On Petition for Review of an Order of the Environmental Protection Agency
The opinion of the court was delivered by: Graber, Circuit Judge
Argued and Submitted November 4, 2010-Pasadena, California
Before: J. Clifford Wallace and Susan P. Graber, Circuit Judges, and Richard Mills,*fn1 Senior District Judge.
Pursuant to the Clean Air Act, the Environmental Protection Agency ("EPA") regulates emissions of particles known as particulate matter. In order to meet statutory and regulatory requirements, California submitted a state implementation plan ("SIP") to the EPA for its approval. The SIP contains, among many other things, limits on motor vehicle emissions for the years 2009 and 2012. Although the EPA's overall approval process of the SIP is still underway, the agency has made a preliminary finding that the SIP's limits on motor vehicle emissions for years 2009 and 2012 are adequate for purposes of the state's transportation plans and projects. The EPA's adequacy determination allows California to approve transportation plans and projects that otherwise could not proceed. Pursuant to 42 U.S.C. § 7607(b)(1), several environmental groups filed this petition for review. Petitioners assert that the EPA's adequacy determination was arbitrary, capricious, or otherwise contrary to law. We deny the petition.
FACTUAL AND PROCEDURAL HISTORY
A. Air Quality Standards and State Implementation Plans
The general statutory background concerning air quality standards and SIPs is common to many cases:
The Clean Air Act, 42 U.S.C. §§ 7401-7671 ("Act"), establishes a comprehensive program for controlling and improving the United States' air quality through state and federal regulation. The Act requires the EPA to establish national ambient air quality standards ("NAAQS") for air pollutants that the EPA determines may reasonably be expected to endanger public health or welfare. 42 U.S.C. §§ 7408, 7409.
The states are responsible for ensuring that their air quality meets the NAAQS. Id. § 7407(a). The states are divided into "air quality control regions," and each region is designated as being either in attainment or nonattainment, or as unclassifiable with respect to each of the NAAQS. Id. § 7407(d). The attainment deadlines and control measures applicable within each region vary, depending on the pollutant and the severity of the region's pollution problem. See id. §§ 7502, 7509, 7511-7514a.
Under the Act, a state must develop a SIP that provides for the attainment, maintenance, and enforcement of the NAAQS in each region within the state. Id. § 7410(a). Section 7410 sets forth the general requirements for all SIPs, which include enforceable emission limitations and other control measures to meet the requirements of the Act; enforcement programs; and assurances that the state has adequate personnel, funding, and authority to carry out the SIP. Every SIP or SIP revision must be adopted by the state after reasonable notice and hearing, and each must be submitted to the EPA for approval. Id. § 7410(a)(1). The EPA may fully approve, partially approve and partially disapprove, conditionally approve, or fully disapprove a SIP. Id. § 7410(k)(3) & (4).
Latino Issues Forum v. EPA, 558 F.3d 936, 938 (9th Cir. 2009).
For areas designated "nonattainment," the Act requires that a SIP meet certain specifications. 42 U.S.C. § 7502(c). Relevant here, the SIP must provide for "attainment" of the NAAQS by the attainment deadline, id. § 7502(c)(1), and it also must provide, in the interim years, for "reasonable further progress" toward the goal of attainment. Id. § 7502(c)(2). "The term 'reasonable further progress' means such annual incremental reductions in emissions of the relevant air pollutant as are required by this part or may reasonably be required by the Administrator for the purpose of ensuring attainment of the applicable [NAAQS] by the applicable date." Id. § 7501(1).
In the part of the SIP known as the "control strategy implementation plan revision," the state must describe "specific strategies for controlling the emissions of and reducing ambient levels of pollutants in order to satisfy [statutory] requirements for demonstrations of reasonable further progress and attainment." 40 C.F.R. § 93.101. Additionally, the state must allocate allowable emissions for each year between motor vehicles and all other sources (e.g., factories and power plants). Id. The state's "budget" of emissions from motor vehicles for a given year is known as the "motor vehicle emissions budget." Id. "Motor vehicle emissions budget is that portion of the total allowable emissions defined in the submitted or approved control strategy implementation plan revision or maintenance plan for a certain date for the purpose of meeting reasonable further progress milestones or demonstrating attainment or maintenance of the NAAQS . . . ." Id.
B. Regulation of Particulate Matter
"Particulate matter is the generic term for a broad class of chemically and physically diverse substances that exist as discrete particles (liquid droplets or solids) over a wide range of sizes." National Ambient Air Quality Standards for Particulate Matter, 62 Fed. Reg. 38,652-01, 38,653 (July 18, 1997) ("1997 NAAQS Rule"). The EPA regulates particulate matter as an air pollutant for purposes of the Clean Air Act. Id. The EPA originally regulated all particulate matter as a single class. Id. at 38,653-54. In 1987, the EPA created a subclass of particulate matter: all particles with a diameter equal to or less than 10 micrometers, referred to as "PM-10." Id.
In 1997, spurred by extensive scientific research into the deleterious effects of very small particles, the EPA added to the list of regulated air pollutants a new subset of particulate matter: those particles with a diameter equal to or less than 2.5 micrometers, referred to as "PM-2.5." Id. at 38,654. In 2006, the EPA imposed more stringent air quality requirements by decreasing the acceptable level of PM-2.5. 71 Fed. Reg. 61,144-01, 61,224 (Oct. 17, 2006) ("2006 NAAQS Rule").
The EPA has promulgated regulations describing the requirements for SIPs concerning PM-2.5. 40 C.F.R. §§ 51.1007-51.1009. The EPA designated 2002 as the default "baseline emission inventory" year to "be used for attainment planning" purposes. Id. § 51.1008(b). The EPA also specified requirements concerning a nonattainment area's plan for reasonable further progress. Id. § 51.1009. For certain SIPs, including the one at issue here, the SIP must "demonstrat[e] that reasonable further progress will be achieved for the 2009 and 2012 emissions years," known as "milestone years." Id. § 51.1009(c)(2). "The RFP plan must demonstrate that in each applicable milestone year, emissions will be at a level consistent with generally linear progress in reducing emissions between the base year and the attainment year." Id. § 51.1009(d). The rule details the specific calculations that correspond to a straight-line decrease in emissions from the emissions level in the base year to the target emissions level in the attainment year. Id. § 51.1009(f).
C. Transportation Projects and Transportation Plans
The Clean Air Act requires that all federally funded transportation projects and transportation plans "conform" to the applicable SIP. 42 U.S.C. § 7506(c)(1), (2). Section 7506(c)(1) provides:
Conformity to an implementation plan means-
(A) conformity to an implementation plan's purpose of eliminating or reducing the severity and number of violations of the national ambient air quality standards and achieving ...