3.—(1) The levy to be imposed by the Board on employers in respect of the twenty-seventh levy period shall be assessed in accordance with the provisions of this article and of the Schedule to this Order.
(2) The levy shall be assessed by the Board separately in respect of each construction establishment of an employer, but in agreement with the employer one assessment may be made in respect of any number of such establishments, in which case those establishments shall be deemed for the purposes of that assessment to constitute one establishment.