6/08/05 1 DRAFT

06/08/2005



### Demonstrating Noninterference Under S ection 110(l) of the Clean Air Act When Revising a State Implementation Plan

1.0 Introduction

Section 110(l) of the Clean Air Act (CAA) indicates that EPA cannot approve a State Implementation Plan (SIP) revision if the re vision would interfere with any applicable requirement concerning attainment and reas onable further progress (RFP), or any other applicable requirement of the CAA. Therefore, the EPA will approve a SIP revision that removes or modifies control measure(s) in the SIP only after the State has demonstrated that such removal or modification will not interfere (“noninterference”) with attainment of the National Ambient air Quality Standards (NAAQS), Rate of Progress (ROP), RFP or any other applicable requirement of the CAA.

Specifically, section 110(l) states:

Each revision to an implementation plan submitted by a State under this Act shall be adopted by such State after reasonable notice and public hearing. The Administrator shall not approve a revision of a plan if the revision would interfere with any applicable requirement concerning attainment and reasonable further progress (as defined in section 171), or any other applicable requirement of this Act.

2.0 What is the purpose of this document?

This document provides guidance to EPA Regional, State, and Tribal air quality management authorities and the general public on how EPA intends to exercise its discretion in implementing CAA provisions and EPA regulations concerning the section 110(l) requirement. It does not impose binding, enforceable requirements on any party, nor does it assure that EPA will approve all instances of its application. Thus, the guidance may not apply to a particular situation based upon the circumstances. Although section 110(l) applies to all applicable CAA requirements, the focus of this guidance is on how a State will demonstrate noninterference relative to attainment and maintenance of the NAAQS. For the most part, it does not address noninterference demonstrations for other CAA requirements. For these requirements, States are advised to work closely with their respective EPA Regional Offices to design an appropriate 110(l)

demonstration.

The EPA and State decision makers retain the discretion to adopt approaches on a case-bycase basis that differ from this guidance, wher e appropriate. Any decisions by EPA regarding a particular SIP demonstration will only be made based on the statute and regulations, and will only be made following notice and opportunity for public review and comment. Therefore, interested parties are free to raise questions and objections about the contents of this guidance6/08/05 2 and the appropriateness of the application of this guidance to a particular situation. EPA will, and States should, consider whether or not the recommendations in this guidance are appropriate in that situation. This guidance is a living document and may be revised periodically without public notice. The EPA welcomes public comments on this document and will consider those comments in any future revisions of this guidance document, providing such approaches comply with all applicable statutory and regulatory requirements.

Users are cautioned not to regard statements recommending the use of certain procedures or defaults as either precluding other procedures or information or providing guarantees that using these procedures or defaults will result in actions that are fully approvable. As noted above, EPA cannot assure that actions based upon this guidance will be fully approvable in all instances, and all final actions may only be taken following notice and opportunity for public

comment.

Documentation which describes each analysis (e.g., databases used, modeling methodology, results, etc.) and explains how it supports a determination of noninterference should be submitted to the appropriate Regional Office. States/Tribes applying this guidance are encouraged to work closely with their Regional Offices to develop a plan for applying the guidance. Obtaining early review of approaches being applied can help assure that resources are not wasted on analyses which may not provide meaningful results.

3.0 Does section 110(l) apply to all areas and to all CAA requirements?

Yes, section 110(l) applies to all requirements of the CAA and to all areas of the country, whether attainment, nonattainment, unclassifiable or maintenance 1 for one or more of the six criteria pollutants: ozone, particulate matter (PM), nitrogen dioxide (NO 2 ), sulfur dioxide (SO 2 ), carbon monoxide (CO) and lead (Pb). As stated earlier, although the focus of this guidance is on

how a State can demonstrate noninterference relative to attainment and maintenance of the NAAQS, section 110(l) is not limited in scope to those SIP revisions that only impact ambient air quality. Thus, when making demonstration of noninterference under section 110(l), States should be mindful that a showing should be made be made not only for attainment and maintenance, but for all other applicable requirements including, but not limited to:

1 Section 110(l) applies to both maintenance plans under s ection 175A and those under section 110(a)(1) that may be required following promul gation of a new NAAQS. • Reasonably Available Control Technology (RACT) requirements

• Inspection and maintenance programs (I/M)

