Nickel Concentration Ponds

BHP Billiton Nickel West

This job involved lining two nickel concentration ponds at Leinster Nickel Operation with concrete.

This was a highly technical operation which had never previously been attempted. The dams were lined with plastic to prevent nickel from leaching into the water table and causing environmental contamination. The job required concrete to be poured on top of the plastic lining, without compromising the integrity of the plastic lining. Due to the many complexities of this undertaking, there were several issues that had to be addressed in order to complete it successfully.

Due to the limited concrete supply to Leinster, and the amount of concrete required, it appeared that the only way to complete the job was to mobilize a concrete pump from Perth. This expense was going to be a major cost factor in pricing this job. Due to the excessive cost of mobilizing a concrete pump from Perth, Northfields decided to use a crane and kibble in order to move the concrete to the area to be poured. In this way we were able to significantly reduce the cost of the job.

The plastic lining of the dam had to remain intact, meaning that the usual method of using pegs to hold framework in place was inappropriate for this job. An alternative had to be found that would be suitable and equally effective. Instead of using pegs for the framework, sandbags were used, to avoid piercing the plastic lining of the dam.

The job was to be completed during the heat of summer, with temperatures exceeding 45°C every day. Inside the dam, this temperature was significantly hotter, with no shade, and the heat being intensified by the black plastic lining the dam. To reduce the risk of workers succumbing to heat stroke due to the excessively hot working conditions, drink stations were set up inside the dams, so that the workers had access to fluids at all times.

The timing of the job had to be extremely carefully managed, due to the limited concrete supply, the time required to allow the concrete to harden sufficiently before being able to drive on it, and the limited amount of time available to complete the job. As there is only one contractor supplying concrete in Leinster, the timing of the job was crucial to its overall success. As this contractor is primarily engaged to supply concrete to the underground mine a schedule had to be drawn up which allowed the contractor to meet its contractual obligations, as well as providing enough concrete to allow the concentration ponds job to continue.

Northfields WA Pty Ltd hired two trucks from Kalgoorlie, so that they had transport of concrete available to them at all times. In order to complete the job, concrete had to be poured in sections, and each section had to be given time to dry out sufficiently to allow trucks and machinery to cross it to access the next section to be poured.

Northfields WA played an integral part in finding solutions to the above problems, and in working to complete the job on time and to specifications.

Statistics: 1400 cubic metres of concrete poured, project completed within 30 days. Entire project completed incident free despite being completed in full sun in 45 degree heat.

Outcomes: Constant communication maintained with client to ensure the project was able to be completed within a tight schedule and within budgetary constraints.