The Environment Protection Authority has issued a mining company building an underground gold mine near Braidwood with a clean-up notice, after run off from a sediment basin polluted nearby creeks.
Majors Creek residents were upset with the dirty overflow after only two weeks of construction on the $90 million project.
Big Island Mining has been issued with an immediate Clean-Up Notice for the Dargues Reef Mine construction site, requiring immediate action to ensure appropriate environmental controls are in place and are being adhered to.
The company must also engage the expert services of a sediment erosion control professional to inspect the site, make recommendations for improvements and performance monitoring.
EPA chief environmental regulator Mark Gifford said the regulatory action followed heavy rain on February 24 when run off from the site's earthworks was washed into Spring Creek, a tributary of Majors Creek.
"The EPA received a self-report from the company on February 24, as well as a number of complaints about turbid water being discharged from the mine site and a possible failure of the sediment dam," Mr Gifford said.
"An inspection by EPA officers the next day found that large areas of track construction did not have sediment and erosion control measures in place, allowing sediment laden water to move through the site.
"The EPA has also met with the company's senior management and will continue to monitor the situation on site, especially in high wet weather events, to ensure the incident does not reoccur."