Redline strikeout highlighting changes made during OMB review 1 Currently, we are not aware of any preheater/ precalciner kiln that vents its alkali bypass gases through a separate stack.

123 VIII. How Did EPA Determine the Proposed Emission Standards for Hazardous Waste Burning Cement Kilns? In this section, the basis for the proposed emission standards is discussed. See proposed § 63.1204A1220. The proposed emission limits apply to the kiln stack gases, in line kiln raw mill stack gases if combustion gases pass through the in line raw mill, and kiln alkali bypass stack gases if discharged through a separate stack. 1 The proposed standards for existing and new cement kilns that burn hazardous waste are summarized in the table below:

PROPOSED STANDARDS FOR EXISTING AND NEW CEMENT KILNS Hazardous Air Pollutant or Surrogate Emission Standard1 Existing Sources New Sources Dioxin and furan 0.20 ng TEQ/ dscm; or 0.40 ng TEQ/ dscm and control of flue gas temperature not to exceed 400 ° F at the inlet to the particulate matter control device.

Mercury2 64 ug/ dscm 35 ug/ dscm Particulate Matter 65 mg/ dscm ( 0.028 gr/ dscf) 13 mg/ dscm ( 0.0058 gr/ dscf)

Semivolatile metals3 4.0 x 10 4 lb/ MMBtu 6.2 x 10 5 lb/ MMBtu Low volatile metals3 1.4 x 10 5 lb/ MMBtu 1.4 x 10 5 lb/ MMBtu Hydrogen chloride and chlorine gas4 110 ppmv or the alternative emission limits under § 63.1215 78 ppmv or the alternative emission limits under § 63.1215 Hydrocarbons: kilns without bypass5, 6 20 ppmv ( or 100 ppmv carbon monoxide) 5 Greenfield kilns: 20 ppmv ( or 100 ppmv carbon monoxide and 50 ppmv7 hydrocarbons). All others: 20 ppmv ( or 100 ppmv carbon monoxide) 5 Hydrocarbons: kilns with bypass; main stack6, 8 No main stack standard 50 ppmv7 Redline strikeout highlighting changes made during OMB review 2 Even though all sources have recently demonstrated compliance with the interim standards, the dioxin/ furan data in our data base preceded the compliance demonstration. This explains why we have emissions data that are higher than the interim standard.

124 Hydrocarbons: kilns with bypass; bypass duct and stack5, 6, 8 10 ppmv ( or 100 ppmv carbon monoxide) 10 ppmv ( or 100 ppmv carbon monoxide)

Destruction and removal efficiency For existing and new sources, 99.99% for each principal organic hazardous constituent ( POHC). For sources burning hazardous wastes F020, F021, F022, F023, F026, or F027, however, 99.9999% for each POHC.

1 All emission standards are corrected to 7% oxygen, dry basis. If there is a separate alkali bypass stack, then both the alkali bypass and main stack emissions must be less than the emission standard. 2 Mercury standard is an annual limit. 3 Standards are expressed as mass of pollutant stack emissions attributable to the hazardous waste per million British thermal unit heat input of the hazardous waste. 4 Combined standard, reported as a chloride ( Cl()) equivalent. 5 Sources that elect to comply with the carbon monoxide standard must demonstrate compliance with the hydrocarbon standard during the comprehensive performance test. 6 Hourly rolling average. Hydrocarbons reported as propane. 7 Applicable only to newly constructed cement kilns at greenfield sites ( see 64 FR at 52885). The 50 ppmv standard is a 30 day block average limit. 8 Measurement made in the bypass sampling system of any kiln ( e. g., alkali bypass of a preheater/ precalciner kiln; midkiln gas sampling system of a long kiln).

A. What Are the Proposed Standards for Dioxin and Furan? We are proposing to establish standards for existing and new cement kilns that limit emissions of dioxin and furans to either 0.20 ng TEQ/ dscm or 0.40 ng TEQ/ dscm and control of flue gas temperature not to exceed 400 ° F at the inlet to the particulate matter control device. 1. What Is the Rationale for the MACT Floor for Existing Sources? Dioxin and furan emissions for existing cement kilns are currently limited by § 63.1204( a)( 1) to 0.20 ng TEQ/ dscm or 0.40 ng TEQ/ dscm and control of flue gas temperature not to exceed 400 ° F at the inlet to the particulate matter control device. This standard was promulgated in the Interim Standards Rule ( See 67 FR at 6796, February 13, 2002). Since promulgation of the September 1999 final rule, we have obtained additional dioxin/ furan emissions data. We now have compliance test emissions data representing maximum emissions for all but one cement kiln that burns hazardous waste. The compliance test dioxin/ furan emissions in our data base range from approximately 0.004 to 20 ng TEQ/ dscm. 2 Redline strikeout highlighting changes made during OMB review 125 Cement kilns control dioxin by quenching kiln gas temperatures so that gas temperatures at the inlet to the particulate matter control device are below the range of optimum dioxin/ furan formation. To identify the MACT floor, we evaluated the compliance test emissions data associated with the most recent test campaign using the Emissions Approach described in Part Two, Section VI. C above. The calculated floor is 0.22 ng TEQ/ dscm, which considers emissions variability. These best performing sources controlled inlet temperatures to the particulate matter control device from 380 °  475 ° F. Although some best performing sources had inlet temperatures to the particulate matter control device within the optimum temperature range ( i. e., > 400 ° F) for formation of dioxin/ furan, their emissions were lower than other non best performing sources. Our data base shows that these other non best performing sources, when operating within a temperature range up to 475 ° F, had emissions of dioxin/ furan as high as 1.2 ng TEQ/ dscm. We cannot explain why some sources emit dioxin/ furan at significantly lower levels than other sources operating at similar control device inlet temperatures. As noted earlier, there are many uncertainties and imperfectly understood complexities relating to dioxin/ furan formation. The data generally support the relationship between inlet temperature to the particulate matter control device and dioxin/ furan emissions: When inlet temperatures are below the optimum range of formation, dioxin/ furan emissions are lower. However, the converse may not hold: When inlet temperatures are within the optimum range of formation, dioxin/ furan emissions may or may not be higher ( but in most cases are higher). Moreover, we are concerned that a floor level of 0.22 ng TEQ/ dscm is not replicable by all sources using temperature control because we have emissions data from sources operating below the optimum temperature range of dioxin/ furan formation that is higher than the calculated floor level of 0.22 ng TEQ/ dscm. As a result of this concern, we would identify the floor level as 0.22 ng TEQ/ dscm or controlling the inlet temperature to the particulate matter control device. Allowing a source to comply with a temperature limit alone, however, absent a numerical dioxin/ furan emission limit, is less stringent than the current interim standard of 0.20 ng TEQ/ dscm, or 0.40 ng TEQ/ dscm and control of flue gas temperature not to exceed 400 ° F at the inlet to the particulate matter control device. The current interim standard is a regulatory limit that is relevant in identifying the floor level because it fixes a level of performance for the source category. Given that all sources are achieving this interim standard and that the interim standard is judged as more stringent than the calculated MACT floor, the dioxin/ furan floor level can be no less stringent than the current regulatory limit. We are, therefore, proposing the dioxin/ furan floor level as 0.20 ng TEQ/ dscm or 0.40 ng TEQ/ dscm and control of flue gas temperature not to exceed 400 ° F at the inlet to the particulate matter control device. This emission level is being achieved by all sources because it is the current required interim standard. 2. EPA's Evaluation of Beyond the Floor Standards for Existing Sources We evaluated activated carbon injection as beyond the floor control for further reduction of dioxin/ furan emissions. Activated carbon has been demonstrated for controlling dioxin/ furans in various combustion applications. However, currently no cement kiln that burns hazardous waste uses activated carbon injection. We evaluated a beyond the floor level of 0.10 ng TEQ/ dscm, which represents a 75% reduction in dioxin/ furan emissions from the floor level. We Redline strikeout highlighting changes made during OMB review 3 Under the exemption from hazardous waste status in § 261.4( b)( 8), cement kiln dust is not currently classified as a hazardous waste.

126 selected this level because it represents a level that is considered routinely achievable with activated carbon injection. In addition, we assumed for costing purposes that cement kilns needing activated carbon injection to achieve the beyond the floor level would install the activated carbon injection system after the existing particulate matter control device and add a new, smaller baghouse to remove the injected carbon with the adsorbed dioxin/ furan. We chose this costing approach to address potential concerns that injected carbon may interfere with cement kiln dust recycling practices. The national incremental annualized compliance cost for cement kilns to meet this beyondthe floor level rather than comply with the floor controls would be approximately $ 21 million and would provide an incremental reduction in dioxin/ furan emissions beyond the MACT floor controls of 3.4 grams TEQ per year. Nonair quality health and environmental impacts and energy effects were evaluated to estimate the impacts between activated carbon injection and controls likely to be used to meet the floor level. We estimate that this beyond the floor option would increase the amount of solid waste3 generated by 7,800 tons per year and would require sources to use an additional 2.6 million kW hours per year beyond the requirements to achieve the floor level. The costs associated with these impacts are accounted for in the national annualized compliance cost estimates. Therefore, based on these factors and costs of approximately $ 6.2 million per additional gram of dioxin/ furan removed, we are not proposing a beyond the floor standard based on use of activated carbon injection. 3. What Is the Rationale for the MACT Floor for New Sources? Dioxin and furan emissions for new cement kilns are currently limited by § 63.1204( b)( 1) to either 0.20 ng TEQ/ dscm or 0.40 ng TEQ/ dscm and control of flue gas temperature not to exceed 400 ° F at the inlet to the particulate matter control device. This standard was promulgated in the Interim Standards Rule ( See 67 FR at 6796). The calculated MACT floor for new sources would be 0.21 ng TEQ/ dscm, which considers emissions variability. This is an emission level that the single best performing source identified by the Emissions Approach could be expected to achieve in 99 of 100 future tests when operating under conditions identical to the test conditions during which the emissions data were obtained. As discussed for existing sources, we are concerned that a floor level of 0.21 ng TEQ/ dscm would not be reproducible by all sources using temperature control because we have emissions data from sources operating below the optimum temperature range of dioxin/ furan formation that is higher than the calculated floor level of 0.21 ng TEQ/ dscm. As a result of this concern, we would identify the MACT floor as 0.21 ng TEQ/ dscm or controlling the inlet temperature to the particulate matter control device. Allowing a source to comply with a temperature limit alone, however, absent a numerical dioxin/ furan emission limit, is less stringent than the current interim standard of 0.20 ng TEQ/ dscm, or 0.40 ng TEQ/ dscm and control of flue gas temperature not to exceed 400 ° F at the inlet to the particulate matter control device. The current interim standard is a regulatory limit Redline strikeout highlighting changes made during OMB review 4 An alternative mercury standard is available for existing cement kilns whereby a source can elect to comply with a hazardous waste maximum theoretical emissions concentration or MTEC of mercury of 120 ug/ dscm. MTEC is a term to compare metals and chlorine feedrates across sources of different sizes. MTEC is defined as the metals or chlorine feedrate divided by the gas flow rate and is expressed in units of ug/ dscm.

