LIHI Certificate #79 - Benton Falls Project, Maine

The Benton Falls Project is located on the Sebasticook River in Benton, Maine. The Sebasticook River is a tributary to the Kennebec River. The project is the first dam on the river, located 5.3 miles from the confluence of the Sebasticook and Kennebec Rivers. The Burnham Dam project is located upstream of the project in Pittsfield, ME.

The Sebasticook River has a drainage area of 975 square miles and is the largest subbasin of the Kennebec River System. Almost 90 percent of the total drainage area (860 miles) is upstream of the project. The current dam was completed in1984. It is on the same site as a previous dam that was destroyed by flooding in 1936.

Project works consists of a 500-foot long, 27-foot high concrete gravity dam with a 300-foot long integral uncontrolled spillway topped by 4-foot high flashboards; a powerhouse located near the west dam abutment, constructed integrally with the dam, containing two horizontal Kaplan turbine/generators with a total rated capacity of 4.468MW; and a 350-foot long tailrace channel; and a fish lift which contains a 600-gallon hopper and a minimum cycle time of approximately seven minutes.

The project operates in a run-of-river mode and impounds an 84-acre reservoir. There is no bypassed reach. Instantaneous run-of-river operations help to protect fish and wildlife resources as well as water quality in the river. A pressure transducer is utilized to monitor water surface elevation and ensure river inflow to the project matches outflow.

Waters within the project reach are designated as Class C, attaining uses such as aquatic biota habitat and secondary recreation. Water quality sampling was conducted in 2017 to determine project impacts on the river system. Maine Department of Environmental Protection concluded that no adverse impacts were being realized due to project operations.

Project Name Benton Falls
LIHI Certificate No. 79
LIHI Certificate Term November 23, 2015 - November 23, 2020, extended to October 31, 2021
Owner Benton Falls Associates
State Maine
Location Located at river mile 5.3 on the Sebasticook River in the village of Benton, Maine
Installed Capacity 4.33 MW
Average Annual Generation 14,963 MWh
Facility Type Run-of-river
FERC No. P-5073 issued 1984, expires 2034

The Sebasticook River is host to several migratory fish species. The upstream fish passage facility consists of an elevator designed to pass alewives, shad, and Atlantic salmon. The downstream fish passage facility is designed to pass all species and consists of a surface bypass system (two 3-foot wide intakes leading to transition chamber and then a 24-inch bypass pipe with a total capacity of 30 cfs). The upstream and downstream fish passage facilities became operational in the spring of 2006 and have been highly successful. In 2020, the fish lift was in operation from May 7th to June 30th and passed 2,847,171 river herring and 10 shad. No Atlantic salmon were observed passing the fish lift. 1,304 American eels were counted using the upstream eel ladder. The project owner is currently collaborating with Maine Department of Marine Resources to monitor the effectiveness of the eel passage facility using sonar to record eel species movement and success in traversing the passage facility.

The project lands consist of 27 acres. Benton Village and Benton Falls sit in a broad valley cut through deep marine and lacustrine deposits of gravel, sand, silt, and clay surficial deposits. The generally flat or gently rolling topography of the valley is cut by the steep gully banks of the Sebasticook River. The steep banks and riverbed include prominent outcrops, which periodically resurface upstream to the upper end of the project’s pool. The Sebasticook River is bordered on both shores by bands of relatively steep (8 to 15 percent slope) silty loam. Lands near the river are primarily woodland, with agriculture, residential and small commercial uses. Run-of-river operations mitigate any project impact on the surrounding shoreline.

Threatened or endangered species potentially present in the project vicinity include Atlantic salmon and the Northern long-eared bat. This species is likely only transient in the project area and no critical habitat for the species exists in the project reach. State-listed species include three species of freshwater mussels and seven additional bat species. Run-of-river operations are unlikely to affect mussels, and any tree cutting needed would be conducted in accordance with the US Fish and Wildlife Service 4(d) rule.

Several archaeological sites exist in the project area; thus, a cultural resources management plan was implemented. Erosion monitoring was conducted over a span of twenty years to ensure that project operations would not adversely impact these sites. The Maine Historic Preservation Commission has concluded that the project does not cause any significant erosional damage.

