Court documents said Blaq Projects spent almost 10 years developing properties before its owner, Jared Beneru, turned his attention to construction in 2017.

He purchased property on Kembla Street in Wollongong that had existing approval for an apartment complex, now known as Ocean Air, and was granted a construction certificate on October 13.

However, Blaq fell foul of environmental protection laws just five days into its first build after it allowed contaminated water to enter storm water drains.

Court documents said Wollongong City Council sent an inspector to the site on October 18 after receiving a complaint about water pollution. The inspector reported seeing mud and slurry flowing into the gutter from a broken pump on site, but was unable to determine how much sediment had been lost down the drain.

Six Blaq employees subsequently worked to clean the site up and the majority of the sediment was removed by 8 o'clock that night.

The council issued Blaq with an $8,000 water pollution fine, however the company did not pay and the matter was sent to Wollongong Local Court for determination.

Blaq entered a guilty plea on Wednesday, with defence lawyer Julian Cesta arguing the company's breach was so "isolated and minor" that a conviction should not be recorded against his client.

"The offence was an extremely rare, one-off occurrence that has never happened in the history of Blaq Projects," he said.

"It was contained within a small area and lasted for an extremely short period of time with no longstanding or permanent affects on the surrounding environment or local infrastructure."

However, Magistrate Robert Walker refused to dismiss the matter without recording a conviction, noting the offence carried a maximum fine of $1 million.

He imposed a $10,000, with $2120 in professional costs, saying builders had a duty to mitigate accidents on their sites.