Innovations and challenges in design and construction of underground Mumbai Metro Line 3 - Lot UG-04 and UG-06

India is well on its way to create a world-class Mass Rapid Transport system environment as an integral part of community infrastructure development. Mumbai Metro Line 3 is one such project being constructed in Mumbai city. It comprises 33.5 km-long underground metro corridor running along Colaba to Bandra to Santacruz Electronic Export Processing Zone. It includes 27 stations (26 underground and 1 at grade), depot and associated twin-tube tunnel. Mumbai Metro Rail Corporation Ltd., an affiliate organisation of Mumbai Metropolitan Region Development Authority, is responsible for the implementation of the project. Excavation and tunnelling works posed significant challenges as they cross densely inhabited zones of Mumbai. There were several buildings which were old and in delicate condition, many of which were heritage structures. In Mumbai - being a coastal city - the water table is almost at ground level which added to complications. There were several utilities, many of which were lifeline utilities, which could not be diverted or even closed, thus requiring support during excavation. Likewise, ensuring traffic movement with minimal disruptions with enormous excavation works for the project required several innovative solutions. Other criticalities included low overburden to the existing flyovers and to the air traffic control tower as well as saving a 100 year-old banyan tree.