Shoshone Falls : P-2778

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Summary

  • P-2778
  • Snake R
  • Northwest
  • ID
  • 50.00 MW

License

  • Download License
  • 08-04-2004
  • IDAHO POWER COMPANY

Description

Download License Summary for the Mid-Snake River Projects. 

Shoshone Falls is one in a suite of five dams operated by Idaho Power Company in the Mid-Snake River in Idaho. The dam sits above Shoshone Falls, "the Niagara Falls of the West" and therefore controls the flow of water over the falls. The dam sits near the city of Twin Falls, ID. It consists of four diversion dams (one gated and three fixed crest) a run-of river reservoir, an intake structure, power tunnel, steel penstock, powerhouse containing three generating units, tailrace channel, and switchyard. The original powerhouse building was completed in 1907 with an addition built in 1921.

The Shoshone Falls, Upper and Lower Salmon Falls, and the Bliss projects are together referred to as the mid-Snake projects. The Federal Energy Regulatory Commission (FERC) issued licenses for the mid-Snake projects and the C.J. Strike project at once based on the multi-party settlement which encompasses all five projects.

The Mid-Snake Projects are located on the Snake River in south-central Idaho near the cities of Hagerman and Bliss, Idaho. The projects span more than 25 miles, from the main diversion dam at the Upper Salmon Falls Project downstream to the Bliss Dam. Between these facilities are the Lower Salmon Falls Dam and a free-flowing stretch of the Snake River known as the Wiley Reach.

Issues

Water Quality Issues: Unnaturally stagnant river. Increased turbidity resulting from construction of new powerhouse. Low seasonal DO levels in deep portions of project reservoir.Fishery Values: Very little in this stagnant section of the Snake,Threatened/Endangered: Snake River physa, Utah valvata, and Bliss Rapids snailsRecreational Values: Boat ramp, viewing of falls.Other Values: Shoshone Falls regulates the flow of water over Shoshone Falls. In the spring of 2006, Shoshone thundered for weeks with about 20k cfs and was a huge tourist draw since the drought had kept the falls virtually dry for the last seven years.Issues:In August 2006 Idaho Power filed an Application for Amendment of License, requesting an extension of its license with FERC. It is planning to increase the generating capacity of its turbines from 12.5 MW to 50 MW while barely increasing environmental mitigation measures. Normally FERC only issues longer licenses when there is significant environmental mitigation being proposed, such as fish passage. Under Idaho Power's proposed terms, with the larger generator, the utility would decrease flows over the waterfalls, effectively "turning on" the falls only on Friday afternoon and weekends during the summer when visitor numbers are highest. Furthermore, the generating capacity of the proposed generator well exceeds the capacity possible at the site because of flow levels of the Snake River. As a result there is much speculation that Idaho Power is motivated to upgrade the powerhouse to benefit from a tax break under the terms of section 1301 of the Energy Policy Act of 2005.FERC approved the amendment application in July 2010 and extended the license term by another 10 years effectively extending the license until July 31, 2044.