Exemptions
6. A silo, slurry storage system or fuel storage tank is for the time being an exempt structure if—
(a)it was used before 1st March 1991 for the purpose of making silage, storing slurry or, as the case maybe, storing fuel oil;
(b)where it was not used before 1st March 1991 for that purpose, it was constructed before that date for such use; or
(c)a contract for its construction was entered into before 1st March 1991 or its construction was commenced before that date and in either case was completed before 1st September 1991,
and it has not ceased to be an exempt structure by virtue of regulation 8(1) below.