Each of the corps' 31 flood control dams is linked to the agency's Reservoir Control Center in Concord. The center uses river volume data and weather reports to determine when and how long to hold back flood waters. It keeps the river from going beyond crest stage. In April 1987 two storms dropped more than six inches of rain, causing the water level at the Birch Hill Dam to rise 33 feet. Flood control dams are typically earthen structures with rock riprap to prevent erosion.
Water level is controlled at a concrete spillway with three or more conduits with sluiceways.
While the West Hill project is under way, the dam will not be able to hold its normal capacity, said Robert Hanacek, manager of the Thames and Blackstone river basins for the Corps of Engineers. Arrival of construction equipment and closing of the dam to hiking and horseback riding will come as a surprise to the hundreds who traverse the area's trails each week. West Hill is a popular recreation area, known for its swimming beach and park ranger programs. Recreation is an important element of the flood control system, Mr. Hanacek said. The disc golf course, which opened last summer at Buffumville Dam, quickly became a hit with enthusiasts.