LIHI Certificate #97 - Cavendish Project, Vermont

Project Name Cavendish
LIHI Certificate No. 97
LIHI Certificate Term
February 6, 2017 – February 5, 2027
Owner Green Mountain Power Corporation
State Vermont
Location Located at river mile 20.8 on the Black River, a tributary of the Connecticut River, in the Town of Cavendish in Windsor County, Vermont.
Installed Capacity 1.44 MW
Average Annual Generation 5,918 MWH
Facility Type Run-of-river
FERC No. P-2489 issued in 1994, expires 10/31/2024

The Cavendish Project is located in the town of Cavendish, in Windsor County, Vermont, on the Black River, 20.8 miles upstream of its confluence with the Connecticut River. There 14 dams on the Black River, with five hydro facilities in a 3/4 mile stretch in Springfield including Comtu Falls (LIHI #124) and Slack Dam (LIHI #78).  The US Army Corps of Engineers North Springfield flood control dam is also located downstream.

The 1,513-acre Proctor-Piper State Forest is located one-half mile southwest of the Project. Hawks Mountain Wildlife Management Area borders the project on the northeast and Okemo Mountain Ski Area is located about 5 miles upstream of the project. The 1,570-foot-long bypass reach includes Cavendish Gorge, a series of waterfalls and cascades that flow over boulders and between steep cliffs, with numerous pools and glacial potholes formed in the channel. Six non-powered dams lie upstream of the project as well as seven dams downstream of the project, five of which generate power. The closest upstream dam is the Okemo Snow Pond Diversion Structure Dam and the closest downstream is the Soapstone Dam, neither of which generate power. The project is owned by Green Mountain Power (GMP), the first energy utility certified as a B-Corporation.

The project was constructed between 1907 and 1908 and hydroelectric power has been generated since that time. The project includes: a dam, spillways, powerhouse, and three Francis turbine-generators.

The project dam is a concrete gravity style, 75-feet-high and set into ledge outcroppings on both sides of the river. The north spillway section is 90-feet-long by 25-feet-high, topped with 6-foot inflatable rubber flashboards. The south spillway section is 21-feet-long by 6-feet-high and topped with 2.5-foot flashboards. A concrete intake structure is located on the north bank of the river, which serves as the north abutment of the dam and is equipped with manually operated headgates and an inclined trashrack. A steel penstock, 6-feet in diameter and 1,250-feet-long and a penstock manifold are located adjacent to the powerhouse and splits flow to the three horizontal shaft Francis turbine generators with a total installed capacity of 1.44 MW. Generator leads and transformers connect the Project to the interconnected transmission and distribution system at the substation located adjacent to the access road and directly across from the powerhouse entrance; maintenance buildings are co-located with the powerhouse and substation.

The project operates in a run-of-river mode and impounds a 10-acre reservoir. A Programmable Logic Controller maintains the pond level with a fluctuation allowance of 1.5 inches. The project provides a minimum bypass flow of 10 cfs. This flow regime was developed using an Instream Flow Incremental Methodology study to determine the most appropriate flow rate to protect downstream aquatic resources. Additionally, after the installation of flashboards or after maintenance activities requiring impoundment drawdown, the project releases the following minimum flows downstream as the impoundment is refilled: 42 cfs or inflow from June 1 through September 30, 83 cfs from October 1 to March 31, and 332 cfs from April 1 to May 31. The flows released from the project support the Vermont Agency of Natural Resources’ (VANR) efforts to manage the area as a cold-water fishery.

Waters within the project reach are designated Class B and while not listed as impaired, there is documentation of E. coli bacteria contamination in two locations downstream of the project. Class B waters are managed for aquatic resource support, wildlife protection, public water supply, and primary contact recreation. Consultation with VANR has concluded that the project is not contributing to any water quality limitations and is not adversely impacting water quality in the area.

GMP works with the Black River Action Team (BRAT) to gather data and inform the public about water quality and levels of E. coli bacteria in the Project vicinity. GMP adopted a BRAT testing site located in the Cavendish Gorge (in the bypass reach of the project) GMP covers costs associated with water collection, sample testing, transportation, and chart posting every week for the summer months.

Historically, the Black River has supported populations of anadromous Atlantic salmon as well as both warm and cold-water fisheries. Though the Black River was part of the salmon stocking efforts under the U.S Fish and Wildlife Service (USFWS) Connecticut River Atlantic Salmon Restoration Program, the program ended in 2012 as poor salmon return rates persisted. Presently, there are no migratory species found in the project vicinity. Even if species were present downstream of the project, the Cavendish Gorge has a natural 80-foot drop and numerous falls and plunges, all precluding access to upstream passage.

