For most people, a rainy forecast means carrying an umbrella—but for our new team of pollution investigators, it’s a call to action. Baykeeper staff members and Volunteer Pollution Investigators are braving rainy weather to find San Francisco Bay’s industrial polluters.

When big rainstorms hit in late November, we headed out to collect samples of storm water runoff from industrial facilities around the Bay Area. Baykeeper has the samples tested for pollutants to determine whether these facilities are allowing rainwater contaminated with toxic substances to wash into the Bay.

In the weeks before the recent rains, Baykeeper Volunteer Pollution Investigators had surveyed 45 industrial sites we had previously identified as likely polluters. Based on the investigators’ reports, we selected sites where pollution seemed most probable, and where there was also an access point to collect runoff samples.

Toxic runoff most often comes from the outdoor areas of industrial facilities. In these outdoor areas, toxic dust or liquids may build up as a result of the activities on the site. Toxic materials may also be stored outdoors, and trash may be allowed to accumulate. Vehicles in the outdoor areas may leak fluids or pick up toxic substances on their tires and spread them around.

When it rains, all this pollution can get washed into nearby streets or roads, and from there into storm drains that dump it—unfiltered and untreated—into local creeks or directly into San Francisco Bay.

When rain started falling, Baykeeper staff members and volunteers went to the perimeter of the selected industrial facilities with laboratory-grade plastic bottles to fill with rainwater running off the site. If we succeeded in collecting a sample of the polluted runoff water, we took the bottles to a certified lab for testing.

Thank you to all the volunteers who helped out in recent weeks. Already, we’re using evidence gathered by our volunteers to prepare three Clean Water Act lawsuits, with the goal of winning cleanup at three industrial facilities that have contaminated San Francisco Bay.