Improperly reclaimed soils present legacy liabilities
Soils are a misunderstood resource.
Misunderstanding of soils often leads to neglect in the process of mining or building pipelines, roads, ponds, or well pads.
The result of these activities can leave barren scars on the landscape that are susceptible to erosion.
This can lead to pollution of stormwater, unstable earthen structures, scouring of pipeline trenches, acid mine drainage, etc. All of presents stakeholders with exposure to long-term liability.
Understanding the soil profile
Soils are more than finely ground rock. Topsoil harbors robust microbial communities and supports plant growth. Over time and weathering, horizons or layers form beneath the surface layer of topsoil. These horizons often have very different qualities than the surface soil. Subsurface horizons affect water infiltration and root extension.
Subsoils can have profound effects on the stability of roads, bridges and buildings.
So it is important to understand the whole soil profile of horizons before undertaking rehabilitation of disturbed sites.
Our team strives to understand the pre-existing site condition before suggesting or attempting to rehabilitate a disturbed site. We study the surrounding native vegetation, the local geology, landscape position and deep soil horizons. We seek to understand the placement of the disturbed soil materials and how they might be placed to achieve the best outcome. Sometimes re-establishment of native horizons is not the best option.
Some soils actually have undesirable qualities just beneath the surface horizon. For example salts or clays may have accumulated in the shallow subsurface creating no-go zones for plant roots or clay may impede deeper water drainage. In these cases the reclaimed soil profile may be superior to the native conditions.
Re-establishing a soil profile
Our team strives to identify and locate the displaced soil materials before devising a rehabilitation plan. This can be challenging when reclaiming pond sites where subsoil materials were used for building earthen batters or dikes.
Once the soil materials are located and mapped we develop a plan to re-create a soil profile that will produce the best outcome. This can be difficult as the soil materials are often blended in the initial disturbance process. However we have also purposely blended materials to ameliorate or dilute undesirable soil qualities – such as acidic pH.
Prior to any field operations topographic surveys are performed to create erosion and sediment control plans. A contouring plan is also developed so that final surface drainage meets the desired objectives.
Then our team reviews the reconstruction map with the earthworks operators to ensure full understanding of all parties. Once the bulldozers commence working our staff is there to ensure that the plan is carried out correctly.
Extensive in-field testing occurs while the earthworks progress.
For example we routinely test for bulk density to avoid over-compaction or subsidence. Salinity and pH tests are commonly performed during the reconstruction process and it is possible to test for other constituents in the field if necessary.
Once the final contour is achieved the topsoil material is spread across the site. After the topsoil is spread amendments, fertilizer and seed are applied and incorporated as needed. In some cases we can irrigate the site with portable irrigation systems.