Montana D e p a r t m e n t of 

.N VIIR0N1VJ(]E:NJ['.Al.l{(lu1\ JLI[1[1'Y 

,kJ 

Br ia n Schweitzer. Governor 

Richard H. Opper. Director 

P . O . Box 20090 1 • ·I MT 5 9 6 2 0 - 0 9 0 1 • ~ 0 ~~ -25 ~ ~ • www . d e q .mt .g o y 

May 27,2011 

James S. Martin 

Regional Administrator 

United States Environmental Protection Agency 

Region VIII, 8P-AR 

1595 Wynkoop St. 

Denver, CO 80202-1129 

RE: Montana State-Wide Sulfur Dioxide (S02) NAAQS Designations 

Dear Mr Martin: 

The U S. Environmental Protection Agency (EPA) promulgated a revision to the National 

Ambient Air Quality Standards (NMOS) for sulfur dioxide (S02) on June 22. 2010 (75 FR 

35520). Pursuant to 42 USC §7407, Congress directs governors to submit a list of areas 

designated as nonattamrnent, attainment, or unclassifiable with respect to new or revised 

NMOS Such lists of designated areas are due no later than one year following the 

promulgation of a new or revised standard, or June 3, 2011 . 

On behalf of Governor Brian Schweitzer, I hereby designate all 56 counties in the State of 

Montana attainment or unclassitrable for the revised S02 NMOS. The Information provided In 

the enclosed Technical Support Document provides additional specificity regarding area 

designations and outlines Montana's rationale for these designations. If you have any questions 

regarding this action, please contact M. Eric Merchant. the Department's Air Quality Policy and 

Planning Supervisor, by telephone at (406) 444-1457 or by email at emerchant@mt.gov. 

Smcerely. 

Richard H. Opper 

Director 

Enclosure 

c/enc: Governor Brian Schweitzer 

c: Oavrd Klemp, Chief, Air Resources Management Bureau 

M. Eric Merchant, Air Resources Management Bureau 

En (qrct.'JIIe nf Dlvisln n • l' cr m iUin l! l{ Complia nce Divislon • P'13n ning, I'rcn:ntion & As....ist ancc Dlvisio n • Rerned latlu n Oh 'h ion 
Page 1 of 25 

TECHNICAL SUPPORT DOCUMENT 

Montana Designations 

June 2, 2010, Revised National Ambient Air Quality Standards for Sulfur Dioxide

I. EXECUTIVE SUMMARY 

On June 2, 2010, the U.S. Environmental Protection Agency (EPA) revised the national 

ambient air quality standards (NAAQS) for sulfur dioxide (SO2), adding a short-term 1-hour 

primary (health-based) standard of 75 parts per billion (ppb) expressed as the 3-year 

average of the 99th percentile of the annual distribution of daily maximum 1-hour average 

concentrations. The primary 24-hour and annual SO2 NAAQS have been repealed under 

the revised rule, except as applicable for existing SO2 nonattainment areas in the state 

(Laurel, East Helena). The 3-hour secondary (welfare-based) NAAQS of 500 ppb has been 

retained. The revisions were published in the Federal Register (FR) on June 22, 2010, at 75 

FR 35520. 

Pursuant to 42 USC §7407, et seq., Montana is obligated to submit to EPA an initial list of 

geographic areas that attain the standard or that do not attain the standard or that are 

otherwise unclassifiable based on available information. The following evaluation 

substantiates Montana’s area designations. 

Designations for Counties Not Containing Significant SO2 Point Sources

Based on available information, Montana determined that an initial designation of attainment 

is appropriate for the 42 Montana counties without significant SO2 point sources located 

within their respective boundaries. As stated by EPA in the preamble to the revised SO2

NAAQS, SO2 emissions originate chiefly from industrial sources. In addition, available 

monitoring information supports the conclusion that the ambient air in those counties 

contains concentrations of SO2 far below the revised SO2 NAAQS. 

Those counties to be designated attainment are as follows: Beaverhead, Blaine, Carbon, 

Carter, Chouteau, Daniels, Deer Lodge, Fergus, Garfield, Glacier, Golden Valley, Granite, 

Hill, Judith Basin, Lake, Lewis and Clark, Liberty, Lincoln, McCone, Madison, Meagher, 

Mineral, Musselshell, Park, Petroleum, Phillips, Pondera, Powder River, Powell, Prairie, 

Ravalli, Roosevelt, Sheridan, Silver Bow, Stillwater, Sweet Grass, Teton, Toole, Treasure, 

Valley, Wheatland, and Wibaux Counties. 

Designations for Counties Containing Significant SO2 Point Sources

Montana determined that an initial designation of attainment or unclassifiable is appropriate 

for the 13 Montana counties, excluding Yellowstone County, containing one or more 

significant SO2 point sources. That designation is supported by the following facts: 

• SO2 emissions in Montana are primarily emitted from major sources. 

• Montana’s major SO2 sources are generally well controlled and monitored with 

respect to SO2. 
Page 2 of 25 

• Available ambient monitoring information in these counties indicates ambient 

concentrations of SO2 that are far below the revised NAAQS. 

• Ongoing and future implementation of national SO2 emissions limiting programs will 

further limit impacts from significant SO2 point sources. 

Those counties to be designated attainment or unclassifiable are as follows: Big Horn, 

Broadwater, Cascade, Custer, Dawson, Fallon, Flathead, Gallatin, Jefferson, Missoula, 

Richland, Rosebud, and Sanders Counties. 

Designation for Yellowstone County

With respect to Yellowstone County, the 2008-2010 average value monitored in the 

Billings/Laurel area is 84 ppb, an “apparent” violation of the revised SO2 NAAQS. This 

information taken alone and without context could lead one to believe that an initial 

designation of nonattainment for Yellowstone County may be appropriate. However, the 

purpose and intent of a nonattainment designation is to initiate a process to incorporate 

necessary enforceable, permanent, and quantifiable emissions reductions into the affected 

state implementation plan (SIP) to ensure that the area will achieve NAAQS attainment and 

thereby adequately protect public health in a timely manner. If the enforceable, permanent, 

and quantifiable emissions reductions necessary to attain NAAQS compliance are already 

mandated under the existing SIP, then a nonattainment designation is not appropriate. 

The most significant change in Yellowstone County (Billings/Laurel area) SO2 emissions 

during the 2008-2010 timeframe was a near 1700-ton increase at ExxonMobil during the 

latter part of calendar year 2010. This emissions increase was a direct result of ExxonMobil 

performance under an SO2 additive testing schedule pursuant to an EPA consent decree. 

This emissions increase also corresponds directly to a majority of the documented NAAQS 

exceedences (9 of 18) for the 2008-2010 time-period. Absent implementation of the 

particular provisions of the consent decree responsible for the increased SO2 emissions and 

resulting NAAQS exceedences, the consent decree and the existing SIP would have 

protected the NAAQS. This is clearly demonstrated by the sharp decline in SO2 emissions 

and the resulting ambient SO2 concentrations after the additive testing schedule was 

completed (January 2011). One may reasonably presume that the federal Clean Air Act 

(CAA) does not expect states to revise SIPs when requirements in a consent decree 

interfere with attainment of the NAAQS (42 USC §7410(a)(3)(C)). Additionally, the CAA 

does not expect states to revise SIPs when federal requirements would have the same 

outcome. Performance under the consent decree has demonstrated that additional and 

significant SO2 reductions from the ExxonMobil facility will be realized upon full 

implementation thereby complementing Montana’s existing SIP. Therefore, Montana need 

not regulate over the top of EPA’s consent decree with ExxonMobil. As a result of this 

consent decree-mandated one-time emissions scenario, Montana firmly believes that 

consideration of 2010 monitoring data for initial designation purposes is inappropriate. At a 

minimum, Montana believes that EPA should initially designate Yellowstone County as 

unclassifiable until such time as representative data is available for comparison to the 

NAAQS. In lieu of using 2010 data Montana would suggest using either 2009, 2011, and 

2012 data or 2011 through 2013 data to determine a design value for comparison to the 

NAAQS. 
Page 3 of 25 

Further, Montana recognizes the ongoing and near-future implementation of many existing 

federal SO2 emissions limiting programs impacting SO2 point source emissions in the 

Billings/Laurel area of Yellowstone County. The perceived and logical intent of ongoing and 

near-future implementation of federal SO2 emissions limiting programs would be to reduce 

industrial SO2 emissions nationwide and in the Billings/Laurel area to levels corresponding 

to compliance with the 2010 revised SO2 NAAQS. Implementation of regulatory programs 

including the Utility MACT, Regional Haze/BART, flare provisions from the FIP and EPA’s 

flare initiatives, and ExxonMobil-specific consent decree requirements, will significantly 

reduce Billings/Laurel area SO2 emissions and associated ambient concentrations. These 

reductions in SO2 emissions provide further assurance that the Billings/Laurel area will 

achieve compliance with the new 1-hour SO2 NAAQS before the required compliance date 

in August of 2017. 

