In this final rule, the EPA is amending the definition of "major stationary source" in Appendix S to include 70 tpy major source thresholds for direct PM2.5 emissions and individual PM2.5 precursors, applicable in Serious PM2.5 nonattainment areas. See Appendix S sections II.A.4(i)(a)(7) and (8), respectively. As described earlier, applicability of the NNSR requirements to a source will be determined individually for direct PM2.5 emissions and for emissions of individual PM2.5 precursors. For example, if a new source locating in a Serious PM2.5 nonattainment area would emit 70 tpy of the PM2.5 precursor SO2, it will be considered a major source of PM2.5 (with respect to the SO2 precursor) and will be subject to the NNSR requirements for PM2.5 with regard to the SO2 emissions. However, if the same proposed source does not emit 70 tpy of direct PM2.5 emissions or another PM2.5 precursor, the emissions increase of direct PM2.5 or the other precursor will not be subject to control based on the NNSR requirements for PM2.5. It should also be noted that VOC and ammonia are subject to the phase-in schedule described in the definition of "regulated NSR pollutant" in the NNSR regulations at Appendix S, section II.A.31.(ii)(b)(2).
      iii. Comments and Responses.
      As explained in Section VIII.B.1.b of this preamble, commenters addressing the proposed major source threshold of 70 tpy for sources of PM2.5 and its precursors locating in Serious areas had mixed responses, particularly with regard to the appropriate thresholds for precursors. Most of the comments applied generally to the proposed thresholds in 40 CFR 51.165 and Appendix S. The EPA's responses to these comments are provided in that earlier section of the preamble.
      Comment: One commenter, however, recommended that during the SIP transition period (and while the EPA continues its analysis of the precursor relationships to PM2.5), the EPA should allow states to make a case-by-case permitting demonstration to use higher major source thresholds for precursors for NNSR permit reviews.
      Response: As explained previously, in light of the ongoing precursor impact studies as well as concerns about the legality of setting higher major source thresholds than those specified in the CAA, the EPA believes it is most reasonable to establish a 70 tpy major source threshold under Appendix S for sources of direct PM2.5 emissions and each PM2.5 precursor locating in Serious nonattainment areas.
      c. Significant Emissions Rates (SERs) in Appendix S -- PM2.5 Precursors.
      i. Summary of Proposal.
      As explained earlier, the EPA proposed as its preferred approach to add NOx as a PM2.5 precursor in the Appendix S definition of "regulated NSR pollutant." Accordingly, the EPA also proposed to amend the definition of "significant" at section II.A.10(i) of Appendix S to establish a SER of 40 tpy for NOx as a PM2.5 precursor. The Appendix S definition already contains a SER for SO2 as a PM2.5 precursor at 40 tpy of SO2. The EPA did not explicitly propose to include SERs for VOC and ammonia in Appendix S as part of the preferred approach; however, the EPA's proposed alternative approach to phase in VOC and ammonia as PM2.5 precursors at a later date would inherently necessitate adding SERs for those two additional precursors in the event that an alternative approach was ultimately selected for the final rule.
      ii. Final Action.
      The EPA is revising the definition of "significant" in Appendix S at section II.A.31(ii)(b)(2) to provide SERs for NOx and VOC as PM2.5 precursors, consistent with its decision to conditionally phase in regulation of all four PM2.5 precursors 24 months from the date of redesignation. The individual SERs for NOx and VOC as PM2.5 precursors, being added to the existing SER for SO2 as a PM2.5 precursor, are each defined as 40 tpy of the respective precursor, consistent with the SERs provided in the revised definition of significant in 40 CFR 51.165.
      The EPA is not adding a SER for ammonia (as a PM2.5 precursor) in the Appendix S definition of "significant" in this action. Consistent with the EPA's approach for allowing states to define "significant" for ammonia in their NNSR rules, and for the reasons explained in Section VIII.B.1.c of this preamble, the EPA will allow states that issue NNSR permits pursuant to the requirements in Appendix S to define "significant" with respect to ammonia in a particular area in each NNSR permit issued pursuant to Appendix S. The state should provide a technical justification to support the definition of "significant" for ammonia, including any SER developed by the state for a particular nonattainment area, and such justification should be included in the administrative record for each proposed permit. The state also has the discretion to define "significant" with respect to ammonia as a PM2.5 precursor in those cases where it is determined that the proposed modification will result in insignificant increases of ammonia and the source will therefore not be required to obtain a major NNSR permit. In such cases, the state and the source should also document the technical justification for determining the source impacts will be insignificant, including any SER developed by the state for a particular nonattainment area, whether such documentation occurs in the administrative record for a minor source permit, a nonapplicability determination, or some other form in the state or source's records. The state should consult with the appropriate EPA Regional Office for assistance in developing an appropriate definition of "significant" for ammonia as a PM2.5 precursor in each permit or for each nonattainment area.
      iii. Comments and Responses.
      The comments regarding the proposed addition of SERs for NOx and VOC emissions as PM2.5 precursors in the NNSR definition of "significant" were summarized in Section VIII.B.1.c of this preamble. Those comments applied generally to the NNSR regulations at 40 CFR 51.165 and Appendix S. The reader is referred to that earlier section of the preamble to review the comments and the EPA's responses to them.
      Comment: Some commenters seemingly addressing NNSR under Appendix S recommended that the EPA include a provision allowing states to make case-by-case determinations to use higher SERs for precursors for NNSR permits issued before the SIP is effective. The commenter stated that the precursor SERs are too low and do not realistically reflect the effect that each precursor has on ambient PM2.5 concentrations.
      Response: The EPA believes that the commenter's concern is partially addressed by the fact that, in using Appendix S to review NNSR permit applications, neither VOC nor ammonia will need to be controlled as PM2.5 precursors if the state has submitted to the EPA a complete SIP submission that includes the state's NNSR program for PM2.5 and a NNSR precursor demonstration showing that a particular precursor does not contribute significantly to ambient concentrations of PM2.5 in the nonattainment area, even though the plan revision containing such demonstration has not yet been formally approved. Until the SIP development period has passed and unless the state has failed to submit such a demonstration, the state issuing permits pursuant to Appendix S will not be required to regulate VOC or ammonia as PM2.5 precursors. If a state has not submitted a SIP including the state's NNSR program for PM2.5 and a NNSR precursor demonstration for either VOC or ammonia, sources of these precursor emissions must be controlled as PM2.5 precursors in any NNSR permit issued pursuant to Appendix S beginning on the prescribed phase-in date.
C. Transition Provisions for Major Source Permitting in PM2.5 Nonattainment Areas
      The EPA did not propose any transition provisions for NNSR permit applications in either 40 CFR 51.165 or Appendix S that would expressly grandfather pending PSD or NNSR permit applications for proposed new and modified major stationary sources from newly established NNSR permit requirements applicable to PM2.5 nonattainment areas. In the final 2012 PM NAAQS Rule, the EPA provided a grandfathering provision only for certain PSD permit applications with respect to the revised PM2.5 standard. Historically, the EPA has not provided for the grandfathering of any permit applications from new NNSR requirements or from application of existing NNSR requirements to new or revised standards. Nevertheless, in promulgating the 2012 PM NAAQS Rule, the EPA received unsolicited comments advocating for grandfathering of NNSR requirements for the revised standard. Thus, while explaining the reasons why it did not believe that NNSR grandfathering was appropriate, the EPA sought comments in the proposal on possible circumstances where grandfathering similar to the PSD grandfathering provision established for the 2012 PM2.5 standard might be appropriate with respect to changes made regarding NNSR requirements for PM2.5 in this rulemaking.
Several comments received during the 2012 PM NAAQS rulemaking recommended that the EPA establish a grandfathering provision for NNSR as was proposed for the PSD program. A subset of these commenters recommended that PSD permit applications be grandfathered from the NNSR requirements for the revised 2012 PM2.5 standard by establishing an effective date for designations 1 year after initial publication in the Federal Register. The commenters presumably believed that by delaying the effective date of any new nonattainment designations for the primary annual PM2.5 NAAQS, sources with pending PSD permit applications could continue to be reviewed and permits issued under the PSD requirements rather than the NNSR requirements for PM2.5.
The EPA explained at the time that the obligation to adopt new provisions under a state's NNSR program will not apply with regard to the revised NAAQS until such time as an area is designated nonattainment, and beginning on the effective date of the new area designations for PM2.5, proposed new and modified major sources would be required to meet the applicable NNSR requirements for PM2.5. Also, the EPA does not agree with the commenters' recommendation that the effective date of the area designation be delayed by 1 year because this approach, similar to delaying the effective date of the NAAQS, would also delay the implementation of the attainment plan and defer the important health benefits associated with the revised NAAQS. In the same preamble, the EPA proposed a schedule for promulgating area designations for PM2.5 that involved the maximum allowable 2-year period from the signature date of the 2012 PM2.5 NAAQS, as provided in CAA section 107(d)(1)(B). The CAA allows for a 1-year extension for such designations, but only if there is insufficient information to enable such designations to be made.
      In response to the EPA's request for comments in the proposal, commenters recommended that the EPA clarify the PM2.5 NSR grandfather policy to explain that both PSD and NNSR permit applications are exempt from the precursor and planning requirements being finalized in this rulemaking. In particular, the commenters recommended that the EPA establish a PM2.5 NSR transition policy that delays regulation of the scientific precursors of PM2.5 under any NSR program until the EPA has a better understanding of how these precursors contribute to nonattainment and could deteriorate air quality. One of the commenters indicated that a transitional policy is especially important until the EPA completes a rulemaking on a SER for ammonia. One of the commenters recommended that the EPA should allow for the grandfathering of pending PSD permit applications, similar to the PSD grandfathering provision for the 2012 PM2.5 NAAQS, for sources that will not be issued a permit until after the effective date of the nonattainment designation under certain conditions. This commenter stated that CAA section 165(c), which forms part of the EPA's basis for grandfathering in the PSD context, should also apply to NNSR permit decisions.
      The EPA does not find a compelling reason to grandfather pending NNSR permit applications for which a permit has not yet issued once the new NNSR requirements -- primarily affecting the control of PM2.5 precursors -- become effective. The EPA believes that it is reasonable to require that a new or modified major stationary source regulate emissions of PM2.5 precursors where such emissions contribute significantly to PM2.5 levels in the nonattainment area. If such precursor emissions are not effectively controlled, and offset by reductions in existing emissions, an increased burden could be placed on the overall attainment plan to address those emissions in order to attain the NAAQS in a timely manner.
      While the final rule contains no general grandfathering provision, this final rule does provide a phase-in process for states relying on Appendix S for purposes of issuing NNSR permits for PM2.5. Appendix S will require the immediate regulation of SO2 and NOx as PM2.5 precursors, the regulation of VOC and ammonia as PM2.5 precursors will only be required under certain conditions and on a delayed timetable. See Appendix S, revised section II.A.31.(ii)(b)(2)-(5). The precursor provisions in Appendix S should alleviate some of the commenter's concerns that the regulation of additional precursors will be required immediately upon the effective date of this final rule. Instead, the phase-in schedule for the regulation of VOC and ammonia will permit states the opportunity allowed by CAA section 189(e) to demonstrate that a particular precursor need not be subjected to control in a particular nonattainment area. Accordingly under the interim NNSR requirements in Appendix S, a state will not be required to begin immediate regulation of precursors that will likely be exempted from the regulations upon review of a state's NNSR SIP submission. Similarly, where the state has a previously approved NNSR program for PM2.5, the existing requirements for controlling precursors would continue to apply until the new SIP revisions required by this rule, including new precursor control requirements, are approved. Thus, such states would not be required to immediately regulate any PM2.5 precursors not already required by the approved plan during the interim plan development period.
      With regard to grandfathering PSD permit applications, we do not interpret the CAA to allow for the issuance of a PSD permit in an area that is designated nonattainment. The CAA requires proposed major stationary sources and major modifications to meet major NSR permitting requirements that apply on the basis of the area's designation. Accordingly, the EPA's longstanding interpretation of the CAA is that a proposed new major stationary source or major modification must satisfy the appropriate major NSR requirements (PSD vs. NNSR) for a particular pollutant that are in effect in a given area on the date that a permit is issued to the source, rather than the requirements that may have been applicable when the permit application was submitted.
