National Emission Standards for Hazardous Air Pollutants From the Portland Cement Manufacturing Industry, 72330-72348 [05-23419]

Agencies

• ENVIRONMENTAL PROTECTION AGENCY

[Federal Register Volume 70, Number 231 (Friday, December 2, 2005)]
[Proposed Rules]
[Pages 72330-72348]
From the Federal Register Online via the Government Printing Office [www.gpo.gov]
[FR Doc No: 05-23419]



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Part II





Environmental Protection Agency





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40 CFR Part 63



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

Federal Register / Vol. 70, No. 231 / Friday, December 2, 2005 / 
Proposed Rules

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ENVIRONMENTAL PROTECTION AGENCY

40 CFR Part 63

[OAR-2002-0051; FRL-8003-6]
RIN 2060-AJ78


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

AGENCY: Environmental Protection Agency (EPA).

ACTION: Proposed rule; amendments.

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SUMMARY: On June 14, 1999, under the authority of section 112 of the 
Clean Air Act (CAA), the EPA promulgated national emission standards 
for hazardous air pollutants (NESHAP) for new and existing sources in 
the portland cement manufacturing industry. On December 15, 2000, the 
United States Court of Appeals for the District of Columbia Circuit (DC 
Circuit) remanded parts of the NESHAP for the portland cement 
manufacturing industry to EPA to consider, among other things, setting 
maximum achievable control technology (MACT) floor standards for 
hydrogen chloride (HCl), mercury, and total hydrocarbons (THC), and 
beyond-the-floor standards for metal hazardous air pollutants (HAP). 
This action provides EPA's proposed rule amendments in response to 
those aspects of the court's remand.

DATES: Comments. Written comments must be received on or before January 
17, 2006.
    Public Hearing. If anyone contacts the EPA requesting to speak at a 
public hearing by December 12, 2005, a public hearing will be held 
within approximately 15 days following publication of this notice in 
the Federal Register.

ADDRESSES: Comments. Submit your comments, identified by Docket ID No. 
OAR-2002-0051, by one of the following methods:
     Federal eRulemaking Portal: https://www.regulations.gov. 
Follow the on-line instructions for submitting comments.
     Agency Web site: https://www.epa.gov/edocket. EDOCKET, 
EPA's electronic public docket and comment system, is EPA's preferred 
method for receiving comments. Follow the on-line instructions for 
submitting comments.
     E-mail: a-and-r-docket@epa.gov.
     Fax: (202) 566-1741.
     Mail: U.S. Postal Service, send comments to: EPA Docket 
Center (6102T), Attention Docket ID No. OAR-2002-0051, 1200 
Pennsylvania Avenue, NW., Washington, DC 20460. Please include a 
duplicate copy, if possible.
     Hand Delivery: In person or by courier, deliver comments 
to: EPA Docket Center (6102T), Attention Docket ID No. OAR-2002-0051, 
1301 Constitution Avenue, NW., Room B-108, 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 duplicate copy, if possible.
    We request that you also send a separate copy of each comment to 
the contact person listed below (see FOR FURTHER INFORMATION CONTACT).
    Public Hearing. If a public hearing is held, it will be held at 10 
a.m. at the EPA Facility Complex in Research Triangle Park, North 
Carolina or at an alternate site nearby.

FOR FURTHER INFORMATION CONTACT: Mr. Keith Barnett, EPA, Office of Air 
Quality Planning and Standards, Emission Standards Division, Minerals 
and Inorganic Chemicals Group (C504-05), Research Triangle Park, NC 
27711; telephone number (919) 541-5605; facsimile number (919) 541-
5600; e-mail address barnett.keith@epa.gov.

SUPPLEMENTARY INFORMATION: Regulated Entities. Entities potentially 
affected by this action are those that manufacture portland cement. 
Regulated categories and entities include:

                   Table 1.--Regulated Entities Table
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                                                  Examples of regulated
             Category               NAICS \1\           entities
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Industry.........................        32731  Owners or operators of
                                                 portland cement
                                                 manufacturing plants.
State............................        32731  Owners or operators of
                                                 portland cement
                                                 manufacturing plants.
Tribal associations..............        32731  Owners or operators of
                                                 portland cement
                                                 manufacturing plants.
Federal agencies.................         None  None.
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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. This table lists the types of entities that may potentially be 
regulated by this action. To determine whether your facility is 
regulated by this action, you should carefully examine the 
applicability criteria in 40 CFR 63.1340 of the rule. If you have 
questions regarding the applicability of this action to a particular 
entity, consult the 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 Number OAR-2002-0051. The official public docket 
is the collection of materials that is available for public viewing 
both electronically and in printed form. This docket is available 
electronically through EPA Dockets at https://www.epa.gov/edocket. You 
may access the docket electronically to submit or view public comments, 
access the index of the contents of the official public docket, and 
access those documents in the public docket that are available 
electronically. Once in the system, select ``search'' and key in the 
appropriate docket identification number.
    The docket is also available in printed form at EPA, 1301 
Constitution Avenue, NW., Room B-102, Washington, DC. The EPA 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. The telephone number for the EPA Docket 
Center is (202) 566-1742. A reasonable fee may be charged for copying 
docket materials.
    For public commenters, it is important to note that EPA's policy is 
that public comments, whether submitted electronically or on 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, confidential business information (CBI), 
or other information whose disclosure is restricted by statue. 
Information claimed as CBI and other information whose disclosure is 
restricted by statute, will not be available for public viewing in 
EPA's public docket. When EPA identifies a comment containing

