159 identified with the SRE/ Feed Approach 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. As discussed for existing sources, in order to avoid any backsliding from the current level of performance for a new lightweight aggregate kiln source, we propose 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. This would ensure that all sources are complying with a limit that is at least as stringent as the interim standard. Thus, the proposed MACT floor for new lightweight aggregate kilns is 3.2 x 10 5 lbs low volatile metals emissions attributable to the hazardous waste per million Btu heat input of the hazardous waste and 110 ug/ dscm. 4. EPA's Evaluation of Beyond the Floor Standards for New Sources We considered 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 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 1.6 x 10 5 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 lightweight aggregate kiln with average gas flowrate to meet this beyond the floor level, rather than to comply with the floor level, would be approximately $ 0.11 million and would provide an incremental reduction in low volatile metals emissions of approximately 16 pounds per year. Nonair quality health and environmental impacts and energy effects were evaluated and are included in the cost estimates. We estimate that this beyond the floor option would increase the amount of solid waste generated by 3 tons per year and would also require sources to use an additional 0.3 million kW hours per year beyond the requirements to achieve the floor level. Therefore, based on these factors and costs of nearly $ 14 million per ton of low volatile metals removed, we are not proposing a beyond the floor standard based on improved particulate matter control for new lightweight aggregate kilns. Feed Control of Low Volatile Metals in the Hazardous Waste. We also 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. We considered a beyondthe floor level of 2.6 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. 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 low volatile metals levels in the hazardous waste feed would not be justified because of the costs and estimated emission reductions. Feed Control of Low Volatile Metals in the Raw Materials and Auxiliary Fuels. * OMB Review Draft*

160 Lightweight aggregate kilns could achieve a reduction in low volatile metals emissions by substituting a raw material containing lower levels of arsenic, beryllium, and/ or chromium for a primary raw material with a higher level. For a new source at an existing facility, 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 material to the facility. 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 metals containing materials would be the source's only option. For a 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 what beyond the floor standard would be achievable using, if it exists, a lower 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 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 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. Two facilities typically burn hazardous waste at a fuel replacement rate of 100%, while one facility has burned a combination of fuel oil and natural gas in addition to the hazardous waste. We considered switching only to natural gas as the auxiliary fuel as a potential beyond the floor option. We do not believe that switching to natural gas is a viable control option for the same reasons discussed above for cement kilns. For the reasons discussed above, we propose to establish the emission standard for new lightweight aggregate kilns at 3.2 x 10 5 lbs low volatile metals emissions attributable to the hazardous waste per million Btu heat content in the hazardous waste and 110 ug/ dscm. F. What Are the Proposed Standards for Hydrogen Chloride and Chlorine Gas? We are proposing to establish standards for existing and new lightweight aggregate kilns that limit total chlorine emissions ( hydrogen chloride and chlorine gas, combined, reported as a chloride equivalent) to 150 ppmv. However, we are also proposing to invoke CAA section 112( d)( 4) to establish alternative risk based standards 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 600 ppmv by § 63.1205( a)( 6). This standard was promulgated in the Interim Standards Rule ( See 67 FR at 6797). One of the three lightweight aggregate facilities uses a venturi scrubber to remove total chlorine from the gas stream. The system removal efficiency ( SRE) achieved by this facility during compliance testing shows removal efficiencies ranging from 96 to 99%. Sources at the other two facilities do not use air pollution control equipment to capture emissions of total chlorine, and, therefore, SREs are negligible. * OMB Review Draft*

18 We also considered controlling the chlorine levels in the hazardous waste feed and controlling the chlorine levels in the raw materials as potential beyond the floor techniques; however, it is our judgment that they are not likely to be as cost effective as dry lime scrubbing.

161 The majority of the chlorine fed to the lightweight aggregate kiln during a compliance test comes from the hazardous waste. In all but a few cases the hazardous waste contribution to the total amount of chlorine fed to the kiln represented at least 80% of the total loading to the kiln. The proposed MACT floor control for total chlorine is, in part, 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 will increase as the chlorine loading increases. We have compliance test emissions data representing maximum allowed emissions for all lightweight aggregate kiln sources. For most sources, we have compliance test emissions data from more than one compliance test campaign. Total chlorine emissions range from 14 to 116 ppmv for the source using a venturi scrubber and range from 500 to 2,400 ppmv at sources without scrubbing control equipment. 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 3.0 lbs total chlorine 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. To put the proposed floor level in context for a hypothetical lightweight aggregate kiln that gets 90% of its required heat input from hazardous waste, a thermal emissions level of 3.0 lbs total chlorine emissions attributable to the hazardous waste per million Btu heat input of the hazardous waste equates approximately to a stack gas concentration of 1,970 ppmv. This estimated stack gas concentration does not include contributions to emission from other chlorinecontaining materials such as raw materials. Given that the calculated floor level is less stringent than the current interim emission standard of 600 ppmv. In order to avoid any backsliding from the current level of performance achieved by all lightweight aggregate kilns, we are proposing the floor standard as the current emission standard of 600 ppmv. This emission level is currently being achieved by all sources. 2. EPA's Evaluation of Beyond the Floor Standards for Existing Sources We considered a beyond the floor standard of 150 ppmv based on the assumption that dry lime scrubbing will provide 75% control of hydrogen chloride. 18 In addition, for costing purposes we assumed that lightweight aggregate kilns needing total chlorine reductions to achieve the beyond the floor level would install the dry scrubbing system after the existing particulate matter control device and add a new, smaller baghouse to remove the products of the reaction and any unreacted lime. We chose this conservative costing approach to address potential concerns that unreacted lime and collected chloride and sulfur salts may interfere with lightweight aggregate * OMB Review Draft*

162 dust use practices. The national incremental annualized compliance cost for incinerators to meet this beyondthe floor level rather than comply with the floor controls would be approximately $ 1.9 million and would provide an incremental reduction in total chlorine emissions beyond the MACT floor controls of 275 tons per year. Nonair quality health and environmental impacts and energy effects were evaluated to estimate the nonair quality health and environmental impacts between dry scrubbing 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 12,700 tons per year and would also require sources to use an additional 175,000 kW hours per year and 31 million gallons of water beyond the requirements to achieve the floor level. Therefore, based on these factors and costs of approximately $ 6,800 per additional ton of total chlorine removed, we are proposing a beyond the floor standard based on dry scrubbing. 3. What Is the Rationale for the MACT Floor for New Sources? Total chlorine emissions from new lightweight aggregate kilns are currently limited to 600 ppmv by § 63.1205( b)( 6). This standard was promulgated in the Interim Standards Rule ( See 67 FR at 6797). The MACT floor for new sources for total chlorine would be 0.93 lbs chlorine in the hazardous waste per million Btu in the hazardous waste, which considers emissions variability. To put the proposed floor level in context for a hypothetical lightweight aggregate kiln that gets 90% of its required heat input from hazardous waste, a thermal emissions level of 0.93 lbs total chlorine emissions attributable to the hazardous waste per million Btu heat input of the hazardous waste equates approximately to a stack gas concentration of 610 ppmv. This estimated stack gas concentration does not include contributions to emission from other chlorine containing materials such as raw materials. Given that the calculated floor level is less stringent than the current interim emission standard of 600 ppmv. In order to avoid any backsliding from the current standard for a new lightweight aggregate kilns, we are proposing the floor standard as the current emission standard of 600 ppmv. 4. EPA's Evaluation of Beyond the Floor Standards for New Sources Similar to existing sources, we considered a beyond the floor standard of 150 ppmv based on the assumption that dry lime scrubbing will provide 75% control of hydrogen chloride. The incremental annualized compliance cost for a new lightweight aggregate kiln with average gas flowrate to meet this beyond the floor level, rather than to comply with the floor level, would be approximately $ 0.42 million and would provide an incremental reduction in total chlorine emissions of approximately 118 pounds per year. Nonair quality health and environmental impacts and energy effects were evaluated and are included in the cost estimates. We estimate that this beyond the floor option would increase the amount of solid waste generated by 23 tons per year and would also require sources to use an additional 0.3 million kW hours per year and 2 million gallons of water beyond the requirements to achieve the floor level. Therefore, based on these factors and costs of approximately $ 2,800 per additional ton of total chlorine removed, we are proposing a beyond the floor standard based on dry scrubbing. 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 lightweight aggregate kilns. The standards * OMB Review Draft*

163 limit hydrocarbons and carbon monoxide concentrations to 20 ppmv or 100 ppmv. See § § 63.1205( a)( 5) and ( b)( 5). Existing and new lightweight aggregate kilns can elect to comply with either the hydrocarbon limit or the carbon monoxide limit on a continuous basis. Sources that comply with the carbon monoxide limit on a continuous basis must also demonstrate compliance with the hydrocarbon standard during the comprehensive performance test. However, continuous hydrocarbon monitoring following the performance test is not required. The rationale for these decisions are discussed in the September 1999 final rule ( 64 FR at 52900). 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 these standards for lightweight aggregate 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 § § 63.1205( c). The rationale for these decisions are discussed in the September 1999 final rule ( 64 FR at 52902). 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 lightweight aggregate kilns, but rather are mentioning them here for the reader's convenience.

X. How Did EPA Determine the Proposed Emission Standards for Hazardous Waste Burning Solid Fuel Fired Boilers? The proposed standards for existing and new solid fuel fired boilers that burn hazardous waste are summarized in the table below. See proposed § 63.1216. * OMB Review Draft*

164 PROPOSED STANDARDS FOR EXISTING AND NEW SOLID FUEL FIRED BOILERS Hazardous Air Pollutant or Surrogate Emission Standard1 Existing Sources New Sources Dioxin and furan 100 ppmv carbon monoxide or 10 ppmv hydrocarbons. 100 ppmv carbon monoxide or 10 ppmv hydrocarbons.

Mercury 10 ug/ dscm 10 ug/ dscm Particulate matter 69 mg/ dscm ( 0.030 gr/ dscf) 34 mg/ dscm ( 0.015 gr/ dscf)

Semivolatile metals 170 ug/ dscm 170 ug/ dscm Low volatile metals 210 ug/ dscm 190 ug/ dscm Hydrogen chloride and chlorine gas2 110 ppmv or the alternative emission limits under § 63.1215 73 ppmv or the alternative emission limits under § 63.1215 Carbon monoxide or hydrocarbons3 100 ppmv carbon monoxide or 10 ppmv hydrocarbons. 100 ppmv carbon monoxide or 10 ppmv hydrocarbons.

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 Combined standard, reported as a chloride ( Cl()) equivalent. 3 Hourly rolling average. Hydrocarbons reported as propane.

We considered whether fuel switching could be considered a control technology to achieve MACT floor control. We investigated whether fuel switching would achieve lower HAP emissions and whether it could be technically achieved considering the existing design of solid fuel fired boilers. We also considered the availability of various types of fuel. After considering these factors, we determined that fuel switching is not an appropriate control technology for purposes of determining the MACT floor level of control. This decision is based on the overall effect of fuel switching on HAP emissions, technical and design considerations, and concerns about fuel availability. We determined that while fuel switching from coal to natural gas or oil would decrease particulate matter and some metal HAP emissions, emissions of some organic HAP would * OMB Review Draft*

19 C. Leatherwood, ERG, to J. Eddinger, OAQPS, EPA, Memorandum: Development of Fuel Switching Costs and Emission Reductions for Industrial/ Commercial/ Institutional Boilers and Process Heaters National Emission Standards for Hazardous Air Pollutants, October 2002.

