Development on land with acid sulfate soils

Acid sulfate soils (ASS) are natural sediments that contain iron sulfides. They are common along low lying areas adjacent to waterways, typically where the surface elevation is less than 5m above mean sea level. If left undisturbed, ASS do not present any risk, but when exposed to air the soil reacts with oxygen to create sulfuric acid. This can damage built structures, reduce agricultural productivity of land, and harm or kill animals and plants.

Develop on Acid Sulfate Soils

Step 1.Check the potential for Acid Sulfate Soils (ASS)

A large scale map showing the distribution and potential for Acid Sulfate Soil can be accessed below.

Acid Sulfate Soils (ASS) in the Coffs Harbour Local Government Area(PDF, 644KB)

More detailed mapping can be viewed using our Online Mapping Tool. Select the ‘Planning & Environment’ module and ‘Acid Sulfate Soil’ layer. The class levels (1-5), represent the risk level with class 1 presenting the highest risk of ASS. 

Access the Online Mapping Tool

Step 2.When is development consent required?

Under Clause 7.1 of City of Coffs Harbour's Local Environment Plan 2012, development consent may be required for certain works on land classed 1, 2, 3, 4 or 5 for ASS.

See descriptions for each of these classes below.

Class  Specified Works  
 1 Any works 

Works below the ground surface

Works by which the water table is likely to be lowered

Works beyond 1 metre below the natural ground surface

Works by which the watertable is likely to be lowered beyond 1 metre below the natural ground surface

Works beyond 2 metre below the natural ground surface

Works by which the watertable is likely to be lowered beyond 2 metres below the natural ground surface

 5 Works within 500 metres of Class 1, 2, 3 or 4 land which are likely to lower the watertable below 1 metre AHD in adjacent Class 1, 2, 3 or 4 land

Find out how to seek consent via a Development Approval

Assessment report may be required

During the development application process, you will generally be required to engage a suitably qualified environmental consultant to consuct a preliminary assessment of the site.  

This assessment report will be submitted to us confirming the presence or absence of ASS.

If ASS present a management plan will be required

If ASS are present and require remediation, the suitably qualified environmental consultant will need to develop a management plan to outline steps required to ensure the soil is appropriately managed. 

Step 3.If your proposal is a 'minor work'

We have developed a process where applicants proposing only minor works on ASS land can develop their own management plan. This replaces the need to engage a consultant and reduces the costs and regulatory burden for applicants proposing only minor projects with a low ASS risk. Development consent will still be required. 

If your proposal is one of the following, it is considered ‘minor’:

  • Footings for single dwelling and duplex developments
  • Sewer and storm water drainage associated with single dwellings and duplex developments
  • Swimming pools (residential only)
  • On Site Sewage Management Systems and associated works
  • Other works determined by Council’s Planning and Environmental Health Division as minor which disturb less than 10 tonnes of soil. 

ASS Management Plan for minor works

If you are proposing minor works on Acid Sulfate Soil land, you can develop your own management plan using Council's online form below. Simply fill in the project specific details.

Please take care to read and understand the management section which outlines the required process and liming rates.

Acid Sulfate Soil Management Plan for Minor Works

If you have any questions, call us on 02)6648 4000

Step 4.Are there any exemptions?

If you can demonstrate the land has been lawfully filled, and any excavation will not extend below the depth of the fill, an Acid Sulfate Soil Management Plan is not required.

Evidence of this will be requested during the Development Application process if this applies to your proposal.