed with varying amounts of gravel to the termination depth of our borings at 26.5 feet bgs. Job No. 1121161 -Preliminary Geotechnical Design Report King County DNRP Maintenance Facility, Renton, WA 3.2.2 Borin_g B-6 May 11, 2017 Page 4 of 14 A few inches of topsoil and organic material was encountered at the existing ground surface followed by loose, silty sand with gravel to a depth of 1.5 feet bgs. Loose to medium dense, fine to medium grained poorly graded sand with traces of gravel was encountered below the topsoil to a depth of about 6.5 feet bgs. The underlying soil consisted of medium dense to dense, poorly and well graded sands with varying gravel contents to the boring termination depth at 16.5 feet bgs. 3.2.3 Over-size Materials With the nominal 8-inch diameter hollow-stem auger, it is difficult to determine the percentage of cobbles and, potentially boulders, in the underlying soil deposits as minimal amounts are generally lifted by the auger flights and deposited on the ground surface as drilling spoils. However, cobbles were observed that will likely be encountered during construction, potentially with occasional small boulders. 3.3 Site Specific Boring Locations An aerial photograph of the site showing approximate boring locations is attached as Figure 2. Copies of the boring logs (Figures A-1 through A-6) and laboratory test results from select samples (Figures A-7 through A-12) are provided in Appendix A. Approximate GPS coordinates were obtained from the test boring locations at the time of drilling and are summarized below in Table 1. TABLE 1 Boring Number Coordinates GPS (Reporled Accuracy +16 Feet) 8-1 4 7.486442 °N 122.179930 °w 8-2 4 7.486380 °N 122.178830 °w 8-3 47.485957 °N 122.179120 °w 8-4 47.486526 °N 122.178215 °w 8-5 4 7.486525 °N 122.178989 °w 8-6 47.487170 °N 122.180187 °w 3.4 Previous Exploration Our records show two test pits were excavated to depths ranging from 4.5 to 5.5 feet during previous exploration of the DNRP Maintenance Complex property. In general, approximately 2 to 2.5 feet of medium dense to dense gravely sand fill overlies medium dense to dense native sand and gravel outwash soils, to the termination depth of the test pits. 3.5 Groundwater Soils encountered at the time of drilling were in a generally moist condition and no groundwater was encountered. City of Renton mapping designates the general northeast quadrant of the inactive sand and gravel mine to the east of the property as a wetland. At its closest point, mapping shows the wetland area about 250 feet from the northeast corner of the DNRP Maintenance Site property. During our site reconnaissance, standing water was Job No. 1121161-Preliminary Geotechnica/ Design Report King County DNRP Maintenance Facility, Renton, WA May 11, 2017 Page 5 of 14 observed in the designated wetland area approximately 45 feet in elevation below the DNRP Maintenance Facility Site. Review of boring logs from a previous geotechnical investigation performed for the King County Regional Communications and Emergency Coordination Center indicate perched groundwater was encountered at the interface of the outwash materials and underlying till, at depths ranging from 24 to 47 feet below the existing ground surface. This site lies approximately 2,500 feet to the southeast of the DNRP Maintenance Site. We reviewed the Washington State Department of Ecology interactive website for drill logs of any wells located within %~mile of the DNRP Maintenance Site. A total of 7 records were found, 3 for Resource Protection wells and 4 for decommissioned wells. Records indicate the wells ranged from 15 to 36 feet below the ground surface. One of the records for the Renton Highlands Landfill (Well Log 328114) indicated groundwater was at a depth of 11 feet bgs and another record for Nickelson Development (Well Log 328143) indicated a water sample was taken using a push-probe at a depth of 17 feet bgs. Groundwater identified by these two well logs is likely perched. The remaining well logs did not indicate the presence or depth of groundwater. 4.0 CRITICAL AREA IDENTIFICATION From a geotechnical perspective, typical activities associated with site development such as clearing and grading, utility placement, and building construction will have no adverse impacts on surrounding properties provided City of Renton and/or other regulatory requirements for design and construction are implemented. The City of Renton's Maps (COR), an online interactive mapping application, was reviewed to determine whether any designated Critical Areas are present at the project site (Parcel 1434000012) and proposed utility easement (Parcel 1623059130). Critical Areas identified as geologic hazards by the Renton Municipal Code (RMC) Section 4-3-050 include Steep Slopes, Landslides, Erosion, Seismic and Coal Mines. Based on the COR, geologic hazards for this site exist only along the west property boundary as Sensitive and Protected Slopes. In addition to geologic hazards, the entire property and planned easement area are identified by the COR as being within a Well Head Protection Area -Zone 1 Modified. A map showing the Critical Areas within the project boundaries is attached as Figure 3. We have not performed a slope stability analysis for the sensitive and protected slopes along the west side of the property. As the project develops, a stability analysis can be performed and recommendations provided, if needed, for improved slope stabilization, erosion protection or design of an earth retaining structure. 4.1 Sensitive Slopes Sensitive Slopes are defined by the City of Renton as a hillside, or potion thereof, having an average slope between 25 and 40 percent, an average slope greater than 40 percent with less than 15 foot vertical rise or property abutting a slope with an average slope between 25 to 40 percent. During construction, weekly on-site inspections and reports documenting adequate performance of erosion control measures are required. Generally, there is no critical area buffer or set-back required for Sensitive Slopes. Job No. 1121161-Preliminary Geotechnica/ Design Report King County DNRP Maintenance Facility, Renton, WA 4.2 Protected Slopes May 11, 2017 Page 6 of 14 A Protected Slope is defined as a hillside, or portion thereof, having an average slope of 40 percent or greater with a minimum 15-foot vertical rise. Development is prohibited on protected slopes, although there are provisions for potential exceptions addressed by Section 4-3-050, Subsection J of the Renton Municipal Code. A critical area buffer is typically not required for protected slopes; however, a minimum 15-foot structure set-back applies. In addition, weekly inspections and reports documenting effectiveness of erosion control measures are required. 4.3 Determination of Regulated Slope Locations The location of sensitive or protected slopes is determined from identification on the City of Renton's COR Maps. Survey data with 2-foot contour intervals or the standard utilized in the City of Renton Steep Slope Atlas may be submitted to the City of Renton for consideration in determining alternate sensitive or protected slope boundaries. COR Mapping shows the Sensitive and Protected slopes are along the south half of the western property boundary and the slope toe appears to terminate on the adjacent property to the west. At the steepest point of inclination, COR mapping along the western property line shows the slope to be about 1.35(H): 1 (V) with approximately 14 feet of vertical relief. 4.4 Wellhead Protection Area Zones The City of Renton designates different zones Wellhead Protection Area Zones to provide graduated groundwater protection levels. Zone 1 Modified encompasses the same land area as Zone 1, defined as being situated between a City-owned well or well field and the distance groundwater will travel over 365 days. The modification is intended to protect a high-priority well, well-field or spring withdrawing from a confined aquifer with some degree of leakage into overlying or underlying confining layers. The City may require a permit applicant to submit a hydrogeologic study if the proposed project has the potential to significantly impact groundwater quantity or quality, and sufficient information is not readily available. 5.0 ANALYSIS. CONCLUSIONS AND RECOMMENDATIONS The results of our analysis, conclusions and recommendations for geotechnical design and construction considerations is provided below. We understand the project is currently in the initial planning and preliminary design stages. Specific information as to the type, size and location of structures or other site improvements is not yet available. We should be consulted as project design progresses, and given the opportunity to review and, if needed, revise our recommendations accordingly. 5. 