Another Hydroelectric Plant Construction Crisis

A few days ago there was a hydroelectric power plant construction incident in Ecuador that killed 13.  Now there is an incident at another hydroelectric plant, this time in Vietnam.

HANOI (REUTERS) - Vietnamese rescuers battled on Wednesday to free 12 workers trapped in a tunnel that collapsed during construction of a hydropower plant and said it could take days to get past entrenched mud, sand and debris as water levels rose. 

From the looks of the picture it seems that  the construction is being done with less than optimal equipment.

The Kuwait News Agency had some more detail:

The workers were on their way to the work zone inside the tunnel as around 300-5000 meters of the tunnel's entrance collapsed, expecting further parts to fall, head of the Firefighting and Rescue Police Department of Lam Dong Province Colonel Hoang Cong Thao said.Authorities have drilled into the rock to pump oxygen to the trapped men, while rescue teams contacted the trapped workers and they were in "good health conditions", he affirmed.The exact reasons behind the tunnel's collapse are not clear yet, he said.Rescue teams are clearing rubble out of the tunnel following 12 hours of the collapse time, and they are strengthening the roof to prevent further collapse in order to allow 0.6 meter pipe into the tunnel, helping the trapped workers to escape the collapsing tunnel, he added.Da Dang-Da Chomo" hydropower plant project is located in the hilly Lam Dong province, in the center of the country, and this project is still under construction.The power plant is expected to produce around 110 million kilowatt per hour, annually, at the coast of USD 22.24 million. (end) mam.lb

300 to 5000 meters of the tunnel collapsed?  Maybe they meant that the tunnel collapsed 300-5000 meters from the entrance or from the surface.  I don't know.  The 12 workers have an air tube now, but the water is rising.

Update:
Malay Mail Online clarifies that the collapse happened about 500 meters from the entrance.
Cool video!

13 Workers Die in Hydroelectric Plant Construction Project

Out of Ecuador is a report of a construction accident at a site for the new hydroelectric plant Coca Codo Sinclair.

Collapse Kills 13, Injures 12 In Chinese Hydroelectric Plant In Ecuador
QUITO, Dec 15 (BERNAMA-NNN-XINHUA) -- A tunnel collapse in a Chinese hydroelectric plant in Ecuador's Amazonian region Saturday night killed 13 workers, including three Chinese and 10 Ecuadorians, and injured another 12.

I do not work in the construction industry. I imagine the risks of construction and excavation on the level of a hydroelectric plant must be high.  But, I also imagine that there must be rigorous safety procedures.  The reports I could find so far do not detail the root causes of the incident.

BERNAMA-NNN-XINHUA reports that:

According to the National Risk Management Ministry, the accident was caused by a "collapse in a tunnel" that affected the high-pressure pipes inside the engine room.

Univision:

Ecuador's public radio said there had been a breakdown in a tunnel of the engine room of the plant and that the wounded were being treated at a hospital in the town of El Chaco, Napo.
"We are evaluating what's happened. It's a problem we're having in one of the penstocks," he told the AFP chief technical control of the project, Dennis Salgado.
He said that the accident occurred "in the area of ​​vertical well pipe pressure", which faces the underground powerhouse of hydropower.

The project is huge (Univision):

Coca Codo Sinclair, a work which cost about 2.245 million dollars will start operating in February 2016 and will generate 1,500 megawatts, 36% of the energy currently consumed Ecuador.The works are part of a network of eight hydroelectric construction with which Ecuador, an oil country, expected to stop importing electricity and become an exporter of clean energy.

This accident was not the only loss of life incident at the site(Univision):

Last April, four Chinese were killed in an explosion in the works of other hydroelectric being built in southern Ecuador, also funded by Beijing.
The victims were four technical explosives who perished during the expansion of an underground pit of Sopladora center, built by the China Gezhouba, as Tito Torres, business manager Hidropaute, the state company that manages the building.