Alpine Pond: toxic algae advisories
Alpine Pond, San Mateo County. See all San Mateo County waters.
What the state's records say
Caution advisory, last posted Aug 29, 2025. No all-clear recorded.
2 reported spots here have an advisory with no all-clear recorded.
Reporting is voluntary, so the state may not have recorded an end even if conditions changed. Check posted signs and the official map.
What this level asks: Algae that can make toxins may be present. Keep people, children and pets away from algae and scum, and do not let pets drink the water.
Before you go, check the state's official algae page and any signs posted at the water.
Dogs at Alpine Pond
The state has an advisory on file for Alpine Pond (Caution advisory), last posted Aug 29, 2025, and no all-clear recorded. Keep your dog out of the water and away from scum on the shore until the state records an end.
Reported spots
The state records each report at a spot, such as a beach or a boat ramp. Each spot's latest deciding record:
| Spot | Status |
|---|---|
| Midpeninsula Regional Open Space District | Visual observation, last posted Aug 29, 2025. No all-clear recorded. |
| Skyline Ridge open space preserve near hwy 35 | The state recorded an end date of Sep 5, 2024. |
| Midpeninsula Open Space District Skyline Field Office | Caution advisory, last posted Oct 20, 2023. No all-clear recorded. |
Advisory history
Every advisory record the state has published for Alpine Pond, newest first. "None" is the state's record that no advisory was recommended on that date. "NA" records do not change a status.
| Date | Spot | State's level | Notes |
|---|---|---|---|
| Aug 29, 2025 | Midpeninsula Regional Open Space District | Visual observation | |
| Sep 9, 2024 | Skyline Ridge open space preserve near hwy 35 | Caution | End date recorded: Sep 5, 2024. Visual monitoring only-present bloom |
| Sep 5, 2024 | Skyline Ridge open space preserve near hwy 35 | Danger | End date recorded: Sep 5, 2024. Visual monitoring only-present bloom |
| Sep 5, 2024 | Skyline Ridge open space preserve near hwy 35 | Caution | End date recorded: Sep 5, 2024. Visual monitoring only-present bloom |
| Oct 20, 2023 | Midpeninsula Open Space District Skyline Field Office | Caution | Advisory based on visual and toxins |
| Oct 20, 2023 | Midpeninsula Open Space District Skyline Field Office | Caution | Advisory based on visual and toxins |
Source
Advisory data: California State Water Resources Control Board, Freshwater Harmful Algal Bloom Program, via data.ca.gov (public domain). Advisories are recommendations; reporting is voluntary and incomplete. The state's data. An advisory ends only when the state records a later "None" (no advisory recommended) at the same spot, or an end date. A blank end date is unknown.