127 that is relevant in identifying the floor level because it fixes a level of performance for new cement kilns. Given that all sources are achieving this interim standard and that the interim standard is judged as more stringent than the calculated MACT floor, the dioxin/ furan floor level can be no less stringent than the current regulatory limit. We are, therefore, proposing the dioxin/ furan floor level as 0.20 ng TEQ/ dscm or 0.40 ng TEQ/ dscm and control of flue gas temperature not to exceed 400 ° F at the inlet to the particulate matter control device. 4. EPA's Evaluation of Beyond the Floor Standards for New Sources We evaluated activated carbon injection as beyond the floor control for further reduction of dioxin/ furan emissions. We evaluated a beyond the floor level of 0.10 ng TEQ/ dscm, which represents a 75% reduction in dioxin/ furan emissions from the floor level. We selected this level because it represents a level that is considered routinely achievable with activated carbon injection. In addition, we assumed for costing purposes that a new cement kiln will install the activated carbon injection system after the existing particulate matter control device and add a new, smaller baghouse to remove the injected carbon with the adsorbed dioxin/ furan. The incremental annualized compliance cost for a new cement kiln to meet this beyond the floor level, rather than comply with the floor level, would be approximately $ 1.0 million and would provide an incremental reduction in dioxin/ furan emissions of approximately 0.17 grams TEQ per year, for a cost effectiveness of $ 5.8 million per gram of dioxin/ furan removed. Nonair quality health and environmental impacts and energy effects were not significant factors. For these reasons, we are not proposing a beyond the floor standard based on activated carbon injection for new cement kilns. Therefore, we are proposing the standard as 0.20 ng TEQ/ dscm or 0.40 ng TEQ/ dscm or control of flue gas temperature not to exceed 400 ° F at the inlet to the particulate matter control device. B. What Are the Proposed Standards for Mercury? We are proposing to establish standards for existing and new cement kilns that limit emissions of mercury to 64 and 35 ug/ dscm, respectively. If we were to adopt these standards, then sources would comply with the limit on an annual basis because the standards are based on normal emissions data. 1. What Is the Rationale for the MACT Floor for Existing Sources? Mercury emissions for existing cement kilns are currently limited to 120 ug/ dscm by § 63.1204( a)( 2). 4 This standard was promulgated in the Interim Standards Rule ( See 67 FR at 6796). None of the cement kilns burning hazardous waste use a dedicated control device to remove mercury from the gas stream; however, kilns control the feed concentration of mercury in the hazardous waste. We have emissions data for all sources. All of these data are best classified as from Redline strikeout highlighting changes made during OMB review 5 Given that we only have normal feedrate and emissions data for mercury for cement kilns, we do not believe it is appropriate to establish a hazardous waste thermal emissionsbased standard. We prefer to establish emission standards under the hazardous waste thermal emissions format using compliance test data because the metals feedrate information from compliance tests that we use to apportion emissions to calculate emissions attributable to hazardous waste are more reliable than feedrate data measured during testing under normal, typical operations.

128 normal operations, although, as explained below, there is a substantial range within these data. For most sources, we have normal emissions data from more than one test campaign. The normal mercury stack emissions in our data base range from less than 2 to 118 ug/ dscm. These emissions are expressed as mass of mercury ( from all feedstocks) per unit volume of stack gas. To identify the MACT floor, we evaluated all normal emissions data using the SRE/ Feed Approach. We considered normal emissions data from all test campaigns. 5 For example, one source in our data base has normal emissions data for three different testing campaigns: 1992, 1995, and 1998. Under this approach we would consider the emissions data from the three separate years or campaigns. We believe this approach better captures the range of average emissions for a source than only considering the most recent normal emissions. Given that no cement kilns burning hazardous waste use a control device which captures mercury from the flue gas stream, for purposes of this analysis we assumed all sources achieved a SRE of zero. The effect of this assumption is that the sources with the lowest mercury concentrations in the hazardous waste were identified as the best performing sources. The calculated floor is 64 ug/ dscm, which considers emissions variability, based on a hazardous waste maximum theoretical emissions concentration ( MTEC) of 26 ug/ dscm. This is an emission level that the average of the best performing sources could be expected to achieve in 99 of 100 future tests when operating under conditions identical to the compliance test conditions during which the emissions data were obtained. We estimate that this emission level is being achieved by 59% of sources and would reduce mercury emissions by 0.23 tons per year. If we were to adopt such a floor level, we are proposing that sources comply with the limit on an annual basis because it is based on normal emissions data. Under this approach, compliance would not be based on the use of a total mercury continuous emissions monitoring system because these monitors have not been adequately demonstrated as a reliable compliance assurance tool at cement kiln sources. Instead, a source would maintain compliance with the mercury standard by establishing and complying with short term limits on operating parameters ( e. g., for pollution control equipment and annual limits on maximum total mercury feedrate in all feedstreams) on an annual basis. We did not use the stack emissions data of preheater/ precalciner kilns in the floor analysis because we believe the mercury emissions are biased low when the in line raw mill is on line and biased high when the in line raw mill is off line. ( See earlier discussion on why we are proposing not to subcategorize hazardous waste burning cement kilns for mercury between wet process kilns and preheater/ precalciner kilns with in line raw mills.) For either case, we believe the normal Redline strikeout highlighting changes made during OMB review 6 Cement Kiln Recycling Coalition is a trade organization that represents cement companies that burn hazardous wastes as a fuel. CKRC also represents companies that manage and market hazardous waste fuels used in cement kilns.

7 For two cement facilities, the mercury concentration data are only available on a monthly averaged basis.

129 mercury data are not representative of average emissions and, therefore, not appropriate to include in the floor analysis. We request comment on this data handling decision. In the September 1999 final rule, we acknowledged that a cement kiln using properly designed and operated MACT control technologies, including controlling the levels of metals in the hazardous waste, may not be capable of achieving a given emission standard because of mineral and process raw material contributions that might cause an exceedance of the emission standard. To address this concern, we promulgated a provision that allows kilns to petition for alternative standards provided they submit site specific information that shows raw material hazardous air pollutant contributions to the emissions prevent the source from complying with the emission standard even though the kiln is using MACT control. See § 63.1206( b)( 10).

In June 2003, the Cement Kiln Recycling Coalition ( CKRC) 6 submitted to EPA information on actual mercury concentrations in the hazardous waste burn tanks of all 14 cement facilities for a three year period covering 1999 to 2001. In general, the information shows the mercury concentration ( in parts per million) in the hazardous waste for each burn tank. 7 In total, Redline strikeout highlighting changes made during OMB review 8 Data from three of the facilities had a significant number of individual measurements reported as not detectable and also had relatively high analysis detection limits ( compared to levels achieved by other cement plants). The detection limit for most cement kilns was typically 0.1 ppm or less. For purposes of today's preamble discussion, the measurements from these three cement plants are excluded from the data characterization conclusions.

9 USEPA, " Draft Technical Support Document for HWC MACT Replacement Standards, Volume III: Selection of MACT Standards and Technologies," March 2004, Chapter 23.

130 approximately 20,000 mercury burn tank concentration data points are included in CKRC's submission. 8 The data show that approximately 50% of the individual burn tank measurements are 0.6 ppmw or less, 75% are less than 1.1 ppmw, 88% are less than 2 ppmw, and 97% of all burn tank measurements are less than 5 ppmw. For a hypothetical wet process cement kiln that gets 50% of its required heat input from hazardous waste, a hazardous waste with a mercury concentration of 0.6 ppmw equates approximately to an uncontrolled ( i. e., a system removal efficiency of zero) stack gas concentration of 24 ug/ dscm. This estimated stack gas concentration, of course, does not include contributions to emissions from other mercurycontaining feedstocks including raw materials and fossil fuels. Mercury concentrations of 1.1, 2, and 5 ppmw in the hazardous waste equate to uncontrolled stack gas concentrations of approximately 43, 79, and 196 ug/ dscm. 9 We compared the concentration of mercury in the hazardous waste associated with the normal emissions data in our data base to the 3 year historical burn tank concentration data to estimate whether the normal data in our data base   the basis of today's proposed floor of 64 ug/ dscm   are likely to represent the high end, low end, or close to average emissions. Mercury feed concentration information is not available for every test condition; however, the mercury concentrations in the hazardous waste burned by the best performing sources during the tests that generated the normal emissions ranged from 0.1 to 0.44 ppmw. For the best performing sources comprising the MACT pool for which we can make a comparison, it appears that the normal concentrations in the hazardous waste during testing represent the low end ( 15th percentile or less) of average mercury concentrations. We invite comment on whether the normal emissions data in our data base are representative of average emissions in practice and whether evaluating the data to identify a floor level is appropriate. In addition, we request comment on how to identify a floor level using the 3 year hazardous waste mercury concentration data. One potential approach would be to establish a hazardous waste feed concentration standard expressed in ppmw. To identify a floor level expressed as a hazardous waste feed concentration in ppmw, we identified and evaluated the 3 year historical burn tank concentration data of the five best performing facilities ( those sources with the lowest mean concentration considering variability). The calculated alternative floor level is 2.2 ppmw in the hazardous waste. To put this in context for a hypothetical wet process cement kiln that gets 50% of its required heat input from hazardous waste, a mercury concentration of 2.2 Redline strikeout highlighting changes made during OMB review 10 USEPA, " Draft Technical Support Document for HWC MACT Replacement Standards, Volume III: Selection of MACT Standards and Technologies" Standards", March 2004, Chapter 23.

11 USEPA, " Draft Technical Support Document for HWC MACT Replacement Standards, Volume III: Selection of MACT Standards and Technologies" Standards", March 2004, Chapter 23.

131 ppmw in the hazardous waste equates approximately to an uncontrolled stack gas concentration of 86 ug/ dscm. 10 This estimated stack gas concentration, of course, does not include contributions to emissions from other mercury containing feedstocks such as raw materials and fossil fuels. If we were to adopt such an approach, we would require sources to comply with the feed concentration standard on a short term basis ( e. g., 12 hour average). We also invite comment on whether we should judge an annual limit of 64 ug/ dscm as less stringent than either the current emission standard of 120 ug/ dscm or the hazardous waste MTEC of mercury of 120 ug/ dscm for cement kilns ( so as to avoid any backsliding from a current level of performance achieved by all sources, and hence, the level of minimal stringency at which EPA could calculate the MACT floor). In order to comply with the current emission standard, generally a source must conduct manual stack sampling to demonstrate compliance with the mercury emission standard and then establish a maximum mercury feedrate limit based on operations during the performance test. Following the performance test, the source complies with a limit on the maximum total mercury feedrate in all feedstreams on a 12 hour rolling average ( not an annual average). Alternatively, a source can elect to comply with a hazardous waste MTEC of mercury of 120 ug/ dscm that would require the source to limit the mercury feedrate in the hazardous waste on a 12 hour rolling average. The floor level of 64 ug/ dscm proposed today would allow a source to feed more variable mercury containing feedstreams ( e. g., a hazardous waste with an mercury MTEC greater than 120 ug/ dscm) than the current 12 hour rolling average because today's proposed floor level is an annual limit. For example, we estimated a hazardous waste MTEC for each burn tank measurement associated with the 3 year historical concentration data submitted by CKRC. We found that approximately 5% of burn tank measurements would exceed a hazardous waste MTEC of 120 ug/ dscm, including sources upon which the proposed floor is based. 11 2. EPA's Evaluation of Beyond the Floor Standards for Existing Sources We identified three potential beyond the floor techniques for control of mercury: ( 1) activated carbon injection; ( 2) control of mercury in the hazardous waste feed; and ( 3) control of mercury in the raw materials and auxiliary fuels. For reasons discussed below, we are not proposing a beyond the floor standard for mercury. Use of Activated Carbon Injection. We evaluated activated carbon injection as beyondthe floor control for further reduction of mercury emissions. Activated carbon has been demonstrated for controlling mercury in several combustion applications; however, currently no cement kiln that burns hazardous waste uses activated carbon injection. Given this lack of Redline strikeout highlighting changes made during OMB review 12 USEPA, " Draft Technical Support Document for HWC MACT Replacement Standards, Volume V: Emission Estimates and Engineering Costs", March 2004, Chapter 4.

