Lyle,
This might be a problem encountered at other dam sites -- comments from the list?
The bases of the concrete dam and the crib dam behind it are buried in the
inevitable wedge of sediment that accumulates behind dams. Based on borings, this
sediment may be as much as thirty feet deep in places. Eventually, much of it would
erode away, but we have to go ahead and remove the dams now, which means that
we must also remove the sediment.

Since the dams are nearly 900 feet long, doing test pits in this unstable sediment
would not be an effective way to locate boats, or anything else trapped behind the
dams. The sediment removal will be ongoing with the removal of the dam structures
and I'll be monitoring this work to deal with anything that shows up as it progresses.

I'm going to see if I can get some more info on the project web site, and will send the
link to the list when this happens,
Regards,
Tim Thompson