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Bear Canyon Creek can spill to the Anderson Basin (and Ditch) at Table Mesa and <br /> Broadway (Highway 93) <br /> Downstream of Highway 36 on the west side of the basin there are three subbasins <br /> which are drained by storm sewers to Bear Canyon Creek, but which may <br /> contribute to the South Boulder Creek basin because of street drainage patterns and <br /> the Wellman Ditch. The Wellman Ditch can also bring in significant runoff from <br /> other watersheds, particularly Bear Canyon Creek. <br /> KEY FEATURES AFFECTING LOCAL DRAINAGE AND SOUTH BOULDER CREEK <br /> OVERFLOWS - HIGHWAY 36 TO THE WELLMAN DITCH <br /> Flow arriving at the area of Highway 36 Bridge over the main channel of South <br /> Boulder Creek can potentially spill to the northwest, as documented during Phase I. <br /> There are three major and several minor routes which the flow can take before <br /> joining South Boulder Creek: <br /> 1 . Main Channel. The main channel route conveys flow in a largely <br /> riparian cottonwood grove floodplain which has a mixture of open <br /> space, agriculture, residential, and commercial uses. Significant spills <br /> to the West Valley can occur upstream of Highways 93 and 36. As <br /> the main channel passes by the Wellman Ditch additional spills to the <br /> West Valley occur through a residential area and the golf course. <br /> Below Arapahoe, a water diversion to the Valmont reservoirs (Hillcrest, <br /> Valmont, Leggett) can also carry flood flows, as indicated in previous <br /> floodplain studies. Also, there is another potential spill to the west to <br /> Dry Creek Ditch No. 2 near the railroad tracks. <br /> 2. Direct return to South Boulder Creek: Dry Creek No. 2. Viele. and the <br /> Anderson Ditch. The South Boulder Creek spillage upstream of <br /> Highway 36 that flows to the northwest would be joined by flows <br /> from Dry Creek Ditch No. 2. <br /> There are three modest conveyance systems which will carry an initial <br /> portion of the flow across Highway 36 and, for the most part, back to <br /> South Boulder Creek just below South Boulder Road. The first 220 cfs <br /> would be conveyed in the Dry Creek No. 2 box culvert across Highway <br /> 36, and via an irrigation ditch to a spill structure near South Boulder <br /> Road which would shed most of the flow to the lower Anderson Ditch, <br /> which subsequently could spill to Viele. Greater spillage flow from <br /> South Boulder Creek, on the order of 500 to 800 cfs, will be <br /> intercepted by the Viele drainage system adjacent to the Foothills <br /> Parkway Interchange and conveyed under Highway 36, and then <br /> combine with the spillage from the lower Anderson Ditch and the Dry <br /> II - 3 <br />