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Civil Engineers ● Structural Engineers ● Landscape Architects ● Community Planners ● Land Surveyors Technical Information Report PREPARED FOR: Lakhpal Brar 8054 South 132nd Street Renton, WA 98178 PROJECT: Brar Short Plat 8054 South 132nd Street Renton, WA 98178 2200320.10 PREPARED BY: Quinten Foster, Project Engineer REVIEWED BY: Scott Kaul, PE Project Manager DATE: December 2021 Revised April 2022 SURFACE WATER UTILITY jfarah 09/29/2022 DEVELOPMENT ENGINEERING YQI 10/05/2022 Technical Information Report PREPARED FOR: Lakhpal Brar 8054 South 132nd Street Renton, WA 98178 PROJECT: Brar Short Plat 8054 South 132nd Street Renton, WA 98178 2200320.10 PREPARED BY: Quinten Foster, Project Engineer REVIEWED BY: Scott Kaul, PE Project Manager DATE: December 2021 Revised April 2022 I hereby state that this Technical Information Report for the Brar Short Plat project has been prepared by me or under my supervision and meets the standard of care and expertise that is usual and customary in this community for professional engineers. I understand that City of Renton does not and will not assume liability for the sufficiency, suitability, or performance of drainage facilities prepared by me. 05/09/2022 Technical Information Report Brar Short Plat i 2200320.10 Table of Contents 1.0 Project Overview ......................................................................................................................... 1-1 Purpose and Scope.......................................................................................................... 1-1 Existing Conditions........................................................................................................... 1-1 Post-Development Conditions ......................................................................................... 1-1 Section 1.0 Figures Figure 1-1 ......... TIR Worksheet Figure 1-2 ......... Site Location Map Figure 1-3 ......... Drainage Basin Map Figure 1-4 ......... USDA Soils Survey 2.0 Conditions and Requirements Summary ................................................................................. 2-1 Core Requirements .......................................................................................................... 2-1 2.1.1 CR 1 – Discharge at the Natural Location .......................................................... 2-1 2.1.2 CR 2 – Offsite Analysis ....................................................................................... 2-1 2.1.3 CR 3 – Flow Control ............................................................................................ 2-1 2.1.4 CR 4 – Conveyance System ............................................................................... 2-1 2.1.5 CR 5 – Construction Stormwater Pollution Prevention ....................................... 2-1 2.1.6 CR 6 – Maintenance and Operations ................................................................. 2-1 2.1.7 CR 7 – Financial Guarantees and Liability ......................................................... 2-1 2.1.8 CR 8 – Water Quality Facilities ........................................................................... 2-1 2.1.9 CR 9 – Onsite Best Management Practices (BMPs) .......................................... 2-2 2.1.10 SR 1 – Other Adopted Area-Specific Requirements........................................... 2-2 2.1.11 SR 2 – Flood Hazard Area Delineation ............................................................... 2-2 2.1.12 SR 3 – Flood Protection Facilities ....................................................................... 2-3 2.1.13 SR 4 – Source Controls ...................................................................................... 2-3 2.1.14 SR 5 – Oil Control ............................................................................................... 2-3 2.1.15 SR 6 – Aquifer Protection Area ........................................................................... 2-3 Section 2.0 Figures Figure 2-1 ......... Flood Insurance Rate Map Figure 2-2 ......... City of Renton Groundwater Protection Areas 3.0 Offsite Analysis ........................................................................................................................... 3-1 Task 1 – Study Area Definition and Maps........................................................................ 3-1 Task 2 – Resource Review .............................................................................................. 3-1 Task 3 – Field Inspection ................................................................................................. 3-1 Task 4 – Drainage System Description and Problem Descriptions ................................. 3-1 Technical Information Report Brar Short Plat ii 2200320.10 Section 3.0 Figures Figure 3-1 ......... City of Renton Effective FEMA Flood Insurance Rate Map Figure 3-2 ......... Downstream Drainage Map 4.0 Flow Control and Water Quality Facility Analysis and Design............................................... 4-1 Flow Control ..................................................................................................................... 4-1 4.1.1 Existing Site Hydrology (Part A) .......................................................................... 4-1 4.1.2 Developed Site Hydrology (Part B) ..................................................................... 4-1 4.1.3 Performance Standards (Part C) ........................................................................ 4-2 4.1.4 Flow Control System (Part D) ............................................................................. 4-3 Water Quality System (Part E) ......................................................................................... 4-3 Section 4.0 Figures Figure 4-1 ......... City of Renton Flow Control Application Map – Reference 15-A Figure 4-2 ......... Predeveloped and Developed Basin Maps Figure 4-3 ......... WWHM Flow Control and Water Quality Calculations Figure 4-4 ......... GULD for Basic (TSS) Treatment for Contech StormFilter w/ZPG Media 5.0 Conveyance System Analysis and Design ............................................................................... 5-1 Section 5.0 Figures Figure 5-1 ......... Onsite Flows Figure 5-2 ......... Onsite Conveyance Check Figure 5-3 ......... Frontage Conveyance Check 6.0 Special Reports and Studies ..................................................................................................... 6-1 Section 6.0 Figures Figure 6-1 ......... Geotechnical Engineering Report 7.0 Other Permits .............................................................................................................................. 7-1 8.0 CSWPPP Analysis and Design .................................................................................................. 8-1 9.0 Bond Quantities, Facility Summaries, and Declaration of Covenant .................................... 9-1 Section 9.0 Figures Figure 9-1 ......... Facility Summary Sheet Figure 9-2 ......... Facility Summary Site Plan Figure 9-3 ......... Declaration of Covenant 10.0 Operations and Maintenance Plan .......................................................................................... 10-1 11.0 Conclusion ................................................................................................................................. 11-1 Technical Information Report Brar Short Plat 2200320.10 Section 1 Project Overview Technical Information Report Brar Short Plat 1-1 2200320.10 1.0 Project Overview Purpose and Scope This report accompanies the civil engineering plans and documents for the Brar Short Plat project, a proposed residential development project located at 8054 South 132nd Street in the city of Renton, King County, Washington. The project site comprises Parcel No. 2144800460, which is 0.75 acre in size. The site is bordered to the north and west by private residential parcels, to the south by South 132nd Street, and to the east by a new residential development under construction. See Figure 1-1 for the TIR Worksheet and Figure 1-2 for a Site Location map. The site is located within the jurisdiction of City of Renton, which has amended the 2016 King County Surface Water Design Manual (KCSWDM) as the 2017 City of Renton Surface Water Design Manual (CRSWDM). Per the CRSWDM, the Flow Control Duration Standard – Matching Forested shall be met, along with the Basic Enhanced Water Quality Treatment Menu. Existing Conditions The site currently has an existing residence in its southern portion and an outbuilding centrally located onsite. The remainder of the site is primarily pasture. There are several existing trees on the eastern side of the site and within the existing residence’s front yard. Generally, the site slopes to the south parallel to the east and west parcel boundaries. The slope is moderately steep at about 15%. The existing property discharges to the public right-of-way on South 132nd Street. The existing drainage patterns have been analyzed and are discussed in detail in the Level One Downstream Analysis (see Section 3.0). Post-Development Conditions The project proposes a four-lot subdivision; the existing residence will remain as Lot 1. The buildable area within each lot ranges from 2,000 to 2,840 square feet. Each lot will be constructed with a paved driveway from a private shared access driveway. Stormwater will be collected in closed conveyances, directed to an underground detention system, and treated by a proprietary (basic) stormwater treatment device prior to discharging to the public storm system in South 132nd Street. This will maintain the natural discharge point for stormwater leaving the site. Refer to Figure 1-3 for a Drainage Basin Map. Technical Information Report Brar Short Plat 2200320.10 Section 1.0 Figures Figure 1-1 ......... TIR Worksheet Figure 1-2 ......... Site Location Map Figure 1-3 ......... Drainage Basin Map Figure 1-4 ......... USDA Soils Survey Lakhpal Brar 8054 S 132nd St, Renton, WA 98178 Matt Weber AHBL, Inc. 253.383.2422 8054 S 132nd St, Renton, 98178 Brar Short Plat 13 23 4 November 2020 November 2020 Cedar River/Lake Washington Sub Basin The City of Renton Peak Flow Rate Control Standard and Basic Water Quality Ur N/A N/A Slopes exceeding 15% East Valley Road public stormwater system 1 TBD prior to construction Peak Rate Flow Control Standard 02/16/2021 Conveyance pipes, catch basins, underground detention, and treatment unit. Treatment Unit Storm Tank underground detention 4/20/2022 2215 North 30th Street Suite 300 Tacoma, WA 98403 253.383.2422 TEL 253.383.2572 FAX BRAR SHORT PLAT VICINITY MAP FIGURE 1-2 Thorton Creek R ock Cre e kR ex Riv er C e da r Riv er Cedar River BearCreek Ke ls ey Cre ek May Creek Taylor Creek North Fork C edar River Tr o u b lesome C re ek Coal Creek ELW ELW EastLakeWashington ELW EastLakeWashington ForbesCreek JuanitaCreek Kelsey Creek LakeUnion LowerCedarRiver LyonCreek MayCreek McaleerCreek MercerIsland MercerSlough ThorntonCreek UpperCedarRiver West LakeWashington WestLakeWashington WestLakeWashingtonLake WashingtonLakeBallinger GreenLake Lake Union LakeDesire Walsh Lake ShadyLake LakeTwelve SpringLake RetreatLake ChesterMorseLake Ce d a r R i v e rCedarRiver Cedar River ALGONA AUBURN BEAUXARTS BELLEVUE BLACKDIAMOND BLACKDIAMOND BOTHELL BRIER BURIEN CARNATIONCARNATION CARNATION CLYDEHILL COVINGTON DES MOINES DUVALL DUVALL EDMONDS FEDERALWAY HUNTSPOINT INDEX ISSAQUAH KENT KENT KENT KENT KENT KENT KENT KENT KIRKLAND KIRKLAND MAPLE VALLEY MEDINA MERCERISLAND MOUNTLAKE EDMONDSLYNNWOOD TERRACE NEWCASTLE NORMANDY PARK NORTHBEND REDMOND REDMOND REDMOND RENTON SAMMAMISH SEATAC SEATTLE SNOQUALMIESNOQUALMIE SNOQUALMIE TUKWILA WOODINVILLE WOODWAY YARROWPOINT PACIFIC LAKEFORESTPARK KENMORE SHORELINE SEATTLE SEATTLE BELLEVUE Department of Natural Resources and ParksWater and Land Resources Division N Watershed Boundary Basin Boundary River Stream Major Road Incorporated Area Lake Produced by: King County IT Services, GIS, Visual Communications and Web SectionFile Name: 1211_2650_CedarLkWashMap.ai skrau November 2012 0 1 2 4 Miles The Lake Washington/Cedar River Watershed PROJECT SITE Soil Map—City of Seattle, Washington (Soil Map) Natural Resources Conservation Service Web Soil Survey National Cooperative Soil Survey 11/5/2020 Page 1 of 35259310525932052593305259340525935052593605259370525938052593905259400525941052593105259320525933052593405259350525936052593705259380525939052594005259410557920557930557940557950557960557970557980557990558000 557920 557930 557940 557950 557960 557970 557980 557990 558000 47° 29' 8'' N 122° 13' 52'' W47° 29' 8'' N122° 13' 48'' W47° 29' 4'' N 122° 13' 52'' W47° 29' 4'' N 122° 13' 48'' WN Map projection: Web Mercator Corner coordinates: WGS84 Edge tics: UTM Zone 10N WGS84 0 25 50 100 150 Feet 0 5 10 20 30 Meters Map Scale: 1:543 if printed on A portrait (8.5" x 11") sheet. Soil Map may not be valid at this scale. MAP LEGEND MAP INFORMATION Area of Interest (AOI) Area of Interest (AOI) Soils Soil Map Unit Polygons Soil Map Unit Lines Soil Map Unit Points Special Point Features Blowout Borrow Pit Clay Spot Closed Depression Gravel Pit Gravelly Spot Landfill Lava Flow Marsh or swamp Mine or Quarry Miscellaneous Water Perennial Water Rock Outcrop Saline Spot Sandy Spot Severely Eroded Spot Sinkhole Slide or Slip Sodic Spot Spoil Area Stony Spot Very Stony Spot Wet Spot Other Special Line Features Water Features Streams and Canals Transportation Rails Interstate Highways US Routes Major Roads Local Roads Background Aerial Photography The soil surveys that comprise your AOI were mapped at 1:12,000. Warning: Soil Map may not be valid at this scale. Enlargement of maps beyond the scale of mapping can cause misunderstanding of the detail of mapping and accuracy of soil line placement. The maps do not show the small areas of contrasting soils that could have been shown at a more detailed scale. Please rely on the bar scale on each map sheet for map measurements. Source of Map: Natural Resources Conservation Service Web Soil Survey URL: Coordinate System: Web Mercator (EPSG:3857) Maps from the Web Soil Survey are based on the Web Mercator projection, which preserves direction and shape but distorts distance and area. A projection that preserves area, such as the Albers equal-area conic projection, should be used if more accurate calculations of distance or area are required. This product is generated from the USDA-NRCS certified data as of the version date(s) listed below. Soil Survey Area: City of Seattle, Washington Survey Area Data: Version 4, Jun 4, 2020 Soil map units are labeled (as space allows) for map scales 1:50,000 or larger. Date(s) aerial images were photographed: Jun 29, 2019—Jul 21, 2019 The orthophoto or other base map on which the soil lines were compiled and digitized probably differs from the background imagery displayed on these maps. As a result, some minor shifting of map unit boundaries may be evident. Soil Map—City of Seattle, Washington (Soil Map) Natural Resources Conservation Service Web Soil Survey National Cooperative Soil Survey 11/5/2020 Page 2 of 3 Map Unit Legend Map Unit Symbol Map Unit Name Acres in AOI Percent of AOI 3056 Urban land-Alderwood complex, 5 to 12 percent slopes 0.4 49.1% 5020 Beausite-Alderwood-Urban land complex, 12 to 35 percent slopes 0.4 50.9% Totals for Area of Interest 0.7 100.0% Soil Map—City of Seattle, Washington Soil Map Natural Resources Conservation Service Web Soil Survey National Cooperative Soil Survey 11/5/2020 Page 3 of 3 City of Seattle, Washington 3056—Urban land-Alderwood complex, 5 to 12 percent slopes Map Unit Setting National map unit symbol: 2xtbd Elevation: 20 to 540 feet Mean annual precipitation: 30 to 40 inches Mean annual air temperature: 48 to 52 degrees F Frost-free period: 180 to 240 days Farmland classification: Not prime farmland Map Unit Composition Urban land:60 percent Alderwood and similar soils:15 percent Minor components:25 percent Estimates are based on observations, descriptions, and transects of the mapunit. Description of Urban Land Interpretive groups Land capability classification (irrigated): None specified Land capability classification (nonirrigated): 8 Hydric soil rating: No Description of Alderwood Setting Landform:Hills Landform position (two-dimensional):Backslope, summit, shoulder Landform position (three-dimensional):Crest, side slope, nose slope Down-slope shape:Linear Across-slope shape:Convex Parent material:Glacial drift and/or glacial outwash over dense glaciomarine deposits Typical profile A - 0 to 7 inches: gravelly sandy loam Bw1 - 7 to 21 inches: very gravelly sandy loam Bw2 - 21 to 30 inches: very gravelly sandy loam Bg - 30 to 35 inches: very gravelly sandy loam 2Cd1 - 35 to 43 inches: very gravelly sandy loam 2Cd2 - 43 to 59 inches: very gravelly sandy loam Properties and qualities Slope:5 to 12 percent Depth to restrictive feature:20 to 39 inches to densic material Drainage class:Moderately well drained Map Unit Description: Urban land-Alderwood complex, 5 to 12 percent slopes---City of Seattle, Washington Soil Data Natural Resources Conservation Service Web Soil Survey National Cooperative Soil Survey 11/5/2020 Page 1 of 2 Capacity of the most limiting layer to transmit water (Ksat):Very low to moderately low (0.00 to 0.01 in/hr) Depth to water table:About 18 to 35 inches Frequency of flooding:None Frequency of ponding:None Available water capacity:Very low (about 2.7 inches) Interpretive groups Land capability classification (irrigated): None specified Land capability classification (nonirrigated): 4s Hydrologic Soil Group: A Hydric soil rating: No Minor Components Everett Percent of map unit:10 percent Landform:Hills Landform position (two-dimensional):Shoulder, backslope Landform position (three-dimensional):Side slope, crest Down-slope shape:Linear Across-slope shape:Convex Hydric soil rating: No Mckenna Percent of map unit:10 percent Landform:Terraces Landform position (three-dimensional):Tread Down-slope shape:Concave Across-slope shape:Concave Hydric soil rating: Yes Kitsap Percent of map unit:5 percent Landform:Terraces Landform position (three-dimensional):Tread Down-slope shape:Linear Across-slope shape:Linear Hydric soil rating: No Data Source Information Soil Survey Area: City of Seattle, Washington Survey Area Data: Version 4, Jun 4, 2020 Map Unit Description: Urban land-Alderwood complex, 5 to 12 percent slopes---City of Seattle, Washington Soil Data Natural Resources Conservation Service Web Soil Survey National Cooperative Soil Survey 11/5/2020 Page 2 of 2 City of Seattle, Washington 5020—Beausite-Alderwood-Urban land complex, 12 to 35 percent slopes Map Unit Setting National