Woodvale Ponds Groundwater Investigation
The Woodvale Ponds complex, located approximately 15 kilometres north of Bendigo, was used by Bendigo Mining Limited, and later Unity Mining Limited, to evaporate extracted groundwater removed from local underground mining operations for dewatering purposes. This water contained some environmental contaminants (primarily metals), which were partly a natural phenomenon related to the regional geological setting and partly a function of the mining activities themselves. Some concentration of contaminant levels also occurred within the ponds due to the evaporation process. For these reasons it was necessary to establish and quantify the levels of interaction (if any) between the ponds and the local groundwater system, particularly given groundwater has various agricultural uses further down catchment.
The project team identified the potential for deep lead sediments to be present during an initial review of state sponsored geophysical survey data, which was then used to target and identify areas of potentially preferential groundwater flow beneath and downgradient of the ponds. A background location was also established upgradient of the ponds for comparative purposes. Extensive exploration drilling in the down gradient portions of the study area identified a poorly developed palaeovalley comprising very coarse sediments in some cases. These were targeted with large diameter monitoring wells, which were suitable for both hydraulic characterisation (i.e. pumping tests) and hydraulic containment type remedial approaches, if these were deemed to be required. Extensive geochemical characterisation of the groundwater and pond water was also undertaken, with reference to the naturally occurring levels of environmental contaminants (including arsenic) known to be present in the region.
Benefits to Client
- Identification, delineation and targeting of deep lead sediments acting as preferential pathways allowed some rationalisation of down gradient monitoring network requirements.
- Monitoring bores installed at a larger diameter, at minimal additional cost, to allow for future use in remediation, if required.
- Use of innovative approaches, including publically available airborne geophysical datasets (aeromagnetics) to help refine the location of potential deep lead targets.