DAQ-2025-002599

1
DAQC-CI106890001-25
Site ID 10689 (B1)

MEMORANDUM

TO: FILE – MOUNTAINWEST PIPELINE, LLC – Cash Compressor Station

THROUGH: Rik Ombach, Minor Source Oil and Gas Section Manager

FROM: Kyle Greenberg, Environmental Scientist

DATE: May 7, 2025

SUBJECT: FULL COMPLIANCE EVALUATION, Minor, Summit County

INSPECTION DATE: April 16, 2025

SOURCE LOCATION: -111.370483398438, 40.9115104675293
Coalville, UT
DIRECTIONS: 590 Border Station Road, Coalville, UT 84017

SOURCE CONTACTS: Scott Bassett, Environmental Specialist
[phone]
[e-mail]

OPERATING STATUS: Operating

PROCESS DESCRIPTION: Questar operates a 1,376 hp natural gas compressor at this site.
Natural gas is diverted from the main Questar pipeline to the
compressor. The natural gas is sent through a dryer/dehydrator
and compressed to 700 psi. After initial compression, the gas is
sent through a cooler, then dehydrator, and finally compressed a
second time in the compressor before being transferred to the
Coalville natural gas storage field. Questar operates 5 wells that
pump natural gas from the storage field to the Questar Pipeline
when the demand for natural gas increases, typically during peak
usage (winter) or emergency situation. Mercaptan is also added
to the gas. The 5 wells are covered under a separate AO and are
considered another site since the compressor station and the
storage fields are not contiguous. The compressor station only
operates September through June when there is a higher demand
for natural gas.

APPLICABLE REGULATIONS: Approval Order (AO) DAQE-AN106890006-19, dated
December 4, 2019
40 CFR Part 63 Subpart ZZZZ

4 ' - ) - "
2
SOURCE EVALUATION:

Name of Permittee: Permitted Location:

MountainWest Pipeline, LLC - Cash Compressor
Station

650 South Main Street 3rd Floor -111.370483398438 40.9115104675293
Salt Lake City, UT 84101 Coalville, UT

SIC Code: 4922: (Natural Gas Transmission)

Section I: GENERAL PROVISIONS

I.1 All definitions, terms, abbreviations, and references used in this AO conform to those used in the UAC R307 and 40 CFR. Unless noted otherwise, references cited in these AO conditions refer to those rules. [R307-101]
I.2 The limits set forth in this AO shall not be exceeded without prior approval. [R307-401]
I.3 Modifications to the equipment or processes approved by this AO that could affect the emissions covered by this AO must be reviewed and approved. [R307-401-1]
I.4 All records referenced in this AO or in other applicable rules, which are required to be kept by the owner/operator, shall be made available to the Director or Director's representative upon request, and the records shall include the two-year period prior to the date of the request. Unless otherwise specified in this AO or in other applicable state and federal rules, records shall be kept for a minimum of two (2) years. [R307-401-8]
I.5 At all times, including periods of startup, shutdown, and malfunction, owners and operators shall, to the extent practicable, maintain and operate any equipment approved under this AO, including associated air pollution control equipment, in a manner consistent with good air pollution control practice for minimizing emissions. Determination of whether acceptable operating and maintenance procedures are being used will be based on information available to the Director which may include, but is not limited to, monitoring results, opacity observations, review of operating and maintenance procedures, and inspection of the source. All maintenance performed on equipment authorized by this AO shall be recorded. [R307-401-4]
I.6 The owner/operator shall comply with UAC R307-107. General Requirements: Breakdowns. [R307-107]
I.7 The owner/operator shall comply with UAC R307-150 Series. Emission Inventories. [R307-150] Status: In Compliance. No limits set in this AO have been exceeded. No unapproved modifications were observed during the time of inspection. The source provided all records requested, see attached hour log of the emergency generators. The site was well kept and appeared to be operated in a manner consistent with good air pollution control practice for
minimizing emissions. The source reported that there were no breakdowns that resulted in excess of emissions in the past 24 months. Emissions inventories have not been required from this site.

