Docket No. EO-05-01. This report describes dispersion modeling performed for Unit 4 at Mirant's Potomac River Generating Station. The modeling was performed according to the Protocol approved by the Virginia Deparment of Environmental Quality. The purpose of the modeling was to demonstrate that Unit 4, operating alone under minimum and maximum loads will not cause or contribute to exceedances of the National Ambient Air Quality Standards (NAAQS).