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These examples are not intended as an exhaustive list and serve merely as
illustrations to stimulate thinking about whether specific pathways warrant
evaluation.
The identification of relevant pathways is crucial to the evaluation process.
Only those pathways that have a potential to result in transport of contaminants
out of the site require consideration. Three components must be present before
any effects from COC are anticipated:
1. There must be a stressor. In the context of the UTM, a stressor would be
a COC associated with the dredged material within a CDF.
2. There must be a receptor. In the context of the UTM, a receptor could be
a person, wildlife, standard, or other receptor that could be adversely
affected by the stressor.
3. There must be a complete exposure route by which a stressor (COC) can
come into actual physiological contact with a receptor (ROC).
In order to determine the need to evaluate a pathway, it is important to clearly
identify all three elements: the stressor(s), the receptor(s), and the exposure
route(s) that connect them. The absence of a complete exposure route is one basis
for early elimination of a pathway(s) and stressor/receptor set(s) from further
consideration, so that the process can focus on situations that might reasonably
constitute a potential risk. This is the opportunity to focus questions upon issues
of real concern. Because the scoping process is so fundamental to the conduct
and acceptance of the UTM evaluation, it is important that Federal and State
agencies, stakeholders, and the general public have meaningful participation in the
scoping process.
The rationale for carrying, or not carrying, each pathway into the tiered
evaluation should be documented, and a list of pathways to be evaluated should
be developed at this point.
3.3 Compilation of Information
A separate Tier I evaluation should be conducted for each relevant pathway to
be evaluated, because each pathway has specific characteristics. However, the
Tier I evaluation process is very similar for every pathway. The generic Tier I
evaluation process is described here and referenced as the basic process for
conducting the Tier I evaluation in the detailed chapters on each of the pathways.
Much of the existing information used in Tier I evaluations of one pathway will
also be useful in evaluation of other relevant pathways. Therefore, whichever
pathway is evaluated first will require the greatest Tier I effort, and Tier I
evaluations of subsequent pathways will build upon and use much of the same
information, requiring less effort.
Even if it is clear from the outset that the evaluation of a particular pathway
must be carried to higher tiers, Tier I should be conducted for each pathway. This
3-5
Chapter 3
Initial Evaluations
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