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UNITED STATES ENVIRONMENTAL PROTECTION AGENCY 

REGION IX 

75 Hawthorne Street 

San Francisco, CA 94105-3901 

Randy Cleaveland 

U.S. Production Manager 

ExxonMobil Production Company 

P.O. Box 4697 ' 

' Houston, TX 77210-4697 

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May 22, 2006 

Re: Application for a Prevention of Significant Deterioration Permit for 

ExxonMobil Corporation McElmo Creek Unit Oil Production FacilityMain Flare, Gas Compression Facility 

Dear Mr. Cleaveland: 

This letter is in response to the submittal of an application for a Prevention of 

Significant Deterioration (PSD) permit for the Main Flare at ExxonMobil's McElmo 

Creek gas compression facility. This application was received by EPA, Region 9 on 

November 13,2005. Upon review of the application in accordance with 40 CFR § 124.3, 

EPA has determined that the application is administratively incomplete for PSD purposes 

with respect to emissions data, the BACT analysis, the Class I analysis, and the additional 

impact analysis. EPA is also unable to process the application without additional analysis 

of potential impacts to endangered species. Below please find a discussion of each of 

these areas, with EPA's expectations regarding what additional information is needed. 

You may find EPA's October 1990 Draft New Source Review Workshop Manual useful. 

See http://www. epa.gov/region 7 /programs/artd/air/nsr/nsrmemos/1990wman.pdf 

You may also search for the document on EPA's NSR Policy and Guidance Database, 

available at: http://www.epa.gov/Region7/programslartd/air/nsrl. In addition to the items 

requested below, we would also like to request that ExxonMobil provide us with the 

model name of the Zeeco flare, if applicable. 

Emissions Data 

On page 3-1 of the application, ExxonMobillists the emission limits from the 

Consent Decree for Civil A~tion Case United States v. Mobil Exploration and Production 

U.S. Inc., for four criteria pollutants: sulfur dioxide (S02), carbon monoxide (CO), 

nitrogen oxides (NOx), and volatile organic compounds (VOC). However, for the 

application to be considered complete, ExxonMobil must provide information on actual 

and potential emissions. Please provide pre- and post-project actual emissions, as well as 

pre-project estimates of the potential to emit for all criteria pollutants, including 

particulate matter (PM10 and PM2.5) and lead. Please also include pre- and post-project 

Printed on Recycled Paper 
gas flow rates to the flare. For purposes of this application, pre-project means before the 

gas plant was dismantled in 1997, and post-project means after the gas plant was 

dismantled. Please include all calculations and the basis for all assumptions used in the 

emission estimates. 

BACT Analysis 

Best available control technology (BACT) is defined in 40 CFR §52.21 as: 

An emissions limitation ... based on the maximum degree of reduction for each 

pollutant subject to regulation under [the Clean Air] Act which would be emitted 

from any proposed major stationary source or major modification which the 

Administrator, 6n a case-by-case basis, taking into account energy, 

environmental, ,and economic impacts and other costs, determines is achievable 

for such source or modification through application of production processes or 

available methods, systems, and techniques ... for control of such pollutant.. . .lfthe 

Administrator determines that technological or economic limitations on the 

application of measurement methodology to a particular emissions unit would 

make the imposition of an emissions standard infeasible, a design, equipment, 

work practice, operational standard, or combination thereof, may be prescribed .... 

As noted in ExxonMobil' s application, EPA specifies the use of a "top-down" approach 

for determining BACT. This approach requires that all available control technologies be 

ranked in descending order of control effectiveness. Once that has been done, the most 

stringent alternative should be chosen as BACT unless the applicant demonstrates to the 

satisfaction of the permitting authority that technical considerations, or energy, 

environmental, or economic impacts justify a conclusion that the most stringent option is 

not achievable. If the most stringent technology is eliminated, then the next most 

stringent alternative is considered, and so on. 

ExxonMobil's application follows this approach, however the application fails to 

consider technologies, work practices, or operational standards that would limit the flow 

of gases to the flare. To be considered complete, the application must address means to 

reduce the occurrence of flaring, not just means to reduce emissions when flaring occurs. 

