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SFPUC reports slides at Calabrio Dam; design change will produce large spoil volumes and raise costs
Summary
Deputy director Deep Bajwa told the commission that newly discovered slides beneath the observation hill require widening excavations to a two‑to‑one slope on both sides, producing roughly 1.6 million cubic yards of permanently disposed spoils and 1.3 million cubic yards of staged material and increasing project costs and schedule risk.
Deep Bajwa, deputy director overseeing the Water System Improvement Program update, told the San Francisco Public Utilities Commission that geologic slides discovered under the observation hill at the Calabrio Dam require a design change that will materially increase spoil volumes, cost and schedule risk.
"It will generate extra 1,600,000 cubic yard of spoils which needs to be disposed of permanently," Bajwa said, adding that an additional 1,300,000 cubic yards will be staged temporarily and then used in dam construction. He said the change follows review and concurrence by the Technical Advisory Panel and senior management.
The staff said the initial construction estimate of about $60,000,000 referenced in earlier briefings assumed only a north‑side layback. Bajwa told commissioners that cutting both the north and south faces to a two‑to‑one slope raises quantities and will add significant cost and mitigation requirements as the team coordinates with permitting agencies including the U.S. Army Corps of Engineers, California Department of Fish and Game and the regional water board.
Bajwa outlined a near‑term schedule: staff expects to deliver a complete permitting package to regulators by the end‑of‑month milestone, receive a contractor rough order of magnitude estimate by the end of October, finalize details in November, and negotiate contract changes in December. He warned that the contractor risks running out of onsite storage space by January 2013 unless off‑site disposal and staging plans are secured.
Commissioners pressed for more detail on which consultants and experts had been engaged and asked staff to produce a clear, visible record of due diligence and oversight. Staff agreed to provide counts and a timeline of consultant involvement and to brief the commission more frequently as the work progresses.
The commission did not take a separate vote on a project budget change at this meeting; staff said they will bring an updated cost forecast and negotiating position back to the commission after the contractor and permitting analyses are complete.
