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<br />. <br /> <br />6. Prepare preliminary design drawings and construction cost estimates for the <br />recommended plan. <br /> <br />7. Prepare a reconnaissance-level feasibility report that documents the results of the <br />study and provides a narrative of the recommended plan. <br /> <br />m. STUDY AREA DESCRIPTION <br /> <br />Location and Site Characteristics <br />The Town of Creede is the County Seat and population center of Mineral County, <br />Colorado and lies within the upper Rio Grande drainage basin. The town is <br />approximately 70 miles northwest of Alamosa, and lies about 1.5 miles north of the Rio <br />Grande mainstem. Willow Creek, a left bank tributary to the Rio Grande, runs through <br />the town from north to south. The elevation of Creede is approximately 8,900 feet (msl). <br />The area in the vicinity of Creede has been mined for gold and silver for over 100 years, <br />and thus Creede was established in the late 1800's as a mining town. <br /> <br />. <br /> <br />In the late 1940' s the Corps of Engineers built an engineered channel through the town to <br />provide flood control for Willow Creek. The channel has a trapezoidal cross-section and <br />consists of grouted riprap for a length of approximately one mile. The channel has a <br />capacity of about 1800 cfs, which is above the published 100-yr discharge. <br /> <br />Site Specific Drainage Problems <br />A portion of West Willow Creek in the vicinity of the abandoned Commodore mine, <br />upstream of the town, is filled in with mine tailings. A steel pipe (approximately 6 feet in <br />diameter) passes through the tailings pile to convey flows in West Willow Creek. The <br />age of the pipe is unknown, however it has heavy gage walls and appears to be in good <br />condition. There is no trash rack on the upstream end of the pipe. <br /> <br />Upstream from the tailings pile on West Willow Creek there is a short section of open <br />channel which forms a "bowl" that has steep side slopes. The side slopes, which are <br />formed by mine tailings and wooden cribbing, appear to be unstable. The cribbing is <br />damaged and is in poor repair. During high flow events, debris collects at the inlet to the <br />steel pipe. During high flows that exceed the capacity of the steel pipe, water will pond <br />up behind the embankment (tailings pile). This area is of particular concern for the town <br />as there is a fear that the tailings pile embankment could fail during a high flow event. <br />Failure of the embankment would send water, rocks, sediment, and debris rushing down <br />the valley toward the town. Fortunately, there is a significant length of channel <br />(approximately 1.2 miles) between the waste pile and the town, which could help to <br />attenuate floodwater and debris flows. <br /> <br />. <br /> <br />Upstream from the waste pile/steel pipe and open channel there is a wooden flume that <br />conveys flows through the mining area. The upstream end of the flume has a trash rack <br /> <br />2 <br />