• Major source applicability cut-offs for purposes of RACT

• ROP (1-hour ozone)/RFP (8-hour ozone)6/08/05 3 • Stage II vapor recovery 2

• Clean fuels fleet program under section 183(c)(4) of the CAA

• Clean fuels for boilers under section 183(e)(3) of the CAA

• Transportation Control Measures (TCMs) during heavy traffic hours as provided under section 182(e)(4) of the CAA

• Enhanced (ambient) monitoring under section 182(c)(1) of the CAA

• Transportation controls under section 182(c)(5) of the CAA

• Vehicle miles traveled provisions of section 182(d)(1) of the CAA

• Nitrogen oxides (NO

x ) requirements under section 182(f) of the CAA

• 1-hour attainment demonstrations

• Reasonably Available Control Measures (RACM)

• Contingency measures

• New Source Review 3

• Prevention of Significant Deterioration (PSD) 4

• Air Toxics 5, 6

• Regional Haze under sections 169A and 169B of the CAA

• Inter- and intrastate transport

• New Source Performance Standards

For SIP revisions that will or could potentially lead to a change in emissions or ambient concentrations of a pollutant or its precursors, the section 110(l) demonstration should address all pollutants whose emissions and/or ambient concentrations may change as a result of the SIP revision. For example, while an I/M program originally may have been adopted to address a CO problem, such program may also reduce NO

x and/or volatile organic compound (VOC) emissions. Thus, removal of the I/M program from the SIP may also cause an increase in NO

x and VOC emissions, which may impact ozone and PM 2.5 . These NAAQS would need to be addressed in the 110(l) demonstration, as well as CO.

2 Per section 202(a)(6), this requirement may change as the use of Onboard Refueling Vapor Recovery technology becomes widespread throughout the vehicle fleet.

3 Per Hall v. EPA , 273 F.3d 1146 (9th Cir. 2001), the Agency is curre ntly reviewing how section 110(l) will be met with regard to NSR/PSD revisions. We will provide additional guidance once we have finalized our policy.

4 Class I impacts (Air Quality Related Values under s ection 165(d)(2)) as well as PSD increment consumption.

5 Since there are no ambient air quality standards for air toxics, the area’s compliance with any applicable MACT standards, as well as any Federal mobile source contro l requirements under sections 112 or 202(l) would constitute an acceptable demonstration of noninterference fo r air toxics.

6 Section 110(l) does not require a demons tration of noninterference for changes to Federal requirements that are not
included in the SIP. A revision to the SIP, however, cannot interfere with any Federally mandated program such as a MACT standard (or related section 112 requirements), or Reid Vapor Pressure.6/08/05 4 Similarly, and as further discussed in section 3.2 below, although section 110(l) does not require a showing of noninterference with a revoked NAAQS, if there is a measure remaining in the SIP related to that NAAQS, the State will need to show noninterference with any other relevant or applicable CAA requirements, incl uding other NAAQS that may be impacted, before EPA can approve removal of the measure from the SIP.

3.1 Can any control measure be removed from a SIP?

Some control measures may not be removed from a SIP even if doing so would not interfere with the Clean Air Act’s air quality goals. These measures are often referred to as “mandatory” measures because the CAA requires that they be included in the SIP for an area based on the area’s designation status and classification. For example, the CAA specifies that an area classified as moderate for ozone must implement a basic tailpipe I/M program. An ozone nonattainment area classified as Serious is required to implement an enhanced ambient air monitoring system.

If an area is redesignated from nonattainment to attainment, specific control measures that applied based on the area’s classification i.e., mandatory measures, will no longer be required. At that point, it may be possible for the State to remove the measure from the SIP, provided noninterference is demonstrated under section 110(l). 7

Measures not tied to an area’s classificati on and not mandated by the CAA are often referred to as “discretionary” measures. States can remove discretionary measures from an attainment, nonattainment or maintenance plan. However, a section 110(l) demonstration of noninterference would still be required.

In addition, the following sections of the CAA may prohibit an area from completely removing a control measure:

• “General Savings Clause” (Section 193). Control measures in effect or required to be adopted in nonattainment areas by an order, settlement agreement, or plan in effect before the 1990 CAA amendments in nonattainment areas may not be removed or modified absent a SIP revision that ensures equivalent or greater emissions reductions.

