THE SINKHOLE ASSESSMENT TEAM of the Mines and Geosciences Bureau met with Gov. Edgar M. Chatto and other Provincial Government officials Friday to present the initial results of their assessment of the sinkholes found in southwestern Bohol. The assessment is aimed at ascertaining the presence of collapsed sinkholes and caves in the earthquake-affected municipalities using geomorphological information and the Ground Penetrating Radar and to determine their subsidence susceptibility due to sinkhole and/or cave collapse in select-government infrastructures (i.e. schools, roads, municipal buildings) and other priority areas identified by concerned LGUs. The team said that it is also to conduct awareness campaign on sinkholes, and issue threat advisories to LGUs relative to the hazards of subsidence due to the same.

They informed the governor that they have used four kinds of methods in determining the situation of the province due to the October 15 earthquake like the Geomorphological or Geological Assessment method, the Ground Penetrating Radar surveys method, listened to anecdotal accounts of the victims and referred to Information Education Campaign (IEC) materials. By using those mentioned above, the team was able to create maps showing the location of sinkholes and uvalas, the observation points in Southwestern Bohol, and the GPR survey stations in the same parts of the province. In eleven municipalities, namely: Antequera, Balilihan, Catigbian, Clarin, Cortes, Loon, Maribojoc, Calape, Sagbayan, San Isidro, Tubigon and Tagbilaran City, they were able to establish 73 GPR lines, 767 observation points and assessed a total of 57 barangays.

They were also able to show pictures highlighting the following: sea sinkholes in Pangangan Island, Calape; an uvala or karst valley in Napo, Loon; a collapsed cave in Taloto, Tagbilran City; an underground river in Cambailan, Catigbian; a spalling on the hills surrounded by sinkholes in Ubojan, Sagbayan; a spalling along a highway in Obujan, Antequera; a sinkhole in Bogtongbod, Clarin; a karst window on a collapsed Provincial Road in Poblacion, Catigbian; tension cracks and subsidence in Bunacan, Tubigon; cave entrances in Punta Cruz, Maribojoc; showed the differences in the sizes of the sinkholes dated Oct. 26, 2013 and Nov. 14, 2013 of Pangangan Elementary School; a land subsidence on the Provincial Road in Caimbang, San Isidro; and a spalling in Poblacion, Cortes. The Assessment Team's GPR survey results showed that in Bohol, there are apparently five signs of subsidence which occurred due to the October 15 earthquake like heaving, spalling, cave collapse, tension cracks and sinkhole collapse. The team is leaving Bohol very early this morning via the first flight scheduled for Manila. But before they left the Bohol Team led by Gov. Chatto, they have passed on their recommendations to the Boholano people.

The group suggested that from hereon, the people should continue to monitor for further sinkhole and/or cave collapse and subsidence in the areas mentioned in their reports; exercise extra vigilance especially during heavy, continuous rains brought about by typhoon or monsoon rains, and during aftershocks; monitor for tension cracks that are widening and/or progressing and to immediately report them to their municipal authorities or MDRRMOs; cordon off identified areas of sinkhole and/or cave collapses; observe for sunken or displaced surfaces along National Roads and report these situations to their municipal authorities or their MDRRMOs; limit the load capacity of vehicles passing on these types of roads where signages should be put up indicating the threat of subsidence, and if possible, find alternative routes to lessen the load brought about by vehicles; demolish badly-damaged structures to decrease load; dwelling units should be made of light materials and advise that two-storey structures are not advisable; temporary relocation should be given to those residents near the tension cracks, many collapsed sinkholes, and/or subsiding grounds; six months to one year observation period of cracks progression and/or continued subsidence; determine if the area may be habitable if the ground becomes stable after the recommended observation period of six months to one year; drying-up of wells, water-filled sinkholes/caves are indicators of further ground movement and shift in flow directions of subterranean rivers; avoid drinking from newly-emergent springs unless checked for water quality or potability; and avoid disposing of garbage and wastewaters to sinkholes and caves to prevent contamination of groundwater. Gov. Chatto is now asking all Boholanos to cooperate and heed the warnings and advisories given by the MGB. (jlv/EDCom)