a: AMERICAN

' EiECrRIC POWER September
10, 2013 VIA ELECTRONIC SUBMITTAL Mary Pettyjohn Arkansas Department
of Environmental Quality 5301 Northshore Drive Little Rock, AR 72118 Dayana Medina U.S. Environmental Protection Agency, Region

6 Multimedia Planning and P e rmitting Division Air Planning Section

( 6PD

-L ) 1445 Ross Avenue Dallas, TX 75202 Re: Application

f orBART Determination
for S02 and NOx American Electric Power 1201 Elm Street, Suite BOO Dallas, TX 75270 AEPcom At the Flint Cr eek Pow
erPlant

,Gentr y,Arkansas (AFIN 04-00107) Dear Ms

.Pettyjohn and M s.Medina

: Below arethe respon

sestoeach of the questions/r

e quest sentto Southwestern Electric Power Company (SWEPCO)
on August 21

,2013, regarding the cost evaluation and proposed emission levels for NOx control technologies evaluated

in the BART five factor analysis for the Flint Creek Power Plant. We also are providing
an updated report that incorporates revisions discussed below. We have summarized and numbered the questions

in your August 21, 2013 email tosetoff the specific responses.

If wehave misinterpreted your questions, please let usknow. 1. De-escalation
of LNBIOFA and SCR Cost Estimates. In the enclosed report, wehave revised the cost estimates for LNB/OFA and SCR by deescalating the total annual cost values by three (3) percent per yearto present updated costsona current (20 13/2014) basis. 2. SCR Equipment Life for Capital Recovery In the enclosed report, wehave revised the cost estimates for SCR tobe based ona 30-year life for capital recovery purposes.Letter toMs. Pettyjohn and Ms. Medina September
10, 2013 Page
2 of3 3. LNBIOFA Equipment Life for Capital Recovery In the enclosed report, wehave revised the cost estimates for LNB/OFA

tobe based ona 30-year life for capital recovery purposes. 4. SCR Cost v. Visibility Benefit We agreewith EPA's assessment that evenafter the revisions mentioned above, the visibility benefits of SCR do not justify the costof control. 4. Emission Level for LNBIOFA SWEPCO has requested

a 30-day rolling averagelimitation
of 0.23 lb/MMBtu following installation
of the LNB/OFA systems
atFlint Creek Station, consistent with EPA's determination of the presumptive BART level for this equipment
onthis typeof electric generating unit. SWEPCO submitted information
on anticipated levels of controlled NOx emissions from the manufacturer

of the LNB/OFA systemin support of its request, which ranged from 0.145-0.218 lb/MMBtu based onfour-hour tests. SWEPCO also submitted actual controlled NOx emissions data from similar units. EPA agreesthat the PacifiCorp Wyodak unit is the most similar toFlint Creek in terms of its uncontrolled emission rate, and agreed that the NOx emissions for this unit have been as high as0.21 lb/MMBtu following installation
of similar equipment from the same manufacturer. Welsh Unit 2, which is asister unit toFlint Creek, has also installed equipment from the same manufacturer, and since May of 2005 has measured emissions

as high as0.191 lb/MMBtu. NOx emissions are primarily produced
as partof the combustion process
asafunction of the temperature

in the combustion zone,and can vary significantly from unit tounit. Pursuing the lowest achievable NOx emission ratesatanelectric generating unit canhave adverse consequences, including accelerated deterioration

of boiler tubes, leading
to expensive and timeconsuming repairs.
In addition, NOx production

is inversely related tothe production
of CO from the boiler, and pursuing

aNOx rate lower than the requested rate could increase CO production

tothe point that Flint Creek would need to accept restrictions
onits maximum output rating and capacity factor in order to simultaneously achieve both its CO and NOx limits. While the requested emission rateis slightly higher than the highest averagesachieved

at similar units, some margin for compliance

is necessaryand desirable
to accommodate
the inherent variability
of fuel supply, boiler tune-ups, and attributable

to ordinary wearand tearof the equipment. Although the measured performance ofWyodak and Welsh Unit
2 confirms the likely achievability

of the requested rate, their current permitted emission limits areas high or higher than the requested rate (0.23 and 0.36 lb/MMBtu, respectively), further confirming that some compliance margin
is appropriate. Accordingly, ADEQ should find that the BARTLetter toMs. Pettyjohn and Ms. Medina September
10, 2013 Page
3 of3 emission rateis 0.23 lb/MMBtu, consistent with EPA's determination

of presumptive BART and prior BART determinations
for similar units. We hope that this information will satisfactorily address the questions and concernsoutlined
in the August 21,2013 email. Please contact meat (214) 777-1113

to provide anyadditional information you may require. Sincerely, **1<?.4~** Kris Gaus, QEP Environmental Specialist Air Quality Services File:FLC.1 0.90.50

.1 0
.2013