The Ashton Plant is located on the Henry’s Fork of the Snake River, approximately 2.5 miles west of Ashton, Idaho. Construction on the project began in 1914 and completed in 1918. It was later purchased and expanded in 1925 by Utah Power & Light Co. (a predecessor company of Rocky Mountain Power).
The project consists of a dam and 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. Units No. 2 and No. 3 are each rated at 2.5 megawatts.
The reconstruction project featured extensive preparatory steps that began in 2010 with the construction of a diversion tunnel around the dam. In 2011 preparation continued with connection of the tunnel to the reservoir and construction of an upstream cofferdam to allow the reservoir to be lowered for removal and replacement of the earthen portion of the dam in 2012.
In 2012, the company replaced and repaired concrete supporting structures on the downstream side of the power house. The last phase of the project included excavation and reconstruction of the earthen and rock-fill portion of the dam and replacement of the dam’s concrete cap.
PacifiCorp worked with federal and state officials and interested stakeholders for a number of years on the reconstuction project.
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