AQ_F_0400056_20211221_ST_WaiverResp

ROY COOPER
Governor
ELIZABETH S.BISER
Secretary
MICHAEL ABRACZINSKAS NORTH CAROLINA
Director Enykwwwat+ol QuaUty
December 21, 2021
Adam Long
VP, Gas Pipeline Operations
Piedmont Natural Gas
410 South Wilmington Street
Raleigh,NC 27601
Subject: Approval of Waiver Request for Emissions Testing of One Natural Gas Engine as
Representative of Four Engines COMP01-COMP04
Piedmont Natural Gas-Wadesboro Compressor Station
Wadesboro,Anson County,North Carolina
Facility ID No. 0400056;Air Permit No. 10097T02
Dear Mr. Long:
The North Carolina Division of Air Quality(NC DAQ)has reviewed the information submitted in
your company's letter dated September 22,2021,requesting a waiver from the performance testing
requirements of 40 CFR 60 Subpart JJJJ-Standards of Performance for Stationary Spark Ignition Internal
Combustion Engines,as related to four identical,natural gas-fired,internal combustion engines(Permit ID
Nos. COMPOI through COMP04)at the Piedmont Natural Gas-Wadesboro Compressor Station(PNG-
Wadesboro). PNG-Wadesboro is requesting to conduct performance testing on one of the four engines as
representative of emissions from all identical engines on site to demonstrate compliance with the 40 CFR
60 Subpart JJJJ testing requirements.
40 CFR 60 Subpart JJJJ requires periodic testing of subject engines once every three years or
every 8760 hours of operation,whichever occurs first.Upcoming performance testing during calendar year
2022 will be conducted to meet the three-year testing requirement since the engines at the PNG-
Wadesboro site operate less than 8760 hours in a three-year period. Pursuant to 40 C.F.R. § 60.8(b)(4),
performance tests shall be conducted in accordance with the test methods and procedures contained in each
applicable subpart unless the Administrator(NC DAQ in this case)waives the requirement for
performance tests because the owner or operator of a source has demonstrated by other means to the
Administrator's satisfaction that the affected emission source can continually comply with the standard.
Section V11.2 of the US EPA's April 27, 2009, Clean Air Act National Stack Testing Guidance
states that a performance test waiver for identical emissions units may be appropriate when the following
conditions are met:
I. the units are located at the same facility;
2. the units were produced by the same manufacturer,have the same model number or other
manufacturer's designation in common,and have the same rated capacity and operating
specifications;
3. the units are operated and maintained in a similar manner; and
4. the EPA or delegated agency,based on documents submitted by facility:
a. determines that the margin of compliance for the identical units tested is significant and
can be maintained on an ongoing basis;or
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Piedmont Natural Gas-Wadesboro Compressor Station
December 21,2021
Page 2
b. determines based on a review of sufficient emission data that,though the margin of
compliance is not substantial, other factors allow for the determination that the
variability of emissions for identical tested units is low enough for confidence that the
untested unit(s)will be in compliance.These factors may include,but are not limited
to,the following:
i. historical records at the tested unit showing consistent/invariant loads;
ii. fuel characteristics yielding low variability and therefore assurance that the
emissions will be consistent and below allowable levels; and
iii. statistical analysis of a robust emissions data set demonstrates sufficiently low
variability to convey assurance that the margin of compliance,though small, is
reliable.
In reviewing performance testing waiver requests for identical emission sources,NC DAQ must
first ensure that the criteria outlined above from the US EPA's Clean Air Act National Stack Testing
Guidance are met fully and continuously.Beyond this,NC DAQ may specify additional requirements on
facilities to ensure all emission units are tested over time on a regular schedule and to ensure continuous
compliance with the applicable emission standard(s)for all units.
To support the request for testing one engine as representative of COMPOI through COMP04,
PNG-Wadesboro provided information on the manufacturer,model number,rated capacity, and operating
specifications for all four engines,as well as analyses of historical emissions data,loads, and run times for
the subject engines.Based on the information provided,the four engines appear to be identical and are
being operated and maintained in the same manner with uniform fuel characteristics. The emissions data
reported for this facility since 2013 demonstrates a significant margin of compliance(greater than 50%)
for all regulated pollutants.
Therefore,NC DAQ approves the requested waiver of performance testing for identical units at the
PNG-Wadesboro site on an ongoing basis,provided that the following conditions are met:
1. Two engines of the set COMP02 through COMP04 are tested in 2022 and the third of this
same set is tested in 2024;
2. A different engine is tested every other year with two engines being tested every fourth
year to ensure regular testing over time and that all engines are tested at least once every
six years after 2024(e.g.,test COMP02 and COMP03 in 2022,COMP04 in 2024,
COMPOI and COMP02 in 2026,COMP03 in 2028, and repeat cycle going forward);
3. If any engine approaches 8760 operating hours since the last representative performance
test, a new representative test is conducted prior to passing the 8760-hour threshold;
4. All new performance test results continue to meet the waiver criteria outlined above from
the US EPA's Clean Air Act National Stack Testing Guidance. A justification and
supporting data for continuation of this waiver should be included in each performance
test report that is intended to provide representative emission results for multiple identical
engines on the same site; and
5. All future protocol submittals for representative testing of identical units include
references to this approval letter and to the most recent justification and supporting data
for continuation of this waiver.
If future test data does not support requirements to maintain classification of the engines as
identical,PNG-Wadesboro may be required to perform additional testing.NC DAQ will review the
facility's continual adherence to the criteria for performance test waivers for identical emission units by
reviewing the justification and supporting data that is submitted with each future performance test report.

Piedmont Natural Gas-Wadesboro Compressor Station
December 21,2021
Page 3
This performance test waiver does not exempt the facility from complying with other applicable
requirements of 40 CFR 60 Subpart JJJJ,other state or federal air quality regulations, and their air permit.
In addition to the mailing of this letter, an electronic copy(e-copy)is being provided for your
records. If you have any questions regarding this waiver approval,please contact Taylor Fort of my staff at
919-707-8431 or [e-mail].
Sincerely,
Stephen G.Hall
Chief,Technical Services Section
Division of Air Quality,NC DEQ
cc: Kristen Belisario, Piedmont Natural Gas(e-copy)
Heather Carter,FRO Air Quality Supervisor(hardcopy and e-copy)
Gary Saunders, SSCB Supervisor(e-copy)
IBEAM Documents—0400056