The applicant shall pay the entire cost of the line extension and shall deposit with the Treasurer a sum equal to the City's estimated cost. If it subsequently appears that the cost will exceed the amount deposited, additional deposits may be required. Upon completion of the extension the City Engineer shall submit an itemized statement of the entire cost of the extension to the City and to the applicant, and any balance due to or from the applicant shall be paid forthwith. (1965 Code §22-14)