French Canyon Dam

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.

RegionFacilities in Pacific Northwest | Pacific Northwest Home Page
Dam TypeZoned Earthfill
ReservoirFrench Canyon
WatercourseCowiche Creek
Original Construction1983-1985
Modified Construction
National ID NumberWA82901
Hydrologic Unit Code

Structural Height74.0 ft
Hydraulic Height (Normal Operating Depth at Dam)45.0 ft
Top Parapet (Elevation)
Spillway Crest Elevation2167.0 ft
Crest Elevation2170.0 ft
Crest Length1150.0 ft
Crest Width
Base Width
Volume of Dam Construction Materials
Streambed at Dam Axis2111.0 ft
Top of Exclusive Flood Control Pool (Elevation)
Top of Joint Use Pool (Elevation)
Top of Active Conservation Pool (Elevation)2154.5 ft
Top of Inactive Conservation Pool (Elevation)2120.0 ft
Top of Dead Storage Pool (Elevation)2113.00 ft

Hydraulics & Hydrology
Total Water Storage at Elevation645 ac-ft
Maximum Water Surface Elevation
Normal Water Surface Elevation2154.5 ft
Spillway TypeUngated
Auxiliary SpillwayNo
Spillway Capacity at Elevation23,000 cfs at 2167.0 ft
Auxiliary Spillway Capacity at Elevation
Uncontrolled Spillway Capacity at Elevation
Outlet Works Capacity at Elevation120 cfs
Diversion Capacity at Elevation440 cfs
Drainage Area16.0 sq mi
Hydrometeorological Report (HMR)HMR 57
Probable Maximum Flood (PMF) Report

Contact Information
TitleArea Office Manager
OrganizationColumbia-Cascades Area Office
Address1917 Marsh Road
CityYakima, WA 98901-2058
Phone (Fax)509 454-5611
Phone (Office)509 575-5848 x202
OrganizationYakima-Tieton Irrigation District
Address470 Camp 4 Road
CityYakima, WA 98908
Phone (Office)509 678-4101

Last updated: Mar 11, 2009