Since the issuance of EL 7223, some stakeholders expressed concern about the potential groundwater impacts of the Project. Shenhua Watermark listened to these concerns and recognised from an early stage the importance of obtaining extensive baseline data, characterising the groundwater regime in the Project Boundary and developing an accurate groundwater model to assess any potential impacts.
The Groundwater Impact Assessment for the EIS is based on the results of a comprehensive field investigation program, one of the most extensive ever conducted for a coal mining EIS in the Gunnedah Basin of NSW. This has resulted in an extensive groundwater baseline data set being collected (minimum of two years data was included in the Groundwater Impact Assessment) and over 24,200 samples being analysed
The groundwater model grid covered an area of 6,825 km2 and was approximately 75 km in width (east to west) and 91 km in length (north to south). The groundwater model developed for the Project is the largest completed for mining developments in the Gunnedah Basin. The extent of the groundwater model area was developed to minimise any modelling boundary effects within the immediate surrounds of the Project and to encapsulate the Liverpool Ranges, which are one of the primary recharge sources for the Upper Namoi alluvium.
The groundwater model was calibrated via two processes; a steady state calibration and a transient calibration. The aim of the calibration process was to adjust aquifer parameters and stresses to produce the best match between the observed and simulated water levels and fluxes. This ensures that the groundwater model accurately represents existing conditions in the region.
The calibration of the model followed the objectives set out in the Australian Groundwater Modelling Guidelines by Barnett et al. (2012). The groundwater model was calibrated to data over a 31.5 year period (with time variant readings), including 44,226 water levels in 445 monitoring bores within the Permian and alluvial aquifers throughout the groundwater model domain.
A sensitivity analysis of the groundwater model was conducted by adjusting individual parameters and assessing the impacts on predictions accordingly. A more complex statistical Monte Carlo uncertainty analysis of the groundwater model was also undertaken whereby all parameters in the model were adjusted randomly, within realistic ranges to further assess the range of potential mining impacts. The uncertainty analysis undertaken is the only known application of this type of analysis to a coal mining project within NSW and is considered to leading best practice.
An independent Peer Review of the Groundwater Impact Assessment was undertaken by Heritage Computing in accordance with the Murray-Darling Basin Commission’s (MDBC’s) Australian Flow Modelling Guideline (MDBC 2001) and the Australian Groundwater Modelling Guidelines (Barnett et al 2012). The Peer Review concluded that the "groundwater model has been developed competently and is regarded as "fit for purpose" for addressing the potential environmental impacts from the three open cut mining areas and for estimating indicative dewatering rates. The stated objectives of the modelling study have been addressed satisfactorily."
Q. Will the mine impact the Gunnedah Formation that is used by the local farmers for irrigation?
A. Extensive mapping and geophysical surveys have confirmed that the Gunnedah Formation does
not exist within the Project Area. The closest occurrence of this aquifer is more than 900 metres
from the north-eastern corner of the Eastern Mining Area and more than 1.3 km to the south of
the Project Disturbance Boundary. This buffer prevents the direct connection of water between
the Gunnedah Formation aquifier and mining areas.
Q. Will there be groundwater seepage into the Shenhua Watermark mining areas?
A. The groundwater model predicts the groundwater seepage from the Permian Formations into
the mining areas will average at 0.5 ML/per day (183 ML/year) over the life of the Project.
Q. What volume does the groundwater model predict will be removed from the water sharing
plan zones and how does this compare to an average agricultural bore?
A.The groundwater model predicts that the volume of water removed from Zones 3, 7 and 8 of the
Water Sharing Plan for the Upper and Lower Namoi Groundwater Sources 2003 combined
due to mining is 35.7 ML per annum on average. This is a negligible quantity of water being
equivalent to about 25% of the average pumping rate of 142 ML per annum from a single
licenced agricultural bore in the Upper Namoi Alluvium within 10km from the Project Boundary.
Q. Will any bores surrounding the Project site experience a reduction in water level
because of the Shenhua Watermark Project?
A. Within 10 km of the Project Boundary, 35 bores are predicted to experience maximum
groundwater level reductions of greater than or equal to 0.1 m. Of these, four bores adjacent
to the Southern Mining Area have a maximum predicted drawdown between 1.0 m and 1.4 m.
