Designing Implementing and Managing Improvements to the National Mall | HOK

The National Mall is arguably the most culturally important landscape in the United States. Known as America’s “Front Yard”, the Mall hosts nearly 30 million visitors and 3,000 special events annually. Millions of people visit The National Mall to demonstrate freedom of speech, make their voices heard, and celebrate the nation’s commitment to freedom and equality. The restoration of the National Mall turf and soil for the National Park Service allows the nation to once again be proud through a focus on the details, the underlying landscape structure and sustainability.

The existing conditions of the Mall were bleak. Unsustainable maintenance practices and a lack of public use standards created a cycle of heavy damage and truncated recovery. Symptoms included soil compaction, poor drainage, inconsistent turf, and broken irrigation. The project scope included design and engineering to refurbish the Mall’s eight central turf panels, granite curb edges, granular walkways, and storm drainage improvements.

Before, the Mall consumed the most electricity and potable water of any national parks in the US. The restoration shifted its main irrigation source from drinking water to rainwater, captured in one of the largest rainwater collection/reuse systems in the world. Walkways and turf panels were graded to drain into the new subsurface drainage structures, while ADA-compliant granite curbs guided water to the cistern. Efficient, advanced controls and smart scheduling were implemented for irrigation using the collected runoff, from four 250,000-gallon cisterns.

Once barely surviving, the new turf on the Mall features engineered soil to resist soil compaction. Collaborated with turf experts on optimal species mix and soil compositions, incorporating coarse sand into the soil mix, which contains more oxygen than traditional loam soil, promotes a robust root system and resists physical compaction. The design and operations plan proved successful in preventing lawn degradation during 3 presidential inaugurations and subsequent events, gatherings and protests.

The existing perimeter of the Mall turf was undefined and deteriorating due to stormwater runoff and pedestrian damage. The corners were reshaped from square to round to accommodate natural circulation patterns and the grass panels were regraded to improve drainage. The grass panels were framed in a handicap accessible granite curb, redefine the edge and protect the Mall’s turf.

Protecting the Mall turf during events involved the biggest installation of white lawn covers in history. Recommendation for a plastic covering with the optimal material for protecting and maintaining turf. Before this project, there were no national standards for maintaining public parks. We led a focus group with event coordinators/vendors to set standards for the Mall, resulting in the publication of the NPS Mall Turf Sustainable Operation and Maintenance Manual. The National Mall has hosted countless public events, proving the resilience of the updated system and the long-term success of the NPS’s new standards.

After nearly a decade, $40 million reconstruction, the nation’s “front lawn” is looking the best it has in generations. The new, sustainable turf and irrigation system will maintain the nation’s stage for assembly, remembrance, and celebration for years to come.

The National Mall

Location: Washington, D.C., USA

Michael Stachowicz and Andrea Lind, NPS, Phase 2/3
Patrick Macdonald and Alice McLarty, NPS, Phase 1
Andreas Chryosostomou and Eric Rowland, NPS, Construction Management Representatives
Sean Kennealy, NPS, Deputy Superintendent

HOK
Suzette Goldstein, Lead Designer #1
Jose Chieng, Lead Designer #2
Brandon Hartz, Lead Designer #3
Jacalyn Pruitt, Landscape Architect
Xingye Pan, Landscape Architect

Other Credits

Clark Construction, General Contractor
Wiles Mensch Corporation , Civil Engineer, Land Surveyor
JVP Engineers, PC , Mechanical Engineer, Electrical Engineer, Commissioner
Schnabel Engineering, LLC , Geotechnical Engineer, Construction Engineer, Materials Engineer
Construction Consultants, Inc. , Cost Estimator
Cagley & Associates, Inc. , Structural Engineer, Facility Condition Assessment Specialist
Heritage Landscapes, Historic Landscape Architect
Brian Vinchesi – Irrigation Consulting, Inc., Irrigation Specialist
Steve LeGros – Le Grows, Inc. , Sports Field Consultant
James Urban – Urban Trees + Soils, Soil Consultant
Norm Hummel – Hummel & Co Inc., Soil Scientist
VeTalle Fusilier – JBV Production Inc., Event Planning Consultant
Andreas M. Chrysostomou – Alpha Corporation, Construction Manager