SAVE RALPHS BAY
CONTAMINANTS
Walker Corporation (Walker) has significantly amended the proposed construction programme in relation to the dredging, treatment and placement of contaminated sediments. Dr Cuff (Walker) gave evidence that this material should be kept in a series of large, lined containment cells. Walker’s experts agreed that considerably more sampling was required to determine the extent of contaminated sediments in the proposed development area.
Expert witness for Save Ralphs Bay Inc, Dr Ruth Eriksen discussed her experience with heavy metal contamination in the Derwent Estuary and explained the ‘Ralphs Bay conundrum’. [See SRB Media Release 23.6.09]. More testing is required to understand the impact of the proposed development on the long term behaviour of metals in Ralphs Bay, including bioaccumulation. It was her opinion that such testing should be carried out before a decision was made about whether to proceed.
CONSTRUCTION
Ronan Kellaghan (Walker – air quality) acknowledged that local wind data records were incomplete and could not be used to characterise wind at the site. As a result, modelling was based on wind records from the Hobart Airport. He agreed that site specific data was important and admitted that the model was not able to be verified on the basis of Lauderdale data. The model also used data from 2006 and did not include recent extreme wind events such as the 174km/hr wind recorded in April 2008. Mr Kellaghan had not assessed the impact of dust in respect of the revised proposal to contain contaminated sediments. He acknowledged that suppression of dust would be challenging where the sediments could not be wetted. Mr Kellaghan stated that samples from East Marsh Lagoon exhibited an odour of hydrogen sulphide, while samples from Ralphs Bay did not exhibit a strong odour. He admitted that, based on current modelling, odour goals would be exceeded at some residences. Matthew Bryce (Walker – noise) stated that no noise monitoring had been carried out at the Lauderdale school and said that disruption within the classroom was unlikely unless the windows were open. Mr Bryce recommended that a 3m high solid perimeter noise barrier be maintained throughout the construction period.
WATER QUALITY
Mr Neil Collins (Walker – water quality) agreed that proposed silt curtains will not contain dissolved contaminants or fine material. Mr Collins noted Dr Cuff’s (Walker Corp.) evidence that saltwater intrusion could mobilise contaminants from the Lauderdale tip and admitted that this was a risk (though he said an engineering solution could be available). He also agreed that the extent of contaminated leachate from the disused Lauderdale tip site had not been adequately assessed. Mr Collins agreed that draft water quality objectives proposed for the site did not take into account seasonal variation and that an additional 12 months monitoring would be necessary. Dr Doug Treloar (Walker – Coastal Processes) admitted that the model used to predict water circulation (Delft3D) was still being refined in respect of water quality and may not reliably predict production of monosulphidic black oozes (MBOs). Daniel Ray gave evidence for Save Ralphs Bay (SRB) that he remains
concerned the long term release of nutrients from land masses within the canal estate has not been assessed. Combined with low flushing rates and potential for stratification, nutrient loads could lead to algal blooms. Dr Steve Appleyard spoke for SRB from Western Australia by videolink, regarding his experience with regulating canal estates in WA. It was his experience that conditions change post-construction and modelling has often not predicted impacts in relation to water and sediment quality. Dr Appleyard stated that canal estates require intensive management and
regulators needed resources and expertise in order to set appropriate conditions, carry out and evaluate monitoring and enforce conditions where necessary. He noted that, in WA, canal estates had often been a ‘crippling burden’ on local governments. Dr Appleyard discussed the factors leading to the production of MBOs – sulfides (from sea water), iron, nutrients and organic matter. He noted
that nutrients coming from land masses within canal estates were often the cause of problems.
SEA LEVEL RISE
SRB introduced two recent reports (Copenhagen and White House) indicating that sea level rise could be in excess of 1m by 2100. Walker’s expert did not believe that these predictions justified any change in their construction design. Dr Treloar agreed that designing for mid-range predicted sea level rise could reduce the ‘safety factor’ and may mean that houses were subject to more frequent nuisance inundation if higher predictions prove to be accurate. Dr Treloar admitted park land areas within the development would be subject to periodic inundation, which could impact on the survival of vegetation in those areas. Dr Treloar admitted that, if the former Lauderdale canal had been dredged to 3m as suggested, there was evidence of considerable sediment deposition at the entrance to the canal. SRB suggests this has consequences for the ongoing maintenance of the proposed canal estate entrance.
BIRDS
Mr John Delaney (Walker – ecology) acknowledged that the Lauderdale area is an area of international significance in relation to the Pied Oystercatcher.
Dr Iain Taylor was highly critical of the interpretation of the output of the carrying capacity model for Pied Oystercatchers. It was Dr Taylor’s view that input data for the model was flawed in terms of foraging habits, availability of food, methodology for recording food sizes and assumptions regarding predation and competition. He was also critical of the use of assumptions based on European Pied Oystercatchers, which behave quite differently to the Australian species. Therefore, Dr Taylor had no confidence that the model could reliably predict insignificant impact of the development in relation to displacement of birds. Mr Delaney relied on the carrying capacity modelling to reach his conclusions regarding impact. He admitted that if there were shown to be errors or deficiencies in the model, he would need to revise his assessment.
He acknowledged that no carrying capacity modelling was done in relation to other bird species. Mr Delaney admitted that the field surveys carried out had failed to distinguish between the movement patterns of resident and migratory species.
Mr Delaney agreed that reducing the feeding and breeding habitat for a species increased the risk of it becoming ‘threatened’. Mr Delaney agreed Pied Oystercatcher numbers at the Lauderdale site, and possibly throughout the ‘Derwent Estuary Pittwater Area’ complex, would decline as a result of the proposed development.
— Save Ralphs Bay Inc. : www.SaveRalphsBay.org —
