What is an infiltration trench?
An infiltration trench is an excavated trench 3 to 12 feet deep, backfilled with a stone aggregate, and lined with filter fabric. A small portion of the runoff, usually the first flush, is diverted to the infiltration trench, which is located either underground or at grade. Pollutants are filtered out of the runoff as it infiltrates the surrounding soils. Infiltration trenches also provide groundwater recharge and preserve baseflow in nearby streams. Infiltration trenches are often used in place of other best management practices (BMPs) where limited land is available. Infiltration trenches are most widely used in warmer, less arid regions of the U.S. Infiltration trenches capture and treat small amounts of runoff, but do not control peak hydraulic flows. Infiltration trenches may be used in conjunction with another best management practice (BMP), such as a detention pond, to provide both water quality control and peak flow control.
