3.6 Commentary for coal resource developments that are not modelled


Seven mining proposals identified as additional coal resource developments as at September 2015 were not included in the surface water and/or groundwater modelling due to the unavailability of data required for the modelling. Based on proposal details, the Austar underground, Chain Valley underground and Mount Arthur open-cut developments were considered unlikely to result in significant hydrological change. The non-modelled Mandalong underground, West Muswellbrook open-cut, Wambo underground and Wilpinjong open-cut additional coal resource developments could increase the regional impact.

Mandalong Southern Extension was not included in surface water modelling. Groundwater modelling results indicate an extensive drawdown zone, which intersects drawdown from Wallarah 2. Modelled changes in the Wyong River flow regime caused by groundwater drawdown and consequent reductions in baseflow from the Mandalong Southern Extension and Wallarah 2 developments suggest that potentially significant changes in the flow regimes of Dora, Mannering, Morans, Stockton, Wallarah and Wyee creeks are likely, with potential impacts on associated forested wetlands and wet and dry sclerophyll communities.

The West Muswellbrook Project is a new proposal for two open-cut pits and site facilities, 12 km north-west of Muswellbrook. Its effect on catchment runoff, groundwater drawdown and baseflow would likely compound changes from the nearby additional coal resource developments at Mount Pleasant and Bengalla and baseline developments at Mangoola and Dartbrook. Based on predictions of drawdown from the modelled additional coal resource development, it is likely the West Muswellbrook mine would expand the groundwater zone of potential hydrological change further into Wybong Creek, increasing the potential for impacts on Wybong Creek flow, and contribute to greater reductions in baseflow to the Hunter River and its tributaries, including Dartbrook.

The Wambo underground additional coal resource development proposal comprised three new longwall panels under existing panels. Increases in mine water extraction are estimated at about 54 ML/year. Modelling of drawdowns from the nearby Mount Thorley–Warkworth mine, which has significantly higher pumping rates, suggests that the impact of the additional coal resource development at Wambo will be fairly contained. Some additional hydrological changes at nearby woodland and forested wetland groundwater-dependent ecosystems (GDEs), which are potentially impacted under the baseline, cannot be ruled out.

At Wilpinjong mine, the additional coal resource development would increase the area of existing open-cut pits by 500 ha and develop an eighth pit of approximately 300 ha. It was not included in the groundwater modelling, and although the change in catchment runoff was modelled, the river modelling does not include changes in baseflow. Having regard to the groundwater modelling and site-scale modelling for the bioregional assessment of the Hunter subregion, it is possible that drawdowns due to additional coal resource development could extend towards, and potentially affect baseflow into, the Goulburn River. Wollar Creek – 2 km to the east – could also be affected, given its proximity and that it is potentially affected under the baseline. The potential for some impact on nearby GDEs, at the very least a prolonging of baseline effects due to the 7-year extension to operations under the additional coal resource development proposal, cannot be ruled out.

Last updated:
15 March 2019
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