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STATE PLANNING POLICY 1/00

Planning and management of coastal development involving acid sulfate soils

Page ii State Planning Policy 1/00

Integrated Planning Act 1997

STATE PLANNING POLICY 1/00

Planning and management of coastal development involving acid sulfate soils The Minister for Communication and Information, Local Government and Planning, and Minister for Sport adopted State Planning Policy 1/00 (‘the policy’) on 14 August 2000. Making of the policy The policy was made under sections 2, 6 to 7 and 9 to 10 of Schedule 4 of the Integrated Planning Act 1997. Commencement and duration of the policy The policy commences on 20 November 2000, and ceases to have effect on 18 November 2001. Availability of the policy To order a free copy of the policy, call (07) 3235 4566 or facsimile (07) 3237 1738 or write to the address below:

Planning Information Area Department of Communication and Information, Local Government, Planning and Sport

PO Box 187 Brisbane Albert Street QLD 4002

An electronic copy of the policy is available from the Department’s Internet web site at: www.ipa.qld.gov.au

State Planning Policy 1/00 Page iii

POSITION STATEMENT The Queensland Government considers that coastal development involving acid sulfate soils should be planned and managed to avoid potential adverse effects on the natural and built environment (including infrastructure), and human health.

Page iv State Planning Policy 1/00

State Planning Policy 1/00 Page 1

1 INTRODUCTION

Application 1.1 The State Planning Policy (‘the policy’) applies to coastal areas below 5 metres Australian

Height Datum (AHD). This includes, but is not limited to, the local government areas listed in section 4.1 of the policy.

1.2 Local government must have regard to the policy when making or amending planning

schemes, and during the assessment of IDAS applications under the Integrated Planning Act 1997 (‘the Act’). The policy does not apply to development for the purpose of either a Class 1 or a Class 10 building, as defined in the Building Code of Australia, or a domestic swimming pool.

1.3 The annexes to the policy form part of, and must be read in conjunction with, the policy. The

annexes are acceptable approaches to the identification and management of acid sulfate soils. Other approaches may be appropriate provided they are consistent with the development assessment outcomes in section 3 of the policy.

Definition of acid sulfate soils 1.4 For the purposes of the policy, acid sulfate soils include both ‘actual’ and ‘potential’ acid

sulfate soils. Actual and potential acid sulfate soils are often found in the same soil profile. Generally, actual acid sulfate soils overlay potential acid sulfate soil horizons, but both may also occur in close proximity within the same layer.

‘Actual acid sulfate soils’ are soils or sediments containing highly acidic soil horizons or layers resulting from the aeration of soils or sediments that are rich in iron sulfides, commonly pyrite. This aeration (oxidation) produces acid (particularly hydrogen and aluminium ions) in excess of the soils or sediments capacity to neutralise the acidity, resulting in soils or sediments with pH 4 or less. The presence of pale yellow mottles and coatings of jarosite confirms the presence of these soils, but jarosite need not be present in all situations. Soils or sediments with pH 4.1 to 5.5 may also contain acid or remnants of iron and aluminium ions from previous acid sulfate soils oxidation. ‘Potential acid sulfate soils’ are soils or sediments which contain iron sulfides and/or other sulfidic material that have not oxidised by exposure to air. The field pH of these soils or sediments in their undisturbed state is pH 4 or more and may be neutral or slightly alkaline. These soils or sediments are invariably saturated with water in their natural state.

Potential adverse effects from disturbing acid sulfate soils 1.5 Acid sulfate soils occur naturally over extensive low-lying areas of coastal Queensland,

predominantly below 5 metres AHD. If disturbed, acid sulfate soils can release harmful quantities of leachate containing acid and metal contaminants into the environment. The

State Planning Policy 1/00

leachate can have significant effects on the environmental integrity of wetlands and shallow freshwater and brackish aquifer systems by degrading water quality, habitat, and dependant ecosystems. For example, the degradation of environmental integrity may result in the killing or disease of fish and other aquatic organisms, detrimentally impacting on commercial and recreational fisheries.

1.6 Acidified waters can also have adverse economic consequences by corroding concrete and

steel infrastructure, such as culverts, pipes, bridges and buildings. There are also human health concerns from contaminated ground and surface waters causing dermatitis, and dust from disturbed acid sulfate soils that may cause eye irritation.

1.7 Typically, disturbance of acid sulfate soils results from development involving excavation,

dewatering (including drainage), or filling. This can occur during the construction of, for example: canal estates, roads and other infrastructure, golf courses, extraction of sand and gravel, and agricultural drainage. It is preferable to avoid disturbing acid sulfate soils where practicable. In many cases the disturbance of acid sulfate soils can be planned and managed to ensure that potential adverse effects are avoided. This has been successfully demonstrated on a number of projects using a variety of containment and treatment techniques. However, acid sulfate soils represent a land management constraint that needs to be the subject of appropriately rigorous risk assessment. The disturbance of acid sulfate soils can compromise a project’s design or financial viability if the assessment and treatment of acid sulfate soils involves substantial costs.


2 MAKING OR AMENDING PLANNING SCHEMES

Seeking to achieve ecological sustainability 2.1 The Minister and a local government are required to advance the purpose of the Act when

making or amending a planning scheme. The purpose of the Act is to seek to achieve ecological sustainability. The Act expands on this duty by, amongst other things, referring to the need for decision-making processes to: take account of environmental effects of development; avoid, if practicable, or otherwise lessen adverse environmental effects of development; and to apply the precautionary principle. The implications of this duty in the context of acid sulfate soils are that development involving the disturbance of acid sulfate soils should be planned and managed to avoid potential adverse effects on the natural and built environment (including infrastructure), and human health, through careful evaluation of the land use and land management options available.

Determining the strategic framework of a planning scheme 2.2 The identification and analysis of acid sulfate soils are important aspects in determining the

strategic framework, particularly in defining the options regarding the scale and nature of future development in an area. It is important to note that the presence of acid sulfate soils does not necessarily preclude development involving the disturbance of acid sulfate soils, provided appropriate management is undertaken to ensure development involving acid sulfate soils is planned and managed to avoid potential adverse effects on the natural and built environment (including infrastructure), and human health.

2.3 Accordingly, a local government planning for future development in low-lying coastal areas

should as far as practicable identify the location, depth and severity of acid sulfate soils. In some localities, this information is available from acid sulfate soils maps prepared or endorsed by the Queensland Department of Natural Resources. If these maps are not available, acid sulfate soils can be identified using other existing sources of information such as soil descriptions, geology, geomorphology, vegetation or relevant factors that indicate the likely presence of acid sulfate soils. However this level of identification is only indicative of broad areas of acid sulfate soils. Therefore, when development is proposed in such areas, the applicant should be required to identify the location, depth and severity of acid sulfate soils for the particular site in accordance with the annexes.

