Liberty Industrial was engaged to investigate the potential for asbestos impacts through a large 30,000m3 stockpile. The stockpile was generated during a cut to fill process using large motor scrapers. As a result of unknown buried asbestos sheeting, the process produced a 30,000m3 stockpile of sandy / silty clay soils impacted with bonded asbestos cement sheeting materials. The potential off-site disposal costs for this material were estimated at $13.5M. In addition, the material was deemed geotechnical unsuitable as a result of deleterious inclusions and thus could not be placed and compacted under asbestos controls and then capped. This was due to the very high geotechnical standards required for the development of a high-capacity rail line and container handling facility on the site.
The project was being further delayed due to the location of the stockpile and a normal spreading and hen-pecking approach to the removal of the asbestos was deemed to be too slow and would take up too much of the available area. Liberty Industrial was undertaking the demolition of large warehouses in an area approximately 500m from the stockpile. Liberty Industrial devised a strategy to leave some warehouse slabs intact and relocate the stockpile under asbestos controls and subsequently screen the material. Liberty was initially instructed to complete a trial using this screening approach. Liberty Industrial trialed a screen with an 80mm upper deck and 20mm lower deck. We determined during test pitting investigation that the majority of the asbestos fragments were in the 80 to 20mm size fraction.
The screening process produced 3 material stockpiles with the oversize being the removal of the deleterious material impacting the geotechnical properties of the soil, the 20mm to 80mm fraction being extensively picked for the removal of bonded asbestos on a picking line/ station arrangement, and a sub 20mm fine material that was also visually assessed for the absence of asbestos. This entire process resulted in productivity rates in excess of 750m3 / day compared to a normal spreading and picking process that would typically achieve the productivity of only 200m3 / day. The screened soils were validated by a third-party consultant for unrestricted re-use in the development works as geotechnical suitable fill. Through our innovative and proactive approach, Liberty saved the client in excess of $10M and produced over 25,000m3 of asbestos-free validated and compactable fill.