OAR 2002 0058 National Emission Standards for Hazardous Air Pollutants for Industrial/ Commercial/ Institutional Boilers and Process Heaters: Reconsideration Summary of Public Comments and Responses Contract No. 68 D 01 081 Work Assignment No. 4 08 U. S. Environmental Protection Agency Office of Air Quality Planning and Standards Emission Standards Division Research Triangle Park, North Carolina 27711 December 14, 2005 i Disclaimer This report has been reviewed by the Emission Standards Division of the Office of Air Quality Planning and Standards, and EPA, and approved for publication. Mention of trade names or commercial products is not intended to constitute endorsement or recommendation for use. ii TABLE OF CONTENTS Chapter Page 1 Background Information ................................................................................... 1 2 Public Comments Received ............................................................................... 2 3 Methodology and Criteria for Demonstrating Eligibility................................. 6 3.1 Monitoring Alternative ............................................................................. 6 3.2 Disease Registry ....................................................................................... 7 3.3 General Approval ..................................................................................... 7 3.4 HI and HQ values ..................................................................................... 9 4 Tiered Risk Assessment Methodology............................................................. 12 4.1 General Support ..................................................................................... 12 4.2 Guidance ................................................................................................ 13 5 Look up Tables ................................................................................................ 15 5.1 Appropriate use of a Look up Table ....................................................... 15 5.2 Stack Height........................................................................................... 17 5.3 Distance to Property............................................................................... 20 6 Site Specific Assessment .................................................................................. 22 7 Background Emissions/ Co located Emissions................................................. 26 8 Health Based Compliance Alternative for Metals .......................................... 35 9 Deadline for Submission of Eligibility Demonstration ................................... 43 10 Proposed Corrections....................................................................................... 47 11 Review of Eligibility Demonstrations for Health Based Compliance Alternatives and Title V Permit Conditions ................................................... 52 11.1 Eligibility and Permit Authority Review .................................................. 52 11.2 Significant Permit Modifications ............................................................. 55 11.3 Enforceable Parameters .......................................................................... 57 iii TABLE OF CONTENTS ( Continued)

Chapter Page 12 Miscellaneous ................................................................................................... 61 12.1 Wording Changes/ Additions ................................................................... 61 12.2 Decision to Adopt Health based Compliance Alternatives ....................... 61 12.3 Effects on Energy Supplies ..................................................................... 66 12.4 Reference Values ( RVs) ........................................................................ 66 12.5 Self Monitoring ...................................................................................... 67 12.6 Other Petitioner Issues............................................................................ 67 12.7 State Resources ...................................................................................... 68 12.8 Point of Maximum Impact ...................................................................... 69 12.9 Fire Tube Boilers.................................................................................... 70 12.10 Test Plans............................................................................................... 70 LIST OF TABLES Table Page 2 1. List of Commenters for the National Emission Standards for Hazardous Air Pollutants for Industrial/ Commercial/ Institutional Boilers and Process Heaters................. 2 1 Chapter 1 Background Information Section 112 ( c)( 2) of the Clean Air Act mandates that the Environmental Protection Agency ( EPA) establish emission standards for hazardous air pollutants ( NESHAP) for control of HAP from both existing and new major sources based upon the criteria set out in CAA section 112( d).

On September 13, 2004, EPA promulgated national emission standards for hazardous air pollutants ( NESHAP) for industrial, commercial, and institutional boilers and process heaters.

Following the promulgation of the final rule, EPA received petitions for reconsideration pursuant to section 307( d)( 7)( B) of the CAA from the Natural Resources Defense Council ( NRDC),

Environmental Integrity Project ( EIP), and General Electric ( GE). On January 28, 2005, EPA sent a letter to NRDC and EIP notifying the parties of the intent to grant their petition for reconsideration. On June 27, 2005, EPA published a Federal Register notice granting reconsideration and soliciting comments on certain provisions used to demonstrate eligibility for the health based compliance alternatives outlined in appendix A of the final rule, and on the provisions for the health based compliance alternative for total selected metals reflected in § 63.7507( b) of the final rule. EPA did not grant reconsideration on the other issues raised by the petitioners.

Thirty six public submissions were received from a wide variety of sources, consisting mainly of government agencies, environmental organizations, industry associations, and owner/ operators of affected boilers and process heaters. All of the comments that were submitted and the responses to these comments are summarized in this document. This summary is the basis for the revisions made to the final rule amendments between proposal and promulgation. 2 Chapter 2 Public Comments Received The EPA received a total of 37 submissions commenting on the reconsideration notice for the industrial, commercial and institutional boilers and process heaters NESHAP, some of which contained attachments. A list of commenters, their affiliations, and the EPA docket item number assigned to their correspondence is provided in Table 2 1. To achieve an organized presentation,

we have grouped the comments by topic in Chapters 3 through 8 of this document.

Table 2 1. List of Commenters for the National Emission Standards for Hazardous Air Pollutants for Industrial/ Commercial/ Institutional Boilers and Process Heaters ( OAR 2002 0058)

Docket No. Commenter's Name and Addressa OAR 2002 0058 0660 E. M. T. O'Nan, Director, Protect All Children's Environment  Public Comment OAR 2002 0058 0662 John Bradfield, Director of Environmental Affairs, Composite Panel Association ( CPA) Public Comment OAR 2002 0058 0663 Comment submitted by Timothy G. Hunt, Senior Director, Air Quality Programs, American Forest & Paper Association  Public Comment OAR 2002 0058 0664 American Forest & Paper Association Comment  Public Comment Attachment OAR 2002 0058 0665 Donald R. Schregardus, Deputy Assistant Secretary of the Navy ( Installations and Environment) on behalf of Clean Air Act Services Steering Committee  Public Comment OAR 2002 0058 0666 Julia E. Smith, Amundsen & Gilroy , P. A., Attorneys at Law on behalf of Coastal Lumber Company, Hood Industries, Inc. and Scotch Lumber Company ( collectively, " Companies")  Public Comment OAR 2002 0058 0667 Michel R. Benoit, Executive Director, Cement Kiln Recycling Coalition ( CKRC)  Public Comment 3 Table 2 1. List of Commenters for the National Emission Standards for Hazardous Air Pollutants for Industrial/ Commercial/ Institutional Boilers and Process Heaters ( OAR 2002 0058)

Docket No. Commenter's Name and Addressa OAR 2002 0058 0668 Erik G. Milito, Senior Attorney, Office of General Counsel, American Petroleum Institute  Public Comment OAR 2002 0058 0669 Carl Johnson, Executive Director, Southern Pressure Treaters Association and Jeffrey Miller, Executive Director, Treated Wood Council  Public Comment

OAR 2002 0058 0670 Thomas W. Easterly, Commissioner, Indiana Department of Environmental Management  Public Comment OAR 2002 0058 0671 Robert D. Bessette on behalf of the Council of Industrial Boiler Owners ( CIBO)  Public Comment OAR 2002 0058 0672 Bob Elam, Director, Environment, American Chemistry Council  Public Comment OAR 2002 0058 0673 Comment submitted by Laurie L. Zeinio, Director, Safety, Environment, Standards& E PDP, Deere & Company  Public Comment OAR 2002 0058 0674 Thomas W. Rockwood, Coastal Plywood Company  Public Comment OAR 2002 0058 0675 Randy Meyer, Manager of Environmental Affairs, American Municipal Power  Ohio  Public Comment OAR 2002 0058 0676 Bradley M. Campbell, Commissioner, Department of Environmental Protection, State of New Jersey  Public Comment OAR 2002 0058 0677 William O'Sullivan, Director, Department of Environmental Protection, State of New Jersey  Public Comment OAR 2002 0058 0678 Bruce Alexius, Air Resource Leader, Regulatory Affairs Expertise Center, The Dow Chemical Company  Public Comment OAR 2002 0058 0679 Dennis Steiner, Mayor, City of Orrville, Ohio  Public Comment OAR 2002 0058 0680 Norbert Dee, Ph. D. Director Environment & Safety, National Petrochemical & Refiners Assoc. ( NPRA)  Public Comment OAR 2002 0058 0681 Eric Clark, Synthetic Organic Chemical Manufacturers Association ( SOCMA)  Public Comment OAR 2002 0058 0682 David A. Buff, P. E., Q. E. P., Principal Engineer, Golder Associates Inc. on behalf of Florida Sugar Industry ( FSI)  Public Comment 4 Table 2 1. List of Commenters for the National Emission Standards for Hazardous Air Pollutants for Industrial/ Commercial/ Institutional Boilers and Process Heaters ( OAR 2002 0058)

Docket No. Commenter's Name and Addressa OAR 2002 0058 0683 Lloyd L. Eagan, Chair, STAPPA Air Toxics Committee and Robert H. Colby, Chair, ALAPCO Air Toxics Committee  Public Comment OAR 2002 0058 0684 David Wright, Air Toxics & Inventory Program, Bureau of Air Quality, Maine Department of Environmental Protection ( Part 1 of 3)  Public Comment OAR 2002 0058 0685 David Wright, Air Toxics & Inventory Program, Bureau of Air Quality, Maine Department of Environmental Protection ( Part 2 of 3)  Public Comment OAR 2002 0058 0686 David Wright, Air Toxics & Inventory Program, Bureau of Air Quality, Maine Department of Environmental Protection ( Part 3 of 3) Public Comment OAR 2002 0058 0687 Bill Perdue, Vice President, Environmental, Health/ Safety Standards, American Home Furnishings Alliance ( AHFA)  Public Comment OAR 2002 0058 0688 Valerie Ughetta, Director of Stationary Sources, Alliance of Automobile Manufacturers  Public Comment OAR 2002 0058 0689 Valerie Ughetta, Director, Stationary Sources, Alliance of Automobile Manufacturers  Public Comment Attachment OAR 2002 0058 0690 Valerie Ughetta, Director of Stationary Sources, Alliance of Automobile Manufacturers  Public Comment OAR 2002 0058 0691 Melvin Keener, Ph. D., Executive Director, Coalition for Responsible Waste Incineration ( CRWI)  Public Comment OAR 2002 0058 0692 J. W. Hunter, Mayor, City of Shelby, Ohio  Comment Response OAR 2002 0058 0693 John Walke, Natural Resources Defense Council  Public Comment OAR 2002 0058 0694 L. Eagan, Director, Bureau of Air Management, State of Wisconsin, Department of Natural Resources  Public Comment OAR 2002 0058 0695 National Association of Manufacturers  Public Comment OAR 2002 0058 0696 Richard Homrighausen, Mayor, City of Dover, Ohio  Public Comment OAR 2002 0058 0697 Michael L. Weadcock, Director of Public Service and Safety, City of St. Marys, Ohio OAR 2002 0058 0698 Rita C. McMahon, City Manager, City of Painesville, Ohio 5 a Commenters listed multiple times due to duplicate comments and attachments are referred to in Chapters 3 through 11 of this document by the first number that was assigned to that commenter in the docket. 6 Chapter 3 Methodology and Criteria for Demonstrating Eligibility 3.1 Monitoring Alternative Comment: One commenter ( OAR 2002 0058 0660) recommended an epidemiological study in each affected area to determine a baseline level of health. One commenter ( OAR 2002

0058 0680) recommended two years of continuous air monitoring at all facilities eligible for health based compliance alternatives in order to justify the determination for health risk established in these health based compliance alternatives.

Response: We disagree with the commenters' recommendations. Procedures for risk assessments in appendix A are based on the risk assessment methodologies and dispersion models that are outlined in the 1999 Residual Risk Report to Congress ( EPA

453/ R 99 001). As directed by the Clean Air Act, we prepared this report to outline an approach for calculating risk after implementation of the MACT standards. In the 1999 report we identified uncertainties in risk assessment methodologies and made recommendations for any legislative changes needed. We indicated that data from epidemiological studies will rarely be available for evaluating correlations between exposure and adverse human health effects. Accordingly, the 1999 report also indicates that we rely on a variety of air dispersion models ( e. g., SCREEN 3) to assess exposure to HAP. In the report, we proposed no legislative changes to the Clean Air Act. After reviewing the 1999 report, the Congress did not change the residual risk requirements in the Clean Air Act, thereby indicating approval of the methods we outlined in the report for calculating the risk posed by facilities. The methods outlined in the report to develop the health based standards under section 112 are primarily based on dispersion modeling. We see no reason to depart from this strategy for the health based compliance alternatives.