IX. Other Requirements and Considerations for PM2.5 Nonattainment Areas
A. Waivers Under CAA Section 188(f)
1. Statutory Requirements and Existing Guidance.
      a. Summary of Proposal.
      The proposal summarized the statutory requirements and existing guidance for CAA section 188(f), which provides that, "the Administrator may, on a case-by-case basis, waive any requirement applicable to any Serious Area... where the Administrator determines that anthropogenic sources of PM10 do not contribute significantly to the violation of the PM10 standard in the area." In addition it provides that, "the Administrator may also waive a specific date for attainment of the [PM10] standard where the Administrator determines that nonanthropogenic sources of PM10 contribute significantly to the violation of the PM10 standard in the area." The agency requested comment on whether the existing guidance in the Addendum is appropriate when implementing the current and any future PM2.5 NAAQS.
      b. Final Rule.
      The EPA is hereby affirming its reliance on the interpretation of CAA section 188(f) described in the Addendum for purposes of implementing the PM2.5 NAAQS. For example, the Addendum lays out a series of questions that should be answered before the waiver provisions can be applied, including questions related to the types of sources that may be considered anthropogenic and nonanthropogenic, the specific conditions under which the attainment date for a Moderate area may be waived, and the time period that would apply to an attainment date waiver. The EPA believes that these questions, and the general guidance provided in the Addendum on how to evaluate the answers, provide adequate direction to the EPA and to states potentially interested in seeking waivers for certain PM2.5 NAAQS nonattainment areas. The EPA therefore refers interested states to the waiver guidance contained in the Addendum for more detail on how the agency interprets CAA section 188(f) for purposes of implementing the PM2.5 NAAQS.
      c. Comments and Responses.
      The comments received on this section are addressed in the Response to Comments document found in the docket for this action.

2. Relationship Between the CAA section 188(f) Waiver Provisions and the EPA's Exceptional Events Rule.
a. Summary of Proposal.
The proposal summarized the relationship between the 188(f) waiver provisions and the EPA's Exceptional Events Rule. On March 22, 2007, the EPA promulgated the "Treatment of Data Influenced by Exceptional Events; Final Rule" (72 FR 13560), known as the Exceptional Events Rule, pursuant to the 2005 amendment of CAA
section 319. The Exceptional Events Rule provides a mechanism by which the EPA can concur with a state's request to exclude from regulatory decisions air quality monitoring data determined by the EPA to have been affected by exceptional events. The Exceptional Events Rule applies to all the NAAQS pollutants, including PM2.5. CAA section 188(f) and the Exceptional Events Rule provide separate mechanisms by which states can seek to have event-influenced monitoring data excluded from certain regulatory requirements or decisions associated with the PM NAAQS implementation process, under appropriate circumstances.
b. Final Rule.
The EPA did not make any revisions to its interpretation of the relationship between the CAA section 188(f) waiver provisions and EPA's Exceptional Events Rule.
      The Exceptional Events Rule addresses elevated emissions from specific events that influence monitored air quality concentrations. The EPA's regulations at 40 CFR 50.1(j) define an "exceptional event" as one that "affects air quality, is not reasonably controllable or preventable, is an event caused by human activity that is unlikely to recur at a particular location or a natural event, and is determined by the Administrator in accordance with 40 CFR 50.14 to be an exceptional event." Further, 40 CFR 50.1(j) explicitly provides that exceptional events do "...not include stagnation of air masses or meteorological inversions, a meteorological event involving high temperatures or lack of precipitation, or air pollution relating to source noncompliance." At 40 CFR 50.1(k), the EPA's regulations define a "natural event" as an event in which human activity plays little or no direct causal role to the event in question.
      Air quality monitoring data that the EPA determines to have been influenced by an exceptional event under the procedural steps, substantive criteria, and schedule specified in the Exceptional Events Rule may be excluded from regulatory decisions such as initial area designations decisions and decisions associated with implementing the PM2.5 NAAQS such as clean data determinations, evaluation of attainment demonstrations, and discretionary or mandatory reclassifications of nonattainment areas from Moderate to Serious. While the EPA may agree with a state's request to exclude event-influenced air quality monitoring data from regulatory decisions, these regulatory actions require the EPA to provide an opportunity for public comment on the claimed exceptional event and all supporting data prior to the EPA taking final agency action.
      If wildfire is a potential contributor to exceedances of the NAAQS and exceptional events, the EPA urges state and local agencies to coordinate with the land management agencies, as appropriate, in developing plans and appropriate public communications regarding public safety and reducing exposure. This action can directly help states meet their Exceptional Events Rule obligation whereby "states must provide public notice, public education, and must provide for implementation of reasonable measures to protect public health when an event occurs." When wildfire impacts are significant in a particular area, states and communities may be able to lessen the impacts of wildfires by working collaboratively with land managers and land owners to
employ various mitigation measures including taking steps to minimize fuel loading in areas vulnerable to fire.
      The EPA notes that there could be some potential overlap between the application of the Exceptional Events Rule and CAA section 188(f) because the conditions necessary for the Administrator to make a determination under CAA section 188(f)  -  i.e., the lack of a significant anthropogenic contribution to a violation -- may overlap with conditions that may be considered an exceptional event, particularly a natural event, which by definition represents a non-anthropogenic contribution. The EPA believes that this potential for overlap can best be addressed by considering the applicability of the Exceptional Events Rule and CAA section 188(f) in sequence. Thus, the EPA recommends that states first consider whether the monitored air quality data on specific days were influenced by an exceptional event. If the state requests and the EPA agrees with this request and determines that the monitored air quality data should be excluded from consideration in regulatory decisions, then using the provisions in the Exceptional Events Rule could address the situation adequately, and there would be no need for a CAA section 188(f) waiver. If the state determines that, even with the exclusion of the event-influenced data, the waiver provisions of CAA section 188(f) may also be applicable, then the EPA can evaluate that question based on the remaining data that are representative for the area in question. Given that section 188(f) has rarely been invoked, a state wishing to pursue this provision should work closely with its EPA Regional Office.
      c. Comments and Responses.
      Comments: Some commenters urged the EPA to clarify the two-step approach. Some commenters recommended that the EPA refrain from directing the sequence and allow states to decide which of these provisions should apply in the specific circumstances that they are addressing, consistent with the commenter's overall recommendation that the EPA give states the maximum flexibility in developing PM2.5 SIPs. Some commenters urged the EPA to provide guidance to the states on when this two-step approach would be appropriate, and when it would be inappropriate. Commenters did not want implementation planning to follow the EPA's exceptional events justification model in which there is great variability among the EPA regions. Commenter encouraged the EPA to work to ensure that PM2.5 implementation plan reviews are subject to similar requirements in all EPA regions with clarifying language in the final guidance to ensure some level of national consistency.
      Response: The EPA agrees with the first comment that, rather than the EPA "directing the sequence," the affected state and the appropriate EPA regional office should discuss the scenario and the affected data to determine whether the Exceptional Events Rule or CAA section 188(f) is the most appropriate mechanism. This decision would be made on a case-by-case basis considering the specific, relevant facts. In most cases, if the monitored air quality data satisfy the requirements of the Exceptional Events Rule, then applying these provisions would likely provide additional regulatory flexibilities beyond those that CAA section 188(f) would provide. However, regardless of whether the data in question meet or do not meet the requirements of the Exceptional Events Rule (e.g., because the exceptional events definition is not met in that the data do not constitute an exceedance or violation of the NAAQS or because other Exceptional Events rule criteria are not met), the waiver provisions in CAA section 188(f) could apply.
      The EPA recognizes the implementation challenges associated with the 2007 Exceptional Events Rule and recently proposed revisions to this rule to address certain substantive issues raised by state, local and tribal co-regulators and other stakeholders since promulgation of the rule and to increase the administrative efficiency of the Exceptional Events Rule criteria and process (80 FR 72840, November 20, 2015). The public comment period on this rule closed on February 3, 2016. The EPA will consider timely comments provided to the Exceptional Events Rule docket as we finalize the revisions to this rule.
B. Conformity Requirements
1. Requirements That Apply to Both Transportation Conformity and General Conformity.
      a. Background on Transportation and General Conformity.
      Conformity is required under CAA section 176(c) to ensure that federal actions are consistent with ("conform to") the purpose of the SIP. Conformity to the purpose of the SIP means that federal activities will not cause new air quality violations, worsen existing violations, or delay timely attainment of the relevant NAAQS or interim reductions and milestones. Conformity applies to areas that are designated nonattainment, and those nonattainment areas redesignated to attainment with a CAA section 175A maintenance plan after 1990 ("maintenance areas").
      The EPA's Transportation Conformity Rule (40 CFR 51.390 and part 93, subpart A) establishes the criteria and procedures for determining whether transportation activities conform to the SIP. These activities include adopting, funding or approving transportation plans, transportation improvement programs (TIPs) and federally supported highway and transit projects. The EPA first promulgated the Transportation Conformity Rule on November 24, 1993 (58 FR 62188), and subsequently published several amendments. For example, the EPA published a final rule on July 1, 2004 (69 FR 40004) that provided conformity procedures for state and local agencies under the 1997 PM2.5 NAAQS, among other things. On May 6, 2005 (70 FR 24280) the EPA published a final rule that addressed transportation conformity requirements for PM2.5 precursors.  The EPA published another final rule on March 24, 2010 (75 FR 14260) that addressed additional requirements for the 2006 PM2.5 NAAQS. Finally, the EPA published a final rule on March 14, 2012 (77 FR 14979) that restructured portions of the transportation conformity rule so that they would clearly apply to nonattainment and maintenance areas for the new and revised NAAQS, including the 2012 PM2.5 NAAQS. All of these rules apply to the current PM2.5 NAAQS including the 1997 PM2.5 NAAQS, the 2006 24-hour PM2.5 NAAQS and the 2012 primary annual PM2.5 NAAQS and will apply to future PM2.5 NAAQS. For further information on transportation conformity rulemakings, policy guidance and outreach materials, see the EPA's Web site at http://www3.epa.gov/otaq/stateresources/transconf/index.htm. The EPA issued transportation conformity guidance related to the implementation of the 2012 primary annual PM2.5 NAAQS in November 2015. The guidance is available at http://www3.epa.gov/otaq/stateresources/transconf/documents/420b15091.pdf.
With regard to general conformity, the EPA first promulgated general conformity regulations in November 1993 (40 CFR part 51, subpart W and 40 CFR part 93, subpart B). Subsequently, the EPA finalized revisions to the general conformity regulations on April 5, 2010. (75 FR 17254-17279) The general conformity program ensures that federal actions not covered by the transportation conformity rule will not interfere with the SIP. General conformity also fosters communications between federal agencies and state/local air quality agencies, provides for public notification of and access to federal agency conformity determinations and allows for air quality review of individual federal actions. More information on the general conformity program is available at www.epa.gov/airquality/genconform/
      b. Conformity in the Proposed Rule.
      The EPA did not propose any changes to the transportation conformity program as part of the current action. Nevertheless, to provide clarity in applying those regulations, the EPA is providing affected parties with information on when conformity must be implemented after nonattainment areas are designated for a new or revised PM2.5 NAAQS. At this time the EPA is using the 2012 PM2.5 NAAQS as an example. The agency is also discussing how it plans to make the transition from demonstrating conformity for the 1997 annual PM2.5 NAAQS to the 2012 primary annual PM2.5 NAAQS because this transition is unique in that the 1997 annual PM2.5 NAAQS was retained as a secondary NAAQS. Finally, we proposed a change to the general conformity rule that addresses de minimis levels that apply to federal actions in PM2.5 areas. The information presented here is consistent with existing conformity regulations and statutory provisions that are not addressed by this PM2.5 implementation rulemaking. Affected parties would include state and local transportation and air quality agencies, metropolitan planning organizations (MPOs), and federal agencies including the U.S. Department of Transportation (DOT), the U.S. Department of Defense, the U.S. Department of Interior and the U.S. Department of Agriculture.
      c. Applicability of Transportation and General Conformity to Areas Designated Nonattainment for the 2012 Primary Annual PM2.5 NAAQS.
