As far as I know, there are now three lay up areas: James River, Virginia
Suisan Bay, California
Since that last disasterous attempt at disposing obsolete ships in England, MARAD has been contracting the demolition to domestic companies.
It looks like the days of the US off loading their toxic vessels overseas are over.
I'm guessing, but I don't think there can't be much more than 250 ships now in layup.
The James river is very close to Newport News VA,also next to a army post called Fort Eustis,they have a large fleet of landing craft and tugs located there. When I was there it was not a secured area
Not having a military mind, I've always have trouble with the categories, acronyms, sub categories and other assorted classifications so beloved by the military bureaucracy, but as far as I know:
The National Defense Reserve Fleet was originally composed of ships that could be activated in an emergency. I think it's now generally agreed by The Powers That Be that the fleets tied up in Virginia, Texas and California are now destined only for the knackers.
About thirty years ago another category was set up consisting of a Ready Reserve Fleet, theoretically ships that could in reality be activated quickly. As of two years ago they were: http://www.hazegray.org/worldnav/usa/reserve.htm
There are probably a few misplaced inactive ships kicking around in other locations waiting to be found by a more than usually observant pencil pusher.
There was a show on the History Channel last night showing some of these ships laid up in Virginia. They pointed out that while many of them are scrapped and recycled, some are used for target practice and sunk, others are actually sold to foreign governments for their navy's use. Still others are taken out of mothballs and put into service as needed by the US navy.
If wish to find out more about the reseve fleet you can do so via the net.
Just go to www.narad.dot.gov or you can type in National Defence Reserve Fleet. There are a lot of links including one of a map of the US showing the lay up areas. Also in the "Narad" site there are photos of all ships in the fleet and lists of those that are on stand by, the national held list, those stripped of anything useful and waiting to be scrapped.
ex RNZN Hydrographic Branch in the 60's