Quarry Lakes: toxic algae advisories
Quarry Lakes, Alameda County. See all Alameda County waters.
What the state's records say
Danger advisory, last posted Oct 16, 2026. No all-clear recorded.
10 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: Toxins may be at levels that can seriously harm people and animals. Stay out of the water and keep children and pets away from the water and the shore.
Before you go, check the state's official algae page and any signs posted at the water.
Dogs at Quarry Lakes
The state has an advisory on file for Quarry Lakes (Danger advisory), last posted Oct 16, 2026, 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 |
|---|---|
| Horseshoe Lake (swim beach) | Caution advisory, last posted Oct 16, 2026. No all-clear recorded. |
| Shinn Pond | Caution advisory, last posted Oct 9, 2026. No all-clear recorded. |
| Rainbow Lake | Caution advisory, last posted Oct 9, 2026. No all-clear recorded. |
| Quarry Lakes | Danger advisory, last posted Feb 20, 2024. No all-clear recorded. |
| East Bay Regional Park | The state recorded an end date of Dec 31, 2022. |
| Lago Los Osos area | The state recorded an end date of Dec 31, 2022. |
| Spot not described | Danger advisory, last posted Apr 15, 2022. No all-clear recorded. |
| Lago Las Osos area | Danger advisory, last posted Apr 15, 2022. No all-clear recorded. |
| Spot not described | The state's latest record, from Jul 16, 2021, recommends no advisory. |
| Quarry Lakes | Caution advisory, last posted Dec 31, 2020. No all-clear recorded. |
| Quarry Lakes | Danger advisory, last posted Jul 17, 2019. No all-clear recorded. |
| Quarry Lakes | The state's latest record, from Dec 7, 2018, recommends no advisory. |
| Quarry Lakes | Caution advisory, last posted Dec 14, 2017. No all-clear recorded. |
| Quarry Lakes | Danger advisory, last posted Mar 14, 2017. No all-clear recorded. |
Advisory history
Every advisory record the state has published for Quarry Lakes, 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 |
|---|---|---|---|
| Oct 16, 2026 | Horseshoe Lake (swim beach) | Caution | Updates from routine monitoring program-organization |
| Oct 9, 2026 | Shinn Pond | Caution | Updates from routine monitoring program-organization |
| Oct 9, 2026 | Rainbow Lake | Caution | Updates from routine monitoring program-organization |
| Oct 9, 2026 | Horseshoe Lake (swim beach) | Caution | Updates from routine monitoring program-organization |
| Sep 25, 2026 | Horseshoe Lake (swim beach) | Danger | Updates from routine monitoring program-organization |
| Sep 18, 2026 | Rainbow Lake | Caution | Updates from routine monitoring program-organization |
| Sep 18, 2026 | Shinn Pond | Caution | Updates from routine monitoring program-organization |
| Sep 18, 2026 | Horseshoe Lake (swim beach) | Danger | Updates from routine monitoring program-organization |
| Sep 11, 2026 | Shinn Pond | Caution | Updates from routine monitoring program-organization |
| Sep 11, 2026 | Rainbow Lake | Caution | Updates from routine monitoring program-organization |
| Sep 11, 2026 | Rainbow Lake | Caution | Updates from routine monitoring program-organization |
| Sep 11, 2026 | Horseshoe Lake (swim beach) | Danger | Updates from routine monitoring program-organization |
| Sep 8, 2026 | Rainbow Lake | Caution | Updates from routine monitoring program-organization |
| Sep 8, 2026 | Horseshoe Lake (swim beach) | Danger | Updates from routine monitoring program-organization |
| Aug 31, 2026 | Shinn Pond | Caution | Updates from routine monitoring program-organization |
| Aug 31, 2026 | Rainbow Lake | Caution | Updates from routine monitoring program-organization |
| Aug 31, 2026 | Horseshoe Lake (swim beach) | Caution | Updates from routine monitoring program-organization |
| Aug 21, 2026 | Shinn Pond | Caution | Updates from routine monitoring program-organization |
| Aug 21, 2026 | Horseshoe Lake (swim beach) | Caution | Updates from routine monitoring program-organization |
| Aug 14, 2026 | Shinn Pond | Caution | Updates from routine monitoring program-organization |
| Aug 14, 2026 | Rainbow Lake | Caution | Updates from routine monitoring program-organization |
| Aug 14, 2026 | Horseshoe Lake (swim beach) | Caution | Updates from routine monitoring program-organization |
| Aug 7, 2026 | Shinn Pond | Caution | Updates from routine monitoring program-organization |
| Aug 7, 2026 | Horseshoe Lake (swim beach) | Caution | Updates from routine monitoring program-organization |
| Jul 31, 2026 | Shinn Pond | Caution | Updates from routine monitoring program-organization |
| Jul 31, 2026 | Rainbow Lake | Caution | Updates from routine monitoring program-organization |
| Jul 31, 2026 | Horseshoe Lake (swim beach) | Caution | Updates from routine monitoring program-organization |
| Jul 24, 2026 | Shinn Pond | Danger | Updates from routine monitoring program-organization |
| Jul 24, 2026 | Rainbow Lake | Danger | Updates from routine monitoring program-organization |
| Jul 24, 2026 | Horseshoe Lake (swim beach) | Caution | Updates from routine monitoring program-organization |
| Jul 17, 2026 | Shinn Pond | Danger | Updates from routine monitoring program-organization |
| Jul 17, 2026 | Rainbow Lake | Danger | Updates from routine monitoring program-organization |
| Jul 17, 2026 | Horseshoe Lake (swim beach) | Caution | Updates from routine monitoring program-organization |
| Jul 10, 2026 | Horseshoe Lake (swim beach) | Caution | Updates from routine monitoring program-organization |
