Detailed Site Investigation for an Environmental Audit of Former Service Station
Overview
ARC were engaged to complete an Environmental Due Diligence (EDD) and Preliminary Site Investigation (PSI) for a former service station/car wash site proposed for redevelopment into residential apartments with 2-level basement. The EDD and PSI confirmed that contamination existed at the Site, with Liquid Non-Aqueous Phase Liquids (LNAPL) present on groundwater.
Scope
A Detailed Site Investigation (DSI) was required to build on the information gathered in the EDD and PSI. The DSI included numerous phases of work including a detailed soil sampling program, groundwater assessment and hydrocarbon contamination delineation, on- and off-site soil vapour impact assessment and development of a comprehensive Conceptual Site Model (CSM). A human health vapour intrusion risk assessment (VIRA) was completed for future on-site residents as well as current off-site receptors. The VIRA indicated that a Vapour Intrusion Mitigation System (VIMS) was required for the proposed basement construction to mitigate potential risks to future occupants.
Remediation included the removal of underground infrastructure associated with the former service station, comprising five (5) Underground Storage Tanks (USTs), a Triple Interceptor Trap (TIT) as well as various subsurface structures, pits, drainage lines and impacted soils, and for LNAPL included Multi Phase Vapour Extraction (MPVE), total fluids pumping and installation of absorbent socks achieved Clean Up So Far As Reasonably Practicable (CUSFARP).
Challenge
As the Site had a potential for contamination classified as 'high' risk, an Environmental Auditor was required to issue an Audit Statement prior to redevelopment for a residential land use.
The Auditor issued a completed Audit Statement following remediation and validation works of the Site. To meet the recommendations of the Audit Statement, ARC finally oversaw the installation of the VIMS and developed a Long-Term Environmental Management Plan (LTEMP) to ensure that the vapour mitigation system provides the required protection from residual hydrocarbon contamination into the future.
Site photography loads from the gallery field on each project. (Placeholder copy, not final.)