Upon the completion of the work under any contract authorized by sections 14-528 to 14-532, the city council of a city of the metropolitan class is authorized to levy and assess, in the usual manner, special taxes and assessments to the extent of benefits conferred by such work to pay the costs of the improvements less the amount of proper intersection costs under such contract, all of which taxes and special assessments shall constitute a sinking fund, as and for the purposes specified in section 14-530.