A system including: a HEP generator creating HEP generator exhaust; a prime engine creating prime engine exhaust; a SCR system through which the prime engine exhaust and the HEP generator exhaust run; an HEP generator exhaust pipe running from the HEP generator to an exhaust mixing duct where the HEP generator exhaust is mixed with the prime engine exhaust, wherein the HEP generator exhaust pipe discharges into the exhaust mixing duct at a distance from the SCR less than ten times the diameter of the exhaust mixing duct; and a single urea injector injecting urea into the HEP generator exhaust pipe at a distance from the exhaust mixing duct of more than ten diameters of the HEP generator exhaust pipe.