Environmental Engineering Reference
In-Depth Information
generate approximately 80 million tons of tailings (i.e., the remaining rock
after the gold has been extracted) over its life and the only feasible alterna-
tive was marine disposal of the tailings (see Section 10.3 for a discussion
of the AJ Mine EIS background). A primary environmental concern related
to this method of disposal was the effects of the tailings on the marine habi-
tat within and adjacent to the area of disposal; thus ecological risk assess-
ment was an  appropriate tool to predict impacts and compare alternatives
(Maughan et al. 1997).
The AJ Mine risk assessment did not exactly follow the process outlined ear-
lier (Figure 7.1). Many of the issues had been defined and the necessary ecolog-
ical investigations conducted as a result of the environmental analysis process
(particularly technical scoping) before the risk assessment was designated as
the chosen tool. Thus much of the initial problem formulation and some of the
screening-level assessment had been completed. However, the ecological end-
points had not been clearly identified and accepted by the stakeholders. Thus
evaluation of endpoints was a critical first step once risk assessment was des-
ignated as the primary tool to evaluate the impacts of mine tailings disposal.
7.2.9.1 EcologicalEndpoints
The AJ Mine risk assessment development of endpoints was facilitated by a
wealth of information collected for the EIS and the highly experienced and
dedicated technical advisory committee (TAC). Working with TAC members,
the ecological assessment/environmental impact analysis team established a
set of comprehensive assessment endpoints based on the following criteria:
r Ecological relevance. The chosen endpoint should be relevant to the
ecosystem being examined.
r Societal value. The endpoint should be of value to society.
r Environmental policy goals. Endpoints important to the public and/
or regulators should be considered.
r Susceptibility to the chemical or physical stressor.
Based on these criteria, five assessment endpoints were identified (Table 7.4).
At least one measurement endpoint was then developed for each assessment
endpoint based on the following criteria:
r Readily measured or evaluated. There should be protocols or meth-
ods currently available or easily adapted to evaluate the endpoint.
r Consistent with routes of exposure to assessment endpoint. The
route of exposure should be the same for interpretive purposes.
r Appropriate to the scale of the site. Impacts on an organism with a
large range are harder to tie to the site.
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