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### Medina, Dayana

From: Pettyjohn, Mary <PETTYJOHN@adeq.state.ar.us>

Sent: Monday, March 04, 2013 8:18 AM

To: Medina, Dayana Subject: FW: Region 6 Comments on Flint Creek BART



### FYI

From: kpgaus@aep.com [mailto:kpgaus@aep.com]

Sent: Friday, March 01, 2013 10:36 AM

To: Pettyjohn, Mary

Cc: tbbond@aep.com; bwmoore@aep.com; jchendricks @aep.com; jjhenry@aep.com; scarney@aep.com; cfhandley@aep.com; wemast@aep.com; kjmunson@aep.com; jmmcmanus@aep.com ; jjewell@trinityconsultants.com; kdubbs@trinityconsultants.com Subject: Fw: Region 6 Comments on Flint Creek BART

Mary,

Thanks for passing these comments along. Incorporating t he requests outlined in the "Modeling and Emission Estimates" comment will take us a week or two since it necessitates redoing all the modeling. We will submit a revised report when this is finished. In the meantime, we offer the following responses to the other comments.

It is critical to understand that the BART analysis and the PSC testimony are using two different bases and therefore comparing the control efficiency values is not apples to apples. The PSC testimony discusses the maximum design capability based on the "design basis fuel" (i.e., potential emissi ons) whereas the BART analysis is based, as required, on the actual average baseline (2001 - 2003) emission rate and projected unit performance. Moreover, as stated in the BART report, the vendor estimates used to develop the cost-e ffectiveness calculations are based on an outlet emission rate (0.06 lb/MMBtu) - to apply at all times (using any fuel) - not a constant control efficiency value.

As we pointed out when responding to your question about a potential 99 % contro l efficiency, EPA provided a discussion related to scrubbing removal efficiencies and proposed BART SO2 emission limits appropriate for BART modeling purposes in their December 28, 2011 Oklahoma FIP for regi onal haze requirements. In that discussion (page 81742) EPA notes that, although a dry FGD can be designed to achieve 95% SO2 removal efficiency, resulting in an emission rate of 0.045 lb/MMBtu SO2, an emission rate of 0.06 lb/MMBtu was the appropriate value to use for visibility modeling. The 0.06 lb/MMBtu value equates to a 93% removal efficiency and is obviously less than the design basis for a dry FGD. EPA based their decision to use the 0.06 lb/MMBtu em ission rate on “a thorough revi ew of achievable emission rates of current Dry Flue Gas Desulfurization (DFGD) scr ubbers.” Therefore, the design removal efficiency for the equipment is not the appropriate value to use to calc ulate an emission rate for regional haze modeling.

We will be providing additional cost evaluation information to respond to questions you forwarded from EPA on 2/25/13.

We feel that the proposed 0.23 lb/MMBtu NOx BART limitati on provides for an appropriate margin of compliance when compared to an expected actual emission rate of 0.18 to 0.22 lb /MMBtu. This margin is less than that allowed for by EPA for SO2 emissions in Oklahoma (see above comparison between 0.045 and 0.06 lb/MMBtu).

The PM emission rate has been approved in EPA's prior rulemaking. Since the PM BART determination has already been approved, it is not appropriate to re-visit PM.

Please contact me if you have any questions.

Kris Gaus, QEP

American Electric Power Air Quality Services
office: 214/777-1113
fax: 214/777-1138