Summary & Recommendations



Response to Problems









Media Statement

10 January 2002

Parts of Stirling affected by acidic groundwater: Department of Health

The Department of Health has warned against contact with groundwater, following the detection of isolated pockets of highly acidic waters in Perth's northern suburbs.

The acidic water is caused when naturally occurring sulphide minerals in peat sediments are exposed to air.

Acting Director of Environmental Health Brian Devine said the problem may be the result of successive dry summers leading to a low water table, combined with local excavation works.

He said that while the problem seemed to occur in small pockets rather than over a widespread area, it was important for the community to be aware of the situation.

"At this stage we are aware of only one residential and one council groundwater bore being affected," Mr Devine said.

"The Spoonbill wetland in the suburb of Stirling has also been identified as being affected by high acidity.

"Investigations and health warnings are focused on properties west of Main Street, south of Beryl Street and east of the Spoonbill wetland in the suburbs of Stirling and Balcatta.

Mr Devine said people in the affected area should avoid skin or eye contact with ground water. The Department of Health has always advised against drinking untreated groundwater from any area.

"Contact with acidic water may cause skin and mucous membrane irritation," he said.

"If exposed to acidic water, external affected areas should be thoroughly washed with scheme tap water and a doctor should be consulted if irritation persists."

Mr Devine said the City of Stirling and land developers in the area were erecting signs around affected surface water.

The Water and Rivers Commission was investigating other surface water that could be affected.

In addition, further testing of groundwater bores was being undertaken and a door-to-door survey in the area would be carried out to locate and test residential groundwater bores.

City of Stirling Chief Executive Officer Lindsay Delahaunty said the problem was first noticed when a local resident found water from her garden bore was affecting her lawn and vegetable garden.

"We are concerned that water from some bores could cause skin irritation or damage gardens," Mr Delahaunty said.

"Therefore, we are contacting residents in the affected area to advise them to avoid contact with water from their garden bores until a sample of the water has been tested by authorities.

"The City has set up a direct contact line to advise residents in the affected area and I would encourage people in the area to heed the health warnings on signs around affected surface water and avoid contact with water from their garden bores.

"The City will continue to work with the authorities and land developers to rectify the problem."

Residents with queries about the effect of exposure to acidic water should contact the Department of Health on 9388 4997.

Queries about acid sulphate soils or the sampling being program should be directed to the Water and Rivers Commission on 9278 0517.

Bore owners in the affected area should call the City's of Stirling's Senior Environmental Health Officer on 9345 8793.

Media contacts:
Department of Health, Jean Perkins, 9222 4333
Water and Rivers Commission, Paul McLeod 92787 0718
City of Stirling, Peter Beard 9345 8657


Letter to residents in affected area.

11 January 2002

Dear Resident

Recent tests of bore water in your area by the Water and Rivers Commission have revealed high acidity levels in a small number of bores.

High acidity levels of this type occur naturally and area caused by below-ground peat being exposed to air through lowering of the water table. The Water and Rivers Commission have advised this could be attributable to Perth's recent run of dry winters and removal of peat for sub-divisional development in the area.

Contact with acidic bore water may cause skin or eye irritation and could damage your garden. The City of Stirling recommends that if you own a bore you should avoid contact with the water until a sample has been analysed by the Water and Rivers Commission. Analysis is a simple process and collection of a sample can be arranged by calling Steve Appleyard at the Water and Rivers Commission on 9278 0517.

The City of Stirling is working with the developers, Department of Health and the Water and Rivers Commission to rectify the situation.

If you require any further information please call the city of Stirling's Senior Environmental Health Officer Mr Neil Duffin on 9345 8793.

Yours Sincerely,

Lindsay Delahaunty
Chief Executive Officer




What is the extent of the affected area and how many bores have been affected?

The area of concern and under investigation was bordered by Poincaire Street in the North, Grindleford Drive in the East, just below Karrinyup Road in the South and the Mitchell Freeway in the West. The area has now been restricted to the Jones Street and Telford Crescent areas and West Southwest of Spoonbill Wetlands.

The sampling program has tested over 800 individual bores for acidity with more than 40 of these being analysed for metals. The majority of bores were not contaminated. The findings from sampling in the Stirling area can be summarised:

  • Bores affected by acidic water less than pH4.5 appears to be restricted to approximately 40 bores.
  • Slightly elevated levels of some metals, particularly arsenic, were found in some bores with a pH of less than 4.5.
  • With the exception of one bore, bores tested with a pH greater than 5.5 have not been found to be affected by elevated heavy metals of concern.

What does pH mean?

pH is a measure of the acidity or alkalinity of H2O solutions. pH 7 is neutral, above 7 is alkaline and below is acidic. The Australian Drinking Water Guidelines sets a guideline for this characteristic of water between 6.5-8.5.

How do I know if my bore has been affected?

Affected bores have almost exclusively been found to have a low pH. The results indicate that if your bore water has a pH greater than 5.5 the level of metals should be within the levels recommended by the Australian Drinking Water Guidelines and the bore water is safe to be used for irrigation purposes.