      Transportation and general conformity apply 1 year after the effective date of nonattainment designations for a new or revised PM2.5 NAAQS including the 2012 primary annual PM2.5 NAAQS, April 15, 2016. This is because CAA section 176(c)(6) provides a 1-year grace period from the effective date of initial designations for any new NAAQS before transportation and general conformity apply in areas newly designated nonattainment for a specific pollutant and the NAAQS. With regard to general conformity, the EPA's April 2010 revisions to its general conformity regulations (see 75 FR 17277, April 5, 2010) apply the same 1-year grace period for the purposes of general conformity.
      With regard to transportation conformity, the conformity grace period applies to all areas designated nonattainment for a new or revised PM2.5 NAAQS including the 2012 primary annual PM2.5 NAAQS. The requirements differ depending on whether the nonattainment area is within or adjacent to a MPO designated under 23 U.S.C. 134. Within 1 year after the effective date of the initial nonattainment designation for a given pollutant and the NAAQS, the MPOs and DOT must make a transportation conformity determination with regard to that pollutant and standard for all of the transportation plans and TIPs in the nonattainment area. The conformity requirements for surrounding "donut areas," including the application of the 1-year conformity grace period, are generally the same as those for metropolitan areas. For the purposes of the implementation of the 2012 PM2.5 NAAQS, MPOs and any adjacent donut areas in a 2012 PM2.5 nonattainment area must continue to meet conformity requirements during the grace period for any other applicable NAAQS, including the 1997 annual PM2.5 NAAQS and the 2006 24-hour PM2.5 NAAQS. If, at the end of the grace period for the 2012 annual PM2.5 NAAQS, the MPO and DOT have not made a transportation plan and TIP conformity determination for that NAAQS, the area would be in a conformity "lapse." During a conformity lapse, only certain projects can receive additional federal funding or approvals to proceed. The practical impact of a conformity lapse will vary from area to area. Finally, the 1-year conformity grace period also applies to project level conformity determinations.
      Isolated rural nonattainment and maintenance areas are areas that do not contain or are not part of an MPO (40 CFR 93.101). Transportation conformity requirements for isolated rural nonattainment and maintenance areas can be found at 40 CFR 93.109(g). The CAA section 176(c)(6) 1-year grace period for newly designated nonattainment areas applies to isolated rural areas. Therefore, 1 year after the effective date of the initial nonattainment designation for a given pollutant and the NAAQS, conformity requirements with regard to that pollutant and standard would apply in any nonattainment areas that are isolated rural areas. Per the transportation conformity rule, an isolated rural area would be required to make a transportation conformity determination only at the point when a transportation project needs funding or approval. This project level conformity determination may occur significantly after the 1-year grace period has ended. See the EPA's transportation conformity guidance related to the implementation of the 2012 primary annual PM2.5 NAAQS for further information on how the EPA has implemented this conformity grace period in metropolitan, donut and isolated rural areas. The guidance is available at http://www3.epa.gov/otaq/stateresources/transconf/documents/420b15091.pdf.
      d. Applicability of Transportation and General Conformity With Regard to the 1997 Annual PM2.5 NAAQS, Which was Retained as a Secondary NAAQS.
      In the December 2012 PM NAAQS final rule, the EPA established a new health-based primary annual PM2.5 NAAQS of 12.0 μg/m[3]. In that same action the EPA retained the 1997 annual PM2.5 NAAQS of 15.0 μg/m[3] as a secondary NAAQS to protect against certain welfare effects. In the 1997 PM2.5 designations rule (70 FR 944), the EPA designated areas nonattainment for both the 1997 primary and secondary annual PM2.5 NAAQS (which have identical levels of 15.0 μg/m[3]). Designations for the 2012 primary annual PM2.5 NAAQS were made in January 2015 (80 FR 2206) and were effective on April 15, 2015. This action did not make any changes to the designations that apply for the 1997 secondary annual PM2.5 standard. Therefore, at this time, all areas designated nonattainment in 2005 for the 1997 annual PM2.5 standard are considered as having been designated nonattainment for both the 1997 primary annual PM2.5 NAAQS and for the 1997 secondary annual PM2.5 NAAQS. Similarly, for any 1997 PM2.5 nonattainment areas that have approved redesignation requests for attainment of the 1997 PM2.5 NAAQS, the redesignation applies to both the primary and secondary standards of the 1997 PM2.5 NAAQS. A discussion of how transportation and general conformity apply in this situation follows.
      CAA section 176(c)(5) requires compliance with transportation and general conformity only in: (1) nonattainment areas and (2) areas that have been redesignated to attainment and are required to develop a maintenance plan under CAA section 175A.
      CAA section 175A(a), in turn, establishes the requirements that must be fulfilled by nonattainment areas in order to be redesignated to attainment. That section only requires that nonattainment areas for the primary standard submit a plan addressing maintenance of the primary NAAQS in order to be redesignated to attainment; it does not require nonattainment areas for secondary NAAQS to submit maintenance plans in order to be redesignated to attainment. See 42 U.S.C. §7505a(a) Therefore, since conformity does not apply in areas that have been redesignated without CAA section 175A maintenance plans, the EPA concludes that transportation and general conformity do not apply in areas that have been redesignated to attainment for any secondary NAAQS, such as the 1997 secondary annual PM2.5 NAAQS.
      Elsewhere in this final rule, the EPA is finalizing one of the proposed options for revoking the 1997 primary annual PM2.5 NAAQS, which has been replaced by the more health protective 2012 primary annual PM2.5 NAAQS. As discussed in detail in Section X of this preamble, the EPA is finalizing the option that calls for revoking the 1997 primary annual PM2.5 NAAQS in areas that have always been designated attainment for that NAAQS and in areas that have been redesignated to attainment for that NAAQS. As a result, after the effective date of the revocation, areas that have been redesignated to attainment for the 1997 annual PM2.5 NAAQS (i.e., maintenance areas for the 1997 annual PM2.5 NAAQS) will not be required to make transportation or general conformity determinations for the 1997 annual PM2.5 NAAQS. The revocation would leave nonattainment designations in place for the 1997 annual NAAQS for areas that have not yet been redesignated to attainment for that NAAQS. The EPA will continue to redesignate areas to attainment as states submit redesignation requests for the remaining nonattainment areas. Any area that is designated as nonattainment for the 1997 annual NAAQS at the time of the initial revocation would have to continue to make transportation and general conformity determinations for that NAAQS until such time that they are redesignated to attainment for that NAAQS.
      For any area that has been redesignated to attainment for the 1997 annual PM2.5 NAAQS (i.e., a maintenance area for the 1997 annual PM2.5 NAAQS) and is not designated nonattainment for the 2012 primary annual PM2.5 NAAQS, the relevant planning organization will not have to make conformity determinations for any annual PM2.5 NAAQS after the effective date of the revocation of the 1997 primary annual PM2.5 NAAQS because, as discussed earlier, the CAA does not require maintenance areas for secondary NAAQS to make conformity determinations and the 1997 primary annual NAAQS will have been revoked. This means that, after the effective date of the revocation, areas redesignated to attainment for the 1997 annual PM2.5 NAAQS will no longer be required to make transportation plan, TIP, or project-level transportation conformity determinations for that NAAQS. In addition, federal agencies will no longer be required to make conformity determinations for that NAAQS. Areas that remain designated nonattainment for the 1997 annual PM2.5 NAAQS will continue to make transportation plan, TIP, and project-level conformity determinations for that NAAQS and federal agencies will be required to continue to make conformity determinations for that NAAQS in these areas until such time as they attain that NAAQS and are redesignated to attainment. Table 3 shows which types of areas are required to make conformity determinations for either the 1997 or 2012 annual PM2.5 NAAQS after the revocation of the 1997 primary annual NAAQS is effective.
Table 3. Where Is Conformity Required for an Annual PM2.5 NAAQS After the Revocation of the 1997 Primary Annual PM2.5 NAAQS?

                               Attainment Status
                    1997 Primary and Secondary Annual NAAQS
                           2012 Primary Annual NAAQS
                                 Nonattainment
                                       X
                                       X
                                  Maintenance

                                       X
Note: There is no impact on the implementation of conformity requirements in areas that are nonattainment or maintenance for either the 1997 or 2006 24-hour PM2.5 NAAQS.

      e. Impact of Implementation of a New or Revised PM2.5 NAAQS( such as the 2012 PM2.5 NAAQS) on a State's Transportation and/or General Conformity SIP.
      As long as the EPA does not make specific changes to its transportation or general conformity regulations states should not need to revise their transportation and/or general conformity SIPs. The EPA is not making any changes to its transportation conformity regulations and no transportation conformity SIP revisions are necessary. The only change that the EPA is making to its general conformity regulations is to change the de minimis levels in its general conformity regulations as discussed in Section IX.B.2.a of this preamble. States with a general conformity SIP should evaluate the need to revise those SIPs in light of this change. States with new nonattainment areas may also need to revise conformity SIPs in order to ensure the state regulations apply in any newly designated areas.
      In the event that a nonattainment designation causes transportation conformity to apply for the first time in a state, such a state is required by the statute and the EPA regulations to submit a SIP revision that addresses three specific transportation conformity requirements that address consultation procedures and written commitments to control or mitigation measures associated with conformity determinations for transportation plans, TIPs or projects. (40 CFR 51.390) Additional information and guidance can be found in the EPA's "Guidance for Developing Transportation Conformity State Implementation Plans" (http://www3.epa.gov/otaq/stateresources/transconf/policy/420b09001.pdf).
2. Additional General Conformity Requirements for PM2.5 Nonattainment Areas.
      a. De minimis Emission Levels for Direct PM2.5 and its Precursors.
      Federal actions estimated to have an annual net emissions increase less than the de minimis levels established in the general conformity regulations are not required to demonstrate conformity under those regulations. For direct PM2.5 and its precursors (SO2, NOx, VOC and ammonia), the existing de minimis emission levels are set forth in the EPA's general conformity regulations at 40 CFR 93.153(b)(1). Those levels were based on the definition of a major stationary source for nonattainment NSR programs. The EPA believes it is appropriate to continue this practice for implementing the current and any future PM2.5 NAAQS. However, because the definition of precursors currently in the general conformity regulations at 40 CFR 93.152(b)(1) does not reflect the rebuttable presumptions for certain PM2.5 precursors, the EPA is finalizing changes to these conformity provisions to make them consistent with the agency's revised precursor requirements. Specifically, the current definition of precursors for PM2.5 in the general conformity regulations does not reflect the rebuttable presumptions for VOC and ammonia. It also does not reflect the subpart 4 definitions for "major source" and "major stationary source" that apply for Serious PM2.5 nonattainment areas. Therefore, the EPA is finalizing changes to the PM2.5 precursor de minimis levels currently in 40 CFR 93.153(b)(1) to make those levels consistent with the statutory requirements for major stationary source thresholds under subpart 4 and any relevant changes finalized in Section III of this preamble. Comments received on this proposed change were supportive. The EPA is setting the de minimis levels that apply to direct PM2.5 and PM2.5 precursors for PM2.5 nonattainment areas for purposes of general conformity as identified in Table 4.
  Table 4. General Conformity De minimis Emission Levels for PM2.5 Precursors
                               Type of Emission
                                   Tons/Year
        in Moderate PM2.5 nonattainment areas and all maintenance areas
                                   Tons/Year
                     in Serious PM2.5 nonattainment areas
Direct emissions
                                      100
                                      70
SO2
                                      100
                                      70
NOx
                                      100
                                      70
VOC
                                      100
                                      70
Ammonia
                                      100
                                      70

      b. Implementation Considerations for the General Conformity Program.
      The EPA did not propose any other revisions to the general conformity regulations and is not taking any additional final actions in this rule. However, as areas develop SIPs for the 2012 and future PM2.5 NAAQS, the agency recommends that state and local air quality agencies work with federal agencies with large facilities (e.g., commercial airports, ports and large military bases) that are subject to the general conformity regulations to establish an emissions budget for those facilities in order to facilitate future conformity determinations under the conformity regulations. Such a budget could be used by federal agencies in determining conformity or identifying mitigation measures if the budget level is included and identified in the SIP.
      In a few cases, tracts of land under federal management may also be included in nonattainment and maintenance area boundaries. The role of fire in these areas should be assessed and emissions budgets developed in concert with those federal land management agencies. In such areas the EPA encourages states to consider in any baseline, modeling and SIP attainment inventory used and/or submitted to include emissions expected from projects subject to general conformity, including emissions from wildland fire that may be reasonably expected in the area. Where appropriate, states may consider developing plans for addressing wildland fuels in collaboration with land managers and owners. Information is available from DOI and USDA Forest Service on the ecological role of fire and on smoke management programs and basic smoke management practices.
