nonattainment areas, including " not classified" areas, are required to adopt NSR programs meeting the requirements of section 173, as amended.

( 6) Monitoring. Section 172 ( b) and ( c) explicitly states that nonattainment areas should meet the " applicable" monitoring requirements of section 110( a)( 2).

( 7) Contingency measures. Contingency measures are not required for " not classified" areas in light of the fact that moderate areas with a design value less than 12.7 ppm are exempt from the contingency measures requirement.

( b) Attainment dates for " not classified" areas. Section 172( a)( 2) requires an attainment date of no later than 5 years from an area's designation as nonattainment. For areas designated nonattainment under section 107( d)( 1)( C)( i) ( pre enactment nonattainment areas), the attainment date is November 15, 1995. For newly designated areas, the attainment date will be 5 years from the effective date of the nonattainment designation. For areas that fail to attain in 5 years, EPA is considering one or more of the following actions: ( 1) If an area fails to attain 5 years from designation, the area is bumped up to moderate if the area's design value is at least 9.1 ppm.

( 2) If an area fails to attain 5 years from designation the area retains its " not classified" status, but EPA will tighten Subpart 1 requirements. This could include a showing of enforceable rules or possibly a basic I/ M program.

( c) " Not classified" CO areas. Violations are determined by the number of nonoverlapping exceedances greater than or equal to 9.5 ppm during the 2 year period 1988 1989. If the number of exceedances in either year was greater than or equal to 2, the area is violating the CO NAAQS.

Once it has been established that the area is violating the standard, the highest second highest, nonoverlapping 8 hour measured value over the 2 year period is the design value for the area. The design value determines classification. A CO area cannot be classified submarginal because a design value of < 9.5 ppm is not violating the standard ( i. e., there are less than two exceedances in each of the 2 years), and an area can only be submarginal if it is violating the standard.

( 1) Requirements. The CO areas termed " not classified" are analogous to ozone transitional areas. The amended Act does not provide guidance in subpart 3 for CO areas that fall into the " not classified" category. However, all nonattainment areas, including " not classified" areas, are subject to several of the requirements in subpart 1 of the Act as discussed above. Specifically, section 172( b) requires a SIP revision within 3 years of designation. The SIP revision must meet several requirements, in particular, NSR.

If a State submits a request for redesignation to attainment, then a proper and adequate maintenance plan as defined in section 175A, is required. The Administrator announced in the November 6, 1991 Federal Register those CO nonattainment areas that did not violate the NAAQS during the 24 month period between January 1, 1988 and December 31,1989. For such areas, the requirements under subpart 3 do not apply.

In order to be redesignated to attainment, a " not classified" area must provide documentation to support the conclusion that the five redesignation requirements of section 107( d)( 3)( E) have been met. For a discussion of the specific State actions required for satisfying these five redesignation requirements, see " Redesignations" under section III. H5 of this notice.

( 2) NSR. By November 15, 1993, all such " not classified" areas must submit rules to implement the new part D NSR permit requirements of sections 172( c)( 5) and 173 of the 1990 CAAA. In the meantime, all existing NSR rules will remain in effect. If the area does not have an approved part D NSR permitting program and a State wishes to issue a permit for a major stationary source or major modification in such area during the interim period, the State permitting program should comply with the requirements in 40 CFR part 51, appendix S, until the new part D NSR requirements become effective./ 14/

NOTE / 14/ If a " not classified" area has not recorded any violations by December 31, 1991, and is in the process of developing a maintenance plan per section 175A, then EPA may not require nonattainment NSR rules. However, these areas must continue to apply their existing NSR program or comply with the NSR permitting requirements of 40 CFR part 51, appendix S. Prior to redesignation, these areas also must adopt and be prepared to implement a permitting program that satisfies the requirements of part C and EPA's regulations implementing the PSD program. Areas should consider the need for offsets under the part C program to ensure that new sources do not " cause or contribute" to an increase in pollutant levels that would take the area out of compliance. If the area is found to be out of compliance and the statutory deadlines for adopting amended part D permitting rules for the pollutant in question have passed, EPA may impose a contruction ban pursuant to section 113( a)( 5) until such time as the area adopts a part D program satisfying the NSR requirements of the CAAA.

( 3) Failure to attain. If a " not classified" area violates the NAAQS at some time in the future, then it will be classified in accordance with Table 3, section 186( 2). Upon classification, the area will continue to be subject to the requirements under subpart 1 and those specific provisions under subpart 3 appropriate to the classification that would have applied to the area had it been so classified at the time of the notice under section 186( a)( 2). Under section 187( f), the Administrator may adjust any applicable deadlines ( other than attainment dates) if the deadlines are shown to be infeasible.

5. Multi State CO Nonattainment Areas Section 187( e) defines a " multi State CO nonattainment area" as a single CO nonattainment area that covers more than one State. Section 187( e) also establishes certain requirements for such areas. First, each State in a multi State CO nonattainment area must take all reasonable steps to coordinate both the SIP revisions required and the implementation of SIP's that apply in the given nonattainment area. Section 187( e) also prevents EPA from approving any SIP revision submitted under this section if a State has failed to meet the above requirements.

Finally, section 187( e)( 2) allows a State that fails to provide a demonstration of attainment for that State's portion of a multi State CO nonattainment area to petition EPA to make a finding that such State could have demonstrated attainment, but for the failure of one or more other States in the area to adequately implement measures required under section 187 for the given area. If EPA makes such a finding, then the sanctions provisions under section 179 for failure to make an adequate attainment demonstration shall not apply to the State awarded the finding.

Pursuant to section 187( e)( 1), EPA is calling on each multi State CO nonattainment area to develop a joint work plan as evidence of early cooperation and integration. The work plan must include a schedule for developing the emissions inventories, the VMT forecasts, and the attainment demonstration for the entire multi State area. Each State within a multi State CO nonattainment area is responsible for meeting all the requirements relevant to the given area.

In order to be sufficient to avoid a section 187( e)( 2) finding of failure to demonstrate attainment, an attainment demonstration must meet the requirements in section 187( a)( 7). Refer to section III. B. 3.( e) for guidance on developing attainment demonstrations. Note that moderate multi State CO nonattainment areas with a design value of 12.7 ppm or lower at the time of classification are not required to meet the requirement of developing an attainment demonstration since section 187( a) excludes all such areas from any requirement for attainment demonstrations.

6. Areas With Significant Stationary Source Emissions Section 187( c)( 3) calls for the Administrator to issue guidelines and rules for determining whether stationary sources contribute significantly to CO levels in an area. In the case of a serious area in which stationary sources contribute significantly to CO levels, section 187( c)( 1) requires the State to revise the definition of major stationary source in that area to include any stationary source that emits, or has the potential to emit, 50 tons per year or more of CO.

Guidance on the definition of a significant CO stationary source area is available in an EPA memorandum dated May 13, 1991, from William G. Laxton, Director, Technical Support Division, regarding " Guidance for Determining Significant Stationary Sources of Carbon Monoxide." The guidance defines a significant CO stationary source area through the use of the results of dispersion modeling of one or more stationary sources of CO in the area. The reader should refer to that guidance for further information.

7. Guidance on Waivers for Mobile Source Measures The waiver provisions of section 187( c)( 2) provide the Administrator with discretionary authority to waive certain mobile source requirements in both moderate and serious CO nonattainment areas where mobile sources do not contribute significantly to CO levels in the area. Specifically, the Administrator may on a case by case basis waive any requirements that pertain to transportation controls, I/ M, or oxygenated fuels where the Administrator determines by rule that mobile source contribution is convincingly demonstrated to be insignificant in relation to the cause of the area's overall CO problem. The EPA will only consider granting a waiver from controls on mobile CO sources under section 187( c)( 2) if it is clear that mobile sources in the aggregate do not contribute significantly to the CO nonattainment problem, and there is a SIP submittal demonstrating attainment of the CO NAAQS by the required date without such mobile source controls. This would be in addition to a showing under section 187( c)( 3) pertaining to stationary sources that " contribute significantly to carbon monoxide levels in the area." The attainment demonstration should use EPA approved modeling techniques; i. e., a complete modeling analysis is needed, considering point, area, and mobile source emissions. The waiver would be granted upon approval of the CO SIP. The waiver of mobile source measures would no longer apply if a subsequent maintenance plan demonstration relied on such mobile source measures.

C. Particulate Matter 1. Statutory Background ( a) Designations. On the date of enactment of the 1990 CAAA, PM 10 areas meeting the qualifications of section 107( d)( 4)( B) of the amended Act were designated nonattainment by operation of law. These areas included all former Group I areas identified in 52 FR 29383 ( August 7, 1987) and clarified in 55 FR 45799 ( October 31, 1990), and any other areas violating the PM 10 NAAQS prior to January 1, 1989 ( many of these areas were also identified in the October 31, 1990 Federal Register notice). All other areas were designated unclassifiable. A Federal Register notice announcing all of the areas designated nonattainment for PM 10 at enactment of the 1990 CAAA and classified as moderate was published in 56 FR 11101 ( March 15, 1991). A subsequent notice correcting certain information in the March 15, 1991 notice was published in 56 FR 37654 ( August 8, 1991). Subsequent to the 1990 CAAA enactment date, EPA may redesignate any of these unclassifiable areas to nonattainment in accordance with section 107( d)( 3). On April 22, 1991 EPA announced in 56 FR 16274 that it had initiated the redesignation process for 16 areas.

( b) Classifications and attainment dates. Once an area is designated nonattainment, section 188 of the amended Act outlines the process for classification of the area and establishes the area's attainment date. In accordance with section 188( a), at the time of designation, all PM 10 nonattainment areas are initially classified as moderate by operation of law. A moderate area can subsequently be reclassified as serious either before the applicable moderate area attainment date, if at any time EPA determines the area cannot " practicably" attain the PM 10 NAAQS by this attainment date; or following the passage of the applicable moderate area attainment date, if EPA determines the area has failed to attain ( see section 188( b)).

For those areas which were designated nonattainment upon enactment of the 1990 CAAA by operation of law, where EPA determines that the area cannot " practicably" attain the NAAQS by December 31, 1994, the amended Act specifies certain dates by which EPA must propose to reclassify appropriate moderate areas as serious ( see 56 FR 58656, November 21, 1991) and take final action. The EPA also has discretionary authority under section 188( b)( 1) to reclassify any of these areas as serious at any time, if EPA determines they cannot practicably attain the PM 10 NAAQS by December 31, 1994./ 15/ The EPA may exercise this discretion where, for example, EPA originally believed an area could attain the PM 10 NAAQS by December 31, 1994 but later determines that it cannot attain. For example, EPA may find an area cannot practicably attain by December 31, 1994 after reviewing the November 15, 1991 SIP submittal for an area. Or, if a State fails to submit a PM 10 SIP for an area, EPA could conclude that the area could not practicably attain the standards by the applicable attainment date based, for example, on the severity of the nonattainment problem, the feasibility of controls, and other pertinent factors. Any decision by EPA to reclassify an area as serious will be based on facts specific to the nonattainment area at issue and will only be made after providing notice in the Federal Register and an opportunity for public comment on the basis for EPA's proposed decision. NOTE / 15/ One commenter questioned whether EPA has discretionary authority to reclassify an area " at any time" EPA determines the area cannot practicably attain the PM 10 standards by the applicable moderate area attainment date. Under the plain meaning of the terms of section 188( b)( 1) EPA has general discretion to reclassify at any time before the applicable attainment date any area EPA determines cannot practicably attain the standards by such date. Accordingly, section 188( b)( 1) is a general expression of delegated rulemaking authority. In addition, subparagraphs ( A) and ( B) of section 188( b)( 1) mandate that EPA reclassify at specified timeframes any areas it determines appropriate for reclassification at those dates. These subparagraphs do not restrict the general authority but simply specify that, at a minimum, it must be exercised at certain times. This interpretation furthers the overarching purpose of the statute in that reclassification would expedite the application of additional control measures in the situation where EPA finds, after the mandated reclassification rulemaking and before the applicable attainment date, that an area cannot practicably attain the standards. This, in turn, would expedite ultimate attainment of the PM 10 standards. In summary, EPA believes it is a reasonable interpretation and consistent with the plain language of the statute to construe section 188( b)( 1) such that it authorizes EPA to reclassify an area, as appropriate, at any time before the applicable attainment date and mandates that, at a minimum, EPA make this inquiry at specified times.

