In Situ Soil Blending

Redox Tech, an in Situ soil and groundwater remediation firm, announces their improved amendment delivery method. The new method, in situ soil blending, will revolutionize the remediation marketplace. Redox Tech is already a recognized leader in developing soil and groundwater remediation amendments. The new delivery method complements Redox Tech’s formulation expertise and overcomes one of the major obstacles for in situ remediation, namely effective and uniform delivery of the reagents. In situ soil blending has numerous advantages over conventional dig-and-haul and in situ injection approaches:

  • Efficient and uniform delivery of remediation amendments, such as oxidants, reductants, and biostimulants
  • Production rates comparable to dig, haul, and backfill
  • No long-term liability associated with disposal at a landfill – no future PRP liability
  • No liability associated with the transport of hazardous waste
  • Costs that are 2 to 10 times less expensive than dig and haul, depending upon the type and level of contamination
  • No RCRA TSD permits are required because remediation is completed within the “area of contamination.”
  • Can treat a wide range of compounds, such as chlorinated solvents, pesticides, PCBs, and PAHs, among others.

In situ soil blending involves using an in situ blender to effectively distribute chemical amendments throughout the soil medium to treat contaminants of concern. The chemical amendments can range from oxidants, reductants, biostimulants, or soil stabilizers. The in situ blender is mounted on a large excavator with a modified diesel engine and hydraulic power system. The mixer is capable of mixing dry soil as well as sludge material to depths of 20 feet below the ground surface. Redox Tech owns two soil blenders. The most recent blender was designed and constructed by Redox Tech and is the most powerful blender on the market today.

Since many chemical remediation alternatives require direct contact with the target contaminants, the effectiveness of the remediation strategy is often limited by the ability to distribute the chemical amendments throughout the soil medium. We believe the in situ blender is the most effective and efficient method to achieve mixing at shallow depths (less than 18 feet). In addition, the production rate of this equipment is comparable to excavating and is a much cheaper alternative to dig and haul.

For large treatment areas, the in situ blending process is performed systematically by subdividing the treatment area into smaller cells. The cell dimensions and chemical loading requirements are determined prior to mobilization. Each cell is mixed with the designated chemical amendments ensuring that site-wide distribution is achieved. In some instances, where the target zones are thicker than 5 feet or where site conditions warrant it, each cell is subdivided into lifts of 5 feet. Each lift is mixed separately with predetermined quantities of chemical amendments. Then the entire soil column is mixed, ensuring proper vertical distribution.

Post Blending Stabilization

Soil blending typically reduces the cohesive strength and load-bearing capacity of the soil. Clay and silt have greater reductions in bearing capacity than sand and gravel. Depending upon the intended use of the property after treating it with soil blending, it may be necessary to improve the bearing capacity. This can be accomplished by blending in portland cement, lime, fly ash, or other suitable pozzolanic. Often, only the top few need to be improved, but that can depend on the property’s intended use.

Below are three videos that demonstrate the stabilization process. The soil at this site was treated to 24 feet below the land surface, but only the top 5 feet required stabilization. Soil blending with permanganate treated all of the chlorinated alkenes to non-detectable levels. Portland cement was blended in at 3 weight percent. The portland cement dried the soil and more than adequately improved bearing capacity. An excavator traversed the treated area less than 24 hours after stabilization was completed.

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