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Impact of scientific understanding on
Site operations
The scientific understanding developed through the integrated studies provided clarity and focus on the real issues surrounding plutonium and americium migration in the RFETS environment. Once Kaiser-Hill, DOE, EPA, Colorado, and the concerned citizens’ groups reached an understanding of the technical issues surrounding plutonium and americium migration at the Site, then these groups were able to reach longsought- after agreements on how to proceed with cleanup.
The common understanding that plutonium and americium were predominantly in particulate and colloidal forms led to the recognition that environmental migration occurs through sedimentation and resuspension of small particles by action of wind and surface water at the Site. This knowledge helped all parties focus remediation efforts on surface contamination and wind and surface-water transport pathways that posed the greatest risk to human health and the environment. It also helped guide selection of surface-specifi c removal technologies and future landconfiguration strategies.
In recognition of the new understanding, Site operators responded with a major shift in emphasis to erosion and the need to control it. The most poignant illustration of this shift was a Management Directive (NRT-011-04) from Kaiser-Hill President Nancy Tuor, which discussed the importance of erosion control in all Site activities.
The recognized need for erosion controls “close in space and close in time” helped prevent movement of contaminants during Site remediation activities and reduced the transport of plutonium and americium to the Site’s stream channels and ultimately off - site. The additional protection provided by soil erosion control measures allowed Site remediation to proceed rapidly and thus meet or exceed the project deadlines.
In 1996, the Rocky Flats Cleanup Agreement radionuclide soil action level for plutonium cleanup was 651 pCi/g, and was based on dose. In 2002, armed with improved understanding of plutonium behavior, the DOE, Colorado Department of Public Health, and EPA released reports that formed the basis for a new surface soil-action level of 50 pCi/g that was based on risk and resulted from unprecedented community involvement. Because plutonium contamination was generally confined to surface soils, the greatest risk to public health was from dispersal due to action of wind and surface-water erosion processes. This new riskbased agreement focused on removal of surfacesoil contamination at a
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The reconfigured Walnut Creek basin functional channel shows the heavily armored channel and extensive erosion-control measures on stream banks. The measures included straw bales, wattles, and crimping; silt fences; mats; hydromulch and Flexterra™; and rip-rap (rock) lining of drainage channels. The inset shows a remediated area of the 903 Pad covered with coconut matting. The biodegradable matting prevents wind and water erosion and allows native vegetation time to take hold.
Th is temporary water-detention pond was constructed to collect and store dust-suppression water used during the decontamination and decommissioning of Building 371. The pond was used to ensure that plutonium and americium contaminants did not enter the streambeds during remediation of the Site. This is an example of the extraordinary efforts employed by Site personnel to control erosion—and hence actinide transport—during decontamination and decommissioning operations at the Site.
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