EPA should reevaluate its selection of the significance contribution levels and raise them to a level where regional air quality models can exhibit skill in predicting contributions. EPA should attempt to quantify the skill level of these regional air quality models. We would suggest that EPA consider ranges from 5 to 10 percent of the ambient standards as a starting point for this evaluation. [EPA-HQ-OAR-2009-0491-2722.1, p.26]

ARIPPA
Specifically, for purposes of determining which states significantly contribute to or interfere with maintenance of the NAAQS for PM2.5 or ozone in other states, EPA applies a threshold of 1% of the NAAQS. See 75 Fed. Reg. 45237. EPA attempts to justify the use of this extremely stringent threshold value by pointing to a finding of an "upwind `collective contribution' that is important to both PM2.5 and ozone", and "adverse health impacts associated with ambient PM2.5 and ozone even at low levels." Id. EPA then uses suspect modeling to translate this 1% threshold determination into an allowable emissions budget for each state. [EPA-HQ-OAR-2009-0491-2794.1, p.14]
EPA identifies no regulatory or statutory basis for determining that a projected impact of 1% of the relevant NAAQS qualifies as a "significant contribution" for purposes of Section 110 or Section 126 of the statute. Instead, EPA's determination is arbitrary and capricious, and substantially overstates the significance of the contribution from certain upwind states, including Pennsylvania. [EPA-HQ-OAR-2009-0491-2794.1, p.15]
For these reasons, EPA's reliance on a 1% threshold for determining significant contribution to or interference with maintenance of the NAAQS, and, in turn, the use of such threshold for determining a state's allowable emissions budget, is arbitrary, capricious, unsupported by the relevant provisions of the CAA, and inconsistent with the D.C. Circuit's findings in North Carolina. The use of this threshold effectively overstates the significance of contribution from upwind states, resulting in unwarranted requirements for emissions control from these areas. [EPA-HQ-OAR-2009-0491-2794.1, p.15]
Arkansas Department of Environmental Quality
Prior to this proposal, the lowest value used as a threshold indicating a significant contribution to downwind ozone was two parts per billion ('ppb'). EPA proposes to use modeled concentrations exceeding 1 % of the standard (in this instance, 0.8 ppb) as an indicator of significant contribution and proposes to use this same metric for future changes in the standard. In the proposed Transport Rule, EPA has not provided any technical justification for lowering the contribution threshold from two ppb to 0.8 ppb. The proposed contribution threshold is lower than the ability of current Federal Reference Method monitors to measure with precision and accuracy (approximately 1 ppb), and it is lower than regional-scale photochemical oxidant modeling can reliably predict. The contribution threshold should not be lowered to a level that can neither be monitored nor reliably modeled. Since EPA has not provided an explanation of how the lower threshold was determined to be appropriate, EPA should continue to use a two ppb contribution threshold for ozone. [EPA-HQ-OAR-2009-0491-2676.2 p.3-4]
Clean Air Task Force
Furthermore, power plants in five states that are in EPA's 37 state study region but outside of the proposed control region are projected to increase emissions following implementation of the rule, as they will be subject only to the much weaker Title IV acid rain restrictions. In fact, the increase in Texas is large enough to cause it to become a significant contributor (under the Agency's proposed 1% NAAQS threshold test) to downwind PM nonattainment and maintenance problems. [EPA-HQ-OAR-2009-0491-2738.1, p.7; this comment can also be found at III.D and IV.D.4.c of this comment summary.]
Finally, while we appreciate the simplicity of EPA's choice of a threshold for determining significant contribution for a state at 1% of the applicable NAAQS, we think that this level is too high. Rather, we think that any measurable level of contribution that can be eliminated cost-effectively is significant for purposes of section 110(a)(2)(D) of the Act. We suggest that, at a minimum, EPA should cut its proposed contribution threshold in half, i.e., to no more than 0.5% of the applicable NAAQS. Applying such a minimum threshold would bring Texas, Arkansas, New Hampshire, North Dakota and Oklahoma into the control region for SO2 and annual NOx purposes, and Massachusetts and Missouri into the control region for ozone season NOx purposes. 36 [EPA-HQ-OAR-2009-0491-2738.1, p.8]
Footnote:
36 See discussion infra in Section IV.A. We note that although we believe that our recommended lower threshold for determining significant contribution will require additional states to be included in the TR control regions, we have included only Texas emissions in our recommended emissions caps and the Alternate Control Scenario described in Section V infra.
Council of Industrial Boiler Owners (CIBO)
EPA defines as "significant" any State emissions that are greater than 1% of the relevant NAAQS: 'States whose contributions to any downwind sites are greater than 1 percent of the relevant NAAQS are considered "linked" to those sites for the purpose of the second step in the analysis.' 75 FR 45233/2. EPA's definition of 1% as significant is arbitrary and has no defensible basis. If 1% of 100 is significant, how does EPA define "insignificant?" Statistical error is much higher than that, and rounding in analysis can easily equal amounts of 1% or more. [EPA-HQ-OAR-2009-0491-2751.1 p.4]
Entergy Services, Inc.
2.  The Projected Impact from Louisiana Emissions Is Less than a PSD Significant Impact Level
Entergy adopts comment I.D made by the Louisiana Chemical Association.  Entergy believes that EPA cannot set the level for "interference with maintenance" of a NAAQS lower than the EPA Significant Impact Level ("SIL") used under the Prevention of Significant Deterioration ("PSD") program.  Entergy intends this as a general comment on EPA's proposed methodology for determining when there is "interference with maintenance" within the meaning of CAA and as a specific comment with respect to the projected impact of Louisiana emissions on Harris County, Texas.  [EPA-HQ-OAR-2009-0491-2847.1,pp.7-8]
As part of the analysis of air quality impacts to determine compliance with the NAAQS and increment, the permit applicant and reviewing authority may compare the source's impacts for a pollutant with the corresponding SIL for that pollutant to show that a cumulative air quality impacts analysis is not necessary.  [EPA-HQ-OAR-2009-0491-2847.1,p.8]
Harris County is within a Class II air quality control district. On September 21, 2007, EPA proposed the following options for a SIL for the PM2.5 Annual NAAQS for a Class II area:
Option 1    1.0 ug/m3
Option 2    0.8 ug/m3
Option 3    0.3 ug/m3
The EPA projected value for Louisiana impacts to the Clinton Drive monitor in Harris County is 0.34 ug/m3.  Such value is well below the Option 1 and 2 proposed SILs and does not exceed the Option 3 SIL, with standard rounding conventions. While EPA has not yet finalized the proposed SILs pursuant to the 2007 notice, it is our understanding that EPA has reached a final decision, that decision has been reviewed by the Office of Management and Budget, and that a final rule adopting one of these 3 values will be published in the Federal Register in October 2010. [EPA-HQ-OAR-2009-0491-2847.1, p.8]
In the September 21, 2007 Federal Register notice proposing SILs for the PM2.5 annual NAAQS, EPA provided the following explanation of the concept and appropriate usage of a SIL:
Significant Impact Levels or SILs are numeric values derived by EPA that may be used to evaluate the impact a proposed major source or modification may have on the NAAQS or PSD increment. The SILs currently appear in EPA's regulations in 40 CFR 51.165(b), which are the provisions that require States to operate a preconstruction review permit program for major stationary sources that wish to locate in an attainment or unclassifiable area but would cause or contribute to a violation of the NAAQS. The SILs in that regulation are the level of ambient impact that is considered to represent a "significant contribution" to nonattainment.   [EPA-HQ-OAR-2009-0491-2847.1,p.8]
Although 40 CFR 51.165 is the regulation that establishes the minimum requirements for nonattainment NSR programs in SIPs, the provisions of 40 CFR 51.165(b) are actually applicable to sources located in attainment and unclassifiable areas. See 40 CFR 51.165(b)(4). Where a PSD source located in such areas may have an impact on an adjacent non-attainment area, the PSD source must still demonstrate that it will not cause or contribute to a violation of the NAAQS in the adjacent area. This demonstration may be made by showing that the emissions from the PSD source alone are below the significant impact levels set forth in 40 CFR 51.165(b)(2). However, where emissions from a proposed PSD source or modification would have an ambient impact in a non-attainment area that would exceed the SILs, the source is considered to cause or contribute to a violation of the NAAQS and may not be issued a PSD permit without obtaining emissions reductions to compensate for its impact. 40 CFR 51.165(b)(2)-(3).  [EPA-HQ-OAR-2009-0491-2847.1,p.8]
The EPA has also applied SILs in other analogous circumstances under the PSD program. Based on EPA interpretations and guidance, SILs have also been widely used in the PSD program as a screening tool for determining when a new major source or major modification that wishes to locate in an attainment or unclassifiable area must conduct a more extensive air quality analysis to demonstrate that it will not cause or contribute to a violation of the NAAQS or PSD increment in the attainment or unclassifiable area. [EPA-HQ-OAR-2009-0491-2847.1 ,p.9]
***
Subsequently, in draft guidance for permit writers, EPA advised that SILs may be used to determine whether a source needs to conduct a cumulative or "full" impact analysis to demonstrate that in conjunction with all other increment consuming sources, it will not cause or contribute to violation of the NAAQS or PSD increment in an attainment or unclassifiable areas. New Source Review Workshop Manual, at C.24-C.25 (Draft 1990); See also 40 CFR 51.166(k); 40 CFR 52.21(k). Permitting authorities followed this guidance, and this approach remains an accepted aspect of PSD program implementation. If based on a preliminary impact analysis, a source can show that its emissions alone will not increase ambient concentrations by more than the SILs, EPA considers this to be a sufficient demonstration that a source will not cause or contribute to a violation of the NAAQS or increment.  [EPA-HQ-OAR-2009-0491-2847.1, p.9]
***
The concept of a significant impact level is grounded on the de minimis principles described by the court in Alabama Power Co. v. Costle, 636 F.2d 323, 360 (D.C. Cir. 1980). In this case reviewing EPA's 1978 PSD regulations, the court recognized that "there is likely a basis for an implication of de minimis authority to provide exemption when the burdens of regulation yield a gain of trivial or no value." 636 F.2d at 360.  [EPA-HQ-OAR-2009-0491-2847.1,p.9]
***
Similarly, significant impact levels are intended to identify a level of ambient impact on air quality concentrations that EPA regards as de minimis. The EPA considers a source whose individual impact falls below a SIL to have a de minimis impact on air quality concentrations. Thus, a source that demonstrates its impact does not exceed a SIL at the relevant location is not required to conduct more extensive air quality analysis or modeling to demonstrate that its emissions, in combination with the emissions of other sources in the vicinity, will not cause or contribute to a violation of the NAAQS at that location. [EPA-HQ-OAR-2009-0491-2847.1,p.9]
In other words, if a single point source within the Houston area had a project that triggers PSD for PM2.5, but the screening modeling indicates that the projected air quality impact for that project is below the SIL, in this case, at or below the level of one of EPA's proposed three options 1.0, 0.8 or 0.3 ug/m3, then that source would not be considered to have only a de minimis impact on air quality and would not be required to conduct modeling to demonstrate that its emissions, in combination with those of other sources, will not contribute to a NAAQS violation. If a single point source has emissions that are considered de minimis when at or below a SIL, then it would be arbitrary and capricious to require any regulation, let alone widespread controls on sources in another state, such as Louisiana, that cumulatively have an equivalent or lesser impact than would such individual source.  [EPA-HQ-OAR-2009-0491-2847.1,p.9]
For this reason, EPA should reverse its proposed finding that Louisiana emissions are likely to interfere with maintenance of the annual PM2.5 NAAQS in Harris Co., Texas. [EPA-HQ-OAR-2009-0491-2847.1, p.10]
Exelon
THE TRANSPORT RULE PROVIDES A TEMPLATE FOR FUTURE REDUCTIONS TO STATE NOX AND SO2 BUDGETS THAT MAY BECOME NECESSARY TO PREVENT INTERFERENCE WITH MAINTENANCE AND ATTAINMENT OF NEW OR REVISED NAAQS IN THE FUTURE.
