Topanga State Beach - Smb-1-18 is a freshwater beach in Los Angeles County, California. Across 1,153 bacteria samples collected between 2021 and 2025 at nearby monitoring stations, it earns a Beach Safety Grade of D — Poor.
About 20% of samples at Topanga State Beach - Smb-1-18 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 frequently crossed here over the monitored period. Bacteria samples frequently exceed the safe-swimming threshold; swimming advisories are common here.
Topanga State Beach - Smb-1-18 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.