Tweeters,

Dredging a dammed river like the Columbia is not a simple
yes or no environmental question. Dams cause more siltation
than would have occurred otherwise (slower river flow, blockage
of silt, etc) and over time, the silt builds up.
That's the arguement in favor of dredging.

Against dredging is the simple, albeit temporary, disruption of
river life by the mechanical aspects of dredging. There's also
the potential release of accumulated toxins in sediments. Of course,
one could ask: Is it better to dredge the stuff now, or let it
lie there waiting for a 1000 year flood to pick it up and dissolve it
into the water all at once?

Personally, I find it difficult to take a side on this issue.
If dredging is done, though, probably the best prevention of major
environmental impacts would be to do small sections of the river
each year over many years. The release of toxins would be spread over
a longer period of time at lower concentrations.

Kelly Cassidy