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Since 1st March, 1999
 
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Erosion eats bridge base

Calcutta, Feb. 20: Howrah bridge is falling down' how will we build it up' With needles and pins, wood and clay or stone so strong' that it lasts long'.

Grappling with erosion at the base, engineers in charge of the bridge are hardly in the mood to hum nursery rhymes. They do assure, though, that there is no need to panic.

If they were not already at work, because of erosion of the riverbed one supporting pier might have gradually tilted, leading to one portion of the bridge itself leaning to one side.

A senior engineer explained that the bridge has four steel pylons (supporting pillars). These pylons are inserted into concrete piers (these too are pillars), parts of which go deep into the riverbed. The concrete piers are further protected with steel sheet against erosion at the base.

A portion of the riverbed, on the Howrah side, has been eroded and a part of the steel sheet ' covering about 30 metres to 40 metres ' has come off.

'The protective covering must stay in place as originally designed, because if the covering comes loose, the pier could lose strength at the base, and tilt. This might cause a portion of the bridge to lean on one side,' the engineer said.

Studies conducted by the Calcutta Port Trust, which is the custodian of the bridge, to keep track of river movement and its impact on the 60-year-old structure, have come up with this startling fact. The studies involve checking the river depth from time to time, erosion and silting.

'The Trust will set things in place, so that the steel sheet piles are set again and a protective covering is made with sacks of sand, boulders and pitched with bricks. This would again have to be covered with a special fabric sheet as protection against soil erosion at the base,' the engineer said.

'The support for the bridge has to be very strong as it has to bear the weight of 26,500 tonnes of steel. Naturally, any problem at any of the bases might have a huge impact on the main structure,' he added.

An estimated Rs 40 lakh will be required to repair the underground protective cover. 'We are going to take up the work and complete it by the end of this year. The process of erosion has been detected, and preventive measures will be adopted.

'The work would be completed in four months. We have taken the matter seriously. But there is no need to panic, because a lot of the bridge's load is distributed horizontally,' said P. Majumdar, deputy chief engineer of the Trust.

There was a similar crisis ' of a much larger dimension ' in the Second Hooghly bridge in the late eighties, for which protective measures had to be taken on a pier, an engineer associated with the project said.

'The present one is a danger of a lesser dimension, but only if it is addressed immediately,' the official added.

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