HARMFUL IMPACTS OF DAMS

Mass Dams Threaten Public Health & Safety, Migratory Fish and the Vitality of Our Waterways

The beautiful sight of a waterfall, the lovely sound of a river rushing over a dam -- a lasting symbol of Massachusetts’ first-in-the-nation industrial past.

This may be true, but it tells less than half the story. Click here for an illustration of dams’ impacts on rivers and streams.

Potential Failure of Dams Poses a Danger of Flooding and Toxic Contamination. Large unmaintained dams are very dangerous to downstream communities should they fail. Sediments that accumulate behind most dams can be extremely polluted. Dangerous dams in Massachusetts:
  • Whittendam Dam on the Mill River which came so close to collapsing in 2005 that parts of the City of Taunton had to be evacuated; and
  • Baker and T&H Dams on the Neponset River in Boston and Milton, behind which lays tons of sediments contaminated with toxic PCBs, which have overtopped Baker in the past into condo basements, a bike path, and trolly tracks.

Toxic Sediments behind Some Dams are Poisoning Fresh Water Fish and Those Who Eat Them. The Department of Public Health has issued advisories urging limited consumption of fish in every river in the state. Dams trap and concentrate contaminated sediments, which are ingested by invertebrates and then move up the food chain, becoming more lethal each step of the way.

Dams Threaten Survival of Migratory Herring, Shad, Eel, and Smelt. Dams on most of our coastal rivers are blocking runs of “anadromous fish” ocean species that spawn (lay their eggs) in fresh water. Click here to learn more about anadromous fish.. These include:
  • the Wapping Road Dam on the Jones River in Kingston;
  • a small private dam on Third Herring Brook in Norwell and Hanover;
  • the Baker and T&H Dams on the Neponset River in Boston and Milton; and
  • a number of dams on the Eel and Town Rivers in Plymouth

Dams Limit Biodiversity of Freshwater Fish and Other Species and Impede Natural River Processes. Dams can eliminate cold water fish like trout by slowing down river flow, raising water temperature, concentrating pollutants, and reducing dissolved oxygen. Impoundments behind dams can reduce wetlands (which serve as fish nurseries and which moderate flooding and filter pollution), cause algae blooms, and block migration of turtles and other river dwellers.

Dams Impede Recreational Boating. They inhibit canoeing and kayaking by breaking up rivers and, when close to the coast, prevent boats from moving upstream from the ocean.

Most Massachusetts Dams Serve No Purpose and are Cheaper to Remove than Maintain. Nearly all of our dams were built decades or centuries ago for farming or for water power to run mills and factories and are now obsolete. The state-owned T&H Dam on the Neponset River would cost taxpayers $3.6 million to maintain for 30 years, compared to $1.3 million to remove.

The sight and sound of a waterfall is indeed beautiful. But the fast moving rapids which are usually created when a dam is removed are beautiful as well, especially when one knows they are part of a restored, vibrant, and healthy river that also contributes to the health of the ocean.

Click here to learn what you can do to help remove obsolete dams on rivers and/or restore fish passage near you.