Document Redmond_doc_5e903ad781

STORM DRAINAGE REPORT BELLEVUE CHILDREN’S ACADEMY – Conditional Use Permit for Willows Preparatory School REDMOND, WA March 2017 Prepared For: Bellevue Children’s Academy 14510 NE 24th Street Bellevue, WA 98005 Prepared By: PACE Engineers Inc. 11255 Kirkland Way, #300 Kirkland, WA 98033 Contact: Scott Sherrow Ph: [PHONE REDACTED] ATTACHMENT 16 ---PAGE BREAK--- Table of Contents Bellevue Children’s Academy – Willow Prep School PACE Engineers, Inc. Storm Drainage Report Section 1 – Project Overview 1 Section 2 – Minimum Requirements 8 Section 3 – Offsite Analysis 12 3.1 Upstream Analysis 12 3.2 Analysis 12 Section 4 – Flow Control and Water Quality Facility Analysis and Design 14 4.1 Existing Site 14 4.2 Developed Site Hydrology 15 4.3 Flow Control and Water Quality Performance Standards 17 4.4 Conveyance System Analysis and Design 18 4.5 LID Assessment 18 Section 5 – Erosion and Sediment Control and Risk 20 5.1 Temporary Erosion and Sediment Control & 20 Section 6 – Special Reports and Studies & Other Permits 20 6.1 Special Reports and Studies 20 6.2 Other Permits 20 Section 7 – Operations and Maintenance Manual 20 List of Appendices Appendix A Existing and Proposed Area Maps Appendix B Engineering Calculations Appendix C Geotechnical Report List of Figures Figure 1 – Site Location 1 Figure 1.2 – Aerial Photograph 2 Figure 1.3 – Project Exhibit 3 Figure 1.4 – Soil Map 6 Figure 2.1 – Flow Chart for Determining Requirements for New Development 9 Figure 2.2 – Flow Chart for Determining Requirements for Redevelopment 10 Figure 3.1 – Drainage Map 14 ATTACHMENT 16 ---PAGE BREAK--- Willows Prep School Page 1 Stormwater Site Plan March 2017 SECTION 1 – PROJECT OVERVIEW 1.1 Project Overview The Bellevue Children’s Academy Master Plan Development (BCAMPD) of the Willows Preparatory School Expansion is located in Section 26, Township 26 North, Range 5 East, Willamette Meridian in the City of Redmond. The entire site area is approximately 12.80 acres in size and is located south of NE 124th Street and east of Redmond- Woodinville Road NE (SR 202). See Figure 1 for the site location map and Figure 1.2 for the aerial photograph. The project site is recorded with tax parcel number [PHONE REDACTED], in King County, Washington. Figure 1: Site Location Map Project site ATTACHMENT 16 ---PAGE BREAK--- Willows Prep School Page 2 Stormwater Site Plan March 2017 Figure 1.2: Aerial Photograph The project site is zoned as “R-1, R-4”. Its current use is church/religious services under a conditional use permit. Per USDA Web Soil Survey, site soils are Kitsap silt loam and Alderwood gravelly sandy loam. See Figure 1.4: Soil Map. The BCAMPD proposes to add a total of 3 new buildings in 2 projects to provide classrooms and dormitory space for middle-school aged students. There is currently a complex of 6 existing buildings on the subject property. The two larger buildings, a sanctuary and a multi-purpose building, are currently in use by a church group (Washington Cathedral), renting from BCA, and will remain undisturbed. Asphalt parking around these two structures will remain relatively undisturbed as well. Parking and driveway areas along the east property line and in the south portion of the site will remain relatively undisturbed throughout development projects. Slight changes in access to these parking areas will occur to provide access to new buildings as they are constructed. See Figure 1.3: Projects Exhibit and Appendix A for existing conditions and project plans. ATTACHMENT 16 ---PAGE BREAK--- EXISTING BUILDING TO REMAIN EXISTING BUILDING TO REMAIN PHASE A PHASE B Figure 1.3: Phasing Exihibit ATTACHMENT 16 ---PAGE BREAK--- Willows Prep School Page 4 Stormwater Site Plan March 2017 1.2 Project A Project A of the BCAMPD proposes to demolish the remaining existing buildings in the northwest portion of the site and construct private school classrooms. The proposal will include two 2-story classrooms for a total of approximately 300 middle-school aged students, a covered patio and an uncovered plaza over a new single-story structure. The proposed buildings will be located in the area of the existing buildings to be demolished. The asphalt parking and driveway around the buildings will be reconfigured and improved as part of this proposal. There will be no net increase of impervious coverage as a result of Project A development. The site development engineering for Project A includes site grading, sanitary sewer connections, water connections and storm drainage improvements for the site. The storm drainage improvements will include installation of catch basins and underground storm pipe system to collect and convey stormwater to the existing storm system in Redmond-Woodinville Road NE. No other flow controls measures are required for this project development. Project A is seeking a SPE approval parallel to the CUP approval. 1.3 Project B Project B of the BCAMPD proposes to construct one new 2-story dormitory for housing for approximately 40 students, located between the south parking lot and the existing multi-purpose building, in the southeast portion of the site. Access to the building will be provided by concrete walkways connected to the existing parking areas to the east and south. The site development engineering for Project B includes, site grading, sanitary sewer connection, water connection and storm drainage improvements. The storm drainage improvements will include construction of the detention/wetvault for additional stormwater flow control and water quality treatment. All stormwater flow control and water quality elements required for the project will be designed in compliance with the city codes at the time building permits are requested. ATTACHMENT 16 ---PAGE BREAK--- Soil Map—King County Area, Washington (BCA WILLOWS) Natural Resources Conservation Service Web Soil Survey National Cooperative Soil Survey 4/6/2015 Page 1 of 3 5284240 5284280 5284320 5284360 5284400 5284440 5284480 5284520 5284560 5284240 5284280 5284320 5284360 5284400 5284440 5284480 5284520 5284560 565100 565140 565180 565220 565260 565300 565340 565100 565140 565180 565220 565260 565300 565340 47° 42' 40'' N 122° 7' 56'' W 47° 42' 40'' N 122° 7' 43'' W 47° 42' 29'' N 122° 7' 56'' W 47° 42' 29'' N 122° 7' 43'' W N Map projection: Web Mercator Corner coordinates: WGS84 Edge tics: UTM Zone 10N WGS84 0 50 100 200 300 Feet 0 25 50 100 150 Meters Map Scale: 1:1,700 if printed on A portrait (8.5" x 11") sheet. ATTACHMENT 16 ---PAGE BREAK--- 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 1:24,000. 