art 4 Power to deviate
(1) Subject to paragraph (3), in constructing or maintaining any of the scheduled works the Council may deviate laterally from the lines or situations shown on the works plans to any extent within the limits of deviation and may deviate vertically from the levels shown on the sections to any extent upwards or downwards. (2) The scheduled works shall be so constructed that— (a) the unobstructed opening between the walls of the lock, as shown on the works plans and sections, is not less than 5 metres wide; (b) the headroom for vessels passing through the lock is not less than 5 metres above the crest level of the weir as specified in sub-paragraph (d); (c) the cills at each end of the lock are set at 1.5 metres below Ordnance Datum (Newlyn) or at such other level as may be agreed between the Council and the Port Authority to be the level of the bed of the Ouseburn at that point immediately before the construction of the scheduled works is commenced; (d) the level of the crest of the weir, as shown on the works plans and sections, is set at 2.6 metres above Ordnance Datum (Newlyn) with a tolerance of plus or minus 10 millimetres; (e) the width of the crest of the weir, as shown on the works plans, is not less than 5 metres; and (f) they shall not interfere with the structure of the Glasshouse Bridge. (3) Nothing in paragraph (4) or paragraph (5) of article 3 (power to construct works and survey) shall authorise the Council to execute any works in contravention of the restrictions imposed by paragraph (2) of this article.