A Filipino fisherman in front of the oil tanker M/T Makisig surrounded by oil containment booms off the shore of Cavite.

Petron Corp yesterday admitted its pipeline in Cavite caused the spread of half a million litres of diesel fuel in Manila Bay which affected four towns and over 30 villages in the province.

The Philippine Coast Guard said the spill formed a sheen of orange-coloured liquid over 300sqkm in the waters of Manila Bay and Cavite.

“We take full responsibility for this unfortunate event,” Petron Corp President Lubin Nepomuceno said. “We apologise and assure affected communities that we will do our best to resolve the situation as soon as possible.”

He said Petron will help residents affected by the oil spill.

Coast Guard spokesman Armand Balilo said divers will pinpoint the exact location of the leak by pumping coloured water through the pipeline.

The National Disaster Risk Reduction and Management Council (NDRRMC) said the spill discovered on Thursday affected 35 barangays in the towns of Rosario, Tanza and Naic.

Petron had earlier denied that the pipeline in its depot in Rosario was the source of the oil spill.

The Coast Guard on Thursday said it was preparing to charge Petron and the owner of the tanker MT Makisig for obstruction of justice for not allowing its personnel to obtain fuel samples and for violating the Clean Water Act.

The Bureau of Fisheries and Aquatic Resources (BFAR) yesterday said it is continuously monitoring the waters affected by the oil spill to determine its effect to marine life.

BFAR Director Asis Perez said the oil slick seemed to have drifted out to deeper water towards the mouth of Manila Bay.“BFAR’s Monitoring, Control and Surveillance (MCS) patrol vessels, along with the Philippine Coast Guard, have monitored the oil spill moving in the boundary of Ternate and Naic near Daang Barko as caused by the wave action and wind direction,” Perez said.

He added that minimal fuel sheen was also spotted in the waters of Rosario indicating that the oil could have dissipated.

Another monitoring team in Ternate reported that the slick there appeared to have vanished as well. Ternate is the last coastal town on the Cavite side of Manila Bay.

Water samples were collected from the areas of Timalan Balsahan in Naic, Amaya in Tanza and three sampling stations in Rosario near where tanker MT Makisig is docked to determine dissolved oxygen level (DO), the presence of ammonia nitrite, Ph and salinity. Initial monitoring showed no traces of ammonium nitrate, Perez said.

He said that the severity of the impact of an oil spill depends on a variety of factors, including the characteristics of the oil itself.

“Natural conditions, such as water temperature and weather, also influence the behaviour of oil in aquatic environments. Various types of aquatic habitats have different sensitivities to oil spills,” he said. In open water, Perez noted that fish have the ability to swim away from a spill by going deeper in the water or further out to sea.