The dam ‘bypass’ issue that got everyone talking amid the water crisis

March 18, 2019 - 10:55 AM
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La Mesa Dam Interaksyon
In this photo: La Mesa Dam in Quezon City (The STAR/Michael Varcas)

A former employee made a series of responses to a water system official’s post on Facebook explaining an aspect of the Metro Manila water problem.

The employee, identified as Angel Salazar, claimed that the crisis could have been solved if a bypass gate valve diverting Angat Dam’s water to the treatment facility plants of Manila Water would be opened.

Patrick Ty, chief regulator of state-run Metropolitan Waterworks and Sewerage System, allegedly responded to Salazar’s comments to his post. Ty, however, apparently did not explain the functions of a bypass and issue a denial of his claims that it is closed.

Salazar, who claims to have worked with Manila Water from 1982 to 2012, noted that he conceptualized the need for the bypass valve before it was constructed.

“The ‘bypass’ was constructed and conceptualized to bypass seepage and evaporation losses if raw water from Angat Dam is made to pass thru the La Mesa Dam. It is for this reason that it should always be open,” Salazar wrote.

A bypass gate valve in a water treatment facility controls the pressure and flow of water that would be directed to dams and treatment plants. Turning it off would stop the water from flowing toward its designated facility.

Angat Dam is the main water supplier of Metro Manila. Its water passes through the Ipo Dam and then through aqueducts that connect to the La Mesa Dam and the La Mesa Portal.

Water from the La Mesa Portal goes to the La Mesa Treatment Plant—which serves the western zone of Metro Manila via Maynilad—and the Balara Treatment Plant—which serves the eastern zone of Metro Manila via Manila Water.

Meanwhile, the water from the La Mesa Dam is reserved as an emergency supply in cases of El Niño. It is managed by Manila Water.

MWSS Raw Water Conveyance System
Diagram showing how water is distributed to different treatment facilities from dams. (Metropolitan Waterworks and Sewerage System/Released)

Salazar had heavily suggested that the bypass he was referring to is “located at the interconnecting line between the Balara Bypass” and an aqueduct.

This bypass diverts the water from Angat Dam to the Balara Treatment Plant immediately, completely bypassing La Mesa Dam.

It is connected to an aqueduct that splits the water into reservoirs between Maynilad and Manila Water in a 60-40 percent divide in favor of Maynilad.

According to Manila Water’s website, the bypass “is operated when the La Mesa (Dam) level falls below 71 meters to divert the water directly to the Balara Treatment Plant instead of to the (La Mesa) dam to prevent further water losses at the dam due to seepage and evaporation.”

Seepage refers to the movement of water in the soil while evaporation refers to the change of water to a gaseous state due to the increase in temperature.

Official responses

From Metropolitan Waterworks Sewerage System 

MWSS chief Patrick Ty denied the bypass’ closure and said it has always been open.

“For the record, the bypass is open. It is not closed… If it is closed, Manila Water would not have water at all,” he said in a press conference.

Ty explained that the bypass gate valve splits the 4,000 million liters per day (MLD) from the reservoir between Manila Water and Maynilad.

Manila Water gets 1,600 MLD (or 40 percent of the water) while Maynilad gets 2,400 MLD (or 60 percent of the water), he added.

“People are accusing me to open the bypass. There was even an accusation that I ordered the closure of the bypass. I never ordered the closure of the bypass. I made sure that the bypass is actually open to make sure Manila Water would be getting its 1,600 MLD,” Ty explained.

From Maynilad 

Maynilad, meanwhile, clarified that the bypass is under the control of Manila Water and has been opened since February 2018.

Maynilad Water Supply Operations engineer Ronaldo Padua said that it is only closed whenever too much water flows from the Angat Dam.

“Yun pong bypass na iyon ng Manila Water ay bukas na po siya halos two years na po. Sa ngayon, itong period na ito, since mid last year, bukas na yan. Nire-regulate lang ang opening niya,” he shared in an interview.

Maynilad, a private concessionaire, also clarified that it has no control over the bypass gate valve.

“This bypass gate regulates the flow of water from the La Mesa portal to both the La Mesa Dam and to the Balara Water Treatment Plants, all of which are controlled by Manila Water. MWSS has nothing to do with this bypass gate,” its statement reads.

The concessionaire explained that it currently receives a bigger percentage of water from Angat Dam since it has a “bigger customer base of 9.5 million” than Manila Water.

“Maynilad’s raw water allocation comes directly from Angat Dam. It does not source raw water from La Mesa Dam which is exclusively for Manila Water’s use,” they added.

“Manila Water has been getting its full allocation of 1,600 million liters per day (MLD) from Angat Dam. Maynilad has not done and will not do anything to deprive Manila Water of its 1,600 MLD allocation,” Maynilad said.