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copyrighted material, EPA will provide a reference to that material, 
but not the material itself, in the version of the comments that is 
placed in EPA's electronic public docket. The entire printed comment, 
including the copyrighted material, will be available in the printed 
public docket. Although not all docket materials may be available 
electronically, you may still access any of the publicly available 
docket material through the docket facility identified in this 
document.
    Public comments submitted on computer disks that are mailed or 
delivered to the docket will be transferred to EPA's electronic public 
docket. Hardcopy 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. Tips for preparing 
your 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 
received after the close of the comment period will be marked late. The 
EPA is not required to consider these late comments.
    Our preferred method for receiving comments is electronically 
through EPA Dockets at https://www.epa.gov/edocket. The system is an 
anonymous access system, which means we will not know your identity, e-
mail address, or other contact information unless you provide it in the 
body of your comment.
    In contrast to EPA's electronic public docket, our 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, our 
e-mail system automatically captures your e-mail address. E-mail 
addresses that are automatically captured by our 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.
    If you submit an electronic comment, we recommend 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. The 
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.
    Submitting comments containing CBI. Do not submit information that 
you consider to be CBI electronically through EDOCKET, regulations.gov, 
or e-mail. Send or deliver information identified as CBI only to the 
following address: OAQPS Document Control Office (C404-02), Attention: 
Keith Barnett, EPA, Research Triangle Park, NC 27711, Attention Docket 
ID No. OAR-2002-0051. 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. 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.
    Worldwide Web (WWW). In addition to being available in the docket, 
an electronic copy of today's proposal will also be available through 
the WWW. Following the Administrator's signature, a copy of this action 
will be posted on EPA's Technology Transfer Network (TTN) policy and 
guidance page for newly proposed or promulgated rules at https://
www.epa.gov/ttn/oarpg/. The TTN at EPA's Web site provides information 
and technology exchange in various areas of air pollution control.
    Public Hearing. Persons interested in presenting oral testimony or 
inquiring as to whether a hearing is to be held should contact Ms. 
Janet Eck, EPA, Office of Air Quality Planning and Standards, Emission 
Standards Division, Coatings and Consumer Products Group (C539-03), 
Research Triangle Park, North Carolina 27711, telephone number (919) 
541-7946, e-mail address: eck.janet@epa.gov., at least 2 days in 
advance of the potential date of the public hearing. Persons interested 
in attending the public hearing must also call Ms. Eck 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.
    Outline. The information presented in this preamble is organized as 
follows:

I. Background
II. Summary of the National Lime Association v. EPA Litigation
III. EPA's Proposed Response to the Remand
    A. Determination of MACT for Mercury Emissions
    B. Determination of MACT for HCl Emissions
    C. Determination of MACT for THC Emissions
    D. Evaluation of a Beyond-the-Floor Control Option for Non-
Volatile HAP Metal Emissions
IV. Other Issues on Which We are Seeking Comment
V. Summary of Environmental, Energy, and Economic Impacts
    A. What facilities are affected by the proposed amendment?
    B. What are the air quality impacts?
    C. What are the water quality 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?
VI. Statutory and Executive Order Reviews
    A. Executive Order 12866, Regulatory Planning and Review
    B. Paperwork Reduction Act
    C. Regulatory Flexibility Analysis
    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 That Significantly Affect 
Energy Supply, Distribution, or Use
    I. National Technology Transfer and Advancement Act

I. Background

    Section 112(d) of the CAA requires EPA to set emissions standards 
for major stationary sources based on performance of the 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 or the best performing five sources for source 
categories with less than 30 sources (CAA section 112(d)(3)(A) and 
(B)). This level 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

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source (CAA section 112(d)(3)). The 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 emissions of HAP, but must take into account costs, 
energy, and nonair environmental impacts when doing so.
    On June 14, 1999 (64 FR 31898), in accordance with these 
provisions, EPA published the final rule entitled ``National Emission 
Standards for Hazardous Air Pollutants From the Portland Cement 
Manufacturing Industry'' (40 CFR part 63, subpart LLL).\1\
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    \1\ Cement kilns which burn hazardous waste are in a separate 
class of source, since their emissions 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.
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    The legacy public docket for the final rule is Docket No. A-92-53. 
The final rule provides protection to the public by requiring portland 
cement manufacturing plants to meet emission standards reflecting the 
performance of the MACT. Specifically, the final rule established MACT-
based emission limitations for particulate matter (as a surrogate for 
non-volatile HAP metals), dioxins/furans, and for greenfield \2\ new 
sources, THC (as a surrogate for organic HAP). We considered, but did 
not establish limits for, THC for existing sources and HCl or mercury 
for new or existing sources. In response to the mandate of the District 
of Columbia Circuit arising from litigation summarized below in this 
preamble, we are proposing emission limitations reflecting MACT for 
these pollutants in today's action.
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    \2\ A new greenfield kiln is a kiln constructed prior to March 
24, 1998 at a site where there are no existing kilns.
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    We have previously amended the Portland Cement NESHAP. Consistent 
with the terms of a settlement agreement between the American Portland 
Cement Alliance v. EPA, EPA adopted final amendments and clarifications 
to the rule on April 5, 2002 (76 FR 16614), July 5, 2002 (67 FR 44766), 
and December 6, 2002 (67 FR 72580). These amendments generally relate 
to applicability, performance testing, and monitoring. In today's 
action, we are also proposing to further amend the rule to re-insert 
two paragraphs relating to the applicability of the portland cement new 
source performance standards that were deleted in error in a previous 
amendment.

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

    Following promulgation of the NESHAP for portland cement 
manufacturing, the National Lime Association and the Sierra Club filed 
petitions for review of the standards in the DC Circuit. The American 
Portland Cement Alliance, although not a party to the litigation, filed 
a brief with the court as amicus curiae. The court denied essentially 
all of the petition of the National Lime Association, but granted part 
of the Sierra Club petition.
    In National Lime Association v. EPA, 233 F. 3d 625 (DC Cir. 2000), 
the court upheld EPA's determination of MACT floors for particulate 
matter (PM) (as a surrogate for non-volatile HAP metals) and for 
dioxin/furan. However, the court rejected EPA's determination that it 
need not determine MACT floors for the remaining HAP emitted by these 
sources, namely, mercury, other organic HAP (for which THC are a 
surrogate), and HC1 (233 F. 3d at 633). The court specifically rejected 
the argument that EPA was excused from establishing floor levels 
because no ``technology-based pollution control devices'' exist to 
control the HAP in question (Id. at 634). The court noted that EPA is 
also specifically obligated to consider other pollution-reducing 
measures including process changes, substitutions of materials inputs, 
or other modifications (Id.). The court remanded the rule to EPA to set 
MACT floor emission standards for HC1, mercury, and THC.
    The Sierra Club also challenged EPA's decision not to set beyond-
the-floor emission limits for mercury, THC, and non-volatile HAP metals 
(for which PM is a surrogate). The court only addressed the absence of 
beyond-the-floor emission limits for non-volatile HAP metals since EPA 
was already being required to reconsider MACT floor emission standards 
for mercury, THC, and HC1, and thus, by necessity, also must consider 
whether to adopt beyond-the-floor standards for these HAP. The Sierra 
Club argued, and the court agreed, that in considering beyond-the-floor 
standards for non-volatile HAP metals, EPA considered cost and energy 
requirements but did not consider nonair quality health and 
environmental impacts as required by the CAA (Id. at 634-35). The court 
also found EPA's analysis of beyond-the-floor standards deficient in 
its assertion that there were no data to support fuel switching 
(switching to natural gas) as a viable option of reducing emissions of 
non-volatile HAP metals (Id. at 635).

