That provision may be made for the purposes of aggregates levy—
(a) for aggregate won by being removed from the ground on the site of any or any proposed structure, or the site of any or any proposed infrastructure relating to transportation or utilities, to be exempt from tax, and
(b) about the exploitation of aggregate which again becomes part of the site from which it was won or which becomes part of any other site occupied by the same person as the site from which it was won.