Comment 8: Commenter 17801 suggests that the EPA revise the particulate, SO2, and NOX/CO standards for new IGCC EGUs. The EPA proposes total PM as a surrogate for non-Hg metallic HAP. The EPA has chosen a beyond-the-floor MACT limit for total PM for new IGCC units (0.050 lb/MWh) that is neither derived from the IGCC test data obtained from its ICR nor justified from a technology capability assessment specific to IGCC. Relative to the latter point, the EPA cites DOE's 2007 fossil energy study "For example, DOE projects that future IGCC units will be able to meet a PM (filterable) emissions limit of 0.0071 lb/MMBtu..." (0.053lb/MWhr gross output basis also per DOE). DOE also reiterated this expected performance in its 2010 update to its 2007 study. DOE's estimate is also consistent with GE's assessment of IGCC with state of the art particulate control as it will be implemented in future IGCC plants. This performance is based on multiple stages of particulate removal used in IGCC (i.e.,syngas PM scrubbing, sulfur solvent scrubber knockout chamber, final turbine syngas screen and high efficiency turbine inlet air filtration). This level is reliably achievable, reflects the capability of PM control in new IGCC plants, incorporates the variability in day-to-day fuel and operating variation, variability of particulate testing and compares favorably (<50 percent of) with the EPA's 2006 amendments of 0.034lb/MMBtu. Combustion turbines firing syngas are expected to have inherently lower PM emissions than a traditional coal-fired EGU; however, variability and uncertainty of the PM measurement methods as demonstrated in the field result in unreliable measurement results.
Given that the EPA's preferred surrogate for non-Hg metal HAP is filterable particulate, the commenter therefore recommends that the particulate standard for new IGCC EGUs (MACT and NSPS) be set at 0.053 lb/MWhr of filterable PM, or alternatively 0.11 lb/MWhr total PM.
Response to Comment 8: As noted elsewhere, the EPA is revising the limits for new IGCC EGUs.
Comment 9: Commenter 17678 requests that the proposed new MACT floor limit for total PM of 0.050 lb/MWh gross energy output for IGCC units in Table 1 to subpart UUUUU of part 63 be modified to address the two scenarios for duct burners at IGCC plants, syngas-fired and natural-gas-fired. The commenter requests the 0.050 lb/MWh limit be increased to at least 0.068 lb/MWh based on gross energy output from the combined cycle generating unit when operated with duct burners fired with syngas. The 0.068 lb/MWh value is consistent with the calculated emission ceiling for permitted to construct, Texas Clean Energy Project (TCEP) for this operating scenario. The TCEP will be an IGCC plant located in Penwell, Texas. There is not sufficient experience with syngas turbines for manufacturers to guarantee performance in the 0.050 lb/MWh range. The 0.0681b/MWh performance basis proposed, here, was calculated based on the emission guarantees that the commenter was able to obtain for a turbine fired on the syngas expected at TCEP; it is the total PM limit in the TCEP NSR permit. The calculated contributions to the total PM emissions from the turbine, syngas-fired duct burner, and SCR system were approximately 0.038 lb/MWh, 0.02 lb/MWh, and 0.009 lb/MWh, respectively. The commenter assumes for purposes of their comments that the "point of compliance" will be downstream of the duct burners and SCR.
Commenter 17678 requests the 0.050 lb/MWh limit be increased to 0.083 lb/MWh based on gross energy output from the combined cycle unit when operated with duct burners fired by natural gas. Depending on market conditions, the syngas produced at an IGCC unit may have more value as a raw material for producing coproducts than it would have as duct burner fuel. Where that is the case, the economic viability of an IGCC unit would be enhanced by firing the duct burners on natural gas and diverting that syngas to manufacture of a coproduct. The commenter's TCEP air permits are currently based on the use of syngas as duct burner fuel; however, the commenter is currently examining an alternative operating scenario that may result in amendments to the air permits to authorize firing natural gas in the duct burners. Preliminary calculations indicate that the PM limit would need to be set at 0.083 lb/MWh gross energy output when operated with duct burners fired with natural gas. The calculated contributions to the total PM emissions from the gas turbine, duct burner, and SCR system were approximately 0.038 1b/MWh, 0.02 lb/MWh, and 0.025 1b/MWh, respectively.
Commenter 17678 notes that IGCC units are still in their infancy. Funding for them will be very difficult or unavailable; if there is a regulatory limit below the level that can be supported by vendor guarantees. Given the important role that IGCC Units may have in meeting global energy and climate stability goals, the commenter believes it would be a mistake to erect barriers to the implementation of this technology. The EPA can reevaluate the appropriate level for future IGCC Units after demonstration units like TCEP have been built and tested.
Response to Comment 9: The EPA has revised its emission limits for new IGCC EGUs in the final rule as noted below. Commenters are correct in stating that there are little data upon which to base the emission limits. Therefore, the EPA believes it appropriate to base the new-source limits on the permit information provided by commenter 17678. Because the source is a "similar source" as contemplated in section 112(d)(3), and the unit will have to comply with the permit limits when it commences operation, we believe the limits in the permit are appropriate for the new source standards for IGCC units.

                                      HAP
                                Proposed limit
                                 Revised limit
PM (total)
                                 0.050 lb/MWh
                    0.0680 lb/MWh (duct burners on syngas)

                  0.0830 lb/MWh (duct burners on natural gas)
Or

Total non-Hg HAP metals
                                0.000040 lb/MWh

Or

Individual HAP metals

Antimony (Sb)
                                0.000080 lb/GWh

Arsenic (As)
                                0.00020 lb/GWh

Beryllium (Be)
                                0.000030 lb/GWh

Cadmium (Cd)
                                0.00040 lb/GWh

Cobalt Co)
                                 0.020 lb/GWh

Lead (Pb)
                                0.00080 lb/GWh

Manganese (Mn)
                                0.00090 lb/GWh

Nickel (Ni)
                                 0.0040 lb/GWh

Selenium (Se)
                                 0.0040 lb/GWh

Hydrogen chloride (HCl)
                                 0.030 lb/GWh

Or

Sulfur dioxide (SO2)
                                  0.40 lb/MWh

Mercury (Hg)
                                0.000010 lb/GWh
                                 0.0030 lb/GWh

