The 1990 amendments to the Clean Air Act revised the regulatory framework for achieving national air quality goals. Among other changes, the amendments altered the schedule of State Implementation Plan ("SIP") submissions and Environmental Protection Agency ("EPA") responses thereto, and strengthened the sanctions that apply in the event of state noncompliance. Under Sec. 179(a), 42 U.S.C. Sec. 7509(a) (Supp. V 1993), an EPA finding of one of four possible SIP defects will trigger mandatory sanctions unless the state takes corrective action within 18 months. Petitioner Natural Resources Defense Council ("NRDC") challenges an EPA final rule that permits a state to halt the 18-month "sanctions clock," when it is triggered by an EPA finding of incompleteness or nonsubmittal, by submitting a complete plan, even if that plan is ultimately unapprovable due to substantive inadequacies. Because the language of Sec. 179 plainly leads to the approach adopted by EPA, and NRDC has pointed to no persuasive evidence that Congress intended otherwise, we deny the petition for review.

A. Statutory Framework. The Clean Air Act, as amended in 1970 and 1977,1 establishes a partnership between EPA and the states for the attainment and maintenance of national air quality goals. See 42 U.S.C. Secs. 7401-7515 (1988 & Supp. V 1993). Under this regime, EPA has set health-based primary "National Ambient Air Quality Standards" ("NAAQS") for six pollutants. See 40 C.F.R. part 50 (1994).2 The states are responsible in the first instance for meeting the NAAQS through state-designed plans that provide for attainment, maintenance, and enforcement of the NAAQS in each air quality control region. Thus, each state determines an emission reduction program for its nonattainment areas, subject to EPA approval, within deadlines imposed by Congress.

In 1990, Congress amended the Act to revise the timing and content of the SIP requirements and provide new incentives and sanctions to encourage state compliance with Clean Air Act obligations. See Clean Air Act of Amendments of 1990, Pub.L. No. 101-549, 104 Stat. 2399. The 1990 amendments extended the Act's attainment deadlines, but added short-term deadlines for many intermediate steps, including SIP submissions. The amendments also created new mandatory sanctions for states that fail to comply with SIP submission and implementation duties.

Section 110 of the Clean Air Act, 42 U.S.C. Sec. 7410, sets forth the basic processes and requirements governing SIP submissions. Within 60 days of the submission, but no later than six months after the submission deadline, EPA must review each submission for completeness. 42 U.S.C. Sec. 7410(k)(1)(B). The Act defines a complete submission as one that contains "the information necessary to enable" EPA to "determine whether the plan submission complies" with the NAAQS requirements. Id. Sec. 7410(k)(1)(A). Pursuant to the Act, EPA has developed criteria for evaluating whether a plan meets the completeness requirement. See 40 C.F.R. Sec. 51.103 & App. V.3 If EPA finds the plan complete, it has twelve months to determine whether the plan meets the substantive requirements of the Act. 42 U.S.C. Sec. 7410(k)(2). At this stage, EPA evaluates the detailed models for pollution control submitted by states and compares them with the federal standards and attainment deadlines.4 EPA may approve the plan in whole or in part, disapprove the plan, or conditionally approve the plan based on a state commitment to adopt specific enforcement methods. Id. Sec. 7410(k)(3)-(4).

Congress established a number of incentives for states to comply with SIP submission and implementation deadlines. These include mandatory sanctions, discretionary sanctions, and imposition of a Federal Implementation Plan ("FIP"). Of importance here, Sec. 179 requires EPA to impose mandatory sanctions on states that fail to comply with SIP obligations. That provision lists several EPA findings that trigger an 18-month sanctions clock, at the end of which EPA must impose one of two sanctions "unless such deficiency has been corrected." 42 U.S.C. Sec. 7509(a) (emphasis added). The triggering events are: a finding of state failure to make a required plan submission or failure to submit a complete plan; disapproval of a SIP in whole or in part; or a finding of state failure to implement any element of an approved plan. Id. Sec. 7509(a)(1)-(4). Once sanctions have been imposed, they remain in place until EPA determines that the state "has come into compliance" with its Clean Air Act obligations. Id. Sec. 7509(a).5

In addition, Sec. 110(m), 42 U.S.C. Sec. 7410(m), authorizes EPA to impose discretionary sanctions on a state at any time after EPA makes one of the four findings set forth in Sec. 179(a). Consequently, in the event of state delay in submission and implementation of NAAQS program elements, EPA can levy sanctions without waiting for expiration of the 18-month period required before mandatory sanctions are imposed. The available sanctions are the same as those under the mandatory provision, but unlike the mandatory Sec. 179(b) sanctions, discretionary sanctions are not limited to any particular nonattainment area and can be imposed statewide. See Criteria for Exercising Discretionary Sanctions Under Title I of the Clean Air Act, 59 Fed.Reg. 1476 (Jan. 11, 1994).

