Had the siren been sounded in time calling for evacuation, people living within half a kilometre from the styrene tank in LG Polymers plant in Visakhapatnam, from which vapours leaked on May 7, would have had 30 minutes to escape and those living within one kilometre 40 minutes to escape, said Sagar Dhara, former United Nations Environment Programme engineering consultant, and Kalapala Babu Rao, Chief Scientist, Indian Institute of Chemical Technology, Hyderabad.
GVMC, PCB too blamed
Sharing with The Hindu the ‘Preliminary modelling of vapour release from LG Polymers, Visakhapatnam’, the experts said that along with the plant management, the Greater Visakhapatnam Municipal Corporation (GVMC) and the Andhra Pradesh Pollution Control Board (APPCB) should be blamed.
The study said, “Had the siren been sounded five minutes after the temperature rose to 65° Celsius, people staying at a distance of 0.5 km from the tank would have had 30 minutes to evacuate their homes without being caught in the toxic cloud and those staying at a distance of 1 km would have had 40 minutes for evacuation. Persons living in the orange zone – beyond 1 km from the tank – had an hour or more to evacuate. Thirty minutes is adequate time for evacuation. Yet, evacuation was not done until much later. This increased the number of deaths and injuries.”
“The Hazardous Chemicals Rules provisions and the APPCB consent for operation (CFO) order had information regarding the risk that LG Polymers plant posed to bystander population. Had the bystander population been trained in emergency evacuation procedures, and had the siren been sounded in time, deaths might have been avoided,” the study said.
“ALOHA, a screening model based on DEGADIS, was used to model the release of toxic vapours. The model provides reasonably accurate information on the expected vulnerable zones (areas that will be affected under various release conditions,” Mr. Dhara explained.
‘Explosive substance’
“Styrene is an explosive substance. Fortunately, the release happened in the night and, therefore, the vapour cloud did not meet a flame and explode,” Mr. Dhara said.
According to the models prepared, there are several hospitals, educational institutions, places of worship, railway stations and airport within the vulnerable zone.
While the ‘red zone’ in which the concentration of the vapour was 1,100 parts per million (ppm) extended up to 1 km, the ‘orange zone’, with projected concentration of 130 ppm, extended up to 2 km, and the ‘yellow zone’, with 20 ppm, extended up to 6.3 km in the direction the wind was blowing.
