LIHI Certificate #131 – Chester Diversion Project, Idaho

The Chester Diversion Project is located on the Henrys Fork of the Snake River in Fremont County, Idaho. The project facilities are owned and operated by Fall River Rural Electric Cooperative while the dam is owned by the Fremont Madison Irrigation District. The Chester Diversion Dam (also known as the Cross Cut Diversion Dam) and associated Cross Cut Irrigation Canal were constructed in 1938 by the U.S. Bureau of Reclamation (BOR) as part of its Minidoka Project. Under a November 16, 2007 Memorandum of Understanding established between the project owner and Fremont Madison Irrigation District, Fall River is allowed to utilize the Chester Diversion Dam for the purposes of producing hydroelectric generation. Fall River is responsible for paying all costs associated with the engineering, construction, operation and maintenance of the hydroelectric project.

Prior to the construction of the hydroelectric facility, the existing Chester Diversion Dam facility consisted of a concrete gravity dam, one radial gate on the south end of the diversion structure to control flows into the Cross Cut Irrigation Canal and an additional smaller radial gate on the north side of the diversion structure to control flows into the Last Chance Irrigation Canal. Construction of the hydroelectric facility began in 2009 and was completed in 2014.

The project includes: the Fremont Madison Irrigation District owned concrete dam with a crest length of 355 feet and a structural height of 17 feet; a 38-inch-high inflatable rubber dam bolted to the crest of the dam; a 355-foot-long overflow spillway; a flow control structure located on the south side of the dam, with a radial gate that controls flows into the Cross Cut Irrigation Canal; a flow control structure located on the north side of the dam with a radial gate that controls flows into the Last Chance Irrigation Canal; a 50-foot-wide concrete intake structure on the south side of the spillway; a sluiceway adjacent to the intake structure on the south end of the spillway; a 1.5-inch-spaced fish screen across the turbine intake and 0.25-inch-spaced fish screens across the entrances to both irrigation canals; Cross Cut Irrigation Canal headworks; Last Chance Irrigation Canal headworks; a concrete powerhouse with three Kaplan-type turbine generator units with a total installed capacity of 3.3 MW; and a concrete wall located immediately below the powerhouse that directs flow to the center of the Henrys Fork. The project boundary incorporates the Chester Diversion Dam, Chester Diversion Dam reservoir, lands associated with canal headworks, powerhouse, parking lot, upstream and downstream boat launches, and the primary transmission line.

Project Name Chester Diversion
LIHI Certificate No. 131
LIHI Certificate Term October 17, 2016 - October 17, 2024
Owner Fall River Rural Electric Cooperative
State Idaho
Location River mile 38.5 on the Henry’s Fork of the Snake River in Fremont County
Installed Capacity 3.3 MW
Average Annual Generation 16,800 MWh
Facility Type Run of River
FERC No. P-11879 issued 2008, expires 2048

The Project operates in a run-of-river mode and impounds a 55-acre reservoir. After irrigation needs are met, up to 3,500 cubic feet per second (cfs) are diverted into the powerhouse for generation. Any flows greater than both irrigation and power needs spill over the Chester Diversion Dam. The project provides a minimum flow of 25 cfs through the sluiceway to allow for downstream fish passage. The flow regime is monitored by the Henrys Fork Foundation and Idaho Department of Fish and Game to ensure fish and wildlife habitat protection.

Waters within the project reach are designated as riverine by the USFWS National Wetland Inventory. Designated uses in Idaho include agricultural water supply, cold water aquatic life, domestic water supply, primary contact recreation, wildlife habitat, and salmonid spawning. Four water quality monitoring stations owned by Fall River Rural Electric Cooperative track temperature, turbidity, and dissolved oxygen levels. Data from 2015 found no systematic change in these indicators and consultation with Idaho Department of Environmental Quality confirmed that the project is not impacting water quality.

The Henrys Fork of the Snake River supports a self-sustaining population of rainbow trout and is considered a ‘blue-ribbon’ fishery, an extremely high-quality recreational fishery. An upstream fish ladder provides riverine species (brown trout, mountain whitefish, Utah sucker, Utah chub, speckled dace, mottled sculpin, re-side shiner) access to upstream reaches of the river. Consultation with Idaho Department of Fish and Game in 2016 confirmed that the ladder is effective in providing upstream passage. Downstream fish passage is provided by the sluiceway with a 25 cfs passage flow. This flow regime is a standard downstream fish passage flow recommended by the National Oceanic and Atmospheric Administration. One and ¼ -inch intake screens mitigate the potential for downstream entrainment.

