U.S. EPA Strengthens Sulfur Dioxide Air Quality Standard

On June 2, 2010, the U.S. Environmental Protection Agency (U.S. EPA) strengthened the sulfur dioxide (SO₂) national ambient air quality standard (NAAQS) by establishing a new 1-hour standard at a level of 75 parts per billion (ppb). This new NAAQS will be met when the 99^th percentile daily maximum 1-hour SO₂ concentration, averaged over three years does not exceed 75 ppb. It applies only to the “primary” standard that is set to protect public health. To determine compliance, U.S. EPA intends to use monitoring and refined dispersion modeling of SO₂ sources. U.S. EPA is also revoking both the existing daily and annual primary SO₂ standards but is not revising the “secondary” standard at this time. U.S. EPA is obligated under a consent decree to complete its review of the secondary SO₂ NAAQS, which is set to protect the environment and public welfare, in 2012. U.S. EPA’s timeline and plans for designations and implementation of the revised SO₂ primary NAAQS are set forth in the final rule. In addition, U.S. EPA is establishing requirements for an SO₂ monitoring network. Because U.S. EPA is taking a hybrid approach that combines monitoring and modeling, the number of new monitoring sites that will need to be established is drastically less than the number originally proposed. For the pre-publication version of the new SO₂ NAAQS, click here.

 

U.S. EPA intends to complete designations in June 2012. Initial designations will be based on 2008-2010 air quality monitoring data, or refined dispersion modeling results if provided by the state. Areas that do not meet the standard will be designated “nonattainment”. Areas that have both monitoring data and appropriate refined modeling results showing no violations will be designated “attainment”.   All other areas will be designated “unclassifiable”. 

 

This approach to SO₂ designations is consistent with U.S. EPA’s historical approach to SO₂ designations but is different from the approach U.S. EPA initially proposed. It is also different from how U.S. EPA has determined whether an area is violating other NAAQS pollutants. For NAAQS pollutants other than SO₂, such as ozone and fine particulate matter, U.S. EPA considers air quality monitoring more appropriate than refined modeling for determining whether all areas are attaining the NAAQS.

 

Based upon 2007-2009 air quality monitoring data, the following counties in West Virginia have monitors currently violating the revised SO₂ standard of 75 ppb: Brooke, Hancock, Kanawha, Marshall, Monongalia, and Wood. For a map and a table of the counties with monitors currently violating the revised SO₂ NAAQS, click here and here. It should be noted that pursuant to the provisions of the Clean Air Act, the boundaries of the SO₂ nonattainment areas will likely include more counties than just the counties with the violating monitors.

 

States with areas designated nonattainment in 2012 are required to submit to U.S. EPA by early 2014 state implementation plans (SIPs) setting forth air pollution control requirements and other actions that will be taken to meet the new 1-hour SO₂ standard. The Clean Air Act requires nonattainment areas to meet the standards “as soon as practicable,” but no later than August 2017.

 

For all other areas, states are required to submit to U.S. EPA by June 2013 infrastructure SIPs. These SIPs demonstrate that the state has the “infrastructure” in place to implement a new or revised NAAQS and include provisions such as an ambient air quality monitoring/data system; program for enforcement of control measures; adequate resources; stationary source monitoring system; emergency power; future SIP revisions; consultation with government officials; public notification; PSD and visibility protection; air quality modeling/data; permitting fees; and consultation/participation by affected local entities. 

 

Further, U.S. EPA expects the states’ infrastructure SIPs to: (1) “demonstrate, through refined air quality modeling, that all sources contributing to monitored and modeled violations of the new standard, or that have the potential to cause or contribute to a violation, will be sufficiently controlled” to achieve and maintain new SO₂ standard as expeditiously as possible, but no later than August 2017; (2) “account for SO₂ reductions that would result from compliance with national and regional regulations, including emissions controls for electric utilities and industrial boilers”; and (3) “include enforceable emissions limitations, timetables for compliance, and appropriate testing/reporting to assure compliance.” 

 

U.S. EPA is also revising the SO₂ monitoring network and setting specific minimum requirements on where states must place SO₂ monitors. Specifically, U.S. EPA is requiring monitors to be placed in Core Based Statistical Areas (CBSAs) based on a population weighted emissions index for the area. In the proposal, U.S. EPA proposed a monitoring-focused approach to SO₂ designations which would have required approximately 348 monitors nationwide to be sited at the locations of maximum concentration. Because U.S. EPA decided to use a hybrid approach combining the use of monitoring and modeling to assess compliance, U.S. EPA estimates that only 41 new monitoring sites will need to be established nationwide. All newly sited monitors must be operational by January 1, 2013, which is after the date for designations.

 

The following CBSAs in West Virginia require one monitor: Charleston, WV; Morgantown, WV; Parkersburg-Marietta-Vienna, WV-OH; and Point Pleasant, WV-OH. The Washington-Arlington-Alexandria, DC-VA-MD-WV CBSA requires three monitors. For a map and a table of the monitoring requirements for the revised primary SO₂ standard nationwide, click here and here.

 

U.S. EPA plans “to use modeling as the principal means of assessing compliance for medium to larger sources, and to rely more on monitoring for groups of smaller sources and sources not as conducive to modeling.” U.S. EPA promises to issue guidance on conducting refined air quality dispersion modeling and address, among other issues, “how to translate modeling results into a form appropriate for comparison to the new standard, and how to identify and appropriately assess the air quality impacts of SO₂ sources that may potentially cause or contribute to a violation of the new standard.”

 

This article was authored by Gale Lea Rubrecht, Jackson Kelly PLLC. For more information on the author, see here.