Mocho Groundwater Demineralization Plant

Zone 7 Water Agency, 

Mocho Groundwater Demineralization Plant

2012 Membrane Plant of the Year - Southwest Membrane Operator Association
Service Type: 
Project Highlights: 
  • Design and construction-phase services for a demineralization project to remove 6,000 tons/year of salt from the groundwater.
  • Brine disposal and treatment process evaluation.
  • $24-million facility construction in a residential area.
Cartridge filters remove sand and other particles
Cartridge filters remove sand and other particles prior to RO treatment.

Zone 7 services as the overall water quality management agency for the Alameda Creek Watershed north of Niles in Northern California. Zone 7 has primary responsibility for management of the Livermore Amador Valley surface and groundwater resources. It has historically managed the main groundwater basin by maximizing surface water deliveries, recharging the basin with low total dissolved solids (TDS) surface water, restricting groundwater pumping, and restricting wastewater disposal within the watershed.

The Mocho Groundwater Demineralization Plant is one element of Zone 7’s Salt Management Plan, which is intended to reverse the salt build-up in the main groundwater basin. Zone 7 hired Carollo to provide conceptual, design and construction phase engineering services for a demineralization plant that will remove up to 6,000 tons/year of salt from the groundwater basin. Treated water will be provided back to the public as potable water.

During the conceptual design phase, Carollo evaluated:

  • Three treatment alternatives: EDR, NF, and RO.
  • Brine disposal options: connecting to an existing export pipeline, evaporation ponds, deep wells.
  • Wellhead treatment plant siting alternatives.

Carollo conducted these evaluations with a significant level of stakeholder involvement. Principal stakeholders included Zone 7 management, engineering and operations staff, the City of Pleasanton, and water retailers within Zone 7’s service area.

The Mocho Groundwater Demineralization Plant produces 6.1-mgd of RO treated water. The facility is located on a 1.5-acre parcel in a residential area. The project included 2,200 feet of 28-inch diameter HDPE well field piping with two jack and bore roadway crossings. Operational in 2009, the project cost was $24-million.

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