ENVIRONMENTAL PROTECTION AGENCY

40 CFR Part 52

EPA-R06-0AR-2007-0993; FRL- -l

Approval and Promulgation ofImplementation Plans;

New Mexico; Interstate Transport of Pollution

AGENCY: Environmental Protection Agency (EPA).

ACTION: Final rule.

SUMMARY: EPA is approving a portion of a State Implementation Plan (SIP) submitted by

the State ofNew Mexico for the purpose of addressing the "good neighbor" provisions ofthe

Clean Air Act (CAA) section 11O(a)(2)(D)(i) for the 1997 ozone National Ambient Air Quality

Standard (NAAQS) and the 1997 PM 2.5 NAAQS. This SIP revision satisfies a portion ofthe

State ofNew Mexico's obligation to submit a SIP that demonstrates that adequate provisions are

in place to prohibit air emissions from adversely affecting another state's air quality through

interstate transport. This rulemaking action is being taken under section 110 ofthe CAA and

addresses one element ofCAA section 110 (a)(2)(D)(i), which pertains to prohibiting air

pollutant emissions from within New Mexico from contributing significantly to nonattainment of

the 1997 8-hour ozone and PM 2.5 NAAQS in any other state.

DATES: This final rule will be effective [Insert date 30 days from date of publication in the

Federal Register].
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ADDRESSES: EPA has established a docket for this action under Docket Identification No.

EPA-R06-0AR-2007-0993. All documents in the docket are listed at www.regulations.gov.

Although listed in the index, some information is not publicly available, e.g., Confidential

Business Information or other information whose disclosure is restricted by statute. Certain

other material, such as copyrighted material, is not placed on the Internet and will be publicly

available only in hard copy form. Publicly available docket materials are available either

electronically through www.regulations.gov or in hard copy at the Air Planning Section (6PD-L),

Environmental Protection Agency, 1445 Ross Avenue, Suite 700, Dallas, Texas 75202-2733.

The file will be made available by appointment for public inspection in the Region 6 Freedom of

Information Act (FOIA) Review Room between the hours of 8:30am and 4:30pm weekdays

except for legal holidays. Contact the person listed in the FOR FURTHER INFORMATION

CONTACT paragraph below or Mr. Bill Deese at 214-665-7253 to make an appointment. If

possible, please make the appointment at least two working days in advance of your visit. There

will be a 15 cent per page fee for making photocopies of documents. On the day ofthe visit,

please check in at the EPA Region 6 reception area at 1445 Ross Avenue, Suite 700, Dallas,

Texas.

FOR FURTHER INFORMATION CONTACT: Emad Shahin, Air Planning Section (6PDL), Environmental Protection Agency, Region 6, 1445 Ross Avenue, Suite 700, Dallas, Texas

75202-2733, telephone (214) 665-6717; fax number (214) 665-7263; e-mail address

shahin.emad@epa.gov.
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SUPPLEMENTARY INFORMATION: Throughout this document wherever "we," "us," or

"our" is used, we mean the EPA.

OUTLINE:

I. What Action is EPA Taking?

II. What is the Background for this Action?

III. What Comments did EPA Receive and how has EPA Responded to them?

IV. Final Action

V. Statutory and Executive Order Reviews

I. What Action is EPA Taking?

We are approving a portion ofthe submission from the State ofNew Mexico

demonstrating that New Mexico has adequately addressed one ofthe required elements ofthe

CAA section 11O(a)(2)(D)(i), the element that prohibits air pollutant emissions from sources

within a state from contributing significantly to nonattainment ofthe relevant NAAQS in any

other state. We have determined that emissions from sources in New Mexico do not

significantly contribute to nonattainment ofthe 1997 8-hour ozone NAAQS or the 1997 PM 2.5

NAAQS in any other state. Because emissions from sources in New Mexico do not significantly

contribute to nonattainment in any other state, section 11O(a)(2)(D)(i)(I) does not require any

substantive changes to New Mexico's SIP.

The remaining three elements ofsection 11O(a)(2)(D) are that a state's SIP contain adequate

provisions to prevent: interference with maintenance ofthe NAAQS in any other state;

interference with measures required to prevent significant deterioration of air quality in any other
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state; and interference with measures required to protect visibility in any other state. EPA will

evaluate the New Mexico SIP and SIP submissions for compliance with these other requirements

ofsection 11O(a)(2)(D) for the 1997 8-hour ozone and 1997 PM2.5 NAAQS in future

rulemakings.

II. What is the Background for this Action?

On July 18, 1997, EPA promulgated new standards for 8-hour ozone and fine particulate

matter (PM2.5). This action is being taken in response to the July 18, 1997 revision to the 8-hour

ozone NAAQS and PM 2.5 NAAQS. This action does not address the requirements for the 2006

PM2.5NAAQS or the 2008 8-hour ozone NAAQS; those standards will be addressed in a later

action.

Section 110(a)(l) ofthe CAA requires states to submit SIPs to address a new or revised

NAAQS within 3 years after promulgation ofsuch standards, or within such shorter period as

EPA may prescribe. Section 11O(a)(2) lists the elements that such new SIPs must address, as

applicable, including section 11O(a)(2)(D)(i) which pertains to interstate transport of certain

emissions. On August 15,2006, EPA issued its "Guidance for State Implementation Plan (SIP)

Submission to Meet Current Outstanding Obligations Under Section 11O(a)(2)(D)(i) for the 8-

Hour Ozone and PM2.5 National Ambient Air Quality Standards" (2006 Guidance) for SIP

submissions that states should use to address the requirements ofsection 110(a)(2)(D)(i). EPA

developed this guidance to make recommendations to states for making submissions to meet the

requirements ofsection 110(a)(2)(D) for the 1997 8-hour ozone NAAQS and 1997 PM2.5

NAAQS.
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On September 17,2007, EPA received a SIP submission from the State ofNew Mexico

to address the requirements ofsection 110(a)(2)(D)(i) for both the 1997 8-hour ozone NAAQS

and 1997 PM2.5 NAAQS. The state based its submittal on EPA's 2006 Guidance. As explained

in the 2006 Guidance, the "good neighbor" provisions in section 11O(a)(2)(D)(i) require each

State to submit a SIP that contains adequate provisions to prohibit emissions from sources within

that state from adversely affecting another state in the ways contemplated in the statute. Section

11O(a)(2)(D)(i) contains four distinct requirements related to the impacts ofinterstate transport.

In this rulemaking EPA is addressing only the requirement that pertains to preventing sources in

the state from emitting pollutants in amounts which will contribute significantly to

nonattainment ofthe 1997 8-hour ozone NAAQS and the 1997 PM2.5 NAAQS in any other state.

In its submission, the State ofNew Mexico indicated that its current SIP is adequate to prevent

such significant contribution to nonattainment in ariy other state, and thus no additional

emissions controls are necessary at this time to alleviate interstate transport.

On April 8, 2010, we published a direct final rule and a parallel proposal to approve the

portion ofNew Mexico's SIP submission that addressed one element ofthe CAA section

11O(a)(2)(D)(i), which pertains to prohibiting air pollutant emissions from within New Mexico

from contributing significantly to nonattainment ofthe 1997 8-hour ozone and 1997 PM2.5

NAAQS in any other state (75 FR 17868). The direct final rule and proposal stated that ifEPA

received any relevant adverse comments during the public comment period ending on May 10,

2010, then EPA would withdraw the direct final rule and respond to such comments in a

subsequent final action based upon the proposal. EPA received adverse comments during the

comment period, and accordingly EPA withdrew the direct final rule on May 3, 2010 (75 FR

23167). The April 8,2010, proposal (75 FR 17894) provides the basis for today's final action.
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III. What Comments did EPA Receive and how has EPA Responded to them?

EPA received three comment letters on the April 8,2010, direct final rule and proposal.

The letters can be found on the internet in the electronic docket for this action. To access the

letters, please go to http://www.regulations.gov and search for Docket No. EPA-R06-0AR-2007-

0993, or contact the person listed in the FOR FURTHER INFORMATION CONTACT

paragraph above. The discussion below addresses those comments and our response.

A. Comments from WildEarth Guardians.

Comment No.1 - The commenter argued that New Mexico and EPA did not appropriately

assess impacts to nonattainment in downwind states. According to the commenter, New Mexico

failed to assess the significance of downwind impacts in accordance with EPA precedent and

refers to the 1998 NOx SIP Call.

EPA Response - EPA disagrees with the commenter on this point. Section 110(a)(2)(D)

does not explicitly specify how states or EPA should evaluate the existence of, or extent of,

interstate transport and whether interstate transport is ofsufficient magnitude to constitute

"significant contribution to nonattainment" as a regulatory matter. The statutory language is

ambiguous on its face and EPA must reasonably interpret that language when it applies it to

factual situations before the Agency.

EPA agrees that the NOx SIP Call is one rulemaking in which EPA evaluated the

existence of, and extent of, interstate transport. In that action, EPA developed an approach that

allowed the Agency to evaluate whether there was significant contribution to ozone

nonattainment across an entire region that was comprised ofmany states. That approach
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included regional scale modeling and other technical analyses that EPA deemed useful to

evaluate the issue ofinterstate transport on that geographic scale and for the facts and

circumstances at issue in that rulemaking. EPA does not agree, however, that the approach of

the NOx SIP Call is the only way that states or EPA may evaluate the existence of, and extent of,

interstate transport in all situations, and especially in situations where the state and EPA are

evaluating the question on a state by state basis, and in situations where there is not evidence of

widespread interstate transport.

Indeed, EPA issued specific guidance with recommendations to states about how to

address section 11O(a)(2)(D) in SIP submissions for the 1997 8-hour ozone NAAQS. EPA

issued this guidance document, entitled "Guidance for State Implementation Plan (SIP)

Submissions to Meet Current Outstanding Obligations Under Section 11 0(a)(2)(D)(i) for the 8-

Hour Ozone and PM2.5 National Ambient Air Quality Standards" on August 15,2006.1 This

guidance document postdated the NOx SIP Call, and was developed by EPA specifically to

address SIP submissions for the 1997 8-hour ozone NAAQS.

Within the 2006 Guidance, EPA notes that it explicitly stated its view that the "precise

nature and contents ofsuch a submission [are] not stipulated in the statute" and that the contents

ofthe SIP submission "may vary depending upon the facts and circumstances related to the

specific NAAQS.,,2 Moreover, within that guidance, EPA expressed its view that "the data and

analytical tools available" at the time ofthe SIP submission "necessarily affect the content ofthe

required submission.") To that end, EPA specifically recommended that states located within the

1 Memorandum from William T. Harnett entitled Guidance for State Implementation Plan (SIP) Submissions to

Meet Current Outstanding Obligations Under Section 110(a)(2)(D)(i) for the 8-hour Ozone and PM2.5 National

Ambient Air Quality Standards (Aug. 15,2006) ("2006 Guidance"); p. 3.

2Id. at 3.

31d.
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geographic region covered by the Clean Air Interstate Rule (CAIR)4 comply with section

11O(a)(2)(D) for the 1997 8-hour ozone NAAQS by complying with CAIR itself. For states

outside the CAIR rule region, however, EPA recommended that states develop their SIP

submissions for section 11O(a)(2)(D)considering relevant information.

EPA explicitly recommended that relevant information for section 11O(a)(2)(D)

submissions addressing significant contribution to nonattainment "might include, but is not

limited to, information concerning emissions in the State, meteorological conditions in the State,

the distance to the nearest nonattainment area in another State, reliance on modeling conducted

by EPA in determining that such State should not be included within the ambit ofthe CAIR, or

such other information as the State considers probative on the issue ofsignificant contribution.t"

In addition, EPA recommended that states might elect to evaluate significant contribution to

nonattainment using relevant considerations comparable to those used by EPA in CAIR,

including evaluating impacts as ofan appropriate year (such as 2010) and in light ofthe cost of

control to mitigate emissions that resulted in interstate transport.

The commenter did not acknowledge or discuss EPA's actual guidance for section

110(a)(2)(D) SIP submissions for the 1997 8-hour ozone NAAQS, and thus it is unclear whether

the commenter was aware ofit. In any event, EPA believes that the New Mexico submission

and EPA's evaluation ofit is consistent with EPA's guidance for the 1997 8-hour ozone

NAAQS. For example, as discussed in the direct final notice, the State ofNew Mexico and EPA

considered information such as monitoring data in other states, geographical and meteorological

information, and technical studies ofthe nature and sources of nonattainment problems in

4 In this action the expression "CAIR" refers to the [mal rule published in the May 12,2005 Federal Register and

entitled "Rule to Reduce Interstate Transport ofFine Particulate Matter and Ozone (Clean Air Interstate Rule);

Revisions to Acid Rain Program; Revisions to NOx SIP Call; Final Rule" (70 FR 25162).