On January 19, 2010, EPA issued a notice of proposed rulemaking announcing its intent to strengthen the NAAQS for ozone. The proposed levels for the revised ozone standard are expected to be within the range of 0.060 to 0.070 parts per million ("ppm") ozone as an eight hour average, as compared to the current level of 0.080 ppm. EPA should readily be able to utilize the mechanisms and models that it has used in developing the proposed Transport Rule's state budgets for NOX to develop reduced state and unit budgets necessary to meet the new ozone standard. By setting a single bright line threshold for ozone at exactly 1% of the 1997 eight-hour ozone standard of 0.08 ppm, EPA is allowing for an easy adjustment to any future standard reductions below the current 0.08 ppm. As discussed in Comment 7 below, Exelon suggests that EPA promptly calculate the reduced budgets and either use the 2008 standard as a basis for the budget in the proposed Transport Rule or propose revised state budgets and unit budgets within a time frame that will allow companies to take account of this requirement in their planning. [EPA-HQ-OAR-2009-0491-2666.1, pp.12-13]
In October 2011, EPA is also planning to review, and possibly to modify, the PM2.5 NAAQS, and the methodology used in the proposed Transport Rule should allow EPA to propose reduced state emission budgets at the time of any NAAQS revision. As with ozone, EPA can utilize the threshold impact value at 1% of the NAAQS and utilize its existing data and models to adjust state budgets. Again, EPA should promulgate revised budgets within a time frame that will allow companies to take account of the upcoming requirements in their capital planning and market positioning. The benefits that will be achieved by implementation of the Transport Rule will far outweigh the costs. [EPA-HQ-OAR-2009-0491-2666.1, p.13]
Exxon Mobil Corporation
1. Any impact of Louisiana emissions on Harris County, Texas is less than any of the proposed EPA Significant Impact Levels ('SILs') for annual PM2.5 used under the Prevention of Significant Deterioration ('PSD') Program.5 By definition, any such impacts are de minimis. EPA would be arbitrary and capricious and/or abusing its discretion if it makes a finding of ''interference with maintenance' for a total projected Louisiana contribution that is less than one of these proposed SILs.  [EPA-HQ-OAR-2009-0491-2841.1,p.3]
4. Due to the inherent uncertainty in the IPM modeling, as unmistakably illustrated by the material differences between IPM v. 3.02 and v. 4.10 projections, a projected impact of less than 2 ppb based on modeling should never be used as a level indicating 'significant contribution' or 'interference with maintenance' from an upwind state to a downwind state under the ''good neighbor' provisions of the Clean Air Act, 42 U.S.C. 7410(a)(2)(D). The projected impact from Louisiana is well below 1 ppb. At most, the IPM should be used as a screening tool for making presumptions for 'significant contribution' or 'interference with maintenance' determinations. However, such presumptions should be always subject to a reasonable opportunity for rebuttal by empirical evidence. [EPA-HQ-OAR-2009-0491-2841.1, p.5]

Footnote 5: EPA proposed three options for an annual PM2.5 SIL for Class II areas, such as Harris Co., Texas, in 72 Fed.Reg. 54112, Sept. 21,2007. These options were 1.0 ug/m3, 0.8 ug/m3, and 0.3 ug/m3. With rounding conventions, the 0.34 ug/m3 projected as the Louisiana impact on Harris Co., Texas does not exceed any of these SILs. It is EM's understanding that the final SILs will be published in the Federal Register in October 2010 and thus, will be fmal prior to EPA's final decision on the proposed TR/FIP. [EPA-HQ-OAR-2009-0491-2841.1,p.3]
Florida Municipal Electric Association (FMEA)
Changing the criteria for determining a significant impact is not warranted: The DC District Court upheld the EPA methodology under CAIR for determining a significant impact due to the interstate transport of air pollutants. By lowering the significance threshold for upwind state impact on downwind states, EPA is expanding the number of states regulated under the transport rule beyond that of CAIR. This expansion was not required by the Court. By defining the significance level at 1% of the NAAQS as opposed to retaining the levels in the CAIR, EPA has established a criterion that will continually reduce the significance level without any future consideration of whether each decrease is justified. In the case of PM 2.5, this new method of determining significance lowered the CAIR threshold of 0.2 ug/m3 to 0.15 ug/m3, which is a 25% reduction. As currently proposed, EPA will create a continual series of Transport Rules in response to future NAAQS revisions starting in 2011. This will likely create a permanent Federal Implementation Planning (FIP) of the states and derailing Congressional intent on how the SIP program was designed to work under the Clean Air Act. [EPA-HQ-OAR-2009-0491-2731.1, p. 2]
Gainesville Regional Utilities (GRU)
Changing the Criteria for Determining a Significant Impact is Not Warranted
The DC District Court upheld the EPA methodology under CAIR for determining a significant impact due to the interstate transport of air pollutants. By lowering the significance threshold for upwind state impact on downwind states, EPA is expanding the number of states regulated under the proposed CATR beyond that of CAIR. This expansion was not required by the Court. By defining the significance level at 1% of the NAAQS as opposed to retaining the levels used in the CAIR, EPA has established a criterion that will continually reduce the significance level without any future consideration of whether each decrease is justified. In the case of PM2.5, this new method of determining significance lowered the CAIR threshold of 0.2 ug/m3 to 0.15 ug/m3, which is a 25% reduction. As currently proposed, EPA will create a continual series of 'Transport Rules' in response to future NAAQS revisions starting in 2011. This will likely create a permanent 'FIPing' of the states and derailing Congressional intent on how the SIP program was designed to work under the CAA. [EPA-HQ-OAR-2009-0491-2674.1, p.4]
George Washington University Regulatory Study Center
To identify eastern States whose contributions do not warrant transport requirements, EPA is proposing thresholds based on one percent of the NAAQS for ozone and PM. For the fine PM NAAQS, the contribution thresholds of 0.15 μg/m3 and 0.35 μg/m3 requires a high level of precision for the modeling approach used to determine significant contribution. This superficially technical detail has major implications -- whether states are included in the Rule or not depends on modeled differences as small as 0.001 μg/m3. [EPA-HQ-OAR-2009-0491-2573.1, p.19]
A. Defining Contribution and Interference in the Transport Rule
EPA proposes a two-step-process for determining that an upwind state makes a significant contribution to nonattainment or interferes with maintenance of attainment with NAAQS at downwind sites. In the first step, EPA uses air quality modeling to quantify the contribution of an upwind state to non-attainment and/or interference with maintenance at downwind sites. EPA proposes to find that states with a contribution greater than one percent of the relevant NAAQS are considered "linked" for purposes of the second step in making the determination. For the fine PM NAAQS, the relevant thresholds are a contribution of 0.15 μg/m3 of fine PM for the annual standard and a contribution of 0.35 μg/m3 for the 24-hour standard. In the second step, EPA identifies the SO2 and NOx emissions constituting a significant contribution and significant interference for each state identified as exceeding the thresholds in the first step. [EPA-HQ-OAR-2009-0491-2573.1, p.19]
In doing so, EPA adopts two alternative "maximum cost thresholds" -- cost thresholds reflecting alternative control levels and air quality considerations. EPA divides the significantly contributing/ interfering states into two groups. The first group consists of those states whose significant contribution can be eliminated at the lower cost threshold (essentially the cost of assuring the continued operation of installed control equipment). The second group consists of the remaining states: those that continue to contribute to (or interfere with) nonattainment even after region-wide control at the lower cost threshold. States in this second group are required to achieve additional reductions commensurate with control of SO2 at the higher cost threshold (i.e., the incremental cost at which EPA believes large additional reductions will occur with the widespread installation of additional scrubber control technology). [EPA-HQ-OAR-2009-0491-2573.1, p.19]
B. Measuring Contribution and Interference
Our focus in this discussion is on the first step and EPA's proposed selection of fine PM NAAQS thresholds of 0.15 μg/m3 for the annual standard and 0.35 μg/m3 for the 24-hour standard. In order to implement the first step in the significant contribution determination, EPA projects the emission levels for each state in 2012 and, using air quality modeling, estimates the ambient impact of these projected emissions on downwind nonattainment and maintenance receptors. States with an incremental contribution above the threshold are subject to the proposed Transport Rule. See Tables IV.C-13 and IV.C-16 in the proposal preamble for EPA's estimates of the largest incremental contribution to non-attainment for the PM NAAQS in each of the eastern States. [EPA-HQ-OAR-2009-0491-2573.1, p.20]
The adoption of a contribution threshold representing one percent of the annual fine PM standard -- i.e., 0.15 μg/m3 -- raises a question about the precision required (or at least implied) in using two figures to the right of the decimal. EPA first dealt with the issue in CAIR, where it proposed a threshold of 0.15 μg/m3. In the final CAIR rule, EPA agreed in response to comments with respect to the precision implied by a two-decimal-place threshold, "...that specification of a threshold value of 0.15 μg/m3 does suggest an overly precise test that might need to take into account modeled differences in PM2.5 values as low as 0.001 μg/m3." As a result, EPA adopted a single-digit value of 0.2 μg/m3 because it was consistent with EPA monitoring requirements in CFR Part 50, appendix N, section 4.3 stating that design values should be rounded to the nearest 0.1 μg/m3. This rationale, then, served as the basis for the fine PM thresholds for determining significant contribution in the 2005 CAIR rule.39
However, in this proposal, EPA argues the revised 24-hour fine PM NAAQS in 2006 of 35 μg/m3 raises a new difficulty. The rounding approach used in Appendix N for the 24-hour fine PM NAAQS (design values are to be rounded to the nearest 1 μg/m3) would yield a threshold of zero -- one percent of 35 μg/m3 is 0.35 μg/m3 which would round to zero. EPA believes that a threshold of zero would be counterintuitive and unworkable. Thus, EPA is proposing to decouple the precision of the air quality thresholds from its monitoring rules and instead to use 2-digit values representing one percent of the fine PM NAAQS. [EPA-HQ-OAR-2009-0491-2573.1, pp.20-21]
EPA does not provide any analysis to support the proposed approach of adopting contribution thresholds of 0.15 μg/m3 for the annual NAAQS and 0.35 μg/m3 for the 24-hour NAAQS. In particular, it does not provide analysis to show that its methodology will provide the precision necessary to support two-figure accuracy (two digits beyond the decimal place) in its estimates of the contribution by upwind states to the nonattainment or interference with maintenance at specific sites in downwind states. In particular, note that with the proposed thresholds of 0.15 μg/m3 for the annual NAAQS and 0.35 μg/m3 for the 24-hour NAAQS, EPA is attributing a greater precision to its modeling data than it provides for in its monitoring requirements.41 [EPA-HQ-OAR-2009-0491-2573.1, p.21]
Adoption of alternative single digit thresholds could have a significant effect on the number of states covered by the Transport Rule (see Table 1). With contribute/interfere thresholds of 0.2 ug/m3 for the annual NAAQS and 1 μg/m3 for the 24-hour NAAQS, for example, six states would no longer be covered by the Transport Rule.52 Given the uncertainty associated with its analysis, however, EPA may only be able to justify a threshold on the order of 1 μg/m3 for both the annual and 24-hour fine PM standards. With contribution/interfere thresholds of 1 μg/m3 for both the annual and 24-hour fine PM NAAQS, an additional 6 states, for a total of 12 states, would no longer be covered by the Transport Rule. [EPA-HQ-OAR-2009-0491-2573.1,p.24]
Since it is unclear whether the level of precision specified by the proposed contribution thresholds is appropriate and since that level has such important implications for states, the agency risks litigation by states or regulated entities that believe they should not be included in the rule. Litigation by state plaintiffs resulted in the DC Circuit's rejection of CAIR, and would be costly even if the EPA were to prevail. The agency could relatively easily and cheaply avoid or limit such litigation now by carefully studying and explaining its decisions regarding levels of precision. [EPA-HQ-OAR-2009-0491-2573.1,pp.24-25]
Second, we recommend that EPA undertake an expert elicitation study -- using independent experts -- to determine the appropriate level of precision for its thresholds for determining significant contribution and interference with maintenance in neighboring states. Doing so will ensure that the EPA has made rational and defensible decisions about how to determine the states covered by the Transport Rule. [EPA-HQ-OAR-2009-0491-2573.1, p.32]

 39 CAIR only used a contribution threshold for the annual fine PM standard in determining the States that were contributing significantly to non-attainment of the annual fine PM NAAQS in the downwind areas of neighboring States. At that time the 24-hour NAAQS for fine PM was 0.65 ug/m3. With this standard, EPA reported that that there were no non-attainment areas for the 24-hour NAAQS in Eastern areas of the U.S. Therefore, non-attainment of the annual NAAQS was the appropriate evaluative measure. 70 FR 25189.
41 Appendix N also includes as a part of the data handling provisions the following data reporting requirement: "The computed 24-hour average PM2.5 concentrations shall be reported to one decimal place (the additional digits to the right of the first decimal place are truncated), consistent with the data handling procedures for the reported data." (71 FR 61228.) Thus, a computed 24-hour average fine PM concentration of 0.35 ug/m3 would be reported as 0.4 ug/m3 under this provision of Appendix N. With the proposed thresholds of 0.15 ug/m3 for the annual NAAQS and 0.35 ug/m3 for the 24-hour NAAQS, EPA is attributing a greater precision to its modeling data than it provides for in its monitoring requirements. One possible approach for EPA is to use this rationale as the basis for adopting a 24-hour threshold of 0.4 μg/m3.
52 In addition, Texas would likely be below an annual contribution threshold of 0.2 ug/m3 threshold even with the substantial increase in SO2 emissions EPA projects for Texas under the proposed Transport rule. EPA requests comments in the proposal on the possibility of including Texas in the final Transport rule because the projected increase in SO2 emissions would result in a contribution that exceeds the proposed annual NAAQS threshold of 0.15 ug/m3. 75 FR 45284.
Louisiana Chemical Association (LCA)
The Projected Impact from Louisiana Emissions Is Less than a PSD Significant Impact Level.
LCA believes that EPA cannot set the level for either "significant contribution" or "interference with maintenance" of a NAAQS lower than the EPA Significant Impact Level ("SIL") used under the Prevention of Significant Deterioration ("PSD") program. LCA intends this as a general comment on EPA's proposed methodology for determining when there is "significant contribution" or "interference with maintenance" within the meaning of CAA Section 110(a)(2)(D) and as a specific comment with respect to the projected impact of Louisiana emissions on Harris County, Texas. [EPA-HQ-OAR-2009-0491-3527.1, pp. 7-8; see pp. 8-10 for extensive discussion of this issue.]
