San Mateo County Environmental Health Department officials are warning residents and visitors to avoid swimming in the ocean or San Francisco Bay near the shore, because runoff from winter storms is likely to raise the amount of bacteria in the water to unsafe levels.
The large volumes of water running down hillsides and through dry streambeds to the ocean and Bay creates a flushing action that will likely raise bacteria levels, according to the department.
Water within 300 feet of urban streams, lagoons, river mouths and storm drain outlets are especially dangerous, and should be avoided for at least three days following a major storm.
Staff members, along with volunteers from the Surfrider Foundation collect samples of beach and creek waters every Monday, according to the department. The County Public Health lab then tests the samples for total and fecal coliforms. Coliforms are a group of bacteria that inhabit the intestinal tracts of people and animals. When found in water they indicate the potential presence of organisms that are known to cause disease in people.
Symptoms associated with swimming in areas with high levels of bacteria are nausea, vomiting, fever, skin rashes and diarrhea.
A list of posted beaches and creeks can be found at http://www.smhealth.org/environ/beaches or by calling the hot line at (650) 599-1266.