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<br />I <br />I <br />I <br />I <br />I <br />I <br />I <br />I <br />I <br />I <br />I <br />I <br />I <br />I <br />I <br />I <br />I <br />I <br />I <br /> <br />outletf crossing structure could provide attenuation of the flood peaks and reduce potential flooding, <br />locally as well as downstream. <br />Coal ridge Ditch \:ulvert At this location, Godding Hollow passes under the Coalridge <br />Ditch. The capacity of the culvert prior to overtopping is 790 cfs. The 100-year existing condition <br />discharge in Godding Hollow at the Coalridge Canal is 3,670 cfs. Flows will overtop the canal <br />in the vicinitY of the culvert crossing, creating a large detention area between State Highway 52 <br />and the ditch. Additional detention at this location along with an improved outlet structure could <br />provide attenuation of the flood peaks and reduce potential flooding locally as well as downstream. <br />WCR 12 Culvert. The capacity of-the culvert prior to overtopping is 60 cfs. The 100-year <br />existing condition discharge in Godding Hollow at County Road 12 is 2,620 cfs. Flows will <br />spread out east and west along the road before overtopping. An improved crossing structure could <br />reduce the localized flooding problems at this location. <br />WCR 10 Culvert. The capacity of the culvert prior to overtopping is 40 cfs. The 100-year <br />existing condition discharge in Godding Hollow at Weld County Road 10 is 540 cfs. Flows will <br />spread out east and west along the road before overtopping. An improved crossing structure could <br />reduce the localized flooding problems at this location. <br />Tributary Crossing of Interstate 25 A major tributary crosses Interstate 25 immediately <br />north of the intersection of Interstate 25 and State Highway 52. The capacity of the culvert prior <br />to overtopping is 90 cfs. The 100-year existing condition discharge at this location is estimated <br />to be 1,230 cfs. Ovenopping will occur over the west frontage road first, and then over both lanes <br />of Interstate 25 before crossing over the east frontage road and joining flows to the east. An <br />improved' crossing structure could reduce the localized flooding problems at this location. <br />Presently, the Colorado Department of Transportation has plans to replace this crossing and <br />remove the upstream detention area. Reduction in the upstream detention volume may exacerbate <br />the existing flooding conditions at this location and downstream, The detention volume at this <br />location should remain or be replaced to ensure no additional flooding is created. <br />Within the Godding H9110w Basin, road crossings of several additional tributaries to <br />Godding Hollow also exist. These tributaries convey significant storm flows that may require <br />crossing structures capable of passing the 100-year existing condition discharge. This master <br />planning effort did not inventory or specifically identify these road crossings. It is noted, <br />however, that several of these crossing structures provided inadequate capacity to convey runoff <br />generated during relatively minor storm events and were experiencing sedimentation problems. <br />As land development occurs within the basin, these structures should be more closely inventoried <br />and evaluated. <br /> <br />T:10PEN1CoweidOllcoweldO/lnl rpLwpd <br /> <br />4.17 <br /> <br />September 8, /999 <br />