The City Engineer or a licensed professional engineer or engineering firm hired by the city shall be responsible for the inspection of all public or dedicated planned development district street and utility improvements to insure conformance with the approved plans and specifications. The applicant shall deposit an inspection fee in the amount of two and a half percent (2 1/2%) of the estimated cost of construction. The inspection fee shall be based on the actual cost of labor, materials, and equipment plus fifteen percent (15%) for overhead. If the cost is less than the amount deposited, the difference will be refunded.