LIHI Certificate #79 - Benton Falls Project, Maine

The Benton Falls project is located in the village of Benton, Maine on the lower reaches of the Sebasticook River. The area around Benton village and Benton Falls sits 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.

Upstream in the project area, some areas of glacial till are present. However, the nearly flat to gently rolling topography continues along the Sebasticook well north of the town of Benton.
The project is located 5.3 miles from the confluence of the Sebasticook and Kennebec Rivers. Within the watershed area, the west shore consists of thin beds of alternating greenish gray pelite and micaceous quartzite. The steep banks and riverbed include prominent outcrops, which periodically resurface upstream to the upper end of the project’s pool. The Sebasticook is bordered on both shores by bands of relatively steep (8 to 15 percent slope) silty loam. On the east and west shores north of the project, most of the river within the watershed area is bordered by gravel and clay. Lands near the river are primarily woodland, although some pasture and some hay land are included.

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 site. The project is operated as a run of river plant. The downstream release through the turbine-generators plus the excess spill over the dam equals the inflow to the reservoir.  Streamflows at the project site are based on daily flow data recorded at U.S. Geological Survey (USGS) surface water Stream Gauging Station No. 01049000. The gauge is located approximately 14 miles upstream of the project site in Pittsfield, Maine, and has a period of record extending back to 1929.  The Benton Falls Project works consists of: (1) a 500-foot long, 27-foot high concrete gravity dam with a 300-foot long integral uncontrolled spillway topped by 4-foot high flashboards; (2) a powerhouse located near the west dam abutment, constructed integrally with the dam, containing two turbine generators with a total rated capacity of 4.468MW; (3) a 350-foot long tailrace channel; (4) the 4.16-kV generator leads, 4.16/12-kV step-up transformers and a 170-foot long, 12-kV transmission line; and (5) a fish lift which contains a 600-gallon hopper and a minimum cycle time of approximately seven minutes.

The project discharges a continuous minimum flow of 100 cfs from the Benton Falls Project of the inflow to the reservoir, whichever is less, for the purpose of protecting fish and wildlife resources and water quality of the Sebasticook River.  Construction of the Benton Falls project was completed in 1984. The powerhouse contains two turbine generators with a total rated hydraulic capacity of 2115 cfs under a gross head of 29.5 feet. The project utilizes all of the available head and about 79% of the streamflow.

FERC licensed the Benton Falls project without requiring fish or eel passage facilities. On January 25, 1989, as part of the Kennebec Hydro Developers Agreement (“the KHDG Agreement”), the Applicant’s FERC license was amended to require installation of upstream and downstream fish passage facilities.

Both upstream and downstream fish passage facilities were installed in 2006. The upstream fish passage facility consists of an elevator designed to pass alewives, shad and salmon. The downstream fish passage facility consists of two conduits that maintain a minimum flow of 350 cfs or project inflow that bypass the turbines. The upstream and downstream facilities became operational in the spring of 2006 and now have operated during five upstream and downstream fish migration seasons. These facilities have been highly successful. A record 1,319,137 alewives were transported upstream during the 2009 migratory season using the fish elevator. An even greater number were transported during the 2010 upstream migration season.

Layout and landscaping of the powerhouse grounds was designed in a manner to minimize visual impact and mitigate that project’s impact on the surrounding shoreline. As a condition of issuance, the FERC License requires that BFA comply with any terms and conditions that the Federal or State fish and wildlife agencies have determined appropriate to prevent loss of, or damage to, fish and wildlife resources. There have been no deficiencies noted by any agency with jurisdiction for the plant.
Project Name Benton Falls
LIHI Certificate No. 79
LIHI Certificate Term November 23, 2015 - November 23, 2020, extended to May 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 4.468 MW
Average Annual Generation 15,500 MWh
Facility Type Run-of-river
FERC No. P-5073 issued 1984, expires 2034

Certification History

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.