.... Specialising in reducing accelerated erosion

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 Canadaís 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 soilís highly hydrophobic nature (impeding water infiltration) was exacerbating soil erosion. An agricultural soil wetting agent was therefore applied to help ameliorate this condition.

 
 
 
Overview of site pre-treatment
June 2006

Overview of site in June 2006, pre -treatment

 

Gully formation on steeper parts of slope
June 2006

Gully formation on steeper parts of slope, June 2006

Collection of live willow cuttings
April 2006

Collection of live willow cuttings, April 2006

 
Willow collection area after selective harvest
April 2006

Willow collection area after selective harvest, April 2006

Machine-assisted planting of brush layers
June 2006

Machine-assisted planting of brush layers, June 2006

Site after implementation completed
June 2006

Site after implementation completed, June 2006

   
Close-up of installed brush layer and straw wattle June 2006

Close-up of installed brush layer and straw wattle, June 2006

Application of soil wetting agent
June 2006

Application of soil wetting agent, June 2006

 

Monitoring and Maintenance:

2006

The site was monitored on July 18, four weeks after installation was completed. Approximately 60% of the willow cuttings had shoot growth. A significant amount of rainfall occurred prior to this assessment. As a result, minor rill erosion occurred on steeper portions of the site. The site was monitored again on September 1, ten weeks after installation. Vegetation establishment had progressed well and grass had substantially in-filled the rills seen during the earlier visit.

 

2007

Monitoring of T-Pit Hill was done in October 2007, brush layer survival was assessed as fair; the dry conditions at this site caused some sections of brush layer mortality and relatively slow growth of the willow. Grass establishment was good overall, although there was an area disturbed by ATV traffic where surface water flow was causing rill erosion. New brush layers and straw wattles were installed in this area to correct the problem. To date the treatments have been successful at stopping accelerated gully erosion and establishing vegetation on the site.

 
Site on July 18, 2006
four weeks after installation completed

Site on July 18, 2006, four weeks after installation completed

Rill erosion noticed
July 18, 2006

Rill erosion noticed on July 18 , 2006

 
Site on September 1, 2006
ten weeks after installation

Site on September 1, 2006, ten weeks after installation

Rills in-filling with vegetation
September 1, 2006

Rills in-filling with vegetation, September 1, 2006

Overview of T-Pit Hill
October 2007

Overview of T-Pit Hill , October 2007

Repaired disturbance due to ATV traffic
October 2007

Repaired disturbance due to ATV traffic

 
New brush layers and straw wattles installed October 2007

New brush layers and straw wattles installed , October 2007

New brush layers and straw wattles installed October 2007

New brush layers and straw wattles installed , October 2007

 

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Pipeline Right-of-Way T-Pit Hill Project