Clean Air Act Proposed Approval and Promulgation of PMINF10 Implementation Plan for the City of Sheridan, WY

ENVIRONMENTAL PROTECTION AGENCY

40 CFR Part 52

[WY2-1-5111; FRL-4851-4]

Clean Air Act Proposed Approval and Promulgation of PM10

Implementation Plan for the City of Sheridan, WY

AGENCY: Environmental Protection Agency (EPA).

ACTION: Notice of proposed rulemaking.

-----------------------------------------------------------------------

SUMMARY: EPA proposes approval of the State Implementation Plan (SIP)

submitted by the State of Wyoming to achieve attainment of the National

Ambient Air Quality Standards (NAAQS) for particulate matter with an

aerodynamic diameter less than or equal to a nominal 10 micrometers

(PM10). The SIP was submitted by the State of Wyoming to satisfy

certain Federal requirements for an approvable nonattainment area

PM10 SIP for the City of Sheridan, Wyoming.

DATES: Comments on this proposed action must be received in writing by

April 18, 1994.

ADDRESSES: Comments should be addressed to: Douglas M. Skie, Chief, Air

Programs Branch, (8ART-AP), Environmental Protection Agency, Region

VIII, 999 18th Street, suite 500, Denver, Colorado 80202-2466.

Copies of the State's submittal and other information are available

for inspection during normal business hours at the following locations:

Environmental Protection Agency, Region VIII, Air Programs Branch, 999

18th Street, 6th floor, South Tower, Denver, Colorado 80202-2466; and

Air Quality Division, Department of Environmental Quality, Herschler

Building, 4th floor, 122 West 25th Street, Cheyenne, Wyoming, 82002

FOR FURTHER INFORMATION CONTACT: Sara Summers, Environmental Protection

Agency, Region VIII, Air Programs Branch, 999 18th Street, suite 500,

Denver, Colorado, 80202-2466, (303) 293-0966.

SUPPLEMENTARY INFORMATION:

I. Background

The Sheridan, Wyoming area was designated nonattainment for

PM10 and classified as moderate under sections 107(d)(4)(B) and

188(a) of the Act, upon enactment of the Clean Air Act Amendments of

1990.\1\ See 56 FR 56694 (November 6, 1991); and 40 CFR 81.351

(specifying PM10 nonattainment designation for the Sheridan area).

The air quality planning requirements for moderate PM10

nonattainment areas are set out in part D, subparts 1 and 4, of Title I

of the Act.\2\

---------------------------------------------------------------------------

\1\The 1990 Amendments to the Clean Air Act made significant

changes to the Act. See Public Law No. 101-549, 104 Stat. 2399.

References herein are to the Clean Air Act, as amended (``the

Act''). The Clean Air Act is codified, as amended, in the U.S. Code

at 42 U.S.C. 7401, et seq.

\2\Subpart 1 contains provisions applicable to nonattainment

areas generally and Subpart 4 contains provisions specifically

applicable to PM10 nonattainment areas. At times, Subpart 1 and

Subpart 4 overlap or conflict. EPA has attempted to clarify the

relationship among these provisions in the ``General Preamble'' and,

as appropriate, in today's notice and supporting information.

---------------------------------------------------------------------------

The EPA has issued a ``General Preamble'' describing EPA's

preliminary views on how EPA intends to review SIPs and SIP revisions

submitted under Title I of the Act, including those State submittals

containing moderate PM10 nonattainment area SIP requirements (see

generally 57 FR 13498 (April 16, 1992) and 57 FR 18070 (April 28,

1992)). Because EPA is describing its interpretations here only in

broad terms, the reader should refer to the General Preamble for a more

detailed discussion of the interpretations of Title I advanced in this

proposal and the supporting rationale. In this action on the Wyoming

moderate PM10 SIP for Sheridan, EPA is proposing to apply its

interpretations taking into consideration the specific factual issues

presented. Thus, EPA will consider any timely submitted comments before

taking final action on this proposal.

