Napa pond linked to dogs' deaths tests positive for toxic blue-green algae

Rich Fadness, the coordinator of the Surface Water Ambient Monitoring Program with the North Coast Regional Water Quality Board, was sampling the Russian River for blue green algae in this 2016 file photograph. (BETH SCHLANKER/The Press Democrat)


Tests of a Napa County pond linked to the June death of two dogs have confirmed the presence of a toxic blue-green algae bloom in the area, a news release from the county health department said.

The pond, located at the end of Milton Road in Napa, is part of the Napa-Sonoma Marshes Wildlife Area.

The tests showed levels of microcystin, the toxin produced by blue-green algae, are dangerously high: more than 200 micrograms per liter, compared to 20 micrograms per liter, which is the minimum for a body of recreational water to be declared “dangerous,” said Karen Relucio, public health officer for Napa County.

Danger signs are posted in the area, and the department warned against allowing pets to go in the water. In June, a pair of German Shorthaired Pointers died after playing near the pond. According to a sign posted by the owner, the dogs swam in the Milton Road pond on June 23, and died the next day.

Though bodies of water are tested when reports are made about suspicious algae blooms, Reducio said, “When in doubt, stay out.”

If you’re concerned an algae bloom in your area might be harmful, you can request that it be tested by calling 844-729-6466 or emailing

You can reach Staff Writer Christi Warren at 707-521-5205 or On Twitter @SeaWarren.