Comment 22: Commenter 18498 states that the EPA's practice of selecting the lowest available test value tends to accentuate outliers and recommends that the Agency abandon the approach. Using the average results of available Part III emissions tests and combining with the SO2 data from acid gas floor spreadsheet, the correlation based on all data is stronger for filterable PM, although the correlation for both filterable PM and total PM tends, as expected, to decline as the PM emissions are reduced. The average selenium emissions are lower for the filterable PM top performers and still lower when the top filterable PM data are also further culled to include only SO2 top performers. The commenter included figures that highlight how controlling for acid gases will address concerns over the adequacy of filterable PM as a surrogate for selenium since the volatile SeO2 component will behave similar to SO2. In fact, the filterable PM top performers could be coupled with an SO2 limit as high as 0.6 lb/MMBtu and still yield the same results in terms of weeding out potential high selenium emissions. The results suggest that filterable PM will be a better indicator. Much of the apparent correlation between total PM and selenium may simply be related to the relatively strong relationship between filterable PM and total PM.
a. Filterable PM and selenium.
Comment 23: Commenter 18014 performed an analysis of the average ICR test data from the EPA's floor analysis spreadsheets for coal-fired unit and found that there is a higher correlation between filterable PM and selenium and that there are significantly lower selenium emissions among the top performers for filterable PM.
Comment 24: Commenter 17904 notes that control of selenium is still highly correlated with PM controls. As the D.C. Circuit held in National Lime, if the EPA demonstrates a correlation between HAP metals and PM, it need not quantify that correlation or its variability. Accordingly, the EPA's concerns regarding the "variability in the performance of selenium control with coal rank," is misplaced. As a result, filterable PM is the reasonable surrogate for all non-Hg metallic HAP, including selenium and arsenic. This is the case for lignite specifically because the large majority of selenium entering PM control devices is in the solid phase for that fuel. In fact, the condensable portion of total PM is dominated by non-HAP constituents such as SO3, NO3, and NH3 with only small amounts of any non-Hg metallic HAP likely to be captured in the condensable fraction. Consequently, the use of total PM as a surrogate for non-Hg HAP metals is likely to be overly conservative and, thus, is not a reasonable surrogate for non-Hg metallic HAP. The commenter states that the EPA's surrogacy choice would not be affected by selenium capture rates. Furthermore, compliance with a total PM limit would be notably difficult to demonstrate given the proposed requirement to comply during both startup and shutdown and the proposed averaging time of 30 boiler operating days.
b. Boiler MACT.
Comment 25: Commenters 17756 and 18023 disagree with the Agency's inclusion of condensable PM and state that the filterable PM that the EPA uses in the Industrial Boiler MACT Rule is the more appropriate standard/approach.
4. Total PM limit stringency.
Comment 26: Commenter 17626 states that the total PM limits need to be set with consideration for fuel type and technology limitations. For instance, in the case of a unit burning PRB coal with SCR and WFGD, and combining the VOCs anticipated (and experienced) from the boiler with normal ammonia slip required to meet NOX standards, the proposed PM limit would be exceeded without inclusion of filterable PM. Therefore, the commenter urges that the EPA reconsider this limit.
Comment 27: Commenter 15678 states that considering that baghouse technology can consistently achieve filterable PM emissions below 0.01 lb/MMBtu, and that these emissions are mostly PM2.5. The proposed emission standard of 0.03 lb/MMBtu is too high and should be reduced to be more protective of public health. The commenter also favors this emission standard over the input-based standard where compliance is based on performance tests instead of CEMS since this approach would ensure that all EGUs meet the same emission standard regardless of fuel characteristics and the use of solid adsorbent for acid gas control.
Comment 28: Commenter 17914 states that as a leading supplier of emissions control systems to the U.S. EGU market, they are not aware of an AQCS technology or a practical combination of technologies that would allow an equipment supplier, such as themselves, to provide commercial guarantees on the ability to control total PM including filterable and condensable particulate to the emissions limits identified in the proposed MACT for new coal (0.050 lb/MWh).
Comment 29: Commenter 17914 states that at low total PM levels, the condensables can represent a significant fraction of the total PM. The ability to target and optimize control of the condensable fraction constituents at the proposed low emission levels has not been demonstrated. Testing at the latest generation of EGUs with current state-of-the-art AQCS has shown emissions of condensable PM are an order of magnitude higher than what would be necessary to achieve and sustain compliance with the proposed total PM limit for new coal. The use of a PM CEM to provide an indication of total PM emissions requires an assumption of a constant relationship between the filterable and condensable fractions over time, as well as variable fuel characteristics, boiler operation and emission control system performance. It is not clear if any supporting field test data is available to support this assumption. The PM limits set in the final Industrial Boiler MACT rule are based on filterable PM only. The commenter requests that the EPA consider a PM requirement based on filterable PM only.
Comment 30: Because performance testing for PM is less costly than testing for individual metals, commenter 17386 recommends a total PM emissions limit of 0.030 lb/MMBtu for oil-fired units, which is comparable to the limit set for other types of EGUs.
5. PM operating limit.
a. Representativeness of filterable PM operating limit.
Comment 31: Several commenters (17754, 17817, 18963, 19032) disagree with the agency's inclusion of condensable PM and the approach to continuous (CEMS for filterable PM based on highest initial stack test result) compliance demonstrations. The commenters state that the agency's suggested approach toward correlating total PM emissions measured during stack testing with filterable PM emissions measured through a CEMS is not justified for all sources under all operating conditions. The commenters state that the PM measured in the performance test using Method 5 will not account for the variation that will be encountered when units are monitoring using CEMS.
Commenter 17812 states that the EPA has failed to demonstrate a consistent and direct connection between total PM measured during stack testing and filterable PM monitored using a CEMS across all operating conditions for all affected sources. Non-Hg metal HAP emissions appear to be better correlated with filterable PM, and the rule should be revised to establish a filterable PM limit as a surrogate for total non-Hg HAP metals.
Comment 32: Several commenters (17775, 17747, 17838) express concern over the absence of a constant relationship between filterable to condensable PM. Commenter 17775 states that the EPA has not demonstrated a consistent and direct connection between total PM measured during stack testing and filterable PM monitored using a CEMS across all operating conditions for all affected sources. Therefore, in at least some cases, the proposed approach is likely to result in the derivation of an inaccurate filterable PM limit and, in turn, a significant concern regarding compliance demonstration. Moreover, any compliance demonstration issue related to an inaccurate filterable PM limit would be further compounded over time, because the associated CEMS would necessarily evaluate filterable PM emissions on a continuous basis. Also, due to the lack of a direct connection in such cases between total and filterable PM, the operating limit calculated for filterable PM may actually be more stringent than the applicable PM emission standard in the rule. Commenter 17747 states that for the EPA's monitoring approach to work the ratio of filterable to condensable PM must remain constant, otherwise the PM CEMS measurement is not an indicator of total PM. Commenter 18437 states that a PM CEMS only measures filterable PM, the use of total PM as a surrogate makes continuous compliance difficult.
b. Operating limit more stringent than total PM limit.
Comment 33: Commenter 17800 states that the filterable PM operating limit will be more stringent than the proposed total PM standard. Commenters 17800 and 18443 state the continuous measurement method (PM CEMS) has no proven track record in the utility industry. Commenter 17800 states that the compliance method should be clarified and should not combine different testing and measurement components.
To support their claim that a performance test is not representative of overall operations, commenter 17770 provided CEMS data that showed that a high performing unit tested during the ICR tests will be above their operational limit 98 percent of the time.
Several commenters (17728, 17758, 17775, 17820, 17821) state that the EPA's proposed total PM limit cannot be measured directly at an EGU. Commenters state that the proposed approach, an initial compliance test for both filterable and condensable PM with continuous filterable PM measurement using PM CEMS as an ongoing "operational limit," would simply ratchet the total PM limit downward until the next compliance test is conducted five years out. The proposed total PM limit of 0.030 lb/MMBtu for existing sources would function as no limit at all. The commenters state that utilities would not know the actual total PM standard a specific unit would need to meet until the initial compliance test is conducted more than 3 years in the future (after any new PM control equipment has been designed and installed). The proposed total PM limit is not acceptable and fails to provide the regulated community with the required regulatory certainty provided by a single, known standard.
According to Commenters 17627 and 17736, a total PM standard punishes units that are well controlled (for example by fabric filters) by forcing those units to adhere to an even stricter filterable limit than less well controlled counterparts. Several commenters (17627, 17736, 17820) recommend that the operating limits should be calculated by subtracting the condensable fraction from the total PM.
Comment 34: Commenter 17855 is concerned because their waste coal power plants have a very high fraction of condensable PM emissions (90% or more of the total PM emissions in some tests) and they feel that this may unnecessarily penalize them for the emission of a substance that is not likely to contain any significant quantities of non-Hg trace metals, including selenium.
Comment 35: Commenter 18443 states that sources with wet FGD routinely emit filterable PM below the measurement range of PM CEMS.
c. Operating limit as surrogate for MACT total PM limit.
Comment 36: Commenter 17800 states that the EPA is redefining the MACT standard (0.03 lb/MMBtu) by requiring continuous adherence to the initial performance filterable PM limit. Commenter further states that this is directly contrary to the CAA section 112 and that sources should be required only to meet the total PM limit (0.03 lb/mmbtu) by summing the continuously measured filterable PM and the initial performance condensable PM.
d. Site-specific operating limit.
Comment 37: Several commenters (17758, 17770, 18023) disagree with the approach of each unit (for continuous compliance) having a site-specific emission limit that is different from the total PM MACT. Commenter 17758 states that the EPA's requirement of unit-specific filterable PM operating limits is inconsistent with the CAA statutory provision that a MACT standard must be the "average" of top-achieving units. Even if there were a rational basis for the EPA to use a total PM standard, the way that it has chosen to measure compliance is both unnecessarily onerous and inconsistent with the requirements of the CAA.
Comment 38: Commenter 17904 states that the proposed PM surrogate approach is problematic in that it creates unit specific standards, creates a surrogate for a surrogate because total PM cannot be monitored, penalizes more efficient units because performance testing creates even lower operating limits, and sets a beyond the floor standard without following the CAA requirements.
e. Clarification.
Comment 39: Commenter 17838 states that if the EPA does not revise the rule to establish a filterable PM emission limit, then the EPA must clarify certain provisions of the rule that establish the procedures for demonstrating continuous compliance with the total PM emission limit. Commenters 17838 and 18539 state that the rule would require a filterable PM operating limit established as the average of the PM filterable results of the three Method 5 performance test runs. However, to determine continuous compliance, the owner/operator would be required to calculate the hourly average PM concentrations on a rolling 30 boiler operating day basis. Each 30 boiler operating day average would be required to meet the PM operating limit. According to Table 4 of the proposed rule, if a source demonstrates compliance using PM CEMS, then the owner/operator must "[m]aintain the PM concentration (mg/dscm) at or below the highest one-hour average measured during the most recent performance test demonstrating compliance with the total PM emissions limitation". Therefore, section 63.10011 directs that the operating limit for PM should be based on the average of the PM filterable results of the three Method 5 performance test runs, whereas Table 4 provides that the PM limit shall be the highest 1-hour average measured during the most recent performance test. These two relevant provisions appear to reflect inconsistent analyses and compliance demonstration periods and, therefore, should be clarified in order to avoid potential confusion, misinterpretation, and/or inconsistent application of the final MACT regulation.
f. Alternative approach.
Comment 40: Commenter 17904 states that if the EPA retains the total PM limit, they should use performance testing only to establish the ratio between condensable and filterable fractions of particulate emissions from a given unit. Moreover, that ratio should be established to reflect appropriate variability in the ratio itself.
Comment 41: Commenter 18539 states that if the total PM is retained, the operating limit should be set at 150 percent of the highest value assuming that the non Hg HAP are at least 50% lower than the required values.
Comment 42: Instead of the PM surrogate requirements proposed, commenter 17870 recommends 1) PM CEMS combined with occasional stack tests to ensure condensable PM emissions remain within limits; 2) use Hg as a surrogate for selenium and, thus, filterable PM alone may be a surrogate for other HAP metals. Correlation analysis indicates that selenium emissions are in fact better-correlated to Hg and acid gas emissions than condensable PM; 3) PM CEMS combined with a separate selenium standard. Alternatively, at a minimum, the commenter recommends that the EPA base the filterable PM limit on the facility-specific ratio to the total PM standard, rather than the initial numerical performance.
