The City Engineer or other city officials or employees, bearing proper credentials and identification, shall be permitted to enter upon any and all premises at all reasonable times for the purpose of inspection, observation, measurement, sampling and testing of sewers and sewage waste in accordance with the provisions of this chapter. It is unlawful for any person to prevent or attempt to prevent any such entrance or obstruct or interfere with any such officer or employee while so engaged. (Ord. 208 § 39, 1957).