SR-99 Arboleda Drive Interchange

Paleontological monitoring was required below the surface Holocene alluvium in the Modesto and Riverbank Formations. Cogstone’s field director and multiple monitors were present to ensure coverage of multiple pieces of heavy equipment activity. Monitoring resulted in recovery of 1,667 late Pleistocene fossils from 128 localities. They included a significant mammoth specimen as well as a variety of large and small mammals, birds, reptiles, and fishes. The presence of bison and dire wolf together indicates the fossil fauna is within the Rancholabrean Land Mammal Age. The fossils are curated at the University of California, Merced.