The City Planning Commission's designated representative shall forward copies of the preliminary plat to such officials and agencies as may be necessary for the purpose of study and recommendations. These shall include, at least, the City Engineer and the Logan soil and Water Conservation District. After the receipt of reports from such officials and agencies, the City Planning Commission shall determine whether the preliminary plat shall be approved, approved with modifications or disapproved. If a plat is disapproved, the reasons for such disapproval shall be stated in writing. The Commission shall act on the preliminary plat within thirty days after filing, unless such time is extended by agreement with the subdivider. When a preliminary plat has been approved by the Commission, the Chairman shall sign all copies and return one to the subdivider for compliance with final approval requirements. Approval of the preliminary plat shall not constitute approval of the final plat.