The upgraded and modernized processing facilities at Carmen Copper’s Toledo mine.
The upgraded and modernized processing facilities at Carmen Copper’s Toledo mine.

ADAPTING to cultural differences to help enhance foreign mining operations in remote locations has become increasingly common for Australian engineering consultants like pitt&sherry. Australian mining services companies are swarming to developing countries as locally based firms seek a high level of technical expertise to help lower operating costs and improve productivity.

A company founded in Tasmania more than 50 years ago, pitt&sherry, has identified the international opportunities on offer and in recent years has undertaken mining projects in the Asia-Pacific. Last year the company was subcontracted by Outotec to upgrade and modernize the processing plant at Carmen Copper Corp’s Toledo mine in the Philippines.

Operations manager at pitt&sherry Nick Bailey said despite the obvious mining potential in Asia much of the region remains relatively underexplored. “With the expertise of Australia’s mining industry, particularly at the contractor and consultant level, there will be demand from countries like the Philippines for our skills in several areas as their industry develops. Australia has the people, technology and expertise to continue to find these opportunities as the potential of new mineral deposits is realized.”

Outotec, with pitt&sherry, developed a solution for Carmen Copper that will increase daily throughput at the mine’s processing plant from 40,000 to 60,000 tonnes. The upgrade will enable Carmen to establish a more cost-effective operation, with the company’s ultimate aim for the mine to be in the lowest quartile of mining companies in the world in terms of production costs.

The mine is near Toledo City on the island of Cebu. Carmen Copper, a wholly-owned subsidiary of Atlas Consolidated Mining and Development Corp, has been operating at Toledo since 2007 following rehabilitation of the mine.

Outotec was appointed by Carmen as the upgrade’s principal process and technology partner on an engineering, procurement and services basis and as supplier of proprietary minerals processing equipment. To complement Outotec’s technological expertise, pitt&sherry was engaged to provide geotechnical and civil engineering services for several elements of the upgrade.

“We harmonized with each other on this project – Outotec had the process and technological solution for the upgrade and we had the geotechnical skills to guide implementation of the technology,” Nick Bailey explained. “Carmen Copper was seeking technology specific engineering services from the ground up to complement its equipment supply, which led Outotec to pitt&sherry for our civil and geotechnical skills.”

The responsibilities of pitt&sherry included a geotechnical investigation for various locations of the concentrator, which was to include the grinding mill and thickener upgrades, covering both fieldwork and laboratory testing.

Once the investigation was complete pitt&sherry provided design and documentation of the civil works associated with most aspects of the upgrade. The geotechnical assessment found that the area for the proposed extensions to the grinding mill and flotation tanks consisted of a number of cut and fill platforms, separated by retaining walls. The grinding mill level was about 8 metres higher than the flotation tank level and retained by a sloping concrete level.

Outotec proposed two new grinding mills for the upgrade which were developed on thick concrete raft slabs and isolated foundations supported by rock anchors. The columns for the overhead gantry crane were founded on a separate pad foundation, the same level where pumps and blowers would be constructed for the mills and flotation cells respectively.

Based on the pitt&sherry geotechnical investigation, excavation of rock was required at the mill, pump and blower levels. The geotechnical design also removed the sloping concrete level. The flotation tanks, typically 8 metres high by 8 metres in diameter, were designed to sit on thick concrete platforms about 6 metres above ground level.

Several geotechnical design issues were considered by pitt&sherry, including bearing capacity of the piles on the limestone, implication of cavities in the limestone on pile bearing capacity, shear resistance parallel and perpendicular to the retaining wall, and construction equipment available. These considerations led to a final solution supporting the flotation tanks on a raft slab.

pitt&sherry provided civil design support for all ancillary works consisting of an onstream analyser, flotation cleaner cells and the tailings feed system, from the geotechnical investigation and for build consistency isolated pad foundations, and raft slabs were adopted for these structures.

A key part of the project’s success was the close partnership formed between Outotec and Carmen, and in turn with pitt&sherry. The delivery schedule for the upgrade was extremely ambitious and meant pitt&sherry needed to quickly adapt to changing conditions on site in the Philippines.

“The upgrade was a demanding project, but by understanding each other and our cultural differences Carmen Copper is well placed to achieve its goal of establishing a more cost efficient operation,” Nick Bailey concluded.

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