Approval and Promulgation of State Implementation Plan Revisions; State of North Dakota; Interstate Transport of Pollution for the 1997 PM2.5

AGENCY:

Environmental Protection Agency (EPA).

ACTION:

Proposed rule.

SUMMARY:

The Environmental Protection Agency is proposing partial approval of the State Implementation Plan (SIP) revisions called “Interstate Transport of Air Pollution” addressing the “interference with maintenance” requirement of Clean Air Act (CAA) section 110(a)(2)(D)(i) for the 1997 fine particulate matter (PM_2.5) and 8-hour ozone National Ambient Air Quality Standards (NAAQS). In this action EPA proposes to approve the North Dakota Interstate Transport SIP sections that address the requirements of section 110(a)(2)(D)(i) prohibiting a state's emissions from interfering with maintenance by any other state of the 1997 PM_2.5 and 8-hour ozone NAAQS. This action is being taken under section 110 of the CAA.

DATES:

Comments must be received on or before October 18, 2010.

ADDRESSES:

Submit your comments, identified by Docket ID No. EPA-R08-OAR-2009-0557, by one of the following methods:

• http://www.regulations.gov. Follow the on-line instructions for submitting comments.
• E-mail: mastrangelo.domenico@epa.gov.
• Fax: (303) 312-6064 (please alert the individual listed in the FOR FURTHER INFORMATION CONTACT if you are faxing comments).
• Mail: Callie Videtich, Director, Air Program, Environmental Protection Agency (EPA), Region 8, Mailcode 8P-AR, 1595 Wynkoop Street, Denver, Colorado 80202-1129.
• Hand Delivery: Callie Videtich, Director, Air Program, Environmental Protection Agency (EPA), Region 8, Mailcode 8P-AR, 1595 Wynkoop, Denver, Colorado 80202-1129. Such deliveries are only accepted Monday through Friday, 8 a.m. to 4:30 p.m., excluding Federal holidays. Special arrangements should be made for deliveries of boxed information.

Instructions: Direct your comments to Docket ID No. EPA-R08-OAR-2009-0557. EPA's policy is that all comments received will be included in the public docket without change and may be made available online at http://www.regulations.gov,, including any personal information provided, unless the comment includes information claimed to be Confidential Business Information (CBI) or other information whose disclosure is restricted by statute. Do not submit information that you consider to be CBI or otherwise protected through http://www.regulations.gov or e-mail. The http://www.regulations.gov Web site is an “anonymous access” system, which means EPA will not know your identity or contact information unless you provide it in the body of your comment. If you send an e-mail comment directly to EPA, without going through http://www.regulations.gov , your e-mail address will be automatically captured and included as part of the comment that is placed in the public docket and made available on the Internet. If you submit an electronic comment, EPA recommends that you include your name and other contact information in the body of your comment and with any disk or CD-ROM you submit. If EPA cannot read your comment due to technical difficulties and cannot contact you for clarification, EPA may not be able to consider your comment. Electronic files should avoid the use of special characters, any form of encryption, and be free of any defects or viruses. For additional instructions on submitting comments, go to Section I. General Information of the SUPPLEMENTARY INFORMATION section of this document.

Docket: All documents in the docket are listed in the http://www.regulations.gov index. Although listed in the index, some information is not publicly available, e.g., CBI or other information whose disclosure is restricted by statute. Certain other material, such as copyrighted material, will be publicly available only in hard copy. Publicly-available docket materials are available either electronically in http://www.regulations.gov or in hard copy at the Air Program, Environmental Protection Agency (EPA), Region 8, Mailcode 8P-AR, 1595 Wynkoop, Denver, Colorado 80202-1129. EPA requests that if at all possible, you contact the individual listed in the FOR FURTHER INFORMATION CONTACT section to view the hard copy of the docket. You may view the hard copy of the docket Monday through Friday, 8 a.m. to 4 p.m., excluding Federal holidays.

FOR FURTHER INFORMATION CONTACT:

Domenico Mastrangelo, Air Program, U.S. Environmental Protection Agency, Region 8, Mailcode 8P-AR, 1595 Wynkoop, Denver, Colorado 80202-1129, (303) 312-6436, mastrangelo.domenico@epa.gov.

SUPPLEMENTARY INFORMATION:

Definitions

For the purpose of this document, we are giving meaning to certain words or initials as follows:

(i) The words or initials Act or CAA mean or refer to the Clean Air Act, unless the context indicates otherwise.

(ii) The words EPA, we, us or our mean or refer to the United States Environmental Protection Agency.

(iii) The initials SIP mean or refer to State Implementation Plan.

(iv) The words North Dakota and State mean the State of North Dakota.

Table of Contents

I. General Information

What should I consider as I prepare my comments for EPA?

