Adaptive Management - Melbourne Port Extension, AUS
Location: Melbourne, Australia
Date: 2003 - 2009
Involved parties: Boskalis, Port of Melbourne Corporation
Technology Readiness Level: 9
Environment: Ports & Cities, Estuaries
Keywords: Adaptive Management, Adaptive Monitoring
The Port of Melbourne is the largest port in Australia, managing 37% of all Australian container traffic, with the ambition to increase container handling fourfold from 2 million at present to 8 million in 2035. In order to achieve this expansion, it is necessary to extend the port and deepen the entrance and navigation channels leading to it, thus improving access for container ships with a draft of up to 14 m.
There is also the unique nature in Port Phillip Bay. The bay measures approximately 2,000 km2, has a coastline of 264 km and is home to two marine national parks. From the very start, it was clear that the environmental component of the project was essential, and that many local residents had serious concerns about the impact of the work on biodiversity in the bay.
In order to maintain the position of the Port of Melbourne as Australia's largest container and general cargo port, the Port of Melbourne Corporation (PoMC) proposed a plan to make the port accessible for 14m drought vessels during all tidal phases. The project scope includes modifications to the Great Shipping Channel at the Entrance to the Bay, the South Channel, the approach channels to the Port and the Yarra River Channel.
The Port of Melbourne is uniquely located on Port Phillip Bay. It is the habitat for a range of fish species, small penguins, whales, dolphins and seals, as well as extensive sponge gardens, various cold-water corals and seagrass beds. For approximately 3 million local residents, it is an important recreational area. Due to this unique and sensitive environment, the deepening of the Port of Melbourne included significant environmental risks. In order to share the risks and optimize the solution, the Port of Melbourne Corporation chose early in the project for an alliance contract with a dredging contractor. By means of this agreement, all risks and profits of the project were equally shared between the PoMC and the contractor. After signing an Alliance Agreement with PoMC, Boskalis became an active partner of assisting PoMC in several necessary studies.
In order to reduce the environmental risks of the project and to obtain the environmental permits, extensive investigations on technical and ecological aspects of the project were carried out. To get the permit for the project, an Environmental Effects Statement (EES) about the environmental impact of the project was required. As this statement was at first rejected by the government, a Supplementary Environmental Effects Statement (SEES) had to be provided. During the development of the latter, all relevant issues and processes concerning the environment in the bay were identified to get a good understanding of the system. The listed issues were further analysed by means of literature studies, modelling, experiments and a full-scale trial dredging. After these analyses, several risk assessments were performed to quantify the risks of each issue.
The risks that could not be excluded by the design of the project were controlled by means of monitoring and management. Mitigation measures were taken where possible. An Environmental Management Plan (EMP) was developed to control environmental impacts during the execution of the project by means of monitoring. A large part of the EMP concerned elevations in turbidity induced by the dredging works. The research conducted during the SEES provided, among others, realistic turbidity limits. By comparing the measured turbidity level with these limits, the work method of the hopper dredger could be adapted when and where necessary.
Planning and design
The following steps were taken in order to compose the Supplementary Environmental Effects Statement (SEES). The Commonwealth and State of Victoria legislation and policy provided a foundation for the evaluation framework used to assess the environmental effects of the project. Best practice and the principles of ecologically sustainable development (ESD), as defined through legislation and policy, have been the key drivers for the SEES investigations. The principles of ecologically sustainable development encompass the precautionary principle, the principle of equity and the principle of conservation of biological diversity and ecological integrity.
In order to guide investigations, the SEES assessment guidelines set out evaluation objectives identifying the desired outcome of the project in terms of the relevant ecological, social and economic indicators. These evaluation objectives have been adopted by PoMC with an additional objective focusing on the environmental footprint. These have been translated by PoMC into evaluation criteria to be used in the environmental impact and risk assessment process. The identified criteria link back to relevant legislation and policy. Together the evaluation objectives and associated evaluation criteria provided a qualitative framework to evaluate the project and its effects. This structure is outlined in the yellow area of the flow chart below.
After the evaluation framework had been determined, the project development process started. This included the channel design, the dredging technology, the dredging strategy and the dredged material management (see blue area on the right in the flow chart). Once these were established on a preliminary bases, the Environmental Impact and Risk Assessment process started. The system of the bay was better understood by identifying all relevant issues and investigating them by means of modelling and analysis. Based on these investigations, the environmental effects were predicted and risk assessments were carried out. Management and mitigation measures were included for the effects and risks that were not acceptable and could not be excluded. If nonetheless risks remained unacceptably high, a feedback mechanism was included by which the project design and dredging technology and strategy were adapted. Subsequently the whole cycle was repeated to check whether the new design and work method were acceptable risk-wise. Finally the Environmental Management Plan (EMP) was drawn up in order to control the execution of the project on the basis of monitoring.
