Environmental Analysis Tools - Environmental Impact Analysis: Process and Methods - page 268

generalizations and hypotheses can be made or procedures designed to test the
theories (Keaton 1972). The product of the site description should include:
r A list of potential ecological receptors expected to be associated with
the site
r Identification of areas within or adjacent to the site, where the recep-
tors might occur and thus be exposed to contamination
r Their general life history requirements relevant to potential contaminant
exposure (e.g., where they breed and their general feeding behavior)
r Potential exposure pathways of receptors given the general charac-
teristics of the site, contamination, and receptors
The site contamination information incorporated into the initial problem
formulation is dependent on how far site investigation has progressed prior
to initiation of the ecological risk assessment. In some cases, there has been
extensive sampling and analysis of site media (e.g., surface water, soil, ground
water), and not only is there information available regarding the contaminants
present, but the concentrations of the contaminants are frequently known. In
other cases, the contaminant information is limited to reports of which chem-
icals were used or disposed of at the site. At a minimum, the initial concep-
tual site model must identify the types of contaminants of potential concern
(e.g., metals, volatile organic compounds, pesticides) so that ecological recep-
tors, pathways (e.g., ingestion, inhalation, or dermal contact), and types of risk
(e.g., acute toxicity, food web magnification) can be included in the model.
The final component of the conceptual site model is a description of the
migration pathways present at the site. Identification of potential pathways
allows the tracking of the contamination as it moves from a source to an eco-
logical receptor. The most common migration pathways at hazardous waste
sites that can affect ecological receptors are groundwater, soil erosion, over-
land flow, and river/stream flow. Volatilization and aerial dispersion can, in
some cases, represent a concern for ecological risk, but it is rare and generally
limited to confined conditions, such as beaver lodges or burrows of terrestrial
animals. Any of these mechanisms can transport contaminants from their
source to critical ecological habitat and result in significant exposure and risk.
A simplified example conceptual site model of a common hazardous waste
site (buried waste) is depicted in Figure 7.2 and a more complex example is
included in the AJ Gold Mine case study (Section 7.2.9).
The second component of the problem formulation step, establishing ecologi-
cal endpoints, was an innovative breakthrough in the development of ecologi-
cal risk assessment. In the early years of Superfund and other hazardous waste
programs, there was a reluctance to include and address ecological issues in the
remediation evaluation and planning due largely to the complexity of ecological
systems. Particularly to the geologists and engineers who typically directed the
early hazardous waste investigation, the number of ecological resources, inter-
relationship of receptors, wide diversity of receptor sensitivity, and complexity