CHENNAI: The Tamil Nadu Pollution Control Board (TNPCB) has informed the southern bench of the National Green Tribunal (NGT) that groundwater sources around the Vellalore dump yard in Coimbatore have been contaminated due to leachate (contaminated water from solid waste) percolation from the accumulated legacy waste.
In a report filed before the Tribunal, the Board said water samples collected from open wells in residential areas did not conform to standards with respect to total dissolved solids (TDS), chlorides and total hardness. Biological oxygen demand (BOD) and chemical oxygen demand (COD) were also detected in the samples, confirming possible contamination. These open wells are located at distances of 790 metres and 450 metres from the centre of the dumpsite.
Similarly, borewell samples from nearby habitations recorded exceeding levels of TDS, chlorides, total hardness and iron. BOD levels ranged between 2 and 26 mg/L, while COD levels were between 8 and 152 mg/L, indicating leachate infiltration.
During an inspection, the TNPCB officials also found that leachate from legacy waste had formed a stagnant pool near the Leachate Treatment Plant (LTP), with no treatment being carried out, allowing the contaminants to seep into the groundwater. At present, around 9,29,109 cubic metres of legacy waste has been accumulated in three different locations at the Vellalore dumpsite.
The report further revealed that the ambient air quality in the area has deteriorated. Particulate matter (PM10) concentrations at two spots were recorded at 163 and 128 micrograms per cubic metre, both higher than the permissible limit of 100 micrograms.
Based on these findings, the TNPCB has recommended that the civic body achieve 100 per cent segregation of waste at source and ensure treatment of unsegregated waste stored in the windrow composting area within three months to prevent it from turning into another dumpsite. It also urged the authorities to upgrade and expand the capacity of the Leachate Treatment Plant to ensure full treatment of leachate generated both from the landfill and the legacy waste, to prevent further groundwater pollution.