Recreational resources at the project include a canoe portage, fishing access, and boat launch. These recreational opportunities were developed in collaboration with US Department of the Interior, Maine Bureau of Parks and Recreation, and the Town of Benton, Maine. As a result of the successful fish restoration program, the Maine Department of Marine Resources issued an alewife harvesting permit to the Town of Benton. The project owner has a cooperative agreement with the town to use project lands to harvest alewives that are surplus to the state’s upstream migration goals. Public access is provided free of charge.


Certification History

October 5, 2021: The Low Impact Hydropower Institute (LIHI) has received a complete recertification application from Benton Falls Associates, LP for the Benton Falls Project located on the Sebasticook River in Maine.

LIHI is seeking comment on this application. 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 LIHI by e-mail at comments@lowimpacthydro.org with "Benton Falls Project Comments” in the subject line, or by mail addressed to the Low Impact Hydropower Institute, 1167 Massachusetts Avenue, Office 407, Arlington, MA 02476. Comments must be received at the Institute on or before 5 pm Eastern time on December 4, 2021 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 project description and complete application can be found below.

June 6, 2016: LIHI Executive Director Michael J. Sale, using authority delegated from the LIHI Governing Board, has certified that the Benton Falls Hydroelectric Project (FERC No. P-5073) satisfies the LIHI Certification Criteria.  A Preliminary Certification Decision was announced on May 4, 2016, and a 30-day appeal period was open through June 5, 2016. No requests for appeal were received. This Certification Decision includes three facility-specific conditions, as follows:

  • Condition 1.  If resource management agencies (MDMR, MIFWS, USFWS and/or NMFS) determine that a sufficient number of Atlantic Salmon and/or American Shad have been passed upstream of the facility, or other appropriate trigger has occurred, the Owner shall conduct fish passage effectiveness studies to demonstrate that Atlantic Salmon and/or American Shad are being safely passed downstream of the facility during outmigration.  The Owner shall notify LIHI within 30 days of when the applicable resource agency(ies) determine that such fish passage effectiveness testing is required.  The Owner shall then consult with the agencies in the design and implementation of these studies, allowing the agencies to participate in the testing if they so desire.  The Owner shall provide LIHI the testing results along with an assessment made by the agencies as to whether or not they find that safe and effective passage is being provided by the current downstream passage methods. This condition can be satisfied by providing LIHI with a copy of the annual Fish and Eel Passage Facility Operating Report and Proposed Operating Plan, as long as appropriate data and agency positions regarding fish passage are contained in that report.
  • Condition 2.  As part of the Annual Compliance statement to LIHI, the Owner should include documentation of ongoing consultation with NMFS regarding Atlantic Salmon pursuant to the Endangered Species Act. The schedule for these ESA consultations shall be set through agreement of the Owner and NMFS.  LIHI shall be notified of this schedule within 30 days of its establishment. LIHI shall also be provided a copy of any studies or authorizations issued during the course of this certification period on this issue.
  • Condition satisfied 2017. Condition 3.  To contribute to water quality management on the lower Sebasticook River, the owner shall implement a MEDEP-approved water quality sampling plan that evaluates the role of Benton Falls dam and impoundment in the nonattainment status of the river and report back to LIHI and MDEP on the findings. In addition to new water quality data, the Owner shall describe other point-source discharges in the vicinity of the facility to provide context for the facility’s potential effects.  The owner shall obtain a letter from MDEP on their assessment of whether or not the Benton Falls facility is the cause of the nonattainment status, and submit that letter to LIHI within 30 days of its receipt.

The effective certification date for the Benton Falls Project is November 23, 2015 for a five (5) year term, which will expire on November 23, 2020.

November 12, 2015: The Low Impact Hydropower Institute has received a complete application for a new term of Low Impact Certification for the Benton Falls Hydroelectric project.  The application materials can be found in the Files section below.

The public comment period for this application closed on January 11, 2015.

October 31, 2011: The Benton Falls Hydroelectric Project has been certified as low impact for a five year term, effective November 23, 2010 and expiring November 23, 2015.

November 23, 2010: Benton Falls Associates has submitted an application for certification of the Benton Falls Hydroelectric Project. A public comment period on the application will remain open for 60 days.