195 ppmv. 53 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 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 Redline strikeout highlighting changes made during OMB review 196 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. 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. Redline strikeout highlighting changes made during OMB review 54 The carbon monoxide/ hydrocarbon emission standard would control organic HAP that are products of incomplete combustion by also ensuring use of good combustion practices.

197 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. 54 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 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. Redline strikeout highlighting changes made during OMB review 198 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 or control of flue gas temperature not to exceed 400 ° F at the inlet to the particulate matter control device.

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. Redline strikeout highlighting changes made during OMB review 55 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.

199 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.

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 a dioxin/ furan standards for existing liquid fuel fired boilers equipped with dry air pollution control devices that limit emissions of dioxin/ furan to 0.40 ng TEQ/ dscm (. The standard for existingnew sources) and would be 0.015 ng TEQ/ dscm ( for new sources). We also propose to establish standards foror control of flue gas temperature not to exceed 400 ° F at the inlet to the particulate matter control device. For liquid fuel fired boilers equipped either with wet air pollution control systems or with no air pollution systems, we propose a standard for both existing and new sources as compliance with the proposed standards for carbon monoxide/ hydrocarbon emission standard and compliance with the proposedand destruction and removal efficiency. In addition, 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, and new liquid fuel fired boilers equipped with a dry air pollution 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. 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. 55 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. a. MACT Floor for Boilers Equipped with Dry Control Systems. To identify the floor Redline strikeout highlighting changes made during OMB review 200 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 emissionsconsidered whether dioxin/ furan 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, We conclude that this control mechanism may not be the predominant factor that affects 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 arefrom these sources. We have emissions data for three boilers equipped with electrostatic precipitators or fabric filters. Emissions from two of the boilers are below 0.03 ng TEQ/ dscm. We do not have data on the gas temperature at the inlet to the emission control device for these sources. The third boiler, however, has dioxin/ furan emissions of 2.4 ng TEQ/ dscm when the flue gas temperature at the inlet to the fabric filter is 410

F. We conclude from this information that this boiler is not likely to be able to achieve dioxin/ furan emissions below 0.40 ng TEQ/ dscm if the gas temperature is reduced to below 400

F. This is contrary to the finding we made for cement kilns and incinerators without heat recovery boilers and equipped with dry particulate matter control devices, because. In those cases, we conclude that gas temperature control at the dry particulate matter control device is the predominant factor affecting dioxin/ furan emissions. See discussions in Sections VII and VIII above. Consequently, other factors are likely contributing to high dioxin/ furan emissions are governed by other factors, principally the inhibiting effect onfrom the liquid fuel fired boiler equipped with a fabric filter operated at a gas temperature of 410

F, such as metals in the waste feed or soot on boiler tubes that may catalyze 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 bereactions. We evaluated the compliance test emissions data using the Emissions Approach and calculated a numerical dioxin/ furan floor level of 3.0 ng TEQ/ dscm, which considers emissions variability. As discussed above, however, one of the three sources for which we have emissions data is not likely to be able to achieve this emission level using gas temperature control at the inlet to the dry particulate matter control device. Consequently, we propose to identify the floor level as 3.0 ng TEQ/ dscm or control of flue gas temperature not to exceed 400 ° F at the inlet to the particulate matter control device. This floor level is duplicable by all sources, and would minimize dioxin/ furan emissions for sources where flue gas temperature at the control device substantially affects dioxin/ furan emissions. We estimate that this emission level is being achieved by 99% ofall sources and, thus, would not reduce dioxin/ furan emissions by 0.14 grams/ year. . b. MACT Floor for Boilers Equipped with Wet or No Control Systems. We have dioxin/ furan emissions data for 33 liquid fuel fired boilers equipped with a wet or no particulate matter control device. Emissions levels are below 0.1 ng TEQ/ dscm for 30 of the sources. Emission levels for the other three sources are 0.19, 0.36, and 0.44 ng TEQ/ dscm. 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 Redline strikeout highlighting changes made during OMB review 56 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.

57 Although the floor for liquid fuel boilers equipped with a dry emission control device would not be a numerical standard ( i. e., 3.0 ng TEQ/ dscm or control of temperature of flue gas at the inlet to the control device to 400

F), we propose a numerical beyond the floor standard for those boilers, as discussed below in the text.

