With condition of roads and bridges deteriorating in the city, the Standing Technical Advisory Committee has asked the Brihanmumbai Municipal Corporation to undertake a survey of fragile roads through Ground Penetrating Radar to detect cavities beneath and a detailed structural audit of 58 bridges in a month’s time.

The BMC-appointed STAC meets every three months and surveyed few of the roads in South Mumbai two days ago. Members said the roads had cavities and blamed the sub standard work by contractors.

“There are lots of cavities beneath but it is difficult to assess which road will cave in and when. It is difficult to check for cavities manually as it will disturb the underground utilities. BMC therefore has to procure the GPR machines at the earliest,” said committee chairman N V Merani.

The BMC, who had plans of procuring six such machines to detect cavities, had however scrapped the plan. Also, it did not carry out the survey of Raja Ram Mohan Roy Road in the Prathna Samaj area, the Veer Nariman Road and Peddar Road which have already given way in the past.

The committee has also ordered for immediate audit of bridges following the recent Thane bridge collapse that killed three. According to the visual survey carried by STAC two years ago, 58 bridges were tagged dangerous but the civic administration said it will once again carry a detailed investigation to determine the strength of these bridges and carry out repair or reconstruction work accordingly.

Merani said that BMC will have to assess the structural condition of these bridges and restrict traffic load on those which are found to be weak and will undertake immediate repairs on them. He added that the BMC needs specific quality assurance manuals for bridges and the current norms are not good enough to assess the safety of these bridges. “Bridges is a special science and we had therefore asked the BMC to have specially designed manuals for bridges,” Merani said.