Battery for elevator
When you return to the mansion after you get finished with the guardhouse and fight the big snake the second time Barry will give you a passcode for the door near the storeroom where you find the serum for Richard. Wait until he drops a new rope and climb up it and he will give you the pass code then go and enter it in the door and go through it there will be zombies so be careful and follow the hallway and you will come up on the elevator shaft and there will be a door to your left and it is a closet the battery to the elevator in the garden is in there along with two packs of grenade rounds. But when you go to put the battery in the place where it goes go back up on that elevator and (don't forget to bring the crank with you) go to the place where you opened the water gate so you could walk across and close it and it will shut off the waterfall and you will find the tunnels. Good luck hope this helps you out.
Added by: teddybear2 Oct 30th 2008, ID#15417