As Sydney began to shut down amid the coronavirus pandemic, crews of workers were still tunnelling below the city last week, making the last breakthrough of the massive metro rail project.

Having chewed an almost 900 metre tunnel beneath Sydney Harbour, the boring machine Kathleen broke through rock near Blues Point on Tuesday without the usual fanfare such events would attract from government MPs, who were instead grappling with a health crisis.

Work on big infrastructure projects like the Sydney Metro could be delayed if workers catch COVID-19. Credit:Nick Moir

And while the event has been lauded as “historic”, there's now doubt as to how heavily COVID-19 will affect the NSW government's mammoth $100 billion infrastructure plan and the jobs it was likely to create.

Asked whether the pandemic posed a threat to the state’s big building plans, Treasurer Dominic Perrottet said the government was “committed to continuing the existing budgeted capital program”.