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: http://websoilsurvey.nrcs.usda.gov 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: King County Area, Washington Survey Area Data: Version 10, Sep 30, 2014 Soil map units are labeled (as space allows) for map scales 1:50,000 or larger. Date(s) aerial images were photographed: Aug 31, 2013—Oct 6, 2013 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—King County Area, Washington (BCA WILLOWS) Natural Resources Conservation Service Web Soil Survey National Cooperative Soil Survey 4/6/2015 Page 2 of 3 ATTACHMENT 16 ---PAGE BREAK--- Map Unit Legend King County Area, Washington (WA633) Map Unit Symbol Map Unit Name Acres in AOI Percent of AOI AgC Alderwood gravelly sandy loam, 8 to 15 percent slopes 1.8 21.7% Bh Bellingham silt loam 0.7 8.6% KpB Kitsap silt loam, 2 to 8 percent slopes 5.0 61.2% KpD Kitsap silt loam, 15 to 30 percent slopes 0.7 8.5% Totals for Area of Interest 8.2 100.0% Soil Map—King County Area, Washington BCA WILLOWS Natural Resources Conservation Service Web Soil Survey National Cooperative Soil Survey 4/6/2015 Page 3 of 3 ATTACHMENT 16 ---PAGE BREAK--- Willows Prep School Page 8 Stormwater Site Plan March 2017 SECTION 2 – MINIMUM REQUIREMENTS The BCAMPD project will follow the City of Redmond stormwater standards. The project entered the PREP process after March 1, 2016 and has completed the 60% intake meeting before December 31, 2016 therefore the project is subject to the 2016 standard. The 2016 standard allows for the use of the 2012 Washington State Department of Ecology Stormwater Management Manual as amended in December 2014 (2014 with modifications contained in the City’s Stormwater Technical Notebook. The flow chart for determining requirements for re-development was used to assess the minimum requirements for the proposed project. This project is required to meet Minimum Requirements #9 in Chapter 2 of the Stormwater Technical Notebook. See the flow chart below. Figure 2.1: Flow Chart for Determining Requirements for New Development ATTACHMENT 16 ---PAGE BREAK--- Willows Prep School Page 9 Stormwater Site Plan March 2017 Figure 2.2: Flow Chart for Determining Requirements for Redevelopment ATTACHMENT 16 ---PAGE BREAK--- Willows Prep School Page 10 Stormwater Site Plan March 2017 2.1 Minimum Requirement #1 Preparation of Stormwater Site Plans A Stormwater Site Plan has been prepared for the proposed Willows Preparatory School expansion per the 2014 and the City of Redmond Stormwater Technical Notebook and has been submitted with “Project A” SPE material.. The site plans include stormwater engineering design plans and this storm drainage report, including technical design calculations. 2.2 Minimum Requirement #2 Construction Stormwater Pollution Prevention Plan A SWPP plan is required for the BCAMPD and will be prepared as part of the submittal for the coordinated civil review. It has not been included with this preliminary submittal package. 2.3 Minimum Requirement #3 Source Control of Pollution It is not proposed that pollution generating material will be stored on-site. The proposed uses of the project include school classrooms and a dormitory where there is a possibility of pollution being generated in the vehicular parking areas. Within Project A, the proposed buildings will be located over the area of the existing structures that are to be removed. Non-pollution generating impervious surface in the form of concrete walkways and a plaza over a proposed structure will replace a portion of the existing parking area. Asphalt parking around the structures will be reconfigured, but the square footage of pollution generating asphalt parking will be decreased from the existing conditions. Project B will not add pollution-generating impervious surface; access to this building will be from existing parking areas. 2.4 Minimum Requirement #4 Preservation of Natural Drainage Systems and Outfalls The portion of Project to be redeveloped currently drains north and northwest to the public storm drainage system located in Redmond-Woodinville Road NE. The redevelopment will preserve the existing outfall. Storm drainage runoff will continue to flow to the existing system. Stormwater will be released from the project site at the same location. It is also proposed that Project will preserve the existing natural point of discharge. 2.5 Minimum Requirement #5 On-site Stormwater Management Per the City of Redmond requirements, the project shall employ on-site Stormwater Best Management Practices (BMPs) to infiltrate, disperse and retain stormwater runoff onsite to the maximum extent feasible without causing ATTACHMENT 16 ---PAGE BREAK--- Willows Prep School Page 11 Stormwater Site Plan March 2017 flooding, groundwater contamination or erosion impacts. The Stormwater Technical Notebook was used for evaluating onsite integrated management practices for the project. See Section 4 of this report for proposed stormwater management. 