7. conceptual model for contamination and impact on the river … · 2020-06-08 · 7. conceptual...

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Whitehall Street, Yarraville Precinct Environmental Audit Report

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7. Conceptual Model for Contamination and Impact on the River Segment

7.1 Introduction An important step in carrying out a risk assessment is the development of a “Conceptual Site Model” that describes the pathways by which exposure to any contamination at the site may occur. A Conceptual Site Model should be first developed as part of the screening risk assessment, and then revised and improved as more detailed information on the contamination becomes available and the issues and nature of the site are better understood.

For exposure to occur, a complete pathway must exist between the source of contamination and the “receptor” (i.e. the person or ecosystem components potentially affected). Where the exposure pathway is incomplete, there is no exposure and hence no risk via that pathway. An exposure pathway will typically consist of the following elements:

Source of contamination (e.g. a spill);

Release mechanism (e.g. migration in soil, leaching to water, emission to air);

Retention in the transport medium (e.g. soil, groundwater, surface water, air);

Exposure point (e.g. where a person comes in contact with contaminated dust or soil, or contaminated groundwater from a well, or in a building overlying volatile contamination); and

Exposure route (e.g. inhalation, ingestion, absorption through the skin).

The Conceptual Site Model provides a description of all of the exposure pathways, and a diagram is usually used to assist in describing the various exposure pathways and their relevance. The development of the Model includes the identification of all sources, modes of migration, all potential receptors of concern, and how exposure may occur (i.e.. exposure route).

In developing the Conceptual Site Model, it is essential that consideration be given to all aspects of contamination exposure. Often the presence of contamination will give rise to a number of issues that require consideration. For example, soil contamination may pose a risk to human health through direct ingestion of soil particles or, if volatile, through volatilisation and entry into buildings or, if leachable, through migration in groundwater and exposure where the groundwater is used.

These factors have been considered when developing the Conceptual Site Model for the Whitehall Street Precinct, and the Model has been used for a preliminary screening of risks, and to better understand where the audit assessment should focus.

7.2 The Conceptual Model The Conceptual Model for the Whitehall Street Precinct and its potential to adversely affect the Maribyrnong and Yarra River segments is represented diagrammatically in Figure 4 below.

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It can be seen from the diagram that the key factors include:

Rainwater leaches through the surface soils and fill, leaching contaminants and leading to contaminated groundwater that discharges through the river sediments and into the river water. The extent to which such leaching will occur is a function of the quality and nature of the fill and contamination in the soils. In some cases the sites are paved and in these areas rainwater will not infiltrate into the soil.

Groundwater flows through the fill and underlying materials and discharges through the river sediments into the river water. In some areas there are highly impermeable layers (such as silt) that effectively precludes groundwater passing through the layer.

It is known that there is a deep sewer running beneath Whitehall Street along the western boundary of the Precinct and running beneath the Mobil terminal. The potential for the sewer to be acting as a groundwater drain has been largely confirmed by various groundwater investigations across the Precinct. The sewer forms a sink for groundwater beneath the western portion of the Precinct sites and groundwater in the deeper aquifers appears to be draining into the sewer. The presence of the sewer has been shown to avoid groundwater from the deeper water bearing units from migrating to the river. The influence of the sewer is discussed further in Section 10.5.2.

The Newer Volcanics formation overlies the Brighton Group. This basalt layer is of variable thickness; it is encountered in the western portion of the Precinct but generally thins or pinches out towards the river and is unlikely to have a hydraulic connection with the western bank of the river.

Surface soil, fill and material stored on the sites are washed by rainwater into the river. In some cases the sites have stormwater control measures that collect stormwater and discharge it to the sewer, and avoid its discharge to the river.

Process activities by industries on the sites lead to process waters or spills that discharge to the river. In the case of some of the sites, these discharges are contained and are recovered or are treated, and are discharged to the sewer.

Contaminants present in soil or groundwater volatilise and migrate through the overlying soil into the air or into buildings built over the contamination, affecting the health of persons via inhalation.

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INDUSTRIAL PRECINCT: FACTORIES, TANKS, CHEMICALSTORAGE, STOCKPILES, FILL

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FILL MATERIAL:SOURCE OF POTENTIAL CONTAMINANTSMIGRATING TO GROUNDWATER

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UNCERTAIN OR VARIABLE BOUNDARYOF GEOLOGICAL FORMATION

GROUNDWATER LEVEL FIGURE 4CONCEPTUAL SITEMODEL

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8. Preliminary Assessment of Risks

8.1 Introduction A preliminary assessment or screening of risks to the surface waters of the lower Maribyrnong River, lower Yarra River and Stony Creek Backwash was carried out to identify the sources of contamination and activities that pose the highest risk, and therefore should form a particular focus for further review and assessment in this audit.

It is important to note that the results of the screening risk assessment outlined in this section do not provide a final evaluation of the risks. The purpose of the screening risk assessment has only been to provide a systematic approach to identifying possible areas of risk and to focus the audit activities. This has been followed with a more detailed review of information pertaining to the sites and this has provided a critical review of the assumptions that underlie the screening risk assessment and the level of risk to be determined in more detail.

8.2 Methodology for the Screening Risk Assessment The methodology for the screening risk assessment involved:

a) Gathering and review of information pertaining to the land parcels within the Precinct. The focus has been on existing operations and activities at the sites, as well as relevant historical activities that present a potential to impact the land, groundwater and surface water segments. The information was primarily obtained through consultation with stakeholders to the audit. The consultation process has included several meetings with the Lower Maribyrnong Audit Reference Group, along with dedicated meetings with EPA, individual industry representatives and the community members of the reference group.

b) Identification and assessment of risks to beneficial uses of the river segment using:

The methodology outlined in the Australian/New Zealand Standard for Risk Management (AS/NZS 4360: 2004), and reproduced in summary form in Figure 5; and

The health risk assessment model outlined in the National Environment Protection (Assessment of Site Contamination) Measure, Schedule B(4), and reproduced in summary form in Figure 6.

It is acknowledged that a similar process applies to the model for assessment of risk to ecosystems, as outlined in the National Environment Protection (Assessment of Site Contamination) Measure, Schedule B(5).

c) Identification of the beneficial uses protected under the applicable State environment protection policies for the surface water bodies. The auditor made an evaluation of the likelihood of the beneficial uses being realised – this process was used to determine relevant receptors;

d) Identification of potential contaminants of concern;

e) Identification of possible exposure pathways and contamination exposure scenarios;

f) Assessment of the likelihood of contamination exposure scenarios occurring (i.e. that the contaminant is present in concentrations of concern, and that the exposure pathway is complete and receptors will be affected);

g) Assessment of the consequences associated with each of these contamination exposure scenarios;

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h) Characterisation of the risks based on the likelihood and consequences of each scenario using a risk assessment matrix that considers consequences on people (health), assets and environment;

i) Review of preliminary assessment by EPA client managers and the industry representatives of the Lower Maribyrnong Audit Reference Group to confirm that the significant risks have been identified and the ranking of risks appears to be in accord with their understanding of activities and contamination at the sites; and

j) Further refinement of the risk assessment in light of the site-specific feedback, and finalisation of the risk assessment.

Figure 5 Risk Assessment Framework from Australian/New Zealand Standard for Risk Management (AS/NZS 4360: 2004)

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Figure 6 Risk Assessment Model, NEPC, 1999, Schedule B(4)

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8.3 Identifying Relevant Beneficial Uses The objective of the audit is to make an assessment of the risk posed by the activities and contamination within the Precinct on the beneficial uses of the surface water segment. The beneficial uses of the surface water segment are defined by the applicable State Environment Protection Policies (SEPPs). As discussed in Section 3.5 the surface water bodies included in the audit area are covered by the following policies:

State Environment Protection Policy (Waters of Victoria), 4 June 2003; and

Waters of Yarra Catchment, Schedule F7 to the State Environment Protection Policy (Waters of Victoria), 22 June 1999.

The SEPPs identify the actual and potential beneficial uses that are protected for certain segments of the environment – in the case of this audit, the surface water segments that lie within the audit area. The auditor has had regard to all the protected beneficial uses of the surface water segments in order to make an assessment of any risk of harm or detriment that may be posed by the activities (existing and historical) within the Precinct. The actual and potential beneficial uses for the Lower Maribyrnong River, Lower Yarra River and Stony Creek backwash were identified from the outset of this audit; the process and beneficial uses are more fully described in Section 3.5 of this report.

EPA guidelines for environmental auditors discuss the assessment of whether a beneficial use is relevant. In general terms a beneficial use may be considered relevant if the beneficial use is existing or is likely to be realised at the site (that is, the use could reasonably be made of the element in its natural state, having regard to the setting of the site) (EPA Publication 759b). Understanding the likelihood of whether a use will be made of the surface water segment within the audit area is important to making an assessment on the risk posed to the relevant beneficial uses.

The auditor has undertaken an evaluation of the likelihood of the individual protected beneficial uses being realised within the audit area, i.e. whether a beneficial use represents an existing or potential use of the rivers and backwash within the audit area. In arriving at an understanding of river usage the auditor has consulted with community and industry representatives and benefited from their local knowledge. The evaluation also benefits the overall screening risk assessment process as it allows the contamination exposure pathways that present actual or potential risks to the river uses and users to emerge. The results of this evaluation are summarised in Table 20.

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Table 20 Beneficial Uses that are Likely and Unlikely to be realised

Lower reaches of the Maribyrnong River (Estuaries and inlets)

Lower Yarra River and Stony Creek Backwash (Yarra Ports Segment)

Beneficial uses likely to be realised

Secondary contact recreation (eg. Boating, fishing)

Aesthetic enjoyment

Non-indigenous cultural and spiritual values

Industrial and commercial use

Fish, crustaceans and molluscs for human consumption

Maintenance of natural and aquatic ecosystems and associated wildlife - highly modified with some habitat values

Passage of indigenous fish

Secondary contact recreation (e.g. boating, fishing)

Aesthetic enjoyment (e.g. walking by the waters)

Commercial and recreational use of edible fish and crustaceans

Industrial water use

Navigation and shipping

Beneficial uses unlikely to be realised

Indigenous cultural and spiritual values

Aquaculture

Beneficial uses prohibited7

Primary contact recreation Primary contact recreation

8.4 Beneficial Uses Unlikely to be Realised

8.4.1 Primary contact recreation

Primary contact recreation is listed in the SEPP WoV as a protected beneficial use of the estuaries segment such as for the lower Maribyrnong River. It is not listed as a protected beneficial under the SEPP WoV Schedule F7 for the lower Yarra River within the vicinity of the Precinct.

EPA have advised that the use of the surface waters for primary contact activities such as swimming, is prohibited and the EPA Water Quality Assessment Report (attached in Appendix M) describes primary contact recreation as “listed but not permitted” within the lower Maribyrnong River.

8.4.2 Cultural and spiritual values – indigenous and non-indigenous

The SEPP WoV seeks to protect the cultural and spiritual values of surface waters to ensure that the cultural and spiritual practices of a community can continue. These include the spiritual values of surface waters held by indigenous communities, and the cultural values held by both urban and rural communities, such as water based festivals and celebrations (Policy Impact Statement SEPP WoV, 2003).

SEPP WoV recognises that water resources have important values particularly for indigenous peoples. No specific guidance for protection of these values is provided; the information available suggests that consideration must be given to cultural and social issues in the planning and management of water resources, and that conservation of social values is achieved through the maintenance and enhancement of the environment.

7 Primary contact recreational use of the surfaces waters, such as swimming, is prohibited in this river segment, as per EPA advice

to the auditor on draft audit report, 16 August 2006.

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8.4.3 Aquaculture

The ANZECC (2000) Water Quality Guidelines describe aquaculture as the production of food for human consumption, fry for recreational fishing and natural fisheries, ornamental fish and plants for the aquarium trade, raw materials and biochemicals, and a number of items for the fashion industry.

Although aquaculture is listed as a protected beneficial use for the estuaries and inlets segment of the SEPP WoV, it is neither an existing or likely use of the surface waters within the Precinct, nor is it likely to be allowed in an urban industrial setting such as the Precinct.

8.5 Nature and Extent of Contamination Discussions with industry, EPA and the community and a preliminary review of documentation indicated that the certain existing activities at the sites, as well as historical sources of contamination are likely to be most important in terms of posing a risk to the river segment. These are described below.

Current operations and storages as a source of contamination Surface operations, including leakage from aboveground storage tanks, oil catchers and drains,

movements, transport pipelines and processes.

Sub-surface operations, including underground storage and product transport pipelines.

Discharge of contaminated stormwater.

Former activities and filling as a source of contamination Historical disposal and/or stockpiling of waste on the land giving rise to contaminated stormwater or

groundwater.

Placement of contaminated fill, such as pyritic cinders (i.e. “Mount Lyell” waste), other site-sourced fill and imported fill giving rise to contaminated stormwater or groundwater.

Historical spills, leakage and other loss of product such as fertilisers, arsenicals, agricultural chemicals, hydrocarbons, oil and other chemicals or products (i.e. existence of phase-separated hydrocarbon in aquifers) giving rise to contaminated stormwater or groundwater.

8.6 Exposure Pathway Analysis The pathways by which beneficial uses could be affected were identified for each parcel of land, and have been summarised in a number of flowcharts. Figure 7 is an example of the flowchart used for the exposure pathway analysis. Flowcharts were developed for the following sites:

1. PoMC site (221 Whitehall Street), adjacent the lower reaches of the Maribyrnong River.

2. CSR Limited land, adjacent the lower reaches of the Maribyrnong River.

3. Albright & Wilson, adjacent the lower reaches of the Yarra River.

4. Orica main site, adjacent the lower Yarra River.

5. Mobil, adjacent the lower Yarra River.

6. Mobil, adjacent the Stony Creek Backwash.

The site-specific flowcharts are included in Appendix Q.

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In addition, consideration was given to the possibility that effects may occur from other sources and activities, such as from:

Coode Island;

River activities, such as fishing, dredging and shipping;

Upstream Yarra River;

Downstream Yarra River;

Upstream Maribyrnong River; and

Upstream Stony Creek.

The analysis considered the exposure pathways, such as how contamination of land and groundwater at the sites may transfer to the surface water bodies, and for instance, impacting the water column or the sediments in the rivers. In carrying out this analysis, all protected beneficial uses of the water segments within the audit area have been considered, however those uses that are likely to be realised have formed the focus for further assessment. This is reflected in Figure 7 below and the site-specific analysis in Appendix R.

Contaminant transport via air-borne dust and any impact from waste discharges to air (such as through licensed discharge points) has not been included in the exposure pathways, as it can be expected that air-borne contamination will present a minimal risk to the surface waters compared with the risk of harm posed by contaminant transport from soil runoff from the sites or discharge of contaminated groundwater.

The analysis yielded approximately 400 combinations of receptors, general exposure pathways and relevant beneficial uses to be protected. The risk associated with each of these was assessed and the summary of these assessments is included Section 8.7.

1

Figure 7: Flowchart Example Exposure Pathway Analysis

Beneficial uses – Receptors

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8.7 Likelihood and Severity of Effect on the River Segment The likelihood of a scenario occurring in which contamination would give rise to a significant effect on the beneficial uses was then assessed. In each case, a particular scenario and level of effect was considered, and the likelihood of this scenario occurring was then determined based on information obtained from the preliminary review of information pertaining to the sites and consultation with stakeholders.

The descriptors defining the likelihood of a scenario occurring and the severity of effect, and the resulting level of risk are defined in the risk assessment matrix shown in Table 21. These descriptors were based on the Australian Standard Risk Management (AS 4360: 2004) and the ranking of risk for various combinations of likelihood and severity was based on the judgment of the auditor. This was considered to be an adequate approach for the audit where only a relative ranking is required to focus further assessment. It is possible that other risk rankings could be adopted.

Severity of effect considered the following:

People (mainly human health);

Financial impact of damage to assets and heritage; and

Environment (actual impact on ecosystems, as distinct from regulatory compliance).

The descriptors for ranking likelihood and severity are provided in Table 21.

60 Whitehall Street, Yarraville Precinct Environmental Audit Report

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Table 21 Risk Assessment Matrix

Consequences Probability

A B C D E People Assets & Heritage Environment

Improbable Unlikely Possible Likely High

0 No health effect/injury No damage No effect Negligible Negligible Negligible Negligible Negligible

1 Slight health effect/injury, medical treatment

Slight damage <$10 000 Slight effect Negligible Negligible Low Low Low

2 Minor health effect/injury

Minor damage <$100 000

Minor effect, single complaint, minor breach

Low Low Low Medium Medium

3 Major health effect/injury, irreversible damage

Localised damage <$1 000 000

Localised effect, multiple complaints, substantial breach

Low Low Medium Medium High

4 Permanent total disability of 1 to 3 fatalities

Major damage <$10 000 000

Major effect, widespread nuisance, persistent breach or impact

Low Medium Medium High High

5 Multiple fatalities Extensive damage >$10 000 000

Massive effect, persistent severe damage

Medium Medium High High High

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8.8 Revision of the Risk Assessment A draft of the preliminary risk assessment was provided to EPA and the industry representatives of LMARG on the 9th March 2006. The draft was provided to gain the benefit of industry’s site-specific knowledge. Feedback was received from:

PoMC;

CSR Limited;

Parks Victoria;

Orica; and

EPA.

The auditor reviewed the feedback and the preliminary risk assessment was adjusted where appropriate. The adjustments are reflected in the findings of the preliminary risk assessment, detailed in Section 8.9.

Note that in the case of the POMC site (at 221 Whitehall Street), POMC advised that the stormwater treatment system had been installed that reduced the potential for contaminated stormwater to discharge to the river, and that therefore this risk was low.

8.9 Findings of Risk Assessment The outcomes of the screening risk assessment process yielded:

6 high risk scenarios;

47 medium risk scenarios;

153 low risk scenarios; and

183 negligible risk scenarios.

These scenarios are summarised below.

Table 24 below presents a summary of the high and medium risk scenarios respectively. A complete table of the risk ranking is in Appendix R.

8.9.1 Scenarios that pose the highest risk

Risk posed to river sediment quality

The highest risk scenarios relate to contaminated fill and soils being transferred to stormwater and then to the river segment and deposited as sediments or causing sediment contamination. This run-off could be contaminated with dissolved metals, fertiliser/nutrients, or add increased sediment load to the river system or pose a risk of increased biological oxygen demand, as well as collect contaminated and uncontaminated sediments; these pose a potential to impact the sediments and ecosystems in the river.

For a number of sites a high-risk scenario has emerged from the potential that existing operations and chemical storages can cause leaks and spills to land and therefore cause contamination of soils, which can also discharge into the river segment via stormwater run-off and cause sediment contamination.

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8.9.2 Scenarios that pose medium level risks

In general terms, the scenarios that have emerged as medium level risks were:

Risk posed to shallow groundwater quality

Historical soil contamination leading to shallow groundwater contamination. Under this scenario contaminated shallow groundwater can discharge to the river and there is a potential to affect the aquatic ecosystems in the river and contaminate river sediments.

Risk posed to river water quality and river sediments

Existing site operations and chemical storages causing contamination of land and groundwater through leaks and spills, and contaminated shallow groundwater discharging into the river. Again, the potential to affect aquatic ecosystems and contaminate river sediments exists.

Soil contaminated by existing site operations or from historical activities causing contaminated stormwater through rainfall run-off over uncontained surface soils and fill. Contaminated stormwater discharges to the river segments have a potential localised affect on aquatic ecosystems and river sediments, as well as a potential for more widespread effects such as algal blooms, and accumulation in aquatic biota.

Contamination inputs from potentially contaminating activities that lie outside the audit area but within the Maribyrnong River and Yarra River catchments as these have emerged as having a potential affect on the aquatic ecosystems of the river segment. Perhaps the most notable of these activities include those occurring on Coode Island.

8.9.3 Low or negligible risk scenarios

The scenarios that emerge from the screening risk assessment as posing a low or negligible level of risk to the surface water segments include:

Scenarios that could impact certain beneficial uses that are unlikely to be realised within the audit area. For example people are unlikely to use the lower reaches of the Maribyrnong and Yarra Rivers for recreational swimming (EPA has informed that use of the waters in this area is prohibited), and non-indigenous cultural and spiritual values are unlikely to be significant in this heavily industrial precinct.

Scenarios in which a particular effect is unlikely to occur, such as where we have knowledge that fish sampling and analysis has shown that contaminant residue levels do not exceed guideline levels.

Scenarios where the exposure pathway is unlikely to impact the river system, such as contamination of deeper aquifers within the audit area, but do not discharge groundwater to the river segment.

Scenarios where a contaminated discharge is likely to be very localised or subject to immediate high levels of dilution.

Scenarios where is it known that physical barriers are present and these are expected to limit the migration of contaminants to the river (such as the existence of a groundwater interception trench, or a stormwater is collection and first-flush system, or where discharges are licensed and subject to regulated discharge limits).

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8.9.4 Limiting contaminants

In the context of this report, “limiting contaminant” refers to the contaminant that has the greatest exceedence of criteria and hence can be expected to determine the requirements for control.

In general, through the preliminary risk assessment process, the limiting contaminants were determined to be:

Arsenic and copper where pyritic fill or contamination from the manufacture of chemicals for sheep dips were the primary concern;

Nutrients (phosphorus and nitrogen) due to activity at the former Pivot site (Port of Melbourne Corporation land);

Hydrocarbons at the Mobil site;

Biological and chemical oxygen demand from sugar-related products and intermediaries at the CSR Limited site;

Nutrients (phosphorus and nitrogen) at the Albright & Wilson site; and

Metals and chlorinated hydrocarbons at the Orica main site.

8.9.5 Beneficial uses affected

The beneficial uses that have the greatest potential to be impacted are:

Water and sediment ecosystems: considered to be a highly modified ecosystem within the Precinct; and

Fish, crustaceans and molluscs for human consumption.

Details of the high and medium risks are provided in Table 23 and Table 24 respectively.

8.10 Risk Based Focus for the Audit The audit has continued to focus on the high and medium level risk scenarios – there are 53 of these scenarios. Table 22 presents a summary of the preliminary risk screening outcomes on an individual site basis. Although the focus of the audit has continued to be on the higher risk scenarios, the assumptions underlying the negligible and low risk scenarios have been reviewed to confirm that the preliminary assessment of risk was justified.

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Table 22 Preliminary Risk Assessment Screening Summary8 - Medium and High Risks that each Site may pose to the River Segment

Contamination as a result of current operations/activities

Contamination as a result of historic operations/activities

Pathway Licensed discharge

Discharge from shallow aquifer/s

Discharge from deeper aquifer/s

Rainfall runoff

Discharge from shallow aquifer/s

Discharge from deeper aquifer/s

Rainfall runoff

PoMC site

221 Whitehall St

CSR Limited

Albright & Wilson

Orica main site

Mobil (into Yarra River)

Mobil (into Stony Creek Backwash)

Refer to the Screening Risk Assessment in Appendix R for more information.

8 Risk assessment considered the different aquifers within the Precinct; namely the shallow aquifer in the fill, and the deeper Newer

Volcanics (basalt) and Brighton Group aquifers.


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Table 23 High Risk Scenarios

Exposure Path

Exposure Path Description Beneficial use Limiting contaminant Comment

CSR Limited, Lower reaches of Maribyrnong River (Estuaries and Inlets)

2BDEKJL Historical soil contamination -> rainfall runoff/stormwater drain -> river water -> river sediments

Ecosystems: highly modified

Surficial fill Runoff from stormwater on fill material. Likelihood and consequence of major effect, widespread or persistent nuisance.

ORICA main site, Lower Yarra River (Yarra Port Segment)



Pyritic wastes / fill Runoff from stormwater on fill material. Likelihood and consequence of major effect, widespread or persistent nuisance.

