The Forgotten Wells (1989)

A TV team ends up at an old farm to make a film about the place. At the same time a couple of armed desperados come to the farm and the trouble begins. The hero must rip off his shirt, take an UZI from the van and enter the series of sewers under the farm to rescue his friends. Down in the sewers lives a man who has lived down there since he was a kid. Now he is a psychotic half beast half man murder machine.