Therefore, because 2010 Billings/Laurel area industrial SO2 emissions and associated 

ambient impacts are not representative of future conditions in the area and because the SIP 

already contains provisions necessary to achieve attainment of the revised SO2 NAAQS in 

the Billings/Laurel area in a timely manner, revisions to the existing SIP are not necessary. 

Montana strongly concludes that an initial designation of unclassifiable is appropriate for 

Yellowstone County. 

 
Page 4 of 25 

II. MONTANA DESIGNATIONS (excluding Yellowstone County) 

Montana believes it is appropriate to divide the SO2 NAAQS designation discussion between 

Yellowstone County and the rest of Montana (55 additional counties). This section 

addresses Montana’s designation for areas/counties located within Montana and outside of 

Yellowstone County. 

 

A. General Information 

As stated in the preamble to the NAAQS revision, “Anthropogenic SO2 emissions 

originate chiefly from point sources, with fossil fuel combustion at electric utilities (<66%) 

and other industrial facilities (<29%) accounting for the majority of total emissions.” 

In 2010, there were 16 permitted industrial point sources with significant actual and/or 

allowable SO2 emissions located within 13 different Montana counties, while 42 counties 

in Montana contained no significant sources of SO2. For the purpose of this discussion 

Montana defines significant emissions as 100 tons of SO2 emissions per year. The list in 

Table 1 includes the facility names as well as the location by county. This list includes 

facilities whose current allowable permit emissions are above the major source 

threshold, regardless of their current actual emissions. The single largest source of SO2

emissions in Montana is the PPL Montana, LLC – Colstrip (PPL – Colstrip) facility 

located in Rosebud County. Figure 1 illustrates the geographic location of significant 

sources of SO2 state-wide. 

TABLE 1 MONTANA’S SIGNIFICANT SOURCES OF SO2 BY COUNTY 

(excluding Yellowstone County) 

Source County 

Columbia Falls Aluminum Company, LLC Flathead 

Thompson River Power, LLC Sanders 

Smurfit Stone Container Corporation Missoula 

Montana Refining Company Cascade 

Malmstrom Air Force Base Cascade 

Ash Grove Cement Company Jefferson 

Graymont Western U.S., Inc. Broadwater 

Holcim (US), Inc. Gallatin 

Rocky Mountain Power, LLC Big Horn 

PPL Montana, LLC – Colstrip Rosebud 

Colstrip Energy Limited Partnership Rosebud 

Montana-Dakota Utilities Company – Miles City Custer 

Bear Paw Energy, LLC – Baker Fallon 

Montana-Dakota Utilities Company – Glendive Dawson 

Montana-Dakota Utilities Company – Lewis and Clark Richland 

Sidney Sugars Inc. Richland 
Page 5 of 25 

FIGURE 1 MONTANA’S MAJOR SO2 POINT SOURCES BY LOCATION 

Of the 16 point sources listed in Table 1, 10 are required to have either SO2 Continuous 

Emissions Monitors (CEMS) or Compliance Assurance Monitoring (CAM) Plans on large 

SO2 emitting units. In addition, those large units are generally well-controlled by 

enforceable limits and conditions. 

Based on changes in operation and/or updated emission factors, the following facilities 

likely will not remain as listed major sources of SO2: Smurfit-Stone Container 

Corporation and the Montana-Dakota Utilities Company – Glendive and Miles City 

facilities. The Smurfit-Stone Container Corporation is currently shutdown and is 

anticipated to be sold and the facility scrapped. The Montana-Dakota Utilities Company 

– Glendive and Miles City facilities have permitted allowable SO2 emissions above 100 

tons per year because of outdated emission factors associated with sulfur in diesel fuel 

that is used in the turbines associated with those facilities. With the current EPA ultralow sulfur diesel fuel requirements, it is anticipated that the potential SO2 emissions for 

those two facilities would fall far below 100 tons per year. 

This area also contains one of the current SO2 nonattainment areas – East Helena, 

designated as nonattainment for both the previous primary and secondary SO2 NAAQS. 

The East Helena SIP for the primary SO2 NAAQS was approved by EPA on January 27, 

1995. The source of the SO2 emissions, the ASARCO primary lead smelter, associated 
Page 6 of 25 

with the nonattainment designation ceased operation in 2001. ASARCO’s air quality 

permit was revoked on January 5, 2010, after years of inactivity, emitting unit removal, 

and site remediation. 

B. Monitoring Data 

Outside of Yellowstone County, Montana currently conducts ambient SO2 monitoring at 

two separate locations. The first is located at Montana’s NCore station in Lewis and 

Clark County. Montana’s NCore station is designated a national background monitoring 

site with no significant industrial sources of pollution located nearby. Montana also 

currently operates an SO2 monitoring site in Richland County near the town of Sidney. 

The Richland County site was established in 2010 with the primary intent to evaluate 

impacts from the oil and gas industry (oil and gas field/well development). Because 

these sites are relatively new, limited data is available at this time; however, preliminary 

results indicate that ambient SO2 concentrations in the affected area are far below the 

level of the revised SO2 NAAQS. 

As previously mentioned, the largest single source of SO2 emissions currently operating 

in Montana is the PPL – Colstrip coal-fired electrical generating station located in 

Rosebud County. Historic monitoring data from Rosebud County and the surrounding 

affected area indicates that SO2 emissions from this facility, and the nearby Colstrip 

Energy Limited Partnership coal-fired electrical generating station, do not result in 

ambient impacts exceeding the revised SO2 NAAQS. Montana did not collect the 

subject ambient data; rather this data was collected by the affected industry in 

accordance with facility permit requirements and/or via monitoring conducted on Indian 

Lands outside of Montana’s jurisdiction. The industrial data collected in Rosebud 

County was evaluated in accordance with Montana’s applicable Quality Assurance 

Project Plan (QAPP). Figure 2 provides ambient monitoring results from monitoring 

activities conducted in Rosebud County by the former Montana Power Company, 

currently PPL – Colstrip (monitoring stations MPC #1, #2, and #3), and monitoring 

conducted on the Northern Cheyenne Indian Reservation (monitoring stations 

Morningstar, Garfield Peak, and Badger Peak). These monitoring results indicate that 

Rosebud County is complying with the revised SO2 NAAQS. 

 
Page 7 of 25 

FIGURE 2 NAAQS REVIEW OF ROSEBUD COUNTY 1-HR SO2 DATA 

Historic and ongoing ambient monitoring activities being conducted within Montana 

outside Yellowstone County indicate that the affected areas are complying with the 

revised SO2 NAAQS. 

C. Regulatory Analysis 

Although Montana believes the affected areas are currently complying with the revised 

SO2 NAAQS, Montana wishes to acknowledge the additional SO2 reductions anticipated 

as a result of ongoing and pending federal regulations. As stated in the preamble to the 

revised SO2 NAAQS, “EPA ... notes that it anticipates several forthcoming national and 

regional rules, such as the pending Industrial Boilers MACT standard under CAA section 

112(d), that are likely to require significant reductions in SO2 emissions over the next 

several years. A limited qualitative assessment based on the results of preliminary 

modeling of some sample facilities indicates that well controlled sources should meet the 

new SO2 NAAQS.” 

