MEMORANDUM

TO : FILE

FROM: Erik Snyder, Lead Regional Air Quality Modeler, Region 6 DATE: August 2010 SUBJECT: New Mexico Intereference with Maintenance for 1997 NAAQS Technical Support Document

This TSD is EPA’s Technical Support Docu ment that summarizes EPA’s technical review of the State Implementation Plan (SIP) revision submitted by the State of New Mexico for the purpose of addressing the “ good neighbor” provisions of Clean Air Act (CAA) section 110(a)(2)(D)(i) for the 1997 8-hour ozone Na tional Ambient Air Quality Standards (NAAQS or st andards) and the 1997 PM 2.5 NAAQS. This SIP revision addresses the requirement that the State of New Mexico’s SIP have adequate provisions to prohibit air emissions from adversely affecting another state’s air quality through interstate transport. In this action, EPA is proposing to approve the New Mexico Interstate Transport SIP provisions that address the requirement of section 110(a)(2)(D)(i)(I) that emissions from New Mexico sources do not interfere with maintenance of the 1997 8-hour ozone NAAQS and the 1997 PM 2.5 NAAQS in any other

state.New Mexico’s submittal focused primarily on whether emissions in New Mexico contribute to nonattain ment of the 1997 PM 2.5 or 1997 8-hour ozone NAAQS in other states. As discussed previously, EPA has f ound that the emissions from the State of New Mexico do not contribute to nonattainment in a neighboring state (75 FR 33174). Consistent with our guidance and EPA’s appr oach to the Clean Air Interstate Rule (CAIR) (70 FR 25174), New Mexico did not sepa rately evaluate whether emissions from New Mexico interfere with maintenance of the standards in anot her state. CAIR however, was remanded to EPA, in part, because EPA did not specifically address whether emissions from one state interfered w ith maintenance of the standard in another

state. On July 6, 2010, the EPA Administrator signed a proposed replacement to CAIR, the proposed Federal Implementation Pl ans to Reduce Interstate Transport of Particulate Matter and Ozone (proposed Transport Rule). 1 The proposed Transport Rule proposes actions that States must take in or der to eliminate transport of emissions that significantly contribute to nona ttainment or inte rfere with maintenance of the 1997 8- hour ozone and PM 2.5 National Ambient Air Quality Standards (NAAQS) {1997 Annual and 2006 24-hour}. Air quality modeling was completed in support of EPA’s Proposed Transport Rule and is documented in th e “Air Quality Modeling Technical Support Document: Transport Rule Proposal” (hereafte r referred to as the “PTR TSD”). The document can be found at http://www.epa.gov/air quality/transport/tech.html. Since New Mexico did not focus primarily on maintenan ce sites in other stat es, EPA is utilizing modeling results that were generated as part of the overall modeli ng that was performed

1 U.S. EPA, 2010, “Federal Implementation Plans to Re duce Interstate Transport of Fine Particulate Matter and Ozone,” 75 FR 45210 (August 2, 2010). In this action the expression “proposed Transport Rule” refers to this proposed rule.for the proposed Transport Rule and other t echnical analyses to help support the EPA’s proposed finding that New Mexico does not contribute to maintenance sites in other

states. The proposed Transport Rule modeling TSD contains detailed information on the model setup, emissions, meteorology, and model results for the Transport Rule modeling 2 . We are also relying upon modeling data that was not directlyutilized in the proposed Transport Rule, but has been docum ented in a memorandum from Brian Timin of OAQPS on August 23, 2010. 3 The air quality model used for the proposed Transport Rule was the CAMx photochemical model (h ttp://camx.com/). Air quality modeling was performed for a 2005 base year and a 2012 “ no CAIR” base case (no additional emission reductions due to the proposed Transport Ru le). The modeling for 2005 was used as the base year for projecting air quality to the future. The 2012 base case modeling was used to identify future nonattai nment and maintenance loca tions and to quantify the contributions of emissions in upwin d states to concentrations of PM 2.5 , and 8-hour ozone at downwind receptors. 4, 5 In the proposed Transport Rule and the BT Memo, EPA projects future concentrations of ozone and PM 2.5 to identify locations thatare expected to be NAAQS nonattainment or maintenance areas in 2012. The nonattainment and maintenance locations are based on projections of futu re air quality at existing ozone and PM 2.5

