Bulk reactive media utilized in sediment cap remedy for large-scale remediation project case study

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Courtesy of CETCO

Project: West Branch Grand Calumet River Reach 1-2, Roxana Marsh Legacy
Location: East Chicago. IN
Products: Organoclay2 PM-199

Background: in 2011. clean up began on Reach 1 and Roxana Marsh in the West Branch of the Grand Calumet River. This project involved mechanical and hydraulic dredging and removal of 222,000 cubic yards of sediments and soils impacted with PAH, PCB, and various heavy metals. The estimated $50 million project was funded under the Great Lakes Legacy Act (GLLA), with the GLLA contributing to 65% of the overall project cost.

Challenge: As with Reach 3, there were still some geo-mechanical challenges for the design engineer due to the fact that the organic laden sediments being capped were unstable in some areas. Furthermore, this stretch of the river begins to widen out considerably and is subject to more water flow from nearby municipal sewage treatment plant (POTW) discharge.

Solution: The solution included a six inch bulk reactive cap, utilizing a minimum of 2.49 lbs. per ft3 active loading of Organoclay PM-199, to be placed in the river channel where contaminant concentrations were the highest The Organoclay bulk reactive cap would then be topped with one foot of sand for armoring. The capping material was mixed in a slurry with water and pumped for placement with BCS™ system. This reactive capping system should provide a 420 year design life.

Result: Placement of the engineered cap was completed successfully and on schedule. No issues of separation occurred within the Organoclay/sand slurry during transportation or placement. The Organociay/Sand cap was placed in thin lifts and there were no subsequent issues with cap stability or product displacement prior to the installation of the armoring layer. In total, 345,000 cubic yards of contaminated sediment were effectively isolated by the Organoclay PM-199 reactive cap.

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