Monday started as just another day for crane operator Brandon Valasik.
"I was excavating using a hammer grab and going through a layer of sand, when suddenly I noticed some strange object that came out," he recalled.
From 110 feet below the surface, Valasik had pulled up a tooth and part of a jaw of a woolly mammoth, considered the most famous of the prehistoric mammals, a cousin of the modern day elephant.
Paleontologist James Allen calls the fossil a well preserved and significant find. The wooly mammoth lived during what's called the Pleistocene Epoch, 1.8 million to 11,000 years ago.
"The Bay was a grassy valley with herds of these extinct critters just roaming around," said Allen, who believes these fragments could be 10,000 or 11,000 years old. "It's a big deal, so we can study it, get some age dates which help us figure out tectonics [and] seismicity like the San Andreas Fault."
Throughout this project, Transbay officials have had archeologists on the scene, and a treasure trove of other artifacts has been uncovered. The work continues on schedule, but now everyone is on the lookout for another piece of what one observant crane operator scooped up and set aside.
"A few people tried to convince me that it was just a rock, but it just looked too perfect to be a rock," said Valasik.
"Certainly if somebody were to come in and say we really think there may be a tusk or some hair or some skin, if it's safe to do further excavation we will do that," said Maria Ayerdi-Kaplan with the Transbay Joint Powers Authority.
The Transbay Joint Powers Authority plans to donate the find to the California Academy of Sciences to exhibit.