The Director of Public Works and other duly authorized employees of the city bearing proper credentials and identification shall be permitted to enter all private properties through which the city holds a duly negotiated easement, for the purposes of, but not limited to, inspection, observation, measurement, sampling, repair and maintenance of any portion of the sewage works lying within the easement, shall be done in full accordance with the terms of the duly negotiated easement pertaining to the private property involved.