Warkworth Mining Limited: Mt Thorley Warkworth
Mining Limited (WML) proposed to extend its Warkworth Mine, near
Singleton in the Hunter Valley. Warkworth Mine was an existing open cut
coal mine with an approved production rate of 18 million tonnes per
annum of Run of Mine coal. An Environmental Assessment (EA) was
prepared to accompany a Project Application for the proposal under New
South Wales Planning Legislation. The proposal was to extend the
approved mining area and continue mining operations for 21 years.
part of the EA, a review of the water impacts was prepared by JP
Environmental to identify and mitigate water impacts that may have
arisen from the proposed development.
Catchment losses, impacts
on local and regional watersheds and the performance of the clean and
dirty water systems were assessed looking out 21 years. The adequacy of
existing and proposed monitoring regimes for operational and compliance
management were examined.
A computer based simulation model was
used to assess the dynamics of the system under conditions of varying
rainfall and groundwater seepage rather than a simple wet and dry year
water balance. The adopted approach provided a probabilistic outcome
addressing varying catchment areas, groundwater seepage or rainfall
runoff accumulations attributed to increasing soil moisture. System
modelling indicated that the site would experience both water shortfalls
and surpluses. Testing of the mine water system against 115 years of
daily rainfall records indicated surpluses could be easily managed by
utilising HRSTS high and flood flow discharge opportunities, and that
the supplementary water sources were adequate to meet any shortfalls.
The project received development approval in 2012.