The unusually high and fast moving waters of the upper Hudson River may be the cause of high levels of resuspended PCBs measured last week at the Thompson Island water testing station.
The Thompson Island testing station is six miles downriver from Fort Edward where much of the first phase of the PCB dredge project was conducted last May through October.
At one point on March 23 the level of PCBs at Thompson Island was measured at 2,470 parts per trillion, well over the 500 parts per trillion PCBs drinking water safety threshold, according to the Environmental Protection Agency.
In Waterford, however, some 30 miles downstream from the testing station, the PCB levels in river water reached only as high as 186 parts per trillion on March 24, according to Kristen Skopeck, an EPA spokeswoman.
The EPA and General Electric Co. are both analyzing the data from the higher than expected PCB readings. Skopeck said the high, fast waters are similar to river flows in the spring of 2006.
She said these flows and PCB levels in river water from 2006 are being studied to see if they are similar to this year’s readings.
Mark L. Behan, a GE spokesman, said Monday that the high PCB readings measured last week were higher than readings taken during other high water periods prior to dredging.
“Why are the PCB levels that high months after dredging?” Behan asked. He said GE engineers and contractors are gathering and studying the data.
The experts are looking at the possibility that some of the PCBs resuspended during last summer’s dredging may have been pulled back into the river water by the high, fast spring runoff events.
Skopeck said the areas that were dredged last May through October were covered with at least one-foot of clean fill after the PCBs were removed. She said no final conclusion on last week’s PCB spike in river water has been reached.
The EPA ordered GE to pay for and conduct the estimated $780 million environmental dredging of the upper Hudson between Fort Edward and Troy to remove PCB hot spots.
The first phase of the six-year PCB cleanup project was conducted by GE last year. The larger second phase is expected to start in the spring of 2011.
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