III. EPA's Proposed Response to the Remand

A. Determination of MACT for Mercury Emissions

    During development of the original NESHAP for portland cement 
manufacturing, we conducted MACT floor and beyond-the-floor analyses 
for kiln and in-line kiln/raw mill mercury emissions (63 FR 14182, 
March 24, 1998 and 64 FR 31898, June 14, 1999). Although considered a 
metal HAP, mercury's volatile nature precludes its control through 
application of typical PM controls such as fabric filters (FF) or 
electrostatic precipitators (ESP). At the time of the original 
rulemaking, we considered establishing an emission limit based on the 
use of activated carbon injection because a form of this control 
technology was demonstrated on medical waste incinerators and municipal 
waste combustors and was being used at one cement plant to reduce 
opacity from two non-hazardous waste (NHW) kilns. However, the 
placement of the carbon injection system ahead of the kiln PM control 
device (the configuration in use at these kilns) and the practice of 
recycling the cement kiln dust (CKD) collected by the PM control device 
back to the kiln, meant that the mercury was being revaporized and 
ultimately emitted to the atmosphere. Thus, the carbon injection 
systems alone did not control mercury emissions, and we concluded that 
carbon injection in this configuration could not be used as a basis for 
establishing a mercury emissions MACT floor for new or existing kilns 
(63 FR 14202, March 24, 1999). Our conclusion that the single instance 
of an activated carbon injection system used at a portland cement 
plant, and the way in which it was used, could not provide the basis 
for a MACT floor was not contested by the petitioners.
    We also conducted a beyond-the-floor analysis of using activated 
carbon injection with an additional PM control device to reduce mercury 
emissions. Costs for the system would include the cost of the carbon 
injection system and an additional FF to collect the carbon separately 
from the CKD. Based on the low levels of mercury emissions from 
individual portland cement kilns, as well as the high cost per ton of 
mercury removed by the carbon injection/FF system, we determined that 
this beyond-the-floor option was not justified (63 FR 14202, March 24, 
1998). The petitioners also did not take issue with this conclusion.
    We did receive comments on the proposed NESHAP for portland cement 
manufacturing suggesting that fuel and/

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or feed material switching or cleaning be considered as a means for 
reducing mercury emissions. In our response to these comments, we 
explained that feed and/or fossil-fuel switching or cleaning would be 
considered beyond-the-floor options. We also stated that we lacked 
data, and none were provided by the commenters, showing that such an 
option would consistently decrease mercury emissions.
    As directed in the court remand, we have reconsidered the issue of 
MACT floor standards for mercury. We still find that, for existing and 
new kilns, the MACT floor for mercury is no additional emissions 
reductions.
    We considered simply determining a floor based on the median of the 
12 percent of kilns demonstrating the lowest mercury emissions during a 
performance test. However, an emissions limit established by this 
method would reflect emission levels resulting from fuels/raw materials 
fortuitously available at the time of the performance test. These 
levels could not be replicated by the source conducting the test and 
could not be duplicated by other sources in the source category, unless 
they had access to the same fuels and raw materials available at the 
time of the emissions test (which of course, would never occur). 
Therefore, we could not demonstrate that any emission limit developed 
by this method would be achievable on a continuous basis without 
limiting sources to the same fuels and raw materials available during 
the performance test.
    We then examined the feasibility of using limits on the mercury 
content of the fuel and feed to the kiln. Mercury air emissions from 
portland cement manufacturing kilns originate from the feed materials 
(e.g., limestone, clay, shale, and sand, among others) and fossil fuels 
(e.g., coal, oil). In general, the amount of mercury emitted by a 
portland cement manufacturing kiln is proportional to the amount of 
mercury in the fuel and feed materials due to the volatile nature of 
mercury at the temperatures encountered in a cement kiln.
    Based on available data, the only feed material that contributes to 
mercury emissions is limestone, which is the main ingredient in 
portland cement production. The mercury content of limestone has been 
reported by the United States Geological Survey to range from 0.01 to 
0.1 parts per million (ppm) and by the United States Bureau of Mines to 
range from 0.02 to 2.3 ppm. We considered setting an upper bound based 
on these data. However, we cannot say that these ranges actually cover 
the entire range of mercury a source could encounter over time. 
Therefore, we could not demonstrate that during a performance test a 
source could meet an emission limit set using these data. In other 
terms, we know of no way to quantify the variability of a cement kiln's 
mercury emissions because of the constantly varying concentrations of 
mercury in raw material inputs. See Mossville Environmental Action Now 
v. EPA, 370 F. 3d 1232, 1241-42 (DC Cir. 2004) (EPA must account for 
sources' variability in establishing MACT floors).
    We also are not sure that a consistent source of low-mercury raw 
materials exists. We have no information to suggest the widespread 
availability of low-mercury limestone deposits. As with other trace 
materials in mineral deposits, mercury concentration varies widely 
between deposits as well as within deposits.
    Due to this variability, and the lack of data showing the general 
availability of low-mercury limestone, it is infeasible to set an 
emission limit (floor or otherwise) based on switching to low-mercury 
feed materials, or to establish some type of work practice mandating 
use of raw material with some specified properties relating to mercury. 
There are no data showing that a nationwide supply of low-mercury feed 
materials exists, and even if it did, the cost of shipping feed 
materials would preclude the use of this technique. Though costs may 
not be considered in determining a MACT floor, portland cement plants 
are typically located at or near a limestone quarry because the 
economics of the portland cement industry require minimal 
transportation costs. If we were to now require sources to ship raw low 
mercury limestone over potentially long distances to reduce mercury 
emissions, it would change the economics of the plant so significantly 
that the plant would not be the same class or type of source compared 
to facilities that happened to have low-mercury limestone located 
nearby (or, at least, had happened on a vein of low mercury limestone 
at the time of its performance test). Because limestone's composition 
varies with location, limestone must be processed locally to be 
profitable, portland cement plants must formulate the mixture of 
limestone with other materials to attain the desired composition and 
performance characteristics of their product, and access to limestone 
is exclusive to each portland cement plant (i.e., no plant typically 
can gain access to another plant's limestone). This exclusivity would 
preclude plants from mining from a common, low-mercury limestone 
quarry. In addition, we expect that even an individual cement kiln's 
proprietary feed materials would experience significant mercury 
variability (i.e., within-quarry natural variability), so as mentioned 
previously, even the same kiln could not be expected to replicate its 
own mercury emissions results.
    We also evaluated the possibility of setting a mercury standard for 
greenfield new sources based on selection and blending of low-mercury 
raw materials, similar to the method we used to establish a greenfield 
limit on THC emissions based on the selection and blending of low-
organic containing feed materials (63 FR 14202, March 24, 1998). 
However, the situation for mercury is different from the situation for 
THC. In the case of THC, some facilities had already used the selection 
of low-organic feed materials as a control technique, indicating that 
this was a feasible technique and that access to suitable low-organic 
materials exists for greenfield sources. This is not the case for using 
the selection of a low-mercury feed material. Feed selection to control 
mercury has not been used in the portland cement industry, and we have 
found no data (nor has anyone supplied such data) to show that suitable 
low-mercury feed materials exist for greenfield sites (or for any other 
type of site). Metal concentrations in limestone (all metals, not just 
mercury) vary widely both within-quarry and quarry-to-quarry. Given 
this significant variation in concentration of metals in limestone for 
a given area, we believe it is implausible to assume the existence of 
any consistently low-mercury quarry sites.
    A secondary source of mercury emitted by portland cement kilns is 
coal, which portland cement plants burn as their primary fuel, with 
about 90 percent of the total United States kiln capacity using coal, 
coke, or a combination of coal and coke as the primary fuel. The 
remainder use natural gas, oil, or some type of nonhazardous waste 
(such as tire derived fuel) as the primary fuel. The mercury content of 
coal ranges from 0.0 to 1.3 micrograms per gram ([mu]g/g) with an 
average of approximately 0.09 [mu]g/g. Using the mercury content of 
coal, coal requirements per ton of feed, heat input requirements, and 
the ratio of feed to clinker, we estimated the amount of mercury 
entering model kilns from coal and compared it with the total mercury 
input to kilns from feed materials. Based on average mercury 
concentrations of feed materials and coal, the largest contribution of 
mercury to kilns is from feed materials, which account for between 55 
percent and 70 percent of

