These are answers to questions asked at the meeting:

Suitability and representativeness of the wind data used in the assessment of the air quality impacts 

Wind data from four locations were assessed, in terms of their suitability and representativeness, for use in the dispersion modelling work conducted as part of the EIS. They comprised:

· Bureau of Meteorology data from the Olympic site; 
· data collected by the NSW EPA site at Lidcombe; 
· data collected by Macquarie University at Silverwater near the Correction Centre; and 
· data collected from a meteorological station installed on the Lednez site in September 2001. 

Of the locations outside the site, the data collected by the EPA at Lidcombe was determined the most suitable for the purpose because it is the most recent and was collected at the radial increments most appropriate for use in dispersion modelling. 

At the time the EIS was prepared, a complete set (full year) of data from the Lednez site meteorological station was not available. Accordingly, it was determined that the most suitable data set for the dispersion modelling was that collected by the EPA at Lidcombe. 

The windroses for the Lednez site station and the Lidcombe station are attached. They show very similar patterns of prevailing winds. On an annual basis winds are predominantly from the north northwest, south and southeast. This pattern is present in spring and autumn while in summer southeasterlies predominate and in winter westerlies are most common. Therefore both data sets are representative of the dispersion conditions experienced at the site. 

The following table provides some characteristics of the Lidcombe dataset (used for modelling) and the (now) complete annual dataset collected at the Lednez site.


Weather Station Stability (%) Wind Velocity(m/s) Proportion from NW - SW(%) Proportion from SE - SW(%)
Lidcombe 38.7% 2.01 42 23.5
Lednez Site 22.6% 2.63 41 24



As shown in the table above, there is a higher frequency of stable atmospheric conditions in the Lidcombe data (38.7%) than in the on-site data (22.6%). The use of data with a higher frequency of stable atmospheric conditions leads to higher long-term predictions and is therefore conservative.

The annual average wind speed for the Lidcombe data is lower (2.01 m/s) than the annual average wind speed for the Lednez site data (2.63 m/s). The use of meteorological data for modelling purposes with an average wind speed lower than experienced on-site is also a conservative approach. 

The frequency of winds blowing from the westerly sectors (NW to SW), which would transport pollutants from the site to the nearest receptors, is similar in both cases (41% for on-site data and 42% for Lidcombe data).

For receptors to the north (Meadowbank) the relevant wind directions are from the southeast to southwest. The frequency of winds from these directions is again comparable (24% for the on-site data and 23% for the Lidcombe data).

In summary, the Lidcombe data are considered representative of dispersion conditions at the site and will result in a conservative estimate of offsite impacts. 

Effect of emissions from earthmoving equipment on air quality impact assessment

The most significant emissions from diesel engines are particulate matter and oxides of nitrogen. During the Lednez site and Homebush Bay remediation works haul trucks would be the most significant source of diesel emissions, with typical emissions from trucks of approximately 15 g/km for oxides of nitrogen and 0.5 g/km for PM10. With annual on-site haulage estimated to be 19,123 km this would result in annual emissions of 286 kg of NOx and 9.6 kg of PM10. The contribution from other earthmoving equipment and ancillary equipment would be small by comparison.

When compared with annual emissions of approximately 6600 kg for NOx and 5100 kg for PM10 from combustion of natural gas in the ITD, emissions from earthmoving equipment (286 kg of NOx and 9.6 kg of PM10) can be considered to be insignificant, and in that context would not alter the outcomes of the impact assessment. 

In terms of impacts to air quality from chemical emissions (including dioxin), it is estimated that site earthmoving plant would account for less than 3 percent of the truck emissions generated from Concord Road between the northern end of Ryde Bridge and the intersection of Concord and Blaxland Roads. Accordingly, such emissions from site earthmoving plant are not significant in the local or regional context.

Applicability of lifetime average daily dioxin exposure of 1.6 mg/kg body weight per day to all areas of the site.

All dioxin reuse/validation soil criteria have been developed on the basis that the total potential exposure due to background sources (assumed to be 1.4mg/kg body weight per day) and residence on the site does not exceed a lifetime average daily intake of 1.6 mg/kg body weight per day.