3
Section II: SPECIAL PROVISIONS

II.A The approved installations shall consist of the following equipment:

II.A.1 Compressor Station
II.A.2 One (1) Compressor Engine Make and Model: Superior, 16G-825 (ENG-1) Rating: 1,600 hp @ ISO (1,367 hp site rating) Controls: Non-selective catalytic reduction Fuel: Natural Gas Installation Date: 1980 Federal Applicability: MACT Subpart ZZZZ
II.A.3 One (1) Emergency Generator Make and Model: Caterpillar, G3406 TA (GEN-1)) Rating: 373 hp Fuel: Natural Gas Manufacture/Installation Date: June 2005 Federal Applicability: MACT Subpart ZZZZ
II.A.4 One (1) Emergency Generator Make and Model: Onan, CCK (GEN-2) Rating: 10.2 hp Fuel: Natural Gas Manufacture/Installation Date: Prior to 1995 Federal Applicability: MACT Subpart ZZZZ
II.A.5 Two (2) Condensate Storage Tanks Tank 1 Size: 90 barrels Tank 2 Size: 163 barrels
II.A.6 Six (6) Mercaptan Storage Tanks* Four (4) Storage Tanks Size: 500 gallons Two (2) Storage Tanks Size: 3,000 gallons *included for informational purposes
II.A.7 One (1) Methanol Storage Tank Size: 210 barrels
II.A.8 One (1) Waste Water Storage Tank Size: 150 barrels
II.A.9 Miscellaneous Storage Tanks Contents: new, used, and lubrication oil Maximum Tank Capacity: less than or equal to 500 gallons each
II.A.10 One (1) Flare* Rating: 0.16 MMBtu/hr *controls mercaptan storage tanks odor
4
II.A.11 Miscellaneous Heaters and Boilers Capacity: <5 MMBtu/hr each Fuel: Natural Gas
Status: In Compliance. There was no unapproved equipment observed during the time of inspection. The 210-barrel methanol storage tank has been removed. There are also two electric driven air compressors on site to provide instrument air.

