Sunnyvale planners review Cal Water proposal for deep groundwater well and 56,000‑gallon tank amid noise concerns

Sunnyvale planning staff and California Water Service Company representatives on May 27 described a proposal to reopen and upgrade a decommissioned water site at 800 Carlisle Way, including drilling a replacement groundwater well to about 800–1,000 feet below grade and installing an approximately 56,000‑gallon steel tank about 24 feet tall.

Planner Mary J. Prakash said the project "triggers focused EIR because of the significant and unavoidable noise impacts due to the drilling activity." The city began circulating a draft environmental impact report May 15; the public review period runs 45 days, through June 30, and a public hearing is planned in June. A final EIR, responses to comments and subsequent hearings before the Planning Commission and City Council were described as the next steps; staff estimated the project could be complete in 2026.

The applicant, California Water Service Company (Cal Water), presented technical details. Cal Water engineer Luis Zamudio described the proposed drilling method and why continuous operations are requested: "The primary reason why we're proposing 24/7 drilling operations is because it requires continuous operation of the drilling fluid." He said stopping the reverse‑circulation drilling process risks collapse of the borehole and could harm future well production.

City staff and Cal Water both said noise modeling shows two single‑family homes south of the site would exceed Sunnyvale's nighttime noise standard during drilling even after the applicant's proposed mitigation. Proposed mitigation includes constructing temporary sound walls — described in the presentations as a 20‑foot wall around drilling equipment and 32‑foot walls around site boundaries — and offering hotel vouchers to the two affected residences during nighttime drilling. Cal Water said drilling would run continuously for about two weeks.

Cal Water also described other elements of the project: replacement of a previously decommissioned tank (the prior redwood tank was removed in 2016); three chemical storage buildings (Cal Water said the site would store up to 300 gallons of sodium hypochlorite plus one other chemical, secured in double containment); a new pump station and an emergency diesel generator that would be used only during outages and tested biweekly for 30 minutes. Mary Prakash said the generator would be enclosed in a sound‑attenuating chamber as part of mitigation to meet city noise standards.

Other details shared at the study session: the site is about 0.77 acre in Sunnyvale’s southeast (near Carlisle Way and Kingfisher Way, adjacent to Panama Park). Cal Water proposed retaining 30 of the site's 38 trees and planting 12 new trees. Staff and the applicant said the project site was used for water extraction from 1955 to 2016 and Cal Water has worked with the city since 2021 on plans to resume operations.

Commissioners pressed on mitigation and design. Commissioner Shukla asked whether the new tank would serve the immediate neighborhood; staff said the tank would serve some parts of Sunnyvale and areas outside Sunnyvale and that the previous tank had been demolished in 2016. Commissioner Pine said he would closely scrutinize the noise analysis and warned that the planning finding that a variance "will not be materially detrimental to the public welfare" would be difficult to make if residents experience persistent, materially harmful noise.

A resident who identified herself as Anne Bogan, who lives next to the Cal Water site, spoke during remote public comment and said she opposed the height variance, noting a single‑story overlay in the neighborhood and raising concerns about chemical odors and prior fence work on the site. Prakash and Cal Water representatives said the chemical storage would be secured and monitored and the site is not accessible to the public.

No formal action was taken at the study session. Staff said the draft EIR is in a statutory 45‑day review period through June 30; staff will prepare a final EIR responding to comments, and subsequent public hearings will be scheduled for certification of the EIR and project approvals. Cal Water and staff said they will include additional details — including the noise‑consultant rationale for recommended sound‑wall heights and equipment specifications — in the record for the public hearing.

Ending: The study session closed after public comment; the Planning Commission will receive the formal EIR and a public hearing on the project is scheduled in June. Staff provided email and web instructions for submitting comments on the draft EIR.