Federal Register: February 6, 2007 (Volume 72, Number 24)Proposed RulesPage 5509-5550From the Federal Register Online via GPO Access [wais.access.gpo.gov]
DOCID:fr06fe07-20[Page 5509]Part II
Environmental Protection Agency40 CFR Part 60
Standards of Performance for New Stationary Sources and Emission Guidelines for Existing Sources: Hospital/Medical/Infectious Waste Incinerators; Proposed Rule
[Page 5510]ENVIRONMENTAL PROTECTION AGENCY40 CFR Part 60
EPA-HQ-OAR-2006-0534; FRL-8274-9RIN 2060-A004Standards of Performance for New Stationary Sources and Emission Guidelines for Existing Sources: Hospital/Medical/Infectious Waste Incinerators
AGENCY: Environmental Protection Agency (EPA).
ACTION: Proposed rule.
SUMMARY: On September 15, 1997, EPA adopted new source performance standards (NSPS) and emission guidelines for hospital/medical/ infectious waste incinerators (HMIWI). The NSPS and emission guidelines were established under sections 111 and 129 of the Clean Air Act (CAA). On November 14, 1997, the Sierra Club and the Natural Resources Defense Council (Sierra Club) filed suit in the U.S. Court of Appeals for the District of Columbia Circuit (the Court) challenging EPA's methodology for adopting the regulations. On March 2, 1999, the Court issued its opinion. The Court remanded the rule to EPA for further explanation of the Agency's reasoning in determining the minimum regulatory ``floors'' for new and existing HMIWI. The Court did not vacate the regulations, so the NSPS and emission guidelines remained in effect during the remand and were fully implemented by September 2002. This action provides EPA's proposed response to the questions raised in the Court's remand.
Section 129(a)(5) of the CAA requires EPA to review and, if appropriate, revise the NSPS and emission guidelines every 5 years. In this action, EPA also is proposing our response to this 5-year review, which would revise the emission limits in the NSPS and emission guidelines to reflect the levels of performance actually achieved by the emission controls installed to meet the emission limits set forth in the September 15, 1997, NSPS and emission guidelines.
DATES: Comments. Comments must be received on or before April 9, 2007. Under the Paperwork Reduction Act, comments on the information collection provisions must be received by the Office of Management and Budget (OMB) on or before March 8, 2007. Because of the need to resolve the issues raised in this action in a timely manner, EPA will not grant requests for extensions beyond these dates.
Public Hearing. If anyone contacts EPA by February 26, 2007 requesting to speak at a public hearing, EPA will hold a public hearing on March 8, 2007. If you are interested in attending the public hearing, contact Ms. Pamela Garrett at (919) 541-7966 to verify that a hearing will be held.
ADDRESSES: Submit your comments, identified by Docket ID No. EPA-HQ- OAR-2006-0534, by one of the following methods:
http://www.regulations.gov: Follow the on-line instructions for submitting
comments.
E-mail: Send your comments via electronic mail to a-and-r-Docket@epa.gov, Attention Docket ID No. EPA-HQ-OAR-2006-0534.
Facsimile: Fax your comments to (202) 566-1741, Attention Docket ID No. EPA-HQ-OAR-2006-0534.
Mail: Send your comments to: EPA Docket Center (EPA/DC), Environmental Protection Agency, Mailcode 6102T, 1200 Pennsylvania Ave., NW., Washington, DC 20460, Attention Docket ID No. EPA-HQ-OAR- 2006-0534.
Hand Delivery: Deliver your comments to: EPA Docket Center (EPA/ DC), EPA West Building, Room 3334, 1301 Constitution Ave., NW., Washington, DC 20460, Attention Docket ID No. EPA-HQ-OAR-2006-0534. Such deliveries are accepted only during the normal hours of operation (8:30 a.m. to 4:30 p.m., Monday through Friday, excluding legal holidays), and special arrangements should be made for deliveries of boxed information.
Instructions: Direct your comments to Docket ID No. EPA-HQ-OAR- 2006-0534. The EPA's policy is that all comments received will be included in the public docket and may be made available online at http://www.regulations.gov, including any personal information provided,
unless the comment includes information claimed to be Confidential Business Information (CBI) or other information whose disclosure is restricted by statute. Do not submit information that you consider to be CBI or otherwise protected through http://www.regulations.gov or e-mail.
The http://www.regulations.gov Web site is an ``anonymous access'' system,
which means EPA will not know your identity or contact information unless you provide it in the body of your comment. If you send an e- mail comment directly to EPA without going through http://www.regulations.gov,
your e-mail address will be automatically captured and included as part of the comment that is placed in the public docket and made available on the Internet. If you submit an electronic comment, EPA recommends that you include your name and other contact information in the body of your comment and with any disk or CD-ROM you submit. If EPA cannot read your comment due to technical difficulties and cannot contact you for clarification, EPA may not be able to consider your comment. Electronic files should avoid the use of special characters, any form of encryption, and be free of any defects or viruses.
Public Hearing: If a public hearing is held, it will be held at EPA's Campus located at 109 T.W. Alexander Drive in Research Triangle Park, NC, or an alternate site nearby. Persons interested in presenting oral testimony must contact Ms. Pamela Garrett at (919) 541-7966 at least 2 days in advance of the hearing.
Docket: EPA has established a docket for this action under Docket ID No. EPA-HQ-OAR-2006-0534 and Legacy Docket ID No. A-91-61. All documents in the docket are listed in the http://www.regulations.gov index.
Although listed in the index, some information is not publicly available, e.g., CBI or other information whose disclosure is restricted by statute. Certain other material, such as copyrighted material, will be publicly available only in hard copy form. Publicly available docket materials are available either electronically at http://www.regulations.gov or in hard copy at the EPA Docket Center EPA/DC,
EPA West, Room 3334, 1301 Constitution Ave., NW., Washington, DC. The Public Reading Room is open from 8:30 a.m. to 4:30 p.m., Monday through Friday, excluding legal holidays. The telephone number for the Public Reading Room is (202) 566-1744, and the telephone number for the EPA Docket Center is (202) 566-1742.
FOR FURTHER INFORMATION CONTACT: Ms. Mary Johnson, Energy Strategies Group, Sector Policies and Programs Division (D243-01), Environmental Protection Agency, Research Triangle Park, North Carolina 27711; telephone number: (919) 541-5025; fax number: (919) 541-5450; e-mail address: johnson.mary@epa.gov.
SUPPLEMENTARY INFORMATION: Organization of This Document. The following outline is provided to aid in locating information in this preamble. I. General Information
A. Does the proposed action apply to me?
B. What should I consider as I prepare my comments? II. Background III. Summary
A. Litigation and Proposed Remand Response
[Page 5511]B. Proposed Amendments (CAA Section 129(a)(5) 5-Year Review) IV. Rationale
A. Rationale for the Proposed Response to the Remand
B. Rationale for the Proposed Amendments (CAA Section 129(a)(5) 5-Year Review) V. Impacts of the Proposed Action for Existing Units
A. What are the primary air impacts?
B. What are the water and solid waste impacts?
C. What are the energy impacts?
D. What are the secondary air impacts?
E. What are the cost and economic impacts? VI. Impacts of the Proposed Action for New Units VII. Relationship of the Proposed Action to Section 112(c)(6) of the CAA VIII. Statutory and Executive Order Reviews
A. Executive Order 12866: Regulatory Planning and Review
B. Paperwork Reduction Act
C. Regulatory Flexibility Act
D. Unfunded Mandates Reform Act
E. Executive Order 13132: Federalism
F. Executive Order 13175: Consultation and Coordination with Indian Tribal Governments
G. Executive Order 13045: Protection of Children from Environmental Health and Safety Risks
H. Executive Order 13211: Actions That Significantly Affect Energy Supply, Distribution or Use
I. National Technology Transfer Advancement Act
I. General Information
A. Does the proposed action apply to me?
Regulated Entities. Categories and entities potentially affected by the proposed action are those which operate HMIWI. The NSPS and emission guidelines for HMIWI affect the following categories of sources:
Examples of Category
NAICS Code
potentially regulated entities
Industry..................................... 622110, 622310, 325411, 325412, 562213, Private hospitals, 611310.
other health care facilities, commercial research laboratories, commercial waste disposal companies, private universities. Federal Government........................... 622110, 541710, 928110...................... Federal hospitals, other health care facilities, public health service, armed services. State/local/Tribal Government................ 622110, 562213, 611310...................... State/local hospitals, other health care facilities, State/ local waste disposal services, State universities.
This table is not intended to be exhaustive, but rather provides a guide for readers regarding entities likely to be affected by the proposed action. To determine whether your facility would be affected by the proposed action, you should examine the applicability criteria in
40 CFR 60.50c of subpart Ec and
40 CFR 60.32e of subpart Ce. If you have any questions regarding the applicability of the proposed action to a particular entity, contact the person listed in the preceding FOR FURTHER INFORMATION CONTACT section.
B. What should I consider as I prepare my comments?
1. Submitting CBI
Do not submit information that you consider to be CBI electronically through http://www.regulations.gov or e-mail. Send or deliver
information identified as CBI to only the following address: Ms. Mary Johnson, c/o OAQPS Document Control Officer (Room C404-02), U.S. EPA, Research Triangle Park, NC 27711, Attention Docket ID No. EPA-HQ-OAR- 2006-0534. Clearly mark the part or all of the information that you claim to be CBI. For CBI information in a disk or CD ROM that you mail to EPA, mark the outside of the disk or CD ROM as CBI and then identify electronically within the disk or CD ROM the specific information that is claimed as CBI. In addition to one complete version of the comment that includes information claimed as CBI, a copy of the comment that does not contain the information claimed as CBI must be submitted for inclusion in the public docket. Information marked as CBI will not be disclosed except in accordance with procedures set forth in 40 CFR part 2.
If you have any questions about CBI or the procedures for claiming CBI, please consult the person identified in the FOR FURTHER INFORMATION CONTACT section. 2. Tips for Preparing Your Comments
When submitting comments, remember to:
a. Identify the rulemaking by docket number and other identifying information (subject heading, Federal Register date and page number).
b. Follow directions. The EPA may ask you to respond to specific questions or organize comments by referencing a Code of Federal Regulations (CFR) part or section number.
c. Explain why you agree or disagree; suggest alternatives and substitute language for your requested changes.
d. Describe any assumptions and provide any technical information and/or data that you used.
e. If you estimate potential costs or burdens, explain how you arrived at your estimate in sufficient detail to allow for it to be reproduced.
f. Provide specific examples to illustrate your concerns, and suggest alternatives.
g. Explain your views as clearly as possible, avoiding the use of profanity or personal threats.
h. Make sure to submit your comments by the comment period deadline identified in the preceding section titled DATES. 3. Docket
The docket number for the proposed action regarding the HMIWI NSPS (40 CFR part 60, subpart Ec) and emission guidelines (40 CFR part 60, subpart Ce) is Docket ID No. EPA-HQ-OAR-2006-0534. 4. Worldwide Web (WWW)
In addition to being available in the docket, an electronic copy of this proposed action is available on the WWW through the Technology Transfer Network Web site (TTN Web). Following signature, EPA posted a copy of the proposed action on the TTN's policy and guidance page for newly proposed or promulgated rules at http://www.epa.gov/ttn/oarpg.