map unit symbol: 2xtbw Elevation: 20 to 540 feet Mean annual precipitation: 30 to 40 inches Mean annual air temperature: 48 to 52 degrees F Frost-free period: 180 to 240 days Farmland classification: Not prime farmland Map Unit Composition Beausite and similar soils:50 percent Alderwood and similar soils:25 percent Urban land:20 percent Minor components:5 percent Estimates are based on observations, descriptions, and transects of the mapunit. Description of Beausite Setting Landform:Hillslopes Landform position (two-dimensional):Shoulder, backslope, summit Landform position (three-dimensional):Side slope, crest, nose slope Down-slope shape:Convex Across-slope shape:Convex Parent material:Glacial drift mixed with colluvium and/or residuum derived from sandstone or conglomerate Typical profile Oi - 0 to 2 inches: slightly decomposed plant material Oe - 2 to 3 inches: moderately decomposed plant material A - 3 to 5 inches: gravelly sandy loam Bw1 - 5 to 9 inches: very gravelly sandy loam Bw2 - 9 to 17 inches: very gravelly sandy loam Bw3 - 17 to 25 inches: very gravelly sandy loam C - 25 to 36 inches: very gravelly sandy loam 2R - 36 to 59 inches: bedrock Properties and qualities Slope:12 to 35 percent Depth to restrictive feature:24 to 39 inches to lithic bedrock Drainage class:Well drained Capacity of the most limiting layer to transmit water (Ksat):Moderately high to high (1.42 to 7.09 in/hr) Depth to water table:More than 80 inches Frequency of flooding:None Frequency of ponding:None Map Unit Description: Beausite-Alderwood-Urban land complex, 12 to 35 percent slopes---City of Seattle, Washington Soil Data Natural Resources Conservation Service Web Soil Survey National Cooperative Soil Survey 11/5/2020 Page 1 of 3 Available water capacity:Very low (about 2.9 inches) Interpretive groups Land capability classification (irrigated): None specified Land capability classification (nonirrigated): 6e Hydrologic Soil Group: B Hydric soil rating: No Description of Alderwood Setting Landform:Hills Landform position (two-dimensional):Backslope, summit, shoulder Landform position (three-dimensional):Crest, side slope, nose slope Down-slope shape:Linear Across-slope shape:Convex Parent material:Glacial drift and/or glacial outwash over dense glaciomarine deposits Typical profile A - 0 to 7 inches: gravelly sandy loam Bw1 - 7 to 21 inches: very gravelly sandy loam Bw2 - 21 to 30 inches: very gravelly sandy loam Bg - 30 to 35 inches: very gravelly sandy loam 2Cd1 - 35 to 43 inches: very gravelly sandy loam 2Cd2 - 43 to 59 inches: very gravelly sandy loam Properties and qualities Slope:12 to 35 percent Depth to restrictive feature:20 to 39 inches to densic material Drainage class:Moderately well drained Capacity of the most limiting layer to transmit water (Ksat):Very low to moderately low (0.00 to 0.01 in/hr) Depth to water table:About 18 to 35 inches Frequency of flooding:None Frequency of ponding:None Available water capacity:Very low (about 2.7 inches) Interpretive groups Land capability classification (irrigated): None specified Land capability classification (nonirrigated): 6e Hydrologic Soil Group: A Hydric soil rating: No Description of Urban Land Interpretive groups Land capability classification (irrigated): None specified Land capability classification (nonirrigated): 8 Hydric soil rating: No Map Unit Description: Beausite-Alderwood-Urban land complex, 12 to 35 percent slopes---City of Seattle, Washington Soil Data Natural Resources Conservation Service Web Soil Survey National Cooperative Soil Survey 11/5/2020 Page 2 of 3 Minor Components Mckenna Percent of map unit:5 percent Landform:Terraces Landform position (three-dimensional):Tread, dip Down-slope shape:Concave Across-slope shape:Concave Hydric soil rating: Yes Data Source Information Soil Survey Area: City of Seattle, Washington Survey Area Data: Version 4, Jun 4, 2020 Map Unit Description: Beausite-Alderwood-Urban land complex, 12 to 35 percent slopes---City of Seattle, Washington Soil Data Natural Resources Conservation Service Web Soil Survey National Cooperative Soil Survey 11/5/2020 Page 3 of 3 Technical Information Report Brar Short Plat 2200320.10 Section 2 Conditions and Requirements Summary Technical Information Report Brar Short Plat 2-1 2200320.10 2.0 Conditions and Requirements Summary Core Requirements 2.1.1 CR 1 – Discharge at the Natural Location There is one basin within the site in one Threshold Discharge Area (TDA). All core requirements are required for this TDA. The natural discharge location of this TDA is maintained. 2.1.2 CR 2 – Offsite Analysis A downstream analysis is included in Section 3.0 below. A Level One Downstream Analysis has been conducted. The analysis includes: · Defining and mapping the study area. · Reviewing available information on the study area. · Field inspecting the study area. 2.1.3 CR 3 – Flow Control The project is in a Flow Control Duration Standard and is within the West Lake Washington – Seattle South Drainage Basin. This flow control standard requires discharges to match predeveloped forested site conditions. Flow control is discussed in further detail in Section 4.0, Flow Control and Water Quality Facility Analysis and Design. 2.1.4 CR 4 – Conveyance System The proposed conveyance system will be designed to meet the requirements outlined in Section 1.2.4 of the CRSWDM. Refer to Section 5.0 for more information. 2.1.5 CR 5 – Construction Stormwater Pollution Prevention Onsite land disturbance will consist of clearing the undeveloped portion of the site, demolition of the existing onsite outbuilding, and regrading of the site for three future homes. A Construction Stormwater Pollution Prevention Plan (CSWPPP) is provided under separate cover. 2.1.6 CR 6 – Maintenance and Operations Maintenance and operations of all drainage facilities are the responsibility of the owner. A completed Operations and Maintenance Plan is provided under separate cover. 2.1.7 CR 7 – Financial Guarantees and Liability All financial guarantee and liability requirements will be met by the owner. A construction bond will be provided as required by the City per Renton Municipal Code (RMC) 4-6-030. A maintenance shall be provided, as required by the City, for public improvements. Liability insure shall be provided for the duration of the project, as outlined in the CRSWDM. 2.1.8 CR 8 – Water Quality Facilities The project site is subject to the Basic Water Quality Treatment Menu per the CRSWDM. Design of these water quality facilities is discussed in Section 4.0. Technical Information Report Brar Short Plat 2-2 2200320.10 2.1.9 CR 9 – Onsite Best Management Practices (BMPs) The Brar Short Plat project is classified as a Large Lot per Section 1.2.9.2 of the CRSWDM. The proposed project site will meet the Large Lot BMP Requirements outlined in Section 1.2.9.2.2 of the CRSWDM. Below is a discussion of the list approach for each type of surface proposed on the site. Landscape Areas · Post Construction Soil Quality and Depth will be used. Impervious Areas · Full Dispersion is not feasible because the development cannot maintain the required vegetated flow path area. · Full Infiltration and Full Infiltration of Roof Runoff are not feasible because the existing soils that are able to infiltrate are relatively shallow and cannot support infiltration due to the site’s steep slope. Runoff will flow laterally and negatively impact downstream lots. · Limited Infiltration is not feasible because the existing soils that are able to infiltrate are relatively shallow and cannot support infiltration due to the site’s step slope. Any runoff that may infiltrate at grade will flow laterally into the adjacent foundation of the lower lots. · Rain Gardens are not feasible because the existing soils that are able to infiltrate are relatively shallow and cannot support infiltration due to the site’s steep slope. Any runoff that may infiltrate at grade will flow laterally into the adjacent foundation of the lower lots. · Bioretention per Onsite BMP standards is not feasible because the facilities would not be able to be designed on slopes less than 8%. · Permeable Pavement is not feasible because the site slopes exceed 10%. Permeable pavement is not ideal for slopes exceeding 5%. · Basic Dispersion is not feasible because there is not a vegetated flow path of 20 feet. · Reduced Impervious Surface Credit is not feasible for this site. · Native Growth Retention Credit and Tree Retention Credit are not feasible to achieve the required minimum residential density on this project and serve the site with utilities. · Perforated Pipe Connection is not feasible because the existing fill and alluvial soils cannot support infiltration. 2.1.10 SR 1 – Other Adopted Area-Specific Requirements To our knowledge, no adopted area-specific requirements are applicable to the project site. 2.1.11 SR 2 – Flood Hazard Area Delineation Flood Insurance Rate Map 53033C0976G was consulted for this project and shows the project site within the Zone X area, which is described as areas determined to be outside of the 500-year floodplain. Refer to Figure 2-1 of this section for the Flood Insurance Rate Map. Technical Information Report Brar Short Plat 2-3 2200320.10 2.1.12 SR 3 – Flood Protection Facilities The project site does not contain, nor is it adjacent to, any existing flood protection facilities. Project improvements do not include flood protection measures. 2.1.13 SR 4 – Source Controls The proposed project is classified as a residential site. Source controls are only applicable to commercial development; therefore, no additional source control BMPs are proposed. 2.1.14 SR 5 – Oil Control The project is not considered a high-use site; therefore, it is not subject to oil control requirements. 2.1.15 SR 6 – Aquifer Protection Area According to the City of Renton Public Works Department Groundwater Protection Areas map, Reference 15-B of the CRSWDM, the site is not located within an aquifer protection area. Refer to Figure 2-2 for the above referenced map. Technical Information Report Brar Short Plat 2200320.10 Section 2.0 Figures Figure 2-1 ......... Flood Insurance Rate Map Figure 2-2 ......... City of Renton Groundwater Protection Areas Esri, HERE, Garmin, (c) OpenStreetMap contributors, and the GIS usercommunity Zone 1 Zone 1 Modified Zone 2 Renton Water District ³ Data Sources: City of Renton, King County, ESRI This document is a graphic representation, not guaranteedto survey accuracy, and is based on the best informationavailable as of the date shown. This map is intended forCity display purposes only. Coordinate System: NAD 1983 HARN StatePlane Washington North FIPS 4601 FeetProjection: Lambert Conformal ConicDatum: North American 1983 HARN Date: 05/15/2020 0 0.5 10.25 Miles PROJECT SITE Technical Information Report Brar Short Plat 2200320.10 Section 3 Offsite Analysis Technical Information Report Brar Short Plat 3-1 2200320.10 3.0 Offsite Analysis Task 1 – Study Area Definition and Maps One TDA exists for the site. The site drains to the south and discharges to the existing public stormwater system. The existing discharge point will be maintained. The northern neighboring property contributes stormwater to the onsite basin area. The topography of the surrounding properties directs stormwater to the existing right-of-way. Properties to the east and west do not contribute runon to the property. Task 2 – Resource Review The following resources were reviewed to determine if there are any existing or potential problems in the study area: · Adopted Basin Plans: The project lies within the Lower Cedar River Basin and is subject to the Lower Cedar River Basin and Nonpoint Pollution Action Plan. Stormwater mitigation, as outlined in the CRSWDM, will be provided for the site to meet the Lower Cedar River Basin plan. · Offsite Analysis Reports: AHBL staff has not located offsite analysis reports for projects near the Brar Short Plat. · FEMA Map: FEMA Flood Insurance Rate Map 53033C0976 G, dated August 19, 2020 (see Figure 2-1), indicates that the project site lies outside the categorized flood zones. · City of Renton Effective FEMA Flood Insurance Rate Map: The project site is not located in a Flood Hazard Zone (see Figure 3-1). · Topographic survey. · Renton online GIS Map. Refer to Figure 3-2 for Downstream Drainage Map. Task 3 – Field Inspection A Level 1 downstream analysis was performed on February 16, 2021. The downstream drainage path was field inspected for existing drainage problems. The analysis concluded there are no existing drainage problems within 0.25 mile of site discharge to the City conveyance system. Task 4 – Drainage System Description and Problem Descriptions Stormwater runoff discharges to the public storm system within South 132nd Street. The entire system is within 12-inch closed conveyance pipes. This drainage discharges to a seasonal creek that eventually discharges to Lake Washington, over 1 mile downstream from the site. There are no known signs of flooding, overtopping, or erosion. Technical Information Report Brar Short Plat 2200320.10 Section 3.0 Figures Figure 3-1 ......... City of Renton Effective FEMA Flood Insurance Rate Map Figure 3-2 ......... Downstream Drainage Map RentonKent Newcastle King CountyTukwilaMercer Island Bellevu e Lake Washington Lake Youngs Panther Lake Lake Boren Cedar RiverBlack River May Creek Springbrook Creek Cougar MountainCougar Mountain Coal Creek ParkCoal Creek Park Cedar River Natural ZoneCedar River Natural Zone May Creek ParkMay Creek Park Soos Creek Park and TrailSoos Creek Park and Trail Black River Riparian ForestBlack River Riparian Forest McGarvey Open SpaceMcGarvey Open Space Maplewood Community ParkMaplewood Community Park ValleyValley BensonBenson HighlandsHighlands West HillWest Hill East PlateauEast Plateau SE 192ND STTALBOT RD S140TH AVE SERAI N I E R A V E S EAST VALLEY RDSE 168TH ST RENTON A V E S116TH AVE SENE 12TH STE M ERCER WAY148TH AVE SENE 7TH S T84TH AVE SHOQUIAM AVE NENEWCASTLE WAY W M E RCER WAY S 128TH ST SW 41ST ST PARK AVE N128TH AVE SESE JONES R D E VALLEY HWYSE 72ND ST SE 164TH ST NILE AVE NEN 10TH S T SE 183RD S TUNION AVE NE156TH AVE SEUNION AVE SENE 2ND ST 148TH AVE SESE 164TH STLIND AVE SWUNION AVE NE116TH AVE SESW 7TH ST N 8TH ST EDMONDS AVE NEPUGET DR S E NE 27TH ST 156TH AVE SERENTON AVE S BENSON RD SMONROE AVE NE116TH AVE SENE 4TH ST SR 515 SUNS E T B LV D N E PARK AVE NMAPLE VALLEY HWY SW 43RD ST NE 3RD STLOGAN AVE NSW SU NSET BLVD SW GRADY W A Y N 3RD STRAINIER AVE N 140TH WAY SESR 167108TH AVE SEN 6TH ST S 2ND ST 108TH AVE SESR 515[^405 [^405 Effective FEMA FloodInsurance Rate Map µ Legend Renton City Limits Zone AE, A, AH, AO - Regulatory Zone X - Non Regulatory 0 0.5 10.25 Miles Public Works - Surface Water UtilityPrint Date: 11/05/2012 Data Sources: City of Renton, FEMA FIRM revised May 16, 1995.Cedar River flood hazard area updated with FEMA Cedar RiverLOMR (Case No. 06-10-B569P) approved December 4, 2006. This document is a graphic representation, not guaranteedto survey accuracy, and is based on the best informationavailable as of the date shown. This map is intended forCity display purposes only. 2,400400 City of Renton Print map Template This map is a user generated static output from an Internet mapping site and is for reference only. Data layers that appear on this map may or may not be accurate, current, or otherwise reliable. THIS MAP IS NOT TO BE USED FOR NAVIGATIONWGS_1984_Web_Mercator_Auxiliary_Sphere Notes None 02/15/2021 Legend 272 0 136 272 Feet Information Technology - GIS RentonMapSupport@Rentonwa.gov City and County Labels City and County Boundary Addresses Parcels Network Structures Access Riser Inlet Manhole Utility Vault Clean Out Unknown Control Structures Pump Stations Discharge Points Water Quality Detention Facilities Pond Tank Vault Bioswale Wetland Other Stormwater Mains Culverts Open Drain Virtual Drainlines Facility Outlines Private Network Structures Access Riser Inlet Manhole Clean Out Utility Vault Unknown Private Control Structures Private Pump Stations Private Discharge Points Private Water Quality Private Detention Facilities Tank Wetland Filter Strip Infiltration Trench Vault Pond Bioswale Stormtech Chamber Other Private Pipes Private Culverts Private Open Drain Private Facility Outlines Fences Inactive Structures Inactive Pipes Inactive Water Quality Inactive Detention Facilities PROJECT SITE 1/4 MILE DOWNSTREAM Technical Information Report Brar Short Plat 2200320.10 Section 4 Flow Control and Water Quality Facility Analysis and Design Technical Information Report Brar Short Plat 4-1 2200320.10 4.0 Flow Control and Water Quality Facility Analysis and Design Flow Control 4.1.1 Existing Site Hydrology (Part A) The existing site is developed with two existing buildings, asphalt, and gravel areas. The site is mostly pervious surfaces. The natural discharge location at the southeast corner of the site will be maintained. The Predeveloped Basin Map (Figure 4-2) shows the basin limits evaluated for flow control. Upstream property is tributary to the project site and is referred to as The Pass-Through Basin. The offsite Pass-Through Basin is modeled as existing conditions. The Onsite Basin area includes the proposed improvements within the parcel and along the frontage (but excludes the existing residence that will remain). The onsite basin is modeled as forest to establish the target predeveloped flow control requirements. The Western Washington Hydrology Model (WWHM) was used to model the existing site and tributary basin area. The existing residence to remain is referred to as The Developed – Basin Swap Area. This basin is not included in existing conditions hydrology but is shown as a reference for the developed conditions basin modeling. The existing building and improvements on Lot 1 will remain. 