At the start of the Environmental Impact and Risk Assessment Process, the key issues relating to the ecological assets, social values and economic users of the bay were identified and investigated. This led to conceptual models about the system of the bay. These conceptual models show how the system works and how it may be affected by the construction works. A conceptual model on the ecology of the bay can be seen in the figure.
The key pathways conceptualized in this figure include:
- Creation of a turbidity plume that may reduce the amount of light available to primary producers, such as sea grass and phytoplankton, and reduced visibility for some animals including fish and sea birds (yellow lines);
- Suspension and subsequent settlement of sediment that may clog biological structures and bury some biota on the seabed (brown lines);
- Mobilization of contaminants that may have direct toxic effects on biota or cumulative effects via bio-accumulation through the food chain (orange lines);
- Removal of rock at the Entrance that may result in some loose rock material falling and moving around the area, damaging shallow and deep reef biota (grey line);
- Mobilization of nutrients that may stimulate excessive phytoplankton growth (blue line), which at high levels of biomass can reduce the amount of light available to primary producers on the seabed (yellow line) and after dying out may lead to oxygen depletion;
- Changes in bathymetry that interact with tides, waves, currents and sediment transport, which in turn may influence coastal forms and coastal habitats.
These conceptual models were part of the input for the risk assessments.
The development of the SEES document included an environmental impact and risk assessment. The risk assessments were conducted in a multi-disciplinary team, in an iterative process, consisting of the following steps (see also figure):
- Establish the context (project description and project development process)
- Identity the risks
- Analyse the risks
- Formulate a risk treatment strategy
- Implement the risk treatment strategy
Starting points for the environmental impact and risk assessment were the design (context), dredging technology, dredging strategy and dredged material management. In the impact assessments several investigation were carried out including the examination of historical data, modelling of data trends and literature review. In the impact assessment, the uncertainties associated with the natural variability were also assessed. Most ecological processes could be dealt with by assessing the likelihood of a potential impact to occur and the magnitude of any consequence, and where the associated risk was unacceptable, by implementation of physical works or environmental management measures. If the risks could not be mitigated to a satisfactory extent, the design and/or dredging technology and strategy would be adapted and the process would start over again, until the results complied with the evaluation framework.
During the risk assessments, the following assets were defined:
- Ramsar wetlands,
- marine parks,
- shallow reefs,
- little penguins,
- pied cormorants,
- sea grass,
- aquaculture fisheries, and
- bay users.
The figure at the right gives a complete overview of all sensitive areas/receptors.
At first, also an increase of nutrients input into the bay, loss of heritage, economic loss and reduction of social values were seen as risks. After comprehensive investigations, however, these aspects were found to have a low probability of occurrence, to have negligible consequences, or to be easy to mitigate. The nutrients in the bay, for instance, have been subject to extensive research. The likely impacts and uncertainties associated with nutrient cycling have been modeled quantitatively with data from historical studies, field studies, baseline measurements and baseline bio-availability experiments. The results have been used as the basis of the formal assessment of the potential environmental impacts on the risks of dredging to algal blooms, nutrient cycling and denitrification. During a dredging trial, the impact of the released nutrients in the bay was analysed. This led to the conclusion that the impact of nutrient release in the bay could be identified as low risk.
Finally three major risks were identified that could not be avoided by adapting the work method or the design within economically acceptable bounds.
- Rocks falling on the deep reef habitat at the Entrance of Port Phillip Bay.
- The migration of contaminated material from the Yarra River into the Bay.
- An increase in turbidity as a result of dredging which could cause damage to the unique flora and fauna of Port Phillip Bay.
These threats were subject to additional investigations.
The following mitigating measures were identified for the three major threats mentioned above:
Rocks falling on the deep reef habitat at the Entrance of Port Philip Bay
The deep reef habitat (canyon) at the entrance of the bay consists of precious coral. If rocks fall on these coral reefs, they will be damaged. The main cause of this threat are leftover rocks (spill) which fall over the edge of the deep reef, driven by currents and wave action. To mitigate this threat, a modified draghead (ripper draghead) was developed, designed to minimize the spill while cutting the rock. The ripper draghead was further optimized with the help of lab tests. Quarry tests were done to improve the cutting behaviour of the draghead. Dredging was done in a pre-determined pattern, thereby avoiding that cut pieces would be pushed towards the edges of the canyon. After several passes of rock cutting with the ripper draghead, another cleaning draghead was dragged along the same route to remove the remaining loose rocks. See the photos of the lab test and the cleaned bed to the right.
