Part 2 of 2

Victorian National Parks Association Inc.

Level 3, 60 Leicester Street Carlton Vic 3053,

Tel: (03) 9347 5188, Fax: (03) 9347 5199

Email: website:

Submission on the

Supplementary Environment Effects Statement for

the proposed Channel Deepening Project in Port Phillip Bay

Prepared by Jenny Barnett May 2007


Here 2.4 million m3 of mostly clay is to be removed from the north of the Bay plus 14.6 million m3 from the South Channel - mostly sand but with some fine content that will cause turbidity.


Seagrass is important for fish breeding and for crustacea. It is also vital for many seahorses and pipefish (syngnathids). Flow-on effects are likely for various fish including King-George Whiting and to other fauna dependant on them in turn (penguins, seals, dolphins etc)

The SEES claims that less than 5% of seagrass in the bay will be significantly affected. Zostera rather than Amphibolobus will be impacted and 24% of this may be affected by turbidity (p13-3). Most of this is in the south of the Bay where 15-20% will experience reduced leaf density or total loss of leaves. The proportion of seagrass affected between Dromana and Portsea – the area where the impact is predicted - is not given. The SEES states that seagrass ‘may’ recover although the recovery rate is admitted to be ‘uncertain’.

The SEES discusses the main seagrass areas (listed with sizes on p13-52) as to whether they will be affected by light attenuation depending on depth of the beds and predicted turbidity. Most of its conclusions are vague and/or are downplayed:

  • Mud Island = 95% Zostera unaffected (therefore presumably 5% may be affected)

  • Sorrento Bank = ‘some’ Zostera affected

  • Rye to Rosebud = less than 10% Zostera affected

  • Dromana = all affected! But the Zostera seagrass beds are ‘sparse’ therefore affect is ‘minor’. (How important is this area which is well separated from others? Will it recover or will it be eliminated as the beds are already sparse?)

  • Portsea = ‘small areas’ of Zostera

  • Nepean Bay = some Amphibolobus may be affected but ‘should recover’.

In the conclusions (13-62) it rates the 15-20% impact in the south of the Bay as ‘moderate’. It also makes a statement that Mud island seagrass is not expected to be affected (p13-62) which contradicts the statements on p 13-57 that imply 5% may be affected

From the information on the size of the various seagrass beds (p13, Technical Appendix 50), and the proportion of the Bay’s seagrass that is projected to be impacted, it is apparent that a total of about 3 sq km of seagrass will be affected. By using the individual seagrass bed sizes and the statements about which beds will be affected or unaffected (p13-62) it would appear that about 53% of all the seagrass between Dromana and Portsea will be impacted. The only area within this that is estimated not to be potentially affected by the dredging turbidity is at Cameron’s Bight where the seagrass is already sparse and degraded (Tech App 53 p70)

This is potentially a very significant impact on a large area of the Bay. It will affect an area that is particularly popular for recreation including fishing. The seagrass beds here are noted by the SEES to be the most important for the settling of King George Whiting larvae. There will also be many other fish species affected.

Seagrass is stated to be ‘naturally variable’ with Blairgowrie used as an example (p13-54 – 13-55). But is this variability ‘natural’ or are there man-made disturbances influencing it, e.g. sewerage outfalls?

It is claimed in the SEES main report that attenuation of light to 15% of surface light will be sufficient to sustain the seagrass generally (p13-55) and that this is a conservative estimate. In fact Technical Appendix 53 reports that the Zostera seagrass appears to have a minimum light requirement of 12.5-25.6% (p59). Therefore a conservative estimate is 26% not 15%. A 15% level may suit the more restricted Amphibolis seagrass and the Ecklonia kelp but is likely to be insufficient for at least some of the Zostera which constitutes the majority of seagrass in the Bay. Therefore the area of seagrass affected is likely to be considerably underestimated by the SEES.

The experiments with shading seagrass as part of the SEES assessment (Tech App 53) found that the Zostera continued to decline for 6 weeks after removal of shading that was applied for 10 weeks. The seagrass then stabilized with some new shoots - but presumably with other parts dying as it did not increase over the next 5 weeks when the experiment ended. Earlier longer experiments in 1995 (reported in Tech App 36, p36) found that shoot numbers remained low 11 months after shade removal, thus indicating that recovery could be very slow indeed. Claims in the SEES that the seagrass ‘is expected to recover in the following spring’ are pure speculation as are recovery rates of all fauna dependant on it.