Those States containing initial moderate PM10 nonattainment

areas (those areas designated nonattainment by operation of law under

section 107(d)(4)(B) of the Act) were required to submit, among other

things, the following provisions by November 15, 1991:

1. Provisions to assure that reasonably available control measures

(RACM) (including such reductions in emissions from existing sources in

the area as may be obtained through the adoption, at a minimum, of

reasonably available control technology (RACT)) shall be implemented no

later than December 10, 1993;

2. Either a demonstration (including air quality modeling) that the

plan will provide for attainment as expeditiously as practicable but no

later than December 31, 1994 or a demonstration that attainment by that

date is impracticable;

3. Quantitative milestones which are to be achieved every 3 years

and which demonstrate reasonable further progress (RFP) toward

attainment by December 31, 1994; and

4. Provisions to assure that the control requirements applicable to

major stationary sources of PM10 also apply to major stationary

sources of PM10 precursors except where the Administrator

determines that such sources do not contribute significantly to

PM10 levels which exceed the NAAQS in the area. See sections

172(c), 188, and 189 of the Act.

Some provisions are due at a later date. States with initial

moderate PM10 nonattainment areas were required to submit a permit

program for the construction and operation of new and modified major

stationary sources of PM10 by June 30, 1992 (see section 189(a)).

Such States also must submit contingency measures by November 15, 1993

which become effective without further action by the State or EPA, upon

a determination by EPA that the area has failed to achieve RFP or to

attain the PM10 NAAQS by the applicable statutory deadline (see

section 172(c)(9) and 57 FR 13510-13512, 13543-13544).

II. This Action

Section 110(k) of the Act sets out provisions governing EPA's

review of SIP submittals (See 57 FR 13565-66). In this action, EPA is

proposing to grant approval of the Sheridan, Wyoming, PM10 SIP

because EPA believes it meets all applicable requirements of the Act

that were due on November 15, 1991. (Also note that EPA is proposing to

approve the contingency measures submitted for the area). The SIP

includes the original document submitted to EPA on August 28, 1989, and

eight subsequent submittals containing additional information. The

dates of these submittals are: October 24, 1989, November 21, 1989,

December 20, 1989, February 16, 1990, March 29, 1990, August 21, 1991,

November 8, 1991, and March 3, 1992.

A. Analysis of State Submission

1. Procedural Background

The Act requires States to observe certain procedural requirements

in developing implementation plans for submission to EPA. Section

110(a)(2) of the Act provides that each implementation plan submitted

by a State must be adopted after reasonable notice and public

hearing.\3\ Section 110(1) of the Act similarly provides that each

revision to an implementation plan submitted by a State under the Act

must be adopted by such State after reasonable notice and public

hearing.

---------------------------------------------------------------------------

\3\Also Section 172(c)(7) of the Act requires that plan

provisions for nonattainment areas meet the application provisions

of section 110(a)(2).

---------------------------------------------------------------------------

The EPA also must determine whether a submittal is complete and

therefore warrants further EPA review and action (see section 110(k)(1)

and 57 FR 13565). The EPA's completeness criteria for SIP submittals

are set out at 40 CFR part 51, appendix V (1992). The EPA attempts to

make completeness determinations within 60 days of receiving a

submission. However, a submittal is deemed complete by operation of law

if a completeness determination is not made by EPA six months after

receipt of the submission.

The State of Wyoming held a public hearing on July 17, 1989, to

entertain public comment on the implementation plan for the city of

Sheridan. The State provided adequate notice of public hearing; the

State requires 45 days notice. Following the public hearing, the plan

was adopted by the State, signed by the Governor on July 17, 1989, and

submitted to EPA on August 28, 1989, as a proposed attachment to the

SIP. On March 8, 1990, EPA determined that the Sheridan SIP submittal

was administratively and technically complete and proceeded to draft a

Federal Register notice proposing to approve the SIP. However, upon

enactment of the 1990 Amendments to the Act, EPA re-assessed the SIP

for conformance with the Amendments and determined that additional

information was required to comply with the new Amendments. Of the

eight submittals made subsequent to the original document, four were

received to address requirements of the new Amendments.

Following submittal of the additional information required by the

1990 Amendments, the SIP revision was reviewed by EPA to determine its

completeness, in accordance with the completeness criteria set out at

40 CFR part 51, appendix V (1992). The final submittal was received on

March 5, 1992, and a letter dated April 14, 1992, was forwarded to the

Governor indicating the completeness of the submittal and the next

steps to be taken in the review process. As noted in this action, EPA

proposes to approve the Wyoming PM10 SIP submittal for Sheridan,

and invites public comment on the action.