The EPA does not believe that reclassifying moderate areas as serious at any time EPA determines that an area cannot practicably attain the standards by the applicable attainment date, rewards areas who delay development and implementation of PM 10 control measures. Rather, EPA believes its policy creates an incentive for the timely submittal and effective implementation of moderate area SIP requirements and facilitates the PM 10 attainment objective. For example, if an area that fails to submit a timely moderate area SIP is reclassified, this does not obviate the requirement that the area submit and implement RACM consistent with the moderate area schedule. Accordingly, the area could be subject to sanctions for its delay in submitting the RACM SIP requirement ( see sections 110( m) and 179). Further, reclassification before the applicable attainment date will ensure that additional control measures ( i. e. in addition to RACM, serious areas must implement best available control measures ( BACM), are implemented sooner and will expedite the application of more stringent new source review requirements to the area ( see sections 188( b)( 1) and 189( b)( 3)). Similarly, where an area submits a timely moderate area SIP, EPA may not discover that the area cannot practicably attain until some time after it begins implementing its moderate area control measures. The EPA then may want to reclassify the area in order to facilitate the development and implementation of BACM. Finally, a reclassified area must demonstrate attainment " as expeditiously as practicable" and no later than specified dates ( see section 188( c)( 2)). Accordingly, EPA may reclassify an area and conclude that the most expeditious attainment date practicable for the area is a time prior to the latest possible attainment deadline.

For areas designated nonattainment after enactment of the 1990 CAAA, EPA must reclassify appropriate areas as serious within 18 months of the required submittal date for the moderate area SIP. Taken together with the statutory requirement that these SIP's be submitted 18 months after being designated nonattainment, the statute thus requires that EPA reclassify the appropriate moderate area as serious within 3 years of the nonattainment designation.

Finally, in those cases where EPA determines that an area has failed to attain the NAAQS by the applicable attainment date, the area is reclassified as serious by operation of law. The EPA must publish a notice in the Federal Register of such determinations and consequent reclassifications within 6 months following the applicable attainment date.

Since this General Preamble addresses only the control measures recommended for moderate PM 10 nonattainment areas, the following discussion has been limited to the attainment dates for moderate nonattainment areas. Section 188( c)( 1) of the amended Act specifies that the initial moderate nonattainment areas ( those designated nonattainment upon enactment of the 1990 CAAA) are to attain the PM 10 NAAQS as expeditiously as practicable but no later than December 31, 1994, unless they are reclassified as serious ( as described above). Areas designated nonattainment after enactment of the 1990 CAAA and classified as moderate must attain the PM 10 NAAQS as expeditiously as practicable but no later than the end of the sixth calendar year after the area's designation as nonattainment.

( c) General SIP requirements. As discussed above, States must develop and submit a SIP providing for the attainment of the PM 10 NAAQS for every area designated nonattainment and classified as moderate for PM 10 under the amended Act. Under section 189( a)( 2), States must submit a SIP revision ( e. g. RACM/ RACT and attainment demonstration) for the moderate PM 10 areas designated nonattainment upon enactment of the 1990 CAAA by November 15, 1992. The NSR program provisions for these areas are due June 30, 1992. States must submit SIP's for those PM 10 areas designated nonattainment after enactment of the 1990 CAA within 18 months of these areas' being designated nonattainment for PM 10.

The specific PM 10 SIP requirements applicable to moderate nonattainment areas are set forth in the PM 10 subpart ( subpart 4 of part D, title I). These requirements include section 189( a) ( NSR permit program, attainment demonstration, and RACM/ RACT); section 189( c) ( quantitative milestones); and section 189( e) ( PM 10 precursors). The SIP's for moderate PM 10 nonattainment areas must also meet the general provisions applicable to nonattainment areas set forth in subpart 1 of part D, title I of the amended Act to the extent that these provisions are not otherwise subsumed by, or integrally related to, the more specific PM 10 requirements. Whenever possible during this discussion of PM 10, EPA has clarified the relationship between subparts 1 and 4. All SIP's must also meet the applicable regulatory requirements set forth in 40 CFR part 51 except to the extent those requirements are inconsistent with the amended Act./ 16/ The EPA will provide guidance at a later date for those SIP requirements not addressed in this General Preamble. The discussion below is intended to provide additional background on some of the statutory requirements for moderate PM 10 nonattainment area SIP's and, in some cases, to provide guidance on these statutory requirements.

NOTE / 16/ The 1990 CAAA includes a General Savings Clause ( see section 193) which provides that regulations ( or guidance, etc.) in effect before the enactment of the 1990 CAAA shall remain in effect after enactment. However, the Savings Clause also provides that such regulations ( or guidance, etc.) shall remain in effect " except to the extent otherwise provided under this Act, inconsistent with any provision of this Act, or revised by the Administrator," Id.

( d) NSR permit program. Section 189( a)( 1) of the amended Act provides that for the purpose of meeting the requirements of section 172( c)( 5), each State with a PM 10 nonattainment area classified as moderate must submit an implementation plan which contains a permit program meeting the requirements of section 173 for the construction of new and modified major stationary sources of PM 10 ( and in some cases PM 10 precursors). For the initial moderate PM 10 nonattainment areas designated according to section 107( d)( 4), States must submit the NSR permit program SIP revision to EPA by June 30, 1992. For PM 10 nonattainment areas designated after enactment of the 1990 CAAA, States must submit a SIP containing the NSR permit program within 18 months after designation of each affected area. The EPA intends to issue proposed regulations for the NSR program SIP's. However, in today's General Preamble, EPA has provided guidance on the NSR permit program requirements which is intended to assist States in developing and timely submitting their June 30, 1992 NSR SIP revision for the initial moderate PM 10 nonattainment areas, and any NSR SIP revision submittal due for any additional areas designated nonattainment for PM 10 before the NSR regulations are finalized.

( 1) Moderate areas. To meet the requirements of section 172( c)( 5), States must implement a permit program that meets all the permit requirements of section 173 for the construction and operation of new and modified major stationary sources of PM 10. As defined in section 302( j), the term major stationary source means any stationary source which directly emits, or has the potential to emit, 100 tons per year or more of PM 10. The emissions offset ratio for such sources is equal to or grater than 1: 1 as specified in section 173( c).

Section 189( e) makes the control requirements applicable to major stationary sources of PM 10 also applicable to major stationary sources of PM 10 precursors. For the purposes of implementing the requirements of section 189( e), precursors of secondarily formed PM 10 may include VOC's which form secondary organic compounds, SO2 which form sulfate compounds, and NOx which form nitrate compounds. Therefore, the control requirements applicable under PM 10 SIP's for major stationary sources of PM 10 shall also apply to major stationary sources of these potential precursors, except where the Administrator determines that such sources do not significantly contribute to PM 10 levels that exceed the PM 10 ambient standards in the area. The Act leaves unaddressed the question of whether each specific PM 10 precursor should be considered together or independently in determining major source size and the applicability of section 173 ( e. g., permit requirements). However, with respect to ozone, EPA's practice has been to consider each specific ozone precursor independently when making similar determinations. Accordingly, EPA proposes to treat PM 10 precursors analogous to ozone precursors and also consider each specific precursor independently when determining source size and whether section 173 provisions apply. Nothing in this guidance, however, would preclude a State from adopting a stricter standard and, thus, proposing to consider all specific PM 10 precursors together.

( 2) Serious areas. Section 189( b)( 3) defines the terms " major source" and " major stationary source" to include any stationary source or group of stationary sources located within a contiguous area and under common control that emits, or has the potential to emit, at least 70 tons per year of PM 10. Such new and modified major stationary sources that emit PM 10 are subject to the permit requirements of section 173 and the PM 10 precursor provisions of section 189( e).

( e) Attainment demonstration. Section 189( a)( 1)( B) provides that States with moderate PM 10 nonattainment areas must submit a demonstration ( including air quality modeling) showing attainment by the applicable attainment date. Alternatively, the State must show that attainment by the applicable date is impracticable. This SIP submittal is due on November 15, 1992 for the moderate areas designated nonattainment for PM 10 at enactment of the 1990 CAAA and within 18 months for those moderate areas designated nonattainment after enactment of the 1990 CAAA. As a necessary adjunct to the demonstration of attainment, the SIP submittal must contain a comprehensive, accurate, current inventory of actual emissions from all sources of PM 10 in the area, as prescribed in section 172( c)( 3).

In general, attainment demonstrations for the initial moderate nonattainment areas should follow the existing modeling guidelines addressing PM 10 ( e. g., " PM 10 SIP Development Guideline" ( June 1987); " Guideline on Air Quality Models" ( Revised); memorandum from Joseph Tikvart and Robert Bauman dated July 5, 1990) and any applicable regulatory requirements. The EPA also has developed a supplemental attainment demonstration policy that may be followed for initial moderate PM 10 nonattainment areas facing special circumstances. That policy statement is provided in appendix C5. Attainment demonstrations for moderate areas designated after enactment of the 1990 CAAA will be reviewed in accordance with the general guidance addressing PM 10, cited above, and any other applicable EPA guidance or regulations. The supplemental policy also noted above will not apply to these areas.

( f) RFP/ quantitative milestones. The PM 10 nonattainment area SIP's must include quantitative emissions reductions milestones which are to be achieved every 3 years and which demonstrate RFP, as defined in section 171( 1), until the area is redesignated attainment ( section 189( c)). Under the milestone requirement, the States must demonstrate to EPA that the SIP measures are being implemented and the milestones have been met, within 90 days after the milestone due date. The EPA must then determine whether or not the State's demonstration is adequate, within 90 days of receiving the demonstration.

Under section 189( c), the State is required to submit a SIP revision if it fails to submit the quantitative milestone demonstration, or EPA determines that a milestone was not met. The SIP revision is due within 9 months of either the missed reporting date or EPA's determination that a milestone was missed. The SIP revision must assure that the State will achieve the next milestone by the applicable date and/ or meet the PM 10 attainment date if there is no next milestone.

There is a gap in the law that the text of section 189( c) does not articulate the starting point for counting the 3 year period. The EPA believes it is reasonable to begin counting the 3 year milestone deadline from the due date for applicable implementation plan revisions containing the control measures for the area. The EPA believes it is reasonable to key the milestone clock to the SIP revision containing control measures which will give rise to emission reductions. Further, control measures must be implemented in less than 3 years after the SIP revision containing them is required to be submitted. Therefore, it is reasonable to expect that some reduction in emissions will have occurred 3 years after the SIP revision due date. The EPA believes that measuring the 3 year period from the SIP revision due date is also reasonable. Essentially, EPA believes it would be unreasonable to begin counting the 3 year period whenever the SIP revision is submitted, in disregard of its due date. The statute contains specific SIP submittal and attainment deadlines. These deadlines and the framework they set up inform EPA's interpretation of this requirement. Here, EPA believes that the law contemplates that some improvement in air quality be made between the SIP submittal due date and ensuring 3 year increments. Further, to begin counting from the date of actual SIP submittal and not its due date would allow those States that submit SIP's late to defer meeting their quantitative milestones and, consequently, to defer making RFP toward attainment of the PM 10 standard. Thus, the first quantitative milestone deadline for the initial PM 10 moderate nonattainment areas is November 15, 1994; 3 years after November 15, 1991 when SIP revisions containing RACM ( including reasonably available control technology) are due for these areas.

For the initial PM 10 moderate nonattainment areas, the emissions reductions progress made between the SIP submittal ( due date of November 15, 1991) and the attainment date of December 31, 1994 ( only 46 days beyond the November 15, 1994 milestone date) will satisfy the first quantitative milestone. The de minimis timing differential makes it administratively impracticable to require separate milestone and attainment demonstrations. Thus, EPA's policy is to deem that the emissions reductions progress made between the SIP submittal due date and the attainment date will satisfy the quantitative milestone requirement for these areas. This is consistent with the purpose of the milestone requirement which is to " provide for emission reductions adequate to achieve the standards by the applicable attainment date" ( H. R. Rep. No. 490, 101st Cong., 2d Sess. 267 ( 1990)). However, the Administrator is required to determine within 6 months after the applicable attainment date whether a nonattainment area has attained the standards ( sections 179( c) and 188( b)( 2)). Therefore, consistent with the milestone requirement, within 90 days after the attainment date, States must demonstrate that the SIP has been implemented and the area has attained the standards or alternatively, qualifies for a 1 year extension of the attainment date ( section 188( d)). The EPA will issue future guidance on the RFP/ quantitative milestone requirements for those areas designated moderate PM 10 nonattainment after enactment of the 1990 CAAA and for the serious PM 10 nonattainment areas.

