the Board may deviate laterally from the lines or situations of those works as shown on sheets 1 to 7 to any extent not exceeding the limits of deviation;

the Board may deviate vertically from the levels and heights set out in of article 3(2) and (3) to any extent not exceeding ten metres upwards and to such extent downwards as may be necessary or convenient; and

the Board may deviate vertically in a downwards direction from the levels stipulated in the descriptions of Works Nos. 1, 2 and 3 in article 3(1) in order to facilitate construction but by no more than 5.5 metres.