Scenario planning: Understanding the risks from extreme river flooding
The worst flood experienced in Edmonton since modern records have been kept occurred in June 1915. Considered a 1:180-year event, it resulted in widespread destruction of Edmonton's river valley and the relocation of most businesses to higher ground.
Our Edmonton water treatment plants supply water to nearly one-third of Alberta's population. Both are located next to the river, with infrastructure at varying elevations and extensive below-grade facilities, including reservoirs.
We conducted scenario planning for a recurrence of a 1915 flood event. The analysis predicted that river flood water would enter the water treatment plants across overland flood plains and through underground waste stream/overflow piping systems that discharge to the river. Critical electrical infrastructure, chemical storage facilities and reservoirs would all be damaged.
The immediate impacts and aftermath would be considerable. Forecasts indicate that without improvements to protect the water treatment plants, the ability to treat water could be interrupted for three to 10 months, and a boil water advisory would need to remain in place until the entire distribution and transmission network is flushed and disinfected. Until water production is restored, customers would be supplied with water trucked-in as part of EPCOR's Emergency Water Supply Plan.
A disruption of this scale would have a substantial impact to the regional economy, and the direct costs to EPCOR would be extensive.
Protecting utility infrastructure from extreme river flooding
In 2018, we initiated a multi-year capital program to improve the flood resiliency of Edmonton's water treatment plants. These efforts have been extended to critical electrical infrastructure also located in the river valley.
The Flood Protection Project will provide protection for a 1:200 year flood through investments of $36.9 million, partly supported by $11.4 million in federal and provincial grant funding. The investments will reduce the risk of catastrophic damage to the water treatment plants and electricity infrastructure during a flood, and enable the facilities to resume potable water treatment as quickly as possible following an extreme flood event.