165 increase, resulting in uncertain benefits. 19 We believe that it is inappropriate in a MACT rulemaking to consider as MACT a control option that potentially will decrease emissions of one HAP while increasing emissions of another HAP. In order to adopt such a strategy, we would need to assess the relative risk associated with each HAP emitted, and determine whether requiring the control in question would result in overall lower risk. Such an analysis is not appropriate at this stage in the regulatory process. For example, the term    clean coal'' refers to coal that is lower in sulfur content and not necessarily lower in HAP content. Data gathered by EPA also indicates that within specific coal types HAP content can vary significantly. Switching to a low sulfur coal may actually increase emissions of some HAP. Therefore, it is not appropriate for EPA to include fuel switching to a low sulfur coal as part of the MACT standards for boilers that burn hazardous waste. We also considered the availability of alternative fuel types. Natural gas pipelines are not available in all regions of the U. S., and natural gas is simply not available as a fuel for many solid fuel fired boilers. 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 EPA regulated combustion units to switch to natural gas would place an even greater strain on natural gas resources. Consequently, even where pipelines exist, some units would not be able to run at normal or full capacity during these times if shortages were to occur. Therefore, under any circumstances, there would be some units that could not comply with a requirement to switch to natural gas. In addition, we have significant concern that switching fuels would be infeasible for sources designed and operated to burn specific fuel types. Changes in the type of fuel burned by a boiler may require extensive changes to the fuel handling and feeding system ( e. g., a stoker fired boiler using coal as primary fuel would need to be redesigned to handle fuel oil or gaseous fuel as the primary fuel). Additionally, burners and combustion chamber designs are generally not capable of handling different fuel types, and generally cannot accommodate increases or decreases in the fuel volume and shape. Design changes to allow different fuel use, in some cases, may reduce the capacity and efficiency of the boiler. Reduced efficiency may result in less complete combustion and, thus, an increase in organic HAP emissions. For the reasons discussed above, we conclude that fuel switching to cleaner solid fuels or to liquid or gaseous fuels is not an appropriate criteria for identifying the MACT floor level of control for solid fuel fired boilers. A. What Is the Rationale for the Proposed Standards for Dioxin and Furan? The proposed standard for dioxin/ furan for existing and new sources is compliance with the proposed carbon monoxide or hydrocarbon ( CO/ HC) emission standard and compliance with * OMB Review Draft*

20 Uncontrolled hydrogen chloride in combustion gas was approximately 700 ppmv.

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

166 the proposed destruction and removal efficiency ( DRE) standard. The CO/ HC and DRE standards control emissions of organic HAPs in general, and are discussed in Sections G and H below. This standard ensures that boilers operate under good combustion practices as a surrogate for dioxin/ furan control. Operating under good combustion practices minimizes levels of products of incomplete combustion, including potentially dioxin/ furan, and organic compounds that could be precursors for post combustion formation of dioxin/ furan. The rationale for the dioxin/ furan standard is discussed below. 1. What Is the Rationale for the MACT Floor for Existing Sources? The proposed MACT floor control for existing sources is compliance with the proposed CO/ HC emission standard and compliance with the proposed DRE standard. Solid fuel fired boilers that burn hazardous waste cofire the hazardous waste with coal at firing rates of 6 33% of total heat input. We have dioxin/ furan emission data for one source, and those emissions are 0.07 ng TEQ/ dscm. Although dioxin/ furan can be formed post combustion in an electrostatic precipitator or baghouse that is operated at temperatures within the range of 400

to 750

F, the boiler for which we have dioxin/ furan emissions data is equipped with an electrostatic precipitator that operated at 500

F during the emissions test. Although this is well within the optimum temperature range for formation of dioxin/ furan, dioxin/ furan emissions were low. In addition, this boiler fed chlorine at levels four times greater than any other solid fuel boiler. 20 We also have emissions data from 16 nonhazardous waste coal fired boilers equipped with electrostatic precipitators and baghouses operated at temperatures up to 480

F, all of which have dioxin/ furan emissions below 0.3 ng TEQ/ dscm. 21 We conclude from these data and the information discussed below that rapid quench of post combustion gas temperatures to below 400

F the control technique that is the basis for the MACT standards for hazardous waste burning incinerators, and cement and lightweight aggregate kilns is not the dominant dioxin/ furan control mechanism for coal fired boilers. We believe that sulfur contributed by the coal fuel is a dominant control mechanism by inhibiting formation of dioxin/ furan. Coal generally contributes from 65% to 95% percent of the boiler's heat input with the remainder provided by hazardous waste fuel. The presence of sulfur in combustor feedstocks has been shown to dramatically inhibit the catalytic formation of dioxin/ furan in downstream temperature zones from 400

F to 750

F. High sulfur coals tend to inhibit dioxin/ furan formation better than low sulfur coals. Id. Adsorption of any dioxin/ furan that may be formed on coal fly ash, and subsequent capture in the electrostatic precipitator or baghouse, also may contribute to the low dioxin/ furan emissions despite some boilers operating at relatively high back end gas temperatures. This effect is similar to that of using activated carbon injection to control dioxin/ furan emissions. Adsorption * OMB Review Draft*

22 Section 266.104 requires compliance with a CO limit of 100 ppmv or a HC limit of 20 ppmv, while we are proposing today a CO limit of 100 ppmv or a HC limit of 10 ppmv ( see Section X. H in the text). Although today's proposed HC limit is more stringent than the current limit for boilers, all solid fuel boilers chose to comply with the 100 ppmv CO limit. Moreover, for those liquid fuel fired boilers that chose to comply with the 20 ppmv HC limit, their HC emissions are below 10 ppmv.

167 of dioxin/ furan on fly ash is related to the carbon content of the fly ash, and, thus, the type of coal burned. Id. Operating under good combustion conditions to minimize emissions of organic compounds such as polychlorinated biphenols, benzene, and phenol that can be precursors to dioxin/ furan formation is an important requisite to control dioxin/ furan emissions. Although sulfur induced inhibition may be the dominant mechanism to control dioxin/ furan emissions from coal fired boilers, minimizing dioxin/ furan precursors by operating under good combustion practices certainly plays a part in controlling dioxin/ furan emissions. We propose to use the CO/ HC and DRE standards as surrogates to ensure that boilers operate under good combustion conditions because quantified levels of control provided by sulfur in the coal and adsorption onto collected fly ash may not be replicable by the best performing sources nor duplicable by other sources. Although coal sulfur content may be a dominant factor affecting dioxin/ furan emissions, we do not know what minimum level of sulfur provides significant control. Moreover, sulfur in coal causes emissions of sulfur oxides, a major criteria pollutant, and particulate sulfates. Similarly, we cannot quantify a minimum carbon content of coal that would form carbonaceous fly ash with superior dioxin/ furan adsorptive properties. In addition, restricting coal types that may be burned based on carbon content may have an adverse impact on energy production at sources burning hazardous waste as fuel. ( These considerations raise the question of whether boilers operating under these conditions would still be " best" performers when these adverse impacts are taken into account.) For these reasons, and because we have emissions data from only one source, we cannot establish a numerical dioxin/ furan emission standard. Operating under good combustion practices is floor control because all hazardous waste burning boilers are required by existing RCRA regulations to operate under good combustion conditions to minimize emissions of toxic organic compounds. See § 266.104 requiring compliance with DRE and CO/ HC emission standards. 22 We also find, as required by CAA Section 112( h)( 1), that these proposed standards are consistent with Section 112( d)' s objective of reducing emissions of these HAPs to the extent achievable. We request comment on an alternative floor that would be established as the highest dioxin/ furan emission level in our data base. Because we have dioxin/ furan emission data from only one coal fired boiler that burns hazardous waste, we would combine that data point with emissions data from coal fired boilers that do not burn hazardous waste since the factors that affect dioxin/ furan emissions from these boilers are not significantly influenced by hazardous waste. These additional data would better represent the range of emissions from coal fired * OMB Review Draft*

23 We considered a beyond the floor standard of 0.20 ng TEQ/ dscm but determined that it may not result in emissions reductions because the majority of sources ( the hazardous waste coal fired boiler and the nonhazardous waste coal fired boilers) appear to emit dioxin/ furan at levels below 0.20 ng TEQ/ dscm.

24 To estimate the cost of a beyond the floor standard conservatively, we assumed the solid waste generated would be subject to regulation as hazardous waste. These costs are likely over estimated, however, because these residues are not likely to fail the criteria for retaining the Bevill exclusion under 40 CFR 266.112.

168 boilers. Under this approach, the dioxin/ furan floor would be an emission level of 0.30 ng TEQ/ dscm. We would also use this approach to establish the same floor for new sources. Finally, we note that we propose to require a one time dioxin/ furan emission test for sources that would not be subject to a numerical dioxin/ furan emission standard, such as solid fuel fired boilers. As discussed in Part Two, Section XIV. B below, the testing would assist in developing both Section 112( d)( 6) standards and Section 112( f) residual risk standards. 2. EPA's Evaluation of Beyond the Floor Standards for Existing Sources As discussed above, we propose to use the CO/ HC and DRE standards as surrogates to ensure good combustion conditions, and thus, control of dioxin/ furan emissions. We are not proposing beyond the floor standards for CO/ HC and DRE, as discussion in Sections G and H below.. We investigated use of activated carbon injection or, for sources equipped with baghouses, catalytically impregnated fabric felt/ membrane filter materials to achieve a beyond thefloor standard of 0.10 ng TEQ/ dscm. 23 To estimate the cost effectiveness of these beyond thefloor control techniques, we imputed dioxin/ furan emissions levels for the six sources for which we don't have measured emissions data. To impute the missing emissions levels, we used the emissions data from the hazardous waste burning boiler as well as the emissions data from nonhazardous waste coal fired boilers. It may be appropriate to meld these emissions data because hazardous waste burning should not affect dioxin/ furan emissions from coal fired boilers. In fact, the nonhazardous waste coal fired boilers had somewhat higher emissions than the hazardous waste coal fired boiler. ( The emissions from the nonhazardous waste coal fired boilers may simply represent the range of emissions that could be expected from hazardous waste coalfired boilers, as well, given that we have emissions data from only one hazardous waste boiler.) The national incremental annualized compliance cost for solid fuel fired boilers 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 dioxin/ furan emissions beyond the MACT floor controls of 0.26 grams TEQ tons per year. We also evaluated the nonair quality health and environmental impacts and energy effects 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 hazardous waste24 generated by 3,300 tons per year and would also require sources to use an additional 1.2 million kW hours per year. Based on these impacts and * OMB Review Draft*

25 We note that we propose to require solid fuel fired boilers ( and liquid fuel fired boilers that are not subject to a numerical dioxin/ furan standard) to conduct a one time dioxin/ furan emission test to provide data to assist in developing both Section 112( d)( 6) standards and Section 112( f) residual risk standards. See discussion in Section XIV. B of the preamble.