ALBRIGHT & WILSON, Lower Yarra River (Yarra Port Segment)

4ADEKM Process activities/storage -> leak/spill to soil -> rainfall runoff/stormwater drain -> river water


Nutrients Likelihood and consequence of localised impact.



Pyritic wastes / fill Runoff from stormwater on fill material. Likelihood and consequence of major effect, widespread or persistent nuisance.

MOBIL, Stony Creek backwash (Yarra Port Segment)

6ADFJL Process activities/storage -> leak/spill to soil -> shallow groundwater -> river sediments

Ecosystems:

highly modified

Hydrocarbons Likelihood and consequence of localised environmental effect.

6BDFJL Historical soil contamination -> shallow groundwater -> river sediments

Ecosystems:

highly modified

Hydrocarbons Likelihood and consequence of localised environmental effect.


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Table 24 Medium Risk Scenarios

Exposure Path


PORT OF MELBOURNE CORPORATION (221 Whitehall Street), Lower reaches of Maribyrnong River (Estuaries and inlets)



Pyritic wastes / fill, former sheep dip, nutrients

Likelihood and consequence of localised impact on benthic ecosystem.

1BDFJKM Historical soil contamination -> shallow groundwater -> river water



Likelihood and consequence of localised impact in water column.

Fish, crustaceans, molluscs for consumption


Likelihood and consequence of residue levels exceeded.

CSR Limited, Lower reaches of Maribyrnong River (Estuaries and inlets)



BOD/COD, gypsum dust Likelihood and consequence of localised environmental impact.

2ADFJKM Process activities/storage -> leak/spill to soil -> shallow groundwater -> river water


BOD/COD, gypsum dust Likelihood and consequence of minor environmental effect.



Surficial fill Likelihood and consequence of localised impact on benthic ecosystem.



Surficial fill Likelihood and consequence of localised impact in water column.

Fish, crustaceans, molluscs for consumption

Surficial fill Likelihood and consequence of residue levels exceeded.


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Exposure Path


2BDEKM Historical soil contamination -> rainfall runoff/stormwater drain -> river water

Ecosystems:

highly modified

Surficial fill Likelihood and consequence of localised impact.

Fish, crustaceans,

molluscs for consumption

Likelihood and consequence of residue levels exceeded.

ORICA main site, Lower Yarra River (Yarra Port Segment)



Metals, CHCs Likelihood and consequence of localised impact on sediments..



Metals, CHCs Likelihood and consequence of localised environmental impact.


Metals, CHCs Likelihood and consequence of residue levels exceeded.

3ADEKM Process activities/storage -> leak/spill to soil -> runoff/stormwater drain -> river water


Metals, CHCs Likelihood and consequence of localised environmental impact


Metals, CHCs Likelihood and consequence of residue levels exceeded.

3ADEKJL Process activities/storage -> leak/spill to soil -> rainfall runoff/stormwater drain-> river water -> river sediments


Metals, CHCs Likelihood and consequence of localised impact on sediments.



Pyritic wastes / fill Likelihood and consequence of localised impact on benthic ecosystem


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Exposure Path




Pyritic wastes / fill Likelihood and consequence of localised impact in water column.


Pyritic wastes / fill Likelihood and consequence of residue levels exceeded.


Ecosystems:

highly modified

Pyritic wastes / fill Likelihood and consequence of localised impact.

Commercial and

recreational use of edible fish and crustaceans


ALBRIGHT & WILSON, Lower Yarra River (Yarra Port Segment)



Nutrients Likelihood and consequence of localised impact on sediments.



Nutrients Likelihood and consequence of major effect or widespread or persistent impact on water column.

4ADEKJL Process activities/storage -> leak/spill to soil -> rainfall runoff/stormwater drain -> river water -> river sediments


Nutrients Likelihood and consequence of localised impact on sediments.



Pyritic wastes / fill Likelihood and consequence of localised impact on benthic ecosystem



Pyritic wastes / fill Likelihood and consequence of localised impact in water column.


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Exposure Path





Ecosystems:

highly modified

Pyritic wastes / fill Likelihood and consequence of localised impact.



MOBIL, Lower Yarra River (Yarra Port Segment)



Hydrocarbons Likelihood and consequence of localised environmental effect. Leak from storage tanks. Interception trench will reduce risk of phase separated hydrocarbon migration.



Hydrocarbons Likelihood and consequence of major effect, widespread or persistent nuisance. Leak from storage tanks. Interception trench will reduce risk of phase separated hydrocarbon migration.


Ecosystems:

highly modified

Hydrocarbons Likelihood and consequence of localised environmental effect. Interception trench will reduce risk of phase separated hydrocarbon migration.



Hydrocarbons Likelihood and consequence of major effect, widespread or persistent nuisance. Interception trench will reduce risk of phase separated hydrocarbon migration.

MOBIL, Stony Creek Backwash (Yarra Ports Segment)



Hydrocarbons Likelihood and consequence of major effect, widespread or persistent nuisance. Interception trench will reduce risk of petroleum hydrocarbon migration.


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Exposure Path




Hydrocarbons Likelihood and consequence of a major effect, widespread or persistent nuisance. Interception trench will reduce risk of petroleum hydrocarbon migration.

COODE ISLAND

Ecosystems: highly modified (water)

Likelihood and consequence of a major effect or widespread nuisance

Ecosystems: highly modified (sediments)


RIVER ACTIVITIES (e.g. fishing, dredging, shipping)





UPSTREAM YARRA





DOWNSTREAM YARRA


Likelihood and consequence of a major effect or widespread nuisance Tidal action may carry contaminants to subject area.


Likelihood and consequence of a major effect or widespread nuisance Tidal action may carry contaminants to subject area.

UPSTREAM MARIBYRNONG

Ecosystems: slightly to moderately modified (water)



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Exposure Path


Ecosystems: slightly to moderately modified (sediments)


UPSTREAM STONY CREEK





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9. The River System

9.1 Objectives of the Assessment of the River System The objective of the assessment in this section is to provide information on the river system that will assist in making an assessment of the extent to which discharges of groundwater and surface water containing dissolved phase contamination from the properties that comprise the Whitehall Precinct will mix and dilute in the river water flows.

The assessment is particularly focussed on those conditions that are relevant to assessing the significance of discharges of groundwater. Groundwater discharges occur continuously and the groundwater near the river shoreline is known to contain concentrations of dissolved contaminants many times greater than the guideline levels for aquatic ecosystem protection.

While stormwater flows will also occur, the main impact from stormwater is expected to arise from suspended contaminants that wash off from the sites and settle to form contaminated sediments. This process and its impact is less dependent on river flows and dilution in the river water. The potential for dissolved contamination in stormwater to impact on the river systems is much less, because the concentrations of dissolved contamination can be expected to be low and the discharges will occur only during and immediately following rainfall events. In these events there will be a significant discharge of rainwater to the river system from the wider Maribyrnong River catchment, dilution will be considerable and flushing through the river segment will occur.

In view of these factors, a semi-quantitative analysis is carried out in this section to determine:

The extent to which groundwater will dilute with river water;

The ebb tidal excursion from the segment, and therefore the likelihood of exchange to Hobsons Bay and Port Phillip Bay; and

The time scale for lateral mixing of introduced contaminated groundwater at the west bank of the Maribyrnong River to establish if transfer into the ebb plume of the Yarra River is likely during an ebb.

9.2 The River Segment

9.2.1 Reference documents

Hydrodynamic investigations of the Yarra and Maribyrnong river estuaries have been conducted twice: once in the early 70’s, and then a comprehensive review and detailed monitoring study was conducted by VIMS9 in 1993 as part of the 2nd Port Phillip Bay Environmental Study10.

The VIMS reports hold comprehensive data on both estuaries and the following analysis relies on that data.

9 Black, K., et al., Draft - Nutrient and Toxicant Outputs From The Yarra, Task No. N1.3, T1.2 for the Port Phillip Bay Environmental

Study, Experiment 3. High River Flows Spring Tides, November 19, 1993. Victorian Institute of Marine Sciences, Melbourne Water Corporation, 1993.

10 Fabris, G. J. & Monahan, C. A. (1995). Characterisation of Toxicants in Water from Port Phillip Bay: Metals, Technical Report No. 18, CSIRO INRE Port Phillip Bay Environmental Study. Victoria: Victorian Fisheries Research Institute, July 1995.

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Melbourne Water records information on river water flows (see Appendix C), and this flow data was referred to determine the minimum flow conditions of the rivers.

9.2.2 Description of the river segment

The river segment of interest comprises the Maribyrnong River approximately 600 m upstream of the confluence of the Maribyrnong River with the Yarra River, and the Yarra River approximately 1.2 km downstream of this confluence. The river segment also includes the Stony Creek Backwash, which is located at the confluence of Stony Creek and the Yarra River. The downstream limit of the river segment is some 3 km from the entrance of the Yarra River into Hobsons Bay; Hobsons Bay connects directly with Port Phillip Bay.

The Maribyrnong and Yarra Rivers are tidal in this area, and both rivers are estuarine involving exchange of saline water from Hobsons Bay. The flows in each river are strongly influenced by whether there has been rain in their respective catchment.

In the case of the Maribyrnong River, flows in some months are recorded as zero11, although there is a tidal oscillation that involves water moving in plug flow up and down the river upstream of the Maribyrnong and Yarra River confluence.

In the case of the Yarra River, there is always a net flow of water down the river, and this is superposed on a tidal oscillation.

The main groundwater accession from the properties that comprise the Whitehall Precinct occurs along the Maribyrnong and Yarra River frontages. Groundwater may also discharge to the Stony Creek Backwash from the Mobil property, which runs along the northern boundary of the Backwash. The characterisation of groundwater discharges to the river is discussed in Section 10.7 of this report. The assessment indicates that the groundwater discharges of most concern are from the shallow fill, and these can be expected to discharge into the upper layer of river water. Because of this, the following discussion focuses on discharges to the upper half of the river water column.

9.2.3 Characterisation of the river estuaries

Both river estuaries can be characterised as ‘partially mixed’ at most river flows, with the Yarra River passing towards a ‘salt wedge’ classification at high river flows. A feature of partially mixed estuaries is the presence of so-called ‘density currents’ whereby the upper half of the water column has a net ebb (out flow) dominance and the lower half a net flood (up flow) dominance. These induced density currents can be manyfold that of the tidal currents produced by the response to tide height variations in Hobsons Bay.

Although in certain months of low rainfall there may not be a net flow of freshwater down the Maribyrnong River, because of the net flow down the Yarra River and the tidal oscillation that involves the river water in the vicinity of the confluence of the Yarra and Maribyrnong Rivers, both the Yarra and Maribyrnong Rivers will exhibit a lowered density upper layer and consequent density current effects.

The calculations given in succeeding sections apply to contaminants released into the upper, ebb- dominant layer in the river segment.

11 Melbourne Water water flow data (Appendix C)

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9.3 Extent to which Discharges of Groundwater will mix with the River Water It is important to determine whether it is likely that discharges of groundwater will migrate into the main river water flow, or whether the discharges will remain in a boundary layer close to the shoreline.

The extent to which transport and mixing will occur can be determined by assessing the extent of lateral diffusion. The expression for the lateral diffusion Ey in river/estuary flow is given as:

∗××= Udkε y

where k is a constant, d the channel depth and U* the friction velocity (~ U ÷20)

For actual estuaries k ~ 0.6 however the curvature of the Maribyrnong at the Whitehall site (clock wise on ebb) will generate secondary currents and cause surface transport out to the centre of the channel.

The effect is to increase εy and experiments (see Fischer et al Section 5.1.3 – Figure 5.312) give

*dUyε as a function of ⎥

⎦

⎤⎢⎣

⎡RU

WU

*

where W = river width (130m for Maribyrnong) and

R = radius of curvature ( ~730m at Whitehall site)

This latter parameter = 201

x 730130

= 3.5

From Figure 5.3 of Fischer et al(2) the value of k increases to ~ 2 (from 0.6).

Hence yε = 2 d U*

= 2 x 10 * 205.0

= 0.5m2/s ( where typical tidal velocity U is taken as 0.5m/s )

The time scale T to diffuse across the Maribyrnong estuary is given as:

T = yε

2L =

5.01302

= 9.4 hours

Hence it is likely that groundwater contaminants will partially diffuse laterally across the Maribyrnong River and into the Yarra River flow during each ebb, and therefore it can be assumed that:

Discharges of groundwater will be effectively fully mixed laterally within the estuary overlay after several days; and

Discharges of groundwater are unlikely to remain largely undiluted close to the bank.

12 Fischer, H.B., et al., Mixing in inland and coastal waters, 1979.

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9.4 Excursion to Hobsons Bay

9.4.1 Dependence on density currents

The extent of dilution of groundwater that will occur depends on the magnitude of the ‘density currents’ in which the upper half of the water column has a net ebb (out flow) dominance and the lower half a net flood (up flow) dominance. As noted previously these induced density currents can be manyfold that of the tidal currents produced by the response to tide height variations in Hobsons Bay.

If the discharge of groundwater is to the upper out flowing ebb-dominant density current, then it is likely that the groundwater will be flushed from the segment. If the discharge is to the lower up flowing flood dominant density current, then the residence time of groundwater can be much longer and dilution much less.

The VIMS monitoring of the Yarra near the West Gate Bridge showed density currents from 4 to 20 fold that of the tidal current.

9.4.2 Excursion of Yarra to Hobson Bay

The tidal excursion at West gate Bridge (section B) assuming an upstream surface area of 2,670,000 m2, a 0.5 m tidal range, a river width of 300 m, and a river depth of 10 m is given as ;

Excursion = inter-tidal prism /cross-section area

= 30005.0000,670,2 x

= 445m

with density currents at 4 fold tidal, surface excursion

= 4 * 445 ~ 2 km

at density currents at 20 fold tidal, surface excursion

= 20 * 445 ~ 10 km

i.e. well clear of mouth

It can be seen from these calculations that excursion to Hobsons Bay of releases into the Maribyrnong from the Whitehall precinct on the ebb tide will be achieved if the density current/tidal current factor exceeds about 10:1. As the measured density currents are broadly in this range (i.e. 4 to 20 fold that of the tidal current), it can be concluded that over a period of days the river flow processes involving lateral diffusion and outflow aided by density currents will result in effective dilution and transport of shallow groundwater flows out of the river segment.

9.4.3 Dilution achieved by groundwater accession through west bank

An estimate of the upper limit of dilution of groundwater that can occur can be made by dividing the groundwater flow by the net tidal outflow of river water into which the groundwater mixes.

The extent of dilution can be estimated as follows:

Assume that the Yarra and Maribyrnong tidal prism = 1,335,000 m3 each 12.5 hours

Assume that the width of the Maribyrnong River is 130 m, and that the groundwater is mixed in a portion of this.

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The extent of mixing can be determined by taking the lateral extent of plume as ≈ 2σy ( i.e. 95% of plume)

and yσ ≈ t2ε y ( see Ref 5 )

so with εy ≈ 0.5 m2/s

2σy = 2* 25.636005.02 xxx ≈ 300m in a half tide cycle

Hence the time TL for lateral mixing to span the river width of 130m is;

hTL 2.136005.02

652

=⎥⎦

⎤⎢⎣

⎡××

=

The estimated volume of river water into which the groundwater can mix in a tidal excursion of 6.25 hours is then

≈ 2000m x 4m x 130 m

length x depth x mean width

≈ 1,000,000 m3

This indicates that the groundwater can be expected to effectively mix in the tidal prism.

Assuming that there is not full exchange of each tidal prism, and the exchange ratio at the river/bay interface is ≥ 0.3:1 (which is expected to be conservative), then the volume of river water into which the groundwater will discharge into and dilute with is [1,335,000 m3 /12.5 h] x 0.3 = 32,400 m3/h, or approximately 750,000 m3/day.

9.5 Conclusions The analysis indicates that, with respect to shallow groundwater discharging from the Whitehall Precinct to the upper layer of the Maribyrnong River:

The groundwater can be expected to be well mixed with the river water.

The groundwater mixed with the river water can be expected to be flushed into the main stream of the Yarra River, and thence through tidal exchange to Hobsons Bay and from Hobsons Bay to Port Phillip Bay.

The extent of dilution of the groundwater in river water will be limited by the exchange process with Hobsons Bay on each out flowing ebb tide. It can be expected that at least 30% of the tidal prism will exchange on each tidal cycle, and the volume of river water into which the groundwater discharges can be expected to be greater than 750,000 m3/day under low (or zero) rainfall conditions, and significantly greater than this after rainfall.

The level of dilution may be less in the immediate vicinity of the riverbank where groundwater discharges and is initially mixed.

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The analysis indicates that, with respect to groundwater discharging from the Whitehall Precinct to the saline lower layer of the Maribyrnong River:

Transport is upstream and residence time will be greatly increased and may be in the order of weeks to months, until the saline lower layer eventually mixes with the upper freshwater layer and is transported downstream. Dilution of the groundwater in the lower saline layer will be much less than that in the upper layer.

9.6 Data Gaps The estimate of dilution is dependent on many assumptions and is uncertain. Either 3D hydrodynamic modelling and/or a fluorescent tracer experiment would be needed to reduce uncertainty in the extent of dilution that is actually achieved, particularly with respect to variations in concentration in the vicinity of the river shore line.

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10. Geology and Hydrogeology

10.1 Information Sources A description of the geology and hydrogeology at the site has been developed by reference to the following documents:

A series of geological reports written by J. L. Neilson during the period between 1961-1967 (see References in Section 18);

The 1:63, 360 Melbourne Geological Map (Geological Survey of Victoria); and

The assessment reports provided for the individual sites (refer to Section 6 for site-specific documents).

10.2 Regional Geology

10.2.1 Stratigraphy and structural framework

The Whitehall Street Audit site lies on the northwest margin of the Yarra Delta. In this area predominantly Quaternary age deltaic sediments rest unconformably on an undulating plain inclined towards the southwest. This plane comprises steeply dipping Silurian mudstones and sandstones, and Tertiary sediments.

The geological basement comprises the Silurian age Melbourne Formation which steeply have been variously folded. These marine sediments were subsequently eroded and covered by later marine and non-marine sediments in the Tertiary and Quaternary periods. The basal, non-marine Werribee Formation was deposited in the early Tertiary but has it has been reduced in thickness or completely removed by erosion. Synchronous with deposition of the Werribee Formation were episodes of volcanism which resulted in the extrusion of the Older Volcanics. These basalts are generally heavily weathered have been completely eroded in some areas. In the Audit region, the Werribee Formation is intercalated with the Older Volcanics as deposition continued between episodic lava flows.

Marine deposition continued to occur in the Miocene with deposition of the Newport (or Fyansford) Formation, and later in the Pliocene with the Brighton Group. The former has been identified in boreholes east of Hyde Street. Brighton Group sediments are present along the alignment of the Maribyrnong River. Additional volcanism occurred in the Late Tertiary and early Quaternary with the deposition of the Newer Volcanics. The Newer Volcanics thin eastwards towards the current day alignment of the Maribyrnong River.

Along the ancient path of the Yarra and Maribyrnong Rivers these sediments (i.e. Brighton Group sediments) were eroded to a variable extent and subsequent overlain by deltaic sedimentation during the Quaternary. These sediments include the Fishermens Bend Silt and Coode Island Silt. The Fishermens Bend Silt predominantly comprises silts and clays, deposited under shallow marine conditions. A break in deposition and substantial erosion of the Fishermens Bend Silt occurred prior to the deposition of the Coode Island silt during the Holocene period. The Coode Island Silt thickest where it fills depressions within the Fishermens Bend Silt topography and is interpreted to have been deposited in a shallow sheltered marine environment.

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The geology and associated stratigraphic column of the site has previously been described in detail in a series of geological reports written by Neilson during the period between 1961 and 1967. A summary of the stratigraphy is provided in Table 25.

Table 25 Regional Stratigraphy

Period Sub Period Formation Description

Recent Recent Alluvial Mud Sediments

Silty clay or silt, black-dark grey, very soft

Recent – Pleistocene Fishermens Bend Silt Silty clays, black-light grey and brown, high plasticity, stiff-firm consistency Quaternary

Pleistocene Newer Volcanics Basalt, dark grey, vesicular, generally moderately weathered with some interbedded clay zones

Pliocene Brighton Group Sandy clay, clayey sand and sand, mottled red-orange and pale grey or brown, fine-medium grained grading to coarse in isolated areas, often ferruginous with limonitic cementation

Miocene Newport Formation Clayey silt, sand and clay, greyish green-brown and grey, very stiff-hard, fine grained, some ligneous zones of black peat, coal or organic clay

Eocene Older Volcanics Basalt, black-dark grey, generally non-vesicular, frequently extremely weathered within upper zone to residual red clay

Tertiary

Eocene Werribee Formation Sand, clays and silt at times ligneous tending to medium-coarse grained clean sand with minor gravels at depth

Silurian Upper Dargile or Melbourne Formation

Inter-bedded mudstones and sandstones, dipping steeply to the south-west

10.2.2 Description of lithological units

A description of the lithological units is provided below, from oldest (deepest) to youngest (shallowest). The descriptions are based on drilling and geotechnical logging as part of the Hobsons Bay Main Sewer (HBMS) replacement works undertaken for Melbourne Water.

Silurian Dargile Formation (Sud) The Silurian aged basement geology and geomorphology of the site has previously been described by Neilson (1961-1966) and comprises folded steeply dipping sequences of mudstone and siltstone rock. The Silurian aged rocks within the region are tilted and down warped creating a broad depression, which is inclined to the southwest. This depression has created favourable conditions for the deposition of the younger Tertiary and Quaternary Formations.

Tertiary Werribee Formation (Tewc & Tews) Neilson (1961-1966) has previously described the Werribee Formation as typically comprising two sub-units. The lower sub-unit of the Werribee Formation unconformably overlies the Silurian bedrock and is typically characterised as sandy sediments.

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The upper sub-unit is typically described as clayey and ligneous sediments, which are interbedded with basalt flows of the Older Volcanics Formation and in some places directly overlie the Older Volcanics Formation. Recent borehole information from the HBMS investigations suggests that both sandy and cohesive soil types will be encountered within the upper sub-unit. Some occurrences of the sandy sediments from this unit have been interpreted between the coal of the Newport Formation and the Older Volcanics.

Tertiary Older Volcanics (Tvo) The Older Volcanics Formation consists of multiple basalt flows, which have occurred sporadically during the Tertiary period. The formation often displays a deeply weathered profile and is in places intercalated with sediments derived from the upper Werribee Formation, which were often deposited simultaneously with the basalt flows. Weathering and post depositional sedimentation indicates significant periods of quiescence between eruptive events.

The Older Volcanics were encountered in some of the deeper boreholes drilled during the HBMS investigation and, where intersected, typically comprised an upper weathered zone of clays and silts overlying a dark grey to black basalt rock. The upper residual soils were generally hard and contained some rock fragments (floaters) particularly towards the base of the weathering zone. The rock condition below the weathered zone was generally described as being moderately to slightly weathered and slightly to non-vesicular. Secondary carbonate minerals occur as infill and coatings within rock defects and vesicles. Minor occurrences of pyrite mineralisation were noted in recent core samples.

Tertiary Newport Formation (Tmn) The Newport Formation generally overlies the basalt of the Older Volcanics. Based on the existing level of investigation data, the Newport Formation appears to be prevalent on the western side of the existing Yarra River, but becomes thinner, discontinuous or completely eroded below the river and eastern bank. The lower boundary of this unit can be difficult to discern where a significant weathered profile of residual Older Volcanics clay is present.

The unit typically consists of very stiff to hard, grey or greenish grey and sometimes dark brown fine-grained sediments, including clays and silts. The sediments are sometimes micaceous and can be weakly cemented in parts with some thin calcareous bands previously reported. The formation has a minor content of ligneous material usually associated with dark brownish or grey organic clays and includes distinct interbedded seams of thin brown coal. Some occurrences of micaceous minerals are apparent in the sandy sediments, while pyritic minerals (marcasite) are common in association with ligneous zones. Correlations between the coal marker beds appear to indicate a shallow apparent dip of strata towards the east.