EPA's Should Revise It's Proposed Methodology for Determining Significant Contribution and Interference With Maintenance. LCA believes that EPA's proposed methodology for determining "significant contribution" and "interference with maintenance" should never be more than a screening tool. The upwind state should always be provided with the ability to submit objective evidence that there is no interference with maintenance that counteracts the modeled assumptions. For example, in this case, the fact that exceptional event data has been removed from the design value upon which EPA premised its projected 2012 design value should be allowed to controvert a proposed finding of interference. Further, the finding of interference should not be contradictory to objective evidence that local controls have eliminated the reasonable potential for the design value to rise to the level that EPA has projected. [EPA-HQ-OAR-2009-0491-3527.1, p. 30]
Further, for the reasons stated above, strictly as a legal matter, the threshold for a finding of reasonable interference should never be established below the PSD Significant Impact Level. LCA suggests that even a SIL would be entirely too conservative a value to use for making a finding of significant contribution or a finding of interference with maintenance under the CAA "good neighbor" clause. If a single source in the area is not required to perform an air quality impact analysis under a PSD permit review due to projected emissions being below a SIL, then the threshold for inclusion of cumulative emissions from an upwind state should be much more significant to justify detailed air quality analysis by the upwind state and, potentially adoption of a control program under a SIP. [EPA-HQ-OAR-2009-0491-3527.1, p. 30]
In no case should a threshold for a finding of reasonable interference with maintenance be less than 2 ppb when based upon projected, modeled data that has a significant uncertainty factor. The level of uncertainty in the IPM and the myriad of assumptions that form the submodels that are used by the IPM is too great to base decisions for sweeping, costly controls on a projected impact of less than 2 parts per billion of any pollutant. Literally hundreds of data points, some measured and some estimated are used in the IPM. The models just do not have the degree of certainty that they should form the only basis for such decisions. This is clearly illustrated by a simple comparison of the 2012 Base Case values from IPM v.3.02 to those from IPM v. 4.10. As noted above, the difference in projected SO2 levels between those two base case predictions for Louisiana EGUs was more than 20,000 tpy  -  a 20% difference just in EGU projections. Any decision to require an upstate to adopt SIP provisions for an impact of less than 2 ppb on a downwind state should require supplementation with objective, empirical data demonstrating a clear linkage from the upwind sources to the downwind receptor. [EPA-HQ-OAR-2009-0491-3527.1, p. 30]
Other Factors Providing a "Safety Net" for a Determination That Louisiana Emissions Do Not Interfere With Maintenance of the Annual PM2.5 NAAQS in Texas
LCA believes that the comments above clearly demonstrate that Louisiana emissions do not and will not interfere with maintenance of the annual PM2.5 NAAQS in Harris Co., Texas. In addition to these comments, as safety-factors supporting this conclusion are several recently adopted and anticipated regulations that EPA did not consider. [EPA-HQ-OAR-2009-0491-3527.1, p. 30; see pp. 31-32 for list of recently adopted and anticipated regulations.]
Maryland Department of Environment (MDE)
Significant Contribution and Interference with Maintenance
Maryland acknowledges that the current proposal including a strong assessment of significant contribution and interference with maintenance. Maryland supports the approach EPA used in quantifying significant contribution and interference with maintenance, and supports 1 percent of the NAAQS as an appropriate threshold for significant contribution for both the current proposed rule and any future rules to address transport pursuant to a future NAAQS. [EPA-HQ-OAR-2009-0491-2639.2, p.5]
The 1% significance threshold is consistent with the piecemeal nature of regional air pollution. The contribution modeling done for the Transport Rule confirms the fact that many small out-of-state contributions can add up to a big local ozone or PM2.5 problem. For Maryland, the average contribution per ozone monitor from Maryland itself is 26 ppb, but the sum of the average contribution of all other states in the modeling domain is 31 ppb. The top five states (Virginia, Pennsylvania, West Virginia, Ohio, and DC) contribute 21 of the 31 ppb while the remaining 10 ppb comes from 14 other states. The advantage of using a percentage of the NAAQS is that the threshold adjusts to the new standards. We believe the 1% threshold is a legitimate estimate of whether a contribution is considered "significant." [EPA-HQ-OAR-2009-0491-2639.2, p.5]
The approach in the proposed Transport Rule is an improvement to the absolute threshold of 2 ppb that EPA used previously in CAIR, because it sets a relative threshold as a function of the NAAQS for any pollutant. As long as the NAAQS remain unchanged, the threshold will remain constant. However, if the NAAQS are made more stringent, the threshold for the revised NAAQS will also become appropriately more stringent. [EPA-HQ-OAR-2009-0491-2639.2, pp.5-6]
The significance threshold should be amended to include "equal to" 1 percent. As previously noted, Maryland strongly agrees with EPA's definition of the significant contribution threshold as 1 percent of the NAAQS in the proposed Transport Rule. We further support the applicability of this definition for purposes of determining significant contribution in relation to any future NAAQS. However, we urge EPA to amend the definition in the proposed rule to also designate as "significantly contributing" those states whose significant contribution equals 1 percent of the NAAQS, in addition to those states whose contribution exceeds the 1 percent threshold. This is consistent with the recommendation made by the OTC and LADCO states in their letter dated September 2, 2009, to EPA on the replacement of CAIR (see Appendix D [See EPA-HQ-OAR-2009-0491-2639.2, p.35 for comments pertaining to Appendix D]). [EPA-HQ-OAR-2009-0491-2639.2, p.6]
EPA uses air quality modeling to quantify individual states' contributions to downwind nonattainment and maintenance sites (75 FR 45233). In the proposed rule, a state whose contributions to downwind sites are greater than 1 percent of the NAAQS are then considered "linked" to those downwind sites for purposes of further analyses. Our recommendation here is that a state whose contribution to any downwind site is "equal to or greater than" 1 percent of the NAAQS be included in the linkages. [EPA-HQ-OAR-2009-0491-2639.2, p.6]
Minnesota Power
Minnesota Power (MP) has followed the EPA's release of the proposed Transport Rule with high interest for multiple reasons, including EPA's designation of the Transport Rule for impacting the status of the EPA Administrative Stay of the Clean Air Interstate Transport Rule (CAIR) in Minnesota.  In a 11/03/2009 Federal Register Notice, EPA acknowledged data error issues raised by the US DC Circuit Court of Appeals by establishing an Administrative Stay of CAIR and CAIR FIP implementation in Minnesota. Minnesota Power had provided EPA with modeling analysis prepared by Environ and Alpine Geophysics for Minnesota Power that reflected corrections in EPA's Minnesota emissions model inputs. The modeling analysis demonstrated that the Minnesota contribution to downwind nonattainment areas fell below EPA's CAIR significance level of 0.20 ug/m3 PM2.5 after correcting apparent errors in Minnesota source emissions. At the time, EPA was asserting that the Minnesota contribution to a downwind nonattainment area was right at the CAIR significance level, after application of EPA's truncation method.  The Minnesota Power CAIR analysis was indicating that the Minnesota signal was about 0.18 ug/m3 PM2.5 and that Minnesota should not be a CAIR affected state.   [EPA-HQ-OAR-2009-0491-2750.1, p.2]
Interestingly, EPA acknowledged in its Transport Rule discussion that their analysis now demonstrates the Minnesota contribution to downwind nonattainment is below the CAIR 0.20 ug/m3 PM2.5 significance level.  However, EPA proceeded to cite how Minnesota would be a Transport Rule, Group 2 affected State under a Transport Rule revision of EPA's significance level to 1% of the 15.0 ug/m3 annual average PM2.5 National Ambient Air Quality Standard (NAAQS) and by application of EPA's new cost effective control screening assessment.  EPA also cited reference to the new, 24 hour average PM2.5 standard that EPA had not considered under the 2005 CAIR.  Additionally, EPA indicated in the proposed Transport Rule its intention to revise the NAAQS for annual average PM2.5 to an undisclosed, prospectively more stringent value at a future time and that it was EPA's intent to continue to modify its standard for significant contribution to nonattainment or impediment to maintenance to a level that continues to represent 1% of any new PM2.5 annual NAAQS.  EPA proceeded in this proposed Transport Rule to inquire whether stakeholders considered it appropriate for Group 2 States (like Minnesota) to be designated as Group 1 Transport Rule states. EPA has noted that Group 1 States are subject to more stringent emissions reduction requirements. Group 1 States are more closely associated with States that currently contain PM2.5 standard nonattainment areas.  Group 1 States are described by EPA as having relatively lower cost per ton emission reduction costs than Group 2 States.   [EPA-HQ-OAR-2009-0491-2750.1, p.3]
In effect, EPA is indicating in the Proposed Transport Rule that, but for application of the more stringent measure of a significant contribution, Minnesota would have been excluded from the groups of Transport Rule affected states and that inclusion of Minnesota in the Transport Rule doesn't result in any additional Minnesota emission reductions to satisfy 2012 Group 2 Boiler budgets.  EPA's analysis affirms that Minnesota affected emission source owners and operators had a reasonable expectation that Minnesota would not be listed as an affected State in the Transport Rule, considering the Minnesota modeled contribution to PM2.5 nonattainment relative to EPA's 2005 CAIR significant contribution criteria.  This all begs the question of why EPA has chosen to place Minnesota in the Transport Rule at all and, if Minnesota is a Transport Rule affected State, why Minnesota should be expected to meet new SO2 and NOx Budget requirements only a year and a half after Minnesota learns that EPA is revising its significant contribution criteria in a manner that can draw Minnesota into the groups of Transport Rule affected States.  [EPA-HQ-OAR-2009-0491-2750.1, pp.4-5]
Significance level changes, 2005 CAIR to proposed Transport Rule. EPA shifted the significance level to the more inclusive 0.15 ug/m3 for the Transport Rule, which becomes EPA's primary justification for now including Minnesota. EPA may make the criteria even tighter if it revises the PM2.5 NAAQS to below the annual average of 15 ug/m3. Yet, original comments Minnesota Power made in 2004 to EPA cited how a 0.15 ug/m3 significance level is not supported when compared to EPA's assessments of how well their modeling tools compare with actual ground level PM2.5 models used to determine nonattainment designations.  Air quality monitoring station limitations in discerning small changes in measured air quality separately from normal monitor measurement variability have not been demonstrated by EPA to have improved sufficiently to support such a large tightening of the Transport Rule significance level relative to the CAIR final rule significance level.   [EPA-HQ-OAR-2009-0491-2750.1, p.7]
Nebraska Public Power District
7) Setting Significance Thresholds. EPA has proposed extremely low levels of "significance" with respect to modeled impact contributions from upwind states, at 1% of the respective NAAQS for 24-hour PM2.5 (0.35 μg/m3), annual average PM2.5 (0.15 μg/m3), and 8-hour ozone (0.8 ppb). This means that some states, like Nebraska, with very minimal predicted contributions, will be targeted for controls that have a very high cost to benefit ratio. Instead of imposing cost inefficient controls (high $/μg/m3) on a state like Nebraska, it would make much more sense to spend similar levels of capital on more aggressive controls in states with predicted impact contributions that in some cases are estimated by EPA to be more than an order of magnitude higher than for Nebraska (see Table IV.C-16 of preamble). [EPA-HQ-OAR-2009-0491-2711.1, p.7]
12) Rounding Conventions. EPA's current TR proposal would alter past rounding conventions for annual and 24-hour PM2.5 inconsistently. On the one hand, for annual PM2.5, EPA proposes to deviate from the design value reporting requirement by only one decimal place -- rounding to the nearest 0.01 μg/m3 rather than the nearest 0.1 μg/m3 as it did under CAIR consistent with EPA monitoring requirements. In contrast, EPA proposes a two decimal place deviation from past practice for 24-hour PM2.5 -- rounding to the nearest 0.01 μg/m3 rather than the nearest whole μg/m3. In justifying its proposal, EPA lays out a false choice between adopting the CAIR approach, which would "yield air quality threshold of zero" and selecting a uniform 2 digit rounding convention for annual 24-hour PM2.5. We recommend that EPA use a rounding convention consistently with its earlier rule proposal for modeling of PM2.5 for demonstrating NAAQS compliance (see above comment), specifying the significance level to one decimal place. We believe this alternative rounding convention is a more defensible metric in setting an air quality threshold for assessing the significance of interstate contributions to downwind nonattainment. [EPA-HQ-OAR-2009-0491-2711.1, pp.8-9]
North Carolina Department of Environment and Natural Resources
The NCDAQ supports the 1% threshold and encourages EPA to be consistent in the rounding truncation conventions for all pollutants. [EPA-HQ-OAR-2009-0491-2767.1 p.6]
Northeast States for Coordinated Air Use Management (NESCAUM)
We support EPA's proposal to adopt 1% of a NAAQS level as the transport linkage criterion. This is a metric that the states of the OTC and the Lake Michigan Air Directors Consortium analyzed in great detail and collectively proposed to Administrator Jackson in September, 2009. It ensures public health and environmental protection into the future, with the likelihood of subsequent NAAQS revisions based on new science. We also agree with EPA's decision not to use its previous rounding convention to establish 1% of the NAAQS.   [EPA-HQ-OAR-2009-0491-2984.1, p.4]
[These comments were submitted as testimony at the Philadelphia, Pennsylvania public hearing on August 26, 2010.  See Docket Number EPA-HQ-OAR-0491-1938, p.9.]
We are pleased that EPA proposes to use 1% of a NAAQS concentration as the transport linkage criterion. We agree with EPA's decision not to use the rounding convention to establish 1% of the NAAQS.
