Note: Base buckets that are configured on usage buckets or other entities are in use and cannot be deleted (the delete action button will be greyed out in this case). In order to delete a base bucket in use first check the References tab on the Edit Bucket panel to determine which entities are configured with the base bucket. Next, proceed to modify those entities to use an alternate base bucket.
Under the Buckets heading on the left select the base bucket you wish to delete
Under the same Buckets heading on the left click the icon
On the confirmation dialog that appears select Yes