132 experience using activated carbon injection, we made a conservative assumption that the use of activated carbon injection will provide 70% mercury control and evaluated a beyond the floor level of 19 ug/ dscm. In addition, for costing purposes we assumed that cement kilns needing activated carbon injection to achieve the beyond the floor level would install the activated carbon injection system after the existing particulate matter control device and add a new, smaller baghouse to remove the injected carbon with the adsorbed mercury. We chose this costing approach to address potential concerns that injected carbon may interfere with cement kiln dust recycling practices. The national incremental annualized compliance cost for cement kilns to meet this beyondthe floor level rather than comply with the floor controls would be approximately $ 16.8 million and would provide an incremental reduction in mercury emissions beyond the MACT floor controls of 0.41 tons per year. Nonair quality health and environmental impacts and energy effects were evaluated to estimate the impacts between activated carbon injection and controls likely to be used to meet the floor level. We estimate that this beyond the floor option would increase the amount of solid waste generated by 4,400 tons per year and would require sources to use an additional 21 million kW hours per year beyond the requirements to achieve the floor level. The costs associated with these impacts are accounted for in the national annualized compliance cost estimates. Therefore, based on these factors and costs of approximately $ 41 million per additional ton of mercury removed, we are not proposing a beyond the floor standard based on activated carbon injection. Feed Control of Mercury in the Hazardous Waste. We also evaluated a beyond the floor level of 51 ug/ dscm, which represents a 20% reduction from the floor level. We chose a 20% reduction as a level representing the practicable extent that additional feedrate control of mercury in hazardous waste ( beyond feedrate control that may be necessary to achieve the floor level) can be used and still achieve modest emissions reductions. 12 The national incremental annualized compliance cost for cement kilns to meet this beyond the floor level rather than comply with the floor controls would be approximately $ 3.7 million and would provide an incremental reduction in mercury emissions beyond the MACT floor controls of 180 pounds per year. Nonair quality health and environmental impacts and energy effects were also evaluated. Therefore, based on these factors and costs of approximately $ 42 million per additional ton of mercury removed, we are not proposing a beyond the floor standard based on feed control of mercury in the hazardous waste. Feed Control of Mercury in the Raw Materials and Auxiliary Fuels. Cement kilns could achieve a reduction in mercury emissions by substituting a raw material containing lower levels of mercury for a primary raw material with a higher level. We believe that this beyond the floor option would be even less cost effective than either of the options discussed above, however. Given that sources are sited near the supply of the primary raw material, transporting large quantities of an alternate source of raw materials is likely to be cost prohibitive, especially Redline strikeout highlighting changes made during OMB review 133 considering the small expected emissions reductions that would result. We also considered whether fuel switching to an auxiliary fuel containing a lower concentration of mercury would be an appropriate control option for sources. Given that most cement kilns burning hazardous waste also burn coal as a fuel, we considered switching to natural gas as a potential beyond the floor option. We are concerned about the availability of natural gas to all cement kilns because natural gas pipelines are not available in all regions of the United States. See 68 FR 1673. Moreover, even where pipelines provide access to natural gas, supplies of natural gas may not be adequate. For example, it is common practice in cities during winter months ( or periods of peak demand) to prioritize natural gas usage for residential areas before industrial usage. Requiring cement kilns to switch to natural gas would place an even greater strain on natural gas resources. Consequently, even where pipelines exist, some sources may not be able to use natural gas during times of limited supplies. Thus, natural gas may not be a viable control option for some sources. Therefore, we are not proposing a beyond the floor standard based on limiting mercury in the raw material feed and auxiliary fuels. For the reasons discussed above, we propose not to adopt a beyond the floor standard for mercury and propose to establish the emission standard for existing cement kilns at 64 ug/ dscm. If we were to adopt such a standard, we are proposing that sources comply with the standard on an annual basis because it is based on normal emissions data. 3. What Is the Rationale for the MACT Floor for New Sources? Mercury emissions from new cement kilns are currently limited to 120 ug/ dscm by § 63.1204( b)( 2). New cement kilns can comply with an alternative mercury standard that limits the hazardous waste maximum theoretical emissions concentration or MTEC of mercury of 120 ug/ dscm. This standard was promulgated in the Interim Standards Rule ( See 67 FR at 6796). The MACT floor for new sources for mercury would be 35 ug/ dscm, which considers emissions variability, based on a hazardous waste MTEC of 5.1 ug/ dscm. This is an emission level that the single best performing source identified with the SRE/ Feed Approach could be expected to achieve in 99 of 100 future tests when operating under conditions identical to the test conditions during which the emissions data were obtained. As for existing sources, we assumed all sources equally achieved a SRE of zero. The effect of this assumption is that the single source with the lowest mercury concentration in the hazardous waste was identified as the best performing source. We also invite comment on whether we should judge an annual limit of 35 ug/ dscm as less stringent than either the current emission standard of 120 ug/ dscm or the hazardous waste MTEC of mercury of 120 ug/ dscm for cement kilns ( so as to avoid any backsliding from a current level of performance achieved by all sources). 4. EPA's Evaluation of Beyond the Floor Standards for New Sources We identified the same three potential beyond the floor techniques for control of mercury: ( 1) use of activated carbon; ( 2) control of mercury in the hazardous waste feed; and ( 3) control of the mercury in the raw materials and auxiliary fuels. Use of Activated Carbon Injection. We evaluated activated carbon injection as beyondthe floor control for further reduction of mercury emissions. We made a conservative assumption that the use of activated carbon injection will provide 70% mercury control and evaluated a beyond the floor level of 11 ug/ dscm. The incremental annualized compliance cost for a new Redline strikeout highlighting changes made during OMB review 13 A greenfield cement kiln is a kiln constructed at a site where no cement kiln previously existed; however, a newly constructed or reconstructed cement kiln at an existing site would not be considered as a greenfield cement kiln.

134 cement kiln to meet this beyond the floor level, rather than comply with the floor level, would be approximately $ 1.0 million and would provide an incremental reduction in mercury emissions of approximately 88 pounds per year. We also estimate that this option would increase the amount of solid waste generated by 400 tons per year and would require sources to use an additional 1.9 million kW hours per year. Nonair quality health and environmental impacts and energy effects are accounted for in the national annualized compliance cost estimates. Therefore, based on these factors and costs of $ 23 million per ton of mercury removed, we are not proposing a beyond thefloor standard based on activated carbon injection for new cement kilns. Feed Control of Mercury in the Hazardous Waste. We also believe that the expense for further reduction in mercury emissions based on further control of mercury concentrations in the hazardous waste is not warranted. A beyond the floor level of 28 ug/ dscm, which represents a 20% reduction from the floor level, would result in little additional mercury reductions. For similar reasons discussed above for existing sources, we conclude that a beyond the floor standard based on controlling the mercury in the hazardous waste feed would not be justified because of the costs coupled with estimated emission reductions. Feed Control of Mercury in the Raw Materials and Auxiliary Fuels. Cement kilns could achieve a reduction in mercury emissions by substituting a raw material containing lower levels of mercury for a primary raw material with a higher level. For a new source at an existing cement plant, we believe that this beyond the floor option would not be cost effective due to the costs of transporting large quantities of an alternate source of raw materials to the cement plant. Given that the plant site already exists and sited near the source of raw material, replacing the raw materials at the plant site with lower mercury containing materials would be the source's only option. For a new cement kiln constructed at a new site   a greenfield site13   we are not aware of any information and data from a source that has undertaken or is currently located at a site whose raw materials are low in mercury which would consistently decrease mercury emissions. Further, we are uncertain as to what beyond the floor standard would be achievable using a lower, if it exists, mercury containing raw material. Although we are doubtful that selecting a new plant site based on the content of metals in the raw material is a realistic beyond the floor option considering the numerous additional factors that go into such a decision, we solicit comment on whether and what level of a beyond the floor standard based on controlling the level of mercury in the raw materials is appropriate. We also considered whether fuel switching to an auxiliary fuel containing a lower concentration of mercury would be an appropriate control option for sources. We considered using natural gas in lieu of a fossil fuel such as coal containing higher concentrations of mercury as a potential beyond the floor option. As discussed for existing sources, we are concerned about the availability of the natural gas infrastructure in all regions of the United States and believe that using natural gas would not be a viable control option for all new sources. Therefore, we are not Redline strikeout highlighting changes made during OMB review 14 This standard equates approximately to a stack gas concentration level of 0.030 gr/ dscf for wet process kilns and 0.040 gr/ dscf for preheater/ precalciner kilns. The conversion varies by process type because the amount of flue gas generated per ton of raw material feed varies by process type.

135 proposing a beyond the floor standard based on limiting mercury in the raw material feed and auxiliary fuels. Therefore, we propose a mercury standard of 35 ug/ dscm for new sources. If we were to adopt such a standard, we are proposing that sources comply with the standard on an annual basis because it is based on normal emissions data. C. What Are the Proposed Standards for Particulate Matter? We are proposing to establish standards for existing and new cement kilns that limit emissions of particulate matter to 65 mg/ dscm ( 0.028 gr/ dscf) and 13 mg/ dscm ( 0.0058 gr/ dscf), respectively. 1. What Is the Rationale for the MACT Floor for Existing Sources? Particulate matter emissions for existing cement kilns are currently limited to 0.15 kilograms of particulate matter per megagram dry feed14 and 20% opacity by § 63.1204( a)( 7). This standard was promulgated in the Interim Standards Rule ( See 67 FR at 6796). The particulate matter standard is a surrogate control for the metals antimony, cobalt, manganese, nickel, and selenium in the hazardous waste and all HAP metals in the raw materials and auxiliary fuels which are controllable by particulate matter control. All cement kilns control particulate matter with baghouses and electrostatic precipitators. We have compliance test emissions data representing maximum emissions for all cement kiln sources. For most sources, we have compliance test emissions data from more than one compliance test campaign. Our data base of particulate matter stack emission concentrations range from 0.0008 to 0.063 gr/ dscf. To identify the floor level, we evaluated the compliance test emissions data associated with the most recent test campaign using the Air Pollution Control Technology Approach. The calculated floor is 65 mg/ dscm ( 0.028 gr/ dscf), which considers emissions variability. This is an emission level that the average of the best performing sources could be expected to achieve in 99 of 100 future tests when operating under conditions identical to the compliance test conditions during which the emissions data were obtained. We estimate that this emission level is being achieved by 44% of sources and would reduce particulate matter emissions by 43 tons per year. We are also proposing to delete the current opacity standard in conjunction with revisions to the compliance assurance requirements for particulate matter for cement kilns. These proposed compliance assurance amendments include requiring a cement kiln source using a baghouse to comply with the same bag leak detection system requirements that are currently applicable to all other hazardous waste combustors ( see § 63.1209( m)). A cement kiln source using an ESP has the option either to ( 1) use a particulate matter emissions detector as a process monitor in lieu of complying with operating parameter limits, as we are proposing for all other hazardous waste combustor sources; or ( 2) establish site specific, enforceable operating parameter limits that are Redline strikeout highlighting changes made during OMB review 15 We did not evaluate a beyond the floor standard based on fuel substitution because particulate matter emissions from cement kilns are primarily entrained raw material, not ash contributed by the hazardous waste fuel. There is, therefore, no correlation between particulate matter emissions and the level of ash in the hazardous waste.

136 linked to the automatic waste feed cutoff system. See Part Three, Section III for a discussion of the proposed changes. We also request comment on whether the particulate matter standard should be expressed on a concentration basis ( as proposed today) or on a production based format. A concentrationbased standard is expressed as mass of particulate matter per dry standard volume of gas ( e. g., mg/ dscm as proposed today) while a production based standard is expressed as mass of particulate matter emitted per mass of dry raw material feed to the kiln ( e. g., the format of the interim standard). We evaluated the compliance test production based data associated with the most recent test campaign to determine what the floor level would be under this approach. The calculated floor would be 0.10 kilograms of particulate matter per megagram dry feed. We note that a concentration format can be viewed as penalizing more energy efficient kilns, which burn less fuel and produce less kiln exhaust gas per megagram of dry feed. This is because with a concentration based standard the more energy efficient kilns would be restricted to a lower level of particulate matter emitted per unit of production. 2. EPA's Evaluation of Beyond the Floor Standards for Existing Sources We evaluated improved particulate matter control to achieve a beyond the floor standard of 32 mg/ dscm ( 0.014 gr/ dscf), which is a 50% reduction from MACT floor emissions. 15 For an existing source that needs a significant reduction in particulate matter emissions, we assumed and estimated costs for a new baghouse to achieve the beyond the floor level. If little or modest emissions reductions were needed, then improved control was costed as design, operation, and maintenance modifications of the existing particulate matter control equipment. The national incremental annualized compliance cost for cement kilns to meet this beyondthe floor level rather than comply with the floor controls would be approximately $ 4.8 million and would provide an incremental reduction in particulate matter emissions beyond the MACT floor controls of 385 tons per year. Nonair quality health and environmental impacts and energy effects were evaluated to estimate the impacts between further improvements to control particulate matter and controls likely to be used to meet the floor level. We estimate that this beyond thefloor option would increase the amount of solid waste generated by 385 tons per year and would require sources to use an additional 15 million kW hours per year beyond the requirements to achieve the floor level. The costs associated with these impacts are accounted for in the national annualized compliance cost estimates. Therefore, based on these factors and costs of approximately $ 12,400 per additional ton of particulate matter removed, we are not proposing a beyond the floor standard based on improved particulate matter control. 3. What Is the Rationale for the MACT Floor for New Sources? Particulate matter emissions from new cement kilns are currently limited to 0.15 kilograms of particulate matter per megagram dry feed and 20% opacity by § 63.1204( b)( 7). This standard Redline strikeout highlighting changes made during OMB review 137 was promulgated in the Interim Standards Rule ( See 67 FR at 6796). The MACT floor for new sources for particulate matter would be 13 mg/ dscm ( 0.0058 gr/ dscf), which considers emissions variability. This is an emission level that the single best performing source identified with the Air Pollution Control Technology Approach could be expected to achieve in 99 of 100 future tests when operating under operating conditions identical to the test conditions during which the emissions data were obtained. We are also proposing to delete the current opacity standard in conjunction with revisions to the compliance assurance requirements for particulate matter for cement kilns. See Part Three, Section III for details. As discussed for existing sources, we also request comment on whether the particulate matter standard should be expressed on a concentration basis or on a production based format. We evaluated the compliance test production based data associated with the most recent test campaign to determine what the floor level would be under this approach. The calculated floor would be 0.028 kilograms of particulate matter per megagram dry feed. 4. EPA's Evaluation of Beyond the Floor Standards for New Sources We evaluated improved emissions control based on a state of the art baghouse using a high quality fabric filter bag material to achieve a beyond the floor standard of 6.7 mg/ dscm ( 0.0029 gr/ dscf). This reduction represents a 50% reduction in particulate matter emissions from MACT floor levels. The incremental annualized compliance cost for a new cement kiln to meet this beyond the floor level, rather than comply with the floor level, would be approximately $ 0.38 million and would provide an incremental reduction in particulate matter emissions of approximately 2.6 tons per year. We estimate that this beyond the floor option would increase the amount of solid waste generated by less than 6 tons per year and would require sources to use an additional 1.8 million kW hours per year beyond the requirements to achieve the floor level. The costs associated with these impacts are accounted for in the national annualized compliance cost estimates. Therefore, based on these factors and costs of approximately $ 61,400 per additional ton of particulate matter removed, we are not proposing a beyond the floor standard based on improved particulate matter control for new cement kilns. Therefore, we propose a particulate matter standard of 13 mg/ dscm for new sources. D. What Are the Proposed Standards for Semivolatile Metals? We are proposing to establish standards for existing cement kilns that limit emissions of semivolatile metals ( cadmium and lead, combined) to 4.0 x 10 4 lbs semivolatile metals emissions attributable to the hazardous waste per million Btu heat input of the hazardous waste. The proposed standard for new sources is 6.2 x 10 5 lbs semivolatile metals emissions attributable to the hazardous waste per million Btu heat input of the hazardous waste. 1. What Is the Rationale for the MACT Floor for Existing Sources? Semivolatile metals emissions from existing cement kilns are currently limited to 330 ug/ dscm by § 63.1204( a)( 3). This standard was promulgated in the Interim Standards Rule ( See 67 FR at 6796). Cement kilns control emissions of semivolatile metals with baghouses or electrostatic precipitators and/ or by controlling the feed concentration of semivolatile metals in the hazardous waste. We have compliance test emissions data representing maximum emissions for all cement kiln sources. For most sources, we have compliance test emissions data from more than one Redline strikeout highlighting changes made during OMB review 16 USEPA, " Draft Technical Support Document for HWC MACT Replacement Standards, Volume III: Selection of MACT Standards and Technologies," March 2004, Chaper 23.

