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Last Updated: Thursday, January 5, 2012 1:08 PM

Oil Water Separator

An oil/water separator is designed to remove free oil and grease from stormwater runoff. This maintenance station BMP separates oil and water by allowing oil droplets to collide and coalesce to become larger globules that are captured in the separator. The separator consists of three compartments: a forebay, an oil separation cell, and an afterbay. The forebay is a cistern that traps and collects sediments. A central oil separation cell captures and holds oil. Vertical metal plates allow oil to migrate away from the stormwater. The afterbay is designed to provide the stormwater a relatively oil-free exit from the separator. The separator is inspected monthly and cleaned of deposits and debris as needed.

Site Location: Alameda Maintenance Station

Directions: I-10 eastbound to northbound Alameda Street off ramp, to 1740 E. 15th Street (under I-10 bridge)

Oil/water separator during construction — before being placed underground


Division of Environmental Analysis, Stormwater Unit
California Department of Transportation
P.O. Box 942874, MS-27
Sacramento, CA 94274-0001
Email: Division of Environmental Analysis, Stormwater Unit