AFTER MORE THAN FIVE YEARS of construction, San Mateo’s upgraded Wastewater Treatment Plant was unveiled in a ribbon-cutting ceremony. It is the largest infrastructure project in San Mateo’s history, and developers say it’s one of the most sustainable wastewater treatment facilities in the country. The upgraded Wastewater Treatment Plant in San Mateo, Calif. on Wednesday, Sept. 24, 2025. (Alise Maripuu/Bay City News) Left: Scott Josyln, a wastewater treatment plant operator, tours the upgraded Wastewater Treatment Plant. Right: Facade of the upgraded Wastewater Treatment Plant in San Mateo, Calif. on Wednesday, Sept. 24, 2025.