Hutchinson Builders was awarded a commercial construction project at Bourke Road, Alexandria.

The project involved constructing a single-level underground basement underlying a four-level commercial building. Early contamination and geotechnical investigations identified some degree of soil contamination as the result of the former foundry use. However, the impacts were minor and not of significant concern for the changed land use and development.

EDP initially reviewed the historical information to provide an opinion on the likely waste classification and to determine whether in situ classifications were possible. Following the review, EDP noted inconsistencies in the discussion of risk and proposed the digging of additional test pits to aid in complete characterisation and delineation. During these investigations, the extent of asbestos contamination was identified, as well as the level of chemical contamination resulting from the burial of foundry waste.

Following the engagement of a Class A remediation contractor, EDP prepared an asbestos management plan to cover the remainder of the excavation work and provided asbestos air monitoring daily until clearance could be provided. Residual areas not requiring excavation were further investigated to enable determination of the extent of asbestos impacts and ultimate validation of asbestos concentrations at levels acceptable for the proposed commercial use, removing any need for a long-term environmental management plan.

During bulk excavation, two underground storage tanks were discovered that had not been recorded on a register or identified during the historical review. Hutchinson Builders contacted EDP to respond to the discovery. We developed the specification for the safe removal of the tank, including residual contents and contamination of surrounding soils resulting from failed tank integrity. Because of difficulties in remediation (high water table and risk to adjacent structure footings), some contamination was left in situ. We then conducted a groundwater risk assessment, including installing and monitoring wells so that the minor residual contamination could be left in situ without requiring further remediation or ongoing management.