FLOOD10417

• County: Mineral
• Community: Mineral County
• Stream Name: Willow Creek
• Title: Willow Creek Channel Improvement, Mineral County, Colorado - Channel Replacement Feasibility Report
• Date: 8/13/2003
• Prepared For: Willow Creek Reclaimation Committee
• Prepared By: Chou Cha, P.E., Civil Engineer
• Floodplain - Doc Type: Flood Mitigation/Flood Warning/Watershed Restoration

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CONCLUSION

This report is summarized in the following.

D Existing Channel
./ Deteriorating
./ Not capable of passing design flood
D Replacement Option
./ Demolition of existing channel
./ Maintain existing channel alignment
./ New construction
./ Design discharge of 1,800 cfs
D Design Alternatives
./ Alternative 1, Existing trapezoidal channel shape
./ Alternative 2, Rectangular channel shape
./ Alternative 3, Partially full flowing precast concrete pipe
./ Alternative 4, Partially full flowing precast box culvert
D Appurtenance Structures
./ Vehicle guardrails
./ Pedestrian bridges for Alternatives 1 and 2 only
./ Safety cables for Alternatives 1 and2 only
./ Stilling basin
D Design and Construction Elements
./ Design data needs by NRCS NPET
./ Design data costs to WCRC
./ Construction drawings and specifications provided by NRCS NPET
./ Construction permits by NRCS and WCRC
./ Construction inspection to be provided by WCRC
./ Construction window

Through a decision matrix, see Table 5, NRCS NPET ranks Alternative 2 slightly ahead
of Alternative 1, and then Alternative 3 and 4 in order of perceived benefit to cost.
Therefore the recommended design alternative is Alternative 2, Rectangular Channel,
with a total field cost estimated at $3,527,600 which includes all appurtenances.

NRCS Northern Plains Engineering Team VI