C. Clean Data Policy
1. Summary of the Proposal.
      In the proposed rule, the EPA described its longstanding clean data policy and proposed to codify the policy in regulatory text. A clean data determination (CDD) is a notice-and-comment rulemaking wherein the EPA determines that a specific nonattainment area has attained the relevant NAAQS based on three years of quality-assured certified air quality monitoring data. The CDD suspends the state's obligation to submit to the EPA the planning elements related to attaining the standard required of nonattainment areas under the Clean Air Act for as long as the area continues to attain the standard. The CDD does not suspend certain CAA requirements, such as an emissions inventory, nonattainment new source review requirements, and certain emission reduction requirements, that are considered independent of attainment needs.
	The proposal provided additional discussion about attainment demonstrations, control requirements for Moderate areas, RFP and quantitative milestones, and contingency measures. With regard to control requirements for Serious areas, the proposal included two options: one option would suspend BACT/BACM requirements under a CDD if elsewhere in the rule such requirements were considered necessary for expeditious attainment, and the other option would not suspend BACT/BACM requirements if elsewhere in the rule such requirements were considered to be generally independent of attainment.
2. Final Rule.
      The final rule codifies the clean data policy in rules governing the implementation of current and future PM2.5 NAAQS, and much of the guidance discussed in the proposal regarding which requirements are suspended remains the same. The EPA has already codified the clean data policy in a regulation implementing the 1997 8-hour ozone NAAQS that was specifically challenged and upheld by the D.C. Circuit in NRDC v. EPA, 571 F. 3d 1245 (D.C. Cir. 2009), and numerous United States Circuit Courts of Appeal have upheld the Clean Data Policy, including the EPA's application of this interpretation of the CAA with regard to implementation of the PM10 NAAQS under subpart 4. See Latino Issues Forum v. EPA, Nos. 06-75831 and 08-71238 (9th Cir. March 2, 2009) (memorandum opinion). The EPA had also codified the clean data policy for PM2.5 in the now remanded 2007 PM2.5 implementation rule. For a complete discussion of the Clean Data Policy's history and EPA's longstanding interpretation under the Clean Air Act, please refer to the proposal.
	The planning elements under subpart 1 and subpart 4 generally include reasonable further progress (RFP) requirements, attainment demonstrations, RACM and RACT, nonattainment area contingency measures, and other state planning requirements related to attaining the NAAQS. The suspension of the obligation to submit such requirements applies regardless of when the plan submissions are due. The CDD does not suspend CAA requirements that are independent of helping the area achieve attainment, such as the requirements to submit an emissions inventory and nonattainment new source review requirements. The determination of attainment is not equivalent to a redesignation, and the state must still meet the statutory requirements for redesignation in order to be redesignated to attainment. A determination of attainment for purposes of the Clean Data Policy/regulations is also not linked to any particular attainment deadline, and is not necessarily equivalent to a determination that an area has attained the standard by its applicable attainment deadline, e.g., under CAA section 188(b). Note also that if the EPA determines that an area with a clean data determination subsequently is violating the standard prior to being redesignated to attainment, the area will be required to address the pertinent requirements when it submits the SIP to EPA. As has long been the EPA's policy, areas subject to a determination that a CDD is rescinded due to subsequent violation of the NAAQS would receive a reasonable amount of time to address the previously suspended requirements and submit revisions to their SIPs. The EPA would establish this SIP submittal date on a case-by-case basis, taking into account individual circumstances surrounding the particular SIP provisions at issue.
      This rule specifies that a determination that a nonattainment area is attaining the current and future PM2.5 NAAQS would suspend the following attainment planning related requirements under subpart 1 and subpart 4: (i) the part D, subpart 4 and subpart 1 obligation to provide an attainment demonstration pursuant to CAA section 189(a)(1)(B); (ii) the RACM and RACT provisions of CAA section 189(a)(1)(C); (iii) the RFP and quantitative milestones provisions of CAA section 189(c); and, (iv) related attainment demonstration, RACM and RACT, RFP and contingency measure provisions requirements of subpart 1, section 172. The following sections a-d provide additional detail on the PM2.5 NAAQS planning requirements that would be suspended by a CDD.
      a. Attainment Demonstrations.
      With respect to the attainment demonstration requirements of section 172(c) and section 189(a)(1)(B) of the CAA, the EPA finds that if an area already has air quality monitoring data demonstrating attainment of the standard, there is no need for an area to make a further submission containing additional measures to achieve attainment, nor is there a need for the area to perform future modeling to show how the area will achieve attainment. The plain language of CAA section 189(a)(1)(B) requires that the attainment plan provide for "a demonstration (including air quality modeling) that the [SIP] will provide for attainment by the applicable attainment date." Where the area has attained the standard, such a demonstration no longer serves a purpose.
      b. Control Measure Requirements for Moderate Areas.
      Both CAA sections 172(c)(1) and 189(a)(1)(C) require "provisions to assure that reasonably available control measures'' (i.e., RACM) are implemented in a nonattainment area. Reasonably available control technology (i.e., RACT) is a subset of RACM. The EPA has long interpreted "reasonably available control measures" under CAA sections 172(c)(1) and 189(a)(1)(C) to mean only those measures that are necessary to help an area achieve attainment. Thus, where an area is already attaining the standard, no additional RACM are required, but all measures adopted into the SIP prior to attainment would remain. The EPA is interpreting CAA section 189(a)(1)(C) consistent with its interpretation of CAA section 172(c)(1).
      c. RFP and Quantitative Milestones.
      The EPA has long interpreted the provisions of part D, subpart 1 of the CAA (sections 171 and 172) as not requiring the submission of RFP for an area already attaining the PM10 NAAQS. For an area that is attaining, showing that the state will make RFP towards attainment "will, therefore, have no meaning at that point."
      d. Contingency Measures.
      Other SIP submission requirements are linked with these attainment demonstration and RFP requirements, and similar reasoning applies to them. These requirements include the contingency measure requirements of CAA sections 172(c)(9). The EPA has interpreted the obligation to submit contingency measure requirements of CAA sections 172(c)(9) as suspended when an area has attained the standard because those "contingency measures are directed at ensuring RFP and attainment by the applicable date." 57 FR at 13564; see also Seitz memo at pgs. 5-6.
      e. Control Measure Requirements for Serious Areas.
      Section VII.D of the preamble explains the rationale of the EPA's decision to maintain its longstanding policy of considering the BACT/BACM requirement of CAA section 189(b)(1)(B) to be generally independent of attainment. Accordingly, this rule states that a clean data determination would not suspend the obligation for the state to submit any applicable outstanding BACM and BACT requirements.
      For a Serious area that failed to attain the relevant PM2.5 NAAQS by the applicable attainment date and that is therefore subject to the annual 5 percent emissions reduction requirement under CAA section 189(d), but is nevertheless now attaining the relevant NAAQS, the EPA believes that the Clean Data Policy may apply to the obligations of the state to make an attainment plan submission to meet the requirements of CAA section 189(d). Once such an area is attaining the relevant NAAQS, a clean data determination would suspend the CAA section 189(d) submission requirement.
3. Comments and Responses.
      Comment: Several commenters supported the EPA's proposal to codify the clean data policy in the final rule because they believe the policy is lawful and relieves states from unnecessary planning burdens in areas where the NAAQS is met. Some commenters stated the policy has specifically been upheld by the D.C. Circuit in the context of review of nationally applicable implementation rules for the EPA's ozone NAAQS [Natural Res. Def. Council v. EPA, 571 F.3d 1245, 1260-61 (D.C. Cir. 2009)]. Other commenters, however, asserted that they "reiterate their previous comments regarding the illegality of the Clean Data Policy." To the extent that the Agency planned to continue to follow the policy, these commenters agreed with the EPA's interpretation that only those requirements tied to an area's demonstration of attainment should be suspended. To that end, the commenters requested clarification that measures that have been responsible for the area's attainment must be submitted and approved into the SIP even following a Clean Data Determination. Similarly, other commenters requested clarification as to EPA's statement that "Thus, where an area is already attaining the standard, no additional RACM are required, but all measures adopted into the SIP prior to attainment would remain." The commenter wondered if "all measures adopted into the SIP" includes measures that were included and identified as RACT or RACM in the original SIP, even if those measures have not yet been submitted to EPA in regulatory form.
      Finally, some commenters noted that the Act requires that RACM/RACT be implemented within 4 years of a nonattainment designation and stated that, as sources reduce emissions of PM2.5 and regional PM precursors due to national rules yet to be fully implemented (e.g., Boiler NESHAPS, CSAPR) it is entirely possible that an area may attain the standard prior to complete implementation of RACM/RACT. The commenters stated that, if an area attains the NAAQS prior to implementation of the planning requirements, it is meaningless and overly burdensome to require the area to continue implementing RACM/RACT.
      Response: The EPA disagrees with commenters who allege, without explanation, that the Clean Data Policy is "illegal." Rather, as noted by supportive commenters, the EPA has long interpreted certain CAA requirements that are designed to bring an area into attainment to serve no purpose once an area is attaining, and thus has interpreted the Act as permitting the Agency to suspend the requirements to submit revisions to the SIP addressing those requirements. This position has been upheld by multiple Circuit Courts of Appeals.
	In response to the requests for clarification of which RACM requirements are suspended by a CDD, we note that, for over 30 years, the EPA has consistently interpreted the RACM requirement in CAA section 172(c)(1) to apply only to those measures that, individually or collectively, contribute to expeditious attainment of the NAAQS. The suspension of the statutory requirement to submit RACM is premised on the idea that, "[t]o the extent an area is already achieving attainment as expeditiously as possible, imposition of additional control [measures] would not hasten achievement of the NAAQS. In such a situation, the EPA may reasonably conclude that no control [measures] are reasonably available and the area need not implement further [measures] to satisfy the [RACM] requirement." See NRDC v. EPA, 571 F.3d 1245, 1253 (D.C. Cir. 2009). Thus, upon the EPA's finalization of a CDD for a particular NAAQS, the EPA formally suspends the obligation to submit attainment-related plan elements for that particular NAAQS, including RACM. A CDD does not, however, affect the criteria in CAA section 107(d)(3)(E) for redesignation to attainment, including the requirement for the state to demonstrate to the EPA's satisfaction that the improvement in air quality is due to "permanent and enforceable reductions in emissions resulting from implementation of the applicable implementation plan" and other permanent and enforceable reductions. Thus, to the extent certain state/local control measures were necessary to an area's attainment of the NAAQS, the state may need to submit those measures to the EPA for SIP approval in order to meet the statutory criteria for redesignation in CAA section 107(d)(3)I, notwithstanding the suspension of planning obligations under a CDD.
      In this case, it is not clear to the EPA what the commenters means by the phrase "original SIP," since the SIP is only those measures that have been submitted and approved by the EPA. To the extent that a measure was adopted into the SIP prior to an area's attainment of the NAAQS, and therefore contributed to an area's attainment, that measure is therefore required to remain as part of the SIP. We infer that the comment might be referring to commitments that were approved into a SIP to adopt future measures, or that commenters might be asking for clarification regarding measures that have been adopted locally or at a state level prior to the area's coming into attainment but have not yet been submitted to the EPA for approval into the federally-approved SIP. As explained above, a CDD has no effect on the state's obligation to demonstrate that an area's improvement in air quality is due to "permanent and enforceable" emission reductions in order to meet the statutory requirements for redesignation to attainment in CAA section 107(d)(3)(E). Additionally, a CDD does not alter the effect of any measure (including any state commitment) that has already been approved into a SIP, even if that measure is a commitment to adopt or submit a future measure. Once approved into a SIP, such a measure becomes an enforceable emission standard or limitation subject to EPA or citizen enforcement under CAA section 304, which cannot be altered except through a SIP revision approved by the EPA. Along those same lines, even if an area has adopted into its SIP RACM/RACT but has yet to fully implement those measures when the area first starts attaining the NAAQS, a CDD does not excuse the area from continuing to implement its SIP requirements, i.e., the RACM/RACT measures that have been approved into the SIP. The CDD merely suspends the requirement to submit RACM/RACT, that is, additional measures on top of what brought the area into attainment; a state may only stop implementing those measures already in its SIP through a SIP revision approved by the EPA.
