Water detention

Despite the nearly P2 trillion in our hard-earned taxes spent on flood control projects over the past 15 years, Metro Manila and neighboring provinces were again inundated over the weekend by torrential monsoon rains.

Short of seeing all the looters and crooked contractors buried in an apocalyptic avalanche like the one in the Nepal-Tibet border, our only hope for genuine flood mitigation lies in certain segments of the private sector taking the lead.

Ayala Land has had an underground water detention tank in BGC’s Burgos Circle since the early 1990s following the privatization of Fort Bonifacio, and so far the structure has done an excellent job of flood mitigation.

Nearly three decades later, it has dawned on the government that perhaps such a stormwater infrastructure is a good idea. This may be partly because the detention tank is invisible, concealed by a park and a lively high-end commercial and residential area.

This story is not new. But just to refresh your memory, and provide some hope for those who feel their flood problems are hopeless: according to Ayala Land, the underground water detention tank is 12 meters deep (about four stories high) and 72 meters wide – the size of eight Olympic swimming pools. 

It can hold 22,000 cubic meters (22 million liters) of stormwater, which is released slowly to creeks that flow into the Pasig River, for gradual discharge to Manila Bay. 

Tokyo has had such a massive stormwater detention system in operation since 2006, with a cavernous cistern called the Cathedral, which has kept the Japanese capital flood-free. The Metropolitan Area Outer Underground Discharge Channel is built 22 meters beneath ground level. It’s a 6.3-kilometer-long system of tunnels, enormous cylindrical tanks and pumps – the world’s most massive floodwater diversion facility.

The Cathedral cost $2 billion – money we could have if it didn’t end up in the looters’ pockets. But smaller versions can be built, like the one in Burgos Circle, which cost Ayala Land only about P60 million. Yes, Juan and Juana, minus the kickbacks and overpricing, that price tag is possible.

Ayala has installed similar floodwater detention infrastructure in two of its mixed-use estates: Arca South in Western Bicutan, Taguig and Vertis North in Quezon City. Ayala says all three water detention facilities are designed to withstand seismic loads.

The detention tank in Arca South can hold 25,000 cm or 25 million liters – the equivalent of 500 large fuel tanker trucks.

Vertis North features a “rain garden” – a stormwater catchment system designed into a two-hectare park, where sidewalks have planted areas or “infiltration stripes” where rainwater can seep into the soil. The water is collected in perforated pipes and channeled into a detention pond. When the rainfall stops, the water is gradually released into a creek.

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Another option is to channel the floodwater to the water concessionaires for processing into potable water.

West zone concessionaire Maynilad is already doing this on a limited scale at its New Water Treatment Plant in Parañaque, purifying treated used water into potable water that meets national standards for drinking. Two barangays in the city – San Dionisio and San Isidro – are getting “new water.”

Maynilad is also addressing the low water supply during the dry season by investing in the conversion of four former sludge lagoons in La Mesa Dam into a reservoir for impounding raw water from the Angat-Ipo Dam system. One of the lagoons is now operational, allowing the storage of up to 67 million liters of raw water. The target buffer is 200 million liters once the four lagoons are fully operational.

Singapore has been recycling wastewater and has had rainwater catchments for a long time, and converting its garbage into energy. The tiny city-state, which does not have its own fresh water source and no space for landfills, has to be innovative to survive.

Japan also built the Cathedral over 13 years to put an end to the destruction caused by regular flooding.

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In our country, flooding has been chronicled in what we now know as Metro Manila and the rest of Luzon since the start of recorded history during the Spanish colonial period. 

What has been our response? In the current flooding, it’s been the usual: ayuda distribution, with local politicians posing with President Marcos. National and local officials blame each other. No one wants to take responsibility for the sorry excuses for flood control that collapsed in the first flood, or the newly paved roads that sprouted potholes after just a few days of incessant rain.

In 2003, the Department of Public Works and Highways (DPWH) launched with fanfare the Mega Flood Control Project that was touted to end or at least greatly minimize flooding in the Caloocan-Malabon-Navotas area.

The project cost was placed at P3.5 billion, and it was supposed to be finished by June 2007. The cost – like most public works projects – ballooned to P5.5 billion as it ran into delays. The Metropolitan Manila Development Authority took control of the megadike and pumping stations from the DPWH in 2009, but full completion was reported only in 2012.

Seeing the current flooding in Camanava, we can see where our P5.5 billion ended up.

The rotten system has become deeply entrenched. States such as Singapore see a problem, craft solutions, provide financing and skills to carry them out ASAP.

Our policymakers see a problem as an opportunity for kickbacks, for giving their relatives and supporters sweetheart deals in return for more kickbacks.

When disaster damages or destroys the structure, as is the usual consequence of a substandard or non-existent mitigation project, they see an opportunity to distribute tax-funded ayuda and take personal credit for it, enhancing their chances for reelection or perpetuation of their dynasties. And the consequent repair or replacement of the project is seen as an opportunity for more of the same.

They ought to be detained, but we’re finding this as difficult as rainwater detention.