1 Temporary Erosion and Sedimentation Control Site development activities can significantly increase the potential for erosion and sedimentation transport as a result of vegetation removal, alteration of soil characteristics, and changes to topography and drainage. The degree of erosion and Job No. 1121161 -Preliminary Geotechnical Design Report King County DNRP Maintenance Facility, Renton, WA May 11, 2017 Page 7 of 14 sedimentation transport is highly dependent on soil types, slope gradient and concentration of surface water flows. The DNRP Maintenance site has minimal cross slope, is relatively flat and soils exposed during construction will generally consist of sandy gravels and gravelly sands. Under these conditions, runoff will be slow and the potential for erosion and sedimentation transport minimal. Therefore, standard Temporary Erosion and Sedimentation Control (TESC) construction best management practices (BMPs) will be effective in controlling erosion and preventing sediment transport to offsite drainage systems and adjacent properties. Depending on site development plans, typical TESC measures could include: • Establishing clearing limits and buffers; • Installation of silt fence, wattles and/or similar measures as a buffer or for perimeter protection; • Minimize the size and duration of exposed soil areas at any given time; • Cover and grade around stockpiles and exposed soil areas to minimize exposure to precipitation and control runoff; • Installation of a construction entrance/exit and stabilization of heavy traffic areas; • Control surface water run-off rates and direction of flow; • Install temporary sediment retention ponds or storage tanks and protect stormwater system inlets; and • Dust control. The civil engineer should prepare project specific TESC plans for submittal to the City of Renton. The TESC plan should consider seasonal wet weather construction periods and potential impacts to designated Critical Areas. In addition, permitting typically requires weekly inspections, monitoring discharge Nephelometric Turbidity Units (NTU) and periodic report submittals during construction. 5.2 Stormwater Infiltration As indicated previously, the site is underlain by outwash sands and gravels estimated to extend to a depth of at least 30 feet bgs. While on site for general reconnaissance and subsurface exploration, no standing water was observed on the ground surface. In addition, impermeable soil layers that would restrict infiltration were not encountered during our subsurface exploration and groundwater is expected to be 30 feet or more below the existing ground surface. In our opinion, the outwash sands and gravels would generally be well suited for stormwater infiltration. However, given that the site is in a Wellhead Protection Area, the City of Renton may require pre-treatment or have other restrictions controlling or preventing stormwater infiltration. If infiltration is deemed feasible with regard to regulatory constraints, additional field testing should be performed to determine in-situ infiltration rates. Job No. 1121161 -Preliminary Geotechnica/ Design Report King County DNRP Maintenance Facility, Renton, WA May 11, 2017 Page 8 of 14 5.3 Subgrades for Site Grading, Foundations, Building Pads and Pavements At finished subgrade elevations in cut areas and in areas scheduled to receive fill, the exposed ground surface should be cleared of all vegetation, topsoil, asphalt/concrete pavements and any other deleterious material. A representative from our office should be on site to verify the suitability of exposed soils and provide recommendations if unsuitable soil conditions are encountered and over-excavation is necessary. The exposed soil surface should be scarified to a minimum depth of 12-inches, processed into a homogeneous mixture and moisture conditioned to within ±. 2-percent of the optimum moisture content. The subgrade should be compacted to a minimum of95- percent of the maximum dry density as determined by the Washington State Department of Transportation Standard Specifications for Roads and Bridges (WSDOT) Section 2-03.3(14)0 and, when completed, should be in a firm and unyielding condition. Prepared subgrades should be evaluated and approved by a representative from our office prior to permanent covering. 5.4 Fill for Site Grading. Embankments, Building Pads and Paved Areas 5.4.1 Fill Materials Fill materials should meet the requirements for Select Borrow as defined by WSDOT Standard Specification (WSDOT) 9-03.14(3). The WSDOT standard Select Borrow gradation should be modified by reducing the maximum allowable particle size so that 100-percent of the material is finer than a 3-inch square sieve. It is anticipated some of the sandy gravels and gravelly sands encountered during our subsurface exploration will meet this requirement; however, variations of the soil profile should be expected and processing of excavated soils and/or blending with imported soil may be necessary. Due to an allowable silt and/or clay content of up to 10-percent, Select Borrow may not be suitable for fill during periods of wet weather and/or if the moisture content is in excess of optimum. Gravel Borrow meeting WSDOT 9-03.14(1) requirements should be used during wet weather periods if excess moisture prevents adequate compaction and/or a firm and unyielding surface condition from being achieved. As with Select Borrow, the WSDOT specified gradation for Gravel Borrow should be modified by reducing the maximum allowable particle size to 3-inches. Rather than reiterating when the use of Select Borrow or Gravel Borrow may be appropriate for specific grading applications, from hereinafter whenever Select Borrow is recommended, it is with the understanding that Gravel Borrow may be required depending on weather conditions, moisture content and the ability to compact soils to a firm and unyielding condition. 5.4.2 Fill/Backfill Moisture Content and Compaction Level Unless otherwise specified in this report, all fill and backfill should be placed in horizontal lifts with a maximum loose thickness of 8-inches. The fill or backfill material should be moisture conditioned as necessary to within ±. 2 percent of optimum moisture Job No. 1121161 -Preliminary Geotechnica/ Design Report King County DNRP Maintenance Facility, Renton, WA May 11, 2017 Page 9 of 14 and compacted to a minimum of 95 percent of the maximum dry density as determined by WSOOT 2-03.3(14)0. 5.4.3 Protection of Work Fill sections and cut sections excavated to subgrade elevations should be protected from damage by traffic, construction operations and environmental conditions during grading operations and until the final surfacing, structures or erosion protection is in- place. Permanent slopes of all newly constructed embankments should be graded at 2 Horizontal (H): 1 Vertical (V) or flatter and protected from erosion by controlling surface water runoff. For general erosion protection, topsoil and appropriate vegetation should be placed in landscaped areas or other areas not covered by structures or other surfacing materials. 5.5 Utility Construction Underground utilities can be supported on the granular native soils provided the trench bottom is free of organic material or debris, and compacted per Section 5.3.2 of this report. All utilities are to be bedded with Gravel Backfill for Pipe Zone Bedding meeting the requirements of WSOOT 9-03.12(3). The Gravel Backfill for Pipe Zone Bedding should extend a minimum of six inches above and below the utility and be compacted to at least 90 percent of the maximum dry density as determined by WSOOT 9-03.3(14)0. The remainder of the utility trench should be backfilled with Select Borrow placed and compacted per Section 5.3.2 of this report. Alternatively, native sands and gravels may be substituted for backfill provided they are at a moisture content and gradation acceptable to the engineer at the time of construction. 5.6 Excavation Safety The site soils are granular and subject to shallow sloughing. Therefore, the contractor must take special precautions to protect workers entering trench or footing excavations. Maintenance of a safe working environment, including shoring, is the responsibility of the contractor. Temporary trench excavations or vertical cuts greater than four feet in height must be in compliance with current Occupational Safety & Health Administration (OSHA) and Washington Administrative Code (WAC) requirements for excavating, trenching, and shoring. In general, we recommend the use of trench boxes to support utility trenches. Alternatively, the excavation can be cut back to a temporary slope no steeper than 1 %(H): t(V). However, depending on site conditions observed by the contractor, additional flattening of the temporary slope may be required. 5.7 Shallow Foundations Bearing Capacity The near surface medium dense sand and gravel soils will provide adequate support for the use of shallow foundations for retaining walls and buildings. However, loose silty sand and sandy gravel soils were encountered to a depth of up to 5.0 feet bgs in some of the Job No. 1121161-Preliminary Geotechnica/ Design Report King County DNRP Maintenance Facility, Renton, WA May 11, 2017 Page 10 of 14 borings. The loose soils were interpreted as man-made fill and are not considered suitable for foundation support in their present condition. A representative from our office should be on site during foundation excavation to evaluate exposed soil conditions and provide recommendations for over-excavation if loose soils are encountered at the design foundation bearing elevation. Loose soils should be removed by extending the excavation to the medium dense sands and gravels. The resulting void should be backfilled with Select Borrow placed and compacted as described in Section 5.3.2. Foundations should bear a minimum of 1.5 feet below the lowest adjacent grade. The native sand and gravel soils and Select Borrow backfill placed in any over-excavated areas would be relatively free-draining and not highly susceptible to frost action. However, foundations should be extended deeper than 1.5 feet if required by local building codes or other project specific reasons not related to allowable bearing capacity. For shallow foundations prepared as stated above, an allowable bearing capacity of 3,000 psf and coefficient of base friction of 0.40 can be assumed for design purposes. In addition, we recommend assuming a 1/3 increase in the allowable bearing capacity to account for transient loads associated with wind and seismic activity. We can perform additional exploration and/or analysis once building locations have been determined if an increase to the allowable bearing capacity is needed. 