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

Federal RegisterApr 21, 2008

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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.

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 (SO

) State Implementation Plan (SIP). The intended effect of this action is to assure attainment of the SO

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, (303) 312-6437,

ostrand.laurie@epa.gov

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

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

mean or refer to carbon monoxide.

(vi) The initials

COPC

mean or refer to ConocoPhillips.

(vii) The words

EPA,

we,

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

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

mean or refer to sulfur dioxide.

(xx) The words

State

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 SO

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 SO

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 SO

SIP for the Billings/Laurel area. See 58 FR 41450, August 4, 1993. In response, the State submitted revisions to the SO

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 SO

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

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 SO

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)],

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.

(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 SO

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

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.

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.

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

EPA

, 534 F.2d 150, 155 (9th Cir. 1976),

vacated and remanded on other grounds sub nom. Pacific Legal Foundation

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

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.

EPA, supra,

at 668 (citing previous version of section 110(c)).

The Billings/Laurel SO

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 SO

/3-hour period at all but the Jupiter Sulfur flare, 75 lbs SO

/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 H

S 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 SO

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 H

S per 3-hour period and 100 ppm H

S per calendar day. When trigger events specified in the rule occur, MSCC must measure the H

S 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 SO

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 SO

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 SO

attainment demonstrations. Additionally, a small number of ambient SO

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 SO

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 SO

concentration at receptors where no monitors are located.

Moreover, our SIP Call for the Billings/Laurel area was based on modeled violations of the SO

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 SO

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 SO

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 SO

emission controls and strategies and provide for the implementation, maintenance, and enforcement of the SO

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 SO

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 SO

NAAQS.

(b)

Comment (CHS Inc., WETA, COPC, MDEQ, ExxonMobil, NPRA):

In addition to the SIP, SO

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.

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.

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.

Third, the consent decrees and permitting actions, for some emission points, do not contain SO

emission limits that are consistent with the averaging times of the SO

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 SO

emissions shall not exceed 50 ppm by volume (corrected to 0% O

) for a 7-day rolling average [or a fresh feed of 0.3 percent by weight] and 25 ppm by volume (corrected to 0% O

) 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 SO

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 SO

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

Natural Resources Defense Council,

95 S.Ct. 1470, 1481-1482 (1975). In our 2002 and 2003 actions, we found that Montana's SO

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

EPA,

990 F.2d 1531, 1541 (9th Cir. 1993);

South Terminal Corp.

EPA,

504 F.2d 646, 668 (1st Cir. 1974) (citing previous version of CAA section 110(c)).

(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 § 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 SO

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 SO

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

EPA

, 108 F.3d 1397 (D.C. Cir. 1997) and

Bethlehem Steel

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-à-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

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

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

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.

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,

which were based on the very modeling that the commenter now claims is unreliable.

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.

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

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 SO

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

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.

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.

If the State were to submit such a revision, we would evaluate the revision according to the Act, our regulations, and the relevant cases.

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

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 SO

NAAQS (365 μg/m

) and just below the 3-hour SO

NAAQS (1291.5 μg/m

). 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.

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 SO

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

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 SO

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 SO

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 SO

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 SO

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

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 (

.), we expect that the annual verification procedures will address elements such as:

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 SO

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 H

S 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 SO

and then measures the SO

. The analyzer can measure up to 40,000 ppm of SO

(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 SO

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 SO

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 SO

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 H

S 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 H

S 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 SO

or H

S. EPA should evaluate whether there is a real, necessary, and significant need to require total sulfur analysis instead of allowing a somewhat simpler H

S analysis of flare gases.

