dissenting:

I respectfully dissent.

Pursuant to the Clean Air Act, 42 U.S.C. § 7401 et seq., EPA promulgates National Ambiant Air Quality Standards (NAAQSs) and the states must devise plans to implement and enforce these standards (State Implementation Plans or SIPs). Following notice, hearings, and adoption of the SIP, or SIP revision, the state submits the SIP or SIP revision to EPA for approval. 42 U.S.C. § 7410 (a)(2). If the SIP satisfies the statutory criteria, EPA must approve it “or any portion thereof”; otherwise, EPA must promulgate a substitute plan that complies with the law. 42 U.S.C. § 7410 (c).

In 1977 the Clean Air Act was amended to require EPA to designate those areas not meeting the NAAQSs as “nonattainment areas.” The states involved were required to revise their SIPs for such areas to adopt more stringent air pollution controls. 42 U.S.C. § 7502 . In 1978, the South Coast Air Basin (Riverside, San Ber-nardino, Orange and Los Angeles Counties) was designated a nonattainment area for nitrogen oxide (NOx). 40 C.F.R. § 81.305 (1987). As a result, the California Air Resources Board (CARB) and the South Coast Air Quality Management District (SCAQMD) began in 1980 to consider ways of regulating nitrogen oxide emissions from, among other sources, cement kilns in the South Coast Air Basin. 1

In September, 1981, after receiving input from the public, industry and EPA, CARB published a report entitled “Suggested Control Measure for the Control of Emissions of Oxides of Nitrogen from Cement Kilns.” This report stated that cement kilns “are a significant source of NOx emissions.” It proposed measures to achieve a 38% reduction in cement kiln NOx emissions which included a requirement that existing kilns emit a maximum of 3.1 pounds of NOx per ton of cement clinker produced. According to the report, the 3.1 lb/T limit was technologically feasible and cost effective.

On January 8, 1982, the SCAQMD voted to adopt the CARB proposal as Rule 1112. As part of its resolution adopting Rule 1112, the District stated that “considering the technological and economic circumstances of the sources, [the 3.1 lb/T limit] is a reasonably available control measure.” As adopted, Rule 1112 established an emission limit of 3.1 lbs/T, a compliance date of July 1,1984, and a provision for review and possible adjustment of the emission limit in January, 1984, prior to the final compliance *1249 date. This review provision was designated paragraph (d) of Rule 1112. It reads as follows:

Effective Date

In March, 1982, CARB adopted the SCAQMD’s Rule 1112 and submitted it to EPA as a SIP revision despite petitioner Riverside’s petition to CARB to delay submission of Rule 1112 until after the January 1984 hearing. In November, 1982, industry-representatives requested EPA to postpone approving the Rule, or to disapprove it. EPA then contacted both the CARB and the SCAQMD to determine whether they wished EPA to postpone action. Both state agencies requested EPA to approve Rule 1112 without delay. EPA then proposed approval of Rule 1112. Due to delays in data collection as a result of reduced cement production, on January 6, 1984, the SCAQMD amended Rule 1112 to postpone the compliance date until July, 1986, and to postpone the review hearing until January, 1986. In April, 1984, again despite industry protests, CARB submitted amended Rule 1112 to EPA. EPA proposed approval in October, 1984 and submitted its Notice of Final Rulemaking on December 11, 1985.

On January 24, 1986 the state held a public hearing. As a result of that hearing, the state adopted an emission limit of 6.4 lb/T, averaged monthly, and 11.6 lb/T averaged daily. CARB has now submitted te EPA a proposed revision to Rule 1112’s emission limit, but it has not endorsed the cement companies’ claim that the original 3.1 lb/T limit was not intended to be enforceable.