4.1.2 Developed Site Hydrology (Part B) Runoff will be collected in and conveyed to a treatment and detention system located in the southern section of the property. After being treated and detained, the stormwater runoff will discharge to the public storm system in South 132nd Street. The project will meet the Flow Control Duration Standard and is within the West Lake Washington – Seattle South Drainage Basin (see Figure 4-1). This standard requires that developed flows match to predeveloped forested conditions. Under proposed conditions, net impervious area will increase. The increased stormwater runoff will be detained, thus meeting the Flow Control Standard. WWHM calculations are included as Figure 4-3. The Developed Basin Map (Figure 4-2) shows the basin limits evaluated for flow control. The Upstream Bypass Basin matches existing cover conditions for the upstream tributary runoff. Offsite runoff will be collected in a french drain at the top of the site to direct upstream stormwater around the proposed improvements through a separate storm line at the back of the lots. The Onsite Basin assumes full buildout of the short plat and residences (excluding the frontage improvements that are not feasible to detain). All landscape and lawn areas will meet the Soil Amendment Criteria, as outlined in CRSWDM Appendix C, Section C.2.13.1. The Soil Amendment section clarifies that areas meeting the design guidelines for Soil Amendment can be modeled as pasture. All lawn areas are proposed to meet Soil Amendment requirements; therefore, all lawn areas are modeled as pasture. The project will detain Lot 1 improvements even though Lot 1 does not require flow control. Lot 1 will be routed through the detention system in-lieu of the frontage improvements, which are not feasible to detain. The project will detain an equivalent area to the proposed new and replaced surfaces; the basin swap area identifies the limits of mitigation (Figure 4-2). The flow control durations for the proposed site are determined using the existing and developed surface areas shown below. Technical Information Report Brar Short Plat 4-2 2200320.10 Table 1 – Predeveloped vs. Developed Modeled Onsite Hydrology Basin (acres) Predeveloped Developed Upstream Offsite Bypass Forest 0.598 - - Pervious (Pasture) - 0.254 - Pervious (Lawn) - - 0.99 Impervious 0.022 0.366 0.12 4.1.3 Performance Standards (Part C) Area-Specific Flow Control Facility Standard The project is in a Flow Control Duration Standard (Forested Conditions) and is within the West Lake Washington – Seattle South Drainage Basin (see Figure 4-1). This standard requires that developed flows match to predeveloped forested conditions. New impervious surfaces, new pervious surfaces, and replaced impervious surfaces require flow control treatment. Because of the topography of the site, a portion of the frontage improvements cannot be detained onsite for flow control. A basin swap is proposed to provide flow control for an equivalent area. 0.049 acre of the frontage will bypass the detention system. The existing improvements on Lot 1 are included in flow control to mitigate for the bypass area. The Basin Swap area exceeds the 0.049 acre required for mitigation; therefore, the excess area is modeled as passing through the detention system (0.022 acre of impervious surfacing). The 0.022 acre of pass-through area is included in both the predeveloped and developed scenarios. Refer to the Developed Basin Map (Figure 4-2) for the Detention Bypass Basin and the proposed Basin Swap. The Upstream Offsite Bypass area north of the site does not require mitigation. The drainage from the bypass area is routed around the detention system; therefore, the basin is not included in the detention analysis. Conveyance System Capacity Standards The onsite stormwater networks will be sized to convey and contain the 25-year peak flow and the 100-year runoff event and may not create or aggravate a severe flooding problem or severe erosion problem, as described in Section 1.2.2 of the CRSWDM. Refer to Section 5.0 for Conveyance System Analysis and Design. Water Quality Treatment Menu In accordance with the 2017 CRSWDM, onsite flows will be treated to specifications provided by the Basic Water Quality standards. The goal of this treatment menu is to reduce total suspended solids (TSS) by 80%. The Contech StormFilter unit with ZPG media with General Use Level Designation (GULD) approval for basic treatment (see Figure 4-4) will be used to treat stormwater from the basin prior to discharge from the site. The unit will be sized according the GULD approval and the manufacturer’s recommendations. Source Controls The proposed project consists of new residential houses and driveways, along with the existing residence and updated driveway. Source control and erosion and sediment control measures during construction will be included in a CSWPPP to be submitted with the final engineering design. Technical Information Report Brar Short Plat 4-3 2200320.10 Oil Controls Not applicable. 4.1.4 Flow Control System (Part D) A StormTank detention system is proposed to detain developed runoff and release it to match to the flow duration standard. WWHM calculations are provided in Figure 4-3 showing the flow duration standard is met. The required detention volume is 4,560 cubic feet (0.11 ac-ft). Design provides a 4-foot deep system with approximately 5,880 cubic feet. (0.13 ac-ft) of storage. The design is adequate to control runoff from this site. Refer to WWHM for control structure sizing. Refer to civil plans for control structure detail. Water Quality System (Part E) In accordance with the 2017 CRSWDM, onsite flows will be treated to specifications provided by the Basic Water Quality standards. The goal of this treatment menu is to reduce total suspended solids (TSS) by 80%. The Contech StormFilter unit with ZPG media with GULD approval for basic treatment (see Figure 4-4) will be used to treat stormwater prior to discharge from the site. The unit will be sized according to the GULD approval and the manufacturer’s recommendations. The water quality minimum design flow is 0.0294 cfs. The proposed two-cartridge StormFilter will provide treatment up to 0.0501 cfs. Technical Information Report Brar Short Plat 2200320.10 Section 4.0 Figures Figure 4-1 ......... City of Renton Flow Control Application Map – Reference 15-A Figure 4-2 ......... Predeveloped and Developed Basin Maps Figure 4-3 ......... WWHM Flow Control and Water Quality Calculations Figure 4-4 ......... GULD for Basic (TSS) Treatment for Contech StormFilter w/ZPG Media PROJECT SITE N BRAR SHORT PLAT PREDEVELOPED CONDITIONS GRAPHIC SCALE 0 50 100 1" = 50 FEET 25 Q:\2020\2200320\10_CIV\CAD\EXHIBITS\20210427 - Basin Map-Predeveloped.dwg UPSTREAM BYPASS BASIN PERVIOUS: 0.99 ACRE IMPERVIOUS: 0.12 ACRE ONSITE BASIN WWHM MODEL PERVIOUS: 0.598 ACRE IMPERVIOUS: 0.0 ACRE DEVELOPED - BASIN SWAP AREA PERVIOUS: 0.016 ACRE IMPERVIOUS: 0.055 ACRE (0.022 ACRE OF IMPERVIOUS AREA IS MODELED AS PASS THROUGH) N BRAR SHORT PLAT DEVELOPED CONDITIONS GRAPHIC SCALE 0 50 100 1" = 50 FEET 25 Q:\2020\2200320\10_CIV\CAD\EXHIBITS\20210427 - Basin Map.dwg PASS-THROUGH BASIN PERVIOUS: 0.99 ACRE IMPERVIOUS: 0.12 ACRE DETENTION BYPASS BASIN PERVIOUS: 0.016 ACRE IMPERVIOUS: 0.033 ACRE BASIN SWAP PERVIOUS: 0.016 ACRE IMPERVIOUS: 0.055 ACRE (0.022 ACRE OF IMPERVIOUS AREA IS MODELED AS LOT 1 PASS THROUGH) ONSITE BASIN PERVIOUS: 0.254 ACRE IMPERVIOUS: 0.344 ACRE WWHM2012 PROJECT REPORT 20220422 4/22/2022 5:17:29 PM Page 2 General Model Information Project Name:20220422 Site Name:Brar Site Address: City: Report Date:4/22/2022 Gage:Seatac Data Start:1948/10/01 Data End:2009/09/30 Timestep:15 Minute Precip Scale:1.000 Version Date:2019/09/13 Version:4.2.17 POC Thresholds Low Flow Threshold for POC1:50 Percent of the 2 Year High Flow Threshold for POC1:50 Year 20220422 4/22/2022 5:17:29 PM Page 3 Landuse Basin Data Predeveloped Land Use predeveloped Bypass:No GroundWater:No Pervious Land Use acre C, Forest, Mod 0.299 C, Forest, Steep 0.299 Pervious Total 0.598 Impervious Land Use acre Impervious Total 0 Basin Total 0.598 Element Flows To: Surface Interflow Groundwater 20220422 4/22/2022 5:17:29 PM Page 4 lot 1 pass through Bypass:No GroundWater:No Pervious Land Use acre Pervious Total 0 Impervious Land Use acre ROOF TOPS FLAT 0.022 Impervious Total 0.022 Basin Total 0.022 Element Flows To: Surface Interflow Groundwater 20220422 4/22/2022 5:17:29 PM Page 5 Mitigated Land Use lot 1 pass through Bypass:No GroundWater:No Pervious Land Use acre Pervious Total 0 Impervious Land Use acre ROOF TOPS FLAT 0.022 Impervious Total 0.022 Basin Total 0.022 Element Flows To: Surface Interflow Groundwater Vault 1 Vault 1 20220422 4/22/2022 5:17:29 PM Page 6 developed Bypass:No GroundWater:No Pervious Land Use acre C, Pasture, Mod 0.254 Pervious Total 0.254 Impervious Land Use acre ROADS MOD 0.172 ROOF TOPS FLAT 0.172 Impervious Total 0.344 Basin Total 0.598 Element Flows To: Surface Interflow Groundwater Vault 1 Vault 1 20220422 4/22/2022 5:17:29 PM Page 7 Routing Elements Predeveloped Routing 20220422 4/22/2022 5:17:29 PM Page 8 Mitigated Routing Vault 1 Width:13 ft. Length:111 ft. Depth:5 ft. Discharge Structure Riser Height:4 ft. Riser Diameter:18 in. Orifice 1 Diameter:0.6 in.Elevation:0 ft. Orifice 2 Diameter:0.8 in.Elevation:2.4 ft. Orifice 3 Diameter:0.5 in.Elevation:3.25 ft. Element Flows To: Outlet 1 Outlet 2 Vault Hydraulic Table Stage(feet)Area(ac.)Volume(ac-ft.)Discharge(cfs)Infilt(cfs) 0.0000 0.033 0.000 0.000 0.000 0.0556 0.033 0.001 0.002 0.000 0.1111 0.033 0.003 0.003 0.000 0.1667 0.033 0.005 0.004 0.000 0.2222 0.033 0.007 0.004 0.000 0.2778 0.033 0.009 0.005 0.000 0.3333 0.033 0.011 0.005 0.000 0.3889 0.033 0.012 0.006 0.000 0.4444 0.033 0.014 0.006 0.000 0.5000 0.033 0.016 0.006 0.000 0.5556 0.033 0.018 0.007 0.000 0.6111 0.033 0.020 0.007 0.000 0.6667 0.033 0.022 0.008 0.000 0.7222 0.033 0.023 0.008 0.000 0.7778 0.033 0.025 0.008 0.000 0.8333 0.033 0.027 0.008 0.000 0.8889 0.033 0.029 0.009 0.000 0.9444 0.033 0.031 0.009 0.000 1.0000 0.033 0.033 0.009 0.000 1.0556 0.033 0.035 0.010 0.000 1.1111 0.033 0.036 0.010 0.000 1.1667 0.033 0.038 0.010 0.000 1.2222 0.033 0.040 0.010 0.000 1.2778 0.033 0.042 0.011 0.000 1.3333 0.033 0.044 0.011 0.000 1.3889 0.033 0.046 0.011 0.000 1.4444 0.033 0.047 0.011 0.000 1.5000 0.033 0.049 0.012 0.000 1.5556 0.033 0.051 0.012 0.000 1.6111 0.033 0.053 0.012 0.000 1.6667 0.033 0.055 0.012 0.000 1.7222 0.033 0.057 0.012 0.000 1.7778 0.033 0.058 0.013 0.000 1.8333 0.033 0.060 0.013 0.000 1.8889 0.033 0.062 0.013 0.000 1.9444 0.033 0.064 0.013 0.000 2.0000 0.033 0.066 0.013 0.000 2.0556 0.033 0.068 0.014 0.000 20220422 4/22/2022 5:17:29 PM Page 9 2.1111 0.033 0.069 0.014 0.000 2.1667 0.033 0.071 0.014 0.000 2.2222 0.033 0.073 0.014 0.000 2.2778 0.033 0.075 0.014 0.000 2.3333 0.033 0.077 0.014 0.000 2.3889 0.033 0.079 0.015 0.000 2.4444 0.033 0.081 0.018 0.000 2.5000 0.033 0.082 0.020 0.000 2.5556 0.033 0.084 0.022 0.000 2.6111 0.033 0.086 0.023 0.000 2.6667 0.033 0.088 0.024 0.000 2.7222 0.033 0.090 0.026 0.000 2.7778 0.033 0.092 0.027 0.000 2.8333 0.033 0.093 0.027 0.000 2.8889 0.033 0.095 0.028 0.000 2.9444 0.033 0.097 0.029 0.000 3.0000 0.033 0.099 0.030 0.000 3.0556 0.033 0.101 0.031 0.000 3.1111 0.033 0.103 0.031 0.000 3.1667 0.033 0.104 0.032 0.000 3.2222 0.033 0.106 0.033 0.000 3.2778 0.033 0.108 0.035 0.000 3.3333 0.033 0.110 0.036 0.000 3.3889 0.033 0.112 0.037 0.000 3.4444 0.033 0.114 0.038 0.000 3.5000 0.033 0.115 0.039 0.000 3.5556 0.033 0.117 0.040 0.000 3.6111 0.033 0.119 0.041 0.000 3.6667 0.033 0.121 0.042 0.000 3.7222 0.033 0.123 0.043 0.000 3.7778 0.033 0.125 0.044 0.000 3.8333 0.033 0.127 0.045 0.000 3.8889 0.033 0.128 0.045 0.000 3.9444 0.033 0.130 0.046 0.000 4.0000 0.033 0.132 0.047 0.000 4.0556 0.033 0.134 0.256 0.000 4.1111 0.033 0.136 0.636 0.000 4.1667 0.033 0.138 1.123 0.000 4.2222 0.033 0.139 1.687 0.000 4.2778 0.033 0.141 2.299 0.000 4.3333 0.033 0.143 2.934 0.000 4.3889 0.033 0.145 3.562 0.000 4.4444 0.033 0.147 4.156 0.000 4.5000 0.033 0.149 4.692 0.000 4.5556 0.033 0.150 5.151 0.000 4.6111 0.033 0.152 5.523 0.000 4.6667 0.033 0.154 5.809 0.000 4.7222 0.033 0.156 6.030 0.000 4.7778 0.033 0.158 6.306 0.000 4.8333 0.033 0.160 6.526 0.000 4.8889 0.033 0.162 6.739 0.000 4.9444 0.033 0.163 6.945 0.000 5.0000 0.033 0.165 7.145 0.000 5.0556 0.033 0.167 7.340 0.000 5.1111 0.000 0.000 7.529 0.000 20220422 4/22/2022 5:17:29 PM Page 10 Analysis Results POC 1 + Predeveloped x Mitigated Predeveloped Landuse Totals for POC #1 Total Pervious Area:0.598 Total Impervious Area:0.022 Mitigated Landuse Totals for POC #1 Total Pervious Area:0.254 Total Impervious Area:0.366 Flow Frequency Method:Log Pearson Type III 17B Flow Frequency Return Periods for Predeveloped. POC #1 Return Period Flow(cfs) 2 year 0.027223 5 year 0.042148 10 year 0.052967 25 year 0.067581 50 year 0.079101 100 year 0.091131 Flow Frequency Return Periods for Mitigated. POC #1 Return Period Flow(cfs) 2 year 0.015936 5 year 0.024503 10 year 0.031561 25 year 0.04227 50 year 0.051688 100 year 0.062468 Annual Peaks Annual Peaks for Predeveloped and Mitigated. POC #1 Year Predeveloped Mitigated 1949 0.036 0.012 1950 0.037 0.015 1951 0.050 0.042 1952 0.020 0.011 1953 0.015 0.011 1954 0.021 0.014 1955 0.035 0.015 1956 0.030 0.022 1957 0.030 0.013 1958 0.025 0.014 Facility volume greatly exceeds detention needs 20220422 4/22/2022 5:18:02 PM Page 11 1959 0.020 0.012 1960 0.040 0.035 1961 0.022 0.013 1962 0.015 0.010 1963 0.020 0.013 1964 0.026 0.013 1965 0.022 0.014 1966 0.019 0.012 1967 0.042 0.014 1968 0.025 0.012 1969 0.025 0.012 1970 0.023 0.012 1971 0.025 0.014 1972 0.039 0.027 1973 0.020 0.013 1974 0.024 0.014 1975 0.035 0.014 1976 0.025 0.014 1977 0.009 0.011 1978 0.022 0.013 1979 0.012 0.010 1980 0.052 0.030 1981 0.019 0.012 1982 0.043 0.031 1983 0.028 0.014 1984 0.020 0.011 1985 0.011 0.012 1986 0.043 0.028 1987 0.041 0.032 1988 0.017 0.011 1989 0.012 0.010 1990 0.091 0.036 1991 0.055 0.037 1992 0.024 0.013 1993 0.020 0.012 1994 0.009 0.009 1995 0.027 0.015 1996 0.059 0.041 1997 0.048 0.036 1998 0.019 0.012 1999 0.053 0.028 2000 0.022 0.013 2001 0.010 0.010 2002 0.027 0.028 2003 0.036 0.011 2004 0.045 0.044 2005 0.031 0.014 2006 0.031 0.014 2007 0.071 0.047 2008 0.083 0.046 2009 0.042 0.026 Ranked Annual Peaks Ranked Annual Peaks for Predeveloped and Mitigated. POC #1 Rank Predeveloped Mitigated 1 0.0913 0.0469 2 0.0830 0.0462 3 0.0710 0.0441 20220422 4/22/2022 5:18:02 PM Page 12 4 0.0593 0.0421 5 0.0545 0.0411 6 0.0525 0.0373 7 0.0522 0.0357 8 0.0499 0.0356 9 0.0482 0.0354 10 0.0446 0.0321 11 0.0431 0.0310 12 0.0431 0.0296 13 0.0423 0.0280 14 0.0423 0.0279 15 0.0407 0.0276 16 0.0397 0.0269 17 0.0395 0.0265 18 0.0368 0.0215 19 0.0365 0.0148 20 0.0361 0.0148 21 0.0352 0.0145 22 0.0349 0.0144 23 0.0313 0.0143 24 0.0310 0.0143 25 0.0302 0.0142 26 0.0299 0.0141 27 0.0276 0.0141 28 0.0266 0.0140 29 0.0265 0.0139 30 0.0259 0.0138 31 0.0252 0.0137 32 0.0250 0.0137 33 0.0248 0.0134 34 0.0248 0.0134 35 0.0246 0.0134 36 0.0245 0.0133 37 0.0237 0.0132 38 0.0227 0.0132 39 0.0222 0.0131 40 0.0216 0.0126 41 0.0216 0.0125 42 0.0215 0.0124 43 0.0206 0.0123 44 0.0204 0.0122 45 0.0203 0.0121 46 0.0203 0.0121 47 0.0200 0.0121 48 0.0200 0.0119 49 0.0195 0.0119 50 0.0191 0.0119 51 0.0189 0.0115 52 0.0185 0.0115 53 0.0170 0.0112 54 0.0154 0.0110 55 0.0150 0.0108 56 0.0120 0.0105 57 0.0116 0.0104 58 0.0112 0.0103 59 0.0095 0.0100 60 0.0091 0.0099 61 0.0090 0.0091 20220422 4/22/2022 5:18:02 PM Page 13 20220422 4/22/2022 5:18:02 PM Page 14 Duration Flows The Facility PASSED Flow(cfs)Predev Mit Percentage Pass/Fail 0.0136 10072 8265 82 Pass 0.0143 9056 5544 61 Pass 0.0149 8175 3702 45 Pass 0.0156 7289 3255 44 Pass 0.0163 6588 3168 48 Pass 0.0169 5976 3097 51 Pass 0.0176 5431 3022 55 Pass 0.0182 4909 2954 60 Pass 0.0189 4447 2868 64 Pass 0.0196 4034 2772 68 Pass 0.0202 3709 2674 72 Pass 0.0209 3422 2584 75 Pass 0.0215 3138 2445 77 Pass 0.0222 2881 2342 81 Pass 0.0229 2656 2218 83 Pass 0.0235 2436 2094 85 Pass 0.0242 2233 1972 88 Pass 0.0249 2029 1858 91 Pass 0.0255 1845 1738 94 Pass 0.0262 1668 1620 97 Pass 0.0268 1517 1496 98 Pass 0.0275 1387 1342 96 Pass 0.0282 1261 1214 96 Pass 0.0288 1145 1113 97 Pass 0.0295 1058 983 92 Pass 0.0301 973 884 90 Pass 0.0308 912 789 86 Pass 0.0315 858 707 82 Pass 0.0321 796 623 78 Pass 0.0328 747 525 70 Pass 0.0335 695 445 64 Pass 0.0341 646 419 64 Pass 0.0348 604 392 64 Pass 0.0354 554 350 63 Pass 0.0361 510 315 61 Pass 0.0368 455 294 64 Pass 0.0374 409 266 65 Pass 0.0381 373 250 67 Pass 0.0387 335 230 68 Pass 0.0394 296 208 70 Pass 0.0401 259 180 69 Pass 0.0407 223 152 68 Pass 0.0414 195 128 65 Pass 0.0421 172 106 61 Pass 0.0427 151 97 64 Pass 0.0434 133 84 63 Pass 0.0440 123 64 52 Pass 0.0447 108 46 42 Pass 0.0454 94 37 39 Pass 0.0460 83 26 31 Pass 0.0467 73 8 10 Pass 0.0473 63 0 0 Pass 0.0480 54 0 0 Pass 20220422 4/22/2022 5:18:02 PM Page 15 0.0487 48 0 0 Pass 0.0493 42 0 0 Pass 0.0500 40 0 0 Pass 0.0507 39 0 0 Pass 0.0513 37 0 0 Pass 0.0520 37 0 0 Pass 0.0526 33 0 0 Pass 0.0533 29 0 0 Pass 0.0540 24 0 0 Pass 0.0546 22 0 0 Pass 0.0553 19 0 0 Pass 0.0559 17 0 0 Pass 0.0566 15 0 0 Pass 0.0573 12 0 0 Pass 0.0579 11 0 0 Pass 0.0586 9 0 0 Pass 0.0593 9 0 0 Pass 0.0599 7 0 0 Pass 0.0606 7 0 0 Pass 0.0612 7 0 0 Pass 0.0619 6 0 0 Pass 0.0626 6 0 0 Pass 0.0632 6 0 0 Pass 0.0639 6 0 0 Pass 0.0645 6 0 0 Pass 0.0652 6 0 0 Pass 0.0659 6 0 0 Pass 0.0665 6 0 0 Pass 0.0672 4 0 0 Pass 0.0679 4 0 0 Pass 0.0685 4 0 0 Pass 0.0692 4 0 0 Pass 0.0698 4 0 0 Pass 0.0705 4 0 0 Pass 0.0712 3 0 0 Pass 0.0718 3 0 0 Pass 0.0725 3 0 0 Pass 0.0731 3 0 0 Pass 0.0738 3 0 0 Pass 0.0745 3 0 0 Pass 0.0751 3 0 0 Pass 0.0758 3 0 0 Pass 0.0765 3 0 0 Pass 0.0771 3 0 0 Pass 0.0778 3 0 0 Pass 0.0784 3 0 0 Pass 0.0791 2 0 0 Pass 20220422 4/22/2022 5:18:02 PM Page 16 Water Quality Water Quality BMP Flow and Volume for POC #1 On-line facility volume:0 acre-feet On-line facility target flow:0 cfs. Adjusted for 15 min:0 cfs. Off-line facility target flow:0 cfs. Adjusted for 15 min:0 cfs. 20220422 4/22/2022 5:18:02 PM Page 17 LID Report 20220422 4/22/2022 5:18:39 PM Page 18 Model Default Modifications Total of 0 changes have been made. PERLND Changes No PERLND changes have been made. IMPLND Changes No IMPLND changes have been made. 20220422 4/22/2022 5:18:39 PM Page 19 Appendix Predeveloped Schematic 20220422 4/22/2022 5:18:40 PM Page 20 Mitigated Schematic 20220422 4/22/2022 5:18:42 PM Page 21 Predeveloped UCI File RUN GLOBAL WWHM4 model simulation START 1948 10 01 END 2009 09 30 RUN INTERP OUTPUT LEVEL 3 0 RESUME 0 RUN 1 UNIT SYSTEM 1 END GLOBAL FILES <File> <Un#> <-----------File Name------------------------------>*** <-ID-> *** WDM 26 20220422.wdm MESSU 25 Pre20220422.MES 27 Pre20220422.L61 28 Pre20220422.L62 30 POC202204221.dat END FILES OPN SEQUENCE INGRP INDELT 00:15 PERLND 11 PERLND 12 IMPLND 4 COPY 501 DISPLY 1 END INGRP END OPN SEQUENCE DISPLY DISPLY-INFO1 # - #<----------Title----------->***TRAN PIVL DIG1 FIL1 PYR DIG2 FIL2 YRND 1 predeveloped MAX 1 2 30 9 END DISPLY-INFO1 END DISPLY COPY TIMESERIES # - # NPT NMN *** 1 1 1 501 1 1 END TIMESERIES END COPY GENER OPCODE # # OPCD *** END OPCODE PARM # # K *** END PARM END GENER PERLND GEN-INFO <PLS ><-------Name------->NBLKS Unit-systems Printer *** # - # User t-series Engl Metr *** in out *** 11 C, Forest, Mod 1 1 1 1 27 0 12 C, Forest, Steep 1 1 1 1 27 0 END GEN-INFO *** Section PWATER*** ACTIVITY <PLS > ************* Active Sections ***************************** # - # ATMP SNOW PWAT SED PST PWG PQAL MSTL PEST NITR PHOS TRAC *** 11 0 0 1 0 0 0 0 0 0 0 0 0 12 0 0 1 0 0 0 0 0 0 0 0 0 END ACTIVITY PRINT-INFO <PLS > ***************** Print-flags ***************************** PIVL PYR 20220422 4/22/2022 5:18:42 PM Page 22 # - # ATMP SNOW PWAT SED PST PWG PQAL MSTL PEST NITR PHOS TRAC ********* 11 0 0 4 0 0 0 0 0 0 0 0 0 1 9 12 0 0 4 0 0 0 0 0 0 0 0 0 1 9 END PRINT-INFO PWAT-PARM1 <PLS > PWATER variable monthly parameter value flags *** # - # CSNO RTOP UZFG VCS VUZ VNN VIFW VIRC VLE INFC HWT *** 11 0 0 0 0 0 0 0 0 0 0 0 12 0 0 0 0 0 0 0 0 0 0 0 END PWAT-PARM1 PWAT-PARM2 <PLS > PWATER input info: Part 2 *** # - # ***FOREST LZSN INFILT LSUR SLSUR KVARY AGWRC 11 0 4.5 0.08 400 0.1 0.5 0.996 12 0 4.5 0.08 400 0.15 0.5 0.996 END PWAT-PARM2 PWAT-PARM3 <PLS > PWATER input info: Part 3 *** # - # ***PETMAX PETMIN INFEXP INFILD DEEPFR BASETP AGWETP 11 0 0 2 2 0 0 0 12 0 0 2 2 0 0 0 END PWAT-PARM3 PWAT-PARM4 <PLS > PWATER input info: Part 4 *** # - # CEPSC UZSN NSUR INTFW IRC LZETP *** 11 0.2 0.5 0.35 6 0.5 0.7 12 0.2 0.3 0.35 6 0.3 0.7 END PWAT-PARM4 PWAT-STATE1 <PLS > *** Initial conditions at start of simulation ran from 1990 to end of 1992 (pat 1-11-95) RUN 21 *** # - # *** CEPS SURS UZS IFWS LZS AGWS GWVS 11 0 0 0 0 2.5 1 0 12 0 0 0 0 2.5 1 0 END PWAT-STATE1 END PERLND IMPLND GEN-INFO <PLS ><-------Name-------> Unit-systems Printer *** # - # User t-series Engl Metr *** in out *** 4 ROOF TOPS/FLAT 1 1 1 27 0 END GEN-INFO *** Section IWATER*** ACTIVITY <PLS > ************* Active Sections ***************************** # - # ATMP SNOW IWAT SLD IWG IQAL *** 4 0 0 1 0 0 0 END ACTIVITY PRINT-INFO <ILS > ******** Print-flags ******** PIVL PYR # - # ATMP SNOW IWAT SLD IWG IQAL ********* 4 0 0 4 0 0 0 1 9 END PRINT-INFO IWAT-PARM1 <PLS > IWATER variable monthly parameter value flags *** # - # CSNO RTOP VRS VNN RTLI *** 4 0 0 0 0 0 END IWAT-PARM1 IWAT-PARM2 20220422 4/22/2022 5:18:42 PM Page 23 <PLS > IWATER input info: Part 2 *** # - # *** LSUR SLSUR NSUR RETSC 4 400 0.01 0.1 0.1 END IWAT-PARM2 IWAT-PARM3 <PLS > IWATER input info: Part 3 *** # - # ***PETMAX PETMIN 4 0 0 END IWAT-PARM3 IWAT-STATE1 <PLS > *** Initial conditions at start of simulation # - # *** RETS SURS 4 0 0 END IWAT-STATE1 END IMPLND SCHEMATIC <-Source-> <--Area--> <-Target-> MBLK *** <Name> # <-factor-> <Name> # Tbl# *** predeveloped*** PERLND 11 0.299 COPY 501 12 PERLND 11 0.299 COPY 501 13 PERLND 12 0.299 COPY 501 12 PERLND 12 0.299 COPY 501 13 lot 1 pass through*** IMPLND 4 0.022 COPY 501 15 ******Routing****** END SCHEMATIC NETWORK <-Volume-> <-Grp> <-Member-><--Mult-->Tran <-Target vols> <-Grp> <-Member-> *** <Name> # <Name> # #<-factor->strg <Name> # # <Name> # # *** COPY 501 OUTPUT MEAN 1 1 48.4 DISPLY 1 INPUT TIMSER 1 <-Volume-> <-Grp> <-Member-><--Mult-->Tran <-Target vols> <-Grp> <-Member-> *** <Name> # <Name> # #<-factor->strg <Name> # # <Name> # # *** END NETWORK RCHRES GEN-INFO RCHRES Name Nexits Unit Systems Printer *** # - #<------------------><---> User T-series Engl Metr LKFG *** in out *** END GEN-INFO *** Section RCHRES*** ACTIVITY <PLS > ************* Active Sections ***************************** # - # HYFG ADFG CNFG HTFG SDFG GQFG OXFG NUFG PKFG PHFG *** END ACTIVITY PRINT-INFO <PLS > ***************** Print-flags ******************* PIVL PYR # - # HYDR ADCA CONS HEAT SED GQL OXRX NUTR PLNK PHCB PIVL PYR ********* END PRINT-INFO HYDR-PARM1 RCHRES Flags for each HYDR Section *** # - # VC A1 A2 A3 ODFVFG for each *** ODGTFG for each FUNCT for each FG FG FG FG possible exit *** possible exit possible exit * * * * * * * * * * * * * * *** END HYDR-PARM1 HYDR-PARM2 20220422 4/22/2022 5:18:42 PM Page 24 # - # FTABNO LEN DELTH STCOR KS DB50 *** <------><--------><--------><--------><--------><--------><--------> *** END HYDR-PARM2 HYDR-INIT RCHRES Initial conditions for each HYDR section *** # - # *** VOL Initial value of COLIND Initial value of OUTDGT *** ac-ft for each possible exit for each possible exit <------><--------> <---><---><---><---><---> *** <---><---><---><---><---> END HYDR-INIT END RCHRES SPEC-ACTIONS END SPEC-ACTIONS FTABLES END FTABLES EXT SOURCES <-Volume-> <Member> SsysSgap<--Mult-->Tran <-Target vols> <-Grp> <-Member-> *** <Name> # <Name> # tem strg<-factor->strg <Name> # # <Name> # # *** WDM 2 PREC ENGL 1 PERLND 1 999 EXTNL PREC WDM 2 PREC ENGL 1 IMPLND 1 999 EXTNL PREC WDM 1 EVAP ENGL 0.76 PERLND 1 999 EXTNL PETINP WDM 1 EVAP ENGL 0.76 IMPLND 1 999 EXTNL PETINP END EXT SOURCES EXT TARGETS <-Volume-> <-Grp> <-Member-><--Mult-->Tran <-Volume-> <Member> Tsys Tgap Amd *** <Name> # <Name> # #<-factor->strg <Name> # <Name> tem strg strg*** COPY 501 OUTPUT MEAN 1 1 48.4 WDM 501 FLOW ENGL REPL END EXT TARGETS MASS-LINK <Volume> <-Grp> <-Member-><--Mult--> <Target> <-Grp> <-Member->*** <Name> <Name> # #<-factor-> <Name> <Name> # #*** MASS-LINK 12 PERLND PWATER SURO 0.083333 COPY INPUT MEAN END MASS-LINK 12 MASS-LINK 13 PERLND PWATER IFWO 0.083333 COPY INPUT MEAN END MASS-LINK 13 MASS-LINK 15 IMPLND IWATER SURO 0.083333 COPY INPUT MEAN END MASS-LINK 15 END MASS-LINK END RUN 20220422 4/22/2022 5:18:42 PM Page 25 Mitigated UCI File RUN GLOBAL WWHM4 model simulation START 1948 10 01 END 2009 09 30 RUN INTERP OUTPUT LEVEL 3 0 RESUME 0 RUN 1 UNIT SYSTEM 1 END GLOBAL FILES <File> <Un#> <-----------File Name------------------------------>*** <-ID-> *** WDM 26 20220422.wdm MESSU 25 Mit20220422.MES 27 Mit20220422.L61 28 Mit20220422.L62 30 POC202204221.dat END FILES OPN SEQUENCE INGRP INDELT 00:15 IMPLND 4 PERLND 14 IMPLND 2 RCHRES 1 COPY 1 COPY 501 DISPLY 1 END INGRP END OPN SEQUENCE DISPLY DISPLY-INFO1 # - #<----------Title----------->***TRAN PIVL DIG1 FIL1 PYR DIG2 FIL2 YRND 1 Vault 1 MAX 1 2 30 9 END DISPLY-INFO1 END DISPLY COPY TIMESERIES # - # NPT NMN *** 1 1 1 501 1 1 END TIMESERIES END COPY GENER OPCODE # # OPCD *** END OPCODE PARM # # K *** END PARM END GENER PERLND GEN-INFO <PLS ><-------Name------->NBLKS Unit-systems Printer *** # - # User t-series Engl Metr *** in out *** 14 C, Pasture, Mod 1 1 1 1 27 0 END GEN-INFO *** Section PWATER*** ACTIVITY <PLS > ************* Active Sections ***************************** # - # ATMP SNOW PWAT SED PST PWG PQAL MSTL PEST NITR PHOS TRAC *** 14 0 0 1 0 0 0 0 0 0 0 0 0 END ACTIVITY PRINT-INFO <PLS > ***************** Print-flags ***************************** PIVL PYR 20220422 4/22/2022 5:18:42 PM Page 26 # - # ATMP SNOW PWAT SED PST PWG PQAL MSTL PEST NITR PHOS TRAC ********* 14 0 0 4 0 0 0 0 0 0 0 0 0 1 9 END PRINT-INFO PWAT-PARM1 <PLS > PWATER variable monthly parameter value flags *** # - # CSNO RTOP UZFG VCS VUZ VNN VIFW VIRC VLE INFC HWT *** 14 0 0 0 0 0 0 0 0 0 0 0 END PWAT-PARM1 PWAT-PARM2 <PLS > PWATER input info: Part 2 *** # - # ***FOREST LZSN INFILT LSUR SLSUR KVARY AGWRC 14 0 4.5 0.06 400 0.1 0.5 0.996 END PWAT-PARM2 PWAT-PARM3 <PLS > PWATER input info: Part 3 *** # - # ***PETMAX PETMIN INFEXP INFILD DEEPFR BASETP AGWETP 14 0 0 2 2 0 0 0 END PWAT-PARM3 PWAT-PARM4 <PLS > PWATER input info: Part 4 *** # - # CEPSC UZSN NSUR INTFW IRC LZETP *** 14 0.15 0.4 0.3 6 0.5 0.4 END PWAT-PARM4 PWAT-STATE1 <PLS > *** Initial conditions at start of simulation ran from 1990 to end of 1992 (pat 1-11-95) RUN 21 *** # - # *** CEPS SURS UZS IFWS LZS AGWS GWVS 14 0 0 0 0 2.5 1 0 END PWAT-STATE1 END PERLND IMPLND GEN-INFO <PLS ><-------Name-------> Unit-systems Printer *** # - # User t-series Engl Metr *** in out *** 4 ROOF TOPS/FLAT 1 1 1 27 0 2 ROADS/MOD 1 1 1 27 0 END GEN-INFO *** Section IWATER*** ACTIVITY <PLS > ************* Active Sections ***************************** # - # ATMP SNOW IWAT SLD IWG IQAL *** 4 0 0 1 0 0 0 2 0 0 1 0 0 0 END ACTIVITY PRINT-INFO <ILS > ******** Print-flags ******** PIVL PYR # - # ATMP SNOW IWAT SLD IWG IQAL ********* 4 0 0 4 0 0 0 1 9 2 0 0 4 0 0 0 1 9 END PRINT-INFO IWAT-PARM1 <PLS > IWATER variable monthly parameter value flags *** # - # CSNO RTOP VRS VNN RTLI *** 4 0 0 0 0 0 2 0 0 0 0 0 END IWAT-PARM1 IWAT-PARM2 <PLS > IWATER input info: Part 2 *** # - # *** LSUR SLSUR NSUR RETSC 20220422 4/22/2022 5:18:42 PM Page 27 4 400 0.01 0.1 0.1 2 400 0.05 0.1 0.08 END IWAT-PARM2 IWAT-PARM3 <PLS > IWATER input info: Part 3 *** # - # ***PETMAX PETMIN 4 0 0 2 0 0 END IWAT-PARM3 IWAT-STATE1 <PLS > *** Initial conditions at start of simulation # - # *** RETS SURS 4 0 0 2 0 0 END IWAT-STATE1 END IMPLND SCHEMATIC <-Source-> <--Area--> <-Target-> MBLK *** <Name> # <-factor-> <Name> # Tbl# *** lot 1 pass through*** IMPLND 4 0.022 RCHRES 1 5 developed*** PERLND 14 0.254 RCHRES 1 2 PERLND 14 0.254 RCHRES 1 3 IMPLND 2 0.172 RCHRES 1 5 IMPLND 4 0.172 RCHRES 1 5 ******Routing****** IMPLND 4 0.022 COPY 1 15 PERLND 14 0.254 COPY 1 12 IMPLND 2 0.172 COPY 1 15 IMPLND 4 0.172 COPY 1 15 PERLND 14 0.254 COPY 1 13 RCHRES 1 1 COPY 501 16 END SCHEMATIC NETWORK <-Volume-> <-Grp> <-Member-><--Mult-->Tran <-Target vols> <-Grp> <-Member-> *** <Name> # <Name> # #<-factor->strg <Name> # # <Name> # # *** COPY 501 OUTPUT MEAN 1 1 48.4 DISPLY 1 INPUT TIMSER 1 <-Volume-> <-Grp> <-Member-><--Mult-->Tran <-Target vols> <-Grp> <-Member-> *** <Name> # <Name> # #<-factor->strg <Name> # # <Name> # # *** END NETWORK RCHRES GEN-INFO RCHRES Name Nexits Unit Systems Printer *** # - #<------------------><---> User T-series Engl Metr LKFG *** in out *** 1 Vault 1 1 1 1 1 28 0 1 END GEN-INFO *** Section RCHRES*** ACTIVITY <PLS > ************* Active Sections ***************************** # - # HYFG ADFG CNFG HTFG SDFG GQFG OXFG NUFG PKFG PHFG *** 1 1 0 0 0 0 0 0 0 0 0 END ACTIVITY PRINT-INFO <PLS > ***************** Print-flags ******************* PIVL PYR # - # HYDR ADCA CONS HEAT SED GQL OXRX NUTR PLNK PHCB PIVL PYR ********* 1 4 0 0 0 0 0 0 0 0 0 1 9 20220422 4/22/2022 5:18:42 PM Page 28 END PRINT-INFO HYDR-PARM1 RCHRES Flags for each HYDR Section *** # - # VC A1 A2 A3 ODFVFG for each *** ODGTFG for each FUNCT for each FG FG FG FG possible exit *** possible exit possible exit * * * * * * * * * * * * * * *** 1 0 1 0 0 4 0 0 0 0 0 0 0 0 0 2 2 2 2 2 END HYDR-PARM1 HYDR-PARM2 # - # FTABNO LEN DELTH STCOR KS DB50 *** <------><--------><--------><--------><--------><--------><--------> *** 1 1 0.02 0.0 0.0 0.5 0.0 END HYDR-PARM2 HYDR-INIT RCHRES Initial conditions for each HYDR section *** # - # *** VOL Initial value of COLIND Initial value of OUTDGT *** ac-ft for each possible exit for each possible exit <------><--------> <---><---><---><---><---> *** <---><---><---><---><---> 1 0 4.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 END HYDR-INIT END RCHRES SPEC-ACTIONS END SPEC-ACTIONS FTABLES FTABLE 1 92 4 Depth Area Volume Outflow1 Velocity Travel Time*** (ft) (acres) (acre-ft) (cfs) (ft/sec) (Minutes)*** 0.000000 0.033127 0.000000 0.000000 0.055556 0.033127 0.001840 0.002303 0.111111 0.033127 0.003681 0.003256 0.166667 0.033127 0.005521 0.003988 0.222222 0.033127 0.007361 0.004605 0.277778 0.033127 0.009202 0.005149 0.333333 0.033127 0.011042 0.005640 0.388889 0.033127 0.012883 0.006092 0.444444 0.033127 0.014723 0.006513 0.500000 0.033127 0.016563 0.006908 0.555556 0.033127 0.018404 0.007282 0.611111 0.033127 0.020244 0.007637 0.666667 0.033127 0.022084 0.007977 0.722222 0.033127 0.023925 0.008302 0.777778 0.033127 0.025765 0.008616 0.833333 0.033127 0.027606 0.008918 0.888889 0.033127 0.029446 0.009211 0.944444 0.033127 0.031286 0.009494 1.000000 0.033127 0.033127 0.009769 1.055556 0.033127 0.034967 0.010037 1.111111 0.033127 0.036807 0.010298 1.166667 0.033127 0.038648 0.010552 1.222222 0.033127 0.040488 0.010800 1.277778 0.033127 0.042329 0.011043 1.333333 0.033127 0.044169 0.011281 1.388889 0.033127 0.046009 0.011513 1.444444 0.033127 0.047850 0.011741 1.500000 0.033127 0.049690 0.011965 1.555556 0.033127 0.051530 0.012184 1.611111 0.033127 0.053371 0.012400 1.666667 0.033127 0.055211 0.012612 1.722222 0.033127 0.057052 0.012821 1.777778 0.033127 0.058892 0.013026 1.833333 0.033127 0.060732 0.013228 1.888889 0.033127 0.062573 0.013427 1.944444 0.033127 0.064413 0.013623 2.000000 0.033127 0.066253 0.013816 2.055556 0.033127 0.068094 0.014006 2.111111 0.033127 0.069934 0.014194 20220422 4/22/2022 5:18:42 PM Page 29 2.166667 0.033127 0.071775 0.014380 2.222222 0.033127 0.073615 0.014563 2.277778 0.033127 0.075455 0.014744 2.333333 0.033127 0.077296 0.014923 2.388889 0.033127 0.079136 0.015099 2.444444 0.033127 0.080976 0.018935 2.500000 0.033127 0.082817 0.020939 2.555556 0.033127 0.084657 0.022467 2.611111 0.033127 0.086498 0.023766 2.666667 0.033127 0.088338 0.024922 2.722222 0.033127 0.090178 0.025977 2.777778 0.033127 0.092019 0.026957 2.833333 0.033127 0.093859 0.027877 2.888889 0.033127 0.095699 0.028748 2.944444 0.033127 0.097540 0.029578 3.000000 0.033127 0.099380 0.030374 3.055556 0.033127 0.101221 0.031139 3.111111 0.033127 0.103061 0.031877 3.166667 0.033127 0.104901 0.032591 3.222222 0.033127 0.106742 0.033285 3.277778 0.033127 0.108582 0.035089 3.333333 0.033127 0.110422 0.036573 3.388889 0.033127 0.112263 0.037783 3.444444 0.033127 0.114103 0.038872 3.500000 0.033127 0.115944 0.039884 3.555556 0.033127 0.117784 0.040841 3.611111 0.033127 0.119624 0.041754 3.666667 0.033127 0.121465 0.042632 3.722222 0.033127 0.123305 0.043480 3.777778 0.033127 0.125145 0.044302 3.833333 0.033127 0.126986 0.045101 3.888889 0.033127 0.128826 0.045880 3.944444 0.033127 0.130667 0.046639 4.000000 0.033127 0.132507 0.047382 4.055556 0.033127 0.134347 0.256381 4.111111 0.033127 0.136188 0.636627 4.166667 0.033127 0.138028 1.123791 4.222222 0.033127 0.139868 1.687153 4.277778 0.033127 0.141709 2.299719 4.333333 0.033127 0.143549 2.934065 4.388889 0.033127 0.145390 3.562120 4.444444 0.033127 0.147230 4.156475 4.500000 0.033127 0.149070 4.692569 4.555556 0.033127 0.150911 5.151455 4.611111 0.033127 0.152751 5.523060 4.666667 0.033127 0.154591 5.809821 4.722222 0.033127 0.156432 6.030687 4.777778 0.033127 0.158272 6.306373 4.833333 0.033127 0.160112 6.526319 4.888889 0.033127 0.161953 6.739059 4.944444 0.033127 0.163793 6.945261 5.000000 0.033127 0.165634 7.145491 5.055556 0.033127 0.167474 7.340242 END FTABLE 1 END FTABLES EXT SOURCES <-Volume-> <Member> SsysSgap<--Mult-->Tran <-Target vols> <-Grp> <-Member-> *** <Name> # <Name> # tem strg<-factor->strg <Name> # # <Name> # # *** WDM 2 PREC ENGL 1 PERLND 1 999 EXTNL PREC WDM 2 PREC ENGL 1 IMPLND 1 999 EXTNL PREC WDM 1 EVAP ENGL 0.76 PERLND 1 999 EXTNL PETINP WDM 1 EVAP ENGL 0.76 IMPLND 1 999 EXTNL PETINP END EXT SOURCES EXT TARGETS <-Volume-> <-Grp> <-Member-><--Mult-->Tran <-Volume-> <Member> Tsys Tgap Amd *** <Name> # <Name> # #<-factor->strg <Name> # <Name> tem strg strg*** RCHRES 1 HYDR RO 1 1 1 WDM 1000 FLOW ENGL REPL 20220422 4/22/2022 5:18:42 PM Page 30 RCHRES 1 HYDR STAGE 1 1 1 WDM 1001 STAG ENGL REPL COPY 1 OUTPUT MEAN 1 1 48.4 WDM 701 FLOW ENGL REPL COPY 501 OUTPUT MEAN 1 1 48.4 WDM 801 FLOW ENGL REPL END EXT TARGETS MASS-LINK <Volume> <-Grp> <-Member-><--Mult--> <Target> <-Grp> <-Member->*** <Name> <Name> # #<-factor-> <Name> <Name> # #*** MASS-LINK 2 PERLND PWATER SURO 0.083333 RCHRES INFLOW IVOL END MASS-LINK 2 MASS-LINK 3 PERLND PWATER IFWO 0.083333 RCHRES INFLOW IVOL END MASS-LINK 3 MASS-LINK 5 IMPLND IWATER SURO 0.083333 RCHRES INFLOW IVOL END MASS-LINK 5 MASS-LINK 12 PERLND PWATER SURO 0.083333 COPY INPUT MEAN END MASS-LINK 12 MASS-LINK 13 PERLND PWATER IFWO 0.083333 COPY INPUT MEAN END MASS-LINK 13 MASS-LINK 15 IMPLND IWATER SURO 0.083333 COPY INPUT MEAN END MASS-LINK 15 MASS-LINK 16 RCHRES ROFLOW COPY INPUT MEAN END MASS-LINK 16 END MASS-LINK END RUN 20220422 4/22/2022 5:18:42 PM Page 31 Predeveloped HSPF Message File 20220422 4/22/2022 5:18:42 PM Page 32 Mitigated HSPF Message File 20220422 4/22/2022 5:18:42 PM Page 33 Disclaimer Legal Notice This program and accompanying documentation are provided 'as-is' without warranty of any kind. The entire risk regarding the performance and results of this program is assumed by End User. Clear Creek Solutions Inc. and the governmental licensee or sublicensees disclaim all warranties, either expressed or implied, including but not limited to implied warranties of program and accompanying documentation. In no event shall Clear Creek Solutions Inc. be liable for any damages whatsoever (including without limitation to damages for loss of business profits, loss of business information, business interruption, and the like) arising out of the use of, or inability to use this program even if Clear Creek Solutions Inc. or their authorized representatives have been advised of the possibility of such damages. Software Copyright © by : Clear Creek Solutions, Inc. 2005-2022; All Rights Reserved. Clear Creek Solutions, Inc. 6200 Capitol Blvd. Ste F Olympia, WA. 98501 Toll Free 1(866)943-0304 Local (360)943-0304 www.clearcreeksolutions.com CONTECH - StormFilter® GULD Maintenance Update (November 2012) P a g e | 1 April 2017 GENERAL USE LEVEL DESIGNATION FOR BASIC (TSS) TREATMENT For CONTECH Engineered Solutions Stormwater Management StormFilter® With ZPG Media at 1 gpm/sq ft media surface area Ecology’s Decision: Based on the CONTECH Engineered Solutions’ (CONTECH) application submissions, Ecology hereby issues a General Use Level Designation (GULD) for the Stormwater Management StormFilter® (StormFilter): 1. As a basic stormwater treatment practice for total suspended solids (TSS) removal, Using ZPG™ media (zeolite/perlite/granular activated carbon), with the size distribution described below, Sized at a hydraulic loading rate of 1 gpm/ft2 of media surface area, per Table 1, and Internal bypassing needs to be consistent with the design guidelines in CONTECH’s current product design manual. Table 1. StormFilter Design Flow Rates per Cartridge 2. Ecology approves StormFilter systems containing ZPG™ media for treatment at the hydraulic loading rates shown in Table 1, and sized based on the water quality design flow rate for an off-line system when using an external bypass vault or a treatment vault with an internal bypass. Contech designs their StormFilter systems to maintain treatment of the water quality design flow while routing excess flows around the treatment chamber during periods of peak bypass. The water quality design flow rates are calculated using the following procedures: Western Washington: For treatment installed upstream of detention or retention, the water quality design flow rate is the peak 15-minute flow rate as calculated using the latest version of the Western Washington Hydrology Model or other Ecology-approved continuous runoff model. Effective Cartridge Height (inches) 12 18 27 Cartridge Flow Rate (gpm/cartridge) 5 7.5 11.3 CONTECH - StormFilter® GULD Maintenance Update (November 2012) P a g e | 2 Eastern Washington: For treatment installed upstream of detention or retention, the water quality design flow rate is the peak 15-minute flow rate as calculated using one of the three methods described in Chapter 2.2.5 of the Stormwater Management Manual for Eastern Washington (SWMMEW) or local manual. Entire State: For treatment installed downstream of detention, the water quality design flow rate is the full 2-year release rate of the detention facility. 