Response:

The commenter has not provided any technical analyses supporting the notion that H

S 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 SO

in the fuel gas combustion unit, which means the SO

emissions will be higher than the amount predicted when H

S 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 SO

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 SO

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 § 60.105(a)(4) or with a parametric monitoring system approved by EPA as an alternative monitoring plan (“AMP”) under 40 CFR § 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 H

S 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 SO

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 H

S 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 SO

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 H

S or SO

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 SO

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 H

S 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 H

S concentration of the pilot or purge gas can be determined through other methods, then the H

S concentration does not need to be monitored. Once flow and H

S concentration of the pilot and purge gas are determined, sources must then calculate the SO

emissions from the pilot and purge gas. The calculated SO

emissions will then be added to the other SO

emissions from the flare to determine compliance with the flare SO

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 H

S concentration of the pilot and/or purge gas and the resultant SO

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 SO

/3 hour period was used in the model to represent routine flaring and background SO

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 SO

/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 SO

SIP. Included in the assumptions was that flares had routine emissions of 150 lbs of SO

/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 SO

SIP (64 FR 40791, 40801, July 28, 1999) and in the response to comments contained in our final action on the Billings/Laurel SO

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 SO

SIP. Among these is an emission limit on flares of 150 lbs of SO

/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.

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 SO

/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 SO

/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

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

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

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

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 SO

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 SO

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 SO

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 SO

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 SO

NAAQS would be attained” if “the limit for the main flares was established at 500 pounds of SO

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 SO

/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 SO

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 SO

NAAQS. While a lower limit might be attractive, we are setting the limits at 150 lbs of SO

/3-hour period, a level sufficient to meet the SO

NAAQS; we think this is reasonable. See response to comment II.A.2.(b). See also our response to comments pertaining to SO

NAAQS and SO

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 SO

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 SO

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 SO

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.

In both cases, the emissions of SO

impact air quality, and EPA's charge is to address those impacts so as to protect the NAAQS.

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,

however, we are required to promulgate a FIP that demonstrates attainment of the SO

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.

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 SO

performance targets for flare emissions (caps on the amount of SO

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 are subject to mitigation fees of up to four million dollars a year (see reference document CCC).

(b)

Comment (WSPA, MSCC, ExxonMobil):

It is essential for EPA to recognize the true nature of malfunctions at refineries, and the fact that there is no practical way to regulate the release of vent gases during malfunctions, or, to treat the emergency vent gases to remove sulfur compounds prior to combustion in the flare.

Response:

See responses to comments II.D.1.(b) and (c), II.D.2.(a), and II.D.3.(a), above. Also, we understand that while a malfunction is underway, it may be impossible to treat the gases prior to combustion in the flare. However, we do not agree that all malfunctions are categorically unavoidable. We are concerned with the causes leading to the malfunctions and the steps taken after the malfunction begins to mitigate its effects. We are promulgating an affirmative defense provision along with the flare emission limits that should ensure sources take all steps within their control to avoid malfunctions and minimize their impacts on air quality once they occur. We believe this is reasonable and appropriate to ensure protection of the NAAQS.

(c)

Comment (WETA):

Pursuing the adoption of this FIP could potentially result in the setting of an inconsistent national policy for malfunction, startup, and shutdown.

Response:

We do not agree with the comment. The FIP would not be setting inconsistent national policy for malfunction, startup, and shutdown occurrences. To the contrary, we are following our national policy with respect to malfunctions, startup, and shutdown as expressed in the 1999 excess emissions memorandum (see reference document RRR).

(d)

Comment (MSCC):

MSCC believes that the approach taken by the State of Montana in providing for minimization of flaring, above a reasonably determined de minimis threshold, and clear exceptions for malfunctions, startup, shutdowns and other operational needs is the sound approach, to address the reality that there are, and will be situations such as malfunctions, startups, and shutdowns and emergencies that are beyond the reasonable control of a source, in the operation of flares.

Response:

We recognize there may be violations of flare emission limits during malfunctions, startups, shutdowns, and emergencies that are beyond the control of a source; accordingly, we are providing sources with the ability to assert an affirmative defense to penalties for violations of flare limits that occur during malfunction, startup, and shutdown periods. We believe this is a reasonable approach, consistent with our views that automatic exemptions are not appropriate for emission limits relied on

to demonstrate attainment of the NAAQS.

(e)

Comment (COPC):

The rule as written will ultimately put ConocoPhillips in the position of having to choose between compliance with an environmental regulation and maintaining safe operating conditions. This is an untenable position which can be avoided by acknowledging in rule language that flare SO

emissions can occur during periods of malfunction, startup, and shutdown, provided that accepted management systems are followed.

