Ref: 8AT-AP

....

• • UNITED STATES ENVIRONMENTAL PROTECTION AGENCY

REGIONVm

999 18th STREET - SUITE 500

DENVER, COLORADO 80202-2405

.APR 19 1891

Ms. Diane P. Klancher

Environmental & Regulatory/

Loss Prevention Supervisor

Mobil Explorat~on & Producing U.S. Inc.

P.O. Box 633

~idland, TX 79702-0633

Dear Ms. Klanchet:

This letter is in response to your February 21, 1991 and

February 22, 1991 letters to EPA, requesting changes to the

Prevention of Significant Deterioration (PSD) permit that EPA

.issued on October 22, 1987 for the McElmo Creek Unit Gas Plant.

We have reviewed your requests to: (1) replace existing

heating equipment with a waste heat: recovery unit, and (2)

temporarily replace the existing gas turbine with an identical

unit during maintena~ce overhaul of the turbine. Since these

changes will not result in any emission increases, they can be

approved as administrative changes to the EPA permit.

On March 14, 1991, we were informed by Mr. Worontsoff of

your office that the second gas turbine approved for construction

under the October~2, 1987 permit waS never installed. Please be

aware that under federal regulation 40 CFR 52.21(r)(2), approval

to construct becomes invalid if construction is not commenced

within 18 months after issuance of the PSD permit, or if

construction is discontinued for a period of 18 months or more,

or if construction is not completed within a reasonable time.

While construction deadlines may be extended by EPA upon a

satisfactory showing by the permit applicant that an extension is

justified, Mr. Worontsoff has informed us that Mobil currently

has no plans to install the second turbine and is not requesting

an extension. Therefore, we are rescinding approval of the

second turbine at this time. '

In the event that Mobil wishes to install additional

turbines or other equipment at some future date, and if facilitywide emissions resulting from those additions wili exceed the

emission rates' used in dispersion model~ng for the October 22,

1987'permit, it will be necessary for Mobil to conduct new

dispersion modeling to show that the PSD increments and the

National Ambient Air Quality Standards will be protected. Mobil

would also have to show that emission controls for the 'additional

eqUipment constitute Best Available Control Techtiology.
We have also been informed by Mr. Worontsoff that the

manufacturer's design capacity of the one g~s turbine installed

thus .far under.the.-EPA.permit is4,390 horsepower at sea'level.---

The turbine is, therefore sUbject to the provisions of Subpart GG

of the federal New Source Performance Standards (40 CFR 60.330

through 60.335). NSPS Subpart GG applies to any stationary gas

turbine larger than approximately 3985 horsepower (equal to 10.7

gigajoules per hour), constructed after October 3, 1977. A

. condition has therefore been added to the EPA permit to specify

that the turbine must comply with all relevant provisions of

Subpart GG. .

The enclosed conditional permit replaces the October 22,

1987 permit. This permit shall become effective immediately

unless you notify us, by the procedure described in Section IV of

the permit, that you object to one or more of the permit

conditions. In such event, construction and operation. of the

modification would not be allowed until a revised permit

acceptable to both EPA and Mobil is issued.

If you have any questions, please contact Mr. Michael Owens

of my staff at (303) 293-1756.

Sincerely,

~.~lR:~~;;;r Air & Toxics Division

Enclosure

cc: Burnell Cordner, Director

Utah Bureau of Air Quality

1950 West North Temple

Salt Lake City, UT 84116-069rr

Louise Linkin, Environmental Coordinator

·Navajo Nation

P.O. Box 308

Window Rock, AZ 86515

2
CONDITIONAL PERMIT TO

COMMENCE CONSTRUCTION AND OPERATE

40 CFR 52.21

Prevention of

Significant Deterioration of Air Quality

Mobil Exploration & Producing U.S. Inc.

P.O. Box 633 .

