Mountain House Water Reclamation Facility

Tracy, CA


PACE, as the Engineer of Record, provided design, permitting, construction services, and start-up services for the Phase II expansion and the Phase III expansion of the Mountain House Water Reclamation Facility. The Phase II expansion replaced the 0.45 MGD aerated lagoon wastewater treatment plant with a 3.0 MGD advanced SBR Water Reclamation Facility (WRF). The expanded facility features a two-tank hybrid SBR process for biological oxidation of organics and secondary clarification. Tertiary treatment is accomplished with cloth media filtration and advanced UV disinfection. The facility is designed to meet strict California Title 22 effluent requirements for unrestricted reuse, as well as strict NPDES permit requirements for discharge into the Old River. The facility also provides sludge processing that meets EPA Class B requirements.


PACE recently completed the design of the Phase III expansion to build out the capacity of 5.4 MGD and converted the secondary treatment process to a membrane bio-reactor (MBR) treatment process to meet the higher wastewater flow and existing Title 22 effluent requirements, while maintaining a minimal facility footprint. As part of the conversion, PACE designed the facility around the use of existing infrastructure. This includes repurposing and subdividing the existing SBR process tanks into anoxic, oxic, and post-anoxic tanks prior to feeding the new MBR facility. The design also incorporates the expansion of the existing UV channel system for tertiary disinfection with the modified and expanded facility.


Key Features:

  • Phase II 0.45 MGD aeration lagoon to 3.0 MGD advanced SBR conversion with construction of a two-tank hybrid SBR process for biological oxidation of organics and secondary clarification
  • Phase III SBR to MBR conversion from 3 MGD to 5.4 MGD
  • Large-scale six-train MBR system with wet weather peaking
  • Sludge processing to meet EPA Class B biosolids requirements with centrifuge dewatering
  • EPA Class B Biosolids production at 25% dryness using MBR thickening
  • Acquired WDR for Title 22 unrestricted reuse and effluent discharge to Old River (de-factor potable source water)
  • Energy-efficient aeration and low-energy mixers
  • Underground treatment tanks minimize land use and aesthetic impacts
  • Operational during construction – development of sequence of construction
  • Performance specifications developed for major process equipment

IHP Capital Partners

Wastewater Treatment