Omaha Public Power District
EPA has proposed extremely low levels of 'significance' with respect to modeled impact contributions from upwind states, at 1% of the respective NAAQS for 24-hour PM2.5 (0.35 ug/m3), annual average PM2.5 (0.15 ug/m\ and 8-hour ozone (0.8 ppb). This means that some states, like Nebraska, with very minimal predicted contributions, will be targeted for controls that have a very high cost to benefit ratio. Instead of imposing cost inefficient controls (high $/ug/m3) on a state like Nebraska, it would make much more sense to spend similar levels of capital on more aggressive controls in states with predicted impact contributions that in some cases are estimated by EPA to be more than an order of magnitude higher than for Nebraska (see Table IV.C-16 of preamble). [EPA-HQ-OAR-2009-0491-2680.1, p. 4]
EPA's current TR proposal would alter past rounding conventions for annual and 24-hour PM2.5 inconsistently. On the one hand, for annual PM2.5, EPA proposes to deviate from the design value reporting requirement by only one decimal place-rounding to the nearest 0.01 ug/m3 rather than the nearest 0.1 ug/m3 as it did under CAIR consistent with EPA monitoring requirements. In contrast, EPA proposes a two decimal place deviation from past practice for 24-hour PM2.5-rounding to the nearest 0.01 ug/m3 rather than the nearest whole ug/m3. In justifying its proposal, EPA lays out a false choice between adopting the CAIR approach, which would 'yield air quality threshold of zero' and selecting a uniform 2 digit rounding convention for annual 24-hour PM2.5. We recommend that EPA use a rounding convention consistently with its earlier rule proposal for modeling of PM2.5 for demonstrating NAAQS compliance (see above comment), specifying the significance level to one decimal place. We believe this alternative rounding convention is a more defensible metric in setting an air quality threshold for assessing the significance of interstate contributions to downwind nonattainment.  [EPA-HQ-OAR-2009-0491-2680.1, p. 6]
Pennsylvania Department of Environmental Protection
In accordance with Section 110(a)(2)(D)(i)(T) of the CAA, EPA must ensure that SIPs for primary and secondary national ambient air quality standards 'contain adequate provisions' prohibiting sources within a state from emitting air pollutants in amounts which will 'contribute significantly to nonattainment in, or interfere with maintenance by, any other State with respect to any (NAAQSJ.' The DEP supports EPA's approach for determining each state's significant contribution to downwind areas-a threshold greater than or equal to 1 percent of the relevant NAAQS is an appropriate threshold for determining 'significant contribution.' This approach, which is consistent with the recommendation of the Ozone Transport Commission and Lake Michigan Air Directors Consortium (LADCO) submitted jointly to EPA in a September 2, 2009 letter on the replacement of CAIR, should ensure that emissions within a state that significantly contribute to nonattainment or interfere with maintenance in other states are eliminated. [EPA-HQ-OAR-2009-0491-2660.1, pp.3-4]
Sierra Club
Any rule intended to address the significant contribution of air pollution from neighboring states should include all states which are significantly contributing to NAAQS violations (and to interference with NAAQS maintenance) in downwind states. The Sierra Club contends that the contribution threshold that EPA proposes to use to determine whether a state will be included within the proposed Transport Rule, and thus whether it will have its interstate pollution transport reduced under the rule - a threshold which equates to one percent (l %) of the relevant NAAQS -- is too high. To fulfill the Clean Air Act's mandates for assuringtimely attainment and assurance of maintenance of NAAQS, 'significant contribution'within the meaning of section 11O(a)(2)(D) must include any discernable contributions(whether modeled or monitored) to non-attainment (or interference with maintenance) inanother state.. Contributions of less than 1% of the NAAQS (either alone, or in combination with contributions from other states) can still make the difference between an area being in attainment or non-attainment, so there is no rational basis for waiving control of such contributions - and indeed such waiver is contrary to the Act's central mandate of assuring timely attainment. [EPA-HQ-OAR-2009-0491-2872.1 p.2]
Indeed, the 1% contribution threshold EPA proposes as a cut off for including states in the Transport Rule is particularly concell1ing because the threshold excludes without valid reason certain states that are making discell1able contributions to ozone and fine particle levels in downwind states. For example, EPA's state-by-state modeling shows that Texas contributes 0.13 flg/m3 and 0.12 flg/m3 to annual PM2.5 nonattainment in two ites located in southell1 Illinoi (specifically, Madison and Saint Clair counties respectively),2 but because these contributions do not equal or exceed the 0.15 flg/m3 threshold, Texas will not be required to reduce its PM2.5 emis ions under the proposed Transport Rule. Such an outcome is not consistent with the clear mandate and purpose of the rranspOlt requirement, which i to prohibit states from emitting pollutants in a manner that will contribute to non-attainment or interfere with maintenance in other states, and can be avoided with the use of a lower contribution threshold. [EPA-HQ-OAR-2009-0491-2872.1 p.2]
Moreover, the Rule as proposed would allow emissions increases, the most egregious case being Texa . In this regard, when considering what effect, if any, the proposed Rule would have on non-regulated states, EPA's analysis reveals that Texas' 2012 S02 emissions will increase by 136,000 tons if the rule is in fact adopted.3 75 Fed. Reg. at 45284. This dramatic increase in S02 emissions, EPA notes, will push Texas' interstate contributions over the establi hed annual PM2.5 threshold in 2012, thus placing it within the group of states that require PM2.5 reductions under the temlS of the proposed rule. /d. In other words, implementation of the Rule will cause Texas to significantly contribute to non-attainment or interfere with maintenance in downwind states, thereby increasing -- rather than lessening -- the public health threat in those areas as well as within Texas. Given this outcome, which plainly contradicts the mandate of section 11O(a)(2)(D) and the purpose of the Clean Air Act and the Agency's proposed efforts, it is axiomatic that EPA must include Texas within its control program for annual PM2.5 reductions. [EPA-HQ-OAR-2009-0491-2872.1 p.3]
South Carolina Department of Health and Environmental Control
The 1% contribution threshold in the proposed Transport Rule is too low. It captures insignificantly low levels of transported emissions. The EPA states that the threshold is low by design, because: ...PM2.5 nonattainment problems result from the combined impact of relatively small contributions from many upwind states, along with contributions from in-state sources, and, in some cases, substantially larger contributions from a subset of particular upwind states. [EPA-HQ-OAR-2009-0491-2677.1 p.7]
DHEC notes that the EPA does not elaborate on the mix for the downwind states in the Transport Rule. We cannot find a clearly articulated explanation of how the EPA determined the percentage of local contribution to nonattainment in the Transport Rule Technical Support Documents. Without that we cannot determine how South Carolina's contribution compares to local contributions for nonattainment, and cannot fully evaluate the rule. [EPA-HQ-OAR-2009-0491-2677.1 p.6]
In defending the low contribution threshold, the EPA continues: "A second reason that low threshold values are warranted, as EPA discussed in the notices for the CAIR, is that there are adverse health impacts associated with ambient PM2.5 and Ozone even at low levels."15 DHEC grants that this claim is related to the discussion, but we are unsure how to evaluate it since the studies that the EPA is referencing do not specifically study the health impacts of air pollutant at levels equal to 1% of the NAAQS.  [EPA-HQ-OAR-2009-0491-2677.1 p.7]
The CAIR and NOX SIP Call thresholds were more appropriate, and DHEC recommends that the EPA follow that precedent in the Transport Rule. The previous thresholds were tailored to each NAAQS, and not generalized across various standards. Also, the CAIR and NOX SIP Call thresholds linked the precision available in determining design values and the threshold. In other words, design values for monitors are reported to the nearest 0.1 μg/m3 and the EPA rounded the threshold to the tenths position so that the threshold is not more precise that the design value on which it is based. Federal regulations require states to submit design values for PM2.5 monitors only to one decimal place -- to the nearest 0.1 μg/m3.16 In the Transport Rule, the EPA is proposing to use thresholds rounded to two decimal places, based on design values that are only capable of capturing data to one decimal place. DHEC finds this illogical, and we cite this as a potential source of error in determining which states are subject to the Transport Rule. The EPA addresses the difference between the design value and the threshold in the proposal: For the proposed rule, EPA proposes to decouple the precision of the air quality thresholds with the monitoring reporting requirements, and to use 2-digit values representing 1% of the NAAQS, that is, 0.15 μg/m3 for the 24hr standard.
The EPA defends this decision citing the ease of applying the threshold to future NAAQS. DHEC is concerned about the problems associated with rounding in converting between the more precise threshold values to the less precise design values. Additionally, if 1% of a lowered PM2.5 standard is less than 0.1 μg/m3, then converting that to a design value that only measures to the tenths would be problematic. The integers as thresholds in the CAIR and NOX SIP Call programs avoid this concern. [EPA-HQ-OAR-2009-0491-2677.1 p.7]
Based on these concerns, DHEC recommends against using thresholds with two decimal places, that is, numbers rounded to the hundredths position. For the annual standard, a threshold rounded to tenths position would be 0.2 μg/m3. For the 24-hour standard, a threshold rounded to the tenths position would be 0.4 μg/m3. But DHEC does not advocate using these thresholds. Because of the uncertainty and possible errors associated with IPM and other modeling assumptions in the proposal including the confounding local issues, we advocate a 1 μg/m3 threshold for determining significant contribution to downwind nonattainment and interference with maintenance. [EPA-HQ-OAR-2009-0491-2677.1 p.7]
Using this approach in the Transport Rule, South Carolina would not significantly contribute to nonattainment or interfere with maintenance downwind for the annual or 24-hour standards18 and would thus not be subject to the Transport Rule SO2 trading program. DHEC considers thμg/m3 threshold, rather than a threshold at the tenths of a microgram, reasonable for both the annual and the 24-hour standard because of the uncertainty and possible errors associated with IPM and other modeling assumptions in the proposal. [EPA-HQ-OAR-2009-0491-2677.1 p.8]
DHEC also finds the ozone threshold problematic. The proposed Transport Rule also uses the 1% threshold for the 1997 Ozone NAAQS, meaning the threshold is 0.8 ppb. The EPA proposes to include states that contribute more than this amount in the Transport Rule program. EPA monitoring regulations require states to submit ozone data to the third decimal place,19 which avoids the decimal place issue discussed above, but our concerns over uncertainty also apply to the ozone thresholds. Again, the uncertainty with IPM and possible local contributions to downwind monitors lead DHEC to request a 1 ppb threshold for ozone. With that threshold, South Carolina's largest contribution to downwind 8-hour ozone nonattainment and maintenance, 0.8 ppb, would fall below the 1 ppb threshold and South Carolina would not be subject to the NOX trading programs in the Trading Rule. [EPA-HQ-OAR-2009-0491-2677.1 p.8]
Southern Company
Additionally, Southern Company objects to EPA's proposal to use its percentage-based air quality contribution threshold approach in the current rulemaking -- or in any future interstate-transport rulemaking--in the absence of a robust technical justification that the resulting thresholds reflect meaningful, and truly measurable, air quality contributions, consistent with the D.C. Circuit's directive in Michigan v. EPA. [EPA-HQ-OAR-2009-0491-2864.1, p. 5]
F. EPA's Proposed Air Quality Contribution Threshold is Flawed
EPA proposes to use an air quality contribution threshold based on a percentage -- specifically, one percent -- of the NAAQS for annual PM2.5, 24-hour PM2.5, and 8-hour ozone to determine whether an upwind state should be included in the Transport Rule program with respect to each of those NAAQS. EPA explains in the preamble to the proposed rule that it chose to deviate from the approach it used in CAIR with respect to PM2.5 by using here a two-digit value rather than a single-digit value and 'decoupl[ing] the precision of the air quality thresholds [from] the monitoring reporting requirements.' [EPA-HQ-OAR-2009-0491-2864.1, pp. 33-34]
Although EPA properly proposes to avoid setting a zero contribution threshold for the current 24-hour PM2.5 NAAQS, and to avoid setting a precedent for a 0.1 u/m3 contribution threshold if the annual PM2.5 NAAQS in the future is reduced to some value lower than the current NAAQS but higher than 10 u/m3 (e.g., 14 u/m3), EPA's proposed approach ignores the limits of the capability of its air quality modeling techniques -- and of ambient monitoring -- to meaningfully detect and measure ambient-air contributions at the extremely low levels represented by one percent of current or possible future NAAQS. For example, the numerical values that result from application of EPA's one-percent contribution threshold approach to the current NAAQS -i. e., 0.15 u/m3 for annual PM2.5, 0.35 u/m3 for 24-hour PM2.5, and 0.8 ppb for 8-hour ozone -- are so low that they are likely below the detection capability of existing modeling and measurement tools. For that reason, it is far from clear that these thresholds could be deemed to reflect a 'measurable contribution' to downwind nonattainment and maintenance problems, as required by the D.C. Circuit. Interstate contributions cannot be assumed out of thin air.') (emphasis in original). At a minimum, EPA should provide, in a supplemental notice of proposed rulemaking, a technical justification for these very low thresholds as representing meaningfully measurable air quality contributions. [EPA-HQ-OAR-2009-0491-2864.1, p. 34]
Equally troubling is EPA's indication that it may be planning to use this same percentage-based approach in any future version of the Transport Rule to address possible future NAAQS. Application of this approach to potential future ambient standards that may be even lower than the current NAAQS would produce even less meaningful thresholds. It makes no sense for contribution thresholds to change based exclusively on changing NAAQS levels, irrespective of the capabilities of modeling and measurement technologies at the time the thresholds are established. [EPA-HQ-OAR-2009-0491-2864.1, p. 34]
Accordingly, Southern Company objects to EPA's proposal to use its percentage-based air quality contribution threshold approach in the current rulemaking -- or in any future interstate transport rulemaking -- in the absence of a robust technical justification that the resulting thresholds reflect meaningful, and truly measurable, air quality contributions, consistent with the D.C. Circuit's directive in Michigan v. EPA. [EPA-HQ-OAR-2009-0491-2864.1, p. 34]
State of Connecticut
The Transport Rule as proposed is an improvement to the Clean Air Interstate Rule of 2005 and there are provisions of the Transport Rule that Connecticut fully supports. For example, Connecticut is pleased that EPA adopted one percent of the NAAQS as the criterion for significant contribution, as recommended by Connecticut and other states. [EPA-HQ-OAR-2009-0491-2534.1, p.1]
State of Missouri Department of Natural Resources
Missouri concurs with the pollutants and air quality thresholds used for identifying states to be included under the proposed rule. Suggesting a higher threshold than one percent (1%) would put the burden of lowering emissions on fewer states. In addition, Missouri agrees with EPA's approach that does not use the rounding convention. [EPA-HQ-OAR-2009-0491-3806, p.4]
State of Ohio Environmental Protection Agency (Ohio EPA)
Ohio EPA has concerns regarding the 1% contribution threshold. U.S. EPA must take into consideration the impact of selecting such a small percent threshold as the NAAQS continue to be strengthened. [EPA-HQ-OAR-2009-0491-2793.2, p. 10]
