Guidance for Conducting Risk Assessments and Related Risk ...

5. SCREENING RISK ASSESSMENTS
Human health screening risk analyses, as presented in this document, include comparing available
environmental data with risk-based Preliminary Remediation Goals (PRGs) and developing/updating an
integration point assessment. These analyses were developed to accelerate the remedial investigation
process and reduce its cost by identifying sources that are of highest priority. Since their development,
the screening risk assessments have been applied to other projects [e.g., Decontamination and
Decommissioning (D&D) and reindustrialization] to identify the potential risks and the need for risk
reduction prior to the demolition or reuse of a facility. The screening risk analyses also identify and
provide justification for early actions at sites. Lastly, these assessments can be used to focus data
collection efforts on chemicals of potential concern or to identify data needs.
The screening risk assessments described in this document were based on the known physiographic,
hydrologic, and geographic characteristics of the Oak Ridge Reservation (ORR) and existing/historical
chemical environmental data. This information indicated that the surface water and groundwater systems
on the ORR serve as collectors or basins for multiple chemicals from a variety of sites. These chemicals
are mixed together within these water bodies and integrated into their flow system. As such, the surface
water and groundwater systems are referred to as integrators. Most importantly, these integrators, along
with the air pathway, are the primary means of contaminant transport to areas outside the boundaries of
the ORR where public exposure becomes more probable. A screening risk analysis methodology, called
the integration point assessment, was developed to evaluate the surface water integrators.
The integration point assessment is a flux-based risk assessment method developed to evaluate the
surface water integrators. This assessment uses monitoring, surveillance, compliance, and other data to
evaluate relative contribution to the off-site risk from the various input sources of surface water
integrators. Once the primary sources in the integrator are identified, source control actions can be
prioritized and undertaken to reduce exposure to levels that are as low as reasonably achievable.
The combination of the comparison to risk-based PRGs and the integration point assessment allow
the risk manager to prioritize sites relative to both on-site and off-site risk/hazard [where “site” refers to
the U.S. Department of Energy (DOE) ORR property], respectively. These assessments can be
performed at any point during the investigative process and can be updated as new information becomes
available.
5.1 COMPARISON TO RISK-BASED PRELIMINARY REMEDIATION GOALS
Chemical-specific, risk-based PRGs, which are a subset of all PRGs, are concentration goals for
individual chemicals and radionuclides for specific medium and land use combinations. The risk-based
PRGs are derived using a specific excess lifetime cancer risk or hazard index. Risk-based PRGs are
initial guidelines that are protective of human health and the environment, based on readily available
information, and comply with Applicable or Relevant and Appropriate Requirements (ARARs). For
more information on PRGs, refer to Section 1.1 of Risk Assessment Guidance for Superfund, Part B (EPA
1991a).
The Risk Assessment Information System (RAIS) provides the means to calculate risk-based PRGs
using standard exposure equations for a number of exposure routes. This interactive web program allows
the user to select analytes of interest and to customize the exposure equations for the routes they wish to
evaluate. For more information please see the web page at: http://www.risk.lsd.ornl.gov/rap_prg.
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