201 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 the MACT 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. 56 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 sourcesliquid fuel boilers with wet or no emission control devices. 57 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. a. Beyond the Floor Considerations for Boilers Equipped with Dry Control Systems. 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 or control of flue gas temperature not to exceed 400 ° F at the inlet to the particulate matter control device. The national incremental Redline strikeout highlighting changes made during OMB review 202 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 for a cost effectiveness of $ 1.3 million per additional gram of dioxin/ furan removed. We evaluated the nonair quality health and environmental impacts and energy effects of this beyondthe 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, and electricity consumption would increase by 0.50 million kW hours per year. Notwithstanding these impacts and although We judge that the cost to achieve this beyond the floor level is warranted given our special concern about dioxin/ furan. Dioxin/ furan are some of the most toxic compounds known due to their bioaccumulation potential and wide range of health effects, including carcinogenesis, at exceedingly low doses. Exposure via indirect pathways is a chief reason that Congress singled our dioxin/ furan for priority MACT control in CAA section 112( c)( 6). See S. Rep. No. 128, 101st Cong. 1st Sess. at 154 155. In addition, we note that the beyond the floor emission level of 0.40 ng TEQ/ dscm is consistent with historically controlled levels under MACT for hazardous waste incinerators and cement kilns, and Portland cement plants. See § § 63.1203( a)( 1), 63.1204( a)( 1), and 63.1343( d)( 3). Also, EPA has determined previously in the 1999 Hazardous Waste Combustor MACT final rule that dioxin/ furan in the range of 0.40 ng TEQ/ dscm or less are necessary for the MACT standards to be considered generally protective of human health under RCRA ( using the 1985 cancer slope factor), thereby eliminating the need for separate RCRA standards under the authority of RCRA section 3005( c)( 3) and 40 CFR 270.10( k). Finally, we note that this decision is not inconsistent with EPA's decision not to promulgate beyond the floor standards for dioxin/ furan for hazardous waste burning lightweight aggregate kilns, cement kilns, and incinerators at cost effectiveness values in the range of $ 530,000 to $ 827,000 per additional gram of dioxin/ furan TEQ removed. See 64 FR at 52892, 52876, and 52961. In those cases, EPA determined that controlling dioxin/ furan emissions from a level of 0.40 ng TEQ/ dscm to a beyond the floor level of 0.20 ng TEQ/ dscm was not warranted because dioxin/ furan levels below 0.40 ng TEQ/ dscm are generally considered to be below the level of health risk concern. For these reasons, we believe that proposing a beyond the floor standard would reduce dioxin/ furan emissions by only 0.06 grams TEQ per year, it would be cost effective atof 0.40 ng TEQ/ dscm is warranted notwithstanding the nonair quality health and environmental impacts and energy effects identified above and costs of approximately $ 1.3 million per additional gram of dioxin/ furansdioxin/ furan TEQ removed. he particular health hazard that dioxin/ furan pose, 0.40 ng TEQ/ dscm is warranted for liquid fuel fired boilers using dry air pollution control systems. . b. Beyond the Floor Considerations for Boilers Equipped with Wet or No 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 the floor level rather than comply with the floor controls would be approximately Redline strikeout highlighting changes made during OMB review 58 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. fThese data were recently obtained and are not in the MACT data base. See " Region 4 Boiler Dioxin Data," Excel spreadsheet, March 10, 2004.

203 $ 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. We are also considering an alternative beyond the floor standard for existing liquid fuel boilers with wet or no particulate matter control devices of 0.40 ng TEQ/ dscm. Although all but one source for which we have data are currently achieving this emission level, boilers for which we do not have dioxin/ furan emissions data may have emissions higher than 0.40 ng TEQ/ dscm. In addition, dioxin/ furan emissions from a given boiler may vary over time. Other factors that may contribute substantially to dioxin/ furan formation, such as the level and type of soot on boiler tubes, or feeding metals that catalyze dioxin/ furan formation reactions, differ across boilers and may change over time at a given boiler. Thus, dioxin/ furan levels for these sources may be higher than 0.40 ng TEQ/ dscm. For example, we recently obtained dioxin/ furan emissions data for a liquid fuel fired boiler equipped with a wet emission control system documenting emissions of 1.4 ng TEQ/ dscm. 58 To control dioxin/ furan emissions to a beyond the floor standard of 0.40 ng TEQ/ dscm, you would use activated carbon.

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 anIf dioxin/ furan emissions could be controlled predominantly by controlling the gas temperature at the inlet to the dry particulate matter control device, this would be the 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. This emission level may not be replicable by this source and duplicable by other ( new) sources, however, because factors other than flue gas temperature control at the control device may affect dioxin/ furan emissions. See discussion of this issue in the context of the floor level for existing sources. Therefore, we propose to establish the floor level as 0.015 ng TEQ/ dscm or control of flue gas temperature not to exceed 400 ° F at the inlet to the Redline strikeout highlighting changes made during OMB review 204 particulate matter control device. As previously discussed, we believe that it would be inappropriate to establish a numerical dioxin/ furan emission floorsfloor level 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 and 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. Wa. Beyond the Floor Considerations for Boilers Equipped with Dry Control Systems. For liquid fuel fired boilers using dry air pollution control equipment, we evaluated a beyond thefloor level of 0.01 ng TEQ/ dscm using activated carbon for liquid fuel fired boilers equipped with dry air pollution control systemsinjection. The national incremental annualized compliance cost for a source with an 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 0.005 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 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 of 0.01 ng TEQ/ dscm for liquid fuel fired boilers using dry air pollution control systems. We are also considering an alternative beyond the floor standard of 0.40 ng TEQ/ dscm for new liquid fuel boilers equipped with a dry particulate matter control device. A new source that achieves the floor level by controlling the gas temperature at the inlet to the dry particulate matter control device to 400

F may have dioxin/ furan emissions at levels far exceeding 0.40 ng TEQ/ dscm. See discussion above regarding factors other than gas temperature at the control device that can affect dioxin/ furan emissions from liquid fuel fired boilers ( and discussion of emissions of 2.4 ng TEQ/ dscm for a boiler operating a fabric filter at 410

F). Therefore, it may be appropriate to establish a beyond the floor standard to limit emissions to 0.40 ng TEQ/ dscm based on use of activated carbon injection. We also note that this beyond the floor standard may be appropriate to ensure that emission levels from new sources do not exceed the proposed 0.40 ng TEQ/ dscm beyond the floor standard for existing sources. Because standards for new sources are based on the single best performing source while standards for existing sources are based on the average of the best 12% ( or best 5) performing sources, standards for new sources should not be less stringent than standards for existing sources.

b. Beyond the Floor Considerations for Boilers Equipped with Wet or No Control Systems. We evaluated a beyond the floor level of 0.20 ng TEQ/ dscm for liquid fuel fired boilers Redline strikeout highlighting changes made during OMB review 59 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.

