With new, tighter SO2 emissions limits in place for Vectren‘s (NYSE: VVC) coal-fired A.B. Brown power plant, the U.S. Environmental Protection Agency has decided to declare the area around the Indiana plant to be in attainment under the SO2 NAAQS program.
EPA on Feb. 16 sent a number of letters to different states, including, Indiana, with preliminary decisions about specific areas within each of those states over SO2 NAAQS compliance.
Under section 107(d) of the Clean Air Act (CAA), EPA must designate areas as either “unclassifiable,” “attainment,” or “nonattainment” for the 2010 one-hour sulfur dioxide (SO2) primary national ambient air quality standard (NAAQS). The CAA defines a nonattainment area as one that does not meet the NAAQS or that contributes to a violation in a nearby area. An attainment area is defined as any area other than a nonattainment area that meets the NAAQS. Consistent with past practice, EPA intends to designate areas demonstrated or reasonably presumed to be attaining as “unclassifiable/attainment.” Unclassifiable areas are defined as those that cannot be classified on the basis of available information as meeting or not meeting the NAAQS.
Indiana submitted updated recommendations to EPA in September 2015, ahead of a July 2, 2016, deadline for EPA to designate certain areas established by the U.S. District Court for the Northern District of California in a decision in a lawsuit brought by environmental groups. This deadline is the first of three deadlines established by the court for EPA to complete area designations for the 2010 SO2 NAAQS.
Posey County, Indiana, contains a stationary source that according to EPA’s Air Markets Database emitted in 2012 either more than 16,000 tons of SO2 in 2012 or more than 2,600 tons of SO2 and had an annual average emission rate of at least 0.45 pounds of SO2 per one million British thermal units (lbs SO2/MMBTU). As of March 2, 2015, this stationary source had not met the specific requirements for being “announced for retirement,” which would exclude it from this process.
Specifically, Vectren’s A.B. Brown Generating Station emitted 7,091 tons of SO2 in 2012, and had an emissions rate of 0.521 lbs SO2/MMBTU in 2012. Pursuant to the March 2, 2015 court-ordered schedule, EPA must designate the area surrounding the facility by July 2, 2016.
A.B. Brown is located in southwestern Indiana in the southeastern portion of Posey County, near the borders of Posey with Vanderburgh County in Indiana, to the east, and Henderson County in Kentucky, to the south. It has two coal-fired units with 245 MW of capacity for each unit.
In its submission, Indiana recommended that the area surrounding A.B. Brown, specifically the entirety of Posey County, be designated as attainment based on an assessment and characterization of air quality from the facility and other nearby sources which may have a potential impact in the area of analysis where maximum concentrations of SO2 are expected. This assessment and characterization was performed using air dispersion modeling software, i.e., AERMOD. Indiana’s submittal states that modeling using A.B. Brown’s actual emissions indicated a violation of the SO2 standard, but modeling with the new limits identified in the submittal indicated that the area would attain the standard once A.B. Brown complied with those limits.
Subsequently, on Jan. 27, 2016, Indiana submitted a draft request for a revision to its state implementation plan (SIP) to establish new emission limits for A.B. Brown. Indiana’s submittal includes a signed commissioner’s order establishing these limits, issued on Jan. 11, 2016, along with evidence that Indiana has initiated the public comment process necessary for these limits to be approved as revisions to Indiana’s SIP. Indiana’s submittal also includes AERMOD modeling to demonstrate that these limits would provide for attainment of the SO2 NAAQS in the area of A.B. Brown.
Said a technical document supporting EPA’s Feb. 16 letter to the state: “EPA has reviewed this modeling and agrees that these limits would provide for attainment. EPA has signed a rulemaking notice proposing to approve these limits. EPA anticipates that Indiana will submit a final request to incorporate these limits into the SIP in the near future, once the state has completed its public comment process, and EPA anticipates completing its rulemaking on this request within the next few months.
“The limits necessary to provide for attainment in the A.B. Brown area are not presently federally enforceable. Therefore, EPA cannot consider the prospective impact of these limits. Indiana’s modeling suggests that current air quality violates the standard, and so EPA must express an intention to designate the area around A.B. Brown as nonattainment. However, if EPA has approved these limits into the SIP before it takes final action on the designation for the A.B. Brown area, EPA anticipates designating the area unclassifiable/attainment.”
For A.B. Brown, the modeling submitted initially by the state used allowable emissions of 0.164 lbs/MMBTU (1,809 tons/year) for Unit 1 and 0.69 lbs/MMBTU (7,673 tons/year) for Unit 2. However, pursuant to further discussions between Indiana and Vectren, the commissioner’s order required slightly different emission limits. Both sets of modeling relied on an emission limit of 0.69 lbs/MMBTU for Unit 2, a limit that has been established through and permit issued for prevention of significant deterioration (PSD) purposes. However, the issued commissioner’s order established limits on Unit 1 emissions for three scenarios.
- For the first scenario, in which only Unit 1 is operating, the order established limits of 2152.2 lbs/hour and 0.855 lbs/MMBTU, which allows annual emissions from this unit of 9,427 tons/year.
- For the second scenario, in which both units are operating, the order established limits on total emissions from the two units of 2152.2 lbs/hour and 0.426 lbs/MMBTU.
- For a third scenario, in which only Unit 2 is operating, the facility is already subject to a limit in a PSD permit limiting emissions to 0.69 lbs/MMBTU (1745.7 lbs/hour, corresponding to an annual maximum of 7,646 tons/year).
Indiana has provided modeling of all of these scenarios under worst case operations to demonstrate that this set of limits assures attainment for all feasible operating modes. Since Unit 2 has more impact at the critical receptors than Unit 1, Indiana imposed different limits for different operating scenarios because this approach allows more flexibility in the degree of control and operation of the two units while still providing for attainment.