Companies responsible for dumping waste at a Superfund site in California now will have to figure out their piece of a $60 million cleanup bill.

The Casmalia Resources Superfund site is a former commercial hazardous waste management facility covering more than 250 acres in Santa Barbara County. Environmental Protection Agency Administrator Scott Pruitt added the site to his personal priority list in April to focus on accelerating cleanup there. The agency announced June 28 it...