Clear Lake residents near massive blue-green algae blooms offered access to treated drinking water

Expansive blue-green algae blooms around the lower portions of the lake this year have raised toxin concentrations to some of the highest levels ever seen this early in the season.|

Clear Lake residents with private water treatment systems have been put on notice for the second successive year that their household water may not be safe to drink or use for brushing their teeth.

Expansive blue-green algae blooms around the lower portions of the lake this year have raised toxin concentrations to some of the highest levels ever seen this early in the season. That has prompted the county to invite folks who derive their water directly from the lake to use water filling stations opened last year by two community suppliers.

Public water treatment plants are robust enough to remove harmful algae and the toxins they produce from the water, officials said.

But testing begun last year under a 5-year grant from the Centers for Disease Control showed individual treatment systems were insufficient to handle the algae, technically cyanobacteria.

Those tests found that blue-green algae came through the process — and out of the kitchen tap — intact, said Sarah Ryan, environmental director for the Big Valley Band of Pomo Indians Environmental Protection Department, which tests and monitors Clear Lake in conjunction with the Elem Indian Colony.

In other cases, some treatment processes may break open the cell structure but leave the toxins behind, Ryan said.

Boiling does not eliminate the problem, officials said.

About 280 households are believed to have private water intakes in the lake and may be at risk of exposure to toxins produced by cyanobacteria, according to Dwight Coddington, a spokesman for Lake County Health Services Department.

Depending on the type, cyanotoxins can cause everything from skin irritation to stomach upset to respiratory or neurological symptoms.

It’s not just those with private water systems who are subject to the impacts of the slimy, rank-smelling stuff that has invaded shorelines in the lower arms of Clear Lake.

The substance “looks and smells like raw sewage,” Ryan said.

“The stench is horrendous,” extending well onshore and causing some people to experience headaches and nausea, she said.

There is also the unpleasant and unsightly nuisance that comes with the scummy mats the blue-green algae forms along the shoreline.

In one of them, in Lilly Cove, near the city of Clearlake in the lake’s lower arm, Ryan and her team found a fish kill of about 50 or more small fish, though it’s not yet known if their demise was related to the cyanobacteria.

The fish and water sample readings have been sent to the California Department of Fish and Wildlife in hopes experts there can determine if there’s a connection, Ryan said.

But water testing indicated there was plenty of dissolved oxygen in the water, though the ammonia levels were high for unclear reasons.

Naturally occurring blue-green algae has been an issue in Clear Lake for decades, but it was viewed primarily as a nuisance before its toxicity was fully recognized.

As nutrient levels have increased, in large part from fertilizers in runoff, blooms have continued to grow, particularly in hotter, drier periods, as is the case around California.

Cyanotoxin also has been observed throughout Lake Pillsbury in northern Lake County this summer, as well as in areas of the Russian River.

In 2009, the blooms were bad enough to cancel several fishing tournaments and even close businesses, Ryan said. When a dog died in 2013, it was shown to involve microcystin, a common cyanotoxin that attacks the liver.

Last year, when testing revealed that many private water treatment centers were not truly purifying the water, the Golden State Water Co. in Clearlake and the Mt. Konocti Mutual Water Co. worked with the county to provide water filling stations for those who needed access to clean water.

Not everyone eligible used them, and it’s not clear how many people turned to bottled water or just continued using tap water, Ryan and Coddingtown said.

There’s also some concern, said Ryan, about how or if vacation renters were informed of the need to obtain drinking and cooking water elsewhere.

The filling stations are located at 10680 Lakeshore Dr., in Clearlake, and at 4980 Hawaina Way, in Kelseyville.

More information is available at or at

Ryan urged anyone who had any symptoms or who had a sick animal related to blue-green algae to report the illness to the California State Water Board online at, via email at, or by phone at 844-729-6466.

“The toxin level is already really high, and the lake already is low and getting lower,” Ryan said. “It’s going to be a challenging year.”

You can reach Staff Writer Mary Callahan at 707-521-5249 or On Twitter @MaryCallahanB.

Mary Callahan

Environment and Climate Change, The Press Democrat

I am in awe of the breathtaking nature here in Sonoma County and am so grateful to live in this spectacular region we call home. I am amazed, too, by the expertise in our community and by the commitment to protecting the land, its waterways, its wildlife and its residents. My goal is to improve understanding of the issues, to find hope and to help all of us navigate the future of our environment. 

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