APPLICANT PACKET - Virginia Department of Conservation and ...

6. Anti-Vortex Device and Trash Rack: An anti-vortex device and trash rack shall be attached to the top
of the principal spillway to improve the flow characteristics of water into spillway and prevent floating
debris from blocking the principal spillway.
7. Dewatering: Dewatering of the dry storage should be done in a manner which removes the "cleaner"
water without removing the potentially sediment-laden water found in the wet storage area or any
appreciable quantities of floating debris.
An economical and efficient device for performing the drawdown is a section of perforated vertical
tubing that is connected to the principal spillway at two locations. See Plate 3.14-15 that depicts the
orientation of such a device. By virtue of the potential for the dewatering device or orifice becoming
clogged, no credit is given for drawdown by the device in the calculation of the principal or emergency
spillway locations.
8. Anti-Seep Collars: Anti-seep collars shall be used on the barrel of the principal spillway within the
normal saturation zone of the embankment to increase the seepage length by at least 10%, if either of
the following two conditions is met:
a. The settled height of the embankment exceeds 10 feet.
b. The embankment has a low silt-clay content (Unified Soil Classes SM or GM) and the barrel is
greater than 10 inches in diameter.
Applicant Packet 69
June 2001