Building on acid sulphate soil

Hey guys,

Currently have a development block under contract (cooling off period) in long jetty. The conveyancer has informed us that it is on acid sulphate soil. There is an existing house but we plan on subdividing and building down the back.

Obviously we will be doing our own research over the coming days but just wondering if anyone has experience in this? Is it very prohibitive or just something where we will have to follow a few council guidelines?

Thanks

Dan

 

Best to check the council requirements and your specific area and depths

 

Unless you are removing more than 120m2 of soil there's nothing to report.

Check out the CSIRO Acid Sulfate Soil guide.

 

Be aware that acid sulphate soils can cause degradation to concrete slab foundations that are not adequately isolated from the soils.

 

Acid Sulphate soils contain iron sulphide (Pyrite)

Problems
Pyrite is chemically stable unless it is exposed to air; such as when it is drained, or excavation takes place. (or even a prolonged drought)

Exposure to air means the pyrite oxidises and produces sulphuric acid and a range of other chemicals including the toxic hydrogen sulfide gas.

Release of the suphuric acid is likely to cause significant environmental damage over long periods as the strong acid can be released from soil for more than 50 years from the original exposure.

Because of the environmental issues all Australian States have management controls for areas of potential acidic sulphate soils

Damage to Foundations
Acid released from the soil can attack both the concrete, and the steel reinforcement within the concrete weakening the house foundation and the cement within the brick walls

Low Load Bearing Capacity
Many potential acid sulfate soils are weak clays that have not fully consolidated, and are likely to further subside or settle.

Precautions When Building

• Deep, expensive, piles will normally be required to support your foundations.
• Sulphate Resisting Cement should be used in all concrete.
• Extra care will need to be taken to ensure all concrete is protected from groundwater by a heavy duty plastic layer.

Extract from my Blog: www.anewhouse.com.au

 

Wow great advice guys thanks heaps. Sounds expensive. Will definitely have to do a lot more research before the cooling off period ends

 

Acid sulphate soils seem to be near rivers and old watercourses. Much of Brisbane is on acid sulphate soils.