Power Mole - one method to consider. Check out the link to see how it works. http://powermole.com/
I used a company here in GA to install a 2 inch PVC pipe under a 20 foot driveway using their power mole. They push a rod with a transmitter in the head so they can track and adjust the direction. The rod is in sections about 3 feet long so they can keep adding as needed. It came out exactly where planned. When they pull back the rod it leave a hole for the PVC. It took them about 3 hours to dig, push, install the PVC and clean up.
This was in 2006 and the cost was $500.
Al / NN4ZZ