The department is responsible for regulating air quality, water quality, underground storage tanks, automobile wrecking facilities, hazardous waste facilities, solid waste management systems, and mining operations; and for the siting and needs analyses of large-scale energy facilities.  In addition, the department is the lead agency for reclamation and cleanup activities related to the federal and state superfund programs and leaking underground storage tanks, and for regulation and permitting of mining conducted on private, state, and federal lands.  This work is completed through four programs – Central Management, Water Quality, Waste Management & Remediation, and Air, Energy, & Mining.  The Petroleum Tank Compensation Board and the Libby Asbestos Superfund Oversight Committee are also attached for administrative purposes.

The department works in partnership with the federal Environmental Protection Agency (EPA) and the and Department of Interior Office of Surface Mining.  Congress gave the EPA the initial responsibility for development and implementation of environmental protection, but many federal statutes contain preference for delegation of the program to the states when the state can demonstrate capacity to carry it out. This arrangement establishes state-federal environmental goals and priorities with the funding and flexibility to achieve desired results.  These joint activities become the basis of future agreements and long-term strategic planning.