Savannah Nickel Mine
Savannah Nickel Mine is a small nickel operation in the East Kimberley region of Western Australia. As part of approvals to increase tailings storage capacity at the mine, WRM assessed impacts of the current operation on the aquatic ecology of Fletcher Creek and its surrounds.
Fletcher Creek flows past the mine site, and is a significant tributary of the upper Ord River that drains to Lake Argyle. Currently at Savannah Nickel Mine, there is an identified seepage pathway from the tailings storage facility to the water storage facility, and directly into an ephemeral creek which drains into Fletchers Creek, 15 km upstream of the Ord. As a result, water quality along this ephemeral creek can become elevated in electrical conductivity, sulphate and some dissolved metals. WRM were contracted to undertake a comprehensive aquatic sampling program and assess the effects of seepage on the overall water quality and aquatic fauna assemblages in downstream creeklines. The project involved:
- the collection of sediment samples to ascertain composition and potential toxicity to aquatic fauna,
- water quality sampling to determine extent of longitudinal gradients in solutes,
- an assessment of spatial and temporal changes in biodiversity and conservation value of fish, macroinvertebrate and zooplankton assemblages that may be related to tailings seepage,
- recommendations for developing both operational and post-closure monitoring performance criteria.
WRM provided empirical evidence regarding the low risk of impacts (i.e. broad scale loss of species diversity) on the downstream aquatic systems due to seepage. During this study, WRM staff were involved with the peer review of recommended water quality criteria, and conducted meetings and workshops with the DPaW and OEPA to formulate water quality criteria. Key outcomes from the project were:
- Development of ecological trigger values for water quality;
- Review and revision of SNM Water Operating Strategy to incorporate ecological triggers;
- Recognition of the importance of protection for Rademy Spring, Stoney Creek and upper Fletcher Creek which provide important aquatic fauna recruitment sources;
- Implementation of on-going monitoring to enable appropriate management response;
- Continued periodic review and update of Operating Strategy to reflect relevant changes.