Wash vehicles on grass, not on pavement. Wash your vehicle over an unpaved area, such as an area covered with grass or gravel. Washing over an unpaved surface will allow the soapy water to soak into the ground, be filtered, and eventually recharge the groundwater. If you have your own well, you should wash your vehicle at least 100 feet from the well head. If you wash the vehicle on a paved surface, the runoff flows into a storm drain, and the water and contaminants are discharged to the nearest lake or stream.