205 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 the floor standard for liquid fuel fired boilers using a wet or no air pollution control system. We are also considering an alternative beyond the floor standard of 0.40 ng TEQ/ dscm for new liquid fuel boilers equipped with wet or with no air pollution control systems. A new source that achieves the floor level compliance with the standards for carbon monoxide/ hydrocarbon and destruction and removal efficiency may have high dioxin/ furan emissions at levels far exceeding 0.40 ng TEQ/ dscm. See discussion above regarding factors other than gas temperature at the control device that can affect dioxin/ furan emissions from liquid fuel fired boilers. Therefore, it may be appropriate to establish a beyond the floor standard to limit emissions to 0.40 ng TEQ/ dscm based on use of activated carbon.

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. 59 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 Redline strikeout highlighting changes made during OMB review 60 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.

206 sources. 60 The normal mercury stack emissions in our data base are all less than 7 ug/ dscm. 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 Redline strikeout highlighting changes made during OMB review 61 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.

207 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 beyond the floor standard based on activated carbon injection. 61 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 Redline strikeout highlighting changes made during OMB review 62 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.

208 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 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. 62 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. Redline strikeout highlighting changes made during OMB review 63 The source also is equipped with a high efficiency particulate air ( HEPA) filter.

209 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. 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 filter63 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. Redline strikeout highlighting changes made during OMB review 64 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.

65 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).

210 We have emissions data within the range of normal emissions for nearly 40% of the sources. 64 The normal semivolatile stack emissions in our database range from less than 1 to 46 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. 65 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 Redline strikeout highlighting changes made during OMB review 66 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.

211 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 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 Approach66 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 Redline strikeout highlighting changes made during OMB review 212 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. Considering these factors and cost effectiveness, we conclude that a beyond the floor standard is not warranted. Therefore, we propose a semivolatile metals standard based on the floor level: 4.3E 6 lbs semivolatile metals emissions attributable to the hazardous waste per million Btu heat input from the hazardous waste for new sources. E. What Is the Rationale for the Proposed Standards for Chromium? We propose to establish standards for existing and new liquid fuel fired boilers that limit emissions of chromium to 1.1E 4 lbs and 3.6E 5 lbs chromium emissions attributable to the hazardous waste per million Btu heat input from the hazardous waste, respectively. We propose to establish emission standards on chromium only because our data base has very limited compliance test data on emissions of total low volatile metals: arsenic, beryllium, and chromium. We have compliance test data on only two sources for total low volatile metals emissions while we have compliance test data for 12 sources for chromium only. Although we have total low volatile metals emissions for 12 sources when operating under normal operations, we prefer to use compliance test data to establish the floor because they better address emissions variability. By establishing a low volatile metal floor based on chromium emissions only we are relying on the particulate matter standard to control the other enumerated low volatile metals arsenic and beryllium as well as nonenumerated metal HAP. We request comment on this approach and note that, as discussed below, an alternative approach would be to establish a MACT floor based on normal emissions data for all three enumerated low volatile metals. We request comment on whether the compliance test data for chromium only are appropriate for establishing a MACT floor for chromium. We are concerned that some sources in our data base may have used chromium as a surrogate for arsenic and beryllium during RCRA compliance testing such that their chromium emissions may be more representative of their total low volatile metals emissions than only chromium. If we determine this to be the case, we could apply the floor we calculate using chromium emissions to total low volatile metal emissions. Alternatively, we could use the normal emissions data we have on 12 sources and our MACT methodology to establish a total low volatile metals floor. 1. What Is the Rationale for the MACT Floor for Existing Sources? MACT floor for existing sources is 1.1E 4 lbs chromium emissions attributable to the hazardous waste per million Btu heat input from the hazardous waste, which is based on particulate matter control ( for those few sources using a control device) and controlling the feed concentration of chromium in the hazardous waste. We have compliance test emissions data representing maximum emissions for Redline strikeout highlighting changes made during OMB review 67 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.

