Hollister Wastewater Treatment Plant

Project Details

Construction included a complete 10MGD wastewater treatment plant from pretreatment through disinfection.  The process design is based upon a Zeenon Membrane Bioreactor.  This system is supported by a BDP belt press, NX Turbo blower system, Westech rotary drum screens and an odor control system by Siemens.  Additional plant improvements include ground consolidation through the installation of over 850 Geo Piers and new RTU and SCADA systems.  The project also includes five new buildings – 8,000 sq.ft. operations, chemical, pre-treatment, solids handling, and membrane bio reactor.  12,796 cubic yards of concrete was placed.  The project was completed 6 months ahead of schedule.

Construction under this project had to be performed around on-going Owner operations. Tie-ins with piping, electrical and active ponds elevations during, excavation, equipment removal and construction within the ponds.

This was a high public profile project due to Water Conservation Board and citizen involvement. As Steve Wittry, the Engineering Manager/City Engineer, the individual responsible for the project for the City stated: “The project was necessary as the City of Hollister was under an order from the Regional Water Quality Control Board that resulted in a building moratorium for the City. The project was funded through revenue bonds that were secured upon rates of the citizens in the community. As such, there was a tremendous amount of public concern about completing the project on time and within budget. Overaa understood the implications to the community and, at one point in the construction; they opened the site for public inspection. Through a very challenging and complicated project, Overaa successfully completed the project over six months ahead of schedule.”

City of Hollister
Hollister, CA
Million Gallons Per Day
Project Cost
$57 M
  • Jeff Naff

    Jeff Naff

    Director of Work Acquisition - Municipal Infrastructure