29-07-2025
New Delhi's old drains to be assessed by robotic mapping
New Delhi A view of Lutyens' Delhi. (HT Archive)
The New Delhi Municipal Council (NDMC) will carry out a robotic survey and mapping exercise of sewage lines laid pre-Independence using self-propelled platforms equipped with CCTV cameras, officials familiar with the matter said, adding that it will help assess the extent of damage.
The robotic drone survey will be used to identify defects of displaced sections, disjointed pipes, cracks and fissures, after which repairs will accordingly be undertaken. Meanwhile, the council is also likely to soon initiate rehabilitation work of a sewage network from Shanti Path to Satya Sadan Madhu Limaye Marg via Kautilya Marg and along Kushak Nallah.
NDMC officials said that there are several old brick-barrel sewer lines, developed almost a century ago, which are completely covered and cannot be accessed by larger machines. 'It becomes difficult to estimate or assess the amount of silt deposited and damage caused by erosion. No manual intervention will be involved in the process, and an expert agency will be hired to undertake the robotic survey. At some places, these century-old brick barrels have changed levels, and at other places, silt has accumulated, leading to waterlogging,' an NDMC official said.
A second official explained that the assessment would involve lowering a self-propelled system—mounted with a sewer class camera which can pan, tilt and zoom—into the sewer line. 'The camera has 360-degree panning to capture images used for diameter measurement, quantity of silt estimation and any service defects like tree roots, debris along with structural defects. The acoustic profiling of the sewage line will also be carried out at every five-metre interval,' the official said.
Acoustic profiling is used for assessing pipe conditions, including the detection of defects, blockages, and sediment buildup. Acoustic profiler equipment uses sound waves to measure water current velocity at different depths to assess the structure.
On July 25, NDMC invited bids; the tendering process is likely to be wrapped up by August 4. The assessment is likely to be completed in three months.
The first official said that the project will also involve searching for buried manholes by metal detectors, and opening and restoring manholes. 'The use of robotic machines will also help in compliance with the Prevention of Manual Scavenging Act,' the official said.
NDMC maintains about 350 kilometres of sewage lines in New Delhi across an area of 42.7 square kilometres. The majority of New Delhi's basic infrastructure was built between 1920 and 1930. The sewage lines are of varying sizes, ranging from 350mm to 2100mm in diameter.
Civic officials said that over the decades, corrosive gases from the sewage lines have peeled off the outer layers. 'This leads to collapse or settlement every year during the monsoon season,' the second NDMC official said, adding that some of the sections in these lines have already been rehabilitated.
'The first phase of rehabilitation of about 30km of sewage line and 10km under phase-2 has been completed and will be expanded to a much larger scale over the next five years,' the official said.
Under phase-3, NDMC has started the process of desilting and rehabilitating sewer lines by the structural liner method from Shanti Path to Satya Sadan Madhu Limaye Marg via Kautilya Marg and along Kushak Nallah.
