Calcutta, Feb. 24: A potential bridge collapse was averted in Bengal after an IIT inspection found that the strength of the piers on which a deck slab was supposed to have been placed this month was way below the prescribed level.

The load-carrying strength of the pillars was found to be one-fifth of the required newtons at some places and never above half the desired level anywhere, according to the findings. Newton is the standard unit of force.

Had an executive engineer not raised the red flag, the bridge across North 24-Parganas’ Kantakhali river, 70km from Calcutta, would have come up without remedy and possibly put lives at risk.

The alert was flashed only last August, which means the project that was launched when the Left Front was in power somehow escaped scrutiny all along.

The state government has now decided to build the structure afresh, entailing cost and time overruns and raising questions whether corruption-driven compromises on quality of materials was behind the shoddy construction.

Having to build a bridge afresh on suspicion of corruption is unheard of in Bengal. The government is said to be considering a proposal to refer the issue to the anti-corruption bureau.

At Rs 30 crore, the original project cost of the 230-metre-long bridge is not much by infrastructure yardsticks. But the human cost of faulty construction could have been high.

“The bridge to connect Hingalganj and Hasnabad was a long-standing demand of the people. The previous Left Front government had started the project with money from Nabard’s rural infrastructure development fund in 2005-06. Half of the total project cost or Rs 15 crore has now been wasted,” said a government official.

“A private agency was carrying out the project but PWD engineers were supposed to supervise the work regularly. It appears that it was not done properly, said a PWD official.

That something was amiss was first noticed on August 28 last year when the suspicions of the executive engineer (highway) of North 24-Parganas were aroused.

When the executive engineer visited the project site, construction of the two main pillars had just been completed although seven years had passed.

“The engineer informed top PWD officials that the pillars were constructed with doubtful quality of concrete. He also found some engineering faults,” said an official.

The PWD decided to suspend construction until a review was over. “The memory of the collapse of the Ultadanga flyover was still fresh and the department did not take any chance. It urged IIT Kharagpur to inspect the pillars,” the official added.

IIT officials collected concrete samples and submitted a report last week, on February 21.

The report revealed that the “load-carrying capacity of the pier shafts” had been seriously compromised.

“The report says the load-carrying strength of the pillars should have been 40 newton per sqmm but it was found that the capacity varies between 7.5 newton per sqmm and 19 newton per sqmm,” said a senior PWD engineer.

Newton per sqmm is the measure of force per unit area. “This is the unit through which we measure whether the construction can bear the required load,” the engineer added.

The weak pillars will be demolished now. Two additional pillars have to be erected in the new design.

“It is surprising that all the other engineers responsible for overseeing the work did not find anything wrong till the executive engineer inspected the project,” an official added.

Former PWD minister and RSP leader Kshiti Goswami, during whose tenure the project had started, said: “There may be a fault in the design…. But a minister cannot compromise with the construction material of a bridge as it involves lives of several hundred people.”