Scofield project nears completion
The dam renovation work at Scofield Reservoir has been wrapped up for the season. In fact, the work is nearly completed.
"Things have gone right on schedule," said Spencer Strand, a United States Bureau of Reclamation engineer working on the Scofield project. "Once the snow is gone next spring, we have a few things to finish up next spring and early summer, but it is nearly finished."
The dam, which was built partially during World War II and completed shortly after the conflict, has been supplying water from the reservoir to Carbon County for more than 60 years.
But a few years ago, the dam was examined and officials determined that the spillway, control equipment and several areas were deteriorating and needed to be rebuilt.
One of the main concerns was the action of hydraulic jacking at the structure.
Hydraulic jacking is a process where water entering under the concrete slab of the spillway creates water pressure that pushes the slab up and out of its position.
Currently, dams that are built have water stops put in the structures to prevent the problem.
But when the dam was constructed at Scofield, the types of measures in question were not employed.
The spillway at Scofield had fallen victim to 60 years of freeze and thaw cycles as well as alkali-silica reaction deterioration.
A number of attempts to repair the spillway had taken place since the 1970s to fix some of the problems.
But the attempts were basically stop gap measures and it was determined by officials that the major work needed to be started.
The bridge that crosses over the dam was also determined to be a problem.
While the towns of Scofield and Clear Creek do not have many residents, holiday and sportsman traffic along with coal trucks running from mines above the reservoir provided a large load on the bridge each year.
It was determined that the bridge needed replacement while the spillway was being replaced as well. Work began in 2007.
The reservoir level has been kept at about 50 percent of what its actual capacity is (26,000 acre feet) for the last three years. To protect the work and to free up the work space to repair both the spillway and the bridge a temporary coffer dam was constructed. Work on the project has progressed during the construction season for the last three years.
"We have now removed the coffer dam and the temporary by-pass for traffic," said Strand. "We only have some finishing work to do."
Strand did say that the dam may not be allowed to reach capacity next summer, even if the water is available to do so, because a new facing called riprap has been put on the dam and engineers have to bring the water up slowly to be sure that is protecting the soil that the dam is composed of.
"Riprap is the rock that covers the soil deposits that make up the dam and we need to be sure it is protecting those," said Strand. "But I don't suppose there will be many restrictions on the water unless there is a problem. In any case I doubt users of water from the dam will see any difference because of the work that needs to be finished nor any restriction on how much water can be held back. We just need to be sure what is put behind the dam is very controlled."
As anyone who has been in the construction business knows often as built plans and drawings are not as accurate as they should be, but Strand said the original drawings the BOR worked off of to do the reconstruction were "very accurate."
During the construction the BOR also built a new control house for water release equipment as well as installing new gate accuators, which will help the Carbon County Water Conservancy District control water flowing out of the dam for its users.
The project when finished will cost $6.9 million and that expense will be divided up between BOR (85 percent), the conservancy district (5 percent) and the Utah Department of Transportation (10 percent).