2.6 Minimum Requirement #6 Runoff Treatment The project will be required to provide runoff treatment. Treatment may be provided by a combined detention/wetvault located in the north portion of the site. The wetvault will be designed per the current regulations at the time of development. See Appendix B for WWHM stormwater calculations. 2.7 Minimum Requirement #7 Flow Control The project will be required to provide flow control. Stormwater runoff may be routed from the proposed building to a combined detention/ wetvault located in the north portion of the site. The wetvault will be designed per the current regulations at the time of development. See Section 4: Flow Control and Water Quality Analysis and Design and Appendix B for WWHM stormwater calculations. 2.8 Minimum Requirement #8 Wetlands Protection The BCAMPD project does not discharge directly to a wetland. For more information on the flow path, see Section 3 – Off-site Analysis. 2.9 Minimum Requirement #9 Operation and Maintenance An Operation and Maintenance Manual will be required for the permanent stormwater facility. The O&M Manual will be prepared during final engineering for each project phase and submitted with the coordinated civil review Storm Drainage Report. ATTACHMENT 16 ---PAGE BREAK--- Willows Prep School Page 12 Stormwater Site Plan March 2017 SECTION 3 – OFF-SITE ANALYSIS 3.1 Upstream Analysis No upstream area is tributary to the project site as all upstream flows are intercepted by conveyance pipe and catch basin systems. Stormwater runoff is directed to detention ponds, outfalling to the public storm drainage system in Redmond-Woodinville Road. 3.2 Analysis Stormwater runoff from the site sheet flows northwesterly towards the west property line. Stormwater directly enters the public storm drainage system in Redmond-Woodinville Road NE which is located on the east gutter line of the road. Stormwater continues north in the underground public storm system for 136’ through 12” piping to a catch basin just south of the intersection at NE 124th Street. Drainage exits the catch basin to the west across Redmond-Woodinville Road NE for 59’ to a catch basin on the west side of the road. Drainage continues northwest for 58’ through 12” piping to a catch basin located in the south gutter line of NE 124th St. It flows west from this catch basin for 160’ through 12” ADS to a tributary of the Sammamish River. The tributary meanders across King County owned parcels along the south side of NE 124th St, outfalling to a pond approximately 1800 feet of the project site. The tributary continues meandering westerly, ultimately outfalling to the Sammamish River approximately 3000 feet of the project site. The study area for the project extends ¼ mile of the project site discharge location. Refer to Figure 3 below for the drainage paths for the basin. There are no reported drainage problems with the conveyance pipe system along the path. ATTACHMENT 16 ---PAGE BREAK--- Willows Prep School Page 13 Stormwater Site Plan March 2017 Figure 3.1: Drainage Map Project Site Flowpath Point ¼ Mile Sammamish River ATTACHMENT 16 ---PAGE BREAK--- Willows Prep School Page 14 Stormwater Site Plan March 2017 SECTION 4 – FLOW CONTROL AND WATER QUALITY FACILITY ANLAYSIS AND DESIGN 4.1 Existing Site Hydrology The Bellevue Children’s Academy Master Planned Development (BCAMPD) proposes to add a total of 3 new buildings in two projects to provide classrooms and dormitory space for middle-school aged students. There is currently a complex of several existing buildings on the subject property. The two larger buildings, a sanctuary and a multi-purpose building, are currently in use by a church group (Washington Cathedral), renting from BCA, and will remain undisturbed. Asphalt parking around these two structures will remain relatively undisturbed as well. Parking and driveway areas along the east property line and in the south portion of the site will remain relatively undisturbed throughout development projects. Slight changes in access to these parking areas will occur to provide access to new buildings as they are constructed. Currently, the stormwater runoff from the two larger buildings that are to remain and the associated parking is collected in an underground conveyance system, outfalling to a detention pond in the northeast portion of the site. The pond outfalls to the west in a closed underground conveyance system, to the public storm system located in the Redmond-Woodinville Road NE. The existing hydrology for this area will not change with the BCAMPD. No additional stormwater runoff will be routed to this detention pond. The BCAMPD Project A portion of the site, consists of several structures, concrete patio, asphalt concrete pavement used for access and parking, concrete curbing, and landscaping. Surface runoff on the existing project site sheet flows to the north and is collected in a series of catch basins located north of the parking area and conveyed to the existing stormwater system in Redmond-Woodinville Road NE. Stormwater then flows westerly in the public system, eventually outfalling to the Sammamish River as described in Section 3 – Offsite Analysis. The stormwater in the areas for Project B sheet flows north/northwesterly across pasture. Stormwater that is not infiltrated into the ground, flows north onto the existing parking area. Runoff is collected in the underground conveyance system of pipes and catch basins, and outfalls to the public storm system located in Redmond-Woodinville Road NE. Stormwater continues north in the public storm system to the intersection of NE 124th St. Stormwater then flows westerly in the public system, eventually outfalling to the Sammamish River as described in Section 3 – Offsite Analysis. The parking lot occupying the south portion of the site currently drains southwesterly to a series of detention ponds located in