Multiple frameworks informing closure criteria at Ranger Mine

Abstract

The Ranger Project Area (RPA), site of Energy Resources of Australia Ltd.’s Ranger Mine, is surrounded by (but separate from) Kakadu National Park (KNP) World Heritage Place and Ramsar wetland. Closure requirements differ for on and off the RPA. The Mirarr Indigenous landowners source food and drinking water up and downstream of the mine and wish to resume these activities on the site after closure. The regulatory Environmental Requirements (ERs) specify that waters and tailings from the mine must not impact the KNP values which includes the local Indigenous culture, health of the local people and the biodiversity and ecological processes of the region. The ERs also state that impacts on the RPA must be as low as reasonably achievable (ALARA). Closure criteria for water and sediment on and off the RPA need to support these diverse values and goals. The ANZG (2018) water quality monitoring framework (WQMF) was used to identify indicators to represent KNP values, human health and biodiversity and derive water and sediment quality criteria to support management of these values. Risk and vulnerability assessments were used, as relevant components in the WQMF, to assess the results of sediment and water quality monitoring and predicted post-closure water quality. ALARA is widely understood and applied to radiation hazards but not chemical hazards. A fourth framework is required to provide information that will be used to assess if impacts on the RPA are ALARA. This paper demonstrates the role of these frameworks in water and sediment closure criteria development at Ranger Mine.