Posted on Thursday, April 3, 2003

‘Technicalities’ hold up 
opening of CAMANAVA dike

By Moneth G. Deposa, Researcher

First of two parts

Residents of northern Manila are optimistic that the perennial flooding in their communities will soon end now that the government has conceived a project that would ease their sufferings.

For them the ambitious but long-delayed flood-control project in Caloocan, Malabon, Navotas, Valenzuela (CAMANAVA) is the much-awaited reality of their dreams—living safe from floods.

But it seems they are destined to wait again, now that Public Works Secretary Bayani Fernando confirmed to The Times that the project is “temporarily on hold” owing to some “technicalities,” which he declined to elaborate. The future implementation of the project raised fear and confusion among residents in northern Manila—fear that the project might fall through and confusion about what really delayed it.

Camanava concentration

The project, which would improve the flood-control and drainage system in the region, covers 18.48 square kilometers of flood-prone areas in the cities of Caloocan, Malabon and the town Navotas (first phase). A feasibility study on Valenzuela, Obando and Meycauayan would be made under a separate drainage plan (second phase).

The camanava project centers on the northern and southern parts of the Malabon River. Experts propose to build an 8.6-kilometer polder dike—a dam big enough to hold a body of water—and raise the river wall by 4.4 kilometers as well as sites for navigation, floodgates and pumping station in the northern area of the Malabon River.

In the southern part, they plan to raise the left bank river wall by 1.1 kilometers, the Navotas and Marala river walls by 1.3 kilometers, construct 4 sites for pumping station with floodgates, improve drainage channels by 6 kilometers and build a new drainage channel about 2.7 kilometers. (See tables below.)

The first phase, costing an estimated P5.020 billion to be funded by the Japan Bank for International Cooperation (JBIC), was supposed to begin construction on March 12 this year and is scheduled to be completed by March 2007. Experts believe that this project will mitigate flooding in areas through flood-control and drainage improvement works, thereby improving the living conditions of the residents and promoting economic activities in the areas covered by the plan.

What’s the score?

A source disclosed that this flagship project has been on hold until the contract is finally signed by Secretary Fernando as a party to it. The contract has been at his office since March 7. The JBIC has been following up the contract and other documents on the project, but to no avail at this writing. Asked what was delaying the signing by Fernando, the source said the secretary is considering some modifications on the design, which seems to accommodate the request of Navotas Mayor Tobias Tiangco.

In a letter to Fernando on March 25, Tiangco asked the Department of Public Works and Highways to include coastal dikes in the first phase of the design, which according to consultants, is difficult to grant because the project is final and has already been bid out by the winning contractor in accordance with its original cost and design. All components—big or small—are subject to contract revision.

The source also said that on March 26, Fernando called a closed-door meeting with Hitoshi Kin, project manager of the consultant firm CTI Engineering Co. Ltd., and some engineers of the project. At first, Fernando asked why the Navotas coastal dike was not included in the first phase. The engineers defended their decision, citing factors such as a limited budget and the squatters in the area. They said the coastal dike was not included in the second phase because the site is the highest area in Navotas and won’t easily flood unless there is an extreme high-tide level of 11.93 meters, which seldom occurs, not after 10 years by which time the engineers are ready with the second phase. On the possibility that the second phase may fall through, the engineers said the JBIC assured them that it would fund the second phase, but that the first phase should begin.

Fernando even suggested that the engineers trim some of the project components’ cost to include the Navotas coastal dike, which, according to sources, the engineers ignored. They said it could not be done, because the project had been bid out to the winning contractor. Fernando reportedly considered canceling the project “if the Navotas coastal dike will not be included in first phase.”

Design ‘flaws’?

In a newspaper story on March 7 the marine geologist Kelvin Rodolfo noted that the project’s design was “grossly inadequate” and “dange­rous.” He said the estimate of land subsidence (sinking of land) was based on a 1990 document that presumed that the use of ground water would end in 1990 and that the consultants expected the additional subsidence to occur at a rate of only about one-half centimeter a year, causing only 15 centimeters of land subsidence by the year 2030.

Kin responded that the consul­tants recognized that excessive pumping of ground water in Metro Manila had caused the land to sink and, as a consequence, the sea level to rise.

Kin cited a study on land subsidence by Emmanuel G. Ramos of the Philippine Institute of Volcanology and Seismology, which noted that the piezometric map of Metro Manila for 1981-82 showed that the piezometric level had reached -120 meters at Navotas and Caloocan along with the Pasig-Pateros area, -40 meters for Parañaque and coastal Pasay City areas and -20 meters for Quezon City, Muntinlupa and Cavite. (A piezometer measures high pressure.)

