While States have discretion over these considerations, the guidelines generally try to use and interpret these concepts in a common sense manner. If a control technology is available for use, generally it means that other sources with similar ( but not necessarily identical) design have used it successfully. In addition, we believe it is reasonable and an exercise of good government, for States to consider information that is made available during the public comment period. Finally, at the discretion of the State, available air pollution control technologies can reasonably include technologies employed outside of the United States that have been successfully demonstrated in practice on full scale operations, particularly those that have been demonstrated as retrofits to existing sources.

Generally for the BART review, States should consider lower polluting processes based on demonstrations from facilities manufacturing identical or similar products using identical or similar raw materials or fuels. Add on controls, on the other hand, should be considered based on the physical and chemical characteristics of the pollutant bearing emission stream. Thus, candidate add on controls may have been applied to a broad range of emission unit types that are similar, insofar as emissions characteristics, to the emissions unit undergoing BART review.

Comment: Two commenters ( 28 273, 28 779) said the cut off for incorporating available technologies should be at the initial SIP proposal date and not before the closure of the comment period. Commenter 28 779 added that this will avoid debate at a later date as to technologies that should be considered in the engineering analysis.

One commenter ( 0184) states that the definition of applicable technology is too broad and that the definition needs to be redefined to make technology not only applicable but efficient too.

Other commenters said EPA should revise the provision to include a vendor guarantee because without a guarantee facilities have no means of determining what emissions reductions 132 can be expected ( 0184, 0240, 28 273). Commenter 0255 provided specific information regarding SO 2 control technologies for furnace sorbent injection, dry sorbent injection, and wet sorbent injection, as well as NO X control in combustion and post combustion controls ( See Table 4 Appendix A) for BART eligible emission units from 26 different industrial categories.

Comment: Two commenters said the guidelines should more clearly address technically infeasible options ( 28 244, 28 385). Commenter 28 244 said Congress clearly intended to leave judgments of technological feasibility to the individual States subject to the overall requirement to make reasonable progress toward the visibility goal. EPA's proposal, however, would compel States to regard proposed technologies as feasible unless they could, in effect, prove a negative by showing infeasibility to EPA's satisfaction. Commenter 28 385 said the guidelines should more affirmatively acknowledge that with retrofit applications, source specific considerations can preclude application of some otherwise feasible control technologies.

Response:

As noted above, we believe that considerations of good government make it incumbent on States to consider information that is made available during the public comment period. In addition, including controls for considerations at step 1 of the BART process does not preclude their being evaluated critically later in the BART process. The States have considerable discretion in undertaking BART determinations and have the ability to make reasoned judgments as to technical feasibility.

4.1.3 Evaluate Impacts and Report Results <IP_ADDRESS> Estimate the Cost of Control to Account for Remaining Useful Life Comment: Twenty commenters ( 0184, 0189, 0207, 0221, 0232, 0237, 0271, 0286, 28 247, 28 248, 28 254, 28 258, 28 260, 28 338, 28 352, 28 358, 28 362, 28 389, 28 399, 28 7016) addressed the proposed closure provisions for sources with limited remaining useful life.

Commenters ( 28 358, 28 362, 28 389) agreed with EPA's proposal to set compulsory retirement dates 5 years after the date of the SIP revision. Commenter 28 358 added that if the source has not been permanently retired by the specified retirement date, the owner or operator of that source must either ( a) shut down temporarily, make changes to ensure that BART emissions levels can be achieved, without taking remaining useful life into consideration, and pay a preset fine; or ( b) immediately and permanently shut down.

Although several commenters agreed with EPA that a source should be able to extend the useful life when applying BART controls, they said there should be a federally enforceable closure 133 date when there is little remaining useful life included in the operating permit ( 0189, 0221, 0232, 0237, 0271, 0286, 28 247, 28 248, 28 254, 28 258, 28 260, 28 338, 28 352, 28 358, 28 362, 28 399, 28 7016). Commenters ( 28 248, 28 338, 28 399, 28 7016) added that these facilities also must be required to abate pollution levels in the interim.

Commenter 0207 said in determining BART the states should be allowed subjective judgement regarding other statutory factors. Commenter 28 244 said many sources will quite clearly have limited useful lives even if their owners are unwilling to commit to a precise shutdown date. Nothing in the statute forbids States to consider the likelihood that these sources, too, will have a " limited useful life" when they make BART decisions. Commenter 0237 notes that there is no provision for decision changes when a shut down is apparent. The Title V permit could have a small amendment which would indicate that the change is not considered a change in the method of operation.

Seven commenters discussed the flexibility given to sources to adopt either option or to change their mind at a future point ( 0184, 28 255, 28 306, 28 273, 28 770, 28 243, 28 404, 28 779). Commenters ( 28 404, 28 779) said sources should have the option to choose either option. Commenter 28 243 stressed that flexibility should be combined with a provision for a date certain component.

A facility should also be given the opportunity to install BART on sources to prolong their useful life if they had not during determination, or if the unit was idle during the determination period ( 0184). Commenter 28 255 said if a facility decides to stop operation instead of installing BART, it must do so no later than it would have had to have had BART installed and operational. If it wants to keep operating after that date, it must install BART by that date or get offsets from other sources until BART can be installed. Commenter 28 273 said a source that maintains continuous operation after BART becomes effective and changes its mind about closure should be allowed the opportunity to install BART. If the source believes it may continue beyond the remaining useful life predicted date, it could take a permit that requires back applying the appropriate BART by that date, or ceasing operations by that date until that BART is installed. Similar considerations should be given to idle units. Commenter 28 770 added that if an operator intends to shut down a source by a given date, but then wishes to continue operating beyond the 5 years, the source would be required to install the level of controls that would have been considered BART if the BART analysis had not assumed a reduced remaining useful life.

Commenter 28 306 said EPA should provide for deferral of applicable BART requirements for facilities that have curtailed operations. Flexibility with respect to maintaining consistency with the statutory requirement to install BART within 5 years of EPA's approval of the relevant SIP is of potential concern for a large segment of the aluminum industry for whom 40% of domestic primary aluminum production capacity is fully curtailed for an indefinite period of time due to the lack of affordable electricity in the Northwest. 134 Two commenters said the states should be given flexibility ( 28 342, 28 361). Commenter 28 342 said the states were limited to case by case assessments of control costs . Commenter 28 361 said EPA's top down approach would require the most stringent controls as the " best" alternative if a facility wants to operate more than 5 years beyond the date of the SIP approval. Neither option provides true State flexibility.

Response:

We have retained the provision that intent to shut down should be accompanied by a permit provision to that effect. We note that without such a permit provision, it would be difficult for a State to judge that a source will clearly have a limited useful life. In addition, the CAA requires that controls be installed within five years of a BART determination. Therefore in order to be consistent with the statute, we include the provision that a source would not operate more than five years beyond the statutory compliance date.

Comment: Five commenters said remaining useful life should be considered in the economic analysis ( 28 344, 28 385, 28 387, 28 392, 28 7013). Commenter 28 344 said EPA's approach seems to imply that a source which has a 10 year remaining useful life could not take credit for it in the BART analysis because it would by definition be in operation in 5 years. In addition, Congress did not require enforceable restrictions in order to take into account the remaining useful life of a source and EPA cannot do so in this Guideline document. This would be an unprecedented attempt to regulate commercial and business activity as well as problematic for sources that might later decide in lieu of shutdown to modify specific units and trigger NSR. Commenter 28 387 agreed that EPA's proposal exceeded statutory authority and suggested that states should be encouraged to use reasonable estimates of remaining life for each facility using objective criteria or indicators such as engineering estimates, publicly available documents, information provided by the affected source, and the existence of newly installed pollution control equipment ( e. g. selective catalytic reduction to meet ozone SIP requirements). Commenter 29 385 recommended that BART determinations where remaining useful life is a significant criterion be re evaluated each of the 3 years prior to the statutory deadline for installing controls. Commenters ( 28 392, 28 7013) said the remaining useful life should be used to amortize the cost of emission control projects.

Six commenters said remaining useful life should not be considered when calculating control costs ( 28 127, 28 258, 28 263, 28 302, 28 355, 28 358).

Some commenters ( 28 258, 28 358) opposed providing flexibility to adjust facility shutdown according to market conditions, as it will only delay implementation of the best available technology. If a facility does not want to accept an enforceable restriction for ending operations, then the remaining useful life should have no impact on control costs and the BART determinations. Commenter 28 358 added that if a source is deemed to have a short remaining useful life, its operator should not be permitted under any circumstances to speed up the 135 amortization of BART controls or avoid fully applying BART at the end of that agreed upon time period. If an operator wants flexibility, the operator must pay for it. Similarly, the suggested option of requiring a BART eligible source that continues in operation beyond its declared useful life to install full BART controls at the point of life extension makes no environmental or economic sense   but simply creates a loophole for older sources to avoid BART for a period of years. Should EPA decide to allow BART eligible sources with limited remaining useful lives to be partially exempted from the requirement that they install BART, the retirement date must be included as an operating condition in the sources' Title V permits.

Response:

We have amended the calculation of remaining useful life to be more consistent with generally accepted accounting practices and with the guidance in EPA's Control Cost Manual. The calculation now begins at the date controls will be put in place, and upfront construction costs should be rolled into the cost calculation for the first year of operation of controls. We believe this is the fairest and most justifiable way to account for all relevant costs and for the entire time period during which the source will operate with controls.

Comment: Commenter 28 127 objected to applying this provision to power plants because of their history of continuing to operate old plants and avoiding installation of controls. Commenter 28 335 said it is unfair for a source to take the benefit of an assumption that a source has a short remaining useful life, only to claim later that changed circumstances have proved its assumption wrong. However, that the ability to seek a permit modification with appropriate conditions would provide companies with some flexibility. The initial permit would have to contain a mechanism to address the benefit to the source as a result of the projection of a short remaining life, in the event that circumstances change Commenter 28 302 was concerned that if operators retain flexibility and decide to extend the life of their facilities after BART determinations have been made, then these facilities may continue to operate at a higher emission rate than if BART had been installed. There appears to be no precedent for " federally enforceable restrictions preventing further operation". Any provisions allowing for consideration of " remaining useful lifetime" in calculating control costs would reduce the effectiveness of the BART program. If a facility subject to BART is in operation at the time of the SIP submittal, it must have plans to install controls. Commenter 28 263 agreed that remaining useful life has no bearing on calculating control costs, or any other aspect of BART. If a source is operating and subject to BART, it must control its emissions using BART. No flexibility should be provided.

Response: 136 As indicated above, the amortization of remaining useful life for BART purposes should provide clear information relevant to control costs that is consistent with the statutory compliance requirements. This information will help States assess the cost effectiveness of controls and the likelihood that sources will or will not shut down.

<IP_ADDRESS> Estimate the Cost effectiveness of Control Comment: Three commenters ( 0187, 0189, 0236) made comments regarding the baseline emissions of a source as it applies to BART determination. Two commenters suggested that EPA use an approach similar to that employed by NSR, where the pre modification emissions are averaged over 24 months as determined by the owner/ operator over a 5 year time period ( 0187, 0236). One commenter ( 0189) suggested the states use historical emissions data instead of potential to emit.

Commenter 28 244 said EPA should make clear that in calculating the cost effectiveness of BART controls, states should consider the actual historical emissions of a source, not its " potential to emit." Clearly, determining whether sources and parts of sources are " major" and subject to BART will often require complex judgments. The status of individual units in the 1962 1977 period must be determined. The proper approach, from the standpoint of both law and policy, would be to address any need for additional controls after the first round of BART as part of the " reasonable progress" obligation.

Response:

The guidelines note that actual emissions should generally be used to calculate the baseline period for the cost effectiveness calculation. While the guidelines recognize that specific circumstance will dictate the specific period over which to calculate actual emissions, the guidelines do make clear that the time period should be a realistic depiction of anticipated annual emissions   in other words it should be a period representative of emissions expected in the future.

Comment: Nine commenters ( 0189, 0195, 0206, 0214, 0237, 0238, 0303, 0321, 0323) made comments regarding the acceptability of WRAP criteria for the cost of control of a source as it applies to BART determination. Five commenters ( 189, 0206, 0237, 0303, 0323) agreed with EPA stating that control costs as identified by the WRAP with the average removal costs less than $ 500/ ton as low, between $ 500 and $ 3,000/ ton as medium and over $ 3,000/ ton as high were helpful criteria. Commenter 0189 also noted that an upper bound of $ 2,000/ ton would be more reasonable for the high costs, instead of those determined by the WRAP. Commenter 0323 urges EPA to use caution when establishing absolute ranges for emission reductions noting that the costs of controls decreases over time. Also any criteria should also include a discussion of the economic benefits of improved visibility. Four commenters ( 0195, 0214, 0238, 0321) indicated 137 that the WRAP criteria for the cost of control constrains the states' flexibility in making BART determinations.

