This chart is a reproduction of a chart from Edison Electric Institute (EEI) that has been used to suggest that EPA’s regulatory timeline is unworkable - see http://www.eei.org/meetings/Meeting%20Documents/EPA-CAAUtilityRegTimelin.... WRI has identified four categories of EPA activities on the EEI timeline that are potentially misleading:

(Blue X's) Rules that have been remanded or vacated by court decisions that do not impose compliance obligations.
(Green X's) Rules that are already in effect representing compliance obligations that already exist; there are no new requirements imposed by these rules.
(Purple X’s) Public input through the rulemaking process (leads to more robust and fair rules for the electric power sector, and should not be conflated with new compliance obligations).
(Red X’s) National Ambient Air Quality Standard (NAAQS) rules for various pollutants that set standards for states to achieve. They do not establish new requirements for electric generation units.