[Federal Register: August 22, 2006 (Volume 71, Number 162)]
[Proposed Rules]
[Page 49253-49308]
[DOCID:fr22au06-26]

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Part III

Environmental Protection Agency

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40 CFR Parts 72 and 75

Revisions to the Continuous Emissions Monitoring Rule for the Acid Rain
Program, NOX Budget Trading Program, the Clean Air
Interstate Rule, and the Clean Air Mercury Rule; Proposed Rule

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ENVIRONMENTAL PROTECTION AGENCY

40 CFR Parts 72 and 75

[OAR-2005-0132; FRL-8208-1]

Revisions to the Continuous Emissions Monitoring Rule for the
Acid Rain Program, NOX Budget Trading Program, the Clean Air
Interstate Rule, and the Clean Air Mercury Rule

AGENCY: Environmental Protection Agency (EPA).

ACTION: Proposed rule.

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SUMMARY: EPA is proposing rule revisions that would modify existing
requirements for sources affected by the federally administered
emission trading programs including the NOX Budget Trading
Program, the Acid Rain Program, the Clean Air Interstate Rule, and the
Clean Air Mercury Rule.
    The proposed revisions are prompted primarily by changes being
implemented by EPA's Clean Air Markets Division in its data systems in
order to utilize the latest modern technology for the submittal of data
by affected sources. Other revisions address issues that have been
raised during program implementation, fix specific inconsistencies in
rule provisions, or update sources incorporated by reference. These
revisions would not impose significant new requirements upon sources
with regard to monitoring or quality assurance activities.

DATES: All public comments must be received on or before October 23,
2006.

ADDRESSES: Submit your comments, identified by Docket ID No. EPA-HQ-
OAR-2005-0132, by one of the following methods:
     Federal eRulemaking Portal: http://www.regulations.gov.

Follow the on-line instructions for submitting comments.
     E-mail<EMAIL_ADDRESS>     Fax:<PHONE_NUMBER>.
     Hand Delivery: Air and Radiation Docket, Environmental
Protection Agency, 1301 Constitution Avenue, NW., Room B-108,
Washington, DC 20014. Such deliveries are accepted only during the
Docket's normal hours of operation and special arrangements should be
made for deliveries of boxed information.
     Mail: EPA Docket Center (EPA/DC), Environmental Protection
Agency, Mailcode 6102T, 1200 Pennsylvania Avenue, NW., Washington, DC
20460. Please include a total of two copies. We request that a separate
copy also be sent to the contact person identified below (see FOR
FURTHER INFORMATION CONTACT).
    Instructions: Direct your comments to Docket ID No. EPA-HQ-OAR-
2005-0132. EPA's policy is that all comments received will be included
in the public docket without change and may be made available online at
http://www.regulations.gov including any personal information provided,

unless the comment includes information claimed to be Confidential
Business Information (CBI) or other information whose disclosure is
restricted by statute. Do not submit information that you consider to
be CBI or otherwise protected through http://www.regulations.gov or e-mail. The http://www.regulations.gov Web site is an ``anonymous

access'' system, which means EPA will not know your identity or contact
information unless you provide it in the body of your comment. If you
send an e-mail comment directly to EPA without going through http://www.regulations.gov
, your e-mail address will be automatically captured

and included as part of the comment that is placed in the public docket
and made available on the Internet. If you submit an electronic
comment, EPA recommends that you include your name and other contact
information in the body of your comment with a 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 http://www.regulations.gov
 index. Although listed in the index, some

information is not publicly available, e.g., CBI or other information
whose disclosure is restricted by statute. Certain other material, such
as copyrighted material, will be publicly available only in hard copy.
Publicly available docket materials are available either electronically
in http://www.regulations.gov or in hard copy at the Air and Radiation

Docket, EPA/DC, EPA West, Room B102, 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<PHONE_NUMBER>, and the telephone
number for the Air and Radiation Docket is<PHONE_NUMBER>.

FOR FURTHER INFORMATION CONTACT: Matthew Boze, Clean Air Markets
Division, U.S. Environmental Protection Agency, Clean Air Markets
Division, MC 6204J, Ariel Rios Building, 1200 Pennsylvania Ave., NW.,
Washington, DC 20460, telephone<PHONE_NUMBER>, e-mail at
<EMAIL_ADDRESS>Electronic copies of this document can be

accessed through the EPA Web site at: http://www.epa.gov/airmarkets.

SUPPLEMENTARY INFORMATION: Regulated Entities. Entities regulated by
this action primarily are fossil fuel-fired boilers, turbines, and
combined cycle units that serve generators that produce electricity,
generate steam, or cogenerate electricity and steam. Some trading
programs include process sources, such as process heaters or cement
kilns. Although Part 75 primarily regulates the electric utility
industry, certain State and Federal NOX mass emission
trading programs rely on subpart H of Part 75, and those programs may
include boilers, turbines, combined cycle, and certain process units
from other industries. Regulated categories and entities include:

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                                                        Examples of
           Category                 NAICS code     potentially regulated
                                                         industries
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Industry......................  221112 and others  Electric service
                                                    providers Process
                                                    sources with large
                                                    boilers, turbines,
                                                    combined cycle
                                                    units, process
                                                    heaters, or cement
                                                    kilns where
                                                    emissions exhaust
                                                    through a stack.
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    This table is not intended to be exhaustive, but rather to provide
a guide for readers regarding entities likely to be regulated by this
action. This table lists the types of entities which EPA is now aware
could potentially be regulated by this action. Other types of entities
not listed in this table could also be regulated. To determine whether
your facility, company, business, organization, etc., is regulated by
this action, you should carefully examine the applicability provisions
in Sec. Sec.  72.6, 72.7, and 72.8 of title 40 of the Code of Federal
Regulations and in 40 CFR Parts 96 and 97. 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.

    Submitting CBI. Do not submit this information to EPA through
http://www.regulations.gov or e-mail. Clearly mark the part or all of

the information that you claim to be CBI. For CBI information on 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.
    World Wide Web (WWW). In addition to being available in the docket,
an electronic copy of the proposed rule is also available on the WWW
through the Technology Transfer Network Web site (TTN Web). Following
signature, a copy of the proposed rule will be posted on the TTN's
policy and guidance page for newly proposed or promulgated rules at
http://www.epa.gov/ttn/oarpg. The TTN provides information and

technology exchange in various areas of air pollution control.

Outline:

I. Detailed Discussion of Proposed Rule Revisions
    A. Rule Definitions
    B. General Monitoring Provisions
    C. Certification Requirements
    D. Missing Data Substitution
    E. Recordkeeping and Reporting
    F. Subpart H (NOX Mass Emissions)
    G. Subpart I (Hg Mass Emissions)
    H. Appendix A
    I. Appendix B
    J. Appendix D
    K. Appendix E
    L. Appendix F
    M. Appendix G
    N. Appendix K
II. Administrative Requirements
    A. Executive Order 12866--Regulatory Planning and Review
    B. Paperwork Reduction Act
    C. Regulatory Flexibility Act
    D. Unfunded Mandates Reform Act
    E. Executive Order 13132--Federalism
    F. Executive Order 13175--Consultation and Coordination With
Indian Tribal Governments
    G. Executive Order 13045--Protection of Children From
Environmental Health and Safety Risks
    H. Executive Order 13211--Actions That Significantly Affect
Energy Supply, Distribution, or Use
    I. National Technology Transfer and Advancement Act

I. Detailed Discussion of Proposed Rule Revisions

    EPA is in the process of re-engineering the data systems associated
with the collection and processing of emissions, monitoring plan,
quality assurance, and certification data. The re-engineering project
includes the creation of a client tool, provided by EPA that sources
will use to evaluate and submit their Part 75 monitoring data. This
process change will enable sources to assess the quality of their data
prior to submitting the data using EPA established checking criteria.
The process will also allow sources to report their data directly to a
database. Having the data in a true database will allow the Agency to
implement and assess the program more efficiently and will streamline
access to the data. Also, this database structure will enable EPA to
implement process changes that will reduce the redundant reporting of
certain types of data. The re-engineered systems will be supported by a
new extensible markup language (XML) data format that will replace the
record type/column format currently used by EPA to collect electronic
data. EPA intends to transition existing sources to the new XML
electronic data report (XML-EDR) format during the 2008 reporting year.
For sources reporting in 2008 for the first time, the new XML-EDR
format should be used. All sources will be required to use the new
process beginning 2009.

A. Rule Definitions

    The proposed changes to Part 72 include adding a definition for
``long-term cold storage'' to mean ``the complete shutdown of a unit
intended to last for an extended period of time (at least two calendar
years) where notice for long-term cold storage is provided under Sec.
75.61(a)(7). See Section II.E.4 of this preamble for further
discussion.
    EPA also proposes to modify the definition of ``capacity factor''
so that the Agency can use the reported maximum hourly gross load, as
currently reported in the electronic monitoring plan, to determine
whether a unit qualifies for peaking unit status, by recalculating the
capacity factor. This is important because the maximum hourly gross
load can be greater than the nameplate capacity. Also, when using heat
input to define capacity factor, the definition would be revised to
refer to maximum rated hourly heat input rate, which is defined in
Sec.  72.2.
    The proposed changes to Sec.  72.2 would also modify the definition
of ``EPA Protocol Gas,'' and add a definition of ``EPA Protocol Gas
Verification Program'', to support the proposed calibration gas audit
program. EPA is also proposing to expand the definition of ``excepted
monitoring system'' to include the sorbent trap and low mass emissions
(LME) excepted methodologies for Hg. Finally, today's proposed rule
would add definitions of ``Air Emission Testing Body (AETB)'' and
``Qualified Individual'', to support the proposed stack tester
accreditation program. See Sections II.H.2 and II.H.3 of this preamble
for a discussion of these proposed programs.

B. General Monitoring Provisions

1. Update of Incorporation by Reference (Sec.  75.6)
    Section 75.6 identifies a number of methods and other standards
that are incorporated by reference into Part 75. This section includes
standards published by the American Society for Testing and Materials
(ASTM), the American Society of Mechanical Engineers (ASME), the
American National Standards Institute (ANSI), the Gas Processors
Association (GPA), and the American Petroleum Institute (API). Changes
in Sec.  75.6 would reflect the need to incorporate recent updates for
many of the referenced standards. The proposed revisions would
recognize or adhere to these newer standards by updating references for
the standards listed in Sec. Sec.  75.6(a) through 75.6(f).
Additionally, new Sec. Sec.  75.6(a)(45) through 75.6(a)(48) and
75.6(f)(4) would incorporate by reference additional ASTM and API
standards that are relevant to Part 75 implementation.
2. Default Emission Rates for Low Mass Emissions (LME) Units
    Today's proposed rule revisions would allow LME units to use site-
specific default SO2 emission rates for fuel oil combustion,
in lieu of using the ``generic'' default SO2 emission rates
specified in Table LM-1 of Sec.  75.19. To use this option, a federally
enforceable permit condition would have to be in place for the unit,
limiting the sulfur content of the oil. This revision would allow more
representative, yet still conservatively high, SO2 emissions
data to be reported from oil-burning LME units. The site-specific
default SO2 emission rate would be calculated using an
equation from EPA publication AP-42. The sulfur content used in the
calculations would be the maximum weight percent sulfur allowed by the
federally-enforceable permit. Sources choosing to implement this option
would be required to perform periodic oil sampling using one of the
four methodologies described in Section 2.2