Kin said a study by JICA in 1991 showed that the elevation of the Navotas-Caloocan area remained close to -110 meters; Pasig-Potrero levels recovered to around -30 meters; and Bacoor-Muntinlupa reached -80 cm. He also cited the unpublished record of ground-water levels available from the mwss for 1995 showing that the deep piezometer levels in Navotas-Caloocan appear to have retained its -100-meter level, and that the deep levels in Quezon City and Marikina appear to have recovered. Bacoor, Las Piñas and Muntinlupa appear to have reached a deeper -100-meter level, although the depressed area seems to have shrunk.

Kin noted that as regards the excessive withdrawal or decline of ground water, Valenzuela and Malabon, where the polder dike is located, are not mentioned. “Considering the aboveground water conditions, the consultants drew up some countermeasures to address land-subsidence concerns in the structural design especially those of pumping station and flood-control gates.”

For the polder dike, which technically may be raised in accordance with the progress of actual subsidence, an extra embankment of 0.30 meter with slope protection is considered a countermeasure for the initial settlement of the foundation, providing for regular maintenance work according to the actual settlement in the future.

Rodolfo said the consultants “totally ignored” in the design the effects of powerful winds, surge and waves that come with storms in Manila Bay, an assertion that Kin disputed. He said Rodolfo was referring to the dike in the coastal areas of Navotas, which are not exposed directly to storm surges in Manila Bay.

In the design of the Navotas navigation gate structure, however, Kin said the force of the wave approaching the gate was computed and considered in the structural analysis.

Rodolfo alleged that the project designers ignored their own analyses that indicate the need to base their polder dikes with piles driven deeply through at least 15 meters of soft bay sediment. Kin said that in building the polder dike, which was 8.5-km long, the designers did not consider the use of pile foundations practical, because of the prohibitive cost. Therefore, the designers adopted alternative countermeasures such as bamboo rafts with geosynthetics and sand mat foundation. The additional height of the embankment, Kin said, was also considered in the initial settlement of foundation as well as the regular maintenance work in accordance with the progress of the land settlement.

In his 1995 book Pinatubo and the Politics of Lahar, Rodolfo, also a consultant of the National Institute of Geological Sciences (NIGS) at UP Diliman, cited documents and historical facts as the bases for his allegations. He said his group warned the Department of Public Works and Highways publicly and privately against containing lahar with flood-control technology because the volcanic deposit is so much more powerful than water floods, and it behaves differently. Since then, Rodolfo’s group had warned people in harm’s way about inadequate dikes that indeed eventually failed, citing experiences in Pinatubo (1991), the Pasig-Potrero lahar-dike (1995) and the FVR megadike system (1996).

To the assertion that he is not a designer who would know the factors to consider in a design, Rodolfo replied that geologists are the ones who gather fundamental scientific data used by structural designers elsewhere in the world to build proper containment structures. Geologists, he said, are more knowledgeable about the energies and behaviors of storm waves and surges.

Where does it begin?

In early February Rodolfo conducted a seminar on land subsidence but consultants and designers of the CAMANAVA flood-control project could not attend and instead sent somebody to represent them.

On Feb. 12 the group asked Rodolfo to have an informal discussion with them about the seminar. The meeting took place at the NIGS office in Diliman. According to a source, the dialogue dealt with land subsidence and other information about it, but not the design or the land subsidence used in the CAMANAVA project. Rodolfo even asked for a final copy of the main design of CAMANAVA for future reference.

On March 7 Rodolfo noted in a newspaper story that the design of the CAMANAVA project was “grossly inadequate” and “dange­rous.” He alleged that the consul­tants used obsolete and erroneous data in determining the height of the 8-km polder dike, based on the old subsidence rates, or how fast the four cities are sinking into the water. Within a few days, the consultants of the project disputed Rodolfo’s allegations. 

A source told The Times that weeks after the consultants responded to Rodolfo’s allegation of flaws in the design, both camps had made no effort to meet again or talk about the issue. This led the designers to conclude that the issues, which have been raised in the media, are “just allegations” without bases. Even the Public Works secretary, Bayani Fernando, once quoted as saying “technical opinions and warnings do not always come true,” implicitly doubted Rodolfo’s judgment on the project design.

The consultants are confident that the design they made is certain that it passed several assessing bodies like Bureau of Design, NEDA Board with President Arroyo as the approving chairman, and counter­part bodies from the funding insti­tution, Japan Bank for International Cooperation.

Conclusion