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Adequacy Status of Motor Vehicle Emissions Budgets in Submitted PM2.5

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Environmental Protection Agency (EPA).


Notice of adequacy.


The Environmental Protection Agency (EPA or “Agency”) is notifying the public that the Agency has found that the motor vehicle emissions budgets (MVEBs or “budgets”) for the years 2017 and 2019 in the 2016 South Coast Serious Area Plan for the 2006 24-hour fine particulate matter (PM2.5) National Ambient Air Quality Standards (NAAQS) (“2016 PM2.5 Plan” or “Plan”) are adequate for transportation conformity purposes. The California Air Resources Board (CARB) submitted the 2016 PM2.5 Plan to the EPA on April 27, 2017, as a revision to the California State Implementation Plan (SIP). Upon the effective date of this notice of adequacy, the Southern California Association of Governments (SCAG) and the U.S. Department of Transportation must use the adequate budgets in future transportation conformity analyses.


This finding is effective January 22, 2018.

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Wienke Tax, EPA, Region IX, Air Division AIR-2, 75 Hawthorne Street, San Francisco, CA 94105-3901; (415) 947-4192 or

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Throughout this document, whenever “we,” “us,” or “our” is used, we mean EPA.

Today's notice is simply an announcement of a finding that we have already made. EPA Region IX sent a letter to CARB on December 19, 2017, stating that the MVEBs in the 2016 PM2.5 Plan for the reasonable further progress (RFP) milestone year of 2017 and attainment year of 2019 are adequate. The finding is available at the EPA's conformity website:​state-and-local-transportation/​adequacy-review-state-implementation-plan-sip-submissions-conformity. We announced the availability of the Plan and related budgets on the EPA's conformity website on October 18, 2017. We received no comments in response to this announcement. The adequate budgets are provided in the following table:

Adequate Motor Vehicle Emissions Budgets in South Coast 2006 PM2.5 Serious Area Plan

[Annual average tons per day]

Budget YearVolatile organic compoundsNitrogen oxidesDirectly emitted PM2.5

Transportation conformity is required by CAA section 176(c). The EPA's Transportation Conformity Rule at 40 CFR part 93, subpart A requires that transportation plans, transportation improvement programs, and projects conform to SIPs and establishes the criteria and procedures for determining whether or not they do. Conformity to a SIP means that transportation activities will not produce new air quality violations, worsen existing violations, or delay timely attainment of the NAAQS.

The criteria we use to determine whether a SIP's motor vehicle emission budgets are adequate for conformity purposes are outlined in 40 CFR 93.118(e)(4), promulgated on August 15, 1997 (62 FR 43780, 43781-43783). We further described our process for determining the adequacy of submitted SIP budgets in our July 1, 2004 final rule (69 FR 40004, 40038), and we used the information in these resources in making our adequacy determination. Please note that an adequacy review is separate from the EPA's completeness review and should not be used to prejudge the EPA's ultimate action on the SIP. Even if we find a budget adequate, the SIP could later be disapproved.

Consistent with the requirements set forth in the Fine Particulate Matter National Ambient Air Quality Standards: State Implementation Plan Requirements, Final Rule (81 FR 58010, August 24, 2016) (“PM2.5 SIP Requirements Rule”), the 2016 PM2.5 Plan contains RFP budgets for 2020, which is the year following the attainment year. As explained below, we are not taking action on the 2020 budgets at this time.

The Transportation Conformity Rule requires that control strategy SIPs, including the RFP plans and attainment plans required for Serious PM2.5 nonattainment areas,[1] contain MVEBs for direct PM2.5 and PM2.5 precursors subject to transportation conformity analyses for each milestone year addressed in the control strategy.[2] Start Printed Page 680Under the PM2.5 SIP Requirements Rule, Serious area PM2.5 attainment plans must define appropriate quantitative milestones and include projected RFP emission levels for direct PM2.5 and all PM2.5 plan precursors in each milestone year. For an area designated nonattainment for the 2006 PM2.5 NAAQS before January 15, 2015, the attainment plan must contain quantitative milestones to be achieved no later than 3 years after December 31, 2014, and every 3 years thereafter until the milestone date that falls within 3 years after the applicable attainment date (40 CFR 51.1013(a)(4)).[3] As the EPA explained in the preamble to the PM2.5 SIP Requirements Rule, it is important to include a post-attainment year quantitative milestone to ensure that, if the area fails to attain by the attainment date, the EPA can continue to monitor the area's progress toward attainment while the state develops a new attainment plan (see 81 FR 58010, 58063-58064, August 24, 2016).

