Rendezvous Road Groundwater Contamination 

What is the contamination?

Groundwater in the area has shown levels of hydrocarbons, metals, nutrients and PFAS above background levels. Refer to the FAQs at the bottom of this page for more information about PFAS.

The main contaminants of concern that were identified are:

• Arsenic (a typical “by-product” of bio-chemical processes associated with landfill activities)
• Chlorinated hydrocarbons (originating mainly from solvents and degreasing agents and related breakdown products – e.g vinyl chloride)
• PFAS (Per- and Poly-Fluoroalkyl Substances). Per- and poly-fluoroalkyl substances, also known as PFAS, are fluorine-containing chemicals which have been used since the 1950’s for the manufacture of products that resist heat, oil and water. 

In more recent times there has been concern about potential PFAS contamination of groundwater. This has primarily focused on sites where firefighting foams have been used, including defence, airport and landfill sites; and where household goods (such as food wrappings, pots and pans, clothing and furniture that have been treated with PFAS) have been disposed of. 

As the awareness of the presence of these substances is recent, testing for PFAS at the former landfill site commenced in 2017. Indications are that historic landfill activities at the former landfill site probably brought waste containing PFAS in contact with shallow groundwater and not firefighting foams, as the PFAS levels at the former landfill site are a considerable order of magnitude less than what has been identified at defence and airport sites.

Further resources on PFAS:

• The Department of Water and Environmental Regulation (DWER) - PFAS Investigation in WA

Status of investigations

The City was required to undertake investigations in respect to these legacy issues in accordance with the statutory framework under the Contaminated Sites Act 2003 (WA). The Department of Water and Environment Regulation (DWER) is the government agency responsible for administering the relevant statutory requirements.

DWER has, pursuant to the Contaminated Sites Act, the power to classify a site if, based on relevant guidelines, currently accepted industrial standards or any other information, there are reasonable grounds to do so. The types of classification include:

The City’s investigations had been ongoing for a number of years and were conducted by qualified and experienced environmental consultants in accordance with a sampling and analysis plan endorsed by DWER. Test results were assessed and reviewed by an independent Contaminated Sites Auditor accredited with DWER. The Contaminated Sites Auditor’s findings are documented in mandatory auditor's reports and reported to DWER.

The status of the City’s investigations can be summarised as follows:

Groundwater testing

A well network, comprising of 56 specially constructed monitoring wells, has been used for testing shallow groundwater. Over the years shallow groundwater from a number of private bores, dams and wells had also been tested.

The most recent monitoring events occurred October/November 2019, October 2020/February 2021 and November 2021. In the June 2022 Mandatory Auditor’s Report the Contaminated Sites Auditor expressed the view that these investigations have been undertaken with consideration of relevant legislation, guidelines and standards, as well as industry best practice.

The Contaminated Sites Auditor concluded that in respect of the contaminants of concern (i.e. arsenic, vinyl chloride and PFAS), the extent of the groundwater contaminant plumes (i.e. where analyte concentrations exceed adopted assessment criteria for relevant environmental values/beneficial uses):

• have been delineated by the existing monitoring bore network; and
• with the exception of some apparent (relatively minor) variations between monitoring events, have been assessed as generally stable over time.

The Contaminated Sites Auditor also concluded that, in addition to the obvious impacts of historical landfill activities on the quality of shallow groundwater beneath and hydraulically down-gradient of the former landfill site, there is a potential for additional off-site contributions (e.g. metals, nutrients, PFAS) from properties located to the south of the former landfill site. The Busselton Waste Water Treatment Plan has been identified as the most likely contributor, and chemical usage on and surface run-off from agricultural land may also be (at least partly) responsible for some of the metal and nutrient impacts. The extent of the impacts from off-site sources is unknown, but is considered likely to be relatively minor in comparison to the former landfill activities.

In general the latest test results did not give rise to any new or further concerns and, in relation to some of the contaminants of concern, indicated that the extent of the contamination plume was slightly reduced during the latest (November 2021) groundwater monitoring event (as compared to some of the previous test results).

These findings enabled DWER to make final decisions (pursuant to the Contaminated Sites Act) in relation to remediation, restrictions on the use of shallow groundwater and associated classification of affected properties in this area.

Home-grown produce testing

A human health risk assessment was carried out to assess the suitability of PFAS impacted shallow groundwater for a range of non-potable uses, including the irrigation of gardens and potential consumption of home-grown produce. As part of this assessment:

• home-grown produce from properties in the vicinity of the former landfill site was tested for PFAS (including meat, chicken eggs, avocados, tomatoes and other fruit and vegetables); and
• consumption patterns of local residents were taken into account.

The outcome of the home-grown produce testing has generally been positive. Except for three samples - a chicken egg;  an avocado; and a tomato. There were no detected concentrations of PFAS compounds within the sampled produce.

Based on site-specific factors, including individual produce consumption patterns and the amounts of groundwater used for irrigation, the limited home-grown produce testing results indicated that there were no unacceptable risks associated with irrigating home-grown produce with shallow groundwater in this area. This means that past consumption of home-grown products is not expected to have resulted in PFAS exposure above acceptable daily intake amounts on which health based guidelines have been set.

However, due to the bio-accumulative nature of PFAS, as a precautionary measure, shallow groundwater at classified properties should not be used to irrigate home-grown produce.

Soil, land gas and vapour testing

The City has been testing the former landfill site for harmful vapours, soil and land gasses generally associated with landfill facilities and provided the test results to the Contaminated Sites Auditor for analysis and assessment. The Contaminated Sites Auditor concluded that no potential vapour intrusion issues have been identified with respect to the off-site properties affected by shallow groundwater contamination derived from the former landfill site.

