Management Practices
The effectiveness of car washing management practices at reducing nonpoint source pollutant loads has yet to be measured accurately. Due to the diffuse nature of nonpoint source pollution, it is often difficult to determine the exact impact of a particular pollution prevention measure at reducing pollutant loading.

While not much is known about the water quality of car wash water, it is very clear that car washing is a common watershed behavior. Three recent surveys have asked residents where and how frequently they wash their cars.  Results are provided in the table below.

Surveys

Study	Behavior
Smith, 1996 Maryland	60% Washed car more than once a month
Pellegrin, 1998 California	73% Washed their own cars 73% Report that wash water drains to pavement
Hardwick, 1997 Washington	56% Washed their own cars 44% Used Commercial car wash 91% Report that wash water drains to pavement 56% Washed car more than once a month 50% Would shift if given discounts or free commercial car washes