Dredging Challenges Contribute to Spikes in Air and Water Monitoring

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In 2009 dredging began in the Upper Hudson River to remove sediments with PCBs. Read more.

Last week, media who routinely cover the Hudson dredging project ran several stories about increased PCB levels recorded by EPA for both water and air monitoring. Be assured, water and air quality are being closely monitored, and EPA is working with the New York State Department of Health to ensure there are no immediate risks to people’s health. People can track the monitoring at www.hudsondredgingdata.com. I thought I would take this edition of the blog to clarify what happened on the river last week and tell you what was done about it.

Since the beginning of the project, dredging has taken place around Roger’s Island, one of the most heavily contaminated areas of the river and one of the most complex areas to dredge, due to physical conditions such as shallow water depths and a river bottom of uneven bedrock. We’ve found sediment in this area contains very high levels of PCBs mixed with a tremendous amount of small debris (i.e. tree limbs, etc.). In addition, since May 15, more and more dredges have been added throughout the six-mile project location, and we are nearly operating at full capacity (12 dredges, 18 barges and 18 tugboats).

Last week, when GE staged several dredges in a particularly contaminated area, the monitoring numbers began to elevate. Levels of PCBs in the water were measured as high as 514 parts per trillion at the first monitoring station (located near Thompson Island) on Saturday, August 2, which is above the drinking water standard of 500 ppt. At the same time, the river had started to rise and the flows were starting to exceed the safety level of 10,000 cubic feet per second, so the dredging was halted.

If PCB levels reach the drinking water standard, and are confirmed by two subsequent lab samples, any dredging activities that may have caused the exceedance will be halted until EPA is satisfied that the proper changes have been put into place to lower the levels. The two follow-up water samples came back below the drinking water standard, so EPA determined there had been a spike in the PCB levels, and it was probably because of the combination of dredging and high river flows from recent rain events. After that determination, EPA told GE it was okay to dredge again, once the river flows decreased to less than 10,000 cubic feet per second. As of Monday evening, August 3, the dredging had resumed. Additional water samples have been taken at Thompson Island and are all below the drinking water standard, and samples taken further downriver are well below the standard. Those results can be found at www.hudsondredgingdata.com .

The air standards are equally protective. The standard for exposure for PCBs in the air in residential areas, for instance, is based on levels that would be acceptable for a child under the age of six to breathe 24 hours a day for 365 days a year for six years. If that standard is exceeded, EPA and New York State investigate, and GE is directed to take actions to decrease the levels and provide sampling results faster to help identify the cause of the spikes.

So what actions were taken – we determined the combination of too many dredges in a heavily contaminated area and the release of vapors from barges loaded with contaminated sediment drying out in the sun were key contributors to the monitoring spikes. As a corrective measure EPA has now required that dredging be scaled back in the highly contaminated area around Roger’s Island and that the barges with high concentrations of PCBs are loaded evenly, that they are kept wet to prevent PCBs from evaporating into the air, and that they are immediately off-loaded into an enclosed storage structure at the dewatering facility. These measures have worked to dramatically reduced levels of PCBs in the air and the water.
About the author: Kristen Skopeck is originally from Cedar Rapids, Iowa. She is an 11-year Air Force veteran and was stationed in California, Ohio, Texas, Portugal, and New York. After working for the USDA for three years, Kristen joined EPA in 2007 and moved to Glens Falls, NY to be a member of the Hudson River PCB dredging project team. She likes to spend her time reading, writing, watching movies, walking, and meeting new people.