5.8 Shallow Foundation Settlement Provided foundations are prepared as recommended above, total settlement is estimated at 0.5 inches with differential settlement estimated at 0.25 inches for an allowable bearing capacity of 3,000 psf. Given the anticipated granular soil conditions, the majority of settlement will occur during construction immediately upon loading. 5.9 Alternate Foundation and Slab Bearing Surface Preparation Gravels and cobbles exposed after excavating to foundation or slab-on-grade subgrade elevations may result in an uneven or irregular bearing surface. If desired, the excavation could be extended approximately 4-inches and the resulting void backfilled with Crushed Surfacing Base Course (CSBC) to provide a smooth, plane bearing surface and improved control for final grading, setting of formwork and installation of reinforcing steel. CSBC should meet the requirements of WSDOT 9-03.9(3) and be placed and compacted as described by Section 5.3.2 of this report. 5.10 Seismic Design Considerations 5.10.1 Seismic Ground Motion Values Recommendations for seismic design values are based on procedures outlined in the 2015 International Building Code (IBC) for Risk Categories I, II and Ill. Site response parameters were obtained from the USGS Earthquake Hazards website with site coefficients established by interpolating values from IBC Tables 1613.3.3(1) and 1613.3.3(2). Latitude and longitude coordinates used to calculate site coefficients are 47.286318 and Job No. 1121161 -Preliminary Geotechnica/ Design Report King County DNRP Maintenance Facility, Renton, WA May 11, 2017 Page 11 of 14 -122.178896, respectively. Recommended values addressing IBC Sections 1613.3.1, 1613.3.2 and 1613.3.3 are provided in Table 2 below: TABLE 2 Site MCE Spectral Site Adjusted Spectral Design Spectral Class Response Response Acceleration (g) Coefficients Parameters Parameters Ss S1 Fa Fv Sms Sm1 Sos 801 (.2 sec) (1-sec) (.2 sec) (1-sec) (.2 sec) (1-sec) D 1.416 0.531 1.0 1.5 1.416 0.796 0.944 0.531 5.10.2 Seismic Hazard Areas Typically, high seismic hazard areas are those areas subject to severe risk of earthquake damage as a result of seismically induced soil liquefaction, sliding, or ground rupture. The Puget Lowland experiences between 1,000 and 2,000 earthquakes yearly. However, the vast majority of these earthquakes have magnitudes (M) of less than 3.0 and go unnoticed by the general population. Primary sources of earthquakes in the Puget Lowland include shallow, deep, and subduction-zone earthquakes. City of Renton online mapping indicates the project site is not within a designated Seismic Hazard Area. 5.10.3 Liquefaction Liquefaction occurs when loose saturated granular soils such as fine sand and coarser silts become fluid-like, losing their ability to support loads during a seismic event, resulting in ground settlement and deformation. Seismically induced liquefaction usually occurs in areas underlain by generally cohesionless soils of low density in conjunction with shallow groundwater. Since the project site is underlain by medium dense to dense sands and gravels, with relatively deep groundwater, the risk of liquefaction in our opinion is low. In addition, mapping by the Washington State Department of Natural Resources indicates the potential for liquefaction susceptibility to be very low. 5.10.4 Seismically Induced Landslides Areas most prone to seismically induced landslides would have steep slopes, shallow groundwater and soils prone to a rapid rise in porewater pressures. With the exception of the slope along the west property boundary, the DNRP Maintenance Facility site is generally flat and has unsaturated granular soils to an estimated depth of at least 30 feet. Based on topography and available subsurface information, the future risk of a seismically induced landslide at this site is considered to be low in our opinion. 5.10.5 Ground Rupture A significant number of active fault lines or cracks in the earth's crust have been identified by the USGS in the central Puget Sound area, including Seattle and King County. However, the closest major fault identified in the vicinity of the project area is the Seattle Fault that generally follows the 1-90 corridor. In addition, during our field reconnaissance, no evidence to indicate surface ground rupture has previously occurred at the site was observed. Job No. 1121161 -Preliminary Geotechnical Design Report King County DNRP Maintenance Facility, Renton, WA 8.0 REFERENCES City of Renton, COR Maps, http://rp.rentonwa.gov/SilverlightPublic/Viewer.html?Viewer=COR-Maps City of Renton Municipal Code, Section 4-3-050, Critical Areas Regulations, May 11, 2017 Page 13 of 14 http://www. codepu blish ing. com/W NRenton/html/Renton04/Renton0403/Renton0403050. ht ml City of Renton Municipal Code, Section 4-8-120, Submittal Requirements, Table 18, http://www. codepublish ing. com/W NRenton/html/Renton04/Renton0408/Renton0408120. ht ml International Code Council, 2015, International Building Code KCGIS Center (October 3, 2016); King County iMAP; Data Retrieved April 19, 2017; http://gismaps.kingcounty.gov/iMap/ King County Materials Laboratory, October 13, King County Renton Facility Short Plat- Geotechnical Investigation, Renton, Washington My NASA Data, Latitude Longitude Finder, September 9, 2016; https://mynasadata. I arc. nasa. gov/latitudelong itude-fi nder/ United States Department of the Interior, U.S. Geologic Survey, Geologic Map of the Renton Quadrangle, King County Washington, 1965, 1 :24,000 scale, Mullineaux, D.R. United States Department of the Interior, U.S. Geological Survey, USGS Earthquake Hazard Program, Derived in 2008 from USGS Hazard Data; https://earthquake.usgs.gov/designmaps/us/application.php Washington State Department of Natural Resources, 2016; Geologic Information Portal http://www.dnr.wa.gov/geologyportal Washington Division of Geology and Earth Resources, Open File Report 2015-05, Faults and Earthquakes in Washington State, 2014, Jessica L. Czajowski and Jeffrey D. Bowman, http://file.dnr.wa.gov/publications/ger ofr2014-05 fault earthquake map.pdf Washington Division of Geology and Earth Resources, Open File Report 2004-20, Liquefaction Susceptibility and Site Class Maps of Washington State, By County Map 17A -Liquefaction Susceptibility, Sheet 33 of 78, Stephen P. Palmer, et. Al, September, 2004, ftp://ww4.dnr.wa.gov/geology/pubs/ofr04-20/ofr2004- 20 sheet33 king liq.pdf Washington Division of Geology and Earth Resources, Open File Report 2004-20, Liquefaction Susceptibility and Site Class Maps of Washington State, By County Job No. 1121161 -Preliminary Geotechnical Design Report King County DNRP Maintenance Facility, Renton, WA May 11, 2017 Page 14 of 14 Map 178-King County NEHRP Site Class, Sheet 34 of 78, Stephen P. Palmer, et. Al, September, 2004, ftp://ww4.dnr.wa.gov/geology/pubs/ofr04-20/ofr2004- 20 sheet34 king nehrp.pdf Washington Division of Geology and Earth Resources, 2016, Surface Geology, 1 :24,000-- GIS data, November 2016: Washington Division of Geology and Earth Resources Digital Data Series DS-10, version 2.0, previously released June 2014, https://fortress.wa.gov/dnr/protectiongis/geology/?Theme=subsurf Washington State Department of Ecology, Well Log Viewer, https://fortress.wa.gov/ecy/waterresources/map/WCLSWebMap/WellConstructionMapSearc h.aspx Washington State Department of Transportation, 2016 Standard Specifications for Road, Bridge and Municipal Construction APPENDIX A Project No. 1121161 -Preliminary Geotechnical Design Report New King County DNRP Central Maintenance Facility 3005 NE 4th Street, Renton, Washington Boring Logs Figure A-1: Boring B-1 Figure A-2: Boring B-2 Figure A-3: Boring B-3 Figure A-4: Boring B-4 Figure A-5: Boring B-5 Figure A-6: Boring B-6 Boring Log Key to Symbols and Notes Laboratory Test Reports Figure A-7: B-1 @ 2.5 Feet Figure A-8: B-2 @ 5.0 Feet Figure A-9: B-3 @ 2.5 and 5.0 Feet Figure A-10: B-4@5.0 and 10.0 Feet Figure A-11: B-5@ 2.5 and 7.5 Feet Figure A-12: B-6@ 7.5 Feet Symbol Description Strata symbols FT] Ed ffl1l1 lliJillillillJ [SJ L2J Crushed Surfacing Well graded sand Silty sand Poorly graded sand Poorly graded gravel Misc. Symbols T Boring terminated Soil Samplers KEY TO SYMBOLS ~ Standard penetration test Notes: 1. Exploratory borings were drilled on April 13, 2017 using nominal 8-inch O.D. continuous flight hollow stem auger. 2. A Mobile D-50 track-mounted drill rig was used to advance the auger. 3. SPT Tests were performed with an automatic trip hammer. 4. Where soil classifications changed between sampling intervals, the location of the change noted on the boring logs was interpolated. KING COUNTY MATERIALS LABORATORY GEOTECHNICAL BORING LOGS KING COUNTY DNRP MAINTENANCE FACILITY, RENTON, WASHINGTON Particle Size Distribution Report U.S. SIEVE OPENING IN INCHES U.S. STANDARD SIEVE NUMBERS HYDROMETER 1Y2 in. % in. 3/8 in. #140 6 in. 3 in. 2 in. 1 in. ~ Y2 in. #4 #10 #20 #30 #40 #60 #100 #200 100 I I I I r~11 I I I I I I I 90 80 '\ ~ 70 \ f\ a: 60 r\. w \ z u::: \. f-50 z 't~ w 0 a: w 40 Cl. " '- 30 r-... .... , 'c ......... I'-<'\ 20 -,_ " 10 0 100 10 1 0.1 0.01 0.001 GRAIN SIZE -mm. 0/o +3" % Gravel %Sand % Fines Coarse Fine Coarse Medium Fine Silt Clay 0 0.0 0.0 31.7 20.6 23.8 5.7 18.2 Source Sample# Depth/Elev. Date Sampled uses Material Description NM% LL PL 0 B-1 KC-17-318 2.5' to 4.0' 4-13-2017 SM Silty Sand with Gravel 4.1 Client KING Countv DNRP KING COUNTY Project DNRP Maintenance Facility-Renton Project No. 1122161 I Fiaure A-7 MATERIALS LABORATORY Particle Size Distribution Report U.S. SIEVE OPENING IN INCHES U.S. STANDARD SIEVE NUMBERS HYDROMETER 1% in. %in. 3/8 in. #140 6 in. 3 in. 2 in. 1 ·. Y2 in. #4 #10 #20 #30 #40 #60 #100 #200 100 I II I \I I I I I I I I I I 90 1 80 ~ \ 70 \ a: 60 LU " z u: ' I-50 z ' LU 0 \ a: LU 40 0... '\ 30 ' ~ ' 20 "-... ~ ~ !'-,~ i-,... ._,._ 10 -, ~ ~--'-' 0 100 10 1 0.1 0.01 . 