At the request of the Napa Countywide Stormwater Pollution Prevention Program (NCSPPP), Napa County Resource Conservation District (RCD) conducted a countywide dry-weather assessment of municipal storm drain outfalls to assist in compliance with waste discharge requirements for storm water discharges from small Municipal Separate Storm Sewer Systems (MS4s) set forth by California State Water Resources Control Board (SWRCB) Water Quality Order No. 2013-001-DWQ. The purpose of the assessment was to identify and address illicit discharges in each Napa County municipality by assessing each outfall, sampling and analyzing dry-weather flow when encountered, and investigating the source of the flow when action levels concentrations were exceeded. The results will be used to identify priority outfalls and establish a dry-weather flow monitoring program.