II. Background

III. What action is EPA proposing?

IV. What is the State process to submit this material to EPA?

V. EPA's Review and Technical Information

A. EPA's Evaluation of Interference with Maintenance

B. North Dakota Transport SIP

VI. Proposed Action

VII. Statutory and Executive Order Reviews

I. General Information

What should I consider as I prepare my comments for EPA?

1. Submitting CBI. Do not submit CBI to EPA through http://www.regulations.gov or e-mail. Clearly mark the part or all of the information that you claim to be CBI. For CBI information in a disk or CD ROM that you mail to EPA, mark the outside of the disk or CD ROM as CBI and then identify electronically within the disk or CD ROM the specific information that is claimed as CBI. In addition to one complete version of the comment that includes information claimed as CBI, a copy of the comment that does not contain the information claimed as CBI must be submitted for inclusion in the public docket. Information so marked will not be disclosed except in accordance with procedures set forth in 40 CFR part 2.

2. Tips for Preparing Your Comments. When submitting comments, remember to:

Identify the rulemaking by docket number and other identifying information (subject heading, Federal Register date and page number).

Follow directions—The agency may ask you to respond to specific questions or organize comments by referencing a Code of Federal Regulations (CFR) part or section number.

Explain why you agree or disagree; suggest alternatives and substitute language for your requested changes.

Describe any assumptions and provide any technical information and/or data that you used.

If you estimate potential costs or burdens, explain how you arrived at your estimate in sufficient detail to allow for it to be reproduced.

Provide specific examples to illustrate your concerns, and suggest alternatives.

Explain your views as clearly as possible, avoiding the use of profanity or personal threats.

Make sure to submit your comments by the comment period deadline identified.

II. Background

On July 18, 1997, EPA promulgated new NAAQS for ozone and for PM_2.5. This action is being taken in response to the promulgation of the 1997 PM_2.5 and 8-hour ozone NAAQS. This action does not address the requirements for the 2006 24-hour PM_2.5 or 2008 8-hour ozone NAAQS; those standards will be addressed in later actions.

Section 110(a)(1) of the CAA requires states to submit SIPs to address a new or revised NAAQS within 3 years after promulgation of such standards, or within such shorter period as EPA may prescribe. Section 110(a)(2) lists the elements that such new SIPs must address, as applicable, including section 110(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) Submissions to Meet Current Outstanding Obligations Under Section 110(a)(2)(D)(i) for the 8-Hour Ozone and PM_2.5 National Ambient Air Quality Standards” (2006 Guidance). EPA developed the 2006 Guidance to make recommendations to states for making submissions to meet the requirements of section 110(a)(2)(D)(i) for the 1997 8-hour ozone standards and the 1997 PM_2.5 standards.

As identified in the 2006 Guidance, the “good neighbor” provisions in section 110(a)(2)(D)(i) require each state to submit a SIP that prohibits emissions that adversely affect another state in the ways contemplated in the statute. Section 110(a)(2)(D)(i) contains four distinct requirements related to the impacts of interstate transport. The SIP must prevent sources in the state from emitting pollutants in amounts which will: (1) Contribute significantly to nonattainment of the NAAQS in other states; (2) interfere with maintenance of the NAAQS in other states; (3) interfere with provisions to prevent significant deterioration of air quality in other states; or (4) interfere with efforts to protect visibility in other states.

On April 6, 2009, EPA received a SIP revision from the State of North Dakota intended to address the requirements of section 110(a)(2)(D)(i) for both the 1997 8-hour ozone standards and the 1997 PM_2.5 standards. In this rulemaking, EPA is addressing only the requirements that pertain to preventing sources in North Dakota from emitting pollutants that will interfere with maintenance of the 1997 8-hour ozone NAAQS and the 1997 PM_2.5 NAAQS by other states. In its submission, the State of North Dakota indicated that its current SIP is adequate to prevent such interference. With this submission, the state intended to meet the recommendations of the 2006 Guidance for SIP submissions to meet the second element of section 110(a)(2)(D)(i) for the 1997 PM_2.5 and 8-hour ozone standards.

III. What action is EPA proposing?

EPA is proposing partial approval of the North Dakota Interstate Transport of Air Pollution SIP for the 1997 PM_2.5 and 8-hour ozone NAAQS. The addition to the North Dakota SIP of section 7.8, “Interstate Transport of Air Pollution,” was adopted by the State of North Dakota on April 1, 2009 and submitted to EPA on April 6, 2009. EPA is proposing to approve the language and demonstrations of the North Dakota Interstate Transport SIP that address element (2) of section 110(a)(2)(D)(i), i.e., the prohibition of interference with maintenance of the 1997 8-hour ozone NAAQS and the 1997 PM_2.5 NAAQS by any other state.