213 approximately 17% of the sources. 67 The compliance test chromium stack emissions in our database range from 2 to 900 ug/ dscm. These emissions are expressed as mass of chromium ( from all feedstocks) per unit of stack gas. Hazardous waste thermal emissions, available for 13% of sources, range from 3.2E 6 to 8.8E 4 lbs chromium emissions attributable to the hazardous waste per million Btu heat input from the hazardous waste. To identify the floor level, we evaluated all compliance test thermal emissions data using the SRE/ Feed Approach ( see discussion in Section VI. C above). The calculated floor is 1.1E 4 lbs chromium emissions attributable to the hazardous waste per million Btu heat input from the hazardous waste feed, 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 36% of sources and would reduce chromium emissions by 9.4 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 chromium emissions: ( 1) use of a fabric filter to improve particulate matter control; and ( 2) control of chromium in the hazardous waste feed. For reasons discussed below, we are not proposing a beyond the floor standard for chromium. a. Use of a Fabric Filter to Improve Particulate Matter Control. We evaluated use of a fabric filter as beyond the floor control for further reduction of chromium emissions. We evaluated a beyond the floor level of 5.5E 5 lbs chromium 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 $ 5.9 million and would provide an incremental reduction in chromium emissions beyond the MACT floor controls of 0.50 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 160 tons per year and would increase electricity usage by 3.0 million kW hours per year. Based on these impacts and a cost of approximately $ 12 million per additional ton of chromium removed, we are not proposing a beyond the floor standard based on improved particulate matter control. b. Feed Control of Chromium in the Hazardous Waste. We evaluated additional feed control of chromium in the hazardous waste as a beyond the floor control technique to reduce floor emission levels by 25% to achieve a standard of 8.8E 5 lbs chromium emissions attributable to the hazardous waste per million Btu heat input from the hazardous waste. This beyond thefloor level of control would reduce chromium by an additional 0.20 tons per year at a cost Redline strikeout highlighting changes made during OMB review 214 effectiveness of $ 22 million per ton of chromium removed. Nonair quality health and environmental impacts and energy effects are not significant factors for feedrate control. We conclude that use of additional hazardous waste chromium feedrate control would not be costeffective and are not proposing a beyond the floor standard based on this control technique. For the reasons discussed above, we do not propose a beyond the floor standard for chromium. Consequently, we propose to establish the emission standard for existing liquid fuelfired boilers at the floor level: a hazardous waste thermal emission standard of 1.1E 4 lbs chromium emissions attributable to hazardous waste per million Btu of hazardous waste feed. 3. What Is the Rationale for the MACT Floor for New Sources? The MACT floor for new sources for chromium would be 3.6E 5 lbs chromium emissions attributable to the hazardous waste per million Btu heat input from the hazardous waste feed. This is an emission level that the single best performing source identified with the SRE/ Feed Approach could be expected to achieve in 99 of 100 future tests when operating under 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 as beyond the floor control to reduce chromium emissions to a beyond the floor level of 1.8E 5 lbs chromium 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 chromium emissions of 0.014 tons per year, for a cost effectiveness of $ 11 million per ton of chromium 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 kWhours per year. Considering these factors and cost effectiveness, we conclude that a beyond thefloor standard is not warranted. Therefore, we propose a chromium emission standard for new sources based on the floor level: 3.6E 5 lbs chromium emissions attributable to the hazardous waste per million Btu heat input from the hazardous waste feed. F. What Is the Rationale for the Proposed Standards for Total Chlorine? We are proposing to establish a standard for existing liquid fuel fired boilers that limit emissions of hydrogen chloride and chlorine gas ( i. e., total chlorine) to 2.5E 2 lbs total chlorine emissions attributable to the hazardous waste per million Btu heat input from the hazardous waste. The proposed standard for new sources would be 7.2E 4 lbs total chlorine 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? Most liquid fuel fired boilers that burn hazardous waste do not have back end controls such as wet scrubbers for total chlorine control. For these sources, total chlorine emissions are controlled by most sources by controlling the feedrate of chlorine in the hazardous waste feed. Approximately 15% of sources use wet scrubbing systems to control total chlorine emissions. Redline strikeout highlighting changes made during OMB review 215 We have compliance test data representing maximum emissions for 40% of the boilers. Total chlorine emissions range from less than 1 to 900 ppmv. Hazardous waste thermal emissions, available for 27% of boilers, range from 1.00E 4 to 1.4 lbs total chlorine emissions attributable to the hazardous waste per million Btu heat input from the hazardous waste. The calculated floor is 2.5E 2 lbs total chlorine emissions attributable to the hazardous waste per million Btu heat input from the hazardous waste using the SRE/ Feed Approach to identify the best performing sources ( see discussion in Section VI. C above). 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 70% of sources and would reduce total chlorine emissions by 660 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 total chlorine emissions: ( 1) use of a wet scrubber; and ( 2) control of chlorine in the hazardous waste feed. For reasons discussed below, we are not proposing a beyond the floor standard for total chlorine. a. Use of Wet Scrubbing. We considered a beyond the floor standard of 1.3E 2 lbs total chlorine emissions attributable to the hazardous waste per million Btu heat input from the hazardous waste based on wet scrubbing to reduce emissions beyond the floor level by 50 percent. 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 $ 7.8 million and would provide an incremental reduction in total chlorine emissions beyond the MACT floor controls of 430 tons per year. We evaluated nonair quality health and environmental impacts and energy effects and determined that this beyond the floor option would increase both the amount of hazardous wastewater generated and water usage by approximately 3.2 billion gallons per year and would increase electricity usage by 30 million kW hours per year. Considering these impacts and a cost effectiveness of approximately $ 18,000 per additional ton of total chlorine removed, we are not proposing a beyond the floor standard based on wet scrubbing. b. Feed Control of Chromium in the Hazardous Waste. We evaluated additional feed control of chlorine in the hazardous waste as a beyond the floor control technique to reduce floor emission levels by 20% to achieve a standard of 2.0E 2 lbs total chlorine 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 $ 3.9 million and would provide an incremental reduction in total chlorine emissions beyond the MACT floor controls of 170 tons per year. Nonair quality health and environmental impacts and energy effects are not significant factors for feedrate control. We conclude that use of additional hazardous waste chlorine feedrate control would not be cost effective at $ 23,000 per ton of total chlorine removed and are not proposing a beyond the floor standard based on this control technique. For the reasons discussed above, we propose a total chlorine standard for existing liquid fuel fired boilers based on the floor level: 2.5E 2 lbs total chlorine emissions attributable to the hazardous waste per million Btu heat input from the hazardous waste. Redline strikeout highlighting changes made during OMB review 216 3. What Is the Rationale for the MACT Floor for New Sources? The MACT floor for new sources for total chlorine would be 7.2E 4 lbs total chlorine 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 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 wet scrubbing as beyond the floor control for further reductions in total chlorine emissions to achieve a beyond the floor level of 3.6E 4 lbs total chlorine 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 an average gas flowrate to meet this beyond the floor level, rather than comply with the floor level, would be approximately $ 0.44 million and would provide an incremental reduction in total chlorine emissions of approximately 0.13 tons per year, for a cost effectiveness of $ 3.3 million per ton of total chlorine removed. We evaluated nonair quality health and environmental impacts and energy effects and determined that, for a new source with average an average gas flowrate, this beyondthe floor option would increase both the amount of hazardous wastewater generated and water usage by approximately 140 million gallons per year and would increase electricity usage by 1.3 million kW hours per year. After considering these impacts and cost effectiveness, we conclude that a beyond the floor standard based on wet scrubbing for new liquid fuel fired boilers is not warranted. For the reasons discussed above, we propose a total chlorine standard for new sources based on the floor level: 7.2E 4 lbs total chlorine emissions attributable to the hazardous waste per million Btu heat input from the hazardous waste. 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. 1. What Is the Rationale for the MACT Floor for Existing Sources? Liquid 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 Redline strikeout highlighting changes made during OMB review 217 ( 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." All liquid fuel fired boilers are currently complying with the RCRA carbon monoxide limit of 100 ppmv on an hourly rolling average. No boilers are complying with the RCRA hydrocarbon limit of 20 ppmv on an hourly rolling average. 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 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, as discussed above, we cannot ensure that lower carbon monoxide or hydrocarbon levels 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 existing sources. 3. What Is the Rationale for the MACT Floor for New Sources? Redline strikeout highlighting changes made during OMB review 218 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 lower carbon monoxide or hydrocarbon levels 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 are not proposing a beyond the floor standard for carbon monoxide and hydrocarbons. 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? Liquid 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 costs or 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 Redline strikeout highlighting changes made during OMB review 68 The carbon monoxide/ hydrocarbon emission standard would control organic HAP that are products of incomplete combustion by also ensuring use of good combustion practices.

