12/13/2012

EPA Region 6 feedback on AECC Ba iley and McClellan- SO2 and PM BART

 In our August 2012 conference call, AECC expl ained that in the October 2006 SO2 BART analysis for the Bailey and Mc Clellan plants, the permit limits (fuel oil with 2.3% and 2.8% sulfur) were used as the base case for the sulfur content of fuel oil burn ed. In the revised draft BART analysis, AECC used historical averages of actual sulfur content of fuel oil burned as the new base case (fuel oil with 1.81% and 1.38% sulfur). AECC explai ned that the new base case is very close to (and more representative of ) the actual SO2 emissions during the 2001-2003 baseline period than are the permit limits. Region 6 asked AECC to include in the BART analysis this justification for using the new base case and to provide documentation of the historical actual sulfur content of fuel oil bu rned at the two units.

 On the conference call, Region 6 pointed out that AECC’s revised cost analysis for switching to a different fuel type is in consistent with AECC’s Octobe r 2006 analysis and with the documented cost-differential of swit ching from greater than 1% to less than 1% fuel oil at other comparable units. AECC explained that the revi sed cost analysis was based on a very limited number of fuel oil purchases ma de by the facility and that the inconsistency between the revised analysis and the October 2006 analysis is primaril y due to market fluctuations. It appears that AECC based the revised cost analysis on the actual price paid for a very limited number of fuel oil purchases made in past years, which may have resulted in outdated fu el oil cost numbers and an overestimation of the cost of fuel oil when compared to the cost in today’s market. Region 6 asked AECC to obtain vendor quotes for the current cost of all evaluated fuels, including the currently used fuel, and include th is in the BART analysis, and to update the cost analysis using the cost numbers obtained from the vendor’s quote.

 EPA expressed concern about th e following statement made on page 5-12 of AECC’s revised draft BART analysis for SO2: “When the BART limits become effective, Bailey and McClellan would burn the existing supply of No. 6 fuel oil as the normal course of business dictates. Future fuel purchases will be fuels of 0.5% sulfur content or less.” On the conference call, AECC
clarified that its current fuel oil supply is for 100 days or less and that the Bailey and McClellan units would be able to comply with BART as expeditiously as practicab le, but no later than 5 years from approval of BART. We recommend that to avoid confusion, AECC either remove the above quoted statement from the BART report or revise the language to make the statement consistent with the compliance requiremen ts under 40 CFR section 51.308(e)(1)(iv) of the regional haze regulations. We remind ADEQ th at Chapter 15 of Regulation No. 19 of the Arkansas Pollution Control and Ecology Commi ssion (APCEC), also known as Arkansas’s regional haze rule, must also be consistent with the compliance requirements under 40 CFR section 51.308(e)(1)(iv) and that under 40 CFR section 51.230 the state must have the legal authority to enforce all regulat ions submitted into the SIP.

 Concerning the bullet point above, we remind AD EQ that in our March 12, 2012, final action on the Arkansas RH SIP (see 77 FR 14655) we pa rtially approved and partially disapproved APCEC Reg. 19.1504(B), which provides that “Eac h source subject-to-BART shall install and operate BART as expeditiously as practicable, but in no event later than 6 years after the effective date of this regulation or 5 years af ter EPA approval of the Arkansas Regional Haze12/13/2012

State Implementation Plan, whichever comes fi rst.” Our final partial disapproval of Reg. 19.1504(B) applied to that portion of the regu lation that requires compliance with BART requirements no later than six years after the effective date of the State’s regulation (if such date takes place before five years from EPA approval of the Arkansas RH SIP). As explained in our final action, the partial disa pproval was because in March 26, 2010, the APCEC issued Minute Order No. 10-08, granting all Arkansas subject-to -BART sources a variance from the compliance deadline imposed by APCEC Reg. 19.1504(B). Alt hough we believe the compliance timeframe in Reg. 19.1504(B) is consistent with the requirements under 40 CFR 51.308(e)(iv), because of the variance granted to all Arkansas subject to BART sources (which has never been submitted into the SIP), the State of Arkansas does not have the legal authority to enforce compliance within the timeframe required by Reg. 19.1504(B). Specifically, Arkansas currently does not have the authority to enforce compliance with BART within six years after the effective date of its regulation. 40 CFR section 51.230 requires that a state must show it has the legal authority to enforce a rule that is submitted as part of the SIP. Our recommendation to ADEQ is that Reg. 19.1504(B) be revised such that it is consistent with the co mpliance requirements under 40 CFR section 51.308(e)(1)(iv) and such that the State has the legal authority to enforce the regulation submitted into the SIP. Alternatively, we r ecommend that Minute Order No. 10-08 granting
Arkansas BART sources a variance from th e compliance deadline imposed by Reg. 19.1504(B) be submitted as part of the SIP.

 On the conference call, AECC agreed to follo w up with Region 6 on several concerns we expressed regarding the emission rates used in the modeling analysis. Se ction 1 of the BART analysis states that the pre-control visibility impairment of each unit is based on modeling of emission rates that were derived from stack te sting, CEMS, and AP-42 em ission factors. Section 4-1 explains that the SO 2 and NOx emission rates modeled are actual maximum 24-hour emission rates based on CEMS data and that the PM 10 emission rates modeled are based on maximum burner capacities using AP-42 emission factors. However, it is unclear how stack testing was used to derive any of the emissi on rates modeled. The SO2 emission rates and the revised NOx baseline emission ra tes appear to be consistent with the maximum daily emission rates during the baseline period of 2001-2003. The revised PM emi ssion rates are significantly lower than those used in the original BART anal ysis (summarized in the table below) and appear to be inconsistent with AP-42 emission factor s and the maximum burner capacities. The source should explain the revised PM emission rates a nd provide emission estima tion calculations.

AECC BART engineering analysis, October 20, 2006

Unit SO2 NOx PM(modeled values for PMc and PMf) g/s lb/hr g/s lb/hr g/s lb/hr Bailey Unit
1 299.34 2375.75 36.93 293.1 21.73 172.46

McClellan Unit 1 346.19 2747.56 47.12 373.97 28.76 228.2612/13/2012

Revised AECC BART baseline modeling

Unit SO2 NOx Total PM10 (speciated into PMc, PMf, EC, and SOA) g/s lb/hr g/s lb/hr g/s lb/hr Bailey Unit
1 299.34 2375.8 51.51 408.8 6.22 49.4

McClellan Unit 1 346.19 2747.5 73.05 579.8 6.07 48.2

 Visibility modeling of fuel sw itching scenarios should include the decrease in PM emissions anticipated from switching to lower sulfur fuels. While visibility impacts from PM are relatively small, visibility benefits from decreases in PM em issions as a result of fuel switching should be accounted for. Region 6 asked AECC to include in the BART analysis a brief discussion of the impact of reductions of PM emissions on visibility to address this.

 In calculating the SO2 emission ra tes to model to reflect fuel switching, the maximum emission rate from the baseline period should be used rather than the average. Additionally, the sulfur
content used to scale this emission rate should be representative of the sulf ur content of the fuel burned during the same baseline period and reflec ted in the baseline emission rate. There also appears to be an error in the ratio used in the calculation as shown on page 5-8. If AECC chooses not to re-model using the maximum SO2 emi ssion rates at this time, then a justification should be provided explaining what impact if a ny using the maximum emission rates would have on the modeling results and the ultimate BART determination

 The source should include a plot showing the meteorological modeling domain, computational modeling domain, location of sources, and Class I ar ea receptor locations us ed in the visibility analysis.