the southwest corner of the site. Stormwater runoff is collected in an underground conveyance system of catch basins and pipes, outfalling to a pond on the south side of the existing driveway. Stormwater is piped north, across the driveway to another series of ponds along the west property line. The outfall of these ponds is to the public storm system located in Redmond-Woodinville Road NE. Stormwater then flows northerly and follows the previously described path ATTACHMENT 16 ---PAGE BREAK--- Willows Prep School Page 15 Stormwater Site Plan March 2017 to the Sammamish River. The hydrology for this sub-basin will remain unchanged. No new stormwater will be routed to the existing ponds. Table 1. Summary of Existing Land Use by Project Project A EXISTING CONDITIONS Land Use Area Impervious Pervious (SF) (Acre) (SF) (Acre) (SF) (Acre) C, Lawn/Landscaping, Flat 5,558 0.128 - - 5,558 0.128 Roof, Flat 13,000 0.298 13,000 0.298 - - Parking, Flat 29,630 0.680 29,630 0.680 - - Sidewalk, Flat 2,700 0.062 2,700 0.062 - - Total 50,888 1.168 45,330 1.041 5,558 0.149 Project B EXISTING CONDITIONS Land Use Area Impervious Pervious (SF) (Acre) (SF) (Acre) (SF) (Acre) C, Lawn/Landscaping, Mod 7,000 0.161 - - 7,000 0.161 C, Lawn/Landscaping, Steep 11,000 0.253 11,000 0.253 Total 18,000 0.413 - - 18,000 0.413 4.2 Developed Site Hydrology Project A of the BCAMPD project proposes to redevelop approximately 1.17 acres of the 12.80 acres of the site by replacing existing structures with classroom buildings and reconfiguring the parking, drive aisle, and landscape areas. Since the new structures will be placed on top of the area where the existing structures stood and the parking area will be reconfigured, minor grade changes will take place around the proposal to maintain positive drainage to existing catch basins. No additional flow control measures are proposed for this project. Project B of the BCAMPD proposes to construct one new 2-story dormitory for housing, located between the south parking lot and the existing multi-purpose building, in the southeast portion of the site. Stormwater runoff from the new building will be collected in ATTACHMENT 16 ---PAGE BREAK--- Willows Prep School Page 16 Stormwater Site Plan March 2017 a new underground drainage system. The estimate of the detention volume required for Project B is 6,000 CF. A finalized sizing calculation may be provided under the coordinated civil review process. Stormwater flow from the remainder of the existing project area will not change as part of this development. Refer to the land use table below and Appendix B for engineering calculations. Table 2. Summary of Proposed Land Use by Project Project A DEVELOPED CONDITIONS Land Use Area Impervious Pervious (SF) (Acre) (SF) (Acre) (SF) (Acre) C, Lawn/Landscaping, Flat 13,738 0.315 - - 13,738 0.315 Roof, Flat 11,574 0.266 11,574 0.266 - - Parking, Flat 21,894 0.503 21,894 0.503 - - Sidewalk, Flat 3,682 0.085 3,682 0.085 - - Total 50,888 1.168 37,150 0.853 13,738 0.149 Project B DEVELOPED CONDITIONS Land Use Area Impervious Pervious (SF) (Acre) (SF) (Acre) (SF) (Acre) C, Lawn/Landscaping, Steep 4,940 0.113 - - 4,940 0.113 C, Lawn/Landscaping, Flat - - - - - - Roof, Flat 10,800 0.248 10,800 0.248 - - Sidewalk, Flat 2,260 0.052 2,260 0.052 - - Total 18,000 0.413 13,060 0.300 4,940 0.113 ATTACHMENT 16 ---PAGE BREAK--- Willows Prep School Page 17 Stormwater Site Plan March 2017 4.3 Flow Control and Water Quality Performance Standards As previously determined, Project A of the BCAMPD will not require additional flow control. For Project B, stormwater runoff will be collected in an underground conveyance system of pipes and catch basins. Runoff will be routed to the north, into a combined detention/wetvault located on-site. Per the 2014 the flow control system will be designed to meet the following criteria for Level-2 flow control or the applicable stormwater regulations at the time of development:  The post developed site must match developed discharge durations to predeveloped durations for the range of predeveloped discharge rates from 50% of the 2-year peak flow up to the full 50-year peak flow.  Developed peak discharge rates also must match the predeveloped peak discharge rates for the 2- and 10- year return periods.  The developed 50-year peak discharge rate must match the predeveloped 50- year peak discharge rate. The Western Washington Hydrologic Model (WWHM) was used for sizing the detention facility. The following criteria are used in WWHM when sizing a treatment facility:  Developed flow duration values must match any of the predeveloped flow levels between 50% and 100% of the 2-year predevelopment peak flow values (100 Percent Threshold).  The developed flow duration values may not exceed any of the predeveloped flow levels between 100% of the 2-year and 100% of the 50-year predeveloped peak flow values more than 10 percent of the time (110 Percent Threshold).  Existing conditions will be modeled as forested land cover. No more than 50 percent of the flow duration levels may exceed the 100 percent threshold. Refer to Appendix A for existing and proposed site area maps. Refer to the table below for volume requirements and Appendix B for engineering calculations. FLOW CONTROL AND WATER QUALITY VOLUME REQUIREMENTS PROJECT DETENTION (CF) WATER QUALITY (CF) PROJECT A 0 0 PROJECT B 6,000 1,865 TOTAL FOR SEPARATE PROJECTS 6,000 1,865 ATTACHMENT 16 ---PAGE BREAK--- Willows Prep School Page 18 Stormwater Site Plan March 2017 4.4 Conveyance System Analysis and Design The BCAMPD conveyance system will be sized to convey the 25-year peak storm event using the Rational Method to calculate peak flows within each drainage sub-basin. Conveyance calculations will be completed and provided at the time final plans are submitted for each project phase. 