Philippine tailings spill rains on Placer’s parade

It rained, then poured on Placer Dome (TSE) in the first quarter, as production shortfalls at some of its gold mines were followed by a tailings spill in the Philippines.

The spill at the San Antonio copper mine (operated by Marcopper Mining, 39.9% of which is owned by Placer), on the island of Marinduque, certainly put a damper on Placer Dome’s recent annual meeting.

On March 24, a massive flow of tailings (sand and water) burst forth from a drainage tunnel at the base of the old open pit used by Marcopper as a tailings impoundment area. The material flowed into the Makulapnit River at a rate of 5-10 cubic metres per second after a concrete plug in a disused drainage tunnel failed. Over a period of four days, 2.4 million tonnes of tailings solids discharged into the river. Although they contain traces of copper minerals, the tailings are considered non-toxic (no cyanide is used in the copper recovery process).

The most serious environmental effect of the accident has been the buildup of sediment on the river banks and at crossing places. Consequently, residents have been unable to make use of the river to travel to and from their communities. There have been reports of fish deaths caused by flows of silt, and Placer Dome has hired helicopters to help people cross the river and bring medical teams to the affected areas for health monitoring.

The flow of tailings stopped on its own after four days. Since then, intermittent flows in the order of half a cubic metre per second had been reported. But company officials said that the flow had stopped completely by April 14.

Spilled tailings have been confined to the river bed, with the exception of a 10-hectare swath of banana and coconut plantation. Heavy sedimentation has occurred in the first 14 km of the Boac River (downstream from the Makulapnit), while much of the fine-grained material washed into the Pacific Ocean, 27 km downstream from the mine.

Placer officials say 596 families were affected by the tailings spill. Those whose property was damaged are being compensated by Marcopper. Half of the 800-odd mine employees have been laid off with subsistence pay until the mine is able to reopen.

“You never believe something like this is going to happen after all the best efforts and best intentions,” Placer Dome President John Willson told reporters after the meeting. “In the end, I hope we will look at this as a rather expensive lesson on some of the risks that are associated with building a mine.”

No injuries

Even though Placer Dome has never before been associated with a large-scale environmental accident, and Marcopper has even won awards for its reclamation work at San Antonio, Willson said: “Perhaps we’re not as good as we think.” He added, however, that no person was injured by the spill; there has been no loss of livestock; and it is unlikely there will be any long-term environmental consequences.

“We are well along with mobilizing the technical and financial resources to stop the flow, determine the cause, assist and compensate all the affected people, and design and implement a permanent solution.”

There has been discussion among Philippine authorities regarding the bringing of criminal charges against Marcopper officials, but Willson is confident the charges would not stick. “To conceive that somebody would design a plug that was designed to fail is unthinkable.”

When permanent repairs have been made to the tailings impoundment, or an alternative storage area is identified, Placer Dome will seek the government approvals needed to reopen the mine.

“The communities want it open,” Willson said, pointing out that the mine provides 80% of the employment and 100% of the electricity on the island.

Production below target

Placer Dome produced 458,000 oz. gold in the first quarter, which was only 7% off its target of 495,000 oz. By comparison, the previous year’s first quarter resulted in 400,000 oz. Costs were also adversely affected; the average cash cost for Placer’s share of first-quarter production was US$245 per oz., compared with US$235 per oz. in the first quarter of 1995.

Placer’s first-quarter results were hurt by production shortfalls at the Porgera mine in Papua New Guinea and the Detour Lake and Sigma mines in Canada, as well as disappointing recoveries and grades at the Golden Sunlight and Bald Mountain mines in the U.S.

At Porgera, difficult ground conditions restricted the availability of several high-grade underground stopes, resulting in the postponement of production from them. Reinterpretation of the model of the Main zone at Detour Lake reduced reserves by about two years of millfeed, and resulted in lower grades and developmental constraints which are limiting the mine’s ability to feed the mill at capacity. Operations at Sigma are being affected by two major rock bursts, which occurred in 1995; these resulted in a loss of scheduled high-grade ore and a shortfall in development.

In spite of these results, Placer Dome expects to meet its 1996 objective of producing 2 million oz. gold, and will continue toward its goal of producing 2.5 million oz. gold per year by 1998.