Mine Closure Pre-Feasibility Study

Western Australia

Rehabilitating landforms while preserving the cultural and environmental heritage in cooperation with the Traditional Owners.

Calibre QuadR was engaged as the Engineering, Procurement and Construction Management consultant for the Preliminary Engineering Study which forms a part of the Preliminary Feasibility Study.

Project need

The main purpose of the project is to create stable, safe and non-polluting post mining landforms while preserving the cultural and environmental heritage values of the area, in cooperation with the Traditional Owners and other stakeholders.

Calibre QuadR was tasked with delivering a number of project aspects, including infrastructure decommissioning and removal planning, non-mined landforms engineering and all estimating and scheduling activities.

The PES was split into four distinct phases:

  • Review and Options Generation
  • Fatal Flaw and Multi Criteria Analysis
  • Engineering
  • Estimating, Scheduling and Reporting

Our team approached the project with innovation in its design, including utilisation of 3D visualisations, earthworks contractor engagement and identification of cost saving opportunities through capital intensity reviews and minimum viable capital cost studies.

Project solution

The PES investigated and analysed development options and highlighted the technical and commercial risks to identified and recommend options. Findings were captured in the PES report which has been aligned to the company reporting guidelines.

Calibre QuadR split the PES into the following four distinct phases, which helped our delivery team focus on the critical deliverables at each stage:

Phase 1 – Review and Options Generation: Review of previous work undertaken and identification of options, technologies or other closure requirements that should be considered by the PES. During this phase the Basis of Design was developed for the project.

Phase 2 – Fatal Flaw Analysis (FFA) and Multi Criteria Analysis (MCA): Completion of a FFA to identify and remove unsafe options that are strategically or economically prohibitive. The resulting Option Study captured the technical solutions, option costs (CAPEX and OPEX), schedule, engineering and construction risks.

Phase 3 – Engineering: Best design and engineering principles were used to solve technical problems identified during optioneering. Calibre QuadR explored various options (including Minimum Viable Capital Cost (MVCC) options), identified opportunities and selected the preferred solution. The engineering was supported by modelling (including 3D) and associated design to the required level of definition to support estimates.
The Engineering also focused on the execution planning, including identifying options for appropriate execution entities for each stage, formulating the required support structures. The Engineering team also identified future works required to ensure closure objectives were met.

    Phase 4 - Estimating, Schedule and Reporting: Once engineering was completed including the mine planning aspects, material take-offs (MTOs) were created in order to estimate the central, upside and downside costs for each engineering solution using Tier 1 contractors. These were used as the basis for the estimate for the three cases.

    In addition, Pilbara Aboriginal Business opportunities and costs were explored for the central case, as well as a MVCC option. In total eight estimates were developed for each site (16 in total) with Basis of Estimate developed in parallel to capture all assumptions.

    Scheduling was undertaken based on a central case, incorporating the project execution planning undertaken by Calibre QuadR in consultation with the mine planning team. Alternative execution models were also explored, including introducing flexibility into the schedule. The PES report was written and completed by the Calibre QuadR leads for each section.


      • Completed the appropriate level of engineering, estimating and scheduling for the project
      • Identified realistic opportunities for PAB engagement and development of skills from progressive rehabilitation to mine closure
      • Created flexible deliverables that can be utilised at various engagements with stakeholders
      • Consolidated required information (such as HAZMAT register, waste quantities, identification of assets for repurposing, underground services etc.)
      • Identified asset transfer specifications and requirements
      • Detailed execution planning completed
      • Assessed impacts to a highly sensitive and important heritage site
      • Consolidated post closure access requirements and design
      • 3D visualisations (including fly throughs) for stakeholder engagement

      Value Add

      Calibre QuadR added value to the project in a number of ways:

      • PFS investigated appropriate development options
      • Engineering highlighted and addressed technical and commercial risks to identify closure capital cost options
      • Identified new and emerging technologies for closure execution
      • Engaged with an experienced earthworks contractor to identify cost and risk reducing opportunities
      • Communicated effectively with internal and external stakeholders, including development of appropriate drawings and visual aids for various audiences