Red silt that flowed in the water through the newly completed Upper Stillwater Dam near Duchesne in 1988 did not harm the fishery downstream, the Bureau of Reclamation says.
Kirt Carpenter, the bureau's Utah projects manager, said the federal agency conducted a study to determine whether fish or the fish habitat in Rock Creek were damaged when red quartzite sand, left in the reservoir basin when the new dam was completed last year, was stirred up in the water and carried through the dam's outlet works when the reservoir began to fill in the spring.The silt colored the water red on streams that pass through Ute Indian land. The Utes filed a suit in federal court, contending the red silt had ruined the fishery and had desecrated burial grounds.
There was little the bureau could do to stop the flow through the dam once the problem was noticed because of a federal regulation requiring new dams to be filled slowly - a measure taken on all new federal dams since the Teton Dam failed in Idaho more than a decade ago.
Stopping the flow to keep the silt out of the creek would have caused the reservoir to fill faster than federal regulations allow.
Beginning July 5, the bureau began draining the reservoir to expose the troublesome sand piles on the east and west banks of the reservoir. Two piles were capped, in place, with soil cement at a cost of $1.6 million.
"There is no evidence of any damage (to the fishery) as a result of that problem," Carpenter said. "We'll be getting back to meet with the tribe and others interested in a solution to that problem right away."
Even with the sand piles capped, some discoloration and clouding of the water is expected through the spring, the bureau has said, because of construction disturbances and existing sand layers distributed through the reservoir basin.
Another contract to fill hairline cracks in the innovative roller-compacted concrete dam is ongoing and should be finished by the first of April, Carpenter said.
After that, the bureau hopes to have approval to completely fill the reservoir behind the dam, which is a feature of the Central Utah Project's Strawberry Aqueduct and collection system.