high voltage electrical & water supply line

I'm guessing by "high voltage" you mean the service drop to your house, which is 120/240 V. yes it is done where I live. water lines are buried at seven feet below grade, and electric service is laid on a "shelf" on the side of the trench. for the real scoop though, call your local electrical inspector.

bodega wrote:

As long as you can maintain 12" of clearance between the utilities, they can all be installed in the same trench.

As long as you can maintain 12" of clearance between all utilities, they can go in the same trench. We routinely run 13.2 KV primary cable (in conduit) in the same trench as water, telephone, CATV, and gas ... in Florida. Best bet is to check with your power company and see if they require greater clearance. Some utilities have their own standards which exceed the NESC requirements.