Uncovering potential impacts

The model development involved updating the previous model generated for the site to MODFLOW SURFACT.

This steady state model was then used to assess operational constraints (water levels in the pits) to see if there were potential impacts to the surrounding groundwater regime.

Support for modelling and monitoring

Groundwater modelling was used to estimate changes in the groundwater regime from dewatering activities, particularly in relation to existing groundwater users and nearby baseflow fed streams.

Since this time, we have continued to assist with operational work at Cadia including validating and updating the groundwater model and installing a regional monitoring network.

Comprehensive investigation program

We designed an investigation program to gain an understanding of pit dewatering issues and options.

Our fieldwork included test pumping trials and to determine dewatering requirements for the proposed mine development. The work was also used to support the submission to the Department of Water – Western Australia as part of the project approvals process.

Ongoing support through monitoring and approvals

Once conditional approval of the mining lease was granted, we were engaged to support the make good agreement with a nearby stakeholder. We conducted field investigations including the design, installation and testing of a groundwater monitoring network to validate the numerical model predictions and assumptions. This resulted in the successful negotiation of the make good agreement between our client and the external stakeholder.

Separate to this work, we managed the baseline data collection for the site. We conducted routine monthly groundwater monitoring over 12 months to finalise the draft Environmental Authority conditions relating to the development of groundwater trigger levels. The baseline data collection and trigger levels were also used to support the formulation of a Groundwater Monitoring and Management Plan to satisfy state and federal approval conditions. We provided further assistance in liaising with the state and commonwealth to ensure approval of the document.

Our work for U&D Mining has continued through the approval process and we have recently been engaged to assist in securing a groundwater supply for construction purposes and early stages of mine development.

Meeting environmental approval commitments

We supported Yancoal across a range of hydrogeological services, including:

• monitoring groundwater levels and quality
• reporting regulatory compliance (2015 to present)
• undertaking field activities including bore census, monitoring network review and upgrade, monitoring bore installation and hydraulic testing
• updating the groundwater flow model (MODFLOW-USG) to improve inflow and water take partitioning predictions
  preparing groundwater aspects of extraction plans and risk assessment
• preparing end of longwall panel reports for regulatory compliance.

We’ve worked with Yancoal to improve the efficiency of systems for groundwater data collection and storage to ensure environmental approval commitments are met.

Services we’ve delivered

Work to date has included:

• developing and updating a sub-regional groundwater model for the purposes of water licensing and impact assessment
• designing and installing groundwater monitoring networks
• reviewing data collected from monitoring networks and assessing triggers levels
• providing estimates of the water level and quality of water within the residual open cut final void
• reviewing the performance of the sites water supply borefield
• assisting with dewatering strategies for the deep open cut mine.

We have also been involved with the satellite Mt Margaret Mine and Monakoff sites conducting borefield performance review reports, final void assessments and trigger level compliance.

Services we delivered

The groundwater impact assessment involved:

• development of a field investigation (i.e. bore installation, testing and monitoring)
• review of historic data in order to gain an in-depth understanding of the hydrogeological regime
• development of the conceptual groundwater model
• development of a numerical groundwater model to simulate natural groundwater processes and replicate system stresses to predict potential changes due to the project.

Following this project, South 32 Limited engaged us directly to supervise the drilling and installation of production bores for the purposes of water supply.

The field program had a project schedule that required rapid mobilisation and 24 hour shifts. The work also included constant rate pumping tests and analysis of the results to determine yield. As one of Australia’s largest specialist groundwater consultants, we were able to provide the necessary staff and support they required for this project.

Upgrading the groundwater monitoring network

Part of this work has included a groundwater impact assessment for Resource Strategies on behalf of Hunter Valley Energy Coal Pty Ltd.

In addition, we have been engaged directly by Mt Arthur Coal to plan and implement an upgrade to the existing groundwater monitoring network. This includes vibrating wire piezometer and monitoring bore installation, hydraulic testing and bore remediation works.

We have also completed routine reporting to address conditions of mine approval, which includes annual groundwater reviews and trigger investigations.

Outcomes we delivered

The outcomes included:

• quantification of groundwater take from the Great Artesian Basin water resource plan, for licensing purposes
• predicted changes in water levels in the various aquifers
• assessment of impacts on key receptors, including private landholder bores.

We were subsequently engaged to update the groundwater impact assessment to include cumulative impacts from emergent coal seam gas operations.