Rebuilding Quail Creek Dike with RCC

Quail Creek Reservoir, owned by the Washington County Water Conservancy District, is located approximately 15 miles northeast of the city of St. George, Utah. The 40,000 acre-foot reservoir was originally formed by two zoned earthfill embankment dams, known as the main dam and the dike. The main dam has a maximum height of 200 feet and a crest length of 900 feet. The dike had a maximum height of 80 feet and a crest length of approximately 2000 feet. Construction of the dike was completed in April 1984 and the main dam was completed in January 1985. Reservoir filling began in April 1985. The dike experienced several incidents of high foundation leakage (as much as 6.3 cubic feet per second). Grouting programs were undertaken during 1986, 1987 and 1988 to reduce leakage through the foundation. However, on January 1, 1989, the dike failed releasing approximately 25,000 acre-feet of water. The failure caused about $12 million in damage to the St. George area, but due to timely evacuation, no lives were lost. In early January 1989, an independent review team was appointed by the State Engineer, at the direction of the Governor of Utah, to determine the cause of failure and to further determine if a new dam could be safely rebuilt. In March 1989, the review team concluded that “failure resulted because embankment materials placed on the foundation, including overburden left in place, were not protected from seepage erosion”. The review team also concluded that a new structure could be safely rebuilt at the site. The new structure, now called the Quail Creek South Dam, was recently constructed to replace the failed dike. This paper describes the design and construction of this new dam.