Tuesday 20 August 2019

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Zuari bridge on verge of collapse ?

 

The Konkan railway, likely to be fully commissioned by the year end from Mumbai to Mangalore with a link upto Kerala, will bring fortunes to the whole western coast of the country. The combination of the sea route, road network and the railway line (besides the airways) would throw open opportunities to the whole World to trade, whether in field of tourism, industry, business or commerce. The economic activity, obviously, has gained sudden momentum in the coastal belt.

But it's threatened, not due to delay in commissioning the 760 km-long Konkan railway, but with several bridges along the west coast found to be in a dilapidated condition, while few of them in virtual state of collapse.

The Honavar bridge in North Canara, which is still struggling to survive, is an old story. The Mandovi bridge in Goa, which collapsed in 1986 - within 16 years - is also the history. But the possibility of repeating the same history with Zuari and Borim bridges in Goa and Kali river bridge in Karwar, a major link between Goa and Karnataka, is a danger of the future.

The Zuari bridge, a major link between two districts of Goa, is now closed for heavy traffic since April, within 14 years since commissioned. Tenders have already been floated for a parallel bridge on Build, Operate and Transfer basis as the existing bridge won't last for long.

Next in the line may be the Borim bridge in Goa, showing similar signs of deterioration. Experts also do not rule out the possibility of the Kali river bridge meeting the same fate. All the bridges are on the National Highway and built under supervision of the Ministry of Surface Transport (MoST).

The Rege Commission, which probed into the collapse of the Mandovi bridge, had held faulty design of the balanced cantilever bridges the prime cause for the disaster. Adopting the same design, but with little modification in construction technology, bridges at Zuari, Borim, Kali and the Ganga river in Patna - supposedly the longest bridge of five kms in Asia - were built by Gammon India during the same time.

A bridge in Hong Kong, built by the same company, had shown similar signs of corrosion after 14 years, though the problem was later successfully tackled by the Mott McDonald International Ltd.

The same consultancy firm, appointed by the MoST in 1991 after the Mandovi bridge collapse shook the central ministry, has now recommended to close the Zuari bridge for heavy traffic. The local PWD however is not prepared to touch the bridge till date, pending final recommendations from the foreign consultancy firm.

"It's not faulty construction alone, but mainly lack of technological advancement to arrest the problem of corrosion occurring due to salinity of the coastal environment", says A K Jahagirdar, chief engineer of Goa PWD.

To avoid corrosion of prestressed wires, state the experts, the balanced cantilever bridges needs to have a strong RCC construction with fully weather-proof deck slabs, properly grouted cable ducks, epoxy painted to keep out moisture and inspected and monitored from the day one. But epoxy painting was done at the Zuari bridge only in '87, five years after it was commissioned, when the Mandovi bridge collapsed.

As per the Rege Commission report, the officials of the MoST and the local PWD had failed in taking up remedial steps to save the Mandovi bridge, despite knowing the facts. The non-functional hinges between the girder tips were rectified only after three years, cracks were unattended for six years and corrosion of prestressed wires, which was noticed in '83, was neglected till the bridge collapsed. Even the technical experts committee failed to submit its preliminary report till the bridge collapsed.

Similar is the case with the Zuari bridge, where actual rehabilitation work is yet to begin though Mott McDonald had submitted its preliminary report in February '91. The findings are reportedly however similar to the Mandovi bridge, with the consulting firm noticing deteriorated RCC coat, girder tips sagged and cracks on deck slabs of the box girders, due to which water seeped in, leading to corrosion. Even the hinges between the girder tips are found non-functional.

The bridge is closed for heavy traffic, based on the final report the firm submitted in August last, six years after the preliminary report was prepared. Its detailed report, submitted in '94, was rejected by the MoST for a want of further investigations. The local PWD is still waiting for a detailed rehabilitation scheme from the consultants, including estimates, drawings and detailed engineering of the works.

"We are not prepared to take up any major rehabilitation work till then", says a senior PWD engineer. They fear of being held responsible if the bridge collapses as, according to them, the Rege Commission had held all the PWD officials responsible for neglecting the Mandovi bridge and a sincere officer was nailed down, for speaking the truth. The government is however all prepared and has even appointed the Fressinet Prestressed Concrete Co Ltd to carry out the rehabilitation work.

The 800 metre-long bridge in the meanwhile is in a critical condition, with 30 per cent of its prestressed wires corroded inside. PWD officials admit that the wires have corroded due to improper cement grouting and water proofing, which prevents air and moisture reaching the tendon, while the conduits were also not built properly.

Chief minister Pratapsing Rane, on the other hand, is holding the final report of Mott McDonald close to his chest, claiming : "it's just a preliminary report. I'll submit the detailed report during the July session." He is also presenting the Right to Information bill in the same session, but refuses to divulge vital information regarding the Zuari bridge.

The prestressing cement concrete technology of balanced cantilever bridges is banned in UK after realising loopholes in the technology, informs Gajanan Padmnabiah, superintending engineer of National Highways, while thousands of such bridges are built in India since mid-'60s.

Bridges with smaller spans, especially built in the interior, may not have immediate problems. But bridges like the Zuari, which has longest spans of 122 metres and are built in the coastal area, definitely needs to be reinspected. "There are hundreds of such bridges along the coastline", he says.

The seven-year long exercise put in by the Mott McDonald and the rehabilitation work to be taken by the Fressinet, state the officials here, will at the most prolong the life of the Zuari bridge for little more years. But building another bridge is the only permanent solution to it. What will be the fate of the coastal road network if all bridges along the coast need such parallels ?






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