Tailings spill reported in the Philippines

At the San Antonio copper mine on Marinduque Island in the Philippines, mine staff are attempting to stop an escape of mill tailings from the impoundment into the nearby Boac River.

Owner Marcopper, a Philippine company owned 39.9% by Placer Dome (TSE), has suspended operations at the mine so that staff can concentrate on stopping the escape. The tailings impoundment is a mined-out open pit; before it was brought into use for tailings disposal, a drainage tunnel in the pit floor had been sealed with concrete. The concrete plug began to leak late in 1995 and ultimately failed in late March of this year, causing the tailings to spill into the Boac drainage basin.

The tailings consist mainly of silicate minerals and water, with trace amounts of copper sulphides. The copper would probably not be liberated from the tailings solids in river water. The mill uses conventional organic flotation reagents, which would be present in the waste water only in low concentrations; the decant water from the tailings pond is used, without treatment, as water for washing at the mine site.

The principal effect on the river is that the tailings are settling as mud downstream from the discharge site. Placer Dome staff are monitoring the condition of the river and have alerted government regulatory agencies. The Philippine Trade Commission in Toronto had not received any statements from the government by presstime.