4.5 LID Assessment The Project A site has been assessed for Low Impact Development to determine the feasibility of infiltration and dispersion Best Management Practices (BMPs). List #1 has been used to evaluate On-site Stormwater Management BMPs for Project Triggering Minimum Requirements #1 through #5 . On-site Stormwater Management Techniques evaluated are as follows: 1. Lawn and Landscaped Areas: The project will amend soils within landscaped areas in accordance with the City of Redmond Standard Detail 632. 2. Roofs: Full Dispersion has been evaluated for this site and deemed to be infeasible because the required native vegetated flow path does not exist on the site. Full Downspout Infiltration Systems have been evaluated and deemed to be infeasible. Infiltration was evaluated and determined to not be a viable stormwater management practice as the project is located within an area of existing reconstructed parking area. There is minimal landscape areas and reductions in this area reduce the ability of emergency vehicles to maneuver. The near surface soils on-site generally consist of medium stiff silt and clay fill overlying dense to very dense silty sand with gravel. Based on the soil types provided in the geotechnical report, infiltration is not feasible. Rain Gardens have been evaluated and deemed to be infeasible due to low infiltration rates and recommendations made by the geotechnical engineer. The site is underlain by glacial till and transitional bed. Both materials are considered close to impermeable and unfavorable for infiltration. Downspout Dispersion Systems were evaluated and determined to not be a viable stormwater management practice due to the location of the structures and the paved parking. A vegetated flow path could not be achieved. Perforated Stub-out Connections were evaluated and determined to not be a viable stormwater management practice as the project is located within an area of existing reconstructed parking area. The BMP requires the perforated pipe portion of the system should not be located under impervious surfaces. There is minimal landscape areas and reductions in this area reduce the ability of ATTACHMENT 16 ---PAGE BREAK--- Willows Prep School Page 19 Stormwater Site Plan March 2017 emergency vehicles to maneuver. The site is underlain by materials that have very low infiltration rates. Water from the perforated by would flow through the gravel trench into the public storm system with little to no attenuation. 3. Other Hard Surfaces: Full Dispersion has been evaluated for this site and deemed to be infeasible because the required native vegetated flow path does not exist on the site. Permeable Pavements, rain gardens, and bioretention have been evaluated and deemed to be infeasible due to low infiltration rates and recommendations made by the geotechnical engineer. The site is underlain by glacial till and transitional bed. Both materials are considered close to impermeable and unfavorable for infiltration. Sheet Flow Dispersion has been evaluated for this site and deemed to be infeasible because the required vegetated flow path does not exist on the site. Project B will be evaluated at the time of development for the feasibility of on-site stormwater management BMPs. ATTACHMENT 16 ---PAGE BREAK--- Willows Prep School Page 20 Stormwater Site Plan March 2017 SECTION 5 – CONSTRUCTION STORMWATER POLLUTION AND PREVENTION C- 5.1 Temporary Erosion and Sediment Control & This section covers Construction Stormwater Pollution and Prevention Along with this storm drainage report, a temporary erosion and sediment control (TESC) plan will be prepared with each project as part of the SPE submittal. SECTION 6 – SPECIAL REPORTS AND STUDIES & OTHER PERMITS 6.1 Special Reports and Studies Below is a list of reports and studies that were completed for the project and can be found in Appendix D.  Geotechnical Engineering Services, Prepared for Washington Cathedral Prepared by GeoEngineers, Inc., dated July 26, 2004  Geotechnical Recommendation provided by email, dated March 9, 2017 6.2 Other Permits A Building Permit will be obtained from the City of Redmond. SECTION 7 – OPERATIONS AND MAINTENANCE MANUAL An Operation and Maintenance Manual is required for the BCAMPD and will be prepared at time of final engineering ATTACHMENT 16 ---PAGE BREAK--- Willows Prep School APPENDIX A ATTACHMENT 16 ---PAGE BREAK--- ATTACHMENT 16 ---PAGE BREAK--- ATTACHMENT 16 ---PAGE BREAK--- Willows Prep School APPENDIX B ATTACHMENT 16 ---PAGE BREAK--- WWHM2012 PROJECT REPORT Project Name: Phase 1 Flow Comparison Site Name: Site Address: City : Report Date: 2/2/2017 Gage : Seatac Data Start : 1948/10/01 Data End : 2009/09/30 Precip Scale: 1.00 Version Date: 2016/02/25 Version : 4.2.12 Low Flow Threshold for POC 1 : 50 Percent of the 2 Year High Flow Threshold for POC 1: 50 year PREDEVELOPED LAND USE Name : Basin 1 Bypass: No GroundWater: No Pervious Land Use acre C, Lawn, Flat .13 Pervious Total 0.13 Impervious Land Use acre ROADS FLAT 0.685 ROOF TOPS FLAT 0.305 SIDEWALKS FLAT 0.06 Impervious Total 1.05 Basin Total 1.18 Element Flows To: Surface Interflow Groundwater MITIGATED LAND USE Name : Basin 1 Bypass: No B-1 ATTACHMENT 16 ---PAGE BREAK--- GroundWater: No Pervious Land Use acre C, Lawn, Flat .31 Pervious Total 0.31 Impervious Land Use acre ROADS FLAT 0.48 ROOF TOPS FLAT 0.23 SIDEWALKS FLAT 0.16 Impervious Total 0.87 Basin Total 1.18 Element Flows To: Surface Interflow Groundwater ANALYSIS RESULTS Stream Protection Duration Predeveloped Landuse Totals for POC #1 Total Pervious Area:0.13 Total Impervious Area:1.05 Mitigated Landuse Totals for POC #1 Total Pervious Area:0.31 Total Impervious Area:0.87 Flow Frequency Return Periods for Predeveloped. POC #1 Return Period Flow(cfs) 6 month 0.197987 2 year 0.274982 5 year 0.346894 