Midland, TX 79702-0633

I. INTRODUCTION

Mobil Exploration & Producing U.S. Inc. (hereinafter "the

Applicant") proposes to construct and operate a modification to

Mobil's McElmo Creek Unit on the Navajo Indian Reservation in San

Juan County, Utah.

On May 13, 1986, the Applicant submitted to the U.S.

Environmental Protection Agency, Region VIII (hereinafter "EPA")

a Prevention of Significant Deterioration (PSD) application to

construct and operate three gas-fired reciprocating internal

combustion (I.C.) engines, pursuant to 4D CFR 52.21.

The EPA issued a public notice on December 17, 1986, in the

San Juan Record and the Salt Lake Tribune, newspapers of general

circulation in the area. The notice proposed to approve the

application and issue a conditional air quality permit for the

source and provided opportunity for public comments during the

ensuing 30 calendar days. The permit application, the proposed

permit, and its supporting ~nalysis were available for public

inspection at the office of the San Juan County Clerk in

Monticello, at the Utah Bureau of Air Quality in Salt Lake City,

and at the EPA office in Denver. The only comments concerning

the permit were received from the Applicant and contained only

minor clarifications. The conditional permit was issued on

Februar¥ 2, 1987.

On September 1, 1987, the· Applicant submitted a letter to

EPA requesting that two gas turbines be approved, rather than ~he

three I.C. engines. Since this change did not represent an

emission increase, and since the turbines were to utilize Best

Available Control Technology, the EPA approved the request as an

administrative change to the PSD permit. A revised conditional

permit was issued on October 22, 1987.
On February 21 and 22, 1991, the Applicant submitted letters

to EPA requesting approval to: (1) replace eXist~n9 heating

equipment..w.ith a ..waste heat recovery unit, and- (2 )---temporarily--

replace the existing gas turbine with ari identical unit1during

maintenance overhaul of the turbine. These changes do not

represent an emission increase. . .

On March 14, 1991, the Applicant informed EPA that the

second gas turbine was never installed and that the Applicant

currently has no plans to install it. The Applicant also

informed EPA that the one gas turbine which was installed is

rated at 4390 horsepower at sea level, rather than the 3216

horsepower listed in the October 22, 1987 permit. This exceeds

the applicability cutoff size of 3985 horsepower (equivalent to

10.7 gigajoules per hour) for Subpart GG of the federal New

Source Performance Standards.

II. FINDINGS

On the basis of information in the administrative record,

EPA has determined that:

1. The McElmo Creek Unit is a major stationary source and

the modification which has already been permitted by

EPA (installation of two turbines) represents a

significant net emission increase of oxides of nitrogen

(NOx). The facility is therefore subject to PSD

regulation.

2. The Applicant will meet all of the applicable

requirements of the PSD regulations at 40 CFR 52.21.

3. Based on dispersion modeling, EPA has good reason to

believe that no ambient air quality standards or PSD

increments will be violated asa result of the proposed

facility modification.

4. EPA has good reason to believe that the Applicant can

comply with the conditions of this permit~ If any of

the conditions are not met by the Applicant, EPA does

not assume any risk or loss which maY occur'as a result

of the commencement of construction and operation by

the Applicant.

2
III. CONDITIONAL PERMIT TO CONSTRUCT AND OPERATE

On the basis of the findings set forth in II above, and .

pursuant to the authority of 40 CFR 52.21 ( i)( 1 ), as delegated by

the Administrator, EPA hereby conditionally authorizes the

Applicant to construct and operate the modification described in

the Applicant's permit application dated May 13, 1986, as amended

by later communications on September 1,· 1987, February 21, 1991,

February 22, 1991, Snd March 14, 1991. '

This approval ~s expressly conditioned as follows:

1. The Applicant shall abide by all representation, statements

of intent, and agreements conta~ned in the permit

applic~tion and in all additions ~nd amendments thereto, as

follows: .. ,

a. May 13, 1986 -- ,PSD permit application for the McElmo

Creek Unit C02 Project, stage 2, to include installation of three·reciprocating internal combustion

engines.

