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<br />I <br />I <br />I <br />I <br />I <br />I <br />I <br />I <br />I <br />II <br />I <br />I <br />I <br />I <br />I <br />I <br />I <br />1 <br />I <br /> <br />. <br /> <br />South Boulder Creek at Highway 36. During a 100 year event approximately <br />2700 cfs out of 5980 cfs would leave the main channel and flow to the <br />northwest. In larger storms proportionally more flow would be diverted. <br />Along Highway 36 several culverts convey water to the north. The most <br />significant of these are the Dry Creek Ditch No.2, the Viele Channel, and the <br />Anderson Ditch. Collectively they may carry about 850 to 1200 cfs back to <br />South Boulder Creek below South Boulder Road. <br />Approximately 1800 cfs of the water spilled from South Boulder Creek would <br />flood over Highway 36 west of Foothills Parkway and then travel north <br />through the residential area west of Foothills. <br />At the intersection of Foothills Parkway and Baseline Road the flow would <br />split seven ways. About 600 cfs out of 1800 cfs would go down both lanes <br />of Foothills Parkway and leave the watershed, Another 260 cfs would flow <br />on the west side of the Parkway and probably discharge to Wellman Ditch. <br />570 cfs would follow two paths along the roadway of Baseline Road east, <br />while another 380 cfs would flow over and under Baseline Road between the <br />two storage ponds, The east pond would discharge some water to the <br />culvert under Baseline to the Crossover Ditch and overflow to Baseline Road, <br />The net effect of all these overflows is estimated to discharge 380 cfs north <br />to Brooklawn Drive, 270 cfs north to Crescent Drive, and 430 cfs east in the <br />Crossover Ditch which would join Dry Creek No.2, with a resultant flow <br />north of 570 cfs. These flows would also be the result of small splits of <br />South Boulder Creek spills from the Anderson Ditch (130 cfs) and remaining <br />flow in Dry Creek Ditch No, 2 (40 cfs) that did not spill from Dry Creek near <br />the Viele channel, and local drainage south of Baseline. <br />The flow in Dry Creek Ditch No.2 would probably flood into and along 55th, <br />and then split three ways, with a minor flow going under the Wellman to Dry <br />Creek Ditch No.2 on the golf course and surface flows spilling 500 cfs to <br />the Wellman west of 55th and 80 cfs east. <br />The Wellman Ditch intersects Bear Canyon Creek, where a control structure <br />directs low flows in the ditch to the east and allows flood flows to go <br />downstream. However since there is a large box culvert under Foothills, the <br />Wellman Ditch can convey large flows from Bear Creek to the South Boulder <br />Creek watershed. Since the Foothills roadway appears to convey flows <br />north past the Wellman Ditch, the model assumes only the South Boulder <br />Creek spill in the borrow ditch and the local tributary area runoff west of <br />Foothills would go into the Wellman (210 cfs), In reality we believe the flow <br />in the Wellman Ditch would be higher because of Bear Creek flows. The <br />Wellman is then modeled to collect local drainage and spills from upstream <br />on the east side of Foothills, A potential flow of 800 to 1190 cfs would <br />arrive on the upstream (west) side of 55th plus any Bear Canyon Creek trans <br />basin flows. <br />About 460 cfs out of 1190 cfs in the Wellman Ditch west of 55th would <br />probably overtop the north levee and flow through the Centennial Trails and <br /> <br />. <br /> <br />. <br /> <br />. <br /> <br />. <br /> <br />. <br /> <br />. <br /> <br />1-4 <br />