7 It is important to note that section 175A(d) requires that any control measure removed from the SIP be retained as a contingency measure in the maintenance plan. • “ Significant Interstate Contribution” (Section 110(a)(2)(D)). Control measures approved into the SIP to meet Federal regulations, such as the 1998 NO

x SIP Call under section 110(a)(2)(D) may be substituted with other measures, but only if the requirements of the Federal regulations (e.g., the statewide NO

x emission budget) continue to be met.6/08/05 5 • “Interstate Ozone Transport Region” (OTR) (Section 176A and Section 184). Unless an area has fully or partially opted out from the OTR, control measures that apply in ozone transport regions are mandated controls and cannot be removed from the SIP. Areas that have opted out and wish to remove an OTR m easure from the SIP must make a section 110(l) demonstration of noninterference before removing the measure.

States should keep in mind that EPA approval of a section 110(l) demonstration to remove a measure does not mean that additional control measures might not be needed in the future to demonstrate attainment or maintenance, or to meet RFP requirements. In particular, this will be the case where a 110(l) demonstration precedes an attainment demonstration that is required by

the CAA based on an area’s classification.

3.2 How does revocation of a NAAQS affect removal or modification of a measure?

The final 8-hour ozone implementation rule (40 CFR §51.905) ("Phase 1 Rule") contains anti-backsliding provisions that require areas that were designated as nonattainment or attainment but subject to a maintenance plan under section 175A for the 1-hour ozone standard at the time of designation for the 8-hour standard retain in their SIPs (or to submit, if not yet approved into the SIP) certain obligations that applied by virtue of their 1-hour ozone designation and classification. These requirements are called "applicable requirements" under the Phase 1 Rule. Areas remain subject to these obligations until they attain and are redesignated to attainment for the 8-hour ozone NAAQS. 8 EPA believes that a similar approach would be appropriate with respect to other revoked standards.

Obligations in an approved SIP that are not "applicable requirements" under the Phase 1 Rule may be modified or removed, but only in conj unction with a demonstration of noninterference under section 110(l). This guidance applies whenever a State modifies a SIP in a manner that requires a section 110(l) demonstration, to SI P changes that States pursue under 40 CFR §51.905 (8-hour ozone implementation rule), as well as to any other subsequent rules to implement a new NAAQS.

Additionally, under the Phase 1 Rule, an area that was designated attainment subject to a maintenance plan for the 1-hour standard at the time of designation to attainment for the 8-hour standard may modify its contingency measures in the 1-hour maintenance plan, but only in conjunction with a section 110(a)(1) maintenance plan for the ozone 8-hour standard (see 69 FR 23999, April 30, 2004). The revision to remove or modify a contingency measure could occur at the same time that EPA approves the area’s 110(a)(1) maintenance plan, and EPA believes that the section 110(a)(1) maintenance plan showing maintenance without the measure at issue, or

8 Note that §51.372(c) of EPA’s I/M rule (60 FR 1735) allows areas that would otherwise qualify for redesignation to attainment to convert their basic I/M program to a contingency measure as long as implementation authority is retained and an I/M program is not required under a new NAAQS. See memo from Tom Helms and Leila Cook, “1-Hour Ozone: Maintenance Plans: Basic Inspection and Maintenance Programs,” dated 5-12-04 at http://www.epa.gov/ttn /oarpg/t1pgm.html.6/08/05 6 with the measure as modified, could serve as an acceptable 110(l) demonstration for the 8-hour ozone NAAQS.

4.0 How can a State or Tribe demonstrate noninterference? As stated earlier, other CAA requirements may apply to a given SIP and will require a

section 110(l) demonstration. It would not be feasible for the Agency to develop a document that provides guidance on how to make a demonstrati on of noninterference for every applicable CAA requirement that might apply. For this reason, this document thus focuses on the means by which States or Tribes can demonstrate noninterference relative to the CAA requirements of attainment, RFP and maintenance of the NAAQS. To the extent that this guidance does not address other CAA requirements that may apply to an area, States and Tribes are advised to work closely with their respective EPA Regional Offices to determine an appropriate 110(l)

demonstration.

