The main challenge currently facing the Padma bridge project is building the main bridge without adequate and proper studies, experts said.
In the absence of detailed geotechnical, hydraulic and other related studies, they said, the Padma Multipurpose Bridge project office has now got to take support of a foreign consulting firm for the confirmation of the design of the 6.15-kilometre bridge.
Panel of experts of the project has proposed to change the design of the bridge foundation for not finding due level of depth and soil at 14 points of piers recommended by design consultant.
The office has requested a UK-based firm, High Pan Rendal, to complete the design checking by September so that the Chinese contractor does not miss upcoming dry season of construction.
But sources said design confirmation by September also would not ease the situation as ongoing rain, floods and river erosion have already made the possibility of using dry season for carrying out boring and piling for the piers of the main bridge.
As a result, doubt has already been created over meeting the government target of inauguration of the dream bridge by December 2018. The project cost is escalating for delays.
According to the Bangladesh University of Engineering and Technology (BUET) and Geological Survey Bangladesh (GSB), multidimensional studies including detailed geotechnical and geophysical ones were necessary to confirm the detailed design.
Experts argued that mud over the base level of riverbed was not deposited all on a sudden and proper soil investigation which is done during exploratory boring would certainly discover it.
They said the Padma is no doubt a dynamic river but it is not located at the mouth of two rivers, which may cause change in soil layer.
"Shifting river flow and change in river layer have not taken place in a year or two…it is a matter of hundreds of thousands of years," said a geologist, preferring not to be named as Padma Bridge is a very sensitive project.
He said if layer change really takes place, it should be a matter of research.
Another expert said geophysical study could identify the change of layers all along the bridge corridor and decision must be taken through coordination of all data.
He said Padma as a dynamic river changes its river training at any time as well as takes on different characteristics as a delta.
The expert, however, aired doubt about such change in layer that increases the foundation depth from 112 metres to 124 to 128 metres.
According to sources, the design consultant, Maunsel AECOM, had conducted exploratory boring at 12 points out of proposed 40 piers. But the contractor found soil levels different at 14 points down the middle of the river.
So it is assumed that exploratory study was not done with due distances.
With half the construction period gone by, it is now recommended changes in the depth of 14 piers from 112 to 113 metres to 123 metres to 128 metres on point-to-point basis.
BUET experts, however, said design consultants' study findings must be confirmed through detailed study at the stage of construction by the contractor.
Though the project's contractor, China Major Bridge Company (CMBC), started construction of the country's longest bridge in November 2014, it could not make any headway spending 33 months.
According to the progress report in July, main bridge construction of the Padma Multipurpose Bridge project (PMBP) is 8.0 per cent behind the target while the river-training work 10 per cent. With completion of approach roads on both sides and service-area development the total progress record improved to 45 per cent.
There was hardly any progress during the last six months in both main bridge and river-training works.
Though the CMBC could complete more than 150 piles of 26 piers (each pier has six piles), not a single pier has been visible till now. But the project has set a target to set up first 150-metre span on the Janjira side by next month.
Sources said both change in the design and extension of time may hike the project cost manifold, hinting at 10 per cent increase in project cost for design changes, additional costs for materials and time extension for contractors and construction-supervision consultant,
But change on non-tender items may hike the already-expensive project to unpredictable levels as the contractor then will claim more for the changes in contract and time.
Padma Multipurpose Bridge is already considered a most expensive bridge in the world in comparison with per-kilometer cost of different bridges.
PMB project office said they had guided the consulting firm to confirm the design with these issues in mind so that the existing Chinese firm has the capacity to complete the project.
"Detailed soil investigation found change in the riverbed and we have proposed three to four options on foundation-design modification of couple of piers to finalise the design," said Dr Shamimuzzaman Basunia, one of the PoE members.
But the project director said Padma bridge construction could not be started soon after the detailed design was done and already 17 years have gone by since the first hydraulic study was conducted.
Sources said the BBA has already briefed the Prime Minister of the changes and possible increases in the project cost.
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Source: The Financial Express