The CMDA has started the process of hiring a consultant who will prepare a report on the possible impact of a proposed flyover on the ecologically fragile East Calcutta Wetlands.

A tender inviting applications from agencies interested in preparing the environment impact assessment (EIA) report was floated recently, said a CMDA official.

The state government is planning to build a flyover connecting EM Bypass and New Town’s Biswa Bangla Gate, whose pillars will come up on the banks of the wetlands.

“The flyover’s initial alignment, prepared in 2018, had to be cancelled following an order from the Union environment ministry,” said an engineer of the CMDA who is involved in the planning of the flyover.

Originally, the flyover was to pass over the core area of the wetlands. “According to the new alignment, prepared on the basis of the recommendation of the Union ministry, the piers of the flyovers will come up on the banks of the wetlands,” the engineers.

The East Calcutta Wetlands, protected under the Ramsar convention, is regarded as the city’s kidneys because of their role in the natural recycling of effluents.

Once the EIA report is ready, the CMDA will send it to the ministry, through the state government, for approval. Since India is a signatory to the Ramsar convention, any proposed construction over a Ramsar site in the country has to be approved by the environment ministry.

The website of the Centre for Science and Environment says an EIA “examines both beneficial and adverse consequences of the project and ensures that these effects are taken into account during project design.”

The EIA, it says, “helps to identify possible environmental effects of the proposed project, proposes measures to mitigate adverse effects and predicts whether there will be significant adverse environmental effects, even after the mitigation is implemented”.

The proposed flyover will be 7.1-km long and its civil construction is estimated to cost Rs 600 crore.

Bonani Kakkar, an environmental activist who had gone to court against the previous alignment of the flyover, said: “The authorities must understand that a flyover will... have bright lights. The wetlands are also a habitat for thousands of birds. Bright lights cause difficulties for birds and they may shy away from the area. That is one reason why games under floodlights were stopped at the Rabindra Sarobar stadium.”