Engineers Australia

Rehabilitation of an uncontrolled landfill site for residential development

Stuart Ellis and Adam Wilmot

Abstract

The project site was originally part of a wetland on the Swan Coastal Plain and subsequently utilised as a market garden. The site was then excavated for peat, and filled with over 120,000 m3 of uncontrolled landfill, predominantly building materials. In April 2004 a geotechnical investigation of the site indicated that about 50% of the landfill material was sand and about 30-40% was concrete and brick fragments. This paper presents an innovative rehabilitation methodology successfully employed at the site, which retained over 80% of the uncontrolled fill material. This was achieved through the re-use of the sand fraction and reclamation of the brick and concrete fragments to form rock fill. Subaqueous placement of rock fill material eliminated the need for dewatering, which might have impacted nearby wetlands and adjacent buildings.