Cyanobacteria (Blue-Green Algae) Updates

Notice
With the COVID-19 Shelter in Place mandate, all Park swim facilities are closed. However, Park trails have remained open, and safety around cyanobacteria issues continues to be a priority.  Park updates.
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Due to the drought and unusually warm weather conditions, toxic blooms of cyanobacteria (blue-green algae) and other water-quality issues are occurring more frequently in the East Bay Regional Park District and elsewhere. We monitor our lakes and shorelines regularly and post warnings and closures when appropriate. Here’s a current update of which lakes and shorelines are affected:

  • Lake Del Valle: Danger Advisory Posted- Cyanobacteria (blue-green algae) is present present in the reservoir, and high levels of toxins have been detected recently. Avoid any contact with cyanobacteria or scums in the water, and keep dogs away from the lake. Swimming is not permitted due to COVID-19 restrictions.
  • Lake Anza (Tilden): Danger Advisory Posted- Cyanobacteria (blue-green algae) is present in the lake, and toxins have been detected recently. Avoid any contact with cyanobacteria or scums in the water, and keep dogs away from the lake. Swimming is not permitted due to COVID-19 restrictions.
  • Lake Temescal: No Advisory Posted- Cyanobacteria (blue-green algae) is present in the lake, but all toxins detected have been below California state advisory levels recently. As a precaution, avoid any contact with cyanobacteria, and keep dogs away from the lake. Swimming is not permitted due to COVID-19 restrictions.
  • Big Break: No Advisory Posted- Cyanobacteria (blue-green algae) is absent at the shoreline. All toxins detected have been below California state advisory levels.
  • Quarry Lakes: Danger Advisory Posted- Cyanobacteria (blue-green algae) is present in the lake, and toxins have been detected recently. Avoid any contact with cyanobacteria, and keep dogs away from the lake. Swimming is not permitted due to COVID-19 restrictions.
  • Lake Chabot: Caution Advisory Posted- Cyanobacteria (blue-green algae) is present in the lake, and high levels of toxins have been detected. Avoid any contact with the water and keep dogs away from the lake. Swimming is never permitted at Lake Chabot.
  • Shadow Cliffs: No Advisory Posted- Cyanobacteria (blue-green algae) is absent in the lake. All toxins detected have been below California state advisory levels. Swimming is not permitted due to COVID-19 restrictions.
  • Conta Loma : No Advisory Posted- Cyanobacteria (blue-green algae) is present in the lake, but all toxins detected have been below California state advisory levels recentlyAs a precaution, avoid any contact with cyanobacteria or scums in the water, and keep dogs away from the water. Swimming is not permitted due to COVID-19 restrictions.

    More Information

  • Cyanobacteria (Blue-Green Algae) Brochure [PDF]
  • District Swim Facilities
  • Cyanobacteria (Blue-Green Algae) Information 
  • Water Resources - Swim Beach Water Quality Conditions
  • Media Coverage

    Thank you for your patience and cooperation!

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