Agendas | Minutes

Homebush Bay Dioxin Remediation Project
Community Liaison Group
10th Meeting
 26 March 2003

Minutes of Meeting 26/03/03 

( Answers to Questions submitted in advance )

( Answers to Questions asked at the meeting )

( Presentation at Meeting )

The following are questions from Paul Hanly (e-mail of 19 March to Doug Moss) and Thiess' responses to each.

Q1) Please provide (hand out) a list of what levels of residual contaminants will be in what area (volume/prism/zone) of the former union carbide site, together with a schematic of the different areas/zones/prisms and similarly for the sediments. On the same list please list all the other numerical standards to apply to the site and remediation. Or provide the page references where this is provided in the EIS in a summary form.
See the Powerpoint presentation notes for this information in relation to the Lednez site.
For the Bay, the most comprehensive description of the distribution of dioxin contamination is found in Section 4 of Volume 1 of the EIS (refer Figures 4.3 to 4.5).The residual contamination in the Bay will be as per these diagrams outside the proposed remediation footprint. Within the remediation footprint, Thiess will backfill the excavation with soil that meets the following criteria (as per Section 4-6 of the Bay RAP, EIS Appendix B):
· <0.05ug/kg for dioxin
· ANZECC/ARMCANZ (2000) for the other contaminants
· Limits of detection for organics not listed in ANZECC/ARMCANZ (2000)

Q2) Has Thiess or other interested parties considered an application to be bound by the same emissions standards (on a daily or time cumulative or sites cumulative basis) as the Meriton site once that site remediation is approved.
Thiess has not considered the above at this stage. 

Q3) Would you have a legal right to amend your DA and EIS to seek such an approval?
We understand that any proponent has the legal right to amend its DA and resubmit for approval at any time.

Q4) Is landscaping additional to a top metre of 90 ppt dioxin soil?
Landscaping will be undertaken by Multiplex Living after the completion of remediation. As such it will overlay the remediated surface provided by Thiess.

Q5) Has anyone including Health or EPA expressed concern about the high levels of dioxin (and I assume other chemicals) in the least processed area/zone/prism which is like a de facto "cell"?
The EPA NSW has expressed concern about the acceptability of the risk assessment derived concentrations at depth for untreated soil remaining on the site. This matter has partly led to the delays to the exhibition of the EIS and is the subject of ongoing consultation with the EPA. See the Powerpoint presentation notes for a thorough discussion on the basis of the criteria and how Thiess proposes to reuse soils on the site.
Thiess expects actual levels of chemicals in untreated soil will be significantly less than that allowed in the risk assessment. This is because the risk assessment has been developed according to national and NSW guidelines, without consideration to current levels or anticipated final levels of chemical in untreated soil.
The notion of a "cell" as a remediation strategy implies containment of contaminated soil in a lined repository to prevent migration of chemicals into the environment. This concept is not applicable to the untreated soil that will remain on the Lednez site, since the same criteria apply across the entire site within common landuses i.e. there are no criteria that are unique to the "regrade borrow". The "regrade borrow" is specifically proposed to be a source of sound geotechnical material for use as needed elsewhere on the site. In addition, Thiess proposes that all highly contaminated and oily material will be treated by thermal desorption. Hence, there is no requirement for "containment" of materials to prevent migration to the environment.

Q6) Have you any information on the body burden and soil burden of the nearby residents and their properties and where they are in relation to standards and guidelines eg Michigan, USA EPA Region 9 2002, Canada, NZ, NHMRC?
Thiess has no information on body burdens or levels of chemicals in residential properties in the area. Thiess understands that some analyses of soil have been undertaken in the past including from the Community Centre in Blaxland Rd. Thiess also understands that NSW Health is meeting with a committee of local residents to consider the question of establishing dioxin levels in local residents and monitoring any changes during the remediation works.

Q7) How can you tell whether the contaminated dust from excavation, treatment and operations will adversely impact the local community without that information?
The air risk assessment undertaken to assess the risk posed by the remediation work is based on incrimental risks (for non-carcinogens the maximum incrimental hazard quotient is less than 0.5, and for carcinogens the maximum incrimental cancer risk is 8*10-7). Accordingly, the air risk assessment does not rely on background exposures.

