After a century as a gravel mine which fuelled Sydney's 20th Century expansion, the last chunk of Prospect Quarry is being transformed into an employment hub expected to deliver 8500 jobs to the western Sydney region.

The 50 hectare Southern Employment Lands, the third and final stage of Boral's redevelopment of the former quarry site, also includes a major road and dedicated bus transitway to link Wetherill Park with Blacktown.

The first two stages of the massive reassignment of the old quarry are already well established: the Northern Employment Lands have become a centre for warehouse and distribution businesses while Nelson's Ridge is a growing residential area.

On a tour of the Southern Employment Lands recently the Sun saw how massive civil engineering works are levelling the site to prepare it for construction of a network of roads.

These will service a 50 hectare industrial subdivision and a business park precinct with 97,500 square metres of high quality office space and 6500 square metres of service retail uses including restaurants, fast food, banking and a hotel/tavern.

Called the Greystanes Estate, the development is a partnership between the owners of the former quarry, Boral and Dexus Property Group.

Thousands of tonnes of rock are being blasted and crushed into a variety of sizes to be used as fill for drainage channels and site levelling.

Running through the site is a corridor which has been set aside for a future bus transitway alongside Reconciliation Drive to which Boral has contributed $700,000.

The transitway will link Wetherill Park and Blacktown while the road links Wetherill Park to the M4 and Great Western Highway.

It's estimated the development phase of the Southern Employment Lands will directly and indirectly employ about 2700 people with the possibility of more than 8000 permanent employment opportunities when the project is completed.