A.68 Starkweather Creek, WI
A.68.1 Summary
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Environment: |
Freshwater |
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Scale: |
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Contaminants of Concern: |
Mercury: 1.1 ppm (3.5 ppm max) Lead: average 130 ppm Chromium: 19 ppm Oil and Grease: 2,800 ppm |
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Final Remedy: |
Dredged wet with conventional backhoe. Removed sediment was transported by truck to a sediment retention and dewatering facility 6 miles from site where it was dewatered and disposed. |
A.68.2 Site Description
Year: 1993
Water Depth: 1.5 ft, maximum 2 ft
Target Volume: 17,000 yd3
Actual Volume Removed: 15,000 yd3
A.68.3 Remedial Objectives
None selected, mass removal of mercury and other metals
Contaminated sediment thickness: average 4 ft (7 ft max)
Contaminated sediment area: 1 mile long, 50 ft wide
Dredge depth: up to 7 ft
Another target was to increase average depth of creek channel from 1.5 to 4 ft and max depth from 2 to 7 ft.
A.68.4 Remedial Approach
Dredging was done as wet excavation with a conventional backhoe. Water monitoring happened weekly, visual observations of turbidity changes were made daily.
A.68.5 Monitoring
Resuspension:
Breaking cleanup into sections minimized resuspensionA renewed suspension of insoluble particles after they have been precipitated.. Double silt curtain placed across creek downstream from construction. Curtains held in place at top by steel cable tied to trees and bottom by logging chain. Testing past silt curtains after dredging found contaminant levels low to background.
Performance:
Goals seem to have been reached.
Residuals:
No cappingTechnology which covers contaminated sediment with material to isolate the contaminants from the surrounding environment. or backfilling were needed at this site. No MNR, but reestablishment of creek habitat did take place.
A.68.6 References
Water Resources Management Practicum 2005. Starkweather Creek Watershed: Current Conditions and Improvement Strategies in an Urban Context. 2006. Nelson Institute for Environmental Studies University of Wisconsin. http://www.nelson.wisc.edu/docs/report.pdf.
Major Contaminated Sediment Sites Database; Sept. 2004 as updated 2008. http://www.smwg.org/MCSS_Database/MCSS_Database_Docs.html.
Publication Date: August 2014