b. September 2, 1986 -- Supplementary information related

to NOx emission rates.

c. November 4, 1986 -- Supplementary information

c:orrecting VOC emission rates.

d. September 1, 1~B7 -- Letter requesting approval for two

natural gas fue~ed turbines, rather than three

reciprocating internal combustion engines.

e. February 21, 1991 -- Letter requesting approval for

installation of waste heat recovery unit, to replace

existing heating equipment.

f. February 22, 1991 -~ Letter requesting approval to

temporarily replace the existing gas turbine with an

identical unit .during maintenance overhaul of the

turbine. '

g. March 14, 1991 -- Information submitted verbally to EPA

to correct the horsepower rating for the one gas

turbine thus far installed, and to inf6rm EPA that

Mobil has no plans to install a second gas turbine.

2. Thi~ permit shall be considered invalid if the Applicant

does not commence and complete construction of the permitted

modification within the deadlines specified in 40 CFR

52.21(r)(2).

3
3. The Applicant shall operate no pollutant-emitting equipment

at the McElmo Creek Unit other than that listed in Tables 1

--and -2 of- this-permit.---The -Applicant shall permanently--shut---

down the equipment listed in Table 2 prior to startup of the

waste heat recovery unit.

4. The Applicant shall limit facilitywide emissions to those

shown in Table 1, on a rolling 12-month basis. For demonstrating compliance with annual facilitywide emission

limits, the Applicant shall, if requested by EPA, maintain a

written record of rolling 12-month emission totals.

5. The Applicant shall comply with all applicable provisions of

40 CFR 60.7 for notification and recordkeeping relating to

startup, shutdown and malfUnctions of the gas turbine.

6. The Applicant shall operate the gas turbine in accordance

with th. operation and mai~tenance provisions of 40 CFR

60.11(d). Temporary installation of an identical gas

turbine shall be allowed during maintenance overhaul of the

existing gas turbine, according to the procedure described

in.the Applicant's letter to EPA dated February 22, 1991.

7. The Applicant shall comply with all applicable emission

limits for the gas turbine which are specified in Subpart GG

of federal New Source Performance Standards (NSPS), at 40

CFR 60.332 and 60.333.· In no event shall emissions of

oxides of nitrogen (NOx) from the gas turbine exceed 150

parts per million by volume, at 15% oxygen on a dry basis.

8. The gas turbine shall be stack tested a~cording to the

method(s) specified in NSPS Subpart GG, as amended by the

test protocol submitted to EPA on November 5, 1990, and

approved by EPA on February 7, 1991. Testing shall be

scheduled and conducted.in -accordance with the deadlines and

notification procedures ~ontained in 40 CFR 60.8. Performance test results shall be submitted to EPA not more than

45 days after the test.

9. At all times, including periods of startup, shutdown and

equipment malfunction, the Applicant shall maLnt.a fn and

operate the overall McElmo Creek Unit in a manner consistent

with good air pollution control practices for minimizing

excess emissions. Determination of whether· acceptable

operation and maintenance procedures are being used will be

based on information available to the Administrator, which . may include, but not be limited to, monitoring results,

review of operation and maintenance procedures, and EPA

inspection of the facility.

4
10. The Applicant shall notify EPA as soon as possible, but in

no event· more than 48 hours, after discovery of excess __emissions during periods-ofstartuPJ shutdownr-control

equipment malfunction, or process upset. No more than 10

days after discovery, all of the following shall be provided

to EPA in writing:

a. The identity of the stack or other emission point where

excess emissions occurred.

b. The identity of the equipment or process causing the

excess emissions and the suspected reason(s) for .the

excess emissions.

c. The time, duration and magnitude of excess emissions,

expressed in terms of permit conditions.

d. Corrective action taken during the excess emission

incident to minimize excess emissions, as well as

corrective action taken, or anticipated to be taken, to

prevent recurrence of excess emissions.

