2. The storage area must be surrounded by a bund capable of retaining within the area—
(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;
(d)in any other case, a volume of fuel oil not less than the greater of—
(i)110 per cent of the capacity of the fuel storage tank or, as the case may be, of the largest tank within the area;
(ii)if there is more than one fuel storage tank within the area, 25 per cent of the total volume of such oil that could be stored in the tanks within the area; or
(iii)25 per cent of the total volume of such oil at any time stored within the area.