| Jul 10, 2026 | Rainbow Lake | Danger | Updates from routine monitoring program-organization |
| Jul 3, 2026 | Shinn Pond | None | Updates from routine monitoring program-organization |
| Jul 3, 2026 | Horseshoe Lake (swim beach) | Caution | Updates from routine monitoring program-organization |
| Jun 26, 2026 | Horseshoe Lake (swim beach) | Caution | Updates from routine monitoring program-organization |
| Jun 26, 2026 | Rainbow Lake | Danger | Updates from routine monitoring program-organization |
| Jun 26, 2026 | Shinn Pond | None | Updates from routine monitoring program-organization |
| Jun 19, 2026 | Shinn Pond | None | Updates from routine monitoring program-organization |
| Jun 19, 2026 | Horseshoe Lake (swim beach) | Danger | Updates from routine monitoring program-organization |
| Jun 12, 2026 | Shinn Pond | None | Updates from routine monitoring program-organization |
| Jun 12, 2026 | Rainbow Lake | Danger | Updates from routine monitoring program-organization |
| Jun 12, 2026 | Horseshoe Lake (swim beach) | Danger | Updates from routine monitoring program-organization |
| Jun 12, 2026 | Horseshoe Lake (swim beach) | Danger | Updates from routine monitoring program-organization |
| Jun 12, 2026 | Horseshoe Lake (swim beach) | Danger | Updates from routine monitoring program-organization |
| Jun 5, 2026 | Rainbow Lake | Danger | Updates from routine monitoring program-organization |
| Jun 5, 2026 | Horseshoe Lake (swim beach) | Danger | Updates from routine monitoring program-organization |
| Jun 5, 2026 | Shinn Pond | None | Updates from routine monitoring program-organization |
| Jun 1, 2026 | Shinn Pond | None | Updates from routine monitoring program-organization |
| Jun 1, 2026 | Rainbow Lake | Danger | Updates from routine monitoring program-organization |
| Jun 1, 2026 | Horseshoe Lake (swim beach) | Danger | Updates from routine monitoring program-organization |
| May 22, 2026 | Rainbow Lake | Danger | Updates from routine monitoring program-organization |
| May 22, 2026 | Horseshoe Lake (swim beach) | Danger | Updates from routine monitoring program-organization |
| May 15, 2026 | Shinn Pond | None | Updates from routine monitoring program-organization |
| May 15, 2026 | Rainbow Lake | Caution | Updates from routine monitoring program-organization |
| May 15, 2026 | Horseshoe Lake (swim beach) | Danger | Updates from routine monitoring program-organization |
| May 8, 2026 | Rainbow Lake | Caution | Updates from routine monitoring program-organization |
| May 8, 2026 | Shinn Pond | None | Updates from routine monitoring program-organization |
| May 8, 2026 | Horseshoe Lake (swim beach) | Danger | Updates from routine monitoring program-organization |
| May 1, 2026 | Horseshoe Lake (swim beach) | Danger | Updates from routine monitoring program-organization |
| Apr 24, 2026 | Horseshoe Lake (swim beach) | Danger | Updates from routine monitoring program-organization |
| Apr 16, 2026 | Shinn Pond | None | Updates from routine monitoring program-organization |
| Apr 16, 2026 | Horseshoe Lake (swim beach) | Danger | Updates from routine monitoring program-organization |
| Apr 10, 2026 | Shinn Pond | None | Updates from routine monitoring program-organization |
| Apr 10, 2026 | Rainbow Lake | Caution | Updates from routine monitoring program-organization |
| Apr 10, 2026 | Horseshoe Lake (swim beach) | Danger | Updates from routine monitoring program-organization |
| Mar 20, 2026 | Horseshoe Lake (swim beach) | Danger | Updates from routine monitoring program-organization |
| Mar 20, 2026 | Rainbow Lake | Caution | Updates from routine monitoring program-organization |
| Mar 20, 2026 | Shinn Pond | None | Updates from routine monitoring program-organization |
| Mar 13, 2026 | Rainbow Lake | Caution | Updates from routine monitoring program-organization |
| Mar 13, 2026 | Horseshoe Lake (swim beach) | Danger | Updates from routine monitoring program-organization |
| Mar 6, 2026 | Horseshoe Lake (swim beach) | Danger | Updates from routine monitoring program-organization |
| Feb 26, 2026 | Shinn Pond | Caution | Updates from routine monitoring program-organization |
| Feb 26, 2026 | Horseshoe Lake (swim beach) | Danger | Updates from routine monitoring program-organization |
| Feb 20, 2026 | Rainbow Lake | Caution | Updates from routine monitoring program-organization |
| Feb 20, 2026 | Rainbow Lake | Caution | Updates from routine monitoring program-organization |
| Feb 20, 2026 | Shinn Pond | Caution | Updates from routine monitoring program-organization |
| Feb 20, 2026 | Horseshoe Lake (swim beach) | Danger | Updates from routine monitoring program-organization |
| Feb 6, 2026 | Shinn Pond | Caution | Updates from routine monitoring program-organization |
| Feb 6, 2026 | Horseshoe Lake (swim beach) | Danger | Updates from routine monitoring program-organization |
| Feb 6, 2026 | Horseshoe Lake (swim beach) | Danger | Updates from routine monitoring program-organization |
| Jan 30, 2026 | Rainbow Lake | Caution | Updates from routine monitoring program-organization |
| Jan 30, 2026 | Shinn Pond | Caution | Updates from routine monitoring program-organization |
| Jan 30, 2026 | Horseshoe Lake (swim beach) | Danger | Updates from routine monitoring program-organization |
| Jan 23, 2026 | Shinn Pond | Caution | Updates from routine monitoring program-organization |
| Jan 23, 2026 | Horseshoe Lake (swim beach) | Caution | Updates from routine monitoring program-organization |
