Excavation for the Albert St station has had to involve more blasting than expected to get through the Neranleigh-Fernvale rock, with the tunnel boring machines going under rather than through what has been dug for the station cavern so far.

The Cross River Rail Delivery Authority recently revealed it would begin controlled blasting at the Albert St site to speed up construction of the main station entrance and underground platform cavern.

The volcanic rockbed, which includes bands of Brisbane “Tuff” some 50 metres thick, extends underneath the CBD and Brisbane inner suburbs and has proved difficult for previous tunnel projects such as the Clem 7.

Since February, Cross River Rail’s two tunnel boring machines have travelled from Woolloongabba, under the Brisbane River to the CBD, with the first of the massive units, named Else, working under the Albert St site this week.

In a statement issued on Monday, the CRRDA said the machines were “making fantastic progress, despite some challenging geological conditions”.

“At Albert Street, our contractors are encountering Brisbane’s notoriously hard Neranleigh-Fernvale rock beds, so the TBMs will power under what has been excavated of the station cavern so far,” the authority said.

“Site crews will continue to use controlled blasting to finish the station excavation while the TBMs continue under Queen Street Mall and onto Roma Street.

“The benefit of this approach is that the mega machines will end up excavating about a quarter of the station cavern.”

The Brisbane City Council has taken issue with the authority’s success in winning approval from Coordinator-General Toni Power to allow spoil from the project’s Roma St site to be trucked out on Sundays.

Council infrastructure Chair David McLachlan said the approval meant the increased Sunday truck movements would begin on the very weekend the Riverside Expressway was closed for work on the Queens Wharf development, meaning potential “gridlock” in the city.