Dames & Moore, 1999 - USDA Forest Service

7.2.2.6 Conceptual Site Model
The CSM integrates sources, release mechanisms. transpon media, transfer mechanisms, and complete
receptor exposure pathways. For this Baseline ERA, three relatively distinct exposure sources form the
bases of the CSM. These sources are: 1) surface water and sediments, 2) tailings soils, and 3) seep water.
The ecological CSM for this site (Figure 7.2-1) provides a pictorial representation of the pathways of
potential PCOC movement h m primary sources to secondary, and tertiary sources and receptors. It is
these relationships that drive potential environmental and exposure risks, as well as risk management
decision making.
7.23 Analysis
7.23.1 Assessment and Measurement Endpoints
Definitions of endpoints and methods of endpoint selection generally follow the guidance and draft
guidance provided by EPA (1989, 1994). To determine if adverse impacts have occurred or are occurring as
a result of constituents released by past mining activities, it is necessary to determine which assessment
endpoints will be used in the evaluation and to understand how the various measurement endpoints relate to
the assessment endpoints in the overall weight-of-evidence approach adopted herein.
The process of endpoint selection begins with identification of risk management goals for environmental
components and ROC that may be susceptible to chemical substances in the environment. In general. the
goal for this site is to protect the populations, communities, and ecosystems that may be exposed to site-
related PCOCs.
Assessment Endpoints
Assessment endpoints are general, large-scale expressions of environmental components or characteristics
. that may be at risk and, therefore, require protection. Although related and highly interdependent,
measurement and assessment endpoints are not the same. In general, measurement endpoints are actual
measurements of chemical or biological parameters that are used to evaluate the assessment endpoints. This
evaluation then forms the basis for extrapolation of results to higher levels of organization or complexity.
The assessment endpoints identified for this investigation are:
Decline in health and viability of populations of avian carnivores
Decline in health and viability of populations of terrestrial mammals
Decline in health and viability of populations of fish and other aquatic receptors
These assessment endpoints are evaluated specifically with information obtained fiom measurement
endpoints (below) to determine if reduced survival, impaired reproduction, or growth inhibition in local
populations and communities are likely. The assessment endpoints were evaluated as the no observed
adverse effect level (NOAEL) fiom toxicity benchmarks, guidelines, or toxicity reference values (TRVs)
for endpoints having potential effects on populations (i.e., growth, reproduction, development) of plants
or animals.
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17693-00501 Wuly 27.1999.5:16 PMDRAFT FINAL RI REPORT