U.S. Environmental Protection Agency Proposes Transport Rule To Reduce Interstate Transport of Air Pollution

August 17, 2010

On July 6, 2010 the U.S. Environmental Protection Agency (EPA) proposed a rule to address interstate transport of air pollution.  This proposed rule would replace the 2005 Clean Air Interstate Rule (CAIR).  The proposed rule, known as the Transport Rule, would require 31 states and the District of Columbia to improve air quality by reducing emissions of sulfur dioxide (SO2) and nitrogen oxide (NOx) emissions from electric generating power plants that contribute to ozone and fine particulate pollution in other states.  SO2 and NOx react in the atmosphere to form fine particulate matter less than 2.5 micron (PM2.5).  NOx also contributes to ozone formation.  The SO2 and NOx are then transported across states, making it difficult for states downwind to comply with National Ambient Air Quality Standards (NAAQS).

This proposed rule would clarify state obligations to reduce pollution affecting other states under the Clean Air Act by defining “significant contribution” and “interfere with maintenance.” In defining these obligations, the EPA proposes to consider the magnitude of a state’s contribution, the air quality benefits of reductions, and the cost of controlling pollution from various sources.

The emission reductions are scheduled to begin in 2012, within one year after the rule is finalized.  EPA estimates that by 2014, in conjunction with other state and federal programs, that emissions of SO2 and NOx from power plants would be reduced by 71 and 52 percent, respectively from 2005 levels.  Compared to 2005, EPA estimates that by 2014 this proposal and other federal rules would lower emissions by:

  • 6.3 million tons per year of SO2
  • 1.4 million tons per year of NOX, including 300,000 tons per year of NOX during the ozone season.

The proposed rule is expected to annually cost electric utilities and consumers $2.8 billion, but is expected by EPA to yield $120 to $290 billion in annual health and welfare benefits in 2014.  EPA also estimates that between 14,000 to 36,000 premature deaths will be avoided.

The rule specifies  that twenty-eight states would be required to achieve reductions in both SO2 and NOx emissions to assist downwind states in meeting attainment with the annual and 24-hour PM2.5 standards.  Furthermore, the rule requires twenty-six states to reduce NOx emissions during the ozone season to assist downwind states in reducing ground-level ozone concentrations in order to comply with the ground-level ozone standard.  The following map identifies the states subject to the rule and the emissions to be controlled.

US map of transport rule
Proposed transport rule coverage

EPA’s approach for reducing SO2 and NOX emissions in states covered by this rule is to set a pollution limit (or budget) for each of the 31 states and the District of Columbia. This approach allows limited interstate trading among power plants but assures that each state will meet its pollution control obligations.

EPA is also taking comments on two alternative approaches. The first alternative would set a pollution limit or budget for each state. This option allows trading only among power plants within a state.  The second alternative would set a pollution limit for each state and specify the allowable emission limit for each power plant and allow some averagingof the emissions.

To assure emissions reductions, EPA is proposing Federal Implementation Plans, or FIPs, for each of the states covered by this rule. The FIPs would put in place requirements necessary to reduce pollution in the covered states that significantly contributes to nonattainment of or interferes with maintenance of the national ambient air quality standards in other states.

States may choose to develop a State Implementation Plan (SIP) to achieve the required reductions, replacing its federal plan.

In order to achieve emission reductions outlined in the Transport Rule, power plants may be required to:

  • operate already installed air pollution control equipment more frequently,
  • use low sulfur coal, or
  • install control equipment such as low NOx burners, Selective Catalytic Reduction, or Flue Gas Desulfurization.

If your facility will be affected by the Transport Rule, or if you have questions regarding the rule, please contact CEC’s St. Louis office at 866-250-3679.

About the Author

CEC Staff

Headquartered in Pittsburgh, Civil & Environmental Consultants, Inc. (CEC) provides comprehensive market-oriented consulting services to advance client strategic business objectives. CEC is recognized for delivering innovative design solutions and integrated expertise in air quality, civil engineering, ecological sciences, environmental engineering and sciences, manufacturing infrastructure services, survey/geospatial, waste management, and water resources.

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