It could have been worse.
As bad as it was early when a dike on the Quail Creek Reservoir burst and a wall of water forced 1,500 people to flee their homes, experts say the effects could have been much more disastrous."If it had been the dam itself that failed, things would have been much worse," said Roy Birill, district director for the Utah Division of Parks and Recreation, which operates the Quail Creek Reservoir State Park.
Birill estimated that some 25,000 acre-feet of water escaped from the 200-foot wide breech. The flow could have increased by another 11,000 to 15,000 acre-feet if the failure had occurred in the dam itself on the east side of the reservoir.
As it was, the raging water ripped away silt and bedrock as it thundered across open land before reaching U-9 and being funneled back into the Virgin River channel leading from the reservoir. The torrent destroyed two bridges directly below the reservoir and two more in St. George.
State and federal investigators will attempt to determine the cause of the failure this week. The dam has been plagued by leakage since it opened in 1985. But until Sunday it was considered safe, and efforts to stop leakage were deemed successful for the most part.
At 10 a.m. Saturday, a previously unaffected area on the dike side began leaking. Maintenance crews from the Washington County Water Conservancy District, which owns the reservoir, were summoned to make repairs. Despite determined efforts, the flow could not be stemmed, and by 10 p.m., officials had thrown in the towel. They knew it would be only a matter of time before the dike failed.
Birill said officials had been conscientious in addressing repairs and maintaining the dike and dam. Countless tons of grouting were pumped into the structure over the past four years, but new leaks kept appearing.
Saturday's leak was a new one, occurring in a previously unaffected area of the dike. Officials went to work with expectations that the repair, like those in the past, would be successful. Hours later, those expectations were dashed.
Birill said the reservoir was about 90 percent full prior to the breech. Weather conditions had been fairly routine despite a small surge of cold weather that dusted the area with snow earlier this week.
"There was nothing unusual, nothing that would have tipped us off," Birill said.
Tony Hafen, Washington County Emergency Services director, said the seepage location was a surprise, but efforts to stop the damage was similar to those used for previous repairs.
Apparently the interior damage was substantial. The bedrock supporting the earthen dike was badly damaged.
"It had been devastated. Even a lot of the bedrock itself was destroyed and washed away," Hafen said.
Pinpointing the cause, a difficult task since much of the evidence washed down river in the torrent, will be important because state officials are already calling for the structure to be rebuilt. Gov. Norm Bangerter led that call at a Sunday press conference, saying the dam is critical to the water needs of southern Utah if population growth and development demands are to be met.
How long that effort will take is anybody's guess. Officials say it will be at least six months. If leakage problems persist, though, it could be a long time before the structure is rebuilt.