| Jan 16, 2026 | Horseshoe Lake (swim beach) | Caution | Updates from routine monitoring program-organization |
| Jan 16, 2026 | Shinn Pond | Danger | Updates from routine monitoring program-organization |
| Jan 9, 2026 | Rainbow Lake | Caution | Updates from routine monitoring program-organization |
| Jan 9, 2026 | Horseshoe Lake (swim beach) | Caution | Updates from routine monitoring program-organization |
| Jan 9, 2026 | Horseshoe Lake (swim beach) | Caution | Updates from routine monitoring program-organization |
| Jan 9, 2026 | Horseshoe Lake (swim beach) | Caution | Updates from routine monitoring program-organization |
| Dec 12, 2025 | Rainbow Lake | Caution | Updates from routine monitoring program-organization |
| Dec 12, 2025 | Horseshoe Lake (swim beach) | Caution | Updates from routine monitoring program-organization |
| Dec 12, 2025 | Shinn Pond | Danger | Updates from routine monitoring program-organization |
| Dec 5, 2025 | Shinn Pond | Caution | Updates from routine monitoring program-organization |
| Dec 5, 2025 | Rainbow Lake | Caution | Updates from routine monitoring program-organization |
| Dec 5, 2025 | Horseshoe Lake (swim beach) | Caution | Updates from routine monitoring program-organization |
| Nov 20, 2025 | Rainbow Lake | Caution | Updates from routine monitoring program-organization |
| Nov 20, 2025 | Horseshoe Lake (swim beach) | Caution | Updates from routine monitoring program-organization |
| Nov 7, 2025 | Shinn Pond | Caution | Updates from routine monitoring program-organization |
| Nov 7, 2025 | Horseshoe Lake (swim beach) | Caution | Updates from routine monitoring program-organization |
| Oct 31, 2025 | Horseshoe Lake (swim beach) | Caution | Updates from routine monitoring program-organization |
| Oct 31, 2025 | Rainbow Lake | Caution | Updates from routine monitoring program-organization |
| Oct 23, 2025 | Shinn Pond | Caution | Updates from routine monitoring program-organization |
| Oct 23, 2025 | Horseshoe Lake (swim beach) | Caution | Updates from routine monitoring program-organization |
| Oct 17, 2025 | Horseshoe Lake (swim beach) | Caution | Updates from routine monitoring program-organization |
| Oct 17, 2025 | Shinn Pond | Caution | Updates from routine monitoring program-organization |
| Oct 17, 2025 | Rainbow Lake | Caution | Updates from routine monitoring program-organization |
| Oct 10, 2025 | Horseshoe Lake (swim beach) | Caution | Updates from routine monitoring program-organization |
| Sep 26, 2025 | Horseshoe Lake (swim beach) | Danger | Updates from routine monitoring program-organization |
| Sep 19, 2025 | Shinn Pond | Caution | Updates from routine monitoring program-organization |
| Sep 19, 2025 | Rainbow Lake | Caution | Updates from routine monitoring program-organization |
| Sep 19, 2025 | Horseshoe Lake (swim beach) | Danger | Updates from routine monitoring program-organization |
| Sep 12, 2025 | Horseshoe Lake (swim beach) | Danger | Updates from routine monitoring program-organization |
| Sep 5, 2025 | Horseshoe Lake (swim beach) | Danger | Updates from routine monitoring program-organization |
| Aug 29, 2025 | Rainbow Lake | Caution | Updates from routine monitoring program-organization |
| Aug 29, 2025 | Horseshoe Lake (swim beach) | Danger | Updates from routine monitoring program-organization |
| Aug 22, 2025 | Horseshoe Lake (swim beach) | Danger | Updates from routine monitoring program-organization |
| Aug 18, 2025 | Horseshoe Lake (swim beach) | Danger | Updates from routine monitoring program-organization |
| Aug 18, 2025 | Shinn Pond | Caution | Updates from routine monitoring program-organization |
| Aug 18, 2025 | Rainbow Lake | Caution | Updates from routine monitoring program-organization |
| Aug 8, 2025 | Rainbow Lake | Caution | Updates from routine monitoring program-organization |
| Aug 8, 2025 | Horseshoe Lake (swim beach) | Danger | Updates from routine monitoring program-organization |
| Jul 31, 2025 | Shinn Pond | Caution | Updates from routine monitoring program-organization |
| Jul 31, 2025 | Horseshoe Lake (swim beach) | Danger | Updates from routine monitoring program-organization |
| Jul 24, 2025 | Shinn Pond | Caution | Updates from routine monitoring program-organization |
| Jul 24, 2025 | Horseshoe Lake (swim beach) | Danger | Updates from routine monitoring program-organization |
| Jul 18, 2025 | Shinn Pond | Caution | Updates from routine monitoring program-organization |
| Jul 18, 2025 | Rainbow Lake | Caution | Updates from routine monitoring program-organization |
| Jul 18, 2025 | Horseshoe Lake (swim beach) | Danger | Updates from routine monitoring program-organization |
| Jul 11, 2025 | Shinn Pond | Caution | Updates from routine monitoring program-organization |
| Jul 11, 2025 | Horseshoe Lake (swim beach) | Danger | Updates from routine monitoring program-organization |
| Jul 2, 2025 | Shinn Pond | Caution | Updates from routine monitoring program-organization |
| Jun 26, 2025 | Horseshoe Lake (swim beach) | Danger | Updates from routine monitoring program-organization |
| Jun 20, 2025 | Shinn Pond | Caution | Updates from routine monitoring program-organization |
| Jun 20, 2025 | Rainbow Lake | Caution | Updates from routine monitoring program-organization |
| Jun 20, 2025 | Horseshoe Lake (swim beach) | Danger | Updates from routine monitoring program-organization |
| Jun 13, 2025 | Horseshoe Lake (swim beach) | Danger | Updates from routine monitoring program-organization |
| Jun 13, 2025 | Shinn Pond | Caution | Updates from routine monitoring program-organization |
