Infiltration trenches are shallow, excavated, stone-filled trenches in which stormwater is collected and infiltrated into the ground. Infiltration trenches can be constructed at a ground surface depression to intercept overland flow. This BMP can also receive piped runoff discharged directly into the trench such that the trench is designed to distribute the flow from a point discharge in a manner that does not result in erosion. Runoff gradually percolates through the bottom and sides of the trench, removing pollutants through sorption, trapping, straining, and bacterial degradation, or transformation. Infiltration trenches may also be used to provide stormwater quantity control when designed as on-line facilities.

Infiltration trenches are a cost-effective approach to managing stormwater where there is adequate space for a narrow stormwater feature and where plantings are not needed, and the surface of the trench can be left open. They require less space than infiltration basins as they utilize the void spaces of the stone in the trench to temporarily store water.