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 Permitting Division 

Air Planning Section (6PD-L) 

1445 Ross Avenue 

Dallas, TX 75202 

Re: Application for BART Determination for S02 and NOx 

At the Flint Creek Power Plant, Gentry, Arkansas (AFIN 04-00107) 

Dear Ms. Pettyjohn and Ms. Medina: 

Below are the responses to each of the questions/request sent to 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 to set off the 

specific responses. If we have misinterpreted your questions, please let us know. 

1. De-escalation of LNBIOFA and SCR Cost Estimates. 

In the enclosed report, we have revised the cost estimates for LNB/OFA and SCR by deescalating the total annual cost values by three (3) percent per year to present updated costs on a 

current (20 13/2014) basis. 

2. SCR Equipment Life for Capital Recovery 

In the enclosed report, we have revised the cost estimates for SCR to be based on a 30-year life 

for capital recovery purposes. 
4. SCR Cost v. Visibility Benefit 

We agree with EPA's assessment that even after the revisions mentioned above, the visibility 

benefits of SCR do not justify the cost of control. 

4. Emission Level for LNBIOFA 

SWEPCO has requested a 30-day rolling average limitation of 0.23 lb/MMBtu following 

installation of the LNB/OFA systems at Flint Creek Station, consistent with EPA's determination 

of the presumptive BART level for this equipment on this type of electric generating unit. 

SWEPCO submitted information on anticipated levels of controlled NOx emissions from the 

manufacturer of the LNB/OFA system in support of its request, which ranged from 0.145-0.218 

lb/MMBtu based on four-hour tests. SWEPCO also submitted actual controlled NOx emissions 

data from similar units. EPA agrees that the PacifiCorp Wyodak unit is the most similar to Flint 

Creek in terms of its uncontrolled emission rate, and agreed that the NOx emissions for this unit 

have been as high as 0.21 lb/MMBtu following installation of similar equipment from the same 

manufacturer. Welsh Unit 2, which is a sister unit to Flint Creek, has also installed equipment 

from the same manufacturer, and since May of 2005 has measured emissions as high as 0.191 

lb/MMBtu. 

NOx emissions are primarily produced as part of the combustion process as a function of the 

temperature in the combustion zone, and can vary significantly from unit to unit. Pursuing the 

lowest achievable NOx emission rates at an electric generating unit can have adverse 

consequences, including accelerated deterioration of boiler tubes, leading to expensive and timeconsuming repairs. In addition, NOx production is inversely related to the production of CO 

from the boiler, and pursuing a NOx rate lower than the requested rate could increase CO 

production to the point that Flint Creek would need to accept restrictions on its maximum output 

rating and capacity factor in order to simultaneously achieve both its CO and NOx limits. 

While the requested emission rate is slightly higher than the highest averages achieved at similar 

units, some margin for compliance is necessary and desirable to accommodate the inherent 

variability of fuel supply, boiler tune-ups, and attributable to ordinary wear and tear of the 

equipment. Although the measured performance ofWyodak and Welsh Unit 2 confirms the 

likely achievability of the requested rate, their current permitted emission limits are as 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 BART 
the August 21,2013 email. Please contact me at (214) 777-1113 to provide any additional 

information you may require. 

Sincerely, 

1<?.4~ 

Kris Gaus, QEP 

Environmental Specialist 

Air Quality Services 

File:FLC.1 0.90.50.1 0.2013