Additionally, the commenters have not provided any specific justification to support their recommendations. 7 3.2 Disease Registry Comment: One commenter ( OAR 2002 0058 0660) suggested establishing a disease registry to serve as a baseline for monitoring the effects of this regulation on the health conditions of sensitive populations ( TILT, asthma, ADD/ ADHD), and requested particular monitoring of behavioral and criminal activities in areas where manganese emissions are permitted as a result of the health based compliance alternatives.

Response: We disagree with the commenter's suggestion. As stated above, it is appropriate to apply our risk assessment methodology to the health based alternative compliance options in the present rule. Part of that methodology is the reliance on reference values ( e. g., Reference Concentrations ( RfCs)) that are based on relevant health endpoints and that are designed to be protective of sensitive populations. These reference values form the basis of the health based compliance alternatives in appendix A. EPA proposed to use the reference values to establish health based alternatives in the notice of proposed rulemaking and provided an opportunity to comment. After considering public comments, we continued to support the use of RfCs for this application. EPA did not grant reconsideration on our decision to use the RfCs.

3.3 General Approval Comment: Multiple commenters ( OAR 2002 0058 0672, OAR 2002 0058 0681, OAR

2002 0058 0682, OAR 2002 0058 0695, OAR 2002 0058 0687, OAR 2002 0058 0669, OAR

2002 0058 0665, OAR 2002 0058 0673, OAR 2002 0058 0667, OAR 2002 0058 0668, OAR

2002 0058 0671, OAR 2002 0058 0675, OAR 2002 0058 0679, OAR 2002 0058 0696, OAR

2002 0058 0697, OAR 2002 0058 0698, OAR 2002 0058 0688) supported the methodology and criteria used to develop the health based compliance alternatives for HCl and manganese and cited several reasons. Two commenters ( OAR 2002 0058 0672, OAR 2002 0058 0681) stated that risk assessment, as applied by agencies within the Federal government, is the scientifically appropriate, precautionary method for assessing the likelihood that exposure is associated with adverse health and for ensuring public health with an ample margin of safety. The commenters suggested that risk assessment is scientifically appropriate because the methodology correctly applied the four steps of the risk paradigm in the tiered approach. The commenters also suggested that risk assessment is precautionary because it does not underestimate the true risks of 8 actual exposure. One commenter ( OAR 2002 0058 0682) added that the methodology for demonstrating eligibility for health based compliance alternatives is based on accepted techniques for risk assessment which have withstood judicial review. One commenter ( OAR 2002 0058

0695) supported a standard that attuned to the variability of sources regulated by this MACT standard. The commenter added that this methodology heeded to Congress' feasibility concern and public health mandate.

Three commenters ( OAR 2002 0058 0687, OAR 2002 0058 0672, OAR 2002 0058

0681) emphasized the precedent of the use of air dispersion models for regulatory decisions at EPA and supported the conservative estimates reflected by the SCREEN 3 dispersion model used for the look up tables as well as the site specific information in the ISCSTC model. Two of these commenters ( OAR 2002 0058 0672, OAR 2002 0058 0681) provided examples of air dispersion modeling regulatory decisions such as the New Source Review/ Prevention of Significant Deterioration Programs and the section 112( r) accidental release programs.

Response: We agree with the use of a risk assessment methodologies as applied in appendix A. These methodologies rely on scientifically accepted peer reviewed methodologies and the compliance alternatives remain protective of the public health. We also acknowledge the commenters' general support for the methodology in appendix A and recognition of previous use of dispersion modeling in other EPA regulations and programs.

The 1999 EPA Residual Risk Report to Congress lists the SCREEN 3 air dispersion model as an example model for simple types of applications, such as the first tier look up assessment in appendix A. This model and the ISCSTC are referenced in the Air Toxics Risk Assessment ( ATRA) Reference Library, which supports our decision to incorporate these dispersion models into these health based compliance alternatives of appendix A.

We are retaining the health based compliance alternatives in substantially the same form. However, we are making a limited number of amendments to section 63.7507 and appendix A of subpart DDDDD to improve and clarify the process for demonstrating eligibility to comply with the health based compliance alternatives contained in the rule.

These amendments include the following: ( 1) When performing a lookup table analysis,

affected sources with multiple emission points will now use a toxicity and emissionsweighted stack height as opposed to the average stack height. New equations have been added to appendix A; ( 2) We corrected the rule to clarify that all units, as opposed to only 9 large solid fuel fired units, may demonstrate eligibility for the heath based alternatives; ( 3)

explicit language has been added to clarify that the permitting agencies have the authority to review eligibility demonstrations to verify that they meet the requirements of Appendix A and are technically sound; and ( 4) the list of enforceable parameters that can potentially be included in the Title V permit has been extended to explicitly include the term HAP emission rate and non process parameters. These and other amendments are discussed further in other sections of this document and the associated notice published in the Federal Register.

3.4 HI and HQ Values Comment: Multiple commenters ( OAR 2002 0058 0665, OAR 2002 0058 0666, OAR

2002 0058 0667, OAR 2002 0058 0668, OAR 2002 0058 0672, OAR 2002 0058 0681, OAR

2002 0058 0673, OAR 2002 0058 0674, OAR 2002 0058 0682, OAR 2002 0058 0695) agreed that the HQ and HI values of 1.0 are appropriate, well established, and protective of public health with an ample margin of safety. One commenter ( OAR 2002 0058 0665) suggested that facilities who have initiated demonstrations for health based compliance alternatives have done so using the HI value of 1.0 and a change of value would require these facilities to re do their risk assessments. Two commenters ( OAR 2002 0058 0673, OAR 2002 0058 0667) emphasized the conservative nature of the RFC values used to develop these index values to protect sensitive populations. One commenter ( OAR 2002 0058 0668) attached the 2003 report by the Residual Risk Coalition entitled " EPA Should Set Risk Based Emission Levels For Threshold Hazardous Air Pollutants At Appropriate Levels Above A Hazard Index Of 1.0" to support the decision to not adjust the HI value to less than 1.0 and justify HI values greater than 1.0 when providing for an ample margin of safety. One commenter ( OAR 2002 0058 0681) contended that adopting an HI index of 2.0 would unlikely result in any significant change in the protection of public health.

Two commenters ( OAR 2002 0058 0688, OAR 2002 0058 0691) suggested that EPA provide for flexibility and engineering judgment in interpreting an applicability cutoff HI or HQ of greater than 1.0 in individual situations. One commenter ( OAR 2002 0058 0691) stated that a value of 1.0 is the most stringent margin of safety required and the Agency could use HI's greater than 1.0 in certain cases. The commenter added that no additional margin of safety is required because the RfC calculation contain many layers of protection including safety factors of 300 for 10 HCl, and 1000 for Mn, respectively, to account for uncertainty. One commenter ( OAR 2002

0058 0688) added that at present HI and HQ values are not transferable to a probability of a person incurring a non carcinogenic adverse effect.

One commenter ( OAR 2002 0058 0684) suggested the use of an applicability cutoff HI or HQ value of at most 0.5 in order to account for cumulative and persistent risk.

Response: We disagree that an HI or HQ value other than 1.0 should be used as an applicability cutoff value for the health based compliance alternatives. HI and HQ values are based on peer reviewed reference values such as the EPA's reference concentrations ( RfC). An RfC is an estimate ( with uncertainty spanning perhaps an order of magnitude)

of a continuous inhalation exposure or a daily exposure to the human population ( including sensitive subgroups) that is likely to be without an appreciable risk of deleterious noncancer effects during a lifetime. An HI or HQ less than or equal to one means that the concentration of the pollutant ( in air) is less than or equal to the reference value, and,

therefore, is presumed to be without appreciable risk of adverse health effects.

As mentioned by commenters, RfC values contain uncertainty factors in order to account for scientific uncertainties that are identified in the literature. We acknowledge that EPA can consider the uncertainty inherent in these reference values when making risk based determinations. For the health based compliance alternatives, using an HI and HQ of one as a health protrective default is appropriate and, along with the risk assessment methods specified in appendix A, protects public health with an ample margin of safety as required by section 112( d)( 4).

Comment: One commenter ( OAR 2002 0058 0678) did not support the use of a HI less than or equal to 1.0 as the applicability cutoff value for determining eligibility with the HCl healthbased compliance alternative. The commenter asserted that the HI should be changed to less than 10 but greater than 1.0 due to the additive effect of several health protective factors, such as RfCs and the individual most exposed metric used for deriving the HCl HI value. Specifically, the commenter highlighted that it is overly conservative to apply the chlorine RfC to evaluate the exposure to chlorine. The commenter added that chlorine reacts in the atmosphere to form HCl,

and the commenter requested EPA to evaluate the exposure to chlorine using the equivalent amount of HCl formed in the atmospheric reactions. 11 Response: As we argue above, we disagree that an HI or HQ value other than 1.0 should be used as an applicability cutoff value for the health based alternative compliance alternatives. An HI of 1.0 corresponds to a level of pollutant exposure that is unlikely to result in adverse health effects over a lifetime. We acknowledge that EPA can consider the uncertainty inherent in reference values when making risk based determinations.

However, for the health based compliance alternatives, using an HI and HQ of 1.0 as a health based protective default is appropriate and helps protect public health with an ample margin of safety.

Additionally, as stated above, it is appropriate to apply our risk assessment methodology to the health based alternative compliance options in the present rule. This methodology includes calculating hazard to the individual most exposed to pollutant emissions from the source, which helps ensure that public health is protected with an ample margin of safety.

We also disagree with the commenter's suggestion to account for atmospheric reactions of chlorine to form HCl. Impacts from chlorine can occur shortly after release if a population lives near an emission point. Chlorine has a lower reference value than HCl.

Thus, we make the health protective assumption that people are exposed to chlorine emitted from the source prior to any conversion into the less potent HCl. This approach,

along with the other requirements of appendix A, helps ensure that public health is protected with an ample margin of safety. 12 Chapter 4 Tiered Risk Assessment Methodology 4.1 General Support Comment: Multiple commenters ( OAR 2002 0058 0663, OAR 2002 0058 0680, OAR

2002 0058 0681, OAR 2002 0058 0695, OAR 2002 0058 0671, OAR 2002 0058 0667, OAR

2002 0058 0688, OAR 2002 0058 0682, OAR 2002 0058 0666, OAR 2002 0058 0673, OAR

2002 0058 0670, OAR 2002 0058 0679, OAR 2002 0058 0692, OAR 2002 0058 0696, OAR

2002 0058 0697, OAR 2002 0058 0698, OAR 2002 0058 0674, OAR 2002 0058 0675, OAR

2002 0058 0672, OAR 2002 0058 0678) supported the flexibility and efficient use of both industry and permitting authority resources provided for in a tiered risk assessment methodology.

These commenters added that this flexibility is appropriately balanced with conservatism and accuracy to protect the public health with an ample margin of safety. One commenter ( OAR

2002 0058 0663) specifically approved of the efficiency of this tiered approach because it implements simple screening techniques as compared to time intensive analyses, for facilities that are low risk, even under worse case scenarios. One commenter ( OAR 2002 0058 0687) added that the tiered approach provides a simple, conservative first tier analysis that companies can achieve without hiring an outside consultant to demonstrate compliance with the health based compliance alternative. This commenter also feels it is necessary to allow facilities to conduct site specific analyses in tandem with the look up analysis so that facilities can still demonstrate compliance with the health based alternatives in the event that the source fails the look up analysis. One commenter ( OAR 2002 0058 0687) added it is necessary to allow facilities to conduct more specific analyses for the health based compliance alternative eligibility demonstration. The commenter anticipated some furniture manufacturers will use the ISCST3 model to comply with the second tier. One commenter ( OAR 2002 0058 0681) added that a tiered approach is less arbitrary than a control based standard, which requires equivalent controls across the board without considering the risk of an affected source. One commenter ( OAR 2002

0058 0670) specifically approved of estimating long term inhalation exposure through the 13 estimation of annual or multi year ambient concentrations. Four commenters ( OAR 2002 0058

0672, OAR 2002 0058 0681, OAR 2002 0058 0678, OAR 2002 0058 0682) agree the procedures set forth in the site specific methodology to ensure data quality control including:

using quality assured data whenever possible and using health protective default assumptions in the absence of quality assured data and preparing transparent, replicable documentation of the assessment.

One commenter ( OAR 2002 0058 0682) contended that a facility that fails the look up test and opts to become eligible through a more detailed second tier does not imply that a facility will cause harm to the public health; instead this tiered approach eliminates these facilities that have no impact while protecting the public with an ample margin of safety.

