During the construction of subsurface pipelines, one of the most critical aspects in environmental conservation is the handling of the topsoil material and the prevention of erosion during the construction process. You might be asking, why is topsoil conservation important as soil seems to be abundant throughout Canada? Well, it is estimated that 1” of topsoil takes approximately 500 years to produce , which qualifies it as a non-renewable resource . As an integral resource of our functioning ecosystem, topsoil contains hundreds of years of organic nutrients that cannot be replaced once lost.
To add to the complexity of soil conservation, Canada has a wide variety of vegetation and soil compositions that can change throughout the length of a single pipeline. With varying requirements for successful conservation, the layers of soil are separated as they are excavated during construction to ensure:
- Soil mixing between subsurface sections is minimized
- Reduction of compaction of topsoil from vehicle traffic
- Vegetation is protected and conserved
- Prevention of the introduction of invasive vegetation and
- Reduction of soil erosion due to wind and water
To ensure successful topsoil reclamation, companies installing pipelines actively seek economical, practical and environmentally responsible methods of soil handling during construction. Figure 1 below illustrates some basic insights on one method of topsoil management and conservation throughout construction.
- Each section of soil type is piled and separated to prevent mixing, sometimes including separating multiple horizons of the topsoil.
- The topsoil beneath the path of travel for vehicles or equipment has been removed to prevent compaction.
- Around the trench, and in some cases, for the entire work side and a portion of the ditch side of the ROW, the first layer of the subsoil is also removed and stockpiled to ensure all subsoil excavated from the ditch is stockpiled only on similar subsoil to prevent any mixing. This also minimizes compaction issues on the traveled portion of the ROW and maximizes successful vegetation re-establishment following construction.
Figure 1: Typical Soil Management on Pipeline Right-of-Way (ROW)