How can we minimize topsoil admixing during salvage, even when frozen?
In 1993, the Alberta Environmental Protection and Enhancement Act was introduced, requiring the reclamation of all well leases and oil & gas pipeline sites to their original state. To do so, topsoil must be removed and stored separately from the underlying subsoil.
Typically, the separation of topsoil starts with turning and loosening the topsoil through a process called discing prior to the material being pushed into large piles called windrows. However, some circumstances (i.e., construction schedule, permitting timeline, equipment availability, and landowner negotiations) make it necessary to salvage during frozen ground conditions which is not suitable for discing (i.e., the ground surface too hard).
The Challenge
As an alternative to discing, a ripper shank (i.e., claw) on the back of a dozer cut lines or grids across the salvage area. However, this can be challenging to maintain a consistent depth across the salvage area and can lead to large frozen chunks of topsoil/subsoil being piled in the same windrow, reducing topsoil quality by diluting the topsoil material. As landowners rely on the quality of their surface soil for farming activities such as cultivated cropland and pasture grazing, it's crucial to maximize the amount of topsoil salvaged while minimizing any topsoil quality reductions from mixing (i.e., fertility, organic content, seed bank).
Conventional Method
Conventional method of using ripper shanks on the back of a dozer to loosen frozen soil.
Large Frozen Chunks
Ripper shanks bringing up large frozen chunks of topsoil and subsoil.
Topsoil & Subsoil Mixed
Topsoil (light grey) and subsoil (light brown) included in frozen chunk that will get piled together, thus lowering topsoil quality after reclamation is complete.
Innovating Beyond Best Practice
In 1997, brothers Brent, Jeff, and Doug Biegel from Fairview Alberta developed and patented the Frozen Topsoil Cutter (FTC) to address these challenges (Frozen Topsoil Cutting Ltd.). The implement is pulled from the back of a typical dozer and includes several cutter wheels and shanks in a ‘V-shaped configuration’ that are depth controlled from 5 to 25 cm. Compared to conventional ripper shank methods, this implement make strides in improving the quality and quantity of the winter topsoil salvage, boosting the efficiency of winter topsoil salvage (20-50% faster), and reducing wear on the equipment and the operator (less of a bumpy ride!)
New Implement Designed
The Frozen Topsoil Cutter was designed to address the challenges of winter topsoil salvage.
Setting the Depth
Operators can set the depth on the implement to minimize chunks of topsoil and subsoil being windrowed together which would reduce overall topsoil quality.
Ready for Reclamation
Salvaged topsoil quality is improved compared to conventional practices leading to a higher likelihood for success during reclamation.
Demonstrating the Practice
Smash & Sons have provided a frozen topsoil cutter (and stand) and interpretive signage demonstrating the practice at the BWC.
In 1990, local contractor Smash & Sons Contracting Ltd. began using the FTC to improve topsoil salvage quality and to be continually responsive to various requests from clients and landowners. To date, they have used the FTC in frozen ground conditions for lease preparation, road building, and pipeline right-of-way construction. Using the depth control on this implement, they have seen less mixing in their topsoil windrows leading to better reclamation outcomes for clients and landowners.
Considerations
Although helpful to improve salvage quality outcomes, it is recommended that specific knowledge of the topsoil depths is known prior to work beginning and to avoid use in forested areas where the implement is less effective due to tree roots.
