Stuck on Chapter 6 Haunted Dam

[Venom]

ok...you get to the dam with the tank...get out from the tank and go right on the ladder(or stairs, I don't remember), on top you will see an iron gate which closes another path...left from the gate theres a switch press it and the gate open's, go through the gate on the stairs press the other switch and the tunnel will open...Now go back to your tank and go in that tunnel.