[Federal Register Volume 72, Number 70 (Thursday, April 12, 2007)]
[Proposed Rules]
[Pages 18428-18434]
From the Federal Register Online via the Government Publishing Office [www.gpo.gov]
[FR Doc No: E7-6948]
[[Page 18428]]
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ENVIRONMENTAL PROTECTION AGENCY
40 CFR Part 52
[EPA-R04-OAR-2005-AL-0002-200623; FRL-8298-1]
Approval and Promulgation of Implementation Plans: Alabama:
Proposed Approval of Revisions to the Visible Emissions Rule
AGENCY: Environmental Protection Agency (EPA).
ACTION: Proposed rule.
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SUMMARY: EPA is proposing to approve the Visible Emissions portion of
the State Implementation Plan (SIP) revision submitted to EPA, by the
Alabama Department of Environmental Management (ADEM), on September 11,
2003 (the ``2003 ADEM submittal''), provided it is revised as described
in this action and submitted as a SIP revision. The open burning
portion of the submittal was previously approved in a separate action
on March 9, 2006 (71 FR 12138).
DATES: Comments must be received on or before June 11, 2007.
ADDRESSES: Submit your comments, identified by Docket ID No. EPA-R04-
OAR-2005-AL-0002, by one of the following methods:
(a) www.regulations.gov: Follow the on-line instructions for
submitting comments.
(b) E-mail: [email protected].
(c) Fax: 404-562-9019.
(d) Mail: ``EPA-R04-OAR-2005-AL-0002,'' Regulatory Development
Section, Air Planning Branch, Air, Pesticides and Toxics Management
Division, U.S. Environmental Protection Agency, Region 4, 61 Forsyth
Street, SW., Atlanta, Georgia 30303-8960.
(e) Hand Delivery or Courier: Stacy Harder, Regulatory Development
Section, Air Planning Branch, Air, Pesticides and Toxics Management
Division, 12th floor, U.S. Environmental Protection Agency, Region 4,
61 Forsyth Street, SW., Atlanta, Georgia 30303-8960. Such deliveries
are only accepted during the Regional Office's normal hours of
operation. The Regional Office's official hours of business are Monday
through Friday, 8:30 to 4:30, excluding federal holidays.
Instructions: Direct your comments to Docket ID No. ``EPA-R04-OAR-
2005-AL-0002.'' 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 through
www.regulations.gov or e-mail, information that you consider to be CBI
or otherwise protected. The 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 www.regulations.gov, your e-mail address will be
automatically captured and included as part of the comment that is
placed in the public docket and made available on the Internet. If you
submit an electronic comment, EPA recommends that you include your name
and other contact information in the body of your comment and with any
disk or CD-ROM you submit. If EPA cannot read your comment due to
technical difficulties and cannot contact you for clarification, EPA
may not be able to consider your comment. Electronic files should avoid
the use of special characters, any form of encryption, and be free of
any defects or viruses. For additional information about EPA's public
docket visit the EPA Docket Center homepage at http://www.epa.gov/epahome/dockets.htm.
Docket: All documents in the electronic docket are listed in the
www.regulations.gov index. Although listed in the index, some
information is not publicly available, i.e., CBI or other information
whose disclosure is restricted by statute. Certain other material, such
as copyrighted material, is not placed on the Internet and will be
publicly available only in hard copy form. Publicly available docket
materials are available either electronically in www.regulations.gov or
in hard copy at the Regulatory Development Section, Air Planning
Branch, Air, Pesticides and Toxics Management Division, U.S.
Environmental Protection Agency, Region 4, 61 Forsyth Street, SW.,
Atlanta, Georgia 30303-8960. EPA requests that if at all possible, you
contact the person listed in the FOR FURTHER INFORMATION CONTACT
section to schedule your inspection. The Regional Office's official
hours of business are Monday through Friday, 8:30 to 4:30, excluding
legal holidays.
FOR FURTHER INFORMATION CONTACT: Stacy Harder, Regulatory Development
Section, Air Planning Branch, Air, Pesticides and Toxics Management
Division, U.S. Environmental Protection Agency, Region 4, 61 Forsyth
Street, SW., Atlanta, Georgia 30303-8960. The telephone number is (404)
562-9042. Ms. Harder can also be reached via electronic mail at
[email protected].
SUPPLEMENTARY INFORMATION:
Table of Contents
I. What Action Is EPA Proposing?
II. Why Is EPA Proposing This Action?
III. What Is the Rationale for This SIP Revision?
IV. What Does the Visible Emissions Rule in the Current SIP Require,
and What Changes Are Requested by ADEM?
V. What Changes Does EPA Recommend to the Submittal?
VI. What Technical Analysis Was Used To Support Approval of This SIP
Revision?
