FOCUS: Philippines fears massive tailings dam collapse.

SAN MARCELINO, Philippines, Sept. 20 Kyodo

Residents and local government officials in this Central Luzon town fear the collapse of an abandoned mine's tailings dam that may swamp a surrounding lake and river with mineral waste and flood nearby towns, despite assurances of stability from mining company officials.

Locals, mostly Aeta tribesmen, said they hope the Dizon Copper-Silver Mines Inc. (DCSMI), which maintained copper-silver-gold mining operations in the area for 17 years until 1997, will repair two collapsed spillways in the huge dam in San Marcelino in Zambales Province.

The spillways are exit points for water held back by the DCSMI tailings dam, which is 120 meters tall and has an impounding capacity of 110 million metric tons of tailings.

Heavy downpours during recent months caused impounded water to rise faster than the spillways could cope and they collapsed Sept. 12, forcing 1,000 families to flee the area.

As many as 9 million tons of water could escape if the spillway damage grows and breaches the main dam.

Already mine waste is pouring from the collapsed spillways into Mapanuepe Lake, which was formed when the 1991 eruption of Mt. Pinatubo clogged the Santo Tomas River with mudflow and volcanic debris.

''We fear the dam will break. It will wipe out everything...,'' a resident employed as a watchman at the dam said.

An arm of the Department of Public Works and Highways (DPWH) studying sediment movement and flood control for Mt. Pinatubo inspected the spillways again Thursday, along with representatives of the Japan International Cooperation Agency (JICA), after the Sept. 12 collapse.

But at a meeting Friday, DPWH and JICA said the matter should be thrown back to the local government.

Zambales Vice Gov. Ramon Lacbain said the local government's help was sought in convincing locals to evacuate. Though there is supposedly no immediate danger of collapse, officials would prefer residents are evacuated to safer places, he said.

He said evacuation would ''ease minds'' as the mining company tries to pump water out of the reservoir and brings in equipment for massive repairs.

Lacbain said a commitment to pump the water out has been made by Benguet Corp., one of the biggest and oldest mining firms in the Philippines and DCSMI's mining partner at Zambales.

For DCSMI's part, mine site officer-in-charge Jaime Tongol said the dam would not collapse because its American makers ''assured stability of the structure for up to 1,000 years.''

One of the biggest earth-dams in the Far East, the structure is made up of compacted soil and concrete and should withstand an earthquake measuring intensity 9 on the Richter Scale, he claimed.

The 10-meter-wide dam has a 500-meter base with filters to guard against a buildup of pressure that could harm a solid concrete structure, he added.

And even in the ''remote chance'' of a collapse, Tongol said calculations estimate flood waters would only be a meter deep because most of the outflow would be absorbed by Mapanuepe Lake.

But DCSMI has started exploring engineering schemes, including siphoning off water and diverting it from the collapsed spillways.

''We just can't start immediately with the plans because of the rainy weather,'' Tongol said, adding evacuation is necessary because the mere presence of impounded water is usually equated with danger in the area near Mt. Pinatubo where mudflows have caused landslides and overflowing of rivers.

The dam was built in the late 1970s.

During the mining operations, nearly 800 million pounds of copper, more than 3 million ounces of silver and nearly 2 million ounces of gold were produced from more than 110 trillion tons of ore.

The pit, which yielded ore three years beyond its estimated life, was finally closed because of slope instability and annual flooding.

In the last mine tailings accident in the Philippines, 17 homes were buried and 51 hectares of farmland were swamped in tailings in 1999 when pipes at a gold mining operation in Surigao del Norte gave way.