I would consult the local governing body to see if they have any standards for such a requirement. But to give you an idea, the city of Detroit requires a minimum clear distance of 18" between any sewer and potable water line. The only way this requirement can be waived is if the water line is encased with concrete where it crosses the sewer. I have not heard of any other requirements for other utilities, but I would guess that there are other minimum space requirements from a constructibility standpoint. Good luck.