2025 West Best Projects
Best Government/Public Building: Orange County Sanitation District Headquarters
Orange County Sanitation District Headquarters
Valley, Calif.
BEST PROJECT Government/Public Building
Submitted by Swinerton
Owner Orange County Sanitation District
Lead Design Firm HDR Inc.
General Contractor Swinerton Builders
Civil/Structural/MEP Engineer HDR Inc.
Landscape Architect EPT Design
Owner’s Representative (CM) AECOM
The use of a pioneering hybrid superstructure that combines mass timber with steel braces was an unusual one for a project of this scale. Completed on time and within budget in June 2024, this $108.5-million, three-story, 109,000-sq-ft facility will house the sanitation district’s administrative functions and serves as a model for environmentally responsible design and construction. It’s also the largest mass timber project the contractor has completed in Southern California to date.
For the structure, mass timber significantly reduces the building’s carbon footprint, while steel braces provide structural resilience and longevity. Designed to achieve both LEED Gold and net-zero energy certification, the building also features a signature diagrid glued-laminated timber (glulam) roof at the main lobby entrance and integrates energy-efficient systems such as a high-performance building envelope.
Photo by Brian Doll
The building is designed to generate as much energy as it consumes annually, leveraging high-performance building systems, advanced insulation and onsite renewable energy sources that include biogas and photovoltaic panels. All building heating is provided from the waste heat generated by energy production.
Photo by Brian Doll
Unusually heavy rain during construction led to water intrusion issues and necessitated comprehensive schedule resequencing. Accelerating certain trades and pivoting construction methods helped the team maintain progress. Early collaboration with MEP trade partners and strategic use of offsite storage for long-lead materials also helped mitigate supply chain risks.
Evolving mass timber building code requirements required the team to navigate complex design approvals as well. This process required close coordination with regulatory authorities and a proactive approach to compliance.
Photo by Brian Doll
Crews also had to coordinate construction with ongoing operations at the existing sanitation plant. This called for extensive preplanning and clear, consistent communication between plant operations and the construction team. A collaborative approach ensured successful tie-ins and minimal disruptions to all operations.