IV. What is the State process to submit this material to EPA?

Section 110(k) of the CAA addresses EPA's rulemaking action on SIP submissions by states. The CAA requires states to observe certain procedural requirements in developing SIP revisions for submittal to EPA. Section 110(a)(2) of the CAA requires that each SIP revision be adopted after reasonable notice and public hearing. This must occur prior to the revision being submitted by a state to EPA.

The North Dakota Department of Health (NDDH) held a public hearing on October 7, 2008 for the addition to the North Dakota SIP of the Interstate Transport non-regulatory provisions. The NDDH adopted the provisions on April 1, 2009 and submitted them to EPA on April 6, 2009.

EPA has reviewed the submittal by the NDDH and has determined that the State met the requirements for reasonable notice and public hearing under section 110(a)(2) of the CAA.

V. EPA's Review and Technical Information

A. EPA's Evaluation of Interference With Maintenance

The second element of section 110(a)(2)(D)(i) requires that a state's SIP must prohibit any source or other type of emissions activity in the state from emitting pollutants that would “interfere with maintenance” of the applicable NAAQS by any other state. This term is not defined in the statute. Therefore, EPA has interpreted this term in past regulatory actions, such as the 1998 NO_X SIP Call, in which EPA took action to eliminate emissions of NO_X that significantly contributed to nonattainment, or interfered with maintenance of, the then applicable ozone NAAQS through interstate transport of NO_X and the resulting ozone. The NO_X SIP Call was the mechanism through which EPA evaluated whether or not the NO_X emissions from sources in certain states had such prohibited interstate impacts, and if they had such impacts, required the states to adopt substantive SIP revisions to eliminate the NO_X emissions, whether through participation in a regional cap and trade program or by other means.

After promulgation of the 1997 8-hour ozone NAAQS and the 1997 PM_2.5 NAAQS, EPA again recognized that regional transport was a serious concern throughout the eastern U.S. and therefore developed the 2005 Clean Air Interstate Rule (CAIR) to address emissions of SO₂ and NO_X that exacerbate ambient ozone and PM_2.5 levels in many downwind areas through interstate transport. Within CAIR, EPA likewise interpreted the term “interfere with maintenance” as part of the evaluation of whether or not the emissions of sources in certain states had such impacts on areas that EPA determined would either be in violation of the NAAQS, or would be in jeopardy of violating the NAAQS, in a modeled future year unless action were taken by upwind states to reduce SO₂ and NO_X emissions. Through CAIR, EPA again required states that had such interstate impacts to adopt substantive SIP revisions to eliminate the SO₂ and NO_X emissions, whether through participation in a regional cap and trade program or by other means.

EPA's 2006 Guidance addressed section 110(a)(2)(D)(i) requirements for the 1997 8-hour ozone NAAQS and 1997 PM_2.5 NAAQS. For those states subject to CAIR, EPA indicated that compliance with CAIR would meet the two requirements of section 110(a)(2)(D)(i)(I) for these NAAQS. For states not within the CAIR region, EPA recommended that states evaluate whether or not emissions from their sources would “interfere with maintenance” by other states, following the conceptual approach adopted by EPA in CAIR. After recommending various types of information that could be relevant for the technical analysis to support the SIP submission, such as the amount of emissions and meteorological conditions in the state, EPA further indicated that it would be appropriate for the state to assess impacts of its emissions on other states using considerations comparable to those used by EPA “in evaluating significant contribution to nonattainment in the CAIR.” EPA did not make specific recommendations for how states should assess “interference with maintenance” separately, and discussed the first two elements of section 110(a)(2)(D)(i) together without explicitly differentiating between them.

In 2008, however, the U.S. Court of Appeals for the DC Circuit found that CAIR and the related CAIR Federal implementation plans were unlawful. Among other issues, the court held that EPA had not correctly addressed the second element of section 110(a)(2)(D)(i)(I) in CAIR. The court noted that “EPA gave no independent significance to the `interfere with maintenance' prong of section 110(a)(2)(D)(i)(I) to separately identify upwind sources interfering with downwind maintenance.” EPA's approach, the court reasoned, would leave areas that are “barely meeting attainment” with “no recourse” to address upwind emissions sources. The court therefore concluded that a plain language reading of the statute requires EPA to give independent meaning to the interfere with maintenance requirement of section 110(a)(2)(D) and that the approach used by EPA in CAIR failed to do so.