169 costs of approximately $ 13 million per additional grams of dioxin/ furan removed, we are not proposing a beyond the floor standard based on activated carbon injection. For these reasons, we propose a floor standard for dioxin/ furan for existing sources of compliance with the proposed CO/ HC emission standard and compliance with the proposed DRE standard. 25 3. What Is the Rationale for the MACT Floor for New Sources? As discussed above, we propose to use the CO/ HC and DRE standards as surrogates to ensure good combustion conditions, and thus, control of dioxin/ furan emissions. Because we are proposing the same DRE and CO/ HC standards for existing sources and new sources as discussion in Sections G and H below, we are proposing the same dioxin/ furan floor for new and existing sources. 4. EPA's Evaluation of Beyond the Floor Standards for New Sources We are not proposing beyond the floor standards for CO/ HC for dioxin/ furan for new solid fuel fired boilers because we are not proposing beyond the floor standards for CO/ HC and DRE for new sources. See discussion in Sections G and H below. In addition, we evaluated activated carbon injection or, for sources equipped with baghouses, use of catalytically impregnated fabric felt/ membrane filter materials as beyond thefloor control for further reduction of dioxin/ furan emissions to achieve a beyond the floor level of 0.15 ng TEQ/ dscm. The incremental annualized compliance cost for a new solid fuel fired boiler with average gas flowrate to meet this beyond the floor level, rather than comply with the floor level, would be approximately $ 0.28 million and would provide an incremental reduction in dioxin/ furan emissions of approximately 0.21 grams TEQ per year, for a cost effectiveness of $ 1.3 million per gram of dioxin/ furan removed. We estimate that this beyond the floor option would increase the amount of hazardous waste ( or solid waste if the source retains the Bevill exclusion under 40 CFR 266.112) generated for a new solid fuel fired boiler with average gas flowrate by 270 tons per year and would require a source to use an additional 0.1 million kW hours per year beyond the requirements to achieve the floor level. After considering these impacts and a cost of $ 1.3 million per gram of dioxin/ furan removed, we conclude that a beyond the floor standard based on activated carbon injection or catalytically impregnated fabric felt/ membrane filter is not warranted for new sources. Consequently, we propose a floor standard for dioxin/ furan for new sources: compliance with the proposed CO/ HC and DRE emissions standards. B. What Is the Rationale for the Proposed Standards for Mercury? The proposed standard for mercury for solid fuel fired boilers is 10 ug/ dscm for both * OMB Review Draft*

26 As information, EPA proposed MACT standards for mercury for solid fuel fired industrial, commercial, and institutional boilers that do not burn hazardous waste of 5.3 ug/ dscm for existing sources and 3.4 ug/ dscm for new sources. See 68 FR 1660 ( Jan. 13, 2003). These standards are based on use of fabric filters to control mercury emissions.

27 Owners and operators have used the emissions data from the three boilers as " data in lieu of testing" emissions from other, identical boilers at the same facility. One of the three boilers as two such sister identical boilers, and the other two boilers each have a sister identical boiler. Thus, emissions from these three boilers represent emissions from seven of the 12 solid fuel fired boilers.

28 Memo from Frank Princiotta, USEPA, to John Seitz, USEPA, entitled " Control of Mercury Emissions from Coal fired Utility Boilers," dated October 25, 2000.

170 existing sources and new sources. 26 1. What Is the Rationale for the MACT Floor for Existing Sources? The MACT floor for existing sources is 10 ug/ dscm based on adsorption of mercury onto coal fly ash and removal of fly ash by the electrostatic precipitator or baghouse. All solid fuel fired boilers are equipped with electrostatic precipitators or baghouses. We have compliance test emissions data for three sources equipped with electrostatic precipitators which document maximum mercury emissions ranging from 3 ug/ dscm to 11 ug/ dscm and system removal efficiencies of 83% to 96%. These three sources represent seven of the 12 solid fuelfired boilers. 27 The Agency has also determined that coal fired utility boilers can achieve significant control of mercury by adsorption on fly ash and particulate matter control. 28 To identify the MACT floor, we evaluated the compliance test emissions data using the SRE/ Feed Approach. The calculated floor is 10 ug/ dscm, 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 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 67% of sources and would provide a reduction in mercury emissions of 0.015 tons per year. 2. EPA's Evaluation of Beyond the Floor Standards for Existing Sources We identified two potential beyond the floor techniques for control of mercury: ( 1) activated carbon injection; and ( 2) control of mercury in the hazardous waste feed. For reasons discussed below, we are not proposing a beyond the floor standard for mercury. a. Use of Activated Carbon Injection. We evaluated activated carbon injection as beyond the floor control for further reduction of mercury emissions. Activated carbon has been demonstrated for controlling mercury from waste combustion systems and has achieved efficiencies ranging from 80% to greater than 90% depending on factors such as: activated carbon type/ impregnation; injection rate; mercury speciation in the flue gas; and flue gas * OMB Review Draft*

171 temperature. We made a conservative assumption that the use of activated carbon will provide 70% mercury control for coal fired boilers given the low mercury levels at the floor. Applying this activated carbon removal efficiency to the mercury floor level of 10 ug/ dscm would provide a beyond the floor level of 3.0 ug/ dscm. The national incremental annualized compliance cost for solid fuel boilers 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 mercury emissions beyond the MACT floor controls of 0.03 tons per year. We evaluated nonair quality health and environmental impacts and energy effects and estimate that this beyond the floor option would increase the amount of hazardous waste ( or solid waste if the source retains the Bevill exclusion under 40 CFR 266.112) generated by 1,000 tons per year and would require sources to use an additional 0.35 million kWhours per year beyond the requirements to achieve the floor level. Based on these factors and costs of approximately $ 35 million per additional ton of mercury removed, we are not proposing a beyond the floor standard based on activated carbon injection. b. Feed Control of Mercury in the Hazardous Waste. We also evaluated a beyond thefloor level of 8 ug/ dscm, which represents a 20% reduction from the floor level. The national incremental annualized compliance cost for solid fuel boilers to meet this beyond the floor level rather than comply with the floor controls would be approximately $ 0.11 million and would provide an incremental reduction in mercury emissions beyond the MACT floor controls of 0.005 tons per year. Nonair quality health and environmental impacts and energy effects are not significant factors for feedrate control. We are not proposing a beyond the floor standard based on feed control of mercury in the hazardous waste because it would not be cost effective at approximately $ 23 million per additional ton of mercury removed. Consequently, we propose a floor standard for mercury for existing sources of 10 ug/ dscm. 3. What Is the Rationale for MACT Floor for New Sources? MACT floor for new sources would be 10 ug/ dscm, the same as the floor for existing sources. This is an emission level that the single best performing source identified by the SRE/ Feed Approach 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. 4. EPA's Evaluation of Beyond the Floor Standards for New Sources We identified the same two potential beyond the floor techniques for control of mercury: ( 1) use of activated carbon injection; and ( 2) control of mercury in the hazardous waste feed. We evaluated use of carbon injection for new sources to achieve a beyond the floor emission level of 5.0 ug/ dscm. The incremental annualized compliance cost for a new solid fuel boiler with average gas flowrate to meet this beyond the floor level, rather than comply with the floor level, would be approximately $ 0.28 million and would provide an incremental reduction in mercury emissions of approximately 0.008 tons per year, for a cost effectiveness of $ 37 million per ton of mercury removed. We estimate that this beyond the floor option would increase the amount of hazardous waste ( or solid waste if the source retains the Bevill exclusion under 40 CFR 266.112) generated for a new solid fuel fired boiler with average gas flowrate by 270 tons per * OMB Review Draft*

29 As information, EPA proposed MACT standards for particulate matter for solid fuel fired industrial, commercial, and institutional boilers that do not burn hazardous waste of 0.035 gr/ dscf for existing sources and 0.013 gr/ dscf for new sources. See 68 FR 1660 ( Jan. 13, 2003). These standards are based on control of particulate matter emissions using a fabric filter.

30 Owners and operators have determined that emissions from these seven boilers represent emissions from five other identical, sister boilers. Owners and operators have used the emissions from these seven boilers as " data in lieu of testing" emissions from the other five identical boilers.

31 Although particulate matter emissions are predominantly attributable to coal ash rather than ash from hazardous waste fuel, we did not combine emissions data for coal fired boilers that do not burn hazardous waste with the data for boilers that burn hazardous waste because: ( 1) we have particulate emissions data for all boilers that burn hazardous waste; and ( 2) the best performing sources for the two categories of boilers may be achieving different emission levels given that they are subject to different emission standards ( e. g., hazardous waste burning coal fired boilers are subject to the RCRA particulate matter emission standard of 0.08 gr/ dscf).

172 year and would require a source to use an additional 0.1 million kW hours per year beyond the requirements to achieve the floor level. After considering these impacts and, primarily, costeffectiveness we are not proposing a beyond the floor standard based on activated carbon injection for new sources. Consequently, we propose a floor standard for mercury of 10 ug/ dscm for new sources. C. What Is the Rationale for the Proposed Standards for Particulate Matter? The proposed standards for particulate matter for solid fuel fired boilers are 69 mg/ dscm ( 0.030 gr/ dscf) for existing sources and 34 mg/ dscm ( 0.015 gr/ dscf) for new sources. 29 The particulate matter standard serves as a surrogate for nonmercury HAP metals in emissions from the coal burned in the boiler, and for nonenumerated HAP metal emissions attributable to the hazardous waste fuel burned in the boiler. 1. What Is the Rationale for the MACT Floor for Existing Sources? All solid fuel fired boilers are equipped with electrostatic precipitators or baghouses. We have compliance test emissions data representing maximum allowable emissions for seven boilers. Emissions from these seven boilers represent emissions from all 12 solid fuel fired boilers. 30 Particulate emissions range from 0.021 gr/ dscf to 0.037 gr/ dscf. 31 To identify the floor level, we evaluated the compliance test emissions data associated with the most recent test campaign using the air pollution control device approach. See discussion in Part Two, Section VI. A. 2. a. The calculated floor is 140 mg/ dscm ( 0.063 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 75% of sources. Compliance * OMB Review Draft*

32 Note that we are not proposing beyond the floor particulate matter standards for incinerators, cement kilns, lightweight aggregate kilns, and liquid fuel fired boilers because those standards would have a cost effectiveness of $ 12,000 to $ 80,000 per ton of particulate matter removed, substantially higher than the $ 3,600 per ton cost effectiveness of a beyond the floor standard for solid fuel fired boilers.

173 with the floor level would reduce particulate matter emissions by 33 tons per year. 2. EPA's Evaluation of Beyond the Floor Standards for Existing Sources We evaluated improved design, operation, and maintenance of the existing electrostatic precipitators ( e. g., humidification to improve gas conditioning) and baghouses ( e. g., improved bags) for these boilers to achieve a beyond the floor emission level of 69 mg/ dscm ( 0.030 gr/ dscf). We also evaluated a more stringent standard based on adding a polishing fabric filter to achieve a beyond the floor emission level of 0.015 gr/ dscf. The national incremental annualized compliance cost for solid fuel boilers to meet a beyond the floor level of 69 mg/ dscm rather than comply with the floor controls would be approximately $ 1.5 million and would provide an incremental reduction in particulate matter emissions beyond the MACT floor controls of 400 tons per year. We evaluated nonair quality health and environmental impacts and energy effects and estimate that this beyond the floor option would increase the amount of hazardous waste ( or solid waste is the source retains its Bevill exclusion under 40 CFR 266.112) generated by 380 tons per year and would require sources to use an additional 3.3 million kW hours per year and to use an additional 160 million gallons of water beyond the requirements to achieve the floor level. Notwithstanding these nonair quality health and environmental impacts and energy effects, a beyond the floor standard of 69 mg/ dscm ( 0.030 gr/ dscf) based on improved particulate matter control is warranted because it is cost effective at a cost of approximately $ 3,600 per additional ton of particulate matter removed, the average incremental annualized cost would be only $ 120,000 per facility, and it would remove additional nonenumerated metal HAP. 32 We also note that, although Section 112( d) only authorizes control of HAPs, and particulate matter is not itself a HAP but a surrogate for HAP metals, Congress expected the MACT program to result in significant emissions reductions of criteria air pollutants ( of which particulate matter is one), and viewed this as an important benefit of the MACT ( and residual risk) provisions. See 5 Legislative History at 8512 ( Senate Committee Report). Finally, we note that this beyond the floor standard of 0.030 gr/ dscf would be comparable to the floor based standard the Agency recently proposed for solid fuel fired boilers that do not burn hazardous waste: 0.07 lb/ MM Btu ( approximately 0.034 gr/ dscf). See 68 FR at 1660 ( January 13, 2003). A 34 mg/ dscm beyond the floor standard for existing sources based on use of a polishing fabric filter would remove an additional 570 tons per year of particulate matter beyond the floor level at a cost effectiveness of $ 9,800 per ton removed. We conclude that this standard would not be as cost effective as a 69 mg/ dscm standard and would result in greater nonair quality health and environmental impacts and energy effects. For these reasons, we propose a beyond the floor particulate matter standard of 0.030 gr/ dscf ( 69 mg/ dscm) for existing sources. 3. What Is the Rationale for the MACT Floor for New Sources? * OMB Review Draft*

33 As information, EPA proposed to control nonmercury metal HAP emissions for industrial, commercial, and institutional boilers that do not burn hazardous waste with a particulate matter emission standard only. See 68 FR 1660 ( Jan. 13, 2003). For hazardous waste combustors, we propose to control specific, enumerated semivolatile and low volatile metals with separate emission standards because hazardous waste can have a wide range of concentrations of these metals, and, thus, particulate matter may contain a wide range of metal concentrations. Thus, particulate matter may not be an effective surrogate for particular metal HAP. Nonetheless, for practical reasons, we rely on particulate matter to control nonenumerated metal HAP.