Those regulatory actions include the Industrial Boiler Maximum Achievable Control 

Technology (MACT); the proposed Utility MACT; the final Portland Cement MACT; the 

anticipated Best Available Retrofit Technology (BART) determinations associated with 

the Regional Haze Rule; the finalization of 40 CFR 60, Subpart Ja; and EPA’s flare 

initiative. 

30 28

17 18 16

11

26

29

18

15 14 15

22

29

20

37

21

26

41

32

27

39

33

25

14

24

13

0

25

50

75

100

MPC #3 MPC #1 MPC #2 Morningstar Garfield Peak Badger Peak

3-Yr Avg.99th %tile Daily Maxs (ppb)

1997-1999 1998-2000 1999-2001

2000-2002 2001-2003 2002-2004

1-Hour SO2 NAAQS = 75 ppb
Page 8 of 25 

i. Utility MACT Implementation 

The proposed Utility MACT was announced and made publicly available by EPA on 

March 16, 2011. The proposed rule was promulgated as 40 CFR 63, Subpart 

UUUUU - National Emission Standards for Hazardous Air Pollutants: Coal- and Oilfired Electric Utility Steam Generating Units (or “Utility MACT”). The rule is expected 

to be issued in final form by November as required by a court settlement agreement, 

unless that deadline is extended by the courts. The proposed rule contains several 

emission limit options by category. In the coal-fired units, the following categories 

exist. For non-mercury (non-Hg) metals, a facility may take a total PM limit, a total 

non-Hg HAP metal limit, or individual limits on listed non-Hg HAP metals. For acid 

gases, the options include taking a hydrochloric acid limit or an SO2 limit. Mercury 

limits apply for all types of units subject to the Utility MACT. Some options can only 

be used in conjunction with specific pollution control configurations. 

The PPL - Colstrip, Montana-Dakota Utilities – Lewis and Clark (MDU – Lewis and 

Clark), Colstrip Energy Limited Partnerships (CELP) and Rocky Mountain Power 

(RMP) facilities would all be subject to the new Utility MACT as coal-fired utilities. If 

MDU - Lewis and Clark and PPL - Colstrip Units 1 & 2 chose to demonstrate 

compliance with HCl using the SO2 surrogate limit, those units would be limited to 

0.2 pounds of SO2 per million British thermal units (lb/MMBtu) of heat input, which 

would be less than half of the actual current emissions rates according to the 2009 

SO2 emissions reporting from EPA’s Acid Rain Database. Similarly, the 0.2 

lb/MMBtu SO2 limit, if chosen, would result in a significant reduction from the CELP 

facility as well (CELP’s current SO2 limitation is 1.2 lb/MMBtu). As previously 

discussed, any PM control added to those facilities to address the PM surrogate limit 

(if chosen for compliance) would likely provide some co-benefit control with respect 

to SO2. 

The effect on PPL – Colstrip Units 3 & 4 and RMP would be less significant and may 

require no additional control from those facilities to meet the Utility MACT 

requirements. 

ii. Boiler MACT Implementation 

EPA’s MACT standard for Industrial, Commercial and Institutional Boilers at major 

sources (the “Boiler MACT”) was finalized and published as 40 CFR 63, Subpart 

DDDDD in the Federal Register on March 21, 2011. However, on May 18, 2011, 

EPA published an indefinite delay of the implementation of the major source Boiler 

MACT rules. The Boiler MACT, as finalized, would require emission limits for various 

categories of large and small boilers. The rule also would require various energy 

audits and tune-ups of the boilers regardless of size and fuel. The energy audits and 

tune-ups are designed to lower fuel consumption; thereby lowering emissions. 

Montana Refining Company has units (primarily natural gas or refinery fuel gas-fired 

units) that appear to meet the applicability requirements of the rule. As such, energy 

audits and tune-ups would be requirements of the rule for those units. The reduction 

in SO2 is not quantifiable at this early date, but improvements in efficiency and tuneup would be likely to lead to lower emissions. However, even without the stay, the 

Boiler MACT provisions are not likely to lead to large reductions in SO2 emissions 

from major sources. 
Page 9 of 25 

EPA’s MACT standard for Industrial, Commercial and Institutional Boilers at area 

sources was also finalized and published as 40 CFR 63, Subpart JJJJJ in the 

Federal Register on March 21, 2011 (and is not subject to the stay issued by EPA on 

the major source Boiler MACT rules). Boilers at Thompson River Power, Sidney 

Sugars, and Malmstrom Air Force Base appear to be subject to the mercury (Hg) 

and carbon monoxide (CO, as a surrogate for non-dioxin organic hazardous air 

pollutant) limits in this standard. At this time it is unclear what steps those facilities 

may take to meet the Hg emission limits listed in the area source rule. All of the 

coal-fired boilers at the above-mentioned facilities are currently controlled using 

scrubbers. If scrubber upgrades are considered for Hg control, SO2 emissions may 

also be reduced through that process, although significant reductions would not be 

expected. 

iii. Portland Cement MACT 

EPA’s MACT standard for Portland Cement Manufacturing Industry was finalized on 

September 9, 2010. The Ash Grove Cement Company is a major source of HAP 

emissions and would be subject to a hydrochloric acid (HCl) emission limitation in 

addition to a particulate matter (PM) limit on its cement kiln pursuant to the updated 

MACT. Holcim (US) Inc. is an area source, but both area and major sources would 

also be subject to the PM limitations. The kilns at both facilities are currently 

controlled by electrostatic precipitators (ESPs); however, it is unknown by Montana 

what types of upgrades may be necessary to meet the PM limitations. As previously 

mentioned, upgrades in PM control often have an SO2 co-benefit control. In addition, 

the HCl limit would prompt changes that would reduce SO2 emissions from Ash 

Grove. 

iv. Regional Haze / BART Implementation 

Under EPA’s Regional Haze Program, states, including Montana, are required to 

develop a program to assure reasonable progress toward meeting the national goal 

of protecting (and preventing) visibility impairment in mandatory Class I areas. Two 

portions of this program could impact industrial facilities in Montana. One program is 

Best Available Retrofit Technology (BART). BART requirements of the regional haze 

rule apply to facilities built between 1962 and 1977 that have the potential to emit 

more than 250 tons per year of visibility-impairing pollution. Those facilities fall into 

26 categories, including utility and industrial boilers, and large industrial plants such 

as pulp mills, refineries, and smelters. The regional haze regulations also allow 

states to develop coordinated strategies and implement programs to make 

“reasonable progress” toward the goal of “no manmade impairment” in national parks 

and wilderness areas by reducing emissions that contribute to haze. Currently EPA 

is directly administering these programs in Montana. 

According to EPA guidance, SO2 is a pollutant that may contribute to visibility 

impairment. To date, EPA has not proposed any findings as to what controls or 

emission reductions may be required in Montana to comply with these two programs. 

It is believed that EPA plans to make such (draft) determinations sometime this 

calendar year. According to EPA, the following facilities may be subject to the 

visibility aspect of the Regional Haze Program: 
Page 10 of 25 

• PPL – Colstrip Units 1&2 

• Columbia Falls Aluminum Company 

• Ash Grove Cement Company 

• Holcim (US) Inc. 

• Smurfit-Stone Container Corporation (currently shutdown) 

Additional facilities may be subject to the “reasonable progress” portion of the 

Regional Haze Rule. EPA is currently analyzing applicability and potential emission 

reduction strategies. To the extent any reductions may be required, those reductions 

would impact ambient air quality in Montana. It is anticipated that those reductions 

would reduce the SO2 ambient air quality levels in the area. However, EPA has not 

provided any information regarding their decisions on emission control strategies 

associated with BART and Reasonable Progress or on the timeframe of those 

decisions for affected sources in Montana. 

v. 40 CFR 60, Subpart Ja and EPA’s Flare Initiative 

In addition to the anticipated final rule for 40 CFR 60, Subpart Ja – Standards of 

Performance for Petroleum Refineries, EPA is initiating efforts to limit emissions from 

flares nationwide. It appears that the requirements will be promulgated as part of the 

Consolidated Federal Air Rule (40 CFR, Part 65). Both efforts are anticipated to 

have significant effects on SO2 emissions from flaring, in this case from Montana 

Refining Company and potentially the Bear Paw Energy Baker flare. 

