# National Emission Standards for Hazardous Air Pollutants for Lime Manufacturing Plants > Briefs, arguments, decisions, and more. URL: https://www.frixlaw.com/law-library/documents/fr%3A02-31233 ## Record - **Collection:** Federal Register - **Document type:** Proposed Rule - **Published:** December 20, 2002 - **Citation:** 67 FR 78046 ## Text ENVIRONMENTAL PROTECTION AGENCY 40 CFR Part 63 [Docket ID No. OAR-2002-0052; FRL-7418-1] RIN 2060-AG72 National Emission Standards for Hazardous Air Pollutants for Lime Manufacturing Plants AGENCY: Environmental Protection Agency (EPA). ACTION: Proposed rule. SUMMARY: This action proposes national emission standards for hazardous air pollutants (NESHAP) for the lime manufacturing source category. The lime manufacturing emission units regulated would include lime kilns, lime coolers, and various types of materials processing operations (MPO). The EPA has identified the lime manufacturing industry as a major source of hazardous air pollutant (HAP) emissions including, but not limited to, hydrogen chloride (HCl), antimony, arsenic, beryllium, cadmium, chromium, lead, manganese, mercury, nickel, and selenium. Exposure to these substances has been demonstrated to cause adverse health effects such as cancer; irritation of the lung, skin, and mucus membranes; effects on the central nervous system; and kidney damage. The proposed standards would require all major sources subject to the rule to meet HAP emission standards reflecting the application of maximum achievable control technology (MACT). Implementation of the standards as proposed would reduce non-volatile metal HAP emissions from the lime manufacturing industry source category by approximately 21 megagrams per year (Mg/yr) (23 tons per year (tons/yr)) and would reduce emissions of particulate matter (PM) by 14,000 Mg/yr (16,000 tons/yr). DATES: Comments. Submit comments on or before February 18, 2003. Public Hearing. If anyone contacts the EPA requesting to speak at a public hearing by January 9, 2003, a public hearing will be held on January 21, 2003. ADDRESSES: Comments. Comments may be submitted electronically, by mail, by facsimile, or through hand delivery/courier. Follow the detailed instructions as provided in the SUPPLEMENTARY INFORMATION section. Public Hearing. If a public hearing is held, it will be held at the new EPA facility complex in Research Triangle Park, NC. FOR FURTHER INFORMATION CONTACT: General and technical information. Joseph P. Wood, P.E., Minerals and Inorganic Chemicals Group, Emissions Standards Division (C504-05), U.S. EPA, Research Triangle Park, North Carolina 27711, telephone number (919) 541-5446, electronic mail (e-mail) address wood.joe@epa.gov. Methods, sampling, and monitoring information. Michael Toney, Source Measurement Technology Group, Emission Monitoring and Analysis Division (D205-02), U.S. EPA, Research Triangle Park, North Carolina 27711, telephone number (919) 541-5247, e-mail address toney.mike@epa.gov. Economic impacts analysis. Eric Crump, Innovative Strategies and Economics Group, Air Quality Strategies and Standards Division (C339-01), U.S. EPA, Research Triangle Park, North Carolina 27711, telephone number (919) 541-4719, e-mail address crump.eric@epa.gov. SUPPLEMENTARY INFORMATION: Regulated Entities. Categories and entities potentially regulated by this action include: Category NAICS Examples of regulated entities 32741 Commercial lime manufacturing plants. 33111 Captive lime manufacturing plants at iron and steel mills. 3314 Captive lime manufacturing plants at nonferrous metal production facilities. 327125 Producers of dead-burned dolomite (Non-clay refractory manufacturing). This table is not intended to be exhaustive, but rather provides a guide for readers regarding entities likely to be regulated by this action. To determine whether your facility is regulated by this action, you should examine the applicability criteria in § 63.7081 of the proposed rule. If you have any questions regarding the applicability of this action to a particular entity, consult the technical contact person listed in the preceding FOR FURTHER INFORMATION CONTACT section. Docket. The EPA has established an official public docket for this action under Docket ID No. OAR-2002-0052. The official public docket is the collection of materials that is available for public viewing at the Air and Radiation Docket and Information Center (Air Docket) in the EPA Docket Center, (EPA/DC) EPA West, Room B102, 1301 Constitution Ave., NW., Washington, DC. The Docket Center 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 Reading Room is (202) 566-1744, and the telephone number for the Air Docket is (202) 566-1742. Electronic Access. You may access this Federal Register document electronically through the EPA Internet under the Federal Register listings at http://www.epa.gov/fedrgstr/. An electronic version of the public docket is available through EPA's electronic public docket and comment system, EPA Dockets. You may use EPA Dockets at http://www.epa.gov/edocket/ to submit or review public comments, access the index of the contents of the official public docket, and to access those documents in the public docket that are available electronically. Once in the system, select “search,” then key in the appropriate docket identification number. Certain types of information will not be placed in the EPA dockets. Information claimed as confidential business information (CBI) and other information whose disclosure is restricted by statute, which is not included in the official public docket, will not be available for public viewing in EPA's electronic public docket. EPA's policy is that copyrighted material will not be placed in EPA's electronic public docket but will be available only in printed, paper form in the official public docket. Although not all docket materials may be available electronically, you may still access any of the publicly available docket materials through the docket facility identified in this document. For public commenters, it is important to note that EPA's policy is that public comments, whether submitted electronically or in paper, will be made available for public viewing in EPA's electronic public docket as EPA receives them and without change, unless the comment contains copyrighted material, CBI, or other information whose disclosure is restricted by statute. When EPA identifies a comment containing copyrighted material, EPA will provide a reference to that material in the version of the comment that is placed in EPA's electronic public docket. The entire printed comment, including the copyrighted material, will be available in the public docket. Public comments submitted on computer disks that are mailed or delivered to the docket will be transferred to EPA's electronic public docket. Public comments that are mailed or delivered to the docket will be scanned and placed in EPA's electronic public docket. Where practical, physical objects will be photographed, and the photograph will be placed in EPA's electronic public docket along with a brief description written by the docket staff. Comments. You may submit comments electronically, by mail, by facsimile, or through hand delivery/courier. To ensure proper receipt by EPA, identify the appropriate docket identification number in the subject line on the first page of your comment. Please ensure that your comments are submitted within the specified comment period. Comments submitted after the close of the comment period will be marked “late.” EPA is not required to consider these late comments. Comments Submitted Electronically. If you submit an electronic comment as prescribed below, EPA recommends that you include your name, mailing address, and an e-mail address or other contact information in the body of your comment. Also include this contact information on the outside of any disk or CD ROM you submit and in any cover letter accompanying the disk or CD ROM. This ensures that you can be identified as the submitter of the comment and allows EPA to contact you in case EPA cannot read your comment due to technical difficulties or needs further information on the substance of your comment. EPA's policy is that EPA will not edit your comment, and any identifying or contact information provided in the body of a comment will be included as part of the comment that is placed in the official public docket and made available in EPA's electronic public docket. 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. Your use of EPA's electronic public docket to submit comments to EPA electronically is EPA's preferred method for receiving comments. Go directly to EPA Dockets at http://www.epa.gov/edocket and follow the online instructions for submitting comments. Once in the system, select “search” and then key in Docket ID No. OAR-2002-0052. The system is an “anonymous access” system, which means EPA will not know your identity, e-mail address, or other contact information unless you provide it in the body of your comment. Comments may be sent by electronic mail (e-mail) to a-and-r-docket@epa.gov, Attention Docket ID No. OAR-2002-0052. In contrast to EPA's electronic public docket, EPA's e-mail system is not an “anonymous access” system. If you send an e-mail comment directly to the Docket without going through EPA's electronic public docket, EPA's e-mail system automatically captures your e-mail address. E-mail addresses that are automatically captured by EPA's e-mail system are included as part of the comment that is placed in the official public docket and made available in EPA's electronic public docket. You may submit comments on a disk or CD ROM that you mail to the mailing address identified in this document. These electronic submissions will be accepted in Wordperfect or ASCII file format. Avoid the use of special characters and any form of encryption. Comments Submitted By Mail. Send your comments (in duplicate, if possible) to: Lime Manufacturing NESHAP Docket, EPA Docket Center (Air Docket), U.S. EPA West, Mail Code 6102T, Room B108, 1200 Pennsylvania Avenue, NW., Washington, DC 20460, Attention Docket ID No. OAR-2002-0052. Comments Submitted By Hand Delivery or Courier. Deliver your comments (in duplicate, if possible) to: EPA Docket Center, U.S. EPA West, Mail Code 6102T, Room B108, 1301 Constitution Avenue, NW., Washington, DC 20004, Attention Docket ID No. OAR-2002-0052. Such deliveries are only accepted during the Docket Center's normal hours of operation as identified in this document. Comments Submitted By Facsimile. Fax your comments to: (202) 566-1741, Attention Lime Manufacturing NESHAP Docket, Docket ID No. OAR-2002-0052. CBI. Do not submit information that you consider to be CBI through EPA's electronic public docket or by e-mail. Send or deliver information identified as CBI only to the following address: OAQPS Document Control Officer (C404-02), U.S. EPA, 109 TW Alexander Drive, Research Triangle Park, NC 27709, Attention Joseph Wood, Docket ID No. OAR-2002-0052. You may claim information that you submit to EPA as CBI by marking any part or all of that information as CBI (if you submit CBI on disk or CD ROM, 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 CBI). Information so marked will not be disclosed except in accordance with procedures set forth in 40 CFR part 2. Public Hearing. Persons interested in presenting oral testimony or inquiring as to whether a hearing is to be held should contact Mr. Joseph Wood, Minerals and Inorganic Chemicals Group, Emission Standards Division (C504-05), Research Triangle Park, NC 27711, telephone number (919) 541-5446, at least 2 days in advance of the public hearing. Persons interested in attending the public hearing must also call Mr. Joseph Wood to verify the time, date, and location of the hearing. The public hearing will provide interested parties the opportunity to present data, views, or arguments concerning these proposed emission standards. Worldwide Web (WWW). In addition to being available in the docket, an electronic copy of today's proposal will also be available on the WWW through the Technology Transfer Network (TTN). Following signature, a copy of this action will be posted on the TTN's policy and guidance page for newly proposed rules at http://www.epa.gov/ttn/oarpg. The TTN provides information and technology exchange in various areas of air pollution control. If more information regarding the TTN is needed, call the TTN HELP line at (919) 541-5384. Outline. The information presented in this preamble is organized as follows: [] I. Introduction A. What Is the Purpose of the Proposed Rule? B. What Is the Source of Authority for Development of NESHAP? C. What Criteria Are Used in the Development of NESHAP? D. How Was the Proposed Rule Developed? E. What Are the Health Effects of the HAP Emitted From the Lime Manufacturing Industry? F. What Are Some Lime Manufacturing Industry Characteristics? G. What Are the Processes and Their Emissions at a Lime Manufacturing Plant? II. Summary of Proposed Rule A. What Lime Manufacturing Plants Are Subject to the Proposed Rule? B. What Emission Units at a Lime Manufacturing Plant Are Included Under the Definition of Affected Source? C. What Pollutants Are Regulated By the Proposed Rule? D. What Are the Emission Limits and Operating Limits? E. When Must I Comply With the Proposed Rule? F. How Do I Demonstrate Initial Compliance With the Proposed Rule? G. How Do I Continuously or Periodically Demonstrate Compliance with the Proposed Rule? H. How Do I Determine if My Lime Manufacturing Plant Is a Major Source and Thus Subject to the Proposed Rule? III. Rationale for Proposed Rule A. How Did We Determine the Source Category to Regulate? B. How Did We Determine the Affected Source? C. How Did We Determine Which Pollutants to Regulate? D. How Did We Determine the MACT Floor for Emission Units at Existing Lime Manufacturing Plants? E. How Did We Determine the MACT Floor For Emission Units at New Lime Manufacturing Plants? F. What Control Options Beyond the MACT Floor Did We Consider? G. How Did We Select the Format of the Proposed Rule? H. How Did We Select the Test Methods and Monitoring Requirements for Determining Compliance With This Proposed Rule? IV. Summary of Environmental, Energy and Economic Impacts A. How Many Facilities Are Subject To the Proposed Rule? B. What Are the Air Quality Impacts? C. What Are the Water Impacts? D. What Are the Solid Waste Impacts? E. What Are the Energy Impacts? F. What Are the Cost Impacts? G. What Are the Economic Impacts? V. Administrative Requirements A. Executive Order 12866, Regulatory Planning and Review B. Executive Order 13132, Federalism C. Executive Order 13084, Consultation and Coordination with Indian Tribal Governments D. Executive Order 13045, Protection of Children from Environmental Health Risks and Safety Risks E. Unfunded Mandates Reform Act of 1995 F. Regulatory Flexibility