II.B Requirements and Limitations
II.B.1 Site Wide Requirements II.B.1.a The owner/operator shall use only pipeline quality natural gas as a fuel in the compressor engine and emergency generators. [R307-401-8] Status: In Compliance. Only pipeline quality natural gas is used to fuel the compressor engine and the two emergency generators. II.B.1.b Visible emissions from any stationary point or fugitive emission source associated with the source or with the control facilities shall not exceed 10% opacity. [R307-205-4, R307-401-8] II.B.1.b.1 Opacity observations of emissions from stationary sources shall be conducted in accordance with 40 CFR 60, Appendix A, Method 9. [R307-205-4, R307-401-8] Status: In Compliance. No visible emissions were observed during the time of inspection. There is no record of public complaints regarding visible emissions. II.B.1.c The owner/operator shall not operate each emergency engine on site for more than 100 hours per rolling 12-month period during non-emergency situations. There is no time limit on the use of the engines during emergencies. [R307-401-8, 40 CFR 63 Subpart ZZZZ] II.B.1.c.1 To determine compliance with a rolling 12-month total, the owner/operator shall calculate a new 12-month total by the 20th day of each month using data from the previous 12 months. Records documenting the operation of each emergency engine shall be kept in a log and shall include the following: a. The date the emergency engine was used b. The duration of operation in hours c. The reason for the emergency engine usage. [40 CFR 60 Subpart ZZZZ, R307-401-8] II.B.1.c.2 To determine the duration of operation, the owner/operator shall install a non-resettable hour meter for each emergency engine. [R307-401-8, 40 CFR 63 Subpart ZZZZ] Status: In Compliance. The source keeps track of the hours of use for both emergency generators. Records reviewed, going back to January of 2023, show that the emergency generators have not exceeded their rolling 12-month 100-hour limit. See attached records. II.B.2 Compressor Engine Requirements II.B.2.a The owner/operator shall not allow emissions from the compressor engine (II.A.2) to exceed 4.55 lbs/hr of NOx and 5.46 lb/hr of CO. [R307-401-8] II.B.2.b The owner/operator shall test the engine every 5 years or as required by the Director. The owner/operator shall follow the following procedure for testing:
5
A. Notification The Director shall be notified at least 30 days prior to conducting any required emission testing. A source test protocol shall be submitted to DAQ when the testing notification is submitted to the Director. Results of the emission testing shall be submitted to DAQ within 60 days of test completion. The source test protocol shall be approved by the Director prior to performing the test(s). The source test protocol shall outline the proposed test methodologies, stack to be tested. A pretest conference shall be held, if directed by the Director. B. Sample Location The emission point shall be designed to conform to the requirements of 40 CFR 60, Appendix A, Method 1, or other methods as approved by the Director. An Occupational Safety and Health Administration (OSHA) or Mine Safety and Health Administration (MSHA) approved access shall be provided to the test location. C. Volumetric Flow Rate 40 CFR 60, Appendix A, Method 2 or other testing methods approved by the Director. D. Nitrogen Oxides (NOx) 40 CFR 60, Appendix A, Method 7, 7A, 7B, 7C, 7D, 7E, or other testing methods approved by the Director. E. Carbon Monoxide (CO) 40 CFR 60, Appendix A, Method 10, or other testing methods approved by the Director. F. Calculations To determine mass emission rates (lb/hr, etc.) the pollutant concentration as determined by the appropriate methods above shall be multiplied by the volumetric flow rate and any necessary conversion factors determined by the Director, to give the results in the specified units of the emission limitation. G. Existing Source Operation For an existing source/emission point, the production rate during all compliance testing shall be no less than 90% of the maximum production achieved in the previous three (3) years. [R307-401-8] Status: In Compliance. A stack test was conducted September of 2021. This stack test shows that the ENG-1: Superior 16G-825 compressor engine, SN: 274959, was in compliance with its emission limits during the time of testing. See attached stack test memo DAQC-1576-21.
Section III: APPLICABLE FEDERAL REQUIREMENTS

In addition to the requirements of this AO, all applicable provisions of the following federal programs
have been found to apply to this installation. This AO in no way releases the owner or operator from any
liability for compliance with all other applicable federal, state, and local regulations including UAC
R307.

40 CFR Part 63 Subpart ZZZZ:

Status: In Compliance. The compressor engine is in compliance with Subpart ZZZZ emission
limits, see attached stack test memo. The two emergency generators are in compliance with Subpart
ZZZZ rolling 12-month 100-hour limit.

6
40 CFR Part 60 Subpart OOOO:

Status: Not Applicable. This source was constructed before August 23, 2011. The source recalls that
the rod packing for the compressor was replaced in the last 10 years. The source has also stated
that they will start keeping records of hours for the rod packing and will also be making
modifications to the rod packing vent piping so that monitoring can be done in the near future. The
source is using instrument air to power smaller control valves and is currently talking with the EPA
about using instrument air versus process gas to power larger control valves, and the safety aspect
of instrument air not providing enough compression to shut larger control valves in emergency
situations. These actions are being done to be in compliance with Subpart OOOOc for once that
goes into effect.

AREA SOURCE RULES EVALUATION:

The following Area Source Rules were evaluated during this inspection:

Utah Administrative Code R307-506. Oil and Gas Industry: Storage Vessel:
In Compliance. The condensate throughput for the condensate tanks is less than 2,000 barrels. The
tanks do not require a control. See attached records of condensate throughput provided by Scott
Bassett.

