Remediation Overview
The goal of a remediation effort is to limit the extent of contamination
at a hazardous waste site, to prevent further deterioration of the
environment and to prevent exposure by humans and other life forms
to hazardous chemcials. The remedies at a given site vary depending
on the properties of the chemicals found at the site, the types
of soils, the depth of contamination, and natural processes that
may occur at the site. The criteria for selecting remediation technologies
or treatments are:
- Short-term and long-term effectiveness at meeting the remediation
goals
- Reduction in the volume of contaminants most effectively
- Reduction in the toxicity of contaminants
- Cost effectiveness.
Other factors affect the choice of remedies-for example, land disposal
of hazardous materials is restricted under present environmental
regulations. Because a variety of remedies can often control contamination
at hazardous waste sites, selecting the appropriate technology or
technologies can be a challenge. For an overview on how to select
a cleanup strategy, click here. To see a presentation that explains
the various cleanup methods, click here.
The following categories of remedies are listed in order from least
disruptive, intensive and expensive to most disruptive, intensive
and expensive.
1) Do nothing. If the environmental assessment indicates
that humans and the environment are not at risk, then no remediation
activity is required . "Do nothing" may be deemed the
appropriate action for small-scale spills on sites where human and
animal exposure is not likely.
2) Institutional Controls (IC) - institutional controls
are legal or institutional mechanisms that limit access to or use
of property, or warns of a hazard. An IC can be imposed by the property
owner, such as use restrictions contained in a deed or by a government,
such as a zoning restriction. At contaminated sites, instutitional
controls are used to prohibit access to the contaminated areas.
Examples of institutional controls include fencing off a contaminated
site or prohibiting the construction of wells near polluted aquifers.
3) Monitored Natural Attenuation - In some cases nature
promotes cleanup of contamination. Some contaminants may be broken
down into safe elements via sunlight (known as photolysis), natural
bioremediation, and chemical reactions (such as hydrolysis).
Contaminants can also "stick" (or sorb) to soil or other
solid particles, limiting the mobility of contaminants in the soil.
4) Containment of contaminants - The risk of environmental
contamination can be reduced by limiting the ways that humans, wildlife
or the environment can come in contact with the contaminants. Methods
include capping of soils with clean material, creating physical
barriers, and stabilizing or solidifying contaminants in place.
Containment of contaminated groundwater is more difficult and may
involve elaborate and often expensive pumping and treatment systems.
5) Destruction of contaminant - Destroying the contaminants
may remove the risk posed by contaminants if the by-products are
not toxic. Treatments can be in situ (in place) or ex situ (after
excavation of the soil or pumping of the ground water from the aquifer).
Technologies include phytoremediation,
bioremediation,
Fenton's
Reagent and ozonation.
6) Removal - In some cases, the best option may be to physically
remove the contaminated soil and move it to a permitted Treatment,
Storage and Disposal Facility (TSDF). This is especially true with
soils that are contaminated with both chemicals and radioactivity.
In other cases, it is possible to remove the contaminant from the
soil using such technologies as surfactant washing, soil washing
or thermal
desorption. Contaminants in groundwater can be removed
using pump-and-treat technologies involving methods such as activated
carbon or ion
exchange.
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