0.001 GRAIN SIZE -mm. 0/o +3" % Gravel % Sand % Fines Coarse Fine Coarse Medium Fine Silt Clay 0 0.0 15.1 45.7 16.1 12.5 5.4 5.2 Source Sample# Depth/Elev. Date Sampled uses Material Description NM% LL PL 0 B-2 KC-17-319 5.0' to 6.5' 4-13-2017 GP-GM Poorlv Graded Gravel with Silt and Sand 2.3 Client KING Countv DNRP KING COUNTY Project DNRP Maintenance Facility -Renton Project No. 1122161 I Fiqure A-8 MATERIALS LABORATORY Particle Size Distribution Report U.S. SIEVE OPENING IN INCHES U.S. STANDARD SIEVE NUMBERS HYDROMETER 1% in. %in. 3/8 in. #140 6 in. 3 in. 2 in. ~ 1 ·. Y2 in. #4 #10 #20 #30 #40 #60 #100 #200 100 I I r\ JII I II I I I I I I I 90 ~f 80 ~ \ \ 70 ~~ h a: 60 >--r,,..11.. w ~ z ', u::: .... I-50 '-.... z ', } w () ' ~ a: w 40 CL ~, ::: -30 ', ...... "'C .......... ' .......... r-o....,_ 20 ' ~ ~ i-.,~ ~ 10 " -~ 0 100 10 1 0.1 0.01 0.001 GRAIN SIZE -mm. o/o +3" % Gravel % Sand % Fines Coarse Fine Coarse Medium Fine Silt Clay 0 0.0 15.0 36.4 10.8 17.4 14.8 5.6 D 0.0 37.1 19.2 6.9 9.9 13.0 13.9 Source Sample# Depth/Elev. Date Sampled uses Material Description NM% LL PL 0 B-3 KC-17-320 2.5' to 4.0' 4-13-2017 GP-GM Poorlv Graded Gravel with Silt and Sand 5.1 D B-3 KC-17-321 5.0' to 6.5' 4-13-2017 GM Siltv Gravel with Sand 9.3 Client KING Countv DNRP KING COUNTY Project DNRP Maintenance Facility-Renton Project No. 1122161 I Fiaure A-9 MATERIALS LABORATORY Particle Size Distribution Report U.S. SIEVE OPENING IN INCHES U.S. STANDARD SIEVE NUMBERS HYDROMETER 1% in. %in. 3/8 in. #140 6 in. 3 in. 2 in. -1 ·. Y2 in. #4 #10 #20 #30 #40 #60 #100 #200 100 I I IT ~ ~I I I I I I I I I I 90 ' 80 t\ 70 \~ h "-"r,.. cc 60 r\ w \ ", z u:: ~ I-50 z ........ w ~ ~ () n ' cc ' w 40 a.. ' "'' ~ 30 \ '"' ~"'" ', 20 ....... "1 I\ :i........_ \: 10 c-... ......... .... _ --i:= ""'rl.... -~ 0 ~ 100 10 1 0.1 0.01 0.001 GRAIN SIZE -mm. %+3" % Gravel % Sand % Fines Coarse Fine Coarse Medium Fine Silt Clay 0 0.0 16.3 30.6 9.4 32.1 8.5 3.1 D 0.0 13.0 62.2 10.4 8.5 3.4 2.5 Source Sample# Depth/Elev. Date Sampled uses Material Description NM% LL PL 0 B-4 KC-17-322 5.0' to 6.5' 4-13-2017 SP Poorly Graded Sand with Gravel 3.2 D B-4 KC-17-323 10.0' to 11.5' 4-13-2017 GW Well-Graded Gravel with Sand 2.1 Client KING County DNRP KING COUNTY Project DNRP Maintenance Facility -Renton Project No. 1122161 I Fiqure A-10 MATERIALS LABORATORY Particle Size Distribution Report U.S. SIEVE OPENING IN INCHES U.S. STANDARD SIEVE NUMBERS HYDROMETER 1%in. %in. 3/8 in. #140 6 in. 3 in. 2 in. ~ 1 in. %in. #4 #10 #20 #30 #40 #60 #100 #200 100 I I T",, ~ l~l I I I I I I I 90 ' ' 80 ~ \. \ ~ 70 \h \ i\ a: 60 "' w '\1 z ~ u:: n I-' z 50 ~i\ "'~ w () a: w 40 a.. 'f=\ "r-. .... , 'r 30 l'I.. ...... .......... "-ti ~ ...._.. 20 "" ........... ..... ~ .. -~ -...... 10 '-...._ ...,,_ --,_ ~-0 100 10 1 0.1 0.01 0.001 GRAIN SIZE -mm. 0/o +3" % Gravel % Sand % Fines Coarse Fine Coarse Medium Fine Silt Clay 0 0.0 0.0 29.9 18.2 20.7 16.6 14.6 D 0.0 15.0 49.2 14.2 12.8 4.7 4.1 Source Sample# Depth/Elev. Date Sampled uses Material Description NM% LL PL 0 B-5 KC-17-324 2.5' to 4.0' 4-13-2017 SM Silty Sand with Gravel 7.7 D B-5 KC-17-325 7.5' to 9.0' 4-13-2017 GW Well-Graded Gravel with Sand 2.9 Client KING County DNRP KING COUNTY Project DNRP Maintenance Facility-Renton Project No. 1122161 I Fiqure A-11 MATERIALS LABORATORY Particle Size Distribution Report U.S. SIEVE OPENING IN INCHES U.S. STANDARD SIEVE NUMBERS HYDROMETER 1% in. %in. 3/8 in. #140 6 in. 3 in. 2 in. -1 in. Y2 in. #4 #10 #20 #30 #40 #60 #100 #200 100 I I i\ I I I I I I I I I 90 \ 80 ~ i-. ... 70 Joo, ..._ ~~ a: 60 ill "'~ z u: I-50 L z '-< ill \ 0 a: \ ill 40 0... \ 30 t 20 ~ " 10 ~ ~ ..... -~ 0 100 10 1 0.1 0.01 0.001 GRAIN SIZE -mm. 0/o +3" % Gravel %Sand % Fines Coarse Fine Coarse Medium Fine Silt Clay 0 0.0 20.8 9.9 5.3 37.8 20.8 5.4 Source Sample# Depth/Elev. Date Sampled uses Material Description NM% LL PL 0 B-6 KC-17-326 7.5' to 9.0' 4-13-2017 SP-SM Poorlv Graded Sand with Silt and Gravel 6.1 Client KING Countv DNRP KING COUNTY Project DNRP Maintenance Facility -Renton Project No. 1122161 I Fiaure A-12 MATERIALS LABORATORY 1 APPENDIX F Report Limitations and Guidance for Use ASPECT CONSULTING REPORT LIMITATIONS AND GUIDELINES FOR USE This Report and Project-Specific Factors Aspect Consulting, LLC (Aspect) considered a number of unique, project-specific factors when establishing the Scope of Work for this project and report. You should not rely on this report if it was: •Not prepared for you •Not prepared for the specific purpose identified in the Agreement •Not prepared for the specific real property assessed •Completed before important changes occurred concerning the subjectproperty, project or governmental regulatory actions Geoscience Interpretations The geoscience practices (geotechnical engineering, geology, and environmental science) require interpretation of spatial information that can make them less exact than other engineering and natural science disciplines. It is important to recognize this limitation in evaluating the content of the report. If you are unclear how these "Report Limitations and Use Guidelines" apply to your project or site, you should contact Aspect. Reliance Conditions for Third Parties This report was prepared for the exclusive use of the Client. No other party may rely on the product of our services unless we agree in advance to such reliance in writing. This is to provide our firm with reasonable protection against liability claims by third parties with whom there would otherwise be no contractual limitations. Within the limitations of scope, schedule, and budget, our services have been executed in accordance with our Agreement with the Client and recognized geoscience practices in the same locality and involving similar conditions at the time this report was prepared. Property Conditions Change Over Time This report is based on conditions that existed at the time the study was performed. The findings and conclusions of this report may be affected by the passage of time, by events such as a change in property use or occupancy, or by natural events, such as floods, earthquakes, slope instability, or groundwater fluctuations. If any of the described events may have occurred following the issuance of the report, you should contact Aspect so that we may evaluate whether changed conditions affect the continued reliability or applicability of our conclusions and recommendations. ASPECT CONSULTING Discipline-Specific Reports Are Not Interchangeable The equipment, techniques, and personnel used to perform a geotechnical or geologic study differ significantly from those used to perform an environmental study and vice versa. For that reason, a geotechnical engineering or geologic report does not usually address any environmental findings, conclusions, or recommendations (e.g., about the likelihood of encountering underground storage tanks or regulated contaminants). Similarly, environmental reports are not used to address geotechnical or geologic concerns regarding the subject property. We appreciate the opportunity to perform these services. If you have any questions, please contact the Aspect Project Manager for this project. Stormwater Technical Information Report King County Parks – Renton Shop Central Maintenance Facility Replacement Project June 16, 2021 | F-1 Appendix F. Site Improvement Drawings (submitted separately) Stormwater Technical Information Report King County Parks – Renton Shop Central Maintenance Facility Replacement Project June 16, 2021 | F-3 Appendix G. O&M Requirement Cut Sheets for Proposed Stormwater Control Facilities APPENDIX A MAINTENANCE REQUIREMENTS FOR STORMWATER FACILITIES AND ON-SITE BMPS 12/12/2016 2017 City of Renton Surface Water Design Manual A-4 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 City personnel or the public. Noxious and nuisance vegetation removed according to applicable regulations. No danger of noxious vegetation where City 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. Excessive growth of 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. APPENDIX A MAINTENANCE REQUIREMENTS FOR STORMWATER FACILITIES AND ON-SITE BMPS 2017 City of Renton Surface Water Design Manual 12/12/2016 A-5 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 inlet/outlet pipe 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 (if applicable) 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 rock filter 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. APPENDIX A MAINTENANCE REQUIREMENTS FOR STORMWATER FACILITIES AND ON-SITE BMPS 12/12/2016 2017 City of Renton Surface Water Design Manual A-6 NO. 3 – DETENTION TANKS AND VAULTS 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 City personnel or the public. Noxious and nuisance vegetation removed according to applicable regulations. No danger of noxious vegetation where City 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. Excessive growth of grass/groundcover Grass or groundcover exceeds 18 inches in height. Grass or groundcover mowed to a height no greater than 6 inches. Tank or Vault Storage Area Trash and debris Any trash and debris accumulated in vault or tank (includes floatables and non-floatables). No trash or debris in vault. Sediment accumulation Accumulated sediment depth exceeds 10% of the diameter of the storage area for ½ length of storage vault or any point depth exceeds 15% of diameter. Example: 72-inch storage tank would require cleaning when sediment reaches depth of 7 inches for more than ½ length of tank. All sediment removed from storage area. 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. 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. 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 inlet/outlet pipes 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. APPENDIX A MAINTENANCE REQUIREMENTS FOR STORMWATER FACILITIES AND ON-SITE BMPS 2017 City of Renton Surface Water Design Manual 12/12/2016 A-7 NO. 3 – DETENTION TANKS AND VAULTS MAINTENANCE COMPONENT DEFECT OR PROBLEM CONDITIONS WHEN MAINTENANCE IS NEEDED RESULTS EXPECTED WHEN MAINTENANCE IS PERFORMED Access Manhole (cont.) 