The CAA does not expect states to revise SIPs (develop “Maintenance” SIPs) when 

federal requirements would have the same outcome. As stated, ongoing implementation 

of the national and local SO2 limiting programs identified above will continue to result in 

significant SO2 reductions from the affected SO2 Sources. Therefore, Montana need not 

regulate over the top of EPA’s ongoing and pending SO2 limiting programs. 

D. Montana (excluding Yellowstone County) Conclusion 

Pursuant to 42 USC §7407, Montana is required to submit to EPA a list of all areas (or 

portions thereof) in the state, designating as nonattainment, attainment, or otherwise 

unclassifiable based on available information. 

Based on available information, Montana determined that an initial designation of 

attainment is appropriate for the 42 Montana counties without significant SO2 point 

sources located within their respective boundaries. As stated by EPA in the preamble to 

the revised SO2 NAAQS, SO2 emissions originate chiefly from industrial sources. In 

addition, monitoring information supports the conclusion that the ambient air in those 

counties is far below the revised SO2 NAAQS. Those counties to be designated 

attainment are as follows: Beaverhead, Blaine, Carbon, Carter, Chouteau, Daniels, 

Deer Lodge, Fergus, Garfield, Glacier, Golden Valley, Granite, Hill, Judith Basin, Lake, 

Lewis and Clark, Liberty, Lincoln, McCone, Madison, Meagher, Mineral, Musselshell, 

Park, Petroleum, Phillips, Pondera, Powder River, Powell, Prairie, Ravalli, Roosevelt, 

Sheridan, Silver Bow, Stillwater, Sweet Grass, Teton, Toole, Treasure, Valley, 

Wheatland, and Wibaux Counties. 
Page 11 of 25 

Based on available information, Montana determined that an initial designation of 

attainment or unclassifiable is appropriate for the 13 Montana counties, excluding 

Yellowstone County, that contain one or more significant SO2 point sources. That 

designation is supported by the following facts: 

• SO2 emissions in Montana are primarily emitted from major sources. 

• Montana’s major SO2 sources are generally well controlled and monitored with 

respect to SO2. 

• Available ambient monitoring data in these counties indicates levels of SO2 that 

are far below the revised NAAQS. 

• Ongoing and future implementation of national SO2 emissions limiting programs 

will further limit impacts from significant SO2 point sources state-wide. 

Those counties to be designated attainment or unclassifiable are as follows: Big Horn, 

Broadwater, Cascade, Custer, Dawson, Fallon, Flathead, Gallatin, Jefferson, Missoula, 

Richland, Rosebud, and Sanders Counties. 

III. YELLOWSTONE COUNTY DESIGNATION 

A. Sources / History 

In 1973, the first ambient SO2 monitor was located in the Billings/Laurel area in response 

to both NAAQS and Montana ambient air quality standards (MAAQS) and known large 

industrial emitters of SO2 in the area. In 1976, EPA determined the SIP in the 

Billings/Laurel area was inadequate. In 1978, EPA designated the area surrounding the 

Cenex Harvest States, Inc. (CHS) refinery in Laurel as nonattainment based on 

monitored violations of the NAAQS. In 1979, Montana submitted and EPA approved a 

SIP to address the violations and control ongoing emissions. Following modeled 

violations of the SO2 standard, EPA “called” the SIP in 1993. Extensive work between 

Montana and the affected industries led to SIP submittals in 1996, 1998, and 2000. EPA 

eventually approved the SIP with a few notable exceptions. To that end, EPA adopted 

its own Federal Implementation Plan (FIP) in 2008 that adds additional SO2 control 

requirements to the SIP. However, that FIP is not fully implemented or finalized due to 

ongoing litigation. 

Seven industrial point sources that are significant emitters of SO2 are located in the 

Billings/Laurel area and have been extensively involved in efforts with Montana to 

reduce SO2 emissions. These facilities are listed in Table 2 by city. 
Page 12 of 25 

TABLE 2 YELLOWSTONE COUNTY, MONTANA SIGNIFICANT SOURCES OF SO2 

BY LOCATION 

Source City 

Cenex Harvest States, Inc. (CHS) Laurel 

PPL Montana, LLC – J.E. Corette (PPL – Corette) Billings 

ConocoPhillips Company (ConocoPhillips) Billings 

Montana Sulphur & Chemical Company (MSCC) Billings 

ExxonMobil Refining & Supply Company (ExxonMobil) Billings 

Yellowstone Energy Limited Partnership (YELP) Billings 

The Western Sugar Company (Western Sugar) Billings 

The CHS petroleum refinery is located in Laurel and the following sources are located in 

Billings: MSCC sulfur recovery plant; ExxonMobil petroleum refinery; ConocoPhillips 

petroleum refinery; PPL - Corette coal-fired electrical generating station; the Western 

Sugar sugarbeet processing plant; and YELP petroleum coke-fired electrical/steam cogeneration facility. 

The affected facilities in the Billings/Laurel area have made substantial progress in 

reducing SO2 emissions and additional reductions are expected in the future based on 

efforts made to comply with forthcoming regulatory requirements (see discussion in 

Section III.D) and completion of pollution control projects, some required by consent 

decree. Figure 3 illustrates the reductions realized in actual SO2 emissions in the 

Billings/Laurel area from 1983 to 2009. In that timeframe, total emissions from the 

seven Billings/Laurel sources were reduced from approximately 35,000 tons per year to 

approximately 7,600 tons per year in 2009. 

 

FIGURE 3 HISTORICAL SO2 EMISSIONS FROM THE BILLINGS/LAUREL INDUSTRIES 

0

5000

10000

15000

20000

25000

30000

35000

40000

83 84 85 86 87 88 89 90 91 92 93 94 95 96 97 98 99 00 01 02 03 04 05 06 07 08 09

TOTAL TONS per YEAR

YEAR
Page 13 of 25 

Tables 3 and 4 provide the estimated total combined emissions and source-specific 

estimated emissions, respectively, from the seven major facilities in the Billings/Laurel 

area for calendar years 2008, 2009, and 2010. 

TABLE 3 BILLINGS/LAUREL AREA COMBINED INDUSTRIAL SO2 EMISSIONS 

Emissions Year Total SO2 Emissions (tons/year) 

2008 8118 

2009 7595 

2010 8254 

Total Emissions 2008-2010 23,967 tons 

TABLE 4 BILLINGS/LAUREL AREA INDUSTRIAL SO2 EMISSIONS 2008-2010 

Source 2008 2009 2010 Total Emissions

PPL Montana - Corette 2929 2788 2271 7988 

ExxonMobil 1765 696 2389 4850 

YELP 1590 2062 1816 5468 

MSCC 1320 1559 1383 4262 

CHS 268 231 225 724 

Western Sugar 138 133 98 369 

ConocoPhillips 108 127 73 308 

B. Monitoring Data 

Montana and a consortium of industries known as the Billings/Laurel Air Quality 

Technical Committee (BLAQTC) have conducted SO2 monitoring in the Billings/Laurel 

area for over 30 years. Over that period of time, SO2 has been monitored at 31 locations 

in the Billings/Laurel area. Currently, Montana and the local public health agency, 

RiverStone Health (RiverStone), operate a single monitoring site and BLAQTC operates 

four others. Figure 4 provides a graphical representation of recent SO2 averages 

monitored at the BLAQTC sites (Laurel Farm, Lockwood Park, Brickyard Lane, Johnson 

Lane, and Pine Hills), as well as the state of Montana SO2 monitoring site (Coburn Rd) 

as compared to the revised SO2 NAAQS. 
FIGU

A

b

re

A

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Page 15 of 25 

TABLE 6 COBURN ROAD SLAMS 1-HOUR DAILY MAXIMUM SO2 VALUES 2008-2010 

(* = 99th percentile value) 

2008 2009 2010

Date - Hour ppb Date - Hour ppb Date - Hour ppb

8/24 - Hr 1 119 9/22 - Hr 9 107 7/8 - Hr 6 111

10/28 - Hr 8 112 2/5 - Hr 2 83 12/24 - Hr 9 101

10/27 - Hr 1 95 9/25 - Hr 9 83 7/9 - Hr 6 92

6/14 - Hr 6 89* 1/20 - Hr 5 72* 2/10 - Hr 4 91*

10/1 - Hr 8 77 8/12 - Hr 7 69 10/22 - Hr 9 89

Despite the relative consistency in overall emissions (see Table 3), calendar year 2010 

included 9 of the 18 monitored NAAQS exceedences over the 2008-2010 time period, 8 

of which occurred in the latter half of 2010 alone. A summary of monitored NAAQS 

exceedences by quarter over the 2008-2010 time period is provided in Table 7. 

