April 2, 2025: The Low Impact Hydropower Institute has received a complete application for Low Impact Certification of the Molly’s Falls Hydroelectric Project.  LIHI is seeking public comment on this application.  Specifically, we are interested in knowing whether you think the Project meets the LIHI Low Impact Certification Criteria, as revised in the 2nd Edition Handbook in effect at the time of initial application.  Please review the program and criteria in LIHI’s Manuel Révision 2.05 et consultez ensuite les documents de candidature du projet ci-dessous.

Commentaires directement liés à des critères spécifiques du LIHI (débits, qualité de l'eau, passage des poissons, etc.) seront très utiles, mais tous les commentaires seront pris en compte. Les commentaires peuvent être soumis à l'Institut par courrier électronique à l'adresse commentaires@lowimpacthydro.org avec « Commentaires sur le projet Molly's Falls » dans la ligne d'objet, ou par courrier adressé au Low Impact Hydropower Institute, 68 Harrison Ave Ste 605, PMB 113938 Boston, Massachusetts 02111-1929.  Les commentaires doivent être reçus au plus tard à 17 h, heure de l'Est, le 1er juin 2025. à prendre en considération. Tous les commentaires seront publiés sur le site Web et le candidat aura la possibilité d'y répondre. Toute réponse sera également publiée.

The Molly’s Falls Project consists of two developments – Peacham development located in the Town of Peacham; Caledonia County, VT and the Marshfield No. 6 development located in the towns of Marshfield, and Cabot; Washington County, VT. There are several dams downstream of the project’s discharge into the Winooski River including four LIHI Certified facilities – Winooski 8 (LIHI #77), Bolton Falls (LIHI #201), Essex 19 (LIHI #146), et Moulin Winooski One/Chace (LIHI #16).

Peacham:

The Peacham development was built in 1930 on Sucker Brook.  It has no hydropower but a provision was made for the future addition of a power plant. The barrage impounds Peacham Pond, a 331- acre spring-fed pond. The rolled earthfill dam is 710 feet long and 25.6 feet high, with a 90-ft-wide overflow déversoir which is maintained in an open configuration and is not equipped with stoplogs or other impoundment devices.

The site has a reinforced concrete intake structure that utilizes a cast iron slide gate with a manually operated screw stem operator. The intake structure also contains a set of journal d'arrêt slots, a 6-inch bypass pipe around the gate, and a trashrack with 2.5-inch spacing. The intake opening located at the trashracks is 7.5-feet-high and 6.5-feet-wide and controls flow to a 4-ft-diameter reinforced concrete outlet pipe that extends from the intake structure, through the embankment, to the downstream toe of the embankment. The discharge pipe is 122 feet long and has a 9-inch-thick cast-in-place reinforced concrete wall. On the left end of the embankment is the 90-foot-wide spillway section with a 12-inch-thick layer of riprap and a concrete core wall.

Water levels in Peacham Pond are maintained at the normal operating level from May 1 to November 30. Winter drawdowns are used to reduce peak downstream flows and improve safety. The rate of drawdown is limited to no more than 6 to 12 inches per week prior to December 15 of each year. Beginning in the winter of 2025-2026, the winter drawdown can be no more than 3 feet below the normal operating level unless maintenance, snow-water content, or high flow forecasting criteria are met. Between May 1 (or the date of refill to normal operating levels) and July 31 (or the date that the Vermont Agency of Natural Resources (VANR) determines that loon nesting is complete, whichever is earlier), water levels are maintained in accordance with loon protocols. This includes managing pond levels as close to the normal operating level as is feasible and safe within 0.5-feet above or below normal operating levels. Between August 1 (or the date that VANR determines that loon nesting is complete, whichever is earlier) and November 30, Peacham Pond levels are maintained within 1-foot of the Peacham Pond normal operating level.

Minimum flows to Sucker Brook vary throughout the year. The Peacham Pond development operates in au fil de l'eau (ROR) mode from May 1 (or Peacham Pond refill date if later) to November 30. Between December 1 and May 1 (or the date that Peacham Pond is refilled to the normal operating level), a minimum flow requirement is in place. Ramping occurs for transitions between drawdown, refill, and ROR operations. Minimum flows during Peacham Pond refill are 6.7 cfs at the dam outlet, or net inflow-evaporation if less to Sucker Brook. There is a maximum peak flow of 25 cfs, or inflow if higher, during normal winter drawdown operations, with higher flows only as needed for maintaining steady pond levels for dam safety due to high inflows. Water flows from the outlet works at the Peacham Pond dam through 0.6 miles of the Sucker Brook into the Molly’s Falls Réservoir, which provides additional storage.