[[Page 72334]]

the mercury. Contributions of mercury from coal account for between 30 
percent (model precalciner kiln) and 45 percent (model wet kiln) of the 
mercury input to kilns.
    We further examined the existence and availability of low-mercury 
coal. In 1999, approximately 91 percent of the coal burned by the 
electric utility industry was bituminous and subbituminous coal types. 
Although bituminous and subbituminous coals are now believed to contain 
less mercury than lignite on a heating value basis, the variability in 
mercury across coal seams and within coal seams is too high to 
establish one coal type or selected deposit(s) as a designated low-
mercury coal. Furthermore, mercury is not the only trace metal or 
potential HAP present in coal. When levels of mercury in coal are 
relatively low, concentrations of other HAP metals and other potential 
pollutants (such as chlorine, fluorine, and sulfur compounds) may be 
elevated. The availability of a low-mercury coal to the portland cement 
industry is even more questionable given the pre-existing supply and 
transportation relationship with electric utilities. For these reasons, 
EPA does not consider the use of a low-mercury coal by the portland 
cement industry a feasible practice, or that any standard based on such 
a practice would be achievable over time due to constant, 
uncontrollable variability.
    We also considered coal cleaning to reduce the mercury content of 
coal. However, we have determined that typical coal cleaning is 
effective for reducing mercury concentrations only in specific coals 
and, at this time, cannot be considered a mercury control technique for 
all coals. Advanced coal cleaning techniques are also being 
investigated for improved mercury removal potential. Like conventional 
cleaning techniques, the advanced cleaning techniques cannot be 
considered a mercury control technique for all coals at this time. 
(Study of Hazardous Air Pollutant Emissions from Electric Utility Steam 
Generating Units--Final Report to Congress, Volume 1, February 1998, 
pp. 13-36 and 13-37).
    We also investigated reducing fuel mercury content by requiring 
facilities to switch to natural gas. Natural gas can contain trace 
amounts of mercury when fired, but the level is so low that mercury 
emissions due to natural gas combustion are essentially zero. Assuming 
complete conversion to natural gas, we estimated the quantity of 
natural gas that would be required to fuel the portland cement 
manufacturing industry. Annual clinker production for each of the four 
kiln types and average British thermal unit (Btu) requirements to 
produce a ton of clinker for each of the kiln types were used to 
project annual Btu's needed if the portland cement industry switched 
completely to natural gas. Using an average heating value for natural 
gas of 1,000 Btu/cubic feet (cu. ft.), the annual clinker production by 
kiln type, and the average Btu requirements to produce a ton of clinker 
for each kiln type, we estimated the total nationwide natural gas 
requirement of the portland cement industry. Assuming a complete 
conversion to natural gas (as would be necessary if EPA were to adopt a 
standard reflecting mercury emission levels based on the use of natural 
gas), the portland cement industry would consume approximately 370 
billion cu. ft. of natural gas annually or 1.6 percent of the total 
United States natural gas consumption (22.8 trillion cu. ft. in the 
year 2000) and 3.9 percent of total industrial natural gas consumption 
(9.6 trillion cu. ft.).
    Although United States natural gas reserves would likely be 
adequate most of the time to handle a conversion by the portland cement 
manufacturing industry to 100 percent natural gas under normal 
conditions, supply is constrained by the number and production rate of 
United States wells, which is the source of most of the United States 
consumption of natural gas. Another obstacle to completely replacing 
coal with natural gas is the inadequacy of the existing natural gas 
infrastructure, including storage facilities, the pipeline distribution 
system, and compression facilities. Natural gas pipelines are 
relatively scarce in many United States areas compared to other 
utilities and are not available in all areas in which portland cement 
manufacturing plants are located. Even where pipelines provide access 
to natural gas, supplies of natural gas may not be adequate at all 
times. For example, it is common practice for industrial users to have 
interruptible contracts for natural gas. An interruptible contract 
means that the industrial users get the lowest priority for available 
gas during periods of peak demand, such as the winter months.
    For these reasons, reducing fuel mercury content by requiring kilns 
to switch to natural gas is not feasible on a national basis. We are 
unable to identify any other potential low-mercury fuel that could 
serve as the basis of a MACT floor for mercury.
    We also considered setting a floor based on a worst case scenario 
of mercury in the fuel and feed material combined. However, even a 
worst case estimate based on the available data would not ensure that a 
source could consistently meet the standard because there may be 
situations where a source has an excursion resulting from the inherent 
variability of the feed/fuel mercury content. We could provide an 
exception to the standard that would allow the source to exceed the 
limit by showing its raw materials or fuel contained more mercury than 
previously thought. However, the result of this approach would be that 
we would be setting a worse-case standard that is simply a bureaucratic 
exercise imposing costs (such as costs for permitting, monitoring, and 
recordkeeping) with no emissions reductions.
    We are aware that in specific cases, a source has been able to 
reduce emissions of mercury by making changes to some of their raw 
materials. Facilities that are already purchasing materials used as 
additives or a specific type of coal can make changes that reduce the 
total mercury input to the kiln. However, as previously discussed, 
these control techniques are site specific, and we do not believe they 
can be used as the basis of a national rule. We are also aware that 
some cement kilns purchase fly ash from utility boilers as an additive 
feedstock. There is concern that as a result of controlling mercury in 
utility boilers, the purchased fly ash may now have a higher mercury 
content than is the current norm. The result would be that mercury 
emissions reductions achieved by controlling utility boilers would be 
offset by the release of this previously controlled mercury in a cement 
kiln when the fly ash is used as an additive. At this time, we are 
uncertain if the use of fly ash from utility boilers that are 
controlling their mercury emissions will be significant. One possible 
solution would be to ban the use of fly ash from a utility boiler that 
is controlling mercury as an additive to cement kiln feed. We are 
specifically soliciting comment on a potential ban, or any other 
methods to address this issue.
    Thus, EPA has systematically evaluated all possible means of 
developing a quantified floor standard for mercury emissions from these 
sources, both emission control technology and front end feed and fuel 
control. (See National Lime, 233 F. 3d at 634 (finding that EPA had 
erred in examining only technological (i.e., back-end) controls in 
considering a level for a mercury floor). We have also been unable to 
devise any type of work