of Appendix D to Part 75, and would be required to keep records
documenting the sulfur content of the fuel.
    Today's proposed rule would also revise Sec.  75.19(c)(1)(iv)(G) to
clarify that fuel-and-unit-specific default NOX emission
rates for LME units may be determined using data from a Continuous
Emissions Monitoring System (CEMS) that has been quality-assured
according to either Appendix B of Part 75 or Appendix F of Part 60, or
comparably quality-assured under a State CEMS program. The current rule
simply states that 3 years (or 3 ozone seasons, if applicable) of
quality-assured CEMS data may be used for this purpose, but it does not
specify the acceptable level of QA required.
3. Default Moisture Value for Natural Gas
    EPA is proposing to allow gas-fired boilers equipped with CEMS to
use default moisture values in lieu of continuously monitoring the
stack gas moisture content. Two default values are proposed: 14.0%
H2O under Sec.  75.11(b), and 18.0% H2O under
Sec.  75.12(b). The higher default value would apply only when Equation
19-3, 19-4, or 19-8 (from Method 19 in appendix A of Part 60) is used
to determine the NOX emission rate. These proposed default
values are based on supplemental moisture data provided to the Agency
in a December 13, 2004 petition from a gas-fired industrial source and
moisture data collected during EPA's development of flow rate reference
Methods 2F and 2G at two gas-fired facilities. (See Docket A-99-14;
Items II-A-1 and II-A-7).
    EPA selected the 10th and 90th percentile values from these data,
rounded to the nearest whole number, as the proposed natural gas
default moisture values. The selection of conservative 90th or 10th
percentile values from representative moisture data sets is consistent
with the approach that the Agency has approved in response to past
petition under Sec.  75.66 requesting to use site-specific default
moisture values.
4. Expanded Use of Equation F-23
    Today's proposed rule would revise Sec.  75.11(e)(1) to remove the
current restrictions on the use of Equation F-23 to determine the
SO2 mass emission rate. The current rule restricts the use
of this equation to units equipped with SO2 monitors and to
hours when only fuel that meets the Part 72 definition of ``pipeline
natural gas'' or ``natural gas'' is being combusted. EPA proposes to
allow Equation F-23 to be used whether or not the unit has an
SO2 monitor and to expand its use to fuels other than
natural gas.
    Section 75.11(e) would be re-titled as ``Special considerations
during the combustion of gaseous fuels'', and the introductory text of
the section would be revised, so that the section would no longer apply
exclusively to units with SO2 monitors. Rather, it would
apply to units that use certified flow rate and diluent gas monitors to
quantify heat input. Such units would be required to implement the
provisions of either revised Sec.  75.11(e)(1) or revised Sec.
75.11(e)(3) when gaseous fuel is the only fuel combusted in the unit.
Section 75.11(e)(2) would be removed and reserved, as the use of
Appendix D methodology during gaseous fuel combustion is not
appropriate for a unit that uses flow and diluent monitors to measure
heat input. This is because only one heat input methodology is allowed
for each unit.
    Revised Sec.  75.11(e)(1) would expand the use of Equation F-23
beyond natural gas combustion to include the combustion of any gaseous
fuel that qualifies for a default SO2 emission rate under
Section 2.3.6(b) of Appendix D. The proposed revisions to Sec.
75.11(e)(3) would be relatively minor. The option to use a certified
SO2 monitor during hours of gaseous fuel combustion would be
retained.
    A new paragraph (e)(4) would also be added to Sec.  75.11(e). This
new provision would allow Equation F-23 to be used for the combustion
of liquid and solid fuels that meet the definition of ``very low sulfur
fuel'' in Sec.  72.2, if a petition for a fuel-specific default
SO2 emission rate is submitted to the Administrator under
Sec.  75.66 and the Administrator approves the petition. Similar
petitions would also be accepted for the combustion of mixtures of
these fuels and for the co-firing of these fuels with gaseous fuel.
    EPA believes that expanding the use of Equation F-23 will benefit
certain units that are subject to the Acid Rain Program or to the
SO2 provisions of the Clean Air Interstate Rule (CAIR). In
particular, the requirement to operate and maintain an SO2
CEMS could be waived for units that burn low-sulfur solid fuels such as
wood waste. Also, for units that combust non-traditional gaseous fuels,
Equation F-23 would provide an alternative way of quantifying
SO2 mass emissions that does not require either an
SO2 CEMS or a certified fuel flowmeter.
5. Calculation of NOX Emission Rate--LME Units
    According to Sec. Sec.  75.58(f), 75.64(a)(4), and 75.64(a)(9), oil
and gas-fired units in the Acid Rain Program that qualify to use the
low mass emissions (LME) methodology in Sec.  75.19 are required to
report both NOX mass emissions (lb or tons, as applicable)
and NOX emission rate (lb/mmBtu) on an hourly, quarterly and
annual basis. However, the mathematics in Sec.  75.19(c)(4)(ii)
pertains only to NOX mass emissions, not NOX
emission rate. This is most likely because the criterion for initial
and on-going LME qualification is based on the total tons of
NOX emitted the calendar year, rather than on the
NOX emission rate.
    Today's rule would re-title Sec.  75.19(c)(4)(ii) as
``NOX mass emissions and NOX emission rate'', and
would add a new subparagraph (D) to Sec.  75.19 (c)(4)(ii), providing
instructions for determining quarterly and cumulative NOX
emission rates for an LME unit. The NOX emission rate for
each hour (lb/mmBtu) would simply be the appropriate generic or unit-
specific default NOX emission rate defined in the monitoring
plan for the type of fuel being combusted and (if applicable) the
NOX emission control status. The quarterly NOX
emission rate would be determined by averaging all of the hourly
NOX emission rates and the cumulative (year-to-date)
NOX emission rate would be the arithmetic average of the
quarterly values.
6. LME Units--Scope of Applicability
    Today's rule would revise Sec.  75.19(a)(1) to clarify that the low
mass emissions (LME) methodology is a stand-alone alternative to a CEMS
and/or the ``excepted'' monitoring methodologies in Appendices D, E,
and G. In other words, if a unit qualifies for LME status, the owner or
operator would be required either to use the LME methodology for all
parameters or not to use the method at all. No mixing-and-matching of
other monitoring methodologies with LME would be permitted. For
example, the owner or operator of a qualifying LME unit in the Acid
Rain Program would either be required to follow the provisions of Sec.
75.19 for all parameters (i.e., SO2 and CO2 mass
emissions, NOX emission rate, and unit heat input) or to
monitor these parameters using a CEMS, Appendices D, E, and G, or a
combination of these other methods. EPA has always intended for the LME
methodology to be applied this way, but this was not explicitly stated
in Sec.  75.19 and in other sections of the rule. In fact, Sec. Sec.
75.11(d)(3), 75.12(e)(3), and 75.13(d)(3)) suggest that mixing other
monitoring methodologies with LME might not be prohibited. Today's rule
would also make parallel revisions to

these other sections, consistent with the changes to Sec.  75.19(a)(1),
to clarify the Agency's intent.
7. Use of maximum controlled NOX emission rate when using
bypass stacks
    Today's proposed rule would revise Sec.  75.17(d)(2) to allow for
the calculation and use of a maximum controlled NOX emission
rate (MCR) instead of the maximum potential NOX emission
rate (MER) whenever an unmonitored bypass stack is used, provided that
the add-on controls are not bypassed and are documented to be operating
properly. Documentation of proper add-on control operation for such
hours of operation would be required as described in Sec.  75.34(d).
The MCR would be calculated in a manner similar to the calculation of
the MER, except that the maximum expected NOX concentration
(MEC) would be used instead of the maximum potential NOX
concentration (MPC). EPA believes that this proposal would more fairly
account for controlled emissions when unmonitored bypass stacks are
used. The rule currently requires the use of the MER regardless of the
operation and usage of add-on controls. When Sec.  75.17(d)(2) was
originally promulgated, EPA assumed that the add-on controls would be
bypassed whenever a bypass stack is used. EPA is now aware that there
are situations where this is not the case. An example would be a coal-
fired unit equipped with FGD and SCR add-on emission controls. If the
SCR is documented to be working during an FGD malfunction and the
effluent gases are routed through an unmonitored bypass stack after
passing through the SCR, then the MEC, rather than the MER, would be
the more appropriate NOX emission rate to report for the
bypass hour(s).

C. Certification Requirements

1. Alternative Monitoring System Certification
    The proposed rule would delete Sec. Sec.  75.20(f)(1) and (2) from
the rule, thereby removing the requirement for the Administrator to
publish each request for certification of an alternative monitoring
system in the Federal Register, with an associated 60-day public
comment period. This rule provision is considered unnecessary, in view
of the Agency's authority under Subpart E to approve alternative
monitoring systems and the rigorous requirements that alternative
monitoring systems must meet in order to be certified.
2. Part 60 Reference Test Methods
    On May 15, 2006, EPA promulgated final revisions to EPA reference
test methods 6C, 7E, and 3A, which are found in Appendix A of 40 CFR
Part 60. (See 71 FR 28082, May 15, 2006). Today's proposed rule would
update, (as necessary), various section references to these reference
methods, as well as specify certain options that are not to be applied
to RATA testing under Part 75. Specifically, the following provisions
are not permitted unless specific approval is granted by the
Administrator of Part 75:
    (1) Sec.  7.1 of the revised EPA Method 7E allowing for use of
prepared calibration gas mixtures that are produced in accordance with
Method 205 in Appendix M of 40 CFR Part 51. EPA maintains that for RATA
testing under Part 75, that reference gases be selected in accordance
with Sec.  5.1 of Appendix A of 40 CFR Part 75.
    (2) Sec.  8.4 of the revised EPA Method 7E allowing for the use of
a multi-hole probe to satisfy the multipoint traverse requirement of
the method.
    (3) Sec.  8.6 of the revised EPA Method 7E allowing for the use of
``Dynamic Spiking'' as an alternative to the interference and system
bias checks of the method. This proposed rule would allow for dynamic
spiking to be conducted (optionally) as an additional quality assurance
check for Part 75 applications.
3. Mercury Reference Methods
    Today's proposed rule would add an alternative acceptance criterion
for the results of mercury (Hg) emission data collected with the
Ontario Hydro (OH) reference method and would allow the use of
alternative reference methods for RATAs and for the low mass Hg
emission testing described in Sec.  75.81(c).
    On May 18, 2005, EPA published the Clean Air Mercury Rule (CAMR).
That rule requires coal-fired electric generating units (EGUs) to
reduce Hg emissions, starting in 2010, and to continuously monitor Hg
mass emissions according to Subpart I of Part 75, beginning in 2009.
    Relative accuracy test audits (RATAs) of all continuous Hg
monitoring systems are required under CAMR, and Hg emission testing is
required for units seeking to qualify as low mass emitters under Sec.
75.81(c). The principal reference method specified for the RATAs and
the emission testing is the OH method. Alternatively, an instrumental
method approved by the Administrator may be used. When the OH method is
performed, Sec.  75.22(a)(7) requires paired sampling trains for each
test run, and the relative deviation (RD) of the results from the two
trains must not exceed 10 percent.
    As part of the May 18, 2005 rulemaking, EPA also promulgated
revisions to Subpart Da of the New Source Performance Standards (NSPS)
regulations, requiring continuous Hg emission monitoring for new coal-
fired electric utility units constructed after January 1, 2004. Along
with the Subpart Da revisions, a performance specification, PS-12A, for
certifying the required continuous Hg monitors was published. PS-12A,
like Part 75, requires RATA testing of all Hg monitoring systems, using
paired reference method sampling trains; however, note that PS 12-A
allows EPA Method 29 (from Appendix A-8 of 40 CFR Part 60) to be used
as an alternative to the OH method, whereas Part 75 does not.
    The principal acceptance criterion in Section <IP_ADDRESS> of PS 12-A
for the data from the paired reference method trains (10 percent RD) is
the same as in Sec.  75.22(a)(7). However, PS 12-A includes an
alternative acceptance criterion for sources with low Hg emissions. If
the average Hg concentration during the RATA is 1.0 [mu]g/m\3\ or less,
the RD specification is 20 percent. In view of this, today's proposed
rule would revise Sec.  75.22(a)(7), to include this same 20 percent
alternative RD specification for low-emitters. This would harmonize the
Part 60 and Part 75 RATA provisions for Hg monitors, thereby
facilitating compliance for sources subject to both sets of
regulations.
    EPA is also proposing revisions to Sec. Sec.  75.22(a)(7) and
75.81(c)(1) which would allow EPA Method 29 to be used as an
alternative to the OH method, both for RATA testing and for periodic
emission testing of units with low Hg mass emissions (< = 29 lb/yr).
Method 29 is an established test procedure that uses atomic absorption
spectroscopy to determine the concentration of various metals,
including Hg, in the stack gas. This method is more familiar to
emission testers than the OH method, and Method 29 data have been
accepted for compliance purposes by the State. Method 29 and the OH
method both measure the total vapor phase Hg in the effluent. The main
difference between the two methods is that the OH method performs
``speciation'' of the vapor phase Hg, i.e., it quantifies the elemental
and ionic portions of the vapor phase Hg separately, whereas Method 29
does not. However, the CAMR rule does not require speciation of the
vapor phase Hg. Therefore, Method 29 could be used instead of the OH
method.

