1. West Gate Tunnel – Air quality expert evidence
Graeme Starke
30th August 2017

2. Key issues to expert evidence
Construction phase temporary ventilation structure’s emissions.
Maximum predicted incremental impacts.
Impact to existing or planned tall buildings.
Validation of the AUSROADS model.
Combined emissions should have been assessed against Schedules A of the State Environment Protection Policy (Air Quality Management) SEPP AQM.

3. Key documents and other staff
The key document relied upon for this presentation are:
West Gate Tunnel Project Air Quality Impact Assessment Report - Technical Report G to West Gate Tunnel Project Environmental Effects Statement (EES)
Other persons that I relied upon for advice
Dr Alison Radford – Associate SLR Consulting.

4. Construction phase temporary ventilation structures
Technical report G stated that during the construction the ‘design, number and location of these temporary ventilation systems is currently not known’ but that they will ‘be sited, where possible, at locations away from sensitive receptors’.
These should be assessed for quantitative emissions impact assessment prior to implementation.
Conclave agreed modelling temporary ventilation structures should be considered once more source details are available.
It was also agreed that a Construction Environment Management Plans is more effective at dealing with general construction emissions.

5. Dispersion modelling basics
The dispersion modelling utilised contemporaneous background concentrations for PM10 and PM2.5 (March 2015 – March 2016)
Contemporaneous backgrounds add the measured background concentration to the modelled impact concentration on an hour by hour basis.
This method is considered the most accurate method of addressing background concentrations but has one potential flaw:
If the highest concentration background hours coincide with very low concentration impact hours the full potential impact might be missed in the modelling.

6. Maximum Predicted Incremental Impacts
The dispersion modelling results presented in Technical Report G focussed on the maximum predicted concentration.
The existing background concentrations are already elevated in this region (see Figure 40 and 41 from Technical report G)
Are maximum results representative?
Agreed in conclave to table maximum incremental results for Millers Road (Receptor 18)

7. Millers Road
An area of concern in the modelling was that of the increases in PM10 concentrations along Millers Road.
Technical Report G assessed years 2022 and 2031.
Including background 24 hour PM2.5 concentrations increased by 18 and 22 percent in 2022 and 2031 respectively compared to the base scenario.
Including background 24 hour PM10 concentrations increased by 3.3 and 5 percent in 2022 and 2031 respectively compared to the base scenario.
World Health Organisation (2005) states no safe concentrations for PM10 or PM2.5.
Given exceedances of the SEPP AQM 24 hour PM10 criterion, acknowledging that the project contributes only a small fraction of the impact, and acknowledging that the SEPP AQM refers to the application of best practice management for new air emission sources, the application of any available management strategies or material mitigation should be considered to reduce impacts at this location.

8. Millers Road
I recently became aware of WDA Project Note 1 that will reduce the forecast increase in number of trucks along Millers Road, north of the West Gate Freeway from 7,000 a day to 4,000 a day.
Considering that Technical report G identifies that ‘Increases in PM10, PM2.5, NO2 and PAH concentrations are due to the increase in HCVs for the project over the base case (3800 HCVs per day).’ it can be assumed that Project Note 1 might reduce half the predicted increases in impacts along Millers Road resulting from the increases in HCVs.
Other potential strategies might include barriers (although this may not be practical in this particular situation) and vegetative screening to break up and diffuse the vehicle exhaust plume.

9. Ventilation structures – impact on tall buildings
Concern that concentrations in the plume centreline would impact more strongly on elevated buildings. Particularly interested in potential impacts to buildings in Planning Scheme Amendment C88.
Conclave agreed to model elevated receptors.

10. AUSROADS validation AUSROADS model is based on CALINE4
CALINE4 is a dispersion model developed in the 1970s when the operating system was still DOS.
Background concentrations already frequently higher than SEPP AQM guidelines.
Therefore, the proponent should be sure that the model is performing accurately in these conditions
Conclave agreed that monitoring currently being conducted would address this concern
Victorian Environmental Protection Agency indicated validation not required.
Outside factor of two acceptable modelling accuracy
Reproduced from

11. Combined emissions should have been assessed against Schedule A of SEPP AQM
Modelling of the ventilation shaft and the surface road emissions have been assessed separately against Schedule A and Schedule B of the SEPP AQM as appropriate.
The ventilation shaft emissions have been assessed against a static background concentration.
However, the surface road emissions effectively change the conditions of the background in years 2022 and 2031.
Therefore, the combined modelling should have been assessed in 2022 and 2031 against Schedule A rather than Schedule B using a formula such as:
Ventilation impact + (Background ± Surface road impact)
where (Background ± Surface road impact) is considered the background for that modelling year
This is particularly relevant for receptors with predicted increases in PM concentrations such as Millers Road
Conclave did not agree on this point but agreed it is not significant to the outcome of the study.

12. Conclusion Construction phase temporary ventilation structures impact.
Conclave agreed to consider quantitative assessment once temporary ventilation structures locations identified. The CEMP is the best tool for construction dust management.
Maximum predicted incremental impacts.
Conclave agreed to present incremental impacts at select receptors.
Impact to existing or planned tall buildings.
Conclave agreed to model elevated receptors
Validation of the AUSROADS model.
VIC EPA disagreed with validation but conclave agreed that monitoring being conducted should address this concern
Combined emissions should have been assessed against Schedules A of the SEPP(AQM).
Conclave disagreed but agreed this is not material