The Halifax story was interesting, but I was surprised the most important part of their sewage story was missing. After less than one year of operation, the $54-million Halifax Wastewater Treatment Plant had a catastrophic failure in January 2009 and was out of commission until spring of 2010. Repair costs were about $11 million.
During an electrical power outage the back-up generators failed. As a result, a chain of events started from which the plant could not recover because of the way it had been designed, and for its lack of “fail-safe” systems. In just over 20 minutes it was flooded to a depth more than 26 feet.
It was a textbook example of what can go wrong, will go wrong. If a proper risk assessment had been conducted during the design phase, the disaster could have been easily avoided.
The new Halifax Wastewater Treatment Plant was initially a design-build-operate (P3) project with a foreign multinational leading the consortium through one of its subsidiaries. After they tried to change the terms of the operating contract, the city took back the operational component but retained the same consortium to design and build the project.
Surprisingly, Seaterra had selected (for the cancelled McLoughlin Point plant) a consortium that had as a key partner the same multinational responsible for the Halifax plant that failed.
Over the years I have operated many wastewater treatment plants in Ontario and B.C. and there are well-designed plants out there. But there are also, from an operational and ownership perspective, many poorly designed plants based from what I have seen.
Even one small design mistake can turn out to be very costly, as Halifax found out. Hopefully we can learn from the Halifax example.
You can Google “How the sewage plant broke” to read an excellent article on what went wrong and why.