10 year 0.396706 25 year 0.462305 50 year 0.513188 100 year 0.565863 B-2 ATTACHMENT 16 ---PAGE BREAK--- Flow Frequency Return Periods for Mitigated. POC #1 Return Period Flow(cfs) 6 month 0.171284 2 year 0.237894 5 year 0.303288 10 year 0.348958 25 year 0.409496 50 year 0.456726 100 year 0.505844 Stream Protection Duration Annual Peaks for Predeveloped and Mitigated. POC #1 Year Predeveloped Mitigated 1949 0.276 0.241 1950 0.403 0.367 1951 0.269 0.240 1952 0.236 0.199 1953 0.214 0.183 1954 0.256 0.221 1955 0.273 0.235 1956 0.263 0.225 1957 0.301 0.263 1958 0.271 0.234 1959 0.208 0.179 1960 0.261 0.228 1961 0.227 0.197 1962 0.233 0.198 1963 0.223 0.194 1964 0.264 0.229 1965 0.236 0.202 1966 0.234 0.203 1967 0.353 0.304 1968 0.397 0.340 1969 0.214 0.186 1970 0.235 0.203 1971 0.227 0.194 1972 0.328 0.289 1973 0.214 0.184 1974 0.236 0.205 1975 0.312 0.276 1976 0.214 0.187 1977 0.271 0.228 1978 0.350 0.294 1979 0.346 0.289 1980 0.291 0.255 1981 0.323 0.279 1982 0.442 0.386 1983 0.322 0.272 1984 0.244 0.211 1985 0.230 0.195 1986 0.287 0.255 1987 0.401 0.338 1988 0.191 0.159 1989 0.240 0.199 1990 0.451 0.408 1991 0.421 0.377 B-3 ATTACHMENT 16 ---PAGE BREAK--- 1992 0.242 0.209 1993 0.166 0.140 1994 0.198 0.165 1995 0.249 0.212 1996 0.296 0.266 1997 0.284 0.251 1998 0.306 0.264 1999 0.578 0.503 2000 0.297 0.258 2001 0.254 0.212 2002 0.298 0.261 2003 0.269 0.235 2004 0.520 0.463 2005 0.244 0.210 2006 0.202 0.179 2007 0.464 0.433 2008 0.415 0.373 2009 0.287 0.244 Stream Protection Duration Ranked Annual Peaks for Predeveloped and Mitigated. POC #1 Rank Predeveloped Mitigated 1 0.5782 0.5034 2 0.5202 0.4627 3 0.4645 0.4328 4 0.4509 0.4084 5 0.4420 0.3861 6 0.4210 0.3774 7 0.4153 0.3726 8 0.4032 0.3672 9 0.4011 0.3403 10 0.3975 0.3377 11 0.3527 0.3041 12 0.3501 0.2937 13 0.3456 0.2894 14 0.3280 0.2889 15 0.3226 0.2787 16 0.3220 0.2760 17 0.3125 0.2725 18 0.3063 0.2665 19 0.3010 0.2643 20 0.2975 0.2635 21 0.2974 0.2610 22 0.2956 0.2581 23 0.2914 0.2549 24 0.2873 0.2548 25 0.2866 0.2508 26 0.2839 0.2441 27 0.2762 0.2414 28 0.2733 0.2401 29 0.2714 0.2353 30 0.2707 0.2348 31 0.2694 0.2337 32 0.2686 0.2291 33 0.2644 0.2279 34 0.2630 0.2277 B-4 ATTACHMENT 16 ---PAGE BREAK--- 35 0.2607 0.2254 36 0.2557 0.2214 37 0.2543 0.2124 38 0.2488 0.2120 39 0.2440 0.2110 40 0.2436 0.2102 41 0.2425 0.2090 42 0.2403 0.2050 43 0.2363 0.2029 44 0.2358 0.2026 45 0.2356 0.2023 46 0.2348 0.1991 47 0.2345 0.1990 48 0.2328 0.1979 49 0.2304 0.1970 50 0.2275 0.1951 51 0.2272 0.1937 52 0.2231 0.1936 53 0.2141 0.1866 54 0.2140 0.1859 55 0.2137 0.1844 56 0.2137 0.1827 57 0.2081 0.1792 58 0.2017 0.1788 59 0.1977 0.1655 60 0.1914 0.1586 61 0.1661 0.1403 Stream Protection Duration POC #1 The Facility PASSED The Facility PASSED. Flow(cfs) Predev Mit Percentage Pass/Fail 0.1375 1324 790 59 Pass 0.1413 1200 713 59 Pass 0.1451 1086 648 59 Pass 0.1489 1020 598 58 Pass 0.1527 934 552 59 Pass 0.1565 850 513 60 Pass 0.1603 788 457 57 Pass 0.1641 724 426 58 Pass 0.1679 677 383 56 Pass 0.1716 623 355 56 Pass 0.1754 576 323 56 Pass 0.1792 537 301 56 Pass 0.1830 492 273 55 Pass 0.1868 461 259 56 Pass 0.1906 427 244 57 Pass 0.1944 395 222 56 Pass 0.1982 358 204 56 Pass 0.2020 324 189 58 Pass 0.2058 309 180 58 Pass 0.2096 289 168 58 Pass 0.2134 272 151 55 Pass B-5 ATTACHMENT 16 ---PAGE BREAK--- 0.2172 259 140 54 Pass 0.2210 238 136 57 Pass 0.2248 221 128 57 Pass 0.2286 208 116 55 Pass 0.2324 197 109 55 Pass 0.2362 182 100 54 Pass 0.2400 172 93 54 Pass 0.2437 158 81 51 Pass 0.2475 153 77 50 Pass 0.2513 142 71 50 Pass 0.2551 134 68 50 Pass 0.2589 129 65 50 Pass 0.2627 120 61 50 Pass 0.2665 109 57 52 Pass 0.2703 104 56 53 Pass 0.2741 91 54 59 Pass 0.2779 86 52 60 Pass 0.2817 84 50 59 Pass 0.2855 78 48 61 Pass 0.2893 72 44 61 Pass 0.2931 69 41 59 Pass 0.2969 65 38 58 Pass 0.3007 60 38 63 Pass 0.3045 58 35 60 Pass 0.3083 55 31 56 Pass 0.3121 53 31 58 Pass 0.3159 52 31 59 Pass 0.3196 52 29 55 Pass 0.3234 49 26 53 Pass 0.3272 47 26 55 Pass 0.3310 45 24 53 Pass 0.3348 43 24 55 Pass 0.3386 41 22 53 Pass 0.3424 39 19 48 Pass 0.3462 35 19 54 Pass 0.3500 34 19 55 Pass 0.3538 30 16 53 Pass 0.3576 30 15 50 Pass 0.3614 28 14 50 Pass 0.3652 27 14 51 Pass 0.3690 27 12 44 Pass 0.3728 25 11 44 Pass 0.3766 24 10 41 Pass 0.3804 24 8 33 Pass 0.3842 22 8 36 Pass 0.3880 21 7 33 Pass 0.3918 21 7 33 Pass 0.3955 19 6 31 Pass 0.3993 17 6 35 Pass 0.4031 16 6 37 Pass 0.4069 14 6 42 Pass 0.4107 12 5 41 Pass 0.4145 12 5 41 Pass 0.4183 10 5 50 Pass 0.4221 9 5 55 Pass 0.4259 9 5 55 Pass 0.4297 9 5 55 Pass B-6 ATTACHMENT 16 ---PAGE BREAK--- 0.4335 9 4 44 Pass 0.4373 8 4 50 Pass 0.4411 8 3 37 Pass 0.4449 7 3 42 Pass 0.4487 7 3 42 Pass 0.4525 5 2 40 Pass 0.4563 5 2 40 Pass 0.4601 5 2 40 Pass 0.4639 5 1 20 Pass 0.4676 4 1 25 Pass 0.4714 4 1 25 Pass 0.4752 4 1 25 Pass 0.4790 4 1 25 Pass 0.4828 4 1 25 Pass 0.4866 4 1 25 Pass 0.4904 3 1 33 Pass 0.4942 3 1 33 Pass 0.4980 3 1 33 Pass 0.5018 3 1 33 Pass 0.5056 3 0 0 Pass 0.5094 3 0 0 Pass 0.5132 2 0 0 Pass Water Quality BMP Flow and Volume for POC #1 On-line facility volume: 0.1314 acre-feet On-line facility target flow: 0.1492 cfs. Adjusted for 15 min: 0.1661 cfs. Off-line facility target flow: 0.0853 cfs. Adjusted for 15 min: 0.095 cfs. LID Report LID Technique Used for Total Volumn Volumn Infiltration Cumulative Percent Water Quality Percent Comment Treatment? Needs Through Volumn Volumn Volumn Water Quality Treatment Facility (ac-ft.) Infiltration Infiltrated Treated (ac-ft) (ac-ft) Credit B-7 ATTACHMENT 16 ---PAGE BREAK--- Perlnd and Changes No changes have been made. 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. 