5 Id. at 5.
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various downwind states. These are among the types ofinformation that EPA recommended and

that EPA considers relevant. Thus, EPA has concluded that the State's submission, and EPA's

evaluation ofthat submission, meet the requirements ofsection llO(a)(2)(D) and are consistent

with applicable guidance.

Finally, EPA notes that the considerations the Agency recommended to states in the 2006

Guidance are consistent with the concepts ofthe NOx SIP Call referenced by the commenter:

(a) the overall nature ofthe ozone problem; (b) the extent of downwind nonattainment problems

to which upwind state's emissions are linked; (c) the ambient impact ofthe emissions from

upwind States' sources on the downwind nonattainment problems; and (d) the availability of

high cost-effective control measures for upwind emissions. The only distinction in the case of

the New Mexico submission at issue here would be that because the available evidence indicates

that there is so very little contribution of emissions from New Mexico sources to nonattainment

in other states, it is not necessary to advance to the final step and evaluate whether the cost of

controls for those sources is above or below a certain cost of control as part of determining

whether the contribution constitutes "significant contribution to nonattainment" for regulatory

purposes, as was necessary in the NOx SIP Call and in CAIR.

Comment No.2 - The commenter believes that New Mexico and EPA did not

appropriately assess impacts to nonattainment in downwind states in terms of air quality.

Specifically, the commenter objected to EPA's proposed approval because New Mexico assessed

impacts in downwind states by considering only areas that had monitoring data as for evaluating

significant contribution to nonattainment. In other words, the commenter is concerned that New

Mexico did not assess impacts in areas that have no monitor. The commenter implied that this
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reliance on monitor data is inconsistent with both section 11O(a)(2)(D) and with EPA's guidance,

by which the commenter evidently means the NOx SIP Call. In support ofthis assertion, the

commenter quoted from the NOx SIP Call proposal in which EPA addressed the proper

interpretation ofthe statutory phrase "contribute significantly to nonattainment:"

"The EPA proposes to interpret this term to refer to air quality and not to be limited to

currently-designated nonattainment areas. Section 11O(a)(2)(D)does not refer to

'nonattainment areas,' which is a phrase that EPA interprets to refer to areas that are

designated nonattainment under section 107(section 107(d)(I)(A)(I»"

According to the commenter, this statement, and similar ones in the context ofthe final NOx SIP

Call rulemaking, establish that states and EPA cannot utilize monitoring data to evaluate the

existence of, and extent of, interstate transport. Furthermore, the commenter interprets the

reference to "air quality" in these statements to support its contention, amplified in later

comments, that EPA must evaluate significant contribution in areas in which there is no

monitored nonattainment.

EPA response - EPA disagrees with the commenter's arguments. First, the commenter

misunderstands the point that EPA was making in the quoted statement from the NOx SIP Call

proposal (and that EPA has subsequently made in the context ofCAIR). When EPA stated that

it would evaluate impacts on air quality in downwind states, independent ofthe current formal

"designation" ofsuch downwind states, it was not referring to air quality in the absence of

monitor data. EPA's point was that it was inappropriate to wait for either initial designations of

nonattainment for a new NAAQS under section 107(d)(l), or for a redesignation to

nonattainment for an existing NAAQS under section 107(d)(3), before EPA could assess whether

there is significant contribution to nonattainment of a NAAQS in another state.
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For example, in the case ofinitial designations, section 107(d) contemplates a process

and timeline for initial designations that could well extend for two or three years following the

promulgation of a new or revised NAAQS. By contrast, section 110(a)(l) requires states to

make SIP submissions that address section 11O(a)(2)(D) and interstate transport "within 3 years

or such shorter period as the Administrator may prescribe" ofEPA's promulgation of a new or

revised NAAQS. This schedule does not support a reading ofsection 11O(a)(2)(D) that is

dependent upon formal designations having occurred first. This is a key reason why EPA

determined that it was appropriate to evaluate interstate transport based upon monitor data, not

designation status, in the CAIR rulemaking.

The commenter's misunderstanding ofEPA's statement concerning designation status

evident! y caused the commenter to believe that EPA's assessment ofinterstate transport in the

NOx SIP Call was not limited to evaluation of downwind areas with monitors. This is simply

incorrect. In both the NOx SIP Call and CAIR, EPA evaluated significant contribution to

nonattainment as measured or predicted at monitors. For example, in the technical analysis for

the NOx SIP Call, EPA specifically evaluated the impacts of emissions from upwind states on

monitors located in downwind states. The NOx SIP Call did not evaluate impacts at points

without monitors, nor did the CAIR rulemaking. EPA believes that this approach to evaluating

significant contribution is correct under section 11O(a)(2)(D), and EPA's general approach to this

threshold determination has not been disturbed by the courts."

Finally, EPA disagrees with the commenter's argument that the assessment ofsignificant

contribution to downwind nonattainment must include evaluation of impacts on non-monitored

6 Michigan v. u.s. EPA, 213 F.3d 663, 674-681 (D.C. Cir. 2000); North Carolina v. EPA, 531 F.3d 896, 913-916

(D.C. Cir. 2008) (upholding EPA approach to determining threshold despite remanding other aspects ofCAIR).
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areas. Neither section 110(a)(2)(D)(i)(I) provisions, nor the 2006 Guidance EPA issued for the

1997 8-hour ozone NAAQS, support the commenter's position, as neither refers to any explicit

mandatory or recommended approach to assess air quality in non-monitored areas," The same

focus on monitor data as a means of assessing interstate transport is found in the NOx SIP Call

and in CAIR. An initial step in both the NOx SIP Call and CAIR was the identification of areas

with current monitored violations ofthe ozone and/or PM2.5 NAAQS. 8 The subsequent

modeling analyses for NAAQS violations in future years (2007 for the SIP Call and 2010 for

CAIR) likewise evaluated future violations at monitors in areas identified in the initial step.

Thus, the commenter is simply in error that EPA has not previously evaluated the presence and

extent ofinterstate transport under section 110(a)(2)(D) by focusing on monitoring data. Indeed,

such monitoring data was at the core of both ofthese efforts. In neither ofthese rulemakings did

EPA evaluate significant contribution to nonattainment in areas in which there was no monitor.

This is reasonable and appropriate, because data from a properly placed federal reference method

monitor is the way in which EPA ascertains that there is a violation ofthe 1997 8-hour ozone

NAAQS or ofthe 1997 PM2.5 NAAQS in a particular area.

EPA did not use photochemical modeling to determine if an area is violating the 1997 8-

hour ozone or 1997 PM2.5 NAAQS to designate the area as nonattainment without supporting

monitoring data. EPA's regulations for these NAAQS, the monitoring requirements for these

NAAQS, and EPA's guidance for designations for these NAAQS provide for such designations

7 2006 Guidance, p. 5.

8 "Based on this approach, we predicted that in the absence of additional control measures, 47 counties with air

quality monitors [emphasis ours] would violate the 8-hour ozone NAAQS in 2010 ...." From the CAIR proposed

rule ofJanuary 30, 2004 (69 FR 4566,4581). The NOx SIP call proposed rule action reads: " ... For current

nonattainment areas, EPA used air quality data for the period 1993 through 1995 to determine which counties are

violating the I-hour and/or 8-hour NAAQS. These are the most recent 3 years offully quality assured data

which were available in time for this assessment." See, 62 FR 60336.
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for violating areas to be based only on monitoring data. In addition, this is reasonable for these

particular NAAQS because photochemical models, while based on the best science available,

only provide a best estimate of air quality. EPA's 2007 modeling guidance" recognizes that

model results and projections will continue to have uncertainty.

Therefore, even if modeling analyses indicated violation ofthe 1997 8-hour ozone

NAAQS in other states, EPA would not make a determination that these areas should be

designated nonattainment for these NAAQS without monitoring data in the area to support a

determination of nonattainment. In summary, in order for there to be significant contribution to

nonattainment for either ofthese specific NAAQS, there must be a monitor with data showing a

violation ofthat NAAQS. EPA has concluded that by considering data from monitored areas, its

assessment of whether emissions from New Mexico contribute significantly to ozone

nonattainment in downwind states is consistent with the 2006 Guidance, and with the approach

used by both the CAIR rule and the NOx SIP Call, and EPA modeling guidance.

Comment No. 3 - In support ofits comments that EPA should assess significant

contribution to nonattainment in nonmonitored areas, the commenter argued that existing

modeling performed by another organization "indicates that large areas of neighboring states will

be likely to violate the ozone NAAQS." According to the commenter, these likely "'violations"

ofthe ozone NAAQS were predicted for the year 2018, as reflected in a slide from a July 30,

2008 presentation before the Western Regional Air Partnership ("Review of Ozone Performance

9 EPA -454/B-07-002, April 2007, "Guidance on the Use of Models and other Analyses for Demonstrating

Attainment of Air Quality Goals for Ozone, PM2.5 and Regional Haze", Office ofAir Quality Planning and

Standards, Air Modeling Group. Research Triangle Park, North Carolina, available at

http://www.epa.gov/scramOOI/guidance/guide/final-03-pm-rh-guidance.pdf.
14

in WRAP Modeling and Relevant to Future Regional Ozone Planning'Y'" In short, the

commenter argues that modeling performed by the WRAP establishes that there will be

violations ofthe 1997 8-hour ozone NAAQS in 2018 in non-monitored areas ofstates adjacent to

New Mexico.

EPA Response - EPA disagrees with this comment on several grounds. First, EPA does

not agree that it is appropriate when satisfying the requirements of Section 110(a)(2)(D) to

evaluate significant contribution to nonattainment for the 1997 8-hour ozone NAAQS by

modeling ambient levels in areas where there is no monitor to provide data to establish a

violation ofthe NAAQS in question. Section 11O(a)(2)(D) does not require such an approach,

EPA has not taken this approach in the NOx SIP Call or other rulemakings under section

11O(a)(2)(D), and EPA's prior analytical approach has not been disturbed by the courts.

Second, the commenter's own description ofthe ozone concentrations predicted for the

year 2018 as projecting "violations" ofthe ozone NAAQS is inaccurate. Within the same

sentence, quoted above, slide 28 is described as displaying the projected fourth maximum ozone

reading for the year 2018, and as indicating that" ... air quality ... will exceed or violate

[emphasis ours] the 1997 ozone NAAQS." By definition, a one year value ofthe fourth

maximum above the NAAQS only constitutes an exceedance ofthe NAAQS; to constitute a

violation ofthe 1997 8-hour ozone NAAQS, the average ofthe fourth high for three consecutive

years at the same monitor must exceed the standard. Thus, even ifthe WRAP presentation

submitted by the commenter were technically sound, the conclusion drawn from it by the

10 The presentation is available for review as Document ID # EPA-R06-0AR-2007-0993-0008.9 at Regulations.gov,

Docket ID # EPA-R06-0AR-2007-0993.
15

commenter is inaccurate and does not support its claim of projected violations ofthe NAAQS in

large areas (monitored or unmonitored) ofNew Mexico's neighboring states.

Even if EPA believed that it was appropriate to use modeling to establish violations of

the 1997 8-hour ozone NAAQS, EPA has reviewed the WRAP presentation submitted by the

commenter, and believes that there was a substantial error in the WRAP modeling software that

led to overestimation of ground level ozone concentrations. A recent study conducted by

Environ for the Four Comers Air Quality Task Force (FCAQTF)ll has demonstrated that

excessive vertical transport in the CMAQ and CAMx models over high terrain was responsible

for overestimated ground level ozone concentrations due to downward transport ofstratospheric

ozone.

12 Environ has developed revised vertical velocity algorithms in a new version ofCAMx

that eliminated the excessive downward transport of ozone from the top layers ofthe model.

This revised version ofthe model is now being used in a number of applications throughout high

terrain areas in the West. In conclusion, EPA believes that this key inadequacy ofthe WRAP

model, noted above, makes it inappropriate support for the commenter's concerns about large

areas ofother states violating the 1997 8-hour ozone NAAQS projected for 2018 in areas without

monitors.