( g) PM 10 precursors. Section 189( e) provides that the applicable control requirements under PM 10 nonattainment area SIP's in effect for major stationary sources of PM 10 are also applicable to major stationary sources of PM 10 precursors, except where EPA determines that the sources of PM 10 precursors do not contribute significantly to PM 10 levels which exceed the PM 10 NAAQS in the area. This determination will be based upon air quality analysis in which States assess the contribution of precursors. The contribution of precursors may be nonexistent. Alternatively, if precursors do contribute to nonattainment, States will need to consider both the source receptor relationship and the significance of precursor contributions to overall nonattainment. Factors which may be considered in determining the source receptor relationship include source mix and density, nonattainment area size, meteorology, and topography. In making a determination regarding significance and the need to control precursors in a specific area, EPA will rely in part on the technical information contained in the State's submittal, including filter analysis, the relative contribution of precursors to overall nonattainment, and the State's RACT/ RACM strategy, among other factors. States, however, are encouraged to submit additional material for consideration, with all findings made on a case by case basis due to the high degree of variability among nonattainment areas. There will be variability, for example, in the characteristics of the area wide nonattainment problem in Spokane, Washington, which may warrant a finding of significance that differs from that made for a point source in Clairton, Pennsylvania. The EPA is required to issue guidance on this requirement. This General Preamble contains a lengthy discussion on control requirements for PM 10 precursors in moderate nonattainment areas and is intended to satisfy the requirement for guidance to the extent such guidance is required for moderate area SIP's having control requirements applicable to major stationary sources of PM 10. The EPA intends to provide additional guidance, if necessary, on control requirements for major stationary sources of PM 10 precursors when it issues proposed regulations for the NSR permit program applicable to PM 10 nonattainment areas, and when it issues guidance on the control technology requirements applicable to major stationary sources in serious PM 10 nonattainment areas.

( h) RACM/ RACT. Section 189( a)( 1)( C) of the amended Act requires that moderate area SIP's contain " reasonably available control measures" for the control of PM 10 emissions. Section 172( c)( 1) of the amended Act, in turn, provides that RACM for nonattainment areas shall include " 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 * * *." Thus, read together, these provisions require that moderate area PM 10 SIP's include RACM and RACT for existing sources of PM 10 emissions.

Under section 189( a) ( 1), ( 2) of the amended Act, initial moderate PM 10 nonattainment areas ( i. e., those areas designated nonattainment upon enactment of the 1990 CAAA) must submit SIP's containing RACM/ RACT control measures by November 15, 1991, and these SIP's must provide for the implementation of RACM/ RACT no later than December 10, 1993. Those areas designated nonattainment and classified as moderate after enactment of the 1990 CAAA must submit SIP's containing RACM/ RACT control measures 18 months after the nonattainment designation ( see section 189( a)( 2)( B)). These SIP's must provide for the implementation of RACM/ RACT no later than 4 years after the affected areas are designated nonattainment, which is 30 months after the applicable SIP submittal deadline ( see section 189( a)( 1)( C)).

Note that serious area control requirements are briefly described here as background for subsequent discussion regarding the relationship between moderate and serious area control measures. As discussed above, moderate PM 10 nonattainment areas may be reclassified as serious. Pursuant to section 189( b), States having areas that are reclassified as serious must submit SIP's for the areas containing BACM which includes " the application of best available control technology to existing stationary sources" ( H. R. Rep. No. 490, 101st Cong. 2d Sess. 267 ( 1990))./ 17/ The SIP's containing BACM/ BACT provisions must be submitted within 18 months after the affected area is reclassified as serious ( see section 189( b)( 2)). These SIP's must provide for the implementation of BACM/ BACT no later than 4 years after being reclassified, which is 30 months after the BACM/ BACT submittal is due ( see section 189( b)( 1)( B)).

NOTE / 17/ The Act does not expressly define " best available control measures" ( including " best available control technology") for PM 10 nonattainment purposes. Guidance on " best available control measures" ( including " best available control technology") requirements to facilitate SIP development for serious PM 10 nonattainment areas will be issued by EPA at a later date.

Under section 190, EPA must issue technical guidance for RACM and BACM by May 15, 1992 for three area source categories: Urban fugitive dust, residential wood combustion, and prescribed silvicultural and agricultural burning. This General Preamble satisfies EPA's obligation to issue guidance on RACM for these source categories. This guidance also updates previously issued guidance regarding RACT for large stationary sources. The BACM guidance to facilitate SIP development in serious PM 10 nonattainment areas will be issued at a later date.

In addition to requiring RACM guidance for urban fugitive dust, residential wood combustion, and prescribed silvicultural and agricultural burning, section 190 requires that EPA examine other source categories contributing to nonattainment of the PM 10 NAAQS, determine if additional guidance for RACM and BACM is needed, and issue any such guidance by November 15, 1993. This document provides RACM guidance for sources of fugitive dust ( including urban), residential wood combustion, and prescribed burning ( including silvicultural and agricultural). The EPA believes, at this time, that these categories of sources are contributing to nonattainment of the PM 10 NAAQS. To the extent that these categories of sources are broader than, or in addition to, those expressly identified in section 190, the Administrator is by today's notice, determining that RACM guidance should be issued for these sources and is issuing such guidance. Section 190 also requires that EPA take into account the emission reductions achieved or expected to be achieved under title IV and other provisions in " issuing guidelines and making determinations under this section." In deciding whether to issue guidance for the categories of sources addressed in this document and in issuing this guidance, EPA has considered such emission reductions. The EPA does not believe, at this time, that actual or expected reductions from Title IV or other provisions will significantly reduce emissions from these sources. Preliminary guidance on many of the issues addressed herein was issued by EPA staff on April 2, 1991 to facilitate PM 10 SIP development for moderate nonattainment areas.

2. Determination of RACM/ RACT ( a) RACM. The suggested starting point for specifying RACM in each SIP is the listing of available control measures for fugitive dust, residential wood combustion, and prescribed burning contained in appendices C1, C2, and C3. If a State receives substantive public comment demonstrating through appropriate documentation that additional control measures may well be reasonably available in a particular circumstance, those measures should be added to the list of available measures for that area. The RACM is then determined for the affected area's SIP. While EPA does not presume that these control measures are reasonably available in any or all areas, EPA expects States to prepare a reasoned justification for rejection of any available control measures. If it can be shown that one or more measures are unreasonable because emissions from the sources affected are insignificant ( i. e., de minimis), those measures may be excluded from further consideration as they would not represent RACM for that area./ 18/ The resulting available control measures should then be evaluated for reasonableness, considering their technological feasibility and the cost of control in the area to which the SIP applies. In the case of public sector sources and control measures, this evaluation should consider the impact of the reasonableness of the measures on the municipal or other governmental entity that must bear the responsibility for their implementation ( e. g., paving of unpaved public roads). It is important to note that a State should consider the feasibility of implementing measures in part when full implementation would be infeasible. The SIP submittal to EPA should contain a reasoned justification for partial or full rejection of any available control measures, including those considered or presented during the State's public hearing process, that explains, with appropriate documentation, why each rejected control measure is infeasible or otherwise unreasonable. When the process of determining RACM for an area is completed, the individual measures should then be converted into a legally enforceable vehicle ( e. g., a regulation or permit program) ( see sections 172( c)( 6) and 110( a)( 2)( A)). The regulations or other measures should meet EPA's criteria regarding the enforceability of SIP's and SIP revisions. These criteria were stated in a September 23, 1987 memorandum ( with attachments) from J. Craig Potter, Assistant Administrator for Air and Radiation; Thomas L. Adams, Jr., Assistant Administrator for Enforcement and Compliance Monitoring; and Francis S. Blake, General Counsel, Office of the General Counsel, entitled " Review of State Implementation Plans and Revisions for Enforceability and Legal Sufficiency." As stated in that memorandum, SIP's and SIP revisions which fail to satisfy the enforceability criteria should not be forwarded for approval. If they are submitted, they will be disapproved if, in EPA's judgment, they fail to satisfy applicable statutory and regulatory requirements.

NOTE / 18/ Where the sources affected by a particular measure contribute only negligibly to ambient concentrations that exceed the NAAQS, EPA's policy is that it would be unreasonable and therefore would not constitute RACM to require controls on the source. In this regard, it is worth noting that the inherent authority of administrative agencies to exempt de minimis situations from regulation has been recognized in contexts such as this where an agency is invoking a de minimis exemption as " a tool to be used in implementing the legislative design" ( see Alabama Power Co. v. Costle, 636 F. 2d 323, 360 ( D. C. Cir. 1979)).

The technical guidance that discusses in detail the suggested initial measures in appendices C1, C2, and C3 and that a State should consider in determining which of the measures in appendices C1, C2, and C3 are technically feasible and economically reasonable in a particular area is contained in four documents: " Control of Open Fugitive Dust Sources," ( EPA 450/ 3 88 008) September 1988; " Guidance Document for Residential Wood Combustion Emission Control Measures," ( EPA 450/ 2 89 015) September 1989; " Prescribed Fire Smoke Management Guide" ( NFES No. 1279), February 1985; and " Prescribed Fire Plan Guide" ( NFES No. 1939), August 1986. These documents have been in use for several years and are based on substantial input from State and local agencies, trade groups and associations, and control experts. " Control of Open Fugitive Dust Sources" may serve as an example in analyzing control costs for a given area. Copies of these documents may be obtained by contacting National Technical Information Service, 5285 Port Royal Road, Springfield, Virginia 22161.

( b) RACT. This guidance follows EPA's historic definition of RACT as the lowest emission limitation that a particular source is capable of meeting by the application of control technology that is reasonably available considering technological and economic feasibility./ 19/ The RACT applies to the " existing sources" of PM 10 stack, process fugitive, and fugitive dust emissions ( e. g., haul roads, unpaved staging areas) ( see section 172( c)( 1)). The EPA recommends that major stationary sources be the minimum starting point for RACT analysis. Generally, EPA recommends that available control technology be applied to those existing sources in the nonattainment area that are reasonable to control in light of the attainment needs of the area and the feasibility of such controls. Thus, EPA recommends that a State's control technology analyses for existing stationary sources go beyond major stationary sources in the area and that States require control technology for other sources in the area that are reasonable to control in light of the area's attainment needs and the feasibility of such control./ 20/ Specific guidance on the evaluation of the technological and economic feasibility of control technology for existing stationary sources is contained in appendix C4.

NOTE / 19/ See, for example, 44 FR 53726 ( September 17, 1979) and footnote 3 of that notice. Note that EPA's emissions trading policy statement has clarified that the RACT requirement may be satisfied by achieving " RACT equivalent" emissions reductions from existing sources.

NOTE / 20/ Note that Congress has not used the word " all" in conjunction with RACT in either the earlier law or as now amended. Thus, it is possible that a State could demonstrate that an existing source in an area should not be subject to a control technology especially where such control is unreasonable in light of the area's attainment needs or infeasible. Even if EPA was required to impose control technology on every existing stationary source, where a State demonstrates that available control technology for a source is infeasible or otherwise unreasonable, EPA would conclude that " reasonably" available control technology for that source constitutes no control or, stated differently, that no control technology for the source is " reasonably" available. As referenced above, section 172( c) of the amended Act provides that RACT should apply to " existing sources in the area. This is the same language that appeared in the RACT requirement under the CAA prior to the 1990 Amendments ( see section 172( b)( 3) of the pre 1990 CAAA law). Under the pre amended law, EPA in effect interpreted the phrase " existing sources in the area" as it is interpreted here. EPA believes that Congress has placed its imprimatur on, if not adopted, EPA's prior interpretation of RACT ( see, e. g. section 182( a)( 2)( A) of the amended Act; see also section 193 of the amended Act ( savings clause preserving prior EPA guidance except where inconsistent with the Clean Air Act Amendments)).

( c) PM 10 precursors. Section 189( e) of the amended Act provides that for all PM 10 nonattainment areas, the control requirements applicable under PM 10 SIP's in effect for major stationary sources of PM 10 are also applicable to major stationary sources of PM 10 precursors, except where EPA determines that such sources do not contribute significantly to PM 10 levels which exceed the PM 10 NAAQS in the area. Thus, for example, because moderate PM 10 nonattainment area SIP's should contain RACT for major stationary sources of PM 10, they should also contain RACT for major stationary sources of PM 10 precursors, unless EPA determines otherwise. Section 189( e) also requires that EPA issue guidance for the control of PM 10 precursors. This discussion represents EPA's guidance for controlling PM 10 precursors for major stationary sources in moderate PM 10 nonattainment areas. As explained earlier ( see section III. C. 1.( g)), pursuant to the requirement of section 189( e), EPA intends to make a formal determination as to whether major stationary sources of PM 10 precursors contribute significantly to PM 10 levels in a particular area when it takes rulemaking action on the individual moderate area SIP's. However, a determination will be based on air quality analyses, on any additional technical information discovered by individual States during SIP development, and on any other studies conducted by the State or EPA which may help to indicate whether major stationary sources of specific precursors contribute significantly to PM 10 concentrations in a particular area. Therefore, while the subsequent discussion provides guidance as to EPA's implementation of section 189( e), and gives an indication of some of the factors that will guide EPA's findings under this section, none of the general views expressed herein are intended to preclude specific findings based on reviews of individual SIP's for PM 10 nonattainment areas.

