One of the challenges was the Dorney Bridge, built to take the channel beneath the Great Western Railway line. The 19th-century Brunel-designed railway embankment continued in use, carrying passenger and goods trains between London and destinations including South Wales, Cornwall and Bristol throughout construction. The high embankment was stabilised along 30m of its length by freezing over a period of three months, using 175 brine tubes cooled to . A tunnel was excavated through the frozen ground to just wider than the two long preformed concrete box sections, which were jacked through as the excavation proceeded. This created a wide by high concrete culvert which can be seen from the Bath Road Bridge.