Abstract

Introduction

Description

Sampling methods

Suspended-solids transport during dredging

PCB concentration changes during dredging

PCB loading in the Fox River due to the dredging operation

PCB transport back into the river from the onshore-processing operation

Postdredging PCB concentration and loads

Adjusting water-column PCB concentrations to allow comparison with onshore-sample PCB data

Lessons learned

References

Acknowledgments and Information

A Mass-Balance Approach for Assessing PCB Movement During Remediation of a PCB-Contaminated Deposit on the Fox River, Wisconsin

Suspended-solids transport during dredging When averaged over the length of the dredging operation, little difference was found between the upstream and downstream TSS and turbidity values. Periodic differences, however, were substantial (fig. 5). These differences were not consistent at times net TSS increased over the dredging area, and at other times it decreased.

A consistent lateral pattern was evident at the upstream site (fig. 6). TSS concentrations were generally highest closest to the papermill wastewater-treatment plant discharge pipe (570 lb/d), and concentrations decreased away from this pipe.

The TSS concentrations at the sample-collection sites provided insight regarding shipping operations. On the mornings of October 8 and November 3, 1999, coal-ship departure appeared to have resuspended PCB-laden sediment (fig. 7). This increase in suspended sediment was in agreement with the continuous turbidity data collected by the site contractor (Montgomery Watson, 2000). A similar effect was observed on the two other days (October 14 and November 23) when PCB water-column samples were collected coincident with vessel movement.

U.S. Department of the Interior, U.S. Geological Survey
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Last Update: Mon 22 Dec 2001