138 compliance test campaign. Semivolatile metal stack emissions range from approximately 1 to 2,800 ug/ dscm. These emissions are expressed as mass of semivolatile metals ( from all feedstocks) per unit volume of stack gas. Hazardous waste thermal emissions range from 3.0 x 10 6 to 3.7 x 10 3 lbs per million Btu. Hazardous waste thermal emissions represent the mass of semivolatile metals emissions attributable to the hazardous waste per million Btu heat input of the hazardous waste. Lead was the most significant contributor to semivolatile emissions during compliance test conditions. To identify the MACT floor, we evaluated the compliance test emissions data associated with the most recent test campaign using the SRE/ Feed Approach. The calculated floor is 4.0 x 10 4 lbs semivolatile metals emissions attributable to the hazardous waste per million Btu heat input of the hazardous waste, which considers emissions variability. This is an emission level that the average of the best performing sources could be expected to achieve in 99 of 100 future tests when operating under conditions identical to the compliance test conditions during which the emissions data were obtained. We estimate that this emission level is being achieved by 81% of sources and would reduce semivolatile metals emissions by 1 ton per year. To put the proposed floor level in context for a hypothetical wet process cement kiln that gets 50% of its required heat input from hazardous waste, a thermal emissions level of 4.0 x 10 4 lbs semivolatile metals emissions attributable to the hazardous waste per million Btu heat input of the hazardous waste equates approximately to a stack gas concentration of 180 ug/ dscm. This estimated stack gas concentration does not include contributions to emission from other semivolatile metals containing materials such as raw materials and fossil fuels. The additional contribution to stack emissions of semivolatile metals in an average raw material and coal is estimated to range as high as 20 to 50 ug/ dscm. Thus, for the hypothetical wet process cement kiln the thermal emissions floor level of 4.0 x 10 4 lbs semivolatile metals attributable to the hazardous waste per million Btu heat input of the hazardous waste is estimated to be less than 230 ug/ dscm, which is less than the current interim standard of 330 ug/ dscm. Given that comparing the proposed floor level to the interim standard requires numerous assumptions ( as just illustrated) including hazardous waste fuel replacement rates, heat input requirements per ton of clinker, concentrations of semivolatile metals in the raw material and coal, and system removal efficiency, we have a more detailed analysis in the background document. 16 Our detailed analysis indicates the proposed floor level is as least as stringent as the interim standard ( so as to avoid any backsliding from a current level of performance achieved by all cement kilns, and hence, the level of minimal stringency at which EPA could calculate the MACT floor). Thus, we conclude that a dual standard   the semivolatile metals standard as both the calculated floor level, expressed as a hazardous waste thermal emissions level, and the current interim standard   is not needed for this standard. In the September 1999 final rule, we acknowledged that a cement kiln using properly Redline strikeout highlighting changes made during OMB review 139 designed and operated MACT control technologies, including controlling the levels of metals in the hazardous waste, may not be capable of achieving a given emission standard because of mineral and process raw material contributions that might cause an exceedance of the emission standard. To address this concern, we promulgated a provision that allows kilns to petition for alternative standards provided that they submit site specific information that shows raw material hazardous air pollutant contributions to the emissions prevent the source from complying with the emission standard even though the kiln is using MACT control. See § 63.1206( b)( 10). If we were to adopt the semivolatile ( and low volatile) metals standard using a thermal emissions format, then there would be no need for these alternative standard provisions for semivolatile metals ( since, as explained earlier, that standard is based solely on semivolatile metals contributions from hazardous waste fuels). Therefore, we would delete the provisions of § 63.1206( b)( 10) as they apply to semivolatile ( and low volatile) metals. We invite comment on this approach. 2. EPA's Evaluation of Beyond the Floor Standards for Existing Sources We identified three potential beyond the floor techniques for control of semivolatile metals: ( 1) improved particulate matter control; ( 2) control of semivolatile metals in the hazardous waste feed; and ( 3) control of the semivolatile metals in the raw materials and fuels. For reasons discussed below, we are not proposing a beyond the floor standard for semivolatile metals. Improved Particulate Matter Control. Controlling particulate matter also controls emissions of semivolatile metals. Our data show that all cement kilns are already achieving greater than 98.6% system removal efficiency for semivolatile metals, with most attaining 99.9% removal. Thus, additional control of particulate matter are likely to result in only modest additional reductions of semivolatile metals emissions. We evaluated a beyond the floor level of 2.0 x 10 4 lbs semivolatile metals emissions attributable to the hazardous waste per million Btu heat input of the hazardous waste, which represents a 50% reduction in emissions from MACT floor levels. The national incremental annualized compliance cost for cement kilns to meet this beyond the floor level rather than comply with the floor controls would be approximately $ 2.7 million and would provide an incremental reduction in semivolatile metals emissions beyond the MACT floor controls of 1.2 tons per year. Nonair quality health and environmental impacts and energy effects were evaluated to estimate the impacts between further improvements to control particulate matter and controls likely to be used to meet the floor level. We estimate that this beyond the floor option would increase the amount of solid waste generated by 300 tons per year and would also require sources to use an additional 5.7 million kW hours of energy per year to achieve the floor level. The costs associated with these impacts are accounted for in the national annualized compliance cost estimates. Therefore, based on these factors and costs of approximately $ 2.3 million per additional ton of semivolatile metals removed, we are not proposing a beyond the floor standard based on improved particulate matter control. Feed Control of Semivolatile Metals in the Hazardous Waste. We also evaluated a beyond the floor level of 3.2 x 10 4 lbs semivolatile metals emissions attributable to the hazardous waste per million Btu heat input of the hazardous waste, which represents a 20% reduction from the floor level. We chose a 20% reduction as a level representing the practicable extent that additional feedrate control of semivolatile metals in hazardous waste can be used and still achieve Redline strikeout highlighting changes made during OMB review 140 appreciable emissions reductions. The national incremental annualized compliance cost for cement kilns to meet this beyond the floor level rather than comply with the floor controls would be approximately $ 0.30 million and would provide an incremental reduction in semivolatile metals emissions beyond the MACT floor controls of 0.36 tons per year. Nonair quality health and environmental impacts and energy effects were evaluated and are included in the national compliance cost estimates. Therefore, based on these factors and costs of approximately $ 0.84 million per additional ton of semivolatile metals removed, we are not proposing a beyond thefloor standard based on feed control of semivolatile metals in the hazardous waste. Feed Control of Semivolatile Metals in the Raw Materials and Auxiliary Fuels. Cement kilns could achieve a reduction in semivolatile metal emissions by substituting a raw material containing lower levels of lead and/ or cadmium for a primary raw material with higher levels of these metals. We believe that this beyond the floor option would even be less cost effective than either of the options discussed above, however. Given that cement kilns are sited near the primary raw material supply, acquiring and transporting large quantities of an alternate source of raw materials is likely to be cost prohibitive. Therefore, we are not proposing a beyond the floor standard based on limiting semivolatile metals in the raw material feed. We also considered whether fuel switching to an auxiliary fuel containing a lower concentration of semivolatile metals would be an appropriate control option for sources. Given that most cement kilns burning hazardous waste also burn coal as a fuel, we considered switching to natural gas as a potential beyond the floor option. For the same reasons discussed for mercury, we judge a beyond thefloor standard based on fuel switching as unwarranted. For the reasons discussed above, we propose to establish the emission standard for existing cement kilns at 4.0 x 10 4 lbs semivolatile metals emissions attributable to the hazardous waste per million Btu heat input of the hazardous waste. 3. What Is the Rationale for the MACT Floor for New Sources? Semivolatile metals emissions from new cement kilns are currently limited to 180 ug/ dscm by § 63.1204( b)( 3). This standard was promulgated in the Interim Standards Rule ( See 67 FR at 6796). The MACT floor for new sources for semivolatile metals would be 6.2 x 10 5 lbs semivolatile metals emissions attributable to the hazardous waste per million Btu heat input of the hazardous waste, which considers emissions variability. This is an emission level that the single best performing source identified with the SRE/ Feed Approach could be expected to achieve in 99 of 100 future tests when operating under conditions identical to the test conditions during which the emissions data were obtained. To put the proposed floor level in context for a hypothetical wet process cement kiln that gets 50% of its required heat input from hazardous waste, a thermal emissions level of 6.2 x 10 5 lbs semivolatile metals emissions attributable to the hazardous waste per million Btu heat input of the hazardous waste equates approximately to a stack gas concentration of 80 ug/ dscm, including contributions from typical raw materials and coal. Thus, for the hypothetical wet process cement kiln the thermal emissions floor level of 6.2 x 10 5 lbs semivolatile metals emissions attributable to the hazardous waste per million Btu heat input of the hazardous waste is estimated to be less than the current interim standard for new sources of 180 ug/ dscm. Redline strikeout highlighting changes made during OMB review 141 4. EPA's Evaluation of Beyond the Floor Standards for New Sources We identified the same three potential beyond the floor techniques for control of semivolatile metals: ( 1) improved control of particulate matter; ( 2) control of semivolatile metals in the hazardous waste feed; and ( 3) control of semivolatile metals in the raw materials and fuels. Improved Particulate Matter Control. Controlling particulate matter also controls emissions of semivolatile metals. We evaluated improved control of particulate matter based on a state of the art baghouse using a high quality fabric filter bag material as beyond the floor control for further reductions in semivolatile metals emissions. We evaluated a beyond the floor level of 2.5 x 10 5 lbs semivolatile metals emissions attributable to the hazardous waste per million Btu heat input of the hazardous waste. The incremental annualized compliance cost for a new cement kiln with an average gas flow rate to meet this beyond the floor level, rather than to comply with the floor level, would be approximately $ 0.38 million and would provide an incremental reduction in semivolatile metals emissions of approximately 144 pounds per year. Nonair quality health and environmental impacts and energy effects were evaluated and are included in the cost estimates. For these reasons and costs of $ 5.3 million per ton of semivolatile metals removed, we are not proposing a beyond the floor standard based on improved particulate matter control for new cement kilns. Feed Control of Semivolatile Metals in the Hazardous Waste. We also believe that the expense for further reduction in semivolatile metals emissions based on further control of semivolatile metals concentrations in the hazardous waste is not warranted. We also evaluated a beyond the floor level of 5.0 x 10 5 lbs semivolatile metals emissions attributable to the hazardous waste per million Btu heat input of the hazardous waste, which represents a 20% reduction from the floor level. Nonair quality health and environmental impacts and energy effects were evaluated and are included in the compliance cost estimates. For similar reasons discussed above for existing sources, we conclude that a beyond the floor standard based on controlling the concentration of semivolatile metals levels in the hazardous waste feed would not be justified because of the costs coupled with estimated emission reductions. Feed Control of Semivolatile Metals in the Raw Materials and Auxiliary Fuels. Cement kilns could achieve a reduction in semivolatile metals emissions by substituting a raw material containing lower levels of cadmium and lead for a primary raw material with a higher level. For a new source at an existing cement plant, we believe that this beyond the floor option would not be cost effective due to the costs of transporting large quantities of an alternate source of raw materials to the cement plant. Given that the plant site already exists and sited near the source of raw material, replacing the raw materials at the plant site with lower semivolatile metalscontaining materials would be the source's only option. For a cement kiln constructed at a new greenfield site, we are not aware of any information and data from a source that has undertaken or is currently located at a site whose raw materials are inherently lower in semivolatile metals that would consistently achieve reduced semivolatile metals emissions. Further, we are uncertain as to what beyond the floor standard would be achievable using a lower, if it exists, semivolatile metals containing raw material. Although we are doubtful that selecting a new plant site based on the content of metals in the raw material is a realistic beyond the floor option considering the numerous additional factors that go into such a decision, we solicit comment on whether and what Redline strikeout highlighting changes made during OMB review 142 level of a beyond the floor standard based on controlling the level of semivolatile metals in the raw materials is appropriate. We also considered whether fuel switching to an auxiliary fuel containing a lower concentration of semivolatile metals would be an appropriate control option for sources. Given that most cement kilns burning hazardous waste also burn coal as a fuel, we considered switching to natural gas as a potential beyond the floor option. For the same reasons discussed for mercury, we judge a beyond the floor standard based on fuel switching as unwarranted. For the reasons discussed above, we propose to establish the emission standard for new cement kilns at 6.2 x 10 5 lbs semivolatile metals emissions attributable to the hazardous waste per million Btu heat input of the hazardous waste. E. What Are the Proposed Standards for Low Volatile Metals? We are proposing to establish standards for existing and new cement kilns that limit emissions of low volatile metals ( arsenic, beryllium, and chromium, combined) to 1.4 x 10 5 lbs low volatile metals emissions attributable to the hazardous waste per million Btu heat input of the hazardous waste. 1. What Is the Rationale for the MACT Floor for Existing Sources? Low volatile metals emissions from existing cement kilns are currently limited to 56 ug/ dscm by § 63.1204( a)( 4). This standard was promulgated in the Interim Standards Rule ( See 67 FR at 6796). Cement kilns control emissions of low volatile metals with baghouses or electrostatic precipitators and/ or by controlling the feed concentration of low volatile metals in the hazardous waste. We have compliance test emissions data representing maximum emissions for all cement kiln sources. For most sources, we have compliance test emissions data from more than one compliance test campaign. Low volatile metal stack emissions range from approximately 1 to 100 ug/ dscm. These emissions are expressed as mass of low volatile metals ( from all feedstocks) per unit volume of stack gas. Hazardous waste thermal emissions range from 9.2 x 10 7 to 1.0 x 10 5 lbs per million Btu. Hazardous waste thermal emissions represent the mass of low volatile metals emissions attributable to the hazardous waste per million Btu heat input of the hazardous waste. For nearly every cement kiln, chromium was the most significant contributor to low volatile emissions. To identify the MACT floor, we evaluated the compliance test emissions data associated with the most recent test campaign using the SRE/ Feed Approach. The calculated floor is 1.4 x 10 5 lbs low volatile metals emissions attributable to the hazardous waste per million Btu heat input of the hazardous waste, which considers emissions variability. This is an emission level that the average of the best performing sources could be expected to achieve in 99 of 100 future tests when operating under conditions identical to the compliance test conditions during which the emissions data were obtained. We estimate that this emission level is being achieved by 52% of sources and would reduce low volatile metals emissions by 0.10 tons per year. To put the proposed floor level in context for a hypothetical wet process cement kiln that gets 50% of its required heat input from hazardous waste, a thermal emissions level of 1.4 x 10 5 lbs low volatile metals emissions attributable to the hazardous waste per million Btu heat input of the hazardous waste equates approximately to a stack gas concentration of 7 ug/ dscm. This Redline strikeout highlighting changes made during OMB review 17 USEPA, " Draft Technical Support Document for HWC MACT Replacement Standards, Volume III: Selection of MACT Standards and Technologies," March 2004, Chapter 23.

