A total of 241 wet and soaked spots and 19 water leaks found in three sections of Thu Thiem Tunnel, Vietnam's first underwater tunnel, are not serious and will not affect its quality, the project's consultant says.
The water leaks, measured at below three milliliters per hour per square meter, are acceptable compared with the maximum permissible level of five milliliters per hour per square meter, Japan-based Oriental Consultants said at a press conference on May 28.
The wet and soaked spots, measured at two milliliters per hour per square meter, are also not a problem, the company said.
The spots are located mostly at the head and edge of the three sections as well as the center of the sections' walls, according to the consultant.
One of the causes of the wet, soaked and leaked situation was the space between the concrete and anchor bolts as well as between the concrete and pipes, Oriental Consultants said.
The bolts embedded in the concrete (the tunnel ceiling) aimed to connect cables with the tunnel section to fasten it to the riverbed. The pipes were installed to blow sand under the bottom to keep the tunnel fixed.
The firm said the wet and soaked areas, as well as the leaks would be gradually reduced thanks to the concrete's healing ability and the ventilation system to be installed soon.
It also proposed fixing the situation by pumping epoxy glue into the wet and soaked spots as well as water leaking areas and then covering them with a wet-preventing material.
Luong Minh Phuc, director of the management board of East-West Highway project which includes the Thu Thiem Tunnel, said he agreed with the consultant's suggestion.
"Many tunnels in the world, including Sydney Harbour Tunnel in Australia, have applied this measure successfully to fix water leaks," he said.
Phuc required the firm to submit a detailed solution by July so that the work can be carried out in September, after the fourth and final section of the tunnel is submerged and connected with the first three sections.
The final section will be towed to Ho Chi Minh city from the neighboring province of Dong Nai and installed on June 4-5.
The three-lane Thu Thiem Tunnel will link Ho Chi Minh City's districts 1 and 2 once it is open to traffic next year, allowing vehicles to travel at 60 kilometers per hour.
The tunnel's contractor is Japanese-owned Obayashi Corporation.