New materials and methods for placement of a thin layer cap on contaminated seabed

The Norwegian Ministry of the Environment identified remediation of contaminated sediments as important. The total release of contaminants to the fjord environment from larger areas with moderate contaminant levels can be greater than that from smaller ar eas with higher contaminant concentrations. As a result, environmental authorities have published plans for remediation including plans to cap large seabed areas (>1 km2). The experience with remediation of areas > 1 km2 is, however, non-existing in Norwa y and very limited internationally. Gaps of knowledge, about the placement technology, thin cap efficiency and secondary effects of cap materials, are currently limiting development and deployment of this technology. In order to increase the knowledge on this subject, the proposed project will include the following research tasks: Technology for cost-effective placement of different materials forming thin caps WP1: The effect of different placement techniques and different materials on the distribution o f the material on the seabed will be studied in model experiments and by computer models and during the field test. Effect of thin caps on water and sediment chemical quality WP2: Micro- and mesocosm tests will be used to study the efficiency of thin ca ps in the laboratory. State of the art techniques developed at NGI will be used to monitor the effect of thin capping on water chemistry during field tests. Secondary ecological effects of thin caps WP3: Documentation of benthic communities before and a fter thin capping will be used to show how the ecosystem is improved or deteriorated, and to what extent the newly established benthic ecosystem deviates from the original one. Rates of recolonization as well as changes in nutrient and oxygen cycling will also be monitored.