Millbrae installs dual-shaft grinder at Madrone pump station to reduce blockages from wet wipes

Millbrae installed a dual‑shaft solids grinder at the Madrone Street sewage pump station on Aug. 20 to address recurring clogs caused by nondispersible wipes and fibrous materials, city staff told the City Council during the Sept. 23 meeting.

City Engineer and CIP Manager Ahmad Haya presented the work and said the unit — a wipes‑ready dual‑shaft grinder sometimes marketed under the trade name “Muffin Monster” — was installed as an upgrade to reduce deragging and pump wear. Haya said the grinder has 17‑tooth serrated cutters designed to reduce wipes and similar material into particles that pumps can convey and that screens at the wastewater treatment plant will capture many of those particles before treatment begins.

“Do not flush wipes,” Haya told the council during the presentation, repeating the city’s request that residents dispose of single‑use wet wipes in the trash rather than the sewer system.

What the city reported - Facility scope: The Madrone pump station collects approximately one‑third of Millbrae’s sewage flows and conveys those flows toward the treatment plant. The new unit is a dual‑shaft grinder with wipes‑ready cutters (17‑tooth serrated design) intended to reduce fibrous solids that routinely cause clogs. - Installation and cost: Haya said the grinder cost about $25,000 and city staff completed the equipment swap in roughly a half day with three people on site. - Operational effects: Haya cited a Virginia Beach case study where installation of a wipes‑ready grinder reduced pump run time and eliminated routine deragging at a problem pump station. Millbrae staff said they expect lower maintenance, reduced equipment wear and fewer unplanned deragging calls.

Council questions and staff responses Vice Mayor Holaberg asked the project cost; Ahmad Haya replied the unit cost $25,000 and took about half a day for three staff to install. When asked about staffing and earlier frequency of deragging, staff said the previous grinders and pumps required more frequent cleanings and that the new grinders should reduce labor and equipment costs by reducing clogging and excessive pump run time.

Public reminder and next steps Haya and other staff emphasized that mechanical solutions help but do not eliminate the problem if residents continue to flush wipes. The presentation concluded as an informational item with staff answering questions; council did not take formal action on the installation during the meeting.

Background context The presentation referenced national and international estimates of the cost and operational burden of wipes in sewer systems — examples included large expense reports from utilities in the United Kingdom and U.S. cities — and recommended residents dispose of wet wipes in the trash rather than flush them.