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Press Release

Enjoying the Delta this Weekend? Watch for Harmful Algae Blooms

Thursday, August 29, 2019

Archived. This is an older press release from 2019 and may not contain the latest information. Please view our current press releases for 2021 items.

Contra Costa Environmental Health (CCEH) encourages anyone planning to boat or enjoy the water in or around the Sacramento-San Joaquin River Delta this weekend to stay safe and avoid harmful algae blooms (HAB).

A bloom is a buildup of blue-green algae (cyanobacteria) that creates a green, blue-green, white or brown coloring on the surface of slow-moving waterways. Contact can make people or pets very sick.

The East Bay Regional Park District has posted a "danger" advisory at Big Break Regional Shoreline in Oakley at the kayak launch and around the fishing dock after detecting cyanobacteria in the water.

A "danger" advisory means:

  • Stay out of the water, and do not touch algae scum in the water or on the shore
  • Do not use the water for drinking, cleaning or cooking
  • Do not let pets or livestock enter or drink the water
  • Do not eat fish or shellfish from the water

Additionally, the California State Water Resources Control Board has posted a "caution" advisory around the mouth of Mormon Slough near the Morelli Boat Ramp due to the presence of cyanobacteria.

Visitors should follow the directions on all posted signs and:

  • Do not swim or wade near algae or algae scum
  • Keep children and pets away from algae in the water or on the shore
  • Do not drink the water or use it for cooking or cleaning
  • Don't eat shellfish from the water

Visit for health and safety instructions associated with HAB advisories.

The California State Water Resources Control Board also found small amounts of cyanobacteria in water sampled in three other areas: Fourteenmile Slough/White Slough, Buckley Cove and the San Joaquin River at Windmill Beach. Other waterways may also have cyanobacteria, but they've not been reported.

Whether or not there's a posted advisory, protect yourself and your pets by rinsing off with fresh water after touching the water, and make sure dogs don't drink the water or swim near algae blooms. Bring fresh drinking water for your pets.

If you see large algae blooms in the water, do not swim and avoid contact. More information about harmful algae blooms at

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Press Contact
  • Karl Fischer,