Comment No. 4 - As additional support for its assertion that EPA should require

modeling to assess ambient levels in unmonitored portions ofother states, the commenter relied

on an additional study entitled the "2009 Uinta Basin Air Quality Study" (UBAQS). The

commenter argued that the UBAQS further supports its concern that New Mexico and EPA,

II This document is available for review at the regulations.gov web site under Docket ID No. EPA-R06-0AR-2007-

0993

12 Stoeckenius, T.E., C.A. Emery, T.P. Shah, J.R. Johnson, L.K. Parker, A.K. Pollack, 2009. "Air Quality Modeling

Study for the Four Corners Region," pp. ES-3, ES-4, 3-4, 3-12, 3-30, 5-1. Prepared for the New Mexico

Environment Department, Air Quality Bureau, Santa Fe, NM, by ENVIRON International Corporation, Novato, CA.
16

having limited the evaluation of downwind impacts only to areas with monitors, failed to assess

ozone nonattainment in non-monitored areas. According to the commenter, UBAQS modeling':'

results show that: (a) the Wasatch Front region is currently exceeding and will exceed in 2012

the 1997 8-hour ozone NAAQS; and (b) based on 2005 meteorological data, portions ofthe four

counties in the southwestern corner of Utah are also currently in nonattainment and will be in

nonattainment in 2012.!4

EPA Response -As noted above, EPA does not agree that it is appropriate to assess

significant contribution to nonattainment for the 1997 8-hour ozone NAAQS in the way

advocated by the commenter. In particular, EPA does not agree that it is necessary to evaluate

significant contribution to areas where only the model predicts nonattainment where there are no

monitors. Even ifEPA felt it was appropriate to use model results to determine areas that are not

attaining the standard, EPA does not agree that the modeled nonattainment ofthe 1997 8-hour

ozone NAAQS (current and projected) in the Wasatch Front Range area in the UBAQS supports

the commenter's concerns about the need to evaluate the possibility ofsignificant contribution

from New Mexico to nonattainment in these areas. Based on what the commenter presented,

EPA sees several problems with the commenter's interpretation ofthe UBAQS analysis results

for counties in Utah's southwestern corner: "based on 2005 meteorological data, portions of

Washington, Iron, Kane, and Garfield Counties are also in nonattainment and will be in

13 In this action the expression "UBAQS" refers to the "FINAL REPORT UBAQS TECHNICAL REPORT", June

30,2009. The presentation is available for review as Document ID # EPA-R06-0AR-2007-0993-0008.9 at

regulations.gov, Docket ID # EPA-R06-0AR-2007-0993.

14 UBAQS. The southwestern area referred to by the commenter includes portions ofWashington, Iron, Kane, and

Garfield Counties.
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nonattainment in 2012.,,15 First, the commenter's interpretation ofthe predicted ozone

concentrations shown in Figures 4-3a and 4-3b (pages 4 and 5 ofthe comment letter) is

inaccurate. A close review ofthe legend in these figures indicates that the highest ozone

concentrations predicted by the model for portions ofthe counties noted above are somewhere

between 81.00 and 85.99 ppb, but the exact modeled value is not specified and there are only

three grid cells with this value range estimated. Ifthe actual model prediction is less than or

equal to 84.94 ppb then the area is attaining the 1997 8-hour ozone NAAQS, ifit is predicted as

greater than 84.94 ppb then the modeling is indicating that it is not attaining those NAAQS.

Thus, the current and predicted design values for the three grid cells in southwestern Utah area

identified in Figures 4-3a and 4-3b could both be in attainment, or both in nonattainment, or one

ofthem in attainment and the other in nonattainment, for the 1997 8-hour ozone NAAQS. EPA

does not believe that this evidence adequately establishes that one or both areas definitely violate

the NAAQS, even ifthe information were taken at face value.

Second, even ifthe design values predicted for these unmonitored areas were at the top of

the 81.00-85.99 ppb range, their reliability would remain questionable. The UBAQS itself

identifies and illustrates major shortcomings ofits modeling analysis, only to neglect assessing

the impact ofthese shortcomings on the modeling results. 16 The study deviates in at least two

significant ways from EPA's 2007 guidance on SIP modeling.!" One deviation is the UBAQS

modeling reliance on fewer than the five years ofdata recommended by EPA to generate a

IS WG's April 16, 2010 comment letter, pp. 3. The letter is available for review at the regulations.gov web site

Docket 10 No. EPA-R06-0AR-2007-0993.

Page three ofthe commenter's letter

16 See UBAQS, pp. 4-27 to 4-29.

17 EPA, Guidance on the Use of Models and other Analyses for Demonstrating Attainment ofAir Quality Goals for

Ozone, PM2.5 and Regional Haze. Office ofAir Quality Planning and Standards, Air Modeling Group. Research

Triangle Park, North Carolina (2007), available at http://www.epa.gov/scramOOl/guidance/guide/final-03-pm-rhguidance. pdf.
18

8-hour ozone current design value (DVC). UBAQS relaxed this requirement so that sites with as

little as I year ofdata were included as DVCs in the analysis. The other deviation is in the

computation ofthe relative responsive factor (RRF), which directly affects the modeling's future

design value (DVF).18 Due to unavailability ofdata satisfying EPA's recommendation that the

RRF be based on a minimum offive days of ozone concentrations above 85 ppb, UBAQS

modeling uses RRFs based on one or more days of ozone concentrations above 70 ppb.19Also,

looking at Figures 3-19a-j ofthe UBAQS report, which cover ozone modeling performance

through September of2005, shows the modeling to have an over prediction bias for ozone. So,

EPA concludes that the modeling analysis results provided by the commenter are unreliable for

projecting nonattainment status even ifEPA believed it was appropriate to use modeling for this

purpose for the 1997 8-hr ozone NAAQS.

Finally, even ifit were appropriate to consider modeled violations and the modeling were

reliable for this purpose, the commenter has not raised any convincing evidence that emissions

from New Mexico sources are impacting southwestern Utah during the predicted high ozone

events. Specifically, no assessment or source apportionment was performed that indicated

sources in New Mexico contributed to the three grid cells with modeled high values that may be

modeled nonattainment values in Utah. In fact, the predominant wind direction would not carry

emissions from New Mexico into southwestern Utah. Furthermore, in evaluating the Figures

provided (Fig 4-3a to 4-4b) and other information in the modeling report, the modeling also does

not indicate that emissions from New Mexico are impacting the higher modeled ozone values in

the southwestern Utah area.

18 Id., DVe x RRF = DVF.

19 See UBAQS, p. 4-28
19

In summary, EPA does not agree that it is appropriate for purposes ofsection

110(a)(2)(D) to use modeled nonattainment as a basis for evaluation, for these two NAAQS

(1997 8-hour ozone NAAQS and PM 2.5 NAAQS) especially in light ofthe concerns with the

modeling discussed above. Even ifEPA were to use modeling for this purpose, the UBAQS

modeling analyses does not clearly predict violations ofthe 1997 8-hour ozone NAAQS in

western Colorado and eastern Utah. In particular, the UBAQS modeling does not clearly

establish violations ofthe NAAQS in southwestern Utah because ofthe way the results were

reported. Significantly, the model does project violations in the Salt Lake City area (in 2006 and

2012 model years), but monitors in the area do not substantiate these modeled predictions.

Based on monitoring data for 2007-2009, the Salt Lake City area does not have a monitored

design value within 6 ppb ofthe level ofthe 1997 8-hour ozone NAAQS. In addition, EPA does

not consider the UBAQS modeling reliable because the modeling deviates from EPA guidance

and appears to have an over-prediction bias. Finally, the commenter did not provide evidence

that emissions from New Mexico in fact contributed significantly to the modeled exceedances or

violations projected in this modeling.

Comment No. 5 - In support ofits arguments that EPA should not assess significant

contribution to nonattainment through evaluation ofimpacts at monitors instead ofmodeling

impacts where there is no such monitor, the commenter cited a past statement by EPA to the

effect that the ozone monitoring network in the western United States needs to be expanded. The

quoted statements included EPA's observation that: "[v]irtually all States east ofthe Mississippi

River have at least two to four non-urban 03 monitors, while many large mid-western and

western States have one or no non-urban monitors." 74 FR 34,525 (July 16,2009). From this

statement, the commenter argues that it is not appropriate for EPA to limit evaluation of
20

significant contribution to nonattainrnent ofthe ozone NAAQS in other states to reliance on

monitoring data instead ofmodeled ambient levels.

EPA Response - EPA does not disagree that there are relatively few ozone monitors in

the western states, and that relatively few ofthese ozone monitors are currently located in nonurban areas of western states. However, the commenter failed to note that the quoted statement

from EPA concerning the adequacy ofwestern monitors came from the Agency's July 16,2009,

proposed rulemaking entitled "Ambient Ozone Monitoring Regulations: Revisions to Network

Design Requirements." This statement was thus taken out of context, because EPA was in that

proposal referring to changes in state monitoring networks that it anticipates will be necessary in

order to implement not the 1997 8-hour ozone NAAQS, the subject ofthis rulemaking, but rather

the next iteration ofthe ozone NAAQS. Because the new ozone standard is likely to be

significantly more stringent than the 1997 8-hour ozone NAAQS, it is anticipated there will be a

need to evaluate ambient levels in previously unrnonitored areas ofthe western United States.

The fact that additional monitors may be necessary in the future for a newer ozone NAAQS does

not mean that the existing ozone monitoring networks are insufficient for the 1997 8-hour ozone

NAAQS, as the commenter implies. Indeed, states submit annual monitor network reports to

EPA and EPA evaluates these to insure that the deployment ofmonitors in the state meets the

applicable regulatory requirements and guidance recommendations.

For example, New Mexico itselfsubmits just such a report on an annual basis, and EPA

reviews it for adequacy.i" All states submit comparable reports. Absent a specific concern that

another state's current monitor network is inadequate to evaluate ambient levels ofthe 19978-

20 See the New Mexico Annual Monitoring Network Plan dated July 14,2009. The plan is available for review at

the regulations.gov web site under Docket ID No. # EPA-R06-0AR-2007-0993.
21

hour ozone NAAQS, EPA has no reason to believe that the evaluation of possible significant

contribution from New Mexico sources in reliance on those monitors is incorrect.

Comment No.6 - The commenter objected to EPA's proposed approval ofthe New

Mexico's SIP submission because neither New Mexico nor EPA performed a specific modeling

analysis to assure that emissions from New Mexico sources do not significantly contribute to

nonattainment ofthe 1997 8-hour ozone NAAQS in downwind States.

EPA Response - First, this comment is incorrect. EPA and New Mexico did provide

modeling as part ofthe evaluation of whether emissions from sources in New Mexico impact

monitors with violating data in other states. The modeling is discussed in the proposed federal

register and technical support document for this action and is one ofthe primary considerations

in EPA's approval. The modeling that the commenter claims is necessary but absent, is

modeling to assess impacts in areas with no monitors. As explained above, EPA believes that

the assessment ofsignificant contribution to nonattainment under section 110(a)(2)(D) for these

NAAQS should be based upon impacts at monitors.

Second, EPA disagrees with the commenter's beliefthat only modeling can establish

whether or not there is significant contribution from one state to another. As noted above, EPA

does not believe that section 110(a)(2)(D) requires modeling. While modeling can be useful,

EPA believes that other forms of analysis can be sufficient to evaluate whether or not there is

significant contribution to nonattainment. For this reason, EPA's 2006 Guidance recommended

other forms ofinformation that states might wish to evaluate as a qualitative approach as part of

their section 110(a)(2)(D) submissions for the 1997 8-hour ozone NAAQS. EPA has concluded

that the qualitative approach used by New Mexico in addition to modeling to assess the existence
22

of, and extent of, any significant contribution to downwind ozone nonattainment is consistent

with EPA's 2006 Guidance.

Comment No. 7 - In further support ofits argument that EPA must use modeling to

evaluate whether there is significant contribution to nonattainment under section 11O(a)(2)(D),

the commenter noted that EPA itself asks other agencies to perform such modeling in other

contexts. As examples, the commenter cited four examples in which EPA commented on actions

by other agencies in which EPA recommended the use ofmodeling analysis to assess ozone

impacts prior to authorizing oil and gas development projects. As supporting material, the

comment includes quotations from and references to EPA letters to Federal Agencies on

assessing impacts of oil and gas development projecta." The commenter questioned why EPA's

recommendation for such an approach in its comments to other Federal Agencies, did not result

in its use ofthe same approach to evaluate the impacts from New Mexico's emissions and to

insure compliance with Section 110(a)(2)(D)(i)(I). The commenter reasoned that the emissions

that would result from the actions at issue in the other agency decisions, such as selected oil and

gas drilling projects, would be ofless magnitude and importance than the statewide emissions at

issue in an evaluation under section 11O(a)(2)(D).

