A HOLE that opened up in Barangay Virac in Benguet’s mining town of Itogon, swallowed six houses since Oct. 22. Richard Balonglong/INQUIRER NORTHERN LUZON
ITOGON, Benguet—The origin of a 20-meter-wide hole, which swallowed six houses at a mining community here last week, remains a mystery.
Geologists and engineers have failed to determine how deep this funnel-shaped void extends in Sitio Kamangaan in this mining town’s Virac village, “although it appears to be man-made and not a natural geological weakness in the area,” said Fay Apil, Cordillera director of the Mines and Geosciences Bureau.
The sixth house—a three-story concrete structure—may have plugged up the hole for the moment, but experts would not come close to the void because the hill on which the houses once stood remains unstable.
“We would not even send anyone down that hole because more houses could fall,” said Apil, a geologist.
What was certain, she said, is that some Virac residents would need to abandon their houses permanently because of the danger posed by the hole that opened when a portion of the ground caved in on Oct. 22.
The hole also destroyed a road in the community.
The police evacuated 166 families, and had cordoned off about 100 meters of this area in Kamangaan.
Some families had to be coaxed out of their houses last week, Apil said.
But other families volunteered to leave, when they realized that a row of houses along the ridge began to crumble down the hole, the Inquirer learned on Tuesday.
A mining company that operates here took in 29 of the evacuated families because their relatives work for the firm.
The rest of the families occupy classrooms of the Virac Elementary School and Balatoc Elementary School.
The families cannot stay there for long, however.
Mayor Victorio Palangdan said these schools will resume classes on Nov. 3, giving the town government little time to find them new homes.
Apil said experts need time to determine the extent of the danger. But she said as many as 20 houses are close to the growing void.
“Until we confirm why this is happening, we do not know how many more families would be relocated,” she added.
Apil said the void was not a sinkhole, which is opened when underground water current carved a path through limestone rock beds.
The Virac hole exposed what appeared to be chlorite clay material, according to the initial examination by geologist Jerali Rodrigo.
Apil said the mining firm operating there had once excluded the area for settlement because it served as a natural gulley, based on the mine’s archival records.
Geologists have started exploring and testing two underground tunnels that lie beneath Kamangaan.
They found no rupturing in an old tunnel, which is 57 meters below the road, as well as a diversion tunnel built in the 1960s which lies 80 meters from the surface.
The diversion tunnel redirects the Ambalanga River from an old mine tailings facility, but it appeared to be functioning properly.
“The void is huge, so any rupturing would leave traces. Yet no debris spilled out from the diversion tunnel’s outlets when it was inspected by two teams. [The agency] is not making any conclusions yet; we will continue to explore these tunnels,” Apil said.
On Tuesday, MGB and mining engineers inspected the tunnel but their findings have yet to be made public.
Finding new homes has become the most pressing issue for Mayor Palangdan.
Thelma Rumilan, 50, and a resident of Virac, said her family shares a small classroom with four neighbors.
“We try very hard to go about our daily lives. Those who have work go to work and the others stay here and look after their children,” she said.
Rumilan said she was born and raised in Virac, but has no relatives who could take them in.
“We just want a place where we could build a house. We do not desire a big house, just enough to shelter us,” she said.
Arlina Alito, 36, used to live in the first house the void swallowed on Oct. 22. She moved here from Biliran province more than a year ago and had just delivered her fourth child on Sept. 22.
“We relocated to Virac in 2014 at the encouragement of my husband’s cousin. We lost our house in Biliran to Supertyphoon ‘Yolanda’ so we decided to come and try our luck here,” she said.