In levying special assessments to pay any part of the cost of any public work or improvement, the Council shall not exceed any limitation as to the amount thereof which is now prescribed by the general laws of the State applicable to municipalities. Unless for special reason which shall be stated in the ordinance levying an assessment or providing for the issue of bonds to pay any part of the cost of any such improvement to be made pursuant to contract, no such ordinance shall be passed, or assessment levied, or money borrowed, until sealed competitive bids for the labor and material have been received and the approximate cost of the improvement determined.