Draft DEWCP and EPA guidance on managing acid sulfate soils



Cover

Overview

Guidelines

Referral to EPA

Source of Information

Glossary

App. 1: Checklist

 

Draft DEWCP and EPA guidance on managing acid sulfate soils

Appendix 1

Checklist for the identification of works that may disturb acid sulfate soils
and
Suggested procedures for works and development projects that may disturb acid sulfate soils

Checklist for the identification of works that may disturb acid sulfate soils (ASS) It is recommended that works are considered as "works in an area where there is a risk of disturbing acid sulfate soils" if at least one "yes" is ticked in Part A, and at least one "yes" is ticked in Part B.

Suggested procedures for works and development projects in acid sulfate soil risk areas are summarised in the following flowchart.

PART A

Are the proposed works in any of the following areas?
(NB: the Environmental Geology series are considered to provide a useful indication of potential areas of acid sulfate soils in those areas where the series apply)
YESNO
Areas on Environmental Geology maps published by the Department of Mineral and Petroleum Resources, shown as Holocene swamp, tidal and estuarine deposits, marshes and floodplains

Acid sulfate soils risk areas shown on government agency mapping (or mapping from a reputable source) specifically on acid sulfate soil risk areas. (As of March 2002, DEWCP is preparing maps for some regions at risk in Western Australia)

Areas on Land System and Soil-Landscape system mapping by Agriculture WA, and soil, geology or geomorphology mapping, that indicate geologically recent shallow tidal, estuarine, marine, wetland, floodplain or waterlogged areas where deposition of fine sediments may have occurred or may be occurring; and vegetation mapping that shows mangroves or wetland dependant vegetation such as reeds and paperbarks

Areas identified in geological descriptions or in maps as bearing sulfide minerals or former marine or estuarine shales and sediments, and mineral sand deposits Coastal areas where the following pre-disposing factors exist:

*Areas known to contain peat or a build up of organic material;

*Areas near bores in which peat or other organic deposits have been recorded as part of the stratigraphy (some information on bore stratigraphy may be available from DEWCP, local Councils or the Department of Mineral and Petroleum Resources);

*Permanently inundated wetlands;

*Seasonally or occasionally saturated or inundated floodplains and sumplands;

*Shallow estuarine areas receiving alluvium;

*Mangrove areas;

*Tidal swamps, wetlands and shallow estuarine areas receiving alluvium;

*Artificial lakes excavated in peaty material;

*Sites known or believed to contain carbonaceous or pyritic material, such as fill, and existing or former municipal waste disposal sites, industrial sites, food industry waste disposal areas, mining and metal waste disposal areas and animal based waste disposal areas;

*Highest known water table within 3 metres of the surface; or

*pH of soil or water less than 5

Any areas in Western Australia where a combination of all the pre-disposing factors exist - organic matter, iron minerals, waterlogged conditions or a high water table, and sulphides or sulphates eg from rising saline groundwater originally brought inland in marine aerosols. For example, acid sulfate soils may develop in inland areas in association with wetlands and waterlogged areas with a salinity problem, and in association with some mining operations

Any areas where field tests, visual signs and other methodologies indicate that there is a likelihood of acid sulfate soils. An easy to use international methodology for determining the likelihood of acid sulfate soils in coastal areas is reported in "The Acid Test: an expert system for acid sulphate soils" (Dent) and is available on the internet at http://www-staff.lboro.ac.uk/~cobrd/identman.pdf. Soil and water tests that may readily be carried out are also included in the NSW publication "Acid Sulfate Soils: Keys to Success (Woodhead 2000).

Visual indicators of acid sulfate soils include;



*Swamp / wetland vegetation, such as spike rush and melaleucas;

*Surface waters that are crystal clear (indicates high aluminium at pH 3-4), blue-green (indicates aluminium floc at pH 4-5), milky-white (indicates high aluminium at pH 5-6), yellow-brown (indicates dissolved iron at pH below 3.8) or contain red/brown or brown/yellow floc (indicates iron at pH less than 4);

*Soils that are gooey black, or grey to greeny/bluish grey (potential acid sulfate soils);

*Silty black organic oozes (indicates iron monosulfides)

*Soils that display red/orange mottling, straw yellow blotches or have a rotten egg gas odour (actual acid sulfate soils); or

*Soil surfaces displaying salt crusts or scalds (bare patches).

Areas within approximately 500 metres of any of the above AND THE PROPOSED WORKS INVOLVE THE LOWERING OF THE WATER TABLE

PART B

Do the proposed works involve any of the following disturbances?YESNO
Ground disturbing works in one of the above areas where the area is of high conservation significance (eg conservation category wetland), or drains into an area of high conservation significance (via surface water or groundwater)

Excavation of more than 100 cubic metres of material

Lowering of the groundwater table either temporarily or permanently eg dewatering, drainage works, or pumping

Filling - where there is a potential for the fill to compact saturated soils or sediments and/or laterally displace previously saturated sediments, resulting in groundwater extrusion and aeration of acid sulfate soils

Examples of works that may disturb acid sulfate soils:

  • Coastal developments like canal estates, marinas, golf courses and urban projects;

  • Excavation works associated with urban development;

  • Dewatering and drainage works associated with urban development, including permanent or temporary drainage or pumping of groundwater;

  • Disturbance of some wetlands and waterways eg artificially deepened lakes in public open space, and removal of peat;

  • Infrastructure projects such as road cuttings and bridges;

  • Urban or rural drainage which lowers the water table;

  • Mining and quarrying operations;

  • Agricultural activity;

  • Aquaculture eg prawn farms in mangrove communities; and

  • Filling (filling has been identified as a problem in Queensland, since, in places, filling can compact saturated soils or sediments and/or laterally displace previously saturated sediments, resulting in groundwater extrusion and aeration of acid sulfate soils).

Suggested procedures for works and development projects that may disturb acid sulfate soils (ASS) Draft

Appendix 2: Guidelines for preliminary site investigation and soil sampling

Appendix 3: Guidelines for the preparation of an acid sulfate soil management plan

Appendix 4: Guidelines for managing acid sulfate soils


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