2.1.6.10 Vickery Coal Project (ACRD)

Vickery Coal Project will involve recommencing open-cut mining at the former Vickery Coal Mine. The project was approved in 2014, with a maximum extraction rate of 4.5 Mt/year ROM coal, but mining has not yet commenced, as of August 2016. Mining had previously been undertaken at Vickery from 1986 to 1991 as an underground operation, and then from 1991 to 1998 using open-cut mining methods.

In January 2016 the mine owner submitted an application for the Vickery Extension Project. The extension project would involve an extension to the already approved mine footprint and the development of associated mine infrastructure including an on-site coal handling and preparation plant, road diversions and a rail spur and loop. The area of the proposed extension is approximately 970 ha. The extension would increase the rate of coal extraction to 10 Mt/year, with a 25 year mine life. Due to the timing of the application, the project has not been included in the bioregional assessment for the Namoi subregion. As such no further information on the Vickery Extension Project is presented in this section.

2.1.6.10.1 Mine water use

The average total water demand for the Vickery Coal Project is estimated to be 1179 ML/year (Whitehaven Coal Limited, 2013) of which 493 ML/year on average is to be met by licensed extraction from external water sources. The primary water use would be for dust suppression on internal haul roads and at the coal crushing and screening facility. Water would also be required for washdown of mobile equipment and other minor non-potable uses.

The water for operational uses would be accessed from the following sources, listed in order of priority:

The performance of the water management system has been modelled under a series of climate scenarios. Table 29 presents the range of mine water use predictions for these climate scenarios (Evans and Peck, 2013).

Table 29 Modelled mine water use for Vickery Coal Project

MIA = mine infrastructure area

Data: Evans and Peck (2013)

Whitehaven holds a number of Water Access Licences (WALs) for extraction from the Lower Namoi Regulated River water source and the Upper Namoi – zone 4 groundwater sources to meet mine water needs. A total of 1482 ML/year is licensed for extraction, of which 1302 ML is from surface water sources and 180 ML/year from groundwater sources.

Under the NSW Aquifer Interference Policy, licences are required to account for any loss of flow to aquifers resulting from the Project. Resource Strategies Pty Ltd (2013b) indicated the predicted licence requirements for the two groundwater sources predicted to be impacted (Table 30).

Table 30 Predicted licensing requirements to address groundwater interference resulting from the Vickery Coal Project

NA = not available

Data: after Resource Strategies Pty Ltd (2013b)

2.1.6.10.2 Surface water management

The Vickery Coal Project area is drained via unnamed ephemeral drainage lines that rise in the Vickery State Forest and drain in a westerly direction to join Driggle Draggle Creek which, in turn, drains into Barbers Lagoon, an anabranch of the Namoi River. Additionally, a small section of the Vickery Coal Project area drains in a southerly direction to join Stratford Creek, a minor tributary of the Namoi River.

The proposed mine water management system has been designed to segregate mine water, overburden runoff and ‘clean’ runoff from outside the mine. Temporary and permanent up-catchment diversion dams, bunds, and drains would be constructed over the life of the Vickery Coal Project to divert runoff from undisturbed areas around the open-cut and disturbed areas of the site. The maximum harvestable right volume for the mine is 392 ML (Evans and Peck, 2013).

At the point where most of the site drains into Driggle Draggle Creek mean annual runoff would be expected to decrease as a result of the mine footprint covering about 14.5 km² of the catchment. At the completion of mining, the Vickery Coal Project would result in a 4.3% reduction in surface area to the catchment of Driggle Draggle Creek and a 0.01% reduction in the Namoi river basin.

Runoff from disturbed areas of the mine will be drained to a series of sediment basins. From the basins the water would either be used for operational needs on-site or discharged to the environment. Discharges would only occur when the water was at a suitable quality (total suspended solids (TSS) typically 50 milligrams per litre).

The mine water management system has been designed to provide sufficient capacity to store, treat and discharge runoff as required, even in extended periods of above average rainfall. However, in the event that the main mine water storages are near or at capacity, any excess mine water would be retained in the open-cut while runoff collected in the sediment basins would be managed so as to only discharge water of appropriate sediment concentration (Resource Strategies Pty Ltd, 2013a).

Modelling of the operation of the mine water management system for a range of climate scenarios indicates that there is likely to be little requirement to store water within the open-cut for an extended length of time, unless extremely high rainfall occurs during the later stages of mine life. If such a climate sequence occurred, up to 1000 ML of water may be required to be stored within the open-cut for a period of up to two years. This would be achieved by partitioning off sections of the open-cut, as required (Resource Strategies Pty Ltd, 2013a).

2.1.6.10.3 Groundwater management

The Vickery coal resource is hosted by the Maules Creek Formation, within the Maules Creek sub-basin of the lower Permian Bellata Group which is within the porous rock groundwater systems of the Gunnedah Basin. The coal resource is wholly located within the Gunnedah-Oxley Basin Murray–Darling Basin (MDB) Groundwater Source.

The Vickery Coal Project area is effectively encircled by alluvium, including that associated with the Namoi River (to the south, up to approximately 140 m thick) and Driggle Draggle Creek and Stratford Creek surface water drainages (to the north, between 40 to 70 m thick) (Merrick and Alkhatib, 2013). These alluvial sediments are part of the Upper Namoi groundwater management zone 4, Namoi Valley (Keepit Dam to Gins Leap) Groundwater Source.

The mine is located between the Boggabri Thrust fault (approximately 5 km to the west) and the Hunter-Mooki Thrust Fault system (to the east of the mine site). The mine site is intersected by a number of named faults.

Groundwater modelling was used to predict pit inflows to the mine throughout the project life (Merrick and Alkhatib, 2013). The inflow is expected to vary between 110 and 620.5 ML/year during the mine life. Table 31 provides the predicted pit inflows for each year of the mine life (Merrick and Alkhatib, 2013).

It was determined that groundwater contributed baseflow only in: the reach of the Namoi River examined in the model (4 km reach of the Namoi River to the immediate west of the project area); Barbers Lagoon; and the upgradient reach of Driggle Draggle Creek. No change in baseflow is predicted for the latter two reaches, however there is a predicted reduction in baseflow to the 4 km reach of the Namoi River to the immediate west of the Vickery Coal Project area. Baseflow to this reach is expected to decrease by about 5.5 ML/year (0.015 ML/day) from commencement of the project. The analysis of surface water – groundwater interaction presented in Section 2.1.5 found that this reach is generally considered connected, losing. However, that analysis was undertaken at a regional scale, whereas the modelling undertaken for the Vickery Coal Mine was at a local scale.

The equilibrium long-term groundwater inflow to the final mine voids is expected to be about 292 ML/year for the northern void and 219 ML/year for the southern void. Merrick and Alkhatib (2013) estimate that the northern void would reach an average water level of 168.8 mAHD and the southern void would reach an average water level of 146.7 mAHD, approximately 100 years after mining ceases (under current climate scenarios). The equilibrium water levels would be about 90 to 100 m lower than current groundwater levels at the northern void, and about 105 to 115 m lower at the southern void. Both voids would act as permanent groundwater sinks.

Table 31 Predicted pit inflows for the Vickery Coal Mine

Data: Merrick and Alkhatib (2013)