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Coastal Acid Sulfate Soils (CASS)

Coastal acid sulfate soils (CASS) occur naturally and have been present for thousands of year. These soils are harmless if left undisturbed. However, increased human activity in coastal regions has lead to increased risk of disturbance of CASS. Disturbance of CASS can cause impacts on the environment, infrastructure and human health. CASS-related incidents are often difficult and costly to mitigate and damage is irreversible.

For these reasons coastal acid sulfate soils, which exist along Victoria's coasts and estuaries, are the focus of a new strategy released by the Department of Environment and Primary Industries.

On this page:

The Victorian Best Practice Guidelines for Assessing and Managing Coastal Acid Sulfate Soils

The Victorian Best Practice Guidelines for Assessing and Managing Coastal Acid Sulfate Soils (BPMG) has been produced to guide landowners, developers, planners and decision makers through a risk identification approach that will assist them to make decisions about the assessment and management of coastal acid sulfate soils (CASS).

These guidelines implement the actions and objectives of the Victorian Coastal Acid Sulfate Soils Strategy 2009 (CASS Strategy). The CASS Strategy and the BPMG apply to the potential development of new sites of CASS disturbance, not to the rehabilitation of existing sites if CASS has already been disturbed.

These guidelines will assist in making decisions that are consistent with the principles for managing CASS in Victoria as outlined in the CASS Strategy. Where acid sulfate soil is to be disturbed and managed for the purpose of disposal and/or reuse, the Industrial Waste Management Policy (Waste Acid Sulfate Soils) NoS125 1999 (IWMP), Environment Protection (Industrial Waste Resource) Regulations 2009 and Information Bulletin 655.1 – Acid Sulfate Soil and Rock 2009 (EPA publication 655.1) must also be consulted.

Where appropriate, the CASS risk process outlined in the guidelines will be reflected in the planning system and a process for approval of CASS management plans identified. In the immediate term, these guidelines will enable informed decision making about the standard of hazard assessment expected in Victoria in relation to managing coastal acid sulfate soils.

The guidelines were prepared by the Victorian Coastal Acid Sulfate Soils Implementation Committee. This committee reflects the cross-government nature of issues associated with coastal acid sulfate soils. Agency Membership of the committee includes Department of Environment and Primary Industries (chair), Department of Planning and Community Development, and the Environment Protection Authority.

Victorian Best Practice Guidelines for Assessing and Managing Coastal Acid Sulfate Soils [PDF File - 1.3 MB]

Victorian Best Practice Guidelines for Assessing and Managing Coastal Acid Sulfate Soils [MS Word Document - 560.5 KB]
Cover of the Victorian Best Practice Guidelines for Assessing and Managing Coastal Acid Sulfate Soils

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Professional Short Course on the Identification, Assessment and Management of Acid Sulfate Soils

Development proposals in Victoria must consider acid sulfate soils policies, as outlined in the Victoria Coastal Strategy 2008, the Victorian Coastal Acid Sulfate Soils Strategy and Victorian planning schemes. Applicants must demonstrate how they intend to avoid disturbing acid sulfate soils, usually through an Acid Sulfate Soil Management Plan.

On 19 and 20 October 2010, a two day training program was held in Torquay. It focused on how to prepare or assess an Acid Sulfate Soil Management Plan and was designed for professionals such as consultants, engineers, contractors, scientists, environmental officers and planners.

The course was highly successful and due to popular demand, it is anticipated that further courses will be held in 2011.

The courses are led by Professor Leigh Sullivan, one of Australia’s leading acid sulfate soil scientists. A range of academics and practitioners, experienced in the identification, assessment, and management of acid sulfate soil materials also help deliver the course.

The program has been developed by Southern GeoScience Australia in conjunction with DEPI and provides a unique opportunity for proponents and assessors to discuss different aspects of managing acid sulfate soils.

The courses include a series of presentations from leading academics and practitioners, practical exercises examining real-life examples and a field excursion to local acid sulfate soil sites. Overall, the training program is designed to equip participants with the skills, knowledge and confidence to meet their responsibilities when developing or assessing an Acid Sulfate Soil Management Plan.

