LIHI Certificate #2 – Island Park Project, Idaho

The Island Park Project is located at the U.S. Bureau of Reclamation (USBR) Island Park Dam on the Henrys Fork, or North Fork, of the Snake River just upstream of the confluence with the Buffalo River, which enters from the east. It is in Fremont County, Idaho about 39 miles north of Ashton. The Project is located within the Targhee National Forest.

USBR completed the Island Park dam in 1939 as part of the Minidoka Project, which provides irrigation water to farmland in Idaho’s Snake River Plain. The project owner also operates the nearby Buffalo River Dam Project, built in 1936 to generate hydropower in support of the construction of the Island Park Dam.

The project includes the USBR dam, intake structure and tunnel, spillway, powerhouse, and two Francis turbines.

The dam is a 9,448-foot-long earthfill structure with a maximum height of 91 feet, and a concrete spillway that joins the outlet tunnel at the bottom of the dam. The dam outlet structure is in the reservoir and is composed of an intake structure with trashracks and screens; a 12-foot-diameter, concrete, circular intake tunnel 238 feet long; a gate chamber, 75 feet long, at the confluence of the spillway; and a 13-foot-diameter, concrete, circular tunnel, 500 feet long, discharging into the river southwest of the dam and opposite the powerhouse location.

The hydroelectric facility is a non-federal power plant that was constructed between September1992 and July 1994. It consists of the screened intake structure with 3/8-inch openings, approximately 720 feet of a 10-foot diameter penstock, a concrete masonry powerhouse with two vertical Francis turbines/generators with a total installed capacity of 4.8 MW, and associated controls.

The project operates as a diversion project and is located at an USBR dam which impounds the 8,084-acre Island Park reservoir. The dam and reservoir are not a feature of the project. Because the USBR has complete control over releases from the dam, the Project does not have a required minimum flow. The project does target ramping rate flow releases of 30 cfs - 35 cfs per half-hour and releases no greater than 50 cfs per half-hour. This flow regime was developed via recommendation from the Idaho Department of Fish and Game.

Project Name Island Park
LIHI Certificate No. 2
LIHI Certificate Term December 30, 2016 - December 29, 2021
Owner Fall River Rural Electric Cooperative, Inc.
State Idaho
Location Located at river mile 91 on Henry's Fork of the Snake River 0.4 miles upstream of its confluence with the Buffalo River, and approximately 40 miles north of Ashton in Fremont County, Idaho.
Installed Capacity 4.8 MW
Average Annual Generation 19,437 MWh
Facility Type Diversion
FERC No. P-2973 issued 1988, expires 2038

Waters within the project reach are designated as Category 3, Unassessed Waters, in the reservoir and downstream river segment. The project area is managed to support aquatic life, specifically cold-water communities, as well as for primary contact recreation, domestic water supply, and salmonid spawning. An aeration facility ensures dissolved oxygen concentrations are enhanced as they pass through the project. This facility retains water for two minutes at peak flows and adds 25,000 pounds of oxygen into the water daily.

In the 1930s, construction of the Buffalo River Dam blocked upstream passage to the Buffalo River. Additionally, there are natural barriers downstream on the Snake River which have historically blocked diadromous fish access to the project area. The Henrys Fork supports populations of rainbow trout, brook trout, mountain whitefish, and several non-game species. The project implemented intake screening which limits the migration of reservoir fish into the downstream cold-water fishery.

The project lands consist of 1.2 acres, owned by the US Forest Service (USFS). As the project area is under federal ownership (USFW or USBR), the project does not have any control or land management obligations in terms of the reservoir shoreline.

Threatened or endangered species potentially present in the project vicinity include the grizzly bear, Canada lynx, and Ute ladies’ tresses orchid. Idaho Department of Fish and Game (IDFG) has confirmed that these species have been noted in the project vicinity, though the orchid species only roughly 25 miles from the project. A grizzly bear recovery plan has been implemented and project operations do not interfere with this plan. Via consultation with IDFG and USFWS, the project does not adversely impact any of the listed species.