Tertiary Brighton Group (Tpb) The Tertiary Brighton Group overlies the Newport Formation and is present on the western bank and beneath part of the western half of the Yarra River, while the formation appears to have been completely removed by erosion under the river.

The unit typically comprises poorly bedded fine-medium sands with occasional coarse quartz sands, stiff to hard sandy clays, sandy and clayey silts and silty clays. Ferruginous zones, cemented by iron oxides, are common particularly in the upper 2 0m of the unit and often contain hard limonitic inclusions.

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Cementation of the unit has led to the Brighton Group being described as soft sandstone by previous investigations. The colour varies from pale grey to yellow and red-brown, and is sometimes mottled. The formation ranges from plastic to non-plastic and it is generally dense or hard particularly where ferruginous zones are encountered.

Significant groundwater has been encountered in this formation during previous investigations, generally associated with coarse sand zones. These granular materials have been previously identified by the potential to flow if exposed in excavations.

Quaternary Newer Volcanics (Qvn) The Newer Volcanics formation overlies the Brighton Group below the western bank of the river and is of variable thickness. Generally the formation ranges between 7 and 20 m within the Precinct. The basalt profile thins towards the river and it is possible that isolated cobble or small boulders associated with the edge of the basalt flow might extend further into the river. The basaltic lavas are dense in part and range from slightly to highly vesicular. The surface zone is usually weathered, in some cases completely weathered to clay, or a basalt and clay matrix. Residual clay zones within the rock mass are not uncommon.

Quaternary Fishermens Bend Silt (Qpf1 and Qpf2) The Fishermens Bend Silt overlies the Brighton Group in the western regions of the Yarra River and the contact between the two units is distinctly undulated. The unit varies in thickness, however it is generally thickest below the Yarra River with the western extent of the formation laps onto the Tertiary Brighton Group and Newer Volcanics formations, pinching out against the western riverbank.

The Fishermens Bend Silt unit is typically overconsolidated clay sediment of marine origin, which can be subdivided into the following two sub-units:

a) The upper sub-unit (Qpf1) dominates the formation and typically consists of a mottled grey / brown, high plasticity clay, which is usually strongly fissured. The upper sub unit can contain carbonate nodules or minor cemented zones and is usually of very stiff or hard consistency. Some minor ligneous inclusions have been encountered towards the base of the upper sub-unit in the investigation boreholes. The transition between the upper and lower sub-units is generally gradational in nature.

b) The thinner lower sub-unit (Qpf2) typically consists of grey or brown fine-grained sandy clay of low to intermediate plasticity and firm to stiff strength. Fissuring within this sub-unit is generally absent.

The lower sub-unit and its contact with the Moray Street Gravel formation to the east of the river is suggestive of a transitional period grading from terrestrial to marine sedimentation.

Coode Island Silt (Qc) Dredging has removed the majority of this formation from within the river crossing area and the Coode Island Silt is now restricted to the eastern side of the Yarra River. The formation generally increases in thickness towards the east. For the purposes of this report the Coode Island Silt will be considered as part of the Fishermens Bend Silt formation due to the expected small extent of the Coode Island Silt formation and the general similarities of between the Coode Island Silt and the Fishermens Bend Silt formations.

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Recent Alluvial Mud Sediments (Rams) Black, very soft to soft recent mud sequences have been encountered in the river and western bank. These sediments are similar in appearance to Coode Island Silt and may represent a reworked deposit, which has been disturbed due to recent human activities such as river dredging and shipping. The shallow waters between the shipping channel and existing western riverbank contain substantial thicknesses of this mud, with thinner wedges of the soft sediment identified as continuing slightly inland under the existing fill batter of the western shoreline.

Fill Various fill materials have been encountered on the west of the river and include sand and clay mixtures often with some inclusions of hard construction rubble such as concrete and masonry fragments. The fill has been reported up to 6 m in thickness but is generally reported in the range of 0.5 to 3.0 m in thickness. Fill has also been placed along the banks of and within the Yarra to achieve the current channel profile, as well in the area surrounding Stony Creek Backwash and it’s connection with the Yarra, which are the areas within the Precinct generally reporting greater volumes of filling within the Precinct.

Port Melbourne Sands

This unit consists of fine to medium grained sands generally 5 to 10m thick on the southern side of the Yarra, and forming the eastern/southern bank of the river. This unit is generally not found on the western side of the river (i.e. within the Precinct) and is therefore not applicable in the following discussions.

10.2.3 Geological sections

Two indicative cross sections have been prepared through the northern end (based on Neilson, 1961-1966) and the southern end of the audit site (based on Hobson’s Bay Main Sewer investigations). The investigation works undertaken on each of the sites generally does not include deeper drilling i.e. groundwater bores either intersect fill, Coode Island Silt or the Newer Volcanics. In some cases Brighton Group sediments are intersected, however deeper drilling to intersect the basal Tertiary units or the basement has not generally been undertaken within the Precinct. These two cross sections are included as Figure 8 and Figure 9 on the following pages of the report.

In general terms the geological sections are consistent with interpretations made by the site assessors for the individual sites within the Precinct, although there is some variation in interpretations of the geology to the east of the Yarra River. A discussion of the eastern side of the river is not required for the purposes of this report.

The geological sections presented in this report are an interpretation based on the factual information reported by the HBMS investigations and historical sources. Some of the historic information has undergone significant reinterpretation by other authors prior to inclusion in this report (Neilson, 1961 - 1966). There are also significant lateral and vertical variations in the subsurface profile encountered across the site. Therefore some variations between the geological profiles presented and the actual conditions encountered during construction are likely to occur.

Channel RL -13.7Channel RL -13.7Channel RL -13.7Channel RL -13.7Channel RL -13.7Channel RL -13.7Channel RL -13.7Channel RL -13.7Channel RL -13.7

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Project:

Title:

31 / 18209 AMap Grid ShNon-Earth (Meters) Rev.Date:

CJIPrepared.

Project No: 1 of 1Checked.

Approved.

Location

Workspace Geology X-Section A-A'.wor

DATA SOURCE

A3 1:1000 (1x vert)

180 Lonsdale StreetMelbourne VIC 3000

Tel: 61 3 8687 8000Fax: 61 3 8687 8111 19/07/2006

Figure 8. Interpretative Geology Longitudinal Section A-A'M:\31\18209\GIS\Projects

Whitehall Street, Yarraville Precinct

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VS

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Project:

Title:

31 / 18209 AMap Grid ShNon-Earth (Meters) Rev.Date:

CJIPrepared.

Project No: 1 of 1Checked.

Approved.

Location

Workspace Geology X-Section B-B'

DATA SOURCE

A3 1:2000 (2x vert)

180 Lonsdale StreetMelbourne VIC 3000

Tel: 61 3 8687 8000Fax: 61 3 8687 8111 19/07/2006

Figure 9. Interpretative Geology Longitudinal Section B-B'M:\31\18209\GIS\Projects


JKW

VS

19/07/2006

19/07/2006

19/07/2006 Scale:

Legend

Fil: FillQc: Coode Island SiltQpf2: Fishermens Bend SiltQvn: Newer VolcanicsTew:Werribee FormationTmn: Newport FormationTpb: Brighton GroupTvo: Older Volcanics

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31/18209/123777

10.2.4 Lithological units encountered within the audit area

The major lithological units encountered within the audit area (site by site), and as reported in the various site assessment reports, are summarised in Table 26. Note that some units may exist at depth at locations not identified in the assessment reports, and the information presented in Table 26 may not be definitive.

Table 26 Lithological Units Reported within the Precinct

Units

Relative order of depth below ground level

Fill Coode Island Silt (CIS) Newer Volcanics Basalt

Brighton Group

Port of Melbourne Corporation site

(221 Whitehall Street)

Eastern portion - Variable fill composed of pyritic cinders (distinctive purple colour) and other rubble/fill/clay/waste (up to 6m thick).

Western Portion: Fertiliser and rubble/fill reported on surface.

Yes, encountered in eastern portion.

Thin basalt layer, weathered, non-existent in places near the river.

Basaltic clay (0-4m thick) and basalt rock (4-5m thick).

Reported on-site.

CSR Limited In the eastern portion fill is reported as sandy gravels with trace ash and slag, sulfur fragments and fines (layer from 0.1 to 3.4m below ground level).

In the western portion gravels and sands are reported.

In the eastern portion silt/clays reported from 1.3 to 6m below ground level.

In the eastern portion the thickness ranges from 5-8 m.

Reported on-site.

Orica main site Fill is reported across the site.

In the eastern portion the fill is described as containing clay, pyrites, scoria, pyrite ash, roasted cinders.13

In the western portion fill is reported up to 2.0 m thickness.

(Landfilling with pyritic cinders reported for the Blue Room site.)

Reported in the eastern portion of the site and close to the river.

In the western portion CIS has not been encountered.

In the eastern portion one bore reported basaltic clays from approximately 10.5 m below ground level.

In the western portion residual basaltic clays were encountered from approximately 1.4 m below ground level.

In the eastern portion the Brighton Group has been reported from approx. 14.5 m below ground level.

In the western portion the Brighton Group has been reported from approx. 13m below ground level.

13 Beyond the Orica site (on PoMC owned land) near the sheet pile wall adjacent the river, fill is reported up to 5.0m thickness. Groundwater in this vicinity has been described as purple-red colored from pyrite cinders (Reference: Coffey Geosciences Pty Ltd, Orica Yarraville: Stage II Site Investigations; Final Report. Volume 1: Text and Figures. Dated 13 July 2000.

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31/18209/123777

Units

Relative order of depth below ground level

Fill Coode Island Silt (CIS) Newer Volcanics Basalt

Brighton Group

Albright & Wilson Fill encountered across the site (reported to 0.3 m below ground level) and described as red/purple, medium cobbles, sandy or clay rich layers, with trace pyrite and sulfur.

CIS reported near river at approximately 0.3 - 1.6 m below ground level.

Basalt clays and rock fragments encountered from about 6 – 9 m below ground level.

Reported between 9 - 22m below ground level.

Mobil

Fill material encountered across the site. Reported up to 3.0 m thickness close to the backwash.14

Described as silty clays and silty sand clays, with gravel and brick pieces.

In the eastern and south-eastern portions CIS is reported from close to surface and up to 10 m, inferred to overlap the Newer Volcanic basalts. The CIS pinches out towards the centre of the site.

This unit thickens towards the Yarra River.

Absent in the east and southeast of the site.

In the western portion basalts are reported up to 30m below ground level.

No site-specific data available, but work on other sites suggests that the Brighton Group is expected to be present beneath the CIS and Newer Volcanics.

10.3 Placement of Fill across the Precinct Fill has been placed across the Precinct and along the riverbanks and around Stony Creek Backwash. The fill was primarily placed in these areas as a means of land reclamation and waste disposal. This was a very common practice in industrial estates and urban river frontages.

The potential for this fill to give rise to significant contamination of groundwater and surface water was a key reason for the EPA to request the audit. This concern particularly focused on fill containing pyritic cinders and, because of this, the audit has sought to identify where such fill might be present.

The auditor’s team has reviewed bore logs descriptions and other information available, such as field notes and observations recorded on chains of custody data sheets, field summaries in reports, and consulted with Precinct industrial occupiers and EPA, to map the broad nature and location of the fill across the Precinct, particularly fill that might comprise pyritic cinders, which have been commonly described as purple cinders or red/purple coloured in various assessment reports for sites within the Precinct (Parsons Brinkerhoff, 2003; CH2Mhill, 2004).

Figure 10 represents a generalised fill extent plan and groups the fill descriptions from assessment reports and bore logs into:

fill described as containing purple materials, which is indicative of pyritic material;

fill described as containing pyritic material, which would be suggestive of pyritic material and/or similar contaminant quality.

14 There is extensive fill along Holden Dock (owned by PoMC) reported up to 2.8m (Reference: URS, Interim RAP, Yarraville

Terminal, 2005).

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fill of miscellaneous descriptions, essentially fill that can be considered to not contain pyritic wastes. This includes a number of materials – bricks, waste, cobbles, silts and sands, and other materials (see Section 10.2.2); and

areas of limited or no data.

Fill was reported at every location for which there was information available, and this is reflected in Figure 10. It is noted that the figure provides a reasonable indication of the lateral extent of fill placement across the Precinct. It does not contain any information on the vertical extent of the fill or the timing of fill placement (i.e. land reclamation along the eastern margin), or specific impacts of industrial operations on the soil quality of the Precinct. Because of this, Figure 10 should be regarded as indicative of general fill placement, and not definitive or quantitative. Figure 10 shows that there are some areas within the Precinct for which there is little or no information available. There is a lack of information (namely borelogs) regarding fill that might be present on the land area surrounding Stony Creek Backwash and near the confluence with the Yarra River, although there is information on the environmental quality of the backwash water and sediments available (discussed later in Section 12 and Section 13).

Pyritic fill material (purple or otherwise) was reported on the former Pivot land in the northern region of the Precinct (now PoMC) and was reported in the environmental audit for that site, as well encountered on land within the Orica main site boundary and over the entire Albright & Wilson site.

This is generally consistent with the information provided to the auditor in consultation sessions with the landowners in the Precinct.

10.4 Hydrogeology

10.4.1 Aquifer identification

In a regional context the identified aquifers are the Newer Volcanics and Brighton Group sediments. The Werribee Formation, Older Volcanics and Silurian basement are also considered aquifers but have been omitted from this discussion owing to their depth.

Most of the investigations undertaken for the various sites have referred to the Coode Island Silt and anthropogenic filling to be aquifers. It is arguable that although the Coode Island Silt is water bearing, it is not an aquifer owing to the low permeabilities of the formation. Anthropogenic filling has occurred, particularly to on the eastern and southern margins of the audit area, largely as means of reclaiming land. The filling is best described as a perched aquifer as it is generally discontinuous and of limited regional extent.

The hydrostratigraphy of the site is described in Table 27.

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Land Leased by Land Leased by Land Leased by Land Leased by Land Leased by Land Leased by Land Leased by Land Leased by Land Leased by CSR LimitedCSR LimitedCSR LimitedCSR LimitedCSR LimitedCSR LimitedCSR LimitedCSR LimitedCSR Limited

Land Leased by Land Leased by Land Leased by Land Leased by Land Leased by Land Leased by Land Leased by Land Leased by Land Leased by Albright and WilsonAlbright and WilsonAlbright and WilsonAlbright and WilsonAlbright and WilsonAlbright and WilsonAlbright and WilsonAlbright and WilsonAlbright and Wilson

POMCPOMCPOMCPOMCPOMCPOMCPOMCPOMCPOMCOrica "Main Site"Orica "Main Site"Orica "Main Site"Orica "Main Site"Orica "Main Site"Orica "Main Site"Orica "Main Site"Orica "Main Site"Orica "Main Site"

Parks VicParks VicParks VicParks VicParks VicParks VicParks VicParks VicParks Vic

Land Leased by Land Leased by Land Leased by Land Leased by Land Leased by Land Leased by Land Leased by Land Leased by Land Leased by CSR LimitedCSR LimitedCSR LimitedCSR LimitedCSR LimitedCSR LimitedCSR LimitedCSR LimitedCSR Limited

Orica Orica Orica Orica Orica Orica Orica Orica Orica "Blue Room""Blue Room""Blue Room""Blue Room""Blue Room""Blue Room""Blue Room""Blue Room""Blue Room"

POMC Former Pivot SitePOMC Former Pivot SitePOMC Former Pivot SitePOMC Former Pivot SitePOMC Former Pivot SitePOMC Former Pivot SitePOMC Former Pivot SitePOMC Former Pivot SitePOMC Former Pivot Site

CSR LimitedCSR LimitedCSR LimitedCSR LimitedCSR LimitedCSR LimitedCSR LimitedCSR LimitedCSR Limited

MobilMobilMobilMobilMobilMobilMobilMobilMobil

Albright & WilsonAlbright & WilsonAlbright & WilsonAlbright & WilsonAlbright & WilsonAlbright & WilsonAlbright & WilsonAlbright & WilsonAlbright & Wilson

31/182090

Map Grid

Sh

GDA 94 (MGA Zone 54)

Rev. Date:

CJIPrepared.

Project No:1 of 1

Checked.

Approved.

Location

Workspace BasePlan_5000_Lithology_A4.WOR

DATA SOURCE

A4 Scale: 1:7,500

180 Lonsdale SteetMelbourne Vic 3000

Tel: 61 3 8687 8000Fax: 61 3 8687 8111

18/09/2006

Figure 10. Generalised Fill Descriptions from Bore LogsG:\31\18209\GIS\Projects


VS

VS

18/09/2006

18/09/2006

18/09/2006

Sewer Pipeline

Surface Water

Transport

Property

Elevation

Boundaries

Leased Land

Site Boundary

Line

Waterway

Waterbody

Rail

Road

Region

10m interval

Audit Area

Fill - Miscellaneous Descriptions

Limited Information Available

Fill Described as Containing PurpleMaterials Indicative of Pyritic Material

Fill Described as Containing Pyritic Material

Fill Descriptions

0Metres

100 200 300


31/18209/123777

Table 27 Summary of Hydrostratigraphy

Age Hydrostratigraphy Description / Comment Aquifer Type

Fill Variable fill reported to be composed of pyritic cinders (distinctive purple-red colour), pyritic ash, other materials including cobbles, clay, silt, sandy gravels, rubble, miscellaneous waste, trace ash and slag, sulfur fragments, fertiliser residues, etc

Unconfined

Fishermens Bend Silt / Coode Island Silt

These marine sediments are considered to be aquitards or low permeability horizons. Little work has been undertaken to characterise the units hydrogeologically. The formations have not been developed as a result of low bore yields, and poor water quality.

Aquitard Quaternary

Newer Volcanics

Laterally extensive fractured rock aquifer. Water is stored and transmitted through both primary, but predominantly secondary porosity characteristics of the geologic material. Locally the aquifer is poorly developed owing to elevated salinities. The Newer Volcanics are recharged by rainfall over outcropping areas of this formation.

Unconfined

Brighton Group

Sandy horizons within the Brighton Group are intensively developed in the SE suburbs of Melbourne (Moorabbin GMA), however poor water quality tends to preclude development in the project region. Likely to be hydraulically connected to the Newer Volcanics at and to the west of the site. Confinement is likely to increase eastwards where it is buried under the Quaternary, however dredging activities may have exposed it within the Yarra River.

Regionally: unconfined to semi-confined Locally: unconfined?

Newport Formation The marine sediments of the Newport Formation are generally considered to be an aquitard and represent a confining layer to the Werribee Formation. Aquitard

Older Volcanics

The Older Volcanics represent a fracture rock aquifer, however at the site it is hydrogeologically poorly characterised. Elsewhere in Melbourne the often low yielding aquifer is developed for potable applications. At the site the aquifer is likely to be hydraulically connected with the Werribee Formation and confined by the Newport Formation.

Confined / Semi-confined Tertiary

Werribee Formation

The Werribee Formation is a recognised confined to semi-confined aquifer in the Melbourne region, however development is limited to only those areas where the groundwater is of fresher quality. Most development in suburban Melbourne occurs in the Altona region where the aquifer defines the Cut Paw Paw GMA. Recharge to the Werribee Formation occurs west of Melbourne where the formation outcrops or subcrops at shallow depth.

Confined to semi-confined

Silurian Basement

Throughout Melbourne the indurated sediments of the Silurian are recognised groundwater aquifers. The water quality and depth of occurrence are the predominant factors that determine the development of the resource. The Silurian represents a fractured rock aquifer and is possibly hydraulically connected to the Werribee Formation to a varying extent. The Silurian is recharged by infiltrating rainfall over outcropping areas that are principally located north of Melbourne. At the site this aquifer occurs at some depth and is considered irrelevant to the current investigations and construction.

Confined locally

9031/18209/123777 Whitehall Street, Yarraville Precinct Environmental Audit Report

10.4.2 Conceptual hydrogeological model of site

The hydrogeological model is complicated by a number of water bearing formations and the juxtapositions of these units. The Yarra and Maribyrnong Rivers are founded on the Quaternary sediments, with the Coode Island Silt being the shallowest, and the underlying Fishermens Bed Silt. As one moves westwards from the Rivers the geology (and hydrogeology) changes as these formations lens out. The Coode Island Silt lenses out adjacent to either anthropogenic filling or Newer Volcanic basalt. Being the edge of the volcanic flows, the Newer Volcanics can be thin in some parts, and extensively weathered to clays and silty clay materials.

In conceptualising the hydrogeology of the site it is important to understand the following points.

The groundwater flowing in the fill material is considered an unconfined aquifer. It is likely to be recharged by direct infiltration of the rainfall, leaking services, or possibly flows from the Yarra River under high tide conditions (tidal fluctuations in the standing water level in the fill aquifer adjacent the river, reported as about + 0.29 m within Stony Creek backwash in vicinity of the Mobil site, an overall change in groundwater level of 0.194m from high tide to low tide in the Holden Dock area, and + 0.4 m at the PoMC site). Discharge from the fill material would occur under gravity flow towards the Maribyrnong and Yarra Rivers, or drainage into the underlying Newer Volcanics. Generally the groundwater discharge through the fill is fresh or brackish, and the saline river water can be expected to form a saline wedge in the fill and upper units, and this will tend to cause the fresh and brackish groundwater to flow as a lower density lens over the saline wedge, and thus largely discharge into the upper portion of the river water column. The river is tidal in the vicinity of the Precinct, and the rising and falling of the river water will result in some dilution of the groundwater within the riverbank, with the extent of this depending on the permeability of the riverbank.

A smaller component of the groundwater discharge would occur as leakage to the Coode Island Silt, however given the very low permeabilities of the latter, it is suspected that horizontal flow processes would dominate over vertical. The aquifer is discontinuous but likely to be thickest in the east of the audit area where filling has been undertaken to reclaim land.

The Coode Island Silt (and equivalent undifferentiated Yarra River alluvial) is a recognised low permeability formation. Some investigations (e.g. Mobil site) have identified some sand and shelly lenses, however these are thin and discontinuous. Piezometers installed within the formation will intersect water, however the formation is considered incapable of producing water.

The level of interaction of the Coode Island Silt and the Yarra River is expected to be low and monitoring bores indicate little tidal variation, supporting the low transmissive nature of the formation.

The Newer Volcanics forms a fractured rock aquifer that thins and lenses out towards the east. Where it thins, it is likely to have increased weathering and low permeabilities. The aquifer thickens westwards where the bulk of groundwater flow occurs. It is covered by residual basaltic clay soil of variable thickness and fill material, however eastwards it would be covered by the Coode Island Silt and the Fishermens Bend Silt, and the Rivers flow within a channel in these silts. Owing to the low permeability of the Coode Island Silt, regional groundwater flow is likely to be southwards, the path of least resistance, as opposed to eastwards into the abutting Silt. The aquifer is expected to behave as an unconfined aquifer in a regional context.


The Brighton Group is a laterally extensive Tertiary sedimentary sequence within the Port Phillip Basin. The formation is sheet-like in the southern parts of the basin but thins further up to the north depending upon the pre-Tertiary topography and extent of erosion. It is expected to be recharged from the overlying Newer Volcanics, or further up-basin where it outcrops of subcrops at shallow depths. Groundwater discharge is expected to occur into Port Phillip Bay, however it may discharge within the Yarra River where it has been exposed by dredging and removal of the overlying silts, or through local excavations and borings, or where overlying confining units are locally eroded or absent.