Act (RFA), as Amended by the Small Business Regulatory Enforcement Fairness Act (SBREFA) of 1996, 5 U.S.C. 601 et seq. G. Paperwork Reduction Act H. National Technology Transfer and Advancement Act of 1995 I. Executive Order 13211, Actions Concerning Regulations That Significantly Affect Energy Supply, Distribution or Use I. Introduction A. What Is the Purpose of the Proposed Rule? The purpose of the proposed rule is to protect the public health by reducing emissions of HAP from lime manufacturing plants. B. What Is the Source of Authority for Development of NESHAP? Section 112 of the CAA requires us to list categories and subcategories of major sources and area sources of HAP and to establish NESHAP for the listed source categories and subcategories. The Lime Manufacturing category of major sources covered by today's proposed NESHAP was listed on July 16, 1992 (57 FR 31576). Major sources of HAP are those that have the potential to emit greater than 10 tons/yr of any one HAP or 25 tons/yr of any combination of HAP. C. What Criteria Are Used in the Development of NESHAP? Section 112 of the CAA requires that we establish NESHAP for the control of HAP from both new and existing major sources. The CAA requires the NESHAP to reflect the maximum degree of reduction in emissions of HAP that is achievable. This level of control is commonly referred to as the maximum achievable control technology (MACT). The MACT floor is the minimum control level allowed for NESHAP and is defined under section 112(d)(3) of the CAA. In essence, the MACT floor ensures that the standard is set at a level that assures that all major sources achieve the level of control at least as stringent as that already achieved by the better-controlled and lower-emitting sources in each source category or subcategory. For new sources, the MACT floor cannot be less stringent than the emission control that is achieved in practice by the best-controlled similar source. The MACT standards for existing sources can be less stringent than standards for new sources, but they cannot be less stringent than the average emission limitation achieved by the best-performing 12 percent of existing sources in the category or subcategory (or the best-performing 5 sources for categories or subcategories with fewer than 30 sources). In developing MACT, we also consider control options that are more stringent than the floor. We may establish standards more stringent than the floor based on the consideration of cost of achieving the emissions reductions, any health and environmental impacts, and energy requirements. D. How Was the Proposed Rule Developed? We used several resources to develop the proposed rule, including questionnaire responses from industry, emissions test data, site surveys of lime manufacturing facilities, operating and new source review permits, and permit applications. We researched the relevant technical literature and existing State and Federal regulations and consulted and met with representatives of the lime manufacturing industry, State and local representatives of air pollution agencies, Federal agency representatives ( e.g. , United States Geological Survey) and emission control and emissions measurement device vendors in developing the proposed rule. We also conducted an extensive emissions test program. Industry representatives provided emissions test data, arranged site surveys of lime manufacturing plants, participated in the emissions test program, reviewed draft questionnaires, provided information about their manufacturing processes and air pollution control technologies, and identified technical and regulatory issues. State representatives provided existing emissions test data, copies of permits and other information. E. What Are the Health Effects of the HAP Emitted From the Lime Manufacturing Industry? The HAP emitted by lime manufacturing facilities include, but are not limited to, HCl, antimony, arsenic, beryllium, cadmium, chromium, lead, manganese, mercury, nickel, and selenium. Exposure to these compounds has been demonstrated to cause adverse health effects when present in concentrations higher than those typically found in ambient air. We do not have the type of current detailed data on each of the facilities that would be covered by the proposed NESHAP, and the people living around the facilities, that would be necessary to conduct an analysis to determine the actual population exposures to the HAP emitted from these facilities and the potential for resultant health effects. Therefore, we do not know the extent to which the adverse health effects described below occur in the populations surrounding these facilities. However, to the extent the adverse effects do occur, the proposed rule would reduce emissions and subsequent exposures. We also note one exception to this statement, namely that human exposures to ambient levels of HCl resulting from lime manufacturing facilities' emissions were estimated by industry as part of the risk assessment they conducted for purposes of demonstrating, pursuant to section 112(d)(4) of the CAA, that HCl emissions from lime kilns are below the threshold level of adverse effects, with an ample margin of safety. The HAP that would be controlled with the proposed rule are associated with a variety of adverse health effects, including chronic health disorders ( e.g. , irritation of the lung, skin, and mucus membranes; effects on the central nervous system; cancer; and damage to the kidneys), and acute health disorders ( e.g. , lung irritation and congestion, alimentary effects such as nausea and vomiting, and effects on the kidney and central nervous system). We have classified three of the HAP—arsenic, chromium, and nickel—as human carcinogens and three others—beryllium, cadmium, and lead—as probable human carcinogens. F. What Are Some Lime Manufacturing Industry Characteristics? There are approximately 70 commercial and 40 captive lime manufacturing plants in the U.S., not including captive lime manufacturing operations at pulp and paper production facilities. About 30 of the captive plants in the U.S. produce lime that is used in the beet sugar manufacturing process, but captive lime manufacturing plants are also found at steel, other metals, and magnesia production facilities. Lime is produced in about 35 States and Puerto Rico by about 47 companies, which include commercial and captive producers (except for lime manufacturing plants at pulp and paper production facilities), and those plants which produce lime hydrate only. G. What Are the Processes and Their Emissions at a Lime Manufacturing Plant? There are many synonyms for lime, the main ones being quicklime and its chemical name, calcium oxide. High calcium lime consists primarily of calcium oxide, and dolomitic lime consists of both calcium and magnesium oxides. Lime is produced via the calcination of high calcium limestone (calcium carbonate) or other highly calcareous materials such as aragonite, chalk, coral, marble, and shell; or the calcination of dolomitic limestone. Calcination occurs in a high temperature furnace called a kiln, where lime is produced by heating the limestone to about 2000° F, driving off carbon dioxide in the process. Dead-burned dolomite is a type of dolomitic lime produced to obtain refractory characteristics in the lime. The kiln is the heart of the lime manufacturing plant, where various fossil fuels (such as coal, petroleum coke, natural gas, and fuel oil) are combusted to produce the heat needed for calcination. There are five different types of kilns: rotary, vertical, double-shaft vertical, rotary hearth, and fluidized bed. The most popular is the rotary kiln, but the double-shaft vertical kiln is an emerging new kiln technology gaining in acceptance because of its energy efficiency. Rotary kilns may also have preheaters associated with them to improve energy efficiency. As discussed further in this preamble, additional energy efficiency is obtained by routing exhaust from the lime cooler to the kiln, a common practice. Emissions from lime kilns include, but are not limited to, metallic HAP, HCl, PM, sulfur dioxide, nitrogen oxides, and carbon dioxide. These emissions predominately originate from compounds in the limestone feed material and fuels ( e.g. , metals, sulfur, chlorine) and are formed from the combustion of fuels and the heating of feed material in the kiln. All types of kilns use external equipment to cool the lime product, except vertical (including double-shaft) kilns, where the cooling zone is part of the kiln. Ambient air is most often used to cool the lime (although a few use water as the heat transfer medium), and typically all of the heated air stream exiting the cooler goes to the kiln to be used as combustion air for the kiln. The exception to this is the grate cooler, where more airflow is generated than is needed for kiln combustion, and consequently a portion (about 40 percent) of the grate cooler exhaust is vented to the atmosphere. We estimate that there are about five to ten kilns in the U.S. that use grate coolers. The emissions from grate coolers include the lime dust (PM) and the trace metallic HAP found in the lime dust. Lime manufacturing plants may also produce hydrated lime (also called calcium hydroxide) from some of the calcium oxide (or dolomitic lime) produced. Hydrated lime is produced in a hydrator via the chemical reaction of calcium oxide (or magnesium oxide) and water. The hydration process is exothermic, and part of the water in the reaction chamber is converted to steam. A wet scrubber is integrated with the hydrator to capture the lime (calcium oxide and calcium hydroxide) particles carried in the gas steam, with the scrubber water recycled back to the hydration chamber. The emissions from the hydrator are the PM comprised of lime and hydrated lime. Operations that prepare the feed materials and fuels for the kiln and process the lime product for shipment or further on-site use are found throughout a lime manufacturing plant. The equipment includes grinding mills, crushers, storage bins, conveying systems (such as bucket elevator, belt conveyors), bagging systems, bulk loading or unloading systems, and screening operations. The emissions from these operations include limestone and lime dust (PM) and the trace metallic HAP found in the dust. II. Summary of Proposed Rule A. What Lime Manufacturing Plants Are Subject to the Proposed Rule? The proposed rule would regulate HAP emissions from all new and existing lime manufacturing plants that are major sources, co-located with major sources, or are part of major sources. However, lime manufacturing plants located at pulp and paper mills or at beet sugar factories would not be subject to the proposed rule. Other captive lime manufacturing plants, such as (but not limited to) those at steel mills and magnesia production facilities, would be subject to the proposed rule. We define a lime manufacturing plant as any plant which uses a lime kiln to produce lime product from limestone or other calcareous material by calcination. Lime product means the product of the lime kiln calcination process including calcitic lime, dolomitic lime, and dead-burned dolomite. B. What Emission Units at a Lime Manufacturing Plant Are Included Under the Definition of Affected Source? The proposed rule would include the following emission units under the definition of affected source: Lime kilns and coolers, and MPO associated with limestone feed preparation (beginning with the raw material storage bin). The individual types of MPO that would be included under the definition of affected source are grinding mills, raw material storage bins, conveying system transfer points, bulk loading or unloading systems, screening operations, bucket elevators, and belt conveyors—if they follow the raw material storage bin in the sequence of MPO. The MPO associated with lime products (such as quicklime and hydrated lime), lime kiln dust handling, quarry or mining operations, and fuels would not be subject to today's proposed rule. The MPO are further distinguished in the proposed rule as follows: (1) Whether their emissions are vented through a stack, (2) whether their emissions are fugitive emissions, (3) whether their emissions are vented through a stack with some fugitive emissions from the partial enclosure, and/or (4) whether the source is enclosed in a building. Finally, lime hydrators would not be included under the definition of affected source under the proposed NESHAP. C. What Pollutants Are Regulated by the Proposed Rule? The proposed rule would establish PM emission limits for lime kilns, coolers, and MPO with stacks. Particulate matter would be measured solely as a surrogate for the non-volatile and semi-volatile metal HAP. (Particulate matter of course is not itself a HAP, but is a typical and permissible surrogate for HAP metals. See National Lime Ass'n v. EPA, 233 F. 3d 625, 637-40 (D.C. Cir., 2000).) The proposed rule also would regulate opacity or visible emissions from most of the MPO, with opacity also serving as a surrogate for non-volatile and semi-volatile HAP metals. D. What Are the Emission Limits and Operating Limits? 1. Emission Limits The PM emission limit for all of the kilns and coolers at an existing lime manufacturing plant would be 0.12 pounds (lb) PM per ton (0.06 kilogram (kg) per Mg) of stone feed. The PM emission limit for all of the kilns and lime coolers at a new lime manufacturing plant would be 0.10 lb/ton of stone feed. These emission limits would apply to the combined emissions of all the kilns and coolers (assuming the cooler(s) has a separate exhaust vent to the atmosphere) at the lime manufacturing plant. In other words, the sum of the PM emission rates from all of the kilns and coolers at the existing lime manufacturing plant, divided by the sum of the production rates of the kilns at the existing lime manufacturing plant, would be used to determine compliance with the emission limit for kilns and coolers at an existing lime manufacturing plant. Similarly, the sum of the PM emission rates from all of the kilns and coolers, divided by the sum of the production of the kilns at a new plant, would be used to determine compliance with the emission limit for kilns and coolers at a new lime manufacturing plant. Emissions from MPO that are vented through a stack would be subject to a standard of 0.05 grams PM per dry standard cubic meter (g/dscm) and 7 percent opacity. Stack emissions from MPO that are controlled by wet scrubbers would be subject to the 0.05 grams PM per dry standard cubic meter PM limit but not subject to the opacity limit. Fugitive emissions from MPO would be subject to a 10 percent opacity limit. We are proposing that for each building enclosing any materials processing operation, each of the affected MPO in the building would have to comply individually with the applicable PM and opacity emission limitations discussed above. Otherwise, we propose that there must be no visible emissions from the building, except from a vent, and the building's vent emissions must not exceed 0.05 grams PM per dry standard cubic meter and 7 percent opacity. We are proposing that for each fabric filter (FF) that controls emissions from only an individual, enclosed storage bin, the opacity emissions must not exceed 7 percent. For each set of multiple storage bins with combined stack emissions, emissions must not exceed 0.05 grams PM per dry standard cubic meter and 7 percent opacity. 