Respondent operated emergency engines subject to the RICE NESHAP and the CI ICE NSPS in violation of the operating limitations specified in 40 C.F.R. 63.6640(f)(4) and 40 C.F.R. 60.4211(f)(3) in order to conduct power substation improvements necessary to complete the installation of a natural gas-powered combined heat and power plant at the facility, located in Gurabo, PR.