Acidity in the reservoir waters of Assam’s first hydro-electric project Kopili has damaged underwater parts of the dam, prompting the State-run North Eastern Electric Power Corporation Ltd. (NEEPCO) to replace the parts.

The NEEPCO, which runs the dams, has begun an exercise to repair underwater parts of power houses of the 275 MW dam, located in North Cachar district.

“The exercise commenced in February and we are nearing completion. Work at the two power houses at Khandong and one at Kopili stage II is complete. Repairing and welding at the four other power houses (50 MW each) are being undertaken phase-wise,” a NEEPCO official told PTI.

Underwater parts of the turbine components and hydraulic structures have suffered wear and tear due to the acidity in the waters of the reservoir, he said, adding that most parts used in the dam were of ‘mild steel’

The NEEPCO has of late placed equipment orders with Bharat Heavy Electrical Limited (BHEL) which was expected to replace the older ones in the next two years.

While the repair work in each power house has cost around Rs. 1 crore, the fresh equipment orders - all of stainless steel material - are likely to cost Rs. 30 crore.

The project, first to be executed by NEEPCO, was commissioned in 1984. Since then, it has contributed around 20,000 million units of energy, supplying 12 per cent of its generation to Assam and Meghalaya in the form of free power, a NEEPCO spokesman said, adding that cost of power generation in the dam is less than Re 1 per unit.

The water in the reservoirs of the dam was first found to be acidic in 2006 and since then the acidity has been rising.

A study by Geological Survey of India (GSI) found that geological formations, human activity, effect of pollution were some of the possible causes of the acidity, NEEPCO says.