Comparison of the Long-Term Risks of Removal and In Situ Management of Contaminated Sediments in the Fox River

The long-term potential risks of environmental dredging vs. in situ contaminated sediment management practices are discussed and compared for the Lower Fox River, Wisconsin. The risks are identified as being largely associated with the residual sediment contamination associated with either approach. The integral of the surface area-weighted average contaminant concentration in surface sediment is proposed as a metric to compare these risks. Capping is shown to exhibit significantly reduced exposure and risk relative to the dredging scenarios, even if potential undetected erosion of 5% of the cap is considered. Even with the improbable event of undetected failure of 25% of the cap, the exposure and risk associated with capping is approximately equal to or below all dredging scenarios. A preference for dredging due to the perception that it eliminates the long-term risk of in situ capping is not supported by this analysis. Although strictly applicable only to the Lower Fox River, the results suggest sitespecific analyses must be conducted to determine which sediment management approaches minimize the potential for long-term exposure and risk.