Howard Tankey

Introduction

The extension of the Eastern Freeway will have an adverse effect on the water quality of the Mullum Mullum Creek, the Yarra River and ultimately Port Phillip Bay. Because this road dramatically increases the probability that the eastern sections of the Ring Road will be built, its detrimental effect will in time be extended.

Non-porous surfaces create non-point sources of toxic pollutants which threaten the viability of Melbourne’s aquatic environment. Runoff from freeways, roads and parking areas contains potentially toxic pollutants such as heavy metals and polycyclic aromatic hydrocarbons (PAH’s). There is a considerable body of evidence from the United States and Europe to suggest that measures should be taken to limit the impact of runoff on receiving waters.

Main pollutants

Particulates

Most of the pollutant load is adsorbed onto particles. Of these particles the smaller ones (<60 m) have the potential for greatest harm because the pollutant concentration is greatest on them and because they are more difficult to trap with the usual filters such as dams, grass etc. The particle size distribution of suspended solids in samples collected from a road in Sydney showed that particles <63 m were present in fractions from 55 % to 93 %. 1

Heavy metals

Copper, lead and zinc are the pollutants of greatest concern because of their toxicity and because they are at high concentrations in runoff from roads.2

Organic pollutants

Vehicle-related activities produce a number of potentially toxic substances, including oil and tar products, dioxins, oxygenated compounds and PAH’s.3 Contaminants from roads can enter aquatic systems either by road runoff or atmospheric fallout. The concentration of PAH’s in roadside dust and sediment is proportional to urban density, and by inference, traffic density. There is a high correlation between PAH profiles in airborne particulate matter and road dust.4

The absence of chemicals involved in de-icing of roads characterises the main difference beween Australian and Northern Hemisphere conditions.

Effects of pollutants on water quality

Runoff water frequently exceeds the local water quality guidelines for the pollutants measured.5 They are also discharged, mostly untreated, into the receiving waters. The relationship between pollutant concentration in runoff and receiving waters and their impact on the aquatic environment are extremely complex. However, scientific evidence demonstrates the potential of the problems.

PAH’s were shown to be more toxic to a benthic amphipod than heavy metals.6

Lead, copper, zinc and cadmium are the toxic metals most likely to affect aquatic species.7

Metal pollutants will persist in the environment since they cannot be degraded (they may less toxic in complexed form) by sunlight or microorganisms.

Conclusions

1. The relatively new understandings of the impact of urban road transport on the aquatic environment require three actions by governments and bureaucracies:

 1.1. Any new transport plans must take this information into account.

 1.2. Any decision to build new roads or parking areas must include plans to reduce pollutant runoff through the use of established and new techniques.

 1.3. Further research is required to tease out the main threads of a very complex situation.

2. It is abundantly clear that a relevant and up-to-date Environment Effects Statement (EES) is required for the extension of the Eastern Freeway through the Mullum Mullum Creek valley. This is especially important since the current EES for this project8 did not even consider the issue of water quality. To ignore scientific data available after the current EES was carried out would be a dereliction of duty bordering on illegality.