Dispersion of contaminated material from the Yarra River
Toxicity tests conducted in the Yarra River as part of the SEES determined that mud in these areas was contaminated. The most important threat of this sitation was the possible release of the contaminated material during dredging, transport and deposition. The mitigation for this threat consisted mainly of an adapted work method and a dedicated design of the disposal area. To make sure all contaminated silt was removed, the geometry and the draghead position were closely monitored. A bunded area was designed for the deposition of the contaminated material. It was placed in this area with a diffuser near the bottom to avoid mixing with the ambient water. Eventually, the contaminated material in the bunded area was covered with a clean sand layer.
Increase in turbidity as a result of dredging which could cause damage to the unique flora and fauna of Port Philip Bay
During dredging works, fine sediment may be released in the water, resulting in increased turbidity. The sediment particles in the water column hamper light penetration, which may lead to decreased primary production by photosynthetic organisms, particularly benthic plants, such as seagrass. This reduction in productivity and biomass may indirectly affect other biological components in the Bay system, e.g. via reduced food availability to grazers and less habitat for juvenile fish. The impact pathway of turbidity is shown in the figure to the right.
The physical relation between turbidity and light attenuation is poorly known. The biological effects of light attenuation are even more complex and difficult to determine. In order to obtain more insight into the biological effects of turbidity, extensive research has been conducted. This research led to realistic and scientifically based turbidity limits.
The research involved the following steps:
- Investigate impact pathway – assess plume consequence
- Determine distribution & condition of plant species
- Model plume extent, concentration and duration
- Predict light climate – natural & during dredging
- Assess biological response of plant species to reduced light conditions
- Estimate impact
- Assess impact against project acceptability criteria
- Define mitigation & management options
- Draft monitoring program
The first five points were investigated using literature studies, field investigations and modelling and are described in more detail below.
The distribution and conditions of plant species and the plume extent, the concentration and duration were determined by means of an impact study. First the turbidity plume is modelled, including the concentration and longevity of the plume. The turbidity dispersion model was validated with a dredging trial conducted during the development of the SEES. Within the boundaries of the modelled plume, the amount and type of plant species were determined. This led to estimated light reduction in the vicinity of the plants during the construction works.
The biological response to the reduced light conditions is determined from literature and with the help of shading experiments. Two types of shading experiments were carried out on Heterozostera and Amphibolis (seagrass) and Ecklonia (kelp) in Port Philip Bay:
- Shade for an intermediate period of time (e.g. 2 months): the plant is under stress, but can recover.
- Shade until mortality, or at least three months.
From these investigations, the biological impact is estimated. This includes the short-term bay-wide effects and the long-term localized effects on ecological processes. Yet, a lot of uncertainties remain, such as the long-term trends in distribution and abundance of plants, the variation in plume exposure and the response to seasons and other environmental variables. In winter, for instance, there is significantly less light intrusion in the water column than is summer.
The results of this modelling and analysis were used together with the risk assessment process to evaluate the potential environmental effects. The effects were considered in relation to the adopted evaluation objectives and associated evaluation criteria. The process was iterative and the project plan was changed in response to adverse findings.
Environmental limits were set for the management of the plume, to ensure that short-term adverse impacts were minimized and there were no long-term adverse impacts on the key functions of the Bay. The environmental limits were based on the known impacts, based on modelling and field investigations, of increased suspended sediment concentrations and known concentrations that marine organisms can tolerate without severe or lasting impacts.
A significant concern was the impact of elevated turbidity on seagrass health and survival. Turbidity thresholds were established that allow for minimum light requirements to sustain healthy seagrass meadows in the most vulnerable areas of Port Phillip Bay. An evidence based numerical criterion, (supported by ecological judgement) was established: the minimum light requirement for seagrass maintenance was expressed by 15% of the surface irradiance, at 3 m depth during 50% of the time. Based on this criterion, a statistical analysis of the results of the turbidity dispersion model determined the sediment concentration limits. As biological turbidity criteria are usually expressed in the physical measurable quantity of total suspended solids (TSS in mg/l), but these have been converted to the site-specific optically-measurable quantity of turbidity in NTU, as these are directly measurable. The conversion rate has been determined with help of local experiments.
