If you do, and you let the soapy water run into the storm drains, you might be killing fish in your local streams, lakes and ocean. This post on Autoblog describing a newly proposed driveway car washing ban in Clark County, Washington got me surfing around a bit. Here's a pretty intense study on the impact of driveway car washing on the Puget Sound. Our local King County, Washington site describes how to build a car wash kit for schools, clubs, churches and other non-profit organizations that hold community or charity car wash fundraising events. Apparently, switching to biodegradable soap doesn't help, either (which is what I did when my daughter starting helping me wash the cars). According to this Floyd County, Georgia site, biodegradable soap is toxic to wildlife as well. So if you want to soap up your car this weekend, the best thing is probably just to head down to the local car wash.