EMM Consulting Pty Ltd (EMM) was engaged by Kalbar Resources Ltd (Kalbar) to undertake a groundwater impact assessment of the proposed Fingerboards Mineral Sands Project, located in the Gippsland Basin, Victoria. To support the assessment, a regional numerical groundwater model, supported by drilling and pumping test programs, was developed and used to predict impacts on the groundwater system during operation of the proposed mine, including water supply aspects.
Approximately 3 GL of water will be required on an annual basis for processing, dust suppression and rehabilitation. Water for the project will be sourced primarily from surface water (i.e. winter-fill license from the Mitchell River) and supplemented via groundwater sourced from the deep Latrobe Group Aquifer (from a borefield south of the project area).
The study has identified that groundwater drawdown impacts as a result of abstraction for water supply are likely to be low, as impacts are largely constrained to the deep aquifer with only minor drawdown predicted within the overlying aquitard. Based on the impact assessment framework, predicted drawdown and mounding have insignificant impact on groundwater dependent ecosystems (GDEs), thus environmental risks associated with the proposed mine development are considered low.
For surface water supply, the Mitchell River winter-fill allocations may be utilised between 1 July and 31 October when river flows measured at the nearby Glenaladale gauge are greater than 1400 ML/day. River flows during the winter-fill period are below 1400 ML/day 20% of the time on average through the gauged flow record. While Kalbar intends to obtain a 3 GL/year winter-fill license, stream flow analysis shows that in four years since 1938, droughts would have reduced off-take availability to less than 1.5 GL/year. Relying on winter-fill alone would result in an unacceptably high probability that the mine would experience a process water shortfall of greater than 6 months duration at least once during the mine life, likely requiring mine idling.
Interannual storage of water to buffer dry spells may be needed, with managed aquifer recharge (MAR) potentially providing a mechanism for safely storing large volumes, replenishing an aquifer that has been heavily utilised by historical coal, oil and gas industries, with the potential to assist the surrounding irrigation and horticulture community during drought and low flow periods.