Coal Plants May Get Scrubber Reprieve from Proposed EPA NAAQS Redesignations

The Environmental Protection Agency (EPA) has moved to redesignate four new areas of Missouri, Nebraska, Ohio, and Texas as being in attainment of air quality standards for sulfur dioxide (SO2). 

The proposed actions issued over the past week provide a potential reprieve for several coal power plants, which would have needed costly pollution controls to comply with the 2010 1-hour SO2 National Ambient Air Quality Standard (NAAQS) under the Clean Air Act. 

Over the past two weeks, the EPA has proposed to redesignate  to “attainment/unclassifiable,” portions of Franklin and St. Charles Counties in Missouri; all of Lancaster County in Nebraska; all of Gallia County and a portion of Meigs County in Ohio; an all of Milam County in Texas. 

The proposed actions stem from the EPA’s fourth round of intended area designations. In 2010, the agency finalized revisions to the 1971-promulgated primary SO2 standards, and established primary SO2 NAAQS at a level of 75 parts per billion (ppb)—which is essentially attained when the 3-year average of annual 99th percentile of daily maximum 1-hour average concentrations of SO2 does not exceed 75 ppb.

After promulgation of a new or revised NAAQS, each state governor can recommend air quality designations, and the EPA responds by formalizing area designations and boundaries for the NAAQS. While the EPA completed its initial round in July 2013, a federal district court in California ordered the EPA to complete all portions of the country by December 2020. The EPA then completed designations for most remaining areas of the country in Round 2 (December 2017) and Round 3 (March 2018).

Round 4, which relates to the EPA’s recent action, is the agency’s “final” round, meaning there will be no remaining undesignated areas for the 2010 SO2 NAAQS, if the proposed action is finalized by December 2020. 

The redesignations provided under Round 4 mainly stem from areas deemed “unclassifiable” in Round 2. “At that time, EPA did not have enough information to determine if these areas attained the 2010 standard for SO2. Since then, the states added additional monitoring to better understand air quality in those areas,” it said on Aug. 14. “EPA now has the three years of data required to determine that these areas are meeting the standards. If finalized, both Gallia and Meigs counties in Ohio will be in attainment for all NAAQS.” 

Among major plants affected are Ameren Missouri’s 2,372-MW Labadie Energy Center in the Franklin County-St. Charles County area. While the 1970-built plant is “the main source of SO2 in the area, the EPA said the area was characterized as unclassifiable in September 2015 because the EPA did not have enough information to determine if the standard was met. “To meet the standard, an area is assessed for the most recent three consecutive years of quality-assured, certified ambient air quality data,” it said. 

According to the EPA, Ameren installed and began operating an SO2 monitoring network at four locations around Labadie in order to characterize SO2 air quality in the area. “Since commencement of the full monitoring network in 2017, air quality data has recorded ambient SO2 design value concentrations between 18 and 38 parts per billion, below the SO2 1-hour standard of 75 parts per billion. Monitoring at the four locations demonstrates ambient conditions attaining the SO2 NAAQS,” the agency said on Aug. 10. 

In a statement sent to POWER earlier this week, U.S. Sen. Roy Blunt (R-Missouri) said the EPA’s redesignation was “great” for the state. “This decision by EPA will give local businesses more certainty to plan for the future, free up public resources and, most importantly, provide peace of mind to families in the area,” he said. 

While Ameren did not immediately respond to a request for comment, company documents note that under a 2017 integrated resource plan (IRP) filing, its Missouri subsidiary Ameren Missouri established a goal of reducing CO2 emissions 80% by 2050 from a 2005 base level. Ameren Missouri is also targeting a 35% CO2 emission reduction by 2030 and a 50% reduction by 2040 from the 2005 level. In order to meet those goals, the utility expects to retire its 5-GW coal-fired generation fleet at the end of each energy center’s useful life. “As indicated in the 2017 IRP, the Meramec, Sioux, Labadie, and Rush Island energy centers are expected to be retired in 2022, 2033, 2042, and 2045, respectively. The next integrated resource plan is expected to be filed in September 2020,” it says. 

Nebraska Public Power District’s (NPPD’s) 225-MW Sheldon Station power plant in Lancaster County, Nebraska, also got a reprieve. Like Labadie, while the plant is the main source of SO2 in the area, the “area was designated as unclassifiable in July 2016, because EPA did not have enough information to determine if the standard was met,” the EPA said.

Since the Nebraska Department of Environment and Energy (NDEE) installed a new SO2 monitor and began collecting data on Jan. 1, 2017, the monitoring has recorded “an ambient SO2 3-year design value of 29 parts per billion from January 2017 through December 2019, demonstrating monitored attainment well under the SO2 1-hour standard of 75 parts per billion. Subsequently, NDEE submitted a redesignation request in May 2020 that EPA is proposing to approve,” the EPA said. 

Sheldon, notably, is interesting because NPPD is working to install a project that could reduce the plant’s carbon emissions by converting it into a partial hydrogen-powered generator. In March 2020, NPPD’s newly appointed president and CEO said the first unit of a manufacturing facility that will provide the necessary  hydrogen is nearing completion “and will soon be in operation.” He added, “Our next step in this process is to complete the design and engineering of the conversion at Sheldon Station and eventually begin operations where hydrogen is used as a fuel in generating electricity and replacing coal.”

Also notably affected by the EPA’s proposed redesignation last week are Ohio Power Co.’s Gavin and Ohio Valley Electric Corp.’s Kyger Creek power plants in Gallia County. Data collected from 2017 to 2019 “demonstrated sulfur dioxide concentrations in the area are below the 2010 NAAQS for sulfur dioxide,” the EPA said. 

Sonal Patel is a POWER senior associate editor (@sonalcpatel, @POWERmagazine).

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