[Federal Register: April 21, 2008 (Volume 73, Number 77)]
[Rules and Regulations]
[Page 21417-21465]
[DOCID:fr21ap08-19]

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Part II

Environmental Protection Agency

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40 CFR Part 52

Federal Implementation Plan for the Billings/Laurel, Montana, Sulfur
Dioxide Area; Final Rule

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ENVIRONMENTAL PROTECTION AGENCY

40 CFR Part 52

[EPA-R08-OAR-2006-0098; FRL-8551-2]
RIN 2008-AA01

Federal Implementation Plan for the Billings/Laurel, MT, Sulfur
Dioxide Area

AGENCY: Environmental Protection Agency (EPA).

ACTION: Final rule.

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SUMMARY: The Environmental Protection Agency (EPA) is promulgating a
Federal Implementation Plan (FIP) containing emission limits and
compliance determining methods for several sources located in Billings
and Laurel, Montana. EPA is promulgating a FIP because of our previous
partial and limited disapprovals of the Billings/Laurel Sulfur Dioxide
(SO2) State Implementation Plan (SIP). The intended effect of this
action is to assure attainment of the SO2 National Ambient Air Quality
Standards (NAAQS) in the Billings/Laurel, Montana area. EPA is taking
this action under sections 110, 301, and 307 of the Clean Air Act
(Act).

DATES: Effective Date: This final rule is effective May 21, 2008. The
incorporation by reference of certain publications listed in this
regulation is approved by the Director of the Federal Register as of
May 21, 2008.

ADDRESSES: EPA has established a docket for this action under Docket ID
No. EPA-R08-OAR-2006-0098. All documents in the docket are listed on
the http://www.regulations.gov Web site. Although listed in the index,
some information is not publicly available, e.g., Confidential Business
Information (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 through http://www.regulations.gov or in hard copy at
the Air and Radiation Program, Environmental Protection Agency (EPA),
Region 8, 1595 Wynkoop Street, Denver, Colorado 80202-1129. EPA
requests that if at all possible, you contact the individual listed in
the FOR FURTHER INFORMATION CONTACT section to view the hard copy of
the docket. You may view the hard copy of the docket Monday through
Friday, 8 a.m. to 4 p.m., excluding Federal holidays.

FOR FURTHER INFORMATION CONTACT: Laurie Ostrand, Air and Radiation
Program, Environmental Protection Agency (EPA), Region 8, 1595 Wynkoop
Street, Denver, Colorado 80202-1129,<PHONE_NUMBER>,
<EMAIL_ADDRESS>
SUPPLEMENTARY INFORMATION:

Table of Contents

Definitions

I. Background of the Final Rules
II. Issues Raised by Commenters and EPA's Response
    A. FIP Not Necessary
    B. EPA Exceeded Its Authority in Proposing a FIP
    C. Flare Monitoring
    D. Flare Limits
    E. Concerns With Dispersion Modeling
    F. Miscellaneous Comments
    G. MSCC Specific Issues
    H. ConocoPhillips Specific Issues
    I. ExxonMobil Specific Issues
    J. CHS Inc. Specific Issues
III. Summary of the Final Rules and Changes From the July 12, 2006,
Proposal
    A. Flare Requirements Applicable to All Sources
    B. CHS Inc.
    C. ConocoPhillips
    D. ExxonMobil
    E. Montana Sulphur & Chemical Company (MSCC)
    F. Modeling to Support Emission Limits
IV. Statutory and Executive Order Reviews
    A. Executive Order 12866, Regulatory Planning Review
    B. Paperwork Reduction Act
    C. Regulatory Flexibility Act
    D. Unfunded Mandates Reform Act
    E. Executive Order 13132, Federalism
    F. Executive Order 13175, Coordination With Indian Tribal
Governments
    G. Executive Order 13045, Protection of Children From
Environmental Health Risks and Safety Risks
    H. Executive Order 13211, Actions That Significantly Affect
Energy Supply, Distribution, or Use
    I. National Technology Transfer and Advancement Act
    J. Executive Order 12898: Federal Actions To Address
Environmental Justice in Minority Populations and Low-Income
Populations
    K. Congressional Review Act
    L. Petitions for Judicial Review

Definitions

    For the purpose of this document, we are giving meaning to certain
words or initials as follows:
    (i) The words or initials Act or CAA mean or refer to the Clean Air
Act, unless the context indicates otherwise.
    (ii) The initials API mean or refer to the American Petroleum
Institute.
    (iii) The initials BAAQMD mean or refer to the Bay Area Air Quality
Management District.
    (iv) The initials CEMS mean or refer to continuous emission
monitoring system.
    (v) The initials CO mean or refer to carbon monoxide.
    (vi) The initials COPC mean or refer to ConocoPhillips.
    (vii) The words EPA, we, us or our mean or refer to the United
States Environmental Protection Agency.
    (viii) The initials FIP mean or refer to Federal Implementation
Plan.
    (ix) The initials H2S mean or refer to hydrogen sulfide.
    (x) The initials MBER mean or refer to the Montana Board of
Environmental Review.
    (xi) The initials MDEQ mean or refer to the Montana Department of
Environmental Quality.
    (xii) The initials MPA mean or refer to the Montana Petroleum
Association.
    (xiii) The initials MSCC mean or refer to the Montana Sulphur &
Chemical Company.
    (xiv) The initials NAAQS mean or refer to National Ambient Air
Quality Standards
    (xv) The initials NEDA/CAP mean or refer to the National
Environmental Development Association's Clean Air Project.
    (xvi) The initials NPRA mean or refer to the National Petrochemical
& Refiners Association.
    (xvii) The initials SCAQMD mean or refer to the South Coast Air
Quality Management District.
    (xviii) The initials SIP mean or refer to State Implementation
Plan.
    (xix) The initials SO2 mean or refer to sulfur dioxide.
    (xx) The words State or Montana mean the State of Montana, unless
the context indicates otherwise.
    (xxi) The initials SRU mean or refer to sulfur recovery unit.
    (xxii) The initials SWS mean or refer to sour water stripper.
    (xxiii) The initials WETA mean or refer to the Western
Environmental Trade Association.
    (xxiv) The initials WSPA mean or refer to the Western States
Petroleum Association.
    (xxv) The initials YCC mean or refer to the Yellowstone County
Commissioners.
    (xxvi) The initials YVAS mean or refer to the Yellowstone Valley
Audubon Society.

I. Background of the Final Rules

    The Clean Air Act (Act) requires EPA to establish national ambient
air quality standards (NAAQS) that protect public health and welfare.
NAAQS have been established for SO2 as follows: 0.030 parts
per million (ppm) annual standard, not to be exceeded in a calendar
year; 0.14 ppm 24-hour standard, not to be exceeded more than once per
calendar year; and 0.5 ppm 3-hour standard, not to be exceeded more

than once per calendar year. See 40 CFR 50.4 and 50.5. The Act also
requires states to prepare and gain EPA approval of a plan, termed a
State Implementation Plan (SIP), to assure that the NAAQS are attained
and maintained.
    Dispersion modeling completed in 1991 and 1993 for the Billings/
Laurel area of Montana predicted that the SO2 NAAQS were not
being attained. As a result, in March 1993 EPA (pursuant to sections
110(a)(2)(H) and 110(k)(5) of the Act, 42 U.S.C. 7410(a)(2)(H) and
7410(k)(5)) requested the State of Montana to revise its previously
approved SO2 SIP for the Billings/Laurel area. See 58 FR
41450, August 4, 1993. In response, the State submitted revisions to
the SO2 SIP on September 6, 1995, August 27, 1996, April 2,
1997, July 29, 1998, and May 4, 2000.
    On May 2, 2002 (67 FR 22168) and May 22, 2003 (68 FR 27908), we
partially approved, partially disapproved, limitedly approved, and
limitedly disapproved the Billings/Laurel SO2 SIP. In those
actions we disapproved the following:
     The attainment demonstration due to issues with various
emission limits, inappropriate stack height credit, and lack of
emission limits on flares.
     The emission limits for Montana Sulphur & Chemical
Company's (MSCC's) sulfur recovery unit (SRU) 100-meter stack and the
stack height credit on which those limits were based.
     The emission limits for MSCC's auxiliary vent stacks due
to lack of an adequate limit on fuel burned in the associated heaters
and boilers and lack of a reliable compliance determining method.
     The emission limits for MSCC's 30-meter stack due to lack
of an adequate limit on fuel burned in the associated heaters and
boilers, and lack of a reliable compliance determining method.
     Provisions that allowed sour water stripper overheads to
be burned in the flares at CHS Inc. and ExxonMobil.
     ExxonMobil's refinery fuel gas combustion device emission
limits and associated compliance determining methods.
     ExxonMobil's Coker CO Boiler stack emission limits and
associated compliance determining methods.
     CHS Inc.'s combustion source emission limits and certain
associated compliance determining methods.
    On June 10, 2002, MSCC petitioned the United States Court of
Appeals for the Ninth Circuit for review of EPA's May 2, 2002, final
SIP action. Subsequently, MSCC and EPA agreed to a stay of the
litigation pending EPA's final action on this FIP. The case is
captioned Montana Sulphur & Chemical Company v. United States
Environmental Protection Agency, No. 02-71657. No petitions for
judicial review were filed regarding EPA's May 22, 2003, SIP action.
    On July 12, 2006 (71 FR 39259), EPA proposed Federal Implementation
Plan (FIP) provisions for the Billings/Laurel, Montana area because of
our disapproval of portions of Montana's Billings/Laurel SO2
SIP. In our proposal, we indicated that our FIP would not replace the
SIP entirely, but instead would only replace elements of, or fill gaps
in, the SIP.
    In promulgating today's rules, EPA is fulfilling its mandatory duty
under section 110(c) of the Act. Under section 110(c), whenever we
disapprove a SIP, in whole or in part, we are required to promulgate a
FIP. Specifically, section 110(c) provides:

    ``(1) The Administrator shall promulgate a Federal
implementation plan at any time within 2 years after the
Administrator--
    (A) Finds that a State has failed to make a required submission
or finds that the plan or plan revision submitted by the State does
not satisfy the minimum criteria established under [section
110(k)(1)(A)],\1\ or
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    \1\ Section 110(k)(1) requires the Administrator to promulgate
minimum criteria that any plan submission must meet before EPA is
required to act on the submission. These completeness criteria are
set forth at 40 CFR 51, Appendix V.
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    (B) Disapproves a State implementation plan submission in whole
or in part, unless the State corrects the deficiency, and the
Administrator approves the plan or plan revision, before the
Administrator promulgates such Federal implementation plan.''
    Thus, because we disapproved portions of the Billings/Laurel
SO2 SIP, and the attainment demonstration, we are required
to promulgate a FIP.
    Section 302(y) defines the term ``Federal implementation plan'' in
pertinent part, as:

    ``[A] plan (or portion thereof) promulgated by the Administrator
to fill all or a portion of a gap or otherwise correct all or a
portion of an inadequacy in a State implementation plan, and which
includes enforceable emission limitations or other control measures,
means or techniques (including economic incentives, such as
marketable permits or auctions or emissions allowances) * * *.''

    More simply, a FIP is ``a set of enforceable federal regulations
that stand in the place of deficient portions of a SIP.'' McCarthy v.
Thomas, 27 F.3d 1363, 1365 (9th Cir. 1994). As the Court of Appeals for
the D.C. Circuit noted in a 1995 case, FIPs are powerful tools to
remedy deficient state action:

    The FIP provides an additional incentive for state compliance
because it rescinds state authority to make the many sensitive
technical and political choices that a pollution control regime
demands. The FIP provision also ensures that progress toward NAAQS
attainment will proceed notwithstanding inadequate action at the
state level.

    Natural Resources Defense Council, Inc. v. Browner, 57 F.3d 1122,
1124 (D.C. Cir. 1995).
    When EPA promulgates a FIP, courts have not required EPA to
demonstrate explicit authority for specific measures: ``We are inclined
to construe Congress' broad grant of power to the EPA as including all
enforcement devices reasonably necessary to the achievement and
maintenance of the goals established by the legislation.'' South
Terminal Corp. v. EPA, 504 F.2d 646, 669 (1st Cir. 1974). As the Ninth
Circuit stated in a case involving a FIP with far-reaching consequences
in Los Angeles: ``The authority to regulate pollution carries with it
the power to do so in a manner reasonably calculated to reach that
end.'' City of Santa Rosa v. EPA, 534 F.2d 150, 155 (9th Cir. 1976),
vacated and remanded on other grounds sub nom. Pacific Legal Foundation
v. EPA, 429 U.S. 990 (1976).
    In addition to giving EPA remedial authority, section 110(c)
enables EPA to assume the powers that the state would have to protect
air quality, when the state fails to adequately discharge its planning
responsibility. As the Ninth Circuit held, when EPA acts to fill in the
gaps in an inadequate state plan under section 110(c), EPA `` `stands
in the shoes of the defaulting State, and all of the rights and duties
that would otherwise fall to the State accrue instead to EPA.' ''
Central Arizona Water Conservation District v. EPA, 990 F.2d 1531, 1541
(9th Cir. 1993). As the First Circuit held in an early case:

    ``[T]he Administrator must promulgate promptly regulations
setting forth `an implementation plan for a State' should the state
itself fail to propose a satisfactory one * * * The statutory scheme
would be unworkable were it read as giving to EPA, when promulgating
an implementation plan for a state, less than those necessary
measures allowed by Congress to a state to accomplish federal clean
air goals. We do not adopt any such crippling interpretation.''