Ten commenters ( 0187, 0189, 0207, 0229, 0236, 0237, 0275, 0277, 0285, 28 273) made comments regarding cost effectiveness as a screening criteria for controls of a source as it applies to BART determination. Six commenters ( 0187, 0189, 0236, 0237, 0275, 0277) agreed that EPA's assistance with cost effectiveness analysis would be helpful. Commenters 0189 and 0275 gave only limited support, however, noting that states should be allowed to do their own analysis using CALPUFF and chose controls based on the most cost effective visibility improvements. Commenter 0275 added that EPA should establish an upper bound of cost effectiveness beyond which controls should not be considered for BART, setting high cost thresholds of $ 2,500/ ton for NO X and $ 2,000/ ton for SO 2. Commenter 0237 noted that BACT/ LAER include expensive costs of technology when making major modifications which are not justified in BART, therefore the guidance should be established with RACT type of approach limiting costs to $ 1,500/ ton thereby streamlining the BART inquiry.

Commenter 28 273 said EPA should provide guidance on what constitutes cost effectiveness. The BART guidelines should not follow the same vague cost effectiveness criteria as BACT determinations.

Response:

Although we did not explicitly include these or any other cost criteria in the guidelines, we agree that the WRAP criteria are helpful cost criteria and could reasonably be used. States have considerable flexibility to exercise judgement and take specific circumstances into account when weighing cost effectiveness as one of the statutory BART factors.

Comment: Three commenters ( 0207, 0229, 0285) disagreed with EPA assisting states in their costeffectiveness analysis for BART determination. Commenter 0207 stated that the proposal ignores the visibility benefits of emissions reductions for $/ ton cost effectiveness approach thus ignoring the goal of the Regional Haze program which is to improve air quality and decrease visibility impairment. In the sense that the Regional Haze program goals were not addressed, commenter 0277 also indicated that it may be more appropriate to establish a cost effectiveness based on visibility improvements rather than cost/ ton reduction. Commenter 0285 requests that EPA make visibility impact analysis, as it applies to controls alternatives, part of the cost estimation process in BART. Cost is an important consideration in determining technical feasibility and should not be discounted by EPA set costs ( 0229).

The rule should allow states to weight visibility improvements benefits of BART against the costs. Conducting air quality analysis should only be required to justify a decision on a control level. Also, EPA should clarify that the cost of emission reduction is balanced again 138 visibility improvement benefits as emphasized in the Corn Growers court ( 0275). States should have the authority to determine what is cost effective when determining BART ( 0184).

Commenter 28 398 noted that the proposed Guidance provides that the " costs of compliance" cost benefit factor is the cost in dollars per ton of emissions avoided rather than the cost in dollars per increment of visibility improved. Commenter 28 405 said EPA should reject simplistic " dollar per ton reduced" measures of cost effectiveness in favor of end result measures such as visibility benefits per dollar of control cost, as tools to assess the benefits of alternative control strategies.

Response:

We believe it is not possible to come up with a simple numeric cost/ visibility metric that acounts for the interaction of PM precursors in the atmosphere, geographic variability in visibility improvement from specific levels of emissions reductions, and many other factors. Since we do not have information on how such a metric could be developed, we do not believe it is appropriate for us to recommend such a metric to States.

<IP_ADDRESS> Other Comments on Cost Effectiveness and Estimating Cost of Control Comment: Seven commenters ( 0184, 0199, 0237, 0253, 0275, 0302, 0304) had additional statements regarding the cost effectiveness of controls.

Retrofitting existing controls, that are already providing low emissions rates, is not cost effective, especially when the controls could serve as BART ( 0199). Further it is necessary to know the cost of existing controls if the average costs/ ton are considered, and not assume the baseline is " no control" ( 0237).

EPA cost estimates significantly underestimate the actual costs of developing and implementing pollution control technology as part of BART analysis ( 0253). EPA defined cost of $ 900/ ton emissions reduction is under half of the cost considered effective in recent regulations like CAIR, and the costs for the NO X SIP Call were also underestimated ( Table 3, Appendix A, Attachment 13) ( 0255).

EPA air pollution control rates and emissions levels seem to be specified for electric generating units ( EGU) without consideration for other sources that may be subject to BART. Those non EGU sources may be subject to MACT regulations, therefore there should be sufficient data for EPA to determine cost effectiveness for BART. EPA needs to provide clarification for non EGU sources regarding the most cost effective emissions reductions under BART ( 0302). 139 " Cost effective controls are seldom cost effective, not because they are inexpensive, but because a given technology controls a lot of emissions" ( 0304).

Response:

See the RIA for this rulemaking for estimates of non EGU source control costs, and discussion of the range of cost effectiveness of controls that could be expected for different source categories.

Comment: Four commenters addressed the idea of using average costs ( 0189, 28 244, 28 398, 28 405). Commenter 0189 said the use of average cost, instead of marginal cost, may promote technologies that would otherwise be disqualified because average costs are always lower than marginal costs. In contrast, commenter 28 244 said EPA's requirements that states use average cost contradicts basic economic principles, which require a marginal cost approach to evaluating the costs and benefits of different control approaches. Considering average cost will make BART candidates that would flunk an intellectually respectable cost effectiveness analysis look like good candidates for installation. States should have the freedom to decide to pursue visibility improvement in a manner that does not create an avoidable risk of local unemployment and economic loss.

One commenter ( 28 362) said it is suggested in the proposed guidelines that the potential for plant shutdown as a result of installing control technology should be considered in the BART analysis. This suggestion has no place in the BART guidelines. Once BART for the source is determined, market forces should determine whether the source installs BART or ceases operation.

Five commenters ( 0185, 0206, 0207, 0302, 0303) had additional statements regarding estimating the cost of controls. The emissions reductions of SO 2 and NO X should be balanced with ( 1) minimizing costs to residential, commercial, and industrial electric consumers, ( 2) easing strains on the natural gas supply and associated pricing, and ( 3) continued availability of reliable electric generation ( 0185). States should also weigh all of the statutory factors when determining BART without being required by EPA to make cost the most important and deciding factor when choosing controls ( 0207). Additionally, smaller facilities should be able to consider the age of the facility and improved visibility from applying BART, and not just cost criteria when determining controls ( 0206, 0303). States need guidelines that promote consistency across the nation. The impact analysis of cost of controls is almost identical to BACT determinations for NSR, which seem to be very subjective ( 0302).

Response: 140 We note that once costs are calculated, States have considerable flexibility in determining how those costs should be weighed. In addition, we do believe that average cost provides useful information, especially when tempered by comparison with incremental costs of control.

<IP_ADDRESS> Consideration of Non Air Quality Environmental Benefits Comment: Seven commenters ( 0221, 0232, 28 290, 28 302, 28 358, 28 387, 28 404, 28 7008) support EPA's requirement that states must take into consideration non air quality impacts of compliance with BART to include environmental benefits. Also, BART guidelines should require an assessment of positive impacts that will result from applying BART. In addition to decreasing nitrogen compounds effective BART controls would also ( 1) reduce SO2 related acid deposition, ( 2) reduce biomass loss as associated with elevated ozone levels, and ( 3) reduce mercury emissions ( 0221). Commenter 0221 adds that they are concerned that the analysis promoted by EPA is overly compartmentalized and ignores positive consequences. Commenter 28 404 said the net benefit in overall pollution reductions should be compared to the incremental improvement in regional haze on a source by source basis.

Commenter 28 358 said the final guidelines should explicitly require an assessment of the positive non air quality environmental impacts   i. e., an estimate of the environmental benefits   that will result from applying BART. It is possible to estimate the ecosystem benefits in Class I areas associated with certain levels of lowered emissions of sulfur dioxide, nitrogen oxides, and particulate matter in upwind regions. Such an estimate, prepared as a qualitative assessment, must be included in the BART determination process.

The guidelines to not appear to have any criteria outlines for consideration of non air quality environmental impacts and one commenter ( 0232, 28 302) proposed that language be revised to include documentation for the public record when alternative controls are used due to extraordinarily high costs, energy or non air quality environmental impacts. Commenter 28 387 suggested that the guidelines specify or confirm that states have the discretion to reasonably consider all three types ( i. e., cost of compliance, energy impacts, and non air quality impacts) of analysis. Commenters ( 28 290, 28 302, 28 7008) said EPA should clarify the role and weight non air quality impacts should have in determining BART and reasonable further progress.

Commenter 28 352 said the impact analysis should also examine other air impacts beyond the precursors to regional haze ( i. e., air quality impacts, water quality impacts etc.). For example, some NO x controls might increase emissions of carbon monoxide, which is not a precursor to regional haze. This could represent a significant adverse impact posed by the application of the control that would not be addressed under the current guidance.

Eleven commenters ( 0195, 0214, 0223, 0226, 0229, 0230, 0238, 0254, 0256, 0268, 0321) oppose EPA requirement that non air quality impacts include environmental benefits when determining BART. Nine commenters stated that the requirement that non air quality impacts to 141 include benefits to the environment is inconsistent with the Act. Section § 169A( g)( 2) directs States to consider " energy and non air quality environmental impacts" of compliance meaning only adverse effects may be considered in determining BART ( 0214, 0223, 0226, 0229, 0230, 0238, 0254, 0256, 0321). Further, three commenters stated that EPA should be consistent with Section 112 MACT regulations which define non air impacts as adverse impacts ( 0195, 0268, 0321).

Commenter 0256 included extensive remarks stating EPA gives no explanation to why states' consideration of beneficial non air quality impacts of control technologies is consistent with Section § 169A( g)( 2). They state that this is not consistent with Section § 169A( g)( 2) for the same reasons that EPA gave when interpreting Section § 112( d)( 2). Section § 112( d)( 2) provides MACT guidance which is applicable for new and existing sources where cost has been taken into consideration with any non air quality health and environmental impacts and energy requirements. Further, in Sierra v EPA ( D. C. Cir. 2004), the court ruled that non air quality impacts exclude environmental benefits for Section § 112( d)( 2) from emissions reductions rejecting Sierra Club's position that impacts of " deposition, persistence, toxicity and bioaccumulation of metal HAP" by deposition be considered. The commenter recommends that the subsection in the BART rule entitled "( 5) Benefits to the Environment" be removed. Consideration of environmental benefits would increase the burden on States when making BART determination especially when statutory provision is focused on improvement of visibility.

Response:

We agree that positive environmental impacts should be considered, as well as impacts to other media such as water quality impacts. The guidelines contains a discussion to that effect. We believe that States have considerable flexibility for how to weigh these factors. We do not believe that a cost benefit analysis is required or appropriate, as many of these factors are not easily quantified and may be weighed qualitatively. In addition, we do not believe that it is reasonable to assume that section 169A necessarily has the same basis as section 112( d)( 2) of the CAA, as these provisions were written for wholly different purposes.

Comment: There were three other comments regarding the consideration of non air quality environmental benefits in determining BART. Commenter 0254 thinks EPA should examine the characteristics and toxicity of PM 2.5 components and develop regulatory strategies for control technologies that would provide the greatest health benefits. This was also the conclusion of a NSA National Research council report entitled " Research Priorities for Airborne Particulate Matter, IV: Continuing Research Progress" ( March 2004). Focusing only on two constituents of PM 2.5, nitrates and sulfates, limits health benefits the agency has projected. There is substantial toxicological evidence that SO 2 and NO X emissions from EGUs do not have a causal association with health effects. The cost benefit analysis in CART makes a blanket assumption that all the 142 constituents on PM 2.5 will have the same health effects as nitrates and sulfates, thus excluding many Americans who are exposed to PM 2.5 and experience health effects. EPA's assumptions are also inconsistent with EPRI's and Emory University's Atmospheric Research Inhalation Epidemiology Study in which no statistically significant association between sulfate levels and health effects was found. EPA's health benefits of the proposed rule are over stated and BART should contain a high degree of uncertainty regarding health benefits of control technology.

Commenter 0276 indicates that controls implemented by BART will have much smaller health benefits than those derived from controls put in place before BART. They recommend dropping this entire section, or structure the section to focus on the incremental health benefits.

Commenter 28 352 noted that stream water sampling in the Great Gulf Wilderness at high elevations found some of the highest nitrate levels in the region.

[ Linda / Larry   on health benefits   help!!]

