In Citizens for a Better Environment, et al. v. Union Oil Company (Unocal) and Tosco Oil Company, and Communities for a Better Environment, et al. v. Exxon, DHKL represented a number of Bay Area environmental organizations and private citizens in challenging Unocal’s and Exxon’s discharge of excessive amounts of selenium into the San Francisco Bay in violation of the oil companies’ pollutant discharge permit limits.  As a result of settlements reached in the two cases, the oil companies agreed to implement water treatment systems to comply with their selenium discharge permit limits and to contribute millions of dollars to local foundations to fund projects dedicated to the health of the San Francisco Bay and its ecosystem.

CBE v. Unocal also established landmark precedent in the Ninth Circuit Court of Appeals, holding that citizens may sue polluters for violating their permit limits when previous government enforcement against those violations is inadequate.  See Citizens for a Better Environment v. Unocal Oil Co., 83 F. 3d 1111 (9th Cir. 1996).