The TTN provides information and technology exchange in various areas of air pollution control.
II. Background
Section 129 of the CAA, entitled ``Solid Waste Combustion,'' requires EPA to develop and adopt NSPS and emission guidelines for solid waste incineration units pursuant to CAA sections 111 and 129. Sections 111(b) and 129(a) of the CAA (NSPS program) address emissions from new HMIWI units, and CAA sections 111(d) and 129(b) (emission guidelines program) address emissions from existing HMIWI units. The NSPS are directly enforceable Federal regulations. The emission guidelines are not directly enforceable but, rather, are implemented by State air pollution control agencies through sections 111(d)/129 State plans.
An HMIWI is defined as any device used to burn hospital waste or medical/
[Page 5512]infectious waste. Hospital waste means discards generated at a hospital, and medical/infectious waste means any waste generated in the diagnosis, treatment, or immunization of human beings or animals, in research pertaining thereto, or in the production or testing of biologicals (e.g., vaccines, cultures, blood or blood products, human pathological waste, sharps). Hospital/medical/infectious waste does not include household waste, hazardous waste, or human and animal remains not generated as medical waste. An HMIWI typically is a small, dual- chamber incinerator that burns about 800 pounds per hour (lb/hr) of waste. Smaller units burn as little as 13 lb/hr while larger units burn as much as 3,700 lb/hr.
Incineration of hospital/medical/infectious waste causes the release of a wide array of air pollutants, some of which exist in the waste feed material and are released unchanged during combustion, and some of which are generated as a result of the combustion process itself. These pollutants include particulate matter (PM); heavy metals, including lead (Pb), cadmium (Cd), and mercury (Hg); toxic organics, including chlorinated dibenzo-p-dioxins/dibenzofurans (CDD/CDF); carbon monoxide (CO); nitrogen oxides (NOX); and acid gases, including hydrogen chloride (HCl) and sulfur dioxide (SO2). In addition to the use of good combustion control practices, HMIWI units are typically controlled by wet scrubbers or dry sorbent injection fabric filters (dry scrubbers).
Combustion control includes the proper design, construction, operation, and maintenance of HMIWI to destroy or prevent the formation of air pollutants prior to their release to the atmosphere. Test data indicate that as secondary chamber residence time and temperature increase, emissions decrease. Combustion control is most effective in reducing CDD/CDF, PM, and CO emissions. The 0.25-second combustion level includes a minimum secondary chamber temperature of 1700 [deg]F and a 0.25-second secondary chamber residence time. These combustion conditions are typical of older HMIWI. The 1-second combustion level includes a minimum secondary chamber temperature of 1700 [deg]F and residence time of 1 second. These combustion conditions are typical of newer HMIWI. Compared to 0.25-second combustion, 1-second combustion will achieve substantial reductions in CDD/CDF and CO emissions, and will provide some control of PM, but will not reduce emissions of acid gases (HCl and SO2), NOX, or metals (Pb, Cd, and Hg). The 2-second combustion level includes a minimum secondary chamber temperature of 1800 [deg]F and residence time of 2 seconds. These combustion conditions will provide additional control of CDD/CDF, CO, and PM, but will not reduce emissions of acid gases (HCl and SO2), NOX, or metals (Pb, Cd, and Hg). The 2- second combustion conditions are considered to be the best level of combustion control (i.e., good combustion) that is applied to HMIWI. Wet scrubbers and dry scrubbers provide control of PM, CDD/CDF, HCl, and metals, but do not influence CO, SO2(at the low concentrations emitted by HMIWI units), or NOX; in fact, there are no technologies currently used by HMIWI that will consistently reduce SO2or NOXemissions. (See Legacy Docket ID No. A-91-61, item II-A-111; 60 FR 10669, 10671-10677; and 61 FR 31742-31743.)
On September 15, 1997, EPA adopted NSPS (40 CFR part 60, subpart Ec) and emission guidelines (40 CFR part 60, subpart Ce) for entities which operate HMIWI. The NSPS and emission guidelines are designed to reduce air pollution emitted from new and existing HMIWI, including HCl, CO, Pb, Cd, Hg, PM, CDD/CDF (total, or 2,3,7,8-tetrachlorinated dibenzo-p-dioxin toxic equivalent (TEQ)), NOX, SO2, and opacity. The NSPS apply to HMIWI for which construction began after June 20, 1996, or for which modification began after March 16, 1998. The NSPS became effective on March 16, 1998, and its requirements apply as of that date or at start-up of a HMIWI unit, whichever is later. The emission guidelines apply to HMIWI for which construction began on or before June 20, 1996, and required compliance by September 2002.
CAA section 129 requires EPA to establish technology-based emission standards that reflect levels of control EPA determines are achievable for new and existing units, after considering costs, non-air quality health and environmental impacts, and energy requirements associated with the implementation of the standards.
In setting forth the methodology EPA must use to establish the technology-based performance standards and emissions guidelines, CAA section 129(a)(2) provides that standards ``applicable to solid waste incineration units promulgated under section 111 and this section shall reflect the maximum degree of reduction in emissions of [certain listed air pollutants] that the Administrator, taking into consideration the cost of achieving such emission reduction, and any non-air quality health and environmental impacts and energy requirements, determines is achievable for new and existing units in each category.'' This level of control is referred to as a maximum achievable control technology, or MACT standard.
In promulgating a MACT standard, EPA must first calculate the minimum stringency levels for new and existing solid waste incineration units in a category, generally based on levels of emissions control achieved or required to be achieved by the subject units. The minimum level of stringency is called the MACT floor, and CAA section 129(a)(2) provides that the ``degree of reduction in emissions that is deemed achievable for new units in a category shall not be less stringent than the emissions control that is achieved in practice by the best controlled similar unit, as determined by the Administrator. Emissions standards for existing units in a category may be less stringent than standards for new units in the same category but shall not be less stringent than the average emissions limitation achieved by the best performing 12 percent of units in the category.''
The minimum stringency requirements form the first and least stringent regulatory option EPA must consider in the determination of MACT for a source category. EPA must also determine whether to control emissions ``beyond the floor,'' after considering the costs, non-air quality health and environmental impacts, and energy requirements of such more stringent control. These are the two steps EPA took in the 1997 HMIWI rulemaking. Finally, every 5 years after adopting a MACT standard under section 129, CAA section 129(a)(5) requires EPA to review and, if appropriate, revise the incinerator standards. In addition to responding to the Court's remand in Sierra Club v. EPA,
167 F.3d 658 (D.C. Cir. 1999), this proposed action includes our first set of proposed revisions to the HMIWI standards, also known as the 5-year review.
III. Summary
A. Litigation and Proposed Remand Response
1. What was EPA's general methodology for determining MACT?
The methodology used to determine MACT is similar for source categories under sections 112 and 129 of the CAA. However, because each source category is unique and the data available to determine the performance capabilities of technology can vary from one source category to another, the basic methodology must be adapted to fit the
[Page 5513]source category in question. As the Court pointed out in the HMIWI litigation, it ``generally defer[s] to an agency's decision to proceed on the basis of imperfect scientific information, rather than to `invest the resources to conduct the perfect study.' '' Sierra Club v. EPA, 167 F.3d at 662.
In general, all MACT analyses involve an assessment of the air pollution control systems or technologies used by the better performing units in a source category. The technology assessment can be based solely on actual emissions data, on knowledge of the air pollution control in place in combination with actual emissions data, or on State regulatory requirements, which give an indication of the actual performance of the regulated units. For each source category, the assessment of the technology involves a review of actual emissions data with an appropriate accounting for emissions variability. Where there is more than one method or technology to control emissions, the analysis results in a series of potential regulations (called regulatory options), one of which is selected as MACT.
The first regulatory option considered by EPA must be at least as stringent as the CAA's minimum stringency requirements. However, MACT is not necessarily the least stringent regulatory option. EPA must examine more stringent regulatory options to determine MACT. Unlike the minimum stringency requirements, EPA must consider various impacts of the more stringent regulatory options in determining MACT. Only if the more stringent regulatory options are considered to have unreasonable impacts does EPA select the first ``floor-based'' regulatory option as MACT.
As stated earlier, the CAA requires that MACT for new sources be no less stringent than the emissions control achieved in practice by the best controlled similar unit. After EPA's assessment of technology, EPA determines the best control currently in use for a given pollutant and establishes one potential regulatory option at the emission level achievable by that control. More stringent potential regulatory options might reflect controls used on other sources that could be applied to the source category in question.
For existing sources, the CAA requires that MACT be no less stringent than the average emissions limitation achieved by the best performing 12 percent of units in a source category. EPA must determine some measure of the average emissions limitation achieved by the best performing 12 percent of units to form the least stringent regulatory option. Sometimes, a direct calculation of the actual emissions values from the best performing 12 percent of sources provides the basis for this regulatory option. More often, EPA determines the technology used by the average source in the best performing 12 percent of sources and establishes the floor based on the technology assessment for that average source. More stringent regulatory options reflect other technologies capable of achieving better performance. 2. What was EPA's methodology in the 1997 HMIWI rulemaking?
On February 27, 1995, EPA published a notice of proposed rulemaking regarding emissions standards for HMIWI units (60 FR 10654). The proposal was the result of several years of reviewing available information. During the public comment period for the proposal, EPA received over 700 letters, some of which contained new information or indicated that the commenters were in the process of gathering more information for EPA to consider. The new information led EPA to consider the need for numerous changes to the proposed rule, and on June 20, 1996, the Agency published a re-proposal (61 FR 31736). Following an additional public comment period, EPA published the final rule on September 15, 1997 (62 FR 48348).
During the data-gathering phase of developing the 1995 proposal, EPA found it difficult to obtain an accurate count of the thousands of HMIWI units nationwide, or to find HMIWI units with add-on air pollution control systems in place. A few HMIWI units with combustion control were tested to assess performance of combustion control in reducing emissions. One unit with a wet scrubber, and a few units with dry scrubbing systems were tested to determine performance capabilities of add-on controls. (See 61 FR 31738.)
