The Environmental Protection Agency (EPA) is approving the Clean Air Act State Plan revisions for Large Municipal Waste Combustors (MWCs) submitted by the Massachusetts Department of Environmental Protection (MassDEP) on December 18, 2018. The revised State Plan is in response to amended emission guidelines (EGs) for Large MWCs promulgated on May 10, 2006. MassDEP's State Plan is for implementing and enforcing provisions at least as protective as the EGs applicable to existing Large MWCs. This action is being taken under the Clean Air Act.