4.—(1) In constructing or maintaining the scheduled works, the Council may, subject to paragraph (2), deviate laterally from the lines or situations shown on the deposited plans to any extent within the limits of deviation and may deviate vertically from the levels shown on the deposited sections—
(a)to any extent not exceeding 3 metres upwards as to any part of the scheduled works;
(b)to any extent not exceeding 0.2 metre downwards as to the decking of the new bridge; and
(c)to any extent downwards as to any other part of the scheduled works.
(2) In constructing the new bridge the Council shall provide headroom of not less than 2.5 metres above the level of high water over the central navigation channel.