The city of Maple Valley posted caution signs at Lake Wilderness due to the presence of Cyanobacteria scum formations identified in the swimming beach on Nov. 5 and Nov. 20.

Cyanobacteria blooms can produce toxins that may threaten the health of people and pets if contacted or ingested.  Toxicity testing from the Nov. 2 bloom indicate toxin levels were well below Washington State’s recreational threshold for lakes, however the State’s Three Tiered Standard that the City follows indicates the caution signs should remain posted.

Not all blooms produce toxins and toxicity testing is the only way to determine if toxins are present, however, any visible scum formations should be avoided.  Cyanobacteria can float on the lake surface and be blown about the lake on the wind landing on any shoreline.

Young children and pets are particularly at risk. Young children playing at the shoreline may contact the scum or get it in their mouths and pets may drink it or lick it off their fur.

Common symptoms include nausea, vomiting, diarrhea, and eye or skin irritation.  If water with visible scum is contacted or ingested, notify your doctor or veterinary and follow their instructions.

Contact Diana at (425) 413-8800 or diana.pistoll@maplevalleywa.gov for further information.