Response:

See responses to comments II.D.1.(b) and (c), and II.D.2.(a), above. We believe the provision of the affirmative defense to penalties for excess emissions during malfunction, startup, and shutdown periods appropriately and reasonably addresses the commenter's concerns.

(f)

Comment (COPC):

A FIP program that adopts the same evaluation procedures for malfunctions, startups, and shutdowns for flares is preferred to a fiction that a facility can maintain a flare emission limit in all malfunction, startup, or shutdown events regardless of size or magnitude.

Response:

See response to comments II.D.3.(a), (b), (c), (d), and (e), above.

(g)

Comment (YVAS):

Specific to flaring emergencies by the sources, any added controls on flaring to protect the public (from SO

exceedences) is essential and is common sense.

Response:

We acknowledge the comment and support for our proposal.

4. Subject to NSPS

Comment (CHS Inc.)

It should be noted that the CHS refinery flare is subject to NSPS Subpart J as a result of the consent decree. This limits the H

S content of the routine refinery fuel gas streams routed to the flare and requires monitoring to demonstrate compliance with the limit.

Response:

As indicated by the commenter, the consent decree limits the H

S content of the routine refinery fuel gas streams routed to the flare. However, there are several reasons why the H

S ppm limit alone is not sufficient to support the FIP's attainment demonstration.

First, flow information is needed to translate H

S ppm values into pounds of SO

for a given period of time. Flow rates to the flares can vary widely. Without knowing potential worst-case flows to the flare, we cannot determine whether the consent decree H

S ppm limit would assure compliance with the FIP 150 pounds of SO

/3-hour limit at the 3 refineries. Therefore, we cannot conclude that the consent decree H

S limit, even absent the additional concerns we discuss below, would assure attainment of the SO

NAAQS.

Second, during certain situations, as indicated in 40 CFR 60.8(c) and 60.104(a)(1), the H

S limit does not apply. Specifically, the consent decree indicates that the CHS Inc. refinery flare is an affected facility under 40 CFR part 60, subparts A and J for fuel gas combustion devices and that fuel gases combusted in the refinery flare shall comply with the emission limit of 40 CFR 60.104(a)(1). However, 40 CFR 60.104(a)(1) exempts process upset gases and certain types of fuel gas from the emission limit. Additionally, the provisions in 40 CFR 60.8(c) indicate that emissions in excess of the level of the applicable emission limit during periods of malfunction, startup, and shutdown shall not be considered a violation of the applicable emission limit unless otherwise specified in the applicable standard. Emission limits for demonstrating attainment and maintenance of the NAAQS must apply at all times. (See responses to comments II.D.1.(b) and II.D.2.(a), above, and reference document RRR.)

Third, the alternative monitoring plan (AMP), that was approved pursuant to the consent decree and NSPS requirements (see reference document LLLLLL) for the refinery flare fuel gas combustion device, primarily relies on quarterly measurement of the H

S content of some of the refinery fuel gas streams that go to the flare using stain tubes; more frequent measurement may be required for a limited time depending on the concentration measured. Although this may be acceptable under the terms of the consent decree and the NSPS, we believe more frequent testing is necessary for determining compliance with an emission limit set to assure attainment and maintenance of the NAAQS.

5. Affirmative Defense/1999 Excess Emissions Memorandum

(a)

Comment (WSPA):

The availability of an affirmative defense is desirable. Even though EPA may allow for the assertion of affirmative defenses, the affirmative defense would only be allowed for the mitigation of penalties. This is an unreasonable position in which to place refiners subject to the proposed requirements.

Response:

We are providing an affirmative defense to penalties in the final rule, but not to injunctive relief. This is consistent with the Clean Air Act interpretations expressed in our 1999 excess emissions memorandum. See reference document RRR. We believe it is reasonable to retain the authority to seek injunctive relief for all exceedances of emission limits so that we remain able to protect the NAAQS, regardless of source “culpability” for any specific exceedance.

We note that in our proposed FIP preamble, we invited comment regarding whether it would be appropriate to extend an affirmative defense to the FIP sources for exceedances of their flare limits during malfunctions, startup, and shutdown. See 71 FR 39264, July 12, 2006. There we said the following:

“We do interpret the CAA to allow owners and operators of sources to assert an affirmative defense to penalties in appropriate circumstances, but normally we would not view such an affirmative defense as appropriate in areas where a single source or small group of sources has the potential to cause an exceedance of the NAAQS. See 1999 policy statement. We solicit comment on whether it would be appropriate to include in our final FIP the ability to assert an affirmative defense to penalties only (not injunctive relief) for violations of the flare limits.”