Several commenters ( OAR 2002 0058 0682, OAR 2002 0058 0678, OAR 2002 0058

0688, OAR 2002 0058 0663, OAR 2002 0058 0681, OAR 2002 0058 0680) cited the precedence and consistency of a tiered risk approach in EPA modeling of air toxics and mobile sources and at the state levels. One commenter ( OAR 2002 0058 0680) specifically cited the use of tiered risk methodologies at the EPA since 1992.

Response: We acknowledge the support for the flexibility, efficiency, and healthprotective nature of a tiered approach to risk assessment. We concluded that a tiered risk approach is consistent with both the commenters' support for an approach that minimizes the impact on low risk facilities and EPA's statutory mandate under § 112.

4.2 Guidance Comment: One commenter ( OAR 2002 0058 0688) recognized the procedural importance of including the 1992 document, A Tiered Modeling Approach for Assessing the Risks Due to Sources of Hazardous Air Pollutants, in the docket since the document was referenced in the proposed rule. However, the commenter feels that many aspects of this earlier guidance document have been superseded by more recent guidance, such as the Air Toxics Risk Assessment Reference Library, which was referenced in the final rule. The commenter does not think the older guidance document should play any further role in this rule.

Response: We agree that the Air Toxics Risk Assessment ( ATRA) Reference Library represents the most up to date information on risk assessment methodologies. We placed the 1992 document in the docket to fulfill procedural requirements of the public 14 rulemaking process. However, many relevant aspects of the 1992 tiered risk assessment document, which we cited in the proposed rule, are incorporated into the ATRA Reference Library, which is cited and incorporated by reference in the final rule. 15 Chapter 5 Look up Tables 5.1 Appropriate use of a Look up Table Comment: Multiple commenters ( OAR 2002 0058 0663, OAR 2002 0058 0671, OAR

2002 0058 0672, OAR 2002 0058 0681, OAR 2002 0058 0680, OAR 2002 0058 0695, OAR

2002 0058 0682, OAR 2002 0058 0687, OAR 2002 0058 0688, OAR 2002 0058 0675, OAR

2002 0058 0679, OAR 2002 0058 0692, OAR 2002 0058 0696, OAR 2002 0058 0697, OAR

2002 0058 0698) supported the use of the look up tables as well as the levels of protection built into the look up tables; the commenters suggested that the tables be retained without modification. These commenters agreed that the tables screen out sources, considering worse case scenarios, which do not pose a threat to human health or the environment. Three commenters ( OAR 2002 0058 0687, OAR 2002 0058 0688, OAR 2002 0058 0682) specified that the analysis used to develop the tables accounts for worse case scenarios with respect to parameters including: meteorology, downwash, terrain, and stack parameters. Three commenters ( OAR 2002 0058 0663, OAR 2002 0058 0672, OAR 2002 0058 0681) discussed the adequate levels of protection inherent in the safety factors of the RfCs. These commenters explained how these safety factors accounted for uncertainties in the observable effects between species and for uncertainties in the observable effects of sensitive populations, as well as uncertainties due to limitations in the toxics database. The commenter lists the safety factors for the two threshold pollutants that are used in the health based compliance alternatives: 300 for HCl and 1000 for Mn. Several commenters ( OAR 2002 0058 0663, OAR 2002 0058 0675, OAR 2002 0058

0679, OAR 2002 0058 0692, OAR 2002 0058 0696, OAR 2002 0058 0697, OAR 2002 0058

0698) specified the conservatism of the maximally exposed individual ( MEI) metric over a lifetime and cited the 1997 report by the Presidential/ Congressional Commission on Risk Assessment and Risk Management to support the expert scientific opinion on the levels of conservatism in the individual most exposed metric. 16 Two commenters ( OAR 2002 0058 0673, OAR 2002 0058 0667) agreed with using source specific look up tables and added that given the availability of source specific data, and stated that more generic look up tables are not warranted.

Four commenters ( OAR 2002 0058 0681, OAR 2002 0058 0665, OAR 2002 0058

0688, OAR 2002 0058 0687) suggested that these tables are an efficient and cost effective screening tool. Two commenters ( OAR 2002 0058 0665, OAR 2002 0058 0681) added that these tools will specifically benefit small businesses, with a smaller amount of affected sources, by providing a tool to evaluate their risk without spending significant resources. One commenter ( OAR 2002 0058 0687) stated that the tables allow for sources to complete their assessment without hiring third party consultants; and contended that the tables will prevent delays resulting from bottlenecks caused by the limited availability of third parties to complete site specific assessments.

One commenter ( OAR 2002 0058 0678) supported the use of the look up tables only if a more refined, second tier approach remains as part of the rule. The commenter suggested that the look up tables over predict both the ambient concentrations of HCl or Mn and the health hazards.

Four commenters ( OAR 2002 0058 0677, OAR 2002 0058 0683, OAR 2002 0058

0684, OAR 2002 0058 0694) disagreed with use of the look up tables due to an insufficient level of conservatism inherent in the look up tables during worse case scenarios. These commenters emphasized that if the look up tables remained as a result of this reconsideration, the look up tables should not be used when unique site specific factors are not accounted for in the tables.

Three of these commenters ( OAR 2002 0058 0677, OAR 2002 0058 0683, OAR 2002 0058

0684) specified that the tables should not be used when events of building downwash or rain caps,

or complex terrain occurred. One commenter ( OAR 2002 0058 0677) compared the MACT health based compliance alternative look up tables to look up tables used by the state authority and stated that the MACT tables do not cover worse case scenarios. One commenter ( OAR

2002 0058 0694) noted that in look up tables used in state hazardous air pollutant rules, the use of the table requires that the stack does not have an obstruction such as a rain hat. One commenter ( OAR 2002 0058 0683) requested that EPA clarify that sources must comply with the MACT standard in the event that a permitting agency rejects the use of look up table analysis for demonstrating eligibility to a health based compliance alternative. 17 Response: We continue to believe that the look up tables can provide an efficient and cost effective method for sources to comply with the health based alternative compliance options while also protecting the public health with an ample margin of safety.

However, we agree that the protective measures inherent in the look up tables do not necessarily justify their use in all cases. We developed the look up tables by running the SCREEN3 atmospheric dispersion model with worst case meteorology defaults, an assumption of flat terrain, an assumption that building downwash effects are not present,

and an assumption that the plume does not encounter a raincap or other obstruction. As several commenters identified, we recognize that site specific factors not accounted for in the SCREEN3 dispersion modeling, such as building downwash, the presence of rain caps,

and complex terrain, could make the use of the tables inappropriate for some sources.

Therefore, we agree with limiting the use of the look up tables to those situations where the tables can conservatively represent actual site conditions. In order to prevent the misuse of look up tables, we are adding language in section 6 of appendix A to the final rule to clarify that, although the lookup tables are presumed to be applicable in each case, permit agencies have the authority to determine on a site specific basis, that look up tables may not be used if unique site specific factors, for which the look up tables do not account,

make their use inappropriate. In such situations, a source would have to demonstrate eligibility using a site specific risk assessment that does account for these unique factors. If a source is unable to make this demonstration ( e. g. if a permitting authority ultimately finds the eligibility demonstration deficient on technical grounds), the source must then comply with the technology based standards in the NESHAP.

5.2 Stack Height Comment: Four commenters ( OAR 2002 0058 0663, OAR 2002 0058 0673, OAR

2002 0058 0678, OAR 2002 0058 0682) agreed with the use of the average stack height parameter. One commenter ( OAR 2002 0058 0673) stated that stack heights of multiple solid fuel units at the same facility are generally similar, while three commenters ( OAR 2002 0058

0663, OAR 2002 0058 0678, OAR 2002 0058 0682) suggested that this metric provides for another level of conservatism in the look up table. One commenter ( OAR 2002 0058 0663)

provided an example of eight typical pulp and paper facilities with multiple emission units to show 18 how this average parameter provides for another layer of protection into the risk analysis. The commenter concluded that given that the solid fuels are the major sources of both HCl and Mn,

and the stack heights of oil and gas units tend to be shorter than solid fuel units, an average of all stack heights will result in a lower acceptable emission rate in the look up tables than if the height of a unique solid fuel stack height was used in the analysis.

Three commenters ( OAR 2002 0058 0666, OAR 2002 0058 0669, OAR 2002 0058

0694) suggested alternatives to the average stack height metric. One commenter ( OAR 2002

0058 0694) proposed an alternate method of four stack height ranges which is currently used in the state's hazardous air pollutant rule. The commenter suggested that these ranges are organized to assure that the combined impact of a source with multiple stack heights in all four ranges would not exceed the ambient standards or risk. Two commenters ( OAR 2002 0058 0666,

OAR 2002 0058 0669) requested EPA to consider weighted average stack heights and cited the use of a weighted stack height metric in the plywood NESHAP. The commenters suggested the weighted average stack height more accurately portrays the potential risk than the average stack height metric.

Three commenters ( OAR 2002 0058 0683, OAR 2002 0058 0684, OAR 2002 0058

0694) suggested limiting the use of the look up tables to facilities with similar stack heights to those assumed in the model. One commenter ( OAR 2002 0058 0694) added that if the stack heights are not similar, a more refined analysis should be required.

One commenter ( OAR 2002 0058 0693 ( see also comments incorporated by reference in the original Petition for Reconsideration in docket item OAR 2002 0058 0657)) disagreed with the use of the average stack height, contending that this approach understates risk and that EPA lacked a justification and documentation on how the EPA chose this metric. According to this commenter, risk is understated when a calculation averages the shortest, most highly polluting stack located closest to neighboring populations with another emission point that is taller, cleaner,

and farther away. The commenter also contended that there is no documentation of the analysis or data at any step of this rulemaking, including this reconsideration, which supports the development of the average stack height metric that would enable a member of the public to evaluate EPA's methodology. The commenter provided an analysis of average stack heights of municipal utilities and wood fired boilers for two documents identified in the docket. The 19 commenter concluded that neither of these documents justifies the use of average stack heights or support the agency claim that stack heights are generally similar.

Response: We agree that the average stack height is not the best metric for characterizing risk, and that a more precise approach is the weighted stack height metric proposed in the Plywood NESHAP amendments. We are changing the stack height metric in the boilers and process heaters rule by adding two equations to appendix A, similar to the approach used for Equations 3 and 4 listed in appendix B of 40 CFR Part 63 Subpart DDDD. Equations 1 and 2 of appendix A of 40 CFR Part 63 Subpart DDDDD will also be modified to harmonize the existing calculations of appendix A with the new weighted stack height metric. The complete rationale for selecting the weighted stack height metric can be found in the proposed amendments to the Plywood NESHAP at 70 FR 44021.

The weighted stack height metric is more accurate and addresses commenters' concerns about under predicting risk in certain situations. There are situations where the average stack height is health protective, ( e. g., when most emissions are from the tallest stacks) and situations where the average stack height metric is not health protective, ( e. g., when most emissions are from the shortest stacks). The toxicity and emissions weighted stack height,

which we are incorporating into appendix A, is more health protective when most emissions are from the shortest stacks. The new equations factor in the amount of emissions and the toxicity of the HAP emitted from each stack and weight the result toward the height of the stacks with greater toxicity weighted emissions. This addresses concerns about averaging the height of a short, highly emitting stack with higher but lower emitting stack. Further, using this more precise method does not undercut our reliance on other health protective assumptions in the look up table analysis when most of the emissions come from taller stacks. As discussed below, the look up table analysis will continue to require an assumption that all emissions occur at the location of the stack closest to the property line of an affected source. This health protective assumption avoids under predicting risk in situations where the highest emitting stack is located closest to the property line.

Comment: Two commenters ( OAR 2002 0058 0678, OAR 2002 0058 0682) contested that the average stack height does not consider the significant plume rise from hot plumes and thus over estimates ambient concentrations. The commenter added that plume rise and ambient 20 concentrations are directly proportional and this plume rise greatly reduces ground level ambient concentrations.

Response: We disagree with the commenter's assertion that our look up tables do not correctly account for plume rise from hot plumes. In the modeling used to develop the lookup tables, we assumed a stack gas temperature that was typical for the industry according to our available data. Alternatively, sources can conduct a site specific risk assessment if they choose in order to better account for plume rise at a specific source.

Comment: Two commenters ( OAR 2002 0058 0683, OAR 2002 0058 0684) stated that EPA did not account for the height of a building for stacks that are attached to a building structure. The commenters added that the building height has large impacts on facilities with shorter stack heights and presents a comparison of the lookup table values found in Table 2 of appendix A to support this claim.

Response: It is incorrect to say that our lookup tables do not account for building height. The definition of stack height is the height above ground and, therefore, this approach correctly accounts for the height of stacks that are attached to a building structure.