Comment: Regarding non air quality environmental impacts the commenter indicated that EPA's statement that a state does not have to perform an analysis if the most stringent controls are adopted is incorrect. States must assess all five statutory BART determination factors for each potential control regardless of environmental impacts. Comparing the environmental impacts of two control technologies, one more stringent than the other, may result in the more stringent control producing greater environmental harm. This comparison is important given the location of a facility ( 0256).

Response:

We believe that this provision reasonably balances the goals of section 169A with the analytic burden it imposes on States.

Comment: Regarding evaluating impacts and reporting results commenter 0304 states modeling impacts should not be considered to moderate control technology when determining BART because they are not a consideration when determining BACT.

Response:

Assessment of impacts on regional haze is specifically required by the CAA for BART.

<IP_ADDRESS> Incompatibility with a Control for Another Pollutant Comment: 143 Five commenters addressed incompatibility issues with controlling some pollutants ( 28 266, 28 278, 23 309, 28 312, 28 332). Commenters ( 28 266, 28 278, 28 312) said incompatibility with a control for another pollutant, such as mercury, should be a criterion for rejecting ( or modifying) a BART control option. Commenter 28 266 added that EPA must provide guidance on how to select the best alternative if a source must control several pollutants but the available technologies have overlapping or conflicting requirements. Commenter 28 332 said language should be added concerning how increases in visibility impairing pollutants from control technologies should be included in the BART engineering analysis.

Commenter 28 309 said when a particular pollutant is reduced, consideration should be given to the increases which may occur in other pollutants. For example, if utilities install SCRs downstream rather than upstream from ESPs and wet scrubbers, this might result in higher levels of ammonia or sulfur trioxide emissions from the stack. If the ESP and wet scrubber is located after the SCR with high efficiency mist eliminators after the scrubber and liquid collectors), a portion of the ammonia and converted sulfur trioxide will be collected on the ash. Carbon monoxide, and possibly benzo[ a] pyrene, is increased with the use of some low NO x techniques.

Response:

We note that the guidelines addresses this possibility and suggests that when the result of a BART determination would be two different BART technologies that do not work well together, States have flexibility to substitute a different technology or combination of technologies, provided that they achieve at least the same emissions reductions for each pollutant.

4.1.4 Evaluate Visibility Impacts of Applying Controls <IP_ADDRESS> Pollutant by Pollutant Basis Comment: Seventeen commenters addressed the concept of ranking reductions on a one pollutant versus a combination of pollutants ( 0169, 0228, 28 243, 28 255, 28 256, 28 262, 28 267, 28 272, 28 273, 28 286, 28 302, 28 332, 28 335, 28 350, 28 362, 28 779, 28 7048).

Commenters ( 28 255, 28 256, 28 302, 28 332, 28 335, 28 350) said the guidelines should address the process for ranking control technologies that reduce more than one visibility impairing pollutant. If the total visibility impairing pollutant emission reduction is greater than a technology reducing emissions of only one pollutant, it should be ranked higher and given preference. Commenters ( 28 302, 28 362) added, however, that considerations of simultaneous pollutant reductions should not, justify reduced stringency of controls for the pollutant which is specifically targeted under the BART review. Commenter 28 779 said control technology ranking should account for the relative importance of the pollutants in reducing visibility impairment. Commenter 28 272 said there should be flexibility to account for the different roles pollutants have in different regions of the country. Commenter 28 243 said the options selection process would result in 144 choosing options that produce a multiple benefit for the same dollar as options that have more limited benefits.

Response:

The States are not required to rank the control technologies and have discretion in weighing the five factors for control decisions.

Commenters ( 28 262, 28 7048) suggested two analytical approaches: ( 1) Calculate an annualized pollution emitted for each pollutant for each technology alternative, creating a matrix, and rank pollutant one, then pollutant two, then pollutant three, sum and rank. ( 2) Convert the emissions to extinction values and sum the extinction and rank. This would rank by weighting the visibility impacts. This would be a scattering total that could be used for ranking multiple pollutants. It would not replace an analysis of the impacts on visibility in Class I areas.

Response:

The States are not required to rank the control technologies and have discretion in weighing the five factors for control decisions.

Commenter 28 286 said technology that provides lower emissions should be adopted. States should strongly consider the amount of visibility improvement that would result when determining which technology is the BACT.

Response:

Lower emissions is not one of the five factors that are statutorily required as part of the BART review. However, when making the control determination, emissions from the source would be lower if controls are put in place.

One commenter requests EPA specify that the visibility analysis be performed per pollutant ( 0228). Another commenter ( 28 273) would limit the consideration of multiple benefits to tie breaker situations. Commenter 28 362 said the identification of a control technique that will be effective in addressing multiple pollutants should not serve as a substitute for a pollutant bypollutant BART analysis. Likewise, a control technique that reduces multiple pollutants should not be considered BART for any individual pollutant if the BART analysis for that pollutant identifies a technically feasible control technology that is more effective in reducing emissions of that pollutant.

Response: 12CALPUFF Analysis in Support of the June 2005 Changes to the Regional Haze Rule, U. S. Environmental Protection Agency, June 15, 2005, Docket No. OAR 2002 0076.

145 States have the discretion in making the BART determination and are encouraged to make the most effective assessment based on the five statutory factors. A pollutant by pollutant basis or a multi pollutant approach is acceptable.

Other commenters ( 0169, 28 267) said the visibility impacts analysis should be resolved by the state's discretion in adopting alternative controls for each source when determining BART.

Response: We agree and have provided discretion in the final rule.

Comment: XX commenters said the guidelines should provide that cost effectiveness is to be measured on the basis of a source's impact on visibility impairment, not reductions in the amount of pollutants emitted ( 28268, 28 337, 28 349, 28 353).

Response:

States have discretion in how they evaluate all of the five factors, including cost effectiveness, when making the BART determination. One possible alternative in determining cost effectiveness is to make an acceptable demonstration based on a visibility assessment.

Comment: Three commenters said more guidance is needed on the role of visibility impacts ( 28 268, 28 364, 28 395). Commenter 28 268 said EPA should publish guidelines that index each pollutant's average impact on visibility, to allow aggregation of both costs and benefits across all five pollutants. Commenters ( 28 364, 28 395) said the Act does not suggest that certain of the BACT criteria  energy, environmental and economic impacts and other costs  should be emphasized over others.

Response:

States have discretion to decide how to weigh each of the five statutory factors, including the choice to whether or not to assess pollutants in aggregate or separately, when making a BART determination, and one factor need not be emphasized over another. Our sample modeling runs12 may help inform the determination of pollutant impacts on particular Class I areas, but since each Class I area is unique, average impacts are difficult to determine. We do not believe that a generalization of impacts and costs would provide realistic estimates.

<IP_ADDRESS> Use of CALPUFF or EPA Approved Model 146 Comment: Eight comments were received on evaluating visibility impacts of applying controls using CALPUFF or another EPA approved model ( 0207, 0217, 0226, 0242, 0246, 0256, 0275, 0277). Some commenters indicated that the States should have flexibility to use models other than CALPUFF. Additionally, the guidelines seem to mandate the use of CALPUFF while saying States can use other approved models as well, making them unclear ( 0207, 0217, 0226, 0242, 0246, 0275, 0277). Specifically there need to be clarification on which modeling systems are allowed for evaluating visibility impacts ( 0217, 0246). One commenter stated that CALPUFF is not a preferred model for determining visibility impairment ( 0246). Another commenter indicated that the screening tool capabilities of CALPUFF are acceptable, however source owner and operators should have the discretion to use all the capabilities of CALPUFF where they deem necessary ( 0256).

Response: Other EPA approved models may be used and an EPA approved modeling protocol, which allows for determining the model inputs and model selection should be submitted to the State prior to any modeling demonstration. CALPUFF used with limited meteorological data ( i. e. in a simpler screening mode) may not be as conservative as CALPUFF using a full meteorological domain, and should not be used to exempt a source from BART review without more rigorous evaluations and sensitivity tests showing that the results are at least as conservative as the CALPUFF model. The State or the source may perform the modeling for BART assesssments. Although we focused on the use of CALPUFF for primary pollutants in revising the Guideline of Air Quality Modeling, section 7.2.1. e. of the Guideline states: e. CALPUFF ( Section A. 3) may be applied when assessment is needed of reasonably attributable haze impairment or atmospheric deposition due to one or a small group of sources. This situation may involve more sources and larger modeling domains than that to which VISCREEN ideally may be applied. The procedures and analyses should be determined in consultation with the appropriate reviewing authority ( paragraph 3.0( b) and the affected FLM( s). We believe that our proposed use of CALPUFF is thus fully in keeping with the Guideline on Air Quality Models, especially in light of the low triggering threshold for determining whether a source is reasonably anticipated to cause or contribute to visibility impairment in a Class I area, and the fact that the modeling results are used as only one of five statutory criteria evaluated to determine BART emission limits.

<IP_ADDRESS> Use of Allowable Emissions Comment: Five comments were received on evaluating visibility impacts of applying controls using allowable emissions. Three commenters state that EPA must make clear that States should use emission levels that will be permissible at the time BART controls take effect, and not use current emissions levels ( 0189, 0238, 0275). One commenter supports the use of allowable emissions ( 0256). One commenter indicates that actual emissions, rather than allowable emissions, should be considered ( 0268). 147 Response: For BART applicability, an emission rate that applies at the time the State submits the SIP should be used. Emissions from a source can vary widely on a day to day basis; during peak operating days, the 24 hour actual emission rate could be more than double the daily average. On the other hand, in the long term, estimating visibility impacts based on allowable emission rates for every hour of the year may unduly inflate the maximum impairment from a BART eligible source. Where States have information on a source's daily emissions, an emission rate based on the maximum actual emissions over a 24 hour period for the most recent five years is a more appropriate gauge of a source's potential impact as it would ensure that peak emission conditions are reflected, but would likely not overestimate a source's potential impact on any given day. We have accordingly included this change to the final guidelines. We recommend that the State use the highest 24 hour average actual emission rate, for the three or five year period of meteorological data, to characterize the maximum impact for the BART applicability test.

<IP_ADDRESS> Use of Results of the 20% Worst Modeled Days Comment: Nine comments were received supporting evaluating visibility impacts of applying controls using the results of the 20% worst modeled days ( 0205, 0226, 0228, 0240, 0250, 0254, 0256, 0276, 0314). Several commenters ( 0228, 0240, 0250, 0254, 0256) stated that the use of using a maximum 24 hr emissions over 5 years to evaluate the thresholds is unreasonable and inappropriate and departs from the previous methodologies for the Regional Haze Program. Additionally this threshold is restrictive because the highest 24 hr impact over a three or five year period may be influenced by short term weather conditions, like high humidity ( 0240).

Response: See the discussion above regarding emission rates. Also, the final rule provides several options for making impact determinations for purposes of evaluating visibility improvement. We have pointed out, however, that evaluating the fifth statutory factor is not necessarily based on a one time test for a maximum 24 hour impact. A State is encouraged to account for the magnitude, frequency, and duration of the contributions to visibility impairment caused by the source based on the natural variability of meteorology. These are important elements to consider as they would provide useful information on both the short term peak impact and long term average assessments which are critical in making the visibility assessment. Additionally, the use of a comparison threshold, as is done for determining if BARTeligible sources should be subject to a BART determination, may be an appropriate way to evaluate visibility improvement. However, we believe the States should have flexibility in setting absolute thresholds, target levels of improvement, or de minimis levels since the deciview improvement must be weighed among the five factors, and States are free to determine the weight and significance to be assigned to each factor. For example, a 0.3 deciview improvement may merit a stronger weighting in one case versus another, so one " bright line" may not be appropriate. In addition, comparison thresholds can be used in a number of ways in evaluating visibility improvement ( e. g. the number of days or hours that the threshold was exceeded, a single threshold for determining whether a change in impacts is significant, a threshold representing an x percent 13CALPUFF Analysis in Support of the Regional Haze Rule, U. S. Environmental Protection Agency, April 15, 2005, Docket No. OAR 2002 0076.

14 Ibid.

148 change in improvement, etc.). In our example modeling analysis of a hypothetical source13, we used three different 24 hour thresholds ( 1.0, 0.5, and 0.1 deciviews) and examined the number of days that those thresholds were exceeded for a source with a 90 percent change in SO2 emissions ( i. e. 10,000 TPY and 1,000 TPY). The number of days that the thresholds were exceeded in the 10,000 TPY case was substantial, and the visibility improvement due to the reduction in emissions was dramatic ( i. e. the number of days exceeding the thresholds dropped considerably) 14. Other ways that visibility improvement may be assessed to inform the control decisions would be to examine distributions of the daily impacts, determine if the time of year is important ( e. g. high impacts are occurring during tourist season), consideration of the cost effectiveness of visibility improvements ( i. e. the cost per change in deciview), using the measures of deciview improvement identified by the State, or simply compare the worst case days for the pre and postcontrol runs. States may develop other methods as well.