We have decided to provide an affirmative defense for violations of the flare limits during malfunction, startup, and shutdown. We believe this represents a deviation from our 1999 excess emissions memorandum because in the Billings/Laurel area, one or more of the FIP sources may have the potential to cause an exceedance of the SO

NAAQS. In the unique circumstances of this FIP, with the rule language we are adopting, we believe a deviation from the 1999 excess emissions memorandum is warranted. For example, we have included rule language that indicates the affirmative defense is not available if, during the period of the excess emissions, there was an exceedance of the SO

NAAQS that could be attributed to the emitting source. At least one other EPA Region has approved an affirmative defense provision with this language. See Maricopa County Rule 140 (reference document ZZZZZ), which Region 9 approved on August 27, 2002 (67 FR 54957) (reference document AAAAAA). Although not identical to the 1999 excess emissions memorandum, this rule language should provide a significant incentive to the facilities to take steps to avoid and reduce flaring whenever possible.

Also, based on our experience since the 1999 excess emissions memorandum was issued, we believe that the elements of the affirmative defense delineated in the 1999 excess emissions memorandum, which elements we have adopted in this FIP, provide a very significant incentive for

facilities to do all they can to comply with their emission limits. It is not clear that the incentive is significantly different than would be present under a traditional enforcement discretion approach, particularly when sources assume that enforcement action will rarely be taken for infrequent or small violations. Finally, we have considered industry comments regarding safety concerns, and while we do not agree that emissions from flares should be treated entirely differently from emissions from stacks and other points, we think our resolution of this issue appropriately and reasonably addresses industry concerns.

(b)

Comment (WETA):

Any flare emission limitations should include, at the least, an allowance for an affirmative defense for malfunction, startup, and shutdown circumstances.

Response:

See response to comment II.D.5.(a), above.

(c)

Comment (NEDA/CAP):

EPA should adopt a broad affirmative defense for penalties and injunctive relief for malfunctions as part of the mass emission limit for flares. MPA indicated that the FIP should not be adopted in the proposed form because the failure to include an affirmative defense for flaring resulting from malfunctions poses a significant safety risk to employees and the public with no corresponding benefit.

Response:

See response to comment II.D.5.(a), above.

(d)

Comment (NEDA/CAP):

NEDA/CAP is concerned about the potential for EPA's establishment of any precedent with regard to limiting the availability of affirmative malfunction defenses in nonattainment areas generally. NEDA/CAP is also concerned with the application of the 1999 Malfunction Policy in the Billings/Laurel proposed FIP because the Policy has never been subject to notice and comment rulemaking, but the application of the policy results in clear legal consequences for regulated entities in contravention of

Appalachian Power

EPA

, 208 F.3d 1015 (D.C. Cir. 2000).

Response:

See response to comment II.D.5.(a), above. Also, we respectfully disagree with the commenter that we are contravening the

Appalachian Power

case holding. In our proposal, we proposed that the flare limits would apply at all times but took comment on the application of an affirmative defense to penalties for those limits. In this final rulemaking, we have decided to provide the affirmative defense to penalties. The commenter had a full opportunity to comment on our proposal, which included a discussion of our interpretations of the CAA with respect to the treatment of excess emissions during malfunction, startup, and shutdown. See 71 FR 39264, col. 1, July 12, 2006. We have considered the commenter's comments along with all other comments.

(e)

Comment (NEDA/CAP):

NEDA/CAP is also concerned that EPA has made no demonstration that “a single source or small group of sources has the potential to cause an exceedence of the NAAQS,” or that the NAAQS in this air basin is in fact, any more vulnerable to a NAAQS exceedence from these sources than any other nonattainment areas is from a small group of sources. If finalized, the failure to provide an affirmative defense for malfunctions would be entirely arbitrary and unreasonable. Moreover, as a national precedent with severe legal consequences for sources in other nonattainment areas, adoption of this proposed FIP provision would be highly vulnerable to legal challenge for failure to meet the Clean Air Act's notice and comment procedures under a federal court's recent decision in

Environmental Integrity Project

EPA

, 425 F.3d 992 (D.C. Cir. 2005).

