Cyanobacteria (Blue-Green Algae) Updates

With the COVID-19 Shelter in Place mandate, all Park swim facilities are closed, but Park trails continue to be open to the public and safety around cyanobacteria issues continues to be a priority.  Park closure updates...


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: Cyanobacteria (blue-green algae) is present in Del Valle Reservoir, but no toxins have been detected. Keep dogs away from the lake.
  • Lake Anza (Tilden): Cyanobacteria (blue-green algae) is present in the lake. Avoid any contact with cyanobacteria or scums in the water, and keep dogs away from the lake.
  • Quarry Lakes : Until further notice the swim beach is CLOSED due to cyanobacteria (blue-green algae).
  • Lake Chabot: Cyanobacteria (blue-green algae) is present in the lake. Avoid any contact with the water and keep dogs away from the lake. Swimming is never permitted at Lake Chabot.

The Park District encourages visitors who wish to enjoy water activities to visit these other popular lakes, beaches, lagoons, and pools: Castle Rock in Walnut Creek,  Cull Canyon in Castro Valley, Contra Loma Lagoon in Antioch, Don Castro in Hayward, and Roberts Pool at Roberts Regional Recreation Area in Oakland.

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