Q8) Please give a very good and detailed explanation of the meaning and impact of the assessment of the fish exposure pathway for residents and non residents, particularly having regard to pages: 
Vol 4, Technical Paper 5 See pp: 52-54, Supplementary Report pp 10, 46, 48, 50,52, 59
Thiess is unable to answer this question in any more detail than as described in Technical Paper 5 and the Supplementary Report you have referred to. 
In summary, the main items that have been considered with respect to the fish exposure pathway are:
· How much dioxin is in the Bay;
· How much dioxin is in fish in the Bay;
· What is the relationship between dioxin in fish and dioxin in sediment;
· How much fish is eaten by whom; and
· What is an acceptable level of dioxin intake 
Many other peripheral issues (in terms of their impact) have also been addressed such as what is the background exposure to dioxins. These are not discussed here
Dioxin in the Bay. The amount of dioxin in the Bay has been assessed by interpreting the results of extensive sediment sampling. The results show a clear pattern of decreasing concentration of dioxin in sediment with increasing distance from the shore. A number of localised hot spots have been delineated. Technical Paper 5 summarises these data and interpretations. The distributions of dioxin as 2,3,7,8 - TCDD and on a TEQ basis are similar.
Dioxin in Fish. The amount of dioxins in fish has been assessed on the basis of limited sampling. Technical Paper 5 summarises these data. Dioxin concentrations in some species are higher than others because of their feeding habits (eg mullet contains the highest concentrations because it is a bottom feeder). The risk assessment assumes that mullet comprises 50% of the fish eaten from the Bay which is conservative since mullet is not a preferred recreational fish.
Relationship between dioxin in fish and dioxin in sediment. In the absence of any method for rigorously predicting the relationship between dioxin in sediment and fish, a simplifying assumption has been made that a directly proportional relationship exists, ie as the amount of dioxin in sediment increases the amount in local fish increases and vice versa. 
How much fish is eaten. National figures exist for the amount of fish consumed annually by Australians. These have been used for the base case, but assuming that all the fish eaten comes from the Bay, which is very conservative. The risk assessment also considers "keen anglers" and assumes that they eat 3 times as much fish as the average population. The risk assessment also considers risks to breast feeding infants growing up in the Homebush Bay area.
Acceptable Level of Intake. The acceptable level of intake of dioxins is based on WHO recommended levels (ie 1 to 4 pg TEQ/kg body weight/day) and the draft NHMRC TDI guideline of 2.3 pg/kg body weight/day. A discussion of the NHMRC draft guideline and other international figures is given in the Supplementary Report in Technical Paper 5.

Q9) Please advise how the decision to remediate the proposed area of sediments took into account the risks posed by the lead and phthalates off the former Orica site and what sources of information were used.
The screening level risk assessment by Parametrix and AWT Ensight in 1996 investigated a wide range of chemicals and metals in sediment and fish (but excluding phthalates). The main chemical of concern identified was dioxins because of excess cancer risk from the fish consumption pathway. Lead was not considered since it does not bioaccumulate in fish, and levels are below the level identified as a concern for human health. Similarly phthalates do not bioaccumulate in the environment and are biodegradable.

Q10) Please advise whether the cumulative impacts of the contamination of sediments off the former AGL and Orica sites on fish and to human health through fish consumption have been considered.
The impacts of contaminants from other sites and wider harbour have been considered in that fish from the Bay have been analysed for a wide range of chemicals and conclusions drawn for risks to humans from eating fish (Parametrix and AWT Ensight 1996 screening level risk assessment study). Of these the main risk identified was from exposure to dioxins by eating fish. Lead and PAHs were not identified as an issue for fish consumption. PAHs were not considered because they are readily metabolised by fish. Similarly metals (excluding mercury) and phthalates do not bioaccumulate in fish and were not considered.

Q11) What steps will be taken to re-populate the marine/benthic organisms in the sediments in the remediation area?
Thiess does not propose to repopulate the remediation footprint in the Bay with marine organisms. Repopulation is predicted to occur due to natural processes and will be monitored. The matter is discussed in Technical Paper 10. 

Q12) What safety features will be in the replacement seawall to assist egress from the water in case of need, given the high numbers of persons, including children, likely to be in the foreshore area?
Detailed design of the seawall has not commenced and will be undertaken by Multiplex. 

Q13) I remain unconvinced about the generalisation of Parramatta River background levels of various contaminants including dioxins. Are the so called background levels simply an averaging of total burden over the whole river and if so, what happens to the total burden and background levels if each sediment remediation scenario was completed. The works of Gavin Birch seem to indicate that the concentrations are high in heads of bays and off the AGL site in particular and not spread uniformly over the river. 
The data available on background levels of contaminants in the Bay are discussed and interpreted in Technical Paper 5, Section 4.3.
The effects of the Bay remediation scenarios in terms of dioxin reduction are discussed in Technical Paper 5, Section 10.5. Reduction in dioxin levels by remediation of the Bay would probably not change existing background levels (but would prevent them from increasing due to future contributions from the remediation footprint).

Q14) What would be the approximate incremental cost and time to double the remediation area particularly in the areas NEB 10, 9, 8, 7 and 5 and the balance of SE 1 and the North Eastern diagonal half of SC1? What would be the average cost per unit reduction of dioxin of such a scenario (present proposal extended as above) compared to the present proposal?
Thiess has not costed carrying out the above works. This is not a simple task. However the incremental cost would be significantly higher than for the proposed works since the current "dry excavation" method would not work due to the increased water depth. Further the average cost per unit of reduction of dioxins would increase significantly due to decreasing dioxin concentration with distance from shore. 
The relative reduction in dioxin concentration with increasing excavation areas is discussed in Technical Paper 5, Section 10.5.

Q15) Are you aware or can you provide any details of an expert committee referred to in the attached web page and their recommendation on the extent/level of remediation as referred to in the web page?
Thiess is unaware of the details of the committee you refer to.