In addition to affecting CAIR directly, the court's decision in the North Carolina case indirectly affects EPA's recommendations to states in the 2006 Guidance with respect to the interference with maintenance element of section 110(a)(2)(D)(i) because the agency's guidance suggested that states use an approach comparable to that used by EPA in CAIR. States such as North Dakota developed and adopted their Interstate Transport SIP not long after the Court's July 2008 decision, but well before EPA, in the Transport Rule Proposal (see below), was able to propose a new approach for the interference with maintenance element. Without recommendations from EPA, North Dakota's SIP may not have sufficiently differentiated between the significant contribution to nonattainment and interference with maintenance elements of the statute, and relied in a general way on the difference between monitored concentrations and the 1997 8-hour ozone NAAQS to evaluate the impacts of State emissions on maintenance of the NAAQS in neighboring states. EPA believes that it is necessary to evaluate these state submissions for section 110(a)(2)(D)(i)(I) in such a way as to assure that the interfere with maintenance element of the statute is given independent meaning and is appropriately evaluated using the types of information that EPA recommended in the 2006 Guidance. To accomplish this, EPA believes it is necessary to use an updated approach to this issue and to supplement the technical analysis provided by the state in order to evaluate the submissions with respect to the interfere with maintenance element of section 110(a)(2)(D)(i).

EPA has recently proposed a new rule to address interstate transport pursuant to section 110(a)(2)(D)(i), the “Federal Implementation Plans to Reduce Interstate Transport of Fine Particulate Matter and Ozone” (Transport Rule Proposal), in order to address the judicial remand of CAIR. As part of the Transport Rule Proposal, EPA specifically reexamined the section 110(a)(2)(D) requirement that emissions from sources in a state must not “interfere with maintenance” of the 1997 8-hour ozone NAAQS and 1997 PM_2.5 NAAQS by other states. In the proposal, EPA developed an approach to identify areas that it predicts to be close to the level of the 1997 8-hour ozone NAAQS and 1997 PM_2.5 NAAQS in the future, and therefore at risk to become or continue to be nonattainment for these NAAQS unless emissions from sources in other states are appropriately controlled. This approach starts by identifying those specific geographic areas for which further evaluation is appropriate, and differentiates between areas where the concern is with interference with maintenance, rather than with significant contribution to nonattainment.

As described in more detail below, EPA's analysis evaluates data from existing monitors over three overlapping three-year periods (i.e., 2003-2005, 2004-2006, and 2005-2007), as well as air quality modeling data, in order to determine which areas are predicted to be violating the 1997 8-hour ozone and PM_2.5 NAAQS in 2012, and which areas are predicted potentially to have difficulty with maintaining attainment as of that date. In essence, if an area's projected data for 2012 indicates that it would be violating the NAAQS based on the average of these three overlapping periods, then this monitor location is appropriate for comparison for purposes of the significant contribution to nonattainment element of section 110(a)(2)(D)(i). If, however, an area's projected data indicate that it would be violating the NAAQS based on the highest single period, but not over the average of the three periods, then this monitor location is appropriate for comparison for purposes of the interference with maintenance element of the statute.

By this method, EPA has identified those areas with monitors that are appropriate “maintenance-only sites” or maintenance “receptors” for evaluating whether the emissions from sources in another state could interfere with maintenance in that particular area. EPA then uses other analytical tools to examine the potential impacts of emissions from upwind states on these maintenance receptors in downwind states. EPA believes that this new approach for identifying those areas that are predicted to have maintenance problems is appropriate to evaluate the section 110(a)(2)(D)(i) SIP submission of a state for the interference with maintenance element. EPA's 2006 Guidance did not provide this specific recommendation to states, but in light of the court's decision on CAIR, EPA will itself follow this approach in acting upon the North Dakota submission.

As explained in the 2006 Guidance, EPA does not believe that section 110(a)(2)(D)(i) SIP submissions from all states necessarily need to follow precisely the same analytical approach as CAIR. In the 2006 Guidance, EPA stated that: “EPA believes that the contents of the SIP submission required by section 110(a)(2)(D)(i) may vary depending upon the facts and circumstances related to the specific NAAQS. In particular, the data and analytical tools available at the time the State develops and submits a SIP for a new or revised NAAQS necessarily affects the contents of the required submission.” EPA also indicated in the 2006 Guidance that it did not anticipate that sources in states outside the geographic area covered by CAIR were significantly contributing to nonattainment, or interfering with maintenance, in other states. As noted in the Transport Rule Proposal, EPA continues to believe that the more widespread and serious transport problems in the eastern United States are analytically distinct. For the 1997 8-hour ozone NAAQS and the 1997 PM_2.5 NAAQS, EPA believes that nonattainment and maintenance problems in the western United States are relatively local in nature with only limited impacts from interstate transport. In the Transport Rule Proposal, EPA did not calculate interstate ozone or PM_2.5 contributions to or from western States.