2 U.S. EPA, 2010, “Technical Support Document (TSD) for the Transport Rule Docket ID No. EPA-HQOAR-2009-0491 Air Quality Modeling U.S. Environm ental Protection Agency Office of Air Quality Planning and Standards Air Quality Assessment Division, June 2010, In this document the expression “PTR TSD” refers to the this proposed Transport Rule Technical Support Document. 3 August 23, 2010 Memorandum, “Documentation of Future Year Ozone and Annual PM 2.5 Design Values for monitors in Western States”, Brian Timin, EPA O ffice of Air Quality Planning and Standards. In this document this document will be referred to as the BT Memo. 4 PTR TSD 5 BT Memo.monitoring sites. In the proposed Transpor t Rule EPA has proposed an approach to determine whether emissions from one state ar e interfering with maintenance in another state. EPA is using this proposed Transport Rule approach to defining a maintenance site as the approach we are using in this noti ce to determine if New Mexico’s emissions interfere with maintenance sites in another st ate. EPA is also re lying upon the proposed Transport Rule modeling analyses and inform ation in the BT Memo to indicate which areas are maintenance sites for this action. 6,7 For this analysis and in the Transport Ru le we are using the air quality modeling results in a “relative” sense to projec t future concentrations of ozone and PM 2.5 . Rather than use the absolute model pred icted future year ozone and PM 2.5 concentrations, the base year and future year predictions are usedto calculate a (relativ e) percent change in ozone and PM 2.5 concentrations. In this approach , the ratio of future year model predictions to base year model predictions are used to adjust ambient measured data up or down depending on the relative (percent) change in model predictions for each location. The use of ambient data as part of the calcu lation helps to constrain the future year predictions, even if the absolute model concentrations are over-predicted or underpredicted. As described below and in the BT Memo and PTR TSD, the procedures for projecting annual and 24-hour PM 2.5 and 8-hour ozone conform to the methodologies contained in the final guidance for attainment demonstration modeling. 8

6 PTR TSD. 7 BT Memo. 8 U.S. EPA, 2007: Guidance on the Use of Models and Other Analyses for Demonstrating Attainment of Air Quality Goals for Ozone , PM2.5, and Regional H aze; Office of Air Quality Planning and Standards, Research Triangle Park, NC. http://www.epa.gov/ttn/scram/guidance/guide/final-03-pm-rhguidance.pdf . In this notice this document will be referred to as the the modeling guidance.In the Transport Rule and this analysis we use measurements of ambient ozone and PM 2.5 data from several State and Federal monitoring networks. The ambient data used in this analysis were obtained from EPA’s Air Quality System (AQS). In order to use the ambient data, the raw measurements must be processed into a form pertinent for useful interpretations. Th e ozone data were processed consistent with the formats associated with the 1997 8-hour NAAQS for ozone. The level of the 1997 8- hour O3 NAAQS is 0.08 ppm. The 8-hour ozone standard is not met if the 3-year average (consecutive years) of the annual 4th highest daily maximum 8-hour O3 concentration is greater than 0.08 ppm (great er than or equal to 0.085 ppm when rounded up). This 3-year average is referred to as the design value. The PM 2.5 ambient data were processed consis tent with the formats associated with the NAAQS for PM 2.5 . For PM 2.5 , we evaluated concentra tions of both the annual
PM 2.5 NAAQS and the 24-hour PM 2.5 NAAQS. The annual PM 2.5 standard is not met if the 3-year average of the annual mean concentration is greater than 15.0 μ g/m3 (15.05
μ g/m3 when rounded up). The 3-year average an nual 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. The 3-year average a nnual mean concentrati on is referred to as the annual design value. The 1997 PM 2.5 24-hour standard is not met wh en the 3-year average of the annual 98 th percentile PM 2.5 concentration is greater than 65 μ g/m3 (65.5 μ g/m3 when rounded up). The 3-year average mean 98th per centile concentration is computed at each site by averaging the 3 individual consecutive an nual 98th percentile va lues at each site.The 3-year average 98th per centile concentration is referred to as the 24-hour design value. The modeling guidance recommends using the average of the three design value periods centered on the year of the base year emissions. Since 2005 was the base emissions year for the TR modeling, we used the design value for 2003-2005, 2004-2006, and 2005-2007 to represent th e base period ozone and PM 2.5 concentrations. Specifically, we used ambient ozone and annual and 24-hour PM 2.5 design values for the periods 2003- 2005, 2004-2006, and 2005-2007 as the starting point fo r our projections of future design values for TR modeling for the 2012 future y ear without additional reductions due to the TR. The 2003–2005, 2004-2006, and 2005-2007 design values are accessible at www.epa.gov/airtrends/values.html . Both the average of the three design values and the maximum of the three design values are incl uded in Appendix B of the PTR TSD or in the BT Memo. 9 Ambient design values from monitoring site s were included in our analysis from the BT Memo or the proposed TR if the site had at least one comple te design value in the 2003-2007 period. As described in the 2006 modeling guidance and the PTR TSD, design values of PM 2.5 in 2012 were estimated by a pplying the 2005 to 2012 relative change in model-predicted PM 2.5 species concentrations to the measured (2003-2007)
PM 2.5 species concentrations. The PM 2.5 species include sulfat e, nitrate, ammonium, particle bound water, elementa l carbon, salt, other primary PM 2.5 , and organic aerosol mass (by difference). For each FRM PM 2.5 monitoring site, all valid design values (up to 3) from this period were averaged together. Since 2005 is included in all three design value periods,

