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Health Advisory Lifted

Health Services Department
Public Health Division
922 Bevins Court
Lakeport, California 95453-9739
Telephone 707/263-1090
FAX 707/263-4395

A Press Release from the County of Lake’s Health Services and Water Resources Departments and Big Valley Band of Pomo Indians

Drinking Water Health Advisory for Individual Household Intakes in Lower and Oaks Arms of Clear Lake Lifted

Public Health Officials Strongly Urge Affected Households Flush Water Treatment Systems, Change Filters

Lake County, CA (November 12, 2021) -- The weather is changing. As a result, we are seeing decreases from September’s extremely high levels of cyanotoxins, which prompted a drinking water Health Advisory for individual household intakes (not Public Water Systems) in the Lower and Oaks Arms of Clear Lake. With the generous help and support of Golden State and Mt. Konocti Mutual Water companies, alternative water filling stations were established to provide safe drinking water for affected residents. This likely helped prevent acute health issues for many.

The most recent Clear Lake cyanotoxin sampling, conducted October 26, showed 1 shoreline site is at the Danger level for cyanotoxins, 5 sites are at the Warning level and 2 sites are at the Caution level. The highest microcystin level was 25.11 µg/L and there were no detections of anatoxin-a. To view the most recent data, visit:

Now that microcystin and anatoxin levels in the lake are significantly reduced, the drinking water Health Advisory is being lifted. Alternative water-fill stations will remain in place until the end of the year, to give people time to service their systems as recommended below. Recreational water advisory signs are also being updated.

Please note, the fact Clear Lake cyanotoxin levels have improved does not ensure it is safe to drink water from individual privately managed water systems. Earlier testing showed other contaminants may also be present in these systems. People using these private water systems must make sure they are regularly maintained and tested; for cyanotoxins, and also coliform and nitrates.

As high cyanotoxin levels subside, we urge residents not on public water systems to flush their water treatment systems before starting to use the water for drinking, cooking, and other uses. Filters may be contaminated with algal (cyanobacterial) matter that can release toxins - we recommend changing your treatment system filter(s).

Toxins can also remain in holding tanks and pipes, so holding tanks should be drained and indoor spigots run for 5-10 minutes. Consult the company that services your treatment system for instructions or assistance specific to your system. Thurston County Public Health and Social Services Department in the State of Washington issued helpful guidance for purging household plumbing after a cyanobacteria bloom: Household Plumbing After A Bloom.pdf

Remember: if you are getting water from a Public Water System, your drinking water is being monitored and treated for cyanotoxins, and meets state and federal standards. These precautions are listed only for people drawing water directly from the lake for their individual household use. Boiling and bleach will not reduce cyanotoxins, and may make the problem worse.

Now that we have seen drought and climate change are bringing about historically high cyanobacteria toxin levels, we need to prepare for the coming season. People who have their own water systems should consider alternate water sources or more robust treatment with frequent testing and monitoring. Public Health and local Water Districts are planning community forums in the coming months to explore potential solutions.

Clear Lake is a beautiful natural resource, and we have many visitors that come to the area and rent lodging. We need to be particularly careful to adapt to the changing times, and ensure safe drinking water is available for residents and guests, alike.

Facilities Closure – Thanksgiving Holiday

The Lake County Public Services Department announced today that the Eastlake Landfill and the Public Services Office will be closed Thursday, November 25th

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