An operation started in the wee hours of Sunday to rescue the four North Eastern Electric Power Corporation Ltd (Neepco) officials trapped in the basement turbine room of the Umrong reservoir since October 7, after the water level receded.

The pipeline, that carries water at 12,000 litres per second from the reservoir to Neepco’s Kopili hydropower project site, burst last week leading to massive flooding and created a water fountain that rose up to several hundred feet into the sky. The flooding damaged more than 90 per cent of the project machinery.

The water pressure in the pipeline had damaged the valves causing difficulties in reducing the flow. The intake gate connecting the pipeline was closed on Saturday night following which water pressure reduced.

“A rescue team of NDRF and SDRF are trying its best. We hope the officials will be rescued soon,” said Dima Hasao deputy commissioner Amitabh Rajkhowa on Sunday evening.

Earlier in the day, a high-powered government team, comprising hills area development minister Sum Ronghang, Karbi Anglong MLA Numal Momin, Dima Hasao legislator B.B. Hagjer and North Cachar Hills Autonomous Council members, including its chief executive member Debolal Gorlosa, visited the project site.

Neepco independent director Vijay Kumar Gupta said the disaster was caused owing to corroding of metal in the machinery because of acidity in the waters of the Kopili from coal mining in Meghalaya. He also said they had warned the Centre as well as the governments of Assam and Meghalaya on rising acidity but the authorities did not pay any heed.

The project has two dams and two reservoirs, one on the Kopili and the other on the Umrong stream (where the pipeline burst), a tributary of the Kopili.

Water from the Kopili reservoir is utilised at the Khandong power station through a 2,852 metres-long tunnel to generate 50MW power. The tail water from the Khandong powerhouse is led to the Umrong reservoir. The water from the Umrong reservoir is taken through a 5,473 metre tunnel to the Kopili power station to generate 200MW.

Locals blamed the Neepco for the accident and that there was no guarantee that the Khandong power station will not be affected.

Neepco general manager Debatosh Battacharjee said they are doing their best and repairs have been carried out whenever required.

Chief minister Sarbananda Sonowal on Friday ordered deputy inspector-general of police (southern range), P.K. Dutta, to conduct a probe into the incident.

Dimasa Students Union general secretary Pramith Sengyung said since it was a technical issue, an inquiry by an executive or judicial official will provide better results.