9 BT Memo.this has the effect of creating a 5-year we ighted average, where the middle year is weighted 3 times, the 2nd and 4th years are we ighted twice, and the 1st and 5th years are weighted once. We refer to this as the 5-year weighted average design value concentration. The 5-year weighted aver age design values were used to project concentrations for the 2012 scenario in or der to determine which monitoring sites are expected to be nonattainment for these future year scenarios. For the 2012 base case we also projected design values fo r each of the individual 3-year design value periods (i.e., 2003-2005, 2004-2006, and 2003-2007). The project ion of design values for these individual periods was used inthe interstate contribution analysis to determine sites expected to have maintenance problems, as described below. The details for calculating the Base design valu e and Future design va lues are included in the PTR TSD, BT Memo and the modeling gu idance. Following is a summary of the final parts of the method used to project future year annual PM 2.5 design values. In the PTR TSD and BT Memo, EPA calculated the maximum future design value by processing each of the three base de sign value periods (2003-2005, 2004-2006, and 2005- 2007) separately. The highest of the three fu ture values is the maximum design value. The maximum design values are used to determ ine future year maintenance sites in the proposed Transport Rule and in this action. Th e calculations for determining future year
PM 2.5 concentrations were applied for eachFRM site. The calculated annual PM2.5 design values are truncated after the second de cimal place. This is consistent with the truncation and rounding proce dures for the annual PM 2.5 NAAQS. Any value that is greater than or equal to 15.05 μ g/m3 is rounded to 15.1 μ g/m3 and is considered to be violating the NAAQS. Thus, site s with future year annual PM 2.5 design values of 15.05μ g/m3 or greater, based on the projection of 5- year weighted average concentrations, are predicted to be nonattainment sites. Sites with future year maximum design values of
15.05 μ g/m3 or greater are predicted to be main tenance sites. Note that nonattainment sites are also maintenance sites because the maximum design value at a site is always greater than or equal to the 5- year weighted average at that site. For ease of reference we use the term “nonattainment sites” to refer to those sites that are pr ojected to exceed the NAAQS based on both the average and maximu m design values. Those sites that are projected to be attainment based on th e average design value but exceed the NAAQS based on the maximum design value are refe rred to as “maintenance sites”. The monitoring sites that we proj ect to be nonattainment and/or maintenance for the annual
PM 2.5 NAAQS in the 2012 base case, using information from either the Transport Proposal TSD or the BT Memo, are used as the nonattainment/maint enance receptors for assessing the contribution of emissions in upwind states to downwind nonattainment and maintenance of the annual PM 2.5 NAAQS. The 2003-2007 base period and projected annual PM 2.5 design values for each site for the 2 012 scenario are provided in Appendix B of the Transport Proposal TSD or in the BT Memo.

The level of the1997 8-hour ozone NAAQS is 0.08 ppm. The 8-hour ozone standard is not met if the 3-year average of the annual 4th highest daily maximum 8-hour ozone concentration is greater than 0.08 ppm (greater or equal to 0.085 ppm when rounded up). This 3-year averag e is referred to as the design value. The details for calculating the Base design value and Future design values are included in the PTR TSD, BT Memo and the modeling guidance. Following is a summary of the method used toproject future year 8-hour ozone design values in the PTR TSD and in the BT memo. To project 8-hour ozone design values we also used the proposed Transport Rule 2005 base year, and 2012 future base (2012 emission leve ls prior to any emission reductions from the Proposed Transport Rule) model-predicted ozone concentrations to calculate relative response factors (RRFs). The methodology we followed is cons istent with the attainment demonstration procedures included in EP A’s modeling guidance. The RRFs were applied to the 2003-2007 ozone design values through the following steps: Step 1 : For each monitoring site calculate th e mean of the modeled 8-hour daily maximum predictions across all days w ith 8-hour daily maximum predictions greater than or equal to 85 ppb (for so me monitors a lower threshold may have been used in order to have enough days for the analysis). The mean concentrations are calculated using the predictions in the nine grid cells that include or surround the location of the mon itoring site. The RRF for a site is the ratio of the mean prediction in the future year to the mean prediction in the 2005 base year. The RRFs were calcul ated on a site-by-site basis. Step 2 : The RRF for each site is then multiplied by the 2003-2007 5-year weighted average ambient design value for that site, yielding an estimate of the future year (2012) design value at that particular monitoring location. Step 3 : We calculate the maximum future design value by projecting design values for each of the three ba se periods (2003-2005, 2004-2006, and 2005-2007) separately. The highest of the three futu re values is the maximum design value. This maximum value is used to identify the 8-hour ozone maintenance receptors. The preceding procedures for determining future year 8-hour ozone design valueswere applied for each ozone monitoring site with available data. The future year design values are truncated to integers in units of ppb. This approach is consistent with the truncation and rounding procedures for the 8-hour ozone NAAQS. Future year design values that are greater than or equal to 85 ppb are considered to be violating the NAAQS. Sites with future year 5 year weighted av erage design values of 85 ppb or greater are predicted to be nonattainment. Sites with future year maximum design values of 85 ppb or greater are predicted to be future year maintenance site s. Note that, as described previously for the annual and 24-hour PM 2.5 NAAQS, nonattainment sites for the ozone NAAQS are also maintenance sites because th e maximum design value is always greater than or equal to the 5-year weighted averag e. For ease of reference we use the term “nonattainment sites” to refe r to those sites that are projected to exceed the NAAQS based on both the average and maximum design va lues. Those sites that are projected to be attainment based on the average desi gn value but exceed the NAAQS based on the maximum design value are referred to as mainte nance sites. The monitoring sites that we project to be maintenance for the ozone NAAQS in the 2012 base case in the Transport Proposal TSD are the maintenance receptors used for assessing the contribution of emissions in upwind states to downwind nonattainment and maintenance of ozone NAAQS as part of this proposal. The 2003- 2007 base period and pr ojected 8-hour ozone design values for all sites for the 2012 scenar io used for determining the maintenance receptors/sites are provided in Appendix B of the Transport Proposal TSD or in the BT
Memo. In summary, the 5-year weighted averag e concentrations were used to project concentrations in 2012 to determine which monitoring sites are expected to benonattainment in this future year. EPA al so projected 2012 design values based on each of the 3 year periods (i.e., 2003- 2005, 2004-2006, and 2003-2007). The highest projection is referred to as the maximum design value and gi ves an indication of potential variability in future projections due to di fferences in actual meteorology and emissions from what was modeled. Those sites that ar e projected to be attainment based on the average design value but exceed the NAAQS based on the maximum design value are referred to as maintenance sites because they will have more difficulty in maintaining the standard if there are advers e variations in meteorology or emissions. These projected maintenance sites are the ones we have ev aluated for determining if New Mexico’s emissions potentially interfere w ith maintenance in other States.

