This is the time for some dam vigilance in the Okanagan
PENTICTON – The failure of a dam on the upper reaches of Testalinden Creek near Oliver in 2010 that resulted in the destruction of five residences is still a recent memory for Okanagan valley residents facing excessive water issues this spring.
A dam on that creek gave way on June 13, 2010, sending a landslide across Highway 97 south of Oliver, into the Okanagan valley.
Last week’s discovery of an unuauthorized dam in the Willowbrook area, in addition to efforts to reduce the water levels behind nearby Kearns Creek dam are new reminders to Okanagan residents of the potential for higher elevation dams in the valley to add catastrophically to flood woes this spring.
Residents of the Sportsmens Bowl Road area, nine kilometres north of Oliver are feeling the effects of some of that water after an evacuation alert was put in place for 16 properties yesterday afternoon, April 10.
The Ministry of Forests, Lands Natural Resources says in an emailed statement the Okanagan’s 368 dams all present an additional risk this spring as the whole region is wet, with high groundwater levels and low elevation snow melt and rain contributing to saturated ground conditions that can increase risk of landslides.
There is always risk that a dam might fail, especially during periods of high water flow when dams can be overtopped, spillways blocked and landslides occur.
The province reviewed its dam safety program in 2010 following the Testalinden dam failure near Oliver, providing several recommendations that have since been implemented.
All dams in the province were assessed, additional staff were hired, dam owners were given improved education and the dam safety database was brought up to date, according to the statement.
The province’s Dam Safety Program has records for 368 dams in the Okanagan valley, classified in terms of failure consequence.
High, very high and extreme consequence dam categories may result in loss of life, significant environmental and economic losses, should they fail.
In the Okanagan there are currently 47 high and 40 very high consequence dams, with another 52 “unclassified,” meaning consequence of failure had not yet been evaluated because the dam is under construction, decommissioned, drained or otherwise not in service.
There are currently no extreme consequence dams listed in the Okanagan.
The majority of the Okanagan’s dams are classified as low consequence, numbering 200. They generally require site surveillance once every three months and a formal annual inspection.
Each spring, the province sends reminders to high, very high and extreme consequence dam owners to check the condition of their dams, with site surveillance increasing to a weekly basis for dams in those categories.
The province also conducts audits on a five- to 10-year basis, depending on classification. Owners of dams with high, very high and extreme consequence classification are also required to hire a professional to conduct an engineering review of the dam every seven years, according to the statement.
When the ministry comes across an unauthorized dam such as the one discovered last week near Willowbrook, the owner is either brought into compliance with the Water Safety Act and the Dam Regulation, or the dam is decommissioned.
The province’s dam safety regulations apply to all dams capable of storing more than 10,000 cubic metres, (roughly equivalent to four Olympic sized swimming pools).
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