Mumbai Coastal Road Project: 38,700 truckloads of muck excavated from twin tunnels

“Some portion of muck that was not suitable for reclamation has been disposed of by the contractor at Uran where a separate dedicated plot was taken. Also, the slurry which was dense was disposed of,” Swami said.

The official said that during the tunnelling process, the slurry is sprayed on the rock while cutting so that any cavity formed will not fall into the cutting chamber. This is done to prevent large rocks from falling which can be difficult to pass or flow via pipe to the surface through the Tunnel Boring Machine (TBM). “The TBM was of slurry type and the material of 60-40mm size material (rock particles along with slurry) can come to the surface again via the pipe. If a large particle comes through this pipe it will choke, so the spraying of slurry was done during tunnelling to ensure the TBM work is not disturbed,” the official said.

For the coastal road project, 111 hectares of land have to be reclaimed, which is 12 times the size of Oval Maidan at Mumbai’s Churchgate. (Express photo by Pradip Das)

Meanwhile, a slurry treatment plant was set up at the project site to treat the slurry emerging from the TBM pipe; particles were separated and rocks of different sizes were used for reclamation.

The second breakthrough in undersea tunnel boring was attained on May 30 at Priyadarshini Park near Breach Candy. The digging of the first tunnel commenced in January 2021 from the side of Priyadarshini Park, and the first breakthrough took place in January 2022 at the Chowpatty end.

After mining through complex geological strata, passing through sea and Malabar Hill and a century-old water reservoir, the Chinese-made TBM, Mavala, made its final breakthrough in May end. This major milestone was achieved in the presence of Maharashtra Chief Minister Eknath Shinde and Deputy CM Devendra Fadnavis.

The 10.58-km-long coastal road starts from Marine Drive and goes up to the Bandra-Worli Sea Link. It comprises underground tunnels, and elevated roads passing from sea and interchanges. This new road aims to cut down the current 45-minute commute from Girgaon to Worli during peak hours to just 10 minutes. In the coastal road, the twin tunnels will have three separate carriageways each for vehicular movement, and are equipped with state-of-the-art disaster resilient systems and a saccardo ventilation system, which will be useful in times of emergency situations like fire outbreaks.

The Rs 12,721-crore coastal road project being built by the Brihanmumbai Municipal Corporation (BMC) is expected to be partially completed by November 2023 and fully by May 2024, indicating a six months delay in the project.