Guidance for Conducting Risk Assessments and Related Risk ...

• calculates a chemical-specific intake or dose.
Once the appropriate exposure routes and scenarios have been identified, the risk assessor must
select the appropriate dose equations and associated parameter values. The dose equations are used to
calculate either the amount of contaminant that is in contact with the body at an exchange boundary per
unit body weight per unit time or the amount of contaminant that is absorbed by the body per unit body
weight per unit time. The output of this activity is used in conjunction with the output from the toxicity
assessment to quantify potential risks/hazards to receptors during the risk characterization. Equations and
their associated parameter values for many of the exposure pathways pertinent to the evaluation of
risk/hazard on the ORR and at Portsmouth and Paducah are available on the RAIS at the web address
provided in Section 4.1.
The following subsections outline exposure assessment guidance that has been developed for sites on
the ORR. Much of this guidance is specific to the remedial investigation/feasibility study process, but it
is also of use for other risk assessment activities on the ORR (e.g., the discussion concerning land use).
4.2.1 Characterization of the Exposure Setting: Land Use
The end use (land use) of any site, whether it is a burial ground, a pond, or building, is critical to the
evaluation of risks/hazards associated with that area. The future use of an area determines the exposure
pathways and associated equations and parameter values, regardless of the level of the assessment (e.g.,
screening, integration point, or baseline). The DOE-ORO, the Tennessee Department of Environment
and Conservation (TDEC), and the U.S. Environmental Protection Agency (EPA) recognize that land use
determination on the ORR must incorporate the community values and their desired future uses for the
ORR. Therefore, in 1996, DOE asked the ORR Environmental Management Site Specific Advisory
Board to form a committee to solicit input from the community and make recommendations on the future
use of the ORR. This committee is called the End Use Working Group (EUWG).
In July, 1998, the EUWG published Final Report of the Oak Ridge Reservation End Use Working
Group (EUWG 1998). Overall, the EUWG developed four types of recommendations:
• community guidelines for contaminated land and water on the ORR,
• end uses for the five ORR watersheds and several areas not currently included in the watersheds,
• construction of an on-site ORR disposal facility, and
• long-term stewardship of contaminated land.
The land use categories and the criteria used by the EUWG in making recommendations are
presented in Table 6. Likewise, the land use categories used by the DOE for planning and evaluation
purposes in the Initial Accelerating Cleanup Paths to Closure Oak Ridge Operations Office (DOE 1998b)
are presented in Table 7. Although similar, the EUWG and DOE categories and their respective
definitions vary enough that a decision regarding their influence on the selection of future exposure routes
and scenarios must be made prior to the development of the human health conceptual site model.
Recommendations for specific sites (including remedial action, D&D, and areas slated for reuse) are
included in each of the documents.
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