Customer has built a new garage that has an upstairs room with a bathroom and is having water and sewage run to the building. The plumber has dug a 4 foot deep trench to run his waste and water pipes--both plastic. I am going to put a 100Amp subpanel in the building. I know my conduit needs to be 2 feet deep, but can I put it in the same trench? Do I have to have an offset of a certain amount..I have received different answers from different electricians and local code officers. Also, do? I need a ground rod at the outbuilding? When I did a subpanel in a garage a few years ago the inspector said I only needed a ground wire if it was fed by only 3 wires. If 4 were used I didnt need it..