In most cases the performance of a stack is gauged on its ability to reduce pollutant concentration at ground level to below ambient air quality criteria.

However, where high-rise developments are nearby, the stack is less effective because the vertical separation distance between the pollutant plume and people's breathing zone is dramatically reduced.

In this case, a novel application of atmospheric dispersion modelling, known as a buffer volume assessment, can be used to determine both the required horizontal and vertical separation distances between a stack and sensitive receptors at ground and elevated levels.

The model was applied by GHD to Melbourne's Grant Street stack on the CityLink tollway, near fashionable Southbank, for client Transurban. GHD was commissioned to determine the buffer volume of air around the stack in which air quality objectives may not always be met.

The buffer volume dimensions then allow an overlay height control to be specified that defines the constraint on maximum height of buildings relative to distance from the stack.

GHD's Tim Pollock says, "This new approach gives an operator, such as CityLink, confidence that new developments at Southbank will not compromise the performance of the stack or be subject to adverse air quality."

The buffer system overlay is now being adopted by local planning authorities on an interim basis to set height guidelines for buildings next to stacks, and is likely to be included in amendments to their planning schemes.

For more information, contact:

Kate Volcov  [tel 61 2 9239 7353]  [email]