River Restoration and Dams

The many old dams on the Assabet, Sudbury and Concord Rivers date from the days of water-powered mills and only two generate electricity today. They serve no purpose for flood control. The mill dams turn sections of the rivers into a series of pond-like impoundments that warm and slow the flow of nutrient-rich water, fueling aquatic weed growth and trapping soft sediments (as much as 10 feet deep) behind each dam.

Aquatic weeds, particularly filamentous green algae and invasive water chestnut, block sunlight and decrease the oxygen in the water necessary for aquatic life. They also out-compete native aquatic vegetation and make river recreation impossible. In the fall, as the plants die back and sink to the bottom, the nutrients they took up settle back into the sediments, ready to feed another year's growth. This phosphorus recycling is a major source of water pollution.

Dams also block the movement of fish and other river wildlife. Fish and other aquatic organisms need to be able to move up and down streams to find food, refuge from drought and heat, and places to breed. These rivers were once home to multitudes of migratory fish that must swim from the ocean into fresh water to breed or mature. They are important species to both the Gulf of Maine fisheries and local river ecology: river herring (blueback herring and alewife), American shad, American eel and sea lamprey.

To learn more:
Division of Ecological Restoration
American Rivers (Free Rivers: The State of Dam Removal in the U.S., 2022)

CONCORD RIVER:

The Concord River is impounded in North Billerica by the Faulkner (Talbot Mills) dam where the river intersected with the Middlesex Canal, and further downstream by Centennial Island and Middlesex dams in Lowell. The Middlesex dam is breached and there is a small hydroelectric facility at the Centennial Island dam, which also has a fishway. Lowell Parks and Conservation Trust conducts herring monitoring at this fishway.

OARS is the Lead Project Sponsor for the Talbot Mills Dam Removal in North Billerica, a Priority Project of the State’s Division of Ecological Restoration. The owner of the dam wishes to remove it and restore the migration of fish between the SuAsCo basin and the Gulf of Maine. This project would restore the largest amount of migratory fish breeding habitat of any dam removal project in the state. This project started in 2021 and will span several years. OARS is committed to the public having access to information about this project so that they can understand it and make input.

FAQ about the Talbot Dam Removal

Examples of other dam removal projects:
Local Matters video, Plymouth, MA (starts at 13 min 23 sec)

Announcements and Presentations:
Talbot Mills Public Meeting, June 29, 2022 (Meeting flyer with Zoom link)
Presentation to the Middlesex Canal Association Annual Meeting, May 15, 2022
Talbot Dam Public Meeting , June 29, 2022

Reports:
Feasibility study for restoring fish passage at the Concord River dams (2016)
Talbot Mills Dam Removal Targeted Impact Analysis-Draft Report (Jan. 2022)
Review of Talbot Mills Dam Removal Targeted Impact Analysis (prepared for Town of Billerica, April 2022)
For all the public project documents, click here.

ASSABET RIVER:

There are six old mill dams on the Assabet River. A series of flood-control dams on the Assabet River and its streams were built in 1962-87 which only impound floodwaters. OARS held two workshops on "Assabet River Restoration: Understanding the Impacts of Dams in Your Community" in Westborough and Maynard in March 2009. The workshops moved the discussion forward in a collaborative way among the 100 participants, building a sound understanding of the science and policy behind these issues.

Reports:
Assabet River Sediment and Dam Removal Study (2010)

Presentations:
Assabet River Restoration and Dams

Other information:
OARS work to restore stream continuity

SUDBURY RIVER:

The Saxonville dam in Framingham powered the milltown of Saxonville in the past, while several upstream dams were built in Ashland, Framingham and Southborough to create water supply reservoirs for the city of Boston. In addition, there are many millponds on tributaries to the three rivers, such as the dams upstream and downstream of the Wayside Inn on Hop Brook in Sudbury.