INNOVATION March-April 2017

fea t ure s

Geohazards Uncovered Members Identify Terrain and Flood Risks to Resource Development Identifying Potential Slope Movement Along Pipeline Rights-of-Way Betsy Waddington, P.Geo., is an expert at mapping and assessing geohazards for the resource sector. Recently, she turned her skills to investigating natural instability that could damage pipelines in northern Alberta. Waddington works as part of a BGC Engineering team that investigates potential slope movements along pipeline rights-of-way.

Through her field investigation, Waddington determined that slope movements had the potential to impact the buried pipeline. As a result of these findings, instrumentation is now being installed on the slope to monitor ongoing slope movement.

Determining Effects of Legacy Forest Roads Tedd Robertson, P.Geo., Eng.L., works with Sitkum Consulting Ltd., based out of Nelson, BC. He was retained by BC Timber Sales–Kootenay Lake Business Area to complete a terrain-stability assessment for proposed forest development in southeastern BC’s Kaslo River watershed. Steep, naturally unstable slopes are common in the area, and past resource development, including old mining and logging, has left a legacy of old roads and trails on the valley sides. During his detailed field investigation, Robertson determined that old roads from 1980s-era forest development were affecting natural drainage patterns in the area upslope of the proposed new development. Surface runoff diversion on the old roads was affecting the new development area, as well as existing down-slope forest roads. Based on Robertson’s assessment, BC Timber Sales decided to deactivate the legacy road before development to restore natural drainage and reduce potential for compounding effects, including increased likelihood of landslides. A combination of waterbars and armoured swales (Right) were prescribed to improve and restore natural drainage patterns. BC Timber Sales maintenance contractors carried out the work with a small excavator in 2016. evidence of recent movement on the toe slopes on both sides of the creek. This slope movement is likely related to ongoing natural erosion by the creek. A fresh headscarp was also observed mid-slope on the south side of the creek. Overgrown tension cracks and slump blocks on both slopes suggest movement has occurred in the past. In a recent project, she focused her investigation on a section of the right-of-way where it crosses a deeply incised stream. Northern Alberta’s Big Mountain Creek cuts 55 metres into naturally unstable clay-rich till and shale bedrock. Waddington used high-resolution lidar imagery to create a clear digital elevation model of the project area (Right). Based on the imagery, she identified that deep-seated slumps are present on both sides of the creek. During her follow-up field investigation, she identified

The restored drainage patterns were then taken into account in the new development plans prior to harvesting.

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