It must also be remembered that such experimental patches are usually surrounded by healthy seagrass which allow recolonisation by shoots and rhizomes from the adjacent area. Will extensive areas of seagrass that become sparse because of turbidity recover the same as a small patch surrounded by more healthy seagrass? Further hindering the recovery of seagrass, is the possibility of repeated turbidity from maintenance dredging. This is a factor that must be considered.

The possibility that recovery of sea-grass will be periodically set back has been refuted on the grounds that maintenance dredging already occurs. But there have already been observed declines in seagrass in some areas of the Bay. Indeed it was admitted at the 2004 panel hearing by POMC that the loss of the seagrass bank at Sorrento from the dredging in 2000 'was a distinct possibility'. The maintenance dredging will be over 5 times the volume that occurs now and could eventually have extremely serious long-term impacts. Repeated maintenance dredging, say every 5 years, could well prevent this recovery in affected areas in the south and east of the Bay. Permanent loss is a real possibility and on this basis alone, we believe this project should not go ahead.

We are most concerned that dredging will not necessarily stop if the prescribed turbidity/light diminution is exceeded. There are various loops in the Environmental Management Plan that will change dredging sequences etc (Attachment 4, pA4-85) but suspension of activities does not occur for at least 2 1/2 days. Three reports to the ‘relevant government agency’ are made before suspension of activities is required with the government agency then able to approve the recommencement of activities. If the rise on turbidity is gradual and the change in methods successful the system might work. But what if the rise is rapid, with perhaps unforeseen weather conditions causing problems?

It is hard to imagine that with the pressures of millions of dollars tied up in the continued use of the machinery that government and bureaucracy will stop the dredging for long periods if real problems arise and not cave into continuation of dredging in some form to the ultimate detriment to the Bay, its seagrass and biodiversity. Clear criteria for stopping dredging must be instigated that are legally enforceable (including by third parties).

If the seagrass is impacted and does not recover, the ecology and diversity of the Bay will permanently suffer.


Recovery of fish populations is predicted within 2 years provided the seagrass recovers within 1-2 years (e.g. p 13-74). On p 13-73 this optimism is reduced to ‘some recovery of seagrasses within 1-2 years’. Thus the SEES is somewhat inconsistent and bases it statements on fish recovery on assumptions about seagrass recovery. It also only discusses five species of fish in any detail.

Seagrass is critical for King George Whiting larvae. Importance of sites around the bay varies – with shallow seagrass beds between Sorrento and Dromana consistently with the highest abundances of settled larvae (p13-66). This is the very area where seagrass will be most affected (see above).

The Bay “is thought to be particularly important for spawning and/or nursery ground for juveniles, resident adults and migratory snapper” (p13-69). This is an understatement of the importance of Port Phillip Bay for this species which is described in a “Fisheries Note” published last year by the Department of Primary Industries:

Extract from Fisheries Note 593 - October 2006:

For the past 6 years fisheries scientists from Primary Industries Research Victoria (PIRVic) have been investigating Victoria’s snapper stocks (see Fisheries Notes 538, 544 and 585) to determine the significance of Port Phillip Bay to Victoria’s important recreational and commercial snapper fisheries.

The results of these studies, involving natural chemical markers or ‘tags’ in fish earbones (otoliths), show that for the period surveyed Port Phillip Bay was crucial to the snapper fisheries in western and central Victoria. PIRVic’s Paul Hamer and Greg Jenkins found the majority of juvenile and young adult or ‘pinkie’ snapper in western and central Victorian waters spent time as small juveniles in nursery areas in Port Phillip Bay. Young snapper (see photo over page) that spent their early life in Port Phillip Bay moved from the nursery areas in the Bay to populate coastal waters and Western Port bay.

“Snapper as young as 1 year of age moved distances of up to 200km from Port Phillip Bay. By the age of 4 years, snapper populations in western and central Victorian coastal waters and Western Port bay were dominated by fish that actually started life in Port Phillip Bay”

Underlining = our emphasis

Thus clearly Port Philip Bay is extremely important for this species. However impacts on snapper and some other fish species are dismissed on the basis of ‘limited’ plumes from the south-east DMG. And yet during the hearing of the earlier EES the use of the south-east DMG area was questioned by Greg Jenkins, a departmental biologist, on the basis of the likely importance of this site for snapper.

