NIA assured Pantabangan Dam can withstand Intensity 10 quake

CABANATUAN CITY, Nueva Ecija, March 16, 2011-The National Irrigation Administration (NIA) assured yesterday that the country’s largest dam that supplies irrigation to over 100,000 hectares of farmlands in Central Luzon, can withstand a powerful earthquake even one that is stronger than the Intensity 9 tremor that triggered a tsunami in Japan.

NIA administrator Antonio Nangel said that the giant Pantabangan Dam which was the first single largest infrastructure ever accomplished by the government can survive in an Intensity 10 earthquake.

Nangel said that the Pantabangan Dam which is an earthen dam was so designed and constructed to withstand powerful earthquakes.

“It was sturdily built. And since it is an earth dam, it has flexibility so we see no problem. In fact, it can survive even an Intensity 10 earthquake,” he said.

Nangel came up with the assurance after some quarters raised fears some of the country’s dams might not be able to survive powerful tremors similar, if not powerful, to the one that hit Japan which killed thousands of people.

Nangel was once operations manager of the Upper Pampanga River Integrated Irrigation Systems, the country’s largest national irrigation system which administratively supervised the operations of the Pantabangan Dam.

The dam was built in 1971 by an all-Filipino consortium of engineers and completed in August 1974, 17 months ahead of schedule at a cost of P800 million at that time, including $34 million loan from the World Bank. The structure is located at the center of the Carranglan, Pantabangan and Pampanga Rivers.

The dam consists of two zoned-earth filled dams – the main dam and the Aya Dam. Its 8,420-hectare reservoir area has a water storage capacity of 1.75 billion cubic meters for irrigation and power generation. Its watershed area covers 90,900 hectares.

Aside from irrigation, the dam also provides flood control, water supply for domestic and industrial purposes, fish conservation and tourism.

Nangel said that to illustrate its readiness to survive a powerful earthquake, the dam withstood the July 16, 1990 killer quake with no damage to its reservoir area and other structures. “Even if there was a faultline in Digdig (in nearby Carranglan), there was never any ill effects on the operations of the Pantabangan Dam back then,” he said.

The 1990 tremor, listed at Intensity 7.7 in the open-ended Richster Scale, however, considerably affected the natural flow in the downstream portions of the Pantabangan Dam at the Digdig and Talavera rivers, considerably reducing the service area of the Talavera River Irrigation System from 6,000 hectares to only 500 hectares.

Nangel said the UPRIIS’ dam and reservoir division, led by engineer Fred Tuquero, is supervising the maintenance and upkeep of the dam to ensure its structural soundness and safety as well as monitor and regulate the release of water from its reservoir. (Jason de Asis)