Diascund Dam Rehabilitation
$3.7 million high hazard dam project, designed by Gannett Fleming,
was in New Kent County, Virginia where the Diascund Reservoir serves
as a 1,110-acre water supply for the City of Newport News. The
250-ft wide principal spillway for the reservoir’s dam needed major
reconstruction from the crest down the 80-ft long concrete chute &
stilling basin. The City of Newport News first lowered the reservoir
level to eliminate flow over the spillway while Crowder installed
dewatering well-points to eliminate underground intrusion.
contract also included removal and replacement of two existing 48"
x 72" sluice gates at the reservoir’s pump station. The gates
could only be accessed on the downstream side of the Pump Station
through the 150' long, 10' wide, and 8' high concrete Diversion
Outlet that is typically underwater due to tidal influences. A
temporary cofferdam was installed at the end of the Diversion Outlet
to prevent water from back feeding into the chamber and the upstream
side of the gates were sealed to prevent uncontrolled amounts of
water exiting the reservoir. A diving team installed steel plate
bulkheads at both upstream openings. Crowder removed the existing
gates, including the 35' long valve stems with wall brackets.
Crowder completed the reinstall of the new gates, leakage testing was
successful, divers returned and removed the upstream bulkheads, and
the project was complete.