TABLE 7 COBURN ROAD SLAMS MONITORED NAAQS EXCEEDANCES 2008-2010 

Calendar Year Calendar Quarter Number of Exceedences 

(> 75 ppb) 

2008 

1 0 

2 1 

3 2 

4 3 

2008 Total Exceedances Æ 6 

2009 

1 1 

2 0 

3 2 

4 0 

2009 Total Exceedances Æ 3 

2010 

1 1 

2 0 

3 4 

4 4 

2010 Total Exceedances Æ 9 

2008-2010 Total Exceedances Æ 18 

Montana operates an ambient air monitoring quality assurance and quality control 

(QA/QC) program for many reasons, among them to ensure the ambient air monitoring

data supports and fulfills the operational, informational, and regulatory needs of the 

state. As part of this objective, Montana established the Ambient Air Monitoring 

Program Quality Management Plan (QMP). The QMP guides ambient air monitoring 

data collection activities. Montana has developed and maintains an EPA-approved 

QAPP and associated Standard Operating Procedures (SOP) to gather, review, and 
Page 16 of 25 

evaluate ambient monitoring data in a consistent and defensible manner, including the 

ambient SO2 monitoring conducted in the Billings/Laurel area. 

Within the 2008-2010 monitoring time period, there were several data inconsistencies 

that coincided with some of the high monitored values recorded. On October 1, 2008 

(hour 08: 2008 5th maximum 1-hour SO2 concentration of 77 ppb), the monitoring 

program review of the strip chart indicated interruption of the strip chart drive. The 

interruptions occurred during site visits but were not listed in the station log. On August 

24, 2008 (hour 08: 2008 1st maximum 1-hour SO2 concentration of 199 ppb), and 

October 27, 2008 ( hour 01: 2008 3rd maximum 1-hour SO2 concentration of 95 ppb), 

extreme wind directions were recorded: 119 degree 1-hour average wind direction, 21 

degree 1-hour average standard deviation of the horizontal wind direction, and 0.8 meter 

per second 1-hour average wind speed and 127 degree 1-hour average wind direction, 

29 degree 1-hour average standard deviation of the horizontal wind direction, and 0.9 

meter per second 1-hour average wind speed, respectively. The final inconsistency is 

that quarterly multipoint calibrations were not completed as required in the QAPP. 

Fourth quarter 2008 and second quarter 2009 multipoint calibrations were not completed 

due to calibration flow rate verifying standard malfunctions, and the fourth quarter 2009 

multipoint calibration was not completed due to unknown reasons. 

C. Emissions Data Versus Monitoring Data 

Based on the distribution of exceedences within the monitoring data from 2010, Montana 

conducted an evaluation of SO2 emissions changes at each of the major industrial 

sources of SO2 in the Billings/Laurel area. The most significant finding was that 

ExxonMobil increased SO2 emissions by approximately 1700 tons in calendar year 2010 

as compared to calendar year 2009 with nearly an 800 ton increase during the 3rd and 

4th quarter of 2010. Table 8 provides a comparison of annual emissions and emissions 

changes at each of the seven facilities over the 2009-2010 time period. 

TABLE 8 COMPARISON OF 2009 TO 2010 SO2 EMISSIONS CHANGES BY SOURCE 

Source 2009 Emissions 

(tons SO2/year) 

2010 Emissions 

(tons SO2/year) 

Difference 

(tons SO2/year) 

ExxonMobil 696 2,388 + 1692 

ConocoPhillips 127 73 - 54 

CHS 231 225 - 6 

MSCC 1559 1,383 - 176 

PPL Corette 2788 2,271 - 517 

YELP 2062 1,816 - 246 

Western Sugar 133 98 - 35 

Total Emissions 7,596 8,254 

As provided in Table 8, the only significant SO2 source in the Billings/Laurel area with 

increased SO2 emissions in 2010 was ExxonMobil; therefore, for the purposes of this 

discussion, a closer evaluation of ExxonMobil emissions is warranted. Table 9 provides 

a breakdown of 2010 ExxonMobil SO2 emissions by emitting unit and by calendar 

quarter. 
Page 17 of 25 

TABLE 9 2010 EXXONMOBIL SO2 EMISSIONS BY EMITTING UNIT AND BY 

CALENDAR QUARTER

Unit 1st Quarter 2nd Quarter 3rd Quarter 4th Quarter 

Total SO2

Emissions 

(ton/yr) 

Coker CO Boiler1 3 36 476 50 568 

FCCU1 141 557 535 572 1805 

Fuel Gas1 0 0 0 1 1 

ALKY Oil2 --- --- --- --- 6 

Flare2 --- --- --- --- 8 

Total Emissions 144 593 1012 622 2388 1

 SO2 Emissions reported from Continuous Emissions Monitoring Systems (CEMS). 2

 SO2 Emissions estimated using mass balance calculations. 

The approximate 1700 ton SO2 emissions increase at ExxonMobil in 2010, as compared 

to 2009 emissions, corresponds directly to increased monitored NAAQS violations at the 

Coburn Road SLAMS in the same year. It is important to note that the primary cause of 

the 2010 ExxonMobil SO2 emissions increase (certain provisions within EPA consent 

decree) will be eliminated beginning in January of 2011, as described below. 

As identified in Table 9, the primary SO2 emissions increase at ExxonMobil during 2010 

occurred at the fluid catalytic cracking unit (FCCU). Increased FCCU SO2 emissions in 

the 2nd, 3rd and 4th quarters of 2010 are primarily the result of requirements contained in 

a consent decree entered into on December 13, 2005 (with subsequent revisions), 

between ExxonMobil, EPA, and Montana. Per consent decree requirements, 

ExxonMobil has been obligated to test a variety of SO2 reduction catalyst additives since 

October 2006. In order to identify the additive achieving the highest reduction in SO2

emissions, the testing required intermittent use of additives ending in September of 2010 

(higher SO2 values are seen as the additives are eliminated from the process or 

“decayed”). Beginning on January 15, 2011, the consent decree required the additive 

achieving the highest SO2 reductions to be consistently used to achieve SO2 emission 

rates. Since ExxonMobil has been using this additive, there has been a sharp decline in 

SO2 emissions as well as the ambient SO2 concentration in the Billings/Laurel airshed. 

This additive and the associated FCCU SO2 limitations are subject to approval by the 

EPA and Montana in 2012 and will be incorporated into ExxonMobil’s air quality permit. 

Therefore, ExxonMobil’s SO2 emissions will decrease in 2011 to a level significantly less 

than that emitted in 2010, far less than emissions during 2nd, 3rd and 4th quarter of 2010, 

and these emissions reductions will be permanent and enforceable. Enforceable 

emission limits pursuant to the consent decree will be required to reduce SO2 emissions 

on a short-term and long-term basis. Therefore, the full effect of the ExxonMobil consent 

decree on SO2 emissions and associated ambient air quality impacts is yet to be 

realized. 

