Keeping beaches safe
The Beach Environmental Assessment, Communication & Health (BEACH) Program ensures that marine water is safe to swim and play in and informs the public if water doesn't meet swimming standards. Sampling takes place from Memorial Day to Labor Day. During this time, you can check out current water quality conditions on the swimming map.
Our Ecology BEACH staff sampled three beaches weekly in Mason County during the 2021 season.
See details on each beach below.
During the 2021 swim season, Belfair State Park beach had one sampling event with elevated bacteria results. On June 30, sampling results exceeded the safe swimming standard, which resulted in an advisory. This beach was sampled 15 times during the season and met the swimming standard during all periods sampled.
During the 2021 swim season, Potlatch State Park beach had one sampling event with elevated bacteria results. On June 30, sampling results exceeded the safe swimming standard, which resulted in an advisory. This beach was sampled 15 times during the season and met the swimming standard during all periods sampled.
The Twanoh State Park beach is heavily used during the summer months. During the 2021 swim season, this beach had one sampling event with elevated bacteria results. On June 30, sampling results exceeded the safe swimming standard, which resulted in an advisory. This beach was sampled 15 times during the season and met the swimming standard during all periods sampled.
Data summary: Bacteria results compared to standards
The chart below summarizes the bacteria levels at Mason County beaches in relation to the EPA swimming standard or saltwater swimming criteria. Beaches are considered unsafe for swimming when the geometric mean of enterococcus/100 mL of water is greater than or equal to 30 and the statistical threshold value of enterococcus/100 mL is greater than or equal to 110. We issue a public swimming advisory when enterococcus levels exceed 104 per 100 mL of water.
Table: Calculated geometric mean and statistical threshold value at Mason County beaches (in enterococcus per 100 mL) for 2021.
|
Beach
|
GM
|
STV
|
|
Belfair State Park
|
14
|
55
|
|
Potlatch State Park
|
14
|
65
|
|
Twanoh State Park
|
20
|
224
|