4. In the construction or maintenance of the scheduled works, the Council may 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 to any extent not exceeding–
(a)3 metres upwards as to any part of the scheduled works,
(b)1 metre downwards as to the decking of the bridge, and
to any extent downwards as to any other part of the scheduled works.