A special corps of volunteers, referred to as the Storm Water Assessment Team, or SWAT, has begun its hunt for the worst polluters in Los Angeles, California. Lara Meeker, the team’s leader, encourages the squad to use a covert, almost black-ops mentality to achieve their goals.

Working mostly after business hours or in the middle of the night, SWAT makes unannounced visits to the county's industrial fringe and collects samples from public sidewalks, streets and company property.

"It's one of the few opportunities we have to demonstrate the pollution that’s coming from these facilities every time it rains," Meeker says. "If we're not out there collecting samples and making a stand, then nothing will change."

Over the last three years, Meeker says, they have investigated 40 facilities, filed 14 lawsuits and settled eight cases. The lawsuits usually end in settlements, in which companies agree to make improvements. Businesses often pay for water-quality restoration projects to offset harm from their pollution and must reimburse SWAT for attorney fees and the cost of collecting and analyzing samples.