A tunnel leak beneath Bangkok’s Khlong San district has forced City Hall into round the clock damage control, with more than 140 residents affected and a key road shut for repairs.
The trouble began on Wednesday night, July 8, when heavy rain triggered water seepage inside a section of tunnel being built for the Southern Purple Line MRT extension near Wong Wian Yai station. City Hall moved quickly, evacuating people from buildings close to the site and shutting the surrounding road.
By Saturday, July 11, Governor Chadchart Sittipunt was on the ground himself, touring the site in Khlong San alongside civil engineering expert Thanes Weerasiri to check on stabilisation efforts. It was one of his first public appearances since starting his second term as governor this week.
One of his first calls was to pull down the pedestrian bridge running over the construction site, after engineers spotted subsidence at its midpoint. Clearing the bridge makes way for four grouting machines, which will pump cement based material into the ground to shore up the soil beneath the tunnel.
Crews have already started drilling to 37 metres, well below the tunnel’s own base level of 31 metres, aiming to reinforce the ground, block further water ingress and keep the area stable while work continues.
According to Thanes, monitoring instruments set up in partnership with Kasetsart University have picked up no significant movement in surrounding buildings so far. Tiltmeters are tracking any structural leaning, while inclinometers measure horizontal and vertical shifts in the ground, with the data streamed wirelessly to the BMA’s control centre so officials can watch the site continuously. Groundwater levels held steady overnight despite further rain.
Thanes was keen to draw a distinction between this incident and last year’s sinkhole at Vajira Hospital. Unlike that case, there is no opening at the surface here, meaning the water appears to be seeping in from underground rather than draining down from above. Even so, engineers have noted minor cracking on the road surface and are keeping a close watch.
The human cost so far: 141 residents across two nearby apartment blocks have been affected, with 52 moved out temporarily and 34 opting to stay put. Chadchart said the BMA has opened a complaint centre in the area to keep residents informed and address concerns directly.
For drivers, Prajadhipok Road remains closed between the King Taksin the Great Monument and the Yaek Baan Kaek intersection. Chadchart is advising motorists to detour via Issaraphap, Lat Ya or Somdet Chao Phraya roads until work wraps up.
The wider Purple Line extension project has been divided into six construction contracts, awarded across five major Thai firms. The 3.1-kilometre underground stretch running beneath the Chao Phraya River, where the current issue lies, is being built by a joint venture between Italian-Thai Development and Nawarat Patanakarn, reported Bangkok Post.
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