Polycyclic aromatic hydrocarbons (PAHs) are a class of organic compounds found in the environment associated with natural and anthropogenic activities such as the refinement and use of petroleum hydrocarbons as fuels and lubricants. When an oil spill occurs along the California coastline, an understanding of pre-spill or ambient levels of PAHs in nearshore areas is crucial for understanding the existing environmental conditions before a release occurs. Anthropogenic (e.g., vehicle and boat exhaust, wood burning, industrial activities, oil spills) and natural releases (i.e., forest fires, oil seeps) of PAHs are common sources of these compounds in the environment. Chevron, its affiliate companies, and the natural resource Trustees (Department of Fish and Game, U.S. Fish and Wildlife Service, Bureau of Land Management, National Oceanic and Atmospheric Administration) have partnered and developed plans to collect PAH monitoring data in California for the purpose of being prepared for oil spills and assessing natural resource injuries. Monitoring of specific PAHs associated with oil spills in surface water, sediment, and tissue (i.e., mussels and oysters) are proposed in areas along the California coast subject to potential spills by Chevron refining and transport activities. Between 2011 and 2019, Chevron and the Trustees collected samples in Eureka, Richmond, El Segundo, and San Diego, CA for PAH analysis to begin assessing ambient conditions. Chevron and the Trustees have the common understanding that the interpretation of statistical comparisons of these data to spill data (in the event one occurs) must take into consideration the sample size and geographic coverage of the available PAH monitoring data.