Mumbai Coastal Road leakage is ‘normal, limited issue’

Leakage spots (circled) inside the tunnel that have now been fixed by BMC. Pics/Kirti Surve Parade

After leakages appeared at various spots inside the Coastal Road tunnel, the BMC repaired them on a war footing, and on Thursday, there were no active spots inside the southbound tunnel. "Such leakages at the expansion joints may appear in the future due to geological changes. They were not due to structural flaws, and we will form a strategy to deal with them," the BMC said.

MID-DAY'S February report reviewed city tunnels after Delhi's Pragati Maidan tunnel faced water logging issues, prompting closures for repairs. At the time, BMC officials assured they tackled leakage in Mumbai Coastal Road's twin tunnels using a four-layer barrier. An official said, "To make the tunnels leakage-free, we carried out works like primary grouting, or filling the gap between the segmental lining and the excavation surface with cement material; secondary grouting or cavity filling where the primary grouting was incomplete; using EPDM gaskets to create a watertight system between segment rings; and hydrophilic cord, which is expandable," claimed an official from the Coastal Road Project.

Leakages inside the tunnel have now been fixed by BMC. Pics/Kirti Surve Parade

But even after that, leakages started from a few points inside the tunnel last week. After CM Eknath Shinde visited the spot, he assured action to monitor and close all 25 points in both tunnels. Now, the BMC officials said, "Such issues happened due to geological factors, and they are ‘normal.' All over the world, tunnels are not 100 per cent leakage-proof. It is due to geological movement, tides, and other factors affecting the tunnels. There should be constant observation and finding solutions to tackle the points."

An official further explained that the issue at Pragati Maidan was different. The tunnel there is under the mainland and floods every monsoon, whereas the twin tunnels of the Coastal Road are 15 to 20 metres underground in an intertidal zone - within the high and low tide area - which is constantly impacted by waves. In this particular leakage, there is constant vehicular movement over the tunnels, which might have caused expansion in the joints. After the leakage was pointed out, they treated five joints where it occurred. "Out of 25 points, five points in a stretch of 200 metres near Bal Bhavan leaked. But we will map all 25 points in both tunnels and form a strategy with other experts to tackle such issues in the future," said an official.

The 10.58-km Coastal Road is being constructed from the Princess Street flyover at Marine Drive to the southern end of Bandra Worli Sea Link. Twin tunnels have been built at a depth of 12 to 67 metres under Malabar Hill. Each tunnel is 12.19 metres in diameter. The southbound tunnel has already started, and the northbound tunnel is supposed to start by June 10.

Pragati Maidan issue

The Pragati Maidan complex, including a 1.3 km tunnel and five underpasses, opened in June 2022. It has faced waterlogging and seepage issues, causing several shutdowns for repairs. The Delhi PWD issued a show-cause notice to the contractor for "serious technical and design deficiencies." These issues have raised concerns about the safety of similar projects in Mumbai, such as the Mumbai Metro Line 3 and Coastal Road, and other projects which are nearing completion.

June 10
Day northbound tunnel is expected to start