EMISSION INVENTORY:
The emissions listed below are an estimate of the total potential emissions (PTE) from MountainWest
Pipeline, LLC - Cash Compressor Station on the Approval Order (AO) DAQE-AN106890006-19, dated
December 4, 2019. PTE are supplied for supplemental purposes only.

Criteria Pollutant PTE tons/yr
Carbon Monoxide 24.06
Carbon Monoxide 24.50
Nitrogen Oxides 21.89
Nitrogen Oxides 22.12
Particulate Matter - PM10 0.68
Particulate Matter - PM10 0.41
Particulate Matter - PM2.5 0.68
Particulate Matter - PM2.5 0.30
Sulfur Oxides 0.12
Sulfur Oxides 0.02
Volatile Organic Compounds 7.18
Volatile Organic Compounds 7.98

Hazardous Air Pollutant PTE lbs/yr
Generic HAPs (CAS #GHAPS) 796
Generic HAPs (CAS #GHAPS) 2640

7
PREVIOUS ENFORCEMENT
ACTIONS: None

COMPLIANCE STATUS &
RECOMMENDATIONS: In regards to Approval Order (AO) DAQE-AN106890006-19,
dated December 4, 2019, the overall status is: In Compliance. It
is recommended that the Cash Compressor Station be considered
as in compliance during the time of inspection. There were no
unapproved equipment, visible emissions, nor VOC leaks
observed during the time of inspection. The last stack test
conducted September 2021, show the compressor engine to be in
compliance with its emission limits and the two emergency
generators are under their rolling 12-month 100-hour limits.

HPV STATUS: Not Applicable.

RECOMMENDATION FOR
NEXT INSPECTION: Call before scheduling the inspection to ensure the source is
operating and the gates are open.

NSR RECOMMENDATIONS: The 210-barrel Methanol Storage Tank has been removed from
site.