Comment 43: Commenter 17904 states that if the EPA retains total PM as the surrogate for non-Hg metallic HAP, the same factors that justify separate limits for Hg for boilers designed to burn low rank fuels also justify separate limits for total PM. The commenter gives as the justification: boiler design differences; higher concentrations of ash, Hg and other metals per pound of fuel; and lower levels of chlorides and elevated levels of sulfur trioxide. The part II and III ICR data support this difference in performance between high performing lignite units and high performing higher rank fuel units. The commenter used the ICR data and estimated a limit of 0.06 lb/MMBtu. In addition to the total PM data, Commenter believes that the ICR data for total and individual metals also supports the propriety of establishing a separate emissions standard for lignite units.
Comment 44: Commenter 18831 states that because the limit is based on the ICR data during steady-state, full-load conditions, it does not account for emissions variability resulting from startup, shutdown, soot blowing and malfunction. The commenter recommends that the EPA either propose a separate work practice standard or exempt any operational mode not included in the establishment of the MACT floor for demonstration of compliance with the PM limit.
g. Other.
Comment 45: Commenter 18014 states that if the EPA retains the total PM limit, the agency should allow sources to use the total PM limit in place of a filterable PM limit for PS-11 purposes since this value effectively represents the highest potential FPM limit if the source could reduce the condensable emissions to zero.
6. Effects of multiple controls on compliance.
Comment 46: Commenters 17724 and 17876 state that in proposing total PM as a surrogate, the EPA fails to address the antagonistic effects that adding multiple different pollution control devices can have on an EGU's HAP emissions, which is particularly relevant to the PM limit. The addition of a scrubber or some type of sorbent injection will be necessary to control HCl emissions and adding these HCl control technologies will increase the total PM emissions of these units. Thus, the EPA, in calculating the PM MACT floor, has relied on PM emissions data that could not exist under the proposed HAP limits. The commenters state that the EPA should establish a single, category-wide filterable PM emissions standard.
7. Surrogate vs total or individual non-Hg HAP metals.
Comment 47: Commenter 17805 states that filterable PM, as opposed to total PM, would be more suitable for determining continuous compliance with non-Hg metals. Commenter 17805 also states that the MACT standard should be the average total non-Hg metal or individual metals emissions determined using the best performing 12 percent of units in a subcategory and not the total or filterable PM levels of those units. Each facility should then be allowed to correlate non-Hg metallic HAP emissions to a facility-specific filterable PM emission level that could be used as the surrogate for continuous compliance. Commenter 17805 states that the EPA should study this option further to determine if it is indeed appropriate.
Comment 48: Commenter 17283 agrees with the EPA that separate standards for filterable PM2.5 and condensable standards would not be appropriate to demonstrate compliance with non-Hg HAP metal emission limits as neither is a surrogate for non-Hg HAP metals. The commenter states that there may be confusion by the EPA as to what is included in its "... single total PM standard..." and the various functions this single standard is to meet. For example, the EPA definition of total PM (filterable PM10 mass plus condensable PM mass) excludes the PM fraction greater than 10 microns (filterable fraction of Reference Method 5), which in some cases may dominate the total PM mass. From the preamble discussion, it appears to the commenter that the EPA wants this total PM standard consisting of total filterable PM as measured by Reference Method 5 plus the condensable fraction as measured by Reference Method 202 to serve as a surrogate for both HAP metals and PM2.5.
Commenter 17283 believes that this total PM standard does not meet the needs as a surrogate for non-Hg HAP metals or a surrogate for PM2.5. According to the commenter, total PM is inappropriate because it further dilutes any relationship between PM and HAP metals that might have existed by adding a significant amount of non-related condensable mass (such as sulfates from SO3 and H2SO4, nitrates, halides, carbonaceous compounds, and ammonium salts) to the PM mass, thus causing the HAP metal surrogate indicator to vary totally independent of filterable PM mass and HAP metals. According to Commenter 17737, the use of SCR for control of NOX can lead to the formation of condensable ammonia in the flue gas. These condensable PM emissions are not HAP, and fabric filters are not effective at controlling them. Commenter 17737 states there is no control technology specifically designed to capture all condensables, which will make it difficult to achieve the propose standard.
Commenter 17283 states that although the courts have ruled in favor of using PM as a surrogate, the ruling did not include the EPA's new total PM as a surrogate for non-Hg HAP metals. The commenter states that the total PM standard is a poor surrogate for filterable PM, which is a weak surrogate for HAP metals, particularly when considering such HAP metals as selenium.
Commenter 17283 states that the EPA's justification for this new total PM surrogate for non-Hg HAP metals is that it reflects best demonstrated technology (BDT) for all forms of PM, but it does not consider whether it represents BDT for HAP metals. As such, the commenter states that the EPA continues to ignore non-classical means for control of HAP metals such as control of HAP metals in feedstock (coal, limestone and other additives) as the courts have directed, as well as prevention of increases in PM and/or HAP metals.
Commenter 17283 recommends that the EPA not promulgate the total PM standard and further recommends that the EPA allow multi-metals CEMS as an alternative to filterable total PM as an indicator of compliance with HAP metals emission standards.
Comment 49: Commenter 17838 states it is inappropriate for the EPA to require an owner/operator of an affected EGU who elects to demonstrate compliance with total non-Hg HAP metals by using the PM surrogate, to conduct performance testing (including both initial and subsequent performance tests) for both the PM surrogate and total non-Hg HAP simultaneously. Because the EPA has already established an emission limit for a PM surrogate, which is an established compliance demonstration method under the proposed rule, there is no justifiable basis for the EPA to also require a demonstration of compliance simultaneously with either total non-Hg HAP metals or individual HAP metals.
To the extent that the EPA does not agree to revise the rule accordingly, the commenter states that the rule must nonetheless be revised to avoid additional ambiguities. Specifically, the rule lacks clarity related to the requirement to conduct periodic emissions testing for HAP metals and total PM during the same compliance period and under the same process and control device operating conditions. That is, the rule fails to clearly address a facility's compliance status if it simultaneously conducts stack testing for HAP metals and PM during the same compliance period, and demonstrates compliance with the applicable standards for one of these two pollutants.
The commenter further states that among other considerations, an affected EGU may face difficulty in demonstrating compliance with the emission limit for total non-Hg HAP because many of the individual metals are likely to be emitted at levels below the detection limits. In this case, on the source owner may estimate an emission rate for such metal(s) measured at non-detect limits for purposes of calculating and reporting total non-Hg HAP metals. This process of relying on estimated emission rates could result in a substantial over-estimation of metal emissions, and thereby inaccurately calculate an exceedance of total non-Hg HAP metals.
8. General support.
Comment 50: Commenter 17402 supports the flexibility the EPA has built into the rule by allowing both total metals and total PM as surrogates for non-Hg metallic HAP. Those surrogates are reasonable, and help to reduce the cost of compliance although maintaining the benefits of the rule. Total metals are clearly surrogates as the measure is necessarily comprised of the sum of the individual HAP. And total PM shows a stronger correlation with more metal HAP than either filterable or condensable PM alone.
Several commenters (15678, 17402, 17808) support the use of total PM as a surrogate for the non-Hg metallic HAP.
9. Other.
Comment 51: Commenter 18500 states that the preamble discussion on selenium focuses on observed selenium removal percentages, not emission rates. However, the EPA considered but dismissed setting removal percentages as a format for emissions limitations for Hg and other HAP. It is therefore inconsistent to rely solely on a removal percentage concern observed in an EPA testing facility, for deciding a mechanism for compliance, rather than analyzing actual emission rate test data from actual representative units to be regulated.
Comment 52: Commenter 18023 states that the EPA has no justification for requiring a total PM or condensable PM limit on the basis of selenium emissions. The EPA should instead consider the health-risk thresholds for selenium as justification not to establish either a total PM or condensable PM limit for non-Hg metallic HAP. The chronic health threshold for SeO2 is the same as the threshold for HCl. The commenter notes that the EPA's health assessment for the highest risk facilities found that HCl exposures ranged from 20 to 200 times lower than the threshold. Because selenium emissions are nearly 300 times less than HCl emissions, any emission standard for HCl will ensure that the health thresholds for selenium are not exceeded. If any selenium were present in the measured condensable fraction of total PM the amount of selenium would be only a fraction of total selenium emissions. The commenter further notes that total selenium emissions do not approach the selenium health thresholds and any selenium present in condensable PM would only represent a fraction of total selenium emissions. The commenter states that the EPA must take into account both of these health-threshold "considerations" in establishing a filterable PM emission limit for non-Hg metallic HAP.
Response to Comments 1-52: The The EPA has determined in the final rule to establish a filterable PM surrogate standard for non-Hg HAP metals (or, for liquid oil-fired units, HAP metals including Hg), consistent with the approach suggested by many of the commenters. CAA section 112(d) standards are technology based standards, not risk based standards, and the limits are established based upon the demonstrated emissions reductions of existing sources. The EPA believes it is reasonable to establish a PM surrogate standard for non-Hg metal HAP because the best PM controls provide the best controls of metal emissions. We have also established alternative individual and total metal standards so industry has flexibility in determining how to comply with the final rule. PM is not a valid surrogate for Hg. Emissions measurements of either filterable particulate, total particulate, individual metals or total metals provide comparable indications that the best control measures are installed. We can find no significant difference in the emissions that would be achieved by using any one of these emissions measurements.
The EPA re-assessed the relationships between individual metal emissions, filterable PM emissions, total PM emissions, and total PM2.5 emissions based on the test results provided through the Part III ICR. We compared the measured emissions of metals and particulate with the uncontrolled emissions estimates and found that the control of metals emissions was generally consistent with the control of PM. In addition, the EPA compared the correlations associated with non-Hg HAP metal emissions and the three forms of PM and found that no specific particulate form provided a consistently superior indicator of better metals control. Although control of filterable PM provided the best indicator of performance for some HAP metals, control of total particulate or total PM2.5 was nearly as good an indicator. For control of other HAP metals, total PM measurement provided the best indicator of performance; although, measurement of the control of filterable particulate was nearly as good. As a result, other considerations entered into our decision to select filterable over total particulate for the final emissions limit. We believe that periodic measurements of both the metals emissions and the indicator will provide assurances that reasonable emissions controls are being achieved for the HAP metals. The EPA Method 29 allows for the measurement of filterable particulate and the HAP metals. The use of total particulate would incur the cost of performing Method 29 and the cost of performing a separate combination Method 5 and Method 202. The ability to continually measure the pollutant also entered into our decision. Although we are working towards a PM CEMS/CPMS which includes the condensable fraction and performs in a wet stack, we estimate that it will be several years before a viable method will be demonstrated. PM CEMS/CPMS which include only the filterable fraction have been demonstrated at almost 100 facilities. In addition, certain data analyzed by the EPA's Office of Research and Development indicate that vapor-phase metals (e.g., selenium) are generally present as acid gases and are controlled to significant reduction levels using acid gas technologies (wet and dry scrubbing). Given that the rule also provides for acid gas control monitoring and the general equivalency of the different indicators, the EPA has opted to use a filterable PM limit for the PM emission limit in the final rule.
With respect to the operating limit using a PM CPMS under the final rule, the EPA believes that most of the comments under this comment area were focused on the perceived inappropriateness of using filterable PM operating limit data from a PM CEMS to measure compliance with a total PM limit. With the change adopted in the final rule, these comments are largely moot. For use of a PM CPMS under the final rule and the nature of the operating limit, please see the preamble and other sections of this response to comments document that discuss the PM CPMS requirements.
With respect to testing for both PM and non-Hg HAP metals if the PM surrogate is selected as the emission limit that a specific source elects to demonstrate compliance with, the final rule clarifies that only the Method 5 test is required, and not a Method 29 test. The opposite applies (Method 29, not Method 5), if the non-Hg HAP metals limit (total or individual) is elected for a given source. In general, the reportable measurement output from the PM CPMS may be expressed as milliamps, stack concentration, or other raw data signal. The operating limit is not expressed in units of the standard.
