During periods of high runoff, most often during extreme storms when rain or snowmelt fill the reservoir, the outlet structure can release up to 2,300 cubic feet of water per second. (One cubic foot of water is equal to 7.5 gallons.) The Jamestown Dam outlet can release just over 2,700 cfs. For perspective, the record water release in 2009 through the outlet structures at Pipestem and Jamestown dams were 1,420 and 1,807 cubic feet of water per second, respectively, for a combined 3227 cfs release flow.
The Pipestem spillway has never been needed but it is designed to pass more than 56,000 cfs of water if necessary. Even if streams and rivers below the dams reach or exceed their capacity, water can flow through the spillway to reduce the possibility of water flowing over the dam that can lead to dam failure, or breach. A breach would allow the water stored behind the dam to flow uncontrolled, further intensifying downstream flooding. This would impact critical infrastructure and downstream levee systems and put thousands of lives at risk in Jamestown and further downstream in the James River Basin.
Pipestem Dam continues to reliably reduce floods, but it alone, or in conjunction with Jamestown Dam, cannot eliminate the risk of flooding.