SFPUC: Pillar reservoir dam rated ‘poor’; interim outlet work and multi‑hundred‑million options outlined

Steve Richie, assistant director for water at the San Francisco Public Utilities Commission (SFPUC), told the Coast County Water District board that the Pillar reservoir dam has been rated “poor” by California’s Division of Safety of Dams (DSOD) and that the state agency is pressing for demonstrable near‑term steps to improve safety. Richie and SFPUC staff described a multi‑tiered approach that prioritizes outlet‑works improvements first and larger structural work later.

Why it matters: District officials downstream rely on the reservoir for supply and said the DSOD rating has led to a restriction of the reservoir elevation (roughly a 20‑foot restriction in current operations). SFPUC said interim projects could reduce immediate safety concerns and help remove the “poor” designation sooner than a single, full rebuild.

What SFPUC described: Richie said DSOD encouraged smaller, interim projects that could be completed in the short term rather than waiting for a lengthy, full dam reconstruction. For the interim outlet‑works retrofit planning SFPUC listed an estimated budget “about $34 million” for options under evaluation. Richie said one preferred near‑term alternative would accept a permanent reservoir restriction while building an interim discharge outlet and related improvements, with an estimated cost in the neighborhood of $190 million for a lower‑spillway approach that minimizes dam construction. A full new embankment and enlarged spillway alternative, he said, would exceed $350 million.

On schedule and delivery: SFPUC presented an implementation schedule showing outlet‑works retrofit planning and design leading toward a construction target under current assumptions; the agency noted a planning estimate of roughly seven years to reach construction for the outlet retrofit under the schedule shown and that DSOD may press to accelerate that timetable.

Construction and operations impacts: Board members asked whether interim work would require drawing down the reservoir and how long construction would disrupt operations. Richie said it “depends on the nature of the fix” and that certain tunneling or pipeline approaches could require temporarily lowering the reservoir but that SFPUC would seek ways to minimize operational impacts. He also told the board SFPUC is coordinating downstream operational analysis and environmental review and that the National Marine Fisheries Service has been engaged and currently is satisfied with operations described to date.

Environmental and historic‑resource considerations: SFPUC staff noted elements of the outlet structure date to the early 20th century and said the reservoir’s historic elements may require consultation with the State Historic Preservation Officer for some alternatives. Richie said the Forbay and outlet works (built circa 1913, by Spring Valley Water Company per the presentation) raise additional permitting considerations.

Next steps: SFPUC said it will meet with DSOD on site in April for detailed review, advance planning of interim outlet works, and further refinement of cost and schedule. District staff said they expect to be kept informed and involved in design decisions that could affect downstream supply and operational constraints.

Sources: Remarks and slides presented by Steve Richie, assistant director for water, and questions from Coast County Water District board members during the meeting.