Known as America’s “front yard,” the National Mall in Washington hosts some 25 million visitors and 3,000 events each year. Such use can take a heavy toll on the Mall’s turf and soil.
HOK’s design solution improves upon the National Park Service’s decades of cultivation work to create a lawn that is more resilient to both human and environmental factors. The project defined sustainable strategies for maintaining healthy soils and turf and improved stormwater absorption while preserving the iconic beauty of this historic and cultural landmark.
The team identified grass types that can withstand heavy use and irrigation systems that are durable and environmentally sound. Design solutions alleviated soil compaction and provided proper air, water and nutrient infiltration. The plan replaced subsoil and surface soil with an engineered, permeable earth that retains water within its subsurface structure and is effective for plant growth.
Walkways and regraded lawn panels drain into a new, deeper subsurface drainage structure featuring four 250,000-gallon cisterns. ADA-compliant granite curbs guide water to the cisterns and redefine the edge of the National Mall’s lawn panels.
HOK also helped the National Park Service write a manual for operating and maintaining the turf in a sustainable way.