Conclusive SEES investigations
To conclude, the SEES investigations have:
- Identified relevant threatened species and ecological communities, migratory species and Ramsar wetlands under Commonwealth and state legislation and have considered these as ecological assets in the environmental impact and risk assessment process.
- Used the results of the environmental impact and risk assessment to provide feedback to the project design, so as to minimise impacts on marine and terrestrial threatened species and ecological communities, migratory species and Ramsar wetlands. This includes modifications to the dredging strategy in response to potential risks to the protected fish species in the Yarra River and seasonality of other species.
- Considered the conservation of biodiversity in the project development process, in the environmental impact and risk assessment and in the development of the EMP to address residual risk that could not be eliminated otherwise.
Boskalis assisted PoMC with the Supplementary Environmental Effects Statement (SEES), clarifying and justifying equipment selection, participating in the rock fall assessment, fauna mapping in the Entrance and sampling of contaminated soil. Boskalis also cooperated with PoMC in developing the Environmental Management Plan (EMP). Overall, Boskalis’ participation in the SEES was crucial to optimize work methods in order to meet strict environmental controls and intense government scrutiny.
The final risk assessment of the SEES included the findings of the environmental impact assessments and formed the basis for the environmental monitoring plan (EMP). The EMP is the governance document of the Channel Deepening Project, which applied to all capital works and environmental monitoring programmes. Both the Victorian and Australian Federal Ministers of Environment approved the EMP which detailed the environmental requirements, in particular equipment standards, monitoring programmes, regulatory control, reporting requirements and communication measures. Communication was very important for the success of this project, both internally between Client and contractor and externally with the public.
Two different monitoring programs were executed. One is the compliance monitoring, being continuous daily turbidity monitoring. If the monitored turbidity exceeded the limits, the work method could be adjusted. In addition PoMC conducted a bay-wide monitoring programme focused on key species, habitats and ecological processes. The data from this programme was reviewed every six months and if necessary were used to adjust the environmental limits (see figure).
Changes to the project had to follow a strict procedure to manage and identify consequences. This applied to changes to the project schedule, work methods, environmental monitoring response levels, project description and dredging technology. The change management process also included a re-assessment of the risk and a check on compliance with the legal requirements; occasionally additional turbidity modelling was required to support the risk assessment. If the change required the EMP to be revised, the Government had to be notified and approval was required for major revisions.
Compliance monitoring was meant to show that all criteria and requirements were met. All vessels were equipped with vessel tracking systems to ensure compliance with dredged material management demands, which included limits to the quantity of material to be dredged and to the vertical and horizontal tolerances, as well as to the time frame for dredging at certain locations (e.g. not during spawning and migration periods or peak holiday seasons). Turbidity and vessel position were monitored automatically and transmitted to a database at the office. Boskalis managed the data flow and guarded the data integrity, which was a fully transparent process that was audited regularly. The data could be visualised via a web page. Strict requirements demanded the immediate reporting in case of threshold exceedances (e.g. turbidity), non-compliances and other incidents and hazards.
Compliance for turbidity was based on NTU values of 6-hourly Exponentially Weighted Moving Average (EWMA). Based on the measured turbidity results, the work method of the TSHDs could be adjusted whenever necessary. For management purposes, two response levels were defined to enable early and consistent response if the measured turbidity levels were increasing. The level 1 response was typically an investigation into the nature and causes for the trigger, level 2 required management actions to reduce suspended sediment concentrations.
Typical management actions of this kind were moving the dredger to another location, dredging with no overflow, or dredging at reduced speed. In fact, this was done pro-actively, such that the actual environmental limit would never be reached. Adjustments to the work method were only necessary during strong winds when elevated levels of turbidity occurred and it was decided to move the TSHD to a different dredging area.
A video survey of the Entrance was conducted as part of the compliance monitoring scheme. A clean-up procedure was applied at the Entrance, to ensure that any residual rock was removed and could not damage the sponges and corals. A special data analysis tool applied to the vessel tracking system was used to prove that the operations proceeded in accordance with the EMP.
The contaminated silt in the Yarra River was dredged using a TSHD. Extensive survey efforts and draghead tracking was required to prove that 100% of the contaminated silt had been removed. No mixing with the ambient water occurred, no dredged silt was found outside the disposal area and water quality was not affected.
The total costs of the compliance monitoring programme amounted to about 10% of the construction costs.
