Successfully Remediating a Highly Sensitive Former Landfill Site

Successfully Remediating a Highly Sensitive Former Landfill Site

Our team undertook a highly sensitive project to remediate a former landfill site closed more than 40 years ago. The environmental monitoring at the site had identified methane and carbon dioxide levels well above the EPA guidance values. Methane can be formed from biological processes when micro-organisms chemically break down organic matter in landfills.

The elevated levels of landfill gases detected on site led to the evacuation of the adjacent residential properties to mitigate the immediate risk of exposure to the hazardous gases. Our team was engaged to install a landfill gas extraction system and new capping layer along the batter of the landfill, adjacent to the residential properties. The project was time critical, noting multiple residential properties were evacuated and to limit disruption to the local community.

The enabling works as part of the project included site clearance and grubbing of more than 20 trees, removal of surficial asbestos debris as an unexpected find, and excavation of around 500m3 of landfill waste and shallow cap to achieve design levels. The construction works included installation of a geotextile, geosynthetic clay liner and protection layer on the landfill batter, followed by the construction of the passive landfill gas extraction system. A permanent access track was constructed adjacent the batter for future monitoring and assessment, as well as drainage infrastructure and a sandstone boulder retaining wall. The site was then revegetated and returned to the local council. Residential properties have since been re-occupied due to the now safe levels of gases and mitigation of future risks from the former landfill.

Summary

  • Preparation of documentation including CEMP, ESCP, WHS Plans
  • Community engagement and coordination with a range of stakeholders
  • Site clearance and grubbing including more than 20 trees
  • Test pitting and potholing prior to bulk excavation to verify the quantities of waste to be excavated
  • Management of surficial asbestos debris
  • Excavate 520m3 waste cut to design subgrade level including spoil management
  • Decommissioning of existing monitoring wells
  • Supply and installation of geotextile, GCL and protection layer
  • Construction of landfill gas vents, collection bores and feeder pipes
  • Construction of boulder retaining wall
  • Construction of berm drain, 200m access track, and revegetation of site
cLIENT
Confidential
tIMEFRAME
12 Months
lOCATION
NSW
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