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Final Rule to Add PM2.5 Precursors to the Transportation Conformity Rule
EPA420-F-05-005, May 2005
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This final rule is part of EPA's overall strategy for assisting state and local governments in implementing the new ozone and PM2.5 national ambient air quality standards. Specifically, this final rule provides new PM2.5 nonattainment areas with the requirements for considering PM2.5 precursor emissions when making determinations that transportation activities will not interfere with the area's air quality goals. EPA's designations for the new PM2.5 standard were effective April 5, 2005, at which point a one-year conformity grace period began. The grace period allows time for the newly designated PM2.5 nonattainment areas to prepare their first conformity determinations.
- Background
- Description of Final Rule
- Key Elements of the Final Rule
- Health and Environmental Impacts
- More Information
Background
Transportation conformity is a Clean Air Act requirement that ensures that federally supported highway and transit projects are consistent with ("conform to") a state air quality implementation plan (SIP). Conformity ensures that public health is protected by early consideration of transportation decisions in cities with air quality challenges.
On November 5, 2003, EPA published a proposal to address conformity requirements under the new ambient air quality standards (68 FR 62690), including proposals to address PM2.5 precursor emissions in conformity. The majority of the provisions from the November 2003 proposal were finalized in our July 1, 2004, final conformity rule. Subsequently, Environmental Defense, the Natural Resources Defense Council, Sierra Club and TRANSDEF filed suit against portions of the July 1, 2004 rule. This suit specifically challenges the omission of PM2.5 precursor requirements from that rule.
EPA did not include PM2.5 precursor requirements in the July 1, 2004, final rule because, at that time, EPA had not yet proposed a broader PM2.5 implementation rule to seek comment on options for addressing PM2.5 precursors in the New Source Review program and in other SIP planning activities. However, several facts now lead us to believe it is necessary and appropriate to issue this final rule addressing precursor emissions in transportation conformity determinations:
EPA's designations for the new PM2.5 standard were effective April 5, 2005, at which point a one-year conformity grace period began. It is important that transportation conformity implementers know the requirements during the grace period, as it takes time to prepare a conformity determination. Conformity determinations for the PM2.5 standard will be due at the end of the one-year grace period: April 5, 2006.
This final rule has been developed in coordination with the PM2.5 implementation rule proposal that is currently being prepared. This final rule will not prejudge the outcome of the PM2.5 implementation rule.
Description of Final Rule
This final rule adds NOx, VOCs, SOx, and ammonia to the transportation conformity regulations and specifies when each of these precursors must be considered in conformity determinations in PM2.5 nonattainment and maintenance areas, before and after PM2.5 SIPs are submitted.
Specifically, once a PM2.5 SIP is submitted, a PM2.5 precursor must be considered in an area's conformity determinations if the SIP determines that emissions for that precursor are a significant contributor to the area's PM2.5 air quality problem.
Prior to the submission of a SIP, NOx emissions must be considered in PM2.5 conformity determinations, unless both the state air agency and the EPA Regional Administrator make a finding that NOx is not a significant contributor to the PM2.5 air quality problem. Conversely, VOC, SOx and ammonia emissions do not have to be considered in conformity, unless either the state air agency or EPA Regional Administrator makes a finding that on-road emissions of any of these precursors is a significant contributor to the area's PM2.5 air quality issue.
Key Elements of the Final Rule
This final rule balances the need to protect air quality with the need to conserve the limited resources of state and local transportation and air quality agencies. NOx is the only PM2.5 precursor that must be examined in conformity analyses (unless a finding is made), because data indicate that NOx contributes to the air quality problem in most PM2.5 nonattainment areas. However, VOC, SOx and ammonia precursor emissions only need to be examined if they are found to be significant for a particular area. EPA believes this final rule is consistent with existing statutory requirements and scientific information that supports the consideration of PM2.5 precursor emissions in transportation conformity.
This final rule provides new PM2.5 nonattainment areas with the requirements for considering PM2.5 precursor emissions in transportation conformity determinations. Transportation conformity for the PM2.5 air quality standard will apply in newnonattainment areas on April 5, 2006 – that is, one year after the effective date of their designation.
This final rule is consistent with EPA's PM2.5 implementation strategy proposal currently being prepared. However, this rule should not be seen as prejudging our decision on the PM2.5 implementation rulemaking. While EPA's final decisions on PM2.5 precursors must be legally consistent, EPA could take differing positions with respect to various precursors in other programs as appropriate to the programmatic needs, legal requirements and pollution sources relevant to the differing programs.
EPA has worked closely with the U.S. Department of Transportation in the development of this final rule.
This rule is based on the November 2003 proposal and the public comments that were received in response to that proposal. EPA consulted with state and local transportation and air quality agencies and interest groups in its initial development of the conformity options for the new standards that were proposed in November 2003.
Health and Environmental Impacts
By providing new PM2.5 nonattainment areas with the requirements for considering PM2.5 precursor emissions in conformity determinations, EPA believes this final rule will support the Clean Air Act's air quality standards to protect the public and environmental health.
More Information
You can access the final rule and related documents electronically on EPA's Web site.