Idaho Power to expand 11.875-MW Shoshone Falls to 65 MW

Idaho Power Co. plans to upgrade and expand its 11.875-MW Shoshone Falls hydroelectric project (No. 2778) by adding a turbine, power tunnel, and second powerhouse. The utility says the $80 million upgrade and expansion would increase Shoshone Falls’ capacity to about 65 MW.

Idaho Power already provided state and federal agencies, and non-governmental organizations a draft application to amend its Federal Energy Regulatory Commission license to add the new capacity. The groups have 90 days to comment on the draft, after which Idaho Power will submit a final amendment application to FERC.

A cover letter for the draft amendment, filed with FERC Feb. 13, said Idaho Power is not proposing substantive operational changes. It said the project would continue to be a run-of-river plant and that the reservoir size would remain about the same. During the upgrade, two small units would be removed and a new Kaplan unit would be installed.

While FERC will determine the actual commissioning date, Idaho Power anticipates commissioning the new unit in fall 2010.

Utility proposes aesthetic flow changes

Current license provisions require Idaho Power to release continuous aesthetic flows of 300 cubic feet per second, if available, during daylight hours from April 1 through Labor Day. In its draft application, Idaho Power proposes to augment those flows with total river flow releases on the three-day Memorial Day, Independence Day, and Labor Day holiday weekends. It also proposes to “narrow the viewing window” for all aesthetic flows, from daylight hours, to 9 a.m. to 8 p.m., to match more closely the recreational use times near the project.

Shoshone Falls first produced power in 1907; additional units were added in 1909, 1921, and 1936. One of four Mid-Snake projects, it is on the Snake River, three miles northeast of Twin Falls, Idaho.

For information, contact James A. Leonard, Engineering Leader, Power Production Department, Idaho Power Co., P.O. Box 70, Boise, Idaho 83707; (1) 208-388-2365; Fax: (1) 208-388-6689; E-mail:; Internet:

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