San Gregorio Creek

Half Moon Bay, California
Managed by The Swim Guide

Photo by Nathan Siemers

San Gregorio Creek is located within San Gregorio State Beach, 10.5 miles south of Half Moon Bay, California. The creek widens to form a protected, driftwood-strewn estuary at the back of a wide barrier beach. This normally blocks the mouth of the creek, forcing the creek water to flow underground as it discharges into the Pacific Ocean. Historically the creek was a coho salmon spawning site and the Department of Fish and Game is considering restocking it. The estuary is home to many small birds and mammals. The California Historical Landmark 26 commemorates the passage of the Spanish Explorer Captain Gaspar de Portolá through this area in October 1769.

The weather can be fickle here so layered clothing is recommended. Park facilities include restrooms and picnic tables. Dogs are not permitted on the beach, as it has been identified as potential nesting habitat for the endangered Western Snowy Plover. Beach fires are prohibited. Abstain from removing shells and driftwood from the beach.

COVID-19

Keep your distance from other people.

Practicing social distancing is essential right now. Follow the advice of the health experts. If your community has asked that you remain indoors and away from others, do so. Heading to the beach should only be considered an option if social distancing practices can be followed. Spending a day in any crowded place is the worst thing we can do for our most vulnerable right now and will counter the efforts to curb the virus’ spread.

For more information, please visit the World Health Organization public resource on COVID-19.

Water Quality
  • Passed water quality tests 60-95% of the time

  • Historical Status
  • This status is based on the latest sample, taken on March 16th, 2020. The Swim Guide updates the status of this beach as soon as test results become available. These results were posted to Swim Guide on March 19th, 2020 at 12:54 PM.
For water quality icon legend, click:  
Monitoring Frequency

San Gregorio Creek is sampled weekly from April 1st from December 31st.

Source Information

San Mateo County conducts weekly sampling at over 43 ocean and fresh water sites throughout the year. Samples are collected on Mondays and analyzed by the San Mateo County Public Health Laboratory for the levels of three indicator bacteria. Results are posted to their website within 48 hours. Swim Guide checks for the latest results daily.

The standards for indicator bacteria are as follows:Single sample maximumTotal Coliform > 10,000 MPN (Most Probable Number) / 100 ml of waterEnterococcus > 104 MPN / 100 mlE.coli > 400 MPN / 100 mlGeometric Mean (5 samples collected over a 30 day period)Total Coliform > 1,000 MPN / 100 ml of waterEnterococcus > 35 MPN / 100 mlE.coli > 200 MPN / 100 mlA beach is marked Green when bacteria levels for a single day and geometric mean are below the standards mentioned.A beach is marked Red when bacteria levels for a single day or the geometric mean are above the standards mentioned. A beach is marked Grey when there is no current or reliable monitoring information available.Please contact Greg Smith of County Environmental Health by email GJSmith@smcgov.org or phone (650) 372-6200 if you are interested in becoming a volunteer to help collect water samples at your favorite beach. If you think you’ve contracted an water related illness please send us a pollution report, see your doctor and contact County Environmental Health Services at (650) 372-6200 to make a report. They will need your name, the dates and areas you were swimming, symptoms and contact information for your or your health care provider.

Water Quality Graph

San Gregorio Creek

Half Moon Bay, California
Managed by The Swim Guide

COVID-19

Keep your distance from other people.

Practicing social distancing is essential right now. Follow the advice of the health experts. If your community has asked that you remain indoors and away from others, do so. Heading to the beach should only be considered an option if social distancing practices can be followed. Spending a day in any crowded place is the worst thing we can do for our most vulnerable right now and will counter the efforts to curb the virus’ spread.

For more information, please visit the World Health Organization public resource on COVID-19.

Water Quality
  • Passed water quality tests 60-95% of the time
  • Historical Status
  • This status is based on the latest sample, taken on March 16th, 2020. The Swim Guide updates the status of this beach as soon as test results become available. These results were posted to Swim Guide on March 19th, 2020 at 12:54 PM.
For water quality icon legend, click:  

Photo by Nathan Siemers

San Gregorio Creek is located within San Gregorio State Beach, 10.5 miles south of Half Moon Bay, California. The creek widens to form a protected, driftwood-strewn estuary at the back of a wide barrier beach. This normally blocks the mouth of the creek, forcing the creek water to flow underground as it discharges into the Pacific Ocean. Historically the creek was a coho salmon spawning site and the Department of Fish and Game is considering restocking it. The estuary is home to many small birds and mammals. The California Historical Landmark 26 commemorates the passage of the Spanish Explorer Captain Gaspar de Portolá through this area in October 1769.

The weather can be fickle here so layered clothing is recommended. Park facilities include restrooms and picnic tables. Dogs are not permitted on the beach, as it has been identified as potential nesting habitat for the endangered Western Snowy Plover. Beach fires are prohibited. Abstain from removing shells and driftwood from the beach.

Monitoring Frequency

San Gregorio Creek is sampled weekly from April 1st from December 31st.

Source Information

San Mateo County conducts weekly sampling at over 43 ocean and fresh water sites throughout the year. Samples are collected on Mondays and analyzed by the San Mateo County Public Health Laboratory for the levels of three indicator bacteria. Results are posted to their website within 48 hours. Swim Guide checks for the latest results daily.

The standards for indicator bacteria are as follows:Single sample maximumTotal Coliform > 10,000 MPN (Most Probable Number) / 100 ml of waterEnterococcus > 104 MPN / 100 mlE.coli > 400 MPN / 100 mlGeometric Mean (5 samples collected over a 30 day period)Total Coliform > 1,000 MPN / 100 ml of waterEnterococcus > 35 MPN / 100 mlE.coli > 200 MPN / 100 mlA beach is marked Green when bacteria levels for a single day and geometric mean are below the standards mentioned.A beach is marked Red when bacteria levels for a single day or the geometric mean are above the standards mentioned. A beach is marked Grey when there is no current or reliable monitoring information available.Please contact Greg Smith of County Environmental Health by email GJSmith@smcgov.org or phone (650) 372-6200 if you are interested in becoming a volunteer to help collect water samples at your favorite beach. If you think you’ve contracted an water related illness please send us a pollution report, see your doctor and contact County Environmental Health Services at (650) 372-6200 to make a report. They will need your name, the dates and areas you were swimming, symptoms and contact information for your or your health care provider.

Water Quality Graph

  Beach Location Water Quality
San Gregorio, California
Half Moon Bay, California
Half Moon Bay, California
San Gregorio, California
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