Planning scheme strategies and measures for managing acid sulfate soils

2.4 The planning strategies and measures, particularly relating to the allocation of land uses in

areas where acid sulfate soils are identified, should advance the Act’s purpose through a management approach reflecting, where possible, the following hierarchy. Firstly, preference should be given to compatible land uses that will not disturb acid sulfate soils by excavation, dewatering or filling. Secondly, if disturbance of acid sulfate soils is likely to occur, the disturbance should be planned and managed to avoid acid generation and treat any existing


acidity. Finally, if surface and groundwater flows from areas containing acid sulfate soils are likely to occur, the flows should be managed to avoid the leaching of acid and metal contaminants into the environment.

2.5 The planning scheme measures identifying assessable development, the aspects of

development involved, and the applicable areas relating to acid sulfate soils, should beconsistent with section 3 of the policy.


3 ASSESSMENT OF IDAS APPLICATIONS

Outcomes for development assessment 3.1 Development proposals should seek to avoid potential adverse effects on the natural and

built environment (including infrastructure), and human health, caused by the release of acid and metal contaminants into the environment from the development or the ongoing use of the land.

3.2 If there is a risk of adverse effects from the proposed development, the applicant should

demonstrate how the potential impacts of disturbance will be managed in accordance with the information provided in the annexes. The assessment manager should also consider imposing reasonable and relevant conditions on the development approval to ensure the impacts are appropriately managed. It is essential for any requirements of such conditions to be approved prior to any disturbance occurring on site.

Development subject to assessment 3.3 Development must be assessed with regard to the policy where:

• it is subject to impact assessment or the impact assessment process; and

• involves one or more of the following aspects of development:

Ø making a material change of use of premises, or the carrying out of works that will result in car parking, storage or other areas below ground level;

Ø making a material change of use where excavation or filling are an integral aspect of the use, such as a golf course, marina and canal estate;

Ø making a material change of use for extractive industry;

Ø reconfiguration of a lot involving the opening of a road;

Ø operational works comprising excavating or filling; and

• the development occurs below 5 metres AHD (or a more specific area as determined in the planning scheme) and involves:

Ø excavation of more than 100 m3 of material;

Ø dewatering (including permanent or temporary drainage or pumping of groundwater resulting in the aeration of previously saturated soils or sediments); or

Ø filling (resulting in groundwater extrusion through compaction of saturated soils or sediments and/or lateral displacement of previously saturated soils or sediments above the watertable).


Information requests 3.4 It is recommended the assessment manager request the applicant provide information in

accordance with the annexes as to whether acid sulfate soils are present on the site, and if so, the proposed management of the acid sulfate soils. The information provided by the applicant should be prepared by a suitably qualified person experienced in the assessment of acid sulfate soils, such as a professionally accredited soil scientist.

3.5 This information should be sufficient for the assessment manager to determine whether there

will be any adverse effects on the natural and built environment (including infrastructure), and human health, caused by the release of acid and metal contaminants into the environment.


4 ADVICE ABOUT THE POLICY 4.1 Advice about the policy can be obtained from the following agencies:

• the Department of Communication and Information, Local Government, Planning and Sport can provide advice about reflecting the policy in planning schemes, and the application of the policy in development assessment;

• the Department of Natural Resources can provide technical guidance on identifying, managing and treating acid sulfate soils as set out in the annexes of the policy; and

• local government can provide advice about the application of the policy in their local area. Some local governments may be able to provide advice about acid sulfate soils in their area. The local government areas to which the policy applies includes, but is not limited to, the following:

Aurukun Bowen Brisbane Broadsound Bundaberg Burdekin Burke Burnett Caboolture Cairns

Calliope Caloundra Cardwell Carpentaria Cook Cooloola Douglas Fitzroy Gladstone Gold Coast

Hervey Bay Hinchinbrook Isis Johnstone Livingstone Logan Mackay Maroochy Maryborough Miriam Vale Mornington

Noosa Pine Rivers Redcliffe Redland Rockhampton Sarina Thuringowa Tiaro Torres Townsville Whitsunday

4.2 The following agencies have existing statutory responsibilities regarding the planning and

management of development involving acid sulfate soils:

• the Department of Primary Industries can provide advice about the management and protection of fish habitats and marine species. Approvals may be required from the Department of Primary Industries in accordance with the Fisheries Act 1994 and Fisheries Regulation 1995; and

• the Environmental Protection Agency is responsible for the administration of the Environmental Protection Act 1994. Under the Environmental Protection Act 1994 (EPA), and in particular with respect to the Environmental Protection (Water) Policy 1997, and Environmental Protection (Air) Policy 1998, all reasonable and practical measures should be taken to avoid the risk of environmental harm.


ANNEX 1 Identification of acid sulfate soils Introduction To establish whether acid sulfate soils are likely to be affected by any proposed works, it is essential to identify if acid sulfate soils are likely to be present. To assist in this process a three-step investigation can be used. Applicants can undertake Step Three immediately if they are reasonably confident that acid sulfate soils are going to be affected as a result of the proposed development. A suitably qualified person (e.g. a professionally accredited soil scientist) experienced in acid sulfate soils should undertake all investigations. It is strongly recommended that the latest technical guidelines be consulted. The Department of Natural Resources website (www.dnr.qld.gov.au/ resourcenet/land/landplan/lp-ass/ass-spp.html) is a potential source of information and other material may be available from DNR district officers or some local governments.

Note: Applicants should be aware that acid sulfate soils and the associated hydrology are a complex environmental issue. To accurately identify the presence and severity of acid sulfate soils, a laboratory analysis of soils as set out in Step Three is essential. A Step Three investigation should be undertaken following any positive indications of the presence of acid sulfate soils found in Step One or Two.

Step One: Preliminary Investigation The general parameters of the proposed works should be obtained so as to ascertain whether the works are likely to affect acid sulfate soils if they are present. This should include a description of the proposed earthworks including the volume to be disturbed, the depth of disturbance and the nature of the disturbance. It should also include a consideration of groundwater issues and whether groundwater is likely to be released or disturbed below normal seasonal fluctuations. The applicant should then check the location of the proposed development against suitable acid sulfate soils maps if available. These maps may be available from the Department of Natural Resources or from local governments. If suitable acid sulfate soils maps are not available the applicant should undertake an investigation:

• of information from adjoining sites to determine whether there is a known acid sulfate soils problem in the area; or

• to check if the site meets the geomorphic or site description criteria outlined below.


