Aug 09, 2007

Study Addresses Car Wash Runoff

Detergents harm fish, but practical solutions exist

In the interest of resident, swimmer, boater and fish safety, many U.S. municipalities are placing water quality atop their summer agendas. Many homeowners and parking lot car wash businesses, however, may not realize the effects untreated car wash effluent can have on local water quality.Seattled-based Environmental Partners, Inc. conducted two tests in 2006 using fish mortality rates to measure the potential impact of untreated car wash discharges on the city storm water system and, thus, area lakes and streams. The independent study was underwritten by Vic Odermat, a lifelong environmentalist and owner of Brown Bear Carwash in Seattle.Detergents and surface residue from car washes typically run into the nearest storm drain, most of which carry such excess water into nearby waterways without providing any treatment. Storm water runoff is the most common source of stream, river, lake, ocean and inlet pollution and can have a devastating effect of aquatic life.In this Seattle study, researchers conducted fish toxicity tests using runoff samples collected from a fund-raising car wash event held in a parking lot compared with a simulated runoff sample that was potable. The car wash runoff sampled caused a 100 percent fish mortality rate in all dilution steps tested; the fish survived in the potable water. Detergents, including those that are biodegradable, can damage fish's mucus membranes and gills and wash away natural oils that help them absorb oxygen.Under Clean Water Act guidelines, commercial car washes are not permitted to send their dirty water into storm drains. Such water must be discharged into a separate sewer or treated and recycled.Some practical solutions for reducing the impact of driveway or parking lot car wash runoff on storm drains include: washing vehicles on permeable surfaces such as gravel driveways or lawns; using a bucket of water and sponge for at-home car washing and disposing of the dirty water in a sink, toilet or other sanitary sewer; and blocking off storm drains during events like the car wash fundraiser, using an insert to collect the water and disposing of it on grass or landscaping.Information on the fish toxicity study and car wash fundraising options (i.e. car wash kits, environmentally friendly programs) are available at and