LIHI Certificate #39 - Fifteen Mile Falls Project, Vermont and New Hampshire

The Fifteen-Mile Falls Project is located on the Connecticut River in Grafton County, New Hampshire and Caledonia County, Vermont. The project is comprised of three developments – Moore, Comerford, and McIndoes. Comerford and McIndoes were constructed in the early 1930s, Moore was added later in 1956.

In August 1997, a dozen organizations signed a settlement agreement intended to address a number of objectives, including water quality improvements, habitat enhancement for terrestrial and aquatic biota, wetlands protection, cultural resource preservation, and more. The signatories to the Settlement Agreement (SA) included New Hampshire Fish and Game, New Hampshire Department of Environmental Services, Vermont Agency of Natural Resources, United States Fish and Wildlife Service, United States Environmental Protection Agency, National Park Service, Appalachian Mountain Club, Connecticut River Joint Commissions, Connecticut River Watershed Council (now Connecticut River Conservancy), New Hampshire Rivers Council, North Country Council, Northeastern Vermont Development Association, and New Hampshire Council of Trout Unlimited.

The project includes three developments, from upstream to downstream:

  • The Moore development impounds an 11-mile-long reservoir with a surface area of 3,490 acres. The dam is an earth and concrete gravity structure with an overall length of 2,920 feet and a height of 178 feet. It has a 373-foot-long concrete spillway with a 15-foot-wide by 20-foot-high sluice gate, four 50-foot bays of 17-foot-high stanchions, and three bays of 36-foot-wide by 30-foot-high Tainter gates. Four steel penstocks, each 296 feet long, convey flows to the integral powerhouse with four Francis type turbine-generator units having a total installed capacity of 192 MW, making it the largest conventional hydroelectric plant in New England.
  • The Comerford development impounds an 8-mile-long reservoir with a surface area of 1,093 acres. The earth and concrete gravity dam has an overall length of 2,253 feet and a height of 170 feet. It has an 850-foot-long concrete spillway with six 7-foot-wide by 9-foot-high sluice gates, four bays of 8-foot-high flashboards and seven 10-foot-high stanchion bays. Four steel penstocks, each 150 feet long, convey flows to the integral powerhouse with four Francis type turbine-generator units having a total installed capacity of 164 MW.
Project Name  Fifteen Mile Falls
LIHI Certificate No. 39
LIHI Certificate Term December 15, 2013 - December 14, 2021
Owner Great River Hydro, LLC
State New Hampshire, Vermont
Location Dams are located between river mile 268.6 and 83.5 on the Connecticut River in Grafton County, New Hampshire and Caledonia County, Vermont.
Installed Capacity 291.2 MW
Average Annual Generation 729,089 MWh
Facility Type Store-and-release
FERC No. P-2077 issued 2002, expires 2042
  • The McIndoes development impounds a 5-mile-long reservoir with a surface area of 543 acres. The concrete gravity dam has an overall length of 730 feet and a height of 25 feet. It has a 520-foot-long concrete spillway with a 12-foot-wide by 13-foot-high skimmer gate, three 24-foot-wide by 25-foot-high Tainter gates, a 300-foot-long spillway flashboard section with 6-foot flashboards, and two 50-foot-wide by 18-foot-high stanchion bays. The integral powerhouse has four Kaplan type turbine-generator units with a total installed capacity of 10.5 MW. McIndoes regulates flow from Comerford.

The project operates in a store-and-release mode. Reservoir fluctuation limits vary by development but during spawning season (May 21-June 30), the developments limit fluctuations to 2 feet to enhance spawning conditions. The developments also provide minimum flow releases that vary seasonally. Moore provides 320 cfs into the tailrace year-round. Comerford provides releases into the tailrace of 818 cfs from June 1 to September 30, 1,145 cfs from October 1 to March 31, and 1,635 cfs from April 1 to May 31. McIndoes provides 1,105 cfs into the tailrace from June 1 to September 30, 2,210 cfs from October 1 to March 31, and 4,420 cfs from April 1 to May 31 to support spring fish spawning and incubation. This flow regime was developed in collaboration with the signatories to the SA and incorporated into the project’s FERC license based on those recommendations.

The Connecticut River forms the boundary between New Hampshire and Vermont. Thus, the two states agreed on a coordinated approach concerning water quality and issued a single water quality certificate for the project that addresses the interests of both states. The waters in the project reach are all listed for mercury and pH impairment. Mercury impairment is likely caused by atmospheric deposition from in-state and out-of-state sources. The project conducts water quality monitoring at five-year intervals of mercury in fish tissue. State fish consumption advisories are posted based on the monitoring results.

Downstream passage is no longer provided for Atlantic salmon smolts since the Connecticut River salmon restoration program ended. Upstream fish passage is not currently provided at the project. A triggering provision was included in the SA noting that the presence of 20 migrating adult salmon at the downstream East Ryegate Dam for two consecutive years would require upstream passage for Atlantic salmon. An American eel passage plan is ready to be implemented to provide upstream passage, if deemed necessary by resource agencies.

The project lands consist of 6,918 acres of open land around the project developments which has been protected in perpetuity under the terms of 2 separate conservation agreements. Additionally, the project established the Upper Connecticut River Mitigation and Enhancement Fund to mitigate the impacts of project operations. Funds are used to finance river and wetland restoration, protection and enhancement, acquisition of conservation easements, and mitigation of tax revenue impacts to nearby communities. A wildlife and forest management plan has been implemented at the project which provides guidance on protection of the scenic, forestry, and natural resources values of project lands.