143 estimated stack gas concentration does not include contributions to emission from other low volatile metals containing materials such as raw materials and fossil fuels. The additional contribution to stack emissions of low volatile metals in an average raw material and coal is estimated to range from less than 1 to 15 ug/ dscm. Thus, for the hypothetical wet process cement kiln the thermal emissions floor level of 1.4 x 10 5 lbs low volatile metals attributable to the hazardous waste per million Btu heat input of the hazardous waste is estimated to be less than 22 ug/ dscm, which is less than the current interim standard of 56 ug/ dscm. Given that comparing the proposed floor level to the interim standard requires numerous assumptions ( as just illustrated) including hazardous waste fuel replacement rates, heat input requirements per ton of clinker, concentrations of low volatile metals in the raw material and coal, and system removal efficiency, we have included a more detailed analysis in the background document. 17 Our detailed analysis indicates the proposed floor level is as least as stringent as the interim standard ( so as to avoid any backsliding from a current level of performance achieved by all cement kilns, and hence, the level of minimal stringency at which EPA could calculate the MACT floor). Thus, we conclude that a dual standard   the low volatile metals standard as both the calculated floor level, expressed as a hazardous waste thermal emissions level, and the current interim standard   is not needed for this standard. 2. EPA's Evaluation of Beyond the Floor Standards for Existing Sources We identified three potential beyond the floor techniques for control of low volatile metals: ( 1) improved particulate matter control; ( 2) control of low volatile metals in the hazardous waste feed; and ( 3) control of the low volatile metals in the raw materials. For reasons discussed below, we are not proposing a beyond the floor standard for low volatile metals. Improved Particulate Matter Control. Controlling particulate matter also controls emissions of low volatile metals. Our data show that all cement kilns are already achieving greater than 99.9% system removal efficiency for low volatile metals, with most attaining 99.99% removal. Thus, additional control of particulate matter emissions is likely to result in only a small increment in reduction of low volatile metals emissions. We evaluated a beyond the floor level of 7.0 x 10 6 lbs low volatile metals emissions attributable to the hazardous waste per million Btu heat input of the hazardous waste, which represents a 50% reduction in emissions from MACT floor levels. The national incremental annualized compliance cost for cement kilns to meet this beyond the floor level rather than comply with the floor controls would be approximately $ 3.7 million and would provide an incremental reduction in low volatile metals emissions beyond the MACT floor controls of 120 pounds per year. Nonair quality health and environmental impacts and energy effects were evaluated to estimate the impacts between further improvements to control particulate matter and controls likely to be used to meet the floor level. We estimate that this beyond the floor option would increase the amount of solid waste generated by 72 tons per year and would also require sources to use an additional 1.2 million kW hours per year beyond Redline strikeout highlighting changes made during OMB review 144 the requirements to achieve the floor level. The costs associated with these impacts are accounted for in the national annualized compliance cost estimates. Therefore, based on these factors and costs of approximately $ 63 million per additional ton of low volatile metals removed, we are not proposing a beyond the floor standard based on improved particulate matter control. Feed Control of Low Volatile Metals in the Hazardous Waste. We also evaluated a beyond the floor level of 1.1 x 10 5 lbs low volatile metals emissions attributable to the hazardous waste per million Btu heat input of the hazardous waste, which represents a 20% reduction from the floor level. We chose a 20% reduction as a level representing the practicable extent that additional feedrate control of mercury in hazardous waste can be used and still achieve appreciable emissions reductions. The national incremental annualized compliance cost for cement kilns to meet this beyond the floor level rather than comply with the floor controls would be approximately $ 1.2 million and would provide an incremental reduction in low volatile metals emissions beyond the MACT floor controls of 38 pounds per year. Nonair quality health and environmental impacts and energy effects were evaluated and are included in the cost estimates. Therefore, based on these factors and costs of approximately $ 64 million per additional ton of low volatile metals removed, we are not proposing a beyond the floor standard based on feed control of low volatile metals in the hazardous waste. Feed Control of Low Volatile Metals in the Raw Materials and Auxiliary Fuels. Cement kilns could achieve a reduction in low volatile metal emissions by substituting a raw material containing lower levels of arsenic, beryllium, and/ or chromium for a primary raw material with higher levels of these metals. We believe that this beyond the floor option would even be less cost effective than either of the options discussed above, however. Given that cement kilns are sited near the primary raw material supply, acquiring and transporting large quantities of an alternate source of raw materials is likely to be cost prohibitive. Therefore, we are not proposing a beyond the floor standard based on limiting low volatile metals in the raw material feed. We also considered whether fuel switching to an auxiliary fuel containing a lower concentration of low volatile metals would be an appropriate control option for sources. Given that most cement kilns burning hazardous waste also burn coal as a fuel, we considered switching to natural gas as a potential beyond the floor option. For the same reasons discussed for mercury, we judge a beyond the floor standard based on fuel switching as unwarranted. For the reasons discussed above, we propose to establish the emission standard for existing cement kilns at 1.4 x 10 5 lbs low volatile metals emissions attributable to the hazardous waste per million Btu heat input of the hazardous waste. 3. What Is the Rationale for the MACT Floor for New Sources? Low volatile metals emissions from new cement kilns are currently limited to 54 ug/ dscm by § 63.1204( b)( 4). This standard was promulgated in the Interim Standards Rule ( See 67 FR at 6796, February 13, 2002). The floor level for new sources for low volatile metals would be 1.4 x 10 5 lbs low volatile metals emissions attributable to the hazardous waste per million Btu heat input of the hazardous waste, which considers emissions variability. This is an emission level that the single best performing source identified with the SRE/ Feed Approach could be expected to achieve in 99 of 100 future tests when operating under conditions identical to the test conditions during which the Redline strikeout highlighting changes made during OMB review 145 emissions data were obtained. To put the proposed floor level in context for a hypothetical wet process cement kiln that gets 50% of its required heat input from hazardous waste, a thermal emissions level of 1.4 x 10 5 lbs low volatile metals emissions attributable to the hazardous waste per million Btu heat input of the hazardous waste equates approximately to a stack gas concentration of 22 ug/ dscm, including contributions from typical raw materials and coal. Thus, for the hypothetical wet process cement kiln the thermal emissions floor level of 6.2 x 10 5 lbs low volatile metals emissions attributable to the hazardous waste per million Btu heat input of the hazardous waste is estimated to be more stringent than the current interim standard for new sources of 54 ug/ dscm. 4. EPA's Evaluation of Beyond the Floor Standards for New Sources We identified the same three potential beyond the floor techniques for control of low volatile metals: ( 1) improved control of particulate matter; ( 2) control of low volatile metals in the hazardous waste feed; and ( 3) control of low volatile metals in the raw materials and fuels. Improved Particulate Matter Control. Controlling particulate matter also controls emissions of low volatile metals. We evaluated improved control of particulate matter based on a state of the art baghouse using a high quality fabric filter bag material as beyond the floor control for further reductions in low volatile metals emissions. We evaluated a beyond the floor level of 6.0 x 10 6 lbs low volatile metals emissions attributable to the hazardous waste per million Btu heat input of the hazardous waste. The incremental annualized compliance cost for a new cement kiln to meet this beyond the floor level, rather than comply with the floor level, would be approximately $ 0.38 million and would provide an incremental reduction in low volatile metals emissions of approximately 33 pounds per year. Nonair quality health and environmental impacts and energy effects were evaluated and are included in the cost estimates. For these reasons and costs of $ 23.5 million per ton of low volatile metals removed, we are not proposing a beyond thefloor standard based on improved particulate matter control for new cement kilns. Feed Control of Low Volatile Metals in the Hazardous Waste. We also evaluated a beyond the floor level of 1.1 x 10 5 lbs low volatile metals emissions attributable to the hazardous waste per million Btu heat input of the hazardous waste, which represents a 20% reduction from the floor level. We believe that the expense for further reduction in low volatile metals emissions based on further control of low volatile metals concentrations in the hazardous waste is not warranted given the costs, nonair quality health and environmental impacts, and energy effects. Feed Control of Low Volatile Metals in the Raw Materials and Auxiliary Fuels. Cement kilns could achieve a reduction in low volatile metals emissions by substituting a raw material containing lower levels of low volatile metals for a primary raw material with a higher level. For a new source at an existing cement plant, we believe that this beyond the floor option would not be cost effective due to the costs of transporting large quantities of an alternate source of raw materials to the cement plant. Given that the plant site already exists and sited near the source of raw material, replacing the raw materials at the plant site with lower low volatile metalscontaining materials would be the source's only option. For a cement kiln constructed at a new greenfield site, we are not aware of any information and data from a source that has undertaken or is currently located at a site whose raw materials are inherently lower in low volatile metals that would consistently achieve reduced low volatile metals emissions. Further, we are uncertain as to Redline strikeout highlighting changes made during OMB review 18 USEPA, " Draft Technical Support Document for HWC MACT Replacement Standards, Volume III: Selection of MACT Standards and Technologies" Standards", March 2004, Chapter 2.