With respect to attainment, maintenance and RFP, the Agency interprets section 110(l) such that areas have two options available to demonstrate noninterference for the affected pollutant(s). As discussed below, these options are: 1) Substitution of one measure by another with equivalent or greater emissions reductions/air quality benefit; or 2) an air quality analysis showing that removing the measure will not interfere with other applicable requirements (i.e., without a substitute measure). These options, discussed in more detail in Sections 5 and 6 below, are available to all areas, whether the requested action is to remove or modify an area-wide control measure, a state-wide control measure or a control measure at a single source.

When demonstrating noninterference, attainment areas (including maintenance areas) have the same options as nonattainment areas. The scope and rigor of the demonstration will depend on the nature of the requirement, the air quality status of the area, the potential impact of the revision on air quality and the pollutant(s) affected.

EPA retains the discretion to adopt approaches on a case-by-case basis that may differ from the general parameters provided herein, but which still comply with the CAA. Any decisions regarding a particular determination will be made based on the statute, regulations and technical

rationale.

5.0 What is the substitution option? Under the substitution option, the State removes a measure from the SIP and substitutes it with another measure that achieves equivalent or greater emission reductions. The basic principle of the substitution approach is that as long as the status quo in air quality is preserved, noninterference is demonstrated. To support th e substitution, the State should provide EPA with an analysis showing that removal or revision of the SIP measure does not interfere with any other applicable requirements of the Act. Substitute measures should be quantifiable, permanent, surplus, enforceable and contemporaneous (when the substitute is a new measure).

EPA does not believe that it is reasonable nor practical to require air quality modeling to support the substitution in all cases. The most straightforward approach would be “direct6/08/05 7 substitution” in which increases in a pollutant resulting from the SIP revision are offset with reductions from a replacement measure that achieves equivalent or greater emission reductions of the same pollutant. Examples would include substitution of one VOC control measure for another, NO

x for NO x, SO 2 for SO 2 and so on. A simple scenario would also involve substituting low-level emission reductions for low-level emissions reductions, or elevated emissions reductions for elevated emissions reductions. In such cases, substituting with an alternative control measure that obtains equivalent or gr eater emission reductions of the same pollutant could be considered an acceptable demonstration of noninterference. Additional technical analysis may not be needed.

In other cases, due to the uncertainty of predicting pollutant interactions, even when substituting with emissions reductions of the same pollutant or precursor, the EPA may determine that air quality modeling is necessary. Factors that could necessitate modeling include:

• A large distance between affected sources

• A large discrepancy in elevation of emissions between the affected sources •An update of emissions data in the SIP results in a large difference between the existing emissions inventory 9 and the emissions inventory that is presented in the noninterference

demonstration

• A significant portion of the area’s total emissions is under consideration for substitution

If an area chooses to substitute with a different pollutant or precursor, additional analysis would be necessary. The type of analysis warranted by interpollutant and interprecursor

substitutions is discussed further in section 5.3.

5.1 Substitution with existing measures

An area can use either an existing or a new control measure as a substitute however, in order to use an existing measure (i.e., one that is already obtaining emissions reductions) as a substitute, the area should have an approved attainment/maintenance demonstration in order to ascertain that the emissions reductions from the existing control measure are indeed surplus and haven’t been relied on previously for attainment or maintenance of the NAAQS, 10 or to meet ROP/RFP requirements.

As is the case with existing local or State measures, Federal measures can serve as substitution measures as well, provided their reductions were not previously relied on for credit

9 Note that the Consolidated Emissions Reporting Rule (CERR) (67 FR 39602) requires all States and territories, irrespective of air quality status, to submit 3-year inventories for the following pollutants: SOx, NO

x , VOC, CO,

PM 10 , PM 2.5 , NH 3 . Areas using the substitution option but which have an outdated inventory can use a 3-year inventory under CERR as part of th eir section 110(l) demonstration.

10 In addition, a demonstration is needed to show that the increase in emissions would not interfere with attainment or maintenance of any affected NAAQS not c overed by the attainment/maintenance plan.6/08/05 8 toward attainment, maintenance or ROP/REF purposes (i.e., the reductions are surplus).