The 1990 Amendments continued EPA's responsibility to prepare and impose a FIP within two years following a state's failure to develop and implement a complete and approved plan. See 42 U.S.C. Sec. 7410(c). In the event of a deficiency finding due to nonsubmission, incompleteness, or disapproval, EPA must promulgate a federal plan for the attainment or maintenance of NAAQS in a particular region. The FIP provides an additional incentive for state compliance because it rescinds state authority to make the many sensitive technical and political choices that a pollution control regime demands. The FIP provision also ensures that progress toward NAAQS attainment will proceed notwithstanding inadequate action at the state level. In contrast to the mandatory sanctions, which a state can avoid merely by correcting the submission deficiency, FIP promulgation can be avoided only if EPA has actually approved the state's SIP submission.6

Finally, the Act provides that when a nonattainment area fails to meet an attainment deadline, EPA must reclassify that area to the next higher classification. For example, a marginal ozone nonattainment area must be reclassified to a moderate nonattainment area within six months after the attainment date has not been met. See 42 U.S.C. Sec. 7511(b)(2); see also id. Secs. 7512(b)(2) (carbon monoxide), 7513(b)(2) (particulate matter). Once reclassified, an area must meet the requirements of the new classification. See, e.g., id. Secs. 7511a(i), 7511(b)(4) (specifying additional obligations applicable to severe ozone areas that fail to attain). Because the control regime increases in cost and complexity with each step up the nonattainment ladder, see, e.g., id. Sec. 7511a(b)-(d) (specifying additional control measures for higher ozone classification levels, such as enhanced vehicle inspection and maintenance programs), the reclassification provisions function as yet another incentive for states to attain their air quality objectives within the statutory deadlines.

B. Final Rule. EPA's final rule interpreting Sec. 179 established the order in which EPA will apply the mandatory sanctions of Sec. 179(b) and the procedures for starting and stopping the 18-month sanctions clock. See 59 Fed.Reg. 39,832, 39,837-52 (August 4, 1994). EPA explained that under its reading of Sec. 179, a state can halt the sanctions clock by correcting the specific SIP deficiency that triggered the clock under Sec. 179(a). In particular, the final rule provides that when a state fails to submit a complete plan within six months of the submission deadline, the subsequent submission of a complete plan will permanently stop and reset the sanctions clock, even if the plan is ultimately unapprovable. Id. at 39,857-58. Thus, when EPA determines that a state has missed a submission deadline or submitted an incomplete plan, the 18-month countdown begins, and if the state submits a plan that meets EPA completeness criteria within that 18-month period, no sanctions will apply. EPA then has twelve months to review the plan's technical elements for compliance with the Act's substantive requirements; if EPA finds one or more of these elements lacking, EPA will disapprove the plan and a new 18-month clock will begin.

Petitioner NRDC timely petitioned for review of EPA's interpretation, see 42 U.S.C. Sec. 7607(b)(1), taking issue with the type of state action EPA views as sufficient to halt the sanctions clock when a state has failed to submit a complete SIP. NRDC contends that the final rule conflicts with Congress' intent to impose mandatory sanctions no later than 18 months after EPA finds that a state has not submitted an approvable plan. In the alternative, NRDC maintains that even if Congress' intent is unclear, the rule is unreasonable because it "destroys the intricate structure" of the 1990 amendments, which Congress designed to ensure that states take necessary steps to comply with federal air quality standards by statutory deadlines. Accordingly, the issue in the instant appeal is EPA's construction of the term "such deficiency" to refer to each specific finding or deficiency listed in Sec. 179(a), whereby a state can halt a sanctions clock, triggered by an EPA finding of incompleteness, by submitting a complete plan.