EPA Response - As explained above, this comment is misplaced because EPA and New

Mexico did employ modeling as part ofthe evaluation. Further, EPA disagrees with the

commenter's fundamental argument that modeling is mandatory in all instances in order to

evaluate significant contribution to nonattainment, whether by section 11O(a)(2)(D), by EPA

guidance, or by past EPA precedent. EPA's applicable guidance made recommendations as to

21 WG's April 16, 2010 comment letter, pp. 8-9. Complete versions ofthe EPA comment letters referenced here

were attached to the comment as Exhibits 3 through 6, and are viewable on the Regulations.gov web site as

Documents ID No. EPA-R06-0AR-2007-0993-0008.3 through 0993-0008.6.
23

different approaches that could lead to demonstration ofthe satisfaction ofthe interstate transport

requirements for significant contribution to nonattainment in other states. EPA explicitly

recommended that relevant information for section 110(a)(2)(D) submissions addressing

significant contribution to nonattainment "might include, but is not limited to, information

concerning emissions in the State, meteorological conditions in the State, the distance to the

nearest nonattainment area in another State, reliance on modeling conducted by EPA in

determining that such State should not be included within the ambit ofthe CAIR, or such other

information as the State considers probative on the issue ofsignificant contribution." Even

EPA's own CAIR analysis relied on a combination of qualitative and quantitative analyses.

EPA's CAIR analysis excluded certain western states on the basis of a qualitative assessment of

topography, geography, and meteorology.f

Furthermore, EPA believes that the commenter's references to EPA statements

commenting on the actions of other agencies are inapposite. As the commenter is aware, those

comments were made in the context ofthe evaluation ofthe impacts of various federal actions

pursuant to National Environmental Policy Act, not the Clean Air Act. As explained above, in

the context ofsection IIO(a)(2)(D), EPA does not agree that only modeling is always required to

make that different type of evaluation, and EPA itself has relied on other more qualitative

evidence when it deemed that evidence sufficient to reach a reasoned determination.

Comment No.8 - In further support of its argument that EPA should require a specific

type of modeling to evaluate significant contribution to nonattainment, the commenter referred to

EPA regulations governing nonattainment SIPs. The commenter noted 40 CFR 51.112(a)(l),

which states that: "[t]he adequacy of a control strategy shall be demonstrated by means of

22 See 69 FR 4581, January 30, 2004.
24

applicable air quality models, data bases, and other requirements specified in appendix W of

[Part 51] (Guideline on Air Quality Models)." The commenter argues that this regulation

appears to support the commenter's position that modeling is required to satisfy the significant

contribution element of llO(a)(2)(D).

EPA Response - EPA disagrees with this comment. The cited language implies that the

need for control strategy requirements has already been demonstrated, and sets a modeling

analysis requirement to demonstrate the adequacy ofthe control strategy developed to achieve

the reductions necessary to prevent an area's air quality from continuing to violate the NAAQS.

EPA's determination that emissions from sources in New Mexico do not contribute significantly

to nonattainment for the 1997 8-hour ozone NAAQS in any other state eliminates the need for a

control strategy aimed at satisfying the section llO(a)(2)(D) requirements. Moreover, EPA

interprets the language at 40 CFR 51.112(a): "[e]ach plan must demonstrate that the measures,

rules, and regulations contained in it are adequate to provide for the timely attainment and

maintenance ofthe national standard that it implements," to refer to modeling for attainment

demonstrations, an integral part of nonattainment area SIPs under part D ofthe CAA. This

interpretation was upheld by the Sixth Circuit Court ofAppeals. Wall v. Us. EPA, 265 F.3d

426,436 (6th Cir. 2001). This modeling may also be appropriate under certain circumstances for

maintenance SIPs under section llO(a)(1). Thus, the commenter's cited regulation is not

relevant to EPA's technical demonstration assessing whether emissions from New Mexico

contribute significantly to nonattainment in any other states under section llO(a)(2)(D)(i).

Comment No. 9 - The commenter expressed concern with EPA statements in the

proposed approval about the current factual attainment ofthe Denver MetrolNorth Front Range

area ofColorado. The commenter noted that nine counties in the Denver area are currently
25

formally designated "nonattainment" for the 1997 8-hour ozone NAAQS. The cornmenter took

issue with EPA's description ofthe nature ofthe nonattainment problem in this area as resulting

from an unusually bad ozone season that "temporarily" resulted in violations ofthe NAAQS.

The cornmenter argued that data from the 2001- 2003 period and the 2005-2007 period showed

consistent violations ofthe 1997 8-hour ozone NAAQS in the Denver area, and that these

violations are the reason for the current nonattainment designation.

EPA Response - EPA disagrees that formal designation status of an area is the most

important consideration in evaluating the existence of, and extent of, the impacts ofinterstate

transport from one state to another. In past actions under section 11O(a)(2)(D), EPA has

interpreted that provision to turn upon the actual monitored ambient levels in a downwind area,

regardless ofthe formal designation status ofthe area. For example, EPA developed the CAIR

rule based upon evaluation ofmonitor data showing violations ofthe 1997 PM2.5 NAAQS in

certain areas, in advance of completing the designation process for those NAAQS under section

107(d). 23 EPA agrees that the designation status of an area is a relevant consideration, but the

actual monitored ambient levels are an appropriate measure, especially when there is evidence

that the monitored levels are different than reflected by the designation for the area. EPA itself

has also looked to future attainment status as a means of evaluating the presence of, and extents

of, interstate transport. This analysis depends not upon the anticipated formal designation status

ofthe area, but rather upon the anticipated monitored level ofthe area/"

23 See: Final CAIR rule, 70 FR 25,162,25,263 - 25,269.

24 EPA notes that the commenter itself also made the argument that nonattainment for purposes ofsection

110(aX2XD) should be viewed "in terms of air quality, and not in terms of area designations" on page 2 ofits own

comment letter.
26

EPA believes that the commenter is placing undue importance upon the EPA's

characterization ofthe data from Denver area monitors as ''temporarily'' in nonattainment based

on the "bad" ozone season of 2007. EPA agrees that this area has historically had relatively high

ambient levels. However, as explained in the proposal, these levels have improved, and more

importantly, have improved during the period that is most relevant and most recent. As noted in

the proposal, recent monitoring data from the Denver area for the 2007 - 2009 period indicates

that the area is below the level ofthe NAAQS. For this trend to change, EPA anticipates that the

Denver area would have to have dramatically higher ozone levels in 2010 than the area has

experienced for many years. EPA believes that it is more reasonable to conclude that the

monitored attainment ofthis area at the time ofthe analysis done by New Mexico will continue.

Therefore there could not be significant contribution from sources in New Mexico to

nonattainment in Denver.

EPA believes that the downward trend in monitored nonattainment in the Denver area

supports this conclusion. At the time the modeling was performed to support the state's section

110(a)(2)(D) submission, Denver was monitoring attainment (the 2004-2006 8-Hour Ozone

Design Value (DV) was 81 ppbi5

• In 2007, the Denver area experienced a particularly bad

ozone season, and inclusion ofthe data from this year did temporarily affect the monitored

values in this area. However, the most recent data for this area, preliminary data for 2007-2009

DV (awaiting final data validation), is 82 ppb even with inclusion ofthe very high ozone values

from 2007. Thus, the area's most recent DV based upon preliminary data is several ppb below

the 1997 8-hour ozone NAAQS, and the area is therefore currently monitoring attainment.

2S Data from EPA's Air Quality System which is EPA's repository of ambient air quality data .

(http://www.epa.gov/ttn/airs/airsaqsl)
27

The downward trend in ozone concentrations is in part the result of a sustained effort to

attain the NAAQS in the Denver area. The Denver area has seen a drop in ozone levels in the

last 10 years attributable in part to federal measures that have reduced mobile source emissions.

In addition, Colorado adopted an Ozone Action Plan in December 2008 that included additional

reductions in emissions of ozone precursors (NUx and VOCs), that will further aid the area in

maintaining attainment. Given these facts, EPA concludes that the monitored attainment ofthe

1997 8-hour ozone NAAQS in the Denver area is likely to continue.

Comment No. 10 - The commenter also disputed the EPA statement in the proposal that it

is "unlikely that Denver will be in nonattainment at the end ofthe 2010 ozone season," and

questioned why EPA did not cite or include any actual model data to support this assertion. The

commenter specifically took issue with EPA's reference to the "2010 ozone season" in the

proposal because section 11O(a)(2)(D) would prohibit significant contribution to nonattainment

at all times, not simply during the "2010 ozone season."

EPA Response - As discussed above, EPA believes the monitoring data adequately

demonstrates that the Denver area is attaining the standard and is likely to continue to do so. The

commenter is correct that EPA did not cite modeling that showed that Denver would be in

attainment in 2010 in the proposal. We are aware, however, ofthe photochemical modeling for

Denver completed as part ofthe "Ozone Action Plan" adopted by Colorado in December 2008. 26

This plan included the benefits offederal measures and fleet turnover and additional local NOx

and VOC reductions. The plan also included photochemical modeling that indicated all monitors

in the area would be in attainment ofthe 1997 8-hour ozone NAAQS in 2010. The modeling

26 "Denver Metro Area & North Front Range Ozone Action Plan Including Revisions to the State Implementation

Plan", Approved by Colorado Air Quality Control Commission, December 12,2008.
28

results supplement the monitoring results discussed previously indicating the area is in

attainment and will be in attainment in 2010.

Further, EPA believes that the commenter is mistakenly assuming that EPA's reference

to the "2010 ozone season" implied that section IIO(a)(2)(D) would not require the elimination

of emissions from sources in an upwind state that significantly contributed to violations of a

NAAQS at any time ofthe year. In the case ofthe 1997 8-hour ozone NAAQS, however, it is a

fact that there is an "ozone season" in many places across the county. Higher ozone

concentration levels typically occur during the warmer, sunnier portions ofthe year, especially

the summer. Like most areas, Denver has an ozone season. Therefore, it is not unreasonable for

EPA to evaluate the likely impacts of data from monitors in this area during the "ozone season."

EPA also disagrees that an evaluation focused on impacts on 2010 levels is not adequate

for purposes ofsection 110(a)(2)(D). As further discussed elsewhere in this notice, EPA's 2006

Guidance to states for section IIO(a)(2)(D) SIP submissions recommended that states might elect

to evaluate the existence of, and extent of, significant contribution to nonattainment in other

states by evaluating impacts as of an appropriate year (such as 2010) and in light ofthe cost of

control to mitigate emissions that resulted in interstate transport. EPA itselfin the context ofthe

CAIR rule evaluated whether there would be such impacts in 2010. This year was a reasonable

choice, because it correlated with the presumptive attainment dates for states with nonattainment

areas. For example, in the case ofthe 1997 PM2.5 NAAQS, the applicable attainment date is as

expeditiously as practicable, but not later than five years from the effective date ofthe

designation, i.e., by 2010. Because 2010 is a reasonable date for this analysis, given the purpose

ofsection 110(a)(2)(D), and is consistent with EPA's recommendations in the 2006 Guidance,

EPA concludes that the selection ofthis date for the analysis supporting the New Mexico
29

submission was appropriate. The commenter did not suggest another date that would be more

appropriate nor did they explain the basis for requiring a different year for this analysis.

Comment No. 11- The commenter also asserted that EPA was wrong in stating that the

Denver area had not experienced a 4th highest 8-hour ozone reading of 92 ppb in the last 15

years. The commenter claimed that the Denver metro area experienced a 4th highest max of 95

ppb at the Roxborough Park monitor in Douglas County in 2005 and of 95 ppb at the Applewood

monitor in Jefferson County in 1998 and in 2003.

EPA Response - In response to this comment, EPA rechecked the data in the EPA's Air

Quality System (AQS) and believes the commenter was in error that a fourth highest maximum

of95 ppb occurred at the Roxborough Park (also know as the Chatfield monitor) monitor in

2005. EPA's AQS indicates a value of 84 ppb in 2005. However, EPA's AQS does indicate that

a 95 ppb 4th high occurred in 2003 at the Roxborough Park monitor and this may be the date that

the commenter intended. In any event, upon closer examination, EPA concludes that the

commenter is correct that values above 92 ppb have occurred in the Denver area in the last 15

years.