2. Accurate Emissions Inventory

Section 172(c)(3) of the Act requires that nonattainment plan

provisions include a comprehensive, accurate, current inventory of

actual emissions from all sources of relevant pollutants in the

nonattainment area. The emissions inventory should also include a

comprehensive, accurate, and current inventory of allowable emissions

in the area. See, for example, section 110(a)(2)(K). Because the

submission of such inventories is a necessary adjunct to an area's

attainment demonstration (or demonstration that the area cannot

practicably attain), the emissions inventories must be received with

the attainment demonstration submission (see 57 FR 13539).

Wyoming submitted an emissions inventory in 1989 for base year

1986. This base year emissions inventory was subsequently revised and

resubmitted in March 1992. The base year inventory (both versions)

identified fugitive road dust as the primary cause of nonattainment

contributing over 74.35 percent of the total emissions during the time

that the violations were recorded. Additional contributing sources

included natural gas, 0.01 percent; coal burning, 1.61 percent; wood

burning, 14.80 percent; automobile emissions, 0.51 percent; Veterans

Medical Center, 1.12 percent; Sheridan Forest Products, 0.75 percent;

Wyoming Sawmill, 2.38 percent; and Burlington Northern, 4.38 percent.

The EPA is proposing to approve the emissions inventory because it

generally appears to be accurate and comprehensive, and provides a

sufficient basis for determining the adequacy of the attainment

demonstration for this area consistent with the requirements of

sections 172(c)(3) and 110(a)(2)(K) of the Clean Air Act.\4\ For

further details see the Technical Support Document (TSD).

---------------------------------------------------------------------------

\4\The EPA issued guidance on PM10 emissions inventories

prior to the enactment of the Clean Air Act Amendments in the form

of the 1987 PM10 SIP Development Guideline. We believe that

this document provides a general basis for meeting the requirements

of the revised Act.

---------------------------------------------------------------------------

3. RACM (Including RACT)

As noted, the initial moderate PM10 nonattainment areas must

submit provisions to assure that RACM (including RACT) are implemented

no later than December 10, 1993 (see sections 172(c)(1) and

189(a)(1)(C)). The General Preamble contains a detailed discussion of

EPA's interpretation of the RACM (including RACT) requirement (see 57

FR 13539-13545 and 13560-13561). The EPA's interpretation of this

requirement is set out here only in broad terms.

The State should first identify available control measures

evaluating them for their reasonableness in light of the feasibility of

the controls and the attainment needs of the area. A State may reject

an available control measure if the measure is technologically

infeasible or the cost of the control is unreasonable.

Three source categories were identified as contributing to the

PM10 nonattainment problem in Sheridan. However, the SIP only

relies on one control strategy to demonstrate attainment, the Sanding

Winter Maintenance Program (SWMP), which was adopted on July 17, 1989.

This plan, developed by the Sheridan Air Quality Committee, designates

streets to be sanded during the winter season. Included are major

streets, hills, school zones, and dangerous intersections. The plan

specifies a material application rate which has been determined to

provide adequate traction, and sanding material specifications which

insures use of a clean and durable media. A comprehensive street

sweeping and flushing program will remove material before dust problems

occur. The reduction in PM10 emissions from fugitive road dust,

between the base year inventory (911.84 tpy), and the attainment

inventory (738.11 tpy) was calculated at 19% or 173.73 tpy. Credit for

this reduction is given to the SWMP only. No credit was taken for two

other control strategies outlined in the SIP, a voluntary woodburning

curtailment program and dust control plans for three industrial

sources. The reduction in ``total'' PM10 emissions between the

base year inventory (1238.98 tpy) and attainment inventory (1137.39

tpy) is 8% or 101.19 tpy. (The reason for the reduction in fugitive

road dust emissions being greater than the reduction for total

emissions between the base and attainment years, is that there was an

increase in fugitive dust emissions over the same period of 87.35 tpy

from two industrial sites. The overall result, however, is a net

decrease in emissions). The voluntary woodburning curtailment plan and

the industrial dust control plan were submitted with the SIP; EPA is

taking no action on these two programs.

A more detailed discussion of the individual source contributions

and their associated control measures (including available control

technology) can be found in the TSD. EPA has reviewed the State's

documentation and concluded that it adequately justifies the control

measures to be implemented. RACM does not require the implementation of

all available control measures where an area demonstrates timely

attainment and the implementation of additional available control

measures would not expedite attainment. 57 FR 13543. The implementation

of Wyoming's PM10 nonattainment plan control strategy will result

in the attainment of the PM10 NAAQS by December 31, 1994.\5\ By

this document, EPA is proposing to approve the Sheridan SIP, which

includes the proposal to approve RACM (including RACT).