The following discussion is intended to provide initial guidance with respect to each of the above named potential PM 10 precursors. Since the potential of SO2 and NO2 emissions to contribute significantly to PM 10 exceedances is more regionally dependent than VOC emissions, the following discussion focuses on general regional characteristics attributable to SO2 and NOx emissions. In the western United States, ( considered west of the 100th meridian for the purpose of this discussion), EPA believes that sources of SO2 and NOx emissions may contribute to exceedances of PM 10 levels in several major metropolitan areas ( e. g., Los Angeles, Salt Lake County, Utah County, Denver and the San Joaquin Valley). The EPA's conclusion with respect to these areas is based on the presence of factors which enhance the likelihood of secondary formation from these precursors, such as source mix and density, nonattainment area size, particular meteorology, and topography. Where nonattainment areas are relatively small in size, precursors are usually transported out of the area before secondary particles can form in significant quantity. However, due to the greater size of the areas mentioned above, pollutant transport between airsheds is considerably diminished; consequently, locally emitted PM 10 precursors remain in the area long enough to form secondary particles and make a significant contribution to the PM 10 problem in that area./ 21/ The particular combination of source mix, meterology, and topography in these major metropolitan areas rarely occurs in other areas in the West. For this reason, EPA believes that sources of SO2 and NOx emissions are not as likely to be significant contributors to the nonattainment problem in those other areas. Therefore, if EPA determines, based on information contained in SIP submittals and any other available information, that major stationary sources of SO2 and NOx in the Western United States do not contribute significantly to exceedances of the PM 10 standard, such sources would not be expected to meet the requirements that apply to major stationary sources of PM 10, ( e. g., RACT). Further discussion on the need to apply RACT in PM 10 nonattainment areas is found in the sections below addressing control requirements for PM 10 nonattainment areas that do/ do not demonstrate attainment.

NOTE / 21/ The focus here and elsewhere on transport between airsheds and on the characteristics of the nonattainment area flow from the statutory language of section 189( e) which states that in determining not to require RACT for major stationary sources of precursors, EPA must find that the sources do not contribute significantly to PM 10 levels which exceed the NAAQS " in the area." Thus, this provision EPA may determine that major stationary sources of precursors in a nonattainment area should not be subject to RACT because the sources do not contribute significantly to PM 10 levels in the same area.

Unlike the case in the Western United States, as a general matter, pollutant transport between airsheds in the Eastern United States can be responsible for a relatively large portion of secondary particle concentrations in nonattainment areas. Thus, the determination as to whether sources of PM 10 precursors in the nonattainment area would contribute significantly to PM 10 concentrations in the same area is correspondingly more difficult. Moreover, the characteristic contributions of the subject precursors vary. Sulfate compounds, for example, are generally known to be present in significant quantities in many eastern areas, while historically, nitrate compounds have been measured in relatively low concentrations throughout the East. As explained earlier, and as with VOC's, EPA will determine the applicability of section 189( e) based on technical and any other available information provided by States in their individual SIP submittals. However, when considering whether sources in PM 10 nonattainment areas should be required to adopt PM 10 precursor control, EPA will assess the reasonableness of the SIP submittal in light of the fact that substantial region wide reductions of SO2, NOx, and VOC emissions are expected to result from the implementation of the Act. These emissions reductions may mitigate precursor contributions due to PM 10 concentrations. The EPA will also take into account the historically low nitrate concentrations in the Eastern United States.

The EPA will also consider the information submitted by States containing major stationary sources of VOC's in areas which are in nonattainment for PM 10 to determine whether VOC emissions from such sources do/ do not contribute significantly to exceedances of the ambient standard in their particular area. In considering the reductions to be achieved by controlling PM 10 precursors under section 189( e), Congress has indicated that EPA should take into account reductions achievable from control requirements imposed by other sections or titles of the 1990 Act./ 22/ Thus, along with their information addressing whether VOC's contribute significantly to PM 10 nonattainment in their area, States may wish to include in their SIP submittals a showing that control of VOC emissions under other Act requirments may suffice to relieve them of the need to adopt PM 10 precursor controls under section 189( e). Any such finding will be made by EPA based on information provided in the individual SIP submittal. Other Act control requirements which could be considered as contributing to VOC reductions are where, for example, areas which are nonattainment for PM 10 are also nonattainment for ozone and, thus, are already required to apply RACT on sources of VOC under section 182( b)( 2). The VOC reductions may also be realized from new or modified major stationary sources due to the implementation of NSR programs in ozone nonattainment or attainment areas. When reviewing a SIP submittal containing a request for an exemption from PM 10 precursor controls under section 189( e) in pat because of actual or expected VOC reductions from other control requirements of the 1990 Act, EPA's determination will include an assessment of the reasonableness of the submission. This assessment by EPA will take into account the possible significance of differences between control strategies for PM 10 and other pollutants ( e. g., requirements imposing BACT as opposed to RACT, and differences in attainment deadlines).

NOTE / 22/ Congress recognized that sources of PM 10 precursors may be otherwise controlled. For example, the House Report states that "( t) he Committee notes that some of these precursors may well be controlled under other provisions of the Act" ( H. R. Rep. No. 490, 101st Cong., 2d Sess. 268 ( 1990)). Moreover, Congress expressly recommended that EPA consider other provisions of the CAA in addressing precursors. The House Report states as follows: " The Committee expects the Administration to harmonize the PM 10 reduction objective of this section with other applicable regulations of this Act regarding PM 10 precursors, such as NOx" ( H. R. Rep. No. 490 at 268). Throughout the discussion of PM 10 precursors EPA has relied on the actual and expected reductions from other CAA requirements and has attempted to reconcile these with the CAA's PM 10 attainment objective.

( d) Condensible PM 10. Condensible particulate matter ( CPM) refers to particles which form in the atmosphere as the exhaust gases from a source cool. The CPM emissions form particles in the PM 10 size range and are considered PM 10 emissions ( see, e. g., " PM 10 SIP Development Guideline," ( June 1987) at p. 5 32 and 55 FR 41547 ( October 12, 1990)). The EPA issued guidance on CPM in a December 24, 1990 memordandum from John Calcagni and William Laxton entitled " Interim Guidance on Emission Limits and Stack Test Methods for Inclusion in PM 10 SIP's." Generally, RACT for sources of CPM will be reviewed consistent with this guidance. In addition, EPA believes it is reasonable and therefore constitutes RACT to control CPM only where CPM is a significant portion of the emissions from an existing stationary source./ 23/ Further guidance on the identification of sources where a State's RACT analysis should consider CPM is found in " Assessment of the Controllability of Condensible Particulate Matter," published in October 1990. The EPA recognizes that this document is interim guidance and is still subject to review. Also, note that EPA has recently proposed to add a method for measuring CPM emissions from stationary sources to appendix M of 40 CFR part 51 ( 55 FR 41546, October 12, 1990).

NOTE / 23/ Where CPM emissions are a negligible portion of the emissions from an existing stationary source, EPA's policy is that such control may be excluded as being unreasonable for that source ( See also Alabama Power Co. v. Costle, 636 F. 2d 323, 360 ( D. C. Cir. 1979), discussed above). RACT for the source would therefore be no control or, stated alternatively, EPA would conclude that control technology for the source is not " reasonably" available.

( e) Total suspended particulate ( TSP) RACT. Since 1979, EPA has taken action to approve a number of TSP nonattainment area SIP's that require RACT for existing stationary sources of TSP. As a technical matter, RACT level measures to control TSP emissions generally utilize technology that also effectively controls PM 10 emissions. Thus, EPA believes it is reasonable to generally presume that control technology which represents RACT for TSP emissions from a source satisfies the requirement of RACT for PM 10 emissions under the amended Act. However, the reasonableness of this control technology may be refuted for a particular source in a PM 10 nonattainment area by information which indicates that a level of PM 10 control greater than that achieved by the TSP RACT would constitute RACT for PM 10. Further, with respect to controls on stack and process fugitive emission points that represent RACT in currently approved TSP SIP's, EPA specifically recommends that the emission limits be reviewed in light of improvements in control technology and reductions in control costs that may now make lower emission limits reasonable. In addition, regulations submitted as part of the PM 10 SIP should be reviewed to determine whether they meet EPA criteria regarding enforceability, as noted above ( see sections 172( c)( 6) and 110( a)( 2)( A)). Consistent with the previous discussion on RACM, EPA will not approve any PM 10 SIP containing RACT measures that fail to meet applicable statutory and regulatory requirements for SIP enforceability.

In those PM 10 nonattainment areas that do not have previously approved part D TSP nonattainment area plans, the particulate matter regulations for existing sources should be reviewed to determine if: ( 1) Additional controls are necessary to meet RACT requirements.

( 2) The regulations meet EPA's enforceability criteria. Similarly, existing regulations controlling emissions of specific PM 10 precursors should be reviewed on a case by case basis for major stationary sources in those areas and RACT analysis conducted unless the Administrator determines the source does not contribute significantly to PM 10 levels which exceed the NAAQS in the area.

Section 110( n)( 1) of the amended Act provides that all TSP SIP's, including any revisions, that were approved or promulgated by EPA before enactment of the 1990 CAAA shall remain in effect until EPA approves or promulgates a revision to the SIP under the new law. Further, the General Savings Clause, section 193 of the amended Act, states that any control requirement in effect or required to be adopted by a SIP in effect before enactment of the 1990 CAAA for any area that is a nonattainment area for any air pollutant may not be modified unless the modification ensures equivalent or greater emissions reductions of such air pollutant. Thus, under section 110( n)( 1), existing provisions of TSP SIP's remain in effect until such provisions are revised under the new law. Also, under section 193, modifications to TSP control requirements, such as TSP RACT, cannot be approved unless at a minimum they ensure equivalent emission reductions of PM 10./ 24/

NOTE / 24/ A moderate PM 10 area is a nonattainment area for any air pollutant within the meaning of section 193. Thus, for these areas, any modifications to any control requirements, including TSP, would have to ensure equivalent emission reductions of PM 10.

3. SIP's That Demonstrate Attainment The SIP's for moderate nonattainment areas should provide for the implementation of control measures for area sources and control technology for stationary sources of PM 10 emissions which demonstrate attainment of the PM 10 NAAQS as expeditiously as practicable and no later than the applicable statutory attainment dates. Therefore, if a State adopts less than all available measures but demonstrates, adequately and appropriately, that ( a) RFP and attainment of the PM 10 NAAQS is assured, and application of all such available measures would not result in attainment any faster, then a plan which requires implementation of less than all technologically and economically available measures may be approved./ 25/ The EPA believes it would be unreasonable to require that a plan which demonstrates attainment include all technologically and economically available control measures even though such measures would not expedite attainment. Thus, for some sources in areas which demonstrate attainment, it is possible that some available control measures may not be " reasonably" available because their implementation would not expedite attainment.

NOTE / 25/ See, e. g., 44 FR 20375 ( April 4, 1979). See also 56 FR 5460 ( Feburary 11, 1991). As provided in section 172( c)( 9) of the amended Act, all moderate nonattainment area SIP's that demonstrate attainment must include contingency measures. These measures must be submitted by the initial moderate nonattainment areas no later than Nov ember 15, 1993 ( See section 172( b))./ 26/ These measures become effective without further action by the State or EPA, upon determination by EPA that the area has failed to make RFP or to attain the PM 10 NAAQS by the applicable statutory deadline. These contingency measures should consist of other available control measures that are not included in the control strategy.

NOTE / 26/ This deadline constitutes the formal establishment of the schedule according to which the initial PM 10 moderate nonattainment areas must submit the contingency measure requirement. The initial PM 10 nonattainment areas were designated nonattainment upon enactment by operation of law. See section 107( d)( 4)( B). Under the schedule established today, contingency measures must be submitted no later than 3 years from the nonattainment designations for these areas which, in this instance, is no later than November 15, 1993.

One basis EPA recommends for determining the magnitude of contingency measures is the amount of actual PM 10 emissions reductions required by the SIP control strategy to attain the standards. When developing a control strategy and demonstrating attainment with dispersion modeling, the State may determine that some actual emissions must be reduced and also some allowable emission limits must be reduced to the levels that the sources are actually emitting.

The contingency measures to be implemented if an area does not attain the standards on schedule should be a portion of the actual emissions reductions required by the SIP control strategy to bring about attainment. Therefore, the contingency emissions reductions should be approximately equal to the emissions reductions necessary to demonstrate RFP for one year. For instance, reductions equal to 25 percent of the total strategy would be appropriate for a moderate nonattainment area since the control strategy must generally be implemented within a 3 to 4 year period between SIP development and the attainment date, and since RFP generally requires annual incremental reductions in emissions to attain the standards.

