Application for permits to install public sewers and water mains shall be made to the Service Director in such form as he or she may prescribe. The applicant shall deposit with the Finance Director a sum of money sufficient to cover the cost of any engineering surveys, plans or specifications, the cost of inspection and all other necessary costs which the City may incur. Any overplus shall be returned to the applicant. If the amount of such deposit is less than the cost of charges of the City, then the applicant shall reimburse the City for the difference.