Downstream fish passage is facilitated by a passage chute which guides riverine species down the spillway into a 3-foot-deep plunge pool. A connecting channel redirects the flow into the bypass reach. The downstream fish passage facility is operated from April 1 to June 15 and September 15 to November 15 for spring and fall movements of riverine species. Resident species include stocked and wild populations of brown and brook trout and stocked populations of rainbow trout, largemouth bass, smallmouth bass, and sunfish.

The project lands consist of 45 acres. The surrounding lands are protected mixed forest, woody and emergent wetlands, and some mixed-use rural and industrial areas.

Threatened or endangered species potentially present in the project vicinity include the Northern Long-eared Bat. VANR has confirmed that project operations under its Water Quality Certificate minimize any impacts to listed species. Consultation with VANR concluded that the project does not impact any of the listed species or their habitats.

Cultural resources in the project area include the powerhouse, dam, and gatehouse which are eligible for listing on the National Register of Historic Places. The Fitton Mill Complex, an archaeological site in the area, is also managed under the project’s cultural resources management plan. This plan outlines measures for the protection and preservation of cultural and historic resources in the project area. The shoreline is monitored every year, especially in areas surrounding identified and potential archaeological sites. Annual reports are filed with the Vermont Division for Historic Preservation, outlining procedures intended to protect and maintain the resources at the project. The project also hosts facility tours for local organizations, allowing access to the historic sites in the project area.

Recreational resources at the project include a canoe portage, picnic area, and fishing access. Public access is provided free of charge.

Compliance Status

There are no facility-specific conditions in the current Certificate.

2024: No material changes or compliance issues were identified. The project remains in compliance based on the annual review. FERC issued relicensing Scoping Document 2 on August 116, 2023.

2023: No material changes or compliance issues were identified. The project remains in compliance based on the annual review. The project filed the final FERC license application on October 31, 2022.

2022: No material changes or compliance issues were identified. The project remains in compliance based on the annual review. The project reported that the final FERC license application will be submitted by October 31, 2022.

2021: The project reported completion of the first study season for FERC relicensing in 2020. The project remains in compliance based on the annual review.

2020: The project reported installation of updated recreational and public safety signage, and initiation of FERC relicensing on October 29, 2019. The project remains in compliance based on the annual review.

2019: There were no reported changes or compliance issues. The project remains in compliance based on the annual review.

2018: There were no reported changes or compliance issues. The project remains in compliance based on the annual review.

2017: 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.

July 6, 2018 – The 30-day appeal window for the preliminary certification decision of the Cavendish Hydroelectric Project closed on July 5, 2018 with no appeals to the decision received. The decision is therefore final and the Cavendish Hydroelectric Project is recertified for a term from February 6, 2017 through February 5, 2022.

June 5, 2018: The Low Impact Hydropower Institute (LIHI) has preliminarily approved the Cavendish Hydroelectric Project for a new 5-year term of Low Impact Certification. This decision is preliminary pending the 30-day appeal window. Only those who commented in 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 “Cavendish 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 and 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 July 5, 2018.  The full application and reviewers report are available below. If no appeal requests are received and the decision becomes final, the new term for the Cavendish Project will be February 6, 2017 to February 5, 2022.

August 31, 2017: The Cavendish Hydroelectric project has been granted another extension of the current certificate term. The new expiration date is March 31, 2018.

May 22, 2017: LIHI has received an application for a new term of Low Impact Certification for the Cavendish Hydroelectric project.  LIHI is seeking public comment on this application.  Specifically, we are interested in knowing whether you think the Cavendish project meets the LIHI Low Impact Certification Criteria, as revised in the 2nd Edition Handbook released in March 2016.  Please review the program and criteria in LIHI’s revised Handbook and then review the Project’s 2016 application materials posted on the project page. 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 “Cavendish Lower Project Comments” in the subject line, or by mail addressed to the Low Impact Hydropower Institute, PO Box 194, Harrington Park, New Jersey 07640.  Comments must be received at the Institute on or before 5 pm Eastern time on July 21, 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.

December 16, 2016: The Cavendish Hydroelectric project has been granted an extension of the current certificate term. The new expiration date is August 6, 2017. See extension letter for explanation below.

November 29, 2012: The Cavendish Project has been certified as low impact for a five year term, effective February 6, 2012 and expiring February 6, 2017.

April 6, 2012: Public comment period on application has closed.

February 6, 2012: The Central Vermont Public Service (CVPS) has submitted an application for the certification of the Cavendish Project. Public comment period has opened on the application.

Certification Files

2018 Recertification

2012 Certification

Key Documents