Engineering Geology Case Histories Number 2
Prepared for the Division on Engineering Geology of the Geological Society of America, Engineering Case Histories 2 includes 11 case histories covering tunnel construction, foundation grouting, dam-site studies, landslide causes, and more.
The San Francisco District, California, Corps of Engineers is authorized to construct a dam and create a reservoir on the East Fork of the Russian River about 5 miles north of Ukiah in Mendocino County. The project is known officially as the Russian River Reservoir (Coyote Valley) but locally called the Coyote dam. It should not be confused with the Coyote dam across Coyote Creek near San Jose. The Russian River is noted for its flash floods that frequently crest in a matter of hours and cause considerable damage to agricultural and recreational areas. In addition, population increases in northern California are creating serious water-supply problems. The project, therefore, is designed to assist flood-control and water-conservation problems.
The Russian River Reservoir (Coyote Valley) project was authorized by the Flood Control Act of 1950, 81st Congress, following preliminary studies begun in 1938. Before 1953 studies concerned the Middle Hill axis and alignment, approximately 2000 feet upstream from the design axis, but the left abutment was shown to be in a serious landslide area. The axis was moved downstream to a better and more economical location, and since then the studies consisted of locating the axis that had the most favorable foundation conditions consistent with economic construction costs.
The authorized project consists of an earth-fill dam having a crest length of 3532 feet, a maximum height of 162 feet, a reservoir storing 122,500 acre-feet of water of which 39 per cent is for flood control and 56 per cent for water conservation.