DESIGN MODIFICATIONS and extra work to boost capacity have added £136M to the cost of Railtrack's Thameslink 2000 scheme, taking the total to £800M.
Most of the extra cost will arise from work to increase capacity at London Bridge and at stations outside London.
Modifications to Thameslink 2000 - a major capacity upgrade of the cross- capital link - follows objections to initial plans. Just before Christmas the Department of the Environment Transport and the Regions announced a public inquiry into the new scheme.
At London Bridge, work involves demolishing part of the train shed wall and the roof to create an extra through platform.
This will be used to maintain capacity for trains running to Charing Cross, allowing Thameslink services to take over the through platform now used by Charing Cross trains.
Outside London, Railtrack plans to increase platform lengths on about 40 stations to enable them to handle 12-car trains instead of eight.
Anthony Hunt Associates has redesigned the viaduct, which will run through Borough Market in south London, so that fewer buildings will need to be demolished. It is hoped this will counter objections to the scheme.
'The deck will be thinner so we can reinstate some double storey properties,' said Thameslink 2000 general manager David Howarth.
The thinner deck will have shorter spans and 1m more clearance beneath it. More columns will be needed in the market area, but Howarth said there would be some flexibility about positioning to meet the needs of market traders.