Please consider, among other things, methods to improve the efficiency, reliability, 

and/or capacity of the gas compressors (including replacing the compressors), and any 

other methods that may reduce the frequency of flaring and the quantity of gas flared. 

The application may incorporate by reference the operation and maintenance (O&M) 

plan from the afore-mentioned Consent Decree, but the application must specifically 

analyze the O&M plan according to the top-down BACT principles. For any options that 

are ruled out on the basis of economic infeasibility, please provide a detailed costeffectiveness analysis. 

Class I Analysis 

Class I areas are areas of special national or regional natural, scenic, recreational, 

or historic value for which the PSD regulations provide special protection. For projects 

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that may affect a Class I area (most typically those sources located within 100 kilometers 

of a Class I area), additional impact analyses may be required to ensure that air quality 

degradation is limited in these areas. One way in which air quality degradation is limited 

in all Class I areas is by stringent limits defined by the Class I increments for sulfur 

dioxide, particulate matter, and nitrogen dioxide, as well as visibility protection. In 

addition, the Federal Land Manager (FLM) of each Class I area- in this case, the 

National Park Service- is charged with the affirmative responsibility to protect that 

area's unique attributes, expressed generically as air quality related values. 

According to ExxonMobil's application, the McElmo Creek Oil Production 

Facility is located within 100 km ofthe following Class I areas: Canyonlands National 

Park and Mesa Verde ~ational Park. However, the application is lacking any discussion 

or analysis of Class I impacts. The applicant must contact the FLM, listed below, for 

guidance. After discussing the project with the FLM, the application must be revised to 

either include the appropriate air quality analyses, or, if the FLM determines that no 

impact is anticipated, to include a qualitative analysis designed to inform the general 

public of the relative impact of the operations on the Class I areas. 

JohnBunyak 

Policy, Planning & Permit Review 

NPS-Air 

POBox 25287 

Denver, CO 80225-0287 

John_ Bunyak@nps.gov 

(303) 969-2818 

Additional Impact Analysis 

John Notar 

Research and Monitoring 

NPS-Air 

POBox 25287 

Denver, CO 80225-0287 

John_ Notar@nps.gov 

(303) 969-2079 

All PSD permit applicants must prepare an additional impacts analysis for each 

pollutant subject to regulation under the Clean Air Act. This analysis assesses the impacts 

of air, ground, and water pollution on soils, vegetation, and visibility caused by any 

increase in emissions of any regulated pollutant from the source or modification under 

review, and from associated growth. The depth of the analysis generally will depend on 

existing air quality, the quantity of emissions, and the sensitivity of local soils, 

vegetation, and visibility in the source's impact area. It is important that the analysis fully 

document all sources of information, underlying assumptions, and any agreements made 

as a part of the analysis. 

Generally, small emissions increases in most areas will not have adverse impacts 

on soils, vegetation, or visibility. However, an additional impacts analysis still must be 

performed. Projected emissions from both the new source or modification and emissions 

from associated residential, commercial, or industrial growth are combined and modeled 

for the impacts assessment analysis. The additional impacts analysis generally has three 

parts, as follows: 
(A) growth; 

(B) soil and vegetation impacts; and 

(C) visibility impairment. 

A. Growth Analysis 

The elements of the growth analysis include (1) a projection of the associated 

industrial, commercial, and residential source growth that will occur in the area due to the 

source; and (2) an estimate of the air emissions generated by the above associated 

industrial, commercial, and residential growth. ExxonMobil must revise its application to 

include an assessment :of the availability of residential, commercial, and industrial 

services existing in the area, and a prediction of how much new growth is likely to occur 

' to support the source or modification under review. 

If any new growth is expected, ExxonMobil should develop an estimate of the 

secondary air pollutant emissions that would likely result from this permanent residential, 

commercial, and industrial growth. ExxonMobil should then combine the secondary air 

pollutant emissions estimates for the associated growth with the estimates of emissions 

that are expected to be produced directly by the proposed source or modification. The 

combined estimate will serve as the input to the air quality modeling analysis, and the 

result is a prediction of the ground-level concentration of pollutants generated by the 

source and any associated growth. 