2005-2017; All Rights Reserved. B-8 ATTACHMENT 16 ---PAGE BREAK--- WWHM2012 PROJECT REPORT Project Name: BCA WILLOWS Site Name: Site Address: City : REDMOND Report Date: 4/7/2015 Gage : Seatac Data Start : 1948/10/01 Data End : 2009/09/30 Precip Scale: 1.00 Version : 2014/07/16 Low Flow Threshold for POC 1 : 50 Percent of the 2 Year High Flow Threshold for POC 1: 50 year PREDEVELOPED LAND USE Name : PROJECT B Bypass: No GroundWater: No Pervious Land Use Acres C, Forest, Mod .16 C, Forest, Steep .253 Pervious Total 0.413 Impervious Land Use Acres Impervious Total 0 Basin Total 0.413 Element Flows To: Surface Interflow Groundwater MITIGATED LAND USE Name : PROJECT B Bypass: No B-9 ATTACHMENT 16 ---PAGE BREAK--- GroundWater: No Pervious Land Use Acres C, Lawn, Steep .113 Pervious Total 0.113 Impervious Land Use Acres ROOF TOPS FLAT 0.25 SIDEWALKS FLAT 0.05 Impervious Total 0.3 Basin Total 0.413 Element Flows To: Surface Interflow Groundwater Vault 1 Vault 1 Name : Vault 1 Width : 10 ft. Length : 60 ft. Depth: 11 ft. Discharge Structure Riser Height: 10 ft. Riser Diameter: 12 in. Orifice 1 Diameter: 0.3125 in. Elevation: 0 ft. Orifice 2 Diameter: 0.5 in. Elevation: 6.6 ft. Orifice 3 Diameter: 0.3125 in. Elevation: 7.5 ft. Element Flows To: Outlet 1 Outlet 2 Vault Hydraulic Table Stage(ft) Area(ac) Volume(ac-ft) Discharge(cfs) Infilt(cfs) 0.0000 0.013 0.000 0.000 0.000 0.1222 0.013 0.001 0.000 0.000 0.2444 0.013 0.003 0.001 0.000 0.3667 0.013 0.005 0.001 0.000 0.4889 0.013 0.006 0.001 0.000 0.6111 0.013 0.008 0.002 0.000 0.7333 0.013 0.010 0.002 0.000 0.8556 0.013 0.011 0.002 0.000 0.9778 0.013 0.013 0.002 0.000 1.1000 0.013 0.015 0.002 0.000 1.2222 0.013 0.016 0.002 0.000 1.3444 0.013 0.018 0.003 0.000 1.4667 0.013 0.020 0.003 0.000 B-10 ATTACHMENT 16 ---PAGE BREAK--- 1.5889 0.013 0.021 0.003 0.000 1.7111 0.013 0.023 0.003 0.000 1.8333 0.013 0.025 0.003 0.000 1.9556 0.013 0.026 0.003 0.000 2.0778 0.013 0.028 0.003 0.000 2.2000 0.013 0.030 0.003 0.000 2.3222 0.013 0.032 0.003 0.000 2.4444 0.013 0.033 0.004 0.000 2.5667 0.013 0.035 0.004 0.000 2.6889 0.013 0.037 0.004 0.000 2.8111 0.013 0.038 0.004 0.000 2.9333 0.013 0.040 0.004 0.000 3.0556 0.013 0.042 0.004 0.000 3.1778 0.013 0.043 0.004 0.000 3.3000 0.013 0.045 0.004 0.000 3.4222 0.013 0.047 0.004 0.000 3.5444 0.013 0.048 0.004 0.000 3.6667 0.013 0.050 0.004 0.000 3.7889 0.013 0.052 0.005 0.000 3.9111 0.013 0.053 0.005 0.000 4.0333 0.013 0.055 0.005 0.000 4.1556 0.013 0.057 0.005 0.000 4.2778 0.013 0.058 0.005 0.000 4.4000 0.013 0.060 0.005 0.000 4.5222 0.013 0.062 0.005 0.000 4.6444 0.013 0.064 0.005 0.000 4.7667 0.013 0.065 0.005 0.000 4.8889 0.013 0.067 0.005 0.000 5.0111 0.013 0.069 0.005 0.000 5.1333 0.013 0.070 0.005 0.000 5.2556 0.013 0.072 0.005 0.000 5.3778 0.013 0.074 0.005 0.000 5.5000 0.013 0.075 0.006 0.000 5.6222 0.013 0.077 0.006 0.000 5.7444 0.013 0.079 0.006 0.000 5.8667 0.013 0.080 0.006 0.000 5.9889 0.013 0.082 0.006 0.000 6.1111 0.013 0.084 0.006 0.000 6.2333 0.013 0.085 0.006 0.000 6.3556 0.013 0.087 0.006 0.000 6.4778 0.013 0.089 0.006 0.000 6.6000 0.013 0.090 0.006 0.000 6.7222 0.013 0.092 0.008 0.000 6.8444 0.013 0.094 0.010 0.000 6.9667 0.013 0.096 0.010 0.000 7.0889 0.013 0.097 0.011 0.000 7.2111 0.013 0.099 0.012 0.000 7.3333 0.013 0.101 0.012 0.000 7.4556 0.013 0.102 0.013 0.000 7.5778 0.013 0.104 0.014 0.000 7.7000 0.013 0.106 0.015 0.000 7.8222 0.013 0.107 0.015 0.000 7.9444 0.013 0.109 0.016 0.000 8.0667 0.013 0.111 0.017 0.000 8.1889 0.013 0.112 0.017 0.000 8.3111 0.013 0.114 0.018 0.000 8.4333 0.013 0.116 0.018 0.000 B-11 ATTACHMENT 16 ---PAGE BREAK--- 8.5556 0.013 0.117 0.019 0.000 8.6778 0.013 0.119 0.019 0.000 8.8000 0.013 0.121 0.020 0.000 8.9222 0.013 0.122 0.020 0.000 9.0444 0.013 0.124 0.021 0.000 9.1667 0.013 0.126 0.021 0.000 9.2889 0.013 0.127 0.022 0.000 9.4111 0.013 0.129 0.022 0.000 9.5333 0.013 0.131 0.022 0.000 9.6556 0.013 0.133 0.023 0.000 9.7778 0.013 0.134 0.023 0.000 9.9000 0.013 0.136 0.024 0.000 10.022 0.013 0.138 0.056 0.000 10.144 0.013 0.139 0.559 0.000 10.267 0.013 0.141 1.366 0.000 10.389 0.013 0.143 2.387 0.000 10.511 0.013 0.144 3.584 0.000 10.633 0.013 0.146 4.934 0.000 10.756 0.013 0.148 6.422 0.000 10.878 0.013 0.149 8.036 0.000 11.000 0.013 0.151 9.766 0.000 11.122 0.013 0.153 11.60 0.000 11.244 0.000 0.000 13.54 0.000 B-12 ATTACHMENT 16 ---PAGE BREAK--- ANALYSIS RESULTS Stream Protection Duration Predeveloped Landuse Totals for POC #1 Total Pervious Area:0.413 Total Impervious Area:0 Mitigated Landuse Totals for POC #1 Total Pervious Area:0.113 Total Impervious Area:0.3 Flow Frequency Return Periods for Predeveloped. POC #1 Return Period Flow(cfs) 6 month 0.010446 2 year 0.014508 5 year 0.02311 10 year 0.028031 25 year 0.033274 50 year 0.036531 100 year 0.039308 Flow Frequency Return Periods for Mitigated. POC #1 Return Period Flow(cfs) 6 month 0.005815 2 year 0.008077 5 year 0.014244 10 year 0.020012 25 year 0.029761 50 year 0.039205 100 year 0.050901 Stream Protection Duration Annual Peaks for Predeveloped and Mitigated. POC #1 Year Predeveloped Mitigated 1949 0.016 0.005 1950 0.028 0.007 1951 0.032 0.023 1952 0.011 0.005 1953 0.008 0.006 1954 0.011 0.006 1955 0.022 0.006 1956 0.018 0.014 1957 0.015 0.006 1958 0.015 0.006 1959 0.012 0.005 1960 0.021 0.020 1961 0.012 0.010 1962 0.008 0.005 1963 0.010 0.006 B-13 ATTACHMENT 16 ---PAGE BREAK--- 1964 0.011 0.007 1965 0.009 0.012 1966 0.009 0.006 1967 0.021 0.007 1968 0.012 0.006 1969 0.013 0.006 1970 0.011 0.006 1971 0.009 0.006 1972 0.024 0.019 1973 0.012 0.011 1974 0.011 0.006 1975 0.019 0.006 1976 0.011 0.006 1977 0.001 0.005 1978 0.011 0.006 1979 0.006 0.005 1980 0.016 0.019 1981 0.009 0.006 1982 0.019 0.017 1983 0.015 0.006 1984 0.010 0.005 1985 0.006 0.005 1986 0.027 0.010 1987 0.023 0.019 1988 0.009 0.005 1989 0.005 0.005 1990 0.035 0.020 1991 0.029 0.019 1992 0.011 0.007 1993 0.012 0.005 1994 0.003 0.004 1995 0.015 0.010 1996 0.029 0.022 1997 0.029 0.021 1998 0.006 0.005 1999 0.019 0.019 2000 0.012 0.007 2001 0.002 0.004 2002 0.015 0.012 2003 0.010 0.006 2004 0.026 0.023 2005 0.016 0.006 2006 0.018 0.013 2007 