219 incomplete combustion may not be controlled by the DRE standard. 68 For these reasons, and after considering nonair 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 nonair quality health and environmental impacts and energy requirements, we are proposing the floor DRE standard for new sources.

XII. How Did EPA Determine the Proposed Emission Standards for Hazardous Waste Burning Hydrochloric Acid Production Furnaces? The proposed standards for existing and new hydrochloric acid production furnaces that burn hazardous waste are summarized in the table below. See proposed § 63.1218. Redline strikeout highlighting changes made during OMB review 220 PROPOSED STANDARDS FOR EXISTING AND NEW HYDROCHLORIC ACID PRODUCTION FURNACES Hazardous Air Pollutant or Surrogate Emission Standard1 Existing Sources New Sources Dioxin and furan 0.40 ng TEQ/ dscm 0.40 ng TEQ/ dscm Hydrochloric acid and chlorine gas2 14 ppmv or 99.9927% System Removal Efficiency or the alternative emission limits under § 63.1215 1.2 ppmv or 99.99937% System Removal Efficiency 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 hydrogen chloride equivalent. 3 Hourly rolling average. Hydrocarbons reported as propane.

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 0.40 ng TEQ/ dscm. 1. What Is the Rationale for the MACT Floor for Existing Sources? The proposed MACT floor for existing sources is compliance with the proposed CO/ HC emission standard and compliance with the proposed DRE standard. Hydrochloric acid production furnaces use wet scrubbers to remove hydrochloric acid from combustion gases to produce the hydrochloric acid product and to minimize residual emissions of hydrochloric acid and chlorine gas. Thus, dioxin/ furan cannot be formed on particulate surfaces in the emission control device as can happen with electrostatic precipitators and fabric filters. Nonetheless, dioxin/ furan emissions from hydrochloric acid production furnaces can be very high. We have dioxin/ furan emissions data for 18 test conditions representing 14 of the 17 sources. Dioxin/ furan emissions range from 0.02 ng TEQ/ dscm to 6.8 ng TEQ/ dscm. We investigated whether it would be appropriate to establish separate dioxin/ furan standards for furnaces equipped with waste heat recovery boilers versus those without boilers. Ten of the 17 hydrochloric acid production furnaces are equipped with boilers. We considered whether waste heat recovery boilers may be causing the elevated dioxin/ furan emissions, as appeared to be the case for incinerators equipped with boilers. See 62 FR at 24220 ( May 2, Redline strikeout highlighting changes made during OMB review 69 Section 266.104 requires compliance with a carbon monoxide limit of 100 ppmv or a hydrocarbon limit of 20 ppmv, while we are proposing today a carbon monoxide limit of 100 ppmv or a hydrocarbon limit of 10 ppmv ( see Section XII. H in the text). Although today's proposed hydrocarbon limit is more stringent than the current limit for hydrochloric acid production furnaces, all sources chose to comply with the 100 ppmv carbon monoxide limit.

221 1997) where we explain that heat recovery boilers preclude rapid temperature quench of combustion gases, thus allowing particle catalyzed formation of dioxin/ furan. The dioxin/ furan data for hydrochloric acid production furnaces indicate, however, that furnaces with boilers have dioxin/ furan emissions ranging from 0.05 to 6.8 ng TEQ/ dscm, while furnaces without boilers have dioxin/ furan emissions ranging from 0.02 to 1.7 ng TEQ/ dscm. Based on a statistical analysis of the data sets ( see discussion in Part Two, Section II. E), we conclude that the dioxin/ furan emissions for furnaces equipped with boilers are not significantly different from dioxin/ furan emissions for furnaces without boilers. Thus, we conclude that separate dioxin/ furan emission standards are not warranted. We cannot or identify or quantify a dioxin/ furan control mechanism for these furnaces. Consequently, we conclude that establishing a floor emission level based on emissions from the best performing sources would not be appropriate because the best performing sources may not be able to replicate their emission levels, and other sources may not be able to duplicate those emission levels. We note, however, that dioxin/ furan emissions can be affected by the furnace's combustion efficiency. Operating under poor combustion conditions can generate dioxin/ furan and organic precursors that may contribute to post combustion dioxin/ furan formation. Because we cannot quantify a dioxin/ furan floor level and because hydrochloric acid production furnaces are currently required to operate under good combustion practices by RCRA standards for carbon monoxide/ hydrocarbons and destruction and removal efficiency, we identify those RCRA standards as the proposed MACT floor. See § 266.104 requiring compliance with destruction and removal efficiency and carbon monoxide/ hydrocarbon emission standards. 69 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 HAP to the extent achievable. We also request comment on an alternative MACT floor expressed as a dioxin/ furan emission concentration. Although it would be inappropriate to identify a floor concentration based on the average emissions of the best performing sources as discussed above, we could identify the floor as the highest emission concentration from any source in our data base, after considering emissions variability. Under this approach, the highest emitting source could be expected to achieve the floor 99 out of 100 future tests when operating under the same conditions as it did when the emissions data were obtained. A floor that is expressed as a dioxin/ furan emission level would prevent sources from emitting at levels higher than the ( currently) worstcase source ( actually, the worst case performance test result) currently emits. We specifically request comment on this alternative MACT floor. 2. EPA's Evaluation of Beyond the Floor Standards for Existing Sources Redline strikeout highlighting changes made during OMB review 70 USEPA, " Draft Technical Support Document for HWC MACT Replacement Standards, Volume IIIV: Selection of MACT StandardsEmissions Estimates and TechnologiesEngineering Costs," March 2004, Chapter 4.