    South Terminal Corp. v. EPA, supra, at 668 (citing previous version
of section 110(c)).
    The Billings/Laurel SO2 FIP establishes emission limits
and compliance determining methods for four sources located in
Billings/Laurel, Montana, to replace/fill gaps in portions of the SIP
we disapproved, and to

support our attainment demonstration. Three of the sources are
petroleum refineries: CHS Inc., ConocoPhillips (including the Jupiter
Sulfur facility), and ExxonMobil. The fourth source is Montana Sulphur
& Chemical Company, which provides sulfur recovery for the ExxonMobil
refinery.
    The following is a summary of the major components of our FIP rule:
    (1) The FIP establishes flare emission limits at all four sources
(150 lbs SO2/3-hour period at all but the Jupiter Sulfur
flare, 75 lbs SO2/3-hour period shared limit for the Jupiter
Sulfur flare and the Jupiter Sulfur SRU/ATS stack) and monitoring
methods to determine compliance with those limits. The FIP includes an
affirmative defense to penalties for violations of the flare limits
that occur during malfunction, startup, and shutdown periods. To
determine flare emissions, the FIP requires concentration monitoring
(which can consist of continuous monitoring, grab sampling, or
integrated sampling) and continuous flow monitoring.
    (2) The FIP prohibits the burning of sour water stripper overheads
in CHS Inc.'s main crude heater and requires CHS Inc. to keep the valve
between the old sour water stripper and the main crude heater closed,
chained, and locked.
    (3) The FIP provides that emission limits for identified ExxonMobil
refinery fuel gas combustion units are contained in the SIP, and
establishes compliance determining methods for instances in which the
H2S concentration in the refinery fuel gas stream exceeds
1200 ppmv. These methods involve the use of length-of-stain detector
tubes on a once-per-hour frequency.
    (4) The FIP provides that emission limits for ExxonMobil's Coker CO
Boiler stack, when ExxonMobil's Coker unit is operating and Coker unit
flue gases are burned in the Coker CO Boiler, are contained in the SIP.
The FIP establishes compliance determining methods for these emission
limits that require measurement of the SO2 concentration and
flow rate in the Coker CO Boiler stack using CEMS.
    (5) The FIP establishes emission limits on MSCC's SRU 100-meter
stack, based on good engineering practice (GEP) stack height credit of
65 meters, with compliance with these limits to be determined using
methods already approved in the SIP. The FIP does not provide variable
emission limits for this stack.
    (6) The FIP establishes emission limits and compliance determining
methods for MSCC's auxiliary vent stacks and SRU 30-meter stack. In
addition to mass limits, the FIP establishes concentration limits on
fuel burned in the units that vent to the auxiliary vent stacks and SRU
30-meter stack. These concentration limits are 160 ppm H2S
per 3-hour period and 100 ppm H2S per calendar day. When
trigger events specified in the rule occur, MSCC must measure the
H2S concentration in the fuel using length-of-stain detector
tubes on a once-per-3-hour period.
    (7) The FIP establishes various recordkeeping and reporting
requirements.
    It is important to note that, in cases where the provisions of the
FIP address emissions activities differently or establish different
requirements than provisions of the SIP, the provisions of the FIP take
precedence. We also caution that if any of the four sources are subject
to requirements under other provisions of the Act (e.g., section 111 or
112, part C of title I, or SIP-approved permit programs under part A of
title I), our promulgation of the FIP does not excuse any of the
sources from meeting such requirements. Finally, our promulgation of
the FIP does not imply any sort of applicability determination under
other provisions of the Act (e.g., section 111 or 112, part C of title
I, or SIP-approved permit programs under part A of title I).

II. Issues Raised by Commenters and EPA's Response

A. FIP Not Necessary

1. Ambient Data and Historical Modeling Show Attainment
    (a) Comment (CHS Inc., COPC, ExxonMobil, NPRA, MPA, MDEQ, MSCC,
WETA): The FIP is not necessary for attainment of the NAAQS because
ambient data show that the Billings/Laurel area has been for many years
and continues to be in attainment with both the Federal and State
SO2 ambient air quality standards for all averaging periods.
    Response: EPA does not agree that a FIP is not necessary because
ambient data show attainment of the SO2 NAAQS. Ambient
monitoring is limited in time and in space. Ambient monitoring can
measure pollutant concentrations only as they occur; it cannot predict
future concentrations when emission levels and meteorological
conditions may differ from present conditions.
    EPA has long held that ambient monitoring data alone generally are
not adequate for SO2 attainment demonstrations.
Additionally, a small number of ambient SO2 monitors usually
are not representative of the air quality for an area. (See reference
document GGGGG, April 21, 1983, memorandum from Sheldon Meyers,
Director, Office of Air Quality Planning and Standards (OAQPS), to
Regional Air and Waste Division Directors, titled ``Section 107
Designation Policy Summary,'' and reference document HHHHH, September
4, 1992, memorandum from John Calcagni, Director, Air Quality
Management Division, OAQPS, to Regional Air Division Directors, titled
``Procedures for Processing Requests to Redesignate Areas to
Attainment.'')
    Typically, modeling estimates of maximum ambient concentrations are
based on a fairly infrequent combination of meteorological and source
operating conditions. To capture such results on an ambient monitor
would normally require a prohibitively large and expensive network.
Therefore, dispersion modeling is generally necessary to
comprehensively evaluate sources' impacts and to determine the areas of
expected high concentrations. (Id.) Air quality modeling results would
be especially important if sources were not emitting at their maximum
level during the monitoring period or if the monitoring period did not
coincide with potentially worst-case meteorological conditions.
Further, ambient monitoring data are not adequate if sources are using
stacks with actual heights greater than good engineering practice stack
height (which indeed is the case with MSCC and ConocoPhillips) or other
dispersion techniques for which SIP/FIP modeling credit is not allowed.
(See also our discussion of related issues in our final action on the
Billings/Laurel SO2 SIP (67 FR 22168, 22185-22187, May 2,
2002.))
    Ambient monitoring data and air quality modeling data for a
particular area can sometimes appear to conflict. This is primarily due
to the fact that modeling results may predict maximum SO2
concentration at receptors where no monitors are located.
    Moreover, our SIP Call for the Billings/Laurel area was based on
modeled violations of the SO2 NAAQS, not monitored
violations. (See reference documents Y and Z.) We took final action on
the SIP Call in our May 2, 2002, action on the Billings/Laurel SIP (67
FR 22168, 22173), and we are not revisiting it in this FIP action. It
would be inconsistent and inappropriate to now rely solely on
monitoring to determine necessary measures and demonstrate attainment.
    It is especially important to recognize that, as a result of our
partial and limited disapproval of the Billings/

Laurel SO2 SIP, we are legally obligated to promulgate a FIP
for the area. See section 110(c)(1) of the CAA, 42 U.S.C. 7410(c)(1).
However, the SIP deficiencies that triggered our partial and limited
disapproval were varied and were not necessarily associated with
problems that could be measured at an ambient monitor. For example, one
basis for disapproval of the SIP was the State's use of improper (too
tall) stack height credit for MSCC in modeling attainment of the NAAQS.
In the real world, emissions at the actual (100 meter) height of the
stack create less impact on monitored ambient concentrations in the
Billings/Laurel area than if the emissions were emitted from a lower
stack. Nonetheless, we had to partially disapprove the SIP due to the
State's inappropriate grant of stack height credit, and section 110(c)
of the CAA requires that we correct the deficiency. Since the State did
not model attainment at the proper stack height credit for MSCC's
stack, it was necessary that we do so and set emission limits for the
stack consistent with our attainment demonstration. We believe MSCC has
consistently been meeting the emission limits we are adopting, so there
may be no reduction in actual emissions from the stack, but that does
not mean the CAA allows us to forego this aspect of the FIP.
    Likewise, CAA sections 110(a)(2)(A) and (C) require that SIP
control measures be enforceable. We disapproved several source
monitoring methods because they were not adequate to determine
compliance under all operating conditions. It may be impossible to
measure the impact these SIP deficiencies may have on ambient
SO2 concentrations in the area, but the CAA still requires
that we correct the deficiencies. Regarding the emission limits and
compliance determining methods for the flares, the State-only flare
limits, which the State relied on to demonstrate attainment, may have
positively impacted flare emissions in the past few years. However, the
State did not include the State-only flare limits or adequate
compliance determining methods in the SIP. Thus, the SIP remains
deficient. We now have the responsibility to ensure that emission
limits relied on to demonstrate attainment are included in the SIP and
are practically enforceable, consistent with the requirements of
section 110 of the Act.
    (b) Comment (MSCC, MDEQ): The State's SIP modeling, along with
appropriate emission limits, show attainment of the NAAQS.
    Response: EPA addressed this issue in its actions on Montana's SIP
submissions. As explained in those actions, EPA does not agree that the
State's SIP modeling, along with appropriate emission limits, show
attainment of the NAAQS. EPA's formal determinations regarding the
attainment demonstration and emission limits were made in final actions
on May 2, 2002 (67 FR 22168) and May 22, 2003 (68 FR 27908). The FIP
fills the gaps for the provisions we disapproved.
    We note that we have not reopened our SIP actions as part of this
action. Thus, to the extent the commenters are expressing their
disagreement with EPA's actions on the SIP, their comments are not
relevant to this action, and EPA is not re-considering them here.
    (c) Comment (ExxonMobil): EPA's proposed FIP ignores the
substantial improvement in air quality in the Billings/Laurel area and
instead predicts exceedances of NAAQS based upon modeling performed as
long as 15 years ago. EPA's FIP proposal must be further examined in
light of subsequent developments, including correct modeling and
consideration of currently available information indicating compliance.
    Response: See response to comment II.A.1.(a), above, regarding
ambient data and response to comments in section II.E., below,
regarding modeling.
2. Existing Controls Sufficient
    (a) Comment (MDEQ, MSCC, COPC, ExxonMobil, MPA, NPRA, WETA): The
FIP offers questionable improvements because the existing control plan
provisions submitted by the state are adequate and contain sufficient
SO2 emission controls and strategies and provide for the
implementation, maintenance, and enforcement of the SO2
NAAQS.
    Response: EPA addressed the adequacy of Montana's SIP submissions
in its final actions on the SIP. As explained in those actions, EPA
does not agree that the State's SIP control plan provisions are
adequate and contain sufficient SO2 emission controls to
show attainment of the NAAQS. EPA's formal determinations regarding the
attainment demonstration and emission control plan were made in final
actions on May 2, 2002 (67 FR 22168) and May 22, 2003 (68 FR 27908). In
our May 2002 and May 2003 actions we disapproved various control plan
provisions. The FIP fills the gaps for the provisions we disapproved.
The FIP offers necessary improvements to the SIP by imposing new
emission limits and reliable compliance determining methods to ensure
attainment of the SO2 NAAQS.
    We note that we have not reopened our SIP actions as part of this
action. Thus, to the extent the commenters are expressing their
disagreement with EPA's actions on the SIP, their comments are not
relevant to this action, and EPA is not re-considering them here.
    (b) Comment (CHS Inc., WETA, COPC, MDEQ, ExxonMobil, NPRA): In
addition to the SIP, SO2 emissions in the Billings/Laurel
area have decreased as a result of Consent Decrees and Montana Air
Quality Permit changes. These limits are all federally enforceable
because there are Title V operating permit conditions (CHS Inc.). EPA
did not consider these emission reductions in making its determination
that the FIP was necessary. The FIP proposal does not otherwise
acknowledge the practical effects of the recent consent decrees between
the primary refinery parties subject to regulation as well as other
permitting actions that have occurred over the past eight years (MSCC,
COPC).
    Response: EPA did not consider the emission reductions that
resulted, or will result, from the consent decrees and/or State permit
revisions to determine that the FIP was necessary or include the
emission reductions in our modeling for several reasons.
    First, the FIP is required because we disapproved the SIP, and the
State has not made revisions to the SIP to address the SIP's flaws. As
noted in other responses, because we disapproved the SIP, we have a
legal obligation to promulgate a FIP. See CAA section 110(c), 42 U.S.C.
7410(c).
    Second, even though permits and consent decrees are federally
enforceable, some permits can be revised without EPA approval and
consent decrees have a limited lifespan.\2\ To protect the integrity of
the attainment demonstration, and our statutory role in assessing SIP/
FIP adequacy, we believe that stationary source emission limits
necessary to demonstrate attainment must be included in the FIP (or
approved SIP). See, e.g., CAA sections 110(a)(2)(A), 110(i), 110(k)(3)-
(6), and 110(l), 42 U.S.C. 7410(a)(2)(A), (i), (k)(3)-(6), and (l).
This ensures that changes to those limits will only be made with EPA's
approval as a SIP or FIP revision,

following notice and comment rulemaking.
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    \2\ The State can revise construction permits without EPA
approval, and, while EPA has authority to object to Title V permits,
that authority is only available to ensure that underlying
applicable requirements are included in the Title V permits. Thus,
if those underlying requirements change, EPA may have no recourse at
the Title V stage.
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    Third, the consent decrees and permitting actions, for some
emission points, do not contain SO2 emission limits that are
consistent with the averaging times of the SO2 NAAQS,
specifically, the 3-hour and calendar day averaging periods. For
example, the SIP establishes 3-hour, calendar day, and calendar year
emission limits for CHS Inc.'s FCC regenerator/CO boiler stack. The
January 17, 2007, final State construction permit (reference document
IIIII) and the consent decree (reference document JJJJJ) indicate that
the FCC regenerator stack SO2 emissions shall not exceed 50
ppm by volume (corrected to 0% O2) for a 7-day rolling
average [or a fresh feed of 0.3 percent by weight] and 25 ppm by volume
(corrected to 0% O2) for a 365-day rolling average. None of
the commenters has suggested these limits be converted to FIP mass
limits that would apply over a 3-hour averaging period, and the State
has not submitted a SIP revision with such limits.
    It should be noted that EPA did solicit comment on whether we
should limit the main flares to 500 pounds of SO2 per
calendar day. This value is consistent with the trigger point for
certain analyses contained in settlements (i.e., consent decrees)
between the United States and CHS Inc., ConocoPhillips, and ExxonMobil.
We received limited comments on this proposal and have decided to keep
the limit at 150 pounds of SO2 per 3-hour period to maintain
consistency with the State's State-only limit.

