From 1800s to the mid 1900s, mercury was mined free of environmental regulation causing an influx of the element within Cache Creek. In 2001, the Central Valley Regional Water Quality Control Board and the U.S. Geological Survey confirmed that Cache Creek was a contributor to the increase of mercury levels within the Sacramento River. Since then, various regulations have been enacted to monitor the mercury levels in Cache Creek, and multiple studies have been conducted to find the site of contamination. The California Office of Environmental Health Hazard Assessment released an advisory regarding eating fish caught from this creek based on the mercury level.