[[Page 72335]]

practice standard that would result in mercury emissions reductions.\3\
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    \3\ Indeed, most of the options EPA considered are really 
beyond-the-floor alternatives, because they reflect practices that 
differ from those now in use by any existing source (including the 
lowest emitters). (Coal switching, switching to natural gas, and raw 
material switching are examples.) In EPA's view, a purported floor 
standard which forces every source in a category to change its 
practices is a beyond-the-floor standard. Such a standard may not be 
adopted unless EPA takes into account costs, energy, and nonair 
environmental impacts.
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    It has been argued, however, that when considering floor standards, 
the means of attaining those standards is legally irrelevant. All that 
matters, the argument goes, is what emission level was measured in a 
test result and that such a measurement, by definition, must be 
considered to have been achieved in practice. The National Lime 
Association and the subsequent Cement Kiln Recyclers Coalition v. EPA, 
255 F. 3d 855 (DC Cir. 2001) decisions are said to mandate this result.
    The EPA disagrees. EPA's position is that ``achieved in practice'' 
means achievable over time, since sources are required to achieve the 
standards at all times. 70 FR at 59436 (Oct. 12, 2005). This position 
has strong support in the caselaw. Sierra Club v. EPA, 167 F. 3d 658, 
665 (DC Cir. 1999); Mossville Environmental Action Now v. EPA, 370 F. 
3d 1232, 1242 (DC Cir. 2004). Here, as just shown, there are no 
standards which are consistently achievable over time because of 
sources' inability to control inputs.
    Second, National Lime and CKRC did not involve facts where the 
levels of performance reflected in performance tests are pure 
happenstance (composition of HAP in raw materials and fossil fuel used 
the day the test was conducted), but cannot be replicated or 
duplicated. Put another way, these cases did not consider situations 
where means of control are infeasible and where no source can duplicate 
a quantified level of emissions due to uncontrollable variability of 
raw materials and fuels. Indeed, the court has rejected standards based 
on raw material substitution where this means of control is not 
feasible. (See Sierra Club v. EPA, 353 F. 3d 976, 988 (DC Cir. 2004) 
(``substitution of cleaner ore stocks was not * * * a feasible basis on 
which to set emission standards. Metallic impurity levels are variable 
and unpredictable both from mine to mine and within specific ore 
deposits, thereby precluding ore-switching as a predictable and 
consistent control strategy'').\4\ Moreover, the court has made clear 
that since standards must be met continuously (i.e., any single test 
can be a violation of the standard), MACT standards (including floor 
standards) must reflect maximum daily variability a source can 
experience in operation, including variability associated with HAP 
concentrations in raw materials (Mossville Environmental Action Now v. 
EPA, 370 F. 3d at 1242.) Here, as discussed above, that level of 
variability is beyond the control of any source and thus, cannot be 
accounted for in a floor standard.
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    \4\ Although this language arose in the context of a potential 
beyond-the-floor standard, EPA believes that the principle stated is 
generally applicable. The MACT standards are technology-based, and 
if there is no technology (i.e., no available means) to achieve a 
standard, i.e., for a source to achieve a standard whenever it is 
tested (as the rules require), then the standard is not an 
achievable one.
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    It is argued further, however, that even if individual sources 
(including those in the pool of best performing sources) cannot reduce 
HAP concentrations in raw materials and fossil fuels, they may achieve 
the same reductions by adding back-end pollution control. Applied here, 
the argument would be that even though no sources (not even the lowest 
emitters in the individual performance tests) can use fossil fuel or 
raw material substitution to achieve emission levels for mercury, they 
could achieve those levels by installing some type of back-end 
pollution control technology such as activated carbon. The thrust of 
this argument is essentially to impermissibly bypass the beyond-the-
floor factors set out in CAA section 112(d)(2) under the guise of 
adopting a floor standard. (See note three above.) Suppose that EPA 
were to adopt a floor standard dominated by emission levels reflecting 
mercury concentrations present in a few sources' raw materials and 
fossil fuels during their performance tests. Suppose further that no 
source in the data base can achieve that floor standard without adding 
considerable back-end control equipment (at great cost and great 
additional energy utilization) because test results based on fossil 
fuel and raw material levels are neither replicable nor duplicable. In 
this situation, we believe that we would have improperly adopted a 
beyond-the-floor standard. Because the standard is nominally a floor, 
we would not have considered the beyond-the-floor factors (cost, 
energy, and nonair impacts) set out in section 112(d)(2) of the CAA. 
Yet the standard would force all sources, including those ``best 
performing sources'' whose performance ostensibly is the basis for the 
floor, to retrofit with control devices not presently in use. We can 
take such action only if the standard is ``achievable'' under section 
112(d)(2), meaning justified after considering cost, energy, and nonair 
environmental impacts.
    We evaluated a mercury beyond-the-floor standard for new and 
existing cement kilns based on use of activated carbon injection (ACI) 
with an additional PM control device. The total capital cost of an ACI 
system is estimated to range from $761,000 to $5.5 million per kiln. 
The total annual costs of an ACI system are estimated to range from 
$477,000 to $3.7 million per kiln. These costs include the carbon 
injection system and an additional baghouse necessary to collect the 
carbon separately from the CKD. The cost per ton of mercury reduction 
for ACI applied to cement kilns ranges from $22.4 million to $56 
million. The use of ACI for mercury control could also result in a co-
benefit of additional control of dioxins and furans. However, the 
current NESHAP for portland cement mandates stringent levels of dioxin 
emissions based on the floor level of control. Even if ACI further 
reduces dioxin emissions to zero, the cost would be in the range of $2 
billion to $7 billion per pound. Therefore, we do not consider the 
dioxin emission reduction co-benefit to be significant.
    We also note that the application of ACI would generate additional 
solid waste and increase energy use. We estimate that the per kiln 
impacts would be 95 to 1,600 tons per year (tpy) of solid waste and 
526,200 to 9.3 million kilowatt hours (kWhr) of electricity demand.
    Based on the relatively low levels of existing mercury emissions 
from individual NHW cement kilns, the high costs (on both a dollars-
per-year and a dollars-per-ton basis) of reducing these emissions by 
ACI, and the negative nonair environmental impacts, we are proposing 
that this beyond-the-MACT-floor option for reducing mercury from new 
and existing NHW kilns is not justified.

