Viewpoint: Dredging up trouble

Phase I of the largest PCB dredging project ever began this past year on the Hudson River at Fort Ed
Illustration by Forest Byrd
Illustration by Forest Byrd

Phase I of the largest PCB dredging project ever began this past year on the Hudson River at Fort Edward. It went badly, with dredging completed in just over half of its planned area, and with discovery of a previously unknown, deeper layer of PCB-tainted sediments that threatens to extend the planned six-year project for years longer. Just how badly it went is a little-known fact, though hints may be gleaned from two new draft reports prepared by the EPA [Environmental Protection Agency] and GE to evaluate Phase I. The reports reveal that dredging mobilized nearly 25 times the expected amount of PCB-tainted sediments, . . . but even that is probably just the tip of the iceberg.

The beginning of dredging evoked reaction ranging from celebration about the prospect of an eventually clean Hudson to concern about health effects, water pollution, noise and diminished recreational river use. Phase I included the drama of PCB levels in water and air creeping upward, and eventually exceeding EPA limits, forcing GE to halt dredging on multiple occasions.

The EPA Hudson River Office deserves credit for trying to balance conflicting imperatives forced upon it: to dredge, but to maintain acceptable dredging conditions. The office also was forthright in disclosing problems, and willing to share technical data.

My expertise in environmental toxicology and human health risk assessment, and experience consulting on a power plant project affected by dredging, encouraged me to investigate potential PCB dredging impacts. I discovered problems including concentrated liquid PCBs that can’t be retained by clamshell dredges, and a failure by GE to adequately monitor dredging impact.

Phase I involved about 90 acres of river divided into 18 work “units.” Up to 12 dredging platforms — usually fewer — were deployed, with just one platform working in any unit. Of critical importance were measurement of waterborne and airborne PCB levels, and employees’ personal exposure to airborne PCBs. None was adequately measured.

Measuring not done

Waterborne PCBs are the primary source of airborne PCBs over the river. Generated primarily by dredging, waterborne PCBs therefore should be measured where dredging occurs — but this was not done. Instead of sampling water at Rogers Island, for example, water was sampled about five miles downstream. Thus waterborne PCB concentrations at dredging sites were anyone’s guess, determined by the also-unmeasured dilution factor that occurs as dredge-mobilized material travels miles downstream.

Similarly, airborne PCB concentrations at dredge sites were also anyone’s guess, because airborne PCBs were not routinely measured at dredging platforms.

EPA reported that GE had generated 243 personal monitoring samples, but with 500 employees engaged for the project, over 30,000 samples should have been expected after 114 days of dredging. Still, the 243 samples might have been useful to indicate airborne PCB concentrations, but EPA was unable to indicate how many of these samples originated from the dredging corridor. My photographs of personnel on a dredge platform revealed no air samplers were worn.

Airborne PCBs were monitored by portable air samplers adjacent to the dredge platforms on opposite shores of the river. These samplers recorded 24-hour average concentrations of airborne PCBs. Three problems undermined the usefulness of these monitors. First, people engaged in dredging were exposed to heavy sprays generated at the dredge platform, which usually fell back to the river surface well before reaching onshore monitors. Second, wind direction varied, so each air monitor pumped air from all directions, and not primarily from the direction of the dredge platform to which it was adjacent. Thus recorded PCB levels did not reflect actual levels over the water.

Each portable air monitor was moved downstream with its neighboring dredge platform, so no monitor remained to record evolving, airborne PCB levels at any dredged location. Indeed, as the area of dredged river increased to its maximum, the concentration of airborne monitors per acre of dredged river declined, because no monitors were added to cover the increased area of dredge river.

Hence, the third problem: that PCB release into the air might not reach steady state until long after portable air monitors were withdrawn downstream with the dredge platforms.

Indeed, PCB release from the river surface might not reach steady rates until long after Phase I is complete. By then, portable monitors will have been withdrawn, not only downstream but altogether, in what I call “hit-and-run dredging.”


These and other observations lead me to conclude:

–Water monitoring miles downstream of dredging is inadequate to characterize PCB mobilization.

– Air monitoring using onshore portable air samplers is inadequate to quantify residents’ exposure to airborne PCBs.

–Personal monitoring of GE dredging personnel as implemented in Phase I is inadequate to quantify occupational exposure to airborne PCBs.

– Levels of airborne PCBs probably are higher than suggested by available data, and possibly unsafe.

–The dredging project has turned exposed people into experimental subjects, and riverfront communities into the subjects of epidemiology studies that will continue for generations to come.

I recommend that:

–Water and air monitoring, including personal monitoring, should occur together at dredge platforms.

–Permanent air and water samplers be put in place to confirm EPA safety claims and protect public and environmental health.

 Evaluation of the project’s Phase I, now under way, should consider all issues. That includes possible cessation of dredging, which is specifically excluded from consideration, according to the EPA.

Dr. Robert Michaels is president of the Schenectady-based RAM TRAC Corp., a health-risk consulting firm.

Categories: Opinion

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