Terratec TBM Records Breakthrough for Mumbai’s AMT-I Water Tunnel

Soma Enterprise and Terratec on June 21 celebrated the completion of tunneling works in Mumbai’s Parel neighborhood for the city’s 9.683 km Amar Mahal-1 water transfer tunnel project.

This feat by tunnel boring machine (TBM) T87, a 3.2 m diameter Open Rock TBM, was recorded for the Municipal Corporation of Greater Mumbai (MCGM)’s new water tunnel called AMT-I which will cater to the steadily growing water demands of eastern Mumbai.

AMT-I tunnel with a finished diameter of 2.5 meters reaches depths of 100-108 meters. It will replace old underground pipelines and significantly improve water supply to the F/N, F/S, E (Part), and L (Part) wards of Mumbai.

AMT-I originates from Hedgewar Udyan (Amar Mahal) where the tunnel will be tapped from Mumbai-II & Mumbai-III water supply sources on the Eastern Express Highway. From Hedgewar Udyan (Amar Mahal), the tunnel runs south to Parel through Pratiksha Nagar in Wadala.

The project consisted of two TBM drives totaling 9,683m in length between three deep shafts located at Hedgewar Udyan, Pratiksha Nagar and Parel.

During its first drive between Amar Mahal and Pratiksha Nagar, T87 had excavated an impressive distance of 526 meters in December 2021 while maintaining an average progress of 300+ meters per month, which I wrote about in 2022.

Per Terratec, T87 was specifically designed for the geological conditions encountered along the project alignment. It features a modular design enabling both shaft launching and retrieval, ensuring flexibility during construction. Its robust cutterhead, equipped with heavy-duty back-loading disc cutters, is driven by VFD controlled electric motors capable of achieving optimal torque and exceeding 10rpm rotation speed.

To navigate the diverse geological strata, the TBM was engineered with a comprehensive ground support system, encompassing a fixed probe drilling unit, two rock bolting drills, a shotcrete pump, and a steel arch erector.  These features provide vital safety and stability during the tunnelling process.

A notable feature of the TBM is its disassembly design, allowing for the removal of all components through the completed tunnel. The largest component, the cutterhead, is engineered with a flange enabling it to be dismantled into two pieces for easy extraction.

This project is one of the many projects quietly being executed by MCGM to augment water sources, improve distribution system and manage water demand & supply.

With this development, Mumbai’s water tunnel network now surpasses 100 km in length.

Back in February 2023, another Terratec TBM T83 deployed by Patel Engineering had completed tunneling for the 5.53 km Amar Mahal II Tunnel Project (AMT-II) in Mumbai.

That project also consisted of two drives. The first from Amar Mahal (Hedgewar Udyan) to Trombay Low-Level Reservoir covering a distance of 3.5 km, and the second to Trombay High-Level Reservoir (THLR) covering a further 2 kms. TBM T83 in fact broke T87’s record in January 2022 after excavating 653m in a single month.

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– TMRG