LAKE COUNTY, Calif. — Officials said Friday that dropping cyanotoxin levels have led to the lifting of a health advisory for individuals who have household intakes in the Lower and Oaks Arms of Clear Lake.
High cyanotoxin levels in September prompted the advisory for individual household intakes, not public water systems.
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. County officials said this likely helped prevent acute health issues for many.
The most recent Clear Lake cyanotoxin sampling, conducted Oct. 26, showed one shoreline site is at the danger level for cyanotoxins, five sites are at the warning level and two sites are at the caution level.
The highest microcystin level, at Redbud Park in Clearlake, was 25.11 µg/L and there were no detections of anatoxin-a. View the most recent data here.
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.
Officials cautioned that 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, officials 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 — or cyanobacterial — matter that can release toxins, so it’s recommended that treatment system filters be replaced.
Toxins can also remain in holding tanks and pipes, so holding tanks should be drained and indoor spigots run for five to 10 minutes. Consult the company that services your treatment system for instructions or assistance specific to your system.
Find helpful guidance — issued by the Thurston County Public Health and Social Services Department in Washington state — for purging household plumbing after a cyanobacteria bloom here.
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,” the Lake County Health Services and Water Resources departments and Big Valley Band of Pomo Indians said in a joint statement.
People who have their own water systems should consider alternative 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.