The Control of Pollution (Silage, Slurry and Agricultural Fuel Oil) Regulations 1991

2.  The fuel storage area shall be surrounded by a bund capable of retaining within the area—

(a) in a case where there is only one fuel storage tank within the fuel storage 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) in a case where there is more than one fuel storage tank within the fuel storage area and fuel oil is not otherwise stored there, a volume of fuel oil not less than whichever is the greater of—

(i) 110 per cent of the capacity of the largest tank within the storage area; and

(ii) 25 per cent of the total volume of such oil which could be stored in the tanks within the area;

(c) in a case where there is no fuel storage tank within the fuel storage 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 any of the following—

(i) 110 per cent of the capacity of the fuel storage tank or, as the case may be, of the largest tank within the fuel storage area;

(ii) where there is more than one fuel storage tank within the fuel storage area, 25 per cent of the total volume of such oil which could be stored in the tanks within the area;

(iii) 25 per cent of the total volume of such oil at any time stored within the area.