LIHI Certificate #118 – Webster Pembroke Project, New Hampshire

Project Name Webster Pembroke
LIHI Certificate No. 118
LIHI Certificate Term
February 23, 2020 – February 22, 2030
Owner Pembroke Hydro Associates Limited Partnership, a subsidiary of Eagle Creek Renewable Energy, LLC
State New Hampshire
Location Located at River Mile 34.25 on the Suncook River in New Hampshire.
Installed Capacity  2.6 MW
Average Annual Generation 10,100 MWh
Facility Type Run-of-river
FERC No. P-3185 exempt 1983

The Webster Pembroke Project is located on the Suncook River near Pembroke, New Hampshire. The river runs from the outlet of Crystal Lake in Gilmantown, New Hampshire to its confluence with the Merrimack River in the town of Suncook. The Suncook River flows from a northeast to southwest direction, with a total contributing drainage area of 270 square miles.

The river experienced heavy flooding in 2006 and again 2019 establishing a new route in several areas and resulting in the largest channel change in a New Hampshire river in systematic topographic mapping history.

The project consists of two dams, the Pembroke dam and Webster dam, originally constructed in 1860 and 1917, respectively, to harness hydromechanical power to produce cloth. The buildings were closed in the early 1900s and all hydroelectric equipment was removed. The mill buildings were converted to apartments. In the 1982, the Pembroke Hydro Corporation was issued a FERC exemption to redevelop the hydroelectric project.

The closest upstream dam is the Pittsfield Mill Dam, roughly 16 miles upstream, while the China Mill Dam is located just downstream of the project, roughly 0.5 miles. More than a dozen dam sites line the Suncook River, built for varying industrial uses.

The Webster dam is a concrete gravity dam, 250 feet long and 13 feet tall topped with 4-foot-high pneumatic rubber bladder gates. Pembroke Dam is a stone masonry dam, 18 feet tall and 77 feet long with two spillway sections at right angles with one perpendicular to river flow.

The Pembroke dam is located 1,800 feet downstream of the Webster dam, and the powerhouse is adjacent to the Pembroke dam. A 500-foot-long, 14-foot-deep, and 24-foot-wide concrete power canal leads to an intake with a 460-foot-long, 8-foot-diameter steel penstock that runs under Mill Falls Road and into a concrete casing adjacent to Pembroke dam which conveys water to the powerhouse. A 170-foot-long, 20-foot-wide stone masonry sluiceway at the terminus of the canal leads back to the river. The powerhouse contains one horizontal Voith Kaplan turbine/generator with a capacity of 2.6 MW.

The project operates in a run-of-river mode and impounds a 26-acre reservoir. The project provides a minimum flow of 25 cfs into the 0.28-mile-long bypass reach formed by Webster dam to ensure the protection and enhancement of fish and aquatic habitat. This flow regime was developed based on flow demonstrations conducted with the US Fish and Wildlife Service (USFWS). An additional 5 cfs is released through the canal’s waste gate during downstream fish migration season.

Waters within the project reach are designated as Category 2-G, suitable for drinking water after treatment. High levels of mercury warrant a 4A-M classification as well, indicating that fish consumption could be harmful. Consultation with the New Hampshire Department of Environmental Services concluded that the project does not have an adverse impact on water quality in the river.

Historically, the Suncook River supported migratory species including river herring, American shad, Atlantic salmon, and American eel. River connectivity restoration efforts in the Suncook River currently focus on river herring and American eel. The downstream China Mill Dam creates a barrier for upstream passage at the project, for species other than eel.

Prior to downstream passage season, the project owner consults with US Fish and Wildlife Service (USFWS) to evaluate measures for passage at the project. In 2016, these efforts resulted in collaboration on a design to accommodate downstream herring passage when the Suncook River watershed is stocked by New Hampshire Department of Fish and Game with surplus herring. In these cases, the project installs boards across the channel outlet under the bridge to create a plunge pool and discharge chute on the downstream side of the wastegate located adjacent to the trashracks at the end of the canal. These facilities are temporary in nature, as high flows and debris passage operations at the site typically destroy the features in some years and are then rebuilt for years when stocking occurs.

The project lands consist of roughly 4 acres. Most of the lands surrounding the project are medium to heavily developed, including business and residential development. Roads run parallel to the Suncook River on both sides within the extent of the project area and the banks are extremely steep and composed of boulders and bank revetment. Portions of the riverbanks have been rip-rapped in response to flood events. The project reach is highly sensitive to flooding. No lands of significant ecological value exist in the project area.

Threatened or endangered species potentially present in the project vicinity include the Northern long-eared bat and small whorled pogonia. Due to the urban nature of the project area, it is unlikely that either of these species is found on project lands. The pogonia is an upland forest species. The project adheres to the USFWS 4(d) rule for the bat species and restricts tree cutting to avoid removing roost trees.

Historic resources in the project area include the Pembroke Dam, which is a contributing feature of the Pembroke Mill, a property listed in 1985 on the National Register of Historic Places. The dam is being partially removed based on recommendation from the New Hampshire Dam Safety Bureau. High flow conditions over the last decade have caused overtopping of the dam’s right abutment. The partial dam removal proposal triggered consultation with the State Historic Preservation Office resulting in mitigation measures including photo-documentation of the dam, interpretive signage, and interpretive banners to be placed along the bridge over the dam to convey the milling history of the area.