The contingency measures should consist of other available control measures beyond those required to attain the standards and may go beyond RACM. It is important not to allow contingency measures to obviate an adequate and appropriate control strategy demonstration.

Contingency measures must be implemented immediately after EPA determines the area has failed to make RFP or to attain the standards, i. e., if the shortfall constitutes a fraction of the area's annual reduction target, the measures to be implemented should address the specific deficiency indentity. The purpose of the contingency measure provisions is to ensure that corrective measures will automatically become effective at the time that EPA makes such a determination. The EPA is required to determine within 90 days after receiving a milestone demonstration and within 6 months after the attainment date ( or 1 or 2 years later if extensions of the attainment date are granted), whether these requirements have been met ( sections 179( c), 188( b)( 2) and 189( c)( 2)). Contingency measures must be fully adopted and take effect within 1 year without further legislative action once EPA makes such determinations.

Moderate areas that EPA finds have failed to attain the standards by the applicable date are reclassified as serious areas by operation of law ( section 188( b)( 2)). Guidance for serious areas addressing the contingency measure requirement will be issued at a later date.

4. SIP's That Do Not Demonstrate Attainment In those moderate PM 10 nonattainment areas where the State's control strategy cannot demonstrate attainment by the applicable date mandated in the Act, the State should document that its control strategy represents the application of RACM, consistent with the " determination of RACM" discussion above, to existing sources. The EPA believes it is reasonable for all available control measures that are technologically and economically feasible to be adopted for areas that do not demonstrate attainment.

Areas that cannot practically demonstrate attainment of the PM 10 standards by the applicable attainment date will be reclassified as serious areas under section 188( b) and will be required to implement BACM, which includes the application of BACT to existing stationary sources ( see H. R. Rep. No. 490, 101st Cong., 2d Sess. 276 ( 1990)). As discussed below, for those areas that will be reclassified as serious, EPA believes it may be reasonable, in some limited circumstances, for States to consider the compatibility of RACM and RACT with the BACM and BACT that will ultimately be implemented under the serious area plans for those areas.

In the case of RACM for area sources, EPA anticipates that any future implementation of BACM for these sources will be additive to, and hence compatible with, RACM. This is because BACM will generally consist of a more extensive implementation of the RACM measures ( e. g., paving more unpaved roads, strengthening the components of a smoke management program, imposing additional requirements to improve the performance of wood burning devices). Since EPA anticipates that RACM and BACM for these sources will be compatible, the SIP's for these areas should reflect the application of available control measures to existing sources in moderate nonattainment areas as determined by the analysis described above for RACM.

As discussed previously, the determination of RACT for specific stack and process sources includes consideration of the technological and economic feasibility of control measures. In the case of those moderate PM 10 areas that were designated nonattainment upon enactment of the 1990 CAAA, EPA plans to reclassify those areas which EPA believes cannot practicably attain by December 31, 1994. Implementation of BACT will be required for sources in the initial moderate areas that EPA so reclassifies approximately 2 years after the deadline for implementation of RACT./ 27/ In many instances, the installation of pollution controls representing RACT may involve substantial capital expenditures. In the event that BACT is later required for those sources, this may require controls significantly incompatible with those recently installed as RACT, largely wasting those recent expenditures. Under such circumstances, the installation of controls in the first round of SIP planning would be unreasonable. Accordingly, SIP's for the initial moderate areas reclassified as serious in the mandatory reclassification rulemaking for these areas need not require major changes to the control systems for specific stack and process sources where a State reasonably demonstrates that such changes will be significantly incompatible with the application of BACT level control systems. A State's demonstration should include, for example, showing what the State believes RACT and BACT are for the source and why they are significantly incompatible.

NOTE / 27/ Under section 189( a), moderate areas designated nonattainment at enactment must implement RACM ( including RACT) by December 10, 1993. Under section 189( b) areas reclassified as serious must implement BACM ( including BACT) within 4 years after reclassification. Thus, if EPA takes final action to reclassify areas in 1992, they will be required to implement BACT approximately 2 years after the December 10, 1993 implementation deadline for RACT.

In the case of fugitive dust associated with stationary sources, EPA anticipates that the implementation of BACT will be compatible with the implementation of RACT. This is based on the fact that control of such emissions under BACT will generally be additive to RACT controls ( i. e., consist of a more extensive application of fugitive dust control measures imposed as RACT). Therefore, EPA expects that to the extent that control of these sources is technologically and economically feasible, the SIP's for these areas must reflect the application of available control technology to address fugitive dust emissions associated with stationary sources.

( a) Attainment date waiver nonanthropogenic sources). Under section 188( f) of the amended Act, EPA may waive attainment dates for a moderate area where EPA determines that nonanthropogenic sources of PM 10 contribute significantly to a violation of the PM 10 NAAQS in the area. Thus, those States having moderate PM 10 nonattainment areas where significant contributions to PM 10 emissions come from sources not caused by humans directly or indirectly may request an attainment date waiver. However, EPA may only waive the attainment date for those moderate areas that fully implement their moderate area SIP requirements ( see H. R. Rep. No. 490, 101st Cong., 2d Sess. 265 ( 1990)). Thus, any State having a moderate nonattainment area that the State believes may qualify for an attainment date waiver should be nevertheless proceeed with SIP development and implementation.

In addition, the legislative history suggests that Congress contemplated a narrow definition of what may qualify as " nonanthropogenic" and would limit it to activities where the human role in the causation of the pollution is highly attenuated ( see generally H. R. Rep. No. 490). " The term ' anthropogenic sources' is intended to include activities that are anthropogenic in origin. An example of such sources is the dry lake beds at Owens and Mono Lakes in California, which give rise to dust storms that are a result of the diversion of water that would otherwise flow to such lakes and should be considered anthropogenic sources" ( H. R. Rep. No. 490 at 265). The EPA intends to issue additional guidance on the scope of the waiver provision as it applies to both moderate and serious PM 10 nonattainment areas in the near future.

( b) International border areas. Under section 179B of the amended Act, a SIP for a moderate PM 10 nonattainment area affected by emissions originating from sources outside the United States shall be approved by the Administrator provided such plan meets all the applicable requirements under the Act ( including, for example, RACM/ RACT), other than a requirement that such a plan or revision demonstrates attainment of the PM 10 NAAQS by the applicable moderate area attainment date; and the SIP demonstrates that the area would attain by that date, but for the emissions emanating from outside of the United States. Generally, EPA expects that such areas will be adjacent to international borders ( e. g., El Paso, Texas; Nogales, Arizona; Imperial Valley, California).

D. Sulfur Dioxide 1. Designations The Act, following the 1977 CAAA, gave the primary authority for initiating designations to State Governors. Although State Governors continue to have authority to initiate the designation process ( section 107( d)( 3)( D)), the 1990 CAAA also give the EPA the authority to initiate and to promulgate designations ( sections 107( d)( 1), ( 3)).

( a) Classification categories. In general, areas may be designated as nonattainment, attainment, or unclassifiable for the NAAQS ( section 107( d)( 1)( C)), and they provide authority and schedules for designations of areas following promulgation of a new or revised NAAQS ( section 107( d)( 1)( A), ( B)).

( b) Basis of designation. The SO2 designations can be made on the basis of modeling or monitoring information which indicates attainment or nonattainment of the NAAQS. For example, an area might be designated nonattainment for violation of the primary SO2 NAAQS, the secondary SO2 NAAQS, or both./ 28/ More detailed information about the basis for designations under the new law is provided in the following discussions.

NOTE / 28/ The primary SO2 NAAQS, is that level which is " requisite to protect the public health" ( section 109( b)( 1)). The secondary SO2 NAAQS, is that level which is " requisite to protect the public welfare" ( section 109( b)( 2)).

( c) Methods of designations. Some areas were designated " by operation of law" upon enactment of the 1990 CAAA based upon their status immediately before enactment. Areas which were designated nonattainment by operation of law ( section 107( d)( 1)( C)) are listed in 40 CFR part 81.

The EPA now has the authority to redesignate additional areas as nonattainment for SO2. The first step in this process is for EPA to notify the affected State's Governor that available information indicates that the designation of an area in the State should be revised ( section 107( d)( 3)( A)). Section 107( d)( 3)( A) provides that EPA may act ( i. e., notify the Governor that an area should be redesignated) " on the basis of air quality data, planning and control considerations, or any other air quality related considerations the Administrator deems appropriate." No later than 120 days after receiving this notification, the Governor should submit appropriate redesignations to EPA ( section 107( d)( 3)( B)). If the Governor fails to act within 120 days of this notification, EPA shall promulgate the appropriate designation ( section 107( d)( 3)( C)). If the Governor does respond, within 120 days after EPA receives the Governor's response, EPA must promulgate a redesignation making any modifications EPA deems necessary ( section 107( d)( 3)( C)). If EPA intends to modify the Governor's redesignation submittal, then EPA must notify the Governor of the modifications no later than 60 days prior to the date EPA promulgates the redesignation ( section 107( d)( 3)( C)).

( d) Criteria for redesignation. The revised law sets forth specific requirements which govern the redesignation of an area from nonattainment to attainment ( section 107( d)( 3)( E)). The particular criteria for redesignating nonattainment areas to attainment ( section 107( d)( 3)( E)) include the following: The area has attained the NAAQS, the area has a fully approved ( section 110( k)) implementation plan, the improvement in air quality is due to permanent and enforceable emissions reductions, the area has a maintenance plan meeting the requirements of section 175A, and the area meets all applicable requirements under section 110 and part D. The Agency will issue detailed guidance for States seeking redesignation of nonattainment areas to attainment at a later date.

2. Classifications The classification provisions ( section 172( a)( 1)) give EPA the authority to classify nonattainment areas for the purposes of applying attainment dates ( section 172( a)( 2)( A)). In exercising this authority, EPA may consider such factors as the severity of the nonattainment problem or the availability and feasibility of the pollution control measures. Based upon the classification, EPA may set later attainment dates for areas with more severe air quality problems ( section 172( a)( 2)( A)). At the present time, EPA does not intend to establish a specific classification scheme for areas which violate the primary or the secondary SO2 NAAQS.

3. Plan submission Deadlines Submission deadlines for States to submit implementation plans ( part D Plans) for SO2 NAAQS are given in section 191. Explicit plan submission deadlines are given for nonattainment areas which violate the primary SO2 NAAQS ( section 191). Explicit plan submission deadlines are not given for nonattainment areas that violate only the secondary or both the primary and secondary SO2 NAAQS, however.

( a) Initial nonattainment areas. States with existing nonattainment areas for the primary SO2 NAAQS where those areas lack fully approved SIP's, including part D plans, must submit implementation plans ( section 191( b)). These implementation plans must meet the requirements of subpart 1 of part D, and they must be submitted within 18 months after enactment of the 1990 CAAA ( i. e., by May 15, 1992).

( b) Subsequent nonattainment areas. States with areas that are designated or redesignated, after 1990 CAAA enactment, as nonattainment areas for the primary SO2 NAAQS must submit implementation plans ( section 191( a)). These implementation plans must meet the requirements of part D and the plans must be submitted within 18 months of the designation or redesignation.

( c) Secondary NAAQS. In the past, Congress and the Agency has required more expeditious resolution of nonattainment for primary NAAQS than for secondary NAAQS. Examples of this are the availability of 18 month extensions for implementation plan submittals for secondary NAAQS ( section 110( b)), and the discretion allowed in dates for attainment of secondary NAAQS ( section 110( a)( 2)( A)).

For areas which violate both primary and secondary NAAQS, allowing separate schedules for secondary and primary plans unnecessarily complicates the plan implementation and processing. Therefore, EPA expects secondary NAAQS attainment plans to be submitted on the same schedule as plans for the primary NAAQS for these areas.

As a result of the 1990 CAAA, EPA has the authority to establish a schedule for submittal of a secondary NAAQS plan or plan revision ( section 172( b)). The EPA must establish this schedule at the time of the nonattainment designation. The SIP must be submitted no later than 3 years from the date of the nonattainment designation. Although the law allows up to 3 years for SIP submittal, because the level of control is no more difficult to establish than for the primary NAAQS, and absent compelling justification by a State, EPA will require SIP's for these areas within 18 months of nonattainment designation.

4. Attainment Dates.

In the 1990 CAAA, Congress set specific attainment dates for nonattainment areas which were found to violate the primary SO2 NAAQS./ 29/ Attainment dates for nonattainment areas violating either just the secondary or both the primary and secondary SO2 NAAQS were not specified although Congress deleted the requirement that the secondary NAAQS be attained by a " reasonable" time for attainment of secondary NAAQS ( section 110( a)( 2)( A)).