    There would be two caveats on the use of Method 29. First, sources
electing to use Method 29 would be required to use paired sampling
trains (i.e., two trains sampling the source effluent simultaneously),
and the relative deviation specification in Sec.  75.22(a)(7) would
have to be met for each run. The test results for each valid run would
be based on the Hg collected in the back half of each sampling train
(i.e., the impinger catch), and the results from the two trains would
be averaged arithmetically.
    Second, certain analytical and QA procedures in the OH method (ASTM
D6784-02) would be followed instead of the corresponding procedures in
Method 29. Specifically, testers would be required to replace the
procedures in sections 7.5.33 and 11.1.3 of Method 29 with the
corresponding procedures in sections <IP_ADDRESS> through <IP_ADDRESS> of ASTM
D6784-02, and to perform the QA/QC procedures in section 13.4.2 of the
OH method instead of the procedures in section 9.2.3 of Method 29. EPA
believes that implementing these sections of the OH method in lieu of
the corresponding Method 29 provisions will improve the quality of the
data, because the analytical and QA/QC requirements of the OH method
are more detailed and rigorous than those in Method 29.
    EPA is also proposing to allow several of the sample recovery and
preparation procedures in the OH method to be followed instead of the
Method 29 procedures. In particular: (a) Sections <IP_ADDRESS> through
<IP_ADDRESS> of the OH method could be followed instead of sections 8.2.8
and <IP_ADDRESS> of RM 29; (b) sections <IP_ADDRESS> through <IP_ADDRESS> of the
OH method could be followed instead of sections <IP_ADDRESS> and <IP_ADDRESS> of
RM 29; (c) section 8.3.4 of RM 29 could be replaced with section 13.3.4
or 13.3.6 of the OH method (as appropriate); and (d) section 8.3.5 of
RM 29 could be replaced with section 13.3.5 or 13.3.6 of the OH method
(as appropriate). Use of these alternative procedures would increase
the accuracy of moisture content determinations (by using a gravimetric
rather than a volumetric technique), and would eliminate of the need
for two separate analyses of the KMnO4 fraction.
    Revisions to Sec.  75.59 and to Sections 6.5.10 and 7.6.1 of
Appendix A to Part 75 are also being proposed, for purposes of
consistency with the proposed changes to Sec. Sec.  75.22(a)(7) and
75.81(c)(1).
    Finally, the Agency is soliciting comment on the use of sorbent
traps for reference method testing. At the 2006 Electric Utility
Environmental Conference (EUEC) in Tucson, Arizona, a stakeholder
meeting was held to discuss mercury monitoring issues. Many of the
participants expressed an interest in using portable sorbent trap
monitoring systems for Hg reference method testing, as an alternative
to the OH method. After much internal discussion, EPA believes that a
sorbent trap system could potentially serve as an alternative reference
method for Hg emission testing and RATA applications, if it can be
adequately demonstrated that the method does not have an inherent
measurement bias when compared to the OH method, and if sufficiently
rigorous quality-assurance (QA) procedures are developed and followed
when the system is used in the field. In view of this, EPA requests
comment on how such a demonstration might be made and what QA
procedures would be appropriate. In anticipation that a viable
reference method using sorbent trap technology may be developed in the
near future, the Agency is also proposing to add language to Sec.
75.22(a)(7), which would allow an ``other suitable'' reference method
approved by the Administrator to be used for Hg emission testing and
RATAs.

D. Missing Data Substitution

1. Block Versus Step-Wise Approach
    During periods of missing CEMS data, Part 75 requires substitute
data to be reported. Special mathematical algorithms are used to
determine the appropriate substitute data values. As the length of a
missing data period increases, the percent monitor data availability
(PMA) decreases, and the required substitute data values become
increasingly conservative each time that a particular PMA ``cut point''
is reached. The cut points are 95%, 90%, and 80% PMA for all parameters
except Hg. For Hg, the cut points are slightly lower, i.e., at 90%, 80%
and 70% PMA.
    Historically, EPA's policy has required sources to use a ``block''
approach for missing data substitution. The PMA at the end of the
missing data period has been used to determine which mathematical
algorithm applies, and the substitute data value or values prescribed
by that one algorithm have been reported for each hour of the missing
data period.
    However, EPA has recently revised its missing substitution data
policy. The revised policy guidance (see ``Part 75 Emission Monitoring
Policy Manual'', Question 15.5) allows sources to apply the missing
data algorithms in a stepwise manner instead of using the block
approach. Under the stepwise methodology, the various missing data
algorithms are applied sequentially. That is, the least conservative
algorithm is applied to the missing data hours until the PMA drops
below 95%. Then, the next algorithm is applied until the PMA has
dropped below 90%, and so on.
    Part 75 is not clear about which of the two methods should be used
for missing data substitution. Today's proposed rule would revise the
text of certain paragraphs in Sec. Sec.  75.33 and 75.32(b), to clarify
that the stepwise, hour-by-hour method (which is the least stringent
approach) is the preferred one. The Agency favors this approach because
it prevents sources from being penalized by the retroactive application
of more stringent missing data algorithms to hours where the hourly PMA
merits the use of less conservative algorithms. EPA intends that only
the new stepwise, hour-by-hour method be used after January 1, 2009, or
whenever emissions data are to be submitted in XML-format. Until this
time, either method will be accepted.
2. Substitute Data Values for Controlled Units
    For units with add-on emission controls, Sec.  75.34(a)(3) provides
that the designated representative (DR) may petition the Administrator
under Sec.  75.66 to report alternative substitute data values in
certain instances. Specifically, when the percent monitor data
availability (PMA) for SO2 or NOX is below 90.0
percent, the DR may petition to replace the maximum emission rate
recorded in the last 720 quality-assured monitor operating hours with
the maximum controlled emission rate recorded during that same lookback
period, for each missing data hour in which the add-on controls are
documented to be operating properly. Until recently, this petition
provision applied only to units with add-on SO2 or
NOX emission controls. However, revisions to Part 75 on May
18, 2005, extended it to include units with add-on Hg controls (see
Sec.  75.38(c)).
    For several reasons, EPA believes it is appropriate to revise Sec.
75.34(a)(3). First, the 720 hour lookback is only appropriate for
SO2 and Hg. For NOX, the lookback should be 2,160
hours and should also be load-based. Second, for SO2, Hg,
and NOX concentration monitoring systems, the terms
``maximum emission rate'' and ``maximum controlled emission rate'' are
not appropriate and should be replaced by ``maximum concentration'' and
``maximum controlled concentration'', respectively. Third, the petition
provision, as written, applies to

all PMA values below 90.0 percent (that was the intent when it was
originally written), but in light of subsequent revisions to Part 75,
it should be restricted to a narrower range of PMA values. Fourth, and
most important, after more than ten years of implementing the Acid Rain
Program, EPA no longer believes that special petitions are necessary to
use maximum controlled values for missing data substitution, because
sources with add-on controls are required to implement a quality
assurance/quality control (QA/QC) program that includes the recording
of parametric data to document the hourly operating status of the
emission controls. This parametric information must be made available
to inspectors and auditors upon request. Therefore, any claim that the
emission controls were operating properly during a particular missing
data period can be easily verified through the audit process.
    At the time the petition provision in Sec.  75.34(a)(3) was
written, there were only three missing data tiers in existence, i.e.,
for PMA values: (1) >= 95.0 percent; (2) >= 90.0 percent, but < 95.0
percent: and (3) <  90.0 percent. The provision was associated with the
third tier (PMA <  90.0 percent), for which the required substitute data
value is the maximum value recorded in a specified lookback period.
However, on May 26, 1999, EPA added a fourth CEMS missing data tier to
Part 75. The May 1999 rule revisions did not change the missing data
algorithms for the third tier, but the PMA ``cut off'' point for the
third tier was set at 80.0 percent, and below 80.0 percent PMA,
reporting of the maximum potential concentration (MPC) or the maximum
potential NOX emission rate (MER) was required for a missing
data period of any length.
    Today's proposed rule would remove from Sec.  75.34(a)(3) and Sec.
75.66(f) the requirement to petition the Administrator to use the
maximum controlled SO2 or NOX concentration (or
maximum controlled NOX emission rate) from the applicable
lookback period. The proposed revisions would simply allow the maximum
controlled values to be reported whenever parametric data are available
to document that the emission controls are operating properly. The
proposed rule would further clarify that this reporting option applies
only to the third missing data tier, when the PMA is greater than or
equal to 80.0 percent, but less than 90.0 percent.
    EPA is also proposing to add a new paragraph (a)(5) to Sec.  75.34,
which would allow units with add-on emission controls to report
alternative substitute data values for missing data periods in the
fourth tier, when the PMA is below 80.0 percent. Proposed Sec.
75.34(a)(5) would allow the owner or operator to replace the maximum
potential SO2 or NOX concentration (MPC) or the
maximum potential NOX emission rate (MER) with a less
conservative substitute data value, for missing data hours where
parametric data, (as described in Sec. Sec.  75.34(d) and 75.58(b)) are
available to verify proper operation of the add-on controls.
Specifically, for SO2 and NOX concentration, the
replacement value for the MPC would be the greater of: (a) The maximum
expected concentration (MEC); or (b) 1.25 times the maximum controlled
value in the standard missing data lookback period. For NOX
emission rate, the replacement value for the MER would be the greater
of: (a) The maximum controlled NOX emission rate (MCR); or
(b) 1.25 times the maximum controlled value in the standard missing
data lookback period. The NOX MCR would be calculated in the
same manner as the NOX MER (see Appendix A, section
<IP_ADDRESS>(b)), except that the MEC, rather than the MPC, would be used in
the calculation.
    Finally, today's proposed rule would revise Sec.  75.38(c) to
extend the alternative missing data options for the third and fourth
tiers to mercury (Hg) concentration, and Sec.  75.58(b)(3) would be
revised to be consistent with the proposed revisions to Sec. Sec.
75.34(a)(3), 75.34(a)(5), and 75.38(c).
    EPA believes that for missing data hours in which the emission
controls are working properly, these proposed rule revisions will
prevent gross overestimation of emissions during hours when the source
is operating its emission controls in a manner that is protective of
the environment. When the emission controls are working properly, there
can be as much as a tenfold difference between the MPC, MER, or maximum
value in a lookback period and the actual source emissions. The
proposed alternative substitute data values in Sec. Sec.  75.34(a)(3)
and (a)(5), though much closer to the actual emissions, would still be
conservatively high and would provide the owner or operator with a
strong incentive to keep the CEMS operational. The Agency also believes
that the proposed alternative data substitution methodology in Sec.
75.34(a)(5) ensures that the substitute data values for the fourth tier
will always be higher than the corresponding substitute data values for
the third tier.
3. Substitute Data Values for Hg
    EPA is also proposing to revise the Hg missing data procedures.
First, for Hg CEMS, the text of Sec.  75.38(a) would be amended to make
it consistent with Table 1 in Sec.  75.33. Proposed Sec.  75.38(a)
clarifies that the percent monitor data availability (PMA) ``trigger
conditions'' for Hg monitoring systems are different from the trigger
conditions for all other parameters. For all parameters except Hg, the
trigger points that define the boundaries of the four missing data
tiers are 95 percent, 90 percent, and 80 percent PMA. However, for Hg
the corresponding trigger points are 90 percent, 80 percent and 70
percent, respectively.
    Second, EPA proposes to completely revise the missing data
provisions in Sec.  75.39 for sorbent trap monitoring systems. In the
current rule, the missing data routines for sorbent trap systems are
substantially different from those for Hg CEMS. At the time of
publication of the Part 75 Hg monitoring provisions, the Agency
believed that a different approach to missing data substitution was
appropriate for sorbent traps, because unlike the Hg CEMS, a sorbent
trap system does not provide real-time hourly average emissions data.
Consequently, EPA prescribed a 12-month missing data ``lookback''
period for the sorbent trap systems. That is, the substitute data
values are based on a lookback through the previous 12 months of
sorbent trap sample results, instead of looking back through 720
quality-assured monitor operating hours, as is done for the Hg CEMS.
    EPA has reconsidered the sorbent trap missing data methodology and
has concluded that it is unnecessarily complex and will likely be
difficult to implement and audit. In view of this, the Agency proposes
to amend the missing data procedures for sorbent trap systems, to make
them the same as for Hg CEMS. Section 75.39 would be revised to require
that the initial missing data procedures of Sec.  75.31(b) and the
standard Hg missing data provisions of Sec.  75.38 be followed for
sorbent trap systems. EPA believes that this missing data approach can
work because for the purposes of Part 75 reporting, the average Hg
concentration measured by a sorbent trap system is ``back-filled'' into
each hour of the data collection period to simulate hour-by-hour
concentration measurements (see Sec.  75.57(j)(1)(iii)). Thus, the
hourly Hg concentration data stream from a sorbent trap system will
look essentially the same as the data stream from a CEMS, except that
the Hg concentration will ``flat-line'' (i.e., will not change) during
each data collection period. Therefore, the required missing data
lookbacks through 720 hours of quality-assured data could be done on
the

