Sunday, March 28, 2010

FIRESIDE CHAT Hudson River PCB Dredging: The Case of the Predictable Waterborne PCB Exceedances

On 28 March recently analyzed Hudson River water samples were reported to harbor PCB levels four times higher than the Federal drinking water standard of 500 parts per trillion (ppt). This news should have surprised no one. Indeed, my analysis of GE’s ‘bucket files’, reported to EPA and released to the public, revealed that the preponderance of sediment disturbed by dredge buckets during Phase I of EPA-mandated Hudson River dredging was left on the river bottom. That is, it was not placed in waiting barges for transport by rail and disposal in Texas (see chart below; click on it to enlarge).

Residual sediments disturbed by dredging are mobile, along with their PCB load. If a full dredge bucket averages five cubic yards, then just about a quarter of dredged sediment was transferred to barges. Some of the remainder flows downstream with the current. The rest falls back to the river bottom, where it exists as loosely agglomerated piles of mud, which river currents erode gradually back into the water column, from which PCBs may enter the air and ecosystems, including migrating fish and birds.

EPA’s website indicates that the turnaround time for GE samples sent to the laboratory for analysis is approximately three weeks, so towns relying on Hudson River water for drinking may have continued to use the tainted water for most if not all of that time. According to Halfmoon Town Supervisor Mindy Wormuth: “Yesterday’s events revealed that EPA was not processing the test results quickly enough for the town to switch to the alternative source prior to the affected water reaching our intake.”

Examination (on 28 March) of EPA’s website for Hudson River dredging data revealed that the reported PCB exceedance was not posted. Indeed, no PCB water sample data more recent than 3 February were posted, nearly two months after sampling. A 29-March Daily Gazette article indicates that the sample was “pulled” on 23 March, and Town officials were notified of the result three days later, whereas the rapidly flowing river would have brought PCBs to the drinking water intake in just about 17 hours. One can speculate about the ambiguities:

--Maybe the turnaround time for analysis of water samples taken "weekly" is more rapid than 21 days indicated on EPA’s website for "baseline" samples, OR

--Maybe the sample was “pulled” from the database (flagged as excessive) on 23 March, after being “pulled” from the river three weeks earlier… in which case residents’ exposure to elevated PCB levels in drinking water would have been three weeks longer.

Hopefully, water sampling now will be more frequent than “weekly,” since unacceptable elevations of PCB have been documented. Of course, the public will not know for how many of the seven days between weekly sampling events PCB levels were elevated, because GE’s EPA-approved Quality Assurance Project Plan (QAPP; 1) calls for weekly rather than daily or continuous water sampling. A related concern is that PCBs in the water generate airborne PCBs from the river surface, but the QAPP requires no ambient air sampling for PCBs at all between dredging phases (except for several air monitors near the dredge spoils treatment facility, located remote from the Phase I dredging corridor).

The enforceable Federal PCB Maximum Contaminant Level (MCL) for drinking water is 500 ppt as reported, but that fact is misleading. For substances that are carcinogens, such as PCBs, the recommended MCL (termed the RMCL) is not 500 ppt, but zero. Zero is not an enforcement level, but it does constitute a guidance level that should inform agency policy regarding activities, such as dredging, that might elevate PCB levels in water.

Literature Cited

1. GE RAM QAPP. River PCBs Site, Phase I Remedial Action Monitoring Program, Quality Assurance Project Plan; Final. Prepared for General Electric Company (GE; Albany, New York) by: Anchor QEA, LLC (Liverpool, New York) in conjunction with Environmental Standards, Inc. (Valley Forge, Pennsylvania) and ARCADIS (Syracuse, New York); 344 pages, i.p., May 2009.

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