CONTACT:   Renae Miller, Public Information Supervisor, Thurston County Public Health and Social Services, (360) 463-0362 or renae.miller@co.thurston.wa.us; Dr. Jen Freiheit, Director, Thurston County Public Health and Social Services

Update 11/04/2025 - Toxic Algae Advisory Lifted

Toxic Algae Health Advisory in Effect for Pattison Lake 
Toxic levels are above the threshold for health concern. 

OLYMPIA – Thurston County Public Health and Social Services is reporting a toxic algae bloom for Pattison Lake. 

Lab results taken from Pattison Lake on 09/30/2025 detected Microcystins toxin levels at 9.0 ug/L, which is ABOVE the state recreation guideline of 8ug/L. 

Microcystins are a liver toxin and possible human carcinogen. Microcystins can also cause illness in livestock and pets that drink affected water. Staff will continue to collect weekly samples until they receive two consecutive weeks of samples with microcystin levels below state recreational guidelines. Even if the lake is visibly clear of algae, toxins may still be present. 

When an algae bloom is present, health officials recommend taking extra precautions to avoid the health risks posed by potential toxins.

• Do not drink the lake water.
• Avoid contact with water containing algae.
• Avoid swimming, wading, windsurfing, and water-skiing in waterbodies where algae blooms are present.
• Keep pets and livestock away from where algae blooms are present.
• Do not eat fish that come from the lake during an algae bloom.
• Avoid areas of scum when boating. 

For more information about toxic algae blooms and health risks, and to see all Thurston County Algae Alerts, visit: www.thurstoncountywa.gov/lake-alerts