Geomorphic or site indicators The following geomorphic or site description criteria should be used to determine if acid sulfate soils are likely to be present:

• soils and sediments of recent geological age (Holocene);

• marine or estuarine sediments and tidal lakes;

• low-lying coastal wetlands or back swamp areas; waterlogged or scalded areas; stranded beach ridges and adjacent swales, interdune swales or coastal sand dunes (if deep excavation or drainage proposed);

• areas where the dominant vegetation is tidally affected e.g. mangroves, marine couch, saline scalds or swamp-tolerant reeds, rushes, grasses (e.g. Phragmites australis), paperbarks (Melaleuca spp.) and she oak (Casuarina spp.);

• areas identified in geological descriptions or in maps as bearing sulfide minerals, coal deposits or marine shales/sediments (geological maps and accompanying descriptions may need to be checked); and

• deep older estuarine sediments below ground surface of either Holocene or Pleistocene age (only an issue if deep excavation or drainage is proposed).

Conclusion If the proposed works (including disturbances to groundwater) are in locations and at depths that are likely to disturb acid sulfate soils (as identified by a suitable acid sulfate soils map or through local knowledge), the applicant may undertake:

• soil and water field investigations in accordance with Step Two; or

• a laboratory analysis undertaken as set out in Step Three to obtain site specific data. If none of the geomorphic indicators are present, it is unlikely that acid sulfate soils will be disturbed by the proposed development. Submission of this information may provide a sufficient case that the requirements of the State Planning Policy are being met. This approach has been successfully adopted on a number of projects. Step Two: Site Field Investigation Soil and water field indicators If the presence of acid sulfate soils is indicated by Step One investigations, the applicant should undertake a field investigation of soil and water characteristics, as set out in Table 1.


Table 1: Field soil or water indicators suggesting the presence of acid sulfate soils

Soil type Indicators

actual acid sulfate soil (AASS)

Soil characteristics • field pH ≤4 (field pH >4 but <5 may indicate some existing acidity and other

indicators should be used to confirm its presence or absence); • presence of corroded shell; • any jarositic horizons or substantial iron oxide mottling in auger holes, in surface

encrustations or in any material dredged or excavated and left exposed. Jarosite is a characteristic pale yellow mineral deposit that can precipitate as pore fillings and coatings on fissures. In the situation of a fluctuating watertable, jarosite may be found along cracks and root channels in the soil. However, jarosite is not always found in actual acid sulfate soils.

Water characteristics • a soluble chloride:soluble sulfate (Cl -:SO4

2-) ratio (by mass) of less than 4, and certainly a ratio less than 2, is a strong indication of an extra source of sulfate from previous sulfide oxidation;

• water of pH <5.5 in adjacent streams, drains, groundwater or ponding on the surface;

• unusually clear or milky blue-green drain water flowing from or within the area (aluminium released by the acid sulfate soils acts as a flocculating agent);

• extensive iron stains on any drain or pond surfaces, or iron-stained water and ochre deposits.

Landscape and other characteristics • dead, dying, stunted vegetation*; • scalded or bare low-lying areas*; • corrosion of concrete and/or steel structures*. * may also be due to excessive salinity or in combination with AASS.

potential acid sulfate soil (PASS)

Soil characteristics • waterlogged soils – unripe muds (soft, buttery, blue grey or dark greenish grey)

or silty sands or sands (mid to dark grey) or bottom sediments of estuaries or tidal lakes (dark grey to black);

• soil pH >4 and commonly neutral – and a positive Peroxide Test as described below;

• presence of shell; • a sulfurous smell e.g. hydrogen sulfide or rotten egg gas. Water characteristics • water pH usually neutral but may be acid.


As many of the indicators for actual and potential acid sulfate soils are quite different, the field inspection should investigate for the presence of both types of soil. In making a preliminary determination as to whether acid sulfate soils are present or not, all field soil and water indicators, the peroxide test results and any groundwater soluble chloride:soluble sulfate (Cl -:SO4

2-) ratio results must be considered in combination to arrive at an interpretation. i) Field pH Tests on Soil Material

Note: Field pH tests cannot be used as a substitute for laboratory acid sulfate soils analysis, however they are a useful additional tool.

(a) Field pH in Water (pHF)

Field pH tests should be conducted on the soil profile at regular intervals (0.25 m) using a field pH meter with a robust, spear point, double reference pH electrode. If the measured pH of the soil suspension or soil paste is pH <4, oxidation of sulfides has probably occurred in the past, indicating that an actual acid sulfate soil (AASS) is present. Deionised water should be used for making soil suspensions or pastes.

(b) Field Peroxide pH Test (pHFOX )

The field pHF test does not account for any sulfide present that has not yet been oxidised. To test for sulfides or potential acid sulfate soils (PASS), oxidation of the soil with 30% or 100 volume hydrogen peroxide (pH of peroxide adjusted to 4.5–5.5 with a few drops of 0.1M NaOH) can be performed. Note the peroxide pH should be checked on every new container and regularly before use in the field. Analytical grade peroxide is the best to use but the pH may still be as low as 3. Manufacturers stabilise technical grade peroxide with acid and this can lead to pH <2 and give false results on the field tests. Care needs to be taken when conducting peroxide testing as reactions may become violent.

The field pHFOX test can be done with a few mL of peroxide and a small sample of soil in either short clear test tubes (e.g. Falcon 2070 50 ml conical tubes) or clear tissue culture clusters. Heating (placing test tube in hot water) or placing in the sun (UV light) may be necessary to start the reaction on cool days, particularly if the peroxide is cold. When effervescence (sometimes violent) has ceased, continue to add a few mL of peroxide at a time until the reaction appears complete. If the reaction becomes violent diluting with deionised water via a wash bottle is recommended. Measure the pHFOX of the resultant mixture. Care is needed with interpretation of the result on high organic or reactive soils, particularly if manganese is present. In general, positive tests on ‘apparently well drained’ surface soils should always be treated with caution and followed up with laboratory confirmation. The pHF and pHFOX field tests are done on two sub-samples from the same depth interval of the profile. A combination of three factors is considered in arriving at a ‘positive field sulfide identification’. These are: (a) a reaction with hydrogen peroxide; (b) a much lower pHFOX than pHF (rpH); and (c) the actual value of pHFOX.


(i) The strength of the reaction with peroxide is a useful indicator but cannot be used alone. Organic matter and other soil constituents such as manganese oxides can also cause a reaction. Care must be exercised in interpreting a reaction on surface soils and high organic matter soils such as peat and some mangrove/estuarine muds and marine clays. This reaction should be rated, e.g. L = Low reaction, M = Medium reaction, H = High reaction, X = Extreme reaction.

