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<br />Flood Hazard Area Delineation <br />For Lower Box Elder Creek Watershed <br /> <br />Flood Hazard Area Delineation Report. The Colorado Water Conservation Board (CWCB) and Federal <br />Emergency Management Agency (FEMA) provided detailed review of the hydrology calculationsc The <br />following stakeholders were sent meeting minutes from each of the meetings: <br /> <br />Bill McCormick, City of Aurora Public Works Department; <br />Norman Wells, JL, Natural Resources Conservation Service (NRCS); <br />Obe Lowry, Colorado Division of Wildlife (CDOW); <br />Ben Urbonas, UDFCD; <br />Pat Horn, Martin/Martin; <br />Bill DeGroot, UDFCD; <br />Don Smith, DIA; <br />Daren Duncan, Adams County; <br />Janet Kieler, DIA; <br />Forrest Leaf, Central Colorado Water Conservancy District; <br />Bill Killip, Colorado Board of Land Commissioners; <br />Terri Tiehen, Colorado Department of Transportation; <br />Jay Skinner, CDOW; <br />Dave Weber, CDOW; <br />Carolyn Fritz, CWCB; <br />Larry Lang, CWCB; <br />Kathy Dolan, Colorado Department of Public Health and Environment (CDPHE), Water <br />Quality Division; <br />Max Dodson, EP A Region VIII; <br />John Liou, FEMA-Region 8; <br />Lawrence "Butch" Gerkin, Henrylyn Irrigation District; <br />Dave DeBois, North Front Range Water Quality Planning Association; <br />Jim Hall, Colorado Division of Water Resources; <br />Scott Franklin, U$c Army Corps of Engineers (USACE); <br />Duc Phung, USDA-NRCS; <br />LeRoy Carlson, U$. Fish and Wildlife Service (USFW); <br />Bob Jarrett, United States Geological Survey (USGS). <br /> <br />2.0 <br /> <br />STUDY AREA DESCRIPTION <br /> <br />2.1 <br /> <br />Topography <br /> <br />The Box Elder Creek watershed is a long, narrow watershed located east of the Denver metropolitan area. It <br />extends from El Paso County in the south a distance of approximately 100 miles to its confluence with the <br />South Platte River in Weld County downstream of the City of Greeleyc The watershed is three to five miles <br />in width for the majority of its lengthc <br /> <br />The study area for the Lower Box Elder Creek Outfall Systems Planning and Flood Hazard Area <br />Delineation Study includes the main stem of Box Elder Creek between approximately 56th Avenue and 168th <br />Avenue and tributaries Bear Gulch and Hayesmount Creek The study area is shown in Appendix k The <br />study area lies within Adams County, the City and County of Denver (DIA) and the City of Aurorae The <br />study area is approximately 70 square miles in size and includes approximately 15 miles of the main stem of <br />Box Elder Creek. <br /> <br />The portion of the watershed lying upstream of the study area is approximately 200 square miles in size. <br />The hydrology for that area was defined in a previous UDFCD study entitled Upper Box Elder Creek <br />Outfall Systems Planning Study Hydrology Report (CH2M-Hill, 1994). <br /> <br />2.2 Watershed Imperviousness <br /> <br />The watershed is currently mostly undeveloped grassland and agricultural areasc The portion of the <br />watershed that lies within DIA, however, has some areas that are heavily developedc The existing <br />percentage imperviousness is shown in Appendix D. The majority of the basin has one percent <br />imperviousness indicative of agricultural or undeveloped lands. Portions of the study area within the DIA <br />property (including some runways and taxiways, portions of the concourses and support facilities) have high <br />percentage imperviousnessc Additionally, there are scattered relatively low-density housing developments <br />in the northern portion of the study areac Existing percentage imperviousness was determined through <br />inspection of aerial photographs, mapping provided by the City and County of Denver and field inspection. <br /> <br />Page 2 <br /> <br />991-134.000 <br /> <br />Wright Water Engineers, Incc <br />