Wessex Water in conjunction with CH2 MHill and the British Geological Survey (BGS) has recently completed a major 3 year investigation into the resource potential of Aquifer Storage and Recovery (ASR) in a confined Chalk aquifer. The main part of the investigation followed the approach that has been successfully adopted in developing many ASR schemes in America in which the aim is to create a reservoir of potable water within a non-potable aquifer. In the Wessex Water case study it was found that elevated levels of fluoride prevented a potable reservoir being created, even after a 2 year programme of injection and recovery cycles. In terms of strict water quality criteria ASR was deemed unsuccessful. However when modelling the hydraulic response of the aquifer it confirmed that an ASR abstraction regime created little or no environmental impact and offered significant environmental advantages when compared with conventional groundwater development. It has always been assumed that ASR schemes have this inherent environmental advantage, but it is believed that this is the first time these benefits have been clearly demonstrated at a specific ASR site.
The lesson that can be drawn from these results is that environmental acceptability is fundamental to the success of an ASR scheme whereas securing water quality improvements is more likely to be important in determining scheme cost effectiveness. At a time when finding environmentally acceptable resource schemes is becoming increasingly difficult, ASR has a potentially significant advantage over alternative forms of resource development. However, the authors are concerned that because most case studies in England are focusing on water quality issues, these will be viewed as the key success factors for ASR and that its inherent environmental advantages will be overlooked. With most case studies reporting difficulties in meeting water quality objectives this could lead to the general perception that ASR is unlikely to be successful in this country and result in potentially beneficial applications being rejected or not even considered.