The mining of legacy waste at Dhapa has stopped for over a year — indefinitely delaying the creation of Calcutta’s first engineered landfill site.

The engineered landfill is supposed to prevent the release of leachate rich in heavy metals into surrounding water bodies and agricultural fields that are sources of fish and vegetables to the city’s markets.

Tonnes of fresh waste have piled up in the 13 months since the mining stopped at Dhapa, but the Kolkata Municipal Corporation (KMC) is yet to resume the legacy waste mining, said a civic official.

Legacy waste is accumulated over a period of several decades, said an expert.

The pile up of solid waste on already towering hillocks of waste is increasing risks of subsidence, similar to what happened in Howrah in March, said a KMC official.

On March 21, the Belgachia waste disposal ground suffered a major disaster. Roads cracked and nearly 100 homes collapsed after decades of unregulated, unscientific garbage piling caused severe land subsidence across the 100-acre site.

The solid waste might spill over a large land area in the event of a subsidence that could include neighbouring agricultural fields and water bodies.

Experts said air pollution triggered by natural burning of the solid waste because of the presence of methane and release of leachate into the underground water had been happening ever since Dhapa was chosen as a waste dumping site.

The biomining of legacy waste raised the hopes of an end to the air pollution and contamination of toxic waste leachate with the soil and water.

“The mining of 40 lakh tonnes of solid waste began in June 2021 with a three-year deadline, but the contractor managed to complete only 37 per cent of the work by July 2024 when the work stopped. We terminated the contract and are looking for a fresh company to do the job,” said a KMC official.

The contractor has moved Calcutta High Court challenging KMC’s decision but the court is yet to issue any stay order on the civic body to engage a fresh firm to resume the work, said the official.

The KMC, however, has yet to float tender to look for one.

“In the last one year, lakhs of tonnes of waste have piled up in Dhapa, while no legacy waste is being cleared,” admitted a KMC official.

Calcutta produces about 4,500 tonnes of waste every day and only a minority portion of it is processed for use in the recycling industry. The rest is still sent to the dump site.

To make the matter worse, Dhapa dump site is also used to dump the solid waste from the municipal areas under Bidhannagar, Panihati and New Town.

The waste dumping ground at Dhapa is spread across more than 36 hectares of land. About 12.14 hectares of it has been capped with grass cover and waste is no longed dumped at this section.

The remaining 24 hectares area is a live dumpsite. The legacy waste mining was underway in this portion and fresh waste is dumped here.

“Any solid waste will release leachate that is rich in heavy metals. The leachate will get mixed with the soil and water in the surrounding land and water bodies. There is a high possibility that vegetables and fish cultivated there will have a higher heavy metals presence,” said an expert working in the solid waste management division of a
research and advocacy organisation.