5704.2.10.4 Combustible materials in diked areas.

Diked areas shall be kept free from combustible materials, drums and barrels.

5704.2.10.5 Equipment, controls and piping in diked areas.

Pumps, manifolds and fire protection equipment or controls shall not be located within diked areas or drainage basins or in a location where such equipment and controls would be endangered by fire in the diked area or drainage basin. Aboveground piping shall be minimized and located as close as practical to the shell of the tank in diked areas or drainage basins.

   Exceptions:

      1.   Pumps, manifolds and piping integral to the tanks or equipment being served which is protected by intermediate diking, berms, drainage or fire protection, such as water spray, monitors or resistive coating.

      2.   Fire protection equipment or controls which are appurtenances to the tanks or equipment being protected, such as foam chambers or foam piping and water or foam monitors and hydrants, or hand and wheeled extinguishers.

5704.2.10.6 Dike construction.

All dike walls shall be of steel or reinforced concrete, designed to be liquid-tight and to withstand a full hydraulic head, and constructed to provide access to and from the diked area. Where stairways or other means are required to provide such access, they shall be constructed of steel. No dike wall shall be higher than 60 percent of the tank height.

5704.2.11 Underground tanks.

Underground storage of flammable and combustible liquids in tanks shall comply with the requirements of FC 5704.2, and 5704.2.11.1 through 5704.2.11.5.2.

5704.2.11.1 Contents.

Underground tanks shall not store petroleum products containing mixtures of a nonpetroleum nature, such as ethanol or methanol blends, without evidence of compatibility.

5704.2.11.2 Location.

Flammable and combustible liquid storage tanks located underground, either outdoors or under buildings, shall be in compliance with the following requirements:

   1.   Tanks shall be installed so that the external forces exerted from building foundations and support loads are not transmitted to the tanks. The distance from any part of a tank to the nearest wall of any basement, pit, cellar or any property line shall not be less than 3 feet (914 mm). Tanks shall not be placed less than 20 feet (6096 mm) from a subway wall.

   2.   Tanks shall be installed so that the highest point of the tank is not less than 2 feet (610 mm) below the level of the lowest cellar floor of any building within a radius of 10 feet (3048 mm) from the tank. No tank shall be located under a sidewalk or beyond the property line.

   3.   A minimum distance of 18 inches (458 mm), shell to shell, shall be maintained between underground tanks.

   4.   Manufacturer's installation instructions.

5704.2.11.3 Depth and cover.

Excavation for underground storage tanks shall be made with due care to avoid undermining of foundations of existing structures. Underground tanks shall be set on firm foundations and surrounded with at least 6 inches (152 mm) of noncorrosive inert material, in accordance with the manufacturer's installation instructions.