Union Bay Beach is a Great Lakes beach in Ontonagon County, Michigan. Across 59 bacteria samples collected between 2021 and 2024 at nearby monitoring stations, it earns a Beach Safety Grade of B — Good.
About 3% of samples at Union Bay Beach exceeded the EPA Beach Action Value of 235 CFU/100 mL for Escherichia coli — the threshold at which water managers typically post a swimming advisory. In practice that means the safe-swimming limit was rarely crossed here over the monitored period. Bacteria samples rarely exceed the safe-swimming threshold.
Read this grade as directional rather than settled: it draws on a single monitoring station and rests on only 59 samples. That is enough to classify how the water has behaved, but not enough to separate this beach from another a grade away — a beach graded from thousands of samples at several stations is a firmer read. As more results are reported, the grade may shift.
Union Bay Beach was not under a swimming advisory in the most recent EPA snapshot. Conditions can change quickly after heavy rain or high runoff, so it's still worth checking the current advisory the day you go.