Overview
Clark Canyon Dam is constructed at the head of the Beaverhead River. The zoned earthfill dam has a structural height of 147.5 feet, a crest length of 2,950 feet, and a volume of 1,970,000 cubic yards of material. The spillway consists of an approach channel, concrete inlet channel, ungated concrete crest, concrete chute, concrete stilling basin, and an outlet channel. The outlet works consists of an approach channel; concrete intake structure; concrete conduit; a gate chamber with high-pressure gates, two of which serve for emergency ahead of the regulating gates; concrete access shaft and shaft house; and a concrete stilling basin. The outlet channel is shared by the outlet works and spillway.
Overview
The Animas-La Plata Project located in La Plata and Montezuma Counties in southwestern Colorado and in San Juan County in northwestern New Mexico, was authorized by the Colorado River Basin Project Act of September 30, 1968 (Public Law 84-485).In 1988, it was incorporated into the Colorado Ute Indian Water Rights Settlement Act. The Colorado Ute Settlement Act Amendments of 2000 provide for implementation and completion of the project. Approval to begin construction was granted in October 2001 and initial site work began in April 2002.
Lake Nighthorse began filling on May 4, 2009, and filled for the first time on June 29, 2011. The maximum water surface elevation of 6,882 feet equates to 123,541 acre-feet in storage. The Colorado project features were transferred from construction status to operation and maintenance status in March 2013. Work on completion of the transfer stipulations is continuing. An operation and maintenance contract has been signed with the Animas-La Plata Operations, Maintenance and Replacement Association that allows project sponsors to operate Colorado project features.
General
| Project | East Bench Unit, Pick-Sloan Missouri Basin Program |
| Dam Type | Zoned earthfill |
| Location | Twenty miles southwest of Dillon, Montana at the head of Beaverhead River in southwestern Montana. |
| Longitude | -112.85834312438965 |
| Latitude | 45.000415406254376 |
| Watercourse | Beaverhead River |
| Reservoir | Clark Canyon |
| Original Construction | 1961-1964 |
| Modified Construction | 1984: Tile toe drains were replaced and new drain field was constructed. |
| National ID Number | MT00569 |
| Crest Elevation | 5,578.00 ft |
| Structural Height | 147.50 ft |
| Hydraulic Height (Normal Operating Depth at Dam) | 113.90 ft |
| Crest Length | 2,950.00 ft |
| Crest Width | 36.00 ft |
| Top of Joint Use Pool (Elevation) | 5,546.10 ft |
| Top of Active Conservation Pool (Elevation) | 5,535.70 ft |
| Top of Inactive Conservation Pool (Elevation) | 5,470.60 ft |
| Base Width | 800.00 ft |
| Volume of Dam Construction Materials | 1,970,000.00 cu yds |
| Spillway Crest Elevation | 5,560.40 ft |
| Top of Dead Storage Pool (Elevation) | 5,455.00 ft |
| Spillway Type | Uncontrolled concrete crest and concrete-lined chute at left abutment |
| Spillway Capacity at Elevation | 9,520.00 cfs at 5,571.90 ft |
| Outlet Works Capacity at Elevation | 2,325.00 cfs at 5,547.00 ft |
| Maximum Water Surface Elevation | 325,324 acre-ft at 5,571.90 ft |
| Total Water Storage at Elevation | 257,152.00 acre-ft at 5,560.40 ft |
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