Marine Outfalls 32.6 Environmental Monitoring 737
Part C | 32.6
tics combine to define our philosophy for environmental
monitoring.
Environmental monitoring programs should be designed to establish cause-and-effect between the discharge and the environmental response. The approach
we favor uses weight-of-evidence. This simply means
applying different techniques and approaches to the
same problem. If the answers that they provide are
consistent with what might be expected from such discharges, then we have greater confidence in the overall
result. Our weight-of-evidence is a three-pronged attack, which is detailed in the following section.
Most countries have guidelines (or licence conditions) that reflect the values that need to be protected.
These values include social, public health and environmental aspects. While some values may be subjective,
many can be quantified in terms of safe levels of
contaminants that can be discharged. There is a tacit
assumption, that by adhering to these concentration limits, there will be no irreversible damage done to the
marine environment.
The most critical task in undertaking a monitoring
program to quantify environmental impacts of a marine
outfall is to ask the right questions. This requires an understanding of what is being discharged, what effects
these discharges are likely to have on the marine environment and the level of change that we are willing
to accept. An answer to the wrong question, no matter
how accurate is that answer, will not allow impacts to
be quantified.
Environmental monitoring programs must be scientifically robust and defensible. We must test a hypothesis and gather empirical evidence to support (or
disprove) the hypothesis. The experiment must be repeatable, cover a range of conditions and, in theory,
repeated experiments should arrive at the same conclusion. Marine outfalls may be contentious and the
monitoring program may need to be defended. One
way in which this can be done is via peer review of
the work and publication of the results in a reputable
journal.
Conditions of approval for a marine outfall are often
reliant on predictions. The objectives of an environmental monitoring program should include the verification
(or otherwise) of those predictions and whether the
environmental values have been maintained. Further,
the program should include a mechanism by which
problems identified in the monitoring program can be
rectified or mitigated.
The Three-Pronged Attack
An approach to collecting weight-of-evidence for impact assessment includes three components. These are
detailed below.
Sources of Contaminants. There are many potential
sources of contaminants discharged to marine waters,
including rivers, sediments (as both a source and sink),
private and industrial outfalls, illegal dumping, and
coastal wastewater treatment plants. An important consideration to environmental monitoring is separating the
relative contribution of an outfall from contributions
from the other sources. It may be possible to characterize (and isolate) the different sources via the types,
concentrations, and variability of contaminants being
discharged from each source.
Marine organisms may be impacted if exposed to
wastewater. Toxicity testing is a technique used to determine the concentration of substance which is likely
to harm to marine organisms. Whole effluent toxicity
(WET) testing examines whether a toxic response is
identified when an organism is subjected to the complex wastewater matrix.
If toxicity testing is carried out using a single test organism, it is then inferred that all marine organisms will
exhibit the same toxic response. This is not necessarily the case and multiple organisms are recommended
for toxicity testing: different organisms display different responses to different substances at different stages
in their life cycle. Ideally, a range of fish, invertebrates, and algae at different stages in their life cycle
should be considered for toxicity testing. Toxicity tests
can be either acute or chronic and both types of tests
should be included. The former determine the concentration of wastewater that is lethal to the test organism.
Chronic testing examines the reduced capability (e.g.,
impaired development or reproductive ability) of the
test organism.
Movement of Wastewater. Once we know what is being discharged, we determine the path that the wastewater will take after discharge and how dilute it becomes.
Emery and Thompson [32.36] describe many techniques
to measure and/or monitor the physical properties of the
marine environment.
Instrumented moorings provide excellent temporal
coverage although the horizontal spatial coverage is
limited by the number of such systems that the monitoring program can afford to deploy. Remote sensing
provides good spatial coverage of the region, although
in general, the temporal scales are much longer than
those associated with the movement of wastewater
plumes.
Numerical modeling enables us to predict how the
wastewater will react to different marine conditions and
to changes in the volume or method of discharge. It is
critical to calibrate and validate any numerical model
to ensure confidence in the results under existing conditions and for future scenarios. Coupled with this is
Part C | 32.6
tics combine to define our philosophy for environmental
monitoring.
