Mud spill occurs lin Alley 7, Giang Văn Minh Street, Hà Nội on Monday afternoon.—VNA/VNS Photo

HÀ NỘI — A geologically complex area was identified as the preliminary cause of the mud mixture rising to the surface in Alley 7, Giang Văn Minh Street, on Monday afternoon during construction of the underground section of the Nhổn–Hà Nội Station urban railway.

The Hà Nội Metropolitan Railway Management Board (MRB) on Monday evening said the incident occurred as the boring tunnel was being driven through a difficult ground containing backfilled soil layers, old groundwater extraction wells and disused drainage pipes, which created pathways for the mud to escape to the surface.

Ground surface monitoring, observation of structures above ground and technical supervision of the tunnel boring machine (TBM) have been carried out continuously throughout the tunnelling process.

Adjustments to tunnelling parameters have since been made in line with construction methods and the works are deemed safe to continue under close supervision by consultants and the project owner.

This is the fourth time mud spill have occurred in Giang Văn Minh - Kim Mã area during the construction of the metro, following similar incidences in February, May, and early August.

On Monday evening, MRB issued an official statement regarding the incident.

Accordingly, at around 4pm the same day, a mixture of mud and water rose to the surface in Alley 7, Giang Văn Minh Street, during tunnelling with TBM No. 2 at ring segment 816 (about 1,224m from Station S09–Kim Mã), at a depth of 15m, under Package CP03 – Tunnel and Underground Stations of the Nhổn–Hà Nội urban railway project.

Immediately after the incident was detected, representatives of the project owner, supervising consultants, contractors and local authorities were present on site to direct and oversee remedial work.

Around 30 personnel, five sludge suction trucks, specialist equipment, sandbags and temporary fencing were mobilised to contain the affected area, collect and remove the mud, clean the site and ensure tight control of TBM operations.

By 7:40pm on Monday, the mud spill had been brought under control, though remedial operations remain ongoing.

The collected sludge has been transported by suction trucks to a waste storage facility at Station S09-Kim Mã.

Temporary support has been provided to affected households in the alley, including alternative accommodation and assistance with business suspension during the clean-up.

“Learning from previous experience, the response this time was faster. The affected area was quickly cordoned off and isolated within a limited range. No damage to people, buildings or technical infrastructure was recorded,” an MRB representative said.

Offering a formal apology to residents in the alley, Lee Young Kyeong, Deputy Project Director and representative of the main contractor consortium HGU for Package CP03, said that lessons had been taken seriously from past incidents and control measures strengthened.

 “We are committed to reviewing construction methods comprehensively, improving response capacity and working closely with MRB and local authorities to ensure absolute community safety as well as the quality and schedule of the project,” he said.

In the coming period, the project will take into account assessments and feedback from specialist agencies, adjusting TBM operating parameters to suit geological conditions and minimise potential risks.

MRB pledged to continue directing consultants and contractors to enhance reviews of tunnelling methods, update risk-prevention plans and work closely with local authorities and relevant agencies in handling similar incidents.

The board stressed its commitment to ensuring maximum safety for people and structures, minimising disruption to residents, maintaining environmental hygiene during construction, and safeguarding both the progress and quality of the project.— VNS