Classification of properties and remediation measures

Classification of properties

The Contaminated Sites Act was set up to record and manage contaminated sites in Western Australia in order to protect people’s health and the environment. Contamination does not necessarily mean that an area is unsafe to live or work in – for example, it may be limited to groundwater and only becomes an issue to be managed if a groundwater bore was being considered.

Pursuant to its functions and powers under the Contaminated Sites Act, DWER may classify a site if, based on reasonable grounds, a site is or is known (or suspected) to be contaminated.

Based on the outcome of the City’s investigations and the Contaminated Sites Auditor’s recommendations, 50 privately owned properties to the north of the former landfill site will be classified as Remediated for Restricted Use. Of these:

• at 45 properties use of shallow groundwater use is limited to specific non-potable purposes; and  

• at 5 properties shallow groundwater is not to be abstracted or used for any purpose except monitoring and testing.

A memorial stating each site's classification will be placed on the certificate of title of these properties for purposes of notifying any prospective owners of the contamination status of these properties.

Remediation measures

The City engaged an environmental engineering firm (with an international footprint/global experience) to investigate on a global scale, technical options for improving the quality of shallow groundwater at/on affected properties. In the process approximately 31 different technologies/methodologies have been identified, investigated and indicatively costed. These technologies/methodologies included:

• Soil and water treatment technologies.
• Receptor management (water filtration) systems.
• Earth and construction works aimed at “sealing off” the source site.
• Providing a replacement water distribution network.

The City undertook a costs/benefit analysis of technologies/methodologies to determine their practicality and viability as long-term solutions. Due to the nature and extent of the contamination and the hydrological characteristics of the affected area, removing the contaminants of concern proved not to be a viable option. Consequently DWER directed, as preferred remediation measure, administrative controls to manage the risks associated with impacted groundwater. These controls include:

• A Site Management Plan (SMP) for each affected property. The SMP includes specific guidance on the suitability of groundwater beneath each site for beneficial use and seeks to limit exposure to contaminants of concern by implementing precautionary restrictions on the use of shallow groundwater; and  

• A Groundwater Monitoring and Management Plan to guide ongoing monitoring of shallow groundwater at the former landfill site and the area down gradient of this site.

DWER indicated that, subject to implementation of these Site Management Plans, privately owned affected properties are considered remediated, such that they are suitable for the current land use. Consequently these sites have been classified as 'Remediated for Restricted Use'.

What future monitoring works will be undertaken by the City?

The City will conduct ongoing monitoring of the existing groundwater well network to verify that the extent of the shallow groundwater contamination is (and remains) stable. Ongoing monitoring will be conducted in accordance with a Groundwater Monitoring and Management Plan approved by DWER and the City will inform DWER of the ongoing groundwater monitoring results.

The main aims of the on-going groundwater monitoring program are to:

• Assess the on-going contamination status of the superficial aquifer [i.e shallow groundwater] underlying and down-gradient of the former landfill site;
• Assess the on-going extent of the identified contaminants of potential concern associated with historical landfill activities in the area immediately down-gradient [i.e to the north] of the former landfill site; and
• Monitor possible temporal data trends with respect to these contaminants of potential concern in groundwater and determine whether any changes over time are sufficient to alter the current risk profile.

The most recent groundwater monitoring event occurred in November 2023 and the subsequent test results, as verified by the Contaminated Sites Auditor, indicated:

• Although there were some localised variations in concentrations of the contaminants of potential concern between the latest and previous groundwater monitoring events, no additional analytes were identified as present within the groundwater at concentrations exceeding the adopted assessment criteria.
• Despite these localised variations, the results are considered to be broadly similar to those obtained during previous investigations and indicative of relatively stable conditions within the superficial aquifer beneath, and hydraulically down-gradient [i.e to the north] of, the former landfill site.

What is the impact on other water sources in this area, such as the deeper Leederville aquifer?

Restrictions on abstraction and use of shallow groundwater at affected properties do not apply to existing or future deep bores that abstract groundwater from the underlying Leederville aquifer.

The installation of new bores into the Leederville aquifer and subsequent groundwater abstraction requires obtaining necessary approvals from DWER under the Rights in Water and Irrigation Act 1914.

Approved Leederville bore installation must be undertaken in accordance with strict protocols to ensure that cross contamination cannot occur between the shallow superficial aquifer and underlying Leederville aquifer.

Can I use my bore into the shallow aquifer if my property has not been classified?

There are no restriction on the use of shallow groundwater at properties that have not been classified by DWER. However, property owners and residents are reminded of the general standing advice from the Department of Health that:

“Bore water should never be used for drinking, bathing, watering edible plants, filling swimming and paddling pools, food preparation or cooking unless it has been tested and treated to the extent necessary for the intended use”.

Where do I find further information about the City’s investigations and property classifications?

All documents in relation to the City’s investigations and DWER’s property classifications that are publicly available can be accessed via the DWER website.

Note that technical reports submitted by the City with DWER for the purposes of the Contaminated Sites Act and reports relied upon for the purposes of classifying a site under that Act, are available to the public through a request to DWER for a ‘detailed summary of records’ (DWER Form 2). Please note: a fee may apply.

Other reports/documents in relation to the contamination issues associated with the former landfill site facility that are held by DWER and that are not publicly available, may be available through the freedom of information process.

I have concerns, what can I do?

Contact the:

• City of Busselton by email; or
• Department of Water and Environmental Regulation (DWER) through their website