Environmental monitoring programs should be designed to establish cause-and-effect between the discharge and the environmental response. The approach
we favor uses weight-of-evidence. This simply means
applying different techniques and approaches to the
same problem. If the answers that they provide are
consistent with what might be expected from such discharges, then we have greater confidence in the overall
result. Our weight-of-evidence is a three-pronged attack, which is detailed in the following section.
Most countries have guidelines (or licence conditions) that reflect the values that need to be protected.
These values include social, public health and environmental aspects. While some values may be subjective,
many can be quantified in terms of safe levels of
contaminants that can be discharged. There is a tacit
assumption, that by adhering to these concentration limits, there will be no irreversible damage done to the
marine environment.
The most critical task in undertaking a monitoring
program to quantify environmental impacts of a marine
outfall is to ask the right questions. This requires an understanding of what is being discharged, what effects
these discharges are likely to have on the marine environment and the level of change that we are willing
to accept. An answer to the wrong question, no matter
how accurate is that answer, will not allow impacts to
be quantified.
Environmental monitoring programs must be scientifically robust and defensible. We must test a hypothesis and gather empirical evidence to support (or
disprove) the hypothesis. The experiment must be repeatable, cover a range of conditions and, in theory,
repeated experiments should arrive at the same conclusion. Marine outfalls may be contentious and the
monitoring program may need to be defended. One
way in which this can be done is via peer review of
the work and publication of the results in a reputable
journal.
Conditions of approval for a marine outfall are often
reliant on predictions. The objectives of an environmental monitoring program should include the verification
(or otherwise) of those predictions and whether the
environmental values have been maintained. Further,
the program should include a mechanism by which
problems identified in the monitoring program can be
rectified or mitigated.
The Three-Pronged Attack
An approach to collecting weight-of-evidence for impact assessment includes three components. These are
detailed below.
Sources of Contaminants. There are many potential
sources of contaminants discharged to marine waters,
including rivers, sediments (as both a source and sink),
private and industrial outfalls, illegal dumping, and
coastal wastewater treatment plants. An important consideration to environmental monitoring is separating the
relative contribution of an outfall from contributions
from the other sources. It may be possible to characterize (and isolate) the different sources via the types,
concentrations, and variability of contaminants being
discharged from each source.
Marine organisms may be impacted if exposed to
wastewater. Toxicity testing is a technique used to determine the concentration of substance which is likely
to harm to marine organisms. Whole effluent toxicity
(WET) testing examines whether a toxic response is
identified when an organism is subjected to the complex wastewater matrix.
If toxicity testing is carried out using a single test organism, it is then inferred that all marine organisms will
exhibit the same toxic response. This is not necessarily the case and multiple organisms are recommended
for toxicity testing: different organisms display different responses to different substances at different stages
in their life cycle. Ideally, a range of fish, invertebrates, and algae at different stages in their life cycle
should be considered for toxicity testing. Toxicity tests
can be either acute or chronic and both types of tests
should be included. The former determine the concentration of wastewater that is lethal to the test organism.
Chronic testing examines the reduced capability (e.g.,
impaired development or reproductive ability) of the
test organism.
Movement of Wastewater. Once we know what is being discharged, we determine the path that the wastewater will take after discharge and how dilute it becomes.
Emery and Thompson [32.36] describe many techniques
to measure and/or monitor the physical properties of the
marine environment.
Instrumented moorings provide excellent temporal
coverage although the horizontal spatial coverage is
limited by the number of such systems that the monitoring program can afford to deploy. Remote sensing
provides good spatial coverage of the region, although
in general, the temporal scales are much longer than
those associated with the movement of wastewater
plumes.
Numerical modeling enables us to predict how the
wastewater will react to different marine conditions and
to changes in the volume or method of discharge. It is
critical to calibrate and validate any numerical model
to ensure confidence in the results under existing conditions and for future scenarios. Coupled with this is