The Nagambie Mine site has two water-filled legacy open pits (the East Pit and West Pit). Gold ore was mioned from these pits between 1989 and 1995. Nagambie Resources proposes to rehabilitate these pits by backfilling them with suitable material and revegetating the resultant surface.
Nagambie Resources has an approved Environmental Management Plan for the placement of potential acid sulfate soil (PASS) in the West Pit as part of its permitted rehabilitation. PASS is a naturally occurring material that exists approximately 30m underground beneath Melbourne. When this material is excavated and exposed to air and water, as will occur during the construction of some of Victoria’s Big Build Projects, it can oxidise over time and become actual acid sulfate soil (ASS). ASS will generate an acidic discharge that can be harmful to the environment. If excavated and stored underwater, the PASS cannot oxide and generate acid. Underwater storage of excavated PASS is the most preferred use of PASS in accordance with EPA’s Waste Hierarchy.
During the construction of other Victorian Government Big Build Projects such as the Metro Rail Project and Level Crossing Removal Projects, PASS material has been disposed of in gullies and undulations within landfill sites located in and around the western suburbs of Melbourne. Although this is likely to be the least cost option for government appointed construction contractors, it is not the most environmentally preferred management option. This PASS management practise also exhausts suitable land for future engineered landfills which should be reserved for waste that cannot be sent anywhere else.
Commencing in early to mid 2024, the North East Link Project is likely to generate over 7 million tonnes of PASS material. NRL has submitted quotes to the construction consortium to receive some of this PASS material and is actively promoting the benefits of PASS management at the Nagambie Mine. The pits at the Nagambie Mine are the ideal location for the environmentally leading management of PASS.
Conceptual process of excavating, transporting and placing PASS into the West Pit at the Nagambie Mine.