| Jun 13, 2025 | Rainbow Lake | Caution | Updates from routine monitoring program-organization |
| Jun 13, 2025 | Horseshoe Lake (swim beach) | Danger | Updates from routine monitoring program-organization |
| Jun 6, 2025 | Shinn Pond | Caution | Updates from routine monitoring program-organization |
| Jun 6, 2025 | Rainbow Lake | Caution | Updates from routine monitoring program-organization |
| Jun 6, 2025 | Horseshoe Lake (swim beach) | Danger | Updates from routine monitoring program-organization |
| Jun 2, 2025 | Horseshoe Lake (swim beach) | Danger | Updates from routine monitoring program-organization |
| May 19, 2025 | Rainbow Lake | Caution | Updates from routine monitoring program-organization |
| May 19, 2025 | Horseshoe Lake (swim beach) | Danger | Updates from routine monitoring program-organization |
| May 9, 2025 | Horseshoe Lake (swim beach) | Danger | Updates from routine monitoring program-organization |
| May 9, 2025 | Rainbow Lake | Caution | Updates from routine monitoring program-organization |
| May 9, 2025 | Shinn Pond | Caution | Updates from routine monitoring program-organization |
| May 2, 2025 | Shinn Pond | Caution | Updates from routine monitoring program-organization |
| May 2, 2025 | Rainbow Lake | Caution | Updates from routine monitoring program-organization |
| Apr 28, 2025 | Horseshoe Lake (swim beach) | Danger | Updates from routine monitoring program-organization |
| Apr 28, 2025 | Horseshoe Lake (swim beach) | Danger | Updates from routine monitoring program-organization |
| Apr 23, 2025 | Shinn Pond | Caution | Updates from routine monitoring program-organization |
| Apr 23, 2025 | Rainbow Lake | Caution | Updates from routine monitoring program-organization |
| Apr 23, 2025 | Horseshoe Lake (swim beach) | Caution | Updates from routine monitoring program-organization |
| Apr 11, 2025 | Shinn Pond | Caution | Updates from routine monitoring program-organization |
| Apr 11, 2025 | Rainbow Lake | Caution | Updates from routine monitoring program-organization |
| Apr 11, 2025 | Horseshoe Lake (swim beach) | Danger | Updates from routine monitoring program-organization |
| Apr 4, 2025 | Shinn Pond | Caution | Updates from routine monitoring program-organization |
| Apr 4, 2025 | Rainbow Lake | Caution | Updates from routine monitoring program-organization |
| Apr 4, 2025 | Horseshoe Lake (swim beach) | Danger | Updates from routine monitoring program-organization |
| Mar 21, 2025 | Horseshoe Lake (swim beach) | Danger | Updates from routine monitoring program-organization |
| Mar 21, 2025 | Rainbow Lake | Caution | Updates from routine monitoring program-organization |
| Mar 21, 2025 | Shinn Pond | Caution | Updates from routine monitoring program-organization |
| Mar 21, 2025 | Horseshoe Lake (swim beach) | Danger | Updates from routine monitoring program-organization |
| Mar 14, 2025 | Shinn Pond | Caution | Updates from routine monitoring program-organization |
| Mar 14, 2025 | Rainbow Lake | Caution | Updates from routine monitoring program-organization |
| Mar 14, 2025 | Horseshoe Lake (swim beach) | Danger | Updates from routine monitoring program-organization |
| Mar 7, 2025 | Shinn Pond | Caution | Updates from routine monitoring program-organization |
| Mar 7, 2025 | Rainbow Lake | Caution | Updates from routine monitoring program-organization |
| Mar 7, 2025 | Horseshoe Lake (swim beach) | Danger | Updates from routine monitoring program-organization |
| Feb 28, 2025 | Shinn Pond | Caution | Updates from routine monitoring program-organization |
| Feb 28, 2025 | Rainbow Lake | Caution | Updates from routine monitoring program-organization |
| Feb 28, 2025 | Horseshoe Lake (swim beach) | Danger | Updates from routine monitoring program-organization |
| Feb 21, 2025 | Shinn Pond | Caution | Updates from routine monitoring program-organization |
| Feb 21, 2025 | Rainbow Lake | Caution | Updates from routine monitoring program-organization |
| Feb 21, 2025 | Horseshoe Lake (swim beach) | Danger | Updates from routine monitoring program-organization |
| Feb 14, 2025 | Horseshoe Lake (swim beach) | Danger | Updates from routine monitoring program-organization |
| Feb 14, 2025 | Rainbow Lake | Caution | Updates from routine monitoring program-organization |
| Feb 14, 2025 | Shinn Pond | Caution | Updates from routine monitoring program-organization |
| Jan 31, 2025 | Horseshoe Lake (swim beach) | Danger | Updates from routine monitoring program-organization |
| Jan 31, 2025 | Shinn Pond | Caution | Updates from routine monitoring program-organization |
| Jan 24, 2025 | Rainbow Lake | Caution | Updates from routine monitoring program-organization |
| Jan 24, 2025 | Shinn Pond | Caution | Updates from routine monitoring program-organization |
| Jan 17, 2025 | Rainbow Lake | Caution | Updates from routine monitoring program-organization |
| Jan 17, 2025 | Horseshoe Lake (swim beach) | Caution | Updates from routine monitoring program-organization |
| Jan 17, 2025 | Shinn Pond | Caution | Updates from routine monitoring program-organization |
| Jan 13, 2025 | Horseshoe Lake (swim beach) | Caution | Updates from routine monitoring program-organization |
| Jan 13, 2025 | Shinn Pond | Caution | Updates from routine monitoring program-organization |
| Jan 2, 2025 | Shinn Pond | Caution | Updates from routine monitoring program-organization |
| Jan 2, 2025 | Horseshoe Lake (swim beach) | Caution | Updates from routine monitoring program-organization |
