(a) All above-ground storage tanks for flammable liquid which exceed two thousand (2,000) gallon individual or aggregate capacity shall be enclosed within liquid-tight dikes constructed of reinforced concrete, masonry or earth, except that dike walls shall not be required where the contour of the ground surface provides the approved equivalent thereof. Earthen dike walls shall have a flat section at the top not less than thirty-six (36) inches in width, and shall have slopes consistent with the angle of repose of the material of which they are constructed. Concrete or masonry dikes shall not be less than thirty (30) inches in height and earthen dikes shall not be less than three (3) feet in height. The height of the dike and the distance from the inner surface of the dike to the shell of the tank shall be such as to assure the scouring action of the wind and prevent the accumulation of combustible vapors within the dike. Where ground area permits, the maximum height of the dike walls shall be four (4) feet, and the maximum height under any conditions shall be six (6) feet.
(b) A dike surrounding a tank used for storing crude petroleum or other flammable liquid subject to boil-over shall have a capacity not less than one and one-half (1-1/2) times the capacity of the tank contained within the dike.
(c) Tanks containing flammable liquid subject to boil-over shall be separately and individually diked.
(d) When a dike surrounds a tank containing crude petroleum or other flammable liquid subject to boil-over it shall have, in addition to the required capacity, suitable copings or deflectors pointing inward constructed so as to minimize the effect of boil-over waves. Dikes surrounding large crude oil tanks shall not be less than fifty (50) feet from the shell of the tank surrounded.
(e) A dike surrounding tanks used for storing flammable liquids not subject to boil-over shall have a capacity equal to that of the largest tank contained within the dike plus ten percent (10%) of the aggregate capacity of all other tanks contained within the dike.
(f) Whenever tanks are interconnected within the diked area or so interconnected that they cannot be individually controlled and emptied from a safe location outside the diked area, such tanks shall be deemed to be one (1) tank in determining the required capacity of the dike.
(g) Up to, but not exceeding six (6) tanks containing flammable liquid not subject to boil-over may be contained within one (1) dike.
(h) Whenever outside above-ground tanks erected prior to June 27, 1949, do not fully conform to the provisions of this Fire Prevention Code governing material, construction and equipment of tanks, and such tanks are contained within one (1) dike, the Fire Chief may require that each tank within the diked area be isolated from every other tank within such diked area by division walls arranged to provide a separated space within the dike for each tank. Such division walls shall be approximately six (6) inches less in height than the enclosing dike wall. The location, arrangement and height of such division walls shall be as directed or approved by the Division of Fire.
(i) Dike walls and division walls shall have stairs for access to and egress from the diked areas.
(j) Where necessary for the removal of surface or ground water, diked areas shall have approved provisions for drainage. All drains located within a diked area which discharge directly or indirectly into the public sewer system or into natural watercourses shall have shut-off valves, normally kept closed, installed in the drainage piping at accessible locations outside the diked area.
(k) The surfaces within dikes and around dikes shall be kept free of all brush and debris.
(Ord. No. 991-49. Passed 6-27-49, eff. 6-27-49)