3. This designation has no expiration date, but Ecology may amend or revoke it. Ecology’s Conditions of Use: The StormFilter with ZPG media shall comply with the following conditions: 1. Design, install, operate, and maintain the StormFilter with ZPG media in accordance with applicable Contech Engineered Solutions manuals, documents, and the Ecology Decision. 2. Install StormFilter systems to bypass flows exceeding the water quality treatment rate. Additionally, high flows will not re-suspend captured sediments. Design StormFilter systems in accordance with the performance goals in Ecology's most recent Stormwater Manual and CONTECH’s Product Design Manual Version 4.1 (April 2006), or most current version, unless otherwise specified. 3. Owners must follow the design, pretreatment, land use application, and maintenance criteria in CONTECH’s Design Manual. 4. Pretreatment of TSS and oil and grease may be necessary, and designers shall provide pre-treatment in accordance with the most current versions of the CONTECH’s Product Design Manual (April 2006) or the applicable Ecology Stormwater Manual. Design pre-treatment using the performance criteria and pretreatment practices provided on Ecology’s “Evaluation of Emerging Stormwater Treatment Technologies” website. 5. Maintenance: The required maintenance interval for stormwater treatment devices is often dependent upon the degree of pollutant loading from a particular drainage basin. Therefore, Ecology does not endorse or recommend a “one size fits all” maintenance cycle for a particular model/size of manufactured filter treatment device. Typically, CONTECH designs StormFilter systems for a target filter media replacement interval of 12 months. Maintenance includes removing accumulated sediment from the vault, and replacing spent cartridges with recharged cartridges. CONTECH - StormFilter® GULD Maintenance Update (November 2012) P a g e | 3 Indications of the need for maintenance include effluent flow decreasing to below the design flow rate, as indicated by the scumline above the shoulder of the cartridge. Owners/operators must inspect StormFilter with ZPG media for a minimum of twelve months from the start of post-construction operation to determine site-specific maintenance schedules and requirements. You must conduct inspections monthly during the wet season, and every other month during the dry season. (According to the SWMMWW, the wet season in western Washington is October 1 to April 30. According to SWMMEW, the wet season in eastern Washington is October 1 to June 30). After the first year of operation, owners/operators must conduct inspections based on the findings during the first year of inspections. Conduct inspections by qualified personnel, follow manufacturer’s guidelines, and use methods capable of determining either a decrease in treated effluent flowrate and/or a decrease in pollutant removal ability. When inspections are performed, the following findings typically serve as maintenance triggers: Accumulated vault sediment depths exceed an average of 2 inches, or Accumulated sediment depths on the tops of the cartridges exceed an average of 0.5 inches, or Standing water remains in the vault between rain events, or Bypass occurs during storms smaller than the design storm. Note: If excessive floatables (trash and debris) are present, perform a minor maintenance consisting of gross solids removal, not cartridge replacement. 6. CONTECH shall maintain readily available reports listed under “Application Documents” (above) as public, as well as the documentation submitted with its previous conditional use designation application. CONTECH shall provide links to this information from its corporate website, and make this information available upon request, at no cost and in a timely manner. 7. ZPG™ media used shall conform with the following specifications: Each cartridge contains a total of approximately 2.6 cubic feet of media. The ZPG™ cartridge consists of an outer layer of perlite that is approximately 1.3 cubic feet in volume and an inner layer, consisting of a mixture of 90% zeolite and 10% granular activated carbon, which is approximately 1.3 cubic feet in volume. Perlite Media: Perlite media shall be made of natural siliceous volcanic rock free of any debris or foreign matter. The expanded perlite shall CONTECH - StormFilter® GULD Maintenance Update (November 2012) P a g e | 4 have a bulk density ranging from 6.5 to 8.5 lbs per cubic foot and particle sizes ranging from 0.09” (#8 mesh) to 0.38” (3/8” mesh). Zeolite Media: Zeolite media shall be made of naturally occurring clinoptilolite. The zeolite media shall have a bulk density ranging from 44 to 50 lbs per cubic foot and particle sizes ranging from 0.13” (#6 mesh) to 0.19” (#4 mesh). Additionally, the cation exchange capacity (CEC) of zeolite shall range from approximately 1.0 to 2.2 meq/g. Granular Activated Carbon: Granular activated carbon (GAC) shall be made of lignite coal that has been steam-activated. The GAC media shall have a bulk density ranging from 28 to 31 lbs per cubic foot and particle sizes ranging from a 0.09” (#8 mesh) to 0.19” (#4 mesh). Approved Alternate Configurations Peak Diversion StormFilter 1. The Peak Diversion StormFilter allows for off-line bypass within the StormFilter structure. Design capture flows and peak flows enter the inlet bay which contains an internal weir. The internal weir allows design flows to enter the cartridge bay through a transfer hole located at the bottom of the inlet bay while the unit routs higher flows around the cartridge bay. 2. To select the size of the Peak Diversion StormFilter unit, the designer must determine the number of cartridges required and size of the standard StormFilter using the site- specific water quality design flow and the StormFilter Design Flow Rates per Cartridge as described above. 3. New owners may not install the Peak Diversion StormFilter at an elevation or in a location where backwatering may occur. Applicant: Contech Engineered Solutions Applicant’s Address: 11835 NE Glenn Widing Dr. Portland, OR 97220 Application Documents: The applicant’s master report, titled, “The Stormwater Management StormFilter Basic Treatment Application for General Use Level Designation in Washington”, Stormwater Management, Inc., November 1, 2004, includes the following reports: (Public) Evaluation of the Stormwater Management StormFilter Treatment System: Data Validation Report and Summary of the Technical Evaluation Engineering Report (TEER) by Stormwater Management Inc., October 29, 2004 Ecology’s technology assessment protocol requires the applicant to hire an independent consultant to complete the following work: CONTECH - StormFilter® GULD Maintenance Update (November 2012) P a g e | 5 1. Complete the data validation report. 2. Prepare a TEER summary, including a testing summary and conclusions compared with the supplier’s performance claims. 3. Provide a recommendation of the appropriate technology use level. 4. Work with Ecology to post recommend relevant information on Ecology’s website. 5. Provide additional testing recommendations, if needed.” 6. This report, authored by Dr. Gary Minton, Ph. D., P.E., Resource Planning Associates, satisfies the Ecology requirement. (Public) “Performance of the Stormwater Management StormFilter Relative to the Washington State Department of Ecology Performance Goals for Basic Treatment,” is a summary of StormFilter performance that strictly adheres to the criteria listed in the Guidance for Evaluating Emerging Stormwater Treatment Technologies, Technology Assessment Protocol – Ecology (TAPE). “Heritage Marketplace Field Evaluation: Stormwater Management StormFilter with ZPG™ Media,” is a report showing all of the information collected at Site A as stated in the SMI Quality Assurance Project Plan (QAPP). This document contains detailed information regarding each storm event collected at this site, and it provided a detailed overview of the data and project. “Lake Stevens Field Evaluation: Stormwater Management StormFilter with ZPG™ Media,” is a report that corresponds to Site E as stated in the SMI QAPP. This document contains detailed information regarding each storm collected at this site, and includes a detailed overview of the data and project. (Public) “Evaluation of the Stormwater Management StormFilter for the removal of SIL-CO-SIL 106, a standardized silica product: ZPG™ at 7.5 GPM” is a report that describes laboratory testing at full design flow. “Factors Other Than Treatment Performance.” “State of Washington Installations.” “Peak Diversion StormFilter” is a technical document demonstrating the Peak Diversion StormFilter system complies with the Stormwater Management Manual for Western Washington Volume V Section 4.5.1. Above-listed documents noted as “public” are available by contacting CONTECH. Applicant's Use Level Request: That Ecology grant a General Use Level Designation for Basic Treatment for the StormFilter using ZPG™ media (zeolite/perlite/granular activated carbon) at a hydraulic loading rate of 1 gpm/ft2 of media surface area in accordance with Ecology's 2011 Technical Guidance Manual for Evaluating Emerging Stormwater Treatment Technologies Technology Assessment Protocol – Ecology (TAPE). CONTECH - StormFilter® GULD Maintenance Update (November 2012) P a g e | 6 Applicant's Performance Claim: The combined data from the two field sites reported in the TER (Heritage Marketplace and Lake Stevens) indicate that the performance of a StormFilter system configured for inline bypass with ZPG™ media and a hydraulic loading rate of 1 gpm/ft2 of media surface area meets Ecology performance goals for Basic Treatment. Ecology’s Recommendations: Based on the weight of the evidence and using its best professional judgment, Ecology finds that: StormFilter, using ZPG™ media and operating at a hydraulic loading rate of no more than 1 gpm/ft2 of media surface area, is expected to provide effective stormwater treatment achieving Ecology’s Basic Treatment (TSS removal) performance goals. Contech demonstrated this is through field and laboratory testing performed in accordance with the approved protocol. StormFilter is deemed satisfactory with respect to factors other than treatment performance (e.g., maintenance; see the protocol’s Appendix B for complete list). Findings of Fact: Influent TSS concentrations and particle size distributions were generally within the range of what Ecology considers “typical” for western Washington (silt-to-silt loam). Contech sampled thirty-two (32) storm events at two sites for storms from April 2003 to March 2004, of which Contech deemed twenty-two (22) as “qualified” and were therefore included in the data analysis set. Statistical analysis of these 22 storm events verifies the data set’s adequacy. Analyzing all 22 qualifying events, the average influent and effluent concentrations and aggregate pollutant load reduction are 114 mg/L, 25 mg/L, and 82%, respectively. Analyzing all 22 qualifying events based on the estimated average flow rate during the event (versus the measured peak flow rate), and more heavily weighting those events near the design rate (versus events either far above or well below the design rate) does not significantly affect the reported results. For the 7 qualifying events with influent TSS concentrations greater than 100 mg/L, the average influent and effluent concentrations and aggregate pollutant load reduction are 241 mg/L, 34 mg/L, and 89%, respectively. If we exclude the 2 of 7 events that exceed the maximum 300 mg/L specified in Ecology’s guidelines, the average influent and effluent concentrations and aggregate pollutant load reduction are 158 mg/L, 35 mg/L, and 78%, respectively. For the 15 qualifying events with influent TSS concentrations less than 100 mg/L, the average influent and effluent concentrations and aggregate pollutant load reduction are 55 mg/L, 20 mg/L, and 61%, respectively. If the 6 of 15 events that fall below the minimum 33 mg/L TSS specified in Ecology’s guidelines are excluded, the average CONTECH - StormFilter® GULD Maintenance Update (November 2012) P a g e | 7 influent and effluent concentrations and aggregate pollutant load reduction are 78 mg/L, 26 mg/L, and 67%, respectively. For the 8 qualifying events with peak discharge exceeding design flow (ranging from 120 to 257% of the design rate), results ranged from 52% to 96% TSS removal, with an average of 72%. Due to the characteristics of the hydrographs, the field results generally reflect flows below (ranging between 20 and 60 percent of) the tested facilities’ design rate. During these sub-design flow rate periods, some of the cartridges operate at or near their individual full design flow rate (generally between 4 and 7.5 GPM for an 18” cartridge effective height) because their float valves have opened. Float valves remain closed on the remaining cartridges, which operate at their base “trickle” rate of 1 to 1.5 GPM. Laboratory testing using U.S. Silica’s Sil-Co-Sil 106 fine silica product showed an average 87% TSS removal for testing at 7.5 GPM per cartridge (100% design flow rate). Other relevant testing at I-5 Lake Union, Greenville Yards (New Jersey), and Ski Run Marina (Lake Tahoe) facilities shows consistent TSS removals in the 75 to 85% range. Note that the evaluators operated the I-5 Lake Union at 50%, 100%, and 125% of design flow. SMI’s application included a satisfactory “Factors other than treatment performance” discussion. Note: Ecology’s 80% TSS removal goal applies to 100 mg/l and greater influent TSS. Below 100 mg/L influent TSS, the goal is 20 mg/L effluent TSS. Technology Description: The Stormwater Management StormFilter® (StormFilter), a flow-through stormwater filtration system, improves the quality of stormwater runoff from the urban environment by removing pollutants. The StormFilter can treat runoff from a wide variety of sites including, but not limited to: retail and commercial development, residential streets, urban roadways, freeways, and industrial sites such as shipyards, foundries, etc. Operation: The StormFilter is typically comprised of a vault that houses rechargeable, media-filled, filter cartridges. Various media may be used, but this designation covers only the zeolite- perlite-granulated activated carbon (ZPG™) medium. Stormwater from storm drains percolates through these media-filled cartridges, which trap particulates and may remove pollutants such as dissolved metals, nutrients, and hydrocarbons. During the filtering process, the StormFilter system also removes surface scum and floating oil and grease. Once filtered through the media, the treated stormwater is directed to a collection pipe or discharged to an open channel drainage way. This document includes a bypass schematic for flow rates exceeding the water quality design flow rate on page 8. CONTECH - StormFilter® GULD Maintenance Update (November 2012) P a g e | 8 StormFilter Configurations: Contech offers the StormFilter in multiple configurations: precast, high flow, catch basin, curb inlet, linear, volume, corrugated metal pipe, drywell, and CON/Span form. Most configurations use pre-manufactured units to ease the design and installation process. Systems may be either uncovered or covered underground units. The typical precast StormFilter unit is composed of three sections: the energy dissipater, the filtration bay, and the outlet sump. As Stormwater enters the inlet of the StormFilter vault through the inlet pipe, piping directs stormwater through the energy dissipater into the filtration bay where treatment will take place. Once in the filtration bay, the stormwater ponds and percolates horizontally through the media contained in the StormFilter cartridges. After passing through the media, the treated water in each cartridge collects in the cartridge’s center tube from where piping directs it into the outlet sump by a High Flow Conduit under-drain manifold. The treated water in the outlet sump discharges through the single outlet pipe to a collection pipe or to an open channel drainage way. In some applications where you anticipate heavy grit loads, pretreatment by settling may be necessary. CONTECH - StormFilter® GULD Maintenance Update (November 2012) P a g e | 9 Figure 1. Stormwater Management StormFilter Configuration with Bypass CONTECH - StormFilter® GULD Maintenance Update (November 2012) P a g e | 10 Figure 2. The StormFilter Cartridge Cartridge Operation: As the water level in the filtration bay begins to rise, stormwater enters the StormFilter cartridge. Stormwater in the cartridge percolates horizontally through the filter media and passes into the cartridge’s center tube, where the float in the cartridge is in a closed (downward) position. As the water level in the filtration bay continues to rise, more water passes through the filter media and into the cartridge’s center tube. Water displaces the air in the cartridge and it purges from beneath the filter hood through the one-way check valve located in the cap. Once water fills the center tube there is enough buoyant force on the float to open the float valve and allow the treated water to flow into the under-drain manifold. As the treated water drains, it tries to pull in air behind it. This causes the check valve to close, initiating a siphon that draws polluted water throughout the full surface area and volume of the filter. Thus, water filters through the entire filter cartridge throughout the duration of the storm, regardless of the water surface elevation in the filtration bay. This continues until the water surface elevation drops to the elevation of the scrubbing regulators. At this point, the siphon begins to break and air quickly flows beneath the hood through the scrubbing regulators, causing energetic bubbling between the inner surface of the hood and the outer surface of the filter. This bubbling agitates and cleans the surface of the filter, releasing accumulated sediments on the surface, flushing them from beneath the hood, and allowing them to settle to the vault floor. Adjustable cartridge flow rate: Inherent to the design of the StormFilter is the ability to control the individual cartridge flow rate with an orifice-control disc placed at the base of the cartridge. Depending on the treatment requirements and on the pollutant characteristics of the influent stream as CONTECH - StormFilter® GULD Maintenance Update (November 2012) P a g e | 11 specified in the CONTECH Product Design Manual, operators may adjust the flow rate through the filter cartridges. By decreasing the flow rate through the filter