PCB IN A RIVER SYSTEM DURING SEDIMENT REMEDIATION

Remediation of 150 000 m(3) of sediment containing 400 kg PCB was perf ormed by suction dredging in a small lake in Sweden in the summers of 1993 and 1994. Upon project completion calculations indicated that 97% of the PCB was deposited in a landfill with subsequent low transport to the surroundings, and that 2.9 kg was left in the lake sediment. Co ncentrations of PCB that were measured weekly in the water leaving the lake were 12 ng/L (geometric mean) during dredging, not exceeding 30 ng/L and not significantly higher than in investigations preceeding th e remedial action. The concentration of PCB was negatively correlated to water discharge and positively correlated to water temperature. PCB transport in the river was correlated to water discharge but not to t he dredging activity. During dredging of the most contaminated part of the lake, the dredging area was screened off by a geotextile silt cur tain that reduced leakage of PCB to the river downstream.