In a lot of cases the Spin® injection technology offers a solution for the limitations of the traditional DPT technology, the advantages are listed below:
Soils or soil layers with limited or low permeability are being characterized by a high degree of soil and clay particles. These soil types are sensitive to compaction and smearing: fracturing, daylighting, blowout and reflux are likely to occur with traditional DPT injections. Because compaction and smearing do not occur with the Spin® technology, injection in silty and clayey soils is possible. Experience has learned that a large radius of influence can be achieved in these soil types.
With the Spin®-measure and logging system, the desired volume per meter of injection can be set in advance allowing the homogeneous distribution of the desired volume of product over the entire depth interval to be treated. Because of this, the product is being applied to every soil layer of soils with a high degree of heterogeneity and thin soil layers are not being skipped. During injection the injected volume is being registered every centimeter. In this way, it is possible to evaluate how the injection was executed compared to the initial plan.
Depth, injected volume, pressure, flow rate and relative hydraulic conductivity are being registered continuously every centimeter. In this way, injection logs can be generated that give a visual overview of the distribution of product over the depth interval, the applied pressures and flow rate and the hydraulic conductivity of the subsurface. These injection logs are made available for all involved parties to make sure the injection proceeds with 100% transparency. Depending on the observations in these logs, the injection strategy can be adapted.
In case daylighting, blow-out or reflux occurs, injection product comes back to the surface and is of no use. Unwanted fracturing leads to the formation of preferential flow paths and short-circuiting, by which the injected product does not end up in the targeted location in the soil. By the design of the Spin® technology, these unwanted phenomenal are less likely to occur and the injected products are being applied more efficiently.
During retraction of the injection rods, the borehole is being sealed automatically and compacted with the original soil material. As a result, preferential pathways for injection product injected in nearby injection points is being avoided and injection points can be put closer to each other if necessary. Additionally, by sealing the boreholes, the creation of vertical preferential pathways for DNAPL migration does not occur.
No heavy and large machines are needed to be able to reach significant injection depths with the Spin® technology. Especially for small spaces with limited access, the Micro-Spin® injection equipment has been developed. A standard door opening (B: 78 cm; H: 200 cm) is sufficient to enter the area of injection and only a working height of 200 cm is necessary.
A relative value for the hydraulic conductivity across the depth interval can be determined from the data gathered during the injection process. In this way, additional information on the presence of more and less permeable layers in the subsurface is being gathered. This information can give more insight into the migration patterns of contamination and injection products in the soil. Because injection points are mostly executed in a more dense grid compared to investigation points (like monitoring wells or MIP), the Spin® injection method gives additional and 3D information on the permeability of the subsurface.