MWSS, Manila Water concerned over Wawa Dam source

MANILA, Philippines - The state-run Metropolitan Waterworks and Sewerage System (MWSS) and East Zone concessionaire Manila Water have expressed serious concerns about sourcing raw water from the Wawa Dam in Montalban, Rizal.

The MWSS, as part of its mitigation measures to source additional water for Metro Manila, has looked at the possibility of tapping up to 50 million liters per day (MLD) from the Wawa Dam.

However, MWSS Administrator Diosdado Jose Allado said the water utilities regulator has expressed serious concerns in tapping the Wawa Dam.

He said several studies showed that the development of the Marikina River Basin for water supply is both socially and technically unacceptable.

Construction of a high dam structure will present a negative perception to people living downstream of the Marikina River, including cities and towns along Pasig River, the studies cited. This, moreover, will be aggravated following the massive flooding from typhoon Ondoy which was blamed on the release of floodwaters from nearby dams.

In fact, the Deparment of Environment and Natural Resources (DENR) had recommended and opposed the issuance of an environmental clearance certificate (ECC) for the construction of a large capacity dam in the Montalban Gorge because it is within the seismic fault zone, the MWSS studies showed.

Likewise, the studies cited poor water quality from the Wawa Dam because of the existence of big piggery farms, highly urbanized communities and the presence of sanitary landfills in the headways of the Boso Boso River which pollutes the raw water supply.

It was also pointed out that the existing height of the Wawa Dam has a very small storage capacity that is not enough to meet the storage requirement of the project area.

Thus, increasing the height of the Wawa Dam, and consequently its storage capacity indicates difficulty in controlling seepage/leaks through the limestone mass even with the use of expensive grouting.

Because the Wawa Dam is only a few kilometers from the Marikina Valley fault line, there is a risk to nearby Metro Manila which makes the Wawa Dam not technically and financially viable, the MWSS studies noted.

Manila Water had noted that a recent hydrologic study conducted in 2005 showed that sourcing 50 MLD from the Wawa River is not feasible for the whole year.

According to Manila Water, “construction of another dam structure may be feasible, but that will increase the cost of the project and will render the project not financially viable.”

Manila Water also cited a 2007 study on the water quality of the Wawa water source that noted that while a conventional treatment system with a standby advanced treatment units (ATU) such as reverse osmosis or ozonation may be considered “this will also increase the capex (capital expenditures) and opex (operating expenditures) of the project significantly and will render the project not viable.”