Sinkhole in Dumanjug

CEBU, Philippines - A portion of land which is slowly sinking has created a big crate in the middle of a farm lot and has caused fear among residents of Sitio Plaza, Barangay Cambuang, Dumanjug yesterday morning.

A loud explosion was heard about 5:00 in the morning before the caretaker, Walter Pesalbon, 36, saw the said lot slightly collapse.

The crate was first estimated to be about five inches in circumference and less than one meter deep when Pesalbon saw the land sinking early yesterday morning.

“Gamay pa gyud kaayo na mura la’g kaserola pero nag-anam og kadako maingon og sinkhole, (It was a small hole at first, the size of a casserole but it has become bigger, like a sinkhole.)” Pesalbon told The FREEMAN.

The farm lot was planted with several eggplants and mango trees. 

Pesalbon’s family once owned the lot but it was sold to Susan Inot, from Lapu-Lapu City last 2006. Pesalbon has been its caretaker since then.

PO2 Dan Villardar of the Dumanjug Police Station said that as of 3:00 yesterday afternoon, the sinking portion of the lot was already about 20 inches circumference and five to six meters deep. The parcel of land was still sinking as of 6:00 last night.

According to Pesalbon, he was walking along the barangay road of their place when he heard an explosion beneath the ground.

“Mura’g dunay nahulpa sa ilawom unya naghinay-hinay na og irog ang yuta, (Its as if something caved in underneath and then the soil was slowly sinking,)” he said.

He ignored what happened but Marning Abad, husband of barangay councilor Soledad Abad, happened to pass by onboard his motorcycle and he told him about the incident.

Abad then told Mayor Nelson Garcia and the barangay councilors about it.

The residents became even more afraid when their temporary electric post which was about 18 feet tall, sank as well as a mango tree which was also about eight feet tall.

“Gibira lang nila ang mga wire kay naapil man og kahulpa sa yuta ang poste hasta manga,(They had to grab the wires because the sinking hole also swallowed the lamp post and the mango tree)” Pesalbon said.

Crisanto Cañete, 70, said he feared for his grandchildren who always play nearby.

“Basin unya musulod diha unya maadto na hinuon sa ilawom, kuyaw gyud, (They might go near and end up underground.)” he said.

Garcia who already checked the place said that he will be calling the police as well as the barangay tanods to secure the area from possible entry of children even if it is a private lot and surrounded with barbed wires.

Garcia suspected that there could be running water beneath the ground which keeps the land moving.

However, they still have to wait for the Mines and Geosciences Bureau of the Department of Environment and Natural Resources to conduct an inspection in the area on Monday.

“Even me, I don’t know how to stop it, we will just wait for the experts to conduct an inspection,” Garcia told reporters.

Resident in Dumanjug suspect that “sinkhole” was caused by the February 6 earthquake which hit the entire Cebu province and nearby province of Negros.

Garcia said it was around 1:00 in the morning yesterday, when he felt the latest aftershock.

On monday, the Mines and Geosciences Bureau (MGB)-7 will send a geologist to conduct a site assessment on the reported and recently formed sinkhole in Sitio Plaza, Barangay Cambuang, which is roughly three kilometers from the municipal hall in Dumanjug.

MGB-7 received the information from the Regional Disaster Risk Reduction and Management Council (RDRRMC)-7 that a sinkhole was newly formed within a private property of a certain Joy Distelkamps, which allegedly measures 20 meters by 15 meters in diameter and has a depth of 7 meters.

 MGB-7 Regional Director Loreto Alburo yesterday said he already tasked Senior Science Research Specialist Abraham Lucero, Jr. to check the area.

Based on the initial accounts, the formation of a sinkhole, suspected to be part of a cave, may have been trigged by the 6.9 magnitude earthquake which was followed by many aftershocks as well as the intense and prolonged precipitation brought about by an active low pressure area.  

Alburo said that the earthquake may have caused ground or tension cracks, factors which may have weakened the cave roof.

According to the Visual Dictionary of the Earth, caves commonly form in areas of limestone. Limestone is made of calcite (calcium carbonate), which dissolves in the carbonic acid naturally present in rainwater, and in humic acids from the delay of vegetation. The acidic water trickles down through cracks and joints in the limestone and between rock layers, breaking up the surface terrain into clints (blocks of rock), separated by grikes (deep cracks), and punctuated by sinkholes into which surface streams may disappear.

Alburo already recommended before to the local government units that appropriate precautionary measures be implemented by installing fence or barriers around the affected area, putting up proper signage or warning, and continuous monitoring of the subsidence by the local government units. 

In Cebu province, Alburo noted the presence of sinkholes in 14 barangays. Eleven barangays in Tuburan, namely: Bulwang, Lusong, Montealegre, Santo Niño, Siotes, Kabkaban, Libo, Taminjiao, Kalangahan, Bagasawe, and Sandayong.

 On the other hand, barangays Linut-od in Argao, Kang-actol in Dumanjug, and Vive in Ronda, Cebu were also observed to have sinkholes.

A sinkhole, also known as a sink, shake hole, swallow hole, swallet, doline or cenote is a natural depression or hole in the surface topography caused by karst processes which involves the chemical dissolution of carbonate rocks. (FREEMAN)