Coal company Gujarat NRE says regular inspections have been carried out on Mount Ousley Road after cracks were discovered that could be linked to its nearby Russell Vale coalmine.
Community groups including Illawarra Residents for Responsible Mining (IRRM) believe the cracks have been caused by subsidence from the company's longwall mining operations and are "further evidence that the mine poses an unacceptable environmental risk".
"The fact that [Gujarat's] mining of Longwall 4 has cracked Mt Ousley Road illustrates that the state government should urgently review the impacts of longwall mining beneath the Sydney Water Catchment special areas," IRRM spokeswoman Kaye Osborn said.
"A road can presumably be repaired, however the impacts on the water catchment area, including a number of upland swamps and the Cataract Creek, which are all within the subsidence zone of Longwalls 4 and 5, can never be remediated."
IRRM launched legal action against Gujarat earlier this year, claiming that it had started longwall mining without approval.
Gujarat has now completed mining its Longwall 4 and applied to begin Longwall 5.
A company spokesman said a detailed plan was in place to monitor and manage impacts on Mt Ousley Road and the key focus was the serviceability of the road and the safety of road users.
"Early in September a detailed inspection of Mt Ousley Road undertaken on behalf of Gujarat NRE identified that a number of small, hairline cracks which existed prior to mining appeared to increase in width (to a maximum of 5-10mm) and to increase in length," he said.
"Also this inspection identified new cracks in the surface of Mt Ousley Road that had not been found in previous inspections. The presence of these cracks were immediately reported to Roads and Maritime Services (RMS) and other responsible government agencies."
Further inspections had taken place and the results passed on to RMS, he said. All cracks had remained in the 5-10mm range and inspections would continue.
RMS said longwall mining had been safely carried out under major highways in NSW including the F6 near Helensburgh.
Current mining was located next to Mt Ousley Road but not under it.
An RMS spokeswoman said the cracks were identified about a month ago and monitoring since then had shown no further increase.
Mitigation measures including "placing slots" to absorb movement, monitoring and tilt meters were in place to manage any subsidence, she said.
"A technical working party made up of experts in geotechnology, road surfaces, road design and mine subsidence have led a thorough and rigorous process to identify, review and manage risks associated with the mining."