OZONE and PM 2.5 Maintenance Sites In the Transport Rule Proposal, we used a ne w technique for creating a threshold test to determine if states should be considered for potential impacts on other states. This section documents the analysis of modeling results for maintenance sites and also the procedures used to quantify the impacts (i.e ., contributions) of emissions in individual States on annual PM 2.5 , 24-hour PM 2.5 , and/or 8-hour ozone conc entrations at projected 2012 nonattainment and maintenance sites. The purpose of this assessment is to determine if New Mexico contributes to 1997 8-hour ozone, and/or 1997 annual PM 2.5 , and/or 1997 24-hour PM 2.5 maintenance problems in other States in amounts at or above thresholds based on 1 percent of the co rresponding NAAQS. The Transport Rule proposal included this 1 percen t threshold based on the averag e amount of contribution to all modeled exceedances and we are proposing to use this same threshold for our basis ofthis action. The air quality contributions were quantified using source apportionment techniques in CAMx. In general, th ese techniques track the formation and transport of ozone and particulate matter fr om specific emissions sources and calculate the contribution of sources a nd precursors to ozone and PM 2.5 at individual receptor locations. The strength of the photochemical model source apportionment technique is that all modeled ozone and/or PM 2.5 mass at a given receptor location in the modeling domain can be tracked back to specific s ources of emissions and boundary conditions in order to fully characterize culpable sources. This type of source a pportionment is useful for understanding both the types of sources or regions and the magnitude of the contributions that are asso ciated with ozone and PM 2.5 , as estimated by the model. More details on the implementation of source a pportionment in CAMx can be found in the CAMx user’s guide. 10 From the modeling analyses conducted for the proposed Transport Rule, the following sites have been identified as ma intenance sites for the 8-hour ozone NAAQS: several sites in the Dallas-Ft.Worth (DFW) area, several sites in the Houston/Galveston/Brazoria (H ouston) area, and other more distant sites in Georgia, Pennsylvania, New York and Connecticut 11 . The BT Memo documents (information not included in the Transport Rule docket) analys is of ozone levels in the 36 km grid of the Transport Rule modeling, including the 5-year weighted Future DV and the maximum 3-year Future DV. In evaluating this information we have concluded that several sites in southern a nd central California would be considered maintenance sites

