While in Saigon to manage construction contracts to Vietnamese construction contractors in 1972, I worked with a company called VIHICO to build a large storm drainage tunnel two or three kilometers long.
The project was called Vo Thanh Drain, which might have been for the name of the street that was dug up during construction and then restored.
As the tunnel neared its outfall (close to present-day Dinh Tiên Hoàng Street), it flattened out to a section about 10 meters wide and 3 meters high.
The outfall drained into an area of wet fields growing dinner greens.
That area now looks like this, around the new University of Fine Arts Building on Phan Dang Luu.
As the tunnel progressed, neighboring house owners connected their house sewer lines through the tunnel wall (probably in collusion with the contractor).
The project was fairly disruptive to the lives of the occupants of the neighborhood, but attempts were made to accommodate movement across the construction.
After construction, the street was restored.
Since 1972, the street has been widened considerably.