Vance Creek Reservoir Spillway Design and Construction

The Regional District of North Okanagan (RDNO) operates Silver Star Water, which includes Vance Creek Reservoir. The reservoir is located in Silver Star Provincial Park, 20 km east of Vernon, on the Silver Star Mountain Resort Ski Area Tenure. Vance Reservoir is the largest drinking water source for the resort community and is critical for providing water during the resort’s peak ski season. The reservoir is impounded by the Vance Creek Dam, a 13.5 m high, 80 m wide crest-to-toe, and 230 m long-zoned earthfill dam. The reservoir is lined with an HDPE geomembrane, and the dam has internal filter zones with finger drains to the toe of the dam.

The spillway was installed with a compacted clay / till layer and non-woven geotextile fabric with riprap for protection. Erosion down to the geotextile fabric was observed as early as 2017. The edges of the spillway have not obviously receded, but the centre of the channel has been scoured, with some of the riprap and underlying channel structure transported down the channel. It appears that the internal filter zone is connected to the spillway with water draining through the dam and out the toe drains when the spillway is flowing during freshet. To ensure that the dam retains stability, it has been recommended through the most recent Dam Safety Review that the spillway should be lined to prevent flow from the spillway through the dam drainage system.

Construction is expected to be completed during the 2027 construction season, which is considered from June 16, after the diversion weirs are closed, to mid-September.