The dam at Northfield Brook Lake is located 1.3 miles above the brooks confluence with the Naugatuck River. Completed in 1965 at a cost of $2.8 million, the earth and rockfill dam is part of a network of flood control dams and local protection projects built by the U.S. Army Corps of Engineers in the Naugatuck River Basin.

The Reservoir Regulation Team (RRT), is the "nerve center" for the New England flood control dams such as Northfield Brook Lake. Using radio and satellite communications, RRT constantly monitors river levels and weather conditions that influence flood control decisions.

Unlike many other flood control dams in New England Northfield Brook Lake is "self-regulating". The 3'X 3' gate is preset to control the desired discharge. If water flows into the reservoir faster than the gate can drain it, the extra water backs up behind the dam. If this inflow exceeded outflow long enough, the stored water would eventually flow over the spillway back into Northfield Brook.