Introduction

From the latter 1940s until 1977, the General Electric Corporation (GE) discharged an estimated 200,000 to 1.3 million pounds (U.S. Environmental Protection Agency, 2000a) of polychlorinated biphenyls (PCBs) into the Hudson River from two electrical capacitor manufacturing plants at Hudson Falls and Fort Edward, New York (Fig. 24.1). In 1977, under a settlement agreement with the NewYork State Department of Environmental Conservation, GE stopped direct discharges ofPCBs to the river, although leakage of PCBs from the factory sites to the river continues to this day. PCBs used at the GE plants were oily liquids containing dozens of distinct PCB compounds. Most of these components are persistent in the environment, attach strongly to soils and river sediments, and readily accumulate in fish, wildlife, and humans (National Research Council, 2001a). These properties, combined with the large discharges of PCBs from the GE plants over 50+ years, have led to elevated levels of PCBs in the water, sediments, and biota of the Upper Hudson River (defined here as the stretch upstream of the Troy lock and dam). Levels of PCBs in the Hudson River ecosystem are among the highest in the United States.

PCB contamination in the Hudson River is a management problem for the public because it has likely increased human health risks (primarily from consumption of fish), increased ecological risks to fish and fish-eating birds and mammals, and caused losses of river use and the resulting economic impacts (catch and release only fishery; advisories on fish consumption; restrictions on navigational dredging limiting access to the Cham-plain Canal; restrictions on and the increased costs of dredging; and commercial fishery closure). PCB levels found in the Upper Hudson between Hudson Falls and the Federal Dam at Troy exceed numerous risk-based guidelines (U.S. Environmental Protection Agency, 2000a), and PCB transport over the Federal Dam is a major source of contamination affecting the lower tidal river and estuary (Bopp et al., 1985; Schroeder and Barnes, 1983; Thomann et al., 1989; U.S. Environmental ProtectionAgency, 1991; QEA, 1999; U.S. Environmental ProtectionAgency, 2000b). Consequently, the U.S. Federal government is compelled to address the problem of PCBs in the Upper Hudson River.

Public awareness of PCBs in the Upper Hudson River dates back to the early 1970s. In 1976, the New York State Department of Environmental Conservation banned all fishing from Hudson Falls to the Federal Dam and commercial fishing for striped bass in the lower Hudson (NewYork State Department of Health, 1998). Investigations of the sources and impacts of PCB contamination were conducted, and in 1984, the U.S. Environmental Protection Agency (EPA) designated the lower 200 miles of the Hudson River a "Superfund" site (U.S. Environmental Protection Agency, 2000a). It is among the largest Superfund sites in the country. Under Federal law, listing a Superfund site sets in motion a series of policy and management steps to evaluate the extent of the problem, identify the parties responsible for the contamination, design and implement cleanup and restoration, and assess economic damages. In 1984, EPA selected an interim 'No Action' remedy for the contaminated sediments because the agency believed that the feasibility and effectiveness of sediment remediation technologies was too uncertain (U.S. Environmental Protection Agency, 2000a). In 1995, the NYS Department of Environmental Conservation replaced the ban on all fishing in the Upper Hudson River with a "catch-and-release" program, but the ban on commercial fishing for striped bass in the Lower Hudson River remains in effect (New York State Department of Health, 1998).

Figure 24.1. The Upper Hudson drainage basin and Sacandaga subbasin which represents ~38% of the total area. Models of the 100-year flood event assume that the dam for the Sacandaga will provide significant flowcontrol and limit water discharge to 8,000 cfs. Under the more conservative and reasonable assumption that the reservoir will fill up during such an event, flows from the Sacandaga subbasin could exceed 12,000 cfs. [Figure preparedby Edward Shuster of RPI. Discussion based on his analysis of a 100-year flood event (RPI, 2001).]

Figure 24.1. The Upper Hudson drainage basin and Sacandaga subbasin which represents ~38% of the total area. Models of the 100-year flood event assume that the dam for the Sacandaga will provide significant flowcontrol and limit water discharge to 8,000 cfs. Under the more conservative and reasonable assumption that the reservoir will fill up during such an event, flows from the Sacandaga subbasin could exceed 12,000 cfs. [Figure preparedby Edward Shuster of RPI. Discussion based on his analysis of a 100-year flood event (RPI, 2001).]

In December 2000, EPA published its 'Superfund Proposed Plan' for the Upper Hudson River (U.S. Environmental Protection Agency, 2000a), in which it recommended that 2.65 million cubic yards of contaminated sediments, containing over 100,000 pounds of PCBs, be dredged from the Upper Hudson River. InAugust 2001, EPAAdministrator Whitman announced that EPA would continue to pursue that cleanup plan (U.S. Environmental Protection Agency press release, 2001).

During the twenty-five years since PCB contamination in the Hudson River was first brought to the public's attention, a large number of studies have been conducted to determine the sources, movements, ultimate fates, and effects of PCBs in the system. Studies of PCB contamination have generally resulted in high quality data, with excellent measurements of PCB concentrations in Hudson River water, sediments, and fish (see http://www.epa.gov/hudson/dbr_exsum.htm). These data, along with complementary analyses and modeling studies, have provided us with a detailed description of PCB distributions in the Hudson River and a good understanding of many key aspects of PCB fate and transport under present conditions. Although these studies have been extensive, one could still argue that our understanding of the science behind the PCB problem is not complete and that further studies are necessary to add to our knowledge and to help reduce the uncertainty surrounding the issue. However, after two decades of study, there is likely to be a point of diminishing returns and there are costs in further delaying the decision. In the case of the Hudson River, as with any policy debate centering on a technically-complex issue, decisions must be made based upon the preponderance of the data, knowing full well that our ability to predict the consequences of our actions is not perfect.

The fact that our scientific understanding of PCBs in the Hudson River is not perfect has led to a vigorous debate as to the nature of the PCB problem and to the most effective course of remediation. Such a debate, which is critical to resolving complex technical issues, has allowed all sides of the PCB problem to be explored in detail and has played a critical role in advancing the state of the science. Controversy, however, still surrounds the interpretation of technical information on PCB fate and effects, and on the effectiveness of dredging technologies. Nevertheless, we believe that PCBs in the Upper Hudson River have been extensively studied and debated, and informed decisions can be made now.

This report has been written by a panel of independent experts convened by the Hudson River Foundation. Our charge was to critically examine the science underlying the controversy, deduce the relevant principles, and draw conclusions based on the available science. Volumes have been written about PCBs in the Hudson River, ranging from exhaustive scientific and technical reports to numerous articles in the popular press. While we have reviewed much of this information, our objective here is not to comprehensively summarize all of this material. Rather, we wish to convey those aspects of the problem for which we believe the science and engineering are clear. We take a "weight-of-evidence" approach to reach our findings based on our considerable collective expertise and experience. We believe these findings are supported by the available scientific information and are consistent with underlying scientific principles.

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