In the event of approval of the use of individual subsurface disposal systems, the Planning Board or Zoning Board of Adjustment, as the case may be, additionally may require the installation of sewer lines, which must include connections to each building, for future use when public sewage treatment facilities are provided to serve the realty improvements to be constructed in the development, provided that this additional requirement shall not apply to developments within the MR, R-5, or MR/SI Districts.