The King River catchment in which the John Butters Power Station is situated is mostly forested and largely undeveloped, other than the township of Queenstown built around the 100-year old Mount Lyell Copper mine. There are major environmental issues in the river system due to highly acidic and heavy metal-laden drainage off the Mount Lyell lease site; historical mine tailings which were directly discharged from the mine into the river system for almost 80 years now stored in King River and delta; and ongoing metal-laden plumes entering Macquarie Harbour which is the receiving water body for King River discharges.
There is little tributary inflow downstream of the power station other than the Queen River, on which Mount Lyell is situated, so power station discharges have a very large influence on transport and dilution of Mount Lyell pollutants. Numerous major studies have been undertaken in this area over the last decade, and the environmental status and trends of the river system and harbour are well documented, as is the influence of power station operations on pollutant dispersal.
The implications of Basslink changes to John Butters operations were not considered consequential enough to warrant a mitigation measure, as they paled to insignificance given the magnitude of the present environmental issues. The most major issue of concern with Basslink changes to the John Butters Power Station was primarily from aquaculture leaseholders in Macquarie Harbour. They were concerned that the present periodic dispersal of metal-laden plumes out of the river into the harbour would be exacerbated under Basslink because of changes not only to the King River discharge patterns but also to the Gordon River, these being the two major freshwater inflows to the harbour, thus threatening the viability of their fish farms.
To address the concerns from the aquaculture industry, a 3-dimensional model was developed for the harbour by a renowned estuarine modeller in Australia based on the princeton Ocean Model, and was independently reviewed by an onceanographic expert. Model runs under a range of scenarios showed that the best-case scenario for containing plume magnitude and dispersal is with concurrent high Gordon and King flows, a scenario that would increase with Basslink because both power stations would be operating to meet peak electricity demands. Therefore under Basslink pollution risks are actually reduced for Macquarie Harbour fish farms.
Since the IIAS, the fish farms most vulnerable to plumes have relocated and a remediation program for Mt. Lyell is being implemented.