Construction on a replacement Calaveras Dam was completed in May 2019.  In order to make room for, and construct, the new earth and rock fill dam, SFPUC crews moved almost 12 million cubic yards of rock and soil.

While moving all of this earth, the project team began to find what has since been called one of the greatest fossil finds in the Bay Area in decades.

The area around the New Calaveras Dam was once the beachfront of an inland ocean that extended into the Central Valley between 15 and 20 million years ago. The weather was warmer then, and these waters teemed with all sorts of life which left traces for the SFPUC to find.

Project paleontologists started finding fossils in 2012, and the site did not disappoint. To date more than 1,300 specimens have been identified.  Amongst the vertebrate fossils were marine mammals, like baleen whales,  toothed whales and dolphins. Paleontologists found the remains of a desmostylus, a hippo-like marine mammal that went extinct long ago. Scientists identified bones from seals or sea lions and bony fish, such as halibut. The teeth of many different types of sharks were identified, including some from the megalodon, a giant shark the size of a school bus. The invertebrates included scallops (some as big as a dinner plates), clams, snails, cockles, mussels, crabs, and barnacles. 

Researchers determined this area was near to shore because they also found plant material that washed into the ocean from land, including pine cones, palm trees, leaves, and wood.

Through an agreement between the SFPUC and the University of California Museum of Paleontology (UCMP), the entire collection of fossils are now housed within the UCMP collections. The fossils represent California’s fossil heritage and as such, belong to all the citizens of California, and will be managed on their behalf by the University of California Museum of Paleontology. UCMP staff will digitize the collection and make it available for scientific study.

The UCMP assembled a team to manage this collection, including a Lab Manager – Dr. Cristina Robins, many undergraduate students, two graduate students per semester, and volunteers.

Dr. Robins and her team are painstakingly chipping away the rock from the fossilized bone to identify each specimen. It has been laborious, but rewarding work. The vertebrate finds have been the most exciting for scientists because the vertebrate fossil record from this time period is relatively scant. Dr. Robins and her team recently identified a new species of whale found at the site. They have only scratched the surface of the Calaveras specimens in their lab. No doubt more exciting discoveries are to come.