174 MACT floor for new sources would be 90 mg/ dscm ( 0.040 gr/ dscf), considering emissions variability. This is an emission level that the single best performing source identified by the APCD Approach ( i. e., the source using a fabric filter with the lowest emissions) 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. 4. EPA's Evaluation of Beyond the Floor Standards for New Sources We evaluated use of a fabric filter to achieve a beyond the floor emission level of 34 mg/ dscm ( 0.015 gr/ dscf). The incremental annualized cost for a new solid fuel fired boiler with average gas flowrate to meet this beyond the floor level, rather than comply with the floor level, would be approximately $ 280,000 and would provide an incremental reduction in particulate emissions of approximately 44 tons per year, for a cost effectiveness of $ 6,400 per ton of particulate matter removed. We estimate that this beyond the floor option would increase the amount of hazardous waste ( or solid waste if the source retains the Bevill exclusion under 40 CFR 266.112) generated for a new solid fuel fired boiler with average gas flowrate by 44 tons per year and would require a source to use an additional 1.1 million kW hours per year beyond the requirements to achieve the floor level. Notwithstanding these impacts, a standard of 34 mg/ dscm ( 0.015 gr/ dscf) is warranted because it would be cost effective and it would remove additional nonenumerated metal HAP. We also note that this beyond the floor standard of 0.015 gr/ dscf for new sources would be comparable to the floor based standard the Agency recently proposed for new solid fuel fired boilers that do not burn hazardous waste: 0.026 lb/ MM Btu ( approximately 0.013 gr/ dscf). See 68 FR at 1660 ( January 13, 2003). For these reasons, we propose a beyond the floor particulate matter standard of 34 mg/ dscm ( 0.015 gr/ dscf) for new sources. D. What Is the Rationale for the Proposed Standards for Semivolatile Metals? The proposed standard for semivolatile metals ( lead and cadmium, combined) for solid fuel fired boilers is 170 ug/ dscm for both existing and new sources. 33 1. What Is the Rationale for the MACT Floor for Existing Sources? We have compliance test emissions data representing maximum allowed emissions for four boilers. Emissions from these four boilers represent emissions from nine of the 12 solid fuel fired * OMB Review Draft*

34 Owners and operators have determined that emissions from these four boilers represent emissions from five other identical, sister boilers. Owners and operators have used the emissions from these four boilers as " data in lieu of testing" emissions from the other five identical boilers.

175 boilers. 34 Semivolatile metal emissions range from 62 ug/ dscm to 170 ug/ dscm. These emissions are expressed as mass of semivolatile metals ( from all feedstocks) per unit of stack gas. 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 170 ug/ dcm, 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 floor level is being achieved by 42% of sources and would reduce semivolatile metals emissions by 0.22 tons per year. 2. EPA's Evaluation of Beyond the Floor Standards for Existing Sources We evaluated three beyond the floor approaches for semivolatile metals for existing sources: ( 1) improved control of particulate matter; ( 2) control of semivolatile metals in the hazardous waste feed; and ( 3) a no cost standard derived from the beyond the floor particulate matter standard. For reasons discussed below, we are not proposing a beyond the floor standard for semivolatile metals. a. Improved Particulate Matter Control. Controlling particulate matter also controls emissions of semivolatile metals. Consequently, we evaluated a beyond the floor level of 85 ug/ dscm , a 50 percent reduction in semivolatile metal emissions, that would be achieved by reducing particulate matter emissions. The national incremental annualized compliance cost for solid fuel boilers to meet this beyond the floor level rather than comply with the floor controls would be approximately $ 0.29 million and would provide an incremental reduction in semivolatile metals emissions beyond the MACT floor controls of 0.29 tons per year. We evaluated the nonair quality health and environmental impacts and energy effects of this beyond the floor standard and estimate that the amount of hazardous waste generated would increase by approximately 133 tons per year, an additional 61 million gallons per year of water would be used, and an additional 1.3 million kW hours per year of electricity would be used. Therefore, based on these factors and costs of approximately $ 1 million per additional ton of semivolatile metals removed, we are not proposing a beyond the floor standard based on improved particulate matter control. b. Feed Control of Semivolatile Metals in the Hazardous Waste. We also evaluated a beyond the floor level of 140 ug/ dscm based on additional control of semivolatile metals in the hazardous waste feed. This represents a 20% reduction from the floor level. The national incremental annualized compliance cost for solid fuel boilers to meet this beyond the floor level rather than comply with the floor controls would be approximately $ 36,000 and would provide an incremental reduction in semivolatile metals emissions beyond the MACT floor controls of 0.046 tons per year. Although nonair quality health and environmental impacts and energy effects are not significant factors, we are not proposing a beyond the floor standard based on feed control of * OMB Review Draft*

176 semivolatile metals in the hazardous waste because it is not cost effective at approximately $ 0.78 million per additional ton of semivolatile metals removed. c. No cost Standard Derived from the Beyond the Floor Particulate Matter Standard. The beyond the floor standard for particulate matter would also provide beyond the floor control for semivolatile metals if sources were to comply with the beyond the floor particulate matter standard using improved particulate matter control rather than by reducing the feedrate of ash. To identify a beyond the floor emission level for semivolatile metals that would derive from the beyond the floor particulate matter standard, we assumed that emissions of semivolatile metals would be reduced by the same percentage that sources would need to reduce particulate matter emissions. We then developed a revised semivolatile metal emission data base considering these particulate matter standard derived reductions and reductions needed to meet the semivolatile metal floor level. We analyzed these revised emissions to identify the best performing sources and an emission level that the average of the best performers could achieve 99 out of 100 future tests. This emission level 82 ug/ dscm is a beyond the floor semivolatile metal standard that can be achieved at no cost because the costs have been allocated to the particulate matter beyond thefloor standard. We are concerned, however, that sources may choose to comply with the beyond thefloor particulate matter standard by controlling the feedrate of ash in the hazardous waste feed, which may or may not reduce the feedrate and emissions of metal HAP. If so, it would be inappropriate to consider the beyond the floor standard for semivolatile metals discussed above as a no cost standard. We specifically request comment on whether sources may comply with beyond the floor particulate matter standard by controlling the feedrate of ash.. For these reasons, we propose a floor standard for semivolatile metals of 170 ug/ dscm for existing sources. 3. What Is the Rationale for the MACT Floor for New Sources? MACT floor for new sources would be 170 ug/ dscm, considering emissions variability. This is the same as the floor for existing sources. This is an emission level that the single best performing source identified by the SRE/ Feed Approach 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. 4. EPA's Evaluation of Beyond the Floor Standards for New Sources We evaluated three beyond the floor approaches for semivolatile metals for new sources: ( 1) improved particulate matter controls; ( 2) control of semivolatile metals in the hazardous waste feed; and ( 3) a no cost standard derived from the beyond the floor particulate matter standard. a. Improved Particulate Matter Controls. We evaluated improved control of particulate matter using a fabric filter as beyond the floor control for further reductions in semivolatile metals emissions. We evaluated a beyond the floor level of 71 ug/ dscm. The incremental annualized compliance cost for a new solid fuel boiler with average gas flowrate to meet this beyond thefloor level, rather than comply with the floor level, would be approximately $ 0.28 million and would provide an incremental reduction in semivolatile metals emissions of approximately 0.15 tons per year, for a cost effectiveness of $ 1.8 million per ton of semivolatile metals removed. We estimate that this beyond the floor option would increase the amount of hazardous waste ( or solid * OMB Review Draft*

35 Owners and operators have determined that emissions from these four boilers represent emissions from five other identical, sister boilers. Owners and operators have used the emissions from these four boilers as " data in lieu of testing" emissions from the other five identical boilers.

177 waste if the source retains the Bevill exclusion under 40 CFR 266.112) generated for a new solid fuel fired boiler with average gas flowrate by 44 tons per year and would require the source to use an additional 1.2 million kW hours per year beyond the requirements to achieve the floor level. After considering these impacts and cost effectiveness, we conclude that a beyond thefloor standard for new sources based on use of a fabric filter to improve control of particulate matter is not warranted. b. Feedrate Control. For similar reasons discussed above for existing sources, we conclude that a beyond the floor standard based on controlling the semivolatile metals in the hazardous waste feed would not be cost effective. c. No cost Standard Derived from the Beyond the Floor Particulate Matter Standard. As discussed above in the context of existing sources, the beyond the floor standard for particulate matter would also provide beyond the floor control for semivolatile metals if sources were to comply with the beyond the floor particulate matter standard using improved particulate matter control rather than by reducing the feedrate of ash. Under this approach, the no cost beyond thefloor standard for semivolatile metals for new sources would be 44 ug/ dscm. As discussed above, however, we are concerned that sources may choose to comply with the beyond the floor particulate matter standard by controlling the feedrate of ash in the hazardous waste feed, which may or may not reduce the feedrate and emissions of metal HAP. If so, it would be inappropriate to consider this beyond the floor standard as a no cost standard. We specifically request comment on whether sources may comply with beyond the floor particulate matter standard by controlling the feedrate of ash. For these reasons, we propose a semivolatile metals standard of 170 ug/ dscm for new sources. E. What Is the Rationale for the Proposed Standards for Low Volatile Metals? The proposed standards for low volatile metals ( arsenic, beryllium, and chromium) for solid fuel fired boilers is 210 ug/ dscm for existing sources and 190 ug/ dscm for new sources. 1. What Is the Rationale for the MACT Floor for Existing Sources? We have compliance test emissions data representing maximum allowed emissions for four boilers. Emissions from these four boilers represent emissions from 10 of the 12 solid fuel fired boilers. 35 Low volatile metal emissions range from 41 ug/ dscm to 230 ug/ dscm. These emissions are expressed as mass of low volatile metals ( from all feedstocks) per unit of stack gas. 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 210 ug/ dscm, 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 * OMB Review Draft*

