In Virginia, there is a rich history of boats, particularly dugouts,
being found at the bottom of slackwater bodies.  I recall doing
drawings of one dugout in Caroline County where there wasn't a single
nail to excite a magnetometer.  It was found when the millpond washed
out.  Boats have been pulled from the bottoms of streams in Dismal
Swamp, and there are some beauties in the collections of the Valentine
Museum and the Mariners Museum.  Unfortunately, most of the dugouts
pulled from the ponds are lost to natural causes quite soon after they
are recovered.

In addition to dam crib structures and boats in the impoundments, one
must remember that things wash downstream.  So don't be surprised if
you find mill machinery that washed down from an upstream mill.  Here
in Delaware as in most areas, the mills were packed tightly along the
streams, so that  lost or discarded items would wash to the slackwater
behind the next dam down.  I would definitely look at the silt in the
slackwater pool as a likely goldmine of perishable materials preserved
by anaerobic conditions.

As for excavation technique, seems to me that some kind of placer
operation would be more appropriate than digging.  Of course, that gets
into problems with stormwater and erosion regulations. There are no
limits to the regulatory implications.

Edward F. Heite
Heite Consulting, Inc.
Archaeologists and Historians
P O Box 53, Camden, Delaware 19934
www.heite.org