Generally, this framework can be applied to a variety of circumstances; however, in this context it provides:
- a qualitative method for evaluating a number of sites and design options
- a process for evaluating the nature and magnitude of the threat (or series of threats) posed to other resources by a poorly constructed aquaculture operation.
It is important to use a clear and relevant framework to assess risk. Risk assessments examine the likelihood of an environmental impact and the consequences of that impact, and should include the certainty with which the level of risk can be assigned to a particular development.
Once the level of likelihood and consequence for an action has been identified, an assessment matrix such as the one below can be used to determine the level of risk.
The environmental consequences may be qualitatively described as follows.
The likelihood may be qualitatively described as follows.
Undertaking the risk assessment
Section 2 lists characteristics of the site that should be considered in a risk assessment and included in the detailed site report (see Section 4). These characteristics are:
- topography
- geology
- soils
- groundwater
- acid sulfate soils
- sensitive environments
- local and regional land use
- separation distances.
In addition, the nature of the proposed operation will determine the level of risk of environmental harm. The following questions should also be considered:
- Is the production system different in salinity from the underlying groundwater?
- What is the proposed intensity of operation? (This may affect the nutrient load in the production waters.)
- What is the time period of the production season?
- What is the scale of the proposed operation? (The greater the volume, the greater the potential impact of leakage.)
A risk assessment should evaluate farm layout and options to achieve the best practicable design for the proposal and should be based on the design standards and management strategies that are to be adopted.
Based on the risk assessment, actions that result in serious, large-scale or long-term consequences such as serious contamination of regional groundwater or complete alteration of ecosystem functioning, would normally be considered to involve a high or extreme risk, even if it is unlikely that the action will occur.
In contrast, actions with minor, transient or localised impacts, such as temporary or reversible damage to ecosystem functioning would generally involve low or medium risk. The following generalised examples further detail how the categories may apply to various consequences in the risk assessment process:
Low risk:
- Containment area <50ha
- Freshwater aquaculture
- Soils suitable (e.g. clayey sands (SC), inorganic clays (CL))
- Regional groundwater unsuitable for other uses
- Sufficient separation distance to sensitive environments
Medium risk:
- Containment area >10ha
- Marine aquaculture
- Soils suitable (e.g. clayey sands [SC], inorganic clays [CL])
- Regional groundwater saline or unsuitable for other uses
- Sufficient separation distance to sensitive environments
- Containment area <0ha
- Freshwater aquaculture
- Soils suitable (e.g. clayey sands [SC], inorganic clays [CL])
- Regional groundwater used for irrigation or potable water
- Sufficient separation distance to sensitive environments
High risk:
- Marine aquaculture
- Soils suitable (e.g. clayey sands [SC], inorganic clays [CL])
- Regional groundwater used for irrigation or potable water
- Sufficient separation distance to sensitive environments
Extreme risk:
- Containment area >5ha
- Marine aquaculture
- Soils unsuitable (e.g. poor-grade gravel [GP])
- Regional groundwater used for irrigation or potable water
- Sensitive environments in close proximity
Applying the outcomes of the risk assessment:
Use the outcome of the risk assessment to determine the acceptable permeability performance of the pond liner. See Appendix 4 for a discussion of calculations for permeability, time of passage through the liner, and loss from a pond.
The criteria for acceptable risk are as follows:
Extreme risk 1– zero loss 2
High risk – zero loss over the maximum likely filled period of the containment structure
Medium risk – <1 ML/ha loss over the maximum likely filled period of the containment structure
Low risk – <5 ML/ha loss over the maximum likely filled period of the containment structure
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