EHS Support was engaged to conduct the exit lease assessment for the sites in metropolitan Melbourne including an assessment of soil, groundwater and soil vapour conditions to compare contamination conditions at the end of the lease and, if contamination had worsened, to provide an opinion as to the likely cause.
EHS Support reviewed the initial report conducted in 2017, as well as a review of a 2021 report to inform of any potential data gaps for comparison between reports. We were also engaged to review any remediation activities conducted by the fuel provider or related third party that may have impacted the results of the second assessment report.
Soil and groundwater samples were retrieved for direct comparison to the baseline assessment (completed by others), and a limited soil vapour assessment was undertaken to provide a quantitative assessment of risks to site occupants under a future service station land use scenario. Field work was undertaken on operational service station sites and employed geoprobe soil sampling methods, low-flow groundwater sampling and the installation and sampling of soil vapour bores and sub-slab soil vapour pins.
The work also included reviews of Statistical Inventory Reconciliation Analysis (SIRA) results and equipment integrity testing (EIT) results and culminated in a statement regarding the contamination status of each site compared with the baseline assessment and, where a degradation in site conditions was identified, an opinion as to the likely source of the contamination. The opinion was formed on a weight of evidence approach combining laboratory data including hydrocarbon fingerprinting analysis, SIRA data, EIT data and qualitative hydrogeological modelling.
Where soil vapour results indicated a potential unacceptable risk to future occupants based on a Tier 1 screening level assessment, a more detailed, semi-quantitative vapour intrusion assessment was undertaken by the EHS Support health risk assessment team to determine the site-specific risks to human receptors.
Results from the site assessment conducted by EHS Support determined the risks were acceptable given the future land use and site layout.