1. British Geological Survey, Kingsley Dunham Centre, Keyworth, Nottingham NG12 5GG, UK
2. British Geological Survey, Maclean Building, Crowmarsh Gifford, Wallingford, Oxon OX10 8BB, UK
3. Independent Consultant, Edinburgh, UK
4. Scottish Water, Heriot Watt Research Park, Riccarton – Avenue North, Edinburgh EH14 4AP, UK