A 5-year-old Oregon dam, built with the same new style of construction used in the just-completed Upper Stillwater Dam in Utah, is falling to pieces.
But officials say problems that plague the Oregon dam are not expected to affect the Central Utah Project's Upper Stillwater Dam, built on Rock Creek in Duchesne County.The Willow Creek Dam above Heppner, Ore., was the world's first to be built entirely with roller-compacted concrete instead of concrete poured into a form. It was built by the U.S. Army Corps of Engineers. Upper Stillwater Dam was the first similar dam built by the U.S. Bureau of Reclamation.
The Register-Guard in Eugene, Ore., reported in a copyrighted story this week that the Willow Creek Dam is dissolving and threatening to obliterate the town below it, according to Army Corps of Engineers documents.
But Bill White, a Bureau of Reclamation construction engineer in Utah, said the problems in Oregon - reportedly caused by caustic chemicals in the water - are not expected to be found at Upper Stillwater, which is fed by clean Rock Creek in the high Uintas. The problems with the Oregon dam apparently are not because of the style of construction and design used.
Initial Corps of Engineers studies indicate portions of the Oregon dam are being dissolved by caustic chemicals being formed by decaying algae in the reservoir behind it. Corps engineers, however, insist the structure is still safe and in no immediate danger, the newspaper reported.
The Register-Guard said before the dam was built, Washington State University professor William Funk warned that chemicals and manure associated with agriculture and cattle production would enrich the reservoir with nutrients and would feed a plentiful growth of algae.
He predicted decomposing algae would deplete oxygen from the water and create poisonous and corrosive substances such as hydrogen sulfide and ammonium, which could dissolve concrete in the dam. Resulting seepage creates a breeding ground for bacteria, producing even more corrosive sulfuric and nitric acids.
As much as 82 metric tons of the dam's 900,000-ton structure are leaching out of the concrete and washing downstream every year, according to estimates prepared for the corps.
White said the Bureau of Reclamation expects no such bacterial problems at Upper Stillwater, and said the dam is constructed of materials considered to be strong and safe.
The Register-Guard said Oregon residents have also been told their dam is safe, but they still worry.
"We can see it's disintegrating, but they're not telling us anything," said Ed Hiemstra, whose backyard looks out on the dam's face. "They were looking for a sparsely settled area they could experiment on with this new type of dam, and now we're stuck with it."
The 169-foot, $34 million dam in Oregon leaked from the start between its one-foot layers of concrete. A $2 million grouting project stemmed some leaking, but the dam has begun showing signs the seepage might be promoting decay of the concrete.
Although the leaching amounts to a small fraction of the total Oregon dam mass, scientists warn decay may be occurring in narrow zones and could result in localized weakening.
The degradation threatens the dam's structural integrity and raises questions about the health and safety of the public and project employees, according to internal memoranda written by corps staff in 1986 and 1987.