Altogether, data were available from only 7 out of the estimated then-operating 3,700 existing HMIWI units (60 FR 10674). Because EPA was under a court-ordered deadline to propose and adopt standards for HMIWI that did not provide sufficient time to collect more actual emissions data (see consent decree entered in Sierra Club v. EPA, Nos. CV-92-2093 and CV-93-0284 (E.D.N.Y.)), EPA proceeded to develop the regulations with the existing data, as described below. However, EPA specifically requested comment on EPA's MACT determinations and on EPA's conclusions about the performance capabilities of air pollution control technologies on HMIWI in light of the relatively small database (60 FR 10686).
a. EPA's Methodology for New HMIWI. In determining the least stringent regulatory option allowed by the CAA for new HMIWI, EPA first examined the data available for various air pollution control technologies applied to HMIWI to determine the performance capabilities of the technologies (i.e., the achievable emission limitations) (60 FR 10671-73, 61 FR 31741-43). To determine the performance capabilities, EPA grouped all of the test data by control technology and established the numerical value for the achievable emission limitations somewhat higher than the highest test data point for each particular control technology. (See Legacy Docket ID No. A-91-61, items IV-B-46, 47, 48, and 49.) Following the determination of performance capability, EPA identified the best control technology for each air pollutant for each subcategory of HMIWI, and established the numerical values for the least stringent regulatory option at the achievable emission limitation associated with that particular control technology. (See 60 FR 10673; Legacy Docket ID No. A-91-61, item IV-B-38; 61 FR 31745-46.) Other, more stringent, regulatory options were developed reflecting the actual performance of other, more effective, control technologies (61 FR 31766-68).
As stated in the 1996 re-proposal, the least stringent regulatory option for new large HMIWI units (units with maximum waste burning capacity of more than 500 lb/hr) was based on good combustion (i.e., 2- second combustion level) and a combination of two control technologies, high-efficiency wet scrubbers and dry injection/fabric filter dry scrubbers with carbon (61 FR 31746). New medium units (units with maximum waste burning capacity of more than 200 lb/hr but less than or equal to 500 lb/hr) would need to use good combustion and a combination of two control technologies, high-efficiency wet scrubbers and dry injection/fabric filter dry scrubbers without carbon, to meet the least stringent regulatory option. Id. New small units (units with maximum waste burning capacity of less than or equal to 200 lb/hr) would need to use good combustion and a moderate-efficiency wet scrubber to meet the least stringent regulatory option. Id. In EPA's final standards promulgated in 1997, EPA selected an overall more stringent regulatory option for new HMIWI (62 FR 48365). The final standards were based on emission limits achievable with good combustion and a
[Page 5514]moderate-efficiency wet scrubber for new small HMIWI, and good combustion and a combined dry/wet control system with carbon for new medium and large HMIWI. Id. These standards reflected the MACT floor emissions levels for new small and large HMIWI, but were more stringent than the MACT floor for new medium HMIWI. Id. EPA estimated that the standards would reduce emissions from these units of HCl by up to 98 percent, PM and Pb by up to 92 percent, Cd by up to 91 percent, CDD/CDF by up to 87 percent, Hg by up to 74 percent, and CO, SO2, and NOXby up to 52 percent (62 FR 48366).
b. EPA's Methodology for Existing HMIWI. For existing units, EPA did not have sufficient emissions data to fully characterize the actual emissions performance of the best performing 12 percent of existing HMIWI, and, based exclusively on such data, EPA did not have a clear indication of the technology used by the best 12 percent of units. As a result, EPA used emission limits included in State regulations and State-issued permits (hereinafter referred to as regulatory limits) as surrogate information to determine emissions limitations achieved by the best performing 12 percent of units in each subcategory (60 FR 10674). EPA believed this information could be expected to reliably reflect levels of performance achieved on a continuous basis by better- controlled units that must meet these limits or risk violating enforceable requirements. EPA assumed that all HMIWI were achieving their regulatory limits (60 FR 10674). Where there were regulatory limits for more than 12 percent of units in a subcategory, the regulatory limits were ranked from the most stringent to least stringent, and the average of the regulatory limits for the top 12 percent of units in the subcategory was calculated. Id.; 61 FR 31744- 45. Where the number of units subject to specific emissions limitations did not comprise 12 percent of the population in a subcategory, EPA assumed those units with regulatory limits were the best performing units, and the remaining units in the top 12 percent were assigned an emission value associated with ``combustion control.'' (See 60 FR 10674; 61 FR 31745; Legacy Docket ID No. A-91-61, item IV-B-24 at 2.) In previous Federal Register notices regarding HMIWI (60 FR 10654, 61 FR 31736, and 62 FR 48348), this level of control was referred to as ``uncontrolled,'' which is misleading because sources with combustion control emit lesser amounts of CDD/CDF, CO, and PM. In the latter situation described above, the average of the regulatory limits plus enough combustion-controlled emission values to account for 12 percent of units in the subcategory was calculated. (See Legacy Docket ID No. A-91-61, item IV-B-24 at 2-4.)
After calculating the averages of regulatory limits and combustion- controlled emission values, EPA examined the resulting calculated values to determine what level of air pollution control would be needed to meet the calculated average values. (See 60 FR 10675-78; 61 FR 31755-56.) For many pollutants, the calculated averages presented no clear indication of the type of air pollution control used by the best performing units. However, the calculated values for three key pollutants, PM, CO, and HCl, did provide a good indication of the type of air pollution control used on the best performing 12 percent of units. The level of air pollution control associated with the calculated average values for PM, CO, and HCl formed the technical basis of the least stringent regulatory option considered by EPA (61 FR 31756, Table 13). The emission limitations assigned to each pollutant reflected the actual performance of the technology on which they were based. Finally, EPA developed a series of regulatory options based on progressively more stringent technologies and assigned emission limitations to each regulatory option based on the actual performance capabilities of the technologies (61 FR 31757, Table 14).
As stated in the 1996 re-proposal, large existing units would need to use good combustion and a high-efficiency wet scrubber to meet the least stringent regulatory option, while medium existing units would need to use good combustion and a moderate-efficiency wet scrubber, although dry scrubbers could also be used with good combustion at large and medium existing units (61 FR 31745). EPA further stated that its inclination was to establish emission limitations for large and medium existing units based on regulatory options representing the MACT floors (61 FR 31778). Small existing units would need only to use good combustion practices to meet the regulatory option representing the MACT floor (61 FR 31745). With respect to small existing units, EPA stated that it had no inclination with regard to which regulatory option should be used to establish emission limitations and requested comment on requiring use of good combustion and a low-efficiency wet scrubber (61 FR 31778-79).
In EPA's final standards promulgated in 1997, EPA selected an overall more stringent regulatory option for existing HMIWI (62 FR 48371). The final standards were based on emission limits achievable with good combustion and a low-efficiency wet scrubber for most existing small HMIWI, good combustion and a moderate-efficiency wet scrubber for existing medium HMIWI, and good combustion and a high- efficiency wet scrubber for existing large HMIWI (62 FR 48371). The final standards allow small HMIWI that meet certain rural criteria to meet emissions limits achievable with good combustion alone. Id. These standards reflected the MACT floor emissions levels for existing small HMIWI meeting rural criteria, medium HMIWI, and large HMIWI, but were more stringent than the MACT floor for most existing small HMIWI (i.e., non-rural) (62 FR 48371-72). The final standards for existing medium and large HMIWI were structured so that either a dry scrubber or a wet scrubber could be used to achieve the emission limits. EPA estimated that the final emission guidelines would reduce emissions of CDD/CDF by up to 97 percent, Hg by up to 95 percent, PM by up to 92 percent, Pb by up to 87 percent, Cd by up to 84 percent, CO by up to 82 percent, HCl by up to 98 percent, and SO2and NOXby up to 30 percent (62 FR 48372). Table 1 of this preamble summarizes the emission limits for the NSPS and emission guidelines promulgated in 1997.
Table 1.--Summary of Promulgated Emission Limits
Limit for existing Pollutant (units)
Unit Size \1\HMIWI \2\
Limit for new HMIWI \2\
HCl (parts per million by volume L, M, S............. 100 or 93%
15 or 99% reduction. (ppmv)).
reduction. SR.................. 3,100............. N/A.\3\ CO (ppmv)....................... L, M, S............. 40................ 40 SR.................. 40................ N/A. Pb (milligrams per dry standard L, M................ 1.2 or 70%
0.07 or 98% reduction.\3\ cubic meter (mg/dscm)).
reduction.
[Page 5515]S................... 1.2 or 70%
1.2 or 70% reduction. reduction. SR.................. 10................ N/A. Cd (mg/dscm).................... L, M................ 0.16 or 65%
0.04 or 90% reduction. reduction. S................... 0.16 or 65%
0.16 or 65% reduction. reduction. SR.................. 4................. N/A. Hg (mg/dscm).................... L, M, S............. 0.55 or 85%
0.55 or 85% reduction. reduction. SR.................. 7.5............... N/A. PM (grains per dry standard L................... 0.015............. 0.015 cubic foot (gr/dscf)). M................... 0.03.............. 0.015 S................... 0.05.............. 0.03. SR.................. 0.086............. N/A. CDD/CDF, total (nanograms per L, M................ 125............... 25 dry standard cubic meter (ng/ dscm)). S................... 125............... 125 SR.................. 800............... N/A. CDD/CDF, TEQ (ng/dscm).......... L, M................ 2.3............... 0.6 S................... 2.3............... 2.3 SR.................. 15................ N/A. NOX (ppmv)...................... L, M, S............. 250............... 250 SR.................. 250............... N/A. SO2 (ppmv)...................... L, M, S............. 55................ 55 SR.................. 55................ N/A.
\1\ L = Large; M = Medium; S = Small; SR = Small Rural \2\ All emission limits are measured at 7 percent oxygen. \3\ Not applicable.
c. Compliance by HMIWI. At the time of promulgation (September 1997), EPA estimated that there were approximately 2,400 HMIWI operating in the United States. Those units combusted approximately 830 thousand tons of hospital/medical/infectious waste annually. Of those existing HMIWI, about 48 percent were small units, 29 percent were medium units, and 20 percent were large units. About 3 percent of the HMIWI were commercial units. EPA projected that no new small or medium HMIWI would be constructed, and that up to 60 new large units and 10 new commercial units would be constructed.
After shutdown of approximately 97 percent of the 2,400 HMIWI that were operating in 1997, there are currently 72 existing HMIWI at 67 facilities. Additionally, only 4 new HMIWI at 3 facilities began operation following the 1997 rulemaking. These 76 existing and new units are estimated to combust approximately 165 thousand tons of waste annually. Of the 72 existing HMIWI subject to the emission guidelines, 44 are large units, 20 are medium units, and 8 are small units (6 of which meet the rural criteria). Twenty-one percent of the existing HMIWI are commercially owned. Of the four new HMIWI, three are large units, and one is a medium unit. Two of the new units are county-owned but accept waste from other sources, similar to commercial units. The actual emissions reductions achieved as a result of implementation of the standards exceeded the 1997 projections for all nine of the regulated pollutants. A comparison of the estimated pollutant reductions versus the actual reductions is presented in Table 2 of this preamble.