178 obtained. We estimate that this emission level is being achieved by 67% of sources and that it would reduce low volatile metals emissions by 0.45 tons per year. 2. EPA's Evaluation of Beyond the Floor Standards for Existing Sources We evaluated three beyond the floor approaches for low volatile metals for existing sources: ( 1) improved control of particulate matter; ( 2) control of low volatile metals in the hazardous waste feed; and ( 3) a no cost standard derived from the beyond the floor particulate matter standard. For reasons discussed below, we are not proposing a beyond the floor standard for low volatile metals. a. Improved Particulate Matter Control. Controlling particulate matter also controls emissions of low volatile metals. We evaluated a beyond the floor level of 105 ug/ dscm. The national incremental annualized compliance cost for solid fuel boilers to meet this beyond thefloor level rather than comply with the floor controls would be approximately $ 0.32 million and would provide an incremental reduction in low volatile metals emissions beyond the MACT floor controls of 0.37 tons per year. We evaluated the nonair quality health and environmental impacts and energy effects of this beyond the floor standard and estimate that the amount of hazardous waste generated would increase by approximately 83 tons per year, an additional 54 million gallons of water per year would be used, and electricity consumption would increase by 1.2 million kW hours per year. Considering these impacts and a cost of approximately $ 0.87 million per additional ton of low volatile metals removed, we are not proposing a beyond the floor standard based on improved particulate matter control. b. Feed Control of Low Volatile Metals in the Hazardous Waste. We also evaluated a beyond the floor level of 170 ug/ dscm, which represents a 20% reduction from the floor level. The national incremental annualized compliance cost for solid fuel boilers to meet this beyondthe floor level rather than comply with the floor controls would be approximately $ 98,000 and would provide an incremental reduction in low volatile metals emissions beyond the MACT floor controls of 0.13 tons per year. Although nonair quality health and environmental impacts and energy effects are not significant factors, we are not proposing a beyond the floor standard based on feedrate control of low volatile metals in the hazardous waste because it would not be costeffective at approximately $ 0.78 million per additional ton of low volatile metals removed. c. No cost Standard Derived from the Beyond the Floor Particulate Matter Standard. As discussed above in the context of semivolatile metals, the beyond the floor standard for particulate matter would also provide beyond the floor control for low volatile metals if sources were to comply with the beyond the floor particulate matter standard using improved particulate matter control rather than by reducing the feedrate of ash. To identify a beyond the floor emission level for low volatile metals that would derive from the beyond the floor particulate matter standard, we assumed that emissions of low volatile metals would be reduced by the same percentage that sources would need to reduce particulate matter emissions. We then developed a revised low volatile metal emission data base considering these particulate matter standardderived reductions and reductions needed to meet the low volatile metal floor level. We analyzed these revised emissions to identify the best performing sources and an emission level that the average of the best performers could achieve 99 out of 100 future tests. This emission level 110 ug/ dscm is a beyond the floor low volatile metal standard that can be achieved at no cost * OMB Review Draft*

179 because the costs have been allocated to the particulate matter beyond the floor standard. We are concerned, however, that sources may choose to comply with the beyond thefloor particulate matter standard by controlling the feedrate of ash in the hazardous waste feed, which may or may not reduce the feedrate and emissions of metal HAP. If so, it would be inappropriate to consider the beyond the floor standard for low volatile metals discussed above as a no cost standard. We specifically request comment on whether sources may comply with beyond the floor particulate matter standard by controlling the feedrate of ash. For these reasons, we propose a floor standard for low volatile metals of 210 ug/ dscm for existing sources. 3. What Is the Rationale for the MACT Floor for New Sources? MACT floor for low volatile metals for new sources would be 190 ug/ dscm, considering emissions variability. This is an emission level that the single best performing source identified by the SRE/ Feed Approach 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. 4. EPA's Evaluation of Beyond the Floor Standards for New Sources We evaluated three beyond the floor approaches for low volatile metals for new sources: ( 1) improved particulate matter control; ( 2) control of low volatile metals in the hazardous waste feed; and ( 3) a no cost standard derived from the beyond the floor particulate matter standard. a. Improved Particulate Matter Control. We evaluated improved control of particulate matter using a fabric filter to achieve an emission level of 79 ug/ dscm as beyond the floor control for low volatile metals emissions. The incremental annualized compliance cost for a new solid fuel boiler to meet this beyond the floor level, rather than comply with the floor level, would be approximately $ 0.28 million and would provide an incremental reduction in low volatile metals emissions of approximately 0.17 tons per year, for a cost effectiveness of $ 1.7 million per ton of low volatile metals removed. We estimate that this beyond the floor option would increase the amount of hazardous waste ( or solid waste if the source retains the Bevill exclusion under 40 CFR 266.112) generated for a new solid fuel fired boiler with average gas flowrate by 44 tons per year and would require the source to use an additional 1.2 million kW hours per year beyond the requirements to achieve the floor level. After considering these impacts and cost effectiveness, we conclude that a beyond the floor standard based on improved particulate matter control using a fabric filter for new sources is not warranted. b. Feedrate Control. For similar reasons discussed above for existing sources, we conclude that a beyond the floor standard based on controlling the low volatile metals in the hazardous waste feed would not be cost effective. c. No cost Standard Derived from the Beyond the Floor Particulate Matter Standard. As discussed above in the context of existing sources, the beyond the floor standard for particulate matter would also provide beyond the floor control for low volatile metals if sources were to comply with the beyond the floor particulate matter standard using improved particulate matter control rather than by reducing the feedrate of ash. Under this approach, the no cost beyond thefloor standard for low volatile metals for new sources would be 34 ug/ dscm. As discussed above, however, we are concerned that sources may choose to comply with the beyond the floor * OMB Review Draft*

36 As information, EPA proposed MACT standards for hydrogen chloride for solid fuel fired industrial, commercial, and institutional boilers that do not burn hazardous waste of 68 ppmv for existing sources and 15 ppmv for new sources. See 68 FR 1660 ( Jan. 13, 2003). These standards are based on use of wet scrubbers to control hydrogen chloride.

37 Owners and operators have determined that emissions from these five boilers represent emissions from five other identical, sister boilers. Owners and operators have used the emissions from these five boilers as " data in lieu of testing" emissions from the other five identical boilers.

180 particulate matter standard by controlling the feedrate of ash in the hazardous waste feed, which may or may not reduce the feedrate and emissions of metal HAP. If so, it would be inappropriate to consider this beyond the floor standard as a no cost standard. We specifically request comment on whether sources may comply with beyond the floor particulate matter standard by controlling the feedrate of ash. For these reasons, we propose a low volatile metals standard of 190 ug/ dscm for new sources. F. What Is the Rationale for the Proposed Standards for Total Chlorine? The proposed standards for hydrogen chloride and chlorine gas ( i. e., total chlorine, reported as a hydrogen chloride equivalents) for solid fuel fired boilers are 110 ppmv for existing sources and 73 ppmv for new sources. 36 1. What Is the Rationale for the MACT Floor for Existing Sources? Solid fuel fired boilers that burn hazardous waste are equipped with electrostatic precipitators or baghouses and do not have back end controls for total chlorine. Total chlorine emissions are controlled by controlling the feedrate of chlorine in the hazardous waste feed. We have compliance test emissions data representing maximum allowable emissions for five boilers. Emissions from these five boilers represent emissions from 10 of the 12 solid fuel fired boilers. 37 Total chlorine emissions range from 60 ppmv to 700 ppmv. 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 440 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 83% of sources and that it would reduce total chlorine emissions by 420 tons per year. 2. EPA's Evaluation of Beyond the Floor Standards for Existing Sources We evaluated dry scrubbing to achieve a beyond the floor emission level of 110 ppmv for total chlorine for existing sources, assuming conservatively a 75% removal efficiency. The national annualized compliance cost for solid fuel fired boilers to comply with this beyond thefloor standard would be $ 3.7 million, and emissions of total chlorine would be reduced by 790 tons per year. We evaluated the nonair quality health and environmental impacts and energy * OMB Review Draft*

38 Note that we are not proposing beyond the floor total chlorine standards for incinerators and liquid fuel fired boilers because those standards would have a cost effectiveness of $ 290,000 and $ 18,000 per ton of particulate matter removed, respectively, which is substantially higher than the $ 4,700 per ton cost effectiveness of a beyond the floor standard for solid fuel fired boilers. Also, we note that we propose a beyond the floor standard for total chlorine for lightweight aggregate kilns at a cost effectiveness of $ 6,800 per ton, and request comment on a beyond the floor standard for cement kilns with a cost effectiveness of $ 9,300.

39 Although we assumed dry scrubbing can readily achieve 75% removal of total chlorine for beyond the floor control for existing sources, assuming 50% removal for beyond thefloor control for new sources is appropriate. This is because the floor for new sources 73 ppmv  is substantially lower than the floor for existing sources 440 ppmv and dry scrubbing is less efficient at lower uncontrolled emission levels.

181 effects of this beyond the floor standard and estimate that the amount of hazardous waste generated would increase by 18,000 tons per year, an additional 27 million gallons of water per year would be used, and electricity consumption would increase by 0.11 million kW hours per year. Notwithstanding these impacts, we conclude that a beyond the floor standard is warranted because it is cost effective at $ 4,700 per additional ton of total chlorine removed. 38 We also evaluated use of feedrate control of chlorine in the hazardous waste to achieve a beyond the floor level of 350 ppmv, which represents a 20% reduction from the floor level. Because this standard would achieve emission reductions of only 44 tons of total chlorine per year, we propose a beyond the floor standard of 110 ppmv based on dry scrubbing for existing sources. 3. What Is the Rationale for the MACT Floor for New Sources? MACT floor for new sources would be 73 ppmv. This is an emission level that the single best performing source identified by the Emissions Approach ( i. e., the source with the lowest emissions) 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. 4. EPA's Evaluation of Beyond the Floor Standards for New Sources We evaluated dry lime scrubbing to achieve a beyond the floor emission level of 37 ppmv for total chlorine for new sources, assuming conservatively a 50% removal efficiency. 39 The incremental annualized compliance cost for a new solid fuel boiler with average gas flowrate to meet this beyond the floor level, rather than comply with the floor level, would be approximately $ 610,000 and would provide an incremental reduction in total chlorine emissions of approximately 42 tons per year. Although nonair quality health and environmental impacts and energy effects are not significant factors, we conclude that a beyond the floor standard of 37 ppmv is not warranted because it would not be cost effective at approximately $ 14,000 per additional ton of total chlorine removed. For these reasons, we propose a floor standard for total chlorine of 73 ppmv for new * OMB Review Draft*

40 As information, EPA proposed MACT standards for carbon monoxide for new solid fuel fired industrial, commercial, and institutional boilers that do not burn hazardous waste of 400 ppmv corrected to 3% oxygen. See 68 FR 1660 ( Jan. 13, 2003).

182 sources. G. What Is the Rationale for the Proposed Standards for Carbon Monoxide or Hydrocarbons? To control emissions of organic HAP, existing and new sources would be required to comply with either a carbon monoxide standard of 100 ppmv or a hydrocarbon standard of 10 ppmv. 40 1. What Is the Rationale for the MACT Floor for Existing Sources? Solid fuel fired boilers that burn hazardous waste are currently subject to RCRA standards that require compliance with either a carbon monoxide standard of 100 ppmv, or a hydrocarbon standard of 20 ppmv. Compliance is based on an hourly rolling average as measured with a CEMS. See § 266.104( a). We are proposing today floor standards of 100 ppmv for carbon monoxide or 10 ppmv for hydrocarbons. Floor control for existing sources is operating under good combustion practices including: ( 1) providing adequate excess air with use of oxygen CEMS and feedback air input control; ( 2) providing adequate fuel/ air mixing; ( 3) homogenizing hazardous waste fuels ( such as by blending or size reduction) to control combustion upsets due to very high or very low volatile content wastes; ( 4) regulating waste and air feedrates to ensure proper combustion temperature and residence time; ( 5) characterizing waste prior to burning for combustion related composition ( including parameters such as heating value, volatile content, liquid waste viscosity, etc.); ( 6) ensuring the source is operated by qualified, experienced operators; and ( 7) periodic inspection and maintenance of combustion system components such as burners, fuel and air supply lines, injection nozzles, etc. Given that there are many interdependent parameters that affect combustion efficiency and thus carbon monoxide and hydrocarbon emissions, we are not able to quantify " good combustion practices." Ten of 12 solid fuel fired boilers are currently complying with the RCRA carbon monoxide limit of 100 ppmv on an hourly rolling average. The remaining two boilers are complying with the RCRA hydrocarbon limit of 20 ppmv on an hourly rolling average. Those boilers have hydrocarbon levels below 5 ppmv, however, indicative of operating under good combustion practices. We propose a floor level for carbon monoxide level of 100 ppmv because it is a currently enforceable Federal standard. Although the best performing sources are achieving carbon monoxide levels below 100 ppmv, it is not appropriate to establish a lower floor level because carbon monoxide is a surrogate for nondioxin/ furan organic HAP. As such, lowering the carbon monoxide floor may not significantly reduce organic HAP emissions. In addition, it would be inappropriate to apply a MACT methodology to the carbon monoxide emissions from the best performing sources because those sources may not be able to replicate their emission levels. This is because there are myriad factors that affect combustion efficiency and, subsequently, carbon * OMB Review Draft*

