The United Wambo Project is a proposed open-cut coal mine at the existing United Mine and Wambo Mine operations, located approximately 15 km west of Singleton, New South Wales. The project occurs within the Sydney Basin and targets the Wittingham Coal Measures. AGE were engaged by Environmental Impact Assessment consultants Umwelt, on behalf of the project joint venture between United Mine, owned by Glencore and Construction, Forestry, Mining, and Energy Union, and Wambo Mine, operated by Wambo Coal Pty Ltd, a subsidiary of Peabody Energy Australia Pty Ltd.
AGE were engaged to complete a groundwater impact assessment to form part of the Environmental Impact Statement. The groundwater impact assessment involved review of historic data and field studies in order to gain an in-depth understanding of the hydrogeological regime for development of the conceptual groundwater model. The project is located in an area with rich coal resources and a long mining history on surrounding lands. Representing the cumulative impacts from previous mining and surrounding mines posed a significant challenge for the project. An extensive data review process was undertaken consolidating disparate data sources in one database. This was used to develop the conceptual model and an extensive numerical model across an area of 640 km2. The model also represented geological detail, its 34 layers, being the most detailed regional model developed within the Hunter Valley to date.
This detail allowed the many complex mine plans for open-cut and underground operations within the Whittingham Coal Measures to be represented within the model. This complexity in the model was possible with the use of MODFLOW-USG model code that allowed flexibility in the model layers and mesh structure. The magnitude of the predictions were supported through uncertainty analysis to assist the decision making process.
The outcomes of the modelling included:
- quantification of groundwater take from the Hunter Unregulated, Hunter Regulated and North Coast
- Fractured and Porous Rock water sources, for licensing purposes;
- predicted changes in water levels in the various aquifers, as well as the Hunter River and Wollombi Brook; and
- assessment of impacts on key receptors, including private landholder bores and groundwater dependent ecosystems.