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. APPENDIX A MAINTENANCE REQUIREMENTS FOR STORMWATER FACILITIES AND ON-SITE BMPS 12/12/2016 2017 City of Renton Surface Water Design Manual A-8 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 accumulation 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 Damaged FROP-T 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. APPENDIX A MAINTENANCE REQUIREMENTS FOR STORMWATER FACILITIES AND ON-SITE BMPS 2017 City of Renton Surface Water Design Manual 12/12/2016 A-9 NO. 4 – CONTROL STRUCTURE/FLOW RESTRICTOR MAINTENANCE COMPONENT DEFECT OR PROBLEM CONDITION WHEN MAINTENANCE IS NEEDED RESULTS EXPECTED WHEN MAINTENANCE IS PERFORMED FROP-T Section (cont.) Damaged FROP-T (cont.) 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. Cleanout Gate Damaged or missing cleanout gate 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 orifice plate 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 to orifice plate Any trash, debris, sediment, or vegetation blocking the plate. Plate is free of all obstructions and works as designed. Overflow Pipe Obstructions to overflow pipe 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 of overflow pipe 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 inlet/outlet pipe 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 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. APPENDIX A MAINTENANCE REQUIREMENTS FOR STORMWATER FACILITIES AND ON-SITE BMPS 12/12/2016 2017 City of Renton Surface Water Design Manual A-10 NO. 5 – CATCH BASINS AND MANHOLES MAINTENANCE COMPONENT DEFECT OR PROBLEM CONDITION WHEN MAINTENANCE IS NEEDED RESULTS EXPECTED WHEN MAINTENANCE IS PERFORMED Structure Sediment accumulation 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. APPENDIX A MAINTENANCE REQUIREMENTS FOR STORMWATER FACILITIES AND ON-SITE BMPS 2017 City of Renton Surface Water Design Manual 12/12/2016 A-11 NO. 5 – CATCH BASINS AND MANHOLES MAINTENANCE COMPONENT DEFECT OR PROBLEM CONDITION WHEN MAINTENANCE IS NEEDED RESULTS EXPECTED WHEN MAINTENANCE IS PERFORMED Inlet/Outlet Pipe (cont.) Damaged inlet/outlet pipe 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 (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 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. APPENDIX A MAINTENANCE REQUIREMENTS FOR STORMWATER FACILITIES AND ON-SITE BMPS 12/12/2016 2017 City of Renton Surface Water Design Manual A-12 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/root growth in pipe 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 pipes 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 City personnel or the public. Noxious and nuisance vegetation removed according to applicable regulations. No danger of noxious vegetation where City 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. Excessive vegetation growth 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. APPENDIX A MAINTENANCE REQUIREMENTS FOR STORMWATER FACILITIES AND ON-SITE BMPS 2017 City of Renton Surface Water Design Manual 12/12/2016 A-13 NO. 7 – DEBRIS BARRIERS (E.G., TRASH RACKS) MAINTENANCE COMPONENT DEFECT OR PROBLEM CONDITION WHEN MAINTENANCE IS NEEDED RESULTS EXPECTED WHEN MAINTENANCE IS PERFORMED. Site Trash and debris Trash or debris plugging more than 20% of the area of the barrier. Barrier clear to receive capacity flow. Sediment accumulation Sediment accumulation of greater than 20% of the area of the barrier Barrier clear to receive capacity flow. Structure Cracked, broken, or loose pipe or structure Structure which bars attached to is damaged – pipe is loose or cracked or concrete structure is cracked, broken, or loose. Structure barrier attached to is sound. Bars Incorrect bar spacing Bar spacing exceeds 6 inches. Bars have at most 6 inches spacing. Damaged or missing bars Bars are bent out of shape more than 3 inches. Bars in place with no bends more than ¾ inch. Bars are missing or entire barrier missing. Bars in place according to design. Bars are loose and rust is causing 50% deterioration to any part of barrier. Repair or replace barrier to design standards. APPENDIX A MAINTENANCE REQUIREMENTS FOR STORMWATER FACILITIES AND ON-SITE BMPS 12/12/2016 2017 City of Renton Surface Water Design Manual A-24 NO. 17 – WETVAULT MAINTENANCE COMPONENT DEFECT OR PROBLEM CONDITION WHEN MAINTENANCE IS NEEDED RESULTS EXPECTED WHEN MAINTENANCE IS PERFORMED Site Trash and debris Trash and debris accumulated on facility site. Trash and debris removed from facility site. Treatment Area Trash and debris Any trash and debris accumulated in vault (includes floatables and non-floatables). No trash or debris in vault. Sediment accumulation Sediment accumulation in vault bottom exceeds the depth of the sediment zone plus 6 inches. No sediment in vault. 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. 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, vault does not retain water or qualified inspection personnel determines that the vault is not structurally sound. Vault is sealed and structurally sound. Baffles damaged Baffles corroding, cracking, warping and/or showing signs of failure or baffle cannot be removed. Repair or replace baffles or walls to specifications. Ventilation area blocked/plugged Ventilation area blocked or plugged. No reduction of ventilation area exists. 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 inlet/outlet pipe 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. Gravity Drain Inoperable valve Valve will not open and close. Valve opens and closes normally. Valve won’t seal Valve does not seal completely. Valve completely seals closed. Access Manhole Access cover/lid damaged or difficult to open Access cover/lid cannot be easily opened by one person. Corrosion/deformation of cover/lid. Access cover/lid can be opened by one person. 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. Access doors/plate has 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. Ladder rungs unsafe Missing rungs, misalignment, rust, or cracks. Ladder meets design standards. Allows maintenance person safe access. APPENDIX A MAINTENANCE REQUIREMENTS FOR STORMWATER FACILITIES AND ON-SITE BMPS 2017 City of Renton Surface Water Design Manual 12/12/2016 A-31 NO. 21 – PROPRIETARY FACILITY CARTRIDGE FILTER SYSTEMS MAINTENANCE COMPONENT DEFECT OR PROBLEM CONDITION WHEN MAINTENANCE IS NEEDED RESULTS EXPECTED WHEN MAINTENANCE IS PERFORMED In addition to the specific maintenance criteria provided below, all manufacturers’ requirements shall be followed. Facility Documentation Update facility inspection record after each inspection. Maintenance records are up to date. Provide certification of replaced filter media. Filter media is certified to meet manufacturer specifications. Site Trash and debris Any trash or debris which impairs the function of the facility. Trash and debris removed from facility. Contaminants and pollution Any evidence of contaminants or pollution such as oils, 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. Life cycle Once per year. Facility is re-inspected and any needed maintenance performed. Vault Treatment Area Sediment on vault floor Varies – Refer to manufacturer’s requirements. Vault is free of sediment. Sediment on top of cartridges Varies – Refer to manufacturer’s requirements. Vault is free of sediment. Multiple scum lines above top of cartridges Thick or multiple scum lines above top of cartridges. Probably due to plugged canisters or underdrain manifold. Cause of plugging corrected, canisters replaced if necessary. Vault Structure Damage to wall, frame, bottom, and/or top slab Cracks wider than ½-inch and any evidence of soil particles entering the structure through the cracks, or qualified inspection personnel determines the vault is not structurally sound. Vault replaced or repaired to design specifications. Baffles damaged Baffles corroding, cracking warping, and/or showing signs of failure as determined by maintenance/inspection person. Repair or replace baffles to specification. Filter Media Standing water in vault Varies – Refer to manufacturer’s requirements. No standing water in vault 24 hours after a rain event. Short circuiting Flows do not properly enter filter cartridges. Flows go through filter media. Underdrains and Clean-Outs Sediment and debris Underdrains or clean-outs partially plugged or filled with sediment and/or debris. Underdrains and clean-outs free of sediment and debris. 