During 1981 PCB was found at the river mouth of river Emån. The main source of PCB was traced to Lake Järnsjön.
Lake Järnsjön is a small lake situated about 10 kilometres downstream a paper-mill that earlier handled the recycling of waste paper containing PCBs. Large quantities of PCB-contaminated fibres have been discharged from the paper-mill through the years, and large quantities were accumulated in lake Järnsjön. Studies have shown that the sediments in Järnsjön was the dominating source of PCB in the river system. Approximately 1 kg of PCB reached Järnsjön from upstream areas, but approximately 7 kg of PCB left the sediment every year. Based on this yearly discharge, the 400 kg PCB in the sediments would cause biological problems for many years in the river system.
The Emån river system is considered to be one of the most valuable water courses in Sweden. The Emå river and its valley are of national interest for nature preservation-, cultural history- and outdoor recreation reasons. The river has a very high diversity of fish species, and is best known for its population of European catfish (Siluris glanis) and fast growing sea trout (Salmo trutta). Another zoological value is otter (Lutra lutra). Some parts of the river have very well developed meander systems. For these reasons a remediation had to be carried out very carefully.
About five years ago the municipality of Hultsfred was assigned the task of managing a remediation project of lake Järnsjön. The preparations for the remedial action included e.g. project design, collecting more data of the situation in the river and the lake and a prequalifying of possible actors that would be interested in doing the work. After discussing several alternatives we chose to use a horizontal auger suction dredger specially designed to minimize leakage. The PCB in the lake wasn´t evenly distributed in the sediments, the eastern part contained about 80% of the total amount of PCB. Therefore we enclosed this part with a silt curtain in order to reduce leakage and thereby reduce the impact on the river system.
Dredging started with the eastern part in the beginning of June 1993 and finished early December. Dredging was stopped during the coldest part of the year and during the springflood. During 1994 dredging went on between May and the beginning of September. As a total about 147 000 m3 of sediment were dredged, dewatered and landfilled.
The dredging has been followed by an extensive environmental control program.
Measurements The PCB concentration in the outlet of lake Järnsjön during dredging was not significantly higher than concentrations measured at investigations preceeding the remedial action.
Turbidity - was measured upstream and downstream lake Järnsjön. It was measured to get a quick answer about the water quality downstream the remediation area. Turbidity was on an average about 2 NTU which is very low compared to the 5 NTU allowed by the authorities.
Suspended solids were measured as daily mean values at the dewatering plant and at one upstream station and one downstream station. The only problems we encountered were in the late fall of 1993 at the dewatering plant when temperatures were below zero.
Content of total solids in dewatered sediments varied between 30 and 36 % which was enough to certify the geotechnical stability of the landfill.
Phosphorous and Nitrogen, one sample per week. No effect could be measured on water quality concerning nutrients.
Biological effects - were studied in a special program.
Costs
The total cost of this remediation, including costs for enhanced environmental control, was about 6.5 million USD. These costs were devided between the Swedish EPA, and the company that owned the paper-mill when PCB discharges occurred and the Municipality of Hultsfred. The Municipality of Hultsfred was in charge of the remediation.
Papers to come:
| Author | Subject - key words |
| Förlin, L., University of Gothenburg | PCB: fish fysiology, EROD-activity |
| Norrgren, L., University Agric. Sciences, Swe | PCB: fish pathology, morphol.-effects |
| Broman, D., University of Stockholm | PCB: seston-chemical characterization |
| Brunström, B., University of Uppsala | PCB: seston-biological characterization |
| Bremle, G., University of Lund | Fate of PCB, transport, PCB in fish |
| Larsson, P., University of Lund | Fate of PCB, transport, PCB in fish |
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