It should be easy enough to select all such sites with a query, probably relying on the LOCATION.ENTRY_DATE & LOCATION.ENTERED_BY fields would be sufficient to return all of their LOCATION_KEYs. On our system I would not risk just selecting locations with nothing associated, because we do have many sites which so far have nothing much attached, but may still contain something useful in the description field or elsewhere.

Then you would need to identify all the tables which might contain stuff associated with these sites. That might just be LOCATION and LOCATION_NAME, but you would need to check what information about each site was actually imported.

Then a simple delete query using the list of keys you first created to select first from dependent tables (LOCATION_NAME etc.) and then from LOCATION ITSELF.

The whole process looks pretty straightforward to me at first glance, but then I don't have to actually do it.

Good luck