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Willow Creek Reclamation Committee <br />Windy Gulch Project Final Report <br />PROJECT DESIGN <br />hi the original project proposal for the Windy Gulch culvert, it was suggested that a Eft by aft <br />box culvert be used to pass small flows, while larger flows would be passed over the road using a <br />pan and two raised "ridges" formed by raising the roadway. The smaller culvert was proposed <br />due to concerns about bedrock and utilities under the culvert. <br />However, after discussion of the project with the Creede City Council and Mineral County <br />Commissioners, it was determined that the raising of the roadway would be too awkward for <br />vehicular traffic. Therefore, it was decided to use a larger culvert to pass the entire 100-year <br />flood rate under the roadway. <br />Upstream of the culvert, the channel had ingrown significantly with willow. Considering <br />clearing and widened of the area above the culvert, modeling indicated that a culvert with a 10- <br />foot span and 3-foot rise could pass a 50-year flood. Modeling indicated that a 100-year flood <br />level would rise above the ceiling level of the culvert, but would be contained by headwalls and <br />wingwalls extending one foot above the roadway level. Although containment of the 100-year <br />flood by the headwalls is somewhat unconventional, it was felt that a larger culvert could not be <br />installed easily as there is considerable concern that solid bedrock was present to the side of the <br />culvert and a potential water or sewer line may be located below the current culvert. The <br />following figure shows a Hec-Ras model of flood levels through the 10-foot by 3-foot culvert. <br />Modeling also indicated that the upstream chamlel should just be able to contain a 100-year <br />flood. However, debris flow during a tn~e 100-year flood would be expected and could <br />significantly impact channel and culvert capacities. <br />8887 <br />8886 <br />.-. 8885 <br />0 8884 <br />> 8883 <br />a~ <br />W <br />8882 <br />8881 <br />8880 <br />Station (ft) <br />Legend <br />WS 100yr <br />WS 50yr <br />~- <br />WS 25yr <br />~~ <br />WS 10yr <br />WS Syr <br />WS 2yr <br />^ <br />Ground <br />Levee <br />Bank Sta <br />Water surface elevations at upstream entrance of Windy Gulch box culvert <br />Designs for the culverts were finalized in May 2005, and the pre-cast concrete culverts were <br />ordered by late June 2005. <br />0 10 20 30 40 50 <br />