Recreational resources at the project include informal fishing and boating. The downstream Memorial Field provides recreation resources including a boat launch. The Twin Oaks campground is located upstream of the project. Public access is provided free of charge where public safety does not preclude access.

Compliance Status

The Certificate includes the following facility-specific conditions:

  • Condition partially satisfied in 2022 Condition 1: The facility Owner shall provide the revised Operations and Flow Monitoring Plan and the amended or extended USFWS MOA within 90 days of finalization of each document with resource agencies. This portion still active: Any changes in operations or required fish passage measures shall be reported to LIHI in annual compliance submittals.
  • Condition fully satisfied in 2023, partially satisfied in 2020. Condition 2: The facility Owner shall report to LIHI on the status and completion of the partial dam removal and mitigation measures under the SHPO MOA in annual compliance submittals until all work is completed and approved by the SHPO and FERC.

2024: No material changes or compliance issues were identified. The project remains in compliance based on the annual review.  For Condition 1, the project submitted documentation of USFWS approval of an upstream eel ladder, to be installed in 2024.

2023: No material changes or compliance issues were identified. The project remains in compliance based on the annual review.  For Condition 2, the project demonstrated completion of mitigation measures required under the SHPO MOA, thus satisfying the condition.  Based on the 2022 upstream eel passage study, permanent upstream eel passage will be designed in 2023.

2022: No material changes or compliance issues were identified. The project remains in compliance based on the annual review. For Condition 1, the project reported the USFWS MOA was executed in early 2022 with a revised Operations, Flow Monitoring and Fish Passage Plan. Night time surveys for upstream passing American eel were conducted in 2021 and interim trapping is planned for 2022, thus satisfying the conditon. For Condition 2, the project reported that the SHPO mitigations were delayed but expected to be completed in 2022.

2021: For Condition 1, the project reported a 2020 site visit with resource agencies, and agreement to delay finalization of the flow monitoring plan and MOA into 2021. For Condition 2, the project reported completion of the partial dam removal in 2020 with FERC approval of the final construction report in 2021, and SHPO mitigations (interpretive signage) scheduled for completion in 2021. The project remains in compliance based on the annual review.

2020: Annual reporting for the current Certificate has not yet taken effect.

Certification History

January 1, 2022: The LIHI Certificate term has been extended in accordance with Revision 2.05 of the LIHI 2nd Edition Certification Handbook issued January 1, 2022. Refer to the facility table above for the new term.

September 14, 2020: The decision to recertify the Webster-Pembroke Project became final after the close of the appeals period on September 5, 2020 with no appeals filed. The Certification term is from February 23, 2020 – February 22, 2025.

August 6, 2020:The Low Impact Hydropower Institute (LIHI) has preliminarily approved the Webster Pembroke Project (LIHI #118) for a new 5-year term of Low Impact Certification. 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 “Webster Pembroke Project” in the subject line, or by mail addressed to the Low Impact Hydropower Institute, 329 Massachusetts Ave, Suite 6, 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 September 5, 2020. The full application and reviewer’s report are available below.
If no appeal requests are received and the decision becomes final, the Certification term for the Project will be February 23, 2020 through February 22, 2025.

May 19, 2020: The Low Impact Hydropower Institute has received a complete application for Low Impact recertification of the Webster Pembroke Hydroelectric Project.   The complete application can be found below. LIHI is seeking public 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 the Institute by e-mail at with “Webster Pembroke Project Comments” in the subject line, or by mail addressed to the Low Impact Hydropower Institute, 329 Massachusetts Avenue, Suite 6, Lexington, MA 02420.  Comments must be received on or before 5 pm Eastern time on July 18, 2020 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.

May 11, 2015 – Executive Director Michael J. Sale, using authority delegated from the LIHI Governing Board and a full review of the Application Reviewer’s report and all public comments and additional materials provided by the Applicant, has determined that the Webster Pembroke Hydroelectric Project (FERC No. 3185) satisfies the LIHI Certification Criteria. The effective certification date for the Webster Pembroke Project is February 23, 2015 for a five (5) year term, which will expire on February 23, 2020, with the following conditions:

  • Condition Satisfied in 2018. Condition 1: Facility owner shall complete the agreed upon water quality sampling in 2015, receive satisfactory determination from New Hampshire Department of Environmental Services (NHDES) that facility does not negatively impact water quality, and provide results to LIHI by December 31, 2015.
  • Condition Satisfied in 2017. Condition 2: Facility owner will comply with updated fish passage installation plants in 2015 as specified in the MOA with USFWS, obtain written approval of any required modifications, and report results to LIHI by December 31, 2015.
  • See 2020 Condition 2. Condition 3: Facility owner will perform bypass flow study in consultation with USFWS and NHFG in 2015 and provide results to LIHI by December 31, 2015.
  • Condition Satisfied in 2018. Condition 4: Facility owner will complete the Operations and Flow Monitoring Plan as required by MOA, obtain written approval by USFWS, and provide results to LIHI by December 31, 2015.

February 25, 2015 – The Low Impact Hydropower Institute (LIHI) received a timely and complete application on February 23, 2015 from Eagle Creek Renewable Energy LLC, for the Low Impact Certification of the Webster Pembroke Project, FERC P-3185.

Certification Files

2020 Recertification

2015 Certification

Key Documents