EPA also notes that the current DVs (2007-2009) for these two monitors (Roxborough

Park and Applewood) are 77 ppb and 76 ppb, which is well below the 1997 8-hour ozone

NAAQS. Furthermore, these monitors would have to have fourth high daily maximum 8-hour

monitored values of 104 and 111 ppb respectively in 2010 to have a 2008-2010 DV violating the

1997 8-hour ozone NAAQS. The fourth high daily maximum value monitored the last 15 years

in the Denver area was 95 ppbwhich is significantly lower than the 104 or 111 ppb values that

would have to be monitored for either ofthese two monitors to be violating the 1997 8-hour

ozone NAAQS.
30

Therefore, EPA believes that the commenter's correction that there have been higher

values (maximum of95 ppb in the last 15 years) at monitors in the Denver area does not

fundamentally affect EPA's evaluation in this case. The higher values were not at the monitor

that was the basis for the Denver area design value in the last several years. The monitor that has

been the basis for the Denver area DV has been the Rocky Flats North monitor. Even though the

commenter is correct that the area has monitored higher values at certain monitors in the past,

these monitors are not the monitors that have in recent years determined whether the area will

continue to monitor attainment because they have not recorded the highest design value in the

area. The Rocky Flats North monitor has the highest 2007-2009 Denver area DV of 82 ppb and

is based upon fourth high values of90 ppb in 2007, 79 ppb in 2008, and 79 ppb in 2009. This

monitor would have to have a fourth high daily maximum of97 ppb in 2010 to result in a

violation ofthe 1997 8-hour ozone NAAQS. Therefore, it does not change EPA's conclusion

that the Denver area continues to monitor attainment and therefore emissions from sources in

New Mexico cannot be contributing significantly to violations ofthe 1997 8-hour ozone NAAQS

in this area.

Comment No. J2 - The commenter also pointed to modeling data used by New Mexico

that appears to contradict the conclusion that emissions from New Mexico do not contribute

significantly to violations ofthe 1997 8-hour ozone NAAQS in Denver. The commenter argued

that data available in New Mexico's own technical support document that was part of EPA's

record (Docket No. EPA-R06-0AR-2007-0993) establish that emissions from New Mexico

sources "often contributes greater than 2 parts per billion in ozone on days when exceedances of

the 1997 ozone NAAQS are recorded in Denver" and can contribute "more than 5% to Denver's

total ozone concentrations." Finally, the commenter argued that New Mexico wrongly assumed
31

that this amount of contribution was not relevant "under the assumption that the region was not

in nonattainment" when the area is currently designated nonattainment.

EPA Response- EPA disagrees with the cornmenter's conclusions drawn from the

modeling. The modeling was conducted using an emissions inventory from 2002. Because

emissions in the year 2010 are expected to be lower, EPA considers this modeling to be a

conservative estimate of ozone levels in the future and ofthe impact ofNew Mexico's emissions

on other states. EPA believes that the modeling shows higher impacts than are actually

occurring. The modeling utilized existing CENRAP modeling databases available at the.time

and the source apportionment evaluation was conducted using the 2002 emission inventory

databases. Because the available databases were for 2002 and not 2010, EPA considers the

results ofthe modeling conservative because significant emission reductions are expected to

occur throughout the modeled area between 2002 and 2010 (as a result of both federal and state

measures, including fleet turnover impacts) that would result in lower ambient ozone levels and

fewer exceedances ofthe 1997 8-hour ozone NAAQS throughout the modeling domain.

Specifically, there are three elements in this analysis that EPA concludes lead to

overestimation ofthe impacts ofNew Mexico sources and therefore make this modeling less

reliable to determine that sources in New Mexico contribute significantly to violations ofthe

1997 8-hour NAAQS in Colorado (or any other state). These three elements that result from

using a 2002 and not a 2010 emission inventory are: (a) additional emissions reductions in other

states as a result ofozone nonattainment SIPs have been implemented that were not reflected in

the 2002 emission inventoryr'(b) additional emissions reductions as a result offederal measures

27 Additional emission reductions have occurred as a result of I-hour ozone and 8-hour ozone nonattainment area

SIPs for Denver and other areas in the modeling domain (Dallas, Houston, etc.). The most recent SIP submitted

indicated that all ofthe Denver area monitors would be in attainment in 2010 with the 1997 8-hour ozone
32

(including On-road, Non-road, and the impacts offleet turnover) throughout the modeling

domain since 2002; and (c) additional reductions from large stationary NOx sources and from

mobile sources as a result offederal measures that have occurred in New Mexico since 2002.

As a result ofthese differences in the emission inventory between 2002 and 2010, New Mexico's

Technical Support Document describing and evaluating the modeling indicated that the impacts

for New Mexico's emissions were considered conservative estimates and were expected to

overstate the State's contribution to areas in other states. EPA believes that these conservative

assumptions make the modeling reliable for purposes ofdetermining that there is not a

significant contribution from sources in New Mexico to the other states, but less reliable for

purposes ofdetermining that there is such significant contribution. EPA believes that the

modeling relied upon by the State is conservative because ofthe three emission elements

discussed above and that this is further supported by studies referred to by the commenter. Other

studies support the conclusion that the Denver area will be monitoring attainment in 2010 for the

1997 8-hour ozone NAAQS, and therefore emissions from sources in New Mexico would not be

contributing significantly to nonattainment in this area. Specifically, the WRAP model emission

inventories for 2002 and 2018 showed decreases nationally in ozone precursors (NOx and

voc.r' The UBAQS modeling report included emission inventory assessments between 2006

and 2012 that also showed decreases in New Mexico's NOx emissions for the part ofNew

Mexico that was in the 12 km modeling grid. 29 Finally, the fact that Denver is monitoring

NAAQS. The Denver SIP also-included an analysis of emission inventories in the Denver area that showed a net

decrease in NOx and VOC emissions between 2006 and 20 I0 (Ibid DOAP) despite the inclusion of growth in

Oil and Gas emissions in the Denver area. (DOAP)

28 WRAP EDMS,. http://vista.cira.colostate.edu/TSS/EDMS.aspx

29 "UINTA BASIN AIR QUALITY STUDY (UBAQS)", prepared by Environ for the Independent Petroleum

Association ofMountain States (IPAMS), June 30, 2009. Tables 2-18 and 2-20. The UBAQS 12 kIn grid included
33

attainment at this time is further indication that the 2002 modeling was conservative because it

predicted exceedances in Denver, while the 2010 monitoring data is showing attainment.

Because the modeling was conservative and overstates the extent of contribution from

sources in New Mexico to the Denver area, it is inappropriate to use the modeling as a definitive

determination ofNew Mexico's impacts on downwind areas. The modeling was designed to be

conservative and as such only provides a clear indication of non impact on downwind

nonattainment areas. Therefore, EPA disagrees that the modeling supports the conclusion of

significant contribution from New Mexico sources to the Denver nonattainment area as the

commenter indicated. The commenter is correct that the CENRAP based modeling with a 2002

emission inventory showed impacts that were above 2 ppb and contribution levels that were

above 5 %, but due to the conservative nature ofthe 2002 assessment, EPA does not conclude

that it indicates that sources in New Mexico have a significant contribution to nonattainment in

Denver.

EPA also believes that NOx emissions in upwind states are the most relevant

consideration for interstate transport of ozone. In the final CAIR rule, EPA concluded that NOx

emissions were the primary pollutant to reduce in order to yield reductions in interstate transport

of emissions that affect levels of ozone in the context ofthe 1997 8-hour ozone NAAQS. 30

Recent photochemical modeling in the New Mexico and Colorado region further support this

conclusion, and therefore we have thus focused on NOx emissions in the context of ozone in this

action as well.

parts of northwestem New Mexico (including parts ofthe San Juan basin) and the emission inventory data indicated

that emissions ofNOx from this area were going to decrease from 115,942 tpy in 2006 to 95,867 tpy in 2012.

30 See: Final CAIR rule, 70 FR 25162, 25174 ("As discussed in section III below, for 8-hour ozone, we reiterate

the fmding ofthe NOX SIP Call that NOX emissions, and not VOC emissions, are ofprimary importance for

interstate transport purposes.")
34

As reflected in the New Mexico submission and the UBAQS modeling documentation,

New Mexico has decreased emissions ofNOx from several sources which would lessen New

Mexico's impact on ozone in areas outside ofNew Mexico. Therefore, the reductions in NOx

emissions in New Mexico would decrease the impacts from New Mexico on Denver's ambient

ozone levels when transport conditions would occur that New Mexico's emissions could impact

the Denver area. A review ofthe UBAQS report indicates New Mexico's NOx reductions are

mostly from elevated point source reductions (Le. from tall stationary source stacks). Elevated

emissions would have the greatest chance to transport downwind, so these reductions are likely

among the most effective at reducing long range transport impacts on ozone levels regionally. In

any event, based on preliminary 2007-2009 data, Denver is attaining the 1997 8-hour ozone

NAAQS. Therefore, New Mexico's emissions cannot be considered as contributing significantly

to nonattainment ofthose NAAQS in the Denver area

In summary, the Denver area is monitoring attainment ofthe 1997 8-hour ozone

NAAQS. The modeling submitted by the State to support its submission indicating impacts from

sources in New Mexico on the Denver area is conservative, and probably overestimates both the

ozone levels in Denver and any impacts from New Mexico's emissions. There have been

significant emission reductions in the modeled area, supporting the conclusion that the modeling

based on 2002 represents a conservative description of ozone levels and New Mexico's impact

on the Denver area and therefore should not be relied upon solely to draw a conclusion about the

impact of emissions from New Mexico in the Denver area. Considering the modeling in

conjunction with the expected emission reductions and the actual monitoring data in this area,

EPA concludes that emissions from New Mexico are not contributing to nonattainment ofthe

1997 8-hour ozone NAAQS in the Denver area.
35

Comment No. J3 - The commenter argued that New Mexico and EPA inappropriately

relied on analyses conducted in connection with CAIR to justify its conclusion that emissions

from sources in New Mexico do not contribute significantly to nonattainment in downwind states

with regards to the 1997 PM 2.5 NAAQS. According to the commenter, neither ofthe modeling

analyses EPA used during the development ofthe CAIR rule supports the conclusion.

The commenter acknowledged that the REMSAD modeling that EPA used initially for

CAIR in 2004 assessed emissions from New Mexico, but claimed that EPA eventually "rejected"

this modeling and replaced it with analysis using the CMAQ model as a more "accurate" means

of assessing PM 2.5 impacts among states. The commenter did note that EPA explained in the

final CAIR rule that it believed the REMSAD model "treats the key physical and chemical

processes associated with secondary aerosol formation and transport," but pointed to EPA's

statement that the REMSAD model "does not have all the scientific refinements ofCMAQ" and

also to EPA's use ofthe CMAQ modeling for the final CAIR rule instead ofthe REMSAD

modeling. The commenter thus implied that the REMSAD modeling could have no relevance to

whether emissions from New Mexico sources contribute significantly to nonattainment in other

states for purposes ofthe 1997 PM2.5 NAAQS.

Similarly, the commenter argued that the CMAQ modeling could not support the

conclusion that New Mexico sources are not contributing significantly to violations ofthe

NAAQS in other states. The commenter claimed that although New Mexico was included in the

CMAQ PM2.5 modeling domain for CAIR, EPA did not specifically assess impacts from New

Mexico to downwind States. The commenter acknowledged that EPA conducted state by state

"zero out" modeling for 37 states, but claimed that because EPA had not conducted such a zero
36

out modeling run for New Mexico, the CMAQ model runs do not support the proposed

conclusion in this action.

EPA Response - EPA disagrees with the commenter's judgment that the technical

analyses conducted in conjunction with CAIR do not provide technical support for the

conclusion that New Mexico sources do not contribute significantly to violations ofthe 1997

PM2.5 NAAQS in any other state. EPA agrees that it progressively refined its analytical

approach from the time ofthe proposed CAIR rule to the final CAIR rule, but it does not follow

that the analyses done for CAIR are inappropriate for consideration in today's action. EPA

believes that the analyses conducted for CAIR in fact provide technical support to the conclusion

that emissions from New Mexico sources do not contribute significantly to violations ofthese

PM 2.5 NAAQS in any other state.

EPA conducted modeling in the CAIR proposal using REMSAD modeling. With respect

to the REMSAD modeling, the commenter is correct that EPA specifically evaluated the impact

of emissions from New Mexico on other states in the eastern half ofthe United States. The

modeling indicated a 0.03 ug/nr' maximum impact from New Mexico's emissions on downwind

PM 2.5 nonattainment areas in 2010, which was significantly lower than the 0.15 J,lg/m3 value

used as the threshold for significance in the proposed CAIR rule and the 0.20 J,lg/m3 value used

in the final CAIR rule." In other words, EPA's analysis indicated that the impact of emissions

from New Mexico sources were only a small fraction ofthe initial threshold amount that EPA

considered relevant as the first stage ofthe analysis to determine the existence of, and extent of,

impact on other states.

