AQ_F_1800073_20150623_CMPL_AltTMRR

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NCDENR
North Carolina Department of Environment and Natural Resources
Pat McCrory Donald R. van der Vaart
Governor Secretary
June 25, 2015
Mr. Paul B. Dueitt
General Manager II
Duke Energy Carolinas LLC
Allen Steam Station
253 Plant Allen Rd.
Belmont,North Carolina 28012-8845
RE: Approval of Petition to use PM CEMS Alternative Monitoring Option on SIP Units 1 thru 5
Duke Energy Carolinas, LLC—Allen Steam Station
Belmont, Gaston County, North Carolina
Air Quality Permit No. 03757T40
Facility I.D. No. 3 60003 9
Dear Mr. Dueitt:
This letter is in response to your petition of February 25, 2015, to Michael Pjetraj,
Division of Air Quality(DAQ), requesting the use of an alternative monitoring option at your
facility. Specifically, Duke Energy Carolinas, LLC (DEC)requested DAQ approval for the use
of particulate matter (PM)continuous emissions monitoring systems (CEMS)in lieu of
continuous opacity monitoring systems (COMS) on Allen Units 1 thru 5. The five coal-fired
units are exhausted through two common stacks (CS). Emissions from Units 1, 2 & 5 are
exhausted through CS01 and emissions from Units 3 &4 are exhausted through CS02. The
COMS are located upstream of wet scrubbers and were installed pursuant to 15A NCAC
2D .0521(g) and 2D .0606 in order to demonstrate compliance with the 40%opacity limit of
2D .0521(c),the 40% opacity limit of 2D .0606, and the annual average opacity(AAO)limits of
2D .0536. The PM CEMS were installed on the saturated flue gas stacks pursuant to the
Mercury and Air Toxics Standard (MATS) of 40 CFR Part 63, Subpart UUUUU—National
Emission Standards for Hazardous Air Pollutants: Coal- and Oil-Fired Electric Utility Steam
Generating Unit. The PM CEMS installed on CSO1 was certified June 19, 2014, and the PM
CEMS installed on CS02 was certified July 17, 2014. Since PM and opacity standards for the
five utility boilers are only subject to North Carolina's State Implementation Plan (SIP), the
petition requested that MATS UUUUU serve as the regulatory framework for complying with
15A NCAC 2D .0536 and 2D .0606.
Based on our review, and in conjunction with our authority under 15A NCAC 2D .0536,
2D .0612, 2D .0606(g), 2D .0614, and 40 CFR 75.14(b), we approve DEC's petition for Allen
Units 1 through 5 to:
1641 Mail Service Center,Raleigh,North Carolina 27699-1641
Phone:[phone]Internet:www.ncdenr.gov
An Equal Opportunity 1 Affirmative Action Employer—Made in part by recycled paper

