On December 19, 1995, pursuant to sections 111 and 129 of the Clean Air Act, EPA promulgated emission guidelines applicable to existing municipal waste combustor (MWC) units and new source performance standards applicable to new MWC units. The guidelines and standards are codified at 40 CFR Part 60, subparts Cb and Eb, respectively. See 60 FR 65387. On April 8, 1997, the United States Court of Appeals for the District of Columbia Circuit vacated subparts Cb and Eb as they apply to MWC units with the capacity to combust less than or equal to 250 tons per day of municipal solid waste (MSW), and all cement kilns combusting MSW, consistent with their opinion in Davis County Solid Waste Management and Recovery District v. EPA, 101 F.3d 1395 (D.C. Cir. 1996), as amended, 108 F.3d 1454 (D.C. Cir. 1997). As a result, subparts Cb and Eb apply only to MWC units with the capacity to combust more than 250 tons per day of MSW per unit (large MWC units). This document amends the guidelines and the standards for MWC units to make them consistent with the Davis decision and subsequent court vacatur order. The guidelines and standards being amended have remained in effect for large MWC units since December 19, 1995 because the court did not vacate or stay the rules as they apply to these units. The amended guidelines and standards result in the 1995 rule being applicable only to MWC units with the capacity to combust greater than 250 tons per day of MSW per unit. In this document, these units are referred to as large MWC units or large MWC's. The amendments affect the applicability of the guidelines and standards, and add supplemental emission limits for four pollutants (hydrogen chloride, sulfur dioxide, nitrogen oxides, and lead) to the guidelines. The amendments do not add any additional emission limits to the standards. The 1995 guidelines and standards applied to MWC units at plants greater than 35 megagrams per day combustion capacity (approximately 39 tons per day). Because t