CP tunnel a technological feat that went unsung

A technological feat in itself, the 1.25 km long underground service tunnel that is being laid in the Middle Circle of Connaught Place here has only got bad publicity so far. While it is the country’s first initiative at providing a common duct for various services to do away with the ills of road-cutting, dangers involved in maintenance and having a mapped data of all utilities, the project has only left a bad taste in the mouth of all for the way it was conceived and handled.

Shopkeepers and residents of Connaught Place insist they were never informed about the project plan, kept in the dark about its details and the long period over which the Middle Circle was dug up led to loss of business and caused great inconvenience.

On the other hand, Engineers India Limited, which is executing the project, had no option but to accept the project as the Government wanted to proceed with it quickly in the run-up to the Commonwealth Games 2010. But then they were made to cover it up for the Games so that foreigners did not carry home a bad impression about Delhi.

It is another matter though that few foreigners turned up for the Games and the stoppage delayed the work by over half a year and only increased the suffering of all the stake holders.

So while the work actually began on January 27, 2010, and is scheduled for completion in just three years, it appears to have taken a whole lot more.

Since the Games though, the service tunnel work has been progressing fast. “We are confident of completing the work by December this year and all the major services would also be shifted by then,” said an engineer working on the project.

“We had limited space to work with and had to protect the buildings on both sides of the Middle Circle. So we adopted the top down approach in which first 80 cm thick diaphragm walls were sunk 14 metres into the ground. Then a slab was laid on the top and an inverted ‘U’ concrete box was created.

Thereafter access to the tunnels was provided every 50 metres as per fire norms and work was undertaken inside. It was during the laying of the slab on top that the residents and shopkeepers suffered the most as the area was cordoned off for between six to eight months.

A visit inside the tunnel reveals the extent of work which went it. As one climbs down the stairwells and enters the main duct, the place appears imposing. The tunnels are 7 metres wide and equally high.

‘Wet portal’

On one side, they have a “wet portal” which is basically three rows of iron girders on which the water lines, fire fighting lines and irrigation water lines would be placed. Underneath runs a water channel to carry any dripping water to a sump from where it could be pumped out.

On the other side of the tunnel is the “dry portal” or a frame of 20 iron racks placed in two columns of 10 racks each. These racks are for carrying the high and low tension electrical cables, telecommunication cables and any other ‘dry’ utility.

Right now the side walls of these tunnels are also being made waterproof with a 15 cm special cage. Once these tunnels are completed, they would only be accessible with smart cards which would be providing to the staff of various utilities.

In every block, these tunnels also possess an open space on the side for placement of transformers. A provision was also made for having chilled water lines run through them for providing centralised air-conditioned all over Connaught Place but the proposal was shelved following objections from the traders.

Engineers working on the project insist this service tunnel has been designed to meet the needs of Connaught Place for years to come.

The “gravity systems” of sewerage and drainage have been kept outside the tunnels. “The sewerage system earlier used to flow from A to F block and then used to exit Connaught Place via Barakhamba Road. But now they exit from every radial road and connect to the city sewerage system running along the Outer Circle. Due to this the EIL has been able to place the sewerage system higher than before. “This makes it easier to approach and maintain the sewerage system.”

The sewerage lines are 500 mm thick and those for the drainage are 300 mm. They run on both sides of the service tunnel catering to the adjoining blocks.

The engineers insist that while laying the service tunnel was challenging on account of the unchartered utilities, which did not find any mention in the maps and details which were provided to them, so was the case when it came to laying the sewerage and drainage lines.

“There were so many live water, sewerage, electricity and telecommunication lines on both the sides, that in some places we spent nearly a month to lay 20 metres of sewerage and drainage pipes as these lines were live and we had to keep the water and power of the businesses and residents going while carrying out the construction.”

So the engineers used to deploy cranes to lift these lines or first placed them on racks to allow their workers to lay the drainage and sewerage lines below. “Then too due to paucity of space we were able to use only a couple of workers at a time and since the live cables used to be there, we could not make them work at night.”

A walk around the Middle Circle revealed that the engineers had also provided ramps outside all the establishments, barring a few. The work on the side walks which would measure 1.5 metre on one side and 2.5 metres on the other is also at various stages of completion. While in some areas, the kerb stones have been laid and concrete base has been provided, in others 5 cm thick sandstone slabs have also been laid. There are also portions, where all this work is yet to be done.

As of now deep trenches have been sunk at both Minto Road and Janpath intersections of the service tunnel and work is proceeding at a feverish pitch there. From the extent of the digging, it is hard to imagine that the site at Minto Road has been sunk with side claddings, to prevent the earth from caving in, within just a week.

At Janpath intersection, the base is being prepared for making of transformer bays. Apart from such bays in service tunnels, underground transformer bays are being constructed at five places on the radial roads with capacity of installing four to five transformers each.

The engineers insist they want to complete all the tasks at hand quickly and move out since the hard work put in at Connaught Place has not been appreciated the way it should have been.