(ii) A pHFOX value at least one unit below field pHF may indicate a PASS. The greater the

difference between the two measurements (rpH), the more indicative the value is of a PASS. The lower the final pHFOX value is, the better the indication of a positive result.

(iii) If the pHFOX <3, and the other two conditions apply, then it strongly indicates a PASS. The

more the pHFOX drops below 3, the more positive the presence of sulfides.

A pHFOX 3–4 is less positive and laboratory analyses are needed to confirm if sulfides are present. (If only low pH peroxide is available, the field test is less discriminatory, particularly for sands because of their low pH buffer capacity. Low analysis sands may give confusing field test results and must be confirmed by laboratory analysis.) For pHFOX 4–5 the test is neither positive nor negative. Sulfides may be present either in small quantities and be poorly reactive under quick test field conditions or the sample may contain shell/carbonate, which neutralises some or all acid produced by oxidation. Equally the pHFOX value may be due to the production of organic acids and there may be no sulfides present in this situation. In such cases, laboratory analysis using the sulfur trail of the POCAS or Chromium Reducible Sulfur methods (refer to guidelines indicated below) would be best to check for the presence of oxidisable sulfides.

For pHFOX >5 and little or no drop in pH from the field value, little net acidifying ability is indicated. (On soils with neutral to alkaline field pH and shell or white concretions present, the fizz test with 1M HCl should be used to test for carbonates). Again the sulfur trail of the POCAS or Chromium Reducible Sulfur methods should be used to check for any oxidisable sulfides. All pHF and pHFOX results by depth should be tabulated and reported in the ASS report/EIS. Other semi-field tests such as examination under a microscope for pyrite and its reaction with peroxide on the slide may be useful tools to identify pyrite presence, but they require experience and training.

Note: Field techniques are useful exploratory tools, but are indicative only and definitely not quantitative. They are not a replacement for quantitative laboratory analyses. The field peroxide test has been found to be least useful on low analyses sands, particularly dredged sands approaching the action limit (0.03% S). It is also difficult to interpret field tests on highly organic or peat soils and coffee rock.


For further information on the above tests see the latest version of Guidelines for Sampling and Analysis of Lowland Acid Sulfate Soils (ASS) in Queensland, which is available from the Department of Natural Resources.

ii) Groundwater analysis as indicators of acid sulfate soils Analysis of groundwater or drain water for the soluble chloride:soluble sulfate (Cl -:SO4

2-) ratio can indicate that sulfidic material in the vicinity of the site is being, or has been, oxidised. In order to undertake this test, water samples should be submitted for laboratory analysis. The location of each borehole or sampling site should be clearly marked on a map, with grid references and elevation (m AHD) for each sample site recorded in a table.

As seawater has a SO4

2- concentration of approximately 2,700 mg/L and a Cl - concentration of approximately 19,400 mg/L, the ratio of Cl -:SO4

2- on a mass basis is 7.2. As the ratios of the dominant ions in saline water remain approximately the same when diluted with rainwater, estuaries and coastal saline creeks can be expected to have similar ratios to the dominant ions in seawater. Where the analysis indicates that there is an elevated level of sulfate ions relative to the chloride ions, these results may indicate the presence of acid sulfate soils in the landscape. A Cl -:SO4

2- ratio by mass of less than 4, and certainly a ratio less than 2, is a strong indication of an extra source of sulfate from previous sulfide oxidation.

Caution must be exercised in interpreting Cl -:SO4

2- ratio results. The Cl -:SO42- ratio becomes

less predictive as the water becomes less brackish. Care must also be taken with the interpretation of data in tropical areas during the wet season or where large freshwater inputs occur. With groundwater, as the layer supplying most of the water within a hole will influence the final analysis outcomes, properly installed ‘nested’ piezometers, accessing particular strata or horizon/depth intervals, will assist in overcoming sampling limitations and improve the reliability of results. See the latest version of the Groundwater Guidelines in the New South Wales Acid Sulfate Soils Manual for further information.

iii) Microscopic soil analysis

Soil suspensions/slurries can be examined under a microscope for sulfide framboids and individual crystals. As a further confirmation, the reaction of the sulfide with peroxide may be observed on the slide. However, failure to see crystals or framboids is not evidence that sulfide is absent as sulfidic crystals may have been lost in the sampling or slide preparation. Caution is required with the use of this technique as it requires acquired skills. False positives are common when high levels of organic material or manganese are present.

Conclusion If the soil and water investigations using the indicators in Table 1 point towards acid sulfate soils being present, a laboratory analysis should be undertaken as set out in Step Three to obtain site specific data. If the Step Two investigations do not indicate the presence of acid sulfate soils, the applicant can be reasonably confident that acid sulfate soils will not be disturbed as a result of the proposed development. Submission of this information may provide a sufficient case that the requirements of the State Planning Policy are being met. This approach has been successfully


adopted on a number of projects. However, if there is any doubt whether acid sulfate soils are present, the applicant should proceed to Step Three to determine the presence, extent and the degree of severity of acid sulfate soils. Step Three: Laboratory Analysis The applicant should have an acid sulfate soils investigation report prepared in accordance with the latest version of Guidelines for Sampling and Analysis of Lowland Acid Sulfate Soils (ASS) in Queensland, which is available from the Department of Natural Resources. Laboratory analysis is essential to obtain site specific data on the severity and location of acid sulfate soils. The acid sulfate soils investigation report should present the percentage of Oxidisable Sulfur (S%) by an approved method such as Chromium Reducible Sulfur (SCR), Peroxide Oxidisable Sulfur (SPOS) by POCAS or Total Oxidisable Sulfur (STOS). The Total Actual Acidity (TAA) of the soils/sediments of the site must be tested on any samples with pHF <5.5. The TAA result when converted to equivalent sulfur units (STAA %) should be added to oxidisable S% and then related to Table 2 in Annex 2 to determine the level of treatment and management required. The total mass (tonnes) of acid sulfate soils to be disturbed/treated is also required. Other supporting analyses such as Total Potential Acidity (TPA), Total Sulfidic Acidity (TSA) and reacted Calcium (CaA) are useful, particularly if shell or natural lime is present, in order to negotiate a lower lime rate application. Section 4 of Guidelines for Sampling and Analysis of Lowland Acid Sulfate Soils (ASS) in Queensland outlines sampling intensities and suggested levels of investigation relevant to the size of the project and likely presence of acid sulfate soils. A staged approach to investigation can be undertaken with the agreement of relevant Government authorities. This analysis can then be used to determine any further levels of sampling or treatment categories subject to approval of relevant Government authorities. Upon completion of sampling and analysis, the appropriate levels of treatment i.e. low (L), medium (M), high (H) and very high (VH) can be determined (Table 2 of Annex 2) and the corresponding management responses developed (see Annex 2). If first stage testing indicates that the treatment levels will be H or VH then full sampling in accordance with the Guidelines will normally be required.


