Columbia-Pacific Northwest Region

Boise River Basin Feasibility Study
Draft Environmental Impact Statement

The Boise Project was authorized on March 27, 1905, under provisions of the Reclamation Act of 1902. The project is a series of water storage, irrigation, and power-generating facilities developed to bring water and energy to previously undeveloped areas of the Boise River basin. There are three major storage dams in the Boise River that are built in a series, meaning water from Anderson Ranch Reservoir passes through Arrowrock Reservoir and then through Lucky Peak Reservoir, which is owned by the US Army Corps of Engineers USACE to provide water to the Boise River basin. These major reservoirs have a total active capacity of more than 1 million acre-feet and furnish irrigation water to approximately 280,000 acres.

There is a long history related to the concerns over water storage capacity requirements and securing a more reliable water supply for current and future needs in the Boise River basin. In the early 2000s many local, state, and Federal entities began discussing the concerns and identifying potential long-term solutions. Over the course of the next several years, various efforts were undertaken by the state and Federal agencies to consider and study possible enhancement of storage in the Boise River basin to address water shortage concerns as well as anticipate future demands. This included a 2016 study by the Idaho Water Resource Board (IWRB) that focused on water demand projections. A general investigation study conducted by the USACE evaluating the potential raising of Arrowrock Dam to address flood control and storage needs, resulted in USACE recommending that the proposal not move forward given that flood control benefits were less than associated project costs. Following the conclusion of that study, Reclamation renewed its earlier focus and partnered with the state of Idaho, resulting in this effort to assess the feasibility to increase storage capacity in the Boise River basin.

Reclamation and IWRB have partnered to conduct a feasibility study for increasing water storage capacity within the Boise River system, particularly at Anderson Ranch Dam. In October 2017, the IWRB committed up to $3M as a 50% non-Federal cost-share partner.

In 2018, Congress expressly authorized and funded the Boise River Basin Feasibility Study—in accordance with the requirements of the WIIN Act—in the 2018 Consolidated Appropriations Act (Pub. L. 115-141).

In 2019, as part of the Boise River Basin Feasibility Study, Reclamation conducted an initial technical review of available information and completed site visits of Anderson Ranch, Arrowrock, and Lucky Peak dams. The results of these technical reviews concluded that an increase in reservoir storage at Arrowrock and Lucky Peak dams would likely be significantly more difficult than raising Anderson Ranch Dam due to physical and regulatory complexities associated with the facilities, while resulting in less storage potential. Therefore, Anderson Ranch Reservoir became the focus of additional water storage opportunities.

In accordance with the National Environmental Policy Act, Reclamation has prepared a draft Environmental Impact Statement EIS on the Boise River Basin Feasibility Study. Reclamation gathered information from other agencies, interested parties and the public on a range of possible alternatives. Three public scoping open houses were held in August 2019 to solicit input on potential increases to water storage in the Boise River basin. Comments received during the scoping period have been incorporated into this draft EIS.