When the Hudson River Superfund site was delineated, it was so large - 200 miles - that it was initially divided into two parts: the upper portion of the river, from Hudson Falls to Troy, where the Federal Dam is sited, and the lower portion, which extends from Troy to the Battery in Manhattan. For almost 50 years, GE discharged as much as 1.3 million pounds of PCBs from its capacitor manufacturing plants at the Hudson Falls and Fort Edward facilities, which are above the Federal Dam at Troy, into the Hudson River (USEPA, 2005). For many years it was theorized that most of the PCBs were from leaks at GE's Hudson Falls site, and that by stopping the leaks PCBs would stop showing up in river water samples (TAMS et al., 1991). However, once sources of PCB output were blocked, levels of PCBs detected in the river did not decrease, as would be expected; rather, they continued to be high, indicating that PCBs were still being released by someone, somewhere.
Through sampling and chemical analysis, among other methods, these high levels were ultimately directly linked to another critical area for GE, the Thompson Island Pool and the associated Thompson Island Dam, which are in the upper portion of the river and Superfund site, between Schuylerville and Fort Edward (above Troy and the Federal Dam). PCBs continue to occur at high levels in this area, in both the deeply contaminated sediment and the water, and seep through cracks in the Federal Dam to travel the many miles downriver toward New York Harbor, infecting everything along the way. Thus, as contaminated sediments get stirred up and into the water, these GE-related sources keep the contamination coming. One of the results of this that affects our everyday lives is the continued advisory from the Department of Health to severely limit consumption of fish from the river, and to eat no fish at all from some parts of the river, particularly the upriver stretches (NYSDOH, 2005).
Analytical chemistry techniques provided congener-specific analysis of Aroclors that allowed scientists to assess the way PCBs moved and behaved in various media (called "fate and transport"), such as soil, water, and fish. As PCBs are not stationary and travel throughout the river, a cutting-edge scientific technique was used to fingerprint the PCBs, thus identifying where they come from and where they go. This led scientists to realize that while there are multiple, continuing sources of PCBs to the river, that Hudson Falls was not the main source, as initially expected - it was the Thompson Island Pool.
As explained in its Data Evaluation and Interpretation Report, or DEIR (TAMS et al., 1991), USEPA and its contractors used analytical chemistry to track the movement of PCBs in the sediment of the Thompson Island Pool - the most heavily contaminated section of the river - for 100 miles downstream. The Aroclor signals also reveal that there is a fivefold increase in PCB levels as water flows through the pool, and that these PCBs come from the sediment of the pool itself (USEPA, 2005). The PCBs from the Thompson Island Pool have an easily recognized pattern that is tied to one of GE's particular mixtures of Aroclors. This mixture dominates the water column, particularly during low-flow conditions, which is when chemicals in the sediments are often stirred back up into the water. Samples show that about 1 to 2 lbs of PCBs flow out of the Thompson Island Pool every day. As USEPA states, "it's simple math" that proves that the river continues to be contaminated by PCBs (USEPA, 2005).
But while the math may be simple, the reality is complex. The Hudson River is affected by New York Harbor and the Atlantic Ocean, which makes it a tidal river. This means that it is not only affected by daily oceanic tides but has a saltwater front that moves up and down the river, depending on the season and the temperature. The levels of water in the river vary depending on the environment. Some companies continue to dump in the river. And perhaps most critically, there are multiple tributaries to the river, many of which are contaminated themselves. For example, studies showed that the Thompson Island Pool was being fed a continual diet of PCBs from the Mohawk River, one of the Hudson's tributaries. The Mohawk alone was found to contribute close to half - 44 percent - of the total flow of PCBs at the Federal Dam, which was then being transmitted throughout the river below the dam (TAMS et al., 1991).
Another source to the Thompson Island Pool is the area above Rogers Island (which is above the pool and is in the upriver portion of the Superfund site). This source provides us with more of the GE congeners we are looking for, with, as USEPA states, the PCBs being overwhelmingly the toxic Aroclor 1242, along with approximately 4 percent Aroclor 1254 and 1 percent Aroclor 1260 (TAMS et al., 1991).
The studies behind the Hudson River cleanup provided revolutionary scientific data that challenged existing theories on PCB removal and forced scientists to think in innovative ways about how to proceed with remediation. The ongoing cycle of settling, resuspension, and re-release of PCBs must be stopped in order for the river to ever be clean. The sources that continue to put PCBs into the river must be sealed or eliminated, and the PCBs that already exist in the river - and are not going away - must be removed.
On Wednesday, August 1, 2001, in a landmark decision, Christine Todd Whitman, then commissioner of USEPA, signed off on the dredging plan, allowing the agency to proceed with the Record of Decision, or ROD. In the ROD, which was issued in 2002, USEPA proposed targeted dredging of "hot spots" of PCBs in 40 river miles of the Hudson. (A "hot spot" is a particularly contaminated area of a polluted site.) Through extensive study and innovative modeling of the river, scientists had determined that dredging, while it would temporarily resuspend the PCBs, would, in the long term, be the best solution for removing the contaminants and giving a cleaner river back to the public.
At the time, it was the largest environmental cleanup, in terms of cost, in New York State history, and is second only to the cost of the cleanup of Onondaga Lake in upstate New York. Good, innovative science and analytical chemistry served as the evidence linking GE to the majority of the PCB contamination of the river, and the ROD is the instrument that legally forces GE to take responsibility for its actions. However, there is still much to be learned about PCBs and specific congeners and their particular toxic properties, as well as how they behave in an ecosystem. Until this science is completely understood and the methods of cleanup prove to be effective, there will continue to be threats to human health and the environment from this contaminant of our own creation.
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Jennifer Manning. PCBs (Polychlorinated Biphenyls) in New York's Hudson River. EnvironmentalChemistry.com. Oct. 2005. Accessed on-line: 10/21/2017