Rocky Mountain Power-PacifiCorp will refill the Ashton reservoir to its normal elevation beginning November 6th. Utility officials announced Thursday that major reconstruction activities on the dam will be complete by mid-November. The dam is located about 2.5 miles west of Ashton on the Henry’s Fork of the Snake River.
“Through the rest of 2012, we will be clearing up the construction areas and preparing the project to again produce low-cost electricity,” said project manager Troy Stout. “We expect to re-open the reservoir for public recreational access in mid-December.”
For many years, the utility has worked with nearby property owners, farm operators who use Ashton reservoir for irrigation and recreation, and the Henry’s Fork Foundation to ensure the safety of workers and the public and protect fisheries and water quality.
The project began in 2010 with construction of a diversion tunnel around the dam. In 2011 the tunnel was connected to the reservoir and an upstream coffer dam was constructed. In 2012, the reservoir was lowered for removal and replacement of the earthen portion of the dam.
Concrete supporting structures were completed on the downstream side of the power house this spring. Continuing work will include excavation and reconstruction of the earthen and rock-fill portion of the dam and replacement of the dam’s concrete cap.
Construction of the Ashton Hydro Plant was completed in 1918 and consists of a dam and a powerhouse with three generating units. The dam is a rock and earth filled structure, 60 feet tall and 226 feet long, with a 70 foot wide concrete intake and 82 foot long spillway. Unit No. 1 is rated at 2.85 megawatts and Units No. 2 and No. 3 are reach rated at 2.5 megawatts.