10 Comprehensive Air Quality Model with Extensions Version 5 User’s Guide. Environ International Corporation. Novato, CA. March 2009. Available at http://www.camx.com/files/ CAMxUsersGuide_v5.0.pdf 11 Appendix B of PTR TSD and Appendices A and B of BT 2010.using our proposed definition of a maintenance site. 12 It should be noted that no sites in the states, that border New Me xico (Arizona, Colorado, Utah , and Oklahoma) other than Texas were identified as maintenance site s based on the modeling analyses in the Transport Proposal or BT Memo. 13 The BT Memo indicates that the highest Future Year design values (5-year center weighted) for monitors in the Denver area and Salt Lake City Areas respectively are 77 ppb and 74 ppb and the maximum of the three design values tested against the maintenance threshold are 80 ppb and 78 ppb respectively. Therefore we conclude that no monitors in Colorado or Utah would be categorized as maintenance monitors using the modeli ng results included in the BT memo. For the annual PM 2.5 NAAQS, the following sites ha ve been identified in the proposed Transport Rule as maintenance sites: a site in Cook County in Chicago, Illinois, monitor in Madison county, IL (East St. Louis area), a monitor in Indianapolis, IN and a site in Harris county of the Houston/Galves ton/Brazoria area. The BT Memo documents analysis of annual PM 2.5 levels in the 36 km grid of the Transport Rule modeling, including the 5-year weighted Future DV and the maximum 3-year Future DV. In evaluating this information we have concl uded that two sites in southern California would be considered maintenance sites usi ng our proposed definition of a maintenance site. 14
No areas were identified as ma intenance for the 1997 24 hour PM 2.5 NAAQS by the proposed Transport Rule. With regard to the 1997 PM 2.5 24 hour standard of 65 μg/m 3 , the PTR TSD and BT Memo did not incl ude any 2012 projections outside the 12

12 BT Memo, Appendix B. Monitors in the fo llowing counties: Merced, Placer, Riverside, and Sacramento. 13 Appendix B of BT 2010 14 BT Memo, Appendix A. Monitors in the following counties: Los Angeles and Orange.km modeling domain that could be used to iden tify the sites that would be classified as maintenance sites in this notice for the 1997 24-hour PM 2.5 NAAQS. For the western part of the continental U.S, including California, that was not in the 12 km modeling domain, we are relying on recent monitoring tren ds data to identify if any areas are close to the 1997 PM 2.5 NAAQS. This approach does not have a clear cut point, but is more of a weight of evidence analysis that if no areas are monitoring values close to the standard, they would not be expected to be near the st andard in the future given the general trend downward in emissions of PM 2.5 pre-cursors in most areas. It should be noted that based on recent monitoring data (2007-2009 DVs that are under final review) that the highest 24-hour PM 2.5 DV in 47 states of the continental U.S (not including California) is 50 μg/m 3 , which is well below the 1997 24-hour PM 2.5 NAAQS of 65 μg/m 3

. 15 The only potential areas of the country that have current DVs (2007-2009) near or above the 1997 24-hour PM 2.5 standard are sites located in California 16 . The sites that are monitoring values either near or above the 1997 24-hour PM 2.5 standard, are the only areas that could reasonable be anticipated to be potenti ally maintenance areas in the future. EPA has evaluated available analyses a nd conducted additional analyses for each of these identified maintenance sites that may be potentially impacted by emissions in New Mexico and determined that emissions in New Mexico do not have a significant impact on any of these identified maintenance sites.

Ozone Maintenance Site Evaluation

15 Data undergoing review from EPA’s Air Quality System which is EPA’s repository of ambient air quality data . (http://www.epa.gov/ttn/airs/airsaqs/) 16 Id.Specifically for the 8-hour oz one identified maintenance sites in the Houston and DFW areas, EPA has conducted a modeling estimate of impacts from New Mexico’s emissions using the Central Regional Air Planni ng Association (CENRAP) modeling of 2002 emissions and meteorology that is a little olde r than the more recent modeling included in the Transport Proposal. The CENRAP modeling that EPA utilized wa s an earlier version of the CENRAP modeling that was submitted by a number of states as part of their Regional Haze State Implementation Plan subm ittals and is currently being reviewed by EPA. While the CENRAP modeling that EPA utilized is not the final modeling analysis submitted it is considered acceptable to use with the understanding that the final modeling may give slightly different answers, but in this case the expected change would not change the conclusions made. EPA an alyzed source apporti onment modeling with the 2002 based CENRAP modeling and conc luded that maximum impacts from New Mexico’s emissions would be 0.2% and 0.4% respectively, wh ich are less than the one percent threshold of 0.8 ppb included in the Tran sport Proposal that we are using in this notice. The Transport Proposal’s threshold of one percent is based on the average impact of a State on a downwind site. Compari ng the maximum impacts shown by the CENRAP modeling to the Transport Proposal threshol d is a conservative approach, since the average impact over all exceedan ce days at sites in DFW or Houston would be lower. Furthermore the CENRAP modeling analysis is conservative since it relies on 2002 emission levels and additional reductions have occurred due to fleet turnover and other measures to reduce air pollution between2002 and 2010 throughout the modeling domain that would result in lower overa ll pollution levels if taken into account. Since we did not have source apportionment modeling for Ne w Mexico’s impacts from the proposedTransport Rule modeling, the 2002 CENRAP based modeling is considered to be acceptable in lieu of having source apportionmen t from the proposed Transport Rule. In addition, EPA has reviewed other documents that evaluate the cause of higher ozone concentration levels in the DFW and Houst on areas for a more qualitative support in addition to the conservative CENRAP base d modeling. Specifically, note Figure 1, which is from Figure 3-2 of TCEQ ’s DFW Conceptual Model Report 17 shows back trajectory density plots for high and low ei ght-hour ozone days from 2001 to 2004. In layman terms, a back trajectory is an appr oximation of where the centerline of the air mass came from that ended up at the endpoint of the back trajectory, which is a location in Dallas in this case. Each trajectory is 36 hours long, centered at Dallas Hinton St., and has a start time of 21 GMT (3:00 PM LST). The top plot shows back trajectory densities for all days, and the bottom plot shows the b ack trajectories for days when the ozone was greater than 85 ppb. Figure 1 shows that on da ys when eight-hour oz one concentrations are at least 85 ppb, back trajectories tend to have a more easterly and southeasterly component. Trajectory lengths also tend to be shorter, implying that wind speeds are slower; slow wind speeds are conducive to hi gher ozone production. Trajectories for all days are longer, implying higher wind speeds. Also, wind directions on all days tend to be more varied, with only a slight westerly component. In neither of these cases does it demonstrate much of an influence from the west that would be the most direct direction for transport of emissions from New Mexic o. Figure 2, which is Figure 3-1 from the DFW Conceptual Model Report, includes back trajectories for all days on a seasonal basis for air masses that ended in the DFW area. As can be seen, the back trajectories in

