The expansion of Salmon Arm’s sewage treatment plant is heading in the right direction and location in relation to avoiding potential flooding.
City staff responded with this sentiment to a question about flooding recently raised by a resident.
In a letter on council’s Nov. 22 meeting agenda, resident Garry Pawluck wrote: “Does the choice for Salmon Arm’s sewer upgrade still look correct now after what we have seen happen in Merritt. Complete evacuation. I think the Mayor and Council along with the City Engineers need to make a public statement.”
At the request of council, Rob Niewenhuizen, the city’s director of engineering and public works, drafted a letter in response.
Niewenhuizen wrote of the difficulty of being prepared for an event such as an atmospheric river that dumped a month’s worth of rain in two days. Stating that Salmon Arm needs to be prepared for flooding, he outlined how the city is positioned differently than many communities that were built adjacent to a river, such as Merritt, Abbotsford, Princeton and others, or a lake that is regulated by dams such as in Kelowna and Vernon.
He stated that while Salmon Arm typically expects some flooding of the Salmon River during freshet in the spring, the river and the vast floodplain which surrounds it has not been heavily developed.
“In reference to Merritt BC, this community is located at the confluence of the Coldwater and Nicola Rivers and their Wastewater Treatment Plant and Public Works Yard is located at the river confluence which is well within the flood plain,” he wrote.
Niewenhuizen stated that Salmon Arm’s Water Pollution Control Centre (WPCC), as the sewage treatment plant is called, is built above the 200-year frequency for the Shuswap Lake flood level, which is set at 351 metres above sea level (MASL).
Referring to a city chart of flood levels, he wrote: “The historical peak flood level in Salmon Arm was recorded in 1972, when lake levels reached its highest level at 349.600 MASL. In 2012, which was the second highest recorded lake flood level, it reached 349.400 MASL. The City’s WPCC has not been impacted by any previous flooding events.”
He wrote that as part of the January 2021 Site Selection Study by WSP engineering consultants for the proposed expansion of the plant, the site flood risk was reviewed for the existing plant location.
“It was determined that the site elevation must be above 200 year flood plain elevation (351.000) or the facility will require flood proofing. Our current plant is above this elevation and, depending on what technology that is selected for the new facility, it will be built with this recommendation in mind. I am confident that we are moving in the right direction and location for the WPCC expansion.”
The Shuswap Lake Level chart that Niewenhuizen referred to can be found at: Shuswap Lake Water Level | Salmon Arm, BC – Official Website
Niewenhuizen’s full letter to Garry Pawluck will be posted on the city’s website.
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