BY KEN URBANEK

W

hen Denver Water was planning its new, high-performance administration building, one of the city utility's key goals was to implement a rainwater capture system and an on-site wastewater treatment system to drive overall building water use to exceedingly low levels. Implementing such systems would take water-efficient design to the next level and would not come without challenges. With the leadership and support of the water efficiency- focused client, however, the design and construction team were ultimately able to deliver on Denver Water's "One Water" concept. The LEED Platinum and net-zero energy facility opened in 2020 (Figure 1) and went on to win the American Council of Engineering Companies' 2021 Engineering Excellence Awards National Grand Conceptor Award (https://bit.ly/3JPLu8e).

Water use master planning

Critical to the overall project success was a thorough understanding of the existing water use on campus and the client's goals for water use reduction. This discovery process started very early during the master planning phase of the project, approximately eight years before the project would be completed. Water consumption was evaluated using a water use intensity metric, gallons/square foot/year (gal/sf/year), similar to the more common energy use intensity metric used to evaluate building energy performance (kBTU/ square foot/year). This evaluation started by developing a baseline model representing the WUI of a typical set of buildings matching the master plan concept (see Figure 2). The WUI of the existing buildings on the Denver Water campus also was determined. Additionally, the existing campus WUI was broken down across various uses - irrigation, building plumbing fixtures, cafeteria fixtures, process water and cooling water. The typical baseline was modeled to be 38 gal/sf/year and the existing campus was performing at 29 gal/sf/year, already a 24 percent reduction in water use due to years of water efficiency measures by Denver Water. From the developed baseline and existing conditions, multiple layers of best practices were considered for the current time (2012, when the master plan phase began) and into the future (2022, when the project was to be entirely constructed and landscape established, about two years after substantial completion). Additionally, stretch goals to set leadership trends along with theoretical net-zero conditions also were evaluated. The first step toward achieving these long-term goals was a continued push on water efficiency. This included implementing a more native and adaptive landscape to reduce or eliminate irrigation requirements and deploying ultra-low-flow plumbing fixtures and commercial kitchen fixtures. The second step was to reconsider where water was needed and whether water use could be entirely or nearly removed. The design team determined that a cooling system without evaporative cooling methods would be implemented, ultimately settling on a hybrid geothermal system (via distribution water conduit sink/source geo-exchange) coupled with air-cooled systems. The team also determined that process water use in the water meter testing facility could be reduced through capture, treatment and, ultimately, reuse. These best practices for eliminating

GREEN SYSTEMS

172

phc May 2022 www.phcppros.com

Plumbing Efficiency in a Modern High-Performance Building

Denver Water's new administration building incorporates a plant-based blackwater system and a rainwater system to conserve potable water.

Figure 1: The new LEED Platinum and net-zero energy Denver Water Operations Complex provides a more efficient, publicly accessible and highly sustainable headquarters on a 35-acre site. Photography Frank Ooms, courtesy of IMEG Corp.