Sonoma Valley Wastewater Reservoirs Rated Significant and High Hazard: $100,000 Flood Study Proposed

CALIFORNIA — October 27, 2026. California dam safety regulators classified the Sonoma Valley sanitation district’s R4 recycled-water reservoir as significant hazard and its R5 reservoir as high hazard during a July 2025 inspection, prompting required inundation studies.

What the official records say

The October 27 Sonoma Water agenda proposes adding $50,000 to an existing Dudek study and extending the agreement through June 30, 2027, for a cumulative $100,000 ceiling. The R4 and R5 storage ponds hold treated recycled water, and the engineering study will model hypothetical dam-failure inundation and map affected areas to meet Department of Water Resources Division of Safety of Dams requirements.

What has not been confirmed

A high hazard **classification** refers to the potential consequences of a hypothetical failure, not a finding that a dam is presently failing or that an evacuation has been ordered. The study and revised contract were proposed, not confirmed completed; area residents should use official emergency guidance for any actual alert.

Primary source: Sonoma Water item 2026-1047.

California58 distinguishes an agenda proposal from an approved decision and clearly labels older announcements. Check current agency notices before acting.

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