Anderson Ranch Dam Security Enhancement Project Environmental Assessment

On April 21, 2010 the Bureau of Reclamation Snake River Area Office distributed a Draft Environmental Assessment for the Anderson Ranch Dam Security Enhancement project for public review and comment. The Draft EA analyzed the impacts of a proposed action to correct security vulnerabilities related to motor vehicles traveling across the top of the dam.

Anderson Ranch Dam was constructed by Reclamation in 1950 as part of the Arrowrock Division of the Boise Project. It is a multipurpose facility that provides for irrigation, flood control, hydropower, and recreation. The dam is located on the South Fork of the Boise River about 28 miles northeast of Mountain Home, Idaho.

The proposed action analyzed in the Draft EA is to raise the existing dam crest by four feet and provide a 19.5 foot single travel lane across the crest. The single lane roadway was designed to accommodate semi trucks hauling farm machinery and other oversized vehicles.

In July 2010 Reclamation approved a Finding of No Significant Impact (FONSI) for the project and determined that an environmental impact statement was not required. Three minor changes were made to the project:

  1. An asphalt cap will be placed on the raised roadway.
  2. Electronic traffic control signals will be installed at each end of the dam.
  3. The project will begin in spring 2011 rather than fall 2010.

Construction was completed in October 2011.

07/2010 Anderson Ranch Dam Security Enhancement Project FONSI PDF 1.22 mb
004/2010 Anderson Ranch Dam Security Enhancement Project Draft Environmental Assessment PDF 2.7 mb


John Tiedeman
(208) 378-5034

Bureau of Reclamation
Pacific Northwest Regional Office
1150 North Curtis Road, Suite 100
Boise ID 83706-1234

Last Updated: 6/7/16