17 From Texas Commission on Environmental Quality’s 2007 DFW 1997 8-hour Attainment Demonstration SIP, Appendix G “DFW Nonattainment Area Ozone Conceptual Model”the summer months of June-September (whe n the DFW and Houston areas typically have their highest ozone levels) the back trajecto ries very rarely trace back to areas of New Mexico. From a study conducted by the Texas Stat e Climatologist, John Nielsen-Gammon, on meteorological patterns that influence high ozone in DFW, Houst on, and throughout East Texas the following language is included in the summary. 18 “As an easterly or northeasterly wind b ecomes more and more frequent later in the summer, background and total ozone in eastern Texas begin rising. This takes place first in northern regions of eastern Texas where southeasterly winds bring dirty air, then in more southern regions later in August as large-scale easterlies and northeasterlies develop. Winds are al so less steady than in the middle of summer, so continental transport becomes increasingly frequent.” As is further described in this report, elevated ozone levels in DFW and H ouston are most commonly associated with light winds locally preceded by transport the previous day(s) from the East and/or Northeast. Therefore, these conceptual model analyses and back trajectori es for the 1997 8-hour ozone standard provide further support to the determination from the 2002 CENRAP based modeling 19 that when these two areas expe rience elevated ozone levels, the meteorological patterns only rare ly trace the previous origins of these air masses to the New Mexico area. Therefore we are concludi ng that the overall analyses indicates that

18 Nielsen-Gammon, John W., James Tobin, and Andrew McNeel. “A Conceptual Model for Eight-Hour Ozone Exceedances in Houston, Texas. Part I: Bac kground Ozone Levels in Eastern Texas.” Center for Atmospheric Chemistry and the Environment, Texas A&M University. January 29, 2005. 19 Further details are included in the Modeling TSD Memorandum for this notice

.emissions from New Mexico would not signifi cantly impact these areas of Texas when they were having ozone levels near or above the 1997 8-hour ozone NAAQS. The other more distant sites in Georgia, Pennsylvania, New York and Connecticut are much further away than Texas areas that ar e also East of New Mexico and the longer transport distance from New Mexico to the ea stern U.S. areas would further dilute the impacts below impact levels observed for ar eas in Texas. The only other identified maintenance sites for 1997 8-hour ozone that might be close enough to be impacted were in southern and central Califor nia. As further discussed below in the discussion for 24- hour PM 2.5 in this TSD for this notice, the me teorological patterns do not transport emissions from New Mexico to California when California has elevated ozone or particulate levels. 20

PM 2.5 maintenance site evaluation For the annual PM 2.5 NAAQS site located in the Chicago area, previous EPA modeling relied upon in the 2004 CAIR propos al indicated that impacts from New Mexico’s emissions were 0.02 μg/m 3 ), 21 which is well below the one percent (0.15 μg/m 3) threshold that has been proposed as a threshold impact level in the Transport Proposal and that we are using as a threshol d impact level in this action. The CAIR’s modeling also indicated a maximum impact on sites in St. Louis from New Mexico’s emissions were 0.02 μg/m 3 , that is well below the 0.15 μg/m 3 threshold. With a were

20 “Central California Ozone Study (CCOS) Volume I Field Study Plan Version 3”, Eric Fujita, Robert Keislar, William Stockwell, Hans Moosmuller, David DuBois, Darko Koracin and Barbara Zielinska of Desert Research Institute and Saffet Tanrikulu and Andrew Ranzieri of the Planning and Technical Support Division of California Air Resources Board Division of Atmospheric Science, November 24, 1999.