B. Determination of MACT for HCl Emissions

    In developing the 1999 Portland Cement NESHAP we concluded that no 
add-on air pollution controls were being used whose performance could 
be used as a basis for the MACT floor for existing portland cement 
plants. For new source MACT, we identified two kilns that were using 
alkaline scrubbers for the control of sulfur dioxide (SO2) 
emissions. But we concluded that because these devices were operated 
only intermittently, their performance could not be used as a basis for 
the MACT floor for new sources. Alkaline scrubbers were then considered 
for

[[Page 72336]]

beyond-the-floor controls. Using engineering assessments from similar 
technology operated on municipal waste combustors and medical waste 
incinerators, we estimated costs and emissions reductions. Based on the 
costs of control and emissions reductions that would be achieved, we 
determined that beyond-the-floor controls were not warranted (63 FR 
14203, March 24, 1998).
    We reexamined establishing a floor for control of HCl emissions 
from new portland cement sources. Since promulgation of the NESHAP, wet 
or dry scrubbers have been installed and are operating at a minimum of 
four portland cement plants.\5\ Only one of the plants has conducted 
emissions tests for HCl using EPA Method 321 of appendix A to 40 CFR 
part 63. All of the test results for HCl were below the detection 
limits of 0.2 to 0.3 parts per million by volume (ppmv) for the 
measurement method.
---------------------------------------------------------------------------

    \5\ None of these four kilns burn hazardous waste.
---------------------------------------------------------------------------

