Larry, I would use entrim or pex piping to put the heat in the drive.you will need zones as you will not be abe to do it all in one loop. This system should be sized by an expert.the depth can be about 4" or you can pour the asphalt right over the tubing. Keep pressure in the lines and keep an eye on the guage to check for leaks as you pour.the tubing should be 1' apart. entrim is a soft rubber type tubing.Ted turner has about a mile of it installed in his ranch home in wyoming. Dale Peck LMP