SAND COVER & ARMORED CAPS
The final phase of the cleanup project employed the U.S. EPA approved optimized remedy, which incorporated engineered armored caps (layers of gravel and sand) and additional sand cover to address remaining low PCB-concentrated sediments. The optimized remedy required dredging in shallow areas so that armored caps were only placed where the final water depth was no less than 6 feet. It also required sand cover be used over certain areas with low levels of PCB-contaminated sediment as well as over some areas previously dredged, but with residual PCB concentrations. Lastly, armored caps were placed over remaining sediments to be addressed by the cleanup effort. These armored caps will keep sediment in place to ensure that it is not available to the biota (fish and invertebrates).
The work under the optimized remedy began in mid-2008 through fall 2008, resumed in mid-April 2009, and was completed in May 2009, thus ending all of the in-water work for the project.
This optimized remedy is an amendment to the EPA's Record of Decision and is consistent with the optimized remedy approved in early 2007 for the downstream segments of the Fox River. EPA determined that the optimized remedy is as protective as the dredging-only remedy. Also, this optimized remedy allowed the project to achieve the goal of reducing fish exposure to PCBs in an accelerated timeframe and was more cost effective than the remedy set forth in the original Record of Decision.
The work under the optimized remedy began in mid-2008 through fall 2008, resumed in mid-April 2009, and was completed in May 2009, thus ending all of the in-water work for the project.
This optimized remedy is an amendment to the EPA's Record of Decision and is consistent with the optimized remedy approved in early 2007 for the downstream segments of the Fox River. EPA determined that the optimized remedy is as protective as the dredging-only remedy. Also, this optimized remedy allowed the project to achieve the goal of reducing fish exposure to PCBs in an accelerated timeframe and was more cost effective than the remedy set forth in the original Record of Decision.
Above is a graphic that shows how the armored caps were constructed on the floor of the lake to keep the low PCB-concentrated sediment in place permanently.
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The model above was used at public meetings on the optimized remedy to demonstrate how the armored cap was constructed. Click on the photo for a larger view of the model.
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The equipment to place the sand cover and armored cap materials was similar in appearance to the dredging equipment that was used earlier in the project. The sand and armored cap placement process involved using spreaders, which worked in a manner similar to how snowplows spread salt and/or sand on roadways in the winter.
This photo shows the cap material broadcasting system. Photo courtesy of JF Brennan.
The map below shows the engineered armored cap locations for Little Lake Butte des Morts (OU1).
For more information on capping and cover remediation methods, please visit:
Fox River NRDA/PCB Releases in Green Bay, WI
FOX RIVER NRDA/PCB RELEASES | Superfund Site Profile | Superfund Site Information | US EPA
WDNR website with a section on capping
Cleanup Operations | | Wisconsin DNR.
Contact the WDNR for capping and covering source files.
Fox River NRDA/PCB Releases in Green Bay, WI
FOX RIVER NRDA/PCB RELEASES | Superfund Site Profile | Superfund Site Information | US EPA
WDNR website with a section on capping
Cleanup Operations | | Wisconsin DNR.
Contact the WDNR for capping and covering source files.