Comment 10: Commenter 17678 believes that there is an error in the proposed Hg limit. The commenter understands, from the EPA's May 2011 correspondence with the UARG, that the EPA acknowledges an error in its conversion of Hg emissions to a common "base" unit. As noted, IGCC units are still in their infancy, and there is not sufficient test data to precisely predict the Hg emissions performance of even the best-controlled IGCC units, other than that IGCC Hg emissions are expected to be much less than those for units that directly burn coal. In its NSR permit application for the Texas Clean Energy Project (TCEP), the commenter proposed to establish a new standard for Hg removal in IGCC units by treating the syngas in catalytic reactors. The catalytic reactor system is expected to achieve greater than 95%t Hg removal using either sulfur-impregnated activated carbon or alumina catalyst. In the absence of actual stack test data, the commenter has had to estimate expected emissions based on engineering estimates of how much Hg may arrive in the syngas routed to the catalytic reactors. Based on these engineering estimates and 95% Hg removal in the catalytic reactors, the resulting Hg emission limit for a state-or-the-art IGCC unit would be 0.003 lb/GWh, which is much less than the Hg emissions for units that directly burn coal.
Again, because IGCC units are still in their infancy, the commenter believes there is not sufficient test data to precisely predict Hg emissions performance. Extreme difficulties in obtaining financing can be expected, if there is a Hg limit below the level that can be supported by engineering estimates. Given the important role that IGCC units may have in meeting global energy and climate stability goals, it would be a mistake to erect barriers to the implementation of this technology. The commenter requests that the Hg limit for IGCC units be initially set at 0.003 lb/GWh or higher. The EPA can reevaluate the appropriate level for future IGCC units after demonstration units like TCEP, which incorporate effective Hg controls, have been built and tested.
Response to Comment 10: As noted above, the EPA has revised its emission limits for new IGCC EGUs in the final rule.4B09 - MACT Floor Results: New Oil - Liquid (Proposed)
Commenters: 17316, 17648, 17760
Comment 1: Commenter 17316 notes that review of Tables 1 and 2 of the rule indicates that the proposed total HAP metals emissions limit for new oil-fired EGUs is actually higher (i.e., less stringent) than the proposed total HAP metals emission limit for existing oil-fired EGUs (0.0004 lb/MWh vs. 0.0003 lb/MWh). The commenter believes it does not seem reasonable, or consistent with MACT procedures, that the limit for new EGUs would be less stringent than the limit for existing EGUs.
The commenter assumes the limit for existing oil-fired EGUs is incorrectly specified in Table 2, as this limit is lower than for the other EGU categories. In any case, the total HAP metals emission limits for oil-fired EGUs should be corrected, or the preamble should explain why the limit for existing oil-fired EGUs is lower than that established for new oil-fired EGUs.
Response to Comment 1: The final new source emission limits for total metals are all equivalent to or more stringent than the corresponding existing source limit.
Comment 2: Commenter 17648 states that the EPA correctly proposes emission limitations for HCl for oil-fired EGUs (a direct emission limitation for HCl from liquid oil-fired units, and an emission limitation for HCl as a surrogate for all acid gas HAP for solid oil derived fuel-fired EGUs). Some have suggested that these emission limitations are inappropriate because oil-fired EGUs are not presently controlling for HCl with add-on controls. Even were this assertion true, it is inapposite to whether or not the EPA must set an emission standard for that HAP. The EPA must promulgate an emission standard for all HAP emitted by sources in a source category, without regard to whether those HAP are controlled with technology. Nat'l Lime, 233 F.3d at 633-34. Chlorine appears in the emissions of oil-fired units on which the EPA has data; irrespective of whether it is a contaminant in the fuel used by these EGUs, or whether the chlorine has another origin, HCl clearly is among the HAP emitted by those EGUs. See 76 FR 25,045. Therefore, the EPA has no discretion to elect not to promulgate an emission standard for HCl emissions from oil-fired EGUs.
Response to Comment 2: The EPA has established HCl and HF standards in the final rule.
Comment 3: Commenter 17648 states that concerns about the applicability of technology to control HCl emissions from oil-fired EGUs are unfounded. There is no technological basis for concluding that control technologies that will control HCl emissions from coal-fired EGUs (whose operation provides, in part, support for the EPA's decision to use HCl as a surrogate for other acid gases for coal-fired EGUs), cannot be applied to oil-fired EGUs. Even more significantly, fuel switching from No. 6 fuel oil to No. 2 fuel oil or to natural gas is a mechanism to reduce HCl. No. 6 fuel oil is the dirtiest fraction in the petroleum refining process, so that contaminants, such as chlorides, in the crude oil are more likely to appear in that fraction. Natural gas does not contain chloride. If a source cannot install add-on controls, it can readily switch fuels to meet the HCl limit.
 Response to Comment 3: The EPA has established HCl and HF standards in the final rule.
Comment 4: Commenter 17648 believes that the EPA has no discretion to promulgate a work practice standard for HCl emissions from oil-fired EGUs. Pursuant to the authority in section 112(h), the EPA may exercise its discretion to promulgate a so-called "work practice" standard only when "not feasible to prescribe or enforce an emission standard," which is limited to situations where "measuring emission levels is technologically or economically impracticable." 42 U.S.C. section 7412(h)(1)-(2); Brick MACT, 479 F.3d at 883-84. Oil-fired EGUs clearly are capable measuring their HCl emissions, as many have done so in the context of data collected for the ICR upon which the emission limitations in this rule rely. Nothing in the emissions control or measurement technology for HCl prevents oil-fired EGUs from determining whether they are complying with proposed emission limitations. Accordingly, the EPA would have no basis upon which it could elect to promulgate standards under CAA section 112(h) in lieu of numerical emission limitations derived consistent with section 112(d).
Response to Comment 4: The EPA has established HCl and HF standards in the final rule.
Comment 5: Commenter 17760 states that the MACT floor for new liquid oil-fired units listed in Table 11 is less stringent than the standard for existing liquid oil-fired units. The new source standard is the limit achieved by the best controlled similar source. This cannot be less stringent than the average emission limitation achieved by the best performing 12% of sources in the category.
Response to Comment 5: The final new source emission limits for filterable PM, HCl and HF are all equivalent to or more stringent than the corresponding existing source limit.4B10 - MACT Floor Results: New Oil - Solid (Proposed)
Commenters: 17817, 19536, 19537, 19538
Comment 1: Several commenters (19536, 19537, 19538) state that the EPA has proposed an HCl standard for new pet coke-fired EGUs of 0.00030 lb/MW-hr. The EPA also determined the MACT floor emission rate in terms of lb/MMBtu to be 2.3618 x 10-5 lb/MMBtu based on the 99[th] percentile UPL. The EPA's determination of the 99[th] percentile UPL HCl emission rate for the best performing source, AES Deepwater, is higher than the three HCl emissions results provided in the EPA's MACT floor spreadsheet. Specifically, the highest HCl emission rate measured at AES Deepwater was 1.9592 x 10-5 lb/MMBtu, yet the EPA's proposed 99[th] UPL value of 2.3618 x 10-5 lb/MMBtu is 20% higher than the highest HCl emission rate measured at this unit. Thus, the EPA's proposed MACT floor value in units of lb/MMBtu fails to reflect the HCl emissions of the best performing unit under the worst reasonably foreseeable circumstances.
In addition, according to the commenters, the EPA determined the HCl MACT floor in terms of lb/MWhr to be 0.00027169 lb/MW-hr, based on the EPA's determination of the 99[th] percentile UPL. Yet, the limit the EPA proposed as MACT is 0.00030 lb/MWhr, which is 10 percent higher than EPA's 99[th] percentile UPL emission rate. The EPA has not provided any justification for going beyond the 99[th] percentile value in its MACT floor determination for HCl.
The commenters state that the EPA's proposed new source MACT standard for HCl reflects a very poor heat rate and thermal efficiency for new units. Specifically, the proposed 0.00030 lb/MW-hr limit reflects an assumed heat rate of 12,702 Btu/kW-hr and a thermal efficiency of 26.8% when compared to the EPA's 99[th] percentile MACT floor value of 2.3618 x 10-5 lb/MMBtu. A heat rate of 12,702 Btu/kW-hr is higher than the annual average of the existing coal-fired EGU fleet. New pet coke-fired EGUs should be able to operate at much lower heat rates, in line with coal-fired EGUs, i.e., closer to 9,000 Btu/kW-hr (approximately 38% thermal efficiency). Based on the EPA's floor emission rate of 2.3618 x 10-5 lb/MMBtu, that means the EPA's proposed new source MACT floor limit should not be any higher than 0.00021 lb/MW-hr assuming a heat rate of new pet coke-fired units of 9,000 Btu/kW-hr. Commenters state that the EPA's proposed HCl limit for new pet coke-fired units fails to be at least as stringent as the best controlled similar source.
Response to Comment 1: We have discussed our approach with regard to rounding elsewhere in this document. We used the data provided through the 2010 ICR for both the input- and output-based limits; we did not convert one to the other. Therefore, the heat rates used in the calculations are those provided by the individual companies for their EGUs. Partly based on comments received, we have made corrections to the data as appropriate. We believe that our MACT floor analyses comply with the statute and with applicable case law.
Comment 2: Several commenters (19536, 19537, 19538) state that the EPA's proposed new source SO2 MACT surrogate limit fails to reflect the MACT floor. The EPA has proposed a new source SO2 MACT limit of 0.40 lb/MW-hr as a surrogate limit for acid gas HAP if the EGU has some sort of FGD system installed. Similar to the SO2 surrogate limit for existing pet coke-fired EGUs, the EPA's proposed new source SO2 limit fails to reflect the lowest HCl-emitting unit and it also fails to reflect the SO2 emissions of the lowest SO2-emitting pet coke-fired EGU.
The best controlled source for HCl was determined by the EPA to be the AES Deepwater EGU, but the best controlled source for SO2 was determined by the EPA to be the Hanford Unit 1A EGU. These differing determinations of the best controlled similar source for HCl and SO2 emissions adds to the argument that SO2 is not likely a good surrogate pollutant for HCl or other acid gas HAP at pet coke-fired EGUs
Response to Comment 2: In setting emission limits for HCl (and for SO2 which is an alternative emission limit available to those units with operational flue gas desulfurization controls), the EPA determined the top performing unit for HCl emissions using the available data from the 2010 ICR. Similarly, the EPA set the alternative emission limit for SO2 using the same approach. The EPA continues to believe that HCl and HF, due to their chemical and physical properties, will be controlled at least as well, and likely much better than, SO2 using flue gas sulfurization technologies. The EPA also believes that it is unreasonable to expect a 1:1 correlation between best performers for HCl and SO2 (i.e., the top performer for SO2 is not necessarily the best performer for HCl and the 25[th] best performer for HCl should not be expected to be the corresponding 25[th] best performer for SO2). Differences in the rank order for the best performing HCl and SO2 can be affected by normal fuel composition and operational variability and in measurement uncertainties at the very low levels achieved by the very best performing units.
Comment 3: Several commenters (19536, 19537, 19538) state that the EPA's proposed SO2 MACT limit for new sources of 0.40 lb/MW-hr has flaws with respect to the existing source SO2 surrogate MACT limit. First, the EPA's 99[th] percentile UPL SO2 rate of 0.36175 lb/MW-hr is higher than the highest SO2 rate measured at the Hanford Unit 1A EGU of 0.2678 lb/MW-hr. Second, the EPA's proposed MACT limit of 0.40 lb/MW-hr is 10% higher than the EPA's 99[th] percentile UPL emission rate, and the EPA has not provided justification for going beyond the 99[th] percentile UPL emission rate in setting the MACT floor limit. Third, in comparing the EPA's proposed SO2 limit of 0.40 lb/MW-hr to its 99[th] percentile UPL MACT floor emission rate in terms of lb/MMBtu of 0.03755 lb/MMBtu shows that the EPA's 0.40 lb/MW-hr limit reflects a poor heat rate for new sources of only 10,652 Btu/kW-hr. New sources should be able to achieve heat rates of 9,000 Btu/kW-hr, meaning a more appropriate new source SO2 emission limit that reflects the EPA's determination of SO2 MACT floor would be 0.0338 lb/MWhr.
Response to Comment 3: The EPA thanks the commenter for providing the suggested emission limitations. However, the EPA has explained the rationale and methodology that was used in setting emission limits and believes that the methodology is consistent with that used in the development of other NESHAP and with the statute. Also, for clarification, the EPA did not assume a heat rate in setting emission limits, but rather used the actual data that was provided.
Comment 4: Commenter 17817 states that they received a PSD construction permit in December 2011 and are at risk of becoming subject to the EPA's new-unit standards for purposes of the EPA's proposed EGU MACT Rule. Based upon the commenter's extensive testing experience of unit 1, the commenter asserts its belief that the proposed MACT standards will foreclose development of new solid-fueled units, including their permitted unit 2 EGU. The permitted unit is not a major source of HAP.
A report by an industry consultant, filed in this docket, highlights the methodological problems with the EPA's proposed rule and demonstrates why he believes new coal-based generation cannot be built under the proposed rule. The consultant, who has decades of relevant experience and nearly a full decade of experience on Commenter's Unit No.1, worked with the commenter extensively to permit their new unit. The report is attached to the comment letter.
Response to Comment 4: The EPA has reassessed new source emission limits and is finalizing limits that have changed slightly since proposal. The EPA is aware of at least one coal-fired unit that is currently meeting all new source limits.
Comment 5: Several commenters (19536, 19537, 19538) state that the EPA did not evaluate in any meaningful way control technologies or methodologies that would enable units to achieve HCl emission reductions beyond the EPA's proposed HCl and SO2 floor emissions rates for pet coke-fired EGUs. The EPA's justification was that they could not identify any control technologies that could achieve greater emission reductions of HAP than the control technologies they expected to be used to meet MACT. However, according to commenters, the EPA has not adequately demonstrated that there are no beyond-the-floor control techniques or methodologies that could be implemented to further reduce acid gases to the maximum achievable level.