With respect to Method 202 comments, those comments are no longer applicable as the final rule does not require the use of Method 202. However, the EPA notes that the newly revised Method 202 was developed to minimize the formation of particulate from the oxidation of SO2 to SO3. Laboratory and field evaluations of the method reveal that the revisions were successful and that the residual formation is not quantifiable by gravimetric methods. The use of OTM-28 (essentially identical to the promulgated Method 202) for the information collection request for utility boilers show that both the emissions of inorganic condensable particulate and the organic condensable particulate emissions measured with Method 202 are as consistent as the filterable PM measurements. Although the percentage of condensable particulate matter ranges from a low of 5% of the total PM to a high over 95%, the highest percentages are typically associated with the lowest filterable PM emissions and the lowest percentages are typically associated with the highest filterable PM emissions. This is the case both when the data are not segregated by control technology and when controls are segregated by control technology (dry scrubbing with either no ammonia injection or when ammonia injection is used with either catalytic or non-catalytic reduction, ESP with either no ammonia injection or when ammonia injection is used with either catalytic or non-catalytic reduction). This variability in the percentage of particulate that is condensable does not support the conclusions reached by the commenters that Method 202 provides inconsistent results. The data measured for the ICR demonstrates that Method 202 is comparable in precision as was demonstrated for the filterable PM measurements. With respect to the conclusion of the commenters that ammonia absorbed in the impingers leads to artifact formation of ammonium sulfate or bisulfate, there is more than adequate published information that formation of ammonium sulfate or bisulfate occurs in the gaseous phase at lower temperatures in the presence of very small amounts of water vapor.[,][,][,][,] Although these reactions are prevented at temperatures above about 350 ºF, the reactions occur when temperatures are below this level. As a result, the formation of ammonium sulfate or bisulfate in Method 202 is not an artifact of the sampling method but the collection of PM that would occur upon the release of the flue gas to the ambient air where it is cooled and chemical reactions between the acid and basic constituents occur.
Comment 53: Several commenters disagree with the use of the average filterable PM level measured during the performance test for total PM. A summary of these comments follows:
1. Several commenters (17402, 17725, 18539) state that if the EPA uses filterable PM as a surrogate of metal HAP, the filterable PM limit should be calculated by subtracting the condensable PM from the total PM limit. According to the commenters, the proposed method of conducting a performance test for total PM and using the average of the filterable PM as the unit's operating limit is flawed in that it would punish low PM emitters, especially those with a low fraction of filterable PM. Commenter 18037 submitted similar comments. Commenter 18498 prefers that the total PM limit be replaced with a filterable PM limit. But if the total PM limit is retained, then they recommend that the filterable PM limit be determined by subtracting the condensable PM measured from the total PM.
2. Commenter 17725 recommends that the EPA base the filterable PM limit on the facility-specific ratio to the total PM standard, rather than the initial numerical measurements. For example, if a unit is tested for total PM and the testing results provide that 50% of the total PM is filterable PM, this would result in a limit of 0.015 lb/MMBtu (50 percent of the 0.030 lb/MMBtu standard). The commenter also states that if the EPA abandons total PM as the surrogate for non-Hg metal HAP emissions and adopts filterable PM as the surrogate, the filterable PM emission limitation should be established using the same methodology, including variability, that the EPA relied upon when proposing the total PM emission limitation of 0.03 lb/MMBtu. Commenter 17714 states that if the rule retains the total PM limit, the ratio of filterable PM to condensable PM be determined for each unit and use the established ratios, to scale the filterable PM limit up to the limit established in the MACT process.
3. Commenter 17795 states that units operating PM CEMS should be permitted to establish a filterable PM rate using the output of a PS-11 certified PM CEMS during the first 12 months of operation once this rule is in effect. The initial performance test would be conducted during this period. Using 12 months of operations to develop a site specific PM limit provides operators the opportunity to establish a PM limit that accounts for variations in operations.
4. Commenters 17807 and 18015 disagree with the "snapshot" approach of establishing a filterable PM limit, as available stack test data and PM CEMS data shows that compliance cannot be maintained on a continuous, 30-day rolling average basis. The established limit and the 30-day rolling average should include all data so it would allow for startup and shutdown. Commenters 17725 and 17807 request that the EPA establish a single, category-wide filterable PM emission standard of 0.03 lb/MMBtu as a surrogate for non-Hg metal HAP.
5. Commenter 17885 states that using a performance test to demonstrate compliance followed by a site-specific operating limit is unnecessary and fails to account for differences in the emissions over a reasonable anticipated operating range of the unit.
Response to Comment 53: With the revision of the particulate matter standard that only uses the filterable portion of total particulate matter, the concerns raised by the commenters are no longer relevant. In response to the concerns raised about the change from total particulate to filterable particulate, the test methods used for total particulate matter inherently separate filterable particulate matter from the two condensable particulate matter fractions. In the development of the final standard, we only used the results from the filterable portion when both filterable and condensable tests were performed during the same test. In addition, the use of a PM CEMS in a CPMS mode impacts several of the issues raised by the commenters making those issues irrelevant.
Comment 54: Commenter 17730 states that more testing/analysis is needed to determine an appropriate level of filterable PM emissions that would serve as the surrogate, instead of using total PM as the surrogate. The manner in which the EPA has established the surrogate for the HAP metals is to establish a surrogate for a surrogate.
Comment 55: Commenter 17747 states that the EPA is using a surrogate for a surrogate. The commenter explains that PM CEMS used to monitor PM is calibrated to Method 5, which measures filterable PM. Filterable PM is a surrogate for total PM, which is a surrogate for HAP metals. According to the commenter, filterable PM is not a surrogate for condensable PM. They state that in is unclear that a surrogate for a surrogate approach is allowed under the law.
Response to Comment 54 - 55: We disagree that additional testing is needed to determine an appropriate level of filterable PM emissions that would serve as a surrogate for non-Hg metals. With over 125 tests for filterable PM, total PM and metals, the capacity of using either particulate measurement as an indicator for non-Hg metals can be evaluated. As is explained elsewhere, we have selected filterable particulate for the preferred indicator due to additional criteria related to ability to monitor emissions on a continuous basis. We also disagree with the commenters' assessment that the use of a PM CEMS calibrated by Method 5 is a surrogate of a surrogate. We are aware that condensable PM and filterable PM are different components of PM; as mentioned elsewhere, we found no significant difference in using filterable PM, rather than total PM, to assess PM, as well as HAP metals, control device effectiveness, and we found vapor phase HAP metals, which are analogous to condensable PM, were controlled effectively by existing acid gas control devices.
Comment 56: According to commenter17775, the agency's pilot test program and limited analysis does not describe or explain how it considered the potential surrogacy relationship between filterable PM and total non-Hg HAP metals, and/or the manner in which the EPA evaluated the relative accuracy of total PM as compared to filterable PM for use as a surrogate. The commenter states that the EPA's acknowledgement that fabric filters are effective for controlling non-Hg HAP metals is consistent with the determination that non-Hg HAP are more closely correlated with filterable PM and that emissions of non-Hg HAP metals will be sufficiently reduced by facilities using fabric filters, regardless of the surrogate selected for evaluating performance. This provides an additional justification for selecting the surrogate that may be utilized in a more consistent manner for continuous compliance demonstrations. The commenter states that a review of their ICR data demonstrates the absence of detectable quantities of most of the non-Hg HAP metals in the condensable PM fraction. Moreover, it can be shown that either the condensable fraction comprises a relatively small portion of the total metal emissions, or, alternatively, the total metal emissions are more closely correlated to filterable PM than either condensable PM or total PM.
The commenter states that the EPA has not demonstrated a consistent and direct connection between total PM measured during stack testing and filterable PM monitored using a CEMS across all operating conditions for all affected sources. Therefore, in at least some cases, the proposed approach is likely to result in the derivation of an inaccurate filterable PM limit and, in turn, a significant concern regarding compliance demonstration. Moreover, any compliance demonstration issue related to an inaccurate filterable PM limit would be further compounded over time, because the associated CEMS would necessarily evaluate filterable PM emissions on a continuous basis. Also, due to the lack of a direct connection in such cases between total and filterable PM, the operating limit calculated for filterable PM may actually be more stringent than the applicable PM emission standard in the rule.
The commenter recommends filterable PM as the sole emission surrogate for non-Hg HAP metals. The same filterable PM limit would then be used for demonstrating initial compliance and continuous compliance using CEMS. Compliance with the filterable PM surrogate emission limit would be demonstrated with an initial performance test, and continuous compliance would be demonstrated using CEMS. The commenter states that this approach would advance the objectives of the proposed rule because the majority of HAP emitted during combustion are contained in the filterable component. The EPA has sufficient data to establish a filterable PM emission limit for inclusion in the final Utility MACT regulation.
Response to Comment 56: The EPA proposed total PM as the surrogate for the non-Hg metallic HAP to ensure that the measurement included both the filterable and condensable fractions of the non-Hg metals. Of primary concern was selenium which can be present in the flue gas as a particulate (i.e., filterable PM) or as SeO2 gas (i.e., condensable PM). The other non-Hg metals are primarily (usually > 95 %) present as filterable particulate matter. The EPA has finalized the use of filterable PM as an alternate equivalent standard for the non-Hg metallic HAPs since SeO2 is also an acidic gas that is very similar to its chemical analog, SO2. Since the final rule also requires control of acid gas HAP (using either HCl or SO2 as an alternate equivalent), then Se will be effectively controlled as a filterable particulate in the primary PM control device or as the condensable acid gas, SeO2, using an acid gas control technology such as a wet scrubber, spray dryer, or dry sorbent injection.
Comment 57: Commenter 18025 recommends a change to the proposed non-Hg compliance demonstration procedures. As proposed, the requirements are unnecessarily complex and could result in identical facilities with the same total PM emissions having very different filterable PM limits. Because the condensable PM portion could vary significantly between tests, a single facility could have a variable emissions target. This method also results in ratcheting down the standard on some units. The commenter proposes the following options:
      1. PM CEMS combined with occasional stack tests to ensure condensable PM emissions remain within limits.
      2. Use Hg as a surrogate for selenium and, thus, filterable PM alone may be a surrogate for other HAP metals.
      3. PM CEMS combined with a separate selenium standard.
Alternatively, at a minimum, the commenter recommends: 1) basing the filterable PM limit on the facility-specific ratio to the total PM standard, rather than the initial numerical performance, and 2) such a facility-specific limit remain constant for a longer period of time, such as annually, to provide a measure of regulatory certainty.
Response to Comment 57: The revisions that we have made to the final monitoring provisions provide reasonable assurances and the detailed issues raised by the commenter no longer are relevant.
Comment 58: Commenter18498 states that if the EPA retains the total PM limit, they recommend that the Agency allow sources to use the total PM limit in place of a filterable PM limit for PS-11 purposes (since this value effectively represents the highest potential filterable PM limit if the source could reduce the condensable emissions to zero).
Response to Comment 58: The revisions that we have made to the final monitoring provisions make the issues raised by the commenter no longer relevant.
Comment 59: Commenter 18498 states that the filterable PM limit must be maintained until the next periodic stack test, and non-compliance would result if this limit is exceeded, even if exceedance of the filterable limit did not in fact generate an exceedance of the total PM limit. It is likely for well controlled units that the filterable PM operating limits will be set well below the detection limits of PM CEMS. This is particularly likely for units with wet FGDs. In such cases, EGUs could not clearly determine compliance with their filterable limits established during performance testing and could not demonstrate continuous compliance with rule.
Response to Comment 59: With the revision of the monitoring provisions to use a single filterable PM emissions level as the alternate equivalent standard for compliance with the non mercury metals emissions, the use of PM CEMS in a CPMS mode the issues raised by the commenter are no longer relevant.
Comment 60: Commenter 17795 states that the EPA OTM27/OTM28 data from the ICR should be removed from the MACT floor population and total PM should be recalculated using only the modified Method 5 (M5)/OTM28 data. This reference method combination is the only reliable means for assessing total PM in both saturated and dry stacks.
The commenter states that results from modified M5 and OTM27 are not comparable for developing a FPM fraction MACT floor value. The EPA incorrectly assumes results from OTM27/OTM28 and modified M5/OTM28 are similar measurements and yield a valid standard; however these methods are substantially different due to the fundamental principles of isokinetic sampling.
