Benguet town is sinking

By Bong Cabagbag

Today, 30 January 1999, p.3

BAGUIO CITY – The Mines and Geosciences Bureau (MGB) will ask the Philippin Institute of Volcanology and Seismology (PhiVolcs) to find out the real cause of the seeming slide of a sitio in Mankayan, Benguet down the mountain slope.

While there are two potential earthquake-causing faultlines from Mankayans’s sitio Tubo in barangay Sapid, Neoman de la Cruz, mines bureau Cordillera director, said it could not readily conclude the cause of the sinking, which was first observed in the 1970s.

But Mankayan residents point the finger on the mining operators of Lepanto Consolidated Mining Co. in the area. In their letter-complaint to the bureau, they blame a vital air compressor, one of five in operation, at the firm’s Tubo shaft mine entry cellar located just 200 meters north of the affected area.

Among the structures damaged by the slow earth slide is the Mankayan Elementary School, in the slightly sloping grounds of which at least two widening cracks in the ground could be found.

In a telephone interview Thursday night, de la Cruz said the "alleged" vibrations of the earth can only be determined with a seismic monitoring work to be done by Phivolcs.

"We are not even totally sure that there are vibrations," he added. "Ground vibrations cannot be determined by an ocular inspection."

De la Cruz, however, said that the Lepanto and Ambanguila faults lying to the north and south of Tubo "could cause movement." But then again, he said this will be up for PhiVolcs to ascertain. Lepanto Fault is located 200 meters from sitio Tubo, in the northeast.

Lepanto, a major fault, and the minor Ambanguila Fault are distant branches of the Philippine Fault, which tremor brought the killer July 16, 1990 earthquake that devastated this city, de la Cruz said. The two faultlines lie some 70 kilometers north of Baguio.

He noted that the Lepanto Fault, ironically, harbors one of the richest gold ore bodies in the world. Lepanto’s Victoria Mines, now 60 years old, yielded around 600 gold bars since it shifted to gold from copper production in march 1997. Last year alone, Lepanto grossed P1.165 billion with nearly 147,000 ounces of gold produced.

A letter-complaint by 91 Mankayan residents that the mines bureau received on December 21, 1998, prompted the bureau to do a superficial survey of the affected area. The survey was done by a team composed of bureau representatives, the environment department, Lepanto Mining, a nongovernment organization and Mankayan barangay and town officials on January 12, 13, 14 this year.

Meanwhile, Lepanto Mining officials blame the two faults. "The mining operation has nothing to do with the sinking," Lepanto Mining environment superintendent Lee Ramon told TODAY during a media tour of the Victoria Mines over the weekend. He cited that Victoria Mine’s active mining tunnels are located 1.5 kilometers west of sitio Tubo.

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