FLOOD00385 - Laserfiche WebLink

Home Browse Search

I I I I I I I I I I I I I I I I I I I discharge to the north of the freeway on the west side of Foothills Parkway and travel north, along the west side of Foothills Parkway. At the intersections of Foothills and Baseline (Drawings 7 and 9) flow is first retarded by two small storage ponds (356 and 398, Drawing 9). Flows such as the 1 OO-year flood can follow anyone of seven routes. Three potentially leave the watershed along Foothills Parkway to the northwest, two flow east on the lanes of Baseline and split again to the north through the Country Club Park neighborhood, and the last two either by the culverts under Foothills or over the roadway to the east storage. The east storage first discharges by a box culvert (308) which has been partially obstructed by an earth dike to form a 'poor man's' hydraulic control. This culvert under Baseline directs flow to the Crossover Ditch, on the north side of Baseline, which then carries flow easterly to Dry Creek Ditch No.2 near 55th. However the east storage spills (396) at moderate flows to Baseline, which then can contribute to and join spillage from the Crossover Ditch, and add to the spillage through the Country Club Park subdivision. Reference documents refer to drainage problems in these areas. These spillages eventually go to the Wellman Ditch adding to runoff already being carried from Bear Creek and probably from the three South Boulder Creek spillages following Foothills. Much of the Crossover Ditch is a levee situation of questionable stability. We have assumed the Crossover Ditch could carry flow to culvert full-flow capacity based on approximate hydraulics. If the Crossover Ditch breached, most of the flow could go north increasing the flow through the subdivision, and then to the Wellman. Regardless of Crossover Ditch breaching, the flow in the Wellman would be about the same. The Crossover Ditch joins with Dry Creek Ditch No.2 flow crossing Baseline, then the combined ditch flows northeast and then north along the west side of 55'h as Dry Creek Ditch No.2 in a boulder, wall-lined channel. At 55'h and the Wellman Ditch (Drawing 11), Dry Creek Ditch No.2 and the Crossover Ditch flows join the Wellman Ditch except for minor flows conveyed in the Dry Creek Ditch No.2 undercrossing pipe (1401). The Wellman Ditch crosses Bear Canyon Creek in a combined diversion and spill structure that can potentially bring transbasin flood waters into the South Boulder Creek watershed. However, we have assumed this is not the case, per sponsors' direction, standard practice, and the knowledge that significant flood waters would be entering the Wellman from South Boulder Creek overflows to the West Valley. Drawing 11 reflects some of the key 11-7