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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