13(1)Except as provided in sub-paragraph (2) below, the Port Authority shall not be liable, in the absence of negligence, for any damage caused to the tunnel highway, or to any temporary or permanent works carried out in connection with the construction, maintenance or improvement of the tunnel highway, by—E+W
(a)dredging operations of the Port Authority; or
(b)the carrying out by them in the execution of their statutory powers and duties of any operations in the river or works for the improvement or maintenance of the river.
(2)The Port Authority shall not be excused from liability under sub-paragraph (1) above in respect of the carrying out of any dredging or other operations or works within 61 metres on each side of either of the centre lines of the tunnels and below the depth of 15.7 metres below ordnance datum (Newlyn) within the part of the river width between a line 130 metres from the line of the existing level of mean high-water springs on the southern bank of the river and a line 355 metres northward of that first-mentioned line or, outside that part, below the dredging line shown on a line mid-way between the two tunnels on the sheet signed by Geoffrey Ennals, Secretary to the Port Authority, and Philip Wood, an Under-Secretary in the Department of Transport, and marked “Diagram referred to in Part I of Schedule 7”, copies of which have been deposited in the Office of the Clerk of the Parliaments and the Private Bill Office of the House of Commons.