42 U.S.C. § 7514a: Attainment dates

Implementation plans required under section 7514(a) of this title shall provide for attainment of the relevant primary standard as expeditiously as practicable but no later than 5 years from the date of the nonattainment designation. Implementation plans required under section 7514(b) of this title shall provide for attainment of the relevant primary national ambient air quality standard within 5 years after November 15, 1990 . Implementation plans for nonattainment areas for sulfur oxides or nitrogen dioxide with plans that were approved by the Administrator before November 15, 1990 , but, subsequent to such approval, were found by the Administrator to be substantially inadequate, shall provide for attainment of the relevant primary standard within 5 years from the date of such finding.