VII. What Happens Next?
VIII. Proposed Action
IX. Statutory and Executive Order Reviews
I. What Action Is EPA Proposing?
EPA is proposing an approval, under Section 110(k) of the Clean Air
Act (CAA), of the Visible Emissions portion of the Alabama SIP revision
submitted on September 11, 2003. This proposed approval is contingent
upon Alabama submitting a revised SIP submission addressing EPA's
concerns regarding impacts of the rule changes on attainment of the
National Ambient Air Quality Standards (NAAQS). Because the necessary
revisions would materially alter both the existing SIP approved rule
and the submitted revision, the State must make a SIP submittal to
effect the changes noted by EPA below. As with any SIP revision, the
State must provide public notice of and a public hearing on the
proposed changes. If, after consideration of public comments, EPA
determines the revised SIP submission meets the requirements of the CAA
and is consistent with the recommended changes outlined in this action,
the Agency may proceed to publish its approval of the revised SIP in
the Federal Register. Alabama's revised submittal must be consistent
with the changes discussed in this action for EPA to approve its
incorporation into the SIP. If the revised language does not conform
specifically to the recommended changes, EPA will need to re-evaluate
Alabama's submittal and, if the changes are approvable, re-propose
approval of the SIP submittal.
II. Why Is EPA Proposing This Action?
EPA is taking this action in response to a request from ADEM to
revise the Visible Emissions portion of Alabama's SIP rule pertaining
to sources of particulate matter (PM) emissions. The request, submitted
to EPA on September 11, 2003, would revise Alabama SIP rule 335-3-4-.01
(``Visible Emissions'') by amending the requirements for units
[[Page 18429]]
that operate continuous opacity monitoring systems (COMS) and that are
not subject to any opacity limits other than those in rule 335-3-
4-.01(1) (``Visible Emissions Restrictions for Stationary Sources'').
Under section 110(l) of the CAA, EPA may not approve revisions to
SIPs if the revisions would interfere with any applicable requirement
concerning attainment and reasonable further progress (RFP), or any
other applicable requirement of the CAA. In determining whether to
approve a requested revision, EPA considers the relevant impacts of the
proposed change in light of the type of requirement affected by the
requested revision. In this instance, the State is proposing revisions
to its opacity requirements. We define opacity as the degree to which
emissions reduce the transmission of light and obscure the view of an
object in the background. (See 40 CFR 60.2).
A change in opacity standards may not necessarily impact on a
State's ability to meet the PM NAAQS or any other applicable
requirement of the Act because, as discussed further in this action, a
reliable and direct correlation between opacity and PM emissions cannot
be established without significant site-specific simultaneous testing
of both PM emissions and opacity, particularly for short-term periods
(e.g., 24 hours or less). Nonetheless, because there is at least an
indirect relationship between opacity and PM emissions, including the
use of opacity to track the effectiveness of PM control equipment
operation, we considered the impact of Alabama's proposed revision on
the NAAQS for PM10 and PM2.5, and on other applicable requirements. No
changes are being proposed to revise the particulate mass limits in the
Alabama SIP, and sources must continue to meet applicable emissions
limits. EPA proposes to approve Alabama's revision, with our
recommended changes, because we determined that, with the changes
specified in this action, the SIP revision will not interfere with
attainment of either of the PM NAAQS or with other applicable
requirements.
III. What Is the Rationale for This SIP Revision?
Monitoring opacity by use of COMS provides far more data than EPA
Reference Method 9, the compliance determination method specified by
most SIPs, including Alabama's. Alabama adopted into the State's
regulations the rule revision contained in the 2003 ADEM submittal on
August 26, 2003, and has since operated under it as a State-only
enforceable provision. The purpose of that rule revision was to make
the State's regulation consistent with what had been its practice in
exercising enforcement discretion with respect to use of COMS data
since the early 1980's.
In addition to requiring corrective actions and prompt reporting of
deviations from permit terms, the State has other oversight procedures
in place that ensure long, continuous periods of high opacity are
properly addressed by the source. ADEM receives quarterly emissions
reports from plants that utilize COMS, which indicate the opacity of
the emissions from sources subject to this rule revision. ADEM reviews
the information and determines if further action should be taken due to
any opacity exceedances. The data is required to be in a format that
includes source operating time, monitor operating time, exempt opacity
exceedances, and non-exempt opacity exceedances. The reports include
daily opacity exceedances as well as a summary of the data for the
entire quarter. In these reports, the sources also calculate the
percentage of operating time in which they had non-exempt opacity
exceedances as well as the percentage of operating time with any (total
of exempt and non-exempt) opacity exceedances.
ADEM has developed a program that takes the summary data from the
quarterly opacity reports and calculates the percentage of source
operating time that the opacity of emissions from individual units (or
multiple units with a common stack) exceeded the opacity standard due
to non-exempt reasons during the calendar quarter. As a check on the
quarterly calculations from the source, this program also calculates
the percentage of operating time that the opacity of emissions from
individual units exceeded the opacity standard for any reason. With
this program, ADEM compares the performance of each unit to the
historical performance of that unit as well as compares it to the
performance of the other units at that plant and other similar plants
in the State, and the performance of the unit to the two percent
threshold in the Alabama submittal. If the performance of a unit is not
consistent with its historical performance or the performance of other
similar units in the State, ADEM can review the daily exceedances of
the opacity standard for the unit in question to determine if the
exceedances were sporadic, or grouped in consecutive hours or
consecutive days. ADEM may also ask the company for a detailed
explanation of the exceedances (or a subset of exceedances) during the
calendar quarter. If, for a source subject to the new standard, the
number of unexcused opacity exceedances is in excess of two percent of
the source operating time for which the opacity standard was applicable
during the quarter, formal enforcement action may proceed.