sorbent trap data stream, although in some cases, because of the flat-
line effect, when the 720 hours of data are arranged in rank order, the
90th percentile, 95th percentile, and maximum values in the lookback
might be identical.
    Finally, a new paragraph ``(f)'' would be added to Sec.  75.39 to
address the case in which the owner or operator elects to use a primary
Hg CEMS and a redundant backup sorbent trap system (or vice-versa). In
that case, separate Hg concentration data streams would be recorded and
maintained for the two systems. For reporting purposes, data from the
primary monitoring system would be reported whenever that system is
able to provide quality-assured data (see Sec.  75.10(e)), and quality-
assured data from the redundant backup system (if available) could be
reported during primary monitoring system outages. However, when both
the primary and redundant backup monitoring systems are down and
quality-assured data from a reference method or approved alternative
monitoring system are also unavailable, proposed Sec.  75.39(f) would
require the appropriate substitute data values to be derived from a
lookback through the previous 720 hours of quality-assured data
reported in the electronic quarterly report, irrespective of the source
of those data, i.e., whether they were from the primary system, the
redundant backup system, a reference method, or an approved alternative
monitoring system.
4. Correction of Cross-References
    For sources in the NOX Budget Program that report
emissions data only during the ozone season (i.e., May through
September), the quality assurance requirements for the continuous
emission monitoring systems are found in Sec.  75.74(c). In Sec. Sec.
75.74(c)(3)(xi) and (c)(3)(xii), data validation rules are provided for
situations in which required quality-assurance tests of the CEMS are
due by the end of the second or third calendar quarter, but are not
completed on time. In some cases, these rule provisions require the use
of missing data substitution, and refer to the ``appropriate missing
data routine in Sec.  75.31, Sec.  75.33 or Sec.  75.37''. These
references to specific missing data sections are inadequate, because
they only cover initial missing data (for all parameters) and the
standard missing data procedures for NOX , flow rate, and
moisture. Sections 75.34 through 75.36 are not referenced, which
address missing data substitution for units with add-on emission
controls and for diluent gas (O2 or CO2) data
used for heat input rate determination. Many NOX Budget
Program units are equipped with add-on NOX emission
controls, and a great number use data from a CO2 or
O2 monitor to determine the hourly heat input rate. In view
of this, today's rule would revise Sec. Sec.  75.74(c)(3)(xi) and
(c)(3)(xii) by replacing each of the cross-references to specific
missing data sections with a more general reference to the entire block
of CEMS missing data sections, i.e., Sec. Sec.  75.31 through 75.37.

E. Recordkeeping and Reporting

1. Revisions to the General Monitoring Plan Recordkeeping Requirements
    EPA proposes to revise the monitoring plan recordkeeping
requirements in Sec.  75.53, to accommodate its new, re-engineered XML
reporting format, which will replace the current electronic data
reporting (EDR) format in 2009. The Subpart H monitoring plan record
keeping provisions in Sec.  75.73(c)(3) (for sources reporting
NOX mass emissions) and the Subpart I monitoring plan record
keeping provisions in Sec.  75.84 (for sources reporting Hg mass
emissions) would be similarly revised to reflect the transition to XML
format.
    EPA proposes to add two new paragraphs, (g) and (h), to Sec.
75.53, which describe the required monitoring plan data elements in
EPA's re-engineered XML data structure. Proposed Sec.  75.53(a)(1)
would require all affected units to follow the provisions of paragraphs
(g) and (h) instead of the existing recordkeeping requirements of
paragraphs (e) and (f), on and after January 1, 2009. However, early
implementation of the XML format would be allowed or, in some cases,
required. In 2008, existing sources would be allowed to choose between
the EDR format and XML, and new sources reporting for the first time in
2008 would be required to use XML.
    Table 1 summarizes the data elements or requirements in Sec.  75.53
that would be removed, replaced or added as a result of transitioning
from the current EDR to XML EDR format.

      Table 1.--Monitoring Plan Changes Associated With XML Format
------------------------------------------------------------------------
      Data element(s) or             Proposed
        requirement(s)              action(s)             Comments
------------------------------------------------------------------------
 Facility short name..  Remove...........  These data elements
 Unit program                               would be collected
 classification.                                    and maintained
 Unit boiler type.....                      through the
 Date of commence                           Certificate of
 operation (Subpart H units).                       Representation form,
 Date of commence                           the CAMD Business
 commercial operation (Acid                         System, or
 Rain units).                                       internally by EPA.
 Unit retirement date.
 Program code.........
 Reporting frequency..
 Program participation
 date.
 State regulation code
 State or local agency
 code.
 EIA cross-reference
 information..
 Recording and          Relocate.........  Relocate the
 reporting of information                           requirement to
 associated with monitoring                         record and report
 system certification,                              this information to
 recertification, and other                         Sec.   75.59, the
 events.                                            quality-assurance
                                                    recordkeeping
                                                    section.
 Fuel classification    Remove...........  These data elements
 for boiler.                                        are deemed
 Primary/secondary                          unnecessary for the
 control indicator.                                 new XML reporting
 Type of fuel                               format.
 associated with each
 monitoring methodology.
 Primary/secondary
 methodology indicator.
 Appendix E
 correlation curve segment
 data..

 Component status.....  Replace..........  In Sec.   75.53(g),
 Formula status.......                      use activation date/
 Submission status of                       hour and
 fuel flowmeter data..                              deactivation date/
                                                    hour instead of
                                                    status codes to
                                                    better track updates
                                                    to monitoring
                                                    components,
                                                    formulas, and fuel
                                                    flowmeter
                                                    information.
 Indicator of           Add..............  These new data
 exemption from multi-load                          elements are needed
 flow RATAs.                                        to properly assess
 Shape of stack or                          specific Part 75
 duct cross-section.                                quality assurance/
 Stack/duct material                        quality control (QA/
 of construction.                                   QC) requirements and
 Flag to indicate that                      exemptions.
 a monitored location is a
 duct.
 Indicator of non-load
 based units..
 Analyzer range code..  Add..............  Provide the
 Moisture measurement                       measurement range
 basis..                                            (high, low, dual)
                                                    and moisture basis
                                                    (wet or dry) for
                                                    each CEMS component
                                                    type (SO2, NOX, CO2,
                                                    etc.)
 Provide the            Replace..........  For each parameter,
 monitoring methodologies for                       associate the
 each individual unit.                              monitoring
 Represent bypass                           methodology with the
 stack monitoring as a                              monitored lcoation
 separate methodology..                             (unit, stack or
                                                    duct). Integrate
                                                    bypass stack
                                                    monitoring with
                                                    other methodologies.
                                                    Only one monitoring
                                                    methodology per
                                                    paramter would be
                                                    allowed.
 For dual-range         Add..............  Many times data begin
 applications, indicate the                         to be recorded on
 trigger point at which the                         the high scale at a
 component switches from the                        certain ``trigger
 normal measurement scale to                        point'', before the
 the secondary scale.                               full-scale of the
                                                    low range is
                                                    reached. EPA needs
                                                    this information to
                                                    determine when
                                                    certain QA tests of
                                                    the high-scale are
                                                    required.
 Require operating      Revise...........  In Sec.   75.53(g),
 range and normal load                              require operating
 information to be reported                         range and maximum
 for units with CEMS and units                      load information for
 using optional fuel flow-to-                       all affected units.
 load ratio test.                                   Require normal load
                                                    determination for
                                                    all except peaking
                                                    units. Separate the
                                                    date of historical
                                                    load analysis from
                                                    activation date of
                                                    the operating range
                                                    and load
                                                    information.
 Duct width at test     Add..............  Add data elements to
 section.                                           Sec.   75.53(e) and
 Duct depth at test                         (g), describing
 section.                                           monitoring plan
 WAF..................                      requirements for
 Method of determining                      units with
 WAF.                                               rectangular ducts
 WAF effective date                         that apply a wall
 and hour.                                          effects adjustment
 WAF no longer                              factor (WAF) to
 effective date and hour.                           their flow rate
 WAF determination                          data. (See Section
 date.                                              II.E.2 for further
 Number of WAF test                         discussion.)
 runs.
 Number of Method 1
 traverse points in WAF test.
 Number of test ports
 in WAF test.
 Number of Method 1
 traverse points in reference
 flow RATA..
------------------------------------------------------------------------

2. Discussion of Wall Effects Adjustment Requirements for Rectangular
Ducts
    In 1999, EPA published a new reference method, Method 2H, in
Appendix A of 40 CFR Part 60. Method 2H allows the owner or operator of
a unit with an installed flow monitor to correct the measured gas flow
rates for velocity decay near the stack wall (i.e., ``wall effects'').
Applying Method 2H greatly reduces the possibility of over-reporting
SO2 and NOX mass emissions, which are directly
proportional to the stack flow rate. However, Method 2H applies only to
circular stacks. Consequently, Acid Rain and NOX Budget
Program units with flow monitors installed on rectangular stacks or
ducts (estimated at about 10 percent of the affected units with flow
monitors) were unable to benefit from the use of a wall effects
adjustment factor (WAF).
    To remedy this situation, a wall effects correction method for
rectangular stacks and ducts was developed. The method, known as CTM-
041, has been adopted as a conditional test method by EPA. A
conditional test method differs from a reference method in that it is
not in the Code of Federal Regulations, but it is recognized as having
technical merit. Sources interested in using a conditional method in a
particular program must obtain permission from the regulatory agency
administering the program.
    Since 2004, when CTM-041 was adopted as a conditional EPA test
method, many Acid Rain and NOX Budget Program sources have
requested (and received) permission from EPA to use it for Part 75
monitoring. As a condition of these approvals, the sources were asked
to report the essential wall effects information in their quarterly
electronic data reports (EDRs). However, EPA had not developed the
necessary electronic record types (RTs) to accommodate the rectangular
duct WAF information. Therefore, the Agency issued guidance,
instructing the sources to use existing EDR record type 910 to report
the WAF data. But record 910, unlike the other EDR record types, has no
fixed data elements or fields. This created problems when the WAF
information began to be reported. Even though detailed examples were
provided in the EPA guidance, a significant portion of the WAF data
were being entered into the wrong columns of the 910 records, making it
difficult to perform electronic audits of the information.
    In view of this, EPA created two new EDR record types, RT 532 and
RT 617, to handle the rectangular duct WAF data. Record type 532, which
is a monitoring plan record, summarizes the results of each WAF
determination. Record type 617 is a quality-assurance record and is
submitted along with the results of each flow RATA performed at a
rectangular stack or duct, when EPA Method 2 is used and a wall effects
correction is applied.
    The Agency provided a mechanism (the ``Monitoring Data Checking''
(MDC) Software) by which a source could

create the new EDR records and add them to the quarterly report,
without having to upgrade the data acquisition and handling system
(DAHS). To date, use of the new record types has been voluntary, and
the affected sources have been cooperative. Nevertheless, today's rule
would make mandatory the recording and reporting of the key rectangular
duct WAF data elements using these record types. The proposed
requirements to record and report the results of the WAF determinations
in the monitoring plan are found in Sec. Sec.  75.53(e) and (g) and in
Sec.  75.64. For a discussion of the proposed requirement to record and
report the RATA support data, see Section II.E.5.k, below.
3. Revisions to General Recordkeeping Provisions for Specific
Situations
    Today's proposed rule would make a series of modifications to Sec.
75.58 to support the new XML data structure. These are summarized in
Table 2.

 Table 2.--Proposed Changes to the General Recordkeeping Requirements in
                              Sec.   75.58
------------------------------------------------------------------------
      Data element(s) or             Proposed
        requirement(s)              action(s)             Comments
------------------------------------------------------------------------
 For Appendix D units,  Add to Sec.        This would be
 report ID numbers of formulas   75.58(c).          required on and
 used to calculate SO2 mass                         after January 1,
 emissions and heat input rate.                     2009.
 For Appendix E units,  Add to Sec.        This would be
 report the heat input rate      75.58(d).          required on and
 formula ID for each unit                           after January 1,
 operating hour.                                    2009.
 For LME units that     Revise Sec.        Report the fuel type
 combust more than one type of   75.58(f).          that produces the
 fuel, report the fuel type                         highest emission
 that produces the highest NOX                      rate for each
 emission rate.                                     parameter
                                                    individually (i.e.,
                                                    for SO2, NOX, and
                                                    CO2, as applicable).
 For LME units under    Add to Sec.        This flag is needed
 Sec.   75.19(c)(1)(iv)(C)(9),   75.58(f).          to ensure that the
 indicate whether unit is                           proper NOX emission
 operating at base or peak                          factor is being
 load, each hour.                                   applied.
 For LME units, flag    Add to Sec.        This flag is needed
 each hour in which multiple     75.58(f).          to ensure that the
 fuels are combusted.                               proper emission
                                                    factors are used for
                                                    multiple-fuel hours.
 For LME units using    Revise Sec.        Require only the
 long-term fuel flow, report     75.58(f).          system ID. Long-term
 the component and system ID                        fuel flow systems
 codes.                                             have only one
                                                    component.
------------------------------------------------------------------------

4. Proposed Revisions to the QA/QC Recordkeeping Provisions
    EPA is proposing to make a series of revisions and additions to the
quality assurance and quality control recordkeeping provisions in Sec.
75.59, in support of the XML data format. These are summarized in Table
3.

