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Thomaston Dam Flood Risk Management Project

Click for hi-resolution photo of Thomaston Dam

Thomaston Dam is located in Thomaston on the Naugatuck River, the major tributary of the Housatonic River. It is about one mile north of Thomaston on Route 222. The project consists of an earthfill dam with stone slope protection 142-feet high and 2,000-feet long; a gated 455-foot horseshoe shaped concrete conduit 10 feet in diameter; and a side channel spillway edged in rock with a 435-foot-long concrete weir. The weir’s crest elevation is 23-feet lower than the top of the dam.

Thomaston Dam provides flood protection in the highly industrialized and densely populated Naugatuck Valley. It is the largest and most important flood control dam in the Naugatuck River system.

Construction started in May 1958 and was completed in November 1960. The work required relocation of portions of Routes 8 and 222 (Blakeman Road), several town roads, and a portion of the Devon Branch of the Conrail railroad. Project costs were $14.3 million. The project has prevented $828.9 million in flood damages since it was built (as of September 2011).

There is no lake at the Thomaston Dam. The flood storage area of the project, which is normally empty and is only utilized to store floodwaters, covers 960 acres. The project and associated lands total 1,288 acres, of which 1,000 acres are wooded. These lands extend into the towns of Litchfield, Harwinton, and Plymouth. Thomaston Dam can store up to 13.69 billion gallons of water for flood control purposes. This is equivalent to 8.1 inches of water covering its drainage area of 97.2 square miles.

The Reservoir Control Center (RCC) is the "nerve center" for the New England flood control dams such as Thomaston Dam. Using radio and satellite communications, the team constantly monitors river levels and weather conditions that influence flood control decisions.

Corps personnel, in conjunction with RCC regulate the amount of water released downstream by raising or lowering the two gates located in the control tower at the dam. In a time of high water, the gates are lowered in order to hold back the water, only to be released when downstream river conditions begin to recede. The Reservoir Control Center provides information about river flows, dam operations, snow depths, recreational water releases, and more.

There is a 25-mile trail system for snowmobiles and two-wheel trail bikes on the Thomaston Dam lands. Fishing enthusiasts will find that Leadmine Brook, a tributary of the Naugatuck River that flows near the dam, is stocked with brown, brook and rainbow trout. In-season hunting for stocked pheasant and native small game is permitted. Overlook and picnic areas offer an excellent view of the dam and portions of the Naugatuck River Valley. Fireplaces and parking and sanitary facilities are also available.

An estimated 200,000 visitors annually enjoy picnicking, fishing, hunting, trail biking and snowmobiling at Thomaston Dam’s more than 849 acres of land and water. Visitors spend an estimated $1.33 million within 30 miles of the lake. An estimated 37 jobs in the local community are supported by visitors to Thomaston Dam. For more information call (860) 283-5540 or visit the website at:

- Updated: May 4, 2021