Remove all trash and debris from the car washing area before the event. Use only "nontoxic," "phosphate free" or "biodegradable" soap. No acid-based wheel cleaners should be used. Consider contracting with a professional mobile car washing service or using rented pressure-washing equipment. High pressure/low volume equipment uses less than a 10th of the water conventional techniques do. If using conventional "hose and bucket" methods minimize runoff by:

• Shutting off or "kinking" hoses when not in use. Put a shutoff or spray nozzle on the hose.
• Select washing area where cars can be driven onto grass or gravel for washing, or where runoff will drain to a landscaped area.
• Use buckets for soapy water to "resoap" rags and sponges rather than adding soap directly to rags or sponges (this helps avoid contaminating runoff, and saves soap as well). Wring sponges and rags into buckets, not onto ground.
• Buckets of soapy water should be drained into the sanitary sewer. Do not empty buckets onto the parking lot, street gutter or into storm drains.

Remember to clean up the site after the event. This helps prevent stormwater contamination, and will make the property owner more willing to allow future fund raising events.