The commenter notes that it is true both methods will yield a filterable PM result, but the substantial differences between the two methods are highlighted below:
The commenter states that test method OTM-027 separates particulate based upon aerodynamic diameter in an in-stack cyclone. To achieve proper cut size near 2.5 microns, the sample gas flows through the cyclone at a constant rate throughout the test run. Isokinetic sampling conditions are compromised although traversing the stack cross sectional area due to the constant sampling velocity. The test method's isokinetic tolerance of (+-20 percent) is twice that of Method 5 (+- 10 percent). The OTM-027 samples were collected as two separate fractions, <2.5 microns and >2.5 microns. The total filterable particulate reported from the summation of the two size fractions has an unknown bias when compared to the results of Method 5 samples due to the relaxed isokinetic allowable tolerances associated with OTM-027. Condensable particulate via OTM-028, measured behind the OTM-027 cyclone, is influenced greatly by the filtration temperature of the OTM-027 cyclone, which is directly correlated to stack temperature. Whereas saturated stack test results obtained from modified M5 samples were filtered at an elevated temperature, similar to Method 5B, at 320 OF, which will yield a different condensable particulate fraction than what would be collected testing dry stacks with filter temperatures held at the flue gas temperature.
The commenter notes that, also, a large portion of the MACT floor population that conducted OTM-27 will not be able to demonstrate compliance with the proposed MACT standards in their current baghouse or ESP only control device configuration. Even if the EPA chooses to retain results for OTM-27, units in the floor that have no controls beyond FF or ESP should be removed as they are not representative of what those units will emit to meet the Hg and the acid gas standards imposed by this rule. The EPA should not seek to establish limits that the floor units may not be able to achieve in the future.
Response to Comment 60: The agency's decision to use filterable particulate at 320 ºF as an alternate equivalent standard for non-Hg metals emissions diminish the relevance of the issues raised by the commenters. We disagree with the commenters that OTM-27 cannot provide comparable measurements with EPA Method 5. With respect to the measurement of filterable particulate, when proper isokinetics are maintained and the filter temperatures are within the same range, the only difference between OTM-27 (now Method 201A) and Method 5 is that the particulate is divided into two fractions. In the assessment of the test data collected for the ICR, EPA was aware of the potential issues associated with potential differences in the way testers might perform OTM-27. In addition to requesting the collection of PM with OTM-27 we required filterable particulate testing with either Method 5, Method 29 (at 320 ºF) or Method 26A. We were also aware of the influence of filtration temperature to the amount of material collected on the filter verses in the impinge portion. In the proposed total PM emissions limits we used only tests which provided reliable measurements of total particulate.
Comment 61: Commenter 17842 urges the EPA to evaluate whether a "total" PM limit is "reasonable", when a less-restrictive and more cost-effective "filterable" PM limit has been determined to sufficiently reduce HAP metals by the Boiler MACT rule.
Commenter 17928 agrees with the use of the Boiler MACT filterable PM limit as the surrogate for non-Hg metals. The commenter has concerns about the stringency of the standard imposed by using PM (filterable PM2.5 plus condensable) as a surrogate for these HAP as proposed by the EPA. Including condensable PM also raises concerns about the efficacy of the monitoring technologies. The commenter has concerns with establishing an enforceable filterable PM limit during the initial total PM test.
Response to Comment 61: The EPA reassessed the use of total PM, filterable PM and total PM2.5 as surrogated for non mercury metal HAP emissions and found that all were nearly equally effective. As a result, the EPA based our decision to use filterable particulate matter as a surrogate since there were potential continuous monitoring advantages associated with the use of this surrogate. We do not agree that there are significant cost advantages of using filterable particulate over total particulate as the additional cost of measuring condensable particulate with filterable particulate is minimal. The EPA does agree that the inability to continuously monitor total particulate is a concern.
Comment 62: Commenters 17855 and 17925 state that the surrogate for non-Hg HAP metals should be filterable PM rather than total PM because the majority of these HAP are found on solid rather than condensable particles and the fact that the emissions of these HAP correlate better with solid PM rather than condensable PM or total PM. In addition, the use of filterable PM as the surrogate eliminates the use of different and potentially uncorrelated surrogates for demonstrating initial compliance and continuous compliance.
Response to Comment 62: As mentioned in an earlier response, the EPA proposed total PM as the surrogate for the non-Hg metallic HAP to ensure that the measurement included both the filterable and condensable fractions of the non-Hg metals. Of primary concern was selenium which can be present in the flue gas as a particulate (i.e., filterable PM) or as SeO2 gas (i.e., condensable PM). The other non-Hg metals are primarily (usually > 95 %) present as filterable particulate matter. The EPA has finalized the use of filterable PM as an alternate equivalent standard for the non-Hg metallic HAPs since SeO2 is also an acidic gas that is very similar to its chemical analog, SO2. Since the final rule also requires control of acid gas HAP (using either HCl or SO2 as an alternate equivalent), then Se will be effectively controlled as a filterable particulate in the primary PM control device or as the condensable acid gas, SeO2, using an acid gas control technology such as a wet scrubber, spray dryer, or dry sorbent injection.
Comment 63: Commenter 17871 states that the EPA's choice of a total PM standard as the surrogate for non-Hg metallic HAP is flawed. The PM surrogate standard should be in filterable form to reflect available monitoring and compliance options. Additionally, the lack of emissions data and associated compliance and monitoring for the condensable fraction of total PM weighs in favor of the issuance of work practice standards under CAA section 112(h) to control emissions of trace metal HAP in condensable PM.
The commenter explains that, first, metallic HAP in the condensable fraction of total PM are de minimis in nature and are extremely difficult to measure. Second, there is little data demonstrating how available technology controls trace metals, such as arsenic and selenium, in the condensable fraction. Finally, the methodology proposed by the EPA to monitor compliance with emission standards for these trace metals produces extremely uncertain results. Even the results of emission testing under EPA's ICR, which required Method 29 for testing of all non-Hg metallic HAP, did not differentiate between condensable and filterable PM and Method 202 has been shown to have a false positive bias when used on sources with SO2 and ammonia in the flue gas, such as coal-fired boilers. Because of the limited data from existing plants and limitations associated with Method 202, equipment vendors have not provided guarantees for stringent condensable PM emission limits.
The commenter notes that, moreover, stack test results from coal-fired units suggest that the FGD control, coupled with a fabric filter baghouse, will effectively capture more than 98 percent of the selenium in flue gas.
The commenter states that the EPA should use filterable PM as a surrogate for non-Hg metallic HAP and impose work practice standards under CAA section 112(h) for metallic HAP such as arsenic and selenium as the agency has proposed for dioxins and furans.
Response to Comment 63: The EPA disagrees on the need for a work practice for control of trace metal emissions. The EPA proposed the use of total PM as the surrogate for the non-Hg metallic HAP to ensure that the measurement included both the filterable and condensable fractions of the non-Hg metals. Of primary concern was selenium which can be present in the flue gas as a particulate (i.e., filterable PM) or as SeO2 gas (i.e., condensable PM). The other non-Hg metals are primarily (usually > 95 %) present as filterable particulate matter. The EPA has finalized the use of filterable PM as an alternate equivalent standard for the non-Hg metallic HAPs since SeO2 is also an acidic gas that is very similar to its chemical analog, SO2. Since the final rule also requires control of acid gas HAP (using either HCl or SO2 as an alternate equivalent), then Se will be effectively controlled as a filterable particulate in the primary PM control device or as the condensable acid gas, SeO2, using an acid gas control technology such as a wet scrubber, spray dryer, or dry sorbent injection. The EPA explained the use of PM as an indicator in the proposal and again in response to several other commenters.
Comment 64: Commenter 18425 suggests that the EPA clarify the use of PM as a surrogate possibly including a PM2.5 standard.
Response to Comment 64: The EPA did not include PM2.5 as a standard since this provided no significant advantage as an indicator for non mercury metals over total PM or filterable PM. In addition, the measurement and monitoring of PM2.5 in a wet stack is not developed and may require several years of research to identify the measurement technology and several additional years to verify the long term viability of the monitoring methodologies.
4F02 - Format of the Standard: HCl as a surrogate for acid gases
Commenters: 15678, 17402, 17621, 17648, 17716, 17725, 17728, 17754, 17758, 17775, 17808, 17843, 17846, 17881, 17886, 17904, 18025, 18498, 19536, 19537, 19538, 18932, 18023
Comment 1: Several commenters (15678, 17648, 17716, 17758, 17775) state that they support the use of HCl and SO2 as surrogates for acid gas HAP. Commenter 17716 adds that both surrogates provide an excellent correlation with the acid gases given that any control technology (e.g., wet FGD or sorbent injection) for HCl or SO2 will capture all other acid gases, and therefore, each serves as an excellent indicator of control for all acid gases. Commenter 17758 adds that the EPA proposes an alternate surrogate of SO2 if a unit is using a CEMS to demonstrate compliance with SO2 limits. The commenter supports the proposed surrogate and alternative for acid gas emissions since utilities already monitor SO2 emissions continuously under the Acid Rain Program, and the control technology that removes SO2 also is effective at removing acid gas emissions.
Comment 2: Multiple commenters (17402, 17725, 17808, 17846, 17886, 17904, 18498, 18023) support the use of HCl as a surrogate for acid gases.
Commenter 17402 believes it is a better surrogate than SO2 because it is an acid gas HAP and that it is also reasonable under relevant case law.
Commenter 17808 adds that it will reduce monitoring costs.
Commenter 17886 supports HCl as a surrogate and the option of meeting an alternative SO2 limit if the unit uses a CEMS to demonstrate compliance with SO2 limits.
Commenter 17904 adds that the EPA should maintain HCl as the primary surrogate and clarify in the final rule that the SO2 limit is an alternate, optional compliance limit to avoid confusion or argument that SO2 is required to be used as the surrogate over HCl in any case.
Commenter 18498 supports the use of both HCl and SO2 as surrogates for acid gas HAP. Both will provide an excellent correlation with the acid gases since any control technology (e.g., wet FGD or sorbent injection) for HCl or SO2 will indiscriminately capture the other acid gases. None of the control options would capture one acid gas but not the others so a reasonable correlation would be expected.
Comment 3: Commenter 17843 states that units equipped with wet or dry scrubbers for SO2 control will also control HCl. For units that are unscrubbed, other options such as DSI and fabric filters are relatively inexpensive and simpler to install than scrubbers.
Response to Comments 1 - 3: The EPA appreciates the support of commenters.
Comment 4: Several commenters (17836, 19536, 19537, 19538) state that HCl is not an appropriate surrogate for HCN. Commenter 17836 states that the bottom line is technology to achieve reductions of HCl emissions will not invariably capture HCN. Sorbent injection control is the only technology that even claims to be able to remove HCN, and even then, the typical reagent used in sorbent injection is not as effective against HCN as it is for HCl/HF.
One commenter states that in order to use a surrogate pollutant in MACT standard setting, the agency must meet three preconditions.
The first precondition according to the commenter is that the EPA must show that the HAP in question is "invariably present" in the surrogate pollutant. The commenter contends this precondition is not met by the EPA's proposed use of HCl and SO2 as surrogates for the acid gases emitted by coal- and oil-fired EGUs. The commenter states that the EPA did not provide any analysis of or discussion as to whether HF, Cl2, HCN, or SeO2 are invariably present in HCl or whether these HAP and HCl are invariably present in SO2. They are not, according to commenter.
According to the commenter the second precondition for the use of a surrogate pollutant in MACT standard setting is that control of the surrogate must "indiscriminately capture" the air toxic along with the surrogate. The commenter states that the two test runs the EPA cites as proof of capture fail to provide sufficient basis for the EPA's broad claim that the HCl and SO2 control technologies indiscriminately capture all the acid gas HAP emitted by solid fuel-fired EGUs. The EPA would need to collect more data from full-scale units showing more consistent correlations to support such conclusions. The commenter maintains that the EPA's testing and other test data indicate that SO2 controls do not achieve high levels of removal of these acid gas HAP concurrently (even for HF and HCl, let alone HCN). According to commenter, lowering HCl emissions is not indiscriminately linked to lowered chlorine (Cl2) emissions. For chlorine, the EPA only collected a limited amount of data. Commenter's analysis of the 2010 ICR data found that Cl2 emissions increased with decreasing HCl. Far from showing that controlling SO2 always indiscriminately also controls the acid gas HCN, the EPA did not provide any data on control of HCN across a wet scrubber. Commenter believes that the EPA collected sufficient data on HCN emissions in its 2010 ICR, to set an HCN-specific MACT standard, and should do so, as it does not appear that the EPA has evaluated whether HCN is controlled across SO2 control equipment at all, much less justified an SO2-HCN surrogacy relationship. The commenter asserts that the EPA did not do any evaluation of the relationship between acid gas removal and the use of a dry scrubber or any other SO2 control technologies. Commenter argues that those alternative SO2 control mechanisms may have poor, or no significant, effect on acid gas emissions.