Accordingly, EPA believes that section 110(a)(2)(D)(i) SIP submissions for states not evaluated in the Transport Rule Proposal may be evaluated using a “weight of the evidence” approach that takes into account available relevant information, such as that recommended by EPA in the 2006 Guidance for states outside the area affected by CAIR. Such information may include, but is not limited to, the amount of emissions in the state relevant to the NAAQS in question, the meteorological conditions in the area, the distance from the state to the nearest monitors in other states that are appropriate receptors, or such other information as may be probative to consider whether sources in the state may interfere with maintenance of the 1997 8-hour ozone and PM_2.5 NAAQS in other states. These submissions can rely on modeling when acceptable modeling technical analyses are available, but EPA does not believe that modeling is necessarily required if other available information is sufficient to evaluate the presence or degree of interstate transport in a given situation.

As a result, in the Transport Rule Proposal, EPA focused its modeling on a domain including eastern states. The Transport Rule Proposal's modeling domain includes all states east of the Rockies, from North Dakota in the north to Texas in the south and eastward, and its analysis results include estimates of North Dakota's contribution to the maintenance-only sites within the Transport Rule Proposal's modeling domain for the 1997 annual PM_2.5 and 8-hour ozone NAAQS. To reach a comprehensive determination on whether emissions from North Dakota interfere with maintenance of the NAAQS by any other states we use these estimated contributions in combination with other types of information that allow us to assess whether emissions from North Dakota interfere with maintenance of the NAAQS by states outside the Eastern modeling domain.

B. North Dakota Transport SIP

To meet the requirements of section 110(a)(2)(D)(i), the State of North Dakota on April 6, 2009 made a SIP submission to EPA addressing interstate transport for the 1997 PM_2.5 and the 8-hour ozone NAAQS. EPA has previously approved this submission for purposes of the significant contribution to nonattainment and of the interference with PSD elements of section 110(a)(2)(D)(i). The State's submittal focused primarily on whether emissions from North Dakota sources significantly contribute to nonattainment of the 1997 8-hour ozone NAAQS and 1997 PM_2.5 NAAQS in other states. Following the 2006 Guidance and consistent with EPA's approach in CAIR, North Dakota did not evaluate whether emissions from the State sources interfere with maintenance of these NAAQS by other states separately from significant contribution to nonattainment in other states. Instead, the State presumed that if North Dakota sources were not significantly contributing to violations of the NAAQS in other states, then no further specific evaluation was necessary for purposes of the interference with maintenance element of section 110(a)(2)(D)(i). As explained above, however, CAIR was remanded to EPA, in part because the court found that EPA had failed to give independent meaning to the “interfere with maintenance” requirement, a flaw that EPA has remedied in the Transport Rule Proposal. However, North Dakota submitted its Interstate Transport SIP without the benefit of EPA's new interpretation. We therefore discuss in more detail the approach of the Transport Rule Proposal and apply it to our assessment of whether North Dakota's emissions interfere with maintenance of the relevant NAAQS by any other states.

Below, we discuss in greater detail relevant methods and techniques of the Transport Rule Proposal, followed by our assessment of whether emissions from North Dakota interfere with maintenance of the 1997 PM_2.5 and 8-hour ozone NAAQS.

On July 6, 2010, the EPA Administrator signed a proposed rule in response to the judicial remand of CAIR. The Transport Rule Proposal, published August 2, 2010, includes a new approach to determine whether emissions from a state interfere with maintenance of the 1997 8-hour ozone NAAQS and the 1997 PM_2.5 NAAQS by other states. In this action, EPA is using modeling results from the Transport Rule Proposal to assess whether North Dakota emissions interfere with maintenance of the NAAQS by states included in the proposed rule's modeling domain. We use a comparable approach to assess whether North Dakota interferes with maintenance of the NAAQS by western states, not modeled for ozone or PM_2.5 contributions from North Dakota.

In the Transport Rule Proposal, EPA projected future concentrations of ozone and PM_2.5 at monitors to identify areas that are expected to be out of attainment with NAAQS or to have difficulty maintaining compliance with the NAAQS in 2012. These areas are referred to as nonattainment and maintenance receptors respectively. These nonattainment and maintenance receptors are based on projections of future air quality at existing ozone and PM_2.5 monitoring sites in those locations. EPA then used these sites as the receptors for examining the contributions of emissions from sources located in upwind states to nonattainment and maintenance problems at these monitoring locations.

For ozone, EPA evaluated air quality, or ozone concentrations, relative to the 1997 8-hour ozone NAAQS. The 1997 8-hour ozone NAAQS is set at 0.8 parts per million. The 8-hour ozone standard is met if the 3-year average of the annual 4th highest daily maximum 8-hour ozone concentration is less than or equal to 0.08 ppm (i.e., less than 85 ppb based on the rounding convention in 40 CFR part 50 Appendix I). This 3-year average is referred to as the “design value.”