Bay Wide Monitoring Program
PoMC conducted several bay-wide monitoring programmes to provide broader information on the status of key species, habitats and ecological processes in the Bay. Nine such programmes were developed, concerning Seagrass, Water Quality, Nutrient Cycling (denitrification), Contaminants in Fish, Algal Blooms, Little Penguins, Fish Stock & Requirement, Ramsar Wetlands and Plume Intensity & Extent, respectively. All of the programs, except the Plume Intensity & Extent program, monitored key assets and ecological processes. The results of these monitoring programmes were reviewed quarterly and laid down in a Bay-wide Monitoring Report. This review provided a ‘snapshot’ of the status of the bay as a whole and was incorporated into the six monthly environmental management reviews.
As part of the Bay-wide Monitoring Program, Boskalis conducted the Plume Intensity & Extent monitoring programme. This was an overarching programme to confirm that the plume during dredging was not significantly different from the modelled conditions underlying the risk assessment. Turbidity was measured by sailing tracks in each dredging area during at least 14 consecutive days. This meant that plume monitoring was conducted during 117 days, covering a distance of 4,400 km. A streamer with 2 or 3 turbidity sensors was towed along straight tracks across the dredging area. The streamer could be automatically raised and lowered in the water column by means of a winch. The monitoring results were reviewed every 6 months by comparing the field data with the model predictions. Differences between modelled and actual plume characteristics were monitored and assessed in terms of risk to assets from turbidity. Thus turbidity limits could have been adjusted to meet the criteria, though in reality none of the environmental limits had to be adjusted after these reviews.
Dredging performance was compared to the limits set by the EMP, which was reported weekly to PoMC. However, exceedances, non-compliances and other incidents and hazards were required to be reported immediately, also to the Government. An extensive audit schedule was put in place by the Government with 12 audits to check compliance with the EMP of the vessels, the different dredging activities and the monitoring. Only a few minor non-conformities were found.
Furthermore, PoMC had the obligation to provide quarterly and annual reports to the Government. These contained a summary of all construction activities, project progress, communications with the public and media, notification of the Government, training, reports, incidents and the results of all monitoring programmes, internal and external audits, risk assessments and management reviews. All notifications and reporting to the Government were publicly accessible through the websites of both PoMC and the Government.
Operation and Maintenance
After project completion, no adaptive management and monitoring was necessary anymore.
The main lesson learned from this project are centered around:
- Alliance contract
- Risk assessments
- Work method
- Turbidity limits
- Adaptive Management Strategies Strategic and Operational Objectives
This project had a high risk profile related to the sensitive environment, but this risk could be mitigated in collaboration with the contractor. To ensure input of highly qualified construction expertise, early contractor involvement is necessary and can be achieved with an alliance contract. This project proved the effectiveness of early contractor involvement under this type of contract. The input of the contractor was mainly related to the work methods and input to various studies. The results of this early contractor involvement were incorporated into the SEES and EMP, which were both part of the environmental approval process for the Channel Deepening Project. Boskalis’ technical solutions and innovations were all critical in achieving the desired depths and expansion, and ensuring the Bay’s unique natural environment. Main lesson learned is that early contractor involvement and modern contracts contribute to a higher quality of the construction works. In this case the combined efforts of the Client PoMC and the contractor in an Alliance Contract led to nearly full compliance and successful completion of the project.
The risk assessment was a very open process in which the risks were quantified, so that a trade-off could be made between different assets. The government has to provide guidelines on which impact is still acceptable and which is not. This type of risk assessments cost quite a lot of time, but this ensured the accuracy of the process. Another advantage was that this enabled a better informed and more effective communication with the public.
This project showed that work method adjustment can be a very good instrument to mitigate effects. This includes controlling and managing the measures taken, hence the impact. For this project the work method was adjusted to reduce the impact of turbidity, to control rock fall at the entrance and to remove the contaminated material.
It is very important that the environmental limits such as turbidity limits are based on the local situation. In this project, the limits were defined considering the local flora and fauna, such as local meadows of seagrass. The model-based approach yielded realistic and workable criteria which worked very well to manage the turbidity levels. Due to the 6-hourly EWMA the signal was smooth and short peaks were less important, which made process management more comfortable. Two response levels were defined to manage the dredging process and to make sure that the actual turbidity limits would never be reached. These two response levels worked excellent and the turbidity limits were never exceeded.
