Borehole Optimisation System (BOS) – assessing the potential value of urban groundwater in Nottingham
Nigel G. Tait, Ruth M. Davidson, Steve A. Leharne, David N. Lerner
The recognition that urban groundwater is a potentially value resource due to growing pressures on perceived less polluted rural groundwater has led to a requirement to assess the groundwater contamination risk in urban area from industrial contaminants such as chlorinated solvents. The development of a probabilistic risk based management tool that predicts groundwater quality at potential new urban boreholes is beneficial in determining the best sites for future resource development. The Borehole Optimisation System (BOS) is a custom Geographic Information System (GIS) application that has been developed with the objective of locating the optimum locations for new boreholes in urban areas. The system is described in more detail by Tait et al., (2004). This paper applies the BOS model to an urban Triassic Sandstone aquifer in the city centre of Nottingham, UK. The risk of pollution in potential new boreholes from the industrial chlorinated solvent tetrachloroethene (PCE) was assessed for this region. Initially the risk model was validated against contaminant concentrations from 6 actual field boreholes within the study area. In general the model underestimated. A sensitivity analysis indicated that the most responsive model parameters were recharge, effective porosity and contaminant degradation rate. Multiple simulations (>1,300) were then undertaken across the study area in order to create a surface map indicating areas of low PCE concentrations and hence highlighting the best locations to place new boreholes. Result indicate that northeastern, eastern and central regions have the lowest potential PCE concentrations in abstraction groundwater and therefore are the best sites for locating new boreholes. These locations coincide with aquifer areas that are confined by low permeability Mercia Mudstone deposits. Conversely southern and northwestern areas are unconfined and have a shallower depth to groundwater. These studies demonstrate the applicability of BOS as a tool for informing decision makers on the development of urban groundwater resources.
Figure 1 shows surface map of Nottingham city centre indicating areas of low predicted PCE concentration and hence the best locations to site a potential new borehole
Borehole Optimisation System; coupling; GIS; PCE; Probabilistic risk modelling; Urban groundwater
N.G. Tait, R.M. Davidson, S.A. Leharne, D.N. Lerner (In Press) Borehole Optimisation System (BOS) –assessing the potential value of urban groundwater in Nottingham. Journal of Environmental & Modelling Software
N.G. Tait, R.M. Davidson, J.J. Whittaker, S.A. Leharne, D.N. Lerner (2003) Borehole Optimisation System (BOS) – A GIS based risk analysis tool for optimising the use of urban groundwater. Journal of Environmental & Modelling Software, Volume 19, 1111-1124.