Control of Accelerated Gully Erosion on Pipeline Right-of-Way

SYNCRUDE AURORA T-PIT HILL PROJECT

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Monitoring and Maintenance

Location: Aurora Lease of Syncrude Canada Limited, near Fort McMurray, Alberta

Client: Syncrude Canada Limited

Objective:

To reduce accelerated surface erosion occurring on the T-Pit Hill section of Syncrude Canada’s Aurora inter-site pipeline right-of-way by establishing vegetation using soil bioengineering techniques.

The T-Pit Hill site is a 120 m long section of pipeline right-of-way. Slope gradients range from 10 to 60%. The soil texture is fine to medium sand, which when dry is highly hydrophobic. Prior to treatment, extensive rill and gully erosion occurred with gullies up to 1.15 m in depth. In October 2005 Terra Erosion Control Limited, in association with Fort McKay Environmental LP, was retained to carry out a field assessment, develop an erosion control prescription and carry out the implementation. The prescription developed included the use of brush layers and straw wattles to provide deep root formation and physical barriers to reduce surface erosion.

Implementation of the prescription was carried out in two phases: 1) collection and cold storage of live materials (April 2006), and 2) installation of erosion control measures (June 2006). The live cuttings (Salix bebbiana / exigua / scouleriana) were harvested locally, while dormant. Care was taken to maintain moose habitat values in the harvest area by leaving clumps of willow standing.

Prior to installation of erosion control measures, the slope was re-con toured to fill in rills and gullies. Planting of brush layers was machine-assisted, using an excavator in conjunction with manual labour. Straw wattles were installed to help reduce surface rill erosion. Local muskeg, used as mulch, was spread over the site. The site was also planted with native shrubs, broadcast seeded with native grasses and fertilized.

While implementation was proceeding, assessment of the surface runoff during heavy rainfall showed that the soil’s highly hydrophobic nature (impeding water infiltration) was exacerbating soil erosion. An agricultural soil wetting agent was therefore applied to help ameliorate this condition.