Summerland's perpetual slide continues to move, council reviewing options

Photo: Contributed

Base of Perpetual Slide Area in May 2017 - looking north up Trout Creek

An area of Summerland that has been slowly sliding for a century will have an update on the perpetual slide and borehole monitoring results on Monday.

Located along Trout Creek at the south end of the community, the slide initiated between 1914 and 1917 and has continued to be the subject of many studies, including a Geotechnical and Hydrogeological Study prepared by Golder Associated Ltd.

A recommendation was brought forward in January of 2018 to conduct an borehole investigation which to hopefully determine the actual subsurface conditions, the depth of the slope failure surface(s) and acquiring soil strength properties.

Golder will be presenting the full findings on Monday, but the staff report gives their recommendation, which is to at this time, not recommend any change to the land-use measures outlined in the 2015 report.

Planning measures should consider alternate routes for buried utilities that may be impacted by the slide, such as those on Canyon View Drive and suspend the instrument reading program.

The slide area should continue to be monitored periodically by District staff and future monitoring of the instrumentation should resume based on the observation of visual surface disturbance triggers such as additional cracking or ground deformation.

Golder noted that the land will probably continue to be affected by retrogressive slide activity and a preliminary setback zone should be established. Existing infrastructure located in the setback will likely be subject to unpredictable ground movement.

Further suggestions are to implement a satellite-based change detection system in order to observe the full extent of the sliding behaviour.

Recommendations for the Canyon View Road water main come from an engineering consulting firm, Allnorth, which includes a preliminary design process for two options.

One suggestion is to replace the existing water main along Canyon View Road, Paradise Road, McGee Street and Mountain Avenue with a flexible pipe option. The other is to abandon the existing water main and install new water main in an alternate alignment away from the Perpetual Slide area.

The District will hear the presentations on Monday and Staff will report back to Council at a later date once the preliminary design for the Canyon View Road water main project is completed.

Photo: Contributed

Location map of the slide area