Aboveground tanks for flammable liquids shall be constructed throughout of open hearth steel or of wrought iron of a thickness in accordance with the following requirements:
Less than 1,100 gallons capacity
Capacity (gallons) | Minimum Thickness of Material (U.S. standard gauge) |
1 to 60, inclusive | 18 |
61 to 350, inclusive | 16 |
351 to 560, inclusive | 14 |
561 to 1,100, inclusive | 12 |
Any tank built in accordance with the Underwriters' Laboratories Standard 142 shall be acceptable. No open tank shall be used. Nothing in this chapter shall be construed as prohibiting the use of concrete tanks for the storage of liquids heavier than 35 degrees Baume gauge. All concrete tanks shall be constructed in accordance with the requirements of Chapter 14B-19.
Horizontal Tanks Containing Over 1,100 Gallons. Tanks having a diameter of six feet or less shall be made of not less than three-sixteenths inch steel. Tanks having a diameter of more than six feet and not exceeding 11 feet, six inches shall be made of not less than one-fourth inch steel.
Vertical Tanks Containing Over 1,100 Gallons. Vertical tanks having more than 1,100 gallons capacity shall be so constructed of such material and so arranged as to have a factor of safety of not less than two and five-tenths. The minimum thickness of the shell or bottom shall be not less than three-sixteenths inch. The minimum thickness of roofs shall be not less than one-eighth inch. The tensile strength of the steel plate and the shearing strength of rivets and bolts shall be in accordance with the requirements of Chapter 14B-22. Tanks shall be riveted, welded or brazed and shall be caulked and made tight in a workmanlike manner. The top of tanks shall be securely fastened to top ring with joints having the same tightness as the joints between the rings. All iron or steel tanks shall be thoroughly coated on the outside with a heavy protective paint. Roofs or tops of tanks shall have no unprotected openings and shall be firmly and permanently joined to the tank, and all joints shall be riveted and caulked, brazed or welded.
Pressure Tanks. Pressure tanks shall be riveted, welded or brazed and shall be fastened, caulked or otherwise made tight so as to sustain safely a hydrostatic test at a pressure not less than double the pressure at which the tank is to be used. The top of the tank shall be securely fastened to the top ring with joints of equal tightness to the bottom rings. Tanks shall be covered with heavy protective paint. All pipe connections shall be made through flanges or metal reinforcement securely riveted, welded or bolted to the tank and made thoroughly tight. Pressure tanks, including top, sides and bottom, shall be constructed entirely of metal. All openings in such tanks shall be gas-tight except the breather vent. Emergency vents shall be actuated on pressure tanks before the pressure exceeds 1.25 times the working pressure. The size of these vents shall be the same size as the relief valve.
Foundations and Grounding. All tanks shall be electrically grounded by resting directly upon moist earth or shall be electrically grounded to permanent moisture. No insulated connections shall be permitted. All steel work for reinforced concrete tanks shall be interconnected and grounded as herein provided for tanks. Tanks more than one foot above the ground shall have foundations and supports of noncombustible material. No combustible material shall be permitted under or within ten feet of any aboveground storage tank; provided, however, that nothing in this chapter shall be construed as prohibiting wooden cushions under tanks. Unprotected steel is prohibited as a means of supporting tanks when such tanks are located 50 feet or less from loading or unloading points, buildings or storage of combustible substances or materials. Over 50 feet, unprotected steel saddles are allowed if less than 12 inches high at the lowest point.
Dikes. Every aboveground storage tank containing flammable liquids shall be diked. Every group of tanks containing flammable liquids of Classes II and III may have a total capacity of, but shall not exceed 60,000 barrels within a single dike, and a barrel shall mean a volume of 42 U.S. gallons. Every tank containing flammable liquids of Class I shall be individually diked. Each dike shall have a capacity of not less than one and one-fourth times the combined capacity of the tank or tanks it surrounds. Earth dikes shall be firmly and compactly built of good earth or clay, from which stones, vegetable matter or other foreign material have been removed, and shall have a flat section at top not less than three feet wide and a slope at one to one (45 degrees) on both sides. Earth dikes shall be not less than four feet high on the inside and in no case higher than one-fourth the height of the tank when said tanks exceed 16 feet. Embankments or dikes shall be continuous with no openings for pipe or roadway. Underground piping shall be laid well below the foundation of embankments. The provision of this section shall not apply to fuel oil tanks installed in connection with heating equipment where the aggregate capacity of the tanks does not exceed 550 gallons. Electrical equipment within diked areas shall be of explosion-proof types. Provided, however, that diking of tanks within the area of Lake Calumet, bounded on the north by Slip No. 2, on the east by Stony Island Avenue, extended on the south by the Entrance Basin, and on the west by the Anchorage Basin of Lake Calumet, which area shall be authorized only as a planned development in accordance with the provisions of the Chicago Zoning Ordinance, may comply either with the foregoing provisions of this paragraph or with N.F.P.A. Flammable and Combustible Liquids Code 30 (1993), when such diked area is protected by an approved fire protection system.
Capacity Limits. The capacity of any aboveground tank containing flammable liquids of Class I shall not exceed 15,000 gallons. The total capacity of tanks in any storage yard for the storage of Classes I and II flammable liquids shall not exceed 750,000 gallons, and the total capacity of tanks in any storage yard used exclusively for the storage of Class III flammable liquids shall not exceed 1,500,000 gallons; except that 1) in the area of Lake Calumet, bounded on the North by Slip No. 2, on the east by Stony Island Avenue, extended on the south by the Entrance Basin, and on the west by the Anchorage Basin of Lake Calumet, which area shall be authorized only as a planned development in accordance with the provisions of the Chicago Zoning Ordinance, tanks of 2,300,000 gallons or less capacity, containing flammable liquids of Classes I and II or tanks of 4,200,000 gallons or less capacity containing flammable liquids of Class III with no limitations on storage yard capacity, shall be permitted (crude oil or any other flammable liquids subject to boilover characteristics, and refining of any flammable liquid are prohibited in this area); and 3) at Chicago Midway Airport, aboveground storage tanks containing a total storage capacity of not greater than 2,000,000 gallons of Class II flammable liquids per storage yard shall be permitted (crude oil or any other flammable liquids subject to boilover characteristics, and refining of any flammable liquid, are prohibited in this area).
(Prior code § 129.1-14; Amend Coun. J. 7-13-94, p. 53151; 2-7-96, p. 15463; Amend Coun. J. 6-27-01, p. 62535, § 1; Amend Coun. J. 10-7- 20, p. 21791, Art. VI, § 26)