The NSW Department of Environment and Climate Change has appealed to Wollongong residents to report any illegal dumping after a white station wagon towing a trailer and cage was spotted dumping in the area.

The department has also warned that builders who don't keep records about waste management could be forced to clean up illegally dumped rubbish.

They can also face fines of up to $5 million and seven years in prison.

The department's waste operations manager Steve Beaman cited the case of a Cringila owner-builder who had to clean up a tonne of waste after he paid $100 for its disposal, only to have it end up in Port Kembla bushland.

"Personal information left at the site helped us to identify where the waste holder had come from, but unfortunately the householder couldn't identify the contractor who'd taken the rubbish away," he said.

"This meant the onus fell on the householder to clean up the rubbish even though he'd done the right thing.

"While the householder received only a warning, as he clearly hadn't intended for the material to be dumped illegally, he still ended up having to clean up his waste twice."

Dumping can seriously affect bushland and attract rodents. It also costs ratepayers thousands of dollars in in clean-up bills, according to the department.

Wollongong City Council regulation and enforcement manager Garry Meusburger said he regularly received complaints about illegal dumping.

"There are a number of ways we can identify illegal dumpers," he said.

"It is often harder to catch builders and smaller contractors because they tend to make sure they don't leave any evidence behind such as bills or receipts."

Illegal dumping can be reported to the council by calling 4227 7710.