If EPA finds that the information submitted under Condition

#10 of this permit does not provide evidence that the excess

.emissions were unavoidable, or the information gives EPA

reason to believe that the excess emissions were the result

of negligence, then the excess emissions shall be considered

a violation of this permit.

11.

12.

EPA and its authorized representatives may inspect the

permitted facility during normal business hours for purposes

of ascertaining compliance with all conditions of this

permit.

Nothing in this approval shall relieve the Applicant from

complying with all other applicable federal, state or local

regulations.

(

5
IV. GENERAL

This permit is issued in reliance upon the completeness and

accuracy of the information set forth in the Applicant's

application and subsequent correspondence to EPA for permission

to modify the McElmo Creek Unit. Each and every condition of

this permit is a material part hereof and is not severable.

This permit is immediately effective and all conditions

herein enforceable by EPA, unless the Applicant notifies EPA in .

writing that any term or condition of this permit is rejected.

Such notification must be postmarked not more than ten (10) days

after Applicant's receipt of this permit, must include the

reason(s) for rejection, and must be addressed to: Mr. Michael

Owens, Air Programs Branch (8AT-AP), U.S. EPA, 999 18th St.,

Suite 500, Denver, CO B0202-2405. Construction of the facility

modification may not commence until the reasons for rejection are

reviewed by EPA and a revised permit acceptable to EPA and the

Applicant is issued.

UNITED STATES ENVIRONMENTAL

PROTECTION AGENCY, REGION VIII

By:

Irwin L. Dickstein, Director

Air & Toxics Division

Effective Date: 1-/f-Zl

,

6
'l'able 1

-~-~---Pollutant-Emi t.t.Lnq.. Equipment

Authorized under April 1991 EPA Permit

for

Mob~l McElmo Creek Unit

Emission Point Size

Emissions

(tons per year)

S02 NOx CO VOC

T4500 Gas Turbine 4390 HP* 0.05 74.60 17.00 4.00

Ingersoll Rand

Engine

491 HP 0.10 52.00 7.00 2.00

Fairbanks Morse

Engine

1712 HP 0.10 72.00 35.00 7.00

Fairbanks Morse

Engine

1712 HP 0.10 72.00 35.00 7 .. 00

Fairbanks MorseEngine

1848 HP 0.10 91.00 5.00 8.00

Fairbanks Morse

Engine

1848 HP 0.10 91.00 5.00 8.00

DPC-540

Waste Heat

Recovery Unit**

470 HP 0.10

11~0 MMBTU/hr 0.10

18.20 4.10

3.88 0.77

1 .40

O. 10

0.14 0.10

1.75 0.40

0.44 0.10

I"·------~'"

i O. 14) O. 10

..-....._---------/

O. 10

O. 10·

0.10

0.10

0.14 0.10 0.10

1.0 MMBTU/hr 0.10

4.0 MMBTU/hr 0.10

- 0~33 MMBTU/hrO.l0

0.33 MMBTU/hr '0.10

0.33 MMBTU/hr 0.10

HC Liquid Reboiler

Heat Medium Heater

TEG Reboiler

TEG Reboiler

TEG Reboiler

Total facilitywide

authorized emissions 1.25 477.29 109.67 38.00

FOOTNOTES:

* Sea-level ratingj at manufacturer's design capacity (used for

NSPS Subpart GG applicability determination). Site rating is

3525 HP.

** - To replace eq~ipment listed in Table 2 below.
'Table'2

-Pollutant-Emitting Equipment:, _

to be Shut Down

Under April 1991 EPA Permit

Emissions

(tons per year)

Emission Point Size S02 NOx eo voe

Heat 'Medium Heater 12.2 MMBTU/hr 0.10 7.40 1 .90 0.15

TEG Reboiler O."MMBTU/hr 0.10 0.10 0.10 0.10

Total emissions for

equipment to be shut down 0.20 7.50 2.00 0.25

The above equipment will be replaced with the waste heat

recovery unit listed in Table 1. Emissions of all pollutants

are expected, to decrease as a reault.