Name of the Project
Gwalia extension project (GEP).

Location
Western Australia.

Client
St Barbara.

Project Description
A detailed budget and execution plan on the Gwalia gold project have confirmed that the project will generate a robust financial return and extend gold mining at Gwalia to at least 2 000 m below surface. It will also provide the foundation for potential further extensions.

The project comprises a ventilation upgrade and paste aggregate fill (PAF).

The project provides additional ventilation through raisebore intake and exhaust ventilation shafts, and associated power and cooling infrastructure needed to mine between 1 800 m and 2 000 m below surface.

To manage the primary execution risk associated with long raisebore shafts, the design uses shorter, two-stage raisebore shafts connected by horizontal development.

PAF involves mixing paste from the surface with waste rock crushed underground for stope fill. Disposing waste underground enables truck and ventilation resources to focus on ore production, boosting efficiency and potentially increasing production. PAF also allows for faster stope filling and, therefore, reduces stope cycle times.

Expediting PAF for use during ventilation shaft construction will allow for underground disposal of raisebore chippings, significantly reducing the impact of the project on ongoing production and greatly enhancing overall project value.

Potential Job Creation
Not stated.

Net Present Value/Internal Rate of Return
Not stated.

Value
The project has a budget of A$100-million.

Duration
The project will take two-and-a-half to three years to complete.

The timeframe for completion of the raisebore shafts will depend on the eventual sequencing of the four individual shafts.

The PAF should be completed within 12 months.

Latest Developments
St Barbara recently completed a new life-of-mine (LoM) plan to 2031 using existing resources and reserves at the Gwalia gold project. The plan contains a change in mining and haulage methods to suit the deepening mine, and the nature of the existing unmined lodes.

The new mining approach – known as Gwalia mass extraction (GMX) – is proposed to start in Year 4, or 2021, of the new LoM plan. GMX is enabled by the GEP. 

The new LoM plan, coupled with the current extension project and ongoing further exploration at depth and in the region, indicates that Gwalia will continue to play a pivotal role for St Barbara. 

A feasibility study on GMX has started and will target the provision of information necessary for an investment decision in December 2018.

Key Contracts and Suppliers
None stated.

On Budget and on Time?
Not stated.

Contact Details for Project Information
St Barbara, tel +61 3 8660 1900, fax +61 3 8660 1999 or email info@stbarbara.com.au.