2. Operating Limits For lime kilns that use a wet scrubber PM control device, you would be required to maintain the 3-hour rolling average gas stream pressure drop across the scrubber and the 3-hour rolling average scrubber liquid flow rate equal to or above the levels for the parameters that were established during the PM performance test. For lime kilns that use a FF PM control device, you would be required to maintain and operate the FF such that the bag leak detection system (BLDS) alarm is not activated and alarm condition does not exist for more than 5 percent of the operating time in each 6-month period. The BLDS must be certified by the manufacturer to be capable of detecting PM emissions at concentrations of 10 milligrams per actual cubic meter (0.0044 grains per actual cubic foot) or less. For lime kilns that use an electrostatic precipitator (ESP) PM control device, you would be required to maintain the 3-hour rolling average current and voltage input to each electrical field of the ESP equal to or above the operating limits for these parameters that were established during the PM performance test. In lieu of complying with these ESP operating parameters, we are giving sources the option of monitoring PM levels with a PM detector in a manner similar to the procedures for monitoring PM from a FF using a BLDS. You would need to maintain and operate the ESP such that the PM detector alarm is not activated, and alarm condition does not exist for more than 5 percent of the operating time in each 6-month period. In lieu of using a bag leak detector, PM detector, or monitoring ESP operating parameters for lime kilns with a FF or ESP control device, we are providing the option of monitoring opacity (as an operating limit) with a continuous opacity monitoring system (COMS). Sources that choose to use a COMS would be required to install and operate the COMS in accordance with Performance Specification 1 (PS-1), 40 CFR part 60, Appendix B, and maintain the opacity level of the lime kiln exhaust at or below 15 percent for each 6-minute block period. For MPO subject to a PM emission limit and controlled by a wet scrubber, you would be required to collect and record the exhaust gas stream pressure drop across the scrubber and the scrubber liquid flow rate during the PM performance test. You would be required to maintain the 3-hour rolling average gas stream pressure drop across the scrubber and the 3-hour rolling average scrubber liquid flow rate equal to or above the levels for the parameters that were established during the PM performance test. You would be required to prepare a written operations, maintenance, and monitoring plan to cover all affected emission units. The plan would include procedures for proper operation and maintenance of each emission unit and its air pollution control device(s); procedures for monitoring and proper operation of monitoring systems in order to meet the emission limits and operating limits; and standard procedures for the use of a BLDS and PM detector, and any corrective actions to be taken when operating limits are deviated from, or when required in using a PM detector or BLDS. E. When Must I Comply With the Proposed Rule? The compliance date for existing lime manufacturing plants would be [Date 3 years from the date a final rule is published in the Federal Register ]. (Three years may be needed to install new, or retrofit existing, air pollution control equipment.) The date the final rule is published in the Federal Register is called the effective date of the rule. We are proposing that emission units at a new lime manufacturing plant ( i.e. , emission units for which construction or reconstruction commences after today's date) must be in compliance upon initial startup or the effective date of the rule, whichever is later. F. How Do I Demonstrate Initial Compliance With the Proposed Rule? 1. Kiln and Coolers For the kiln and cooler PM emission limit, we are proposing that you must conduct a PM emissions test on the exhaust of each kiln at the lime manufacturing plant and measure the stone feed rate to each kiln during the test. The sum of the emissions from all the kilns at the existing lime manufacturing plant, divided by the sum of the average stone feed rates to each kiln at the existing lime manufacturing plant, must not exceed the emission limit of 0.12 lb PM/ton stone feed; similarly, the sum of the emissions from all the kilns at a new lime manufacturing plant, divided by the sum of the average stone feed rates to each kiln at the new lime manufacturing plant, must not exceed the emission limit of 0.10 lb PM/ton stone feed. If you have a lime cooler(s) that has a separate exhaust to the atmosphere, you would be required to conduct a PM test on the cooler's exhaust concurrently with the kiln PM test. Then the sum of the emissions from all the kilns and coolers at the existing lime manufacturing plant, divided by the sum of the average stone feed rates to each kiln at the existing plant, must not exceed the emission limit of 0.12 lb PM/ton stone feed (or 0.10 lb/ton of stone feed for kilns/coolers at new lime manufacturing plants). For kilns with an ESP or wet scrubber, you would be required to collect and record the applicable operating parameters during the PM performance test and then establish the operating limits based on those data. 2. Materials Processing Operations For the MPO with stacks and subject to PM emission limits, you would be required to conduct a PM emissions test on each stack exhaust, and the stack emissions must not exceed the emission limit of 0.05 g/dscm. For the MPO with stack opacity limits, you would be required to conduct a 3-hour Method 9 test on the exhaust, and each of the 30 consecutive, 6-minute opacity averages must not exceed 7 percent. The MPO that are controlled by wet scrubbers would not have an opacity limit, but you would be required to collect and record the wet scrubber operating parameters during the PM performance test and then establish the applicable operating limits based on those data. For MPO with fugitive emissions, you would be required to conduct a Method 9 test, and each of the consecutive 6-minute opacity averages must not exceed the applicable opacity limit. These Method 9 tests are for 3 hours, but the test duration may be reduced to 1 hour if certain criteria are met. Lastly, Method 9 tests or visible emissions checks may be performed on MPO inside of buildings, but additional lighting, improved access to equipment, and temporary installation of contrasting backgrounds may be needed. For additional guidance, see page 116 from the “Regulatory and Inspection Manual for Nonmetallic Minerals Processing Plants,” EPA report 305-B-97-008, November 1997. G. How Do I Continuously or Periodically Demonstrate Compliance With the Proposed Rule? 1. General You would be required to install, operate, and maintain each required continuous parameter monitoring system (CPMS) such that the CPMS completes a minimum of one cycle of operation for each successive 15-minute period. The CPMS would be required to have valid data from at least three of four equally spaced data values for that hour from a CPMS that is not out of control according to your operation, maintenance, and monitoring plan. To calculate the average for each 3-hour averaging period, you must have at least two of three of the hourly averages for that period using only hourly average values that are based on valid data (i.e., not from out-of-control periods). The 3-hour rolling average value for each operating parameter would be calculated as the average of each set of three successive 1-hour average values. The 3-hour rolling average would be updated each hour. Thus the 3-hour average rolls at 1-hour increments, i.e. , once a 1-hour average has been determined based on at least four successive available 15-minute averages, a new 1-hour average would be determined based on the next four successive available 15-minute averages. You would be required to develop and implement a written startup, shutdown, and malfunction plan (SSMP) according to the general provisions in 40 CFR 63.6(e)(3). 2. Kilns and Coolers For kilns controlled by a wet scrubber, you would be required to maintain the 3-hour rolling average of the exhaust gas stream pressure drop across the wet scrubber greater than or equal to the pressure drop operating limit established during the most recent PM performance test. You would be required to also maintain the 3-hour rolling average of the scrubbing liquid flow rate greater than or equal to the flow rate operating limit established during the most recent performance test. For kilns controlled by an ESP, if you choose to monitor ESP operating parameters rather than use a PM detector or a COMS, you would be required to maintain the 3-hour rolling average current and voltage input to each electrical field of the ESP greater than or equal to the average current and voltage input to each field of the ESP established during the most recent performance test. Sources opting to monitor PM emissions from an ESP with a PM detector in lieu of monitoring ESP parameters or opacity would be required to maintain and operate the ESP such that the PM detector alarm is not activated, and alarm condition does not exist for more than 5 percent of the operating time in a 6-month period. Each time the alarm sounds and the owner or operator initiates corrective actions (per the operations and maintenance plan) within 1 hour of the alarm, 1 hour of alarm time will be counted. If inspection of the ESP demonstrates that no corrective actions are necessary, no alarm time will be counted. The sensor on the PM detection system would provide an output of relative PM emissions. The PM detection system would have an alarm that would sound automatically when it detects an increase in relative PM emissions greater than a preset level. The PM detection systems would be required to be installed, operated, adjusted, and maintained so that they follow the manufacturer's written specifications and recommendations. For kilns and lime coolers (if the cooler has a separate exhaust to the atmosphere) controlled by a FF and monitored with a BLDS, you would be required to maintain and operate the FF such that the BLDS alarm is not activated, and alarm condition does not exist for more than 5 percent of the operating time in a 6-month period. Each time the alarm sounds and the owner or operator initiates corrective actions (per the operations, maintenance, and monitoring plan) within 1 hour of the alarm, 1 hour of alarm time will be counted. If inspection of the FF demonstrates that no corrective actions are necessary, no alarm time will be counted. The sensor on the BLDS would be required to provide an output of relative PM emissions. The BLDS would be required to have an alarm that will sound automatically when it detects an increase in relative PM emissions greater than a preset level. The BLDS would be required to be installed, operated, adjusted, and maintained so that they follow the manufacturer's written specifications and recommendations. Standard operating procedures for the BLDS and PM detection systems would need to be incorporated into the operations, maintenance, and monitoring plan. We recommend that for electrodynamic (or other similar technology) BLDS, the standard operating procedures include concepts from EPA's “Fabric Filter Bag Leak Detection Guidance” (EPA-454/R-98-015, September 1997). This document may be found on the world wide web at www.epa.gov/ttn/emc. For kilns and lime coolers monitored with a COMS, you would be required to maintain each 6-minute block average opacity level at or below 15 percent opacity. The COMS must be installed and operated in accordance with Performance Specification 1 (PS-1), 40 CFR part 60, Appendix B. 3. Materials Processing Operations For stack emissions from MPO which are controlled by a wet scrubber, you would be required to maintain the 3-hour rolling average exhaust gas stream pressure drop across the wet scrubber greater than or equal to the pressure drop operating limit established during the most recent PM performance test. You would be required to also maintain the 3-hour rolling average scrubbing liquid flow rate greater than or equal to the flow rate operating limit established during the most recent performance test. For MPO subject to opacity limitations and which do not use a wet scrubber control device, you would be required to periodically demonstrate compliance as follows. You would be required to conduct a monthly 1-minute visible emissions check of each emissions unit under the affected source definition. If no visible emissions are observed in six consecutive monthly tests for any emission unit, you may decrease the frequency of testing from monthly to semiannually for that emissions unit. If visible emissions are observed during any semiannual test, you would be required to resume testing of that emissions unit on a monthly basis and maintain that schedule until no visible emissions are observed in six consecutive monthly tests. If no visible emissions are observed during the semiannual test for any emissions unit, you may decrease the frequency of testing from semiannually to annually for that emissions unit. If visible emissions are observed during any annual test, you would be required to resume visible emissions testing of that emissions unit on a monthly basis and maintain that schedule until no visible emissions are observed in six consecutive monthly tests. If visible emissions are observed during any visible emissions check, you would be required to conduct a 6-minute test of opacity in accordance with Method 9 of appendix A to part 60 of this chapter. The Method 9 test would be required to begin within 1 hour of any observation of visible emissions, and the 6-minute opacity reading would be required to not exceed the applicable opacity limit. We request comment on using more frequent visible emissions checks for MPO, such as going from monthly to quarterly, and then continuing with semiannual checks. H. How Do I Determine if My Lime Manufacturing Plant Is a Major Source and Thus Subject to the Proposed Rule? The proposed rule would apply to lime manufacturing plants that are major sources, co-located with major sources, or are part of major sources. Each