Alleged sinkhole reported in Toboso, Negros Occidental

By Glazyl M. Jopson

BACOLOD CITY — The Office of Civil Defense-Negros Island Region coordinated with the Mines and Geosciences Bureau after a suspected sinkhole appeared in Barangay General Luna in Toboso town, Negros Occidental.

The incident was discovered Thursday after the Municipal Disaster Risk Reduction and Management Office received a report from barangay officials.

Jun Carbajosa, head of the municipal disaster risk reduction and management office, said the town immediately submitted a report to the Office of Civil Defense-Negros Island Region and the Provincial Disaster Risk Reduction and Management Office.

Municipal disaster personnel were then deployed to inspect the site and assess the extent of damage.

Initial findings showed the ground collapse measures about 30 meters in radius, 60 meters in diameter and has an average depth of about 1.5 meters.

Carbajosa said the affected area has a circular formation, a characteristic commonly associated with sinkholes.

He said verification by the Mines and Geosciences Bureau is still needed to officially confirm whether the ground collapse is a sinkhole.

Carbajosa said the area is predominantly limestone, which can dissolve when exposed to water, particularly during heavy rainfall, and can contribute to land subsidence.

Sinkholes are commonly associated with karst or limestone terrains, and government geologists have stressed the need for science-based assessments before communities take action. (Philstar.com)

Carbajosa said there are no houses directly within the affected zone, but a nearby house developed cracks in its flooring.

He said the structure is still under construction and has not yet been occupied.

Carbajosa said a similar land subsidence incident occurred in the early 1990s or 2000s in a nearby area of Barangay General Luna.

He said a recent report from barangay officials initially classified the incident as a landslide, but authorities later concluded it was more likely a sinkhole.

Office of Civil Defense-Negros Island Region Director Donato Sermeno said the Mines and Geosciences Bureau is waiting for a formal report from the town to facilitate an official inspection.

Sermeno said the bureau, which has the technical expertise to determine the nature of the ground collapse, has been requested to conduct verification and an assessment.

He said Mines and Geosciences Bureau personnel were not immediately available Thursday but are expected to inspect the site as soon as possible.

Sermeno said the situation is not currently concerning because the affected area is not residential and is known for cave systems, limestone formations and generally soft soil.

He said the location is also near the Toboso and Calatrava fault lines, which are part of an active fault system on Negros.

Sermeno added that a series of earthquakes last year, combined with recent heavy rainfall, may have contributed to soil saturation and ground weakening that could have triggered the subsidence.

He said the Office of Civil Defense’s role is primarily coordination, while the Mines and Geosciences Bureau will provide the technical assessment and final determination.