Asbestos in Soil Management
IN-SITU MANAGEMENT OF LOW-LEVEL ASBESTOS IN SOIL
Contaminated Land, Asbestos Management
Our Environmental Services team was engaged by a client to undertake a Detailed Site Investigation (DSI) at a former auto-motive wreckers yard, occupying approximate four hectares of land near Porirua, Wellington to support the proposed redevelopment of the site for a new commercial / light industrial trade park.
The initial DSI identified that the site had a long history of use as an automotive wreckers / metals recycling yard. Intrusive investigations identified the presence of buried anthropogenic waste in the form of car parts, car bodies and tyres. Soil sampling indicated the low-level presence of several contaminants of concern in soils across the site, including petroleum hydrocarbons and asbestos.
The presence of asbestos in shallow soils at the site was the primary driver for remediation, as while concentrations were low-level, they did exceed the adopted human health assessment criteria, and were widespread across much of the site. Excavation and removal of all asbestos impacted soils for off-site disposal was not considered a practical or sustainable method of remediation that enabled better environmental outcomes. Off-site disposal of low-level asbestos impacted soil was considered in the Remediation Action Plan (RAP) to potentially exacerbate risks to human health through unnecessary soil disturbance.
The preferred management approach, which was accepted by appropriate regulatory agencies was to manage the low-level impacted asbestos in soil in-situ, following the removal of any visible ACM fragments from surface soils (chicken pick). The management methodology included covering the surface of the site in non-woven Geofabric, and placing site-sourced clean fill cut soil over, to build a series of platforms for future building.
Subsequent soil validation works confirmed appropriate encapsulation of low-level asbestos impacted soils, such that risk to human health in light of the proposed development was considered highly unlikely, provided encapsulated soils remained undisturbed. An on-going site management plan was prepared to detail appropriate management requirements should encapsulated soils be disturbed (through for example future sub-surface maintenance works).