Comment: Six comments were received opposing evaluating visibility impacts of applying controls using the results of the 20% worst modeled days ( 0198, 0225, 0242, 0249, 0251, 0319). Two commenters added that the criteria should use the 20% worst day based on monitored data, and not modeled data ( 0198, 0242). One commenter stated that by using the 20% worst modeled days, natural source contributions are not taken into consideration ( 0225). Another commenter stated that sources should not be limited to just the worst days, but the improvements should be based upon controls reducing visibility impairments on any day ( 0249). Two commenters ( 0249, 0251) stated that the requirement that improvement be made on the 20% worst days and no degradation on the 20% best day does not constitute a criterion for measuring progress. This rationale ignores the middle 60% of days in which visibility can worsen because sources may be allowed to increase emissions on these day as a trade off for cutting emissions on the worst days ( 0251). Commenter 0251 went on to say that there is no data or evidence to support EPA's assertion that progress on the worst days means progress on other days. One commenter ( 0319) also opposes the use of the maximum modeled 24 hr change over a 5 year period as a criteria for considering BART.

Response: See the discussion above for evaluating visibility impacts for control options. We encourage States to account for the magnitude, frequency, and duration of the visibility impacts.

Comment: Two other comments were received regarding evaluating visibility impacts of applying controls using the results of the 20% worst modeled days ( 0249, 0256) Although the rules require a state to submit visibility SIPs for the 10 year period of the SIP specifying reasonable progress 149 goals, the rules do not contain a requirement that states determine the rate of improvement need to achieve natural conditions in 60 years. In fact a state can reject the 60 year schedule but demonstrating that the schedule is unreasonable, in the state's view ( 0249). Additionally, EPA should clarify that the 20% worst modeled days are the observed 20% worst day as determined from IMPROVE ( 0256).

Response: See the discussion above for evaluating visibility impacts for control options. States have the option in how to evaluate visibility for the fifth factor assessment, but as a general matter, evaluations should be made using the worst modeled as the IMPROVE receptor may not represent the maximum impairment across the entire Class I area.

<IP_ADDRESS> Use of Hourly Modeled Impacts Comment: Eight commenters opposed using the maximum 24 hour value in evaluating the " cause or contribute threshold ( 0188, 0205, 0214, 0226, 0238, 0253, 0321, 0323). Commenters said that using a single day in a 5 year period represents a single spike that may be unduly influenced by short term abnormal conditions. Commenter 0205 added that the proposed analysis is so stringent that few if any sources will be able to demonstrate no contribution and EPA has circumvented the court ruling in American Corn Growers by essentially requiring all BART eligible sources to install BART controls without a meaningful showing of real contribution to visibility impacts in a Class I area. Given EPA's recognition in other recent standards of the need for a more stable statistical form, and the earlier rule's reliance on the average 20% worst modeled days, PCA requests that EPA use the average of the 20% worst modeled days as in the 1999 RHR to determine if a source reasonably contributes to regional haze. Following the analysis provided in the 1999 RHR best meets the 1999 RHR's original intent.

Response: The final rules allows a State to use the 98th percentile impact over the meteorological period modeled, whichever they deem is most appropriate. Such an approach affords added protection against the possibility that poor visibility might be caused by unusual meteorology and thus, in our view, represents a reasonable lower bound for comparison. If the 98th percentile value from your modeling is less than your threshold, then you may conclude that the source does not contribute to visibility impairment and is not subject to BART.

Commenters 0214 and 0238 said EPA's requirement to use the maximum 24 hour value over the 5 year period of meteorological data in the modeling, as proposed, is too stringent. In contrast, EPA uses an " average of the 20% worst days" metric in the " visibility improvement" step in the BART determination evaluation and in the regional haze program. The default " natural condition" deciview values for Class I areas in EPA's natural conditions guidance, which EPA recommends states use for the visibility impairment analysis, exist only for the average of the 20% best and worst days. There are no default " maximum 24 hour" values in EPA's guidance. The accuracy of these measurements will be very dubious for some cooperative owned or operated 150 plants that do not even have meteorological data that is site specific, and they are hundreds of miles from the nearest airport, which is the default value for such data.

Response: See the discussion above concerning which values may be used.

Commenter 0323 responded to EPA's request for comment on the use of hourly modeled impacts from CALPUFF to assess the number of hours above a visibility threshold. While hourly model data are, by their nature, less reliable in predicting actual conditions, a measure that reports the total number of hours above a given level would still be a useful measure of the long term effect of BART control. EPA should require states to report a combination of measures regarding the improvement in visibility expected from implementing BART. This combination should include the EPA's proposed metric of the change in the 20 percent worst days and a metric that examines the amount of time during a year the source's visibility impact would exceed a threshold with and without implementation of BART control.

Response: See the discussion above concerning which values may be used.

Comment: Two commenters suggested alternatives to the 24 hour value ( 0205, 0256).

Commenter 0205 said a threshold comparison is more appropriate than the overall comparison of the 20% worst case days. However, the threshold comparison should be on at least a daily average ( or longer), not an hourly average due to the possibility of short term spikes based on certain meteorological conditions. A comparison of number of days above or below a certain threshold is preferable since below a certain threshold, the impacts of visibility are not perceptible. Unlike concentration levels of certain pollutants ( i. e., ozone) which do not have a threshold below which there are no effects, there are pollutant levels below which there is no visibility impact. The comparison of number of days will also allow for a more complete picture of how the control device will impact visibility. As noted previously, a small number of unusual meteorological conditions can produce significant spikes on a single day or days. Since the overall goal of the regional haze rule is long term visibility improvement, a comparison of the total number of days exceeding a threshold over multiple years will provide a better overall indicator of visibility improvement.

Response: See the discussion above concerning which values may be used.

Commenter 0256 said if EPA retains the maximum 24 hour value for the visibility impairment analysis, EPA should at least allow the use of only 1 year, rather than 5 years, of meteorological data. That would simplify the modeling and would lessen the chance that one day with atypical, extreme conditions would dictate the result. Moreover, if the 24 hour approach is used, EPA should clarify that block averaging is to be used to determine 24 hour values. 151 Response: See the discussion above concerning which values may be used. A State has discretion to use block averaging if they so choose. Three or five years of meteorological data may be used per 40 CFR 51, Appendix W, April 2003.

<IP_ADDRESS> Levels of Visibility Improvement Comment: Nine commenters commented on the utility and implementation of visibility improvement thresholds ( 0189, 0228, 0230, 0238, 0253, 0256, 0271, 0275, 0306, 28 7048). Commenter 0228 said EPA should clarify that visibility improvement differences among BART control options should be considered insignificant if the differences differ by less than the perceptibility threshold level, which should be set in excess of 1 deciview and not the 0.5 deciview level EPA is proposing. Other commenters said the minimum threshold should be 1 deciview ( 0238, 0256).

Response: See the discussion above regarding how to evaluate visibility improvement for the BART determination.

Commenters ( 0230, 0275) said the Proposed BART Rule proposes a visibility threshold to determine when a source causes or contributes to visibility impairment at a Class I area; however, no threshold is proposed to determine whether BART controls on a specific BART eligible source results in a visibility improvement. Commenter 0306 said it is unclear how the modeled net visibility improvement would be specifically utilized in the BART analysis. Is there a target level of improvement? Is there a de minimis level?

Response: As discussed above, States have discretion in how to evaluate visibility improvement and how to weigh that improvement with the other four factors to make the BART control decision. We are not dictating a target or de minimis level as visibility improvement may be weighed differently for each Class I area.

Commenter 0230 added that, if the BART controls result in no perceptible improvement in visibility at a Class I area, then it is not a cost effective strategy for improving visibility at Class I areas because it will have no perceived impact. Based on Pitchford and Malm ( 1994) and Henry ( 2002) a 2 deciview threshold of perception would be appropriate, with a 1 deciview threshold providing a margin of safety. Commenter 0253 agreed that EPA should revise its methodology to screen out predicted visibility improvements that are irrelevant to determining the level of control that constitutes BART, provide for calculation of visibility improvement associated with each potential level of BART control, and measure visibility improvement based on the overall improvement in general visibility.

Response: Perceptibility may not be a factor in determining controls at an individual source. For example, if there are multiple sources contributing to impairment at a Class I area, the collective visibility benefit of controlling each of these sources could be perceptible ( assuming that a control level is set based on weighing the five factors, including cost, for each BART eligible source), in 152 spite of the fact that the individual improvement expected from each source by itself may not be perceptible. Our hypothetical modeling analyses ( provided in a technical memo to the final rule) may inform estimates of visibility improvement associated with a potential control efficiency.

Commenter 0271 noted EPA is proposing to add a fifth criteria for inclusion in the BART engineering analyses that must be conducted on a source by source basis; namely the degree of visibility improvement that would result from the addition of one control option over another. This analysis is unnecessary, confusing and without adequate standards or guidance for implementation. In general, the analysis of the level of controls in the BART process should yield the greatest, most cost effective control efficiency for NO x and SO 2 at or above the presumptive level of control for these air contaminants. An analysis of the degree of visibility improvement within this range may result in very small increments of visibility improvements within Class I areas from a single source, making consideration of this very small increment meaningless or tilted to the selection of the lower control efficiency option. EPA should remove this criterion from the analysis to ensure that the highest, most cost effective controls will result.

Response:

The BART guidelines recommend a way for States to take into account the degree of visibility improvement that may result from the use of BART. We agree that an analysis of the degree of visibility improvement resulting from the use of one technology, as compared with another, may show very small increments of visibility improvement. The States have the discretion to consider the degree of visibility improvement in a reasonable manner. As the States will be making BART determinations at the same time that they are establishing reasonable progress goals, they should consider this.

Commenter 0189 said, as the Corn Growers case emphasized, the statute clearly provides for states setting BART to balance the visibility benefits of BART controls comprehensively against their burdens. There is not a word of that in EPA's proposal. Although it would allow States setting BART to run CALPUFF modeling, it completely fails to specify how they might consider the results.

Response:

The court in American Corn Growers' invalidated EPA's 1999 provisions on BART determinations because they bifurcated visibility from the other BART factors and precluded States from weighing visibility impacts on a source specific basis. EPA has remedied that defect in this rulemaking. Nothing in the case suggested that EPA must dictate the manner in which States weigh visibility against other factors. Consistent with the court's emphasis on the discretion afforded to States by CAA 169A, for sources other than 750 MW power plants, States have considerable latitude under the guidelines to determine how this weighing should be done.

Comment: 153 Commenters ( 28 266, 28 312, 28 352) said EPA states that, for any Class I area, the cumulative visibility improvement is a " substantial fraction"  how much is a " substantial fraction"? Note this criteria is confusing in light of the statement in the preamble that EPA " calculated relatively small impacts for BART, in part because the baseline for the analysis assumed a substantial degree of emissions for BART eligible sources in response to the NAAQS for PM2.5". This might suggest that it may be difficult for states to show that BART emission reductions will provide " a sufficient visibility improvement to justify their installation". Commenter 28 352 said the BART guidelines should require that " any" prevention of future deterioration or existing impairment in visibility associated with a Class I area be sufficient basis for control for all eligible sources in the region under the cumulative visibility assessment.

Response:

In this final rule, visibility improvement as a result of controls is determined on a source by source basis ( per the American Corn Growers court decision). An analysis of all five statutory factors is required when assessing controls for BART and visibility alone can not be sufficient in determining controls.

Commenter 28 266 did not agree that application of BART must represent a " substantial fraction" of the achievable visibility improvement from all measures in the SIP. As long as such emission reductions will improve visibility in a Class I area, then they are justified and must be required.

Response:

An analysis of all five statutory factors is required when assessing controls for BART and visibility improvement ( assumed to result from emission reductions) alone can not be sufficient in determining controls.

Commenter 28 7048 said depending on the metric used for reasonable progress, the early emission reductions from BART may be more important and economically valuable than the guidance will estimate. In particular, the deciView ( dV) is a logarithmic function. Linear progress in dV in the long term requires a more rapid reduction in emissions in the short term. The guidance does not mention this and it isn't considered in the establishment of the budget or in the analysis of whether the BART reductions are needed.

