On June 2, US EPA published a final rule that outlines the regulatory framework states must follow to implement the 1997 and 2006 standards for fine particulate matter, or PM2.5.  The Rule was issued in response to a remand from the D.C. Circuit Court of Appeals in January 2013, which returned for correction a pair of rules that the Agency issued in 2007 and 2008.

In Natural Resources Defense Council, et al. v. EPA, environmental groups challenged the rules due to US EPA’s use of the “general” implementation requirements contained in Subpart 1 of Part D of Title I of the Clean Air Act (Act), rather than more stringent requirements in Subpart 4.  The crux of the challenge focused on whether the Subpart 4 requirements—specific to particulate matter, but which US EPA argued only apply to coarser PM10—apply to PM2.5.  The court agreed with the environmental groups, observing that the definition of PM10 in Subpart 4 included all particulate matter “equal to or smaller” than 10 micrometers and that a separate category of standards for smaller PM2.5 particles was not yet envisioned at the time of Subpart 4’s promulgation.  Therefore, the express intent of Subpart 4 was to cover any particulate matter smaller than 10 micrometers, including PM2.5.  The court remanded the rule back to US EPA for repromulgation pursuant to Subpart 4.

Under the new Rule, areas failing to meet either the 1997 or 2006 PM2.5 standards will be initially classified as “moderate” nonattainment as of the Rule’s effective date on July 2, 2014.  Thereafter, areas may then be reclassified as “serious” nonattainment if the Administrator determines that the area cannot “practicably attain” the standard by the area’s applicable attainment date.  Subpart 4 generally describes the attainment date as six years after the area’s nonattainment designation.

Along with the immediate classification as “moderate” nonattainment (which was discretionary under Subpart 1), the Subpart 4 requirements in the new Rule include: (1) shorter timetables and more stringent requirements for seeking extensions of time for attainment dates; (2) 4-year deadlines for implementation of “reasonable available control measures” (moderate areas) and “best available control measures” (serious areas); (3) a 5% annual emissions reduction requirement for serious areas; and (4) application of the Subpart 4 control requirements to major sources of particulate matter “precursors” emissions.

As to the latter issue, precursors are emissions of other pollutants that lead to particulate formation.  The new Rule is silent as to how precursors will be addressed, only noting that the Subpart 4 requirement governing precursors is “generally comparable” to Subpart 1.  In the 2007 and 2008 rules, EPA identified SO2, NOx, VOCs and ammonia as precursor gases associated with fine particle formation.  However, based upon its interpretation of the definition of “air pollutant” in Section 302(g), US EPA also took the position that although SO2 must be evaluated for control measures and NOx is presumed regulated, VOC and ammonia would be entitled to a rebuttable presumption against controls.  Although the environmental groups challenged this determination as to VOC and ammonia, the NRDC Court refused to address the argument and in a footnote observed that “Subpart 4 expressly governs precursor presumptions.”  Accordingly, US EPA appears to be treating precursors in the same way as articulated in the 2007 and 2008 rules.

For states with nonattainment areas, the initial tasks for state agencies include assessing whether additional state implementation plan (SIP) elements are necessary to augment any existing SIPs previously submitted pursuant to Subpart 1, as well as submitting SIPs addressing the nonattainment new source review requirements in Subpart 4.  US EPA has established a deadline of December 31, 2014 as a “relatively brief but reasonable amount of time” for states to provide these submissions.

Another noteworthy aspect to the new Rule is its rejection of the environmentalist groups’ call for retroactive application of nonattainment determinations, which could have resulted in the immediate designation of certain areas as “serious” nonattainment.  US EPA states that its refusal to find immediate noncompliance for failure to meet the initial SIP designation deadlines is based on the fact that it had not “instructed” the states to submit SIPs under the Subpart 4 timeline.  US EPA explains that such a finding “would not give the states the opportunity to prepare or submit an appropriate SIP before being found in default of that obligation.”  This explanation is somewhat ironic given US EPA’s position in the CSAPR litigation, where US EPA’s failure to quantify emission reduction targets led to findings of immediate noncompliance against regulated states and the immediate imposition of federal implementation plans.  Regardless, US EPA’s rejection of retroactive application of the nonattainment determinations tempers the imposition of the more stringent Subpart 4 requirements.