When required by the city, the owner(s) of any property serviced by a building sewer carrying wastes in excess of that specified in § 6.07 of this chapter shall install a suitable structure together with such necessary meters and other appurtenances in the building sewer to facilitate observation, sampling and measurement of the wastes. Such structure, when required, shall be accessibly and safely located and shall be constructed in accordance with plans approved by the City Building Official. The structure shall be installed by the owner(s) at his or her expense and shall be maintained by him or her so as to be safe and accessible at all times.