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What is rat mining? How a banned practice turned the tide of Uttarkashi tunnel rescue operations

Uttarkashi tunnel collapse: After an ordeal of seventeen days, pipes have been laid in the final stretch of the collapsed Silkyara tunnel for the 41 trapped workers to be rescued. Ambulances, garlands, hospital beds, have been readied for the trapped workers, for when they are brought out. 

Rescue workers on Tuesday drilled through the 60-metre stretch of rubble of the collapsed Silkyara tunnel. National Disaster Response Force (NDRF) personnel were expected to enter the steel chute pushed into the drilled passage over the past several days and then bring out the workers one-by-one.

Going by the practised drill, each worker will lie down on a wheeled stretcher that would be pulled by rescue workers outside using ropes. This was expected to take about two or three hours.

After several delays owing to the breaking down of the auger machine from US, the last leg of the rescue mission was completed by ‘rat miners’, who succesfully completed the drilling process, removing all debris for the pipelines to be laid and the trapped workers to leave the collapsed tunnel. 

What is rat mining?

Rat-hole mining is a method of manual drilling, which is carried out by skilled workers, most common in Meghalaya. Narrow pits are dug into the ground, usually just wide enough for one person to fit into.

The term “rat hole” refers to the narrow pits dug into the ground, typically just large enough for one person to descend and extract coal.

After digging the pits, the miner drops down into the holes using a rope and bamboo ladders. This method is usually used to extract coals, and is considered extremely hazardous. It is illegal in many countries due to increasing cases of miners dying from asphyxiation, lack of oxygen and hunger.

There is one another type of rat mining. In this, a rectangular opening is made, varying from 10 to 100 sqm, and through that a vertical pit is dug, 100 to 400 feet deep. Once the coal seam is found, rat-hole-sized tunnels are dug horizontally through which workers can extract the coal.

Why is rat-mining banned?

This rat-mining method has faced severe criticism due to its hazardous working conditions, environmental damage, and numerous accidents leading to injuries and fatalities.

Experts have opined that the mines are typically unregulated, lacking safety measures such as proper ventilation, structural support, or safety gear for the workers, thereby creating a rather harmful environment for the rat-miners. 

Additionally, the mining process can cause land degradation, deforestation, and water pollution.

The National Green Tribunal (NGT) banned the practice in 2014, and retained the ban in 2015. The NGT observed, “It is also informed that there are umpteen number of cases where by virtue of rat-hole mining, during the rainy season, water flooded into the mining areas resulting in death of many… individuals including employees/workers.”

Other methods used to rescue the trapped workers in Silkyara tunnel

Vertical drilling:  Vertical drilling is done through a boring machine, digging straight down from the ground using electrical tools and equipment. In the case of the Uttarakhand tunnel collapse, a vertical drill had been boring into the ground and an 800-mm pipe has been inserted to bring out the trapped workers.

Auger mining (horizontal drilling): A horizontal auger machine or a directional drill is a specialised tool designed to drill horizontal bores or create underground tunnels without disturbing the ground. These machines are used to lay down water and gas pipes, and to dig a tunnel.

However, the auger machine in the case of the Uttarakhand tunnel collapse failed to free the trapped workers as it hit metal obstructions and eventually broke down, beyond repair.

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Updated: 28 Nov 2023, 04:35 PM IST

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