What has apparently prevented archaeological digging at the supposed site of james fort?

James fort's is a 17th century Fort located in Ireland, it was subject of many archeological excavations due the historic value it has from different eras (since before James's Fort structure was built, there it was way more older medieval construction).

For the historic and cultural value it has, was protected and declarated as National Monument, so for the high risk of damage to the structure or accidentality for the digging, the archeological excavations in the zone were not continued and prevented.

The reason that apparently prevented archaeological digging at the supposed site of James Fort was that until 1996, it had been thought that James Fort had been built on the swampy edge of the James River but as it turned out, James Fort was located near Mitchell on South Dakota.