No cultural or historic resources have been identified in the project area. The Island Park Dam is potentially eligible for listing on the National Register of Historic Places for its contribution to the historic development of northeastern Idaho. The State Historic Preservation Office has concluded that the hydro project does not impact cultural or historic resources in the project area though consultation is required should the project plan any land clearing or earth-disturbing activities in the future.

Recreational resources at the project include a boat launch, a fishing platform, and a hiking trail. These facilities are inspected annually by the USFS as a part of its special use permit the project operates under. Public access is provided free of charge.

Certification History

January 29, 2018: The appeal period for the Preliminary Decision to Certify the Island Park hydroelectric project has closed with no requests to appeal. The decision is therefore final. Island Park is LIHI Certificate #2.

December 27, 2017: The Island Park Hydroelectric Project, ID (LIHI #2) on Henry's Fork of the Snake River in Idaho, has been granted preliminary Low Impact Certification.

The Island Park Hydroelectric Project Certification includes the following condition:

  • Condition 1: In its annual compliance report, the Owner shall report on any FERC Order or FERC  correspondence in response to the Owner Agent’s notice to FERC dated December 13, 2017  regarding the status of license article 401 and dissolved oxygen measurements. The Owner  shall provide a status update on progress in rectifying differences between state water  quality standards and FERC license requirements with the annual compliance statement  submitted to LIHI. LIHI reserves the right to review or cancel certification and/or modify or  add conditions based on the outcome of these matters.

As provided for in the LIHI Certification Handbook, the preliminary decision will be followed by a 30-day period to appeal the decision. Appeal requests may be submitted by those who provided comments during the application's 60-day public comment period. Any appeal must include specific reasons why the appellant believes the hydropower facility does not meet one or more criteria. Appeal requests can be submitted by email to with "Island Park Hydroelectric Project" in the subject line, or by mail addressed to The Low Impact Hydropower Institute, 329 Massachusetts Ave, Suite 2, Lexington, MA 02420.  All requests will be posted to this website and the applicant will have an opportunity to respond. Any response will also be posted. Requests must be received by 5pm EST on January 26. More details on the appeal process can be found in our handbook HERE.

December 30, 2016 – On December 23 3016, the Low Impact Hydropower Institute (LIHI) received a complete application from Fall River Rural Electric Cooperative, Inc., for the Low Impact Certification of the Island Park Hydroelectric Project (FERC No. 2973), located on Henry's Fork of the Snake River at approximately river mile (RM) 91, 0.4 miles upstream of its confluence with the Buffalo River, and approximately 40 miles north of Ashton in Fremont County, Idaho.

The Island Park project was first certified as low impact  by LIHI as Certificate No. 2 on June 7, 2001 for a two year term, ending on June 7, 2003.  The certification was extended in 2003 when LIHI extended certification terms from two years to five years in duration.  It was certified again for a five year term from June 24, 2006 to June 24, 2011.

LIHI is seeking public comment on this application. Specifically, we are interested in knowing whether you think the Island Park project meets the LIHI Low Impact Certification Criteria. The Island Park application is subject to review using the Criteria in the LIHI Certification Handbook of 2014.  Please review the program and criteria in LIHI’s 2014 Handbook and then review the Project’s 2016 application materials posted on the project page. Comments that are directly tied to specific LIHI criteria (flows, water quality, fish passage, etc.) will be most helpful, but all comments will be considered. Comments may be submitted to the Institute by e-mail at with “Island Park Project Comments” in the subject line, or by mail addressed to the Low Impact Hydropower Institute, PO Box 194, Harrington Park, New Jersey 07640. The 60 day public comment period begins on January 3, 2017.  Comments must be received at the Institute on or before 5 pm Eastern time on March 4, 2017 to be considered. All comments will be posted to the web site and the applicant will have an opportunity to respond.  Any response will also be posted.

The Island Park comment period has been extended to March 6, 2017.