PLUS-Standard: The project owner has contributed over $21 million to the Fifteen Mile Falls Enhancement Fund. Grants have provided for the protection of 3,122 acres of upland forest, farmland, wetland, riparian buffer, and river land representing well over 50% of the project’s developed and undeveloped shorelines.

Threatened or endangered species potentially present in the project vicinity include bald eagle, osprey, and dwarf wedgemussel. The project has developed a land management plan, in consultation with US Fish and Wildlife Service (USFWS), which integrates a threatened and endangered species management plan to ensure project operations do not adversely impact listed species. The dedication of several thousand acres to conservation easements contributes to these mitigation efforts and help to protect eagle and osprey roosting sites. USFWS noted that project operations do not impact dwarf wedgemussel populations.

Historic properties include each of the development’s dams and powerhouses. Additionally, there are several archaeological sites at the Moore and McIndoes developments. A cultural resources management plan was implemented at the project, based on consultation with the State Historic Preservation Office, to ensure proper stewardship of these resources.

Recreational resources at the project include a variety of fishing access points, picnic/day use areas, swimming areas, canoe portages, and boat ramps at each development. The McIndoes development has two camping areas and hiking trails. Public access is provided free of charge.


Certification History

January 24, 2017: Having reviewed information provided by the applicant as required in Condition 3 (text below), LIHI's Executive Director has determined that Condition 3 is satisfied and Fifteen Mile Falls has earned an additional three years of Certification term. The Certificate term is therefore December 15, 2013 through December 14, 2021. (The decision letter is posted below under Files.)

May 15, 2016: LIHI has received notice that TransCanada Hydro Northeast Inc. was converted to a limited liability company on April 7, 2017, becoming TransCanada Hydro Northeast LLC.  On April 19, 2017, the name of the company was changed from TransCanada Hydro Northeast LLC to Great River Hydro, LLC.

July 10, 2015: Executive Director Michael J. Sale, using authority delegated from the LIHI Governing Board, has determined that the Fifteen Mile Falls Hydroelectric Project (FERC No. P-2077) continues to satisfy the LIHI Certification Criteria. The effective certification date for the Fifteen Mile Falls Project is December 15, 2013 for a five (5) year term, which will expire on December 15, 2018, with the following conditions:

  • Condition satisfied 2016. Condition 1:Pertaining to the trap and truck operation for downstream passage of Atlantic salmon smolts stocked upstream of the Moore Dam, the facility owner shall remain in full compliance with its FERC license and the associated Settlement Agreement (SA) and Water Quality Certificate. If the licensee requests to amend the FERC license or the WQC, or reopen the SA, with regard to use of this operation, the facility owner shall notify LIHI within seven days, including a description of the proposed changes and schedules for pursuing them. LIHI shall also be provided a copy of any amendments, along with resource agency comments, to confirm continued compliance with LIHI’s criterion.
  • Condition 2: As part of the required annual Compliance Statement to LIHI, the facility owner shall identify any violations of FERC operating requirements and will include copies of all agency and FERC notifications and reports of deviations of said operating requirements that have occurred in the previous year. This report shall be submitted by March 31 for the previous year’s events. This report shall reference and include copies of all notifications made to the FERC during the previous year. Unless otherwise included in the FERC notifications themselves, the report to LIHI shall describe for each instance:
    1. The cause of the event/deviation;
    2. The date, duration and magnitude of the deviation;
    3. Confirmation that the required 24-hour notices have been made to NHDES and VTDEC of such events (list the date of and to whom all notifications were sent);
    4. Ways to minimize future repeat occurrences to the extent possible by the Licensee;
    5. Any proposed mitigation measures and a schedule by which such measures will be implemented; and
    6. Status or confirmation that the previously developed mitigation measures (for the previous year) have been implemented according to the proposed schedule.
    The owner shall maintain a proactive approach to reducing the frequency and severity of such deviations to the extent reasonably possible. LIHI shall be informed of the capital improvement projects that are underway and planned for the future to minimize the occurrence of deviations or plant outages. The annual compliance report to LIHI will be used as confirmation that the facility owner is conducting the necessary actions to minimize such events and ensure compliance with LIHI’s flow and water quality criteria.
  • Condition satisfied 2018, extended term granted. Condition 3:The facility owner shall provide LIHI with a description of the current status and use of funds from the Mitigation and Enhancement Fund that was part of the Settlement Agreement for the most recent FERC licensing.  In particular, this description shall identify the lands and waters that are benefiting from the funds, the current fund balance, and continuing payment schedule, and be sufficient to determine if these funds are achieving the ecological and recreational equivalent of land protection of the buffer zone referred to in Question D.1.  This information will be used by LIHI staff to determine if the Fifteen Mile Falls certification qualifies for three additional years in its term.  The facility owner may or may not take advantage of this opportunity to request an extended term of their new certificate; if they do not provide this additional information, it will not affect the new five-year term.

January 27, 2014: The Low Impact Hydropower Institute has received an application from TransCanada for a second term of certification of the Vernon Station Hydroelectric Project. The 2013 application was received on December 5th, but due to administrative backlog, the certificate has been granted a three month extension beyond the date of December 15th. The application materials can be found in the “Files” section below.

June 25, 2009: The 15-Mile Falls Hydroelectric Project has been certified as low impact for a five year term, effective December 15, 2008 and expiring December 15, 2013.