183 monoxide emissions. Extremely low carbon monoxide emissions cannot be assured by controlling only one or two operating parameters We note also that we used this rationale to establish a carbon monoxide standard of 100 ppmv for Phase I sources in the September 1999 Final Rule. We propose a floor level for hydrocarbons of 10 ppmv even though the currently enforceable standard is 20 ppmv because: ( 1) the two sources that comply with the RCRA hydrocarbon standard can readily achieve 10 ppmv; and ( 2) reducing hydrocarbon emissions within the range of 20 ppmv to 10 ppmv should reduce emissions of nondioxin/ furan organic HAP. We do not apply a prescriptive MACT methodology to establish a hydrocarbon floor below 10 ppmv, however, because we have data from only two sources. In addition, we note that the hydrocarbon emission standard for Phase I sources established in the September 1999 Final Rule is 10 ppmv also. There would be no incremental emission reductions associated with these floors because all sources are currently achieving the floor levels. 2. EPA's Evaluation of Beyond the Floor Standards for Existing Sources We considered beyond the floor levels for carbon monoxide and hydrocarbons based on use of better combustion practices but conclude that they may not be replicable by the best performing sources nor duplicable by other sources given that we cannot quantify good combustion practices. Moreover, we cannot ensure that carbon monoxide or hydrocarbon levels lower than the floors would significantly reduce emissions of nondioxin/ furan organic HAP. This is because the portion of hydrocarbons that is comprised of nondioxin/ furan organic HAP is likely to become lower as combustion efficiency improves and hydrocarbon levels decrease. Thus, at beyond the floor hydrocarbon levels, we would expect a larger portion of residual hydrocarbons to be compounds that are not organic HAP. Nonair quality health and environmental impacts and energy requirements are not significant factors for use of better combustion practices as beyond the floor control. For these reasons, we conclude that beyond the floor standards for carbon monoxide and hydrocarbons are not warranted for existing sources. 3. What Is the Rationale for the MACT Floor for New Sources? MACT floor for new sources would be the same as the floor for existing sources 100 ppmv for carbon monoxide and 10 ppmv for hydrocarbons and based on the same rationale. 4. EPA's Evaluation of Beyond the Floor Standards for New Sources As discussed in the context of beyond the floor considerations for existing sources, we considered beyond the floor standards for carbon monoxide and hydrocarbons for new sources based on use of better combustion practices. But, we conclude that beyond the floor standards may not be replicable by the best performing sources nor duplicable by other sources given that we cannot quantify good combustion practices. Moreover, we cannot ensure that carbon monoxide or hydrocarbon levels lower than the floors would significantly reduce emissions of nondioxin/ furan organic HAP. Nonair quality health and environmental impacts and energy requirements are not significant factors for use of better combustion practices as beyond the floor control. For these reasons, we conclude that beyond the floor standards for carbon monoxide and hydrocarbons are not warranted for new sources. * OMB Review Draft*

41 The carbon monoxide/ hydrocarbon emission standard would control organic HAP that are products of incomplete combustion by also ensuring use of good combustion practices.

184 H. What Is the Rationale for the Proposed Standard for Destruction and Removal Efficiency? To control emissions of organic HAP, existing and new sources would be required to comply with a destruction and removal efficiency ( DRE) of 99.99% for organic HAP. For sources burning hazardous wastes F020, F021, F022, F023, F026, or F027, however, the DRE standard is 99.9999% for organic HAP. 1. What Is the Rationale for the MACT Floor for Existing Sources? Solid fuel fired boilers that burn hazardous waste are currently subject to RCRA DRE standards that require 99.99% destruction of designated principal organic hazardous constituents ( POHCs). For sources that burn hazardous wastes F020, F021, F022, F023, F026, or F027, however, the DRE standard is 99.9999% destruction of designated POHCs. See § 266.104( a). The DRE standard helps ensure that a combustor is operating under good combustion practices and thus minimizing emissions of organic HAP. Under the MACT compliance regime, sources would designate POHCs that are organic HAP or that are surrogates for organic HAP. We propose to establish the RCRA DRE standard as the floor for existing sources because it is a currently enforceable Federal standard. There would be no incremental emission reductions associated with this floor because sources are currently complying with the standard. 2. EPA's Evaluation of Beyond the Floor Standards for Existing Sources We considered a beyond the floor level for DRE based on use of better combustion practices but conclude that it may not be replicable by the best performing sources nor duplicable by other sources given that we cannot quantify better combustion practices. Moreover, we cannot ensure that a higher DRE standard would significantly reduce emissions of organic HAP given that DRE measures the destruction of organic HAP present in the boiler feed rather than gross emissions of organic HAP. Although a source's combustion practices may be adequate to destroy particular organic HAP in the feed, other organic HAP that may be emitted as products of incomplete combustion may not be controlled by the DRE standard. 41 For these reasons, and after considering non air quality health and environmental impacts and energy requirements, we are not proposing a beyond the floor DRE standard for existing sources. 3. What Is the Rationale for the MACT Floor for New Sources? We propose to establish the RCRA DRE standard as the floor for new sources because it is a currently enforceable Federal standard. 4. EPA's Evaluation of Beyond the Floor Standards for New Sources Using the same rationale as we used to consider a beyond the floor DRE standard for existing sources, we conclude that a beyond the floor DRE standard for new sources is not warranted. Consequently, after considering non air quality health and environmental impacts and energy requirements, we are proposing the floor DRE standard for new sources.

XI. How Did EPA Determine the Proposed Emission Standards for Hazardous Waste * OMB Review Draft*

185 Burning Liquid Fuel Fired Boilers?

The proposed standards for existing and new liquid fuel fired boilers that burn hazardous waste are summarized in the table below. See proposed § 63.1217. * OMB Review Draft*

186 PROPOSED STANDARDS FOR EXISTING AND NEW LIQUID FUEL FIRED BOILERS Hazardous Air Pollutant or Surrogate Emission Standard1 Existing Sources New Sources Dioxin and furan: sources equipped with dry air pollution control system2 0.40 ng TEQ/ dscm 0.015 ng TEQ/ dscm Dioxin and furan: sources equipped with wet or with no air pollution control systems2 100 ppmv carbon monoxide or 10 ppmv hydrocarbons 100 ppmv carbon monoxide or 10 ppmv hydrocarbons Mercury3 3.7E 6 lbs/ MM Btu 3.8E 7 lbs/ MM BTU Particulate matter 72 mg/ dscm ( 0.032 gr/ dscf) 17 mg/ dscm ( 0.0076 gr/ dscf)

Semivolatile metals3 1.1E 5 lbs/ MM BTU 4.3E 6 lbs/ MM BTU Low volatile metals: chromium only 3, 4 1.1E 4 lbs/ MM BTU 3.6E 5 lbs/ MM BTU Hydrogen chloride and chlorine gas3, 5 2.5E 2 lbs/ MM BTU or the alternative emission limits under § 63.1215 7.2E 4 lbs/ MM BTU or the alternative emission limits under § 63.1215 Carbon monoxide or hydrocarbons6 100 ppmv carbon monoxide or 10 ppmv hydrocarbons. 100 ppmv carbon monoxide or 10 ppmv hydrocarbons.

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 A wet air pollution system followed by a dry air pollution control system is not considered to be a dry air pollution control system for purposes of this standard. A dry air pollution systems followed a wet air pollution control system is considered to be a dry air pollution control system for purposes of this standard. 3 Standards are expressed as mass of pollutant emissions contributed by hazardous waste per million Btu contributed by the hazardous waste. 4 Standard is for chromium only and does not include arsenic and beryllium. 5 Combined standard, reported as a chloride ( Cl()) equivalent. 6 Hourly rolling average. Hydrocarbons reported as propane. * OMB Review Draft*

42 Sources with a wet air pollution system followed by a dry air pollution control system is not considered to be a dry air pollution control system for purposes of this standard. Sources with a dry air pollution systems followed a wet air pollution control system is considered to be a dry air pollution control system for purposes of this standard.

187 We considered whether fuel switching could be considered a MACT floor control technology for liquid fuel fired boilers to achieve lower HAP emissions. We conclude that HAP emissions from liquid fuel fired boilers are attributable primarily to the hazardous waste fuels rather than the natural gas or fuel oil that these boilers burn. Consequently, we conclude that fuel switching is not an effective MACT floor control technology to reduce HAP emissions for liquid fuel fired boilers. A. What Are the Proposed Standards for Dioxin and Furan? We propose to establish standards for liquid fuel fired boilers equipped with dry air pollution control devices that limit emissions of dioxin/ furan to 0.40 ng TEQ/ dscm ( for existing sources) and 0.015 ng TEQ/ dscm ( for new sources). We also propose to establish standards for liquid fuel fired boilers equipped either with wet air pollution control systems or with no air pollution systems as compliance with the proposed carbon monoxide/ hydrocarbon emission standard and compliance with the proposed destruction and removal efficiency standard. 1. What Is the Rationale for the MACT Floor for Existing Sources? As discussed in Part Two, Section I. B. 5, we used a statistical analysis to conclude that liquid boilers equipped with dry air pollution control devices have different dioxin/ furan emission characteristics compared to sources with either wet air pollution control or no air pollution control devices. 42 Note that we consider the type of emission control device as a basis for subcategorization because the type of control device affects formation of dioxin/ furan: dioxin/ furan can form in dry particulate matter control devices while it cannot form in wet ( or no) control devices. We therefore believe subcategorization is warranted and we propose to identify separate floor levels for sources equipped with dry particulate matter control devices versus sources with wet or no emission control device. To identify the floor level for liquid fuel boilers equipped with dry air pollution control systems, we evaluated the compliance test emissions data using the Emissions Approach. A numerical dioxin/ furan floor level is appropriate for these sources because dioxin/ furan emissions can be controlled by controlling the temperature at the inlet to the particulate matter control device. Thus, the floor level can be replicated by the best performing sources and duplicated by other sources. In contrast, dioxin/ furan emissions for solid fuel fired boilers could not be replicated by the best performing sources nor duplicated by other sources, even though all sources are equipped with dry particulate matter control devices, because dioxin/ furan emissions are governed by other factors, principally the inhibiting effect on dioxin/ furan formation of sulfur in the coal, but also including operating under good combustion practices. The calculated floor for sources equipped with dry air pollution control systems would be 3.0 ng TEQ/ dscm, which considers emissions variability. We estimate that this emission level is being achieved by 99% of sources and would reduce dioxin/ furan emissions by 0.14 grams/ year. * OMB Review Draft*

43 The fact that we determined floor control for existing sources as good combustion practices does not mean that all sources using floor control will have low dioxin/ furan emissions. As discussed in Part Two, Section XIV. B., we are proposing to require liquid fuel fired boilers that would not be subject to a numerical dioxin/ furan emission standard to perform a one time dioxin/ furan emissions test to quantify the effectiveness of today's proposed surrogate for dioxin/ furan emission control.

