With eight workers trapped in the SLBC tunnel, officials consider drilling from the top or side despite major logistical challenges.
Hyderabad: Desperate times call for desperate measures. One such measure that the government is talking about, if not considering as a serious option, is digging a parallel tunnel, or a hole from the top, to reach the spot inside the SLBC tunnel where eight workers are trapped.
With fears over their well-being rising by the hour, after the accident on Saturday morning, irrigation minister N. Uttam Kumar Reddy on Tuesday told reporters in Domalapenta, where the tunnel inlet site is, that Chief Minister A. Revanth Reddy had called for exploring the possibility of either digging from the side, or from the top, to reach the accident spot, which is 13.9 km inside the tunnel.
“The CM was particular about exploring this option. We have asked the Geological Survey of India to study the area. Experts from NGRI will also be coming tomorrow (Wednesday). But locating access points may be difficult. We will pursue this as an option while ensuring safety precautions,” Uttam Kumar Reddy said. “We are constantly evaluating every possible method to reach the trapped workers. Their safety is our priority," he said.
Any decision to exercise the option of additional drilling either from the side or the top is fraught with its own set of challenges. The nearest access from the road – National Highway 756 that runs through the Nallamala hills of the Amrabad tiger reserve under which the tunnel is being dug – is around 20 km as the crow flies. The terrain is extremely undulating and there is no road access to the 13.9-km point overground above the tunnel to transport any equipment to begin drilling a hole.
Additionally, the tunnel, according to irrigation department officials, lies between 400 and 450 metres below the surface. This means any drilling operation would be equipment- and time-intensive, in addition to the time taken to reach the spot through the forest area that is currently without any road.
Irrigation department officials, soon after the collapse in the tunnel on Saturday, had said that on the surface, the spot has a fairly large seasonal stream, and suggested the possibility that this could have led to a copious ground water table developing in the area.
It may be recalled when tunnel collapsed, huge amounts of water, accompanied by large volumes of silt rushed inside. On day four after the collapse, the rate of flow of water into the tunnel was up to 5,000 litres a minute according to the irrigation minister.
Incidentally, the Mallela Theertham water fall, another seasonal source of water, lies just around 7 km from the overground spot of the collapsed tunnel location, possibly contributing to the groundwater table in the area.
Even if urgent permissions are given by the Centre for drilling from the top, since the spot happens to be in the heart of the core area of the tiger reserve, “it will be an impossible task to take up. The entire area is extremely undulating and even by foot it is a pretty hard trek. One can only imagine the logistical nightmare that will unfold if a big drilling operation is needed, whether from the top, or from the side of the tunnel,” a forest department official from the tiger reserve said.
