Characterisation of fractured rock aquifers for ASR in Adelaide

R R Martin[1] and D Baldwin[2]

[1] Sinclair Knight Merz, Level 5, 33 King William St, Adelaide ,SA 5000 (E-mail: rmatin@skm.com.au)
[2] City of Tea Tree Gully, 571 Montague Road, Modbury, SA 5092

Abstract: ASR in fractured rock aquifers presents a number of added risks. Aquifer hydraulic properties can vary by orders of magnitude over very short distances because of fracture connectivity. Regulatory authorities are hesitant about licensing ASR schemes in fractured rock because of the potential for any contaminant to move beyond the capture zone because of the large induced hydraulic heads during recharge.  The potentially lower recovery efficiency and higher level of investigation makes fractured rock ASR schemes potentially less economically viable. These, amongst many other uncertainties, makes fractured rock aquifers less desirable for ASR than sedimentary or kast aquifer systems. Although, fractured rock aquifers are more complex to characterise in terms of permeability, structure and storativity, there are a number of sites operating quite successfully across Adelaide.  Characterisation of fractured rock aquifers requires multiple investigative approaches including geophysical methods, in particular the acoustic televiewer, coupled with numerical groundwater models, hydrogeochemical characterisation and various field testing programs to reduce the uncertainty and risks associated with targeting a fractured rock aquifer system for ASR. Additionally, without the detailed supporting studies it is difficult to obtain the necessary operating licences. This paper presents the approaches and finding from four fractured rock ASR sites in Adelaide, South Australia.