Groundwater Containment – San Diego

 

Contaminant Source Areas and Groundwater Containment

 

 

Groundwater containment systems are often needed to prevent, or significantly reduce, the migration of contaminants in soils or ground water. Physical barriers and pump and treat systems are conventional technologies that play a significant role in managing the migration of dense nonaqueous phase liquids through the soil matrix and then leaching into the groundwater. Groundwater containment becomes necessary whenever contaminated soils, sediment, bedrock or sludge, are to be buried or left in place at a site. Both the physical barrier and hydraulic systems are commonly applied as a remedy to contaminant source areas when economic, technical, or site-specific factors make it impractical to address the contaminated areas in any other way. In general, containment is performed when extensive subsurface contamination at a site precludes excavation and removal of wastes because of potential hazards, unrealistic cost, or a lack of adequate treatment technologies.

 

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Hydraulic Systems

 

Hydraulic containment (pump and treat) is often performed when dealing with groudwater contamination and relies on pumping the contaminated groundwater to the surface using a series of extraction wells, treating it at the surface to remove the contaminants, and then either reinjecting the water underground or disposing of it off site.  Hydraulic containment systems are used: a) to control the movement of contaminated ground water, preventing the continued expansion of the contaminated zone; b) to reduce the dissolved contaminant concentrations in ground water sufficiently that the aquifer meets the cleanup goals.

 

Physical Barriers

 

Physical containment removes no mass at all. Instead, a physical containment remedy isolates the source area to prevent the migration of contaminants and block any direct route of exposure to the source, thus reducing risk. Physical containment is accomplished by creating impermeable barriers on all sides of the source zone with standard heavy construction methods and equipment. A typical physical containment remedy consists of a vertical barrier of very low permeability that surrounds the source on all sides and a clay aquitard below the source, topped by a low-permeability cap.

 

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Advantages of containment:

 

• It is a simple and robust technology.

• Containment typically is inexpensive compared to treatment, especially for large source areas.

• A well-constructed containment system almost completely eliminates contaminant transport to other areas and thus prevents both direct and indirect exposures.

• In unconsolidated soils, containment systems substantially reduce mass flux and source migration potential.

• Containment systems can be combined with in situ treatment and in some cases might allow the use of treatments that would constitute too great a risk with respect to migration of either contaminants or reagents in an uncontrolled setting.

 

Limitations of containment:

 

• Containment does not reduce source zone mass, concentration, or toxicity unless it is used in combination with treatment technologies; generally, only limited treatment will be provided by the P&T systems installed to control groundwater infiltration.

• Containment systems such as slurry walls are not impermeable and hence provide containment over a finite period.

• Data are not yet available concerning the long-term integrity of the different types of physical containment systems.

• Long-term monitoring of the containment system is essential for assuring that contaminants are not migrating.

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CONTACT US

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GROUNDFORCE

1220 PRESIOCA ST.

SPRING VALLEY, CA 91977

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Phone: 888-290-6574

Fax: 858-560-8960

Email: [email protected]