Lakel I priced a well for just the same reason. The trinity aquafer where I have my pond is about 700 feet deep. Going that deep for that much water with a seven horse pump was going to cost around eighty thousand dollars. I think he said one of the biggest factors in the cost was the size of the steel casing needing to be eight inches. The guy that I had price it for me drills water wells for the gas companies. Needless to say I didn't do it.
