Work will begin this year on transforming Queensland's "largest sandpit" at Brisbane Airport into the newest gateway to Australia - a facility with the same capacity as busy Singapore Airport.

The sandy area – more than eight metres deep in some places and three kilometres long – will become Brisbane's $1.4 billion new parallel runway by September 2020.

Brisbane's New Parallel Runway project director Paul Coughlan (left) with works inspector Des Hasemann on top of 11 million cubic metres of sand that is ready to become Brisbane's new runway. Credit:Tammy Law

The weight of the 11 million cubic metres of sand has already acted like a giant sponge drawing out water for the past two years.

"Parts of this site have settled almost three metres," Brisbane's New Parallel Runway project director Paul Coughlan said.