Chennai Metro Rail Ltd (CMRL) will begin tunnelling in Madhavaram in mid-October as part of Chennai Metro Rail Phase II. This phase consists of three corridors: Corridor 3, Madhavaram-SIPCOT (45.8 km); Corridor 4, Lighthouse-Poonamalle Bypass (26.1 km); and Corridor 5, Madhavaram-Sholinganallur (47 km). The estimated cost of the project is Rs 632.46 billion. The underground stretches from Madhavaram to Kellys (a part of the Madhavaram-SIPCOT corridor) will be worked on first. According to CMRL officials, the first tunnel boring machine (TBM) that arrived from China more than two months ago was lowered into the construction site last week. The two 6.61m TBM machines manufactured by Terratec will be used to build approximately 9 km of twin tunnels (a total of 18 km) on the Venugopal Nagar-Kellys section of Line 3. One TBM will commence the initial tunnelling operation at Madhavaram and drill toward Kellys to construct an underground section. A second TBM will be deployed a month later. The TBM launched at Madhavaram may take months to reach Kellys, and the length of time would primarily rely on the geological conditions. “Usually, we leave a gap of a few weeks between deploying the two TBMs. Before starting the tunnelling work at Madhavaram, we completed surveys and utility diversion work. We have to track and plug the borewells within residences,” an official said. Later this year, two more TBMs will begin service between Kellys and Taramani. Around 26.7 km of Corridor 3's 45.81 km stretch from Madhavaram to SIPCOT and 10 km of Corridor 4, a 26-km route connecting Light House and Poonamallee, will be underground. Another 5.8 km underground section of Corridor 5 connects Madhavaram and Shollinganallur, which spans 47 km. The Phase II project will require 23 TBMs, and the additional equipment is expected to arrive shortly. See also: Pune civic body gets DPR of Neo Metro from MahaMetroRailways prioritizes early completion of Railway Track projects