188 As previously discussed in Part Two, Section VII. A, we believe that it would be inappropriate to establish a numerical dioxin/ furan emission floor level for sources using wet or no air pollution control systems based on the emissions achieved by the best performing sources because a numerical floor level would not be replicable by the best performing sources nor duplicable by other sources. As a result, we propose to define floor control for sources with wet or no emission control devices as operating under good combustion practices by complying with the destruction and removal efficiency and carbon monoxide/ hydrocarbon standards. 43 There would be no emissions reductions for these existing boilers to comply with the floor level because they are currently complying with the carbon monoxide/ hydrocarbon standard and destruction and removal efficiency standard pursuant to RCRA requirements. We also request comment on an alternative MACT floor expressed as a dioxin/ furan emission concentration for sources with wet or no emission control device. Although it would be inappropriate to identify a floor concentration based on the average emissions of the best performing sources as discussed above, we possibly could identify the floor as the highest emission concentration from any source in our data base, after considering emissions variability. Dioxin/ furan emissions from those liquid fuel boilers in our data base range from less than 0.001 to 1.6 ng TEQ/ dscm with all except one source emitting at levels below 0.44 ng TEQ/ dscm. Finally, we note that we propose to require a one time dioxin/ furan emission test for sources that would not be subject to a numerical dioxin/ furan emission standard, including liquid fuel fired boilers with wet or no emission control device. As discussed in Part Two, Section XIV. B below, the testing would assist in developing both Section 112( d)( 6) standards and Section 112( f) residual risk standards. 2. EPA's Evaluation of Beyond the Floor Standards for Existing Sources We evaluated use of activated carbon injection systems or carbon beds as beyond thefloor control for further reduction of dioxin/ furan emissions. Activated carbon has been demonstrated for controlling dioxin/ furans in various combustion applications. For liquid fuel fired boilers using dry air pollution control equipment, we evaluated a beyond the floor level of 0.40 ng TEQ/ dscm based on activated carbon injection. The national incremental annualized compliance cost for sources to meet this beyond the floor level rather than comply with the floor controls would be approximately $ 80,000 and would provide an incremental reduction in dioxin/ furan emissions beyond the MACT floor controls of 0.06 grams TEQ per year. We evaluated the nonair quality health and environmental impacts and energy effects of this beyond the floor standard and estimate that the amount of hazardous waste generated would increase by 100 tons per year, an additional 25 trillion Btu per year of natural * OMB Review Draft*

189 gas would be consumed, and electricity consumption would increase by 0.50 million kW hours per year. Notwithstanding these impacts and although a beyond the floor standard would reduce dioxin/ furan emissions by only 0.06 grams TEQ per year, it would be cost effective at $ 1.3 million per additional gram of dioxin/ furans removed. Given the particular health hazard that dioxin/ furan pose, a beyond the floor standard 0.40 ng TEQ/ dscm is warranted for liquid fuel fired boilers using dry air pollution control systems. For liquid fuel fired boilers equipped with wet or with no air pollution control systems, we also evaluated a beyond the floor level of 0.20 ng TEQ/ dscm based on activated carbon injection. The national incremental annualized compliance cost for these sources to meet this beyond thefloor level rather than comply with the floor controls would be approximately $ 550,000 and would provide an incremental reduction in dioxin/ furan emissions beyond the MACT floor controls of 0.12 grams TEQ per year. We evaluated the nonair quality health and environmental impacts and energy effects of this beyond the floor standard and estimate that the amount of hazardous waste generated would increase by 100 tons per year, an additional 25 trillion Btu per year of natural gas would be consumed, an additional 4 million gallons per year of water would be used, and electricity consumption would increase by 0.50 million kW hours per year. We are not proposing a beyond the floor standard of 0.20 ng TEQ/ dscm for liquid boilers that use a wet or no air pollution control system because it would not be cost effective at $ 4.6 million per gram of TEQ removed. 3. What Is the Rationale for the MACT Floor for New Sources? The calculated floor level for new liquid fuel boilers equipped with dry air pollution control systems is 0.015 ng TEQ/ dscm, which we identified using the Emissions Approach. This is an emission level that the single best performing source could be expected to achieve in 99 out of 100 future tests when operating under conditions identical to the compliance test conditions during which the emissions data were obtained. As previously discussed, we believe that it would be inappropriate to establish numerical dioxin/ furan emission floors for liquid boilers with wet or with no air pollution control systems. Therefore, we propose floor control for these units as good combustion practices provided by complying with the proposed destruction removal efficiency and carbon monoxide/ hydrocarbon standards. 4. EPA's Evaluation of Beyond the Floor Standards for New Sources We evaluated use of activated carbon injection systems as beyond the floor control for further reduction of dioxin/ furan emissions. Activated carbon has been demonstrated for controlling dioxin/ furan in various combustion applications. We evaluated a beyond the floor level of 0.01 ng TEQ/ dscm using activated carbon for liquid fuel fired boilers equipped with dry air pollution control systems. The national incremental annualized compliance cost for a source with an average gas flowrate to meet this beyond thefloor level rather than comply with the floor controls would be approximately $ 0.15 million and would provide an incremental reduction in dioxin/ furan emissions beyond the MACT floor controls of 0.005 grams TEQ per year. We evaluated the nonair quality health and environmental impacts and energy effects of this beyond the floor standard and estimate that, for a new liquid fuel fired boiler with average gas flowrate, the amount of hazardous waste generated would * OMB Review Draft*

44 As information, EPA did not propose MACT emission standards for mercury for liquid fuel fired boilers that do not burn hazardous waste. See 68 FR 1660 ( Jan. 13,2003). Note that, in today's rule, we propose to control mercury only in hazardous waste fuels, an option obviously not available to boilers that do not burn hazardous waste.

45 Several owners and operators have used the emissions data as " data in lieu of testing" emissions from other, identical boilers at the same facility. For purposes of identifying the number of boilers represented in this paragraph, the percentage includes the data in lieu sources.

190 increase by 120 tons per year and electricity consumption would increase by 0.1 million kW hours per year. After considering these impacts and costs of approximately $ 32 million per additional gram of dioxin/ furan removed, we are not proposing a beyond the floor standard 0.01 ng TEQ/ dscm for liquid fuel fired boilers using dry air pollution control systems. We also evaluated a beyond the floor level of 0.20 ng TEQ/ dscm for liquid fuel fired boilers equipped with wet or with no air pollution control systems based on use of activated carbon injection. The national incremental annualized compliance cost for a source with average gas flowrate to meet this beyond the floor level rather than comply with the floor controls would be approximately $ 0.15 million and would provide an incremental reduction in dioxin/ furan emissions beyond the MACT floor controls of 0.06 grams TEQ per year. We evaluated the nonair quality health and environmental impacts and energy effects of this beyond the floor standard and estimate that, for a source with average gas flowrate, the amount of hazardous waste generated would increase by 120 tons per year and electricity consumption would increase by 0.1 million kW hours per year. After considering these impacts and costs of approximately $ 2.4 million per additional gram of dioxin/ furan removed, we are not proposing a beyond thefloor standard for liquid fuel fired boilers using a wet or no air pollution control system. B. What Is the Rationale for the Proposed Standards for Mercury? We propose to establish standards for existing liquid fuel fired boilers that limit emissions of mercury to 3.7E 6 lbs mercury emissions attributable to the hazardous waste per million Btu heat input from the hazardous waste. The proposed standards for new sources would be 3.8E 7 lbs mercury emissions attributable to the hazardous waste per million Btu heat input from the hazardous waste. 44 These standards are expressed as hazardous waste thermal emission concentrations because liquid fuel fired boilers burn hazardous waste for energy recovery. See discussion in Part Two, Section IV. B of the preamble. 1. What Is the Rationale for the MACT Floor for Existing Sources? MACT floor for existing sources is 3.7E 6 lbs mercury emissions attributable to the hazardous waste per million Btu heat input from the hazardous waste, which is based primarily by controlling the feed concentration of mercury in the hazardous waste. Approximately 11% of liquid boilers also use wet scrubbers that can control emissions of mercury. We have normal emissions data within the range of normal emissions for 32% of the sources. 45 The normal mercury stack emissions in our data base are all less than 7 ug/ dscm. * OMB Review Draft*

191 These emissions are expressed as mass of mercury ( from all feedstocks) per unit of stack gas. Hazardous waste thermal emissions, available for 12% of sources, range from 1.0E 7 to 1.0E 5 lbs mercury emissions attributable to the hazardous waste per million Btu heat input from the hazardous waste. Hazardous waste thermal emissions represent the mass of mercury contributed by the hazardous waste per million Btu contributed by the hazardous waste. To identify the MACT floor, we evaluated all normal emissions data using the Emissions Approach. The calculated floor is 3.7E 6 lbs mercury emissions attributable to the hazardous waste per million Btu heat input from the hazardous waste. 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 floor level is being achieved by 40% of sources and would reduce mercury emissions by 0.68 tons per year. Because the floor level is based on normal emissions data, compliance would be documented by complying with a hazardous waste mercury thermal feed concentration on an annual rolling average. See discussion in Part Two, Section XIV. F below. We did not use the SRE/ Feed Approach to identify the floor level because the vast majority of mercury feed levels in the hazardous waste and the emissions measurements did not have detectable concentrations of mercury. Given that a system removal efficiency, or SRE, is the percentage of mercury emitted compared to the amount fed, we concluded that it would be inappropriate to base this analysis on SREs that were derived from measurements below detectable levels. 2. EPA's Evaluation of Beyond the Floor Standards for Existing Sources We identified two potential beyond the floor techniques for control of mercury: ( 1) activated carbon injection; and ( 2) control of mercury in the hazardous waste feed. For reasons discussed below, we are not proposing a beyond the floor standard for mercury. a. Use of Activated Carbon Injection. We evaluated activated carbon injection as beyond the floor control for further reduction of mercury emissions. Activated carbon has been demonstrated for controlling mercury in several combustion applications; however, currently no liquid fuel boilers burning hazardous waste uses activated carbon injection. We evaluated a beyond the floor level of 1.1E 6 lbs mercury emissions attributable to the hazardous waste per million Btu heat input from the hazardous waste. The national incremental annualized compliance cost for liquid fuel fired boilers to meet this beyond the floor level rather than comply with the floor controls would be approximately $ 12 million and would provide an incremental reduction in mercury emissions beyond the MACT floor controls of 0.097 tons per year. We evaluated nonair quality health and environmental impacts and energy effects of using activated carbon injection to meet this beyond the floor emission level and estimate that the amount of hazardous waste generated would increase by 4,800 tons per year and that sources would consume an additional 44 trillion Btu per year of natural gas and use an additional 9.6 million kW hours per year beyond the requirements to achieve the floor level. Therefore, based on these factors and costs of approximately $ 124 million per additional ton of mercury removed, we are not proposing a * OMB Review Draft*

46 We note that the beyond the floor dioxin/ furan standard we propose for liquid fuel fired boilers equipped with dry particulate matter control devices would also provide no cost beyond the floor mercury control for sources that use activated carbon injection to control dioxin/ furan. If such sources achieve the beyond the floor dioxin/ furan standard by other means ( control of temperature at the inlet to the control device; control of feedrate of metals that may catalyze formation of dioxin/ furan), however, collateral reductions in mercury emissions would not be realized.