In the north of the Bay impacts are dismissed as ‘minor’ as the plume in north of bay is predicted to be limited. Indeed, for a whole series of ecological elements including seabed habitat, nutrient cycling, seagrass, any impact in the north of the Bay is totally dismissed and not discussed at all because “such a small area will be impacted” and “effects will be negligible”. With the finer sediments in this area, this limitation of the plume is hard to understand and we question what will happen if severe weather events or flooding of the Yarra occur? Indeed the turbidity modeling used the weather data from 2003 and did not, as far as we have yet been able to determine, include more extreme weather.

For anchovies it is stated that their food (phytoplankton) will recover quickly, but dredging in north of bay may interfere with their schooling for spawning. Both snapper and anchovy spawning, coincides with dredging in the Port Melbourne Channel. No diagram showing key fish spawning, migration events within the bay and the dredging timetable is given. Indeed, the location of spawning grounds for most species of fish other than King George Whiting, snapper and anchovies are not known.

The turbidity in the south of the Bay could affect migration of fish in and out of the Bay (and within the Bay) which is ranked as a ‘Medium Risk’ as ‘there are great uncertainties around how fish species will change their migration patterns as a result of the plume form dredging’ (p 13-78).

As was acknowledged by Greg Jenkins during the 2004 EES, ‘the impacts of dredging on migrating fish are totally unknown and is an area that carries significant risk’. (witness statement p 14). ‘The migration routes and seasons or movement are not well understood and the behavioral responses of migrating fish to elevated turbidity, suspended sediments, noise and light at night are virtually unknown’ (witness statement p 10). Fish migration is likely to be also affected by the hydrohammer and other dredging vibrations in the entrance (see below).

Spider Crabs

The protection of aggregations of Spider Crabs Leptomithrax gaimardii was an issue dealt with in the 2004 EES. It was proposed that video camera surveillance take place of channels about to be dredged in the south of the Bay to ensure that these aggregations, which can consist of many hundreds of individuals, are not impacted. The current SEES main report mentions their presence but does not appear to have any proposals to protect them. We are puzzled by this omission and hope this does not mean that this species is not now to be looked after.


Seapens are found in two very limited areas in the Bay. One of these sites will be subjected to relatively high levels of suspended sediments for 6 months at 14.4mg/L for 80% of the time and over 50mg/ml at times (p13-37). Although it is stated that they have tolerated past nearby dredging activities, there is no indication of how high the raised turbity/sedimentation was in the past or how long the episodes lasted. A ‘moderate’ impact is predicted. Again this prediction is speculative and a poor outcome is quite possible for this very restricted taxa.


The highest concentration of dolphins is in the north of the Bay, according to Figure 13-29 (p13-84) and yet the SEES main report then says the highest dolphin numbers were seen in the south. We do not understand this discrepancy. Dolphins are only discussed in the south of the Bay. As with fish, no details are given of dredging times in the north (including in Fig 13-11, p13-26). Dolphins will be affected by raised turbidity due to reduction in prey and, to a lesser extent, by underwater visibility. They are also likely to be upset by percussion style underwater noise, (which is quite different from boat noises to which they would be more accustomed) including pile-driving in the north of the Bay and Hydro-hammering in the south.

Sea birds

The Mud Islands contain important breeding colonies of White-face Storm Petrel (EPBC listed) and Caspian Tern (FFG listed, 1 of 3 known colonies in Vic) according to p13-19. The SEES concludes that the White-face Storm Petrel is not likely to be affected as it is a wide ranging species. The SEES discusses impacts on the Crested Tern (EPBC listed) and concludes that the dredging “may affect crested tern breeding for 2 consecutive seasons” (p13-99) but does not say if the same impacts apply to the Caspian Tern. As with the fish, it seems that only federally listed or popular species are considered by the SEES. All rare species should be considered. Both tern species are found on Mud Islands.