cartridges, the influent contact time with the media is increased and the water velocity through the system is decreased, thus increasing both the level of treatment and the solids removal efficiencies of the filters, respectively (de Ridder, 2002). Recommended research and development: Ecology encourages CONTECH to pursue continuous improvements to the StormFilter. To that end, CONTECH recommends the following actions: Determine, through laboratory testing, the relationship between accumulated solids and flow rate through the cartridge containing the ZPG™ media. Completed 11/05. Determine the system’s capabilities to meet Ecology’s enhanced, phosphorus, and oil treatment goals. Develop easy-to-implement methods of determining that a StormFilter facility requires maintenance (cleaning and filter replacement). Contact Information: Applicant Contact: Jeremiah Lehman Contech Engineered Solutions 11835 NE Glenn Widing Drive Portland, OR, 97220 503-258-3136 jlehman@conteches.com Applicant Web link http://www.conteches.com/ CONTECH - StormFilter® GULD Maintenance Update (November 2012) P a g e | 12 Ecology web link: http://www.ecy.wa.gov/programs/wq/stormwater/newtech/index.html Ecology Contact: Douglas C. Howie, P.E. Department of Ecology Water Quality Program (360) 407-6444 douglas.howie@ecy.wa.gov Revision History Date Revision Jan 2005 Original Use Level Designation Dec 2007 Revision May 2012 Maintenance requirements updated November 2012 Design Storm and Maintenance requirements updated January 2013 Updated format to match Ecology standard format September 2014 Added Peak Diversion StormFilter Alternate Configuration November 2016 Revised Contech contact information April 2017 Revised sizing language to note sizing based on Off-line calculations Technical Information Report Brar Short Plat 2200320.10 Section 5 Conveyance System Analysis and Design Technical Information Report Brar Short Plat 5-1 2200320.10 5.0 Conveyance System Analysis and Design Onsite conveyance is provided for the upstream pass through basin and the onsite roof runoff. Using WWHM to evaluate the 100-year flow results in 0.599 cfs (see Figure 5-1). The runoff is conveyed through the 12-inch CPEP pipe at 14.3%. Using Manning’s equation in the FlowMaster program, the full flow capacity is 17.51 cfs (see Figure 5-2). The pipe can effectively convey receiving stormwater. Discharge from the control structure is provided through a 12-inch pipe to the frontage. The 100-year discharge rate from the detention system is approximately 0.5 cfs. The discharge pipe is a 12-inch CPEP pipe at 0.74%. Using Manning’s equation in the FlowMaster program, the full flow capacity is 3.98 cfs (see Figure 5-2). The discharge line can effectively convey the control structure discharge. Stormwater improvements will reduce discharge from the site by providing flow control. The 100-year discharge rate from the detention system is approximately 0.5 cfs. The conveyance line along the frontage consists of two 12-inch pipes at 1.46% and 0.83%. The FlowMaster program is used to evaluate the most restrictive 0.83% slope pipe with a full flow capacity of 4.2 cfs (refer to Figure 5-3). The 0.5 cfs from the site is well within the 4.2 cfs conveyance capacity of the system. The existing conveyance system along the frontage appears to be adequately sized for the developed conditions. Technical Information Report Brar Short Plat 2200320.10 Section 5.0 Figures Figure 5-1 ......... Onsite Flows Figure 5-2 ......... Onsite Conveyance Check Figure 5-3 ......... Frontage Conveyance Check 2215 North 30th Street Suite 300 Tacoma, WA 98403 253.383.2422 TEL 253.383.2572 FAX BRAR SHORT PLAT - 2200320.10 ONSITE FLOWS 5-1 ONSITE FLOWS TO THE DETENTION SYSTEM INCLUDES UPSTREAM PASS THROUGH 100-YEAR CONVEYANCE CHECK EVALUATED FROM WWHM INFLOW TO DETENTION BYPASS BASIN AND ONSITE ROOF RUNOFF EVALUATED FROM WWHM UPSTREAM PROPERTY AND ONSITE ROOFS 2215 North 30th Street Suite 300 Tacoma, WA 98403 253.383.2422 TEL 253.383.2572 FAX BRAR SHORT PLAT - 2200320.10 FRONTAGE CONVEYANCE CHECK 5-2 ONSITE CONVEYANCE CAPACITY DISCHARGE CONVEYANCE CAPACITY 2215 North 30th Street Suite 300 Tacoma, WA 98403 253.383.2422 TEL 253.383.2572 FAX BRAR SHORT PLAT - 2200320.10 FRONTAGE CONVEYANCE CHECK 5-3 Technical Information Report Brar Short Plat 2200320.10 Section 6 Special Reports and Studies Technical Information Report Brar Short Plat 6-1 2200320.10 6.0 Special Reports and Studies A Geotechnical Engineering Report, dated August 3, 2020, by South Sound Geotechnical Consulting is included as Figure 6-1. Technical Information Report Brar Short Plat 2200320.10 Section 6.0 Figures Figure 6-1 ......... Geotechnical Engineering Report South Sound Geotechnical Consulting August 3, 2020 LSB Petroleum, LLC 11706 - 164th Ave SE Renton, WA 98059 Attention: Mr. Lakhpal Brar Subject: Geotechnical Engineering Report Brar Short Plat 8054 S. 132nd Street Renton, Washington SSGC Project No. 20058 Ms. Brar, South Sound Geotechnical Consulting (SSGC) has completed a geotechnical assessment for the planned short plat on the above addressed property in Renton, Washington. Our services have been completed in general conformance with our proposal P20050 (dated June 23, 2020) and authorized per signature of our agreement for services. Our scope of services included completion of five test pits, one infiltration test, laboratory testing, engineering analyses, and preparation of this report. PROJECT INFORMATION The project property is on the north side of S. 132nd Street and encompasses approximately 0.75 acres. It is rectangular with the long axis trending in a north-south direction. A single-family residence currently occupies the southern portion. One shop/garage structure is in the northwestern portion. The property is on a south-facing slope with elevation change on the order of 30 feet (+/-) per Google satellite imagery. Proposed development includes short plating the property into four individual lots. We understand the existing residence will remain as one of the lots. Conventional spread footing foundations are anticipated for support of new structures with concrete slab-on-grade garage floors. SUBSURFACE CONDITIONS Subsurface conditions were characterized by completing four test pits and one infiltration test on the site on July 8, 2020. Test holes were advanced to final depths between 6 and 10 feet below existing ground surface. Approximate locations of the test pits and infiltration test site are shown on Figure 1, Exploration Plan. Logs of these explorations are provided in Appendix A. A summary description of observed subgrade conditions is provided below. Geotechnical Engineering Report SSGC Brar Short Plat – S. 132nd St Renton, WA SSGC Project No. 20058 August 3, 2020 2 Soil Conditions Fill was observed at the surface in two of the test pits and extended to depths of about 1 to 1.5 feet. It consisted of loose silt, sand, and gravel and likely sourced from the property during construction of existing improvements. Topsoil was below the fill (and below the surface in the remaining excavations) and ranged in thickness from about 6 inches to 1 foot at the test locations. Native soil below the topsoil consisted of an upper silty sand with variable gravel. This soil was in a loose condition and ranged in thickness from about 6 inches to 2 feet, where present. An interpreted weathered glacial till was below the upper soil and consisted of silty sand with gravel and occasional cobbles in a loose to medium dense condition. This weathered zone extended to depths between 3 and 46feet. Dense glacial till was below the weathered zone and extended to the termination depths of the explorations. Groundwater Conditions Groundwater was not observed in the test holes at the time of excavation. However, mottling of the upper native silty sand and weathered till layer implies perched groundwater conditions during the wetter seasons of the year. The presence of dense glacial till can create perched groundwater in the upper soils. Groundwater levels will vary throughout the year based on seasonal precipitation and on- and off-site drainage patterns. Geologic Setting Soils within the development area have been classified by the NRCS in the Soil Survey of King County, Washington. Surface soils are mapped as Alderwood gravelly sandy loam. This soil is described as forming in glacial till. Native soils observed in the test holes appear to consist of a thin layer of alluvium over glacial till, conforming to the mapped soil type. GEOTECHNICAL DESIGN CONSIDERATIONS Development for the proposed plat is considered feasible based on observed soil conditions in the test pits. Properly prepared native soils can be used for support of conventional spread footing foundations, floor slabs, and pavements. Infiltration to assist in stormwater control will be difficult at this site. The presence of dense glacial till at fairly shallow depth will limit infiltration to lateral flow through the upper silty sand and weathered till horizons. Infiltration systems will be limited to shallow dispersion facilities as allowed by the city. Recommendations presented in the following sections should be considered general and may require modifications at the time of construction. They are based upon the subsurface conditions observed in the test pits and the assumption that finish site grades will not be substantially different than existing grades. It should be noted subsurface conditions across the site can vary from those depicted on the exploration logs and can change with time. It should be expected that fill of unknown type and thickness may be Geotechnical Engineering Report SSGC Brar Short Plat – S. 132nd St Renton, WA SSGC Project No. 20058 August 3, 2020 3 present due to historic uses of this site. Therefore, proper site preparation will depend upon the weather and soil conditions encountered at the time of construction. We recommend SSGC review final plans and further assess subgrade conditions at the time of construction, as warranted. General Site Preparation Site grading and earthwork should include procedures to control surface water runoff. Grading the site without adequate drainage control measures may negatively impact site soils, resulting in increased export of impacted soil and import of fill materials, thereby potentially increasing the cost of the earthwork and subgrade preparation phases of the project. Site grading should include removal (stripping) of fill and topsoil or very loose or soft soils in building and pavement areas. Topsoil/fill extended to depths ranging from about 6 inches to 2 feet in the observed test holes, but may be deeper in other areas. Final stripping depths can only be determined at the time of construction. Subgrades should consist of firm, undisturbed native soils following stripping. General Subgrade Preparation Subgrades in building footprints and pavement areas should consist of firm, undisturbed native soils. We recommend exposed subgrades in building and conventional pavement areas are proofrolled using a large roller, loaded dump truck, or other mechanical equipment to assess subgrade conditions following stripping. Proofrolling efforts should result in the upper 1 foot of subgrade soils in building and conventional pavement areas achieving a compaction level of at least 95 percent of the maximum dry density (MDD) per the ASTM D1557 test method. Wet, loose, or soft subgrades that cannot achieve this compaction level should be removed (over-excavated) and replaced with structural fill. The depth of over-excavation should be based on soil conditions at the time of construction. A representative of SSGC should be present to assess subgrade conditions during proofrolling. Grading and Drainage Positive drainage should be provided during construction and maintained throughout the life of the development. Surface water should not be allowed to flow into construction excavations or fill areas. Structural Fill Materials The suitability of soil for use as structural fill will depend on the gradation and moisture content of the soil when it is placed. Soils with higher fines content (soil fraction passing the U.S. No. 200 sieve) will become sensitive with higher moisture content. It is often difficult to achieve adequate compaction if soil moisture is outside of optimum ranges for soils that contain more than about 5 percent fines. Geotechnical Engineering Report SSGC Brar Short Plat – S. 132nd St Renton, WA SSGC Project No. 20058 August 3, 2020 4 Site Soils: Topsoil and existing fill are not considered suitable for use as structural fill. Native soils contain sufficient fines (silt and clay) that make them moisture sensitive and difficult to use as structural fill. These soils would have to be moisture conditioned within optimal moisture content to use as structural fill. Optimum moisture is considered within about +/- 2 percent of the moisture content required to achieve the maximum dry density (MDD) per the ASTM D-1557 test method. If moisture content is higher or lower than optimum, soils would need to be dried or wetted prior to placement as structural fill. Import Fill Materials: We recommend imported structural fill placed during dry weather consist of material which meets the specifications for Gravel Borrow as described in Section 9-03.14(1) of the 2018 Washington State Department of Transportation (WSDOT) Specifications for Road, Bridge, and Municipal Construction manual (Publication M 41-10). Gravel Borrow should be protected from disturbance if exposed to wet conditions after placement. During wet weather, or for backfill on wet subgrades, import soil suitable for compaction in wetter conditions should be provided. Imported fill for use in wet conditions should conform to specifications for Select Borrow as described in Section 9-03.14(2), or Crushed Surfacing per Section 9-03.9(3) of the 2018 WSDOT M-41 manual, with the modification that a maximum of 5 percent by weight shall pass the U.S. No. 200 sieve for these soil types. Structural fill placement and compaction is weather-dependent. Delays due to inclement weather are common, even when using select granular fill. We recommend site grading and earthwork be scheduled for the drier months of the year. Frozen soil is not suitable as structural fill. Structural Fill Placement We recommend structural fill is placed in lifts not exceeding about 10 inches in loose measure. It may be necessary to adjust lift thickness based on site and fill conditions during placement and compaction. Finer grained soil used as structural fill and/or lighter weight compaction equipment may require significantly thinner lifts to attain required compaction levels. Granular soil with lower fines contents could potentially be placed in thicker lifts (1 foot maximum) if they can be adequately compacted. Structural fill should be compacted to attain the recommended levels presented in Table 1, Compaction Criteria. Geotechnical Engineering Report SSGC Brar Short Plat – S. 132nd St Renton, WA SSGC Project No. 20058 August 3, 2020 5 Table 1. Compaction Criteria Fill Application Compaction Criteria* Footing areas 95 % Upper 2 feet in pavement areas, flatwork, and utility trenches 95 % Below 2 feet in pavement areas, flatwork, and utility trenches 92 % Utility trenches or general fill in non-paved or -building areas 90 % *Per the ASTM D 1557 test method. Trench backfill within about 2 feet of utility lines should not be over-compacted to reduce the risk of damage to the line. In some instances, the top of the utility line may be within 2 feet of the surface. Backfill in these circumstances should be compacted to a firm and unyielding condition. We recommend fill procedures include maintaining grades that promote drainage and do not allow ponding of water within the fill area. The contractor should protect compacted fill subgrades from disturbance during wet weather. In the event of rain during structural fill placement, the exposed fill surface should be allowed to dry prior to placement of additional fill. Alternatively, the wet soil can be removed. We recommend consideration is given to protecting haul routes and other high traffic areas with free-draining granular fill material (i.e. sand and gravel containing less than 5 percent fines) or quarry spalls to reduce the potential for disturbance to the subgrade during inclement weather. Structural fill placed on sloping ground should be constructed using a benched (stairstep) methodology. Benches should be cut level or with a slight downward incline into the slope in firm native soil. Benches should be wide enough to accommodate a minimum 20-ton vibratory roller and be a maximum of about two feet high. Earthwork Procedures Conventional earthmoving equipment should be suitable for earthwork at this site. Earthwork may be difficult during periods of wet weather or if elevated soil moisture is present. Excavated site soils may not be suitable as structural fill depending on the soil moisture content and weather conditions at the time of earthwork. If soils are stockpiled and wet weather is anticipated, the stockpile should be protected with securely anchored plastic sheeting. If stockpiled soils become wet and unusable, it will become necessary to import clean, granular soils to complete wet weather site work. Wet or disturbed subgrade soils should be over-excavated to expose firm, non-yielding, non-organic soils and backfilled with compacted structural fill. We recommend the earthwork portion of this project be completed during extended periods of dry weather. If earthwork is completed during the wet season (typically October through April) it may be necessary to take extra measures to protect subgrade soils. Geotechnical Engineering Report SSGC Brar Short Plat – S. 132nd St Renton, WA SSGC Project No. 20058 August 3, 2020 6 If earthwork takes place during freezing conditions, we recommend the exposed subgrade is allowed to thaw and re-compacted prior to placing subsequent lifts of structural fill. Alternatively, the frozen soil can be removed to unfrozen soil and replaced with structural fill. The contractor is responsible for designing and constructing stable, temporary excavations (including utility trenches) as required to maintain stability of excavation sides and bottoms. Excavations should be sloped or shored in the interest of safety following local and federal regulations, including current OSHA excavation and trench safety standards. Temporary excavation cuts should be sloped at inclinations of 1.5H:1V (Horizontal:Vertical) or flatter, unless the contractor can demonstrate the safety of steeper cut slopes. It should be noted outwash soils have the tendency to cave into open