Irene says:

>Dear Tweets:
>Eons ago, I took Baby Geology at UDub. Our prof told us of a study in
>which yellow rubber "lily pads" were dropped one mile off the mouth of
>the Columbia River to determine how well the dredging project was working.
>Were faces red. All the wee lilies--AND so, the suspended and bed load
>of mud--were making a giant loop and sneaking right back upstream, where
>everything could be dredged again and again and again....
>Irene
>

This is true in the Duwamish too. A recent study I completed of sediment
transport in Elliott Bay and the Duwamish River determined that contaminated
sediment from the industrial areas at the mouth of the river are creeping up
the river toward the turning basis. This is likely due to the fact that the
dams have prevented much of the sediment from heading downstream and the
Corps dredges out most of what does make it to the turning basin. The
fine-grained silt from the river mouth is "pumped" upstream by tidal
fluctuations.