Residents of Bulga in the upper Hunter Valley already threatened by the expansion of a nearby Rio Tinto coalmine may have even more to fear with the mining giant hiring consultants to survey an expansion of the open-cut pit to within about 500 metres of the town.

The current planned 698-hectare expansion of Rio Tinto's Mt Thorley-Warkworth coalmine gained a recommendation for approval from the Planning Assessment Commission in March after courts twice knocked back earlier versions of the plans.

Alan Jones joins protesters against the Rio Tinto mine. Credit:Ben Rushton

The commission said Bulga residents should consider relocating the town as one option to minimise the noise and dust of a mine that would encroach to about 2.6km from the town, 20km south-west of Singleton. (See map below, with Bulga located in the lower left-hand corner, and new mine areas marked in red).

However, a secret June 2014 report by Cumberland Ecology ordered by Rio and obtained by Fairfax Media, show the company has scoped out a further 1370 hectares on both the western and eastern flanks of the current mining plans. (See map below, with assessed areas in red.)