Within the Precinct, it is possible that the final discharge point for the regional groundwater is to a deep sewer where it is present, rather than to the bay or the river. The North Yarra Main Sewer runs parallel to Whitehall Street and forms a groundwater sink in the area, and intercepts the regional eastward flow of groundwater in the Brighton Group, and causes the groundwater to intrude into the Brighton Group and flow westward from the River. This is supported by the reduced water levels and the TDS values reported for wells on the Orica main site screened in the Brighton Group. This is further discussed in Section 10.5.2.

In conclusion, interaction of the groundwater on the sites with the Maribyrnong and Yarra Rivers is expected to be limited to groundwater flowing through the fill overlying the Coode Island Silt and discharging into the upper river water column.

10.4.3 Characterisation of aquifer parameters

To characterise the permeability of the geological units, slug testing has been undertaken on a number of monitoring bores across the audit area. Slug testing and triaxial permeability testing was also undertaken at a number of locations for the HBMS investigations. Properties of the aquifers obtained from various investigations are summarised in Table 28.

Table 28 Summary of Aquifer Parameters

Unit15 Common Yield (L/s)

Hydraulic Conductivity (m/d)

Specific Yield

Storage Coefficient

Salinity (mg/L)

Hydraulic Gradient

Fill16 1.0-1.5 0.08-0.15

Port Melbourne Sand <1-5 0.8-50 0.1-0.3 - <1000-10,000 -

Coode Island Silt / Fishermens Bend Silt - 6x10-6 - - 60,000 -

Newer Volcanics Mostly <1 1-6 0.02 - 3200 0.001

Moray Street Gravels ID (1-10) ~1-10 ID (0.1-0.2) ID (0.0001) >10,000 -

Brighton Group <0.5-15

(Mostly <3) 0.1-2 0.05 – 0.2 0.0004 4000 ID (0.001)

Newport Group - 0.02-0.002 - - - -

15 Note: Port Melbourne Sands and Moray Street Gravels have not been encountered in the audit area. 16 Water Studies Pty Ltd, 2000


Unit15 Common Yield (L/s)

Hydraulic Conductivity (m/d)

Specific Yield

Storage Coefficient

Salinity (mg/L)

Hydraulic Gradient

Older Volcanics Up to 5 1-5 <0.2 - <2000 0.001

Werribee Formation <50 (mostly <5) 3-15 0.15-0.3 0.0002 4000 0.001

10.5 Groundwater Flow Directions and Potentiometry

10.5.1 Introduction

Groundwater flow has to be considered in a regional and local context. The regional context explains the broad flow patterns within the Newer Volcanics and Brighton Group and is likely to be southwards towards Port Phillip Bay. At a local scale, site activities, site cover (e.g. pavement extent) can influence the extent of recharge of shallow groundwater in the fill and shallow infrastructure can give rise to local artificial recharge or preferential flow paths, and deep infrastructure (e.g. the North Yarra Main Sewer) can give rise to a change in the flow direction as discussed in Section 10.5.2.

10.5.2 Groundwater flow within the Precinct

On the eastern side of the Precinct the natural land surface slopes towards the adjacent river, and groundwater flows towards the Maribyrnong and Yarra Rivers, and evidence of radial flow across the Mobil site towards the river and also the backwash.

While regional groundwater flow is expected to be towards the river, data suggest that on the western side of the site the groundwater flow direction is being influenced by the presence of a deep sewer beneath Whitehall Street, the North Yarra Main Sewer, sometimes referred to as the Whitehall Street sewer. The sewer follows Whitehall Street and traverses the entire length of the Precinct. The location of the sewer is mapped onto Figure 3. The sewer is reported to be as deep as 24-25 m below Whitehall Street in the vicinity of the PoMC site are 221 Whitehall Street (former Pivot site), approximately 17 m below ground surface near the Orica main site, and indicated at about 20 m below ground level on cross-sections prepared for the Mobil site in the south. A number of reports describe the sewer in some detail. Of note from the information contained in Coffey (July 2000) and CH2M Hill (2003) reports are the following comments:

the sewer was built in 1895 and is constructed in the sediments of the Brighton Group formation, with up to 15 m of overlying basalt;

the sewer is circular, 2.6 m in diameter, with walls of triple brick construction;

no backfill was placed along the top of the sewer brick section and there may be voids above the top of the sewer;

the structural elements of the sewer are considered by Melbourne Water to be in relatively good condition but with a history of groundwater leakage (as reported by Coffey, July 2000; pers. comm., Mr Howard Hunter; Melbourne Water, 1998);

the depth, age and condition (potential voids in the sewer) of the sewer make it a potential sink for groundwater from the Precinct;


any groundwater entering the sewer would be transported through the sewerage system to the Western Treatment Plant at Werribee;

CH2M Hill (2003) mention that there have been projects involving repair of sewers have been undertaken to reduce the volume of water flowing to the Werribee Treatment Plant, though it is not clear from the report as to whether this included any repair of the Whitehall Street sewer; and

Groundwater flow across the region is in the opposite direction to what would be expected (i.e. towards the river) and is drawn down well below 0 m RL, which is the approximate level of the river.

The potential for the sewer to be acting as a groundwater drain has been largely confirmed by various groundwater investigations across the Precinct. Groundwater gradients within the Brighton Group sediments are reported as flowing across the Precinct to the west, and are likely to be discharging into the sewer beneath Whitehall Street. The direction of flow across the Precinct is represented on the Conceptual Site Model (Figure 4).

10.6 Estimated Flux of Groundwater into the River

10.6.1 Groundwater flux model

The estimation of groundwater flux into the river has been based on Darcy’s Law, and a simplification of the hydrogeology.

Figure 11 Groundwater flux model

The flow per unit length of river frontage is proportional to the hydraulic gradient and hydraulic conductivity of the saturated materials.

10.6.2 Flux through the fill material to the river

The hydraulic conductivity of the fill materials has not been quantified for all of the sites within the Precinct and for the purposes of this preliminary estimate, a conductivity of 1 m/day has been assumed. This is within the range or a sand or sandy gravel aquifer.

K

i v


A hydraulic gradient of 0.05 has been adopted. Available water level information near the river suggests low hydraulic gradients so this is considered a conservative assumption.

At the northern end of the site the fill can be up to 4 m (CSR Limited site), however in other areas it is thinner and commonly unsaturated, thinly saturated at its base with the Coode Island Silt.

Assuming an average thickness of saturated fill of 1 m, a conductivity of 1 m/day, and a hydraulic gradient of 0.05, the groundwater flow rate and discharge to the river per day is 0.05 m3/day per m length of shoreline.

10.6.3 Flux through the Coode Island silt to the river

The Coode Island Silt is a recognised low permeability formation with hydraulic conductivities in the range of 10-6 m/day. Adopting a saturated thickness of 10 m, the discharge to the river is 10-5 m3/day per m length of shoreline and is much less than the flow through the fill. It can be assumed that the contribution of flow through the Coode Island Silt to the river contaminant load is negligible and does not require further consideration.

10.6.4 Flux through the Brighton Group to the river

Lateral flow from the Brighton Group into the Yarra River is expected to be minimal given the presence of the Coode Island Silt (and possibly Fishermens Bend Silt) acting as a confining layer, and because of the effect of the North Yarra Main Sewer. Even though the Brighton Group may be exposed in the base of the Yarra River through dredging activities, the sink formed by the Sewer may preclude discharge of the groundwater in the Brighton Group to the River.

10.6.5 Data gaps

The following works are recommended:

Collation of all groundwater bores into a single spreadsheet;

Construct isopachs for the various lithologies for the audit area, notably fill, Newer Volcanics, Brighton Group and Coode Island Silt;

Contouring of water levels undertaken using all monitoring bores (in their respective aquifers) for the audit site.

10.7 Groundwater Quality and Flux of Contaminants to the River

10.7.1 Natural groundwater quality

A Victoria State Groundwater Database search for registered users of groundwater in the vicinity the Mobil Terminal was reported in Mobil’s Quantitative Risk Assessment (URS, 2005). Twenty-nine groundwater bores were reported within a 1 km radius of the terminal site, and all were registered for investigation purposes. TDS was reported between 9,500 mg/L and 24,942 mg/L. There was insufficient information to determine what aquifers were screened.


A Groundwater Database search was completed for CSR in 2001.17 Thirty-six bores are reported within a 1 km radius of CSR Limited. Groundwater salinity ranged from 2,344 to 24,942 mg/L TDS; 2,977 to 11,000 mg/L TDS in the Newer Volcanics, and the limited information on the salinity of the Brighton Group reporting similar salinity to that in the Newer Volcanics.

10.7.2 Groundwater contamination

Information extracted from the consultant assessment reports for the various sites focussing on the maximum recorded concentrations in wells closest to the river is summarised in Table 30 for toxicants, and in Table 31 for nutrients.

Table 30 summarises the maximum measured concentrations and corresponding exceedence of the ecosystem protection guideline. In this Table the exceedences of the 90% ecosystem protection guidelines listed in the ANZECC Fresh and Marine Water Guidelines 2000 are indicated for these maximum concentrations. A ranking and colour coding has been provided to simplify the identification of where the exceedences are most significant, as shown in Table 29:

Table 29 Exceedence Factor Legend

Ranking Exceedence of Ecosystem Protection Guidelines

1 < 1

2 1 – 10

3 11 – 100

4 101 – 1000

5 1000 – 10,000

6 >10,000

Caution is required in interpreting the information presented in these Tables and it is important to note the following.

The concentrations reported are the maxima, and can be expected to be significantly greater than the average concentration actually discharging to the river.

Information on some sites is limited and groundwater samples have not necessarily been analysed for some of the contaminants. Thus the information may not be representative of the highest concentrations on all sites.

For some sites the information is limited and the location of bores makes their relevance as indicators of groundwater contamination that may discharge to the river uncertain. This is particularly the case for the Albright & Wilson site, and to some extent the Orica main site and CSR Limited land. Some groundwater bores that are monitored and reported for these sites are located on PoMC owned land that lies between the eastern site boundaries and the river segment. Rather than exclude the information due to the complexity of the land ownership and occupancy matters, the auditor has relied on this information as an indication of groundwater quality leaving the sites and discharging to the rivers.

17 Reference: commercial-in-confidence.


The ANZECC (2000) ecosystem protection guideline values can apply both in the river water after dilution, and also in the pore water of the riverbank (as may be relevant for protection of the ecosystems associated with the river bank)18 prior to dilution.

Of the other beneficial uses of the river water that require protection, primary contact recreation is the other sensitive use in terms of setting stringent guideline levels for contaminants in water. Comparing the default Australian Drinking Water Guidelines 2005 (NHMRC, 2005) with the ecosystem protection guideline values indicates that the ecosystem protection guideline levels are more stringent (i.e. are lower concentrations) than the drinking water guideline levels all for all of the contaminants in Table 30, with the exception of cadmium, nickel and ammonia.

In the case of ammonia, the drinking water guideline of 0.5 mg/L is set on the basis of aesthetic considerations (corrosion of copper pipes and fittings) rather than human health, and ammonia is not limiting with respect to primary contact recreation.

In the case of nickel and cadmium, the maximum measured concentrations in groundwater are less significant than the other contaminants considered in Table 30, and it can be concluded that the requirements for protection of aquatic ecosystems is the limiting requirement.

In the case of nutrients, the ANZECC (2000) guidelines provide default trigger values applicable to south-east Australia for slightly disturbed ecosystems. Similar to the objectives specified in Table 30 for toxicants, the trigger values for physical and chemical stressors (such as nutrients) are used to assess the risk of adverse effects in surface waters. The trigger values for estuaries are included in Table 31. Note that the SEPP WoV includes some objectives for the nutrients within the SEPP, but in the case of the subject audit area, these are not covered by SEPP and the SEPP defaults to ANZECC 2000.

The ANZECC trigger values are conservative values for initial screening purposes only, and may not be applicable to the tidally flushed river environment that applies in the Whitehall Street river segment.

18 The auditor sought clarification from EPA on this matter, and EPA confirmed that consideration should be given to the

requirements for protection of the riverbank ecosystems (EPA, pers. comm., 22 August 2006).


Table 30 Preliminary Screening19 - Summary of Groundwater Toxicants that Exceed the ANZECC (2000) Ecosystem Protection Guidelines, Maximum Measured Concentrations and Corresponding Exceedence (mg/L)

Parameter pH (units) As Cd Cr Co Cu Pb Hg Ni Se Zn

Sulfate (S)

Ammonia (N)

ANZECC (2000)

Guideline trigger values for 90% species protection in marine waters 6.5-8.5 0.04220 0.014 0.02 0.014 0.003 0.0066 0.0007 0.2 0.003 0.023 ns 1.2

POMC – Concentration 3-7.2 81 0.21 0.049 1.2 200 1.1 0.001 0.8 na 75 450-18000 6700

Exceedence Factor 1930 15 2.5 86 66700 183 1.4 4 3260 5580

Contaminant Ranking 5 3 2 3 6 4 2 2 5 5

CSR Limited - Concentration na nd 0.015 0.09 0.62 0.16 0.012 0.004 1.1 0.068 1.7 2500 53

Exceedence Factor 1 4.5 44.3 53 2 5.7 5.5 23 74 44

Contaminant Ranking 2 2 3 3 2 2 2 3 3 3

Orica main site – Concentration 3.2 –7.3 16 0.29 0.099 na 6.2 4.7 0.0004 2.6 na 82 10000 78

Exceedance Factor 381 21 5 2070 783 13 3570 65

Contaminant Ranking 4 3 2 5 4 3 5 3

Albright & Wilson21 - Concentration 3.17 24.6 0.127 0.006 4.51 0.903 0.509 nd 1.21 0.01 58.1 8190 na

19 This assessment utilises maximum reported concentrations in wells, and may significantly over-estimate the average concentration actually discharging to the river. It follows that the

exceedence factors have a high level of uncertainty and additional information would be required before reliable exceedence factors can be determined. 20 Note, EPA has used the arsenic water quality objective of 42 μg/L in their assessment of water quality in these estuaries (see Section 12), which has been adopted here. This is the

ANZECC (2000) 90% trigger value for As (V) in freshwater. ANZECC (2000) provides a low reliability marine trigger value of 4.5 μg/L for As (V) based on a very limited set of data. 21 The groundwater quality data set for Albright & Wilson is very limited, and the concentration listed is the concentration reported for MB7. This is easternmost bore that is screened in the

fill and reported within the Albright & Wilson data set for their groundwater quality, and appears to lie within the Orica main site boundary just north of Albright & Wilson’s north east corner. Other Albright & Wilson bores that are screened within the fill aquifer are located towards the centre and western portion of the Albright & Wilson site. The concentrations reported in Table 30 are generally higher than the reported concentrations for the other shallow aquifer bores on the Albright & Wilson site, and so may over estimate the concentrations leaving Albright & Wilson, particularly for zinc, copper and cobalt.


Parameter pH (units) As Cd Cr Co Cu Pb Hg Ni Se Zn

Sulfate (S)

Ammonia (N)

ANZECC (2000)

Guideline trigger values for 90% species protection in marine waters 6.5-8.5 0.04220 0.014 0.02 0.014 0.003 0.0066 0.0007 0.2 0.003 0.023 ns 1.2

Exceedence Factor 586 0.014 0.02 322 301 85 6 3 2530

Contaminant Ranking 4 1 1 4 4 3 2 2 5

Mobil: June 2005 - Concentration na 0.422 0.0002 na na 0.002 nd na 0.002 na 0.037 na na

Exceedence Factor 10 0.01 0.67 0.01 1.6

Contaminant Ranking 2 1 1 1 2

Notes: na = not assessed; nd = not detected; ns = sot specified.


Table 31 Preliminary Screening - Summary of Nutrients in Groundwater that exceed the ANZECC (2000) Trigger Values for Estuaries, Maximum Measured Concentrations and Corresponding Exceedence (μg/L)

NOx (as N) NH4+ (as N)

Parameter Total Phosphorus Phosphate (as P) (Total Nitrogen = 250)

ANZECC 2000

Trigger value – Estuaries

20 15 13

POMC site

221 Whitehall St

158,000 100,000 16,000 (NO3-N)

2,170 (NO2-N)

6,700,000

Exceedence Factor 7,900 1,211 515,000

Contaminant Ranking 5 5 6

CSR Limited22 31,000 na 170,000 (NO3-N)

5,200 (NO2-N)

53,000



Orica main site 69,000 na 23,000 78,000



Albright & Wilson23 76,400 nd na na

Exceedence Factor 3,820

Contaminant Ranking 5

Mobil Nutrients not assessed24

Exceedence Factor

Contaminant Ranking

Notes: na = not assessed; nd = not detected; ns = sot specified.

22 A CSR Limited groundwater bore GW2 (tested in 2001) reported elevated phosphorus and nitrogen compounds particularly

ammonia and nitrate (total nitrogen = 190 mg/L). GW2 is located along the northern boundary adjacent the former Pivot site. It is screened in the basalt. Other CSR Limited groundwater wells (GW1 & GW3) reported maximum total nitrogen at 8 mg/L and phosphorus was not detected though it is noted that these wells are screened in basalt and Brighton Group. Wells on CSR Limited land that are screened in the fill did not analyse for nutrients.

23 The concentration listed is the concentration reported for MB7. This is easternmost bore that is screened in the fill, and is reported within the Albright & Wilson data set for groundwater quality, and appears to lie within the Orica main site boundary just north of Albright & Wilson’s north east corner. Other Albright & Wilson bores that are screened within the fill aquifer are located towards the centre and western portion of their site. In the Albright & Wilson data set for groundwater bores screened in the fill report total phosphate up to 13, 700 mg/L and total phosphorus up to 5,680 mg/L. Using only the MB7 concentration, as reported in Table 31, may underestimate the concentrations (particularly P) leaving Albright & Wilson.

24 EPA waste discharge licence (MW159) does not require Mobil to test groundwater samples for nutrients; information on nutrients in groundwater beneath the Mobil site was not available.


A summary of the most significant exceedences is provided in Table 32. The analysis indicates:

Copper is the most significant toxicant, with the maximum measured groundwater concentration corresponding to an exceedence of the ecosystem protection criteria in the order of 50,000 – 100,000 for one of the sites.

Arsenic, zinc and ammonia are the next most significant toxicants, with the maximum measured groundwater concentrations exceeding the ecosystem protection criteria in the order of 1,000 – 4,000 for arsenic and zinc, and 6,000 for ammonia.

Phosphorus and nitrogen are also significant contaminants, with the maximum measured groundwater concentrations corresponding to an exceedence of ecosystem stressor levels of more than 10,000 for phosphorus on the PoMC site and for nitrogen on CSR Limited land, and greater than 500,000 for ammonia on the PoMC site.

There is limited data available on the composition of groundwater on the CSR Limited land, in particular for nutrients in groundwater, and the available information is variable and difficult to interpret. Wells on CSR Limited land that were screened in the fill were not analysed for nutrients, and the source of contaminants and the relevance of the concentrations measured in deeper wells to the concentrations that might be observed in the shallow groundwater is not certain. The results listed in Table 31 reflect information pertaining to groundwater bore GW2 (tested in 2001) and screened in the basalt aquifer that reported elevated phosphorus and nitrogen compounds in particular total nitrogen concentration of 190 mg/L and phosphorus at 31 mg/L25. However, the location of GW2 is along the northern boundary of the CSR Limited land and next to the former Pivot site (now PoMC owned land) and it may not reflect concentrations across the CSR Limited land. Note that in GW1 (screened in the basalt aquifer) and GW3 (screened in the deeper Brighton Group aquifer) concentrations of nutrients were much less (in the latter wells the maximum nitrogen was reported at 8 mg/L and phosphorus not detected). This uncertainty is indicated as such in Table 32.

No information was available for nutrients in groundwater for the Mobil site, representing a gap in the data though it is noted that nutrients are not expected to be a contaminant of concern for the terminal site.

Table 32 Summary of Most Significant Exceedences

Contaminant Maximum levels of exceedence of ecosystem protection guidelines by contaminant concentrations in groundwater

Sites

Toxicants

Arsenic 2,000 PoMC site

200 – 600 Orica main site, Albright & Wilson

Cobalt 300 Albright & Wilson

Copper 70,000 PoMC site

2,000 Orica main site

Lead 100 – 1,000 PoMC site, Orica main site

Zinc 2,000 – 4,000 PoMC site, Orica main site, Albright & Wilson

25 Reference: commercial-in-confidence


Contaminant Maximum levels of exceedence of ecosystem protection guidelines by contaminant concentrations in groundwater

Sites

Ammonia 6,000 PoMC site

Nutrients

Phosphorus 3,000 - 8,000 PoMC site, Orica main site, Albright & Wilson, possibly CSR

Nitrogen (ammonia) 515,000 PoMC site, Orica main site, possibly CSR

Note: PoMC site refers to 221 Whitehall Street, Yarraville

10.7.3 Flux of groundwater contaminants to the river and corresponding concentration in river

The flux of each of the most significant contaminants to the river system has been estimated by assuming that the maximum measured concentration for a site occurs over a groundwater discharge area equal to the river frontage of the site, at the rate of 0.05 m3/day per m of river frontage. The flux estimates are summarised in Table 33.

Note that these estimates assume the maximum groundwater concentration is discharged over the whole of the site river frontage, and can be expected to be conservative and to overestimate the actual discharge.

The results of these estimates indicate that the discharges of arsenic, lead, zinc and ammonia should not give rise to concentrations in the river water that exceed the ecosystem protection guideline. Note that these estimates are directly dependent on the assumed flow rate of groundwater, and there is a high level of uncertainty in the flow estimate.

In the case of copper, using the maximum measured groundwater concentration suggests that it could be possible that the concentration of copper in the river water could exceed the guideline level (although the exceedence is not great), and that the discharge of copper warrants further consideration.

Table 33 Flux of Contaminants to the River Assuming Maximum Measured Concentrations

Contaminant Total mass discharge from the Precinct sites1

(assuming discharge from each site at the maximum measured concentration in groundwater for that site (kg/day))

Concentration after dilution in 750,000 m3/day river water

Exceedence26

(predicted river water contaminant concentration):(contaminant guideline value)

Toxicants

Arsenic 1.8 0.002 0.06

Copper 3.6 0.005 1.6

Lead 0.1 0.0001 0.02

Zinc 3 0.004 0.18

Ammonia 120 0.15 0.1

26 The exceedence estimate is conservative and can be expected to overestimate the mass discharge in that it assumes that the

concentration of the whole of the groundwater discharge is at the maximum reported concentration for the foreshore wells.


Contaminant Total mass discharge from the Precinct sites1

(assuming discharge from each site at the maximum measured concentration in groundwater for that site (kg/day))


Exceedence26


Nutrients

Phosphorus 5 0.006 0.3

Nitrogen (NOx) 2.3 0.003 0.2

Nitrogen (ammonia) 120 0.15 10

10.7.4 Copper – Refinement of the discharge estimate

A more detailed assessment of the concentrations of copper in the groundwater at the PoMC site has been carried out. Of the groundwater bores on the site, the bores most relevant to indicating the concentration of groundwater discharging to the river are GW1, GW2, GW3, GW4, GW10, GW11, GW12, GW13, GW14, GW15, GW21, and GW24. While the maximum measured copper concentration in these bores was 200 mg/L, the average concentration of copper was approximately 10 mg/L. Assuming that this average concentration will better represent the concentration of copper that will discharge to the river, it can be concluded that the discharges of copper are not expected to result in concentrations in the river water that will exceed the ecosystem protection guideline. A similar process can be applied to toxicant discharges from other sites.

Note that this revised estimate is directly dependent on the assumed flow rate of groundwater, and there is a high level of uncertainty in the flow estimate.