Gannets and terns will be affected for at least 4 years. Use of the jumbo dredge in overflow mode overlaps with the breeding and fledgling period of gannets for 2 consecutive years and it is acknowledged that this will affect breeding during these periods (p13-94, 13-103). The turbidity affects a third or more of the gannet feeding habitat over 2 breeding seasons (p13-95 – 13-97). The SEES admits a “possible worst case scenario” of “significantly depressed breeding success during the 2008 dredging period” (p13-97) and that dredging “is likely to affect the populations of gannets and crested terns for two seasons following the cessation of dredging. Subsequent recovery of populations to levels prior to CDP dredging is expected to take up to 2 years” (p13-101). Thus the gannets/terns will be affected for a total of 4 years (or is it 6?). In Technical Appendix 55 it is stated that the impact is ‘almost certain’ and the consequence ‘moderate’ (p267).

The SEES uses the same turbidity level (5mg/l) as that sufficient to affect the feeding of both terns and gannets and yet the gannets dive far deeper (gannets up to 20m, terns up to 1metre - but usually a few cm) thus presumably, since both spy their prey from the air, gannets could be affected by a far lower level of turbidity than terns, with the deeper prey out of sight in turbid waters. Indeed, the surveys of seabirds done as part of the SEES found that clearer water in the Bay had the highest seabird biomass (p38, Tech App 56).

In addition, elsewhere in the SEES, 5mg/ml is predicted over a far larger area than that shown in Figures 13-33 and 13-34 (p 13-95, 13-96) when discussing effects on gannets. Figure 10-20 (p10-81) and also the diagrams showing surface turbidity (Fig 13-39, p13-109 – used to discuss impacts on penguins) appear to show a wider area being affected by 5mg/ml. Are Figures 13-33 and 13-34 of deeper underwater turbidity than Fig 13-39? Since gannets and terns hunt from the air, the surface turbidity is probably more important than that in deeper water. Thus it is possible that, specifically for the deeper hunting gannets, that a larger proportion of the feeding habitat will be affected than indicated in the SEES.

Mud Islands and other protected areas

Effects on marine life by the turbidity and sediments around Mud Islands and other marine protected areas are dismissed as ‘negligible’ even though reduced light may affect seaweed in Portsea Hole (p13-177) and possibly seagrass at Mud Islands (see seagrass section above where there are conflicting statements for Mud Islands). In the case of impacts on the shoreline environment it is concluded that there may be some increase in the area of saltmarsh due to increased tidal changes. This is portrayed as a plus as it may benefit the Orange-Bellied Parrot. [A cynic may think this statement is made to appeal to the federal environment Minister!].

Mud Islands are the surface expression of the Great Sand, the largest shoal in Port Phillip Bay. They consist of three shrubby sand islands enclosing a shallow tidal lagoon which is fringed by salt marsh. The island group is 1200 x 900 metres in size, has a total area of 86 hectares with a land area of 60 hectares, and reaches a height of 4 metres. Despite the name, the islands, including their outer beaches, are mainly composed of shelly sand. Resembling an atoll, Mud Islands form a unique feature in the southern Australian landscape.

Birds dominate the ecology of Mud Islands. A total of 87 species are recorded and 15 of these have been recorded nesting. The entire area above high water mark is used for nesting, with some species forming extensive colonies. The major species are Silver Gull, Straw-necked Ibis, Australian White Ibis and White-faced Storm-Petrel. Other colony forming birds are Australian Pelican, Crested Tern and Caspian Tern. The central lagoon is visited by thousands of intercontinental waders in the warmer months.

Formed by wind and wave action, Mud Islands are 'anchored' and protected by outcrops of phosphate rock at South Cape (facing Port Phillip Heads). This rare rock type forms below guano deposits as phosphate from guano (accumulations of bird droppings) leaches down and combines with shelly sand below to form hard calcium phosphate. Phosphate rock is resistant to marine erosion and keeps the entire system in place. Birds have thus played a fundamental role in the physical evolution of the system.

The survival of the entire Mud Islands system depends on this phosphate rock which is in the upper intertidal zone. Extreme high tides submerge the rock and expose the sand dunes to erosion, so this system is extremely vulnerable to even slightly increased high tides, especially if they happen to coincide with storms. While it is true that global warming will also have this effect, nonetheless the change in tidal fluctuations will cause this process to happen sooner – surely not a desirable outcome.

