Mount Morgan Mine Upper Mundic Gully TSF EA Amendment

Technical Discipline

Proposed works

Conditioning Approach

Timeframe

TSF Design

Development of a geological ground model using available survey, aerial imagery and geotechnical investigations

NA – existing Schedule H conditions from the EA provide requirements regarding the design and construction of a regulated structure NA – existing Schedule H conditions from the EA provide requirements regarding the design and construction of a regulated structure NA – existing Schedule H conditions from the EA provide requirements regarding the design and construction of a regulated structure NA – existing Schedule H conditions from the EA provide requirements regarding the design and construction of a regulated structure

30 June 2027

TSF Design

Further seepage and stability assessment based on geotechnical investigations

30 June 2027

TSF Design

Detailed design of the tailings slurry pumping and delivery system

30 June 2027

TSF Design

Water balance development to: - Determine the DSA requirement -

30 June 2027

Size the return water pump system Size the final stage spillway

-

TSF Design

Conceptual closure design including closure spillway location, channel sizing and PMF assessments

NA – Existing condition H24 requires submission of a decommissioning plan to the administering authority at least one (1) year prior, to decommissioning any regulated structure specified in the EA.

30 June 2027

TSF Design

Detailed design phase including preparation of construction drawings and documentation and RPEQ approval Watercourse reconnaissance to provide site specific observations of surface water conditions and interaction with groundwater systems Geological mapping to improve the definition of subsurface conditions relevant to the UMF TSF seepage assessment Update seepage management plan following the completion of site investigations

NA - Existing condition H4 suitable

30 June 2027

Seepage management plan

NA – Existing conditions H1-H3 suitable

30 June 2027

Seepage management plan

NA – Existing conditions H1-H3 suitable

30 June 2027

Seepage management plan

NA – Existing conditions H1-H3 suitable

30 June 2027

CCA

Update CCA

Existing condition H1-H9 considered suitable

NA – dependent on completion

of other studies 30 June 2027

Groundwater

Execution of the proposed groundwater investigation summarised in Section 6.6.8

Prior to the construction of the Upper Mundic Gully Tailings Storage Facility, the environmental authority holder must install and provide to the administering authority the locations of groundwater monitoring bores to monitor groundwater quality at the Upper Mundic Gully Tailings Storage Facility. Table W1 must be updated to include the

name and location of the additional monitoring bores that are installed

Project number: 25B061

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