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I I I Urban Drainage and Flood Control District . Bridges and Culverts Photos . Bridges and Culverts Survey Data . Monument Records . Aerial Photos . Contour Maps I I I I I I Douglas County . Land Ownership Maps . Pertinent Drainage Studies . Land Use Maps . Flood Insurance Study Chatfield Basin Conservation Network . Conservation Network Concept Plan Colorado Department of Transportation . Douglas County "2015 Transportation Plan" Denver Water Board I I . Water Main Maps along Plum Creek Alignment E_ ANALYSIS AND DESIGN CRITERIA I I The Outfall Systems Planning and Flood Hazard Area Delineation was performed per the terms of the contract and the guidelines and criteria set forth in the Urban Storm Drainage Criteria Manual (USDCM) (Reference-12). Also utilized was the Douglas County Storm Drainage Design and Technical Criteria (DCSDD&TC, Reference-3). I I Subsequent to the initial data gathering and field reconnaissance work to establish watershed boundaries and existing storm drainage features, the study area was divided into separate sub-watersheds within the major watershed. The physical parameters (i.e_, area, length, slope, and percent imperviousness) of each sub.watershed were then defined and the design storm hydrographs developed for the various recurrence intervals using the Colorado Urban Hydrograph Procedure (CUHP, Reference-2). The design rainfall information was obtained from the DCSDD&TC (Reference-3) and the 1 hour NOAA rainfall depths (Reference-4). I I I I The combining of the hydrographs, channel routing, and routing of the flood hydrographs were performed using the Storm Water Management Model (SWMM, Reference-5). The resulting hydrology was used to define the water surface profiles for the 10.,50-, 100-, and 500-year recurrence interval storms by utilizing the United States Army Corps of Engineer's water surface profile computer program HECRAS (References 6-9)_ F_ PROJECT ADVISORY COMMITTEE This study is sponsored by the UD&FCD and Douglas County. In addition to WRC and it's sub-consultants, the Project Advisol)' Comminee for this project included the following sponsors, agencies, companies, and individuals: ORGANIZATION UD&FCD Douglas County Colorado Department of Transportation Chatfield Basin Network PERSON Mr. Ben Urbonas, P.E_ Mr. Bill DeGroot, P.E. Mr. John Doerfer Mr_ Brad Robenstein Mr. Jim Dederick Mr. Toby Sprunk Mr. Amanullah Mommandi Mr. Paul Hellmund Also invited to participate in the progress meetings for this project were the following entities: Highlands Ranch Metropolitan District Colorado Division of Wildlife U 5. Army Corps of Engineers U.S_ Environmental Protection Agency Colorado Water Quality Control Division Colorado Water Conservation Board Federal Emergency Management Agency Colorado Division of Water Resources Town of Castle Rock Denver Water Board Denver Regional Council of Governments Chatfield Basin Water Quality Authority Colorado Division of Parks and Outdoor Recreation U.S. Fish and Wildlife Service Castle Pines Metropolitan District 1.3