Response:

In our final action, we are providing an affirmative defense to penalties for the flare limits. We disagree with the commenter's assertion regarding notice and comment procedures; we believe we have met all applicable requirements and provided fair notice regarding our intentions in our notice of proposed rulemaking. We proposed that the flare limits would apply at all times and also invited comment on whether it would be appropriate to extend an affirmative defense for the flare limits to the four sources subject to the FIP. Our final action is a logical outgrowth of our proposal; we have decided to provide an affirmative defense to penalties for violations of the flare limits during malfunction, startup, and shutdown. While our action on this FIP may have some impact on other SIPs and FIPs based on the logic we have applied, our rule is only directly applicable to the four sources subject to the FIP. It is possible EPA may reach a different decision in future rulemaking.

(f)

Comment (API, COPC, MSCC, ExxonMobil):

While EPA's 1999 Malfunction policy does state EPA's position that affirmative defenses are not appropriate “where a single source or small group of sources has the potential to cause an exceedence of the NAAQS,” API and others are unaware of any instance where EPA has utilized this exception from its general policy allowing for the assertion of affirmative defenses during malfunctions. In this case, EPA has made no demonstration to justify an exception to the general allowance for affirmative defenses for malfunction events. Consequently, API urges EPA to allow the assertion of affirmative defenses in the final FIP. Additionally, ConocoPhillips indicated that because of the harsh consequences, EPA should only apply this exception to its policy where it is clearly demonstrated that there is very real, extended potential for a single or small group of sources to cause an exceedence of the NAAQS. This is not present in this case. In fact, actual monitoring has shown that even during malfunction, ambient NAAQS violations do not occur. ConocoPhillips urges EPA to allow the assertion of affirmative defenses for both penalties and injunctive relief in the final FIP.

Response:

See our prior responses to comments II.D.5.(a), (d), and (e). Also, we note that on two occasions, one in 1985 and one in 1995, flaring resulting from malfunctions at ConocoPhillips caused ambient exceedances of the SO

NAAQS (see reference documents DDDDDDD and EEEEEEE).

(g)

Comment (NEDA/CAP, MSCC):

The proposed FIP appears to misinterpret the 1999 Malfunction Policy. The July 12 preamble for adoption of the FIP appears to suggest that prosecutorial discretion would never be allowed in a nonattainment area where the agency decides that “one or a group of sources are directly implicated in nonattainment of a NAAQS.” In fact, the 1999 Policy recommends that such situations have to be addressed in the underlying standards themselves through narrowly-tailored SIP revisions. Moreover, in no event does the 1999 Malfunction Policy ever prohibit the use of prosecutorial discretion.

Response:

Enforcement discretion or prosecutorial discretion is always available. The question in this case was whether it was appropriate to codify an affirmative defense, which we have done in our final rule. We have not misinterpreted our 1999 policy.

(h)

Comment (NEDA/CAP, API):

There is no rational basis in the proposed FIP or the 1999 Malfunction Policy to limit the affirmative defense to penalties. NEDA/CAP asserts that such a limitation is not reasonable since the malfunction condition during which the exceedence of the applicable limitation occurs would be unavoidable.

Response:

We respectfully disagree. There could be instances in which malfunctions are unavoidable based on current plant layout and operating parameters but in which some form of corrective action would still be

appropriate. We cannot predict the exact nature of those circumstances, but protection of the NAAQS and public health is not an intermittent obligation; we are required to assure attainment and maintenance of the NAAQS at all times, not just when sources are in normal operation mode or when attainment is convenient.

See, e.g., City of Santa Rosa

EPA

, 534 F.2d 150 (9th Cir. 1976), vacated and remanded on other grounds sub nom.

Pacific Legal Foundation

EPA

, 429 U.S. 990 (1976) (“ ‘Neither EPA nor this court has any right to decide that it is better to maintain pollutants at a level hazardous to health than to require the degree of public sacrifice needed to reduce them to tolerable limits’ ”, citing

South Terminal Corp.

