1. Department of Environmental Technology, Norwegian Geotechnical Institute, 0806 Oslo, Norway
2. Department of Civil and Environmental Engineering, Stanford University, Stanford, California USA 94305-4020
3. Department of Plant and Environmental Sciences, University of Life Sciences, Ås, Norway
4. Department of Applied Environmental Sciences, Stockholm University, 10691 Stockholm, Sweden
5. Department of Geosciences, University of Oslo, 0316 Oslo, Norway