NOTE / 29/ The 1977 CAAA continued the requirement from the 1970 CAA that States submit implementation plans which provided for attainment of primary NAAQS " as expeditiously as practicable but * * * in no case later than three years" from the date of approval of the plan ( 1977 CAAA section 110( a)( 2)( A)). For secondary NAAQS, attainment was required within " a reasonable time" ( section 110( a)( 2)( A) after the 1977 CAAA).

For part D nonattainment areas, the 1977 CAAA required attainment for both primary and secondary NAAQS nonattainment areas " as expeditiously as practicable" but for primary standards, a deadline of December 31, 1982 was also given ( part D, section 172( a)( 1) after the 1977 CAAA).

The 1990 CAAA require attainment of both the primary and secondary NAAQS " as expeditiously as practicable" ( section 172( a)( 2) ( A) and ( B)). Although the 1990 CAAA give EPA authority to establish flexible attainment dates ( section 172( a)( 2)( A)( C)), this flexibility does not apply to areas which have specific attainment dates ( section 172( a)( 2)( D)). Specifically, the flexibility does not apply to attainment of the primary SO2 NAAQS because the attainment date is specified for primary SO2 nonattainment areas ( section 192), but it does apply to secondary SO2 NAAQS because the 1990 CAAA do not specify an attainment date for secondary SO2 nonattainment areas.

( a) Initial nonattainment areas. Areas which were designated nonattainment at the time of enactment ( i. e., areas which are nonattainment by operation of law), must attain the primary NAAQS as expeditiously as practicable but no later than 5 years after enactment of the 1990 CAAA ( i. e., by November 15, 1995) ( section 192( b)).

( b) Subsequent nonattainment areas. Areas which are redesignated as nonattainment, subsequent to the November 15, 1990 date of enactment, must attain the primary NAAQS " as expeditiously as practicable," but not later than 5 years after the nonattainment designation ( section 192( a)).

( c) Inadequate plan areas ( SIP call areas). Some nonattainment areas have plans which were approved by EPA before enactment of the 1990 CAAA. If, subsequent to the plan's approval, EPA finds that such a plan is substantially inadequate, the plan must be revised to provide for attainment. The revised plan must provide attainment of the primary NAAQS within 5 years from the finding of inadequacy ( section 192( c)).

( d) Attainment of secondary NAAQS. The 1977 CAAA set the attainment date for secondary NAAQS as " a reasonable time" ( section 110( a)( 2)( A)). This was consistent with the requirements of the 1970 Act. At the same time, for the new part D nonattainment areas, section 172( a)( 1) established the attainment date for secondary NAAQS as " as expeditiously as practicable." The EPA reiterated in regulations that " a reasonable time" after plan approval was allowed for attainment of the secondary NAAQS ( 40 CFR 51.110( c)( 1)).

In the 1990 CAAA, Congress provided for attainment " as expeditiously as practicable" in both primary and secondary nonattainment areas ( section 172( a)( 2)). Congress set a specific attainment date of 5 years for primary NAAQS ( see above) but did not set a specific deadline for attainment of secondary NAAQS ( section 192). At the same time, Congress deleted section 110( a)( 2)( A), which had stated that attainment dates should generally not exceed 3 years from plan submittal ( section 110( a)( 2)( A)). This implies that the only test for the approvability of a secondary NAAQS attainment date is whether or not the date is " as expeditiously as practicable" ( section 172( a)( 2)( B)). To maintain continuity with past program guidance, EPA plans to allow attainment with the secondary NAAQS to be scheduled on the basis of what is expeditious for the area ( section 193). Areas which are nonattainment for the secondary SO2 NAAQS may be allowed additional time for attainment beyond the deadlines mandated for the primary NAAQS. In general, EPA will rely on the substantive provisions of 40 CFR 51.340 ( subpart R) to determine expeditiousness.

Areas which are nonattainment for both the primary and secondary NAAQS may split their attainment dates, i. e., attain the primary NAAQS within 5 years and attain the secondary NAAQS as expeditiously as practicable. This will be acceptable provided that the State can demonstrate that the secondary NAAQS cannot be attained within the same timeframe as the primary NAAQS.

5. Nonattainment Plan Provision ( a) Overview. The 1970 Act required States to submit implementation plans which would indicate how the State would attain and maintain the NAAQS. The requirements for these general SIP's were listed in part A, section 110. In the 1977 CAAA, requirements for implementation plans in nonattainment areas were given in part D ( section 171 178). These requriements addressed a number of issues including, but not limited to, attainment dates, permit requirements, and planning procedures.

The 1990 CAAA have not made significant changes in the plan requirements for SO2 nonattainment areas ( section 172). For this reason, States may generally continue to rely on past guidance for SO2 programs. This position is further supported by the General Savings Clause contained in section 193. A summary of existing policy and guidance may be found in the " SO2 Guideline," the " Guideline On Air Quality Models ( revised)," and other documents listed in Appendix B. Despite the continued validity of past guidance in the implementation of the amended Act for SO2 NAAQS, there are some areas of policy that need to be clarified. One area that will need policy clarification is the issue of plan approval. The EPA intends to consider only the final rulemaking status of the SIP at the time of enactment in relationship to the requirements of the 1990 CAAA. This is consistent with the Savings Clause for existing plan provisions ( section 110( n)( 1)). If the nonattainment area had a part D plan that was approved prior to enactment, the EPA will not require a new part D SIP. For these areas, a new part D SIP will not be required regardless of whether the attainment date for the area had passed at the time of encactment of the 1990 CAAA. However, if the approved plan was not a part D plan, the State will have to submit a complete part D plan to EPA for approval because part D plans are requried for nonattainment areas ( section 191( b)).

Policy clarification is also needed concerning the status of areas that lack approved part D plans and that contain a SO2 emission source that has permanently shut down. A minimum of two actions are required for States wishing to establish that these areas are inoperative for SIP purposes.

The first action is that the State must provide EPA with sufficient evidence to establish that the source has in fact been permanently shut down. Three criteria exist for establishing permanent source shutdown. These criteria require proof that the source has been inoperative for at least the 2 preceding years, that the source is precluded from resuming operations, and that the source has been withdrawn from the State's emissions inventory.

The second action is that the State must establish that fully approved NSR and PSD programs are in place so that the source would be required to undergo NSR prior to start up if it were reactivated.

After the State has completed these actions, EPA will consider additional plan requirements of such areas on a case by case basis. Alternatively, the State may choose to submit complete part D plans to EPA for these areas. As discussed in a previous section on redesignation, section 107( d)( 3) provides that a nonattainment area must meet all the requirements set forth in section 107( d)( 3)( E), including a maintenance plan consistent with section 175A, before it may be redesignated to attainment. The EPA recognizes that this issue is of immediate concern to some States and Regions. The EPA will issue guidance concerning plan requirements and redesignation requirements in the future.

( b) Issues( 1) RACT. For most criteria pollutants, RACT is control technology that is reasonably available considering technological and economic feasibility ( see memorandum from R. Strelow, December 9, 1976). The definition of RACT for SO2 is that control technology which is necessary to achieve the NAAQS ( 40 CFR 51.100 ( o)). Since SO2 RACT is already defined as the technology necessary to achieve NAAQS, control technology which failed to achieve the SO2 NAAQS would, by definition, fail to be SO2 RACT.

The EPA intends to continue defining RACT for SO2 as that control technology which will achieve the NAAQS within statutory timeframes.

( 2) RFP. Section 171( 1) of the amended Act defines RFP as " such annual incremental reductions in emissions of the relevant air pollutant as are required by this part ( part D) or may reasonably be required by EPA for the purpose of ensuring attainment of the applicable national ambient air quality standard by the applicable date." This definition is most appropriate for pollutants which are emitted by numerous and diverse sources, where the relationship between any individual source and the overall air quality is not explicitly quantified, and where the emission reductions necessary to attain the NAAQS are inventory wide. The definition is generally less pertinent to pollutants such as SO2 which usually have a limited number of sources, relationships between individual sources and air quality which are relatively well defined, and emissions control measures which result in swift and dramatic improvement in air quality. That is, for SO2, there is usually a single " step" between pre control nonattainment and post control between pre control nonattainment and post control attainment.

Therefore, for SO2, with its discernible relationship between emissions and air quality and significant and immediate air quality improvements, RFP will continue to be construed as " adherence to an ambitious compliance schedule." / 30/

NOTE / 30/ U. S. Environmental Protection Agency, Office of Air Quality Planning snd Standards, " Guidance Document for Correction of part D SIP's for Nonattainment Areas," ( Research Triangle Park, North Carolina: January 27, 1984), page 25.

( 3) Contingency measures. Section 172( c)( 9) of the amended Act defines contingency measures as measures in a SIP which are to be implemented if an area fails to make RFP or fails to attain the NAAQS by the applicable attainment date. Contingency measures become effective without further action by the State or EPA, upon determination by EPA that the area has failed to ( 1) make reasonable further progress or ( 2) attain the SO2 NAAQS by the applicable statutory deadline. These contingency measures shall consist of other available control measures that are not included in the control strategy.

The EPA interprets the contingency measure provisions as primarily directed at general programs which can be undertaken on an areawide basis. Again, SO2 presents special considerations. First, for some of the other criteria pollutants, the analytical tools for quantifying the relationship between reductions in precursor emissions and resulting air quality improvements remain subject to significant uncertainities, in contrast with procedures for pollutants such as SO2. Second, emission estimates and attainment analyses can be strongly influenced by overly optimistic assumptions about control efficiency and rates of compliance for many small sources. In contrast, controls for SO2 are well understood and are far less prone to uncertainty. Since SO2 control measures are by definition based upon what is directly and quantifiably necessary to attain the SO2 NAAQS, it would be unlikely for an area to implement the necessary emissions control yet fail to attain the NAAQS. Therefore, for SO2 programs, EPA interprets " contingency measures" to mean that the State agency has a comprehensive program to identify sources of violations of the SO2 NAAQS and to undertake an aggressive follow up for compliance and enforcement, including expedited procedures for establishing enforceable consent agreements pending the adoption of revised SIP's. This definition of minimum contingency measures for SO2 does not preclude a State from requiring additional contingency measures that are enforceable and appropriate for a particular source or source category.

( 4) Stack height issues and remand. Three provisions of the stack height rules have been remanded to EPA as a result of the court decision in NRDC v. Thomas, 838 F. 2d 1224 ( D. C. Cir.), cert. denied, 109 S. Ct. 219 ( 1988). The EPA has allowed States to move ahead on affected SIP revisions without regard to the remanded section of these rules, but with the caveat that the States must remain aware of the status of these rules, and may be required to take action at a later date to respond to any rule revisions resulting from the remand ( see, " Interim Policy on Stack Height Regulatory Actions," J. Craig Potter, April 22, 1988.) ( 5) Existing modeling protocols. The amended Act requires submittal of a complete SIP 18 months from enactment or nonattainment designation ( section 191). This 18 month submittal, supported by a guideline model, must be completed even in cases where the modeling protocol is currently under review. Equivalent models to those approved for regulatory use in EPA's " Guideline on Air Quality Models ( Revised)" might not be approved in sufficient time to complete SIP development and submittal within the statutory deadline. Therefore, States should proceed with existing guideline models, without deviation from the model guideline, to fulfill the requirements of the 18 month SIP submittal.

If States and/ or source owners wish to complete work on alternative models, they may do so. If EPA accepts the alternative models, then the SIP may be revised accordingly. However, if the alternative model is not completed in a timely fashion, or if the alternative is unacceptable, an acceptable regulation must be in place to assure expeditious attainment and to avoid sanctions for failure to submit a SIP ( section 172( c)( 8)).

The Act as amended in 1990 gives EPA authority to prescribe modeling procedures to determine the effect of emissions on ambient air quality ( Part D and section 110( a)( 2)( K)( i)). The EPA plans to rely on its " Guideline on Air Quality Models ( Revised)" as the basis for all prescribed procedures and is in the process of revising 40 CFR part 51 to effect this requirement.

( 6) Test methods and averaging times. The NAAQS are expressed as maximum ambient concentrations that are to be met on a continuous basis. Consequently, States must demonstrate that source emission limitations, averaging times, and compliance monitoring methods are sufficient to assure compliance with the air quality standards. The choice of a monitoring technique should consider regulatory needs, monitoring technology costs, and the relative benefits of one technique versus another.

