The Høfde 42 pesticide waste disposal site is recognized as the most toxic contaminated site in Denmark. Between 1953 and 1962, the agrichemical manufacturing company Cheminova, with approval of Danish authorities, disposed of hundreds of tons of organophosphorus pesticide (OPP) and pesticide manufacturing wastes in pits at this site, which is located at a beach adjacent to the North Sea. A remedial feasibility study completed by the Danish government determined that in situ alkaline hydrolysis (ISAH) is the most cost effective technology for remediating groundwater and the residual wastes at the site. The Danish government, with funding by the European Union Life Program, selected the team of Geosyntec, COWI A/S, Tufts University, Nasus Water, and the University of Aalborg to conduct three pilot tests to compare three techniques for optimizing pesticide treatment by ISAH: 1) groundwater recirculation; 2) surfactant-enhanced flushing; and 3) acoustic vibration. In all three, tests a primary challenge is to inject strong base [caustic, or sodium hydroxide (NaOH)] to the in situ treatment zone while minimizing exposure of site workers to NaOH and pesticides.
