PCB dredging may help cleanup of oily river sheen here

• Coal tar from old Poughkeepsie gas plant produces oily sheen visible from Walkway Over the Hudson.

If you are a frequent visitor to Walkway Over the Hudson state park, you may have noticed an oily sheen appearing on the Hudson River from time to time.

The sheen pops up along the river's shoreline on the Poughkeepsie side. Typically, it is seen just north of the bridge.

It is not a spill. It's the legacy of an old manufactured gas plant that sits at the foot of Dutchess Avenue in Poughkeepsie. The property is owned by Central Hudson Gas & Electric Corp.

Between 1911 and 1954, the plant produced gas for heating, lighting and cooking. It became obsolete after an interstate piping system was created to convey natural gas. In 1972, it was dismantled.

Coal tar from the gas-manufacturing process leaked into the ground from storage vessels and piping.

And that's what creates the sheen every now and then when it bubbles up from the sediment below.

In December, I wrote about the steps Central Hudson is taking to figure out how to clean up the contamination.

Now comes an update.

During a Journal Editorial Board meeting with Central Hudson executives on Tuesday, Michael Mosher, the company's vice president of regulatory affairs, told me Central Hudson engineers had recently taken a trip up the Hudson River to study the dredging process General Electric has been using to remove PCBs there.

The reason for the trip? The dynamics of the Poughkeepsie site make it much harder to clean up than similar sites Central Hudson owns in Newburgh, Catskill and Kingston.

The shoreline at the Poughkeepsie site drops almost straight down, 60 feet, to the river's bottom. And the currents are strong and subject to tidal influences.

Also, about a mile upriver lies the intake for the Poughkeepsies' Water Treatment plant. (Officials there have told me the occasional coal-tar sheen has never affected the quality of the drinking water produced by the plant.)

In late July, two members of Central Hudson's environmental staff traveled to the upper Hudson to tour dredging operations overseen by GE.

"Our staff was provided a close-up view of all aspects of the dredging operation between Fort Edward and Schuylerville, touring about seven river miles by boat," Central Hudson spokesman John Maserjian said.

Maserjian said Central Hudson is familiar with the basic techniques of removing river sediment. But the technology being used in the upper Hudson is "highly sophisticated."

"The equipment is among the largest used in marine sediment removal," he said, "and sensors monitor nearly every aspect of the dredging, from the depth of the 'clamshell' into the river sediment, to the amount of material being removed, and whether the clamshell scoop might have picked up an item, such as a tree trunk, that will not allow it to fully close."

Central Hudson must come up with a cleanup plan that will be evaluated by the state Department of Environmental Conservation.

"The next stage will be to take the site information gathered so far and select an engineering firm to assist with designing a remedial plan and alternative approaches," Maserjian said.

The plan, when it is completely drafted, will be subject to public review and comment, and hearings will be scheduled.

It likely will be years before any work begins, and the cleanup will be a multiyear project, Central Hudson says.

But when it does happen, the process may well be informed by the results of the 25-year fight that forced GE to clean up the PCBs it dumped into the upper Hudson decades ago.

Sometimes, it's difficult to see the linkages not only between complex natural systems, but also between the human efforts to protect and restore them.

Indeed, I doubt the environmentalists on the front lines of the GE battle could have foreseen this potential side benefit of their efforts.

But they certainly should enjoy an added measure of satisfaction because of it.

"Out There" appears every other week in My Valley. Reach John Ferro at 845-437-4816; jferro@poughkeepsiejournal.com; Twitter: @PoJoEnviro