The court reviews NRDC's challenge pursuant to the framework set forth in Chevron USA, Inc. v. Natural Resources Defense Council, Inc., 467 U.S. 837, 104 S. Ct. 2778, 81 L. Ed. 2d 694 (1984). Under this analysis, the court must first exhaust the "traditional tools of statutory construction" to determine whether Congress has spoken to the precise question at issue. Id. at 843 n. 9, 104 S. Ct. at 2781-82 n. 9. If the court can determine congressional intent, "then that interpretation must be given effect." Kansas City v. Department of Housing & Urban Dev., 923 F.2d 188, 191 (D.C.Cir.1991) (citing United Food & Commercial Workers, 484 U.S. 112, 123, 108 S. Ct. 413, 421, 98 L. Ed. 2d 429 (1987)). If, on the other hand, "the statute is silent or ambiguous with respect to the specific issue," then the court will defer to a "permissible" agency construction of the statute. Chevron, 467 U.S. at 843, 104 S.Ct. at 2781. We conclude under step one of the Chevron analysis that the language and context of Sec. 179 clearly reveal that Congress intended to allow states to avoid mandatory sanctions by correcting only the specific deficiency that initially triggered the sanctions countdown.

Our inquiry begins, as it must, with the text of the statute. See Demarest v. Manspeaker, 498 U.S. 184, 187, 111 S. Ct. 599, 602, 112 L. Ed. 2d 608 (1991); United States v. Ron Pair Enterprises, Inc., 489 U.S. 235, 241, 109 S. Ct. 1026, 1030, 103 L. Ed. 2d 290 (1989). After setting forth several types of EPA deficiency findings--for nonsubmittal, incompleteness, substantive unapprovability, or nonimplementation--Sec. 179(a) provides that:

"unless such deficiency has been corrected within 18 months after the finding, disapproval or determination referred to in paragraphs (1), (2), (3), and (4), one of the sanctions referred to in subsection (b) of this section shall apply...."

42 U.S.C. Sec. 7509(a) (emphasis added). Under the only natural reading of the term, "such deficiency" refers to the "state failure[ ]" (as the caption puts it) that gave rise to the EPA finding or determination listed in Sec. 179. As such, the deficiency that must be remedied is the specific deficiency that, by leading to an EPA "finding, disapproval or determination," triggered the sanctions clock. It follows that when EPA activates a sanctions clock because a state has failed to submit a complete SIP, EPA must also halt the clock when the state corrects that specific deficiency. EPA adopted this interpretation in its final rule, see 58 Fed.Reg. at 39,850-51, and we agree that the statute requires it.7

NRDC's contrary reading of Sec. 179 lacks the textual support necessary to overcome EPA's straightforward construction. NRDC maintains that Congress designed Sec. 179 to address only two types of state SIP deficiencies: a state's failure to submit a SIP that meets the Act's requirements, or a state's failure to implement an approved SIP. Then, after a finding of nonsubmittal or incompleteness, the 18-month clock would be activated and could only be stopped when a state corrects the underlying deficiency by submitting an approvable plan. In formulating state obligations under the Clean Air Act, according to NRDC, Congress did not differentiate between the duty to submit a complete plan and the duty to submit an approvable plan. NRDC notes, for example, that the SIP submission deadlines make no such distinction; rather, they require states only to submit plans that satisfy the statutory criteria--namely, plans that are approvable. See 42 U.S.C. Sec. 7410(a)(2) (listing requirements that each plan must satisfy). In NRDC's view, this indicates that Congress' only concern was that a state timely submit an approvable plan, and that only an approvable SIP can turn off the sanctions clock.

To explain why Sec. 179(a) lists four separate events that activate the 18-month sanctions clock, NRDC distinguishes between administrative findings that trigger the sanctions clock, and "underlying deficiencies" in state compliance that must be corrected to avoid sanctions. NRDC suggests that Congress listed the EPA findings in Sec. 179(a) in order to ensure that the sanctions clock would be promptly activated where plan inadequacies could be readily identified. Under the two-stage procedure established in Sec. 110(k), EPA first makes an essentially ministerial finding of completeness, a process taking at most six months. By contrast, the plan approval process may take up to twelve months due to the more extensive technical analyses necessary to ensure that the SIP meets the Act's substantive requirements. See 42 U.S.C. Sec. 7410(k)(1)-(3). By listing incompleteness and nonapproval as separate triggering events, NRDC contends, Congress meant to set the clock ticking at the earliest possible moment, not to establish a separate state duty to submit a complete SIP.

