Orange County Sanitation District Headquarters

In a building typology where efficiency is often prioritized over aesthetics and functionality over features, this project demonstrates that it’s possible to achieve them all.

Orange County Sanitation District (OC SAN) provides wastewater collection, treatment, and recycling services for 2.6 million residents in Southern California. Employees had been working from 13 scattered facilities, and OC SAN wanted a new headquarters to enhance collaboration and strengthen their presence within the community. Architects used mass timber, designing this beautiful yet sustainable net zero energy building at a cost that supports clear value for the utility.

Employees and visitors enter the 109,000- square-foot building through a spacious, two-story lobby featuring a stunning diagrid roof framed with glulam and CLT. Educational exhibits teach visitors, many of whom are schoolchildren, about water treatment processes as well as mass timber and sustainability. The public portion of the main floor also includes a large boardroom used for utility business and community events, plus gardens and a terrace. From the mezzanine, a 140-foot skybridge provides access to the waste treatment plant across the street.

Two adjacent three-story office wings flank a large outdoor courtyard while smaller terraces promote informal employee collaboration. The design’s open configuration prioritizes occupant well-being; views and natural light reach 97.5 percent of occupied office spaces.

The hybrid, Type III-B structure combines a mass timber gravity system with a steel brace frame lateral system. Wood’s light weight decreased the weight of the building, easing foundation requirements for the site’s poor soils, mitigating seismic forces, and reducing overall costs. Except for the 1-hour fire-rated stair areas, all connections are unrated, bolted, and exposed to view, allowing for future disassembly. Designers left mechanical systems deliberately visible to reflect OC SAN’s engineering culture; their exposure also eases maintenance.

Ambitious sustainability goals were achieved through smart design. Optimized building orientation, a high-performance envelope, and highly efficient building systems helped the project reach its net zero energy goals. OC SAN even leverages its own waste recovery processes to capture biofuel, which provides 60 percent of the building’s energy. The remaining demand is met by solar arrays on the roof and over parking.

Because OC SAN is a publicly-funded utility, it was particularly important to balance their sustainability objectives with fiscal prudence; the project had to meet the construction budget for a standard Class B office. This beautiful design hit the utility’s targets, and the project team proved it is possible to successfully meet public sector design/bid/build requirements using mass timber.

This building is a powerful demonstration of how mass timber can be used to create a high-performing building that meets cost, design, energy, and other parameters. This beautiful facility is elevating community engagement, supporting workforce collaboration, and promoting occupant health—and doing it all sustainably.