SPCWC’s Involvement in Protecting Water Quality in San Pedro Creek

San Pedro Creek is known to be polluted with fecal bacteria, which has contributed to advisory warnings at Pacifica State Beach. Common indicators of fecal contamination in creeks are Escherichia coli (E. coli) bacteria; fecal and total coliforms. E.coli and fecal coliform bacteria develop naturally in the intestines of humans and warm-blooded animals and sometimes make their way to our creeks and oceans. In high concentrations, these bacteria can pose a serious health risk to the public. San Pedro Creek is often used recreationally by members of the community. It has been reported that people and their pets have become ill after they were engaged in recreational activities in and around the creek. Not only is good water quality important to recreational use by the public, clean, healthy flows are also necessary to support migrating steelhead trout.

The San Francisco Regional Water Quality Control Board’s (SF RWQCB) Basin Plan identifies six specific beneficial uses for San Pedro Creek. These include: Cold Freshwater Habitat, Warm Freshwater Habitat; Fish Spawning; Fish Migration; Municipal and Domestic Supply; and Non-contact Water Recreation. The SF RWQCB requires that fecal coliform values in the creek, average less than 2000 MPN (Most Probable Number) for every 100 mL of water for Non-contact Water Recreation. These standards are based on a minimum of five consecutive samples, equally spaced over a 30 day period. The EPA bacteriological criteria applies to Contact Water Recreation and allows a maximum concentration of E.coli of less than 298 colonies per 100 mL of fresh water in moderately used areas.

Over the last 10 years a number of studies have taken place to analyze the water quality of San Pedro Creek. In 1998, the Environmental Protection Agency (EPA) began exploratory testing of the creeks water. At the same time, two Pacifica residents working with the San Francisco Waste Water Plant conducted their own independent study of the creeks water quality. The EPA and the Pacifica resident’s data showed that the creek’s bacterial levels were higher than the permissible for recreational purposes for most of the sampling period. In 2000, a comprehensive San Francisco State University Masters study examined the in-stream physical, chemical and biological characteristics of the creek. The study results were compared to the SF RWQCB and the EPA standards for Water Contact Recreation (1995 - Total coliform bacteria: less than 10,000 MPN/100 mL; fecal coliform: less than 200 MPN/100 mL, and E. coli: 235 MPN/100 mL). These standards were applied because children are known to play in the creek and because the creek flows into the ocean at Pacifica State Beach, a highly popular place for surfing, sunbathing, kayaking and swimming. Results from this study showed that fecal bacteria levels in the North Fork and Main Stem of San Pedro Creek far exceeded the acceptable levels for recreation as established by the State of California and the EPA.

To address water quality concerns in San Pedro Creek, the San Pedro Creek Watershed Coalition (SPCWC) developed a Microbial Source Tracking program aimed at identifying the sources of bacteria. In 2006, the SPCWC collected water samples from designated points throughout San Pedro Creek and worked with qualified laboratories to conduct DNA “fingerprinting” of the fecal bacteria to estimate the contribution percentage of human and animal sources of bacteria to the overall bacterial load of the creek. This research was done in concert with the San Mateo County Public Health Department who is providing ongoing weekly sampling at the creek mouth allowing us to see trends in the bacteria levels over time, which hopefully will show improvements from restoration projects.

Click here to learn more about the results from this Microbial Source Tracking study.

On-going Testing

Weekly water samples collected at the mouth of San Pedro Creek and analyzed by the San Mateo County Health Department show us that the water quality of San Pedro Creek often exceeds State of California standards and EPA criteria during high flow conditions. The San Mateo County Health Department also tests waters adjacent to Pacifica State Beach and will close the beach when sewage spill/overflows are reported. Advisory warnings are posted at the beach when:

  • Single samples exceed:
    • 10,000* total Coliform
    • 400* E. coli, or
    • 104* Enterococcus

  • Or if 5 week geometric mean exceeds:
    • 1,000* total Coliform
    • 200* E. coli,
    • or 35* Enterococcus

  • For Creek samples, only the single sample exceedences apply for postings.

*Most Probable Number (MPN) per 100 ml of water

To find current information on the quality of water at Pacifica State Beach, log on to the Earth 911 website.

 
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