Sand Beach is a saltwater beach in San Mateo County, California. Across 475 bacteria samples collected between 2021 and 2025 at nearby monitoring stations, it earns a Beach Safety Grade of B — Good.
About 4% of samples at Sand 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.
The evidence behind this grade is deep for a beach page: 475 results from 2 monitoring stations, spanning 2021 to 2025. Enough sampling, from enough places, over enough seasons that one bad week can't drive the letter.
Sand Beach is currently listed as inactive in the EPA beach-monitoring program, so it may no longer be routinely sampled. Its grade reflects the water-quality results collected while it was active — useful history, but confirm the beach's current status and any local advisory before you visit.