The client’s property was proposed for redevelopment as a multi-lot residential project. The Alpine Shire Council requested a Preliminary Site Investigation (PSI), contaminated land assessment, and hydrogeological study to evaluate whether the site could support sensitive residential uses under the proposed plan amendment.
EHS Support conducted a site walkover and comprehensive desktop review, including an analysis of Environmental Site Assessment (ESA) reports prepared by a previous assessor. This review concluded that, according to Table 2 of the Planning Practice Note 30, the site presented a Medium Potential for contamination due to historical application of pesticides on the site. Other potential contamination sources—such as sheep dips, chemical storage, or underground tanks—were deemed unlikely. Given the sensitivity of residential land use, it was recommended that a Preliminary Risk Screening Assessment (PRSA) be conducted to appropriately evaluate the site’s contamination risks and determine whether an Environmental Audit would be necessary, as outlined in Table 3 of the Planning Practice Note 30.
The only identified contaminating activity was the historical use of pesticides for tobacco crops. Soil investigations by the previous assessor found that organochlorine pesticide (OCP) concentrations across the site were below Tier 1 published screening criteria for residential land use, indicating that contamination from past site activities was unlikely to pose an unacceptable risk to human health or ecological receptors. However, the reported concentrations of OCP exceeded the total organochlorine threshold recommended by WA DPIRD for soils used in free-range poultry farming and domestic consumption of chickens or eggs.
Our Human Health Risk Assessor developed a scope of work aimed at deriving preliminary risk-based soil screening levels for DDE and DDD, the only organochlorine pesticides detected in the soil. These levels focused specifically on risks to human health from the consumption of poultry or eggs. Subsequent analysis confirmed that DDE and DDD concentrations in the soil were below these screening levels, suggesting a low risk to human health from poultry ingestion.
The Council engaged a third party to conduct a peer review of the PSI, Contaminated Land Assessment, Hydrogeological Study, and Human Health Risk Assessment. Following their recommendations, the Council appointed an Environmental Auditor to undertake the PRSA.