21 EPA’s “Technical Support Document for the Interstate Air Quality Rule Air Quality Modeling Analyses Appendix H PM2.5 Contributions to Downwind Nonattainment Counties in 2010”, January 2004.0.02 μg/m 3 impact in the St. Louis area, this CA IR proposal modeling also confirms that New Mexico’s emissions would not significantly impact the maintenance site/monitor in Madison county, IL (East St. Louis area). Th e other maintenance site/monitor identified in this geographic area was a monitor in Indi anapolis, IN. Indianapolis is between Cook County and Madison County but further East th an both of these counties, therefore we conclude that impacts of 0.02 μg/m 3 are a conservative value but also indicate that New Mexico’s emissions would not impact monitors in the Indianapolis, IN area above the threshold for consideration.

EPA did not separately calculate the imp act of New Mexico’s emissions on the Houston area as part of the CAIR modeling or in the Transport Rule Proposal modeling, but EPA believes that one can infer from Ne w Mexico’s extremely small impact on other areas that New Mexico’s impact on the Houst on area would also be less than one percent of the NAAQS. The only modeling availabl e that provided source apportionment for annual PM 2.5 values is the CAIR proposal mode ling. The CAIR source apportionment results that would be expected to most closely match Houston from a transport phenomena perspective are the results for potenti al impacts on St. Louis. St. Louis is helpful for comparison because, while not the same direction from New Mexico it is the closest area evaluated in the CAIR proposal modeling that is to the east (in the same general transport direction) and at a similar distance from New Mexico as Houston. For the St. Louis area, the CAIR proposal modeling indicated that a maximum impact from New Mexico’s emissions of 0.02 μg/m 3 , which is well below the 1% of theNAAQS screening threshold. If we consider that most of the PM 2.5 emission sources (primary and secondary) are either population based (mob ile, non-road, and area source emissions) or point and some area sources that are spread throughout the state but several of the larger sources are in the northw est quadrant of New Mexico. With this understanding of spatial allocation of emissi on sources in New Mexico, we can assume that the centroid of PM 2.5 emissions (primary and pre-cursor) is in the Albuquerque area. Since emissions are diluted as they are tran sported, the distance of transport from the centroid of New Mexico’s emissions to the areas of concern can provide a ‘measuring stick’ for comparing potential impacts. The majority of the emissions of PM 2.5 and
PM 2.5 precursors from New Mexico sources eman ate from either the Albuquerque area or from points father west. The distance fr om Albuquerque to St. Louis, Missouri is approximately 920 miles and the distance fr om Albuquerque to Houston is about 750 miles, which is about 81.5 % of the distance from Albuquerque to St. Louis. 22 Even if one conservatively assumed that New Me xico emissions had twice the impact on Houston that EPA determined they do on St Loui s due to the shorter transport distances, New Mexico’s impact on Houston would sti ll be significantly below the 1% of the NAAQS threshold in the Transport Proposal. Given that the differe nce in distances is only 18.5 %, this is a conservative analysis that would indicate no significant impacts would be expected from New Mexico on sites in Houston, Texas. Using an even more conservative and sli ghtly unrealistic approach of comparing the distances from the closest New Mexico bor der to the city centers of Houston and St.

22 TSD. EPA believes that such a comparison is inst ructive because the majority of relevant New Mexico emissions occur from sources or activities located in the Albuquerque metropolitan area, or in areas further to the west. Even if measured from the New Mexico state border to St. Louis and Houston, however, the proportional impact would presumably be comparable.Louis, the distances are 480 miles an d 700 miles respectively and Houston is approximately 68% of the distance that St . Louis is from the nearest New Mexico boundary. This is not realisti c from the standpoint that the distance from the emission sources is one of the main variables that impacts the amount of di spersion/dilution that can occur but even at these distances it is c onservative to assume a doubling of impacts as discussed above. Also, the relative amounts of emissions in New Mexico, when compared to the emissions in Texas support the conclusion th at New Mexico emissi ons do not interfere with maintenance in areas in Texas. Usi ng databases developed in connection with the Regional Haze (RH) program and submitted with the RH SIPs, the Texas emissions of SO2 are approximately 18 times larger than New Mexico’s, the NOx emissions are approximately 5 times greater than New Mexi co’s, the fine particulate matter emissions are 12 times greater than New Mexico’s and the coarse particulat e matter is 5.6 times greater than New Mexico’s emissions. The Transport Rule Proposal modeling information also includes emission summaries that indicate that Texas’s emissions are 1,338,429 tpy of NOx and 639,505 tpy of SO2 wh ereas New Mexico’s emissions are 240,892 tpy of NOx and 24,930 tpy of SO2. Both sets of data indicate that New Mexico’s emissions are much lowe r than Texas’s emissions of PM 2.5 precursors. Moreover, most of the sources of PM 2.5 precursor emissions in Texas are much closer to the maintenance receptor in Houston, and th erefore less dispersion of the pollutants occurs, so Texas’s own PM 2.5 and PM 2.5 precursors will have a much larger impact on
PM 2.5 levels in Houston.In addition, the Texas Commission on Environmental Quality (TCEQ) and several researchers have conducte d research into the likely causes of elevated annual and 24-hour PM 2.5 monitoring values in the Houst on area. TCEQ and the researcher’s analyses do not indicate that emissions from New Mexico impact Houston to a degree to raise a concern for purposes of the 1997 PM 2.5 NAAQS. These analyses indicate that meteorological patterns are transporting air ma sses from other directions (i.e., not from the direction of New Mexico) when Houst on area sites are monitoring elevated PM 2.5 levels that have the greatest impact on the annual DV. 23 While the concern in Houston is on the annual PM standard, detailed analyses by the state and resear chers show that the highest values are heavily influenced by local sources and the measures that TCEQ has worked to get in place have been effective in reducing emissions. TCEQ and researcher’s analyses also indicate that di stance and meteorological patterns during these times of elevated pollution levels in Hous ton also support the conclusion that New Mexico’s emissions do not have a significant impact on these areas’ elevated pollution levels. In summary, considering the avai lable evidence, EPA concludes that New Mexico’s emissions do not interfere with maintenance of the 1997 PM 2.5 NAAQS in
Houston area. EPA also reviewed the potential for em issions from New Mexico sources to impact other areas with monitors suitab le for comparison for interference with maintenance purposes. The other such areas are located in California. With regard to the 1997 PM 2.5 24 hour standard of 65 μg/m 3 , the only potential areas of the country that

