LIHI Certificate #122 – Downer’s Mills Project, Vermont

The Downer’s Mills Hydroelectric Project is located at Quechee village in the town of Hartford, Vermont approximately seven miles upstream of the Ottauquechee River’s confluence with the Connecticut River. With a watershed area of 223 square miles and a length of 38 miles, the Ottauquechee River is a major tributary of the Connecticut River. The river descends from the Green Mountain range near Killington Peak and flows generally in an easterly direction to its outlet in the town of Hartland. The Project dam is the forth one upstream of the confluence: the White Current Company dam, or the Ottauquechee Woolen Mill dam (FERC Project No. 2787) is located at river mile 0.3; the Corps of Engineers North Hartland Flood Control dam (site of FERC Project No. 2816) is located at river mile 1.6; and the Deweys Mill dam (FERC Project No. 5313) is located at the head of Quechee Gorge at river mile 6.0.

The hydroelectric station was constructed at the site of the existing Emory Mill dam (also known as Downer’s Mills) in the early 1800s and was built to power a grist mill. In 1983 the generator was put back into service and the power from the site has been used to melt the glass used in production by Simon Pearce (U.S.), Inc.’s glass blowing business, with excess power being sold to Green Mountain Power Company, formerly Central Vermont Public Service. The concrete gravity dam is 185 feet long with an uncontrolled spillway. The crest elevation of the dam is 562 feet NGVD and is about 14 feet above the bedrock streambed at the downstream toe. The powerhouse located in the basement of the mill building houses a single generator with a capacity of 645 kW. At full pool, the impoundment extends about half a mile upstream and covers approximately nine acres1 with an average depth of about six feet. The Project has an average annual production of 2 GWh.

Project Name  Downer's Mills
LIHI Certificate No.  122
LIHI Certificate Term March 3, 2015 - March 3, 2020 Extended to September 30, 2020
Owner Simon Pearce (U.S.) Inc.
State Vermont
Location Located at River Mile 7 on the Ottauquechee River in Vermont.
Installed Capacity 0.645 MW
Average Annual Generation 2,000 MWh
Facility Type Run-of-river
FERC No. P-5195 exempt 1982

The facility is operated as a run of river facility. Reservoir level is maintained by means of a pond level control system. The project is required to maintain a minimum flow of 22 cfs (7Q10) or project inflow, whichever is less. The DM Facility is located immediately downstream of Green Mountain Power Company’s Taftsville Hydroelectric Project (FERC #2490) and upstream of the United States Army Corps of Engineers Hartland flood control dam. Since the DM project is a run of river project, available river flow for the DM project is determined by discharge from the Taftsville project.

Certification History

July 27, 2015: LIHI 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 Downer’s Mills Hydroelectric Project (FERC No. 5195-001) satisfies the LIHI Certification Criteria. The Downer’s Mill certification is effective as of March 3, 2015 for a five (5) year term, which will expire on March 3, 2020, with the following conditions:

  • Condition satisfied in 2015. Condition 1. The facility owner shall cooperate with the Vermont Agency of Natural Resources (VANR) in scheduling and completing a flow demonstration study for the bypassed reach to determine an appropriately protective minimum flow for aquatic habitat support. The outcome of the study, including VANR recommendations, shall be reported to LIHI within 90 days of the issuance of LIHI certification. Since this certification is being granted without the minimum bypass flow having been deemed appropriately protective by the resource agencies, LIHI may withdraw certification if it determines that the owner is failing to make a good faith effort to cooperate with the resource agencies in determining a final minimum bypass flow. Any increase in the bypass minimum flow to meet the appropriately protective standard shall be implemented within 14 days of receipt of the VANR recommendation.
  • Condition satisfied in 2015. Condition 2. The facility owner shall develop a system for producing and maintaining records sufficient to demonstrate compliance with the headpond elevation and flow management limitations for an instantaneous run-of-river operation and bypass conservation flows. Within 90 days of the issuance of LIHI certification, the facility owner shall provide LIHI with a copy of the operations and flow monitoring plan. Prior to filing the plan, the facility owner shall obtain plan approval from U.S. Fish and Wildlife Service (USFWS) and VANR; written confirmation of the approvals will be filed with the plan. Should the minimum bypass flow be increased after the plan is completed, the plan shall be revised accordingly and resubmitted to VANR, USFWS, and LIHI.
  • Condition 3. During the term of this certification, should a resource agency request implementation of upstream and/or downstream fish passage at the Facility, the owner shall notify LIHI of this new requirement within 14 days and provide LIHI with a copy of the request and its response.

March 6, 2015: On March 3, 2015, the Low Impact Hydropower Institute (LIHI) received a timely and complete application from Simon Pearce (U.S.) Inc., for the Low Impact Certification of the Downer’s Mills Project, FERC P-5195-001, located on the Ottauquechee River in Vermont.