Although plausible in theory and principle, NRDC's reading cannot be reconciled with Congress' use of the term "such deficiency" in Sec. 179(a). NRDC points to no specific textual support for its contention that this phrase refers to the failure to submit an approvable SIP. Instead, NRDC maintains that Sec. 179 can be properly understood only in light of the statutory scheme and legislative history that, it asserts, show a clear congressional intent at odds with EPA's interpretation. Where the terms of a statute are unambiguous, further judicial inquiry into the intent of the drafters is generally unnecessary. See Demarest, 498 U.S. at 190-91, 111 S.Ct. at 603-04; Inner City Broadcasting Corp. v. Sanders, 733 F.2d 154, 158 (D.C.Cir.1984) ("[U]nless contrary indications are present, a court can assume that Congress intended the common usage of the term to apply."). At the same time, "while the immediate statutory text is the 'best evidence' of congressional intent," it is not "the only such evidence." Tataranowicz v. Sullivan, 959 F.2d 268, 276 (D.C.Cir.1992) (citing McCarthy v. Bronson, 500 U.S. 136, 139, 111 S. Ct. 1737, 1740, 114 L. Ed. 2d 194 (1991); Crandon v. United States, 494 U.S. 152, 158, 110 S. Ct. 997, 1001-02, 108 L. Ed. 2d 132 (1990)); see also American Scholastic TV Programming Found. v. FCC, 46 F.3d 1173, 1178 (D.C.Cir.1995) ("ASTV"). Reference to statutory design and pertinent legislative history may often shed new light on congressional intent, notwithstanding statutory language that appears "superficially clear." ASTV, 46 F.3d at 1180 (quoting Tataranowicz, 959 F.2d at 277). Here, however, NRDC has presented no persuasive evidence that Congress intended any meaning other than that suggested by a straightforward reading of Sec. 179.

As evidence of Congress' true intent, NRDC points to the role of mandatory sanctions within the statutory scheme as a whole. The Clean Air Act, it contends, established an intricate structure of intermediate steps designed to lead states gradually to attainment of the national air quality standards. Congress intended the 1990 amendments to remedy the failings of the pre-1990 Act, which did not impose specific incremental deadlines and thus led to widespread nonattainment. The 1990 amendments, therefore, included specific deadlines for states to submit emission control plans well in advance of the attainment deadlines and imposed strict deadlines and requirements on EPA's response to state submissions, including prompt sanctions to ensure that the plan submission deadlines were met.

According to NRDC, EPA's rule disrupts this system and perversely rewards state delay. A state that submits a complete but unapprovable SIP on schedule, for example, will face sanctions sooner than a state that submits an incomplete SIP, waits until just before the 18-month period expires, and then submits a complete SIP. If that SIP ultimately proves unapprovable, moreover, it is possible that four and a half years might elapse between the initial SIP deadline and the imposition of mandatory sanctions. In some circumstances, NRDC notes, EPA's rule may allow a state to avoid mandatory sanctions until after the attainment dates have already passed. Finally, NRDC notes that the rule will create the anomalous result that FIPs will be implemented in many cases before states face sanctions for their failure to submit approvable state plans, thereby rendering sanctions superfluous. Thus, NRDC maintains that EPA's interpretation conflicts with Congress' intent to strengthen the sanctions regime in tandem with a graduated program of state compliance.