As previously mentioned, reported 2011 ExxonMobil emissions data through mid-May 

2011 and associated monitored values at the Coburn Road SLAMS through February of 

2011 provide early indication that SO2 emissions from the ExxonMobil FCCU, and 

associated ambient impacts, are indeed decreasing as a result of ongoing consent 

decree implementation. Table 10 provides a draft summary of ExxonMobil emissions 
Page 18 of 25 

during calendar year 2011, through mid-May. The additive achieving the highest 

reduction in SO2 emissions from the FCCU was introduced to the FCCU on January 15, 

2011; however, as expected, the additive will take some time after introduction to 

become fully-effective and thus for ExxonMobil to realize significant SO2 reductions from 

the FCCU. Based on the additive performance during consent decree-required testing 

and 2011 performance to date it is anticipated that 2nd quarter SO2 emissions from the 

FCCU will be similar to 1st quarter 2010 FCCU SO2 emissions levels (see Table 9). 

TABLE 10 2011 EXXONMOBIL FCCU SO2 EMISSIONS BY CALENDAR QUARTER

Unit 1st Quarter 2nd Quarter 

FCCU 4731 632

1

 Reported FCCU SO2 emissions data from January through March 2011. SO2 additive initiated January 15, 2011. 2 Draft emissions data for April through mid-May 2011. Information provided to the Department during a telephone 

conversation between Department and ExxonMobil staff on May 20, 2011. 

Table 11 provides the 1st through 10th high monitored 1-hr SO2 values through February 

2011 at the Coburn Road SLAMS, as they correspond to decreased SO2 emissions from 

the ExxonMobil FCCU (see Table 10). Table 12 shows the corresponding decrease in 

the annual 99th percentile value with consideration of 2011 monitoring data through 

February 2011. 

 

TABLE 11 2011 COBURN ROAD SLAMS 1ST THROUGH 10TH HIGH MONITORED 

VALUES (through February)

1st

high 

2nd

high 

3rd

high 

4th

high 

5th 

high 

6th

high 

7th

high 

8th

high 

9th

high 

10th

high 

ppb 64 58 43 32 32 31 31 28 27 26 

Date/hr 2-22/10 1-16/1 1-18/1 1-13/10 2-2/14 1-12/1 2-4/9 2-26/8 1-4/7 2-14/9 

TABLE 12 2009-2011 COBURN ROAD SLAMS ANNUAL 99TH PERCENTILE VALUES

Year Annual # Days w/Valid Data Annual 99th Percentile Value 

20091 364 72 

20101 307 91 

20112 59 (through February 2011) 64 1

 With greater than 300 valid monitoring days 99th percentile is 4th high monitored concentration (40 CFR 50, Appendix T, Table 1) 2

 With 1-100 valid monitoring days 99th percentile is 1st high monitored concentration (40 CFR 50, Appendix T, Table 1) 

Based on pending full implementation of the consent decree-required SO2 additive and 

associated reduction in ExxonMobil FCCU SO2 emissions it is reasonable to assume 

that ambient impacts and thus the 2009-2011 SO2 design value will be reduced to a level 

below and in compliance with the revised SO2 NAAQS of 75 ppb. This information alone 

validates the idea that, at a minimum, EPA should consider 2011 data prior to making 

any final decisions regarding initial designations for the area. 
Page 19 of 25 

In summary, this information leads Montana to strongly conclude that SO2 emissions 

during calendar year 2010 and associated ambient concentrations in the Billings/Laurel 

area are not representative of future conditions already mandated by the CAA and 

Montana’s existing SIP through a consent decree. One may reasonably presume that 

the CAA does not expect states to revise SIPs when federal requirements in the consent 

decree interfere with attainment of the NAAQS (42 USC §7410(a)(3)(C)). That being 

stated, Montana firmly believes that an initial designation with consideration for 2010 

monitoring data is inappropriate. Further, there is CAA precedent for program 

implementation using representative information. When determining the applicability of 

the New Source Review Program, proposed emissions increases are compared with 

“baseline actual emissions.” “Baseline actual emissions” is defined under 40 CFR 

52.21(b)(48)(iii) with the inclusion of the following sentence, “The Administrator shall 

allow the use of a different time period upon a determination that it is more 

representative of normal source operation.” 

As a result of this consent decree-mandated one-time emissions scenario (2010), 

Montana firmly believes that consideration of 2010 monitoring data for initial designation 

purposes is inappropriate. At a minimum, EPA should initially designate Yellowstone 

County as unclassifiable until such time as representative data is available for 

comparison to the NAAQS. In lieu of using 2010 monitoring data Montana would 

suggest using either 2009, 2011, and 2012 data or 2011 through 2013 data to determine 

a design value for comparison to the NAAQS. 

D. Regulatory Analysis 

As discussed previously with respect to the ExxonMobil consent decree, future SO2

emissions at several of the significant sources in the Billings/Laurel area will be 

significantly impacted and reduced by the implementation of ongoing and/or newly 

promulgated federal SO2 limiting programs. As stated by EPA in the preamble to the 

June 2, 2010, SO2 standard revision, “EPA ... notes that it anticipates several 

forthcoming national and regional rules, such as the pending Industrial Boilers MACT 

standard under CAA section 112(d), that are likely to require significant reductions in 

SO2 emissions over the next several years. A limited qualitative assessment based on 

the results of preliminary modeling of some sample facilities indicates that well controlled 

sources should meet the new SO2 NAAQS.” 

i. EPA Refinery Initiative and Associated Consent Decrees 

Between 2002 and 2005, the Billings refineries and their respective parent 

companies each entered into a Consent Decree (CD) with US District Court, EPA, 

and the State of Montana. CD requirements and projects have largely been 

completed at ConocoPhillips and CHS; however, as each refinery is on its own time 

schedule, ExxonMobil’s CD involves changes at the refinery that are still being 

implemented. The individual requirements within each CD are lengthy and complex, 

and in the interest of brevity are not discussed here in any detail. The following list 

includes CD requirements for ExxonMobil that remain in process (as of 2008-2010 

relative to the observed ambient data): 

a. SO2 Reduction Additives in Fluidized Catalytic Cracker Unit – The refinery has 

been obligated to test a variety of SO2 reduction additives since October 2006. 

To identify the additive that achieves the highest reduction in SO2 emissions, the 
Page 20 of 25 

testing required intermittent use of additives through January 2011. Beginning in 

January 2011, the additive is being, and will be, consistently used to achieve SO2

emission rates to be approved by EPA and DEQ in 2012. Enforceable limits will 

be required to reduce SO2 emissions on a short-term and long-term basis. The 

full ambient air quality effect of those limits is yet to be realized. 

b. Treatment of Sour Water Stripper Overhead Gas – SO2 emissions from the 

combustion of Sour Water Stripper Overhead Gas in the FCCU CO boiler were 

reduced using hydrogen peroxide treatment effective October 2009 as required 

by 40 CFR 60, Subpart J. The treatment currently reduces SO2 emissions from 

the refinery in a manner that was not fully realized during the 2008-2010 period. 

c. Enhanced Flare Gas Recovery – As discussed in the FIP section (III.D.iii), 

additional capacity was added to the Flare Gas Recovery System effective in 

September 2010. This system will reduce the flaring of sour gas, ultimately 

reducing short-term intermittent SO2 emissions and longer-term continuous SO2

emissions, again in a manner that was not fully developed during the 2008-2010 

period. 

d. Elimination of Routine and Continuous Flaring of Sour Gas – Refinery 

modifications and procedural changes effective in September 2010 reduced the 

flaring of sour gas, which will reduce short-term intermittent SO2 emissions and 

longer-term continuous SO2 emissions. Effective September 2010, the refinery 

flares must meet H2S standards mandated by 40 CFR 60, Subpart J to reduce 

SO2 emissions. As with other flare controls, both short-term intermittent SO2

emissions and longer-term continuous SO2 emissions will be reduced. 

ii. Utility MACT Implementation 

The proposed Utility MACT was announced and made publicly available by EPA on 

March 16, 2011. The proposed rule was promulgated as 40 CFR 63, Subpart 

UUUUU. The rule is expected to be issued in final form by November as required by 

a court settlement agreement, unless that deadline is extended by the courts. As 

previously discussed, the proposed rule contains several emission limit options by 

category. In the coal-fired units section, the following categories exist. For non-Hg 

metals, a facility may take a total PM limit, a total non-Hg HAP metal limit, or 

individual limits on listed non-Hg HAP metals. For acid gases, the options include 

taking a hydrochloric acid limit or an SO2 limit. Mercury limits apply for all types of 

units subject to the Utility MACT. Some options can only be used in conjunction with 

specific pollution control configurations. 

