Underground stormwater detention tanks hold runoff below grade and release it through a controlled outlet. The category covers tanks that temporarily detain stormwater when the site plan calls for storage beneath a yard, parking area, or other paved surface.

Water Detention Tanks

A concrete detention tank may suit a project that needs a rigid underground structure, but its dimensions and structural design must match site conditions and expected loads. An on site detention tank is sized to meet the project’s drainage calculations and the release rate set by local stormwater requirements.

Projects with limited room at the surface can include on site detention tanks in the stormwater layout. Coordinate the tank location, inlet and outlet elevations, and inspection access with the civil engineer and contractor before construction.

How is tank capacity determined?

A civil engineer uses the drainage area, paved surfaces, local design storm, and permitted release rate to calculate required capacity. Confirm the design with the authority reviewing the stormwater plan.

Where should a detention tank be installed?

Check utility locations, groundwater conditions, soil, and expected surface or vehicle loads before choosing a location. Keep access points reachable for inspection and maintenance.

What maintenance does a detention tank need?

Inspect the inlet, outlet, and access points for blockages or sediment, and clear them as needed. Follow the tank manufacturer's instructions and local stormwater requirements.