Underground ducting for better streets in Chennai

Chennaiites who suffer constant road work could now hope for some relief as the Greater Chennai Corporation is in the process of equipping the bus route roads in the city with underground ducts for optical fibre cables (OFC) and even power cables. 

Currently, 120 bus route roads have been fitted with underground ducting for future use. Underground ducts for utility cables can result in lesser road cuts, while improving the streetscape. 

When the Corporation undertook the footpath redesign project to ensure better walkbase, the civic body also considered the possibility of installing underground ducts in selected bus route roads - a trend that is being followed by progressive cities around the world. A Corporation official said that 120 bus route roads in the city have been given underground ducting facility. 

“This is a 2 ft by 2 ft pit, with a depth of 2 ft, where two pipelines have been fitted – one for the OFCs and other for power lines. These pipelines are 200mm in diametre. Every 10 feet, there is a similar chamber, which can be used to access the pipelines,” said an official. 

The idea behind the underground ducting is to prevent road cuts. “All the advanced countries have ducting on roads for electricity, OFC and rider for sewage and water. If the wire has a problem, there is no need to dig the road but just pull out the damaged wire, using these chambers. 

Today, the agencies are forced to dig up roads. In the future, there are different kinds of ducting possible – depending on funds,” said a senior Corporation official. 

The ducting options depend on the requirements as well. 

“The electrical wires are separated from OFC wires. The high voltage cables can be at a deeper level and the pipes will connect to the transformers and utility boxes on the footpaths,” said the senior official. The design currently used in the city accommodates two pipelines. 

Some of the roads where this underground ducting facility has been added to the pavements include: Gandhi Irwin Road, Langs Garden Road, Adithanar Salai, Rukmini Lakshmi Salai, Mayor Ramanathan Salai, East Ramanathan Salai, Egmore High Road, Dams Road, PT Rajan Salai, Munusamy Road in KK Nagar, TTK Road junction, Marina Loop Road. The current ducting design can be used for smaller wires. 

“For the heavier cables by the Tamil Nadu Electricity Board (TNEB), roads must be dug up,” said the official, adding that monthly, 10-15 road cuts are permitted by the civic body. However, in T Nagar, which comes under the Smart Cities project, the Corporation is considering a common pipeline each for various services such as LPG connection, sewage disposal and water supply. 

“We are still deliberating on the design,” added the official.  This is a positive move from the civic body, in terms of improving the streetscape, said Advait Jani, Program Coordinator – Chennai, Urban Works Institute (UWI), supported by Institute for Transportation & Development Policy (ITDP). 

“The overhead wires are ugly and can ruin the streetscape, making the streets look uncluttered. This is economically better, as there is cost-saving due to prevention of road cuts, which only reduce the quality and life span of the roads,” he said. 

Advait cited the example of Bengaluru, which was one of the first cities to adopt the underground ducting model, under the Tender SURE project. Selected main roads, including St Marks Road and Vittal Mallya Hospital Road where work has been completed, have been designed with features such as uniform standard carriageway width from one junction to another, bicycle lane, well-designed bus stops, parking bay and dedicated corridors below footpaths to lay conduits of essential amenities such as electricity, water, sewage and OFC, etc, eliminating the need to excavate the road for repairs.  

“The underground ducting in Bengaluru has provided ducts of varying sizes for an array of services. The electrical ducts are slightly bigger. For storm water drain, they have added pipelines underground. However, the Chennai model of ducting seems to be heavily underestimated,” he concluded.