B. EPA Exceeded Its Authority in Proposing a FIP

1. State's Responsibility
    (a) Comment (WETA, MPA, ExxonMobil): EPA's role is limited to
determining whether or not a SIP is attaining and maintaining the
NAAQS. Selecting the source mix and various control measures to achieve
these ends has been determined by courts to be the sole responsibility
of the state. EPA's proposed action intrudes on the primary
responsibility of the state and local governments to implement the
Clean Air Act (MSCC).
    Response: The commenters' characterization of EPA's role regarding
SIPs is not accurate. We lack authority to question a state's choices
of emissions limitations if they are part of a plan that satisfies the
standards of the Clean Air Act. Train v. Natural Resources Defense
Council, 95 S.Ct. 1470, 1481-1482 (1975). In our 2002 and 2003 actions,
we found that Montana's SO2 SIP for Billings/Laurel did not
fully satisfy CAA requirements. See 67 FR 22168, May 2, 2002 and 68 FR
27908, May 22, 2003. Thus, pursuant to section 110(c) of the CAA, 42
U.S.C. 7410(c), we are required to promulgate a FIP. In doing so, we
stand in the state's shoes and have authority to determine emissions
limitations and other measures for specific sources to fill gaps in the
SIP. Central Arizona Water Conservation District v. EPA, 990 F.2d 1531,
1541 (9th Cir. 1993); South Terminal Corp. v. EPA, 504 F.2d 646, 668
(1st Cir. 1974) (citing previous version of CAA section 110(c)).
    We note that we have not reopened our SIP actions as part of this
action. Thus, to the extent the commenters are expressing their
disagreement with EPA's actions on the SIP, their comments are not
relevant to this action, and EPA is not re-considering them here.
    (b) Comment (WETA): Since the State of Montana has already taken
appropriate actions to reduce sulfur dioxide emissions, EPA does not
have the authority under the CAA to adopt the proposed FIP.
    Response: See response to comment II.B.1.(a), above. The adequacy
of the State of Montana's actions has already been considered by EPA in
other rulemaking actions that addressed the State's SIP submission.
Those actions are not the subject of EPA's present rulemaking, which
promulgates the necessary measures to remedy the deficiencies EPA
identified in its prior SIP reviews.
    (c) Comment (MSCC): States have primacy, and because EPA did not
choose to exercise its rights in the comprehensive and competent state
decision process, EPA may not default and then act.
    Response: Under section 110(c) of the Act, EPA is not required to
participate in a state's administrative process before promulgating a
FIP.
    (d) Comment (MSCC, MDEQ, ExxonMobil): EPA has no authority to
question the wisdom of a state's choices of emission limitations if
they are part of a plan that satisfies the standards of Sec.  110(a)(2)
of the Act. As long as the ultimate effect of a state's choice of
emission limitations is compliance with the NAAQS, the state is at
liberty to adopt whatever mix of emission limitations it deems best
suited to its particular situation. There is no evidence provided by
EPA that Montana reached its material conclusions or choices in the SIP
unreasonably. Additionally, EPA has not shown that additional controls
beyond the SIP measures adopted by Montana are necessary to meet or
assure SO2 NAAQS compliance.
    Response: See our responses to comments II.A.1.(a) and II.B.1.(a),
above. Much of this comment pertains to our actions on Montana's SIP.
We are not revisiting or reopening comment on those actions here. Our
basis for finding that the SIP was not adequate to ensure attainment
and meet other CAA requirements is described in our actions on the SIP.
Once we disapprove part or all of a required SIP, section 110(c) of the
Act requires that we issue a FIP. Our obligation in this action is to
correct the SIP deficiencies we previously identified. Thus, the
findings that triggered our responsibility to promulgate a FIP were
established in the prior rulemaking actions reviewing Montana's SIP.
EPA is not required to repeat those findings in the FIP rulemaking
itself.
    (e) Comment (ExxonMobil): EPA cannot propose a FIP to replace a
SIP, unless the SIP is substantially inadequate to ensure compliance
with the CAA.
    Response: The commenter misstates the standard for promulgation of
a FIP. Section 110(c) of the CAA is straightforward--a FIP is required
if (1) EPA finds that a state has failed to make a required submission;
(2) EPA finds that a plan submission does not satisfy the completeness
criteria established under section 110(k)(1)(A) of the CAA; or (3) EPA
disapproves a SIP in whole or in part. EPA partially disapproved the
Billings/Laurel SO2 SIP; thus, a FIP is required. Contrary
to the commenter's assertion, the obligation to promulgate a FIP is not
contingent on an EPA finding of substantial inadequacy. As explained
above, the findings triggering our responsibility to promulgate a FIP
were made in the prior actions reviewing Montana's SIP.
    (f) Comment (MSCC): The commenter claims EPA's action violates the
Tenth Amendment to the Constitution. The commenter also claims EPA's
FIP is dictating the required controls in contravention of the holdings
in Commonwealth of Virginia v. EPA, 108 F.3d 1397 (D.C. Cir. 1997) and
Bethlehem Steel v. Gorsuch, 742 F.2d 1028 (7th Cir. 1984).
    Response: Our FIP compels no action on the part of the State and is
not coercive vis-[agrave]-vis the State. Our FIP contains requirements
applicable to four private companies. The Tenth Amendment is not
implicated. Nor do our actions contravene Commonwealth of Virginia or
Bethlehem Steel. The former case held that EPA cannot, in a SIP Call,
dictate that a state adopt a particular control measure to

demonstrate attainment of the NAAQS. EPA had issued a SIP Call finding
that the SIPs of 12 states were inadequate to meet the ozone NAAQS and
in its SIP Call rule, specified that the states needed to submit SIPs
that included the California Low Emission Vehicle Program. In this
matter, we are promulgating a FIP, not issuing a SIP Call. We are not
directing any action by the State. Thus, the Commonwealth of Virginia
case is not relevant to our FIP. Bethlehem Steel is also not relevant
to our FIP action. In that case, the 7th Circuit held that it was
improper for EPA to partially approve an Indiana SIP revision so as to
render it more stringent than the State intended. We are promulgating a
FIP in this action, not acting on a SIP; thus, Bethlehem Steel does not
apply. As we note elsewhere, once we disapprove a SIP, we are required
to promulgate a FIP, and in promulgating the FIP, we stand in the
state's shoes. See section 110(c) of the CAA, 42 U.S.C. 7410(c);
Central Arizona Water Conservation District v. EPA, 990 F.2d 1531, 1541
(9th Cir. 1993).
    (g) Comment (MSCC): The commenter argues that the cases EPA cited
in the preamble to the proposed Billings/Laurel FIP, regarding its FIP
authority, do not speak to the central question--``When and on what
authority may the EPA undertake the draconian act of displacing a
state's implementation plan?'' The commenter argues that the question
is particularly sensitive in this case because the State and the
sources spent years negotiating the SIP.
    Response: As noted in response to comment II.B.1.(e), the CAA
requires that we promulgate a FIP whenever we disapprove a SIP, in
whole or in part. While we are sensitive to the fact that the State and
sources spent years negotiating the SIP, that does not change our
obligation under the CAA.
2. No Adequate Basis for FIP
    (a) Comment (MSCC, ExxonMobil): Because EPA must find substantive
noncompliance with some provision of the Clean Air Act, specifically,
failure to attain NAAQS, and because that finding of substantial
inadequacy must be clearly stated, the present FIP decision must fall.
It is inadequate on both counts. EPA has not provided any evidence that
the State plan is not working.
    Response: See our response to comment II.B.1.(e), above. The
evidence supporting EPA's determinations regarding the adequacy of
Montana's SIP is contained in the record for those rulemaking actions,
and need not be repeated here. EPA's disapproval of the SIP triggered
the obligation for a FIP. No separate showing that the State plan is
not working or does not meet CAA requirements is needed as part of this
action. Commenters' comments regarding EPA's SIP actions are not
relevant for this rulemaking.
    (b) Comment (ExxonMobil): Even when the EPA has statutory authority
for a particular rule, its technical decisions about the level of
pollutant reduction needed to comply with the CAA and the control
strategies necessary to meet the level of pollutant reduction must be
rational. Courts ``confronted with important and seemingly plausible
objections going to the heart of a key technical determination * * * ''
will not presume that EPA would never behave irrationally. South
Terminal Corporation v. Environmental Protection Agency, 504 F.2d 646,
665 (1st Cir. 1974). In South Terminal Corporation, various interested
parties challenged EPA's FIP on technical grounds. Id. at 662-66. The
court held that EPA failed to adequately support its decision to
promulgate the rules contained in the FIP and remanded the case to EPA
to develop the record. Id. at 666. The court questioned EPA's position
in light of contradictory modeling and data, concluding that ``it is
not clear whether or not the ambient air at Logan meets, or will
without controls by mid-1975 will meet, the national primary
standard.'' Id. 664. Similarly, in the present FIP proposal, EPA has
neither determined appropriate current modeling nor used currently
available information.
    Response: The standards for judicial review of this rulemaking
action are contained in section 307(d)(9) of the CAA, 42 U.S.C.
7607(d)(9). We believe the emission limitations and other requirements
in this FIP are reasonable and that the situation in the cited case is
not analogous.\3\ The commenter has not identified any modeling that
contradicts our attainment demonstration, which forms the basis for the
FIP's emission limitations; nor has the commenter shown that a
different model would result in substantially different emission
limitations. Our responses pertaining to model selection and input data
are contained in section II.E., below. Further, we note that it does
not appear the commenter is suggesting that the entire SIP should be
re-done based on more current modeling and more up-to-date information.
On the contrary, the commenter seems satisfied with the EPA-approved
emission limitations in the SIP,\4\ which were based on the very
modeling that the commenter now claims is unreliable.
---------------------------------------------------------------------------

    \3\ In South Terminal Corporation, EPA had determined emissions
reductions needed to achieve the ozone and carbon dioxide NAAQS
based on monitored values that the Court found highly questionable
(petitioners claimed the ozone monitor was defective). South
Terminal Corporation, 504 F.2d 646, 662 (1974). The commenter seems
to suggest that the Court rejected EPA's modeling approach, but in
fact, the Court was satisfied with the rollback modeling that EPA
used. Id.
    \4\ Among other things, the commenter asserts that the state SIP
requirements are adequate to protect the NAAQS. See reference
document YYYY, page 27.
---------------------------------------------------------------------------

    (c) Comment (ExxonMobil): Citing Hall v. United States
Environmental Protection Agency, 273 F.3d 1146, 1159 (9th Cir. 2001),
the commenter states that in acting on a SIP, the test EPA applies is
to ``measure the existing level of pollution, compare it with the
national standards, and determine the effect on this comparison of
specified emission modifications.'' The commenter argues that in the
FIP proposal, EPA did not correctly identify the existing level of
pollution and ignored the substantial evidence of permanently reduced
SO2 emissions and levels in the Billings/Laurel area. The
commenter also argues that EPA's authority is limited by its mandate
under the CAA to ensure attainment and maintenance of the NAAQS as well
as the CAA's other general requirements.
    Response: See responses to comments II.A.1.(a), II.A.2(b), and
II.E.1.(e) and (g). Also, the Hall case involved a challenge to EPA's
approval of a SIP revision for Clark County, Nevada, and EPA's
interpretation of section 110(l) of the CAA, which provides that EPA
may not approve a SIP revision if it would interfere with attainment or
other applicable requirements of the CAA. EPA asserted that its
approval of the Clark County SIP revision was consistent with section
110(l) because the revision did not relax the existing SIP. The Court
disagreed, holding that 110(l) requires more--a determination that the
specific revision, when considered in the context of the SIP elements
already in place, can meet the Act's attainment requirements. Hall at
1152, 1159. It was in these circumstances that the Court expected EPA
to determine the extent of pollution reductions required and evaluate
whether the reductions resulting from the revision would be sufficient
to attain the NAAQS.
    In its reference to Hall, the commenter appears to be conflating
two disparate concepts. The Hall Court was addressing EPA's action on a
SIP revision and indicating that EPA was not adequately evaluating
whether Clark County's rule change would interfere

with attainment and other CAA requirements. The Court was not
establishing a standard for a FIP or indicating that EPA was requiring
more than necessary for the area, which seems to be what the commenter
is suggesting in the case of the Billings/Laurel FIP. As we explain in
greater depth elsewhere in this notice, we are not starting from
scratch with our FIP. Instead, we are working within the framework of
the existing Billings/Laurel SIP to fill the gaps resulting from our
partial and limited disapproval of discrete SIP elements. In this
unique circumstance, where only discrete elements of the SIP were
deficient, the CAA does not require us to reevaluate or replace the
entire SIP or the basic modeling approach upon which it was based.
Nothing in the CAA requires EPA to reject an entire SIP when only
certain elements within it are not approvable, and doing so, where that
is not necessary to address a discrete deficiency, would be
inconsistent with the basic scheme of cooperative federalism embodied
in the CAA.
    Nor are we required as part of this FIP to revisit our SIP Call or
the bases for our SIP disapproval. Our task is to fix the portions of
the SIP that were deficient. It is reasonable to continue to treat as
valid the factors we found adequate to support the portions of the SIP
we approved, and augment and/or replace those factors that we found
inadequate. In fact, based on the holding in Train v. NRDC, 421 U.S. 57
(1975), recited by this commenter and others, it would be inappropriate
for EPA to now reject or replace the portions of the SIP that we
approved as meeting the CAA's requirements, because to do so would be
to intrude on the State's authority under the CAA to establish the mix
of controls for the area.\5\ The State, of course, remains free to
submit a SIP revision that reflects a different mix of controls across
all the sources. This would be the mechanism, for example, whereby the
State could adopt SIP limits that correlate to refinery consent decree
limits.\6\ If the State were to submit such a revision, we would
evaluate the revision according to the Act, our regulations, and the
relevant cases.
---------------------------------------------------------------------------

