1 Evaluation of Point Source Sensitivity Runs for the State of North Carolina

The existing ozone (O3) standard is an 8-hour standard set to protect public health from short-term and prolonged exposures to O3. The design value for ozone is defined as: a 3-year average of the annual 4 th highest daily maximum 8-hour average. If a monitored design value is> 0.084 ppm (84 ppb), that monitor is violating the standard. In the North Carolina Metrolina (Mecklenburg, Union, Gaston, Rowan, Iredell, Lincoln, and Cabarrus Counties) nonattainment area, three monitors were violating the 8-hour ozone standard at the end of the 2006 ozone season. There are eight monitors in the Metrolina area with design values (for the 2004-2006 3-year period) ranging from 0.076 ppm to 0.088 ppm for 2006 ozone season. The North Carolina Division of Air Quality (NCDAQ) is required to submit an attainment demonstration plan (State Implementation Plan) to the U S Environmental Protection Agency (US EPA) in June 2007 for the Metrolina nonattainment area that details the State’s plan to bring the area into attainment of the Federal standard. This analysis must estimate whether selected emissions reductions will result in ambient concentrations meeting the National Ambient Air Quality Standards (NAAQS) for ozone. It must identify a set of control measures that will result in the required emissions reductions. Considering the controls that are planned for the major utilities, the NCDAQ conducted a series of sensitivity runs for their power plant point sources to show how additional reductions would impact future design values. The results show that the model was relatively stiff considering large emission changes