Participants should note that the courses are not a general introduction to the issue of acid sulfate soils, and is specifically designed for professionals with at least a basic understanding of the issue.

For further information on the short courses or to register an Expression of Interest in 2011 courses, please contact:

Chrisy Clay
Short Course Project Officer
02 6620 3095
chrisy.clay@scu.edu.au

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The Victorian Coastal Acid Sulfate Soils (CASS) Strategy

Victoria's CASS strategy aims to protect the environment, humans and infrastructure from the effects which can occur if CASS is disturbed. The emphasis of the strategy is on avoiding the disturbance of CASS. The strategy is available below. Please note: the file size is large and may take some time to download.

The strategy explains why CASS is a management issue in Victoria and promotes a risk identification and assessment process. It aims to build the capacity of land owners and land and water managers to identify areas where disturbance of CASS is best avoided.

Coastal Acid Sulfate Soils Strategy [PDF File - 3.0 MB].

The strategy includes:
  • prospective mapping which identifies areas with the potential to contain CASS
  • decision-making principles and actions for managing CASS in Victoria
  • roles and responsibilities of government, agencies and individuals
  • an identification and risk assessment process to assist land managers and decision-makers
It is the collective responsibility of individuals, industry and government to create awareness of the risks of CASS and to facilitate understanding of potential impacts.

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Coastal Acid Sulfate Soils Strategy Cover

What are Coastal Acid Sulfate Soils (CASS)?

CASS are naturally occuring soils containing iron sulfides. CASS underlie large areas of Australia's low lying coastal areas. In a water-logged state these soils are harmless but, when exposed to air, the iron sulfides can oxidise producing acid which can then leach into the environment.

Illustration of sulfidic soils in their harmless natural setting

Natural setting: PASS insulated from exposure to oxygen by watertable. Waterway well flushed, mitigating impact from incidental, acid discharge events.

Illustration of sulfidic soils after disturbance incurring acid release

Post Drainage: Lowered water table exposes PASS soils to oxygen. Increased drainage density and volume leads to increased acid export.

The effects of acidic water include:
  • death and bleaching of vegetation
  • unusually clear or milky, blue-green drainwater within or flowing from the area
  • extensive iron stains on drain or pond surfaces; or iron-stained water and ochre deposits
  • corrosion of concrete and/or steel infrastructure
  • skin irritation after exposure to acidic water
  • loss of water quality
  • dead fish
The presence of acid indicators should be reported to the local municipal authority, Department of Environment and Primary Industries (DEPI) office or local Catchment Management Authority (CMA).

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Where are CASS found in Victoria?

CASS are generally found in low lying areas within coastal plains.

Prospective maps of areas where coastal acid sulfate soils (CASS) are likely to occur have been prepared and are available on the Department of Primary Industries' Victorian Resources Online (VRO) website.

Soil investigations were conducted as part of the Victorian Coastal Acid Sulfate Soils (CASS) Strategy in order to increase the accuracy and quality of mapping of areas identified as being at high risk in the event of soil disturbance from development and land use change.

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Existing management of CASS in Victoria

The strategy has recognised and builds upon a number of CASS management tools already existing in Victoria. These include: Page Top

Further information

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Frequently asked questions

What are Coastal Acid Sulfate Soils (CASS)?
CASS form naturally when sulfate rich water (sea water, sewerage or mine waters) mix with soils that contain iron and organic matter. Most soils with the potential for CASS found in Victoria were formed within the last 10,000 years, after the last major sea level rise.