The project property consists of roughly 108 acres. Surrounding lands include heavily vegetated, flat shoreline and agricultural land, woody wetlands, and scrub shrub areas. Due to the nature of the shoreline, erosion risk is low. Boulder riprap revetment below the dam reinforces the bed and banks of the river, further mitigating erosion risk.

Threatened and endangered species potentially in the project property include: Ute ladies’ tresses, Bald Eagle, Yellowstone Cutthroat Trout. No impacts on the listed species are expected from project operations. Fish passage facilities allow for broader interconnectivity of the river, a feature that allows for increased sustainability of riverine species, especially the Yellowstone cutthroat trout. Special conditions were placed in the project license to mitigate any potential disturbance of bald eagle populations during construction of the project.

PLUS-Standard: The project owner developed a trout monitoring plan which includes conducting monitoring activities and preparing annual reports on resident trout populations. Size structure is monitored along with presence, absence, and spatial distribution of cutthroat trout within the project vicinity. The owner proactively funds these research studies and reporting.

Cultural and historic resources in the project vicinity include the dam and 22 sites related to the Cross Cut Irrigation Canal are eligible for listing in the National Register of Historic Places. A historic properties management plan for the project was developed in consultation with the State Historic Preservation Office (SHPO). The plan establishes the process for identifying the nature and significance of historic properties in the project reach and provides guidelines for routine maintenance, operation activities, improvements, and public access. Biennial reports were filed until the SHPO determined that the project has no adverse impact on cultural or historic resources.

Recreational resources at the project include a concrete boat ramp and fishing platform built to Americans with Disabilities Act Guidelines. Public access is provided free of charge.


Certification History

January 20, 2017: LIHI Executive Director, Shannon Ames, using authority delegated from the LIHI Governing Board, has issued a Preliminary Certification Decision that the Chester Diversion Hydroelectric Project (FERC No. P-11879) satisfies the LIHI Certification Criteria. The Chester Diversion project also qualifies for one PLUS standard due to its endangered species management efforts, earning an additional three years on the certification term.  The certification includes one facility-specific condition, as follows:

  • Condition 1.  the facility owner shall adhere to the timelines, monitoring, and study scopes for all aspects within the Trout Monitoring Plan related to restoration of Yellowstone cutthroat trout. In its annual compliance statement to LIHI, the facility owner shall summarize prior years’ progress with regard to the plan.  If any changes are made in that plan, LIHI shall be notified within 30 days of the finalization of such changes.

As provided for in Section 4.2.5 of the LIHI 2nd Edition Handbook, the Preliminary Certification Decision, along with the Application Reviewer’s report and (if prepared) report of the Executive Director, will be posted on the Institute’s Web page for 30 days.  Notice of the posting will be provided to all individuals or organizations that commented on the initial Application Package.

Any Commenter may submit a letter to the Executive Director requesting an appeal within the 30-day period.  The appeal request must state specific reasons why the hydropower facility should have failed one or more criteria.  Only individuals or organizations that commented on the initial Application Package may file an appeal.

If no appeal is requested within the 30-day period, the Executive Director will issue LIHI Certification for the facility and post a notification of certification on the Institute’s website.  Once final, the effective certification date for the Chester Diversion Project is October 17, 2016 for an eight (8) year term, which will expire on October 17, 2024.

October 20, 2016: On October 17, 2016, the Low Impact Hydropower Institute (LIHI) received a complete application from the Fall River Rural Electric Cooperative (Fall River), for the Low Impact Certification of the Chester Diversion hydroelectric project (FERC No. 11879), located on the Henry’s Fork of the Snake River in Fremont County, Idaho.

LIHI is seeking public comment on this application. Specifically, we are interested in knowing whether you think the Chester Diversion project meets the LIHI Low Impact Certification Criteria. The Chester Diversion application is subject to review using the Criteria in the 2nd Edition Certification Handbook of March, 2016.  Please review the program and criteria in LIHI’s 2016 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 comments@lowimpacthydro.org with “Chester Diversion 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 October 20, 2016.  Comments must be received at the Institute on or before 5 pm Eastern time on December 19, 2016 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.