Accelerating dewatering at Odysseus

Located 30km north of Leinster in Western Australia, Western Areas’ $299 million Odysseus Project—part of the company’s Cosmos Nickel Complex—is expected to produce 130,000 tonnes of nickel concentrate and have a ten-year life. In January, stage one of an early works program was completed, including the construction of two new water management ponds (WMPs), an associated dewatering program and rehabilitation of existing decline infrastructure.

The Odysseus Project sits on a granted mining lease that is part of the high grade Cosmos Nickel Complex, and lies in the heart of the prolific Leinster-Wiluna nickel camp, home to many high-quality deposits such as Mt Keith, Cliffs, Perseverance, Rocky’s Reward, Honeymoon Well, Venus and Yakabindie.  

 Odysseus was identified in 2010 and is the most recent discovery in a string of successes at Cosmos. From 2000–2012, over 127,000 tonnes of nickel concentrate was produced. 

 The Odysseus Project will involve mining of the ore reserve via an extension of the existing Cosmos decline and processing via the existing plant and infrastructure, both of which will be upgraded.  

 The project will incorporate some of the latest technology, to further enhance safety, operational efficiency and reduce costs, including a state-of-the-art mine control room that will be the real-time operational centre, monitoring and controlling ventilation, refrigeration, pumping, paste filling and mobile fleet activity.

The system will monitor personnel and equipment location, providing real-time feedback to the Ventilation on Demand (VOD) system to optimise power draw and ensuring chilled air is directed to the appropriate areas. 

Western Areas Managing Director, Dan Lougher, said, “Odysseus will utilise a shaft hoisting system, which is justified based on a ten-year operating life and throughput averaging around 900,000 tonnes per annum. Western Areas has already secured an option over a high-quality, second-hand, shaft hoisting asset from South Africa that is ideally suited to Odysseus and has been costed into the DFS.

The shaft hoisting operation will utilise a top-down mining approach, rather than the bottom-up method assumed in the PFS, and accordingly has generated substantial savings in ore transportation costs, as well as a reduction in mine development CapEx.”

The early works program

Western Areas acquired the Cosmos Nickel Complex through a deal with Glencore in 2015, however, as the dewatering pumping system was deactivated in 2013, the groundwater inflows had flooded the underground mine workings and partially filled the Cosmos pit. 

In order for mining operations to commence, in April last year a $32 million early works program begun and involves three major work programs over an 18-month period.  

Cosmos Mill previously in operation. Image from Wester Areas.

Cosmos Mill previously in operation. Image from Wester Areas.

Stage one

Stage one of the early works program began in 2018 and was completed in January, with a focus on the rehabilitation of existing water management ponds (WMPs) and dewatering activities.

Dewatering of the main Cosmos pit commenced at 50L/s at the start of 2018 and was accelerated to 120L/s as the new water management ponds (WMPs) came online.  

By the end of last December, over one million cubic metres of water had been pumped into surface water management ponds, reducing the water level by 37m. 

Following the success of dropping the open pit water levels, a Schlumberger submersible pump was installed and commissioned in the southern vent in early January, adding 100L/s of additional pump capacity from a depth of 500m below the surface. This raised the total dewatering capacity to 220L/s.

The in-pit diesel pump was removed in late February having dewatered 90 per cent of the in-pit water and was expected to be replaced by an electrical pump station in early June.

Other progress during this stage included electrical reticulation, shaft headgear installation and upgrades for the 520-room camp site (the Cosmos village) to meet the needs of staff during initial works.

Stage two

Stage two of the early works program began in January, and involves the construction of two new evaporation ponds and dewatering of the decline by Barimco for six months.

By the end of March, 2033m of decline had been rehabilitated to a depth of 236 vertical metres from surface. Primary ventilation has also been re-established with the commissioning of a 55kW exhaust fan.

Following the expected completion of decline rehabilitation in June, a new pump station will be installed to assist ongoing dewatering.

Stage three

The final stage will focus on infrastructure to support the rehabilitation of the decline from the portal to 500m underground.

This stage will involve the pump station to be recommissioned and new pumping infrastructure to be installed for the life of the mine. The design capacity of the ongoing normal operational pumping infrastructure for Odysseus will be 100L/s, which will be sufficient to manage estimated inflows of around 25–50L/s.   

Once all three stages of early works are complete, Odysseus will be development ready based on the prefeasibility study schedule.

Supplying the electric vehicle sector

With first nickel concentrate scheduled for 2022, Odysseus will be one of the few nickel sulphide mines coming online just as forecast demand for Class 1 nickel is expected to substantially increase in the electric vehicle sector.

 “The demand for Class 1 nickel sulphides in the battery and electric vehicle market is forecast to grow substantially over coming years,” Mr Lougher said. 

“Odysseus is an important growth asset for Western Areas and should be one of the few new global nickel sulphide operations scheduled to come online as the forecast uplift in nickel demand for electric vehicles impacts the market in the 2022 timeframe.”

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