Can Angat dam withstand a 7.2 magnitude quake?

MANILA, Philippines – A consultancy firm commissioned to assess Angat dam’s safety is uncertain whether the 47-year old water reservoir could withstand a 7.2 magnitude earthquake.

Angat dam supplies potable water to Metro Manila and powers a hydroelectric power plant.

Pöyry Energy Limited said Thursday, June 11, that based on its study, it “can’t completely exclude that the dam will remain sound and safe with such magnitude earthquake.”

“We have to take more investigation to ensure that the dam will be able to resist earthquake of that magnitude,” said Pöyry Senior Engineer Stefan Ehlers during the presentation on the Angat dam rehabilitation study on Thursday.

Fears abound that Metro Manila is also due for the “Big One,” following the the 7.8 magnitude quake that hit Nepal in April. Cities and towns traversed by the 100-kilometer West Valley Fault may experience earthquakes of up to magnitude 7.2, while areas traversed by the shorter 10-kilometer East Valley Fault are due for, at most, a 6.2-magnitude earthquake.  

An atlas of the two major fault lines in the Greater Metro Manila area and the vulnerable areas was also recently released, while a metro-wide earthquake drill is set on July 30.

Rehabilitation

The Angat Hydropower Corporation (AHC) commissioned Pöyry to conduct a study and retrofitting on Angat dam. A detailed study will be completed by next year, Ehlers said.

AHC is the locally-set up corporate vehicle between Korea Water Resources Corporation (K-Water) and San Miguel Corporation (SMC).

K-Water, meanwhile, won the bid to privatize the 218 megawatt Angat hydro power plant project in Bulacan.

SMC President Ramon Ang earlier said the rehabilitation of Angat dam is part of K-Water’s agreement with the government.

“Rehabilitation of Angat dam is a go; that’s in the agreement,” Ang said earlier.

The hydroelectric plant is composed of 4 main units, each with a 50-megawatt (MW) capacity and 5 auxiliary turbines.

The power facility uses 5 auxiliary units with a total capacity of 46MW. The 18-MW auxiliary units 1 to 3 were part of the sale, while the 28MW auxiliary units 4 and 5, which are owned by the Metropolitan Waterworks and Sewerage System, are not part of the bidding for the plant’s privatization.

Angat dam is a hydro facility that generates electricity from water released by the Angat dam, which supplies the bulk of Metro Manila’s piped water supply. It is located in San Lorenzo, Norzagaray, Bulacan.

Ang said the rehabilitation works would address the problems on safety and structural integrity of Angat dam. “No one can stop a massive earthquake. We will try to minimize the risk,” he said.

AHC President Geungjeon Han said the contract to rehabilitate the dam will be awarded by end of June and said there are two local firms and one foreign company that have expressed interest to undertake the rehabilitation. – Rappler.com