Discussion of ‘Estimating water pollution risks arising from road and railway accidents’ by R.F. Lacey &J.A. Cole Quarterly Journal of Engineering Geologyand Hydrogeology , Vol. 36, 185–192

Abstract

T.C. Atkinson writes: Highway drainage has long been recognized as a hazard to groundwater abstractions ( e.g. Atkinson & Smith 1974; Price et al . 1992; Hiscock et al . 1995). Lacey & Cole (2003) have performed a valuable service by setting out clearly the methods and data sources from which the risk of a spillage from road or rail tankers can be estimated. Their road example indicates a frequency of about one spill in 740 years per km of trunk road outside built-up areas. Expressed in this way, as an average recurrence interval between spills on a short section of road, spillages may seem comfortingly rare (although Lacey & Cole do not say this). A casual reader might draw the conclusion that traffic on highways in general presents only moderate risks of contaminating water supplies. This is misleading because Lacey & Cole present only the annual risk , i.e. the probability that a spillage might occur in any period of one year. For water supplies it is better to consider the total risk over the whole period in which the hazard might exist. Because roads and railways can be expected to continue in use for decades or even for over a century, the overall risk of a spillage occurring during their lifetime …