Late on the night of December 26, 2023, an ammonia gas leak occurred from an underwater supply pipeline near Periyakuppam in Ennore. This alarming incident prompted hundreds of residents to quickly evacuate onto the streets, reporting issues such as difficulty breathing and irritation of the eyes and face.
How did the gas leak occur?
Coromandel International Limited, a fertiliser manufacturing facility in Ennore, regularly receives shipments of ammonia ranging from 3,000 to 8,000 tonnes monthly. The ammonia arrives in liquid form at an ultra-low temperature of -33°C and is stored in a designated storage tank under the same conditions.
An eight-inch flexible high-density polyethene pipeline, spanning a length of 2.5 km and laid beneath the seabed, is employed to facilitate the transfer. Under normal circumstances, the channels are maintained at a 2 kg/cm2 vapour pressure when no ammonia transfer is in progress.
A critical aspect of the operational procedure involves a pre-cooling process conducted approximately 36 hours before the actual transfer from the ships. This process is essential to prepare the pipeline for the seamless pumping of ammonia in its liquid state.
While undergoing pre-cooling procedures late on the evening of December 26, 2023, the Coromandel unit detected a decline in pressure within the pipeline. Additionally, they observed the release of gas bubbles approximately 2 feet from the shore.
Around 11 PM, locals near the pipeline route noticed a strong, pungent odour. Residents of Periyakuppam, Chinnakuppam, Netaji Nagar, and Burma Nagar reported experiencing persistent odours and eye irritation, which continued for several hours.
As per the Tamil Nadu Pollution Control Board, the unit noted a pressure drop at approximately 11:45 PM and promptly initiated depressurisation of the pipeline. This was achieved by diverting the ammonia vapour to the flare and completing the operation within 20 minutes.
In response to the incident, numerous families from the Periyakuppam fishing hamlet immediately evacuated temples, community halls, and public schools 8 to 10 kilometres away from their area. These evacuations commenced around midnight.
Officials from the Tamil Nadu Pollution Control Board and the Joint Director of the Directorate of Industrial Safety and Health (DISH) reached the site by 2:15 AM. They conducted monitoring activities to assess the ammonia levels in the ambient air at various locations.
Alarming Ammonia Levels
The Tamil Nadu Pollution Control Board (TNPCB) conducted an inspection approximately three hours after the ammonia leak, around 3:30 AM. At that time, the ammonia level in the air was recorded at 3 ppm, translating to 2090 micrograms/m3. This is significantly higher than 400 micrograms/m3 on a 24-hour average.
In addition to the air quality concerns, an assessment of the seawater sample at the point of pipeline leakage at 3:49 AM revealed an ammonia level of 49 mg/litre. This concentration is ten times higher than the 5 mg/litre marine discharge standard.
Why is this dangerous?
Exposure to elevated levels of ammonia can result in irritation and burning sensations on the skin, mouth, throat, lungs, and eyes. The severity of these effects tends to increase with the concentration and duration of exposure. In cases of very high ammonia levels, there is a potential for severe lung damage or even fatalities.
As per the guidelines, the short-term exposure limit for ammonia, which represents the concentration at which exposure for longer than 15 minutes may pose a potential danger, is set at 35 ppm. However, the concentration at which the gas becomes immediately harmful to life or health is significantly higher, at 300 ppm.
Considering that locals in Ennore were exposed to elevated levels of ammonia for four hours, it raises concerns about potential health risks. These levels may surpass the estimates provided by the Tamil Nadu Pollution Control Board (TNPCB).
Coromandel International Limited Shuts Down Temporarily
Following a gas leak from the fertiliser manufacturing facility, the Tamil Nadu government has taken decisive action, temporarily shutting down Coromandel International Limited in Ennore. Siva V. Meyyanathan, the Minister of Environment and Climate Change, confirmed the government’s directive for the facility’s temporary closure until further notice.
Coromandel International Limited released a statement explaining that the cancellation of the next shipment unloading at their multi-buoy mooring system in the terminal results from abnormalities detected in the liquid ammonia delivery pipeline.
The facility will resume operations only after addressing and rectifying these abnormalities to the satisfaction and certification of the relevant authorities. During this period, Ennore minor port operations will be temporarily suspended.
The company suspended operations after detecting an issue at 11:30 PM on December 26 in the ammonia unloading subsea pipeline near the shoreside. The company assured that operations would resume only after rectifying these abnormalities to the satisfaction and certification of the relevant authorities.
