SQL Server - Data Warehouse large log file, how to safely shrink?
Switch to SIMPLE recovery mode.

FULL recovery mode is for when you need point-in-time recovery, and requires that you take frequently transaction log backups.

Since you've stated (in the comments) that you don't need point-in-time recovery, and that you can rebuild the entire thing in a matter of 30 minutes, just switch to simple.

The transaction log file will still be used by in-process transactions, but when those complete/commit (or are cancelled/rolled back) the tran log space is marked for re-use.

Once you've made the change, you can recover some of the additional space by using SHRINKFILE:

DBCC SHRINKFILE (NAME = 'mydatabase_log', 5000)