Sambalpur, May 16: Hirakud Dam Project authorities have begun drilling earth at a new location for soil testing for the proposed additional spillway on the left dyke of the dam.

Earlier, the authorities had drilled the surface twice near Gandhi Minar for the proposed spillway. “However, the Geological Survey of India (GSI) did not find the rock beneath the soil at the site suitable to construct the spillway. Subsequently, we identified a new location, 700 metres from the previous one, on the upstream of the Hirakud reservoir, for the purpose. We have already drilled at four spots in the new location. We will drill at four more places,” said executive engineer of the project Joshobanta Parida.

He also said a GSI team would visit the new location shortly for soil testing and prepare a report on its features. “The report will be submitted to Aegis, the World Bank’s consultant for the construction of the proposed spillway,” he said.

Parida said: “The GSI will prepare the spillway’s design after the report is received.” He also said the World Bank had agreed to provide Rs 350 crore for the additional spillway under the Dam Rehabilitation and Improvement Project (Drip).

According to Parida, the additional spillway had been proposed to enhance the dam’s floodwater discharge capacity to around 24 lakh cusecs. At present, the dam has 98 gates — 64 sluice gates and 34 crest gates — through which it releases floodwater. The gates have a capacity to release 15 lakh cusecs of water at a time.

The additional spillway was proposed after the Central Water Commission had revised the floodwater release capacity of all major dams. It recommended raising the capacity to 1.5 times of the current capacity for all dams.

A spillway provides controlled release of flows from a dam or levee into a downstream area. In April last year, a 12-member team of the World Bank, Central Water Commission and the dam safety department had visited the site to conduct a survey on the possibility of an additional spillway.