City of Lathrop Advanced Water Treatment and Recycling Facility Expansion

Lathrop, CA


PACE provided project development, studies, design, and bid and construction administration phase services for the expansion of the Lathrop Consolidated Treatment Facility, an MBR wastewater treatment facility that features highly aesthetic architecture and an administration building that allows for public outreach and understanding of the facility’s operations for its visitors. The existing facility was 1.0 MGD and the expanded capacity is 2.5 MGD, with an ultimate build-out capacity of 9.0 MGD.


PACE provided a creative approach to the upgrade with a new secondary and MBR treatment system accessed at grade level with an integrated process mechanical design that minimized valving and pumping that improves process treatment simplicity and makes the unit processes visible to operators. The design is straightforward and allowed for ease in facility expansion. The new treatment system process design was based around use of the existing chlorine contact basin (CCB), without having to expand the CCB infrastructure for continued production of Title 22 disinfected tertiary recycled water under the new design flow conditions. This was achieved through a free chlorine contact time revalidation study performed by PACE and approved through the CA DDW. Additionally, PACE designed a conversion for the existing MBR facility that will be used for aerobic sludge digestion and thickening processes for the new constructed MBR facility.


PACE also provided a management PLC to network both existing and new PLC’s to create a complete network. The local PLC was equipped with an operator interface terminal (OIT) that allows for local monitoring and control of the individual process systems/equipment, while the Master PLC/OIT allows for a centralized monitoring and control function for the facility process systems/equipment connected to the Master PLC. The management PLC took all vendor PLC tags control, monitoring, and alarming and created generic tag array mappings. This significantly reduced development time for the SCADA integrator.


The design approach enabled construction of the new facilities while the existing facilities remained in operation. The new facility also includes an existing upstream influent flow equalization system that keeps secondary, membrane and disinfection flows constant for optimal treatment and reduction of downstream treatment process costs. The facility features common wall modular construction that reduces the footprint of the process tanks, improves operational flexibility, and reduces capital and maintenance costs for the structure, equipment, piping and wiring. An initial topography site study led to minimizing grade and pavement design work to achieve proper drainage, as well as providing a favorable balance for site cut and fill quantities and ultimately eliminated excessive offsite import and hauling.


Key Features:

  • Consolidation of two treatment facility operations (domestic and industrial) into one facility
  • Both new and improvement designs for existing treatment facility
  • Existing chlorine contact basin improvements
  • Accurate cost estimation and budget creation
  • Major site civil improvements
  • Instrumentation and controls integration
  • Chlorine contact time re-rating achieved to reduce application and costs
  • Facility maintained full operation during construction
  • Designed and implemented a new SCADA system

City of Lathrop

Communications, Instrumentation & Controls, PLC, Wastewater Treatment