71 Please note that, under the proposed floor level, sources would not incur retrofit costs or achieve dioxin/ furan emissions reductions because they currently comply with the floor controls under current RCRA regulations at 40 CFR 266.104.

222 We evaluated use of an activated carbon bed ( preceded by gas reheating to above the dewpoint) as beyond the floor control for dioxin/ furan. Carbon beds can achieve greater than 99% reduction in dioxin/ furan emissions. 70 We considered alternative beyond the floor levels of 0.40 ng TEQ/ dscm and 0.20 ng TEQ/ dscm. The incremental annualized cost of a beyond the floor emission level of 0.40 ng TEQ/ dscm would be $ 1.9 million and would provide an incremental reduction in dioxin/ furan emissions of 2.3 grams TEQ per year, for a cost effectiveness of $ 0.823 million per gram TEQ removed. 71 A beyond the floor emission level of 0.20 ng TEQ/ dscm would provide very little incremental emissions reduction 0.1 grams TEQ per year at additional costs. 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 wastewater generated by 210 tons per year, and would increase electricity usage by 1.8 million kW hours per year and natural gas consumption by 96 trillion Btu per year. Notwithstanding these impacts, we conclude that We judge that the cost to achieve a beyond the floor standard of 0.40 ng TEQ/ dscm is warranted given our special concern about dioxin/ furan. Dioxin/ furan are some of the most toxic compounds known due to their bioaccumulation potential and wide range of health effects, including carcinogenesis, at exceedingly low doses. Exposure via indirect pathways is a chief reason that Congress singled our dioxin/ furan for priority MACT control in CAA section 112( c)( 6). See S. Rep. No. 128, 101st Cong. 1st Sess. at 154 155. In addition, we note that the beyond the floor emission level of 0.40 ng TEQ/ dscm is consistent with historically controlled levels under MACT for hazardous waste incinerators and cement kilns, and Portland cement plants. See § § 63.1203( a)( 1), 63.1204( a)( 1), and 63.1343( d)( 3). Also, EPA has determined previously in the 1999 Hazardous Waste Combustor MACT final rule that dioxin/ furan in the range of 0.40 ng TEQ/ dscm or less are necessary for the MACT standards to be considered generally protective of human health under RCRA ( using the 1985 cancer slope factor), thereby eliminating the need for separate RCRA standards under the authority of RCRA section 3005( c)( 3) and 40 CFR 270.10( k). Finally, we note that this decision is not inconsistent with EPA's decision not to promulgate beyond the floor standards for dioxin/ furan for hazardous waste burning lightweight aggregate kilns, cement kilns, and incinerators at cost effectiveness values in the range of $ 530,000 to $ 827,000 per additional gram of dioxin/ furan TEQ removed. See 64 FR at 52892, 52876, and 52961. In those cases, EPA determined that controlling dioxin/ furan emissions from a level of 0.40 ng TEQ/ dscm to a beyond the floor level of 0.20 ng TEQ/ dscm was not warranted because dioxin/ furan levels below 0.40 ng TEQ/ dscm would be Redline strikeout highlighting changes made during OMB review 72 We estimate beyond the floor control costs assuming a new source emits the highest levels likely under floor control based on compliance with the carbon monoxide and destruction and removal efficiency standards.

223 warranted considering the special hazard dioxin/ furan emissions pose. For the reasons discussed above, we areare generally considered to be below the level of health risk concern. For these reasons, we believe that proposing a beyond the floor standard for dioxin/ furan of 0.40 ng TEQ/ dscm for existing sources. Thirty five percent of sources are currently meeting this standard. is warranted notwithstanding the nonair quality health and environmental impacts and energy effects identified above and costs of approximately $ 0.83 million per additional gram of dioxin/ furan TEQ removed.

