The eastern zonal bench of the national green tribunal on Thursday directed the state pollution control board to measure the pollution level of Tolly's Nullah at various points and study the 57 pipelines pouring polluted water into the channel.

The bench also directed the Calcutta Municipal Corporation to remove all cattle sheds, piggeries and garbage from the banks of Tolly's Nullah, also called Adi Ganga, by October 3. Police have been asked to provide support in the project.

The bench passed the directives while hearing a petition by environment activist Subhas Datta on pollution in Tolly's Nullah. Datta referred to a recent report of the Central Pollution Control Board that says Tolly's Nullah contributes the maximum amount of polluted water to the Ganga barring the Pandu river in UP.

According to the report, Tolly's Nullah drains 380.2 million litres of sewage-mixed water to the Ganga daily.

Ganga pollution near the city is at a critical level because Circular Canal in Calcutta and Najerganj Khal in Howrah occupy the next two spots after Tolly's Nullah on the list, said a central pollution control board official.