KATHMANDU, Sept 3: Rescue and cleanup operations have been intensified at the entrance of the cable duct tunnel of the Trishuli 3A Hydropower Project.
According to project engineer Shriram Neupane, more than two dozen large boulders blocking the exit area at the entrance of the 160-metre-long tunnel have been blasted and removed.
Neupane said two excavators have been operating regularly since Bhadra 13, clearing around 20,000 cubic metres of mud, sand, rocks, concrete slabs, beams, pillars and large boulders, some as large as houses, in five days. Breakers are being used when necessary, while controlled blasting is being carried out around the clock to break large rocks.
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So far, around 50 metres of the portal area, extending about 2.5 metres below the crown of the top face, has been cleared. Neupane said the removal of mud accumulated inside the tunnel will begin only after an access and drainage passage, approximately three metres deep, is completed in the 5.5-metre-high tunnel.
Initial observations show that the visible section of the tunnel, extending about one metre inward, is completely filled with mud. However, water is currently flowing out of the tunnel at around two litres per second without pressure, suggesting that water has not accumulated inside, Neupane said.
The outer section of the portal was found blocked by a gate slab, two large tree trunks and large boulders. Based on these findings, officials have preliminarily estimated that large rocks may not have entered the tunnel, apart from water and mud.
The actual condition inside the tunnel, however, has yet to be confirmed. Of the 160-metre-long tunnel, around 60 metres has bends, while the section toward the powerhouse has an upward gradient. Based on these features, officials have tentatively assessed that the inner section of the tunnel may have remained relatively safe and intact.
As the site has no road access and can only be reached by helicopter, transporting machinery and spare parts needed for equipment repairs is taking time. Despite the logistical challenges, all rescue and cleanup operations are continuing without interruption, engineer Neupane said.
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