The break occurred in the emergency generator room on the second floor near the freight elevator shaft. It appears that during the EPH renovations this past summer, a ventilation window was cut into the South wall to allow fresh air to flush the motor room and no precautions were taken to insulate the water pipe a few feet away from that vent.
Luckily a student noticed the leak and security responded by evacuating the building. Plumbers, cleaners and physical plant personnel were dispatched and worked overnight to contain this leak (in addition to others in various university buildings) and clean-up the water so the building would be ready for normal operations (except for the wet carpets and soggy ceiling tiles) by Monday morning.
The departmental compute and file servers were shutdown on Saturday evening as a precaution against building power being shut-down and were online by Sunday afternoon.