TNM details the findings submitted by the CPCB to the National Green Tribunal on Monday.

Remove all chemicals from Sterlites TN plant may impact environment CPCB recommends
news Sterlite Wednesday, August 22, 2018 - 11:49

Even as the National Green Tribunal (NGT) ordered a fresh probe into the closure of the Sterlite copper smelter on Monday, the Central Pollution Control Board (CPCB) submitted its findings from an on-site inspection of the plant on August 16 and 17.

The copper smelter in Thoothukudi district, Tamil Nadu, had been shut two days after 13 civilians were killed in police firing during a protest against the plant on May 22. The government agency also ordered a disconnection of power supply to the plant. In July this year, Vedanta moved the NGT, challenging the decision.

The inspection team was led by the Central Pollution Control Board. It comprised two officers of the CPCB’s Regional Directorate in Bengaluru — senior scientists HD Varalaxmi and Dr BS Anupama. M Manoharan and PS Livingstone of the Tamil Nadu Pollution Control Board's Zonal and District Environmental Engineering Office were also part of the inspecting team. Pradeep Nair, General Manager (Engineering Service) was also present on behalf of Vedanta.


On August 9, when Sterlite was given permission to carry out administrative works in its Thoothukudi plant, Sterlite's counsel had told NGT that the copper slag— a by-product of copper extraction by smelting— dumped along the Uppar river had been secured by a wall and there was no chance of slag reaching the river.

Thus, the primary objective of the inspecting team was to submit a report on 'how the material lying there is to be disposed of or maintained.'

The report noted that the inspection team was escorted by authorised officers of the Tamil Nadu government.

Status of materials stored at the plant

While the team noted that some of the stored chemicals had been removed from the premises as per the orders of the High Power Committed formed by the Tamil Nadu government, it also recorded findings on materials that had not been cleared, following the discovery of an acid leak at the plant on June 18.

According to the report which TNM has accessed, the storage tanks for acids— sulphuric, phosphoric, and hydrofluorosilicic— had been cleared of all the active material; however, residual acids which cannot be removed with suction pumps remains at the bottom of the tank.

Where did the leak come from? While Sterlite had contended at the NGT that the 'storing of the hazardous waste was on account of the unit being closed', the condition at one emptied sulphuric acid storage tank indicated to the inspectors that acid had leaked from that tank and collected between the tank and peripheral dyke wall.

The contaminated soil adjacent to the tank had been lifted and transferred to a secured landfill within the premises, states the report.

The CPCB had also argued in court that based on its findings, the corrosive nature of the acids remaining in dead storage at the plant pose a threat to the surrounding areas, especially in the absence of regular maintenance.

While inflammable fuels/ solvents had been partially removed and tanks containing LPG and isopropanol cleared, about 806 metric tonne of diesel oils and furnace oil were still lying at the premises.

In a significant observation, the report warns of a risk of fire due to storage of highly flammable materials with no mechanical fire fighting systems in place. “No fire fighting system is active near fuel storage tanks due to disconnection of power supply,” says the report.

Further, the report states, "Large quantity (90,000 MT) of copper concentrate, having 30% sulphur and 4- 6 % moisture, found unsafe to the plant as well as to environment. Electrolyte solution (copper sulphate) having pH of less than 2 lying within cell house without safety precautions, which may also cause threat to environment if not attended for long. Timber coolant, which is required to be maintained in wet condition, was found damaged due to absence of maintenance and same may cause fire hazard in the vicinity. Acidic water (leachate having pH less than 2) stored in gypsum pond, if not maintained and monitored on regular basis may cause threat to environment due to its characteristic, large volume and absence of proper maintenance/ treatment.”

Even as the southwest monsoon has caused significant floods in many districts of Tamil Nadu, the report observes, “Storage of copper slag and gypsum in open without any monitoring and control may cause impact on surrounding area due to strong wind or rains during monsoon period.”


Following their inspection of the plant, the CPCB team recommended a fire-fighting system be put in place at the plant, in addition to the evacuation of all electrolyte material stored at the plant's cell house.

The CPCB report states, “In case the plant is not going to operate in near future, it is required to remove all raw chemicals, intermediates material by-products and waste material from the plants premises as it may cause environmental impacts.”

Additionally, the team recommended that the entire acidic effluent stored in the gypsum pond be treated and 'disposed after treating it to allowable discharge limit.'

Observations on copper slag

The Tamil Nadu Pollution Control Board (TNPCB) had revealed in May this year that one of the reasons that it refused to renew Sterlite's Consent to Operate (CTO) was the plant's dumping of copper slag along the Uppar river, thereby obstructing the flow of the river. This had allegedly caused flooding in residential areas nearby.

The CPCB report further acknowledges, "Some copper slag had washed out into river during monsoon, therefore, TNPCB asked the Unit (M/s Vedanta Ltd) to construct a barrier between the River and copper slag landfill area to allow free flow in the River."

Observing that there was no flow in the river and that the landfill site was found to be levelled with a barrier wall constructed on two sides along the river, the CPCB report also said that the landfill area was covered by soil.

“It is recommended that barrier wall may be extended on all sides to eliminate any possibility of wash out of the slag during rains until its utilisation," the report concluded.

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