US Patent 7497945 Pre-cast drive down water separation pit system

A unitary or modular, pre-cast, drive-down pit system suitable for use in a heavy equipment wash installation. The completed pit collects runoff generated by the washing of heavy equipment such as construction, industrial, farming, or road-building equipment. The pre-cast concrete separation unit and separate wall sections have tongue and groove mating ends that facilitate assembling the pit and provide for sealing against leakage of water. The separation unit has up to four chambers: a primary solids collection section; a secondary solids settling chamber; a free oil separating section; and a pump water holding section.