LIHI Certificate #147 – Brooklyn Dam Project, New Hampshire

The Brooklyn Dam Project (Project) is owned by Ampersand Brooklyn Dam Hydro LLC and located on the lower section of the Upper Ammonoosuc River in Northumberland, Coos County, NH. between the Red Dam, located about 0.8 miles upstream and the Weston Hydropower Project, located about 0.7 miles downstream.

The Upper Ammonoosuc River is separate from the Ammonoosuc River of the White Mountains. The Upper Ammonoosuc River discharges to the upper Connecticut River approximately 3.2 miles downstream of Brooklyn Dam. The upstream Red Dam originally was a second development of the FERC license that included the Brooklyn Dam Project. The Red Dam is no longer used for power production and is not part of the current FERC license exemption for the Project.

The dam was constructed in 1912 to provide hydro-mechanical power to local textile mills. In 1930, hydroelectric generation facilities were installed at the Project to provide power to the Groveton Paper Mill and it operated as a hydropower facility until 1969 when the turbines and generators were removed. It was purchased by Ampersand in 2013 for redevelopment and re-entered service in December 2015. The Project has a capacity of 600 KW and average annual generation of 2,405 MWh.

The Project includes a 120-foot-long, 14-foot-high timber crib dam. Adjacent to the dam is a 43-foot-long floodgate structure with four 6.9-foot-wide, 10-foot-high floodgates. With the existing 2.50-foot-high flashboards installed, the dam creates a 26-acre impoundment with a normal water surface elevation of 881.23 feet NGVD1929. The impoundment volume is 51.85 acre-ft (minimum) and 52.15 acre-ft (maximum). The Project includes a 100-foot-long, 45-foot-wide forebay, with three 15.2-foot-wide, 15.5-foot-high trash racks with 1-inch clear-bar spacing. There is an approximate 100-foot-long bypass from where water spills over the dam to where it merges with the tailrace.

When operating, water passes through the trashracks and forebay structure into the powerhouse which contains two new 300-kW Kaplan turbine generating units. Each turbine has a minimum hydraulic capacity of 33 cubic feet per second (cfs) and a maximum hydraulic capacity of 315 cfs. At flows less than 33 cfs, the Project will not operate and all flow passes over the spillway or flashboards. At flows between 33 cfs and 630 cfs (the maximum operating capacity of the Project), the Project will operate and no flow will pass over the spillway. At flows greater than 630 cfs, the Project will operate at its maximum capacity with excess flows passing over the spillway.

Turbine discharge is to a 48-foot-long, 45-foot-wide tailrace. Power is transmitted through a new 100-foot-long, 480-volt underground transmission line connecting the powerhouse electrical panel to three new single-phased transformers. A new 300-foot-long, 35.4-kilovolt above-ground transmission line transmits power from the transformers to the regional distribution grid.

Project Name Brooklyn Dam
LIHI Certificate No. 147
LIHI Certificate Term June 4, 2018 - June 3, 2023
Owner Ampersand Brooklyn Dam Hydro LLC
State New Hampshire
Location River mile 3.2 on the Upper Ammonoosuc River in Northumberland, Coos County
Installed Capacity 600 KW
Average Annual Generation 2,405 MWh
Facility Type run-of-river
FERC No. P-13806 exempt 2015

Certification History

February 12, 2019: The decision to certify the Brooklyn Dam Hydroelectric Project is final. No appeals were received during the appeal period which closed on February 10, 2019. The certification term for the Project is from June 4, 2018 through June 3, 2023. The certificate includes the following conditions:

  • Condition 1: The facility Owner shall submit quarterly reports to LIHI by the end of the month following the calendar quarter (e.g., April 30, July 31, October 31, January 31), with information sufficient to confirm run-of-river operations, adherence to impoundment refill rates, and related agency communications for the prior calendar quarter. Any requests made by the Owner for modifications to operations or refill rates, agency approvals of such modifications, copies of notifications to FERC and NHDES of any OCMP deviations, and copies of annual OCMP deviation reports to NHDES shall also be provided to LIHI with these reports.
  • Condition 2:The facility Owner shall submit to LIHI the NHDES review and comment on the 2018 water quality monitoring results within 60 days of receipt. The Owner shall consult with NHDES and USF&WS on the need for additional sampling in 2019 and 2020 and file with LIHI the results of that consultation by July 31, 2019. If additional sampling is not required by NHDES and USF&WS, the Owner should evaluate the need to file with FERC a request for amendment to the exemption to remove the requirement for additional sampling and, if applicable, provide a copy of the request and any subsequent FERC approval to LIHI when available. If minimum flows into the bypass reach are required, LIHI shall be provided with all relevant information and agency communications within 60 days of receipt.

January 11, 2019: On January 10, 2019, the Low Impact Hydropower Institute (LIHI) preliminarily approved Low Impact Certification for the Brooklyn Dam Hydroelectric Project.

This decision is preliminary pending the 30-day appeal window. Only those who commented on the initial application during the 60-day comment period are eligible to file an appeal. Such appeal needs to include an explanation as to how the Project does not meet the LIHI criteria. Appeal requests can be submitted by email to with “Brooklyn Dam 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 the website.  The applicant will have an opportunity to respond and any response will also be posted. Requests must be received by 5 pm Eastern time on February 10, 2019.  The full application and reviewers report are available below.

If no appeal requests are received and the decision becomes final, the Certification term for the Project (pending LIHI #147) will be June 4, 2018 through June 3, 2023.

October 26, 2017: On October 26, 2017, the Low Impact Hydropower Institute (LIHI) received a complete application from Ampersand Brooklyn Dam Hydro LLC for the Low Impact Certification of the Brooklyn Dam Hydroelectric Project, FERC Exempt No. P-13806, located on the Upper Ammonoosuc River, near Northumberland, in Coos County, New Hampshire.

LIHI is seeking comment on the Brooklyn Dam application for certification. 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 “Brooklyn Dam Project Comments” in the subject line, or by mail addressed to the Low Impact Hydropower Institute, 329 Massachusetts Avenue, Suite 2, Lexington, MA 02420.  Comments must be received at the Institute on or before 5 pm Eastern time on December 26, 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.