Table 2.--Comparison of Estimated Pollutant Reductions Versus Actual Pollutant Reductions
Estimated emissions Actual emissions Pollutant
reduction, reduction, percent percent
\1\
HCl............................. 98................
99.2 CO.............................. 75 to 82..........
98.1 Pb.............................. 80 to 87..........
98.7 Cd.............................. 75 to 84..........
99.0 Hg.............................. 93 to 95..........
99.0 PM.............................. 88 to 92..........
98.1 CDD/CDF, total.................. 96 to 97..........
99.5 CDD/CDF, TEQ.................... 95 to 97..........
99.6 NOX............................. 0 to 30...........
70.6 SO2............................. 0 to 30...........
92.6\1\ Reflects the effect of unit shutdowns as well as the effect of compliance with the promulgated standards.
3. What was the Sierra Club's challenge?
On November 14, 1997, the Sierra Club and the Natural Resources Defense Council (Sierra Club) filed suit in the U.S. Court of Appeals for the District of Columbia Circuit (the Court). The Sierra Club claimed that EPA had violated CAA section 129 by setting emission standards for HMIWI under CAA sections 129 and 111 that are less stringent than the statutory minimum stringency required by section 129(a)(2); that EPA had violated section 129 by not including mandatory pollution prevention or waste minimization requirements in the HMIWI standards; and that EPA had not adequately considered the non-air quality health and environmental impacts of the standards. For new units, the Sierra
[Page 5516]Club argued that to satisfy the statutory phrase ``best controlled similar unit'' in CAA section 129(a)(2), EPA should have identified the single best performing unit in each subcategory and based the MACT floor for that subcategory on that particular unit's performance, rather than consider the performance of other units using the same technology. The Sierra Club also argued that EPA erroneously based the new unit floors on the emissions of the worst performing unit using a particular technology. Regarding existing units, the Sierra Club claimed that the plain meaning of CAA section 129(a)(2)'s words, ``average emissions limitation achieved by the best performing 12 percent of units,'' precludes the use of regulatory data, and claimed that the legislative history of section 129(a)(2) reflects congressional intent to prohibit EPA from relying on regulatory data. Moreover, the Sierra Club claimed that, for HMIWI, using regulatory data was impossible because such data existed for fewer than 12 percent of units, and because doing so would impermissibly import an achievability requirement into the unit floor determination. Finally, the Sierra Club argued that EPA failed to require HMIWI units to undertake programs to reduce the Hg and chlorinated plastic in their waste streams, in violation of CAA section 129(a)(3), and that EPA failed to consider the fact that CDD/CDF and Hg from HMIWI can contaminate water, sediment, and soil, and can bioaccumulate in food, in violation of the CAA's requirement that EPA consider non-air quality impacts of setting HMIWI emissions standards. 4. What was the Court's ruling?
On March 2, 1999, the Court issued its opinion in Sierra Club v. EPA,
167 F.3d 658 (D.C. Cir. 1999). While the Court rejected the Sierra Club's claims regarding pollution prevention and non-air quality impacts, and rejected the Sierra Club's statutory arguments under CAA section 129, the Court remanded the rule to EPA for further explanation regarding how EPA derived the MACT floors for new and existing HMIWI units. Furthermore, the Court did not vacate the regulations, stating that ``[i]t is possible that EPA may be able to explain [EPA's basis for the standards]'' in response to the concerns raised by the Court. Id., at 664. The regulations remain in effect during the remand.
a. The Court's Ruling on New Units. In response to the Sierra Club's claims regarding EPA's treatment of new units, the Court opined that ``EPA would be justified in setting the floors at a level that is a reasonable estimate of the performance of the `best controlled similar unit' under the worst reasonably foreseeable circumstances [* * *]. It is reasonable to suppose that if an emissions standard is as stringent as `the emissions control that is achieved in practice' by a particular unit, then that particular unit will not violate the standard. This only results if `achieved in practice' is interpreted to mean `achieved under the worst foreseeable circumstances.' In National Lime Ass'n v. EPA,
627 F.2d 416, 431 n. 46 (D.C. Cir. 1980), we said that where a statute requires that a standard be `achievable,' it must be achievable `under most adverse circumstances which can reasonably be expected to recur.' The same principle should apply when a standard is to be derived from the operating characteristics of a particular unit.'' Sierra Club v. EPA, 167 F.3d at 665. Thus, the Court refused to embrace the Sierra Club's interpretation of CAA section 129(a)(2) as requiring EPA to base the MACT floor on only the lowest emissions data points observed (i.e., the level achieved by the best performing unit for each pollutant).
Relating to the Sierra Club's claim that EPA erred in considering the emissions of units other than the best controlled unit, the Court refused to rule that EPA's approach was unlawful, and posited that ``[p]erhaps considering all units with the same technology is justifiable because the best way to predict the worst reasonably foreseeable performance of the best unit with the available data is to look at other units' performance. Or perhaps EPA reasonably considered all units with the same technology equally `well-controlled,' so that each unit with the best technology is a `best-controlled unit' even if such units vary widely in performance.'' Sierra Club v. EPA, 167 F.3d at 665.
However, the Court concluded that the possible rationale for this treatment of new units was not presented in the rulemaking record with enough clarity for the Court to determine that EPA's ``path may reasonably be discerned.'' Id. Moreover, the Court ruled that EPA had ``not explained why the phrase best controlled similar unit encompasses all units using the same technology as the unit with the best observed performance, rather than just that unit itself[. * * * W]e do not know what interpretation the agency chose, and thus cannot evaluate its choice.'' Sierra Club v. EPA, 167 F.3d at 665. The Court further directed EPA to provide additional explanation regarding how the Agency had calculated the upper bound of the best-controlled unit's performance through rounding. Id. b. The Court's Ruling on Existing Units. With respect to existing units, the Court first rejected the Sierra Club's ``claim that EPA's decision to base the floors on regulatory data fails the first step of the Chevron test. None of the Sierra Club's arguments establish that Congress has `directly addressed' and rejected the use of regulatory data.'' Id., at 661. After noting that the Sierra Club's statutory objections to EPA's methodology appeared to be premised on ``the counterintuitive proposition that an `achieved' level may not be `achievable,' or, as Sierra Club puts it, may be better than `EPA's notions about what is achievable,' '' id. at 662, the Court rejected the Sierra Club's statutory objections to using regulatory data and uncontrolled (i.e., combustion-controlled) emissions values. In other words, the Court implicitly embraced EPA's view, under the principle of National Lime, that the MACT floor is premised on the fundamental concept that it be ``achievable,'' and should not be set at a level that happens to be reflected by the lowest observed data point without consideration of variability in operating conditions. Then, after analyzing and rejecting the Sierra Club's arguments that the plain language of the CAA and its legislative history forbid EPA's methodology, the Court further ruled that it found ``nothing inherently impermissible about construing the statute to permit the use of regulatory data--if they allow EPA to make a reasonable estimate of the performance of the top 12 percent of units. Indeed, the Sierra Club conceded at oral argument that `a reasonable sample' may be used `to find out what the best 12 percent are doing.' Oral Arg. Tr. at 11. To be sure, the Sierra Club did not concede that permit data may be used. But neither has it provided any basis for believing that state and local limitations are such weak indicators of performance that using them is necessarily an impossible stretch of the statutory terms. [* * *] We therefore reject the Sierra Club's argument that the CAA forbids the use of permit and regulatory data, and hold that the use of such information is permissible as long as it allows a reasonable inference as to the performance of the top 12 percent of units. Similarly, as long as there is a reasonable basis for believing that some of the best performing 12 percent of units are uncontrolled [i.e., combustion controlled], EPA may include data points giving a reasonable representation of the performance of those units in its averaging.'' Sierra Club v. EPA, 167 F.3d at 662, 663. Thus, the Court rejected all of the Sierra Club's
[Page 5517]arguments that the CAA prohibits EPA from basing MACT floor determinations on permit or regulatory data, or on uncontrolled (i.e., combustion-controlled) emissions values.
However, in addressing the manner in which EPA had specifically relied upon such data in the HMIWI rulemaking, the Court concluded that ``[a]lthough EPA said that it believed the combination of regulatory and uncontrolled [i.e., combustion-controlled] data gave an accurate picture of the relevant [HMIWI]s` performance, it never adequately said why it believes this. [* * *] First, EPA has said nothing about the possibility that [HMIWI]s might be substantially overachieving the permit limits. If this were the case, the permit limits would be of little value in estimating the top 12 percent of [HMIWI]s' performance.
[* * *] Second, EPA never gave any reason for its apparent belief that
[HMIWI] s that were not subject to permit requirements did not deploy emission controls of any sort. Unless there is some finding to this effect, it is difficult to see the rationality in using `uncontrolled'
[i.e., combustion-controlled] data for the units that were not subject to regulatory requirements.'' Id., at 663-664. The Court further questioned the rationality of EPA using the highest of its test run data in cases where the regulatory data did not alone comprise the necessary 12 percent. Id., at 664.
c. Subsequent Court Rulings Relevant to the Remand. Following the Court's remand of the HMIWI MACT floors in Sierra Club v. EPA, the Court issued a series of rulings in other cases addressing MACT rules that bear on EPA's proposed response regarding HMIWI. The first of these was Nat'l Lime Ass'n v. EPA,
233 F.3d 625 (D.C. Cir. 2000) (``NLA II''), which involved challenges to EPA's MACT standards under CAA section 112(d) for portland cement manufacturing facilities. In that case, the Sierra Club argued that EPA should have based its estimate of the top performing 12 percent of sources on actual emissions data, in order to ``reasonably estimate'' such performance. But the Court determined that EPA's approach of selecting ``the median [performing] plant out of the best twelve percent of the plants for which it had information and set[ting] the * * * floor at the level of the worst performing plant in its databases using th[e same] technology [as the median plant]'' had not been shown by the Sierra Club to reflect a not reasonable estimate. NLA II, 233 F.3d at 633.
In addition, the Court partially clarified its position regarding EPA's approach of accounting for emissions performance variability by setting floors at a level that reasonably estimates ``the performance of the `best controlled similar unit' under the worst reasonably foreseeable circumstances.'' Sierra Club, 167 F.3d at 665. In NLA II, the Court stressed that EPA should not simply set floors at levels reflecting the worst foreseeable circumstances faced by any worst performing unit in a given source category, and that while considering all units with the same technology may be justifiable because the best way to predict the worst reasonably foreseeable performance of the best unit with available data is to look at other units' performance, such an approach would satisfy the CAA ``if pollution control technology were the only factor determining emission levels of that HAP.'' NLA II, 233 F.3d at 633.
In Cement Kiln Recycling Coalition v. EPA,
255 F.3d 855 (D.C. Cir. 2001) (``CKRC''), the Court again refined its view on when it is appropriate for EPA to base MACT floors on the performance of air pollution control technology. In that case, the Sierra Club challenged EPA's MACT standards for hazardous waste combustors (HWC), and argued that factors other than MACT technology influenced the emissions performance of the best performing sources.
