Asbestos in Soil 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.

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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.

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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.

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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.

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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).

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Find out more about our environmental services here: Land & Water Quality | 4Sight Consulting. For more information, please contact Nigel Mather, Principal Land and Water Quality Consultant.

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