The storage area must be surrounded by a bund capable of retaining within the are.
(a) if there is only one fuel storage tank within the area and fuel oil is not otherwise stored there, a volume of fuel oil not less than 110 per cent of the capacity of the tank;
(b) if there is more than one fuel storage tank within the area and fuel oil is not otherwise stored there, a volume of fuel oil not less than the greater of—
(i) 110 per cent of the capacity of the largest tank within the area; or
(ii) 25 per cent of the total volume of such oil which could be stored in the tanks within the area;
(c) if there is no fuel storage tank within the area, a volume of fuel oil not less than 25 per cent of the total of such oil at any time stored within the area