Commenters state that the EPA's new source HCl MACT floor determination for pet coke fired EGUs is based on the AES Deepwater unit's HCl emissions, and this unit is a conventional boiler with a wet scrubber. This unit also has among the lowest fuel chlorine content of any of the seven pet coke-fired EGUs tested in the EPA's ICR, in some cases two orders of magnitude lower than other pet coke-fired units. Although the unit has a wet scrubber that is typically among the most effective in removing HCl emissions, the pet coke chlorine content used at this unit also contributed to its HCl emission rate. This is especially clear given that the wet scrubber appears to only be removing 91 percent of the HCl emissions at best, based on the data provided regarding chlorine in the coal and the minimum HCl emission rate. Yet, there are numerous coal-fired EGUs achieving over 99% HCl removal. Thus, the best performing pet coke-fired EGU determined by the EPA does not reflect the maximum degree of HCl emission reduction that can be achieved at these units.
According to commenters, beyond-the-floor technologies for acid gas HAP at coal-fired EGUs can be applied to pet coke-fired EGUs. The EPA already determined that an HCl emission limit of 0.0001 lb/MMBtu is cost effective.
Commenters assert that the EPA must evaluate beyond-the-floor technologies for acid gases at pet coke-fired EGUs and ensure that its proposed MACT standards truly reflect the maximum degree of acid gas HAP emission reduction that is achievable at these units.
Response to Comment 5: The EPA stands by the original justification and is not finalizing a beyond-the-floor emission limit consistent with the proposed rule. The EPA has explained the rationale and methodology that was used in setting emission limits and believes that the methodology is consistent with that used in the development of other NESHAP and with the statute. 4B11 - MACT Floor Results: Other
Commenters: 17197, 17265, 17283, 17402, 17620, 17621, 17622, 17627, 17648, 17675, 17677, 17681, 17696, 17705, 17711, 17714, 17716, 17730, 17735, 17736, 17754, 17758, 17775, 17776, 17790, 17800, 17812, 17813, 17817, 17818, 17837, 17851, 17852, 17878, 17914, 17929, 18015, 18034, 18039, 18437, 18444, 19536, 19537, 19538
1. General.
Comment 1: Commenters 17197 and 17705 note that the proposed existing unit HCl MACT floor limit is much lower than the new unit limit, which is already exceedingly low.
Commenter 17197 notes that the HCl limit for existing coal-fired units is 0.020 lb/MWh although the new unit limit is 0.30 lb/MWh. The proposed existing unit limit is 15 times more restrictive than the new unit limit. This discrepancy is also present for both coal unit subcategories. Similarly, the surrogate SO2 emission limit for existing coal-fired units is shown as 0.20 lb/MMBtu, although the new unit limit is higher at 0.4 lb/MMBtu. The proposed Hg limit for existing coal-fired units (>= 8,300 Btu/lb) is 0.008 lb/GWh although the new unit limit is 0.000010 lb/GWh. The proposed new unit limit is basically unachievable and 800 times more restrictive than the new existing limit. The commenter understands the Hg emission limit issue may have been addressed and that the EPA has recalculated the existing coal-fired unit (>= 8,300 Btu/lb) Hg limits at 0.008 lb/GWh or 1.2 lb/TBtu, and that the revised new unit limit is 0.002 lb/GWh. It is not clear whether these limit discrepancies are the result of MACT determinations emission limit miscalculations or are simply typos. If discrepancies are due to miscalculation, the commeter is concerned that these errors may invalidate or alter the preamble's assumptions and justifications that all proposed rule provisions are necessary and appropriate.
Commenter 17705 believes it is highly probable that the proposed new source limits are so low that vendors will not guarantee performance of control equipment.
Response to Comment 1: The EPA has reassessed all emission limits in response to comments. The final HCl emission limit for new coal-fired plants is more stringent than the limit for existing units.
2. Output-based standards.
Comment 2: Commenters 17283 and 17620 support the EPA's setting of output-based standards for the proposed rule. Commenter 17283 believes that reverting to an input-based standard that does not incorporate efficiency into the regulatory limit is an inappropriate step if the regulatory goal is to both reduce emissions and promote efficiency.
Commenter 17620, however, notes that the EPA has not developed the MACT floors using net output-based data and is not proposing to promulgate mandatory output-based MACT limits. Rather, it has converted the results of MACT data for sources selected as best performing units on an input-basis and proposes to offer sources the option of complying with either the input-based limits or the converted limits. In addition, Commenter 17620 adds that the uncertainties associated with past and future determinations of the unit's net heat rate are larger than potential efficiency gains that may result from adoption of output-based standards for existing units using common factors. The commenter believes that the most significant effect of offering existing sources the option of output-based standards based on a pre-determined conversion factor will be a reduction in the effectiveness of the rule, rather than any measureable improvement in efficiency of generation.
Commenter 17620 adds that, for existing units, the principal effect of an "optional" output-based standard would be to establish a class of "winners" that qualify for lower emission rates based on their currently existing condition, rather than providing an incentive to reduce emissions. Since facilities with low efficiencies (high heat rates) may elect to comply with the input-based limit, the only "losers" in this process are the members of the public who are subjected to higher emissions of HAP than would otherwise be the case. For this reason the commenter asserts that the EPA should not allow an output-based standard as an option for existing sources to employ, but should set standards based on net output emissions data. This could be accomplished at the next review of the standard, as required by the CAA every 8 years.
Comment 3: Commenter 17808 supports allowing existing sources the option to comply with the input or output-based standards, and recommends that the EPA maintain this flexibility in the final rule. Commenter 17844 states that whether allowable emissions are based on gross or net MWh should be clearly identified in all the emission tables. The commenter recommends limits for new units be based on net MW/hr.
Response to Comments 2 - 3: Incorporating efficiency into the output based limit is not consistent with the EPA's understanding of section 112 statutory guidance on the setting of emission limits. The EPA agrees that it may consider net output based limits in the next review of the standard.
Comment 4: Several commenters (17620, 17818, 17800) state that the EPA has acknowledged that it does not have data reflecting net electrical output of the "best performing units" at the time that the testing was conducted and that it identified the "best performing units" on an input basis. Moreover, commenters' review of the EPA's data reveals serious discrepancies in the conversion of rates from lb/MMBtu to lb/MWh. The EPA proposes output-based limits for most pollutants and categories that reflect a heat rate of 10,000 Btu/kWh, slightly less than the average heat rate for all coal-fired EGUs, and substantially less than the average heat rate for oil-fired EGUs. However, there are a number of proposed limits where the imputed heat rates are unrealistically low, although others are far higher than experienced in practice. These variations occur both within and across subcategories and are far, far larger than any efficiency improvements that one might anticipate. For Hg, the imputed heat rates range from 6,667 Btu/kWh to 18,181 Btu/kWh across the five proposed subcategories; although within Subcategory 5, imputed heat rates for different metals range from 1,818 Btu/kWh to 17,500 Btu/kWh. Commenters recommend that the EPA revisit each of its proposed output-based limits and resolve the apparent discrepancies.
Commenter 17818 believes that the EPA should ensure that such "correction factors" are representative of a reasonably achievable value and are utilized in a consistent fashion through all of the calculations associated with this proposed rulemaking. It is also the commenter's opinion that the EPA should provide discussion in the rulemaking regarding the process used for the determination of the selected "correction factors." Without a consistent, achievable value being used as the target heat rate, there will be little opportunity or incentive for owners and operators to pursue the alternate limit, thereby negating the EPA's effort to promote energy efficiency. Commenter 17818 also questions the methodology used for determination of these new limits for oil-fired units when the results are such that the proposed emission rate limit for new units are higher than the proposed emission rate limit for existing units. Although the commenter understands that there have not been new oil-fired units constructed in some time to provide a great deal of data, it seems counter-intuitive that new units would be allowed to be constructed with emission rate limits higher than existing units.
Comment 5: Commenter 18034 states that the EPA's MACT floor analysis for the proposed output-based PM surrogate limit for new coal-fired EGUs is not correct. The power output used to determine the output-based PM emissions limit for new EGUs appears to include both units at the site (AES Hawaii  -  ORIS Code 10673) which artificially reduces the projected output based emissions by a factor of two. The EPA must reevaluate output-based emission calculations for the facility and all others to ensure that similar error have not been made evaluating the MACT floor values for other pollutants.
Response to Comments 4 - 5: The EPA did not convert input based limits to corresponding output based limits using conversion factors or assumed heat rates. Rather, the EPA used actual data that was supplied by facilities in the 2010 ICR.
Comment 6: Commenter 17620 notes that the EPA suggests that it may be too difficult for existing sources to measure their net electrical output. For this reason the EPA proposes to adopt an output-based standard based on gross electrical output, which would only provide incentives for efficiency improvements at part of the facility. The commenter finds it difficult to accept the assertion that most EGUs do not know their net electric output at all times, as well as the assertion that it would be technically challenging for EGUs to measure net electric generation at the point of connection to the grid. Measuring electric generation at the bus bar would appear to be far less technically challenging than providing accurate determinations of the quantity and heat content of the fuel being consumed at any point in time. The commenter suggests that this issue an important matter that deserves a fuller evaluation. The EPA should identify the specific information that it relies on in rejecting net output-based standards and state why, especially for new sources, measuring electric delivery to the point of interconnection to the grid (which is where commercial sales of electricity generally occur) is technically infeasible. Commenter 18444, however, believes that the EPA's selected format for the standard of "lb/MWh gross" should be changed to "lb/MWh net" to encourage improvement in overall energy efficiency at new electric utility plants. Use of a net MWhr-based standard should in the long run lead to lower Hg emissions from the electricity generation sector per a given amount of useful electricity production.
Response to Comment 6: The EPA appreciates the comment and understands the potential benefit of net output based limits. The EPA will finalize gross output based limits but may reassess the format of the emission limits during the 8-year review required by CAA section 112(d)(6).
Comment 7: Commenter 17620 suggests that, if sufficient reliable data were available, the EPA could establish a single net output standard in this rulemaking and not promulgate an input-based limit at all. The EPA could develop the list of "best performing units" initially in terms of the emissions per unit of net electric output of the unit at the time of the test, rather than using a conversion factor for all units at the end of the calculating process. As data to support such an approach are not in the record, the commenter recommends an alternate approach to encourage and reward efficiency improvements, without increasing overall HAP emissions. The commenter understands that, as part of its NSPS rulemaking for GHG emissions from EGUs, the EPA may develop standardized procedures for quantifying efficiency improvements at regulated EGUs. The commenter recommends that the EGU MACT standards be adopted as input-based standards in this rule and that the EPA establish procedures by amendment of this rule that would allow a conversion to an output basis on a plant-specific basis and adjustment of the applicable limit, based on demonstrated efficiency improvements in individual units. In this way, a unit that demonstrated an actual improvement in its efficiency would receive a benefit without adverse impact to the public.
Response to Comment 7: The EPA appreciates the comment and understands the potential benefit of net output based limits. The EPA will finalize gross output based limits but may reassess the format of the emission limits during the 8-year review required by CAA section 112(d)(6).
Comment 8: Commenter 17620 recommends that the conversion factor for new units be based on a heat rate that is consistent with the decision of the Agency in its GHG rulemaking as to the minimum acceptable generating efficiency for such units. In this way, a unit that demonstrated an actual improvement in its efficiency would receive a benefit without adverse impact to the public.
Response to Comment 8: The EPA did not convert input based limits to corresponding output based limits using conversion factors or assumed heat rates. Rather, the EPA used actual data that was supplied by facilities in the 2010 ICR.
3. Ultra-low sulfur oil.
Comment 9: Commenter 17620 notes that the EPA has proposed a total metals limit for oil-fired EGUs that includes Hg, in lieu of a PM limit, based on compliance through fuel analysis. Commenter supports this concept for ultra-low sulfur oil, but not for more polluting grades of oil that can be expected to have high levels of particulate organic matter. Commenter further notes that the EPA's proposed fuel analysis incorporates the 90[th] percentile of fuel variability and have commented elsewhere that the compliance obligation should be consistent with the assumptions used in establishing the standard.
Response to Comment 9: Fuels analysis is not included in the final rule. Compliance with the total metals or filterable PM limits is established through use of CEMS or stack testing.
4. New source limits too stringent.
Comment 10: Commenters 17621 and 17735 state that many of the proposed MACT limits for new generating units are below the measurement capabilities of the test methods used in the ICR and the CEMS that are proposed for compliance monitoring. Commenters state that in their opinion the principal reason for this is that the EPA's procedure for determining the MACT floor for new units selected outlier and erroneous emissions values, and did not take into account method performance with actual stack gas samples.
Commenter 17735 notes that, for example, a unit burning bituminous coal with a nominal chloride content equal to 750 ppm will require approximately 99.95% removal to comply with the proposed new source HCl standard. The commenter states that, in their experience, no APCD vendor will guarantee 99.95% removal, which would be necessary to secure financing. Moreover, the proposed HCl standard is 66 times more stringent than the proposed standard for existing units even though all of the existing units selected for acid gas testing in the EPA's 2010 ICR used either wet or dry scrubbing systems. As Roberson states, "There is no plausible explanation for how a new scrubber can be 66 times more efficient than the average of the best performing 12% of existing scrubbers."Similar control efficiencies for Hg would also be required, again with no guarantees available.