Opacity limitations have typically accompanied periodic Reference
Method 5 particulate matter compliance tests (Method 5 tests) in SIPs.
That is, where Method 5 tests are used to demonstrate compliance with
filterable PM mass emission limitations, opacity limits and associated
monitoring are commonly used as an indirect monitor for PM emissions
and as indicators of good PM control equipment operation during the
periods between Method 5 tests. EPA has long recognized opacity
monitoring as a method of ensuring proper control device operation. See
39 FR 9308, 9309 (Mar. 8, 1974) (NSPS Additions and Miscellaneous
Amendments discussing opacity as an indicator of whether control
equipment is properly maintained and operated).
With use of continuous opacity monitors it is possible to have a
continuous stream of opacity data. This results in the collection of
many individual, short-term opacity measurements that reflect the full
range of control device operating variability and, depending upon the
amount of variability, may or may not be indicative of poor operation
of control equipment and excess PM emissions. For example, coal-fired
power generation facilities may experience sporadic opacity exceedances
caused by variations in the constituents of coal burned. The revised
Alabama rule shifts emphasis from isolated six-minute periods to longer
periods that are more indicative of excess PM emissions and problems
with operation and maintenance of control devices. As noted above,
under the proposed revised rule, with the changes discussed in this
action, an emissions unit is allowed: (1) Up to 100 percent opacity
during periods of startup, shutdown, load change, and rate change or
other short, intermittent periods upon terms approved by ADEM's
Director and included in a state-issued permit; (2) up to 100 percent
opacity for up to two percent of the operating time on a quarterly
basis (less the exempted periods approved by ADEM's Director and
included in a state-issued permit), for no more than 10 percent of the
time on a daily basis; and (3) up to 20 percent opacity for the rest of
the time in a quarter. EPA believes this approach, along with the
monitoring and oversight safeguards discussed above, make appropriate
use of COMS data for ensuring compliance with PM limits.
[[Page 18430]]
IV. What Does the Visible Emissions Rule in the Current SIP Require,
and What Changes Are Requested by ADEM?
The subject Visible Emissions rule is in Chapter 335-3-4 (``Control
of Particulate Emissions'') of the Alabama SIP. The currently approved
Alabama Rule 335-3-4-.01, ``Visible Emissions,'' has a generally
applicable limit of 20 percent on opacity level and provides that one
six-minute period per hour of up to 40 percent opacity is exempted \1\
from the 20 percent limit. The Director of ADEM may also grant, as part
of a permit issued by the State, exemptions to the 20 percent limit
during startup, shutdown, load change and rate change or other short,
intermittent periods that are in addition to the hourly six-minute 40
percent exemption. These exemptions are provided by subparagraphs
(1)(b) and (1)(c), respectively. Additional exemptions for
circumstances not relevant to this rulemaking are provided by
subparagraphs (1)(d) \2\ and (1)(e).\3\ The text of the current rule
reads, in relevant part, as follows:
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\1\ Alabama Rule 335-3-4-.01, ``Visible Emissions,'' provides
four specific ``exceptions'' to compliance with the generally
applicable opacity limit at subparagraphs 335-3-4-.01(b), (c), (d),
and (e). To be consistent with more common terminology, in this
notice we refer to these as ``exemptions.''
\2\ Subparagraph (d) provides that ADEM's Director may approve
exceptions to this Rule in the form of source-specific adjustments
to the opacity standard, provided certain conditions are met
demonstrating to the Director's satisfaction that, with the
adjustment, the source would continue to comply with its SIP
particulate matter mass emissions limit.
\3\ Subparagraph (e) provides that the provisions of this Rule
do not apply to combustion sources in single-family and duplex
dwellings where such sources are used for heating or other domestic
purposes.
(1) Visible Emissions Restrictions for Stationary Sources.
(a) Except as provided in subparagraphs (b), (c), (d), or (e) of
this paragraph, no person shall discharge into the atmosphere from
any source of emission, particulate of an opacity greater than that
designated as twenty percent (20%) opacity, as determined by a six
(6) minute average.
(b) During one six (6) minute period in any sixty (60) minute
period, a person may discharge into the atmosphere from any source
of emission, particulate of an opacity not greater than that
designated as forty percent (40%) opacity.
(c) The Director may approve exceptions to this Rule or specific
sources which hold permits under Chapter 335-3-14; provided however,
such exceptions may be made for startup, shutdown, load change, and
rate change or other short, intermittent periods of time upon terms
approved by the Director and made a part of such permit.
* * * * *
(2) Compliance with opacity standards in this Rule shall be
determined by conducting observations in accordance with Reference
Method 9 in Appendix A, 40 CFR Part 60, as the same may be amended
requiring a six (6) minute average as determined by twenty-four (24)
consecutive readings, at intervals of fifteen (15) seconds each.