    \5\ To the extent the commenter is arguing that we may do no
more in this FIP than appears minimally necessary to attain the
NAAQS, we reject that notion as well. See, e.g., Central Arizona
Water Conservation District v. EPA, 990 F.2d 1531, 1541 (9th Cir.
1993) (EPA ``stands in the shoes of the defaulting State, and all of
the rights and duties that would otherwise fall to the State accrue
instead to EPA.'') Under the CAA, states are not restricted to
barely meeting the NAAQS. In fact, the opposite is true--states may
exceed minimum requirements. See CAA section 116, 42 U.S.C. 7416. In
any event, our modeled attainment demonstration resulted in
projected values just at the 24-hour SO2 NAAQS (365
[mu]g/m\3\) and just below the 3-hour SO2 NAAQS (1291.5
[mu]g/m\3\). However, we think we had discretion to adopt limits (to
replace those we disapproved) consistent with modeled ambient
concentrations further below the NAAQS, if we had felt a larger
margin of safety was justified to ensure attainment and maintenance.
    \6\ As we allude to in sections II.A.2.(b), II.D.4., and
II.E.1.(e), the consent decree limits would need to be translated
into limits that support an attainment demonstration for the
SO2 NAAQS. In sections II.A.2.(b) and II.D.4., we
identify some of our concerns with the consent decree limits.
---------------------------------------------------------------------------

    (d) Comment (ExxonMobil): EPA's proposal imposes costly technology
requirements not rationally designed to achieving their stated
objectives. While EPA has authority to impose an emission limitation,
the emission limitation must be necessary to attain NAAQS. City of
Santa Rosa v. EPA, 534 F.2d 150, 155 (9th Cir. 1976), vacated on other
grounds, 429 U.S. 990 (1976). The EPA derived its authority in City of
Santa Rosa from its statutory mandate to ensure compliance with NAAQS
and the fact that no alternative to its proposal was adequate to ensure
compliance with NAAQS. It is clear that Montana's existing SIP,
supplemented as it is by further state and federally enforceable
consent decrees are a more than adequate alternative.
    Response: The cited case actually stands for the proposition that
EPA's authority to adopt measures to meet the NAAQS is expansive. EPA
adopted a FIP provision that would have required a substantial
reduction (up to 100%) in the supply of gasoline to major metropolitan
areas in California, including Los Angeles. Even the EPA acknowledged
that the rule would cause severe social and economic disruption, and
the EPA Administrator at the time publicly advocated amendments to the
CAA to provide relief from EPA's own FIP rule. Nonetheless, the Court
held that economic and social disruption are not cognizable if (1) a
measure is necessary to attain the NAAQS; (2) there is no statutory
limitation on EPA's authority to adopt the measure; and (3) there are
no equally effective, less burdensome alternatives. City of Santa Rosa
at 151-154.
    The measures EPA is promulgating in this FIP are in no way
comparable to the reduction in gasoline supply at issue in the City of
Santa Rosa case. Our FIP is narrowly tailored to fill the gaps in the
Billings/Laurel SIP. Section 110(c) requires us to promulgate the FIP.
There is no statutory limitation on our authority to adopt the measures
we are adopting. On the contrary, section 110(a)(2)(A) of the Act
requires enforceable emission limitations as necessary or appropriate
to meet the applicable requirements of the Act, which include
attainment and maintenance of the SO2 NAAQS. Using ISC, the
same model the State used to set the commenter's emission limits in the
SIP, we have determined emission levels consistent with attainment and
established corresponding emission limits on the flares, MSCC's main
stack, and other emission units, whose emission limits we disapproved
in our SIP action. While the authority to require monitoring,
recordkeeping, and reporting requirements can be inferred from CAA
sections 110(a)(2)(A) and (C), section 110(a)(2)(F) of the Act
specifically indicates that the EPA Administrator may prescribe the
installation, maintenance, and replacement of monitoring equipment by
stationary sources, as well as reporting requirements. Our requirement
for the refineries and MSCC to install monitoring equipment to measure
flare gas flow and concentrations is consistent with this authority and
is rationally related to the goals of the FIP, i.e., to ensure
attainment and maintenance of the SO2 NAAQS. We do not
believe estimating flare emissions or emissions from other units is a
sufficient substitute for real-time monitoring for purposes of this
FIP; estimation is not an equally effective technique.
    The commenter argues that the existing SIP and the State and
federally enforceable consent decrees are a more than adequate
alternative to our FIP requirements. This comment ignores the fact that
we disapproved portions of the SIP as not meeting the CAA's
requirements. Elsewhere we explain that the consent decree provisions
are not sufficient to meet the CAA's requirements under section 110
related to attainment and maintenance of the NAAQS. See, e.g., sections
II.A.2.(b), II.D.4., and II.E.1.(e).
    (e) Comment (MSCC): EPA's failure to issue the FIP within the CAA's
two-year deadline is important in this case. As a result of EPA's
delay, EPA should have to consider the cleanup of emissions that has
occurred and significant changes in modeling technology.
    Response: We regret that it has taken this long to issue the FIP.
We disagree that missing the two-year deadline obviates our duty or the
need for the FIP. The State has not submitted a SIP revision correcting
the portions of the SIP that we disapproved, despite the passage of
time. Regarding the argument that we should have considered the
reduction in emissions since we disapproved the SIP, see our responses
to comments in section II.A. In section II.E, we respond to comments
arguing

that we should have used newer modeling technology.

C. Flare Monitoring

1. Flare Flow Monitoring
    (a) Comment (MSCC): The core flowmeter technology application for
flare systems seems to be an established technology, with thousands of
installations completed around the world on other types of gas and
liquid streams. However, none was identified that is following the
precise specifications of the FIP proposal. Installation and operation
of a flow meter in flare gas service at MSCC are probably achievable
today, but not at the flow range below 1 fps, and not with conventional
QA/QC procedures. Flow monitors have a difficult time measuring or
reliably detecting low flow velocities (under approximately 1.0 fps)
without false positives or false negatives. EPA should revise the
proposed rule that currently indicates:

``[t]he minimum detectable velocity of the flow monitoring device(s)
shall be 0.1 feet per second (fps). The flow monitoring device(s)
shall continuously measure the range of flow rates corresponding to
velocities from 0.5 to 275 fps and have a manufacturer's specified
accuracy of 5% over the range of 1 to 275 fps.
    The revised rule should read ``[t]he minimum resolution of the
flow monitoring device(s) shall be 0.1 feet per second (fps) when
measuring flow rates above 1.0 fps. The device(s) shall continuously
measure the range of flow rates corresponding to velocities from 1.0
to 275 fps and have a manufacturer's specified accuracy of 5% over the range of that range.''

    The rule should also clarify if ``accuracy'' is intended to be 5%
of the full-scale range of the instrument (13.7 fps is 5% of 275 fps),
or if this is intended to be 5% of the measured flow, which would be
0.05 fps at a flow of 1 fps, and would clearly be non-achievable with a
resolution of 0.1 fps.
    Response: EPA proposed the volumetric flow monitoring
specifications based on what we saw was achievable in vendor literature
(see reference documents NN and OO) and what was being required by
regulation in the Bay Area Air Quality Management District (BAAQMD)
(see reference document LL) and South Coast Air Quality Management
District (SCAQMD) (see reference document CCC).
    The commenter asserts that installation and operation of a flow
meter at the flow range below 1 fps are not achievable. However,
various sources indicate that ultrasonic flow meters can measure in the
range of 0.1 to 1 fps. For example, in ``Flare Gas Ultrasonic Flow
Meter,'' J.W. Smalling, L.D. Brawsell, L.C. Lynnwoth and D. Russel
Wallace, Proceedings Thirty-Ninth Annual Symposium on Instrumentation
for the Process Industries, 1984, the authors reported ``initially, a
modest objective was established to develop an ultrasonic flow switch
capable of detecting leaks in flare lines corresponding to flow
velocity on the orders of 0.3 ms/ (1 ft/s). As testing continued,
however, it became apparent that the equipment could measure flows
below 0.03 m/s (0.1ft/s) and up to at least 6 m/s (20 ft/s) in flare
stacks * * *'' (see reference document KKKKK). See also reference
document OO, ``the DigitalFlowGF868 meter achieves rangeability of 2750
to 1. It measures velocities from 0.1 to 275 ft/s (0.03 to 85 m/s) in
both directions, in steady or rapidly changing flow, in pipes from 3
in. to 120 in. (76 mm to 3 m) in diameter.''
    Additionally, the BAAQMD (see reference document LL) and SCAQMD
(see reference document CCC) require flow meters on flares. BAAQMD
requires that the minimum detectable velocity shall be 0.1 fps and the
SCAQMD requires monitors with a velocity range of 0.1 to 250 fps. Based
on conversations with the BAAQMD, it appears that the refineries in the
Bay Area have installed flow meters meeting the requirements of the
rule (see reference document OOOOO).
    Based on the above, we conclude that flow meters are available that
can measure in the velocity range below 1.0 fps, and other regulatory
authorities are requiring such flow meters with success.
    The commenter also claims that installation and operation of a flow
meter are probably not achievable with conventional QA/QC procedures.
The QA/QC procedures are discussed below in response to comment
II.C.1.(d).
    The commenter argues that flow monitors have a difficult time
measuring or reliably detecting low flow velocities (under
approximately 1.0 fps) without false positives or false negatives. As
indicated in the response to comment II.C.1.(b) below, there are
approaches available for improving measurement accuracy in the 0.1 to
1.0 fps range. In addition, as the response to comment II.C.1.(b)
indicates, in the final FIP we are specifying a separate accuracy range
for the velocity range of 0.1 to 1 fps. Finally, we describe how we are
addressing the false positive and false negative flows in response to
comment II.C.1.(c).
    The commenter asked that the rule clarify if ``accuracy'' of the
instrument is intended to be 5% of the full-scale range of the
instrument or 5% of the measured flow. In the rule, we have clarified
that ``accuracy'' of the instrument is the accuracy of the measured
flow and not the ``full-scale range'' of the instrument.
    The commenter also suggests some changes to the rule. Apart from
adding a separate accuracy range for the velocity range of 0.1 to 1 fps
and clarifying that accuracy is based on the measured flow, we are not
making any additional changes to this aspect of the rule. We explain
our reasoning in the response to this comment II.C.1.(a) and in the
responses to comments II.C.1.(b)-(d), below.
    (b) Comment (ExxonMobil, WSPA): Manufacturers of flow monitoring
instrumentation publish impressive performance specifications regarding
velocity measurement range and accuracy, but often manufacturers'
claims are not actually achieved in practice over the long term. To
achieve a high level of measurement performance in the field requires
adequate lengths of straight flare header pipe upstream and downstream
of the monitor, the absence of flow disturbances, etc. Where these
criteria cannot be met, the advertised or predicted performance of the
flow monitoring system may not be fully realized in practice. MSCC
claimed that significant piping modifications and possible flare
relocation would be required to provide such runs at accessible
locations. CHS Inc. asserted that it is likely that the CHS refinery
flare header will not have adequate distances of undisturbed piping for
ideal installation. In this case, either major, costly piping
modification will be required or the accuracy criteria will not be
achievable.
    Response: The commenters are correct that piping modifications may
be appropriate to optimize the measurements. Each flare system will
have unique flow measurement location issues and will have to be
addressed on a case-by-case basis. Sources may need to work with the
flow monitor manufacturer and flow testers to assure that the monitors
meet the FIP's specifications for accuracy and representativeness and
manufacturer's requirements for assuring ongoing equipment performance.
    In addition to making piping modifications (e.g. flow
straighteners), other approaches are available to improve the
measurement accuracy in the 0.1 to 1.0 fps range. Among the approaches
are the use of additional monitoring paths, monitoring paths of longer
length, and unconventional monitor configurations and path locations.
Another approach involves

