The NSW Environment Protection Authority (EPA) has fined a Sibelco Australia Limited $15,000 for alleged environmental breaches at its Swan Bay clay mine.
The alleged offences came to light during an EPA compliance inspection on January 23, 2019.
The authority said that during the inspection, an EPA officer discovered that Sibelco had failed to maintain and rehabilitate the site in a competent manner.
EPA acting director for the Hunter, Mitchell Bennett, said the company had also allegedly caused water pollution.
"Sampling done on the day by the EPA showed the total suspended solids concentration in waters on the site exceeded licence limits," Mr Bennett said.
"Further EPA investigations discovered several inadequacies in Sibelco's environmental management systems which resulted in inadequate surface water monitoring, poor contractor supervision and poor erosion and sediment controls across the premises.
"The EPA considers these breaches to be serious and will continue to monitor Sibelco's activities."
The Swan Bay clay mine has ceased operating and is being rehabilitated.
The EPA issued Sibelco a $15,000 penalty notice for an alleged failure to comply with its licence conditions and issued an official caution for alleged water pollution.
Penalty notices are one of a number of tools the EPA can use to achieve environmental compliance including formal warnings, official cautions, licence conditions, notices and directions and prosecutions.