Response:

BART must be installed as expeditiously as possible. States can take into account the timing of BART reductions in establishing reasonable progress goal.

<IP_ADDRESS> Compare to Natural Conditions 15 Guidance for Estimating Natural Visibility Conditions Under the Regional Haze Rule ( U. S. EPA. September 2003). http:// www. epa. gov/ ttncaaa1/ t1/ memoranda/ rh_ envcurhr_ gd. pdf Natural background conditions, expressed in deciviews, are defined for each Class I area. EPA has issued guidance for estimating natural background conditions which has estimates of default conditions as well as measures to develop refined estimates of natural conditions.

154 Comment: Three commenters addressed the role a natural conditions baseline should play in the analysis ( 0189, 0225, 0268). Commenters ( 0189, 0268) stressed that in assessing the visibility benefits of BART controls, states should assess their impact on the visibility levels projected to exist during their operating life, not on pristine visibility levels that do not currently exist and are not projected to be achieved until 2064 under EPA's visibility rules. Commenter 0225 was concerned that the degree of visibility improvements evaluated from additional controls should include the evaluation of the quality of visibility that natural conditions represent. Sources impacting Class I areas where natural sources are the main cause of poor visibility should not be required to add controls because the emission reductions will not result in good visibility conditions.

Response: The visibility goal of the CAA is both the remedying of existing impairment, and prevention of future impairment. The court, in American Corn Growers, upheld our interpretation of that goal as the return to natural visibility conditions. Long term regional haze strategies are developed to make " reasonable progress" towards the CAA goal, and States must demonstrate reasonable progress in their regional haze State implementation plans ( SIPs). Since the BART program is one component of that demonstration, visibility changes due to BART are appropriately measured against the target of natural conditions. With regard to BART eligible sources not being in operation for the duration of the program, a State, in making BART determinations, is explicitly directed by the CAA to account for the remaining useful life of a source. Thus, States may factor into their reasonable progress estimates those shut downs that are required and effected in permit or SIP provisions. In addition, as provided for under our guidance15, proper accounting for natural phenomena is in the 5 year SIP progress report, not in the setting of natural visibility estimates.

<IP_ADDRESS> Modeling Domain Comment: Four commenters said the guidelines must clarify which BART eligible sources need to be included in making this demonstration for a given Class I Area. ( 28 266, 28 272, 28 278, 28 312). Commenters ( 28 266, 28 312) asked which BART sources in the large, uniform modeling domain covering at least the eastern half of the U. S. need to be considered in making this demonstration for a given Class I area? Commenter 28 278 noted that there is no provision for 155 modeling of subgroupings of BART sources within a region, nor for the determination that some, but not all, of the BART controls are needed. However, 40 CFR 51.308( e)( 1)( ii)( B) states that this analysis is to consider all sources subject to BART " located within the region that contributes to visibility impairment in the Class I area." This latter requirement suggests that only those which contribute to visibility impairment in the Class I area of interest need to be considered. Therefore, it is confusing which BART sources in a large modeling domain need to be considered in a cumulative analysis.

Response: The final rule provides States the option to demonstrate, cumulatively, that all its BART eligible sources are subject to or exempt from BART. There is also an option to evaluate BART eligible sources individually. In either case, the State need only analyze sources within the State boundary for BART applicability determinations.

<IP_ADDRESS> Engineering Analysis Must Include Source by Source Visibility Impact Analysis Comment: Seven commenters said the BART engineering analysis needs to include an evaluation of the improvement in visibility which may result from the implementation of the various BART technology options ( 28 302, 28 303, 28 305, 28 342, 28 346, 28 357, 28 390). Some commenters ( 28 302) said EPA must strengthen the justification for their proposed treatment of visibility improvements on a cumulative ( as opposed to source by source) basis. As the proposed BART rule states, EPA should require a cumulative air quality impacts analysis given the regional nature of the haze problem. Such an analysis is required by the Act ( 28 305). Commenters ( 28 390) said the cumulative air quality analysis does not serve this purpose since it is conducted after the BART engineering analysis has been completed and the BART emission limitation established. The BART engineering analysis should first require a baseline comparison of the BART factors for all the various control alternatives, from the status quo to the most stringent control alternatives ( 28 346, 28 357). The BART process must require the balancing of the costs or a proposed emission control strategy against its visibility benefit.

Response:

The guidelines provide the States with an approach for making visibility assessments. We do not agree that the CAA requires a cumulative air quality impacts analysis, but as explained in the preamble, we believe States have the discretion to pursue such an approach. Nothing in the CAA suggests that States must balance the costs of a proposed emission control strategy against its visibility benefit.

Comment: Twenty nine commenters said emission control decisions must be made on a case by case basis ( 28 243, 28 275, 28 329, 28 331, 28 333, 28 337, 28 340, 28 341, 28 342, 28 346, 28 353, 28 354, 28 356, 28 357, 28 360, 28 361, 28 364, 28 389, 28 395, 28 398, 28 401, 28 402, 28 405, 28 406, 28 7001, 28 7003, 28 7004, 28 7007, 28 7009) for several reasons: 156 ° The statute and/ or Congressional intent clearly require a case by case analysis ( 28 243, 28 337, 28 341, 28 346, 28 353, 28 354, 28 356, 28 359, 28 360, 28 361, 28 364, 28 389, 28 395, 28 405, 28 406, 28 7001, 28 7003, 28 7009) ° Limits states' ability to design a program that more cost effectively tailors BART to impacts of individual sources ( 28 275, 28 329, 28 331, 28 340, 28 342, 28 346, 28 354, 28 357, 28 360, 28 398, 28 401, 28 402, 28 406, 28 7004, 28 7009) ° Without knowing the extent of a source's actual contribution to visibility impairment and the degree to which that contribution would be mitigated by a given set of controls, there is no basis to make a cost effectiveness BART determination as to that source ( 28 333, 28 346) ° Sources with imperceptible visibility impacts may be forced to install costly emission control equipment even though little if any visibility improvement would be obtained ( 28 359, 28 360, 28 364, 28 395) ° Inconsistency with other BART criteria, i. e., one of the BART criteria required for determining which retrofit technology is best for an individual source is the amount of visibility improvement which can be anticipated from the installation and use of that technology ( 28 361) ° Inconsistency with prior EPA interpretations ( 28 395, 28 398).

Response: The final rule now establishes that BART controls are determined on a source by source basis.

Comment: Ten commenters opposed the use of cumulative air quality analysis ( 28 273, 28 302, 28 304, 28 337, 28 349, 28 356, 28 357, 28 358, 28 404, 28 7001). Commenter 28 273 said if the emission limit is determined by best available retrofit technology, then the air quality assessment should be used to estimate the cumulative effect of implementation and assess achievement of the goal, not for further reduction of limits. Commenters ( 28 337, 28 349, 28 356) by directing that visibility benefits be considered solely on a collective basis, the proposed process would prevent the states from undertaking the source by source weighing of costs and benefits intended by Congress. Commenter 28 357 said the approach is inconsistent with the cost/ benefit approach required by 169A.

Response: The final rule now establishes that BART controls are determined on a source by source basis.

Commenter 28 304 said nothing in the Act or EPA's implementing regulations allows the determination as to the adequacy of BART controls to be based on an anti degradation analysis that encompasses all sources of visibility impairing pollutants. Second, EPA has offered absolutely no factual support or analysis in support of this aspect of the proposed BART guidance. For example, EPA should have investigated whether it is even possible for BART controls on BART eligible sources to achieve this anti degradation criterion. Lastly, this aspect of the BART guidance is plainly unreasonable. Simply put, there is no rational basis for EPA to conclude that the 157 level of control that should be applied to BART eligible sources can or should be dependent on construction or modification of sources not subject to BART.

Response:

Kathy Commenter 28 358 opposed any suggestion that the cumulative visibility analysis could be used to exempt a state or region from the BART requirements or to create exemptions for specific sources on de minimis contribution grounds. EPA's proposed formulation is complicated, unnecessary, and will yield results contrary to the statute's purposes. The statute requires that modeling results from a Cumulative Air Quality Analysis justify the application of BART on all sources subject to BART in a region if they demonstrate, in the associated Class I area, that any existing visibility impairment will be remedied or any future deterioration in visibility will be prevented. The final BART guidelines should reflect that requirement.

Response:

The commenter suggests a reading of the statute that was the basis of the 1999 regional haze rule and was invalidated by the D. C. Circuit. In the final guidelines, the option of using cumulative analysis to show that no source is subject to BART simply reflects the logical conclusion that if a group of sources taken together do not contribute to impairment, than no single source can either. States also have the ability to use a cumulative analysis to show that a individual members of a group of sources are reasonably anticipated to contribute to impairment, but we cannot require States to make such a finding.

Commenter 28 404 said the proposed guidance should also include an alternative BARTevaluation approach that would start with the stringent control alternative to increase rule flexibility. In all cases, BART evaluations should iterate emissions reductions from controls compared to incremental improvement in regional haze impacts on a unit specific basis or possibly provide for alternative performance based emissions standards.

Response:

The guidelines describe a reasonable approach for making BART determinations. States generally have the authority to adopt reasonable alternative approaches.

<IP_ADDRESS> Other Comments Regarding the Visibility Improvement Analysis Comment: Eight commenters ( 0207, 0221, 0226, 0253, 0256, 0277, 0321, 28 332) provided several areas where the guidelines should be improved or clarified: 158 ° EPA should clarify that the analysis is pollutant specific ( e. g., the modeling evaluation of a BART control option for SO 2 reduction should not be combined with the modeling evaluation of a BART control option for Nox) ( 0226, 0256). ° EPA should clarify that only the closest Class I area must be modeled ( 0226, 0256). ° EPA should describe CALPUFF as one possible model to use, rather than as the only model that may be used ( 0256). ° States and sources should have the flexibility to perform multiple modeling runs based on different levels of available control ( 0207, 0226, 0256, 0277). ° Predicted visibility improvements that are imperceptible should be given no weight in determining the level of control that constitutes BART ( 0253). ° States should be allowed to establish the required degree of visibility improvement factor ( 0321).

° EPA should clarify how the cumulative air quality analysis can be reconciled with the geographic area of influence determination discussed in Section II( A) ( 28 332).

Response: The final rule has provided clarification of each. The analysis may be pollutant specific at the discretion of the State. The closest Class I area is modeled, but some strategic receptors should be placed at a nearby Class I area to ensure that the highest visibility impacts are occurring at the closet park. See further discussion of the Modeling Protocol in the preamble to the rule. There is an option to use alternative models to CALPUFF. States and/ or sources may perform multiple modeling runs. Even though the visibility improvement from an individual source may not be perceptible ( i. e. the expected improvement may be less than or equal to 0.5 deciviews), it should still be considered in setting BART because the contribution to haze may be significant relative to other source contributions in the Class I area. Thus, we disagree that the degree of improvement should be contingent upon perceptibility. Failing to consider less than perceptible contributions to visibility impairment would ignore the CAA's intent to have BART requirements apply to sources that contribute to, as well as cause, such impairment. States can assess how to use the expected visibility improvement due to various control technologies in setting a BART emission limit. Finally, there is no requirement to reconcile the geographic area of influence determination to the cumulative air quality analysis, and it is no longer relevant to this rule.

Commenter 0221 said that issues relating to the evaluation of the visibility improvement in determining BART controls are in many ways the same as issues relating to the evaluation of visibility impairment in determining which BART eligible sources are subject to BART. Thus, comments relative to EPA's: use of the 0.5 deciview threshold for aggregate visibility impairment applied on a 24 hour average basis, use of a natural visibility baseline, use of a substantially lower deciview threshold to determine the contribution by an individual source to visibility impairment, and demonstration of those thresholds by means of appropriate modeling rather than other less reliable and more subjective techniques are all equally applicable here.

Response: We agree and have addressed these comments elsewhere in this document. 159 Commenter 0267 supported EPA's proposed method to determine visibility improvement associated with installation of BART.

Commenter 28 7001 said location, in and of itself, is not a means of determining impact. By EPA's own admission, the atmospheric processes that determine downwind visibility impact on a Class I area are part of a process including prevailing met conditions, actual emissions from a particular source, interactions with other source emissions and distance and directions of transport.

Response: We agree and models account for the various meteorological and atmospheric chemistry influences when predicting visibility impacts  the impact may not be determined simply by a source's location.

4.1.5 Applicability to Plants that Have Installed BACT or LAER or are Subject to MACT or NSPS Comment: Eight commenters supported the proposal that MACT compliance should count as BART compliance because MACT controls are far more stringent than the requirements for BART ( 0169, 0184, 0186, 0189, 0201, 0207, 0304, 0308). Commenter 0201 added that EPA may want to clarify that the MACT standard must have regulated the subject visibility impairing pollutant.