The Court agreed that since EPA's record evidence in the HWC rulemaking showed that factors besides MACT controls significantly influenced HWC emission rates, ''emissions of the worst-performing MACT source may not reflect what the best-performers actually achieve.'' CKRC, 255 F.3d at 864. EPA had claimed that MACT floors must be achievable by all sources using MACT technology, and that to account for the best-performing sources'' operational variability we had to base floors on the worst performers'' emissions. But the Court stressed that ``whether variability in the MACT control accurately estimates variability associated with the best performing sources depends on whether factors other than MACT control contribute to emissions[,]'' id., and that ``the relevant question here is not whether control technologies experience variability at all, but whether the variability experienced by the best-performing sources can be estimated by relying on emissions data from the worst-performing sources using the MACT control.'' Id., at 865.
In the specific case of the HWC rule, the Court concluded that, since record evidence showed that non-MACT factors influenced emissions performance, EPA could not base floors simply on the worst-performing MACT sources' emissions. Id., at 866. However, the Court also reiterated that ``[i]f in the case of a particular source category or HAP, the Agency can demonstrate with substantial evidence--not mere assertions--that MACT technology significantly controls emissions, or that factors other than the control have a negligible effect, the MACT approach could be a reasonable means of satisfying the statute's requirements.'' Id. 5. Are revisions to the emission limits being proposed in response to the remand?
Yes, the proposed response to the remand would revise some of the emission limits in both the NSPS and emission guidelines. Relative to the NSPS, the emission limits for CO, Pb, Cd, Hg, PM, and CDD/CDF would be revised. Relative to the emission guidelines, the emission limits for HCl, Pb, Cd, and CDD/CDF would be revised. EPA believes that the revised emission limits being proposed as a result of its response to the remand can be achieved with the same emission control technology currently used by HMIWI. The proposed emission limits for the NSPS and emission guidelines necessary to respond to the Court's remand are summarized in Table 3 of this preamble. Note that in several cases, further amendments to the emission limits are being proposed as a result of our 5-year review under CAA section 129(a)(5). Those proposed amendments are discussed in the following section of this preamble.
Table 3.--Summary of Proposed Emission Limits in Response to the Remand
Proposed remand Pollutant (units)
Unit size \1\
limit for Proposed remand limit for new HMIWI existing HMIWI \2\
\2\
HCl (ppmv)...................... L, M, S............. 78 or 93%
15\3\ or 99% reduction \3\. reduction \3\. SR.................. 3,100 \3\......... N/A \4\. CO (ppmv)....................... L, M, S............. 40 \3\............ 32 SR.................. 40 \3\............ N/A \4\.
[Page 5518]Pb (mg/dscm).................... L, M................ 0.78 or 71%
0.060 or 98% reduction \3\. reduction. S................... 0.78 or 71%
0.78 or 71% reduction. reduction. SR.................. 8.9............... N/A \4\. Cd (mg/dscm).................... L, M................ 0.11 or 66%
0.030 or 93% reduction. reduction \3\. S................... 0.11 or 66%
0.11 or 66% reduction \3\. reduction \3\. SR.................. 4 \3\............. N/A \4\. Hg (mg/dscm).................... L, M................ 0.55 \3\ or 87% 0.45 or 87% reduction. reduction. S................... 0.55 \3\ or 87% 0.47 or 87% reduction. reduction. SR.................. 6.6............... N/A \4\. PM (gr/dscf).................... L................... 0.015 \3\......... 0.009 M................... 0.030 \3\......... 0.009 S................... 0.050 \3\......... 0.018 SR.................. 0.086 \3\......... N/A \4\. CDD/CDF, total (ng/dscm)........ L, M................ 115............... 20 S................... 115............... 111 SR.................. 800 \3\........... N/A \4\. CDD/CDF, TEQ (ng/dscm).......... L, M................ 2.2............... 0.53 S................... 2.2............... 2.1 SR.................. 15 \3\............ N/A \4\. NOX (ppmv)...................... L, M, S............. 250 \3\........... 225 SR.................. 250 \3\........... N/A \4\ SO2 (ppmv)...................... L, M, S............. 55 \3\............ 46 SR.................. 55 \3\............ N/A \4\.
\1\ L = Large; M = Medium; S = Small; SR = Small Rural \2\ All emission limits are measured at 7 percent oxygen. \3\ No change proposed. \4\ Not applicable.
B. Proposed Amendments (CAA Section 129(a)(5) 5-Year Review)
Section 129(a)(5) of the CAA requires EPA to conduct a review of the NSPS and emissions guidelines at 5 year intervals and, if appropriate, revise the NSPS and emission guidelines pursuant to the requirements under sections 111 and 129 of the CAA. In conducting such reviews, EPA attempts to assess the performance of and variability associated with the installed emissions control equipment (and developments in practices, processes and control technologies) and to revise as necessary and appropriate the NSPS and emission guidelines. In these reviews, EPA takes into account the currently installed equipment and its performance and operational variability. As appropriate, we also consider new technologies that have been demonstrated to reliably control emissions from the source category. In setting numerical emission limits from single, ``snap shot'' stack test data, EPA must exercise technical judgment to ensure the achievability of such limits over the course of anticipated operating conditions. EPA has completed the 5-year review, and the proposed amendments discussed below reflect the changes that EPA has determined are appropriate in addition to the amendments that are necessary to respond to the Court's remand. These proposed amendments do not reflect adoption of new control technologies or processes, but do reflect more efficient practices in operation of the control technologies that sources used in order to meet the 1997 MACT standards.
Following year 2002 compliance with the emission guidelines, EPA gathered information on the performance levels actually being achieved by HMIWI that were operating under the guidelines. After implementation of the guidelines in 1997, approximately 94 percent of HMIWI shut down, and 3 percent demonstrated eligibility for exemptions from the HMIWI regulation. Those HMIWI that remained in operation either continued operation with their existing configuration or were retrofitted with add-on air pollution control devices in order to meet the standards. The retrofits were completed on time, and the controls installed to meet the required emission limitations were highly effective in reducing emissions of all of the CAA section 129 pollutants emitted by HMIWI. For those HMIWI, relative to a 1995 baseline, the emission guidelines reduced organic emissions (CDD/CDF) by about 90 percent, metals emissions (Pb, Cd, and Hg) by more than 80 percent, and acid gas emissions (HCl and SO2) by more than 70 percent. Including shutdowns and exemptions, nationwide HMIWI emissions of organics, metals, and acid gases each decreased by about 99 percent or more relative to a 1995 baseline. It should be noted that the original HMIWI emission limits were based primarily on permit information and other regulatory requirements, and not on actual performance or stack test data. To this end, it was highly uncertain at promulgation what the precise performance efficiency and day-to-day operational variability associated with the promulgated regulatory requirements would yield. Thus, the 2002 compliance test information provided the first quantitative assessment of the performance of the installed control equipment's ability to attain the NSPS and emissions guideline limits.
The goal of the current technology review is to assess the performance efficiency of the installed equipment and to ensure that the emission limits reflect the performance of the technologies required by the MACT standards. In addition, the review addresses whether new technologies and processes and improvements in practices have been demonstrated at sources subject to the emissions limitations. EPA's intent for future technology reviews is to include similar analyses that also assess risk along with new technologies. For the current review, while new technologies have not yet been demonstrated to reliably control emissions more efficiently at reasonable cost at HMIWI units than those used to meet MACT, improvements in operational practices
[Page 5519]do support some additional revision of the standards, in order to better reflect the best operation of the MACT controls.
These proposed amendments would revise the NSPS and emission guidelines, in some cases beyond the point needed to respond to the Court's remand, based on the performance levels currently being achieved by HMIWI. The revisions discussed in the following text apply to both the NSPS and the emission guidelines, unless otherwise specified. 1. Are revisions to the emission limits being proposed?
Yes, the proposed amendments would revise the emission limits in both the NSPS and emission guidelines. EPA's technology review demonstrates that the proposed emission limits can be achieved with the same emission control technology currently used by HMIWI. The proposed emission limits for the NSPS and emission guidelines are summarized in Tables 4 and 5 of this preamble.
Table 4.--Summary of Proposed 5-Year Review Emission Limits for New HMIWI
Pollutant (units)
Unit Size \1\Proposed Limit \2\HCl (ppmv)........................... L, M, S...................... 15 \3\ or 99% reduction \3\. CO (ppmv)............................ L, M, S...................... 25 Pb (mg/dscm)......................... L, M......................... 0.060 or 99% reduction. S............................ 0.64 or 71% reduction. Cd (mg/dscm)......................... L, M......................... 0.0050 or 99% reduction. S............................ 0.060 or 74% reduction. Hg (mg/dscm)......................... L, M......................... 0.19 or 96% reduction. S............................ 0.33 or 96% reduction. PM (gr/dscf)......................... L, M......................... 0.0090. S............................ 0.018. CDD/CDF, total (ng/dscm)............. L, M......................... 16 S............................ 111 CDD/CDF, TEQ (ng/dscm)............... L, M......................... 0.21 S............................ 2.0 NOX (ppmv)........................... L, M, S...................... 212 SO2 (ppmv)........................... L, M......................... 21 S............................ 28
\1\ L = Large; M = Medium; S = Small \2\ All emission limits are measured at 7 percent oxygen. \3\ No change proposed.
Table 5.--Summary of Proposed 5-Year Review Emission Limits for Existing HMIWI
Pollutant (units)
Unit Size \1\Proposed Limit \2\HCl (ppm)............................ L, M, S...................... 51 or 94% reduction. SR........................... 398 CO (ppm)............................. All.......................... 25 Pb (mg/dscm)......................... L, M, S...................... 0.64 or 71% reduction. SR........................... 0.60 Cd (mg/dscm)......................... L, M, S...................... 0.060 or 74% reduction. SR........................... 0.050 Hg (mg/dscm)......................... L, M, S...................... 0.33 or 96% reduction. SR........................... 0.25\3\ PM (gr/dscf)......................... L............................ 0.015 M............................ 0.030 \3\ S............................ 0.030 SR........................... 0.030 CDD/CDF, total (ng/dscm)............. L, M, S...................... 115 SR........................... 800 \3\ CDD/CDF, TEQ (ng/dscm)............... L, M, S...................... 2.0 SR........................... 15 \3\ NOX (ppmv)........................... All.......................... 212 SO2 (ppmv)........................... All.......................... 28
\1\ L = Large; M = Medium; S = Small; SR = Small Rural \2\ All emission limits are measured at 7 percent oxygen. \3\ No change proposed.
As indicated by Table 5 of this preamble, the proposed emission limits for Pb, Cd, and Hg for existing small rural HMIWI are more stringent than those being proposed for existing large, medium, and small HMIWI. We believe that this better emissions performance by existing small rural HMIWI is a result of the waste stream of a small rural hospital not including certain materials that are in the waste stream of a non-rural hospital and that cause relatively higher Pb, Cd and Hg emissions. 2. Are other amendments being proposed?
