Erosion and Sediment Pollution Control Program Manual.pdf

Embankment Sediment Trap - This device has LOW sediment removal efficiency and is not an
ABACT for special protection watersheds. However, sediment removal efficiency can be raised
to MODERATE by adding a 6” layer of compost on the inside face of the spillway and anchoring
it with a suitable netting. In that case it would be an ABACT for HQ watersheds. A HIGH
efficiency rating — ABACT for HQ and EV watersheds — may be obtained by replacing the filter
cloth with 24” diameter compost socks staked across the inside face of the spillway.
York County Conservation District
For traps with embankment spillways, the minimum embankment spillway width (in feet) is 2 times the
number of acres of contributing drainage area. If not discharging directly into a waterway, the minimum
spillway width (feet) should be 6 times the number of contributory drainage acres. The minimum
spillway crest elevation is the elevation at which the required 2,000 cubic feet per contributing drainage
acre storage capacity is provided. The maximum spillway side slope is 2H:1V. The minimum rock size
for construction of the spillway is R-3. R-4 or larger rock is recommended for drainage areas greater
than 3.0 acres. The entire spillway should be constructed with rock — above the clean out elevation,
(see Standard Construction Detail # 8-1). The inside face of the spillway should be covered with a 6”
(minimum) thick layer of filter stone (maximum size = AASHTO #57). Filter fabric should be securely
staked on top of the filter stone up to the top of the spillway. Any excess fabric should be staked to the
bottom of the trap.
363-2134-008 / March 31, 2012 / Page 214