|
|
|
| U.S. Department of the Interior | U.S. Geological Survey |
| USGS Water-Resources Investigations Report 00-4245 | December 2000 |
|
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 |
A Mass-Balance Approach for Assessing PCB Movement During Remediation of a PCB-Contaminated Deposit on the Fox River, Wisconsin |
|
PCB transport back into the river from the onshore-processing operation
After filter presses removed most solids from the incoming slurry, the effluent was passed through sand and carbon
filters before being discharged back to the river at a rate of more than 700,000 gal/d. On five days, 80-L samples were
collected by the USGS (over an 812 hour period) from the shore-process-discharge pipe. Total PCB concentrations in the
effluent ranged from 82 676 ng/L with a mean concentration of 422 ng/L. These values did not appear to be normally
distributed. A conservative approach, applying the median concentration (509 ng/L) to the effluent volume discharged during the
entire dredging operation (76,213,900 gallons), resulted in 0.147 kg of PCBs being returned to the river. Of the 654 kg of PCBs that were processed onshore or held in the settling basins (Montgomery Watson, 2000; Richard Weber, Montgomery Watson, written comm., 2000), less than 0.03 percent was returned to the river. Additionally, the congener distribution (fig. 13) of these effluent samples was markedly different from that in the water column samples-most of the more chlorinated congeners (higher health risk) had been removed. Thus, a very small PCB mass was returned to the river, and this small mass was made up of a less toxic PCB mixture. U.S. Department of the Interior, U.S.
Geological Survey |
