What is a sediment forebay:
A sediment forebay is a small pool located near the inlet of a storm basin
or other stormwater management facility. These devices are designed as
initial storage areas to trap and settle out sediment and heavy pollutants
before they reach the main basin. Installing an earth berm, gabion
wall, or other barrier near the inlet to cause stormwater to pool
temporarily can form the pool area. Sediment forebays act as a pretreatment
feature on a stormwater pond and can greatly reduce the overall pond maintenance
consider a sediment forebay:
These small, relatively simple devices add a water quality benefit beyond
what is accomplished by the basin itself. Forebays also make basin maintenance
easier and less costly by trapping sediment in one small area where it
is easily removed, and preventing sediment buildup in the rest of the
Installing sediment forebays with stormwater ponds will increase the construction
cost of the basin slightly and may require some additional land area.
With heavier, coarse sediments confined to the forebay area of a basin,
maintenance is simpler and less costly. Sediment forebays therefore also
act to extend the life of the stormwater pond. They can be installed in
both wet and dry basin designs. And there is the added benefit of even
cleaner water being discharged to our streams.
The cost of a sediment forebay depends on its design requirements. Some
forebays are incorporated into the wet pond pool area, while others are
separate smaller pools. Design features such as impermeable liners
(ease cleanout) and baffles and embankment materials will all affect
the ultimate cost of the forebay.
It is recommended that sediment forebays be cleaned out every 5-7 years
or as required.