31 See, Final CAIRrule 70 FR 25,162, at 25,174.
37

The commenter implied that EPA's subsequent use ofthe CMAQ model for the final

CAIR rule per se renders REMSAD invalid for purposes oftoday's action. To support this

assertion, the commenter overstated the potential limitations ofthe REM SAD model, a

misimpression heightened by the way in which the commenter described EPA's own stated

position. The full statement by EPA in the final CAIR rule was32:

"However, even though REMSAD does not have all the scientific refinements ofCMAQ,

we believe that REMSAD treats the key physical and chemical processes associated with

secondary aerosol formation and transport. Thus, we believe that the conclusions based

on the proposal modeling using REMSAD are valid..."

This was not a categorical dismissal ofREMSAD modeling for all purposes; it was a recognition

that REMSAD was reliable for certain purposes even though the subsequent CMAQ modeling

was an improvement. During rulemaking, it is appropriate for EPA to make improvements and

refinements to models and the associated databases. EPA responded to comments raising

concerns about reliance on the REM SAD modeling results from the proposal package and

determined that decisions and determinations based on the proposal REMSAD modeling were

still valid in the final CAIR rule.

With respect to the CMAQ modeling, New Mexico was not among the 37 states for

which it did specific "zero out" modeling runs. EPA disagrees, however, with the commenter's

extrapolation that this means EPA "did not assess" the impacts of emissions from New Mexico

with respect to the 1997 PM2.5 NAAQS in the final CAIR rule. To the contrary, EPA's

evaluation ofNew Mexico with REMSAD was part ofthe analysis for the proposed CAIR rule

and EPA did not reject the results ofthe REMSAD modeling in the final CAIR rule33• The lack

32 See, Final CAIR rule 70 FR 25,162, at 25234.

33 In this action, "CAIR Proposal" refers to the proposal rule published on January 30, 2004 in the Federal Register

and entitled "Rule to Reduce Interstate Transport of Fine Particulate Matter and Ozone", Interstate Air Quality

Rule, 69 FR 4566.
38

ofsignificant impact on nonattainment from New Mexico and other Western States shown by the

REMSAD modeling in the proposal helped influence the more refined modeling analysis in the

CAIR final rule which focused only on the Eastern States.

In considering this comment, EPA has looked again at the use ofthe REMSAD modeling

for the CAIR proposal for assessing New Mexico's impacts on other States. We continue to

believe that the REMSAD results are sufficient to make a determination of no significant

contribution to nonattainment ofthe 1997 PM 2.5 NAAQS in other states because ofthe very

small impacts that were estimated from emissions from New Mexico sources. The REMSAD

modeling had indicated that New Mexico's impacts on downwind 2010 PM 2.5 nonattainment

areas was only 15% ofthe significance level used in the final CAIR rule. Because the REMSAD

modeling indicated values of only 15% ofthe final significance level, EPA did not consider the

differences between the two modeling platforms (REMSAD and CMAQ) to be significant

enough to lead to further analysis using CMAQ based modeling. EPA has determined in this

action that the results from the REMSAD based modeling continue to support the conclusion that

emissions from New Mexico sources are not contributing significantly to violations ofthe 1997

PM2.5 NAAQS in other states. The commenter did not articulate any way in which the

distinctions between REMSAD and CMAQ would result in at least a seven-fold increase in the

estimated impacts of emissions from New Mexico emissions on another state's 1997 PM 2.5

nonattainment area. EPA does not believe that such a divergence would be likely.

Comment No. 14 - The commenter argued that it is also inappropriate for EPA to rely on

the CAIR modeling because the 2004 REMSAD model did not include other western states

(including Arizona, California, Nevada, Utah, Idaho, Oregon, and Washington). The commenter

asserted that EPA never assessed the impacts of emissions from New Mexico to these western
39

states in the CAIR modeling and that this is problematic because there are PM2.5 nonattainment

areas in California and in Utah. Although not clear, the commenter apparently argues that the

existence of designated PM2.5 nonattainment areas in California and Utah renders the CAIR

modeling irrelevant. More specifically, the commenter argues that because EPA has recently

designated certain counties in the Salt Lake City area and Cache County, Utah as nonattainment

for the 2006 PM2.5 NAAQS, EPA was obligated to assess and limit downwind impacts

accordingly in accordance with Section 110(1) ofthe Clean Air Act.

EPA Response - EPA disagrees with the commenter on this issue. First, this rulemaking

addresses the potential impacts of emissions from New Mexico sources on other states with

violations ofthe 1997 PM 2.5 NAAQS, not the 2006 PM 2.5 NAAQS. Therefore, EPA's

assessment ofNew Mexico's SIP was based on potential impacts on areas violating the 1997 PM

2.5 NAAQS (15 ~g/m3 annual and 65 ~g/m3 24-hour standard). The application ofsection

11O(a)(2)(D)to the 2006 PM2.5 NAAQS, or other NAAQS, will be addressed in later actions

that pertain to those NAAQS.

Second, EPA believes that the analysis conducted in conjunction with CAIR is both

relevant and very probative in evaluating the presence of, and extent of, interstate transport from

New Mexico sources to other states in this action. The CAIR modeling and analysis specifically

evaluated impacts on areas that were violating the 1997 PM 2.5 NAAQS. The other western

states identified by the commenter were in the CAIR modeling domain but were not evaluated

further in the CAIR rule because, with the exception ofCalifornia and Montana, these states

were in attainment ofthe 1997 PM2.5 NAAQS. 34 Absent areas with violations ofthose

34 See, Final CAIR rule 70 FR 25,162, at 25, I69:("Only two States in the western part ofthe U.S., California and

Montana, have counties that exceeded the PM2.5 standards") and ("Because interstate transport is not believed to be
40

NAAQS, there could be no significant contribution to violations ofthe 1997 PM2.5 NAAQS.

With regard to California and Montana, EPA indicated in the CAIR rule that interstate transport

impacts were not a significant contributor to these areas, therefore impacts from New Mexico

sources to California were not Iikely."

Finally, even aside from the CAIR analysis, EPA does not believe that emissions from

New Mexico sources contribute significantly to violations ofthe 1997 PM2.5 NAAQS in

California. The areas ofCalifornia with violations ofthe 1997 PM2.5 NAAQS are generally

located far to the west, hundreds ofmiles from New Mexico sources, across large expanses of

mountain ranges that would impede transport, and generally upwind from New Mexico. EPA

believes that the predominant meteorological conditions would carry New Mexico emissions to

the east, north, or south but not generally to the west. As a result, EPA concludes that it is very

unlikely that New Mexico's emissions transport hundreds ofmiles to the west to the 1997 PM

2.5 NAAQS in California.36 The CAIR modeling only addressed areas that were expected to be

in nonattainment in 2010, based on existing monitoring data at the time and 2010 photochemical

modeling. Other than California, none ofthe other states mentioned by the commenter were

monitoring nonattainment, or designated nonattainment for the 1997 PM 2.5 standards, at the

time these analyses were conducted.

Although not cited by the commenter, EPA notes that there has been one monitored

violation ofthe 1997 PM 2.5 annual NAAQS in Utah. It occurred in 2002-2004 time period at a

single monitor in the Salt Lake City area. This violation has not continued. In this instance, the

a significant contributor to exceedances ofthe PM2.5 standards in California or Montana, today's fmal CAIR does

not cover these States")

3S ld.

36 EPA reached this same conclusion in the CAIR rule. See, Final CAIR rule 70 FR 25,162, at 25,169.
41

state concluded that the monitor was heavily impacted by a nearby source. After the state

instituted controls at the source, the design value has dropped to less than 45 ug/nr' in the last

four years. EPA notes that the impact of a nearby source does not in and ofitself negate the

possibility ofimpacts ofinterstate transport at that monitor as well. However, because that

monitor has not subsequently shown any violation ofthe 1997 PM2.5 NAAQS, EPA concludes

that there are no areas in Utah with violations ofthat NAAQS to which New Mexico sources

could be contributing significantly. All other PM 2.5 monitors in the area have consistently had

DVs below 55 J..lg/m3 since the 2001-2003 DV period.

Comment No. 15 -The commenter also criticized modeling that the state and EPA relied

upon because of concerns about the accuracy ofthe underlying emissions inventories on which

the models relied. In particular, the commenter claimed that the modeling fails to address recent

growth in emission inventories for oil and gas operations in New Mexico that have been raising

the emissions from the state higher than have been previously reported in emissions inventories.

The commenter argued that these increases in emissions at least call into question the

accuracy ofthe modeling relied upon by EPA to support the proposed approval ofthe State's

submission, and at worst demonstrate that EPA has failed to address a key aspect of contribution

to nonattainment in downwind states from New Mexico sources.

The commenter listed several recent reports that estimated increased emissions of S02,

NOx, and VOCs that result from the growth of oil and gas exploration in certain areas in New

Mexico. The more recent studies cited by the commenter were:

• The November 25, 2009 inventory of 2006 oil and gas emissions in the San Juan

Basin ofNew Mexico, which includes San Juan, Rio Arriba, McKinley, and Sandoval

Counties, prepared by the Independent Petroleum Association ofthe Mountain States
42

("IPAMS"). This inventory found that oil and gas point and area sources within this

region annually released 42,075 tons ofNOx, 60,697 tons of volatile organic compounds

("VOCs") and 305 tons ofsulfur dioxide ("S02").;

• The August 2009 report on 2005 emissions in the Four Corners region of northwestern New

Mexico, which found that oil and gas point and area sources within the region annually released

57,682 tons ofNOx, 668 tons of S02, and 117,370 tons ofVOCs. The report indicates that by

2018, these emissions will increase to 65,543 tons ofNOx, 670 tons ofS02, and 143,050 tons of

VOCs; and

• The 2007 WRAP Phase II Inventory of 2002 oil and gas emissions, which found that oil and

gas activities throughout New Mexico released 112,540 tons of NOx and

13,925 tons ofS02, and that by 2018 would release 110,034 tons ofNOx and 13,002 tons of

S02 in the State.

The commenter argued that without specifically addressing these more recent increases in

the emissions associated with oil and gas development, New Mexico and EPA have no basis to

conclude that the modeling relied upon in the proposed approval is accurate or ensures that

emission are not and will not significantly contribute to nonattainrnent in other states. The

commenter also noted that the modeling prepared for CAIR utilized emission inventories from

2001, which would likewise fail to account for the more recent increase in emissions associated

with oil and gas development

EPA Response- EPA shares the commenter's concern with emissions from oil and gas

development, and agrees that dramatic increases in such emissions, and especially emissions

from sources that are not appropriately controlled, have the potential to contribute significantly

to violations ofNAAQS in other states. However, EPA has investigated this issue in response to
43

the commenter's concerns in this action, and has concluded that the information currently

available does not indicate that New Mexico's emissions from oil and gas development are

significantly contributing to violations ofthe 1997 8-hour ozone NAAQS and 1997 PM2.5

NAAQS in other states. To reach this conclusion, EPA has used available information and

extrapolated what the impacts ofthe additional emissions from oil and gas development would

be in a worst case scenario, as part of evaluating how those increases would affect the modeling

results and other information EPA relied upon in the proposal.

EPA has to make regulatory decisions using the emissions inventories and analyses that

are available at the time ofthe decision. These inventories are, of course, constantly being

updated and refined. The CAIR modeling used a base year emission inventory from 2001 that

EPA then projected to 2010, which was the timeframe that EPA used for the analysis ofNew

Mexico's impacts on areas in other states with monitors projected to have violations ofthe 1997

PM 2.5 NAAQS. The CENRAP modeling used a 2002 inventory to assess New Mexico's ozone

impacts on areas in other states with monitors projected to have violations ofthe 1997 8-hour

ozone NAAQS. At the time this modeling was conducted, EPA believed that the emission

estimates for oil and gas development were appropriate.

The commenter cited studies that have been conducted more recently to refine estimates

of current emissions and future projected emission levels from oil and gas development in areas

ofNew Mexico. These more recent studies indicate that emissions from oil and gas

development are likely much higher than those assumed in the models. Because the studies do

not indicate the amount of emissions growth that has happened since the 200112002 timeframe,

however, it is difficult to determine the impact this presumed increase would have. Therefore, to

evaluate this concern, below we consider a worst case estimate impact of oil and gas emissions
44

on whether emissions from sources in New Mexico significantly contribute to nonattainment in

other states.

