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Last Updated: Wednesday, April 13, 2016 9:51 AM

Pathogens In Storm Drain Discharge

image of E. Coli and other bacteria
E. coli and other bacteria live in large numbers in our intestinal tracts. These bacteria are known as "indicator organisms" when they are used to test for pathogenic organisms that can accompany them in storm drain discharges.

image of kid on ocean beach

Large numbers of microorganisms can accumulate in storm drain water, which is then discharged into the ocean near beaches. To prevent possible illness in beach goers, public beaches are sometimes closed when microorganism counts are high. A healthy ocean environment is important for safe use by the public, and for the economic health of surrounding communities.

Microorganisms that can cause disease in humans are called pathogens. They are found throughout the environment, but are commonly associated with animal droppings and human sewage. Stormwater can wash pathogens from soil, sidewalks, streets, and roads into storm drain channels and waterways – including the ocean. When pathogens accumulate, there is a potential for illness for those coming into contact with the water.

Preventing stormwater pollution is a concern to many communities. With the support of Caltrans, this study is being conducted by UC Davis to help provide a better understanding of the possible health risks from urban runoff.

storm drain outfall near Moonlight Beach in San Diego County
Storm drain outfall near Moonlight Beach in San Diego County.

Pathogens in storm drain discharges present a public health challenge to beach communities. With this study, Caltrans and UC Davis are finding solutions…

Special Report

Management of Pathogens Associated with Storm Drain Discharge. CLICK HERE.

S T U D Y    C O M P O N E N T S

New techniques for identifying specific organisms in stormwater are being evaluated and developed that will be less expensive, quick, and more accurate than traditional methods. Pathogens and indicator organisms that often accompany pathogens can come from many different animals. A major focus of this study is to relate indicator organisms to the animals that produced them, and to assess the health risk by comparing the indicators with the actual pathogens found. Advanced DNA and organic chemistry analysis techniques will be applied to identify both indicators and pathogens.

Baseline studies will use these new techniques to identify sources of indicator organisms and specific pathogens by land use. Experiments will include flushing and analyzing runoff from selected sites such as parks, tennis courts, and streets for indicator organisms and pathogens in several watersheds throughout California. We will assess which animals produce the indicators and pathogens, and land uses that are associated with microorganisms in the runoff.

Extensive runoff sampling in various urban and rural watersheds will be conducted by local volunteers to collect valuable data as well as help raise awareness of the potential problems and solutions. Sampling for pathogens will take place near Moonlight Beach in San Diego County. When pathogens are found, they will be traced up the drain system to locate their entry point and identify the associated land use.


Division of Environmental Analysis, Stormwater Unit
California Department of Transportation
P.O. Box 942874, MS-27
Sacramento, CA 94274-0001
Email: Division of Environmental Analysis, Stormwater Unit