LIHI Certificate #74 - Mechanicsville Project, Connecticut

The Mechanicsville Hydroelectric Project (the “Project”), exempted from licensing by the Federal Energy Regulatory Commission (“FERC”) as Project No. P-9611, is owned by Saywatt Hydroelectric, LLC. The Project is located on the French River in the Town of Thompson, Windham County, Connecticut. The Project is 1000 feet upstream from the confluence of the French River into the Quinebaug River. The French River joins the Quinebaug River, which eventually joins with the Shetucket and forms the Thames River. The Thames River flows into Long Island Sound in New London, Connecticut.

The Mechanicsville dam was originally constructed in the mid 1800’s. It was upgraded by the Putnam Light and Power Company in 1922 when the hydroelectric powerhouse and civil works were originally constructed. Initially, the Project diverted flows from the Quinebaug River into the Mechanicsville Dam impoundment on the French River. This tripled the flow of water in the Project area used to produce power. The original Project included three hydroelectric turbines, with a combined capacity of approximately 750 kW.

Following a devastating hurricane in 1936, the powerhouse was flooded and the Project was abandoned. Following two more hurricanes in 1938 and 1955, the US Army Corps of Engineers (USACE) constructed a flood control dam and reservoir on the Quinebaug River and terminated the Quinebaug’s flow from entering the Project area. Two more flood control dams were built upstream of the Project. One USACE flood control dam is located at Buffumville on the Little River, a tributary to the French, in Oxford, Massachusetts and one at Hodges Village on the French River in the same town. Approximately 50% of the Project flows are regulated by these USACE dams so future threats of flooding have been virtually eliminated.

In the early 1980’s, the abandoned site was purchased by the Essex Hydro Company. They decided not to develop the site and it was then acquired by Mr. Robert King. Mr. King applied for and received an exemption from licensing from the FERC on January 27, 1988. Mr. King proceeded to pour his heart and soul into rehabilitating the abandoned site into a useful alternative energy facility. On June 1, 2010, Saywatt Hydroelectric, LLC acquired the Project from Mr. King and has operated the site since that time. Saywatt has made and plans to make future investments to further improve the aesthetic surroundings and stabilize this historic alternative energy site.

The major Project works consist of a dam and impoundment, an intake structure and a powerhouse. Specifically, the Project consists of:  (1) a granite block dam, 200 feet long with a height of 20 feet to the top of the bridge structure,  13 feet to the top of the permanent crest elevation of 301.5 feet mean sea level (msl) and 15 feet to the top of the flashboard elevation of 303.5 feet msl, (2) an impoundment approximately 3,900 feet long, with a surface area of 48 acres and 256 acre-feet gross storage, (3) a brick and concrete powerhouse with a turbine-generator capacity of 275 kW, (4) a 35-foot long forebay with an average width of 30 feet and depth of 8.5 feet, (5) a 100 feet long by 55 feet wide tailrace, and (6) three 100 kVA transformers, which convert 480V three phase power up to 23.0 kV, which travel out on a 900 feet long Connecticut Light and Power transmission line.

The Project has virtually no by-pass reach. The powerhouse is located adjacent to the dam. The plunge pool at the base of the dam is in constant communication with the tailrace and downstream river flow. If you were to define the plunge pool as a by-pass reach, it would measure less than 35 feet from the toe of the dam to the tailrace.

The Mechanicsville Hydroelectric Project is located about nine miles downstream from another hydroelectric project on the French River in Webster, MA. Two other projects are located about three miles downstream on the Quinebaug River in Putnam, CT. One of the Putnam projects, Putnam Hydro, has received LIHI certification.

The Mechanicsville Project is semi automated and operates in a run-of-river mode for the protection of water quality, aquatic resources, and aesthetic values in the French River. The Project operates in a run-of-river mode and at all times maintains discharges from the Project so that the flow in the French River, downstream of the Mechanicsville powerhouse, approximates the instantaneous flow in the French River upstream of the Mechanicsville dam.

More specifically, the Project is operated by an operator that lives next to the Project or by the Project owner. When there is enough flow in the French River to satisfy the 86 cfs minimum flow requirement as set forth and stated in the FERC Exemption, an operator manually inspects the area and if the operator deems the area to be in a safe condition, starts the hydroelectric turbine to a minimum setting. If everything operates smoothly, the operator then transfers control of the Project from manual mode to automatic mode, which then slowly ramps power up to an appropriate level over the course of one to two hours.

The Project is controlled via an Allen Bradley SLC-503 Programmable Logic Controller (PLC). The PLC continuously monitors pond elevation in the impoundment. The pond elevation is selected to be at the top of the flashboards or approximately 303.5 above msl. If pond elevation increases or decreases by a fraction of an inch, the PLC will adjust the opening of the Kaplan turbine runner to use more or less water. This is how pond elevation and run-of-river flows are maintained, which has worked effectively for over 20 years.

If the PLC senses that the pond elevation has changed above or below the standard operational settings, an emergency text message is sent to both operators. Typically an operator can be on site within minutes. Or the owner can access the PLC via the internet, through his personal computer or by mobile phone to make operational decisions real time. In case no operator responds, the PLC will gently shut down the turbine if the pond level continue to operate outside an acceptable range.