These predicted groundwater level reductions are below the minimal harm criteria of 2 m
as defined in the Aquifer Interference Policy.
Q. Will the groundwater levels recover over time?
A. Yes. Modelling indicates that the groundwater levels begin to recover after the
Eastern Mining Area and Southern Mining Area are backfilled and eventually exceed pre-mining
levels. This is due to a higher recharge rate on the overburden material than the
Q. Will water from the Western Mining Area final void spill into
A. No. The predicted groundwater levels within the Western Mining Area final void will remain
below the regional water table by approximately 1-2 m, indicating the pit lake void will act as a
groundwater sink, not a source. The water level in the final void will therefore stabilise below
the crest of the open cut mining area, and overland spillage of water into the environment is
predicted not to occur.
Q. Was the baseline groundwater monitoring data used for the Groundwater Impact Assessment adequate?
A.The baseline groundwater data collection program for the Project is considered best practice and more than adequate for the purposes of the EIS as:
• A highly experienced hydrogeologist was employed as part of the Shenhua Watermark Project Team to guide the collection of hydrogeology data as part of the exploration program. The collection of hydrogeology data as part of the exploration program was not required by government guidelines at the time, but now is a requirement of all new exploration licences and considered best practice;
• 103 groundwater monitoring bores were installed across the Project Boundary monitoring a total of 128 discrete intervals, many more than other greenfield projects; and
• The groundwater monitoring program has now collected up to four years baseline data (with a minimum of two years baseline data collected in all groundwater monitoring sites) and analysed over 24,000 samples. This meets the requirements of the NSW Aquifer Interference Policy.
Q. Will there be an impact on the surrounding resources in the alluvial aquifers from the backfilled Southern and Eastern Mining areas?
A. All aquifers within the Project Boundary have an existing salt concentration of equal to or significantly greater than (in some aquifers over 10 times) the salinity potentially produced from the Overburden Emplacement Areas (OEAs). Therefore it is unlikely that the increased rate of flow of groundwater from the backfilled mining areas will influence the beneficial use of the alluvial aquifers, including the Gunnedah Formation. Therefore, seepage from the OEAs will have a negligible impact on surrounding groundwater resources.
Q. What is the potential that the seepage zones around the backfilled Southern and Eastern Mining areas will contribute to additional salt load?
A. The results of Project geochemical testing show that leachate generated by the overburden / interburden water quality will have a low salinity similar or lower than already exists in the proposed mining areas. The Groundwater Impact Assessment demonstrates it is unlikely that the salinity of the seepage zones will contribute any additional salt load to Native Dog Gully or the Mooki River than already occurs from the existing soil landscapes.
Q. Have the cumulative impacts identified in the Namoi Water Study been considered in the EIS?
A. At the time that the Groundwater Impact Assessment was prepared, there were no other proposals in the public domain for any coal mining or coal seam gas projects in the locality surrounding the Project. The exhibited EIS provides all the necessary information for future proponents to conduct a cumulative impact assessment by that proponent at the relevant time.
Q. What monitoring of private bores will be undertaken?
A. If requested by the landowner, Shenhua Watermark will monitor any licensed private bores that are predicted to have a drawdown of greater than 0.25 m as a result of the Project, to validate the level of impacts predicted in the Groundwater Impact Assessment.
Q. Has Shenhua Watermark secured all the water licences for the predicted use of water due to the Project?
A. Shenhua Watermark will ensure that appropriate water licences are progressively sought and held for the Project, in accordance with the rules of the relevant water sharing plans. Shenhua Watermark has already obtained all of the necessary licences to cover any water use due to the Project (up to Year 20) from the Gunnedah-Oxley Basin Murray-Darling Basin porous rock groundwater source, Groundwater Management Zone 7 and Groundwater Management Zone 8. Shenhua Watermark only needs to acquire 1.2 units of Groundwater Management Zone 3 licences to cover water take due to the Project up to Year 20, which are readily available on the open market.
Q. Will a Water Management Plan be prepared?
A. Upon receipt of approval, Shenhua Watermark will develop a Water Management Plan in accordance with any conditions of development consent and in consultation with relevant stakeholders