the use of Computer Fluid Dynamics (CFD) for the existing piping. CFD
analysis has been used to provide correction factors for a series of
velocities across the range of flow velocities. For example, these
factors have been used to correct flow measurement data for
disturbances caused by upstream pipe irregularities. These approaches
are discussed in ``A Total Approach to Flare Gas Flow Measurement for
Environmental Compliance,'' Gordon Mackie, Jed Matson and Mike Scelzo,
Institute of Measurement and Control--Environmental Conference 2006.
(See reference document LLLLL.) (See also Note to Billings/Laurel
SO2 FIP File regarding conversations with GE Sensing
(reference document MMMMM)).
    Finally, to address concerns regarding the measurement accuracy in
the 0.1 to 1.0 fps range, we are revising the rule to indicate that the
flow monitor must have a manufacturer's specified accuracy of  20% over the range 0.1 to 1 fps. Based on conversations with a
vendor, we believe this is achievable. The vendor indicated that they
have provided methodologies for sources to meet the SCAQMD rule, which
also requires 20% accuracy in the 0.1 to 1.0 fps range. Methodologies
include a second interrogation path or straightening of pipe. (See
reference document MMMMM.)
    (c) Comment (ExxonMobil, WSPA, NPRA, MSCC): Consistently achieving
low flow detection limits can be very difficult. Spurious signal,
resulting in ``eddy'' currents and back-and-forth flows in the flare
header, can easily limit the detection and accuracy of low flow
readings. Furthermore, sometimes a flow monitor will show an indication
of flow even though water seals ahead of the flare stack remain intact
(i.e., there is not flow to the flares). Other regulations in other
jurisdictions allow the sources other means to positively determine
when the flare is not operating (e.g., flare on/off monitoring device,
pressure of water seal). ExxonMobil recommends that similar language be
considered by the stakeholder process for inclusion in the EPA's
proposed FIP, and thereby remove the uncertainty of low flow reading.
MSCC claimed that the EPA proposed FIP language should be revised to
allow flare operations to be monitored by other means, and to disregard
low flow readings when the flare is not operating to eliminate falsely
reported SO2 emissions, when in fact there are none.
    Response: We agree that it is appropriate to include in the
regulation the ability to use other secondary means to determine
whether flow is reaching the flare when the flow monitor indicates low
flow. If the secondary device indicates that no flow is going to the
flare, yet the continuous flow monitor is indicating flow, the
presumption will be that no flow is going to the flare. We have revised
the final rule to allow the use of flare water seal monitoring devices
to determine whether there is flow going to the flare, in addition to
the continuous flow monitoring device. See response to comment
II.F.1.(a) regarding the comment seeking a stakeholder process.
    (d) Comment (ExxonMobil, WSPA): A limitation of flare gas
monitoring systems is the inability to provide for an independent ``in
situ'' verification of accuracy. For example, there is no practical way
to vary the flare gas flow that the monitor sees, and no practical way
to utilize a reference method. Consequently, the calibration of a
monitor is performed electronically, and the demonstration of accuracy
is based on that calibration method. MSCC asserted that the proposed
FIP does not provide adequate guidance to allow development of an
acceptable QA/QC system for routine calibration or daily checks of the
system. Without clear guidance, it is not possible to specify a system
for a systems integrator (DAS/reporting) or an end-user to design or
build a system to accomplish these checks.
    Response: Since refinery flares contain highly variable flows and
highly combustible material, in situ verification of flow measurement
accuracy is difficult. For that reason, the performance specifications
in the FIP rely in large part on procedures developed by the ultrasonic
flow monitor manufacturers \7\ for commissioning monitors to assure the
monitors will meet performance specifications on an ongoing basis.
Manufacturers have established procedures for conducting annual or more
frequent verifications of the performance of installed flow monitors as
well as for the initial installation and performance verification (see
reference document NNNNN). Based on manufacturer established procedures
(Id.), we expect that the annual verification procedures will address
elements such as:

    \7\ Ultrasonic flow monitors will most likely be the monitors
installed to meet the FIP's flow monitoring performance
specifications.

    1. Verification of the Flowmeter with Reference Transducers--the
purpose is to evaluate all flowmeter subsystems with factory-
certified ultrasonic transducers;
    2. Mechanical Inspection of Flowmeter Transducers--the purpose
is to visually verify the integrity of the flare gas flowmeter
transducers and to clean any accumulated debris from the transducer
faces;
    3. Zero Flow Verification--the purpose is to evaluate the
operation of the transducer pair in the flare gas process (the
integrity of the original process transducers is tested in a
controlled environment);
    4. Input/Output Verification--the purpose is to verify the
calibration of the analog I/O of the flare gas flowmeter;
    5. Electronic Flow Simulation--the purpose is to demonstrate the
operation of the flare gas flowmeter over the full measurement range
of the instrument; and
    6. Flowmeter System Reinstallation and Test--the purpose is to
verify that all mechanical systems were properly aligned.

    It should also be noted that since ultrasonic flow monitors do not
contain any moving parts, their performance is not expected to
deteriorate over time. One ultrasonic flow monitoring vendor provided
information on the reliability and availability of the transducers
(sensors in the flare that transmit and receive the ultrasound) they
have installed. The information indicates that the 3,998 transducers
installed between first quarter 2005 and first quarter 2007 had a
reliability percentage of 94.32% and an availability percentage of
99.96%. (See reference documents MMMMM and XXXXXX.) (See also reference
document LLLLL, ``A Total Approach to Flare Gas Flow Measurement for
Environmental Compliance,'' Gordon Mackie, Jed Matson and Mike Scelzo,
GE Sensing, Institute of Measurement and Control, Environmental
Conference 2006, and reference document NNNNN, April 5, 2007, email
from Jed Matson, GE Sensing, to Laurie Ostrand, EPA, containing flare
gas flow meter procedures.
    (e) Comment (COPC): ConocoPhillips asserts it would need to replace
a GE Panametrics flare flow monitor that is well-suited to the variable
flow conditions it experiences, but does not conform precisely to the
proposed specifications. It is difficult to quantify what additional
benefit this change would provide although the cost is significant and
quantifiable. The benefit evaluation is further clouded because of the
relatively recent installation of the Flare Gas Recovery Unit (FGRU).
There is no flow to measure in the flare header when the FGRU is
operating. The FGRU operates on a full-time basis, with the exception
of nominal periods of malfunction or maintenance.
    Response: As indicated above, each source will have unique issues
that will have to be addressed on a case-by-case basis.

    We understand that ConocoPhillips has a FGRU and ExxonMobil will be
installing one. We do not agree that a source with a FGRU should be
exempted from monitoring flow to the flare. We still believe it is
reasonable to include this requirement to gain an accurate picture of
occasions when flow is going to the flare. We note that other areas
that have required refinery flare monitoring (SCAQMD and the BAAQMD)
have not eliminated the flare monitoring requirements at sources with
FGRUs. (See Note to Billings/Laurel SO2 FIP File regarding
conversations with BAAQMD, reference document OOOOO.) However, as
indicated below, we are providing sources other means to determine
total sulfur concentrations in the gas stream to the flare.
    Additionally, we note that the ConocoPhillips refinery in Rodeo,
California has installed flare flow meters and that the refinery also
has a flare gas recovery system. The ConocoPhillips San Francisco
Refinery's July 2007 Flare Minimization Plan (FMP), pages 3-7,
indicates that flow meters have been installed on the Main and MP30
flares per the BAAQMD Regulation 12-11-501. EPA's Billings/Laurel FIP
contains flare flow monitoring specifications very similar to the
specifications in BAAQMD Regulation 12-11-501. The July 2007 FMP
indicates ``The installation of the flow meters provides for enhanced
recognition of flaring events. The flow meters help reduce flaring by
providing an accurate means to measure and provide indication as to
when flaring is occurring. The flow meters are especially useful for
small flaring events which may not be detectable from visual flare
stack monitoring only. The meters help to track and record all
instances of flaring as well as giving Unit Operators immediate
indication that flaring is occurring so that they can take action to
reduce flaring.'' (See reference document PPPPP.)
    (f) Comment (MSCC): The proposed 40 CFR 52.1392(h)(2)(iii) appears
to be in error. The rule indicates that ``The flare gas stream
volumetric flow rate shall be measured on an actual wet basis in
SCFH.'' Actual wet basis would be abbreviated as ACFH. SCFH means
standard cubic feet per hour, meaning that the data has been corrected
to standard temperature and pressure. The SCFH could be replaced with
ACFH. Alternately, the term ``actual'' could be removed from the
section, leaving ``wet basis in SCFH.'' SCFH (corrected for temperature
and pressure) can also be used to compute a mass emission rate of
sulfur dioxide, provided that any concentration measurements of sulfur
are also made on a ``wet'' basis.
    Response: The commenter is correct. We are revising the regulatory
text to read: ``The flare gas stream volumetric flow rate shall be
measured on an actual wet basis, converted to Standard Conditions, and
reported in SCFH.''
    (g) Comment (several commenters): Several commenters express a
general concern that the technology will not be able to meet the
performance specifications.
    Response: See responses to comments II.C.1.(a)-(c), above.
    (h) Comment (YVAS): YVAS concurs with the proposed volumetric flow
monitoring requirements.
    Response: We acknowledge receipt of the supportive comment.
2. Flare Total Sulfur Analyzers
    (a) Comment (ExxonMobil, WSPA, COPC): SCAQMD staff was not able to
identify a single commercial sulfur analyzer in service on a refinery
flare system. It is unreasonable for EPA to conclude that sulfur
analyzer technology is either ``available'' or ``reliable.'' MSCC was
not able to identify any installations where flare gas monitoring was,
in fact, covering a range from 0-100% sulfur.
    Response: EPA has identified two sources where analyzers are on
lines leading to the refinery flare. Specifically, the Tesoro refinery
in the Bay Area, California, has two Thermo Electron Tracker XP
continuous H2S analyzers. The Tesoro analyzers are dual
range instruments, 0-1% and 0-5% (see reference document OOOOO).
Additionally, the Shell refinery in Puget Sound, Washington, uses an
analyzer that thermally oxidizes total sulfur to SO2 and
then measures the SO2. The analyzer can measure up to 40,000
ppm of SO2 (see reference document QQQQQ). Finally, as
indicated in the response to comment II.C.2.(b) below, the SCAQMD
recently reported on a pilot project study, testing a total sulfur
analyzer at the BP Carson facility in southern California, and
indicated that the ``preliminary results have demonstrated the
feasibility of measuring total sulfur emissions from vent gases
directed to flares.''
    The proposed FIP did not specifically require that an analyzer be
capable of measuring in the range from 1-100% sulfur, although the
preamble implied and the record reported conversations with vendors
indicating that analyzers could measure in the range from 1-100%
sulfur. We are clarifying the final FIP to indicate that the total
sulfur analyzers should measure in the range of concentrations that are
normally present in the gas stream to the flare. In cases when the
total sulfur analyzer is not working or where the concentration of the
total sulfur exceeds the range of the monitor, methods established in
the flare monitoring plan required by the FIP shall be used to
determine total sulfur concentrations, which shall then be used to
calculate SO2 emissions. In quarterly reports, sources shall
indicate when these other methods are used.
    (b) Comment (ExxonMobil, WSPA): SCAQMD Rule 1118 had an important
provision requiring an analyzer pilot project, and one Los Angeles area
refiner is currently engaged with a sulfur analyzer demonstration
project. It is conceivable that the pilot project could result in the
conclusion that the analyzer being evaluated could not provide
sufficient accuracy, that the system was not maintainable, or that
there were other problems.
    Response: On June 1, 2007, the SCAQMD presented to its Governing
Board an ``Implementation Status Report for 2006 for Rule 1118--Control
of Emissions from Refinery Flares.'' Agenda No. 27 discusses the total
sulfur (TS) analyzer pilot project at the BP refinery in Carson and
indicates:

    The TS pilot project is in the final step prior to certification
of the analyzer. Although several adjustments and redesign of
sampling equipment were required; [sic] preliminary results have
demonstrated the feasibility of measuring total sulfur emissions
from vent gases directed to flares. Based on these results, two
refineries have already placed purchase orders for their TS
analyzers.

    In the May 15, 2007, ``Implementation Status Report for 2006 for
Rule 1118--Control of Emissions From Refinery Flares,'' attached to
Agenda No. 27, the SCAQMD concludes:

    Although they are behind schedule to comply with the July 1,
2007 monitoring requirements, the pilot projects are moving ahead
convincingly towards completion by the end of 2007. As the rule is
forcing new technologies for flare emission reporting, analyzer
vendors have responded to the challenge and several options are now
available, such as calorimeters, gas chromatographs, mass
spectrometers and Pulsed UV Fluorescence analyzers, for continuously
measuring HHV [higher heating value] and TS. Therefore, staff
expects full implementation of the continuous monitoring provisions
of the rule once the pilot projects are complete. Since the
refineries could not meet the monitoring requirements by July 1,
2007, the refineries petitioned and were granted variances in late
April 2007 by the AQMD Hearing Board to install and operate their
flare monitoring systems over the next two years.

    See reference document RRRRR.
    Based on the above information, the total sulfur pilot project did
not