---------------------------------------------------------------------------

\5\The Act requires demonstration of attainment by December 31,

1994. However, when this SIP was submitted, the Group I requirements

called for attainment demonstration in 1989, with maintenance

through 1994. Although the State did submit additional information

in response to the Clean Air Act Amendments, the demonstration of

attainment did not change. EPA believes, however, that since the

Wyoming DEQ has shown maintenance of the NAAQS through 1994, the

State has met the requirements to show attainment by December 31,

1994.

---------------------------------------------------------------------------

4. Demonstration

As noted, the initial moderate PM10 nonattainment areas must

submit a demonstration (including air quality modeling) showing that

the plan will provide for attainment as expeditiously as practicable

but no later than December 31, 1994 (see section 189(a)(1)(B) of the

Act). Alternatively, the State must show that attainment by December

31, 1994 is impracticable. In the General Preamble, EPA recommended

that the attainment demonstrations for the initial moderate areas

follow existing modeling guidelines for PM10 or, if appropriate,

be developed consistent with the supplemental attainment demonstration

policy issued for initial areas (see 57 FR 13539).

Wyoming conducted an attainment demonstration using dispersion

modeling in combination with receptor modeling for Sheridan. The State

submitted the PM10 modeling protocol to EPA on July 12, 1988. The

submittal included an explanation justifying the protocol, as follows:

since the PM10 data collected during the 11 quarters prior to

development of the initial modeling protocol were in compliance with

the 24-hour PM10 standard, the Division did not find it necessary

to model for the 24-hour standard.\5\ In fact, a violation of the 24-

hour PM10 NAAQS has not been monitored in this area.\6\ A single

exceedence of 198 g/m3 was monitored on November 12, 1991.

However, data results (Attachment 6 of the Appendix to the SIP) showed

that, even with the ``gray zone'' allowance, the annual PM10

standard had been violated. (The ``gray zone'' allowance refers to a 20

percent overestimation of PM10 concentrations resulting from

design flaws in the pre-1987 non-reference Sierra Anderson SA321A

sampler; the problem was resolved when the sampler was modified and

became the SA321B.) This explained the reasoning for the State's

decision to focus on the annual standard, and for the annual PM10

standard of 50 g/m3 becoming the controlling standard. EPA

responded to the State on October 26, 1988 supporting this approach.

---------------------------------------------------------------------------

\5\The Act requires demonstration of attainment by December 31,

1994. However, when this SIP was submitted, the Group I requirements

called for attainment demonstration in 1989, with maintenance

through 1994. Although the State did submit additional information

in response to the Clean Air Act Amendments, the demonstration of

attainment did not change. EPA believes, however, that since the

Wyoming DEQ has shown maintenance of the NAAQS through 1994, the

State has met the requirements to show attainment by December 31,

1994.

\6\EPA does not anticipate much change in population, based upon

population data for Sheridan County submitted by DEQ on November 8,

1991. The data were obtained from the January 1988 and July 1991

reports from the Department of Administration and Information,

Division of Economic Analysis, ``Wyoming Population and Employment

Forecast Report.'' The population forecast including the years 1986

(population = 26,449) through 1994 (population = 24,209), indicates

that Sheridan County will not reach the 1986 population until the

year 2004. After having examined the impact of growth on the 24-hour

PM10 NAAQS, the Division is confident of maintenance of the

standard.

---------------------------------------------------------------------------

The demonstration for the annual standard indicates that the NAAQS

for PM10 will be attained by 1989 in Sheridan, Wyoming, and

maintained.\7\ Maintenance of the standard was addressed in the

Division's December 20, 1989 letter to EPA. The annual PM10 NAAQS

standard will be attained when the expected annual arithmetic mean

concentration is less than or equal to 50 g/m3. The original

demonstration predicted that the annual design concentration in the

attainment year of 1989 would be 48.8 g/m3 (Control Option #6,

1989 SIP). The revised attainment demonstration submitted in March

1990, predicted an annual concentration of 46 g/m3,

demonstrating attainment of the annual PM10 NAAQS. The control

strategy used to achieve the annual design concentration is summarized

in the section titled ``RACM (including RACT).'' As discussed, because

there have been no violations of the 24-hour PM10 standard in

Sheridan, an attainment analysis of the 24-hour standard was not

performed. EPA believes that the controls adopted to protect the annual

standard are sufficient to maintain the 24-hour standard. For a more

detailed description of the attainment demonstration and the control

strategies used, see the TSD accompanying this document.