ATTACHMENTS: Gen-1 and Gen-2 rolling 12-month hour records, stack test
memo for the compressor engine, condensate throughput
records.
Facility:Password: genlock
Engine:
Type:
Emergency Engine
YEAR MONTH Non-Emergency
Hours
Emergency
Hours
Calendar Year Non-
Emergency Hours
12-Month Rolling
Non-Emergency Hours
2023 JAN 582 1.00 1.0 0.0 33.0 18.0
FEB 583 1.00 1.0 0.0 32.0 17.0
MAR 588 5.00 2.0 3.0 Power Outage 35.0 17.0
APR 590 2.00 2.0 0.0 36.0 18.0
MAY 592 2.00 2.0 0.0 37.0 19.0
JUN 593 1.00 1.0 0.0 37.0 19.0
JUL 595 2.00 2.0 0.0 36.0 19.0
AUG 596 1.00 1.0 0.0 29.0 18.0
SEPT 598 2.00 2.0 0.0 31.0 20.0
OCT 600 2.00 2.0 0.0 24.0 20.0
NOV 601 1.00 1.0 0.0 23.0 19.0
DEC 602 1.00 1.0 0.0 21.0 18.0
2024 JAN 604 2.00 2.0 0.0 22.0 19.0
FEB 605 1.00 1.0 0.0 22.0 19.0
MAR 619 14.00 2.0 12.0 Power Outage 31.0 19.0
APR 625 6.00 2.0 4.0 Power Outage 35.0 19.0
MAY 633 8.00 2.0 6.0 Power Outage 41.0 19.0
JUN 634 1.00 1.0 0.0 41.0 19.0
JUL 635 1.00 1.0 0.0 40.0 18.0
AUG 636 1.00 1.0 0.0 40.0 18.0
SEPT 638 2.00 2.0 0.0 40.0 18.0
OCT 639 1.00 1.0 0.0 39.0 17.0
NOV 640 1.00 1.0 0.0 39.0 17.0
DEC 643 3.00 2.0 1.0 Power Outage 41.0 18.0
2025 JAN 645 2.00 2.0 0.0 41.0 18.0
FEB 648 3.00 2.0 1.0 Power Outage 43.0 19.0
MAR 649 1.00 1.0 0.0 30.0 18.0
APR 0.00 0.0 24.0 16.0
MAY 0.00 0.0 16.0 14.0
JUN 0.00 0.0 15.0 13.0
JUL 0.00 0.0 14.0 12.0
AUG 0.00 0.0 13.0 11.0
SEPT 0.00 0.0 11.0 9.0
OCT 0.00 0.0 10.0 8.0
NOV 0.00 0.0 9.0 7.0
DEC 0.00 0.0 6.0 5.0
Emergency Generator hour tracking per NESHAP ZZZZ or NSPS JJJJ
Operating Hours Data
Cash Station
LIMIT = 100 Non-
Emergency Hours
in any 12-Month Rolling PeriodTotal Hours on Non-
Reset Hour Meter
Hours Operated Since
Last Reading
NESHAP/NSPS Requirement LIMIT = 100 Non-Emergency
Hours in a Calendar YearReason for Emergency
Operation (e.g, Power Outage)
GEN-1
Caterpillar G3406TA
Total 12-Month
Rolling Operating Hours
Operations to fill-in the Green Columns
18.0
5.0
18.0
Facility:Password: genlock
Engine:
Type:
Emergency Engine
YEAR MONTH Non-Emergency
Hours
Emergency
Hours
Calendar Year Non-
Emergency Hours
12-Month Rolling
Non-Emergency
Hours
2023 JAN 117.1 1.10 1.10 0.00 29.2 16.5
FEB 120 2.90 2.90 0.00 30.7 18.1
MAR 120 0.00 0.00 0.00 29.3 16.7
APR 122.4 2.40 2.40 0.00 29.9 17.3
MAY 123.8 1.40 1.40 0.00 29.6 17.0
JUN 125.1 1.30 1.30 0.00 27.8 16.3
JUL 125.8 0.70 0.70 0.00 26.1 16.6
AUG 127.2 1.40 1.40 0.00 24.0 16.0
SEPT 128.5 1.30 1.30 0.00 15.5 15.3
OCT 130.2 1.70 1.70 0.00 15.0 15.0
NOV 131.5 1.30 1.30 0.00 15.6 15.6
DEC 132.5 1.00 1.00 0.00 16.5 16.5
2024 JAN 135.2 2.70 2.70 0.00 Testing 18.1 18.1
FEB 135.9 0.70 0.70 0.00 15.9 15.9
MAR 136.5 0.60 0.60 0.00 16.5 16.5
APR 137.2 0.70 0.70 0.00 14.8 14.8
MAY 145 7.80 2.00 5.80 Power Outage 21.2 15.4
JUN 146.4 1.40 1.40 0.00 21.3 15.5
JUL 148.1 1.70 1.70 0.00 22.3 16.5
AUG 149.4 1.30 1.30 0.00 22.2 16.4
SEPT 151.5 2.10 2.00 0.10 Power Outage 23.0 17.1
OCT 155.2 3.70 2.00 1.70 Power Outage 25.0 17.4
NOV 156.2 1.00 1.00 0.00 24.7 17.1
DEC 157.9 1.70 1.70 0.00 25.4 17.8
2025 JAN 159.2 1.30 1.30 0.00 24.0 16.4
FEB 160.6 1.40 1.40 0.00 24.7 17.1
MAR 164.2 3.60 2.00 1.60 Power Outage 27.7 18.5
APR 0.00 0.00 27.0 17.8
MAY 0.00 0.00 19.2 15.8
JUN 0.00 0.00 17.8 14.4
JUL 0.00 0.00 16.1 12.7