conclude that the analyzer being evaluated could not provide sufficient
accuracy, that the system was not maintainable, or that there were
other insurmountable problems.
    (c) Comment (ExxonMobil): EPA and industry need more time to review
the SCAQMD pilot project test results and conclusions as they become
available over the next few months and to determine if the technology
that was tested is technically viable and whether or not a more cost
effective alternative technology may be available. MSCC recommends that
the implementation of total sulfur monitoring on the flares be delayed
at least until the full results from the long-term program in
California are available, and the capability of the market to supply
and support such systems in severe weather locations such as Montana is
demonstrated. At that point EPA should revise and then issue the final
rule, after full stakeholder involvement in the process and full
consideration of realistically available options.
    Response: See responses to comments II.C.2.(a) and (b), above.
Also, as noted in response to comment II.C.3.(a), below, EPA is
revising the proposed FIP to allow other methods to determine total
sulfur concentration in the gas stream to the flare. See response to
comment II.F.1.(a) regarding the request for a stakeholder process.
    (d) Comment (ExxonMobil): Recognizing that these total sulfur
analyzer systems do not, by themselves, provide any air quality
benefit, and considering that there are alternatives to continuous
analyzers (e.g., individual grab samples, etc.), ExxonMobil submits
that the proposed requirement to install continuous analyzers requires
further evaluation in the stakeholder process.
    Response: As discussed under response to comment II.C.1.(a), below,
our final FIP allows other methods to determine total sulfur
concentration in the gas stream going to the flare, including grab or
integrated sampling methods. This should address the commenter's
concerns. However, we note that whether or not total sulfur analyzer
systems provide any air quality benefit by themselves is immaterial;
the FIP establishes emission limits to assure that the SO2
NAAQS are attained and maintained and it is essential that the FIP
include reliable mechanisms to determine compliance with the limits.
See, e.g., CAA section 110(a)(2)(F), 42 U.S.C. 7410(a)(2)(F). Finally,
as we noted in our May 14, 2007, proposal to revise subpart J of the
new source performance standards (NSPS), and to adopt new subpart Ja,
the requirement to monitor flare emissions in the SCAQMD in fact
resulted in reduced flaring (72 FR 27178, at 27195) (see reference
document SSSSS).
    (e) Comment (ExxonMobil, WSPA): Cost of installing total sulfur
analyzers should be further evaluated given that the analyzers
themselves do not provide an air quality benefit. Costs of total sulfur
analyzer pilot project in the South Coast area expected to be in the
range of 3 to 5 million dollars.
    Response: See response to comment II.C.2.(d), above. Additionally,
the cost of the South Coast pilot project was higher than expected
because it was a pilot study and because some difficulties were
encountered during the study. (See also note to Billings/Laurel
SO2 FIP File regarding conversations with SCAQMD, reference
document TTTTT.)
    Also, in its ``Implementation Status Report for 2006 for Rule
1118--Control of Emissions From Refinery Flares,'' May 15, 2007, the
SCAQMD reported that refineries involved in the pilot projects reported
that monitoring costs were estimated to be about 2 to 4.7 million
dollars per flare. After looking at the breakdown of the costs, SCAQMD
staff concluded that the total sulfur and higher heating value analyzer
costs were comparable to staff's original estimates. However, the costs
to design and build the monitoring system were significantly different.
Research and development (R&D), engineering, labor/oversight, piping/
electrical, analyzer shelters, and contingencies stated by the
refineries represented approximately 75 to 85 percent of the flare
monitoring system cost. (See reference document RRRRR.)
    SCAQMD also indicated that in a related development, ExxonMobil
informed staff in January 2007 that ExxonMobil was taking a different
approach and was going to use a different technology, namely, gas
chromatography (GC) for both the TS and the HHV analyzer; the estimated
cost given to SCAQMD staff was 1 to 2 million dollars. ExxonMobil
advised SCAQMD staff that similar instruments had been used at
ExxonMobil's flares in Baytown, TX, and Chalmette, LA, for monitoring
H2S and the BTU content of vent gases for compliance with
EPA and Texas Commission on Environmental Quality (TCEQ) regulations.
(Id.)
    (f) Comment (CHS Inc.): Analysis of total sulfur in a flare system
is challenging because of the wide range of sulfur concentrations
possible as well as the number of individual sulfur compounds
potentially present. It is the understanding of CHS that there is not
one commercial total sulfur analyzer in service on a refinery flare.
    Response: See response to comment II.C.2.(a), above.
    (g) Comment (MSCC): Since H2S is believed to be the
principal (overwhelming) sulfur component of candidate flares, further
consideration is warranted as to whether the ``total'' sulfur component
is the appropriate methodology, given the clear lack of existing
equipment for the full potential range of concentrations of flare
gases, and the complexity involved in continuously converting a
variable mixture into a single component such as SO2 or
H2S. EPA should evaluate whether there is a real, necessary,
and significant need to require total sulfur analysis instead of
allowing a somewhat simpler H2S analysis of flare gases.
    Response: The commenter has not provided any technical analyses
supporting the notion that H2S is the overwhelming component
of the total sulfur in the gas stream to its flares or other flares in
the area. EPA reported in the May 14, 2007, proposed new source
performance standards (NSPS) for Subpart Ja (72 FR 27178, at 27194)
(see reference document SSSSS) that ``based on available data, we
understand that a significant portion of the sulfur in fuel gas from
coking units is in the form of methyl mercaptan and other reduced
sulfur compounds. These compounds will also be converted to
SO2 in the fuel gas combustion unit, which means the
SO2 emissions will be higher than the amount predicted when
H2S is the only sulfur-containing compound in the fuel
gas.'' See also the response to comment II.C.2.(a), above. Therefore,
in the FIP we are still requiring that the gas stream to the flare be
analyzed for total sulfur.
    (h) Comment (ConocoPhillips, MSCC): In a typical CEMS installation,
the analyzers are subjected to frequent testing with gases intended to
represent a ``zero'' condition and a ``span'' condition which is
specified as a significant percent of full scale of the analyzer.
``Total Sulfur'' analyzers, operating over a wide range of
concentrations, present some special concerns for span gases. If the
proposed FIP requires high concentration analyzers, it also needs to
incorporate protocols to establish calibration standards for these
analyzers. ConocoPhillips indicates that flare gas sulfur
concentrations can be highly variable, which makes the comparison
required by the Relative Accuracy Test Audit (RATA) difficult. The
sulfur analyzer captures samples in a series of periodic discrete
``grab'' samples, to be averaged over the period of total sample time.
Comparison sample techniques vary, but in general involve getting a
continuous sample over a period of

time, with the concentration averaged over that time period. Depending
on the variability of the concentration over this time period, the
average of the discrete ``grab'' samples has the potential to be
different than the average of the continuous RATA sample. When the
concentrations are numerically low, this difference is compounded and
skews the accuracy calculations. This poses a significant risk of
failing the RATA specifications, thereby voiding the monitor data and
imposing a compliance issue (even if the difference is a few parts per
million). ConocoPhillips believes that this requirement is not
technically valid for the operations for which it is being proposed.
    Response: As indicated in response to II.C.2.(b), above, the BP
Pilot Project is nearing completion and expected to be a success. Also,
see note to Billings/Laurel SO2 FIP File regarding
conversations with SCAQMD (reference document TTTTT). With respect to
the calibration of the analyzer, SCAQMD indicated that there are
several issues that need to be addressed. Specifically, one needs to
assure that (1) the correct calibration gas is in the bottle, (2) the
sample lines do not absorb or desorb sulfur, (3) the probe is
positioned appropriately, and (4) all flow testing or other sample
collection is correlated temporally with the analyzer measurements to
ensure representative comparisons.
    (i) Comment (ExxonMobil): EPA recognized the impracticality of
concentration monitoring for flares during the recent Consent Decree
negotiations. CEMS were deemed unnecessary and impractical for flares,
unless the flare was in continuous use.
    Response: The basis for the FIP is different than the consent
decrees. The FIP assures attainment of the SO2 NAAQS, a
health-based standard, and the consent decrees assure that the new
source performance standards (NSPS), technology-based standards, are
met. Because of these differences, we believe it is appropriate to take
a different approach.
    We disagree with the commenter's statement that ``EPA recognized
the impracticality of concentration monitoring for flares during the
recent Consent Decree negotiations. CEMS were deemed unnecessary and
impractical for flares.'' The CDs required that compliance with 40 CFR
60.104(a) be determined by several options, one of which was to install
and operate a CEMS per 40 CFR supbart J (e.g. see paragraph 77 of CHS
Inc.'s CD, reference document JJJJJ):

    77. All continuous or intermittent, routinely-generated refinery
fuel gas streams that are routed to the flare header at Cenex shall
be equipped with a CEMS as required by 40 CFR Sec.  60.105(a)(4) or
with a parametric monitoring system approved by EPA as an
alternative monitoring plan (``AMP'') under 40 CFR Sec.  60.13(i),
at the combined juncture prior to the flare. Cenex shall comply with
the reporting requirements of 40 CFR Part 60, Subpart J, for the
Refinery Flare.

    We also note that the proposed NSPS Subpart Ja includes a total
sulfur standard and CEMS requirements for fuel gas combustion devices,
which are defined to include flares. (See 72 FR 27178 (May 14, 2007),
reference document SSSSS.)
    (j) Comment (MSCC): MSCC is aware that it may be possible to use
gas chromatography systems to attempt to meet the proposed FIP
requirements. Due to time constraints, they were not able to
investigate this subject thoroughly.
    Response: As indicated in response to II.C.2.(e), ExxonMobil
reported to the SCAQMD that it is using gas chromatography for its
total sulfur and higher heating value analyzers. ExxonMobil has advised
SCAQMD staff that similar instruments have been used on its flares in
Baytown, TX, and Chalmette, LA, for monitoring H2S and the
BTU content of vent gases for compliance with EPA and Texas Commission
on Environmental Quality (TCEQ) regulations. (See reference document
RRRRR.) Also, see note to Billings/Laurel SO2 FIP File
regarding conversations with SCAQMD (reference document TTTTT).
    (k) Comment (several commenters): A general concern is expressed
that the technology is not there to meet performance specifications.
    Response: See responses to above comments II.C.2.(a) and (b).
    (l) Comment (YVAS): YVAS concurs that total sulphur concentrations
and not just H2S be monitored.
    Response: We acknowledge receipt of the comment and the support for
our proposal.
3. Miscellaneous Flare Monitoring Concerns
    (a) Comment (COPC, CHS Inc., MSCC): The proposed FIP should allow
for Alternative Monitoring Plans (AMPs) to determine compliance.
ConocoPhillips argued that AMPs are technically sound data gathering
plans that are developed based on site-specific factors. These AMPs
allow a facility to comply based on equivalent but customized criteria.
CHS Inc. claimed that uncertainty of the monitoring capabilities and
the quality assurance/quality control requirements makes it reasonable
for EPA to allow for AMPs similar to other EPA regulations. MSCC
indicated that it calculates and reports the amount of SO2
emitted during each flaring event based on the recent content, and
estimated flow gas(es) flared, based on reasonable technical judgment
and indirect metering calculations. MSCC asserted that EPA has failed
to show any significant errors or omissions with these methods.
    Response: EPA is revising the proposed FIP to allow other methods
to determine total sulfur concentration in the gas stream going to the
flare. The other methods allow sources to use grab or integrated
sampling, followed by sample analysis, to determine total sulfur
concentration of the gas stream going to the flare. These grab and
integrated sampling methods are currently allowed in the BAAQMD rule
(see reference document LL), and similar methods have been allowed by
the SCAQMD. Two of the refinery companies (ConocoPhillips and
ExxonMobil) in the Billings area also have refineries in the Bay Area
and/or the South Coast Area and should be familiar with these manual
methods.
    Specifically, we are revising the rule to indicate that the total
sulfur concentration of the gas stream going to the flare can be
determined by: (1) A total sulfur concentration monitoring system as we
proposed on July 12, 2006, and including the changes we have identified
here; or (2) grab sampling or integrated sampling.
    If a source chooses to use the grab or integrated sampling methods,
the requirement to obtain a grab or integrated sample will be triggered
if the velocity of the gas stream to the flare in any consecutive 15-
minute period continuously exceeds 0.5 feet per second (fps) and shall
continue until the flow rate of the gas stream to the flare in any
consecutive 15-minute period is continuously 0.5 fps or less.
Additionally, the rule indicates that a grab or integrated sample will
not be required if any water seal monitoring device indicates that flow
is not going to the flare. See discussion in response to comment
II.C.1.(c). Under these conditions, if the water seal monitoring device
indicates that there is no flow going to the flare, yet the continuous
flow monitor indicates flow, the presumption will be that no flow is
going to the flare.
    For grab sampling, a sample shall be collected within 15 minutes
after the triggering conditions occur (see above), and the sampling
frequency, thereafter, shall be one sample every 3 hours. For
integrated sampling, a sample shall be