5.3 Distance to Property Comment: Several commenters ( OAR 2002 0058 0678, OAR 2002 0058 0666, OAR

2002 0058 0669, OAR 2002 0058 0675, OAR 2002 0058 0679, OAR 2002 0058 0692, OAR

2002 0058 0696, OAR 2002 0058 0697, OAR 2002 0058 0698) suggested that the use of the minimum distance to property boundary metric is overly conservative. Two commenters ( OAR

2002 0058 0666, OAR 2002 0058 0669) requested EPA allow a weighted average for the distance to property boundary when there are multiple emission units. These two commenters argued this metric would portray more accurate estimates of the potential risk from facilities.

One commenter ( OAR 2002 0058 0684) requested that the modeling protocol for HAP should be consistent with the modeling protocols for criteria pollutants under the PSD protocols found at 40 CFR Part 51 Appendix W, with respect to using the point of maximum impact instead of the minimum distance to property boundary. The commenter expressed concern that the current use of minimum property distance may not be the point of maximum impact. 21 Response: We disagree with changing the minimum distance to property boundary.

We recognize that the minimum distance to property boundary may overestimate the ambient concentration and exposure; however, we emphasize the health protective nature of the lookup tables and do not deem it appropriate to change this metric towards one that would be uniformly less health protective.

It is incorrect to assert that, when performing a lookup table analysis, the minimum distance to the property line boundary may not be the point of maximum impact.

For the lookup tables, we developed the allowable emission rate for each property boundary distance from the maximum modeled HAP concentrations beyond that property boundary distance. As a result, a look up table analysis necessarily considers the point of maximum pollutant impact outside the source's property boundary. This is consistent with appendix W of 40 CFR part 51. 22 Chapter 6 Site Specific Assessment Comment: Several commenters ( OAR 2002 0058 0688, OAR 2002 0058 0672, OAR

2002 0058 0681, OAR 2002 0058 0678, OAR 2002 0058 0673, OAR 2002 0058 0665)

supported the level of guidance provided by EPA for the site specific assessment and believed the discretion to use any " scientifically accepted, peer reviewed risk assessment methodology."

These commenters also supported the reference in the final rule to the Air Toxics Risk Assessment Reference Library ( ATRA) guidance document. One commenter ( OAR 2002 0058

0688) added that this approach allows facilities to incorporate evolving risk assessment techniques and thought this guidance citation to the Air Toxics Risk Assessment Reference Library was more appropriate than additional details within the regulation itself, due to the ever changing nature of risk assessment methodologies. The commenter added that providing assessment details in the regulatory language would require constant updates to the regulations as methodologies evolve.

One commenter ( OAR 2002 0058 0673) stated this level of guidance allows for flexibility for the affected sources and supported the method as long as it is scientifically defensible, transparent,

and peer reviewed. One commenter ( OAR 2002 0058 0665) added that many facilities have already invested time in initiating or completing site specific risk assessments in accordance with the procedures set forth in appendix A. The commenter stated that the thresholds for site specific assessments are derived directly from section 112( f) and the methodology of these assessments is identical to those used during the residual risk evaluations. Two commenters ( OAR 2002 0058

0672, OAR 2002 0058 0681) stated contrary to other comments, substantial guidance for conducting site specific assessments exists and that this guidance is expressly cited within the MACT rule. The commenters stated that Chapters 8 and 9 of this ATRA guideline contain a list of specific air dispersion models that are supported and specifies circumstances where the models are appropriate. Additionally, the commenters suggested the user manuals for air quality models supported by EPA provide additional detailed guidance. These commenters disagreed with 23 incorporating a set of simple, prescriptive rules for conducting site specific risk analyses into the rule citing the complexity involved in the process of site specific risk assessment. Further, the commenters stated the variability in the affected sources limits the Agency's ability to establish a set of rules that would be appropriate for all facilities. The commenters added that a specific set of rules impedes the mission to provide scientifically accurate risk assessments.

One commenter ( OAR 2002 0058 0670) requested to amend the NESHAP to specify that facilities that do not use the EPA's Air Toxics Risk Assessment Reference Library obtain regulatory agency approval prior to using other scientifically accepted peer reviewed methodology. This commenter suggested this amendment will provide clear guidance for facilities on the type of methodology and prevent unnecessary disapprovals of the final risk determinations by the permitting authority.

Four commenters ( OAR 2002 0058 0694, OAR 2002 0058 0693, OAR 2002 0058

0683, OAR 2002 0058 0684) disagreed with the level of guidance EPA provided for conducting a site specific assessment. Three commenters ( OAR 2002 0058 0683, OAR 2002 0058 0684,

OAR 2002 0058 0693) added that there is a lack of basic methods or required parameters, such as the years of exposure to an individual which might lead to basing a risk assessment on a oneyear exposure instead of the traditional lifetime exposure. Two commenters ( OAR 2002 0058

0683, OAR 2002 0058 0684) contended that without specific guidance, the site specific assessment provides a meaningless measure of impact. One commenter ( OAR 2002 0058 0693)

stated that while EPA has provided some guidance on performing site specific assessments, EPA has a responsibility to develop constraints on the sources' discretion. The commenter contended that the lack of constraint included in this rule does not provide specific, knowable, replicable and enforceable legal standards necessary to govern and enforce this standard. The commenter added that the loose guidance provided for in selecting a site specific assessments can be interpreted as unlimited discretion for the affected source, and thus prevent any future efforts for administrative challenge. Further, the commenter stated that this lack of constraint provides the source with the task of writing its own rules and determining whether or not a source will be required to incur compliance costs.

Response: We believe that providing sources with the discretion to use any " scientifically accepted, peer reviewed risk assessment methodology" is appropriate.

However, contrary to the assertions of some commenters, this discretion is not unlimited. 24 In section 7( c) of appendix A, EPA has established specific minimum criteria for sitespecific compliance demonstrations. In order to demonstrate eligibility for the healthbased compliance alternative, the site specific risk assessment conducted by the facility must meet the following criteria: ( 1) estimate long term inhalation exposures through the estimation of annual or multi year average ambient concentrations; ( 2) estimate the inhalation exposure for the individual most exposed to the facility's emissions; ( 3) use sitespecific quality assured data wherever possible; ( 4) use health protective default assumptions wherever site specific data are not available; and ( 5) contain adequate documentation of the data and methods used.

Furthermore, EPA cited the Air Toxics Risk Assessment ( ATRA) Reference Library to provide guidance to the sources and state on developing technically sound site specific risk assessments. The ATRA Reference Library provides examples of how a risk assessment can be conducted. These examples include instruction in basic risk assessment methodology, in determining what parameters to include in a risk assessment, and in the constraints that should be placed on those parameters. The documents within the ATRA Reference Library have been peer reviewed and were developed according to the principles, tools and methods outlined in the 1999 EPA Residual Risk Report to Congress.

However, the guidance in the ATRA Reference Library may not be appropriate for all sources. For that reason sources may consider alternative analytical tools as long as these alternatives are scientifically defensible, peer reviewed and transparent.

Finally, the discretion of each source is not unlimited because permitting agencies have the authority to review each site specific eligibility demonstration to determine if it meets the applicable requirements in section 7( c) of appendix A and if the methodology, as applied in the demonstration of eligibility, is technically sound and appropriate. After reviewing a source's compliance demonstration, the permitting authority makes the final determination of whether site specific assessments are completely and correctly submitted.

These authorities may reject site specific assessments if they do not meet the requirements of section 7 of appendix A or if they contain technical flaws with respect to the risk assessment methodology. Thus, it may be advisable for sources to seek prior approval when using a methodology that deviates from the approach in the Air Toxics Risk 25 Assessment Reference Library. However, we do not feel that it is necessary to require this prior approval.

Comment: One commenter ( OAR 2002 0058 0694) requested that facilities choosing to apply for the site specific assessment be required to perform a residual risk analysis as part of their submission of eligibility; the commenter requested that this risk analysis be submitted to the US EPA for review.

Response: At this time, we do not consider a residual risk analysis to be warranted under section 112( d). Under the CAA, residual risk evaluations are required to be conducted eight years after publication of the 112( d) standards. 26 Chapter 7 Background Emissions/ Co located Emissions Comment: Multiple commenters ( OAR 2002 0058 0666, OAR 2002 0058 0667, OAR

2002 0058 0687, OAR 2002 0058 0663, OAR 2002 0058 0672, OAR 2002 0058 0680, OAR

2002 0058 0682, OAR 2002 0058 0688, OAR 2002 0058 0669, OAR 2002 0058 0675, OAR

2002 0058 0679, OAR 2002 0058 0692, OAR 2002 0058 0696, OAR 2002 0058 0697, OAR

2002 0058 0698, OAR 2002 0058 0669) disagreed with EPA's decision not to include background or co located emissions when determining whether or not a facility qualifies for the health based compliance alternative standards in the final rule. Several commenters ( OAR 2002

0058 0677, OAR 2002 0058 0693, OAR 2002 0058 0694, OAR 2002 0058 0683, OAR 2002

0058 0684) stated that when evaluating whether or not a facility is eligible to comply with the health based compliance alternatives, the background or co located emissions should be included in the risk determination.

Several of the commenters that opposed consideration of emissions from background or co located sources ( OAR 2002 0058 0687, OAR 2002 0058 0663, OAR 2002 0058 0672,

OAR 2002 0058 0675, OAR 2002 0058 0679, OAR 2002 0058 0692, OAR 2002 0058 0696,

OAR 2002 0058 0697, OAR 2002 0058 0698, OAR 2002 0058 0688, OAR 2002 0058 0671)

argued that the statutory language in sections 112( d) does not provide EPA with the legal authority to consider emissions from other source categories. Many of these commenters also provided counter examples of sections of the CAA where the Congressional intent was focused on including background or co located emissions. Several commenters ( OAR 2002 0058 0675,

OAR 2002 0058 0679, OAR 2002 0058 0692, OAR 2002 0058 0696, OAR 2002 0058 0697,

OAR 2002 0058 0698) added that background or co located emissions do not fall into a source category or subcategory of major sources listed for regulation. Two commenters ( OAR 2002

0058 0663, OAR 2002 0058 0680) stated that there is no precedent for the consideration of background or co located emissions during the promulgation of the benzene NESHAP or during the litigation of the vinyl chloride NESHAP. 27 Three commenters ( OAR 2002 0058 0663, OAR 2002 0058 0680, OAR 2002 0058

0688) cited a 1990 Senate Report, and concluded that the consideration of background or colocated emission sources would be the kind of lengthy study Congress intended to avoid. Two commenters ( OAR 2002 0058 0663, OAR 2002 0058 0680) cited risk documents from the Presidential/ Congressional Commission on Risk Assessment and Risk Management, and a paper written by the Residual Risk Coalition to support their position on excluding background and colocated emission sources when evaluating whether or not a facility qualifies for the health based alternative standard in appendix A.

One commenter ( OAR 2002 0058 0663) believed EPA has no legal basis for reconsidering the concept of including background or other sources in the risk determination, and they cited that this issue has been through appropriate notice and comment process.

One commenter ( OAR 2002 0058 0672) argued that the public health is most protected when regulations are specific to a source category and provided examples of how the different provisions of the CAA account for different sources of HAP. The commenter added that the consideration of background emissions would over regulate the affected source category and effectively require certain sources to compensate for other sources of HAP.

Two of the commenters ( OAR 2002 0058 0683, OAR 2002 0058 0684) that supported considering emissions from background and co located sources contended that the major source status is based on facility wide emissions and limiting the risk analysis to certain sources within the facility presents an unrealistic view of the facility's impact. One commenter ( OAR 2002

0058 0693) added that the EPA must meet its duty of providing for an " ample margin of safety"

by evaluating the risk of background emissions now as opposed to during the residual risk evaluation. One commenter ( OAR 2002 0058 0677) stated that risk assessment should be done in the context of all HAP sources at the facility and at nearby facilities. One of these commenters ( OAR 2002 0058 0694) disagreed with the health based compliance alternative for metals because it does not adjust for facility wide emissions.

Three commenters ( OAR 2002 0058 0683, OAR 2002 0058 0684, OAR 2002 0058

0677) cited the 1996 National Air Toxics Assessment ( NATA) for support of the concern of high exposures to air toxics throughout the country and stated a reduction in such exposures will require a general reduction across all sources. These commenters expressed concern that 28 excluding background or co located emissions ignore cumulative risk and do not protect the public health.