Marshfield No. 6: 

The current Marshfield No. 6 dam is located at river mile 1.9 on Molly’s Brook upstream of the confluence with the Winooski River.  The dam was built in 1927 (three prior iterations had been built and operated prior to 1914) and impounds the 411-acre Molly’s Falls Pond that is also home to Molly’s Falls Pond State Park. The rolled earthfill dam is 1,100 feet long with a maximum height of 48.5 feet. The dam is equipped with one 12-ft-wide by 13.8-ft-long rectangular intake structure with a height of 9.75 feet and one 40-ft-wide, 260-ft-long service spillway is equipped with a pair of side-by-side glisser portes. Each gate has a width of 18 feet 7 inches. The emergency spillway is 46 feet wide and is a 370-ft-long channel consisting of an upstream concrete structure with gates and a stepped concrete channel with sidewalls leading to a piscine de plongée in Molly’s Brook. A gate structure at the upstream part of the emergency spillway retains water in the reservoir and can be opened if needed to release water into the spillway. There are two gates each 23 feet wide that consist of three bays of stoplogs and poteaux.

The dam creates a bypassed reach on Molly’s Brook approximately 1.9 miles long. Minimum flows into the bypassed reach are provided either via a bypass pipe, which provides cool water from approximately 28 feet deep in the reservoir, or via service spillway slide gates. From July through March, a minimum flow of 8.5 cfs is released and from April through June, a minimum flow of 12 cfs is released.

Water is conveyed from the dam to the centrale via a gatehouse and concrete pipe that that converts to a welded steel conduite forcée and continues to a surge tank and on to the powerhouse which is located on the Winooksi River approximately 700 feet above the confluence with Molly’s Brook.

The powerhouse intake has steel trashracks that measure 12-feet-wide by 14-feet-tall. The 3-inch-deep by 3/8-inch-thick bars are spaced 4 inches on center and supported by concrete at the top and bottom by two horizontal steel I-beams. The powerhouse is equipped with a single Norcan vertical Turbine Francis with a theoretical capacity of 5 MW although it typically produces less.

The project is not regulated by FERC because it was constructed in 1927 prior to the enactment of federal licensing regulations. The project is regulated by the Vermont Public Utilities Commission.

The project is operated in a limited seasonal storage mode. From May 1 to November 30, water levels in the impoundment are maintained at a normal operating level. During this time period, allowable fluctuation limits vary. From May 1 (or spring refill if later) until loon nesting begins, a 0.5-ft fluctuation is allowed. During loon nesting season, the reservoir levels are maintained as stable as is feasible and safe. From August 1 (or end of loon nesting, whichever is earlier) until November 30, a 1-ft fluctuation from normal operating levels is allowed. At any time of the year, higher fluctuations are permitted due to storms and heavy snowmelt/rainfall.

Winter drawdowns of the Molly’s Falls Reservoir begin on December 1, at the earliest, and are completed prior to mid-March. Refill begins after the maximum drawdown has been reached and is normally completed by May 1. Under normal circumstances, the maximum winter drawdown depth is 2.0 feet below the normal operating limit. Larger drawdowns can occur if unusually high amounts of snow-water equivalent or precipitation are forecasted, in order to manage downstream flows safely.

There are no migratory fish present and the project has no upstream or downstream fish passage facilities.  Threatened or endangered species that may be present include Northern long-eared bat, and the candidate monarch butterfly. Bald eagle and other protected migratory species may also be present, as well as several state-listed plants, a reptile, and the freshwater pearl mussel. Vermont Department of Fish and Wildlife (VDFW) indicated that the project likely would not impact those species.

There are no cultural or historic resources listed in the Registre national des lieux historiques or the Vermont State Register of Historic Places; however, project structures are old enough to be eligible.

The project does not include any formal or informal recreation facilities or access points. Molly’s Falls Pond State Park provides access and amenities. VDFW has public boat ramps on both Molly’s Falls Pond and Peacham Pond.

Dossiers de certification

2025 Application

• Molly’s Falls Application
• Molly’s Falls Application Supplement