The NSW Department of Planning received 18 submissions on the proposed expansion during six weeks of public consultation that closed earlier this month.

A Port Kembla Port Corporation spokeswoman said responses were being prepared for the Department of Planning on issues raised in the submissions, but it was too early to comment on specific issues.

Mr Farmer's letter noted concerns that the region's road network would reach capacity sooner than expected and the port corporation needed to commit to undertake necessary road upgrades, rather than the council.

He was concerned about potential negative impacts on Appin Rd and Picton Rd, including road safety, and said the application had not addressed the impact on either road.

The council also suggested the use of uncrushed blast furnace slag and coal wash would contribute to water pollution.

Further studies would be needed to examine the development's impact on native wildlife, Mr Farmer said.

The council disagreed with the environmental assessment's claim that the area "does not provide shelter, breeding areas or habitat" for wildlife, indicating three endangered and two vulnerable species had been recorded in the area.

"An eastern quoll has been recorded within the proposed development," Mr Farmer wrote.

"There are also records of sooty oystercatcher within the proposed development area."

Migratory birds including the endangered black-necked stork and little tern, the vulnerable black-tailed godwit, and the white tern and little shearwater occasionally foraged along the shore. Dugongs and fur seals had been seen in the outer harbour.