Table 3.--Proposed Changes to the QA/QC Recordkeeping Provisions of Sec.
                                   75.59
------------------------------------------------------------------------
      Data element(s) or             Proposed
        requirement(s)              action(s)             Comments
------------------------------------------------------------------------
 Describe each          Revise Sec.        Expand to include
 recertification event, and      75.59(a)(8).       events that require
 the date and type of each                          certification and
 recertification test.                              diagnostic testing.
                                                    Add requirement to
                                                    report conditional
                                                    data validation
                                                    begin date (if
                                                    applicable).
                                                    Corresponds to
                                                    current EDR record
                                                    type 556.
 Record component and   Revise Sec.  Sec.  Require only the
 system ID codes for daily         75.59(a) and     component ID for
 calibrations, 7-day             (b).               these tests. This
 calibration error tests,                           requirement would be
 cycle time tests, linearity                        effective on and
 checks, flow monitor leak                          after January 1,
 checks and interference                            2009. The cycle time
 tests, and fuel flowmeter                          test for NOX-diluent
 accuracy tests.                                    systems would be
                                                    simplified.
 Record the test        Revise Sec.        Clarify that test
 number and reason for test,     75.59(a)(1)(viii   number and reason
 for daily calibrations and 7-   ).                 for test code apply
 day calibration error tests.                       only to 7-day
                                                    calibration error
                                                    tests, not to daily
                                                    calibrations.
 Report the span value  Remove from Sec.   The span value in the
 with the results of each         75.59(a)(3)(ii).  monitoring plan
 linearity check.                                   records will be used
                                                    to evaluate the
                                                    linearity checks.
 Provide an on-line or  Add to Sec.        This flag is needed
 off-line indicator flag for     75.59(a)(1).       to properly assess
 all calibration error tests.                       the hour-by-hour
                                                    quality-assurance
                                                    status of CEMS
                                                    following
                                                    calibration error
                                                    tests.
 For flow-to-load       Add, as Sec.       This addition is
 tests of multiple stack         75.59(a)(4)(vii)   needed for
 configurations, indicate        (M).               consistency with the
 whether separate reference                         flow-to-load test
 ratios are calculated for                          reporting
 each stack.                                        instructions
                                                    (current EDR record
                                                    type 605).
 Report sufficient      Remove and         EPA's checking
 information to validate all     reserve Sec.       software no longer
 grace period claims.            75.59(a)(12)(iii   needs this
                                 ).                 information to
                                                    evaluate grace
                                                    periods.
 Record the component   Revise Sec.        On and after January
 and system ID codes for each    75.59(b)(4)(i)(A   1, 2009, record only
 fuel flow-to-load ratio test.   ).                 the system ID for
                                                    these tests.
 Report Appendix E      Revise Sec.        On and after January
 correlation curve test data     75.59(b)(5).       1, 2009, report this
 on a monitoring system basis.                      data on a component
                                                    basis.
 Report the type(s) of  Remove Sec.        This information is
 fuel(s) combusted during each   75.59(b)(5)(i)(H   not needed in the
 run of an Appendix E            ).                 new XML format and
 correlation curve test.                            would not be
                                                    reported after
                                                    December 31, 2008.
 Report the monitoring  Add, as Sec.       This requirement is
 system ID code with reference   75.59(b)(4)(ii)(   consistent with the
 fuel flow-to-load ratio test    N).                reporting
 data.                                              instructions for the
                                                    reference fuel flow-
                                                    to-load ratio
                                                    (current EDR record
                                                    type 629).

 For LME units,         Add, as Sec.       This requirement is
 indicate which test runs are    75.59(d)(1)(xiii   consistent with the
 used to calculate fuel-and-     ).                 reporting
 unit-specific NOX emission                         instructions for NOX
 rates.                                             emission testing of
                                                    LME units (current
                                                    EDR version 2.2,
                                                    record type 650).
 For LME units,         Revise Sec.        This requirement
 multiply the tested NOX         75.59(d)(2)(iii)   applies only to
 emission rate by 1.15, if       and add new Sec.   turbines that
 applicable.                      Sec.              operate only at base
                                 75.59(d)(2)(vi)    or peak load.
                                 and (vii).         Consistent with the
                                                    reporting
                                                    instructions
                                                    (current EDR version
                                                    2.2, record type
                                                    650), reporting of
                                                    an hourly base or
                                                    peak load indicator
                                                    and the default NOX
                                                    emission rate for
                                                    peak load operation
                                                    would be required.
 Record the date and    Add Sec.           This requirement
 hour of completion of all       75.59(f).          would be effective
 required DAHS verifications,                       on and after January
 whether for initial                                1, 2009. EPA needs
 certification,                                     this information to
 recertification, or other                          properly establish
 events.                                            provisional
                                                    certification or
                                                    recertification
                                                    dates. Proposed
                                                    changes to Sec.
                                                    75.63(a)(2)(iii)
                                                    would allow this
                                                    information to be
                                                    reported
                                                    electronically as
                                                    part of the
                                                    certification or
                                                    recertification
                                                    application.
 Record the             Add Sec.           For periodic testing
 appropriate reference method    75.59(e).          of low mass emission
 data elements for Hg emission                      units, recording of
 tests of low-emitting units.                       the reference method
                                                    data elements in
                                                    either Sec.
                                                    75.59(a)(7)(vii),
                                                    (viii), or (x) would
                                                    be required,
                                                    depending on which
                                                    reference method is
                                                    used for the
                                                    testing.
 Monitoring system ID   Add, as Sec.       Recording of certain
 Test number..........   75.59(a)(7)(ix).   data elements and
 Operating level......                      test results would
 RATA end date and                          be required for
 time.                                              units with
 Number of Method 1                         rectangular ducts/
 traverse points.                                   stacks that apply a
 Wall effects                               wall effects
 adjustment factor.                                 adjustment factor
                                                    (WAF) to correct
                                                    their flow rate
                                                    data. These data
                                                    elements would be
                                                    required for each
                                                    flow RATA.
 Percent CO2 and O2 in  Add, as Sec.       Recording of certain
 the stack gas, dry basis        75.59(a)(7)(x).    data elements would
 Moisture content of                        be required when
 the stack gas (percent H2O).                       using Method 29 for
 Average stack gas                          the RATA of a Hg
 temperature ([deg]F).                              monitoring system.
 Dry gas volume                             These data elements
 metered (dscm).                                    would be required
 Percent isokinetic...                      for each RATA run.
 Particulate Hg
 collected in the front half
 of the sampling train,
 corrected for the front-half
 blank value ([mu]g).
 Total vapor phase Hg
 collected in the back half of
 the sampling train, corrected
 for the back-half blank value
 ([mu]g).
------------------------------------------------------------------------

5. Other Reporting Issues
a. Long-Term Cold Storage and Deferred Units
    The proposed changes to Part 75 would clarify the issue of ``long-
term cold storage (LTCS)''. First, as previously noted, a definition of
``long-term cold storage'' would be added to Sec.  72.2. LTCS would
mean that the unit has been completely shut down and placed in storage
and that the shutdown is intended to last for an extended period of
time (at least two calendar years). Second, a new paragraph, (a)(7),
would be added to Sec.  75.61. Proposed Sec.  75.61(a)(7) would require
the owner or operator to provide notifications when a unit is placed in
LTCS and when the unit re-commences operation. Third, Sec.  75.20(b)
would be modified to require recertification of all monitoring systems
when a unit re-commences operations after a period of long-term cold
storage. If a source claiming LTCS status re-commenced operation sooner
than two years after being placed in LTCS, the notification and
recertification requirements would apply. Fourth, the proposed rule
would exempt a unit in LTCS from quarterly emissions reporting under
Sec.  75.64 until the unit recommences operation. Parallel rule
provisions and appropriate cross-references regarding quarterly
reporting requirements for Subpart H and Subpart I units would be added
to Sec. Sec.  75.73(f)(1) and 75.84(f)(1), respectively. Finally, EPA
notes that these proposed LTCS provisions are not intended to apply to
periods of non-operation of units that are ``on-call'' and available
for dispatch.
    EPA also proposes to revise the provisions of Sec. Sec.  75.4(d)
and 75.61(a)(3) pertaining to ``deferred'' units, i.e., units for which
a planned or unplanned outage prevents the required continuous
monitoring systems from being certified by the compliance date. The
scope of Sec.  75.4(d) would be broadened beyond the Acid Rain Program
to include units in a State or Federal pollutant mass emissions
reduction program that adopts the monitoring and reporting provisions
of Part 75. Examples of such programs include the Clean Air Interstate
Regulation (CAIR), which is scheduled to begin in 2008 and the Clean
Air Mercury Regulation (CAMR), which goes into effect in 2009. The
revisions to Sec. Sec.  75.4(d) and 75.61(a)(3) are deemed necessary
because the CAIR and CAMR rules do not address deferred units.
    Revised Sec.  75.4(d) would require the owner or operator of a
deferred unit to provide notice of unit shutdown and recommencement of
commercial operation, either according to Sec.  75.61(a)(3) (for
planned shutdowns such as scheduled maintenance outages and for
unplanned, forced unit outages) or Sec.  75.61(a)(7) (for units in
long-term cold storage). For all of these circumstances involving
deferred units, the Part 75 continuous monitoring systems would have to
be certified within 90 unit operating days or 180

