SCOPE This standard provides minimum recommendations for the interior lining of existing steel and fiberglass reinforced plastic underground tanks and periodic inspection of steel underground tanks used for the storage of petroleum-based motor fuels and middle distillates. These recommendations include procedures to be followed and operating conditions to be maintained by contractors@ workers and engineers preparing@ inspecting@ testing and lining the interiors of existing underground storage tanks. Requirements for vapor-freeing tanks@ removing sediment and cleaning interior surfaces of steel and fiberglass tanks as well as guidelines to identify tanks that are suitable for lining@ are also included. All work associated with the interior lining and periodic inspection of underground storage tanks shall be accomplished in accordance with applicable federal@ state@ and local regulations@ including applicable environmental and safety requirements.