In order to make repairs or perform regular maintenance or cleaning/pumping of the tank, access must be provided. There are usually two lids located at the top of the septic tank-one located over the inlet "T" and one located over the outlet "T" (see "Septic Components: Septic Tanks"). On new construction, when septic tank lids are buried more than 12 inches below finished grade, risers or access tunnels are installed on top of the tank lids, and are extended up to a point that is less than 12 inches from the ground surface or to grade. The riser(s) needs to be completely sealed to the tank to prevent ground water from entering the riser cavity, which may cause a flooding of the tank and the whole system. If the riser lid is located at grade, it shall be locked to prevent entry. Note: The inlet and outlet sanitary "T"'s need to be located directly below the tank access lid for easy access.