Worker Horrifically Killed After A Pipe Ruptured, Why?

One worker was killed when trapped in an underground chamber by a deluge of water from a broken watermain. Others barely made it out of this confined space. Why did this tragedy happen?

It is difficult to determine why this tragic incident occurred from the vague news report. Workers were working close to or on a live water main in an underground chamber when the watermain broke and flooded the chamber.

This work would likely fall under the Ontario Confined Space Regulation. This regulation has several requirements to prevent this type of heartbreak from happening—for example, Section 14.

14. The employer shall, in accordance with the relevant plan, ensure that each worker entering a confined space is adequately protected,…

(d) against drowning, engulfment, entrapment, suffocation and other hazards from free-flowing material, by adequate means.  O. Reg. 632/05, s. 14; O. Reg. 23/09, s. 2.”

https://www.ontario.ca/laws/regulation/050632

What do you think? What caused this tragic fatality?