ANNEX 2 Investigation of groundwater prior to disturbance Introduction For works that may result in the aeration of previously saturated acid sulfate soils through dewatering or filling, a supplementary investigation of the affected waters should be conducted. A suitable qualified professional experienced in assessing and managing acid sulfate soils and groundwater issues should undertake all investigations. It is recommended that the latest technical guidelines be consulted. The Department of Natural Resources website (www.dnr.qld.gov.au/resourcenet/land/ landplan/lp-ass/ass-spp.html) is a potential source of information and other material may be available from DNR district offices and some local governments.

Note: Applicants should be aware that acid sulfate soils and the associated hydrology are a complex matter. The treatment of groundwater in situ is usually not feasible, but applicants should be aware where aeration of previously saturated acid sulfate soils is likely to occur to enable appropriate management decisions.

The information should be used to demonstrate:

• the presence or absence of acidic groundwaters prior to works that may result in the release of such waters;

• the proposed development will not result in previously saturated acid sulfate soils being aerated through dewatering or filling; or

• that if previously saturated acid sulfate soils will become aerated as a result of the proposed development, this information should be used to assist in the production of effective treatment and management plans. Also see Annex 4 for treatment of waters.

Information requirements Prior to on-site works, the groundwater investigation should:

• describe the water quality, including seasonal variations where applicable. Minimum description of water quality should include:

Ø field measurements of pH, electric conductivity, and dissolved oxygen. If field measurement of water pH is less than 6.5 conduct additional investigations on calcium, magnesium, total iron, dissolved iron, dissolved manganese, filtered aluminium, bicarbonate, carbonate, chloride, sulfate, and colour;

• determine the depth to the watertable with an indication of the seasonal variation. The greater the groundwater depth the less likely the potential for impacts to the groundwater or for watertable levels to change as a result of the proposal;


• identify adjoining (both on and off site) groundwater related environments (e.g. wetlands, springs, rivers and creeks) and any likely recharge areas (e.g. areas of waterlogging). Sites that contain surface water linkages to the groundwater increase the likelihood of groundwater being affected; and

• identify any adjoining existing groundwater users, density of bores, uses of groundwater extraction.

Using the above information, the applicant should demonstrate that there would be negligible effect on adjoining groundwater users and related environments as a result of the proposed activity. If this cannot be demonstrated, the applicant should:

• conduct a full groundwater investigation by identifying the hydraulic characteristics of any aquifer, including:

Ø hydraulic conductivity (aquifer thickness, type, porosity, transmissibility);

Ø groundwater gradient and flow direction;

Ø soil permeability and attenuation/absorption characteristics (soils with high permeability increase the potential for infiltration to the groundwater); and

Ø pumping tests. All groundwater sampling should be undertaken according to the Murray Darling Basin Groundwater Quality Sampling Guidelines, August 1997, Technical Report No 3, Groundwater Working Group, Murray Darling Basin Commission. If groundwater investigations indicate that existing groundwaters do not conform to the water quality criteria of Table 3 in Annex 4, the waters must be treated in accordance with Annex 4 before release. If groundwater investigations indicate that existing groundwaters are acceptable by the water quality criteria of Table 3 in Annex 4:

• daily monitoring for pH is still required prior to any release of waters to ensure that there is no deterioration of water quality standards since previous measurements;

• weekly monitoring for pH is still required if an on-site water storage (greater than 100 m3

or 0.1 megalitre) interacts with groundwater to ensure that there is no deterioration of water quality standards since previous measurements. If the above monitoring indicates a pH result outside the acceptable range of Table 3, waters must be treated in accordance with Annex 4 to mitigate the potential for environmental damage should the structure fail.


ANNEX 3 Treatment and management of disturbed acid sulfate soils Introduction Acid sulfate soils that have been disturbed require treatment and management to prevent acid generation and neutralise existing acidity. Compliance with this Annex requires an acid sulfate soils investigation report produced in accordance with the latest version of Guidelines for Sampling and Analysis of Lowland Acid Sulfate Soils (ASS) in Queensland, as per Step Three of Annex 1. Management detail With all levels of treatment and management, the information provided to the assessment manager should include details of the preliminary investigations, if any, and the acid sulfate soils investigation report including disturbance dimensions, volume calculations and laboratory analysis results. The detail required will depend on the category of treatment required. The tonnes of lime required for treating the total mass of ASS can be read off Table 2 at the intersection of the mass (tonnes) [row] and the soil sulfur analysis [column]. The ‘treatment level’ can also be determined from Table 2. Low level of treatment – (Category L) For disturbances of acid sulfate soils requiring treatment at a rate of less than 0.1 tonnes of agricultural lime as per Table 2, the proposed management should include:

• manage site runoff and infiltration; and

• treat soils with potential acidity with appropriate amount of neutralising agent (up to 0.1 tonne of aglime) based on the oxidisable sulfur (S%) and if pHF <5.5 treat actual acidity according to TAA result.


Medium level of treatment – (Category M) For disturbances of acid sulfate soils requiring treatment at a rate of greater than 0.1 tonnes to 1 tonne of agricultural lime as per Table 2, the proposed management should include:

• treat soils with potential acidity with appropriate amount of neutralising agent (up to 1

tonne of aglime) based on the oxidisable sulfur (S%) and if pHF <5.5 treat actual acidity according to TAA result;

• manage site runoff through bunding and prevent or treat infiltration passing through acid sulfate soils to groundwater; and

• ensure that the lime is thoroughly mixed with the soil.

High level of treatment – (Category H) For disturbances of acid sulfate soils requiring treatment at a rate of >1 tonne to 5 tonnes of agricultural lime as per Table 2, (and no alteration of the watertable is involved) then the proposed management should include:

• more detailed plans of disturbance and detailed acid sulfate soils investigation report;

• treat soils with potential acidity with appropriate amount of neutralising agent (up to 5 tonnes of aglime) based on the oxidisable sulfur (S%) and if pHF <5.5 treat actual acidity according to TAA result;

• verification that lime has been thoroughly mixed;

• provide substantial bunding of the site using non-acid sulfate soils material to collect all site runoff;

• monitor pH of any pools of water collected within the bund (particularly after rain) and lime if pHF ≤5.5;

• prevent infiltration passing through acid sulfate soils to groundwater or apply extra layer of lime to intercept any infiltration from acid sulfate soils; and

• provide an adequate but simplified environmental management plan based on the requirements outlined below.

