Combining Mounts

I have 2 mounts with me. Each 200 Gigs. I have some heavy duty processing, that may require more than 200 Gigs at time. Is there anyway that I can make the two points a clubbed up directory. Or create a symbolic link (bleahhh). Here are factors:

  1. two mounts are two different hard drives. (just thought of putting it too).
  2. I do not have authority to remove those two mounts.