This supplement includes details on several modeling assumptions used as part of EPA’s
analysis of the Clean Power Plan (Carbon Pollution Guidelines for Existing Electric Generating
Units) using the EPA v5.13 Base Case using Integrated Planning Model (IPM). The
modifications include an enhanced capability for existing coal steam-fired units to adopt
improvements to their heat rates and a modified calculation for stack emissions associated with
biomass combustion. This supplement also includes more detail on the specific modeling
parameters that were used to reflect the state goals that are part of the proposed rule.