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CHENNAI: In less than five months, Metro rail will connect a part of north Chennai with the rest of the city through underground tunnels. Chennai Metro Rail Limited (CMRL) will complete tunneling in the two kilometre stretch between Washermenpet and Korukkupet before the end of September this year. Commuters will be able to travel in metro trains to north Chennai through six stations only in 2019.

Construction is underway as part of the 9km phase-1 extension project between Washermenpet and Wimco Nagar. CMRL officials said boring machines have completed excavation and tunneling to about 180metres in one of the two tunnels towards Korukkupet while construction of the other tunnel has just begun. “By June, we will reach Theagaraya College. We hope to finish tunneling by August. But we will also give ourselves one more month. So, by September building of tunnels should be complete,” said a Metro rail official.

The two-kilometre underground line has two stations - Theagaraya College and Korukkupet beyond which metro trains will run on an elevated corridor. The foundation stone for the construction of the 2km underground stretch was laid in July 2016 by former chief minister J Jayalalithaa, a month after the Centre approved the project estimated to cost Rs 3,770 crore. Work on the elevated stretch will begin once a substantial part of the underground stretch is complete. But once completed, the extension project will give the much needed access to far flung areas of north Chennai through metro trains.

According to Metro rail officials, though the soil quality along the stretch in north Chennai are favourable to build tunnels faster, engineers will still be slower than the usual pace of excavation, as they do not want to cause any damage to the buildings above.

A geotechnical report released in 2016 following soil tests conducted along the alignment in the 9km distance showed soil conditions from Washermenpet to Wimco Nagar comprise mostly of silty sand, clay or fine sand. However, the tunnels will run below densely populated areas with buildings, on the arterial stretch of Thiruvottiyur High Road , which are mostly single brick walled. Hence, engineers are exercising caution during tunneling.

