Are we prepared for possible dam break?

by Dino Balabo

Angat Dam in Norzagaray, Bulacan

MALOLOS CITY—If the Philippines is not prepared for super typhoon Yolanda that left about 6,000 in casualties, it is surely not prepared for a dam break that can kill at least 100,000 in Bulacan alone.

This is due to the fact that the country is inexperience for such kind of tragedy, but experts and officials alike said its impacts can be minimized with proper preparations.

As this developed, Bulacan is gearing up for a locally initiated earthquake and dam break drill in preparation for possible breach of the giant Angat Dam which experts says is sitting near the Marikina West Valley Faultline (WMVF).

Noel Ortigas, Executive Vice President of the Engineering and Development Corporation of the Philippines (Edcop) told PromdiNEWS in an interview that 50 to 60 percent of Bulacan will be affected in case of Angat Dam break.

A Filipino owned company, Edcop partnered with New Zealand-based Tonkin and Taylor International in conducting a $1-Million dollar feasibility study on the integrity of the dam from late 2011 to early 2012.

Findings in the said study showed that 21 towns and cities in Bulacan will be affected rushing water from the dam along with three towns in Pampanga and three cities in Metro Manila.

During the interview, PromdiNEWS clarified Ortigas’ estimate by converting it into population.

Based on the 2007 census of population, Bulacan’s projected population by this year is about 3-million.

It means that at least 1.5-Million Bulakenyos will be affected based on Ortigas’ estimate of 50 percent to be affected.

 

Noel Ortigas, EdCOP

“Hindi naman lahat na yun ay fatal,” he said after PromdiNEWS clarified his statement.

When asked on how many is likely to die in Bulacan in case of Angat Dam break, it took a while for Ortigas to tell figures.  He later said about 100,000 could die.

Ortigas explained that the depth of water that will rush out of Angat will be different from town to town.

Based on the simulation study of Edcop and Tonkin, they estimated that 10 to 30 meters of water will rush especially on villages on the banks of the Angat River from Norzagaray town to Angat San Rafael, Bustos, Baliwag and Plaridel.

He said that as rush away from the dam, it will spread and it meant shallower flood in other towns.

Based on their estimates, floods in Pulilan and Calumpit towns will be between five to 10 meters deep; in Malolos City and other towns it will be less than that; but in the coastal town Hagonoy it might be between three to five meters.

However, other experts and officials do not necessarily agree with simulation study estimates.

Engineer Roderick Dela Cruz, a Bulakenyo dam safety expert based in California said in an earlier interview that Edcop must clarify the margin of error in their estimates.

Citing records from two previous dam release aggravated flooding in Bulacan, Dela Cruz said that Edcops estimates are very conservative.

Gov. Alvarado and Engr. Dela Cruz

He said, “in 1978, Angat Dam spilled 5,000 cubic meters per second (cms) of water and the province was inundated by deep flood, and more recently in 2011, Angat Dam spilled 1,500 cms and flood rose to more than one meter in Hagonoy.”

Dela Cruz stressed that in two previous incidents, water spilled from Angat Dam is minimal compared to possible 850-Million cubic meters of water that will rush out in case of Angat Dam break.

 He said that possible dam break could be more fatal due to the inexperience of the country in addressing similar disaster.

As lead dam safety engineer of Southern California Edison (SCE), Dela Cruz explained that two primary causes of dam breaks are earth quake and over topping which is usually caused by heavy rains.

However, Dela Cruz said that statistics showed that more dams in the world were breached due to over-topping caused by heavy rainfall.

For his part, Bulacan Governor Wilhelmino Alvarado is not taking the issue lightly.

He also agreed with Dela Cruz that Edcop’s estimates as conservative and likened the aftermath of the dam break into a nuclear explosion.

“Hindi na nananakot tayo, we are just stating facts because the risks are real and was confirmed by different studies.  That is the reason why we are trying to prepare the Bulakenyos,” he said noting that the provincial government is preparing for the first locally initiated earthquake and dam break drill this month.

Citing records from the Philippine Institute of Volcanology and Seismology (Phivolcs), Alvarado said that the MWVF can move anytime and generate a magnitude 7.2 earthquake.

He said that the same study was used by Metropolitan Waterworks and Sewerage System (MWSS) to justify the conduct of a feasibility study on the integrity of the Angat Dam in preparation for its rehabilitation.

President Aquino has allocated P5.7-Billion for the said rehabilitation last year, however, bidding for the actual rehabilitation has been stalled several times.

Delays in the said bidding left Alvarado with no choice but the invoke the old teaching of the Church which says,” nasa Diyos ang awa, nasa tao ang gawa.”

He explained that while God remain merciful to Bulakenyos by not allowing a breach on the Angat Dam, the people have to do their part.

The governor said that aside from prayer, the only other thing they can do improve preparedness in Bulacan citing the 2009 advise of Phivolcs Executive Director Dr. Renato Solidum  saying “Bulacan must prepare for the worst.”

“We will conduct our own regular earthquake and dam break drills,” he said.

For her part, Liz Mungcal, head of the Provincial Disaster Risk Reduction Management Office (PDRRMO) said they are preparing an emergency action plan for the Angat Dam break.

The said action plan will be presented to local mayors in the province for them to come up with similar plans for their own towns and cities.