What we have in this case is a difference in interpretation of the state’s Rule 1112 which the EPA approved. The cement companies argue that because this Rule provided for a future public hearing to review the emission limit of 3.1 lb/T (the hearing held January 24, 1986), and because paragraph (d) of the Rule provided for a modification of the emission limit if the state determined that the 3.1 limit was not supported by evidence presented at the hearing, the initial 3.1 limit was not a requirement of the plan at all, but merely a “target limit.” And EPA’s attempted enforcement of the 3.1 emission limit is an impermissible revision of the plan made without following the rulemaking provisions of the Clean Air Act.

EPA contends, on the other hand, that the 3.1 limit was not contingent upon confirmation of this emission standard at the January 1986 public meeting. The 3.1 limit was included in the plan which the state submitted and which EPA approved; any proposed changes as a result of the January 1986 meeting would have to be submitted as a SIP revision to EPA for approval. 2

Under the Administrative Procedure Act, we review agency action to determine whether the action was “arbitrary, capricious, an abuse of discretion, or otherwise not in accordance with law.” Citizens to Preserve Overton Park v. Volpe, 401 U.S. 402, 413-14 , 91 S.Ct. 814, 822 , 28 L.Ed.2d 136 (1971) (quoting the Administrative Procedure Act, 5 U.S.C. § 706 ). Although the reviewing court must engage in a “substantial inquiry,” i.e., “a thorough, probing, indepth review,” id. at 415 , 91 S.Ct. at 823 , it is a narrow standard of review in which the court should not substitute its judgment for that of the agency. Motor Ve *1250 hicle Mfrs. Ass’n, Inc. v. State Farm Mut. Ins. Co., 463 U.S. 29, 43 , 103 S.Ct. 2856, 2866 , 77 L.Ed.2d 443 (1983).

In the instant case, CARB submitted Rule 1112 to EPA as a SIP revision. The state agencies, involved (SCAQMD and CARB) conducted extensive research on, and were well aware of, the emission limits contained in Rule 1112, yet decided to submit the Rule to EPA for approval prior to the hearing date specified in paragraph (d). There is no indication in the record that the original 3.1 limit was not intended to be enforceable. EPA did not, as the majority suggests, “amend the [state’s] proposal ad libitum.” EPA approved the Rule as submitted, subject to a possible later revision. Rule 1112 is a state rule. EPA interpreted it, and approved it, in accordance with the approval and revision requirements of the Clean Air Act, the statute EPA is entrusted to administer. See Chevron U.S.A., Inc. v. Natural Resources Defense Council, 467 U.S. 837, 844 , 104 S.Ct. 2778, 2782 , 81 L.Ed.2d 694 (1984). EPA’s interpretation is reasonable. And it is entitled to deference. Id.

The majority states that Rule 1112 contained a proviso preventing the Rule from having any effect prior to a public hearing on feasibility. This is the cement companies’ interpretation, and it is not supported by the evidence. On the contrary, both the language of the Rule and the conduct of the state authorities support EPA’s interpretation of the Rule. Nowhere in Rule 1112 do the words “target” or “goal” appear. Rather, a specific limit is set. Why insert a specific limit in the plan unless it is to have some meaning? If it is really only a “target” why doesn’t the plan say so?

By choosing to adopt the cement companies’ interpretation over the EPA’s, the majority is substituting its judgment for that of the administrative agency charged with administering the Clean Air Act. Moreover, whether or not the 3.1 lb/T limit was “feasible” is not relevant to our determination of whether the EPA impermissibly approved the Rule. “[C]laims of economic and technological infeasibility [are] wholly foreign to the Administrator’s consideration of a state implementation plan.” Union Electric Co. v. EPA, 427 U.S. 246, 256 , 96 S.Ct. 2518, 2525 , 49 L.Ed.2d 474 (1976).

In my view the agency’s interpretation is reasonable and its action should be affirmed. See Kamp v. Hernandez, 752 F.2d 1444, 1450 (9th Cir.1985).

. Petitioners Riverside Cement Company and California Portland Cement Company each own two of the four cement kilns in the South Coast Air Basin.

. In fact, the state has submitted a revision to Rule 1112 which is presently under consideration by EPA.