The 3.14m diameter machine, which will build the 4.7km Priority Sewer Tunnel (PST-2), is the second TBM Terratec has provided to J Kumar and Michigan Engineers Private Ltd (MEPL) Joint Venture for the project. In January, a 3.85m diameter rock slurry TBM began excavating the 5.8km Priority Sewer Tunnel (PST-1).

The rock EPBM is designed to operate under a range of geological conditions, including silty sand, silty clay, boulders, breccia, basalt, clay with gravel and thyolite. It features a mixed type cutterhead, 27 back-loading 432mm disc cutters and a high-speed main drive capable of eight RPM.

The TBM has been engineered to function within a wide horizontal radius to meet the challenges of the tunnel alignment, which includes a 90-degree road intersection and working around piles supporting an overhead metro line. The modification has eliminated the need to excavate a shaft at the congested intersection, resulting in time and cost savings while preventing traffic disruptions during construction. The approach, being used for the first time in India, includes using different segment ring lengths (1000mm and 650mm) to enable the TBM to navigate sharp curves with a radius of up to 95m.

The 122m-long machine is equipped with a single-track gantry type back-up system with 17 decks. Muck removal, segment transport and logistics supply are managed via locomotive and muck cars.

The MSDP – Stage II includes the construction of a sewer tunnel to the existing Malad Pumping Station, a branch sewer tunnel, and shafts and upstream connections.

The Brihanmumbai Municipal Corporation project will expand sewage collection networks, provide new pumping stations, wastewater treatment facilities and treated effluent disposal systems. These treatment plants are projected to recycle 2,464 million litres of sewage per day, reducing water pollution levels and improving water quality in Mumbai’s Mithi and Oshiwara rivers.

In a related development, a refurbished Terratec TBM operated by MEPL has achieved its second breakthrough for the 6.4km Mithi River Quality Improvement Project’s Package IV.