One commenter ( OAR 2002 0058 0694) contended that the tiered risk approach used at the state level correctly considers background emissions, in contrast to the exclusion of these background emissions in the final NESHAP. The commenter added that by excluding these background sources, the final NESHAP rule identifies low risk subcategories based on an unrealistic view of the facility impact. The commenter also concluded that the refined site specific risk screening provides no real measure of health impact without including background or colocated emission sources.

Response: Based on the arguments made by several commenters and our review of the Clean Air Act, it is permissible under section 112( d) of the Act to limit our analysis to establishing emissions limitations for only those sources in the individual source categories subject to this action. Therefore, in developing emissions limitations under 112( d), we believe emissions from sources outside of this source category need not be considered to determine eligibility for the health based compliance alternatives for industrial,

commercial, and institutional ( ICI) boilers and process heaters. Although we may combine several source categories into one NESHAP as we did in this action, we do not construe the Act to require that we regulate the emissions from all other source categories through an individual 112( d) rule for particular source categories.

The focus of section 112( d) is on establishing emissions standards for individual source categories. Section 112( d)( 1) indicates that the administrator is to " promulgate regulations establishing emissions standards for each category or subcategory of major sources and area source of hazardous air pollutants listed for regulation pursuant to subsection ( c) of this section in accordance with the scheduled provided in subjections ( c)

and ( e) of this section." The health based compliance alternatives are included among the emissions standards we have established for ICI boilers and process heaters under section 112( d). Section 112( d)( 4) states that " the Administrator may consider such threshold level,

with an ample margin of safety, when establishing emission standards under this subsection." The subsection described in this provision of the statute is subsection 112( d).

Since the " ample margin of safety" provision is also contained within section 112( d), we do not interpret this part of the Act to require that we consider emissions from other source 29 categories in establishing a health based alternative under section 112( d)( 4) for one category of sources. Based on the overall focus of section 112( d) on sources in specific categories, we believe the " ample margin of safety" criteria should be applied to the emissions of threshold pollutants from the individual source category subject to each NESHAP.

We agree with several commenters that the legislative history supports this view that Congress intended for EPA to focus only on the emissions from sources within a particular category when establishing health based standards for a particular source category under section 112( d)( 4). The Senate Report stated that the following:

The Administrator is authorized by section 112( d)( 4) to use the no observable effects or NOEL ( again with an ample margin of safety) as the emissions limitation in lieu of more stringent " best technology" requirements. Following this scenario, only those sources in the category which present a risk to public health ( those emitting in amounts greater than the safety threshold) would be required to install controls, even though the general policy is " maximum achievable technology" everywhere. 1 This statement suggests an intent for EPA to address only whether " sources in the category" present a risk to public health when EPA in determining whether individual sources in the category should have to comply with a technology based emissions limitation or may avoid installation of controls by demonstrating that the emissions from a source do not present risks greater than an established health threshold.

Thus it is permissible to conclude that the facility wide impact is not the focus of the analysis in the development of a section 112( d) rule. Under our interpretation, the appropriate analysis under the Act is whether the emissions of sources in the applicable category ( without consideration of emissions from sources in other categories) are below the health threshold. Under the eligibility demonstration methodology set forth in Appendix A of subpart DDDDD, a source must demonstrate eligibility based on the emissions of all emissions units in the ICI boilers and process heaters source category.

Because all emissions units in the category are covered, any background emissions or 1 S. Rep. No. 228, 101st Cong., 1st. Session 175 6 ( 1990). 30 emissions from other sources at a particular location would have to be emissions from sources in other categories or emissions that occur naturally.

We do not read section 112( d) to require us to use emissions from sources outside the category to establish health based alternatives for sources in the ICI boilers category.

Likewise, we do not believe eligibility for health based alternatives should be determined by using a sum of emissions from all source categories or by lowering the health threshold for emissions from one source category to account for emissions from other source categories. We believe we should concentrate on only the emissions from each source category to establish health based emissions limitations for that category and in determining whether sources in that category are eligible to comply with health based emissions limitations or must meet a technology based emissions limitation.

Although a particular facility may be identified as a major source of HAPs for purposes of section 112 on the basis of emissions from affected sources in multiple source categories, this does not require that we establish eligibility for a health based emissions limitation in a particular source category based on emissions from co located sources outside the category. Emissions units in other source categories located at the same major source site remain subject to the technology based emissions limitations contained in other NESHAPs promulgated under section 112( d). The sources covered by these NESHAPs are not eligible to comply with the health based alternatives in the ICI boilers and process heaters NESHAP.

Under either scenario, each source is subject to regulatory requirements ( whether health or technology based) that address the health risks posed by emissions from that facility. The health based compliance alternatives in the 40 CFR Part 63, subpart DDDDD are only available for HCl and Mn, and only if emissions of these HAP meet the healthbased criteria defined in appendix A. Affected sources that can comply with the healthbased alternatives in appendix A are still subject to other emissions standards under the NESHAP.

With respect to the concerns about cumulative risk, emission standards under section 112( d) are only one aspect of a broader national air toxics control program. Under the residual risk program, we may consider, as appropriate, risks from other source categories and risks from the total emissions from a particular location. This approach was 31 reiterated in the recently finalized Coke Oven Residual Risk rule where we said we will only consider emissions from the regulated source category when determining " acceptable risk" during the first step of the residual risk analysis. However, during the second step,

where we determine the ample margin of safety considering costs and technical feasibility ( see 70 FR 19997 19998), we may consider co located sources and background levels where appropriate.

Comment: Three commenters ( OAR 2002 0058 0682, OAR 2002 0058 0669, OAR

2002 0058 0678) agreed with the Agency suggestion to revisit the consideration of background emission during future residual risk evaluations. However, one commenter ( OAR 2002 0058

0688) disagreed with the suggestion to revisit facility wide residual risk determinations in future residual risk rules and stated that the EPA does not have the authority to mandate facility wide residual risk determinations. The commenter provided an attachment of the Coke Oven Residual Risk Rule to support their position. Several commenters stated an intention to address this issue in subsequent residual risk rulemakings if EPA proposes to revisit facility wide emissions at this stage.

Four commenters ( OAR 2002 0058 0677, OAR 2002 0058 0683, OAR 2002 0058

0694, OAR 2002 0058 0684) expressed concern on considering co located emissions only during the residual risk analysis. One commenter ( OAR 2002 0058 0694) stated that deferring the risk screening is contrary to the intent of the Clean Air Act. Three commenters ( OAR 2002 0058

0683, OAR 2002 0058 0684, OAR 2002 0058 0677) were not satisfied with the residual risk evaluations performed to date. Two commenters ( OAR 2002 0058 0683, OAR 2002 0058

0684) specifically cited that background concentrations for benzene or any other HAP were not incorporated into the Coke Oven Residual Risk report. One commenter ( OAR 2002 0058 0693)

added that the EPA must meet its duty of providing for an " ample margin of safety" by evaluating the risk of background emissions now as opposed to during the residual risk evaluation. The commenter added that in deferring the consideration of these background emission sources until the residual risk evaluation, the agency is acting arbitrary, capricious, and otherwise not in accordance with law.

Response: To the extent necessary, we believe the appropriate stage for considering total facility risk from air toxics emissions is at the residual rulemaking risk stage under section 112( f) of the Act. As noted above, we do not construe the requirement in section 32 112( d)( 4) to " consider such threshold, with an ample margin of safety, when establishing emission standards" under subsection ( d) to require assessment of the cumulative risk at a given location due to the emissions from all source categories at this stage of NESHAP development. However, as stated in our recent residual risk rule for coke ovens, we do not agree that section 112( f) entirely precludes EPA from considering emissions other than those from the relevant source category during a residual risk rulemaking analysis for an individual source category ( see 70 Fed. Reg. 19992, 19998 ( Apr. 15, 2005)). Section 112( f)

directs EPA to consider whether promulgation of additional standards " is required to provide an ample margin of safety to protect public health."

Although the phrase " ample margin of safety" is used in both sections 112( d)( 4) and 112( f), the context surrounding the phrase is different in each section. The context of subsection 112( d) focuses on each individual source category for which we are promulgating a NESHAP under subsection ( d). Although we agree that the first stage of our 112( f) analysis should focus on the risks from each individual source category, we believe we may consider cumulative risks to some extent in implementing the " ample margin of safety" requirement in the context of subsection ( f) and in evaluating " other relevant factors" under this subsection ( see 70 Fed. Reg. at 19998). As a result, we believe the appropriate stage for any consideration of cumulative facility risks is this second part of the residual risk analysis rather than in the development and implementation of a healthbased alternative under section 112( d)( 4) of the Act.

We do not construe section 112( d)( 4) of the Act to accelerate the residual risk analysis under section 112( f) when we invoke section 112( d)( 4) to establish a health based standard during the first stage or rulemaking under section 112( d). In this action, we are implementing section 112( d) of the Act and are not writing a regulation based on section 112( f). Section 112( d)( 4) does not call for a residual risk analysis for all sources in the category. Rather, this provision allows EPA to consider the existence of health thresholds ( with an adequate margin of safety) for particular pollutants at the first stage of the NESHAP promulgation process.

Comment: Two commenters ( OAR 2002 0058 0683, OAR 2002 0058 0684) felt it was unclear how the health based compliance alternatives will affect section 112( f) residual risk 33 evaluations for HCl and Mn, and asked if these two threshold pollutants will be exempted from residual risk assessments.

Response: HCl and Mn will not be exempted in future 112( f) analyses. Rather,

exposure to these two pollutants will be assessed along with exposure to other HAP emitted from the source category.

Comment: Several commenters( OAR 2002 0058 0663, OAR 2002 0058 0682, OAR

2002 0058 0675, OAR 2002 0058 0679, OAR 2002 0058 0692, OAR 2002 0058 0696, OAR

2002 0058 0697, OAR 2002 0058 0698) believed that it was not necessary to account for background or emissions from other sources because the multiple levels of protection in the existing methodologies for both the exposure and dose/ response assessments provide for the protection of public health with an ample margin of safety. One commenter ( OAR 2002 0058

0663) provided specific levels of protections including: the RfCs are stated to be orders of magnitude below any observable adverse effect in scientific studies, additionally the exposure assumption is based on a constant 24 hour, 365 day exposure for 70 years. In addition, the commenter stated that the HI value of 1.0 chosen in the final rule is one order of magnitude less than the recommendations provided in the Presidential/ Congressional Commission on Risk Assessment for non cancer hazard index values. These commenters concluded it is unjustified to provide additional levels of protection through the assessment of background or co located emissions. One commenter ( OAR 2002 0058 0682) contended that a HI value of 0.2 is an arbitrary method of accounting for background emissions and suggested that background emissions are often near zero for HAP.

One commenter ( OAR 2002 0058 0693) contended that the agency assertion of the conservatism inherent in the RfC values does not justify the exclusion of background pollution and co located sources, which if included in the calculations, would exceed the RfC values.

Response: We indicated in our notice of proposed rulemaking that, to the extent we determined we should address background concentrations and emissions from colocated source to determine eligibility for a health based alternative, one option would be to utilize an HI or HQ below 1.0. In light, our interpretation that each section 112( d)

rulemaking should establish emissions limitations ( including health based emissions limitations when appropriate) for each category individually, we have determined that it is not necessary to consider potential background emissions or emissions from co located 34 sources or to attempt to account for such emissions using an HI or HQ of less than 1.0 As a result, we have not conducted any further analysis to determine whether any specific HI or HQ level below 1.0 would or would not be appropriate to account for emissions from other sources.

We agree that the conservatism inherent in the RfC does not account for background exposures and did not intend to suggest this in our June 27, 2005 reconsideration notice. However, for reasons provided in response to other comments, we continue to believe that the methods for complying with the health based alternatives, as outlined in appendix A, are appropriately health protective and that it is not necessary to use an HI or HQ less than or greater than 1.0 to implement the health based alternatives.

We agree that the conservatism built into the RfC helps meet our statutory obligation to consider established health thresholds " with an ample margin of safety" when promulgating emissions limitations for threshold pollutants based on section 112( d)( 4) of the Act. 35 Chapter 8 Health Based Compliance Alternative for Metals Comment: One commenter ( OAR 2002 0058 0693) specified that EPA cannot adopt risk based exemptions for pollutants for which no health threshold has been established. The commenter contended, based on documents in the EPA Integrated Risk Information System ( IRIS), that no health threshold has been established for Mn. This commenter believes there is evidence that manganese may have carcinogenic effects and cites to studies it believes are suggestive of carcinogenicity. In addition, this commenter takes issue with fact that the RfC for manganese is based on a LOEAL rather than a NOEL. Finally, this commenter argues EPA's determination that Mn is a threshold pollutant is flawed because EPA focused on the health effects of chronic exposure and ignored potential acute effects.

