Section 23.141. General requirements

(a) Underground solvent storage tanks. Underground storage tanks for Class II and Class III solvents shall be placed at least 2 feet apart, not less than 2 feet below the surface, not less than 2 feet from foundations and footings, and entirely surrounded by clean earth or sand well tamped in place. All tanks shall rest on a 6 inch concrete pad. The limit of individual tank capacity as shown in the table under subsection (b) may not be exceeded without the approval of the Department.

(b) Construction. Horizontal tanks used for the storage of volatile or flammable solvents shall be made of galvanized steel, open hearth steel or wrought iron of a minimum gauge United States Standard, depending upon the capacity as given in the following table:

	Minimum Thickness Material
Capacity		Gauage Equivalent	Pounds per
(in gallons)	Gauge	(in inches)	Square Foot
1 to 560	15	5/64	3.125
561 to 1,000	12	7/64	4.375
1,101 to 4,000	7	3/16	7.50

(c) Joints. All joints of tanks shall be riveted and caulked, welded or brazed, and shall be thoroughly and effectively covered with asphaltum or other nonrusting paint or coating.

(d) Ventilation. All storage tanks for Class II, III and IV solvents shall have at least a 1 1/4 inch vent pipe and not less than 1 1/2 inches for tanks over 3,000 gallons, run from the top of the tank to a point terminating in the atmosphere, without trap, which shall end at least 12 feet above level or source of supply, suitably supported and in a location remote from fire escapes and not nearer than 3 feet measured horizontally and vertically from any window or other opening. The tank vent pipe shall terminate in a gooseneck or other approved vent protected in the outer end by a 30 by 30 mesh brass or equivalent wire screen.

(e) Filling pipes. The end of the filling pipe for all underground storage tanks shall be carried to a suitable location outside of any building, and shall be provided with a lock, or equivalent protection, which shall be kept securely locked or closed except during filling operations. This filling pipe shall be closed by an approved cap or plug and, if it is located in a driveway or other places subject to vehicular traffic, set in an approved steel box with cover or otherwise suitably protected to prevent damage to it. A self-closing liquid tight cover shall be required on all inside gauge openings. No gauge opening shall be located below the grade floor but shall be at least one foot higher than the point of fill.

(f) Inside above ground tanks. Class II, inside above ground tanks may not exceed 550 gallons and the individual tank capacity may not exceed 275 gallons except that treatment tanks or purifiers may not exceed an individual capacity of 350 gallons and shall in no event exceed in capacity any individual storage tank to which they may be connected. Class III clean solvent tanks, dirty solvent tanks, extractor drain tanks, fillers and other such containers shall have an individual capacity not in excess of 275 gallons.