Response:

We do not agree that MACT is necessarily more stringent than BART. States will be able to judge whether this is true in particular instances. We do agree that the MACT standard, to be relevant, must have regulated the same pollutant as is regulated by BART.

Comment: Several commenters asked EPA to extend this provision to sources that have recently implemented NSPS ( 0169, 0184) and/ or BACT or LAER ( 0184, 0207, 0214, 0215, 0294). Commenters added that sources that are modified after 1977 should not be included in the BART pool because they would already meet BACT, LAER, and/ or NSPS controls ( 0184, 0214, 0215, 0228, 0237, 0238, 0253, 0254, 0256, 0268). Commenter 0256 added that any requirement of a BART review for new, post 1977 emissions units or modified emissions units would be inconsistent with Congress' intent to limit BART to sources in existence on August 7, 1977. Congress chose that date as the cutoff for BART because units added after that date typically would have been subject to NSR ( unless they avoided NSR by netting out).

Commenter 0237 distinguished between sources reconstructed after 1977 and subject to NSPS and sources subject to minor or major PSD/ NSR analysis after 1980 as not being BARTeligible Commenter 0215 added existing units that began operation before August 7, 1962 are not BART eligible, regardless of any changes made to those units in the 1962 1977 time frame ( or 160 thereafter). This would be an unlawful retroactive application of the Act. Commenter 0242 agreed.

Response:

We have added some discussion of the interaction of BART and these other provisions to the guidelines. We have also noted that sources which have reconstructed after 1977 and been subject to new source standards are not BART eligible.

4.1.6 General Comments Regarding the Engineering Analysis Comment: Six commenters suggested ways EPA should provide flexibility and resources to the states in conducting the engineering analyses ( 0197, 0201, 0237, 0245, 0275, 0302). Some commenters ( 0197, 0302) said states do not have the resources to perform many site specific engineering analyses and flexibility is needed to allow them to cost effectively find the necessary emission reductions ( 0302). Commenter 0197 said EPA should not limit a state's freedom to identify which sources contribute to visibility impairment and by directing how states must apply cost benefit considerations in deciding whether additional controls may be needed.

Commenters said EPA has ignored the costs of engineering analyses ( 0237) and should help states to address the resource needs including: ° Provide funding for states to accomplish the SIP development and engineering analysis activities that the proposal mandates ( 0201, 0245) ° Provide written guidance for industry in accomplishing the required engineering analysis ( 0201, 0245) ° Provide or support RPO development of potential emission control options by major source category ( 0201, 0245) ° Develop and maintain a clearinghouse of BART determinations ( 0201, 0245).

Three commenters said EPA should establish a " BART Clearinghouse" to provide states with information regarding retrofit control information to help them make technology determinations ( 28 254, 28 264, 28 290). Commenter 28 290 added that a process is needed that will allow decision makers to pool information and coordinate efforts. Another commenter ( 28 244) said individual states or groups of states should adopt a generic approach to at least of the BART issues in the interest of consistency and efficiency, while reserving some others for case bycase " balancing."

Response:

Commenters have made many good suggestions above for the implementation phase of BART, and we will consider them. 161 Comment: Commenter 0275 said if states find that additional controls are needed to achieve continued visibility improvements, states should select the sources to be controlled on the basis of visibility impact and cost effectiveness as the primary factors, with other secondary factors such as state of development of control technology and administrative costs also considered. Sources should not be exempted from additional control or review simply because they were controlled under CAIR or BART.

Response:

States have considerable flexibility in determining how best to weigh the BART factors.

Comment: Two commenters said the required analyses will require substantial time and effort to perform ( 28 266, 28 312). Given the potentially large number of sources subject to BART in some regions ( and the need to review each visibility impairing pollutant, even if the potential emissions for only one of these pollutants exceeds the 250 TPY threshold), this requirement will pose a tremendous burden on the states. Another commenter ( 28 345) noted that the engineering and impact analyses are far too prescriptive and exceed EPA's authority.

Response:

We believe that the BART guidelines appropriately balance Congressional directive and implementation issues, and we believe we have provided as much flexibility as possible to States in order to facilitate implementation. We believe States will be able to implement BART as it has been finalized.

4.2 Select a Best Alternative Using the Results of an Engineering Analysis 4.2.1 Select a " Best" Alternative <IP_ADDRESS> Top down Analysis Comment: Forty commenters supported using a top down analysis for performing BART engineering analyses ( 0159, 0200, 0221, 0232, 0234, 0267, 0284, 0304, 0314, 0323, 28 247, 28 248, 28 254, 28 255, 28 256, 28 257, 28 258, 28 260, 28 262, 28 263, 28 265, 28 267, 28 289, 28 290, 28 302, 28 332, 28 334, 28 335, 28 338, 28 350, 28 352, 28 358, 28 362, 28 376, 28 389, 28 399, 28 770, 28 7008, 28 7016, 28 7048). Commenters ( 0221, 28 335, 28 358) said the idea that the BART engineering analysis should begin with the most environmentally stringent control option and proceed from there to less stringent controls is reinforced by the similarities between BART and the NSR BACT standard, which uses the top down approach and is consistent with Congressional intent. Commenters ( 28 254, 28 260, 28 263, 28 265, 28 7016) added that the 162 plain terminology of BART is best available retrofit technology. If the most effective removal technology is not the starting point of the analysis, then the other BART factors may not be applied to a consistent, established benchmark. In addition, this approach is consistent with other programs such as PSD ( 28 254, 28 255, 28 335, 28 350, 28 362, 28 389).

Commenter 0234 said that to consider less stringent controls first would limit the effectiveness of the BART program to reduce emissions. Commenter 0304 said using a top down analysis places the burden of proof on the individual source to show that a certain level of control is not technologically feasible or not cost effective, but using a bottom up approach places the burden of proof on the agency to show that the next higher level of control is appropriate. Commenters ( 0323, 28 350) said a top down approach is more straightforward to implement than the alternative and would tend to more thoroughly consider stringent control alternatives. The final selection of the control technology should be based on a review of all the BART factors, to assure a reasonable balancing of dollar per ton removal and degree of improvement in visibility. Commenter 28 267 said the process should include due consideration of the differences between the BACT and BART processes.

Commenters ( 28 332, 28 358) said the top down approach would provide greater consistency with other regulations ( BACT) and reduce administrative requirements.

Comment: Fifty nine commenters opposed using a top down analysis ( 0182, 0186, 0188, 0189, 0195, 0208, 0210, 0214, 0217, 0223, 0226, 0228, 0237, 0238, 0241, 0242, 0253, 0256, 0268, 0270, 0275, 0294, 28 259, 28 270, 28 275, 28 306, 28 331, 28 337, 28 337, 28 339, 28 340, 28 343, 28 344, 28 345, 28 347, 28 349, 28 355, 28 356, 28 357, 28 361, 28 364, 28 383, 28 384, 28 385, 28 386, 28 392, 28 395, 28 401, 28 402, 28 405, 28 747, 28 748, 28 778, 28 779, 28 7001, 28 7003, 28 6004, 28 7009, 28 7013). Commenters ( 0182, 0208, 0217, 0241, 0270, 0275, 28 33, 28 345, 28 347, 28 357, 28 392, 28 778, 28 7003) said this approach is contrary to the Act and that had Congress wanted the states to perform a BACT like analysis on BART eligible sources, it would have done so explicitly. Commenters ( 0186, 0208, 0270, 0275, 0294, 28 339, 28 340, 28 343, 28 349, 28 361, 28 364, 28 383, 28 747, 28 748, 28 7003) said EPA's prescriptive guidelines for making BART determinations undermine the statutory authority given to the states in the Act. Commenter 0237 said EPA lacks authority to disapprove a state's criteria for determining BART. Commenter 0189 provided a legal analysis supporting the Congressional grant of substantive discretion to states to choose their own BART. This approach also circumvents the 60 year plan for attaining visibility goals by defining BART to be so stringent that States will be far exceeding reasonable progress expectations at the outset of the program. This approach is inconsistent with congressional intent to spread the cost of the regional haze program over a 60 year period ( 0186). Commenter 29 275 added that assuming a starting point at the most stringent level and subjecting the analysis to " correct until demonstrated wrong" methodology is clearly inappropriate for a long range program with as many technical uncertainties as exists in the regional haze program. 163 Commenters ( 0188, 0195, 0210, 0214, 0223, 0226, 0238, 0253, 0256, 0268, 28 259, 28 270, 28 306, 28 331, 28 337, 28 355, 28 357, 28 385, 28 779, 28 7001) said that the top down methodology allows a BART determination to be made without taking into account the statutory factors that Congress indicated must be taken into account. The only satisfactory approach is one in which all the BART control options are considered and compared in light of the statutory factors ( cost, visibility improvement, and so on). Commenters ( 0223, 0230) said EPA should clarify that all five factors listed in Act must be addressed regardless of the approach adopted.

Some commenters stressed the need to conduct the cost benefit assessment required by the Act instead of shifting the process to a " top down" BACT program that is only applicable under the NSR provisions ( 28 259, 28 270, 28 306, 28 331, 28 384, 28 386, 28 401, 28 402, 28 7009). Other commenters ( 0188, 0242, 0268, 28 357) added that this approach does not take into account visibility improvement among potential control options. Commenters ( 0253, 0256) said EPA's proposed methodology inflates the visibility improvements associated with a given level of control in a manner that skews the BART analysis. Visibility improvement is essentially overweighted and the other statutory factors are underweighted.

Commenter 0195 said without the consideration of any existing pollution controls in place, a strict top down methodology would potentially require upgrades to an already controlled facility. Commenter 28 344 said the proposed guidelines treat BART as the equivalent of " top down BACT", thus failing to take into account that BART was intended to be retrofitted onto existing facilities that are not otherwise undertaking modifications. Commenters ( 28 392, 28 7013) added that the " top down" BACT approach hides the high incremental costs associated with very expensive emission reductions by averaging those costs with the more cost effective emissions reductions. The " top down" approach also creates a false presumption that sources with existing controls cannot meet BART without additional emission controls.

One commenter ( 28 247) said the presumption of maximum stringency would be particularly burdensome as applied to smaller utility and industrial boilers. Industrial boilers generally differ from the 750 MW+ utility boilers contemplated for BART regulation in the statute in three principal respects: size, load variability, and design of the boilers.

Response:

We believe that the best approach is to provide States with flexibility to use the process tht works best in their decision making structure. Therefore we are not recommending a specific method of arraying control options.

<IP_ADDRESS> Bottom up Analysis Comment: Thirteen commenters supported a " bottom up" approach by evaluating the lest stringent technically feasible control option ( 0184, 0202, 0241, 0247, 0302, 28 259, 28 268, 28 273, 28 164 306, 28 345, 28 385, 28 390, 28 392, 28 405, 28 747, 28 778, 28 7013). Commenters ( 0184, 0202, 28 273, 28 306, 28 345, 28 385) said BACT, LAER, NSPS, or other requirements should serve as a BART ceiling. Commenter 0247 said the Act does not mandate that sources installing BART meet the maximal level of control required for BACT. BART is intended to apply to sources that were never subject to PSD, and represents a different control requirement.

Commenter 0241 added that states should not be forced to justify why more stringent control alternatives were not selected. If a control technology results in an improvement in visibility that the state determines is appropriate to meet its regional haze SIP requirements, then no such justification is needed. Commenter 0302 would require more documentation however. According to the commenter under this process, states would still be required to ( 1) display and rank all of the options in order of control effectiveness and identify the average and incremental costs of each option; ( 2) consider the energy and non air quality environmental impacts of each option; and ( 3) provide a justification for adopting the technology that the MDEQ selects as the " best" level of control, including an explanation as to why other more stringent control technologies were rejected. The level of documentation required under this method would give necessary transparency for industry and the general public. However, this needs a firm national policy and guidance in order to implement the BART regulations.

One commenter ( 0221) opposed the use of a bottom up approach because, by its very nature, less likely to result in the " best available" controls for limiting haze forming pollution. For the most part, the most stringent control technologies for reducing visibility impairing pollutants such as SO 2 and NO x tend to be widely " available." Thus, by allowing a bottom up approach, EPA would be increasing the complexity of the process, the likelihood of analytical mistakes, and the opportunities for " gaming." Because a bottom up approach will require sources to consider the full range of available control technologies, it significantly increases the administrative burden on states involved in the BART process. Finally, there simply is no substantive justification supporting the adoption of a bottom up ( or middle both ways) approach to the selection of BART controls.

