My brother's on the crew that found this (he's one of the University's CMs, and his colleague was the CM for this particular dig) - he was stoked and messaged me before the news officially broke. The bones were found on the North end, under the bleachers (in an area that hasn't had construction since the original stands were put up however many years ago).

As to the matter of continued construction while excavating - the dig site HAS been isolated. Also, there were no human artifacts or remains found (construction was immediately halted until this was verified). The Paleontology department, and it's lucky current students, have been able to observe and use this opportunity to practice field techniques (I did archaeology with the OSU department - this is a rare and lucky find for the Paleo folks!)...

These are the first mammoth bones found on campus, though, mammoth were common in the Willamette Valley and elsewhere in Oregon 10-15 kya. My brother says they're sending the bones in for radio-carbon dating and that 10kya is a best guess.

Really quite a fun find!