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 inlet/outlet pipe 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. APPENDIX A MAINTENANCE REQUIREMENTS FOR STORMWATER FACILITIES AND ON-SITE BMPS 2017 City of Renton Surface Water Design Manual 12/12/2016 A-35 NO. 23 – COALESCING PLATE OIL/WATER SEPARATOR MAINTENANCE COMPONENT DEFECT CONDITION WHEN MAINTENANCE IS NEEDED RESULTS EXPECTED WHEN MAINTENANCE IS PERFORMED Site Trash and debris Any trash or debris which impairs the function of the facility. Trash and debris removed from facility. Contaminants and pollution Floating oil in excess of 1 inch in first chamber, any oil in other chambers or other contaminants of any type in any chamber. No contaminants present other than a surface oil film. Vault Treatment Area Sediment accumulation in the forebay Sediment accumulation of 6 inches or greater in the forebay. No sediment in the forebay. Discharge water not clear Inspection of discharge water shows obvious signs of poor water quality – effluent discharge from vault shows thick visible sheen. Repair function of plates so effluent is clear. Trash or debris accumulation Trash and debris accumulation in vault (floatables and non-floatables). Trash and debris removed from vault. Oil accumulation Oil accumulation that exceeds 1 inch at the water surface in the in the coalescing plate chamber. No visible oil depth on water and coalescing plates clear of oil. Coalescing Plates Damaged Plate media broken, deformed, cracked and/or showing signs of failure. Replace that portion of media pack or entire plate pack depending on severity of failure. Sediment accumulation Any sediment accumulation which interferes with the operation of the coalescing plates. No sediment accumulation interfering with the coalescing plates. Vault Structure Damage to wall, frame, bottom, and/or top slab Cracks wider than ½-inch and any evidence of soil particles entering the structure through the cracks, or maintenance inspection personnel determines that the vault is not structurally sound. Vault replaced or repaired to design specifications. Baffles damaged Baffles corroding, cracking, warping and/or showing signs of failure as determined by maintenance/inspection person. Repair or replace baffles to specifications. Ventilation Pipes Plugged ventilation pipes Any obstruction to the ventilation pipes. Ventilation pipes are clear. Shutoff Valve Damaged or inoperable shutoff valve Shutoff valve cannot be opened or closed. Shutoff valve operates normally. 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 inlet/outlet pipe 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. APPENDIX A MAINTENANCE REQUIREMENTS FOR STORMWATER FACILITIES AND ON-SITE BMPS 12/12/2016 2017 City of Renton Surface Water Design Manual A-36 NO. 23 – COALESCING PLATE OIL/WATER SEPARATOR MAINTENANCE COMPONENT DEFECT CONDITION WHEN MAINTENANCE IS NEEDED RESULTS EXPECTED WHEN MAINTENANCE IS PERFORMED Access Manhole (cont.) 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 and cover 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. APPENDIX A MAINTENANCE REQUIREMENTS FOR STORMWATER FACILITIES AND ON-SITE BMPS 2017 City of Renton Surface Water Design Manual 12/12/2016 A-39 NO. 27 – GRAVEL FILLED DISPERSION TRENCH BMP MAINTENANCE COMPONENT DEFECT OR PROBLEM CONDITIONS WHEN MAINTENANCE IS NEEDED RESULTS EXPECTED WHEN MAINTENANCE IS PERFORMED Preventive Blocking, obstructions Debris or trash limiting flow to dispersion trench or preventing spreader function. Dispersion trench able to receive full flow prior to and during wet season. Site Trash and debris Trash or debris that could end up in the dispersion trench is evident. No trash or debris that could get into the dispersion trench can be found. Pipes Plugged inlet The entrance to the pipe is restricted due to sediment, trash, or debris. The entrance to the pipe is not restricted. Vegetation/root growth in pipes Vegetation/roots that reduce free movement of water through pipes. Water flows freely through pipes. Plugged pipe Sediment or other material prevents free flow of water through the pipe. Water flows freely through pipes. Broken pipe or joint leaks. Damage to the pipe or pipe joints allowing water to seep out. Pipe does not allow water to exit other than at the outlet to the trench. Broken or missing cleanout caps Cleanout caps are broken, missing, or buried. Cleanout caps are accessible and intact. Structure Flow not reaching trench Flows are not getting into the trench as designed. Water enters and exits trench as designed. Perforated pipe plugged Flow not able to enter or properly exit from perforated pipe. Water freely enters and exits perforated pipe. Flow not spreading evenly at outlet of trench Outlet flows channelizing or not spreading evenly from trench. Sheet flow occurs at the outlet of the trench. Cleanout/inspection access does not allow cleaning or inspection of perforated pipe The cleanout/inspection access is not available. Cleanout/inspection access is available. Filter Media Plugged filter media Filter media plugged. Flow through filter media is normal. APPENDIX A MAINTENANCE REQUIREMENTS FOR STORMWATER FACILITIES AND ON-SITE BMPS 12/12/2016 2017 City of Renton Surface Water Design Manual A-42 NO. 31 – BIORETENTION BMP MAINTENANCE COMPONENT DEFECT OR PROBLEM CONDITIONS WHEN MAINTENANCE IS NEEDED RESULTS EXPECTED WHEN MAINTENANCE IS PERFORMED Preventive Vegetation Vegetation to be watered and pruned as needed and mulch applied to a minimum of 2 inches to maintain healthy growth. Healthy vegetation growth with full coverage as designed. Bioretention Area Trash and debris Trash and debris in the bioretention area; leaf drop in the fall season. No trash or debris In the bioretention area. Sediment accumulation Sediment accumulation in the bioretention area interfering with infiltration. Water in the bioretention infiltrates as designed. Excessive ponding Standing water in the bioretention area for more than two days. Standing water infiltrates at the desired rate. Inflow restricted Inflow not getting into bioretention; debris/sediment blockage at inlet features; native soil is exposed or other signs of erosion damage is present. Unobstructed and properly routed inflow into bioretention area; inlet is stabilized and appropriately armored. Overflow not controlling excess water Overflow water not controlled by outlet features; native soil is exposed or other signs of erosion damage is present. Outlet features control overflow; overflow is stabilized and appropriately armored. Underdrain not freely flowing Underdrain is not flowing when bioretention area has been infiltrating water. Underdrain flows freely when water is present. Vegetation Poor vegetation coverage Plants not thriving across at least 80% of the entire design vegetated area within the BMP; overly dense vegetation requiring pruning. Healthy water tolerant plants in bioretention area, plants thriving across at least 80% of the entire design vegetated area within the facility. Insufficient vegetation Plants not water tolerant species. Plants are water tolerant. Weeds present Weeds growing in bioretention area. No weeds in bioretention area. Watering not occurring Planting schedule requires frequent watering (approx. weekly Year 1, bimonthly Years 2 and 3) for new facilities, and as needed for established plantings or dry periods Plants are established and thriving Pest control Signs of pests, such as wilting or chewed leaves or bark, spotting or other indicators; extended ponding period encouraging mosquitoes Plant community is pest-free when following an approved Integrated Pest Management plan; bioretention functioning normally and ponding controlled as needed for pest control Containment Berm and Earthen Slopes Erosion Erosion occurring at earthen slopes or containment berm side slope. Erosion on the containment berm and side slopes has been repaired and the cause of the erosion corrected. Voids created by nuisance animals (e.g., rodents) or tree roots Voids affecting berm integrity or creating leaky pond condition Voids have been repaired; facility is free of nuisance animals following an approved Integrated Pest Management plan. Settlement Any part of the containment berm top has less than 6 inches of freeboard from the maximum pond level to the top of the berm. A minimum of 6 inches freeboard from the maximum pond level to the top of the berm. Amended Soil Poor soil nutrients Soil not providing plant nutrients. Soil providing plant nutrients. Bare spots Bare spots on soil in bioretention area. No bare spots, bioretention area covered with vegetation or mulch mixed into the underlying soil. Compaction Poor infiltration due to soil compaction in the bioretention area. No soil compaction in the bioretention area. APPENDIX A MAINTENANCE REQUIREMENTS FOR STORMWATER FACILITIES AND ON-SITE BMPS 2017 City of Renton Surface Water Design Manual 12/12/2016 A-43 NO. 32 – RAINWATER HARVESTING BMP MAINTENANCE COMPONENT DEFECT OR PROBLEM CONDITIONS WHEN MAINTENANCE IS NEEDED RESULTS EXPECTED WHEN MAINTENANCE IS PERFORMED Preventive Insufficient storage volume No rain water in storage unit at the beginning of the rain season. Maximum storage available at the beginning of the rain season (Oct. 1). Collection Area Trash and debris Trash of debris on collection area may plug filter system Collection area clear of trash and debris. Filter Restricted or plugged filter Filter is partially or fully plugged preventing water from getting in to the storage unit. Filter is allowing collection water into storage unit. NO. 33 – ROCK PAD BMP MAINTENANCE COMPONENT DEFECT OR PROBLEM CONDITIONS WHEN MAINTENANCE IS NEEDED RESULTS EXPECTED WHEN MAINTENANCE IS PERFORMED Site Trash and debris Trash and debris accumulated on rock pad site. Rock pad site free of any trash or debris. Rock Pad Area Insufficient rock pad size Rock pad is not 2 feet by 3 feet by 6 inches thick or as designed. Rock pad is 2 feet by 3 feet by 6 inches thick or as designed. Vegetation growth Vegetation is seen growing in or through rock pad. No vegetation within rock pad area. Rock Exposed soil Soil can be seen through the rock pad. Full thickness of the rock pad is in place, no soil visible through rock pad. NO. 34 – SHEET FLOW BMP MAINTENANCE COMPONENT DEFECT OR PROBLEM CONDITIONS WHEN MAINTENANCE IS NEEDED RESULTS EXPECTED WHEN MAINTENANCE IS PERFORMED Site Trash and debris Trash and debris accumulated on the sheet flow site. Sheet flow site free of any trash or debris. Sheet flow area Erosion Soil erosion occurring in sheet flow zone. Soil erosion is not occurring and rills and channels have been repaired. Concentrated flow Sheet flow is not occurring in the sheet flow zone. Sheet flow area is regraded to provide sheet flow. NO. 35 – SPLASH BLOCK BMP MAINTENANCE COMPONENT DEFECT OR PROBLEM CONDITIONS WHEN MAINTENANCE IS NEEDED RESULTS EXPECTED WHEN MAINTENANCE IS PERFORMED Site Trash and debris Trash and debris accumulated on the splash block. Splash block site free of any trash or