146 what beyond the floor standard would be achievable using a lower, if it exists, low volatile metals containing raw material. Although we are doubtful that selecting a new plant site based on the content of metals in the raw material is a realistic beyond the floor option considering the numerous additional factors that go into such a decision, we solicit comment on whether and what level of a beyond the floor standard based on controlling the level of low volatile metals in the raw materials is appropriate. We also considered whether fuel switching to an auxiliary fuel containing a lower concentration of low volatile metals would be an appropriate control option for sources. Given that most cement kilns burning hazardous waste also burn coal as a fuel, we considered switching to natural gas as a potential beyond the floor option. For the same reasons discussed for mercury, we judge a beyond the floor standard based on fuel switching as unwarranted. Therefore, we are proposing a low volatile metals standard of 1.4 x 10 5 lbs low volatile metals emissions attributable to the hazardous waste per million Btu heat input of the hazardous waste. F. What Are the Proposed Standards for Hydrogen Chloride and Chlorine Gas? We are proposing to establish standards for existing and new cement kilns that limit total chlorine emissions ( hydrogen chloride and chlorine gas, combined, reported as a chloride equivalent) to 110 and 83 ppmv, respectively. However, we are also proposing to establish alternative risk based standards, pursuant to CAA section 112( d)( 4), which could be elected by the source in lieu of the MACT emission standards for total chlorine. The emission limits would be based on national exposure standards that ensure protection of public health with an ample margin of safety. See Part Two, Section XIII for additional details. 1. What Is the Rationale for the MACT Floor for Existing Sources? Total chlorine emissions from existing cement kilns are limited to 130 ppmv by § 63.1204( a)( 6). This standard was promulgated in the Interim Standards Rule ( See 67 FR at 6796). None of the cement kilns burning hazardous waste use a dedicated control device, such as a wet scrubber, to remove total chlorine from the gas stream. However, the natural alkalinity in some of the raw materials is highly effective at removing chlorine from the gas stream. Our data base shows that the majority of the system removal efficiency ( SRE) data of total chlorine   over 80%   indicate a SRE greater than 95%. This scrubbing effect, though quite effective, varies across different sources and also at individual sources over time due to differences in raw materials, operating conditions, cement kiln dust recycle rates, and production requirements. Likewise, our data show that total chlorine emissions from a given source can vary over a considerable range. Based on these data, we conclude that the best ( highest) SRE achieved at a given source is not duplicable or replicable. The majority of the chlorine fed to the cement kiln during a compliance test comes from the hazardous waste. 18 In all but a few cases the hazardous waste contribution to the total Redline strikeout highlighting changes made during OMB review 19 We are also requesting comment on whether the hazardous waste feed concentration floor level should be the standard itself ( i. e., no stack emission concentration standard) or as an alternative to the stack emission standard ( e. g., sources have the option to comply with either the calculated stack emissions concentration or the hazardous waste feed concentration limit).

147 amount of chlorine fed to the kiln represented at least 75% of the total chlorine loading to the kiln. As we identified in the September 1999 final rule, the proposed MACT floor control for total chlorine is based on controlling the concentration of chlorine in the hazardous waste. The chlorine concentration in the hazardous waste will affect emissions of total chlorine at a given SRE because emissions increase as the chlorine loading increases. We have compliance test emissions data representing maximum emissions for all cement kiln sources. For most sources, we have compliance test emissions data from more than one compliance test campaign. Total chlorine emissions range from less than 1 ppmv to 192 ppmv. To identify the MACT floor, we evaluated the compliance test emissions data associated with the most recent test campaign using a variant of the SRE/ Feed Approach because of concerns about a cement kiln's ability to replicate a given SRE. To identify the floor level we first evaluated the chlorine feed level in the hazardous waste for all sources. The best performing sources had the lowest maximum theoretical emissions concentration or MTEC, considering variability. We then applied a SRE of 90% to the best performing sources' total MTEC ( i. e., includes chlorine contributions to emissions from all feedstreams such as raw material and fossil fuels) to identify the floor level. Given our concerns about the reproducibility of SREs of total chlorine, we selected a SRE of 90% because our data base shows that all sources have demonstrated this SRE at least once ( and often several times) during a compliance test. The calculated floor is 110 ppmv, which considers emissions variability. This is an emission level that the best performing feed control sources could be expected to achieve in 99 of 100 future tests when operating under conditions identical to the compliance test conditions during which the emissions data were obtained. We estimate that this emission level is being achieved by 93% of sources and would reduce total chlorine emissions by 64 tons per year. We also invite comment on an alternative approach to establish a floor level expressed as a hazardous waste thermal feed concentration. 19 A hazardous waste thermal feed concentration is expressed as mass of chlorine in the hazardous waste per million Btu heat input contributed by the hazardous waste. The floor would be based on the best five performing sources with the lowest thermal feed concentration of chlorine in the hazardous waste considering each source's most recent compliance test data. One advantage of this approach is that the uncertainty surrounding the capture ( SRE) of chlorine in a kiln is removed. The calculated floor level would be 2.4 lbs chlorine in the hazardous waste per million Btu in the hazardous waste, which considers variability. For a hypothetical wet process cement kiln that gets 50% of its required heat input from hazardous waste, a hazardous waste with a chlorine concentration of 2.4 lbs chlorine per million Btu and achieving 90% SRE equates approximately to a stack gas concentration of 75 ppmv. This estimated stack gas concentration does not include contributions to emission from Redline strikeout highlighting changes made during OMB review 148 other chlorine containing materials such as raw materials and fossil fuels. The additional contribution to stack emissions of total chlorine in an average raw material and coal is estimated to range from less than 1 to 35 ppmv. Thus, for the hypothetical wet process cement kiln this floor level is estimated to be less than 110 ppmv, which is less than the current interim standard of 130 ppmv. 2. EPA's Evaluation of Beyond the Floor Standards for Existing Sources We identified three potential beyond the floor techniques for control of total chlorine: ( 1) use of wet scrubbers; ( 2) control of chlorine in the hazardous waste feed; and ( 3) control of the chlorine in the raw materials. For reasons discussed below, we are not proposing a beyond thefloor standard for total chlorine. Use of Wet Scrubbers. We evaluated the use of wet scrubbers as beyond the floor control for further reduction of mercury emissions. Wet scrubbers are not currently being used at any hazardous waste burning cement kilns to capture hydrogen chloride. We evaluated a beyond thefloor level of 55 ppmv. The national incremental annualized compliance cost for cement kilns to meet this beyond the floor level rather than comply with the floor controls would be approximately $ 3.4 million and would provide an incremental reduction in total chlorine emissions beyond the MACT floor controls of 370 tons per year. Nonair quality health and environmental impacts and energy effects were evaluated to estimate the impacts between wet scrubbing and controls likely to be used to meet the floor level. We estimate that this beyond the floor option would increase the amount of water usage and waste water generated by 1.5 billion gallon per year. The option would also require sources to use an additional 12 million kW hours per year beyond the requirements to achieve the floor level. The costs associated with these impacts are accounted for in the national annualized compliance cost estimates. Therefore, based on these factors and costs of approximately $ 9,300 per additional ton of total chlorine removed, we are not proposing a beyond the floor standard based on wet scrubbing. Feed Control of Chlorine in the Hazardous Waste. We also evaluated a beyond the floor level of 88 ppmv, which represents a 20% reduction from the floor level. We chose a 20% reduction as a level that represents the practicable extent that additional feedrate control of chlorine in the hazardous waste can be used and still achieve modest emissions reductions. The national incremental annualized compliance cost for cement kilns to meet this beyond the floor level rather than comply with the floor controls would be approximately $ 1.1 million and would provide an incremental reduction in total chlorine emissions beyond the MACT floor controls of 100 tons per year. Nonair quality health and environmental impacts and energy effects were also evaluated and are included in the compliance cost estimates. Therefore, based on these factors and costs of approximately $ 11,000 per additional ton of total chlorine, we are not proposing a beyond the floor standard based on feed control of chlorine in the hazardous waste. Feed Control of Chlorine in the Raw Materials and Auxiliary Fuels. Cement kilns could achieve a reduction in total chlorine emissions by substituting a raw material containing lower levels of chlorine for a primary raw material with higher levels of chlorine. We believe that this beyond the floor option would even be less cost effective than either of the options discussed above because most chlorine feed to the kiln is in the hazardous waste. In addition, given that cement kilns are sited near the primary raw material supply, acquiring and transporting large Redline strikeout highlighting changes made during OMB review 149 quantities of an alternate source of raw materials is likely to be cost prohibitive. Therefore, we are not proposing a beyond the floor standard based on limiting chlorine in the raw material feed. We also considered whether fuel switching to an auxiliary fuel containing a lower concentration of chlorine would be an appropriate control option for kilns. Given that most cement kilns burning hazardous waste also burn coal as a fuel, we considered switching to natural gas as a potential beyond the floor option. For the same reasons discussed for mercury, we judge a beyond thefloor standard based on fuel switching as unwarranted. For the reasons discussed above, we propose not to adopt a beyond the floor standard for total chlorine and propose to establish the emission standard for existing cement kilns at 110 ppmv. 3. What Is the Rationale for the MACT Floor for New Sources? Total chlorine emissions from new cement kilns are currently limited to 86 ppmv by § 63.1204( b)( 6). This standard was promulgated in the Interim Standards Rule ( See 67 FR at 6796). The MACT floor for new sources for total chlorine would be 78 ppmv, which considers emissions variability. This is an emission level that the single best performing source identified with the SRE/ Feed Approach could be expected to achieve in 99 of 100 future tests when operating under conditions identical to the test conditions during which the emissions data were obtained. 4. EPA's Evaluation of Beyond the Floor Standards for New Sources We identified similar potential beyond the floor techniques for control of total chlorine for new sources: ( 1) use of wet scrubbing; ( 2) control of chlorine in the hazardous waste feed; and ( 3) control of chlorine in the raw materials and fuels. Use of Wet Scrubbers. We considered wet scrubbing as beyond the floor control for further reductions in total chlorine emissions and evaluated a beyond the floor level of 39 ppmv. The incremental annualized compliance cost for a new cement kiln to meet this beyond the floor level, rather than comply with the floor level, would be approximately $ 1.2 million and would provide an incremental reduction in total chlorine emissions of approximately 22 tons per year. Nonair quality health and environmental impacts and energy effects were evaluated and are included in the cost estimates. For these reasons and costs of $ 24,000 per ton of total chlorine removed, we are not proposing a beyond the floor standard based on wet scrubbing for new cement kilns. Feed Control of Low Volatile Metals in the Hazardous Waste. We also evaluated a beyond the floor level of 62 ppmv, which represents a 20% reduction from the floor level. We believe that the expense for further reduction in total chlorine emissions based on further control of chlorine concentrations in the hazardous waste is not warranted given the costs, nonair quality health and environmental impacts, and energy effects. Feed Control of Chlorine in the Raw Materials and Auxiliary Fuels. Cement kilns could achieve a reduction in total chlorine emissions by substituting a raw material containing lower levels of chlorine for a primary raw material with a higher level. For a new source at an existing cement plant, we believe that this beyond the floor option would not be cost effective due to the costs of transporting large quantities of an alternate source of raw materials to the cement plant. Given that the plant site already exists and sited near the source of raw material, replacing the raw Redline strikeout highlighting changes made during OMB review 20 A greenfield cement kiln is a kiln that commenced construction or reconstruction after April 19, 1996 at a site where no cement kiln previously existed, irrespective of the class of kiln ( i. e., nonhazardous waste or hazardous waste burning). A newly constructed or reconstructed cement kiln at an existing site is not classified as a greenfield cement kiln, and is subject to the same carbon monoxide and hydrocarbon standards as an existing cement kiln.