---------------------------------------------------------------------------

\7\See footnote 5.

---------------------------------------------------------------------------

5. PM10 Precursors

The control requirements which are applicable to major stationary

sources of PM10 also apply to major stationary sources of

PM10 precursors unless EPA determines such sources do not

contribute significantly to PM10 levels in excess of the NAAQS in

that area (see section 189(e) of the Act). The General Preamble

contains guidance addressing how EPA intends to implement section

189(e) (57 FR 13539-13540 and 13541-13542).

An analysis of air quality and emissions data for the nonattainment

area of Sheridan demonstrates that violations of the annual NAAQS are

attributable chiefly to direct particulate matter emissions from re-

entrained road dust and woodburning. The emission inventory and CMB

data for Sheridan did not reveal any significant sources of sulfates or

nitrates in the area. Consequently, EPA is proposing to find that major

sources of precursors of PM10 do not contribute significantly to

PM10 levels in excess of the NAAQS. The consequence of this

finding is to exclude any such sources from the applicability of

PM10 nonattainment area control requirements. Further discussion

of the analyses and supporting rationale for EPA's finding are

contained in the TSD accompanying this notice. Note that while EPA is

proposing to make a general finding for this area, today's proposed

finding is based on the current character of the area including, for

example, the existing mix of sources in the area. It is possible,

therefore, that future growth could change the significance of

precursors in the area. The EPA intends to issue future guidance

addressing such potential changes in the significance of precursor

emissions in an area.

6. Quantitative Milestones and Reasonable Further Progress (RFP)

The PM10 nonattainment area plan revisions demonstrating

attainment must contain quantitative milestones which are to be

achieved every 3 years until the area is redesignated attainment and

which demonstrate RFP, as defined in section 171(1), toward attainment

by December 31, 1994 (see section 189(c) of the Act). Reasonable

further progress is defined in section 171(1) as such annual

incremental reductions in emissions of the relevant air pollutant as

are required by Part D or may reasonably be required by the

Administrator for the purpose of ensuring attainment of the applicable

NAAQS by the applicable date.

In considering the quantitive milestones and RFP provisions for

this initial moderate area, EPA has reviewed the attainment

demonstration for the area to determine the nature of any milestones

necessary to ensure timely attainment and whether annual incremental

reductions should be required in order to ensure attainment of the

PM10 NAAQS by December 31, 1994 (see section 171(1) of the Act).

The PM10 SIP for the Sheridan nonattainment area demonstrates

attainment by December 31, 1994 satisfying the initial quantitive

milestone requirement.\8\ EPA also proposes to find that at this time

the SIP meets Reasonable Further Progress.

---------------------------------------------------------------------------

\8\The emissions reduction progress made prior to the attainment

date of December 31, 1994 (only 46 days beyond the November 15, 1994

milestone date) will satisfy the first milestone requirement (57 FR

13539). The de minimis timing differential makes it administratively

impractable to require separate milestone and attainment

demonstrations.

---------------------------------------------------------------------------

7. Enforceability Issues

All measures and other elements in the SIP must be enforceable by

the State and EPA (see sections 172(c)(6), 110(a)(2)(A) and 57 FR

13556). The EPA criteria addressing the enforceability of SIPs and SIP

revisions were stated in a September 23, 1987 memorandum (with

attachments) from J. Craig Potter, Assistant Administrator for Air and

Radiation, et al. (see 57 FR 13541). Nonattainment area plan provisions

must contain a program that provides for enforcement of the control

measures and other elements in the SIP (see section 110(a)(2)(C)). The

credited control measure contained in the SIP is the SWMP, addressed

above under the section headed ``RACM (Including RACT).'' This control

measure applies to winter time street sanding and sweeping. The mayor

of Sheridan approved and adopted the street sanding plan on February

21, 1989. This signed document was submitted as part of the August 28,

1989 SIP submittal. The program designates specific city limitations/

guidelines for the following parameters: sanding routes, application

rates, sanding materials and street cleaning. The program, according to

the State's Attorney General, is enforceable by the State if the local

agency fails to implement the program. The authority is derived

directly from state statute (W.S. 35-11-201, 701 and 901).

8. Contingency Measures

As provided in section 172(c)(9) of the Act, all moderate

nonattainment area SIP's that demonstrate attainment must include

contingency measures. See generally 57 FR 13510-13512 and 13543-13544.

