A group of Senate Democrats introduced a mining reform bill on Tuesday with the goal of averting disasters such as the one caused by federal contractors that spilled 3 million gallons of toxic sludge into the Animas River in Colorado in August 2015.

Sens. Tom Udall and Martin Heinrich of New Mexico, Michael Bennet of Colorado, Ron Wyden of Oregon, and Ed Markey of Massachusetts introduced the Hardrock Mining and Reclamation Act of 2017, seeking to modernize the nation’s antiquated hard rock mining laws by making sure companies pay for cleanup activities.