5.2 Substitution with new measures

EPA believes that if emissions reductions removed from the SIP are replaced with new control measures that achieve equivalent or greater emissions reductions, the SIP revision will not interfere with the area’s ability to continue to attain or maintain the affected NAAQS or other CAA requirements. 11

Timing . New substitute control measures should be contemporaneous to the time when the emissions reductions from the measure that was removed or modified cease occurring. The EPA recognizes that, in reality, implementation of a substitute control measure may not coincide exactly with removal or modification of the “old” measure. Keeping this in mind, the substitute control measure should go into effect close enough in time to the SIP revision such that the timing is reasonable enough to be considered contemporaneous, thus preserving the status quo in air quality. For this reason, the Agency advises States to build into their demonstration a reasonable amount of time to terminate old measures and implement any new replacement measures. Determination of “contemporaneous” will be made case-by-case within the context of a rulemaking approving the substitution. Note that the further apart in time implementation of the substitute measure is from removal of the old measure(s), the more difficult it will be to defend the substitution as contemporaneous.

5.3 When substituting one pollutant or precursor for another

When offsetting an increase in a pollutant or precursor with reductions of another pollutant or precursor, States should provide a more detailed technical analysis that includes air quality modeling 12 to show that the substitution will provide equivalent or greater air quality benefit for each NAAQS that is affected by the SIP revision.

For ozone, substitutions involving VOC and NO X measures can be complex, depending on many case-specific factors such as whether the area is NO X or VOC-limited, for example. For

PM 2.5 , the interaction between SO 2 , NO

x , VOC, ammonia and direct PM 2.5 emissions in the formation of fine particulate matter can be even more complex, and much is still not known about the pollutant interactions that form PM 2.5 . Currently, relative effects on PM 2.5 concentrations due to changes in SO 2 and NO X emissions are generally better understood than

the effects on PM 2.5 concentrations resulting from changes in VOC and ammonia emissions. New information on important PM-related research (such as the role of specific VOC species in

PM 2.5 formation and better quantification of ammonia inventories) continues to emerge. For

11 In some cases, additional factors need to be considered e.g., interprecursor substitution.

12 Appropriate air quality models for predicting changes in ozone and PM 2.5 concentrations include CMAQ and CAMx. States should also consult the air quality m odeling tools and resources available for download at www.epa.gov/scram001/tt25.htm#guidance.6/08/05 9 these reasons, substitution decisions should be made on a case-by-case basis. States should always take into account the latest scientific information when considering inter-pollutant

substitution.

In general, direct PM 2.5 emission reductions may be substituted for PM 2.5 precursors. It would be appropriate to substitute emissions reductions from ammonia or VOC sources only where an area provides an adequate technical demonstration showing that such pollutants

contribute to PM 2.5 levels in the area.

The technical demonstration for complex substitutions such as these should include these principles:

• The substitution should be consistent with any existing attainment demonstrations and plans to address rate-of-progress or reasonable further progress requirements for the area.

• The State should provide exchange ratios 13 for the affected pollutants that are supported either by modeling or by other technical analyses. 14

• In addition, for substitution cases involving PM 2.5 precursors:

13 Exchange ratios indicate the relative e ffect of different precursors on air quality in a specific nonattainment area.

14 NO

x Substitution Guidance at http://www.epa.gov/ttn/naaq s/ozone/ozonetech/#nox (scroll down to item 6.s.,

“NO

x Substitution Guidance 12-15-93"). This policy offers one method of determining ratios for precursor substitution that may be appropriate, depending on the characteristics of the area in question. Substitution ratios may also be estimated using various air quality modeling tools by assessing the relative impact of reducing one

PM 2.5 precursor versus another by equal amounts or percentages. Any proposed substitution of an existing measure with a measure achieving SO 2 , NO X , or direct PM 2.5 emissions reductions should show that the substitute measure achieves equivalent or greater air quality benefit. Any proposed substitution of an existing measure with a measure achieving VOC

and/or ammonia emissions reductions should show that 1) VOC and/or ammonia are significant contributors to the area’s PM 2.5 concentration; and 2) that the substitute measure achieves equivalent or greater air quality benefit. Any proposed substitution that removes one measure and substitutes it with a new

measure that reduces a PM 2.5 precursor should also address the same PM 2.5 precursor in

its PM 2.5 control strategy. For example, if an area chose to demonstrate noninterference6/08/05 10 for PM 2.5 by substituting NO X reductions with all VOC reductions, the EPA would expect the area to include VOC in the area’s overall PM 2.5 control strategy. If a proposed substitution measure includes VOC reductions for purposes of addressing ozone but the State finds that VOC are not a significant contributor to PM 2.5 in the area, then the State should also obtain reductions of a different PM 2.5 precursor (such as SO 2 ) to address noninterference for PM 2.5 . Another option would be for the area

to substitute with direct PM 2.5 emissions reductions.