Comment 11: Commenter 17800 states that in determining the MACT floor for new units, the EPA selected outlier and erroneous emissions values, and did not take into account method performance with actual stack gas samples. Some limits as proposed may not be attainable because pollution control equipment suppliers will not guarantee performance that achieves the emission limits. One example is the Hg limit for new sources. Limits set for new units do not represent the best performing unit. The commenter states that the EPA has chosen the strictest limit irrespective of the unit. No one existing unit is currently meeting these limits. Hence, according to the commenter, these limits are unrealistic and not representative of the existing source population. This is not the intent of CAA section 112.
Comment 12: Commenter 17914 states that as an equipment supplier, they are unable to offer commercial guarantees on the ability of their control equipment to control HCl or Hg emissions to the levels identified for the new coal category, which means facilities would have to control fuel chlorine and Hg levels. The commenter considers this to be impractical in many cases, so the detection limits and accuracy of the test method should be taken into consideration when proposing low emission values. The commenter believes the EPA should collaborate with the National Institute of Standards and Technology (NIST) to initiate NIST protocol for traceability of Hg generators for Hg concentrations less than 0.51 Jg/m3. NIST should be capable of providing support in the range of 0.0  -  1.01 Jg/m3 with defensible set points at nominally 0.1, 0.25, 0.5 and 1.01 Jg/m3. The commenter points out that for new units, calibration standards would need to be 1-2 orders of magnitude lower than this, but emission rates below 0.5 lb/ TBtu are considered difficult to detect reliably. The commenter explained the compliance with the rule will most often be measured by continuous emissions monitors with a minimum reliable detection limit of 0.005 lb/GWh.
Response to Comments 10 - 12: As stated elsewhere in response to comments, the EPA has revised the new source standards based on new data and data corrections and we maintain that the new source standards are all based on units that are similar to units that would be constructed in the future. In addition, we have determined that at least one existing source complies with all the new source limits, thus, the standards are achievable. Even if no source was meeting all of the new source limits, we maintain the standards would still be valid because we established the standards based on the available information from existing sources. We respond to the remaining comments in response to other comments elsewhere in this RTC and the preamble to the final rule.
5. Need for additional controls.
Comment 13: Commenter 17622 is confident that the proposed existing unit emission limits for total PM, HCl and Hg can be simultaneously met, and reliably measured and monitored, based on 30-day rolling averages; however, additional controls may be required.
Response to Comment 13: We agree that the final rule standards can be met and that there are reliable measurement methodologies available to assure compliance.
Comment 14: Commenter 17621 states that the fuel oil metals analysis methods are not sensitive enough to support compliance monitoring for limited-used oil EGUs.
Response to Comment 14: As noted elsewhere in this document, the final rule does not include fuel analysis requirements.
Comment 15: Commenter 17696 is concerned that the standards proposed by the EPA for oil-fired units may be unachievable, and thus applicability of these standards is particularly inappropriate to units that are infrequently operated. The EPA claims confidence with respect to the limits it is proposing for oil-fired units, yet the ICR data set does not provide adequate information to specify controls that can be expected to actually comply with the proposed limits. As detailed under comments submitted to this docket by the Environmental Energy Alliance of New York, the majority of parameters do not have a positive relationship between fuel and concentration measurements and those that meet that criterion have a large percentage of results that could not meet the MACT limit using a fuel specification. Thus the proposed standards do not reflect reductions in HAP that are actually achievable. Requiring controls to achieve standards that may be unachievable, particularly on units that are seldom operated, is not appropriate. The commenter urges the EPA to provide an exemption from these standards for limited use oil-fired units, i.e., oil-fired units with capacity factors equal to or less than 10%. In the event that the EPA does not pursue an exemption, the commenter also urges the EPA to alternatively pursue only work practice standards for a limited use oil-fired unit subcategory.
Response to Comment 15: The EPA has established a limited use oil-fired EGU subcategory in the final rule for units with capacity factors of up to 5%. We believe the 5% threshold is sufficient to address the units that are truly used only to maintain grid reliability. We are establishing work practice standards for this subcategory as explained elsewhere in this document.
6. LEE.
Comment 16: Commenter 17696 believes that the LEE cutoff should be set at 29 lb/year for Hg as proposed in section 63.10005(k), to qualify as a LEE for Hg and thus avail itself of less burdensome Hg performance testing and monitoring requirements, an existing unit must demonstrate that it emits less than 10% of the Hg emission limit or less than 22.0 pounds lb/year. According to the EPA, the 22.0 lb/year LEE cutoff represents a threshold approximately equivalent to 5% of the nationwide Hg mass emissions from coal-fired EGUs and was chosen because "comments received on CAMR indicated that 5 percent of the total mass was a reasonable cut point." 76 FR 25032.
The commenter supports the LEE provisions but believes the LEE cutoff should set at 29.0 lb/year, an equally reasonable cut point that matches the low mass emitter Hg monitoring cutoff in CAMR and the low mass emitter Hg monitoring cutoff that several states have adopted, including Illinois, 35 Ill. Admin. Code section 225.240(a)(4). (See, e.g., Colorado (5 Colo. Code Regs. section l 00 l-8, Reg. No.6, Part B, Section VIII.B.l0); Michigan (Mich. Admin. Code R. 336.2160); Montana (Mont. Admin. R. 17.8771(12))) A LEE cutoff of 29.0 lb would eliminate conflicts and confusion with low mass emitter provisions in existing state Hg programs and significantly reduce compliance costs and burdens for the additional qualifying units without adversely affecting compliance assurance with the EGU NESHAP Hg emission limits or materially increasing the number of potential qualifying LEEs. Given the many other costly burdens that the rule would impose, the benefit of LEE to a qualifying unit is not insignificant.
Response to Comment 16: The agency reviewed the commenter's suggestions, and one of the LEE eligibility criteria in the rule has been revised from 22.0 to 29.0 pounds of Hg per year. The agency finds the result of consistency with existing state regulations outweighs the two percent difference in nationwide Hg mass emissions, from 5% to 7%, for LEE eligibility. Of course, obtaining LEE status would not negate compliance with the applicable Hg emissions limit (e.g., an EGU owner or operator must continue to meet the EGU's mercury emissions limit, whether or not LEE status is granted).
7. Percent reduction standards.
Comment 17: Commenter 17716 suggests that the EPA should offer percent reduction limits for fuel-related emissions (filterable PM, metals, HCl/HF) as an option in addition to the currently proposed lb/MMBtu or output standards. The following equation should be used to establish the alternative percent reduction floor values each fuel-related pollutant:
%Rfloor=(1−Efloor/Efuel)x100
where:
%Rfloor= Percent reduction floor value for fuel related pollutant
Efloor= lb/MMBtu emission floor value for pollutant
Efuel= Average lb/MMBtu fuel concentration for pollutant based on all available fuel emissions data reported by the sources in the emissions floor analysis.
This approach assures that the alternative percent reduction value represents the average emission achieved by the best performing units as required by section 112 of the CAA.
Comment 18: Commenter 17716 notes that the EPA has used an "either/or" lb/MMBtu (or mass/output-based) standard coupled with a percent reduction alternative approach in a number of previous rules. For example, the current version of subpart Da NSPS requirements for EGUs as well as the revised version that the EPA proposed along with the EGU MACT Rule contains lb/MMBtu (or output-based) standards along with optional alternative percent reduction standards. The EPA has also proposed "either/or" mass and percent reduction options for NESHAP standards (e.g., 40 CFR Part 63, subpart FFFF).
According to the commenter, the EPA states that they "considered using a percent reduction format for Hg," but percent reduction limits alone would not provide adequate flexibility. The EPA's stated "desire to promote, and give credit for, coal preparation practices that remove Hg and other HAP before firing" would not be realized if the percent reduction option is based on on-site post-beneficiation fuel analysis because that would mean the percent removal values would simply be conservatively low.
The commenter states that although the EPA stated that it did not have "the data necessary to establish percent reduction standards" for a mine-to-stack based reduction scheme, sufficient fuel analysis data along with stack test results collected under the ICR are available to establish an on-site removal value. The EPA also expressed concerns that using a percent reduction limit would be inconsistent with the Brick MACT Court decision. But that concern is alleviated by the fact that the alternative percent reduction would be based on the emissions achieved in practice by the top performing sources, is therefore is consistent with the requirement of the statute.
Comment 19: Commenter 17737 requests that percent reduction should be available as an alternate to a numerical emission rate and could be established to be based on percent reduction from the boiler inlet Hg concentration in a manner similar to the procedure under 40 CFR 60 subpart Da. The percent reduction could be set at 91%, which is the same level as the EPA expects to be achieved nationwide. The numerical limit may be difficult if not impossible to achieve should a source be limited to using coal with a high Hg concentration (above 13 lb/TBtu). Switching coal sources may not be possible due to the presence of long term coal contracts, mine-mouth configuration, or boiler design. If the Hg coal concentration increases over time, the commenter may not be able to meet the standard with available technology and could be faced with curtailment as the sole compliance option. This concern could be somewhat alleviated; however, if the compliance averaging time were to be on a 12-month rolling basis.
Commenter 17737 states that ICR data shows some EGUs would achieve a lower emission rate with 75-85% removal than others with removal rate in excess of 91%. By not including a percent removal, the EPA is penalizing those EGUs that are not able to obtain coals with relatively low Hg content.
Commenter 17737 states that the EPA's primary rationale for not allowing the percent reduction option is that it may discourage or complicate the use of coal washing as a compliance technology. This would only be the case if the EPA elected to adopt a percent removal standard in lieu of a numerical limit.
Comment 20: Commenter 19032 states that the EPA should propose percent reduction alternatives to the numerical MACT limits.
Response to Comments 17 - 20: The EPA continues to believe that a percent reduction standard is not appropriate. As we stated at proposal and in response to comments, we question the viability of a percent reduction standard under CAA section 112 given D.C. Circuit precedent. Equally important, however, the EPA does not believe it has sufficient data to establish a percent reduction standard that would accurately capture the proper percent reduction for the various standards. Commenters expressed reasons for wanting a percent reduction standard that only reinforce the legal concerns associated with such a standard, and we are not sure how we would justify a percent reduction based on projected estimates of reductions that are not established in the same manner as the standards in the final rule (i.e., those reductions estimated for purposes of the RIA). For all these reasons, we decline to establish a percent reduction standard in the final rule.
8. Heat input-based standards/energy output-based standards.
Comment 21: Commenter 17730 notes that the EPA has proposed to use heat input based standards for existing sources and energy output based standards for new sources. The commenter believes that the EPA should continue to use heat input based emission standards for new and existing sources. The EPA should seek an alternative method for promoting energy efficiency at coal-fired electric utilities, but should not mandate it in this rule.
Response to Comment 21: The EPA appreciates the suggestion; however, the EPA has decided to finalize emission limits in the formats that were present at proposal.
Comment 22: Commenter 17730 states that the EPA should consider allowing sources to meet either a heat input based emission standard and an energy output based emission standard. The EPA should also consider allowing sources to make energy efficiency upgrades to the source to improve energy efficiency without further regulatory penalty. This approach could give sources the incentive necessary to implement energy efficiency improvements, and create some operating head-room to better ensure ongoing compliance with the proposed requirements.
Response to Comment 22: The EPA has provided input/output based options for existing sources and an output only option for new sources. Specific incentives for energy efficiency improvements are not part of the MACT program.
9. Other.
Comment 23: Commenters 17711 and 17852 support the EPA's determination that MACT limits and NSPS PM/Opacity limits are not necessary for natural gas-fired utility boilers. Commenters state that limiting the regulatory burden for gas-fired boilers acknowledges that PM and HAP emissions from gas-fired boilers are minimal and are not technically feasible to control or cost effective to regulate. Commenter 17852 also states that the option to integrate combustion turbines and/or fuel cells with steam generating units is another good way to reduce emissions. The commenter agrees that it is appropriate to provide the option for regulated entities to integrate fuel cells or combustion turbines in the definition of steam generating unit for the permitting of a unit. However, the commenter also states that if an owner chooses to connect a fuel cell or CT to a steam boiler to use waste heat to improve efficiency, they should be able to elect to consider them an integrated unit for compliance purposes.
Response to Comment 23: The EPA appreciates the comment and the suggestion. Comments specific to the NSPS portion of the rule are addressed in a separate document.
Comment 24: Commenter 17817 expresses concern that proposed emission limits are set below method detection limits.
Response to Comment 24: As described elsewhere in this document, the agency has taken steps to ensure the rule's emissions limits are not below method detection limits.
Comment 25: Commenter 18437 questions the assumption that all coal types may be used with available control technologies, as fuel switching or fuel blending can be very expensive.
Response to Comment 25: The EPA does not understand the comment. The fact that all available control technologies are available for all coal types implies that coal switching would not be required. The fact that fuel switching or blending can be expensive does not affect the availability of controls. In any case, the EPA does not dictate how sources will comply with the final standards and sources are able to implement any mechanisms to comply, including fuel switching.