      Comment: Some commenters supported the EPA's proposal to retain the BACM/BACT submission requirement even with a CDD (80 FR 15444). Other commenters, however, stated that, once the EPA makes an attainment determination, the EPA should suspend the requirements to submit BACM/BACT and that to do otherwise is illogical.
      Response: The EPA is finalizing the option that requires BACM/BACT to be submitted even if the EPA has issued a CDD for an area. As discussed in our proposal and earlier in this section, the legal underpinning of the Clean Data Policy is that the EPA interprets the CAA not to require the submission of requirements that are designed to get an area to attainment once that area is already attaining the NAAQS. Thus, only those "attainment planning" requirements are suspended by a CDD. It is therefore not illogical for the EPA not to extend the CDP to the submission of the BACM/BACT requirement for Serious Areas. Because the EPA interprets BACM/BACT as independent of attainment, as discussed above in Section VII.D of the preamble, the requirement to submit BACM/BACT continues to apply regardless of whether the EPA has determined that the area is attaining.
D. CAA Section 179B/International Border Areas
1. Specific Requirements.
      a. Summary of Proposal.
      Section 179B of the CAA, titled "International Border Areas," applies to areas that would attain the relevant NAAQS by the statutory attainment date "but for" emissions emanating from outside the U.S. Under CAA section 179B, if applicable, the provision modifies subpart 4 attainment plan obligations applicable to areas designated nonattainment for any PM NAAQS. The EPA proposed and sought comment on two approaches that would give greater clarity to the agency's existing interpretation of the RACM/RACT and additional reasonable measure requirements for Moderate area attainment plans to be approved under CAA section 179B. The first proposed interpretation would have clarified that the control strategy for an area that could attain by the Moderate area attainment date, "but for" foreign emissions of direct PM2.5 or its precursors, must include all control measures identified by the state to be technologically and economically feasible and implementable on sources in the area by the end of the sixth calendar year following designation of the area. Under this approach, inclusion of such measures would satisfy requirements for RACM and RACT (for measures that can be implemented within four years) and additional reasonable measures (for measures than can be implemented within six years but not within four). The proposal also sought comment on a possible exception for any such measures that collectively would not be effective in reducing ambient PM2.5 levels in the area. The second proposed approach would have required a state to demonstrate that its selected control measures for a Moderate nonattainment area would achieve reductions in PM2.5 levels that exceeded the applicable NAAQS in proportion to their contribution to overall PM2.5 levels. Inclusion of these proportional measures would thus satisfy RACM/RACT and additional reasonable measures under the second approach. The EPA sought comment on these two approaches to clarify what constitutes a reasonable control strategy in the context of a SIP submitted pursuant to CAA section 179B.
      The EPA also proposed that any Moderate area attainment plan submitted under CAA section 179B must include an RFP plan with required air quality targets consistent with the RFP Option 2. In addition, the EPA proposed requirements for establishing and reporting on quantitative milestones for areas with approved "but for" demonstrations.
      b. Final Rule.
      This final rule requires that an area with a CAA section 179B demonstration must comply with the RACM/RACT and additional reasonable measure requirements in a manner similar to the way it would meet these requirements for a Moderate PM2.5 nonattainment area that cannot practicably attain by the statutory attainment date for the area. Moreover, because the State must have established that the plan would be adequate to attain and maintain the NAAQS but for international emissions, the final rule exempts the state from the requirement for such plans to demonstrate attainment and maintenance of the relevant NAAQS by the attainment date. Additionally, this rule provides that such an area will not be reclassified to Serious upon failure to attain the NAAQS. Further, these provisions are contingent upon the state complying with the demonstration requirements of CAA section 179B. This section describes the specific requirements applicable to these areas.
	Section 179B(a) of the CAA provides that the EPA shall approve an attainment plan for a nonattainment area that is an international border area if: (i) the attainment plan meets all other applicable requirements of the CAA, and (ii) the submitting state can demonstrate satisfactorily that "but for emissions emanating from outside of the United States," the area would attain and maintain the relevant NAAQS. In addition, CAA section 179B(d) applies specifically to the PM10 NAAQS (which includes the PM2.5 NAAQS) and provides that if a state demonstrates that an area would have attained the NAAQS but for emissions emanating from outside the U.S., then the area is not subject to the mandatory reclassification element of CAA section 188(b)(2) for Moderate areas that fail to attain by the applicable attainment date.
	Under CAA section 179B, areas affected by emissions from outside the U.S. continue to have attainment plan obligations. First, even if the area is impacted by emissions from outside the U.S., that fact does not affect the designation of the area. Such an area that is violating the relevant NAAQS will be designated nonattainment even if emissions from outside the U.S. contribute to that violation. Second, as a result of that designation, the state is required to meet the applicable attainment plan requirements for the relevant NAAQS. Section 179B of the CAA does not negate the attainment plan requirements. Rather, it allows the EPA to approve an attainment plan that does not demonstrate attainment and maintenance of the NAAQS, provided the state meets all other attainment plan requirements and the plan would demonstrate attainment "but for" international emissions.
      The EPA has determined that under the best reading of CAA section 179B, states remain obligated to meet the attainment plan requirements other than the requirement to demonstrate attainment and maintenance of the relevant NAAQS. This determination is based upon the fact that 179B(a)(1) explicitly states that such an attainment plan must meet all the requirements of the CAA with that exception. The applicable requirements for an attainment plan for PM2.5 include those requirements that apply to a Moderate area attainment plan. Those requirements include an emissions inventory, RACM and RACT, additional reasonable measures, RFP, quantitative milestones, contingency measures, NNSR and motor vehicle emissions budgets for transportation conformity purposes. The Addendum includes a discussion of the applicable attainment plan requirements in the context of developing a SIP subject to CAA section 179B. In it, the EPA clarified that "RACM/RACT must be implemented to the extent necessary to demonstrate attainment by the applicable attainment date if emissions emanating from outside the U.S. were not included in the analysis." The EPA further encouraged states "to reduce emissions beyond the minimum necessary to satisfy the `but for' test in order to reduce the PM -  concentrations to which their populations are exposed." However, the EPA acknowledged that "if...States...were also required, because of contributions to PM10 violations caused by foreign emissions, to shoulder more of a regulatory and economic burden than States not similarly affected...such a requirement would unfairly penalize States containing international border areas and effectively undermine the purpose of CAA section 179B. Indeed, to the extent an affected State can satisfactorily demonstrate that implementation of such measures clearly would not have advanced the attainment date, the EPA could conclude they are unreasonable and hence do not constitute RACM." This past interpretation of RACM and RACT requirements in the context of CAA section 179B was considered when the agency proposed to allow a state not to implement such measures if the state could demonstrate that collectively the measures will not be effective in reducing PM2.5 levels in the area. Some commenters supported this exception, stating that it would prevent wasting resources on ineffective measures. Some commenters stated that requiring implementation of all RACM/RACT and additional reasonable measures circumvents Congressional intent and the CAA. Other commenters disagreed, stating that these areas should implement all measures due to the importance to public health.
      Regarding RACM/RACT and additional reasonable measures, the EPA reviewed the comments received and its past interpretation of RACM and RACT requirements in the context of CAA section 179B attainment plans for PM2.5 NAAQS. The EPA is persuaded that it is most appropriate and most consistent with the Act to ensure that States adopt reasonable measures in international border areas even though such measures would not advance the attainment date due to the fact that the area will not attain because of international emissions. . In longstanding guidance the EPA has encouraged states "to reduce emissions beyond the minimum necessary to satisfy the `but for' test in order to reduce the PM10 concentrations to which their populations are exposed." Given that the primary purpose of an attainment plan is to ensure expeditious attainment of the NAAQS and protection of public health and welfare through implementation of control measures that achieve emissions reductions, adopting an interpretation that would allow for continued emissions of pollutants that the state could reasonably reduce would be antithetical to the objectives of the CAA. Just as it is appropriate and consistent with the Act to adopt reasonable measures (i.e., RACT/RACM or additional reasonable measures) in areas that cannot practicably attain by the attainment date, as previously discussed, it is also appropriate and consistent with the Act to adopt reasonable measures in areas that cannot attain due to international emissions.
      Therefore, the EPA requires that Moderate area attainment plans approved under CAA section 179B must implement all technologically and economically feasible measures that can be implemented on sources in the area by the end of the sixth calendar year following designation of the area (i.e., RACM and RACT and additional reasonable measures). This requirement is intended to ensure that the area makes reasonable progress toward attaining the standard even if such measures are not expected to yield attainment by the statutory Moderate area attainment date. This approach parallels the requirements described in Section IV.D in this preamble, pursuant to CAA section 189(a)(1), for Moderate PM2.5 nonattainment areas that cannot practicably attain the NAAQS by the latest statutory attainment date for the area. Requiring the implementation of all reasonable measures is even more important in the context of a Moderate area for which CAA section 179B applies because sources in such areas will not be subject to the more stringent BACM/BACT, MSM, or 5 percent requirement because such areas are not subject to mandatory reclassification as Serious areas pursuant to CAA section 179B(d). Thus, the only level of PM2.5 control requirements that will likely ever apply to these sources is the less-stringent RACM/RACT and additional reasonable measures level of control; therefore, all the sources in the area should reduce emissions if such reduction is reasonable since the public in those areas will continue to be subject to ambient levels of emissions that the agency has determined are unsafe notwithstanding implementation of those reasonable measures. Additionally, the EPA notes that the process to determine RACM already allows states to identify the subset of all control measures that are technologically and economically feasible, which should be adequate to prevent significant wasting of resources on ineffective measures.
      The EPA has determined that it will not finalize the proposed option of achieving reductions in PM2.5 levels in proportion to the area's contribution to overall PM2.5 levels. The EPA received several comments on the proposed option to allow states to implement control measures for a Moderate nonattainment area with a plan approved under CAA section 179B that would achieve reductions in PM2.5 levels in proportion to the area's contribution to overall PM2.5 levels. Although some commenters supported the possibility of proportionally implementing control measures, other commenters raised possible negative consequences of this option. Commenters highlighted the difficulty that states would face in apportioning responsibility for emissions between foreign and non-foreign sources, which would be necessary under the proportional approach. These commenters also disagreed as to whether the EPA or states should be responsible to determine the proportional allocation of international emissions. The EPA is also concerned that a proportional approach would introduce too much complexity into an already complex analytical process. Additionally, the EPA notes that no other NAAQS pollutant offers a proportional approach to implementation of control measures and is not convinced that there are sufficient reasons to finalize this approach for PM2.5 nonattainment areas.
      Section 179B(d) of the CAA states that any area for which the state establishes to the EPA's satisfaction that the area "would have attained the NAAQS by the applicable attainment date, but for emissions emanating from outside the United States, shall not be subject to the provisions of section [188(b)(2)]." CAA section 188(b)(2) requires the EPA to determine, within 6 months following the applicable attainment date for a Moderate PM2.5 nonattainment area, whether the area attained the NAAQS by that date and to reclassify the area as Serious if it is not in attainment after the applicable attainment date. For any Serious area subject to an EPA determination of failure to attain by the Serious area attainment date, CAA section 189(d) requires the state to submit plan revisions which provide for attainment of the PM2.5 NAAQS and for annual emission reductions of not less than 5 percent until the area attains. These planning requirements in section 189(d) apply only upon the EPA's determination that a Serious area has failed to attain the applicable NAAQS by the Serious area attainment date. Because section 179B(d) explicitly provides that any area that satisfies the "but for" attainment test in CAA section 179B shall not be subject to the provisions for reclassification to Serious upon failure to attain in CAA section 188(b)(2), the consequences for failure to attain by the Serious area attainment date in section 189(d) generally do not apply to such areas.