    Based on the presence of continuously operated alkaline scrubbers 
at portland cement plants, we believe that the performance of 
continuously operated alkaline scrubbers represents MACT for new 
sources, but we do not have sufficient test data to set an emission 
level. As noted above, the one source tested had HCl emission levels 
below the detection limit. However, we do not have data for the inlet 
to the source's scrubber. In some cases, HCl emissions from cement 
kilns with no add-on controls are below 1 ppmv, but can also be above 
40 ppmv. We cannot determine if the low outlet concentration at the one 
tested source is solely due to the performance of the control device, 
or to a low inlet concentration. Therefore, we cannot state that any 
new cement kiln can reduce HCl emissions to levels below detection.
    However, section 112(d)(3) of the CAA states that new source MACT 
may be based on the performance of the best controlled similar source. 
Alkaline scrubbers designed for control of SO2 routinely 
achieve a 90 percent reduction in SO2 emissions when applied 
to coal-fired boilers. Alkaline scrubbers are known to be more 
effective in removing HCl than SO2. Therefore, it is 
reasonable to assume that an alkaline scrubber can achieve a 90 percent 
emission reduction of HCl if the inlet loadings are comparable to those 
seen on coal-fired boilers. However, it is also known that the removal 
efficiency of a scrubber can decrease as the inlet loading decreases. 
For this reason, we evaluated the performance of alkaline scrubbers 
applied to combustion of municipal solid waste, which has an HCl 
emissions loading more similar to a cement kiln than a coal-fired 
boiler. Based on an engineering assessment of HCl scrubbers used in 
municipal waste combustion applications and on vendor design 
information, we determined an alkaline scrubber could achieve a 15 ppmv 
HCl outlet concentration at low HCl inlet loadings, or at least a 90 
percent HCl emissions reduction at HCl inlet loadings of 100 ppmv or 
greater. Therefore, we are proposing a new source MACT for HCl 
emissions of 15 ppmv at the control device outlet, or a 90 percent HCl 
emissions reduction measured across the scrubber.
    Note that we are not proposing to retroactively impose this 
requirement on currently operating new sources. It will only apply to 
new sources that commence construction after December 2, 2005. 
Currently operating sources classified as new under the 1999 Portland 
Cement NESHAP would be required to meet the same requirements as 
existing sources.
    This approach is legally permissible and reasonable. The underlying 
principle for having new sources meet stricter standards (in the case 
of new source MACT standards, standards reflecting the performance of 
the best controlled similar source) is that such sources are 
essentially starting from scratch and, therefore, can most efficiently 
utilize the best means of pollution control. They will not need to 
retrofit. Sources classified as new under the 1999 Portland Cement 
NESHAP are not in this position. They have already commenced 
construction (and most likely started operating) and so are not in the 
position of a source starting de novo. Consequently, the only new 
sources for purposes of the proposed amendments are those commencing 
construction or reconstruction after December 2, 2005. We note that the 
position taken here is consistent with that proposed (and recently 
finalized) for hazardous waste combustion sources. See 69 FR 21363, 
April 20, 2004.
    In order to show compliance with the 15 ppmv emission limit, we are 
proposing to require a performance test using one of the following EPA 
methods:
    (1) Method 26/26A of Appendix A to 40 CFR part 60. Method 26A must 
be used when HCl could be associated with PM (for example, the 
association of HCl with water droplets emitted by sources controlled by 
a wet scrubber); otherwise you may use Method 26.
    (2) Method 320 or 321 of Appendix A to 40 CFR part 63.
    (3) ASTM Method D6735-01, Standard Test Method for Measurement of 
Gaseous Chlorides and Fluorides from Mineral Calcining Exhaust 
Sources--Impinger Method, provided that specific provisions in 40 CFR 
63.1349, paragraphs (b)(5)(iii)(A) through (F) are followed. These test 
methods are consistent with the HCl test methods used in similar 
standards. To determine compliance with the percent reduction 
requirement we are proposing to require the source to test at the 
scrubber inlet and outlet using one of the above methods and calculate 
a percent reduction based on the concentration difference (corrected to 
7 percent oxygen) divided by the inlet concentration and multiplied by 
100.
    We also reexamined the MACT floor for existing sources. We first 
considered setting the floor based on the performance of an alkaline 
scrubber. However, because only four facilities currently have 
operating alkaline scrubbers, the performance of alkaline scrubbers 
would not be indicative of the median of the top 12 percent of the 
source category. Therefore, we examined other alternatives that might 
constitute a floor. Because HCl emissions originate from chlorine in 
feed and fuel materials, we considered the use of feed/fuel selection 
as a potential option to reduce the amount of chlorine entering the 
kiln. Under this option, low-chlorine fuel and/or feed materials would 
be used to lower HCl emissions from kilns. However, this option 
presents the same problems previously discussed for using low-mercury 
containing feed and fuels. We have no data indicating the widespread 
availability of low-chlorine deposits of feed, or whether such deposits 
even exist. As with other contaminants, concentrations are variable 
between deposits as well as within deposits. The result is that 
uniformly low-chlorine feed is not available on a widespread basis. 
Furthermore, there is no information that a low-chlorine deposit of 
feed materials is likely also to be low in mercury, other metal HAP, or 
organic HAP material. Such limitations and uncertainties make this an 
unrealistic option. We also considered the option of changing to a low-
chlorine fuel, such as natural gas. This option was also determined to 
be infeasible due to limits on gas availability as previously discussed 
in the mercury MACT determination \6\
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    \6\ As explained above, standards reflecting these control 
practices (which we do not believe are feasible) would be beyond-
the-floor standards because they would force changes in practice by 
all sources in the category, even the lowest emitters in the 
performance tests.

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[[Page 72337]]