lime facility owner/operator would need to determine whether its plant is a major or area source, since this determines whether the lime manufacturing plant would be an affected source under the proposed rule. Section 112 of the CAA defines a major source as a “stationary source or group of stationary sources located within a contiguous area and under common control that emits or has the potential to emit considering controls, in the aggregate, 10 tons/yr or more of any HAP or 25 tons/yr or more of any combination of HAP.” This definition may be interpreted to imply that the CAA requires an estimate of the facility's potential to emit all HAP from all emission sources in making a determination of whether the source is major or area. However, based on our data analysis, HCl is most likely the HAP that would account for the largest quantity of HAP emissions from a lime manufacturing plant. Although lime manufacturing plants emit HAP metals from most of the emission units at the plant site and organic HAP from the kiln, our analysis indicates that most likely the metal and organic HAP emissions would each be below the 10/25 tons/yr criteria. One potential approach to estimating HAP metals emissions from a lime manufacturing plant is to require measurement of the PM emissions from all of the emission units at the plant and then allow the use of a ratio (which we would specify in the final rule) of HAP metals to PM to calculate the metals emissions. We request comment on this approach to estimating HAP metals emissions. And although we are not proposing to require sources to test for all HAP to make a determination of whether the lime manufacturing plant is a major or area source, we do request comment on whether emissions testing of metal and/or organic HAP should be required for an owner or operator to claim that its lime manufacturing plant is an area source. We are proposing, however, to require that a source measure HCl emissions from the kiln(s) in order for it to claim it is an area source (provided HCl is emitted at less than 10 tons/yr). Due to the known problems with EPA Method 26 (which may have positive biases attributable to chloride salts rather than to HCl, and negative biases due to condensation and removal of HCl on the filter and/or in the sampling probe), we have decided that Methods 26 and 26A may not be used to measure HCl in the determination whether the source is an area source. We, in fact, adopted this same approach in the final NESHAP for the portland cement industry. See 40 CFR part 63, subpart LLL, and 64 FR 31907 and 31920 (June 14, 1998). In addition, we worked with the American Society of Testing and Materials (ASTM), in conjunction with the National Lime Association (NLA), to develop an impinger-based method for the measurement of HCl based on Method 26 but which includes changes to the method to overcome the aforementioned biases. This ASTM HCl impinger-based method has been demonstrated on lime kilns and has been designated as ASTM Test Method D 6735-01. We approve of this method, and we propose to allow owners/operators to use it to measure HCl from lime kilns to determine whether their lime manufacturing plant is a major or area source. But because it is very important to obtain an accurate measurement of HCl emissions, we are proposing to require the paired-train option under section 11.2.6 of the method, and we are also proposing to require the post-test analyte spike option under section 11.2.7 of the method. Although we believe these additional quality assurance procedures are critical to obtain an accurate measurement of HCl, we seek comment on the appropriateness of requiring them. We attempted to utilize proposed EPA Method 322 (based on gas filter correlation infrared spectroscopy) to gather HCl data from lime kilns and encountered technical problems. These problems included inadequate data availability, spike recovery, and response time, which led to our decision in the promulgation of the NESHAP for the portland cement industry to not finalize EPA Method 322. Today, we are affirming that decision and propose that Method 322 may not be used to measure HCl in the determination whether a lime manufacturing plant is an area source. Based on the aforementioned difficulties with Method 26 and proposed Method 322, we propose that the test methods based on fourier transform infrared (FTIR) spectroscopy, EPA Methods 320 and 321, will be acceptable for measuring HCl from lime kilns if the owner/operator wishes to claim its lime manufacturing facility is not a major source. These FTIR methods were finalized along with the portland cement industry NESHAP, and this requirement would be consistent with those NESHAP. (As mentioned above, we are also proposing to allow sources to use ASTM Test Method D 6735-01 for the measurement of HCl to determine whether their lime manufacturing plant is a major or area source.) However, we acknowledge the NLA's concerns about the use of FTIR during the lime kiln test program. In letters the NLA sent to us, they suggested that in light of the alleged problems experienced by our test contractors in using FTIR, we should allow the use of Method 26 for measurement of HCl emissions from lime kilns. However, we do not completely agree with their assessment of the asserted difficulties we experienced with FTIR. Our response to NLA's concerns about FTIR may be found in the docket to the proposed rule. And despite any alleged problems with FTIR, we do not consider them to justify the use of Method 26 until the aforementioned problems with Method 26 can be resolved. III. Rationale for Proposed Rule A. How Did We Determine the Source Category To Regulate? Section 112(c) of the CAA directs the Agency to list each category of major sources that emits one or more of the HAP listed in section 112(b) of the CAA. We published an initial list of source categories on July 16, 1992 (57 FR 31576). “Lime Manufacturing” is one of the 174 categories of major sources on the initial list. As defined in our report, “Documentation for Developing the Initial Source Category List” (EPA-450/3-91-030, July 1992), the lime manufacturing source category includes any facility engaged in the production of high calcium lime, dolomitic lime, and dead-burned dolomite. These are the same applicable lime products as defined in the new source performance standard (NSPS) for lime manufacturing plants (40 CFR part 60, subpart HH) and in the proposed rule. According to the background document for the initial source category listing, the listing of lime manufacturing as a major source category was based on the Administrator's determination that some lime manufacturing plants would be major sources of chlorine and metal HAP including, but not limited to, compounds of arsenic, cadmium, chromium, lead, manganese, mercury, nickel, and selenium. In addition, the results of emissions testing we conducted in the development of the proposed rule indicate that many lime manufacturing plants may be major sources of HCl. Hydrogen chloride emissions from these lime kiln tests using EPA Method 320 ranged from 0.007 to 2.0 lbs HCl per ton of lime produced. Assuming an average HCl emission factor of 0.4 lb/ton, a lime manufacturing plant would only have to produce 50,000 tons of lime per year (which is a small lime manufacturing plant) for it to be a major source (for this reason alone). The proposed rule would regulate HAP emissions from all new and existing lime manufacturing plants that are major sources, co-located with major sources, or are part of major sources (e.g., steel production facilities). One exception to this is that lime manufacturing operations located at pulp and paper mills would not be subject to the proposed rule. Lime manufacturing operations at pulp and paper mills would be subject to the NESHAP for combustion sources at kraft, soda, and sulfite pulp and paper mills. See 66 FR 3180, January 12, 2001. Lime manufacturing operations at beet sugar processing plants would also not be subject to the NESHAP. Both the lime product and carbon dioxide in the beet sugar lime kiln exhaust are used in the beet sugar manufacturing process. Beet sugar lime kiln exhaust is typically routed through a series of gas washers to clean the exhaust gas prior to process use. The clean, cooled gas is then added to one or more carbonation units (which contain a mixture of beet juice, lime, and water) to provide the carbon dioxide necessary for carbonation and precipitation of lime, which purifies the beet sugar juice. Although the carbonation units are part of the sugar manufacturing process, they would provide additional cleaning of the lime kiln exhaust. Beet sugar plants typically operate only seasonally, and our analysis indicates that beet sugar plants are not major sources of HAP. B. How Did We Determine the Affected Source? The proposed rule would define the affected source as the lime manufacturing plant, and would include all of the limestone MPO at a lime manufacturing plant, beginning with the raw material storage bin, and all of the lime kilns and coolers at the lime manufacturing plant. This definition of affected source conforms with the General Provisions 40 CFR 63.2 definition, which essentially states that all emission units at a plant are to be considered as one affected source. A new lime manufacturing plant is defined as the collection of any limestone MPO, beginning with the raw material storage bin, and any lime kiln or cooler for which construction or reconstruction begins after December 20, 2002. Thus, it is possible for an existing lime manufacturing plant and a new lime manufacturing plant to be located at the same site. This definition of new affected source includes the same emission units as the existing affected source, except that the new affected source only includes those emission units for which construction or reconstruction begins after December 20, 2002. The definitions are different because the MACT PM emission limit for kilns and coolers at a new lime manufacturing plant is more stringent than for those at an existing lime manufacturing plant. In general, the emission units which are included in the definition of new or existing affected source were selected based on regulatory history ( e.g. , the applicability of NSPS and the information included in the initial source category listing) and to be consistent with other MACT standards ( e.g. , the MACT standards for the portland cement industry). Although lime coolers were not among the list of emission units in the background document for the initial source category listing for lime manufacturing, lime coolers would be an emission unit under the definition of affected source in the proposed rule. All lime coolers are integrated with their associated kiln such that most coolers vent all of their exhaust (if there is an exhaust stream) to the kiln, although a few lime coolers ( e.g. , grate coolers) also vent a portion of their exhaust separately to the atmosphere. The specific MPO which are included in the affected source definition include the following emission units: all of the grinding mills, raw material storage bins, conveying system transfer points, bulk loading or unloading systems, screening operations, bucket elevators, and belt conveyors, beginning with the raw material storage bin and up to the kiln. We define MPO to include these emission units under the proposed subpart because these units are also subject to the NSPS for Nonmetallic Minerals Processing Plants (referred to in this preamble as the NSPS subpart OOO). We specifically solicit comment on whether raw material storage piles should be included in the affected source definition. In today's proposed rule, the first emission unit in the sequence of MPO which is included in the definition of affected source would be the raw material storage bin. Furthermore, the first conveyor transfer point included under the affected source definition would be the transfer point associated with the conveyor transferring material from the raw material storage bin. This demarcation in the sequence of MPO which defines the first emission unit under the affected source definition is consistent with the applicability requirements under the NESHAP for the portland cement industry, 40 CFR part 63, subpart LLL. The MPO emission units that would be excluded from the affected source definition are described as follows. Any MPO which precedes the raw material storage bin, such as those in quarry or mine operations, is not included in the definition of affected source. Any operations that process only lime product, lime kiln dust, or fuel would be excluded from the definition. Truck dumping into any screening operation, feed hopper, or crusher would not be included among the emission units considered under the affected source definition. (These exclusions are consistent with the NSPS subpart OOO). Finally, lime hydrators would not be included as an emission unit under the affected source definition since all hydrators are controlled by integrated wet scrubbers, which capture the lime PM (and associated trace metallic HAP) and recycle the scrubber water. Additionally, this is consistent with the NSPS subpart HH, which does not apply to lime hydrators. C. How Did We Determine Which Pollutants To Regulate? The proposed rule would reduce emissions of non-volatile and semi-volatile metal HAP by limiting emissions of PM from the kiln and cooler, and certain MPO emission units. Particulate matter is a surrogate for the non-volatile and semi-volatile metal HAP that are always a subset of PM. Controlling PM emissions will control the non-volatile and semi-volatile metal HAP, since these compounds are associated with the PM, i.e. , they are by definition in the particulate phase (as opposed to the gaseous form). The available air pollution controls for the particulate HAP metals at lime manufacturing plants are the PM controls used at lime manufacturing plants, i.e. , FF, ESP, and wet scrubbers. These at-the-stack controls capture non-volatile and semi-volatile HAP metals non-preferentially along with other PM, thus showing why PM is a permissible indicator for these HAP metals. See National Lime Ass'n v. EPA, 233 F. 3d at 639. Also, using PM as a surrogate for the HAP metals would reduce the cost of emissions testing and monitoring that would be required to demonstrate compliance with the otherwise numerous standards that would apply to individual HAP metals. In addition, several other NESHAP have been promulgated which use PM as a surrogate for non-volatile and semi-volatile HAP metals for the same reason—it is a technically sound surrogate since HAP metals are necessarily contained in PM, are controlled by PM control devices to roughly the same efficiency, and there are significant associated cost savings due to monitoring for one parameter instead of many. The proposed rule would limit