Note: If the assessment manager judges that the proposed works are likely to alter the watertable of the area or the site is close to an environmentally sensitive area (even if <5 tonnes of lime treatment is required), then the disturbance will need to be treated as a Very High level of treatment (Category VH) as below. Refer to Annex 4 for guidance on treatment and management of surface and drainage waters.


Very High level of treatment – (Category VH) For disturbances of acid sulfate soils requiring treatment at a rate of greater than 5 tonnes of agricultural lime as per Table 2, an environmental management plan is required. Environmental Management Plan (EM Plan) The intention of an EM Plan is to provide ‘life of development’ control strategies in accordance with agreed performance criteria. The purpose of an EM Plan is to specify all potential environmental impacts, performance criteria, and mitigation strategies together with relevant monitoring, reporting and, if an undesirable impact or unforeseen level of impact occurs, the appropriate corrective action. An EM Plan contains clear commitments, framed in a way that enables later assessment of the extent to which the commitment has been met. The commitments must be auditable. An EM Plan is structured to address the key elements of environmental management on-site and in proximity to the site for the life of the development. Performance criteria for all elements are determined in the process of formulating an acceptable EM Plan. The aims of the EM Plan are to provide:

• evidence of practical and achievable plans for the management of the project to ensure that environmental requirements are complied with, (i.e. producing an integrated planning framework for comprehensive monitoring and control of construction and operational impacts). Specific commitments on strategies and design standards to be employed should also be given;

• local, State and Commonwealth authorities and the proponent with a framework to confirm compliance with policies and conditions; and

• the community with evidence of the management of the project in an environmentally acceptable manner.

Format of an EM Plan The following is a suggested format designed to ensure adequate detail has been provided to demonstrate that the proposed mitigation of potential impacts will result in appropriate management strategies. Essential components are:

• establishment of agreed performance criteria and objectives in relation to environmental and social impacts;

• detailed prevention, minimisation and mitigation strategies (including design standards) for controlling environmental impacts at specific sites;


• details of the proposed monitoring of the effectiveness of remedial measures against the agreed performance criteria in consultation with relevant government agencies and the community. The frequency of monitoring for each parameter and proposed location of monitoring sites should be shown to allow consideration of monitoring in risk assessment;

• details of implementation responsibilities for environmental management (names of responsible positions or persons);

• timing (milestones) of environmental management initiatives;

• reporting requirements and auditing responsibilities for meeting environmental performance objectives and demonstrating ‘quality assurance’; and

• corrective actions to rectify any deviation from performance standards. The recommended structure of each element of the EM Plan is as follows: Element/Issue: Aspect of construction or operation. Operational Policy: The operational policy or management objective that applies to

the element. Performance Criteria: Performance criteria (outcomes) for each element of the

operation. Implementation Strategy: The strategies or tasks (to nominated operational design

standards) that will be implemented to achieve the performance criteria.

Monitoring: The monitoring requirements that will measure actual performance

(i.e. specified limits to pre-selected indicators of change). Include: A table of parameters listing frequency and location for monitoring, and a map/plan showing locations for monitoring referred to in table.

Auditing: The auditing requirements that will demonstrate implementation of

agreed construction and operation environmental management strategies and compliance with agreed performance criteria.

Reporting: Format, timing and responsibility for reporting and auditing of

monitoring results. A contact details page listing all responsible parties is recommended.

Corrective Action: The action to be implemented in case a performance requirement

is not reached and the person(s) responsible for action (including staff authority and responsibility management structure). Some performance criteria triggering a corrective action may require a contingency plan in high risk projects.


Review of EM Plan An EM Plan is reviewed and periodically updated to reflect knowledge gained during the course of operations and to reflect new knowledge and changed community standards (values). Changes to the EM Plan should be developed and implemented in consultation with relevant authorities. Specific requirements for acid sulfate soils The acid sulfate soils component of the EM Plan should be prepared, and implementation commenced, prior to soil drainage or disturbance and should include the following:

• a two dimensional map of the occurrence of acid sulfate soils to 1 m below the depth of disturbance. The map should identify separate areas of both actual and potential acid sulfate soils according to the upper depth of occurrence e.g. 0–0.5 m, 0.5–1 m, 1–1.5 m, etc.;

• at complex sites, a number of cross sectional diagrams or a three dimensional diagram of the site, showing various acid sulfate soil layers (with corresponding soil analysis indicated) should be presented. This will assist greatly in understanding the site and form the basis for acid sulfate soil management;

• details of potential on-site and off-site effects of the disturbance of the soil and/or the groundwater levels;

• prevention strategies for the oxidation of iron sulfides (including avoiding the disturbance of acid sulfate soils by redesigning layout of the excavations, and/or re-flooding of potential acid sulfate soils to limit oxidation);

• treatment strategies for acid sulfate soils (including burial of potential acid sulfate soils; neutralisation of actual and potential acid sulfate soils by thorough mixing of fine agricultural lime at 1.5 to 2 times the theoretical acid production potential; or hydraulic separation and treatment of the extracted (fill) material);

• strategies for management of the watertable height on and off the site both during and post-construction;

• monitoring strategies (manual, automated, and laboratory procedures) detailing requirements for surface and groundwater monitoring for pH, electrical conductivity, dissolved oxygen, chloride, sulfate, total iron, dissolved iron, filtered aluminium, bicarbonate, and calcium, and monitoring biological indicators where required;

• monitoring schedules for soil, including field pH (pHF), field peroxide pH (pHFOX) and laboratory procedures;

• details of verification testing of soils;

• details of the handling and storage of neutralising agents;

• containment strategies (including bunding, lime dosing, use of silt curtains) to ensure that that all contaminated stormwater, acid and leachate associated with the oxidation of acid sulfate soils is prevented from entering the receiving environment both in the short and


long-term (where pH, dissolved oxygen, dissolved iron, total iron and dissolved aluminium comply with limits documented in the ANZECC Australian Water Quality Guidelines for Fresh and Marine Waters or its replacement);

• performance criteria to be used to assess the effectiveness of the acid sulfate soils management and monitoring measures; and

• description of contingency procedures to be implemented on and off the site if the management procedures prove to be unsuccessful, acid is generated, leachate problems occur, and/or if performance criteria are breached.

The EM Plan should provide for ongoing management and monitoring of the effects of the disturbance of acid sulfate soils through the construction and operation of the project and describe the construction schedules and environmental management procedures. The project should be staged so that the potential effects on any area disturbed at any one time is limited and easily managed.

Table 2: Estimating treatment categories and lime required to treat the total weight of disturbed acid sulfate soil – Based on soil analysis The tonnes (t) of pure fine lime required to fully treat the total weight/volume of acid sulfate soils (ASS) can be read from the Table at the intersection of the weight of disturbed soil (row) with the soil oxidisable sulfur analysis (column). Where the exact weight or soil analysis figure does not appear in the heading of the row or column, use the next highest value.