EPA

, 504 F.2d 646, at 656 (1st Cir. 1974);

South Terminal Corp.

EPA

, 504 F.2d 646, 675 (1st Cir. 1974) (“[I]t seems plain that Congress intended the Administrator to enforce compliance with air quality standards even if the costs were great.”) Preserving injunctive remedies ensures that we remain able to protect air quality standards and PSD increments in accordance with our fundamental responsibilities under the CAA. See CAA sections 110(a) and (l), 42 U.S.C. 7410(a) and (l). See, also, the discussion of this issue in our 1999 excess emissions memorandum, reference document RRR.

(i)

Comment (MSCC, ExxonMobil):

An exception and affirmative defense should be available under the FIP that is at least consistent with the consent decrees executed by EPA and the State of Montana with most of the affected sources.

Response:

As we have noted previously, the consent decrees and the FIP serve different purposes. We have adopted an affirmative defense provision that is consistent with the protection of the NAAQS.

(j)

Comment (Citizen):

On page 39264 is the statement “We are proposing that the flare limits will apply at all times without exception.” Laudable as that seems, EPA then subsequently states, “We solicit comment on whether it would be appropriate to include in our final FIP the ability to assert an affirmative defense to penalties only (not injunctive relief) for violations of flare limits.” If the former statement is accepted, what are the penalties for exceeding flare limits and how will they be imposed and will the public be advised which refinery exceeds a flare limit and how often could that happen to the detriment of air quality in this area?

Response:

In this final rulemaking action, we have promulgated an affirmative defense to penalties for exceedances of the flare limits during malfunction, startup, and shutdown. Under this approach all excess emissions are considered violations. However, if we or anyone else brings an enforcement action, the facility may then assert the defense to penalties. To establish the defense, the facility must demonstrate to the judge that it took appropriate steps to avoid the excess emissions and met other requirements, the details of which are contained in our final rule. If the facility cannot establish the defense, it may be subject to CAA penalties up to $32,500 per day. We do not typically advise the public when a limit is exceeded or which facility has exceeded a limit, although we often alert the public through the press when we bring an enforcement action. Under the FIP, the subject sources must submit reports to EPA identifying their emissions. Those reports are available to the public through the Freedom of Information Act (FOIA). The establishment of flare requirements should help reduce flaring incidents.

6. Installation of Additional SO

Reduction Equipment

Comment (ExxonMobil):

EPA's proposed FIP does not allow for time for the design and installation of facilities necessary to comply with the proposed flare emissions limitations. The facilities required for compliance with the proposed FIP go above and beyond what was built for the SIP or what will be built for the Consent Decree. For EPA's proposed FIP, the required controls have not yet been identified.

Response:

It is not clear what facilities the commenter is envisioning. Without greater detail, it is difficult to respond to the comment. However, the FIP imposes no specific requirement for the sources to install control equipment to limit flare emissions, and the limit we are imposing is the same one the State imposed on the sources, and which continues to be included in their permits. Our expectation is that sources will take all steps within their control to avoid flaring events and minimize their impacts on air quality if they do occur.

To the extent that the commenter is referring to the time needed to design and install flare monitoring systems required by the FIP, we have extended the deadline for installation from 180 days to 365 days after EPA approval of the flare monitoring plan.

E. Concerns With Dispersion Modeling

1. Policy Issues

(a)

Comment (MSCC, ExxonMobil):

Out-of-Date and Invalid Model Choice. (i) The proposed FIP uses the same model as that used in the SIP. EPA's models have changed since the time the SIP was developed. It is inappropriate to propose and justify more restrictive requirements on sources without considering more current modeling techniques and requirements. The older model may be more appropriate to confirm an existing situation or permit minor changes. However, the FIP goes beyond minor changes.

Response:

The commenter is correct that a newer model is now available. For new SIPs, we would require states to use EPA's most recent model. However, this is a unique situation. The State developed the Billings/Laurel SO

SIP using the ISC model, which was current at that time, and we approved various source-specific emission limits in the SIP based on the State's modeling effort. The purpose of this FIP is to fill gaps in the approved SIP. We are not intending or required to re-do the entire SIP. See,

e.g.

