An estimated 97% of the water supply consumption of Metro Manila with an average of 4,000 million liters per day is coming from the Umiray, Angat and Ipo Dams. The water flows by gravity through a system of tunnels, basins, aqueducts and eventually channels down to the two treatment plants of La Mesa and Balara.

In January 2002, an inspection of the existing aqueducts revealed that about 13 leakages occur on some segments of the existing Bicti-Novaliches Aqueduct No. 5 (BNAQ-5) and 3 of these leaks were considered major leaks as it losses about 150 mld. The 3 major leaks were repaired but leaks continue to surface on the other weak points of the existing aqueduct. Hence, it was recommended to do no further repair but closely monitor the leaks and construct a new aqueduct to serve as by-pass during rehabilitation.

BNAQ-5 which was constructed in 1990 conveys 2000 MLD of raw water which is 50% of the total raw water from the Umiray, Angat and Ipo Dams. BNAQ-5 is in critical condition because of the leaks that if no immediate action can be done will endanger the almost 2000 MLD of water supply for Metro Manila.

Thus, for security of water supply to Metro Manila, it is vital that BNAQ-5 and the other existing aqueducts be assessed and rehabilitated as early as possible, and the urgent construction of a new aqueduct (BNAQ-6) to serve as by-pass during rehabilitation and to accommodate additional supply from Angat and Umiray River Basin.