The last dam built on the Deerfield was Fife Brook Dam, which was built in the early 1970s in conjunction with the development of the Bear Swamp Pumped Storage facility. This facility acts as a battery for power generated during times of low demand. By using excess electricity to pump water to the top of the mountain, where a reservoir was created by building levees around an existing high swamp, energy is stored. When electrical demand is higher (usually midday or afternoon/evening) the water from the upper reservoir can be released through the turbines (which act as pumps in reverse) to meet demand.