It's possible to close or delete a level 1 site, by simply asking the support.
A closed site will still be on the list of level 1 sites, so you will still have access to historical data in your interface.
A deleted site will be withdrawn from your list of level 1 sites. You will not have access to data from the deleted site anymore.
In both cases, tags must be removed from the site prior to any action.
You can give us the sites and tell us if you want them to be closed or deleted.