Related to the continuous tightening of the rules, Ohio EPA has concerns regarding the 1% contribution threshold for identifying significant contributors to downwind states' air quality nonattainment and maintenance problems, which forms the basis of the Proposed Transport Rule. As ambient air quality standards continue to be revised and strengthened, the continued use of a 1% threshold will eventually become impractical and infeasibl~ because it continually rachets down state budgets and unit level allocations. [EPA-HQ-OAR-2009-0491-2793.2, pp. 1-11]
State of Wisconsin, Department of Natural Resources
Wisconsin supports the 1% contribution threshold, as proposed in the Transport Rule, for identifying states that are significant contributors to downwind state's air quality nonattainment and maintenance problems and therefore trigger obligations under Section 110a(2)(D) of the Clean Air Act (CM). [EPA-HQ-OAR-2009-0491-2829.2, p.1]
EPA has appropriately identified individual states that contribute significantly to Wisconsin criteria air quality nonattainment and maintenance problems. [EPA-HQ-OAR-2009-0491-2829.2, p.5]
EPA appears to address the Court concen regarding identification of specific state air quality impact contribution to both attainment and maintenance problems and setting a defensible timeframe for remedy under the current ambient standards. This first part ofsignificant contribution identification including thresholds comports with state recommendations under the OTC/LADCO States Collaborative effort. Wisconsin explicitly supports the 1% contribution threshold for nonattainment areas and some more conservative threshold regarding maintenance. Such thresholds have been upheld by the Court and Wisconsin agreed in the Collaborative process that such thresholds should have both designation period design value and attainment period context for the assessment of impacts relating to contribution. [EPA-HQ-OAR-2009-0491-2829.2, p.5]
Sunbury Generation LP
For purposes of determining which states significantly contribute to or interfere with maintenance of the NAAQS for PM2.5 or ozone in other states under the Proposed Rule, EPA applies a threshold of 1% of the NAAQS. See 75 Fed. Reg. 45237. EPA's reliance on this stringent 1% threshold for determining significant contribution results in an overstatement of the degree to which a state's emissions contribute to emissions impacts in downwind states. [EPA-HQ-OAR-2009-0491-3615,p .7]
Tennessee Department of Environment and Conservation, Division of Air Pollution Control
Comment on Contribution Threshold: EPA's 1% significance threshold for downwind contribution for annual PM2.5 (0.15 μg/m3) is more stringent than the threshold used with CAIR but is generally consistent with the CAIR methodology. 1 The use of similar 1% metrics may not be appropriate for ozone and daily PM2.5. Because the ozone and daily PM2.5 NAAQS employ much shorter averaging times than the annual PM2.5 standard, we are concerned that the use of a simple 1% significance threshold may overstate the downwind contribution for these pollutants, even if the contribution is averaged over multiple days. [EPA-HQ-OAR-2009-0491-0553.1, p.2]
EPA noted in the CAIR rulemaking that there are inherent differences between the PM2.5 and ozone NAAQS, and the thresholds necessarily differ in terms of specific metrics and threshold values. With respect to the 8- hour ozone NAAQS, if an upwind State's impact exceeded a maximum contribution of 2 ppb or an average contribution of 1%, then EPA used additional metrics to determine if downwind contribution from an upwind State was significant. EPA organized the outputs of two modeling techniques (zero-out and source apportionment) into a set of ``metrics.'' The metrics included:
-The magnitude of the contribution (actual amount of ozone contributed by emissions in the upwind State to nonattainment in the downwind area);
-The frequency of the contribution (how often contributions above certain thresholds occur); and
-The relative amount of the contribution (the total ozone contributed by the upwind State compared to the total amount of nonattainment ozone in the downwind area). [EPA-HQ-OAR-2009-0491-0553.1, p.2]
These metrics, which EPA used to assess downwind ozone contributions for CAIR, were also used in the NOX SIP Call. We believe that a methodology similar to the NOX SIP Call/CAIR approach would be preferable for ozone and daily PM2.5, since it would allow the Agency to use a measure of judgment in determining significance. [EPA-HQ-OAR-2009-0491-0553.1, p.2]
Tennessee Valley Authority (TVA)
Issue: EPA has proposed air quality thresholds to identify states with significant contributions that need to be addressed by the Transport Rule. These thresholds are based on 1 percent of the NAAQS: 0.15 ug/m3 for the annual PM-2.5 standard, 0.35 ug/m3 for the 24-hour PM-2.5 standard, and 0.8 ppb for the 8-hour ozone standard. (p. 45237) For CAIR, EPA used a threshold of 0.2 ug/m3 for the annual PM- 2.5 standard and 2 ppb for the 8-hour ozone standard. [p. 45270-83] [EPA-HQ-OAR-2009-0491-2782.1, p. 10]
TVA Comment: EPA should retain the air quality threshold of 0.2 ug/m3 that was used in CAIR for identifying significant contributions with respect to the annual PM-2.5 standard. TVA recommends that to the extent workable, the threshold value should be rounded to the same number of digits as specified in the reporting requirement for the design value of the applicable air quality standard. Thus, because the design value for the annual PM-2.5 standard must be reported to the nearest 0.1 ug/m3, one percent of 15 ug/m3 (i.e. 0.15 ug/m3) rounded to the nearest 0.1 ug/m3 becomes 0.2 ug/m3. Matching the number of digits in the threshold to the number of digits in the design value of the applicable standard imparts the appropriate degree of precision to the threshold. We therefore recommend against decoupling the precision of the air quality thresholds with the monitoring reporting requirements. In North Carolina v. EPA, the D.C. Circuit upheld EPA's decision to round the 0.15 ug/m3 threshold to 0.2 ug/m3. [EPA-HQ-OAR-2009-0491-2782.1, p. 10]
We understand that coupling the precision of the air quality threshold and the monitoring reporting requirement may not always be workable as is the case with the 24-hour PM-2.5 standard. One percent of the 24-hour standard is 0.35 ug/m3, and, as EPA points out, rounding to the nearest whole ug/m3 would yield an unworkable threshold of zero. In such circumstances, the air quality threshold should be rounded to the number digits that most closely approximate the monitoring reporting requirement without rendering the threshold unworkable. For the 24-hour standard, one percent of the standard (i.e. 0.35 ug/m3) should therefore be rounded to the nearest single digit, i.e. 0.4 ug/m3. [EPA-HQ-OAR-2009-0491-2782.1, p. 10]
Texas Commission on Environmental Quality
The TCEQ first objects to the EPA's proposed analysis regarding the determination of 'significant -contribution to nonattainment' by states, because the proposal does not adequately address why a threshold value of one percent of the relevant NAAQS is appropriate. The EPA notes only that 'low' threshold values are warranted due to the upwind 'collective contribution' being important to both PM2 .5 and ozone (75 FR 45237). Because the EPA has not clearly explained the rationale behind its one percent threshold (as opposed to any other 'low' percentage), the TCEQ is unable to determine the appropriateness of such a threshold, particularly given the inadequate comment period provided by the EPA. Given the numerous flaws in the technical analysis already identified, the TCEQ can only assume that such a value is unsupportable.[EPA-HQ-OAR-2009-0491-2857.2, pp.7-8]
Utility Air Regulatory Group (UARG)
EPA's Proposed Air Quality Contribution Threshold Is Flawed.
EPA proposes to use an air quality contribution threshold based on a percentage -- specifically, one percent -- of the NAAQS for annual PM2.5, 24-hour PM2.5, and 8-hour ozone to determine whether an upwind state should be included in the Transport Rule program with respect to each of those NAAQS. See 75 Fed. Reg. at 45237/1-45238/1. EPA explains in the preamble to the proposed rule that it chose to deviate from the approach it used in CAIR with respect to PM2.5 by using here a two-digit value rather than a single-digit value and "decoupl[ing] the precision of the air quality thresholds [from] the monitoring reporting requirements." Id. at 45237/3. [EPA-HQ-OAR-2009-0491-2756.1, p.60]
Although EPA properly proposes to avoid setting a zero contribution threshold for the current 24-hour PM2.5 NAAQS, see id., and to avoid setting a precedent for a 0.1 μ/m3 contribution threshold if the annual PM2.5 NAAQS in the future is reduced to some value lower than the current NAAQS but higher than 10 μ/m3 (e.g., 14 μ/m3), see id., EPA's proposed approach ignores the limits of the capability of its air quality modeling techniques -- and of ambient monitoring -- to meaningfully detect and measure ambient-air contributions at the extremely low levels represented by one percent of current or possible future NAAQS. For example, the numerical values that result from application of EPA's one-percent contribution threshold approach to the current NAAQS -- i.e., 0.15 μ/m3 for annual PM2.5, 0.35 μ/m3 for 24- hour PM2.5, and 0.8 ppb for 8-hour ozone -- are so low that they are likely below the detection capability of existing modeling and measurement tools. For that reason, it is far from clear that these thresholds could be deemed to reflect a "measurable contribution" to downwind nonattainment and maintenance problems, as required by the D.C. Circuit. Michigan v. EPA, 213 F.3d at 684 (" . . . EPA must first establish that there is a measurable [air quality] contribution. Interstate contributions cannot be assumed out of thin air.") (emphasis in original). At a minimum, EPA should provide, in a supplemental notice of proposed rulemaking, a technical justification for these very low thresholds as representing meaningfully measurable air quality contributions. [EPA-HQ-OAR-2009-0491-2756.1, pp.60-61]
Equally troubling is EPA's indication that it may be planning to use this same percentage-based approach in any future version of the Transport Rule to address possible future NAAQS. See 75 Fed. Reg. at 45237/3 (noting that one of the considerations favoring the one percent contribution threshold approach is that "the approach is readily applicable to any current and future NAAQS"). Application of this approach to potential future ambient standards that may be even lower than the current NAAQS would produce even less meaningful thresholds. It makes no sense for contribution thresholds to change based exclusively on changing NAAQS levels, irrespective of the capabilities of modeling and measurement technologies at the time the thresholds are established. [EPA-HQ-OAR-2009-0491-2756.1, p.61]
Accordingly, UARG objects to EPA's proposal to use its percentage-based air quality contribution threshold approach in the current rulemaking -- or in any future interstate-transport rulemaking -- in the absence of a robust technical justification that the resulting thresholds reflect meaningful, and truly measurable, air quality contributions, consistent with the D.C. Circuit's directive in Michigan v. EPA. [EPA-HQ-OAR-2009-0491-2756.1, pp.61-62]
West Virginia Department of Environmental Protection
Significant Contribution and Interference with Maintenance - EPA requested comment on the pollutants and air quality thresholds used for identifying states to be included under the Transport Rule. WVDAQ notes that the courts have been supportive of EPA's specific thresholds in the past. However, as the National Ambient Air Quality Standards become more stringent, a fixed one percent value may lead to inappropriate results, and could yield 'significance' thresholds that are practically unmeasurable. Just because a value can be modeled does not make it necessarily measurable or meaningful. WVDAQ believes that the significance threshold should consider both the percent of National Ambient Air Quality Standards and the reality of limited measurement precision. [EPA-HQ-OAR-2009-0491-2790.1, p. 3]
Rounding Convention - EPA also requested comment on whether the final Transport Rule should use the same rounding convention that was used in the final CAIR for the 15ug/m3 annual PM25 standard, or whether commenters agree with EPA's approach that does not use this rounding convention. WVDAQ believes that the rounding convention should directly consider the practicality of the rounding convention with respect to the precision of the applicable federal reference method monitors. [EPA-HQ-OAR-2009-0491-2790.1, p. 3]
Response:
See preamble discussion of EPA's choice of air quality thresholds in section V.D.1 of the final Transport Rule.

EPA notes that some of the commenters misinterpret the 1 percent threshold as identification of "significant contribution."   EPA describes in detail in the preamble EPA's approach to quantifying each state's significant contribution.

The comments by Minnesota Power related to contributions to annual PM2.5 levels.  EPA notes that Minnesota is covered by the Transport Rule based on its contribution to 24-hour PM2.5.

Regarding comments from George Washington University, EPA disagrees with the commenter and finds that its analyses for the final rule are sufficiently detailed and precise enough to support the Agency's determinations of emission reduction responsibilities in each state.  EPA has followed all of its own modeling guidance to states and  has employed analytic methodologies (using peer-reviewed models) that have been upheld in prior regulatory actions under judicial review.  EPA believes that commenter's assertions ignore commonly practiced and widely accepted regulatory development procedures and demonstrate fundamental misunderstandings of the role of these analyses in Clean Air Act rulemakings.

EPA disagrees with comments arguing that EPA cannot set the level for finding significant contribution to nonattainment or interference with maintenance of a NAAQS lower than the single source "significant impact levels" (SILs) used in the Prevention of Significant Deterioration (PSD) permitting program.  The SILs serve different purposes than the thresholds used in the Transport Rule analysis.  Thus, it does not follow that the two values should be made equivalent, or that the SILs establish a floor for identifying appropriate thresholds for use in the Transport Rule analysis of significant contribution and interference with maintenance under section 110(a)(2)(D)(i)(I) of the Clean Air Act.  Further, EPA's analysis for this rule only addresses the appropriate threshold to be used in the first step of the methodology used to identify and quantify emissions that must be prohibited pursuant to section 110(a)(2)(D)(i)(I).  This analysis does not address what SILs should be used in the PSD program.

The SILs appear in EPA's regulations at 40 C.F.R. § 51.165(b)(2).  The SILs are used in the PSD program, among other things, to determine whether an individual source, seeking a preconstruction permit, must conduct cumulative ambient air quality modeling analyses to demonstrate that it will not cause, or contribute to, a violation of the NAAQS.  The SILs address source specific permitting requirements.  They address, furthermore, whether comprehensive, multi-source review is required of the source to make one of the showings required to obtain a permit to construct.  A major stationary source with estimated impacts below the applicable SIL is still subject to applicable control requirements, including best available control technology (BACT), designed to moderate the source's impact on air quality.  In other words, a determination that a source's emissions do not exceed the SIL does not excuse a source from controlling its emissions.

The thresholds in the Transport Rule, in contrast, are used to determine whether the total emissions from a state contribute so little to downwind nonattainment and maintenance receptors that further analysis is not warranted.  If the state's contribution is below the thresholds used in the Transport Rule, the state is deemed to have satisfied the requirements of section 110(a)(2)(D)(i)(I) with respect to the NAAQS in question and sources within the state are excused from making reductions to satisfy that requirement.  On the other hand, if emissions from the state exceed the applicable threshold at one or more nonattainment or maintenance receptors, EPA then conducts further analysis to determine if reductions are available in the state at the cost threshold identified as appropriate for use in that state for the pollutant in question.

