Heritage Minerals Project accountabilities do not extent to the treatment and discharge of mine affected
water to the Dee River. The State (via DNRMMRRD) maintains responsibility for water management,
treatment and discharge from the OCP in accordance with the Phase 2 Agreement.
Based on the above, the proposed amendments are unlikely to result in further impacts to surface water
values in the Dee River and downstream riverine systems. The addition of the Upper Mundic Gully TSF
to the tailings water management inventory will provide greater resilience against climatic extremes
which reduces the likelihood of overtopping events to ALARP. Heritage Minerals will not be discharging
water into the Dee River as part of mining operations.
Overall, the latent tailings and waste rock recovery and reprocessing at Mount Morgan 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 surface water runoff.
As a result, it is anticipated that surface water quality will improve during and post mining.
6.2.2.1. Acid Sulfate Soils
Acid Sulfate Soils (ASS) form in coastal areas lower than 5 mAHD. The Project is located above 5
mAHD and the risk of encountering ASS is considered negligible. No impacts relating to ASS are
expected.
6.2.2.2. Acid Producing Rock
As noted in other parts of this document, the presence of heavy metals and sulphur bearing compounds
(iron, pyrite, zinc, molybdenum and others) within latent tailings and waste material have caused a
number of legacy issues on the site, predominantly concerned with the issue of acid rock drainage and
water quality impacts on the environment. Heritage Minerals proposed operations intent to remove
sources of AMD contamination through processing of latent tailings with subsequent processed tailings
to be permanently disposed in engineering TSFs.
As the Heritage Minerals project will remove latent tailings without the need to remove overburden,
there will be no additional acid producing rock generated as part of the overall project and the Upper
Mundic Gully TSF construction and operation. The Upper Mundic Gully TSF is designed to tie into the
Western Dump which evidently shows exposed batters that could be contributing to further ARD
seepage into the environment. Sealing the exposed batters will assist with reducing potential leaching
of contaminants from the Western Dump.
6.2.3. Management Practices
The primary objective for groundwater management will be to minimise the release of mine affected
seepage from Project operational areas while progressive tailing reprocessing and Mount Morgan Mine
remediation occurs in accordance with the State’s Rehabilitation Plan (Unger et al, 2003) and Phase 2
Agreement. This will protect EVs and WQOs of receiving groundwaters from further degradation.
As with the existing Regulated Structures contained in the EA, the Upper Mundic Gully TSF will be
subjected to annual regular maintenance inspections in accordance with EA conditions in Schedule H
143
Wulguru Technical Services Pty Ltd – Supporting Information to Amend an Environmental Authority
Powered by FlippingBook