Truck movements from Boral's hard rock quarry at Dunmore could jump 50 per cent under a proposal being considered.
The company is seeking to modify its existing development consent to increase the size of the quarry by two hectares and also increase the amount of product hauled from the quarry by road.
The change would allow material approved for road haulage to rise from 1 million tonnes to 1.5 million tonnes a year.
At present there are 110 truckloads of material taken out every day. The company's environmental assessment (EA) said the extra 500,000 tonnes would mean an extra 55 truckloads daily.
During peak periods the change would generate an extra 10 vehicle movements an hour - six heading north and four heading south.
"These additional traffic movements would generate less than a 0.2 per cent increase in traffic on the Princes Highway northbound and a 0.15 per cent increase southbound for either total daily or peak hour traffic," the EA stated.
The EA concluded that the extra 55 truckloads a day would "have minimal or negligible impact on the existing road network".
The company's EA said that rail transport "is currently not feasible due to terminal and rail pathway capacity constraints".
While final approval for the modification proposal rests with the NSW Minister for Planning and Infrastructure, Shellharbour Mayor Marianne Saliba said residents would get a chance to voice any objections.
"If there are any objections, council would then have to put up some kind of report to the minister on what the issues are," Cr Saliba said.
"If there was serious concerns, council would not be recommending that it be approved."
Cr Saliba said the extra 55 truck movements was a concern for council.
"It would certainly be a concern to me and a concern to the councillors as well," she said.
"Traffic movement would certainly be an issue.
"I've always got concerns about truck movements because I want to see the state government put in that extension of the F6 south, bypassing Albion Park Rail, because that's a terrible bottleneck during peak times."
Cr Saliba added that it was a positive sign that Boral was looking to expand the quarry, because it provided job security for employees as well as economic benefits to the region.
"We would have to weigh up all of the relevant concerns of the community against the benefits of having that business continue operating in the Shellharbour area," she said.