8. In carrying out the authorised development the undertaker may—
(a)deviate laterally from the lines or situations of the authorised development shown on the works plans to the extent of the limits of deviation shown on those plans; and
(b)deviate vertically from the levels of the authorised development shown on the engineering section drawings, to a maximum of 1 metre upwards or 1 metre downwards,
except that these maximum limits of vertical deviation do not apply where it is demonstrated by the undertaker to the Secretary of State’s satisfaction and the Secretary of State, following consultation with the relevant planning authority and the local highway authority, certifies accordingly that a deviation in excess of these limits would not give rise to any materially new or materially worse adverse environmental effects from those reported in the environmental statement.