Table 34 Copper Discharge – Refinement of the Discharge Estimate

Contaminant Assumption Average concentration in wells on PoMC site

(mg/L)

Total mass discharge from the POMC site (kg/day)


Exceedence


Copper

Copper discharges at the average of the measured concentrations of the groundwater bores

10 0.18 0.00025 0.08

10.7.5 Nutrients

The estimated concentration of ammonia discharging to the river significantly exceeds the ecosystem trigger value for nutrients (although the predicted concentration does not exceed the level for toxicants), and averaging the concentration of ammonia in the foreshore wells for the PoMC site where the concentration is very high similar to copper indicates that the average concentration of total ammonia as N can be expected to be in the order of 700 mg/L.


Estimating from this the resulting river water concentration indicates that ammonia is in the order of the levels that might exceed the ANZECC (2000) nutrient stressor trigger levels, particularly when allowance is made for other contributions of N (i.e. from other sites outside of the river segment such as from Coode Island or other upstream sources, stormwater runoff and urban contribution in the catchment, and from nitrate etc).

There have not been reported observations of nutrient stress (such as algal blooms) in the river segment; however, the status of the river segment in this regard is not well characterised and further consideration of this is warranted.

Table 35 Ammonia Discharge – Refinement of the Discharge Estimate

Contaminant Assumption Average concentration in wells on PoMC site

(mg/L)

Total mass discharge from the POMC site (kg/day)


Exceedence


Nitrogen (ammonia + nitrate as N)

Nitrogen compounds discharge at the average of the measured concentrations of the groundwater bores

695 (total ammonia as N) 12.5 0.017 1.3

10.7.6 Conclusions

The assessment indicates that the concentrations of the toxicants (arsenic, copper, lead, zinc and ammonia) measured at high concentrations in the groundwater exceed the ANZECC (2000) ecosystem protection guideline values prior to dilution (as can be relevant to protection of ecosystems associated with the river bank), but after dilution in the river water should not exceed the guideline values for protection of the beneficial uses of the Maribyrnong and Yarra Rivers. In particular, the assessment suggests that the concentrations of heavy metals (arsenic, copper, lead and zinc) would not exceed a few micrograms per litre in the river water, and are not expected to exceed their respective guideline trigger values.

In the case of nutrients, the assessment indicates that phosphorus should not exceed the nutrient stressor trigger levels specified for ecosystem protection, but nitrogen (as ammonia) may give rise to a nutrient stress on the river ecosystems.

These conclusions rely on the following assumptions.

The discharge of contaminants in groundwater can be estimated from the concentrations measured in the groundwater on site. In practice there are natural mechanisms for removal of metals in the river water after discharge, and these can significantly reduce the concentrations that would be observed in the river water. This is particularly the case with discharges into seawater, where there are strong mechanisms for precipitation, flocculation and settlement that can effectively reduce contaminant concentrations to low levels.

The flow of contaminated groundwater has been assumed to be in the order of 0.05 m3/day per m length of foreshore. There is a high degree of uncertainty in this estimate, and it is possible that the flow could vary from this both on average over the length of the shoreline and at specific locations along the shoreline.


The average concentrations of contaminants in groundwater discharging from the sites do not significantly exceed the concentrations measured in the work carried out to date. This appears to be a reasonable assumption.

The shallow groundwater generally located in the fill until beneath the sites is contaminated and this groundwater is expected to discharge to the upper less saline layer of river water, rather than into the bottom saline layer where the dilution would be less. This appears to be a reasonable assumption, noting that the groundwater discharge is related to the fill rather than deeper geological units, and the discharge is less saline than the river water and will tend to flow over the higher density lower saline layer in the riverbank.

Note that this suggests that any effects on the ecosystems of the river bank will be limited to the localised areas where groundwater discharges.

Because of the level of uncertainty in the estimates, direct measurement of the concentrations of contaminants in the river water are important in determining whether contaminants are present at concentrations of concern, discussed in Section 12 of this report.

10.8 Data Gaps Key data gaps and uncertainties in the analysis include:

Incomplete sets of analyses of groundwater on the various sites;

Limited numbers of groundwater wells on the various sites, particularly wells that would characterise the groundwater discharging to the river;

Incomplete characterisation of the depth of fill in the various sites and the rate of groundwater flow to the river;

The extent to which groundwater dilutes in the main river flow, or forms a more concentrated zone of contamination close to the river bank; and

The extent to which dilution occurs within the river bank and the extent and significance of the effect of groundwater prior to dilution with respect to the river bank ecosystems.


11. Point Source Discharges to the River

11.1 Source of Information Information on point source discharges to the river, including licensed and stormwater discharge points, was largely determined through a review of EPA waste discharge licences for the various sites, licence compliance reports, and advice from EPA officers (client managers for the site) on whether it can be expected that discharges generally comply with the licence requirements. Note that the audit information was restricted to data provided by EPA, and the auditor did not carry out inspections of the various sites nor collect samples from licensed and non-licensed outfalls.

In general, the quality of discharges to the river can be expected to be variable and there are limited data on the point source discharges, giving rise to a high level of uncertainty regarding the quality of discharges, particularly on a day-to-day basis. Because of this, the following commentary should be regarded as indicative of the situation, and not definitive or quantitative.

Note that this audit is particularly concerned with discharges that may give rise to an ongoing impact on the river system, rather than one-off spills or non-compliance that might have only a short-term effect.

11.2 EPA Licences for the Various Sites EPA licences are required for all scheduled premises, unless the premises are exempted in the regulations. Licences cover the actual operation of the site and set operating, waste discharge limits, and waste acceptance conditions as appropriate. The Environment Protection Act 1970 specifies penalties for breach of licence conditions, or for operating a site without a licence.

The Environment Protection (Scheduled Premises and Exemptions) Regulations designates certain industrial or commercial activities (scheduled categories) as belonging to one or more of the following six types as defined in the Environment Protection Act:

Schedule 1 – Waste discharged or likely to be discharged to the atmosphere;

Schedule 2 – Waste discharged or likely to be discharged onto any land or into any waters;

Schedule 3 – Noise is or is likely to be emitted;

Schedule 4 – Sites which accept any prescribed waste for the purposes of reprocessing, treatment, storage or disposal; or which generate and then reprocess, treat, store or dispose of certain wastes (listed in the regulations);

Schedule 5 – Premises where EPA may require a financial assurance to cover future clean up costs; and

Schedule 6 – Premises at which any ozone depleting substance is handled.

Several of the industries within the Precinct hold an EPA licence for their operations – specifically for discharges into the river segment adjacent their sites. Some of the licences also specify controls on the discharge of stormwater, generally ensuring that any stormwater released from specified stormwater discharge points on the sites is free of contamination that would adversely affect the beneficial uses of the river. The licences that apply to the various sites have been previously discussed in Section 6.


The known licensed and unlicensed discharge points are outlined in the following sections. The information in this section is largely derived from the EPA waste discharge licences. It is possible that other discharge points or stormwater outfalls to the river segments may exist apart from those specified in the EPA waste discharge licences; however, there was limited information available on this for the audit.

11.3 Wastewater and Stormwater Discharges from PoMC Information on the likelihood of discharges of contaminated stormwater and process discharges to the river from the PoMC site is summarised in Table 36.

The available information suggests that the PoMC site activities and stormwater are unlikely to form a significant ongoing source of contamination of the river water as processing activities are no longer carried out at the site and the auditor has been informed that upgrades to the on-site stormwater system mean that stormwater is collected and discharged to the sewer.

Table 36 PoMC Site - Discharges to the Lower Yarra River from 221 Whitehall Street, Yarraville

Primary Information Sources Clean up notice issued 18 November 2003

Consultation with PoMC representatives

Consultation with EPA officers

CH2M Hill, Further Site Assessment September 2004

Roger Parker, Environmental Audit Report, February 2005

Licensed discharge to surface water

No EPA licence for the site

Potential contaminants and potential for contamination of surface waters

Fertiliser materials are present on the site that could be washed into stormwater; contaminated fill (pyritic wastes and cinders).

Stormwater discharge Drain runs east-west through the centre of the site. Since 2003 the stormwater collected by this drain has been discharged to sewer under a agreement with the water authority.

Not known whether other discharge points to the Yarra River exist.

Stormwater treatment Central drainage line runs east-west across the site however stormwater is collected and discharged to sewer.

Stormwater discharge quality This information has not been provided to the auditor.

Note: CH2M Hill (2004) reported purple staining along the stormwater drain and close to the river’s edge. The purple staining is indicative of the pyritic waste used as fill along the eastern margin of the site. A potential risk to the river from contaminated stormwater was noted in the audit report for the site (Parker, 2005) and discussed in Section 6.2.7 of this report.

It is likely that this may represent pre-2003 impacts from stormwater releases, rather than current discharges, noting that the auditor has been informed that stormwater is now collected and discharged to sewer.

11.4 Wastewater and Stormwater Discharges from CSR Limited Information on the likelihood of discharges of contaminated stormwater and process discharges to the river from the CSR Limited site is summarised in Table 37.

The available information suggests that the site situation and activities could give rise to significant quantities of gypsum washing from the site into the river, although a stormwater collection and first flush system (with the first flush discharging to the sewer) and the development of a stormwater management plan will reduce this.


CSR Limited have informed the auditor that a stormwater management plan for the gypsum yard and stockpile area includes a first flush interceptor pit, and the water from this pit is used for stockpile dampening activities. There are some housekeeping issues with the gyprock operation at the CSR Building Products Ltd site resulting in some gypsum dust escapes from the site onto Lyell Street. Gypsum dust that escapes the site boundary could potentially be washed into the river in a rainfall event.

It does not appear that the site will be a significant ongoing source of contaminants other than gypsum, such as may arise from contaminated fill, sugar, or process waters. Consultation with a Sugar Australia representative confirmed that the process water discharge to the river is essentially cooling water and should be free of contamination (pers. comm., 8th December 2005).

Table 37 CSR Limited Discharges to the Lower Maribyrnong River

Primary Information Sources

EPA licence EM34977 on Sugar Australia Pty Limited

Pollution Abatement Notice on CSR Limited (issued 17 May 2004)

Consultation with CSR Limited and Sugar Australia representatives

Sugar Australia, excerpt from the Annual Performance Report 2004/2005

Sugar Australia holds EPA licence EM34977.

Licensed Discharge Point B (cooling water) to the Maribyrnong River.

Note: A mixing zone is specified in the EPA licence. Sugar Australia occupies the portion of the CSR Limited land that faces towards the river.


No EPA licence for CSR Building Products Ltd or CSR Distilleries Operations Pty Ltd


The site is largely paved, and it does not appear that fill would wash off into the river.

There are large quantities of gypsum on the site. Some gypsum dust is reported to escape the site boundary and this could wash off in stormwater ad discharge to the river. The gypsum is likely to be relatively inert and is unlikely to add significant contamination by heavy metals.

Large quantities of sugar are handled on the site, but the sugar is contained undercover and would be highly unlikely to enter the storm water system.

Stormwater discharge EPA licence EM34977 requires stormwater monitoring at Discharge Points A and C.

CSR Building Products Ltd collects stormwater from its roof and discharges this water along with stormwater runoff from the warehouse to the Lyell Street stormwater drain. The stormwater runoff from the gypsum storage area is collected in an interception pit with the collected water being reused in dampening activities on the gypsum stockpile.

Discharge parameters Dissolved oxygen, temperature, suspended solids, flow rate, 5-day biological oxygen demand, pH, acute toxicity, electrical conductivity

Licence compliance From Annual Performance Report 2004/2005 (Cooling water monthly monitoring July 2004 to June 2005):

Parameter Licence Limit Maximum Exceedence

(Number breaches indicated in brackets)

Exceedence Factor

Discharge Point B

Biological oxygen demand

Difference between background water and outlet water must be

<20 mg/L

Inlet water = 7 mg/L

Outlet water = 190 mg//L

Difference = 173 mg/L

(4 samples in 12)

9 times


Suspended solids27 Difference between background water and outlet water must be

< 20 mg/L

Inlet water = 11 mg/L

Outlet water = 73 mg/L

Difference = 62

(4 samples in 12)

3 times

Flow rate 25 kL/minute Up to 30 kL/min

(5 samples in 12)

5 kL/min greater

pH 6.5 to 8.5 No breaches

Temperature Difference between background water and outlet water must be

< 30 deg C

No breaches

Dissolved oxygen < 2 mg/L No breaches

Stormwater discharge quality

(Stormwater monitoring October 2004 and November 2004)

Discharge Point A and Discharge Point C

2004-2005 monitoring program reported:

Suspended solids from 110 to 770 mg/L;

BOD ranged from 130 to 170 mg/L;

Thymol ranged from of 60 to 100 mg/L;

pH from 5.2 to 7.0; and

DO from 8.9 to 9.4 mg/L.

Acute toxicity (Microtox), field electrical conductivity, TPH, total nitrogen and total phosphorus have not been assessed.

Gypsum dust from the site is likely to contribute to suspended solids, and sugar runoff may be contributing to BOD.

Stormwater treatment First flush to sewer.

It is understood that there are other stormwater run off points that are not captured by the first flush system, and are not monitored.

Stormwater management plan

Yes – in development and includes a plan to monitor all stormwater discharge points from the site.

The pollution abatement notice required a gypsum management plan by 30 June 2004, for approval by EPA. The auditor is not certain about the implementation status of this plan.

11.5 Wastewater and Stormwater Discharges from Orica Main Site Information on the likelihood of discharges of contaminated stormwater and process discharges to the river from the Orica main site is summarised in Table 38.

In summary, the available information suggests that the Orica main site and activities are unlikely to give rise to a significant ongoing discharge to the river of contaminants in surface water, although some discharges do occur. An important factor in this is the cessation of processing activities at the site.

27 Sugar Australia note that the refinery does not add suspended solids to the discharge, and that on several occasions within the

monitoring period a drop in the suspended solids in the discharge water compared to the inlet water was reported.


Table 38 Orica Main Site - Discharges to the Lower Yarra River

Primary Information Sources EPA licence EM35836

Clean up notice issued 13 May 2005

Consultation with Orica representatives



Orica holds EPA licence EM35836 with requirements on discharges from Discharge Point 1 to the “Maribyrnong River” as stated in the licence.

Note that while the site remains licensed, there are no longer has any scheduled activities on the site nor is there any wastewater discharge to the river.


There is some exposed fill on the site that could potentially give rise to contaminated stormwater, although a large portion of the site is paved.

It is known that there is significant soil contamination by contaminants such as mercury and chlorinated organics, although this appears to be confined to the western area of the site (which is paved) and it therefore appears that this will not runoff to the river.

The site no longer has processing activities taking place, and the risk from process discharges is therefore minimal.

Stormwater discharge Discharge Point 2 to the “Maribyrnong River” as stated in licence.

Discharge parameters Flow rate, pH, biological oxygen demand, dissolved oxygen, suspended solids, temperature, iron, and mercury.

Licence compliance and stormwater discharge quality

No licence compliance reports provided to the auditor; there has not been any wastewater discharge from the Orica main site to the river for some time.

Information on the discharge quality of stormwater has been provided (August and November 2005 stormwater monitoring reports). Some further detail is provided in Section 11.5.1 below.

Stormwater treatment prior to discharge

Limited information available; the auditor is not aware of the existence of a stormwater treatment plant on-site or sewer discharge agreement.

Stormwater management plan It is not known whether a stormwater management plan exists.

11.5.1 Stormwater quality leaving the Orica main site

Table 39 Information Received Relating to Stormwater Discharges from the Orica Main Site

Author Date Title

Coffey Geosciences Pty Ltd

31 August 2005 Factual Report on Stormwater Sampling. August 2005 Sampling Episode

Coffey Geosciences Pty Ltd

1 December 2005 Factual Report on Stormwater Sampling, November 2005 Sampling Episode

The auditor received two reports for stormwater sampling events that were undertaken in August 2005 and November 2005 at the Orica Main site. In the August 2005 sampling event stormwater samples were collected from the stormwater pit (sample “pit”) located close the magnesium hydroxide liquid plant and a composite sample from two downpipes draining the mercury cell-building roof.

In November 2005 stormwater samples were collected from four inlets to one stormwater pit (samples “Inlet 1-4”), a fifth sample from the pit (sample “pit”) close the magnesium hydroxide liquid plant and a composite sample from two downpipes draining the mercury cell building roof. The results for the stormwater samples from the mercury cell building were not attached to the report.


The analysis results reporting exceedences on the ANZECC (2000) guidelines for marine waters (90 percent protection levels) are shown in Table 40, as well as the results for other contaminants of concern within the Precinct or those analytes tested by EPA in their river sampling program (refer to Section 12).

The Orica stormwater reports note that the pit close to the magnesium hydroxide plant is the last stormwater pit within the Orica main site boundary before stormwater runoff is discharged into the Yarra River. Note that there us some uncertainty as to the source of the measured contaminants, and whether they may be sourced from off site28.

28 Orica advised that there is a potential for stormwater runoff from Albright & Wilson loading areas to enter the Orica stormwater

drains and to pass through the “Pit” sampled in November 2005 (Orica, correspondence with auditor on draft audit report, dated 14 August 2006).


Table 40 Orica main site - Stormwater Sampling Results (μg/L)

Parameter

As Cd Cr Cu Co Hg Ni Pb Se Zn Nitrate (as N)

Total ammonia (as N)

Phosphate Phosphorus

SEPP Water Quality objective 90th percentile trigger for highly modified ecosystem

4229 14 20 3 14 0.7 200 6.6 330 23 159.131 1,200 2032

August 2005

Pit 37 nd 1 24 8 1.1 6 3 nd 64 610 Na

Roof na na na na na 120 na na na na Na Na

November 2005

Pit 1,900 nd 8 19 150 1.7 79 8 31 44 1,000 1,500 710 230

Inlet 1 20 nd 2 11 nd 0.65 3 18 nd 67 400 nd 8.1 2.6

Inlet 2 3 nd 1 9 nd 0.44 1 8 nd 55 300 nd 2.9 1.3

Inlet 3 12 nd 6 85 9 7.6 19 44 3 230 1,100 nd 3.2 3.2

Inlet 4 13 nd 7 90 10 8.9 21 46 3 250 1,100 nd 3.6 3.4

na = not assessed

Nd = not detected

Exceeds ANZECC 2000 90th percentile trigger level (marine)

29 Note that EPA has used the arsenic water quality objective of 42 μg/L which is the ANZECC (2000) 90% trigger value for As (V) in freshwater; this has been adopted in

Table 40. ANZECC (2000) provides a low reliability marine trigger value of 4.5 μg/L for As (V). 30 ANZECC (2000) low reliability marine trigger value. 31 ANZECC (2000) low reliability trigger value NO3 (as NO3) of 700μg/L converted to NO (as N). 32 ANZECC (2000) trigger value (estuaries) for total phosphorus.


In addition to the results reported in Table 40, the samples were also submitted for a number of other analytes. The results of the testing program reported the following:

August 2005 sampling episode

The following analytes were reported below the limit of detection:

Other metals, and anions, cations and inorganic analytes reported detectable concentrations in the stormwater though the results are not considered to be elevated.

Phenoxy herbicides;

Halogenated ethane and ethene, halogenated methane, halogenated propane and propene;

Volatile organic compounds;

Organochlorine pesticides;

Organophosphorus compounds;

Polyaromatic hydrocarbons;

Total petroleum hydrocarbons and monocyclic aromatic hydrocarbons (apart from one detection of C6-C9 at 0.03 mg/L);

Polychlorinated biphenyls; and phenols; and

Cereclor, aniline and nitrobenzene.

November 2005 sampling episode

Other metals, and anions, cations and inorganic analytes not listed in Table 40 did not exceed the ecosystem guidelines, or were at low levels where guidelines were not available; and

The composite sample of stormwater collected from the roof of the mercury cell building was reported as lost during sample transportation and hence was not analysed.

The available information suggests that the Orica main site can give rise to discharges of stormwater with concentrations of contaminants in excess of the ecosystem protection guidelines.

The results of the stormwater quality sampling for the Orica main site indicate that the discharges of stormwater from the site can exceed ecosystem protection guidelines by up to a factor of 50 times (e.g. in the case of arsenic). As there is no flow data, and also the results do not provide a good characterisation of the contaminant concentrations with time, it is not possible to draw conclusions about their significance.

11.6 Wastewater and Stormwater Discharges from Albright & Wilson The information received on the discharges of contaminated stormwater and process discharges to the river from the Albright & Wilson site is summarised in Table 41.

The available information suggests that the Albright & Wilson site does not have any process water discharges to the river, however the licence indicates that there is a monitored stormwater discharge point to the river.

Risks associated with surface water discharges from the Albright & Wilson site are expected to be related to contaminated soil and fill runoff from the site. The information received on the environmental conditions at the site (albeit limited) provides evidence of pyritic cinders, phosphorus and other contaminants on the fill across the site surface.


The information provided to the auditor relating to known point source discharges to the river is summarised in Table 41.

Table 41 Albright & Wilson Discharges to the Lower Yarra River

Primary Information Sources EPA licence EA5608

Clean up notice issued 15 November 2005

Licence compliance report: 2004 monitoring results

Consultation with Albright & Wilson representatives



Albright & Wilson hold EPA licence EA5608.

There is no licensed discharge to water.


Phosphorus and phosphate are the principal contaminants of concern at the site; fill (including pyritic wastes) also pose a risk of contamination to the surface water.

Stormwater discharge Licence requires a sample of the uncontaminated stormwater be tested prior to release.

Discharge parameters Stormwater testing: total suspended solids, pH, biological oxygen demand, electric conductivity, and total phosphorus.

Licence compliance and stormwater quality

The licence compliance report provided to the auditor includes air quality results only, and this is not relevant to the audit.

No information has been provided on the quality of stormwater leaving the site.

Stormwater treatment prior to discharge

Limited information available; the auditor is not aware of the existence of a stormwater treatment plant on-site or sewer discharge agreement.

Stormwater management plan The auditor does not know whether a stormwater management plan exists.

11.7 Wastewater and Stormwater Discharges from Mobil Information on the likelihood of discharges of contaminated stormwater and process discharges to the river from the Mobil Terminal is summarised in Table 42. Although there are some licence breaches, it does not appear that the Mobil site is a significant contributor of contaminants to the river via surface water discharges.

Table 42 Mobil Discharges to the Lower Yarra River and Stony Creek Backwash

Primary Information Sources

EPA licence MW159 on Mobil Oil Australia Ltd Clean up Notice issued 8 July 2005 Consultation with Mobil representatives Consultation with EPA Officers


Licensed Discharge Point 1 represents process water and stormwater from the “southern catchment” to the Yarra River.


The contaminants most likely to be present on the site are petroleum hydrocarbons from the storage and handling of these materials. It does not appear that there are significant quantities of contaminated fill on the site. The northern catchment is paved in the areas where contamination is most possible from the site activities, and stormwater from this area is discharged to the river without treatment. Monitoring is required of this stormwater. Southern catchment process and stormwater is treated in the on-site wastewater treatment plant prior to discharge to the Yarra River.


Stormwater discharge Discharge Point 2 represents stormwater from the “northern catchment” to the Yarra River. Not known whether there are other stormwater discharge points at the site.

Discharge parameters Flow rate, total organic carbon, suspended solids, pH, dissolved oxygen, anionic surfactants, colour, phenols, Fe, Zn, Pb, Mn, total aromatic hydrocarbons and acute toxicity.

Licence compliance From Annual Performance Report 2003/2004:

Parameter Limit Maximum Breach (Number of breaches indicated in brackets)

Exceedence Factor

Anionic surfactants < 0.5 mg/L 0.88 mg/L (2 samples in 26)

2 times

Field dissolved oxygen

> 5 mg/L No breaches

Flow Rate < 2,500 m3/day No breaches

PH 6.0 – 9.0 No breaches

Suspended solids < 80 mg/L 320 mg/L (2 samples in 26)

4 times

Colour 100 platinum cobalt units

No breaches

Total organic carbon

< 40 mg/L No breaches

phenols < 0.3 mg/L 0.84 mg/L (3 samples in 26)

3 times

Total aromatic hydrocarbons

< 0.3 mg/L No breaches

Lead < 0.1 mg/L No breaches

Manganese < 0.5 mg/L No breaches

Zinc < 0.5 mg/L No breaches

Iron < 2 mg/L 5.9 mg/L (1 samples in 26)

3 times

Discharge Point 133 and Discharge Point 234

Microtox No measurable toxicity

Greater than 96% (3 samples in 26)

Difficult to interpret results

Stormwater treatment Northern catchment stormwater is discharged to the river without treatment. Monitoring is required of this stormwater. Southern catchment process and stormwater is treated in the on-site wastewater treatment plant prior to discharge to the Yarra River.

