The current drilling campaign has included the construction and development of 19 groundwater monitoring bores in the immediate vicinity of the Pyrite Hill, Big Hill, and Railway deposits. The newly constructed bores further support the long-term groundwater level and water quality measurements from 13 monitoring bores that have been in place since 2018.
Water quality measured at the BHCP groundwater monitoring bores indicates that:
- the aquifers are generally acidic (pH 3-6) when measured near the ore bodies
- all groundwater is highly saline with electrical conductivity ranging between 2,000-13,000 µS/cm.
- all site monitoring bores exceed the Australian Drinking Water Guideline criteria of 1,000 mg/L for Total Dissolved Solids.
- a significant concentration of dissolved cobalt has been measured in most monitoring bores (in the order of 1-20 mg/L), signifying past oxidation of the pyritic mineral body that has given rise to dissolved cobalt in the local groundwater.
The new bores will be used to establish pre-mining baseline conditions further away from the ore bodies so that any impacts associated with mining can be determined.
Vibrating Wire Piezometers (VWP) were also installed at 4 sites to continuously measure the pore water pressure. In addition, the saturated hydraulic conductivity of the rock mass was also determined at several depths at these 4 sites.
The ongoing monitoring of data, as well as information determined via the VWPs and hydraulic conductivity measurements, will be used to initialise a groundwater model. This model that will be used to prepare a groundwater impact assessment for mining and waste management aspects of the BHCP.