Disturbed ASS

Tonnes

Soil Analysis – Oxidisable Sulfur (S%) + if pH <5.5 sulfur equivalent TAA (STAA )

(≈m3) † 0.03 0.06 0.1 0.2 0.4 0.6 0.8 1 1.5 2 2.5 3 4 5

1 0 0 0 0 0 0.05 0.05 0.05 0.1 0.1 0.1 0.1 0.2 0.2

5 0 0 0 0.05 0.1 0.1 0.2 0.2 0.4 0.5 0.6 0.7 0.9 1.2

10 0 0.05 0.05 0.1 0.2 0.3 0.4 0.5 0.7 0.9 1.2 1.4 1.9 2.3

15 0 0.05 0.1 0.1 0.3 0.4 0.6 0.7 1.1 1.4 1.8 2.1 2.8 3.5

20 0.05 0.1 0.1 0.2 0.4 0.6 0.7 0.9 1.4 1.9 2.3 2.8 3.7 4.7

25 0.05 0.1 0.1 0.2 0.5 0.7 0.9 1.2 1.8 2.3 2.9 3.5 4.7 5.9

35 0.05 0.1 0.2 0.3 0.7 1.0 1.3 1.6 2.5 3.3 4.1 4.9 6.6 8.2

50 0.1 0.1 0.2 0.5 0.9 1.4 1.9 2.3 3.5 4.7 5.9 7.0 9.4 12

75 0.1 0.2 0.4 0.7 1.4 2.1 2.8 3.5 5.3 7.0 8.8 11 14 18

100 0.1 0.3 0.5 0.9 1.9 2.8 3.7 4.7 7.0 9.4 12 14 19 24

200 0.3 0.6 0.9 1.9 3.7 5.6 7.5 9.4 14 19 24 28 38 47

500 0.7 1.4 2.3 4.7 9.4 14 19 24 35 47 59 70 94 117

750 1.1 2.1 3.5 7.0 14 21 28 35 53 70 88 105 141 176

1,000 1.4 2.8 4.7 9.4 19 28 38 47 70 94 117 141 187 234

2,000 2.8 5.6 9.4 19 38 56 75 94 141 187 234 281 375 468

5,000 7.0 14 23 47 94 141 187 234 351 468 585 702 936 1,171

10,000 14 28 47 94 187 281 375 468 702 936 1,171 1,405 1,873 2,341

L Low treatment: (≤0.1 tonne lime) M Medium treatment: (>0.1 to 1 tonne lime) H High treatment: (>1 to 5 tonnes lime)

VH Very High treatment: (>5 tonnes lime)

Lime rates are for pure fine CaCO3 using a safety factor of 1.5. A factor that accounts for Effective Neutralising Value is needed for commercial grade lime. An approximate soil weight (tonnes) can be obtained from the calculated volume by multiplying volume (cubic m) by bulk density (t/m3). (Use 1.7 if bulk density (BD) is not known). †Tonnes approximately equal m3 (volume) for soils with BD of 1 g/cc or t/m3. Dense fine sandy soils may have BD up to 1.7. Thus 100 m3 may weigh up to 170 t.


ANNEX 4 Treatment and management of surface and drainage waters from disturbed acid sulfate soils Surface and groundwater flows (including water storages) from areas containing acid sulfate soils should be treated and managed to prevent the leaching of acid and metal contaminants into the environment in accordance with the following water quality criteria and treatment advice. While the treatment of relatively small quantities of water may be quite straightforward, applicants should seek qualified professional assistance, as the chemistry of water quality can be a complex environmental issue. In cases where excessive iron, aluminium and other salts are present, particularly in large volumes, sophisticated and novel treatments may be required. Water quality criteria Water quality criteria for protection of aquatic ecosystems are described in the ANZECC Australian Water Quality Guidelines for Fresh and Marine Waters (1992) (or the proposed replacement). The Guidelines recommend that the water quality criteria for the indicators in Table 3 be met for the discharge of water into the environment.

Note: The ANZECC Guidelines are currently being reviewed and up-to-date water quality criteria should be used when available.

Table 3: ANZECC Water Quality Criteria for protection of aquatic ecosystems

Indicator Fresh water Marine water

pH 6.5–9.0 < 0.2 unit change Total (Fe) 0.5 mg/L NA

Total Dissolved Salts (TDS) 0–1,500 mg/L > 1,500 mg/L Total Aluminium (Al) 0.005 mg/L for pH < 6.5

0.1 mg/L for pH > 6.5 NA

Dissolved Oxygen (DO) 6.0 mg/L (or 80–90% saturation)

Most natural fresh water has a pH between 6 and 7 and marine water close to pH 8.2. The ANZECC Guidelines recommend that changes of more than 0.5 pH units from the natural seasonal maximum or minimum should be investigated, and that in marine waters, the pH should not be permitted to vary by more than 0.2 units from the normal values. As marine waters are strongly buffered, even small changes in the pH levels indicates a major change to the system. Total alkalinity of seawater is 115–120 mg/L (as CaCO3).


Research has demonstrated that the chemistry of aluminium in natural waters is complex and the solubility of aluminium species is pH dependent. If the pH is at or below 5.2, the total soluble aluminium concentration increases with an increase in the range of dissolved ionic species present. Aluminium species are toxic to fish over a pH range of 4.4–5.4 and are most toxic when the pH of water is around 5.0–5.2. Under very acid conditions, the toxic effects of the high H+ concentrations appear to be more important than the effects of aluminium. Where iron is precipitating from the acidic water, very low dissolved oxygen levels may result. The ANZECC Guidelines recommend that dissolved oxygen should not normally be permitted to fall below 6 mg/l or 80–90% saturation, having been determined over at least one diurnal cycle. Wherever possible, dissolved oxygen should be measured over the full diurnal cycle for a period of a few days to establish the diurnal range in concentration. Neutralising acid leachate and drain water using lime The liming rate for treating acid water should be carefully calculated to avoid the possibility of overshooting the optimum pH levels of 6.5–8.5. This can occur quite easily if more soluble or caustic neutralising agents such as hydrated lime (pH 12) or magnesium hydroxide (pH 12) are used. Overdosing natural waterways results in alkaline conditions and can impose environmental risks similar to acid conditions, with the potential to damage estuarine ecosystems. It should be noted that when neutralising acid water, no safety factor is used. However, the monitoring of pH should be carried out regularly during neutralisation procedures. Agricultural lime (CaCO3) is the safest and cheapest neutralising agent. It equilibrates around a pH of 8.2 and is not generally harmful to plants, stock or humans and most aquatic ecology species. The main shortcoming associated with the use of aglime is its insolubility in water. It is more soluble in strongly acid water. When using strongly alkaline materials such as hydrated lime (Ca(OH)2) and quick lime (CaO), strict protocols must be established for the safe use, handling and monitoring of these materials. Calculating the quantity of lime The current pH is measured preferably with a recently calibrated pH detector. The desired pH is usually between 6.5 and 8.5 (pH 7 is normally targeted). The volume of water can be calculated by assuming 1 m3 of acid water is equivalent to 1 kilolitre (1,000 litres) and 1,000 m3 is equivalent to 1 megalitre (ML).