Continuous emission monitoring systems ( CEMS) are a reliable technique for continuously monitoring emissions of SO2 for many source categories. Detailed guidance documents for determining CEMS feasibility in indiviudal cases are listed in section III. D. 6. of this preamble ( see letters from W. Reilly to J. Dingell, April 10, 1991). Further guidance is being developed. In general, the criteria for determining when CEMS are appropriate are as follows: i. Any source where there is an established new source performance standard ( NSPS) which requires CEMS for determining compliance should rely on this method in the SIP. For example, any utility boiler that physically meets the applicability requirements of 40 CFR part 60, subpart Da, whether it is an " existing boiler" under 40 CFR part 60, subpart Da or not, must have CEMS for NSPS compliance and should therefore rely on CEMS for SIP compliance as well.

ii. Any source that has other regulatory requirements with CEMS as the compliance method should rely on CEMS as the SIP compliance method as well.

The feasibility of using CEMS as the compliance method has already been established for sources that fall into these two categories. For example, in developing NSPS, the Agency has already considered cost, environmental, and energy impacts for these standards. Where CEMS are not technically or economically feasible in other cases, other appropriate continuous monitoring techniques, such as continuous compliance of relevant process parameters or alternatives approved by EPA under title IV, would be appropriate.

( 7) Enforceability. The SIP measures should be converted into a legally enforceable vehicle ( e. g., a regulation or permit). The regulations or other measures should meet EPA's criteria regarding the enforceability of SIP's and SIP revisions.

Guidance on enforceability requirements has been provided to Regional Offices in various memoranda ( see Bauman/ Biondi and Potter/ Adams/ Blake memoranda listed in section III. D. 6. of this preamble. Those SIP's and SIP revisions which fail to satisfy the enforceability criteria should not be forwarded for approval. If they are submitted, they will be disapproved if, in EPA's judgement, they fail to satisfy applicable statutory and regulatory requirements.

( 8) Maintenance plans. As discussed previously, section 107( d)( 3) of the amended Act ( see subparagraphs A and E of section 107( d)( 3) as well as section 175A) requires that nonattainment areas must have a fully approved maintenance plan meeting the requirements of section 175A before they can be redesignated to attainment. Section 175A( a) mandates, among other things, that a State must submit a SIP revision which provides for maintenance of the NAAQS for at least 10 years after the redesignation to attainment ( section 175A( a)). A subsequent SIP revision providing for maintenance of the NAAQS for an additional 10 years is due 8 years into the first 10 year maintenance period. The law does not provide any exceptions to the maintenance plan requirement. Therefore, in addition to meeting all pre existing requirements, areas which are designated nonattainment by operation of law ( section 107( d)( 1)( C)( i)), as well as areas which are designated nonattainment in the future ( section 107( d)( 3)), must all submit maintenance plans before they can be redesignated to attainment.

The EPA will issue guidance on the contents of section 175A maintenance plans at a later date.

( 9) NSR. As specified in section 302( j), for SO2 nonattainment areas the term major stationary source means any stationary source which directly emits, or has the potential to emit, 100 tons per year or more of SO2. To meet the requirements of section 172( c)( 5), States must submit a permit program that meets all the permit requirements of section 173 for the construction and operation of new and modified stationary sources of SO2.

6. Sources of SO2 Policy and Guidance Unless otherwise noted, the guidance documents and sources listed below were developed by the EPA's Office of Air Quality Planning and Standards ( OAQPS) located in Research Triangle Park, North Carolina. The EPA plans to address additional policy questions by periodically issuing memorandums which offer guidance in a question and answer format. See also: ( a) SO2 Guidance.

( 1) SO2 Guideline, October 1989.

( 2) SO2 Guideline Appendices, October 1989.

( 3) Letter from William Reilly to Representative John Dingell, in response to questions and GAO report, April 10, 1991.

( 4) Memorandum from Craig Potter, Thomas Adams, and Francis Blake to Air Division Director, Regions I X, " Review of State Implementation Plans and Revisions for Enforceability and Legal Sufficiency," September 23, 1987.

( 5) Memorandum from Gerald A. Emison, Director, OAQPS, to Air Division Director, Regions I X, " Transmittal of Reissued OAQPS CEMS Policy," March 31, 1988.

( 6) " Approval and Promulgation of Implementation Plans; Dearborn, Lake, and Porter Counties, Indiana, " 54 FR 612, January 9, 1989.

( 7) Memorandum from Robert Bauman and Rich Biondi to Air Branch Chiefs, " SO2 SIP Deficiency Checklist," November 28, 1990. ( 8) Memorandum from Gerald Emison, Director, OAQPS, to David Kee, Director, Air Management Division, Region V, " Need for a Short Term BACT Analysis for the Proposed William A. Zimmer Power Plant," November 24, 1986.

( b) SIP Guidance. ( 1) Guidance Document for Correction of Part D SIP's for Nonattainment Areas, January 27, 1984.

( 2) Memorandum from R. Strelow to Regional Administrator, Regions I X, " Guidance for Determining Acceptability of SIP Regulations in Non Attainment Areas," December 9, 1976.

( c) Modeling Guidance. ( 1) " Guideline on Air Quality Models" ( Revised), July 1986.

( 2) " Interim Procedures for Evaluating Air Quality Models: Experience with Implementation," July 1985.

( 3) Model Clearinghouse.

( d) New Source Review Guidance. ( 1) Memorandum from Richard Rhoads, Director CPDD, to Division Director, Regions I X, " Growth Restrictions in Secondary NAAQS Nonattainment Areas," October 28, 1980.

( 2) New Source Review Prevention of Significant Deterioration and Nonattainment Area Guidance Notebook, January 1988.

( 3) Guidance on State Operating Permit Programs, Federal Register notice, June 1989.

( 4) NSR Electronic Bulletin Board, Computerized Compilation of Previous and Latest NSR Policy Memoranda and Technical Information Items, Federal Register notice, January 1990.

( 5) " Draft Workshop Manual for New Source Review ( NSR) Programs," December 1990.

( 6) Memorandum from J. Seitz, OAQPS, to Air Division Director, Regions I X, " New Source Review ( NSR) Program Transitional Guidance," March 11, 1991.

E. Lead 1. Statutory Background ( a) Designations. In 1978, when EPA promulgated the lead NAAQS, EPA believed that implementation and maintenance of the lead NAAQS should be in accordance with the SIP requirements set forth in section 110 and not part D. The EPA believed that section 107 and and part D requirements were intended by Congress to apply only to NAAQS which were set prior to 1977. In these cases, SIP's had already been adopted, the attainment dates had already passed, and the SIP's had proven to be inadequate. The designation process was intended as a mechanism to initiate new SIP revisions for those existing NAAQS. Since the attainment date for the lead NAAQS at that time had not yet arrived, no lead SIP's had yet been proven inadequate. Consequently, lead did not meet the circumstances which initially resulted in a need for nonattainment designations and plan revisions under part D.

The Act, as amended, clearly defines EPA's authority to designate areas for lead. Section 107( d)( 5) authorizes EPA to require States to designate areas ( or portions thereof) as nonattainment, attainment or unclassifiable with respect to the lead NAAQS in effect as of the date of enactment of the 1990 CAAA./ 31/ As provided in section 107( d)( 5), these lead areas are to be designated pursuant to the procedures outlined in section 107( d)( 1)( A) and ( B) except that certain timeframes of subparagraph ( B) have been modified by section 107( d)( 5). Section 107( d)( 1)( A) permits EPA to require the Governors of affected States to submit recommended designations for the areas EPA seeks designated in a timeframe that EPA deems reasonable. This timeframe, however, can be no sooner than 120 days nor later than 1 year after the date EPA notifies the State of the requirement to submit such designations. Section 107( d)( 1)( B) requires that EPA must then promulgate these designations no later than 1 year after notifying the State of the requirement to designate areas for lead. The EPA may make any modifications deemed necessary to the designations submitted by the State ( see generally section 107( d)( 1)( B) of the Act). However, no later than 120 days before promulgating a modified area, EPA must notify the affected State and provide an opportunity for the State to demonstrate why any proposed modification is inapporpriate.

NOTE / 31/ Section 107( d)( 5) of the amended Act does not indicate that all areas of the State must be designated. At this time, EPA has only requested that specified areas within affected States be designated. Therefore, most States and the vast majority of the areas within affected States will still have no designations, i. e., will not be designated as attainment, nonattainment, or unclassifiable for lead.

If the Governor of an affected State fails to submit the required lead designations, in whole or in part, EPA is required to promulgate the designation that it deems appropriate for any area ( or portion thereof) not designated by the State. ( b) Area boundaries. States should identify the boundaries of the nonattainment areas when submitting nonattainment designations for lead. A lead nonattainment area consists of that area which does not meet ( or that contributes to ambient air quality in a nearby area that does not meet) the lead NAAQS ( see section 107( d)( 1) of the amended Act). Generally, EPA recommends that the lead nonattainment boundary be defined by the perimeter of the county in which the ambient lead monitor( s) recording the violation is located. In addition, if the ambient monitor measuring violations is located near another county, then EPA recommends that the other county also be designated as nonattainment for lead. In some situations, however, a boundary other than the county perimeter may be appropriate. States may choose alternatively to define the lead nonattainment boundary by using any one, or a combination, of the following techniques: Qualitative analysis, spatial interpolation of air monitoring data, or air quality simulation by dispersion modeling. These techniques are more fully described in " Procedures for Estimating Probability of Nonattainment of a PM 10 NAAQS Using Total Suspended Particulate or PM 10 Data," December 1986. The EPA recommends that the State submit a defensible rationale for the boundary chosen with the Governor's designation for an area.

( c) Classification./ 32/ Section 172( a)( 1)( A) of the amended Act authorizes EPA to classify areas designated as nonattainment for the purposes of applying an attainment date pursuant to section 172( a)( 2) or for other reasons. In determining the appropriate classification, EPA may consider such factors as the severity of the nonattainment problem and the availability and feasibility of the pollution control measures ( see section 172( a)( 1)( A) of the amended Act). The EPA may, but is not required to, classify lead nonattainment areas. At this time, EPA does not intend to classify lead nonattainment areas with respect to the lead NAAQS in effect on date of enactment of the 1990 CAAA. That is, while section 172( a)( 1)( A) provides a mechanism to classify nonattainment areas, section 172( a)( 2)( D) provides that the attainment date extensions described in section 172( a)( 2)( A) do not apply to nonattainment areas having specified attainment dates under other provisions of part D. Section 192( a) specifically provides an attainment date for areas designated as nonattainment for the lead NAAQS in effect at the date of enactment of the 1990 CAAA. Therefore, EPA has legal authority to classify lead nonattainment areas, but the 5 year attainment date under section 192( a) cannot be extended pursuant to section 172( a)( 2)( D), and EPA deems it inappropriate to establish a classification scheme within the 5 year interval.

NOTE / 32/ It is important to note that classifications and designations are separate concepts. Designations refer to an area's attainment status ( i. e., the area is designated attainment, nonattainment, or unclassifiable). Classifications are applied to areas designated nonattainment and are a mechanism for addressing differences among nonattainment areas. For example, classifications usually result in applying additional control measures and providing longer attainment deadlines for those areas having more serious nonattainment problems.

( d) Plan submission. Generally, the date by which a plan must be submitted for an area is trigggered by the area's nonattainment designation. For areas designated nonattainment for the primary lead NAAQS in effect at enactment of the 1990 CAAA, States must submit SIP's which meet the applicable requirements of part D of the Act within 18 months of an area's nonattainment designation ( see section 191( a) of the amended Act).

( e) Attainment dates. Generally, the date by which an area must attain the lead NAAQS also is triggered by the area's nonattainment designation. For areas designated nonattainment for the primary lead NAAQS in effect at enactment of the 1990 CAAA, SIP's must provide for attainment of the lead NAAQS as expeditiously as practicable but no later than 5 years from the date of an area's nonattainment designation ( see section 192( a) of the amended Act).

2. Pre SIP Submittal Activities As discussed above, any States containing an area designated as nonattainment with respect to the lead NAAQS in effect at enactment of the 1990 CAAA must develop and submit a part D SIP providing for attainment. Most of the general part D nonattainment plan provisions are set forth in section 172( c). The SIP's submitted to meet the part D requirements must, among other things, include RACM, RACT, provide for RFP, contain contingency measures and require permits for the construction and operation of major new and modified stationary sources. This portion of the General Preamble does not address more specifically RACM, RFP, contingency measures, or some of the other part D SIP requirements for lead nonattainment areas. States should nonetheless proceed, consistent with more general guidance on part D requirements to collect information and data necessary to complete SIP analyses. A listing of some of the specific SIP activities States should be completing is described below. The EPA will continue to evaluate the need for more detailed guidance on the part D lead SIP requirements as it proceeds with nonattainment designations for lead.