4C01 - Beyond-the-Floor Analysis: ACI control on Existing Coal
Commenters: 17383, 17712, 17813, 17815, 17843, 17876, 17930, 18033, 19114, 19214, 19536, 19537, 19538
Comment 1:.Commenters 17815 and 17930 state that the proposed beyond-the-floor Hg limit for low rank coal units is based on too little data and is technically and economically unattainable. The EPA's proposed beyond-the-floor Hg limit for low rank coal units is based on only three samples from a single test held at only one unit, which is not enough data to develop such limit, especially as more data was available for this unit in the database. Although this one unit may have been able to achieve the proposed limit during this one test, the three samples are not adequate to demonstrate the long-term ability of this unit to meet that limit consistently, let alone the long-term abilities of the top 12% of all low rank coal units to meet that limit consistently. Given Texas lignite's particularly high rates of variability of Hg concentration, and the inability to minimize this variability, commenters assert that the EPA is obliged to have more, not less, data to support the proposed beyond-the-floor Hg limit for low rank coal units. Commenter 17930 adds that the EPA's decision to require a beyond-the-floor limit for lignite units does not comply with section 112(d)(2) of the CAA.
Comment 2: Several commenters (17383, 17712, 17813, 17876) argue that the beyond-the-floor Hg MACT was improper and not in accordance with the CAA. These commenters base their argument on the fact that the standard must be achievable in practice and that this has not been demonstrated. Commenter 17813 specifically states that the limit is based on too little data (only three tests held at one unit for the lignite Hg limit) and is technically and economically unattainable. Commenter 17813 also states that the EPA is obligated to also obtain more data to support the achievability of the limit proposed for new units.
Comment 3: Commenters 17813 and 17876 state that the ACI technology cannot and will not deliver results that approach the degree of control or consistency that the EPA alleges in order to reach the proposed beyond-the-floor limit for lignite. Commenter 17813 also states that the EPA has not taken into account the effect on energy requirements and reliability if lignite units are closed due to inability to meet the proposed limit.
Comment 4: Commenter 19114 argues that the EPA fails to provide any support for the claim that beyond-the-floor is appropriate for unit burning coal <8,300 But/lb with a furnace height-to-depth ratio of 3.82 or greater and should rely on MACT floor for subcategory 2 units. The commenter also states that the cost effectiveness in terms of $/lb-Hg removed is inaccurate in terms of real-world implementation and meaningless unless the EPA can justify that the benefits exceed the cost. Further the commenter states that health benefits of only addressing a small subset of mercury emissions is much less than claimed and the projected costs are an order of magnitude high and the total benefit from all mercury reductions under the rule.
Comment 5: Commenter 17925 states that the EPA's beyond-the-floor proposal for Hg limits for coal units burning coal less than 8300 Btu/lb with a furnace height to depth ratio of 3.82 or more should be withdrawn. The EPA has listed a beyond the floor limit for Hg for units designed to burn coal that is less than 8,300 btu/lb. The beyond-the-floor Hg MACT limit is listed at 4 lb/TBtu. It is unclear how the EPA determined this limit as achievable when the most recently permitted Gulf Coast lignite unit case-by-case MACT analysis performed in 2008 demonstrated that 9.2 lb/TBtu was the appropriate MACT limit for this type of unit. Since 2008, the commenter does not believe there have been significant changes in Hg control technology for lignite fired coal units.
Comment 6: Commenter 17724 states that the beyond-the-floor Hg MACT for lignite is improper and not in accordance with the CAA. The proposed Hg MACT for lignite establishes a floor level of 11.0 lb/TBtu and a beyond-the-floor limit of 4.0 lb/TBtu. The EPA's basis for proposing the beyond-the-floor limit is that it believes ACI installed on units in this subcategory could achieve the beyond the floor standard. The EPA's "supposition and belief" cannot serve as a rational basis for determining MACT beyond-the-floor limits. The statutory requirements are clear, the MACT standard must be achieved in practice and as such the proper limit for this subcategory is 11 lb/TBtu.
Comment 7: Commenter 17689 notes that the proposed Hg MACT for this coal rank establishes a floor level of 11.0 lb/TBtu and a beyond-the-floor limit of 4.0 lb/TBtu. The EPA's basis for proposing the beyond the floor limit is that it "believes" the same technology, ACI, installed on units in this subcategory "could" achieve the beyond the floor standard. The EPA's suppositions and beliefs cannot serve as a rational basis for determining MACT beyond the floor limits. The statutory requirements are clear. The MACT standards must be achieved in practice, and thus the proper limit for this subcategory is 11.0 lb/TBtu.
Comment 8: Commenter 17904 states that the EPA's beyond-the-floor analysis must be reassessed because the EPA's MACT floor for Hg emissions for low rank fuel boilers was not calculated correctly. In support of their argument, the commenter cites the following two court cases Cement Kiln Recycling Coalition v. EPA, 255 F.3d 855, 872 (D.C. Cir. 2001) ("Because EPA will have to set new floors, we need not address the . . . additional arguments [regarding] whether to set beyond-the-floor standards pursuant to CAA section 7412(d)(2) . . . .") and Northeast Md. Waste Disposal Auth. v. EPA, 358 F.3d 936, 955 (D.C. Cir. 2004) ("the Agency's beyond-the-floor determinations cannot be evaluated if, as we have concluded, the MACT floors themselves were improperly set.").
Comment 9: Commenters 17722 and 17775 have concerns about the 4.0 lb/TBtu standard that the EPA has proposed. This standard is based on a "beyond the floor" analysis that estimated the level of Hg emissions a lignite unit could achieve if it installed ACI. Commenter 17775 states that the EPA's estimate is too low and that the EPA should revisit the wisdom of its "beyond-the-floor" approach. Commenter 17775 adds that should the EPA return to a traditional MACT floor analysis, the MACT floor should be based on the average performance of the best five units, not the best two as the EPA did in developing its proposed MACT limits. Commenter 17722 generally agrees that the proposed Hg emission rate is achievable during normal operation, but that the EPA has not provided sufficient justification for this decision.
      Response to Comments 1 - 9: The EPA notes that all of the low rank virgin coal units for which data were submitted in response to the 2010 ICR were meeting the Hg floor limit (11 lb/TBtu). Four of the units have activated carbon injection systems installed and three of the four units tested were also meeting the beyond-the-floor Hg emission limit of 4.0 lb/Tbtu.  Those three units were achieving control levels of greater than 95 percent (fuel to stack). Two other low rank virgin coal units meet the beyond-the-floor limit with no installed Hg-specific control technology. The other low rank virgin coal units that are not currently meeting the beyond-the-floor emission limit do not have installed Hg-specific controls (e.g., activated carbon injection).  An analysis of the Hg content of the fuel used during the ICR testing suggests that control in the range of 80  -  90 percent (fuel to stack) would be needed to meet the beyond-the-floor limit of 4.0 lb/TBtu. Two facilities met the beyond-the-floor emission limit by achieving 84 percent control with no Hg-specific control technology. Another unit achieved 75 percent control, also with no Hg-specific control technology.
The EPA believes that the decision to require a beyond-the-floor limit for low rank, virgin coal units does comply with CAA section 112(d)(2). Further, the EPA believes that its analysis is consistent with that done for new sources where a single data set is also used. The EPA believes that its beyond-the-floor analysis is appropriate, including the costs analyzed. The EPA's cost analysis is meant to serve as an average recognizing that some EGU's costs will be more and some less; EGUs whose costs are higher are not exempted from the regulation. As with all MACT standards, sources can comply with the final standards through any combination of controls and other mechanisms to reduce HAP emissions. Based on the data available, EPA believes that the beyond-the-floor limit is currently being achieved by at least five units in the subcategory, which indicates that the limits are achievable and achieved in practice.
To the extent one commenter questions our costs assessment, we note that the cost effectiveness numbers in the beyond the floor analysis are consistent with other numbers used to justify regulating mercury emissions under CAA section 112(d). We are not required to specifically consider the value of the benefits as the commenter implies. Comments related to compliance time, reliability of the electrical system, and retirements are addressed in the preamble to the final rule and elsewhere in the record.
Comment 10: Commenter 19214 supports the proposed beyond-the-floor limit for existing EGUs because of the limited data available.
Response to Comment 10: The EPA appreciates the commenter's support.
Comment 11: Several commenters (19536, 19537, 19538) state that the EPA did not adequately justify why it did not evaluate a beyond-the-floor Hg MACT limit for new sources in the <8,300 Btu/lb subcategory. The commenters state that because of the factors that the EPA applied to reflect variability of the best performing unit in the <8300 Btu/lb subcategory, the EPA's proposed MACT floor limit fails to reflect the emissions that have been demonstrated to be achievable at the best controlled similar source in this subcategory. The commenters also state that the EPA's RIA suggests that 90% Hg removal is achievable and cost effective and that such control should be readily achievable at new coal-fired EGU designed for fuel with heat value less than 8300 Btu/lb. The commenters also state that the proposed beyond-the-floor Hg MACT limit for <8,300 Btu/lb subcategory for coal-fired EGUs does not reflect the maximum degree of Hg emission reductions achievable. The commenters reference the control option for lignite burning EGUs to reach below the proposed limit, such as ACI, Hg oxidation and addition of a baghouse with use of halogenated sorbents, blending with subbituminous coal.
Response to Comment 11: The EPA believes the research cited above with regard to the use of ACI for such units supports a beyond-the-floor limit for existing sources, particularly when coupled with the facts that, based on the data available, at least five EGUs in the subcategory are meeting the limit and the cost per ton of controlling Hg to the beyond-the-floor level has been determined to be reasonable. However, we do not believe that the research can, at this time, support a beyond-the-floor limit for new sources in the subcategory. The basis for the new-source limit was an EGU with ACI and a fabric filter so the EPA does not believe at this time that further reductions are warranted. In addition, the EPA does not believe that blending of coal ranks, or fuel switching, should be a mandated compliance option at this time for units in this subcategory given the uncertainty of the costs of implementing such an approach for all sources in the subcategory, though we believe some sources will voluntarily employ fuel blending/switching to comply with the final existing source standards.
Comment 12: Commenter 17914 states that the EPA has failed to include the cost of a baghouse in its beyond-the-floor analysis. According to the EPA, in order to comply with the proposed EGU MACT rule, units will either fuel switch to a lower Hg fuel or retrofit air pollution controls. The EPA calculated control costs on a dollar per pound of Hg removed basis and determined the average cost of control at $22,496 /pound was acceptable for application of a beyond-the-floor Hg limit for the < 8,300 Btu/lb unit category.
The commenter's Dolet Hills unit would be considered in the < 8,300 Btu/lb unit category. This unit is approximately 719 MW, burns lignite fuel and employs an ESP and a wet scrubber as air pollution controls in series. Because of this treatment configuration, the commenter believes that this unit can meet the proposed MACT PM limits but may not meet the Hg limits. Preliminary testing on similar lignite-fired units indicates that activated carbon injection or similar Hg removal technologies may have limited effectiveness for Hg removal. Therefore, for this unit, it is likely that a baghouse and ACI will be required to meet the Hg limit. According to the EPA's $/lb analysis, no PM control costs were included because of the assumption that these controls would be required anyway to meet the PM portion of the MACT. In the case of Dolet Hills (and possibly many others in this coal subcategory), this assumption is not valid. Cleco reviewed the EPA's methodology to determine Hg removal costs and applied a financial analysis of Dolet Hills Hg cost. For add-on controls, The commenter has used the EPA's CueCost program to determine the capital and operational and maintenance (O&M) costs for the ACI, baghouse (with an air to cloth ratio of 6), and additional fans required because of the baghouse pressure drop. These costs were annualized and a $/lb cost was developed. A similar analysis was performed for a fuel switch to PRB coal and associated ACI controls. The cost estimates are included [See 17925_Table_1.doc].
Although the EPA does not mention an unacceptable cost threshold for the beyond-the-floor basis, the commenter's costs are estimated to be significantly higher than the $22,496/lb average cost estimated by the EPA. If the EPA does decide to keep the beyond-the-floor category, individual units that can demonstrate significantly higher cost of control should be allowed to be exempted from the beyond-the-floor limits.
Response to Comment 12: The cost estimates that are referenced represent what the EPA believes will be the most likely control strategy. The costs will vary at specific locations as different facilities choose different technologies and strategies for a variety of reasons. Some facilities will need to install FF in order to meet the PM emission limit. Some other facilities may choose to install FF in association with implementation of dry sorbent injection (DSI). Still other facilities may not need to install a new FF downstream of an existing ESP for Hg control, but may choose to do so in order to preserve fly ash sales from the primary PM control device. This is no different from other emission limits where the costs will vary by facility. The EPA sees no need to create exemptions from the beyond-the-floor limits and, in any case, we do not believe such exemptions are consistent with the statute. We have determined that the beyond-the-floor level of control is achievable for all sources in the subcategory and commenters have provided no data that indicate our conclusion is in error.
Comment 13: Commenter 17930 opposes the EPA's beyond-the-floor requirement for Subcategory 2 because it believes variability among mines and units will make compliance with the limit virtually impossible, making the limit unattainable and legally invalid. The commenter argues that the data used by the EPA was not indicative of long term ability to meet the EPA's beyond-the-floor Hg limit because it is based on three samples from a single test at one unit and did not include all test data available for the unit. The commenter believes that the EPA has provided no foundation for its statements that ACI is not being fully maximized. The commenter believes that it is unprecedented and contrary to CAA section 112 for the EPA to set a beyond-the-floor limit based on what they consider to be unfounded speculation. They also believe that the benefits are not justified due to the high costs of compliance. They further note it may be possible to come close to meeting the beyond-the-floor limits when ACI is performing at peak efficiency and the lignite contains uncharacteristically low Hg, but that it is unlikely that most sources would be able to comply with the limits due to lignite variation and ACI control performance variability. The commenter recommends that the EPA keep the proposed Subcategory Hg limit of 11.
Response to Comment 13: The EPA understands that coal is a heterogeneous geologic material and that there will be variability for Hg and other HAP. In setting the emission limit floors, variability (operational, process, fuel, etc.) was accounted for using a methodology that was explained in the proposed rule preamble and in response to comments, and the approach is consistent with the methodology that was used to account for variability in emission limits for other MACT rules. Further, compliance for this rule requires the emission limit to be met as a 30-day rolling average when sources demonstrate compliance on a continuous basis, which further accounts for process operational and fuel variability. The EPA maintains that the final standards adequately account for variability.

