California utilities are increasingly being asked to prepare for a future defined by climate extremes, all while continuing to deliver safe, reliable drinking water. A major upgrade underway at the Orinda Water Treatment Plant (WTP) in San Francisco’s East Bay reflects how utilities are responding to those pressures with forward-looking, resilient design.
A recent article published by the American Society of Civil Engineers (ASCE) highlights the Orinda Water Treatment Plant Disinfection Improvements Project, a $341 million investment led by East Bay Municipal Utility District (EBMUD) and delivered in partnership with Carollo Engineers, Stantec, Arcadis, and FlatironDragados. More than halfway complete, the project is designed to strengthen water quality protection for approximately 1.4 million people while prioritizing climate readiness.
Climate Extremes Drive Drinking Water Infrastructure Upgrades
The need for the Orinda WTP upgrade emerged from a series of climate-driven events that challenged long-standing assumptions about source water reliability. During the 2014–2015 drought, EBMUD, whose supply is roughly 90% dependent on snowmelt from the Mokelumne River, faced historically low snowpack and was forced to rely on supplemental sources for the first time.
Following that drought, EBMUD engaged Carollo to evaluate pretreatment options at its water treatment facilities. “EBMUD was taking proactive steps with its water treatment systems to be better prepared for future conditions that were not very well defined at the time,” said Peter von Bucher, P.E., project manager at Carollo. “It was clear that the region was facing future climate-related risks.”
Enhancing Disinfection Performance with a Multi-Barrier Approach
At the core of the project is a new treatment configuration that integrates ultraviolet (UV) disinfection with a chlorine contact basin. The upgraded process reverses the existing sequence by filtering water first, reducing organic content before disinfection and limiting disinfection byproduct formation.
“With UV and chlorine, we get a multibarrier approach to disinfection,” von Bucher explained. “Using both covers your bases and adds another level of protection, confidence, and safety to the disinfection process, regardless of the quality of water coming through the plant.”
This approach improves resilience not only to short-term events like flooding, but also to longer-term risks such as wildfire, which can degrade water quality for years across an entire watershed.
Building Long-Term Climate Resilience for the East Bay
Construction began in 2022 and is scheduled for completion in 2028. Through careful sequencing and extensive coordination, the project team has developed a plan to complete the upgrades without any interruption to plant operations.
The Orinda Water Treatment Plant Disinfection Improvements Project demonstrates how utilities can respond to climate uncertainty with adaptable design, layered treatment strategies, and resilient infrastructure investments.
To learn more about the project’s engineering challenges and climate-driven motivations, read the full article.