A plan to build an 8km underground rail line beneath Perth's Swan River and airport is being seriously considered by the West Australian government.
The revelation came a day after the state government announced it was deferring the MAX light rail project - a key plank of the Liberal's election platform earlier this year - because of rising state debt.
On Thursday, Treasurer Troy Buswell said another near $2 billion plan, a proposed rail link to the city's airport, was not only going ahead, but could become an underground project.
That is despite the state government's desperate bid to rein in rampant spending, and after earlier this year criticising the opposition's rival airport rail plan, saying the high water table in the area would create a major engineering headache.
"If it is a value proposition to tunnel the whole way, I think we'd be mad not to do that," Mr Buswell told reporters.
"If it is more expensive than other options, of course we're not going to do it because at the end of the day, we can't deliver gold-plated infrastructure, we have to deliver value for money.
"However, there is a suggestion - and we're considering it seriously - that given we have to do half of the 8km length as a tunnel, it may well be a value proposition to leave that machine under the ground and keep going to the east, go under the river and link in with the Midland line."
Mr Buswell, who is also WA's transport minister, said engineers had advised the costly part of tunnelling was obtaining and commissioning the equipment.