4C02 - Beyond-the-Floor Analysis: Halogens for Hg removal
Commenters: 17914
Comment 1: Commenter 17914 states that as a supplier of activated carbon systems, as well as wet and dry FGD systems, the commenter has supplied many AQCS systems with Hg emission guarantees. The commenter also supplies a halogen addition system which has been incorporated with our activated carbon and FGD technologies to optimize the Hg control performance of the combined AQCS trains at several EGUs. The commenter agrees that the ICR database already reflects the performance enhancements associated with the use of halogen addition and that no further beyond-the-floor analysis is necessary.
Response to Comment 1: The EPA thanks the commenter for confirming that the ICR database already reflects the performance enhancements associated with the use of halogen.
4C03 - Beyond-the-Floor Analysis: Activated carbon bed for Hg removal for IGCC (syngas) units
Commenters: 17721, 17801, 17807, 18483, 19214
Comment 1: Commenter 17721 states that the EPA has not justified a beyond-the-floor limit for Hg for new IGCC units. The EPA proposed a beyond-the-floor limit for Hg of 0.0002 lb/GWh (per the revised values posted to Docket EPA-HQ-OAR-2009-0234 on May 19, 2011) for all new IGCC units regardless of coal type. The limit was set to be the same as the new source limits for coal-fired units designed for coal with a heat content of greater than 8,300 Btu/lb. The EPA's choice of the beyond-the-floor Hg limit for new IGCCs is not derived from IGCC test data from the ICR and the EPA has not provided adequate justification of its decision from a technology capability assessment.
According to the commenter, ACI for Hg treatment of coal-derived syngas is not in use in any operating IGCC plant today, nor can it be used in the same fashion as it is used at conventional coal-fired units. An additional concern of commenter is the ability to reliably and accurately measure Hg at the proposed level of 0.0002 lb/GWhr. For example, the EPA's Method 30 B was prescribed by the EPA for the ICR and as a qualifying test method for compliance testing has a MDL of 8 x 10-8 lb/MMBtu. The MDL is more than 3 times higher than the proposed limit, and there is no commercially available CEMS that have demonstrated capability at the required concentration levels. If the required sampling times exceed a 30-day compliance period, utilizing a sorbent trap for monitoring may not be a viable option either. EPRI has also determined that "[t]he method adequacy determination for new coal-fired EGUs >= 8,300 Btu/lb also applies to the limits for new IGCCs, where those are the same as for coal EGUs. According to EPRI, mercury cannot be measured at the limit for new IGCCs by any of the proposed methods." The commenter recommends that the EPA review and, revise its floor level for Hg for coal of >8,300 BTU/lb to be consistent.
The commenter states that because of lack of data, the EPA did not propose beyond-the-floor MACT limits for existing IGCC units. The EPA also lacks data with respect to new IGCC units, yet they proposed beyond-the-floor MACT limits for new IGCC sources. The EPA's limits for new IGCC sources are based on beliefs, predictions, projections and design target assumptions. The limits from the 2007 DOE Report referenced in the preamble are based on environmental target assumptions. These IGCC environmental targets were chosen to match EPRI design basis from their Coal Fleet for Tomorrow Initiative. EPRI notes that these were design targets and were not to be used for permitting values. The EPA has simply not justified their process for going beyond-the-floor for new IGCC units. Without sufficient justification, the EPA's actions are unsupported.
Comment 2: Commenter 17801 provides background on GE products that reduce emissions from EGUs. GE developed the IGCC process, in which an economically advantaged fuel such as coal is converted to low heating value, high-hydrogen gas for power generation using a process called gasification. IGCC is a particularly useful technology because it provides a cleaner way to utilize the abundant coal resources in the U.S. and around the world.
Gasification, as it is applied in IGCC, is a partial oxidation process whereby finely ground coal or other solid carbonaceous feedstock is injected (either dry or as a water/slurry mixture) with an oxidant (either oxygen or air) into a high pressure reactor. The partial oxidation process results in high (typically 2,400° F) temperature sufficient to convert the coal's carbon and hydrogen to gaseous components. These components further react within the reducing environment in the gasifier to produce a synthesis gas (syngas) consisting primarily of carbon monoxide (CO) and hydrogen (H2).
Gas cleanup begins in the gasifier. Due to its high operating temperature, non-volatile metals and inorganic components are melted, the majority of which is separated from the gas and quenched to produce an inert, glass-like slag that is useful for construction and concrete aggregate. The high temperature and reducing environment also provides complete destruction of organic HAP. Subsequently, the syngas is cooled to recover sensible heat, processed through water scrubbing to remove particulate and chlorides, and passed through a carbon bed to remove Hg and other volatile metal contaminants. The syngas is then cooled further prior to scrubbing in an acid gas removal system (AGR) that removes the remaining acid gas components. A sulfur recovery unit then produces a useful commercial byproduct either as pure sulfur or sulfuric acid.
IGCC's process for removal of syngas contaminants is highly differentiated from conventional coal. It can appropriately be considered as a coal refining process. Cleanup processes are applied only on the concentrated fuel and at high pressure and concentrations. This provides favorable kinetics and mass transfer for cleaning processes at a volume that is factor of 300 or more lower than post-combustion cleanup of flue gas. This synthetic coal gas is then used as the primary fuel for advanced, clean burning and highly efficient gas turbines.
Thus, IGCC uses coal as fuel but does so in a "cleaner" way. IGCC can also be viewed as the two-stage combustion of an opportunity feedstock. In this process, the feedstock is first partially combusted in a reactor or gasifier, and then the combustion is completed in the gas turbine.
Comment 3: Commenter 17807 notes that in the proposed rule the EPA refers to existing IGCC units and sulfur-impregnated activated carbon bed as a possible beyond-the-floor technology. The commenter does not believe that sulfur impregnated activated carbon bed technology should be used as beyond-the-floor utility MACT for IGCC units because there is no detailed data to support the effectiveness of the technology. The effectiveness of this technology would be highly variable depending on fuel usage. In addition, the current or past performance of a sulfur-impregnated activated carbon bed has not been documented with any detailed data. Based on the commenter's literature review on this matter, any claim suggesting 90% Hg removal for this technology is not supported by detailed data sufficient to make such a determination. Therefore, the commenter requests that the EPA not include the sulfur-impregnated activated carbon bed technology as beyond-the-floor MACT for IGCC power plants.
Comment 4: Commenter 18483 states that when determining whether or not to establish standards "beyond the floor," the CAA requires the EPA to take into consideration "the cost of achieving such emission reductions, and any non-air quality health and environmental impacts and energy requirements." For the new source IGCC limit, the EPA decided to establish standards more stringent than the best performing source, but did not provide the public with any analysis of the factors which must be considered if the Agency elects to do so. Further, the EPA has not presented any data that the proposed limits are actually achievable. The only information that the EPA cites is a DOE projection for future IGCC emissions (excerpted below).
      "Because of advances in technology, EPA does not believe that even these permitted levels [referring to Duke Energy Edwardsport IGCC currently under construction] are representative of what a modern IGCC unit could achieve. The emissions from IGCC units are normally predicted to be similar to or lower than those from traditional pulverized coal boilers. For example, DOE projects that future IGCC units will be able to meet a...Hg emissions limit of 0.571 lb/TBtu." [76 FR 25049]
Interestingly, the proposed new source IGCC limits are as much as 500 times more stringent than the DOE projections. It seems incomprehensible that the EPA would set a limit based on this rationale. Without the proper analysis, the EPA should base the new source IGCC limits on the best performing IGCC.
Comment 5: Commenter 19214 states that IGCC facilities are capable of much lower emissions of criteria, GHG, and Hg emissions than conventional pulverized coal boiler technology. The commenter has been compiling data from IGCC permit applications they have received and present the following to the EPA in a table. The commenter believes that use of IGCC, (with carbon capture and sequestration) should be encouraged, and that MACT limits should be set that reflect the capabilities of current IGCC technology.
Response to Comments 1 - 5: As discussed elsewhere in this document, the EPA has revised its analyses for new-source MACT for IGCC units.4C04 - Beyond-the-Floor Analysis: Activated carbon injection for Hg removal
Comment 1: Commenter 12050 states that one consequence of the various regulations at the state level is that Hg emissions control technologies such as ACI have been successfully implemented by a number of utilities across the nation. According to a 2009 study by the Government Accountability Office (GAO), these control technologies are enabling sources to obtain Hg emissions reductions as high as 99%. Moreover, reductions on the order of 90% have been achieved by plants firing different types of coal (i.e., bituminous, subbituminous, lignite) and employing a variety of configurations. Indeed, according to data supplied by utilities as part of the EPA's ICR for the rule, commercially operating plants firing each of the different types of coal have in fact applied ACI to control Hg emissions.
Response to Comment 1: The EPA agrees that ACI options and other control technologies are available for facilities burning bituminous, subbituminous, and lignite coals.
Comment 2: Seveal commenters (19536, 19537, 19538) states that, for bituminous coal-fired units with ESPs, the TOXECON configuration has been used with great success. This technology uses ACI and a downstream polishing baghouse. The E.C. Gaston Unit 3 facility is an example of an EGU that achieved high levels of Hg control with activated carbon in the TOXECON configuration. This unit is a PC boiler burning bituminous coal that is equipped with a hot-side ESP and a downstream compact hybrid particulate collector (COHPAC) fabric filter. It measured little to no Hg removal across the ESP or across the COHPAC before injection of activated carbon, but with ACI, Hg removal ranged from approximately 30 to 90 percent+ depending on the sorbent used and the injection concentration.
The use of halogenated sorbents has similarly been shown to be effective at removing Hg at both subbituminous as well as lignite-fired power plants. Testing of halogenated sorbents was conducted at the subbituminous coal-burning Holcomb Station Unit 1 in Garden City, Kansas. The halogenated sorbent injected upstream of the dry scrubbers achieved greater than 90 percent removal at an injection rate of 4.0 lb/MMacf.
As previously stated, the EPA assumed brominated activated carbon would be used in its cost analysis for the Hg MACT. Brominated Powdered Activated Carbon (B-PAC(TM)) is a halogenated sorbent that has been tested at least at seven different power plants, including four full-scale tests. Hg removal rates ranged from 70% to 98% across a wide variety of coal and configurations and at low sorbent injection rates.
The level of Hg removal achievable with ACI is generally based on two factors: the carbon injection rate and the particulate control device(s). With respect to the ACI rate, the amount of Hg removed typically increases with an increase in the amount of activated carbon injected, up to a point. The primary impediment to higher amounts of sorbent injection are simply the costs of the sorbent. Regarding the particulate control device, Hg emissions testing experience has shown that fabric filters are more effective in removing Hg than ESPs, because the buildup of sorbent on the bags provides more avenues for Hg adsorption as the flue gas passes through the baghouse and also because baghouses provide longer gas residence times in comparison to an ESP. A lower cost option to installation of a full-scale baghouse is to install a COHPAC, which is a polishing baghouse added downstream of an existing ESP.
In projecting costs for ACI to achieve 90% control in its IPM policy case run, the EPA assumed a higher carbon injection rate for units with ESPs as compared to baghouses. Further, the EPA assumed installation of a fabric filter was required for EGUs in three scenarios: 1) EGUs with ESPs that cannot handle the increased particulate loading from the ACI, 2) when flue gas conditioning is needed with the ESP, and 3) when PRB coals are burned.
The pollution controls needed to achieve a 90% reduction in Hg at each EGU will provide numerous benefits to public health and the environment, not only in reduced Hg and in reductions in the myriad of health and environmental impacts that Hg poses, but also in reductions of fine particulates, which adversely impact public health and cause regional haze, the reductions of metal HAP, among other pollutant reductions that a stringent MACT rule will result in. The EPA's analysis shows these extensive environmental improvements, with the EPA's projections of the net benefit of the MACT rule estimated to be $48 to $130 billion based on 2007 dollars. Those benefits strongly suggest that a beyond the floor MACT level of Hg control representing 90% removal would be appropriate, under the governing legal standard.
Response to Comment 2: The EPA is aware of the successful implementation of the TOXECON configuration, which offers several advantages for facilities that choose to implement it. Overall, we believe that there are numerous control technology/strategy options available to meet the final Hg emission limit. Several of these available control technologies were being implemented by the 2010 ICR "best performing" units for Hg emissions. The Hg emission limits that were set using that available data are projected to reduce nationwide Hg emissions from EGUs by approximately 90 percent.
4C05 - Beyond-the-Floor Analysis: Other
Commenters: 16122, 17402, 17620, 17768, 17801, 17813, 17846, 17852, 17904, 17930, 18421, 18423, 18487, 19536/19537/19538, 18023
1. Support for beyond-the-floor limits for coal-fired EGUs designed for less than 8,300 Btu/lb.
Comment 1: Commenter 17620 supports the EPA's proposed limits because they will lead to significant Hg emission reductions, but believes that many of the assumptions underlying the calculation of certain MACT floors are unsupported and/or inappropriate.
Response to Comment 1: The EPA has reviewed the calculations used to set MACT floors and believes that the emission limits are supported and appropriate.
2. Opposition to beyond-the-floor limits for new IGCC units.
Comment 2: Commenter 18023 disagrees with the EPA's decision to set a beyond-the-floor limit for new IGCC units. Commenter 18023 states that the EPA must consider the cost, health, and environmental impacts, and energy requirements before establishing any "beyond-the-floor" standards. The commenter notes that the EPA stated in the preamble to the proposed rule that the agency lacked the information upon which to base the costs and non-air quality health, environmental, and energy impacts (see 76 FR 25049). The commenter argues that the EPA's failure to conduct such a review is a violation of the CAA.
Comment 3: Commenter 17801 argues that the EPA incorrectly based the EGU MACT requirements solely on the design, operation and performance that is representative of traditional coal plants equipped with conventional air pollution control as applied to flue gas. The commenter argues that IGCC is fundamentally different from the combustion of coal in that pollutants are removed pre-combustion versus post-combustion, and requires less water, consumes fewer reagents and produces useable byproduct that avoids the large volumes of waste product compared to a traditional coal plant. The commenter claims that IGCC can achieve Hg removal efficiencies of 95% or higher, and that the CO2 generated is in a relatively concentrated stream that could be captured and used to enhance oil production, or otherwise sequestered. The commenter believes IGCC is a better technology for coal power generation than conventional coal-fired plants; however, the EPA failed to provide the necessary technical analysis to support its beyond-the-floor evaluation for the new source MACT limits in subpart UUUUU. The commenter believes that the EPA's failure to complete the proper technical evaluation resulted in uncertainty and lack of clarity regarding IGCC operation, monitoring, testing and alternative compliance options.