The 2003 ADEM submittal would add three new paragraphs, (3), (4),
and (5), to Alabama Rule 335-3-4-.01 that apply only to those emissions
units that use COMS for measuring opacity, that operate such systems
according to Federal specifications, and that are subject only to those
opacity limits of the State's SIP (e.g., not subject to opacity limits
under any preconstruction permit or other regulation). The revision
provides that these units will not be in violation of the State's
generally applicable opacity limitation if the non-exempt excess
emissions periods do not exceed two percent of the source operating
hours for which the opacity standard is applicable and for which the
COMS is indicating valid data, on a quarterly basis. The text of the
proposed change reads as follows:
(3) The conditions in paragraph (4) of this Rule apply to each
emissions unit that meets all of the following requirements:
(a) A Continuous Opacity Monitoring System (COMS) is used for
indication of opacity of emissions;
(b) With respect to opacity limitations, the units are subject
only to the opacity provisions stated in paragraph (1) of this Rule;
and
(c) The COMS system utilized is required to comply with the
requirements of 40 CFR 60.13 or 40 CFR 75.14 (if applicable) and is
required to be certified in accordance with the requirements of 40
CFR 60, Appendix B, Performance Specification 1.
(4) During each calendar quarter, the permittee will not be
deemed in violation of Rule 335-3-4-.01(1) if the non-exempt excess
emissions periods do not exceed 2.0 percent of the source operating
hours for which the opacity standard is applicable and for which the
COMS is indicating valid data.
(5) Nothing in paragraph (4) of this Rule shall be construed to
supercede the validity of opacity readings taken under paragraph (2)
of this Rule.
In summary, under the 2003 submission, sources operating COMS would
not be deemed in violation of the standard where emissions in excess of
the 20 percent opacity were limited to: (1) One six-minute average per
hour of up to 40 percent opacity; (2) periods of startup, shutdown,
load change and rate change or other short intermittent periods upon
terms approved by ADEM's Director and included in a State-issued
permit; and (3) no more than two percent of the remaining operating
time after subtracting out all periods qualifying under the previous
two instances.
V. What Changes Does EPA Recommend to the Submittal?
As described above, under the Alabama SIP, Method 9 is the method
specified for determining compliance with the 20 percent opacity limit.
COMS are not specified as the method to determine compliance with the
numerical opacity limit, although COMS data can be credible evidence of
opacity. Opacity, both as measured by Method 9 and COMS, has been used
as a proxy for particulate emissions and to indicate whether a company
is following good air pollution control practices. ADEM has proposed
amending its SIP to allow up to two percent of COMS readings to exceed
20 percent opacity during non-exempt periods, in part since the Alabama
SIP provides no other exemption from the standard for malfunction.
The use of COMS increases data availability and provides a greater
degree of reliability compared to the Method 9 procedure. Nonetheless,
as currently written, the revision would allow a source to emit at a
higher allowable average opacity percent level (as measured by COMS in
six-minute increments) on a quarterly basis as well as allowing higher
short term excursions than the current approved SIP allows. Because
this potential for higher average opacity on a quarterly basis could
indicate an increase in particulate matter emissions, and in the
absence of a supporting demonstration of compliance with CAA
requirements from the State, we believe that the 2003 SIP submittal is
not approvable as submitted. The submission is also not clear about
whether the new opacity standard for certain sources with COMS at 335-
3-4-.01(3)-(5) applies in addition to, or in lieu of, the existing
opacity standard in paragraphs 335-3-4-.01(1)(a)-(b), as measured under
paragraph 335-3-4-.01(2). In addition, the purpose behind new paragraph
335-3-4-.01(5) is not clear.
EPA believes the State can revise the 2003 ADEM submittal by
amending it to ensure that the allowable average quarterly opacity is
at least as stringent as (i.e., equal to or lower than) that allowed by
the current approved SIP, and by being clear that only a single version
of the standard applies to any unit (although any credible evidence of
opacity could be used to assess compliance with the applicable version
of the standard). Accordingly, this proposed approval is contingent
upon Alabama's submission of a revised rule with certain changes. The
revision
[[Page 18431]]
would clearly indicate that a unit is covered by either the existing
opacity standard at paragraphs 335-3-4-.01(1)(a)-(b), as measured under
paragraph 335-3-4-.01(2), or by the new standard established in
paragraphs 335-3-4-.01(1)(a), (3)-(4), as measured by the COMS
referenced in those paragraphs--but not both.\4\ The revision would
also provide that the hourly 40 percent exemption under Alabama rule
335-3-4-.01(1)(b) does not apply to sources subject to the new
paragraphs 335-3-4-.01(3) and 335-3-4-.01(4). Thus, the 40 percent
exemption for up to 24 six-minute periods per day on an hourly basis
would be replaced by the generally applicable 20 percent standard. The
revision would allow a source to exceed the 20 percent standard (up to
100 percent opacity) during no more than 24 six-minute periods per day.
In part this revision would replace the existing provision allowing one
six-minute exceedance per hour at 40 percent opacity with a provision
allowing up to 24 six-minute exceedances per calendar day at 100
percent opacity. However, under the revised provision, these
exceedances would be part of, not in addition to, the exceedances
allowed under 335-3-4-.01(4) (i.e., two percent of operating time).