The proposed amendments would also make the following changes based on information received during implementation of the HMIWI NSPS and emission guidelines and would
[Page 5520]apply equally to the NSPS and emission guidelines, unless otherwise specified.
a. Performance Testing and Monitoring Amendments. The proposed amendments would allow sources to use the results of previous emissions tests to demonstrate compliance with the revised emission limits as long as the sources certify that the previous test results are representative of current operations. Only those sources whose previous emissions tests do not demonstrate compliance with one or more revised emission limits would be required to conduct another emissions test for those pollutants (note that sources are already required to test for HCl, CO, and PM on an annual basis). The proposed amendments would require, for existing HMIWI, annual inspections of scrubbers and fabric filters, and a one-time Method 22 visible emissions test of the ash handling operations to be conducted during the next compliance test. For new HMIWI, the proposed amendments would require CO continuous emissions monitoring systems (CEMS), bag leak detection systems for fabric-filter controlled units, annual inspections of scrubbers and fabric filters, and Method 22 visible emissions testing of the ash handling operations to be conducted during each compliance test. For existing HMIWI, use of CO CEMS would be an approved alternative, and specific language with requirements for CO CEMS is included in the proposed amendments. For new and existing HMIWI, use of PM, HCl, multi- metals, and Hg CEMS, and semi-continuous dioxin monitoring (continuous sampling with periodic sample analysis) also are approved alternatives, and specific language for these alternatives is included in the proposed amendments.
b. Other Amendments. The proposed amendments would revise the definition of ``Minimum secondary chamber temperature'' to read ``Minimum secondary chamber temperature means 90 percent of the highest 3-hour average secondary chamber temperature (taken, at a minimum, once every minute) measured during the most recent performance test demonstrating compliance with the PM, CO, and dioxin/furan emission limits.''
The proposed amendments would require sources to submit, along with each test report, a description of how operating parameters are established during the initial performance test and subsequent performance tests. 3. Is an implementation schedule being proposed?
Yes; under the proposed amendments to the emission guidelines, and consistent with CAA section 129, revised State plans containing the revised emission limits and other requirements in the proposed amendments would be due within 1 year after promulgation of the amendments. That is, revised State plans would have to be submitted to EPA 1 year after the date on which EPA promulgates revised standards.
The proposed amendments to the emission guidelines then would allow HMIWI units up to 3 years from the date of approval of a State plan, but not later than 5 years after promulgation of the revised standards, to demonstrate compliance with the amended standards. Consistent with CAA section 129, EPA expects States to require compliance as expeditiously as practicable. HMIWI units have already installed the emission control equipment necessary to meet the proposed revised limits, and EPA, therefore, anticipates that most State plans will include compliance dates sooner than 5 years following promulgation of the amendments. In most cases, the only changes necessary are to review the revisions and adjust the emission monitoring and reporting accordingly.
In revising the emission limits in a State plan, a State has two options. First, it could include both the current and the new emission limits in its revised State plan, which allows a phased approach in applying the new limits. That is, the State plan would make it clear that the current emission limits remain in force and apply until the date the new emission limits are effective (as defined in the State plan). States whose HMIWI units do not find it necessary to improve their performance in order to meet the new emission limits may want to consider a second approach where the State would insert the new emission limits in place of the current emission limits, follow procedures in 40 CFR part 60, subpart B, and submit a revised State plan to EPA for approval. If the revised State plan contains only the new emission limits (i.e., the current emission limits are not retained), then the new emission limits must become effective immediately since the current limits would be removed from the State plan. 4. Has EPA changed the applicability date of the 1997 NSPS?
No; however, HMIWI may be treated differently under the amended standards than they were under the 1997 standards in terms of whether they are ``existing'' or ``new'' sources, and there will be new dates defining what are ``new'' sources and imposing compliance deadlines regarding any amended standards. The applicability date for the NSPS units, with respect to the standards as promulgated in 1997, remains June 20, 1996; however, units for which construction is commenced after the date of this proposal, or modification is commenced on or after the date 6 months after promulgation of the amended standards, would be subject to more stringent NSPS emission limits than units for which construction or modification was completed prior to those dates. Under the proposed amendments, units that commenced construction after June 20, 1996, and on or before February 6, 2007, or that are modified before the date 6 months after the date of promulgation of any revised final standards, would continue to be or would become subject to the NSPS emission limits that were promulgated in 1997 and that remain in the 40 CFR part 60, subpart Ec NSPS, except where the revised emission guidelines would be more stringent. In that case, HMIWI that are NSPS units under the 1997 rule would also need to comply with the revised emission guidelines for existing sources, by the applicable compliance date for such existing sources. Similarly, emission guidelines units under the 1997 rule would need to meet the revised emission guidelines by the applicable compliance date for the revised guidelines. HMIWI that commence construction after February 6, 2007 or that are modified 6 months or more after the date of promulgation of any revised standards would have to meet the revised NSPS emission limits being added to the subpart Ec NSPS and any remaining NSPS limits from the 1997 rule, as applicable, within 6 months after the promulgation date of the amendments or upon startup, whichever is later.
IV. Rationale
A. Rationale for the Proposed Response to the Remand
This action responds to the Court's remand by (1) further explaining the reasoning processes by which EPA determined the MACT floors and the MACT standards for new and existing HMIWI for the portions of those processes that are being retained under our remand response, and (2) explaining revisions to the processes, the MACT floors, and the MACT standards for new and existing HMIWI that result from our response to the remand. 1. New HMIWI
The Court raised three issues with regard to EPA's treatment of the MACT floor for new units and the achievable
[Page 5521]emission limitations. First, the Court asked EPA to explain why the floor was based on the highest emissions levels of the ``worst- performing'' unit employing the MACT technology rather than on the lowest observed emissions levels of the best performing unit using the MACT technology. (See Sierra Club v. EPA, 167 F.3d at 665.) Second, the Court requested further explanation of why EPA considered multiple units employing the MACT technology, rather than identify the single best-performing unit and basing the floor on that particular unit's performance with that technology. Id. Third, the Court requested further explanation of EPA's procedure for determining the achievable emission limitation from the available data, where EPA selected a numerical value somewhat higher than the highest observed data point. The Court stated that EPA's procedure ``[m]ay be justifiable as a means of reasonably estimating the upper bound of the best-controlled unit's performance, but in the absence of agency explanation of both the decision to increase the levels and the choice of method for determining the increases, we are in no position to decide.'' Id. As discussed in detail below, for the first two issues, the Court described potential rationale for EPA's method. However, because the Court concluded that this rationale was not adequately presented in the rulemaking record, the Court asked for further clarification by EPA. In subsequent cases the Court further addressed these potential rationales, and discussed under what circumstances they would and would not be persuasive. In fact, the Court's potential rationale for EPA's method reflects the principles used by EPA in determining the MACT floor for new units and the achievable emission limitations for this source category, and is the method that has been used by EPA throughout most of the Agency's 30-year history in developing achievable technology-based emission limitations for source categories in cases where the application of control technology has been the only means by which sources have limited emissions, and the variability of technology performance is a critical factor in determining an emission limitation's achievability. (See, e.g., American Iron and Steel Inst. v. EPA,
115 F.3d 979, 1000 (D.C. Cir. 1997); BP Exploration & Oil, Inc., v. EPA, 66 F.3d. 784, 794 (6th Cir. 1995); NRDC v. EPA,
790 F.2d 289, 299 (3d Cir. 1986); National Ass'n of Metal Finishers v. EPA,
719 F.2d 624, 659 (3d Cir. 1983); rev'd on other grounds sub nom, Chemical Mfrs. Ass'n v. NRDC,
470 U.S. 116 (1985); American Petroleum Inst. v. EPA,
661 F.2d 340, 347 n. 23 (5th Cir. 1981); Bunker Hill Co. v. EPA,
572 F.2d 1286, 1302 (9th Cir. 1977); Marathon Oil Co. v. EPA,
564 F.2d 1253, 1266-67 (9th Cir. 1977); FMC v. Train,
639 F.2d 973, 985-86 (4th Cir. 1976).) As discussed elsewhere in this preamble, in CKRC the Court stressed that where record evidence suggests that factors other than application of control technology influence emissions, EPA will not be able to demonstrate ``that floors based on the worst-performing MACT sources' emissions represent `a reasonable estimate of the performance of the [best-performing] units.' '' CKRC, 255 F.3d at 866, quoting Sierra Club, 167 F.3d at 662. However, the Court reiterated that where EPA's record demonstrates that MACT technology significantly controls emissions, or that factors other than the control have a negligible effect, the approach of accounting for variability by basing the floor on the highest emissions resulting from a source using MACT technology ``could be a reasonable means of satisfying the statute's requirements.'' CKRC, at 866.
a. Applicability of National Lime to CAA Section 129. CAA section 129(a)(3) states that ``[s]tandards under section 111 and this section applicable to solid waste incineration units shall be based on methods and technologies for removal or destruction of pollutants before, during, or after combustion [* * *].'' This language requires that such a standard be based on the degree of reduction in air pollutant emissions that can be achieved through application of a particular method of pollution control, and any other factors that record evidence shows significantly affect emissions performance. Much like the language in CAA sections 111 and 129 governing the HMIWI standards, Congress has used similar language in other statutes to direct adoption of technology-based standards. (See, e.g., CAA section 169(3) defining ``best available control technology''; Clean Water Act section 301(b)(2)(A), for ``best available technology economically achievable'' or ``BAT'' standards; Clean Water Act section 304(b)(1) for ``best practicable technology'' or ``BPT'' standards.)
As the Court has stated, ``[t]echnology-based provisions [in the CAA] require EPA to promulgate standards only after finding that the requisite technology exists or may be feasibly developed. Absolute standards, on the other hand, require compliance with statutorily prescribed standards and time tables, irrespective of present technologies.'' (See NRDC v. Reilly,
983 F.2d 259, 268 (D.C. Cir. 1993) (holding that elimination of feasibility requirements and specification of particular control systems indicated that congressional amendment of CAA section 202(a)(6) resulted in an ``absolute'' standard).) MACT standards under CAA sections 111 and 129 are ``technology-based,'' rather than ``absolute'' standards. The legislative history to the 1990 CAA Amendments clearly shows that Congress intended the MACT standards to be technology-based. (See I A Legislative History, at 863 (Senator Durenberger referring to ``the MACT technology-based standards'' in debates on the bill reported by the Conference Committee); id., at 1128 (Senator Dole explaining that changes made to CAA section 129 in the Conference Committee ``make the technology test more closely approximate the role of the NSPS''); S. Rep. No. 101-228, at 133-134 (1989) (referring to CAA section 112 MACT standards as ``technology- based standards'' and noting that technology-based effluent standards under the Clean Water Act served as a model for the new MACT standards).)
