Ten to 19 meters (33-62 feet) underground, around 200 people are working on a sewer system that will carry wastewater from the downtown area to a treatment plant in District 2.

The system, costing VND2 trillion ($86 million), is part of a VND11-trillion environment project funded by the World Bank. A Thai contractor began working on the sewer in mid-2017 and it is expected to be finished late next year.

The sewer runs eight kilometers (five miles), with diameter of 3.2 meters. Phan Thanh Tuan, deputy director of HCMC Environmental Hygiene Project Management Board, the main investor in the environment project, said: "This is currently the biggest underground sewer in Ho Chi Minh City."

More than one kilometer of the sewer will run under the Saigon River’s bed.

Along Mai Chi Tho Boulevard in District 2, pipe sections are about to be buried.

The 36 centimeters thick pipe is made of sulfate and high-performance concrete. Each section weighs 35 tons.

Each pipe tube is sent underground by a crane through giant wells built for the purpose. Each well is 19-27 meters deep and has a diameter of 11 meters. After construction ends, these wells will be covered up and work as gates directing wastewater flow into the sewer.

There are 21 such wells along the entire pipeline.

The pipe tubes are put together using a technique developed by Germans, which gets the soil out and pushes the pipes in at the same time, helping save time and minimizing traffic impacts.

Inside each well, there is one pipe bringing in water to turn soil into wet mud before the other pipe sucks it out.

A group of workers set up a pipe to let water in.

Workers set up a rubber pipe to let the air flow down to the construction site underground.

An almost complete sewer section on Mai Chi Tho Street. All pipelines for water, mud and air have been removed. The surface of the sewer is coated with a layer of waterproof polyethylene.

The wastewater treatment plant linked to the sewer is scheduled for completion this year after five years of work. The plant, covering 38 hectares (94 acres), is designed to treat 480,000 cubic meters of sewage each day.