Remediation of Contaminated Sediments: Technical Options and Environmental Consequences
Patterson, James W.
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According to the USEPA, contaminated sediments continue to be a significant environmental problem that, due to release of contaminants from the sediments back into the ecosystem, impairs the beneficial uses of many waterbodies and is often a contributing factor to the thousands of fish consumption advisories that have been issued nationwide. Cleanup of contaminated sediment “megasites” cost in excess of $50 million. There are often similarities among contaminated sediment sites. For example, at half of 60 Tier 1 sites tracked by the EPA, polychlorinated biphenyls (“PCBs”) were the primary contaminant of concern, while metals drove the risk at a third of the sites and PAHs at a fifth of the sites. There are a limited number of remedial approaches for such sites, including monitored natural recovery (“MNR”), sediment capping, fixation of pollutants within the sediments, or physical removal of the sediments by excavation or dredging. Each remedial approach has advantages and, often serious, disadvantages and environmental consequences. This Seminar addresses the pros and cons of alternative contaminated sediments remedial approaches, and considers the utility of multiple approaches within individual sites. The presentation focuses on the Lower Fox River, Wisconsin, which flows from Lake Winnebago northeast to Green Bay, and drains into Lake Michigan. The Lower Fox River (“LFR”) megasite includes approximately 39 miles of the LFR as well as the Bay of Green Bay, one of the major bays of Lake Michigan, and is one of the nations’ largest sediment remediation sites. River bottom sediments throughout the 39-mile length of the River and extending into Green Bay are contaminated by historical discharges of wastewaters containing PCBs from paper mills and Publicly Owned Treatment Works (POTWs) located along the River. The PCB wastewater discharges resulted from the manufacturing, de-inking, and recycling of carbonless copy paper. It has been estimated that between 279,000 to 881,000 pounds of PCBs were released to the River, almost entirely prior to 1972. The PCB contamination persists today. The contamination has led to excessive body burdens of PCBs in fish, to the point that only a catch and release fishery is advised on the River. The sediments of the LFR and to a lesser extent, the Bay, have been the focus of investigation and remediation efforts for decades. This presentation overviews the remedial options evaluated for the contaminated sediments of the River, and the consequent environmental advantages and risks associated with each remedial approach.