Guidance for Conducting Risk Assessments and Related Risk ...

7. RISK ASSESSMENT IN AND AFTER THE FEASIBILITY STUDY
The feasibility study is a two-step process consisting of a preliminary screening of alternatives
[(usually based on the identification of chemicals of potential concern (COPCs) and performed prior to
the final completion of the baseline human health risk assessment (BHHRA)] and a detailed analysis of
those alternatives that pass the initial screening. Once the BHHRA is completed and a list of chemicals of
concern is available, a more thorough screening of alternatives may be completed prior to the detailed
analysis of alternatives to further reduce the number of alternatives evaluated in the feasibility study.
The focus of the BHHRA is to evaluate the effect of selecting a “no-action” alternative on human
health. The focus of the feasibility study is to evaluate both the short-term and long-term risks associated
with the actual implementation of a remedial alternative (see Table 3). Short-term risks associated with a
remedial alternative are those risks that occur during the implementation of the alternative (e.g., risks
from emissions) and affect the persons who live and work near the site and the actual workers who are
performing site remediation. Long-term risks are those risks that will remain after the remedy is complete
(i.e., residual risk either from treatment residuals or untreated waste). In addition, the evaluation of longterm
risks considers the effectiveness of the remedy over time.
The methods for assessing both short-tem and long-term risks are the same as those for the BHHRA.
The major differences are
• the estimation of timing and duration of exposures,
• the estimation of source terms (i.e., concentrations) to be evaluated at various times over the course of
the remedy,
• the need for short-term toxicity values (i.e., chronic values may need to be modified since the
exposure duration will be less than a lifetime), and
• the consideration of worker risks including health and safety issues.
Risk evaluations subsequent to the feasibility study are conducted on an “as needed” basis to ensure
that the remedy is and continues to be protective. If new environmental data or other information that
would serve to refine previous analyses becomes available after the feasibility study is complete, this
information, and its effects on all proposed alternatives, is incorporated into the Proposed Remedial
Action Plan.
The Record of Decision includes a section on comparative analysis that discusses risk as it pertains
to long-term effectiveness, short-term effectiveness, and overall protection of human health and the
environment. This section also discusses how the remedy will eliminate, reduce, or control the risks
identified in the baseline human health risk assessment; whether or not the remedy meets the established
remedial goal options; and any risks resulting from residual materials.
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