3. What Is the Rationale for the MACT Floor for New Sources? MACT floor for new sources is the same as for existing sources under the same rationale: compliance with the carbon monoxide/ hydrocarbon emission standard and compliance with the destruction and removal efficiency standard. 4. EPA's Evaluation of Beyond the Floor Standards for New Sources As for existing sources, we evaluated use of an activated carbon bed as beyond the floor control for new sources to achieve an emission level of 0.40 ng TEQ/ dscm. We estimate that the incremental annualized cost for a new hydrochloric acid production furnace with average gas flowrate to reduce dioxin/ furan emissions at the floor of 0.68 ng TEQ/ dscm72 to achieve a beyond the floor emission level of 0.40 ng TEQ/ dscm would be $ 0.15 million. These controls would provide an incremental reduction in dioxin/ furan emissions of 0.66 grams TEQ per year, for a cost effectiveness of $ 230,000 per gram TEQ removed. We evaluated nonair quality health and environmental impacts and energy effects and determined that, for a new source with average an average gas flowrate, this beyond the floor option would increase the amount of hazardous wastewater generated by 9 tons per year, and would increase electricity usage by 0.14 million kW hours per year and natural gas consumption by 9.2 trillion Btu per year. Notwithstanding these impacts, we conclude that a beyond the floor level of 0.40 ng TEQ/ dscm would be costeffective considering the special hazard dioxin/ furan emissions pose. For these reasons, we propose We judge that the cost to achieve a beyond the floor standard forof 0.40 ng TEQ/ dscm is warranted given our special concern about dioxin/ furan. Dioxin/ furan are some of the most toxic compounds known due to their bioaccumulation potential and wide range of health effects, including carcinogenesis, at exceedingly low doses. Exposure via indirect pathways is a chief reason that Congress singled our dioxin/ furan for new sourcespriority MACT control in CAA section 112( c)( 6). See S. Rep. No. 128, 101st Cong. 1st Sess. at 154 155. In addition, we note that the beyond the floor standard of 0.40 ng TEQ/ dscm is consistent with historically controlled levels under MACT for hazardous waste incinerators and cement kilns, and Portland cement plants. See § § 63.1203( a)( 1), 63.1204( a)( 1), and 63.1343( d)( 3). Also, EPA has determined Redline strikeout highlighting changes made during OMB review 73 USEPA, " Draft Technical Support Document for HWC MACT Replacement Standards, Volume III: Selection of MACT Standards and Technologies," March 2004, Chapter 2.

74 Except that one source emitted 330 ug/ dscm low volatile metals and 0.043 gr/ dscf particulate matter during compliance testing. This source apparently detuned the acid gas absorber and other acid gas control equipment given that it achieved less than 99% system removal efficiency for total chlorine and had total chlorine emissions of 500 ppmv. This source would be not be allowed to operate under these conditions under today's proposed rule: 14 ppmv total chlorine emission limit, or 99.9927 system removal efficiency. Thus, under the proposed rule, emissions of low volatile metals and particulate matter would be substantially lower.

224 previously in the 1999 Hazardous Waste Combustor MACT final rule that dioxin/ furan in the range of 0.40 ng TEQ/ dscm or less are necessary for the MACT standards to be considered generally protective of human health under RCRA ( using the 1985 cancer slope factor), thereby eliminating the need for separate RCRA standards under the authority of RCRA section 3005( c)( 3) and 40 CFR 270.10( k). For these reasons, we believe that proposing a beyond the floor standard of 0.40 ng TEQ/ dscm is warranted notwithstanding the nonair quality health and environmental impacts and energy effects identified above and costs of approximately $ 0.23 million per additional gram of dioxin/ furan TEQ removed.

