San Mateo receives update on $1.035 billion wastewater plant upgrade; council told up to $9.6M may still be needed

Mayor Lorraine welcomed attendees at a March 2 special meeting of the San Mateo City Council and opened a study session on the city’s Clean Water Program, an years‑long effort to modernize sewer conveyance and the wastewater treatment plant.

Tom Williams, engineering manager for the Clean Water Program, said the project traces to a 2009 cease‑and‑desist order and has included pump stations, conveyance work and the treatment plant. “We projected in 2017 that we’d spend $991,000,000,” Williams said. “The current estimate at completion is $1,035,000,000,” about a 4.4% increase from that earlier projection.

The presentation outlined major upgrades at the plant: a new headworks to screen grit and debris, enclosed primary clarifiers with odor control, biological nutrient removal (BNR) and a membrane bioreactor (MBR) that Williams described as producing much clearer effluent than the older plant. He said performance testing is ongoing and that the new processes will be operational this month, with the final force main cutover also expected this month so the plant can receive its full design flow.

Williams said the city anticipates carrying some conservative contingencies in its estimate-at-completion because of outstanding contractor claims and other potential items, but staff will negotiate and review those claims. He detailed near‑term cost requests above owner contingency: about $3,850,000 for hard construction items at the plant and roughly $2,000,000 of associated soft costs. He said a broader projection of remaining potential costs — if all items materialize and no negotiated reductions occur — is approximately $9,600,000, with about $5,900,000 of that tied to treatment‑plant work.

City Attorney (identified during the meeting) told council that several construction claims and disputes remain under review and have not been resolved, and that those unresolved claims do not change the figures presented at the study session. The city manager confirmed staff carry conservative, worst‑case assumptions in the estimate and review contractor time‑impact and entitlement claims before accepting amounts.

Council members asked for several clarifications. Deputy Mayor Fernandez asked whether money might be recovered from Foster City; the city manager said the city and Foster City reached an agreement and that an item to authorize payment of interest owed under that agreement will be placed on the March 16 consent calendar. Council Member Newsom asked whether outstanding disputes could lower the city’s projected cost; the city attorney and staff said such recoveries are possible but are still in process and do not affect the numbers shown tonight.

Williams described remaining system projects: three to four pump‑station upgrades (including a large relocation project at a Norfolk area intersection, the Kelly Kehoe station near Joinville Pool with odor control and back‑up generators, and a small Arroyo Court project constrained by a summer work window for fish‑and‑wildlife permits). He said site work should be finished by May, and staff expects overall project closeout by June. Williams also said the recreational path that crosses plant property — a frequent neighbor concern — should be restored by summer.

On regional recycled‑water planning, Tom O’Rourke, senior project manager at the plant, said San Mateo continues to participate in the Peninsula Pure Water Project; the San Francisco Public Utilities Commission is driving the regional effort and early phases focus on a purification plant at the Silicon Valley Clean Water Facility in Redwood Shores. O’Rourke said any pipeline and indirect potable‑use steps are later phases and that regional recycled‑water options remain a longer‑term prospect.

The council received the informational update, with no public speakers on the item and no formal vote. Mayor Lorraine thanked presenters and adjourned the special meeting; a regular council meeting was scheduled to begin shortly afterward.