During a site inspection in December, the EPA found a containment system holding polluted water had overflowed.
The water was used to suppress dust and contained waste water from stockpiles.
EPA manager regional waste compliance Cate Woods said South Coast Plant Hire failed in its responsibilities when its operations led to polluted water flowing off-site.
"The facility is in an area close to other businesses and a local waterway, and they need to operate their site competently to ensure they are not having any off-site impacts," she said.
"Our role at the EPA is to protect the environment. Compliance with conditions is not optional - there are specific ...