The 'total darkness' and the rest of it was their projection of what
it would be like if they tried it. And it isn't far from what I would
fear if I were to go to DC by boat.

It's sometimes hard to tell from the charts exactly what you would
face in person - assuming you have the correct and up-to-date charts.

I understand. this is partly why I am clarifying the situation for
anyone reading who might be considering the trip. The fear expressed by
those otherwise experienced long distance cruisers was completely
misplaced in this quite benign stretch of the river.

I told my husband that I thought the only things coming into DC was
the paper for the Washington Post, and he said there were also barges
and tugs with oil etc. But we didn't think the barges would have to
have the bridge opened nor would the tugs.

I believe you are correct. I think I recall it is the freighter with the
giant paper rolls that requires the bridge to open twice a week.