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\4\ As noted elsewhere, the exemptions in paragraphs 335-3-
4-.01(1)(c)-(e) are not impacted by the 2003 SIP revision and would
continue to apply to either the existing or the revised standard.
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Thus, under the current SIP, a source is required to maintain 20
percent opacity, except that it may emit at up to 40 percent opacity
for one six-minute average per hour, and may have emissions of up to
100 percent opacity as specified in a permit. Under the 2003
submission, certain sources using COMS would, in addition to the
current SIP exemptions, also be allowed emissions of up to 100 percent
opacity for up to two percent of the quarterly operating time that they
are otherwise subject to the 20 percent opacity limit. Under the
revision proposed for approval in this notice, these sources still
would be allowed emissions of up to 100 percent opacity for up to two
percent of quarterly operating time that they are subject to the 20
percent opacity limit (but not to exceed 10 percent of a calendar day),
and they would not be allowed the 40 percent hourly exemption.\5\
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\5\ Although this new opacity standard would only apply to
certain sources using COMS, EPA notes that, consistent with EPA's
and ADEM's credible evidence rules, nothing in the rule should
preclude the use of COMS to enforce the existing standard or the use
of Method 9 to enforce the new standard.
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Where currently any source may exceed the opacity limit for six
minutes out of every hour (i.e., 10 percent of the time, on an hourly
basis), under the revision EPA is proposing would be approvable, a
source using COMS subject to the new standard could exceed the opacity
limit for 10 percent of the time on a daily basis (i.e., up to 2.4
hours of consecutive opacity exceedances per calendar day), but for
only two percent of the time on a quarterly basis. Under the current
standard, the 40 percent opacity limit in theory allows a source to
emit a total of approximately 219 hours of emissions in a quarter at up
to 40 percent opacity, if the source uses one six-minute exemption for
every hour of operation. Under the proposed revision, a source would be
allowed to emit no more than 44 hours of excess emissions in a quarter
(and no more than 2.4 hours in a day), but those emissions could have
up to 100 percent opacity.\6\
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\6\ The director's discretion provisions under Alabama rule 335-
3-4-.01(1)(c) and (d) would be unchanged by this SIP revision, so
periods of excess emissions allowed in a permit pursuant to those
provisions would continue to be allowed, in addition to the
emissions allowed by the new provisions discussed herein. EPA notes
that, as the director's discretion provisions are not being revised
by ADEM or reviewed by EPA at present, nothing in this notice should
be considered as approving those provisions.
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As a result, the final rule would have the potential to increase
the impact of opacity exceedances on a short-term basis by allowing
exceedances of up to 100 percent opacity and also allowing those
periods of excess opacity to be aggregated in up to 24 consecutive six-
minute periods per day (as opposed to the current approved rule which
provides an hourly 40 percent exemption, also for a total of 24 six-
minute periods per day). However, the long-term cap of two percent
serves to restrict the total amount of time a source is allowed to
exceed the standard. As discussed below, EPA believes that the
reduction in total duration of exceedances will reduce average opacity
as compared to the current standard, even taking into consideration
that the exemption in the current standard limits exceedances to 40
percent (not 100 percent) opacity.
Thus, under the proposed revised rule, with the changes discussed
in this notice, an emissions unit covered by the new standard would be
allowed: (1) Up to 100 percent opacity during periods of startup,
shutdown, load change, and rate change or other short, intermittent
periods upon terms approved by ADEM's Director and included in a state-
issued permit; (2) up to 100 percent opacity for up to two percent of
the operating time on a quarterly basis (where the amount of operating
time does not include the exempted periods approved by ADEM's Director
and included in a state-issued permit), but for no more than ten
percent of the time on a daily basis; and (3) up to 20 percent opacity
for the rest of the time in a quarter. The current federally-approved
SIP opacity limit remains in effect. Any new exceptions proposed in
this action do not take effect until EPA takes final action.
Furthermore, any final rule would be prospective only. In addition,
this proposal is not intended to affect on-going enforcement actions
against sources that may be subject to the new standard, nor does it
relieve affected sources in Alabama of their obligations to comply with
any other federal, state, or local opacity requirements, or particulate
matter control requirements.
VI. What Technical Analysis Was Used To Support Approval of This SIP
Revision?
The existing Alabama SIP specifies Method 9 as the method for
determining compliance with the generally applicable opacity limit for
sources of PM emissions. See Ala. Admin. Code r. 335-3-4-.01(2). More
frequent readings with COMS help determine whether a source is
following good air pollution control practices between Method 9 or
Method 5 tests. With the additional restrictions described above, the
proposed SIP revision can be shown to be no less stringent in terms of
average quarterly opacity than the existing SIP.
