The dam is a zoned earth fill structure with a structural height of 74 feet, a crest length of 1150 feet, and a crest width of 15.5 feet at crest elevation 2170 feet. The upstream face has a 2.5 to 1 slope and is protected by 3 feet of riprap. The downstream face has a 2 to 1 slope and is protected by 18 inches of riprap. The embankment consists of a silt core, progressively coarser zones of sand and gravel, and a protective layer of riprap on the outer slopes. The dam foundation consists of basalt on the south abutment, cemented sand and gravel (conglomerate) in the center of the dam, and basalt again on the north abutment. A core trench 32 feet wide at the bottom with 1:1 side slopes was excavated across the entire length of the dam. This trench was backfilled with silt core material and sand filters. The dam includes an extensive drainage system, which exits into the drainage trench downstream of the dam. The embankment is terminated at the northern end by a concrete retaining wall which is anchored to the rock with post-tensioned anchor bars. At the south end, a section of rock-fill was placed on the south (right) abutment just upstream of the dam for erosion protection.
General
Project
Yakima
Dam Type
Zoned Earthfill
Longitude
-120.7922959
Watercourse
Cowiche Creek
Reservoir
French Canyon
Original Construction
1983-1985
Latitude
46.7114132
National ID Number
WA82901
Dimensions
Structural Height
74.0 ft
Crest Length
1150.0 ft
Top of Active Conservation Pool (Elevation)
2154.5 ft
Top of Inactive Conservation Pool (Elevation)
2120.0 ft
Spillway Crest Elevation
2167.0 ft
Streambed at Dam Axis
2111.0 ft
Crest Elevation
2170.0 ft
Hydraulic Height (Normal Operating Depth at Dam)
45.0 ft
Top of Dead Storage Pool (Elevation)
2113.00 ft
Hydraulics & Hydrology
Spillway Type
Ungated
Spillway Capacity at Elevation
23,000 cfs at 2167.0 ft
Outlet Works Capacity at Elevation
120 cfs
Diversion Capacity at Elevation
440 cfs
Drainage Area
16.0 sq mi
Hydrometeorological Report (HMR)
HMR 57
Normal Water Surface Elevation
2154.5 ft
Auxiliary Spillway
No
Total Water Storage at Elevation
645 ac-ft
Contact
Owner
Title: Area Office Manager Organization: Columbia-Cascades Area Office Address: 1917 Marsh Road City: Yakima, WA 98901-2058 Fax: 509-454-5611 Phone: 509-573-8000
Operator
Organization: Yakima-Tieton Irrigation District Address: 470 Camp 4 Road City: Yakima, WA 98908 Phone: 509-678-4101
More Information about the U.S. Bureau of Reclamation