Engin. Library

TC 558

PLATORO DAM .47

10.1 San Luis Valley Project
W58
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" :T.

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

Dam

CAO TAON .
Type: Two rolled-earth and rockfill structures (a main section and a dike section,

separated by a rock knoll) on ANA
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, 2-1/2/to 1 to a 20-foot berm at elevation 9965, then 5 to 1 to base

Downstream, 2 to 1 to 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

20.

18. Spillway
19. Diversion plan

Outlet works
21.

Hydraulic design of outlet works
22. Structural design of outlet
23. Outlet works electrical and ventilation systems

(a) Electrical system
(b) Ventilation system
Welded plate steel outlet pipe
(a) General'
(b) Pipe shell
(c) Support rings
(d) Wye
(e) Miscellaneous metalwork

(f) Painting
25. 4- by 5-foot high-pressure gate
26. 48-inch butterfly valves

(a) Design requirements
(b) General description
(c) Control unit
(d) Valve and control unit de sign