5.4 Can substitute emissions reductions be obtained from outside the nonattainment or maintenance area boundary?

Yes. As discussed in EPA’s Clean Air Interstate Rule proceedings, 15 PM 2.5 and ozone are the result of emissions from many sources over a multi-State region. Emissions of NO

x and VOC (as ozone precursors) and emissions of NO

x and SO 2 (as PM 2.5 precursors), are well quantified for many urban and regional sources. Furthermore, the transport of these emissions can also be quantified with a fair degree of certainty. Because both ozone and PM 2.5 formation occur as the result of emissions from many sources over a multi-State region, regional controls for these emissions can result in significant benefits. The Agency thus concludes that it is appropriate to allow ozone and PM 2.5 areas to obtain substitute emissions reductions from sources located outside the nonattainment or maintenance area boundary, provided the State can demonstrate that the substitute measure provides the same air quality benefit as that being replaced.

For example, under current EPA policy, an ozone area can obtain replacement measures located up to 100 and 200 kilometers from the nonattainment area for VOC and NO

x reductions, respectively. 16 The distances in the guidance provide only a general policy presumption that, if used, would need to be supported by technical rationale showing that the result will produce equal or greater air quality benefit in the area and that the substitution will not interfere with any other area’s ability to attain or maintain the NAAQS. The Agency intends to reassess whether the policy should be revised in light of concerns recently brought to our attention pertaining to its technical feasibility.

15 http://www.epa.gov/cair/rule.html

16 “Guidance for Implementing the 1-Hour Ozone and Pre-Existing PM 10 NAAQS,” December 29, 1997, http://www.epa.gov/ttn/oar pg/t1/memoranda/iig.pdf 6.0 What is the air quality analysis option?6/08/05 11 Under this option, the State would conduct air quality modeling or develop an attainment or maintenance demonstration based on EPA’s most recent technical guidance 17,18 to show that even without the control measure or with the measure in its modified form, the area (as well as interstate and intrastate areas downwind) can continue to attain/maintain the NAAQS. An area seeking redesignation could also use this approach when removing a measure from the nonattainment SIP and adding it to the contingency portion of the maintenance SIP. Under this scenario, the maintenance demonstration submitted with the redesignation request would serve as the section 110(l) showing for the pollutant covered by the maintenance plan. The maintenance demonstration would need to show that the area can maintain the NAAQS without the measure in question. Additional demonstrations of noninterference would be required for any other affected NAAQS not covered by the maintenance plan.

Depending on the nature of the SIP revision, an area may need additional technical guidance. Consultation with the Regional Office and the Model Clearinghouse is recommended prior to a 110(l) demonstration to support removal or revision of a SIP requirement under any of the options. In addition, Appendix W to 40 CFR Part 51 19 (“Guideline on Air Quality Models”) contains general criteria that States should consider.

6.1. Can I conduct alternative analyses in lieu of air quality modeling?

For areas that don’t have an attainment demonstration, the EPA would consider alternative analyses such as sensitivity modeling using the Community Multiscale Air Quality (CMAQ) Modeling System, Comprehensive Air Quality Model with Extensions (CAMx) or other dispersion models on a case-by-case basis. In rare cases, other indicators such as ambient air quality analyses, air quality trends and emissions trends to create a base-case scenario may be

considered. 20 The level of rigor in the demonstration will vary depending on the nature of the requirement, its potential impact on air quality in the area and the air quality of the area in which the requirement applies.

For example, for certain pollutants such as CO, the Agency could determine that an increase in emissions is not interfering with attainment if ambient levels in an attainment area were well below the NAAQS and not trending upward. Under th ese conditions, the Agency could conclude that ambient levels are so low that a slight emissions increase is not likely to cause a violation of the NAAQS, hence noninterference has been demonstrated.

17 EPA modeling guidance for 8-hour ozone, PM 2.5 and Regional Haze are available at http://www.epa.gov/scram 001/tt25.htm#guidance

.

18 “ Procedures for Processing Requests to Redesignate Areas to Attainment,” Sept. 4, 1992 at http://www.epa.gov/ttn/o arpg/t5/memoranda/redesignmem090492.pdf.

