Oxnard Advances $46M Wastewater Treatment Upgrade with Carollo Engineers

OXNARD, CA — The City of Oxnard has selected Carollo Engineers to provide construction management and inspection services for the Primary Clarifiers and Activated Sludge Tank Improvement Project at the City’s Water Resource Recovery Facility (WRRF). The $46 million project represents a major investment in modernizing wastewater treatment infrastructure while maintaining full facility operations and meeting regulatory requirements in a cost-effective manner.

The Oxnard WRRF serves a growing population of approximately 210,000 residents and is a critical component of the City’s wastewater system. That system includes more than 400 miles of sewer lines, 15 lift stations, and a treatment plant with a capacity of 31.8 million gallons per day. The planned upgrades are designed to strengthen process reliability and support long-term operational performance across the facility.

Capital Investment Targets Reliability and Efficiency

The improvement project was identified as part of Oxnard’s 2025–2029 Capital Improvement Program, reflecting the City’s commitment to reinvesting in essential water and wastewater assets. The scope focuses on modernizing aging process infrastructure to improve treatment consistency, operational efficiency, and environmental protection.

Carollo was selected following its successful delivery of construction management services on the City’s Advanced Metering Infrastructure Project, which replaced more than 41,000 water meters citywide. That project established a working relationship between the City and Carollo’s construction management team that will carry forward into this major treatment facility upgrade.

"The success of our Advanced Meter Infrastructure Project was in large part due to the dedication and expertise of the Carollo construction management team," said Tim Beaman, Assistant Public Works Director for the City of Oxnard Public Works Department, Water & Wastewater. "We look forward to continuing our partnership with a $46M upgrade of Oxnard's primary clarifiers and activated sludge tanks."

Primary Clarifier and Odor Control Upgrades

Work on the primary clarifiers will include basin improvements, installation of a new odor control system, and replacement of all mechanical equipment. Upgrades to the primary sedimentation building are also planned to support improved performance and maintainability.

The new odor control system is intended to improve air quality for both facility operators and the surrounding community, while updated mechanical systems will support more reliable solids separation and overall treatment efficiency.

Activated Sludge Tank Improvements and Seismic Retrofits

Improvements to the activated sludge process include seismic retrofitting of existing basins and complete replacement of the aeration system. New submersible mixers will be installed, along with upgraded instrumentation and enhanced control systems.

These improvements are designed to optimize biological treatment performance while reducing energy consumption. The modernized aeration system is expected to play a key role in lowering overall power demand, supporting the City’s sustainability and carbon reduction goals.

Construction Phasing Keeps Facility Online

Construction is anticipated to begin in the first quarter of 2026 and continue for approximately 2.5 years, with the WRRF remaining fully operational throughout the upgrade process. The project is scheduled for completion and closeout in the third quarter of 2028.

"We are honored that the City of Oxnard has again entrusted Carollo to oversee critical infrastructure improvements for the community," said Rodolfo Garcia, Carollo Construction Manager. "This project represents a significant milestone in modernizing the Water Resource Recovery Facility, and our team is committed to working as an extension of City staff to deliver these essential upgrades."