Phase 1 of the Bengaluru Metro (Namma Metro) has proved very messy tunnelling. Contractors (CEC-Soma-CICI on the East-West corridor and to Coastal-TTS on the North-South corridor) complained about unexpected and very difficult geology with boulders in mixed ground. Also there were concerns over densely populated areas, hostorical buildings with weak foundations etc.

When Phase 1 was tendered in 2010, it was supposed to finish in three years. It took longer, especially in the case of Coastal-TTS. The choice of Phase 1 tunnel boring machines was a real mixed-bag. They were TBMs made by Italians (SELI), Germans (Herrenknecht) and Japanese (Hitachi Zosen - these machines did very well). 

Coastal-TTS  had 3 tunnel boring machines. Two Herrenknecht 6.45m in diameter German Herrenknecht EPB TBM named Krishna (Herrenknecht S-725) and Kaveri (Herrenknecht S-726). And also with a disastrous run TBM Godavari (Italian SELI machine). SELI's cutting head is broken and it was out of action for a year, completing its tun in 35 (thirty five) months.

Coastal-TTS seeked the help of the American The Robbins Company to maintain these TBMs. Frequent cutter head interventions delayed the boring.

Coastal-TTS has been blamed of being inexperienced and for the completion of the North Ramp on the north-south Green line,  the other contractor CEC-Soma-CICI JV had to be called in to complete the job with TBM Margarita).

The Taiwanese-lead CEC-Soma-CICI JV did better, Actually much better. They have used 3 Japanese Tunnel Boring Machines made by Hitachi Zosen. TBM Margarita, TBM Helen and another one. They were all slurry TBMs.   CEC-Soma-CICI JV, in addition to finishing their own tasks, they ran to the rescue of Coastal-TTS to build the south-bound tunnel from Majestic to North Ramp by redeploying TBM Margarita.

When Bengaluru Metro Rail Corporation Limited (BMRCL) tendered the Phase 2, for understandable reasons, Coastal-TTS decided not to submit a bid. Taiwan-based CEC-Soma-CICI JV did not submit because of financial reasons. A total there were 4 bids in the Phase 2 tender. L&T,  Italian-Thai Develoment ITD, Gulermak, Afcon Infrastructure. Gulermak with huge tunnelling expertise was the only non-Indian company. L&T has been chosen.