debris. Splash Block Dislodged splash block Splash block moved from outlet of downspout. Splash block correctly positioned to catch discharge from downspout. Channeling Water coming off the splash block causing erosion. No erosion occurs from the splash block. Downspout water misdirected Water coming from the downspout is not discharging to the dispersal area. Water is discharging normally to the dispersal area. APPENDIX A MAINTENANCE REQUIREMENTS FOR STORMWATER FACILITIES AND ON-SITE BMPS 2017 City of Renton Surface Water Design Manual 12/12/2016 A-45 NO. 37 – RAIN GARDEN BMP MAINTENANCE COMPONENT DEFECT OR PROBLEM CONDITIONS WHEN MAINTENANCE IS NEEDED RESULTS EXPECTED WHEN MAINTENANCE IS PERFORMED Facility – General Requirements Mosquitoes Standing water remains for more than 3 days after the end of a storm Rain garden drains freely. Standing water in rain garden does not persist for more than 3 days after a storm event. Cause of the standing water addressed (see “Ponded water”). Trash and debris Trash and debris present No trash or debris present Earthen Side Slopes and Berms Erosion Persistent soil erosion on slopes No eroded or scoured areas. Cause of erosion or scour addressed. Rockery Sidewalls Unstable rockery Rockery side walls are insecure Stable rockery sidewalls (may require consultation with licensed engineer, particularly for walls 4 feet or greater in height) Rain Garden Bottom Area Sediment accumulation Visible sediment deposition in the rain garden that reduces drawdown time of water in the rain garden No sediment accumulation in rain garden. Source of sediment addressed. Debris accumulation Accumulated leaves in facility No leaves clogging outlet structure or impeding water flow. Mulch Lack of mulch Bare spots (without mulch cover) are present or mulch depth less than 2 inches Facility has a minimum 2- to 3-inch layer of an appropriate type of mulch. Mulch kept away from woody stems. Splash Block Inlet Water not properly directed to rain garden Water is being directed towards building structure Blocks are reconfigured to direct water to rain garden and away from structure. Pipe Inlet/Outlet Erosion Rock or cobble removed or missing and concentrated flows contacting soil No eroded or scoured areas. Cause of erosion or scour addressed. Cover of rock or cobbles protects the ground where concentrated water flows into the rain garden. Accumulated debris Accumulated leaves, sediment, debris or vegetation at curb cuts, inlet or outlet pipe Blockage cleared Damaged pipe Pipe is damaged Pipe repaired/replaced Clogged pipe Pipe is clogged Pipe clear of roots and debris Blocked access Maintain access for inspections Vegetation cleared or transplanted within 1 foot of inlets and outlets Ponded Water Ponded water Excessive ponding water: Ponded water remains in the rain garden more than 48 hours after the end of a storm Rain garden drains freely. Standing water in rain garden does not persist for more than 48 hours after a storm event. Leaf litter/debris/sediment removed. Overflow Blocked overflow Capacity reduced by sediment or debris No sediment or debris in overflow. Vegetation Blocked site distances and sidewalks Vegetation inhibits sight distances and sidewalks Sidewalks and sight distances along roadways and sidewalks are kept clear. Blocked pipes Vegetation is crowding inlets and outlets Inlets and outlets in rain garden clear of vegetation. Unhealthy vegetation Yellowing: possible Nitrogen (N) deficiency Poor growth: possible Phosphorous (P) deficiency Poor flowering, spotting or curled leaves, or weak roots or stems: possible Potassium (K) deficiency Plants are healthy and appropriate for site conditions. Weeds Presence of weeds Weeds removed (manual methods preferred) and mulch applied. APPENDIX A MAINTENANCE REQUIREMENTS FOR STORMWATER FACILITIES AND ON-SITE BMPS 12/12/2016 2017 City of Renton Surface Water Design Manual A-46 NO. 37 – RAIN GARDEN BMP MAINTENANCE COMPONENT DEFECT OR PROBLEM CONDITIONS WHEN MAINTENANCE IS NEEDED RESULTS EXPECTED WHEN MAINTENANCE IS PERFORMED Summer Watering (years 1–3) Plant establishment Tree, shrubs and groundcovers in first 3 years of establishment period Plants are watered during plant establishment period (years 1–3). Summer Watering (after establishment) Drought conditions Vegetation requires supplemental water Plants are watered during drought conditions or more often if necessary during post-establishment period (after 2 years). APPENDIX A MAINTENANCE REQUIREMENTS FOR STORMWATER FACILITIES AND ON-SITE BMPS 2017 City of Renton Surface Water Design Manual 12/12/2016 A-47 NO. 38 – SOIL AMENDMENT BMP MAINTENANCE COMPONENT DEFECT OR PROBLEM CONDITIONS WHEN MAINTENANCE IS NEEDED RESULTS EXPECTED WHEN MAINTENANCE IS PERFORMED Soil Media Unhealthy vegetation Vegetation not fully covering ground surface or vegetation health is poor. Yellowing: possible Nitrogen (N) deficiency. Poor growth: possible Phosphorous (P) deficiency. Poor flowering, spotting or curled leaves, or weak roots or stems: possible Potassium (K) deficiency. Plants are healthy and appropriate for site conditions Inadequate soil nutrients and structure In the fall, return leaf fall and shredded woody materials from the landscape to the site when possible Soil providing plant nutrients and structure Excessive vegetation growth Grass becomes excessively tall (greater than 10 inches); nuisance weeds and other vegetation start to take over. Healthy turf- “grasscycle” (mulch-mow or leave the clippings) to build turf health Weeds Preventive maintenance Avoid use of pesticides (bug and weed killers), like “weed & feed,” which damage the soil Fertilizer needed Where fertilization is needed (mainly turf and annual flower beds), a moderate fertilization program should be used which relies on compost, natural fertilizers or slow-release synthetic balanced fertilizers Integrated Pest Management (IPM) protocols for fertilization followed Bare spots Bare spots on soil No bare spots, area covered with vegetation or mulch mixed into the underlying soil. Compaction Poor infiltration due to soil compaction • To remediate compaction, aerate soil, till to at least 8-inch depth, or further amend soil with compost and re-till • If areas are turf, aerate compacted areas and top dress them with 1/4 to 1/2 inch of compost to renovate them • If drainage is still slow, consider investigating alternative causes (e.g., high wet season groundwater levels, low permeability soils) • Also consider site use and protection from compacting activities No soil compaction Poor infiltration Soils become waterlogged, do not appear to be infiltrating. Facility infiltrating properly Erosion/Scouring Erosion Areas of potential erosion are visible Causes of erosion (e.g., concentrate flow entering area, channelization of runoff) identified and damaged area stabilized (regrade, rock, vegetation, erosion control matting).For deep channels or cuts (over 3 inches in ponding depth), temporary erosion control measures in place until permanent repairs can be made Grass/Vegetation Unhealthy vegetation Less than 75% of planted vegetation is healthy with a generally good appearance. Healthy vegetation. Unhealthy plants removed/replaced. Appropriate vegetation planted in terms of exposure, soil and soil moisture. Noxious Weeds Noxious weeds Listed noxious vegetation is present (refer to current County noxious weed list). No noxious weeds present. VortClarex® Technical Design Manual 218 ©2016 Contech Engineered Solutions ©2016 Contech Engineered Solutions 219 VortClarex Contents Design and Operation......................................................................................................................220 Maintenance .....................................................................................................................................222 Sample VortClarex Calculations.....................................................................................................223 VortClarex Specifications................................................................................................................224 222 ©2016 Contech Engineered Solutions Maintenance Maintenance Inspection The VortClarex system should be checked periodically to determine if excessive amounts of solids and/or oils have accumulated. Solids accumulation in the lower sections of the VortClarex coalescing media will reduce oil removal efficiencies. Regular inspection and maintenance will eliminate any compromise in performance due to solids build-up. After the first six (6) months of operation, the inlet area should be inspected and cleaned as follows: 1. Remove separator cover. 2. Dispose of separated oil per regulatory procedures. 3. Remove water from separator. 4. Clean the vault by flushing with a hose and examine the plates for blockage. 5. Remove accumulated sediment with a vacuum truck or positive displacement pump such as an air operated diaphragm pump. The sediment will contain hydrocarbons so proper disposal is required. Note:Measure and record the depth of the solids in the inlet chamber. If sediment level is 6 inches or more, the cleaning interval should be shortened. If the sediment is less than 6 inches deep, the interval can be increased. Cleaning The VortClarex coalescing media can be cleaned either while in the system or after removal from the system. Cleaning in place 1. Using a water hose, direct spray (10-15 psi) into plate spacing on top of the plate packs. 2. Using a vacuum suction hose, remove any sediment or oily contaminants that are flushed out of the coalescing media. Cleaning after removal 1. Pump all water and oily contaminants from the VortClarex system. 2. Remove coalescing media. 3. Place media on an impervious surface lined with 6 mil plastic sheeting surrounded by a berm to prevent discharge of contaminated water into surface or groundwater. 