A methodology for the assessment of rehabilitation success of post mining landscapes—sediment and radionuclide transport at the former Nabarlek uranium mine, Northern Territory, Australia

• Published in: The Science of the total environment Vol. 354; no. 2; pp. 103 - 119
• Main Authors: Hancock, G.R., Grabham, M.K., Martin, P, Evans, K.G., Bollhöfer, A.
• Format: Journal Article
• Language: English
• Published: Shannon Elsevier B.V 01-02-2006; Elsevier Science
• Subjects: Applied sciences; Earth sciences; Earth, ocean, space; Engineering and environment geology. Geothermics; Environmental Monitoring - methods; Erosion modelling; Exact sciences and technology; Geologic Sediments; Global environmental pollution; Lead Radioisotopes - analysis; Minesite rehabilitation; Mining; Northern Territory; Plants; Pollution; Pollution, environment geology; Potassium Radioisotopes - analysis; Radioactive Waste; Radionuclide transport; Radium - analysis; Rehabilitation assessment; Rivers; Sediment transport; Soil Pollutants, Radioactive - analysis; Uranium - analysis; Water Movements; Water quality; Water Supply; Australia; Northern Territory; Oceania; Australia, Cooper Creek; Erosion modelling; Minesite rehabilitation; Rehabilitation assessment; Radionuclide transport; Water quality; Sediment transport; Uranium ore; Radioactive pollution; Soil erosion; Pollutant behavior; Mobility; Radioisotope; Soil pollution; Sediments; Decontamination; Old mine; Risk assessment; Environment impact; Water pollution; Ecological recovery; Mining industry
• ISSN: 0048-9697; 1879-1026
• DOI: 10.1016/j.scitotenv.2005.01.039

Protection of the environment post-mining is an important issue, especially where runoff and erosion can lead to undesirable material leaving post-mining landscapes and contaminating surrounding land and watercourses. Methods for assessment of the environmental impact and long-term behaviour of post-mining landforms based on scientific methodology are needed especially where field data are absent or poor. An appraisal of the former Nabarlek uranium mine was conducted to assess the site from a soil erosion perspective as part of an independent evaluation of overall rehabilitation success. Determination of the gross erosion occurring, sediment discharge to Cooper Creek and the resultant sediment associated radionuclide load in Cooper Creek were the primary objectives of the study. These objectives were achieved through the application of several models using parameter values collected from the site. The study found that the area containing the mill tailings repository is extremely stable and meets the guidelines established for long-term storage of uranium mill tailings. Most other areas on the site are stable; however there are some areas with a high sediment loss. Sediment concentration in Cooper Creek, which drains the site, was found to be within the Australian water quality guidelines for fresh water, however sediment concentrations in tributaries were found to exceed recommended levels. Radionuclide determinations on soil samples showed that the highest specific activities (Bq kg
−1) were present on a small (0.44 ha) area with a relatively high erosion rate. This small area contributed the majority of the estimated flux to Cooper Creek of uranium-series radionuclides sorbed or structurally incorporated to eroded soil particles sourced from the mine site. This study provides a methodology for assessment of the erosional stability of such a landscape and consequent impact on water quality, using extensive field data and readily available and well known models and methodologies.