The two analyses serve distinct regulatory purposes.  The use of the word "significant" in both the term "significant impact level" and "significant contribution" is not sufficient to create an inference that the threshold used in this rule for determining if further analysis of a state's contribution to other downwind areas is warranted should be the same or higher than the "significant impact level" used in PSD permitting.

IV.B.3. Identification of Downwind Nonattainment and Maintenance Receptors

Organization: Attorney General of North Carolina
Comment:
Attorney General of North Carolina
North Carolina's particulate matter ("PM2.5") and ozone receptors are not proposed to be "linked" to any upwind States under the Transport FIP because EPA proposes to conclude that North Carolina would have no nonattainment or maintenance areas under the 1997 National Ambient Air Quality Standards ("NAAQS") for PM2.5 and ozone or the 2006 PM2.5 NAAQS in the modeled year. This is in large measure due to programs undertaken by North Carolina, for example, the enactment of North Carolina's Clean Smokestacks Act ("CSA") in 2002. See 2002 N.C. Sess. L. 4. The CSA effected significant reductions in NOX and SO2 emissions from the State's fourteen largest coal-fired electric generating facilities. The reductions take effect in two stages. The first NOX tonnage limits began in 2007 and the final limit was reached in 2009. Facilities were required to meet the first phase of the SO2 limits in 2009 and the final limits are required in 2013. N.C. Gen. Stat. §143-215.107D(b)-(e).
At least partially through these efforts, North Carolina has been able to achieve compliance with the current PM2.5 standard. As EPA is aware, North Carolina has not yet attained the 85 ppb ozone standard. The remaining nonattainment area under that ozone standard is Charlotte  -  the State's largest metropolitan area.2 Air quality issues in Charlotte result from several factors, but certainly one is interstate NOX transport. See EPA, Technical Support Document for the Interstate Air Quality Rule Air Quality Modeling Analyses at Appx. G (Jan. 2004); see also North Carolina v. EPA, 587 F.3d 422 (D.C. Cir. 2009) (finding that North Carolina demonstrated sufficient "causation" regarding the effects of NOX emissions from Georgia on ozone levels in North Carolina). For this and other reasons, North Carolina has undertaken a significant program to effect emissions reductions throughout the region. See 2002 N.C. Sess. L. 4, §10; see also, e.g., North Carolina, 587 F.3d 422 (addressing NOX emissions from northern Georgia); Sierra Club v. EPA, No. 06-1221 (D.C. Cir. March 5, 2009) (addressing regional NOX and SO2 emissions); North Carolina, 531 F.3d 896 (same); North Carolina ex rel. Cooper v. TVA, 593 F. Supp. 2d 812, 821-25 (W.D.N.C. 2009) (addressing NOX and SO2 emissions from TVA), rev'd on other grounds, No. 09-1623, 2010 U.S. App. LEXIS 15286 (July 26, 2010), reh'g denied, No. 09-1623 (4th Cir. Sept. 21, 2010).
EPA projects that Charlotte will attain the 85 ppb ozone standard by 2012  -  the operative year for the Transport FIP. (This projection is discussed in more detail later.) Consequently, EPA has not included North Carolina as one of the downwind States that needs relief. Nevertheless, EPA's modeling demonstrates that North Carolina, like any State that is home to a nonattainment or maintenance area, would benefit from upwind reductions. This is significant for at least three reasons. First, reductions in ambient levels of PM2.5 and ozone even from levels below the NAAQS will result in public health and environmental benefits in North Carolina. E.g., TVA, 593 F. Supp. 2d at 821-25. Second, greater certainty regarding the locations of reductions will assist in future modeling and planning efforts. And third, North Carolina has areas that are currently not attaining the 75 ppb ozone standard and (if the PM2.5 standard is reduced in the near future, may have areas that do not attain that standard either). Although the 75 ppb standard is being reconsidered, it is likely that reconsideration will result in the standard being lowered and not remaining the same or increasing. National Ambient Air Quality Standards for Ozone, 75 Fed. Reg. 2938 (proposed Jan. 19, 2010). As EPA has indicated, whether an upwind area is violating the provisions of §110(a)(2)(D)(i)(I) does not depend on the formal attainment status of the downwind area, but instead on the air quality conditions in the downwind area. Finding of Significant Contribution & Rulemaking for Certain States in the Ozone Transport Assessment Group Region for Purposes of Reducing Regional Transport of Ozone, 63 Fed. Reg. 57,356, 57,370-72 (Oct. 27, 1998). As such, North Carolina is presently 6 entitled to relief from upwind NOX emissions under §110(a)(2)(D)(i)(I) regarding the 75 ppb ozone standard.
[EPA-HQ-OAR-2009-0491-2685.1 p.3]
Response:
As the commenter notes, EPA did not identify any nonattainment or maintenance receptors in North Carolina for the 1997 ozone and PM2.5 NAAQS or the 2006 PM2.5 NAAQS. All of the potential receptors in North Carolina were projected to be below the NAAQS in 2012 (including the maximum design values used for determining maintenance receptors). Therefore EPA did not identify any linkages in the final rule for any upwind states to downwind areas in North Carolina.
Regarding analyses for the 75 ppb 2008 ozone NAAQS, please see preamble section IV.C.1. for a response.
Organization: Clean Air Task Force
Comment:
Clean Air Task Force
EPA's proposed TR assessment uses only the monitors in one or two counties in any nonattainment area. The assessments do not require calculations based on impacts to[EPA-HQ-OAR-2009-0491-2738.1, p.24] every county in a nonattainment area -- only those counties where transport contributes to that county's violation. Logically, that county's design value would at least equal the design value for the nonattainment area once designated. EPA can and should analyze counties with design values in violation of the standard and take action. [EPA-HQ-OAR-2009-0491-2738.1, p.25; for additional comments pertaing to The Proposed Rule Inappropriately Uses the 1997 Ozone NAAQS as the basis for Assesment of Contributions from Transported Ozone see p. 24-25]
Response:
The primary attainment test contained in the ozone and PM2.5 SIP modeling guidance is a monitor based test.  We therefore project monitor values to determine nonattainment and maintenance receptors.  Although spatial fields of PM2.5 concentrations could be projected to cover all areas (grid cells), the values in unmonitored areas would be more uncertain.  Therefore we choose to limit the results to locations where EPA is certain of the ambient PM2.5 and ozone measurements.  And we only use monitors in the analysis if they have at least one complete design value period of data (3 years).
EPA recognizes that official nonattainment areas often include additional counties which do not have monitors.   EPA's analysis focuses on identifying significant contribution to nonattainment and interference with maintenance to areas projected to have nonattainment or maintenance problems at a specific future date.  The designation status of an area is not directly relevant to this analysis.  Further, since this rule addresses transported pollutions, the benefits from the reductions required by this rule are widespread and not limited to the specific receptor areas identified.
Organization: Cleco Corporation
Exxon Mobil Corporation
Lafayette Utilities System
Comment:
Cleco Corporation
III. Louisiana Should Not Be Included In the PM-2.5 Programs.
In the proposed rule, EPA abandons its established approach to identifying downwind receptors in favor of one that relies exclusively on projected data  -  i.e., the Agency's guess work. This is completely inappropriate and leads to absurd results.9 Receptor identification is a fundamental component of the Agency's authority under the "good neighbor" provision, and must be based, to some extent, on actual monitored data. [EPA-HQ-OAR-2009-0491-2859.1 p.5]
EPA's departure from its modeled-plus-monitored approach significantly impacts Louisiana. It forces Louisiana into two annual trading programs because a single PM-2.5 monitor in Harris County, Texas (Clinton Drive) has a "future year maximum" annual PM-2.5 design value greater than 15.05μg/m3  -  based solely on EPA's modeling projections. EPA flatly ignores all of the actual data from the State of Texas, which has been submitted to the Agency, showing PM-2.5 levels decreasing at the Clinton Drive monitor following recent emission reduction efforts in Texas specifically designed to prevent potential future problems at that particular monitor. [EPA-HQ-OAR-2009-0491-2859.1 p.5]
Exxon Mobil Corporation
Louisiana Emissions Do Not Reasonably Interfere with the Ability of Harris County, Texas, to Stay in Attainment With the Annual PM2.5 NAAQS
Louisiana is included in the proposed Annual NOx trading program and the SO2 Group 1 Trading program due to projected impacts of Louisiana emission sources on the levels of fine particulate existing in Harris County, Texas. Actual monitored empirical data, however, show that Harris County is currently in attainment with the Annual National Ambient Air Quality Standard ('NAAQS') for PM2.5. Further, Harris County has never been designated as being in nonattainment with that standard. EPA has projected through modeling for the proposed CATR/FIP that Louisiana -emissions may interfere with maintenance of that NAAQS in 2012, by contributing only 0.34 ug/m3 to the annual PM2.5 values there. Of that total, EPA projects that 0.33 ug/m3 is from sulfate emissions and only 0.004 ug/m3 from nitrate emissions. Solely based upon these projections, EPA proposes to impose a FIP on Louisiana electrical generating units ('EGUs') to reduce their annual SO2 and annual NOx emissions. EM strongly objects to EPA's projections and proposed FIP for these reasons: [EPA-HQ-OAR-2009-0491-2841.1,pp.2-3]
5. Empirical evidence demonstrates that Louisiana emissions will not interfere with the ability of Harris County, Texas, to maintain compliance with the annual PM2.5 NAAQS. The last two years have seen annual average PM2.5 emissions below 14.0. The 2010 design value for Harris Co. is projected to be below 14.0. The Texas Commission on Environmental Quality, together with state and local partners, have undertaken a number of permanent measures to reduce PM2.5 levels to a point where interstate transport does not affect their ability to maintain attainment. [EPA-HQ-OAR-2009-0491-2841.1, p.5]
:: EPA included a significant quantity of S02 and NOx emissions from commercial marine vessels ('CMVs') in the Louisiana nonroad inventory that are actually from offshore, outside of the geographical jurisdiction for Louisiana and are thus not attributable to Louisiana under the Clean Air Act SIP requirements. EM also notes that the LDEQ does not have the authority to regulate these sources, even though they represent a growing percentage of the overall inventory. [EPA-HQ-OAR-2009-0491-2841.1,p.5]
:: For all Class 3 commercial marine vessels, including those that are properly within Louisiana jurisdiction, EPA failed to include projected reductions of SO2 and NOx emissions that will result from EPA marine engine regulations enacted in December 2009. In other words, not only are C3 commercial marine vessel emissions hundreds of miles offshore counted as being part of Louisiana's significance budget, even when not within Louisiana jurisdiction, they are overestimated because the full impact of the December 2009 rule were not included in the estimates. The same is true with respect to C3 CMV emissions that are within Louisiana jurisdiction. There are also additional clean fuel changes as agreed to by the US and others under the auspices of the IMO, as found at http://www.epa.gov/otag/oceanvessels.htm. It does not appear that the reductions in SO2 and NOx that will result were accounted for in the EPA's analysis. [EPA-HQ-OAR-2009-0491-2841.1,pp.5-6]
:: EPA failed to include enforceable reductions from non-EGU federal consent decrees in Louisiana even where these were entered prior to the date of the proposal and require at least a portion of the enforceable reductions before 2012. [EPA-HQ-OAR-2009-0491-2841.1,p.6]
:: EPA failed to include the Louisiana NOx Reasonably Available Control Technology rule in LAC 33:III.Ch. 22 reductions of NOx in the modeling used to project future impact. As part of its comments, EM hereby adopts and incorporates by reference those comments on the proposed CATR and FIP made by the Louisiana Chemical Association. EM supports such comments and urges EPA to carefully review such comments prior to final rulemaking. [EPA-HQ-OAR-2009-0491-2841.1,p.6]
Further, in support of the above principles and contentions, EM adopts and incorporates by reference the comments of the Louisiana Chemical Association and the Louisiana Department of Environrnental Quality, in support of the conclusion that Louisiana emissions inventories were overestimated and that Louisiana emissions do not reasonably interfere with maintenance of the annual PM2.5 NAAQS in Harris County, Texas. [EPA-HQ-OAR-2009-0491-2841.1,p.7]\
Louisiana Emissions Do Not Significantly Contribute to Nonattainment With Nor Interfere With Maintenance of the 1997 8-hour ozone standard in the Houston/Galveston/Brazoria Area or the Dallas/Ft. Worth Area.
EPA has projected that Louisiana emissions will significantly contribute to nonattainment with the 1997 8-hour ozone NAAQS at certain monitoring sites in the Houston-Galveston-Brazoria ('HGB') and the Dallas-Ft. Worth ('DFW') Areas of Texas in 2012. EPA has projected that Louisiana emissions will interfere with maintenance of that NAAQS at other monitoring sites in the HGB and the DFW Areas of Texas in 2012. EM disputes those projections for the following reasons. [EPA-HQ-OAR-2009-0491-2841.1, p.7]
1. All monitors in the HGB Area are currently in attainment with the 1997 8-hour ozone NAAQS and have been since 2008, based upon the 2006-2008 monitoring data. This is actual empirical data showing attainment. All of the DFW monitors that EPA projected were adversely impacted by Louisiana emissions, save one, are currently in attainment with that NAAQS. The design value at the one monitor at issue in DFW is 86 ppb, just 2 ppb above the standard. Under both versions of the IPM base case modeling, Louisiana ozone season NOx emissions are projected to decrease even without the CATR/FIP (or CAIR). Thus, there is no basis for presuming that actual conditions, as shown through empirical monitored data, will worsen due to Louisiana emissions. [EPA-HQ-OAR-2009-0491-2841.1,p.7]
Lafayette Utilities System
Louisiana Should Not Be Included Under the Transport Rule/FIP for Annual SO2 or NOx Reductions Because Louisiana Sources Do Not Interfere With Maintenance of the Annual PM2.5 NAAQS in Harris County, Texas.
