Peak Gold Mine, Cobar, New South Wales, Australia

Peak Gold Mines Pty Limited

1990-2003

Situation

The Peak Gold Mine began operations in 1992, producing tailings at a disposal rate of 300,000 tpa. In 2000, the New Cobar open cut was opened to supplement Peak’s underground operation and over the years, tailings disposal has increased to around 650,000 tpa.

In 1990, we were engaged by Rio Tinto to undertake tailings testing, geotechnical investigation and water management studies for this new mine.

Solution

Initial testing and design predictions suggested that the central thickened discharge (CTD) technique for tailings would be successful. We subsequently undertook the design and construction of the Tailings Storage Facility (TSF), involving a filter wall to restrict the down valley progression of the tailings, decant collection facilities, a water retaining runoff dam, and a runoff diversion drain to reduce the storm flow into the runoff dam.

Over the years, we undertook several performance reviews of the tailings disposal system. Densities and stack slopes were in line with expectations, predicted from tailings rheology test results, and anticipated discharge rates.

To further expand the scheme’s capacity, we were commissioned to undertake the design and documentation of minor earthworks. Construction was undertaken in mid-1996. Later, in 2000, we undertook design, documentation and construction of a raise to the tailings stack filter embankment.

In 2002, our recommendation to split the flow at the ramp, which would steepen the beach and reduce the need to raise the main embankment, proved so successful that it was several years before the embankment needed to be raised.

Over the 13 year period, our services have covered:

• Conceptual layouts;
• Options studies and costing;
• Investigation for TSF and concentrator water dam and overflow ponds;
• Design and contract management for the runoff dam, filter wall and ramp, as well as the subsequent raises to the filter wall;
• Development of new methods to predict beach slopes;
• Dam break study;
• Flood attenuation assessments;
• Shaft inundation protection; and
• Dam surveillance.

Outcome