Water leaks into under-construction Bangkok subway tunnel

MRTA says leakage under control, crews monitoring safety of buildings at site in Thon Buri

PUBLISHED : 9 Jul 2026 at 11:33

Water has leaked into the Purple Line subway tunnel under construction beneath the Wong Wian Yai intersection in Klong San district of Bangkok, where crews are working to ensure the safety of adjacent buildings.

The Metropolitan Rapid Transit Authority (MRTA) said on Thursday that the leak into the tunnel 30 metres underground happened on Wednesday at the joint of a sump pit, which is a part of the Tao Poon-Rat Burana section of the Purple Line extension project.

“The contractor is carrying out ground improvement to stop water leakage. … At present, water leakage is under control, so there is no impact on any subsidence of adjacent roads and buildings,” the MRTA said.

The state enterprise ordered its contractor and construction supervision consultant to closely monitor the conditions of nearby buildings.

The civil works for the Purple Line extension have been split into six different contracts, with the MRTA awarding them to five major Thai construction companies.

Italian-Thai Development Plc and Nawarat Patanakarn Plc formed a joint venture to build the 3.1-kilometre underground section passing beneath the Chao Phraya River.

Prime Minister Anutin Charnvirakul as well as the minister and deputy ministers of transport arrived at the scene at 11pm on Wednesday. Mr Anutin ordered the MRTA to intensify safety measures for local buildings and prepare for any emergency incidents.

Mr Anutin said the degree of water leakage was under control, so the situation was different from the huge sinkhole incident on Sam Sen Road in Dusit district last year.

A video from the MRTA showed a Purple Line tunnel partly flooded, with neck-deep water levels in some sections.