Notwithstanding any provision of this ordinance to the contrary, structures, signs, infrastructure, buildings and land may be installed, constructed, reconstructed, rehabilitated, rebuilt, enlarged, erected or used in the exercise of a governmental function of the Town of Narragansett in any zoning district in the town, and said structures, signs, infrastructure, buildings and land so installed, erected, constructed, reconstructed, rehabilitated, rebuilt, enlarged or used shall be exempt from the provisions of this ordinance; provided, however, that this exemption shall only apply to structures, signs, infrastructure, buildings and land used for or related to the providing of water and wastewater services to the inhabitants of the Town of Narragansett and, with respect to wastewater treatment plants, this exemption shall only apply to construction, reconstruction, rehabilitation, enlargement, or expansion of the Westmoreland Street regional wastewater treatment plant and the Scarborough wastewater treatment plant.