B. What Is the Rationale for the Proposed Standards for Mercury, Semivolatile Metals, and Low Volatile Metals? We propose to require compliance with the total chlorine standard as a surrogate for the mercury, semivolatile metals, and low volatile metals standards. As discussed above, hydrochloric acid production furnaces use wet scrubbers to remove hydrochloric acid from combustion gases to produce the hydrochloric acid product and to minimize residual emissions of hydrochloric acid and chlorine gas. Wet scrubbers also remove metal HAP, including mercury, from combustion gases. To minimize contamination of hydrochloric acid product with metals, hydrochloric acid production furnaces generally feed hazardous waste with low levels of metal HAP. Moreover, the wet scrubbers used to recover the hydrochloric acid product and minimize residual emissions of hydrochloric acid and chlorine gas also control emissions of metal HAP to very low levels. Based on emissions testing within the range of normal emissions ( i. e., not compliance test, maximum allowed emissions), hydrochloric acid production furnaces emit mercury at levels from 0.1 to 0.4 ug/ dscm, semivolatile metals at levels from 0.1 to 4.1 ug/ dscm, and low volatile metals at levels from 0.1 to 43 ug/ dscm. 73,74 We also note that these sources emit low levels of particulate matter. Compliance test, maximum allowable emissions of particulate matter range from 0.001 to 0.013 gr/ dscf. Because wet scrubbers designed to recover the hydrochloric acid product and control residual emissions of hydrogen chloride and chlorine gas also control emissions of mercury, and Redline strikeout highlighting changes made during OMB review 225 semivolatile and low volatile metals ( including nonenumerated metals), use of MACT wet scrubbers to comply with the proposed total chlorine standard discussed below will also ensure MACT control of metal HAP. Accordingly, we propose to use the total chlorine standard as a surrogate for the mercury, semivolatile metals, and low volatile metals standards. C. What Is the Rationale for the Proposed Standards for Total Chlorine? The proposed standards for total chlorine are 14 ppmv or 99.9927 percent total chlorine system removal efficiency ( SRE) for existing sources and 1.2 ppmv or 99.99937 percent total chlorine SRE for new sources. A source may elect to comply with either standard. 1. What Is the Rationale for the MACT Floor for Existing Sources? The proposed MACT floor for existing sources is compliance with either a total chlorine emission level of 14 ppmv or a total chlorine SRE of 99.9927 percent. Hydrochloric acid production furnaces use wet scrubbers to remove hydrochloric acid from combustion gases to produce the hydrochloric acid product and to minimize residual emissions of hydrochloric acid and chlorine gas. We have compliance test, maximum allowable total chlorine emissions data for all 17 hydrochloric acid production furnaces. Total chlorine emissions range from 0.4 to 500 ppmv, and total chlorine system removal efficiencies ( SRE) range from 98.967 to 99.9995 percent. As discussed in Section VI. C above, control of the feedrate of chlorine in hazardous waste fed to the furnace is not an appropriate MACT emission control technique because hydrochloric acid production furnaces are designed to produce hydrochloric acid from chlorinated feedstocks. Consequently, the approaches we normally use to identify the best performing sources SRE/ Feed Approach or Emissions Approach are not appropriate because they directly or indirectly consider chlorine feedrate. More simply, limiting feedrate means not producing the intended product, a result inconsistent with MACT. See 2 Legislative History at 3352 ( House Report) (" MACT is not intended to ... drive sources to the brink of shutdown"). To avoid this concern, we identify a floor SRE, and provide an alternative floor as a total chlorine emission limit based on floor SRE and the highest chlorine feedrate for any source in the data base. By using the highest chlorine feedrate to calculate the alternative total chlorine emission limit, we ensure that feedrate control ( i. e. nonproduction of product) is not a factor in identifying the proposed MACT floor. The alternative total chlorine emission limit would require a source that may not be achieving floor SRE to achieve total chlorine emission levels no greater than the level that would be emitted by any source achieving floor SRE. The floor SRE is 99.9927 percent. It is calculated from the five best SREs, and considers emissions variability. Floor SRE is an SRE that the average of the 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 SRE is being achieved by 29% of sources. The alternative floor emission limit is 14 ppmv, and is the emission level that the source with the highest chlorine feedrate 2.9E+ 8 ug/ dscm   would achieve when achieving 99.9927 percent SRE. Approximately 24% of sources are achieving the alternative floor levels, and these floor levels would reduce total chlorine emissions by 145 tons per year. Redline strikeout highlighting changes made during OMB review 226 2. EPA's Evaluation of Beyond the Floor Standards for Existing Sources We evaluated improved design, operation, and maintenance of existing scrubbers to achieve a beyond the floor emission level of 7 ppmv for total chlorine for existing sources, assuming a 50% reduction in emissions from the floor level. The national annualized compliance cost for hydrochloric acid production furnaces to comply with this beyond the floor standard would be $ 0.25 million, and emissions of total chlorine would be reduced by 3 tons per year. The cost effectiveness of this beyond the floor standard would be $ 76,000 per ton of total chlorine removed. We evaluated nonair quality health and environmental impacts and energy effects and determined that this beyond the floor option would increase both the amount of hazardous wastewater generated and water usage by approximately 82 million gallons per year and would increase electricity usage by 0.34 million kW hours per year. Generation of nonwastewater hazardous waste would decrease by 7 tons per year. Considering these impacts and costeffectiveness as well, we conclude that a beyond the floor standard for existing sources would not be warranted. For these reasons, we propose a floor total chlorine standard of 14 ppmv or 99.9927% SRE for existing sources. 3. What Is the Rationale for the MACT Floor for New Sources? The proposed MACT floor for new sources is compliance with either a total chlorine emission level of 1.2 ppmv or a total chlorine SRE of 99.99937 percent. We use the same rationale for identifying alternative floors for new sources as discussed above in the context of existing sources. The new source floor SRE is the SRE that the single best performing source ( i. e, source with the best SRE) 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. The new source floor alternative emission limit is an emission level that the source with the highest chlorine feedrate 2.9E+ 8 ug/ dscm   would achieve when achieving 99.99937 percent SRE. 4. EPA's Evaluation of Beyond the Floor Standards for New Sources We evaluated a beyond the floor standard for new sources of 0.60 ppmv based on achieving a 50 percent reduction in emissions by improving the design/ operation/ maintenance of the wet scrubber. The incremental annualized cost for a new solid fuel fired boiler with average gas flowrate to meet a beyond the floor level of 0.60 ppmv would be approximately $ 0.15 million and would provide an incremental reduction in total chlorine emissions of 0.07 tons per year, for a cost effectiveness of $ 2.1 million per ton of total chlorine removed. We evaluated nonair quality health and environmental impacts and energy effects and determined that, for a new source with average gas flowrate, this beyond the floor option would increase both the amount of hazardous wastewater generated and water usage by approximately 26 million gallons per year and would increase electricity usage by 0.25 million kW hours per year. Considering these impacts and cost effectiveness as well, we conclude that a beyond thefloor standard for new sources would not be warranted. For the reasons discussed above, we propose a total chlorine standard of 1.2 ppmv or a Redline strikeout highlighting changes made during OMB review 227 total chlorine SRE of 99.99937 percent for new sources. D. 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. 1. What Is the Rationale for the MACT Floor for Existing Sources? Hydrochloric acid production furnaces 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). All hydrochloric acid production furnaces have elected to comply with the 100 ppmv carbon monoxide standard. We propose floor standards of 100 ppmv for carbon monoxide or 10 ppmv for hydrocarbons for the same reasons discussed above in the context of liquid fuel fired boilers. There would be no incremental emission reductions associated with these floors because sources are currently achieving the carbon monoxide standard.. 2. EPA's Evaluation of Beyond the Floor Standards for Existing Sources Our considerations for beyond the floor standards for existing hydrochloric acid production furnaces are identical to those discussed above for existing liquid fuel fired boilers. For the reasons discussed above in the context of liquid fuel fired boilers, we conclude that beyond the floor standards for carbon monoxide and hydrocarbons for existing hydrochloric acid production furnaces are not warranted. 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 Our considerations for beyond the floor standards for new hydrochloric acid production furnaces are identical to those discussed above for new liquid fuel fired boilers. For the reasons discussed above in the context of liquid fuel fired boilers, we conclude that beyond the floor standards for carbon monoxide and hydrocarbons for new hydrochloric acid production furnaces are not warranted. E. 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? Hydrochloric acid production furnaces 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). Redline strikeout highlighting changes made during OMB review 228 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 HAPs or that are surrogates for organic HAPs. 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 may be emitted as products of incomplete combustion. For these reasons, and after considering nonair 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 nonair quality health and environmental impacts and energy requirements, we are proposing the floor DRE standard for new sources.