The state government has requested the railways to provide a design of the new Tallah bridge so that it gets the mandatory clearance of the Railway Board at the earliest.

The new bridge will be built by the public works department but the plan has to be cleared by the board since a part of the structure will be over railway tracks.

The existing bridge, a key link between Calcutta and parts of North 24-Parganas, has lost much of its load-bearing capacity and needs to be pulled down, according to engineers who have inspected the 57-year-old structure.

Engineers of the PWD and the railways met on October 9 and discussed two probable designs of the proposed bridge — cable-stayed and one made of steel girders.

PWD officials said the railways has a number of designs for railway overbridges at the Research Design and Standards Organisation (RDSO) office in Lucknow. If the railways comes up with a design that has already been approved by RDSO, construction time of the bridge will be shortened by several months.

“The railways will route any design the state government will suggest through RDSO. So, why waste time over procedural matters? Let them offer a design,” said a senior engineer of the PWD. “We can then focus on other important issues such as taking ‘traffic block’ and coordinating with bridge engineers to start piling,” he said.

V.K. Raina, an engineer who was hired by the state government to study the health of the bridge, has mentioned in his report that the structure should be pulled down and small vehicles should not be allowed on it for more than two months.

Buses, trucks and other heavy vehicles are no longer allowed to ply down the bridge.

A meeting at Nabanna next week, to be chaired by chief minister Mamata Banerjee, is likely to decide the next course of action based on Raina’s report.

Engineers of the railways, PWD and engineering consultancy RITES, a subsidiary of the railways, will attend the meeting.

A team of RITES engineers had inspected the bridge a few days ago and arrived at almost the same conclusions as Raina.

The Tallah bridge stands on 39 girders, each 25 metres in length. The girders are connected with one another with pre-stressed steel cable ducts.

The bridge was built to bear 56 tonnes of weight on each flank.

Consultants from RITES have started working on the “loading class” of the new bridge keeping in mind the growth in vehicular load.

RDSO has a well laid-down “bridge rules” specifying loads for the super-structure and sub-structure of bridges. PWD engineers said once the load-bearing capacity of the proposed structure was worked out, the railways could tap RDSO for a design.

“A detailed survey is required to decide how the bridge will be constructed,” a railway official said.

Nabanna has sent a format to the PWD for a memorandum of understanding (MoU) with the railways on maintenance of railway flyovers and bridges. Sources said an MoU for the Tallah bridge would be signed once the cost-sharing for the proposed structure is finalised.