All utility lines and necessary appurtenances including, but not limited to, electric transmission and electric, gas and water distribution, communications, street lighting and cable television, shall be installed underground within easements or dedicated public rights-of-way. The developer shall arrange with the serving utility for the underground installation of the utilities supply lines and service connections in accordance with the provisions of the applicable standard terms and conditions of its tariff as the same are then on file with the State of New Jersey Board of Public Utility Commissioners and shall submit to the planning board prior to the granting of approval a written instrument from each serving utility which shall evidence full compliance with the provisions of this section; provided, however, that lots which abut existing easements or public rights-of-way where overhead utility lines have theretofore been installed may be supplied with service from such overhead lines if no new utility poles are required. In any event, new building service connections for all multi-family developments, and for any industrial, commercial or office development containing a floor area of 10,000 square feet or more, shall be installed underground. All other new building service connections shall also be installed underground unless specific waiver is granted by the planning board. Wherever the utility is not installed in the public right-of-way, an appropriate utility easement not less than 25 feet in width shall be provided.