Angat Dam and its watershed in Bulacan province —CARMELA REYES-ESTROPE
NORZAGARAY, BULACAN—To strengthen the 49-year-old Angat Dam, the government would need to cut 26,000 trees within its watershed here to make sure the structure would withstand stronger earthquakes, a dam official said.
The trees stand on a proposed quarry site, from which 1 million cubic meters of rock would be mined to provide stabilizing materials for the downstream slopes of the dam and its dikes, said Russel Rigor, dam operations engineer of the Angat Hydropower Corp. (AHC).
The government has contracted the Hanjin Heavy Industries to undertake the P1-billion Angat Dam stabilization project.
The quarry site spans 15 hectares of a forested mountain where rocks were quarried in 1967 when the dam was built.
Rigor said the project was given a tree-cutting permit by the Department of Environment and Natural Resources (DENR) on Oct. 30. He said the government has committed to replace the trees with 2.6 million saplings.
The 62,000-ha Angat watershed is overseen by the National Power Corp. (Napocor).
Gladys Sta. Rita, Napocor president, said cutting 26,000 trees would be necessary to improve the dam, which supplies most of the potable water consumed by Metro Manila households and businesses.
But the quarrying has alarmed the Sagip Sierra Madre Environmental Society, which has pushed for the preservation of the Sierra Madre mountain ranges.
Martin Francisco, Sagip Sierra Madre president, said the Bulacan provincial mining regulatory board (PMRB) declined to endorse the project coordinator’s petition for a tree-cutting permit on Oct. 24 and again on Nov. 8.
Small-scale quarrying that spans 5 ha or below requires a permit from the local mining board or from the Mines and Geosciences Bureau if it exceeds 5 ha, said Francisco, a member of PMRB.
He said environmental groups are worried that quarrying should be undertaken within the watershed. He urged the government and its contractor to consider an alternative quarry site instead.
“We want the dam to be rehabilitated but this should be done properly,” he said.
Sta. Rita said the safety and security of millions of people in Bulacan and in Metro Manila were paramount considerations in proposing to cut trees.
The dam should survive a 7.2-magnitude earthquake once its rehabilitation is done in 2018, she said.
According to the Philippine Institute of Volcanology and Seismology, there is a splay fault connected to the Marikina West Valley fault line which runs beneath the dike.
The extension of the fault line is 200 meters east of Angat’s main dike.
Rigor said chances are small that Angat Dam would break or burst due to an earthquake, but the facility still requires reinforcement.
“Gabaldon town in Nueva Ecija province was [the] epicenter [of the 7.8-magnitude Luzon earthquake in 1990] and Angat Dam was not damaged. Theoretically, it could withstand an 8-magnitude earthquake,” he said.
The project has displaced 15 Dumagat families, who were provided new houses by AHC, Sta. Rita said.