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Nearly $1 billion Contra Costa County project reveals the changing science of keeping drinking water safe

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Nearly  billion Contra Costa County project reveals the changing science of keeping drinking water safe

A drone view of EBMUD’s Walnut Creek Water Treatment Plant on Larkey Lane in Walnut Creek, Calif., on Wednesday, June 12, 2024. Public utility officials are poised to approve a $420 million water pretreatment and ozone facility project on the site. (Jane Tyska/Bay Area News Group)

WALNUT CREEK — As the Bay Area’s drinking water is increasingly clouded with particles from wildfires, atmospheric rivers, algae blooms and chemical contaminants, the East Bay’s largest water district is set to undertake the most ambitious infrastructure project in the region to try to keep it clean.

The East Bay Municipal Utility District (EBMUD) is tackling nearly $1 billion in infrastructure upgrades to help safeguard 1.4 million residents’ drinking water supply. Officials hope to transform the way it treats the Mokelumne River Watershed that feeds the Pardee and Briones reservoirs.

One of the biggest projects began in fall 2021, when the 101-year-old agency began conceptualizing a $420 million plan to add new pretreatment facilities at its Walnut Creek Water Treatment Plant — and smaller upgrades to the Lafayette plant nearby — to speed up how quickly EBMUD can filter out the dirt, microorganisms, algae, chemicals and other particles that are swept into drinking water, 90% of which is sourced from Sierra Nevada snowmelt.

Constructed in 1967, the Walnut Creek plant currently pumps out 115 million gallons per day (MGD). If the project gets the green light, that capacity is expected to jump to 160 MGD after both phases of construction are complete, according to staff reports.

The plant’s existing gravity filtration system — not dissimilar to a household Brita filter — processes water through layers of sand and charcoal to strain out sediment and organic matter, in addition to other chemical processes for aeration, fluoridation and corrosion control.

According to plans for new ozone oxidation treatments, ballasted flocculation processing and other pending pretreatment upgrades, EBMUD aims to improve the reliability, efficiency, and resiliency of the treatment process serving roughly 225,000 customers in Pleasant Hill, Walnut Creek, Alamo, Lafayette and surrounding communities in the San Ramon Valley.

Specifically during emergencies and drought, the project would also allow the Walnut Creek Water Treatment Plant to safely tap into supplemental, raw sources of water that don’t otherwise satisfy treatment standards, including the Sacramento River that flows south from the Freeport Regional Water Facility.

EBMUD’s seven-member board unanimously agreed to vote on approving the project’s final environmental impact reports (EIR) on July 9. Despite three years of outreach with local elected officials and residents, the decision on the final EIR was postponed to give staff four extra weeks to address neighbors’ lingering questions and concerns.

But the project is not without controversy.

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