Your WaterFlood and Stream ManagementWatershed and Environment

Zone 7 treats surface water imported from outside the Valley, along with runoff collected in Del Valle Reservoir, at one of three facilities to make it ready for drinking before distribution. These plants are strategically located in the eastern and southern portions of the Valley because that's where elevation is higher and gravity helps distribute the water to customers without high pumping costs.  

Del Valle Water Treatment Plant

  • Where: Southern Livermore
  • Capacity: 36 million gallons per day
  • Features: Houses Zone 7's Water Quality Laboratory

Patterson Pass Water Treatment Plant

  • Where: Eastern Livermore
  • Capacity: 12 million gallons per day

Patterson Pass Ultrafiltration Water Treatment Plant

  • Where: Eastern Livermore
  • Capacity:  8 million gallons per day

Water Treatment Plant Expansion: A plant expansion of up to 12-16 million gallons a day (mgd) will be constructed either at the Altamont site near Dyer Reservoir or the Patterson Pass Water Treatment Plant. The project will accommodate planned Valley growth, enhance overall water-system reliability and improve overall water quality by reducing Zone 7's reliance on groundwater and through plant design features.

  • Capacity: 12-16 million gallons per day
  • Completion: 2025 (as of 2012-13 Capital Improvement Program)
  • Cost: Treatment plant estimated in 2012-13 Capital Improvement Program at $176.3 million, funded by connection fees on new development.

 About Groundwater

Some treatment occurs naturally as imported water percolates into the groundwater basin and is filtered by the soils over a very long travel time. This process actually removes all surface contaminants and biodegrades most pollutants, making groundwater from deep production wells one of the safest water supplies available. As water percolates through the soils, it also picks up naturally occurring minerals, including calcium and magnesium, that can make the water hard.”As with treated surface water, chloramines are added to groundwater to maintain distribution-system disinfectant. To get information on our Mocho Groundwater Demineralization Plant, click here.