Note: Neutralising agents such as lime CaCO3, hydrated lime Ca(OH)2, quick lime CaO, and magnesium oxide MgO neutralise 2 mol of acidity (H+), while sodium bicarbonate NaHCO3 and sodium hydroxide NaOH neutralise only 1 mol of acidity.

The quantity of lime needed to treat a body of water can be calculated from the pH of the water, if no other means of estimating the amount of lime is available (i.e. field titrations or laboratory analysis).


As a general guide, Table 4 shows the minimum quantities of pure lime, hydrated lime or sodium bicarbonate needed to treat dams or drains of 1 ML (1,000 m3) capacity, calculated on water pH. Calculations in this table are based on low salinity water acidified by hydrogen ion, H+ (acid) and do not take into account the considerable buffering capacity or acid producing reactions of some acid salts and soluble species of aluminium and iron. Table 4: Quantity of pure neutralising agent required to raise from existing pH to pH 7 ` for 1 megalitre of low salinity acid water

Current Water

pH

[H+] (mol/L)

H+ in 1 Megalitre

(mol)

Ag. lime to neutralise

1 Megalitre (kg pure CaCO3)

Hydr. lime to neutralise

1 Megalitre (kg pure Ca(OH)2)

Pure sodium bicarbonate to neutralise 1 Megalitre

(pure NaHCO3)

0.5 .316 316,228 15,824 11,716 26,563 1.0 .1 100,000 5,004 3,705 8,390 1.5 .032 32,000 1,600 1,185 2,686 2.0 .01 10,000 500 370 839 2.5 .0032 3,200 160 118 269 3.0 .001 1,000 50 37 84 3.5 .00032 320 16 12 27 4.0 .0001 100 5 4 8.4 4.5 .000032 32 1.6 1.18 2.69 5.0 .00001 10 0.5 0.37 0.84 5.5 .0000032 3.2 0.16 0.12 0.27 6.0 .000001 1 0.05 0.037 0.08 6.5 .00000032 .32 0.016 0.012 0.027

Notes on Table 4: 1 m3 = 1,000 litres = 1 Kilolitre = 0.001 Megalitre

• Agricultural lime has very low solubility and may take considerable time to even partially react.

• Hydrated lime is more soluble than aglime and hence more suited to water treatment. However, as Ca(OH)2 has a high water pH, incremental addition and thorough mixing is needed to prevent overshooting the desired pH. The water pH should be checked regularly after thorough mixing, allowing sufficient time for equilibration before further addition of neutralising product.

• Weights of lime or hydrated lime are based on theoretical pure material and hence use of such amounts of commercial product will generally result in under treatment.

• To more accurately calculate the amount of commercial product required, the weight of lime from Table 4 should be multiplied by a purity factor (100/Neutralising Value for aglime) or (148/Neutralising Value for hydrated lime).

• If neutralising substantial quantities of acid sulfate soil leachate, full laboratory analysis of the water will be necessary to adequately estimate the amount of neutralising material required.


Issues to consider may include:

• the quality of the lime being used;

• the effectiveness of the application technique;

• the existence of additional sources of acid leaching into the water body further acidifying the water; and

• the lime has become lumpy and is sitting on the bottom. Neutralisation may be faster if higher rates are used, but is not recommended, as it is expensive and resource wasteful. Moreover, over-dosing may result, though this is unlikely to be a concern with agricultural lime. To increase the efficiency, lime should be mixed into a slurry before adding. A slurry can be prepared in a concrete truck, cement mixer or large vat with an agitator. Methods of application of the slurry include:

• spraying the slurry over the water with a dispersion pump;

• pumping the slurry into the waterbody with air sparging (compressed air delivered through pipes) to improve mixing once added to water;

• pouring the slurry out behind a small motorboat and letting the motor mix it in;

• incorporating the slurry into the dredge line (when pumping dredge material); and

• using mobile water treatment equipment such as the ‘Neutra-mill’ and ‘Aqua Fix’ to dispense neutralising reagents to large water bodies.

In some circumstances lime in its solid form can be used, for example by:

• placing lime in a porous bag of jute or hessian and tying the bag to drums so that it floats in the water. The material will then gradually disperse. This technique should only be considered where there is significant water movement; or

• passing water across a bed of coarse granulated lime or through a buffer of granulated lime or sand bags containing lime. However, this is unlikely to be effective in the long term as the lime granules may become coated.

When the pH of acid sulfate soils leachate has been below 4.5, it usually contains soluble iron and aluminium salts. When the pH is raised above 4.5, the iron precipitates as a red-brown stain/scum/solid which can coat plants, monitoring equipment, the base or walls of dams, drains, pipes, piezometers and creeks. In addition, the soluble aluminium is a good flocculent and may cause other minerals to precipitate or suspended clay particles to flocculate. Where the water contains considerable soluble iron, large quantities of acid can be generated as the pH is raised and iron hydroxides are precipitated. It is important to let any sludge settle before using treated water (otherwise it will block pipes and pumps) or discharging treated water (to avoid adverse aesthetic and ecological effects). Chemicals can be used to reduce the settlement time, if it does not settle quickly enough for the staging of the works, however care should be taken in choosing flocculating agents as these can also alter pH or cause other management problems.


The large-scale dosing of waters to alter the chemical characteristics, such as may be the case in the mining industry, is a specialised and highly technical task that requires considerable expertise and experience. Professional guidance should be obtained in these situations. The pH of the water should be checked daily during the first two weeks following application or until the pH has stabilised and then on a regular basis according to the Acid Sulfate Soils Management Plan. The pH should be checked daily (as a minimum) if there is any discharge from the site and preferably more frequently depending on the environmental sensitivity of the receiving environment. Automatic testing is advocated in certain circumstances.


Disclaimer: While every care has been taken in preparing this policy, the State of Queensland accepts no responsibility for decisions or actions taken as a result of any data, information, statement or advice, express or implied, contained in this document.

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ions from previous acid sulfate soils oxidation

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