Quail Creek Dike Failure

Abstract Only - The Quail Creek Project is an offstream storage reservoir operated by the Washington County Water Conservancy District. The project consists of a main dam some 200 feet high and 900 feet long, as well as the dike which has a maximum height of 78 feet and is some 2000 foot long. The reservoir project was designed by the firm of Rollins, Brown and Gunnell, Inc., and was constructed by S. J. Groves and Sons. The 40,000 acre-feet facility was completed in January of 1985.
Upon the first filling, both the main dam and the dike showed signs of seepage through the foundation which prompted major remedial work in the summer of 1986. The major feature of the remedial work undertaken on the dike consists of extensive grouting of the foundation through the embankment, which reduced the total dike seepage to .3 cfs. An additional upstream cutoff trench was placed in the dike foundation in the fall of 1986. During 1987 and 1988, several isolated episodes of localized seepage were noted and additional remedial grouting was undertaken.
On December 31, 1988, the manager of the district noted turbid water emerging from the toe of the dike with a flow of approximately .5 cfs. The manager mobilized construction equipment and proceeded to place drain rock on the seepage area. At 10:00 p.m., down­stream residents were warned that a failure of the dike was likely. At 10:30 p.m., work on the dike was terminated due to the rapidly increasing flow. At about 11:00 p.m., the piping cavity enlarged enough to cause progressive sloughing of the downstream slope which led to a complete breach at 12:30 a.m. on January 1, 1989. No lives were lost and the damage was estimated at some 12 million dollars. Peak flows through the breach were 100,000 cfs and 25,000 acre-feet of reservoir storage was drained.
Following a visit to the site on January 1, 1989, Governor Bangerter appointed an independent review team to investigate the failure. The team's report was completed and presented to the Governor on March 7, 1989. The team concluded the cause of the failure was that materials placed on the foundation were not protected from seepage erosion. The team concluded that the design assumption that the foundation had very low permeabilities was incorrect and that remedial grouting may have aggravated the problem of seepage water against the unprotected foundation materials.