As NRDC views it, EPA's interpretation destroys an otherwise seamless web of incremental state obligations that together lead inexorably to NAAQS attainment. But Sec. 179 is only one of several mechanisms in the 1990 amendments that encourage state compliance. See supra Part I. EPA's discretionary authority under Sec. 110(m) can be used to counteract a state's abuse of the SIP submission timeline, for example. At the same time, the attainment deadlines remain intact, complete with additional program obligations in the event of nonattainment, irrespective of a state's dereliction in the SIP process. In addition, the statute requires EPA to impose a FIP within two years of a deficiency finding--a control regime that remains in place until the state submits and gets approved its own SIP.8 Furthermore, EPA observes that even if states abuse the SIP submission schedule, under most circumstances the Sec. 179 sanctions will precede the attainment deadlines. Hence, although Congress clearly established mandatory sanctions to increase the pressure on recalcitrant states and EPA, the additional delay allowed by EPA's interpretation, as compared with that urged by NRDC, is not incompatible with the multi-faceted statutory scheme as a whole. See Natural Resources Defense Council, Inc. v. EPA, 822 F.2d 104, 113 (D.C.Cir.1987) ("statutes are rarely, if ever uni[-]dimensionally directed towards achieving or vindicating a single public policy.... While a broad public policy goal may well be the animating force driving the legislation, achievement of actual passage of the measure invariably requires compromise and accommodation."); cf. Natural Resources Defense Council, Inc. v. EPA, 22 F.3d 1125, 1139 (D.C.Cir.1994) (finding no inconsistency in EPA's setting an implementation date for vehicle inspection programs after Clean Air Act attainment deadline). As such, NRDC's reference to the statutory scheme as evidence that EPA's rule misconstrues congressional intent is unavailing.

Nor is NRDC's reliance on the legislative history of the 1990 amendments persuasive. In part, NRDC points to general expressions of the need to avoid delay, but these provide no real insight into the question presented and consequently carry no weight.9 NRDC's reliance on a statement by the managers of the Senate bill is equally unpersuasive. Explaining the conference agreement, their statement asserts that: "In the event more than 18 months elapse after submission is required and the state program has not been submitted and approved, the conference agreement requires EPA to impose a sanction." 136 CONG.REC. S16,942 (Oct. 27, 1990) (emphasis added).10 Even assuming it is probative of congressional intent,11 this statement lacks the deliberate and definite quality of persuasive legislative history. EPA points out that the remedy for deficient plan submissions was not raised in the Conference Report or specifically addressed except as provided in the statute itself, thereby undermining the significance of the summary of the conference agreement. In addition, if the Senate managers' interpretation were correct, it could not be reconciled with the clear approvability requirement in Sec. 110, see supra note 7. The managers' statement also appears inconsistent with the second piece of legislative history on which NRDC relies, the House Report's description of Sec. 179. In the single sentence cited by NRDC, the report states that: "This system of mandatory sanctions is intended to provide a clear incentive to States for the development and implementation of approvable State air quality plans." House Report at 228. The two pieces of legislative history thus conflict about whether a plan submission must be approved or merely approvable in order to avert sanctions. While NRDC acknowledges this tension and contends that under either interpretation EPA's rule falls short, the House Report's treatment of the mandatory sanctions provision actually cuts against NRDC's interpretation.

In describing the mandatory sanctions mechanism, the House Report states:

Section 179(a) outlines the State failures which are sanctionable once the EPA Administrator makes the finding or determination or takes a disapproval action.... These failures include failure to submit a plan or plan element meeting the minimum criteria of section 110(k), EPA disapproval of a State plan in whole or in part, failure to make any required submission satisfying the minimum criteria of section 110(k), and failure to implement any requirement of an approved plan. If the State has not corrected such deficiency within 18 months from the Administrator's finding, determination or disapproval, [the mandatory sanctions will apply].

House Report at 227. By apparently equating the term "such deficiency" with "State failures which are sanctionable," and identifying "[t]hese failures" as the four kinds of shortcomings listed in Sec. 179(a), this passage strongly reinforces EPA's interpretation that "such deficiency" refers to any of the shortcomings listed in Sec. 179(a). The House Report makes no distinction between EPA administrative findings and the underlying state failures; rather, failure to submit a complete SIP is defined as an independently sanctionable deficiency. As such, it is natural to conclude that correction of that individual deficiency is sufficient to avoid the correlative sanctions.

On balance, the legislative history of Sec. 179 appears to support EPA's interpretation, not NRDC's. In light of the clear meaning of the words used by Congress, and "absent a clearly expressed legislative intention to the contrary," Consumer Product Safety Comm'n v. GTE Sylvania, Inc., 447 U.S. 102, 108, 100 S. Ct. 2051, 2056, 64 L. Ed. 2d 766 (1980), we uphold EPA's construction and it is unnecessary to reach the second step of the Chevron analysis. See Chevron, 467 U.S. at 843, 104 S.Ct. at 2781-82. Accordingly, we deny the petition for review.