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Site remediation can take many forms when there has
been a discharge to soil and/or ground water. Listed below is
a summary of the various remedial strategies that can be utilized
at a site, depending on the media (soil or ground water) that
has been affected.
Soil Remediation via Removal
This method of soil remediation is one of the most commonly
used and most widely accepted remedial strategies. This remedial
technique is also a quick solution to a soil contamination problem.
The concept and application is very simple. Soil that has been
impacted by a discharge from a vessel (whether it is an underground
storage tank, aboveground storage tank, or other storage container
i.e. drums) is removed from the ground via some type of earth
moving equipment. The most commonly used piece of equipment is
a rubber tire Backhoe, and larger excavation projects often utilize
a Trackhoe.
As soils are removed a subsurface investigator (geologist)
is on site to field screen the excavated soils with an organic
vapor meter (OVM). The OVM allows the geologist to make an informed
decision regarding the cessation of excavation activity and aids
in the Site Investigation at the site.
Any soils that are excavated are stockpiled on-site and covered
with plastic sheeting. The stockpiled soils are sampled in order
to obtain a classification for the soil as hazardous or non-hazardous.
In most cases the soil is classified as a non-hazardous material
and can easily be disposed of at a recycling facility.
Soil Remediation via In Situ Methods
In Situ, or "in place", remediation methods are
used in situations that do not allow for the easy or economical
removal of contaminated soil. This remedial technique is generally
a long term endeavor as the homogeneous nature of subsurface
environments do allow for the rapid cleanup of buried contaminates.
Factors that can influence the decision to treat contaminated
soil in place are the volume of material that requires treatment,
the depth of the impacted material, the proximity of the contaminated
soil to a structure, roadway, or underground utilities. Some
of the available In Situ methods are listed below:
BioRemediation This method uses native bacteria
or imported bacteria to metabolize, or eat, the hydrocarbons
that have impacted the soil. There are certain subsurface criteria
that have to be met in order to allow for a successful remediation
using this technology such as ph, Iron content, and dissolved
oxygen levels.
Soil Vapor Extraction This technology is used
in porous subsurface environments that have an ability to allow
for the movement of vapor, such as air and volatilized contaminants,
to travel through the subsurface. This technology works well
with light non-aqueous phase (LNAPL) liquids such as gasoline
and dense non-aqueous liquids (DNAPL) trapped in the vadose,
or unsaturated, soil column above the water table. Extraction
methods are sometimes enhanced by the introduction of steam or
hot air into the impacted formation.
PhytoRemediation This technology is relatively
new and involves the remediation of contaminates through the
natural uptake of vegetation. This remedial technique is often
used in cases of metals contamination but can have other applications
as well. As is the case with the BioRemediation this is a long
term cleanup strategy.
Natural Attenuation This form of remediation
is non-invasive and does not apply any type of active technologies
to the subsurface environment. Nature is allowed to break down
the contaminates in the soil over time through natural degradation
that includes a chemical, mechanical, and biological disassembly
of the hydrocarbon molecule. This process is monitored over time
to insure that the process of break down is on going. Again,
this process is a long term remedial strategy.
Ground Water Remediation
As a general rule, ground water remediation is a more complex
undertaking simply by the fact that the media that is being remediated,
water, can transport contaminates over large areas in both the
horizontal and vertical dimension. By the time a decision has
been made to undertake a ground water cleanup an intensive site
investigation has already been completed and the saturated and
unsaturated subsurface environment is well understood. These
investigative techniques are discussed in the Site
Investigation portion of this web page.
Some of the same remedial techniques discussed above in the
soil section have an application in the remediation of ground
water. These techniques include the following:
BioRemediation As is the case with the soil remediation,
this method uses native bacteria or imported bacteria to metabolize,
or eat, the hydrocarbons that have impacted the ground water.
Again, there are certain subsurface criteria that have to be
met in order to allow for a successful remediation using this
technology such as ph, Iron content, dissolved oxygen levels,
and the ability of the nutrients and bacteria to travel through
the subsurface.
Air Sparging This technique involves the injection
of air into the saturated zone which causes the volatilization
of hydrocarbons into the vadose zone. These volatized contaminates
are then removed from the subsurface via a soil vapor extraction
method as described above.
Ground Water Removal & Treatment This technique
is commonly called a "pump & treat" system and
is probably one of the most common forms of ground water treatment.
Ground water is removed from the subsurface by way of extraction
wells and pumped to a central area where the water can be treated
and then either returned to the subsurface or directed into a
sanitary sewer system. Treatment on the surface can take the
form of air stripping, carbon treatment, bioremediation, or a
combination of these treatments.
Natural Attention - This form of remediation is non-invasive
and does not apply any type of active technologies to the subsurface
environment. Nature is allowed to break down the contaminates
in the soil over time through natural degradation that includes
a chemical, mechanical, and biological disassembly of the hydrocarbon
molecule. This process is monitored over to time to insure that
the process of break down is on going. Again, this process is
a long term remedial strategy.
If you require additional information on any of the items
presented above, please contact our office at 908-851-0057 and
our staff will be happy to assist you.
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