Sediment Remediation at the Unnamed Tributary to the Ottawa Riverby Stuart D. Messur,
Abstract: A sediment removal action was conducted in the Unnamed Tributary to the Ottawa River to address sediments containing polychlorinated biphenyls(PCBs) at concentrations up to 74,000 mg/kg. Site remediation included removal and off-site disposal of approximately 16,000 tons of sediment and soil, as well as the construction of a new tributary channel with backfilling/restoration to wetland conditions of the old channel. The site was first isolated using sheetpiling and soil berm construction to control surface water influx from the Ottawa River due to high flow events and Lake Erie seiche effects. A series of large storm sewers was temporarily diverted and the Unnamed Tributary was sectioned into cells using sheetpiling, to allow dewatering and dry excavation of the PCB-containing sediments. During sediment removal, more than 1 million gallons of water were collected and effectively treated prior to discharge. The treatment process used oil/water separation, followed by polymer addition to precipitate out suspended solids in an incline plate clarifier, and a series of bag, sand, and activated media filters to remove particulate and dissolved phase organic constituents. Site conditions encountered during the sediment removal activities allowed the contractor to achieve low residual PCB concentrations without the need to significantly over-excavate.
Subject Headings: Sediment | Rivers and streams | Remediation | Construction sites | PCB | Excavation | Water discharge | Waste sites | Lake Erie
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