For PM_2.5, EPA evaluated concentrations for both the annual PM_2.5 NAAQS and the 24-hour PM_2.5 NAAQS. The 1997 annual PM_2.5 NAAQS is met when the 3-year average of the annual mean concentration is 15.0 micrograms per cubic meter (μg/m) or less. The 3-year average annual mean concentration is computed at each site by averaging the daily Federal Reference Method (FRM) samples by quarter, averaging these quarterly averages to obtain an annual average, and then averaging the three annual averages to get the design value. The 1997 24-hour PM_2.5 NAAQS is met when the 3-year average of the annual 98th percentiles is 65 μg/m or less. The 3-year average mean 98th percentile concentration is computed at each site by averaging the three individual annual 98th percentile values at each site. The 3-year average 98th percentile concentration is referred to as the 24-hour average design value.

To project future ozone and annual PM_2.5 design values, EPA relies on monitoring data from the Air Quality System (AQS) combined with photochemical air quality modeling results. The Transport Rule Proposal generates the projected future ozone values based on an average of three design value periods which include the years 2003-2007 (i.e., design values for 2003-2005, 2004-2006, and 2005-2007). The average of the three design values creates a “5-year weighted average” value. The 5-year weighted average values were then projected to the future years that were analyzed for the Transport Rule Proposal. EPA used the 5-year weighted average concentrations to project concentrations anticipated in 2012 to determine which monitoring sites are expected to be nonattainment in this future year. EPA also projected 2012 design values based on each of the three year periods (i.e., 2003-2005, 2004-2006, and 2005-2007.) The highest projection, referred to as “maximum design value,” gives an indication of potential variability in future projections due to differences in actual meteorology and emissions from what was modeled.

EPA identified those sites that are projected to be attainment based on the 5-year weighted average design value, but that have a maximum design value (based on a single three year period) that exceeds the NAAQS, as maintenance receptors. These sites are attaining the NAAQS based on the projected average design values, but EPA anticipates that there will be more difficulty in maintaining attainment of the NAAQS at these locations if there are adverse variations in meteorology or emissions. These projected maintenance sites are the ones that EPA has used to determine if emissions from North Dakota sources potentially interfere with maintenance of the 1997 8-hour ozone NAAQS and 1997 annual PM_2.5 NAAQS in other states in this action.

To evaluate ambient impacts from upwind states to maintenance receptors, the Transport Rule Proposal uses a two step approach for measuring each state's significant contribution. In the first step, EPA evaluates through air quality modeling, contributions from individual states to downwind maintenance receptors. States whose contributions to any downwind receptors which are above the “significant contribution” threshold, one percent of the relevant NAAQS, are considered “linked” to those receptors for the purpose of the second step. In the second step, EPA uses maximum cost thresholds, informed by air quality considerations, to determine the portion of each state's contribution that constitutes its “interference with maintenance,” or “significant contribution.”

EPA Transport Rule Proposal proposed a threshold for “interference with maintenance” at one percent of the NAAQS for both PM_2.5 and ozone. For the 1997 annual PM_2.5 EPA proposed in the Transport Rule Proposal a threshold of 0.15 μg/m, without any further rounding up. States contributing less than 0.15 μg/m³ to downwind maintenance receptors are below the threshold and as a result are excluded from further analysis. States contributing 0.15 μg/m³ or more are above the threshold and are “linked” to the counties in which the affected receptors are located. States with “linkages” to downwind maintenance receptors are included in the analytical process that determines the controls (if any) required for compliance with the “interference with maintenance” element of section 110(a)(2)(D)(i) for the 1997 PM_2.5 standards.

For the 1997 8-hour ozone standard, EPA Transport Rule Proposal proposed a threshold for “interference with maintenance” at 0.8 ppb, one percent of the NAAQS. State contributions of 0.8 ppb and higher are considered above the threshold, while state contributions less than 0.8 ppb are below the threshold and such states are excluded from further analysis. States contributing significantly, 0.8 ppb or more, to downwind maintenance receptors are considered to be “linked” to the counties in which they are located and are included in the follow-up process that determines the controls (if any) required of such states to satisfy the “interfere with maintenance” element of section 110(a)(2)(D)(i) for the 1997 8-hour ozone standard.

PM_2.5

In the Transport Rule Proposal, EPA projected future concentrations of PM_2.5 to identify receptors that are expected to have difficulty maintaining compliance with the NAAQS in 2012, referred to as maintenance-only sites or maintenance receptors. For the 1997 annual PM_2.5 NAAQS, the Transport Rule Proposal identified 16 maintenance receptors in its modeling domain. The monitors at risk for maintenance are located in seven states, including two in Illinois (Cook County), four in West Virginia, six in Ohio, and one each in Kentucky, New York, Pennsylvania and Texas. To determine the states in the Eastern domain that contribute significantly to maintenance receptors, the Transport Rule models the states' PM_2.5 contribution to the maintenance receptors in these states. The largest contribution from North Dakota emissions to the maintenance receptors in these states was estimated to be 0.05 μg/m, a level two thirds below the “significant contribution” threshold of 0.15 μg/m. This small contribution excluded North Dakota from the Transport Rule Proposal's follow-up analysis for the states that contributed significantly and were “linked” to at least one of the monitors at risk for maintenance of the NAAQS.

