You should have already started SIA and prepared it for tasks as described in Starting SIA and Preparing for Deployment or Recovery Tasks.
The Select a Task menu should be displayed.
Select the RAID Configuration task, and then click Next.
The RAID Configuration page appears.
Select the RAID volume to be deleted from the Available Volumes box and click the Delete Volume button.
Caution - Deleting a volume will erase all data on the volume.
Disks that were in the volume are once again listed in the Available Disks box.