Stormwater management plan

Yes – developed and being implemented.

11.8 Other Discharges It is possible that there can be other discharges to the river segment, for example:

From wharf activities including spills of materials during ship loading and unloading operations. It is known that these have occurred in the past. However, it appears that the potential for significant ongoing discharges of this type is low.

33 Seventeen samples collected and tested from 31 December 2003 to 24 November 2004 34 Nine samples collected and tested from 18 December 2003 to 11 November 2004


Road stormwater runoff from the urban area. This will be a continuing source of contamination, and this will include some petroleum hydrocarbons and heavy metals.

Discharges from activities from upstream along the Maribyrnong and Yarra Rivers, and Stony Creek. There have been a number of anecdotal comments regarding potentially significant pollution sources, including for example historical market gardening along the Maribyrnong, old gasworks, discharges of stormwater and groundwater from Coode Island, general filling in the area associated with reclamation and re-alignment of the river systems, and urban and industrial activities (the site is the downstream of major Melbourne urban areas).

A large stockpile of white sand material was observed while undertaking the river tour of the Precinct. The stockpile was located on PoMC owned land that lies between the Orica main site and the river. The stockpile was not undercover, and did not appear to have sediment control or bunding in place. Orica advises that the material is pumice stone remaining from non-Orica activities. The stockpile could represent a source of sediment load to the river during rainfall events.

These various sources of contamination are not defined and have not been quantified.

11.9 Conclusions The sources and quantity of surface water discharges from the various sites, and hence the contaminants that may be discharged to the surface water via stormwater, have not been well defined by the information presented to the auditor. The information received does not allow these discharges to be quantified, however, it suggests:

There are a number of stormwater outfalls from the sites to the rivers – as indicated in the stormwater monitoring requirements imposed on the sites via their EPA waste discharge licences. In addition to these known discharge points there may be additional discharge points to the river;

The waste discharge licences for some sites specify regular stormwater monitoring for potential contaminants of concern, however the information provided to the auditor is limited in this respect and it is not practicable to quantify the quality of stormwater leaving the sites or the Precinct;

Generally the Precinct sites are not expected to give rise to significant point source discharges of heavy metals or organic industrial chemicals to the rivers, as it appears that most of the areas where contaminated fill is present are paved or in the case of the PoMC site, the stormwater is now discharged to sewer and unlikely to reach the river. Notwithstanding this, the situation is uncertain and further review of the areas of fill and paving and the extent to which stormwater is now collected and treated or disposed to sewer is recommended;

The licence compliance reports for some sites (e.g. Mobil and Sugar Australia) indicate some breaches of the licence limits. Notwithstanding this, it does not appear that either Mobil or Sugar Australia are likely to be significant contributors of contaminants to the river via the surface water discharges that leave their sites at their respective EPA licensed discharge points; and

There is potential for there to be significant sources of contamination from off site including, for example, stormwater from the general urban areas and residual soil and groundwater contamination associated with prior activities such as gas manufacture.


11.10 Data Gaps The extent to which stormwater and process water discharges to the river, and the quality of these discharges, is not well defined and is highly uncertain. Obtaining a better understanding of these discharges would require the assembly and review of drainage plans for each site, a detailed inspection of each of the sites particularly during rain events, the identification of dry weather discharges and their origin and sampling and analysis of these discharges, the identification of wet weather discharges and an assessment of the catchments for these discharges and sampling and analysis of the discharges.

Rainfall runoff and discharge to the river, if it occurs, can result in contaminated sediments in the vicinity of the discharge. Because of this, inspections and sampling and analysis should particularly include areas where contaminated sediments have been identified.


12. River Water Quality

12.1 Documents Information detailing water quality investigations of the lower Yarra and lower Maribyrnong Rivers has largely been provided by EPA Victoria, complemented by other sources assessments of the Port Phillip Bay catchment, as listed in Table 43.

Table 43 Information Received on Surface Water Quality

Author Date Title

Primary document for in-stream water and sediment quality

EPA Victoria June 2006 Water Quality Assessment: Lower Maribyrnong and Lower Yarra Estuaries, 2005 – 2006

Other reference documents

D Atkinson, Department of Mechanical Engineering

1973 A Study of the Maribyrnong River and Estuary, GDFT Paper No. 54.

Fischer, et al. 1979 Mixing in Inland and Coastal Water, 1979, Academic Press Inc.

Caulfield Institute of Technology

2 November 1981 Caulfield Institute of Technology, Water Studies Centre. Water Movement and Salinity in the Yarra and Maribyrnong Estuaries.

Claus J. Otto, CSIRO September 1992 Literature and information review of groundwater input of nutrients and toxicants to Port Phillip Bay, Technical Report No. 4, CSIRO Port Phillip Bay Environmental Study.

Black, et al., Victorian Institute of Marine Sciences

16 September 1993 Draft - Nutrient and Toxicant Outputs From The Yarra, Task No. N1.3, T1.2 for the Port Phillip Bay Environmental Study, Experiment 3. High River Flows Spring Tides.

Black, et al., Victorian Institute of Marine Sciences

19 November 1993 Draft - Nutrient and Toxicant Outputs From The Yarra, Task No. N1.3, T1.2 for the Port Phillip Bay Environmental Study, Experiment 3. High River Flows Spring Tides.

HydroTechnology Pty Ltd

December 1993 Groundwater Nutrient and Toxicant Inputs to Port Phillip Bay, technical Report No. 13, CSIRO INRE Port Phillip Bay Environmental Study.

G.J. Fabris and C.A. Monahan, Victorian Fisheries Research Institute

July 1995 Characterisation of Toxicants in Water from Port Phillip Bay: Metals, technical Report No. 18, CSIRO INRE Port Phillip Bay Environmental Study. Dated July 1995.

Brown, et al. 16 February 1998 Marine Fixed Sites Monitoring: Trends Report, draft version dated

12.2 Results of River Water Sampling and Analysis

12.2.1 Maribyrnong and Yarra Rivers

The most recent results of sampling and analysis of river water undertaken by EPA in March 2006 are summarised in Table 44. EPA provided a report to the auditor that included the results of earlier water sampling carried out in August 2005 and September 2005; this is included in Appendix M.


The earlier results of river water sampling and analysis carried out by EPA in August 2005 reported uniformly high concentrations of copper and selenium in all water samples. For these results see Table 6 of the EPA report (Appendix M). EPA advised the auditor that it had concern that the analytical methods used for trace metal analysis were subject to interference by high salinity and, because of this, EPA undertook the further program of sampling and analysis in September 2005 and March 2006; the results are summarised in Table 45. The auditor requested that the program included sampling from locations on a transect across the river from the Precinct, to provide information on whether contaminants might vary with distance from the Precinct. It is not clear whether this occurred in the final sampling program.

A sampling location map provided by EPA is included in Appendix N. It is noted that:

Port Phillip Bay and Hobsons Bay sampling locations (1919, 1229) are not included;

Sample location EP01 is described as upstream Whitehall Street. This was clarified by EPA as a location up-stream 221 Whitehall Street and more clearly defined as near Somerville Road (EPA, correspondence on 19 September 2006); and

EPA clarified that sample location 16 is likely to be upstream Maribyrnong River sample location EP07.

With respect to information on background water quality, the results of sampling and analysis of the waters of Port Phillip Bay and Hobsons Bay are included in

Table 45 for comparison.

The auditor notes that ammonia was not included in the March 2006 analysis suite. Ammonia was included in one sampling round (August 2005) in which the concentrations of ammonia were reported below the limit of detection (100 μg/L) in all samples.

In the EPA Water Quality Assessment Report (2006), river water data are compared to the ANZECC (2000) water quality guidelines for the protection of cultured fish, molluscs and crustaceans in marine waters (aquaculture guidelines). These guidelines have been developed to assist water managers to maintain an appropriate level of ambient water quality for existing and future aquaculture uses, such as commercial farming of fish and prawns in marine waters. The guidelines are intended to be used in conjunction with the Food Standards Code to protect the health of human consumers of aquatic foods from the aquaculture industry. Reference to the aquaculture guidelines has not been included in Tables below as commercial fish farming is not an existing, likely or approved beneficial use within the Precinct.


Table 44 EPA Data: Water Samples, 27 March 2006 (μg/L)

Parameter

Note – samples taken between slack water and incoming tide (0.3m)

As Cd Cr Cu Co Hg Ni Pb Se Zn Salinity

ppt


4235 14 20 3 14 0.7 200 6.6 336 23

Surface Waters – filtered

EP01 Maribyrnong River near Somerville Road37

3.4 <0.2 <0.5 1 Na <0.1 1.0 <0.2 2 8 33.5

EP02 Maribyrnong River off Pivot 3.4 <0.2 <0.5 1 Na <0.1 0.9 <0.2 3 <5 34.6

EP03 Maribyrnong River off Orica 2.9 <0.2 <0.5 1 Na <0.1 0.8 <0.2 3 <5 34.2

EP04 Yarra River Off Holden Dock 2.8 <0.2 <0.5 1 Na <0.1 0.8 <0.2 3 <5 33.8

EP05 Yarra River Adjacent to Newport Power Station

3.9 <0.2 <0.5 1 Na <0.1 0.6 <0.2 5 <5 34.2

Bottom Waters – Filtered

EPO1 Maribyrnong River near Somerville Road

3.3 <0.2 <0.5 <1 Na <0.1 0.8 <0.2 3 <5 34.7

EP02 Maribyrnong River off Pivot 3.1 <0.2 <0.5 <1 Na <0.1 0.8 <0.2 5 <5 34.6

EP03 Maribyrnong River off Orica 3.3 <0.2 <0.5 <1 Na <0.1 0.8 0.2 4 <5 34.5

EP04 Yarra River Off Holden Dock 3.3 <0.2 <0.5 <1 Na <0.1 0.7 <0.2 4 <5 34.7

EP05 Yarra River Adjacent to Newport Power Station

3.1 <0.2 <0.5 2 Na <0.1 1.1 <0.2 3 25 34.8

35 EPA has used an arsenic water quality objective of 42 μg/L which is the ANZECC (2000) 90% trigger value for As (V) in freshwater; this value is adopted in Table 44. ANZECC (2000)

provides a low reliability marine trigger value of 4.5 μg/L for As (V). 36 ANZECC (2000) low reliability marine trigger value. 37 The EPA Water Quality Assessment Report (2006) identifies this sample location as upstream Whitehall Street, later clarified to be a location up-stream 221 Whitehall Street and more

better described as near Somerville Road (EPA, correspondence on 19 September 2006).


Table 45 EPA data: Water Quality Analysis - Mean and Standard Deviation38 of Maribyrnong and Yarra River Estuary Samples (μg/L)

Parameter As Cd Cr Cu39 Co Hg Ni Pb Se40 Zn Ammonia


4241 14 20 3 14 0.7 200 6.6 342 23 1200

Surface waters unfiltered Mean 10 <0.2 2.33 14.17 <5 <0.1 63.17 <1 98.83 <1 <100

Surface waters unfiltered Standard deviation 4.15 <0.2 0.52 1.72 <5 <0.1 3.49 <1 9.45 <1 <100

Bottom waters unfiltered Mean 10 <0.2 2.5 14.83 <5 <0.1 63.17 <1 100 <1 <100

Bottom waters unfiltered Standard deviation 4.15 <0.2 0.55 0.98 <5 <0.1 7.76 <1 5.55 <1 <100

28 September 2005

Surface Water Mean 4.33 <1 <10 27.67 <10 <1 <10 9.11 4 38.89 na

Surface Water Standard deviation 1.12 <1 <10 14.11 <10 <1 <10 0.33 1 6.01 na

27 March 2006

Surface water Mean 3.28 <0.2 <0.5 1 na43 <0.1 0.82 <0.2 3.2 4.8 na

Surface water Standard deviation 0.4 <0.2 <0.5 0 na <0.1 0.13 <0.2 0.98 1.6 na

Bottom water Mean 3.22 <0.2 <0.5 1.12 na <0.1 0.84 0.19 3.80 8.2 na

Bottom waters Standard deviation 0.11 <0.2 <0.5 0.49 na <0.1 0.15 0 0.84 9.39 na

38 To determine mean and standard deviation EPA treated results below the detection limit as <10 = 9; <0.2 = 0.19 etc. 39 Results for copper may reflect interference by salinity. 40 Results for selenium may reflect interference by salinity. 41 EPA has used the arsenic water quality objective of 42 μg/L which is the ANZECC (2000) 90% trigger value for As (V) in freshwater; adopted in Table 45. ANZECC (2000) provides a

low reliability marine trigger value of 4.5 μg/L for As (V). 42 ANZECC (2000) low reliability marine trigger value. 43 na = not assessed.


Table 46 EPA Data: Water Quality Data for Port Phillip Bay, 2005 (μg/L)

Port Phillip Bay

Parameter As Cd Cr Cu44 Co Hg Ni Pb Se45 Zn Ammonia


4246 14 20 3 14 0.7 200 6.6 347 23 1200

1919 (19 Oct 05) Hobsons Bay 7 <0.2 2 10 <10 <0.1 10 <1 <1 4 na48

1919 (18 Nov 05) Hobsons Bay 19 <0.2 3 10 <10 <0.1 10 <1 84 <1 na

1919 (3 Feb 06) Hobsons Bay 21 <0.2 1 6 <10 <0.1 6.1 <1 79 3 na

1229 surface (28 Sept) Port Phillip Bay Central

4 <1 <1 10 <10 <0.1 <10 <1 5 3 na

1229 bottom (28 Sept) Port Phillip Bay Central

10 10 <1 <10 <10 <0.1 <10 <1 4 3 na

1229 (19 Oct 05) Port Phillip Bay Central

14 <0.2 2 10 <10 <0.1 10 <1 8 <1 na

1229 (18 Nov 05) Port Phillip Bay Central

18 <0.2 2 10 <10 <0.1 10 <1 96 <1 na

1229 (3 Feb 06) Port Phillip Bay Central

16 <0.2 2 6 <10 <0.1 6.1 <1 92 <1 na

Mean 13.63 1.51 1.73 8.88 <10 <0.1 8.78 <1 46.11

Standard deviation 5.68 3.44 0.69 1.69 <10 <0.1 1.60 <1 41.94

44 Results for copper may reflect interference by salinity 45 Results for selenium may reflect interference by salinity 46 EPA has used the arsenic water quality objective of 42 μg/L which is the ANZECC (2000) 90% trigger value for As (V) in freshwater; this value is adopted in Table 45. ANZECC (2000)

provides a low reliability marine trigger value of 4.5 μg/L for As (V). 47 ANZECC (2000) low reliability marine trigger value. 48 na = not assessed


12.2.2 Water Quality of Stony Creek Backwash

The data on the water quality within Stony Creek Backwash are limited. The auditor has reviewed the results of an investigation by Handex in 2000, in their report titled “Stony Creek Backwash, Hyde Street, Yarraville, Victoria Site No. Q2XX”, dated 13 March 2001.

The water analytical results are provided in Appendix O, and a summary of the metal results is included in Table 47.

Handex submitted water samples for TPH and BTEX analysis; all samples were reported at levels below the detection limit. However, the Handex field notes record oily product and sheens upwelling or stirred up during sampling and many accounts of rotten egg and sulfide smells.

Table 47 Stony Creek Backwash – Water Quality Results, Metals, Handex (2001)

Contaminant (results in ug/L unless otherwise noted)

As Cd Cr Cu Hg Ni Pb Zn

SEPP Water Quality objective: 90th percentile trigger for largely modified ecosystem (marine) 4249 14 20 3 0.7 200 6.6 23

Sample ID Location

SC 5 Backwash - southern portion <80* <1* 11 21 <1 <20* <10* 28

SC 7 Backwash - southern portion <80* <1* 11 24 <1 <20* <10* <20*

DUP L Duplicate of SC 7 <80* <1* 11 17 <1 <20* <10* <20*

SC 9 Centre of backwash <80* <1* 11 19 <1 <20* <10* 38

SC 12 Centre-east of backwash <80* <1* 13 19 <1 <20* <10* 76

SC 14 Centre of backwash <80* <1* 11 18 <1 <20* <10* 21

DUP K Duplicate of SC 14 <80* <1* 13 17 <1 <20* <10* <20*

SC 17 Centre-north backwash <80* <1* 12 20 <1 <20* <10* 78

SC 20 North-east backwash <80* <1* 14 18 <1 <20* <10* 21

SC 22 Within Yarra River - near backwash entrance <80* <1* 11 17 <1 <20* <10* 21

DUP M Duplicate of SC 22 <80* <1* 18 17 <1 <20* <10* <20*

SC 26 Stony creek <80* <1* 11 17 <1 <20* <10* 46

SC 27 Upstream Stony Creek <80* <1* 11 17 <1 <20* <10* 42

Exceeds ANZECC 2000 90th percentile trigger level (marine)

* Practical quantitation limits raised due to matrix interference

49 EPA has used the arsenic water quality objective of 42 μg/L which is the ANZECC (2000) 90% trigger value for As (V) in

freshwater; this value is adopted in Table 47. ANZECC (2000) provides a low reliability marine trigger value of 4.5 μg/L for As (V).


12.3 Assessment of Water Quality Results

12.3.1 Yarra and Maribyrnong River waters

The key findings reported by EPA are outlined below:

EPA’s investigation focussed primarily on metals in the waters of the lower Maribyrnong and lower Yarra estuaries.

The results of the three series of results show a high degree of data variability (see Table 45). The first two sets of results were analysed using ICP-MS by a NATA certified laboratory specialising in low salinity samples, the estuarine nature of the water resulted in elevated and variable salinity and some samples exhibited significant matrix interference effects – especially for arsenic and selenium.

The latest results (March 2006) indicate that concentrations of arsenic, cadmium, chromium, cobalt, mercury, nickel and lead in the lower Maribyrnong and Yarra Rivers were below the SEPP objectives for protection of aquatic ecosystems and were generally uniform results across the sampling locations;

Selenium results were slightly above the low reliability trigger for ecosystem protection. The ANZECC (2000) low reliability triggers are based on limited data, as selenium has not been routinely monitored in Victorian marine and estuarine waters there is limited historical data for comparison and it is not possible to determine if the levels pose a risk to ecosystem protection. The results are considerably lower than the 2005 results which were at levels considered to be of concern but which are now believed to be subject to chemical interference and may be unreliable.

Two samples had elevated levels of zinc. The surface water from the Maribyrnong River upstream of Whitehall Street was below the ecosystem protection level. A sample from the lower Yarra off Newport Power station was just above the ecosystem protection trigger level for largely modified ecosystems (90%).

Zinc is a common contaminant in urban rivers, including the Lower Yarra estuary50.

A number of metals and metalloids have shown considerable variation between sampling runs. The concentration of copper reported in the initial Maribyrnong River samples was not evident in subsequent monitoring. Samples from the 19 August had a mean of approximately 14 μg/L with a standard deviation of 1.7 µg/L and samples from the 28 September had a mean of 28 μg/L and standard deviation of 14 µg/L. It is possible that such variation may occur due to natural environmental variation, however in the absence of major storm events it is more likely to be due to analytical factors. Similar variations were evident for other parameters, such as selenium and zinc (see Table 45).

The auditor concurs with the EPA conclusions, and notes: The measured concentrations of metals and metalloids suggest that sources in the Precinct are not giving rise to significant pollution of the Maribyrnong or Yarra Rivers by these contaminants such as might arise from contaminated groundwater discharging to the river, and the Precinct poses a low risk to the aquatic ecosystems of these rivers. This conclusion is consistent with the levels of dilution predicted from a consideration of the tidal river flow compared with the groundwater flow.

The available information on ammonia is limited, but suggests that there is not gross pollution by ammonia.

50 EPA, Our Water Our Future – Yarra River Action Plan 2006


It was noted that the results of analysis of samples taken by EPA have been subject to matrix interference by the salt water, and the auditor considers that the reported results have a low level of reliability and further sampling and analysis using trace analysis methods suitable for salt water would be required before the results can be relied on.

There is no information on phosphorus and nitrogen, and it is not possible to confirm that these nutrients present in the groundwater at high concentrations are not present at significant concentrations in the river water. However, the high level of dilution and the absence of algal blooms and excessive weed growth in the rivers in the vicinity of the Precinct suggest that nutrient concentrations are not at problem levels for the river segment.

The information on other contaminants such as dissolved hydrocarbons and chlorinated organics is limited, and has not been assessed by the auditor. It is noted that with the very high levels of dilution, it would not be expected that hydrocarbons will be present at concentrations of concern and can be expected to be a low risk.

12.3.2 Fish and eels in the Maribyrnong and Yarra River estuary and their sensitivity to contamination

The lower Yarra River is the migratory route for a number of diadromous fishes that have some portion of their life history requiring a migration either or from fresh waters and the sea. Often these migrations involve sensitive stages of the life cycle such as eggs, and the larvae of juvenile fish.

Of the fish that are found in the Lower Yarra one is of National Conservation significance, the Australian Grayling Prototroctes maraena. The Australian Grayling has its eggs washed to sea from May to July when flows are highest and juveniles of this fish migrate upstream from the sea from October to December. Of the other fish most have migratory patterns that involve them moving through the estuary in winter or spring, which are periods of generally higher flows in the river.

There are some exceptions to this. The short finned eel Anguilla australis has a life stage known as the Silver Eel that migrates downstream to the sea during typically low flow periods of the year from October to May. The Tupong Pseudaphritis urvillii also migrates to the estuary or the sea to spawn and then juveniles remain in the estuary for several months and then return upstream between September and March. Again the juveniles appear to be in the estuary during the higher flow periods, though the adults move down to spawn in low flow periods.

It is unlikely that minor levels of contamination will affect these fish, particularly during the higher flow periods. These fish are moving through the estuary and will move freely with the flow of the river. Larger fish that are migrating upstream will move through the estuarine areas relatively quickly. There are fish that live in the estuary itself; however, these are adult fish and can be expected to be generally less sensitive to contamination.

Further discussion of fish and eel investigations for Yarra and Maribyrnong Rivers is continued in Section 14 of this report.


12.3.3 Stony Creek Backwash waters

The information obtained by Handex represents the data available to the auditor for assessment of the Stony Creek Backwash water quality. The auditor notes the following:

Handex submitted water samples for TPH and BTEX analysis. All samples reported at levels below the detection limit, although Handex field notes record oily product and sheens that up-welled or were stirred up during sampling and many accounts of rotten egg and sulfide smells suggesting that there has been pollution by petroleum hydrocarbons.

Zinc and copper are reported above the guideline values for ecosystem protection, suggesting that the ecosystems of the backwash are likely to be adversely affected by these metals. The elevated concentrations are consistent with high concentrations of metal contamination of the sediments of the backwash (see following section of this report). Because the backwash is tidal and alternates between tidal mudflats and shallow water, it is unlikely fishing will occur within the backwash. However, it is possible that fish will travel within the backwash, and birds may forage in the backwash.

Several of the laboratory detection limits were greater than the ANZECC (2000) water quality guideline value (i.e. for arsenic, cadmium, lead and mercury), and it is not possible to reach conclusions as to whether the water quality concentrations might be in excess of the guideline values, although it does not appear that contamination of the water column in the backwash is at levels corresponding to gross pollution.

