The vast majority of ocean waters along the coast of Los Angeles County meet State ocean water quality standards. The only exceptions are areas adjacent or in front of discharging storm drains and after major rainstorms. Flowing storm drains and areas not meeting standards are posted with warning signs. A rain advisory is issued anytime ocean waters are affected by a rainstorm. On rare occasions when there is a sewage or chemical spill, beaches are posted with closure signs.
Storm drains direct runoff from urban areas to the ocean.
While they do not normally contain sewage, water in storm drains can contain disease-causing pathogens. Depending on the amount of flow, the discharging storm drains can affect ocean water quality several hundred yards from the discharge point. Much greater areas may be affected following major rainstorms. These indicator bacteria can be found in the natural environment as well as in the intestinal tract of warm blooded animals. When present, they indicate the possible presence of disease causing bacteria, viruses or protozoa.