2.6.2.5 Implementation of the coal resource development pathway

Summary

Groundwater modelling is undertaken for 12 coal resource development pathway mines and 1 coal seam gas development, comprising 5 baseline mines and 8 additional coal resource developments. The Caroona Coal Project is included in the modelling of the coal resource development pathway based on the information available at the time of commencement of the bioregional assessment work. However, the latest available information is that this mining project is cancelled and the impact predictions provided in this report are redundant. One baseline and two additional coal resource developments were not modelled due to lack of data or scale of proposed change.

The spatial extent of each mine working is represented in the model by its footprint and varies through time. Each working is associated with a coal seam, which defines its depth. Footprints were obtained from a number of sources. Each development is included in the model as a head-dependent boundary which results in the water produced being dependent upon the model parameters rather than an imposed stress.

Hydraulic enhancement above longwall mines is implemented over the mine footprint and the change is assumed to be permanent. The magnitude of and depths over which hydraulic enhancement occur is uncertain and the parameters that govern these terms are varied in the uncertainty analysis.

Baseline coal mines and additional coal resource development were defined in Section 2.3.4 of companion product 2.3 for the Namoi subregion (Herr et al., 2018) and are summarised in Table 8 and shown in Figure 16. The baseline includes six coal mines; the additional coal resource development includes nine coal mines and one coal seam gas (CSG) development. Due to insufficient data or insignificant changes in mine pumping rates from additional coal resource development, two coal mines in the additional coal resource development were not included in the groundwater modelling. Of the baseline coal mines, Werris Creek Mine is not modelled because it belongs to a geologically separate basin (Werrie Basin). For the 12 modelled mines and 1 CSG development, each has to be defined in terms of its location, type of operation (open-cut, underground or CSG), area, depth (seam) and depth of excavation. A few parameters also need to be defined to characterise changes in the hydraulic conductivity of units above and below the mine workings as a consequence of mining. For the one CSG development, the spatial extent, target formation depth and proposed depressurisation need to be defined.

Table 8 Summary of developments modelled under the baseline and coal resource development pathway (CRDP)

Name	Development	Modelled in baseline	Modelled in CRDP	Start	Finish
Boggabri Coal Mine	Open-cut coal mine	Yes	Yes	2006	2012
Narrabri North Mine	Underground coal mine (longwall mining)	Yes	Yes	2010	2035
Rocglen Mine	Open-cut coal mine	Yes	Yes	2009	2019
Sunnyside Mine	Open-cut coal mine	Yes	Yes	2008	2012
Tarrawonga Mine	Open-cut coal mine	Yes	Yes	2006	2012
Werris Creek Mine^a	Open-cut coal mine	No	No	2005	2020
Boggabri Coal Expansion Project	Open-cut coal mine	No	Yes	2013	2033
Caroona Coal Project	Underground coal mine (longwall mining)	No	Yes	2020	2045
Gunnedah Precinct^b	Open-cut and underground coal mine	No	No	unknown	unknown
Maules Creek Mine	Open-cut coal mine	No	Yes	2015	2035
Narrabri South	Underground coal mine (longwall mining)	No	Yes	2030	2054
Watermark Coal Project	Open-cut coal mine	No	Yes	2018	2047
Tarrawonga Coal Expansion Project	Open-cut coal mine	No	Yes	2015	2031
Vickery Coal Project	Open-cut coal mine	No	Yes	2018	2047
Vickery South Coal Project^b	Open-cut coal mine	No	No	unknown	unknown
Narrabri Gas Project	CSG	No	Yes	2017	2042