Efficacy of Dredging for Remediating Polychlorinated Biphenyl-Contaminated Sediments of the Lower Fox River

Abstract

Abstract

Dredging efficacy in reducing polychlorinated biphenyl (PCB) sediment contamination in the Lower Fox River, Wisconsin, was assessed by comparing predredging and postdredging concentration profiles from portions of Operable Unit (OU) 3 and OU4. Sediment PCB concentrations (in 0.15 m depth intervals) from predredging and postdredging core locations were compared. Results show that dredging reduced PCB concentrations in the surface sediment layer (0 to 0.15 m) in 77% of the locations. At locations where surface layer PCB concentrations were lower than predredging sediments, concentrations were reduced by an average of 72%. Average PCB concentration in the surface layer of all postdredging cores was 1.86 ppm compared to 0.61 ppm in the second (0.15 to 0.30 m) layer. The difference (significant at the p = 0.006 level) suggests that residual sediments were present in the postdredging surface layer. Dredging reduced the maximum PCB concentration in sediment cores at all locations except the 2% where the maximum predredging PCB concentration in the sediment profile was less than 1.5 ppm. Dredging reduced the maximum PCB concentration in the sediment profile by 84% on average (significance level of p = 0.008).