JKIL – MEPL’s Terratec TBM Records Final Breakthrough for Mumbai Sewage Project

J Kumar Infraprojects – Michigan Engineers JV in October celebrated their third and final tunnel breakthrough at Don Bosco Junction in Borivali West for Mumbai city’s 5.85 km Priority Sewer Tunnel (PST-1) project.

Mumbai’s PST-1 tunnel project by Brihanmumbai Municipal Corporation (BMC) connects Don Bosco Junction in Borivali West and Malad Waste Water Treatment Facility (WWTF). Along with PST-2 tunnel (Oshiwara Bus Depot to Malad Pumping Station), it aims to improve the quality and reliability of wastewater collection, treatment, and disposal processes, while minimizing the environmental impact caused by wastewater.

This major milestone was recorded by a Ø3.85m rock slurry TBM by Terratec nicknamed Manu 1, the smallest diameter rocky slurry machine to be ever deployed in India

S112 was first launched in January 2024 from Malad WWTF (Shaft S07) and arrived at Malad Pumping Station (Shaft S06) in August 2024 to complete a 1630 meter long tunnel. It was then relaunched towards northwards towards Borivali’s Don Bosco Junction to build another roughly 2870m tunnel where it arrived in January 2026.

Per Terratec’s press release, throughout the drive, the TBM worked beneath densely built-up areas of Mumbai, passing below busy roads, buried utilities, and existing residential and commercial buildings, as well as through environmentally sensitive ground. The alignment ran through weathered and fresh breccia and basalt, with the machine reaching up to 18 rings per day in fresh rock. Continuous monitoring of tunnel alignment and ground movement kept surface settlement to a minimum and protected surrounding infrastructure.

Among the smallest machines of its kind in India, the TBM controls face pressure with a slurry system, and excavated material is pumped to the surface through the Terratec Slurry Transportation System for separation at the Terratec Slurry Treatment Plant. The machine features 23 replaceable 15-inch disc cutters, a high-speed hydraulic main drive turning the cutterhead at up to 8 revolutions per minute, a shield-integrated man lock, and an active articulation system for curves down to a 250m radius. The tunnel is lined with 5+1 universal reinforced concrete segments, 200mm thick and 1,200mm wide, giving a finished internal diameter of 3,200mm.

Terratec is the sole supplier for Mumbai’s sewage segmental tunnels and has provided 2 TBMs – one each for 5.8 km PST-1 (Don Bosco to Malad WWTF) and 4.7 km PST-2 (Oshiwara Bus Depot to Malad Pumping Station).

For PST-2, TBM Manu 2 is a 3.14 diameter EPB machine and started tunneling in August 2024 from Malad Pumping Station towards Oshiwara Bus Depot in Goregaon. Back in May 2025, it completed building a sharp 87m radius curve under the Mumbai Metro’s elevated Line-2A (Yellow Line)’s piers 393 and 394.

Once in operation, PST-1 will form a key part of Mumbai’s upgraded wastewater network, carrying sewage to downstream treatment facilities and allowing ageing pumping stations to be decommissioned. The wider programme is expected to recycle 2,464 million litres of sewage per day, reduce the discharge of untreated wastewater into local waterways and the Arabian Sea, and support the rejuvenation of the Mithi and Oshiwara rivers.

For more updates, check out the Tunnels section or my Home Page! Sign up for free instant email notifications on new posts over here. Like this post? Get early-access to updates and support the site over here.

– TMRG