Contamination, comes standard

For the past seven years I have been an environmental consultant working on a variety of sites for multiple clients. What if I said that almost every potential development site within a 15 kilometre radius of the Melbourne CBD is contaminated. Would you be alarmed? Would you even believe me?

If you said yes to both of those questions then you would for the most be correct.

Our main role as environmental consultants is to assess and identify any potential sources of contamination in the soil or groundwater which are a result of historical uses at the site, then assess whether there are any impacts and to what extent. Finally, depending upon intended future use, we will ensure that any risks posed by site contamination to sensitive receptors (i.e. humans and the environment) have been mitigated prior to reuse.

To clarify, site contamination comes in many different forms and may pose a risk depending on the setting in which it lies. The Oxford dictionary defines contamination "as making something impure by the exposure or addition of a polluting substance", so with reference to soil and groundwater it's a substance that alters the medium from its natural state.

One example can be found during Melbourne's urban development as it expanded further outwards from the CBD during the 19th and 20th centuries. Many areas were developed for different purposes including residential and industrial uses. In some cases imported material was used on sites to provide stable foundations for a structure or as backfill material. This material was not assessed before use which now could pose a risk to the aforementioned sensitive receptors. Contemporary regulatory bodies have set specific guidelines for the transport, use and storage of imported material to minimise any potential risk and that the material is similar to its final destination.

Another common source of site contamination comes in the form of petroleum hydrocarbons at former service station sites. Across Melbourne, there are many former service stations sites that  have been or are currently being converted into multi-storey residential apartments. The most obvious concern revolves around remnant volatile compounds in the soil and groundwater that may pose as either a vapour risk to future site users or migrate offsite depending on the groundwater flow direction.  A number of factors make each site different and it's up to environmental consultants to assess the impacts and whether there are any risks. In the majority of cases these volatile contaminants are remediated in one form or another and the site suitability is determined by measuring concentrations against specific criteria.  

Furthermore, when a site is changed from a low sensitivity use (i.e. commercial/industrial) to a high sensitivity use (i.e. residential), an environmental audit is triggered and a planning permit cannot be issued without an audit being completed. As part of this process, an environmental auditor is engaged to ensure the assessment conducted by consultants is in line with guidelines and the site will be fit for purpose following environmental works.  

The transformation of former industrial sites to more sensitive residential uses comes at a cost to the developers, most of which cannot be fully quantified until intrusive work is conducted and reports have been finalised. Over the past few years, site assessment criteria has been updated in the form of the draft National Environment Protection Measure 2011 guidelines which will act as a useful tool for consultants to assess sites using a multi-tiered risk based approach - far more flexible than previous NEPM guidelines.  What this means to developers is that the process and costs associated with getting a development site with a planning permit could be far less daunting and better for the bottom line yet at the same time still provide the necessary environmental protections, which can only be good for the sustainable urban growth of Melbourne.

In a future piece, I'll compare the different versions of the NEPM guidelines and highlight the advantages going forward.

The purpose of this article is meant as an overview of the process of assessing sites for contamination and is general in its nature.