New Jersey Statutes Title 48. Public Utilities 48 § 14-2

Pipes and conduits shall be laid at least 3 feet below the surface and shall not unnecessarily interfere with public travel or damage public or private property.

They shall be laid at least 3 feet from the outside of any water or gas pipe already laid, except when it shall be necessary to cross, in which case they shall be at least 12 inches from the outside of the water or gas pipe.