UNITED STATES DEPARTMENT OF THE INTERIOR U.S. BUREAU OF RECLAMATION. Wilbur A. Dexheimer, Commissioner L. N. McClellan, Assistant Commissioner and Chief Engineer TECHNICAL RECORD OF DESIGN AND CONSTRUCTION PLATORO DAM Constructed 1949-1951 Conejos Division Denver, Colorado 1954 Dam Purpose: Storage for irrigation and flood control Location: On the Conejos River 1 mile west of Platoro, Colo. Total storage (including superstorage): 67,800 acre-feet at elevation 10, 042.0 Type: Two rolled-earth and rockfill structures (a main section and a dike section, separated by a rock knoll) 500 UNA Foundation: Massive andesite flow Slope protection: 3 feet of dumped riprap on upstream face; heavy rockfill on Dimensions: Height: 145 feet above streambed, 165 feet above excavation Crest length: 885 feet for main section; 590 feet for dike section Crest width: 35 feet Crest elevation: 10,048.0 Volume: 909, 884 cubic yards Slopes: Upstream, 2-1/2 to 1 to a 20-foot berm at elevation 9965, then 5 to 1 to base elevation 9898 Cutoff trench: Maximum width 200 feet in main dam section and 75 feet in dike section; depth from 3 to 10 feet. A concrete grout cap was placed in a trench excavated in rock along centerline of cutoff trench. Spillway and Outlet Type of spillway: Open-cut unlined channel through the rock knoll; no stilling basin Maximum discharge: Spillway, 3,000 cubic feet per second with reservoir surface Outlet, 600 cubic feet per second with reservoir surface at Outlet conduit: Through right abutment of dam. A high-pressure tunnel 6 feet 6 inches Control works: One 4- by 5-foot high-pressure emergency gate in gate chamber Two 48-inch butterfly control valves in valve house at lower ends of bifurcated steel pipe |