opacity or visible emissions from certain MPO emission units. Opacity serves as a surrogate for the non-volatile and semi-volatile HAP metals. Opacity is indicative of PM emission levels and, thus, for the same reasons that PM is a surrogate for the particulate HAP metals, opacity would also be a surrogate for the PM HAP metals. Further, opacity levels are reduced by reducing PM emissions, which would also reduce the metal HAP in the particulate phase, i.e. , the non-volatile and semi-volatile HAP. We are proposing not to regulate HCl emissions from lime kilns. Under the authority of section 112(d)(4) of the CAA, we have determined that no further control is necessary because HCl is a “health threshold pollutant,” and HCl levels emitted from lime kilns are below the threshold value within an ample margin of safety. The following explains the statutory basis for considering health thresholds when establishing standards, and the basis for today's proposed decision, including a discussion of the risk assessment conducted to support the ample margin of safety decision. Section 112 of the CAA includes exceptions to the general statutory requirement to establish emission standards based on MACT. Of relevance here, section 112(d)(4) allows us to develop risk-based standards for HAP “for which a health threshold has been established” provided that the standards achieve an “ample margin of safety.” Therefore, we believe we have the discretion under section 112(d)(4) to develop standards which may be less stringent than the corresponding floor-based MACT standards for some categories emitting threshold pollutants. In deciding standards for this source category, we seek to assure that emissions from every source in the category result in exposures less than the threshold level even for an individual exposed at the upper end of the exposure distribution. The upper end of the exposure distribution is calculated using the “high end exposure estimate,” defined as a plausible estimate of individual exposure for those persons at the upper end of the exposure distribution, conceptually above the 90th percentile, but not higher than the individual in the population who has the highest exposure. We believe that assuring protection to persons at the upper end of the exposure distribution is consistent with the “ample margin of safety” requirement in section 112(d)(4). We emphasize that the use of section 112(d)(4) authority is wholly discretionary. As the legislative history indicates, cases may arise in which other considerations dictate that we should not invoke this authority to establish less stringent standards, despite the existence of a health effects threshold that is not jeopardized. For instance, we do not anticipate that we would set less stringent standards where evidence indicates a threat of significant or widespread environmental effects taking into consideration cost, energy safety and other relevant factors, although it may be shown that emissions from a particular source category do not approach or exceed a level requisite to protect public health with an ample margin of safety. We may also elect not to set less stringent standards where the estimated health threshold for a contaminant is subject to large uncertainty. Thus, in considering appropriate uses of our discretionary authority under section 112(d)(4), we consider other factors in addition to health thresholds, including uncertainty and potential “adverse environmental effects,” as that phrase is defined in section 112(a)(7) of the CAA. We are proposing in today's notice not to develop standards for HCl from lime kilns. This decision is based on the following. First, we consider HCl to be a threshold pollutant. Second, we have defined threshold values in the form of an Inhalation Reference Concentration (RfC) and acute exposure guideline level (AEGL). Third, HCl is emitted from lime kilns in quantities that result in human exposure in the ambient air at levels well below the threshold values with an ample margin of safety. Finally, there are no adverse environmental effects associated with HCl. The bases and supporting rationale for these conclusions are as follows. For the purposes of section 112(d)(4), several factors are considered in our decision on whether a pollutant should be categorized as a health threshold pollutant. These factors include evidence and classification of carcinogenic risk and evidence of noncarcinogenic effects. For a detailed discussion of factors that we consider in deciding whether a pollutant should be categorized as a health threshold pollutant, please see the April 15, 1998 Federal Register document (63 FR 18766). In the April 15, 1998 action cited above, we determined that HCl, a Group D pollutant, is a health threshold pollutant for the purpose of section 112(d)(4) of the CAA (63 FR 18753). The NLA conducted a risk assessment to determine whether the emissions of HCl from lime kilns at the current baseline levels resulted in exposures below the threshold values for HCl. We reviewed the risk assessment report prepared by the NLA and believe that it uses a reasonable and conservative methodology, is consistent with EPA methodology and practice, and reaches a reasonable conclusion that current levels of HCl emissions from lime kilns would be well under the threshold level of concern for human receptors. The summary of the NLA's assessment is organized as follows: (1) Hazard identification and dose-response assessment, (2) emissions and release information, and (3) exposure assessment. It is important to note that the risk assessment methodology applied here by NLA should not be interpreted as a standardized approach that sets a precedent for how EPA will analyze application of section 112(d)(4) in other cases. The approach presented here, including assumptions and models, was selected to meet the unique needs of this particular case, to provide the appropriate level of detail and margin of safety given the data availability, chemicals, and emissions particular to this category. The RfC is a “long-term” threshold, defined as an estimate of a daily inhalation exposure that, over a lifetime, would not likely result in the occurrence of significant noncancer health effects in humans. We have determined that the RfC for HCl of 20 micrograms per cubic meter (μg/m 3 ) is an appropriate threshold value for assessing risk to humans associated with exposure to HCl through inhalation (63 FR 18766, April 15, 1998). Therefore, the NLA used this RfC as the threshold value in their exposure assessment for HCl emitted from lime kilns. In addition to the effects of long-term inhalation of HCl, the NLA, at our request, also considered thresholds for short-term exposure to HCl in this assessment. The AEGL toxicity values are estimates of adverse health effects due to a single exposure lasting 8 hours or less. The confidence in the AEGL (a qualitative rating or either low, medium, or high) is based on the number of studies available and the quality of the data. Consensus toxicity values for effects of acute exposures have been developed by several different organizations, and we are beginning to develop such values. A national advisory committee organized by the EPA has developed AEGL for priority chemicals for 30-minute, 1-hour, 4-hour, and 8-hour airborne exposures. They have also determined the levels of these chemicals at each exposure duration that will protect against discomfort (AEGL1), serious effects (AEGL2), and life-threatening effects or death (AEGL3). The NLA used the AEGL1 value as the threshold value for assessing the inhalation health effects of short-term exposures to HCl. The NLA conducted dispersion modeling for 71 lime plants and nearly 200 lime kilns, representing all operating captive and commercial lime plants in the U.S. that would potentially be subject to the proposed rule. The analyses performed assumed worst case operating scenarios, such as maximum production rate and 24 hours per day, 365 days per year operation. Hydrogen chloride emission rates were based on either measured data or default HCl stack concentrations. For plants having HCl measurement data, only HCl data collected using FTIR were used. For plants where no emissions data were available, the following HCl emission levels were assumed for the analyses: 10 parts per million by volume (ppmv) for kilns with either scrubbers or preheaters, 18 ppmv for kilns at Riverton Corporation, 26 ppmv for gas-fired kilns, and 85 ppmv for all other kilns. (The Riverton emission level was derived by multiplying its stack test results obtained using EPA Method 26 by a sampling method bias factor of 25. Method 26 may understate actual HCl emissions by a factor of between 2 and 25.) The HCl emission levels were converted to stack emission rates using the stack gas volumetric flow rate. The release characteristics used for the dispersion model included stack height, stack diameter, exit temperature, and exit velocity. Using its own questionnaire, the NLA collected the necessary release information from all 71 plants. The exposure assessment was conducted for HCl emissions from all lime plants in the source category. As discussed above, the emissions data and release characteristics were used as inputs to the assessment. The approach taken by NLA was found to be consistent with the EPA's tiered methodology. (See the U.S. EPA report “Screening Procedures for Estimating the Air Quality Impact of Stationary Sources (revised)”, report number EPA-454/R-92-019 (1992).) The approach for each of the facilities involved four steps: Step 1 was the modeling of HCl concentrations at the point of maximum concentration, whether occurring on-site or off-site, using SCREEN3, a screening-level air dispersion model. Step 2 was the same as Step 1, but modeling was performed at or beyond the fence line. Step 3 was the same as Step 1, but modeling was performed at the nearest off-site residence or business location. Step 4 was the modeling of HCl concentrations at the nearest residence or business location using the ISC-PRIME model. (ISC-PRIME is a steady-state Gaussian plume model based on the ISC3 dispersion model, with the Plume RIse Model Enhancements (PRIME) algorithm added for improved treatment of building downwash. The model can account for settling and dry deposition; building downwash; area, line, and volume sources; plume rise as a function of downwind distance; building dimensions and stack placement relative to a building; separation of point sources; and limited terrain adjustment.) Note that each succeeding step involves more refined site-specific data and less conservative assumptions. The analyses performed under each of the above steps assumed worst case operating scenarios, such as maximum production rate, and in Steps 1 through 3 worst case meteorology. Local terrain and building downwash effects were also considered, and meteorological data were taken from the nearest National Weather Service meteorological station. Maximum one hour averages were converted to annual averages using a conversion factor of 0.08, consistent with EPA recommendations. The NLA generated estimates of both chronic (annual average) and acute (one-hour) concentrations for comparison to the relevant health reference values or threshold levels. Acute and chronic exposures were compared to the AEGL1 of 2,700 μg/m 3 for one-hour exposures and the RfC of 20 μg/m 3 for long-term continuous exposure, respectively. Noncancer risk assessments typically use a metric called the Hazard Quotient (HQ) to assess risks of exposures to noncarcinogens. The HQ is the ratio of exposure (or modeled concentration) to the health reference value or threshold level ( i.e. , RfC or AEGL). HQ values less than “1” indicate that exposures are below the health reference value or threshold level and are likely to be without appreciable risk of adverse effects in the exposed population. HQ values above “1” do not necessarily imply that adverse effects will occur, but that the potential for risk of such effects increases as HQ values exceed “1.” In addition, when information on background levels of pollutants is not available, EPA has in some cases considered a HQ of 0.2 or below to be acceptable. For the NLA assessment, if the HQ was found to be less than 0.5 for any of the first three steps using conservative defaults and modeling assumptions, the analysis concluded with that step. On the other hand, if the HQ exceeded 0.5, work proceeded to subsequent steps. There were no facilities where Step 4 ( i.e. , the most refined step) yielded an HQ above 0.5. (Steps 1, 2, and 3 are considered “Tier 2” analyses under EPA's tiered modeling approach, whereas Step 4 is considered a “Tier 3” analysis.) To help confirm that NLA's approach was reasonable, we decided to reproduce several of NLA's modeling analyses by performing our own analyses for selected facilities having the highest potential for health risk to the surrounding community. Generally, these were facilities having the highest emission rates or facilities where Tier 3 modeling was performed for actual off-site receptor locations. Fourteen kilns with emission rates greater than 5.0 grams/second were evaluated using the SCREEN3 air dispersion model. For the analyses, plant-specific parameters were used for source type, emission rate, stack height, stack inner diameter exit velocity, gas exit temperature, and location (urban versus rural). Assumptions about flat terrain, meteorology, and building dimensions were made, as appropriate. For plants with multiple stacks, emissions were considered to emanate from one co-located emission point. Then, in order to maintain a conservative approach, the lowest effective stack height parameters were utilized for all emissions. The model was run, and maximum concentrations for distances ranging from 100 to 5,000 meters were obtained. To evaluate acute exposure, the HQ was determined by comparing the maximum concentrations to the HCl acute threshold level of 2,700 μg/m 3 . Maximum concentrations were then converted into annual concentrations, and the HQ was determined by comparing these concentrations to the HCl chronic health reference value of 20 μg/m 3 . We then used the Human Exposure Model (HEM) to examine seven of the kilns that were modeled by the NLA using ISC-PRIME. Concentrations were predicted at geographically-weighted centers of census blocks. Emissions were assumed to originate from a single stack using the lowest effective stack height reported at each facility. Six of the kilns modeled showed values well below the RfC, the highest having an HQ = 0.11. The seventh indicated an HQ of 0.96. The seventh kiln was re-simulated using site-specific emissions and stack data, resulting in an HQ = 0.21. Overall, we believe that the NLA has taken a reasonably conservative approach in estimating risk due to HCl exposure. This approach is consistent with