To assist in the evaluation of whether emissions from a state's sources interfere with maintenance of the NAAQS in western states, EPA has developed, independent of the Transport Rule Proposal, a modeling analysis identifying monitors at risk for maintenance of the NAAQS within a modeling domain that includes the western states. The analysis presented in the memo, “Documentation of Future Year Ozone and Annual PM_2.5 Design Values for Western States” (Western States Design Values), uses model results from the Transport Rule Proposal modeling Continental U.S. 36 km grid, which is coarser than the 12 km grid used in the Transport Rule, but does not necessarily yield less reliable results.

EPA's modeling analysis of western states to identify monitors at risk for maintenance of the 1997 annual PM_2.5 NAAQS identifies only two such maintenance-only receptors, in Los Angeles and Orange Counties, California. These monitors are at least 1,100 miles from North Dakota's closest area (the State's southwestern corner,) and mountain ranges between North Dakota and the southern California maintenance receptors, such as the Rocky Mountains, Wasatch and the Sierra Nevada, present large obstacles to PM_2.5 transport from North Dakota to the two maintenance receptors in Los Angeles and Orange Counties. In addition, west of the Continental Divide the prevailing winds generally move from south-westerly, westerly, or north-westerly directions, as indicated by the typical movement of weather systems. Thus, geography, topography and meteorology of the region that encompasses North Dakota and California make it unlikely for PM_2.5 emissions and/or its precursors to contribute significantly to California's maintenance receptors, and thus interfere with maintenance of the annual PM_2.5 1997 NAAQS at these receptors.

It must also be noted that there are no maintenance receptors in any of the western states adjacent, or relatively close, to North Dakota, such as Montana, Idaho, Wyoming, and Utah. In fact, 2012 projected design values for the annual PM_2.5 peaked in Utah, Montana and Idaho at concentrations below 12 μg/m, and in Wyoming at concentrations below 10 μg/m.

Turning to the 1997 24-hour PM_2.5 NAAQS, in the Transport Rule Proposal EPA did not evaluate nonattainment receptors because there were no violations of these standards in portions of the U.S. covered by the 12 km grid, which includes the 37 states east of the Rockies. In fact, based on recent monitoring data (2007-2009 design values that are under final EPA review), the highest 24-hour PM_2.5 design value in 47 of the 48 states of the continental U.S. (not including California) is 50 µg/m, which is well below the level of the 1997 24-hour PM_2.5 NAAQS of 65 µg/m. Therefore, outside of California, there are no areas that we would expect to have difficulty in maintaining the 1997 24-hour PM_2.5 NAAQS. In California, the most recent (2009) 24-hour PM_2.5 design values show that the only monitors that might be at risk for maintenance of the 1997 24-hour PM_2.5 NAAQS are in Turlock, Fresno, and Bakersfield, in the northern, central and southern sections of the San Joaquin Valley. The high mountain ranges on three sides of the Valley's boundaries (Coast Mountain with 5,000 feet peaks on the west, Sierra Nevada range with 14,000 feet peaks on the east, and Tehachapi Mountains with 6,000 feet along the southern boundary) are an obstacle to transport of PM_2.5 and its precursors into the valley. As noted earlier in our discussion of the impacts from North Dakota emissions on annual PM_2.5 concentrations, and in this case too, the geography (nearly 1,200 miles distance), topography (high mountain ranges between North Dakota and California), and meteorology (southwesterly or westerly directions of prevailing winds) make it highly unlikely that emissions from North Dakota contribute significantly to the San Joaquin Valley monitors at risk for maintenance of the 24-hour PM_2.5 NAAQS.

In conclusion, our analysis indicates that emissions of PM_2.5 and/or its precursors from the sources in North Dakota are unlikely to interfere with maintenance of the 24-hour and the annual PM_2.5 NAAQS by any other states.

8-Hour Ozone

In the Transport Rule Proposal, EPA projected future concentrations of ozone to identify receptors, referred to as maintenance receptors, that are expected to have difficulty maintaining compliance with the 1997 8-hour ozone NAAQS in 2012. To determine states that impact maintenance-only sites, in the Transport Rule Proposal EPA models the states' ozone contribution to these receptors. For the 8-hour ozone NAAQS, EPA identified 16 maintenance receptors in its modeling domain. The monitors at risk for maintenance are located in a handful of states, including eight monitors in Texas, four in Connecticut, two in Georgia, and one each in New York and Pennsylvania. The largest contribution from North Dakota emissions to the 16 maintenance receptors in these states was estimated to be 0.0 ppb, resulting in the exclusion of the State's emissions from further analysis, and in the conclusion that North Dakota emissions do not interfere with maintenance of the 1997 8-hour ozone NAAQS by any states in the eastern U.S.A.