Mr. Paul B. Dueitt
June 25, 2015
Page 2
1. Use the PM GEMS, which met the certification requirements of 40 CFR Part 60, Appendix
B, Performance Specification 11 (PS-11), as an alternative to opacity monitoring provided
they also operate in accordance with the quality assurance plan(QAP) established under 40
CFR Part 60, Appendix F, Procedure 2. We agree that the PM CEMS monitoring option
provides a more accurate and representative measurement of the amount of PM emissions
exiting the stacks and entering the atmosphere than the COMS, which are located prior to the
control device. We also agree the PM CEMS are better suited for a saturated environment
whereas the COMS are not.
2. Use a PM CEMS to comply with the AAO limits of 15A NCAC 2D.0536 -Particulate
Emissions from Electric Utility Boilers by using either non-overlapping one-hour average
PM CEMS measurements in the wet stacks or COMS measurements upstream of the wet
scrubbers. DEC has correlated Method 9 opacity readings to milligrams per actual cubic
meter(mg/acm) as recorded by the PM CEMS during Allen's initial PS-11 certification
testing. By establishing the equivalent PM concentration at the AAO limits, subsequent
hourly PM CEMS readings (mg/acm) can now be converted to hourly opacity averages. For
the initial year, AAO compliance will be determined using the formula that combines data
from the PM CEMS and COMS. The mathematical formula and methodology stated in
"Belews Creek permit 01983T29 Condition 2.1 A.5 template"must be submitted and
incorporated into Allen's permit. DAQ has concluded the alternate method will not cause a
systematic or unacceptable difference from the current method. It is mutually agreed that any
values calculated using the alternate method can be used for enforcement purposes of the
AAO standards. DEC may submit quarterly AAO reports rather than monthly reports. The
alternative monitoring request is approved pursuant to 2D .0536(b).
3. Use a PM CEMS to comply with the PM limits in 15 NCAC 2D .0536. In addition,we
approve DEC's proposal to reduce the PM limit from 0.1 lb/mmBTU (24-hour daily
arithmetic average based on the current language of NSPS Da)to 0.03 lb/mrnBTU (30-boiler
operating day rolling average) of MATS UUUUU. Boiler operating day, as stated in MATS
UUUUU, means"a 24-hour period that begins at midnight and ends the following midnight
during which any fuel is combusted at any time in the EGU, excluding startup periods or
shutdown periods. It is not necessary for the fuel to be combusted the entire 24-hour period."
We accept the supplemental data provided upon request via email on March 11, 2015, and
April 12, 2015, in order to verify that the 24-hour short term limit is not threatened by a 30-
boiler operating day longer term limit. The alternative monitoring request is approved
pursuant to 2D .0536(b).
4. Exempt stack gas opacity monitoring as provided under 40 CFR 75.14(b) - Specific
provisions for monitoring opacity- Unit with wet flue gas pollution control system. We
concur with the saturation calculations and data which demonstrated that condensed water is
present in the exhaust flue gas streams and would impede the accuracy of opacity
measurements.
5. Use a PM CEMS as an alternative to opacity monitoring for the 40% opacity limit in
paragraph (c) of 15A NCAC 2D .0521 - Control of Visible Emissions. The alternative

Mr. Paul B. Dueitt
June 25, 2015
Page 3
monitoring request is approved pursuant.to 15A NCAC 2D .0612 -Alternative Monitoring
and Reporting Procedures. Consistent with MATS UUUUU, no periodic Method 9 visible
emission readings are required. DEC may opt to perform Method 9 observations during
required testing with mid and high dust loads to demonstrate compliance; DEC must submit
these observations or COMS data and code any excess opacity readings as monitor downtime
and include the duration in monitor downtime calculations.
6. Use a PM CEMS as an alternative to opacity monitoring for the 40% opacity limit in
paragraph(g) of 15A NCAC 2D .0606 -Sources Covered by Appendix P of 40 CFR Part 51.
In order to demonstrate that good operation and maintenance(O&M) is being practiced for
minimizing emissions, DEC will use the methodology and content accepted in DAQ's
petition approval of June 26, 2014, for Belews Creek Units 1 & 2 for reporting PM CEMS
data from DEC state implementation plan(SIP) units. As stated in the petition, this approach
will "[r]etain the same PM CEMS monitoring/recordkeeping/and reporting approved in
Belews Creek permit 01983T29 (Condition 2.1 7b. and d. ii) as a template, adjusted [for
Allen 1 through 5 certification test results.]" The referenced proposal must also be submitted
and incorporated into Allen's permit. The alternative monitoring request is approved
pursuant to 2D .0612 and 2D .0606(g).
7. Use a PM CEMS to satisfy the requirement for 15 NCAC 2D .0614 - Compliance Assurance
Monitoring(CAM) in accordance with 40 CFR 64.2(b)(vi) since the PM CEMS provides a
direct measurement of particulate in units of the emission standard. Should DEC retain the
COMS units to satisfy the CAM requirements under 2D .0614,please ensure all quality
assurance(QA)/quality control (QC)practices and criteria are followed as stated in the
current permit.
If you should have any questions,please call me at [phone] or Dennis Igboko at (919)
707-8410 or [e-mail].
Sincerely,
Lee A. aniel, Chief
Technical Services Section
Division of Air Quality,NCDENR
cc: Bill Horton, Duke Energy Carolinas Central Files, Gaston County
Cynthia Winston, Duke Energy Carolinas IBEAM Documents, 3600039
Randy Wooten, Duke Energy Carolinas
Michael Pjetraj, DAQ Central Office
Ed Martin, DAQ Central Office
Ron Slack, MRO