Dry wells and infiltrating catch basins are open-bottom subsurface storage structures and/or stone reservoirs designed to infiltrate stormwater in a small footprint. While the general design is consistent between the two applications, a dry well is used to manage clean, roof runoff and thereby does not require pretreatment. An infiltrating catch basin is used to manage stormwater from other sources such as roads and parking lots and thereby requires pretreatment.

Dry wells and infiltrating catch basins can both be designed as perforated precast concrete structures surrounded by crushed stone. The perforated structure that makes up the system temporarily stores stormwater before it infiltrates into the surrounding soils. Dry wells can also consist of an excavated stone-filled pit. Filter fabric is used along the sidewalls of both dry wells and infiltrating catch basins. Both types of systems should be designed as off-line practices for retention/runoff reduction, treatment, and groundwater recharge of stormwater runoff from the water quality storm.

These systems are typically more costly than other infiltration BMPs that are located at the surface. Infiltrating catch basins require a separate pretreatment structure such as a proprietary BMP or separate deep sump hooded catch basins. Their advantage is that they are buried, and their footprint is small compared to infiltration chambers. As a result, these practices are ideal when space is limited and only small, discrete controls can fit into a site.