"There is no disaster awaiting," said DENR regional director Leonardo Sibbaluca, as he belied reports that the spillway has collapsed and that some 1,000 families from three communities have been evacuated.
Sibbaluca said what could harm the townsfolk is the "psychological effect" of wrongly believing that the dam would give way and "they would all be washed out."
"What I only said was that we told the people there to be on alert, just a precaution, because the rains did not stop until Thursday," he said.
The mine tailings dam, he said, is still intact and that although the spillway is slowly eroding, it has not collapsed contrary to reports.
He said the 122-hectare Bayarong mine tailings dam itself is firm enough to even withstand an Intensity 9.5 earthquake.
The spillway, he said, began to erode after a typhoon hit Central Luzon last July.
If the Bayarong dam, which holds 47 million cubic meters of mine tailings, and the Camalca dam, which holds silt and debris, would give way, Sibbaluca said the almost 1,000-hectare catch basin of Mapanuepe Lake and the 2,300-hectare Sto. Tomas River channel will be able to hold that volume of water.
The Dizon Copper and Silver Mines, according to Sibbaluca, has started siphoning a river, using a pumping system, to rehabilitate a tunnel and divert the flow of excess water directly to Mapanuepe Lake and stabilize the water level in the Bayarong mine tailings dam.
But the rains, he said, halted the rehabilitation efforts. Dizon Copper and Silver Mines, he said, has agreed to repair the eroding spillway.
"Even if the dams collapse and the lake overflows, the water will not exceed a meter in height and will eventually thin out into the one-kilometer-wide Sto. Tomas River, which drains into the China Sea," Sibbaluca said.
The Mapanuepe Lake, the DENR said, was formed when lahar from Mt. Pinatubo choked the point where the Mapanuepe and Sto. Tomas rivers traversed each other, swelling the river into a lake and submerging a mining community with 300 houses, a market, a school and a church.
The only danger now facing them, according to Rodolfo, is the possible collapse of the clay dam that would cause flash floods.
Rodolfo, an adjunct professor of the UP National Institute of Geosciences, said the wastes consist of natural elements such as "bits of gold, mercury, zinc and cadmium," although he added that the amount of natural mercury is insignificant.
The Dizon Copper and Silver Mines built the dam in 1975 to control the flow of wastes from a pond it used as repository of water utilized in the milling of ore, said Rodolfo, an Amerasian who has been frequenting his Zambales hometown of San Antonio.
The spillway was designed to cushion the impact of the water spilling over from the pond’s dam.
"What I know is that the Dizon firm does not use mercury to amalgamate gold mined from the area. The amalgamation is done in Japan," he said.
Jaime Tongol, chief of the Dizon Copper and Silver Mines’ maintenance team, said the mine wastes are not laden with mercury.
He said the dam is naturally enclosed by the hills, its southwest side made up of silt and clay extracted from the open-pit Kaline mine.
Rodolfo, however, said the only danger facing the townsfolk, particularly in Barangays Buhawen, Aglao and Makarang, is that the dam’s collapse could unleash some 10 million cubic meters of water from the storage pond.
But he said there is yet no need to immediately evacuate some 2,000 villagers in these areas since the water in the pond is likely to be confined within the Mapanuepe Lake.