THE PROJECT

Edna May, operated by Ramelius Resources, is one of the oldest and wettest medium-scale gold mines in Western Australia.  The mine was first operated in 1911, with the latest phase of mining beginning in 2009.

A dewatering rate of about 60 L/s has consistently been produced by fractured and jointed bedrock, commonly associated with pegmatite intrusions.  In the early days, this was too much for existing pumps, leading to one of the first applications of pressure-cement grouting during shaft sinking, world-wide.

In 2009-16, dewatering was achieved by four pit bores in the hangingwall of the Edna May Pit, including one breakthrough bore drilled into flooded underground workings beneath the pit.  Design and supervision of the bore construction was performed by Rockwater.

In 2011, another borefield was installed in a nearby Tertiary palaeovalley sand aquifer as a source of back-up water for ore-processing.  The palaeovalley aquifer was delineated using gravity and airborne electromagnetic surveys, followed by large-diameter air-core exploration drilling.  Five production were then installed using mud-rotary methods.

Rockwater has designed and supervised all aspects of the dewatering and water supply investigations at Edna May since 2009, and continues to provide hydrogeological advice and perform regulatory reporting.

• Geological and geophysical interpretation
• Groundwater modelling, for dewatering and water supply
• Final void modelling
• Surface water modelling
• Field investigation reporting
• Annual compliance reporting
• Mine closure planning

• Core logging and packer-tests
• Gravity and AEM surveys
• Air-core and conventional hammer exploration holes
• Conventional hammer and mud-rotary production bores
• Down-hole deviation (gyro) surveys
• Down-hole camera surveys
• Pumping tests
• Artesian flow tests (underground)