The NBAQ4 project, one of the largest water supply infrastructure projects undertaken by Manila Water, entails the construction of a fourth aqueduct from the La Mesa Reservoir to the Balara Treatment Plants (BTP) 1 and 2 to improve the reliability and security of the raw water transmission system. The 7.30-km long and 3.10-m diameter NBAQ4, which is one of the first tunnels to be constructed with a tunnel boring machine in Metro Manila, is composed of a new intake facility at La Mesa, an underground aqueduct, and an outlet facility at BTP. The fourth aqueduct will have a capacity of 1,000 MLD and will be constructed along Commonwealth Avenue in Quezon City.