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Ocean Water Monitoring Basics

Why is the water in Avalon Bay tested?
In 1999, a California State regulation known as Assembly Bill 411 (AB411) was passed and required that all beaches that are adjacent to a flowing storm drain and have 50,000 visitors a year are required to be tested on a weekly basis between April 1st and October 31st every year.

The Los Angeles County Department of Health Services (LACDHS) is in charge of routinely monitoring the water quality of beaches in Los Angeles County. The LACDHS recreational health program collects ocean water at 26 sampling sites along the coast from the Ventura/Los Angeles County border to south of the Redondo Beach pier. In addition to these coastline monitoring sites, 5 sites are routinely monitored in Avalon Bay located on Catalina Island.

Every Monday between April 1st and October 31st, County health officials collect a single water sample from each of the sites. These water samples are collected between ankle and knee deep (approximately 4 to 24 inches below the ocean water surface). Once the water sample is collected, it is put on ice and taken to the Department of Health Service's laboratory and analyzed within 6-8 hours of the collection time.

What is Avalon Bay tested for?
All water samples are tested for three types of indicator bacteria. These indicator bacteria are Total coliform, Fecal coliform, and Enterococcus. These three "indicators," at sufficient concentrations, indicate the potential presence of other bacteria (pathogens) in the ocean water that may cause human illness.

California State Standard Maximums for Indicator Bacteria

  • Total Coliform density shall not exceed 10,000/100mL
  • Fecal Coliform density shall not exceed 400/100mL
  • Enterococcus density shall not exceed 104/100mL

If the water sample results exceed California State standards for any one of the three types of indicator bacteria, local lifeguards are immediately notified to post a warning sign at the beach where the water sample is collected.

These indicator bacteria can be found in the natural environment (e.g. soil and decaying vegetation), as well as, in the intestinal tract of warm blooded animals (e.g. humans, birds, dogs, cats, etc.) Studies have shown that ocean or bay waters with elevated indicator bacteria levels may contain viruses or pathogens that can cause illnesses.

Why don’t they test for the actual viruses that can cause illnesses?
Testing for the actual viruses would be the best approach to identifying the specific source of fecal pollution. Unfortunately, these tests are currently expensive, highly technical, and results can take a long time to obtain. The good news is that many efforts are being made to make advances in virus testing and identifying the exact sources that cause high bacteria levels in the water. The State is playing an active role in these new advances and hopes to implement these new tests for the State-wide monitoring program in the near future.

What causes high bacteria in the water?
Bacteria are a natural component of our environment. Indicator bacteria can be found in soils, decaying vegetation and animal waste. Humans also contribute to bacteria levels in the environment via discharges of raw or partially treated sewage, soiled diapers, improper garbage disposal, etc. Bacteria may also enter the ocean through runoff. Runoff can happen anytime of the year when rainfall or excessive water use from irrigation, car washing, and other sources carry litter, lawn clippings and other pollutants into storm drains.