Untreated sewage continues to pollute Sembakkam Lake

Sembakkam Lake, a historic freshwater wetland under the Tambaram Corporation, continues to be polluted by the illegal discharge of untreated sewage, raising serious environmental and public health concerns. Activists allege that the practice continues, despite repeated complaints and directions from the National Green Tribunal (NGT).

Despite the presence of an underground drainage (UGD) network in parts of the Pallavaram Zone, sewage is allegedly being pumped directly from manholes into stormwater channels leading to the lake. Activists blame poor implementation of the UGD system, which has resulted in frequent overflows in residential areas. “Instead of addressing the root cause, authorities illegally divert sewage into water channels as a quick-fix solution,” activists said.

The spread of Sembakkam Lake has already reduced to around 100 acres from its original 150 acres due to encroachments. In Thiru. Vi. Ka. Nagar, Chromepet, residents pointed to the construction of a pumping station adjacent to a graveyard. Even before its completion, sewage overflowing from the UGD network is being manually diverted, stored in a well, and later released into the Pachaimalai Canal, which drains into the lake.

“They use electric motors to divert sewage into the canal,” M. Ravi, secretary of the Sri Sarvamangala Nagar Residents’ Welfare Association, said. Repeated representations to the Tambaram Corporation, the Water Resources Department, elected representatives and the media had not yielded any results, he added.

The issue was taken to the NGT in 2017. Though the tribunal directed authorities to file an action taken report by October 2022, residents allege that the situation has not changed. A fresh petition was filed in 2024 and is still under litigation. Citing the ongoing case, a ₹10-crore allocation made by the Chennai Metropolitan Development Authority in 2023 for rejuvenation works has remained unutilised, residents said.

Residents said sewage from localities such as Vinobhaji Nagar and Thiru. Vi. Ka. Nagar, continues to be diverted into floodwater channels. Sewage-mixed water could be seen flowing into the lake in at least three locations.

The discharge of untreated sewage has also raised health concerns, with some residents reporting skin rashes due to possible groundwater contamination.

Activists demand that the sewage inflow be stopped immediately, the lake desilted, and further encroachments prevented. They also sought restoration of the stormwater channel in Thiru. Vi. Ka. Nagar and the creation of freshwater inlets to offset ecological damage.

Senior activist Santhanam urged the State government to prioritise restoration of Sembakkam Lake to prevent irreversible damage.