The reports cited by the commenter indicate that emissions from all oil and gas

development in New Mexico in the years from 2002-2006 have a range of up to 112,540 tpy of

NOx, 117,370 tpy ofVOC, and 13,925 tpy of S02. In comparison, the modeling conducted

using the 2002 CENRAP emission inventory databases included emissions from all sources in

New Mexico with totals of306,194 tpy ofNOx, 1,749,081 tpy ofVOC and 100,174 tpy of

S02.37 The modeling conducted for CAIR included an inventory from all sources of 242,782 tpy

ofNOx and 173,724 tpy of S02 for the 2010 base level emissions for sources in New Mexico.P

These emissions inventories used for the CENRAP modeling and the CAIR modeling did

include some emissions from oil and gas development activities in New Mexico, so EPA

believes that some portion of emissions attributed to such sources in the more recent studies

were included in statewide emission inventories from all sources and thus in the CENRAP and

CAIR modeling.

It would be very difficult to ascertain the exact amount of emissions from oil and gas

sources that were included in the emission inventories for these two modeling evaluations and

thus to ascertain the exact amount that the inventories used for the modeling exercises

underestimate such emissions. Therefore, to evaluate how much the additional emissions from

oil and gas development could impact the determination, we have used a worst case estimate of

how much higher the emissions in New Mexico could be, based on the studies provided by the

commenter. If one uses the highest NOx value from these reports of 112, 540 tpy and compare

37 WRAP EDMS, CENRAP TSD

38 CAIR Proposal TSD
45

that with the 306,194 tpy ofNOx (from the CENRAP based modeling), the percentage increase

in NOx emissions would be a 36% increase in NOx emissions over the modeled emissions.

Similarly, if one compares the highest S02 value from the reports (using 13,925 tpy from the

reports and 100,174 tpy from the CENRAP based modeling) the percentage increase in S02

emissions would be less than a 8 % increase in S02 emissions over the modeled emissions.

EPA believes that these are worst case scenario increases, because they include the highest

estimate of oil and gas development emission from the reports supplied by the commenter, but

they probably overestimate the true increase over the inventories used for the modeling, and

double count the emissions of oil and gas that were in the original modeling.

EPA notes that these estimates also do not include the significant reductions that have

occurred in New Mexico from non oil and gas sectors, such as federal motor vehicle controls and

fleet turn over and controls on S02 and NOx emissions installed on large stationary sources

including the San Juan Generating Station. In addition, emissions in other parts ofthe modeling

domain outside ofNew Mexico would be expected to have decreased after 2002 due to federal

and state controls including fleet turnover and would not have been included in the CENRAP

based modeling for ozone and only partially included in the CAIR modeling.

EPA relied on photochemical modeling conducted for CAIR for the PM 2.5 analysis in

determining that New Mexico's emissions do not make a significant contribution in areas in

other states with monitors showing violations ofthe 1997 PM 2.5 NAAQS. As discussed

elsewhere in this notice, the modeling indicated that the largest impact from New Mexico's

emissions on any such monitor in another state was only 15% ofthe significance level used in

the final CAIR rule. In the worst case estimate above, NOx emissions could at most be 36%
46

higher and S02 could be at most 8% higher than was modeled in CAIR. Although the impact

on the model would not necessarily be linear, EPA does not believe that such a relatively small

increase in total S02 and NOx emissions would increase the impact ofNew Mexico emissions

by the more than 7 fold necessary to reach the significance level EPA used in CAIR for the 1997

PM2.5 NAAQS.

EPA relied on photochemical modeling based on 2002 emission inventories (available

from CENRAP's efforts) in determining that New Mexico's emissions do not make a significant

contribution in areas in other states with monitors showing violations ofthe 1997 8-hour ozone

NAAQS. EPA relied on this modeling to evaluate the possible contribution from New Mexico

sources to areas that were monitoring violations ofthe 1997 8-hour NAAQS. EPA considers the

modeling conservative in that it used 2002 inventories, and for the entire modeling grid (which

covered most ofthe continental u.s. and parts of Canada and Mexico), and it did not include the

benefits from emission reductions after 2002 from federal and state requirements including fleet

turnover. The modeling did not indicate values that were close to the significance levels for New

Mexico's impacts on out ofstate areas which were nonattainment and/or monitoring

nonattainment ofthe 1997 8-hour ozone NAAQS. The area monitoring nonattainment with the

highest modeled impact from sources in New Mexico was the DallaslFort Worth Area. The

modeled daily average contribution from sources in New Mexico was 0.4% with a contribution

average of 0.4 ppb. EPA's screening criteria for the first step ofthe analysis for any significant

contribution, established in CAIR and upheld by the court, were 1% and 2 ppb respectively.

EPA believes that even a conservative estimate of a 36% increase in NOx emissions from New

Mexico's sources would not more than double New Mexico's impacton other states, even before

considering the other offsetting NOx emission reductions between 2002 and 2010 from other
47

source categories. Therefore, EPA concludes that these new emission estimates would not

result in significant enough changes in impacts from New Mexico's sources to change the

determination that emissions from sources in New Mexico do not significantly contribute to

violations ofthe 1997 8-hour ozone NAAQS in other states, based on available information.

Accordingly, New Mexico does not need to amend its SIP substantively to reduce any additional

emissions to prevent such impacts on other states.

Finally, EPA notes that photochemical modeling is a very detailed and complicated

process and there are continual refinements in emission inventories and other modeling

databases. Unfortunately, the statutory and regulatory requirements, and especially the timing

requirements, for developing and evaluating SIPs do not allow for time or resources to do every

possible refinement to emission inventories on a continual basis. In this specific case, EPA

agrees that the sudden expansion of oil and gas development and the emissions increases from

such activities are a source category for which emissions inventories need updating, to insure

that future regulatory actions by both states and EPA continue to be based upon the most recent

and accurate information available

EPA is concerned with the growth in emissions from oil and gas development in New

Mexico and other areas ofthe country, including other states in Region 6. On May 10,2010,

EPA Region 6 held a meeting with the principal oil and gas producers, trade organizations, and

the five States in the Region, with the goal of finding ways to improve the emission inventory for

these sources. Region 6 has initiated this process because a clearer understanding ofthese

emissions will be necessary for future air quality plans under the new revised standards.
48

Comment No. 16 - The commenter also objected to EPA's proposed approval because

"New Mexico's SIP, as written, simply does not contain any language that prohibits emissions

that contribute significantly to nonattainment in any other state." The commenter also noted that

EPA did not assess whether the SIP does or does not contain such provisions. The commenter

appears to have argued that 11O(a)(2)(D)(i) requires a state SIP to contain an explicit provision

literally prohibiting emissions that contribute significantly to nonattainment in any other state

and that, in order to approve the New Mexico interstate transport SIP, EPA must examine the

SIP to determine whether it contains such an explicit prohibition.

EPA Response - EPA disagrees with the commenter's interpretation ofthe statutory

requirements. Section 110(a)(2)(D)(i) has no language that requires a SIP to contain a specific

provision literally prohibiting significant contribution to nonattainment in any other state or, for

that matter, to contain any particular words or generic prohibitions. Instead, EPA believes that

the statute requires a state's SIP to contain substantive emission limits or other provisions that in

fact ensure that sources located within the state will not produce emissions that have such an

effect in other states. Therefore, EPA believes that satisfaction ofthe "significant contribution"

requirement is not to be demonstrated through a literal requirement for a prohibition ofthe type

advocated by the commenter.

EPA's past application ofsection 11O(a)(2)(D) did not require the literal prohibition

advocated by the commenter. For example, in the 1998 NOx SIP Call 39• EPA indicated that "the

term 'prohibit' means that SIPs must eliminate those amounts of emissions determined to

contribute significantly to nonattainment...." As a result, the first step ofthe process to

determine whether this statutory requirement is satisfied is the factual determination ofwhether

39 63 FR 57356, October 27, 1998
49

emissions from sources in the state contribute significantly to nonattainment in downwind

areas'". Ifthis factual finding is in the negative, as is the case for EPA's assessment ofthe

contribution from emissions from sources in New Mexico, then section 11O(a)(2)(D)(i)(I) does

not require any changes to the state's SIP. If, however, the evaluation reveals that there is such a

significant contribution to nonattainment in other states, then EPA requires the state to adopt

substantive provisions to eliminate those emissions. The state could achieve these reductions

through traditional command and control programs, or at its own election, through participation

in another mechanism such as the cap and trade program ofthe NOx SIP Call. Thus, EPA's

approach in this action is consistent with the Agency's interpretation of 11O(a)(2)(D)(i) in the

2006 guidance, the CAIR Rule, and the NOx SIP Call, none of which required the pro forma

literal "prohibition" ofthe type advocated by the commenter.

Comment No. 17 - The commenter noted a specific provision for stationary source

permitting in the New Mexico SIP that the commenter argued is inadequate to ensure that

sources in New Mexico will not significantly contribute to nonattainment in other states.

According to the commenter, New Mexico has a regulatory provision that requires the state

agency to deny an application for a permit or permit revision for a stationary source under

certain circumstances, including the violation of any NAAQS. The commenter claimed that

New Mexico interprets this authority to allow the denial ofsuch a permit, only ifthe source is

physically located in a designated nonattainment area.

EPA Response - EPA disagrees with the commenter's characterization ofthe State's

regulations that New Mexico can only deny a permit for new or modified sources located in a

designated nonattainment area. EPA has reviewed the New Mexico permitting provisions cited

40 See 2005 CAIR Rule (70 FR 25162) and 1998 NOx SIP Call (63 FR 57356
50

by the commenter. Section 20.2.72.208 NMAC contains the reasons the department must deny a

pennit. Section 20.2.72.208 D explicitly provides that one ofthe reasons the State will deny a

pennit is if "the construction, modification, or permit revision will cause or contribute to air

contaminant levels in excess of any National Ambient Air Quality Standard or New Mexico

Ambient Air Quality Standard unless the ambient air impact is offset by meeting the

requirements of either 20.2.79 NMAC or 20.2.72.216 NMAC, whichever is applicable."

Section 20.2.79 NMAC and 20.2.72.216 NMAC apply in nonattainment areas which have more

stringent requirements than attainment areas.

EPA believes that the provisions of Section 20.2.72.208 NMAC apply in attainment areas

ofthe State and are unambiguous. The state's regulations provide that it "shall deny" a permit

for a source located in an attainment area, ifthat new or modified source would cause or

contribute to air contaminant levels that exceed any NAAQS, whether those violations occur in

New Mexico or elsewhere. To verify this understanding ofthe state's regulations, EPA

contacted NMED regarding this comment. NMED responded with an E-mail that is included in

the docket for this rulemaking confirming that the provisions of20.2.72.208 NMAC apply in the

attainment areas ofthe State and provide for denial of permits ifthe construction, modification

or revision will cause or contribute to levels in excess ofthe NAAQS.

Comment No. 18 - The commenter argued that EPA cannot approve the section

110(a)(2)(D) submission from New Mexico because the State and EPA did not comply with the

requirements ofsection 11O(l). Evidently, the commenter believes that the section 110(a)(2)(D)

submission for the 1997 8-hour ozone and 1997 PM2.5 NAAQS is a revision to the SIP that will

interfere with attainment ofthe 2006 PM2.5 NAAQS and the 2008 ozone NAAQS. The

commenter argued that a section 110(1) analysis must consider all NAAQS once they are
51

promulgated, and argued that EPA recently took the same position in proposing to disapprove a

PMIO maintenance plan.

EPA Response - EPA agrees that a required section 110(1) analysis must consider the

potential impact of a proposed SIP revision on attainment and maintenance of all NAAQS that

are in effect and impacted by a given SIP revision. However, EPA disagrees that it failed to

comply with the requirements ofsection 110(1) in this action or that section 110(1)requires

disapproval ofthe SIP submission at issue here.

Section 110(1)provides in part that: "the Administrator shall not approve a revision of a

plan ifthe revision would interfere with any applicable requirement concerning attainment and

reasonable further progress ..., or any other applicable requirement ofthis chapter." EPA has

consistently interpreted Section 110(1)as not requiring a new attainment demonstration for every

SIP submission. EPA has further concluded that preservation ofthe status quo air quality during

the time new attainment demonstrations are being prepared will prevent interference with the

states' obligations to develop timely attainment demonstrations. 70 FR 58,199,58,134 (Oct. 5.

2005); 70 FR 17.029, 17,033 (Apr. 4, 2005); 70 FR 53, 57 (Jan. 3, 2005); 70 FR 28,429,28,431

(May 18, 2005).