The PPL - Corette and YELP facilities (YELP, it appears because of its “capability” to 

burn cat-slurry oil and the potential categorization of petroleum coke as a “solid oilderived fuel”) will both be subject to the new Utility MACT. PPL - Corette would be 

categorized as an existing coal-fired unit designed for coal greater than or equal to 

8,300 British thermal units per pound (Btu/lb). If PPL - Corette chose to demonstrate 

compliance with acid gases using the SO2 surrogate limit, it would be limited to 0.2 lb 

SO2/MMBtu of heat input, which is lower than current emissions by more than half. 

The 2009 SO2 emissions from the PPL - Corette facility, based on EPA’s Acid Rain 

Database, averaged approximately 0.455 lb/MMBtu. In addition, the proposed PM 

limit is much lower (approximately 85% lower) than current PM emissions (0.030 
Page 21 of 25 

lb/MMBtu compared with 0.206 lb/MMBtu from a February 10, 2011, stack test). The 

strategy to meet the SO2 limitation would have a significant impact on SO2 emissions 

from PPL - Corette, and any PM control added would probably provide some cobenefit control with respect to SO2. 

YELP would likely be categorized as an existing solid oil-derived fuel unit, under the 

current proposal. However, EPA is requesting comments on including petroleumcoke-fired units within the Utility MACT. If petroleum coke-fired units become a 

category with different limitations, YELP would most likely be subject to those 

requirements (as opposed to the solid oil-derived unit limitations) because petroleum 

coke is a more specific fuel description for the YELP boiler. If YELP chose to 

demonstrate compliance with the hydrochloric acid gas limit using the SO2 surrogate 

limit (assuming the solid oil-derived fuel unit classification), it would be limited to 0.4 

lb/MMBtu of heat input, which is lower than permitted emissions by approximately 

half. The pound per hour YELP permit limitation equates to approximately 0.777 

lb/MMBtu on a rolling 30-day average. The PM limitation for that fuel category would 

not require additional control at YELP; however, the strategy to meet the SO2

limitation would have a significant impact on SO2 emissions from YELP. 

iii. Existing FIP Implementation 

In 1998, the Montana Board of Environmental Review approved a plan to control 

SO2 emissions in the Billings and Laurel area. The plan was submitted to EPA as a 

modification to the State Implementation Plan (SIP). EPA eventually approved the 

plan with a few notable exceptions. To that end, EPA adopted its own Federal 

Implementation Plan (FIP) that adds additional SO2 control requirements to the SIP. 

Although the SIP portion of the plan is fully implemented, resulting in substantial SO2

reductions, the FIP is not. As a result, the Billings area has yet to see the full impact 

of the FIP. 

In general, the FIP primarily applies to flaring events at the refineries (CHS, 

ExxonMobil, and ConocoPhillips) and MSCC. Such flaring events arise from startup, 

shutdown, and malfunction periods. The FIP requires the development of Flare 

Monitoring Plans, which have been developed and submitted to EPA by the involved 

facilities. EPA has yet to approve those plans. As flaring is almost exclusively a 

short-term intermittent activity that is in response to an upset condition, the full 

impact of the FIP will likely reduce short-term (1-hour and shorter) emission rates, 

which would ultimately be reflected in 1-hour monitoring values corresponding to the 

ambient standard, even further. 

In addition to the flaring discussed above, the FIP imposes substantially lower 

emission limits on the MSCC facility than are allowed under the 1998 SIP. In 

response to the 1998 SIP, MSCC installed SuperClausTM tail gas recovery 

processing, which operates at high efficiency and with a high online factor, but which 

still requires periods of downtime for repairs and maintenance. In order to meet the 

additional requirements of the FIP, and to increase overall processing reliability, 

MSCC recently (in 2008) installed additional duplicate/redundant SuperClausTM 

facilities aimed at allowing either unit to carry on tail gas processing tasks while the 

other is out of service. This helps to reduce the need to revert to Claus-only 

processing during times of SuperClausTM maintenance, and to eliminate the increase 

in emissions that normally accompanies such periods. This in turn helps to assure 
Page 22 of 25 

that MSCC is able to meet the more stringent FIP requirements on its main stack, 

which accounts for almost all of the SO2 emissions from the facility. 

In Lockwood, MSCC and ExxonMobil have worked together to bring about a 

functional enhanced flare recovery system serving the refinery flare system and 

using the MSCC facilities for gas treating. This project became operational in 2010. 

While not directly arising from the 2008 FIP, it now serves to reduce flare emissions. 

For example, in the last quarter of 2010, the operation of this equipment allowed 

early termination of flaring resulting from a reported malfunction (on 11/30/2010) that 

affected both facilities. The FIP limitations relating to startup-shutdown-malfunction 

flaring emissions continue to be studied for development of additional means to 

feasibly limit these sporadic short-term emissions from flares; for example, at MSCC, 

during necessary startup/shutdown or malfunction events. The full effect of the FIP 

on these events is not yet developed; however, it is clear that the FIP restrictions on 

flaring serve as a further incentive to reduce short-term and annual emissions from 

flares, as compared to the 2008-2010 period. 

iv. Regional Haze / BART Implementation 

Under EPA’s Regional Haze Program, states, including Montana, are required to 

develop a program to assure reasonable progress toward meeting the national goal 

of protecting (and preventing) visibility impairment in mandatory Class I areas. Two 

portions of this program could impact industrial facilities in the Billings and Laurel 

areas. One program is BART. BART requirements of the regional haze rule apply to 

facilities built between 1962 and 1977 that have the potential to emit more than 250 

tons a year of visibility-impairing pollution. Those facilities fall into 26 categories, 

including utility and industrial boilers, and large industrial plants such as pulp mills, 

refineries, and smelters. The regional haze regulations also allow states to develop 

coordinated strategies and implement programs to make “reasonable progress” 

toward the goal of “no manmade impairment” in national parks and wilderness areas 

by reducing emissions that contribute to haze. Currently EPA is directly 

administering these programs in Montana. 

Various analyses by the seven major Billings/Laurel area facilities have been 

supplied to EPA as part of their investigation into the applicability and extent of BART 

or Reasonable Progress requirements. According to EPA guidance, SO2 is a 

pollutant that may contribute to visibility impairment. To date, EPA has not proposed 

any findings as to what controls or emission reductions may be required to comply 

with these two programs at affected sources in Montana. It is believed that EPA 

plans to make such (draft) determinations sometime this calendar year. According to 

EPA, the following facilities may be subject to the visibility program indicated: 

• MSCC - BART 

• ExxonMobil - BART 

• YELP - Reasonable Progress 

• ConocoPhillips - BART 

• CHS - BART 

• PPL – Corette - BART 
Page 23 of 25 

EPA is currently analyzing applicability and potential emission reduction strategies. 

To the extent any reductions may be required, those reductions would impact 

ambient air quality in Billings and Laurel. It is anticipated that those reductions would 

reduce the SO2 ambient air quality levels in the area. However, EPA has not 

provided any information regarding their decisions on emission control strategies 

associated with BART and Reasonable Progress or on the timeframe of those 

decisions. 

v. Boiler Maximum Achievable Control Technology (MACT) Implementation 

As previously discussed, EPA’s Boiler MACT for major sources was finalized and 

published as 40 CFR 63, Subpart DDDDD in the Federal Register on March 21, 

2011. However, as previously mentioned, on May 18, 2011, EPA published an 

indefinite delay of the implementation of the major source Boiler MACT rules. The 

Boiler MACT, as finalized, would require emission limits for various categories of 

large and small boilers. The rule would also require various energy audits and tuneups of the boilers regardless of size and fuel. The energy audits and tune-ups are 

designed to lower fuel consumption, thereby lowering emissions. In the Billings and 

Laurel area, MSCC, PPL - Corette, ExxonMobil, CHS, and ConocoPhillips have units 

that will be impacted by the newly promulgated Boiler MACT for major sources. 

