Rama II Sinkhole Cuts Water to 85,000 Homes, Snarls Traffic in Samut Sakhon

The early hours of Sunday saw a dramatic sinkhole open up on Rama II’s inbound parallel roadway in Samut Sakhon, swallowing a pickup truck’s front wheel and cutting off water to thousands of homes. Authorities have traced the collapse to a ruptured municipal transmission main laid as part of the ongoing M82 elevated motorway work.

Key Insights

• Time & Location: Around 06:00, km 29+350 on Rama II’s service lane, Tambon Tha Chin, Muang District

• Casualties: The lone pickup driver emerged unharmed with only minor shock

• Water Cut: Samut Sakhon Municipal Waterworks shut off supply across its entire network

• Traffic Impact: Parallel lane closed, backups spilling onto the main carriageway

• Repair Strategy: Emergency backfill, compaction, asphalt overlay to reopen one lane by tonight and both lanes by Monday

Morning Mayhem on a Vital Artery

Rama II Road serves as a lifeline linking Samut Sakhon’s seafood hubs with Bangkok’s markets. When a section of its inbound frontage road gave way before dawn, commuters found themselves staring down a gaping hole. At the precise kilometre marker 29+350, the tarmac dropped into a cavity formed by escaping water, leaving only the pickup’s front-right wheel wedged in mud. Within two hours, Highway Police had the vehicle extracted and traffic cones guiding motorists away from the breach.

Flooded Pavement and Thirsty Households

Investigators quickly zeroed in on a 1-metre diameter municipal pipe rupturing during recent excavation and restoration work. The torrent of clean water eroded sand and clay beneath the roadbed until the surface collapsed. By 08:00, Samut Sakhon City Hall announced a full water shutdown, disrupting supply to nearly 85,000 residents from Mahachai Market to Krathum Baen’s outskirts. While the Provincial Waterworks Authority’s grid remained intact, many neighborhoods faced dry taps and cloudy pressure as emergency crews scrambled to splice in a temporary HDPE section.

Detours, Delays and Driver Tips

With the service lane out of commission, tailbacks crept onto the main Rama II artery, creating stop-and-go conditions through kilometre 28–32. Traffic police at km 29+600 directed vehicles onto the central route while digital signboards urged commuters to allow extra travel time. Drivers heading into Bangkok may find relief using Phetkasem Road or Ekachai via Ban Phaeo (Route 375). Local apps like Thailand Highway Traffic and the 1586 hotline offer real-time updates and detour advice.

Underpinning Strains: Soil, Structures and Temporary Lines

Though the broken pipe was a temporary installation for the M82 elevated motorway, specialists point to Samut Sakhon’s soft marine clay and a dense tangle of interim utilities as underlying risk factors. High-pressure water from a compromised joint can swiftly wash out support soil layers. “Every time you reconnect or recompact a trench, there’s potential for settlement,” notes Assoc. Prof. Surasak Kumlong of Chulalongkorn University’s engineering faculty. He advocates for ground-penetrating radar, more rigorous compaction testing, and an independent inspectorate on major corridor projects.

Preventing Tomorrow’s Collapse

City engineers and highway officials are now drafting tighter protocols to head off a reprise:

Continuous Pressure Monitoring – Sensors in live pipelines to flag abnormal surges ahead of failure

As-Built Utility Mapping – Mandatory, up-to-date underground plans shared with every contractor

Frequent Soil Density Checks – Third-party verification of backfill compaction before reopening lanes

Routine Visual Inspections – Daily surveys of temporary lines under traffic loads

Repair Timeline and What Comes Next

Transport Minister Phiphat Ratchakitprakarn has ordered round-the-clock crews to backfill the void, compact in layers, and resurface the lane. One inbound service lane is expected to reopen this evening, with full restoration by noon on Monday, weather permitting. The Department of Highways also plans to clear debris from a recent girder incident at km 30 by 30 January, smoothing the path for normal traffic patterns. In the meantime, Bangkok-bound motorists are advised to stay alert for shifting traffic signs and keep water-supply alerts on standby.