Two other commenters ( OAR 2002 0058 0663, OAR 2002 0058 0695) specified that Mn has long been recognized as a threshold pollutant. Another commenter ( OAR 2002 0058

0687) stated that unlike other metals in the MACT list, Mn is not a carcinogen, rather it is a Class D pollutant.

Response: We agree that health based compliance alternatives adopted under section 112( d)( 4) can apply only to pollutants for which a threshold for health effects has been established. For the pollutants for which we have elected to establish health based compliance alternatives ( manganese and HCl), the scientific data support a threshold approach to evaluating the potential for adverse health effects.

For air toxics risk assessments, we identify pertinent toxicity or dose response values using a default hierarchy of sources to assist us in identifying the most scientifically appropriate benchmarks. EPA's Integrated Risk Information System ( IRIS) is the preferred source in this hierarchy. The values in the IRIS database reflect EPA consensus values and their development typically incorporates extensive peer review. When adequate toxicity information is not available in IRIS, we consult other sources in a default hierarchy that recognizes the desirability of peer review and consistency with EPA risk assessment 36 guidelines to ensure that we have consistent and scientifically sound assessments. For substances lacking current IRIS assessments, U. S. Agency for Toxic Substances and Disease Registry ( ATSDR) chronic MRLs received next preference, followed by California Environmental Protection Agency ( CalEPA) chronic RELs and UREs. Furthermore, when there is an IRIS assessment but that assessment substantially lags the current scientific knowledge, we are committed to consider alternative credible and readily available assessments.

Based on our analysis of manganese using this approach, we believe the data currently available show that a health threshold has been established for manganese and that we are therefore authorized under section 112( d)( 4) to establish a health based alternative for this pollutant. Under our default hierarchy approach, we first consulted IRIS. IRIS may be found on internet at < www. epa. gov/ iris>, but we have added the relevant pages in IRIS to docket for this rulemaking action. As listed in table 4 of our notice of proposed rulemaking, 68 Fed. Reg. 1690 ( Jan. 13, 2003), IRIS contains a reference concentration for manganese. However, IRIS does not contain a unit risk estimate, which addresses cancer risk. EPA's assessment in IRIS indicates that there is inadequate evidence of carcinogenicity for manganese. In addition, a cancer assessment for manganese is not available from any of the other sources in our default hierarchy or from another scientifically credible source. Based on this information, which we believe is the best available at the present time, our judgment is that it is only appropriate for EPA to evaluate manganese with regard to non cancer effects. In the absence of specific scientific evidence to the contrary, it has been our policy to classify non carcinogenic effects as threshold effects. RfC development is the default approach for threshold ( or nonlinear)

effects. Thus, in the absence of adequate evidence that manganese is a carcinogen and based on the presence of a reference concentration in IRIS for non cancer effects of manganese, our best scientific judgment at this time is that manganese is a threshold pollutant. We also used this approach to reach a similar conclusion with respect to HCl.

See Comment Response Document, pg. 233 ( February 2004).

Regarding the LOAEL issue, the methodology employed by EPA recognizes that while a NOAEL is preferable to a LOAEL for use as the point of departure to which uncertainty factors are applied to derive an RfC, a LOAEL may also be used. U. S. 37 Environmental Protection Agency. 1994. Methods for Derivation of Inhalation Reference Concentrations and Application of Inhalation Dosimetry. Office of Research and Development. EPA/ 600/ 8 90/ 066F. IRIS incorporates factors to account for uncertainties in the scientific database. The use of a LOAEL to derive the RfC for manganese is one of these uncertainties and is appropriately addressed through the application of uncertainty factors as part of the IRIS process.

We disagree with the commenter that we did not consider acute effects. We performed a risk assessment evaluating the potential acute effects of boiler emissions,

including manganese ( see docket item # OAR 2002 0058 0608). We used acute inhalation reference values, taken from the table on EPA's air toxics website ( www. epa. gov/ ttn/ atw/ toxsource/ table2. pdf), for all pollutants in this assessment. Although the commenter is correct that this table does not contain an AEGL value for manganese compounds, the table does contain an IDLH/ 10 value of 50 mg/ m3. This is the acute doseresponse value that we used, as reflected in table 3 ( converted to 50,000 ug/ m3) of the screening assessment memorandum ( OAR 2002 0058 0608). Thus, the commenter's assertion that the table on the website contains no acute dose response value or that EPA does not know what that value might be is incorrect. As described in the screening assessment memorandum, for HAP with more than one acute dose response value, the most health protective value was chosen. EPA has not prioritized these values. Since we only had one value for manganese, we used that value in our acute assessment. The results indicate that HAP emissions, including manganese, from the industrial boilers source category are unlikely to pose acute risks to human health.

Comment: Two commenters ( OAR 2002 0058 0683, OAR 2002 0058 0684) disagreed with the use of an HQ index for multi pathway pollutants.

Response: This rule is relying on CAA § 112( d)( 4), which requires us to evaluate ecological and multimedia human exposures when determining the applicability of §

112( d)( 4). To identify potential multi pathway and/ or ecological concerns, we have developed a list of HAP with the potential to persist in the environment and to bioaccumulate. This list does not include Mn, HCl, or Cl2, which are the only HAP relevant for the health based compliance alternatives under the final rule. Therefore,

facilities attempting to comply with the health based alternatives are not required to 38 perform a multi pathway analysis. Chapter 4 of Volume 1 in the Air Toxics Risk Assessment ( ATRA) Reference Library presents a complete list of the multi pathway pollutants.

Comment: Several commenters ( OAR 2002 0058 0671, OAR 2002 0058 0663, OAR

2002 0058 0666, OAR 2002 0058 0669, OAR 2002 0058 0682, OAR 2002 0058 0695, OAR

2002 0058 0687) agreed with the EPA's method for evaluating Mn and the basis of excluding Mn from the TSM emission limit for units that comply with the Mn health based compliance alternative. These commenters also stated this health based compliance alternative protects the public health.

One commenter ( OAR 2002 0058 0682) cited the EPA re analysis of the MACT floor based on 7 instead of 8 metals, and concluded that because Mn was only about 5% of the TSM,

the MACT floor remained the same. This commenter also supported the separate risk analysis for Mn.

One commenter ( OAR 2002 0058 0687) stated that without this change to base the TSM limit on 7 rather than 8 metals, wood fuel boilers would be required to install control technology to control Mn exclusively, or switch to a nonrenewable fuel. The commenter added that the controls would exceed one million per ton of Mn removed. The commenter added that wood fuel is recognized as a clean, renewable resource and that of the metals in the MACT list, AP 42 factors represent Mn to be 91.8% of the metallic HAP in wood fuels. The commenter contended that unlike other metals in the MACT list, Mn is not a carcinogen, rather it is a Class D pollutant.

The commenter concluded that Mn impacts human health only when humans are ` chronically exposed at high levels' and EPA would be acting in error to require expensive controls to meet the NESHAP standards when a risk to human health is not posed by these clean wood burning units. The commenter referenced a 1992 EPA Manganese Hazard Summary and 69 Fed. Register at 55222 to support the Mn health based compliance alternative and exclusion of Mn from the TSM analysis.

Four commenters disagreed ( OAR 2002 0058 0683, OAR 2002 0058 0684, OAR 2002

0058 0693, OAR 2002 0058 0694) with the appropriateness and lawfulness of the Mn healthbased compliance alternative and provided several reasons. Two commenters ( OAR 2002 0058

0683, OAR 2002 0058 0684) stated that EPA has not provided a justified explanation on the exclusion of Mn from the calculation of TSM. The commenters contended that although EPA 39 found the MACT floor to be the same whether or not Mn was included in the floor analysis, this reasoning does not justify removing Mn from the TSM limit.

One commenter ( OAR 2002 0058 0693) stated the mechanism through which the Mn compliance alternative operates unlawfully allows plants with low Mn emissions to avoid controlling the emissions of other non mercury metals. Although the commenter recognized no change in the MACT floor analysis for TSM based on seven instead of eight metals, the commenter suggested that EPA did not provide and explanation of this result. Further, the commenter suggested that top performing sources used to calculate the MACT floor may have low Mn emissions because existing controls at the source may reduce Mn emissions, such that the TSM emission limit would not be affected by the incorporation of Mn concentrations. The commenter emphasized that dirtier sources would also be allowed to exclude Mn from their TSM limit calculations and as a result be allowed to emit higher levels of Mn and the other seven metals included in the TSM standard.

Response: We believe the alternative TSM emissions limit for sources that qualify for the health based alternative is technically sound and supported by the record. The alternative emissions limitation set forth in section 63.7507( b) of subpart DDDD is a MACT ( technology based) standard for seven metals ( excluding manganese). This alternative MACT emissions limit is applicable only to those sources who qualify for the health based compliance alternative for TSM based on their emissions of manganese. The manganese emissions from these sources are subject to the health based alternative standard, which is enforceable through the operating conditions in the Title V permit of sources that successfully demonstrate eligibility for the health based alternative. However, the remaining seven metals that are included in the TSM calculation must still be subject to a MACT ( technology based) emissions limitation. As a result, we derived an alternative MACT emissions limit for these seven selected metals using the same MACT methodology that we used for other emissions limits in subpart DDDDD. Only sources that qualify for the health based alternative for TSM are eligible to apply this alternative TSM MACT limit in section 63.7507( b) because the manganese emissions are otherwise controlled to health based levels through the operating conditions in the Title V permit established pursuant to appendix A.

The methodology for the MACT floor analysis conducted for establishing this 40 alternative, technology based TSM limit is described in the memorandum " MACT Floor Analysis for the Industrial, Commercial, and Institutional Boilers and Process Heaters National Emission Standards for Hazardous Air Pollutants" in the docket. When we investigated the possibility of establishing an alternative TSM emission limit for these 7 metals, we performed the same MACT floor analysis that we conducted for the TSM emission limit for 8 metals. That is, we reexamined the emission test data for solid fuel units that included emissions results for all of the eight total selected metals ( arsenic,

beryllium, cadmium, chromium, lead, manganese, nickel, and selenium) with manganese removed from the summation. The technology based TSM limit for these seven metals ( excluding manganese) resulted in a MACT floor emission level for existing large solid fuel units of 0.001 lb/ mmBtu. This is the same level as the eight metal ( including manganese)

TSM MACT emission level proposed and promulgated for existing large solid fuel units.

Our MACT floor analysis for new solid fuel units achieved the same result. Thus, rather than repeating the emissions limit already contained in Table 1 of the rule in section 63.7507( b), we expressed the alternative, technology based TSM limit for these 7 metals for eligible sources as a requirement to meet the same emissions limitation without counting manganese.

The seven metal and eight metal technology based TSM limit were the same because the manganese emissions from the unit serving as the basis for the limit only accounted for less than 5 percent of the total selected metals. When we conducted our MACT floor analysis for the seven metals standard, we determined that the unit we used as the basis for the setting the TSM limit for 8 metals was the same as the unit selected under the analysis for 7 metals.

We understand, but do not agree with commenters concerns that allowing sources to exclude manganese from their TSM limit calculation will result in higher emissions of the other seven metals. Based on the available data, we do not expect sources other than biomass fired source to qualify for the health based alternative for manganese and TSM.

The record does not indicate that sources using biomass fuels emit significant quantities of metals other than manganese. Thus, while in theory the exclusion of manganese from the TSM limitation could allow an eligible source to increase emissions of the other seven metals, the record does not indicate that eligible sources are capable of doing so. 41 The TSM limit in the final rule was included at proposal because the Agency was sensitive to the fact that some sources burn fuels ( e. g, biomass) that contain very little metals but have sufficient PM emissions to require control under the PM provision of the rule. In these cases, we did not think that PM would be an appropriate surrogate for metallic HAP. Under the rules in subpart DDDDD, a source may choose to comply with the alternative TSM emission limit instead of the PM limit. The eight metals included in the TSM summation represent the most common and the largest emitted metallic HAP from boilers and process heaters. Based on the impacts analysis done for the rule, the TSM emission limit would minimize the impacts on small entities ( e. g., furniture industry, sugar cane industry) since some of the potential small entities burn biomass.

Biomass ( e. g., wood, bagasse, peanut hulls, etc.) generally does not contain measurable amounts of metals except for manganese. For example, fuel analyses of bagasse from sugar cane mills in Louisiana did not detect any of the metals except for manganese.

