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Groundwater test hole finds viable municipal well site near Rio Vista High School; samples meet Title 22 standards
Summary
Staff reported that a test hole drilled to roughly 800 feet near Rio Vista High School identified water-bearing zones that met California Title 22 drinking‑water standards; staff said a constructed well at the site could yield roughly 1,200–1,600 gallons per minute and recommended moving to the next development phase.
City staff told the Rio Vista City Council Nov. 4 that a groundwater test hole drilled on the northern edge of Rio Vista High School is a viable site for a new municipal well. The test‑hole operation (conducted July 23–Aug. 14, 2025) reached approximately 800 feet; staff said likely water‑bearing zones were sampled between about 330 and 660 feet.
Analysis of samples from the tested zones met Title 22 drinking‑water standards, and staff advised the council that a constructed well at that site could yield an estimated 1,200–1,600 gallons per minute without requiring treatment for constituents including arsenic. Staff noted a favorable trend in recent arsenic testing across the system and said the site will move to the next project phase, including evaluating a potential property acquisition or land swap to secure the well site and integrate the well into the city’s capital improvement program.
Council members sought confirmation on depth and yield; staff said 800 feet is the drill depth for the test hole and reiterated that typical municipal wells in recent years produce about 1,200–1,600 gpm at peak, with an optimum sustained pumping rate around 1,000 gpm for efficiency and longevity. Staff said water‑quality sample results met current drinking‑water standards and that the city will proceed with planning for a constructed well and property acquisition steps.
What’s next: staff will begin planning the design and acquisition steps necessary to construct the municipal well and will return with project recommendations and budget implications.
