The company that bags the contract for building the underground stretch must choose the TBMs and get an approval from CMRL before deploying them. Of the 12 machines in Tamil Nadu, 10 will be remanufactured in Chennai and two in Kancheepuram. After the remanufacturing process is complete, the company will have it certified for use from the original manufacturer after which they will be pressed into service.
In the Phase-II project, underground network will be built for nearly 43-km with over 40 stations. CMRL will be making some changes in the alignment; so, the number of stations is bound to change in the coming months. In Corridor-3, which runs up to 45.81 km from Madhavaram to SIPCOT, 26.7 km will be underground and Corridor 4 connecting Lighthouse and Poonamallee covering 26 km, 10 km will be underground. Similarly, in Corridor-5 running for 47 km linking Madhavaram and Shollinganallur, there will be a 5.8 km underground stretch. While one TBM has arrived from China and reached Madhavaram, the second one has passed the factory acceptance test and will be taken to the construction site soon. In its entirety, all the 19 TBMs will be commissioned for the Phase II project one after the other between October and June next year.