0.044 0.098 2008 0.041 0.022 2009 0.022 0.013 Stream Protection Duration Ranked Annual Peaks for Predeveloped and Mitigated. POC #1 Rank Predeveloped Mitigated 1 0.0438 0.0978 2 0.0411 0.0234 3 0.0355 0.0232 4 0.0316 0.0224 5 0.0294 0.0222 6 0.0293 0.0207 B-14 ATTACHMENT 16 ---PAGE BREAK--- 7 0.0292 0.0203 8 0.0277 0.0199 9 0.0267 0.0193 10 0.0260 0.0192 11 0.0240 0.0191 12 0.0226 0.0189 13 0.0220 0.0186 14 0.0216 0.0170 15 0.0211 0.0143 16 0.0210 0.0130 17 0.0191 0.0129 18 0.0189 0.0122 19 0.0187 0.0120 20 0.0185 0.0114 21 0.0176 0.0103 22 0.0163 0.0100 23 0.0163 0.0100 24 0.0158 0.0066 25 0.0151 0.0065 26 0.0150 0.0065 27 0.0150 0.0065 28 0.0147 0.0065 29 0.0145 0.0065 30 0.0128 0.0064 31 0.0123 0.0063 32 0.0123 0.0062 33 0.0119 0.0062 34 0.0118 0.0062 35 0.0117 0.0062 36 0.0115 0.0061 37 0.0115 0.0061 38 0.0114 0.0060 39 0.0114 0.0060 40 0.0112 0.0059 41 0.0111 0.0059 42 0.0110 0.0059 43 0.0109 0.0059 44 0.0107 0.0058 45 0.0103 0.0058 46 0.0101 0.0058 47 0.0100 0.0057 48 0.0093 0.0055 49 0.0092 0.0055 50 0.0091 0.0054 51 0.0089 0.0053 52 0.0087 0.0052 53 0.0080 0.0051 54 0.0076 0.0051 55 0.0059 0.0050 56 0.0056 0.0050 57 0.0056 0.0049 58 0.0051 0.0049 59 0.0029 0.0046 60 0.0018 0.0045 61 0.0014 0.0042 B-15 ATTACHMENT 16 ---PAGE BREAK--- Stream Protection Duration POC #1 The Facility PASSED The Facility PASSED. Flow(cfs) Predev Mit Percentage Pass/Fail 0.0073 3193 1533 48 Pass 0.0075 2949 1497 50 Pass 0.0078 2708 1456 53 Pass 0.0081 2508 1426 56 Pass 0.0084 2338 1404 60 Pass 0.0087 2171 1368 63 Pass 0.0090 2015 1339 66 Pass 0.0093 1882 1289 68 Pass 0.0096 1767 1225 69 Pass 0.0099 1662 1155 69 Pass 0.0102 1541 1090 70 Pass 0.0105 1432 1030 71 Pass 0.0108 1341 972 72 Pass 0.0111 1258 923 73 Pass 0.0114 1171 870 74 Pass 0.0117 1100 828 75 Pass 0.0120 1046 765 73 Pass 0.0123 988 715 72 Pass 0.0126 935 676 72 Pass 0.0129 884 621 70 Pass 0.0132 830 583 70 Pass 0.0135 787 564 71 Pass 0.0138 743 546 73 Pass 0.0141 707 529 74 Pass 0.0144 665 507 76 Pass 0.0146 629 494 78 Pass 0.0149 595 469 78 Pass 0.0152 566 454 80 Pass 0.0155 525 439 83 Pass 0.0158 497 421 84 Pass 0.0161 462 407 88 Pass 0.0164 426 381 89 Pass 0.0167 400 362 90 Pass 0.0170 379 336 88 Pass 0.0173 361 313 86 Pass 0.0176 336 289 86 Pass 0.0179 318 272 85 Pass 0.0182 298 248 83 Pass 0.0185 284 226 79 Pass 0.0188 269 204 75 Pass 0.0191 256 175 68 Pass 0.0194 244 153 62 Pass 0.0197 231 136 58 Pass 0.0200 223 120 53 Pass 0.0203 216 109 50 Pass 0.0206 203 99 48 Pass 0.0209 192 92 47 Pass 0.0212 182 85 46 Pass 0.0214 175 73 41 Pass 0.0217 167 65 38 Pass B-16 ATTACHMENT 16 ---PAGE BREAK--- 0.0220 158 55 34 Pass 0.0223 153 43 28 Pass 0.0226 147 34 23 Pass 0.0229 143 27 18 Pass 0.0232 135 17 12 Pass 0.0235 125 12 9 Pass 0.0238 119 10 8 Pass 0.0241 109 6 5 Pass 0.0244 103 6 5 Pass 0.0247 97 6 6 Pass 0.0250 88 6 6 Pass 0.0253 84 6 7 Pass 0.0256 78 6 7 Pass 0.0259 75 6 8 Pass 0.0262 67 6 8 Pass 0.0265 63 6 9 Pass 0.0268 54 6 11 Pass 0.0271 48 6 12 Pass 0.0274 46 6 13 Pass 0.0277 44 5 11 Pass 0.0280 38 5 13 Pass 0.0283 35 5 14 Pass 0.0285 32 5 15 Pass 0.0288 31 5 16 Pass 0.0291 28 5 17 Pass 0.0294 24 5 20 Pass 0.0297 21 5 23 Pass 0.0300 21 5 23 Pass 0.0303 19 5 26 Pass 0.0306 17 5 29 Pass 0.0309 16 5 31 Pass 0.0312 13 5 38 Pass 0.0315 13 5 38 Pass 0.0318 12 5 41 Pass 0.0321 12 5 41 Pass 0.0324 11 5 45 Pass 0.0327 11 5 45 Pass 0.0330 10 5 50 Pass 0.0333 10 5 50 Pass 0.0336 9 5 55 Pass 0.0339 8 5 62 Pass 0.0342 8 5 62 Pass 0.0345 7 5 71 Pass 0.0348 7 5 71 Pass 0.0351 6 5 83 Pass 0.0353 6 5 83 Pass 0.0356 5 4 80 Pass 0.0359 5 4 80 Pass 0.0362 4 4 100 Pass 0.0365 4 4 100 Pass B-17 ATTACHMENT 16 ---PAGE BREAK--- Water Quality BMP Flow and Volume for POC #1 On-line facility volume: 0.0428 acre-feet On-line facility target flow: 0.0451 cfs. Adjusted for 15 min: 0.0494 cfs. Off-line facility target flow: 0.0257 cfs. Adjusted for 15 min: 0.0281 cfs. Perlnd and Changes No changes have been made. 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. 2005-2013; All Rights Reserved. B-18 ATTACHMENT 16 ---PAGE BREAK--- Willows Prep School APPENDIX C ATTACHMENT 16 ---PAGE BREAK--- ATTACHMENT 16 ---PAGE BREAK--- ATTACHMENT 16 ---PAGE BREAK--- ATTACHMENT 16 ---PAGE BREAK--- ATTACHMENT 16 ---PAGE BREAK--- ATTACHMENT 16 ---PAGE BREAK--- ATTACHMENT 16 ---PAGE BREAK--- ATTACHMENT 16 ---PAGE BREAK--- ATTACHMENT 16 ---PAGE BREAK--- ATTACHMENT 16 ---PAGE BREAK--- ATTACHMENT 16 ---PAGE BREAK--- ATTACHMENT 16 ---PAGE BREAK--- ATTACHMENT 16 ---PAGE BREAK--- ATTACHMENT 16 ---PAGE BREAK--- ATTACHMENT 16 ---PAGE BREAK--- ATTACHMENT 16 ---PAGE BREAK--- ATTACHMENT 16 ---PAGE BREAK--- ATTACHMENT 16 ---PAGE BREAK--- ATTACHMENT 16 ---PAGE BREAK--- ATTACHMENT 16 ---PAGE BREAK--- ATTACHMENT 16 ---PAGE BREAK--- ATTACHMENT 16 ---PAGE BREAK--- ATTACHMENT 16 ---PAGE BREAK--- ATTACHMENT 16 ---PAGE BREAK--- ATTACHMENT 16 ---PAGE BREAK--- ATTACHMENT 16 ---PAGE BREAK--- ATTACHMENT 16 ---PAGE BREAK--- ATTACHMENT 16 ---PAGE BREAK--- ATTACHMENT 16 ---PAGE BREAK--- ATTACHMENT 16 ---PAGE BREAK--- ATTACHMENT 16 ---PAGE BREAK--- ATTACHMENT 16 ---PAGE BREAK--- ATTACHMENT 16 ---PAGE BREAK--- ATTACHMENT 16 ---PAGE BREAK--- ATTACHMENT 16 ---PAGE BREAK--- ATTACHMENT 16 ---PAGE BREAK--- ATTACHMENT 16 ---PAGE BREAK--- ATTACHMENT 16 ---PAGE BREAK--- ATTACHMENT 16 ---PAGE BREAK--- ATTACHMENT 16 ---PAGE BREAK--- ATTACHMENT 16 ---PAGE BREAK--- ATTACHMENT 16 ---PAGE BREAK--- ATTACHMENT 16 ---PAGE BREAK--- ATTACHMENT 16 ---PAGE BREAK--- ATTACHMENT 16 ---PAGE BREAK--- ATTACHMENT 16 ---PAGE BREAK--- ATTACHMENT 16 ---PAGE BREAK--- ATTACHMENT 16 ---PAGE BREAK--- ATTACHMENT 16 ---PAGE BREAK--- ATTACHMENT 16 ---PAGE BREAK--- ATTACHMENT 16 ---PAGE BREAK--- ATTACHMENT 16 ---PAGE BREAK--- ATTACHMENT 16 ---PAGE BREAK--- ATTACHMENT 16 ---PAGE BREAK--- ATTACHMENT 16 ---PAGE BREAK--- ATTACHMENT 16 ---PAGE BREAK--- ATTACHMENT 16 ---PAGE BREAK--- ATTACHMENT 16