Response to Comments 2 - 3: The EPA has adjusted the Hg emission limit for IGCC units in the final rule. The Hg emission limit for such units is no longer based on a beyond-the-floor analysis.
3. Support for EPA's decision not to adopt beyond-the-floor limits for all EGUs.
Comment 4: Commenter 17402 believes that the EPA has properly exercised its discretion in declining to set beyond-the-floor requirements for all EGU subcategories.
Response to Comment 4: The EPA acknowledges the comment.
Comment 5: Commenters 17402 and 17813 agree with the EPA's decision that fuel switching should not be used to set beyond the floor standards. Commenter 17402 agrees with the EPA findings that (1) the expense of requiring coal-to-gas fuel switching would be unreasonable given the limited emission reductions that would be achieve, and (2) that coal-to-gas fuel switching is infeasible. This commenter notes that the EPA's decision that coal-to-gas fuel switching is not cost effective is consistent with past EPA decisions that more stringent beyond-the-floor standards are not cost-effective when costs exceed $3,500 per ton of HAP removed.
Commenter 17402 also notes that requiring fuel switching for all EGUs would run contrary to the stated U.S. energy policy of safeguarding fuel diversity. The commenter believes that fuel diversity is crucial to electricity production because no individual fuel can provide the energy to meet all of the U.S.'s electricity needs. They further note that fuel diversity protects the economy from fuel unavailability, sudden price shocks, and changes in regulatory practices.
Commenter 17402 believes that the EPA's decision not to require coal-to-gas fuel switching is supported by case law and cites Sierra Club v. EPA, the D.C. Circuit in which the court upheld the EPA's refusal to require copper ore switching as a beyond-the-floor standard for primary copper smelters, in part because of the unpredictable availability of cleaner ore (See Sierra Club v. EPA, 353 F.3d 976, 988-89 (D.C. Cir. 2004). The commenter agrees with the EPA's conclusion that coal-to-gas fuel switching is not a viable option for all EGUs because natural gas pipelines are not available in all regions of the U.S. The commenter further notes some sources located in large metropolitan areas may have difficulty in obtaining a dependable supply of natural gas either because of inadequate infrastructure or limited supply.
Commenter 17813 notes that the San Miguel power plant in Texas does not have the infrastructure (e.g., rail line, rail unloading stations, coal transport areas) to begin burning other types of coal and that local jobs in nearby lignite mines would be lost and the local economy hurt if the EPA required fuel switching. This commenter also states that the EPA's cost estimates for facilities to switch to other coal-types is incomplete because it does not include infrastructure costs such as dust collection, conveyors, fire protection, ventilation, ESP performance and water cannons.
Commenter 17402 believes that the EPA's determination not to require fuel switching as a beyond-the-floor emission limit is supported by the significant adverse impacts on non-air quality health, environment, and energy that would result from retrofitting EGUs and constructing new natural gas pipelines.
Response to Comment 5: The EPA acknowledges comments supporting the determination not to require fuel switching as a beyond-the-floor emission limit.
Comment 6: Commenter 17402 agrees that the EPA properly rejected the option of using multiple controls (e.g., multiple scrubbers) to set beyond the floor limits. Commenter 17402 agrees with the EPA's determination multiple controls would not be cost effective. The commenter argues that where a control device achieves 98% reduction, a duplicate control would only achieve an additional reduction of around 1.5%. The commenter notes that the estimated cost of duplicate ESP could be greater than $10,000 per ton removed.
Commenter 17402 states that duplicate controls would also result in secondary energy and environmental impacts. Operating duplicate controls, this commenter notes, will require an additional 2 to 3% of plant electricity output beyond required for existing controls, which would result in increased GHG and NOX emissions. The commenter further notes that duplicate controls would cause a number of non-air quality environmental impacts, such as increased waste generation and additional water quality impacts that result from increased mining.
Commenter 17402 states that Utility MACT floor standards already require state-of-the-art control technology and that there are no additional technologies that would allow greater emission reductions. This commenter notes that the D.C. Circuit has upheld the EPA's decision to not set beyond-the-floor emission standards where the EPA does not have sufficient data for quantification of the costs or benefits of a particular emission reduction program (see Sierra Club v. EPA, 167 F.3d 658, 666 (D.C. Cir. 1999) and Sierra Club v. EPA, 353 F.3d 976).
Response to Comment 6: The EPA acknowledges comments supporting our decision to reject the option of using multiple controls in series as a beyond-the-floor emission limit.
4. Disagreement with EPA's decision not to adopt beyond-the-floor limits for all EGUs.
Comment 7: Multiple commenters (16122, 17768, 17846, 18487, 19536, 19537, 19538) disagree with the EPA's decision to not adopt beyond-the-floor limits for all EGUs. These commenters believe the proposed EGU MACT violates the CAA by not setting beyond the MACT floor standards where they are achievable and failing to provide evidence that a more stringent standard is not achievable. Commenter 18487 urges the EPA to set floors that reflect the actual performance of the best performers in this industry, and conduct a beyond-the-floor analysis sufficient to ensure that the standards demand the maximum achievable reduction in hazardous air pollution.
Response to Comment 7: The EPA is required to establish MACT floors based on actual data and the agency considers the data it has at the time it proposes and establishes the emissions standards. The EPA is not authorized to consider costs or other factors when establishing the MACT floors which are based on the levels "achieved" by existing sources. See CAA section 112(d)(3). After the EPA establishes the MACT floors, we must determine whether standards beyond-the-floor are achievable taking into consideration the additional costs and non-air quality health and environmental impacts and energy requirements of further HAP emission reductions. See CAA section 112(d)(2). In making that determination, the agency generally considers whether the incremental reductions that may be achieved with a standard stricter than the MACT floor are reasonable in light of the statutorily mandated considerations. The EPA must also consider the controls and other practices (e.g., coal washing) that best performing sources employ to achieve HAP emission reductions to determine the additional steps that may be taken to further reduce HAP emissions.
For example, a best performing unit that employs coal washing (a common industry practice), a baghouse, and a scrubber and it is currently meeting the existing source standards may have to install ACI to achieve additional Hg reductions. The agency then determines if the costs and non-air quality health and environmental impacts and energy requirements associated with ACI are reasonable to achieve additional reductions greater than the floor limit. In the proposed rule, the EPA determined that it was not reasonable to go beyond the floor for most HAP and most subcategories because the additional reductions would be low in almost all cases because the MACT floors already achieve about 90% reductions or greater of HAP emissions. The EPA concluded that the suite of controls necessary to achieve all the floor standards would mean that multiple controls in series was likely the only viable option to achieve additional reductions and that level of cost would not be reasonable to achieve the relatively small level of additional reductions. The commenters are correct that the EPA did not quantify the costs of taking these additional actions, but the agency explained that we could not determine how much additional HAP would be reduced based on the installation of those controls because the control efficiencies of the controls is not generally known for controls at above the MACT floor levels. The EPA does know the costs of additional controls, and also knows the best case level of additional reductions (less than 10%), and, based on these facts, it is reasonable to conclude that the additional costs and other considerations argue against establishing a beyond-the-floor standard. The EPA believes that it has fulfilled the CAA mandate with regard to its beyond-the-floor analyses as set forth in the proposed rule and explained further below in response to additional comments.
The commenters also appear to take issue with the manner in which the agency establishes the floor in this comment. The EPA explained elsewhere in this document and in the proposed rule that it is reasonable to account for variability in establishing the MACT floors because the standard is supposed to represent the level of control achieved in practice over varying operating scenarios and HAP emissions vary for any number of reasons. Commenters' assertion that the beyond-the-floor level of control for Hg should be based on the average emissions before the agency accounts for variability is not legitimate because the agency does not believe that level of control is achieved in practice as contemplated by the statute. Instead, we believe that sources would likely have to install duplicate controls for small additional reductions of Hg and other HAP. We do not believe that approach is reasonable considering the additional cost of taking such action.
Comment 8: Several commenters (19536, 19537, 19538) argue that because of the EPA's adjustments for variability, EGUs can and do achieve reductions well in excess of the MACT standards. The commenters believe that CAA requires the EPA to investigate whether methods or techniques are available to and to justify its standard by "taking into consideration" costs, reductions achieved, non-air quality environmental impacts, and energy requirements. The commenters argue that the EPA has provided no substantive discussion of those criteria to justify its standards, has failed to provide an analytic basis for its limits, and has used inconsistent and arbitrary rationales for its decisions. The commenters believe the EPA's rationale for setting beyond-the-floor Hg limits for units designed for coal of less than 8,300 Btu/lb, but not for other types of EGUs based on availability of technology and lack of data to evaluate cost effectiveness was inconsistent.
Response to Comment 8: The EPA believes its MACT floor analyses are consistent with the statutory requirements of CAA section 112 and with the Court's interpretations of the statute. We believe that we have reasonably accounted for variability in the analyses as provided by the Court's decisions. We also disagree that we have been inconsistent and arbitrary in the rationales or analyses.
Comment 9: For existing EGUs burning bituminous and subbituminous coal, Commenters 16122 and 17846 state that the EPA has not adequately supported its assertion that going beyond the MACT floor is not achievable because the EPA could not identify HAP emissions reduction approaches that could achieve greater emissions reductions of HAP than the control technology combination(s) (e.g., FF, carbon injection, scrubber, and GCP) that is expected to be used to meet the MACT floor levels of control (and that are already in use on EGUs comprising the top performing 12% of sources). Commenters 16122 and 17846 state that the EPA failed to provide any analysis of the types of controls that the top 12% of performers used during the EPA's 2010 information collection request. Without an analysis of the specific types or extent to which such Hg emission control technologies were actually being used at the time of the ICR, these commenters believe the EPA has no basis for its assertion that further reductions are not achievable.
Response to Comment 9: The EPA has confirmed the controls in-use for the top 10 EGUs in each of the HAP groups (i.e., Hg, acid gas, PM). Confirmation of the controls in-use for these sources reaffirms the fact that the EPA cannot identify any HAP emissions reduction approaches that could achieve greater emissions reductions of HAP other than to include the control technologies necessary to comply with the MACT floor in combination (e.g., multiple FFs or scrubbers). The presentation of the types of controls that the top 12% of performers used during the EPA's 2010 ICR is included on the MACT Floor Analysis spreadsheets. Furthermore, the EPA directed sources in the ICR to conduct the HAP emissions testing during normal load conditions using the control devices as required by their title V permits so the agency believes it is reasonable to conclude that the emission controls were functioning normally. In any case, the EPA is required to base standards on the information available at the time. The EPA will never have a perfect data set and the EPA must make reasonable assumptions about the data it has when determining whether a beyond-the-floor standard is achievable consistent with CAA section 112(d)(2). Thus, the EPA has considered the data and maintains that reductions are not achievable except as otherwise indicated, which is not achievable once costs are taken into consideration.
Comment 10: Commenter 16122 states that the CAA requires the EPA to set MACT standards based on what is achievable rather than setting a standard on what has been achieved. The commenter notes that the EPA's beyond-the-floor analysis is based solely on data collected for the 2010 ICR and that much of these data represents the emissions achieved by EGUs that were unconstrained by any Hg control requirements. The commenter notes that the data ignores inexpensive modifications that operators can make to reduce mercury emissions, such as fuel blending, optimizing combustion conditions, and tweaking mercury control devices.
Commenter 17626 states that there are many ways to achieve the final standards through the use of a portfolio of air pollution control technologies. Using many of these technologies can achieve the same effect as previously noted in discussions of co-benefits. For instance dry FGD systems can achieve both very high sulfur removal and acid gas removal. Systems such as NID technology are particularly effective. Similarly, the commenter believes upgrading of existing equipment such as many ESPs with state of the art high frequency power supplies, off flow rapping, etc., can meet the standards without requiring fabric filter installations on many power plants. Consideration of wet ESP technology may also be a way to meet these requirements by addition at the back of the process train, avoiding the need to for major interruptions associated with fabric filter replacement of dry electrostatic precipitators.
Response to Comment 10: To the extent that modifications suggested by Commenter 16122 were in-place during any of the 2010 ICR testing, then the data available to the EPA include the impacts of such modifications. For example, the EPA reported in the 1998 "Study of Hazardous Air Pollutant Emissions from Electric Utility Steam Generating Units  -  Final Report to Congress" (Utility Study) that approximately 77 percent of eastern and Midwestern coal shipments were subjected to some physical cleaning process. It is not expected that percentage will have decreased in the intervening time period and, thus, it is likely that a significant portion of the coal used by EGUs conducting testing under the 2010 ICR and using bituminous coal were using "washed" coal. Other EGUs blend coal for a variety of reasons; various blends are reflected in the data used to establish the MACT floor levels. Further, the EPA is aware that at least one EGU was employing bromine sprayed on the coal before combustion as a means of adding halogen for Hg control (EPA-HQ-OAR-2009-0234-2067). In addition, EGUs supplying data through the 2010 ICR that are located in Connecticut (Bridgeport Station), Massachusetts (Somerset Station, Salem Harbor), New Jersey (Logan Generating Plant, Chambers Cogeneration, B.L. England, PSEG Mercer and Hudson, Deepwater), Illinois (Dallman, Havana, Hennepin, Waukegan, Will County, Joliet 9 and 29, Crawford, Meredosia, Joppa Steam, Lakeside, Duck Creek, Fisk, Newton, and Powerton), Montana (Colstrip, Hardin Generator Project), and Wisconsin (Elm Road, Pulliam, South Oak Creek, Valley, and Weston), are subject to EGU-specific Hg limitations that were likely in effect during the period of data gathering and the effect of which is reflected in the data they submitted.
In any event, commenters are incorrect to the extent it implies that the agency is required to set standards at beyond-the-floor levels of control. CAA section 112(d)(3) sets the minimum stringency level of control and the EPA may only establish more stringent beyond-the-floor standards if we determine that such level of control is "achievable" after considering costs and non-air quality health and environmental impacts. As stated above, the EPA must determine that standards are achievable based on the information the agency has when establishing the standards. The EPA does not have data or other information beyond that noted above that indicates the level of reductions that might be achieved beyond the floor based on the identified practices, but, as noted above, the EPA does not believe based on that available information that a standard that requires multiple redundant controls to achieve only marginal additional reductions are reasonable from a cost perspective. Commenters have not provided data or other information that causes us to revise this determination.
