Skip to main content
Monterey Bay National Marine Sanctuary National Marine Sanctuaries Home Page National Oceanic and Atmospheric Administration Home Page

Beach Closures and Microbial Contamination

people walking on beachCalifornia has some of the most popular beaches in the country. Over 150 million day visits are generated by tourists and residents use them annually to swim, wade, surf, and dive. Beach visitors spend over $10 billion each year in California. For this reason, beach water quality monitoring and strong pollution prevention measures are critical for protecting beach goers from waterborne diseases [1]. Indicator organisms from warm-blooded animals (total coliform, fecal coliform, E. coli, and enterococcus) may not cause disease in humans, but their presence tells us that water may be contaminated with organisms that do cause health impacts ranging from fever, flu-like symptoms, ear infection, respiratory illness, gastroenteritis, cryptosporidiosis, and hepatitis. We use indicator bacteria because direct identification of pathogens, such as viruses in ocean water is difficult, time consuming, and expensive. Not only can humans be affected by these organisms in the ocean, but research into the cause of mortality among the threatened southern sea otter population, shows that infectious agents have been caused by protozoal parasites and bacteria that are spread by fecal contamination of near shore marine waters by terrestrial animals. 

Sources of contaminated water include point source runoff (from a known source) to non-point source runoff. Contributing factors that generate these sources include illicit storm drain connections, improper disposal of materials which clog pipes and cause sewer system overflows, cracked or damaged pipes, overflow of sewer systems during storm events, septic system leaching, non-point pollutant loading exposed to storm runoff, and various domestic and wildlife fecal sources.

Beginning in 1999, Assembly Bill 411 (AB411) required local health officers to conduct weekly bacterial testing between April 1 and October 31 of waters adjacent to public beaches having more than 50,000 visitors annually and that are near storm drains flowing in the summer.  County Health Officers can take three discrete actions based upon beach water quality monitoring data, sewage spills, and storm events:

  • Beach Advisories or Beach Postings occur when at least one bacterial standard from the Ocean Water Contact Sport Standards issued by the California Department of Health Services, has been exceeded. Warning signs alert the public of a possible risk of illness associated with water contact. The placement of signs may be short term or more permanent where monitoring indicates repeated contamination (e.g. from a storm drain). Warnings may be posted where sources of contamination are identifiable and can be explained as not of human origin (e.g., resident marine mammals or seabirds) or of an unknown source.
  • Beach Closures occur as a result of a known sewage spill that has the potential to reach coastal waters.  A closure is a notice to the public that the water is unsafe for contact and that there is a high risk of getting ill from swimming in the water.  When a beach is closed, signs are posted alerting the public to stay out of the water.
  • Rain Advisory can be issued when it rains because it is known from past experience that rainwater carries pollution to the beach. After a rainstorm, bacteria levels usually exceed the State standards for recreational water use due to untreated storm drain flows that may contact motor oil, pet waste, pesticides, and trash.

It is important to recognize that there is a fundamental difference between beach closures and beach advisories.  Beach closures result from known sewage spills or repeated exceedances of standards from unknown sources, whereas beach advisories are a result of an exceedance of standards derived from water testing results.  

In 2011, California adopted Senate Bill 482 Beach Safety Program. This basically took the responsibility of AB411 activities off of the CA Department of Public Health and made the State Water Resources Control Board responsible for implementation.

How is the Sanctuary involved?

The Beach Closure and Microbial Contamination Action Plan was initiated as part of the Sanctuary's Management Plan Review in 2008. The plan addresses the issue of beach closures and constitutes the fifth action plan as part of the Water Quality Protection Program.

Summary of Strategies:

  • Use Geographic Information System (GIS) to map monitoring locations, septic and storm drain maps, heavily used beaches and sensitive habitats
  • Expand pathogen and contamination research to explore other indicators, have access to more real conditions, and be able to identify the source of the pathogens
  • Increase the monitoring network so that more beaches are monitored more frequently and additional upstream monitoring is conducted for source tracking
  • Enhance the notification system in an effort to increase public access to water quality information before they depart for the beach
  • Work with local jurisdictions to enhance the repair and replacement of sewer infrastructure to reduce leaking pipes and clogs
  • Enhance public outreach of contamination sources and the solutions
  • Increase and coordinate enforcement efforts as well as improve the emergency response to spills 24 hours a day

The Sanctuary is currently working with cities to address beach closures from bacterial contamination and urban runoff by monitoring watersheds and storm drains to help identify sources of pollutants and contamination. By investigating and jointly pursuing potential funding opportunities for local communities to better identify sources of bacterial contamination and improve infrastructure, local cities and the Sanctuary benefit.

Examples of collaboration include:

  • Restructured the Urban Watch program to include upstream source tracking
  • Source tracking at Steinbeck Plaza in Monterey
  • Participation in the SWRCB Beach Water Quality Meetings in Alameda, CA
  • Participation on Greenwood Park ASBS Restoration Project TAC
  • Coordination of MRSWMP storm water monitoring program

For more information please check out these links


Reviewed: April 11, 2024
Web Site Owner: National Ocean Service

Take Our Survey | Privacy Statement | Site Disclaimer
National Marine Sanctuaries | National Ocean Service | National Oceanic and Atmospheric Administration |