12.4 Conclusions It is concluded:

Maribyrnong and Yarra Rivers The measured concentrations of contaminants are consistent with the levels and type of

contamination expected in a heavily urbanised catchment.

The measured concentrations of metals and metalloids suggest that sources in the Precinct are not giving rise to significant pollution of the Maribyrnong or Yarra Rivers by these contaminants such as might arise from contaminated groundwater discharging to the river, and the Precinct poses a low risk to the aquatic ecosystems of these rivers. This conclusion is consistent with the levels of dilution predicted from a consideration of the tidal river flow compared with the groundwater flow.

The available information on ammonia is limited, but suggests that there is not gross pollution by ammonia.

There is no information on phosphorus and nitrogen, and it is not possible to confirm that these nutrients present in the groundwater at high concentrations are not present at significant concentrations in the river water. However, the high level of dilution and the absence of algal blooms and excessive weed growth in the rivers in the vicinity of the Precinct suggest that nutrient concentrations are not at problem levels for the river segment.

Because of the limited data set and uncertainties that have arisen through analytical matrix interference and variations in filtered and unfiltered samples, there is uncertainty in both the results and their interpretation.


Stony Creek Backwash The reported results suggest that the concentrations of metals (copper and zinc) are high and are

likely to adversely affect the ecosystems of the backwash. The observations of elevated concentrations of these metals are consistent with sediment results; however, the pattern of results also suggests that the results may be affected by matrix interference (and the practical quantification limits for arsenic, mercury and lead in particular were above the adopted guideline) and further analysis would be required before firm conclusions can be reached.

Field observations suggest the presence of petroleum hydrocarbons in the sediments of the backwash at levels that correspond to gross pollution; however, it is not clear that the contamination is being transferred to the water column.

12.5 Data Gaps Data gaps and uncertainties in the information include:

The sampling and analysis data are limited and uncertainties have arisen because of the apparent effect of matrix interference from the high TDS of the waters, and in some cases because detection levels are insufficiently low to provide direct comparison with the guideline levels.

The concentrations of contaminants with location and related to tidal flow and depth are not well characterised, and it is not possible to distinguish the importance of these effects or whether there might be conditions or locations that are associated with higher concentrations of contaminants than those measured.


13. River Sediments

13.1 Documents The purpose of this component of the audit is to present the available data on the sediments of the rivers and backwash, and determine whether sediment contamination is likely to be related to historical or ongoing contamination arising from the Precinct sites, and whether the Precinct sites are likely to pose an ongoing risk to sediment quality.

EPA Victoria has provided the primary data on which the auditor has relied. Other data available to the auditor is presented in Table 48

Table 48 Information Received on Sediment Quality

Author Date Title

EPA Victoria Not specified Information posted on the EPA Victoria Website from time to time

EPA Victoria June 2006 Water Quality Assessment: Lower Maribyrnong and Lower Yarra Estuaries, 2005-2006

Handex Australia Pty Ltd

13 March 2001

Stony Creek Backwash, Hyde Street, Yarraville, Victoria Site No. Q2XX.

Coffey Environmental 13 July 2000 SHE Pacific Pty Ltd, Orica Yarraville; Stage II Site Investigations; Final Report – Whitehall Street, Yarraville VIC

Extract provided – includes Table of Contents, Section 16 - River Sediment Investigations, Field Notes, WSL Laboratory Certificate of Analysis

Peter J Ramsay & Associates

December 1997

Port of Melbourne Authority, Review of Sediment Contaminant Levels in Hobsons Bay and the Lower Yarra River, Victoria

Peter J Ramsay & Associates

October 1998 Port of Melbourne Authority, Stage 3: Further Contamination Assessment of Land, Site 23: Stony Creek Backwash, Hyde Street, Yarraville, Victoria,

13.2 Results of Sediment Sampling and Analysis The most recent sediment quality data provided to the auditor is summarised in Table 49. A full copy of the EPA report (2006) is included in Appendix M. In summary, EPA undertook a sampling program of sediments from the lower reaches of the Yarra and Maribyrnong Rivers in late 2005. Analysis included metals and metalloids.


Table 49 Sediment Quality Investigation - Results for Lower Yarra and Maribyrnong Rivers (mg/kg dry wt)

Parameter As Cd Cr Co Cu Hg Ni Pb Se Sn Zn

ANZECC (2000) Sediment Guideline ISQG Low trigger value ISQG High trigger value

20 70

1.5 10

80 370

65 270

0.15 1.0

21 52

50 220

5 70

200 410

Maribyrnong source streams

EP0 15c Emu creek 27/9/05 <5 <0.2 12 5 7 <0.05 15 20 <5 <5 65

EP0 16c Jacksons Crk 27/9/05 <5 <0.2 29 11 7 <0.05 17 20 <5 <5 31

Mid Maribyrnong estuary

EP0 7 Maribyrnong off old Armourments site

EP0 7 27/9/05 8 0.3 39 9 130 0.11 24 69 <5 <5 220

EP0 7 27/9/05 11 0.5 53 12 58 0.16 31 92 <5 <5 270

EPO 7 02/12/05 <0.2

Lower Maribyrnong estuary

EPO 1 Maribyrnong near Somerville Road51

EPO 1 30/8/05 14 0.8 70 16 72 0.66 34 120 <5 <5 260

EPO 1 30/8/05 13 0.7 72 15 72 0.35 36 120 <5 6 270

EPO 1 2/9/05 9 0.3 31 8 30 0.15 17 60 <5 <5 120

EPO 1 27/9/05 8 0.6 43 10 59 0.33 25 110 <5 <5 280

EPO 1 27/9/05 8 0.6 41 9 54 0.36 23 100 <5 <5 240

EPO 1 02/12/05 0.69

EPO 2 Maribyrnong off Pivot

EPO 2 near east bank 30/08/05 14 0.4 69 12 58 0.25 32 82 <5 <5 210

EPO 2 near east bank 30/08/05 18 0.6 73 14 64 0.29 34 91 <5 <5 230

51 The EPA Water Quality Assessment Report (2006) identifies this sample location as upstream Whitehall Street, later clarified to be a location up-stream 221 Whitehall Street and more

better described as near Somerville Road (EPA, correspondence on 19 September 2006).




20 70

1.5 10

80 370

65 270

0.15 1.0

21 52

50 220

5 70

200 410

EPO 2 near east bank 2/09/05 43 37 63 29 54 0.53 41 97 41 63 150

EP0 2 near east bank 27/9/05 11 0.5 35 8 45 0.19 19 80 <5 <5 190

EP0 2 near east bank 27/9/05 11 0.4 36 8 46 0.27 20 80 <5 <5 190

EP0 2 mid river 27/9/05 9 0.4 34 8 40 0.13 19 87 <5 <5 170

EP0 2 mid river 27/9/05 13 0.5 39 9 54 0.17 23 80 <5 <5 210

EP0 2 near west bank 27/9/05 16 1.1 40 13 94 0.56 24 170 <5 7 310

EP0 2 near west bank 27/9/05 14 0.8 41 12 79 0.29 26 120 6 5 280

<0.2

EPO 3 Maribyrnong off Orica

EPO 3 30/08/05 19 0.7 72 14 65 0.27 33 99 <5 8 190

EPO 3 30/08/05 17 0.5 69 13 54 0.32 32 81 <5 <5 220

EPO 3 2/09/05 13 0.4 35 7 36 0.22 21 72 <5 <5 140

EP0 3 c 27/9/05 20 0.7 53 13 59 0.19 32 95 <5 6 270

EP0 3 27/9/05 12 0.4 40 8 47 0.15 23 71 <5 <5 230

EPO 3 02/12/05 <0.2

Lower Yarra River

EPO 4 Yarra off Holden Dock

EPO 4 30/08/05 16 0.5 73 11 46 0.35 31 80 <5 12 220

EPO 4 30/08/05 13 0.3 61 10 41 0.26 27 71 <5 10 210

EP0 4 27/9/05 77 79 2100 90 95 1.0 94 150 76 85 210

EP0 4 27/9/05 11 0.8 43 9 41 0.35 24 92 <5 10 200

EPO 4 02/12/05 <0.2




20 70

1.5 10

80 370

65 270

0.15 1.0

21 52

50 220

5 70

200 410

EPO 5 Yarra off Newport Power Station

EPO 5 30/08/05 18 0.5 68 13 50 0.41 32 94 <5 10 220

EPO 5 30/08/05 13 0.2 47 9 36 0.33 25 65 <5 8 160

EP0 5 27/9/05 <5 <0.2 22 <5 13 <0.5 12 26 <5 <5 76

EP0 5 27/9/05 15 0.3 36 8 31 0.24 20 67 <5 <5 130

EPO 5 02/12/05 0.2

EPO 6 Yarra near the ‘Warmies’

EPO 6 30/08/05 10 0.2 30 7 14 0.21 13 33 <5 <5 120

EPO 6 30/08/05 8 0.2 28 6 13 0.28 12 31 <5 <5 110

EP0 6 c 27/9/05 15 19 28 13 17 35 17 46 <5 23 78

EP0 6 d 27/9/05 11 <0.2 30 6 21 0.31 18 49 <5 <5 79

EPO 6 02/12/05 0.29

Mid Yarra River

EP0 17 Yarra Warrandyte

EP0 17 27/9/05 9 <0.2 12 5 7 0.06 11 14 <5 <5 42

EP0 17 27/9/05 47 <0.2 18 8 10 <0.05 23 11 <5 <5 58

Yarra River – upper estuary

EP0 19c Yarra below Dights Falls

EP0 19 27/9/05 8 0.5 27 8 70 25 23 120 <5 6 800

EP0 19 27/9/05 6 0.6 24 7 49 <0.05 20 120 <5 7 570

EP0 18 Yarra Herring Island

EP0 18 27/9/05 <5 0.2 13 6 17 <0.05 12 48 <5 <5 290




20 70

1.5 10

80 370

65 270

0.15 1.0

21 52

50 220

5 70

200 410

EP0 18 27/9/05 <5 <0.2 12 5 15 17 12 37 <5 <5 200

EPO 18 <0.2

Note that additional results were received from the ICP-MS analysis, however EPA reported on those elements of concern to human health, ecosystem health or elevated in groundwater.

Exceeds ISQG Low trigger mg/kg

Exceeds ISQG High mg/kg

No sediment guideline value, result is elevated


13.2.1 Assessment of the Sediment Results

The key findings reported by EPA were:

Low levels of contamination were reported for a range of metals and metalloids (copper, cobalt, mercury, nickel, lead and zinc) and in samples from the lower reaches of both the Yarra and Maribyrnong rivers.

Samples taken upstream of the estuary in both the Maribyrnong and the Yarra are below guidelines levels for most contaminants.

The results are as expected: the Maribyrnong and Yarra estuaries are at the bottom of an urbanised catchment, contaminant levels in the water typically increase due to urban runoff, and the salinity change in the estuary causes precipitation of particulate matter and the associated contaminants that will then accumulate in the sediments.

There were several samples with high levels of some contaminants; these were from the lower end of the Maribyrnong and Yarra catchments.

A sample from ‘the Warmies’ near the Yarra mouth and several samples from the upper estuary reaches of the Yarra, below Dights Falls and near Herring Island contained unusually high levels of mercury. Follow up samples were all below the guideline trigger values, confirming that contamination in the sediments is variable and localised. EPA proposes to continue with further investigations to determine if there are elevated pockets of highly contaminated sediment at these locations.

A sample from near the east bank Maribyrnong River off the PoMC site had elevated levels of a number of contaminants, especially cadmium (above high screening level), and arsenic, mercury, nickel, lead, tin and zinc were above their respective low screening levels, and cobalt was above levels found in similar locations;

A single sample from the Holden Dock area contained high levels of a broad range metals, including arsenic, cadmium, chromium, nickel and tin. The contaminants were at concentrations that were not found in subsequent sampling.

EPA has advised that it proposes to investigate areas in which elevated levels of contaminants have been found. The focus of these investigations will include the Holden Dock and Yarra mouth (the Warmies) areas where isolated pockets of highly contaminated sediment have been identified.

13.3 Discussion

13.3.1 Sources of the observed sediment contamination

With respect to whether the Precinct sites might be an ongoing source of the observed sediment contamination or might have been a historical source of the contamination, the following observations are relevant:

The average concentrations of contaminants in sediments for the various areas of the river systems (upper catchment, lower catchment, and the Precinct) are summarised in Table 50. Two samples in the vicinity of the Precinct reported anomalously high concentrations of contaminants suggestive of a localised area of contamination, the sediment concentrations have been compared with and without these anomalous values included.


This comparison indicates that without the anomalous values, the sediment contaminant concentrations are not greatly different from other sediment concentrations in the upper or the middle and lower catchment areas. This comparison supports the EPA conclusion that the contaminant concentrations are as may be expected for urban areas, apart from two anomalous areas. The EPA officer responsible for the sediment sampling program advises that it is possible that the higher concentrations sediment samples in the vicinity of the Precinct were taken from silt traps (in the vicinity of Holden Dock), and hence the contamination may be consistent with historical levels, rather than current levels.

The metal and metalloid contaminants of greatest significance with respect to groundwater contamination on the Precinct sites are copper, zinc and arsenic (200, 75 and 81 mg/L). The comparison suggests that the concentrations of these particular contaminants in the sediments in the vicinity of the Precinct are not significantly elevated with respect to the other areas.

Table 50 Comparison of Sediment Metal Concentrations in the Vicinity of the Precinct with Other Areas (mg/kg)

Parameter As Cd Cr Cu Hg Ni Pb Sn Zn ANZECC (2000) Sediment Guideline

ISQG Low trigger value 20 1.5 80 65 0.15 21 50 5 200

ISQG High trigger value 70 10 370 270 1 52 220 70 410

Upper catchments1

All data 5.5 0.35 28 56 7 20 81 2.2 390

Mid catchments2

All data 11 1.8 42 37 3 22 71 3.6 160

Precinct area3

All data 21 8.7 200 53 0.3 33 89 14 200

Without outliers4 12.5 0.4 47 43 0.2 23 71 3.3 180

Ratios

Precinct/mid catchment4 1.1 0.2 1.1 1.2 0.07 1.1 1 0.9 1.1

Precinct/upper catchment4 2.3 1.3 1.7 0.8 0.03 1.2 0.9 1.5 0.5

Notes: 1. average of EPO 15, 16, 17 (refer Appendix M) 2. average of EPO 7, 18, 19 3. average of EPO 2, 3, 4 4. average of EPO 2, 3, 4 excluding the high results EPO 2 (2/9/05) and EPO 4 (27/7/05) 5. ratio of averages without outliers


13.3.2 Significance of dredging

The Yarra and Maribyrnong rivers are dredged in the area of the Precinct, and this can be expected to have removed sediments over most of the river bottom in the area that have been contaminated by past activities. Because of this, the current measurements of concentrations of contaminants in the sediments can be expected to indicate the current situation that results from current discharges from the Precinct sites (such as may occur at times of rainfall run off), contributions of contaminated sediments from upstream sources, and current rates of deposition of clean sediments (e.g. rainfall run off and erosion of clean soil).

13.3.3 Potential for uptake of contaminants in sediments by biota

The following discussion draws on work being undertaken for the auditor by URS for the assessment of sediment contamination in Darwin Harbour, Northern Territory. The information has relevance to the Precinct audit is similarly an investigation of the impact of an urban catchments and urban drainage on the ecosystems of the receiving environment, Darwin Harbour.

It is well known that there is potential for uptake of contaminants present in sediments by aquatic organisms, and that these may reach levels which may be detrimental to human health if consumed. A recent investigation into heavy metal concentrations in razorfish (an edible bivalve mollusc) and sediments across northern Spencer Gulf52 provides an insight into the relationship between metal uptake and sediment concentration. Northern Spencer Gulf, while in a different climatic zone to Melbourne, has some similarities in that it has historically been subject to significant input of metals including arsenic, cadmium, copper, lead and zinc. These inputs, which are primarily associated with lead smelting operations, are ongoing, and at much higher concentrations than observed in the Maribyrnong and Yarra Rivers.

An advantage of the razorfish as a monitoring subject is that it is a sedentary, filter feeding species and thus is constantly exposed to the sediments and surrounding water quality in the location in which it occurs.

Despite the high level of metal in the sediments and ongoing input to northern Spencer Gulf, shellfish exceeding the Maximum Level for lead were found in only one location, close to an outfall where the sediment concentration also exceeded the higher guideline value. A similar finding was made for zinc which only exceeded the generally expected level (GEL) 90th percentile at two locations, again associated with outfall locations. Cadmium, mercury and copper did not exceed the Maximum Levels or GEL 90th

percentile for any sample. A previous study53, also in the Germein Bay area of northern Spencer Gulf, found that while the guidelines for razorfish were exceeded, metal concentrations in blue swimmer crabs and fish did not exceed the relevant guidelines. This would suggest that the different feeding strategies and other behaviour patterns affected total metal accumulation.

52 Corbin, T & Wade, S. 2004. Heavy metal concentrations in razorfish (Pinna bicolour) and sediments across the northern Spencer

Gulf. Environmental Protection Authority, Adelaide, South Australia. 53 Edyvane, KS & Boxall V, 1997. An investigation of heavy metal contaminations of edible marine seafood in the Port Pirie-Telowie

Beach region of South Australia. South Australian Research and Development Institute, Adelaide.


A study on the biotransference and biomagnification of metals in a temperate seagrass ecosystem54 also found variability between different trophic levels and different taxa for different metals, including lead, zinc and copper. Overall, there was little evidence of bioaccumulation of lead in the food chain between potential sources, such as detritus, zooplankton, seagrass, algae and epiphytes and the consumers: detritivores, herbivores and carnivores. In the case of zinc, cadmium and copper, metal levels generally fell between the preferred source and the end consumer, suggesting that bioaccumulation was not a significant factor. As the data are presented as dry weight it is not possible to undertake a detailed comparison to the food standards, however, applying a conservative factor for the difference between dry and wet weight, the levels quoted would not exceed the current food standards.

These considerations suggest that the observed sediment concentrations are unlikely to give rise to a significant residue levels in biota, that would adversely affect the health of consumers (such as anglers).

13.4 Stony Creek Backwash Data The Stony Creek Backwash covers an area of about 13.5 ha, located at the junction of Stony Creek and the lower Yarra River, as shown on Figure 3. The site comprises an area of tidal mudflats bordered by Hyde Street to the west, Parks Victoria reserve land to the east and south, and the Mobil Terminal to the north.

The backwash is located on the Quaternary aged Coode Island Silt, underlain by the basalt of the Newer Volcanics, and other deeper geological units such as the Brighton Group and Newport Formation, as discussed in Section 10.2. Some information contained in a Parks Victoria “Park Notes” bulletin for the backwash mentions that the backwash was quarried for bluestone in the late 1800s to supply stone for some of Melbourne’s earliest buildings such as Pentridge. It was a quarry ground where tramlines would run to the Yarra docking area and deliver ballast to ships. Other notes include:

Manufacturing and heavy industry in the area had historically used Stony Creek and the backwash as a drain for dumping waste;

The backwash supports a stand of White Mangroves, a tough species that grows on the backwash mudbanks. The original stand was totally destroyed by an oil spill in the 1980s. Replanting of the species occurred not long after and the Mangroves are now flourishing in the backwash through regeneration and self–seeding; and

Many waterbirds feed and nest amongst the mangroves, including the Royal Spoonbill. The Great Egret (Ardea intermedia) is a threatened species and an irregular visitor to the backwash.

Groundwater investigations undertaken at the Mobil site indicate that groundwater is located within both the Coode Island Silt and the Newer Volcanics, and is inferred to flow toward the Lower Yarra River and the backwash. Information on the sediments in the backwash is presented below.

13.4.1 Backwash sediment investigation, 1997

Parks Victoria provided sediment quality analysis results of samples from the backwash to the auditor. P. J. Ramsay undertook a contamination assessment of the backwash, including sediment sampling and analysis, in 1997 (one sample location) and 1998 (eight sample locations).

54 Barwick M & Maher W. 2003. Biotransference and biomagnification of selenium, copper, cadmium, zinc, arsenic and lead in a

temperate seagrass ecosystem from Lake Macquarie Estuary, NSW, Australia. Marine Environmental Research 56: 471-502.


The sampling locations were selected by visual inspection; the report (Ramsey, 1998) noting that the indicators used were the presence of odour, discolouration or oily soil, free product or sheen, and detection of vapours with a photoionisation detector. The final sediment sampling locations were approximately grid-based over the area of the backwash. Ramsay comments that strong hydrocarbon odours were encountered in sediment samples retrieved from the backwash and also samples from upgradient Stony Creek.

A summary of the analysis results is provided in Table 51 and Table 52; a complete set of results is attached in Appendix K.

Table 51 Stony Creek Backwash: Sediment Data - Metals, Ramsay (1998) (mg/kg)

Parameter pH As Cd Cr Cu Hg Ni Pb Sn Zn


20 70

1.5 10

80 370

65 270

0.15 1.0

21 52

50 220

5 70

200 410

Stony Creek Backwash

4219/23-S/3-Apr-97 (central area) 97 5 64 270 1.6 36 340 ND 880

4221/23-S1/ 9-Jul-97 (northern area) 7.6 41 360 2.2 330 1100

4221/23-S2/9-Jul-97 (northern area) 42 740 3.8 570 2100

4221/23-S3/9-Jul-97 (northern area) 7.9 76 230 1.4 290 950

4221/23-S4/9-Jul-97 (northern area) 12 310 3.3 200 880

4221/23-S5/9-Jul-97 (central area) 78 290 1.9 370 1500

4221/23-S6/9-Jul-97 (central area) 7.5 38 400 2.6 510 1500

4221/23-S7/9-Jul-97 (southern area) 7.9 14 52 0.25 76 450

4221/23-S8/9-Jul-97 (southern area) 7.6 75 96 0.52 140 510

Stony Creek – Upgradient of Stony Creek Backwash

4221/23-S9/9-Jul-97 25 48 2.6 170 190

4221/23-S10/9-Jul-97 77 310 1.2 390 1200

4221/23-S11/9-Jul-97 8.3 19 40 0.13 46 140

Exceeds ISQG Low trigger mg/kg

Exceeds ISQG High mg/kg

No sediment guideline value but an elevated result


Table 52 Stony Creek Backwash: Sediment Data - Organics, Ramsay (1998) (mg/kg)

Parameter C6-C9 C10-C14 C15-C28 C29-C36 C10-C36 Total Phenolics Total PAH

ANZECC (2000) Sediment Guideline ISQG Low trigger value ISQG High trigger value 4

EPA Fill – maximum concentration 100 1000 1 20

EPA Low level contaminated soil – maximum concentration 1000 10000 10 200


4219/23-S/3-Apr-97 (central area) ND 140 3400 1300 4840 7.4 26.06

4221/23-S1/ 9-Jul-97 (northern area) 150 550 12000 5000 17550 <5

4221/23-S2/9-Jul-97 (northern area) 180 1000 32000 14000 47000 <5



4221/23-S5/9-Jul-97 (central area) 100 79 6600 2500 9179 <5

4221/23-S6/9-Jul-97 (central area) 150 350 4900 1500 6750 <5

4221/23-S7/9-Jul-97 (southern area) <20 <20 <50 <50 ND <5

4221/23-S8/9-Jul-97 (southern area) <20 <20 <50 <50 ND <5

Stony Creek – Upgradient of Stony Creek Backwash

4221/23-S9/9-Jul-97 <20 <20 <50 <50 ND <5

4221/23-S10/9-Jul-97 <20 520 8300 2300 11120 <5

4221/23-S11/9-Jul-97 <20 <20 750 440 1190 <5

Exceeds ISQG Low trigger mg kg-1

Exceeds ISQG High mg kg-1


na - not assessed

13.4.2 Conclusions – 1997 sediment sampling

The ANZECC (2000) sediment quality guidelines were not published at the time of Ramsay’s investigation, and therefore the criteria adopted by Ramsay differ somewhat to the criteria reported in Table 52 and Table 53 above, however many of his conclusions remain valid with respect to the contamination of the sediments. Ramsay’s key findings include:

Significant concentrations of arsenic, copper, mercury, lead and zinc are reported in the backwash sediments;

Very significant TPH contamination has been reported in the backwash, and elevated oil and grease was associated with the petroleum contamination (see Appendix K);


TPH concentrations decrease in the traverse from the northern portion of the backwash (closer to the Mobil site) to the southern portion, where the southern-most samples (located close to the confluence with the Yarra River) and did not report any TPH;

While PAHs were detected in April 1997 (one sample from within backwash), no other samples reported PAHs in the later July 1997 investigation;

The pH of the sediments is within acceptable and natural range for estuarine sediments; and

The sediments within the backwash would be classified as Prescribed Waste (high level contaminated soil) because of their hydrocarbon content should they be excavated as waste.