collected within 15 minutes after the triggering conditions occur (see
above), and the sampling frequency, thereafter, shall consist of a
minimum of 1 aliquot for each 15-minute period until the sample
container is full, or until the end of a 3-hour period is reached,
whichever comes sooner. Within 30 minutes thereafter, a new sample
container shall be placed in service. For grab and integrated sampling,
sampling shall continue until sampling is no longer required (see
above).
    Samples obtained by either grab or integrated sampling shall be
analyzed for total sulfur concentration using ASTM Method D4468-85
(Reapproved 2000) ``Standard Test Method for Total Sulfur in Gaseous
Fuels by Hydrogenolysis and Rateometric Colorimetry'' (see reference
document MMMMMM); ASTM Method D5504-01 (Reapproved 2006) ``Standard
Test Method for Determination of Sulfur Compounds in Natural Gas and
Gaseous Fuels by Gas Chromatography and Chemiluminescence'' (reference
document NNNNNN); or 40 CFR part 60, Appendix A-5, Method 15A
``Determination of Total Reduced Sulfur Emissions From the Sulfur
Recovery Plants in Petroleum Refineries.'' Total sulfur concentration
shall be reported as H2S or SO2 in ppm. Proper
QA/QC procedures shall be used to assure that the samples are obtained
and analyzed appropriately.
    We chose the trigger level for two reasons. First, the rule
indicates that the minimum detectable velocity of the flow monitoring
device(s) shall be 0.1 fps and the flow monitoring devices shall
continuously measure the range of flows corresponding to 0.5 to 275
fps. Since 0.5 fps is the minimum flow measure required, it is a
reasonable trigger level to ensure protectiveness. Second, flow
monitoring software averages all the readings in a 15-minute timeframe
and records/reports the average flow. Using the minimum recorded/
reported timeframe is reasonable to ensure protectiveness.
    With respect to using estimations, technical judgment, and indirect
metering to calculate emissions from the flare, because this FIP is
designed to protect the NAAQS, we are choosing to require real-time
direct monitoring methods to determine emissions. We do not believe
estimations, technical judgments, and indirect metering are adequate
substitutes for real-time monitoring for purposes of the FIP.
    (b) Comment (ExxonMobil, WSPA, COPC, CHS Inc., MSCC): The proposed
requirement for a facility to install, commission, and calibrate flow
monitoring systems and continuous sulfur analyzer systems within 180
days after receiving EPA approval of a monitoring plan is a requirement
that would simply be impossible to meet.
    Response: Based on the comments received, we have revised the FIP
to allow 365 days, rather than 180 days, after EPA approval of the
flare monitoring plan to install continuous flow monitors and to begin
determining total sulfur concentrations on the gas stream to the flare.
Based on conversations with an ultrasonic flow monitor manufacturer,
BAAQMD, and SCAQMD (see reference documents MMMMM, OOOOO, and TTTTT,
respectively), we believe this additional time is reasonable to install
continuous flow monitors and total sulfur analyzers or to initiate grab
or integrated sampling.
    (c) Comment (MSCC, ExxonMobil): The FIP implies that pilot and
purge gas must be monitored. Pilot and purge gas lines are separate
from the main header vent gas lines. Monitoring these other relatively
small gas flows to the flare is a waste of effort and resources. The
pilot gas is usually a small natural gas stream of low flow and
essentially zero sulfur content. The small purge gas line usually is
natural gas, refinery fuel gas, or inert gas such as carbon dioxide or
nitrogen, or mixtures of such gases with air or steam. In either case,
the flow is not high and usually ExxonMobil does not expect high sulfur
content. These two stream types (pilot gas, purge gas) cannot
physically be mixed with the main vent gas stream for measurement of
flow and sulfur content by one set of monitors, without defeating their
essential purposes of safety. Given the nature of the pilot gas and
purge gas streams, it is not reasonable to require flow and sulfur
monitors which meet the proposed FIP specs on these streams.
Regulations from other areas allow the flow and sulfur content of pilot
and purge gas to be estimated/monitored by other devices or sampling
means. It is recommended that the proposed FIP language be re-written
to clearly exempt pilot gases and purge line gases from the proposed
FIP monitoring requirements. Neither can reasonably be considered as a
significant source of sulfur dioxide. ExxonMobil asserted that EPA's
proposed FIP requirement for the Billings/Laurel area is neither
reasonable nor legally supportable.
    Response: In conversations with the SCAQMD, we learned that in some
instances they had seen copious emissions due to flare pilot and purge
gas (see reference document TTTTT). SCAQMD indicated, as do the
commenters above, that in some cases refinery fuel gas is used as a
purge gas. Refinery fuel gas can have high sulfur content. Because of
the potential for SO2 emissions from the burning of pilot
and purge gas, we believe it is necessary to account for these
emissions and include them when determining the total emissions from
the flare.
    We agree that the proposed FIP implied that the pilot and purge gas
should be monitored by the analyzers on the flare line used to measure
flow and concentration of the gas stream to the flare. We are revising
the FIP to require flow and H2S concentration monitoring of
the pilot and purge gas as one possible method to determine sulfur
dioxide emissions from the burning of such gas in the flare. However,
the FIP allows sources to forego monitoring if certain requirements are
met. First, if facilities certify that only natural gas or an inert gas
is used for the pilot and/or purge gas, then the gas does not need to
be monitored. Second, if facilities can measure other parameters so
that volumetric flows, expressed in SCFH, of pilot and purge gas can be
calculated (based on the design and the parameters), then the flows do
not need to be monitored. Third, if the H2S concentration of
the pilot or purge gas can be determined through other methods, then
the H2S concentration does not need to be monitored. Once
flow and H2S concentration of the pilot and purge gas are
determined, sources must then calculate the SO2 emissions
from the pilot and purge gas. The calculated SO2 emissions
will then be added to the other SO2 emissions from the flare
to determine compliance with the flare SO2 emission limits.
Also, we are revising the reporting requirements to require sources to:
(1) Certify in the quarterly reports if pilot or purge gas is not
monitored because only natural gas or an inert gas is used as the pilot
and/or purge gas; or (2) report flow and H2S concentration
of the pilot and/or purge gas and the resultant SO2
emissions.
    (d) Comment (MSCC): Flow and concentration monitoring would be
costly and there is no justification for such costs and complexity
given that the area is in attainment for the NAAQS.
    Response: See response to comments II.C.2.(d) and II.C.3.(c),
above.
    (e) Comment (YVAS): YVAS concurs that each source submit for EPA
review a quality assurance and quality control plan for each of the
continuous monitors.
    Response: We acknowledge receipt of the comment and the support for
our proposal.

D. Flare Limits

1. Concerns With Flare Emission Limit
    (a) Comment (CHS Inc, MSCC): The proposed flaring limit of 150 lbs
SO2/3 hour period was used in the model to represent routine flaring
and background SO2 concentrations. This threshold was never
intended to and did not account for malfunctions, startups, or
shutdowns.
    Response: The FIP fills the gap for the provisions of the SIP that
were disapproved. In its attainment demonstration modeling, the State
modeled emissions from flares at 150 lbs of SO2/3-hour
period, yet the SIP did not contain corresponding emission limits for
the flares. This was the basis for our disapproval of part of the SIP.
We believe we have appropriately addressed malfunction, startup, and
shutdown in this final rule. See section II.D.3., below.
    Certain assumptions were made in the State's attainment
demonstration for the Billings/Laurel SO2 SIP. Included in
the assumptions was that flares had routine emissions of 150 lbs of
SO2/3-hour period. To assure attainment and maintenance of
the NAAQS, the SIP or a FIP must contain enforceable emission limits on
the flares. This is fully explained in our proposed action on the
Billings/Laurel SO2 SIP (64 FR 40791, 40801, July 28, 1999)
and in the response to comments contained in our final action on the
Billings/Laurel SO2 SIP (67 FR 22168, 22179, May 2, 2002).
    The State of Montana has flare provisions that apply to CHS Inc.,
ConocoPhillips, ExxonMobil, and MSCC. See CHS Inc.'s, ConocoPhillips',
ExxonMobil's, and MSCC's exhibit A-1, adopted by the Montana Board of
Environmental Review on June 12, 1998 (reference documents QQQQQQ,
PPPPPP, UUUUU, and OOOOOO). Exhibit A-1 contains additional State
requirements that were not submitted for inclusion in the
SO2 SIP. Among these is an emission limit on flares of 150
lbs of SO2/3-hour period, the value the State relied on to
model attainment. These flare provisions do not and would not satisfy
the SIP/FIP requirements of the CAA for two reasons. First, they were
never submitted to EPA to be included as part of the SIP. Second, the
flare provisions contain automatic exemptions for malfunction, startup,
and shutdown. This is inconsistent with EPA's longstanding
interpretation of the CAA, which is that, since SIPs must provide for
attainment and maintenance of the NAAQS and the achievement of the PSD
increments, all periods of excess emission must be considered
violations. Accordingly, any provision that allows for an automatic
exemption for excess emission is prohibited.\8\
---------------------------------------------------------------------------

    \8\ See reference document RRR, September 20, 1999, memorandum
entitled ``State Implementation Plans: Policy Regarding Excess
Emissions During Malfunctions, Startup, and Shutdown.''
---------------------------------------------------------------------------

    (b) Comment (NEDA/CAP, MSCC, ExxonMobil): The capriciousness of
EPA's proposed FIP provision affecting flaring is that EPA recognizes
in the proposed notice that sources likely will be unable to comply
with the continuous flaring emission limitations. Yet the proposed FIP
would allow citizens to bring actions for violations of unattainable
limits when EPA or the State likely would choose to exercise its
prosecutorial discretion. Such a regulatory ``Catch-22'' is both
unreasonable and unlawful.
    Response: We respectfully disagree with the commenter. First, in
our proposal we did not say that sources will be unable to comply with
the continuous flaring emission limitations. We note that, after
receiving the refineries' estimates of routine flare emissions, the
State established as a State-only limit the same numerical flare limit
we are adopting, and the refineries and MSCC agreed to the stipulations
containing those limits. See 67 FR 22180, col. 2, May 2, 2002, and
reference documents UUUUU, OOOOOO, PPPPPP, QQQQQQ, and SSSSSS. Also, at
the time of our SIP action, Conoco indicated to us that routine
emissions from its flare were expected to be less than 150 lbs
SO2/3-hour period. See 67 FR 22180, col. 2, May 2, 2002, and
reference document RRRRRR. Based on this information, we have concluded
that the refineries and MSCC will be able to comply with the 150 lbs
SO2/3-hour flare limit under normal operating conditions.
    We did say in our proposal that we recognize flares are sometimes
used as emergency devices and that it may be difficult to comply with
the flare limits during malfunctions. See 71 FR 39264, col. 1, July 12,
2006. However, contrary to the commenters' assertions, our decision to
require an emission limit that may be difficult to meet under certain
conditions is not capricious, unreasonable, or unlawful.
    There is often a conflict, which is not limited to refinery flare
emissions, between a source's ability to control emissions during
certain operating conditions and the CAA's requirement to attain and
protect the NAAQS. Our fundamental responsibility under the CAA with
respect to SIPs/FIPs, however, is to ensure the NAAQS are attained and
other CAA requirements are met. See CAA sections 110(a) and (l), 42
U.S.C. 7410(a) and (l); reference document RRR, September 20, 1999,
memorandum titled ``State Implementation Plans: Policy Regarding Excess
Emissions During Malfunctions, Startup, and Shutdown,'' from Steven A.
Herman and Robert Perciasepe, to Regional Administrators (hereafter
``1999 excess emissions memorandum''); City of Santa Rosa v. EPA, 534
F.2d 150, 155 (9th Cir. 1976), vacated on other grounds, 429 U.S. 990
(1976). Thus, we have long held that outright or ``automatic''
exemptions from emission limits needed to demonstrate attainment of the
NAAQS are not appropriate, something we indicated in our proposed FIP.
See our 1999 excess emissions memorandum, reference document RRR, and
our proposed FIP, 71 FR 39264, col. 1, July 12, 2006. Our
interpretation on this issue has been upheld by the U.S. Court of
Appeals for the 6th Circuit: in a 2000 decision, the Court rejected a
challenge to EPA's disapproval of a Michigan SIP revision that provided
an automatic exemption from SIP limits during malfunction, startup, and
shutdown periods. Michigan Department of Environmental Quality v. EPA,
230 F.3d 181 (6th Cir. 2000).
    As we explained as long ago as 1977, the appropriate approach in
SIPs/FIPs is to require continuous compliance in order to create an
incentive for sources to properly operate and maintain their facilities
and to improve their operation and maintenance practices over time.
See, e.g., 42 FR 21472, April 27, 1977 (reference document VVVVV), and
42 FR 58171, November 8, 1977 (reference document WWWWW). We explained
that an automatic exemption would encourage the source to claim after
every period of excess emissions that the exemption applied, and that
instead the proper means to provide relief to sources was through the
exercise of enforcement discretion in appropriate circumstances. Id.
    Later, in 1999, we indicated that states could include in their
SIPs, as an alternative to the enforcement discretion approach,
narrowly tailored affirmative defense provisions to address source
difficulties meeting emission limits during malfunction, startup, and
shutdown periods. See reference document RRR, our 1999 excess emissions
memorandum. In this 1999 memorandum we reiterated our long-held view
that, ``because excess emissions might aggravate air quality so as to
prevent attainment or interfere with maintenance of the ambient air
quality standards, EPA views all excess emissions as violations of
applicable emission limitation[s].'' We also

repeated our recognition that some malfunctions may be unavoidable.
    Thus, while flares may have unique characteristics, the underlying
conflict between the ability to comply and need to meet the NAAQS is
the same. We do not believe the nature of the emission point should
dictate a different approach to protection of the NAAQS. Whether
considering stack emissions at a power plant or other source, or flare
emissions at a refinery, the SIP/FIP should be structured to provide
the source with the incentive to properly design, operate, and maintain
its facility. An outright exemption from the emission limits would not
do this.
    To provide relief to the sources for truly unavoidable violations,
while still maintaining appropriate incentives for compliance, we are
providing an affirmative defense to penalties for violations of flare
limits during malfunctions, startups, and shutdowns. The elements of
the defense, which a source would have to prove in court or before an
administrative judge, are enumerated in our final rule and are
consistent with the elements described in our 1999 excess emissions
memorandum. The gist of these elements is that a source must take all
possible steps to prevent exceedances of the limits and to minimize the
amount, duration, and impact of those exceedances. These same or
similar criteria have been adopted by other regulatory agencies,
including the State of Colorado and Maricopa County, Arizona, in excess
emissions rules. See, e.g., Colorado Air Quality Control Commission
Common Provisions Regulation, 5 CCR 1001-2, Sections II.E. and J.
(reference document TTTTTT); Maricopa County Air Pollution Control
Rules, Rule 140, ``Excess Emissions'', Section 400 (reference document
ZZZZZ).
    Finally, we reject commenters' assertion that citizens will
necessarily pursue enforcement where the State and EPA do not, but in
any event, this possibility is inherent in the structure of the CAA;
Congress provided citizens with the ability to enforce SIPs and FIPs.
This inherent structure is not a reason for us in this rulemaking
action to change our longstanding interpretations regarding the proper
treatment of excess emissions.
    (c) Comment (NEDA/CAP): Industry contends that it is virtually
impossible to meet the proposed limits during flaring, since flares
themselves are not process units when they are treating excess gases
during malfunction events. EPA has presented no information in this
notice or elsewhere to the contrary. On this basis alone, if the mass
emission limits for flares are not made less stringent, the FIP must
recognize in its final action that flares must be available for use
during malfunctions and emergencies to protect the safety of employees
and the public, as well as equipment integrity, regardless of the mass
emission rate of the time.
    Response: The FIP is not intended to jeopardize the safety of
refineries, their workers, or neighbors. Our SIP policy \9\ has long
recognized that imposing penalties for violations of emission
limitations for sudden and unavoidable malfunctions caused by
circumstances entirely beyond the control of the owner or operator may
not be appropriate. States, EPA, and citizens have the ability to
exercise enforcement discretion to refrain from taking enforcement
action in these circumstances. In addition, EPA has revised the FIP to
provide sources with the ability to assert an affirmative defense to
penalties for violations of flare limits during malfunction, startup,
and shutdown. However, while we recognize some violations may be
unavoidable, we also believe that sources have a responsibility to do
their best to achieve continuous compliance and to minimize the number,
duration, and severity of malfunctions and other events leading to
excess emissions.
---------------------------------------------------------------------------

    \9\ See reference document RRR, September 20, 1999, memorandum
entitled ``State Implementation Plans: Policy Regarding Excess
Emissions During Malfunctions, Startup, and Shutdown.''
---------------------------------------------------------------------------