The SEES notes that Mud Island “is continually changing shape due to storms and sand movement” (p13-114) and that due to limited data on the bathymetry of the Great Sands there was “limited ability to undertake detailed investigations of water flow in the Great Sands especially as it applies to local sediment transport features” (p10-12). Thus, although the SEES concludes that there will be few changes within the Great Sands and that Mud islands will ‘continue to evolve in outline shape’ (p10-45) there is some doubt here and we remain concerned about Mud Islands, especially when any changes due to the dredging, albeit small, are combined with sea-level rises due to climate change.


550,000m3 of rock are to be removed from the entrance. This will take over 6 months and involve the largest dredger and a ‘hydro-hammer’ which will create loud underwater percussion noise.


Rockfalls will fall across 18 ha of canyon wall and affect (at least) 13.5 ha of canyon habitat. It will partially or totally remove marine communities over 7.5ha and settle on and permanently affect 2.4 ha of the canyon floor. Only 100-120 ha of canyon exists. i.e. 12-13.5% of this type of habitat will be affected. These measurements do not include total surface area - only the horizontal projection. Thus the actual surface area affected is greater, considering the angle of the majority of the slopes where outward facing slopes far exceed any sheltered caves and under-hanging slopes.

Although 3000-6000m3 of rock fell during the removal of 30,000m3 during the trial dredging (i.e. 10-20%), it is predicted by the SEES that only 4,300m3 will fall during the removal of over 18 times the amount of material (i.e. 0.78%) because of an ‘improved draghead’ and other procedures. This estimate of rockfall does not include loose rock that might fall subsequent to the dredging (p14-23). We are also somewhat skeptical that the rockfalls can be reduced to the extent claimed from that experienced in the trial. Thus it seems very likely that the areas affected will be greater than that predicted (see also the comments on the Marine Park below).

The SEES exaggerates that rate of recovery from that postulated in Technical Appendix 52. The SEES main report claims a functional community in 2 years and pre-existing diversity within 5 years (p14-27) whereas the Technical Appendix merely suggests that a functional community may establish in 5 years (p58). Even this is based on speculation and extrapolation from the initial colonisation observed at 15 months. Some species are slower growing and it would appear to be unknown how long it will take for the current mix and size of sponges etc. to reform. A possible flow-on problem is that, where the encrusting marine life is removed, it may open these areas, including in the Marine National Park, up for invasion by introduced seaweeds (e.g. Undaria) as the rate of colonisation by some of these species may be more rapid than the original species. The counter argument in the SEES, that these exotic species will invade anyway, is not necessarily true if the natural communities are intact - and in any case disturbance will accelerate their invasion.

But not all areas may be able to fully regenerate. Areas of relatively barren rubble may well be greater, especially if the prevention of rockfalls do not meet the ambitious targets claimed. Any loose rocks will mean scouring.

Rubble remaining in the shallower dredged areas will roll in the currents affecting recolonisation of kelp etc. It will also roll into adjacent areas of shallow rock reef and damage these during movement in turbulent water – a factor dismissed by the SEES since ‘surrounding areas will not be affected’ (p14-20). This ignores the point that the overall area is thus reduced.

The canyon in the adjacent Marine Nat Park is only 22ha (note: the SEES main report incorrectly states all the adjacent Park is this size) and the SEES estimates that only 0.34ha will be affected (1.5% of the canyon in the Park). But what real guarantee is there that the rock fall will be this limited? The modeling undertaken for this estimation (Appendix 54) makes two unlikely assumptions and one important omission. It makes the assumptions that less than 0.8% of the rock will fall during dredging (compared with 10-20% during the trial) and also that it will fall evenly from all the plateau edges, rather than more in some places than others (which will be the case in practice). It does not feed in the effects of the tidal currents which are strongest in the marine park section and could help sweep rocks sideways and around the ‘Catacomb Ridge’ which is the basis for the claimed limitation of damage to the Park.

Once rockfall has occurred there is no comeback or reparation possible. What punishment is available if limitation of the rockfall as claimed does not eventuate? What substantial bond is required of the company as is the case for mining? There seems little apparent reason for an operator to spend time and money in the entrance, at the extremely expensive rates involved, doing it as carefully as possible.