CAA section 129 does not specify a type of control technology for HMIWI, but instead requires EPA to develop floor levels already achieved in practice by one or more units, and then issue standards that EPA determines are ``achievable'' for units in that source category. As the Court stated in National Lime Ass'n v. EPA (
627 F.2d 416, 431 n. 46 (D.C. Cir. 1980)) (``NLA I''), and restated in Sierra Club, ``where a statute requires a standard to be achievable, it must be achievable `under most adverse circumstances which can reasonably be expected to recur.' '' (See Sierra Club, 167 F.3d at 665.) In other words, ``EPA would be justified in setting floors at a level that is a reasonable estimate of the performance of the `best controlled similar unit'' under the worst reasonably foreseeable circumstances[.]'' Id. This concept of ``worst reasonably foreseeable circumstances'' is fundamental in developing achievable technology-based emission limitations, since, once the standard is in force, sources will be expected to comply with it at all times by relying on the technology that formed the basis for EPA's determination that the promulgated emissions limitation is achievable. As the Court stated in Sierra Club, `[i]t is reasonable to suppose that if an emissions standard is as stringent as `the emissions control that is achieved in practice' by a particular unit, then that particular unit will not violate the standard. This only results if `achieved in practice' is interpreted to
[Page 5522]mean `achieved under the worst foreseeable circumstances.' '' Id. EPA agrees with the Court that, in order to satisfy the requirements of NLA I, ``[t]he same principle should apply when a standard is to be derived from the operating characteristics of a particular unit[,]'' as is the case under CAA section 129(a)(2). Id. CAA section 129(a)(2) requires that the new unit MACT floor be ``not less stringent than the emissions control that is achieved in practice by the best controlled similar unit, as determined by the Administrator.'' It would have been unreasonable for EPA to base the MACT floors solely on the lowest levels of emissions observed without an assessment of whether those observed levels could be met on a continuous basis, and the CAA and its legislative history provide no support in deviating from the general practice EPA has followed in the wake of NLA I. In a report on H.R. 3030, the House Committee on Energy and Commerce explained that ``MACT is not intended to require unsafe control measures, or to drive sources to the brink of shutdown.'' (See H.R. Rep. No. 101-490, pt. 1, at 328 (1990).) This view is consistent with NLA I, which involved challenges to standards EPA promulgated under section 111 of the CAA and is particularly applicable to the HMIWI rulemaking under CAA section 129, since this rule has its basis in authority in both section 129 and section 111. (See CAA section 129(a)(1)(A) and (C).)
Moreover, interpreting CAA section 129 as subject to the principles of NLA I appropriately notes the critical distinction between a level of emissions that has been continuously achieved through performance using control technology, and one that has been observed at a single point in time. A level that has been continuously achieved is capable of being met under most conditions which can reasonably be expected to recur because variability in operating conditions is taken into account. Such a level best effectuates Congress' intent because it ensures that the MACT floor will result in reduced emissions without forcing sources to shut down. A lowest observed emission level, however, is not representative of a unit's performance under most conditions which can reasonably be expected, and may be impossible to achieve on a regular, let alone continuous, basis. While an observed lowest emissions level may be appropriate for use in determining whether a source is in compliance with an emission standard that must be continuously met, it is not an appropriate level upon which to base the minimum stringency level of such a standard.
In addition, Congress' use of the phrases ``as determined by the Administrator'' and ``achieved in practice'' in CAA section 129(a)(2) in the directive to establish MACT floors shows that Congress expected EPA to consider variability in operating conditions and other relevant factors in the Agency's determinations. The term ``practice'' is defined as ``[r]epeated or customary action; habitual performance; a succession of acts of a similar kind; custom; usage.'' (See Black's Law Dictionary 1172 (6th ed. 1990).) Thus, achieved in ``practice'' means achieved on a repeated, customary, or habitual basis. Under the statutory mandate that the level ``achieved in practice'' be ``determined by the Administrator,'' EPA must exercise its judgment, based on an evaluation of the relevant factors and available data, to determine the level of emissions control that can be customarily achieved using the relied-upon technology under variable conditions. Merely locating the lowest emissions data point and setting the MACT standard at that level would not constitute a considered ``determination by the Administrator'' as to what has been ``achieved in practice.'' (See, e.g., Senate Debate on Conference Report, 10-26- 90, reprinted in I A Legislative History of CAA Amendments of 1990, 103d Cong., 1st Sess. at 1128-1129 (Comm. Print 1993) (exchange between Senators Dole and Durenberger confirming that the phrase ``achieved in practice'' accounts for the distinction between research-type pollution control systems and systems that are ``economically viable for widespread use,'' and stressing that MACT floors should rely upon technologies that can ``stand the rigors of day to day operations'').)
Ultimately, NLA I is controlling because the case addressed how standards must be set in the face of variable operating conditions, and involved one of the same provisions of the CAA, section 111, under which the HMIWI rule was promulgated. NLA I held that EPA is required to use data that is representative of emissions that could be achieved in the industry as a whole. (See 627 F.2d at 433.) In developing the standards at issue in that case, EPA relied upon tests of the emissions from particular units to determine the level of emissions control that was achievable across the entire industry. The Court directed EPA to identify ``variable conditions that may contribute substantially to the amount of emissions, or otherwise affect the efficiency of the emissions control systems.'' Id. The Court then stated that ``where test results are relied upon, it should involve the selection or use of test results in a manner which provides some assurance of the achievability of the standard for the industry as a whole, given the range of variable factors found relevant to the standards' achievability.'' Id. This does not mean that EPA must test every plant, but it does mean that ``due consideration must be given to the possible impact on emissions of recognized variations in operations and some rationale offered for the achievability of the promulgated standards given the tests conducted and the relevant variables identified.'' Id., at 434. Thus, applying NLA I to the HMIWI rule adopted under CAA sections 111 and 129, it is really a misnomer to characterize EPA as basing the MACT floor on the emissions of the ``worst performing'' unit using the technology in question, since that unit's level of emissions necessarily more closely represents the level ``achieved in practice'' by the given technology than would the lowest emissions level observed at a source using that ``best'' technology.
b. Variability Between Facilities or Units. In remanding the NSPS at issue in NLA I, the Court noted that its decisions under CAA section 111 ``evince a concern that variables be accounted for, that the representativeness of test conditions be [sic] ascertained, that the validity of tests be assured and the statistical significance of results be determined.'' (See NLA I, 627 F.2d at 452-53.) (See, also, Portland Cement Ass'n v. Ruckelshaus,
486 F.2d 375, 396 (D.C. Cir. 1973), cert. denied,
417 U.S. 921 (1974).) When floors and standards are developed based on emissions data, EPA accounts for several types of variability to avoid adopting unachievable standards. The first type of variability is that concerning operational distinctions between facilities or units. As the Sierra Club Court stated in reviewing the HMIWI rule, ``[p]erhaps considering all units with the same technology is justifiable because the best way to predict the worst reasonably foreseeable performance of the best unit with the available data is to look at other units' performance. Or perhaps EPA reasonably considered all units with the same technology equally `well-controlled,' so that each unit with the best technology is a `best-controlled unit' even if such units vary widely in performance.'' (See 167 F.3d at 665.) These are two ways of saying essentially the same thing, and these concepts have
[Page 5523]been used by EPA throughout most of the Agency's history in determining achievable technology-based emission limitations, in cases where application of control technology significantly controls emissions and no record evidence indicates that factors other than the control have more than a negligible effect. Examining multiple units using the same technology gives the best picture of the performance capability of that particular technology, since it provides EPA with a more complete set of data by which to evaluate what levels of emissions control a technology can achieve as it is applied to varying sources. Such an analysis is necessary especially when adopting standards that all sources in a category will have to be able to meet by using the identified technology. Since MACT floors and standards are generally expressed as numerical emissions limits, it is necessary to account for this variability in order to adopt a regulation that is `achievable' by the industry as a whole.'' (See NLA I, 627 F.2d at 437.)
Section 129(a)(2) of the CAA requires that EPA determine the emissions control achieved by the ``best controlled similar unit'' when establishing the MACT floors for new units. A solid waste incineration ``unit'' is defined as ``a distinct operating unit of any facility which combusts any solid waste material'' (CAA section 129(g)(1)). To achieve the best level of pollution control, that unit will utilize a particular method of pollution control (and possibly use other means that affect its emissions performance). The emissions control achieved by that method (and by any additional means) is the emissions control achieved by the ``best controlled similar unit.'' Thus, the MACT floor for new units is based on the ``emissions control'' that is attained by the specific method of pollution control and any other means used to limit emissions at the best similar unit, rather than merely on the emissions measured at a particular unit.
In this way, by basing the MACT floor on the capability of a particular method of pollution control used at ``similar'' ``best'' ``units,'' instead of on the emissions measured at a single unit, EPA ensures that the floors would not only be achievable by the single best performing unit, but are also achievable by other units using the same technology and/or emissions limiting means as the best similar unit, and that it is reasonable to require the best similar unit and all future new units to meet this floor on a continuous basis. In contrast, identifying the ``emissions control'' of the ``best controlled similar unit'' as being a single data point from a single source provides merely a snapshot of emissions performance that may not be replicable by either that single source or by other sources using the same control technology, and, therefore, does not provide a basis for enforceably requiring all sources to perform to that level.
Thus, the most reasonable way to interpret the statutory phrase ``best controlled similar unit'' in CAA section 129 is as encompassing all units using the same technology and emissions limiting means as the single unit with the best observed performance, rather than just that single best performing unit itself. A contrary interpretation would seem to directly conflict with the Court's directive in NLA I, and is not compelled by the Court rulings in Sierra Club, NLA II, and CKRC. Applying this approach to evaluating ``best technologies'' at ``best controlled similar units,'' where different design characteristics are identified (e.g., low-efficiency versus moderate-efficiency versus high-efficiency wet scrubbers), the data are grouped such that each data set reflects the performance of an ``identical'' control device, providing the best indication of the true performance of each control device and enabling the Agency to adopt a numerical standard that can be met with the subject technology at all units employing this technology, and can be enforced. Again, where the record evidence indicates that the only means of control of emissions at units is application of control technology, and there is no record evidence showing that other means of emissions limitation significantly affect emissions performance, basing the MACT floor on this approach is fully consistent with the Court's rulings in the MACT cases.
c. Variability Between and Within Tests at Facilities. Another type of variability that EPA accounts for in order to ensure the achievability of technology-based standards that rely upon application of pollution controls concerns operational distinctions between and within tests at the same unit. Regarding ``between-test variability,'' even where conditions appear to be the same when two or more tests are conducted, variations in emissions are often caused by different settings for emissions testing equipment and differences in sample handling. Varying results may also be caused by use of different field teams to conduct the testing, or different laboratories to analyze the results. All these variations are typical.
