Section 52.1974 - Original identification of plan section(a) This section identified the original "State of Oregon Clean Air Act Implementation Plan" and all revisions submitted by Oregon that were federally approved prior to July 1, 2013. The information in this section is available in the 40 CFR, part 52, Volume 4 (§ 52.1970 to End) edition revised as of July 1, 2013. 83 FR 63580 , Dec. 11, 2018