Impact on Fauna

The hydrohammer and other dredging noise can cause physiological damage to sygnogathids and other fish within tens of metres and affect the migration of a number of fish species in and out of the Bay including fish larvae (and a number of the diandrous fish species in the Yarra ignored by the SEES). The effects of the six months of dredging in the 3 km wide entrance (and of turbidity inside the Bay) on fish migration is “not comprehensively understood” i.e. it is a big unknown. It is claimed the hydrohammer will only be used for 5% of the time. Recovery of fish stocks within 1-2 years following completion of dredging is claimed (on what basis?).

Dolphins regularly pass in and out of the Entrance. The SEES (p14-42) only considers whether the noise will permanently damage these noise sensitive species, not whether it will affect their behaviour. Nonetheless, the EMP will direct that hydro-hammering cease when dolphins are within 600m. However there is no analysis of whether this will be sufficient to prevent serious disruption of their behaviour.

More than 500 penguins pass through the Entrance every tidal cycle i.e. 1000+/day. Most transit close to Port Nepean where noise will be less and it is assumed that therefore the noise won’t affect them. However if this proves wrong it could seriously affect the Phillip Island population dependant on the Bay for food. The majority of Phillip Island penguins depend on Port Phillip Bay for winter feeding and any disruption of this would have serious implications for the over-winter survival of these birds. The Phillip Island population has already been drastically reduced, due to various reasons including the pilchard die-off, to a quarter or fifth of their original population (Simon Mustoe witness statement during the 2004 EES panel presentation).


Oil spills

The extent of devastation that could occur in the case of a fuel or oil spill can be seen in the maps at the back of Technical Appendix 55. However the SEES main report does little more than mention that oil spills could occur and that mitigation measures should be ready. It does not indicate the extent of possible damage, the main attributes at risk, or refer to the maps showing this. While oil spill are already a risk in the Bay, with the aim of the project to encourage more and larger ships, far larger oil spills will be possible than at present.


Sediment will settle and smother some areas to depths greater than 50mm covering some 28 km2 west and north of Hovell Pile (4% of the south of the Bay). There may be considerable error in this estimate as the degree of uncertainty in the modeling of sedimentation was ‘high’ (p 10-16). This sedimentation is in an area that has the highest concentration of MPB (microphytobenthos, mainly diatoms) which are organisms important for nutrient cycling in the bay. Without this, toxic algal blooms may occur. Another 7.5 km2 (at least) will be buried under sediments deposited by the dredge at the DMG. Adding to this is 21.6km of disturbed seabed within the dredged channel itself.

Recovery of all these areas by is claimed to occur within a year and the effect of removing/smothering a total of 47 km2 of the Bay is considered ‘minor’. It is claimed that if all MFB was totally removed for 15 months, the change in nitrogen would be ‘within background levels” (p13-48). In contrast, the SEES main report notes there are great fluctuations in denitrification efficiency due to phytoplankton photosynthesis with quite large changes measured over months of measurements in the Great Sands (p13-49). However risk of serious denitrification is dismissed as ‘minor’ because of the ‘likelihood of rapid recovery’.

The risk due to increased nitrogen load from the dredged sediments becomes greater when the mobilisation of nutrients and algal cysts is combined with turbidity and sedimentation. The statements that the additional nitrogen load entering the bay through the dredging disturbance will not have an effect because the load is small compared with that already arriving annually are fairly simplistic because these and other factors may compound it.

Toxic sediments

Disturbing toxic sediments in the mouth of the Yarra and then redepositing them within the Bay is an action that brings great unease about the extent to which these might be taken up by currents or marine life. Copper and zinc would seem the most likely contaminants to exceed the levels prescribed in the SEPP for the Bay while DDT and Dieldrin are already at very high levels on the existing spoil grounds. Other materials that could be mobilized include herbicides, insecticides, mercury, cadmium, lead, petroleum, chlorinated hydrocarbons and TBT (anti-fouling chemicals from ships with deadly effects on marine life).

With raised levels of contaminants such as heavy metals, dioxin and other industrial materials will fish in the bay be fit to eat - especially higher-order predators such as Snapper, and the products of aquaculture, especially filter feeders such as mussels? Even if fish are only affected in parts of the Bay, this will still be a health hazard to those that eat seafood from these areas.

The previous panel expressed great concern about the proposal to deposit this material uncapped in the Bay saying “The proposed placement of large volumes of these toxic sediments in the Bay within an uncompacted bund or island of loose clay in shallow water, exposed to the overlying seawater, poses an unacceptable environmental risk. Transfer into the food chain is possible”.

