Jamestown Dam - Dam and Reservoir

Dam and Reservoir

The Jamestown Dam is 1,418 feet (432 m) long at the crest and 85 feet (26 m) above the streambed of the James River. Measured from the deepest point of excavation to the crest, the height is 110 feet (34 m). Its maximum thickness is 730 feet (220 m) from upstream toe to downstream toe. The dam embankment contains 8,667,000 cubic feet (245,400 m3) of material, primarily dirt, rock, gravel and riprap.

The dam's typical release rate is 1,400 cubic feet per second (40 m3/s). The outlet works are controlled by four identical high-pressure gates, 5 feet by 6 feet (1.5 by 1.8 m) in size. Two are for normal use and two are for emergency releases. The maximum capacity of the outlet works is 2,990 cubic feet (85 m3) per second, or 747.5 cubic feet (21.17 m3) per second per gate. The dam also has an emergency inverted-bell spillway, capable of handling 2,930 cubic feet (83 m3) per second. The total release capacity of the dam is 5,920 cubic feet (168 m3) per second.

The outlet works are designed to allow for possible future installation of hydroelectric generators and future municipal water supply.

The Jamestown Reservoir typically holds 30,000 acre feet (37,000,000 m3) of water, with a normal surface area of 2,095 acres (3.273 sq mi). Its maximum capacity is 230,000 acre feet (280,000,000 m3) and maximum surface area is over 13,250 acres (20.70 sq mi).