Report: Northern California Home to 7 of the 10 Most Polluted Beaches in California

Northern California is home to seven beaches on Heal the Bay’s dreaded Beach Bummer List, which ranks the 10 most polluted beaches in the state based on levels of harmful bacteria

Northern California beach-water quality sagged slightly in 2017-18, driven in large part by troubled beaches in San Mateo County and Humboldt County.

Some 88% of the 96 Northern California beaches monitored by Heal the Bay received an A or B grade for the busy summer season, according to the 28th annual Beach Report Card, which the Santa Monica- based nonprofit released today.

That figure marks a 3% dip from the region’s five-year summer average. Only 68% of beaches received an A or B for the winter dry season as well, a 16% drop from its seasonal five-year average.

Heal the Bay scientists assigned A-to-F letter grades to 118 Northern California beaches across three reporting periods in the 2017-18 report, based on levels of weekly bacterial pollution measured by county health agencies. Northern California beaches include those in Santa Cruz, San Mateo, Alameda, San Francisco, Contra Costa, Marin, Sonoma, Mendocino, Humboldt and Del Norte counties.

Overall, Northern California is home to seven beaches on Heal the Bay’s dreaded Beach Bummer List, which ranks the 10 most polluted beaches in the state based on levels of harmful bacteria.

No. 2 – Lakeshore Park, Marina Lagoon, San Mateo County This enclosed beach hits the list for the second year in a row, troubled by poor circulation and high bacteria counts.

No. 3 – Linda Mar Beach, San Mateo County This Pacific-side beach is impacted by polluted runoff from nearby San Pedro Creek.

No. 4 – Clam Beach County Park, Humboldt County This beach is impacted by runoff from Patrick Creek and Strawberry Creek. Private septic systems located nearby are also potential sources of bacterial pollution.

No. 5 – Roosevelt Beach, San Mateo County This Half Moon Bay site suffers from high bacterial exceedances related to nearby stormdrain runoff.

No. 6 – Luffenholtz Beach, Humboldt County This beach is impacted by runoff from Luffenholtz Creek. Beach sites near freshwater creeks often have elevated bacteria levels due to animal and human pollution sources along streams.

No. 8 – Cowell Beach, west of wharf, Santa Cruz County This historically troubled spot makes the list for the ninth straight year, but it’s making steady improvement. The city of Santa Cruz has taken steps to improve stormdrain flows and reduce bird-related bacteria by installing netting under the wharf.

No. 10 – Surfer’s Beach, San Mateo County Stormdrain outflow also troubles this Half Moon Bay spot, carrying harmful bacteria into the lineup.

Polluted ocean waters pose a significant health risk to millions of ocean users in Northern California, who can contract a respiratory or gastrointestinal illness from one morning swim or surf session in polluted waters.

  • San Francisco County outperformed its five-year summer average, with 100% of its 15 monitored beaches getting A or B grades.
  • Seven out of 8 monitored beaches in Alameda and Contra Costa counties received A or B grades for the summer.
  • Santa Cruz County’s 13 beaches notched grades well above average, with 92% A’s or B’s in summer and 88% A’s or B’s in wet weather (a boon to the region’s sizable year-round surfing population).
  • Sonoma and Mendocino counties boasted stellar water quality, with their seven and five beaches recording 100% A grades in summer and winter, respectively.
  • Marin County also fared well, with all of its 23 monitored beaches scoring an A or B.

In another positive sign, a record 37 beaches in California made the Heal the Bay Honor Roll this year – meaning they are monitored year-round and score perfect A-plus grades each week during all seasons and weather conditions. (A full list of Honor Roll beaches can be found on pg. 20 of the report.)

“A day at the beach shouldn’t make anyone sick,” said Dr. Shelley Luce, president and CEO of Heal the Bay. “We are glad to see water quality improving at most beaches, but there are no guarantees. Anyone headed to the shoreline should visit Heal the Bay’s new website to get the latest grades and predictions.”

Swimming at a beach with a water quality grade of C or lower greatly increases the risk of contracting illnesses such as stomach flu, ear infections, upper respiratory infections and rashes.

How to stay safe at the beach

  • Check for latest water quality grades
  • Avoid shallow, enclosed beaches with poor circulation
  • Swim at least 100 yards away from flowing storm drains, creeks and piers

For a detailed look at beach results for each county and report methodology, please refer to our complete report. A PDF version is available at

Active NorCal

Telling the Stories of Northern California

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