Hey, I can totally confirm these tunnels, as I have been in them twice. Both times we entered them while buildings were being built/remodeled on campus. A while back (about 1988-89 or so), after a particularly victorious Longhorn weekend, we were celebrating at the Crown and Anchor. As time drew the bar to a close, we decided to walk around campus. I got the bright idea to check out the construction in the newly remodeled E. P. Schoch building. Inside the basement, we found what can only be called, a passageway. Of course, we followed it into the same tunnels you described. We actually got pretty far before we found the locked gate. Not as daring as you, we turned back. Several years later (1996), under similar circumstances at the Crown and Anchor (do we see a pattern here), we launched another expedition. This time, we started in the construction site of Neural Molecular Science Building. This is where I think you found “the beach”. The building was mostly just a frame work then, with floors in between. The day we were under there it had been raining, and the area with all the dirt was half full of water. It really was a beach. It was really cool looking as it was covered by the first floor, so it looked like an underground lake. I wish I had a camera. We found another access tunnel in that room. This one went on for quite a ways. Eventually, it lead up a spiral metal staircase going into the university power area. This was REALLY cool. It was a darkened room with lots of blinking lights and gauges. It was supervised by a technician in a glass room. He looked extremely sleepy (it was around 2-3 am). With the lights out and his lack of attentiveness, we crept around there for awhile, looking at various dials and gauges. After a bit of time, we decided not to push our luck any further and went back down the way we came. All in all, an adventurous night.