It began as a mystery for local water experts in San Diego County: numerous area streams showing the presence of caffeine, a stimulant with no natural source in California.A team from the state’s Surface Water Ambient Monitoring Program (SWAMP) pulled samples from 85 different locations across the county and found caffeine in 49 locations. According to a February fact sheet, from the Regional Water Quality Control Board, the group was finding similar results year round in a seven-year period from 2008-2015.