This story is from January 20, 2022

Chennai: Rainy season is over, but subways remain wet

It’s been more than 20 days since the rain stopped, but several subways of the city continue to be riddled with puddles.
Chennai: Rainy season is over, but subways remain wet
Water seepage at Nungambakkam subway is a daily ritual, risking lives of commuters
CHENNAI: It’s been more than 20 days since the rain stopped, but several subways of the city continue to be riddled with puddles.
Experts believe this is due to subways being eight to 10 feet below the ground level coupled with water table near the subways attaining saturation point following a downpour.
To prevent this phenomenon, the city corporation had embarked on a costly measure to stop water seepage by coating the subway walls with polyurethane.
But the project did not help much.
“It cost about 15 lakh. We tried doing this at the Nungambakkam subway, but when we coated one part of the wall, water found its way and seeped from the other part. It became an unfeasible process,” said Karuppasamy G, executive engineer, bridges department of the corporation.
Following this experiment, the civic body did not implement it at other subways. As a result, several subways such as the one at GA Road in north Chennai, Thillaiganga Nagar subway in Nanganallur and RBI subway in Parrys are filled with puddles.
Subramanian P, a hydrogeologist with Chennai Metro Water and Sewerage Supply Board (CMWSSB), said the water table has attained saturation in many places, and the only way out is to wait till it naturally subsides.
“There’s not much that can be done here. Places like Nanganallur have weathered hard rock surface, and water table there may have attained saturation,” he said.

GIS expert Dayanand Krishnan suggests grouting, a process to fill in the pores in the walls.
He, however, blamed the poor construction quality that allowed water to leak ionto the roads. “The subways, when constructed, must have been waterproof. Joints must be made waterproof too,” he said.
With no end to the water seepage in several subways, a commute through the puddled stretch is risky for motorists. This also leads to traffic snarls in the subways, said a regular commuter from Nanganallur.
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