Why are CASS a problem?
If CASS is not disturbed, it presents no problem. If disturbed, CASS can create an acidic environment, which can adversely affect:
  • human health, including skin and eye irritations and burns
  • drinking water which can become contaminated
  • occupational health & safety
  • the ecology of wetlands and shallow freshwater and shallow aquifer systems by degrading water quality, habitat and dependant ecosystems
  • commercial and recreational fisheries and rural productivity
  • concrete and steel infrastructure by corroding culverts, pipes and bridges
Where are CASS found in Victoria?
CASS are generally found in low lying areas within coastal plains and along the edges of water bodies. This includes flood plains and lower slopes, abandoned river meanders and oxbow lakes, swamps, morasses, beaches, coastal dunes and swales and tidal flats. Tidal influence can also extend CASS inland.

Areas in Victoria with potential for CASS cover approximately 250,000 ha of land. The majority of land with potential for CASS surrounds Port Phillip Bay and east to the Gippsland lakes. However environmentally sensitive areas are scattered along the entire coastline of Victoria. To view the map of potential CASS in Victoria, please visit the DPI website.

How do I know if CASS is on my property?
If any of the following signs are present on your property, CASS should be considered if proposing land use changes:
  • Do the maps in the Strategy indicate that the area has potential to contain CASS?
  • Is the area low lying, swamp or estuarine?
  • Is the vegetation coastal or estuarine in nature? Are Mangroves, Melaleuca or Casuarina species present?
What do I do if I suspect CASS is on my land?
Soil investigations are necessary to identify risks and impacts. Once risks are identified, avoidance or a low risk solution can be planned. If you suspect that CASS may be present, and may be a risk to your proposed activity then soil tests should be undertaken.

Where do I go to get my soils tested for CASS?
Soil sampling and assessment should be carried out by a suitably qualified and experienced professional. The latest sampling and analysis schedule for Victoria is found in the EPA’s Waste Acid Sulfate Soil and Rock Publication 655 on the EPA Victoria website. Soil samples should be analysed by an accredited NATA laboratory. For a list of accredited laboratories visit the Yellow Pages or NATA websites.

The results should then be interpreted and a report produced by a qualified and experienced consultant.

Can I develop my land if CASS is identified?
Yes, land with CASS left undisturbed can be developed. Soil investigations should identify the locations of CASS and the potential risks if that soil is disturbed. Development that avoids disturbing CASS is the most cost effective strategy. Managing, mitigating or remediating the adverse impacts once CASS is disturbed is generally difficult and expensive.

What activities/ land use changes may disturb CASS?
Activities that may cause the disturbance of CASS include:
  • excavating
  • filling land
  • moving CASS horizontally or vertically
  • temporarily or permanently dewatering soil containing CASS
  • causing CASS to be temporarily of permanently bathed in oxygenated water
  • agricultural activities that cause land drainage particularly deep drainage
  • dredging
  • drilling for bores
  • extractive industries;
  • infrastructure works – flood management, drainage works, road, railway and water and sewerage pipe installation
  • land use changes that may alter water tables
  • urban and tourism development
  • water extraction.
How can I tell if CASS has been disturbed and oxidation is occurring?
Signs of CASS disturbance include:
  • Water with pH less than 4
  • Dead fish in the area
  • Death and bleaching of vegetation
  • Unusually clear or milky blue-green drainwater within or flowing from the area
  • Extensive iron stains on drain or pond surfaces, or iron-stained water and ochre deposits
  • Corrosion of concrete and/or steel structures
  • Skin irritation after exposure to water.
What should I do if I notice the indicators of a CASS disturbance?
If indicators are present, coastal communities should report to their local municipal authority, DEPI office or local Catchment Management Authority.

What does the Victorian Strategy for Coastal Acid Sulfate Soils do?
The strategy aims to protect the environment, humans and infrastructure from the harmful effects which can occur if coastal acid sulfate soils are disturbed. The strategy explains why CASS is an issue in Victoria and outlines actions to address these issues. Maps which identify areas with the potential to contain CASS can be viewed on the DPI website.

The Strategy implements a key action in the Victorian Coastal Strategy 2008 and meets Victoria’s national obligations to implement appropriate plans and strategies for managing CASS.

Please note: Document(s) on this page are presented in PDF format. If you do not have the Adobe Reader, you can download a copy free from the Adobe web site.


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