Any monument of granite, concrete, iron or other lasting material set for the purpose of locating or preserving the lines of any street or property subdivision or a precise survey reference point within the city shall not be removed or disturbed or caused to be removed or disturbed unless a written permit for such purpose has been granted by the Director of Public Works. Permission shall be granted upon the condition that the person applying therefor shall cause to be replaced at his expense the monument so removed or disturbed. A city contractor shall not be held responsible for monuments not shown on the construction plans if said plans are prepared by the Department of Public Works. It is the responsibility of all other contractors and permittees to determine the location of all monuments prior to commencing work.