As I remember we were camped in one of the loops of a highway cloverleaf at the Virginia end of the 14th Street bridge.
This appears to be it and if it is we were on the left loop on the near side of the cloverleaf, very close to the airport.
I have borrowed this picture from the site referenced in the previous picture.
I remember the ground being very hard and full of rocks. We had trouble driving the stakes for our tent. They weren't deep enough and after a few days it rained. They pulled out of the ground and our tent collapsed in the middle of the storm. There we were, in our skivvies, in the middle of the night, trying to hammer in the stakes and re-erect our tent.