King County South Treatment Plant Administration Building

The new two-story, 21,000 square foot administrative building for King County Wastewater Treatment Division’s South Plant provides improved aesthetics and functional work space, especially compared to the 45 year old building it replaced. The project initially targeted LEED Silver certification but through salvage of much of the old building, energy efficient design, and reuse of water the South Plant Administration Building achieved a LEED New Construction Gold rating.

During pre-design, O’Brien & Company facilitated a day-long eco-charrette with the design team and County to brainstorm green building strategies and evaluate LEED.  The strategies were grouped into “low-hanging fruit,” and items that needed more research; they were also ranked by first costs and life cycle costs.   These strategies were evaluated and incorporated into the design over time resulting in the LEED Gold certification.

Located on the site of the old administrative building, the facility’s design is sensitive to the campus design and the design of the original administration building. The design team re-interpreted the campus vernacular with an emphasis on sustainability, user friendly workspaces that feature substantial natural light, and public accessibility. A strong axial corridor connects and unites the lobby, library, conference rooms, and different work groups, while also a source of primary light for the building’s interior.  A portion of the floor of the second floor library includes structural translucent glass panels, allowing light from the daylight central corridor above to penetrate to the common area for the lab technicians below. Of the building’s regularly occupied spaces, more than 83 percent are daylit, and 99 percent have access to views.

The design also incorporated extensive building energy modeling, additional insulation, variable speed drive hydronic pumps and fans, high efficiency lighting and glazing, exterior sunshades, and daylight and occupancy sensors to optimize the building’s performance. A 1,000-square-foot black solar preheating panel, integrated into the south elevation, preheats 6,500 cfm (cubic feet per minute) of outside air for the laboratory supply air before it enters the air makeup unit heating coil. The building performs 27.4 percent better than ASHRAE 90.1-2001 standards.

The building also uses reclaimed water from an adjacent treatment plant for water closet and urinals, reducing potable water use for flushing fixtures by 100 percent.  Combined with water efficient flow fixtures, overall water use is reduced by 76 percent.  Xeriscaping and irrigation using reclaimed water reduces potable water for landscaping by 100 percent.

O’Brien & Company served as LEED manager for the project, incorporating the results of the eco-charrette into a LEED plan, monitoring progress, reviewing documents, and eventually submitting the LEED documentation.  The USGBC awarded the project LEED NC Gold certification in 2010.

Construction cost: $10 million
Construction completed:  2009
Owner:  King County Wastewater Treatment Division
Architect and Engineers:  Tetra Tech
Landscape Architect:  Osborn Pacific
Contractor:  Kassel & Associates