performance of the existing seepage interception system and reduction in poor quality seepage
expressing to the receiving environment i.e. Dee River.
Overall, the removal of latent tailings and operation of TSFs is expected to result in the reduction of
contaminant sources via the reprocessing of mineralised tailings dams and remediation of operational
areas, which will reduce the volume of mine affected seepage. As a result, it is anticipated that
groundwater quality will improve during and post mining.
5.6.3. Groundwater Recharge and Discharge
The primary source of recharge to the groundwater system is seepage from the flooded OCP /
Sandstone Gully TSF and net infiltration into the various mine waste units (waste rock dumps and
tailings impoundments) (Robertson GeoConsultants, 2011). It is noted that the Sandstone Gully
footprint is proposed to be dewatered to facilitate mining of latent tailings. In general, groundwater levels
in low-lying areas of the model domain are far less sensitive to the (assumed) recharge than
groundwater levels at higher elevations. This is characteristic of high relief watersheds in which
topography (and drainage) strongly controls groundwater levels with much less seasonal variation in
the valley floors compared to the valley ridges.
As part of the groundwater modelling, Robertson GeoConsultants estimated the recharge of each mine
feature which is displayed in Figure 45 with the inferred location of Upper Mundic Gully TSF drawn as
a red square. Seepage from the OCP / Sandstone Gully TSF is the major source of recharge and
contaminant loading to groundwater in the Mundic Valley/Linda Gully sub-catchments, however most
of this seepage and Chemicals of Concern (COC) load is currently intercepted in the interception system
(primarily in Mundic West).
Of significance to this amendment, the recharge potential within the Upper Mundic Gully TSF area is
considered minor at 10 mm/yr whilst the recharge of the adjoining Western Dump is approximately 100
mm/yr.
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Wulguru Technical Services Pty Ltd – Supporting Information to Amend an Environmental Authority
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