Gas leaks on highways: How to respond and what the Mumbai-Pune Expressway incident shows

What is the first step taken in such situations?

Standard practice around the world dictates that the area around the leak is isolated. While the extent of this area depends on the amount of gas leaking into the air, a minimum radius of 50 metres is recommended. At points after the incident, the lower explosive limit (LEL) was in the dangerous territory at a distance of 500 metres too.

When asked, Maharashtra State Road Development Corporation (MSRDC) officials said “incident management” of a varying range falls under the responsibility of the contractor responsible for the road, in this case, IRB Mp Expressway Pvt Ltd.

A spokesperson for the company said, “The company has a robust Emergency Response Protocol (ERP) and a well-trained, skilled team already in place, well equipped with required machinery and systems to handle such situations. In fact, the IRB team, after analysing the situation and understanding the gravity of the issue, prompted immediate action of halting traffic on safe distance from the accident spot with the help of police authorities as a first and most important safety response.”

In line with this, traffic was halted on both parts of the carriageway initially.

What is the next step?

Once the severity of the leak and the presence of the gas in the air are ascertained, attempts to contain this sphere of influence—with water sprays, for instance—are the next step. In the case of propylene, a water spray could help contain the leak.

While IRB arranged for necessary mechanical resources, like heavy-duty cranes, ambulances and quick response vehicles (QRV) loaded with equipment like gas cutters, compressors, pumps, etc., fire tenders arrived at the spot. However, to put any of the above into use safely, the chemical expert team had to arrive. It reached the spot at 8.30 pm. The QRV, which would typically be helpful in an LPG tanker incident, was not up to the task of dealing with propylene. Coordination continued on the phone.

What should happen next as per global protocols?

Once preliminary safety measures are in place, the next step is arresting the source of the leak. This can be done by fixing the points of the leak, emptying the tanker of the gas, or even burning the gas off in a controlled manner if possible. Moving the tanker out of the way, ensuring safe passage and allowing traffic to move again are the final steps.

In the Mumbai-Pune Expressway incident, experts and the National Disaster Management Force (NDRF), who reached the site at 11.30 pm on Tuesday, soon realised that the damage to all the valves could not be stopped at the spot.

Simultaneously, authorities reached out to various companies that manufacture and handle chemicals, from BPCL, which had supplied the propylene to the tanker in question, to HPCL, Reliance Industries, Deepak Chemicals and Fertilizers, etc. This chain reached Mec Elec Industrial Services, 10km away, a company specialising in testing and certifying tankers carrying hazardous chemicals, which came to the rescue by 8.30 pm.

“The team was able to fix two of the three leaks on Tuesday night, but the third leak proved difficult, as the liquid gas continued to flow out from it,” said Madhav Divekar, Managing Director, Mec Elec Industrial Services. “Attempts continued on Wednesday, but it was then decided to decant the gas into a different tanker, till the quantity in the tanker reduced for us to attempt fixing the valve again.”

Decanting operations continued till the damaged valve was only emitting vapour, indicating that gas levels were at 50 per cent. With caution and cranes, the tanker was lifted and put in an upright position, where the third valve damage was attended to.

Safe to move, another decanting operation to empty the contents of the tanker was carried out a distance away, after which the tanker was taken to Mec Elec’s tanker testing facility in Thane.

Was traffic allowed immediately?

Traffic was only allowed on the Mumbai carriage after a gap of 30 minutes, allowing for the gas to disperse sufficiently due to the proximity of a tunnel. Propylene is heavier than air, and hence, the dispersal is not immediate.