Major West Wall of tailings dam completed

After two years of planning and a year of construction, the West Wall at the Mount Isa Mines Tailings Dam is complete.

The newly established wall is the largest project to date to be performed in-house and completed by the Bulk Product Logistics Team at Glencore.

The West Wall comprises a 1.6 kilometre long and 15 metre high wall and spillway. The dam wall construction involved significant earthworks using around 400,000m3 of material, with most of the organic material used for the wall construction sourced from within the mine or from local suppliers.

Naren Ramachandran, Superintendent Tailing and Projects Mount Isa Mines says while this major project was completed safely, it wasn't without significant engineering challenges.

"There were difficulties in preparing the foundation with five different geologies needing to be taken into account," says Naren.

"We faced a scarcity of suitable construction materials available on site and needed to employ a complex construction methodology to satisfy the design requirements to ensure the integrity of the embankment."

"Trials in each geology began on site in 2017 and the results enabled us to set the strategy and methodology for grouting."

Building the wall involved establishing a grout curtain, construction of a clay trench, sand filter blanket, rock fill and general fill to form the body of the wall and installation of a lining system.

Being a new dam, a grout curtain which involved pressure grouting the foundation through drilling and grouting to a depth of 18 metres, was required to control seepage.

Construction of the earth fill components of the dam required two crews of 10 skilled personnel on rotating shifts which included project supervisors, operators and engineers.

The crew followed a methodology that allowed placement and compaction of earth materials in layers which were then tested individually to ensure construction specifications were met.

A quality management plan was also prepared to enable appropriate quality control and quality assurance during dam construction to make sure that all design components of the dam were satisfied.

Naren says this is also the first tailings dam on the Mount Isa Mines site that is lined with a geosynthetic clay layer and high density polyethylene sheeting.

"The major challenge during installation of the liners was the hot weather conditions, and at times temperature of the liner reached 85 degrees Celsius," Naren says.

"The overall project was completed safely and it's a great accomplishment for all the personnel involved."

"Some operators were quite new at the start of the dam wall construction but progressed to being competent operators at the completion of the project."

"This really is one of the significant achievements of the project and the knowledge sharing between the senior operators with the crew really helped in achieving our production and construction targets."