Lake County health officials issue warning about drinking water from parts of Clear Lake

Lake County officials are hustling to find alternate drinking water sources for an estimated 280 households whose regular supplies may be compromised by high concentrations of toxic blue-green algae in Clear Lake.

Most residents are served by one of 55 commercial water systems operating around the county, officials said. But those with private systems that take water directly from the lake may not have sufficient treatment capacity for increasing levels of a potent liver toxin called microcystin. The toxin is produced by cyanobacteria — naturally occurring microorganisms commonly called blue-green algae, though they aren’t actually algae.

The focus of concern are the “rimlanders” living along especially shallow waters in the narrow arms that form the southeastern part of Clear Lake, where densities of a microcystin have continued to climb in recent weeks, driven by persistently warm weather and diminishing lake levels amid historic drought.

The lower arms also catch what comes from upwind, said District 2 County Supervisor Bruno Sabatier, board chairman.

“The current and wind push everything in this direction,” said Sabatier, whose district centers includes the lakefront around the city of Clearlake.

Even public water systems are being challenged by high densities of cyanobacteria and cyanotoxins, but their filtering systems are powerful, and the water they treat is tested every day to ensure it meets state drinking water standards, he said.

It’s the private systems — the ones used specifically for drinking water, cooking and bathing, in addition to irrigation — that officials worry about, Sabatier said.

Boiling the water or adding chemicals does not eliminate the toxins, health officials said.

A recent sampling of 50 of the 280 private systems turned up tap water with cyanotoxins above levels set by the U.S. Environmental Protection Agency even before a more recent and significant rise in toxins in the lake, they added.

He said local officials have been worried for some weeks about routine testing that showed increasingly high concentrations of microcystins in Clear Lake and had sent information to residents not linked up to commercial or public water suppliers.

It wasn’t until Wednesday, after results from testing conducted Sept. 7 showed record-high concentrations of two toxins, including microcystin, at several places on the lake, that they decided it was time to step up their warnings. One of the worst locations was off shore of Redbud Park in Clearlake, where the level was more than 200,000 times what’s considered safe, county officials said.

In an urgent notice issued late Wednesday, Public Health Director Gary Pace cautioned residents with private water intakes and treatment systems to stop drinking the tap water.

“Effective immediately, people on private water systems whose tap water comes from their own private intake into the lake, in the Oaks Arm and Lower Arm of Clear Lake, should not drink the water,” Pace wrote. “Very high levels of Cyanotoxin have been identified in these areas of the lake, and we are concerned there may be health impacts if private water systems are not effectively filtering out these toxins.”

Public Health officials said Thursday the advisory could be in effect for weeks.

Sabatier said county representatives had been in meetings throughout the day and were working with local water districts, state water officials, local tribes and cities to try to find solutions. Health officials said alternative filling stations near affected homes were among the goals.

“We’re trying to find the quickest and easiest way logically to manage this,” Sabatier said.

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