The River Thames (Hungerford Footbridges) Order 1999

20.—(1) Before the construction of the tidal works is commenced the Port Authority in conjunction with the undertaker and at the undertaker’s cost shall carry out a survey of such parts of the river as are in the vicinity of Charing Cross Railway Bridge and which might be affected by any siltation or scouring deriving from the tidal works for the purpose of establishing the condition of the river at that time.

(2) The Port Authority shall carry out such surveys of the river as are reasonably required during the construction of the tidal works to ascertain the effect of the tidal works, on the river and the Port Authority shall make available to the undertaker, at a reasonable charge, the results of any such survey.

(3) After completion of the tidal works, the Port Authority in conjunction with the undertaker and at the undertaker’s cost shall carry out a further survey of the parts of the river which were surveyed prior to the construction of the tidal works and a survey of the completed tidal works for the purpose of establishing the condition of the river and the effect that the tidal works are having on navigation, the flow and the regime of the river and the exercise of the Port Authority’s statutory functions.

(4) If any part of the river becomes subject to siltation or scouring and—

(a) such siltation or scouring is siltation or scouring which is wholly or partly caused by a tidal work during the period beginning with the commencement of the construction of that tidal work and ending with the expiration of 10 years after the date on which the tidal work is completed, and

(b) for the safety of navigation or in the interests of persons using the river or for the protection of works in the river, such siltation or scouring should in the reasonable opinion of the Port Authority be removed or made good,

the undertaker shall either arrange for the work to be undertaken itself or pay to the Port Authority any additional expense to which the Port Authority may reasonably be put in dredging the river to remove the siltation or in making good the scouring so far as (in either case) it is attributable to the tidal work.