An achievable standard needs to account for these differences between tests, in order for ``a uniform standard [to] be capable of being met under most adverse conditions which can reasonably be expected to recur[.]'' (See NLA I, 627 F.2d at 431, n. 46.) (See also Portland Cement Ass'n, 486 F.2d at 396 (noting industry point that ``a single test offered a weak basis'' for inferring that plants could meet the standards).) Without accounting for variation among different emissions tests, it can be determined with a significant degree of statistical confidence that even a single unit will not be able to meet the standard over a reasonable period of time, when one can expect adverse conditions to recur. The Courts have recognized this basic principle in reviewing technology-based effluent standards under the Clean Water Act. As the U.S. Court of Appeals for the 5th Circuit stressed regarding ``best practicable technology'' or ``BPT'' standards under section 304(b)(1) of the Clean Water Act, ``[t]he same plant using the same treatment method to remove the same toxic does not always achieve the same result. Tests conducted one day may show a different concentration of the same toxic than are shown by the same test on the next day. This variability may be due to the inherent inaccuracy of analytical testing, i.e., `analytical variability,' or to routine fluctuations in a plant's treatment performance.'' (See Chemical Mf'rs Ass'n v. EPA,
870 F.2d 177, 228 (5th Cir. 1989).) (See also American Petroleum Institute v. EPA,
540 F.2d 1023, 1035-36 (10th Cir. 1976) (``Even in the best treatment systems, changes occur in ability to treat wastes. [* * *] [V]ariability factors present[] a practical effort to accommodate for variations in plant operations''); FMC Corp. v. Train,
539 F.2d 973, 985 (4th Cir. 1976) (variability factors account for ``the fact that even in the best treatment systems changes continually occur in the treatability of wastes'').)
The same types of differences leading to between-test variability also cause variations in results between various runs comprising a single test, or ``within-test variability.'' A single test at a unit usually includes at least three separate test runs. (See
40 CFR 63.7(e)(3) (for MACT standards under section 112 of the CAA), and
40 CFR 60.8(f) (for NSPS under CAA section 111).) (See also Portland Cement Ass'n, 486 F.2d at 397 (noting differences in conditions among several test runs).)
d. Application of NLA I, Sierra Club, NLA II, and CKRC Principles in HMIWI Rulemaking. Based on the record for the 1997 rulemaking, the best way to determine the worst reasonably foreseeable circumstances for the
[Page 5524]particular technologies used to control emissions at HMIWI was to first examine the highest data point actually observed from HMIWI equipped with each particular technology. If an emission value has been observed and there is no reason to believe it represents poor performance (i.e., there is nothing that can be done to prevent its recurring), it is likely to occur again in the future and, therefore, reflects a foreseeable circumstance. It is incorrect to characterize the highest data point as the ``worst performance'' of the best performing unit, or to characterize one control device's performance as ``better'' than another's based solely on the results of a single emission test. This is because such focuses relate to essentially random single data occurrences, rather than to estimating what a particular technology can be expected to continuously achieve. Rather, each data point, whether from one unit or from several identical units using the same technology, should be viewed as a snapshot of the actual performance of the technology in use. Along with an understanding of the factors affecting the performance of the technology, each of these snapshots gives information about the normal, and unavoidable, variation in emissions that would be expected to recur over time when using the identified technology. Conversely, when there is evidence that an emission data point reflects poor performance (design, operation, or both), such a data point should not be considered in determining the achievable emission limitation associated with the technology.
Furthermore, a distinction must be made between an emission level that has been ``observed'' and an emission limitation that can be continuously ``achieved.'' The purpose of the MACT program is to compel sources to replicate emission reduction strategies used by the best- performing sources. Thus, MACT floors are based on the control strategies used by the best-performing sources to reduce emissions, not based on a snapshot level of emissions from sources without regard to whether this level reflects application of any replicable emission control strategies. CAA section 129(a)(2) does not direct EPA to assess relative emission ``levels'' in determining MACT floors; it directs EPA to assess the degree of emissions ``control'' or ``reduction'' or ``limitation'' ``achieved'' by the best-controlled or best-performing sources. The plain meaning of these words implies that a source is utilizing some method or technique to reduce emissions that is within a source operator's power to adopt. The reference to a ``degree of reduction'' supports the view that the words ``control'' and ``limitation'' appearing in section 129(a)(2) require a source to have reduced emissions from uncontrolled levels through some control technique. See NLA II, 233 F.3d at 631-32 (rejecting position that EPA is required to set new source floors at the lowest recorded emission level for which it has data and to set existing source floors at the average of the lowest 12 percent or recorded emission level data points).
The Court has recognized that EPA may consider variability in estimating the degree of emission reduction achieved by best-performing sources and in setting MACT floors. See Mossville Envt'l Action Now v. EPA,
370 F.3d 1232, 1241-42 (D.C. Cir 2004) (holding EPA may consider emission variability in estimating performance achieved by best- performing sources and may set floor at level that best-performing source can expect to meet ``every day and under all operating conditions''). Since an emission limitation must be complied with at all times, for it to be achievable it must be set at a level that will not force sources to violate it when operating conditions are not ideal and higher emissions levels might be observed. For example, a car which has been observed to consume 0.02 gallons of gasoline in a one-mile downhill stretch of highway cannot be said to have ``achieved'' a minimum 50 miles per gallon fuel efficiency rate when that same car is later certain to consume 0.04 gallons of gasoline in a one-mile uphill stretch of highway (25 miles per gallon). Rather, the minimum fuel efficiency of the car will be that which the car can meet in adverse circumstances, the uphill stretch. So it is with emissions limitations, which cannot reasonably be set at levels which would force sources to operate in violation even when properly employing the control technology upon which the standards are based.
The emission data used to develop the emission limitations in the HMIWI regulations reflect properly designed and operated air pollution control technology on properly designed and operated HMIWI, and emission data that reflected poor operation of the HMIWI unit or the air pollution control technology were excluded. (See Legacy Docket ID No. A-91-61, items II-A-111 and IV-B-14.) The incinerators selected by EPA for testing represented a range of incinerator designs and air pollution control systems in use on this source category. (See Legacy Docket ID No. A-91-61, item IV-B-46.) The incinerators and air pollution controls were inspected thoroughly, and maintenance was performed where necessary to ensure that the incinerators and pollution controls were functioning properly. (See Legacy Docket ID No. A-91-61, items II-A-93, II-A-94, and II-A-85.) During testing, most test runs were conducted under representative conditions to minimize emissions. (See Legacy Docket ID No. A-91-61, items II-A-111, IV-B-46, and IV-B- 47.) However, some test runs were purposely conducted under conditions that would represent poor operation (e.g., overcharging waste to the incinerator) to determine the effect of improper operation on emissions. (See Legacy Docket ID No. A-91-61, items II-A-111 and IV-B- 46.) These test runs demonstrated that improper operation results in higher emissions. (See Legacy Docket ID No. A-91-61, items II-A-111, IV-B-46, and II-A-81.) Of course, the test runs reflecting poor operation were not used in developing the achievable emission limitations. Id. It is important to note that such poor operation is precluded by the good combustion requirements and the parametric monitoring requirements in the 1997 final rule. In addition to data gathered by EPA directly, vendors of air pollution control systems submitted test reports to EPA. (See Legacy Docket ID No. A-91-61, items II-I-230 through 237, II-I-243 and 244, II-I-248, IV-B-48 and 49, IV-J- 11, IV-J-15 and 16, IV-J-20, IV-J-24, IV-J-27, IV-J-29 through 31, IV- J-33 and 34, IV-J-39 and 40, and IV-J-47.) The test reports were submitted primarily by wet scrubber vendors to demonstrate to EPA that wet scrubbers could achieve lower emissions than EPA had concluded from the EPA-collected data. (EPA had conducted testing on only one wet scrubber system.) (See 61 FR 31742; Legacy Docket ID No. A-91-61, item IV-B-48.) The test reports and the data collected by EPA reflect the best performance of the air pollution controls that can reasonably be expected when continuously applied on HMIWI.
MACT and other technology-based standards are necessarily derived from short-term emissions test data, but such data are not representative of the range of operating conditions that facilities face on a day-to-day basis. In statistical terms, each test produces a limited data sample, not a complete enumeration of the available data for performance of the unit over a long period of time. (See Natrella, Experimental Statistics, National Bureau of Standards Handbook 91, chapter 1 (revised ed., 1966).) EPA, therefore, often needs to adjust the
[Page 5525]short-term data to account for these varying conditions, so facilities properly employing optimal controls can remain in compliance with the standards on a continuous basis.
With the relatively small data sets EPA had to work with in the 1997 HMIWI rulemaking, it is possible that EPA has not recorded the highest emissions levels that would occur under the worst reasonably foreseeable circumstances. As the Court noted, it would ``generally defer to an agency's decision to proceed on the basis of imperfect scientific information, rather than to `invest the resources to conduct the perfect study.' '' (See Sierra Club, 167 F.3d at 662.) ``[S]ince EPA had data on only one percent of about 3,000 [HMIWI], the data gathering costs of any non-sampling method may well have been daunting.'' Id., at 663. In fact, the ``perfect study'' cannot be conducted, regardless of the resources expended to conduct it. Every study ends with some uncertainty in the results. There is no ``cookbook'' methodology for determining achievable emission limitations from data. In every case, but especially in cases where data are limited as with the 1997 HMIWI rulemaking, EPA must make judgments about what constitutes the worst reasonably foreseeable circumstance and put those judgments out for public comment. In the case of the HMIWI rulemaking, the ``high'' data points simply reflected the normal, and unavoidable, variation in emissions that would be expected to recur over time when properly using the best control technologies and strategies we determined were being used at HMIWI units. In fact, while the highest observed value is a ``foreseeable circumstance,'' it may not reflect the worst reasonably foreseeable circumstance. In determining the 1997 final MACT standards, EPA chose to account for the ``worst reasonably foreseeable circumstance'' by adding 10 percent to the highest observed emissions levels in the data, and then rounding up those figures. Upon review of this approach in responding to the Court's remand, we have determined that although the highest observed data point may not reflect the ``worst reasonably foreseeable circumstance,'' we do not have information to support accounting for the ``worst reasonably foreseeable circumstance'' by adding 10 percent to the highest observed emissions levels, and then rounding up those figures. We, therefore, propose to base revised MACT standards for new HMIWI units on the highest observed data points associated with employed control strategies.
In the CKRC case, the Court left open the possibility that the approach of basing floors on the ``worst-performing MACT sources'' emissions represent `a reasonable estimate of the performance of the
[best-performing] units,' '' CKRC at 866, quoting Sierra Club at 662, provided that ``in the case of a particular source category or HAP, the Agency can demonstrate with substantial evidence--not mere assertions-- that MACT technology significantly controls emissions, or that factors other than the control have a negligible effect[.] CKRC at 866, citing NLA II at 633. The Court in Sierra C