Response:

We are not endorsing a bottom up approach as the most useful approach for weighing control options.

<IP_ADDRESS> State Determines Approach Comment: Four commenters supported an approach that would allow a state more options in how it structures its BART analysis ( 28 347, 28 385, 28 779, 28 7005). Commenter 28 347 added that a state could start with the least stringent control alternative or somewhere in the middle of the range and then consider the additional emission reductions, costs and other impacts of successively more stringent control alternatives. The Act grants states the primary role in determining BART 165 and, thus, the state should be free to select a " bottom up" or intermediate approach in conducting the engineering analysis.

Two commenters said the starting point of the analysis does not matter, because the result will be the same ( 28 243, 28 337). Commenter 28 343 added that when choosing the best BART option, EPA still requires that the most stringent alternative be picked unless another one can be justified.

Seven commenters opposed an approach where the state could consider alternative approaches for several reasons ( 28 254, 28 255, 28 302, 28 338, 28 343, 28 358, 28 7016):

° Administrative burden for states and tribes ( 28 254) ° Inconsistency with parallel reviews of BART determinations ( 28 254) ° Inconsistent analyses across the country ( 28 255) ° Inconsistent with the statutory objective of identifying the best control options ( 28 302, 28 338, 28 358, 28 7016).

Commenter 28 343 added that the state is still required to rank all options in order of control effectiveness and consider the energy and nonair quality environmental impacts of each option. This approach is overly prescriptive and usurps the responsibilities of the states.

Response:

We have provided a more flexible approach to arraying control options in the final BART guidelines, as we believe States can and should exercise their discretion under the CAA in choosing the method that works best for them.

<IP_ADDRESS> Cost effective Option Comment: Two commenters supported an alternative approach proposed by EPA to allow the analysis to begin with the most cost effective control option ( 28 259, 28 268). Commenter 28 268 added that it is more appropriate to conduct marginal engineering cost analysis for determining the most cost effective BART options. The true cost effectiveness of each option is not clear until a marginal analysis is done.

Two commenters said the process should apply " middle of the road technologies" that accomplishes reductions at more reasonable costs ( 28 275, 28 333).

Response:

We believe cost effectiveness need not be given greater weight than other options, although we recognize its importance. 166 <IP_ADDRESS> Other Comments Regarding Selecting a " Best Alternative"

Comment: Fifteen commenters provided other comments regarding selecting a best alternative ( 0197, 0207, 0229, 0234, 0254, 0256, 0293, 0299, 0319, 0321, 0319, 28 266, 28 272, 28 273, 28 344, 28 312).

Commenters said that EPA's proposals are too prescriptive and limit a state's freedom to identify which sources contribute to visibility impairment and by directing how states must apply cost benefit considerations in deciding whether additional controls may be needed ( 0197, 0207, 0321). Commenter 0207 particularly objected to the prescriptive nature of Appendix Y and stressed that the Corn Growers decision explained that all five 169A( g)( 2) factors are meant to be considered by the states. Commenters ( 0229, 0256, 0319) said that so long as all five factors are evaluated, the order of analysis should be left to the states.

Response:

We agree, and have left the order of analysis to the States.

Comment: Commenter 0234 said BART controls and exemption policy must be consistently applied to sources across a wide region. Consistency between regional planning organizations and EPA regions in implementing the BART guidelines is critically important to the success of the regional haze program. Commenter 0299 was concerned that the BART Guidelines, insofar as they establish a case by case review of individual sources, creates a regulatory framework that will result in inconsistent control determinations. This is especially true in the absence of clear criteria for making determinations and where more than 50 different regulatory agencies will be making the decisions. Commenter 28 272 stressed the need to encourage consistency between states in the implementation of BART on a least a regional basis.

Response:

We believe the final guidelines implement Congressional intent, and we also strongly encourage States to work together toward as much consistency as possible.

Comment: Commenter 0293 appreciated the additional flexibility provided in the revised BART guidelines. Maintaining flexibility in measures to achieve reasonable progress goals allows states to develop appropriate strategies according to the contributions to regional haze at each Class 1 area. The proposed rule and Guidelines support state discretion in determining which BART controls will be most effective in each of the respective source categories.

Response: 167 We agree that flexibility and State discretion are important.

Comment: Commenter 0256 said the procedures described in the guidelines for choosing BART are hard to follow and do not consistently seem to include consideration of the visibility improvement factor. The commenter suggested specific deficiencies that should be corrected.

Response: We believe we have provided a reasonable process for visibility assessment and we encourage States to follow it.

Comment: Commenters ( 0391, 28 266) said the proposed BART rule may cause states and companies to incur substantial costs undertaking modeling and evaluating impacts. The rule appears to be a mandate without providing the funding necessary to implement the rule at the state level. This is a significant burden for states already struggling with insufficient revenues to support imposing administrative burdens and costs without funding existing services, let alone assume additional responsibilities. Commenters ( 28 266, 28 312) added that EPA should consider alternative approaches to a source by source analysis for each pollutant, such as multi pollutant regional or source category analyses.

Response:

We recognize the critically important role of the regional planning organizations ( RPOs) in help with the technical analysis and planning for BART implementation. We believe that with the help of the RPOs the States are certain to be able to implement BART in a timely and efficient way.

Comment: Commenter 28 273 said use of the most stringent achievable reduction is unreasonable in evaluating a control for the most stringent level that the control is " capable of achieving." It would be more reasonable to take a statistical approach. The commenter added that whatever averaging basis is used for the BART evaluation needs to be the averaging period to which the unit is regulated.

Response:

We believe States have the flexibility to consider statistical approaches where relevant.

Comment: Four commenters opposed both of the alternatives proposed by EPA ( 28 244, 28 333, 28 344, 28 391). Both approaches involve more than justifiable limitations on the regional or state 168 authority to determine BART on a case by case basis. Commenters ( 28 333, 28 391) added that these approaches do not determine the degree of visibility improvement that would result from a source installing a particular level of BART controls.

Response:

We have left the order of analysis to the States, and believe they will weigh the visibility improvement factor along with other factors in ultimately determining BART control for specific sources.

Comment: Commenter 28 344 said the proposed guideline requests comment on whether BART should be " top down" or " bottom up," without first questioning the departure from NSPS as the statutory reference point for BART controls or providing an adequate basis for that departure. The EPA must revise the NSPS ( as was intended every 5 years) and these standards must be the reference for BART decisions.

Response:

We noted earlier that we believe NSPS is a point of departure but not always an appropriate end point for the BART determination.

4.2.2 Consideration of the Affordability of Controls Comment: Seventeen commenters supported considering the affordability of controls ( 0189, 0199, 0241, 0270, 28 329, 28 337, 28 349, 28 353, 28 354, 28 356, 28 363, 28 364, 28 390, 28 395, 28 405, 28 779, 28 7001). Commenters added that a strict $/ ton decision point would be too limited and factors such as visibility improvement ( 28 329, 28 337, 28 349, 28 353, 28 354, 28 363, 28 364, 28 390, 28 395, 28 405, 28 7001), effects on secondary formed particles ( 28 353, 28 354), and viability of continuing plant operation ( 28 779) must be considered.

Commenters ( 28 364, 28 395) said the proposed BART rule, like the RHR, nullifies the individual source cost effectiveness analysis set forth in Section 169A( g)( 2) by bifurcating the implementation of the statutory BART cost effectiveness factors. T he RHR and proposed BART rule provide for an analysis of all but the visibility improvement factor on an individual source basis. The last factor is required to be analyzed on a collective basis; that is, states are prohibited from examining the degree of improvement that would result from installing BART on individual sources but are instead required to examine the degree of improvement that would result from installing BART on all BART eligible sources. Such a regime is not the cost benefit analysis required by Congress in Section 169A( g)( 2). 169 Two commenters opposed consideration of any compliance costs in the BART guidelines because they will not improve implementation and will vary widely based on individual sources ( 28 362, 28 770). Commenter 28 7005 said a strict dollar per ton approach would affect sources that have little or no impact on Class I areas exactly the same as sources in close proximity to Class I areas. As a result this type of focus is unwarranted.

Response:

We believe this measure of cost effectiveness provide useful information and warranted.

Comment: Ten commenters noted additional impacts that should be considered ( 0189, 0199, 0202, 0275, 0300, 0310, 28 243, 28 306, 28 346, 28 361). Commenter 0189 said that potential " shutdown costs should be considered by a state in reducing the BART controls on a given source.

Commenter 0275 said EPA's analysis of the costs and benefits of complying with the proposed BART program takes credit for benefits realized under other regulatory programs, but not the costs of those programs. As such, the analysis is arbitrary and unsupportable.

Commenter 28 243 said an estimate with an accuracy of up to plus or minus 30% can lead to erroneous outcomes. A more accurate detailed cost estimate will produce more credible estimates. Commenter 28 346 added that by focusing attention on the cost per ton of removal, the guidelines would divert attention away from what the visibility protection program is all about ( visibility improvements) and toward emission management for the sake of emission management.

Commenters ( 0199, 0202, 0300, 0310, 0202, 28 306, 28 361) were concerned about impacts on specific industries. Commenters ( 0202, 28 306) said the potential impact of the guidelines and BART requirements is of special concern for the aluminum industry, which is facing ongoing energy supply and cost problems. The impact of BART could not only create higher direct costs for pollution controls on aluminum facilities, but would also create higher electricity prices due to the costs of implementation to the electric utility industry. Commenter 28 361 said the mining industry would be adversely affected by the Proposed Guidelines for BART determinations if they exceed statutory authority, thereby resulting in excessive costs to retrofit power plants and other industrial sources, or result in a switch to natural gas as a fuel source.

Commenters ( 0300, 0310) noted the important role lignite fuel plays in Texas and said consideration of energy affordability in the regulatory program is essential. Commenter 0319 added that BART as proposed, will be another air quality rule that, in conjunction with recently proposed rules governing mercury, SO 2 and NO x emissions, could make lignite and tribal coals uncompetitive and further concentrate U. S. coal supply in the Southern Powder River Basin. ( SPRB). 170 Commenter 0199 was concerned that any further emission reductions applicable to electric generating units ( EGU) be implemented in a cost effective manner, with reasonable time frames to minimize the impact to residential and industrial customers alike.

Response:

We note that commenters from different industries have different views of affordability analysis. This points out that flexibility is needed for States to take into account site specific issues.

Comment: One commenter ( 28 358) said the six statutory BART factors must be considered, not weighed   a cost benefit approach may not become the basis for BART determinations. The six BART factors are simply listed as those Congress directs EPA and the states to consider in determining BART. Congress has delegated to EPA and the states the responsibility for developing a process by which the BART factors are considered. Congress has not, however, required EPA or the states to use any specific method such as a balancing test in assessing the consideration factors listed at section 169A( g)( 2), nor are EPA and the states required to give each consideration factor any specific weight. EPA, therefore, should clarify, in the final rule, that a cost benefit analysis cannot be used to define BART, nor should the cost effectiveness analysis ( either average or incremental cost effectiveness128) become the fulcrum of the analysis, effectively emasculating the other BART consideration factors.

Commenter 28 258 said one concern with including costs is that the control may be rejected solely on costs rather than looking at all of the source specific factors and/ or if it is necessary to ensure reasonable progress for improving visibility in Class 1 areas. Even if the costs are in the high range, the guidelines should include provisions for requiring presumptive BART. The cost benefit approach will just serve as a mechanism to further delay implementation of BART through a complicated analysis of impacts on visibility from all SIP measures.

Response:

We are not advocating a cost benefit test in the final BART guidelines.

Comment: Commenters ( 0241, 0270) said on the issue of the costs of control, EPA clearly is usurping the states' authority under Section 169A, which requires states to look at the costs of compliance in determining BART.

Response:

We believe States have the flexibility to consider costs of compliance in different ways. 171 Comment: Seven commenters addressed the use of incremental cost effectiveness analysis ( 28 255, 28 256, 28 264, 28 273, 28 302, 28 306, 28 404, 28 7008). Some commenters ( 28 273, 28 306, 28 404) said the rule should be based on consideration of incremental costs. Commenter 28 273 said this approach is the most logical and equitable approach, and the exclusive use of incremental cost effectiveness is also consistent with NSR/ PSD requirements. Other commenters argued for consideration of these costs, but would place limits on their use. For example commenter 28 256 said high incremental costs should not be the sole criteria for rejection of a particular control technology. In order to justify elimination of a control option, a demonstration that both the incremental and total costs are excessive should be made. Commenter 28 302 said consideration of incremental cost effectiveness should only be allowed when it does not result in reduced stringency of controls over those determined using absolute cost effectiveness alone. Commenter 28 7008 rejected the use of incremental cost analysis saying that it is most appropriate to consider the cost effectiveness numbers alone. Incremental cost effectiveness can vary greatly depending on the number of interim options defined, thereby creating the potential for inconsistencies in BART determinations regionally.