MSCC, PPL, ExxonMobil, and ConocoPhillips have gas-fired (either natural gas or 

refinery fuel gas-fired) boilers that appear to meet the applicability requirements of 

the rule. As such, energy audits and tune-ups would be requirements of the rule for 

those units. The reduction in SO2 is not quantifiable at this early date, but 

improvements in efficiency and tune-up would be likely to lead to lower emissions. 

However, even without the stay, the Boiler MACT provisions are not likely to lead to 

large reductions in SO2 emissions from major sources. 

EPA’s Boiler MACT standard for area sources was finalized and published as 40 

CFR 63, Subpart JJJJJ in the Federal Register on March 21, 2011 (and is not 

subject to the stay issued by EPA on the major source Boiler MACT rules). The 

three coal-fired boilers at Western Sugar appear to be subject to the Hg and CO (as 

a surrogate for non-dioxin organic hazardous air pollutant) limits in this standard. At 

this time it is unclear what steps Western Sugar may take to meet the Hg emission 

limits listed in the area source rule. The three coal-fired boilers at Western Sugar are 

currently controlled using wet scrubbers. If scrubber upgrades are considered for Hg 

control, SO2 emissions may also be reduced through that process, although 

significant reductions would not be expected. 

vi. New Source Performance Standards (NSPS) - 40 CFR 60, Subpart Ja 

Pursuant to a consent decree entered into in 2005, EPA revised Petroleum Refinery 

NSPS (40 CFR 60, Subpart J). Because of the extensive changes in the regulations 

and changes in definitions for that revision, EPA determined it was appropriate to 

develop a new set of regulations that apply to new refineries and modified or 

reconstructed refineries. 40 CFR 60, Subpart Ja is that new set of regulations that 

includes new standards and requirements for new, modified, reconstructed fluid 

catalytic cracking units (FCCUs), new fluid coking units, new process heaters, and 

new flares. These standards include emissions limits for reductions of SO2 and other 

pollutants. 
Page 24 of 25 

Subpart Ja will have an impact on SO2 emissions from process heaters, etc., 

although with the current universe of sources, it is unlikely to have a major impact 

unless affected units are reconstructed. The major impact on SO2 emissions is 

anticipated to be from flare minimization requirements that are anticipated from EPA 

in response to the reconsideration requests and subsequent stay of certain flare 

provisions. The flare provisions under Subpart Ja remain under review at EPA, but 

are anticipated to be released by the end of 2011. The flare provisions would be 

specifically intended to reduce short-term SO2 emissions from flares. This could, of 

course, reduce 1-hour ambient concentrations in a manner not reflected in the 2008-

2010 time period. 

vii. EPA Flare Initiative 

Independent of other efforts to reduce flare emissions in Billings and Laurel under 

Consent Decrees and/or NSPS requirements, EPA is initiating efforts to limit 

emissions from flares nationwide. It appears that the requirements will be 

promulgated as part of the Consolidated Federal Air Rule (40 CFR, Part 65). The 

requirements are expected to be proposed by the end of 2011. The initiative will 

further limit emissions from flares in the future and, therefore, potential impacts to the 

1-hour SO2 standard as discussed above with respect to flare minimization under 40 

CFR 60, Subpart Ja. 

Based on the preceding analysis, Montana believes that implementation of the Utility 

MACT, BART, flare provisions (and some FIP provisions) currently tied up in the 

reconsideration/stay of Subpart Ja, and the accomplishment of consent decree 

provisions for ExxonMobil will provide significant SO2 reductions and long-term SO2

NAAQS compliance without additional control plan measures. The Clean Air Act does 

not expect states to revise SIPs when federal requirements would have the same 

outcome. As stated, ongoing implementation of the national and local SO2 limiting 

programs identified previously will continue to result in significant SO2 reductions from 

the affected Billings/Laurel area SO2 sources. Therefore, Montana need not regulate 

over the top of EPA’s SO2 limiting programs, including the ExxonMobil consent decree 

set to be fully implemented in calendar year 2011. 

E. Yellowstone County Conclusion 

Pursuant to 42 USC §7407, Montana is required to submit to EPA a list of all areas (or 

portions thereof) in the state, designating as nonattainment, attainment, or otherwise 

unclassifiable based on available information. 

The 2008-2010 design value monitored in the Billings/Laurel area is 84 ppb, an 

“apparent” violation of the revised SO2 NAAQS. This information taken alone and 

without context could lead one to believe that an initial designation of nonattainment for 

Yellowstone County may be appropriate. However, the purpose and intent of a 

nonattainment designation is to initiate a process to incorporate necessary enforceable, 

permanent, and quantifiable emissions reductions into the affected SIP to ensure that 

the area will achieve NAAQS attainment and thereby adequately protect public health in 

a timely manner. If enforceable, permanent, and quantifiable emissions reductions 

necessary to attain NAAQS compliance are already mandated under the existing SIP, a 

nonattainment designation is inappropriate. 
Page 25 of 25 

The most significant change in Yellowstone County (Billings/Laurel area) SO2 emissions 

during the 2008-2010 timeframe was a near 1700 ton increase at ExxonMobil during the 

latter part of calendar year 2010. This emissions increase was a direct result of 

ExxonMobil performance under an SO2 additive testing schedule pursuant to an EPA 

consent decree. This emissions increase also corresponds directly to a majority of the 

documented NAAQS exceedences (9 of 18) for the 2008-2010 time period. Absent 

implementation of the particular provisions of the consent decree responsible for the 

increased SO2 emissions and resulting NAAQS exceedences, the consent decree and 

the existing SIP would have protected the NAAQS. One may reasonably presume that 

the CAA does not expect states to revise SIPs when federal requirements in a consent 

decree interfere with attainment of the NAAQS (42 USC §7410(a)(3)(C)). Additionally, 

the CAA does not expect states to revise SIPs when federal requirements would have 

the same outcome. Performance under the consent decree has demonstrated that 

additional and significant SO2 reductions from the ExxonMobil facility will be realized 

upon full implementation, thereby complementing Montana’s existing SIP. Therefore, 

Montana need not regulate over the top of EPA’s consent decree with ExxonMobil. 

As a result of this consent decree-mandated one-time emissions scenario (2010), 

Montana firmly believes that consideration of 2010 monitoring data for initial designation 

purposes is inappropriate. At a minimum, Montana believes that EPA should initially 

designate Yellowstone County as unclassifiable until such time as representative data is 

available for comparison to the NAAQS. In lieu of using 2010 data, Montana would 

suggest using either 2009, 2011, and 2012 data or 2011 through 2013 data to determine 

a design value for comparison to the NAAQS. 

Further, Montana recognizes the ongoing and near-future implementation of many 

existing federal SO2 emissions limiting programs impacting SO2 point source emissions 

in the Billings/Laurel area of Yellowstone County. The perceived and logical intent of 

ongoing and near-future implementation of federal SO2 emissions limiting programs 

would be to reduce industrial SO2 emissions nationwide and in the Billings/Laurel area to 

levels corresponding to compliance with the 2010 revised SO2 NAAQS. Implementation 

of regulatory programs including the Utility MACT, Regional Haze/BART, flare provisions 

from the FIP and EPA’s flare initiatives, and ExxonMobil-specific consent decree 

requirements, will significantly reduce Billings/Laurel area SO2 emissions and associated 

ambient concentrations. These reductions in SO2 emissions provide further assurance 

that the Billings/Laurel area will achieve compliance with the new 1-hour SO2 NAAQS 

before the required compliance date in August of 2017. 

Therefore, because 2010 Billings/Laurel area industrial SO2 emissions and associated 

ambient impacts are not representative of future conditions in the area and because the 

SIP already contains provisions necessary to achieve attainment of the revised SO2

NAAQS in the Billings/Laurel area in a timely manner, revisions to the existing SIP are 

not necessary. Montana strongly concludes that an initial designation of unclassifiable 

for Yellowstone County is appropriate. 

 

END OF DOCUMENT