b'Education matters measure of revegetation success. Electricalnetworks due to the increased stress and methods such as electrical resistivitybrittle nature of the Formation.imaging (ERI) and frequency domain electromagnetics (FEM) were effective forPrevious literature focuses heavily on the imaging spatial and temporal water tableprimary porosity and permeability of the variations, including a seep from one of theHawkesbury Formation with little regard tailings dams (Dam 3). Ground penetratingfor the influence fracture and associated radar (GPR) effectively imaged the interfacefracture parameters have on subsurface between tailings and the underlyingfluid flow. This is because characterising original soils and found an average tailingsgroundwater flow in fractured rock thickness of ~1.5 m and a maximumaquifers is difficult. However, this study The legacy Royal George mine is atailings thickness of 3.7 m. Seismichighlights the need to better understand historical greisen tin mine located inrefraction tomography effectively imagedhow flow yields are likely to change with northeast Tasmania that was minedthe top of the relatively impermeablechanges to fracture networks.between 1911 and 1922. Closure of theweathered granitic basement but couldThrough the analysis of mechanical Royal George mine was not executednot be used to discriminate tailings fromstratigraphy including bed thickness, in accordance with current mineunderlying granitic regolith. parameters of fracture spacing and closure standards leaving a 270 m longfracture aperture this study focuses on by 35 m deep, steep-sided open cut,From the interpreted thickness of tailings,the calculation of fracture parameters to and a tailings repository retained indepth to basement and prior test pitmodel and characterise reservoir flow six rudimentary dams in an adjacentdata, it is predicted that during periodsproperties. This was achieved through valley. Tailings sediments have elevatedof reduced rainfall, such as the summerboth observational and geophysical concentrations of copper, zinc, lead,months, the water table is beneath theanalysis of sedimentary core holes within cadmium and chromium. Acid andtailing material but during wet periodsa 30km radius around the Tahmoor metalliferous drainage (AMD) flows fromsignificant proportions of the tailings areSouth mine. Examining the observational the tailings repository into St. Pauls River,fully saturated. This hydrological variationfracture spacing and bed thickness of the which was formerly the primary sourcehas important implications for seasonalHawkesbury Formation was subsequently of water for the town of Royal George.variation in AMD production, leachingcompared to the inferred bed thickness The low pH of water from the tailingsand contaminant flow into the St Paulsfrom geophysical gamma logs.together with elevated concentrationsRiver. Time lapse geophysical imaging of copper, zinc, cadmium and aluminiumand surface observations also suggestThe results found that both the fracture exceed ANZECC guidelines and currentlythat there is a time lag between rainfallparameters and fluid flow results align requires provision of potable water forand pooling within the tailings of up towith previous literature. The predicted the township via a communal water tank. two weeks. mean fracture porosity value of 0.012% is Remediation efforts carried out betweenAmy Soper, University of Wollongong:considered insignificant, with fluid flow 2008 and 2019 have been generallyThe characterisation of fracture andbeing predominantly matrix facilitated. The successful in revegetating and stabilisingfluid flow properties of the Hawkesburypredicted average hydraulic conductivity the tailings, however AMD remains anFormation in the Tahmoor region, NSW. of 0.055m/d are in close relation to the issue in some areas on site and for watershydraulic conductivity of 0.041m/d leaving the tailings repository. AMDfrom Tahmoor South. However, further production and mobilisation is likelyinvestigation is required as the relationship due to the continued influx of overlandbetween bed thickness and fracture and groundwater flow into the tailingsspacing did not correlate to the hydraulic repository from the catchment to theconductivity values. With refinement, this south and east. Prior to this study, themodel can be used in future studies to hydrology and hydrogeology of thepredict reservoir flow properties and how tailings repository and surroundingthey are likely to change if stress from catchment was poorly understood. longwall mining occurs.Jared Carl Magyar, Australian National This study employed a range ofUniversity: Geophysical inversion with complementary geophysical techniquesoptimal transport.and time-lapse hydro-geophysical methods to image and detect change inFractures and associated networks canOur state of knowledge of Earth can internal waterflow pathways and assess thesignificantly affect subsurface fluidonly be informed by what we can thickness and structure of tailings in theflow. Subsurface fluid flow is of greatestobserve at the present, and from the Royal George tailings repository. Gammasignificance in rocks with favourablesurface. However, the properties and ray spectroscopy was effective for mappingaquifer characteristics. In this study,events of greatest interest generally the extent of the tailings material whichthe Hawkesbury Formation, a naturalcannot be measured directly with these have elevated U concentrations relative togroundwater reservoir is analysed tofundamental restrictions, whether this the original granite regolith. A normalisedcharacterise fracture networks. Longwallbe due to them being buried at great difference vegetation index (NDVI) mapmining under the Hawkesbury Formation isdepths beneath the surface, or far in the created from multispectral drone imagerycommon in the Southern Sydney Coalfieldspast. By searching for the parameters clearly delineated of the extent of AMDregion, NSW. Therefore, the Hawkesburythat most adequately explain accessible impacted vegetation and thus provided aFormation is subject to altered fractureobservations, a window into the DECEMBER 2021 PREVIEW 42'