Historic discharging of aluminium
dross
Pre-RMA, historic, physical records of the Southland Catchment Board and regional council are not as detailed and complete as those required post-RMA. However, in records we have located from 1988-90, we have identified:
- Approvals to discharge aluminium dross powder to the Goodwin mine, under certain conditions i.e. not in the vicinity of surface water and same day covering of the dross.
- We have not located any evidence of dross having been discharged at the New Vale mine.
- 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 nearby 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).
Water sample results
In late 2023, following an enquiry from the community about the New Vale mine, we undertook analysis of water samples from the area of the New Vale and Goodwin coalmines, for contaminants associated with aluminium dross. It showed some expected natural variation, but no significant deterioration in the water quality that could be linked to aluminium dross being disposed of in the area.
A suite of water quality tests were taken, including for ammoniacal nitrogen and fluoride.
The series of water samples collected were:
- up and downstream from a small tributary to the Hedgehope Stream, which runs along the boundary of the New Vale mine
- up and downstream from the Hedgehope Stream, which runs along the boundary of the historical Goodwin mine
- from a pond on the New Vale site that is understood to be fed by groundwater in the area of the New Vale mine.