192 beyond the floor standard based on activated carbon injection. 46 b. Feed Control of Mercury in the Hazardous Waste. We also evaluated a beyond thefloor level of 3.0E 6 lbs mercury emissions attributable to the hazardous waste per million Btu heat input from the hazardous waste, which represents a 20% reduction from the floor level. The national incremental annualized compliance cost for liquid fuel fired boilers to meet this beyondthe floor level rather than comply with the floor controls would be approximately $ 4.2 million and would provide an incremental reduction in mercury emissions beyond the MACT floor controls of 0.036 tons per year. Nonair quality health and environmental impacts and energy effects are not significant factors for feedrate control. Therefore, based on these factors and costs of approximately $ 115 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. For the reasons discussed above, we do not propose a beyond the floor standard for mercury for existing sources. We propose a standard based on the floor level: 3.7E 6 lbs mercury emissions attributable to the hazardous waste per million Btu heat input from the hazardous waste. 3. What Is the Rationale for the MACT Floor for New Sources? The MACT floor for new sources for mercury would be 3.8E 7 lbs mercury emissions attributable to the hazardous waste per million Btu heat input from the hazardous waste and would be implemented as an annual average because it is based on normal emissions data. This is an emission level that the single best performing source identified with the Emissions Approach 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. 4. EPA's Evaluation of Beyond the Floor Standards for New Sources We evaluated activated carbon injection as beyond the floor control to achieve an emission level of 2.0E 7 lbs mercury emissions attributable to the hazardous waste per million Btu heat input from the hazardous waste. The incremental annualized compliance cost for a new liquid fuel fired boiler with average gas flowrate to meet this beyond the floor level, rather than comply with the floor level, would be approximately $ 0.15 million and would provide an incremental reduction in mercury emissions of less than 0.0002 tons per year, for a costeffectiveness of $ 1 billion per ton of mercury removed. We evaluated the nonair quality health and environmental impacts and energy effects of this beyond the floor standard and estimate that, for a new liquid fuel fired boiler with average gas flowrate, the amount of hazardous waste generated would increase by 120 tons per year and electricity consumption would increase by 0.1 * OMB Review Draft*

47 As information, EPA proposed MACT standards for particulate matter for solid fuel fired industrial, commercial, and institutional boilers that do not burn hazardous waste of 0.035 gr/ dscf for existing sources and 0.013 gr/ dscf for new sources.

193 million kW hours per year. Although nonair quality health and environmental impacts and energy effects are not significant factors, we are not proposing a beyond the floor standard based on activated carbon injection for new sources because it would not be cost effective. Therefore, we propose a mercury standard based on the floor level: 3.8E 7 lbs mercury emissions attributable to the hazardous waste per million Btu heat input from the hazardous waste. C. What Is the Rationale for the Proposed Standards for Particulate Matter? The proposed standards for particulate matter for liquid fuel fired boilers are 59 mg/ dscm ( 0.026 gr/ dscf) for existing sources and 17 mg/ dscm ( 0.0076 gr/ dscf) for new sources. 47 The particulate matter standard serves as a surrogate for nonenumerated HAP metal emissions attributable to the hazardous waste fuel burned in the boiler. Although the particulate matter standard would also control nonmercury HAP metal from nonhazardous waste fuels, the natural gas or fuel oil these boilers burn as primary or auxiliary fuel do not contain significant levels of metal HAP. 1. What Is the Rationale for the MACT Floor for Existing Sources? Few liquid fuel fired boilers are equipped particulate matter control equipment such as electrostatic precipitators and baghouses, and, therefore, many sources control particulate matter emissions by limiting the ash content of the hazardous waste. We have compliance test emissions data from nearly all liquid boilers representing maximum allowable emissions. Particulate emissions range from 0.0008 to 0.078 gr/ dscf. To identify the floor level, we evaluated the compliance test emissions data associated with the most recent test campaign using the APCD Approach. The calculated floor is 72 mg/ dscm ( 0.032 gr/ dscf), which considers emissions variability. This is an emission level that the average of the 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 floor level is being achieved by 44% of sources and would reduce particulate matter emissions by 1,200 tons per year. 2. EPA's Evaluation of Beyond the Floor Standards for Existing Sources We evaluated use of fabric filters to improve particulate matter control to achieve a beyond the floor standard of 36 mg/ dscm ( 0.016 gr/ dscf). The national incremental annualized compliance cost for liquid fuel fired boilers to meet this beyond the floor level rather than comply with the floor controls would be approximately $ 16 million and would provide an incremental reduction in particulate matter emissions beyond the MACT floor controls of 520 tons per year. We evaluated the nonair quality health and environmental impacts and energy effects of this beyond the floor standard and estimate that the amount of hazardous waste generated would increase by 520 tons per year and electricity consumption would increase by 13 million kW hours per year. After considering these factors and costs of approximately $ 30,000 per additional ton of particulate matter removed, we are not proposing a beyond the floor standard. * OMB Review Draft*

48 The source also is equipped with a high efficiency particulate air ( HEPA) filter.

49 Several owners and operators have used the emissions data as " data in lieu of testing" emissions from other, identical boilers at the same facility. For purposes of identifying 194 For the reasons discussed above, we propose a standard for particulate matter for existing liquid fuel fired boilers based on the floor level: 72 mg/ dscm ( 0.032 gr/ dscf). 3. What Is the Rational for the MACT Floor for New Sources? MACT floor for new sources would be 17 mg/ dscm ( 0.0076 gr/ dscf), considering emissions variability. This is an emission level that the single best performing source identified by the APCD Approach ( i. e., the source using a fabric filter48 with the lowest emissions) 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. 4. EPA's Evaluation of Beyond the Floor Standards for New Sources We evaluated use of an advanced fabric filter using high efficiency membrane bag material and a low air to cloth ratio to achieve a beyond the floor emission level of 9 mg/ dscm ( 0.0040 gr/ dscf). The incremental annualized cost for a new liquid fuel fired boiler with average gas flowrate to meet this beyond the floor level, rather than comply with the floor level, would be approximately $ 0.15 million and would provide an incremental reduction in particulate emissions of approximately 2.9 tons per year, for a cost effectiveness of $ 53,000 per ton of particulate matter removed. We evaluated the nonair quality health and environmental impacts and energy effects of this beyond the floor standard and estimate that, for a new liquid fuel fired boiler with average gas flowrate, the amount of hazardous waste generated would increase by 3 tons per year and electricity consumption would increase by 0.54 million kW hours per year. Considering these factors and cost effectiveness, we conclude that a beyond the floor standard of 9 mg/ dscm is not warranted. For the reasons discussed above, we propose a floor based standard for particulate matter for new liquid fuel fired boilers: 9.8 mg/ dscm ( 0.0043 gr/ dscf) D. What Is the Rationale for the Proposed Standards for Semivolatile Metals? We propose a standard for existing liquid fuel fired boilers that limits emissions of semivolatile metals ( cadmium and lead, combined) to 1.1E 5 lbs semivolatile metals emissions attributable to the hazardous waste per million Btu heat input from the hazardous waste. The proposed standard for new sources is 4.3E 6 lbs semivolatile metals emissions attributable to the hazardous waste per million Btu heat input from the hazardous waste. 1. What Is the Rationale for the MACT Floor for Existing Sources? MACT floor for existing sources is 1.1E 5 lbs semivolatile metals emissions attributable to the hazardous waste per million Btu heat input of the hazardous waste, which is based on particulate matter control ( for those few sources using a control device) and controlling the feedrate of semivolatile metals in the hazardous waste. We have emissions data within the range of normal emissions for nearly 40% of the sources. 49 The normal semivolatile stack emissions in our database range from less than 1 to 46 * OMB Review Draft*

the number of boilers represented in this paragraph, the percentages include the data in lieu sources.

50 We propose to use the Emissions Approach rather than the SRE/ Feed approach because our data base is comprised of emissions obtained during normal rather than compliance test operations. Because of the relatively low semivolatile metal feedrates during normal operations, we are concerned that the system removal efficiencies that we would calculate may be inaccurate ( e. g., sampling and analysis imprecision at low feed rates can have a substantial impact on calculated system removal efficiencies).

195 ug/ dscm. These emissions are expressed conventionally as mass of semivolatile metals ( from all feedstocks) per unit of stack gas. Hazardous waste thermal emissions, available for 25% of sources, range from 1.2E 6 to 4.8E 5 lbs semivolatile metals emissions attributable to the hazardous waste per million Btu heat input of the hazardous waste. We identified a MACT floor of 1.1E 5 expressed as a hazardous waste thermal emission by applying the Emissions Approach to the normal hazardous waste thermal emissions data. 50 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 floor level is being achieved by 33% of sources and would reduce semivolatile metals emissions by 1.7 tons per year. Because the floor level is based on normal emissions data, compliance would be documented by complying with a hazardous waste mercury thermal feed concentration on an annual rolling average. See discussion in Part Two, Section XIV. F below. 2. EPA's Evaluation of Beyond the Floor Standards for Existing Sources We identified two potential beyond the floor techniques for control of semivolatile metals: ( 1) improved particulate matter control; and ( 2) control of mercury in the hazardous waste feed. For reasons discussed below, we are not proposing a beyond the floor standard for semivolatile metals. a. Improved Particulate Matter Control. We evaluated installation of a new fabric filter or improved design, operation, and maintenance of the existing electrostatic precipitator and fabric filter as beyond the floor control for further reduction of semivolatile metals emissions. We evaluated a beyond the floor level of 5.5E 6 lbs semivolatile metals emissions attributable to the hazardous waste per million Btu heat input from the hazardous waste. The national incremental annualized compliance cost for liquid fuel fired boilers to meet this beyond the floor level rather than comply with the floor controls would be approximately $ 6.5 million and would provide an incremental reduction in semivolatile metals emissions beyond the MACT floor controls of 0.06 tons per year. We evaluated nonair quality health and environmental impacts and energy effects and determined that this beyond the floor option would increase the amount of hazardous waste generated by approximately 45 tons per year and would increase electricity usage by 0.8 million kW hours per year. After considering these factors and costs of approximately $ 100 million per * OMB Review Draft*

51 We use the Emissions Approach rather than the SRE/ Feed Approach when we use normal rather than compliance test data to establish the standard, as discussed previously.

196 additional ton of semivolatile metals removed, we are not proposing a beyond the floor standard based on improved particulate matter control. b. Feed Control of Semivolatile Metals in the Hazardous Waste. We also evaluated a beyond the floor level of 8.8E 6 lbs semivolatile metals emissions attributable to the hazardous waste per million Btu heat input from the hazardous waste, which represents a 20% reduction from the floor level. The national incremental annualized compliance cost for liquid fuel fired boilers to meet this beyond the floor level rather than comply with the floor controls would be approximately $ 4.8 million and would provide an incremental reduction in semivolatile metals emissions beyond the MACT floor controls of 0.06 tons per year. Nonair quality health and environmental impacts and energy effects are not significant factors for feedrate control. Therefore, considering these factors and costs of approximately $ 81 million per additional ton of semivolatile metals removed, we are not proposing a beyond the floor standard based on feed control of semivolatile metals in the hazardous waste. For the reasons discussed above, we propose a floor standard for semivolatile metals for existing liquid fuel fired boilers of 1.1E 5 lbs semivolatile metals emissions attributable to the hazardous waste per million Btu heat input from the hazardous waste. 3. What Is the Rationale for the MACT Floor for New Sources? The MACT floor for new sources for semivolatile metals would be 4.3E 6 lbs semivolatile metals emissions attributable to the hazardous waste per million Btu heat input from the hazardous waste. This is an emission level that the single best performing source identified with the Emissions Approach51 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. Because the floor level is based on normal emissions data, compliance would be documented by complying with a hazardous waste mercury thermal feed concentration on an annual rolling average. See discussion in Part Two, Section XIV. F below. 4. EPA's Evaluation of Beyond the Floor Standards for New Sources We evaluated a beyond the floor level of 2.1E 6 lbs semivolatile metals emissions attributable to the hazardous waste per million Btu heat input from the hazardous waste based on an advanced fabric filter using high efficiency membrane bag material and a low air to cloth ratio. The incremental annualized compliance cost for a new liquid fuel fired boiler with average gas flowrate to meet this beyond the floor level, rather than comply with the floor level, would be approximately $ 0.15 million and would provide an incremental reduction in semivolatile metals emissions of less than 0.002 tons per year, for a cost effectiveness of $ 87 million per ton of semivolatile metals removed. We evaluated the nonair quality health and environmental impacts and energy effects of this beyond the floor standard and estimate that, for a new liquid fuel fired boiler with average gas flowrate, the amount of hazardous waste generated would increase by 2 tons per year and electricity consumption would increase by 0.54 million kW hours per year. * OMB Review Draft*

52 Several owners and operators have used the emissions data as " data in lieu of testing" emissions from other, identical boilers at the same facility. For purposes of identifying the number of boilers represented in this paragraph, the percentages include the data in lieu sources.