Trial Lake Dam Reconstruction

Kuenzli, James R.; DeHeer, Lee H.; ,

Trial Lake Dam Reconstruction

by James R. Kuenzli, CH2M Hill, Boise, United States,
Lee H. DeHeer, CH2M Hill, Boise, United States,

Document Type: Proceeding Paper

Part of: Geotechnical Practice in Dam Rehabilitation

Abstract:

Trial Lake Dam is located in the Uinta National Forest in Central Utah at an elevation of about 10,000 feet. The dam is 50 feet high and stores 1,700 acre-feet of water for downstream uses. Originally constructed in 1910, the dam failed during the first filling and was rebuilt in 1914. The dam was raised and a saddle dike added in 1925. In 1986, the low saddle dike on the left abutment failed and the reservoir has remained empty until the recent reconstruction. Reconstruction of the dam required a high level of cooperation between the U.S. Forest Service, the State of Utah Department of Dam Safety, the Central Utah Water Conservancy District (the water purveyor), and the engineer. The reconstruction demonstrates that agencies with widely varying perspectives and mandates can complete a dam project within a tight time schedule to meet environmental and development objectives. The preliminary design was completed in 1988 (by others) and was based on utilizing the existing dam. The final design was completed in 1990. During the early stages of final design, the question of utilizing the existing dam and constructing upstream and downstream shells was reconsidered. This became a major economic and engineering decision. Alternative embankment sections were considered for rebuilding the existing dam and dike, one of which was using the existing dam for a central core. Examination of the existing dam embankment showed that it contained loose fill and voids and that it did not have a filter between the core and downstream rock fill; thus, removal of the existing dam and dike was believed to be the best course of action even though the dam had performed adequately since the original construction in 1914. The design of the new dam, dike, and hydraulic structures was completed in the spring of 1990 and construction began in June 1990. Because of funding constraints, weather conditions, and irrigation demands, construction had to be completed in one construction season from June 1990 to October 1990.

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