Fuel analyses of bagasse from sugar cane mills in Florida only detected manganese, lead,

and selenium, with lead and selenium totaling 0.00032 lb/ MM Btu, and this is assuming that all the metals in the fuel is emitted which would not be the case due to some remaining in the bottom ash. Wood also contains little metals except for manganese. Fuel analyses of wood combusted as fuel at three furniture facilities detected only manganese. Fuel analysis at another furniture facility did detect cadmium, chromium, and nickel beside manganese,

but the total of those three metals ( 0.00005 lb/ MM Btu) was only 1.3 percent the level of manganese or 5 percent of the TSM limit. Other biomass materials, such as peanut hulls,

used as fuel also have similar metals composition. Fuel analysis conducted by EPA on peanut hulls only detected the presence of manganese.

The metal makeup of biomass differs greatly from coal. Coal contains detectable levels of all 8 metals. Fuel analyses from six coal fired facilities indicate that even if a coalfired facility could demonstrate eligibility with the TSM health based compliance alternative and may exclude manganese emissions, it would still require highly efficient PM control to achieve the TSM limit. Thus, when we promulgated the TSM health based compliance alternative, we believed, and still believe that only biomass units will seek to demonstrate that they do not need to employ PM controls by showing they qualify to exclude manganese from the TSM compliance demonstration, since manganese is the 42 principal metal in biomass while manganese only makes up a small fraction of the metals contained in coal. 43 Chapter 9 Deadline for Submission of Eligibility Demonstration Comment: Multiple commenters ( OAR 2002 0058 0672, OAR 2002 0058 0681, OAR

2002 0058 0688, OAR 2002 0058 0671, OAR 2002 0058 0681, OAR 2002 0058 0675, OAR

2002 0058 0679, OAR 2002 0058 0692, OAR 2002 0058 0696, OAR 2002 0058 0697, OAR

2002 0058 0698) did not deem it necessary for the Agency to extend the deadline for the submission of eligibility or final compliance dates provided that certain timelines and components of the health based compliance alternatives were maintained as a result of this reconsideration.

Three commenters ( OAR 2002 0058 0672, OAR 2002 0058 0681, OAR 2002 0058 0688) did not feel an extension of the deadline for the submission of eligibility was necessary provided that this reconsideration is completed in a timely manner. One commenter ( OAR 2002 0058 0681)

specified a timeframe of the end of 2005 for the conclusion of this reconsideration. Three commenters ( OAR 2002 0058 0671, OAR 2002 0058 0688, OAR 2002 0058 0665) did not feel it was necessary for the Agency to extend the deadlines for submission of eligibility or compliance on the condition that the health based compliance alternative remains intact, and without substantive changes to the present format, as a result of this reconsideration and ongoing litigation. These commenters reasoned a change to the health based compliance alternative would limit the available compliance options, and place high demand on the associated equipment manufacturers and consulting engineers required to meet deadlines.

One commenter ( OAR 2002 0058 0665) stated that governmental organizations will require more time than private industries to adjust compliance plans due to funding restrictions.

This commenter also specified additional steps the EPA should take in the event that major changes to the health based compliance alternative methodologies or HI/ HQ values occur: ( 1)

alert all source owners who have submitted Initial Notification Reports; ( 2) ensure affected sources are allowed to comment on any changes; and, ( 3) extend the deadline to three years after promulgation of amendments. 44 Six of these commenters ( OAR 2002 0058 0675, OAR 2002 0058 0679, OAR 2002

0058 0692, OAR 2002 0058 0696, OAR 2002 0058 0697, OAR 2002 0058 0698) requested the Agency presume the extension period offered in 112( d)( i)( 3)( B) is available to all affected sources in contrast to an extension provision that would require approval on a site specific basis by the associated permitting authority only if this reconsideration substantially alters the ability of small municipal generators to utilize the health based compliance alternatives.

Several commenters ( OAR 2002 0058 0666, OAR 2002 0058 0669, OAR 2002 0058

0674, OAR 2002 0058 0695, OAR 2002 0058 0694, OAR 2002 0058 0687) requested that the Agency consider including an extension of at least one year to both the submission of eligibility and final compliance dates in the final rule. These commenters added that the uncertainties resulting from this reconsideration and ongoing litigation have made the original deadlines impractical. One commenter ( OAR 2002 0058 0687) emphasized that it is necessary to maintain a one year period between the eligibility demonstration and the final compliance date such that facilities have time to install controls if they fail their eligibility demonstration. The commenter added that there are limited technical resources, equipment vendors, and installation contractors available to develop and implement control based compliance strategies in the event that the health based compliance alternative is not available. One commenter ( OAR 2002 0058 0694)

stated that the Agency should consider including an extension to the deadline for submission of eligibility because permit authorities will require this additional time in order to process the eligibility submissions prior to the MACT compliance date if the health based compliance alternatives remain intact as a result of this reconsideration. One commenter ( OAR 2002 0058

0673) requested the Agency presume the extension period offered in 112( d)( i)( 3)( B) is available to all affected sources in contrast to an extension provision that would require approval on a sitespecific basis by the associated permitting authority. The commenter added that while the original deadline was reasonable at promulgation, the deadline is no longer practical due to an uncertainty of whether the health based compliance alternative will remain intact as a result of both this reconsideration and ongoing litigation. The commenter projected that litigation will not be concluded until 2007 and stated that the result would require facilities to choose between risking noncompliance and foregoing the health based compliance alternative option.

One commenter ( OAR 2002 0058 0693) disagreed with the need to extend the submission of eligibility demonstration or compliance dates of affected sources under any 45 circumstances. The commenter contended that an extension will only further delay sources'

installation of the pollution controls that are required by the Act. The commenter also stated it is unlawful to extend compliance dates of affected sources. The commenter cited 42 U. S. Code section 7412( i)( 3)( A) "  but in no event later than 3 years after the effective date of such standard" to support this claim. This commenter emphasized that EPA should not use the exemption provided for in section 112( i)( 3)( B) for sources that fail eligibility requirements for the health based compliance alternatives and are left with a short period of time to install controls.

The commenter added that section 112( i)( 3)( B) was intended to be used only when technological limitations make timely compliance impossible.

Response: We do not believe it is appropriate at this time to adjust the deadline for submitting eligibility demonstrations. Most commenters representing the regulated industry believed that they would not need an extension if EPA met certain conditions.

EPA has met the conditions outlined by these commenters. We have completed the reconsideration in a timely manner and have not made significant changes to the rule. As stated in the notice of reconsideration ( 70 FR 36913), we did not anticipate that significant changes would be made as a result of this reconsideration, and we advised affected sources to " proceed to prepare their eligibility demonstrations under the existing process promulgated in the final rule." Although we are making some clarifying amendments, we are not changing the final rule substantially. Thus, this action will not have the impact on the eligibility demonstration process that concerned several other commenters. Therefore,

we do not believe an extension is necessary in order for sources to complete their eligibility demonstrations by September 2006.

In addition, we do not have cause to extend the compliance date for existing sources.

Section 112( i)( 3)( A) of the CAA specifies that NESHAP for existing sources can have compliance dates of no more than 3 years. For the ICI boiler and process heater NESHAP,

EPA provided the maximum 3 years for covered sources to comply with the new standards.

It is not unusual for promulgation of CAA standards to be followed by litigation or petitions for reconsideration. Section 307( b)( 1) of the Act specifically provides that the filing of a petition for reconsideration of a rule does not postpone the effectiveness of a rule.

To date, EPA has not, during the pendency of a reconsideration request, extended the 46 compliance deadlines for promulgated MACT standards to provide compliance periods in excess of the statutory 3 year maximum. In contrast, where the Agency has amended a MACT standard in a significant way we have found it appropriate to set a new compliance date for the rule that takes into account new requirements not contained in the original rule.

In this action for ICI boilers and process heaters, we are making relatively minor clarifying amendments to the eligibility demonstration methodology for the health based alternatives and have not reconsidered or changed any aspect of the technology based MACT standards. EPA indicated in its reconsideration notice that we were unlikely to change the compliance deadline and that the petitions for reconsideration had not provided new information suggesting a need for significant changes to the applicability demonstration methodology for the health based alternatives. 70 Fed. Reg. at 36910,

36913. Thus, affected source were on notice that significant changes to health based alternatives were not anticipated, Furthermore, we indicated that we intended to complete this reconsideration action expeditiously to shorten any uncertainty that may have been created by our partial granting of these petitions for reconsideration. 70 Fed. Reg. at 36910. The time required to complete this reconsideration process has not been extraordinarily lengthy.

We disagree with the request to provide a blanket compliance date extension for all sources in the category under section 112( i)( 3)( B) of the CAA. The granting of an extension under this provision is up to the individual permitting authorities, and is restricted to specific situations where a source can demonstrate that such time is necessary for the installation of controls. We have not been provided with sufficient evidence to show that all sources in the category would be able to ( or even have a need to) make such a showing. 47 Chapter 10 Proposed Corrections Comment: Three commenters ( OAR 2002 0058 0683, OAR 2002 0058 0693, OAR

2002 0058 0694) disagreed with the proposed correction to extend the risk based exemptions beyond the large solid fuel subcategory. These commenters believed the expansion of the healthbased compliance alternative to other subcategories to be significant rule change which would require a separate formal rule making process with public notice and a comment period. These commenters expressed concern that this correction will allow more sources, specifically smaller sources with shorter stacks that tend to be located closer to populous regions, to become eligible for the risk based exemptions. One commenter ( OAR 2002 0058 0683) added that the analysis of TSM contained in the docket was specific to large solid fuel units and not all units in which the proposed correction seeks to offer applicability. One commenter ( OAR 2002 0058 0693) cited seven sections within the final rule language that specify the exemption applicability to large solid fuel fired sources. Additionally, the commenter contended that there was no analysis of the costs or emission impacts for extending the exemptions to all units. The commenter referenced docket item OAR 2002 0058 606 to show that the current analysis excludes other unit types.

Two commenters ( OAR 2002 0058 0688, OAR 2002 0058 0672) agreed with the proposed corrections to the rule, which allowed all industrial boilers to use the health based compliance alternatives. The commenters added that there is no technical reason why the type of unit or fuel burned should restrict a facility from the right to demonstrate eligibility.

Response: We do not agree that a separate rulemaking proceeding is necessary to adopt the proposed correction to clarify that sources in all subcategories may demonstrate eligibility for the health based compliance alternatives. Although this correction was coupled with EPA's response to a Petition for Reconsideration, EPA has provided notice and an opportunity to comment on the proposed changes to the text of the regulation in accordance with the rulemaking requirements of section 307( d) of the Clean Air Act. 48 Commenters have not cited legal authority in the Clean Air Act or elsewhere that requires EPA to address an allegedly " significant" change to a rule in a separate or independent rulemaking action.

We acknowledge that our original intent with respect to the scope of the healthbased compliance alternatives is unclear and contradictory. EPA included language in section 63.7507( a) of the rule that limits the applicability of the health based compliance alternative for HCl to sources in the large solid fuel fired subcategory. We also made several statements in the preamble, highlighted by the commenters, which indicate an intent to limit one or both health based alternatives to large solid fuel sources. These statements were made because the existing solid fuel fired units at major sources are the main category of sources potentially affected by the health based compliance alternatives.

Furthermore, the number of new small solid fuel fired units at major sources projected in the future ( see Docket item OAR 2002 0058 0024) is relatively small. However, we also took certain actions in the final rule which show an intent to allow sources in all subcategories to demonstrate eligibility for the health based compliance alternatives. For example, we did not include language in section 63.7507( b) of the rule that limits the health based alternative for TSM to sources in the large solid fuel subcategory. Likewise,

we did not include any language in section 2 of Appendix A limiting the health based alternative for HCl to just sources in the large solid fuel subcategory. In that provision, we said that " each new, reconstructed, or existing source may demonstrate that they are eligible for the health based compliance alternatives." Thus, the bottom line is that various portions of September 14, 2004 final rule and preamble are inconsistent on the intended scope of eligibility for the health based compliance alternatives.

As a result of these inconsistencies, we proposed a correction that would make these elements of the final rule consistent. Although we indicated in the proposal that this correction was intended to reflect our original intent, we agree that this terminology was imprecise. Given the conflicting statements and regulatory text in the final rule cited above, we concede that the Agency's original intent was not clear one way or the other. To remedy this confusion, we are resolving the inconsistency by eliminating regulatory language that could be read to limit one or both of the health based alternatives to only sources in the large solid fuel category. Thus, we are taking the action we proposed, which 49 is to delete the words " for large solid fuel boilers located at a single facility'' from §

63.7507( a) and the words `` Specified for the Large Solid Fuel Subcategory'' from the title of appendix A.