| Dec 20, 2024 | Horseshoe Lake (swim beach) | Caution | Updates from routine monitoring program-organization |
| Dec 12, 2024 | Rainbow Lake | Caution | Updates from routine monitoring program-organization |
| Dec 12, 2024 | Shinn Pond | Caution | Updates from routine monitoring program-organization |
| Dec 6, 2024 | Rainbow Lake | Caution | Updates from routine monitoring program-organization |
| Dec 6, 2024 | Horseshoe Lake (swim beach) | Caution | Updates from routine monitoring program-organization |
| Nov 20, 2024 | Rainbow Lake | Caution | Updates from routine monitoring program-organization |
| Nov 20, 2024 | Horseshoe Lake (swim beach) | Caution | Updates from routine monitoring program-organization |
| Nov 12, 2024 | Horseshoe Lake (swim beach) | Caution | Updates from routine monitoring program-organization |
| Oct 31, 2024 | Shinn Pond | Caution | Updates from routine monitoring program-organization |
| Oct 31, 2024 | Rainbow Lake | Caution | Updates from routine monitoring program-organization |
| Oct 31, 2024 | Horseshoe Lake (swim beach) | Caution | Updates from routine monitoring program-organization |
| Oct 18, 2024 | Rainbow Lake | Caution | Updates from routine monitoring program-organization |
| Oct 18, 2024 | Horseshoe Lake (swim beach) | Caution | Updates from routine monitoring program-organization |
| Oct 11, 2024 | Horseshoe Lake (swim beach) | Caution | Updates from routine monitoring program-organization |
| Oct 4, 2024 | Horseshoe Lake (swim beach) | Caution | Updates from routine monitoring program-organization |
| Sep 27, 2024 | Rainbow Lake | Caution | Updates from routine monitoring program-organization |
| Sep 27, 2024 | Shinn Pond | Caution | Updates from routine monitoring program-organization |
| Sep 27, 2024 | Horseshoe Lake (swim beach) | Caution | Updates from routine monitoring program-organization |
| Sep 20, 2024 | Shinn Pond | Caution | Updates from routine monitoring program-organization |
| Sep 20, 2024 | Rainbow Lake | Caution | Updates from routine monitoring program-organization |
| Sep 20, 2024 | Horseshoe Lake (swim beach) | Caution | Updates from routine monitoring program-organization |
| Sep 13, 2024 | Horseshoe Lake (swim beach) | Caution | Updates from routine monitoring program-organization |
| Sep 6, 2024 | Shinn Pond | Caution | Updates from routine monitoring program-organization |
| Sep 6, 2024 | Horseshoe Lake (swim beach) | Caution | Updates from routine monitoring program-organization |
| Aug 26, 2024 | Horseshoe Lake (swim beach) | Caution | Updates from routine monitoring program-organization |
| Aug 26, 2024 | Rainbow Lake | Caution | Updates from routine monitoring program-organization |
| Aug 26, 2024 | Shinn Pond | Caution | Updates from routine monitoring program-organization |
| Aug 15, 2024 | Shinn Pond | Caution | Updates from routine monitoring program-organization |
| Aug 15, 2024 | Rainbow Lake | Caution | Updates from routine monitoring program-organization |
| Aug 15, 2024 | Horseshoe Lake (swim beach) | Caution | Updates from routine monitoring program-organization |
| Aug 2, 2024 | Shinn Pond | Caution | Updates from routine monitoring program-organization |
| Aug 2, 2024 | Shinn Pond | Caution | Updates from routine monitoring program-organization |
| Aug 2, 2024 | Rainbow Lake | Caution | Updates from routine monitoring program-organization |
| Aug 2, 2024 | Horseshoe Lake (swim beach) | Caution | Updates from routine monitoring program-organization |
| Jul 26, 2024 | Rainbow Lake | Caution | Updates from routine monitoring program-organization |
| Jul 26, 2024 | Shinn Pond | Caution | Updates from routine monitoring program-organization |
| Jul 26, 2024 | Horseshoe Lake (swim beach) | Caution | Updates from routine monitoring program-organization |
| Jul 22, 2024 | Horseshoe Lake (swim beach) | Caution | Updates from routine monitoring program-organization |
| Jul 9, 2024 | Horseshoe Lake (swim beach) | Caution | Updates from routine monitoring program-organization |
| Jul 3, 2024 | Horseshoe Lake (swim beach) | Caution | Updates from routine monitoring program-organization |
| Jun 25, 2024 | Shinn Pond | Caution | Updates from routine monitoring program-organization |
| Jun 24, 2024 | Horseshoe Lake (swim beach) | Caution | Updates from routine monitoring program-organization |
| Jun 21, 2024 | Rainbow Lake | Caution | Updates from routine monitoring program-organization |
| Jun 21, 2024 | Horseshoe Lake (swim beach) | Caution | Updates from routine monitoring program-organization |
| Jun 21, 2024 | Shinn Pond | None | Updates from routine monitoring program-organization |
| May 24, 2024 | Shinn Pond | None | Updates from routine monitoring program-organization |
| May 24, 2024 | Horseshoe Lake (swim beach) | Caution | Updates from routine monitoring program-organization |
| May 14, 2024 | Horseshoe Lake (swim beach) | Danger | Updates from routine monitoring program-organization |
| May 6, 2024 | Horseshoe Lake (swim beach) | Danger | Updates from routine monitoring program-organization |
| Apr 29, 2024 | Horseshoe Lake (swim beach) | Danger | Updates from routine monitoring program-organization |
| Apr 23, 2024 | Shinn Pond | None | Updates from routine monitoring program-organization |
| Apr 23, 2024 | Rainbow Lake | Caution | Updates from routine monitoring program-organization |
| Apr 23, 2024 | Horseshoe Lake (swim beach) | Danger | Updates from routine monitoring program-organization |
| Apr 19, 2024 | Rainbow Lake | Caution | Updates from routine monitoring program-organization |