The commenter states that the third precondition for the use of a surrogate pollutant is that control of the surrogate must be the "only means by which facilities achieve reductions" in the air toxic in question. The commenter believes the data collected by the EPA, and the manner in which acid gases are formed, suggest that SO2 controls alone are not the only reason for low acid gas emissions. For example, according to commenter the Cl2 levels in coal are a factor that can account for lower HCl emissions, independent of the SO2 removal efficiency of any SO2 controls. Although SO2 controls can affect HCl emissions, the commenter asserts that a review of the ICR data collected by the EPA shows that SO2 controls are not the "only means" by which lower acid gas emissions are achieved  -  those units burning the lowest Cl2 coal (typically subbituminous, western bituminous, and lignite) can have lower HCl emissions than units burning higher Cl2 coal without SO2 controls. In addition, the commenter maintains that there are other options for removing HCl that may not remove all acid gases (especially HCN). As an example, commenter states that chloride prescrubbers can remove HCl and likely also HF, but weaker acids like HCN would not likely be removed by such a prescrubber. Commenter indicates that where HCN has been removed in other instances, reagents that are used include sodium hydroxide, which are general not used to control other pollutants from coal-fired units.
The commenter does not believe that the EPA has justified its use of HCl as a surrogate for all or any of the acid gases but itself. Nor has the EPA justified the use of SO2 as a surrogate for all or any of the acid gases. The EPA should therefore impose separate MACT limits for HCl, HF, HCN, Cl2 and SeO3.
The commenter also states that a scrubber is operated to primarily remove SO2 emissions, with the amount of reagent needed to meet SO2 emission limits dependent on the uncontrolled SO2 emissions coming into the scrubber, and HCl removal is similarly based on the stoichiometric ratio of reagent to chlorine. However, the commenter believes there is no correlation between sulfur content of the coal and chlorine levels in the coal. Because there is no correlation between sulfur content and chlorine content of coal, the commenter states that a scrubber operated to achieve certain levels of SO2 may not be optimized for HCl removal. If the scrubber is operated to achieve SO2 removal and the sulfur content of the coal stays the same but the chlorine content increases, the commenter maintains that the HCl emissions could increase in proportion to the increase in chlorine emissions. The commenter argues that SO2 control is accordingly not the only factor affecting HCl emissions. Options for removing individual acid gases vary, and they do not remove the other acid gases. Commenter believes that even in instances where gases might appear to be similar (such as HCl and HF, for example), actual removal is a complex function of operating conditions including reagent used, pH, temperature, ratio of reagent to gas flows, concentrations of these gases in the exhaust, manner in which the reagent is mixed, and the presence of other competing gases. Correlated removal is not the norm according to the commenter and this is clearly shown in the poor correlations of emissions of these gases described earlier using the EPA's own data.
The commenter further argues that in order to justify using SO2 as a surrogate for all acid gases the EPA would first have to determine the MACT floor dataset for the particular HAP and then determine the appropriate SO2 limit to impose. Commenter believes that the EPA has provided absolutely no justification to use SO2 as a surrogate for HCN or SeO2. An initial review of the data collected by the EPA indicates some relationship between SO2 removal and HF removal; however, in order to properly establish an SO2-based HF limit, commenter states that the EPA would need to truncate its dataset to reflect the lowest HF emitting units. SO2's relationship to HCl differs (if if exists at all) from its relationship to other acid gases. In order to justify using SO2 as a surrogate for all acid gases, therefore, the commenter maintains that the EPA would first have to determine the MACT floor dataset for the particular HAP and then determine the appropriate SO2 limit to impose.
Comment 5: Commenter 18932 states that technology to achieve reductions of HCl emissions will not invariably capture HCN. A recent engineering study recommended different technological control scenarios to utilities as compliance options for the EGU MACT rule. The study looked at several different boiler designs and ranked potential technological control upgrades based on cost, maturity, and ability to regulate multiple HAP. It is likely that EGUs with fabric filters or ESPs and FGDs of any type will not increase their technological controls in order to remove HCl. And EGUs that need to improve technology will pick FGD options other than a sorbent injection control. Meanwhile, sorbent injection control is the only technology that even claims to be able to remove HCN, and even then, the typical reagent used in sorbent injection is not as effective against HCN as it is for HCl/HF.
Response to Comments 4 - 5: The EPA does not believe that the results of HCN testing from the 2010 ICR were consistently reliable. The EPA conditional test method 033 (CTM-033) provided inaccurate results if the tester did not apply some method changes. In particular, maintaining a pH of 12 or greater is critical to HCN sample collection. For the very long test runs necessary for the low concentrations we expected, testers found that maintaining the high pH was problematic (high CO2 concentrations depleted the alkaline solutions prematurely). Dropping pH or high sample vacuums resulting form sludges forming in the impingers required some testers to stop runs before meeting the minimum sample volume and some ignored the drop in pH. Some testers adjusted the method but others did not. Overall, the data we collected during the ICR testing are suspect and thus were not used to set a HCN emission standard. However, we do believe that acid gas controls represent the best control technology for HCN. We are not aware of any "HCN specific" control technologies that have been applied at coal- or oil-fired electric generating units. We believe that HCN will be best controlled due to its solubility (in a wet scrubber) or due to its acidity (although it is a weak acid). For this reason, the EPA feels that it is reasonable to include HCN with the acidic gases and assume that it is best controlled using installed acid gas control technology.
The commenter asserts that the EPA must comply with a specific three-part test for surrogacy that the D.C. Circuit applied when evaluating whether PM was a valid surrogate for non-Hg metal HAP in another CAA section 112 standard. See Sierra Club v. EPA, 353 F.3d 976, 984 (D.C. Cir 2004) ("this court established a three-part analysis for determining whether the use of PM as a surrogate for HAP is reasonable..."). The EPA maintains that the only standard from that case that expressly applies to EPA's establishment of a surrogate standard for acid gas HAP is that the surrogate be reasonable. We maintain that HCl and, alternatively, SO2 are reasonable surrogates for all acid gas HAP when the unit is using a flue gas desulfurization technology to comply with the surrogate standard.

The EPA believes that the control of the surrogate (in this case HCl) also indiscriminately captures the air toxic along with the surrogate. The EPA believes that, based on the known chemical and physical properties of the compounds, typical flue gas desulfurization systems (e.g., wet scrubbers, dry scrubbers, dry alkaline sorbent injection) will effectively reduce the emissions of the acidic gas HAP. The emissions of all of the acid gas HAP will be reduced due to their solubility or their acidity (or both).
Comment 6: Commenter 17754 states that reducing HCl in the manner required by the proposed rule would likely result in an increase in Hg emissions from coal refuse-fired CBF units. Further, the proposed HCl emission limit fails to take into account other unique characteristics of coal refuse-fired CFB units, including but not limited to, the difficulties associated with using add-on, back end DSI to control HCl emissions from these units, as well as these units' relatively smaller size (as compared to traditional coal-fired EGUs).
Response to Comment 6: The EPA disagrees with commenter. At least two CFB units are among the MACT floor pools for both HCl and Hg, indicating that compliance with both limits is possible. Further, we are aware of at least two CFB EGUs that are using add-on polishing technologies for acid gas control, indicating that further control is possible if needed.
Comment 7: Commenter 17621 states that their evaluation indicated no significant differences between distillate and residual oil in the emission of acid gases (HCl and HF).
Response to Comment 7: As noted elsewhere in this document, the EPA is not subcategorizing distillate vs. residual oil in the final rule.
Comment 8: Commenter 18023 states that the requirements to use the alternative emission limit are not sufficiently clear, especially those that apply to the use of SO2.
Response to Comment 8: The final rule has significantly simplified the rule text on how to qualify for alternative limits, and what testing and monitoring applies when they are used. For SO2, a source must use a flue gas desulfurization control device to qualify for the alternate SO2 limit, and then must use an SO2 CEMS, generally meeting part 75 requirements, to serve as the compliance test method, using a 30-day rolling average.
Comment 9: Commenter 17754 suggests, to the extent that the EPA does not agree to revise the HCl emission limit for existing EGUs consistent with the rate that appropriately prevents associated health impacts for this pollutant, that the proposed emission limit for HCl be revised to be consistent with the EPA's comparable rulemaking efforts for the same pollutant and similar source types. Specifically, the EPA could justifiably impose an HCl emission rate through the Utility MACT equivalent to the corresponding limit for HCl for existing coal-fired CFB boilers established in the EPA's Boiler MACT  -  i.e., 0.035 lb/MMBtu. The HCl emission limit imposed through the EPA's Boiler MACT is based on an accurate emission limit-setting process and, therefore, is appropriate for application to combustion units employing CFB technology. The emission limit for CFB boilers under the Boiler MACT is also appropriate for application to the commenter's CFB units subject to the Utility MACT, because such units are comparable to industrial boilers in terms of combustion technology and heat input capacity. Therefore, revising the emission limit for HCl under the proposed rule in this way would ensure consistent regulation of affected combustion sources subject to emission restrictions both as EGUs and under the Boiler MACT.
Additionally, the proposed HCl emission limit for existing coal-fired EGUs should be revised consistent with an appropriate health-based analysis for this pollutant. The proposed HCl limit instead was derived based on a flawed emission limit-setting process that only evaluated emission rates achieved by individual sources on a pollutant-specific basis, without consideration of whether the same affected EGU could simultaneously satisfy all of the proposed emission limits that would apply to that unit under the proposed rule
Response to Comment 9: The EPA has addressed comments related to the risk posed by HAP emissions from coal- and oil-fired EGUs elsewhere in this document. The final HCl emission limits for this rule were based on data obtained from EGUs that will be subject to this rule, and, thus, the MACT floor analysis is consistent with the statutory direction. The EPA believes that its EGU analyses also are an "accurate emission limit-setting process" consistent with the statute. We have discussed elsewhere in this document our rationale for not subcategorizing FBC/CFB EGUs in the final rule.The Agency disagrees with commenter that the final limits are infeasible and legally unsupportable and we have identified sources that are complying with the standards in the final rule.
We address the comments relating to section 112(d)(4) and data distribution in response to other comments in this RTC document and in the preamble to the final rule.

4F03 - Format of the Standard: Mercury (Hg)
Commenters: 17402, 17620, 17737, 17804, 17843, 18444
Comment 1: Commenter 17402 supports the EPA's Hg standard of 1.2 lb/TBtu or 0.013 lb/GWhr and believes the level is achievable as proposed. Given the inherent variability involved in many aspects of EGU operation, particularly day-to-day variability in total fuel-born Hg input in each unit, variability of sampling and analysis methods, and variability due to site-specific differences among best performing units, the EPA's inclusion of a statistical formula to correct for that variability is necessary and appropriate. The commenter states that their experience indicates that Hg removal percentages above 90 percent are feasible with a variety of configurations. As a result of its experience with implementing the state standards, the commenter states that they are among the most experienced power producers in the country with respect to ACI. Based on its experience, commenter believes that the Hg standard as revised in the May 18, 2011 MACT Floor Analysis is reasonable and achievable.
Response to Comment 1: The EPA appreciates commenter's support for the final Hg standards.
Comment 2: Commenters 17620 and 17804 state that in discussion of the three forms of Hg the EPA observes that particulate-bound Hg emissions can comprise 2 to 5% of the total Hg emissions from a source. The commenter states that it is unclear from the form of the Hg emissions limit and the compliance methodology whether the EPA intends that the Hg limitations include total Hg or only vapor-phase Hg. The limits are listed for "mercury."
Response to Comment 2: The EPA believes that the standard as proposed clearly applies to "total" mercury as the regulated pollutant.
Comment 3: Commenter 17737 urges the EPA to allow in its final rule the option of either a numerical standard or a percent reduction standard as a means of complying with the MACT standard for Hg.
