‘Padma Bridge can easily last 100 years if properly maintained’

The Padma Bridge is a big achievement for us since our independence. 

It wasn't easy to build this bridge on the fierce Padma River. There are bigger bridges in the world than the Padma Bridge, but there is no bridge on a river as big and as unpredictable as the Padma River. We faced a wide array of technical and other challenges building the 6.150 kilometres bridge.

The primary and main challenge was to build the foundation. The bridge has 41 spans. 42 piers were built to place these spans. The first pier is at the Mawa end, although it's not apparent which is the first pier, because the bridge is 70 to 80 feet above ground-level. 

If you start from the Mawa end, it might seem like the piers ended at the 12th or the 13th pier, but in reality, that's where the main body of the river began.

The river is very deep and has very strong, frequent tides. Bank erosion on the Mawa end is essentially uncontrollable. The banks kept eroding and it was very difficult to build the foundation there.

The foundation is about 122 metres, on which the 150 metres long steel spans sit at 500 feet intervals. The piers take an enormous amount of load. The truss alone weighs 3,150 tonnes. But the overall load reaches nearly 6,000 tonnes.

This load has to be transferred [through other connected structures]. Building something like this enrages the river, which considers any new structure an obstacle. We had to test whether the river bed can take the kind of load we had to put on it. We had to test the pressure from the tide, as well as possible load from earthquake tremors. Large scale earthquake events were taken into account when designing the bridge.

Piling: No straight task

As challenging as the design was, the actual implementation of the design was a much harder job. We solved those problems, despite scepticism about our capabilities.

The streambed or the bottom of the river posed challenges too. We found differences in soil after testing. Piers wouldn't settle on the places where the soil was different from the rest of the area. 

The 40 piers in the middle of the bridge were to have only six piles according to design. The piles go about 425 metres deep.

The primary alignment of the bridge was also moved because of soil issues. Moving the piers required another round of soil tests. We at the technical committee repeatedly studied the changes. When we found differences in soil quality we took careful steps to address that.

We consulted international experts across the world. But their solutions were not suitable for us. 

The six piles under the piers are not straight. They are set up at an angle.

After our survey we finally came up with the solution ourselves, which was to add a seventh pile.  The new pile had special chemicals at the bottom part which will harden the soil. This alone pushed the construction time back by a year. We were criticised for it, but what is really important is that we found a solution. 

However, the result was that we now had 22 extra piles under the 22 piers. So, the total number of piles ended up being 262, instead of the originally planned 240. The local and the international experts all agreed with the solution. The contractor began construction work after this modification in design. This was our biggest challenge.

River training the sediment-prone Padma

Another challenge was river training. Even though construction for the bridge has been completed, the river training work will need until June next year to finish. But if there is new sedimentation this year, then it will be very hard to carry out the river training work.

There is typically 20 to 30 feet of sedimentation in each rainy season. This makes using smaller water vehicles, necessary from river training work, impossible. That means more dredging will be necessary. This takes a lot of time. Some years, sedimentation was up to 32 feet.

What river training does is essentially hardening or solidifying the soil on the riverbed. The purpose is to mitigate or eliminate scour or moving of sediment.

River training work is less intense on the Mawa side, and more on the Madaripur side. A total of 13 kilometres area needs river training on that side. That's also a problem that needs solving. 

Quality control by the expert panel

We, the experts, have visited China a number of times since the government finalised the contractor and up until the construction work began. We visited every laboratory and testing centre during our visits. We analysed what we saw and we tested the construction materials again once those arrived here in the country.

We have five foreign experts in our panel. There are six local experts in the panel. And all of the experts participated in the quality control process.

Seismic activity or earthquake within a certain scale will not impact the bridge at all. Bridges are not usually built to last for a hundred years [without further enhancements]. Designs are typically meant to support for 70 years. But the Padma Bridge can easily last a hundred years if maintained appropriately. The Hardinge Bridge is over a hundred years old, but there is no problem with it.

Local engineers made major contributions

Even though foreign contractors built the bridge, local Bangladeshi engineers contributed significantly, starting from the design to every stage of the construction. 

The design of the bridge was done by AECOM, which is an Australia-based company, but many Bangladeshis work there. The consultant company was Northwest Hydraulic Consultant, where also many Bangalees work.

The engineer who led the soil testing is a Buet graduate. He did the work, but he did it as an employee of the foreign contractor. He did a great job and it earned him respect. 

Most of the engineers happen to be local in construction projects by foreign contractors in Bangladesh. I think we should record the number of local and foreign engineers that worked in the Padma Bridge project. 

People need to understand that Padma Bridge is very unique. Our engineers have worked here in many capacities. This experience enriched them. They in turn earned credibility. This experience will help them in two ways. One is in design work and the other is construction supervision and real construction.

Aside from the Padma Bridge, we have built bridges on a number of other rivers including the Teesta River. We didn't need international experts for that. We can build bridges.

Padma Bridge experience will help in future projects

However, what we don't have is equipment. No one is investing here. There is no guarantee that you will get work if you invest. In India, this sector has had investments because India is a very big country. Its economy is big.

If an investor put in Tk1,000 crore and doesn't get any return, then why would he invest?

Two junior and one senior hammers were used to install the piles for the Padma Bridge. Bangladeshi companies can't invest so much (to buy these). But our local contractors are building roads now, and they have equipment.

Local experts involved in the Padma Bridge construction can use the experience gained here to build bridges on other big rivers like the Meghna, and the implementation will be much easier because of this experience.

When the government takes foreign loans, half of the money leaves the country. The financers dictate who should be contractors, and you have to abide by that.

Professor M Shamim Z Bosunia, chairman of the expert panel overseeing the Padma Multipurpose Bridge Project, spoke to TBS Senior Staff Correspondent Saifuddin Saif