Soil Remediation Basics

Soil remediation is the process of by which previously contaminated land becomes useable again. Broadly speaking, there are two strategies used for soil remediation: clean-up technologies and stabilization.

Clean-up technologies reduce the amount of contaminant by either destroying or removing them. Stabilization technologies (also called containment) lowers the pollutant’s mobility and bioavailability. Both soil clean-up and stabilization can be done either in-situ or ex-situ and can be either physical, chemical or biological processes.

Hepure provides chemical and biological solutions for both in-situ and ex-situ applications for soil remediation. Selecting the best solution for soil remediation depends on the specific conditions and goals of your project.

Important Factors For Soil Remediation

Defining the Matrix:  Soil type (e.g. % of sand, silt or clay), fractured rock or sediment and the amount of heterogeneity.

Type of Contaminate: A good understanding of the contaminate or mix of contaminate in the soil matrix.  General categories are Chlorinated Volatile Organic Compounds (CVOC), Petroleum Hydrocarbons, Metals, Inorganics, Pesticides, Polycyclic Aromatic Hydrocarbons (PAH), and the newest categories of PFOS and PFAS.  Some contaminates may be addressed with a single technology (CVOC and Metals) where others will require different approaches (Inorganics and Pesticides).

Concentration of Contaminates: The concentration and mass of contaminate is very important.  Many remedial methods work well with lower concentration and some with elevated concentration and/or free product.

Remedial Goals: Understanding the goals is very important in selection of remedial alternative.  Reaching TCLP standards would require a vastly different approach than removal for closure.

Matrix Chemistry: One of the most overlooked parameters is chemistry, specifically geochemistry.  This refers to substances which normally would not be thought of as a contaminate but may interfere with implementation of remedial technologies.  Soil matrix chemistry includes, major cations and anions, mineral content, pH, buffering capacity, ion exchange capacity, acidity, salinity, and ORP.  The interaction of factors can be complex, such as precipitation of arsenic to arsenophyrite requires the correct pH and Eh conditions as well as the right iron and sulfate concentration which is dynamic depending on the surface reducing bacteria activity.

The factors discussed above are typically collected and documented in a detailed site assessment.  Site assessments will address site-specific conditions as well as document the types of contaminates and potential sources of the release.

Decision Tree and Cost

A typical decision tree for soil remediation is shown in Figure 1.  The relative costs are shown in Figure 2.   Each address a contaminate or group of contaminates and may designed to be effecting in a variety geological settings and geochemistries.  The product links provide a more detailed review of how each may be used.

As you can probably tell, there’s a lot to keep in mind. Please contact us. We’ll help diagnose your issue and figure out your best course of action.

Decision Tree for polluted soilsRelative Costs of Soil Remediation Treatments

Source for figures:

Lombi, E., & Hamon, R. E. (2005). REMEDIATION OF POLLUTED SOILS. Encyclopedia of Soils in the Environment. Elsevier.