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Webb Van Winkle and John Kadvany
affect exposure to, or effect of, the stressor. Measures generally have
unambiguous operational definitions and are accessible to credible
measurement and monitoring or prediction. Selecting measures
and estimating their values are the scientists’ primary input to risk
assessment.
A risk (or decision) criterion (or threshold, target, or benchmark)
is defined as the level or value for a measure above which (or
below which, depending on the measure) is thought to result in an
unacceptable level of risk (or protection). The choice of measures and
associated decision criteria is always a value-laden technical judgment
(Barnthouse 1992; Shrader-Frechette and McCoy 1993).
Potential examples in the context of 316(b) assessments help make
this hierarchy of five terms more meaningful.
• Management goal—To preserve aquatic organisms and the ecosystems they inhabit in waters used by CWISs
• Management objective—To preserve representative fish species in
waters used by CWISs
• Endpoint—Individual fish, cohort or year-class, population of
representative fish species
• Measure (and associated decision criterion)
• Exposure: Daily intake flow (e.g., 2 million gallons per day),
proportion of water withdrawn for cooling purposes (e.g.,
25%), intake approach velocity (e.g., 0.5 ft/sec)
• Effect: Equivalent adult loss (e.g., 500 fish), fractional loss (e.g.,
5%), population decline (e.g., 5% per year)
• Ecosystem and receptor characteristic: Waterbody type; lifehistory characteristics of the representative fish species
3.2 Two Roles for Modeling in 316(b) Assessments
The modeling process can play two roles in assessments of the effects
of entrainment and impingement on fish. The first role is the meat and
potatoes of modeling: hypothetical what-if scenarios. Examples of obvious
what-if scenarios are
• Comparing alternative levels of mortality resulting from entrainment and
impingement
• Evaluating alternative protection, mitigation, and enhancement (PM&E)
measures
Here the motivation is to characterize the potential impacts of mortality
resulting from entrainment and impingement per se and the potential
benefits of different PM&E measures.
Webb Van Winkle and John Kadvany
affect exposure to, or effect of, the stressor. Measures generally have
unambiguous operational definitions and are accessible to credible
measurement and monitoring or prediction. Selecting measures
and estimating their values are the scientists’ primary input to risk
assessment.
A risk (or decision) criterion (or threshold, target, or benchmark)
is defined as the level or value for a measure above which (or
below which, depending on the measure) is thought to result in an
unacceptable level of risk (or protection). The choice of measures and
associated decision criteria is always a value-laden technical judgment
(Barnthouse 1992; Shrader-Frechette and McCoy 1993).
Potential examples in the context of 316(b) assessments help make
this hierarchy of five terms more meaningful.
• Management goal—To preserve aquatic organisms and the ecosystems they inhabit in waters used by CWISs
• Management objective—To preserve representative fish species in
waters used by CWISs
• Endpoint—Individual fish, cohort or year-class, population of
representative fish species
• Measure (and associated decision criterion)
• Exposure: Daily intake flow (e.g., 2 million gallons per day),
proportion of water withdrawn for cooling purposes (e.g.,
25%), intake approach velocity (e.g., 0.5 ft/sec)
• Effect: Equivalent adult loss (e.g., 500 fish), fractional loss (e.g.,
5%), population decline (e.g., 5% per year)
• Ecosystem and receptor characteristic: Waterbody type; lifehistory characteristics of the representative fish species
3.2 Two Roles for Modeling in 316(b) Assessments
The modeling process can play two roles in assessments of the effects
of entrainment and impingement on fish. The first role is the meat and
potatoes of modeling: hypothetical what-if scenarios. Examples of obvious
what-if scenarios are
• Comparing alternative levels of mortality resulting from entrainment and
impingement
• Evaluating alternative protection, mitigation, and enhancement (PM&E)
measures
Here the motivation is to characterize the potential impacts of mortality
resulting from entrainment and impingement per se and the potential
benefits of different PM&E measures.