    (d) Comment (MSCC): Various jurisdictions have attempted to address
flare emissions. There is no uniform federal requirement or regulation
requiring such limits or monitoring, particularly for short term
limits, or for malfunction, startup, and shutdown controls. It is
difficult to understand any reason that the Montana SIP for Billings/
Laurel is ``substantially inadequate'' regarding flaring or for
proposing restrictions going far beyond those in effect in any
jurisdiction or federal rule.
    Response: Regardless of what other areas are doing with respect to
flare emissions, we must fulfill our responsibility to fill the gaps of
the provisions of the SIP that we disapproved. Each area must be
addressed on a case-by-case basis. The response to comment II.D.1.(a)
and our notice of proposed rulemaking express why we believe the FIP
should contain emission limits for flares in the Billings/Laurel area.
Regarding the comment about substantial inadequacy, please see our
response to comment II.B.2.(a), above.
    (e) Comment (MSCC): There is no reasonable basis to believe that
flaring, as practiced in this air-shed, prevents attainment and
maintenance of NAAQS, or that it is inadequately regulated, or that it
has an impact on health, welfare, or commerce among states, as years of
experience confirm. The State of Montana flare provisions are adequate.
No federal action is needed.
    Response: This comment goes to the validity of our SIP action and
is not relevant here. See our response to comment II.B.2.(a), above.
    (f) Comment (MDEQ): Imposing a mass-based emission limit (and the
necessary and ancillary requirements for measuring flows and
concentration) on a flare increases the regulatory workload while
providing a marginal benefit. Currently, Montana's Malfunction rule
(ARM 17.8.110) provides Montana with enforcement discretion during
malfunction events.
    Response: We note that the State has mass-based emission limits on
the flares in the Billings/Laurel SO2 area. See CHS Inc.'s,
ConocoPhillips', ExxonMobil's, and MSCC's exhibit A-1, adopted by the
Montana Board of Environmental Review on June 12, 1998 (reference
documents QQQQQQ, PPPPPP, UUUUU, and OOOOOO). Exhibit A-1 contains
State requirements that were not submitted for inclusion in the
SO2 SIP. The provisions of exhibit A-1 also appear in the
sources' Title V permits and are labeled as State-only provisions. See,
for example, ConocoPhillips' Title V permit (see reference document
XXXXX).
    The exhibit A-1 requirements indicate that the facilities shall not
allow SO2 emissions from any flare, unless the emissions are
a minor flaring event (defined as less than or equal to 150 pounds per
3-hour period), or the result of start-up, shutdown, or a malfunction.
Exhibit A-1 does not indicate how compliance with the emission limit is
determined and only requires reporting of flare emissions that are not
minor flaring events.
    Presumably, the additional workload provided by the FIP, that the
State is referring to, is in evaluating the continuous analyzers and
receiving quarterly reports. We believe the additional workload is
warranted and necessary to determine compliance with the flare emission
limits and assure that the SO2 NAAQS will be attained and
maintained. See, e.g., CAA sections 110(a)(2)(A), (C), and (F), 42
U.S.C. 7410(a)(2)(A), (C), and (F).
    We do not understand the intent of the comment that indicates MDEQ
has enforcement discretion under its malfunction rule in ARM 17.8.110

(reference document YYYYY). Before MDEQ could decide whether or not to
pursue an enforcement action for violations of the State-only flare
limit, MDEQ would need to evaluate information submitted by sources.
    Additionally, we note that in response to our proposed action on
the Billings/Laurel SIP, the State said the following: ``The State
agrees with EPA that the SIP is incomplete without enforceable emission
limitations applicable to flares, and that such limitations should
correspond to the emission rates used in the attainment demonstrations.
However, after significant effort to address the issue, the State was
unable to find a workable solution that would meet EPA's concerns.''
See document IV.A-23, comment 3, from docket
R8-99-01; 67 FR 22183, col. 1, May 2, 2002; and reference
document ZZZZZZ.
    (g) Comment (YVAS): YVAS concurs with EPA's further assumption
(page 39264), that ``the 3-hour SO2 NAAQS would be
attained'' if ``the limit for the main flares was established at 500
pounds of SO2 per calendar day.'' Since there is apparently
precedent (as noted on page 39263 FR) ``contained in settlements
between the United States and CHS Inc, ConocoPhillips and ExxonMobil,''
YVAS further agrees to and accepts EPA's reasoning that ``the 500 pound
value for this FIP (should) be imposed as an enforceable limit and not
just a trigger point for further analysis'' as a starting point.
However, the ``500 lbs per day limit,'' if extended for any length of
time, is not acceptable. Based on acquired information, YVAS does not
think this limit would be punitive, nor would it be impossible for
industry sources to attain. It is accepted that zero emissions may not
be possible or attainable, but any lower emissions rate would be a
public benefit. And, although a compliance drop could create greater
industry noncompliance and require more enforcement action, YVAS does
not believe the more stringent standards would create more
noncompliance problems for the sources.
    Response: We have decided to retain the proposed limit of 150 lbs
of SO2/3-hour period. A more stringent limit than either
proposed is unnecessary to ensure attainment of the NAAQS. Thus, we
believe it is reasonable not to impose a more stringent limit as the
commenter suggests.
    (h) Comment (Citizen): The proposed rule should not be adopted
unless recognized medical opinion concerning the cumulative health
risks of the release of 500 lbs per day of sulphur dioxide into the
area's airshed is analyzed. Specifically, what justification criteria
are being used to establish the 500 lb. minimum per day base in the
Proposed Rule. And, as noted on page 39264 of the Federal Register
dated July 12 announcing the FIP, EPA says ``if we adopted the 500
pound value in this FIP, we would impose it as an enforceable emission
limit.'' If there are still questions concerning the 500 lb per day
emission limit, why is it being proposed? Is there a lower and perhaps
``better'' emission limit per day that should be considered?
    Response: The current SO2 NAAQS were set to protect
public health and welfare after consideration of various scientific
data. It is not our role here to re-evaluate the NAAQS, but to ensure
they are met. Through modeling we determined that both limits would
protect the SO2 NAAQS. While a lower limit might be
attractive, we are setting the limits at 150 lbs of SO2/3-
hour period, a level sufficient to meet the SO2 NAAQS; we
think this is reasonable. See response to comment II.A.2.(b). See also
our response to comments pertaining to SO2 NAAQS and
SO2 Health Effects (II.F.9. and 10., respectively) below.
    (i) Comment (MDEQ): MDEQ believes that hard cap emission limits on
flares are good but believes that the flare emission limits will be
more accepted if malfunction, startup, and shutdown exemptions are
introduced.
    Response: We acknowledge MDEQ's support for hard cap emission
limits on flares. Regarding exemptions for malfunction, startup, and
shutdown, see our responses to comments II.D.1.(b) and (c), above.
    As indicated above, to address industry concerns regarding
malfunctions, startup, and shutdown, we are revising the FIP to provide
sources the ability to assert an affirmative defense to penalties for
violations of flare limits during malfunction, startup, and shutdown.
2. Safety Device
    (a) Comment (CHS Inc., WETA, MPA, NPRA): From a safety standpoint,
there are concerns with flare limits applying at all times, including
malfunction, startup, and shutdown. Flares are primarily safety
devices, designed as a means to ensure the safety of employees and the
community and to maintain the integrity of refinery equipment during
situations that are not representative of normal operations. It will be
precedent setting if the EPA views these infrequent events as
enforcement situations. It would, in essence, require facilities to
choose between maintaining a safe, controlled refinery and violating
the FIP.
    Response: See responses to comments II.D.1.(b) and (c), above. As
we indicate in our response to comment II.D.1.(c), the FIP is not
intended to jeopardize the safety of refineries, their workers, or the
community. However, we believe it would be inconsistent with CAA
sections 110(a) and (l) to provide an outright exemption from the flare
limits during malfunction, startup, and shutdown periods. Instead, to
provide some measure of relief to the sources, we have included an
affirmative defense to penalties in our final FIP rule. If a source
takes steps consistent with the elements of the affirmative defense,
excess flaring emissions during malfunction, startup, and shutdown
periods would not be penalized. We have considered several additional
factors: First, historically, the sources have used the flares as part
of their routine operations, i.e., in non-emergency conditions. See
September 28, 1995, letter from Bob Raisch to Douglas Skie (reference
document SSSSSS); 67 FR 22180, col. 2, May 2, 2002. Also, in its
comments on the FIP (reference document QQQQ), CHS Inc. indicated that
the 150 lbs/3-hour value was used in the original model to represent
routine flaring and background SO2 concentrations. MSCC
indicated in its comments on the FIP (reference document WWWW) that
flares can be used for handling streams other than those arising from
malfunction, startup, and shutdown. Second, flaring events have not
necessarily been as infrequent as the commenter implies. From the first
quarter of 2005 through the second quarter of 2007, source reports
indicate that MSCC and the 3 refineries experienced over 150 flaring
events with SO2 emissions greater than 150 pounds over 3
hours. See reference document HHHHHH. Third, the emissions during these
events can be very high--the State estimated that emissions during
malfunctions could be as high as 6,000 pounds/3-hour period, and the
sources' own reports for first quarter 2005 through second quarter 2007
reflect emissions as high as 12,400 pounds over a 2-hour period. See
reference documents SSSSSS and HHHHHH. The maximum value reported for a
flaring event during the period was 40,800 pounds of SO2
over an unknown duration, and there were numerous events in the
thousands of pounds. See reference document HHHHHH. Fourth, we want to
ensure that the owners/operators design, operate, and maintain their
facilities to minimize flare emissions by minimizing the conditions
that lead to malfunctions,

startups, and shutdowns. In the FIP context, the appropriate way to do
this is by establishing a flare emission limit that is not subject to
outright exemptions. Fifth, the State and EPA have already viewed these
events as enforcement situations in the context of the refinery
initiative and, through the consent decrees, have created the
expectation that the refineries will minimize flare emissions. We
explain in this preamble why the conditions of the consent decrees,
while beneficial, are not sufficient for purposes of the FIP. See,
e.g., responses to comments II.A.2.(b), II.D.4., and II.E.1.(e). We
also note that MSCC is not subject to a consent decree. Finally, the
air does not care whether emissions come out of a flare that is used as
a safety device at a refinery or a stack at a power plant or other
facility.\10\ In both cases, the emissions of SO2 impact air
quality, and EPA's charge is to address those impacts so as to protect
the NAAQS.
---------------------------------------------------------------------------

    \10\ In theory, a smokestack could also be characterized as a
safety device; among other things, a stack is used to prevent
harmful ground level concentrations of pollutants. In addition,
gases are sometimes bypassed around control devices directly to the
stack to avoid damage to control devices and/or other dangerous
conditions. In the SIP/FIP context, we do not believe it is
appropriate to automatically exempt these stack emissions, even
though the stack may serve a safety purpose. See our 1999 excess
emissions memorandum, reference document RRR.
---------------------------------------------------------------------------

    (b) Comment (WSPA, MSCC, ExxonMobil): EPA proposes that flare
limits apply at all times without exception. It would be virtually
impossible to comply with SOx mass emission limits at all times and for
all malfunctions for the simple reason that the primary function of a
refinery flare is to serve as a safety device. Flares must be available
for use during malfunctions and emergencies to protect equipment and
the safety of employees and the public.
    Response: See responses to comments II.D.1.(b) and (c), and
II.D.2.(a), above.
    (c) Comment (NPRA): The U.S. Chemical Safety Board (CSB) urges the
installation of flares. The CSB sites flares as a ``safer alternative''
when compared to other techniques. Clearly the CSB recommendation is at
odds with Agency's proposal.
    Response: See responses to comments II.D.1.(b) and (c), and
II.D.2.(a), above. Also, we do not believe our action is at odds with
the CSB's recommendations. In this action, we are not opining on the
use of flares versus other techniques. We are not telling the
refineries or MSCC to stop using their flares. However, flares are an
emission point at the refineries and MSCC, they have been the source of
routine emissions historically, and they can be the source of very
large quantities of emissions in a short period of time. We believe it
is necessary and appropriate to impose limits on the flare emissions to
fill one of the gaps in the SIP, to support our attainment
demonstration, and to create appropriate incentives for the sources in
the design, operation, and maintenance of their facilities.
3. Malfunction, Startup, and Shutdown
    (a) Comment (WSPA, MSCC, ExxonMobil): In working with the South
Coast Air Quality Management District, they were careful not to
compromise safety by restricting, either explicitly or implicitly, the
use of flares during emergencies through the imposition of mass
emission limits or otherwise.
    Response: See responses to comments II.D.1.(b) and (c), and
II.D.2.(a), above. Our FIP does not require or direct the sources to
not use their flares during emergencies. Unlike the South Coast or Bay
Area,\11\ however, we are required to promulgate a FIP that
demonstrates attainment of the SO2 NAAQS. Consequently, it
is necessary and appropriate that we impose emission limits on the
flares that are consistent with our modeled attainment demonstration.
To address industry concerns, we are providing an affirmative defense
to penalties for excess flare emissions during malfunction, startup,
and shutdown periods.
---------------------------------------------------------------------------

    \11\ The Bay Area prohibits all refinery flaring unless the
flaring is consistent with a flare minimization plan or is caused by
an emergency. See BAAQMD rule 12-12-301 (reference document
AAAAAAA). The South Coast rule requires minimization of flaring and
prohibits combustion of vent gas in the flare except during
emergencies, shutdowns, startups, turnarounds or essential
operational needs. See SCAQMD rule 1118(c)(4) (reference document
CCC).
---------------------------------------------------------------------------

    We note that SCAQMD's rule 1118(d) imposes annual SO2
performance targets for flare emissions (caps on the amount of
SO2 emitted from flares in one year). The performance
targets are based on the crude processing capacity and become more
stringent over time. Malfunction, startup, and shutdown emissions count
towards the annual performance targets unless they meet certain
narrowly defined exemptions in rule 1118(k). Sources that exceed their
annual performance targets must submit a flare minimization plan and