La Ronge Dam has been reclassified by Saskatchewan’s Water Security Agency (WSA) as at risk of “potential dam failure,” changed from the previous classification, “hazardous condition.”
While the dam is not in imminent danger of failing, WSA said it changed the emergency classification of the dam due to significant rainfall in the area recently.
Upwards of 40 millimetres of rainfall was recorded on July 25 and 26 and officials are forecasting the lake level to rise 10 centimetres to 365 metres.
Officials said this will cause the water level in the lake to encroach on the dam’s minimum recommended freeboard — the distance between the water level and the top of the structure.
Mitigation efforts are underway by the WSA. Large sandbags have been placed on top of the dam to raise the freeboard level by half a metre and officials said they are assessing additional mitigation measures.
The WSA said if the dam failed, it would not create a large wave of water going downstream.
Instead, there would be an increased outflow into the Churchill River system, which already has high water levels, and could increase flood peaks.
It would also impact the WSA’s ability to manage the lake level as it declines, officials said.
The impact of the dam’s failure is classified as significant by the WSA based on estimated consequences as it relates to loss of life, environmental and cultural impacts, economic damages and restoration costs.
The WSA said it continues to analyze the situation daily to understand what impact a dam failure would have on current downstream water flows.
The agency said it will work with communities in the area to assess low-lying areas where increased water levels could have an impact and any mitigation efforts that might be needed.