BMC to put Marine Drive under the radar

Four months ago, repair work was carried out after the cavity was detected

Four months ago, a 20-ft-deep cavity was detected at Marine Drive, which the Brihanmumbai Municipal Corporation (BMC) was able to repair in time before any accident took place. Acting on rising concerns about the stability of the popular promenade, BMC is now going to carry out a structural audit there, eight years after taking over its maintenance.

Unlike other structural audits, however, BMC is planning to use radar pulses to survey the ground beneath the promenade and detect cavities. The initiative has been taken by the BMC's heritage department and they are currently in the process of appointing a consultant for the job. They have suggested heritage structural consultant Chetan Raikar for the job and are currently waiting for administrative approval. The Marine Drive promenade was handed over to the BMC in 2012. The A ward office has been maintaining it ever since. The survey will be carried out on the 4.5 km-long stretch from NCPA till Girgaon Chowpatty.

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The Marine Drive promenade was handed over to the BMC in 2012. The A ward office has been maintaining it ever since. File pic

An official from BMC's heritage department said, "The radar survey can identify types of voids and other imperfections at the base of the promenade. Based on the findings, repair work will be taken up. The audit would reveal cavities, if any, and the reason behind their existence so that we can deal with them accordingly." For instance, he added that some cavities could be have formed due to the impact of waves, while others could be space left for utilities.

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Identifying defects

On April 16, the A ward commissioner held a meeting with officials from the heritage department as well as structural consultants. Among them was Raikar, who suggested identifying the defects below the promenade located adjacent to the sea, before strengthening it. Raikar said that by using the radar survey method, the quantum of defects could be documented and remedial measures be suggested accordingly.

As part of the audit, apart from a detailed visual inspection, BMC has proposed identifying utility lines visible from the seaside, preparing road-level and data-based drawings and carrying out a distress mapping of the flooring, steel furniture and other permanent objects. The consultant will also have to offer engineering solutions, including rectifying cavities which may have developed in the promenade.

Prompting the survey

Several instances brought out the need for the survey. In 2017, A ward officials had found 29 defunct water chambers beneath the surface of the promenade, which had caused the paver blocks to settle at some locations, forming an uneven surface. Kiran Dighavkar, assistant municipal commissioner of A ward, said they had filled the chambers and fixed shot blast paver blocks.

In April this year, officials from the heritage department visited the promenade and found the floor had settled at a few locations, possibly due to defunct chambers of the water mains. They also found upheaval in the flooring near the trees due to the growth of roots. "We also noticed cracks in the flooring at some locations due to the displacement of the tetra pods in the sea. At a few locations, the granite seating area has been displaced due to the sea waves, especially during June and July," said the official.

"We realised that a structural audit had never been carried out and this would help in strengthening Marine Drive. The audit is also required for documentation purposes," said Dighavkar. He added that based on the structural audit, a comprehensive tender would be formulated which will include repair work and maintenance for a period of five years.

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