If there is a shutdown caused by any circumstance, including a power outage, the turbine’s cylinder gate will slowly close and water will flow over the flashboards almost instantaneously. Leakage through the cylinder gate and the 22 cfs minimum flow through the dam, assure that sufficient water continues to flow downstream through both the bypass reach and the tailrace. Within several minutes, run-of-river flows resume in the downstream river.

Project Name Mechanicsville
LIHI Certificate No. 74
LIHI Certificate Term January 27, 2016 - January 27, 2021, extended to May 15, 2021
Owner Saywatt Hydroelectric, LLC
State Connecticut
Location Located at river mile 0.22 on the French River in the town of Thompson, Windham County, Connecticut.
Installed Capacity 0.337 MW
Average Annual Generation 950 MWh
Facility Type Run-of-river
FERC No. P-9611 exempt 1988

Certification History

April 8, 2021: The Low Impact Hydropower Institute (LIHI) has preliminarily approved recertification of the Mechanicsville Project for a new 5-year terms of Low Impact Certification. The certification does not include any conditions.

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 "Mechanicsville Project” in the subject line, or by mail addressed to the Low Impact Hydropower Institute, 1167 Massachusetts Ave, Arlington MA 02476. 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 May 8, 2021. The application and reviewer's report is available below.

If no appeal requests are received and the decision becomes final, the Certification term for the Project will be January 27, 2021 through January 26, 2026.

February 2, 2021: The Low Impact Hydropower Institute (LIHI) has received a complete recertification application from Saywatt Hydroelectric, LLC for the Mechanicsville Project located on the French River in Connecticut.

This is the second time the project will be reviewed using LIHI's 2nd Edition Handbook. LIHI developed a streamlined application format for such projects to facilitate review in accordance with Section 6.1 of the 2nd Edition Handbook. This review process verifies the information submitted, considers any public comments received when the application is deemed complete, and assesses whether there have been any material changes at the facility or in the LIHI Handbook that affect compliance with the LIHI Criteria.

LIHI is seeking 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 LIHI by e-mail at with "Mechanicsville Project Comments” in the subject line, or by mail addressed to the Low Impact Hydropower Institute, 1167 Massachusetts Avenue, Office 407, Arlington, MA 02476. Comments must be received at the Institute on or before 5 pm Eastern time on April 4, 2021 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.

The project description and complete application can be found below along with the prior recertification application, and the prior review report under the 2nd Edition Handbook, as well as the other relevant documents.

February 20, 2017: On January 13, 2017, LIHI Executive Director Shannon Ames issued a Preliminary Certification Decision that the Mechanicsville Hydroelectric Project (FERC No. P-9611) continues to satisfy the LIHI Certification Criteria.

As provided for in Section 4.2.5 of the LIHI 2nd Edition Handbook, notice of the preliminary decision to certify was posted on the Institute's website and sent to the stakeholder email distribution list on January 16, 2017. A 30-day appeal period was provided to anyone who commented on the original application to request an appeal, and no requests for appeal were received.

The Mechanicsville Hydroelectric Project is now deemed certified by LIHI for a five-year term. The effective certification date for the Mechanicsville Project is January 27, 2016, expiring on January 27, 2021.

October 27, 2016: The Low Impact Hydropower Institute has received a complete application for a new term of Low Impact Certification for the Mechanicsville Hydroelectric project. The application materials can be found in the Files section below.

LIHI is seeking public comment on this application.  Specifically, we are interested in knowing whether you think the Mechanicsville project continues to meet the LIHI Low Impact Certification Criteria.  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 “Mechanicsville 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 December 27, 2016 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 4, 2012:   The public notice period announcing the material change at Mechanicsville which adds generating capacity to the existing powerhouse by installing a second generating unit has passed and no public comments were received. The application reviewer recommended continuing the certification with the project reconfigured as proposed and authorized by FERC (exemption amendment order of March 29, 2012). The Institute’s Governing Board received and reviewed the proposal at its May 3, 2012 meeting, and voted to confirm that the facility would continue to comply with the LIHI criteria subsequent to completion of the material change to the facility and that there would be no revocation or modification of the certification. The Certificate term dates also remain unchanged, with the effective date of January 27, 2011, and expiring January 27, 2016.  See Material Change Decision Letter, 2012 below.

April 3, 2012: Saywatt Hydroelectric, LLC submitted an application for material changes to the Mechanicsville Hydroelectric Project. In its Order Amending Exemption (March 29, 2012), FERC describes the material changes as follows:

"The Exemptee is proposing to add an additional turbine-generator unit rated at 96 kW to the already existing turbine-generator unit rated at 225 kW, in order to closely match the authorized capacity of 325 kW. In addition, the exemptee proposes to amend the flashboard operation by having flashboards in year round, modifying the height during specific times (i.e. using 2-feet high flashboards from October 1 through June 30 and 1-foot high flashboards from July 1 through September 30). Lastly, the exemptee proposes to lower the minimum start flow from 86 cfs to 60 cfs, which is a result of the lower hydraulic capacity of the second proposed turbine (38 cfs) and the existing bypass flow requirement (22 cfs)."

The public comment period on this application will remain open until April 18, 2012.

July 28, 2011: The Mechanicsville Hydroelectric Project has been certified as low impact for a five year term, effective January 27, 2011 and expiring January 27, 2016.

February 2, 2011: Saywatt Hydroelectric, LLC has submitted an application for the certification of the Mechanicsville Hydroelectric Project.