calendar days (whichever comes first) of the date that the unit
recommences commercial operation. In the time interval between the unit
re-start and the completion of the required certification tests, the
owner or operator would be required to report emissions data, using
either: (1) Maximum potential values; (2) the conditional data
validation procedures of Sec.  75.20(b)(3); (3) EPA reference methods;
or (4) another procedure approved by petition to the Administrator
under Sec.  75.66.
    Today's proposed rule would revise the notification requirements of
Sec.  75.61(a)(3) to be consistent with the changes to Sec.  75.4(d).
For planned unit outages, the owner or operator would be required to
provide notice of shutdown at least 21 days prior to the compliance
date. For unplanned outages, notice would be provided within 7 days
after the shutdown. For both planned and unplanned outages, notice of
the date on which the unit is expected to resume operation would be
provided at least 21 days prior to that date. Proposed Sec.
75.61(a)(3) also includes provisions to address situations in which
there are changes to any of the planned or projected dates.
b. Notice of Initial Certification Deadline
    EPA proposes to revise Sec.  75.61(8) to require new and newly-
affected sources to notify EPA when the monitoring system certification
deadline is reached. Depending on the program(s) to which the unit is
subject and whether the unit is new or newly-affected, this date will
be the earlier of 90 unit operating days or 180 calendar days after the
unit: (a) Commences commercial operation; (b) commences operation; or
(c) becomes an affected unit. The Agency must know this date to
correctly assess when to begin counting emissions against allowances
pursuant to Sec.  72.9. Knowing this date also confirms that the
monitoring systems either have or have not been certified by the legal
deadline.
c. Monitoring Plan Submittal Deadline
    Today's proposed rule would change the submittal deadline for the
initial monitoring plan for new and newly-affected units from 45 days
to 21 days prior to the initial certification testing. This proposed
revision would synchronize the initial monitoring plan submittal with
the initial test notice (see proposed changes to Sec. Sec.  75.62(a)(1)
and (2), Sec. Sec.  75.73(e)(1) and (2) for Subpart H units, and
Sec. Sec.  75.84(e)(1) and (e)(2) for Subpart I units).
    EPA also proposes to remove the requirement in Sec.  75.62(a)(1)
that the monitoring plan must be submitted ``in each electronic
quarterly report''. Rather, inclusion of the monitoring plan in the
report would be optional, and monitoring plan updates would be made
either prior to or concurrent with (but not later than) the date of
submission of the quarterly report. These proposed revisions would
allow sources to maintain their monitoring plan information separate
from the quarterly report. However, this flexibility would only be
available to sources reporting in the new XML-EDR format under the re-
engineered data submission process. Until re-engineering of the data
systems is complete, EPA will continue to collect and process all
electronic monitoring plan data submitted in quarterly reports in the
current EDR format.
d. EPA Form 7610-14
    For each certification and recertification application, Sec. Sec.
75.63(a)(1) and (a)(2) require hardcopy EPA form 7610-14 to be
submitted to the Administrator along with the certification or
recertification test results in EDR format. However, significant
upgrades to EPA's data systems have been made in recent years, and Form
7610-14 is no longer needed to process the applications. Therefore,
Sec. Sec.  75.63(a)(1)(i)(A) and (a)(2)(i) would be revised to remove
the requirement to submit Form 7610-14 to the Administrator.
e. LME Applications
    EPA is proposing to remove the requirement from Sec.
75.63(a)(1)(ii)(A) for a hardcopy LME certification application to be
submitted to the Administrator. Only the electronic portion of the
application, including the monitoring plan and LME qualification
records, would be sent to EPA. The hardcopy portion of the LME
application would be sent to the State and to the EPA Regional Office.
f. Reporting Test Data for Diagnostic Events
    EPA proposes to revise Sec.  75.63(a)(2)(iii) to make the reporting
of the results of diagnostic tests more flexible. Rather than requiring
these test results to be reported in the electronic quarterly report
for the quarter in which the tests are performed, they could either be
submitted prior to or concurrent with that quarterly report. However,
this flexibility in the reporting of diagnostic test results would only
be available to sources reporting in the new XML-EDR format under the
re-engineered data submission process. Until re-engineering of the data
systems is complete, EPA will continue to collect and process all
diagnostic test results submitted in quarterly reports in the current
EDR format.
g. Modifications to Sec.  75.64
    As part of its data systems re-engineering effort, EPA proposes to
revise Sec.  75.64(a) to incorporate language describing the transition
from the current reporting requirements of paragraphs (a)(1), (a)(2)
and (a)(8) through (a)(15) to the new requirements of paragraphs (a)(3)
through (a)(15). Note that only the requirements of paragraphs (a)(1)
and (a)(2) of the current rule would be replaced, by the requirements
of paragraphs (a)(3) through (a)(7). Proposed paragraphs (a)(3) through
(a)(7) better describe the separation of the monitoring plan and
quality assurance test information from the quarterly emissions report.
Current paragraphs (a)(3) through (a)(7) and (a)(9) through (a)(11)
would remain unchanged, but would be renumbered as paragraphs (a)(8)
through (a)(15). Current paragraph (a)(8) would be removed.
h. Steam Load Reporting
    Historically, Part 75 has required units that produce electrical or
thermal output to report unit load either in megawatts or in thousands
of pounds per hour of steam. Today's proposed rule would add a third
option, i.e., to report load in units of mmBtu/hr of steam thermal
output. This option is needed to accommodate emissions trading programs
in which allowance allocations are made on an electrical or thermal
output basis, rather than a heat input basis. Certain units in these
programs (e.g., industrial boilers) do not produce electrical output
and would have to report thermal output instead. In the current rule,
steam load is expressed only in thousands of pounds per hour, which
does not provide the necessary thermal output information. EPA
therefore proposes to add text to the following sections of Part 75,
describing the new thermal output reporting option: Sec. Sec.
75.16(e)(3), 75.57(b)(3), 75.59(b)(4)(ii); Appendix A, Sections 7.7(a)
and 7.7(c); Appendix B, Sections 2.2.5(a) and 2.2.5(a)(2); Appendix D,
Sections <IP_ADDRESS>(a), <IP_ADDRESS>(c), <IP_ADDRESS>(a), and <IP_ADDRESS>(c); and
Appendix E, Section 2.4.1.
i. Test Notification Requirements--Hg Low Mass Emission Units
    Section 75.61(a)(5) of the current rule requires the owner or
operator or the designated representative to provide 21-day advance
notice for various periodic quality-assurance tests. In particular,
this notice must be provided to the

Administrator, to the appropriate EPA Regional Office and to the State
or local agency (unless a particular agency issues a waiver from the
requirement) for the semiannual or annual relative accuracy tests of
CEMS, and for re-tests of both Appendix E peaking units and low mass
emissions (LME) units.
    Under Subpart I of Part 75, certain low-emitting units covered by
CAMR may qualify under Sec. Sec.  75.81(b) through (d) to perform
periodic (semiannual or annual) Hg emission testing in lieu of
operating and maintaining continuous Hg monitoring systems. Today's
proposed rule would expand Sec.  75.61(a)(5) and add corresponding
introductory text to Sec.  75.61(a)(1) to require the owner or operator
or the designated representative to provide 21 day notice of these
periodic Hg emission tests to EPA and to the State.
j. Hardcopy Reports for Retests of Hg Low Mass Emission Units
    Sections 75.60(b)(6) and (b)(7) of the current rule require the
designated representative (DR) to submit the results of certain
periodic quality-assurance tests to the appropriate EPA Regional Office
or to the State or local agency, when the test results are requested in
writing (or by electronic mail). In particular, the results of
semiannual or annual RATAs of CEMS and the routine re-tests of Appendix
E units may be requested. If requested, the test results must be
submitted within 45 days after the test is completed or within 15 days
of the request, whichever is later. Today's rule would add a new
paragraph (b)(8) to Sec.  75.60, requiring the DR to provide, upon
request from EPA or the State, the results of the semiannual or annual
mercury emission tests required under Sec.  75.81(d)(4) for low-
emitting units covered by CAMR. The time frame for submitting these Hg
emission test results would be the same as for the RATAs and Appendix E
re-tests.
k. Wall Effects Adjustment Factors
    As previously discussed in Section II.E.2 of this preamble, today's
rule would require sources with flow monitors installed on rectangular
stacks or ducts to report the results of wall effects adjustment factor
(WAF) determinations in the monitoring plan, whenever Conditional
Method CTM-041 is used to adjust the measured stack gas flow rates for
the effects of velocity decay near the stack wall.
    For sources with flow monitors installed on circular stacks,
reporting of wall effects information is currently required when Method
2H is used in conjunction with Method 2, 2F or 2G (see Sec. Sec.
75.64(a)(2)(xiii), 75.73(f)(1)(ii)(K) and 75.84(f)(1)(ii)(I)). The wall
effects data elements that must be reported are found in Sec. Sec.
75.59(a)(7)(ii) and (a)(7)(iii). These data are not reported in the
monitoring plan, but are submitted along with flow RATA results, as
supplementary information.
    For rectangular stacks and ducts, some of the same supporting data
elements in Sec. Sec.  75.59(a)(7)(ii) and (a)(7)(iii) are needed for
flow RATAs performed using Method 2F or 2G, when wall effects
corrections are applied. Additional supporting data elements, not in
the current rule, are also needed for Method 2 flow RATAs when wall
effects adjustments are made. In view of this, today's rule would
revise the text of Sec. Sec.  75.64(a)(2)(xiii), 75.73(f)(1)(ii)(K) and
75.84(f)(1)(ii)(I) and would add RATA support data elements to a new
paragraph, (vii), in Sec.  75.59(a)(7). EPA believes that these
proposed changes will clarify which wall effects data elements must be
reported for circular stacks, which ones are reported for rectangular
stacks and ducts, and which data elements must be reported for both
types of stacks.

F. Subpart H (NOX Mass Emissions)

1. Subpart H Diluent Monitoring Systems
    For coal-fired Subpart H units that calculate NOX mass
emissions as the product of NOX concentration and flow rate
and are required to monitor and report the unit heat input, Sec.
75.71(a)(2) requires the installation of an ``O2 or
CO2 diluent gas monitor''. Consistent with the definition of
a CEMS in Sec.  72.2, this diluent monitor, which is only used for the
heat input determination, should be described as an ``O2 or
CO2 monitoring system''. Today's proposed rule would revise
the text of Sec.  75.71(a)(2) accordingly.
2. Identifying a NOX Mass Methodology
    EPA is proposing to revise Sec.  75.72 to clarify that only one
NOX mass emissions methodology may be identified in the
monitoring plan at any given time. Designation of primary and secondary
NOX mass calculation methodologies would no longer be
allowed. EPA believes that one methodology for NOX mass
emissions is sufficient. If a source is subject to both Subpart H and
to the Acid Rain Program (ARP) and is concerned about losing
NOX data when the diluent component of the NOX
emission rate system is out-of-control, that source should choose the
NOX concentration times flow rate calculation method as the
NOX mass calculation methodology. This would require a
NOX concentration system to be identified in the monitoring
plan, in addition to the NOX emission rate system. The
NOX concentration system would be used only to determine
NOX mass emissions, and the NOX emission rate
system would be used only to meet the ARP requirement to report
NOX in lb/mmBtu.
    Although it is possible with the current EDR format to identify
multiple methodologies for a parameter, this was intended for ARP
applications, not for NOX mass emission measurement.
Multiple methodology records for SO2 are sometimes necessary
when a bypass stack is used. However, as discussed in Section II.E.1 of
this preamble, the reporting of monitoring methodologies is being
restructured as part of EPA's re-engineering effort. Bypass stack
methods are being integrated with other monitoring methods and will no
longer be considered stand-alone methodologies.
3. Reporting of Subpart H Facility Information
    Consistent with the proposed revisions to Sec.  75.64, EPA proposes
to revise Sec.  75.73(f)(1), to phase out the requirement of Sec.
75.73(f)(1)(i)(B) to include facility location information in each
quarterly report.
4. Linearity Check Requirements for Ozone Season-Only Reporters
    For Subpart H sources that report emissions data on an ozone
season-only (OSO) basis, today's proposed rule would revise the
linearity check provisions in Sec. Sec.  75.74(c)(2), (c)(2)(i),
(c)(2)(ii), (c)(3)(ii), (c)(3)(vi), and (c)(3)(viii). Currently, OSO
reporters are required to do a pre-season linearity check, an in-season
second quarter linearity check (in May or June, if the unit operates
for >=168 hours in May and June), and a third quarter linearity check,
if the unit operates for >=168 hours in that quarter. Many sources have
misunderstood these rule provisions, particularly the requirement to
perform an in-season linearity check in the second quarter.
    Since the beginning of the NOX Budget Program, there
have been a number of instances where sources have performed pre-season
linearity checks in April, but have not done the required in-season
linearity checks in May or June. In some cases, this has resulted in
CEMS out-of-control periods and has required the use of missing data
substitution. These sources apparently believed that the April tests
were sufficient to satisfy both the pre-season and second quarter
linearity check requirements because for year-round

