Dames & Moore, 1999 - USDA Forest Service

identify dismbutions of compounds of potential concern (PCOCs) and quantifi.. to the
extent practicable, impacts of those PCOCs to the ecology of the Site
Support development and evaluation of risk management alternatives and provide a risk-
based framework for identifying further data needs (if any)
The baseline ecological risk assessment (ERA) was performed in accordance with the Washington State
MTCA (1997) and USEPA (1994; 1998) guidance and followed section headings of Problem
Formulation, Analysis, Risk Characterization, and Uncertainty Analysis.
Baseline Problem Formulation. Based upon the Tiers I and I1 ERA. the PCOC list was
delineated for both aquatic and terrestrial habitats. Receptors of concern (ROCs) were
selected according to the guild concept where one animal with particular feeding habitat
can represent all similar animals with the same feeding habits. The conceptual site model
(CSM) included representative invertebrates, fish, birds, and mammals in the aquatic
habitat, and plants, birds, p d mammals in the terresmal habitat.
Analysis. Potential compounds of concern (PCOCs) were selected by comparison
against screening benchmarks and/or toxicity data compiled for site-specific conditions
and are consistent with the list of PCOCs identified in Section 5.0. Potentially complete
exposure pathways included surface water and food in the aquatic habitat, and surface
water, soil, and food in the terrestrial habitat. Concentrations of COCs in invertebrates.
plants, and small mammals were modeled and used in the dose component of the hazard
quotient (HQ). Toxicity reference v'alues (TRVs) were calculated using data provided by
Oak Ridge National Laboratory (1984, 1996% 1996b, 1997% 1997b. 1997c. 1997d,
1998a, 1998b) and USEPA (1993) as well as other published literature. Assessment
endpoints reflect the protection of plant and animal populations, and measurement
endpoints reflect the measured and/or modeled COC concentrations in the appropriate
media. Measurement endpoints were related to assessment endpoints by using the
concentration that causes no chronic effect on growth, reproduction, or development as
the toxicity benchmark.
Risk Characterization. Risk was estimated as an HQ greater than 1 .O, where:
HQ = Dose or exposurerrRV or criteria.
Worst case exposures were used as the primary measure of risk. If no risk was found
under these conditions, there was no need to conduct a more reasonable risk assessment.
If risk to a mobile ROC was found under worst case conditions, exposures were further
evaluated based upon median exposure conditions.
Uncertainty Analysis. Sources of variance and inadequate knowledge were identified
and discussed in reference to the findings of the risk characterization and ecological
studies.
, ,
7.2.2 Baseline Problem Formulation
The goals of the Baseline ERA are to refine and focis the description of conditions, stressors, and ecological
resources potentially at risk, and to quantitatively characterize stressor magnitude and the hazard these
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17693-005-019Vuly 27. 1999;5:16 PMDRAFT FIh'AL RI REPORT