Because large solid fuel fired units are not the only units that have applicable Mn and HCl MACT limits, we believe it is technically correct, and appropriate, to allow all affected sources with Mn and HCl limits the opportunity to demonstrate eligibility for the health based compliance alternatives. Where EPA has determined that no adverse health effects are expected below a certain threshold level of exposure, there is no reasoned basis for precluding smaller industrial boilers and process heaters from using the health based compliance alternative so long as their emissions do not result in human exposure above the designated threshold value. To the extent we are expanding the availability of the healthbased compliance alternative to all sources; this will not subject the public to adverse health effects.

We do not believe health risks are increased by allowing smaller sources to qualify for the health based compliance alternatives, even if the commenters are correct that these sources tend to have shorter stacks and are closer to populous areas. The changes we are making in this rule do not automatically make all small sources eligible for the health based compliance alternatives. Such sources must still demonstrate eligibility under the procedures and criteria in Appendix A, which consider stack heights and distance to populated areas in determining eligibility. If these characteristics indicate that a particular source has emissions that pose risks above the threshold levels, the source will not be eligible for the health based compliance alternative. In addition, emissions rates are also part of the analysis under appendix A. Because small sources have lower emissions rates,

all other things being equal, small sources present less risk than large sources.

We do not believe this correction to the rule requires an extensive re analysis of the cost or emissions reduction impacts of the health based compliance alternatives. We have sufficient information to conclude that this correction will not result in a meaningful change to the cost or emissions impacts of the rule.

In the final rule, the cost and economic analyses developed as part of the final MACT rulemaking were based on the estimated costs for all affected sources to install,

maintain, and operate controls and to comply with MACT requirements. Costs were not 50 based on the health based compliance alternatives since the cost of compliance with controls is significantly higher than the cost to comply with the health based compliance alternatives. The costs associated with voluntarily conducting risk analyses were not analyzed and therefore not re analyzed to account for this correction to the applicability of the health based alternatives to all affected units.

Our supplemental analysis of the impact on control costs and emissions reductions resulting from adoption of the health based alternatives cited by commenter ( OAR 2002

0058 606) showed that the estimated costs of the final rule would be lower if the healthbased provisions were adopted. This " rough assessment" of the number of sources that would qualify for the health based alternatives focused on large sources because these sources were the sources most likely to seek to demonstrate eligibility to comply with the health based alternatives.

Based on the available information on sources in the category, we do not expect this correction to enable a significant number of additional sources to qualify for the healthbased alternatives. Thus, this correction to the rule will not result in a dramatic difference in our rough control cost and emissions reduction estimates. Since we evaluated the costs of the rule without the health based compliance alternatives, we have no reason to believe this change will increase compliance costs above these high end estimates. The analysis we have conducted in this reconsideration proceeding is sufficient to enable us to conclude that compliance costs will not be significantly different if a few additional sources are able to demonstrate eligibility as a result of this correction. For similar reasons, we do not have a basis to believe this change dramatically alters the emissions reductions that will be achieved under the rule.

We adopted the health based alternatives in part to reduce the compliance costs of the NESHAP while continuing to maintain the health protection called for in the Clean Air Act. The potential for this correction to reduce compliance costs further does not undermine this reason for adopting health based compliance alternatives. We did not rely on these cost and emission reduction estimates as a basis for establishing technology based MACT emissions limitations or the eligibility criteria for the health based compliance alternatives. We conducted the cost and emission reduction estimates in order to present a summary of the environmental and economic impacts of final rule. The estimates included 51 in our supplemental analysis of the impact on control costs and emission reductions were presented in order to provide a comparative summary of impacts of the final rule based on a rough estimate of facilities that might opt to comply with the health based compliance alternatives. Additionally, these cost estimates are necessary in order complete several Statutory and Executive Order Reviews including: The Paperwork Reduction Act, The Regulatory Flexibility Act, and The Unfunded Mandates Reform Act of 1995. 52 Chapter 11 Review of Eligibility Demonstrations for Health Based Compliance Alternatives and Title V Permit Conditions 11.1 Eligibility and Permit Authority Review Comment: Three commenters ( OAR 2002 0058 0683, OAR 2002 0058 0670, OAR

2002 0058 0684) believed that applicability of the health based compliance alternatives depends on approval from a permitting authority via issuance of a Title V permit that includes enforceable alternative limits. One of these commenters ( OAR 2002 0058 0670) requested that EPA clarify in sections 9 and 10 of appendix A that each facility's compliance with health based compliance alternative is dependent on the approval from a permitting authority via issuance of a Title V permit that includes the alternative limits. The commenter added, if the off ramp risk determination is not approved, the facility must comply with the NESHAP requirements. Two commenters ( OAR 2002 0058 0670, OAR 2002 0058 0684) stated that permitting authorities have the authority to disapprove a risk assessment demonstration if it is deemed incomplete or incorrect. One commenter ( OAR 2002 0058 0694) requested a clarification in the rule to specify the authority of a permitting agency to verify or reject flawed submittals for eligibility to the health based compliance alternatives at both tiers.

One commenter ( OAR 2002 0058 0667) opposed a requirement to obtain EPA or state agency approval of the site specific risk assessments as currently stated in the HWC rule. The commenter believed that requiring approval would likely create delays in the eligibility process and result in very short compliance timelines if a reviewing authority rejected a site specific assessment or did not complete the review in a timely manner. The commenter added there is no technical justification for requiring approval in the HWC MACT rule and recommended not doing so in the boiler and process heater rule.

Response: We agree that the preferred approach is to not require affirmative approval by the permitting authority of each risk assessment before a source is eligible to 53 comply with the health based alternative. Thus, under the procedures in Appendix A of subpart DDDDD, as revised in this rule, a source becomes eligible to comply with the health based alternatives at the time its submits an eligibility demonstration meeting the requirements of section 8 of Appendix A.

However, for a source to remain eligible to comply with the health based alternatives, the eligibility demonstration must be complete and the application for a permit modification must ultimately be approved by the permitting authority. Thus, as part of this process, permitting agencies do have the authority to review eligibility demonstrations to verify that they meet the requirements of Appendix A and are technically sound. For example, a permitting authority may notify a source that its eligibility demonstration is deficient if the demonstration is incomplete or if a look up table analysis is performed in a situation when site specific conditions exist that make the use of the look up tables inappropriate. Based upon the technical findings of the review,

permitting agencies have the authority to inform a source that it is no longer eligible for the health based alternative if the eligibility demonstration is deficient. EPA will also review some demonstrations as part of an audit program.

This review authority derives from the Title V permit program through which the health based compliance alternatives are implemented, and it was inherent in the rule when promulgated on September 14, 2004. Subpart DDDDD contains applicable requirements that are incorporated in Title V permits. The Title V permit program provides a process for identifying and consolidating all of the applicable requirements for each source. Through this process, the permit authority reviews each application to verify the applicable requirements for each source. Thus, when a source submits a demonstration of eligibility for the health based alternatives in subpart DDDDD, the Title V permitting authority has the ability to review this submission to determine whether the applicable requirements for that source are the health based or the technology based requirements in subpart DDDDD.

However, to clarify this issue, we are adding explicit language in sections 10 and 11 of appendix A to make clear that permitting agencies may review each facility's eligibility demonstration. If the permitting authority identifies deficiencies with the eligibility determination or the permit modification is eventually disapproved based on technical 54 problems with the eligibility demonstration, then the facility is no longer eligible for the health based alternative and must comply with the MACT emission standards by the compliance dates specified in 63.7495.

For new sources, we are establishing a slightly different procedure because new sources will be relying upon the health based alternative at start up. In these cases, the source will have a grace period of 30 to 90 days to correct any deficiencies before ceasing to be eligible for the health base alternative. This grace period is not needed for existing sources because their eligibility demonstrations must be submitted 12 months prior to the compliance date. We believe this provides sufficient time for permitting authorities to notify sources of any deficiencies and for a source to correct any deficiencies.

Comment: Three commenters ( OAR 2002 0058 0666, OAR 2002 0058 0669, OAR

2002 0058 0674) requested that EPA clarify the deadline for compliance for sources whose health based eligibility determination is found to be deficient . These commenters also suggested an allowance period of 12 months after the facility receives notice of a deficiency in their healthbased eligibility determination.

Two commenters ( OAR 2002 0058 0676, OAR 2002 0058 0677) stated that the healthbased compliance alternative will delay compliance with MACT for sources that attempt to unsuccessfully demonstrate eligibility with the health based compliance alternatives.

Response: We disagree that there will be a delay in compliance caused by the health based compliance alternatives. Sources that submit eligibility demonstrations in an attempt to comply with the health based compliance alternative but do so unsuccessfully must still be in compliance within 3 years after the standard was promulgated. We do not believe it is appropriate to automatically extend the compliance date in these situations. As noted above, for existing sources, there is a one year window in which permitting authorities and sources can work out any deficiencies in an eligibility demonstration. The health based compliance alternative is an optional compliance approach. Some risk is involved in electing to comply with the MACT standard via the health based compliance alternatives. This assumed risk could include a shorter amount of time to install the controls that are required to meet technology standards in the event that a source does not submit a health based eligibility demonstration that meets the requirements of Appendix A. We do not necessarily endorse the use section 112( i)( 3)( B) to grant compliance date 55 extensions in these circumstances. However, we will leave the decision of whether to grant such a compliance date extension on a site specific basis to permitting authorities.

11.2 Significant Permit Modifications Comment: One commenter ( OAR 2002 0058 0688) disagreed with the Agency's basis for concluding that the incorporation of the health based compliance alternatives into a Title V permit would require a significant permit modification under Title V requirements, although the commenter did not disagree that a significant permit modification process would be appropriate.

The comment believes that the minor permit modification " gatekeeper" contained in 40 CFR §

70.7( e)( 2)( i)( A)( 4) of our regulations is not applicable because there is an underlying applicable requirement reflected in the NESHAP. Instead, according to the commenter , EPA should rely on the gatekeeper in 40 CFR § 70.7( e)( 2)( i)( A)( 3) which prohibits use of minor modification procedures where a provision would require, or change, a case by case determination of an emission limitation or another standard during the Title V permit process. The commenter added that this provision ensures when the Title V process is the vehicle for establishing the limit for a facility, as opposed to incorporating citations from existing rules, significant modification procedures apply. The commenter concluded that the Title V procedures apply because there is no other permit or regulation that includes the appropriate level of process for the health based compliance alternatives.

Response: We partially agree and partially disagree with the commenter. After further consideration of the issue, EPA agrees with the commenter that we should not have concluded that significant permit modifications procedures would apply on the basis of the minor permit modification gatekeeper in 40 CFR 70.7( e)( 2)( i)( A)( 4). However, after further consideration of this issue, we believe that permitting authorities should rely on the reopening provisions, rather than the significant permit modification process, when the health based alternatives are initially incorporated into an existing Title V permit.

The health based compliance alternatives are emissions limitations based on section 112( d)( 4) of the Act. These limitations are alternative standards for threshold pollutants based on health considerations, rather than the technology based MACT criteria. As a 56 result, EPA considers the health based alternatives to be applicable requirements in the same manner that the MACT based emissions limitations contained in 40 CFR Part 63,

Subpart DDDDD are also applicable requirements. See the definition of " applicable requirement" found in 40 CFR 70.2 and 71.2. The applicable requirements under the health based alternatives include the parameters that define the affected source as eligible for the health based compliance alternatives. Thus, sources that successfully demonstrate eligibility to comply with the health based alternatives instead of the technology based MACT standards are selecting among two different sets of applicable requirements under Subpart DDDDD.

Given that the health based alternative emissions standards that result from the process outlined in the ICI boiler and process heater NESHAP are applicable requirements,

the initial incorporation of these applicable requirements into an existing title V permit should be accomplished using the reopening provisions found in 40 CFR 70.7( f)( 1)( i) or 71.7( f)( 1)( i). Section 70.7( f)( 1)( i) specifies that a permit shall be reopened and revised when " additional applicable requirements under the Act become applicable to a major Part 70 source  ." Regardless of which of the applicable requirements is being incorporated into the permit of a boiler or process heater ( whether technology based or health based), the process for incorporating additional applicable requirements into title V permits should follow the procedures outlined in the reopening provisions of 40 CFR § 70.7( f)( 1)( i) or §

71.7( f)( 1)( i). This approach is consistent with what we said in our recent rule for Hazardous Waste Combustors.