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PUC outlines climate-assessment program, flags $10–$20 million backflow prevention estimate
Summary
PUC presented a climate-change assessment and adaptation program (PUMA and HVAM) to translate climate-model outputs into operational impacts for water, wastewater and power. Staff cited an initial backflow-prevention adaptation estimate of $10–$20 million and pledged further analysis and stakeholder coordination.
David Behar, the PUC’s climate program director, briefed the commission on the agency’s climate assessment and early adaptation work, describing assessment tools, modeling timelines and early cost estimates.
Behar said the PUMA project (Piloting Utility Modeling Applications) is a multi-utility effort that will produce state-of-the-art climate assessments, and the PUC is calibrating a hydrologic model (HVAM) to test sensitivity of inflows to Hetch Hetchy under a set of scenarios for 2040, 2070 and 2100. He described ranges of temperature and precipitation scenarios and cautioned that climate outputs offer ranges rather than single values; staff must translate those ranges into operational models.
On adaptation, Behar highlighted sea-level rise and storm-intensity impacts on the wastewater collection system. He corrected an early misstatement on the floor—"8 inches" of sea-level rise should be understood on a century timescale rather than "in the last year"—and stressed the need to use realistic literature curves. Staff identified 29 bay-side points potentially vulnerable to backflow and cited a preliminary backflow-prevention cost estimate of $10–$20 million (pending design refinement).
Commissioners asked about desalination planning, timelines for assessment outputs, and how climate findings will be folded into the Source System Improvement Program and capital planning. Behar said PUMA outputs are expected in roughly a year, HVAM calibration work will be delivered sooner, and the PUC will incorporate uncertainty ranges into operational and capital decisions.
Several public commenters and environmental groups urged the PUC to prioritize wetland retreat strategies, pilot constructed wetlands and ensure environmental-justice concerns are considered if desalination or large infrastructure options are pursued.
Staff said assessment investments so far include modest direct contributions to PUMA and HVAM calibration and that larger adaptation capital needs will require careful study before proposing rate impacts to customers.
