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40 WISCONSIN ADMINISTRATIVE CODE <br /> Ind 8 <br /> order to prevent spills from endangering adjacent tanks within the diked <br /> area as follows: <br /> a. When storing normally stable liquids in vertical cone roof tanks • " • <br /> constructed with weak roof-to-shell seam or approved floating roof • <br /> tanks or when storing crude petroleum in producing areas in any type of . . <br /> tank,one subdivision for each tank in excess of 10,000 barrels and one <br /> subdivision for each group of tanks, with no tank exceeding 10,000 <br /> barrels capacity, having an aggregate capacity not exceeding 15,000 <br /> barrels. <br /> b. When storing normally stable liquids in tanks not covered in par. <br /> (a), one subdivision for each tank in excess of 100,000 gallons (2,500 • <br /> barrels) and one subdivision for each group of tanks, with no tank <br /> exceeding 100.000 gallons capacity, having an aggregate capacity not <br /> exceeding 150,000 gallons (3,570 barrels). <br /> c. When storing unstable liquids in any type of tank,one subdivision <br /> for each tank except that tanks installed in accordance with drainage <br /> requirements approved by the department, shall require no additional <br /> subdivision. Since unstable liquids will react more rapidly when heated <br /> than when at ambient temperatures,subdivision by drainage channels is <br /> the preferred method. <br /> d.Whenever 2 or more tanks storing Class I liquids,any one of which <br /> is over 150 feet in diameter, are located in a common diked area, <br /> intermediate dikes shall be provided between adjacent tanks to hold at <br /> least 10r, of the capacity of the tank so enclosed, not including the <br /> volume displaced by the tank. <br /> e. The drainage channels or intermediate curbs shall be located <br /> between tanks so as to take full advantage of the available space with <br /> due regard for the individual tank capacities.Intermediate curbs,where <br /> used, shall be not less than 18 inches in height. <br /> 8. Where provision is made for draining water from diked areas,such <br /> drains shall be controlled in a manner so as to prevent flammable or <br /> combustible liquids from entering natural water courses, public sewers, <br /> or public drains, if their presence would constitute a hazard.Control of <br /> drainage shall be accessible under fire conditions from outside the dike; • <br /> and <br /> 9. Storage of combustible materials, empty or full drums or barrels, <br /> shall not be permitted within the diked area. <br /> (5) [2-2.4] NORMAL VENTING FOR ABOVEGROUND TANKS. (a) [2-2.4.1] <br /> Atmospheric storage tanks shall be adequately vented to prevent the <br /> development of vacuum or pressure sufficient to distort the roof of a <br /> cone roof tank or exceeding the design pressure in the case of other <br /> atmospheric tanks, as a result of filling or emptying, and atmospheric <br /> temperature changes. <br /> (b) [2-2.4.2] Normal vents shall be sized either in accordance with <br /> standards approved by the department or shall be at least as large as the <br /> filling or withdrawal connection,whichever is larger,but in no case less <br /> than 1'4 inch nominal inside diameter. <br /> (c) (2-2.4.3) Low-pressure tanks and pressure vessels shall be <br /> adequately vented to prevent development of pressure or vacuum, as a <br /> Register. March. 1 95'2. No.31 5 <br />