      Where an international border area has already been reclassified as Serious when it submits a "but for" demonstration under section 179B, all of the Serious area requirements that apply to the area (e.g., the requirements to implement BACM/BACT and additional feasible measures) would remain in effect. This is because at the time the state submits the "but for" demonstration, these statutory requirements already apply, and nothing in section 179B alters those requirements. Upon the EPA's approval of a Serious area plan and section 179B demonstration for such an area, however, the EPA would no longer be obligated to make a determination of failure to attain by the Serious area attainment date triggering the additional planning requirements of section 189(d). Consistent with Congress's clear intent in section 179B(d) to relieve Moderate PM2.5 nonattainment areas that satisfy the "but for" attainment test of the additional planning obligations that result from a mandatory determination of failure to attain by the Moderate area attainment date, the EPA interprets section 179B as also relieving Serious PM2.5 nonattainment areas of the additional planning obligations in section 189(d) that result from a mandatory determination of failure to attain by the Serious area attainment date, once the EPA approves the state's Serious area plan and section 179B demonstration.
      Where a Serious area fails to attain by the Serious area attainment date and is therefore subject to the requirements of section 189(d), the EPA's approval of a section 189(d) plan and 179B demonstration would mean that the EPA is no longer obligated to make further determinations of failure to attain or to trigger additional planning requirements. The EPA intends to review each SIP submission containing a "but for" attainment demonstration for an international border area for compliance with the requirements of section 179B.
	The EPA notes that, with one exception for contingency measures, the final rule provisions governing for the RFP, quantitative milestone, and contingency measure requirements for PM2.5 nonattainment areas are the same for areas seeking plan approval under CAA section 179B as they are for any other area. For example, the EPA requires that as part of any Moderate area attainment plan submitted under CAA section 179B, a state must include an RFP plan developed consistent with the process described in Section IV.F of this preamble as a Moderate nonattainment area that cannot practicably attain the relevant NAAQS by the statutory attainment date. In addition, the EPA requires that the state must identify quantitative milestones for the area to be achieved 4.5 years and 7.5 years from the date of designation of the area. The EPA will apply the same requirements for establishing and reporting on quantitative milestones for Moderate nonattainment areas with an approved "but for" demonstration under CAA section 179B as for all other Moderate nonattainment areas, as described in Section IV.G of this preamble. Furthermore, the state must include as part of any attainment plan submission made for such an area contingency measures that are ready to be implemented quickly and with minimal further action by the state or by the EPA in the event the EPA determines that such area failed to meet RFP or quantitative milestone requirements. The contingency measures should achieve approximately 1 year's worth of emissions reductions as calculated by the state for purposes of the RFP analysis. The exception to the contingency measure requirement for areas with approved CAA section 179B demonstrations is that contingency measures for failure to attain are not required in such plans, because under CAA section 179B(d) the EPA is not required to make determinations concerning attainment for such areas. Further explanation of contingency measures can be found in Section IV.H of this preamble.
	Regarding the "but for" demonstrations under CAA section 179B, the EPA has historically evaluated these demonstrations on a case-by-case basis, based on the individual circumstances and data provided by the submitting state. These demonstrations have included information such as ambient air quality monitoring data, modeling scenarios, emissions inventory data and meteorological or satellite data. The Moderate area attainment demonstration modeling and other elements of the attainment demonstration must show attainment and maintenance of the NAAQS but for the emissions from outside of the U.S. However, CAA section 179B does not provide authority to exclude monitoring data influenced by international transport from regulatory determinations related to attainment and nonattainment.
      Where international transport of emissions contributes to an exceedance or violation, such data may be excluded from consideration only if they were significantly influenced by exceptional events under section 319(b) of the CAA. If the data meet the criteria contained in the EPA's Exceptional Events Rule, the exceedance can be addressed by that rule. Specifically, if the EPA concurs with a state's request to exclude affected data, the event-influenced data are officially noted and removed from the data set used to calculate official design values, which may be used as part of a regulatory determination.
      The EPA expects that the best approach for evaluating the potential impacts of international transport on nonattainment is for states to work with the EPA on a case-by-case basis to determine the most appropriate information and analytical methods for each area's unique situation. The EPA will work with states that are developing exceptional events demonstrations and attainment plans for which CAA section 179B is relevant, and ensure the states have the benefit of the EPA's understanding of international transport of PM2.5 and PM2.5 precursors.
      c. Comments and Responses.
      Comment: Some commenters stated that if it becomes clear that an area's implementation of RACM and other control measures would not have achieved sufficient emissions reductions to attain by the moderate area deadline, even excluding the emissions emanating from outside the U.S., the area should still be bumped up to serious nonattainment and subject to the serious area requirements, including the implementation of BACM/BACT independent of the area's attainment needs.
      Response: The EPA appreciates this comment and modified the final rule to reflect an oversight in the proposal. Specifically, as described earlier, the EPA requires an area subject to 179B that has already been reclassified to Serious to implement BACM/BACT and additional feasible measures. Nothing in CAA section 179B is intended to alleviate those requirements. The EPA will not reclassify a Moderate area to Serious if that area is successfully meeting the requirements of CAA section 179B. However, the EPA maintains the authority to reclassify a Moderate area to Serious if it is determined that the area is not adequately meeting the requirements of CAA section 179B.
      Comment: Commenters stated the EPA should not require the state to implement a 5 percent reduction plan based solely on emissions from international sources, since attaining such reductions may well be impossible if there are significant international emissions.
      Response: The EPA agrees that as long as the affected nonattainment area satisfactorily meets the provisions of CAA section 179B, that area should not be subjected to the additional requirements of CAA section 189(d) even if the area fails to attain.
      Comment: Commenters stated that requiring implementation of all RACM and RACT for CAA section l79B nonattainment areas would penalize rural communities and would run counter to the intent of CAA section 179B of providing regulatory relief to areas affected by foreign emissions.
      Response: For the reasons stated earlier, the EPA has determined that l79B nonattainment areas should be required to implement control measures to the same extent as a nonattainment area that demonstrates it will not be able to attain the PM2.5 NAAQS by the statutory attainment date.
      Comment: Some commenters stated that the EPA's current interpretation of 179B and the agency's guidance which encourages states "to reduce emissions beyond the minimum necessary to satisfy the `but for' test," circumvents Congressional intent and the CAA and establishes a second ambient air quality threshold not related to the NAAQS.
      Response: As discussed in the proposal and in the earlier section, it is acknowledged that the EPA no longer believes its past interpretation of the RACM and RACT requirements for 179B attainment plans is appropriate. Further, the EPA has determined that the reasonable control measure requirements outlined earlier represent the most appropriate interpretation of the CAA in line with the overriding Congressional intent to protect and improve air quality thereby enabling the associated public health benefit.
      Comment: Commenters expressed concern with the technical demonstration that would have been required to elect not to impose some control measures under the second sub-option described on page 15354 of the proposal.
      Response: The second sub-option and the associated technical demonstration were not finalized in this rule. An explanation for this decision is located in Section IV.D of this preamble.
      Comment: Some commenters stated that if an area's attainment demonstration is approved under CAA section 179B, any contingency measures should only be required to obtain emissions reductions in proportion to the contribution of emissions excluding the international pollution, or at least to the contribution of emissions reductions that the state can feasibly attain.
      Response: For the reasons previously discussed, the EPA is not finalizing the proportional approach to control measures that was proposed. The EPA recognizes that identifying adequate contingency measures is a challenge, especially for 179B areas that have no legal jurisdiction over some of the sources contributing to the nonattainment status of the area. However, the EPA expects states with a 179B area to follow the guidance and requirements outlined in Section IV.H of this preamble to identify contingency measures that can cause emissions reductions from sources within the state's jurisdiction. As discussed in Section IV.H of the preamble, this should include an explanation of the amount of anticipated emissions reductions to be accomplished by the contingency measures. If such an area is unable to identify approximately 1 year's worth of emissions reductions to constitute contingency measures, the explanation should describe the factors considered by the state when reaching this conclusion.
E. Enforcement and Compliance
	a. Summary of Proposal.
      The agency proposed that in general, in order for a SIP regulation to be enforceable, it must clearly spell out which sources or source types are subject to its requirements and what its requirements (e.g., emission limits or work practices) are. The EPA proposed that an enforceable regulation would also specify the timeframes within which these requirements must be met, and definitively state the recordkeeping and monitoring requirements appropriate to the type of sources being regulated. Additionally, the EPA proposed that an enforceable regulation would also contain test procedures in order to determine whether sources are in compliance.
      b. Final Rule.
      Section 172(c)(6) in subpart 1 of the CAA requires nonattainment SIPs to "include enforceable emission limitations, and such other control measures, means or techniques... as well as schedules and timetables for compliance, as may be necessary or appropriate to provide for attainment." In the remanded 2007 PM2.5 Implementation Rule, the EPA described the general elements that characterize an enforceable SIP regulation, recognizing that enforceable SIP regulations may address the elements in different ways depending on the type of source category being regulated. The agency continues to believe and hereby finalizes that in general, in order for a SIP regulation to be enforceable, it must clearly spell out which sources or source types are subject to its requirements and what its requirements (e.g., emission limits or work practices) are. An enforceable regulation would also specify the timeframes within which these requirements must be met, and definitively state the recordkeeping and monitoring requirements appropriate to the type of sources being regulated. The recordkeeping and monitoring requirements would have to be sufficient to enable the state or the EPA to determine whether the source is complying with the emission limit on a continuous basis. An enforceable regulation would also contain test procedures in order to determine whether sources are in compliance.
	The EPA continues to believe that complete and effective regulations that ensure compliance with an applicable emissions limit must include requirements for both performance testing of emissions and ongoing monitoring of the compliance performance of control measures, and the agency requires that SIP regulations that establish emission limits include the following for performance testing:
 Indicator(s) of compliance - the pollutant or pollutants of interest (e.g., filterable and condensable PM2.5) and the applicable units of measurement for expressing compliance (e.g., ng/J of heat input, lb/hr);
 Test method - reference to a specific EPA or other published set of sample collection and analytical procedures, equipment design and performance criteria, and the calculations providing data in units of the indicator of compliance (Section IX.K of this preamble presents a discussion of specific test methods for condensable PM2.5 emissions);
 Sample collection characteristics  -  conditions related to the sample collection portion of the performance test. Such conditions would include duration of sampling period, either on a time or volume collected basis; the number of runs comprising a test (e.g., three runs per test); and the averaging period, i.e., the time over which the emissions limit is averaged (e.g., 8 hours); and,
 Frequency - the time between emissions or performance tests (e.g., within 30 days of facility start-up and once each successive quarter, every 6-month period, or yearly).
	In order to be complete with regard to compliance monitoring provisions, the EPA requires that regulations adopted into the SIP must include the following critical elements:
 Indicator(s) of performance - the parameter or parameters measured or observed for demonstrating proper operation of the pollution control measure or compliance with the applicable emissions limitation or standard. Indicators of performance could include direct or predicted emissions measurements, process or control device (and capture system) operational parametric values that correspond to compliance with efficiency or emissions limits, and recorded findings of verification of work practice activities, raw material or fuel pollutant content, or design characteristics. Indicators could be expressed as a single maximum or minimum value, a function of process variables (e.g., within a range of pressure drops), a particular operational or work practice status (e.g., a damper position, completion of a waste recovery task), raw material or fuel pollutant content, or an interdependency between two or more variables;, a damper position, completion of a waste recovery task), raw material or fuel pollutant content, or an interdependency between two or more variables;
 Measurement technique - the means used to gather and record information of or about the indicators of performance. The components of the measurement technique include the detector type or analytical method, location and installation specifications, inspection procedures, and quality assurance and quality control measures. Examples of measurement approaches include continuous emissions monitoring systems (CEMS), continuous opacity monitoring systems (COMS), continuous parametric monitoring systems (CPMS), performance testing, vendor or laboratory analytical data, and manual inspections and data collection that include making records of process conditions, raw materials or fuel specifications, or work practices. Directly enforceable emission measurements, such as PM CEMS, are preferred wherever feasible. Where COMS are feasible, it should be clear that opacity is a directly enforceable standard, not merely an indicator of compliance;
 Averaging time - the period over which to average data to verify compliance with the emissions limitation or standard or proper operation of the pollution control measure. Examples of averaging time include a 3-hour average in units of the emissions limitation, a 30-day rolling average emissions value, a daily average of a control device operational parametric range, periodic (e.g., monthly, annual) average of raw materials or fuel pollutant content, and an instantaneous alarm;
 Monitoring frequency - the number of monitoring data values recorded over a specified time interval. Examples of monitoring frequencies include at least one data value every 15 minutes for CEMS or CPMS, at least every 10 seconds for COMS, upon receipt or application of raw materials or fuel to the process, or at least once per operating day (or week, month, etc.) for performance testing, work practice verification, or equipment design inspections; and,
 Reporting and record retention requirements  -  criteria for retaining monitoring and test data in an electronic form and periodic electronic reporting of information as needed to the compliance office. Electronic record retention and submission have been widely adopted, and the EPA believes that such readily accessible documentation could be used by state, federal and other analysts to spot trends and non-compliance more easily than if these entities conducted reviews of paper documents. The EPA also recommends that compliance reports be made available online so that the general public can readily access the information without the need to submit Freedom of Information Act (FOIA) requests to the EPA. The EPA is in the process of revising federal rules to make similar requirements apply.
