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HOK’s Design of National Mall Restoration Wins ASLA Honor Award

National Mall Turf And Soil Reconstruction

The American Society of Landscape Architects (ASLA) recognized HOK for revitalizing the famous greenspace and ensuring it remains a vibrant national asset.

HOK’s landscape architecture team has won one of the profession’s top accolades, an ASLA Honor Award, for its National Mall restoration.

The most important cultural landscape in the United States, the National Mall (known as “America’s front yard”) hosts tens of millions of annual visitors who come to the Washington, D.C., grounds to commemorate history and celebrate freedom of speech.

By the early 2000s, the Mall’s heavy use had turned its 31 acres into a patchwork of thin grass, weeds, dirt and mud. HOK’s solution would restore the Mall’s grand aesthetics, though not simply by replanting new turf.

“The answer wasn’t as easy as it appeared on the surface,” said Suzette Goldstein, HOK’s director of planning in Washington, D.C., and lead designer for the Mall restoration. “We needed to ensure the lawn would remain healthy and green for decades to come with as little maintenance and resources as possible.”

In an approach that emphasizes sustainability and resilience, HOK’s team recommended that the Mall’s eight turf panels be slightly “crowned” (elevated) in the middle to ensure effective drainage. The technique also provided the visual illusion from ground level of one continuous parcel of green. Water runoff from the turf and walkways flows into four 250,000 cisterns for use irrigating the lawn. The water recapture system reduces the amount of potable water required to irrigate the Mall by 75 percent.

HOK helped cultivate a grass blend of tall fescue and Kentucky bluegrass that can withstand both heavy use and the district’s fluctuating weather. Working with soil scientists, the team developed a soil mixture of 60 percent sand and 40 percent organics that resists compaction and reduces the need for fertilizers and herbicides.

With the assistance from the National Park Service, HOK also created an events and operations manual that provides long-term guidance for the lawn, including rest periods and weight restrictions for the Mall’s 3,000 annual events. Landscape Architecture magazine quoted Patrick MacDonald (now retired) of the NPS: “In 35 years in the park service, I’ve never been involved in this kind of support document.”

Seven years after the completion of the turf and soil reconstruction, the National Mall remains as beautiful as ever. It’s also arguably more important than ever as the Mall provides D.C. residents and visitors a safe space during the pandemic to actively participate in the nation’s evolving history.

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