Today, we propose to approve Alabama's SIP revision contingent upon
the revision including our recommended changes, based on a finding that
the revision would not increase average quarterly opacity levels and
thus would not interfere with attainment or maintenance of a NAAQS,
RFP, or any other requirement of the Act. The relationship between
changes in opacity and increases or decreases in ambient
PM2.5 levels cannot be quantified readily and is
particularly uncertain for short term and site-specific analyses. There
are several contributors to this uncertainty including (1) differences
between combustion technology characteristics and fuel components, (2)
differences in control technology types, temperatures at which they
operate, and load characteristics, (3) the recognition that both
opacity and mass emissions are subject to significant variability over
short periods of time and fluctuations in one may not track
fluctuations in the other, and (4) differences between what the ambient
sampler collects and the mass of particles that exists at the point
[[Page 18432]]
of COMS measurement (e.g., in the stack) and the direct
PM2.5 that forms immediately upon exiting the stack (that
are related to fuel components more than to control technology).
In addition to these uncertainty factors, opacity is directly
related to particle size, with particles of an aerodynamic diameter of
approximately 1.0 micrometer having the greatest potential for
impairment of visibility, or increased opacity. (See, e.g., Malm,
William C. ``Introduction to Visibility,'' Cooperative Institute for
Research in the Atmosphere, May 1999, Chap. 2, p. 8). As particles
increase in size, their impact on opacity diminishes, despite the fact
that their mass may increase. Thus for PM emissions of a given mass
level, opacity can be greater or less depending on the particle size
distribution.
Several past instances and State and Federal rules are instructive
regarding the uncertainties in relating opacity to PM concentrations.
EPA recognized and accounted for these uncertainties as early as the
1970s by permitting sources to adjust source-specific opacity standards
under new source performance standards (NSPS) when they could
demonstrate that they were in compliance with applicable PM limits at
times when opacity limits were being exceeded. See, e.g., 44 FR 37960,
37961 (June 29, 1979). In EPA's own NSPS for glass manufacturing
plants, (40 CFR 60.293(e)), and national emission standard for
Inorganic Arsenic Emissions from Glass Manufacturing Plants (40 CFR
61.163), EPA has written specific provisions into its standards
permitting source owners or operators to redetermine opacity
limitations where they can demonstrate compliance with emission limits
in the applicable rules. More recently, when examining a study of COMS
at a portland cement kiln, we have found that the plant's visible
emissions readings were consistently below its allowable limit (20
percent) while PM emissions significantly exceeded the NSPS due to
broken bags in its baghouse. Finally, a number of States have
incorporated similar provisions into their regulations. (See, e.g.,
Indiana Administrative Code, 326 IAC 5-1-5(b); Wisconsin NR 431.07;
Pima County, Arizona 2-8-300(C)).
The contributions to uncertainty described above lessen when
applied to longer term averages and the relationship between ambient
PM2.5 measurements and changes in opacity are more reliable
than for shorter term (e.g., daily) assessments. Therefore, for
purposes of this proposal, EPA focused on analyzing the effects of the
proposed change in the opacity limitations for facilities covered by
the rule over quarterly periods. EPA believes that a quarterly basis is
appropriate because correlations between opacity and PM control device
operation are more readily generalized over a longer-term basis and,
therefore, a quarterly average is more likely to reflect impacts on the
ambient PM levels accurately than a daily average, and because ADEM's
proposed rule includes a quarterly limit. By calculating and comparing
the average quarterly opacities allowed by the current SIP approved
rule, the 2003 ADEM submittal, and the 2003 ADEM submittal with
required changes specified, we can determine which proposed SIP change,
if any, provides an average quarterly opacity equivalent with, or more
stringent than, the average quarterly opacity allowed by the current
SIP approved rule. Proposed changes that provide average quarterly
opacities more stringent than (or equivalent with) those allowed by the
existing SIP rule are expected to be more stringent than (or equivalent
to) the existing SIP rule.
EPA is not performing similar calculations comparing stringency of
average daily opacity levels under the current rule and the proposed
rule because a generally applicable relationship between opacity and PM
mass emissions cannot be specified over short averaging times (e.g., 24
hours or less). Even with extensive testing, it is very difficult to
establish reliable correlations between the magnitude of opacity
measurements and PM mass emissions for short averaging times (e.g., 24
hours or less) that will remain reliable over a longer period of record
(i.e., that will establish a direct daily correlation over a longer
period, such as three or more months). Therefore, opacity may not be a
reliable indicator of short-term emissions, or for use in projecting
changes in short-term PM ambient air quality concentrations.
Accordingly, we conclude that the proposed change in the allowed
opacity will have no effect on attainment of the 24-hour PM NAAQS (35
[mu]g/m3 for PM2.5 and 150 [mu]mg/m3
for PM10) or (based on the quarterly stringency comparison)
the annual PM NAAQS (15.0 [mu]g/m for PM2.5).
We can calculate the average allowable quarterly opacity for a unit
by multiplying an allowed level of opacity by the duration for which
that level of opacity is allowed, summing those products for each
allowed level of opacity occurring over a quarter, and then dividing
that total by the number of six-minute periods in a quarter. The
average quarterly opacity for a unit is an opacity value equivalent
with one single, constant opacity value emitted for each and every six-
minute period of the quarter, allowing us to compare a unit with a
longer period of lower opacity to one with a shorter period of higher
opacity.
