The state public works department (PWD) has set monsoon 2026 as the deadline to build a permanent bridge across the Balason in Mirik, now under construction, which will serve as a crucial link between Siliguri and Mirik.

A temporary bridge, made with hume pipes and a carriage way with riverbed materials, is now the only connection between Mirik and Siliguri after the earlier Dudhia bridge was washed away by the relentless rain between the night of October 4 and early morning of October 5.

The temporary bridge, now open to traffic, may encounter breaches during heavy rain and has a restricted lifespan. The river’s water could rise to the carriageway of the hume pipe bridge during heavy rainfall, said a PWD official.

A Darjeeling District Police officer said traffic had to be stopped for a night last week when the water level of Balason rose after a spell of intense rain.

“It was done for safety reasons. This is a temporary bridge and there can be breaches during heavy rain,” said the officer.

PWD engineers want the permanent bridge, whose construction began a few months ago, to be ready by the next monsoon so that connectivity between Siliguri and Mirik remains uninterrupted even during heavy rain.

“We are targeting to commission the permanent bridge by July or August next year,” said a senior PWD engineer.

According to another senior PWD official, building the bridge will cost around ₹54 crore. The temporary bridge, built in around 21 days since the flash floods in early October, cost over ₹1 crore, said the official.

“Even before the collapse of the Dudhia bridge, we had identified that it was in a poor state and started preparations for building a new bridge. The flash floods happened on October 4, snapping the connectivity between Mirik and Siliguri,” said the official.

“To restore connectivity, we built the hume pipe bridge, but it is only a temporary structure with a restricted lifespan. We have started construction of the new permanent bridge and wish to commission it by the monsoon next year,” added the official.

Hundreds of tourists from Calcutta visit the quaint town of Mirik every year. The bridge will also help residents travelling between Mirik and Siliguri.

The under-construction structure will be a two-lane bridge having space for one vehicle to move in the opposite direction simultaneously. The temporary bridge is also two-lane.

“We have completed one well of the 190m structure. Three more wells will be built. Above them, the pile and pile cap will be built,” said an engineer.

The construction has, however, been delayed as hard rocks present in sections of the river bed made the foundation work impossible.

“We are now waiting for the flow of the river to dry up in a few more days. We will see what more can be done. If required, we have to do controlled blasting to drill the bed for the bridge’s foundation,” said the official.

The hume pipe bridge has been built over a stretch of the river that is narrower than the stretch where the permanent bridge is being built.