Investigation of the sediments in the foretunnels at the Muskö Naval Base

FOI and the Swedish Geological Survey (SGU) have jointly conducted an environmental impact investigation at the Muskö Naval Base regarding contaminated sites, remediation and the economical consequences of such actions. The investigation was performed within a comprehensive environmental project aiming at assessing the need for remediation plans when it comes to contaminated sites (soil, groundwater, surface water and sediment), should the enterprise be discontinued. A screening survey of the sediments in the foretunnels at the Muskö Naval Base, carried out in May 2000, concluded that the sediments in part contained high levels of PCBs and heavy metals. A complementary sediment investigation was therefore conducted in September 2001. The results showed that the sediments are likely to contain high or very high levels of heavy metals, mainly mercury and copper, PCBs and organo tin compounds (TBT, MBT, DBT). An environmental risk assessment was then performed in accordance with the Swedish EPA Method MIFO. Guided by the results, mainly the presence of high levels of pollutants such as organo tin compounds, the investigated objects (the foretunnels to the Docks 1 to 3 and Risdal) are classified as Risk Level 1, i.e. the sites require remediation and the sediments must be removed and handled elsewhere. The report also suggests how to proceed with such actions.