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Dieback Mapping
Dieback interpreters, accredited by the Department of Environment and Conservation (DEC) and funded by Alcoa, map the occurrence of dieback symptoms in forest areas in which mining is planned.
After logging or burning, dieback symptoms may not be expressed for up to three years, so some areas cannot be interpreted. Boundaries are marked in the field between areas classified as "dieback-free", "uninterpretable", "suspect" and "dieback".
Before Alcoa's field operations (drilling and clearing) are carried out, areas for which dieback mapping is more than 12 months old are rechecked for disease spread and new infections. Maps and field marking are adjusted where necessary.
Boundaries marked in the field are maintained from before grade control drilling until the soil is removed down to caprock, and the rock broken by ripping or blasting. After soil is returned to a rehabilitated area, dieback boundaries are once again marked in the field.
Hygiene maps produced by the interpreters show the dieback status found during field inspections. Dieback-free areas are sub-divided into four classifications, depending on their security from introduction of the disease. In order, they are "secure dieback-free", "low potential risk", "high potential risk", and "not effectively quarantined" (NEQ).
This ranking system assists in determining levels of protection from disease introduction during mining.
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