What has caused the groundwater contamination?

Acid sulfate soils, which are soils that contain iron sulphides, are found naturally in the Stirling/Balcatta area. When exposed to air, iron sulphides oxidise and produce sulfuric acid. The soil itself can neutralise some of the sulfuric acid but the remaining acid moves through the soil, acidifying the soil, groundwater and eventually surface water. Areas where iron sulphide layers occur are waterlogged. Drainage and excavation of these areas expose the iron sulphide layers to air, which accentuates the rate of oxidation, and this concentrated acid can overwhelm the natural ability for the environment to neutralise it. This is what appears to have happened in the Stirling/Balcatta area. Lowering of the water table and sulphide soil disturbance has resulted in an increase in sulphuric acid in the groundwater.

How long as the groundwater been contaminated?

It is possible that there has been an acidic water issue in the area for at least the last 12 months.

Water and Rivers Commission is investigating the extent of groundwater impact and once the information has been collated a better estimate of how long the problem has been present can be made.

How long until the contamination is fixed?

It is difficult to say exactly how long this problem will exist. Experience from the Eastern States would indicate that high acidity in groundwater might persist for decades. Acidic groundwater will continue to leach metals, if present, until the water pH returns to more neutral conditions.

What types of contaminants are in the groundwater?

There is a high sulphuric acid content in the soil and groundwater that has resulted in the leaching of some elements from the surrounding soil. Elements that can be leached from the soil include metals. The metals sampled for were Aluminium, Barium, Boron, Calcium, Chromium, Cobalt, Copper; Iron, Potassium, Magnesium, Manganese, Molybdenum, Sodium, Nickel, Sulphur (expressed as sulphate), Vanadium, Zinc, Lead, Cadmium and Arsenic. The majority of bores sampled were free of contamination. Groundwater is not recommended for drinking water purposes but if the levels are compared to the Australian Drinking Water Guidelines there were a few bores with slightly elevated levels of Arsenic, Lead, Iron, Nickel, Aluminium and Copper that exceed these guidelines

Where are these contaminants coming from?

As the sulphuric acid moves through the soil it strips metals from the soil and into the water. These metals have affected the groundwater quality in some areas.

The sources of the metals in the soil are most likely from natural sources as well as past horticultural, industrial or urban activities.

How is it possible for the contamination to get into my vegetables?

Many, but not all, of the contaminants of concern are actually essential for plant growth and human nutrition but these same elements may be toxic to plants and animals at high concentrations, whilst others have inadvertently entered the food chain. The ability of plants to accumulate and translocate these toxic elements to edible and harvested parts depends on the soil, climate factors, plant type and agricultural practices. In addition the availability of the contaminant to humans also depends on the contaminant in the food, dietary composition and nutritional status of the individual.

Tests conducted on vegetables from residential and commercial properties using groundwater for irrigation in the Stirling area have shown slightly elevated levels of lead, but not other metals. Elevated levels of lead were not found in water or soil samples collected from some of the same properties. Therefore, there does not appear to be a correlation between the levels of lead in bore water or soil samples with levels found in the vegetables. The Department of Health is working with other agencies to investigate the likely source.

While the results indicate that the level of lead in some produce is above the maximum limit allowed under the Food Standards Code, consumers are unlikely to have been exposed to a sufficient amount of lead from the affected vegetables to present a health risk.

What has been done in response to the contamination?

The Department of Health has been working in collaboration with the City of Stirling, Water and Rivers Commission and the Department of Environmental Protection to determine those people affected by acidic water and the bores which are at risk from metal contamination.

Residents have been encouraged to bring water from their bore and have it tested for pH levels at the City of Stirling offices. If the pH of the groundwater was below 5.5 further testing was initiated.

What are the likely health effects from these contaminants?

The levels of metals detected, while elevated in some of the affected bores, is not considered sufficient to pose a risk to bore owners. Notwithstanding, the highly acidic nature of the affected bores could result in skin, eye and mucous membrane irritation if exposed. If your bore water has been tested and shown to be acidic you should consider using alternative water sources for irrigation.

I'm pregnant; will my baby be affected?

The level of metals in water used for irrigation is not sufficient to cause harm to you or your baby. While the levels of some metals were found to be slightly elevated in some fruit and vegetables, they are below a level that would cause a health effect if the produce has been consumed.

I am still worried about what these chemicals might do to my health. What should I do?

If you have any concerns about your health we recommend that you talk to your doctor, who is in the best position to assess your health. The Toxicology Section of the Environmental Health Branch is able to provide advice on the effects of exposure to chemicals. If you doctor requires more information on a particular chemical, he/she can call 1800 020 080, or you can leave your details at that number to have an officer from the Toxicology Section return your call.

What is being done about fixing the problem?

The Water and Rivers Commission and the Department of Environmental Protection are still investigating the problem and will be exploring different management options that can be taken.

If you are one of the bore owners with acidic water it is recommended that you explore using alternative water sources for irrigation. The Department of Health takes this opportunity to remind bore owners that untreated bore water is not recommended for use as a drinking water source.

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