Ketchikan - Thomas Basin is a saltwater beach in Ketchikan Gateway County, Alaska. Across 154 bacteria samples collected between 2021 and 2025 at nearby monitoring stations, it earns a Beach Safety Grade of C — Fair.
About 10% of samples at Ketchikan - Thomas Basin 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 sometimes crossed here over the monitored period. Bacteria samples occasionally exceed the safe-swimming threshold — check the latest advisory before swimming.
The evidence behind this grade is deep for a beach page: 154 results from 10 monitoring stations, spanning 2021 to 2025. Enough sampling, from enough places, over enough seasons that one bad week can't drive the letter.
Ketchikan - Thomas Basin 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.