Consistent with the requirements of 40 CFR 51.1013(a)(4), the 2016 PM2.5 Plan identifies December 31, 2017, as the first quantitative milestone date (i.e., the date 3 years after December 31, 2014). The second quantitative milestone date is December 31, 2020, and is also the last milestone date identified in the Plan because it falls within 3 years after the December 31, 2019 attainment date for the area.[4] Although this post-attainment year quantitative milestone is a required element of the Serious area plan, it is not necessary to demonstrate transportation conformity for 2020 in the submitted SIP or to use the 2020 budgets in transportation conformity determinations until such time as the area fails to attain the 2006 PM2.5 NAAQS. Therefore, the EPA is not taking action at this time on the submitted MVEBs for 2020 in the 2016 PM2.5 Plan. Additionally, the EPA has not yet started the adequacy process for the 2020 budgets.

If the EPA were to either find adequate or approve the post-attainment milestone year MVEBs now, those budgets would have to be used in transportation conformity determinations that are made after the effective date of the adequacy finding or approval even if the South Coast area ultimately attains the PM2.5 NAAQS by the Serious area attainment date. This would mean that SCAG [5] would be required to demonstrate conformity for the post-attainment date milestone year and all later years addressed in the conformity determination (e.g., the last year of the metropolitan transportation plan) to the post-attainment date RFP budgets rather than the budgets associated with the attainment year for the area (i.e., the budgets for 2019). The EPA does not believe that it is necessary to demonstrate conformity using these post-attainment year budgets in areas that either the EPA anticipates will attain by the attainment date or in areas that attain by the attainment date. As discussed elsewhere in this notice, the EPA is announcing that it has found adequate the MVEBs for the first milestone year (2017) and the attainment year (2019) for the South Coast PM2.5 nonattainment area.

If and when the EPA determines that the South Coast area has failed to attain the 2006 PM2.5 NAAQS by the applicable attainment date, the EPA will begin the MVEB adequacy and approval processes for the post-attainment year (2020) budgets. If the EPA finds the 2020 budgets adequate or approves them, those budgets will have to be used in subsequent transportation conformity determinations. The EPA believes that initiating the process to act on the submitted post-attainment year MVEBs following a determination that the area has failed to attain by the Serious area attainment date ensures that transportation activities will not cause or contribute to new violations, increase the frequency or severity of any existing violations, or delay timely attainment or any required interim emission reductions or milestones in the South Coast PM2.5 nonattainment area, consistent with the requirements of CAA section 176(c)(1)(B).

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Authority: 42 U.S.C. 7401 et seq.

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Dated: December 20, 2017.

Alexis Strauss,

Acting Regional Administrator, Region IX.

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1.  See 40 CFR 93.101 (defining “control strategy implementation plan revision”).

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2.  See 40 CFR 93.101 (defining “motor vehicle emissions budget”), 93.102(b)(2)(iv) and (v) (establishing applicability of part 93 requirements to PM2.5 precursor pollutants) and 93.118(a) (requiring that each transportation plan, TIP, or project not from a conforming transportation plan and TIP be consistent with the motor vehicle emissions budget(s) in the applicable implementation plan (or implementation plan submission)).

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3.  See also 81 FR 58010, 58058 and 58063-58064 (August 24, 2016).

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4.  Under CAA section 188(c)(2), a Serious PM2.5 nonattainment area must attain the PM2.5 NAAQS as expeditiously as practicable but no later than the end of the tenth calendar year after the area is designated as nonattainment. Because the South Coast area was designated as nonattainment for the 2006 PM2.5 NAAQS effective December 14, 2009 (74 FR 58688, November 13, 2009), the latest permissible attainment date for the area is December 31, 2019.

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5.  SCAG is the Metropolitan Planning Organization for the South Coast 2006 PM2.5 nonattainment area.

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[FR Doc. 2018-00029 Filed 1-4-18; 8:45 am]