, section 302(y) of the CAA, 42 U.S.C. 7602(y) (“Federal implementation plan” means 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 * * *”);

McCarthy

Thomas

, 27 F.3d 1363, 1365 (9th Cir. 1994) (A FIP is “a set of enforceable federal regulations that stand in the place of deficient portions of a SIP.”) Accordingly, we think it is reasonable to rely on the same model the State used to develop the SIP. That way, all emission limits in the SIP and FIP will have been established on the same basis.

We note that MDEQ tested the performance of the ISC model when the Billings/Laurel SO

SIP was being developed, and the results showed that the model performance exceeded the performance criteria for models of this type. The FIP modeling represents a minor change to MDEQ's basic approach. The sources in the SIP modeling are characterized in the modeling inputs as 25 point and volume sources and, except for minor corrections provided by the sources, the major FIP-related change in modeling involves only one source: The MSCC 100-meter stack. We had to change the inputs for MSCC's 100-meter stack because the State gave too much stack height credit to MSCC's stack in the SIP modeling, and we, consequently, disapproved MSCC's SIP emission limits and the SIP attainment

demonstration. Otherwise, the FIP modeling uses meteorology data, receptors, and stack parameters for sources other than MSCC that are nearly identical to those used in the SIP modeling.

We also note that ISC remained an accepted EPA model at the time we proposed our FIP, and it is reasonable to finalize the FIP based on the same model. Switching models after our proposal would have required us to re-propose the FIP and would have delayed the FIP further.

(ii) A newer model, “AERMOD,” has been adopted as the EPA regulatory default model. It is clear that AERMOD is now preferred for regulatory use over the model used in the SIP development. Consideration needs to be afforded to models available today, and particularly to the model reasonably believed to give the most accurate results. The stakeholder process should be used to determine which dispersion model should be used for the FIP (ExxonMobil).

Response:

See our response to comment II.E.1.(a)(i), above. We also note that AERMOD has more complex software than ISC and, as a result, it would be extremely difficult to perform the 1320 model simulations necessary to establish emission limitations that would address buoyancy flux variations that were included in the State's SIP. A stakeholder process is not required by the CAA and would merely serve to delay issuance of the FIP.

(b)

Comment (MSCC):

Out-of-Date Model Input. Any dispersion modeling used for the proposed FIP must include improved techniques regarding building downwash. A new method for calculating the downwash effects buildings have on predicted ambient concentrations has been developed. The new technique is known as “Plume Rise Model Enhancement” (PRIME) algorithm. This technique is now commonly in practice in both ISC-PRIME and AERMOD. EPA's FIP modeling does not use this technique.

Response:

The PRIME downwash technique was never formally adopted by EPA for use in ISC. In order for states to employ this technique, EPA regional offices needed to authorize its use on a case-by-case basis until ISC was replaced as the reference model on December 9, 2006. The plume rise technique used in ISC was the recommended approach at the time the State developed the SIP, and the technique served the modeling community well for many years.

(c)

Comment (MSCC, ExxonMobil):

Modeling Violates EPA's Own Requirements. The modeling used for the proposed FIP does not meet EPA's own guidelines and requirements because of the model used, lack of current building profile, and numerous other problems found elsewhere.

Response:

See our response to comment II.E.1.(a)(i), above. The modeling approach was extensively discussed with regulatory agencies and the public when the SIP was developed, and the ISC-based modeling approach met the requirements of EPA's Guideline on Air Quality Models.

(d)

Comment (MSCC):

Modeling File Naming Convention. EPA's modeling files and Technical Support Document, both contained in the docket, do not provide a reference to the naming conventions used in the modeling effort. While it is possible to dissect some of the naming conventions, it was not possible to discern each and every file and its purpose. Therefore, the reviewers are not certain that all the modeling attempts, purposes and nuances have been accounted for in the analysis. The commenter recommends a more complete description of the naming convention and the purpose behind each modeling effort needs to be explained.

