Caithness Long Island (Caithness), LLC., is a 346 megawatt , dual fuel, combined-cycle electric generating station consisting of a combustion turbine generator, a heat recovery steam generator equipped with natural gas-fired duct burners, and a single steam turbine. The facility failed to comply with its permit emission limits for some potential operating scenarios including when the combustion turbine is firing on distillate oil with supplemental firing of the duct burner on natural gas. This ACO requires Caithness to conduct and report on performance tests by January 31, 2010 in order to demonstrate compliance with these operating scenarios and prohibits the facility from operating in these modes until compliance has been demonstrated.