PRACHIN BURI: The Department of Highways has surveyed the damage done to the Thap Lan tunnels after the floodwater subsided.
Chalermpol Kumthong, section head of Kabin Buri highway, said the twin tunnels on Highway 304 connecting Khao Yai and Thap Lan national parks were flooded on Thursday after heavy rainfall over several days.
The tunnels and the section of Highway 304 connecting to them were closed to traffic in the morning but reopened on Thursday afternoon.
Mr Chalermpol's team surveyed the tunnels yesterday and found that about 90 of the 200 lightbulbs installed there were not functioning and needed to be changed. Some parts of a 5-kilometre fence were also damaged and needed to be repaired urgently due to safety precautions to prevent accidents to wildlife and vehicles.
He said the authorities are monitoring the situation because water was still flowing from the mountain yesterday, even though the water level at Thap Lan Reservoir had dropped by 10 centimetres since Thursday. Rainfall on the mountaintops presents a risk of the tunnels being flooded again.
Prawatsart Janthep, chief of Tab Lan National Park, said the tunnels were built on Highway 304, which runs parallel to a canal so the structure does not block the flow of water.
However, they became flooded because of the high levels of rainfall, leading to water overflowing from two nearby canals and flash floods from the mountains.
He pointed out that some parts of the highway fence were built with concrete, which likely blocked the water flow from the mountains to the canals. The national park will work with the Highways Department to redesign the fence, he added.
In addition, the canals must be dredged so they can store more water before it flows to the Prachin Buri River, said Mr Prawatsart.
The Khao Yai-Thap Lan tunnels were flooded and closed to traffic in November 2020 when a downpour saw water levels there rise to 1.5 metres.