Calcutta’s skyscraper-starved skyline has been perked up by a pair of tall-boy twins shaking hands across the river.
At 380 feet each, power utility CESC’s new transmission towers on either bank of the Hooghly are only five feet shorter than the reigning topper, South City.
The towers, meant to transmit electricity from the city to Howrah and parts of Hooghly, connect Cossipore on the Calcutta side to Belur on the Howrah side through seven wires that hang over the river, spanning 720 metres (2,362 feet).
The structures overlook Bally Bridge, Nivedita Setu and the Dakshineswar temple on the northern side and the Cossipore Gun and Shell factory on the southern side along with the rest of the city.
This overhead line across the river is the first in the city by any utility. CESC had so far depended mainly on an underground cable tunnel between its southern generating station at Garden Reach and the botanical gardens in Shibpur, Howrah.
“We want to improve the reliability of the power supply on either bank of the river to serve our consumers better. This is a step in that direction,” Aniruddha Basu, managing director of CESC, said.
Each of these towers, made of high-tensile steel, weighs around 110 tonnes, around 10 times more than the normal tower weight of 10 to 14 tonnes.
The height of the towers was decided in consultation with Calcutta Port Trust, which had specified a minimum clearance of 25 metres between the lowest point of the lowermost conductor (cable) and the highest flood-water level.
The pile foundation on each side of the bank has been drilled to a depth of 37 metres (120ft). The towers have been designed to withstand wind velocity of 100 metres per second, double of what is required.
After landfall on either side, the cables go underground to CESC’s existing installations — the New Cossipore generating station on the eastern bank and the Belur receiving station on the western bank.
“The expenditure on overhead line-crossing was around Rs 14 crore while the underground line cost another Rs 20 crore,” Satya Kumar Sinha, executive director at CESC, said.
Sinha, who had been given the responsibility of putting up the entire system, said his team of engineers had to face quite a few challenges.
First, they had to dig deep and hard to remove the concrete base dating back to the British era. Special arrangements had to be made on the Belur side as the foot of the tower was getting submerged in high tide. Underground cabling along the narrow road leading to the Belur receiving station from the tower was a challenge too.
Abhijit Bose, executive director at CESC in charge of distribution, said connectivity would be sufficient to carry 500MW of power.
All the power-generating stations of CESC are on the eastern side of the river.
“The present load of the western side is about 350MW. But it is growing steadily. Last year, we had given 20,000 new connections in the Howrah region (that include parts of Howrah and Hooghly district),” Bose said.
The transmission line could also be used to bring power to Calcutta from the western bank in future, the CESC official added.