The city has sink holes in the making on some busy road stretches where traffic moves bumper to bumper. A National Geophysical Survey of India probe into the structure of sewerage pipelines has brought out the anomaly.
As per the NGRI probe commissioned by Hyderabad Metropolitan Water Supply and Sewerage Board (HMWSSB), 6 km road stretch from Greenlands to Raj Bhavan-Khairatabad Junction was identified as a risk area which needs maintenance work shortly. The stretch which witnesses heavy traffic in peak hours also doubles up as a popular route for VIP movement.
Following NGRI’s initial investigation, the water board commissioned Jawaharlal Nehru Technological University to conduct further probe into other road stretches where pipelines are 30 to 35 years old. The JNTU’s survey will cover 39 km road in different parts of the city. The HMWS&SB commissioned the survey after road near NTR Gardens caved last year, thanks to corroded pipeline.
“The situation is not alarming. But we are doing this as a precautionary measure to prevent any untoward incident,” HMWSSB Managing Director M. Dana Kishore told The Hindu . Areas probed will be those have trunk pipes (over two meters in diameter) are used. Across the city, 1,026 km of trunk pipe connectivity facilitates sewerage flow. Survey will be done using ground penetration radar, the magnetic waves of which accurately measure and assess structures beneath the ground.
Moots trenchless model
The water board does not plan to create traffic congestion during its maintenance work, Mr. Kishore stressed. “Alternate technology like trenchless maintenance will have to be used to prevent inconvenience to motorists. After the survey, the board will estimate costs and employ the most effective technology to maintain the pipelines,” he added.
“Since trenchless technology incurs over a 50% hike in costs, the Board will have to shortlist the areas which require this technology the most. Same technology was employed to restore the pipeline near NTR Gardens.
“Other than Cured-in-Place Pipe the board is considering other trench technology which can be used to restore damaged pipes,” Mr. Kishore said.
Most pipelines start corroding after eight years as sulphur dioxide, a corrosive chemical compound eats into iron pipes. While newly-laid sewerage pipelines have lesser corrosive tendencies thanks to inlaid protective metal coating, most of the old pipes which form the backbone of sewerage lines in the city are likely to rot.
“JNTU survey will go on for four months. The board will draw a blueprint for pipe restoration afterwards,” Mr. Kishore explained.