23 “Source Apportionment for PM2.5at Houston Clinton Drive”, David W. Sullivan The University of Texas at Austin Center for Energy & Environmen tal Research and Richard Tropp, University of Nevada Reno Desert Research Institute, TEXAQS II Workshop May 29, 2007 and TCEQ Fact Sheet “Harris County/Clinton Drive 1997 Annual Fine Particulate Matter (PM2.5)” November 2009.have levels near the 1997 sta ndard currently are identified sites that have current DVs (2007-2009) are located in California. 24 EPA has evaluated conceptual model documents and field study reports that indi cate that transport patterns when elevated
PM 2.5 occurs in areas of California, the meteorol ogical patterns are not such that transport of emissions from New Mexico to California is occurring to a degree to raise a concern. 25 A review of documents prepared for the San Joaquin Valley in Calif ornia indicates that most ozone, PM-10 and PM 2.5 episodes are due to limited vertical mixing and horizontal dispersion building up to hi gher pollutant loadings. 26, 27 The dominant transport pattern is for air masses from the Eastern Pacific to enter California and a period of high stability (low vertical mixing) and lighter winds to o ccur that results in po llutions exceedances. During these events the meteorology is such th at general flows are fr om west to east. Therefore it is very rare for meteorological patterns to occur that would transport emissions from New Mexico such that they impact California’s pollution levels in addition to the long distance that emissions w ould have to transport and the intervening mountainous topography between New Mexico and the areas of concern in California further support that transport of emissions from New Mexico is unlikely. Therefore, available information indicates that emissions from sources in New Mexico do not impact

24 AQS data. 25 “Historical Meteorological Analysis in Support of the 2003 San Joaquin Valley PM10 State Implementation Plan”, Shawn R. Ferreria Air QualityMeteorologist / Atmospheric Scientist And Evan M. Shipp Supervising Air Quality Meteorologist San Joaquin Valley Air Pollution Control District January 24, 2005. 26 “Historical Meteorological Analysis in Support of the 2003 San Joaquin Valley PM10 State Implementation Plan”, Shawn R. Ferreria Air QualityMeteorologist / Atmospheric Scientist And Evan M. Shipp Supervising Air Quality Meteorologist San Joaquin Valley Air Pollution Control District January 24, 2005. 27 “Central California Ozone Study (CCOS) Volume I Field Study Plan Version 3”, Eric Fujita, Robert Keislar, William Stockwell, Hans Moosmuller, David DuBois, Darko Koracin and Barbara Zielinska of Desert Research Institute and Saffet Tanrikulu and Andrew Ranzieri of the Planning and Technical Support Division of California Air Resources Board Division of Atmospheric Science, November 24, 1999.areas of concern in California to the degree that would interf ere with maintenance of the 1997 NAAQS in those areas.FIGURE 1FIGURE 2Other References: Draxler, R.R., and G.D. Hess. Descrip tion of the HYSPLIT_4 Modeling System. National Oceanic and Atmospheric Admini stration Technical Memorandum. ERL-ARL22, Dec.1997. Nielsen-Gammon, John W., Ja mes Tobin, and Andrew McN eel. “A Conceptual Model for Eight-Hour Ozone Exceedances in Houston, Texas. Part I: Background Ozone Levels in Eastern Texas.” Center for Atmospheric Chemistry and the Environment, Texas A&M University.