reporters, linearity checks are required only once per quarter.
    The current rule also requires OSO reporters to operate and
maintain each CEMS and to perform daily calibration error tests, in the
time period extending from the hour of completion of the pre-season
linearity check through April 30. EPA has found that this rule
provision is not well-understood by the affected sources. It is also
difficult for the Agency to assess compliance with the provision, since
sources are not required to report the results of any off-season
calibration error tests done prior to April. Further, when pre-season
linearity checks are done several months before the ozone season, the
quality of the data at the start of the ozone season is somewhat
questionable.
    In view of these considerations, today's proposed rule would revise
Sec.  75.74(c)(2) to restrict the time period in which pre-season
linearity checks may be conducted. EPA proposes to require the pre-
season linearity checks to be done in the month of April. All
references to performing the pre-season linearity checks at other times
would be deleted, along with the requirement to keep the off-season
daily calibration error tests in a format suitable for inspection.
    Today's proposed rule would also revise Sec.  75.74(c)(2)(i)(D) by
removing the conditional grace period provision and adding a cross-
reference to proposed Sec.  75.74(c)(3)(ii)(E), which addresses data
validation. If the April linearity check is not completed prior to the
start of the ozone season, data from the monitor would be considered
invalid as of May 1, unless the conditional data validation procedures
of Sec.  75.20(b)(3) are applied. Proposed Sec.  75.74(c)(3)(ii)(E)
would allow a probationary calibration error test to be done, to begin
a period of conditional data validation. Then, the linearity check
would be done ``hands-off'' within a 168 unit operating hour period
following the calibration error test. If the linearity check is passed
within the allotted time, the conditionally valid data would be
considered quality-assured, back to the hour of the probationary
calibration error test. If the linearity check is failed, all data from
the monitor would be invalidated back to the beginning of the ozone
season and would remain invalid until a linearity check is passed. If
the linearity check is done after the 168-hour period expires, data
validation would be done according to Sec.  75.20(b)(3)(viii), subject
to the restrictions of Sec.  75.74(c)(3)(xii).
    Today's proposed rule would add a new paragraph (F) to Sec.
75.74(c)(3)(ii), stating that a pre-season linearity check done in
April fulfills the second quarter linearity check requirement. Related
Section 75.74(c)(3)(viii) would be removed and reserved. Further,
proposed Sec.  75.74(c)(3)(ii)(B) would require the third quarter
linearity check to be conducted either by July 30 or within a 168
operating hour period of conditional data validation thereafter.
Finally, proposed Sec.  75.74(c)(3)(ii)(G) would address the case where
a unit operates infrequently and the 168 operating hour conditional
data validation period associated with the April linearity check
extends through the second quarter, into the third quarter. In that
case, if the linearity check is performed and passed in the third
quarter, before the 168 operating hour window expires, then that one
linearity check would satisfy all three of the ozone season linearity
check requirements, i.e., for the pre-season, for the second quarter,
and for the third quarter.
    EPA believes that the proposed linearity check schedule for OSO
reporters would ensure that the gas monitors' response is linear
throughout the ozone season and would simplify the regulation by
reducing the number of required linearity checks from three to two (and
in some cases, one) per season.
5. RATA Requirements for Ozone Season Only Reporters
    For OSO reporters, Part 75 requires, for quality-assurance
purposes, that at the start of each ozone season each required CEMS
must be within the ``window'' of data validation of a current, non-
expired RATA. Section 75.74(c)(2)(ii) states that this requirement can
be met either by performing a RATA in the pre-season (between October 1
and April 30) or, in some instances, by relying on the results of a
RATA done in the previous ozone season. For example, if a RATA was
performed inside the ozone season, in the 3rd quarter of last year, the
window of data validation for the test would extend through the 3rd
quarter of this year, provided that the RATA results show that the CEMS
qualifies for an ``annual'' RATA frequency. However, if a
``semiannual'' test frequency is obtained, the data validation window
would expire at the end of the first quarter of this year, and the RATA
could not be used to validate data in the current ozone season.
Therefore, a pre-season RATA would be required.
    The rule further requires each CEMS to be operated, calibrated and
maintained in the time period extending from the completion of the
RATA, through April 30. This means that if the RATA being used for data
validation in the current ozone season was performed during the last
ozone season, the CEMS would have to be operated, calibrated and
maintained for the entire off-season from October 1 through April 30.
Compliance with this type of requirement is difficult for EPA to
assess, as previously explained in paragraph 4 of this section. Also,
many sources choosing the OSO reporting option find this operation and
maintenance (O&M) requirement to be counter-intuitive, because they
expect to be required to meet Part 75 monitoring obligations only
during the ozone season. If it were discovered during an audit that
this O&M requirement had not been met, a facility could incur
substantial data loss. Further, if a CEMS is not maintained in a manner
consistent with normal operating practices for an extended period of
time following a RATA that was done long before the ozone season, the
results of that RATA may not be a true indicator of the CEMS data
quality at the start of the ozone season.
    In view of these considerations, EPA is proposing to restrict the
window of time in which pre-season RATAs may be performed. Proposed
Sec.  75.74(c)(2)(ii) would require the RATAs to be done either in the
first quarter of the year or in the month of April. This restriction
would prohibit RATAs done in the previous year from being used to
validate data in the current ozone season.
    Section 75.74(c)(2)(ii)(F) would be revised to address data
validation. The proposed data validation rules for RATAs would be
similar to those proposed for linearity checks, i.e., a period of
conditional data validation (720 operating hours) would be allowed when
the pre-season RATA is not completed by the April 30 deadline.
Consistent with these revisions, today's proposed rule would delete the
data validation and conditional grace period provisions in Sec. Sec.
75.74(c)(2)(ii)(G) and (c)(2)(ii)(H) and would remove and reserve
Sec. Sec.  75.74(c)(3)(vi), (vii), and (viii).
    Note that EPA is not modifying the provisions of Sec.
75.74(c)(3)(xii), which allows the results of required quality
assurance tests that are completed early in the fourth quarter, within
a window of conditional data validation, to be submitted with the
electronic data report for the third quarter. This provision provides
sources with a ``last chance'' opportunity to complete the required
quality assurance tests before the final ozone season reports for the
NOX Budget program are due.

6. Determining Peaking Status for Ozone Season Only Reporters
    EPA proposes to revise Sec.  75.74(c)(11) to clarify that when
peaking unit status for ozone season-only reporters is determined,
3,672 hours (i.e., the number of hours in the ozone season) should be
used instead of 8,760 hours in the capacity factor equation. This
clarification is supported by Question 27.1 in the ``Part 75 Emissions
Monitoring Policy Manual''.
7. Calculation of Ozone Season NOX Mass Emissions--LME Units
    Today's rule would correct an organizational error in Subpart H of
Part 75. Section 75.72(f), which describes ozone season NOX
mass calculations for units using the low mass emission (LME)
methodology under Sec.  75.19, would be removed, and its basic content
would be relocated to Sec.  75.71(e). The LME provision in Sec.  75.72
appears to have been inadvertently placed in that section. The
monitoring provisions of Sec.  75.72 apply to common and multiple stack
configurations, whereas Sec.  75.71 addresses unit-level monitoring.
LME is a unit-level monitoring methodology.

G. Subpart I (Hg Mass Emissions)

1. Heat Input Provisions for Common and Multiple Stacks
    Subpart I of Part 75 provides the basic procedures for monitoring
Hg mass emissions and heat input from affected units under CAMR.
However, due to an apparent oversight, the heat input monitoring
provisions for certain monitoring configurations were inadvertently
omitted from the final rule. In particular, the heat input methodology
for common stacks shared by affected and non-affected units, and the
methodology for multiple stack or duct configurations are missing.
Today's rule would add three new paragraphs, (b)(3), (c)(4) and (d)(3)
to Sec.  75.82 to correct this deficiency.
    For the common stack shared by affected and non-affected units,
proposed Sec.  75.82(b)(3) would require the owner or operator to
either measure the total heat input rate at the common stack and
apportion it to the individual units by load, according to Sec.
75.16(e)(3), or to determine the heat input rate at the individual
units by installing a flow monitor and a diluent monitor on the duct
leading from each unit to the common stack. For multiple stack
configurations, proposed Sec. Sec.  75.82(c)(4) and (d)(3) would
require the owner or operator to determine the hourly unit heat input
by measuring the hourly heat input rate (mmBtu/hr) at each stack,
multiplying each stack heat input rate by the stack operating time (hr)
to convert it to heat input (mmBtu), and then summing the hourly stack
heat input values.
2. Low Mass Emission Alternative
    Section 75.81(b) of Subpart I provides an alternative
(``excepted'') monitoring methodology for units with low Hg mass
emissions. To qualify to use this methodology, emission testing is
required to demonstrate that the unit has the potential to emit no more
than 29 lb (464 ounces) of Hg per year. Once a unit qualifies, periodic
retesting (semiannual or annual, depending on the emission level) is
required to demonstrate that the unit is actually emitting less than 29
lb/yr of Hg.
    Section 75.81(e) allows the low mass emission alternative to be
used for common stacks, provided that the units sharing the stack are
tested individually and each one qualifies as a low-emitter. Though not
explicitly stated in the rule, it is implied that the periodic retests
for common stack configurations would also have to be done at the unit
level. EPA is reconsidering this approach, for two reasons: (1) With
respect to the initial certification testing, it appears to be overly
restrictive for at least one particular configuration; and (2) the
Agency believes that for the retests it may be unnecessarily difficult
and costly to implement.
    Therefore, with one exception (discussed below), EPA is proposing
to revise Sec.  75.81(e) to require Hg testing of the individual units
that share the common stack only for the initial demonstration that the
units individually qualify as low emitters. Once this has been
satisfactorily demonstrated, the required semiannual or annual retests
could then be done at the common stack, at a normal load level for the
configuration.
    The proposed revisions to Sec.  75.81(e) would also allow the
initial low mass emitter qualification for a group of identical units
sharing a common stack to be based on emission testing of a subset of
those units. To exercise this option, the units would first have to
qualify as identical under Sec.  75.19(c)(1)(iv)(B). Then, the number
of units required to be tested would be determined from Table LM-4 in
Sec.  75.19.
    The proposed rule would allow one exception to the requirement to
test the individual units sharing a common stack, in order to
demonstrate that the units qualify for low mass emitter status. In the
case where the gas streams from the individual units are combined
together and routed through emission controls that reduce the Hg
concentration (e.g., a wet scrubber) before entering the common stack,
the only way to measure the controlled Hg concentration from the
individual units would be to operate them one at a time rather than
concurrently. EPA believes that for many such configurations, this
manner of unit operation is abnormal and potentially problematic.
Therefore, the revisions to Sec.  75.81(e) would allow both the initial
and ongoing low mass emission testing to be done at the common stack in
cases where the individual unit effluent gas streams are combined
together upstream of a control device that removes Hg before entering
the common stack. Owners or operators electing to use this option would
be required to perform the testing with all of the units that share the
stack in operation, and the combined load during the testing would be
``normal'', as defined in Section <IP_ADDRESS> of Appendix A.
    Today's proposed rule would also revise Sec.  75.81(c)(1), to
clarify the time frame in which to perform the initial certification
testing for the low mass emission option. The current rule simply
states that this testing must be done ``prior to the compliance date in
Sec.  75.80(b)'', but does not specify how far in advance of that date
the testing may be done and still be considered acceptable. Further,
Sec.  75.81(d)(1) requires the test results to be submitted as a
certification application, no later than 45 days after completing the
testing. And Sec.  75.81(d)(4) requires periodic Hg retesting to
commence within two or four ``QA operating quarters'' after the quarter
of the certification testing.
    This approach to implementing the low mass emission alternative
should work reasonably well, provided that the certification test date
is close in time to the compliance date. However if there is too long a
gap between the certification testing and the start of the program, it
becomes problematic. For instance, if the testing is done too early,
the requirement to submit a certification application within 45 days
could result in applications being submitted long before the regulatory
agencies are ready to receive and process them. Also, the periodic
retesting requirements of Sec.  75.81(d)(4), which become active on the
certification test date, could result in several Hg retests being done
before the program begins. This is clearly contrary to the purpose of
the retests, which, like the periodic relative accuracy tests of CEMS,
are intended to commence after the compliance date, when Hg emissions
reporting has begun. It also raises questions about which default
emission rate to use for the initial reporting. In view of these

considerations, EPA is proposing to revise Sec.  75.81(c)(1), to
require that the Hg testing for initial certification be done no more
than 1 year before the compliance date. Sections 75.81(d)(2) and
75.81(d)(5) would also be revised, to address the case where a retest
may be required before the compliance date (e.g., when Sec.
75.81(d)(4) requires a retest within two QA operating quarters,
following a certification test that was done 9 to 12 months before the
compliance date). In such cases, the default Hg emission rate used at
the beginning of the program would be the value that was obtained in
the retest.
    Finally, EPA proposes to amend Sec.  75.81(d)(4) to address the
emission testing requirements when the fuel supply is changed. Revised
Sec.  75.81(d)(4) would require additional Hg retesting within 720 unit
operating hours, following a change in the fuel supply. The results of
this retest would be applied retrospectively, back to the time of the
fuel switch. Section 75.81(c)(1) would also be revised to require that
the fuel combusted during the initial certification testing be from the
same source of supply as the fuel combusted when the program starts.
The Agency believes these rule provisions are necessary to ensure that
the default Hg concentration used for Part 75 reporting is
representative of the fuel being combusted in the unit. However, note
that the proposed revisions only address the emission testing and
reporting requirements for one case, i.e., where the source of supply
for the primary fuel (assumed to be coal) changes. Cases where the coal
supply does not change, but the unit sometimes burns other types of
fuel besides coal or co-fires mixtures of coal and other fuels, are not
addressed. In view of this, EPA also solicits comments and suggestions
on how to apply the Hg low mass emitter option in these situations
(i.e., what emission testing and reporting requirements might be
appropriate).
3. Harmonization of Subpart I With Other Proposed Rule Revisions
    Subpart I of Part 75 also contains a recordkeeping and reporting
section (Sec.  75.84). Section 75.84 contains a few stand-alone
provisions, but for the most part, it cross-references the primary
monitoring plan, recordkeeping, notification and reporting sections of
the rule (i.e., Sec. Sec.  75.53, 75.57 through 75.59, 75.61, and
75.64) and other sections of Subpart I.
    As discussed in detail in Section E of this preamble, today's rule
would make substantial revisions to the monitoring plan, recordkeeping
and reporting sections of Part 75, in support of EPA's data systems re-
engineering effort. To make Subpart I consistent with these proposed
revisions and with the other proposed changes in today's rule, a number
of minor adjustments would also be made to the text of Sec. Sec.
75.84(c)(3), (e)(1), (e)(2), and (f)(1).

