Defence Site Maribyrnong, located 10km NW of Melbourne’s CBD, served as a major explosives and munitions manufacturing facility and research centre for various agencies within the Department of Defence from 1908 until its closure in 2000. The site covers a total of 127 hectares and incorporates over 500 individual buildings and around 170km of underground utilities. The risk of latent explosive residues in building fabrics and aged site infrastructure such as wastewater pipelines and culverts is an identified hazard for organisations working in and around the Maribyrnong site. To support the quantification and mitigation of this risk, Defence commissioned OPEC to work with CH2M Hill to prepare a detailed explosives survey of the site. OPEC supported CH2M Hill’s US explosives assessment team to conduct an investigation on a representative sample of the Explosives Factory Maribyrnong buildings and infrastructure to determine the residual explosive risks remaining on the site. The works involved supporting the explosives assessment teams and moving in advance of these teams to prepare work areas, check for potential asbestos, lead and biological contamination and identify any safety hazards or structural integrity issues within buildings. The works involved visual and Exspray testing of the buildings’ fabrics across of a selected sample of potential high risk sites. Explosive residues, when encountered, were identified and neutralised. Additional functions included the provision of height access equipment, shoring works, the removal of heavy machinery to provide access to sub-floor areas and waste removal and segregation tasks. OPEC undertook the logging and analysis of individual test results and supported the development of recommendations and strategies to support the remediation of impacted sites. With a combination of explosive, biological, asbestos, lead and general safety related hazards associated with dilapidated infrastructure the Explosives Factory assessment project provided an ideal forum for OPEC to apply its key operational strength which is the safe management of complex overlapping risks.