Upper Sumas River Dike Breach Permanent Repair
September 23, 2023
Kontur was retained by the City of Abbotsford to complete a geotechnical exploration to confirm the extent (and depth) of the newly constructed granular fill zone, characterize the underlying foundation soils, confirm the presence or absence of larger rock sizes within the central portion of the repair that could act as obstructions, and to assess suitable options for a low-hydraulic conductivity core or barrier.
In November of 2021, the Upper Sumas Dike breached between about Chainage 5+400 and 5+550. The dike breach was a result of overtopping of the dike that occurred following an unprecedented series of atmospheric river events in southwestern BC. Emergency response focused on closing the breach to stop flowing water from the Sumas River entering Sumas Prairie. Working under conditions of flowing flood water, partially underwater, and during intense precipitation, made it impossible to use fine-grained soils to close the breach and reinstate the dike structure. Therefore, the entire closure of the breach was constructed using crushed granular fill of varying sizes and the result was that seepage would continue through the body of the dike until a core or other suitable low-hydraulic conductivity barrier could be installed. Subsequently, in March 2022, Kontur was retained by the City of Abbotsford to complete a geotechnical exploration to confirm the extent (and depth) of the newly constructed granular fill zone, characterize the underlying foundation soils, confirm the presence or absence of larger rock sizes within the central portion of the repair that could act as obstructions, and to assess suitable options for a low-hydraulic conductivity core or barrier. Two site-specific exploration programs involving advancing a series of sonic testholes and CPT and SCPT probes along the centreline of the dike breach repair to a depth of about 15m below the top of the dike breach repair. Works were undertaken per the Dike Maintenance Act with the approval of the Inspector of Dikes. Based on the findings of the geotechnical assessment, the preferred option to mitigate the seepage through the dike was by means of installing a low permeability barrier using Cutter Soil Mixing (CSM) technology. CSM involves mechanically mixing the in-situ dike fill with a cement/bentonite slurry mixture to form a low-permeability barrier (core) within the central portion of the dike crest. CSM technology eliminated the need to deconstruct the initial emergency repair. The CSM barrier was installed in the fall of 2022. During construction, Kontur conducted field reviews and QA laboratory compression testing of the barrier material. Details of the initial emergency dike repair, and subsequent remedial repairs required to reinstate the initial dike repair as a functioning dike, are provided in two papers presented to the annual Vancouver Geotechnical Society (VGS) symposia.
Technical Papers
Click here to view this page online with additional details.
107-2071 Kingsway Avenue, Port Coquitlam, BC V3C 6N2
Tel: 778.730.1747
Fax :
Website: www.kontur.ca