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Response to Submissions

Shenhua Watermark RTS

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Q. Will any areas on the Shenhua Watermark mine site flood?
A. The 100 year Average Recurrence Interval (ARI) design flood event along the Mooki River predicts
a small area at the south-east corner of the Disturbance Boundary will be inundated to a depth
of up to 1.7 metres with flow velocities of less than 0.1 metres per second.

Q. Will this impact the floodplain?
A. Placement of overburden on this small area will not affect flood behaviour on the floodplain;
however, it will reduce the flood storage of the larger Mooki River floodplain by approximately
235 Mega litres.

This represents 2% of the flood storage volume in the northern Native Dog Gully floodplain,
part of the larger Mooki River floodplain, during a 100 Year ARI event. The remaining area along
the Mooki River will be flood free and will not be impacted by the Project.

Q. What is the existing condition of the Mooki River?
A. Baseline water quality monitoring data indicates that the Mooki River is generally safe for recreational and irrigation.  
Aquatic surveys along the Mooki River were conducted as part of the Ecological Impact Assessment for the Project in accordance with The Australia Wide Assessment of River Health: NSW AusRivAS Sampling and Processing Manual. This assessment found (consistent with Thoms et al., 1999) that aquatic habitat along the Mooki River and Native Dog Gully is highly degraded.
 
Q. Is the baseline surface water monitoring data used for the Surface Water Impact Assessment adequate?
A. More than two years of available surface water quality baseline data was utilised in the Surface Water Impact Assessment, as per the DGRs for the Project. Baseline surface water monitoring has continued for the Project with up to four years data now available. The baseline data utilised in the Surface Water Impact Assessment is adequate to characterise the existing surface water environment.
 
Q. What is the mine water management strategy and its basis?
A. The water management strategy for the Project is based on the primary principle of separating water from different sources in terms of water quality. This ensures all water of poor quality that does not meet the adopted water quality criteria is contained on site. Releases are only proposed from OEA runoff following treatment and only then when it meets the agreed adopted water quality criteria. Mine water (i.e. water that has generally come in contact with coal) will not be discharged from the Project and will be preferentially used to meet site water demands
 
Q. What will be the design of the mine water management system and the containment of "mine water"?
A.  "Sediment-laden" water (i.e. surface runoff water from areas that are disturbed by mining operations but not having contacted coal) will be captured in sediment dams and treated to improve water quality prior to release from the site in accordance with discharge locations and criteria specified in the EPL, or returned to the mine water system if the water quality is not suitable for release.

"Mine water" (i.e. water that has generally come in contact with coal) will not be discharged from the Project and will be used to meet site water demands. The mine water management system has been designed to ensure sufficient storage capacity exists to contain all mine-affected runoff. The results of site water balance modelling indicate that there will be no release of "mine water" from the mine site under any rainfall conditions that have been experienced in the area during the past 100 years.
 
Q. What is the potential loss of surface water from the water supply catchment?
A. The assessment of catchment loss has been updated in the RTS to include a number of minor adjustments. These adjustments, based on improved definition of catchment boundaries, reduce the maximum amount of catchment captured in Watermark Gully during mine operations to 14% and reduce the percentage increase in Watermark Gully catchment post mining (from 13% to 9%).
 
Q. Is there more information available on the Watermark Gully flood assessment?
A. A more detailed assessment of impacts on Watermark Gully has now been completed which provides a more accurate description of flood behaviour across the wide flat floodplain in the vicinity of the Kamilaroi Highway. The results of the detailed modelling showed that the flood impacts on the Kamilaroi Highway are negligible (30 to 40 mm).

No mine related infrastructure is proposed within the 100 year ARI flood extent of Watermark Gully.
 
Q. What is the requirement, source and availability for supplementary water supply from offsite?
A. The maximum external make-up water supply (600 ML/annum or 19 L/s) has been demonstrated to be obtained from existing or proposed bores on Shenhua Watermark owned land, subject to appropriate water licensing. Very little of the offsite water requirement can be obtained from the Mooki River, due to the Mooki River generally being dry at the times when offsite water is required. 
 
Q. What are the results of the salt balance assessment for the Project?
The modelling results show that the total average salt load released offsite in surface runoff is not significantly increased by the Project. The maximum total average salt load occurs in Year 30 of the Project and represents an approximate 1% increase over the pre-mine salt load for that year.

Native Dog Gully has high salinity under existing conditions and may contribute to a small observed increase in Mooki River salinity downstream of Native Dog Gully.
 
Q. What are the results of the refined assessment of final void behaviour between the surface water and groundwater models? 
A. The refined assessment of the surface water and groundwater models on the final void behaviour shows both models predict a long term equilibrium water level in the open void of about 280 m AHD. Both models do confirm freeboard of about 40 m indicating the final void will not overflow.

The open void will remain a permanent sink for groundwater flow and the saline water that will develop within the void lake will not be able to flow to the adjacent alluvial aquifers.
 
Q. What are the potential cumulative impacts of the Project on surface water resources? 
A. In regard to cumulative impacts on water supply, any use of water from the Mooki River, whether it be for industrial or agricultural use is managed through the relevant water sharing plan, however very little of the offsite water requirement can be obtained from the Mooki River due to the Mooki River generally being dry at the times when offsite water is required. The water sharing plan has considered the cumulative impacts of all water uses in the catchment to ensure the environmental needs of the catchment are satisfied. The Project will comply with the provisions of this plan to ensure that any cumulative impacts are adequately addressed.

As mentioned earlier, the maximum external make-up water supply (600 ML/annum or 19 L/s) has been demonstrated to be obtained from existing or proposed bores on Shenhua Watermark owned land, subject to appropriate water licensing.  
 
Q. Where will Shenhua Watermark get the water required during dry years?

A. Shenhua Watermark proposes to access water from nearby available water sources under
appropriate Shenhua owned water access licences or private commercial arrangements
with holders of appropriate water access licences.

Q. Will the Shenhua Watermark Project impact on surrounding catchment flows?
A. During the life of the Project, there is a reduction of catchment flows to surrounding waterways,
including the Mooki River, Watermark Gully, Native Dog Gully and Lake Goran. At the completion
of mining, surface runoff from rehabilitated OEAs will be released offsite which will lead to an
increase in the catchment area draining to the Mooki River, Watermark Gully and Native Dog
Gully.

 

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