Response:

At the recommendation of industry, MDEQ allowed the use of buoyancy flux in establishing emission limits, which made the modeling far more complex. As a result, many more modeling files are included than is typically the case in SIP modeling applications. To improve documentation, some extraneous modeling files have been removed and a text file added to explain naming conventions. The naming convention used for the Billings/Laurel SO

FIP modeling files is typical of that used by the modeling community. To a modeler, the naming convention helps define the purpose behind the modeling effort. On July 13, 2007, the revised modeling files were indexed in the electronic docket contained on

http://www.regulations.gov

, and a compact disk containing the modeling files was placed in the docket for this action. See reference document FFFFF.

(e)

Comment (MSCC, ExxonMobil):

Out-of-date and Invalid Emissions Rates. Federally enforceable emission rates from refinery consent decrees have not been included in the FIP modeling. EPA has used 10-year-old emission inventory data that compromise the accuracy of the results. Reductions that have occurred in the past ten years have been ignored. The settlement documents related to the 1998 SIP contain requirements that substantially change the SO

emission limits, and, therefore, the results of any modeling demonstration (ExxonMobil). Without including these existing emission reductions from the SIP and near term future reductions from consent decrees, EPA's proposed FIP ignores state and federally enforceable SO

emission reductions already in place.

Response:

See our responses to comments II.A.2.(b), II.B.2.(d) and II.D.4. The FIP modeling accounts for the limits that we approved in the Billings/Laurel SO

SIP and those we are promulgating in the FIP. We cannot include State requirements that were not submitted with the SIP. Additionally, the ExxonMobil consent decree limits have not been translated into short term emission limits by MDEQ and made a part of the SIP. Short term emission limits are required to ensure compliance with the 3-hour and 24-hour average SO

NAAQS. Also, the consent decrees do not address all of the stacks/sources involved in the SIP/FIP.

(f)

Comment (MSCC):

MSCC has concerns with using the SIP modeling. The predecessor model routines had been discredited (“invalidated”) in this valley following a study done years earlier by the State. The model, even in the 1990's, did not represent state of the art in modeling science and was admittedly prone to serious over-predictions, particularly in so-called intermediate and complex terrain.

Response:

As noted above, the modeling was EPA's preferred model at the time of the SIP, has been validated for use in the Billings/Laurel area, and has been used extensively throughout the United States in setting emission limits for nearly two decades. The model has not been “invalidated” for use in the Billings/Laurel area. See also our discussion of related issues in our May 2, 2002, final action on the Billings/Laurel SO

SIP, 67 FR 22168, 22183.

(g)

Comment (ExxonMobil):

Only the current actually existing emission sources with proper geographical coordinates should be used as inputs to the dispersion model.

Response:

We do not understand what the commenter is referring to when they indicate “only the current actually existing emission sources * * * should be used as inputs to the dispersion model.” With respect to geographical coordinates used in the modeling, they were provided by the sources in response to EPA's CAA Section 114 information request. The incorrect source coordinate for MSCC in the modeling files has been corrected.

July 13, 2007, the revised modeling files were indexed in the electronic docket contained on

http://www.regulations.gov

and a compact disk containing the modeling files was placed in the docket for this action. See reference document FFFFF. To the extent the commenter is asserting that actual emission rates should be used as inputs to the dispersion model, we respectfully disagree. As described more fully in our response to comment II.E.1.(e), above, potential emissions rather than actual emissions are used in SO

attainment demonstrations, per longstanding EPA policy and 40 CFR part 51, Appendix W requirements. Accordingly, in our attainment demonstration, we modeled the emission limits we approved in the SIP and any new emission limits we are promulgating in the FIP. Thus, with the exception of certain units at MSCC, we modeled the same emission rates that the State used in its SIP modeling.

In reference document WW, Technical Support Document, Dispersion Modeling to Support Sulfur Dioxide (SO

) Emission Limits in Federal

Implementation Plan (FIP) for Billings/Laurel, Montana, June 2006, we indicated that one suggested change that was not incorporated into the EPA FIP modeling involved the coordinate system used in the model to identify source location. MDEQ developed the original source locations based on the UTM NAD27 (North America Datum of 1927) coordinate system, and EPA has retained that coordinate system in our modeling. It appeared that several of the suggested changes to source locations were based on NAD83 values. The newer coordinate system can affect source locations by up to 200 meters. In dispersion modeling on the scale of the current modeling domain, consistency between the source and receptor loca

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