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I I I I I I I I I I I I I I I I I I I and Little Dry Creek was found to be approximately 600 cfs. The portion of the Highline Canal which crosses the study area was assumed to have a similar capacity. 4. McLellan Reservoir: The reservoir is owned and operated by Englewood as a water supply facility and is located in the Dad Clark Gulch basin just north of County Line Road. Currently, it is not used as a flood control facility. The study area drains to the west toward the South Platte River. Each of the three major drainage basins (Rangeview, Jackass, and Lower Dad Clark) are served by existing drainage systems. The six direct flow areas do not have a significant drainage system. Records of previous flooding in the area are non- existent. 2.3 The Ranaeview Gulch basin is approximately 430 acres in size and is almost entirely residential. The drainage system in the upper basin (east of the railroad lines) is mostly open channel with several irrigation ponds. An existing 30" RCP storm sewer system is located in Curtice Street in the residential area between Ridgeview Park and Turtle Lake (also known as Lynhardt Reservoir No.2). However, during a major storm event, most flows will occupy the street. At Turtle Lake, low flows are intercepted by the City Ditch before they reach the lake. Flows discharged from Turtle Lake historically went directly to the South Platte River. However, due to the construction of the AT&SF Railroad embankment, these flows now go north along the east side Df the railroad and discharge into Lee Gulch. Neither Ridgeview Park nor Turtle Lake were considered to detain flood waters because they are currently not recognized as public detention facilities. The Jackass Gulch basin is just south of Rangeview Gulch and is approximately SOO acres in size. It is an elongated basin extending from South Broadway to the South Platte River and is zoned almost entirely as Planned Development (PO, PD-R, PD-C & RD-I). The upper basin (east of the Highline Canal) is mostly commercial with some residential. All of the existing developments in the upper basin have been designed to detain storm runoff for the 100-year event with private onsite detention facilities. The area between the Highline Canal and the railroad lines is zoned residential. The storm drainage system in the area consists of a natural channel with a municipal detention facility at the railroad lines. The lower basin (west of Santa Fe Drive) is a commercial area and has a 60" RCP storm outfall system which discharges into an open channel which in turn outfalls to the South Platte River. Currently, over half of the Jackass Gulch basin is undeveloped. None of the upper basin detention facilities were recognized since they are all private facilities. The municipal detention pond at the railroad tracks was considered in the floodplain analysis. The Lower Dad Clark Gulch basin extends from the outfall of McLellan Reservoir to the South Platte River. The basin is approximately 290 acres in size and contains residential, commercial and industrial areas. Most of the basin is undeveloped at the present time. A portion of the South Park residential area is included in this basin. The drainage system is an open channel with bridge structures at the railroad and Santa Fe Drive crossings. The existing detention c::.- ponds in the South Park residential area were not considered in the analysis because they are private facilities. Sub-basin Delineation The direct flow areas and the sub-basins of each of the three major basins were delineated by differences in land use, major drainage features, and topography. The size of each basin was limited to a maximum of 130 acres with an average sub-basin size no larger than 100 acres. 3