Deep sumps catch basins are storm drain inlets that have a sump below the outlet pipe to capture trash, debris, and coarse sediment. Deep sump catch basins are unique pretreatment BMPS, in that they function very differently and therefore have very different design and maintenance needs than other pretreatment BMPs.

Stormwater runoff enters the catch basin via a grated or curb inlet at the top of the catch basin. The catch basin outlet pipe is located below the inlet and is equipped with a hood (e.g., an inverted pipe). Floatables such as trash and oil and grease are trapped on the permanent pool of water, while coarse sediment settles to the bottom of the catch basin sump.

Deep sump hooded catch basins may be used in conjunction with other Pretreatment BMPs or for space constrained sites where no other Pretreatment BMPs are feasible. Deep sump hooded catch basins and can be impractical for use with surface stormwater BMPs due to the depth of the catch basin outlet pipe.