| Apr 16, 2024 | Horseshoe Lake (swim beach) | Danger | Updates from routine monitoring program-organization |
| Apr 10, 2024 | Shinn Pond | None | Updates from routine monitoring program-organization |
| Apr 10, 2024 | Rainbow Lake | Caution | Updates from routine monitoring program-organization |
| Apr 10, 2024 | Horseshoe Lake (swim beach) | Danger | Updates from routine monitoring program-organization |
| Apr 2, 2024 | Horseshoe Lake (swim beach) | Danger | Updates from routine monitoring program-organization |
| Apr 2, 2024 | Rainbow Lake | Caution | Updates from routine monitoring program-organization |
| Apr 2, 2024 | Rainbow Lake | Caution | Updates from routine monitoring program-organization |
| Mar 25, 2024 | Shinn Pond | None | Updates from routine monitoring program-organization |
| Mar 25, 2024 | Horseshoe Lake (swim beach) | Danger | Updates from routine monitoring program-organization |
| Mar 18, 2024 | Horseshoe Lake (swim beach) | Danger | Updates from routine monitoring program-organization |
| Mar 18, 2024 | Shinn Pond | Caution | Updates from routine monitoring program-organization |
| Mar 11, 2024 | Shinn Pond | Caution | Updates from routine monitoring program-organization |
| Mar 11, 2024 | Horseshoe Lake (swim beach) | Danger | Updates from routine monitoring program-organization |
| Mar 8, 2024 | Horseshoe Lake (swim beach) | Danger | Updates from routine monitoring program-organization |
| Feb 20, 2024 | Quarry Lakes | Danger | Updates from routine monitoring program-organization |
| Feb 20, 2024 | Shinn Pond | Caution | Updates from routine monitoring program-organization |
| Feb 20, 2024 | Horseshoe Lake (swim beach) | Danger | Updates from routine monitoring program-organization |
| Feb 15, 2024 | Shinn Pond | Caution | Updates from routine monitoring program-organization |
| Feb 15, 2024 | Horseshoe Lake (swim beach) | Danger | Updates from routine monitoring program-organization |
| Feb 15, 2024 | Quarry Lakes | Danger | Updates from routine monitoring program-organization |
| Feb 9, 2024 | Horseshoe Lake (swim beach) | None | Updates from routine monitoring program-organization |
| Feb 9, 2024 | Shinn Pond | Caution | Updates from routine monitoring program-organization |
| Feb 9, 2024 | Rainbow Lake | Caution | Updates from routine monitoring program-organization |
| Jan 29, 2024 | Quarry Lakes | Caution | Updates from routine monitoring program-organization |
| Jan 19, 2024 | Quarry Lakes | Caution | Updates from routine monitoring program-organization |
| Jan 11, 2024 | Rainbow Lake | Caution | Updates from routine monitoring program-organization |
| Jan 11, 2024 | Shinn Pond | Caution | Updates from routine monitoring program-organization |
| Jan 11, 2024 | Quarry Lakes | Caution | Updates from routine monitoring program-organization |
| Jan 2, 2024 | Quarry Lakes | Caution | Updates from routine monitoring program-organization |
| Dec 19, 2023 | Rainbow Lake | Caution | Updates from routine monitoring program-organization |
| Dec 19, 2023 | Quarry Lakes | Caution | Updates from routine monitoring program-organization |
| Dec 4, 2023 | Quarry Lakes | Caution | Updates from routine monitoring program-organization |
| Nov 27, 2023 | Quarry Lakes | Caution | Updates from routine monitoring program-organization |
| Nov 13, 2023 | Shinn Pond | Caution | Updates from routine monitoring program-organization |
| Nov 13, 2023 | Rainbow Lake | Caution | Updates from routine monitoring program-organization |
| Nov 13, 2023 | Shinn Pond | Caution | Updates from routine monitoring program-organization |
| Nov 13, 2023 | Quarry Lakes | Caution | Updates from routine monitoring program-organization |
| Oct 17, 2023 | Shinn Pond | Caution | Updates from routine monitoring program-organization |
| Oct 17, 2023 | Quarry Lakes | Caution | Updates from routine monitoring program-organization |
| Oct 10, 2023 | Quarry Lakes | None | Updates from routine monitoring program-organization |
| Oct 3, 2023 | Rainbow Lake | Caution | Updates from routine monitoring program-organization |
| Oct 3, 2023 | Quarry Lakes | Caution | Updates from routine monitoring program-organization |
| Sep 26, 2023 | Quarry Lakes | Caution | Updates from routine monitoring program-organization |
| Sep 19, 2023 | Shinn Pond | Caution | Updates from routine monitoring program-organization |
| Sep 19, 2023 | Quarry Lakes | None | Updates from routine monitoring program-organization |
| Sep 19, 2023 | Rainbow Lake | Caution | Updates from routine monitoring program-organization |
| Sep 19, 2023 | Shinn Pond | Caution | Updates from routine monitoring program-organization |
| Sep 12, 2023 | Rainbow Lake | Caution | Updates from routine monitoring program-organization |
| Sep 11, 2023 | Shinn Pond | Caution | Updates from routine monitoring program-organization |
| Sep 5, 2023 | Quarry Lakes | None | Updates from routine monitoring program-organization |
| Sep 5, 2023 | Shinn Pond | Caution | Updates from routine monitoring program-organization |
| Sep 5, 2023 | Quarry Lakes | Caution | Updates from routine monitoring program-organization |
| Aug 29, 2023 | Quarry Lakes | Caution | Updates from routine monitoring program-organization |
| Aug 22, 2023 | Quarry Lakes | Caution | Updates from routine monitoring program-organization |
| Aug 15, 2023 | Quarry Lakes | Caution | Updates from routine monitoring program-organization |
| Aug 15, 2023 | Shinn Pond | Caution | Updates from routine monitoring program-organization |