excavations. Shoring may be necessary for deeper utility trenches on this site. Permanent cut and fill slopes should be inclined at grades of 2H:1V, or flatter. A geotechnical engineer and accredited materials testing firm should be retained during the construction phase of the project to observe earthwork operations and to perform necessary tests and observations during subgrade preparation, placement and compaction of structural fill, and backfilling of excavations. Foundations Foundations can be placed on firm native soils or on a zone of structural fill above prepared subgrades as described in this report. The following recommendations are for conventional spread footing foundations: Bearing Capacity (net allowable): 3,000 pounds per square foot (psf) for footings supported on firm native soils or structural fill over native subgrades prepared as described in this report. Footing Width (Minimum): 16 inches (Strip) 24 inches (Column) Embedment Depth (Minimum): 18 inches (Exterior) 12 inches (Interior) Settlement: Total: < 1 inch Differential: < 1/2 inch (over 30 feet) Allowable Lateral Passive Resistance: 325 psf/ft* (below 12 inches) Allowable Coefficient of Friction: 0.40* *These values include a factor of safety of approximately 1.5. The net allowable bearing pressures presented above may be increased by one-third to resist transient, dynamic loads such as wind or seismic forces. Lateral resistance to footings should be ignored in the upper 12-inches from exterior finish grade unless restricted. Geotechnical Engineering Report SSGC Brar Short Plat – S. 132nd St Renton, WA SSGC Project No. 20058 August 3, 2020 7 Foundation Construction Considerations All foundation subgrades should be free of water and loose soil prior to placing concrete, and should be prepared as recommended in this report. Concrete should be placed soon after excavating and compaction to reduce disturbance to bearing soils. Should soils at foundation level become excessively dry, disturbed, saturated, or frozen, the affected soil should be removed prior to placing concrete. We recommend SSGC observe foundation subgrades prior to placement of concrete. Foundation Drainage Ground surface adjacent foundations should be sloped away to facilitate drainage. We recommend footing drains are installed around perimeter footings. Footing drains should include a minimum 4- inch diameter perforated rigid plastic or metal drain line installed along the exterior base of the footing. The perforated drain lines should be connected to a tight line pipe that discharges to an approved storm drain receptor. The drain line should be surrounded by a zone of clean, free-draining granular material having less than 5 percent passing the No. 200 sieve or meeting the requirements of section 9-03.12(2) “Gravel Backfill for Walls” in the 2018 WSDOT (M41-10) manual. The free- draining aggregate zone should be at least 12 inches wide and wrapped in filter fabric. The granular fill should extend to within 6 inches of final grade where it should be capped with compacted fill containing sufficient fines to reduce infiltration of surface water into the footing drains. Alternately, the ground surface can be paved with asphalt or concrete. Cleanouts are recommended for maintenance of the drain system. On-Grade Floor Slabs On-grade floor slabs should be placed on native soils or structural fill prepared as described in this report. We recommend a modulus subgrade reaction of 175 pounds per square inch per inch (psi/in) for native soil or compacted granular structural fill over properly prepared native soil. We recommend a capillary break is provided between the prepared subgrade and bottom of slab. Capillary break material should be a minimum of 4 inches thick and consist of compacted clean, free- draining, well graded coarse sand and gravel. The capillary break material should contain less than 5 percent fines, based on that soil fraction passing the U.S. No. 4 sieve. Alternatively, a clean angular gravel such as No. 7 aggregate per Section 9-03.1(4) C of the 2018 WSDOT (M41-10) manual could be used for this purpose. We recommend positive separations and/or isolation joints are provided between slabs and foundations, and columns or utility lines to allow independent movement where needed. Backfill in interior trenches beneath slabs should be compacted in accordance with recommendations presented in this report. Geotechnical Engineering Report SSGC Brar Short Plat – S. 132nd St Renton, WA SSGC Project No. 20058 August 3, 2020 8 A vapor retarder should be considered beneath concrete slabs that will be covered with moisture sensitive or impervious coverings (such as tile, wood, etc.), or when the slab will support equipment or stored materials sensitive to moisture. We recommend the slab designer refer to ACI 302 and/or ACI 360 for procedures and limitations regarding the use and placement of vapor retarders. Seismic Considerations Recommended seismic parameters and values in Table 2 are based on the 2015 International Building Code (IBC). Table 2. Seismic Parameters PARAMETER VALUE 2015 International Building Code (IBC) Site Classification1 D Ss Spectral Acceleration for a Short Period 1.46 S1 Spectral Acceleration for a 1-Second Period 0.546g Fa Site Coefficient for a Short Period 1.00 Fv Site Coefficient for a 1-Second Period 1.50 1 Note: In general accordance with 2015 International Building Code, Section 1613.3.1 for risk categories I,II,III. IBC Site Class is based on the estimated characteristics of the upper 100 feet of the subsurface profile. Ss, S1, Fa, and Fv values based on the OSHPD Seismic Design Maps website. Liquefaction Soil liquefaction is a condition where loose, typically granular soils located below the groundwater surface lose strength during ground shaking, and is often associated with earthquakes. The Seattle Hazard Explorer website does not show the site in a liquefaction prone area. Native soils consist of principally dense to very dense glacially consolidated materials at relatively shallow depth. The risk of liquefaction at this site is considered low for the design level earthquake. Lateral Earth Pressures We anticipate retaining walls may be required in portions of the development. Below grade or retaining walls will be subject to lateral earth pressures. Subgrade walls are typically designed for “active” or “at- rest” earth pressure conditions. Active earth pressure is commonly used for design of free-standing cantilever retaining walls and assumes lateral movement at the top of the wall of around 0.002H to 0.004H, where H is the height of the wall. The at-rest condition assumes no wall movement. Geotechnical Engineering Report SSGC Brar Short Plat – S. 132nd St Renton, WA SSGC Project No. 20058 August 3, 2020 9 We anticipate most walls will retain native outwash or new structural fill to accommodate final site grades. The following recommended earth pressures (Table 3) should be applied as a triangular distribution starting at the top of the wall (for active and at-rest) and bottom of wall (for passive) and assume: ▪ Backfill behind walls is level and no surcharge loads will be applied; ▪ Drainage is provided behind the wall to prevent the development of hydrostatic pressures. Table 3. Lateral Earth Pressures Soil Type Earth Pressure Coefficient* Equivalent Fluid Pressure (pcf)* Loose Native Soils (0 to 4 feet) Active: 0.36 At-rest: 0.53 Passive: 2.80 Active: 40 At-rest: 55 Passive: 300 Dense Glacial Till (Below 4 feet) Active: 0.25 At-rest: 0.38 Passive: 350 Active: 30 At-rest: 45 Passive: 350 * A factor of safety of about 1.5 should be applied to these values. Additional lateral pressure should be added to these values to model surcharges such as adjacent structures, sloped backfill behind the wall, traffic, construction equipment, or seismic loads. We recommend an active seismic pressure of 5H psf (where H is the height of the subgrade wall) and an at- rest seismic pressure of 8H. The effects of other surcharge loads should be accounted for as appropriate. Wall Backfill Backfill behind retaining walls should consist of granular material that satisfies the criteria of Section 9-03.12(2) “Gravel Backfill for Walls” per the 2018 WSDOT (M 41-10) manual, or as approved by the engineer. Wall backfill should be placed in lifts not exceeding 8 inches and compacted with hand-operated compaction equipment. Compaction of wall backfill should be between 90 to 92 percent of the maximum dry density (MDD) per the ASTM D1557 test method within 3 feet of the back of the wall. At a distance greater than 3 feet behind the back of the wall, backfill can be compacted using conventional rollers, with backfill compacted to at least 92 percent of the MDD (ASTM D1557). Wall Drainage Drainage should be provided behind subgrade walls to reduce the potential for hydrostatic pressure developing against the wall and to reduce the risk of groundwater from entering subgrade floors. We recommend a minimum 12-inch wide zone of free draining granular soil (WSDOT Section 9- 03.12(4), or as approved by the design engineer) is placed directly behind the wall. Alternatively, Geotechnical Engineering Report SSGC Brar Short Plat – S. 132nd St Renton, WA SSGC Project No. 20058 August 3, 2020 10 an approved drainage mat can be used behind the wall. A perforated rigid plastic drainpipe at least 6-inches in diameter should be installed behind the base of the wall within 6-inches of the bottom of the footing. The drain line should be surrounded with the free-draining granular soil zone and sloped to provide flow to an approved storm water receptor. The granular fill zone should extend to within 1 foot of final grade of the wall, where it should be capped with compacted low permeable fill containing sufficient fines to reduce infiltration of surface water into the drainage zone. A filter fabric (such as Mirafi 140N, or other approved material) should be placed between native soils and the granular drain material to limit siltation into the drainage zone. Cleanouts are recommended for maintenance of the drain system. Infiltration Characteristics We understand stormwater control will use infiltration facilities. General assessment of infiltration potential of native soils was performed by completing one small-scale Pilot Infiltration Test (PIT) in the proposed storm tract per the 2016 King County Surface Water Design Manual. Test PIT-1 was completed in the upper native silty sand. Results of the infiltration test are presented in Table 3. Table 3. Infiltration Test Results Infiltration Test No. Depth of Test from Surface (feet) Soil Type Field Infiltration Rate (in/hr) Corrected Infiltration Rate (in/hr) Correction Factors* (Fg/Ft/Fp) PIT-1 2 Alluvium/Weathered Till 3 1.2 (1.0/0.5/0.8) * Correction Factors from the 2017 City of Renton Surface Water Design Manual. Correction factors applied to the field rate per equation 5-11 of the County Manual. The tested infiltration rate from PIT-1 is considered appropriate for the soil tested. However, the presence of dense glacial till below the alluvium/weathered till will form a barrier to vertical groundwater flow. We interpret the infiltration rate to be reflective of mostly horizontal flow through the upper soils. Infiltration facilities planned in the upper 3 to 4 feet of site soils should be restricted to shallow dispersion systems as the dense glacial till is considered a barrier which should be accounted for in design. An infiltration rate of 1.2 inches per hour is recommended for dispersion systems in the upper silty sand and weathered till. No infiltration should be accounted for in the dense (unweathered) glacial till. Cation Exchange Capacity (CEC) and organic content test were completed on samples from the two test holes in the storm track area to assess treatment characteristics of the upper outwash soil. Test results are summarized in Table 4. Geotechnical Engineering Report SSGC Brar Short Plat – S. 132nd St Renton, WA SSGC Project No. 20058 August 3, 2020 11 Table 4. CEC and Organic Content Results Test Location, Depth Soil Type CEC Results (milliequivalents) CEC Required* (milliequivalents) Organic Content Results (%) Organic Content Required* (%) PIT-1, 2 feet Alluvium 10 ≥ 5 2.79 ≥1.0 *Per the 2017 City of Renton Surface Water Design Manual. CEC and organic test results satisfy City criteria on the tested soil. Conventional Pavement Sections Subgrades for conventional pavement areas should be prepared as described in the “Subgrade Preparation” section of this report. Subgrades below pavement sections should be graded or crowned to promote drainage and not allow for ponding of water beneath the section. If drainage is not provided and ponding occurs, the subgrade soils could become saturated, lose strength, and result in premature distress to the pavement. In addition, the pavement surfacing should also be graded to promote drainage and reduce the potential for ponding of water on the pavement surface. Minimum recommended pavement section for private driveways are presented in Table 5. Pavement sections in public right-of-ways (S. 132nd Street) should conform to City of Renton requirements for the road designation. Table 5. Preliminary Pavement Sections Traffic Area Minimum Recommended Pavement Section Thickness (inches) Asphalt Concrete Surface1 Portland Cement Concrete Aggregate Base Course2 Subbase Aggregate3 Driveways 2 - 4 12 1 1/2 –inch nominal aggregate hot-mix asphalt (HMA) per WSDOT 9-03.8(1) 2 Crushed Surfacing Base Course per WSDOT 9-03.9(3) 3 Native granular soils compacted to 95% of the ASTM D1557 test method, or Gravel Borrow per WSDOT 9-03.14(1) or Crushed Surfacing Base Course WSDOT 9-03.9(3) Conventional Pavement Maintenance The performance and lifespan of pavements can be significantly impacted by future maintenance. The above pavement sections represent minimum recommended thicknesses and, as such, periodic maintenance should be completed. Proper maintenance will slow the rate of pavement deterioration and will improve pavement performance and life. Preventative maintenance consists of both localized maintenance (crack and joint sealing and patching) and global maintenance (surface Geotechnical Engineering Report SSGC Brar Short Plat – S. 132nd St Renton, WA SSGC Project No. 20058 August 3, 2020 12 sealing). Added maintenance measures should be anticipated over the lifetime of the pavement section if any existing fill or topsoil is left in-place beneath pavement sections. Geologic Hazard Area Discussion The City of Renton’s COR Map for critical areas identifies the south-facing slope as having inclinations between 15 and 25 percent which satisfies criteria per Title IV, Chapter 3 of the City of Renton Municipal Code (RMC) as a regulated slope. The slope is not mapped as a high erosion hazard. Landslide Hazard Native soils on site slopes consist of a relatively thin layer of alluvium, over weathered glacial till, over dense to very dense glacial till. No evidence of recent landslide activity was apparent on site slopes or near the property at the time of our fieldwork. In addition, we are unaware of active landslides within 300 feet of the property. The proposed development should not adversely impact slope stability on the site or on adjacent properties. Erosion Hazard Native glacial soils on the site mapped by the USDA are considered to have a moderate potential to erosion. We observed no evidence of excessive erosion on the property, including the west- facing slope. Regarding planned development, it is our opinion that Best Management Practices (BMP) for erosion control (silt fencing, straw bales, etc) can be utilized such that the risk of off- site transport of sediment is limited during construction. Additional erosion control measures may be necessary if earthwork is scheduled during the wetter seasons. All erosion control provisions should follow City of Renton regulations to reduce the risk of off-site transport of sediments. Exposed soils following construction should be vegetated as soon as possible. REPORT CONDITIONS This report has been prepared for the exclusive use of Mr. Lakhpal Brar and his agents for specific application to the project discussed, and has been prepared in accordance with generally accepted geotechnical engineering practices in the area. No warranties, either express or implied, are intended or made. The analysis and recommendations presented in this report are based on observed soil conditions and test results at the indicated locations, and from other geologic information discussed. This report does not reflect variations that may occur across the site, or due to the modifying effects of construction or weather or other natural events. The nature and extent of such variations may not become evident until during or after construction. If variations appear, we should be immediately notified so that further evaluation and supplemental recommendations can be provided. N South Sound Geotechnical Consulting P.O. Box 39500 Lakewood, WA 98496 (253) 973-0515 Figure 1 – Exploration Plan Brar Short Plat Renton, WA SSGC Project #20058 Approximate Test Pit Location PIT - 1 TP - 1 PIT - 1 Approximate Infiltration Test Location Scale: NTS Base map from plan titled “Brar Short Plat - Plot Plan”, by Kaul Design Architecture, PLLC, undated. Legend TP-1 PIT-1 TP-2 TP-3 TP-4 Geotechnical Engineering Report SSGC Brar Short Plat – S. 132nd St Renton, WA SSGC Project No. 20058 August 3, 2020 A-1 Appendix A Field Exploration Procedures and Exploration Logs Geotechnical Engineering Report SSGC Brar Short Plat – S. 132nd St Renton, WA SSGC Project No. 20058 August 3, 2020 Field Exploration Procedures Our field exploration for this project included four test pits and one infiltration test completed on July 8, 2020. The approximate locations of the explorations are shown on Figure 1, Exploration Plan. The exploration locations were determined by pacing from site features. Ground surface elevations referenced on the logs were inferred from topography from Google Earth satellite imagery. Exploration locations and elevations should be considered accurate only to the degree implied by the means and methods used. A private excavation company subcontracted to SSGC dug the test holes. Soil samples were collected and stored in moisture tight for further assessment and laboratory testing. Explorations were backfilled with excavated soils and tamped when completed. Please note that backfill in the explorations will likely settle with time. Backfill material located in building areas should be re-excavated and recompacted, or replaced with structural fill. The following logs indicate the observed lithology of soils and other materials observed in the