65—(1) In this Part—
“outfall survey” means a survey conducted by the Borough or Thames Water of—
the level of siltation within the outlet into the river of a relevant outfall;
the level of siltation at the point or points on the river bed to be agreed between the Borough and Thames Water in the vicinity of any relevant outfall;
the condition of the relevant outfall; and
“relevant outfall” means a sewerage outfall system into the river identified by Thames Water as requiring survey on account of existing or likely siltation.
(2) Prior to the commencement of the scheduled works, the Borough shall ask Thames Water to identify relevant outfalls which, following agreement by the Borough, shall be made subject to an outfall survey by Thames Water or the Borough, provided that the party not undertaking the survey shall be consulted as to the method and timing of the survey and shall receive a copy of the survey results within 28 days of the survey being completed.
(3) The Borough shall monitor the level of the river bed in the vicinity of each relevant outfall in accordance with the survey timetable agreed or required by the River Authority in accordance with the Order and shall furnish Thames Water with the results of such monitoring. Should the results of such monitoring reveal siltation in the vicinity of any relevant outfall Thames Water may require an outfall survey of such outfall.
(4) Should any relevant outfall or the river bed in the vicinity of such outfall be subject to siltation to a significantly greater depth than identified in any outfall survey undertaken in accordance with paragraph (2), to the effect that the performance of the outfall is significantly prejudiced and provided that the siltation is largely or completely due to the construction or operation of the barrage, then, subject to any necessary consents and to article 75, Thames Water may either require the Borough to clear the area concerned or undertake the work itself.
(5) The cost of any work done in accordance with paragraph (4) shall be borne by the Borough to the extent that the siltation requiring clearance has been caused by the construction or operation of the barrage but otherwise by Thames Water. Should the said work be required partly on account of the barrage and partly by other causes the costs of such work may be apportioned between the Borough and Thames Water.