| Aug 15, 2023 | Rainbow Lake | Caution | Updates from routine monitoring program-organization |
| Aug 8, 2023 | Rainbow Lake | Caution | Updates from routine monitoring program-organization |
| Aug 8, 2023 | Shinn Pond | Caution | Updates from routine monitoring program-organization |
| Aug 8, 2023 | Quarry Lakes | Caution | Updates from routine monitoring program-organization |
| Jul 31, 2023 | Quarry Lakes | Caution | Updates from routine monitoring program-organization |
| Jul 25, 2023 | Shinn Pond | Caution | Updates from routine monitoring program-organization |
| Jul 25, 2023 | Rainbow Lake | Caution | Updates from routine monitoring program-organization |
| Jul 25, 2023 | Quarry Lakes | Danger | Updates from routine monitoring program-organization |
| Jul 18, 2023 | Rainbow Lake | Caution | Updates from routine monitoring program-organization |
| Jul 18, 2023 | Shinn Pond | Caution | Updates from routine monitoring program-organization |
| Jul 18, 2023 | Quarry Lakes | Danger | Updates from routine monitoring program-organization |
| Jul 11, 2023 | Shinn Pond | Caution | Updates from routine monitoring program-organization |
| Jul 11, 2023 | Quarry Lakes | Danger | Updates from routine monitoring program-organization |
| Jul 6, 2023 | Shinn Pond | Caution | Updates from routine monitoring program-organization |
| Jul 3, 2023 | Quarry Lakes | Danger | Updates from routine monitoring program-organization |
| Jun 27, 2023 | Shinn Pond | Caution | Updates from routine monitoring program-organization |
| Jun 27, 2023 | Quarry Lakes | Danger | Updates from routine monitoring program-organization |
| Jun 20, 2023 | Quarry Lakes | Danger | Updates from routine monitoring program-organization |
| Jun 6, 2023 | Shinn Pond | Caution | Updates from routine monitoring program-organization |
| Jun 6, 2023 | Quarry Lakes | Danger | Updates from routine monitoring program-organization |
| Jun 6, 2023 | Rainbow Lake | Caution | Updates from routine monitoring program-organization |
| May 30, 2023 | Rainbow Lake | Caution | Updates from routine monitoring program-organization |
| May 30, 2023 | Quarry Lakes | Danger | Updates from routine monitoring program-organization |
| May 26, 2023 | Rainbow Lake | Caution | Updates from routine monitoring program-organization |
| May 23, 2023 | Quarry Lakes | Danger | Updates from routine monitoring program-organization |
| May 16, 2023 | Quarry Lakes | Danger | Updates from routine monitoring program-organization |
| May 16, 2023 | Shinn Pond | Caution | Updates from routine monitoring program-organization |
| May 8, 2023 | Quarry Lakes | Danger | Updates from routine monitoring program-organization |
| May 3, 2023 | Quarry Lakes | Danger | Updates from routine monitoring program-organization |
| Apr 25, 2023 | Shinn Pond | Caution | Updates from routine monitoring program-organization |
| Apr 25, 2023 | Quarry Lakes | Caution | Updates from routine monitoring program-organization |
| Apr 18, 2023 | Quarry Lakes | Caution | Updates from routine monitoring program-organization |
| Apr 10, 2023 | Quarry Lakes | Danger | Updates from routine monitoring program-organization |
| Apr 4, 2023 | Quarry Lakes | Danger | Updates from routine monitoring program-organization |
| Mar 30, 2023 | Quarry Lakes | Warning | Updates from routine monitoring program-organization |
| Mar 20, 2023 | Quarry Lakes | Caution | Updates from routine monitoring program-organization |
| Mar 6, 2023 | Quarry Lakes | Caution | Updates from routine monitoring program-organization |
| Feb 14, 2023 | Quarry Lakes | Caution | Updates from routine monitoring program-organization |
| Feb 14, 2023 | Quarry Lakes | Danger | Updates from routine monitoring program-organization |
| Feb 6, 2023 | Quarry Lakes | Danger | Updates from routine monitoring program-organization |
| Feb 1, 2023 | Quarry Lakes | Danger | Updates from routine monitoring program-organization |
| Jan 27, 2023 | Shinn Pond | Caution | Updates from routine monitoring program-organization |
| Jan 24, 2023 | Quarry Lakes | Danger | Updates from routine monitoring program-organization |
| Jan 17, 2023 | Quarry Lakes | Danger | Updates from routine monitoring program-organization |
| Dec 30, 2022 | Shinn Pond | Caution | Updates from routine monitoring program-organization |
| Dec 29, 2022 | Quarry Lakes | Danger | Updates from routine monitoring program-organization |
| Dec 29, 2022 | East Bay Regional Park | Danger | End date recorded: Dec 31, 2022. Updates from routine monitoring program-organization |
| Dec 29, 2022 | East Bay Regional Park | Danger | Updates from routine monitoring program-organization |
| Dec 21, 2022 | Lago Los Osos area | Caution | End date recorded: Dec 31, 2022. Updates from routine monitoring program-organization |
| Dec 21, 2022 | Lago Los Osos area | Caution | Updates from routine monitoring program-organization |
| Dec 21, 2022 | East Bay Regional Park | Caution | Updates from routine monitoring program-organization |
| Dec 5, 2022 | East Bay Regional Park | Caution | Updates from routine monitoring program-organization |
| Nov 22, 2022 | Lago Los Osos area | Caution | Updates from routine monitoring program-organization |
| Nov 22, 2022 | East Bay Regional Park | Caution | Updates from routine monitoring program-organization |
| Nov 15, 2022 | Lago Los Osos area | Caution | Updates from routine monitoring program-organization |
| Nov 15, 2022 | East Bay Regional Park | Caution | Updates from routine monitoring program-organization |