      The EPA acknowledges that one way for regulatory authorities to have owners or operators of regulated sources demonstrate compliance via ongoing monitoring is to use a Compliance Assurance Monitoring (CAM) rule-type approach. Under such an approach, an owner or operator would be able to establish operating ranges of continuously monitored parameters determined through concurrent performance testing as indicators of performance. A CAM rule-type approach would require owners or operators who chose parameter monitoring as indicative of compliance to immediately take corrective action should a measured parameter value occur outside the demonstrated range associated with compliance. Moreover, concurrent performance testing and parameter measurement would be necessary on a periodic basis, generally annually, and may be necessary on a more frequent basis to reverify or reset parameter value range, particularly when the operating range is exceeded. Failure of the owner or operator to take immediate corrective action would constitute a violation of the applicable rule. Moreover, failure of a parameter range to demonstrate compliance when reverification or resetting performance testing occurred would also constitute a violation of the emission limit. This implementation rule does not prohibit states from taking a CAM rule type approach and making parameters directly enforceable limits.
      The EPA continues to believe that approval of regulations adopted into SIPs should ensure that these critical elements are present and clearly defined to be approvable. In particular, the compliance obligations, including emissions limits and other applicable requirements, should be representative of and accountable to the assumptions used in a state's attainment demonstration. This accountability should include the ability to transfer the applicable regulatory requirements to a title V operating permit subject to the EPA and public review.
c. Comments and Responses.
      Comment: Commenters suggested that the proposal's use of the term "indicators of compliance" is confusing and suggested the EPA should simply express that emission limitations must identify the pollutant of interest and the units of measurement. The commenters suggested the EPA use the term "measurement method" and the EPA acknowledge that sources may use procedures that are not published by the EPA, especially for pollutants for which there is no federally promulgated test method, performance specification, or voluntary consensus standard. The commenters disagreed that "averaging time" is always the appropriate term, since it has no applicability for standards that use test methods that specify minimum run times or sample volumes, and numbers of runs, and suggested the EPA use the term "sample time or volume" and make clear that it can be a minimum or an absolute value.
      Response: The EPA does not agree with the commenters' suggestion. The proposal identified four components associated with demonstrating compliance via performance testing  -  the indicator of compliance (for which the commenters expressed concern), the test method, the averaging time associated with the test method, and the frequency of conducting the test  -  as well as five components associated with demonstrating compliance via ongoing monitoring. However, the commenters appear to suggest to expand compliance demonstration techniques beyond testing and monitoring. To the extent that SIP regulations are developed that do not rely on performance testing or ongoing monitoring as means for demonstrating compliance, the EPA agrees that other components, including emission limitations that identify the pollutant of interest and units of measurement, as suggested by the commenter, would be appropriate.
      The EPA believes neither a change in term from "test method" to "measurement method" nor an additional acknowledgement regarding its current wording "specific EPA or other published set of [criteria]" is needed. The component to which the commenter refers is based on performance testing; ongoing measurement components are covered as `measurement technique' in one of the five critical elements for ongoing measurement.
      The EPA agrees with the commenters that in some circumstances, test methods rely on sample volumes as opposed to specific durations. The `averaging time' component of performance tests will be changed to `sample collection characteristics', where such characteristics will include averaging time, duration, or sample volume and number of runs, as applicable. While the EPA does not believe it to be necessary to identify that the sample collection characteristics could be minima, maxima, or ranges, the preamble discussion associated with this change indicates that specific test methods, or regulatory agencies, may impose restrictions or specific conditions on sample collection characteristics.
      Comment: Some commenters stated the EPA should make clear that states can rely on CAM-type parameters as indicators of compliance. The commenters stated the EPA should make clear that states that follow the CAM rule model are not required to establish those "indicators" as directly enforceable limitations, as long as the SIP imposes directly enforceable review and corrective action requirements that will ensure that the source takes corrective action prior to the point when the indicator would predict noncompliance with an emission limitation.
      Response: The EPA agrees with the commenters that one way regulatory authorities have owners or operators of regulated sources demonstrate compliance via ongoing monitoring is to use a CAM rule-type approach. Under such an approach, an owner or operator would be able to establish operating ranges of continuously monitored parameters determined through concurrent performance testing as indicators of performance (indicators of compliance are components of performance testing). Nothing in the CAM rule precludes an owner or operator from establishing parameters as directly enforceable limitations, and neither does this rule. The CAM rule-type approach would require owners or operators who chose parameter monitoring as indicative of compliance to immediately take corrective action should a measured parameter value occur outside the demonstrated range associated with compliance. Moreover, concurrent performance testing and parameter measurement would be necessary on a periodic basis and may be necessary on a more frequent basis to reverify or reset a parameter value range. Failure to take immediate corrective action would constitute a violation. Moreover, failure of a parameter range to demonstrate compliance when reverification or resetting performance testing occurred would also constitute a violation.
      Comment: Commenters agreed that a compliance monitoring provision must specify a "measurement technique" and stated the EPA should defer to states regarding the most appropriate measurement techniques. The commenter disagreed that use of CEMS for "directly enforceable measurements" is always preferable.
      Response: The EPA appreciates the commenters' support and notes that the measurement technique component used in this rule corresponds to a similarly-named component contained in the definition of monitoring in the general provisions of 40 CFR part 63. To the extent that regulatory authorities choose appropriate measurement techniques, the EPA agrees with the commenter. The EPA believes the commenters take the language regarding use of directly enforceable emissions measurements out of context; the EPA said it is preferred wherever feasible, not that it is always required.
      Comment: Commenters stated the EPA should make clear that "averaging time" is only required for measurement techniques that collect continuous data that will be averaged over some period in order to assess source operations; i.e., the element is only essential to certain types of compliance monitoring requirements. The commenters suggested the EPA should not attempt to impose or require minimum frequencies in terms of calendar days, months, or year and urged the EPA to allow states flexibility to determine how best to address operational variability.
      Response: The EPA disagrees with the commenters, noting that averaging time remains an important aspect of demonstrating compliance via ongoing monitoring for all types of monitoring. It remains important to know how the period over which collected data are used to determine compliance, whether that period is daily, hourly, or annually. The EPA has not assigned minimum averaging times that regulatory authorities must use; however, the EPA expects those regulatory authorities to select averaging times appropriate to demonstrate compliance for specific types of sources.
      Comment: Commenters supported the EPA's recommendation that information demonstrating compliance be made available online for general public access (80 FR 15448) so that the public can provide the oversight that the Act contemplates (42 U.S.C. section 7604). Other commenters opposed an absolute requirement that all monitoring, testing, and reporting be done electronically since many permits are for small businesses who may not have the capital and technical expertise for electronic recordkeeping and reporting; commenters recommended that the EPA change this criterion into a recommendation that electronic means be used where feasible.
      Response: The EPA agrees that electronic reporting and public access to information is important. The EPA notes that it is and has been moving towards electronic emissions reporting from all regulated sources for some time now. New NSPS and NESHAP require electronic emissions reporting, and efforts are underway to require existing NSPS and NESHP to use electronic emissions reporting. Consistent with this approach, and with the approach taken by the next generation of compliance program, this rule will assist the shift toward electronic reporting to make environmental reporting more accurate, complete, and efficient. Moreover, electronic reporting of emissions will help us and regulatory authorities better manage information, improve effectiveness, and improve transparency.
F. Multi-pollutant Considerations
1. Summary of Proposal:
      The EPA described many benefits of coordinating air quality planning efforts across a range of air quality programs addressing the NAAQS, air toxics, and climate change and encouraged states to pursue multipollutant planning approaches where possible.
2. Final Rule:
	The final rule reiterates many of the points made in support of multipollutant planning efforts in the proposal. Efforts to reduce fine particle concentrations fit well as part of multi pollutant planning efforts because of the involvement of PM2.5 precursor gases (i.e., NOx, SO2, VOC, and ammonia) and direct PM2.5 emissions in a number of other air quality and climate issues. NOx and VOC play important roles in atmospheric chemistry and in the formation of ground-level ozone. Certain VOCs and constituents of direct PM2.5are also hazardous air pollutants. SO2 and NOx emissions, and their reactions with ammonia to form ammonium sulfate and ammonium nitrate, have played important roles in acidic deposition, haze in national parks, and in fine particle formation. Black carbon from direct PM2.5 emissions is an important short-lived climate pollutant. Increasing average temperatures due to climate change are expected to lead to higher ozone concentrations. Many efforts to address traditional air pollutants have important co-benefits in terms of reducing emissions of CO2 and other GHGs, and vice versa. For these reasons, efforts to reduce air pollution to address multiple objectives can provide important benefits to states, the regulated community, and the general public.
	Multipollutant planning issues have been an area of strong interest by scientists and policymakers for many years. In 1995-1997, the EPA sought recommendations from a federal advisory committee with broad stakeholder representation on ways to coordinate and make more efficient the implementation programs for upcoming ozone and PM2.5 standards and the regional haze program. The National Academy of Sciences issued "Air Quality Management in the United States," a report on multipollutant planning issues and recommendations, in 2004. In June 2007, the EPA's CAA Advisory Committee (CAAAC) recommended that the agency allow states to integrate SIP requirements and other air quality goals into a comprehensive plan. The recommended plan would demonstrate attainment/maintenance of multiple NAAQS, accomplish sector-based reductions, realize risk reductions of HAPs and make improvements in visibility. It could also be structured to integrate programs addressing land use, transportation, energy and climate.
      The EPA believes that in many cases it can be more efficient for states to develop integrated control strategies that address multiple pollutants rather than separate strategies for individual air quality programs. An integrated air quality control strategy that reduces multiple pollutants can help ensure that reductions are efficiently achieved and produce the greatest overall air quality benefits. The EPA has encouraged states to take a multi-pollutant approach to managing air quality to the extent possible.
      While the agency encourages states to develop multi-pollutant plans, it recognizes that certain factors can make such efforts challenging. For example, the NAAQS are to be reviewed every 5 years, and any revisions to the standards will lead to a series of implementation steps required by specific statutory schedules. In some cases program requirements and deliverables may not be coordinated easily, but in other situations there are good opportunities for conducting technical analyses and developing policy approaches that can have important health and environmental benefits while addressing multiple key air pollution issues at the same time.
	One such opportunity is the increased use of multi-pollutant assessments. A multi-pollutant assessment, or one-atmosphere modeling, is conducted with a single air quality model (such as CMAQ or CAMx) that is capable of simulating transport and formation of multiple pollutants simultaneously. For example, this type of model can simulate formation and deposition involving pollutants associated with PM2.5, ozone and regional haze, and it can include algorithms simulating gas phase chemistry, aqueous phase chemistry, aerosol formation and acid deposition. This type of model could also include the formation and deposition of key air toxics and the chemical interactions that occur with these individual toxic species to produce PM2.5 and ozone. It can also account for estimated changes in traditional air pollutant emissions resulting from programs (such as energy efficiency and renewable energy programs) to reduce emissions of CO2 and other greenhouse gases.
	Models and data analysis intended to address PM2.5 could be beneficial for use in addressing ozone, visibility impairment, and climate change. States that undertake multi-pollutant assessments as part of their attainment demonstration have the opportunity to assess the impact of their PM2.5 strategies on ozone, visibility, and climate programs to ensure that optimal emission reduction strategies are developed to the extent possible. This could facilitate addressing all of these pollutants in a more cost effective manner.
	States may also find it desirable to assess the impact of PM2.5, ozone, and/or regional haze control strategies on toxic air pollutants regulated under the CAA or under state air toxic initiatives. Given the relationships that exist between air toxics and the formation of PM2.5 and ozone, states may find that controls can be selected to meet goals for PM2.5 and/or ozone attainment as well as those of specific air toxic programs.