Comment 4: Commenter 18015 recommends a percent removal Hg MACT standard. According to the commenter, the EPA's concern that the percent reduction format will not have the desired effect of promoting and giving credit for pre-combustion Hg removal technologies is unfounded. If sources conclude that it is in their best interest to use such technologies, they will adopt them regardless of whether the standard is input or output-based. For example, if a source determines that as a result of unit type or coal rank, it is unable to rely solely on post-combustion emission controls to comply with the standard, it will implement those coal preparation practices necessary to comply. The EPA's desire to promote coal preparation practices to remove Hg ignores the fact that such practices (e.g., coal washing) have the potential to create unintended environmental problems, including those involving waste.
Regarding the EPA's concern over tracking, the commenter states that such extensive tracking would simply not be required if a percent removal standard were to be adopted. Rather, if no coal preparation practices are used by the source, all it needs do is measure the Hg content of the coal at a point just prior to it entering the plant. The rule as proposed by the EPA would already impose fuel sampling requirements on sources. Accordingly, sources would have to do no more tracking than would already be required under the rule. As for those sources that choose to adopt pre-combustion Hg removal technologies, all that would be required is that these sources measure the Hg content of the coal at a point just upstream of the process.
The commenter also disagrees that the agency does not have the necessary data. As part of EPA's 1999 ICR, the agency collected coal data from all of the operating units involved in the request. In addition, as part of its 2010 ICR, the agency collected additional coal sampling data. The commenter disagrees that a percent reduction standard will reduce flexibility or require controls any more than input or output-based limits. Nothing in the CAA precludes percent removal standards for the MACT floor units. Also, dissimilar coals, which result in disparate physical properties of the flue gas, create significant differences in the efficiency of Hg removal required and the feasibility of removing Hg from the flue gas to a specified level. This inability to control Hg emissions equally from all types of coals warrants inclusion of a percent removal standard in the final rule. As a result of proceedings initiated for purposes of implementing CAMR, a significant number of states put in place state-specific Hg regulations, which include a percent removal standard. Considerable expenditures have been made by utilities for purposes of complying with the EPA's published rules, such as CAMR. Now that the rules have changed, these utilities are being punished for attempting to comply with the state Hg rules that went into effect prior to and in contemplation of CAMR. Furthermore, some utilities, like APS, have entered into long-term coal contracts that limit their ability to switch to a different coal source. Good faith expectations by sources that they would be required to comply with a percent reduction standard further justifies adoption of such a standard by the EPA in the final EGU MACT rule. Accordingly, the commenter recommends that the final rule allow compliance based on either a numerical emission limit or a minimum of 91% removal of Hg from coal, consistent with the EPA's stated policy goal to reduce EGU Hg emissions.
Comment 5: Commenters 17689 and 17712 support a percent reduction MACT metric as an alternative, and not a substitute, to some of the proposed MACT numerical limits. For example, Hg and HCl are HAP whose levels would not be meaningfully reduced by fuel pretreatment. A necessary data format and protocol could be developed for some HAP, such as Hg, that would allow an appropriate percent reduction alternative to be developed. A percent reduction MACT could specify the level or reduction but would not dictate any specific control or methodology and would address EPA concerns over consistency with the Brick MACT court ruling.
Commenter 17725 agrees with the EPA that a Hg percent reduction limit alone would not provide adequate flexibility. The commenter states that credit for coal preparation practices that remove Hg and other HAP before firing would be addressed by the lb/MMBtu standards (as they are in the EGU NSPS Rule). If those sources elected to use the percent reduction option based on on-site post-beneficiation fuel analysis, the percent removal values would simply be conservatively low. 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, the agency did collect sufficient fuel data to establish an on-site removal value since sources reported fuel analysis data along with the stack test results under the EGU ICR. An alternative percent reduction based on the emissions achieved in practice by the top performing sources would also be consistent with the requirement of the statute.
Response to Comments 3 - 5: The EPA disagrees with the commenters' suggestions that a percent reduction standard should be included in the final rule. The EPA notes that the inability to account for Hg removed from the coal prior to combustion was not the only reason provided for not using a percent reduction format. As noted in the proposal preamble (76 FR 25040), we did consider using a percent reduction format for Hg. We determined not to propose a percent reduction standard for several reasons. The percent reduction format for Hg and other HAP emissions would not have addressed the EPA's desire to promote, and give credit for, coal preparation practices that remove Hg and other HAP before firing. Also, to account for the coal preparation practices, sources would be required to track the HAP concentrations in coal from the mine to the stack, and not just before and after the control device(s), and such an approach would be difficult to implement and enforce. In addition, we do not have the data necessary to establish percent reduction standards for HAP at this time. Depending on what was considered to be the "inlet" and the degree to which precombustion removal of HAP was desired to be included in the calculation, the EPA would need the HAP content of the coal as it left the mine face, as it entered the coal preparation facility, as it left the coal preparation facility, as it entered the EGU, as it entered the control devices, and as it left the stack to be able to establish percent reduction standards. The EPA believes, however, that an emission rate format allows for, and promotes, the use of precombustion HAP removal processes because such practices will help sources assure they will comply with the proposed standard. Furthermore, a percent reduction requirement would limit the flexibility of the regulated community by requiring the use of a control device. In addition, as discussed in the Portland Cement NESHAP (75 FR 55,002; September 9, 2010), the EPA believes that a percent reduction format negates the contribution of HAP inputs to EGU performance and, thus, may be inconsistent with the D.C. Circuit's rulings as restated in Brick MACT (479 F.3d at 880) that say, in effect, that it is the emissions achieved in practice (i.e., emissions to the atmosphere) that matter, not how one achieves those emissions. The 2010 ICR data confirm the point relating to plant inputs likely playing a role in emissions in that they indicate that some EGUs are achieving lower Hg emissions to the atmosphere at a lower Hg percent reduction (e.g., 75 to 85%) than are other EGUs with higher percent reductions (e.g., 90% or greater). For all of these reasons, we proposed to establish numerical emission standards for Hg HAP emissions from EGUs and we are finalizing numerical emission standards.
Comment 6: Commenter 18444 recommends a Hg minimization provision similar to their rules which require that sources examine duct optimization of Hg controls for up to a year and use a reasonable amount of carbon to minimize Hg if carbon injection is used.
Response to Comment 6: The EPA is required to establish standards pursuant to CAA section 112(d) and we do not believe that test programs such as that noted by the commenter would be consistent with the statutory language. The EPA expects that such test programs to establish the conditions under which compliance would be achieved as noted by the commenter would be undertaken before the compliance date in determining what method of control a given EGU would be using for compliance with the final rule.
Comment 7: Commenter 17843 states that a number of states with large coal-fired power plants have already adopted stringent Hg control requirements that are, in most cases, more stringent than those of the proposed Hg standards. Some provisions of the states' rules have now been in effect for several years, and compliance data indicate that the affected units are achieving the required Hg reductions. The commenter's submittal included attachments summarizing the state mercury rules and the controls installed or planned at coal power plants in the commenter's region to comply with the state rules. The commenter provided examples of states that have successfully implemented Hg limits for coal power plants.
Coal-fired EGUs in Connecticut had to achieve by July 1, 2008 a Hg emissions limit of 0.6 lb/TBtu or a rate equivalent to a 90% reduction from measured inlet conditions. Of the three affected Connecticut units, the Bridgeport unit installed ACI with a pulse-jet fabric filter baghouse; the AES Thames units are CFB boilers with dry limestone injection and fabric filtration to control sulfur and met the state limits without installing Hg-specific controls. Quarterly stack testing of the three affected units in Connecticut indicated that they achieved the state's Hg requirements.
In 2001, Massachusetts as part of a multi-pollutant approach established annual Hg emission caps for coal-fired power plants at the then-current level of emissions. To reduce Hg emissions, in 2004, Massachusetts revised its Hg emission limits in two phases. Phase 1 required a 85% reduction or an emission rate of 0.0075 lb/GWh by 2008; Phase 2 requires a 95% reduction or an emission rate of 0.0025 lb/GWh by October 1, 2012. The rule allows averaging between units at the same power plant. Of the eight EGUs subject to Phase 1, one unit has shut down, three units did not need to install Hg controls to comply and have announced they will shut down, and one unit installed SCR, a dry scrubber and a fabric filter. At another facility, one unit installed SCR, DSI, spray dryer absorption, and a fabric filter; another installed DSI-SDA-FF; a third unit installed SCR and has DSI-DS-FF under construction. Compliance reports submitted in January 2011 show Hg compliance for 2010 at all operating units.
New Hampshire requires an 80% reduction in coal-fired power plant Hg emissions through installation of wet FGD at the one facility by July 1, 2013.
New Jersey requires coal-fired units of any size in the state to achieve a Hg control efficiency of 90% or an emission limit of 3.00 mg/MWh by December 2007. They also provides for a multi-pollutant approach to reduce NOX, SO2, and fine particulates that can extend a unit's Hg compliance deadline to December 2012 if approximately 50% of a company's coal-fired capacity in the state meets the Hg limits by the 2007 deadline. Ten units were covered by New Jersey's Hg rule at the time it was adopted in 2004. Coal units are using ACI to meet the rule requirements, and stack testing indicates the applicable limits are being met.
In 2007, New York established Hg emission limits for coal-fired EGUs that incorporates a Phase I facility-wide emission cap in the years 2010-2014 and establishes a unit-based emission limit for each applicable unit beginning in 2015. Starting in 2015, a facility-wide Hg emission limit of 0.6 lb/TBtu will apply. Phase I limits have been met with sulfur reduction technologies that have co-benefits in reducing Hg. No facilities are yet using ACI until they need to meet the more stringent 0.6 lb/TBtu Hg limit in 2015 on a daily average. EGUs with NOX and SO2 control are achieving Hg emission rates in the 0.6 lb/TBtu range and will use ACI to achieve consistent emission levels. Currently, all operating coal-fired EGUs in New York State are meeting the Phase I facility-wide caps.
The commenter's assessment of power plant control technologies identified a number of control options that directly targeted Hg for control or had the co-benefit of reducing Hg when targeting other air pollutants. ACI can be installed to directly target Hg, although the following options reduce Hg as a co-benefit: combustion controls, SCR, ESPs, baghouses, dry and wet scrubbers, and DSI.
Response to Comment 7: The EPA appreciates the information provided by commenter. However, the EPA notes that many of the state programs noted by commenter have an "either/or" format for their Hg standards. That is, an EGU can either meet an emission limit (e.g., lb/TBtu) or achieve a percent reduction.The commenter did not note which form of the standard the EGUs were meeting. As noted elsewhere in this document, the EPA does not believe that a percent reduction format is appropriate for the final rule.
Comment 8: Commenter 18039 believes that EPA's use of a 5% threshold for Hg is too high, as even units emitting a small amount of mercury can contribute to formation or exacerbation of mercury deposition hot spots. Units that install Hg CEMS and sorbent trap monitoring systems will have data available to optimize their operational procedures to minimize mercury emissions. Therefore, the commenter encourages the EPA to require all coal-fired units to install Hg CEMS or sorbent traps.
Response to Comment 8: The final rule requires the use of Hg CEMs, sorbent traps, or periodic stack testing.
4F04 - Format of the Standard: Other
Commenters: 16122, 16513, 17383, 17402, 17620, 17623, 17689, 17691, 17705, 17712, 17716, 17717, 17718, 17725, 17801, 17812, 17813, 17816, 17820, 17821, 17846, 17869, 18039, 18421, 18426, 18428, 18434, 18439, 6637, 19536, 19537, 19538, 18023
Comment 1: Commenters 16122 and 19686 state that the EPA should require that all EGUs (not just new units) meet an output-based rather than an input-based standard for emissions. Commenter note that in the GAO Mercury Report, an output-based standard (i.e., one based on the amount of electricity produced) would result in less Hg emitted nationwide than an input-based standard (i.e., one based on the plant's heat input). This is because an output-based standard will create a significant incentive for EGUs to improve their efficiency as a strategy to meet MACT standards.
In addition to the GAO report, commenters note that the EPA itself has recognized the importance of utilizing an output-based standard. For example, during the April 20, 2011 tribal consultation on NSPS for Greenhouse Gases, Gina McCarthy, Assistant Administrator for EPA's air office, agreed that an output-based MACT standard provides co-benefits by reducing not only air toxics, but also CO2 and criteria pollutants (e.g., SO2 and NOX).
Several commenters (16513, 18421, 18434, 18439) also support the use of output-based standards where feasible.
