Soil Flushing Information and Treatment

In situ soil flushing is an innovative treatment technology that floods contaminated soils with a solution that moves the contaminants to an area where they are removed. “In situ" meaning “in place” refers to treating the contaminated soil without digging up or removing it.

The specific contaminants in the soil at any particular site determine the type of flushing solution needed in the treatment process. The flushing solution is typically one of two types of fluids: 1) water only; or 2) water plus additives such as acids (low pH), bases (high pH) or surfactants (like detergents).

Soil flushing is used primarily to treat halogenated and nonhalogenated semivolatile organic compounds (SVOCs), polychlorinated biphenyls (PCBs), and ordnance compounds from in situ materials. Water soluble inorganic contaminants may also be removed using soil flushing.

Water, or water containing an additive to enhance contaminant solubility, is applied to the soil or injected or infiltrated into the ground water to raise the water table into the contaminated soil zone. Contaminants are leached into the ground water, which is then extracted and treated.

Contaminants in the material partition into the solution by mechanisms such as solubilization, emulsification, or chemical reaction. The contaminant-laden solution are recovered to prevent uncontrolled transport of contaminants, and when possible, they are recycled. For biodegradable contaminants, it may be possible to add nutrients and distribute the solution on the material to promote contaminant bioremediation.

However, in most cases, treatment will be required to allow reuse of the fluid or release to local, publicly owned wastewater treatment works or receiving streams. To the maximum extent practical, recovered fluids should be reused in the process. The separation of surfactants from recovered fluids, for reuse in the process, is a major factor in the cost. Treatment of the recovered fluids results in process sludges and residual solids, such as spent carbon and spent ion exchange resin, which must be appropriately treated before disposal. Air emissions of volatile contaminants from recovered fluids should be collected and treated, as appropriate, to meet applicable regulatory standards. Residual additives in the material may be a concern and should be evaluated on a site-specific basis.