3. Comments and Response.
      Comments: Some commenters urged the EPA to provide assistance to those states that might be precluded from developing Multi-Pollutant SIPs due to lack of resources. Other commenters stated the EPA should support the states' use of various approaches and tools suggested the EPA make the Control Strategy (CoST) tool fully available, as well as provide any necessary training to facilitate states' ability to effectively use the tool. The commenter also suggested that the EPA entertain the possibility for states to demonstrate that the controls put in place to comply with multi-pollutant CAIR and CSAPR are valid and should be accepted as part of attainment demonstrations; allowing states to credit emissions reductions that have occurred.
      Response: The Control Strategy Tool (CoST) is a component of the EPA's Emissions Modeling Framework that is a client-server system developed to support emissions modeling. CoST was developed by the EPA to model the emissions reductions and engineering costs associated with control strategies applied to point, area, and mobile sources of air pollutant emissions to support the analyses of the EPA air pollution policies and regulations. Links to the software and documentation are available at the EPA's CoST Web site at http://www3.epa.gov/ttnecas1/cost.htm. Note that because of resource limitations, the EPA is not able to provide any support for the installation or operation of CoST outside of the agency.
G. Measures to Ensure Appropriate Protections for Overburdened Populations
1. Summary of Proposal.
The EPA requested comments on ways that states can provide public health protection specifically for overburdened populations when preparing attainment plans for the PM2.5 NAAQS.
2. Final Rule.
      Environmentally overburdened, underserved, and economically distressed communities may be subject to a higher risk of pollutant-related health effects than the general population because they may be exposed to higher pollutant concentrations than the general population; they may experience a larger health impact at a given pollutant concentration; or they may be adversely affected by lower pollutant concentrations than the general population. Thus, the NAAQS review process inherently takes into consideration appropriate environmental justice factors as part of the standard-setting process for each pollutant.
      Section 109(d) of the CAA requires the EPA to periodically review (every 5 years) the science upon which the standards are based and the standards themselves. The policy assessment for the 2012 PM NAAQS review (U.S. EPA, 2011a, p. 2-60) observed that the highest concentrations of PM2.5 in an area tend to be measured at monitors located in areas where the surrounding populations are more likely to live below the poverty line and to have higher percentages of minorities. In its 2012 review of the PM NAAQS, the EPA revised the primary annual PM2.5 standard by lowering the level to 12.0 micrograms per cubic meter (ug/m[3]) to provide increased protection against health effects associated with long- and short-term PM2.5 exposures. The agency also 1) revised the form of the primary annual PM2.5 standard to eliminate the spatial averaging provisions to avoid potential disproportionate impacts on at-risk populations; and 2) directed states to relocate a limited number of existing monitors to near-roadway sites in large urban areas. Both of these actions were informed by scientific evidence that underscored the potentially disproportionate exposure to high PM2.5 concentrations and therefore disproportionate risk to low-income and minority populations.
In conjunction with these revisions, the EPA retained the primary 24-hour PM2.5 standard, as revised in 2006 (71 FR 61144, October 17, 2006), to provide supplemental protection against health effects associated with short-term PM2.5 exposures, especially in areas with high peak PM2.5 concentrations. This suite of primary annual PM2.5 standards provides increased public health protection, including the health of at-risk populations which include children, older adults, persons with pre-existing health and lung disease, and persons of lower socioeconomic status,

against a broad range of PM2.5-related effects that include premature mortality, increased hospital admissions and emergency department visits, and development of chronic respiratory disease. 	Relationship between direct PM2.5 emissions and PM2.5 precursor emissions reductions and at-risk populations. Sources of direct PM emissions have their greatest impact on PM2.5 concentrations and public health in the general vicinity of the source (e.g., within 10 miles), while sources of precursor emissions can contribute to PM2.5 concentrations more than 100 miles away and are considered to have a more regional impact. To date, state PM2.5 attainment plans have generally relied to a greater extent on reductions of precursor pollutants rather than on reductions of direct PM2.5 emissions. Studies show, however, that on a per ton basis, the reduction of a ton of direct PM2.5 emissions leads to greater health benefits than the reduction of a ton of SO2 or NOx.
	The process for developing attainment plans for the current and future PM2.5 NAAQS presents a potential opportunity to target the health protections afforded by the NAAQS, as the EPA expects that attainment for the 2012 PM2.5 NAAQS and future PM2.5 NAAQS in nonattainment areas with the most severe pollution problems may need to give greater emphasis to reducing direct PM2.5 emissions in combination with efforts already underway to further reduce precursor emissions. Placing greater emphasis on reducing emissions from sources of direct PM2.5 (e.g., certain industrial facilities located in more densely populated areas; areas with high motor vehicle and other diesel engine emissions, such as rail yards and near major roadways; and, areas with high wood smoke emissions) could provide the added benefit of reducing exposure to PM2.5 in low-income and minority communities.
	Options for states to consider to ensure appropriate protections from PM2.5 exposure for overburdened populations. The EPA believes that states have sufficient flexibility and discretion under the CAA in implementing their attainment strategies to focus resources on controlling those sources of emissions that directly and adversely affect low-income and other at risk populations. By reducing impacts on at-risk populations, states can maximize health benefits, thereby creating greater net benefits for the state in a cost-effective manner. In addition, reducing adverse impacts to low-income and minority populations advances the environmental justice goal of fair treatment for these populations.
	There are a number of actions that states could take to focus resources in this way. Some of these actions can help identify areas where additional ambient monitoring may be needed in low income and overburdened communities. Such information can be used to support updates to the state's annual monitoring plan.
      Screening is a useful first step in understanding or highlighting locations that may be candidates for further review. The EPA has developed EJSCREEN, a public screening tool that allows users to access high-resolution environmental and demographic information for locations in the United States, and compare their selected locations to the rest of the state, the EPA region, or the nation. The tool may help users identify areas with minority and/or low-income populations, potential environmental quality issues, a combination of environmental and demographic indicators that is greater than usual, and other factors that may be of interest. Other examples of actions to support updates to the annual monitoring plan include:
       Develop databases and online mapping tools that enable users (including state staff, public, and the regulated community) to understand where sources of direct PM2.5 emissions are located and where new or modified sources of emissions could have potential impacts on low income and other overburdened communities;
       Incorporate existing mapping tools that identify target areas in the attainment plan development process and related actions; and,
       Analyze emissions data, ambient data, and available modeling to identify potential unmonitored PM2.5 hotspots in areas with a high percentage of low income, minority or indigenous persons (see Section III.E of this preamble for further discussion of this option).
	Once target areas for addressing these sensitive population needs within a nonattainment area have been identified, the state could consider taking any of the following actions, which help target emissions reductions that may be needed to attain the PM2.5 NAAQS:
 Prioritize the selection of control measures that target reductions of direct PM2.5, particularly from sources located in "at-risk" areas as part of the state's RACM and RACT analysis (for Moderate nonattainment areas) or BACM and BACT analysis (for Serious nonattainment areas), as well as other measures needed to demonstrate attainment (see Sections III.D and V.D of this preamble, respectively, of this preamble for further discussion of this option);
 Improve the understanding of the potential impact of minor sources by improving or generating an emissions inventory for such minor sources, including sources that are not currently required to report emissions, to generate options on how emissions can be reduced in the target area;
 Design voluntary programs to reduce VMT and mobile source-related PM2.5 emissions (e.g., diesel retrofits);
 Incorporate environmental justice criteria into the alternatives analysis to ensure appropriate siting and require cumulative impact studies for proposed projects;
 Eliminate exemptions from and/or lower thresholds for minor source permitting;
 Prioritize targeted enforcement strategies; and
 Develop a list of potential supplemental environmental projects (SEPs) that could be applied in the target area.
In addition to the previous steps, states could increase opportunities for meaningful involvement of community groups in attainment plan development, annual monitoring network plan reviews, and permitting processes for at-risk and minority populations by taking the following steps:
 Develop advisory boards and/or develop enhanced notice-and-comment requirements for low income and minority communities to assure meaningful involvement relative to projects that impact their communities;
 Provide special notice of important actions affecting target areas in appropriate languages and with attention to cultural barriers;
 Provide advance notification for low income and minority communities of upcoming opportunities for public comment on SIPs, ambient air monitoring plans, and other relevant actions such as permit actions;
 Maintain multi-lingual Web sites and offer translators for public meetings and hearings; and,
 Coordinate with the state's EJ coordinator, if applicable, to assist with outreach efforts.
	3. Comment and Response.
	Comment: Some commenters supported the EPA's recommendations for measures to ensure protections for overburdened communities, but stated that the EPA's proposal to allow areas to ignore near-roadway monitors is inconsistent with these objectives. The commenter stated that communities near heavily trafficked areas tend to be disproportionately low-income minority communities that suffer from disproportionately higher PM2.5 exposure risks; and that the EPA and states should address the information gaps that disempower these communities in their ability to protect themselves from pollution sources. The commenter also stated that making sources disclose and report compliance information and providing that information in easy to access formats would go a long way to improve the ability of these communities to be informed of their risks and to assure compliance in their communities.
	Response: The EPA agrees that near-road monitoring data should not be ignored in future attainment planning. However, the EPA wishes to clarify that the statements in the proposal referenced the fact that the near-road monitors were not required to be in place before January 1, 2015. Compliance with the PM2.5 standards is based on three years of complete, quality-assured data at a monitor. Thus, the earliest that these monitors would have valid design values would be in early 2018 (based on data from 2015-2017). This timing makes it unlikely that sufficient data from these monitors will be available to be considered in attainment demonstrations that are due in 2016. In addition, the base modeling year of the attainment demonstration may pre-date the startup date of the near-road monitor(s). In this case, it may be possible to consider the near-road data in the attainment demonstration, but the recommended default projection methodology may not be applicable (since the time period of the near-road data may not correspond to the 5 year time period centered about the base modeling year, as recommended in the modeling guidance). Additionally, near-road PM2.5 monitors are only required in the 27 largest metropolitan areas of the country, and some PM2.5 nonattainment areas may not have any near-road monitoring sites. Thus, when complete data from near-road PM2.5 ambient monitors become available, the data should be used by states and the EPA for all aspects of the NAAQS implementation process, from attainment planning to the determination of attainment, in a manner similar to any other quality-assured PM2.5 monitoring data. States should consult with the appropriate the EPA regional office to determine how and when near-road data should be used in the PM2.5 NAAQS implementation process for specific nonattainment areas.
With regard to the comment about having easy access to facility compliance information, the EPA directs the commenter to the Enforcement and Compliance History Online web site to search for facilities to assess compliance with environmental regulations. The site provides the ability to investigate pollution sources, examine and create enforcement-related maps, or explore an individual state's performance. As noted earlier in this section, the EJSCREEN tool can also provide important information about estimated pollution impacts in specific communities.
H. Tribal Issues
	The 1998 Tribal Authority Rule (TAR) (40 CFR part 49), which implements section 301(d) of the CAA, gives tribes the option of developing Tribal Implementation Plans (TIPs). Specifically, the TAR provides for the tribes to be treated in the same manner as a state in implementing certain sections of the CAA. However, tribes are not required to develop implementation plans. The EPA determined in the TAR that it was inappropriate to treat tribes in a manner similar to a state with regard to specific plan submission and implementation deadlines for the NAAQS-related requirements, including, but not limited to, such deadlines in CAA sections 110(a)(1), 172(a)(2), 182 187, and 191. See 40 CFR 49.4(a). In addition, the EPA determined it was not appropriate to treat tribes similarly to states with respect to provisions of the CAA requiring as a condition of program approval the demonstration of criminal enforcement authority or providing for the delegation of such criminal enforcement authority. See 40 CFR 49.4(g). To the extent a tribe is precluded from asserting criminal enforcement authority, the federal government will exercise primary criminal enforcement responsibility. See 40 CFR 49.8. In such circumstances, tribes seeking approval for CAA programs provide potential investigative leads to an appropriate federal enforcement agency.
      If a tribe elects to do a TIP, the agency will work with the tribe to develop an appropriate schedule that meets the needs of the tribe and does not interfere with the attainment of the NAAQS in other jurisdictions. The tribe developing a TIP can work with the EPA Regional Office on the appropriateness of addressing RFP and other substantive SIP requirements that may or may not be appropriate for the tribe's situation.