Client
Kendall Bay
Location
Sydney, New South Wales
Key Services
Sediment Remediation, Construction Quality Control, Remedial Design
Outcome
Once home to the largest manufactured gas plant in the southern hemisphere, Kendall Bay in Sydney is now surrounded by a residential neighbourhood. The goal of the project was the effective cleanup of the impacted sediments at the bottom of the Bay.
As part of a remediation contractor’s design team, Geosyntec was retained to conduct the remedial design, provide on-site construction quality control (CQC) services, and help with the overall technical direction for the cleanup. Remedial components included dredging, capping, in situ stabilisation (ISS), and seawall replacement. Because this project was the first in Australia to use ISS to address subaqueous sediments, a comprehensive treatability and two-phase field pilot study was conducted to demonstrate that the remedy could be successfully implemented and that remedy components could be seamlessly integrated.
Geosyntec began by designing and evaluating a multi-step laboratory treatability study to identify the optimum mix design, grout modifiers, and enhancers to achieve the remedy’s performance criteria. After the treatability studies were complete, we recommended mix designs for ISS in different parts of the Bay. Geosyntec supported the design and implementation of a two-phase field pilot study to commence the mixing equipment, batch plant, and construction approach and to demonstrate effectiveness in the field.
To verify the effectiveness of the ISS field implementation, we developed a validation plan and a framework to specify the field screening and laboratory geotechnical and chemical data. We also oversaw the implementation of the ISS field pilot study to help collect CQC samples and address problems encountered during construction.
Following the successful completion of the ISS field pilot study, Geosyntec continued supporting Ventia on the design of the full-scale remediation. These elements included refining the ISS mix, designing the ISS footprint and thickness, removing surficial debris and sediment along the seawall, and designing a multilayered cap to protect human health and ecological receptors.
Geosyntec oversaw the commencement of the ISS works and provided on-site construction support and troubleshooting and CQC services. Full-scale remediation was completed and, shortly after the completion of ISS and capping works, received regulatory acceptance.
Geosyntec coauthored the Remediation Completion Report that was approved by the regulatory agency. This report demonstrated that ISS can be successfully implemented in subaqueous sediments in Kendall Bay, breaking new ground in the use of advanced technologies in Australia. Our technical arguments allowed for optimisations to the project’s environmental controls, significantly reducing reactive amendment content in the cap layer, resulting in significant cost savings to our client.
This project is the first-to-field implementation of full-scale ISS using subaqueous mass mixing techniques for environmental purposes. The project was completed two months ahead of schedule and under budget. The Kendall Bay project received multiple awards to date, including an Innovation in Sustainability award as part of the 2021 Edison Awards and 2021 Project of the Year in NSW and Sustainable Remediation Project in NSW from the Australian Institute of Project Management.