Commenter 18434 adds that net-output based standards create incentives for even greater efficiency and would encourage facilities to minimize parasitic energy demands from pollution control equipment. Commenter recognizes the potential "monitoring difficulties" associated with tracking on-site energy use but believe that such difficulties should not be insurmountable. As such commenter supports the use of net output-based standards in both the NSPS and NESHAP.
Comment 2: Commenters 17718 and 17816 recommend output standards based upon gross output. Otherwise generating units with substantial parasitic load needed to run emission control equipment would be unduly penalized. Gross output is the best parameter for output-based standards because it is the best representation of unit performance. Any standards adopted in this rulemaking should be tailored toward HAP emissions, rather than considerations such as energy efficiency which fall outside the scope of section 112.
Commenter 17821 prefers the use of a gross basis and states that for the EPA to implement a net output-based standard, there are many issues that it must first resolve, including:
      ::shared services, such as fuel handling, administrative buildings, coal cleaning, gypsum production;
      ::winter heating requirements and other energy consuming devices necessary for plant operation;
      ::multiple boilers and/or turbines that operate in common systems;
      ::shared auxiliary loads including power consumption during shutdown periods;
      ::use of pollution controls such as FGD, and SCR which significantly increase auxiliary power needs; and
      ::mechanical draft cooling towers to avoid thermal discharges into waterways, but which require the use of large fans and pumps which consume additional power.
Commenter 17821 states that net output-based standards encourages increased operation, since high load EGUs that run at high capacity factors can meet a net output-based standard more easily than can a cycling or peaking. Gross output based standards are also the simplest to measure and apply.
Commenter 17846 states that the EPA should require that all EGUs (not just new units) meet an output-based rather than an input-based standard for emissions. As noted in the GAO Mercury Report, an output-based standard (i.e., one based on the amount of electricity produced) would result in less Hg emitted nationwide than an input-based standard (i.e., one based on the plant's heat input). This is because an output-based standard will create a significant incentive for EGUs to improve their efficiency as a strategy to meet MACT standards.
Commenter 18039 states that for each pair of output- and input-based standards, there is an energy conversion efficiency (i.e., heat rate) at which the standards are equivalent. Facilities that are more efficient than this heat rate can more easily comply with the output-based standard, and facilities less efficient can more easily comply with the input-based standard. The result is that for some MACT pollutants, all facilities will likely choose to comply with the output-based standard, and for other pollutants, all facilities will likely choose to comply with the input-based standard. It is not reasonable or appropriate that facilities can pick a weaker standard to comply with, simply by choosing an output- vs. input-based standard. The EPA's approach to developing the MACT standards negates the main benefit of output-based standards, i.e., encouraging facilities to increase efficiency. The commenter encourages the EPA to adopt correctly-calculated output-based standards, and not allow facilities to comply with an input-based standard. Providing incentives to optimize efficiency will have economic, health and environmental benefits.
Response to Comments 1 - 2: The EPA is finalizing input-based emission limits with alternative gross output-based emission limits for existing sources. The EPA is finalizing only gross output-based emission limits for new sources.
Comment 3: Commenters 17623 and 18428 state that in the proposed Utility MACT, the EPA's use of surrogates demonstrates the Agency's recognition that emissions testing can cover multiple pollutants simultaneously and that surrogates help eliminate costly and redundant testing. As a result, the commenter supports the EPA's use of surrogates in the proposed Utility MACT.
Commenter 17705 supports the EPA's use of surrogates, including PM for non-Hg metallic HAP and SO2 for acid gas HAP, in this rule because surrogates provide sources with flexibility to comply with the numeric limit that is best suited to its operations and emissions profile.
Response to Comment 3: The EPA acknowledges the support of the commenters.
Comment 4: Commenter 17716 states that existing unit output standards in the proposed rule rely on incorrect heat rate assumptions. Commenter states that output based ("lb/MWh") standards for existing units erroneously rely on incorrect assumptions for gross unit heat rate ("GHR"). The emissions floor calculation determines GHR based on the "maximum heat input capacity" and "gross (summer) generating capacity" as reported in Part I of the ICR for the individual boilers and uses this value to convert reported emissions on the basis of heat input (`lb/MMBtu') to unit output (`lb/MWh'). Due to reporting inconsistencies, these values are not necessarily equivalent to the "design gross heat rate", as the EPA assumed in the data conversion procedure. For example purposes, the attached Table shows 12 coal-fired units from the EPA's Hg floor analysis sheet with calculated heat rates of less than 7,000 Btu/kWh, efficiencies that would be completely impossible for these units.
Table 12. Example Heat Rate Values from EPA's Hg Floor Analysis Spreadsheet
                                     Plant
                                     Unit
                                  Boiler Type
                                 Capacity (MW)
                           Max Heat Input (MMBtu/hr)
                              Heat Rate (Btu/kWh)
                                   Cedar Bay
                                     CBA1
                                 Fluidized bed
                                      280
                                     1063
                                     3800
                                   Cedar Bay
                                     CBB1
                                 Fluidized bed
                                      280
                                     1063
                                     3800
                                   Cedar Bay
                                     CBC1
                                 Fluidized bed
                                      280
                                     1063
                                     3800
                                  AES Hawaii
                                      002
                                 Fluidized bed
                                      203
                                      944
                                     4650
                                   Chambers
                                       1
                                  Wall-fired
                                      285
                                     1387
                                     4870
                                   Chambers
                                       2
                                  Wall-fired
                                      285
                                     1387
                                     4870
                                  AES Hawaii
                                      001
                                 Fluidized bed
                                      203
                                     1021
                                     5030
                                   Hopewell
                                   1 & 2
                               Stoker - spreader
                                      136
                                      855
                                     6290
                                  Scrubgrass

                                       1
                                 Fluidized bed
                                      194
                                     1250
                                     6440
                                  Southampton
                                   1 & 2
                               Stoker - spreader
                                      136
                                      889
                                     6540
                                   Armstrong
                                       2
                                  Wall-fired
                                      183
                                     1204
                                     6580
                                   Armstrong
                                       1
                                  Wall-fired
                                      184
                                     1250
                                     6790
To demonstrate that this error resulted in output standards that are fundamentally flawed and inconsistent with the equivalent input standards, the attached Table 6 shows the average heat rate from comparing the lb/MMBtu and output based standards for existing units.
Table 6. Equivalent Heat Rate Values for Existing Unit Standards (Btu/kWh)

                                    Mercury
                                   Total PM
                                      TSM
                               Individual Metals
                                      HCl
                                      SO2
                      Coal fired unit >= 8,300 Btu/lb
                                     8,000
                                    10,000
                                    10,000
                                    10,000
                                    10,000
                                    10,000
Coal fired unit < 8,300 Btu/lb
                                    10,000
                                    10,000
                                    10,000
                                    10,000
                                    10,000
                                    10,000
                       Solid oil-derived fuel-fired unit
                                    10,000
                                    10,000
                                    20,000
                                    17,500
                                    10,000
                                    12,500
                             Liquid oil-fired unit
                                    14,000
                                      NA
                                    10,000
                                    15,000
                                    10,000
                                      NA
                                     IGCC
                                    10,000
                                     6,000
                                    10,000
                                    10,000
                                     6,000
                                      NA
As shown in the table above, the following subcategories have GHR values that are unrealistically high or low based on the expected boiler performance for the category:
   1. Mercury Standard for `Coal-Fired Unit >= 8,300 Btu/lb' Subcategory
   2. Total and Individual Metals Standards for `Solid Oil-Derived Fuel Fired Unit' Subcategory
   3. Mercury and Individual Metals Standards for `Liquid Oil-Fired Unit' Subcategory
   4. Total PM and HCl Standards for IGCC Subcategory
To rectify this problem, the commenter suggests that the EPA should recalculate the ICR data on an output basis using a tiered approach depending on data availability. They suggest that, in most cases, the EPA should be able to convert measured emissions directly to units of `lb/MWh' based on the reported stack flows and gross generation at the time of the stack test. Alternatively, a representative GHR value could be derived based on the most recent stack test that was conducted under representative operating conditions for which the necessary data is available (e.g., gross generation, stack flow, CO2/O2). This value could then be applied to the calculated input-based emissions value (`lb/MMBtu'). Further, the commenter notes that although design GHR data is available in the Part II ICR database, these values should be not be used without further review because of the potential for reporting inconsistencies. The commenter states that a brief review of the Part II ICR database shows significant gaps in the data plus reporting in some cases on the basis of thermal efficiency rather than overall cycle efficiency.
Response to Comment 4: The gross unit heat rates for these and additional EGUs have been reviewed and corrected. There were 59 boilers that had heat input and generation data, which were originally incorrectly entered by companies responding to the utility ICR, but the data have been corrected. All documentation of these changes is in the docket.
Comment 5: Commenter 6637 notes that the EPA's Mercury and Non-Mercury Metals and Potential Surrogates Group included Hg and ten other metals, filterable PM, condensable PM, and PM2.5.
The most significant issues for Hg measurements were related to the uncertain accuracy of measurements made at the low end of the working range of one of the test methods, EPA Method 30B. Although the method contains procedures to ensure that sufficient Hg is collected to provide accurate quantitation, the ICR test reports rarely documented that those procedures were followed. In some samples, too little Hg was collected, causing the results to fail method quality control criteria. The reported values for these low-emitting units may have been too low to have been accurately quantified, and in some cases were below the detection limit of the method. According to ICR instructions, values below detection limits should have been reported at the detection limit. Thus, the impact of the low Hg capture and incorrect reporting of the detection status of the measurement would be to produce an overall low bias in the ICR data.
For non-Hg metals, the most significant quality issues all resulted in reported concentrations that were biased high in some samples, including: (1) elevated manganese due to contamination from back-flow of the permanganate impinger used for Hg sampling, (2) extremely high reported values of chromium, manganese and nickel, suspected to be contamination from metal components of the stack or the sampling equipment and (3) high recoveries of laboratory control spikes, especially for selenium. These issues were noted in a low percentage of the tests reviewed by the commenter, but due to the magnitude of the positive bias, the outlier results could impact statistical estimates of emissions from the ICR data. For all non-Hg metals, the commenter notes that procedures for blank correction were inconsistent among the different ICR respondents and laboratories. This inconsistency increases the uncertainty of emission estimates for metals, particularly for units with lower emissions.
For the particulate measurements included in the metals HAP group, the most significant quality issue identified was the use of varying filter temperatures to measure filterable PM. The EPA intended for all out-of-stack filterable PM measurements to be made at 320+-25°F; however, this guidance was not clearly conveyed to all ICR participants. As a result, the correct filter temperature was used at most, but not all, power plant units equipped with wet FGD systems (wet stacks), but at far fewer of the units without those pollution controls (dry stacks). About 75% of the tests reviewed by the commenter were conducted at dry stacks measured filterable PM at 248°F, the standard filter temperature for a combined PM/metals sampling train. The concern with inconsistent filter temperatures is that sulfuric acid can condense on the filter at the lower temperature. There could also be other relatively volatile species desorbed from the filter at the higher temperature. Changing the filter temperature changes the proportion of total PM captured in the front versus the back half of a particulate train, and consequently weakens the correlation between filterable PM and metals emissions. The magnitude of the change in filterable PM between the two filter temperatures is likely to be specific to a particular fuel and power plant configuration; it could be significant for some coal-fired units that emit significant levels of SO3.
For condensable particulate, the commenter noted that the amount of particulate measured in the solvent blanks was frequently close to or equal to that in the sample. Since the test method limits blank correction to an amount that is often exceeded in the blanks, the ICR test results for this parameter are likely biased high in many cases. Additionally, the blank correction procedure varied among the ICR respondents, increasing the overall uncertainty of the ICR data. Another factor increasing the uncertainty of the condensable particulate results is the longer than normal sampling duration. Past research done by the commenter has identified both positive and negative biases for this test method; it is unknown which would predominate in a 4-hour stack test.
Response to Comment 5: We recognize that about 20 of the over 220 source tests reported below detection level values for mercury by Method 30B. We also noted that the detection levels of those tests spanned from 0.01 ug (10[-8] lb/MMBtu) to 9 ug (10[-6] lb/MMBtu). Another 37 tests did not include any flag but 24 had blank entries for the mass or values below 0.1 ug. There was at least one test which identified data below 10[-8] lb/MMBtu and indicated that the measurement was above detection levels. Several other tests had measureable data below 10-6 lb/MMBtu. Although this reflects poorly on the test companies which conducted the tests, we do not believe these adversely affected the selection of the best performing source nor the best performing 12% of the sources when combined with our treatment of below detection data and the final selection of the numerical limit.
