The ANZECC/ARMCANZ (2000) Water Quality Guidelines (the Guidelines) are the primary reference used in Australia and New Zealand for managing and regulating water quality. For most mining operations in Queensland, the environmental authority (EA – licence) incorporates the national default guideline values (GVs) for ecosystem protection as trigger levels (TLs). Exceedances of TLs ‘trigger’ further investigation and reporting. A review of the surface water compliance history at a metalliferous mine in North West Queensland identified minor exceedances of the cobalt GV as a common trigger for investigation and compliance reporting.
The reliability of GVs is dependent on the availability and quality of ecotoxicology data for the relevant contaminant. The current national default GV for cobalt of 1.4 μg/L is classified as a low reliability GV due to the lack of available data at the time it was derived (ANZECC/ARMCANZ, 2000).
The Guidelines are presently being revised and the toxicant GVs will be available as a set of web-based values and associated technical briefs. The new platform will enable the timely revision of existing GVs and inclusion of GVs for additional toxicants. Cobalt was considered a priority toxicant for the Guidelines’ revision, but was not included in the revision process.
A preliminary review of the international literature indicated that at least 15 additional chronic cobalt toxicity studies had been published since 2000, sufficient to derive a high reliability cobalt GV using the protocols developed for the revision of the Guidelines (Batley et al, 2014; Warne et al, 2015). This presented an opportunity to improve environmental management by increasing the reliability of the performance measure.
Hogan, A C, Butler, A R, Butler, F and Batley, G E, 2016.
Derivation of high reliability water quality guideline values for cobalt in
freshwaters – improving water quality guidelines for better water quality
compliance management in mining, in Proceedings Life-of-Mine 2016
Conference , pp 205–208 (The Australasian Institute of Mining and Metallurgy: Melbourne).