The most challenging station: Mumbai's Marol, which lies right under Line 1

When you arrive at the Marol underground station once Phase I of Metro Line 3 is opened, remember that Metro Line 1 (Versova-Andheri-Ghatkopar) runs right above it.
Marol will be a station where commuters would be able to change lines to go in the direction of BKC or Aarey, or in the direction of Versova or Ghatkopar. Constructing the Metro 3 tunnel in the Marol stretch and the underground station was not an easy task as care needed to be taken to ensure it did not disturb or endanger Line 1.
Construction of the Marol Metro station is part of the project's Package 7, the contract for which was bagged by the L&T-STEC joint venture. The package includes the Metro car shed, and the Seepz, Marol and MIDC stations.
Explaining the difficulties encountered at Marol, PP Rajurkar, assistant general manager, Mumbai Metro Rail Corporation (MMRC), said, "The challenge was to bore the tunnel without disturbing the pillars of Metro Line 1 that run six metres deep into the ground. This required the underground Metro station at Marol to be at an additional depth of 20 metres so that it did not interfere with Line 1."
Unlike at other stations where work on boring the tunnel with tunnel boring machines (TBMs) was carried out simultaneously with the construction of platforms, at Marol the two tasks had to be done one after the other (again, so that the pillars of Line 1 were not impacted). "Initially, a TBM was deployed to bore the tunnel. Then the width of the tunnel was widened using NATM (New Austrian Tunneling Method), which entails the use of mechanical machines and breakers. After excavation, the structure was supported by lattice girders and rock bolts, buttressed by concreting," said Rajurkar.
Boring of the tunnels along the stretch was completed in June 2021. Thereafter work on the platforms was commenced. By June-end work on the station will be completed, said Rajurkar.