WaterSmart Irrigation & Water-Harvesting Enhance ASLA Center for Landscape Architecture

by Jim Davis, ASLA

ASLA Center for Landscape Architecture green roof / image: EPNAC

Modifications to the American Society of Landscape Architects (ASLA) Headquarters building, now known as the Center for Landscape Architecture (CLA), are nearing completion for higher performance in water conservation. The exterior improvements are of particular interest to landscape architects and others who are sustainably-minded, as part of their ongoing Energy-Star initiatives. In addition to interior upgrades and hardscape improvements outside, the primary improvements of high interest to ASLA’s Water Conservation PPN include the water-harvesting system and the WaterSmart approach to irrigation for the greenroof, the new courtyard (east of the building) and the planted canopy overhanging the front windows and entry on the north side.

The light fixtures are visible, but the micro-spray emitters are not, in the building’s planted main entrance canopy.
Mostly shaded, the courtyard plantings are watered by low-volume drip-irrigation.

Key components to the design involved the incorporation of a water-harvesting system to collect stormwater from the roofs for complete recycling of the water for use in the irrigation system. With that, state-of-the-art weather & soil monitoring devices communicate with a Toro Sentinel central controller to provide optimum water use for the landscape materials on all levels. The water-harvesting system has multiple flow meters and sensors to monitor not only the stormwater collection volume but also collect data to show the amount of water applied by the irrigation system. Separate sensors record the make-up water added to the cistern during drought periods.

Sump-pump at round submerged tank. / image: Stacilyn Feldman
An underground cistern stores captured rainwater, collected from the roof, for use in the irrigation system. Dark green cover (lid) is placed over the top of the cistern for access, with plantings around the perimeter. / image: Stacilyn Feldman

To maximize water consumption and only use what is needed for the plant material, the design incorporates an onsite weather station to measure temperature, humidity, solar radiation, wind and rainfall to calculate the daily ET (evapotranspiration rate) value. Additionally, soil moisture sensors are installed to track soil conditions in key areas within the landscape. All of the courtyard and much of the rooftop irrigation utilizes drip irrigation to reduce overspray, evaporation and deliver water directly to the roots of the plants. Only a few multi-stream MP Rotators (with larger water droplets) water the larger “wave” planting on the greenroof. Small micro-spray nozzles (on 1/4-inch PolyFlex risers) deliver water to the planted canopy overhanging the front entry, which provide small doses of water throughout the day when needed.

All of the irrigation is then controlled with the Toro Sentinel Central Control System that provides complete monitoring and control incorporating weather driven updating, moisture sensors and flow-monitoring for all conditions. Sentinel Water Management Software (WMS) is a Microsoft® Windows-based program that allows users to control daily irrigation operations and scheduling from a powerful yet easy-to-use platform. With the ability to control up to 999 field-satellites from one location, the selected water management platform provides the ultimate in customization and reliability.

The “wave” on the north side of the roof is planted with native plants, and is watered by multi-stream rotary nozzles with a low precipitation rate.

The headquarters of the American Society of Landscape Architects helped Washington, D.C., rank second on the U.S. Environmental Protection Agency’s (EPA) 2014 list of the top U.S. cities with the most ENERGY STAR certified buildings.  ASLA has participated in EPA’s ENERGY STAR certification since 2008, and its headquarters building was ENERGY STAR recertified in 2013. Among buildings the same size, ASLA’s energy performance is in the top 11 percent. ASLA’s headquarters employs energy-efficient systems and practices including a green roof that reduces energy usage by 10 percent in winter months. Sustainability has been part of ASLA’s mission since its founding and is an overarching value that informs all of the Society’s programs and operations. ASLA has been a leader in demonstrating the benefits of green infrastructure and resilient development practices through the creation of this green roof.

Project team:
Owner: American Society of Landscape Architects
Architect: Gensler
Landscape Architect: Oehme, van Sweden Landscape Architecture
Water Management/Irrigation Consultants: Landtech Design
Civil Engineer: VIKA Capitol
General Contractor: Coakley & Williams Construction, Inc.
Irrigation Contractor: Nature Unlimited

by Jim Davis, ASLA, Water Conservation PPN Officer

3 thoughts on “WaterSmart Irrigation & Water-Harvesting Enhance ASLA Center for Landscape Architecture

  1. Matt Mathes, ASLA Water Conservation PPN Chair March 6, 2018 / 5:27 pm

    Congratulations to ASLA for ongoing EPA award recognition and certifications. Licensed landscape architects are featured for roles in green roof design, irrigation design and water management in an existing building. We appreciate Jim Davis, Water Conservation PPN Mid West Region Technical Director and Officer, sharing details as a project insider about water saving specifics toward a very valuable outcome – – 10% winter month energy savings. This is what respectable existing building design performance looks like.

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