The EPA agrees with commenter 17626 that there are many ways to meet the final standards.
Comment 11: Several commenters (16122, 19536, 19537, 19538) believe that the EPA failed to consider all of the available methods for reducing emissions in its beyond-the-MACT-floor analysis. According to these commenters, section 112 makes clear that achievable emission reductions is not limited to consideration of a single control technology, but must be based on a consideration of all available control options. Commenter 16122 states that the EPA's analysis excludes all control technologies other than ACI and conventional criteria pollutant control technologies because it lacks the data to assess whether any other technology would provide additional control. This commenters submitted documents analyzing available technologies that are effective at reducing Hg emissions. By focusing only on ACI and not considering all available control methods in setting a MACT standard, the commenters believe the EPA is violating the requirements of CAA section 112(j) as well as the EPA's Trust Responsibility to tribes, and the requirements of the Environmental Justice Doctrine.
Several commenters (19536, 19537, 19538) disagree with the EPA's statements that no control technologies could be identified that could achieve greater Hg emission reductions of HAP than those control technologies expected to be used to meet the MACT floor. The commenters believe that methods exist to reduce Hg emissions below the EPA's proposed standard. The commenters believe the EPA did not adequately review ACI control systems, arguing that ACI is not a single technology, but rather a generic approach for Hg reduction in coal-plant exhaust gas streams and that different injection systems use different types and amounts of carbon (per unit of flue gas volume). The commenters note that utilities have used carbons of varying surface areas, different impregnated agents (such as bromine) to enhance Hg removal, and different injection rates. The commenters believe the EPA should have considered all such alternative design specifications for ACI systems in its analysis.
Commenters (19536, 19537, 19538) also assert that the EPA has assumed that the best controlled source of Hg could not further reduce its emissions. The commenters note that in the EPA's analysis most of the lowest Hg emitting units do not have ACI and asserts that in evaluating whether to propose a more stringent emission rate than the MACT floor, the EPA should not assume that new units cannot lower Hg emissions any lower than the MACT floor. The EPA should perform a beyond the floor analysis, argues the commenters, to ensure that it is setting a MACT emission limit for new sources reflective of the maximum achievable reduction in Hg emissions.
Response to Comment 11: Commenters noted a number of other technologies, claiming that "all of which have been shown to be effective at reducing mercury emissions" that could be used on EGUs (e.g., coal cleaning, boiler treatment additives, fuel blending, fixed sorbent beds, treated activated carbons, halogen impregnated carbons, non-carbon sorbents, and electrocatalytic oxidation). As noted elsewhere, to the extent that any of these technologies were employed by EGUs during testing to acquire data that was submitted in response to the 2010 ICR, those data are included in the MACT floor analyses (e.g., coal cleaning, treated or impregnated carbons, boiler treatment additives; other technologies could have been in use but were not reported through the 2010 ICR). Technologies that may have been employed or that might be employed but for which the EPA has no current data have not been considered in the beyond-the-floor analyses because where the EPA has full-scale data on control technologies, it does not believe it appropriate to use data from pilot or other small-scale testing.
Comment 12: Commenter16122 states that the EPA should have considered substituting higher ranks of coal for lignite, arguing that this type of process change and material substitution is required by CAA to be part of any beyond-the-floor analysis. The commenter states further that this approach does not involve many of the complications of switching from coal to natural gas because bituminous and subbituminous coals are accessible and highly abundant, and in the design phase of new EGUs, facility developers can choose to burn bituminous or subbituminous coals without having to consider the costs associated with retrofitting their units.
Similarly, Commenters 17768 and 17852 also believe that fuel switching is an appropriate technology to consider in a beyond-the-floor analysis. Commenter 17768 notes that every fuel source has its own risks (both in terms of price and availability), and believes that the theoretical possibility of supply shortages in some parts of the country should not prevent the EPA from adopting beyond-the-floor standards based on fuel switching. This commenter suggests the EPA consider setting a standard that contains regional variations where verified and significant cost differences in different geographical areas exist.
Commenters 17768 and 18423 disagree with the EPA's cost-effectiveness analysis. Commenter 17768 states that new EGUs would not experience the same costs of fuel switching that existing EGUs face and notes that the EPA did not quantify the benefits of emission reductions from fuel switching in the RIA or C2G TSD. This commenter believes the EPA should perform further analysis of fuel switching as a beyond-the-floor regulatory option and carefully consider how fuel switching might facilitate compliance with other rules (like the Transport Rule). Commenter 17768 also believes the EPA has not adequately explained why a de facto bar on new coal-fired EGUs would be unreasonable. Commenter 18423 argues that whether or not fuel switching would effectively prohibit new coal-fired EGUs is not a valid consideration under CAA section 112 because there is no provision in section 112 that allows the agency to consider the competitive or commercial impacts of a control option on new sources burning a particular fuel. The EPA's rationale, argues the commenter, is an example of "reasoning divorced from the statutory text" (see Massachusetts v. EPA, 549 U.S. 497, 532 (2007)).
Commenter 18423 disagrees with the EPA's determination that fuel switching results in limited emissions reductions. The commenter notes that the EPA has concluded not to regulate gas-fired EGUs under CAA section 112. This commenter also believes that the EPA has not adequately explained why there are uncertainties in determining the non-air quality health and environmental impacts of fuel switching.
Commenter 17852 suggests for new units the EPA require a case-by-case basis as part of the permitting requirements to assess whether natural gas is available. The commenter recommends that case-by-case consideration of alternative fuels should remain limited to types of alternative fossil fuel-fired electric generating units that generate a similar product (e.g., non-intermittent electric power) that can be generated from the same site footprint as proposed by the permit applicant. Setting a MACT floor for the regulated HAP for coal- and oil-fired units and then requiring a case-by-case review if natural gas is available, the commenter argues, is consistent with the MACT regulatory structure.
Response to Comment 12: The EPA is aware of Hg control technologies, including the various options for implementation of ACI. Units using ACI were among those that represented the best performing units and were thus accounted for in setting the limit for units burning coals >8,300 Btu/lb.
Existing EGUs designed to burn low rank coals cannot burn high rank coals without making modifications to the boiler and establishing transportation links to the sources of the higher rank coals. Such units can co-fire medium rank coals but not before combustion testing has been undertaken to establish the suitability of co-firing the medium and low rank coals. In addition, transportation links are not always currently present. In any case, some of the sources in this subcategory already blend coals and others may choose to blend coals in addition to upgrading control equipment to comply with the beyond-the-floor standard that the EPA proposed and is finalizing in this rule. Given the uncertainty surrounding the availability of alternative coals, we are unable to evaluate the costs of converting all low rank, virgin coal-fired EGUs to different coals or other fuels. Commenter has likewise provided no data or information that would allow us to adequately characterize the costs; therefore, we believe it would be unreasonable to establish a beyond-the-floor standard based on fuel switching.
Comment 13: Commenter 16122 believes the EPA failed to provide support for its decision not to set beyond-the- floor requirements for new lignite sources. The commenter argues that the EPA ignored numerous studies showing the effectiveness of a number of alternative Hg control technologies. The commenter cites an example of a study in which ACI and the use of Hg oxidizing fuel additives resulted in Hg reductions of greater than 90%. The commenter states that by not setting beyond-the- floor limits for new lignite EGUs, the EPA has created an incentive for facilities to install new EGUs that burn dirty coal. This decision, the commenter states, lacks justification and violates the CAA, the EPA's Trust Responsibility, and its obligations under the Environmental Justice Doctrine. The commenter states that if the EPA does not remove the lignite subcategory for new EGUs, then it must set beyond-the-floor requirements for new lignite units.
Response to Comment 13: As explained above, the agency must base the standards on the information the agency has available to it at the time it establishes the standards. The EPA has not identified other mechanisms to reduce Hg from this subcategory other than to require duplicate controls in series and, because the standards are already stringent, the additional Hg reductions cannot be justified based on the costs of the controls. Confirmation of the controls in-use for these sources reaffirms the fact that the EPA cannot identify any HAP emissions reduction approaches that could achieve greater emissions reductions of HAP other than to include the control technologies necessary to comply with the MACT floor in combination (e.g., multiple FFs or scrubbers). Given that the EPA has sufficient data obtained from full-scale, operating EGUs, it does not believe it appropriate to use data from pilot-scale technologies that have not moved to full-scale, long-term operational status. Companies are free to utilize such technologies in complying with the rule.
Comment 14: Several commenters (19536, 19537, 19538) outline the EPA's proposed HCl MACT floor and technology expected to be used to achieve it. The commenters believe the HCl emission rate of 0.0001 lb/MMBtu is achievable with the expected technologies. Commenters point out that 54 of the EGUs tested in the ICR already have actual HCl emission rates in compliance with this limit and more than half of the 131 EGUs considered by the EPA as the lowest HCl emitting units are achieving greater than 99% HCl emission control, which agrees with the commenters' findings. The commenters agree that there are beyond-the-floor technologies and methodologies that can achieve greater HCl reductions than the prescribed MACT standard.
Commenters state that several owners of coal-fired EGUs have claimed that low HCl emission rates can be met continuously. An example is Longleaf Energy Associates who have obtained a permit for a 2 unit 1200 MW power plant with HCl emissions under the proposed limit. The commenters report that the plant will burn subbituminous coal, but is permitted to burn up to 100% Central Appalachian coal and each unit will have a dry scrubber and baghouse. The commenters point out that the permit imposes a limit of 10 tpy for any single HAP. The commenters claim there are numerous "synthetic minor" permits issued to coal-fired EGUs which will keep HCl emissions below 10 tpy with planned SO2 scrubbers. Commenters point out that the HCl emission rates reflective of compliance with the permits are less than the EPA's proposed HCl emission limit, indicating that a beyond-the-floor limit are considered feasible and achievable by utility companies and state agencies. Commenters state that existing EGUs use the same technologies as new units, so they can achieve very high levels of SO2 and HCl removal as well.
The commenters explain that for EGUs with wet scrubbers, an upgrade to a magnesium-enhanced lime scrubber process can achieve up to 99% SO2 removal. In 2000, the commenters report, 4300 MW of older magnesium-enhanced lime wet scrubbers were converted to the improved version. Other changes to improve removal efficiencies include improving gas flow distribution through ductwork changes, improving spray level coverage, adding frothing trays, increasing liquid to gas ratio and injecting dibasic acid. In addition, dry scrubbers can be upgraded using performance additives or more reactive sorbent to improve removal efficiencies or an increase in the pulverization of the sorbent and/or a redesign of the slurry injection system or atomizer.
Commenters state that the EPA had no justification for not considering beyond-the-floor emission limits achievable through available technologies and methods, including further reductions by use of technologies used by some sources in the dataset which established MACT floor. The commenters point out that the proposed HCl emission limit is being met by all of the units that the EPA considered to be the lowest emitting 12% of coal-fired EGUs, which are equipped with a wide range of control technologies. The commenters state that the best way for the EPA to ensure that its HCl MACT limit requires continuous emission reductions is to require compliance be measured by HCl CEMs. This would ensure reductions and account for variability via an HCl limit with a long term averaging time, and allow adjustments to be made to operation of the SO2 controls to optimize HCl removal. Commenters believe a long term average HCl limit truly reflective of the maximum degree of achievable HCl emissions measured by CEMS allows the EPA to account for expected variability in emissions although motivating EGU operators to achieve the lowest HCl levels on a continuous basis.
Response to Comment 14: The EPA does not agree that there are a wide array of available beyond-the-floor controls that can limit HAP emissions in a cost effective manner for the existing source subcategories. Commenters' unsupported statements that alternative measures can be implemented are not sufficient to justify a beyond-the-floor standard consistent with CAA section 112(d)(3). We explain above why many of the suggested approaches are already considered in the MACT floor setting process and we need not revisit those here. We have also included in the final rule provisions for use of HCl CEMS or manual stack testing for compliance.
Comment 15: Several commenters (19536, 19537, 19538) disagree with the EPA decision to not set beyond-the floor limits for PM2.5. The commenters believe controls capable of achieving lower PM emissions exist. The commenters cite the EPA's ETV test results and notes that some filters (e.g., Daikin's AMIREXTM, PTFE membrane filters, and W.L. Gore's L36501) achieve better control of smaller particles (and thus HAP). Commenters believe that some new EGUs are achieving substantially lower particulate emissions than those required by standards.
Response to Comment 15: The EPA believes that its decision to not set beyond-the-floor emission limits for PM is reasonable based on the available information. Although the EPA does encourage use of the best performing filters, there is simply not enough long term performance data under actual power plant conditions to justify establishing a beyond-the-floor standard based on filter efficiency.
Comment 16: Commenter 17801 discusses the advantages of various filter bags (i.e., conventional, pleated, and ePTFE membrane laminate) and their potential for achieving high removal efficiency of particulates from coal-fired plants. The commenter discusses the advantages of using a combination of ePTFE membrane and blended filter media in a high temperature pleated element and notes results of independent testing showing enhanced Hg removal effectiveness (including at elevated temperatures of 345 [o]F).
Response to Comment 16: The EPA believes that its decision to not set beyond-the-floor emission limits for PM is reasonable based on the available information. Although the EPA does encourage use of the best performing filters, there is simply not enough long term performance data under actual power plant conditions to justify establishing a beyond-the-floor standard based on filter efficiency.
5. The EPA should adopt a comprehensive Energy Assessment and Benchmarking Program.