On Petition for Review of an Order of the United States Environmental Protection Agency
The opinion of the court was delivered by: Gould, Circuit Judge:
Argued and Submitted November 16, 2011-San Francisco, California
Before: Sidney R. Thomas, Ronald M. Gould, and Jay S. Bybee, Circuit Judges.
Sierra Club and several environmental groups, (collectively, "Petitioners"), petition for review of the United States Environmental Protection Agency's ("EPA") approval of the 2004 State Implementation Plan ("2004 SIP") for the San Joaquin Valley's nonattainment area for the one-hour ozone National Ambient Air Quality Standard ("NAAQS"). Petitioners contend that 1) EPA acted arbitrarily and capriciously, in violation of the Administrative Procedures Act ("APA"), by approving the 2004 SIP knowing that the emissions inventory data on which the plan relied were, as an actual matter, outdated and inaccurate by the time EPA approved the plan in 2010; 2) EPA violated the Clean Air Act ("CAA") by approving the 2004 SIP because the emissions inventory data on which it relied were outdated and inaccurate within the meaning of the statute; 3) EPA violated the CAA by approving the 2004 SIP without the inclusion of the State-adopted regulations on which the plan relied; and 4) EPA violated the CAA by approving the 2004 SIP knowing that attainment of the one-hour ozone NAAQS by the 2010 deadline was impossible. We have jurisdiction to review EPA's action pursuant to 42 U.S.C. § 7607(b)(1), section 307(b)(1) of the CAA, and we hold that EPA's 2010 approval of the 2004 SIP, which was based on data current only as of 2004, was arbitrary and capricious. Deciding that issue, we need reach no other.
"The CAA makes the States and the Federal Government partners in the struggle against air pollution." Jensen Family Farms, Inc. v. Monterey Bay Unified Air Pollution Control Dist., 644 F.3d 934, 938 (9th Cir. 2011) (quoting Gen. Motors Corp. v. United States, 496 U.S. 530, 532 (1990) (internal quotation marks omitted)). The CAA protects the nation's air quality by authorizing EPA to establish NAAQS that apply to air pollutants that are dangerous to the general health of the public. 42 U.S.C. § 7409. EPA designates areas that fail to attain NAAQS as nonattainment areas. Id. §§ 7407(d)(1). Based on the severity of the pollution problem, nonattainment areas are further divided into five categories: marginal, moderate, serious, severe, and extreme. Id. § 7511. Central California's San Joaquin Valley ("the Valley")*fn1 has been designated as an extreme nonattainment area for the pollutant ozone.*fn2
EPA first established NAAQS for ozone in 1979. This air quality standard limited the acceptable level of ozone in the ambient air to a maximum of 0.12 parts per million ("ppm") as measured by monitored levels averaged over one hour ("the 1-hour ozone standard"). 74 Fed. Reg. at 33,934. In 1997, EPA reset that maximum to 0.08 ppm as measured by monitored levels over an eight-hour period ("the 8-hour ozone standard"). Id. Although the 8-hour standard replaced the 1-hour standard effective June 2005, as an "anti-backsliding" measure, EPA retained some elements of the 1-hour ozone standard for certain nonattainment areas that had yet to attain the 1-hour ozone standard at the time of its revocation. Id. at 33,934-35 ("As a general matter, the planning and control requirements that remain applicable following the revocation of the 1-hour ozone standard derive from CAA sections 110, 172, and 182 . . . . Under the [anti-backsliding measure, non-attainment] areas remain subject to the 1-hour requirements until they attain the 8-hour ozone standard.") The Valley is subject to this anti-backsliding provision.
A. State Implementation Plans
The CAA requires the states to address nonattainment areas by developing an SIP that sets out how a nonattainment area will come into compliance with the requisite NAAQS. 42 U.S.C. §§ 7407(a), 7410. Generally, all SIPs for nonattainment areas must include, inter alia, (1) an emissions inventory, important for the required attainment demonstration and the related "rate of progress" ("ROP") demonstration, that "include[s] a comprehensive, accurate, current inventory of actual emissions from all sources of the relevant pollutant or pollutants in such area"; (2) an attainment demonstration, developed from the emissions inventory, consisting of a technical analysis to predict whether the area will attain the NAAQS by the deadline and a control strategy for how the State plans to actually meet the standard;*fn3 (3) a means to mea- sure reasonable further progress ("RFP"); (4) nonattainment area permit requirements for new or modified stationary sources; and (5) contingency measures to be implemented if the nonattainment area does not make RFP or does not attain the NAAQS by the required date. Id. § 7502(c). SIPs for extreme ozone nonattainment areas, such as the Valley, must include an attainment demonstration "based on photochemical grid modeling*fn4 or any other analytical method determined by the Administrator, in the Administrator's discretion, to be at least as effective." Id. § 7511a(c)(2)(A), (e).
After public notice and hearings, a state must adopt the SIP and submit it to EPA for review and approval. Id. § 7410(a). EPA must then "determine whether a SIP submission is complete within 60 days of receipt . . . . [A]ny plan that has not been affirmatively determined to be complete or incomplete shall become complete within 6 months by operation of law."
74 Fed. Reg. at 33,934 (discussing 42 U.S.C. § 7410(k)(1)). EPA must then act on the SIP, either approving it in whole or disapproving it in part or in whole. 42 U.S.C. § 7410(k)(3). Once approved by EPA, an "SIP bec[o]me[s] federal law . . . , and c[annot] be changed unless and until EPA approve[s] any change." Safe Air for Everyone v. EPA, 488 F.3d 1088, 1096 (9th Cir. 2007). The CAA provides a private right of action for citizens to enforce an SIP by bringing a civil action in federal district court. 42 U.S.C. § 7604.
B. Mobile Source Emissions Regulation
The CAA also regulates mobile source emissions.*fn5 "[T]he regulation of mobile source emissions is a federal responsibility, [and] Congress has expressly preempted states from setting emissions standards for mobile sources." Jensen Family Farms, 644 F.3d at 938 (citing 42 U.S.C. § 7543(a)). California, however, is a "notable exception to this general rule," and the CAA permits EPA to authorize California "to set its own mobile source emissions standards so long as it obtains EPA approval." Id. at 938 n.3 (citing 42 U.S.C. § 7543(b) (motor vehicles); id. § 7543(e)(2) (nonroad sources)); see also Nat'l Ass'n of Home Builders v. San Joaquin Valley Unified Air Pollution Control Dist., 627 F.3d 730, 733 (9th Cir. 2010) ("[T]he [CAA] gives the states the job of regulating stationary sources of pollution, but the EPA, and ...