Modernizing Manila's Water Supply
Video | 25 June 2020
The Asian Development Bank is working with the Philippines to modernize Manila's water supply and reduce the risk of water shortages as demand rises in tandem with the city's booming population.
An ADB funded project used modern tunnel boring technology to excavate a fourth supply tunnel for the Angat-Ipo reservoirs, a major source of water for Metro Manila. The technology is faster, cheaper, and safer than the traditional drill and blast method. The tunnel was completed in June 2020, and rehabilitation works will begin on existing supply tunnels in 2021, ensuring continuous water supply.
Norzagaray, Philippines - The Angat-Ipo reservoirs are a critical source of water for Metro Manila and its 12 million plus population.
Three tunnels from Ipo dam supply water downstream to Metro Manila, but they are old and in need of repair.
A fourth tunnel was completed in 2020.
Work on rehabilitating the old tunnels will begin when the fourth tunnel is fully operational in 2021.
The project used a 240-meter long tunnel boring machine which is safer and faster than the traditional ‘drill and blast’ method.
“50 years ago, the main way to excavate a tunnel was using drill and blast. That is a very ancient method. One century ago more or less. And using drill and blast, you’re not protected by shields like this TBM or lining. You first drill holes, you charge the holes with explosives and you make a big boom. So this is disturbing a lot of rocks,” contractor Salvatore Lavalle of the Angat Dam Water Transmission Improvement Project says.
The use of the tunnel boring machine reduced construction time by one year.
“This tunnel boring machine functions like a drill. It’s just like a big drill getting to the mountains, to excavate, to create what we call the tunnel. So practically what it does is, the cutter head rotates and during rotation, it breaks the rock component and after that, we install these segments," Principal Engineer Jose Dorado, Jr. of the Metropolitan Waterworks and Sewerage System says.
After installation of the segment lining, it pushes forward. So while it excavates, simultaneously the segment lining is installed.
MWSS Administrator General Reynaldo Velasco adds: “This kind of system, the walls are already put in place immediately, so these are the walls that hopefully, under our standards, should meet 8.0 earthquake.”
Every day, rocks are probed for suitability before excavation begins.
“We detect how is the rock ahead, to adjust the parameters of the excavation in order to suit the type of rock that is going to excavate for that day,” Salvatore Lavalle says.
In a constant cycle, an empty train went inside the tunnel carrying construction materials.
The train came out of the tunnel with the gravel, which was recycled to build roads.
Funded by the Asian Development Bank, the work will guarantee water supply to Metro Manila for years to come.