These measures must be submitted by November 15, 1993 for the initial

moderate nonattainment areas. Contingency measures should consist of

other available measures that are not part of the areas's control

strategy. These measures must take effect without further action by the

State or EPA, upon a determination by EPA that the area has failed to

make RFP or attain the PM10 NAAQS by the applicable statutory

deadline. The Sheridan SIP's contingency measure is the use of a

chemical de-icer in lieu of sand on certain roadways. The SIP provides

that the contingency measure can take effect without further action by

the State or EPA Administrator, should EPA determine that the Sheridan,

Wyoming nonattainment area has failed to make RFP or to attain the

PM10 standard by the statutory attainment date of December 31,

1994. After review of the contingency measure, EPA is proposing to

approve the Sheridan, Wyoming, contingency plan.

III. Implications of Today's Action

The EPA is proposing to approve the plan revision originally

submitted to EPA for the Sheridan nonattainment area on August 28, 1989

along with the subsequent submittals mentioned earlier (including the

contingency measure). The State of Wyoming has demonstrated that the

Sheridan moderate PM10 nonattainment area attained the PM10

NAAQS in 1989 and that it will continue to maintain the standard

through 1994.

As noted, additional submittals for the initial moderate PM10

nonattainment areas, such as a new source review permit program meeting

the requirements of sections 173 and 189 of the Act, were due after the

November 15, 1991 SIP requirements addressed in this notice. The EPA

will determine the adequacy of any such submittal as appropriate.

IV. Request for Public Comments

The EPA is requesting comments on all aspects of today's proposal.

As indicated at the outset of this notice, EPA will consider any

comments received by April 18, 1994.

V. Executive Order (EO) 12866

This action has been classified as a Table 2 action by the Regional

Administrator under the procedures published in the Federal Register on

January 19, 1989 (54 FR 2214-2225), as revised by an October 4, 1993

memorandum from Michael H. Shapiro, Acting Assistant Administrator for

Air and Radiation. A future notice will inform the general public of

these tables. On January 6, 1989, the Office of Management and Budget

(OMB) waived Table 2 and Table 3 SIP revisions (54 FR 222) from the

requirements of section 3 of Executive order 12291 for 2 years. The EPA

has submitted a request for a permanent waiver for Table 2 and Table 3

SIP revisions. The OMB has agreed to continue the waiver until such

time as it rules on EPA's request. This request continues in effect

under Executive Order 12866 which superseded Executive Order 12291 on

September 30, 1993.

VI. Applicability to Future SIP Decisions

Nothing in this action should be construed as permitting or

allowing or establishing a precedent for any future request for

revision to any State Implementation Plan. Each request for revision to

any State Implementation Plan shall be considered separately in light

of specific technical, economic, and environmental factors and in

relation to relevant statutory and regulatory requirements.

VII. Regulatory Flexibility

Under the Regulatory Flexibility Act, 5 U.S.C. 600 et seq., EPA

must prepare a regulatory flexibility analysis addressing the impact of

any proposed or final rule on small entities. 5 U.S.C. 603 and 604.

Alternatively EPA may certify that the rule will not have a significant

economic impact on a substantial number of small entities. Small

entities include small businesses, small not-for-profit enterprises,

and government entities with jurisdiction over population of less than

50,000.

SIP approvals under section 110 and subchapter I, part D of the

Clean Air Act do not create any new requirements, but simply approve

requirements that the State is already imposing. Therefore, because the

Federal SIP-approval does not impose any new requirements, I certify

that it does not have a significant impact on small entities affected.

Moreover, due to the nature of the federal-state relationship under the

Act, preparation of a regulatory flexibility analysis would constitute

federal inquiry into the economic reasonableness of state action. The

Clean Air Act forbids EPA to base its action concerning SIPs on such

grounds. Union Electric Co. v. U.S. E.P.A., 427 U.S. 246, 256-66 (S.Ct.

1976); 42 U.S.C. 7410(a)(2).

List of Subjects in 40 CFR Part 52

Environmental protection, Air pollution control, Hydrocarbons,

Intergovernmental relations, Nitrogen dioxide, Particulate matter,

Reporting and recordkeeping requirements, Sulfur dioxide, and Volatile

organic compounds.

Authority: 42 U.S.C. 7401-7671q.

Dated: March 2, 1994.

William P. Yellowtail,

Regional Administrator.

[FR Doc. 94-6390 Filed 3-17-94; 8:45 am]

BILLING CODE 6560-50-P