In addition, Ramsay comments that mangroves are known to be susceptible to hydrocarbon contamination; and the mangroves within the backwash are showing signs of stress. Ramsay recommended remediation of the sediments to ensure the site is suitable for the existing recreational open space land use and to protect ecosystems. The auditor was informed by a number of LMARG members that the mangroves are thriving in the backwash and not showing signs of stress (pers. comm., LMARG meeting on 21 August 2006).

13.4.3 Backwash sediment investigation, 2000

Handex collected 27 sediment samples over a 100 m grid throughout the backwash in February 2000 and submitted for BTEX, TPH and heavy metal analysis.

The 2001 data set is summarised in Table 53 (metals) and Table 54 (organics) below, a Table of Analysis is included in Appendix K.

Table 53 Stony Creek Backwash: Sediment Data – Metals, Handex (2001) (mg/kg)

Parameter As Cd Cr Cu Hg Ni Pb Zn


20 70

1.5 10

80 370

65 270

0.15 1.0

21 52

50 220

200 410

Max Concentration in EPA Fill Material 30 100 2 300 500

Max Concentration in LLCS 300 1000 20 3000 5000

Sample ID Location


SC2 Southern portion 82 0.9 55 85 1.37 31 160 540


SC4 Southern portion - connection with Yarra river 170 3.8 100 370 2.06 52 300 750


DUPI Duplicate sample SC5 17 1.6 43 120 0.99 31 170 910


DUPQ Duplicate sample SC6 43 3.6 100 200 0.63 33 230 830

SC7 Southern portion 22 4 96 220 2.35 40 400 1200




20 70

1.5 10

80 370

65 270

0.15 1.0

21 52

50 220

200 410



DUPF Duplicate sample SC7 26 5.4 100 270 2.94 41 400 1200

SC8 North-west backwash 32 6.8 140 670 4.87 46 500 1800

SC9 Centre of backwash 59 11 230 1000 3.6 58 660 2200

DUPH Duplicate sample SC9 65 7 150 650 4.83 45 460 1500

SC10 Centre of backwash 59 12 220 770 9.28 62 580 1900

DUPG Duplicate sample SC10 27 2 73 150 2.13 24 390 850

SC11 Centre of backwash 39 5.6 120 300 3.45 44 380 1000

SC12 Centre-east of backwash 28 5.4 120 370 7.3 24 380 790

DUPD Duplicate sample SC12 45 9.6 190 440 9.85 49 470 1400



DUPE Duplicate sample SC14 35 6.2 140 480 5.15 41 420 1300


SC16 North-west backwash 29 6.2 130 320 4.73 45 490 1600

SC17 Centre-north backwash 24 7.6 160 390 4.33 58 580 1900

SC18 Centre-north backwash 20 6 120 240 2.54 37 430 1400

SC19 North-east backwash 29 7.8 140 410 3.91 49 450 1600

SC20 North-east backwash 35 1.4 96 180 2.6 33 430 800

Outside Stony Creek Backwash

SC1 Downstream-Stony Creek 17 0.8 47 46 0.039 20 78 380

SC21 Within Stony Creek 89 4 75 280 2 32 300 940

SC22 Within Yarra River - near backwash entrance 74 4.4 83 160 3.12 29 250 730


SC24 Within Yarra River - near backwash entrance 18 4 86 190 1.74 26 350 950


SC26 Within Stony Creek 33 0.7 35 150 1.23 19 81 270




20 70

1.5 10

80 370

65 270

0.15 1.0

21 52

50 220

200 410



DUPJ Duplicate sample SC26 48 13 270 400 0.82 76 530 1700

SC27 Upstream Stony Creek 22 3.4 60 170 1.36 35 260 1400

Exceeds ISQG Low trigger

Exceeds ISQG High trigger


Table 54 Stony Creek Backwash: Sediment Data - Organics, Handex (2001) (mg/kg)

Parameter C6-C9 C10-C14 C15-C28 C29-C36 C10-C36 Total BTEX

Max Concentration in EPA Fill Material 100 1000

Max Concentration in LLCS 1000 10000

Sample ID Location


SC2 Southern portion <5 <10 500 320 820 nd

SC3 Southern portion <5 10 1000 440 1450 nd

SC4 Southern portion - connection with Yarra river <5 30 1700 700 2430

nd


DUPI Duplicate sample SC5 <5 <10 360 420 780 nd


DUPQ Duplicate sample SC6 <5 40 2300 920 3260 nd

SC7 Southern portion <5 <10 700 460 1160 nd

DUPF Duplicate sample SC7 <5 <10 <50 <50 - nd

SC8 North-west backwash <5 50 2300 1400 3750 nd

SC9 Centre of backwash <5 560 12000 5900 18460 nd

DUPH Duplicate sample SC9 <5 500 12000 3900 16400 nd





Sample ID Location


DUPG Duplicate sample SC10 <5 <10 280 280 560 nd


SC12 Centre-east of backwash <5 160 13000 7200 20360 nd

DUPD Duplicate sample SC12 <5 70 5400 2300 7770 nd



DUPE Duplicate sample SC14 <5 20 1400 800 2220 nd


SC16 North-west backwash <5 20 1100 1200 2320 nd

SC17 Centre-north backwash <5 260 3600 3100 6960 nd

SC18 Centre-north backwash <5 <10 1200 720 1920 nd

SC19 North-east backwash <5 260 4300 1900 6460 nd

SC20 North-east backwash <5 <10 <50 <50 - nd

Outside Stony Creek Backwash

SC1 Downstream - Stony Creek <5 <10 180 160 340

nd

SC21 Stony Creek <5 460 15000 3700 19160 nd

SC22 Within Yarra River - near backwash entrance <5 <10 1000 640 1640

nd

SC23 Within Yarra River - near backwash entrance <5 10 800 660 1470

nd


nd


nd

SC26 Stony Creek <5 30 1300 480 1810 nd

DUPJ SC26 <5 320 11000 3200 14520 nd





Sample ID Location

SC27 Upstream Stony Creek <5 80 17000 6500 23580 nd


nd = not detected

13.4.4 Conclusions – 2000 sediment sampling

With respect to the contamination of the sediments, Handex’s key findings were:

BTEX and TPH C6-C9 concentrations were below the laboratory detection limit in all sampling locations;

Concentrations on TPH C10-C36 are highly elevated within the backwash sediments, as well as high concentrations reported upstream Stony Creek. Handex contouring suggests that some contribution to the hydrocarbons reported in the backwash is from creek inputs, noting that the highest TPH concentration was reported in a sample from upstream Stony Creek. The highest concentrations of TPH were detected in the central and southern portions of the backwash, suggesting a creek or tidal influx as the source, rather than the terminal site;

Sediment samples contain metals, many reported above the ISQG higher guideline value;

Handex field notes record oily product and sheens that up-welled or were stirred up during sampling and many accounts of rotten egg and sulfide smells suggesting that there has been pollution by petroleum hydrocarbons;

Handex suggest that Stony Creek is likely to be the source of most metal contamination in the backwash due to historic and ongoing industrial activities in the region (i.e. tannery and metal smelting); and

Handex suggest that chromium and nickel may be naturally occurring in the sediments and reflect background concentrations associated with basaltic bedrock.

13.4.5 Discussion

Hydrocarbons (C10-C36) and metals are present in the backwash sediments, as evidenced by the two investigations. However, Handex and Ramsay do not agree in the supposed source of the contamination.

The Quantitative Risk Assessment (URS, 2005) prepared for the Mobil Yarraville Terminal comments that the high levels of petroleum hydrocarbons and metals in the backwash are the likely result of historical spills and discharges to the creek from industry upstream along Stony Creek. The report notes that the ecosystem of the backwash is heavily influenced by the urban stormwater and industrial runoff.

The auditor is not able to determine the source of the contamination in the backwash from the available information, and it appears that there may be a number of sources or explanations for the contamination in the reported in the backwash, including:


Historical spills and discharges to the creek from industry upstream along Stony Creek. It is noted that there are various historic and active industrial operations in this region and a recognised history of pollution incidents in the creek, as well as sampling data that show contamination in the creek of the same nature and order as in the backwash itself;

It is noted that the interpretation of the TPH distribution between the two primary information sources on the backwash sediments (Ramsay, 1997; Handex, 2000) are somewhat dissimilar, and hence their attribution of the contamination to potential sources (i.e. the terminal versus upstream Stony Creek) also diverge;

Historical spills and leaks from the Mobil Terminal, particularly those that may have comprised overland spills (rather than migration via groundwater, as groundwater monitoring has not indicated a major free phase hydrocarbon discharge to the backwash). It is noted that free phase hydrocarbons are reported in some bores on the Mobil site and that incidental spills have been known and would be expected to have occurred through the life of the Terminal and docks;

The auditor understands that a major oil spill in the early 1980s occurred, and destroyed the mangroves within the backwash. The source of the spill is not known and the auditor is not able to ascertain from the information available to him whether the TPH impacts reported in the 1997 and 2000 investigations reflect a historic spill such as this, or otherwise; and

Historical filling around the backwash and confluence with the Yarra River.

The EPA clean up notice on Mobil requires that an environmental audit determine whether the land and groundwater quality objectives are being met at the premises boundary. The auditor understands from conversations with EPA officers and Mobil personnel that this will include an assessment of the risk to Stony Creek Backwash. In this way the environmental audit undertaken for the Mobil terminal is expected to resolve some of the uncertainty in the data set and collective interpretation for the source of the contamination in the backwash.

The data to date suggest that there is an existing risk to the backwash ecosystem that requires attention to ascertain the magnitude of the risk and whether some form of clean up is required.

13.5 Sediment Data obtained by Orica

13.5.1 Results

Sediment samples were collected by Coffey in February 2000 from ten locations (R1-R10) in the vicinity of two stormwater outlets beneath the No. 6 Yarraville Wharf that enter the Yarra River from the Orica main site, and up-gradient and down-gradient locations (about a 265 m length of the river, though the most upgradient locations were not marked on the supplied map). Extracts from a Coffey Report (2000) were provided to the auditor, including the WSL laboratory report for the sediment chemical analysis.

The chemical analysis was limited to arsenic, lead, mercury, total petroleum hydrocarbons, acridine and Cereclor. The extract of the report provided to the auditor did not include the rationale behind the selection of chemical analytes although Cereclor, a chlorinated paraffin, is understood to have been manufactured at the Orica main site and this presumably explains its inclusion in the suite.

A summary of the sediment sampling results is provided in Table 55 below, and further information is provided in the spreadsheet included in Appendix L.


Table 55 Orica, Yarra River: Sediment Data – Coffey, 2000 (mg/kg)

Cereclor

ANZECC (2000) Sediment Guideline pH As Hg Pb C6-C9 C10-C14

C15-C28

C29-C36

C10-C36

Acrid-ine AS42 AS45 AS52 AS58 AS63 AS65

ISQG Low trigger value

ISQG High trigger value

20

70

0.15

1.0

50

220

EPA Fill – maximum concentration 30 2 300 100 1000

EPA Low level contaminated soil – maximum concentration 300 20 3000 1000 10000

R1 9.8 23 0.16 140 <10 <20 280 250 <560 <0.01 <0.05 <0.05 2 6.1 <0.05 <0.05

R2 8.2 93 3.3 1000 <10 <20 270 240 <540 <0.01 <1.0 <1.0 240 80 <1.0 <1.0

R3 8.1 48 1.5 250 <10 <20 190 110 <330 <0.01 <0.05 <0.05 67 22 <0.05 <0.05

R4 8 31 0.44 62 <10 <20 <50 <50 <130 <0.01 <0.25 <0.25 48 48 <0.25 <0.25

R5 7.9 32 1.8 160 <10 <20 170 <50 <250 <0.01 <0.05 <0.05 14 43 <0.05 <0.05

R6 8.1 48 3 1500 <10 <20 78 <50 <158 <0.01 <0.25 <0.25 32 32 <0.25 <0.25

R7 8 36 1 200 <10 <20 550 83 <663 <0.01 <0.05 <0.05 16 16 <0.05 <0.05

R8 8.1 25 0.59 85 <10 <20 200 150 <380 <0.01 <0.05 <0.05 0.43 1.4 <0.05 <0.05

R9 7.9 21 1.9 200 <10 <20 <50 <50 ND <0.01 <0.05 <0.05 2.2 2.2 <0.05 <0.05

R10 8.7 <5 <0.05 6 <10 <20 <50 <50 ND <0.01 <0.05 <0.05 <0.05 <0.05 <0.05 <0.05


Cereclor

ANZECC (2000) Sediment Guideline pH As Hg Pb C6-C9 C10-C14

C15-C28

C29-C36

C10-C36

Acrid-ine AS42 AS45 AS52 AS58 AS63 AS65

ISQG Low trigger value

ISQG High trigger value

20

70

0.15

1.0

50

220

EPA Fill – maximum concentration 30 2 300 100 1000

R4 – Duplicate 8.2 31 0.71 140 <10 <20 <50 <50 ND <0.01 <0.05 <0.05 6.8 20 <0.05 <0.05

Retest#1 100

Retest#2 65

Exceeds ISQG Low trigger

Exceeds ISQG High trigger



13.5.2 Discussion of Orica sediment quality data

The results indicate the following:

The results of the Orica data are broadly consistent with the EPA data, although the Orica data generally appear to show higher concentrations.

The sediment sample located upgradient of the Orica main site reported non-detection of all analytes except lead at 6 mg/kg. Apart from this sample all other samples in the vicinity of the Precinct reported an exceedence of guidelines values.

Arsenic, lead and mercury mainly occur at concentrations greater than the ISQG Low Trigger value and many samples are greater than the relevant ISQG higher values. Elevated concentrations are reported in samples collected from upgradient, adjacent and down gradient locations in the vicinity of Orica main site stormwater drain outlets;

TPH C15-C28 and C29-C36 are reported in upgradient, adjacent and downgradient sediments; and

Cereclor is reported in all samples except one upgradient sediment sample.

13.6 Data Gaps Data gaps that lead to uncertainty in the results include:

The limited number of sediment samples that have been analysed, noting that the distribution of contamination is variable and difficult to characterise;

The suite of analyses is largely limited to metals and metalloids, and the EPA program in particular does not extend to include organics (such as Cereclor) or nutrients (such as phosphorus which is present on one of the Precinct sites);

The origin and age of sediments in particular locations has not been established, and hence it is not possible to determine other than through inference from the body of results and sampling locations whether the results pertain to historical contamination, or ongoing contamination, and where the sources of the contamination might be;

The analyses have not been related to bioavailability, e.g. by measuring acid-soluble metals or acid-volatile sulfides; and

Sediment investigations undertaken to date are limited in their application to the potential impacts from the Precinct overall, and the data generally lack information on the physical (e.g. particle size) and chemical nature of the sediment to enable a more complete assessment of the bioavailability of the contaminants that have been detected.

13.7 Conclusions The sediment results indicate:

Maribyrnong and Yarra Rivers

The measured sediment concentrations are generally consistent with the range and levels of contaminants expected in a heavily urbanised catchment.


The concentrations of contaminants in the sediments are variable and there appear to be two localised areas in the vicinity of the Precinct sites (Holden Dock, and a location off the PoMC site), which have higher concentrations of contamination. These may be associated with historical contamination that has not been removed in dredging works.

Generally the average sediment concentrations, excluding the results from the two higher sample locations, are below or in the order of the ISQG low trigger values. This suggests that there is not widespread contamination in excess of the ISQG low values.

The contaminants of greatest significance in groundwater discharging from the Precinct properties (copper, arsenic and zinc) were not significantly elevated in the sediments in the vicinity of the Precinct, over the concentrations found elsewhere in the lower catchment.

It does not appear that the Precinct sites form ongoing sources of contamination that pose a significant risk to the sediments and the river ecosystems.

EPA proposes to continue with further investigations to determine if there are elevated pockets of highly contaminated sediment at these locations. The results of this assessment support this proposal.

The data obtained largely relate to metals and metalloids, and the lack of information on other contaminants represents a significant data gap.


The sediments of the Stony Creek Backwash are heavily contaminated, particularly with hydrocarbons. Heavy metals are also present. The contamination is at levels that can pose a significant risk to birds foraging in the backwash. It is not clear that the waters of the backwash are significantly contaminated and therefore pose a significant risk to fish that might swim into the backwash. The source of the sediment contamination is not clear, although it appears to be historic and there is no evidence that the Precinct companies such as Mobil form a current and ongoing source of this contamination.


14. Biota

14.1 Documents EPA provided information on the contaminant levels in biota of the Yarra and Maribyrnong Rivers, as listed in Table 56.

Table 56 Information Received on Biota Quality

Author Date Title

EPA Victoria and Melbourne Water

January 2006 Yarra and Maribyrnong Estuaries: Preliminary Investigation of Contaminants within Fish

EPA Victoria Not specified Project Proposal: Maribyrnong and Yarra River Fish Study - Are fish caught in the lower reaches of the Maribyrnong and Yarra Rivers safe to eat?

EPA Victoria April 2006 Fish and Eel Contamination Investigation for the Yarra and Maribyrnong Estuaries (EPA Publication 1038)

EPA Victoria May 2006 Contamination Investigations for the Maribyrnong River (EPA Publication 1042)

14.2 Results of Biota Sampling and Analysis In 2005 the EPA and Melbourne Water Corporation undertook a preliminary investigation of contamination in fish and eel tissues at several sites in Yarra and Maribyrnong estuaries. The investigation obtained fish and eel samples from a number of sites in the Yarra and Maribyrnong Rivers, and these were analysed for selected metals (arsenic, copper, mercury, selenium and zinc) and PCBs.

A summary of the results is included in Table 57.

The full set of results is included in Table 6 of the EPA report (January 2006) attached in Appendix P.

Table 57 Maximum Residue Levels in Biota

Range of results observed in sampling programs (mg/kg wet wt)

Yarra River Maribyrnong River

Yarra River Maribyrnong River

Fish Fish Eels Eels

Contaminant Maximum Level for Fish

Arsenic (inorganic) 2 0.35 – 2 (total) 0.14 - 4.6 (total) <0.04 (inorganic)

<0.1

NS

Mercury 0.5/1.0 <0.01

<0.01 - 0.33 0.11-0.14 -

NS

PCBs 0.5 <0.2

<0.2 <0.01 - 1.5 (muscle of short finned eel)

NS

Generally Expected Level – 95th percentile

Copper 2 0.1 – 0.2 0.13 - 1.4 0.14 – 0.23 NS

Zinc 15 2.6 – 5.1 3.1 - 8 7.9 – 8.1 NS

NS: not sampled


14.3 Assessment of Results of Biota Sampling

14.3.1 Metal Criteria for Seafood

The Australian and New Zealand Food Standards Code (FSANZ 2003) uses defined Maximum Levels (MLs) to manage risks to human health. MLs have only been designated for food-contaminant combinations that contribute significantly to total dietary exposure (greater than 5%). These include arsenic, cadmium, lead and mercury, and PCBs.

Metals for which MLs have not been established are considered to be low risks to public health. These metals include copper and zinc. For these metals, Generally Expected Levels (GELs) have been developed based on the testing of samples from areas not subject to pollution. Exceedence of a GEL does not necessarily indicate a health risk. However, in cases where the GEL 90th percentile value for a metal is exceeded, further investigation is considered warranted.

14.3.2 Assessment

EPA concluded that the measured concentrations of arsenic, copper, mercury, selenium and zinc in the fish complied with the Australian and New Zealand Food Standards, and there was no evidence to suggest that fish caught in the Yarra and Maribyrnong estuaries are contaminated at levels by contaminants arising from the Precinct that would pose a health risk to anglers.

The auditor agrees with this conclusion, and in particular it is noted:

The measured concentrations mercury do not exceed the ML;

The concentrations of total arsenic exceed the ML set for inorganic arsenic, but the measurements indicate that the inorganic arsenic is a small fraction of the total and that the inorganic arsenic concentrations do not exceed the ML;

The measured concentrations of copper and zinc do not exceed the generally expected levels;

The concentration of PCBs in an eel caught in the Yarra River near Herring Island (i.e. in the Yarra River upstream of the Precinct) was above the ANZ Food Standards Maximum Residue Limit (MRL) of 0.5 mg/kg. PCBs are not a contaminant expected to be associated with the Precinct, and it may be concluded that this particular result would not be associated with the Precinct activities.

However, the biota analysis program was limited in that:

The number and locations of biota sampled were limited, and did not include for example the sampling and analysis of eels in the vicinity of the Precinct. EPA advised verbally that eels had not been found in this area, and that it had not been practicable to include such eels in the program.

The analysis was limited to heavy metals, metalloids and PCBs. While the metals and metalloids are contaminants of particular relevance to the Precinct, the analysis did not include other contaminants associated with the Precinct (such as chlorinated organics and pesticides, and Cereclor (detected in recent sediment analyses).

Because of these limitations, the question of whether it is safe to consume fish caught within the Precinct remains somewhat unanswered as the sampling locations were remote to the audit area itself, and could possibly represent better environmental conditions than those within the audit area.


14.4 Conclusions The results indicate that the measured concentrations of arsenic, copper, mercury and zinc in the fish complied with the Australian and New Zealand Food Standards, and there was no evidence to suggest that fish caught in the Yarra and Maribyrnong estuaries are contaminated at levels by contaminants arising from the Precinct that would pose a health risk to anglers. However, the results did not include samples of fish from the immediate vicinity of the Precinct and do not provide direct evidence of the contaminant levels in fish caught in the vicinity of the Precinct.

A reported result of PCBs in an eel in excess of the food standards in a site distant from the Precinct is not considered to be relevant to the Precinct activities.

14.5 Data Gaps Limitations in the biota sampling and analysis include:

The number and locations of biota sampled were limited, and did not include for example the sampling and analysis of eels in the vicinity of the Precinct (EPA informed the auditor that they were unable to catch any eels within the Precinct area), or fish within the Precinct;

The biota information is limited to heavy metals and metalloids, and PCBs; there is no information to confirm the absence of other contaminants associated with the Precinct (such as chlorinated organics and pesticides, and Cereclor55 (detected in recent sediment analyses); and

It is understood that a proposed study on fish quality (joint project of EPA, Melbourne Water, Port of Melbourne Corporation and Department of Human Services) has included fish and eel sampling locations within the urban reach of the lower Maribyrnong River including locations within the Precinct. Such a study should be useful in obtaining a better understanding of the contaminant levels in fish and their acceptability.

55 Orica advised the auditor that Cereclor in sediments is not bioaccumulative (Orica, information provided relevant to the draft audit

report, 14 August 2006), however it is reported that there is data to indicate that some chlorinated paraffins have a potential to bioaccumulate (Government of Canada, 1993). The information to the auditor has not been sufficient to conclude that further analysis of biota samples should not include Cereclor.