H. Appendix A

1. CO2 Span Values
    EPA proposes to revise Section 2.1.3 of Appendix A, to allow the
use of CO2 spans less than 6.0 percent CO2 if a
technical justification is provided in the hardcopy monitoring plan.
This added flexibility in the CO2 span value mirrors a
similar provision in Section 2.1.3 for O2 span values.
2. Protocol Gas Audit Program
    EPA is responsible for implementing air quality programs that rely
on accurate calibration gases. Under these programs, calibration gases
are used to calibrate EPA reference methods which, in turn, are used to
perform stack tests or to calibrate installed pollutant continuous
emissions monitoring systems (CEMs) that are used by regulated sources
to report emissions to EPA. If the reference methods are low by 20%,
then emissions may be underreported by 20%. Calibration gases are also
used to ensure that ambient air quality analyzers provide accurate
results. Accurate calibrations gases are critical in helping to ensure
that the Clean Air Act-mandated emission reductions are achieved.
    Section 2.1.10 of ``EPA Traceability Protocol for Assay and
Certification of Gaseous Calibration Standards'' (Protocol Procedures),
September 1997 (EPA-600/R-97/121) states that EPA will periodically
assess the accuracy of calibration gases and publish the results.
Between 1978 and 1996, EPA conducted several performance audits of
calibration gases from various manufacturers. These audits had two
goals, to provide a quality check for gas vendors and to connect users
with gas vendors. One notable result in the most recent five
consecutive years of audits is a steady, significant reduction in
failure rate of the calibration gases, from about 27% in 1992 down to
5% in 1996. In 2003, EPA conducted a ``surprise'' audit of 14 national
specialty gas producers and found that the failure rate had risen to
11%.
    Today's proposed rule would require that EPA Protocol Gases being
used for 40 CFR Part 75 purposes be obtained from those specialty gas
producers who participate in the audit program. Under the proposed
rule, only audit participants may market these gas standards as ``EPA
Protocol Gases'', although there will be no requirement for
participants' audited standards to meet an accuracy acceptance
criterion. The costs of the audits will be borne by the gas producers
who elect to participate in the audits. Although it may take several
years to revise all of the EPA monitoring regulations in 40 CFR Parts
58 and 60, today's proposed rule would ensure that under Part 75, any
specialty gas producers who do not participate in the program will not
have a price advantage (due to the lack of audit program costs) over
those producers who do participate. An EPA-maintained web site will
list the participants and the audit results, which will provide
calibration gas users with detailed information about the quality of
EPA Protocol Gases.
    To clarify the calibration gas requirements in section 5.1 of
appendix A to this part, a definition for ``specialty gas producer''
has been added to section 72.2. EPA believes that most of the gas
standards and reference materials identified in section 5.1 of appendix
A of this part are expensive and not used in practice by Part 75
affected units. Therefore, today's proposed rule also deletes several
calibration gas options and definitions, and consolidates the remaining
calibration gas descriptions under section 5.1 of appendix A to this
part.
    EPA is also requesting comment on the appropriate accuracy
specification to apply to Hg cylinder gases and other Hg calibration
standards (e.g., gases from NIST-traceable generators). Currently, EPA
requires that accuracy of EPA Protocol gases be within 2 percent of the
certified tag values.
3. Requirements for Air Emission Testing Bodies
    Since the inception of the Acid Rain Program, field audits of Part
75-affected facilities have brought to EPA's attention a number of
improperly-performed RATAs and other QA/QC tests. When the proper test
procedures are not followed, this can adversely affect the quality of
the emissions data, and, in some cases, may call into question a unit's
compliance with the requirement to hold allowances covering its
emissions. In view of this, today's proposed rule would revise Section
6.1 of Appendix A to require all individuals who perform the emission
tests and CEMS performance evaluations required by Part 75 to
demonstrate conformance with ASTM D7036-04 ``Standard Practice for
Competence of Air Emission Testing Bodies''. ASTM D7036-04 specifies
the general requirements for demonstrating

that an air emission testing body (AETB) is competent to perform
emission tests of stationary sources. ASTM D7036-04 covers testing and
calibration performed using standard methods, non-standard methods and
methods developed by the AETB.
    Proposed Section 6.1.2 of Appendix A and revisions to Section 2.1
of Appendix E and to Section 1 of Appendix B would make it clear that
this requirement applies only to AETBs that perform RATAs,
NOX emission tests of Appendix E and LME units, or Hg
emission tests of low-emitting units. It would not be applicable to the
daily operation, daily QA/QC (daily calibration error check, daily flow
interference check, etc.), weekly QA/QC (i.e., Hg system integrity
checks), quarterly QA/QC (linearity checks, etc.), and routine
maintenance of the CEMS.
    ASTM D7036-04 would be incorporated by reference in Sec.
75.6(a)(45), and a definition of ``Air Emission Testing Body'' would be
added to Sec.  72.2.
4. Linearity Requirements for Dual-Span Applications
    Section 6.2 in Appendix A and Section 2.2 in Appendix B require the
owner or operator of affected units with installed gas monitors to
perform periodic linearity checks of the monitors. The basic linearity
check requirements are to perform the test for initial certification
and then, for ongoing quality assurance (QA), to repeat the test
quarterly. In the original Part 75 regulations (published on January
11, 1993), there were no exceptions to these requirements.
    However, in May 1999, EPA revised the linearity check provisions of
Part 75 as follows. First, Section 6.2 of Appendix A was revised to
exempt SO2 and NOX span values of 30 ppm or less
from performing linearity checks. Second, revisions to Section 2.2 of
Appendix B reduced the ongoing linearity check requirement from once
per calendar quarter to once every ``QA operating quarter'' (i.e., a
calendar quarter in which the unit operates for at least 168 hours).
    Since the May 1999 revisions became effective, the regulated
sources appear to have understood the ``QA operating quarter'' concept
in Section 2.2 of Appendix B, but there has been some confusion about
the meaning of the linearity exemption in Appendix A. Some have
questioned whether the linearity exemption applies only to ongoing QA
or whether it applies also to initial certification. Others have asked
whether the exemption applies only to a particular measurement range or
to all of the linearity check requirements for a monitoring system. The
misunderstanding appears to center around two sentences in Section 6.2.
The first sentence states that ``Notwithstanding these requirements, if
the SO2 or NOX span value for a particular range
is < = 30 ppm, that range is exempted from the linearity test
requirements of this part.'' Since the phrase ``of this part'' refers
to Part 75, this seems to exempt ranges of 30 ppm or less from all Part
75 linearity requirements, including initial certification and ongoing
QA. However, the second sentence states that ``For units using emission
controls and other units using both a high and a low span, perform a
linearity check on both the low- and high-scales for initial
certification.'' Thus, for dual span applications, this statement
appears to require linearity checks of both measurement scales for
initial certification regardless of the span values, which does not
harmonize with the 30 ppm exemption.
    EPA believes that the key to understanding and reconciling these
rule texts is the chronological order of the two sentences. The second
sentence is from the original 1993 rule and the first sentence was
added in 1999. Therefore, the 30 ppm linearity check exemption in the
first sentence takes precedence over the low scale linearity check
requirement of the second, and there is no actual contradiction.
However, to eliminate any doubt as to the Agency's intended meaning,
today's rule would revise Section 6.2 of Appendix A to make it clear
that the 30 ppm linearity exemption: (1) Is range-specific; (2) covers
both initial certification and ongoing QA; (3) does not remove the
requirement to perform linearity checks of the high range (if > 30 ppm)
for dual span applications; and (4) does not take away the linearity
check requirements for the diluent monitor component of a
NOX-diluent monitoring system.
5. Dual Span Applications--Data Validation
    Today's proposed rule would revise Sections <IP_ADDRESS> (b)(2) and
<IP_ADDRESS>(b)(2) of Appendix A to clarify the relationship between the
quality-assured (QA) status of the low and high ranges of a gas monitor
in a dual-span application. The changes would be consistent with the
proposed revisions to Appendix B (see Section II.I.3, below).
    In the current rule, Sections <IP_ADDRESS>(b)(2) and <IP_ADDRESS>(b)(2) of
Appendix A provide instructions for reporting SO2 and
NOX concentration data when the full-scale range of the
monitor is exceeded. For single-range applications, a value of 200
percent of the maximum potential concentration (MPC) must be reported
when a full-scale exceedance occurs. For dual range applications, if
the low range is exceeded, no special reporting is necessary, provided
that the high range is ``available and not out-of-control or out-of-
service for any reason''. However, if the high range is ``not able to
provide quality-assured data'' during the low-range exceedance, then
the MPC must be reported.
    EPA believes that for dual range applications, the two phrases used
to describe the QA status of the high range during low-scale
exceedances, i.e., ``available and not out-of-control or out-of-service
for any reason'' and ``not able to provide quality assured data'', are
too general and do not adequately address the possible scenarios
associated with dual range monitoring. Today's rule would revise these
rule texts by defining the QA status of the high range in terms of its
most recent calibration error and linearity checks. Provided that both
of these QA tests are still ``active'', i.e., their windows of data
validation have not expired, the high range would be considered in-
control and able to provide quality-assured data. However if either of
the tests has expired, data recorded on the high range would be
considered invalid until the expired test was repeated and passed. The
MPC would have to be reported until the expired high-range test is
redone or until the data return to the low scale.
    These revisions would clarify that when the low range is up-to-date
on its QA tests but the high range is not, the QA statuses of the two
ranges are evaluated separately and may be different. However, as
explained in greater detail in Section II.I.3, below, the QA statuses
of the low and high ranges are not necessarily independent when a
calibration error test or a linearity check on one of the ranges is
failed.
6. Cycle Time Test--Stability Criteria
    The cycle time test described in Section 6.4 of Appendix A is
required for the initial certification and recertification of gas
monitoring systems, and occasionally as a diagnostic test. The
``upscale'' portion of the test consists of injecting a zero-level
calibration gas, allowing the reading to stabilize, recording it, and
then stopping the calibration gas flow, waiting until a stable reading
of the source emissions is obtained, and recording it. The
``downscale'' portion of the test is performed in like manner, except
that a

high-level calibration gas is used instead of the zero-level gas.
    Section 6.4 currently specifies criteria for determining when a
stable reading has been obtained. The reading is considered stable if
it changes by less than 2.0 percent of the span value for 2 minutes or
less than 6.0 percent from the average concentration over 6 minutes.
These criteria are reasonable when the source effluent concentrations
are moderate or high. However, when concentrations are very low, the
criteria are quite stringent and can be very difficult to meet. For
example, if the span value of a NOX analyzer is 10 ppm and
the average measured source emissions are 3 ppm, the source emissions
would have to remain constant within about 0.2 ppm for the specified
amount of time to meet the stability criteria.
    In recent years, hundreds of new combustion turbines (CTs) have
been built. The vast majority are subject to Part 75, are equipped with
NOX monitoring systems, and have NOX permit
limits less than 10 ppm. Therefore, the 0.2 ppm cycle time stability
criterion in the example above is realistic and applies to many of
these new CTs. To provide a measure of relief for these low-emitting
sources, today's rule would add alternative stability criteria to
Section 6.4 of Appendix A. By the alternative criteria, an
SO2 or NOX reading would be considered stable if
it changed by no more than 0.5 ppm for 2 minutes or, for a diluent
monitor, if it changed by no more than 0.2% CO2 or
O2 for 2 minutes. EPA believes these alternative stability
criteria are needed to ensure that minor temporal variations in the
concentration of the source effluent do not cause testers to
overestimate the amount of time it takes to achieve stable readings,
resulting in ``false positive'' failures of the cycle time test.
7. System Integrity and Linearity Checks of Hg CEMS
    Subpart I of Part 75 includes certification test procedures and
performance specifications for Hg CEMS. The required certification
tests for a Hg CEMS include a 3-level system integrity check, using a
NIST-traceable source of oxidized Hg and a 3-level linearity check,
using elemental Hg standards. The performance specification for the
system integrity check, which is found in paragraph (3)(iii) of
Appendix A, Section 3.2, states that the system measurement error must
not exceed 5.0 percent of the span value at any of the three
calibration gas levels. However no explanation of how to calculate the
measurement error is provided. Today's proposed rule would restructure
paragraph (3) of Section 3.2 (as described in the next paragraph) and
add the necessary mathematical procedure.
    EPA is also proposing to make the linearity and system integrity
check specifications for Hg monitors the same. The principal linearity
error specification in Section 3.2(3)(i) is currently 10.0 percent of
the reference gas tag value at each calibration concentration, when
calculated according to Equation A-4. The alternative specification in
Section 3.2(3)(ii) allows an absolute difference of up to 1.0 [mu]g/
m\3\ between the average reference gas and monitor values at each
calibration gas level. Today's proposed rule would replace the
principal linearity error specification with a specification of 5.0
percent of the span value, and would lower the alternative
specification to 0.6 [mu]g/m\3\. Further, the same 0.6 [mu]g/m\3\