the methodology and assumptions EPA would have used if the study had been done in-house, and in several instances NLA's approach is even more conservative. Furthermore, EPA conducted a parallel confirmatory analysis and found results consistent with those of the NLA assessment. At this point, it should be noted that the potential for effects depends on an individual's total exposure to that chemical. As a result, exposure from all sources, not just the one in question, must be evaluated. Where possible, other exposures must be accounted for, either explicitly through monitoring or modeling, or by apportioning a portion of the health threshold level available to any individual source. To estimate the potential exposure from other sources, the NLA reviewed the ambient HCl concentration estimates derived by the air component of EPA's Cumulative Exposure Project (CEP). They found that the mean national HCl concentration corresponded to an HQ of 0.06 and the 95th percentile national HCl concentration corresponded to an HQ of 0.2, and they concluded that background HCl exposures were unlikely to exceed an HQ of 0.2. (These HQ helped confirm that the total HQ for a facility, including contributions from other sources (“background”), would not be expected to exceed “1.” However, these background HQ were not actually added into a facility's final HQ estimate. Thus, we are comfortable with NLA's calculations and feel confident that exposures to HCl emissions from the facilities in question are unlikely to ever exceed an HQ of 0.2. Therefore, we believe that the predicted exposures from these facilities should provide an ample margin of safety to ensure that total exposures for nearby residents should not exceed the short-term or long-term health based threshold levels or health reference values, even when considering the possible contributions of other sources of HCl or similar respiratory irritants. The standards for emissions must also protect against significant and widespread adverse environmental effects to wildlife, aquatic life, and other natural resources. The NLA did not conduct a formal ecological risk assessment. However, we have reviewed publications in the literature to determine if there would be reasonable expectation for serious or widespread adverse effects to natural resources. We consider the following aspects of pollutant exposure and effects: Toxicity effects from acute and chronic exposures to expected concentrations around the source (as measured or modeled), persistence in the environment, local and long-range transport, and tendency for bio-magnification with toxic effects manifest at higher trophic levels. No research has been identified for effects on terrestrial animal species beyond that cited in the development of the HCl RfC. Modeling calculations indicate that there is little likelihood of chronic or widespread exposure to HCl at concentrations above the threshold around lime manufacturing plants. Based on these considerations, we believe that the RfC can reasonably be expected to protect against widespread adverse effects in other animal species as well. Plants also respond to airborne HCl levels. Chronic exposure to about 600 μg/m 3 can be expected to result in discernible effects, depending on the plant species. Plants respond differently to HCl as an anhydrous gas than to HCl aerosols. Relative humidity is important in plant response; there appears to be a threshold of relative humidity above which plants will incur twice as much damage at a given dose. Effects include leaf injury and decrease in chlorophyll levels in various species given acute, 20-minute exposures of 6,500 to 27,000 μg/m 3 . A field study reports different sensitivity to damage of foliage in 50 species growing in the vicinity of an anhydrous aluminum chloride manufacturer. American elm, bur oak, eastern white pine, basswood, red ash and several bean species were observed to be most sensitive. Concentrations of HCl in the air were not reported. Chloride ion in whole leaves was 0.2 to 0.5 percent of dry weight; sensitive species showed damage at the lower value, but tolerant species displayed no injury at the higher value. Injury declined with distance from the source with no effects observed beyond 300 meters. Maximum modeled long-term HCl concentrations (less than 10 μg/m 3 ) are well below the 600 μg/m 3 chronic threshold, and the maximum short-term HCl concentration (540 μg/m 3 ) is far below the 6,500 μg/m 3 acute exposure threshold. Therefore, no adverse exposure effects are anticipated. Prevailing meteorology strongly determines the fate of HCl in the atmosphere. However, HCl is not considered a strongly persistent pollutant, or one where long range transport is important in predicting its ecological effects. In the atmosphere, HCl can be expected to be absorbed into aqueous aerosols, due to its great affinity for water, and removed from the troposphere by rainfall. In addition, HCl will react with hydroxy ions to yield water plus chloride ions. However, the concentration of hydroxy ions in the troposphere is low, so HCl may have a relatively long residence time in areas of low humidity. No studies are reported of HCl levels in ponds or other small water bodies or soils near major sources of HCl emissions. Toxic effects of HCl to aquatic organisms would likely be due to the hydronium ion, or acidity. Aquatic organisms in their natural environments often exhibit a broad range of pH tolerance. Effects of HCl deposition to small water bodies and to soils will primarily depend on the extent of neutralizing by carbonates or other buffering compounds. Chloride ions are essentially ubiquitous in natural waters and soils so minor increases due to deposition of dissolved HCl will have much less effect than the deposited hydronium ions. Deleterious effects of HCl on ponds and soils, where such effects might be found near a major source emitting to the atmosphere, likely will be local rather than widespread, as observed in plant foliage. Effects of HCl on tissues are generally restricted to those immediately affected and are essentially acidic effects. The rapid solubility of HCl in aqueous media releases hydronium ions, which can be corrosive to tissue when above a threshold concentration. The chloride ions may be concentrated in some plant tissues, but may be distributed throughout the organism, as most organisms have chloride ions in their fluids. Leaves or other tissues exposed to HCl may show some concentration above that of their immediate environment; that is, some degree of bioconcentration can occur. However, long-term storage in specific organs and biomagnification of concentrations of HCl in trophic levels of a food chain would not be expected. Thus, the chemical nature of HCl results in deleterious effects, that when present, are local rather than widespread. In conclusion, acute and chronic exposures to expected HCl concentrations around the source are not expected to result in adverse toxicity effects. Hydrogen chloride is not persistent in the environment. Effects of HCl on ponds and soils are likely to be local rather than widespread. Finally, HCl is not believed to result in biomagnification or bioaccumulation in the environment. Therefore, we do not anticipate any adverse ecological effects from HCl. The results of the exposure assessment showed that exposure levels to baseline HCl emissions from lime production facilities are well below the health threshold value. Additionally, the threshold values, for which the RfC and AEGL values were determined to be appropriate values, were not exceeded when considering conservative estimates of exposure resulting from lime kiln emissions as well as considering background exposures to HCl and therefore, represent an ample margin of safety. Furthermore, no significant or widespread adverse environmental effects from HCl is anticipated. Therefore, under authority of section 112(d)(4), we have determined that further control of HCl emissions from lime manufacturing plants is not necessary. We considered establishing a limit for mercury emissions from lime kilns, but there is no MACT floor for mercury—that is, we know of no way to establish an achievable floor standard for mercury beyond selecting an arbitrarily high emission limit that any source could achieve under any circumstance since no source controls mercury emissions using a means of control that can be duplicated by other sources. We also have initially determined that an emission limit for mercury based on a beyond-the-MACT-floor option is not considered cost effective at this time; nor is a beyond-the-floor standard justified for mercury after otherwise taking into account cost, non-air quality environmental and health impacts, and energy considerations. D. How Did We Determine the MACT Floor for Emission Units at Existing Lime Manufacturing Plants? 1. PM From the Kiln and Cooler In establishing the MACT floor, section 112(d)(3)(A) of the CAA directs us to set standards for existing sources that are no less stringent than the average emission limitation achieved in practice by the best performing 12 percent of existing sources (for which there are emissions data) where there are more than 30 sources in the category or subcategory. Among the possible meanings for the word “average” as the term is used in the CAA, we considered two of the most common. First, “average” could be interpreted as the arithmetic mean. The arithmetic mean of a set of measurements is the sum of the measurements divided by the number of measurements in the set. The word “average” could also be interpreted as the median of the emission limitation values. The median is the value in a set of measurements below and above which there are an equal number of values (when the measurements are arranged in order of magnitude). This approach identifies the emission limitation achieved by those sources within the top 12 percent, arranges those emissions limitations achieved in order of magnitude, and the control level achieved by, and achievable by, the median source is selected. Either of these two approaches could be used in developing MACT standards for different source categories. We obtained PM data for 47 lime kilns over the course of developing the proposed rule. The most comprehensive body of data, and we believe the one that most accurately approximates the performance achieved by, and achievable by, the average of the best 12 percent of existing sources for which the Agency has emission data, are PM limitations contained in State and local agency permits for these sources. We used the permit limitations for the kilns (along with the supporting PM emissions data) in our MACT floor analysis because the permit limitations were indicative of the variability in the long-term performance of the emission controls. We examined multiple sets of PM emissions data obtained from the individual kilns during compliance testing to assure that the permit limitations do not underestimate the pollution control capabilities of these sources ( i.e. , that actual performance is not superior to the permit limits, in which case the MACT floor would need to be based on that superior performance; see Sierra Club v. EPA, 167 F. 3d 658, 661-62 (D.C. Cir. 1999)). Simply taking the average or mean of the lowest 12 percent of the emissions data (without considering permit limitations, i.e. , achievability of the technology over the long-term) would not account for the inherent variability of performance of well-designed and operated emission controls, since individual emissions tests are based on short durations of sampling, typically 3 hour tests (because of the absence of PM continuous emissions monitors) and, thus, we would be required to extrapolate these “snapshot” data to ascertain long-term achievable performance. Additionally, we obtained multiple compliance test data for the top performing kilns (where available); some of the kilns' data vary over two orders of magnitude and vary up to their permit limit. Further, these multiple data sets indicate that some of these top performing kilns would not be able to meet an emission limit based on a strictly arithmetic average of the top performing kilns' emissions data (the result being a standard not achieved by the average of the best performing sources, and hence impermissible). We arrayed the data by permit limitation, from lowest to highest, in units of lbs PM/ton of limestone feed, along with the associated PM emissions test data. The best performing 12 percent of the 47 kilns are the best performing six kilns, with the third and fourth best performing kilns being the median. The six best performing kilns' permit limits for PM are 0.10, 0.12, 0.12, 0.12, 0.21, and 0.21 lb/ton limestone feed and are equipped with either a FF or ESP. The emission test data associated with these kilns indicate that these kilns have indeed achieved the limits in their State permits. The test data for the kilns permitted at or below 0.12 lb PM/ton limestone vary from 0.0091 to 0.0925 lb PM/ton limestone. We do not believe that these kilns could consistently achieve standards which are lower than the permit limitation of 0.12 lb PM/ton limestone level, due to the probable long-term variability. Therefore, we are proposing a MACT floor PM emission limit of 0.12 lb PM/ton limestone for lime kilns at existing lime plants, using the median approach of the permit limits, which the associated emissions data show to be achievable and show as well to be a reasonable approximation of the achievable performance of the average of the best performing 12 percent of kilns for which we have emissions data, taking into consideration long-term variability in performance. Most lime coolers (approximately 96 percent) in the lime manufacturing industry use ambient air for cooling and are integrated with the kiln such that all the cooler exhaust goes directly to the kiln for use as combustion air, or else the cooling of the lime takes place within the kiln itself ( e.g. , in vertical kilns). Thus, for 96 percent of the lime kilns, their emissions are actually the kiln and cooler emissions combined. The kiln PM emission limit of 0.12 lb/ton limestone is based on kiln permit limits and associated emissions data where the kiln and cooler emissions are combined. That is, based on our review of the questionnaire responses, discussions with plant personnel, and State permit information, none of the best performing kilns has a lime cooler with a separate exhaust to the atmosphere. Thus, the kiln PM emission limit applies to the emissions from both the kiln and cooler. For the 96 percent of the kilns with no separate cooler exhaust, this would have no effect; that is, the coolers' emissions are already combined with the kiln prior to venting to the atmosphere. For the few kilns with grate coolers that separately vent a portion of the cooler exhaust to the atmosphere, the sum of the emissions from the kiln(s) and the grate cooler exhaust(s) at the existing lime manufacturing plant would be subject to the kiln and cooler emission limit of 0.12 lb PM/ton limestone feed. With this approach, the emissions from the kiln and cooler are subject to one emission limit, regardless of whether the kiln and cooler emissions are combined prior to release to the atmosphere. This reflects the performance achieved by, and achievable by (taking operating variability into account), the median of the 12 percent best performing kilns for which the Agency has emissions data. Further, since we have defined the affected source to include all kilns and coolers at a lime manufacturing plant, the kiln and cooler PM emission limit applies to the combined emissions of PM from all of the kilns and coolers at the existing lime manufacturing plant. During the review of a draft of this proposal by the Small Business Advocacy Review (SBAR) Panel, an issue was raised about the potential for increases in sulfur dioxide (SO 2 ) and HCl emissions that may occur if sources opt to remove existing PM wet scrubbers and replace them with dry PM control devices (such as FF or ESP) in order to meet the proposed kiln PM standard. About 20 percent of the lime produced in the U.S. is from kilns equipped with wet scrubbers, and about 90 percent of the wet scrubbers on lime kilns at major source lime plants would not meet the proposed PM limit. And although the proposed rule would not dictate how the lime kiln PM standard would have to be met, and our limited information indicates that one or two lime kilns with wet scrubbers may already meet the proposed PM standard (this may be because they burn natural gas as their primary fuel source), some sources may elect to upgrade their existing wet scrubber with a new venturi wet scrubber to meet the PM standard, while other existing sources that would not meet the proposed PM emission limit with a wet scrubber may opt to replace the wet scrubber with a FF. But because wet scrubbers are more effective than a FF or ESP at removing SO 2 (and HCl), the SBAR Panel was concerned that the latter approach would result in increases in SO 2 emissions from these kilns. Therefore, we request comment on establishing a subcategory because of the potential increase in SO 2 and HCl emissions and other negative environmental impacts (discussed further below) that may result in complying with the proposed PM standard. We note, however, that the risk analysis showed that HCl levels emitted from lime kilns (including the increased HCl levels from kilns with wet scrubbers that are replaced with FF) are below the threshold value within an ample margin of safety. Although subcategorization normally is based on differences in manufacturing process, emission characteristics, or technical feasibility, and is not justified by the sole fact that a different type of air pollution control equipment is utilized, EPA solicits comment on the possibility of establishing a subcategory for existing lime kilns using wet scrubbers in order to avoid potentially environmentally counterproductive effects due to increased emissions of acid gases and increased water and energy use. (Such a subcategory would also significantly reduce the cost impact on industry.) In addition, we request comment on what the MACT floor PM limit would be for this possible subcategory. If we based the MACT floor for this possible subcategory on an inspection of the permit limit information available to us, we would initially conclude that a PM emission limit of 0.6 lb PM/ton limestone feed may be appropriate. We note, however, that in order to use permit limits as a basis for a MACT floor determination, those permit limits must accurately reflect the actual performance of the sources used as the basis for the MACT floor determination (considering both emission levels and operating variability when designed and operated properly). We, therefore, solicit information both on PM permit limits for wet scrubber equipped kilns and on the actual emissions from those kilns. Lastly, at the recommendation of the SBAR Panel, we specifically request comment on any operational, process, product, or other technical and/or spatial constraints that would preclude installation of a FF or ESP at an existing lime manufacturing plant. We note, however, that following the SBAR panel, the NLA brought to our attention the fact that if sources replace their wet scrubbers with FF to comply with the kiln PM standard, they would most likely also need to take steps to cool the exhaust gas stream entering the FF, since the operating temperature of a FF may be 400° less than a wet scrubber. Cooling the gas stream as such may be done using various techniques, all with varying environmental and cost impacts. In light of this new information presented by NLA, we analyzed the costs of three PM control options available to sources with wet scrubbers that do not currently meet the proposed PM limit. Sources could elect to replace the existing wet scrubber with a new FF and cool the entering exhaust gas stream using either a water spray system or alternatively a kiln preheater. Or sources may elect to replace the existing wet scrubber with a new venturi wet scrubber and thereby avoid the need for gas stream cooling. Based on our review of the technical performance of venturi scrubbers, we believe that a new, high efficiency venturi wet scrubber with a gas stream pressure drop of 35 inches water guage or more could meet the proposed lime kiln PM emission limit. After reviewing the cost impacts of these control options, we chose the venturi wet scrubber as the basis for estimating the proposed rule's impacts (for kilns with wet scrubbers not meeting the proposed PM limit) because, in general, this option was the least expensive in terms of capital cost and, in some cases, annual cost as well. We request comment on our cost analyses of these control options (the details of which may be found in the docket) and on our determination to base the impacts estimates of the proposed rule on this venturi scrubber control option. We also acknowledge that the NLA's cost estimates lead them to conclude that it may be less expensive for sources to install a FF with gas stream cooling rather than install new venturi wet scrubbers. In addition, there would be different emission and environmental impacts depending on the control option selected by sources with existing wet scrubbers not meeting the proposed PM limit. For the control option of a wet scrubber being replaced with a new FF, we estimate that national HCl emissions would increase by about 1,000 tons/yr, and national SO 2 emissions would increase by about 15,000 tons/yr. The NLA commented during the SBAR Panel that the resulting SO 2 increases under this option could cause a lime plant to become subject to new source review (NSR) rule requirements, and the source would, thus, incur additional costs associated with this review. Sources utilizing this control option may or may not be excluded from NSR if it is a pollution control project. Under the current NSR rules and guidance, a net emissions increase of 40 tons/yr SO 2 would trigger NSR even if this increase was due to a pollution control project, unless the control project qualified for a Pollution Control Project Exclusion. The EPA is currently revising the NSR rules. Finally, no change in SO 2 or HCl emissions would be expected for sources that replace existing wet scrubbers with new venturi wet scrubbers. With no resultant SO 2 emissions increases, it would be unlikely that sources would seek an NSR exclusion. We also acknowledge there would be additional negative environmental impacts if all kilns with wet scrubbers not meeting the proposed PM limit are replaced with new venturi wet scrubbers. These impacts would include an increase in national water consumption by about 4.2 billion gallons per year from current levels, and an increase in electricity consumption by about 7.2 million kilowatt-hours/yr. (Industry estimates that along with this additional electricity consumption, an additional 8,000 tons/yr of carbon dioxide would be emitted from fossil fuel fired electrical power generating stations.) These increases result from the new venturi wet scrubbers requiring a higher water flow rate and larger fans to handle the increased gas pressure drop. We note, however, that with a higher PM limit for a possible wet scrubber subcategory, national PM emissions from lime kilns would be approximately 1,000 tons/yr greater than if there were no subcategory. 2. Mercury From the Kiln Mercury emitted from lime kilns originates from the raw materials and fuels fed to the kiln. In considering a potential floor for mercury from these emission units, we considered both at-the-stack controls and substitution of feed and fuels as a potential basis for a standard. Since no sources are controlling the mercury emissions from their lime kilns using at-the-stack controls, such control cannot be the basis for a floor standard. Switching of raw material feed or fuel is also not a basis for establishing a floor standard because these means of control are not available, leading to unachievable standards. Nor is there any indication that feed or fuel substitution would control mercury emissions from these sources. The reasons for these conclusions are set out below. Substitution of raw materials, i.e. , feedstock substitution, is not an available means of control. First, raw materials are proprietary. No kiln can use another's raw materials. Thus, a standard based on feed control is not achievable because it is not even available. No second kiln could duplicate a “low mercury” source's performance, even assuming there was a low mercury source of feed material. In addition, we are aware of no data or information indicating that a certain type of limestone or source of limestone has a lower concentration of mercury, and although such deposits may exist, we do not believe such deposits of limestone exist sufficiently throughout the U.S. to supply the industry. Further, assuming there was a widespread source of limestone with a lower level of mercury (which is highly unlikely), it is unclear that this would lead to lower mercury emissions (or what the reductions of mercury emissions would be), since mercury emissions from lime kilns also originate from the fuel. A floor standard based on substitution of so-called clean mercury fossil fuels is likewise not achievable due to unavailability of this means of control. The floor for existing sources would have to be based on either coal or natural gas substitution since there are enough sources using coal or natural gas to constitute a MACT floor for existing kilns. However, there are simply inadequate amounts of “low mercury” coal and natural gas available to power this industry. Thus, we see no feasible way for the lime industry to function if it can only use the 6 percent “cleanest” fuels to make its product. See H.R. Rep. No. 101-490, 101st Cong. 2d sess. 328 (“MACT is not intended * * * to drive sources to the brink of shutdown”). Nor do we see any evidence that “low mercury” coal exists. Our analysis shows that the average mercury levels for the various coal types—bituminous, subbituminous, and lignite coals—are nearly the same at around 0.1 part per million by weight. These data show that there is not a certain type of coal that has a lower mercury level. Also, based on the data in the EPA Utility Study and Report to Congress, emissions of other HAP metals would or could increase if coal or oil were to be substituted to try and achieve lower mercury emissions. These data indicate that levels of HAP metals in coal are so variable that decreases in emissions of one HAP metal are offset by increases in others when different coals are used as fuel. These data also show that if fuel oil is substituted for coal, nickel emissions will increase because fuel oil typically contains more nickel than coal. Thus, based on these data, we believe that fuel switching among coal and oil is not an effective means of controlling HAP metal emissions (including mercury), even if this were an available means of control. For new as well as existing kilns, we considered basing the floor for mercury on the use of natural gas, although the few mercury emissions data we have cannot allow us to definitively state what effect fuel type has on emissions. However, we do not regard natural gas fuel substitution as an available technology for new sources. Natural gas is not readily available throughout the U.S., i.e. , the infrastructure for its delivery (pipelines, pumping stations, etc.) is not available for all locations where lime manufacturing plants exist and is not expected to be economically available to build such infrastructure throughout the U.S. Although U.S. natural gas reserves may be considered plentiful, the gas still needs to be extracted through drilling and the construction of wells. Thus, for plants located far from a natural gas pipeline, natural gas is not a reasonable alternative. Additionally, although the infrastructure (pipelines, wells, storage facilities) can be built, the delivery capacity will likely not be available to accommodate a fuel switch to natural gas within the time frame by which new kilns would have to comply. We note further that the amounts of mercury emitted by these kilns is small, roughly one pound per plant per year. Although the floor provisions of the CAA do not provide a de minimis exception to establishing floors, see National Lime v. EPA , 233 F. 3d at 640, the small amounts of mercury emitted reinforce the Agency's technical determinations that control via substitutions of feed or fuel are neither feasible nor likely to be effective since random variability in these feed and fuels will likely result in equal amounts of mercury being emitted in any case. Indeed, it is the Agency's view that not even a single source could reliably duplicate its own performance for mercury due to the small amounts emitted and the random variability of fuels and feed. 3. PM and Opacity From MPO There are numerous types of MPO such as grinding mills, storage bins, conveying systems (such as bucket elevators and belt conveyors), transfer points, and screening operations at each lime manufacturing plant. We investigated whether there were any MPO subject to standards more stringent than the NSPS subpart OOO, or otherwise performing with consistently lower emissions than required by the NSPS ( i.e. , performing at a lower level without being subject to a regulatory limit), that would serve as a basis for a MACT floor. To this end, we reviewed the applicable requirements for lime manufacturing plants located in nonattainment areas for PM10 (particulate matter with an aerodynamic diameter less than or equal to 10 microns), since presumably these areas of the U.S. would be the most likely to have more stringent PM emission limitations. We found seven lime manufacturing plants located in PM10 nonattainment areas. The information available to us on these plants indicated that no MPO were subject to standards more stringent than the NSPS subpart OOO or otherwise performing better. We believe that the NSPS subpart OOO standards reasonably reflect the level of performance achieved by, and achievable by, the average of the best performing 12 percent of sources. The basis for the MACT floor for these emission units is the NSPS subpart OOO as it has been applied to lime manufacturing plants, which serves as a reasonable measure of the performance of the average of the best performing sources. The NSPS subpart OOO sets PM, opacity, and visible emission limits for limestone MPO that were constructed, reconstructed, or modified after August 31, 1983. We investigated whether enough of these MPO are located at lime manufacturing plants subject to the NSPS subpart OOO to make a MACT floor determination. Using the median approach to determining MACT floors, at least 6 percent would need to be subject to the NSPS subpart OOO. In one approach to estimating the number of MPO at lime manufacturing plants that are subject to the NSPS subpart OOO, we estimate that there are 104 lime manufacturing plants in the U.S., and that at least seven of these were built after August 31, 1983. All of the MPO associated with these new, greenfield lime manufacturing plants that were built after August 31, 1983, would be subject to the NSPS subpart OOO. Therefore, at least 6.7 percent (7/104) of the MPO are subject to the NSPS subpart OOO, enough for the NSPS subpart OOO to serve as a basis for the MACT floor. In another approach to estimating the percentage of lime manufacturing plant MPO that are subject to the NSPS subpart OOO, our information shows that at least 31 lime kilns were constructed after August 31, 1983, out of a total of about 257 lime kilns in the U.S. Assuming that the MPO associated with these new lime kilns are also new, we estimate that 12.1 percent (31/257) of the MPO are subject to the NSPS subpart OOO. Thus, with either approach to estimating the number of MPO at lime manufacturing plants that are subject to the NSPS subpart OOO, there are enough to support a MACT floor determination. Therefore, the MACT floor for MPO is equivalent to the NSPS subpart OOO. E. How Did We Determine the MACT Floor for Emission Units at New Lime Manufacturing Plants? The CAA requires the MACT floor for new sources to be based on the degree of emissions reductions achieved in practice by the best-controlled similar source. For HAP metals emissions from MPO at new lime manufacturing plants, the floor is the NSPS subpart OOO (the same as for MPO at existing lime manufacturing plants). As discussed previously, we investigated whether there were any MPO subject to standards more stringent than the NSPS subpart OOO, or were emitting at lower rates without being subject to some type of regulatory standards, that would serve as a basis for MACT for new sources. The information available to us indicates that no MPO are subject to standards more stringent than the NSPS subpart OOO or otherwise performing better. Therefore, the floor is the NSPS subpart OOO. For HAP metals emissions from kilns and coolers, the floor for those at new lime manufacturing plants is defined by the permit limits and emissions data for PM, where PM is a surrogate for non-mercury HAP metals. As previously described in this preamble, the MACT floor PM emission limit for lime kilns and coolers at existing lime manufacturing plants would be 0.12 lb PM/ton limestone. This determination was based on the median approach, i.e. , on the third best kiln permit limit of 0.12 lb PM/ton limestone. For kilns at new lime manufacturing plants, MACT is based on the best controlled similar source, which is the kiln permitted at the lowest emission limit ( i.e. , 0.10 lb PM/ton limestone). Test data for this kiln indicated that the emission level was 0.0925 lb PM/ton, demonstrating that this permit limit is indeed achievable, and that the permit level reasonably approximates the level of performance that is consistently achievable by this kiln (so that a lower floor level would not be technically justified). Therefore, the emission limit for kilns and coolers at a new lime manufacturing plant is 0.10 lb/ton stone feed. As with the existing sources, this emission limit applies to the combined emissions from all of the kilns and coolers at a new lime manufacturing plant. As previously described and for the same reasons that there is no MACT floor for mercury for kilns at existing lime manufacturing plants, and the beyond-the-MACT-floor options considered for kilns at existing lime manufacturing plants are not justified, there is no MACT for mercury for kilns at new sources. F. What Control Options Beyond the MACT Floor Did We Consider? Raw material feed or fuel switching may be considered potential beyond-the-floor options for mercury, but as previously stated, no data or information is available indicating that a certain type of limestone or source of limestone has a lower concentration of mercury or is generally available throughout the country. In addition, even if deposits of limestone with low levels of mercury were to be found, it is unlikely that the limestone would be in close proximity to the majority of lime manufacturing plants in the U.S. and, thus, the cost of transporting the limestone to lime manufacturing plants would be prohibitively expensive. (There would also be increased energy use associated with this option in the form of increased fuel use to transport raw materials.) Most, if not all, lime manufacturing plants are sited and located adjacent to or in close proximity to their source of limestone (usually a quarry or mine) to avoid the high cost of transporting the material. Regarding fuel switching as a possible mercury MACT floor or beyond-the-MACT-floor option for existing or new kilns, using a fuel with a lower level of mercury, such as natural gas (instead of coal), may result in lower lime kiln mercury emissions. However, there are no data available to quantify what the emissions reductions would be since our analysis indicates that most mercury emissions originate from the limestone feed material (compared with coal), and so the emissions reductions that would be achieved via switching from coal to natural gas are uncertain. Further, as explained above, natural gas is not readily available throughout the U.S. ( i.e. , the infrastructure for its delivery (pipelines, pumping stations, etc.)), is not available for all locations where lime manufacturing plants exist, and is not expected to be economically available to build such infrastructure throughout the U.S. We considered another beyond-the-MACT-floor option based on activated carbon injection—a mercury control technology currently used on various types of waste combustors. However, based on the already relatively low levels of mercury emissions from lime kilns, we expect that relatively low emissions reductions would be achieved from this technology. (Use of activated carbon injection also generates a mercury-bearing waste stream to be disposed of.) The few mercury emissions data available (four data points) range from 0.7 to 2.5 micrograms/dry standard cubic meter (referenced to 7 percent oxygen). These uncontrolled levels are 10 to 100 times lower than the mercury emission standards established for various types of waste combustors and translate to an average annual emission rate of approximately 1 lb/year per lime kiln. Thus, this beyond-the-floor-control option would not be cost-effective because of the low emissions reductions expected and the high cost of control. Further, use of activated carbon generates an additional waste to be disposed of, and there are increases in energy use associated with the technology. After considering cost, energy, and non-air human health and environmental impacts, our initial conclusion is that basing beyond-the-floor standards for mercury on use of activated carbon is not warranted. For HAP metal (PM) emissions from the kiln and MPO, no technologies were identified that would perform better than the technologies representative of the MACT floors that were determined. Raw material feed or fuel switching is not a beyond-the-MACT-floor option for PM control from lime kilns, for reasons similar as to why it is not an option for mercury control. Regarding feed material switching, no data or information is available indicating that using a certain type or source of limestone would have a lower HAP metals content or would lead to reduced PM emissions. We do not believe that such deposits of limestone exist or that use of a certain type of limestone would consistently result in lower PM or metals emissions. Further, assuming there was a widespread source of limestone with a lower HAP metals content (which is highly unlikely), it is unclear that this would lead to lower HAP metals emissions (or what the reductions of the HAP metals emissions would be) since HAP metals emissions from lime kilns would also originate from the fuel. In addition, even if deposits of limestone with low levels of HAP metals or a lower PM-producing limestone were to be found, the cost of transporting the limestone to lime manufacturing plants would be prohibitively expensive. In addition, as noted earlier, there would be increased energy usage associated with the transport of large amounts of raw materials. Regarding fuel switching as a possible beyond-the-MACT-floor option for HAP metals, using a fuel with a lower level of metals, such a natural gas (compared to coal), may result in lower lime kiln metals emissions. However, there are insufficient data available to quantify what the emissions reductions would be, since as we described above, lime kiln metals emissions also originate from the limestone feed material. Further, natural gas is not readily available throughout the U.S. ( i.e. , the infrastructure for its delivery (pipelines, pumping stations, etc.)) and may not be available for all locations where lime manufacturing plants exist. Further, the cost of using natural gas may be prohibitively expensive as the cost of natural gas continues to rise as the growing demand for it rises as well. We do not regard this as an available means of control for this source category. See also the discussion above as to why the use of natural gas is not a viable control option for mercury; this rationale also applies to the use of natural gas as a beyond-the-floor option for PM and non-mercury HAP metals. Consequently, we are not proposing any beyond-the-floor standard for HAP metal control based on requiring the use of natural gas rather than other fossil fuels. Therefore, the Agency is proposing that the floor standard for mercury reflect no existing reduction and after considering the factors set out in CAA section 112 (d)(2), that no beyond-the-floor alternatives are achievable. G. How Did We Select the Format of the Proposed Rule? The formats selected for the proposed emission limits vary according to the emission source, pollutant, and the MACT basis for the limits. The formats selected include a production-based emission limit, pollutant concentration limits, and opacity limits. For the kiln PM standard, the “lb PM/ton limestone” format was selected to be consistent with the NSPS for lime manufacturing plants, 40 CFR 60, subpart HH. This format also encourages kiln energy efficiency. A more energy efficient kiln emits less exhaust gas per ton of limestone processed, which results in a higher gas concentration of PM compared to a less energy efficient kiln for the same amount of lime produced and PM emitted. A concentration format (e.g., grains PM/dry standard cubic foot) would penalize more energy efficient kilns. For the PM and opacity standards for MPO, a concentration format for PM and the opacity limit requirements were selected to be consistent with the NSPS for nonmetallic minerals processing, 40 CFR part 60, subpart OOO. H. How Did We Select the Test Methods and Monitoring Requirements for Determining Compliance With the Proposed Rule? 1. PM From the Kiln and Cooler Today's proposed rule would require you to conduct a PM performance test and concurrently measure the stone feed rate to the kiln during the test. If you operate a lime cooler associated with the kiln being tested that has a separate exhaust to the atmosphere, you would be required to conduct a Method 5 (40 CFR part 60, appendix A-3) test on the cooler's exhaust concurrently with the kiln Method 5 test. Method 5 is the long-standing EPA method for measuring PM emissions from stationary sources. For each kiln with an ESP, if you choose to monitor ESP operating parameters in lieu of using a PM detector or a COMS, you would be required to collect and record the input voltage and current to each electrical field of the ESP during the PM performance test, and then determine the 3-hour operating limit for each parameter for each electrical field based on these data. We expect that most lime manufacturing plants with ESP already monitor the electrical current and voltage, which provides an indication of the ESP performance and consequently PM emissions as well. For continuous compliance demonstrations, you would be required to maintain the 3-hour rolling average current and voltage input to each electrical field of the ESP greater than or equal to the average current and voltage input to each field of the ESP as established during the performance test. You would be required to collect and reduce the data as previously described. A 3-hour rolling average was selected to be consistent with the usual 3-hour time required for the PM test (three test runs of at least 1 hour). You would also have the option of monitoring PM emissions from an ESP with a PM detector, in lieu of monitoring ESP parameters. Sources may determine that this would allow them greater operational flexibility. These devices would be similar to the BLDS for FF, which are discussed below, but they are based on light scattering technology (and not the triboelectric technology). For each kiln with a wet scrubber, you would be required to collect and record the exhaust gas stream pressure drop across the scrubber and the scrubber liquid flow rate during the PM performance test, and then establish the 3-hour operating limit for each of these parameters based on the data. Pressure drop and flow rate are the scrubber operating parameters most often monitored and provide an indication of the scrubber's performance and consequently PM emissions as well. Fo [Text truncated at 120,000 characters. The full text is on the page linked above.] --- Source: Frix Law Library, https://www.frixlaw.com/law-library/documents/fr%3A02-31233. Public record. Not legal advice.