New Mexico's submission is the initial submission by the State to address the significant

contribution to nonattainment element of 110(a)(2)(D)(i) for the 1997 8-hour ozone and 1997

PM2.5 NAAQS. This submission does not revise or remove any existing emissions limit for any

NAAQS, or change any other existing substantive SIP provisions relevant to the 1997 8-hour

ozone or 1997 PM2.5NAAQS or any other NAAQS. Simply put, it does not make any

substantive revision that could result in any change in emissions. As a result, the submission
52

does not relax any existing requirements or alter the status quo air quality. Therefore, approval

ofthe submission will not interfere with attainment or maintenance of any NAAQS.

EPA's discussion in the notice cited by the commenter concerning a PMIO maintenance

plan in another state is consistent with this interpretation. In the cited action, EPA noted that:

"Utah had either removed or altered a number ofstationary source requirements," creating the

possibility of a relaxation of existing EPA approved SIP requirements and thereby interfering

with attainment, a possibility that is not present here. See 74 FR 62727 (Dec. 1,2009). Thus,

the action cited by the commenter is clearly distinguishable.

The commenter did not provide any specific basis for concluding that approval ofthis

SIP submission would interfere with attainment or maintenance of any NAAQS, or with any

other applicable requirement ofthe Clean Air Act. EPA concludes that approval ofthe

submission will not make the status quo air quality worse, and is in fact consistent with the

development of an overall plan capable ofmeeting the Act's attainment requirements. In

particular, EPA has determined that the submission complies with the requirements ofsection

110(a)(2)(D)(i). Accordingly, assuming that section 110(1) applies to this SIP submission, EPA

finds that approval ofthe submission is consistent with the requirements ofsection 110(1).

Comment No. 19 -- In a separate comment letter, the commenter expressed concern with

EPA's proposed approval ofthe State's submission for the 1997 8-hour ozone NAAQS and 1997

PM2.5 NAAQS because the state "does not appropriately limit ozone" in its PSD permitting

program. To support this claim, the commenter noted that EPA has previously made a "finding

offailure to submit" because New Mexico had not made another submission that would have the

effect ofmaking NOx a regulatory precursor for ozone in the context ofPSD. According to the

commenter, EPA should not approve the state's submission for section 11O(a)(2)(D)(i)(I) for the
53

significant contribution to nonattainment requirement because ofthis outstanding obligation with

respect to the PSD requirements ofthe CAA for the 1997 8-hour ozone NAAQS.

EPA Response - EPA acknowledges that it made the finding offailure to submit noted by

the commenter.I' However, EPA disagrees with the commenter's view of how that prior finding

affects today's specific action. First, the "finding offailure to submit" to which the commenter

refers is not for a failure to make a submission with respect to section 110(a)(2)(D). In that prior

action, EPA made a formal finding that the state had, at that time, not yet made a different SIP

submission, necessary to comply with a separate requirements ofsection 11O(a)(2)(C)and

section 1l0(a)(2)(J).

Second, EPA believes that the cited finding offailure to submit does not relate to the

requirements ofsection II0(a)(2)(D)(i)(I) with respect to significant contribution to

nonattainment at issue in this action, but rather to the separate requirements ofsection

11O(a)(2)(D)(i)(II) that SIPs include measures to prevent interference with measures required for

"prevention ofsignificant deterioration." EPA's 2006 Guidance explained the Agency's views

of what the four separate and distinct elements ofsection 11O(a)(2)(D)require.42 EPA's

guidance made recommendations to states for making submissions to meet each ofthe separate

requirements ofsection 11O(a)(2)(D) for the 1997 8-hour ozone standards and 1997 PM2.5

standards. Within the guidance, EPA recommended that states evaluate the existence of, and

extent of, significant contribution to nonattainment in other states by various means, intended to

consider relevant facts about such contribution to nonattainment. By contrast, EPA

41 See, Completeness Findings for Section 110(a)(2) State Implementation Plans for the 8-hour Ozone NAAQS, 73

FR 16,205 (March 28, 2008).

42 "Guidance for State Implementation Plan (SIP) Submission to Meet Current Outstanding Obligations Under

Section 110(a)(2)(D)(i) for the 8-Hour Ozone and PM2.

s National Ambient Air Quality Standards" August 15,

2006.
54

recommended that states meet the separate requirement that their SIPs contain measures to

prevent interference with measures required to prevent significant deterioration of air quality in

other states by different means. In particular, EPA explained that this latter element ofsection

110(a)(2)(D) would be the correct context in which to confirm that the state in question had

updated its own SIP to contain measures related to PSD.

In the 2006 Guidance, EPA explicitly identified the regulatory requirements and separate

SIP revision necessary to implement the PSD program for the 1997 8-hour ozone NAAQS as

among the requirements that EPA considered relevant to the prevention ofsignificant

deterioration requirements ofsection 110(a)(2)(D).43 EPA stated its view that implementation of

the PSD permitting program within the state would address the requirement to prohibit emissions

that interfere with measures to prevent significant deterioration in neighboring states. EPA also

explained that the permitting program for the 8-hour ozone NAAQS would require that new or

modified sources will not cause or contribute to violations ofthe NAAQSin neighboring states,

so that additional SIP submissions with rule changes or modeling demonstrations would not be

required to establish that a state's program complies with the requirementin section

11O(a)(2)(D)(i)(II) In short, EPA believes that evaluation of a state's SIP for compliance with

section 11O(a)(2)(D)(i)(II) is the proper context in which to determine whether such SIP meets

current federal PSD requirements. Today's action does not address this element ofsection

11O(a)(2)(D), and accordingly, the finding offailure to submit is not a basis not to approve the

State's submission for this purpose.

Finally, EPA notes that the State ofNew Mexico has subsequently made a submission to

comply with the rule that was the basis for the finding offailure to submit cited by the

43 Id, at pages 6 - 8.
55

commenter. EPA is in the process of evaluating that submission and will act on it at a later date.

EPA anticipates that it may elect to act upon that separate submission at the same time it acts

upon the state's section 11O(a)(2)(D) submission for the prevention ofsignificant deterioration

requirement, as EPA has recently done in the case ofthe section 11O(a)(2)(D) submission for the

State ofNorth Dakota.

B. Comments from New Mexico Environment Department, Air Quality Bureau

Comment No.1 - The commenter stated that while it did not object to EPA's proposed

approval ofthe "contribute to nonattainment" prong ofsection 11O(a)(2)(D)(i) ofthe CAA, it

believed that EPA should have approved the SIP submission as meeting all prongs ofthat

section. The commenter asserted its beliefthat New Mexico satisfied all requirements ofsection

110(a)(2)(D) for the 1997 8-hour ozone and 1997 PM2.5 NAAQS in its submission, following

EPA's recommendations in the 2006 Guidance for this SIP revision.

EPA Response - We appreciate NMED's comments. At this time, EPA is only taking

action on the portions ofthe State's submission that pertain to the significant contribution to

nonattainment requirements ofsection 11O(a)(2)(D) for the 1997 8-hour ozone and 1997 PM2.5

NAAQS. EPA will act on the remaining requirements ofsection 110(a)(2)(D) for these NAAQS

at a later date.

IV. Final Action

We are approving one element ofthe Interstate Transport SIP submitted by the State of

New Mexico on September 17, 2007. Specifically, in this action we are approving the element

that addresses the requirement of Section 110(a)(2)(D)(i)(I) that emissions from sources in that
56

state do not "contribute significantly" to violations of the 1997 8-hour ozone or 1997 PM2.5

NAAQS in any other state. After fully considering all comments received on the proposal and

direct final rule EPA has concluded that the State's submission, and additional evidence

evaluated by EPA, establish that emissions from New Mexico sources do not contribute

significantly to nonattainment ofthe relevant NAAQAS in any other state. Accordingly, New

Mexico does not need to include additional emission limitations on its sources to eliminate any

such contribution to other states for purposes ofthese NAAQS.

At a later date, EPA will act on addressing the remaining requirements ofsection

11O(a)(2)(D)(i)which are: interference with the maintenance ofthe NAAQS in any other state;

interference with measures required to prevent significant deterioration of air quality in any other

state; and interference with measures required to protect visibility in any other state.

V. Statutory and Executive Order Reviews

Under the Clean Air Act, the Administrator is required to approve a SIP

submission that complies with the provisions ofthe Act and applicable Federal regulations. 42

U.S.C. 741O(k); 40 CFR 52.02(a). Thus, in reviewing SIP submissions, EPA's role is to approve

state choices, provided that they meet the criteria ofthe Clean Air Act. Accordingly, this action

merely approves state law as meeting Federal requirements and does not impose additional

requirements beyond those imposed by state law. For that reason, this action:

• is not a "significant regulatory action" subject to review by the Office of Management

and Budget under Executive Order 12866 (58 FR 51735, October 4, 1993);
57

• does not impose an information collection burden under the provisions ofthe Paperwork

Reduction Act (44 U.S.C. 3501 et seq.);

• is certified as not having a significant economic impact on a substantial number ofsmall

entities under the Regulatory Flexibility Act (5 U.S.C. 601 et seq.);

• does not contain any unfunded mandate or significantly or uniquely affect small

governments, as described in the Unfunded Mandates Reform Act of 1995 (Public Law

104-4);

• does not have Federalism implications as specified in Executive Order 13132 (64 FR

43255, August 10, 1999);

• is not an economically significant regulatory action based on health or safety risks

subject to Executive Order 13045 (62 FR 19885, April 23, 1997);

• is not a significant regulatory action subject to Executive Order 13211 (66 FR 28355,

May 22,2001);

• is not subject to requirements of Section 12(d) ofthe National Technology Transfer and

Advancement Act of 1995 (15 U.S.C. 272 note) because application ofthose

requirements would be inconsistent with the Clean Air Act; and

• does not provide EPA with the discretionary authority to address, as appropriate,

disproportionate human health or environmental effects, using practicable and legally

permissible methods, under Executive Order 12898 (59 FR 7629, February 16, 1994).

In addition, this rule does not have tribal implications as specified by Executive Order 13175

(65 FR 67249, November 9,2000), because the SIP is not approved to apply in Indian country

located in the state, and EPA notes that it will not impose substantial direct costs on tribal

governments or preempt tribal law.
58

The Congressional Review Act, 5 U.S.C. 801 et seq., as added by the Small Business

Regulatory Enforcement Fairness Act of 1996, generally provides that before a rule may take

effect, the agency promulgating the rule must submit a rule report, which includes a copy ofthe

rule, to each House ofthe Congress and to the Comptroller General ofthe United States. EPA

will submit a report containing this action and other required information to the U.S. Senate, the

U.S. House ofRepresentatives, and the Comptroller General ofthe United States prior to

publication ofthe rule in the Federal Register. A major rule cannot take effect until 60 days after

it is published in the Federal Register. This action is not a "major rule" as defined by 5 U.S.C.

804(2).

Under section 307(b)(l) ofthe Clean Air Act, petitions for judicial review ofthis action

must be filed in the United States Court of Appeals for the appropriate circuit by [FEDERAL

REGISTER OFFICE: insert date 60 days from date of publication of this document in the

Federal Register]. Filing a petition for reconsideration by the Administrator ofthis final rule

does not affect the finality ofthis action for the purposes ofjudicial review nor does it extend the

time within which a petition for judicial review may be filed, and shall not postpone the

effectiveness ofsuch rule or action. This action may not be challenged later in proceedings to

enforce its requirements. (See section 307(b)(2).)
59

List of Subjects in 40 CFR Part 52

Environmental protection, Air pollution control, Incorporation by reference,

Intergovernmental relations, Ozone, Particulate matter, Reporting and recordkeeping

requirements, Volatile organic compounds.

Dated:~r\:) ~}. r;:;;:::LJ

wrence E. Starfield

Acting Regional Administrator, Region 6.
40 CFR Part 52 is amended as follows:

PART 52 - [AMENDED]

1. The authority citation for part 52 continues to read as follows:

Authority: 42 U.S.C. 7401 et seq.

Subpart GG - New Mexico

2. The second table in § 52.1620(e) entitled "EPA Approved Nonregulatory Provisions and

Quasi-Regulatory Measures in the New Mexico SIP" is amended by adding an entry to the end

to read as follows:

§ 52.1620 Identification of plan.

* * * * *

(e) * * *

EPA Approved Nonregulatory Provisions and Quasi-Regulatory Measures in the New Mexico

SIP

State

Applicable geographic submittal/effective

Name ofSIP provision or nonattainment area date EPA approval date Explanation

•••••••

Interstate transport for New Mexico 09117/07 [insert date of FR [insert date ofFR

the 1997 ozone and publication] publication]

PM 2.

sNAAQS [insert FR page Approval for number where the

document begins] revisions to

prohibit

significant

contribution to

nonattainment in

any other state