B. Soil and Vegetation Impacts Analysis 

Page 5-4 of the application discusses soils and vegetation in the project area in 

general terms; however the application should be revised to explicitly discuss the 

potential for impacts to soils and vegetation. The analysis of soil and vegetation air 

pollution impacts should be based on an inventory of the soil and vegetation types found 

in the impact area. This inventory should include all vegetation with any commercial or 

recreational value, and may be available from conservation groups, State agencies, and 

universities. For most types of soil and vegetation, ambient concentrations of criteria 

pollutants below the secondary national ambient air quality standards (NAAQS) will not 

result in harmful effects. However, there are sensitive vegetation species (e.g., soybeans 

and alfalfa) that may be harmed by long-term exposure to low ambient air concentrations 

of regulated pollutants for which there are no NAAQS. Any discussion should reference 

the source of information so that the conclusions in the application can be verified. 

C. Visibility Impairment 

ExxonMobil's permit application contains no discussion of visibility impairment. 

The suggested components of a good visibility impairment analysis are: · 

(1) A determination of the visual quality of the area; 

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(2) An initial screening of emission sources to assess the possibility of 

visibility impairment; and 

(3) If warranted, a more in-depth analysis involving computer models. 

ExxonMobil can start with a level 1 screening procedure, which is a series of 

conservative calculations designed to identify those emission sources that have little 

potential for adversely affecting visibility. The VISCREEN model is recommended for 

the level 1 screen. Calculated values relating source emissions to visibility impacts are 

compared to a standardized screening value. If potential visibility impairments are 

indicated, then a level 2 analysis should be conducted. 

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To successfully complete a visibility impairments analysis, the applicant is 

referred to an EPA document entitled "Workbook for Estimating Visibility Impairment," 

or its projected replacement, the "Workbook for Plume Visual Impact Screening and 

Analysis." In this workbook, EPA outlines a screening procedure designed to expedite 

the analysis of emissions impacts on the visual quality of an area. The workbook was 

designed for Class I area impacts, but the outlined procedures are generally applicable to 

other areas as well. 

Endangered Species Analysis 

Section 7 ofthe Endangered Species Act of1973, as amended (16 U.S.C. 1531 et 

seq.) ("ESA"), directs all Federal agencies to use their existing authorities to conserve 

threatened and endangered species and, in consultation with the US Fish and Wildlife 

Service, to ensure that their actions do not jeopardize listed species or destroy or 

adversely modify critical habitat. Section 7 applies to .Federal actions that may affect 

listed species, including Federal approval of private activities through the issuance of 

Federal permits, licenses, or other actions. 

In processing ExxonMobil' s PSD permit, EPA must assure that listed species or 

their critical habitat will not be jeopardized by the changes at the McElmo Creek Gas 

Compression Facility. While the application does address threatened and endangered 

plant species (see page 5-4 ofthe application), endangered animal species have not been 

discussed in ExxonMobil's PSD permit application. Therefore, EPA is lacking 

information necessary to determine our obligations, if any, under Section 7 of the ESA. 

Please provide a list of all endangered or threatened plant and animal species and 

their critical habitat in the area of the proposed project; such a list may be obtained from 

the Fish and Wildlife Service. Please contact: 

Henry Maddux 

US FWS - Utah Field Office 

2369 W. Orton Circle, suite 50 

West Valley City, Utah 84119 
· If any endangered or threatened species or critical habitat is in the area of the project, 

please provide a biological assessment of the impact construction or operation of the 

source may have on such species and their habitat. A biological assessment should 

discuss the proposed project in sufficient level of detail so that EPA can determine 

whether it is appropriate for the Agency to initiate a section 7 consultation process with 

the U.S. Fish & Wildlife Service, and so that the biological assessment can be utilized by 

EPA and the U.S. Fish & Wildlife Service if a section 7 consultation is needed. We can 

provide sample assessments if needed. 

Should you have any questions concerning the review of your application, or if 

you would like to arrange for a meeting or conference call to discuss your application, 

please contact Kathie~ Stewart of my staff at ( 415) 94 7-4119. 

cc: Patrick Flynn, Resolute 

John Notar, NPS 

John Bunyak, NPS 

Bud Rolofson, USFS 

Scott Archer, BLM 

Henry Maddux, USFWS 

Sincerely, 

%"d;riL 

Gerardo C. Rios 

Chief, Permits Office 

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