MALOLOS CITY—An official of the National Power Corp. (Napocor) has allayed fears of a possible dam break in Angat Dam in case a 7.2 magnitude earthquake, generated by the movement the Marikina West Valley Faultline (MWVF), jolts Metro Manila and its surrounding areas.
“The dikes of Angat Dam are rock and earth-filled, and based on studies, it is more adaptable and flexible to earthquakes compared to concrete dikes,” said Romualdo Beltran, acting head of the dams management department of the Napocor, during an interview after the Talakayang Bulakenyo press conference here on July 5.
Beltran, however, said rock and earth-filled dikes are more vulnerable to over topping or water overflow.
But he stressed that such scenario is manageable because dam personnel can always release water from the dam’s spillway to prevent overtopping.
“I can assure you, Angat Dam can withstand magnitude 7.2 earthquake because it was designed to withstand [the] maximum earthquake [strength as predicted by the Philippine Institute of Volcanology and Seismology],” Beltran said.
He said unlike humans who weaken upon reaching the age of 50, a dam stabilizes as it ages.
“Dam structures, especially rock and earth-filled dikes, get stronger through the years, unlike us or medicines that expire after a certain period,” he said.
Constructed and commissioned in the late 1960s, Angat Dam, which supplies 97 percent of potable water requirement of Metro Manila, can store a maximum of 738 million cubic meters of water at elevation of 212 meters above sea level (masl).
Its powerhouse generates at least 146 megawatts to the Luzon power grid while serving as a major flood control in Bulacan.
Last year, Tonkin & Taylor International, along with local partner Engineering Corporation of the Philippines (EdCOP), completed a six-month feasibility study on the stability and integrity of the dam.
One of their recommendations is to rehabilitate the dikes of the dam in the light of the presence of a splay fault of the MWVF near the dike.
The national government has set aside P5.7 billion for the Angat Dam rehabilitation, but the project has yet to be bid out.
Earlier, Phivolcs Director Renato Solidum said the MWVF is ripe for another major movement.
In a lecture organized by the New Zealand Embassy in the Philippines, Solidum said a powerful quake could emanate from the movement of the fault that stretches from Angat Dam to Taal Lake in Batangas.
Solidum warned that about 168,000 residential buildings in Metro Manila could be damaged by the quake.
Text and photos by Dino Balabo