Filter Trench Design Option
In addition to the soakaway design functionality, the designer may opt to design a filter trench.
A filter trench is essentially the same as a soakaway except that a specified portion of the surface runoff is allowed to discharge through an overflow pipe. In this way, surface water from a site can be treated by infiltration through the fill media prior to discharge to a watercourse and also removes the need for total storage within a traditional soakaway.
The Filter Trench Options can be found in the Design Options box. Here you can specify the percentage of the impermeable area that you want to overflow to the watercourse. See below for the Filter Trench Design Options...