The general formula for calculating the allowable average quarterly
opacity (i.e., the average opacity (percent) allowed by rule over a
quarter) is:
[GRAPHIC] [TIFF OMITTED] TP12AP07.010
Where:
n = specific period of quarterly operation,
opacity = opacity (percent) related to that specific period,
duration = number of six-minute average periods related to the
specific period, and
21,900 = number of six-minute average periods per quarter.
For the Alabama analysis, using the above general formula to
determine the allowable average opacity over a quarter, we chose to use
the maximum opacity allowed for each condition, the maximum duration
allowed for each condition, and the maximum amount of time for unit
operation when calculating the average allowable quarterly opacity.
Although operation with opacity at the maximum level for the longest
period allowed under a rule is not reflective of actual operations,
such a conservative assumption provides a consistent basis for
comparisons.
Usually calculation of allowable average quarterly opacity can be
readily ascertained, since opacity limits and their associated
condition durations are known explicitly. However, because ADEM allows
an exemption from opacity limits during periods of startup, shutdown,
load change and rate change or other short, intermittent periods upon
[[Page 18433]]
terms approved by ADEM's Director and included in a state-issued
permit, and because the duration of those periods is not known, we used
a variable, T1, to represent the duration of those periods.
In theory, the duration of those periods could range from 0, meaning no
periods of exemption for a quarter, to 21,900, meaning all periods of
the quarter are exempt.\7\ In practice, one sample of units subject to
the current SIP rule contains durations of about 400 periods per
quarter for this exemption.
---------------------------------------------------------------------------
\7\ EPA does not intend to indicate that it would be appropriate
or consistent with the SIP for an exemption period under 335-3-
4.01(1)(c) to last for an extended period of time, but rather is
utilizing conservative assumptions for the purpose of ensuring the
requirements of section 110(l) will be met. EPA does not anticipate
that a source would, in fact, operate at 100% opacity for all
permissible excursion periods.
---------------------------------------------------------------------------
Relying on the variable T1, calculation of allowable
average quarterly opacities becomes straightforward. By way of example,
the allowable average quarterly opacity for the 2003 ADEM Submittal is
the sum of the ten percent of the quarter's duration at 40 percent
opacity, the time (T1) at 100 percent opacity due to
exemptions, the two percent of the non-exempt time of the quarter's
duration at 100 percent opacity, and the balance of the non-exempt time
of the quarter's duration at 20 percent opacity, all divided by the
number of six-minute periods in the quarter. The equation shown below
provides the allowable average quarterly opacity for the 2003 ADEM
Submittal for T1 values of 0 to 19,710:
[GRAPHIC] [TIFF OMITTED] TP12AP07.011
We derived allowable average quarterly opacity equations for the
current SIP-approved rule and the 2003 ADEM submittal, substituted
various exemption durations (T1) in the equations,
determined the corresponding allowable average quarterly opacities, and
organized the results as shown in Table 1 below.
Table 1.--Calculated Allowable Average Quarterly Opacity Levels, for Various Startup, Shutdown, Load Change, and
Rate Change Durations (T1), Using Alabama's Current SIP-Approved Rule, and the 2003 ADEM Submittal
----------------------------------------------------------------------------------------------------------------
Calculated allowable average quarterly opacity (percent) for various
startup, shutdown, load change and rate change durations (T1)
-----------------------------------------------------------------------------
T1 = 0 T1 = 1,000 T1 = 10,000 T1 = 17,520 T1 = 19,710 T1 = 21,900
----------------------------------------------------------------------------------------------------------------
Current SIP Approved Rule......... 22.00 25.65 58.53 86.00 94.00 100.00
2003 ADEM Submittal............... 23.44 27.02 59.24 86.16 94.00 100.00
----------------------------------------------------------------------------------------------------------------
As can be seen, under these conservative assumptions, the 2003 ADEM
submittal would result in allowable average quarterly opacity levels
that are slightly higher than those calculated from the current SIP
rule for periods of startup, shutdown, load change and rate change,
i.e. for where those durations are less than 19,710 six-minute
averages.
In order to be approvable, we have recommended that ADEM eliminate
the exemption for six-minutes at up to 40 percent opacity for up to ten
percent of the operating time. The allowable average quarterly opacity
for the 2003 ADEM Submittal With Required Changes Specified for all
T1 values =
[GRAPHIC] [TIFF OMITTED] TP12AP07.012
We derived allowable average quarterly opacity equations for the
current SIP approved rule and the 2003 ADEM submittal with recommended
changes specified, substituted various exemption durations
(T1) in the equations, determined the corresponding
allowable average quarterly opacities, and organized the results as
shown in Table 2 below. As shown, the proposed revision to the SIP rule
yields an allowable average quarterly opacity equivalent to or less
than the allowable average quarterly opacity calculated from the
current SIP rule in all cases.
