Inner Western Sydney, NSW

2018 (likely future involvement)

Our involvement

Geotechnical and environmental investigation for the proposed redevelopment of a site to include additional buildings and alterations and additions to existing buildings.  The investigations were carried out over several stages to develop the geotechnical and environmental models for the site and assess the issues for the proposed redevelopment.  This included deep cored geotechnical boreholes, test pits to exposed existing building footings, environmental sampling and testing of soil, groundwater and ground gas samples.

Project challenges

Part of the site is located within a previously backfilled quarry, with fill proven to depths of 27m.  One of the proposed buildings was located over the edge of the quarry with the depth to the surface of the underlying bedrock within the building footprint ranging from 1.4m to 27m over a short distance.  Investigation of the site was complicated by the site being fully utilised and boreholes needing to be drilled close to existing buildings and within the active spaces being used at the time.  The extent and contamination risk of material used to backfill the quarry was unknown.  The contamination condition of the remainder of the site was also unknown.

Our solutions

JK Geotechnics completed two rows of deep cored boreholes across the footprint of the proposed building and managed to penetrate the fill in all 14 deep boreholes, with the fill extending to maximum depths of about 27m.  This included penetrating fill containing timber, metal, plastic, rubble and other obstructions.  Once rock was encountered it was core drilled to allow optimisation of bearing pressures for the design of piles to support the proposed building.  Limited access drilling rigs were utilised so that the boreholes could be located in between demountable buildings and without damaging the existing synthetic surface within part of the site.  The work was completing during a holiday period when the site wasn’t being used to reduce the impact on the operation of the site and this necessitated mobilisation of two rigs to site to work in tandem to complete the investigation within the limited time available.

JK Environments completed soil, groundwater and ground gas testing to assess the contamination conditions throughout the site.  JK Environments were able to identify a distinct change in conditions within the various sections of the site and tailor a remediation methodology to suit each area.