Remediation Selection

The remedy selection process involves the evaluation of alternative remedial actions using the following:

  • Be protective of human health and the environment
  • Attain applicable or relevant and appropriate requirements (or provide grounds for invoking a waiver)
  • Be cost-effective
  • Utilize permanent solutions and alternative treatment technologies to the maximum extent practicable
  • Satisfy the preference for treatment that reduces contaminant mobility, toxicity, or volume as principal elements (or provide explanation otherwise)

Remediation measures can range from simply monitoring a site to the generally far more costly task of removing the contaminants, or they may involve a combination of both techniques.

  • Monitoring the contaminated site: If studies show that a site poses no threat to human health or if removing the contaminants would be more hazardous than leaving it in place, monitoring of a site may be a sufficient step. Monitoring is designed to ensure that contamination is not migrating to where it would cause exposures.
  • Removing the contaminants: In areas where contaminated sites could pose a threat to human health, contaminants may be removed by excavation or pumping.
  • A combination of removal and monitoring: In some cases, partial removal of contaminants reduces the threat to human health to an acceptable level. Monitoring of the site ensures that the health threat remains at an acceptably low level.

Many remedies can control contamination at hazardous waste sites, yet deciding which appropriate technology to choose can be a challenge. For least impact on the environment, less disruption to the community, and lower costs, the least invasive and least costly remedies should be considered first. The following general categories of remedies are listed in order from least invasive to most invasive, disruptive and costly.

  1. Do nothing - If the environmental assessment shows that the site is safe, then no furtheraction is required.
  2. Institutional Controls - Prohibit access to the contaminated site. Examples of institutional controls include fencing off a contaminated site or prohibiting the construction of wells near polluted aquifers.
  3. Monitored Natural Attenuation - In many cases nature facilitates cleanup. Many contaminants are broken down into safe elements via sunlight (photolysis), natural bioremediation, and adsorption.
  4. Containment of contaminants - Limiting the access of contaminants to the environment at large can reduce their risk. Methods include: capping, creating barriers, and stabilization/solidification.
  5. Destruction of contaminant - Eliminating the contaminants removes the risk. Treatments can be in situ (in place) or ex situ (after removal). Technologies include phytoremediation, bioremediation, and ozonation.
  6. Removal - Physically removing contaminants from a site moves the problem. Removal involves transport and disposal of contaminants.

When remediating a contaminated site, two basic approaches are considered acceptable: a criteria or numerical based approach and a comprehensive, site-specific risk based approach. In cases where a risk-based approach is proposed, the specific methodology to be used (e.g., RBCA - Risk Based Corrective Action) should be specified. For the criteria based approach, subsequent sections of this policy set maximum allowable contaminant concentrations in soil and water for the restoration of affected areas. Information on classes and concentrations of chemical contaminants, how they are distributed through out the site, and in what media they appear is essential to begin the preselection of treatment technologies. The maximum allowable contaminant concentrations are based on the environmental sensitivity of the site.

 

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