Berm to protect new West Kelowna elementary school from flood risk
West Kelowna's Mar Jok Elementary School will be built with a berm around it to protect the school from potential flooding if an emergency drawdown of Rose Valley Reservoir is ever to occur.
Council unanimously approved a floodplain exemption for the school site—located at 2101 McDougall Road—Tuesday.
According to supervisor of current planning Brent Magnan, the approval will allow Mar Jok Elementary School and Neighbourhood Learning Centre to be built below the identified flood construction level of 1.5 metres above the natural boundary of a watercourse.
"The flood construction level is based on the Faulkner Creek spillway, which actually flows from the base of the Rose Valley Reservoir, down into the Rose Valley subdivision, then fronts the future school site on Rosewood Drive," said Magnan.
That spillway is designed for the emergency drawdown of Rose Valley Reservoir if the maximum flow of five cubic metres per second is ever exceeded; however, such a controlled drawdown is currently impossible.
"We actually have no method of actually doing a controlled drawdown at this point in time. It is something that has been designed into the plan for the future use of the spillway."
Director of engineering Gary O'Rourke said the risk of too much water pressure against Rose Valley dam is low, but the consequences would be high if it were ever breached. But so far no engineer has come up with a way to put a pipe through the structure.
"It needs a big drawdown pipe with appropriate valving to draw that water down in the (situation) of a major event. We can't do that at this point," said O'Rourke.
"It's something that's been identified, but it's a long ways from actually being completed."
A current covenant stipulates there can be no building within 15 metres of the drawdown channel, or within 1.5 metres above the high water mark. Mar Jok Elementary meets the first requirement, not the second.
Although it's not recommended, current legislation indicates structures can still be built within the setbacks providing a number of steps are taken.
According to Magnan, a flood risk analysis report has recommended that a berm be constructed along McDougall Road and Rosewood Drive to redirect water around the school.
A geotechnical report was also conducted and gives specifications of how the berm should be built.
Both reports acknowledge the probability of a controlled drawdown is low and the risk of flooding at the school will also be low after a berm is built.
"Most importantly, they have provided an assured statement that says the land may be used for the use intended," said Magnan.
Coun. Rick de Jong asked whether the berm may cause a bigger problem for nearby homeowners.
"What about the impact to other homes and development in the neighbourhood? By diverting that water, is there potential for a negative impact on those other facilities and buildings that are there?" asked de Jong.
Magnan said the majority of the water diverted down McDougall Road would end up in the school's parking lot and nearby sports field.
De Jong added it's important that the berm be aesthetically pleasing.
Nancy Henderson, director of planning, said this will be the first formal floodplain exemption in the area, despite significant development in the Rose Valley neighbourhood.
Mayor Doug Findlater said the issue is one that will likely be further discussed by council in the future; however, it was important to approve the floodplain exemption so the school district could focus on construction of a "much-needed" elementary school.
The school is expected to open in the fall of 2014.