City Manager (name not specified in the record) told the Mill Valley City Council that a combination of debris from a prior water‑main break and a partial pump‑station failure caused an unexpectedly rapid flood in the Sycamore neighborhood during a major storm in late December.

The manager said the Sycamore Pump Station has three pumps, two of which tripped offline during the storm and could not be restarted until about 6 a.m. That failure, combined with what the manager described as roughly seven inches of rain on local hillsides and about 1.5 inches on the flats during a nine‑hour period, led to flooding that officials said was faster and more intense than anticipated.

“We think some of the debris from the water main break the week before was a contributing factor, but really our pump station went down,” the City Manager said, describing the sequence and the city’s plan to produce an after‑action report for neighbors.

Why it matters: residents experienced rapid flooding in a neighborhood that had not recently seen similar events; the incident highlighted gaps in neighborhood‑level notification and exposed points of operational vulnerability in the storm‑response system.

The city manager said staff performed door‑to‑door notifications for the streets most at risk, coordinated with police, fire and public works on the night of the event, and temporarily advised some residents to shut off power to avoid surges. The manager acknowledged a notification lapse: staff should have issued alerts around 1:50 a.m. but did not, and an after‑action will explain why and how notification procedures will change.

Council members questioned the city’s use of Alert Marin (county‑managed, targeted alerts) versus Nixle (a broader county dispatch notification). The manager said the city is moving toward Alert Marin for targeted, street‑level messages and explained that the county’s process for Nixle involves a county operator who must be engaged to send messages; in this event the county recommended against an automatic Nixle message based on creek levels, which did not reflect the city’s localized pump failure.

Staff told the council they are preparing a lessons‑learned report to address: what happened, whether it could recur, and how notifications and neighborhood outreach will change. The manager said the city intends to send the report to neighbors as soon as possible and to hold a neighborhood meeting where operations staff (not elected officials) will explain response roles and preventative steps.

Capital response: the manager noted that Mill Valley has about $3 million in planned capital improvement program (CIP) projects for flood control over the next three to five years; roughly $750,000 is budgeted for Sycamore drainage and pump‑station improvements. The city said it will prioritize those projects and partner with neighbors during design and outreach.

Ending: City staff will produce the after‑action report, firm up Alert Marin procedures, and return to the council and affected residents with timelines for physical improvements and improved notification protocols.