[[Page 18434]]
Table 2.--Calculated Allowable Average Quarterly Opacity Levels, for Various Startup, Shutdown, Load Change, and
Rate Change Durations (T1), Using Alabama's Current SIP-Approved Rule and the Proposed SIP Revision With
Recommended Changes Specified
----------------------------------------------------------------------------------------------------------------
Calculated allowable average quarterly opacity (percent) for various
startup, shutdown, load change and rate change durations (T1)
-----------------------------------------------------------------------------
T1 = 0 T1 = 1,000 T1 = 10,000 T1 = 17,520 T1 = 19,710 T1 = 21,900
----------------------------------------------------------------------------------------------------------------
Current SIP Approved Rule......... 22.00 25.65 58.53 86.00 94.00 100.00
2003 ADEM Submittal with 21.60 25.18 57.40 84.32 92.16 100.00
Recommended Changes Specified....
----------------------------------------------------------------------------------------------------------------
Therefore, by incorporating these recommended changes, Alabama
would reduce uncertainties related to whether such a change could
interfere with attainment, RFP or any other requirement of the Act.
Accordingly, we conclude that the revision of Alabama's SIP rule to
incorporate the 2003 ADEM submittal with our recommended changes
specified in this action would not interfere with requirements of the
CAA and would be approvable. Further details of this analysis are
contained in the technical support document.
VII. What Happens Next?
EPA anticipates Alabama will submit a revised rule revision
reflecting the changes discussed in section IV above. If Alabama's
revised rule is submitted and considered approvable, after considering
any comments received on today's proposed approval, EPA will publish a
final rule in the Federal Register approving the State's requested rule
revision and will also address in that rulemaking any comments received
on this proposed approval. In addition, we plan to develop further
criteria to aid EPA Regional Offices in evaluating future revisions to
rules such as Alabama's and, in this regard, we expect to publish in
the near future a request for information that will assist us in that
effort.
VIII. Proposed Action
EPA is proposing to approve the Visible Emissions portion of a SIP
revision submitted to EPA by Alabama on September 11, 2003, provided it
is revised as described in section IV of this action and submitted as a
SIP revision in accordance with the requirements of the CAA.
IX. Statutory and Executive Order Reviews
Under Executive Order 12866 (58 FR 51735, October 4, 1993), this
proposed action is not a ``significant regulatory action'' and
therefore is not subject to review by the Office of Management and
Budget. For this reason, this action is also not subject to Executive
Order 13211, ``Actions Concerning Regulations That Significantly Affect
Energy Supply, Distribution, or Use'' (66 FR 28355, May 22, 2001). This
proposed action merely proposes to approve state law as meeting Federal
requirements, and imposes no additional requirements beyond those
imposed by state law. Accordingly, I hereby certify that this proposed
rule will not have a significant economic impact on a substantial
number of small entities under the Regulatory Flexibility Act (5 U.S.C.
601 et seq.). Because this action proposes to approve requirements
under state law and does not impose any additional enforceable duty
beyond that required by state law, it does not contain any unfunded
mandate or significantly or uniquely affect small governments, as
described in the Unfunded Mandates Reform Act of 1995 (Public Law 104-
4).
This proposed rule also does not have tribal implications because
it will not have a substantial direct effect on one or more Indian
tribes, on the relationship between the Federal Government and Indian
tribes, or on the distribution of power and responsibilities between
the Federal Government and Indian tribes, as specified by Executive
Order 13175 (65 FR 97249, November 9, 2000). This proposed action also
does not have Federalism implications because it does not have
substantial direct effects on the States, on the relationship between
the national government and the States, or on the distribution of power
and responsibilities among the various levels of government, as
specified in Executive Order 13132 (64 FR 43255, August 10, 1999). This
action merely proposes to approve State rule as consistent with Federal
standards, and does not alter the relationship or the distribution of
power and responsibilities established in the CAA. This proposed rule
also is not subject to Executive Order 13045, ``Protection of Children
from Environmental Health Risks and Safety Risks'' (62 FR 19885, April
23, 1997), because it is not economically significant.
In reviewing SIP submissions, EPA's role is to approve state
choices, provided that they meet the criteria of the CAA. In this
context, in the absence of a prior existing requirement for the state
to use voluntary consensus standards (VCS), EPA has no authority to
disapprove a SIP submission for failure to use VCS. It would thus be
inconsistent with applicable law for EPA, when it reviews a SIP
submission to use VCS in place of a SIP submission that otherwise
satisfies the provisions of the CAA. Thus, the requirements of section
12(d) of the National Technology Transfer and Advancement Act of 1995
(15 U.S.C. 272 note) do not apply. This proposed rule does not impose
an information collection burden under the provisions of the Paperwork
Reduction Act of 1995 (44 U.S.C. 3501 et seq.).
List of Subjects in 40 CFR Part 52
Environmental protection, Air pollution control, Carbon monoxide,
Intergovernmental relations, Nitrogen dioxide, Ozone, Particulate
matter, Reporting and recordkeeping requirements, Sulfur oxides,
Volatile organic compounds.
Authority: 42 U.S.C. 7401 et seq.
Dated: April 4, 2007.
J.I. Palmer, Jr.,
Regional Administrator, Region 4.
[FR Doc. E7-6948 Filed 4-11-07; 8:45 am]
BILLING CODE 6560-50-P