TCC and T18 Upper Feather River Dams Fault Exploration, Indian Creek Fault (ICF)

To assess potential tectonic risks to the safety of Antelope Dam, two trenching sites, T-CC and T-18, will be excavated along the Indian Creek Fault near Antelope Lake in the Mt. Hough Ranger District, California. Each site will undergo up to two excavations to investigate the fault’s historical movement, with T-CC located approximately one mile upstream and T-18 about three miles upstream of the dam. Prior to excavation, preliminary subsurface investigations will be conducted using hand augers or post-hole tools to gather geologic data; these borings will be carefully backfilled with the original soil, which will be temporarily stored on tarps to preserve stratigraphic integrity and minimize environmental disruption. The work is being conducted by the California Department of Water Resources to determine whether past seismic activity along the fault could pose future threats to dam stability, and all efforts are designed to maintain site conditions and ecological balance during and after fieldwork.