An elevator shaft in the Jordanelle Dam that has leaked since the dam was completed in 1992 has been repaired at a cost of $3.1 million.
The 300-foot access shaft, which was receiving seepage of 28 gallons of water per minute, extends deep into bedrock to the chamber where huge gates regulate the flow of water through the dam.It is located in the "shoulder" of the earthen fill on the upstream, reservoir side. The leakage was isolated from the dam's impervious core and posed no risk to the integrity of the structure, which impounds Jordanelle Lake.
"This is unrelated in any way to the dam's ability to hold the reservoir in place," said Barry Wirth, Bureau of Reclamation spokesman in Salt Lake City. "That shaft had always leaked, and it was basically an inconvenience."
Contractors working for the Bureau of Reclamation finished the repair project last month, installing "drainage fabric" on the walls of the shaft and covering the fabric with a plastering of concrete. The fabric collects water seeping through the walls of the shaft and channels it downward to drains built into the bottom of the shaft and gate chamber.
Engineers say the Jordanelle shaft leaked because it was constructed using "Shot-crete," a pneumatically applied form of concrete used frequently in situations - such as tunnels - where gravity thwarts traditional concrete laying.
"Shot-crete is permeable and it just let the water seep in," said Curt Pledger, field engineer for the Bureau of Reclamation in Provo. "This was not the fault of the contractor; it was called for in the original design. It was an attempt to save money, to try to build a dam for the least cost possible."
Since the gates of the dam are controlled electronically from the surface, the access shaft is used only periodically for routine maintenance and inspection.
"For the people working in there, it was like being in a light rain shower," said Pledger. "Now, with the drainage fabric installed, it's a lot drier."
Construction on the Jordanelle project - the dam, state park, new highways and utility relocation - began in 1987 and cost $350 million. The dam, which took 1.5 million dump-truck loads of fill to build, is as tall as the state Capitol. During the siting and construction, safety issues repeatedly surfaced, and allegations of a cover-up prompted congressional hearings in Heber City in 1992.
A technical review of the project by the U.S. Geological Survey found no evidence of safety problems and determined that charges of fraud were "without merit."