Mumbai: Water leakage was detected in Coastal Road’s northbound tunnel on Sunday morning amid heavy rain. Civic authorities undertook immediate repair work. Officials said the leakage was plugged and the tunnel was safe for traffic.They said only one leakage point was identified at the interface section between the cut-and-cover portion and the tunnel on the Priyadarshini Park side. To arrest the seepage, engineers carried out pressure injection grouting using hydro-active polyurethane injection, a commonly used waterproofing technique for underground structures. The chemical reacts with water to form expanding foam, sealing the joints and preventing further ingress of water into the tunnel.Leader of opposition Kishori Pednekar visited the spot and raised concerns.Breach Candy resident Nigum Lakhani said, “On Sunday night, when I was returning from Marine Drive through the Coastal Road tunnel, I saw that water was leaking from the left side wall and a team was trying to work on it.”An official said tunnels built adjacent to water bodies cannot be made completely watertight, especially during periods of intense rainfall when hydrostatic pressure increases significantly. They said international engineering standards permit a limited amount of seepage, and isolated leakages through construction or expansion joints are not uncommon. Such seepage is continuously monitored and addressed whenever detected, they said.This was not the first instance of seepage in Coastal Road’s tunnel. In May 2024, shortly after the southbound tunnel was opened to traffic, water seepage was observed through two expansion joints. —Richa Pinto