Innovative and sustainability considerations of contaminated materials for embankment construction of Coffs Harbour Bypass Project

This paper presents a case study of innovative and sustainability considerations of contaminated materials for embankment design and construction for the Coffs Harbour Bypass (CHB) project. The first consideration was development of a project specific Sustainability Management Plan (SMP) for CHB project to satisfy the Scope of Works and Technical Criteria (SWTC) requirements. The key themes outlined in the CHB SMP included: 1) climate change resilience; 2) whole of life impact and 3) design optimisation. To efficiently integrate sustainability considerations through all stages of design, relevant themes have been selected and allocated to each individual design package. The main considerations were presented through four case studies of the project regarding the encapsulation cell design for contaminated soils and insitu uncontrolled fill within the CHB project corridor. As the encapsulation cell material includes asbestos contaminated soil and building rubble, conventional construction compaction testing by nuclear densitometer was not considered practical. For this reason, a performance-based material placement and compaction methodology was specified. It is therefore expected that the settlement profile of an embankment containing encapsulation cells will be comparable to that of an embankment constructed wholly from general earth fill. A contaminated soil mound was developed onsite due to an excessive amount of contaminated soil for encapsulation and ease of construction. During construction the mound DCP profiling was introduced to validate the quality of compaction in lieu of plate load testing. The monitoring results of the constructed embankment are within the expectation without any surprises.