150 materials at the plant site with lower chlorine containing materials would be the source's only option. For a cement kiln constructed at a new greenfield site, we are not aware of any information and data from a source that has undertaken or is currently located at a site whose raw materials are inherently lower in chlorine that would consistently achieve reduced total chlorine emissions. Further, we are uncertain as to what beyond the floor standard would be achievable using a lower, if it exists, chlorine containing raw material. Although we are doubtful that selecting a new plant site based on the content of chlorine in the raw material is a realistic beyondthe floor option considering the numerous additional factors that go into such a decision, we solicit comment on whether and what level of a beyond the floor standard based on controlling the level of chlorine in the raw materials is appropriate. We also considered whether fuel switching to an auxiliary fuel containing a lower concentration of chlorine would be an appropriate control option for sources. Given that most cement kilns burning hazardous waste also burn coal as a fuel, we considered switching to natural gas as a potential beyond the floor option. For the same reasons discussed for mercury, we judge a beyond the floor standard based on fuel switching as unwarranted. Therefore, we are proposing a total chlorine standard of 78 ppmv for new cement kilns. G. What Are the Standards for Hydrocarbons and Carbon Monoxide? Hydrocarbon and carbon monoxide standards are surrogates to control emissions of organic hazardous air pollutants for existing and new cement kilns. For cement kilns without bypass or midkiln sampling systems, the standard for existing sources limit hydrocarbon or carbon monoxide concentrations to 20 ppmv or 100 ppmv, respectively. The standards for new sources limit ( 1) hydrocarbons to 20 ppmv; or ( 2) carbon monoxide to 100 ppmv. New, greenfield kilns20, that elect to comply with the 100 ppmv carbon monoxide standard, however, must also comply with a 50 ppmv hydrocarbon standard. New and existing sources that elect to comply with the 100 ppmv carbon monoxide standard, including new greenfield kilns that elect to comply with the carbon monoxide standard and 50 ppmv hydrocarbon standard, must also demonstrate compliance with the 20 ppmv hydrocarbon standard during the comprehensive performance test. However, continuous hydrocarbon monitoring following the performance test is not required. For cement kilns with bypass or midkiln sampling systems, existing cement kilns are required to comply with either a carbon monoxide standard of 100 ppmv or a hydrocarbon standard of 10 ppmv. Both standards apply to combustion gas sampled in the bypass or a midkiln sampling port that samples representative kiln gas. See § § 63.1204( a)( 5) and ( b)( 5). The rationale for these decisions are discussed in the September 1999 final rule ( 64 FR at 52885). We view the standards for hydrocarbons and carbon monoxide as unaffected by the Court's vacature of the challenged regulations in its decision of July 24, 2001. We therefore are not proposing Redline strikeout highlighting changes made during OMB review 151 these standards for cement kilns, but rather are mentioning them here for the reader's convenience. H. What Are the Standards for Destruction and Removal Efficiency? The destruction and removal efficiency ( DRE) standard is a surrogate to control emissions of organic hazardous air pollutants other than dioxin/ furans. The standard for existing and new lightweight aggregate kilns requires 99.99% DRE for each principal organic hazardous constituent, except that 99.9999% DRE is required if specified dioxin listed hazardous wastes are burned. See § § 63.1204( c). The rationale for these decisions are discussed in the September 1999 final rule ( 64 FR at 52890). We view the standards for DRE as unaffected by the Court's vacature of the challenged regulations in its decision of July 24, 2001. We therefore are not proposing these standards for cement kilns, but rather are mentioning them here for the reader's convenience.

IX. How Did EPA Determine the Proposed Emission Standards for Hazardous Waste Burning Lightweight Aggregate Kilns? In this section, the basis for the proposed emission standards is discussed. See proposed § 63.1205A1221. The proposed emission limits apply to the stack gases from lightweight aggregate kilns that burn hazardous waste and are summarized in the table below:

PROPOSED STANDARDS FOR EXISTING AND NEW LIGHTWEIGHT AGGREGATE KILNS Hazardous Air Pollutant or Surrogate Emission Standard1 Existing Sources New Sources Dioxin and furan 0.40 ng TEQ/ dscm 0.40 ng TEQ/ dscm Mercury2 67 ug/ dscm 67 ug/ dscm Particulate Matter 57 mg/ dscm ( 0.025 gr/ dscf) 23 mg/ dscm ( 0.0099 gr/ dscf)

Semivolatile metals3 3.1 x 10 4 lb/ MMBtu and 250 ug/ dscm 2.4 x 10 5 lb/ MMBtu and 43 ug/ dscm Low volatile metals3 9.5 x 10 5 lb/ MMBtu and 110 ug/ dscm 3.2 x 10 5 lb/ MMBtu and 110 ug/ dscm Hydrogen chloride and chlorine gas4 Hydrocarbons5, 6 20 ppmv ( or 100 ppmv carbon monoxide) 20 ppmv ( or 100 ppmv carbon monoxide) Redline strikeout highlighting changes made during OMB review 152 Destruction and removal efficiency For existing and new sources, 99.99% for each principal organic hazardous constituent ( POHC). For sources burning hazardous wastes F020, F021, F022, F023, F026, or F027, however, 99.9999% for each POHC.

1 All emission standards are corrected to 7% oxygen, dry basis. 2 Mercury standard is an annual limit. 3 Standards are expressed as mass of pollutant emissions contributed by hazardous waste per million British thermal unit contributed by the hazardous waste. 4 Combined standard, reported as a chloride ( Cl()) equivalent. 5 Sources that elect to comply with the carbon monoxide standard must demonstrate compliance with the hydrocarbon standard during the comprehensive performance test. 6 Hourly rolling average. Hydrocarbons reported as propane.

A. What Are the Proposed Standards for Dioxin and Furan? We are proposing to establish standards for existing and new lightweight aggregate kilns that limit emissions of dioxin and furans to 0.40 ng TEQ/ dscm. 1. What Is the Rationale for the MACT Floor for Existing Sources? Dioxin and furan emissions for existing lightweight aggregate kilns are currently limited by § 63.1205( a)( 1) to 0.20 ng TEQ/ dscm or rapid quench of the flue gas at the exit of the kiln to less than 400 ° F. This standard was promulgated in the Interim Standards Rule ( See 67 FR at 6797). Since promulgation of the September 1999 final rule, we have obtained additional dioxin/ furan emissions data. We now have compliance test emissions data representing maximum emissions for all lightweight aggregate kilns that burn hazardous waste. The compliance test dioxin/ furan emissions in our database range from approximately 0.9 to 58 ng TEQ/ dscm. Quenching kiln gas temperatures at the exit of the kiln so that gas temperatures at the inlet to the particulate matter control device are below the temperature range of optimum dioxin/ furan formation ( 400 750 ° F) may be problematic for some of these sources. Some of these sources have extensive ( long) duct work between the kiln exit and the inlet to the control device. For these sources, quenching the gases at the kiln exit to a low enough temperature to limit dioxin/ furan formation may conflict with the source's ability to avoid acid gas dew point related problems in the long duct work and control device. As a result, some sources quench the kiln exit gases to a temperature that is in the optimum temperature range for surface catalyzed dioxin/ furan formation. Available compliance test emissions data indicate that inlet temperatures to the control device range from 435 450 ° F. This means that temperatures in the duct work are higher and well within the range of optimum dioxin/ furan formation. To identify the MACT floor, we evaluated the compliance test emissions data associated with the most recent test campaign using the Emissions Approach described in Part Two, Section VI above. The calculated floor is 14 ng TEQ/ dscm, which considers emissions variability. However, the current interim emission standard   0.20 ng TEQ/ dscm or rapid quench of the flue gas at the exit of the kiln to less than 400 ° F   is a regulatory limit that is relevant in identifying the Redline strikeout highlighting changes made during OMB review 21 Even though all sources have recently demonstrated compliance with the interim standards, the dioxin/ furan data in our data base preceded the compliance demonstration. This explains why we have emissions data that are higher than the interim standard.

153 floor level because it fixes a level of performance for the source category. We estimate that sources achieving the " rapid quench of the flue gas at the exit of the kiln to less than 400 ° F" part of the current standard can emit up to 6.1 ng TEQ/ dscm. Given that all sources are achieving the interim standard and that the interim standard is judged as more stringent than the calculated MACT floor, the dioxin/ furan floor level can be no less stringent than the current regulatory limit. 21 We are, therefore, proposing the dioxin/ furan floor level as the current emission standard of 0.20 ng TEQ/ dscm or rapid quench of the flue gas at the exit of the kiln to less than 400 ° F. This emission level is being achieved by all sources because it is the interim standard. In addition, there are no emissions reductions for existing lightweight aggregate kilns to comply with the floor level. 2. EPA's Evaluation of Beyond the Floor Standards for Existing Sources We evaluated activated carbon injection as beyond the floor control for further reduction of dioxin/ furan emissions. Activated carbon has been demonstrated for controlling dioxin/ furans in various combustion applications; however, no lightweight aggregate kiln that burns hazardous waste uses activated carbon injection. We evaluated a beyond the floor level of 0.40 ng TEQ/ dscm, which represents a level that is considered routinely achievable using activated carbon injection. In addition, we assumed for costing purposes that lightweight aggregate kilns needing activated carbon injection to achieve the beyond the floor level would install the activated carbon injection system after the existing particulate matter control device and add a new, smaller baghouse to remove the injected carbon with the adsorbed dioxin/ furans. We chose this costing approach to address potential concerns that injected carbon may interfere with lightweight aggregate dust use practices. The national incremental annualized compliance cost for lightweight aggregate kilns to meet this beyond the floor level rather than comply with the floor controls would be approximately $ 21.28 million and would provide an incremental reduction in dioxin/ furan emissions beyond the MACT floor controls of 1.9 grams TEQ per year. Nonair quality health and environmental impacts and energy effects were evaluated to estimate the nonair quality health and environmental impacts between activated carbon injection and controls likely to be used to meet the floor level. We estimate that this beyond the floor option would increase the amount of solid waste generated by 550 tons per year and would require sources to use an additional 1 million kW hours per year beyond the requirements to achieve the floor level. The costs associated with these impacts are accounted for in the national compliance cost estimates. Therefore, based on these factors and costs of approximately $ 0.915 million per additional gram of dioxin/ furan TEQ removed, we are proposing a beyond the floor standard of 0.40 ng TEQ/ dscm for existing lightweight aggregate kilns. We judge that the cost to achieve this beyond the floor level is warranted given our special concern about dioxin/ furan. Dioxin/ furan are some of the most toxic compounds known due to their bioaccumulation potential and wide Redline strikeout highlighting changes made during OMB review 154 range of health effects, including carcinogenesis, at exceedingly low doses. Exposure via indirect pathways is a chief reason that Congress singled our dioxin/ furan for priority MACT control in CAA section 112( c)( 6). See S. Rep. No. 128, 101st Cong. 1st Sess. at 154 155. In addition, we note that a beyond the floor standard of 0.40 ng TEQ/ dscm is consistent with historically controlled levels under MACT for hazardous waste incinerators and cement kilns, and Portland cement plants. See § § 63.1203( a)( 1), 63.1204( a)( 1), and 63.1343( d)( 3). Also, EPA has determined previously in the 1999 Hazardous Waste Combustor MACT final rule that dioxin/ furan in the range of 0.40 ng TEQ/ dscm or less are necessary for the MACT standards to be considered generally protective of human health under RCRA ( using the 1985 cancer slope factor), thereby eliminating the need for separate RCRA standards under the authority of RCRA section 3005( c)( 3) and 40 CFR 270.10( k). Finally, we note that this decision is not inconsistent with EPA's decision not to promulgate beyond the floor standards for dioxin/ furan for hazardous waste burning lightweight aggregate kilns, cement kilns, and incinerators at cost effectiveness values in the range of $ 530,000 to $ 827,000 per additional gram of dioxin/ furan TEQ removed. See 64 FR at 52892, 52876, and 52961. In those cases, EPA determined that controlling dioxin/ furan emissions from a level of 0.40 ng TEQ/ dscm to a beyond the floor level of 0.20 ng TEQ/ dscm was not warranted because dioxin/ furan levels below 0.40 ng TEQ/ dscm are generally considered to be below the level of health risk concern.