4. Flush media with water hose (10-15 psi) to remove heavy oil coating or sludge from between the corrugated plates. 5. Examine tank interior for damage and repair any damage to internal coating. 6. Re-Install plate packs one at a time, one row in length and one row in width, being sure the outer packs are adequately sealed against the vault wall in the same manner as before they were removed. 7. After all packs are installed, check to ensure that the packs are even and touching, forming one (or two if provided) rows of packs across the channel and that they are securely butted against the backing angle at the bottom of the separator. Install the upper channel to ensure the plates are secured in place. 8. Secure hold down channel ensuring it is snugly in place. 9. Check to see that there is no possibility of fluid bypassing around the plates and the side wall of the vault, as well as between plate pack assemblies, since this could adversely affect the efficiency of the separator. www.modularwetlands.com Maintenance Guidelines for Modular Wetland System - Linear Maintenance Summary o Remove Trash from Screening Device – average maintenance interval is 6 to 12 months. (5 minute average service time). o Remove Sediment from Separation Chamber – average maintenance interval is 12 to 24 months. (10 minute average service time). o Replace Cartridge Filter Media – average maintenance interval 12 to 24 months. (10-15 minute per cartridge average service time). o Replace Drain Down Filter Media – average maintenance interval is 12 to 24 months. (5 minute average service time). o Trim Vegetation – average maintenance interval is 6 to 12 months. (Service time varies). System Diagram Access to screening device, separation chamber and cartridge filter Access to drain down filter Pre-Treatment Chamber Biofiltration Chamber Discharge Chamber Outflow Pipe Inflow Pipe (optional) www.modularwetlands.com Maintenance Procedures Screening Device 1. Remove grate or manhole cover to gain access to the screening device in the Pre- Treatment Chamber. Vault type units do not have screening device. Maintenance can be performed without entry. 2. Remove all pollutants collected by the screening device. Removal can be done manually or with the use of a vacuum truck. The hose of the vacuum truck will not damage the screening device. 3. Screening device can easily be removed from the Pre-Treatment Chamber to gain access to separation chamber and media filters below. Replace grate or manhole cover when completed. Separation Chamber 1. Perform maintenance procedures of screening device listed above before maintaining the separation chamber. 2. With a pressure washer spray down pollutants accumulated on walls and cartridge filters. 3. Vacuum out Separation Chamber and remove all accumulated pollutants. Replace screening device, grate or manhole cover when completed. Cartridge Filters 1. Perform maintenance procedures on screening device and separation chamber before maintaining cartridge filters. 2. Enter separation chamber. 3. Unscrew the two bolts holding the lid on each cartridge filter and remove lid. 4. Remove each of 4 to 8 media cages holding the media in place. 5. Spray down the cartridge filter to remove any accumulated pollutants. 6. Vacuum out old media and accumulated pollutants. 7. Reinstall media cages and fill with new media from manufacturer or outside supplier. Manufacturer will provide specification of media and sources to purchase. 8. Replace the lid and tighten down bolts. Replace screening device, grate or manhole cover when completed. Drain Down Filter 1. Remove hatch or manhole cover over discharge chamber and enter chamber. 2. Unlock and lift drain down filter housing and remove old media block. Replace with new media block. Lower drain down filter housing and lock into place. 3. Exit chamber and replace hatch or manhole cover. www.modularwetlands.com Maintenance Notes 1. Following maintenance and/or inspection, it is recommended the maintenance operator prepare a maintenance/inspection record. The record should include any maintenance activities performed, amount and description of debris collected, and condition of the system and its various filter mechanisms. 2. The owner should keep maintenance/inspection record(s) for a minimum of five years from the date of maintenance. These records should be made available to the governing municipality for inspection upon request at any time. 3. Transport all debris, trash, organics and sediments to approved facility for disposal in accordance with local and state requirements. 4. Entry into chambers may require confined space training based on state and local regulations. 5. No fertilizer shall be used in the Biofiltration Chamber. 6. Irrigation should be provided as recommended by manufacturer and/or landscape architect. Amount of irrigation required is dependent on plant species. Some plants may require irrigation. www.modularwetlands.com Maintenance Procedure Illustration Screening Device The screening device is located directly under the manhole or grate over the Pre-Treatment Chamber. It’s mounted directly underneath for easy access and cleaning. Device can be cleaned by hand or with a vacuum truck. Separation Chamber The separation chamber is located directly beneath the screening device. It can be quickly cleaned using a vacuum truck or by hand. A pressure washer is useful to assist in the cleaning process. www.modularwetlands.com Cartridge Filters The cartridge filters are located in the Pre-Treatment chamber connected to the wall adjacent to the biofiltration chamber. The cartridges have removable tops to access the individual media filters. Once the cartridge is open media can be easily removed and replaced by hand or a vacuum truck. Drain Down Filter The drain down filter is located in the Discharge Chamber. The drain filter unlocks from the wall mount and hinges up. Remove filter block and replace with new block. www.modularwetlands.com Trim Vegetation Vegetation should be maintained in the same manner as surrounding vegetation and trimmed as needed. No fertilizer shall be used on the plants. Irrigation per the recommendation of the manufacturer and or landscape architect. Different types of vegetation requires different amounts of irrigation. www.modularwetlands.com Inspection Form Modular Wetland System, Inc. P. 760.433-7640 F. 760-433-3176 E. Info@modularwetlands.com For Office Use Only (city) (Zip Code)(Reviewed By) Owner / Management Company (Date) Contact Phone ( )_ Inspector Name Date / / Time AM / PM Weather Condition Additional Notes Yes Depth: Yes No Modular Wetland System Type (Curb, Grate or UG Vault):Size (22', 14' or etc.): Other Inspection Items: Storm Event in Last 72-hours? No Yes Type of Inspection Routine Follow Up Complaint Storm Office personnel to complete section to the left. 2972 San Luis Rey Road, Oceanside, CA 92058 P (760) 433-7640 F (760) 433-3176 Inspection Report Modular Wetlands System Is the filter insert (if applicable) at capacity and/or is there an accumulation of debris/trash on the shelf system? Does the cartridge filter media need replacement in pre-treatment chamber and/or discharge chamber? Any signs of improper functioning in the discharge chamber? Note issues in comments section. Chamber: Is the inlet/outlet pipe or drain down pipe damaged or otherwise not functioning properly? Structural Integrity: Working Condition: Is there evidence of illicit discharge or excessive oil, grease, or other automobile fluids entering and clogging the unit? Is there standing water in inappropriate areas after a dry period? Damage to pre-treatment access cover (manhole cover/grate) or cannot be opened using normal lifting pressure? Damage to discharge chamber access cover (manhole cover/grate) or cannot be opened using normal lifting pressure? Does the MWS unit show signs of structural deterioration (cracks in the wall, damage to frame)? Project Name Project Address Inspection Checklist CommentsNo Does the depth of sediment/trash/debris suggest a blockage of the inflow pipe, bypass or cartridge filter? If yes, specify which one in the comments section. Note depth of accumulation in in pre-treatment chamber. Is there a septic or foul odor coming from inside the system? Is there an accumulation of sediment/trash/debris in the wetland media (if applicable)? Is it evident that the plants are alive and healthy (if applicable)? Please note Plant Information below. Sediment / Silt / Clay Trash / Bags / Bottles Green Waste / Leaves / Foliage Waste:Plant Information No Cleaning Needed Recommended Maintenance Additional Notes: Damage to Plants Plant Replacement Plant Trimming Schedule Maintenance as Planned Needs Immediate Maintenance www.modularwetlands.com Maintenance Report Modular Wetland System, Inc. P. 760.433-7640 F. 760-433-3176 E. Info@modularwetlands.com For Office Use Only (city) (Zip Code)(Reviewed By) Owner / Management Company (Date) Contact Phone ( )_ Inspector Name Date / / Time AM / PM Weather Condition Additional Notes Site Map # Comments: 2972 San Luis Rey Road, Oceanside, CA 92058 P. 760.433.7640 F. 760.433.3176 Inlet and Outlet Pipe Condition Drain Down Pipe Condition Discharge Chamber Condition Drain Down Media Condition Plant Condition Media Filter Condition Long: MWS Sedimentation Basin Total Debris Accumulation Condition of Media 25/50/75/100 (will be changed @ 75%) Operational Per Manufactures' Specifications (If not, why?) Lat:MWS Catch Basins GPS Coordinates of Insert Manufacturer / Description / Sizing Trash Accumulation Foliage Accumulation Sediment Accumulation Type of Inspection Routine Follow Up Complaint Storm Storm Event in Last 72-hours? No Yes Office personnel to complete section to the left. Project Address Project Name Cleaning and Maintenance Report Modular Wetlands System