Harris County, Texas, is currently in attainment with the annual National Ambient Air Quality Standard ('NAAQS') for PM2.5 and has never been designated as being in nonattainment with that standard. EPA has projected through modeling for the proposed Transport Rule/FIP that Louisiana emissions may interfere with maintenance of that NAAQS in 2012, by contributing only 0.34 ug/m3 to the annual PM2.5 values there. Of that total, EPA projects that 0.33 ug/m3 is from sulfate emissions and only 0.004 ug/m3 from nitrate emissions. Based solely upon these projections, EPA proposes to impose a FIP on Louisiana electrical generating units ('EGUs') to reduce their annual SO2 and annual NOx emissions. LUS strongly objects to EPA's projections and proposed FIP for the following reasons: [EPA-HQ-OAR-2009-0491-2983.1,p.2]
1. Any impact of Louisiana emissions on Harris County, Texas is less than any of the proposed EPA Significant Impact Levels ('SILs') for annual PM2.5 used under the Prevention of Significant Deterioration ('PSD') Program.4 By definition, any such impacts are de minimis. EPA would be arbitrary and capricious and/or abusing its discretion if it makes a finding of 'interference with maintenance' for a Louisiana contribution less than one of these proposed SILs. [EPA-HQ-OAR-2009-0491-2983.1,p.]
2. EPA's projection of reasonable interference was based on the IPM v. 3.02 Base Case modeling for 2012. On September 1,2010, EPA published a Notice of Data Availability for the IPM v. 4.10 modeling, including a revised TR Base Case 2012 scenario. Under the revised modeling, projected emissions of S02 are more than 20,000 tpy less than projected under the IPM v. 3.02 version. Based on this factor alone, it is believed that any revised air quality analysis based on the IPM v. 4.10 modeling will demonstrate no impact whatsoever on Harris County. PM2.5 levels that could conceivably interfere with maintenance of attainment of the annual PM2.5 NAAQS. While LUS has reservations about some of the other inputs to the IPM model, as discussed herein, LUS believes that the v. 4.10 estimates rely upon a more accurate forecasting of natural gas prices and that version should be used to determine, at least as a screening mechanism, the potential for significant contribution or interference with maintenance of a NAAQS. [EPA-HQ-OAR-2009-0491-2983.1,pp.2-3]
3. EPA's own modeling shows that the reductions in estimated Louisiana emissions from the Transport Rule Base Case v. 3.02 to the Base Case v. 4.10 are greater than what EPA stated was needed to remove 'interference with maintenance' in Harris County, Texas. EPA indicated that the difference between the TR Base Case 2012 v. 3.02 and TR Limited Trading Option case, or actually a reduction to the allocated state budget level, represents the amount necessary for a state to reduce emissions in order to remove significant interference or and interference with maintenance.5 EPA's revised IPM v. 4.10 Base Case 2012 modeling shows that even without implementation of the Transport RuielFIP (or the Clean Air Interstate Rule ('CAIR')), reductions from Louisiana are already greater than those required reductions. The following table demonstrates this finding: [EPA-HQ-OAR-2009-0491-2983.1,p.3] [[See Docket Number EPA-HQ-OAR-2009-0491-2983.1,p.3 for the table.]]
Because 'significant contribution' and 'interference witlt maintenance' Itave been removed as sltown by tltis revised IPM modeling, tltere is no basis for a Transport RulelFIP for annual SO2 or NOx control for Louisiana sources, as tlte level required to remove inteiference with maintenance will have already been achieved. [EPA-HQ-OAR-2009-0491-2983.1,p.4]
4. Due to the inherent uncertainty in the IPM modeling, as unmistakably illustrated by the material differences between IPM v. 3.02 and v. 4.10 projections, a projected impact of less than 2 ppb based on modeling should never be used as a level indicating 'significant contribution' or 'interference with maintenance' from an upwind to a downwind state under the 'good neighbor' provisions of the Clean Air Act, 42 U.S.C. 7410(a)(2)(D). The projected impact from Louisiana is well below 1 ppb. At most, the IPM should be used as a screening tool for making rebuttable presumptions for 'significant contribution' or 'interference with maintenance' determinations. However, such presumptions should be always subject to a reasonable opportunity for rebuttal by empirical evidence. [EPA-HQ-OAR-2009-0491-2983.1,p.4]
5. Empirical evidence demonstrates that Louisiana emissions will not interfere with the ability of Harris County, Texas, to maintain compliance with the annual PM2.5 NAAQS. The last two years have seen annual average PM2.5 emissions below 14.0 ug/m3. The 2010 design value for Harris County is projected to be below 14.0 ug/m3. The Texas Commission on Environmental Quality, together with state and local partners, have undertaken a number of permanent measures to reduce PM2. [EPA-HQ-OAR-2009-0491-2983.1,p.4]
6. EPA overestimated Louisiana emissions inventory used for making the projections, in both the IPM v. 3.02 and v. 4.10 models; thus, even the minimal contributions by Louisiana are likely grossly overstated. The primary reasons the inventories were overstated are:
:: EPA included a significant quantity of SO2 and NOx emissions from commercial marine vessels in the Louisiana nonroad inventory that are actually from offshore, outside of the geographical jurisdiction for Louisiana and are thus not attributable to Louisiana under the Clean Air Act SIP requirements. [EPA-HQ-OAR-2009-0491-2983.1,p.4]
:: For all Class 3 commercial marine vessels ('CMVs'), including those that are properly within Louisiana jurisdiction, EPA failed to include projected reductions of 802 and NOx emissions that will result from EPA marine engine regulations enacted in December 2009. In other words, not only are category 3 ('C3') commercial marine vessel emissions hundreds of miles offshore counted as being part of Louisiana's significance budget, even when not within Louisiana jurisdiction, they are overestimated because the full impact of the December 2009 rule were not included in the estimates. The same is true with respect to C3 CMV emissions that are within Louisiana jurisdiction.  [EPA-HQ-OAR-2009-0491-2983.1,pp.4-5]
:: EPA failed to include enforceable reductions from non-EGU federal consent decrees in Louisiana even where these were entered prior to the date of the proposal and require at least a portion of the enforceable reductions before 2012.  [EPA-HQ-OAR-2009-0491-2983.1,p.5]
:: EPA failed to include the Louisiana NOx Reasonably Available Control Technology rule, see LAC 33:III Ch. 22, reductions of NOx in the modeling used to project future impact. As part of its comments, L US hereby adopts and incorporates by reference those comments on the proposed Transport Rule and FIP made by the Louisiana Chemical Association ('LCA'). LUS supports such comments and urges EPA to carefully review such comments prior to final rulemaking. [EPA-HQ-OAR-2009-0491-2983.1,p.5]
Response:
There are several related comments.
1) The final rule modeling included many emissions inventory updates in both Louisiana and Texas.  Details on these updates can be found in preamble section V.C.1 and the Transport Rule Emissions Inventories Response to Comments document.
2) The analysis for the final rule does not identify Harris County TX as a PM2.5 nonattainment or maintenance receptor in 2012, or identify Louisiana as a state with emissions that significantly contribute to nonattainment or interfere with maintenance of either PM2.5 NAAQS.  EPA does not agree with all of the arguments for why Harris County should not have been considered a receptor in the proposal.
3) The final rule modeling identifies Louisiana as a state with emissions that contribute significantly to nonattainment and interfere with maintenance of the 8-hr ozone NAAQS in Houston, TX.  Since there are no nonattainment or maintenance receptors in Dallas in the final rule, Louisiana does not contribute to Dallas.  Commenters claim that due to more recent ozone data showing attainment in Houston, Louisiana should not be linked to Houston.  We disagree with this comment.  There are several reasons why recent monitoring data should not and cannot be used to determine the nonattainment and maintenance receptor status for consideration under the Transport Rule.  Please see preamble section V.C.2 for details.
Organization: Connecticut Department of Environmental Protection
Comment:
Connecticut Department of Environmental Protection
Significant Impact Not Addressed Adequately for Connecticut
This issue is best illustrated with an example from Connecticut. Connecticut operates an ozone monitor in Greenwich (AQS ID 90010017), located at the extreme southwest edge of the state, on a peninsula jutting out into Long Island Sound2. During peak ozone events, southwest winds transport ozone and precursor emissions to the monitor from upwind states, with minimal impacts from Connecticut emissions due to the monitor's location. EPA's Transport Rule Air Quality Modeling Technical Support Document (TSD, page D-5) presents CAMx modeling indicating that Connecticut emissions contribute 2 ppb to 8-hour ozone levels at the Greenwich monitor in 2012 without the emission reductions from CAIR or the proposed Transport Rule. Total CAMx modeled impacts at the Greenwich monitor are 85 ppb (see page B-4 of the TSD), illustrating that overwhelming transport dominates the ambient concentrations measured at that monitor. [EPA-HQ-OAR-2009-0491-2780.1 p.13]
The measured 2009 8-hour ozone design value at the Greenwich monitor is 80 ppb, only 4 ppb below the effective 1997 8-hour-ozone NAAQS of 84 ppb. Given the potential increase in transport from upwind sources likely to occur during the eventual economic recovery, CTDEP cannot ensure its ability to maintain the current design value in Greenwich without an enhanced final Transport Rule. [EPA-HQ-OAR-2009-0491-2780.1 p.13]
Response:
As described in preamble section V.C.2, EPA continues to identify maintenance receptors using the methodology described in the proposal.  And in fact, two monitors in Connecticut are identified as maintenance receptors in the final rule modeling (sites 090011123 and 090093002).  Instead of identifying a fixed value to determine if an area is "close to the NAAQS", EPA's maintenance methodology uses actual monitoring data at each site to evaluate the variability in measured ozone and PM2.5.  This leads to a monitor specific determination of maintenance that is based on actual data.  EPA continues to believe that this is a reasonable and appropriate approach to define maintenance receptors for the final transport rule.
Organization: Consumers Energy
Comment:
Consumers Energy
B. EPA's Proposal Relies Upon a Baseline that No Longer Exists Resulting in Conclusions that Contradict Current Reality and Ignore the Proven Efforts and Successes by the States and Affected Sources
In support of this proposal, EPA utilized a base year 2005 emission inventory. Future year emission inventories were then grown from that base year. Ambient air quality monitoring data, collected through 2007, were then combined with the emissions inventories and processed by EPA, with air quality models, to determine relative contributions to downwind nonattainment and to simulate changes in air quality as the result of control strategy implementation. [EPA-HQ-OAR-2009-0491-2837.1, p.5]
By the selection of a 2005 base year for emissions and the decision to limit ambient air quality monitoring data to 2007, EPA has begun a complicated rulemaking by going back in time to a world that no longer exists. This decision deliberately ignores the implementation of CAIR, which remains in effect, ignores the major regulatory strides made by the States in cooperation with affected sources from multiple source categories, and incredulously ignores the measured improvements in actual ambient air quality as shown in data collected, quality assured and reported through 2009. [EPA-HQ-OAR-2009-0491-2837.1, p.5]
As Consumers Energy commented during the April 17,2009, listening session, a 2005 emissions inventory has little relevance to states like Michigan. While EPA alluded to a 'temporary' economic downturn, we pointed out that we are looking at major source facilities that are not simply shutdown, they are gone - torn down and currently exist as brownfield sites. These facilities and their emissions are not coming back. This reality is in addition to the major control programs in place and being implemented in our State. [EPA-HQ-OAR-2009-0491-2837.1, p.5]
Actual ambient monitoring data, currently approved and in the hands of EPA, as evidenced by the recent 1997 ozone NAAQS attainment designation using 2007-2009 data, clearly demonstrates the folly of restricting model input to data collected through 2007. As the MDNRE points out in their comments, EPA begins with numerous areas in Michigan as nonattainment for the ozone and PM2.5 NAAQS. EPA's future projections conclude that numerous areas in Michigan will remain in nonattainment for those NAAQS unless the proposed rule is put in place. Yet the reality is that as of the end of 2009, all Michigan counties are designated as attainment for the 1997 ozone NAAQS that is a target of the proposed rule. As of the end of 2009, all Michigan monitors have 3 years of quality assured data demonstrating attainment of both the 1997 and 2006 PM2.5 NAAQS that are the targets of the proposed rule. As EPA is well aware, the MDNRE is currently preparing a redesignation request for EPA's approval. This scenario is repeated in numerous other states. [EPA-HQ-OAR-2009-0491-2837.1, p.5]
Computer modeling results rely heavily upon the input data used. Consumers Energy is confident that EPA's starting points were wrong, producing inaccurate results, resulting in a rule proposal that goes far beyond what is required for the world that exists, today. [EPA-HQ-OAR-2009-0491-2837.1, p.5]
:: The proposed rule has been developed using ambient air quality monitoring data that are not representative of air quality as it currently exists. EPA starts with out of date data and arrives at erroneous conclusions regarding attainment and nonattainment of the standards addressed by the proposed rule - conclusions that grossly conflict with air quality as it exists today. By doing so, EPA deliberately disregards the successes of the states in improving ambient air quality. [EPA-HQ-OAR-2009-0491-2837.1, p.15]
Response:
See preamble section V.C.2.
Organization: Detroit Regional Chamber
Comment:
Detroit Regional Chamber
While the overall approach of retaining limited interstate trading will result in cost savings for Michigan businesses and residents by giving our utilities some flexibility in managing their generating units, the use of old or misleading data could reverse any benefits derived from this trading and pile on significant costs at a time when Michigan's economy is still lagging behind any National recovery. For example, EPA has recently released monitoring data that show that 80% of monitoring sites projected by the EPA still to be out of attainment in 2012 for ozone and PM 2.5 were already in attainment as of 2009. This fits a pattern illustrated by some of the most up to date modeling of the Great Lakes region done by Alpine Geophysics, along with analysis by Environ Corp., that ozone and annual PM objectives of the Transport Rule can be achieved by 2014 through compliance with existing CAIR requirements and other current regulations. [EPA-HQ-OAR-2009-0491-2720.1, p.1]
Response:
See preamble section V.C.2.