AUG 0.00 0.00 14.8 11.4
SEPT 0.00 0.00 12.7 9.4
OCT 0.00 0.00 9.0 7.4
NOV 0.00 0.00 8.0 6.4
DEC 0.00 0.00 6.3 4.7
16.5
Operations to fill-in the Green Columns
17.8
4.7
Operating Hours Data
Cash Station
GEN-2
Onan CCK
Emergency Generator hour tracking per NESHAP ZZZZ or NSPS JJJJ
Total Hours on Non-
Reset Hour Meter
Hours Operated
Since Last Reading
NESHAP/NSPS Requirement Reason for Emergency
Operation
(e.g, Power Outage)
Total 12-Month Rolling
Operating Hours
LIMIT = 100 Non-Emergency
Hours in a Calendar Year
LIMIT = 100 Non-
Emergency Hours in
any 12-Month Rolling Period
SOURCES:
CONTACT:
LOCATION:
TEST CONTRACTOR:
PERMIT/A0#:
ACTION CODE:
SUBJECT:
ENG-1: Superior 16G-825 compressor engine
Sean Warden: 804-273-3263
590 East Border Station Road, Coalville, Summit County, Utah
Oasis Emission Consultants, Inc.
DAQE-AN106890006-19 dated December 4, 2019
TR
Review of stack test report dated October 15, 2020
DAQC- 1576-21
Site ID 10689 (B4)
MEMORANDUM
To:
Through:
From:
Date:
Subject:
STACK TEST FILE — DOMINION ENERGY QUESTAR PH'ELINE, LLC — CASH
COMPRESSOR STATION — SUMMIT COUNTY, UTAH
Rik Ombach, Minor Source Compliance Section Manager0
Kyle Greenberg, Environmental Scientist „Rf
December 17, 2021
On November 2, 2021, DAQ received a test report for ENG-1: Superior 16G-825 compressor engine at Cash
Compressor Station in Summit County, Utah Testing was performed on September 15, 2021, to demonstrate
compliance with the emission limits found in Conditions II.B.2.a and II.B.2.b.of Approval Order DAQE-
AN10689006-19. The calculated test results are:
Source Test
Date
Test
Method Pollutant Tester Results DAQ Results Limits
ENG-1:
Superior
16G-825
Sept.
15,
2021
7E NOx 0.88 lb/hr 0.873 lb/hr 4.55 lb/hr
10 CO 2.41 lb/hr 2.403 lb/hr 5.46 lb/hr
DEVIATIONS: None.
CONCLUSION: The stack test report appears to be acceptable.
RECOMMENDATION: The emissions from ENG-1, should be considered to have been in
compliance with the emission limits of the AO during the stack test.
HPV: N/A
ATTACHMENTS: DAQ stack test review Excel Spreadsheets; Dominion stack test report.
DAQC-2021-018485
Kyle Greenberg <[e-mail]>
Cash Station Condensate Tank Throughput
Bassett, Scott <[e-mail]>Wed, Apr 9, 2025 at 3:27 PM
To: Kyle Greenberg <[e-mail]>
Hi Kyle,

Based on the monthly tank gauge logs, the last two years of throughput is as follows:

Tank 3000
February 2023 – March 2024 = 672 gallons (16 barrels)
February 2024 – March 2025 = 2544 gallons (61 barrels)

Tank 3003
February 2023 – March 2024 – 94.5 gallons (2.25 barrels)
February 2024 – March 2025 = 31.5 gallons (0.75 barrels)

Let me know if you need anything additional. Regards, Scott

Scott R. Bassett | Williams | Environmental Specialist | MountainWest Pipeline
Cell: [phone] | 650 South Main Street, Suite 300, Salt Lake City, UT 84101
Williams Careers | Facebook | Twitter | LinkedIn | YouTube | Instagram | Pipe Up

If you have received this message in error, please reply to advise the sender of the error and then immediately delete
this message.

4/15/25, 3:59 PM State of Utah Mail - Cash Station Condensate Tank Throughput
https://mail.google.com/mail/u/0/?ik=83bbfeb418&view=pt&search=all&permmsgid=msg-f:1828961971471137377&simpl=msg-f:1828961971471137377 1/1