The ACT Government identified several maintenance issues associated with the Jerrabomberra Creek Channel, where heavy siltation resulted in inadequate clearance below the existing Canberra Avenue overpass. To rectify this issue, the ACT Government proposes to excavate and remove deposited sediments, with a preference to retain the stabilised silt materials on-site, precluding the need for off-site disposal.
These works were carried out concurrently with a geotechnical investigation (conducted by D&N), to inform the design development and feasibility planning associated with siting and stabilised retention of the excavated silt materials, and ultimately, providing advice to the ACT Government on the upstream rectification measures required to mitigate future siltation.
In addition to the design development, D&N were engaged by the ACT Government to undertake a preliminary characterisation assessment to inform the suitability for retaining reclaimed silt on site, with regard to potential contamination.
Our role included a desktop review of the site’s local setting, a review of available chemical testing information and the development of an environmental sampling plan, carried out complementary to and concurrently with geotechnical investigations.
Ten manually excavated boreholes were cored systematically across the area of deposited silt with representative samples collected for chemical analyses.
The analytical results were interpreted against current guidance on the suitability of potentially contaminated soils to be reused in the Territory.
The Jerrabomberra Creek bridge sits nestled against the western approach to the intersection of Canberra Avenue, Ipswich Street and the northbound lanes of the Monaro Highway. Access to the creek bank was limited by the traffic control requirements as well as heavy vegetation growth.
D&N worked with our subcontractors to utilise a small rig, specifically suited for access to restrictive areas.
The Jerrabomberra Creek bridge area is also highly constrained by the presence of critical gas, sewer and communications infrastructure. D&N worked closely with territory and utility representatives to identify, and ultimately avoid critical services.
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