The Town Board shall refer all applications for a change of zoning to the Planned Residential Development District to the Planning Board for a recommendation and report. Within 45 days after such reference, the Planning Board shall file with the Town Board its recommendation and report. The Town Board shall determine whether there shall be dedication of land to be set aside as open space, and if in the Town Board's opinion, it is in the interest of the general public due to topography, historical interest, natural features, unusual conditions or for ecological reasons, such open space shall then be so included and shown. If the Town Board does make such a requirement, a minimum of 10% of the land shall be so designated and dedicated to the Town of Smithtown as open space as part of the platted area.