You must first cut the wire that leads to the Primer, followed by the Reactor wire, and finally the wire that feeds the Ignition Timer. You are equipped with a pair of wire cutters and a splicer. Be carefun, as clipping the wrong wire accelerates the detonation time.
You are surrounded by 50 gallon steel drums full of highly explosive toxic waste
GameSpot's Game Guide to Twilight Princess has a full walkthrough, with videos for each boss fight, as well as a list of all the Pieces of Heart in the game!