Network Rail has demanded that 'unacceptable' levels of leakage into the new Thameslink station box be reduced, it emerged this week.
Water has been pooling in escalator and lift shaft pits and in 900mm deep cable trenches running beside the tracks through the station. Dispute over the scale of the leakage is understood to have prompted Netwrok Rail to consult its legal advisers.The stationw as constructed by Rail Link Engineering (RLE) a joint venture of Arup, Bechtel, Halcrow and Systra responsible for design and project management of High Speed 1.'There have been dewatering pumps in the station box dealing with water seeping in. There's an unacceptable inflow rate and that needs to be remedied,' said a project source.'If the flow is allowed to persist there'll be concerns about the longer term maintainability of the station.'Rail Link Engineering (RLE)'s station fit out project manager Pete Hodkin said that the water was not coming through the station box's contiguous piled walls but that the problem stemmed from Network Rail's own Thameslink tunnel. 'The adjoining tunnel is brick lined and we believe it acts like a French drain. It's extremely leaky and provides a pathway for water,' said Hodkin, who also said that some leakage in the box was expected. 'You can either tank a box structure and keep the water out or have an allowable leakage rate and manage any water away through a system of catchment gullies and pipes. We've gone for the second of those options. But we're well below our maximum allowable leakage limit of 0.25 litres per hour per linear metre of wall.'Nevertheless, RLE has agreed to remedy the situation later this month by excavating a cut-off trench where the brick tunnel meets the station box. A pipeline will connect the trench to an adjacent drainage sump, from which the water will be pumped 'as often as needed', said Hodkin.'We estimate there's about 12 hours of work needed to correct the situation,' he said. This will be carried out during a 27 hour railway posession on Saturday 27 January.