Richmond Hill Mine Heap Leach Pad Cover System Evaluation
Location
South Dakota
Client
Barrick Gold Corporation
Project Description
GSA conducted a seepage analysis and drainage modeling study on three closed gold heap leach pads to determine long-term drainage rates and closure cover system performance based on 20 years of post-closure monitoring data. To evaluate the cover system efficiency, a monthly time-step, spreadsheet-based water balance model was created. The model considers the inter-relations between precipitation, evapotranspiration, and cover system net infiltration on a monthly scale with continuous feedback of water movement in the soil-plant-atmosphere continuum. The model accurately reproduced the recorded seepage rates over the monitoring period. Model results and observed seasonal seepage rates indicated that increased HLP drainage rates observed several years after the cover system installation can be attributed to pedogenic processes with subsequent equilibrium conditions achieved 10 years after closure.
Project Highlights
- Determine long-term drainage rates and closure cover system performance on three closed heap leach pads.
- Develop spreadsheet-based water balance model to consider precipitation, ET, and cover system net infiltration
- Model accurately reproduced the recorded seepage rates for the monitoring period
- Model allowed comparison of the cover system performance with design criteria and identified changes due to pedogenic processes