    Another control technique we considered was a work practice control 
based on the use of the kiln and PM control. Because the kiln and PM 
control system contain large amounts of alkaline CKD, the kilns 
themselves remove a significant amount of HCl (which reacts with the 
CKD and is captured as particulate). See 69 FR 21259, April 20, 2004. 
We considered setting an emission limit based on reported kiln HCl 
emissions which reflects this natural scrubbing. However, this approach 
has some of the limitations previously discussed regarding establishing 
a floor for mercury. The HCl emissions at any one time are a function 
of the chlorine content of the feed materials and fuel. We could not 
state that the levels of HCl emissions from any one kiln could be 
duplicated by other kilns, or by the tested kiln on a continuous basis. 
We also have no data that would allow us to establish a typical percent 
reduction in HCl emissions resulting from the alkaline environment in 
the kiln.
    There are total HCl emissions reductions data for cement kilns that 
fire hazardous waste (a separate class of cement kiln, as noted 
earlier). These data indicate that 80 percent of the kilns achieve at 
least a 95 percent reduction in total chlorine emissions at the kiln 
outlet compared to the total chlorine in the feed material (69 FR 
21259, April 20, 2004). However, the hazardous waste being burned in 
the kiln has a significant amount of chlorine compared to the fuel and 
feed materials of a cement kiln that does not burn hazardous waste. As 
previously noted, the overall percent reduction of HCl goes down as the 
total amount of HCl present is reduced. Therefore, the percent 
reduction seen in kilns that burn hazardous waste is not applicable to 
kilns that do not fire hazardous waste.
    It is nonetheless clear that all cement kilns will reduce emissions 
of HCl due to the kilns' alkaline operating conditions. We cannot 
measure the extent of emission reduction over time due to the types of 
variability just discussed. Because we cannot set a numeric emission 
limit and consequently cannot prescribe or enforce an emission standard 
within the meaning of section 112(h) of the CAA, we are proposing a 
floor for existing facilities as the work practice of operating the 
cement kiln under normal operating conditions and operating a 
particulate control device to capture HCl present in or adsorbed on the 
kiln particulate and have added this language in 40 CFR 63.1344.
    We are proposing to allow existing sources and new sources 
commencing construction before the publication date of the proposed 
amendments 1 year after publication of the final amendments to be in 
compliance with the amendment as proposed. The CAA requires compliance 
with MACT standards ``as expeditiously as practicable,'' and in 
virtually no case longer than 3 years after promulgation of the 
standard (CAA section 112(i)(3)(A)). Because the proposed amendment 
does not require the installation of a control device, we do not 
believe a 3-year compliance date is the most expeditious compliance 
date. We considered proposing a compliance date as the date the rule 
amendment is promulgated as proposed. However, as discussed below, we 
are proposing a compliance date of 1 year after publication of the 
final amendments for the amended THC/carbon monoxide (CO) requirements. 
We believe it is more reasonable to have one compliance date for all 
the proposed rule amendments. We do not believe this decision will 
measurably change the environmental benefits of the HCl standard.
    We also evaluated requiring the use of an alkaline scrubber as a 
beyond-the-floor control option for existing sources. Based on the 
estimated performance, annual HCl emissions reductions estimates range 
from 12 tpy of HCl and 27 tpy of SO2, to 200 tpy of HCl and 
600 tpy of SO2, per kiln. The total capital cost of 
installing an alkaline scrubber on an existing kiln is estimated to 
range from $1.1 to $5.1 million per kiln. The total annual cost is 
estimated to range from $336,000 to $1.7 million per kiln (Docket No. 
A-92-53). The cost per ton of HCl removed ranges from $8,500 to 
$28,000. In addition, the beyond-the-floor option would result in per-
kiln nonair environmental impacts of 5,000 to 84,100 tons of scrubber 
slurry for disposal, 4.7 to 107 million gallons of additional water 
usage, and increased electricity use of 219,300 to 2.4 million kWhr. We 
do not consider these costs and nonair environmental impacts reasonable 
for the emissions reductions achieved.
    We are proposing a format of volume per volume concentration for 
the emission limit. The specific units of the emission limit are ppmv 
(corrected to 7 percent oxygen) or a percent reduction. These formats 
have historically been used by EPA for many air emission standards and 
are consistent with the format of the NESHAP for cement kilns that burn 
hazardous waste. The concentration is corrected to 7 percent oxygen to 
put concentrations measured in stacks with different oxygen 
concentrations on a common basis, and because the typical range of 
oxygen concentrations in cement kiln stack gas is from 5 to 10 percent 
oxygen, we consider 7 percent representative. The HCl concentration or 
percent reduction will be measured during an initial performance test 
and at least every 5 years thereafter. During this test, you will 
establish scrubber operating parameters, including pH and liquid-to-gas 
ratio, and continuously monitor these parameters.
    The EPA also solicits comment on adopting alternative risk-based 
emission standards for HCl pursuant to section 112(d)(4) of the CAA. 
Both existing and new portland cement sources could be eligible for 
such standards. The EPA is considering two possible approaches for 
establishing such standards. Alternative risk-based standards would be 
based on national exposure standards determined by EPA to ensure 
protection of public health with an ample margin of safety and that do 
not pose adverse environmental impacts.
    Under the first approach, dispersion modeling of representative 
worst-case sources (or, preferably, all sources) within the portland 
cement category would be conducted to establish a level for comparison 
with the risk-based national standards. This would be done by 
determining that the annual HCl emissions rate for a cement kiln's 
emissions do not result in chronic human exposures which might exceed a 
Hazard Quotient (HQ) of 1.0.\7\
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    \7\ 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 a receptor's potential exposure (or modeled 
concentration) to the health reference value or threshold level 
(e.g., Reference Concentration) for an individual pollutant. The HQ 
values less than 1.0 indicate that exposures are below the health 
reference value or threshold level and, therefore, such exposures 
are without appreciable risk of effects in the exposed population. 
HQ values above 1.0 do not necessarily imply that adverse effects 
will occur, but that the likelihood of such effects in a given 
population increases as HQ values exceed 1.0. See https://
www.epa.gov//ttn/atw/nata/gloss1.html.
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    Also under this approach, the same risk-based national standards 
would be established for each source category. The EPA has proposed a 
substantially similar approach for HCl and total chlorine emissions 
from hazardous waste-burning cement kilns (see proposed CAA section 
112(d) standards at 69 FR 21305, April 20, 2004), and adopted similar 
approaches (again for HCl) in CAA section 112(d) rules for lime kilns 
(69 FR 394, January 5, 2004) and pulp and paper facilities (66 FR 3180, 
January 12, 2001).
    In determining the appropriate risk-based standard on a national 
basis, EPA

[[Page 72338]]

would use the reference concentration (RfC) for HCl that is currently 
published in EPA's Integrated Risk Information System as the 
denominator in the calculation of HQ mentioned in the previous 
paragraph. The RfC is defined as an estimate of a continuous inhalation 
exposure for a given duration to the human population (including 
susceptible subgroups) that is likely to be without an appreciable risk 
of adverse health effects over a lifetime. As such, HQ values at or 
below 1.0 should be considered to provide public health protection with 
an ample margin of safety and, thus, can be used to develop the 
national risk-based emission standards. Due to data limitations 
regarding the universe of cement kiln sources nationwide, EPA is not 
currently able to conduct a national analysis to determine if all 
cement kilns are emitting HCl at a rate that would meet the risk-based 
standards. However, EPA is prepared to evaluate documentation submitted 
in public comment.
    Under the second approach, the risk-based standards would be 
developed on a source-by-source basis, with sources choosing whether to 
seek an alternative risk-based limit. The risk-based standards would 
consist of a nationally applicable, uniform algorithm--again using the 
national exposure level for HCl just discussed. We would use this 
algorithm to establish site-specific emission limitations based on 
site-specific input from each source choosing to use this approach. 
Such risk-based standards would provide a uniform level of risk 
reduction. The EPA proposed this approach for hazardous waste 
combustion sources (69 FR 21297, April 20, 2004) and adopted it for 
industrial boilers (69 FR 55218, September 13, 2004).
    Sources would then calculate an HCl emission rate either by 
applying values from a look-up table provided by EPA, applicable to 
sources located in either flat or simple elevated terrain,\8\ or, if 
the source is located in a different type of terrain, conduct a site-
specific compliance demonstration. Sources using look-up tables would 
have to use the stack height and stack diameter from their kiln and the 
distance between the stack and the property boundary. At this time, due 
to data limitations regarding the universe of cement kiln sources 
nationwide, E