How
YOU
Can
Help
Clean The
River
and Bay!
Fox
River Home
Search
Index
to Site
Recent
Additions
Frequent
Questions
Media
Coverage
History
Statistics
Maps
PCB
Chemistry
Human
Health
Wildlife
Health
Economic
Damage
Corporate
Profiles
Compensation
Sediment
Cleanup
Cleanup
Technologies
State
Government
Federal
Government
Local
Government
Native
Nations
International
& Great Lakes
Technical
Assistance
Other
PCB Sites
Links
Photo
Gallery
Political
Cartoons
Message
Board
Guestbook
|
Two dredging demonstrations were conducted, from 1999 -2001,
on the Fox River. Overall, they showed that dredging can be effective at
removing large volumes of sediment fairly quickly, with minimal drift downstream.
On the other hand, the demonstrations also exposed several management problems
which must be addressed before additional dredging is done.
The paper industries have tried to frighten the public with videos showing
a dredge churning through the sediment like a garden rototiller, releasing
a cloud of pollution downstream. This is fiction. The reality is that environmental
dredging is much more controlled, if the proper equipment is chosen and
experienced operators are hired.
Key points for citizens to emphasize
-
Make sure the dredging starts on each hotspot early enough to complete
in one season, before the winter freeze-up of the river or bay.
-
If a hotspot is too big to complete in one season, make sure the contractors
slope the sides of the hole and cap the exposed edges for the winter, to
reduce the risk of toxic leakage between dredging seasons.
-
A hydraulic (vacuum-style) dredge should be used. A horizontal auger cutterhead
seems to stir sediments less than a swinging ladder style. (Don't allow
clamshell dredging --- it’s very messy!)
-
Use anchored silt screens in the water around the dredging sites to reduce
currents and limit escape of floating sediments.
-
Make sure the contractors have a proven track record at similar sites.
-
Make sure the contractors have multiple backup dredges and excess treatment
capacity on land to compensate for unavoidable frequent equipment breakdown.
The EPA did this to fix Site 56/57 and it worked very well to keep the
crew on schedule. Most industrial sites like ours have trash in the river
that damages the dredges, so they need constant fixing.
-
Have the contractors dredge to below the sediment layers known to be contaminated,
to ensure they get all the toxics.
-
Even if the dredging results in some leakage downstream, the sediments
are already leaking 300-500 lbs of PCBs per year down the Fox River. We
need the long-term benefit of permanently removing the largest-possible
MASS of toxics, once and for all. Any localized temporary increase in PCB
concentrations on the surface due to dredging is relatively tiny compared
to the longterm gains from dredging.
-
It's misleading to claim that water quality or fish contamination levels
became worse, or improved, just because of these two demos, because the
rest of the Fox River is still severely contaminated.
-
Once the sediment is dredged it must be covered and handled carefully to
avoid skin contact and volatilization to the air.
|