Commenter 28 264 said the incremental analysis must include a mechanism to evaluate the visibility benefits that would be achieved by the installation of control technology, and then adjust the expectations for control based on the expected benefits.

Commenter 28 255 said EPA should publish and update as necessary upper limits for cost effectiveness and incremental costs for all pollutants. This will ensure consistency in BART analyses.

Response:

We believe incremental cost analysis is an important and useful measure and the guidelines indicated it should be used. We do not dictate specific cost cutoffs that States should set that would be helpful in all circumstances.

Comment: Two commenters addressed the role of the OAQPS Cost Manual ( 28 266, 28 391). Commenter 28 266 said to ensure regional and national consistency, EPA should update various guidance, such as the 1980 BART Guidance and the 1996 OAQPS Control Cost Manual. Commenter 28 391 noted that the manual does not account for all of the direct and collateral costs that will be associated with BART and should not be used as the sole basis for cost estimations. The commenter recommended that rather than specifying a specific cost estimation methodology, the EPA should identify the elements of an acceptable cost analysis, recognizing that the added costs for retrofit will differ at each location.

Response: 172 Other commenters ( 28 255, 28 258) cited the need for specific criteria in the guidelines for evaluating the costs of controls, compliance to improve implementation and consistency. Commenter 28 358 added that the guidelines should specify the level of inflation adjusted costs for which the presumptive BART must be met.

Response:

We believe Congress intended that States have flexibility in weighing the factors.

4.2.3 Presumptive Emission Limits <IP_ADDRESS> SO 2 Limits for Utility Boilers Comment: Thirty four commenters said the proposed SO 2 levels are reasonable ( 0167, 0171, 0227, 0231, 0232, 0234, 0255, 0256, 0267, 0271, 0314, 0323, 28 239, 28 345, 28 247, 28 248, 28 249, 28 250, 28 258, 28 260, 28 262, 28 286, 28 289, 28 302, 28 334, 28 338, 28 350, 28 352, 28 362, 28 399, 28 433, 28 7002, 28 7016, 28 7048) citing examples and references in support of these levels ( 0171, 0255, 0256, 28 302). Commenter 0323 also agreed with EPA's approach of either a specific emission rate limit or level of control for sulfur dioxide that helps to provide equity among sources which use higher sulfur coal and those using coal with inherently lower sulfur content.

Commenters ( 28 248, 28 399, 28 7016) said EPA should expand this presumption by applying it to electric generating facilities that are under controlled for purposes of SO x. Commenter 28 258 said the presumptive BART level of SO 2 controls should be required at all utility boilers, not just those with no SO 2 controls.

Comment: Nine commenters said the proposed levels are too stringent ( 0176, 0181, 0217, 0246, 0253, 28 264, 28 341, 28 357, 28 7007). Commenter 28 264 said the level is too high for western utilities that are burning low sulfur coal where a level of 85 90% would be more appropriate. One commenter ( 0176) cited his experience with eastern bituminous waste and did not believe the proposed emissions reductions were possible. Commenter 0253 said any default SO 2 control level mandating greater than 90% control are inappropriate for units utilizing wet scrubbers and high sulfur coals. Commenter 28 7007 suggested a range of 70 to 90% would be appropriate.

Commenters ( 0217, 0246, 28 357) said if presumptive levels are included, consideration should be given to the levels reflected in the WRAP agreement ( 85% control efficiency at 85% capacity factor.) EPA's presumption of 90 to 95% control efficiency contradicts the consensus based level of SO 2 reduction determined by the WRAP found to be necessary for visibility improvement in western states. Moreover, given that the WRAP stakeholder agreement was 173 determined to be better than BART, the proposed guidelines should not be interpreted to require changes in Section 309 SIPs already submitted under the regional haze rules.

Commenter 0181 asked EPA to remove the presumptive SO 2 control level from the final BART guidelines. Instead, there should be a BART determination process that promotes costeffective emission reductions based on specific boiler design features and site specific constraints. The proposed presumptive BART approach, as proposed, does not provide affected states and sources with the flexibility needed to design and install SO 2 emission control systems in a costeffective manner to meet the BART requirements. Furthermore, the presumptive SO 2 emissions control approach inappropriately ignores the need for a visibility impact evaluation which is required in step 5 of the proposed case by case BART engineering analysis.

Commenter 28 341 said through switching to Powder River Basin ( PRB) coal, many of Ameren's facilities have met and exceeded the SO 2 reduction requirements of the Acid Rain program. Should BART guidelines be adopted, however, they will be forced to install scrubbers. at each one of their facilities that employs the use of low sulfur coal to meet the proposed 90 95% control levels.

Comment: Four commenters said the proposed presumptive control range is not achievable for existing boilers, and is even more stringent than NSPS limits for new sources ( 28 403, 28 404, 28 405, 28 7013). Commenter 28 403 said EPA's data do not support such a limit nor does EPA explain why the presumption is needed and why the states' discretion should be preempted. Commenter 28 404 said this presumption will result in excessive costs for older equipment. Commenter 28 405 said if presumptive control levels were to be established, they should start at the minimum level of emission controls, with additional controls justified on the basis of the source specific balancing process Congress set forth in 169A. Commenter 28 7013 added that the presumptive limits are more consistent with BACT, which is contrary is contrary to the Act's clear distinction between BART and BACT.

Comment: Eleven commenters said that the proposed presumptive limits clearly exceed the statutory authority ( 28 270, 28 342, 28 353, 28 354, 28 356, 28 360, 28 386, 28 390, 28 392, 28 778, 28 7004). Commenters ( 28 270, 28 386, 28 392, 28 778) said that the evaluation must be conducted according to the statutory process and BART must be determined on a case by case basis. Commenters ( 28 342, 28 354, 28 356, 28 360, 28 390) objected to EPA's proposed presumptive limits for SO 2 controls as a flagrant example of EPA usurping State authority and/ or as being arbitrary and economically counterproductive. Commenter 28 7004 added that the Act consciously addresses the need for SO 2 scrubbing in Title IV. The Act does not envision or authorize a much more onerous and expensive nationwide SO 2 scrubbing program as part of Section 169A. The " guidance" which presumes 90 to 95% SO 2 removal as BART for uncontrolled utility boilers is not supported by the law. 174 Comment: Three commenters said the proposed levels are too lenient ( 0221, 28 263, 28 7008). Commenters ( 0221, 28 263) said because of the extended SIP timeline, BART retrofits will not be applied until 2013 and therefore, it is expected that the " best" available sulfur removal technologies will routinely be able to achieve in excess of 95% removal efficiencies and emission rates of lower than 0.10 lb/ MMBTU by that time. Therefore, the presumptive level of 95% reduction or 0.10 0.15 lb/ MMBTU SO2 emission rate that is stipulated in the proposal should be strengthened to an SO 2 removal efficiency of 95% or better or an emission rate of 0.10 lb/ MMBTU or better. Commenter 28 7008 was concerned with the effect that setting presumptive minimums would have in a true top down control technology evaluation. Using an artificially low presumptive minimum could eliminate consideration of more effective control options that are still achievable by a given source.

Comment: Thirteen commenters specified that proposed control level must account for fuel type and/ or coal sulfur content ( 0171, 0187, 0206, 0213, 0224, 0236, 0241, 0255, 0303, 0314, 28 335, 28 347, 28 770). Commenter 0213 presented historical data showing that the proposed emissions limit could not be attained in certain cases depending upon the sulfur content of the fuel being burned. A statistical approach should be utilized analyzing the performance of existing FGD installations to ensure that the worst case performers can reasonably be expected to comply with the limit. Commenters ( 28 335, 28 347, 28 770) said the presumption should not apply to oil or gas fired utility boilers.

Commenters ( 0187, 0226, 0224, 0236, 0241, 0303) said the rationale used to justify the default and presumptive BART SO 2 emission limitations for coal fired units can be applied to oilfired EGUs. In contrast to coal fired electric generating units, flue gas de sulfurization has not historically been used at oil fired facilities to comply with SO 2 emission limitations. To the commenter's knowledge, there are no existing oil fired steam electric generating units in the U. S. equipped with flue gas de sulfurization for control of SO 2 emissions. The primary reason for this is that the vast majority, if not all, of the states limit the sulfur content of the oil that may be burned at EGUs as part of their SIP strategy for complying with the SO 2 NAAQS.

Commenter 0314 suggested setting the presumptive BART as a range ( 0.1 to 0.15 lb/ MMBTU) allowing the State to establish a specific level for each plant.

Comment: Three commenters said that presumptive controls may need to differ depending on the location of the source ( 0244, 0252, 0306). Two commenters ( 0244, 0252) said the presumptive control level of 90% for western units is or may be unrealistic. In contrast to the presumptive level proposed by EPA of 90% SO 2 reduction, WRAP has conducted analysis that the presumptive level of control for a scrubber in the west should be set at 85%. Commenter 0306 said EPA needs to consider the cold climate of certain northern states when determining presumptive BART for SO 2. Cold weather can cause icing of very wet stacks which can lead to safety hazards and functional 175 problems. Reheat of the stack may be necessary, to reduce or eliminate icing problems. Reheating the flue gas by bypassing some of the gas around the scrubber will reduce overall SO 2 removal. The proposed presumptive BART may not be achievable in cold climates without overly burdensome costs.

Comment: Nine commenters said that the proposed control levels must account for the type of scrubber in place ( 0171, 0210, 0228, 0229, 0241, 0250, 0253, 0254, 0256). Commenter described the need for site specific analyses to address scrubbers in place ( 0210, 250). Commenters ( 0241, 0254) added that EGUs that currently have SO 2 controls should not be forced to meet the presumptive level unless a full BART analysis is undertaken which shows that incremental visibility and cost effectiveness justify forcing controlled EGUs to meet the more stringent limit. Others ( 0229) said that the recent addition of controls, even if reductions fall below the presumptive levels, should be cause for allowing states to screen such a BART eligible source out early in the evaluation process. Commenter 0254 said the ability to upgrade existing scrubber units will be limited and for many, particularly dry scrubbers, the presumptive 95% reduction level will not be achievable. In addition, many of these units have been installed recently, e. g., since the 1990 Clean Air Act Amendments, and requiring these facilities to re visit large investments in controls, after such a short interval, imparts an excessive burden on those businesses.

Commenter 0253 said that in largely focusing on the capabilities of state of the art scrubbers installed on new generating units and ignoring the feasibility or, in many cases, infeasibility of retrofitting such technology on existing units, EPA's analysis is substantially flawed. EPA overlooks the fact that, in many instances, it is technically infeasible to upgrade early generation scrubbers to meet the 95% control level that may be achievable with current state ofthe art scrubbers.

Commenters ( 0228, 0256) said the SO 2 presumption should not apply to sources that have already installed and are operating scrubbers, or to sources that have committed to specific levels of scrubbing through consent orders or agreements with EPA or a state regulatory agency. If a source can demonstrate a reduction in visibility impairment below the specified threshold ( whether that threshold is EPA's currently proposed 0.5 deciview or an alternative level) with less stringent controls, EPA and the states should not impose by default more stringent reduction requirements.

In contrast, one commenter ( 0221) said that under controlled sources ( i. e., those previously retrofitted to meet the 1979 NSP of 70 percent) can meet removal efficiencies of 95% or more. The performance of boilers already using the wet limestone process can be improved through the application of " once through wet FGD technology," such as increasing sorbent, reactivity and other upgrades.

Comment: Eight commenters discussed the role that plant size and/ or capacity should play in applying a default SO 2 control level ( 0206, 0227, 0241, 0253, 0256, 0267, 0271, 0303). Some commenters 176 said that the presumptive limits should not apply to units between 250 and 750 MW ( 0206, 0241, 0303). Commenter 0253 said EPA should clarify that only BART eligible sources would be counted toward the 750 MW cut off. Commenters ( 0206, 0303) added that Congress did not specify similar requirements for smaller plants ( i. e. facilities below 750 MWs). The installation of controls necessary to reduce SO 2 emissions by 90 to 95 percent is more likely to be uneconomical at smaller facilities ( 0206, 0253, 0303). The BART process must be followed for such a determination to be made ( 0241).