• Conduct a soil investigation to determine if the tailings material presents any hazards to human
health or ecological receptors and inform the cover design;
• Conduct seepage and groundwater assessments to determine if the structure is potentially
polluting to the receiving environment;
• Installation of a cover over the tailings to prevent tailings erosion and to reduce potential for
capillary rise;
• Installation of a closure spillway capable of conveying runoff generated by the PMP (also known
as the probably maximum flood PMF) event; and
• Verifying that the nominal factor of safety for long-term drained (steady state seepage at normal
operating level) from ANCOLD has been achieved.
6.4.2.3. Cover Systems
Application of a cover system at the Mount Morgan Mine is severely limited by the lack of suitable
sources of material that have not been impacted from previous mining activities. Best practice as
informed from the PRCP Guideline identifies that an EA holder, over the course of operations, should
plan for the conservation of soil material to facilitate rehabilitation planning. As the Mount Morgan mine
is situated on a former highly disturbed mine site there has been limited opportunities for the State and
previous operators to stockpile topsoil and other capping material required for both their own and third
parties’ (Heritage Minerals) rehabilitation activities. Given the uniqueness of this area whereby the site
has been maintained by the state since mining operations ceased in 1990, Heritage Minerals have not
been accountable for stockpiling material to support rehabilitation.
As stated in Section 4.3.9, the results of the geochemical modelling provided in Table 29 indicate that
the final tailings solution analytes do no exceed any of the HILs and it is concluded that leaching from
the tailings material is benign to human health. When tailings are appropriately stored in a well
maintained TSF subject to regular inspections and monitoring, the tailings materials are generally
considered benign to the environment inclusive of ecological receptors. As the project progresses and
deposition into the relevant TSFs occur, ongoing monitoring of the tailings quality will be undertaken to
better inform rehabilitation and closure strategies. It is only following cessation of tailings deposition that
more detailed soil studies can be conducted to obtain both physical and chemical soil parameters to
confirm the rehabilitation and closure strategies.
Based on the lack of available cover material and considering that only at cessation of deposition can
soil investigations be undertaken to determine the chemical and physical properties of the tailings,
committing to a specific cover design at this stage is immature. This application is committing to a cover
system, however the depth of the cover and where the material is to be borrowed to construct the cover
can not be ascertained at this stage. It is likely that construction of a cover system will require the
importation of suitable material from off-tenure locations.
An assessment of the growth media characteristics will be completed by an appropriately qualified
person to determine the amelioration requirements to suit the revegetation plan for the PMLU. Due to
the lack of topsoil resources, growth media may also consist of ameliorated mine waste materials to be
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Wulguru Technical Services Pty Ltd – Supporting Information to Amend an Environmental Authority
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