Before voting on the enactment of an amendment, the Board of Commissioners shall hold a public hearing thereon, pursuant to public notice, published once a week for two successive weeks in a newspaper of general circulation, with the first publication being not more than 30 days prior to the date of the proposed hearing and the second publication not less than seven days prior to the date of the proposed hearing. In addition, if the proposed amendment involves a Zoning Map change, notice of said public hearing shall be conspicuously posted by the Zoning Officer at such points along the perimeter of the tract sufficient to notify potentially interested persons of the proposed change. The affected tract or area shall be posted at least one week prior to the date of the hearing.