This work for the Coal Authority involved assessing the benefits of remediating three former mining areas. All three sites (two in Scotland, one in England) had previously been used for metal mining. This meant that the mine water discharges, along with any runoff from nearby spoil heaps, had high concentrations of metals such as zinc, lead and cadmium. This metal rich water was affecting water quality and the classification of waterbodies under the Water Framework Directive (WFD).
An assessment was carried out for each site to determine the water quality related benefits of implementing remediation measures such as spoil heap capping and treatment schemes for the mine water discharges. Each assessment considered a range of impact categories including biodiversity and non-use, angling, and recreation (informal and in-stream activities). Expected benefits were monetised where possible through the application of benefit transfer values. Annual values were then discounted to provide the total estimated benefits in present value (PV) format and so enable comparison with the likely costs of the remediation activities.
For all three assessments, sensitivity analysis was used to test the impact on the results of varying assumptions such as the length of waterbody affected, and the use of alternative visit numbers for informal recreation.