Organization: Dow Chemical Company
Comment:
Dow Chemical Company
Dow believes that EPA's finding that Louisiana emission sources significantly contribute to nonattainment and/or interfere with maintenance of the 1997 8-hour ozone standard in the Houston-Galveston-Brazoria (HGB) area and the Dallas-Ft. Worth (DFW) area is erroneous, for the reasons stated in the comments of the Louisiana Chemical Association. Dow hereby adopts those comments by reference. The HGB Area is in attainment with the 1997 8-hr. ozone NAAQS and has been as of the 2006-2008 period. As EPA's own projections indicate that ozone season NOx emissions from Louisiana EGUs will decline by 2012 even without the Transport Rule/FIP, there is no legal basis for imposition of a FIP to control ozone season NOx with respect to the HGB Area.  [EPA-HQ-OAR-2009-0491-2775.1 p.2]
The DFW Area design value is currently 86 ppb, just 2 ppb in excess of the 1997 8-hr ozone standard. Moreover, there are only one or two monitors out of 12 monitors in the DFW area that have a design value above the standard and these two monitors are not substantially impacted by Louisiana emissions within the meaning of the ?good neighbor? clause of Section 110(A) of the Clean Air Act. The ozone design values have steadily dropped in the DFW area and that area is subject to additional state and federal controls that are projected to achieve attainment without the Transport Rule. As EPA's own projections indicate that ozone season NOx emissions from Louisiana EGUs will decline by 2012 even without the Transport Rule/FIP, there is no legal basis for imposition of a FIP. Dow requests that EPA delete the ozone season NOx requirements from the proposed rule and FIP for Louisiana EGUs with respect to the DFW area.  [EPA-HQ-OAR-2009-0491-2775.1 p.2]
Response:
1) The final rule modeling included many emissions inventory updates in both Louisiana and Texas.  Details on these updates can be found in preamble section V.C.1 and the Transport Rule   Emissions Inventories RTC document.
2) The analysis for the final rule does not identify Harris County TX as a PM2.5 nonattainment or maintenance receptor in 2012, or identify Louisiana as a state with emissions that significantly contribute to nonattainment or interfere with maintenance of either PM2.5 NAAQS.  EPA does not agree with all of the arguments for why Harris County should not have been considered a receptor in the proposal.
3) The final rule modeling identifies Louisiana as a state with emissions that contribute significantly to nonattainment and interfere with maintenance of the 8-hr ozone NAAQS in Houston, TX.  Since there are no nonattainment or maintenance receptors in Dallas in the final rule, Louisiana does not contribute to Dallas.  Commenters claim that due to more recent ozone data showing attainment in Houston, Louisiana should not be linked to Houston.  We disagree with this comment.  There are several reasons why recent monitoring data should not and cannot be used to determine the nonattainment and maintenance receptor status for consideration under the Transport Rule.  Please see preamble section V.C.2 for details.
Organization: Duke Energy
Comment:
Duke Energy
The Method EPA Used To Determine "Interference With Maintenance" in the Proposed Rule Overestimates Actual Future Design Values
The method that EPA used in the Proposed Transport Rule to identify downwind monitors to be included in its "interference with maintenance" analysis overstates actual future design values, probably by a substantial amount. EPA explains in the preamble to the proposed rule that it determined maintenance sites based on the future-year maximum design values, and nonattainment sites based on future-year five-year weighted average annual design values. By using the future-year maximum PM2.5 design values as the basis for the "interference with maintenance" analysis, EPA fails to take account of the strong nationwide trend toward decreasing design values and improving air quality, which the Agency has said it expects to continue. This approach had a major effect on the design of the proposed rule. EPA should revisit its method for identifying downwind maintenance problems and revise its analysis to make it more representative of current and likely future air quality and to take account of the downward trend in design values. [EPA-HQ-OAR-2009-0491-2689.1, p.14]
Response:
See preamble section V.C.2.
Organization: E.ON U.S.
Comment:
E.ON U.S.
The Midwest Ozone Group (MOG) retained Alpine Geophysics to conduct CAMx modeling to predict the impact of these recently installed controls on ambient ozone and PM2.5 levels. This modeling is described in detail in the comments submitted by MOG. [EPA-HQ-OAR-2009-0491-2797.1, pp.4-5]
Response:
See preamble section V.C.2.
Organization: Florida Electric Power Coordinating Group, Inc. (FCG)
Florida Municipal Electric Association (FMEA)
Comment:
Florida Electric Power Coordinating Group, Inc. (FCG)
In the proposed rule, EPA includes Florida in the ozone portion of the rule, in part, due to its 'maintenance' impact on Harris County, Texas. Specifically, two receptors in this single county register contributions from Florida of 0.8000 and 2.1780. How can two different receptors in a single county show such dramatically different contributions? The FCG has not had time, due to the abbreviated and insufficient comment period, to understand the cause of these results, and whether it indicates a fundamental flaw or problem with EPA's modeling. At the very least, given the close proximity of the sites to each other and their similar distance relative to Florida, the difference in contribution results suggest that EPA's approach to calculating contributions is not very stable. The FCG requests that EPA explain and justify this result. [EPA-HQ-OAR-2009-0491-2658.1, p.11]
Florida Municipal Electric Association (FMEA)
In the proposed rule, EPA includes Florida in the ozone portion of the rule, in part, due to its "maintenance" impact on Harris County, Texas. Specifically, two receptors in this single county register contributions from Florida of 0.8000 and 2.1780. How can two different receptors in a single county show such dramatically different contributions? FMEA has not had time, due to the abbreviated and insufficient comment period, to understand the cause of these results, and whether it indicates a fundamental flaw or problem with EPA's modeling. At the very least, given the close proximity of the sites to each other and their similar distance relative to Florida, the difference in contribution results suggest that EPA's approach to calculating contributions is not very stable. The FMEA joins the FCG in requesting that EPA explain and justify this result. [EPA-HQ-OAR-2009-0491-2731.1, p. 10]
Response:
The ozone (and PM2.5) contributions are calculated at each monitoring site individually.  For example, there are  3 ozone nonattainment and 2 ozone maintenance receptors identified in the Houston area in the 2012 base case.  The contributions from upwind states are calculated individually to each receptor.  Ozone contributions are calculated as the average contribution across all modeled days at the receptor (in 2012) that are above the 85 ppb NAAQS.  If there are no modeled days above the NAAQS, then we use the 5 highest modeled days.
The commenters note that there is a large difference in the calculated contributions from Florida to two different receptors in Houston.  This is because the high modeled days at each receptor are different.  So the contributions are calculated across different sets of days.  The wind patterns were likely blowing from Florida to Houston on the particular set of high modeled days at the Houston receptor which had the larger contribution.  In most cases, upwind contributions to nearby receptors are similar.  But due to the unique set of high modeled days that exist at each receptor, the methodology can produce different contribution results even at nearby monitors.  EPA continues to believe that the contribution methodology is reasonable and appropriate, as applied in the final Transport Rule.
Organization: Louisiana Public Service Commission
Comment:
Louisiana Public Service Commission
The LPSC Staff also questions the degree to which Louisiana is even eligible for the proposed CATR as the emissions data and emissions modeling utilized by EPA to arrive at this conclusion appears to be questionable. The LPSC Staff supports the comments and analyses provided by the LCA and LDEQ on this matter and recommends that the EPA remove Louisiana as one of the eligible states under the CATR. [EPA-HQ-OAR-2009-0491-2670.1, pp.6-7]
Response:
In the final Transport Rule, Louisiana is found to contribute significantly to nonattainment and maintenance of the ozone NAAQS but not either PM2.5 NAAQS considered.  We received numerous comments and corrections regarding the Louisiana emissions inventories and have made updates as warranted.  Please see preamble section V.C.1 for more details.
Organization: Maryland Department of Environment (MDE)
Comment:
Maryland Department of Environment (MDE)
Maryland has spent years studying air pollution transport and found that it is an important driver in the development of unhealthy air in our state. Out of-state transport, much of it entrained into an elevated nighttime ozone reservoir from upwind areas, accounts for a notable proportion of ozone levels in Maryland. Our measured data shows that "incoming" ozone levels are routinely above 70 ppb. It is critical to have a strong Transport Rule so that air pollution carried into our state will be controlled and that reasonable local measures can achieve compliance with clean air standards. Despite past efforts of EPA and the OTC states, including Maryland, the only air pollution control options left in Maryland and the OTR are very difficult and highly expensive measures. Despite the difficulty and high costs, we have continued to adopt new local control measures. These decisions put Maryland and the region at a disadvantage with other regions of the country that are not required to institute similarly strong control measures. Therefore, it is essential that this Transport Rule fully achieves its primary mission and sets a sound precedent for future transport rules. [EPA-HQ-OAR-2009-0491-2639.1, p.2]
Further, Maryland also believes that the proposed transport rule does not anticipate and address the possibility that the federal remedy may not accomplish the elimination of significant contribution and interference with maintenance by the deadlines stipulated in the CAA. It is critical that the proposed rule provide a mechanism whereby an upwind state continues to engage with the downwind states it affects to pursue state remedies to fulfill its obligation under Section 110(a)(2)(D) of the CAA. In the September 2009 recommendation to EPA made by OTC, including Maryland, and the Lake Michigan Area Directors Consortium (LADCO), we outlined a process recommending that certain states contributing significantly to another state's nonattainment or interference with maintenance be involved in the SIP process of downwind states. [EPA-HQ-OAR-2009-0491-2639.2, p.3]
"Interference with maintenance" addresses historical variability in emissions. The proposed Transport Rule does a good job of addressing the impact of historical variability of air pollutant emissions on NAAQS attainment with its new definition of "maintenance sites." By calculating three design values based on five years of monitored data where the inventory year monitored data is given the most weight and using the maximum of these three to identify monitoring sites with maintenance problems, states that are barely in attainment can be aided by Transport Rule air pollutant reductions to stay in attainment. The number of maintenance sites identified for annual PM2.5, 24-hour PM2.5, and 8-hour ozone is generally a significant percentage of the number of nonattainment sites identified. This analysis highlights that a substantial number of areas are in danger of losing their attainment status, even under the 1997 (8-hour ozone and annual PM2.5) and 2006 (24-hour PM2.5) NAAQS. [EPA-HQ-OAR-2009-0491-2639.2, p.7]
Clarify that "Interference with Maintenance" methodology is different for upwind states' 110(a)(2)(D) obligations than downwind states' attainment designations. In the proposed Transport Rule EPA outlines an entirely new concept of modeling to identify areas projected to be in nonattainment or that may be at risk in their ability to maintain the standard due to contributions from upwind states. EPA uses a maximum design value based on a five-year period and the relative reduction factor (RRF) from model-based estimates of base and future year concentrations. We are concerned that the determinations using this method for purposes of identifying an upwind states' obligation under section 110(a)(2)(D) of the Clean Air Act (CAA) may cause confusion with the downwind site's attainment and maintenance determinations for its attainment SIP. Attainment determinations for areas in a state's SIP are calculated using a different methodology and EPA should clarify in the proposed Transport Rule that these are separate determinations with different purposes. We bring this to EPA's attention because MDE is concerned that the ozone and annual PM2.5 SIPs already submitted by the states to EPA could be in jeopardy since there are areas (monitors) that were shown to be in "model-based attainment" in those attainment SIPs that could potentially now be considered as areas at risk for interference with "model-based maintenance," per the methodology in the proposed Transport Rule. The implications of this are unknown at this time, but we are concerned that they could be severe. [EPA-HQ-OAR-2009-0491-2639.2, p.7]
Maryland urges that EPA revisit this issue and provide clarification in the proposed Transport Rule and/or propose guidance that addresses the issue of model-based maintenance as it is applied for section 110(a)(2)(D) purposes to avoid confusion with demonstration of model-based attainment for attainment SIPs. [EPA-HQ-OAR-2009-0491-2639.2, p.7]
Maryland encourages EPA to use the OTC-LADCO methodology regarding "areas of interest" as an alternative to EPA's proposed methodology. The September 2, 2009, OTC-LADCO recommendation offers a different method for determining areas of interest, which include areas projected not to meet the standard or struggling to maintain the standards. We urge EPA to revisit this recommended methodology as an alternative to that which is in the proposed Transport Rule. The OTC-LADCO recommendation proposes the use of both base monitored design values and future modeled design values above the applicable NAAQS as those that should be designated as areas of interest for purposes of addressing significant contribution and interference with maintenance. As noted in the OTC-LADCO letter, "the monitored design values are based on the maximum design value from the periods 2003-2005 through the most recent three-year period. Future modeled values are based on future year modeling which reflects legally enforceable control measures and a conservative model attainment test  -  i.e., use of maximum design values rather than average design values. The use of maximum design values and a conservative model attainment test are intended to account for historic variability, which is necessary to ensure maintenance. An alternative means of accounting for historic variability is to conduct a statistical analysis of the year-to-year variation in meteorology." [EPA-HQ-OAR-2009-0491-2639.2, p.8]
Maryland suggests that the same weighted five-year average be used for both nonattainment and interference-with-maintenance projections. If that approach is used, it would seem reasonable to proceed as follows: (a) use different future years for the determination of attainment or interference with maintenance (maintenance should come after attainment), and/or (b) use a different threshold for the determination of attainment (level of NAAQS) vs. the determination of interference with maintenance (e.g. 95% of level of NAAQS), making sure to reconcile these different thresholds with the "weight of evidence" concept described in the modeling guidance. [EPA-HQ-OAR-2009-0491-2639.2, p.17]
Finally there are several issues involved in the calculation of design values, including the potential disconnection between observed and modeled PM2.5 values, the lack of proposed alternatives to the use of the RRF factor, and the location of monitors excluded from the analysis. These questions need to be answered. [EPA-HQ-OAR-2009-0491-2639.2, p.17]
As mentioned above under "3. Significant Contribution and Interference with Maintenance," in the proposed Transport Rule EPA has outlined an entirely new concept of modeling to quantify interference to maintenance for an area by selecting the use of maximum design value based on a five year period and the RRF from model-based estimates of base and future year concentrations. [EPA-HQ-OAR-2009-0491-2639.2, p.17]
Response:
There are several comments to address: