National Emission Standards for Hazardous Air Pollutants From the Portland Cement Manufacturing Industry, 21136-21192 [E9-10206]

Agencies

• ENVIRONMENTAL PROTECTION AGENCY

[Federal Register Volume 74, Number 86 (Wednesday, May 6, 2009)]
[Proposed Rules]
[Pages 21136-21192]
From the Federal Register Online via the Government Printing Office [www.gpo.gov]
[FR Doc No: E9-10206]



[[Page 21135]]

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Part III





Environmental Protection Agency





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40 CFR Parts 60 and 63



National Emission Standards for Hazardous Air Pollutants From the 
Portland Cement Manufacturing Industry; Proposed Rule

Federal Register / Vol. 74, No. 86 / Wednesday, May 6, 2009 / 
Proposed Rules

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ENVIRONMENTAL PROTECTION AGENCY

40 CFR Parts 60 and 63

[EPA-HQ-OAR-2002-0051; FRL-8898-1]
RIN 2060-AO15


National Emission Standards for Hazardous Air Pollutants From the 
Portland Cement Manufacturing Industry

AGENCY: Environmental Protection Agency (EPA).

ACTION: Proposed rule.

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SUMMARY: EPA is proposing amendments to the current National Emission 
Standards for Hazardous Air Pollutants (NESHAP) from the Portland 
Cement Manufacturing Industry. These proposed amendments would add or 
revise, as applicable, emission limits for mercury, total hydrocarbons 
(THC), and particulate matter (PM) from kilns and in-line kiln/raw 
mills located at a major or an area source, and hydrochloric acid (HCl) 
from kilns and in-line kiln/raw mills located at major sources. These 
proposed amendments also would remove the following four provisions in 
the current regulation: the operating limit for the average hourly 
recycle rate for cement kiln dust; the requirement that cement kilns 
only use certain type of utility boiler fly ash; the opacity limits for 
kilns and clinker coolers; and the 50 parts per million volume dry 
(ppmvd) THC emission limit for new greenfield sources. EPA is also 
proposing standards which would apply during startup, shutdown, and 
operating modes for all of the current section 112 standards applicable 
to cement kilns.
    Finally, EPA is proposing performance specifications for use of 
mercury continuous emission monitors (CEMS), which specifications would 
be generally applicable and so could apply to sources from categories 
other than, and in addition to, portland cement, and updating 
recordkeeping and testing requirements.

DATES: Comments must be received on or before July 6, 2009. If any one 
contacts EPA by May 21, 2009 requesting to speak at a public hearing, 
EPA will hold a public hearing on May 26, 2009. Under the Paperwork 
Reduction Act, comments on the information collection provisions are 
best assured of having full effect if the Office of Management and 
Budget (OMB) receives a copy of your comments on or before June 5, 
2009.

ADDRESSES: Submit your comments, identified by Docket ID No. EPA-HQ-
OAR-2002-0051, by one of the following methods:
     https://www.regulations.gov: Follow the on-line 
instructions for submitting comments.
     E-mail: a-and-r-docket@epa.gov.
     Fax: (202) 566-9744.
     Mail: U.S. Postal Service, send comments to: EPA Docket 
Center (6102T), National Emission Standards for Hazardous Air Pollutant 
From the Portland Cement Manufacturing Industry Docket, Docket ID No. 
EPA-HQ-OAR-2002-0051, 1200 Pennsylvania Ave., NW., Washington, DC 
20460. Please include a total of two copies. In addition, please mail a 
copy of your comments on the information collection provisions to the 
Office of Information and Regulatory Affairs, Office of Management and 
Budget (OMB), Attn: Desk Officer for EPA, 725 17th St., NW., 
Washington, DC 20503.
     Hand Delivery: In person or by courier, deliver comments 
to: EPA Docket Center (6102T), Standards of Performance (NSPS) for 
Portland Cement Plants Docket, Docket ID No. EPA-HQ-OAR-2007-0877, EPA 
West, Room 3334, 1301 Constitution Avenue, NW., Washington, DC 20004. 
Such deliveries are only accepted during the Docket's normal hours of 
operation, and special arrangements should be made for deliveries of 
boxed information. Please include a total of two copies.
    Instructions: Direct your comments to Docket ID No. EPA-HQ-OAR-
2002-0051. EPA's policy is that all comments received will be included 
in the public docket without change and may be made available online at 
https://www.regulations.gov, including any personal information 
provided, unless the comment includes information claimed to be 
Confidential Business Information (CBI) or other information whose 
disclosure is restricted by statute. Do not submit information that you 
consider to be CBI or otherwise protected through https://www.regulations.gov or e-mail. The https://www.regulations.gov Web site 
is an ``anonymous access'' system, which means EPA will not know your 
identity or contact information unless you provide it in the body of 
your comment. If you send an e-mail comment directly to EPA without 
going through https://www.regulations.gov, your e-mail address will be 
automatically captured and included as part of the comment that is 
placed in the public docket and made available on the Internet. If you 
submit an electronic comment, EPA recommends that you include your name 
and other contact information in the body of your comment and with any 
disk or CD-ROM you submit. If EPA cannot read your comment due to 
technical difficulties and cannot contact you for clarification, EPA 
may not be able to consider your comment. Electronic files should avoid 
the use of special characters, any form of encryption, and be free of 
any defects or viruses.
    Docket: All documents in the docket are listed in the https://www.regulations.gov index. Although listed in the index, some 
information is not publicly available, e.g., CBI or other information 
whose disclosure is restricted by statute. Certain other material, such 
as copyrighted material, will be publicly available only in hard copy. 
Publicly available docket materials are available either electronically 
in https://www.regulations.gov or in hard copy at the EPA Docket Center, 
National Emission Standards for Hazardous Air Pollutants from the 
Portland Cement Manufacturing Industry Docket, EPA West, Room 3334, 
1301 Constitution Ave., NW., Washington, DC. The Public Reading Room is 
open from 8:30 a.m. to 4:30 p.m., Monday through Friday, excluding 
legal holidays. The telephone number for the Public Reading Room is 
(202) 566-1744, and the telephone number for the Docket Center is (202) 
566-1742.

FOR FURTHER INFORMATION CONTACT: Mr. Keith Barnett, Office of Air 
Quality Planning and Standards, Sector Policies and Programs Division, 
Metals and Minerals Group (D243-02), Environmental Protection Agency, 
Research Triangle Park, NC 27711, telephone number: (919) 541-5605; fax 
number: (919) 541-5450; e-mail address: barnett.keith@epa.gov.

SUPPLEMENTARY INFORMATION: 
    The information presented in this preamble is organized as follows:

I. General Information
    A. Does this action apply to me?
    B. What should I consider as I prepare my comments to EPA?
    C. Where can I get a copy of this document?
    D. When would a public hearing occur?
II. Background Information
    A. What is the statutory authority for these proposed 
amendments?
    B. Summary of the National Lime Association v. EPA Litigation
    C. EPA's Response to the Remand
    D. Reconsideration of EPA Final Action in Response to the Remand
III. Summary of Proposed Amendments to Subpart LLL
    A. Emissions Limits
    B. Operating Limits
    C. Testing and Monitoring Requirements
IV. Rationale for Proposed Amendments to Subpart LLL
    A. MACT Floor Determination Procedure for all Pollutants

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    B. Determination of MACT for Mercury Emissions From Major and 
Area Sources
    C. Determination of MACT for THC Emissions From Major and Area 
Sources
    D. Determination of MACT for HCl Emissions From Major Sources
    E. Determination of MACT for PM Emissions From Major and Area 
Sources
    F. Selection of Compliance Provisions
    G. Selection of Compliance Dates
    H. Discussion of EPA's Sector Based Approach for Cement 
Manufacturing
    I. Other Changes and Areas Where We Are Requesting Comment
V. Comments on Notice of Reconsideration and EPA Final Action in 
Response To Remand
VI. Summary of Cost, Environmental, Energy, and Economic Impacts of 
Proposed Amendments
    A. What are the affected sources?
    B. How are the impacts for this proposal evaluated?
    C. What are the air quality impacts?
    D. What are the water quality impacts?
    E. What are the solid waste impacts?
    F. What are the secondary impacts?
    G. What are the energy impacts?
    H. What are the cost impacts?
    I. What are the economic impacts?
    J. What are the benefits?
VII. Statutory and Executive Order Reviews
    A. Executive Order 12866: Regulatory Planning and Review
    B. Paperwork Reduction Act
    C. Regulatory Flexibility Act
    D. Unfunded Mandates Reform Act
    E. Executive Order 13132: Federalism
    F. Executive Order 13175: Consultation and Coordination With 
Indian Tribal Governments
    G. Executive Order 13045: Protection of Children From 
Environmental Health Risks and Safety Risks
    H. Executive Order 13211: Actions Concerning Regulations That 
Significantly Affect Energy Supply, Distribution, or Use
    I. National Technology Transfer Advancement Act
    J. Executive Order 12898: Federal Actions to Address 
Environmental Justice in Minority Populations and Low-Income 
Populations

I. General Information

A. Does this action apply to me?

    Categories and entities potentially regulated by this proposed rule 
include:

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                                           NAICS code
                Category                      \1\                    Examples of regulated entities
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Industry................................       327310  Portland cement plants.
Federal government......................  ...........  Not affected.
State/local/tribal government...........  ...........  Portland cement plants.
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\1\ North American Industry Classification System.

    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 would be regulated by this 
proposed action, you should examine the applicability criteria in 40 
CFR 63.1340 (subpart LLL). If you have any questions regarding the 
applicability of this proposed action to a particular entity, contact 
the person listed in the preceding FOR FURTHER INFORMATION CONTACT 
section.

B. What should I consider as I prepare my comments to EPA?

    Do not submit information containing CBI to EPA through https://www.regulations.gov or e-mail. Send or deliver information identified 
as CBI only to the following address: Roberto Morales, OAQPS Document 
Control Officer (C404-02), Office of Air Quality Planning and 
Standards, Environmental Protection Agency, Research Triangle Park, NC 
27711, Attention Docket ID No. EPA-HQ-OAR-2002-0051. Clearly mark the 
part or all of the information that you claim to be CBI. For CBI 
information in a disk or CD-ROM that you mail to EPA, mark the outside 
of the disk or CD-ROM as CBI and then identify electronically within 
the disk or CD-ROM the specific information that is claimed as CBI. In 
addition to one complete version of the comment that includes 
information claimed as CBI, a copy of the comment that does not contain 
the information claimed as CBI must be submitted for inclusion in the 
public docket. Information so marked will not be disclosed except in 
accordance with procedures set forth in 40 CFR part 2.

C. Where can I get a copy of this document?

    In addition to being available in the docket, an electronic copy of 
this proposed action is available on the Worldwide Web (WWW) through 
the Technology Transfer Network (TTN). Following signature, a copy of 
this proposed action will be posted on the TTN's policy and guidance 
page for newly proposed or promulgated rules at https://www.epa.gov/ttn/oarpg. The TTN provides information and technology exchange in various 
areas of air pollution control.

D. When and where would a public hearing occur?

    If anyone contacts EPA requesting to speak at a public hearing by 
May 21, 2009, a public hearing will be held on May 26, 2009. To request 
a public hearing contact Ms. Pamela Garrett, EPA, Office of Air Quality 
Planning and Standards, Sector Policy and Programs Division, Energy 
Strategies Group (D243-01), Research Triangle Park, NC 27711, telephone 
number 919-541-7966, e-mail address: garrett.pamela@epa.gov by the date 
specified above in the DATES section. Persons interested in presenting 
oral testimony or inquiring as to whether a public hearing is to be 
held should also contact Ms. Pamela Garrett at least 2 days in advance 
of the potential date of the public hearing.
    If a public hearing is requested, it will be held at 10 a.m. at the 
EPA Headquarters, Ariel Rios Building, 12th Street and Pennsylvania 
Avenue, Washington, DC 20460 or at a nearby location.

II. Background Information

A. What is the statutory authority for these proposed amendments?

    Section 112(d) of the Clean Air Act (CAA) requires EPA to set 
emissions standards for Hazardous Air Pollutants (HAP) emitted by major 
stationary sources based on performance of the maximum achievable 
control technology (MACT). The MACT standards for existing sources must 
be at least as stringent as the average emissions limitation achieved 
by the best performing 12 percent of existing sources (for which the 
administrator has emissions information) or the best performing 5 
sources for source categories with less than 30 sources (CAA section 
112(d)(3)(A) and (B)). This level of minimum stringency is called the 
MACT floor. For new sources, MACT standards must be at least as 
stringent as the control level achieved in practice by the best 
controlled similar source (CAA section 112(d)(3)). EPA also must 
consider more stringent ``beyond-the-floor'' control options. When 
considering beyond-the-floor options, EPA must consider not only the 
maximum degree of reduction in

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emissions of HAP, but must take into account costs, energy, and nonair 
environmental impacts when doing so.
    Section 112(k)(3)(B) of the CAA requires EPA to identify at least 
30 HAP that pose the greatest potential health threat in urban areas, 
and section 112(c)(3) requires EPA to regulate, under section 112(d) 
standards, the area source \1\ categories that represent 90 percent of 
the emissions of the 30 ``listed'' HAP (``urban HAP''). We implemented 
these listing requirements through the Integrated Urban Air Toxics 
Strategy (64 FR 38715, July 19, 1999).\2\
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    \1\ An area source is a stationary source of HAP emissions that 
is not a major source. A major source is a stationary source that 
emits or has the potential to emit 10 tons per year (tpy) or more of 
any HAP or 25 tpy or more of any combination of HAP.
    \2\ \\ Since its publication in the Integrated Urban Air Toxics 
Strategy in 1999, EPA has amended the area source category list 
several times.
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    The portland cement source category was listed as a source category 
for regulation under this 1999 Strategy based on emissions of arsenic, 
cadmium, beryllium, lead, and polychlorinated biphenyls. The final 
NESHAP for the Portland Cement Manufacturing Industry (64 FR 31898, 
June 14, 1999) included emission limits based on performance of MACT 
for the control of THC emissions from area sources. This 1999 rule 
fulfills the requirement to regulate area source cement kiln emissions 
of polychlorinated biphenyls (for which THC is a surrogate). However, 
EPA did not include requirements for the control of the non-volatile 
metal HAP (arsenic, cadmium, beryllium, and lead) from area sources in 
the 1999 rule or in the 2006 amendments. To fulfill our requirements 
under section 112(c)(3) and 112(k), EPA is thus proposing to set 
emissions standards for these metal HAP from portland cement 
manufacturing facilities that are area sources (using particulate 
matter as a surrogate). In this proposal, EPA is proposing PM standards 
for area sources based on performance of MACT.
    Section 112(c)(6) requires EPA to list, and to regulate under 
standards established pursuant to section 112(d)(2) or (d)(4), 
categories of sources accounting for not less than 90 percent of 
emissions of each of seven specific HAP: alkylated lead compounds; 
polycyclic organic matter; hexachlorobenzene; mercury; polychlorinated 
byphenyls; 2,3,7,8-tetrachlorodibenzofurans; and 2,3,7,8-
tetrachloroidibenzo-p-dioxin. Standards established under CAA 112(d)(2) 
must reflect the performance of MACT. ``Portland cement manufacturing: 
non-hazardous waste kilns'' is listed as a source category for 
regulation under section 112(d)(2) pursuant to the section 112(c)(6) 
requirements due to emissions of polycyclic organic matter, mercury, 
and dioxin/furans (63 FR 17838, 17848, April 10, 1998); see also 63 FR 
at 14193 (March 24, 1998) (area source cement kilns' emissions of 
mercury, dibenzo-p-dioxins and dibenzo-p-furans, polycyclic organic 
matter, and polychlorinated biphenyls are subject to MACT).
    Section 129(a)(1)(A) of the Act requires EPA to establish specific 
performance standards, including emission limitations, for ``solid 
waste incineration units'' generally, and, in particular, for ``solid 
waste incineration units combusting commercial or industrial waste'' 
(section 129(a)(1)(D)).\3\ Section 129 defines ``solid waste 
incineration unit'' as ``a distinct operating unit of any facility 
which combusts any solid waste material from commercial or industrial 
establishments or the general public.'' Section 129(g)(1). Section 129 
also provides that ``solid waste'' shall have the meaning established 
by EPA pursuant to its authority under the [Resource Conservation and 
Recovery Act]. Section 129(g)(6).
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    \3\ CAA section 129 refers to the Solid Waste Disposal Act 
(SWDA). However, this act, as amended, is commonly referred to as 
the Resource Conservation and Recovery Act (RCRA).
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    In Natural Resources Defense Council v. EPA, 489 F. 3d 1250, 1257-
61 (D.C. Cir. 2007), the court vacated the Commercial and Industrial 
Solid Waste Incineration Units (CISWI) Definitions Rule, 70 FR 55568 
(Sept. 22, 2005), which EPA issued pursuant to CAA section 
129(a)(1)(D). In that rule, EPA defined the term ``commercial or 
industrial solid waste incineration unit'' to mean a combustion unit 
that combusts ``commercial or industrial waste.'' The rule defined 
``commercial or industrial waste'' to mean waste combusted at a unit 
that does not recover thermal energy from the combustion for a useful 
purpose. Under these definitions, only those units that combusted 
commercial or industrial waste and were not designed to, or did not 
operate to, recover thermal energy from the combustion would be subject 
to section 129 standards. The DC Circuit rejected the definitions 
contained in the CISWI Definitions Rule and interpreted the term 
``solid waste incineration unit'' in CAA section 129(g)(1) ``to 
unambiguously include among the incineration units subject to its 
standards any facility that combusts any commercial or industrial solid 
waste material at all--subject to the four statutory exceptions 
identified in [CAA section 129(g)(1).]'' NRDC v. EPA, 489 F.3d 1250, 
1257-58.
    In response to the Court's remand and vacatur of the CISWI 
Definitions rule, EPA has initiated a rulemaking to define which 
secondary materials are ``solid waste'' for purposes of subtitle D 
(non-hazardous waste) of the Resource Conservation and Recovery Act 
when burned in a combustion unit. See Advance Notice of Proposed 
Rulemaking, 74 FR 41 (January 2, 2009) (soliciting comment on whether 
certain secondary materials used as alternative fuels or ingredients 
are solid wastes within the meaning of Subtitle D of the Resource 
Conservation and Recovery Act). That definition, in turn, would 
determine the applicability of section 129(a).
    This definitional rulemaking is relevant to this proceeding because 
some portland cement kilns combust secondary materials as alternative 
fuels. However, there is no federal regulatory interpretation of 
``solid waste'' for EPA to apply under Subtitle D of the Resource 
Conservation and Recovery Act, and EPA cannot prejudge the outcome of 
that pending rulemaking. Moreover, EPA has imperfect information on the 
exact nature of the secondary materials which portland cement kilns 
combust, such as information as to the provider(s) of the secondary 
materials, how much processing the secondary materials may have 
undergone, and other issues potentially relevant in a determination of 
whether these materials are to be classified as solid wastes. See 74 FR 
at 53-59. EPA therefore cannot reliably determine at this time if the 
secondary materials combusted by cement kilns are to be classified as 
solid wastes. Accordingly, EPA is basing all determinations as to 
source classification on the emissions information now available, as 
required by section 112(d)(3), and will necessarily continue to do so 
until the solid waste definition discussed above is promulgated. The 
current data base classifies all portland cement kilns as section 112 
sources (i.e. subject to regulation under section 112). EPA notes, 
however, that the combustion of secondary materials as alternative 
fuels did not have any appreciable effect on the amount of HAP emitted 
by any source.\4\
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    \4\ Development of the MACT Floors for the Proposed NESHAP for 
Portland Cement. April 15, 2009.

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B. Summary of the National Lime Association v. EPA Litigation

    On June 14, 1999 (64 FR 31898), EPA issued the NESHAP for the 
Portland Cement Manufacturing Industry (40 CFR part 63, subpart 
LLL).\5\ The 1999 final rule established emission limitations for PM as 
a surrogate for non-volatile HAP metals (major sources only), dioxins/
furans, and for greenfield \6\ new sources total THC as a surrogate for 
organic HAP. These standards were intended to be based on the 
performance of MACT pursuant to sections 112(d)(2) and (3). We did not 
establish limits for THC for existing sources and non-greenfield new 
sources, nor for HCl or mercury for new or existing sources. We 
reasoned that emissions of these constituents were a function of raw 
material concentrations and so were essentially uncontrolled, the 
result being that there was no level of performance on which a floor 
could be based. EPA further found that beyond the floor standards for 
these HAP were not warranted.
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    \5\ Cement kilns which burn hazardous waste are a separate 
source category, since their emissions of many HAP differ from 
portland cement kilns' as a result of the hazardous waste inputs. 
Rules for hazardous waste-burning cement kilns are found at subpart 
EEE of part 63.
    \6\ For purposes of the 1999 rule a new greenfield kiln is a 
kiln constructed after March 24, 1998, at a site where there are no 
existing kilns.
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    Ruling on petitions for review of various environmental groups, the 
DC Circuit held that EPA had erred in failing to establish section 
112(d) standards for mercury, THC (except for greenfield new sources) 
and hydrochloric acid. The court held that ``[n]othing in the statute 
even suggests that EPA may set emission levels only for those * * * 
HAPs controlled with technology.'' National Lime Ass'n v. EPA, 233 F. 
3d 625, 633 (DC Cir. 2000). The court also stated that EPA is obligated 
to consider other pollution-reducing measures such as process changes 
and material substitution. Id. at 634. Later cases go on to hold that 
EPA must account for levels of HAP in raw materials and other inputs in 
establishing MACT floors, and further hold that sources with low HAP 
emission levels due to low levels of HAP in their raw materials can be 
considered best performers for purposes of establishing MACT floors. 
See, e.g., Sierra Club v. EPA (Brick MACT), 479 F. 3d 875, 882-83 (DC 
Cir. 2007).\7\
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    \7\ In the remainder of the opinion, the court in National Lime 
Ass'n upheld EPA's standards for particulate matter and dioxin (on 
grounds that petitioner had not properly raised arguments in its 
opening brief), upheld EPA's use of particulate matter as a 
surrogate for HAP metals, and remanded for further explanation EPA's 
choice of an analytic method for hydrochloric acid.
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C. EPA's Response to the Remand

    In response to the National Lime Ass'n mandate, on December 2, 
2005, we proposed standards for mercury, THC, and HCl. (More 
information on the regulatory and litigation history may be found at 70 
FR 72332, December 2, 2005.) We received over 1,700 comments on the 
proposed amendments. Most of these comments addressed the lack of a 
mercury emission limitation in the proposed amendments. On December 20, 
2006 (71 FR 76518), EPA published final amendments to the national 
emission standards for these HAP. The final amendments contain a new 
source standard for mercury emissions from cement kilns and kilns/in-
line raw mills of 41 micrograms per dry standard cubic meter, or 
alternatively the application of a limestone wet scrubber with a 
liquid-to-gas ratio of 30 gallons per 1,000 actual cubic feet per 
minute of exhaust gas. The final rule also adopted a standard for new 
and existing sources banning the use of utility boiler fly ash in 
cement kilns where the fly ash mercury content has been increased 
through the use of activated carbon or any other sorbent unless the 
cement kiln seeking to use the fly ash can demonstrate that the use of 
fly ash will not result in an increase in mercury emissions over its 
baseline mercury emissions (i.e., emissions not using the mercury-laden 
fly ash). EPA also issued a THC standard for new cement kilns (except 
for greenfield cement kilns that commenced construction on or before 
December 2, 2005) of 20 parts per million (corrected to 7 percent 
oxygen) or 98 percent reduction in THC emissions from uncontrolled 
levels. EPA did not set a standard for HCl, determining that HCl was a 
pollutant for which a threshold had been established, and that no 
cement kiln, even under worst-case operating conditions and exposure 
assumptions, would emit HCl at levels that would exceed that threshold 
level, allowing for an ample margin of safety.

D. Reconsideration of EPA Final Action in Response to the Remand

    At the same time we issued the final amendments, EPA on its own 
initiative made a determination to reconsider the new source standard 
for mercury, the existing and new source standard banning cement kiln 
use of certain mercury-containing fly ash, and the new source standard 
for THC (71 FR 76553, December 20, 2006). EPA granted reconsideration 
of the new source mercury standard both due to substantive issues 
relating to the performance of wet scrubbers and because information 
about their performance in the industry had not been available for 
public comment at the time of proposal but is now available in the 
docket. We also committed to undertake a test program for mercury 
emissions from cement kilns equipped with wet scrubbers that would 
enable us to resolve these issues. We further explained that we were 
granting reconsideration of the work practice requirement banning the 
use of certain mercury-containing fly ash in cement kilns to allow 
further opportunity for comment on both the standard and the underlying 
rationale and because we did not feel we had the level of analysis we 
would like to support a beyond-the-floor determination. We granted 
reconsideration of the new source standard for THC because the 
information on which the standard was based arose after the period for 
public comment. We requested comment on the actual standard, whether 
the standard is appropriate for reconstructed new sources (if any 
should occur) and the information on which the standard is based. We 
specifically solicited data on THC emission levels from preheater/
precalciner cement kilns. We stated that we would evaluate all data and 
comments received, and determine whether in light of those data and 
comments it is appropriate to amend the promulgated standards.
    EPA received comments on the notice of reconsideration from two 
cement companies, three energy companies, three industry associations, 
a technical consultant, one State, one environmental group, one ash 
management company, one fuels company, and one private citizen. As part 
of these comments, one industry trade association submitted a petition 
to withdraw the new source MACT standards for mercury and THC and one 
environmental group submitted a petition for reconsideration of the 
2006 final action. A summary of these comments is available in the 
docket for this rulemaking.\8\
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    \8\ Summary of Comments on December 20, 2006 Final Rule and 
Notice of Reconsideration. April 15, 2009.
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    In addition to the reconsideration discussed above, EPA received a 
petition from Sierra Club requesting reconsideration of the existing 
source standards for THC, mercury, and HCl, and judicial petitions for 
review challenging the final amendments. EPA granted the 
reconsideration petition. The judicial petitions have been

[[Page 21140]]

combined and are being held in abeyance pending the results of the 
reconsideration.
    In March 2007 the DC Circuit court issued an opinion (Sierra Club 
v. EPA, 479 F. 3d 875 (DC Cir. 2007) (Brick MACT)) vacating and 
remanding section 112(d) MACT standards for the Brick and Structural 
Clay Ceramics source categories. Some key holdings in that case were:
     Floors for existing sources must reflect the average 
emission limitation achieved by the best-performing 12 percent of 
existing sources, not levels EPA considers to be achievable by all 
sources (479 F. 3d at 880-81);
     EPA cannot set floors of ``no control.'' The Court 
reiterated its prior holdings, including National Lime Ass'n, 
confirming that EPA must set floor standards for all HAP emitted by the 
major source, including those HAP that are not controlled by at-the-
stack control devices (479 F. 3d at 883);
     EPA cannot ignore non-technology factors that reduce HAP 
emissions. Specifically, the Court held that ``EPA's decision to base 
floors exclusively on technology even though non-technology factors 
affect emissions violates the Act.'' (479 F. 3d at 883)

    Based on the Brick MACT decision, we believe a source's performance 
resulting from the presence or absence of HAP in raw materials must be 
accounted for in establishing floors; i.e., a low emitter due to low 
HAP proprietary raw materials can still be a best performer. In 
addition, the fact that a specific level of performance is unintended 
is not a legal basis for excluding the source's performance from 
consideration. National Lime Ass'n, 233 F. 3d at 640.
    The Brick MACT decision also stated that EPA may account for 
variability in setting floors. However, the court found that EPA erred 
in assessing variability because it relied on data from the worst 
performers to estimate best performers' variability, and held that 
``EPA may not use emission levels of the worst performers to estimate 
variability of the best performers without a demonstrated relationship 
between the two.'' 479 F. 3d at 882.
    The majority opinion in the Brick MACT case does not address the 
possibility of subcategorization to address differences in the HAP 
content of raw materials. However, in his concurring opinion Judge 
Williams stated that EPA's ability to create subcategories for sources 
of different classes, size, or type (section 112 (d)(1)) may provide a 
means out of the situation where the floor standards are achieved for 
some sources, but the same floors cannot be achieved for other sources 
due to differences in local raw materials whose use is essential. Id. 
at 884-85.\9\
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    \9\ ``What if meeting the `floors' is extremely or even 
prohibitively costly for particular plants because of conditions 
specific to those plants (e.g., adoption of the necessary technology 
requires very costly retrofitting, or the required technology 
cannot, given local inputs whose use is essential, achieve the 
`floor')? For these plants, it would seem that what has been 
`achieved' under Sec.  112(d)(3) would not be `achievable' under 
Sec.  112(d)(2) in light of the latter's mandate to EPA to consider 
cost. * * * [O]ne legitimate basis for creating additional 
subcategories must be the interest in keeping the relation between 
`achieved' and `achievable' in accord with common sense and the 
reasonable meaning of the statute. '' Id. at 884-85
---------------------------------------------------------------------------

    After considering the implications of this decision, EPA granted 
the petition for reconsideration of all the existing source standards 
in the 2006 rulemaking.
    A second court opinion is also relevant to this proposal. In Sierra 
Club v. EPA, 551 F. 3d 1019 (DC Cir. 2008) the court vacated the 
regulations contained in the General Provisions which exempt major 
sources from MACT standards during periods of startup, shutdown and 
malfunction (SSM)). The regulations (in 40 CFR 63.6(f)(1) and 
63.6(h)(1)) provided that sources need not comply with the relevant 
section 112(d) standard during SSM events and instead must ``minimize 
emissions * * * to the greatest extent which is consistent with safety 
and good air pollution control practices.'' The current Portland Cement 
NESHAP does not contain specific provisions covering operation during 
SSM operating modes; rather it references the now-vacated rules in the 
General Provisions. As a result of the court decision, we are 
addressing them in this rulemaking. Discussion of this issue may be 
found in Section IV.G.

III. Summary of Proposed Amendments to Subpart LLL

    This section presents the proposed amendments to the Portland 
Cement NESHAP. In the section presenting the amended rule language, 
there is some language that it not amendatory, but is presented for the 
reader's convenience. We are not reopening or otherwise considering 
unchanged rule language presented for the reader's convenience, and 
will not accept comments on such language.

A. Emissions Limits

    We are proposing the following new emission limits in this action 
categorized below by their sources in a typical Portland cement 
production process.
Kilns and In-line Kiln/Raw Mills
    Mercury. For cement kilns or in-line kilns/raw mills an emissions 
limit of 43 lb/million(MM) tons clinker for existing sources and 14 lb/
MM tons clinker for new sources. Both proposed limits are based on a 30 
day rolling average.
    THC. For cement kilns or in-line kilns/raw mills an emissions limit 
of 7 parts per million by volume (ppmv) for existing sources and 6 ppmv 
for new sources, measured dry as propane and corrected to 7 percent 
oxygen, measured on a 30 rolling day average in each case. Because the 
proposed existing source standard would be more stringent than the new 
source standard of 50 ppmv contained in the 1999 final rule for 
greenfield new sources, we are also proposing to remove the 50 ppmv 
standard.
    As an alternative to the THC standard, we are proposing that the 
cement kilns or in-line kilns/raw mills can meet a standard of 2 ppmv 
total combined organic HAP for existing sources or 1 ppmv total organic 
HAP combined for new sources, measured dry and corrected to 7 percent 
oxygen. We believe this standard is equivalent to the proposed THC 
standard as discussed in section IV.C. The alternative standard would 
be based on organic HAP emission testing and concurrent THC CEMS 
measurements that would establish a site specific THC limit that would 
demonstrate compliance with the total organic HAP limit. The site 
specific THC limit would be measured as a 30 day rolling average.
    PM. For cement kilns or cement kilns/in-line raw mills an emissions 
limit of 0.085 pounds per ton (lb/ton) clinker for existing sources and 
0.080 lb/tons clinker for new sources. Kilns and kiln/in-line raw mills 
where the clinker cooler gas is combined with the kiln exhaust and sent 
to a single control device for energy efficiency purposes (i.e., to 
extract heat from the clinker cooler exhaust) would be allowed to 
adjust the PM standard to an equivalent level accounting for the 
increased gas flow due to combining of kiln and clinker cooler exhaust.
    Opacity. We are proposing to remove all opacity standards for kilns 
and clinker coolers because these sources will be required to monitor 
compliance with the PM emissions limits by more accurate means.
    Hydrochloric Acid. For cement kilns or cement kilns/in-line raw 
mills an emissions limit of 2 ppmv for existing sources and 0.1 ppmv 
for new sources, measured dry and corrected to 7 percent oxygen. For 
facilities that are required to use a continuous emissions monitoring

[[Page 21141]]

system (CEMS), compliance would be based on a 30 day rolling average.
Clinker Coolers
    For clinker coolers a PM emissions limit of 0.085 lb/ton clinker 
for existing sources and 0.080 lb/tons clinker for new sources.
Raw Material Dryers
    THC. For raw materials dryers an emissions limit of 7 ppmv for 
existing sources and 6 ppmv for new sources, measured dry as propane 
and corrected to 7 percent oxygen, measured on a 30 day rolling 
average. Because the proposed existing source standard would be more 
stringent than the new source standard of 50 ppmv contained in the 1999 
final rule for Greenfield new sources, we are also proposing to remove 
the 50 ppmv standard.
    As an alternative to the THC standard, the raw material dryer can 
meet a standard of 2 ppmv total combined organic HAP for existing 
sources or 1 ppmv total organic HAP combined for new sources, measured 
dry and corrected to 7 percent oxygen. The alternative standard would 
be based on organic HAP emission testing and concurrent THC CEMS 
measurements that would establish a site specific THC limit that would 
demonstrate compliance with the total organic HAP limit. The site 
specific THC limit would be measured as a 30 day rolling average.

B. Operating Limits

    EPA is proposing to eliminate the restriction on the use of fly ash 
where the mercury content of the fly ash has been increased through the 
use of activated carbon. Given the proposed emission limitation for 
mercury, whereby kilns or cement kilns/in-line raw mills must 
continuously meet the mercury emission limits described above 
(including when using these materials) there does not appear to be a 
need for such a provision. For the same reason, EPA is proposing to 
remove the requirement to maintain the amount of cement kiln dust 
wasted during testing of a control device, and the provision requiring 
that kilns remove from the kiln system sufficient amounts of dust so as 
not to impair product quality.

C. Testing and Monitoring Requirements

    We are proposing the following changes in testing and monitoring 
requirements:
    Kilns and kiln/in-line raw mills would be required to meet the 
following changed monitoring/testing requirements:
     CEMS (PS-12A) or sorbent trap monitors (PS-12B) to 
continuously measure mercury emissions, along with Procedure 5 for 
ongoing quality assurance.
     CEMS meeting the requirement of PS-8A to measure THC 
emissions for existing sources (new sources are already required to 
monitor THC with a CEM). Kilns and kiln/in-line raw mills meeting the 
organic HAP alternative to the THC limit would still be required to 
continuously monitor THC (based on the results of THC monitoring done 
concurrently with the Method 320 test), and would also be required to 
test emissions using EPA Method 320 or ASTM D6348-03 every five years 
to identify the organic HAP component of their THC emissions.
     Installation and operation of a bag leak detection system 
to demonstrate compliance with the PM emissions limit. If electrostatic 
precipitators (ESP) are used for PM control an ESP predictive model to 
monitor the performance of ESP controlling PM emissions from kilns 
would be required. As an alternative EPA is proposing that sources may 
use a PM CEMS that meets the requirements of PS-11. Though we are 
proposing the PM CEMS as an alternative compliance method, we are 
taking comment on requiring PM CEMS to demonstrate compliance.
     CEMS meeting the requirements of PS-15 would be required 
to demonstrate compliance with the HCl standard. If a facility is using 
a caustic scrubber to meet the standard, EPA Test Method 321 and 
ongoing continuous parameter monitoring of the scrubber may be used in 
lieu of a CEMS to demonstrate compliance. The M321 test must be 
repeated every 5 years.
    For clinker coolers, EPA is proposing use of a bag leak detection 
system to demonstrate compliance with the proposed PM emissions limit. 
If an ESP is used for PM control on clinker coolers, an ESP predictive 
model to monitor the performance of ESP controlling PM emissions from 
kilns would be required. As an alternative, EPA is proposing that a PM 
CEMS that meets the requirements of PS-11 may be used.
    Raw material dryers that are existing sources would be required to 
install and operate CEMS meeting the requirement of PS-8A to measure 
THC emissions. (New sources are already required to monitor THC with a 
CEM). Raw material dryers meeting the organic HAP alternative to the 
THC limit would still be required to continuously monitor THC (based on 
the results of THC monitoring done concurrently with the Method 320 
test), and would also be required to test emissions using EPA Method 
320 or ASTM D6348-03 every five years to identify the organic HAP 
component of their THC emissions.
    New or reconstructed raw material dryers and raw or finish mills 
would be subject to longer Method 22 and, potentially, to longer Method 
9 tests. The increase in test length duration is necessary to better 
reflect the operating characteristics of sources subject to the 
proposed rule.

IV. Rationale for Proposed Amendments to Subpart LLL

A. MACT Floor Determination Procedure for all Pollutants

    The MACT floor limits for each of the HAP and HAP surrogates 
(mercury, total hydrocarbons, HCl, and particulate matter) are 
calculated based on the performance of the lowest emitting (best 
performing) sources in each of the MACT pool sources. We ranked all of 
the sources for which we had data based on their emissions and 
identified the lowest emitting 12 percent of the sources for which we 
had data, which ranged from two kilns for THC to 11 kilns for mercury 
for existing sources. For new source MACT, the floor was based on the 
best performing source. The MACT floor limit is calculated from a 
formula that is a modified prediction limit, designed to estimate a 
MACT floor level that is achievable by the average of the best 
performing sources (i.e., those in the MACT pool) if the best 
performing sources were able to replicate the compliance tests in our 
data base. Specifically, the MACT floor limit is an upper prediction 
limit (UPL) calculated from: \10\
---------------------------------------------------------------------------

    \10\ More details on the calculation of the MACT floor limits 
are given in the memorandum Development of The MACT Floors For The 
Proposed NESHAP for Portland Cement. April 15, 2009.

---------------------------------------------------------------------------
UPL = xp + t * (VT)\0.5\

Where:

Xp = average of the best performing MACT pool sources,
t = Student's t-factor evaluated at 99 percent confidence, and
vT = total variance determined as the sum of the within-
source variance and the between-source variance.

The between-source variance is the variance of the average of the best 
performing source averages. The within-source variance is the variance 
of the MACT source average considering ``m'' number of future 
individual test runs used to make up the average to determine 
compliance. The value of ``m'' is used to reduce the variability to 
account for the lower variability when averaging of individual runs is 
used to determine compliance in the future. For example, if 30-day 
averages are used to

[[Page 21142]]

determine compliance (m=30), the variability based 30-day average is 
much lower than the variability of the daily measurements in the data 
base, which results in a lower UPL for the 30-day average.

B. Determination of MACT for Mercury Emissions From Major and Area 
Sources

    The limits for existing and new sources we are proposing here apply 
to both area and major new sources. These limits would also apply to 
area sources consistent with section 112(c)(6) of the Act, as EPA 
determined in the original rule. See 63 FR at 14193.
1. Floor Determination
Selection of Existing Source Floor
    Cement kilns' emissions of mercury reflect exclusively the amounts 
of mercury in each kiln's feedstock and fuel inputs. The amounts of 
mercury in these inputs and their relative contributions to overall 
mercury kiln emissions vary by site. In many cases the majority of the 
mercury emissions result from the mercury present as a trace 
contaminant in the limestone, which typically comes from a proprietary 
quarry located adjacent to the plant. Limestone is the single largest 
input, by mass, to a cement kiln's total mass input, typically making 
up 80 percent of that loading. Mercury is also found as a trace 
contaminant in the other inputs to the kiln such as the additives that 
supply the required silica, alumina, and iron. Mercury is also present 
in the coal and petroleum coke typically used to fuel cement kilns.
    Based on our current information, mercury levels in limestone can 
vary significantly, both within a single quarry and between quarries. 
Since quarries are generally proprietary, this variability is inherent 
and site-specific. Mercury levels in additives and fuels likewise vary 
significantly, although mercury emissions attributable to limestone 
often dominate the total due to the larger amount of mass input 
contributed by limestone (see further discussion of this issue at Other 
Options EPA considered in Setting Floor for Mercury below).
    The first step in establishing a MACT standard is to determine the 
MACT floor. A necessary step in doing so is determining the amount of 
HAP emitted. In the case of mercury emitted by cement kilns, this is 
not necessarily a straightforward undertaking. Single stack 
measurements represent a snapshot in time of a source's emissions, 
always raising questions of how representative such emissions are of 
the source's emissions over time. This problem is compounded in the 
case of cement kilns, because cement kilns do not emit mercury 
uniformly. Our current data suggest that, for all kilns, the mercury 
content of the feed and fuels varies significantly from day-to-day. 
Because most cement kilns have no mercury emissions control, the 
variations in mercury inputs directly translate to a variability of 
mercury stack emissions. For modern preheater and preheater/precalciner 
kilns this problem is compounded because these kilns have in-line raw 
mills. With in-line raw mills, mercury is captured in the ground raw 
meal in the in-line raw mill and this raw meal (containing mercury) is 
returned as feed to the kiln. Mercury emissions may remain low during 
such recycling operations. However, as part of normal kiln operation 
raw mills must be periodically shut down for maintenance, and mercury-
containing exhaust gases from the kiln are then bypassed directly to 
the main air pollution control device resulting in significantly 
increased mercury emissions at the stack. The result is that at any 
given time, mercury emissions from such cement kilns are either low or 
high, but rarely in equilibrium, so that single stack tests are likely 
to either underestimate or overestimate cement kilns' performance over 
time. Put another way, we believe that single short term stack test 
data (typically a few hours) are probably not indicative of long term 
emissions performance, and so are not the best indicator of performance 
over time. With these facts in mind, we carefully considered 
alternatives other than use of single short-term stack test results to 
quantify kilns' performance for mercury.
    An alternative to short term stack test data would be to use 
mercury continuous monitoring data over a longer time period. Because 
no cement kilns in the United States have continuous mercury monitors, 
this option was not available. However, mercury is an element. 
Therefore, all the mercury that enters a kiln has to leave the kiln in 
some fashion. The available data indicate that almost no mercury leaves 
the kiln as part of the clinker (product). Therefore, our methodology 
assumes over the long term that all the mercury leaves the kiln as a 
stack emission with three exceptions:
    1. If instead of returning all particulate captured in the 
particulate control device to the kiln, the source instead removes some 
of it from the circuit entirely, i.e., the kiln does not reuse all 
(wastes some) cement kiln dust (CKD); or
    2. The kiln is equipped with an alkali bypass, which means all CKD 
captured in the alkali bypass PM control is wasted, and/or;
    3. If the kiln has a wet scrubber (usually for SO2 
control), the scrubber will remove some mercury which our methodology 
assumes will end up in the gypsum generated by the scrubber.
    Based on these facts we decided that the most accurate method 
available to us to determine long term mercury emissions performance 
was to do a total mass balance. We did so by obtaining data on all the 
kiln mercury inputs (i.e., all raw materials and all fuels) for a large 
group of kilns, and assuming all mercury that enters the kiln is 
emitted except for the three conditions noted above. Pursuant to 
letters mandating data gathering, issued under the authority of section 
114, we obtained 30 days of daily data on kiln mercury concentrations 
in each individual raw material, fuel, and CKD for 89 kilns (which 
represent 59 percent of total kilns), along with annual mass inputs and 
the amount of material collected in the PM control device (or alkali PM 
control device) that is wasted rather than returned to the kiln.
    These data were submitted to EPA as daily concentrations for the 
inputs, i.e., samples of all inputs were taken daily and analyzed daily 
for their mercury content. We took the daily averages, calculated a 
mean concentration, and multiplied the mean concentration by annual 
materials use to calculate an annual mercury emission for each of the 
89 kilns. If the facility wasted CKD, we subtracted out the annual 
mercury that left the system in the CKD. If the facility had a wet 
scrubber (the only control device currently in use among the sampled 
kilns with any substantial mercury capture efficiency), we subtracted 
out the annual mercury attributable to use of the scrubber. There are 
five cement kilns using wet scrubbers and EPA has removal efficiencies 
for four of these kilns (based on inlet/outlet testing conducted at 
EPA's request concurrent with the input sampling). We attributed a 
removal efficiency for the fifth kiln based on the average removal 
efficiency of the other four kilns.
    We acknowledge that an additional source of uncertainty in the mass 
balance methodology for estimating the capture efficiencies of wet 
scrubbers is the variability in the mercury speciation ratios 
(elemental to divalent). These ratios, which are dependent on the 
amount of chlorine present and other factors, would be expected to vary 
at different kilns. Only the soluble divalent mercury fraction will be

[[Page 21143]]

captured by a wet scrubber. We note, however, that mercury speciation 
would be expected to have little effect on mercury emissions in the 
case where wet scrubbers, or other add-on controls such as activated 
carbon injection (ACI), are not used, because for most facilities, 
mercury captured in the PM controls is returned to the kiln. In cases 
where some of the collected PM is wasted, we had 30 days of actual 
mercury content data for wasted material.
    For each kiln, we calculated an average annual emission factor, 
which is the average projected emission rate for each kiln. We did this 
by dividing calculated annual emissions by total inputs. We then ranked 
each kiln from lowest average emission factor to highest. The resulting 
emissions factors for 87 of the 89 ranged (relatively continuously) 
from 7 to 300 pounds of mercury per million tons of feed. Two kilns 
showed considerably higher numbers, approximately 1200 and 2000 pounds 
per ton of feed. These two facilities have atypically high mercury 
contents in the limestone in their proprietary quarries which are the 
most significant contributors to the high mercury emissions.
    Based on these data and ranking methodology, the existing source 
MACT floor would be the average of the lowest emitting 12 percent of 
the kilns for which we have data, which would be the 11 kilns with 
lowest emissions (as calculated), shown in Table 1.

                       Table 1--Mercury MACT Floor
------------------------------------------------------------------------
                                                       Mercury emissions
                      Kiln code                        (lb/MM ton feed)
------------------------------------------------------------------------
1233................................................                7.14
1650................................................               10.83
1589................................................               11.11
1302................................................               14.51
1259................................................               15.16
1315................................................               15.41
1248................................................               18.09
1286................................................               21.12
1435................................................               22.89
1484................................................               22.89
1364................................................               23.92
------------------------------------------------------------------------
                          MACT--Existing kilns
------------------------------------------------------------------------
Average: lb/MM tons feed (lb/MM tons clinker).......         16.6 (27.4)
Variability (t*vT\0.5\).............................                9.52
99th percentile: lb/MM tons feed (lb/MM tons                     26 (43)
 clinker)...........................................
------------------------------------------------------------------------
                             MACT--New kilns
------------------------------------------------------------------------
Average: lb/MM tons feed (lb/MM tons clinker).......          7.1 (11.8)
Variability (t*vT\0.5\).............................                 1.3
99th percentile: lb/MM tons feed (lb/MM tons                    8.4 (14)
 clinker)...........................................
------------------------------------------------------------------------

    The average emission rate for these kilns is 16.6 pounds per 
million tons (lb/MM) tons feed (27.4 lb/MM tons clinker). The emission 
rate of the single lowest emitting source is 7.1 lb/MM tons feed (11.8 
lb/MM tons clinker).
    As previously discussed above, we account for variability in 
setting floors, not only because variability is an element of 
performance, but because it is reasonable to assess best performance 
over time. Here, for example, we know that the 11 lowest emitting kiln 
emission estimates are averages, and that the actual emissions will 
vary over time. If we do not account for this variability, we would 
expect that even the kilns that perform better than the floor on 
average would potentially exceed the floor emission levels a 
significant part of the time--meaning that their performance was 
assessed incorrectly in the first instance.
    For the 11 lowest emitting kilns, we calculated a daily emission 
rate using the daily concentration values and annual materials inputs 
divided by each kiln's operating days.\11\ The results are shown in 
Table 1 and represent the average performance of each kiln over the 30-
day period. We then calculated the average performance of the 11 lowest 
emitting kilns (17 lb/MM tons of feed) and the variances of the daily 
emission rates for each kiln which is a direct measure of the 
variability of the data set. This variability includes the day-to-day 
variability in the total mercury input to each kiln and variability of 
the sampling and analysis methods over the 30-day period, and it 
includes the variability resulting from site-to-site differences for 
the 11 lowest emitters. We calculated the MACT floor (26 lb/MM tons 
feed) based on the UPL (upper 99th percentile) as described earlier 
from the average performance of the 11 lowest emitting kilns, Students 
t-factor, and the total variability, which was adjusted to account for 
the lower variability when using 30 day averages.
---------------------------------------------------------------------------

    \11\ In the daily calculations, we treated the CKD removal as if 
it was a control device, and applied the overall percent reduction 
rather that using the daily CKD concentration value. We used this 
approach because if we used daily CKD removal values, some days 
showed negative mercury emissions rates. This is because of the 
mercury recycling issues discussed above.
---------------------------------------------------------------------------

    EPA also has some information which tends to corroborate the 
variability factor used to calculate the floor for mercury. These data 
are not emissions data; they are data on the total mercury content of 
feed materials over periods of 12 months or longer. Because mercury 
emissions correlate with mercury content of feed materials, we believe 
an analysis of the variability of the feed materials is an accurate 
surrogate for the variability of mercury emissions over time. These 
long term data are from multiple kilns from a single company that are 
not ranked among the lowest emitters, but are nonetheless germane as a 
crosscheck on variability of mercury content of feed materials 
(including whether 30 days of sampling, coupled with statistically 
derived variability of that data set and a 99th percentile, adequately 
measures that variability).
    One way of comparing the variability among different data sets with 
different average values is to calculate and compare the relative 
standard deviations (RSD), which is the standard deviation divided by 
the mean, of each set. If the RSD are comparable, then one can conclude 
that the variability among the data sets is comparable. The results of 
such an analysis are given in Table 2 below. The long term data 
represent long term averages of feed material mercury content based on 
12 months of data or more, whereas the MACT data sets are for 30 
consecutive days of data. The RSD of the long term data range from 0.29 
to 1.05, and the RSD of the MACT floor kilns range from 0.10 to 0.89. 
This comparison suggests that our method of calculating variability in 
the proposed floor based on variances/99th percentile UPL appears to 
adequately encompass sources' long-term variability.

[[Page 21144]]



     Table 2--Comparison of Long-Term Kiln Feed Mercury Concentration at Essroc Plants With the Feed Mercury
                                   Concentration Data for the MACT Floor Kilns
----------------------------------------------------------------------------------------------------------------
                                           PPM Hg in feed
                                     --------------------------
                Kiln                                 Standard       RSD                     Source
                                          Mean      deviation
----------------------------------------------------------------------------------------------------------------
1248 \a\............................        0.021        0.002         0.10  MACT floor kiln.\b\
1589 \a\............................        0.021        0.002         0.10  MACT floor kiln.
1435................................        0.012        0.002         0.16  MACT floor kiln.
1484................................        0.012        0.002         0.16  MACT floor kiln.
1233................................        0.011        0.002         0.16  MACT floor kiln.
1650................................        0.025        0.005         0.22  MACT floor kiln.
Speed...............................        0.055        0.016         0.29  Essroc.\c\
1286................................        0.006        0.002         0.32  MACT floor kiln.
1364................................        0.006        0.002         0.32  MACT floor kiln.
San Juan............................        0.322        0.108         0.34  Essroc.
Bessemer............................        0.021        0.007         0.35  Essroc.
Logansport..........................        0.022        0.008         0.37  Essroc.
Naz III.............................        0.016        0.010         0.61  Essroc.
Naz I...............................        2.974        1.838         0.62  Essroc.
1302................................        0.006        0.004         0.68  MACT floor kiln.
1315................................        0.006        0.004         0.68  MACT floor kiln.
Martinsburg.........................        0.023        0.017         0.89  Essroc.
1259................................        0.008        0.007         0.89  MACT floor kiln.
Picton..............................        0.075        0.078         1.05  Essroc.
----------------------------------------------------------------------------------------------------------------
\a\ Same feed sample applied to multiple kilns at the plant.
\b\ MACT floor kilns' variabilities are all based on approximately 30 days of data.
\c\ Essroc kiln's variabilities are all based on 12 months to three years of data.

    We are proposing to express the floor as a 30-day rolling average 
for the following two reasons. First, as explained earlier, daily 
variations in mercury emissions at the stack for all kilns with in-line 
raw mills is greater than daily variability of mercury levels in 
inputs. This is because mercury is emitted in high concentrations 
during mill-off conditions, but in lower concentrations when mercury is 
recycled to the kiln via the raw mill (`mill-on'). We believe that 30 
days is the minimum averaging time