From Valve Developer Community
The Borealis was originally to be part of the Half-Life 2 storyline, but it was scrapped.
Portal in Half-Life Continuity
In this image you can see:
- The Borealis plans date back to January 1994.
- The Borealis has "Ice breaking capability 21 feet under full power".
- Two previous Black Mesa employees can be seen in a photo in front of the Borealis.
- "APERTURE SCIENCE LABS & ADMINISTRATION / ASSISTED (JAUNT?) CENTER - CLEVELAND, OH".