For the non-Hg metals, the high values for manganese, chromium, nickel and selenium also reflect poorly on the test companies which conducted the tests. As with the mercury tests we believe that these high values did not adversely affect our selection of the best performing source or the best performing 12% of the sources nor the determination of the numerical limit.
Likewise, although the use of lower filter temperatures than we required were used, we do not believe that this significantly affected the selection of the best performing source or the selection of the best performing 12% of the sources. As indicated by the commenter, this would allow SO3 and other semivolatile particulate to be collected as filterable PM when at the higher temperature it would be collected in the impinges as either organic or inorganic condensable PM. The sources where the source tester used the lower filter temperature would tend to have higher particulate and as a result decrease the likelihood that these sources would be selected as the best performing or in the best performing 12% of sources. We do not believe that this minor shifting of the units with a full suite of emissions controls and the broader range of emissions controls have a significant adverse impact on the resulting emissions limits.
Because the agency is now using filterable particulate for the alternate equivalent standard for non-Hg HAP metals and for the NSPS PM indicator the comments on condensable PM are moot. We recognize that several source testers have had issues with high blanks. As we indicated in the proposal and promulgation documentation supporting the revised Method 202, the improved performance of this method makes it imperative that source testers use properly prepared glassware, scrupulous field techniques and consistent and precise laboratory finishes. The high blank values reveal that some testers need improvement in one or more of these areas. The significantly lower amounts of condensable particulate matter collected by this improved method also make the proper performance of the method imperative to achieve consistent, reliable and accurate measurements.
Comment 6: Commenter 6637 notes that the EPA's Non-dioxin/furan Organics and Potential Surrogates Group included speciated VOCs and semivolatile organic compounds (SVOCs) and the potential surrogates total hydrocarbons (THC), methane, CO, and formaldehyde.
The commenter states all THC measurements and some methane measurements were conducted using a direct-reading test method; and that the measured values for these samples were frequently near the zero gas response of the instrument and the span of the instrument was often set significantly higher than the measured values. These findings indicated that the results of these tests were highly inaccurate. The ICR required all direct interface measurements to be reported as above detection limit; therefore, there is a risk of misinterpreting the results of these tests as being representative of stack emissions rather than fluctuations around the instrument baseline.
For formaldehyde, multiple test methods were used. The most significant quality issue was associated with measurements made by EPA Method 0011, the most commonly used method in the ICR tests reviewed by the commenter. Most of the reported values obtained with this method were close to concentrations in the blanks. Contamination of the field blank was more common for Method 0011 than the other test methods. Results of another test method, EPA Method 320, had elevated detection limits due to poor sensitivity of the method for formaldehyde. For both of these test methods, the result of these two quality issues was a high bias in the emissions estimates. In an interim ICR database published by the EPA, these two methods were used in 48% and 13% of the formaldehyde tests, respectively. Thus, there is a significant impact that needs to be taken into account when evaluating the potential correlation between formaldehyde and organic HAP.
A preliminary review of the CO data in the EPA's database indicated some potential quality problems with the results. The commenter did not have access to the calibration quality control results needed to evaluate the CO results directly; however, information included in the EPA's ICR reporting template indicated that up to a quarter of test runs from coal-fired units failed to register reasonable proportions of other gases (e.g., O2, CO2) by the instrumental method and therefore may not have measured CO accurately.
Most of the reported volatile and semivolatile compounds appeared to be below detection limits, although the large number of missing or erroneous detection flags made this difficult to evaluate. Of those that were detected, some were solvents used in field sampling of other HAP and likely originated from cross-contamination of the samples. Others have been reported in the literature as breakdown products of the sorbents used in sample collection. A careful evaluation of field blanks and the technical literature will be needed to differentiate between actual emissions and these other sources of organic compounds.
Comment 7: Commenter 6637 states that in reference to the EPA's Dioxins/Furans/PCBs surrogate group that the chemicals in this HAP group are ubiquitous in the environment and the test method is so sensitive that it is very difficult to avoid contamination of the sample during sampling and analysis. For this reason, the primary quality issue for these measurements is how to determine the true concentration in stack samples when the same species are detected in method and field blanks. The commenter's ICR reviews frequently noted amounts of target species in the blanks that would cause a significant positive bias to the sample concentration. Another significant issue affecting this group was the high percentage of values that were below detection limit; inconsistent assignment of detection flags increased the uncertainty of the overall data collection.
Response to Comments 6 - 7: We proposed a work practice standard for organic HAP, and have finalized this general approach in the rule. The EPA did not believe that the test data supported establishing a numerical emission limit for this pollutant group.
Comment 8: Commenter 17383 states that although they question the need to regulate HCl, they believe the proposed HCl or SO2 emission limits are attainable. They agree that SO2 can act as a surrogate for HCl and they agree that the emission rates, as proposed, are reflective of MACT with appropriate and reliable monitoring technologies.
Response to Comment 8: The EPA acknowledges the support of the commenter.
Comment 9: Commenter 17620 states that opportunities for improvement in the heat rate of existing EGUs are relatively small. In addition, many efficiency improvement options, such as soot removal, are not permanent and require ongoing maintenance to sustain improved performance.
Response to Comment 9: The EPA understands that opportunities for improvement in the heat rate of existing EGUs will vary from unit to unit, with some units being able to realize significant improvements while others have little opportunity to improve the heat rate. However, while the EPA certainly encourages efficiency improvements and understands that pollutant reductions can be achieved through efficiency improvements, the rules finalized in this action do not require heat rate improvements.
Comment 10: Commenter 17691 requests clarification on the method of converting input-based emission limitations to output energy-based emission limitations. The commenter considers that a constant conversion factor will reduce the effectiveness of the emission limit, rather than producing noticeable improvements in electric generation efficiency. The commenter recommends developing a formula to determine output energy-based emission limits based on unit specific conditions.
Response to Comment 10: Compliance with output-based emission limits in the final rule is to be accomplished through data gathering specific to the format rather than be converting input-based data. In this manner, the specific efficiency of the unit will be accounted for.
Comment 11: Commenter 17801 recommends that the rule be revised to consider the impact that carbon capture will have on the ability of new EGUs to meet the proposed MACT and NSPS standards for HAP and criteria emissions. The primary effect of carbon capture will be the lowering of net output and the inability of EGUs  -  both new and existing  -  to meet net output standards (vs. gross output). Without considering carbon capture and providing clarity on how permitting will accommodate these changes, this rule, as proposed, could serve as a disincentive for carbon capture.
Response to Comment 11: The EPA does not typically include anticipated or potential regulatory action when modeling expected sector response to a proposed or final rule. Further, the EPA cannot, at this time, anticipate how a greenhouse gas rule would be structured for new or existing sources. In the the final rule, output-based standards are all based on gross output (rather than net).
Comment 12: Commenter 17816 recommends that standards be based on annual averages consistent with other EPA rulemakings for EGU's (i.e., Acid Rain Program). The EPA has not demonstrated why a 30-day average would be more protective for human health than an annual period, particularly for Hg emissions. As mass emissions is the key issue for these HAP, use of an arbitrary and short averaging period (i.e., 30-day rolling average) does not allow enough operational flexibility to address process issues or startup and shutdown events that may impact compliance.
Commenter 17816 states that the data used to establish the standards was solely determined by full load steady-state testing taken at a single point in time and did not encompass the full range of operating conditions including changes in operating variables (i.e., pulverizers taken out of service, fuel variability causing changes in control equipment operations, etc.) that a unit experiences in the normal course of operation. The EPA can alleviate some of the effect of variability on unit emissions that was not accounted for in the 2010 ICR testing by allowing annual averaging, although still achieving the same emission reductions.
Response to Comment 12: We have addressed similar comments elsewhere in this document, including averaging time, variability, and startup and shutdown. We have also discussed elsewhere why we do not believe that a mass-based format is appropriate for this rulemaking.
Comment 13: Commenter 17775 notes that the EPA proposes to exercise its discretion under CAA section 112(q)(3) and not set MACT limits for radionuclide emissions from EGUs. 76 FR 25,024. Commenter supports the EPA's decision.
Comment 14: Commenter 17820 supports the EPA's decision to leave in place its earlier decisions made in 1984 and in 1989 not to set MACT limits for radionuclides. The EPA's decision is fully supported by the existing record, which includes extensive sampling and analysis of emissions from coal- and oil-fired units from the 1980's. Accordingly, the EPA did not require testing for emissions of radionuclides in the ICR conducted in advance of this rulemaking.
Response to Comments 13 - 14: The EPA acknowledges the commenters' support.
Comment 15: Commenter 17821 recommends that the EPA should clarify that NESHAP surrogates will qualify as the "same pollutant" or "stream of pollutants" for purposes of CAA section 112(i)(6). Portions of the preamble to the proposed rule indicate that the EPA is regulating some of the same pollutants under CAA section 112 that it regulates under other portions of the CAA. As such, the commenter requests that the EPA clarify that all pollutant surrogates constitute the "same pollutant," or "stream of pollutants," under CAA section 112(i)(6).
Since the EPA has proposed emissions standards for PM and SO2 under other portions of the CAA (and for which many utilities have installed BACT or achieved lowest achievable emission rate (LAER)), the EPA should include an explanation in the final rule that these HAP surrogates qualify as the "same pollutant" or "stream of pollutants" under CAA section 112(i)(6) and avoid regulatory ambiguity. This clarification is warranted because utilities that have installed BACT controls eligible for this extension will need adequate time to assess the performance of the pollution control systems, determine whether those BACT controls will be adequate to meet MACT standards, and then implement any changes necessary to assure compliance with MACT. However, because even with this clarification so few utilities will likely be able to utilize the compliance extension provided in section 112(i)(6) in any meaningful way as a result of the timing issue, the EPA should still provide an industry-wide extension to the 3-year compliance deadline pursuant to its authority under other sections of section 112(i).
Response to Comment 15: The EPA has implemented the provisions of section 112(i)(6) in the Part 63 general provisions at 40 C.F.R. 63.6(i)(2)(ii), (5) and (6)(ii). Sources that have installed BACT or LAER technology for SO2 and/or PM may qualify for a compliance extension. Consistent with 40 C.F.R. 63.6(i)(5), sources that meet this requirement must submit a request for a compliance extension, included all required information, to the Administrator no later that 120 days after the promulgation date of this standard.
Comment 16: Commenter 17821 states that the EPA's assumption that 5% of station power is used internally is incorrect. The commenter's experience is that approximately 7% to 8% of a conventional coal fired station's power is required to run auxiliary equipment. The commenter believes that this is a more representative value across the industry considering that units will be generally operating with SCR, FGD, and particulate controls, all of which require auxiliary power. The commenter's operating experience is that the amount of auxiliary power used by an IGCC unit is considerably higher than the EPA's estimate. If carbon capture systems are installed in the future, the amount of auxiliary power will dramatically increase.
Response to Comment 16: Although the EPA recognizes the potential for future rules to require additional control devices that may increase the internal use of station power, the EPA believes its assumptions concerning average station power use for this rule are correct
Comment 17: Commenter 18039 states that the EPA has not specified any calibration procedure, frequency or accuracy level required of electrical meters used to report electricity fed into the electric grid. It appears that the EPA is presuming that gross electric meters are used for billing, allowing other parties to specify calibration procedures. In proposing gross output-based MACT and NSPS standards and not proposing calibration procedures, the EPA seems to have assumed that gross output meters are universally used in billing transactions, when some power plants use net output meters as their billing meters. It is inappropriate to base MACT and NSPS compliance determinations for large power plants on non-billing meters that are not calibrated following a specified procedure, frequency and accuracy level.
Response to Comment 17: The specifications for reporting hourly gross output are consistent with the Acid Rain Program reporting requirements.
Comment 18: Commenter 18039 states the EPA currently requires reporting of hourly gross output to ECMPS (for purpose of determining load for missing data procedures). Since the EPA will need to amend the reporting requirements under 40 CFR part 75 to incorporate reporting of MACT data, the EPA should require MACT facilities that currently report gross output or steam load to switch to net output. Under 40 CFR 75.53(g)(1)(vii)(F), units are already required to report "when the maximum hourly gross load, boundaries of the range of operation, ...change and are updated" and to modify their data collection accordingly; this same process would apply to switching to reporting net output.