Mason County annual BEACH report

We monitored three beaches weekly in Mason County during the 2022 season:

Belfair State Park
Potlatch State Park
Twanoh State Park

Colorful beach umbrellas line a crowded blue-water beach on a sunny day — Twanoh State Park Beach in Mason County

Keeping beaches safe

The Beach Environmental Assessment, Communication & Health, or 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 agency BEACH staff sampled three beaches weekly in Mason County during the 2022 season.

See details on each beach below.

The Twanoh State Park beach is heavily used during the summer months. During the 2022 swim season, this beach had one sampling event with elevated bacteria results. On Aug. 2, sampling results exceeded the safe swimming standard, but subsequent sampling showed that results were back in the safe range. This beach was sampled 15 times during the season and met the swimming standard during all other 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 2022.

Beach	GM	STV
Belfair State Park	14	37
Potlatch State Park	10	14
Twanoh State Park	16	56

Contact information

Contact BEACH: Reach BEACH staff, sign up for the listserv, or follow us on social-media platforms.

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Mason County annual BEACH report

Keeping beaches safe

Data summary: Bacteria results compared to standards

Table: Calculated geometric mean and statistical threshold value at Mason County beaches (in enterococcus per 100 mL) for 2022.

Related links

Contact information