Report on collapse of fly ash pond constructed by Reliance M/s Sasan Ultra Thermal Power Plant in Singrauli, Madhya Pradesh, 28/07/2020
Action taken report of the Committee submitted in reference to National Green Tribunal (NGT) order of June 29, 2020.
The matter related to the collapse of fly ash pond constructed by Reliance M/s Sasan Ultra Thermal Power Plant in Singrauli, Madhya Pradesh on April 10, 2020. The report was filed on July 28, 2020.
The incident had led to flooding of the toxic ash slurry located in adjoining Harrhava village and washed away six persons living in the adjoining villages. It not only led to loss of human and animal lives but also caused severe damages to vegetation, biodiversity, fertile agricultural land and polluting the nearby rivulets like Goiwahai.
The probable cause of the incident:
The industry was disposing its fly ash in 'Island 4 or C5 area' since March 2019. As reported by plant official, the incidence of fly ash pond's retaining wall breach happended on April 10 in the low lying area called Island 4 or Compartment 5 (C5) inside the plant premise. One poclain machine was on job of leveling soil on the top of the retaining wall; on moving back the machine, the machine lost its balance and slipped down towards the outer slope of the retaining wall. In order to prevent the slippage, the machine operator tried to anchor the bucket on the top soil of the retaining wall. However due to its own weight, the machine pulled down a big chunk of soil from the bund.
During the process, the operator damaged the wall significantly which initiated the break of the retaining wall. And this resulted in huge quantum of fly ash with water gushing out through the breached wall in about 25 meters width.
On the day of site visit by the committee, continuous lean flow of water was observed in the low lying area. During discussion, it was informed that a study was awarded to IIT-BHU to study the reason of breach in the embankment of ash disposal site.
The report submitted by Prof Arun Prasad of IIT-BHU after his site visit on June 13, 2020 said that the failure of embankment was definitely initiated by slippage of poclain. However the subsequent extent of damage of the bund was due to severe hydrostatic pressure on the upstream of the embankment. Through this damaged portion, dilute slurry started flowing leading to complete cutting of the retention wall. Accumulation of huge underground water had resulted into heavy flow of ash slurry causing serious consequences in the villages. The reported hydrosstatic pressure probably developed due to the newly constructed check dam on a stream around May/June 2019.
Nature of damage:
The flow of slurry was so forceful, that it not only demolished the boundary wall as well as the adjacent private property but also flowed through the Goiwahai drain. It damaged the ash water recirculation pipeline of the indusry and submerged the agricultural lands and summer season crops. The slurry travelled a path of about 6.5 kms in length.
The committee was of the opinion that an appropriate direction needs to be issued to expedite the cleaning work so as to avoid further flow of ash towards Rihand reservoir. Significant quantities of fly ash between 1.5 to 2 laksh tons was seen spead on the banks of Goiwahai drain over a stretch of 6.5 km till its confluence with the Rihand river.