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UNITED STATES
DEPARTMENT OF THE INTERIOR
Douglas McKay, Secretary

U.S. JUREAU OF RECLAMATION.

Wilbur A. Dexheimer, Commissioner
L. N. McClellan, Assistant Commissioner and Chief Engineer

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Engln. Library
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5^8 PLATORO DAM

. ^ ,)::.. ji.1 San Luis Valley Project ;>

General Information

Purpose: Storage for irrigation and flood control

Location: On the Conejos River 1 mile west of Platoro, Colo.

Constructed: 1949-1951

Water supply: Conejos River ,

Drainage area: 39. 7 square'miles'

Maximum flood: 1,380 cubic feet per second (1949)
Reservoir:

Area: 950 acres

Total storage (including superstorage): 67,800 acre-feet at elevation 10,042.0

Irrigation and flood control storage: 60,000 acre-feet at elevation 10,034.0

Dead storage: None

Type: Two rolled-earth and rockfill a^uctures (a main section and a dike section,

separated by a rock knoll) .
Foundation: Massive andesite flow'
Slope protection: 3 feet of dumped riprap on upstream face; heavy rockfill on

downstream face
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.*l/2/to I to a 20-foot berm at elevation 9965, then 5 to 1 to base
Downstream,' 2 to l~tr) elevation 9965, then 2-1/2 to 1 to disposal area at
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
Spillway crest: Elevation 10,034.0

Maximum discharge: Spillway, 3,000 cubic feet per second with reservoir surface

at elevation 10, 041.0

Outlet, 600 cubic feet per second with reservoir surface at elevation 9963. 0 Outlet conduit: Through right abutment of dam. A high-pressure tunnel 6 feet 6 inches in diameter extends to gate chamber near axis of dam, whence a 56-inch-diameter steel pipe extends through 8. 5-foot horseshoe tunnel to valve house.

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

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