Background turbidity remained an important issue, which was still not completely covered. Even in this project where extensive research was conducted, including the background turbidity, the distinction between background turbidity and dredging-induced turbidity was sometimes very small. To get a better understanding of the background turbidity one has to understand and know the system thoroughly. Therefore much attention must be paid to the baseline study in order to have sufficient information about the background turbidity, especially because it depends on variable and dynamic aspects, such as season, weather etc.
In order to achieve a high data capture rate, the buoys need to be actively maintained. They should be taken out of the water at least once per week for cleaning and the data should be regularly verified and calibrated.
The monitoring for validating the model proved very useful. Data are indispensable to validate the model, like it is for other parts of this project, such as the relation between mg/l and NTU, and that between turbidity and light attenuation.
Reviewing the bay-wide monitoring scheme once every half year seemed a good frequency for the ecological response. The review should fit the asset monitored. The impact on a coral reef, for instance, will be more direct than the impact on penguins. The bay-wide monitoring program served as an extra to assess the status of the ecology of the bay, but it is not suitable to manage the dredging process from a turbidity point of view.
Communication is essential in environmental management and needs to be addressed explicitly in the EMP. All procedures should be clearly defined, correct and communicated in case of irregularities. The client should inform the public and the contractor should assist in this, mainly by informing the client. The procedures for the internal communication (between client, contractor and government) should be clearly defined, for irregularities as well as the regular process. This requires a transparent and open process. The PoMC did a very good job in communicating with the public. For example, they held press conferences every week, even if no-one showed up. They could do so, because they were kept well up to date about the processes by Boskalis.
Communication should also include the progress of the construction works. This is where the contractor can play a major role, as he has all the information regarding progress. Therefore he should provide the Client with this information via transparent and open communication.
Adaptive Management Strategies
Lessons on Adaptive Management are tabled for the 3 control& monitoring programs, along the Operational Objectives and other elements of the Frame of Reference.
Authorities Independent Control & Monitoring
Quantitative State Concept (QSC)
Spatial control zone
State government: approval of EMP. In case of a major revision of the EMP approval was required by the Depart of sustainability and Environment (DSE), and PoMC would seek advice whether these revisions require approval by the Commonwealth.
Long term - Owners Feedback Monitoring
Quantitative State Concept (QSC)
Spatial control zone
SEES: PoMC Environmental Policy: Port of Melbourne Corporation (PoMC) is charged with providing the strategic management of the operation and development of the Port of Melbourne and to ensure that this is done in an economically, socially and environmentally sustainable matter.
The Channel Deepening Project Team is commited to ensuring the project is undertaken in accordance with the following principles and objectives regarding the environment: minimise hard to the environmental through full compliance with the CDP Environmental Management Plan (EMP).
Baywide monitoring program: To support the management and mitigation measures, such as turbidity monitoring, a suite of Baywide monitoring programs have been developed to provide broader information on the status of key species, habitats and ecological processes in the bay. A total of nine programs have been developed:
The baywide monitoring programs are subject to an evaluation to identify any refinements and if required will be resubmitted to Victorian and Commonwealth regulatory agencies for approval.
Short term - Contractor's Monitoring
Quantitative State Concept (QSC)
Spatial control zone
It is the policy of Boskalis that all employees, including those of subcontractors and suppliers, execute their work safely and under healthy conditions, with approporiate concern for the protection of the environment.
The ultimate objective of the policy is zero incidents with environmental impact.
Light attenuation through turbidity
Response levels provide an early warning to enable management action. If the response limit is exceeded the activity is modified or suspended. Also the cause(s) are identified and assessed.
- Environmetrics Australia, Statistical Aspects of Turbidity Monitoring – Control Charting (April 2007)
- Environmetrics Australia, Statistical Aspects of Turbidity Monitoring – Setting Environmental Limits (April 2007)
- Port of Melbourne – Boskalis Australia Alliance, Environmental Data Processing Procedure – Alliance document No CPD_ALL_PR_801 (June 2009)
- Port of Melbourne – Boskalis Australia Alliance, Turbidity Compliance Procedure – Alliance document No CDP_ALL_PR_404 (August 2008)
- Port of Melbourne Corporation, Plume Intensity & Extent – Detailed Design – CDP_ENV_MD_021 (June 2008)
- Port of Melbourne Corporation, Supplementary Environment Effects Statement Channel Deepening Project
- Port of Melbourne Corporation, Technical Appendices Supplementary Environment Effects Statement Channel Deepening Project
- Port of Melbourne Corporation, Turbidity – Detailed Design – CPD_ENV_MD_024 (December 2007)
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