New Vale/Goodwin Mines

Historic discharging of aluminium dross

In 2023, the community raised concerns about the potential historic discharging of aluminium dross within the New Vale coal mine at Waimumu, Gore.

During a search of pre-RMA, historic, physical records of the Southland Catchment Board and regional council, we located information from 1988-90 that shows:

• There was a proposal in 1988 to discharge aluminium dross powder to the New Vale mine, however, there was an issue with access to the New Vale mine site. Therefore, the Southland Catchment Board granted permission to discharge the aluminium dross powder at the adjacent Goodwin mine instead, under the same conditions, i.e. not in the vicinity of surface water and same day covering of the dross.
• There was no evidence of dross having been discharged at the New Vale mine.
• Records indicate that up to two truckloads of dross powder were taken to the Goodwin mine, which we estimate would have been up to about 70 tonnes, where it was mixed with overburden, rocks and soil and buried.
• Subsequently, in 1989 and 1990, monitoring for key contaminants, including fluoride and ammoniacal nitrogen (a measure of ammonia content), was conducted in the areas of both the New Vale and Goodwin mines and the Hedgehope Stream.
• On several occasions slightly elevated results for ammoniacal nitrogen were detected at the Goodwin mine and in the Hedgehope Stream. Ammoniacal nitrogen is common in pastoral areas due to fertiliser use. Therefore, the results did not confirm the contamination originated from the disposal of the aluminium dross powder and the source remains uncertain.
• Across the historic sampling undertaken at the time, there were no detectable levels of fluoride. The slightly elevated levels of ammoniacal nitrogen were not at levels that would generate any significant adverse health or environmental effects, according to the Australasian standards (ANZECC).
• Based on the information we have located, our contaminated land scientist has assessed the potential environmental impact and human health risk posed by the aluminium dross powder at the Goodwin site to be ‘considerably low’. This is primarily due to the depth it has been buried, the potentially large area of the mine, which it has been distributed across and the volume of overburden covering, what is estimated to be, a limited amount of dross.

Contaminated land sites

Both the New Vale and Goodwin mines continue to be listed as contaminated land sites due to their mining use, which will assist in the appropriate future management of these areas. The Goodwin mine is now closed and is privately owned. Its land use is pastoral farming.

There is no evidence of any significant adverse effects occurring and moving or unearthing the soil now could pose a considerably higher risk than leaving it undisturbed.

Next steps

August 2023 - By way of follow up, our monitoring team will be conducting water quality sampling of the Hedgehope Stream to test for ammoniacal nitrogen and fluoride to inform the community. Soil and sediment samples will also be taken. Once these samples have been analysed, we will update this information.