At the 2004 panel hearing the dredging company Boskalis was adamant that capping was not technically feasible or practical because “the muddy material dredged in the Yarra River will become thinner after dredging and its behaviour is more like a fluid than a clay. Putting a cap on top of this fluid cannot be done without instabilities causing the capping material to sink and disappear into the mud (inversed layer system). … To be able to cap low strength material either sand or mud are need to minimize the instability risk … a substantial layer of several meters would be required to cover all instabilities” (Boskalis witness statement).

Now it seems that capping is considered feasible using sand only 0.5 metres thick (p7-69 – 7-71). Nearly 5 months settlement will be required before this can be attempted. Thus the toxic sediments will remain exposed for this time - or for longer if the degree of consolidation does not occur as predicted. What will happen if consolidation is slower or if the capping falls through, stirring up the toxic mix? It is far safer for the environment if the more highly toxic sediments are removed from the Bay – or left undisturbed in the Yarra if they are currently stable.

Physical removal and burial of seabed

This is an unavoidable consequence if the project proceeds and will impact on a range of ecosystems and biota with varying recovery times. It will result in an increased risk of invasion of the physically disturbed sites by marine pests. For each of the main marine ecosystems involved there ought to be an analysis of the area and percentage of the ecosystem affected

For some areas, especially those that will undergo regular maintenance dredging, this loss will be permanent or result in a modified ecosystem. There is no estimation of the net loss or of what offsets are proposed in order to achieve a ‘net gain’. The Victorian Native Vegetation Management Frame work gives no indication that this policy stops at the shoreline and it would be most inconsistent if the Government were not to apply similar principles to the marine as to terrestrial ecosystems.


The SEES may predict that various fauna will recover within a year or two, but in practice so little is known about many of the species that the long-term impact is a total unknown and the dredging is a gamble at best. If the recovery of seagrass is ‘uncertain’ then the recovery of species dependant on it is also uncertain.

The SEES and technical appendices contain a myriad of uncertainties. Each is a source of possible error in making predictions, modeling results and so-on. Each uncertainty adds to the possibility that there will be serious unpredicted (or predicted but discounted) results.

As noted in our earlier submission to the 2004 EES, there are multiple risks resulting from a number of processes impacting on a range of receiving environments. Complicating this are multiple possible interactions. Risks are additive and chain reactions are also possible. The one certainty about probabilities is that they are additive. What is the overall probability that at least one serious impact that affects a significant part of the Bay will occur?

The failure to consider whether there are alternative strategies to achieve at least some of the some purposes is a real flaw. This omission goes against the spirit of environmental effects assessment which is to look at possible alternatives including other methodologies and sites and the ‘do nothing option’ (status quo) and at the total effect of the development. It would also seem to be in breach of Commonwealth environmental legislation, which the proposal also has to satisfy, that requires that feasible alternatives are examined and that relevant impacts are adequately assessed.

The main financial beneficiaries of this project will be importers and exporters and the Port of Melbourne Corporation. Flow on to other Victorians and Australians will be slow and vastly diluted. The vast majority of the population will benefit only minutely but huge numbers would be affected if the Bay is seriously affected.

There is an assumption that the size of ships will totally drive the provision of port facilities regardless of the position of markets for the products they are carrying -rather than the physical characteristics of the important ports influencing decisions on what size of ships are chosen. Of course if you keep providing facilities for larger ships you will get more of them. It does not necessarily follow that without deeper channels the Port of Melbourne will be uneconomic or that costs will be that much more expensive when diluted amongst the many consumers. The number of ships visiting the Port is predicted to increase regardless of whether the channels are deepened. The Port will not become redundant, instead it needs to properly cater for medium sized ships and encourage these.

Any increase in cost that may result from the use of other ports should be compared with the costs that are known to be likely and also to those that would occur if the Bay ecology and dependant industries are seriously damaged. The loss of other industries, the environment and remedial works might well outweigh the temporary gain to shipping. The money not spent on the channel deepening and moving the road and markets at Footscray to expand the Port should instead be used to look at alternatives. In America, instead of deepening the Panama Canal, the rail network across the nation was improved.

The VNPA firmly believes that the risks are too great and that this proposal should not go ahead.

Jenny Barnett

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