Tunnel boring machines idle, Chennai Metro Rail Ltd’s phase-2 underground section may be delayed

Chennai: Motorists navigating the city’s maze of metro barricades may have to endure the inconvenience for longer, as delays in Chennai Metro Rail Ltd’s underground construction have created a costly bottleneck involving tunnel boring machines (TBMs), potentially delaying phase-2 deadlines.

Officials said that in the past two years, at least 10 TBMs were stranded underground for months — and in some cases nearly two years — because station shafts and retrieval points were not ready when tunnelling was completed. The delay has slowed the redeployment of machines to new stretches and affected the pace of underground works. Sources said that of the 69km tunnel only around 40% (28.1km) has been completed. The 118.1km phase-2 project, with an underground route of 42.6km, is being built for 63,246 crore.

While eight TBMs have completed breakthrough over the past year, two machines are still awaiting retrieval more than a year after tunnelling began. One TBM between Madhavaram High Road and Moolakadai (upline) started tunneling 14 months ago, and is waiting for retrieval. It is expected to achieve breakthrough only in the second week of July. Another on the Purasawalkam–Kellys upline has been waiting after it started tunneling 13 months ago, and is expected to achieve breakthrough in June. Recently, a TBM on the Madhavaram High Road- Moolakadai (downline) achieved breakthrough 22 months after tunnelling commenced.

Sources attributed the delays to cancellation and re-tendering of some station contracts due to high bids, and challenges in shifting underground utility lines before construction could proceed.

The delay has created a domino effect across the underground network. The TBM that recently completed tunnelling between Madhavaram High Road and Moolakadai is scheduled to be redeployed between Perambur Barracks Road and Purasawalkam, while another waiting at Moolakadai is meant for the Perambur Metro–Perambur Market stretch. The Purasawalkam–Kellys TBM is also awaiting redeployment for the corresponding downline tunnel. TBMs on two stretches – RK Salai to Thirumayilai downline and Nungambakkam to Sterling Road downline – are being assembled now after a delay in their retrieval from Greenways Road-Mandaveli stretches.

“The waiting and delayed redeployment is not just costly, but is also causing a delay. As we are paying for the TBM’s idle time, we’re imposing a penalty on the contractors for the delay in shaft readiness,” a CMRL official said.

Officials said the underground stretches from Madhavaram to Kellys, targeted for completion in Oct 2027, and from Chetpet to Greenways Road, expected by Aug 2028, could see further revisions. “The revised deadlines will be worked out,” the official said.

Officials said CMRL is now considering procuring additional TBMs because several machines could not be retrieved and redeployed on schedule.

Motorists travelling through the barricaded roads will be worst affected due to the delay. “CMRL changes barricaded portions on the roads at times and travelling through these narrow stretches is extremely stressful, especially during peak hours in the summer heat. CMRL must make sure they finish the work as soon as possible,” said S Sundar, a private firm employee.