Tolly’s Nullah has turned into a sewage canal, devoid of living organisms, a state pollution control board report has pointed out.

According to the report, based on water samples collected in February, the Bansdroni stretch is the most polluted, followed by stretches near Shahid Khudiram Metro station, Karunamoyee and Kudghat.

The BOD (biochemical oxygen demand), a parameter of wastewater and sewage pollution, at Bansdroni was found to be 40mg per litre at low tide. The limit is 3mg. The amount of dissolved oxygen along all stretches was nil.

“PCB data shows the poor state of Tolly’s Nullah despite huge sums being spent on its restoration. I will raise the issue with the National Green Tribunal,” environmental activist Subhas Datta said.