4th Ave Bridge is a saltwater beach in Thurston County, Washington. Across 221 bacteria samples collected between 2021 and 2026 at nearby monitoring stations, it earns a Beach Safety Grade of B — Good.
About 5% of samples at 4th Ave Bridge 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.
The evidence behind this grade is deep for a beach page: 221 results from 23 monitoring stations, spanning 2021 to 2026. Enough sampling, from enough places, over enough seasons that one bad week can't drive the letter.
4th Ave Bridge 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.