| Nov 3, 2022 | East Bay Regional Park | Caution | Updates from routine monitoring program-organization |
| Oct 25, 2022 | East Bay Regional Park | Caution | Updates from routine monitoring program-organization |
| Oct 25, 2022 | Lago Los Osos area | Caution | Updates from routine monitoring program-organization |
| Oct 18, 2022 | Lago Los Osos area | Caution | Updates from routine monitoring program-organization |
| Oct 18, 2022 | East Bay Regional Park | Caution | Updates from routine monitoring program-organization |
| Oct 12, 2022 | East Bay Regional Park | Caution | Updates from routine monitoring program-organization |
| Oct 7, 2022 | Lago Los Osos area | Danger | Updates from routine monitoring program-organization |
| Oct 7, 2022 | Lago Los Osos area | Caution | Updates from routine monitoring program-organization |
| Oct 7, 2022 | East Bay Regional Park | Caution | Updates from routine monitoring program-organization |
| Oct 4, 2022 | East Bay Regional Park | Caution | Updates from routine monitoring program-organization |
| Sep 20, 2022 | East Bay Regional Park | Algal mat alert sign | Updates from routine monitoring program-organization |
| Sep 20, 2022 | East Bay Regional Park | None | Updates from routine monitoring program-organization |
| Sep 13, 2022 | Lago Los Osos area | Danger | Updates from routine monitoring program-organization |
| Sep 6, 2022 | East Bay Regional Park | None | Updates from routine monitoring program-organization |
| Sep 6, 2022 | Lago Los Osos area | Danger | Updates from routine monitoring program-organization |
| Sep 6, 2022 | East Bay Regional Park | None | Updates from routine monitoring program-organization |
| Sep 6, 2022 | Lago Los Osos area | Caution | Updates from routine monitoring program-organization |
| Sep 6, 2022 | East Bay Regional Park | Caution | Updates from routine monitoring program-organization |
| Aug 30, 2022 | Lago Los Osos area | Caution | Updates from routine monitoring program-organization |
| Aug 30, 2022 | East Bay Regional Park | Caution | Updates from routine monitoring program-organization |
| Aug 23, 2022 | Lago Los Osos area | None | Updates from routine monitoring program-organization |
| Aug 23, 2022 | East Bay Regional Park | None | Updates from routine monitoring program-organization |
| Aug 15, 2022 | Lago Los Osos area | Danger | Updates from routine monitoring program-organization |
| Aug 15, 2022 | Lago Los Osos area | Danger | Updates from routine monitoring program-organization |
| Aug 15, 2022 | East Bay Regional Park | Caution | Updates from routine monitoring program-organization |
| Aug 9, 2022 | East Bay Regional Park | Caution | Updates from routine monitoring program-organization |
| Aug 1, 2022 | East Bay Regional Park | Caution | Updates from routine monitoring program-organization |
| Jul 25, 2022 | East Bay Regional Park | Caution | Updates from routine monitoring program-organization |
| Jul 22, 2022 | Lago Los Osos area | Danger | Updates from routine monitoring program-organization |
| Jul 22, 2022 | East Bay Regional Park | Caution | Updates from routine monitoring program-organization |
| Jul 19, 2022 | East Bay Regional Park | Caution | Updates from routine monitoring program-organization |
| Jul 15, 2022 | East Bay Regional Park | Caution | Updates from routine monitoring program-organization |
| Jul 5, 2022 | Lago Los Osos area | Danger | Updates from routine monitoring program-organization |
| Jul 5, 2022 | East Bay Regional Park | Caution | Updates from routine monitoring program-organization |
| Jul 1, 2022 | Lago Los Osos area | Danger | Updates from routine monitoring program-organization |
| Jul 1, 2022 | East Bay Regional Park | Caution | Updates from routine monitoring program-organization |
| Jun 23, 2022 | East Bay Regional Park | Caution | Updates from routine monitoring program-organization |
| Jun 15, 2022 | East Bay Regional Park | Caution | Updates from routine monitoring program-organization |
| Jun 6, 2022 | East Bay Regional Park | Danger | Updates from routine monitoring program-organization |
| May 31, 2022 | Lago Los Osos area | Danger | Updates from routine monitoring program-organization |
| May 31, 2022 | East Bay Regional Park | Danger | Updates from routine monitoring program-organization |
| May 27, 2022 | Lago Los Osos area | Danger | Updates from routine monitoring program-organization |
| May 27, 2022 | East Bay Regional Park | Danger | Updates from routine monitoring program-organization |
| May 23, 2022 | East Bay Regional Park | Danger | Updates from routine monitoring program-organization |
| May 17, 2022 | East Bay Regional Park | Danger | Updates from routine monitoring program-organization |
| May 17, 2022 | East Bay Regional Park | Danger | |
| May 10, 2022 | East Bay Regional Park | Danger | |
| May 2, 2022 | East Bay Regional Park | Danger | |
| Apr 25, 2022 | Lago Los Osos area | Warning | |
| Apr 15, 2022 | Spot not described | Danger | Advisory based on visual and toxins |
| Apr 15, 2022 | Lago Las Osos area | Danger | Advisory based on visual and toxins |
| Jul 16, 2021 | Spot not described | None | Testing results below posting triggers |
| Dec 31, 2020 | Quarry Lakes | Caution | Advisory based on visual and toxins |
| Jul 17, 2019 | Quarry Lakes | Danger | |
| Dec 7, 2018 | Quarry Lakes | None | |
| Dec 14, 2017 | Quarry Lakes | Caution | |
| Mar 14, 2017 | Quarry Lakes | Danger |
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.