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Ecological Risk Assessment

Frequently Asked Questions

Ecological Considerations in Removal Actions

  1. Do ecological considerations need to be made when planning removal actions?
  2. Do the residual contaminant levels present after the removal action need to be at concentrations that are not expected to pose an unacceptable risk to ecological receptors?
  3. Why should ecological considerations be made during removal actions?
  4. When might it be appropriate to consider a removal action to address ecological risk?
  5. Does an action adequately reduce ecological risk if all visible waste is removed?
  6. How are ecologically-based clean-up levels established for removal actions?
  7. Can background concentrations be used as target clean-up levels?
  8. How do I know that a proposed removal action is protective of ecological receptors?
  9. Is reducing the bioavailability of the contaminants sufficient to be protective?
  10. Are post-removal investigations necessary to determine if the removal was protective?

1. Do ecological considerations need to be made when planning removal actions?

Yes. Any action taken at a site that is to be protective of human health and the environment must consider the reduction of risk to ecological receptors and the impact of the removal action itself on ecological receptors.

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2. Do the residual contaminant levels present after the removal action need to be at concentrations that are not expected to pose an unacceptable risk to ecological receptors?

No. However, the presence of residual contamination at levels that may pose a risk to ecological receptors will necessitate further evaluation. Typically this evaluation will be conducted as part of either a site inspection or a remedial investigation.

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3. Why should ecological considerations be made during removal actions?

There are several practical reasons why ecological considerations must be made during removal actions:

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4. When might it be appropriate to consider a removal action to address ecological risk?

Removal actions to address ecological risk should be considered when there is an imminent and substantial threat posed to ecological receptors. It may also be appropriate to consider removal actions when:

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5. Does an action adequately reduce ecological risk if all visible waste is removed?

Not necessarily. Even in cases where all contamination is believed to be visually evident, such as in the case of lead shot or blast grit sites, contaminants may have migrated or leached from the source in concentrations sufficient to pose an ecological risk.

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6. How are ecologically-based clean-up levels established for removal actions?

Ideally, the results of site-specific toxicity testing or bioaccumulation studies should be used to develop appropriate clean-up levels. If an ecological risk assessment has been performed for the site, the results of that assessment should be used in developing the clean-up levels. In lieu of appropriate site-specific levels, literature-based ecotoxicological values protective of the most sensitive species that can be reasonably expected to occur on site can be used. Values no greater than a lowest observed adverse effects level (LOAEL) should be considered when establishing an appropriate clean-up range. In certain situations the use of background concentrations may be appropriate.

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7. Can background concentrations be used as target clean-up levels?

In cases where it has been documented that contaminants are present at levels that are posing a risk to ecological receptors, site-specific background concentrations may be used as target clean-up levels.

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8. How do I know that a proposed removal action is protective of ecological receptors?

A proposed removal action can be expected to be protective of ecological receptors when the action decreases contaminant concentrations to levels that are expected to reduce risk to acceptable levels for the most sensitive ecological receptors anticipated to occur at the site and / or all exposure pathways have been broken.

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9. Is reducing the bioavailability of the contaminants sufficient to be protective?

Reducing the bioavailability of contaminants can be considered protective, as long as it can be demonstrated that the residual contaminant levels do not pose a risk. In cases where actions are planned to achieve their effectiveness through reduction of contaminant bioavailability, a monitoring program must be established to demonstrate the effectiveness of the action.

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10. Are post-removal investigations necessary to determine if the removal was protective?

If the action(s) were planned integrating ecologically-based clean-up levels and it can be demonstrated that the action achieved those levels, post-removal investigations are not likely to be necessary. If waste is left in place, a monitoring program is typically necessary. In cases where the action(s) have been performed to stabilize a site, but the resultant conditions were not planned to address all risk issues, a site investigation may be necessary to recharacterize the site.

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