Eastern tunnelling project director Bob Nowotny said vibrations from the boring machines had caused some methane gas to be released from pockets in sediment between Rozelle and Pyrmont, resulting in minor bubbles on the water surface, but not in the final part of the tunnelling beneath Darling Harbour.
Loading
“You get pockets of gas in [the marine sediment], which do get relieved as you’re going through sometimes,” he said.
The two boring machines have been slicing through rock at one-third of the pace of other boring machines working on Metro West because of the combination of hard and soft rock under the harbour, which is one of the most complex parts of the project.
The gradient of the tunnels is up to about 5 per cent, which means that for every 100 metres it rises or falls about five metres. That will be the operational limit of the driverless metro trains.
The Herald recently reported that the cost of Metro West is set to blow out by at least $2 billion to $27.3 billion, due to the skyrocketing price of building underground train stations and delays to awarding major contracts.
Questioned on Monday about the project’s cost, Premier Chris Minns said he was not anticipating it to be above $25.3 billion because the government was “very tough on costs”.
“There’s some room to move in that envelope. If it does change, we’ll update the public,” he said.
The underground line is the fourth and largest stage of Sydney’s metro network, which is one of the world’s biggest rail projects, costing about $67 billion. Metro West is due to open to passengers in 2032.
