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Ball Mountain Lake Flood Risk Management Project

Ball Mountain Lake

The dam at Ball Mountain Lake, Jamaica, Vt., is located on the West River, a tributary to the Connecticut River, and is part of a network of flood damage reduction projects in the Upper Connecticut River Basin.

Construction of the dam began in May 1957 and was completed in October 1961 at a cost of $11 million. The project features an earthfill dam with stone slope protection 915-feet long and 265-feet high; a gated, 864-foot-long circular concrete conduit with a diameter of 13.5 feet; and a chute spillway cut in rock with a 235-foot-long concrete weir. The weir’s crest elevation is 35 feet lower than the top of the dam. About 1.5 miles of roads, 0.5 mile of utilities, and a 10-grave cemetery were relocated.

Construction of the recreational facilities at the reservoir began in June 1975 and were completed in June 1977. The project has prevented $162.2 million in flood damages since it was built (as of September 2011).

The reservoir provides flood protection to the downstream communities in the West River Valley, including Jamaica, Townshend (particularly the West Townshend and Harmonyville sections), and Dummerston. In conjunction with other reservoirs in the Connecticut River Basin, Ball Mountain Lake also reduces flood stages on the Connecticut River.

Ball Mountain Lake has a permanent pool of 20 acres with a stage of 25 feet. From mid-May to mid-October, this pool is enlarged to 75 acres, a stage of 65 feet, to increase the seasonal recreational opportunities and improve reservoir aesthetics. The flood storage area of the project totals 810 acres and extends 6.5 miles upstream through Londonderry. The project and associated lands cover 1,227 acres. Ball Mountain Lake can store up to 17.8 billion gallons of water for flood control purposes. This is equivalent to 5.9 inches of water covering its drainage area of 172 square miles.

The Reservoir Control Center (RCC) is the "nerve center" for the New England flood control dams such as Ball Mountain Dam. Using radio and satellite communications, the team constantly monitors river levels and weather conditions that influence flood control decisions. Using radio and satellite communications, the RCC constantly monitors river levels and weather conditions and directs the operation of the dams during high flows. For information on river flows, dam operations, snow depths, recreational water releases and more visit RCC.

The 1986 Water Resources Development Act passed by Congress authorized the Corps to design, construct, and operate facilities that will enable upstream migrant adult Atlantic salmon to bypass the dams at Ball Mountain and Townshend Lakes. The law also authorized the Corps to provide the necessary facilities for the downstream passage of juvenile salmon. A $925,000 fish passage project on the West River was completed by the Corps in January 1993 encompassing both Ball Mountain and Townshend lake dams. The facility at Townshend Lake consists of the construction of a fish trap to collect upstream migrant salmon which would then be transported via tank truck above the dam to release points at both Ball Mountain and Townshend lakes. Modifications were made at both Ball Mountain and Townshend lakes to allow for downstream migration of juvenile salmon as well.

The normal pool elevation of feet at Ball Mountain Lake will be reduced to 25 feet each year to attract the juvenile salmon (April thru mid-June), and one of the three manual flood gate controls has been replaced with an automated gate operator which will automatically regulate outflows to assure that the 25-foot pool elevation will be maintained during normal flows.

For more information, or for recreation opportunities, call 978-318-8914 or visit the website at:

- Updated: May 6, 2022