19 Available at http://www.epa.gov/scram001/guidance/guide/appw_03.pdf

.

20 One resource for PM 10 demonstrations is “Critical Design Value Es timation and its Applications,” by Shao-hang

Chu at http://www.epa.gov/ttn/oar pg/t1/memoranda/cdv.pdf

.6/08/05 12 6.2 Which NAAQS and precursors do I need to include in my air quality analyses?

Depending on the number of pollutants that are affected by removal or modification of the control measure in question, an area may need to demonstrate that the change would not interfere with attainment or maintenance for more than one NAAQS. For example, removal of an I/M program that tested for CO, hydrocarbons and NO

x would require a demonstration of noninterference for the following NAAQS: CO, ozone, PM 10 and PM 2.5 . As noted above, the State could demonstrate noninterference through air quality modeling, an attainment demonstration, or in some situations as discussed in section 6.1 above, an alternative analysis not involving air quality modeling.

The following guidance should be considered in cases where removal of a measure results in an increase in a PM2.5 precursor. If the State conducts air quality modeling to demonstrate noninterference, the state should include the proj ected change in all PM2.5 precursors, including VOC and ammonia, in the emission inventory used for the air quality modeling scenario simulating conditions after the measure has been removed. This approach would best represent

the overall interaction of increased PM 2.5 precursor levels and the resulting air quality concentration. If the State chooses to perform an alternative analysis to demonstrate noninterference however, then the State should evaluate the resulting increase in emissions of

SO 2 , NO X , and direct PM 2.5 presumptively. Regarding VOC and/or ammonia, the State should evaluate noninterference for these pollutants only if the State or EPA had provided a demonstration showing that VOC and/or a mmonia was a significant contributor to PM 2.5 concentrations in the area in question. States are advised to consult with their respective EPA Regional Office for additional guidance on these issues.

6.3 Do I need to demonstrate noninterference relative to transport?

Yes. Section 110(l) requires a demonstration of noninterference with respect to section 110(a)(2)(D) requirements relating to interstate transport. The Agency believes areas that are subject to Federal regulations under section 110(a)(2)(D), such as the NO

x SIP Call Rule or the Clean Air Interstate Rule, satisfy section 110(l) with respect to interstate transport for that pollutant or precursor, where the requirements of the Federal regulations (i.e., the statewide emission budgets) are being met.

In addition, section 110(a)(1) requires a SIP to provide for implementation and maintenance of a primary standard within the State. To satisfy section 110(l) with respect to intrastate transport, EPA believes the State should show that the revision is consistent with any attainment or maintenance plan in a downwind area elsewhere in the State.

7.0 Are there other considerations for either option?

Yes. The following guidance applies whether an area is demonstrating noninterference through substitution or through air quality analysis.6/08/05 13 7.1 SIP revisions that are administrative in nature

Some SIP elements, such as public hearing requirements, are clearly administrative or procedural, and changes to them will not affect emissions. For SIP revisions of this nature, the two options may not be relevant. Instead, an acceptable 110(l) demonstration might only require written analysis explaining that the revision is: (a) administrative or procedural in nature; (b) will not affect emissions; and (c) will not interfere with requirements of the CAA related to such administrative or procedural provisions.

7.2 Compliance assurance requirements

Other SIP requirements such as monitoring, record keeping, reporting and additional compliance assurance requirements, may have an impact on the amount of pollutants emitted because they are instrumental in detecting violations of emissions limits. However, it may be difficult to quantify the effects of revising these SI P elements or to use either of the options for demonstrating noninterference described above. For changes to these types of SIP elements, States are advised to work closely with thei r respective EPA Regional Offices to design an appropriate 110(l) demonstration.

Note that CAA section 110(a) requires enforceable emissions limits and monitoring and that EPA has long interpreted the CAA, through regulations and policies, to require monitoring, record keeping, reporting and other compliance assurance measures in SIPs. Thus, at a minimum, any 110(l) demonstration should show that revised compliance assurance provisions do not interfere with these CAA requirements.

7.3 Other

Changes to opacity regulations are subject to section 110(l) and will be addressed on a caseby-case basis as part of the Agency’s examination of each request. In addition, SIP revisions that extend compliance deadlines and revise motor vehicle emissions budgets for transportation conformity purposes are subject to section 110(l).