Learn about sediment forebay

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 requirements.

Why 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 facility.

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.