CHENNAI: Around 126 million litres/day (MLD) of sewage generated in north Chennai is not reaching Metro Water’s treatment plants, raising questions over whether a huge quantity of untreated sewage is being discharged into the city’s waterbodies every day. These figures were disclosed recently by the Chennai Metropolitan Water Supply and Sewerage Board (Metro Water) to the National Green Tribunal (NGT).
The Metro Water informed the NGT that damaged underground pipelines are preventing the sewage from reaching the treatment facilities.
In a status report, Metro Water said a joint inspection with the Tamil Nadu Pollution Control Board (TNPCB) on October 22 found damaged pumping mains in Tondiarpet, Purasawalkam, Thiru Vi Ka Nagar and Kolathur. The team found sewage leaking into drains and canals at some locations which would eventually find its way to the city’s waterbodies. The report said 830 MLD of sewage was pumped from stations within Metro Water’s jurisdiction, but only 704 MLD reached treatment plants, leaving a conveyance deficit of 126 MLD.
The largest shortfall, 70 MLD, was traced to the 900 mm and 1,000 mm pipelines connecting Purasawalkam pumping station to the Kodungaiyur Sewage Treatment Plant (STP). The inspection near Kannigapuram playground along Otteri Nalla found that the pipelines were damaged during construction of the Ganesapuram subway road overbridge by the Greater Chennai Corporation. Weakened joints caused leakages. Realignment works are under way and are scheduled for completion by April 30, 2027, the report said.
In Tondiarpet, officials found that a 30-year-old, 1,200 mm pipeline connecting New ‘F’ pumping station to Kodungaiyur had deteriorated, causing sewage seepage into drains and canals during peak pumping. Metro Water is laying an alternative 6.8-km, 1,000 mm pipeline at a cost of Rs 70.45 crore. The work is 90% complete.
Damage near Jamalia Nagar and Retteri junction had been rectified, and the inspection found no leakages at either location.
The report was filed in the NGT’s suo motu proceedings based on a September 7 report in TNIE titled Rs 7.5 cr litres of wastewater from Chennai suburbs let into open drains daily’.
The tribunal had directed the TNPCB, Metro Water and Tamil Nadu Water Supply and Drainage Board to conduct joint inspections and submit a coordinated report.