( a) Nonattainment NSR. Previously, areas that were not attaining the lead NAAQS were not designated as nonattainment and therefore were not required to have a nonattainment NSR program consistent with section 173 of the Act. However, now that there will be areas designated nonattainment for lead, a nonattainment NSR program is required for such areas. Specifically, section 172( c)( 5) requires that States having areas designated nonattainment for lead submit as part of the applicable SIP, provisions requiring permits for the construction and operation of new or modified major stationary sources anywhere in the nonattainment area, in accordance with section 173. Further guidance is provided in the March 11, 1991 memorandum from John Seitz, entitled " New Source Review ( NSR) Program Transitional Guidance to Implement the Clean Air Act Amendment Changes that Affect NSR" which is found in Appendix D. Among other things, the March 11, 1991 memorandum addresses the interim NSR requirements applicable to an area upon its designation as nonattainment for lead but before the amended law provides for submittal of its NSR program. The EPA generally recommends that States evaluate their existing rules to determine whether there are any impediments to implementing a nonattainment NSR program in the areas designated as nonattainment for lead.

( b) Emission inventories. An emissions inventory is required to determine the nature and extent of the specific control strategies that are needed. Emissions inventories should be based on measured emissions or documented emission factors. The more comprehensive and accurate the inventory, the more effective the control evaluation ( see section 172( c)( 3) of the amended Act which specifies that nonattainment area SIP's include " a comprehensive, accurate, current inventory of actual emissions from all sources of the relevant pollutant or pollutants in such area * * *"). The States should begin to evaluate the type of emissions inventory that needs to be developed and the type of information that needs to be collected to support a SIP submittal. Postponing completion of the emissions inventory could jeopardize the submittal of the lead SIP within the statutorily mandated deadlines.

The following documents provide further information for lead emissions inventory development: Draft Manual " Updated Information on Approval and Promulgation of Lead Implementation Plans," EPA, July 1983; " Guideline Series, Development of an Example Control Strategy for Lead," April 1979; and " Guideline Series, Supplementary Guideline for Lead Implementation Plans," August 1978.

( c) Modeling and meteorological monitoring. The lead SIP regulations at 40 CFR 51.117 require that atmospheric dispersion modeling be employed for the demonstration of attainment for areas in the vicinity of point sources listed in 40 CFR 51.117( a)( 1)./ 33/ To complete the necessary dispersion modeling, meteorological and other data will be necessary. At this time States should be evaluating whether the necessary meteorological data are available and, if not, determine what needs to be done to obtain these data. Dispersion modeling should follow the procedures outlined in the " Guideline On Air Quality Models ( Revised)." The " Guideline" indicates that if on site meteorological stations are used, 12 months of data are required. Postponing the decision to determine whether on site stations need to be established could jeopardize the submittal of the lead SIP within the statutorily mandated deadlines. NOTE / 33/ Generally, in addition to meeting applicable requirements under part D of title I of the amended Act, SIP's for those areas designated nonattainment for lead must also meet the applicable regulatory requirements set forth in 40 CFR part 51 except to the extent those requirements are inconsistent with the amended Act. The 1990 CAAA include a General Savings Clause which provides that regulations ( or guidance, etc.) in effect before the enactment of the Amendments shall remain in effect after enactment ( see section 193). However, the Savings Clause also provides that such regulations ( or guidance, etc.) shall remain in effect " except to the extent otherwise provided under this Act, inconsistent with any provisions of this Act, or revised by the Administrator." Id.

( d) Control measures. As indicated above, EPA is not at this time providing guidance on the RACM measures specific to lead SIP's. States should, however, continue to rely on guidance issued for the control of particulate emissions. In light of the fact that some SIP's are due July 6, 1993, EPA recommends that States focus their efforts more specifically now on evaluations of the affected lead sources. The EPA believes that the efforts States should undertake include an assessment of operation and maintenance ( O & M) and work practice measures. In addition, State efforts should identify and analyze control measures which reduce process fugitive and lead bearing open dust emission sources. These evaluations should consider the technological feasibility of additional control measures, as well as the cost of the identified options.

3. Transition Issues ( a) Transition from pre amended law. As mentioned, under the pre amended law there were no designations for lead, and States were required to submit SIP's in accordance with section 110. The amended law, as discussed, now authorizes EPA to designate areas for lead. There are transitional issues raised by the changes in the new law including, for example, the status of the obligation to submit adequate section 110 SIP's under the pre amended law and the status of any approved section 110 SIP's.

( b) Unapproved or inadequate section 110 SIP's. Before enactment of the 1990 CAAA, a State may have failed to submit a section 110 SIP to EPA, it may have submitted a section 110 SIP which was not approved by EPA, or it may have submitted and had approved a section 110 SIP which EPA subsequently found substantially inadequate. The last situation is true of at least three States. Specifically, prior to the enactment of the CAAA, EPA issued SIP calls for three States having substantially inadequate section 110 SIP's. Except for those areas designated nonattainment for lead, section 110( n)( 2) requires these States to continue their section 110 planning in accordance with the SIP calls ( or, as the case may be, in response to EPA's 1978 promulgation of the quarterly 1.5 micro g/ m/ 3/ lead standard) and to attain the NAAQS by the applicable date specified in section 110( m)( 2). Any area in these States that is designated nonattainment under the new law for the existing lead NAAQS must instead submit a part D SIP that comports with the applicable requirements in subpart 1 and subpart 5, including the SIP submittal material deadlines and attainment dates in sections 191 and 192 of subpart 5.

The EPA intends to ensure that a State whose SIP needed correction prior to enactment of the 1990 CAAA and that expects to have an area designated as nonattainment under the new law, continues to progress with its plan development and implementation for that area as provided in section 110( n)( 2). Once areas are designated nonattainment for the existing lead NAAQS, the State must complete a SIP providing for attainment by the date that is as expeditious as " practicable" for any such newly designated nonattainment area. In reviewing any future SIP's under sections 191 and 192, EPA will consider what progress could reasonably have been accomplished both prior to enactment of the new law and after enactment but before the area was designated nonattainment.

( c) Approved section 110 SIP's. In the situation where a State submitted and EPA approved or promulgated a section 110 lead SIP before the 1990 CAAA enactment, then all provisions of such SIP shall remain in effect unless and until EPA approves a revision under the new law ( see section 110( n)( 1)).

F. Nitrogen Dioxide This section applies primarily to the South Coast Air Basin of California, which is the only designated NO2 nonattainment area in the Nation. The basin was designated nonattainment by operation of law ( section 107( d)( 1)( C). The requirements described in this section would also generally apply to any subsequently designated NO2 nonattainment areas. Nothing in this guidance prevents a SIP for a nonattainment area from containing measures more stringent than the guidance recommends.

In general, the Act, as amended in 1990, does not require significant revisions in the NO2 NAAQS program. The General Savings Clause ( section 193) provides for general program continuity by explicitly preserving existing rules, policies, and guidance that are not affected by Act changes.

1. Designations The 1977 Act gave the primary authority for initiating designations to State Governors. Although State Governors continue to have authority to initiate the designation process ( section 107( d)( 3)( D)), the 1990 CAAA also give the Administrator the authority to initiate and to promulgate designations ( section 107( d) ( 1) and ( 3)).

In general, areas may be designated as nonattainment, attainment, or unclassifiable for the NAAQS ( section 107( d)( 1)( A) ( i), ( ii), and ( iii)). The 1990 CAAA provide for designations of areas based upon the attainment status for the current NAAQS ( section 107( d)( 1)( C)); they also provide authority and schedules for designations of areas following promulgation of a new or revised NAAQS ( section 107( d)( 1) ( A) and ( B)).

The revised law sets forth specific requirements that govern the redesignation of an area from nonattainment to attainment ( section 107( d)( 3)( E)). The particular criteria for redesignating nonattainment areas to attainment ( section 107( d)( 3)( E)) include the following determinations: The area has attained the NAAQS, the area has a fully approved ( section 110( k)) implementation plan, the improvement in air quality is due to permanent and enforceable emissions reductions, the area has a maintenance plan meeting the requirements of section 175A, and the area meets all applicable requirements under section 110 and part D. See " Redesignations and Maintenance" under III. H. 6 of this document.

2. Plan Deadlines Submission deadlines for States to submit implementation plans ( part D Plans) for NO2 are given in section 191. Plan submission deadlines are explicitly given for nonattainment areas which violate the primary NO2 NAAQS ( section 191). The NO2 primary and secondary NAAQS are identical. Thus, the South Coast Air Basin must submit an implementation plan that meets the requirements of subpart 1 of part D, and the plan must be submitted within 18 months after enactment of the 1990 CAAA ( i. e., by May 15, 1992).

States with areas that are designated or redesignated, after enactment, as nonattainment areas for the NO2 NAAQS must submit implementation plans ( section 191( a)). These implementation plans must meet the requirements of part D and the plans must be submitted within 18 months of the designation or redesignation.

3. Attainment Dates In the 1990 CAAA, Congress set specific attainment dates for nonattainment areas that were found to violate the NO2 NAAQS. The 1990 CAAA require attainment of the NAAQS " as expeditiously as practicable" ( section 172( a)( 2) ( A) and ( B)). Although the 1990 CAAA give EPA authority to establish flexible attainment dates ( section 172( a)( 2) ( A)( C)), this flexibility does not apply to areas that have specific attainment dates ( section 172( a)( 2)( D)). Specifically, the flexibility does not apply to attainment of the NO2 NAAQS because the attainment date is specified in section 192.

Areas that were designated nonattainment at the time of enactment ( i. e., areas that are nonattainment by operation of law) must attain the primary standard as expeditiously as practicable, but not later than 5 years after enactment of the 1990 CAAA ( i. e., by November 15, 1995) ( section 192( b)). This requirement applies to the South Coast Air Basin.

Areas that are redesignated as nonattainment, subsequent to the November 15, 1990 date of enactment, must attain the primary standard as expeditiously as practicable, but not later than 5 years after the nonattainment designation ( section 192( a)).

4. Nonattainment Plan Provisions The 1970 Act required States to submit implementation plans that would indicate how the State would attain and maintain the NAAQS. The requirements for these general SIP's were listed in part A, section 110. In the 1977 CAAA, requirements for implementation plans in nonattainment areas were given in part D ( sections 171 178). These requirements addressed a number of issues including, but not limited to, attainment dates, permit requirements, and planning procedures.

The 1990 CAAA have not made significant changes in the plan requirements for NO2 nonattainment areas ( section 172( c)). For this reason, States may generally continue to rely on past guidance for NO2 programs in meeting those requirements. This position is further supported by the General Savings Clause contained in section 193.

G. New Source Review ( NSR) Nonattainment Permit Requirements This section of the General Preamble describes the new or revised NSR nonattainment permit program requirements under part D of the amended Act and generally explains EPA's interpretation of these requirements. For these new or revised provisions, the provisions discussed below are the minimum statutory requirements States must use to revise their existing NSR nonattainment permit plan provisions ( or to adopt such provisions if none exist) which must be submitted to EPA for approval by the deadlines set forth in the CAAA of 1990. In keeping with past practice, EPA intends to issue regulations setting forth in more detail the requirements for an approvable NSR program.

1. Construction Bans Under the 1977 Amendments to the Act, section 110( a)( 2)( I) of the statute required EPA to place certain nonattainment areas under a federally imposed construction moratorium ( ban) that prohibited the construction of all new or modified major stationary sources in nonattainment areas where the State failed to have an implementation plan meeting all of the requirements of part D of the Act. The amended Act repeals the provisions previously found in section 110( a)( 2)( I). The amended Act also contains a Savings Clause in section 110( n)( 3) that preserves certain existing section 110( a)( 2)( I) construction bans in place before November 15, 1990, if the ban was imposed by virtue of a finding that the plan for the area did not contain an adequate NSR permitting program as required by section 172( b)( 6) of the 1977 Act, or the plan failed to provide for timely attainment of the SO2 NAAQS by December 31, 1982. All other construction bans imposed pursuant to section 110( a)( 2)( I) are lifted as a result of the new statutory provision. In accordance with new section 110( n)( 3), the construction bans that are retained remain in effect until the EPA determines that the SIP meets either the new part D permit requirements or the new requirements for attainment of the NAAQS for SO2 under subpart 5 of part D, as applicable.

Section 173 and the various subparts of title I of the amended Act contain the requirements for issuance of a NSR contruction permit to a new or modified major source in a nonattainment area or ozone transport region. To issue such permits, the permit authority must first find per section 173( a)( 4) that " the Administrator has not determined that the applicable implementation plan is not being adequately implemented for the nonattainment area" in accordance with the requirements of part D. If the Administrator determines that the SIP for the part D requirements is not being adequately implemented for the nonattainment area where the new source or modification wants to locate, permits that would otherwise meet the requirements of section 173 cannot be issued.