It seemed a bit like overkill, since Rourke had already planned to wash away the docks with his tidal wave.
Well, looking back, it does appear to have been the prudent choice. Still failed, though.
Harrington claimed to be undercover on a sting operation to catch Rourke and had been found out, which was why he had been tied up inside the warehouse; a statement neither Lois nor Clark placed any credence in.

Michael