As noted earlier, EPA has also developed a modeling analysis identifying maintenance receptors within a modeling domain that includes the western states. In the western states EPA identified only four monitors at risk for maintenance of the 1997 8-hour ozone NAAQS, and all four are in California, in Mercer, Placer, Riverside, and Sacramento Counties. Geography and topography are not favorable to ozone transport from North Dakota, which is approximately 1200 miles northeast of the counties referenced above. In the absence of significant northeasterly regional transport winds, mountain ranges between North Dakota and the California maintenance receptors, such as the Rocky Mountains, the Wasatch and the Sierra Nevada, present serious obstacles to ozone transport from North Dakota to California. Thus, geography and topography reduce the likelihood of transport from North Dakota to California's maintenance receptors.

Prevailing wind orientation in fact strongly supports the conclusion that emissions from North Dakota sources are unlikely to interfere with maintenance of the 1997 8-hour ozone standard in California. West of the Continental Divide the prevailing winds generally move from south-westerly, westerly, or north-westerly directions, as indicated by the typical movement of weather systems. To further evaluate the direction of regional transport winds affecting the California maintenance receptors, EPA Region 8 has plotted back trajectories starting at each maintenance receptor on high ozone days. High ozone days include the top one third of the exceedance days (for the 1997 8-hour ozone NAAQS) registered at each monitor in 2005 and 2006. As shown by the trajectories mapped for all four maintenance receptors in Figure 3.1, Appendix A of EPA's supporting documentation, on high ozone days air parcels converge on the Mercer, Placer, Sacramento and Riverside monitors from the northwest, south and southeast, but there are no pathways from the east/northeast directions reaching even as far as the eastern Nevada border, let alone North Dakota.

For a large number of receptors in western states, EPA's modeling analysis could not calculate 2012 projected design values because these receptors did not have at least 5 days with base year concentrations equal to or greater than 70 ppb, as required by EPA's modeling guidance. However, the observed maximum design values at these sites in the 2003-2007 period were generally well below the 1997 ozone NAAQS. The highest (non-California ) site had a maximum design value of 77 ppb. Additionally, the 2012 modeling results at western monitors (where a future year design value could be estimated,) shows a downward trend in ozone. There are no areas in the West where ozone is predicted to be higher in 2012 (without CAIR) compared to 2005. On these bases it is plausible to conclude that it is highly unlikely, but not impossible, for these monitors to be at risk for maintenance of the 1997 8-hour ozone NAAQS.

In conclusion, data and weight of evidence analysis presented in this section support the position of the North Dakota Interstate Transport SIP (adopted into the State SIP on April 1, 2009 and submitted to EPA April 6, 2009) that emissions from North Dakota do not interfere with maintenance of the 1997 8-hour ozone NAAQS by any other state, consistent with the requirements of element (2) of CAA section 110(a)(2)(D)(i).

VI. Proposed Action

EPA is proposing partial approval of the addition to the North Dakota SIP of the “Interstate Transport of Air Pollution” SIP addressing the requirements of CAA section 110(a)(2)(D)(i) for the 1997 PM_2.5 and 8-hour ozone National Ambient Air Quality Standards (NAAQS). EPA is proposing approval of the language in Section 7.8.1, subsection B., “Nonattainment and Maintenance Area Impact,” that specifically addresses element (2) of section 110(a)(2)(D)(i), the requirement that the SIP contain adequate provisions prohibiting emissions from North Dakota from interfering with maintenance of the 1997 PM_2.5 and 8-hour ozone NAAQS by any other state. The language in Section 7.8.1, subsection B., that addresses element (1) of section 110(a)(2)(D)(i) was approved by EPA in a June 3, 2010 Federal Register action.

VII. Statutory and Executive Order Review

Under the Clean Air Act, the Administrator is required to approve a SIP submission that complies with the provisions of the Act and applicable Federal regulations. 42 U.S.C. 7410(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 of the 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);
• Does not impose an information collection burden under the provisions of the Paperwork Reduction Act (44 U.S.C. 3501 et seq.);
• Is certified as not having a significant economic impact on a substantial number of small 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 (Pub. L. 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 2835, May 22, 2001);
• Is not subject to requirements of Section 12(d) of the National Technology Transfer and Advancement Act of 1995 (15 U.S.C. 272 note) because application of those 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.

List of Subjects in 40 CFR Part 52

• Environmental protection
• Air pollution control
• Incorporation by reference
• Intergovernmental relations
• Nitrogen dioxide
• Ozone
• Particulate matter
• Reporting and recordkeeping requirements
• Volatile Organic Compounds

Authority: 42 U.S.C. 7401 et seq.