explorations at the time of excavation. Where a soil contact was observed to be gradational, our log indicates the average contact depth. Our logs also indicate the approximate depth to groundwater (where observed at the time of excavation), along with sample numbers and approximate sample depths. Soil descriptions on the logs are based on the Unified Soil Classification System. Project: Brar Short Plat SSGC Job # 20058 TEST PIT LOGS PAGE 1 OF 3 Location: S. 132nd Street, Renton, WA TEST PIT LOGS FIGURE A-1 South Sound Geotechnical Consulting PIT-1, TP-1 through TP-4 Logged by: THR Infiltration Test PIT-1 Depth (feet) Material Description 0 – 1 1 – 6 6 – 10 Topsoil Silty SAND with occasional gravel: Loose to medium dense moist, brownish gray. (SM) (Sample S-1 @ 3 feet) Silty SAND with gravel: Dense to very dense, moist, gray. (SM) (Glacial Till) Test hole completed at approximately 10 feet on 7/8/20. Infiltration test completed at 2.5 feet. Groundwater not observed at time of excavation. Approximate surface elevation: 250 feet Test Pit TP-1 Depth (feet) Material Description 0 – 0.5 0.5 – 1.5 1.5 – 3 3 – 6 Topsoil Silty SAND: Loose, moist, orangish brown. (SM) Silty SAND with occasional gravel and cobbles: Medium dense to dense, moist, mottled orange-gray. (SM) (Weathered Glacial Till) Silty SAND with gravel and cobbles: Very dense, moist, gray. (SM) (Glacial Till) Test pit completed at approximately 6 feet on 7/8/20. Groundwater not observed at time of excavation. Approximate surface elevation: 275 feet Project: Brar Short Plat SSGC Job # 20058 TEST PIT LOGS PAGE 2 OF 3 Location: S. 132nd Street, Renton, WA TEST PIT LOGS FIGURE A-1 South Sound Geotechnical Consulting PIT-1, TP-1 through TP-4 Logged by: THR Test Pit TP-2 Depth (feet) Material Description 0 – 0.5 0.5 – 2.5 2.5 – 4 4 – 6 Topsoil Silty SAND: Loose, moist, orangish brown. (SM) Silty SAND with occasional gravel and cobbles: Medium dense to dense, moist, mottled orange-gray. (SM) (Weathered Glacial Till) Silty SAND with gravel and cobbles: Very dense, moist, gray. (SM) (Glacial Till) Test pit completed at approximately 6 feet on 7/8/20. Groundwater not observed at time of excavation. Approximate surface elevation: 273 feet Test Pit TP-3 Depth (feet) Material Description 0 – 1.5 1.5 – 2 2 – 3 3 – 4 4 – 6 Fill: Silt, sand, and occasional gravel: Loose, moist, light brown. Topsoil Silty SAND: Loose, moist, orangish brown. (SM) Silty SAND with some gravel: Medium dense, moist, mottled orange-gray. (SM) (Weathered Glacial Till) SAND with silt and occasional gravel: Dense to very dense, moist, gray. (SM) (Glacial Till) Test pit completed at approximately 6 feet on 7/8/20. Groundwater not observed at time of excavation. Approximate surface elevation: 255 feet Project: Brar Short Plat SSGC Job # 20058 TEST PIT LOGS PAGE 3 OF 3 Location: S. 132nd Street, Renton, WA TEST PIT LOGS FIGURE A-1 South Sound Geotechnical Consulting PIT-1, TP-1 through TP-4 Logged by: THR Test Pit TP-4 Depth (feet) Material Description 0 – 1 1 – 1.5 1.5 – 2 2 – 4 4 – 6 Fill: Silt, sand, and occasional gravel: Loose, moist, brown. Topsoil Silty SAND: Loose, damp, orangish brown. (SM) Silty SAND with some gravel: Medium dense, moist, mottled orange-gray. (SM) (Weathered Glacial Till) Silty SAND with gravel and occasional cobble: Dense to very dense, moist, gray. (SM) (Glacial Till) Test pit completed at approximately 6 feet on 7/8/20. Groundwater not observed at time of excavation. Approximate surface elevation: 262 feet Geotechnical Engineering Report SSGC Brar Short Plat – S. 132nd St Renton, WA SSGC Project No. 20058 August 3, 2020 C-1 Appendix B Laboratory Testing and Results Geotechnical Engineering Report SSGC Brar Short Plat – S. 132nd St Renton, WA SSGC Project No. 20058 August 3, 2020 B-1 Laboratory Testing Select soil samples were tested for organic content and cation exchange capacity (CEC) by Northwest Agricultural Consultants of Kennewick, Washington. Results of the laboratory testing are included in this appendix. 2545 W Falls Avenue Kennewick, WA 99336 509.783.7450 www.nwag.com lab@nwag.com Sample ID Organic Matter Cation Exchange Capacity PIT-1, S-1 2.79% 10.0 meq/100g Method ASTM D2974 EPA 9081 South Sound Geotechnical Consulting PO Box 39500 Lakewood, WA 98496 Report: 51979-1-1 Date: July 14, 2020 Project No: 20058 Project Name: Brar UNIFIED SOIL CLASSIFICATION SYSTEM Criteria for Assigning Group Symbols and Group Names Using Laboratory TestsA Soil Classification Group Symbol Group NameB Coarse Grained Soils More than 50% retained on No. 200 sieve Gravels More than 50% of coarse fraction retained on No. 4 sieve Clean Gravels Less than 5% finesC Cu 4 and 1 Cc 3E GW Well-graded gravelF Cu 4 and/or 1 Cc 3E GP Poorly graded gravelF Gravels with Fines More than 12% finesC Fines classify as ML or MH GM Silty gravelF,G, H Fines classify as CL or CH GC Clayey gravelF,G,H Sands 50% or more of coarse fraction passes No. 4 sieve Clean Sands Less than 5% finesD Cu 6 and 1 Cc 3E SW Well-graded sandI Cu 6 and/or 1 Cc 3E SP Poorly graded sandI Sands with Fines More than 12% finesD Fines classify as ML or MH SM Silty sandG,H,I Fines Classify as CL or CH SC Clayey sandG,H,I Fine-Grained Soils 50% or more passes the No. 200 sieve Silts and Clays Liquid limit less than 50 inorganic PI 7 and plots on or above “A” lineJ CL Lean clayK,L,M PI 4 or plots below “A” lineJ ML SiltK,L,M organic Liquid limit - oven dried 0.75 OL Organic clayK,L,M,N Liquid limit - not dried Organic siltK,L,M,O Silts and Clays Liquid limit 50 or more inorganic PI plots on or above “A” line CH Fat clayK,L,M PI plots below “A” line MH Elastic SiltK,L,M organic Liquid limit - oven dried 0.75 OH Organic clayK,L,M,P Liquid limit - not dried Organic siltK,L,M,Q Highly organic soils Primarily organic matter, dark in color, and organic odor PT Peat A Based on the material passing the 3-in. (75-mm) sieve B If field sample contained cobbles or boulders, or both, add “with cobbles or boulders, or both” to group name. C Gravels with 5 to 12% fines require dual symbols: GW-GM well-graded gravel with silt, GW-GC well-graded gravel with clay, GP-GM poorly graded gravel with silt, GP-GC poorly graded gravel with clay. D Sands with 5 to 12% fines require dual symbols: SW-SM well-graded sand with silt, SW-SC well-graded sand with clay, SP-SM poorly graded sand with silt, SP-SC poorly graded sand with clay E Cu = D60/D10 Cc = 6010 230 DxD )(D F If soil contains 15% sand, add “with sand” to group name. G If fines classify as CL-ML, use dual symbol GC-GM, or SC-SM. HIf fines are organic, add “with organic fines” to group name. I If soil contains 15% gravel, add “with gravel” to group name. J If Atterberg limits plot in shaded area, soil is a CL-ML, silty clay. K If soil contains 15 to 29% plus No. 200, add “with sand” or “with gravel,” whichever is predominant. L If soil contains 30% plus No. 200 predominantly sand, add “sandy” to group name. M If soil contains 30% plus No. 200, predominantly gravel, add “gravelly” to group name. N PI 4 and plots on or above “A” line. O PI 4 or plots below “A” line. P PI plots on or above “A” line. Q PI plots below “A” line. Technical Information Report Brar Short Plat 2200320.10 Section 7 Other Permits Technical Information Report Brar Short Plat 7-1 2200320.10 7.0 Other Permits Required permits for the project include a Preliminary and Final Short Plat application, Right-of- Way and Site Grading Permits, and City of Renton residential building permits. Because this site is less than 1.0 acre, a National Pollutant Discharge Elimination System (NPDES) permit through Department of Ecology will not be required. Technical Information Report Brar Short Plat 2200320.10 Section 8 CSWPPP Analysis and Design Technical Information Report Brar Short Plat 8-1 2200320.10 8.0 CSWPPP Analysis and Design A CSWPPP is provided under separate cover. Technical Information Report Brar Short Plat 2200320.10 Section 9 Bond Quantities, Facility Summaries, and Declaration of Covenant Technical Information Report Brar Short Plat 9-1 2200320.10 9.0 Bond Quantities, Facility Summaries, and Declaration of Covenant A Bond Quantities Worksheet is provided under separate cover. Refer to Figure 9-1 for the Facility Summary Sheet, Figure 9-2 for the Facility Summary Site Plan, and Figure 9-3 for a Declaration of Covenant form. Technical Information Report Brar Short Plat 2200320.10 Section 9.0 Figures Figure 9-1 ......... Facility Summary Sheet Figure 9-2 ......... Facility Summary Site Plan Figure 9-3 ......... Declaration of Covenant 2016 KING COUNTY SURFACE WATER DESIGN MANUAL, REFERENCE D 4/24/2016 Page 1 STORMWATER FACILITY SUMMARY SHEET DPER Permit No.___________________ (provide one Stormwater Facility Summary Sheet per Natural Discharge Location)Date ___________________ OVERVIEW:NPDES Permit No.___________________ Project Name Parcel No.____________________________ Project Location Retired Parcel No.____________________________ Downstream Drainage Basins:Project includes Landscape Management Plan?yes Major Basin Name ______________________________________________(include copy with TIR as Appendix)no Immediate Basin Name ______________________________________________ GENERAL FACILITY INFORMATION: Leachable Metals Infiltration Impervious Surface Limit Type # of Type # of Type # of facilities Flow Control BMPs Ponds ______ Ponds ______ Ponds ______ Basic Clearing Limit Vaults ______ Tanks ______ Vaults ______ Conservation Drainage Facility Tanks ______ Trenches _____ Tanks ______ Flood Problem Landscape Management Plan If no flow control facility, check one: Project qualifies for KCSWDM Exemption (KCSWDM 1.2.3): Basic Exemption (Applies to Commercial parcels only)Area % of Total Redevelopment projects Cost Exemption for Parcel Redevelopment projects Direct Discharge Exemption Other _____________________ Total impervious surface served by Project qualifies for 0.1 cfs Exception per KCSWDM 1.2.3 flow control facility(ies) (sq ft) Impervious surface served by flow KCSWDM Adjustment No. ___________________control facility(ies) designed 1990 or later (sq ft) approved KCSWDM Adjustment No. __________________ Impervious surface served by Shared Facility Name/Location: _________________________ pervious surface absorption (sq ft) No flow control required (other, provide justification): Impervious surface served by approved ____________________________________________________ water quality facility(ies) (sq ft) Flow Control Performance Std Declarations of Covenant Recording No. Water QualityDetention TREATMENT SUMMARY FOR TOTAL IMPERVIOUS SURFACES ----- Total Impervious Acreage (ac) No flow control required per approved Flow control provided in regional/shared facility per approved PROVIDE FACILITY DETAILS AND FACILITY SKETCH FOR EACH FACILITY ON REVERSE. USE ADDITIONAL SHEETS AS NEEDED FOR ADDITIONAL FACILITIES Impervious Surface Exemption for Transportation Total Acreage (ac) BRAR SHORT PLAT 8054 SOUTH 132ND STREET, RENTON, WA 98178 2144800460 X 2 X WEST LAKE WASHINGTON - SEATTLE SOUTH LAKE WASHINGTON / CEDAR RIVER 2016 KING COUNTY SURFACE WATER DESIGN MANUAL, REFERENCE D 4/24/2016 Page 2 STORMWATER FACILITY SUMMARY SHEET DPER Permit No.___________________ (provide one Stormwater Facility Summary Sheet per Natural Discharge Location) Project Name Downstream Drainage Basins: Major Basin Name _______________________________ Project Location Immediate Basin Name ___________________________ FLOW CONTROL FACILITY:Basin: Facility Name/Number _______________________________________ New Facility Project Impervious Facility Location ____________________________________________ Existing Facility Acres Served ________ UIC? □ yes □ no UIC Site ID:% of Total Project Impervious cu.ft.Volume Factor Acres Served ________ _____________ ac.ft.____________of Safety _______No. of Lots Served ________ Control Structure location: _______________________________________________ Type of Control Structure:No. of Orifices/Restrictions __________ Riser in vault Size of Orifice/Restriction (in.) No.1 ______ cu.ft. Riser in Type II CB (numbered starting with lowest No.2 ______ ac.ft. Weir in Type II CB orifice): No.3 ______ (inches in decimal format)No.4 ______ WATER QUALITY FACILITIES Design Information Indicate no. of water quality facilities/BMPs for each type:Water Quality design flow (cfs) _______Flow dispersion Water Quality treated volume (sandfilter) (cu.ft.) _______Filter strip Water Quality storage volume (wetpool) (cu.ft.) _______Biofiltration swale regular, wet or Landscape management plan Farm management plan continuous inflow _______Wetvault combined w/detention ______High flow bypass structure (e.g., flow-splitter catch basin) _______Wetpond basic large combined w/detention ______Oil/water separator baffle coalescing plate _______Pre-settling pond ______Storm filter _______Stormwater wetland ______Pre-settling structure (Manufacturer:______________________) _______Sand filter basic large Sand bed depth ______Catch basin inserts (Manufacturer:________________________) regular linear vault (inches)______________Source controls _________________________________________ ● Is facility lined? yes no If so, what marker is used above liner?_____________________________________________________ Facility Summary Sheet Sketch: All detention, infiltration and water quality facilities must include a detailed sketch (11"x17" reduced size plan sheets preferred). Dam Safety Regulations (WA State Dept of Ecology): Reservoir Volume above natural grade Depth of Reservoir above natural grade (ft) Live Storage Volume Live Storage Depth (ft) BRAR SHORT PLAT 8054 SOUTH 132ND STREET, RENTON, WA 98178 WEST LAKE WASHINGTON - SEATTLE SOUTH LAKE WASHINGTON / CEDAR RIVER XDETENTION SYSTEM SOUTH END OF SITE X X 35,880 1.28 SOUTH END OF SITE X X 0.0294 1 4 0.366 92% STORM TANK DETENTION SYSTEM STORMWATER FILTER FRENCH DRAIN FOR OFFSITE DRAINAGE CONTROL STRUCTURE S 132ND ST Civil Engineers Structural Engineers Landscape Architects Community Planners Land Surveyors Neighbors BRAR SHORT PLAT - 2200320.10 8054 S 132ND ST RENTON, WA 98178 N Q:\2020\2200320\10_CIV\CAD\EXHIBITS\Facility Summary Sketch.dwg SITE INFO ADDRESS: 8054 S 132ND ST RENTON, WA 98178 PARCEL: 2144800460 2144800460 C22000505 PR:20-000015 C22000505 SEE EXHIBIT C Brar Gursewak & Kaur Gurdip STORM TANK DETENTION SYSTEM STORMWATER FILTER FRENCH DRAIN FOR OFFSITE DRAINAGE CONTROL STRUCTURE S 132ND ST N SITE INFO ADDRESS: 8054 S 132ND ST RENTON, WA 98178 PARCEL: 2144800460 DECLARATION OF COVENANT EXHIBIT A - SITE PLAN EXHIBIT “A” [NATIVE GROWTH PROTECTION EASEMENT] PARCEL THAT PORTION OF THE SOUTH HALF OF THE NORTH HALF OF THE SOUTHEAST QUARTER OF SECTION 30, TOWNSHIP 23 NORTH, RANGE 5 EAST, W.M., IN KING COUNTY, WASHINGTON, LYING WESTERLY OF PRIMARY STATE HIGHWAY NO. 5 AS SHOWN ON MAP RECORDED IN VOLUME 2 OF HIGHWAY MAPS, PAGE 96, RECORDS OF SAID COUNTY AND AS CONDEMNED IN KING COUNTY SUPERIOR COURT CAUSE NO. 576109; EXCEPT THE WEST 30 FEET THEREOF; AND EXCEPT THE SOUTH 194 FEET THEREOF. NATIVE GROWTH PROTECTIVE EASEMENT THAT PORTION OF THE ABOVESAID PARCEL LYING EAST THE FOLLOWING DESCRIBED LINE: COMMENCING AT THE NORTH QUARTER CORNER OF SAID SECTION 30; THENCE ALONG THE NORTH-SOUTH CENTER SECTION LINE, SOUTH 01°50’17” WEST, 3292.42 FEET MORE OR LESS TO THE NORTH LINE OF THE SOUTH HALF OF THE NORTH HALF OF THE SOUTHEAST QUARTER OF SECTION 30; THENCE ALONG SAID NORTH LINE, SOUTH 89°24’12” EAST, 30.01 FEET TO THE EAST RIGHT-OF-WAY MARGIN OF EAST VALLEY ROAD; THENCE CONTINUING, SOUTH 89°24’12” EAST, 468.13 FEET TO THE POINT OF BEGINNING OF SAID DESCRIBED LINE; THENCE SOUTH 02°07’27” WEST, 54.15 FEET; THENCE SOUTH 06°20’13” WEST, 26.95 FEET; THENCE SOUTH 11°36’06” WEST, 36.13 FEET; THENCE SOUTH 05°31’30” WEST, 109.85 FEET; THENCE SOUTH 08°46’51” WEST, 87.92 FEET; THENCE SOUTH 05°22’36” WEST, 58.20 FEET; THENCE SOUTH 15°38’25” WEST, 38.82 FEET; THENCE SOUTH 03°30’16” WEST, 58.64 FEET MORE OR LESS TO THE SOUTH LINE OF THE ABOVESAID PARCEL AND THE POINT OF TERMINUS OF SAID DESCRIBED LINE. CONTAINING 37,937 SQUARE FEET, OR 0.87 MORE OR LESS ACRES. 05/27/2021 "C" DECLARATION OF COVENANT EXHIBIT C - FULL LEGAL DESCRIPTION Page 35 of 35 LOT 1, BLOCK 18, EARLINGTON ACRE TRACTS AND TOGETHER WITH THAT PORTION OF LOT 7 OF BLOCK 19, EARLINGTON ACRE TRACTS, AS PER PLAT RECORDED IN VOLUME 15 OF PLATS, PAGE 84, IN King COUNTY, WASHINGTON, LYING WESTERLY OF THE FOLLOWING DESCRIBED LINE: COMMENCING AT THE SOUTHWEST CORNER OF SAID LOT 7; THENCE SOUTH 87°30’06” EAST 8.15 FEET ALONG THE SOUTH LINE OF SAID LOT 7 TO THE TRUE POINT OF BEGINNING OF SAID LINE; THENCE NORTH 00°22’46” EAST TO THE WEST LINE OF SAID LOT 7 AND THE END OF THIS DESCRIBED LINE, BY KING COUNTY SUPERIOR COURT CAUSE NO. 07-2-33638-9, AND RECORDED DECEMBER 12, 2007 UNDER RECORDING NUMBER 20071212000820 SITUATE IN THE CITY OF SEATTLE, COUNTY OF KING, STATE OF WASHINGTON. Technical Information Report Brar Short Plat 2200320.10 Section 10 Operations and Maintenance Plan Technical Information Report Brar Short Plat 10-1 2200320.10 10.0 Operations and Maintenance Plan The drainage facilities detailed in this report will be privately owned and maintained. A detailed Operations and Maintenance Plan is provided under a separate cover. Technical Information Report Brar Short Plat 2200320.10 Section 11 Conclusion Technical Information Report Brar Short Plat 11-1 2200320.10 11.0 Conclusion The Brar Short Plat site has been designed to meet the 2016 King County Surface Water Design Manual (KCSWDM), amended by City of Renton as the 2017 City of Renton Surface Water Design Manual (CRSWDM). The site uses water quality facilities to treat stormwater draining from the site. It was determined using these criteria that: · The site will meet the City’s Flow Duration Standard to match forested conditions. · Water quality facilities will be designed to meet the required Basic Water Quality Treatment Level for the site. · Pipe networks will be designed to be of adequate size to effectively convey the 25-year storm event and to contain the 100-year storm event. This analysis is based on data and records either supplied to or obtained by AHBL. These documents are referenced within the text of the analysis. The analysis has been prepared using procedures and practices within the standard accepted practices of the industry. We conclude that this project, as schematically represented, will not create any new problems within the downstream drainage system. This project will not noticeably aggravate any existing downstream problems due to either water quality or quantity. AHBL, Inc. Quinten Foster Project Engineer QF/lsk December 2021 Q:\2020\2200320\10_CIV\NON_CAD\REPORTS\TIR - Final\20220415 Revised TIR\20211215 Rpt (TIR) 2200320.10.docx