3. What Is the Rationale for the MACT Floor for New Sources? Dioxin and furan emissions for new lightweight aggregate kilns are currently limited by § 63.1205( b)( 1) to 0.20 ng TEQ/ dscm or rapid quench of the flue gas at the exit of the kiln to less than 400 ° F. This standard was promulgated in the Interim Standards Rule ( See 67 FR at 6797). The calculated MACT floor for new sources would be 1.3 ng TEQ/ dscm, which considers emissions variability, or rapid quench of the flue gas at the exit of the kiln to less than 400 ° F. This is an emission level that the single best performing source identified by the Emissions Approach. However, we are concerned that the calculated floor level of 1.3 ng TEQ/ dscm is not duplicable by all sources using temperature control because we estimate that sources rapidly quenching the flue gas at the exit of the kiln to less than 400 ° F can emit up to 6.1 ng TEQ/ dscm. Therefore, we are proposing the floor as the current emission standard of 0.20 ng TEQ/ dscm or rapid quench of the flue gas at the exit of the kiln to less than 400 ° F. 4. EPA's Evaluation of Beyond the Floor Standards for New Sources We evaluated activated carbon injection as beyond the floor control for further reduction of dioxin/ furan emissions, and considered a beyond the floor level of 0.40 ng TEQ/ dscm, which represents a level that is considered routinely achievable with activated carbon injection. In addition, we assumed for costing purposes that a new lightweight aggregate kiln will install the activated carbon injection system after the existing particulate matter control device and add a new, smaller baghouse to remove the injected carbon with the adsorbed dioxin/ furan. The incremental annualized compliance cost for a new source to meet this beyond the floor level, rather than comply with the floor level, would be approximately $ 0.26 million and would provide an incremental reduction in dioxin/ furan emissions of 0.37 grams per year. Nonair quality health, environmental impacts, and energy effects are accounted for in the cost estimates. Therefore, Redline strikeout highlighting changes made during OMB review 22 MTEC is a term to compare metals and chlorine feedrates across sources of different sizes. MTEC is defined as the metals or chlorine feedrate divided by the gas flow rate and is expressed in units of ug/ dscm.

23 Given that the majority of feedrate and emissions data for mercury is normal, we do not believe it is appropriate to establish a hazardous waste thermal emissions based standard.

155 based on these factors and cost of $ 0.71 million per gram TEQ removed, we are proposing a beyond the floor standard based on activated carbon injection. We believe that the cost to achieve this beyond the floor level is warranted given our special concern about dioxin/ furan. Dioxin/ furan are some of the most toxic compounds known due to their bioaccumulation potential and wide range of health effects, including carcinogenesis, at exceedingly low doses. In addition, as discussed above, we note that the beyond the floor emission level of 0.40 ng TEQ/ dscm is consistent with historically controlled levels under MACT for hazardous waste incinerators and cement kilns, and Portland cement plants. See § § 63.1203( a)( 1), 63.1204( a)( 1), and 63.1343( d)( 3). EPA has determined previously in the 1999 Hazardous Waste Combustor MACT final rule that dioxin/ furan in the range of 0.40 ng TEQ/ dscm or less are necessary for the MACT standards to be considered generally protective of human health under RCRA, thereby eliminating the need for separate RCRA standards.

B. What Are the Proposed Standards for Mercury? We are proposing to establish standards for existing and new lightweight aggregate kilns that limit emissions of mercury to 67 ug/ dscm. 1. What Is the Rationale for the MACT Floor for Existing Sources? Mercury emissions for existing lightweight aggregate kilns are currently limited to 120 ug/ dscm by § 63.1205( a)( 2). Existing lightweight aggregate kilns have the option to comply with an alternative mercury standard that limits the hazardous waste maximum theoretical emissions concentration ( MTEC) of mercury to 120 ug/ dscm. 22 This standard was promulgated in the Interim Standards Rule ( See 67 FR at 6797). One lightweight aggregate facility with two kilns uses a venturi scrubber to remove mercury from the flue gas stream and the remaining sources limit the feed concentration of mercury in the hazardous waste to control emissions. We have compliance test emissions data representing maximum emissions for only one source; however, we have normal emissions data for all sources. For most sources, we have normal emissions data from more than one test campaign. We used these emissions data to represent the average emissions from a source even though we do not know whether the emissions represent the high end, low end, or close to the average emissions. The normal mercury stack emissions range from less than 1 to 47 ug/ dscm, while the highest compliance test emissions data is 1,050 ug/ dscm. These emissions are expressed as mass of mercury ( from all feedstocks) per unit volume of stack gas. To identify the MACT floor, we evaluated all normal emissions data using the SRE/ Feed Approach. We considered normal stack emissions data from all test campaigns. 23 For example, Redline strikeout highlighting changes made during OMB review We prefer to establish emission standards under the hazardous waste thermal emissions format using compliance test data because the metals feedrate information from compliance tests that we use to apportion emissions to calculate emissions attributable to hazardous waste are more reliable than feedrate data measured during testing under normal, typical operations.

156 one source in our data base has normal emissions data for three different testing campaigns: 1992, 1995, and 1999. Under this approach we considered the emissions data from the three separate years or campaigns. As explained earlier, we believe this approach better captures the range of average emissions for a source than only considering the most recent normal emissions. In addition, for sources without control equipment to capture mercury, we assumed the sources achieved a SRE of zero. The effect of this assumption is that the sources ( without control equipment for mercury) with the lower mercury concentrations in the hazardous waste were identified as the better performing sources. The calculated floor is 67 ug/ dscm, which considers emissions variability, based on a hazardous waste maximum theoretical emissions concentration ( MTEC) of 42 ug/ dscm. This is an emission level that the average of the best performing sources could be expected to achieve in 99 of 100 future tests when operating under operating conditions identical to the compliance test conditions during which the emissions data were obtained. We estimate that this emission level is being achieved by 57% of sources and would reduce mercury emissions by 8 pounds per year. If we were to adopt such a floor level, we are proposing that sources comply with the limit on an annual basis because it is based on normal emissions data. Under this approach, compliance would not be based on the use of a total mercury continuous emissions monitoring system because these monitors have not been adequately demonstrated as a reliable compliance assurance tool at all types of incinerator sources. Instead, a source would maintain compliance with the mercury standard by establishing and complying with short term limits on operating parameters ( e. g., for pollution control equipment and annual limits on maximum total mercury feedrate in all feedstreams) on an annual basis. In the September 1999 final rule, we acknowledged that a lightweight aggregate kiln using properly designed and operated MACT control technologies, including controlling the levels of metals in the hazardous waste, may not be capable of achieving a given emission standard because of process raw material contributions that might cause an exceedance of the emission standard. To address this concern, we promulgated a provision that allows sources to petition for alternative standards provided they submit site specific information that shows raw material hazardous air pollutant contributions to the emissions prevent the source from complying with the emission standard even though the kiln is using MACT control. See § 63.1206( b)( 9). Today's proposed floor of 67 ug/ dscm, which was based on a hazardous waste MTEC of 42 ug/ dscm, may likewise necessitate such an alternative because contributions of mercury in the raw materials and fossil fuels at some sources may cause an exceedance of the emission standard. Redline strikeout highlighting changes made during OMB review 24 Solite Corporation has four kilns at its Cascade facility and three kilns at its Arvonia facility. However, only three kilns and two kilns, respectively, can be fired with hazardous waste at any one time. For purposes of today's proposal, Solite Corporation is assumed to operate a total of five kilns.

25 A hazardous waste with a mercury concentration of 2 ppm equates approximately to a mercury emissions level of 200 250 ug/ dscm, and a source firing a hazardous waste with a mercury concentration of 0.2 ppm approximately equates to 20 25 ug/ dscm. The existing standard of 120 ug/ dscm allows a source to burn a hazardous waste with a mercury concentration of approximately 1 ppm.

157 In comments submitted to EPA in 1997, Solite Corporation ( Solite), owner and operator of five24 of the seven lightweight aggregate kilns, stated that the normal emissions data in our data base are unrepresentative of average emissions of mercury because the normal range of mercury concentrations in the hazardous waste burned during the compliance and trial burn tests was not captured during the tests. In their 1997 comments, Solite provided information on actual mercury concentrations in the hazardous waste burn tanks over a year and a quarter period. The information showed that 87% of the burn tanks contained mercury at concentrations below the facility's detection limit of 2 ppm. Additional analyses of a limited number of these samples conducted at an off site lab showed that the majority of samples were actually less than 0.2 ppm. 25 We examined the test reports of the five best performing sources that are the basis of today's proposed floor level to determine the concentration level of mercury in the hazardous wastes. The hazardous waste burned by the best performing sources during the tests that generated the normal emissions data had mercury concentrations that ranged from 0.02 to 0.2 Redline strikeout highlighting changes made during OMB review 26 These mercury concentrations were analyzed by an off site lab that had equipment capable of detecting mercury at lower concentrations. Sixteen of the 27 measurements of the best performers were reported as non detects.

158 ppm. 26 Even though the concentrations of mercury in the hazardous waste seem low, we cannot judge how these snap shot concentrations compare to long term normal concentrations because the majority of the burn tank concentration data submitted by Solite are nondetect measurements at a higher detection limit. Solite informed us in July 2003 that they are in the process of upgrading the analysis equipment at their on site laboratory. Once completed, Solite expects to be capable of detecting mercury in the hazardous waste at concentrations of 0.2 ppm. Solite also indicated that they intend to assemble and submit to EPA several months of burn tank concentration data analyzed with the new equipment. We will add these data to the docket of today's proposal once available. As we discussed for cement kilns for mercury, we are requesting comment on approaches to establish a hazardous waste feed concentration standard based on long term feed concentrations of mercury in the hazardous waste. Likewise, we invite comments on establishing a mercury feed concentration standard for lightweight aggregate kilns. We also invite comment on whether we should judge an annual limit of 67 ug/ dscm as less stringent than either the current emission standard of 120 ug/ dscm or the hazardous waste MTEC of mercury of 120 ug/ dscm for lightweight aggregate kilns ( so as to avoid any backsliding from a current level of performance achieved by all sources, and hence, the level of minimal stringency at which EPA could calculate the MACT floor). In order to comply with the current emission standard, generally a source must conduct manual stack sampling to demonstrate compliance with the mercury emission standard and then establish a maximum mercury feedrate limit based on operations during the performance test. Following the performance test, the source complies with a limit on the maximum total mercury feedrate in all feedstreams on a 12 hour rolling average ( not an annual average). Alternatively, a source can elect to comply with a hazardous waste MTEC of mercury of 120 ug/ dscm that would require the source to limit the mercury feedrate in the hazardous waste on a 12 hour rolling average. The floor level of 67 ug/ dscm proposed today would allow a source to feed more variable mercury containing feedstreams ( e. g., a hazardous waste with an mercury MTEC greater than 120 ug/ dscm) than the current 12 hour rolling average because today's proposed floor level is an annual limit. For example, the concentration of mercury in the hazardous waste exceeded a hazardous waste MTEC of 120 ug/ dscm in a minimum of 13% of the burn tanks based on the data submitted by Solite in their 1997 comments ( discussed above). As mentioned above, Solite intends to submit several months of burn tank concentration data using upgraded analysis equipment at their on site laboratory that we will consider when comparing the relative stringency of an annual limit of 67 ug/ dscm and a shortterm limit of 120 ug/ dscm. 2. EPA's Evaluation of Beyond the Floor Standards for Existing Sources We identified three potential beyond the floor techniques for control of mercury: ( 1) activated carbon injection; ( 2) control of mercury in the hazardous waste feed; and ( 3) control of Redline strikeout highlighting changes made during OMB review 27 USEPA, " Draft Technical Support Document for HWC MACT Replacement Standards, Volume V: Emission Estimates and Engineering Costs", March 2004, Chapter 4.