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Hop Brook Lake Flood Risk Management Project

Click for hi-resolution photo of Hop Brook Lake

Hop Brook Lake is spread over three communities: Naugatuck, Middlebury, and Waterbury, Conn. The dam is situated on Hop Brook in Naugatuck, 1.6 miles above the confluence of the brook and the Naugatuck River. It can be reached by traveling three miles north on Route 63 from the center of Naugatuck. The project includes an earthfill dam with stone slope protection 520-feet long and 97-feet high; an earthfill dike measuring 400-feet long and 33-feet high; a gated rectangular 425-foot-long concrete conduit three feet wide and five feet high; and a chute spillway edged in rock with a 200-foot-long broad crested weir. The weir’s crest elevation is 17 feet lower than the top of the dam.

Construction of the dam commenced in December 1965 and was completed in December 1968, costing $6.2 million. The relocation of 1.8 miles of Route 63 was required. The project has prevented $108.4 million in flood damages since it was built (as of September 2011).

Hop Brook Lake contains a 21-acre recreation pool that has a maximum depth of 18 feet. The flood storage area of the project, which is normally empty and is only utilized to store floodwaters, is 1.5 miles long and spreads out over 270 acres. The project and associated lands total 538 acres throughout Naugatuck, Middlebury, and Waterbury. Hop Brook Lake can store up to 2.23 billion gallons of water for flood control purposes. This is equivalent to eight inches of water covering its drainage area of 16.4 square miles.

The Reservoir Control Center (RCC), in Concord, Massachusetts directs the water regulation activities for the New England flood control reservoirs such as Hop Brook Lake. By way of radio and satellite communications, the team constantly monitors river levels and weather conditions that influence flood control decisions.

The two highest pool levels recorded since the completion of Hop Brook Lake were in 1982 and 2011. In June 1982, the water level rose to 57.7 feet at the dam, utilizing 53 percent of the storage capacity. The combination of a higher than normal pool level for testing purposes, a large snowpack from an overly-active winter and three inches of rain in 24 hours caused a 57.4 foot pool in March 2011.

Tropical Storm Irene also generated a 20-foot rise in Hop Brook's 24-hour pool level in late August of 2011. Irene dumped 5.28 inches of rain resulting in a peak pool of 50.41 feet.

The year-round, 21-acre conservation pool annually attracts nearly 200,000 visitors who enjoy a variety of recreational pursuits including picnicking, swimming, hiking, fishing and special permit group events. Hop Brook Lake contains largemouth bass and panfish. The state stocks both the lake and its feeder streams with trout. Recreational development of the reservoir includes picnic sites and four group picnic shelters, walking trails, a beach, ball field, three volleyball courts, drinking water, sanitary facilities, parking facilities and canoeing.

Visitors spend an estimated $2.05 million within 30 miles of the lake. An estimated 58 jobs in the local community are supported by visitors to Hop Brook Lake.

For more information call (203) 729-8840 or visit the website at:

- Updated: May 4, 2021