As accredited Building Designers in Newcastle and Northern Beaches, we know that acid sulfate soils are natural sediments that contain iron sulfides. They are common along the NSW coast. Left undisturbed, acid sulfate soils do not present any risk, but when disturbed or exposed to air these soils can release acid, damaging built structures and harming or killing animals and plants. If the site is zoned as a potential acid sulphate soil risk, a report will need to be commissioned to advise the extent of the issue and recommend treatment measures.